Non-random distribution and co-localization of purine/pyrimidine-encoded information and transcriptional regulatory domains.

In order to detect sequence-based information predictive for the location of eukaryotic transcriptional regulatory domains, the frequencies and distributions of the 36 possible purine/pyrimidine reverse complement hexamer pairs was determined for test sets of real and random sequences. The distribution of one of the hexamer pairs (RRYYRR/YYRRYY, referred to as M1) was further examined in a larger set of sequences (> 32 genes, 230 kb). Predominant clusters of M1 and the locations of eukaryotic transcriptional regulatory domains were found to be associated and non-randomly distributed along the DNA consistent with a periodicity of approximately 1.2 kb. In the context of higher ordered chromatin this would align promoters, enhancers and the predominant clusters of M1 longitudinally along one face of a 30 nm fiber. Using only information about the distribution of the M1 motif, 50-70% of a sequence could be eliminated as being unlikely to contain transcriptional regulatory domains with an 87% recovery of the regulatory domains present.


A simple protocol for the automation of DNA cycle sequencing reactions and polymerase chain reactions.

Automated DNA sequencing methods using robotic workstations have been previously reported, however it is often an arduous task to import these technologies into a laboratory. We describe protocols making use of a Beckman Biomek 1000 robotic workstation to prepare polymerase chain reactions (PCRs) and "cycle sequencing" reactions to be performed in a Perkin Elmer Cetus System 9600 thermocycler. The combination of these two instruments allows a high throughput of PCR and DNA sequencing reactions. The programs described are freely available via anonymous file transfer protocol (FTP).


Comparison of the genomic organizations of the rat grp78 and hsc73 gene and their evolutionary implications.

GRP78, a 78-kDa protein localized in the endoplasmic reticulum, is a member of the HSP70 protein family. However, unlike hsp70 which is intronless and belongs to a multigene family, grp78 is a single copy gene and contains intervening sequences. In this aspect, the grp78 gene resembles more closely that of the constitutively expressed heat shock cognate gene, hsc73. In this report, we compare the grp78 and hsc73 genes and show that: (1) the intron/exon junctions of the two genes are not conserved, but occur at similar positions; (2) while the protein sequences are highly conserved, being 62% identical, the conservation is concentrated at discrete regions over the N-terminal three-fourths of the protein; (3) this conservation represents the ATP binding and structural domains shared among the members of the HSP70 family; (4) the C-terminus is highly divergent and likely represents domains specific for the individual family members; and (5) sequences partially homologous to the grp78 5' UTR and signal sequence, which targets GRP78 into the ER, are found within an additional first intron of hsc73. The evolutionary implications of these two genes are discussed.


Gene sequences of chicken BDNF and NT-3.

The respective amino acid sequences of mature brain-derived neurotrophic factor (BDNF) and of mature neurotrophin-3 (NT-3) are identical among mammals, making these among the structurally conserved factors known. Here we show that only a single conservative amino acid substitution distinguishes the chicken mature NT-3 protein from its mammalian counterpart. Chicken mature BDNF shows slightly more variation, differing from mammalian BDNF at several positions. We also note the presence of amino acid sequence motifs in the precursor protein sequences of chicken BDNF and NT-3 that are universally conserved among all known mammalian neurotrophin precursors and have been demonstrated to play a crucial role in promoting correct processing of the pro-proteins.


New protocols for DNA sequencing with dye terminators.

We have developed a new two-step protocol for Taq cycle sequencing using the ABI dye terminators. First, linear PCR is used to extend a single sequencing primer in the absence of dye terminators. This nested set of polynucleotides as well as the original primer then serve as starting points for the cycled termination reactions. Using this method it is easily possible to generate dye terminator raw data with much improved signal intensity beyond 400 to 500 bp. We also present a quick and convenient method to remove excess of dye terminators by gel filtration using 24 mini columns fixed in a block of perspex.


A standard file format for data from DNA sequencing instruments.

There are now a number of machines for determining DNA sequences. These devices are currently of two types: those such as the Applied Biosystems 373A and the Pharmacia A.L.F. which interpret the sequences of samples as they run on gels within the machine, and those, such as the Bio-Rad and Amersham readers that scan and analyse conventional autoradiographs. Both types of machine can produce their data in the form of traces which represent the band intensity of each of the four base types at each position in the sequence. At present all the machines write files in different formats. We describe a machine independent format for storing data derived from automatic sequencing machines. Files in this format can store the derived sequence, the traces and a set of confidence measures for each base. We have adopted the format as the standard for our sequence handling software.


The isolation and sequence of sheep interleukin 4.

A cDNA corresponding to sheep IL-4 has been isolated and sequenced. The cDNA was synthesized using PCR and oligonucleotides designed from conserved regions of IL-4 cDNA published sequences. The nucleotide and amino acid sequences of a sheep IL-4 cDNA are presented and compared with sequences from other species. At the nucleic acid level, the sheep cDNA shared 73 and 62% homology with human and mouse cDNA homologues, respectively, while comparisons at the amino acid level revealed 50% homology with human IL-4 and 33% with the mouse homologue. Total amino acid homology between these species was 27%.


Nucleotide sequence of the bovine interleukin-6 gene promoter.

We report the cloning and sequencing of a 1252 base pairs (bp) DNA fragment containing the bovine interleukin-6 (IL-6) gene promoter. This fragment was isolated from a bovine genomic library constructed in the lambda GEM11 vector. Comparison with human, murine and rat IL-6 gene promoters reveals a high degree of conservation of the 200 bp immediately upstream of the RNA CAP site. This region contains nucleotide stretches matching with consensus sequences recognized by transcription factors, including NF-KB, CREB and NF-IL6. A potential AP-1 binding site is found 284 nucleotides upstream of the RNA CAP site. The bovine IL-6 gene promoter cloned upstream of the bacterial chloramphenicol acetyl transferase (CAT) gene was shown to be active in bovine and ovine cells.


Nucleotide sequence and exon-intron structure of the bovine transition protein 1 gene.

The nucleotide sequence and exon-intron structure of the bovine transition protein 1 gene was determined. It consists of 2 exons (E1, 139 bp; E2, 29 bp) and a single intron (220 bp). The position of the transcription initiation site was determined 30 nucleotides upstream of ATG. TAAATA- and CAAT-boxes were found 60 and 121 bp upstream of the ATG-translation start point, respectively. It was observed that transition protein 1 is highly conserved in mammals at the nucleotide as well as at the amino acid level.


The sea urchin erg homolog defines a highly conserved erg-specific domain.

A genomic clone, isolated from a phage library prepared from the DNA of the sea urchin Lytechinus variegatus, was shown by sequence analysis to be a homolog of the ets family genes, ERG and Fli-1. It contains an open reading frame of which the coding region begins at a consensus 3' splice site and extends for 173 amino acid residues. The first 84 amino acids are homologous with all members of the ets gene family, while the remainder of the sequence is only homologous with the human ERG and murine Fli-1 genes. This latter region, designated R, represents a highly conserved erg-specific domain.


M13 single-strand purification using a biotinylated probe and streptavidin coated magnetic beads.

A new method for M13 single-strand purification has been developed and tested. The procedure gives sufficient DNA for one set of thermally cycled sequencing reactions when analysed on the Applied Biosystems 373A fluorescent DNA sequencer. For this report, 250 random M13 subclones with 1-2 Kb inserts were grown and prepared using this method.


Sequence and pattern of expression of a bovine homologue of a human mitochondrial transport protein associated with Grave's disease.

A human cDNA has been isolated previously from a thyroid library with the aid of serum from a patient with Grave's disease. It encodes a protein belonging to the mitochondrial metabolite carrier family, referred to as the Grave's disease carrier protein (GDC). Using primers based on this sequence, overlapping cDNAs encoding the bovine homologue of the GDC have been isolated from total bovine heart poly(A)+ cDNA. The bovine protein is 18 amino acids shorter than the published human sequence, but if a frame shift requiring the removal of one nucleotide is introduced into the human cDNA sequence, the human and bovine proteins become identical in their C-terminal regions, and 308 out of 330 amino acids are conserved over their entire sequences. The bovine cDNA has been used to investigate the expression of the GDC in various bovine tissues. In the tissues that were examined, the GDC is most strongly expressed in the thyroid, but substantial amounts of its mRNA were also detected in liver, lung and kidney, and lesser amounts in heart and skeletal muscle.


Sequences of the human and bovine genes for the mitochondrial 2-oxoglutarate carrier.

The oxoglutarate carrier transports 2-oxoglutarate across the inner membranes of mitochondria in an electroneutral exchange for malate or other dicarboxylic acids. The sequences of its human and bovine genes have been determined from overlapping genomic clones generated by polymerase chain reactions by use of primers and probes based on the bovine cDNA sequence. The bovine and human genes are split into 6 and 8 exons, respectively, and five introns are found in the same positions in both genes. The coding and protein sequences are 93% and 96.6% identical, respectively. The human oxoglutarate carrier protein is 314 amino acids in length and, in common with the bovine protein, does not appear to have a processed presequence to help to target it into mitochondria.


Indexing the sequence libraries: software providing a common indexing system for all the standard sequence libraries.

We describe a set of programs for creating and using indexes for the distributed forms of the major sequence libraries. The indexes conform to the specification of those distributed on cd-rom by the EMBL sequence library. The programs create entry name, accession number, author and freetext indexes and a brief directory index. If a suitable application program is given an entry name or accession number these indexes allow rapid retrieval of sequences or annotation. Similarly the author and freetext indexes provide the data for extremely fast searching on author names and "keywords". The indexing programs can create indexes for EMBL, Swiss-Prot, GenBANK, PIR and NRL3d libraries. We also describe the organisation and use of the different sequence libraries and their index files.


Presence of IgE class antibodies with cardiolipinic and treponemal specificity in syphilis. Quantitative evaluation by IgE prist radio-immuno-assay.

60 serum samples (reactive in VDRL, ELISA-Reiter, FTA-Abs tests) from 25-45 years old male patients with untreated latent syphilis (EL) (30 cases) and persistent positive treated syphilis (ET+) (30 cases) were tested for IgE by IgE-PRIST. On 30 sera from 25-45 years old male healthy persons, normal mean value for serum IgE was established: 159.63 +/- 124.09 U/ml. Cardiolipin and group treponemal IgE fractions were indirectly calculated by the difference between the specific activity induced by sera as such and that induced by sera absorbed with cardiolipin and group treponemal sorbents. In EL, total IgE level was 197 +/- 107 U/ml; cardiolipin IgE -24.9 +/- 8.3 U/ml and group treponemal IgE 35.8 +/- 6.6 U/ml. In ET, total IgE value was 152.6 +/- 122.5 U/ml, cardiolipin IgE -11 +/- 10.5 and group treponemal IgE -26.6 +/- 14.2 U/ml. Summing up the two specificities, the total specific IgE represent about 1/3 from total IgE in EL and 1/5 in ET+. Taking into account the short half-life (2-3 days) of IgE presence of a significant proportion of specific IgE in those two stages proves, by their continuous synthesis paralleling antigenic stimulation, the presence in various tissular zones of viable treponemas as sources of antigens.


Significance of the positivity of some ELISA tests different as concerning the antigenic source in interpreting the western blot indeterminate sera in monitoring the epidemiology of high risk populations.

The paper analyses 50 pairs of sera pre-elevated within the "sentinel" epidemiological surveillance in a population exposed to a high risk at a 2 months interval. At the first determination all these sera showed an indeterminate Western Blot pattern; after 2 months, 93.7% revealed the occurrence of a certainly positive pattern. The paper is an analysis of the way in which different ELISA kits diagnosed at the first determination the Western Blot indeterminate sera. The purpose of the paper is to adopt a methodology of accurately diagnosing HIV infections in a population exposed to a high risk within an epidemiological surveillance of the "sentinel" type where the receiving of a second serum sample is quite difficult.


The anti-initiator action of p-methoxyphenol phosphate upon the transformation of normal human embryo cells induced by benzo(a)pyrene.

The association of p-methoxyphenol phosphate (10(-5)M) to benzo(a)pyrene treatment (10(-6)M) reduced significantly the anchorage independent growth and the number of transformed foci of the human embryo lung fibroblasts, after six passages from treatment application. Results from cytogenetic analysis show that p-methoxyphenol phosphate induced the decrease of numerical and structural chromosome aberration after the first passage of the treated cells. In terms of the results obtained by cytogenetic analysis the reduction of genetic instability seems to remain constant from the first to the sixth passage in the cell cultures treated with p-methoxyphenol phosphate associated to benzo(a)pyrene.


Molecular basis of loss-of-function mutations in the glp-1 gene of Caenorhabditis elegans.

The glp-1 gene encodes a membrane protein required for inductive cell interactions during development of the nematode Caenorhabditis elegans. Here we report the molecular characterization of 15 loss-of-function (lf) mutations of glp-1. Two nonsense mutations appear to eliminate glp-1 activity; both truncate the glp-1 protein in its extracellular domain and have a strong loss-of-function phenotype. Twelve missense mutations and one in-frame deletion map to sites within the repeated motifs of the glp-1 protein (10 epidermal growth factor [EGF]-like and 3 LNG repeats extracellularly and 6 cdc10/SWI6, or ankyrin, repeats intracellularly). We find that all three types of repeated motifs are critical to glp-1 function, and two individual EGF-like repeats may have distinct functions. Intriguingly, all four missense mutations in one phenotypic class map to the N-terminal EGF-like repeats and all six missense mutations in a second phenotypic class reside in the intracellular cdc10/SWI6 repeats. These two clusters of mutations may identify functional domains within the glp-1 protein.


Development of an irradiated vaccine that protects against enterotoxigenic Escherichia coli diarrhoea.

In the pathogenesis of diarrhoea in man bacteria adhesion to enterocytes is mediated by specific CFA/I or CFA/II antigens. A perorally administered vaccine was prepared from E. coli H10407 (078:H11) by irradiation with electrons with high energy (EHE). Two hours after cimetidine administration rats were immunized per os with 5 irradiated vaccine doses at 4-day intervals. Seven days after the last immunization animals were infected by inoculating 1 x 10(9) germs in the ligated intestinal loop. Reduction of the intestinal secretion by over 50% 18 hours after inoculation was considered an efficient protection marker. The obtained results have proved a significant reduction of the intestinal secretion in immunized animals infected with serotypes 078:H11(63 +/- 4%) and 078:H12(59 +/- 5%) as compared to non-immunized animals. Experimental induction of the intestinal protection against Escherichia coli enterotoxigenic (ETEC) strains points to the possibility of using this type of irradiated vaccine in the prophylaxis of diarrhoea in man.


Experimental study on intradermal antitetanus antityphoid immunization.

A new type of concentrated unadsorbed Tetanus vaccine was administered in animals by intradermal route, associated or not with Typhoid vaccine. The results of the laboratory tests demonstrated that this vaccine is innocuous and produces minimal reactions. A single doses of Tetanus vaccine inoculated in guinea pig or rabbit resulted in a relevant titer which increased when the Typhoid vaccine was associated. Also, in such immunized guinea pigs, a remarkable resistance to tetanic toxin was achieved. The levels of the active or passive typhoid-protective power as well as that of the agglutinating antibodies were not influenced by the association of the Tetanus vaccine to the Typhoid vaccine. Therefore, when the Typhoid vaccine suspended in Tetanus vaccine was administered intradermally to the animals by Jet injector, it had not a negative effect for none of the two components, had a beneficial effect upon the levels of determined antibody production and allowed an easier and more rapid administration of these vaccines.


Anti-sense transforming growth factor alpha oligonucleotides inhibit autocrine stimulated proliferation of a colon carcinoma cell line.

Many carcinoma cells secrete transforming growth factor alpha (TGF alpha). A 23 base anti-sense oligonucleotide that recognizes the TGF alpha mRNA inhibits both DNA synthesis and the proliferation of the colon carcinoma cell line LIM 1215. The effects of the anti-sense TGF alpha oligonucleotide are reversed by epidermal growth factor (EGF) at 20 ng/ml. When the LIM 1215 cells are grown under serum free conditions, the anti-sense TGF alpha oligonucleotides have their greatest effects at high cell density (2 x 10(5) cells/cm2), indicating that the secreted TGF alpha is acting as an exogenous growth stimulus. In addition, at higher cell densities, the kinase activity of the EGF receptor is activated and the receptor is down-modulated. The cell density dependent activation of the EGF receptor is inhibited by the application of the antisense TGF alpha oligonucleotides.


Genetic dissection of the signaling domain of a mammalian steroid receptor in yeast.

The mechanism of signal transduction by steroid receptor proteins is complex and not yet understood. We describe here a facile genetic strategy for dissection of the rat glucocorticoid receptor "signaling domain," a region of the protein that binds and transduces the hormonal signal. We found that the characteristics of signal transduction by the receptor expressed in yeast were similar to those of endogenous receptors in mammalian cells. Interestingly, the rank order of particular ligands differed between species with respect to receptor binding and biological efficacy. This suggests that factors in addition to the receptor alone must determine or influence ligand efficacy in vivo. To obtain a collection of receptors with distinct defects in signal transduction, we screened in yeast an extensive series of random point mutations introduced in that region in vitro. Three phenotypic classes were obtained: one group failed to bind hormone, a second displayed altered ligand specificity, and a third bound hormone but lacked regulatory activity. Our results demonstrate that analysis of glucocorticoid receptor action in yeast provides a general approach for analyzing the mechanism of signaling by the nuclear receptor family and may facilitate identification of non-receptor factors that participate in this process.


The nuclear-mitotic apparatus protein is important in the establishment and maintenance of the bipolar mitotic spindle apparatus.

The formation and maintenance of the bipolar mitotic spindle apparatus require a complex and balanced interplay of several mechanisms, including the stabilization and separation of polar microtubules and the action of various microtubule motors. Nonmicrotubule elements are also present throughout the spindle apparatus and have been proposed to provide a structural support for the spindle. The Nuclear-Mitotic Apparatus protein (NuMA) is an abundant 240 kD protein that is present in the nucleus of interphase cells and concentrates in the polar regions of the spindle apparatus during mitosis. Sequence analysis indicates that NuMA possesses an unusually long alpha-helical central region characteristic of many filament forming proteins. In this report we demonstrate that microinjection of anti-NuMA antibodies into interphase and prophase cells results in a failure to form a mitotic spindle apparatus. Furthermore, injection of metaphase cells results in the collapse of the spindle apparatus into a monopolar microtubule array. These results identify for the first time a nontubulin component important for both the establishment and stabilization of the mitotic spindle apparatus in multicellular organisms. We suggest that nonmicrotubule structural components may be important for these processes.


Biochemical and physiological changes induced by anthrax lethal toxin in J774 macrophage-like cells.

Experiments were performed to probe the mechanism by which Bacillus anthracis Lethal Toxin (LeTx) causes lysis of J774 macrophage-like cells. After incubation of cells with saturating concentrations of the toxin, two categories of effects were found, which were distinguishable on the basis of chronology, Ca(2+)-dependence, and sensitivity to osmolarity. The earliest events (category I), beginning 45 min postchallenge, were an increase in permeability to 22Na and 86Rb and a rapid conversion of ATP to ADP and AMP. Later events (category II) included alterations in membrane permeability to 45Ca, 51Cr, 36Cl, 35SO4, 3H-amino acids, and 3H-uridine, beginning at 60 min; inhibition of macromolecular synthesis, leakage of cellular lactate dehydrogenase and onset of gross morphological changes, at approximately 75 min; and cell lysis, beginning at 90 min. Category II events exhibited an absolute requirement for extracellular Ca2+ and were blocked by addition of 0.3 M sucrose to the medium, whereas category I events were attenuated, but not blocked, by either of these conditions. On the other hand, both ATP depletion and the category II events were blocked in osmotically stabilized medium that was also isoionic for Na+ and K+. This suggests that permeabilization of the plasma membrane to monovalent cations and water may be the earliest of the physiological changes described here. The resulting influx of Na+ and efflux of K+ would be expected to cause depletion of ATP, via increased activity of the Na+/K+ pump. Subsequently the influx of Ca2+, induced by depletion of ATP, imbalances in monovalent cautions, and/or more dramatic changes in permeability due to influx of water, would be expected to trigger widespread changes leading ultimately to cytolysis.


Cross-sectional assessment of weekly urea and creatinine clearances in patients on continuous ambulatory peritoneal dialysis.

In 55 patients on continuous ambulatory peritoneal dialysis, the authors determined daily renal and dialysate clearances of urea nitrogen (CUN) and creatinine (CCr). Results are expressed as weekly CUN in liters (Kt) divided by liters of total body water determined from a nomogram (V). The authors calculated weekly CCr as the weekly dialysis clearance plus the average of renal CUN and CCr (to correct for creatinine secretion); they normalized total weekly CCr to 1.73 m2 body surface area. Mean weekly Kt/V and CCr were 2.1 and 65.2, respectively. Mean dietary protein intake by dietary survey was 0.85 g/kg body weight. Protein catabolic rate (PCR) calculated from urea kinetics was 0.94 g/kg standardized weight (V/0.58); PCR was significantly (p < 0.01) correlated with Kt/V (r = 0.53). The authors used linear regression to determine PCR, as follows: PCR = 0.80 [weekly Kt/V]/3 + 0.39. This slope is nearly 1.5 times that reported for the relationship of PCR to [weekly Kt/V]/3 in hemodialysis patients. Eighty-two percent of patients on continuous ambulatory peritoneal dialysis had more than the targeted minimum weekly Kt/V of 1.7, 71% had a weekly CCr more than the targeted minimum of 50, and 75% had a PCR > 0.8 g/kg/day. In support of the hypothesis that Kt/V requirements are related to peak concentration control rather than to time averaged blood urea nitrogen, patients on continuous ambulatory peritoneal dialysis have a higher PCR at given Kt/V values compared to hemodialysis patients. These patients are more likely to have a PCR > 0.8 if weekly Kt/V > 1.7.


Initial clinical experience with centrifugal pumps coated with the Carmeda process.

From September 5 to November 4, 1991, four consecutive patients placed on centrifugal ventricular assist devices (VADs) for cardiac failure were supported with Biomedicus pumps coated with the Carmeda bioactive surface. The study included three men and one woman aged 52-65 years. Two patients were supported with a right VAD, one with a left VAD, and one with a biventricular VAD. Support ranged from 35.5 to 65.75 hr, and VAD flows ranged from 1.0-5.5 L/min. Three patients were weaned from the VADs, and two survived. At explant, all four systems had clots adherent to the surface of the tubing and connectors on the pump outflow side of the circuit. Two patients had clots in the pump. Some of the clots were firmly adherent, whereas others dislodged easily after being rinsed with saline. All patients received heparin for insertion, and in three patients, heparin was reversed with protamine. Two patients received no further anticoagulation, and two received continuous heparin within 24 hr of implant to maintain activated clotting times of 140-150 sec. All patients had bleeding complications before and after VAD placement, necessitating multiple blood product transfusions. One patient who was weaned and survived had multiple thromboembolic strokes. These data suggest that clots can form on surfaces coated with the Carmeda process, even if a low dosage of heparin is used.


Intraoperative timing may provide criteria for use of post-cardiotomy ventricular assist devices.

When surgeons consider ventricular assist devices (VADs) for post-cardiotomy support, unnecessary delays and early use can have detrimental effects on patient outcome. The authors analyzed the timing of intraoperative events in all patients receiving post-cardiotomy VAD support at their institution during a 2-1/2 year period (N = 17). They used ability to wean patients from VAD support as a measure of outcome. Neither preoperative risk factors nor the timing of distinct intraoperative events (e.g., cross-clamp time, total bypass time, delay to VAD) significantly differed between those patients able (Group I, n = 9) and those unable (Group II, n = 8) to be weaned from VAD support. The authors did find, however, that the time intervals from completion of the cardiac procedure to insertion of either an intra-aortic balloon pump (time to IABP) or VAD (time to VAD) were predictive of outcome when normalized to the duration of the cardiac procedure (DCP). [Time to IABP]/DCP ratios of < 1.0 versus > 1.0 (p = 0.02) and [time to VAD]/DCP ratios of < 2.5 versus > 2.5 (p = 0.10) each segregated Group I and II patients, respectively. Appropriate timing criteria for VAD insertion may be predicted during surgery by consideration of the duration of the cardiac procedure. This approach may attenuate tendencies to delay VAD use without leading to premature VAD insertion in the post-cardiotomy setting.


The importance of patient mobility with ventricular assist device support.

Patients bridged to transplantation with ventricular assist devices (VADs) often require prolonged support. To reduce complications associated with bed rest, the authors developed a program to mobilize patients with VADs. Between August 1986 and May 1992, 25 men and 7 women aged 12-65 years (mean: 42.4 years) were bridged for possible transplantation. The 32 patients were supported with either a Novacor (n = 9) or a Thoratec (n = 23) VAD. Thirty-one patients were turned within 2-12 hr of VAD insertion and received range of motion therapy. Twenty-six patients sat in a chair 2-16 days (mean: 5 days) after VAD insertion. Twenty-one patients used a stationary bicycle, and 23 patients were ambulatory 3-57 days (mean: 11 days) after VAD insertion. Two patients were transplanted within 72 hr of device insertion. Twenty-one of the 23 ambulatory patients were successfully transplanted or weaned from the VAD and discharged from the hospital. Two ambulatory patients who were difficult to rehabilitate (ambulatory 22 and 57 days, respectively, after VAD insertion) died before transplantation. In conclusion, VAD patients should be mobilized early because the VAD can improve exercise capability and survival rate.


A method to reduce thrombogenicity of a graft for small diameter arterial substitution seeded with autologous venous tissue fragments.

The authors successfully applied a method to accelerate endothelialization by tissue fragmentation to a small diameter fabric vascular prosthesis. Tissue fragment seeded grafts showed rapid healing of the neointima. The thrombogenicity of the collagen fibrils in the fragments, however, caused major problems when the method was applied to small diameter grafts: the positively charged collagen fibrils aggregated the negatively charged platelets. The authors masked the fibrils electrostatically with heparin molecules, which are negatively charged. A canine jugular vein was resected, minced into tissue fragments, and suspended in the heparin solution; it then was sieved through the wall of a fabric prosthesis. The grafts (4 mm internal diameter and 3.5 cm in length) were implanted into both carotid arteries of six dogs (12 grafts). Tissue fragment seeded grafts without heparin also were implanted into six dogs. As a control, preclotted fabric grafts were implanted into six dogs (12 grafts). These grafts occluded within 1 week, whereas all the masked grafts were patent without thrombi. In vitro examination of heparin release revealed that approximately 92% of heparin in the graft was released during the first 5 hr, but approximately 6% remained after 25 hr. These results indicate that the method is applicable to small diameter arterial grafts.


In-storage hypothermic perfusion for heart and lung transplantation.

The authors developed a new waterproof-packed infusion device for easy and sterile in-storage hypothermic perfusion during organ transportation for heart and lung transplantation. They examined the accessibility and efficacy of this infusion device for portable heart and lung preservation in canine transplant models. Sixteen heart and bilateral lung blocks were preserved by an in-storage hypothermic perfusion technique using the infusion device with University of Wisconsin solution. Of 16 dog recipients, 5 underwent orthotopic heart transplantation with cardiopulmonary bypass, and 5 dogs received left lung transplantation; the remaining heart and lung blocks were intrathoracically transplanted into 6 dogs. Functional status and histology of 11 heart and 11 lung allografts were evaluated by post-transplant course, hemodynamic parameters, arterial blood gas measurements, microscopic examination, and so on. Eleven transplanted hearts showed good cardiac performance and maintained systemic circulation after weaning from cardiopulmonary bypass. Eleven transplanted lungs had excellent respiratory function, and all five dogs with left lung transplantation survived for 5-46 days (mean: 18.8 days). These results suggest that in-storage hypothermic perfusion with this waterproof-packed infusion device can be a useful technique for long-term organ preservation in heart and lung transplantation.


Photoinduced prevention of tissue adhesion.

Postoperative tissue adhesion causes retarded wound healing and the need for reoperation; it can even be life threatening. In this report, the authors present prototype materials and performance of newly developed tissue adhesion prevention technology based on photocurable polysaccharides. Polysaccharides used were hyaluronic acid and chondroitin sulfate, both of which were partially derived with photoreactive groups such as cinnamoyl, coumarin, and thymine. Photoreactive hyaluronic acids with low degrees of derivatization were soluble in water. Films of cinnamated hyaluronic acid or an aqueous solution of cinnamated chondroitin sulfate were photocured by ultraviolet irradiation, resulting in water adsorbable films or water swollen gels, respectively. Gelation was due to intermolecular dimerization between cinnamoyl groups. The authors provide two potentially applicable examples: 1) a photocured, water swollen hydrogel film, and 2) a photocurable chondroitin sulfate buffer solution. The authors used hydrogel films to cover the peritoneum after mechanically injuring its surface. Histologic examination showed neither tissue nor cell adhesion, and only a minimal inflammatory response. When tissues were coated with a photocurable chondroitin sulfate solution, the viscous solution was converted to a hydrogel upon ultraviolet irradiation, resulting in in situ tissue covering. Although an optimal molecular design has not yet been found, unique features of mucopolysaccharides (e.g., high water uptake; biodegradability and bioresorbability; and nontoxicity of photodimerizable groups) may result in the development of photoinduced tissue adhesion prevention technology.


A bioartificial ventricle used as a totally implantable circulatory assist device.

The authors designed a totally implantable circulatory assist device consisting of a bioartificial ventricle composed of a skeletal muscle ventricle lined with a bioartificial endocardium. The bioartificial endocardium consists of a structural matrix made of a polyurethane porous membrane, fragmented blood vessels, and collagen gel. The authors prepared the polyurethane porous membrane by solvent cocasting with salt powder. They used collagen gel with fragmented goat carotid vein to perform in vitro construction of the bioartificial endocardium. For in vivo construction of the bioartificial endocardium, the authors used a modified version of the tissue fragment method for vascular prostheses. The authors prepared suspensions of tissue fragments using collagen gel with fragmented goat carotid artery. They used a highly porous fabric vascular prosthesis as a structural matrix; tissue fragments were entrapped on the outer surface of the prosthesis, and the prosthesis then was implanted into the carotid artery of four adult goats. In specimens 1 and 3 months postimplantation, cells from the fragmented tissue regenerated an endothelium-like monolayer sheet on the inner surface of the prostheses. Output of a prototype bioartificial ventricle reached 660 ml/min at an afterload of 60 mmHg and a preload of 20 mmHg. Based on these data, the authors conclude that the bioartificial ventricle is promising as an implantable device with excellent antithrombogenicity.


Novel instrumentation monitoring in situ platelet adhesivity with a quartz crystal microbalance.

The quartz crystal microbalance (QCM) in a solution is capable of sensing an extremely small mass change in the nanogram range. In this article, the authors attempted to apply QCM to in situ continuous monitoring of platelet adhesion in plasma. The instrumentation consisted of a piezoelectric quartz crystal vacuum-deposited with gold and connected to two electrodes, an oscillation circuit, a frequency counter, and a DC source (5 V), coupled with a personal computer, a television monitor, and a printer. The authors noted resonant frequency shifts to determine weight increase upon cell adhesion. A QCM sensor, with the sensitivity of 1 ng/Hz, was placed horizontally in platelet poor plasma. The authors did not observe any measurable frequency shift upon adding a suspension of non-adherent cells, such as red blood cells and prostaglandin I2-sensitized platelets, indicating that QCM does not count the increase in the mass of cells that simply settled on the quartz. They did observe, however, a time-dependent frequency shift upon addition of platelet rich plasma. Coupled with visual determination of numbers of adherent platelets and their morphology under scanning electron microscopy, they found that the magnitude of shift and its time dependence seem to correlate not only numbers of adherent platelets, but to their spreading state, indicating that QCM detects only the weight at the focal contact region of adherent cells. This suggested that the former contributes to the early phase of the frequency shift, and the latter contributes to a shift change after a longer period of incubation.(ABSTRACT TRUNCATED AT 250 WORDS)


Prevention and control of bacterial infections associated with medical devices.

Bacteria that grow in association with medical devices always form slime enclosed biofilms, within which they are protected, to a large extent, from the bactericidal activity of chemical biocides and antibiotics. Mature biofilms (> 7 days) are demonstrably resistant to 500-5,000 times the concentrations of these agents than are necessary to kill free floating (planktonic) cells of the same organism. The authors have discovered that this well established inherent resistance of biofilm bacteria to antibacterial agents can be completely obviated if these agents are applied to these adherent populations within an electric field. The killing of biofilm bacteria by antibiotics can be dramatically enhanced by relatively weak electric fields (1.5 V/cm and 15 microA/cm2) that, in themselves, have no deleterious effects on these slime protected populations adherent to plastic or metal surfaces. This bioelectric technology can readily be used to enhance the preimplantation sterilization of medical devices by biocides. The authors suggest that it may also be used to control biofilm formation and consequent infection by electrically enhanced perioperative antibiotic prophylaxis and by electrically enhanced penetration of antibiotics to kill the biofilm bacteria that form the inherently resistant nidus of chronic device related infections.


Influence of Kt/V and protein catabolic rate on hemodialysis morbidity. A long-term study.

Urea clearance over time, divided by volume of total body water (Kt/V) and protein catabolic rate (PCR), were calculated monthly in 88 long-term hemodialysis patients. Patients were divided into four groups: Group A (n = 40), Kt/V > 1.0 and PCR > 1.0 g/kg/day; Group B (n = 7), Kt/V > 1.0 and PCR < 1.0; Group C (n = 24), Kt/V < 1.0 and PCR > 1.0; and Group D (n = 17), Kt/V < 1.0 and PCR < 1.0. Various clinical, biochemical, and morbidity factors were compared. Group A had significantly less morbidity than did the other groups (p < 0.05). Blood urea nitrogen, serum creatinine, serum albumin, and phosphorus were lower in Group B than in the other groups (p < 0.05). These data suggest that determination of Kt/V and PCR is important for predicting dialysis morbidity and that they should be monitored together for adequacy of therapy and dialysis quality assurance.


Total body water measured by bioelectrical impedance in patients after hemodialysis. Comparison with urea kinetics.

Bioelectrical impedance (BEI) measurements have been used to measure total body water volume (VBEI). The VBEI were measured after hemodialysis in 14 patients, as was dialyzer blood water urea clearance (KBW) and dialysate urea clearance (KD). Urea clearance based on the mass transfer coefficient, KoA, was determined (KKoA). Residual renal function was measured, and three point variable volume single pool urea kinetic modeling (UKM) was done. Urea distribution volumes were calculated using the measured urea clearance values from blood water (VBW), dialysate (VD), and KoA (VKoA) as inputs. Direct dialysate quantitation was calculated based on total dialysate collections to measure urea clearance (KDDQ) and urea distribution volume (VDDQ). Total body water estimates were made using the Hume and Watson anthropometric formulas (VHUME and VWATSON). It was found that average VBEI (34.76 L) was larger than VBW (27.50 L) and VD (26.69 L), but it was not different from VKoA (32.15 L), VHUME (35.15 L), or VWATSON (34.53 L). Linear regression revealed a good correlation between VBEI and both VBW and VD (R = 0.873 and 0.882, respectively). The BEI measurements provide a simple method for measuring total body water in dialysis patients that correlated well with UKM volumes.


Cardiopulmonary recirculation in dialysis. An underrecognized phenomenon.

Access recirculation can be determined by measuring blood temperature or blood water concentration in the dialyzer inlet after injecting a bolus of cold saline into the venous line. In patients with access recirculation, some of the cooled venous blood re-enters the blood inlet line soon after injection, resulting in a sharp transient drop in its temperature. There is also a prompt increase in blood water concentration at the dialyzer blood inlet caused by the dilution effect of the recirculated saline. In this study, data are reported on four patients studied under conditions where no access recirculation could occur because blood was returned to a second access or into a central vein. In these patients, transient cooling of the blood in the dialyzer inlet and a transient hemodilution after venous line injection of cold saline was still observed. These observations can be explained by passage of the injected saline through the heart and pulmonary blood vessels and return of a portion of the cooled blood to the vascular access, bypassing the systemic capillary microcirculation. This "cardiopulmonary recirculation" can cause dilution of urea in dialyzer inlet blood, with resulting errors in urea kinetic modeling and in computing access recirculation.


Continuous measurement of blood volume during hemodialysis by an optical method.

A new method is described to noninvasively and continuously measure changes in blood volume (BV) during hemodialysis by means of an optical reflection method with an optical monitor (950 nm) clipped onto the arterial blood line. The amount of reflected light (L) appeared to be linearly proportional to the erythrocyte concentration (r = 0.91). Changes in L correlated well with changes in erythrocyte concentration during hemodialysis (r = 0.94). A study in 10 patients on regular dialysis was done. The BV decrease after 3 hr of treatment was 17.0 +/- 5.2%, and it correlated with the amount of fluid withdrawn by ultrafiltration (mean, 2,519 +/- 589 ml). Five hypotensive episodes were seen that were characterized by a higher rate of BV fall during the preceding 15 min (9.9 +/- 1.9 versus 3.6 +/- 4.3%/hrp; p < 0.05) and by a lower BV value at that moment (78.2 +/- 3.4 versus 84.5 +/- 4.5%; p < 0.025) than in the other five patients at comparable times. It was concluded that this optical method was a means to detect hypovolemia at an early stage and to prevent ultrafiltration induced hypotension.


Microporous small diameter PVDF-TrFE vascular grafts fabricated by a spray phase inversion technique.

Microporous prostheses of 1.5 mm internal diameter were fabricated with a polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE)n co-polymer by the spray phase inversion technique. Some of the grafts were made piezoelectric by poling under a high electrical field. Overall, 24 poled grafts (P) and 24 unpoled grafts (UP) (15-22 mm in length) were implanted in the infrarenal aorta of 48 adult rats. Patency rates in P were 100% (8/8) at 2 days, 100% (8/8) at 2 weeks, 75% (6/8) at 6 months, and 92% total (22 of 24). Patency rates in UP were 100% (8/8) at 2 days, 63% (5/8) at 2 weeks, 100% (8/8) at 6 months, and 88% total (21 of 24). Thus there was no significant difference in patency between the two types of grafts. Both showed similar macroscopic and microscopic findings. At 2 days, fibrin deposition was somewhat heavier on the poled grafts, but no difference in surface platelet deposition could be detected. Endothelialization was observed from both anastomoses at 2 weeks and was almost complete at 6 months. The excellent biocompatibility of PVDF-TrFE and the microporous structure of the grafts were probably the dominant factors in success with these grafts. Although piezoelectric activity in excised cleaned poled prostheses remained significantly higher than that in the control UP, the charges developed may have been too small to exert a biologic effect, either because of insufficient dipole orientation or inadequate mechanical deformation.


Non-invasive determination of recirculation in the patient on dialysis.

Recirculation of blood flow occurs when the fistula flow rate is inadequate to support the desired dialyzer blood flow. The percentage recirculation is normally calculated using the blood urea nitrogen of blood samples from the two dialyzer blood lines and a peripheral blood sample. However, this method is time consuming, costly, and may not always give accurate measurements. A technique was developed to measure recirculation using the injection of saline into the venous dialysis line. For this technique, an optical detector is placed across the arterial dialysis tubing, and the light intensity, which is proportional to the hematocrit, is continually measured using a computerized data collection system. After a baseline data collection period, 10 ml of saline is injected into the venous dialysis line using the sampling port. The saline that appears in the arterial dialysis line as a result of recirculation will cause a dilution of the blood and an increase in light intensity. In vitro testing showed an excellent correlation between the area under the dilution curve and percentage recirculation. This technique will provide a quick, inexpensive, and reliable measurement of recirculation.


Optimal management of a ventricular assist system. Contribution of flow visualization studies.

The Novacor (Baxter Novacor, Oakland, CA) Left Ventricular Assist System (LVAS) incorporates a versatile microprocessor based controller that permits a variety of operating modes. These include internally triggered automatic synchronous counterpulsation, electrocardiogram triggered synchronous operation, and full to empty or fixed rate asynchronous operation. The aim of this pilot study was to determine the extent to which washing of the blood contacting surfaces of the pump may be optimized by suitable choice of operating mode. Visualization of flow fields adjacent to surfaces in confined areas requires small, neutrally buoyant tracer particles for feature extraction. A novel technique using fluorescent tracer particles (100 microns), an argon laser, and a low pass optical filter has been developed for this purpose. Particle motion was tracked from video images and calculations were made of velocity. Flow visualization was performed under conditions that simulated clinically observed hemodynamic conditions, typical of the immediate post-implant period. At a given LVAS output, fluid speed in the vicinity of the inflow valve tended to increase at higher LVAS beat rates (and consequently lower LVAS stroke volumes). This and future work may well be useful in selecting the optimum modes of LVAS operation as a function of the hemodynamic status of the patient.


Effect of stationary guiding vanes on improvement of the washout behind the rotor in centrifugal blood pumps.

In centrifugal pumps, there always exists an area of stagnation between the rear of the rotor and the rear housing wall that promotes thrombus formation around the axle. Some current devices overcome the problem by using holes in the rotor plane, leading to increased hydrodynamic losses and shear stress. In this study, a simple apparatus was developed to overcome this problem. Guiding vanes were fixed to the rear housing wall. These vanes decrease the tangential velocity of the fluid and thus the centrifugal force, leading to an increased secondary flow toward the axle. The effect of such vanes was studied in videographic and ultrasound studies. An increase of washout and mixing between the flow layers could be demonstrated (stay time < 200 msec versus several seconds without vanes). In the first animal experiment using nonoptimized vanes, there was no thrombus at the back plane or the seal, and only a small thrombus at the transition between axle and rotor. Hemolysis was slightly elevated (3.2 mg/dl versus 2.5 mg/dl in control experiments). In conclusion, it is highly likely that this simple system will improve the flow characteristics in centrifugal pumps.


In vitro performance of venous valve prostheses. An experimental model study.

The performance of fresh and glutaraldehyde fixed bovine jugular vein valves (10 mm diameter) was investigated in an experimental flow loop that provides adjustable flow rates and a downstream oscillatory pressure. Three different venous valve (VV) conduit geometries (curved [C], straight [S], and tapered [T]), were tested. The flow loop consisted of two independently adjustable components, with the mean flow generated by adjusting the elevation difference between the head tank and outflow chamber. An adjustable sinusoidal pressure pulse was superimposed on the downstream of a VV to mimic the respiratory effects. Flow visualizations were made using 100 microns mica chip tracers in the laser illuminated flow fields. To assess VV performance under various flow conditions, the closure opening (CO), partial opening (PO), and leaflet fluttering (LF) were evaluated. At a given pulse pressure, the three conduits required different flow rates to reach CO mode. At 12 cm H2O pulse pressure, the fresh valve in C-conduit exhibited stable CO operation at a flow rate of 1.01 ml/sec. That in S and T conduits required 1.67 ml/sec and 2.25 ml/sec, respectively. At higher flow rates, PO and LF performances were observed in all three conduits. Different threshold values of pulse pressure were needed to reestablish the CO operation mode for the C, S, and T conduits, individually. These observations provide some insight into the role of conduit geometry and sinus configuration in the function of VV.


A new, all silicone rubber small vessel prosthesis.

A new small vessel prosthesis composed entirely of silicone rubber was developed. The new prosthesis has a trilaminar wall structure consisting of: 1) a porous blood contacting layer designed to promote the deposition of a pseudoneointima (PNI) from blood flowing over the surface; 2) a solid middle layer the thickness of which is adjusted to provide approximately the same radial compliance as the host artery; and 3) a porous outer layer that promotes connective tissue attachment to the exterior of the prosthesis to limit tissue capsule formation around the implant and preserve its compliance after healing of the perigraft tissues. The new graft also has excellent suture retention in addition to its other desirable physical characteristics. The mechanical integrity of the textured surfaces was first evaluated in vitro with cyclic flexure testing at a 20-30% strain. Grafts of 4 mm inside diameter by 5 cm length were then implanted in the left carotid artery of adult dogs for an 8 week period. Seven animals were studied. Platelet inhibitors were administered postoperatively. The patency rate was 86% (six of seven); all grafts except the first remained widely patent. After the animals were killed, the grafts were surgically exposed, and compliance was measured directly. The PNI from the grafts was then studied with light and scanning electron microscopy, and morphometric measurements were made of PNI thickness over the length of the graft. Overall, the grafts retained 80% of their preimplant compliance (n = 5); however, in the absence of any postoperative complications such as hematoma or infection, the grafts remained essentially isocompliant with the host artery during the duration of this study.


A motor integrated regenerative pump as the actuator of an electrohydraulic totally implantable artificial heart.

The authors have developed a new actuator to drive an electrohydraulic totally implantable artificial heart. The basic concept of this artificial heart is that the blood pumps are implanted in the thorax and an actuator is placed separately in the abdominal region. The actuator is a regenerative pump that pumps fluids against high pressures and is thin enough for easy implantation. The rotor-magnet of the brushless DC motor is mounted on the impeller of the pump to miniaturize the actuator and reduce the number of moving parts. The height, diameter, and weight of the actuator are 32.5 mm, 73 mm, and 360 g, respectively. A pair of oil ports is connected to the left and right blood pumps with mesh reinforced tubes filled with silicone oil. The blood pumps are alternately driven by bidirectional rotation of the motor. Performance of the system was evaluated in in vitro and in vivo experiments. Maximum output of the right heart was 6.7 L/min in both experiments. Systemic circulation was well maintained in acute animal experiments using 49 and 50 kg goats. The feasibility of the actuator was confirmed.


Fabrication of a jellyfish valve for use in an artificial heart.

For a valve to be fabricated seamlessly into an artificial heart (AH) blood pump, a jellyfish valve has been developed, in which a thin membrane is fixed at the center of a valve seat having several spokes to protect against prolapse of the membrane. The valve is superior in performances to a Björk-Shiley valve, and reveals good blood compatibility. The valve would be very useful not only for AH animal study, but for future clinical use in infants to adults. Several institutions are already trying the valve. In this paper, the fabrication of the jellyfish valve is introduced, and in vitro and in vivo results summarized. A computer aided design (CAD) system was developed to cut a male wax mold of the valve seat. The input parameters to the CAD are diameter, height, thickness of rim, number of spokes, width and thickness of spokes, etc. Jellyfish valves with diameters of 4 to 27 mm have already been fabricated for many types of AHs and assist pumps.


Fluid mechanics of left ventricular assist system outflow housings.

Using the Novacor (Baxter Novacor, Oakland, CA) Left Ventricular Assist System (LVAS) as a test bed, phasic flow patterns were analyzed for three outflow valve housing designs: 1) a triple sinus; 2) an axisymmetric concentric sinus (CS); and 3) a modified triple sinus (MS). The 21 mm Carpentier-Edwards trileaflet pericardial heart valve prosthesis was used for all experiments done on the three housing designs. The LVAS was actuated by a laboratory model of the Novacor LVAS control console, and it was connected to a mock flow loop with an adjustable afterload system to provide physiologic pressures and flows (Pao, 120/80 mmHg; pump output [PO], 2-6 L/min). Laser illuminated flow visualization techniques were used to investigate the phasic flow patterns of the housings, and the visualization derived velocity was verified by laser Doppler velocimetry at several selected points in the field. Formation of vortices behind the leaflets during the LVAS ejection phase was observed in each of the housing designs. They were well organized, and they circulated with the greatest strength in MS. These vortices tended to lie in a plane parallel to the main flow axis, with the rotational velocity increasing with the stroke volume of the LVAS. In the CS and the MS housings, a circumferential flow that provided good washing of this region was observed behind the stents.


Quantitation of right ventricular shape changes after left ventricular assist device implantation.

Complex effects of left (LV) and right ventricular (RV) interaction account for changes in RV function during LV assist device (LVAD) support. It has been hypothesized that changes in RV cross-sectional shape (RVS) may be a contributing factor in the development of RV dysfunction during LVAD support. To test the hypothesis that the RVS would become more circular as a result of septal shift during LVAD support, 13 patients were studied before and after LVAD implantation. The shape of the RV was quantified using a shape factor (SF) that was equal to (4 x pi x area)/P2, where P is the perimeter of RVS. The RV area and perimeter were measured from digitized images of the RV obtained by transesophageal echocardiography in patients before and after LVAD implantation. The group SF increased considerably after LVAD (SFpre = 0.78 +/- 0.12 versus SFpost = 0.88 +/- 0.07, p < 0.05). Patients were divided into three groups: 1) patients whose RV exhibited a low SF pre-LVAD that increased significantly, 2) those with a moderate SF pre-LVAD that increased slightly, and 3) those who had high pre-LVAD SF (< 0.90) that did not change. The decompression of the LV caused by LVAD implantation results in a shift of the septum from right to left, increasing SF. This increase is more pronounced in some patients. Quantitation of the degree of RV SF change may help predict the development of RV failure during LVAD support.


Implantation of a cardioverter-defibrillator after coronary artery bypass surgery.

The implantable cardioverter-defibrillator (ICD) has been used in conjunction with surgical coronary revascularization for prevention of postoperative malignant arrhythmias. However, there is no consensus regarding which patient should receive concomitant insertion of the ICD system in a one stage (patches and generator) or two stage (patches, and subsequent implantation of the generator) procedure. To assess differences in hospital course and outcome, the authors studied 8 survivors of sudden death syndrome and 17 patients with preoperative ventricular tachycardia refractory to conventional antiarrhythmic therapy who underwent coronary revascularization and prophylactic implantation of an ICD system in either one or two stages. Patients with advanced coronary disease, poor ventricular function, and silent ischemia received the ICD system in one stage. Those with good ventricular function and well defined coronary pathology received only patches concomitant with myocardial revascularization. Seventy-nine percent of the patients with patches needed subsequent implantation of the ICD generator, as determined by postoperative electrophysiologic studies. There were three postoperative deaths unrelated to arrhythmias. There was no difference between the groups regarding the number of ICD discharges. It was concluded that the prophylactic use of the ICD system is an important adjuvant in the treatment of postoperative malignant arrhythmias for patients undergoing myocardial revascularization. The insertion of the ICD, however, should be based on pathophysiologic considerations and postoperative electrophysiologic findings. This may result in important savings in terms of unnecessary cost and operative procedures.


A new RV-PA conduit with a natural valve made of bovine jugular vein.

A new RV-PA conduit with a natural valve was developed using bovine jugular vein. To maintain the natural, mechanical properties of the veins, a hydrophilic cross-linking reagent, a glycerol polyglycidyl ether polyepoxy compound (PC) was used. The treatment has already been proven in the field of vascular grafts to be able to reduce antigenicity, biodegradability, and degenerative changes such as calcification, to induce antithrombogenicity with hydrogenicity, and to improve affinity to host cells. Bovine jugular veins were cross-linked with the reagent and were implanted as a conduit into the RV-PA position in six dogs. The main PA was ligated after implantation. One animal died due to bleeding 2 days after implantation; the other animals were healthy and allowed to survive until they were sacrificed. The graft was very soft and as pliable as native tissue, and was as strong as a heart valve. Post-operative catheterization and angiography showed adequate function of the valve. Macroscopic and microscopic observations revealed the antithrombogenicity of the graft in this animal study. These results indicated that this newly developed biologic valved conduit has a high probability of overcoming many problems observed in existing RV-PA conduits.


Two-dimensional cell manipulation technology. An artificial neural circuit based on surface microphotoprocessing.

The precise regional control of cell adhesion and growth on a substrate may create two-dimensional tissue formation, as in a neural network. To prepare a neural circuit, micropositioning of neural cells and guidance of extending axons in a given region are required. In general, the adhesion of neural cells and their axonal extension are mediated by adhesive proteins found in the extracellular matrix. This paper describes a novel surface photoprocessing that enables the creation and guidance of regionally selective cell adhesion, leading to a neural network. The non-adherent region was created by chemical fixation of a photoreactive hydrophilic co-polymer of azidostyrene and N, N-dimethylacrylamide on a hydrophobic substrate. Ultraviolet irradiation with the use of a photomask placed on a substrate hydrophilically modified the irradiated regions, which was evident in ESCA and contact angle measurements. The addition of a collagen buffer solution resulted in collagen adsorption only on the non-irradiated hydrophobic portions. Seeded neuroblastoma cells adhered only on collagen-adsorbed pathways 130 microns in width. One day after seeding, nerve growth factor was added to the culture medium, resulting in cell differentiation from growth to axonal extension. The axons grew along the collagen-adsorbed pathways. Sooner or later, cells were interconnected with extended axons, which was clearly visible microscopically. Further culturing completed the honeycomb-like patterning, as designed. The surface processing developed here can manipulate fundamental cellular behavior, leading to two-dimensional patterned tissue, which may provide information on the morphogenesis of the neural network and neurotransmission.


A pathway for information transmission to the inner ear. Application to cochlear implants.

The use of cochlear implants as an aid to neurosensory deafness is becoming an established procedure. The transmission of a processed speech signal is accomplished either transcutaneously via radiofrequency or percutaneously by connector coupling. Whereas the former is sensitive to electromagnetic interference, the latter increases the risk of infection. To overcome these disadvantages, an infrared (IR) system for transmission through the tympanic membrane was devised and tested. The transmitter/receiver consisted of an IR light emitting diode (LED; 920 nm) and a photovoltaic cell. The LED was placed inside the auditory canal of four dogs and the photovoltaic cell in the tympanic cavity over the cochlear promontory. A sinusoidal signal modulation was applied to the LED. The emitted signal was detected undistorted after crossing the tympanic membrane, with an average absorbance of 20%. High frequency cut-off was adequate for cochlear implant purposes and audio prosthetic devices in general. The authors conclude that the tympanic membrane may be used as a translucent sealed interface to transmit data in the audio range to the middle and inner ears, with small power loss, good frequency response, and immunity to interference.


The effect of prolonged left ventricular support on myocardial histopathology in patients with end-stage cardiomyopathy.

To determine the histopathologic effect of prolonged (> 30 days) left ventricular unloading on the myocardium, the authors studied myocardial tissue specimens from eight men (mean age, 40.8 years) with end-stage cardiomyopathy (six idiopathic, two ischemic) who were supported with the HeartMate (Thermo Cardiosystems, Inc., Woburn, MA) left ventricular assist device (LVAD) as a bridge to cardiac transplantation. The average length of support was 79.6 days (range, 31-136 days). Before left ventricular support was instituted, transthoracic echocardiography revealed that all patients had significantly dilated left ventricular cavities (average left ventricular diastolic dimension, 7.2 cm). Tissue specimens from the core of the left ventricular apex, which is removed at the time of LVAD implantation, were compared through pathologic examination with specimens from the explanted hearts at the time of cardiac transplantation. Apical core specimens from all patients exhibited extensive areas of attenuated myocardial fibers, combined with wavy patterns in some areas. In these regions, the nuclei of the cardiac myocytes from idiopathic cardiomyopathy specimens were neither pyknotic nor disappearing, as was noted in an infarcted area of a specimen from one patient with ischemic cardiomyopathy. At the time of heart transplantation, myocardial tissue specimens from the explanted hearts had a significant decrease or disappearance of stretched fibers. There was also a slight increase in interstitial replacement fibrosis, as well as an increase in the diameter of the myocardial fibers. These findings appear to correlate with the clinical impression of improved native ventricular function and with radiographic findings and decreased chamber size during prolonged ventricular support.


Prophylactic implantable defibrillator patches in patients at high risk for malignant ventricular dysrhythmias.

The indications for prophylactically placing implantable cardioverter defibrillator (ICD) patches at cardiac surgery are unclear. Over the past 4 years, 25 patients have undergone placement of prophylactic ICD patches at the authors' institution. Indications were severe coronary artery disease with ventricular tachycardia (VT) (n = 14) or ventricular fibrillation (VF) (n = 2), and left ventricular aneurysmectomy and/or subendocardial resection (SER) (n = 9). Four patients died in-hospital, three from refractory VT (which could be transthoracically cardioverted until recurrence was unremitting), and one from congestive heart failure (CHF). All of the remaining 21 patients underwent post-operative electrophysiologic studies (EPS), and 12 had inducible VT (8/14 CABG, 4/7 SER). Eight of the 12 inducible patients had generators implanted, whereas 3 patients were controlled medically. One patient refused generator implantation and died at home from sudden cardiac death, and one initially non-inducible patient required late ICD generator placement, yielding a total of nine patients who received generators. All nine of these patients are currently alive at 14 +/- 7 months follow-up, and five have subsequently received appropriate ICD discharges. In patients undergoing cardiac surgery considered preoperatively or intraoperatively to be at increased risk for VT/VF and too unstable for preoperative EPS, prophylactic ICD patches should be considered.


Selective feedback control of spastic musculature in a canine model.

Muscular spasm, the etiology of which remains elusive, has been difficult to control. The authors, therefore, proposed selective restraint of forced contractions by a closed-loop circuit. In four dogs, the strap (n = 6) and thyroarytenoid (n = 4) muscles were submitted to tetanic contractions via bipolar supramaximal stimulation (30 Hz, 6 mA, 0.5 msec) of ansa hypoglossi and recurrent laryngeal nerves, respectively. Subsequent reduction of distance between two sonomicrometer crystals embedded into muscle was used in lieu of "spastic information" for a stimulator to deliver blocking signals through tripolar electrodes passed downstream. By modifying frequency (30-110 Hz) and current (60-95%) distribution between the central cathode and the peripheral anodes, significant relaxation (up to 100%) was recorded within "blocking windows," varying with each nerve (3-18 mA sweeps). The selective restraint of unwanted contractions, leaving "normal" subthreshold tone undisturbed, may offer a more mature approach to spastic disorders than destructive procedures, such as nerve section and its chemical counterpart, botulinum toxin injection.


Preparation of an RGD ALB conjugate. In vitro analysis of cellular responses.

RGD (Arg-Gly-Asp) tripeptide was identified as the minimal active core peptide sequence common to adhesive proteins. In this paper, the authors report preparation of RGD containing peptide albumin conjugate (RGD ALB), and its effects on cellular adhesive function in vitro. RGD ALB was prepared via a coupling reaction of albumin with pentapeptide (GRGDS; Gly-RGD-Ser) by water soluble carbodiimide. Bovine endothelial cells (ECs) adhered to and spread well on a surface coated with RGD ALB, whereas few ECs adhered on surfaces coated with GRGESP-albumin conjugate (GRGESP peptide with little cell attachment activity; false control) and albumin. Cellular behavior, such as adhesion, spreading, growth, and migration, on surfaces coated with GRD-ALB, fibronectin (FN), and vitronectin (VN) were quantitatively examined. Adherent cell number on RGD ALB coated surfaces was larger than on those coated with FN and VN. Cell morphology on RGD ALB coated surfaces was similar to that on FN coated surfaces. The cell growth and migration activities on RGD ALB coated surfaces were almost equal to those coated with FN and VN. Thus, RGD ALB was found to promote cell adhesion, migration, and growth as effectively as fibronectin. This indicates that an artificial adhesive protein, simply derived with bioactive peptidyl ligand, can find versatile applications in fields in which cellular events play a critical role--for example, extracellular matrices and wound healing promotion aids.


Patients on hemodialysis rely on nephrologists and dialysis units for maintenance health care.

The extent to which hemodialysis patients rely on nephrologists for primary medical care is unknown. The authors surveyed 74 in-center hemodialysis patients to obtain demographic data and information about primary medical care and subspecialty referrals and follow-up. Health care maintenance was also assessed. All patients were dialyzed in a free-standing university affiliated dialysis unit. The mean age of the patients was 55 +/- 17 years; most were women (43/74) and on hemodialysis more than 3 years (48/74). Most of the patients did not have a family physician and relied on the nephrologist for health maintenance care (80%) and the treatment of minor acute illnesses (91%). The most common non-renal chronic illnesses were gastrointestinal disease (32%), heart disease (26%), and diabetes (26%). Although referrals to subspecialists occurred in 55% of patients during the preceding year, nephrologists usually provided ongoing management care (gastrointestinal disease 21/24, heart disease 10/19, diabetes 12/19). Over half the women had a Papanicolaou's test within 3 years and 72% had a routine mammogram that, in most cases, had been ordered by the nurse practitioner or nephrologist. Because nephrologists provide primary medical care to the majority of dialysis patients, preventive health care protocols, such as mammography and cancer screening, should be incorporated into the nephrology practice in chronic dialysis units.


Inadequate dialysis increases gross mortality rate.

The authors correlated the dialysis parameters of 613 patients on hemodialysis with their morbidity and mortality. Dialysis prescription (Kt/V) was calculated according to the dialyzer, blood flow, and dialysis time. Dialysis delivered was calculated using percentage urea reduction (PUR). Eighty patients who underwent dialysis in three units had only predialysis blood urea nitrogen (BUN) values available. Mean predialysis BUN was between 58 +/- 16 and 83 +/- 17 mg/dl. Patients with predialysis BUN > 100 mg/dl ranged from 0-22%, and those with predialysis BUN < 50 mg/dl ranged from 0-41%. Kt/V prescribed was between 0.45 and 1.75. Mean dialysis time was 191 +/- 28 min, and blood flow was 327 +/- 48 ml/min. Delivered dialysis was 78% of that prescribed. Patients who had a prescribed or delivered Kt/V < 0.8 varied from 0-44.8%. Mortality rate per year was between 11.3% and 54%. The authors attributed elevated BUN to increased protein intake or inadequate dialysis. Low BUNs may have been due to residual renal function or malnutrition. None of the dialysis parameters correlated with mortality rate except for a Kt/V < 0.8 (p < 0.001) that was directly related to mortality rate. Inadequate dialysis increases mortality rate.


Development of an axial flow blood pump LVAS.

Nimbus, Inc., (Rancho Cordova, CA) and the University of Pittsburgh (Pittsburgh, PA) are collaborating to develop an implantable rotary blood pump that can be used as a left ventricular assist system (LVAS). The short-term goal of this project is to show that an LVAS based on this pump can operate safely and reliably during chronic implantations in animals. Work conducted to date includes in vitro testing of hydraulic performance, hemolysis, endurance demonstration, and flow visualization. Results indicate that the pump is capable of generating an output of up to 10 L/min at physiologic pressures. Associated electrical power to drive these pumps is in the range of 6-10 watts. One integrated pump was placed in a mock flow loop and operated continuously at a fixed speed (10,000 rpm), pressure (100 mmHg), and flow rate (6 L/min) for 90 days with no apparent difficulty. In vitro hemolysis test results have consistently ranged between 3-6 g of liberated hemoglobin/day, which is an acceptable range for chronic use. Two in vivo trials of 7 and 14 days were performed using calves, after which tests have been done using sheep as the animal model. Five short-term sheep experiments have been conducted with good results. Future studies will include implantations in sheep of 3 months duration.


Relationship between dialysis induced hypotension and adenosine released by ischemic tissue.

Two types of dialysis induced hypotension apparently exist. One type presents as gradually decreasing blood pressure with eventual symptoms (gradual hypotension), whereas the other presents as abruptly and sharply decreasing blood pressure, along with symptoms (abrupt hypotension). In the current study, the authors found that the plasma hypoxanthine concentration during abrupt hypotension was significantly higher than before the hypotension occurred (20 min after saline was administered or at the beginning of dialysis), whereas comparison of the plasma hypoxanthine concentration during gradual hypotension and that before the hypotension occurred (20 min after saline was administered or at the beginning of dialysis) revealed no significant difference. The current results indicate that abnormally increased adenosine triphosphate (ATP) degradation associated with tissue ischemia occurred during abrupt hypotension but not during gradual hypotension. It can be speculated that the increased release of adenosine due to abnormally increased ATP degradation caused the abrupt hypotension. This conclusion seems reasonable given that adenosine directly decreases small vessel tone and inhibits prejunctional release of norepinephrine.


Baylor multipurpose circulatory support system for short- to long-term use.

A multipurpose circulatory support system has been developed as both a temporary and permanent device in total artificial hearts (TAHs) and ventricular assist devices (VADs). The multipurpose concept was derived from the development of a totally implantable electromechanical, one-piece TAH. The blood pump is pneumatically driven in short-term use and is electromechanically driven in long-term or permanent use. Both TAH and VAD versions consist of the same components, except for the actuation mechanism. The common components are a compact pumping chamber with the same configuration, a blood contacting surface biolized with gelatin, a pusher-plate, a Hexsyn rubber diaphragm (University of Akron, Akron, OH) and bovine pericardial valves. Both TAHs and VADs have 63 ml of stroke volume, and the VADs are compact compared with other available investigational device exemption devices. Currently, 1 week survival has been achieved using the electromechanical TAH and 2 week survival using the electromechanimcal VAD without anticoagulation. Results suggest that the currently developed system could be applied in varied patients as a temporary device after cardiotomy, a long-term device for bridge to transplantation, or a permanent device for end-stage heart disease.


Effect of coexistent diseases on survival of patients undergoing dialysis.

A cohort retrospective study was used to analyze the effect of comorbidity on survival of end-stage renal disease (ESRD) patients undergoing dialysis. The authors analyzed the survival of 255 patients (144 men, 111 women; median age 54 years; range 8-81 years) followed at the District Hemodialysis Unit in Foggia, Italy, over a 15 year period (median follow-up 30 months; range 1-190 months). Two subscales assessing the overall severity of the identified coexistent diseases and overall physical impairment, and a composite four level index of coexistent diseases (ICED) were assembled using information recorded at the time of admission. The Cox proportional hazard model was applied to evaluate the association of various patient characteristics with the probability of death. Mortality risk was associated with patient age (RR = 3.4 for patients aged 42-61; RR = 4.8 for patients older than age 61 compared with patients younger than age 42), initial condition leading to renal failure (RR = 3.1 for diabetes compared with primary renal disease) and ICED (RR = 3.0 for patients with uncontrolled coexistent disease or severe impairment compared with patients with no coexistent disease and no or mild impairment). Gender and type of dialysis were not associated with mortality risk. It was concluded that, as is the case with other chronic conditions, co-morbidity is a powerful independent prognostic factor in determining the mortality of ESRD patients.


Prolonged extracorporeal circulation without heparin. Evaluation of the Medtronic Minimax oxygenator.

Bleeding remains the most common complication of prolonged extracorporeal life support (ECLS). This study evaluated the Medtronic Minimax (Annaheim, CA) microporous oxygenator with the Carmeda Bio Active (heparin bonded) Surface (Stockholm, Sweden) for use in prolonged neonatal ECLS. Eight adult sheep were maintained on venovenous extracorporeal circulation (ECC) for a period of 4 days without systemic heparin. After 4 days of venovenous ECC without anticoagulation, there was no evidence of significant bleeding, circuit thrombosis, or systemic embolism. Gas exchange, hydrodynamic performance, coagulation, and biocompatibility studies suggest that the Minimax is safe and reliable for short-term or long-term ECLS in neonates.


Electrohydraulic ventricular assist device development.

An electrohydraulic ventricular assist device has been developed. An axial flow pump driven by a brushless DC motor provides actuation. Energy is supplied by internal Ni/Cd batteries and by external Ag/Zn batteries, both rechargeable. Electromagnetic induction is used to pass energy through the skin with a transcutaneous energy transfer (TET) system. Physiologic control, battery management, motor commutation, and communication functions are performed by a surface mount internal controller. An infrared data link within the TET coils provides bidirectional communication between the external and internal controllers. A computer model was developed to predict system performance. The dimensions are 180 mm x 116 mm x 40 mm. An in vitro system pumped 5.7 L/min at 10 mmHg inflow and 100 mmHg outflow pressure. The internal battery can provide the projected energy requirements for 40 min after 540 charge/discharge cycles, and the external battery is capable of 4 hr of operation after 150 cycles. The TET system can deliver 60 W of power and exceeds 80% efficiency between 15 and 30 W. The device configuration is based on human cadaver and intraoperative fit trials. The device is being modified for calf implantation by redirecting the blood ports, increasing the output, and incorporating the internal controller in the unified device base.


Rate constants of embolization and quantitation of emboli from the hollow-fiber oxygenator and arterial filter during cardiopulmonary bypass.

A direct technique was developed to estimate parameters related to half life (T1/2) and rate constants of embolization (RCE) and to quantitate emboli of three sizes (small, medium, and large) shed from the oxygenator and arterial filter during cardiopulmonary bypass (CPB). Cardiopulmonary bypass was performed in 16 Yorkshire pigs divided as follows: systemic heparin group (SHG:6), systemic heparin/heparinized circuit group (SH/HCG:5), and Iloprost (Bentley) (2 ng/kg/min)/heparinized circuit group (IHCG:5) with In-111 labeled autologous platelets. The anesthetized pigs (20-25 kg) underwent CPB at 2.5-3.0 L/min for 3 hours. Pigs were injected with In-111 platelets (300-420 microCi) 24 hours before CPB. Cardiopulmonary bypass was instituted with a roller pump and hollow-fiber oxygenator, and thrombosis and embolization on the oxygenator and filter were monitored by a calibrated Geiger probe (WMB Johnson Associates, Montvale, NJ). The radioactivity in the oxygenator and filter reached peak values at 25-45 min after CPB; the radioactivity then declined in the oxygenator but remained at a steady state in the filter, suggesting continuous embolization at the same rate of trapping. The curve stripping technique of the normalized radioactivity time curve of the oxygenator was used for RCE estimation of different sized emboli shed from the oxygenator; 42% of thrombus embolized from the oxygenator in SHG with three rate constants, with T1/2s of 12 min, 42 min, and 13 hr; the SH/HCG embolized 35% with T1/2 of 78 min, and the IHCG embolized 30%, with a T1/2 of 22 min. This indicates that there is less embolization in the IHCG.(ABSTRACT TRUNCATED AT 250 WORDS)


Polyunsaturated fatty acids of the n-3 class in chronic dialysis.

N-3 PUFAs are believed to 1) reduce serum lipids, 2) modify the complement activating system, 3) increase red blood cell elasticity, and 4) decrease thrombotic events. These four parameters were investigated in 19 chronic stabilized dialysis patients assessed by 1) the control of the serum lipids, 2) the degree of leukopenia 10 minutes after the start of dialysis, 3) the degree of red cell fragmentation (RCF) during dialysis, and 4) the reusability of the dialyzer. The patients were their own controls during four periods: 1) no PUFAs for longer than 6 months, 2) 4 x 425 mg of PUFAs/day for 6 weeks, 3) 6 x 425 mg PUFAs/day for 6 weeks, and 4) no PUFAs during at least 6 weeks. Previous diets and medications remained unchanged. It was concluded that there was no significant effect on serum lipids in the given dosages, and no effect on the degree of leukopenia, red blood cell elasticity or bleeding, and/or antithrombotic activity. No change was seen in insulinemia, fibrinogenemia, or arterial pressure. No serious side effects were noted other than a "fishy aftertaste."


Respiratory dialysis. A new concept in pulmonary support.

Use of a new intravenous oxygenator made of hollow fiber membranes arranged around a centrally positioned balloon is reported. In vitro studies using fluorescent image tracking velocimetry and gas exchange analysis demonstrated enhanced convective mixing with balloon pulsations and augmented gas flux (100% increase in pO2) compared with the device in its static configuration. In vivo observations confirmed a greater than 50% increase in O2 flux with balloon activation. Those parameters that produce radial flow and convective mixing in vitro enhance gas flux in vivo, thus confirming the efforts to exceed the fluid limit translate into improved gas exchange.


Use of bone char as an adsorbent in preparation of water for dialysis.

Currently, deionizers (DI) and reverse osmosis (RO) are used to prepare water for dialysis. When water metal levels increase, for example, with the use of alum, the variation in metal content can reduce RO performance. Pretreatment of water with ethylenediaminetetraacetic acid or alkali can be used to reduce Al fouling. The authors examined adsorption of metal water contaminants with bone char (BRIMAC, Biolab, Oakville, Canada) as a cheaper alternative. Water treatment for the unit consists of a blend valve, 30 mu filter, 2 X 3 cu ft adsorption tanks, 5 mu filter, 30,000 grain automatic water softener, 5 mu filter, Millipore RO 1,000, 2 X 7" mixed bed DI in series, and a polysulfone ultrafilter. During 29 weeks of continuous bone char adsorption, raw water Al ranged from 0.022 to 0.298 ppm (mean, 0.097 +/- 0.075 ppm; cf. the Environmental Protection Agency's proposed drinking water standard of < 0.05 ppm). Postadsorption Al ranged from 0.002 to 0.076 ppm (0.041 +/- 0.04), a decrease of 55-91% (83.0 +/- 8.5%). Final water Al was < 0.001 at all times. No fouling of the RO membrane occurred. Residual chlorine after the first adsorption was < 0.02 to 0.09 ppm. Significant reductions in other metals, notably Pb, Cu, and Zn were noted. Bone char is a cheap, effective, and simple alternative for removing excess trace elements from water for hemodialysis. Further study to evaluate the efficacy of bone char in removing other organic and inorganic water contaminants is needed.


Skeletal muscle powered pumps can work under low preload. Design considerations.

Characteristics of a dual chambered, single layered skeletal muscle powered pump (DCSLP) and a single chamber, multilayered pump (SCMLP) made from similar masses of untrained latissimus dorsi muscle (LD) were compared. For the DCSLP, 16 canine LDs (51.5 +/- 1.6 g) were wrapped in a "figure eight" around two parallel mandrels, whereas for the SCMLP, LDs were made in 10 by wrapping the LD (54 +/- 8.5 g) twice around one mandrel. Chamber compliance and pump isovolumic peak developed pressure (PDP), stroke volume (SV), stroke work (SW), and ejection fraction (EF) of single contractions were measured. In six of the DCSLP dogs (LV), heart left ventricular stroke volume (LVSV) and left ventricular stroke work (LVSW) were determined. Stimulation parameters were the same for all. Student's t-test (* = p < 0.05) was used for statistical analysis. Dual chambered, single layered skeletal muscle powered pumps with a diastolic volume/mass ratio of 0.63 were more compliant than SCMLPs with a ratio of 0.37. Single chamber, multilayered pumps generated slightly higher PDP, but this was significant only at 60 mmHg preload. At a preload of 15 and an afterload of 120 mmHg, DCSLPs had higher SV (10.7 +/- 1.1 ml) and SW (0.98 +/- 0.14 x 10(6) ergs) than SCMLPs (6.8 +/- 0.7 ml* and 0.58 +/- 0.08 x 10(6) ergs*), or their LV counterparts (5.3 +/- 0.9 ml and 0.84 +/- 0.22 x 10(6) ergs).(ABSTRACT TRUNCATED AT 250 WORDS)


Development of a polyepoxy compound cross-linked heterologous connective tissue tube.

A heterologous connective tissue tube with "built-in" polyester mesh was developed using a rabbit subcutaneous tissue and polyepoxy compound cross-linking method. To evaluate the graft, 11 grafts were implanted end to end in the position of the thoracic aorta of 11 dogs and evaluated from 1 hr to 80 days after surgery. The graft was white and pliable, and the mesh was seen through the connective tissue. The handling characteristics were good, and no bleeding was observed from either the graft wall or suture holes. Macroscopically, at 1 hour, the luminal surface was covered with a thin thrombus layer. At 80 days, most of the inner surface of the explanted graft was white and shiny without irregularity, but a small area of blood stain was observed. Microscopically, fibroblasts were observed in the graft wall at 7 days; capillaries penetrating to the luminal surface appeared at 29 days. Bleeding was rarely observed around the fabric. A layer of donor connective tissue was still observed at 80 days. No foreign body reaction was observed except around the mesh. It was concluded that the graft healed well and could be an arterial substitute.


Clinical experience with heat sterilization for reprocessing dialyzers.

Use of heat sterilization for dialysis reprocessing offers significant advantages over chemical germicides. Polysulfone dialyzers (Fresenius 60M or 80M) can be sterilized by heating to 105 degrees C for 20 hr, thus permitting clinical trials of this method. One hundred eighty patients received 9,000 treatments. Pyrogenic reactions, sepsis, and subjective symptoms have not occurred. In vitro clearances (Qb 500 ml/min, Qd 800 ml/min) at baseline and after 2-8 uses did not differ (340 +/- 29 vs. 352 +/- 4 ml/min, respectively). KoA determined in vivo did not decrease (baseline 709 +/- 131 vs. 7th use 632 +/- 50 ml/min). Kt/V for urea was not different in 18 patients treated with heat sterilized dialyzers over 6 months when compared with a baseline period with formaldehyde sterilized dialyzers (1.37 +/- 0.12 vs. 1.32 +/- 0.11 at similar time and blood flows). Mean use number was 7.4 (dialyzers limited to 11 uses). Of discarded dialyzers, 44% failed a bedside integrity test (blood side pressurized at > 400 mmHg for 1 min), 36% failed automated fiber bundle or pressure holding tests, 8% had a blood leak, and 12% reached 11 uses. Clinical blood leaks occur in < 0.5% of treatments. Heat sterilization is a safe and effective method of dialysis reprocessing, but quality control of the process is essential. Based on initial clinical experience, heat sterilization of dialyzers for reuse is a promising alternative to chemical disinfection.


Development of an implantable centrifugal blood pump.

The efficacy of centrifugal pumps for short-term (0-30 days) ventricular support has been widely reported and favorably compared with pulsatile systems. A small, durable, implantable centrifugal blood pump is being developed for medium-term use (up to 6 months). The pump is based on the Medtronic Hemadyne system that has existed in multiple forms over the past 30 years. The pump is approximately the size of a tennis ball, weighs 240 g, and is comprised of a 2.5 cm plastic impeller driven by a radially coupled brushless DC motor. In vitro hydraulic performance was recorded over a wide range of flow conditions on a mock circulatory loop. The pump generated 7 L/min flow against an afterload of 100 mmHg pressure, with a maximum power draw of 10.4 watts. Pulsatile flow was preserved when placed in conjunction with a simulated left ventricle. In vivo testing was performed in 10 healthy sheep for 10-292 hr. Heparin was used to facilitate cannulation, and no anticoagulation was administered after pump implantation. Blood chemistries reflecting hematologic, pulmonary, renal, and hepatic functions were recorded and demonstrated no adverse effects with normal pump operation. Complications were related to kinking of blood conduits and thrombus formation within the cannulae. These results are encouraging and warrant further studies to prove feasibility of this pump as a medium-term implantable ventricular assist device.


Pulmonary function in a non-pulsatile pulmonary circulation.

The authors suggested that a mammal immediately accommodates well to nonpulsatile flow in the systemic circulation. In the current study, nonpulsatile pulmonary blood flow using a centrifugal pump was established in chronic models to analyze its influence on the pulmonary circulation. A pulsatile right ventricular assist device (RVAD) was implanted to draw blood from both the right atrium and ventricle and send blood to the pulmonary artery in six goats. After 2 weeks, the pulsatile pump was quickly replaced with a centrifugal pump without anesthesia, and a 100% non-pulsatile pulmonary blood flow was obtained. Cardiac output was kept at 80-120 ml/kg/min during the experiments. No changes were observed in hemodynamic parameters, including pulmonary arterial pressure, pulmonary vascular resistance index, and blood gas data, after the immediate depulsation of the pulmonary blood flow. There was also no significant change in the ventral to dorsal tissue blood flow ratio of the lower lobe of the right lung, which was calculated by a colored microsphere method, between pulsatile and non-pulsatile pulmonary blood perfusion. These results suggest that pulmonary function, including blood flow distribution, is not affected by non-pulsatile pulmonary circulation for periods up to 14 days.


Evaluation of a continuous thermodilution cardiac output catheter.

The authors evaluated a thermodilution catheter designed to continuously measure cardiac output (CO). A 10 cm long surface heating element is positioned in a Swan-Ganz catheter corresponding to a right atrial-ventricular site. Heat is repetitively deposited into flowing blood in a unique, pseudorandom binary form. Small temperature fluctuations are sensed with a high performance thermistor and correlated with the heat input pattern, from which CO is determined. Seven adult sheep were anesthetized and instrumented for both continuous and standard cold bolus injection thermodilution (COM1) flow measurements. Heart rate and blood volume were adjusted to vary CO from 1.5 to 13.2 L/min. Continuous measurements correlated well with triplicate COM1 determinations (Sy,x = 0.56, r = 0.967) that improved with experience (Sy,x = 0.38, r = 0.99 for the last three animals). The surface heat transfer coefficient was measured in water (catheter parallel to flow). Results agreed well with a standard cylinder-in-crossflow correlation. The right ventricle heating element surface temperature was predicted for several CO and heating combinations. Worst case results yielded a 5.8 degrees C surface temperature elevation, suggesting that thermally induced damage is unlikely. Results suggest this catheter provides accuracy at least comparable to that of standard cold bolus injection methods, with no heat induced damage to blood.


A new thermal shape memory Ti-Ni alloy stent covered with silicone.

An attempt was made to develop an airway stent for nonsurgical transluminal implantation using a bronchofiberscope. The stent is composed of a single wire with a diameter of 0.5 mm. The wire is made of thermal shape memory titanium nickel alloy, with a transition temperature of 25-30 degrees C. To avoid direct contact between the metal and the tissue, the wire is covered with a 300 microns thick coating of silicone. The stent is horseshoe shaped in cross-section. It is 15 mm in outer transverse diameter and 40 mm long. Ten stents were implanted in 10 dogs whose tracheal cartilages had been previously broken. The stents were first cooled in ice water to reduce their diameter and then inserted into the target site. The wire was warmed to body temperature and recovered its initial shape within 10 sec. The dogs were killed for examination between 1 week and 6 months after implantation. All the stents were located at the implantation sites and were patent. Tissue reactions, such as ulceration and granulation formation, were less severe than in those with previously implanted non-silicone covered stents. Microscopic observation showed that the wires became gradually covered with epithelium within 2 months. This transluminal technique for preserving airway patency shows promise for clinical application.


Estimation of urea and creatinine clearance in peritoneal dialysis.

The authors performed peritoneal equilibration tests (PET) in children and young adults of widely varying sizes to characterize membrane transport type, and used data (D/P ratios) obtained to predict clearances of urea (KT/Vurea) and creatinine (CrCl). Overall, PET predicted and measured values for KT/Vurea and CrCl were not significantly different. KT/Vurea could be reliably predicted from PET data for all membrane transport types. However, the relationship between predicted and measured CrCl was only significant for patients with high and high average membrane transport. In addition, the relationship between KT/Vurea and CrCl was significant only in patients with high and high average membrane transport.


Development of continuous recirculating peritoneal dialysis using a double lumen catheter.

Continuous recirculating peritoneal dialysis (CRPD) was newly introduced to improve solute removal efficiency in conventional dialysis therapies such as hemodialysis (HD) and continuous ambulatory peritoneal dialysis (CAPD). In CRPD, a part of the dialysate in the peritoneal cavity was drained through a double-lumen catheter and purified by an extracorporeal dialyzer. Urea removal characteristics in CRPD were examined in a canine study. In this study, a recirculation-dialysis experiment using a dog weighing 9.0 kg was carried out under 100 and 200 ml/min of flow for recirculating and delivered dialysates, respectively. An FB-50H (Nipro Medical Industries, Ltd., Osaka, Japan) composed of cellulose diacetate membrane with 0.5 m2 of surface area and Dianeal-1.5 (Baxter Limited Laboratories, Tokyo, Japan) containing urea were used as the extracorporeal dialyzer and dialysate. Urea peritoneal and dialyzer dialysances (DBP and DBD) were 3.05 and 33.3 ml/min by computer simulation using a compartment model for CRPD. This DBP value can be estimated as 20.3 ml/min for a 60 kg human. From this result, time-averaged value for BUN over an 8 hr/day CRPD, combined with three exchanges/day as CAPD is estimated to be 34.3 mg/dl, which is much lower than 45.2 mg/dl for a 12 hr/week HD, or 53.0 mg/dl for conventional CAPD.