Kinetics of swelling of polymers and their gels.

The swelling limit or equilibrium swelling of semicrystalline or cross-linked polymers and of their gels upon immersion in liquids has been investigated extensively. Few studies, however, have dealt with the kinetics of swelling. Theoretical considerations, based on diffusion-controlled swelling, show that first-order kinetics do not apply, even though deviations during the initial and even middle stages of the swelling process may be relatively small. Extensive studies of swelling rate and equilibrium swelling of supported and unsupported gelatin films have been published. Diffusion was always fast. After it was completed, the rate of swelling was controlled by stress relaxation in the amorphous portion of the polymer network. The rate equations for this process, which also apply to regenerated cellulose, are shown to represent second-order kinetics with respect to the remaining swelling capacity. The following interpretation for the applicability of second-order kinetics to the swelling of semicrystalline polymers, such as gelatin and cellulose, is given. The rate of swelling is assumed to be directly proportional to the percent swelling capacity still available at a given time and to the total internal specific boundary area enclosing those sites capable of swelling that have not yet become hydrated and swollen at that time. The latter, in turn, is also directly proportional to the percent unrealized swelling capacity.


Two-dimensional and deuterium-induced, differential-isotope-shift nuclear magnetic resonance characterization of potassium sucrose octasulfate and sucralfate.

Two-dimensional and deuterium-induced, differential-isotope-shift NMR measurements have made it possible to assign completely all of the 1H and 13C resonances of potassium sucrose octasulfate (K8SOS) and thereby prove complete sulfation of the sugar moiety during synthesis. In addition, a comparison of the 13C NMR chemical shifts obtained for K8SOS and sucralfate made it possible to demonstrate that the sugar moiety in sucralfate is sucrose octasulfate (SOS8-). Finally, deuterium-induced, differential-isotope-shift and 13C NMR techniques were shown to be useful tools for detecting and characterizing carbon-containing impurities and hydrolysis products in solutions containing SOS8-.


Improved high-performance liquid chromatographic determination of khellin and visnagin in Ammi visnaga fruits and pharmaceutical formulations.

An improved, simple, selective, and sensitive reversed-phase high-performance liquid chromatographic (HPLC) assay for khellin and visnagin in Ammi visnaga L. fruits was developed by using an internal standardized technique. The HPLC column was a reversed-phase microBondapack C18 column, the mobile phase was water: methanol:acetonitrile (49:49:2), and the flow rate was 1.5 mL/min. Khellin and visnagin were detected and analyzed with a spectrophotometer set at 250 nm. Results of the HPLC analysis indicate a relative standard deviation of less than 0.04%. The analytical procedure was used for the quantification of khellin in various pharmaceutical dosage forms, such as ampules, tablets, and suppositories, with relative standard deviations of 1.2, 1.4, and 1.7%, respectively. As little as 10 ng of khellin or visnagin could be detected accurately in less than 13 min.


Oxidative decarboxylation of naproxen.

The decarboxylation of naproxen (1H) and its salt (1-) was achieved by means of chemical [Ce(IV) or S2O8(2-)] and electrochemical oxidation. The product patterns were compatible with mechanisms involving single-electron transfer from the pi-system or the carboxylate moiety. The results are discussed in connection with the involvement of electron-transfer processes in the reported phototoxicity of naproxen.


Solubilization and dissolution properties of a leukotriene-D4 antagonist in micellar solutions.

7-[3-(4-Acetyl-3-hydroxy-2-propylphenoxy)propoxy]-3,4-dihydro-8- propyl-2H-1-benzopyran-2-propionic acid (1) is a leukotriene-D4 antagonist that is quite insoluble in aqueous media. Increased solubilization of 1 was achieved in micellar solutions of polysorbate 80, sodium glycocholate, sodium taurocholate, lysolecithin, and sodium taurocholate plus monoolein. The intrinsic dissolution rate of 1 was measured in the presence and absence of polysorbate 80 at pH 7.0, 8.0, and 10.0. In all the micellar solutions tested, the solubility of 1 was significantly increased. The intrinsic dissolution rate of this compound was also enhanced in micellar solutions of polysorbate 80 and with increasing values of pH. However, the magnitudes of the enhancement of the intrinsic dissolution rate were much less than expected from the enhancement of aqueous solubility.


Vanadium and copper in clinical solutions of albumin and their potential to damage protein structure.

Solutions of albumin, for injectable use in humans, are shown to contain the transition metals vanadium, copper, and iron. Variation in the concentration of these metal ions among products from six different manufacturers suggests that problems of metal contamination arise through manufacturing processes. Vanadium concentrations correlated with the loss of tryptophan residues in albumin, whereas copper concentrations correlated with loss of thiol groups and tryptophan residues. Incubation of vanadate and cupric salts with the thiol group-containing molecules cysteine and glutathione resulted in reduction of the metal ions to lower oxidation states. Reduced forms of vanadium and copper were able to transfer electrons to molecular oxygen and produce highly reactive and damaging intermediates of oxygen, such as the hydroxyl radical.


Use of fluorometry in assessing the efficacy of a cation-sensitive gel as an ophthalmic vehicle: comparison with scintigraphy.

Gelrite, a heteropolysaccharide that forms a gel in the presence of cations, was tested in humans for its efficacy as an ophthalmic vehicle by a nonivasive fluorometric technique. Fluorescein was used as the tracer, and its concentration in the anterior chamber was used as the principal measure of bioavailability. The gel afforded a twofold increase in penetration of fluorescein compared with an isotonic buffer solution; this increase is slightly more than can be obtained with simple viscous vehicles. The increase in penetration caused by Gelrite was confirmed by measurements of the contact time of fluorescein in the tear film with the cornea. Earlier experiments with scintigraphy suggested a considerably greater contact time of fluorescein with the cornea when Gelrite was used. However, this increased contact time may be because the technique also measures radioactive tracer that had dried out on the lid margins. Accordingly, significant quantities of fluorescein could be eluted from the lids after the penetration experiments were completed.


An antidepressant principle of Lobelia inflata L. (Campanulaceae).

A crude methanolic extract of the leaves of Lobelia inflata exhibited antidepressant activity in mice. The extract was fractionated, monitored by the activity, to give beta-amyrin palmitate as an active component.


Halogenated analogues of tamoxifen: synthesis, receptor assay, and inhibition of MCF7 cells.

This study was conducted to develop a ligand for imaging estrogen-receptor-positive breast tumors by positron emission tomography or single photon emission computed tomography. We synthesized fluoro and iodo analogues of tamoxifen, and these halogenated analogues produced greater affinity for binding to the receptor than tamoxifen. Values of the inhibition affinity constants were as follows: tamoxifen, 15,000 nM; fluoromethyl-N,N-diethyltamoxifen, 2500 nM for the cis isomer and 500 nM for the trans isomer; and iodomethyl-N,N-diethyltamoxifen, 1500 nM for the cis isomer and 1000 nM for the trans isomer. In studies of human MCF7 breast tumor cell growth, concentrations that inhibited tumor growth in 50% of the cases were as follows: tamoxifen, 11 microM; fluoromethyl-N,N-diethyltamoxifen, 4.5 and 11.8 microM for the cis and trans isomers, respectively; and iodomethyl-N,N-diethyltamoxifen, 2.4 and 6.3 microM for the cis and trans isomers, respectively. These studies suggest that both fluoro and iodo analogues of tamoxifen may be useful diagnostic compounds for predicting the response of estrogen-receptor-positive breast tumors to tamoxifen analogues used in chemotherapy.


Biological activity of urease formulated in poloxamer 407 after intraperitoneal injection in the rat.

The advent of genetic engineering has resulted in a proliferation of protein pharmaceuticals available for a variety of therapeutic needs. However, the formulation and delivery of these proteins remain an intriguing challenge. Polymer-based protein drug delivery systems continue to be investigated, although many of the fabrication techniques used to incorporate proteins into the polymer matrix or device result in irreversible inactivation (denaturation) of the proteins. A well-characterized model enzyme, urease, was formulated in 33% (w/w) poloxamer 407 (Pluronic F-127) vehicle and injected intraperitoneally (ip) into rats in an attempt to achieve both preservation of biological activity and sustained release of the protein. The resulting ammonia concentration in plasma-time profiles were compared with those for rats injected with an identical dose (27.6 units of activity per 200 g of body weight) of urease dissolved in pH 7 phosphate buffer. Neither a pH 7 phosphate buffer solution nor poloxamer 407 (33%, w/w) dissolved in pH 7 phosphate buffer, when injected ip into rats, resulted in elevated ammonia levels in plasma. The time to reach a maximum ammonia level in plasma was increased approximately threefold following the injection of the urease-poloxamer 407 formulation, compared with that in control rats administered an identical dose of urease in solution. In addition, hyperammonemia was extended almost threefold in treated rats compared with control rats, without untoward effects. However, prolonged hyperammonemia in animals receiving an ip injection of the urease-poloxamer 407 formulation may have potentially resulted from the reduced clearance of ammonia and ammonium ion in the proximal tubules of the rats.(ABSTRACT TRUNCATED AT 250 WORDS)


Studies of in vitro skin permeation and retention of a leukotriene antagonist from topical vehicles with a hairless guinea pig model.

A leukotriene antagonist [Ro 23-3544; 6-acetyl-7-[5-(4-acetyl-3-hydroxy-2-propylphenoxy)pentyloxy] -3,4-dihydro-2H-1-benzopyran-2-carboxylic acid; 1] was studied in vitro for its permeation through and retention in hairless guinea pig skin from various topical vehicles. Both the free acid and the sodium salt forms of the drug were used. The vehicles evaluated were polyethylene glycol 400, propylene glycol, dimethyl sulfoxide (DMSO), C12-C15 alcohol lactates, dimethyl isosorbide, butyrolactone, methylpyrrolidone, hexyl laurate, isopropyl myristate, and caprylic/capric triglyceride (Neobee M5). For the salt form of the drug, the highest permeability coefficient and retention were obtained from DMSO and methylpyrrolidone, respectively. For the acid form, however, the highest permeability coefficient and retention were obtained from hexyl laurate and DMSO, respectively. The highest permeation and retention values were not obtained from the same vehicle for either the salt or the acid form of the drug. This observation questions the validity of using permeation (flux) measurements to screen topical drugs and formulations. Although the precise reasons for this lack of correlation between permeation and retention are not known at this time, this study has shown that the solubility parameters of the drug and the vehicles used may play an important role. It seems logical to conduct skin retention studies rather than flux measurements in evaluating drug delivery from dermatological products.


Effect of iontophoresis on in vitro skin permeation of an analogue of growth hormone releasing factor in the hairless guinea pig model.

The shortened analogue of growth hormone releasing factor (GRF) Ro 23-7861 (1) has a molecular weight of 3929 daltons [equivalent to GRF (1-29)] and is more potent than the endogenous GRF (1-44). The in vitro hairless guinea pig model and vertical and horizontal diffusion cell assemblies were used to study the effect of iontophoresis on the permeability to skin of 1. The transport of 1 across the skin was studied by monitoring the rate of its appearance in the receiver compartment with a radioimmunoassay. No permeability of 1 was observed without iontophoresis, whereas with iontophoresis, the permeability of 1 was significant. For example, at a current density of 0.23 mA/cm2 and buffer concentration of 0.05 M, the flux of 1 was 56.8 +/- 8.21 ng/cm2.h. The flux of 1 was independent of the design of the permeation apparatus, the electrodes, the donor and receiver volumes, the type of current (constant or pulsed), and the frequency of the pulsed current. The flux of 1 increased curvilinearly with the increase in salt concentration of the buffer and linearly with the increase in current.


Effects of enzymatic inhibition and increased paracellular shunting on transport of vasopressin analogues in the rat.

The Ussing chamber technique was used as an oral absorption model for studies of the relative effects of the inhibition of enzymatic degradation and increased paracellular route on the transport of the poorly absorbed vasopressin analogues lysine vasopressin (LVP) and desmopressin (DDAVP). The rates of transport of LVP or DDAVP at 250 microM across ileum and colon segments were studied in the absence and in the presence of protease inhibitors (aprotinin and bestatin) and cytochalasin-B. During the different treatments, the rates of degradation of the peptides were also studied. Detectable amounts of LVP could only be measured on the serosal side of the intestinal segment in the presence of protease inhibitors or cytochalasin-B. The treatment with cytochalasin-B increased the rates of transport of both peptides severalfold, and the effect was reversible. We suggest that the Ussing chamber technique can be used to evaluate the reasons for low transport rates across intestinal membranes. The results also show that, apart from enzymatic degradation, the vasopressin analogues LVP and DDAVP have additional permeation problems; therefore, it may be necessary to increase the paracellular route to increase the absorption of these peptides.


Preparation of potential anti-inflammatory agents from dehydroabietic acid.

Methyl 16-nor-16-carboxydehydroabietate (22), 16-nor-16-carboxydehydroabietinol acetate (23), methyl 7-keto-16-nor-16-carboxydehydroabietate (29), 16-nor-16-carboxydehydroabietic acid (30), 16-nor-16-carboxydehydroabietinol (31), 7-keto-16-nor-16-carboxydehydroabietic acid (32), methyl 7-hydroxy-16-nor-16-carboxydehydroabietate (33), and 7-hydroxy-16-nor-16-carboxydehydroabietic acid (34) were prepared from dehydroabietic acid. Only 22 and 32 had weak anti-inflammatory activity.


Kinetics and mechanism of chlorine exchange between chloramine-T and secondary amines.

The kinetics and mechanisms of chlorine transfer from chloramine-T (CAT) to several amines are second order and independent of p-toluenesulfonamide concentration; thus, the reaction does not involve disproportionation of CAT to dichloramine-T. From the profile of pH versus rate, the following mechanisms were proposed: (1) reaction of the ionized species of CAT with the ionized amine (ionic mechanism) and (2) reaction of the un-ionized species of CAT with the un-ionized amine (nonionic mechanism). The second-order, pH-independent rate constants calculated for the ionic and nonionic mechanisms were 1.6 and 5 x 10(6) M-1 s-1, respectively. Although these two mechanisms are kinetically indistinguishable, the rate constant for the nonionic mechanism is of the same order of magnitude as those calculated for similar chlorination reactions involving nonionizable chloramines, such as N-chlorosuccinimide, N-chloroquinuclidine, and N-chloro-N-methylbenzenesulfonamide. The proposed mechanism for the chlorine exchange involves a molecule of water in a cyclic, six-membered transition state.


Structure-activity considerations in kinetics and mechanism of chlorine exchange between chloramine-T and secondary amines.

To study the mechanism of N-chlorination of secondary amines by chloramine-T, the kinetics of the reactions of some aromatic-substituted analogues of N-chlorobenzenesulfonamide with various secondary amines were determined. The importance of amine basicity and reactivity of the N-Cl bond of the N-chlorobenzenesulfonamide was also assessed. The results indicate that a mechanism involving the un-ionized species of both reactants (i.e., a molecular mechanism), rather than an ionic mechanism, is operating and that the reaction most likely proceeds via a six-membered-ring transition state that incorporates a water molecule.


Determination of a cephalosporin antibiotic, ceftibuten, in human plasma with column-switching high-performance liquid chromatography with ultraviolet detection.

A column-switching high-performance liquid chromatographic assay combined with a heart-cutting technique and UV detection (LC/LC/UV) was developed to determine ceftibuten, a new oral cephalosporin, in human plasma. Plasma samples were directly injected into the first chromatographic column for sample cleanup and extraction. Thereafter, a switching valve, located at the junction of the first cleanup column and the second analytical column, opened during a 4-6-min interval after injection to transfer the segment containing ceftibuten into the analytical column for quantitation. The method was used routinely in pharmacokinetic studies and has the advantages of simplicity, improved sensitivity, and selectivity. Concentrations of ceftibuten in plasma over a range of 0.1-20 micrograms/mL can be determined with high precision and reproducibility. A single, oral, 200-mg dose of ceftibuten in humans resulted in a maximum concentration of 9.79 micrograms/mL, an area under the plot of concentration of drug in plasma versus time (0-12 h) of 47.77 micrograms.h/mL, and a half-life of 3.2 h. These results document the utility of the LC/LC/UV method in clinical pharmacokinetic studies.


Novel approach to estimate quality of binary random powder mixtures: samples of constant volume. II: Applications of equation to optimize tableting conditions.

In a companion communication, an equation (eq 1) of the homogeneity of binary random mixtures, which applies to constituents differing in particle size and in bulk density, was derived. The present paper demonstrates the practical applications of this equation in optimizing tableting conditions with respect to a high dose uniformity. Tablets of 50:50 (w/w) mixtures of coarse sucrose and of fine microcrystalline cellulose (Avicel PH 101)-talc vehicle were produced on a single-punch machine. Without a spin feeder, the tablets showed variations in content uniformity that were significantly higher than those estimated from eq 1. Correlation analysis between the individual mass and the content of the constituents of the tablets revealed this difference to be due to nonuniformity of the die filling and not due to incomplete mixing. Accordingly, the use of a spin feeder allowed production of tablets with higher dose uniformity, which conformed well with the theoretical optimum predicted with eq 1. Further variation of the processing conditions cannot improve the quality (i.e., varying the tableting speed resulted in equal or in poorer uniformity of dose content).


Factors affecting iontophoretic mobility of metoprolol.

The effect of different factors on the iontophoretic transport of metoprolol was analyzed. In vitro experiments were first performed in a diffusion cell with a cellophane membrane. Comparison of different pH, buffers, and ionic strengths in the donor compartment showed that higher iontophoretic transport was obtained with phthalate buffer (0.01 M) at pH 3. When the current density increased, the flux of metoprolol also increased. A decrease in drug concentration or an increase in viscosity slowed down the iontophoretic transport of metoprolol. The fluxes of metoprolol through hairless rat skin were strongly enhanced compared with passive diffusion. Direct current seemed to be more efficient than pulse current. When the on:off ratio of the pulse current was reduced, the flux also decreased.


A kinetic and mechanistic study of the hydrolysis of camptothecin and some analogues.

Quantitative rate and equilibrium constants for the hydrolysis of the lactone (ring E) in camptothecin (1) and analogues (2-5, all substituted in the A ring of 1) at 25 degrees C in aqueous solution were determined by high-performance liquid chromatography with UV-visible detection and by UV-visible spectrophotometry. It was shown that the lactone was converted to the carboxylate in a pH-dependent equilibrium. No major differences were observed in rate and equilibrium constants for 1-5, a result suggesting that the mechanism of lactone hydrolysis is independent of a variety of substituents on the A ring. The conversion of the lactone to its carboxylate form occurred under neutral and basic conditions and appeared to be largely dependent on hydroxide ion. The conversion of the carboxylate to the lactone was observed under neutral and acidic conditions and was pH independent at pH values greater than 5 and dependent on hydronium ion at pH values less than 5. Significant incorporation of oxygen-18 into the lactone ring of 3, a water-soluble analogue of 1, was observed for the ring opening and subsequent ring closing of 3 in H2(18)O. This finding strongly suggests that the mechanism of lactone ring hydrolysis involved acyl cleavage rather than alkyl cleavage. Kinetic solvent isotope effects (kH2O/kD2O, where kH2O and kD2O are the rate constants in H2O and D2O, respectively), obtained over the pH-rate profile for 1, were used to speculate about the nature of the transition states involved in the opening and closing reactions of the lactone ring.


Improvements in solubility and stability of thalidomide upon complexation with hydroxypropyl-beta-cyclodextrin.

Thalidomide is in clinical use for the treatment of graft-versus-host disease in leukemia patients after bone marrow transplant. Low levels of the drug in plasma after oral administration have made an intravenous thalidomide formulation desirable. Thalidomide, however, is sparingly soluble in aqueous solution (50 micrograms/mL) and unstable. Complexation with hydroxypropyl-beta-cyclodextrin has significantly improved the aqueous solubility and stability of thalidomide. Results obtained with HPLC and 1H NMR spectrometry have demonstrated that the solubility is increased to 1.7 mg/mL and the half-life of a diluted solution is extended from 2.1 to 4.1 h. Hence, an intravenous thalidomide-hydroxypropyl- beta-cyclodextrin solution has the potential to significantly improve current therapy for graft-versus-host disease by providing sustained high levels of drug in the plasma.


A high-performance liquid chromatographic assay for dideoxyinosine in monkey plasma and urine.

A simple, reliable, reproducible, rapid, and sensitive method for high-performance liquid chromatographic assay of dideoxyinosine (DDI) in macaque plasma and urine is described. The method is capable of detecting 25 ng of DDI on-column.


Qualitative analysis of the stability of the oxazine ring of various benzoxazine and pyridooxazine derivatives with proton nuclear magnetic resonance spectroscopy.

A series of 3,4-dihydro-1,3-benzoxazine and 3,4-dihydro-1,3-pyridooxazine derivatives was synthesized, and the hydrolysis of the derivatives was studied with proton nuclear magnetic resonance spectroscopy. The oxazine derivatives underwent various degrees of hydrolysis when H2O was added to dimethyl sulfoxide solutions of the compounds. The rates and extents of decomposition of the oxazine ring systems depended on the electronic effects of substituents within the molecules. Examination of the proton nuclear magnetic resonance spectra that were generated during decomposition of the oxazines and trends in stability of the oxazine derivatives suggest the formation of an intermediate in the hydrolysis mechanism.


Protection against chronic gastric ulceration in the rat with sulfhydryl-containing agents.

Reserpine (intraperitoneal, 5 mg/kg every day for 5 days) produced chronic ulceration of the rat stomach 2 weeks postdose. Gavage with 1% DL-cysteine or DL-methionine-S-methylsulfonium chloride at 1 mL/day for 2 weeks and 5 days protected against ulceration in 30% of the rats, and this protection extended to 80% of cases with 2% solutions. Similar gavage with 5% solutions protected all rats against ulceration without significantly influencing the basal H+ output [13.1 +/- 0.3 and 14.2 +/- 0.2 mumol for DL-cysteine and DL-methionine-S-methylsulfonium chloride, respectively, versus 15.1 +/- 0.4 mumol (mean +/- standard error of the mean; n = 10)]; that is, cytoprotection was achieved.


Predicting the postconsolidation relaxation behavior of sodium chloride tablets.

A model that relates the interparticulate contact stress within a tablet matrix with the compaction stress has been developed. The model permits the application of nonlinear deformation kinetic analysis to quantification of the viscoelastic behavior of tablet constituents. Deformation kinetic analysis assumes that stress relaxation is controlled by thermally activated processes similar in character to those associated with chemical reaction kinetics. The model was tested by measuring the stress relaxation of sodium chloride compacts as a function of temperature and relative density. The experimental activation parameters agree with literature values within experimental errors.


Alkaline hydrolysis of oligomers of tartrate esters: effect of a neighboring carboxyl on the reactivity of ester groups.

The importance and the effect of neighboring groups on the hydrolysis of polymeric esters were demonstrated. Several oligomers of poly(butylene tartrate) were synthesized, and their kinetic behavior was studied under alkaline conditions. The oligomers and their degradation products were monitored by HPLC and identified by fast atom bombardment mass spectrometry. The rates of hydrolysis measured at pH 5-8 and at 75 degrees C indicate that the degradation of the oligomers obeyed pseudo-first-order kinetics. The rate of hydrolysis among the homologous series of oligomers increased as the molecular weight increased. However, the increase in hydrolysis rate was not proportional to the number of ester linkages in the oligomers. This deviation was explained on the basis of electrostatic repulsion of the neighboring carboxylate group toward the hydroxide ion. The calculations revealed that the electrostatic effect was so great that the ester linkage adjacent to the carboxylate anion did not contribute to the overall rate of hydrolysis. The technique presented here can be extended to any multifunctional-group compound that has repeat units and can undergo a specific reaction that can be accurately measured.


High-performance frontal analysis-high-performance liquid chromatographic system for stereoselective determination of unbound ketoprofen enantiomers in plasma after direct sample injection.

An on-line, high-performance frontal analysis (HPFA)-high-performance liquid chromatographic system was developed for the enantioselective determination of a low level of unbound ketoprofen (KP) that is in equilibrium with KP that is bound to protein. The system consists of three subsystems (HPFA system, preconcentration system, and chiral separation system) connected in series in the stated order via column-switching valves. When either a 300-microL portion of buffer solution containing 300 or 550 microM human serum albumin and 100 or 300 microM racemic KP or a 300-microL portion of human plasma containing 12.5-100 microM racemic KP was directly injected onto the HPFA column with the mobile phase at a low flow rate, KP was separated from proteins and eluted as a zonal peak with a plateau. The KP concentration in the eluant of the plateau region was the same as the unbound-KP concentration that was in equilibrium with protein-bound KP in the initial sample solution. A 1-mL portion of the eluant of the plateau region was switched to the preconcentration system, where KP was adsorbed and condensed on an octadecylsilyl silica (ODS) column. The adsorbed KP was eluted out of the ODS column and transferred to the chiral separation system, via another switching valve, where the enantiomers of unbound KP were separated and determined. The results agree well with those obtained by the conventional ultrafiltration method.(ABSTRACT TRUNCATED AT 250 WORDS)


Carbonic anhydrase inhibitors. V: Pyrylium salts in the synthesis of isozyme-specific inhibitors.

Syntheses and physicochemical properties of 2,4,6-tri-, 2,3,4,6-tetra-, or 2,3,4,5,6-pentasubstituted 1-(2-sulfonamido-1,3,4-thiadiazol-5-yl)pyridinium perchlorates are presented. The new compounds, putative inhibitors of membrane-bound carbonic anhydrase, were tested for inhibitory action on the bovine red cell enzyme.


Partition behavior of anilines in bulk-phase and high-performance liquid chromatographic systems: influence on correlation with biological constants.

The partition behavior of a mixed series of ring-substituted anilines in reversed-phase high-performance liquid chromatographic systems is substantially different from that observed in a classical bulk-phase partition system with n-heptane as the aprotic reference solvent. On the basis of the equivalence of each ring substituent in the p-straight-chain methylene groups (v value) as a function of the fraction of organic solvent (acetonitrile or methanol) in the mobile phase, the biased partition behavior for imperfect homologues and heterologues is verified relative to that of perfect homologues. This behavior was tentatively attributed, mainly, to differences in the hydrogen bonding capacity of the compounds, which is associated with the electronic character of the working solvent. These differences cannot be normalized through the use of extrapolated initial partition coefficient (K'o) values because of carryover effects of the solvent. When the chromatographic partition constants (K') and K'o are used, correlations with previously determined intestinal absorption rate constants are definitely worse than the correlations with the reference n-heptane partition coefficients. Possible implications of these observations on lipophilicity-biological activity correlations are briefly discussed.


Basic cholane derivatives. XI: Comparison between acid and basic derivatives.

A series of hydroxycholan-24-amines was synthesized; the carboxyl group of starting unconjugated bile acids was transformed into a basic moiety [-NH2, -NHCH3, -N(CH3)2, or -NHCH2C6H5] at C-24. Solubilities, acidities, partition coefficients, and critical micellar concentrations were measured and compared with those of the corresponding bile acids. Because the steroid nucleus in the amines is the same as that in the bile acids, most of the physical-chemical properties of the two compound classes were similar. The amines were more soluble than the corresponding acids; solubilities depended mainly on the number of steroid hydroxyls and, to a lesser extent, on the side chain. Amines are strong bases in water, whereas unconjugated bile acids can be classified as weak acids. N-Benzylamino derivatives have higher log P (P is partition coefficient) values, as a consequence of the bulky hydrophobic substituent; the log P values were almost the same for the amines and the bile acids and depended on the steroid hydroxyls. Amines can self-aggregate at an acidic pH and form cationic micelles; the critical micellar concentrations of amines were of the same order of magnitude as those of bile acids. The introduction of a basic function in the side chain of the cholane moiety increased the antimicrobial activity toward most gram-positive strains.


Peptide stability in drug development: a comparison of peptide reactivity in different biological media.

Degradation kinetics for several peptides that bind to the major histocompatibility complex on antigen-presenting cells were determined in both human serum (HS; 25%) and synovial fluid (SF; 25%) from patients with rheumatoid arthritis to test whether therapeutic intervention of rheumatoid arthritis by direct intrasynovial injection is feasible (at least in terms of peptide stability). Controls consisted of enzymatically immature 10% fetal calf serum and peptidase-rich 5% liver homogenate (all diluted with RPMI-1040 tissue culture medium). Peptide half-lives ranged from approximately 4 to greater than 10,000 min, with most peptides showing half-lives of approximately 10-100 min. These studies show that, even though the populations of inflammatory and other cell types in SF and HS are different (and may, therefore, generate different peptidase profiles), the observed peptide stabilities in SF and HS are similar. This finding indicates that the effect of SF on peptide stability is similar to that of HS.


Drug and vehicle deposition from topical applications: use of in vitro mass balance technique with minoxidil solutions.

The disposition of minoxidil and propylene glycol from topical solutions was measured by using an in vitro mass balance technique. The experimental approach included assessment of the following compartments of the skin and the diffusion cell as a function of time: (1) donor compartment; (2) hairless mouse skin surface, epidermis, and dermis; and (3) receiver compartment. Excellent mass balance was achieved for minoxidil at three doses. However, the recovery of propylene glycol depended on both application volume and time. The experiment involving the evaporation of propylene glycol and water from the propylene glycol:ethanol:water (20:60:20, v/v) mixture, which was placed in the well of a tissue culture plate at room temperature and 37 degrees C, substantiated the loss of vehicles to the air. When a thin application of 20 microL/cm2 was used, 60% of the propylene glycol was unaccounted for after 16 h. The evaporation of propylene glycol concentrated the solution to supersaturation, precipitated out the drug, and then stabilized the thermodynamic activity of the drug in the vehicle. The amount of formulation applied influences the rate of concentration and, thus, the time at which minoxidil precipitates. The precipitation limits the amount of minoxidil that can be absorbed and leads to poor percutaneous absorption of drug from the formulation.


In vitro percutaneous absorption of thiamine disulfide from a mixture of propylene glycol and fatty acid.

The in vitro percutaneous transport of thiamine disulfide (TDS), an oxidized dimer of thiamine, from propylene glycol through excised abdominal rat skin was studied. The application of saturated, long-chain fatty acids [stearic acid (18:0), myristic acid (14:0), and lauric acid (12:0)] as enhancers to the system was also studied. TDS permeated through rat skin from propylene glycol with a flux of 2.5 +/- 0.8 micrograms/cm2/min. The flux was enhanced 31 times by 12:0 and 1.4 times by 14:0 and was suppressed to 80% of its original value by 18:0. The absorption of TDS could not be explained by TDS permeating across a dialysis membrane, but the interaction between TDS and fatty acids may influence the system. The results show the possibility of developing a transdermal thiamine delivery system.


Stereoselective urinary pharmacokinetics of dl-threo-methylphenidate and its major metabolite in humans.

Stereoselective urinary pharmacokinetics of dl-threo-methylphenidate (MPH) and its major metabolite, dl-ritalinic acid (RA), were examined in a cohort of healthy subjects. On two occasions, separated by one week, each subject received MPH.HCl either intravenously (10 mg) or orally (40 mg). Urine was collected in six time segments, up to 16 h after each dosing. In the first 2 h after oral administration of MPH, d-MPH found in the urine was 10-fold greater than the l-antipode, whereas there was no significant difference between the amounts of MPH enantiomers excreted after the intravenous dose. Examination of RA content in the 0-2-h urine samples after oral administration of MPH indicated the presence of higher levels of l-RA (d-RA:l-RA, 0.37), whereas after intravenous MPH, there was no significant difference between the amounts of RA enantiomers. Moreover, after oral administration of MPH, the ratio of d-MPH to l-MPH was approximately 10 in urine samples from each of the time segments. By contrast, after intravenous administration of MPH, the d:l ratio changed progressively from 1.16 in the 0-2-h urine sample to 9.06 in the 12-16-h sample. These observations suggest that, after oral administration of dl-MPH, the distortion in the ratio of MPH or RA enantiomers in urine samples was attributable to enantioselective presystemic conversion of MPH to RA rather than to enantioselective excretion.


Nasal delivery of [14C]dextromethorphan hydrochloride in rats: levels in plasma and brain.

Dextromethorphan (DM) is a neuroprotective agent. The mechanism of action is believed to be by N-methyl-D-aspartate receptor blockade. The concentration of DM in the brain is believed to be dose and route dependent. Delivery by the nasal route has received a lot of attention recently, because drug absorption from this route follows intravenous profiles with no first-pass effect. The uptake of DM in the brain from the nasal route was 65.9% compared with the intravenous route, whereas the plasma bioavailability from the nasal route was 78.8%. The nasal route is a viable alternative to the parenteral route for DM administration.


Pulmonary deposition of inhaled terbutaline: comparison of scanning gamma camera and urinary excretion methods.

Deposition from a multidose powder inhaler (Turbuhaler, Astra) delivering 500 micrograms of terbutaline sulfate per metered dose was compared by two techniques in a group of six healthy volunteers. The deposition of the radionuclide 99mTc, which was used to label terbutaline sulfate powder, was quantified by gamma camera (G-method). Simultaneously, the gastrointestinal absorption of swallowed drug was blocked with activated charcoal, and the amount of terbutaline in a urine sample, collected over a period of 48 h and corrected by a pharmacokinetic internal standard of intravenous deuterated terbutaline, was used as a measure of lung deposition (U-method). The mean (standard deviation) depositions in lung were 26.9 (3.8%) of the dose for the G-method and 21.1 (3.2)% of the dose for the U-method. Possible reasons for the differences between the two means are discussed. Both methods are suitable for assessing deposition from medical aerosol inhalers; the U-method requires access to gas chromatography-mass spectrometric equipment, and the G-method requires access to gamma camera facilities.


Complexation of steroid hormones with cyclodextrin derivatives: substituent effects of the guest molecule on solubility and stability in aqueous solution.

The inclusion complexation of homologous derivatives of steroid hormones with cyclodextrins and 2-hydroxypropyl-beta-cyclodextrin (2-HP-beta-CD) was investigated with regard to underlying structure-interaction relationship. The interaction was studied by phase solubility analysis and stabilization effects of complex formation with 2-HP-beta-CD. The solubilizing and stabilizing abilities of 2-HP-beta-CD were generally more effective for testosterone derivatives than for estradiol esters. Within a homologous series of steroid hormones, the steepest linear solubility isotherms were found for 17-methyl and 3-methyl derivatives. The solubilization of steroid esters by 2-HP-beta-CD depended on the structure and length of the ester side chain. The interaction of 2-HP-beta-CD with the steroids was hindered by long-chain fatty acid ester groups. With increasing length of the side chain, a decline of the isotherms occurred and the phase solubility behavior changed from linear to exponential. Contrary to expectations, benzoylation of steroids considerably decreased the guest-host interaction. The observed rates of degradation of the steroid esters were significantly reduced by 2-HP-beta-CD, depending on the chain length, and correlated well with the order found in phase solubility analysis. The degradation showed no deviations from pseudo-first-order kinetics, and the degradation mechanism was not changed because of complexation. The results suggest that interaction of 2-HP-beta-CD with steroid esters involves the ester functions of the prodrugs and is more suitable for unsubstituted guest molecules.


Pharmacokinetics of diazepam in the rat: influence of a carbon tetrachloride-induced hepatic injury.

The pharmacokinetics of diazepam in normal rats and in rats pretreated with carbon tetrachloride to induce hepatic cirrhosis (cirrhotic rats) was studied after intravenous and oral administration of the drug (4 mg/kg). Animals pretreated with this hepatotoxic agent showed a significant prolongation in the half-life of diazepam in plasma that is due more to an increase in volume of distribution rather than to a decrease in clearance. This study confirmed that diazepam was highly extracted by the rat liver and was not affected by the hepatotoxic agent, although there probably was a saturation of the activity of the cytochrome P450 enzyme when the drug was administered orally. Diazepam binds to plasma proteins to a high degree in both normal and cirrhotic rats; however, in the latter, a significant increase in the fraction of unbound drug in plasma was observed. Pretreatment of rats with carbon tetrachloride did not produce any change either in the distribution of diazepam into erythrocytes or in the disposition of the metabolite desmethyldiazepam.


Novel approach to estimate quality of binary random powder mixtures: samples of constant volume. III: Range of validity of equation.

The validity of an equation developed to determine the quality of binary random mixtures (eq 1) was evaluated with tablets prepared from random mixtures of a coarse constituent A (sucrose) and fine constituent B [microcrystalline cellulose (Avicel PH 101)-talc] with the A:B ratios (w/w) varying from 10:90 to 80:20. With all A:B ratios, superior agreement was established between the random content variations determined with eq 1 and the content variations found in the tablets. The 80:20 ratio, however, was just at the boundary, and random quality was achieved with the 50-mg tablets but not with the 200-mg tablets because of segregation. From percolation theory, this result is a consequence of the small proportion by volume (bv) of B that is almost equal to the precolation threshold (Pcb) of B of 0.3. With bv less than Pcb, the fine constituent B does not form a coherent lattice, and eq 1 is no longer valid. To estimate the volume proportions av and bv from the mass proportions a and b, two methods were established. Method 1 assumed the bulk densities of A and B to be representative and was used when av was higher than the percolation threshold (Pca) of A of 0.3 (a, 0.5). Method 2 used the true particle density of A and was valid with av values of less than 0.1 (a, 0.3), in which case the particles of A were dispersed as individuals in the matrix of B.


Physicochemical characterization of a model intravenous oil-in-water emulsion.

Photon correlation spectroscopy, nuclear magnetic resonance spectroscopy, electron microscopy, and small-angle X-ray scattering were used for the structural characterization of a model oil-in-water emulsion containing particles in the submicrometer size range. Additionally, small-angle X-ray diffraction, wide-angle X-ray diffraction, and differential scanning calorimetry were applied to raw materials and to binary mixtures. The majority of emulsion droplets have the characteristic of an ideal emulsion droplet, that is, a liquid lipid core covered by an emulsifier monolayer. However, the system contains a certain excess of emulsifier. Particles with bi- and/or oligolayer structures can be deduced. Double-emulsion droplets were detected. Large unilamellar vesicles were not found; however, the existence of small unilamellar liposomes (also referred to as small unilamellar vesicles or SUVs) seems likely. The proportion of all small nonmonolayer structures was quantified by nuclear magnetic resonance spectroscopy. No mixed micellar structures were detectable. Lysophospholipids were not detected in the aqueous phase, indicating their predominant incorporation into the emulsifier layers. Water-soluble phospholipid degradation products were found in the water phase. The existence of at least several monolayers of phospholipids does not seem to be a prerequisite for a stable soybean oil-in-water emulsion, in general.


Influence of dielectric constant on sedimentation rate of concentrated suspensions of aluminum and magnesium hydroxides.

Sedimentation of dilute pharmaceutical suspensions obeys Stokes's law, which assumes that there is no interaction between particles. The behavior of concentrated pharmaceutical suspensions is generally interpreted by use of modifications of Stokes's law that do not consider chemical interaction between particles. Properties of the medium itself, such as dielectric constant and surface tension, have not been included in the established equations. The present work shows that the dielectric constant of the medium has a distinct effect on the rate of sedimentation of the systems investigated.


Quantitative structure-activity relationship study of the biophysicochemical behavior of nitrosamine.

The partition coefficients of 14 aliphatic nitrosamines were measured in six water-organic solvent systems. Correlations between Hansch's hydrophobic parameter (pi) and Kier and Hall's topological index (1 chi) allowed pi to be substituted by 1 chi in the structure-activity correlations of the carcinogenicity data of the nitrosamines studied. The use of high-performance liquid chromatographic capacity factors of nitrosamines in these correlations is also discussed.


Metabolism and distribution of 1-[14C]alprazolam in rats.

Using 14C-labeled alprazolam (1-[14C]APZ) as a model for 1-[11C]APZ, we evaluated the tissue distribution of total radioactivity and assessed the contribution of the polar metabolites of APZ (alpha-hydroxymethyl- and 4-hydroxy-APZ) to radioactivity levels in the plasma and brains of rats over the course of 1 h. The biodistribution data showed that the uptake of radioactivity by rat brain was 0.31% of the injected dose per gram of tissue weight at 10 min postinjection. Pretreating rats reduced the levels in brain to 0.21% of the injected dose at 10 min but had little effect on the distribution of radioactivity in plasma and other tissues studied. Analysis of the metabolites in plasma and brain homogenates by an extraction-thin-layer chromatography-liquid scintillation method revealed that greater than 94% of the radioactivity in the rat brain was due to 1-[14C]APZ over the course of 1 h. APZ, therefore, is stable to metabolic transformations in the rat brain, and the polar metabolites are readily conjugated and excreted so that their cerebral uptake is minimal.


Adaptive computer program for determination of absorption profiles by numerical deconvolution: application to amoxicillin absorption.

We have developed a specific numerical deconvolution program for the Apple Macintosh microcomputer. After comparison with other methods, we used the program to evaluate the influence of nifedipine on the absorption and bioavailability of amoxicillin. The technique provided a model-independent approach. This study shows that the simultaneous administration of nifedipine with amoxicillin leads to a significant increase in both the total quantity of amoxicillin absorbed (+22%) and the rate of absorption. Parameters of clearance, volume of distribution, and elimination were unaffected. Numerical deconvolution analysis showed that nifedipine did not modify the absorption kinetics of amoxicillin, which are characterized by a lag time followed by a constant rate of absorption, suggesting zero-order kinetics with first-order kinetics at the end of the process. The results suggest the existence of a specialized, saturable transport molecule for this antibiotic.


In vitro and in vivo release of poly(DL-lactic acid) microspheres containing neurotensin analogue prepared by novel oil-in-water solvent evaporation method.

Poly(DL-lactic acid) (PLA) microspheres containing a neurotensin analogue [NA; H(CH3)-Arg-Lys-Pro-Trp-tert-Leu-Leu-OEt.3HCl] were prepared by a novel oil-in-water (o/w) solvent evaporation method, and the release behaviors were evaluated in vitro. About 20% of the loaded NA was released initially, and the subsequent release lasted for a month from microspheres prepared with PLA of molecular weight 2000 (PLA 2000). A smaller initial release from PLA 4000 and PLA 6000 microspheres was found, but a lag time of 2-3 weeks during which the drug was not released was observed with PLA 4000 and PLA 6000 microspheres. The addition of relatively hydrophilic monoglycerides decreased the lag time, and a fairly constant release of NA was achieved. The pharmacokinetic behavior of NA from PLA 2000 microspheres was studied in rats. The release of the drug after a subcutaneous injection exhibited pseudo-zero-order kinetics for 1 month. The initial release of the drug from the microspheres was reflected in a sharp increase of the plasma levels of the de-ester form of NA [H(CH3)-Arg-Lys-Pro-Trp-tert-Leu-Leu-OH], and the subsequent steady-state levels agreed well with the predicted levels obtained from analysis of constant-infusion kinetics.


Synthesis and biological activity of new 1,8-diaza-2,9,10-anthracenetrione derivatives.

Diels-Alder heterocycloaddition reactions of 2,5,8-quinolinetriones and 1-azadienes afford 1,8-diaza-2,9,10-anthracenetriones, which are simple analogues of the antitumoral antibiotic diazaquinomicin A. Cytotoxicity in this series and antitumor activity of the lead compound, 6-methyl-1,8-diaza-2,9,10-anthracenetrione, are reported.


Prominent inclusion effect of dimethyl-beta-cyclodextrin on photoisomerization of the thromboxane synthetase inhibitor (E)-4-(1-imidazoylmethyl)cinnamic acid.

The direct photoisomerization of (E)-4-(1-imidazoylmethyl)-cinnamic acid (IMC), a thromboxane synthetase inhibitor, to its (Z)-isomer at pH 2.0 was decelerated by beta-cyclodextrin (beta-CyD) and heptakis(2,6-di-O-methyl)-beta-cyclodextrin (DM-beta-CyD). The photostationary composition [(Z)-isomer:IMC ratio] was shifted in favor of IMC. These effects were much greater with DM-beta-CyD than with the parent beta-CyD. The quantum yield of the photoisomerization was significantly decreased by complex formation with beta-CyDs, whereas the extinction coefficient of the guest was only slightly decreased. This situation was in sharp contrast to those observed in less polar solvents and suggests that the suppressing mechanism with beta-CyD is different from that with less polar solvent systems. Spectroscopic studies (ultraviolet, circular dichroism, and nuclear magnetic resonance) indicated that IMC is tightly included in an axial mode in the cavity of DM-beta-CyD and that the rotation of the photoreactive site is sterically hindered. The results suggest that the suppressing effect of beta-CyDs on the photoisomerization of IMC results mainly from a steric origin.


Interaction of bovine serum albumin with the surface of a microcrystalline aluminum oxide hydroxide compound: a possible new type of phosphate adsorbent.

Aluminum hydroxide gel (ALG) has been effective for ameliorating acidosis associated with phosphatemia caused by hemodialysis. However, aluminum accumulation in the body causes severe side effects. As substitute for ALG, a new type of aluminum oxide hydroxide (tentatively named PT-A) was prepared with the hope of future clinical use. PT-A has a microcrystalline structure with a high resistance to pH change and has more phosphate-binding efficacy than ALG. It was tested for possible interaction with protein by adsorption test, zeta-potential analysis, X-ray diffraction, and scanning electron microscopy. Bovine serum albumin (BSA) was chosen as a model protein. The interaction of BSA with PT-A depended on the amount of adsorbent. Protein adsorption occurred rapidly and reached the maximal level at near neutral pHs. Phosphate adsorption was not affected by the presence of BSA, but the interaction of BSA with PT-A was significantly reduced by the presence of phosphate. Zeta-potential changes on the surface of PT-A indicated that the positively charged surface of PT-A was covered with negatively charged phosphate ions that repelled negatively charged BSA molecules. X-ray diffraction patterns indicated no observable structural alteration caused by adsorption of BSA or phosphate, and scanning electron microscopy revealed that BSA covered the outer surface of PT-A but did not cover small pores, where phosphate can freely penetrate.


Spectrofluorimetric study of the binding of 1-anilinonaphthalene-8-sulfonate to bovine serum albumin.

We studied the binding of the fluorescent probe 1-anilinonaphthalene-8- sulfonate to bovine serum albumin by spectrofluorimetric techniques. The binding of this probe to bovine serum albumin was via two types of sites: one with a high affinity constant but relatively fewer in number and the other with a lower affinity constant but greater in number. The number of binding sites of each type of site and their respective association constants varied with the features of the moiety and the temperature. The results indicate that the simplistic interpretation involving a single type of interaction of hydrophobic nature can no longer be supported and that additional involvement of other, nonhydrophobic types of binding should be considered. This thermodynamic study allowed calculation of changes in enthalpy, Gibbs free energy, and entropy values that are consistent with this hypothesis.


Lipidic peptides. V: Penicillin and cephalosporin acid conjugates with increased lipophilic character.

Lipophilic, double-ester derivatives of beta-lactam antibiotics with methylene, ethylene, and propylene spacers were prepared by crown-ether-assisted coupling of halogenoalkyl esters of 2-(tert-butoxycarbonylamino)decanoic acid to either penicillin G or cefuroxime. The hydroxyethyl ester of penicillin G and the tert-butoxypropyl ester of cefuroxime were also prepared. The lipophilic, double-ester conjugates, the hydroxyethyl ester of penicillin G, and the tert-butoxypropyl ester of cefuroxime showed weak or no antibiotic activity in vitro, as expected. The lipophilic penicillin G conjugates and the tert-butoxypropyl ester of cefuroxime were active in vivo against a nonpenicillinase-producing strain of Staphylococcus aureus after subcutaneous administration. The penicillin G double ester with propylene spacer and the tert-butoxypropyl ester of cefuroxime were inactive in vitro, a fact indicating that both compounds were hydrolyzed in vivo, as desired. After oral administration, the lipophilic, double-ester conjugate of penicillin G with methylene spacer and the tert-butoxypropyl ester of cefuroxime were active.


Talectomy for diabetic Charcot foot. An alternative to amputation.

A talectomy was performed because of Charcot degeneration during recovery from a hallux amputation. The patient was treated conservatively but Charcot degeneration continued, resulting in ulceration and dorsomedial dislocation of the talar head. The patient was hospitalized, and the talectomy was performed. The patient returned to normal activities.


Surgical repair of a talar body nonunion.

Fractures of the talus are significant injuries and are usually intra-articular. The authors discuss the evaluation and management of a patient with a delayed union of a talar body fracture. Assessment of talar vascularity and joint integrity should be performed preoperatively. The role of internal fixation and continuous passive motion is discussed.


Coumadin skin necrosis. Pedal manifestations.

The idiosyncratic dermatologic reaction to coumarin-like agents, most notably, Coumadin (warfarin sodium) has been well described in the world's literature. Although the incidence is reported to be less than 0.1% of patients treated with Coumadin, pedal cases tend to be striking and their treatment seemingly tenuous.


Bilateral bipartite medial cuneiform. A case report.

A fracture to the intermediate cuneiform that was not definitively detected on routine radiographs because of the overlap of the cuneiform was presented. Weightbearing x-rays did not provide additional information. The anatomical location of the fracture was identified only after a computed tomography scan was performed. An incidental finding, bilateral bipartite medial cuneiforms, was also observed on the computed tomography scan, which contributed to the overlap on routine radiographs. The anatomy of the bipartite medial cuneiforms seen on computed tomography was similar to that described by Barlow in 1942. Retrospective comparison to the initial radiographs with the computed tomography scan sections did reveal bipartite medial cuneiforms on these films as well. The podiatric physician should keep bipartition in mind when evaluating x-rays for any osseous pathology, especially fractures.


A successful technique for the treatment of diabetic neurotrophic ulcers.

Over 90% of the diabetic neurotrophic ulcers treated with the felted foam technique at the Cleveland Foot Clinic have completely healed. The average healing time for plantar ulcers has been approximately 8 weeks. After the ulcerations have healed, molded shoes or orthopedic shoes with Plastazote inserts are prescribed. The felted foam technique is simple to perform in an office setting and can be used by both the novice and the experienced practitioner.


Calculating the surgically induced refractive change following ocular surgery.

Calculating the surgically induced refractive change following ocular surgery is important for evaluating the results of keratore-fractive procedures, smaller incisions and various wound closures for cataract surgery, and the effect of suturing techniques and suture removal following corneal transplant surgery. We present a ten-step method of calculating the spherical- and cylindrical-induced refractive change in a manner suitable for a programmable calculator or personal computer. Several applications are given including (1) adding the overrefraction to the spectacle correction, (2) determining the surgically induced refractive change from the preoperative and postoperative refractions, (3) determining the surgically induced refractive change from the K-readings, (4) rotating axes, (5) determining the power at meridians oblique to the principal meridians of a spherocylinder, (6) determining the coupling ratio, and (7) averaging axes. Standard methods for calculating and reporting aggregate results are also given.


Hydrodynamic analysis of intraocular pressure changes during anterior chamber procedures.

Variations in intraocular pressure (IOP), observed by us and other authors in closed-system anterior chamber procedures, are explained using a simple hydrodynamic analysis based on the Bernoulli equation. Calculations show that the sudden increases in IOP (pressure spikes) measured during anterior segment surgery are due primarily to the small size of the infusion cannulas and are exacerbated by high infusion rates. Accurate measurement of these IOP variations requires placement of the pressure sensors in situ and is not possible by remote pressure sensing at the infusion line or the console. This work indicates that closed-system procedures could benefit from accurate monitoring of intraoperative IOP and could use these measurements for automatic IOP control during surgery.


Prospective experimental study of factors related to posterior chamber intraocular lens decentration.

The effect of posterior chamber intraocular lens (IOL) dimensions, design, style, loop fixation, and anterior capsular tears on decentration were investigated in an experimental model. Nine posterior chamber IOLs of various designs and styles with loop diameters between 12.0 and 14.0 mm and optic diameters between 5.0 and 7.0 mm were implanted in human eyes obtained post mortem. Symmetrical and asymmetrical fixation were investigated in eyes with and without radial tears using the Miyake posterior view technique. Location of IOL loops proved to be the most significant factor in IOL decentration. Decentration was least with symmetrical bag/bag fixation and no radial tears (mean = 0.20 +/- 0.05 mm). Asymmetrical bag/sulcus fixation in the presence of anterior capsular tears was associated with the highest decentration rate (mean 0.68 +/- 0.28 mm). Optic size and total loop diameter had no apparent effect on IOL centration in the immediate postoperative period.


Drug interaction with intraocular lenses of different materials.

The uptake and washout kinetics of four drugs representing different classes of ophthalmic medications were measured in intraocular lenses of different materials. The materials ranged from hydrogel lenses to poly(methyl methacrylate) (PMMA), Acrysof (acrylic/methacrylic), and two types of silicone lenses (Chiroflex and AMO SI-18NB). Uptake was determined after seven days of immersion in a large volume of Ringer's solution containing drug concentrations that equaled those found in aqueous humor 30 minutes to one hour after topical administration. Washout was determined after placing lenses in 1 ml of 0.9% saline for 24 hours. Only hydrogel lenses could be digested in acid to measure lens uptake directly. The PMMA, Acrysof, and silicone lenses behaved similarly toward gentamicin and dexamethasone--low uptake (less than 3.5 ng/mg lens) and low washout (less than 4.0%). Their uptake of norepinephrine was lower (less than 0.7 ng/mg lens) but the washout varied from 29% (AMO silicone) to 100% (PMMA and Acrysof). The pilocarpine uptake was the lowest of drugs tested (less than 0.03 ng/mg lens) and the washout varied from 1.5% (acrylic) to 100% (PMMA and Chiroflex silicone). Hydrogel lenses took up the most drug in the following order: dexamethasone greater than pilocarpine greater than gentamicin greater than norepinephrine. Washout was high, ranging from 83% to 98%. Despite the greater uptake and washout, the maximum drug uptake would only provide one-tenth of the greatest aqueous humor concentration that occurs after topical drug administration. Intraocular lenses of the materials tested did not interfere with the intraocular drug pharmacokinetics, nor did the data indicate that presoaking intraocular lenses of these materials in drugs would enhance post-surgical intraocular drug concentrations.


Practice styles and preferences of ASCRS members--1991 survey. American Society of Cataract and Refractive Surgery.

A survey of the practice styles and preferences of 1991 ASCRS members with a U.S. zip code was performed in August 1991. Approximately 3,935 questionnaires were sent and approximately 40% (1,574) were returned after two months. Three main profile questions were used to cross-analyze the results: the age of the ophthalmologist, the volume of cataract surgery per month, and the geographic location. This report also compared the data with previously published surveys of the ASCRS and the Academy memberships.


Changing trends in explanted intraocular lenses: a single center study.

Over a nine-year period, our practice removed 1,091 intraocular lenses. The most common type of lens requiring explantation was the closed-loop anterior chamber lens (58.6%). The Stableflex lens represented the largest percentage of all removed lens types (28.8%). The number of closed-loop anterior chamber lenses requiring removal peaked in 1988 and then gradually declined. All other lens styles have shown gradually increasing removal rates. Older style iris-fixated lenses and rigid anterior chamber lenses, which have not been implanted for several years, have increasing removal rates. Late breakage of fixational polypropylene sutures with pupil-supported iris-fixated lenses have occurred in five cases; the average time from implantation to suture breakage was 112 months.


Explantation of posterior chamber lenses.

A consecutive series of 119 explanted posterior chamber lenses is reviewed. Seventy (58.8%) were removed because of dislocation or improper fixation, 15 (12.6%) because of anisometropia, and 18 (15.1%) because of chronic inflammation. Sixty-two (52.1%) of these explantations probably occurred for reasons that can be avoided by changes in preoperative, operative, or postoperative techniques. The rate of posterior chamber lens explantations is quite low considering the large number of lenses implanted; with changing surgical techniques, we anticipate that the number of lenses requiring removal will decrease.


Intraocular lens implantation in microphthalmic patients.

Microphthalmos is a developmental disorder of the eye consisting of a smaller than normal eye. This disorder can present as an isolated condition or associated with other systemic alterations. It is not uncommon for patients with microphthalmos to have congenital cataracts along with other ocular and systemic abnormalities. This paper reports the experience with 11 microphthalmic eyes of seven patients who had primary or secondary intraocular lens (IOL) implantation over a six-year period from 1985 to 1991. In all cases the IOL had a 13.5 mm or 14.0 mm overall diameter and a 6.0 mm or 6.5 mm optic. It was difficult to obtain documentation of objective visual improvement in many of these cases because of the associated nystagmus. However, all patients reported subjective improvements. These results suggest that with proper technique and lens selection microphthalmic patients should be considered for IOL implantation with relative safety and success.


Long-term study of children with implanted intraocular lenses.

We studied children between five and 15 years of age who were implanted with intraocular lenses (IOLs). The subjects comprised eight cases of traumatic cataract, 11 of congenital cataract, and six of steroid cataract. The follow-up ranged from four months to nine and one half years. Twenty of the eyes studied achieved a postoperative visual acuity of equal to or better than 20/40. Binocular function was retained in most cases. Postoperative complications included seven cases of posterior iris synechia, three of iris capture, one of transitory elevated intraocular pressure, and one of cystoid macular edema. Corneal endothelial studies were normal in the eyes in which posterior chamber IOLs were implanted.


Study of acute intraoperative suprachoroidal hemorrhage.

Acute intraoperative suprachoroidal hemorrhage or effusion (AISH) was studied in a prospective manner over the past three years. In a general cataract surgery population of 2,523 patient eyes, 15 (0.6%) experienced an AISH. Results of a specific surgical management technique are presented. Surgical control of the AISH consisted of immediate closure of the incision and application of pressure directly to the eye. This tamponades the effusion or hemorrhage, which allows coagulation and completion of the case. There was no attempt to drain the suprachoroidal space. All cases were completed the same day, usually within an hour. The postoperative visual acuities were quite good--20/40 or better in 93% of cases. Factors contributing to AISH were 4+ brunescent nuclear sclerosis, the large incision used with nucleus expression extracapsular cataract extraction, and the combination of anticoagulation and systemic vascular disease.


Effect of a superficial and a deep scleral pocket incision on the incidence of hyphema.

Deep tunnel scleral pocket incisions were developed to control surgically induced astigmatism following cataract and intraocular lens implantation surgery. A more superficial, shallow scleral pocket incision was developed to reduce the rate of postoperative hyphema. To test its effectiveness, a randomized prospective clinical study was performed. One hundred twenty-nine eyes of 129 patients were randomized: 66 to receive a deep tunnel pocket and 63 to receive the superficial pocket. In both groups the incision was made 3 mm posterior to the limbus. For the deep pocket cases, a blade setting of 0.27 mm was used and the wound was dissected forward toward the entry site, creating a long, deep, narrow tunnel. For the superficial wound cases, a 0.17 mm blade setting was used and the entire wound was dissected to the edge of the anatomic limbus, creating a thin scleral flap. The left side was then fanned out toward the left with the entry site slightly into clear cornea. At one day after surgery, 22 cases (34%) in the deep pocket group and four cases (6%) in the superficial pocket group had hyphemas. The difference in hyphema rates was statistically significant (P less than .001).


Intraocular pressure following small-incision cataract surgery and polyHEMA posterior chamber lens implantation. A comparison between acetylcholine and carbachol.

Ninety patients who had phacoemulsification and implantation of a flexible polyHEMA intraocular lens (IOGEL 1103) were assigned to three groups. After evacuation of sodium hyaluronate retrolentally from the capsular bag, 0.5 ml of 1% acetylcholine chloride, 0.01% carbachol, or balanced salt solution was instilled into the anterior chamber following wound closure. Intraocular pressure (IOP) was measured the day before, and six hours, 18 hours, and one week postoperatively. No topical or systemic antiglaucomatous drug was given during the study period. Preoperatively and one week postoperatively there was no significant difference between the three groups (P greater than .01). At six hours postoperatively the mean IOP decreased in the carbachol group (-2.8 mm Hg) and increased in the acetylcholine and control groups (+0.6 mm Hg and +/- 4.7 mm Hg) when compared with baseline pressures. At 18 hours the mean change from baseline was -3.0 mm Hg in the carbachol group, +0.8 mm Hg in the acetylcholine group, and +2.3 mm Hg in the control group. At six hours IOP exceeding 22 mm Hg was observed in ten of the control patients (30%) receiving balanced salt solution intracamerally and four of the acetylcholine patients (13.3%) but none of the carbachol patients. At 18 hours IOP remained above 22 mm Hg in three of the acetylcholine patients (10%) and four of the control patients (13.3%). Only one of the carbachol patients developed an increase of IOP up to 26 mm Hg at 18 hours. Removal of viscoelastic substances from behind the IOL reduced the incidence of pressure spikes in the early postoperative period.(ABSTRACT TRUNCATED AT 250 WORDS)


Relationship between postoperative pupil size and disability glare.

A group of 40 postoperative cataract patients had Miller-Nadler glare testing performed before and after midpupillary pharmacologic dilation. The results indicated that pupillary enlargement is associated with increased glare disability. For that reason it is essential to maintain normal pupil shape and function after cataract surgery, a difficult task in cases with miotic pupils.


Cortical cleaving hydrodissection.

In this technique, I/A of cortex as a separate step can be omitted, thereby eliminating that portion of the surgical procedure in which posterior capsular disruption most frequently occurs. Residual cortical cleanup is accomplished in the presence of a posterior chamber IOL which protects the poserior capsule by holding it remote from the aspiration port.


Divide and conquer phacoemulsification. One-handed variant.

A one-handed variation of Gimbel's "divide and conquer" phacoemulsification technique is described. Instead of bimanual cracking, the lens sections are cut, rotated, cut, and removed in sequence.


Preplaced inferior iris suture method for small pupil phacoemulsification.

A surgical method for managing poorly dilating pupils preoperatively is presented. A fine polypropylene suture is preplaced through the inferior iris sphincter prior to an inferior radial iridotomy in preparation for nucleus fracture endolenticular phacoemulsification. Placing the suture prior to the iridotomy assures proper aesthetic and functional alignment of the incised iris pillars, while enlarging the pupil inferiorly accommodates in-the-bag nucleus emulsification. This new surgical method maintains pupillary appearance and function postoperatively.


Small pupil enlargement during cataract extraction. A new method.

A new method for enlarging a small pupil during cataract extraction is described. The technique is simple and safe, and uses new instruments that reduce or entirely eliminate the need to incise or suture the iris. This method of pupil enlargement can be used for extracapsular cataract extraction and phacoemulsification procedures.


Posterior chamber intraocular lens implantation in a patient with oculocutaneous albinism.

A 56-year-old woman with tyrosinase-negative oculocutaneous albinism complained of gradually decreasing vision in the left eye. Her visual acuity was 20/300 in the right eye and hand motion in the left eye. She had pink skin and white hair and cilia. On examination, bilateral hypopigmented irides, an opaque lens in the left eye, a hypopigmented fundus in the right eye, and nystagmus were found. An extra-capsular cataract extraction with posterior chamber intraocular lens (IOL) implantation was performed. After retrobulbar anesthesia was administered, the nystagmus ceased temporarily. Postoperatively, visual acuity in the left eye improved to 20/200. We believe IOL implantation is useful in the treatment of cataracts in albino patients.


Spontaneous extrusion of an intraocular lens implant.

A 51-year-old man with ankylosing spondylitis had intracapsular cataract extraction and anterior chamber lens implantation in the left eye in 1985. He had localized sclerokeratitis around the corneal section and a protracted anterior uveitis in the immediate postoperative period. He developed a spontaneous extrusion of the implant in 1991 (six years later). The extrusion was through a site 1.5 mm posterior to the previous surgical section. There was no corneal decompensation or corneal melt and no history of trauma. Signs of localized scleritis were present. It is suggested that anterior chamber lens implantation should be avoided under these circumstances.


Dose-dependent toxicokinetics of L-689,502, a potent human immunodeficiency virus protease inhibitor, in rats and dogs.

L-689,502, N-[2(R)-hydroxy-1(S)-indanyl]-5(S)-(1,1-dimethylethoxy- carbonylamino)-4(S)-hydroxy-6-phenyl-2(R)-(4-[2-(4- morpholinyl)ethoxy]phenyl)methyl hexanamide, is a potent inhibitor of human immunodeficiency virus-1 protease. The effect of dose on the elimination kinetics of L-689,502 was studied in rats and dogs. After i.v. administration, total plasma clearance of L-689,502 in rats decreased with increasing dose; the clearance decreased from 181 ml/min/kg at 1 mg/kg to 86 ml/min/kg at 20 mg/kg. Similar results were observed in dogs; clearance fell from 29 ml/min/kg at 0.5 mg/kg to 17 ml/min/kg at 10 mg/kg. Bile flow in rats was retarded in a dose-dependent manner after a single i.v. injection of L-689,502. The cholestatic effect was reversible and maximal at 5 mg/kg i.v. Consistent with the cholestatic effect, L-689,502 caused an increase in serum levels of aminotransferase. After i.v. administration of L-689,502 (10 mg/kg), alanine aminotransferase increased from 50 to 370 IU/liter and aspartate aminotransferase from 120 to 700 IU/liter. Moreover, pretreatment of rats with L-689,502 resulted in a significant decrease in the elimination kinetics of antipyrine and diflunisal, as well as of L-689,502 itself. Collectively, these results suggest that the dose-dependent kinetics of L-689,502 in rats and dogs are more likely due to hepatotoxicity caused by the drug than to capacity-limited metabolism.


A comparison of the potency of selective L-calcium channel blockers in human coronary and internal mammary arteries exposed to serotonin.

The actions of L-type calcium channel blockers on the contractile response to serotonin and to K(+)-depolarization have been studied in human coronary artery and in human internal mammary artery. The effect of ketanserin indicated that in both arteries serotonin action may be related not only to 5-serotonin2 but also to other serotonin receptors. In fura-2-loaded coronary and mammary arteries, exposed to serotonin (10 microM), nisoldipine (1 microM) and verapamil (10 microM) reversed completely the increase in [Ca++] cyt but not the contraction. The Ca++ antagonist-resistant contraction was equal to 26.2 +/- 2.1% of controls (n = 57) in coronary artery and to 51.7 +/- 4.2% (n = 19) in internal mammary artery. The concentration inhibiting by 50% the tonic contraction to serotonin sensitive to calcium channels blockade was 61-fold lower in human coronary artery than in human internal mammary artery with nisoldipine, but only 3.7-fold lower with nifedipine. There was no significant difference with diltiazem and verapamil. When human coronary artery and human internal mammary artery were exposed to a 100-mM KCl depolarizing solution, their sensitivity to nisoldipine was not significantly different. Preincubation with calcium antagonists in a 40-mM KCl solution reversibly increased the inhibitory effect of nisoldipine but not that of the other calcium antagonists. Comparison of radioligand and functional data shows that inhibition by calcium antagonists of the response to both serotonin and K(+)-depolarizing solution may be related to interaction with L-type calcium channels. The results indicate that the very high sensitivity to nisoldipine of the tonic response evoked by serotonin in human coronary artery might be related to the voltage-dependence of this dihydropyridine.


Serotonin-induced relaxation in canine coronary artery smooth muscle.

Serotonin (5-HT) is a potent contractile agonist in canine coronary artery devoid of endothelium; however, in higher concentrations 5-HT produces concentration-dependent relaxation by activating an as yet uncharacterized receptor. This study explored the possibility that 5-HT-induced relaxation was mediated by interaction with a member of the 5-HT1, 5-HT2, 5-HT3, or 5-HT4 receptor family. 5-HT, 5-carboxamidotryptamine and 5-methoxytryptamine produced concentration-dependent relaxation in vitro in tissues precontracted with prostaglandin F2 alpha (10 microM). The agonist rank order potency for relaxation was 5-carboxamidotryptamine > 5-HT > 5-MeOT. 8-hydroxydipropylaminotetralin (8-OH-DPAT), dipropyl-5-CT, 5-methyltryptamine, sumatriptan, alpha-methyl-5-HT and 2-methyl-5-HT did not produce significant relaxation. The 5-HT1/beta adrenergic receptor antagonist propranolol (1 microM) did not antagonize 5-HT-induced relaxation. 5-HT-induced relaxation was not blocked by tetrodotoxin (0.3 microM), suggesting that neuronal depolarization to release mediators from nerves was not responsible for the relaxation. Neither ketanserin (1 microM) nor ritanserin (1 microM) antagonized 5-HT-induced relaxation, suggesting that 5-HT2 and 5-HT1C receptors do not mediate relaxation. ICS 205-930 (10 microM), a 5-HT3/5-HT4 receptor antagonist, shifted the 5-HT concentration-response curve modestly to the right (pKB = 5.1 +/- 0.1). Cisapride, a 5-HT4 receptor agonist, was not effective either as an agonist (up to 10 microM), or as an antagonist (1 microM) of 5-HT-induced relaxation.(ABSTRACT TRUNCATED AT 250 WORDS)


Pulmonary accumulation of propranolol in vivo: sites and physiochemical mechanism.

Despite the therapeutic importance of propranolol and the potential usefulness of propranolol extraction measurements for the assessment of lung disorders, the pulmonary disposition of propranolol remains poorly understood. The extraction, accumulation and distribution of propranolol in lungs of conscious and anesthetized sheep were investigated by indicator-dilution methods, lung lymph fistula preparations and bronchoalveolar lavage. Pulmonary extraction of propranolol from plasma (0.81 +/- 0.03) was significantly less than that of imipramine (0.89 +/- 0.03), not significantly different from that of lidocaine (0.74 +/- 0.03) and much greater than that of water (0.44 +/- 0.02), whereas there were no differences in apparent red blood cell extraction of each indicator from plasma in vitro as determined under similar conditions (0.08-0.1). Pulmonary accumulation of imipramine (78 +/- 3%), lidocaine (52 +/- 4%), propranolol (37 +/- 4%) and water (7 +/- 2%), after a single pass through the pulmonary circulation, correlated positively with octanol/saline partition coefficients but not with pKa values. After bolus i.v. injection of [3H]propranolol, tritium concentrations in lung lymph increased rapidly to exceed plasma concentrations within 60 min and tritium concentrations in bronchoalveolar lavage equaled plasma concentrations 5 to 15 min after injection. It is concluded that by a mechanism not involving molecular charge, propranolol permeates capillary endothelium and alveolar epithelium to accumulate in hydrophobic regions of the lungs. This study in normal sheep suggests that reduced propranolol extraction by damaged lungs reflects pathological alterations other than endothelial cell dysfunction, such as pulmonary edema.


Antinociceptive actions of spinal nonsteroidal anti-inflammatory agents on the formalin test in the rat.

Subcutaneous injection of formalin into the dorsal surface of the hindpaw evoked a two-phased flinching (phase 1:0-9 min; phase 2: 10-60 min) of the injected paw. Intrathecal administration of the nonsteroidal anti-inflammatory drugs (NSAID) produced minimal effects upon phase 1, but showed a significant, though submaximal, dose-dependent suppression of the phase 2 response. Ordering of i.t. potency was (ID50 in nmol): indomethacin (1.9) > or = flurbiprofen (2.1) > ketorolac (5.2) > or = zomepirac (5.9) > S(+)ibuprofen (16) > or = ibuprofen(racemic) (19) > acetylsalicylic acid (27) > acetaminophen (250) > R(-)ibuprofen (> 270) = 0. Intraperitoneal administration also produced a dose-dependent inhibition of phase 2, but only at doses which were 100 to 1000 times higher than those required to produce similar effects after i.t. injection. Intrathecal and i.p. dose-response curves showed similar distinct plateaus of maximum achievable inhibition (intrinsic activity) of the phase 2 behavior, ranging from 20 to 50% of the control response. Varying the time of drug injection reveals that injection 9 min after formalin yielded effects the same as those observed when the agent was given 2 min before formalin. Pretreatment at longer intervals indicated that the duration of the antinociceptive effect was between 3 to 6 hr after the i.t. injection. The i.t. injection of the highest doses of the several NSAID were without significant effect upon the 52.5 degrees C hot plate test. These studies indicate that NSAID have a powerful effect upon spinal nociceptive processing evoked by the s.c. injection of formalin.


Membrane potential in myenteric neurons associated with tolerance and dependence to morphine.

Chronic treatment of guinea pigs with morphine produces subsensitivity (tolerance) of the longitudinal smooth muscle-myenteric plexus preparation to a variety of inhibitory agonists (e.g., mu opioid, alpha adrenoceptor and adenosine receptor agonists) and supersensitivity (dependence) to a variety of excitatory agonists (e.g., nicotine, 5-hydroxytryptamine and potassium ions). The present investigation was to determine if these changes in sensitivity could be related to changes in electrical properties of the S and AH neurons in the myenteric plexus. S neurons from morphine-implanted animals were significantly depolarized (7 mV) relative to those from placebo-implanted animals, whereas the membrane potential of AH neurons was unchanged. Approximately 60% of S neurons were hyperpolarized by morphine. In this subset of neurons, membranes were significantly depolarized but the threshold was unchanged in morphine-implanted animals. This means that resting potentials of S neurons from tolerant preparations are closer to threshold. The hyperpolarization produced by morphine (0.1 microM) was similar in preparations from morphine- and placebo-implanted animals. Thus, the partially depolarized state of S neurons in the myenteric plexus is the cause of the subsensitivity and supersensitivity to agonists and can explain both tolerance and dependence. Changes in opioid receptors or their coupling to potassium channels do not appear to contribute to tolerance in the longitudinal smooth muscle-myenteric plexus.


Aldose reductase and myo-inositol in endothelial cell dysfunction caused by elevated glucose.

A possible relationship between aldose reductase activity and myo-inositol levels and endothelium-dependent relaxations was examined in isolated rabbit aorta incubated with elevated concentrations of glucose (44 mM) for 6 hr to mimic hyperglycemic conditions. Rings of aorta incubated in elevated glucose and contracted submaximally by phenylephrine showed significantly decreased endothelium-dependent relaxations induced by acetylcholine compared with aorta incubated in control (5.5 or 11 mM) glucose. Acetylcholine-induced relaxations of aorta incubated in hyperosmotic mannitol (44 mM) were not different from those incubated in control glucose. Treatment with two structurally unrelated aldose reductase inhibitors, sorbinil or zopolrestat, or supplementation with myo-inositol, prevented the abnormal acetylcholine relaxations of aortic rings caused by elevated glucose. No effects of sorbinil, zopolrestat or myo-inositol were observed on the response to acetylcholine of aorta incubated in control glucose. Neither sorbinil nor myo-inositol affected the increase in release of vasoconstrictor prostanoids caused by elevated glucose. These findings suggest that sorbitol accumulation and myo-inositol depletion contribute to the abnormal endothelial cell function caused by exposure to elevated glucose. The increased release of vasoactive prostanoids is either independent of, or possibly contributes to, the abnormal aldose reductase activity and/or myo-inositol depletion in intact blood vessels exposed to elevated concentrations of glucose.


Cardiac effects of 3,5-diiodothyropropionic acid, a thyroid hormone analog with inotropic selectivity.

Thyroid hormone exerts a strong positive inotropic action on the heart and induces alpha-myosin heavy chain (MHC) gene expression. 3,5-Diiodothyropropionic acid (DITPA), a carboxylic acid analog with low metabolic activity, was observed to induce alpha-MHC mRNA in heart cell culture with EC50 approximately 5 x 10(-7) M. To determine if the compound has positive inotropic actions, the effects of DITPA and L-thyroxine on heart rate, left ventricular pressures, left ventricular dP/dt, myosin isoenzymes and hepatic alpha-glycerolphosphate dehydrogenase activity were compared in hypothyroid rats. Binding affinities of DITPA and triiodothyronine for bacterially expressed alpha-1 and beta-1 thyroid hormone receptors (TRs) also were determined. Over the dosage range of 150 to 1500 micrograms/100 g, DITPA produced increases in left ventricular dP/dt comparable to those obtained with L-thyroxine at dosages of 1.5 to 15 micrograms/100 g, but with significantly less tachycardia. The increase in alpha-MHC mRNA was about the same with both compounds whereas alpha-MHC protein content and GPDH activity increased less with DITPA. These differences could not be explained by preferential binding of DITPA to TR subtypes. Because heart rate is a major determinant of myocardial oxygen consumption, DITPA is able to achieve increased cardiac performance at lower myocardial oxygen costs.


The effect of the atypical antipsychotic drug, amperozide, on carrier-mediated striatal dopamine release measured in vivo.

The effect of the novel atypical antipsychotic drug, amperozide, on carrier-mediated dopamine efflux was studied using in vivo microdialysis in the striatum of awake-behaving rats. Amperozide was infused directly through the dialysis probe. This local infusion produced a concentration-dependent increase in striatal dopamine overflow. This increase was attenuated when a Ca(++)-free perfusion medium was used. Local infusion of amperozide blocked dopamine efflux after the systemic administration of amphetamine in a concentration-dependent manner. The antagonistic effect of amperozide (50 microM) on amphetamine-induced efflux of dopamine was not attenuated under Ca(++)-free conditions. Similar to its effects on amphetamine-induced dopamine efflux, amperozide (50 microM) attenuated the increase in dopamine overflow produced by ouabain (10 microM) but not veratridine (15 microM). The systemic coadministration of amperozide (10 mg/kg, i.p.) and haloperidol (2 mg/kg, i.p.) increased extracellular dopamine levels in an additive manner when compared to the increases observed after the administration of either drug alone. Overall, these data indicate that amperozide acts on the dopamine transporter to inhibit carrier-mediated release.


Tamoxifen-resistant human breast cancer cell growth: inhibition by thioridazine, pimozide and the calmodulin antagonist, W-13.

Estrogen receptor (ER)-negative human breast cancer cell lines (MDA-MB-231 and MDA-MB-435) and ER-positive derivatives of the MCF-7 cell line selected for growth in the presence of antiestrogens (LY2 and RR) were used as in vitro models of tamoxifen-resistant human breast cancer in this study. The sensitivity of the tamoxifen-sensitive (MCF-7) and tamoxifen-resistant human breast cancer cell growth to two noncytotoxic neuroleptic drugs, pimozide and thioridazine, and the anticalmodulin agent, W-13, were compared. Inhibition of cell growth was measured as a decrease in cell number following a 72-h incubation with drug. Growth of the ER-negative cell lines MDA-MB-231 and MDA-MB-435 was inhibited by all three drugs. The average Ki values in these two lines were 6.3 and 3.8 microM for pimozide and 4.1 and 15 microM for thioridazine, respectively. Both ER-negative cell lines were more sensitive than MCF-7 cells to growth inhibition by W-13. MCF-7 cells selected for antiestrogen resistance were sensitive to growth inhibition by W-13 and thioridazine (LY2, average Ki = 10.4 microM; RR, average Ki = 5.2 microM). LY2 and RR cells were resistant to pimozide except when treated with estradiol (Ki = 4.6 and 7.9 microM, respectively). Pimozide, thioridazine and W-13 all exerted different effects on the distribution of human breast cancer cells within the cell cycle, suggesting that each drug may utilize a distinct pathway for inhibition of cell growth. We conclude that all three drugs are potential noncytotoxic alternatives to tamoxifen for the treatment of tamoxifen-resistant human breast cancer.


Block of voltage-gated potassium currents by anticonvulsant U-54494A in mouse neuroblastoma cells.

U-54494A [(+-)-cis-3,4-dichloro-N-methyl-N-[2-(1- pyrrolidinyl)-cyclohexyl]-benzamide], an anticonvulsant and Na channel blocker, was examined for its interaction with delayed rectifier K channels in mouse neuroblastoma cells (NIE-115) using whole-cell and inside-out configurations of the patch clamp techniques. U-54494A at anticonvulsant doses reversibly blocked the tetraethylammonium-sensitive outward K current in a time-dependent manner without affecting the current-voltage relationship. Analysis of the time-dependent block suggests interaction of U-54494A with the open state, but not with the resting state of the K channel. Furthermore, the drug showed no interaction with inactivated states of the K channel because it produced no noticeable effect on the steady-state inactivation curve or the recovery of the channel activity from inactivated states. The drug shifted the steady-state activation curve to a hyperpolarizing direction. This shift seems to result from underestimations of the maximal conductance of the K channel in the presence of U-54494A, because of its progressively increasing potency to block the K currents as the membrane potential became more depolarized. The potency of the drug was enhanced not only by depolarized membrane potentials, but also by raising the external pH. These results suggest that U-54494A interacts with a channel binding site which is located within the membrane electric field and approachable from the cytoplasmic side. The proposal was supported further by single channel recordings with inside-out patches in which U-54494A induced flickery blocks of single channel openings of the delayed rectifier.(ABSTRACT TRUNCATED AT 250 WORDS)


Selective inhibitory effects of calcium channel antagonists on the two components of the neurogenic response of guinea pig vas deferens.

The effects of L-type calcium channel antagonists and omega-conotoxin on the contractile responses of guinea pig vas deferens were examined in vitro. Electrical stimulation of the postganglionic hypogastric nerve induced biphasic contraction consisting of rapid phasic and delayed tonic components. L-type calcium channel antagonists, such as diltiazem, verapamil and nicardipine, mainly inhibited the delayed tonic component, whereas omega-conotoxin mainly inhibited the rapid phasic component. Stimulations in the presence of prazosin and alpha, beta-methylene ATP induced rapid transient and delayed contraction, respectively, which were inhibited by omega-conotoxin and L-type calcium channel antagonists, respectively. Short-term stimulation with five pulses induced a small fast phasic contraction. This contraction, which could be desensitized by alpha, beta-methylene ATP, was inhibited by omega-conotoxin, but not by L-type calcium channel antagonists. At the concentrations used in the present study, none of the calcium channel antagonists inhibited the contractions induced by exogenously added ATP or norepinephrine. These findings suggest that L-type calcium channel antagonists and omega-conotoxin inhibit the neurotransmissions mediated by norepinephrine and ATP, respectively, from the postganglionic nerve to the vas deferens of the guinea pig. Inhibition of the voltage-dependent calcium channel is discussed in relation to the mechanism of cotransmission in this preparation.


Prejunctional muscarinic receptors in the deep muscular plexus of canine ileum: comparison with smooth muscle receptors.

Prejunctional muscarinic receptors from the deep muscular plexus of canine ileum were studied, and their properties were compared with those of the postjunctional receptors of the circular smooth muscle. In the purified synaptosomal fraction (a fraction containing primarily the axonal varicosities of deep muscular plexus), the muscarinic ligand N-[3H]methylscopolamine labeled an apparently homogenous population of receptors (nH = 1) with a Kd of 2.7 nM and a Bmax of 195 +/- 44 fmol/mg protein (mean +/- S.D., n = 4). These receptors showed a high affinity for the M3/M1-selective antagonist 4-diphenylacetoxy-N-methylpiperidine methiodide (pKi = 7.41); in contrast, the pKi values of pirenzepine (5.60), methoctramine (5.65) and AF-DX 116 (5.21) implied little selectivity for these subtypes. The binding properties of muscarinic receptors in the synaptosomal fraction were different from the binding properties of muscarinic receptors in the purified circular smooth muscle plasma membranes. Most notably, the circular smooth muscle receptors had significantly lower affinity for N-[3H]methylscopolamine (Kd = 16 nM) with a Bmax value of 2088 +/- 276 fmol/mg. The affinities of the M2 subtype-selective muscarinic antagonists methoctramine and AF-DX 116 were similar in both membrane preparations. The receptor population associated with the deep muscular plexus synaptosomal fraction was linked to the inhibition of adenylate cyclase activity, as demonstrated by a concentration-dependent, atropine-sensitive inhibition of the forskolin-stimulated enzyme in the presence of muscarinic agonists carbachol and oxotremorine. Based on the pharmacological observations presented here, the prejunctional muscarinic receptors in the axonal varicosities of deep muscular plexus are different from the postjunctional receptors present in the circular smooth muscle.


Lipid solubility of sedative-hypnotic drugs influences hypothermic and hypnotic responses of long-sleep and short-sleep mice.

The anesthetic potency of many agents, including alcohols, barbiturates and other sedative-hypnotic drugs, is influenced by lipid solubility. Previous studies from our laboratory, however, have demonstrated that genetic factors influence this relationship. We have reported that mouse lines selectively bred for differences in duration of ethanol-induced anesthesia, the long-sleep (LS) and short-sleep (SS) mice, differ in sleep-time response to water-soluble, but not lipid-soluble, sedative-hypnotic drugs. The studies described here sought to determine whether this same relationship exists for the hypothermic response produced by 17 sedative-hypnotic drugs in the LS and SS mice. Dose-response and time course relationships for hypothermic actions were determined and were compared with the dose-related anesthetic effects of the drugs. Hypothermic potencies increased along with lipid solubility for both the LS and SS mouse lines, but the rate of change differed for the two mouse lines. LS mice were more responsive to ethanol and other water-soluble drugs whereas the SS were more responsive to lipid-soluble drugs; significant correlations were obtained between lipid solubility (log P-octanol-water partition coefficient) and relative LS-SS responsiveness to both the hypothermic and hypnotic actions of the 17 test drugs. Thus, both hypnotic and hypothermic actions of sedative-hypnotic drugs are correlated with lipid solubility. Possible explanation for these correlations include greater LS central nervous system sensitivity to water-soluble drugs and LS-SS differences in distribution of lipid-soluble drugs.