Tropomyosin

Tropomyosin is a two-stranded alpha-helical, coiled coil protein found in actin-based cytoskeletons.
Tropomyosin and the actin skeleton.
All organisms contain organelles that provide physical integrity to their cells. These type of organelles are collectively known as the cytoskeleton, and one of the most ancient systems is based on filamentous polymers of the protein actin. A polymer of a second protein, tropomyosin, is an integral part of most actin filaments in animals.
Tropomyosins are a large family of integral components of actin filaments that play a critical role in regulating the function of actin filaments in both muscle and nonmuscle cells. These proteins consist of rod-shaped coiled-coil hetero- or homo-dimers that lie along the α-helical groove of most actin filaments. Interaction occurs along the length of the actin filament, with dimers aligning in a head-to-tail fashion.
Tropomyosins are often categorised into two groups, muscle tropomyosin isoforms and nonmuscle tropomyosin isoforms. Muscle tropomyosin isoforms are involved in regulating interactions between actin and myosin in the muscle sarcomere and play a pivotal role in regulated muscle contraction. Nonmuscle tropomyosin isoforms function in all cells, both muscle and nonmuscle cells, and are involved in a range of cellular pathways that control and regulate the cell's cytoskeleton and other key cellular functions.
The actin filament system that is involved in regulating these cellular pathways is more complex than the actin filament systems that regulates muscle contraction. The contractile system relies upon 4 actin filament isoforms and 5 tropomyosin isoforms, whereas the actin filament system of the cytoskeleton uses two actin filament isoforms and over 40 tropomyosin isoforms.
Isoforms and evolution.
In direct contrast of the 'one gene, one polypeptide' rule, we now know from a combination of genomic sequencing, such as the Human Genome Project and EST data of expressed proteins that many eukaryotes produce a range of proteins from a single gene. This plays a crucial role in the functionality of higher eukaryotes, with humans expressing more than 5 times as many different proteins (isoforms) through alternative splicing than they have genes. From a mechanistic point of view, it is much easier for an organism to expand on a current gene/protein family (creating protein isoforms) than it is to create an entirely new gene.
From an evolutionary point of view, tropomyosins in higher eukaryotes are notable in retaining all 4 of the potential genes produced by the dual genomic duplication event that took place in early eukaryotic evolution.
Genes and isoforms (isoform complexity).
Within mammals, four genes are responsible for generating more than 40 different tropomyosin isoforms. In terms of structure, the genes are very similar, suggesting that they arose through gene duplication of an ancestral gene. In humans, these genes are no longer linked and are widely dispersed. In humans, the α1-, β-, α3-, and α4-genes are formally known as TPM1, TPM2, TPM3, and TPM4 and are located at 15q22, 9p13, 1q22 and 19p13, respectively. An alternative nomenclature names the four genes (α,β,γ,δ).
Isoforms are defined as highly related gene products that perform, in essence, similar biological functions, with variations existing between the isoforms in terms of biological activity, regulatory properties, temporal and spatial expression, and/or the intercellular location. Isoforms are produced by two distinct mechanisms, gene duplication and alternative splicing. The former mechanism is a process by which multiple copies of a gene are generated through unequal crossing over, through tandem duplication, or by translocation. Alternative splicing is a mechanism wherein exons are either retained in the mRNA or targeted for removal in different combinations to create a diverse array of mRNAs from a single pre-mRNA.
Splicing.
A vast array of tropomyosin isoforms are generated by using a combination of different genes and alternative splicing. In mammals, regardless of the gene, transcription is initiated at the start of either exon 1a or exon 1b. Depending on which promoter and initial exon used, the tropomyosin isoforms can be categorized as either high-molecular-weight (HMW, 284 amino acids) or low-molecular-weight (LMW, 248). HMW isoforms express exon 1a and either 2a or 2b, while LMW isoforms express exon 1b. To date, all known tropomyosins contain exons 3-9. Alternative splicing can occur at exon 6, with the mutually exclusive choice of exon 6a or 6b. At the c-terminus, the transcript is spliced again at exon 9, with the choice of exon 9a, 9b, 9c, or 9d.
Evolution of isoform generation.
In terms of structure, the genes are very similar, suggesting that they arose through gene duplication of an ancestral gene. The most highly related genes are the α- and γ-genes, utilizing two promoters and differing only with the presence of the unique 2a exon in the α-gene. Although substantial differences between alternative exons from the same gene have been revealed by sequence comparison (1a and 1b, 6a and 6b, and the exon 9s), most exons are, however, highly conserved between the different genes. For example, exon 1a and 1b from the α-gene vary considerably in sequence; however, the sequence from exon 1a from the α-, β-, γ-, and δ-genes is highly conserved.
Due to the conservative nature of the genes, it is believed that the genes evolved from a common ancestral gene, giving rise to over 40 functionally distinct isoforms. The expression of these isoforms is highly regulated and variable throughout development. The diversity of tropomyosin expression, both in space and in time, provides the potential not only to regulate actin filament function but to create specialised actin filament populations.
Spatial sorting of tropomyosin isoforms.
Numerous reports detail that tropomyosin isoforms are sorted to different intracellular locations, often associating with actin filament populations that are involved in specific processes. Direct visualization of spatial segregation of isoforms was initially observed by Burgoyne and Norman and soon after by Lin and co-workers. They observed that specific isoforms were associated with distinct cellular structures. Using specific antibodies, they were able to identify the presence of both HMW and the LMW isoforms of the γ-gene in stress fibers; however, only LMW isoforms were detected in ruffling membranes.
These studies have been extended to a number of cell types with similar results. Extensive studies in neuronal cells, fibroblasts, skeletal muscle and osteoclast cells has further highlighted the complex association tropomyosin isoforms have with cellular structures. These studies have led to the realization that the regulation of isoform sorting is extremely complex and highly regulated.
Regulation of sorting.
Sorting of tropomyosin isoforms in discrete intracellular locations is developmentally regulated. Initial studies reported that the sorting of isoforms changed through development, where Tropomyosin 4 was initially localized to the growth cone of growing neurons, but in mature neurons it was relocated to the somatodendritic compartment. These observations have been supported by studies on different tropomyosin isoforms, showing how tropomyosin populations were relocated during neuron maturation. This evidence is supportive of the notion that tropomyosin isoforms are subject to temporal regulation.
Additional studies have identified the role the cell cycle plays in isoform sorting. A study that screened a range HMW products from the α- and β-genes and compared localisation with LMW products from the γ-gene found that the HMW and LMW products are mutually exclusively segregated during the early G1 phase of the cell cycle.
Mechanism of sorting.
While studies suggest that tropomyosin sorting may be influenced by the sorting of mRNAs, there is no absolute correlation between mRNA and protein location. In neurons, Tropomyosin 5NM1 mRNA was found to sort to the pole of the neuron elaborating an axon prior to morphological differentiation. The sorting of Tropomyosin 5NM1/2 mRNA to this location correlated with the expression of the Tropomyosin 5NM1/2 protein. In contrast, the mRNA encoding the Tropomyosin Br2 protein was excluded from the pole of the neuron.
The link between mRNA sorting and protein location has been tested in transgenic mice models. The models were created so that the coding regions of Tropomyosin 5NM1/2 and Tropomyosin 3 were expressed under the control of the β-actin promoter with the a β-actin 3'-untranslated region lacking targeting information. The study found that Tropomyosin 3, an isoform that is not normally expressed in neuronal cells, was broadly distributed throughout the neuron, while exogenous expression of the neuronal isoform Tropomyosin 5NM1/2 was found to sort to the growth cone of neurons as does the endogenous Tropomyosin 5NM1/2. As these two transgenes differ only in the tropomyosin coding region yet are localized in two distinct areas, the findings suggest that, in addition to mRNA sorting, the proteins themselves contain sorting information.
Studies suggest that tropomyosin isoform sorting may also be influenced by the actin isoform composition of microfilaments. In myoblasts, overexpression of γ-actin resulted in the down-regulation of β–actin and the removal of Tropomyosin 2 but not Tropomyosin 5 from stress fibers. It was later found that, when cells were exposed to cytochalasin D, a chemical that results in the disorganization of actin filaments, tropomyosin isoform sorting was disrupted. Upon the washing out of cytochalasin D, tropomyosin isoform sorting was re-established. This is suggestive of a strong relationship between the process of tropomyosin isoform sorting and the incorporation of tropomyosin isoforms into organized arrays of actin filaments. There is no evidence for active transport of tropomyosin isoforms to specific locations. Rather, it appears that sorting is the result of local assembly of preferred isoforms at specific intracellular site. The mechanisms that underlie tropomyosin isoform sorting appear to be inherently flexible and dynamic in nature.
Isoforms are not functionally redundant.
Many studies have led to the understanding that tropomyosins perform essential functions and are required in a diverse range of species from yeast, worms, and flies to complex mammals.
The essential role of tropomyosins was discovered in the Bretscher laboratory, where researchers found that, by eliminating the TPM1 gene of budding yeasts, growth rates were reduced, the presence of actin cables disappeared, defects in vesicular transport were observed, and mating of the yeast was poor. When a second yeast gene, TPM2, was deleted, no observable changes in the phenotype were recorded; however, when deleted in combination with TPM1, it resulted in lethality. This suggests that TPM1 and -2 genes have overlapping function; however, TPM2 cannot fully compensate of the loss of TPM1, indicating that some functions of TPM1 are unique. Similar results have been observed in flies, worms, amphibians, and mammals, confirming previous results and suggestive of tropomyosin's being involved in a wide range of cellular functions. However, the three co-expressed TMP1, 2, and 4 genes cannot compensate for deletion of the TPM3 gene in embryonic stem cells and preimplantation mouse embryos.
Results from gene knockout experiments can be ambiguous and must be carefully examined. In studies in which the deletion of a gene leads to lethality, it can at first appear that the gene product had a truly unique role. However, lethality can also be the result of the inability of the compromised cell to express other isoforms to rescue the phenotype because the required isoform is not naturally expressed in the cell.
Specific roles and functions.
Influencing binding of actin binding proteins to actin filaments.
The actin microfilament system is the fundamental cytoskeletal system involved in the development and maintenance of cell morphology. The ability of this system to readily respond to cellular cues and undergo structural re-organisation has led to the belief that this system regulates specific structural changes within different cellular regions.
Within humans, there are only six actin isoforms, and these isoforms are responsible for an array of unique and complex cellular structures and key cellular interactions. It is thought that the function and form of the actin cytoskeleton is controlled largely by actin-binding proteins (ABP) that are associated with the actin polymer. ABP are a group of proteins that bind to actin. Although tropomyosin is sometimes included as an ABP, it is not a true ABP. The tropomyosin dimer has very low affinity for an actin filament and forms no van der waals contacts with actin. It is only the formation of a tropomyosin polymer's winding around the actin filament that provides stability to the tropomyosin-actin filament interaction.
Many studies suggest that the binding of tropomyosin isoforms to an actin filament may influence the binding of other ABPs, which together alter the structure and convey specific properties and ultimately specific functions to an actin filament. This is demonstrated in neuroepithelial cells, where increased expression of Tropomyosin 5NM1 increases the recruitment of myosin IIB, a myosin motor protein to the growth cone area. However, the over-expression of Tropomyosin Br3 had the opposite effect, decreasing myosin activity in the same region.
In a pioneering study by Bernstein and Bamburg, it was observed that the actin-binding protein "actin depolymerisation factor (ADF)/cofilin", a factor that promotes actin filament depolymerisation, competed with tropomyosin for binding to the actin filament. The expression of Tropomyosin 5NM1 in neuronal cells eliminated ADF/cofilin from the growth cone region, leading to more stable actin filaments. However, the increased expression of Tropomyosin Br3 was observed to recruit ADF/cofilin to actin filaments bound to the Tropomyosin Br3 isoform within the lamellipodium, which led to the disassembly of actin filaments. This phenomenon, whereby a specific tropomyosin isoform directs specific interactions between actin-binding proteins, and the actin filament has been observed in a variety of model systems with a range of different binding proteins (reviewed in Gunning et al., 2008). These interactions, under the influence of tropomyosin isoforms, allow actin filaments to be involved in a diverse range of cellular functions.
Function in skeletal muscle contraction.
Skeletal muscle is composed of large, multi-nucleated cells (muscle fibers). Each muscle fiber is packed with longitudinal arrays of myofibrils. Myofibrils are composed of repeating protein structures or sarcomeres, the basic functional unit of skeletal muscle. The sarcomere is a highly structured protein array, consisting of interdigitating thick and thin filaments, where the thin filaments are tethered to a protein structure, the Z-line. The dynamic interaction between the thick and thin filaments results in muscle contraction.
Myosin belongs to a family of motor proteins, and the muscle isoforms of this family comprise the thick filament. The thin filament is made of the skeletal muscle isoforms of actin. Each myosin protein 'paddles' along the thin actin filament, repeatedly binding to myosin-binding sites along the actin filament, ratcheting and letting go. In effect, the thick filament moves or slides along the thin filament, resulting in muscle contraction. This process is known as the sliding filament model.
The binding of the myosin heads to the muscle actin is a highly regulated process. The thin filament is made of actin, tropomyosin, and troponin. The contraction of skeletal muscle is triggered by nerve impulses that in turn stimulate the release of Ca2+. The release of Ca2+ from the sarcoplasmic reticulum causes an increase in the concentration of Ca2+ in the cytosol. Calcium ions then bind to troponin, which is associated with tropomyosin. Binding causes changes in the shape of troponin and subsequently causes the tropomyosin isoform to shift its position on the actin filament. This shifting in position exposes the myosin-binding sites on the actin filament, allowing the myosin heads of the thick filament to bind to the thin filament.
Structural and biochemical studies suggest that the position of tropomyosin and troponin on the thin filament regulates the interactions between the myosin heads of the thick filament and the binding sites on the actin of the thin filament. X-ray diffraction and cryoelectron microscopy suggest that tropomyosin sterically blocks the access of myosin to the actin filament.
Although this model is well-established, it is unclear as to whether the movement of tropomyosin directly causes the myosin head to engage the actin filament. As such, an alternative model has emerged, whereby the movement of the tropomyosin in the filament functions as an allosteric switch that is modulated by activating myosin binding but does not function solely by regulating myosin binding.
Regulation of contraction in smooth muscle.
Smooth muscle is a type of non-striated muscle, and, unlike striated muscle, contraction of smooth muscle is not under conscious control. Smooth muscle may contract spontaneously or rhythmically and be induced by a number of physiochemical agents (hormones, drugs, neurotransmitters). Smooth muscle is found within the walls of various organs and tubes in the body such as the esophagus, stomach, intestines, bronchi, urethra, bladder, and blood vessels.
Although smooth muscles do not form regular arrays of thick and thin filaments like the sarcomeres of striated muscles, contraction is still due to the same sliding filament mechanism controlled by myosin crossbridges interacting with actin filaments. The thin filament of smooth muscle is made of actin, tropomyosin, caldesmon, and calmodulin. Within this type of muscle, caldesmon and calmodulin control the tropomyosin-mediated transition between on and off activity states. Caldesmon binds to actin, tropomyosin, calmodulin, and myosin, of which its interactions with actin are most important. The binding of caldesmon is strongly influenced by tropomyosin. Caldesmon is an inhibitor of actinomyosin ATPase and motility, and both actin binding and caldesmon inhibition are greatly enhanced in the presence of tropomyosin.
Smooth muscle contraction is initiated by the release of Ca2+. Ca2+ binds to and activates calmodulin, which then binds to caldesmon. This binding causes the caldesmon protein to disengage from the actin filament, exposing the myosin-binding sites on the actin filament. Myosin motor heads are phosphorylated by myosin light-chain kinase, allowing the myosin head to interact with the actin filament and cause contraction.
Role in cytoskeleton function.
The cytoskeleton is an elaborate network of filaments required for the proper functioning of a range of cellular processes including cell motility, cell division, intracellular trafficking, and the maintenance of cell shape. The cytoskeleton is composed of three distinct filament systems: microtubules, intermediate filaments, and microfilaments (also known as the actin cytoskeleton). It is the dynamic interactions between these filaments that provide cells with unique structures and functions.
A number of regulatory mechanisms, employing many actin-binding proteins, have evolved to control the dynamics of the actin filament system. It is believed that tropomyosins play a pivotal role in this regulatory system, influencing the associations the actin filament has with other ABPs. Together, these associations confer specific properties on the filament, allowing these structures to be involved in a wide range of cellular processes, but also to rapidly respond to cellular stimuli.
Role in diseases.
Cancer.
Many studies have shown that there are specific changes to the repertoire of tropomyosins expressed in cells that are undergoing cellular transformation. These highly reproducible results suggest that, during the process of cellular transformation, a process whereby a normal cell becomes malignant, there is a decreased synthesis of HMW tropomyosin isoforms. In the initial studies, transformation of rat embryo fibroblast cell line REF-52 and of normal rat kidney cells led to decreased synthesis of HMW tropomyosins. In both of these systems, the down regulation was contributed to a decrease in the mRNA levels. These early results suggested that tropomyosins played a critical role in facilitating certain processes that occurred during cell transformation, such as actin filament re-organisation and changes in cell shape. These studies have been reproduced in other laboratories and in other cell lines, with similar results (reviewed in Gunning et al., 2008).
Furthermore, studies have highlighted a link between tropomyosin isoform expression and the acquisition of metastatic properties. A study compared isoform expression between a low- and highly-metastatic Lewis lung carcinoma cell line. The study found that as cells become more metastatic, there is a marked decrease in the expression of HMW tropomyosin 2 protein and mRNA levels.
These results have been confirmed in primary tumors and human models. Studies in colon and bladder cancer found increased expression of the LMW tropomyosin "Tropomyosin 5NM1". The elevated expression of this isoform has also been seen in transformed rat fibroblasts, and it is thought that this isoform is required for the motility of highly metastatic melanoma. In addition, elevated expression of Tropomyosin 4 has been linked with lymph node metastasis in breast cancer.
All of these studies suggest that changes in the expression and complement of tropomyosin isoforms are integral to cancer and cancer progression. The consensus is that, in general, cancer cells become more reliant on LMW tropomyosins as HMW tropomyosins disappear with increasing malignancy. This discovery has led to the development of novel anti-tropomyosin compounds as potential anti-cancer agents.
Autoimmunity.
Tropomyosins have been implicated in the autoimmune disease ulcerative colitis, a disease of the colon that is characterised by ulcers or open sores. The link between this disease and tropomyosin was first acknowledged in a study that found blood serum taken from 95% of patients with ulcerative colitis contained antibodies that reacted positively to tropomyosin. Additional studies have confirmed these results, but also identify Tropomyosin 5 and Tropomyosin 1 as the primary tropomyosins involved in the pathogenesis of ulcerative colitis. Tropomyosin 5 has been related to the development of pouchitis in the ileal pouch following surgery for ulcerative colitis. The elevated number of IgG-producing cells in the colonic mucosa of ulcerative colitis patients is largely committed to producing IgG against Tropomyosin 5-related epitopes. Tropomyosin 5 is, therefore, capable of inducing a significant T-cell response. A physicochemical analysis of common structural motifs present in 109 human autoantigens revealed that tropomyosins have the highest number of such motifs, and thus a very high propensity to act as autoantigens.
In addition to the role tropomyosins play in ulcerative colitis, tropomyosin antibodies have also been reported in acute rheumatic fever
and the inflammatory disorder Behcet's syndrome. In both instances, it is unclear as to whether these antibodies play a direct role in the pathogenesis of these human conditions or reflect the high antigenicity of tropomyosins released from compromised cells.
Muscle diseases.
Nemaline myopathy is a muscle disease that is characterised by the presence of electron-dense rod bodies in skeletal muscle fibers. These electron-dense rod bodies are composed mainly of α-actinin and actin. The disorder is often clinically categorized into several groups, including mild (typical), intermediate, severe, and adult-onset; however, these distinctions are somewhat ambiguous, as the categories frequently overlap. Causative mutations have been detected in skeletal α-actinin, tropomyosin, nebulin, and troponin. Within humans, mutations in both the γ-Tropomyosin and β-Tropomyosin genes have been identified. No mutations in the α-Tropomyosin gene have been identified in this condition for humans.
Allergy.
'Shellfish' includes crustaceans and molluscs. Tropomyosin is the protein primarily responsible for shellfish allergy.
Tropomyosin also causes some cases of cockroach allergy.
Tools and technologies to study tropomyosins.
Antibodies.
Within the scientific community, there is great interest in tropomyosin isoforms, and, given the vast array of processes that this protein has been reported to be involved with, it is not surprising.
One way in which this protein and, what is more important, specific isoforms can be studied in detail is through the use of antibodies. These specific antibodies can be used in protein-blotting experiments and applied to cells or tissue sections and observed under a microscope. This allows researchers not only to determine the level or concentration of an isoform or a group of isoforms but also to identify the cellular location of a particular isoform and associations with other cellular structures or proteins.
At the present time, there are many commercially available antibodies; however, many of these antibodies are sold with minimal information regarding the antigen used to raise the antibody and, therefore, the isoform specificity, as such some research groups develop their own antibodies. Before these antibodies can be used, they must be extensively characterised, a process whereby the specificity of the antibody is examined to ensure that the antibody does not cross-react with other tropomyosins or other proteins.


Snakefish

Snakefish is a colloquial term used for a number of species of fish that resemble snakes. "Trachinocephalus myops", native to parts of both the Atlantic and Pacific oceans, is known by this name in particular.


Ascandra biscayae

Ascandra biscayae is a species of calcareous sponge from the Bay of Biscay.


Pluteus larva


2020 in paleomalacology

This list 2020 in paleomalacology is a list of new taxa of ammonites and other fossil cephalopods, as well as fossil gastropods, bivalves and other molluscs that are scheduled to be described during the year 2020, as well as other significant discoveries and events related to molluscan paleontology that are scheduled to occur in the year 2020.


Macroperipatus

Macroperipatus is a genus of Neotropical velvet worms in the Peripatidae family.
Species.
The genus contains the following species:
"Macroperipatus geayi" is considered a "nomen dubium" by Oliveira et al. 2012.


Spixiana

Spixiana is a biannual peer-reviewed scientific journal published by Verlag Dr. Friedrich Pfeil on behalf of the Bavarian State Collection of Zoology, covering research in zoology. "Spixiana" publishes original works in the fields of taxonomy, morphology, phylogeny, and zoogeography. It also publishes monographs in supplements.


Spitz (protein)

Spitz is a protein in fruit flies which is the major activator of Epidermal Growth Factor Receptor (EGFR).
Function.
Spitz is produced as a transmembrane protein in the endoplasmic reticulum. There it associates with a cargo receptor called "Star" and is trafficked to the Golgi. In the Golgi, Spitz is cleaved by a protease called "Rhomboid", which releases Spitz to be trafficked to the cell membrane and released out of the cell. From here it can bind EGFR on the surface of other cells, activating the receptor. Alternatively, Spitz can be bound and inactivated by Argos, inhibiting EGFR activation.
Structure.
Spitz is structurally similar to TGF-α.


Endosome

Endosomes are a collection of intracellular sorting organelles in eukaryotic cells. They are part of endocytic membrane transport pathway originating from the trans Golgi network. Molecules or ligands internalized from the plasma membrane can follow this pathway all the way to lysosomes for degradation or can be recycled back to the cell membrane in the endocytic cycle. Molecules are also transported to endosomes from the trans Golgi network and either continue to lysosomes or recycle back to the Golgi apparatus.
Endosomes can be classified as early, sorting, or late depending on their stage post internalization. Endosomes represent a major sorting compartment of the endomembrane system in cells.
Function.
Endosomes provide an environment for material to be sorted before it reaches the degradative lysosome. For example, low-density lipoprotein (LDL) is taken into the cell by binding to the LDL receptor at the cell surface. Upon reaching early endosomes, the LDL dissociates from the receptor, and the receptor can be recycled to the cell surface. The LDL remains in the endosome and is delivered to lysosomes for processing. LDL dissociates because of the slightly acidified environment of the early endosome, generated by a vacuolar membrane proton pump V-ATPase. On the other hand, EGF and the EGF receptor have a pH-resistant bond that persists until it is delivered to lysosomes for their degradation. The mannose 6-phosphate receptor carries ligands from the Golgi destined for the lysosome by a similar mechanism.
Types.
There are three different types of endosomes: "early endosomes", "late endosomes", and "recycling endosomes". They are distinguished by the time it takes for endocytosed material to reach them, and by markers such as rabs. They also have different morphology. Once endocytic vesicles have uncoated, they fuse with early endosomes. Early endosomes then "mature" into late endosomes before fusing with lysosomes.
Early endosomes mature in several ways to form late endosomes. They become increasingly acidic mainly through the activity of the V-ATPase. Many molecules that are recycled are removed by concentration in the tubular regions of early endosomes. Loss of these tubules to recycling pathways means that late endosomes mostly lack tubules. They also increase in size due to the homotypic fusion of early endosomes into larger vesicles. Molecules are also sorted into smaller vesicles that bud from the perimeter membrane into the endosome lumen, forming intraluminal vesicles (ILVs); this leads to the multivesicular appearance of late endosomes and so they are also known as multivesicular endosomes or multivesicular bodies (MVBs). Removal of recycling molecules such as transferrin receptors and mannose 6-phosphate receptors continues during this period, probably via budding of vesicles out of endosomes. Finally, the endosomes lose RAB5A and acquire RAB7A, making them competent for fusion with lysosomes.
Fusion of late endosomes with lysosomes has been shown to result in the formation of a 'hybrid' compartment, with characteristics intermediate of the two source compartments. For example, lysosomes are more dense than late endosomes, and the hybrids have an intermediate density. Lysosomes reform by recondensation to their normal, higher density. However, before this happens, more late endosomes may fuse with the hybrid.
Some material recycles to the plasma membrane directly from early endosomes, but most traffics via recycling endosomes.
More subtypes exist in specialized cells such as polarized cells and macrophages.
Phagosomes, macropinosomes and autophagosomes mature in a manner similar to endosomes, and may require fusion with normal endosomes for their maturation. Some intracellular pathogens subvert this process, for example, by preventing RAB7 acquisition.
Late endosomes/MVBs are sometimes called "endocytic carrier vesicles", but this term was used to describe vesicles that bud from early endosomes and fuse with late endosomes. However, several observations (described above) have now demonstrated that it is more likely that transport between these two compartments occurs by a maturation process, rather than vesicle transport.
Another unique identifying feature that differs between the various classes of endosomes is the lipid composition in their membranes. Phosphatidyl inositol phosphates (PIPs), one of the most important lipid signaling molecules, is found to differ as the endosomes mature from early to late. PI(4,5)P2 is present on plasma membranes, PI(3)P on early endosomes, PI(3,5)P2 on late endosomes and PI(4)P on the trans Golgi network. These lipids on the surface of the endosomes help in the specific recruitment of proteins from the cytosol, thus providing them an identity. The inter-conversion of these lipids is a result of the concerted action of phosphoinositide kinases and phosphatases that are strategically localized
Pathways.
There are three main compartments that have pathways that connect with endosomes. More pathways exist in specialized cells, such as melanocytes and polarized cells. For example, in epithelial cells, a special process called transcytosis allows some materials to enter one side of a cell and exit from the opposite side. Also, in some circumstances, late endosomes/MVBs fuse with the plasma membrane instead of with lysosomes, releasing the lumenal vesicles, now called exosomes, into the extracellular medium.
There is no consensus as to the exact nature of these pathways, and the sequential route taken by any given cargo in any given situation will tend to be a matter of debate.
Golgi to/from endosomes.
Vesicles pass between the Golgi and endosomes in both directions. The GGAs and AP-1 clathrin-coated vesicle adaptors make vesicles at the Golgi that carry molecules to endosomes. In the opposite direction, retromer generates vesicles at early endosomes that carry molecules back to the Golgi. Some studies describe a retrograde traffic pathway from late endosomes to the Golgi that is mediated by Rab9 and TIP47, but other studies dispute these findings. Molecules that follow these pathways include the mannose-6-phosphate receptors that carry lysosomal hydrolases to the endocytic pathway. The hydrolases are released in the acidic environment of endosomes, and the receptor is retrieved to the Golgi by retromer and Rab9.
Plasma membrane to/from early endosomes (via recycling endosomes).
Molecules are delivered from the plasma membrane to early endosomes in endocytic vesicles. Molecules can be internalized via receptor-mediated endocytosis in clathrin-coated vesicles. Other types of vesicles also form at the plasma membrane for this pathway, including ones utilising caveolin. Vesicles also transport molecules directly back to the plasma membrane, but many molecules are transported in vesicles that first fuse with recycling endosomes. Molecules following this recycling pathway are concentrated in the tubules of early endosomes. Molecules that follow these pathways include the receptors for LDL, epidermal growth factor (EGF), and the iron transport protein transferrin. Internalization of these receptors from the plasma membrane occurs by receptor-mediated endocytosis. LDL is released in endosomes because of the lower pH, and the receptor is recycled to the cell surface. Cholesterol is carried in the blood primarily by (LDL), and transport by the LDL receptor is the main mechanism by which cholesterol is taken up by cells. EGFRs are activated when EGF binds. The activated receptors stimulate their own internalization and degradation in lysosomes. EGF remains bound to the EGF receptor (EGFR) once it is endocytosed to endosomes. The activated EGFRs stimulate their own ubiquitination, and this directs them to lumenal vesicles (see below) and so they are not recycled to the plasma membrane. This removes the signaling portion of the protein from the cytosol and thus prevents continued stimulation of growth - in cells not stimulated with EGF, EGFRs have no EGF bound to them and therefore recycle if they reach endosomes. Transferrin also remains associated with its receptor, but, in the acidic endosome, iron is released from the transferrin, and then the iron-free transferrin (still bound to the transferrin receptor) returns from the early endosome to the cell surface, both directly and via recycling endosomes.
Late endosomes to lysosomes.
Transport from late endosomes to lysosomes is, in essence, unidirectional, since a late endosome is "consumed" in the process of fusing with a lysosome. Hence, soluble molecules in the lumen of endosomes will tend to end up in lysosomes, unless they are retrieved in some way. Transmembrane proteins can be delivered to the perimeter membrane or the lumen of lysosomes. Transmembrane proteins destined for the lysosome lumen are sorted into the vesicles that bud from the perimeter membrane into endosomes, a process that begins in early endosomes. When the endosome has matured into a late endosome/MVB and fuses with a lysosome, the vesicles in the lumen are delivered to the lysosome lumen. Proteins are marked for this pathway by the addition of ubiquitin. The endosomal sorting complexes required for transport (ESCRTs) recognise this ubiquitin and sort the protein into the forming lumenal vesicles. Molecules that follow these pathways include LDL and the lysosomal hydrolases delivered by mannose-6-phosphate receptors. These soluble molecules remain in endosomes and are therefore delivered to lysosomes. Also, the transmembrane EGFRs, bound to EGF, are tagged with ubiquitin and are therefore sorted into lumenal vesicles by the ESCRTs.


Calmasuchus

Calmasuchus is a genus of capitosaurian temnospondyl which lived during the middle Triassic (lower-middle Anisian age). Fossils of "Calmasuchus" have been recovered from the La Mora site of the Catalan basin in Barcelona of Spain. Identified from a partial skull roof and palate (holotype IPS-37401 (LM-83)), skull fragments (IPS-37401 (LM-63, LM-101, L and M1)) and complete hemi-mandible (IPS-12 42407 (LM-4)), it was named by Josep Fortuny, Àngel Galobart and Carles De Santisteban in 2011. The type species is "Calmasuchus acri".


Styraconyxidae

The Styraconyxidae are a family of tardigrades. The family was first described by Reinhardt Møbjerg Kristensen and Jeanne Renaud-Mornant in 1983.
Genera.
The family includes the following genera:


Moodyz

, also known as Mr. President, is one of Japan's largest adult video (AV) producers, featuring an extensive catalog of video titles.
Company information.
The Moodyz website, www.moodyz.com, went online in March 2000 and the company released its first videos in September 2000 starting with "Costume Princess" starring Maiko Yuki. One of the studios earliest stars was AV Idol Bunko Kanazawa who appeared in her own installment of the "Costume Princess" series in December 2000. In October 2002, the company's fortunes were boosted by signing An Nanba to an exclusive contract for Moodyz beginning with her debut video "Number.1!"
To mark their fifth anniversary in September 2005, the studio released the fantasy costume drama, "A Queendom of Eros", directed by KINGDOM and starring Chihiro Hara, Azusa Ayano, Jun Seto, Miki Komori, Shuri Himesaki and Yuna Takizawa. The work's elaborate sets and props made it one of the most expensive adult videos produced.
Moodyz is part of the large AV conglomerate Hokuto Corporation, which distributes Moodyz produced videos through retail sales and via mail order and digital download from its portal DMM.com. The Moodyz company manager and representative is Hitomi Niwa (丹羽ひとみ).
The company produces about 30-35 new releases and compilation videos per month and in September 2011 the DMM website listed more than 4000 DVD titles and over 1200 VHS tapes available under the Moodyz name.
Moodyz labels.
Moodyz produces various genres of videos under different labels. These range from softer glamour works to more hardcore scenes featuring bukkake, gokkun, anal sex, simulated rape, and interracial videos with black actors. Listed below are the labels used by Moodyz over the years.
Directors.
Directors who have worked extensively for Moodyz include:
Actresses.
Since its inception a number of prominent AV Idols have performed in Moodyz videos, including the following actresses:
Bonenkai and Moodyz Awards.
Beginning in December 2001, Moodyz has held an annual year-end bonenkai (忘年会) party for its actresses and staff. This gala event with participants in full evening dress started out modestly with 217 participants at the "Nepushisu" Restaurant in Tokyo on December 27, 2001. The 2002 party had 400 guests and by 2003 the number had risen to 700 and then to over 1000 for the 2005 event. Guests included actresses and staff, managers, friends, and the press. The party was also the venue for the annual Moodyz Awards celebrating the work of Moodyz actresses and directors.
Video series.
"Dream School" series.
The "Dream School" (ドリーム学園) or "Dream Gakuen" series is one of Moodyz oldest, best selling and most honored set of videos. The first volume was released in July 2001 when Moodyz had been in existence only a little over a year. "Dream School 2" and "Dream School 5" were the 2001 and 2002 winners of the Grand Prize Moodyz Award at the annual Moodyz Awards while "Dream School 7" won the 2003 award for most sales. In 2006 "Dream School 10" was the Moodyz entry in the AV Open contest where it took the 2nd Place Award. Again in 2007, Moodyz nominated another entry in the series, "Dream School 11", for the AV Open where it won the 3rd Place Award. The series has continued with "Dream School 12", released in June 2008.
The "Dream School" videos, all directed by Taikei Shimizu, have usually been major productions running 3 or 4 hours and having a large cast of actors and actresses. They are plotted as dramas taking place in a high-school setting and include a medley of porn genres including bukkake, gokkun, S&M, simulated rape, urolagnia, anal sex, orgies and even occasionally scat and bestiality. Several AV stars have appeared in the series including Bunko Kanazawa, Izumi Seika, Nao Oikawa, Chihiro Hasegawa, Mayura Hoshitsuki, Kokoro Amano, Akira Watase, Hotaru Akane and Chihiro Hara.
Other series.
This is a selected listing of the more than 200 thematic video series which have been produced under various Moodyz labels.


Cephalodella

Cephalodella is a genus of rotifers in the family Notommatidae.
"Cephalodella vittata" is a species endemic to Lake Baikal.


Asynchronous muscles

Asynchronous muscles are muscles in which there is no one-to-one relationship between electrical stimulation and mechanical contraction. These muscles are found in 75% of flying insects and have convergently evolved 7-10 times. Unlike their synchronous counterparts that contract once per neural signal, mechanical oscillations trigger force production in asynchronous muscles. Typically, the rate of mechanical contraction is an order of magnitude greater than electrical signals. Although they achieve greater force output and higher efficiency at high frequencies, they have limited applications because of their dependence on mechanical stretch.
Structure.
Molecular.
The exact molecular mechanisms used by asynchronous muscles are unknown, but it is believed that asynchronous muscles have no unique molecular structures as compared to their synchronous counterparts. A study investigating the asynchronous power muscles in bumblebees with X-ray diffraction videos showed that actin and myosin alone are sufficient for generating asynchronous behavior. This finding helps explain how asynchronous muscles independently evolved across insect taxa. More recent work using similar X-ray diffraction techniques in "Lethocerus" discovered that troponin bridges may play a critical role in stretch activation. As the muscle is stretched, these bridges move tropomyosin to reveal myosin-actin binding sites. The muscle can only produce force when these sites are activated.
Macroscopic.
Several changes to asynchronous muscles' macroscopic structure provide it with high force production and efficiency at high contraction frequencies. A critical adaptation is that asynchronous muscles maintain a tonic level of calcium instead of cycling calcium between contractions. This is evident in their long twitch duration. This is due to relatively spare sarcoplasmic reticulum. Because of requirements for high force production, myofiber and myofibril diameters are increased and the large amount of ATP necessary leads to high mitochondria densities. In "Cotinus mutabilis," asynchronous muscles are composed of 58.1% myofibril, 36.7% mitochondria, and 1.6% sarcoplasmic reticulum. In comparison, synchronous muscles in "Schistocerca americana" are composed of 65% myofibril, 23.5% mitochondria and 9.6% sarcoplasmic reticulum. Although synchronous muscle has a higher percentage of myofibril, the cross-sectional area of asynchronous myofibril is 3.7 µm2 as opposed to 0.82 µm2 in synchronous muscle for the previously described species.
Properties.
Asynchrony between electrical stimulation and muscle contraction.
The defining characteristic of asynchronous muscles is that there is no direct relationship between neural activation and muscle contraction. Typically, the number of muscle contractions is an order of magnitude greater than the number of action potentials sent to the muscle. Instead of directly controlling force generation, neural signals maintain [Ca2+] above a threshold for stretch-activation to occur. For asynchronous muscles, neural inputs are typically thought of as an "on-off" switch while mechanical stimulus leads to individual muscle contractions. However, recent studies using genetically engineered "Drosophila" revealed correlations between [Ca2+] and force production. Further work has shown bilateral calcium asymmetries in "Drosophila". These results indicate that there is some level of neural control beyond a simple "on" or "off" state.
Delayed stretch activation and delayed shortening deactivation.
Delayed stretch activation and delayed shortening deactivation allow asynchronous muscles to generate positive work under cyclic oscillations. When the muscle shortens, force drops and continues dropping even when the muscle length remains constant. Similarly, when the muscle lengthens, force increases and continues increasing after the muscle length remains constant. Because of these delays, the work produced by the muscle during shortening is greater than the work absorbed during lengthening, therefore producing positive work. In contrast, synchronous muscles absorb work under similar conditions. Both types of muscles consume ATP to drive force production and produce work.
Long twitch duration.
Long twitch duration is a functional consequence of the macroscopic properties of asynchronous muscle. Because asynchronous muscle can generate power without cycling calcium between contractions, the required rate of calcium regulation is significantly slower. In addition to the reduction in sarcoplasmic reticulum, relatively large myofibril diameters lead to increased diffusion times of Ca2+.Under isometric twitch experiments, asynchronous muscle in "Cotinus mutabilis" were found to have a twitch duration of 125 ms. In the same study, synchronous muscle in "Schistocerca americana" had a twitch duration of 40 ms. Therefore, asynchronous muscles respond slowly to neural stimulus. In the case of insect flight, electrical stimulation alone is too slow for muscle control. For "Cotinus mutabilis", the twitch duration is ten times as long as a wingbeat period.
Functional significance.
Resonant properties.
Asynchronous muscles produce work when they undergo mechanical oscillations provided there is sufficient Ca2+. This can be achieved in one of two ways. First, two antagonistic muscles can be configured with elastic structures such that the contraction of one muscle stretches the other, causing it to activate and vice versa. This configuration is found in the power muscles of flying insects. Second, a single asynchronous muscle can deform an elastic element which then stretches the muscle and causes the muscle to contract again. This setup is used by "Drosophila" to oscillate mechanosensory organs known as halteres. As long as neural stimulus turn the muscles "on," both systems will continue to oscillate. These systems can be thought of as resonant systems, for which the oscillation frequency is dependent on the elasticity, damping, and force applied to the system.
In a simplified case, this can be thought of as a linearly damped harmonic oscillator, for which the damped resonant frequency is
formula_1
The damping ratio, "ζ ," is dependent on c, the damping coefficient, m, the mass of the system, and k, the stiffness of the system as shown
formula_2
Power-control tradeoffs.
Asynchronous muscles sacrifice neural control and flexibility in exchange for high force production and efficiency. Given the long twitch duration of asynchronous muscle, neural control is too slow to power flight. For instance, the asynchronous muscles in "Cotinus mutabilis" contract ten times faster than expected given their twitch duration. Because these muscles rely on stretch activation, they must be configured such that they can be stretched by an external force. Furthermore, they are only useful when evolutionary pressures select for a muscle that reactively contracts against an imposed stretch. For example, in grasping tasks, it would be detrimental for antagonist muscles to spontaneously contract. Despite these disadvantages, asynchronous muscles are beneficial for high frequency oscillations. They are more efficient than synchronous muscles because they do not require costly calcium regulation. This allows for changes in their macroscopic structure for increased force production.
Applications.
Insect flight.
Miniaturization of insects leads to high wingbeat frequencies with midges reaching wingbeat frequencies of 1000 Hz. Because of their high force production and efficiency, asynchronous muscles are used to power insect flight in 75% of species. These insects possess two pairs of antagonistic asynchronous muscles that produce the majority of the power required for flight. These muscles are oriented such that as one pair contracts, it deforms the thorax and stretches the other pair, causing the second pair to contract. The same thoracic deformations oscillate the wings. By utilizing the elastic thorax to store and return energy during wing deceleration and subsequent acceleration, "Drosophila" is able to reduce energetic costs by 10%. This leads to a highly-efficient resonant system.
When wingbeat frequencies match the resonant frequency of the muscle-thorax system, flight is most efficient. In order to change wingbeat frequencies to avoid obstacles or generate more lift, insects use smaller "control" muscles such as the pleurosternal muscles to stiffen the thorax. From the equations in the Resonant properties section, it is clear that the natural frequency of the system increases with stiffness. Therefore, modulating the stiffness of the thorax leads to changes in wingbeat frequency.
Mammalian hearts.
Although heart muscles are not strictly asynchronous, they exhibit delayed stretch activation properties. As cardiac muscle is lengthened, there is an instantaneous rise in force caused by elastic, spring-like elements in the muscle. After a time delay, the muscle generates a second rise in force, which is caused by delayed stretch activation as seen in purely asynchronous muscle. This property benefits heart function by maintaining papillary muscle tension during the entire systolic cycle well after the electrical wave has passed. Through stretch activation, the heart can rapidly adapt to changes in heart rates.
Bioinspired robotics.
Because of challenges arising from miniaturization such as poor scaling of electric motors, researchers have turned towards insects to develop centimeter-scale flying robots. Although the actuators in the RoboBee are not asynchronous, they use elastic elements to transmit forces from its "muscles" (piezoelectric actuators) to flap the wings. Similar to flying insects, they exploit resonance to improve efficiency by 50%.


Charles Foster Batchelder

Charles Foster Batchelder (July 20, 1856 – November 7, 1954) was an American ornithologist and naturalist. He was an early member and President of the American Ornithologists' Union, and of the Nuttall Ornithological Club. He also edited "The Auk", and before it, the "Bulletin of the Nuttall Ornithological Club".
Biography.
Batchelder was born to Francis Lowell Batchelder and Susan Cabot Foster-Batchelder, and grew up next to Harvard University in Cambridge, Massachusetts. As a youngster, he developed a friendship with a number of future figures in ornithology, such as William Brewster, Henry Wetherbee Henshaw, Henry Augustus Purdie, Charles Johnson Maynard and William Earl Dodge Scott. Batchelder hardly knew his father, who had died when he was 18 months old. His sister also died at about the time he entered Harvard, having completed his studies at the local public high school.
In university, he came in contact with several leading thinkers, and had a particular admiration for Nathaniel S. Shaler and Henry L. Eustis. He graduated in 1882 with a degree in engineering science. During that time, the group of nature-inclined youth led by Brewster met at the latter's home, and these meetings would eventually evolve into the Nuttall Ornithological Club (officially in 1873), of which Batchelder became a member in 1877. Two years later he was elected vice-president before later becoming treasurer, a position he would keep for half a century.
After his graduation, he traveled and collected extensively in the Southwestern United States. He pursued a brief career in his original vocation upon his return in 1884, which only served to shake his frail health, a situation that was not helped by his subsequent travel to Europe, which lasted until 1887. His health would only be restored a few months before his return. Stuck in his oversea quarters, he worked on developing better labels and checklists.
He married Laura Poor Stone in February 1895. Of their four sons, only two survived to adulthood: Laurence and Charles Foster Jr. The family moved twice before settling at Peterborough, New Hampshire, on a farm with dilapidated lands that Batchelder used to make horticultural experiments, commenting: "there is no danger of my undertakings reaching such complete fruition that I shall be left with idle hands at the end." In the latter part of his life, the couple was renowned for their hospitality. Batchelder himself had a great capacity to analyze his fellow humans, and knew how to ask questions without antagonizing his interlocutor. He was also known for his dry wit and a habit of thinking aloud and abruptly changing subjects. In one instance he commented of another ornithologist, aged 85: "I think he is beginning to get old. I was very much tempted to give him a piece of my mind, but, under the circumstances, I think perhaps the best thing to do is to let matters slide." Batchelder's age at the time was ninety-five.
Batchelder was a founding member of the American Ornithologists' Union (AUO). He was always very keen to dispel the originally widespread impression that the AOU had originated in the Nuttall Ornithological Club. In fact, the Nuttall members were not very happy with how the Club was "rather unwillingly compelled" to transfer control of its "Bulletin", which was to become "The Auk", to the AOU. Despite these tensions, Batchelder served as associate editor of the new publication from 1888 to 1893, and vice-president, then President (1900–1905) of the AOU.
As editor, he was envied for his ability to obtain any amount of money necessary to maintain the publication. Within the Nuttall Club, however, he kept in the background. After the death of Brewster, who had been President almost continuously since the Club's inception, the meetings naturally transferred to Batchelder's house, but he refused to be elected even as honorary President. He also originated and hosted the annual New Year party, at least until 1949, when his increasing deafness and loss of eyesight made these too difficult. At the time, he was also handicapped following a hip fracture in 1943 that forced him to use crutches.
Although ornithology was his main interest, he also worked in botany and zoology, taking notes on, amongst other things, the activities of the hedgehogs living under his barn. He was a founding member of the New England Zoological Club in 1899, of which he published the proceedings, which Thomas Barbour characterized as "a modest but enduring monument". Although he had taken classes in the subject, he became a member of the New England Botanical Club (and thus began regular contact with established botanists) only in 1905. He would contribute much to the collection of herbarium specimens (over 5,000) from southern New Hampshire, but generally thought little of his achievements in the subject. He was elected a Fellow of the American Academy of Arts and Sciences in 1932.
Between 1934 and 1954 he was associated under one title or another with the Museum of Comparative Zoology at Harvard. He was a fellow of the American Association for the Advancement of Science. In his later life, he compiled a meticulous bibliography of C J. Maynard as a form of atonement for the harsh feelings he had developed against the man when Maynard had abandoned his functions as first editor of the "Bulletin of the Nuttall Club", and became quite distressed upon learning that he had missed an item.
Wendell Taber concluded his obituary with an account of his last encounter with the man:


ARF6

ADP-ribosylation factor 6 (ARF6) is a member of the ADP ribosylation factor family of GTP-binding proteins. ARF6 has a variety of cellular functions that are frequently involved in trafficking of biological membranes and transmembrane protein cargo. ARF6 has specifically been implicated in endocytosis of plasma membrane proteins and also, to a lesser extent, plasma membrane protein recycling.
Function.
This gene encodes a member of the human ARF gene family, which is part of the Ras superfamily. The ARF genes encode small guanine nucleotide-binding proteins that stimulate the ADP-ribosyltransferase activity of cholera toxin and play a role in vesicular trafficking and as activators of phospholipase D. The product of this gene is localized to the plasma membrane, and regulates vesicular trafficking, remodelling of membrane lipids, and signaling pathways that lead to actin remodeling. A pseudogene of this gene is located on chromosome 7.
ARF6 can interact with βarrestin upon receptor activation.
Interactions.
Arf6 has been shown to interact with:


Clathria

Clathria is a large genus of demosponges in the family Microcionidae.
Taxonomy.
"Clathria" was first formally named in Eduard Oscar Schmidt's 1862 "Die Spongien des adriatischen Meeres" ("The sponges of the Adriatic Sea"). The type species is "Clathria" ("Clathria") "compressa".
The genus is divided into several subgenera:
Species.
The following species are recognised in the genus "Clathria":
Subgenus Clathria (Axosuberites)


Foreyia

Foreyia is an extinct genus of coelacanth lobe-finned fish which lived during the Middle Triassic period in what is now Canton of Graubünden, Switzerland. It contains a single species F. maxkuhni.
Description and classification.
"F. maxkuhni" is an aberrant-looking member of the family Latimeriidae, with a proportionally enormous head, a curved, beak-like maxilla, an underbite, and a low, horn-like point on its otherwise dome-like head. Despite such a bizarre appearance, phylogenetic analyses squarely place "F. maxkuhni" as the sister taxon of "Ticinepomis", another latimeriid also found in the same strata. The two latimeriids share numerous anatomical traits with each other, strongly suggesting a close relation.
Naming.
The generic name honors the late Peter L. Forey for his contributions to the study of coelacanth fishes. The specific epithet honors Max Kuhn, who had been instrumental in preparing fossils from Monte San Giorgio for 12 years, including the holotype and paratype specimens of "F. maxkuhni".


Aegialodontia

Aegialodontia is a clade of extinct early mammals, close to the origin of Boreosphenida. The clade includes some of the oldest known tribosphenic taxa, until the discovery of "Tribactonodon" from the Berriasian Durlston Formation in 2001, "Aegialodon" from the Valanginian Wadhurst Clay Formation was the oldest taxon with the tooth form. The Aptian to Albian taxon "Kielantherium" from Mongolia, formerly a synonym of "Aegialodon", is also within the group, sister to "Aegialodon" within Aegialodontidae.


Bathymicrops multispinis

Bathymicrops multispinis is a species of aulopiformes in the family Ipnopidae.


Scavenger endothelial cell

The term scavenger endothelial cell (SEC) was initially coined to describe a specialized sub-group of endothelial cells in vertebrates that express a remarkably high blood clearance activity. The term SEC has now been adopted by several scientists.
In vertebrates.
The term "scavenger endothelial cell", first appearing in the scientific literature in 1999, was coined to distinguish a highly specialized subclass of endothelium in vertebrates that was observed to express a remarkably avid blood clearance activity. Blood borne waste macromolecules are known to be efficiently cleared from the blood circulation via scavenger receptors (stabilin-1, stabilin-2), the mannose receptor, and the Fc gamma receptor IIb2 of the mammalian liver sinusoidal endothelial cells.
Ligands that are efficiently cleared from blood by receptor-mediated endocytosis in liver sinusoidal endothelial cells in mammals, are also avidly cleared by liver sinusoidal endothelial cells in birds, reptiles and amphibia, as in mammals.
However, in bony fish (teleosts) the same macromolecules accumulate in either heart endocardium (e.g. in the Atlantic cod) or kidney sinusoids (e.g. in carp and salmonid fishes), but not in liver. Furthermore, in animal species of phylogenetically older vertebrate classes, i.e. cartilaginous (e.g. ray) and jawless (lamprey and hagfish) fishes, only specialized endothelial cells in gills exhibit the same active blood clearance capability as observed in liver sinusoidal endothelial cells in the four land-based vertebrate classes. In all these cases the clearance cells are not macrophages, but a special type of endothelial cells that have been named scavenger endothelial cells to distinguish them functionally from other types of vertebrate endothelia.
Recently is was shown that the endothelial cells in the caudal vein plexus of the embryonic zebrafish, also exhibit characteristic scavenger functions. These SECs, but not macrophages, avidly and preferentially clear colloidal waste and viral particles, as well as endogenous exosomes that are specifically internalized in a dynamin- and scavenger receptor dependent pathway to be targeted to lysosomes for degradation. Anionic nanoparticles are primarily taken up by these zebrafish SECs by the scavenger receptor, stabilin-2 in this process, which is also a signature scavenger receptor of mammalian liver sinusoidal endothelial cells.
Analogues in invertebrates.
Although true endothelial cells are only found in vertebrates, insect hemocytes and nephrocytes have similar scavenger functions to vertebrate macrophages and SECs, sharing the task of waste clearance and defense against foreign intruders. Colloidal vital dyes, such as ammonia carmine and trypan blue, are rapidly and preferentially taken up by insect pericardial and garland nephrocytes. Nephrocytes, but not hemocytes of the common blow fly (Calliphora) avidly endocytose and degrade ligands that are also recognized by stabilin-2 of mammalian scavenger endothelial cells. In "Drosophila", nephrocytes remove microbiota-derived peptidoglycan from systemic circulation to maintain immune homeostasis. Nephrocytes that strongly resemble insect nephrocytes are found in several other major invertebrate classes.
The dual-cell principle of waste clearance.
It appears that the major scavenger cell systems of vertebrates and invertebrates are based on a dual-cell principle of waste clearance. In vertebrates, distinct populations of scavenger endothelial cells represent the professional pinocyte, clearing the blood of a wide range of soluble macromolecules and small particles (<200 nm) by clathrin-mediated endocytosis, while the macrophage represents the professional phagocyte, eliminating larger particles (>200 nm).


Stellate veins

The stellate veins are veins that lie beneath the fibrous tunic of the kidney. They are stellate in arrangement and are derived from the capillary network, into which the terminal branches of the interlobular arteries break up. These join to form the interlobular veins, which pass inward between the rays.


Mary E. Rice

Mary Esther Rice (August 3, 1926 – April 29, 2021) was an American invertebrate zoologist specializing in systematics, evolution and the development of marine invertebrates. She worked at the Smithsonian Institution as a curator, educator, research advisor, and administrator from 1966 until her retirement in 2002. She is known for her work on the life histories of Sipuncula, as well as for serving as the first director of the Smithsonian Marine Station at Fort Pierce.
Biography and education.
Mary E. Rice was born in Washington, D.C. on August 3, 1926 to Daniel Gibbons Rice and Florence Catherine Pyles Rice. She grew up on a farm in southern Maryland and attended school in Oxon Hill.
In 1947, Rice graduated from Drew University in Madison, New Jersey with an A.B. in Biology. She first attended graduate school at Oberlin College in Ohio, earning an M.A. in Zoology in 1949. Rice then returned to New Jersey to teach Biology at Drew.
In 1950, Rice began working as a research associate at Columbia University's Department of Radiology. She left Columbia in 1953 to accept an appointment as a general physiologist at the National Institutes of Health's National Institute of Arthritis and Metabolic Diseases. In 1955, she advanced to the position of biologist at the National Cancer Institute.
Rice decided in 1961 to pursue a PhD in Zoology at the University of Washington, Seattle, studying the development and phylogeny of sipunculan worms.
Upon completion of her PhD in 1966, Rice was appointed Curator and Research Zoologist in the National Museum of Natural History's Department of Invertebrate Zoology. In charge of curating the sipunculan and echiuran collections, Rice devoted her career to the study of Sipuncula, focusing her research on their evolution and development.
In 1981, Rice became Director of the Smithsonian Marine Station at Fort Pierce, Florida. When she retired in 2002 after thirty-six years at the Smithsonian Institution, Rice was named Senior Research Scientist Emeritus at the Smithsonian Marine Station. She continues researching sipunculan worms in her retirement.
Administrative career.
As the founding director of the Smithsonian Institution Marine Station at Link Port, Mary E. Rice guided its growth into a major research center by developing research laboratories and programs and securing support for research fellowships. In 1999, the facility was moved to an eight-acre campus at Seaway Drive. The expanded facility was renamed the Smithsonian Marine Station at Fort Pierce.
Educational career.
Over the course of her career, Mary E. Rice was affiliated with several universities. She has served as an Adjunct Associate Professor at the University of Miami (1968–74) and the George Washington University (1970–75). She was also an Affiliate Professor of Biology at George Mason University (1994-2000) and a member of the Graduate Faculty at the Florida Institute of Technology (1996-2000). Rice has mentored many students, including those developing the Evo-Devo approach, and has advised over thirty postdoctoral fellows and eight short-term graduate fellows. She has served as a committee member for thirteen doctoral candidates.
Rice was also responsible for the creation of the Smithsonian Marine Ecosystem Exhibit. Working with nearby officials, she developed the St. Lucie County Marine Center, a county-run facility where the exhibit is housed. Located opposite the Smithsonian Marine Station, the focal point of the exhibit is an enormous 3,300-gallon coral reef aquarium that was previously displayed at the National Museum of Natural History in Washington.
Publications.
Rice's first publication, “The influence of glycolytic factors on the potassium and sodium content of Saccaromyces cerevisiae,” was co-written in 1951 with G. T. Scott and M. A. Jacobson. It concerned the physiological effects of sodium on yeast.
Rice's first sipunculan paper appeared in 1967, and was entitled, “A comparative study of the development of Phascolosoma agassizii, Golfingia pligettensis, and Themiste pyroides with a discussion of developmental patterns in the Sipuncula,”.
Rice has written or co-written over eighty papers in total, most on the classification, development and evolution of the genus Sipuncula.
Honors and awards.
Rice has served as President of the American Society of Zoologists and the American Microscopical Society. She was also an elected fellow of the American Association for the Advancement of Science. In 2019 she was awarded the A.O. Kovalevsky Medal for extraordinary achievements in evolutionary developmental biology and comparative zoology by the St. Petersburg Society of Naturalists.


Oroperipatus

Oroperipatus is a genus of Neotropical velvet worms in the family Peripatidae.
Species.
The genus contains the following species:
"Oroperipatus goudoti" , "Oroperipatus quitensis" , and "Oroperipatus peruanus" are considered "nomina dubia" by Oliveira "et al". 2012.


Muricellisis

Muricellisis is a genus of deep-sea bamboo coral in the family Isididae, containing two species:


Beetle larva


Hyperlioceras

Hyperlioceras is an extinct genus of cephalopod included in the ammonitid family Graphoceratidae that lived during the Bajocian stage of the Middle Jurassic. The type species is "Hyperlioceras discites" (Waagen, 18567)
Morphology.
The shell of "Hyperlioceras" is very compressed and involute, with a tall persistent keel and a deep umbilicus.
Biostratigraphic significance.
The International Commission on Stratigraphy (ICS) has defined the base of the Bajocian Stage of the Jurassic as the lowest occurrence of the genus "Hyperlioceras", at 170.3 ± 1.4 million years ago, which defines base of the "Hyperlioceras discites" Zone. This point also marks the end of the preceding Aalenian Stage. The upper boundary of the Bajocian is indicated by the lowest occurrence of the ammonite "Parkinsonia (G.) convergens", at about 167.7 Ma, which defines base of "Zigzagiceras zigzag" Zone.
Distribution.
Luxembourg, Saudi Arabia, Spain and the United Kingdom.


Thyestes (fish)

Thyestes is an extinct genus of osteostracan agnathan vertebrate of Europe whose fossils are found in Middle to Late Ludlow-aged marine strata of Late Silurian Europe. Individuals of "Thyestes" superficially resembled "Cephalaspis", but were more closely related to "Auchenaspis" and "Tremataspis".


Filograna

Filograna is a genus of marine polychaete worms in the family Serpulidae.
Species.
The following species are classified in this genus:
Synonyms.
The following genera are synonyms of "Filograna":


Superior tarsal muscle

The superior tarsal muscle is a smooth muscle adjoining the levator palpebrae superioris muscle that helps to raise the upper eyelid.
Structure.
The superior tarsal muscle originates on the underside of levator palpebrae superioris and inserts on the superior tarsal plate of the eyelid.
Nerve supply.
The superior tarsal muscle receives its innervation from the sympathetic nervous system. Postganglionic sympathetic fibers originate in the superior cervical ganglion, and travel via the internal carotid plexus, where small branches communicate with the oculomotor nerve as it passes through the cavernous sinus. The sympathetic fibres continue to the superior division of the oculomotor nerve, where they enter the superior tarsal muscle on its inferior aspect.
Function.
Its role is not fully clear, but may be an accessory muscle to raise the upper eyelid.
Clinical significance.
Damage to some elements of the sympathetic nervous system can inhibit this muscle, causing a drooping eyelid (partial ptosis). This is seen in Horner's syndrome. The ptosis seen in Horner's syndrome is of a lesser degree than is seen with an oculomotor nerve palsy.
History.
The muscle derives its name , typically used for drying.
The term "Müller's muscle" is sometimes used as a synonym. However, the same term is also used for the circular fibres of the ciliary muscle, and also for the orbitalis muscle that covers the inferior orbital fissure. Given the possible confusion, the use of the term "Müller's muscle" should be discouraged unless the context removes any ambiguity.
See also.
Heinrich Müller (physiologist)


Cardiodictyon

Cardiodictyon is a genus of lobopodian known from the Chengjiang Lagerstätten. It has ~25 pairs of legs, each associated with a pair of dorsal plates.
Each leg terminates in a pair of claws. It may or may not have a head shield, though it certainly has an expanded head.


Henry H. Bauer

Henry Hermann Bauer (born November 16, 1931) is an emeritus professor of chemistry and science studies at Virginia Polytechnic Institute and State University (Virginia Tech). He is the author of several books and articles on fringe science, arguing in favor of the existence of the Loch Ness Monster and against Immanuel Velikovsky, and is an AIDS denialist. Following his retirement in 1999, he was editor-in-chief of the "Journal of Scientific Exploration", a fringe science publication. Bauer also served as dean of the College of Arts and Sciences at Virginia Tech, generating controversy by criticising affirmative action.
Life and work.
Henry Bauer was born in Austria. As the Nazis came to power in German-speaking Europe, Bauer and his family emigrated to Australia. He attended Sydney Boys High School from 1943-44. Bauer received his Ph.D. from the University of Sydney in Australia in 1956. He conducted post-doctoral research at the University of Michigan, then taught at Sydney and in Michigan. In 1966, he moved to a faculty position at the University of Kentucky. Bauer became dean of the School of Arts and Sciences at Virginia Polytechnic Institute and State University (Virginia Tech) in 1978, a position he held until 1986. Bauer was a professor of science studies and chemistry at Virginia Tech until his retirement in 1999. Bauer has had short-term teaching assignments at the University of Southampton and with a program of the Japan Society for the Promotion of Science: at the University of Kyoto and in 1974 at Sophia University and Rikagaku Kenkyusho.
Although trained as a chemist, Bauer's interests shifted in the late 1960s from electrochemistry to science studies, an interdisciplinary mix of history, philosophy, and sociology of science. His special interest is in what he calls "scientific unorthodoxies", like the Loch Ness Monster, Immanuel Velikovsky, and other topics. After retiring from Virginia Tech, Bauer became the editor of the "Journal of Scientific Exploration", a publication devoted to fringe and non-mainstream science. He also wrote several books and maintains a website claiming that HIV is not the necessary and sufficient cause of AIDS (a position without scientific support that is known as AIDS denialism).
From chemistry to science studies.
Bauer was trained as an electrochemist and reported his research in numerous publications during the 1950s and 60s. From the 1970s, although he remained a professor of chemistry in title, Bauer researched fringe science and pseudoscience topics. At Virginia Tech, Bauer was a founding member of a program for science studies. Bauer's book on science studies, "Scientific Literacy and the Myth of the Scientific Method", was reviewed in "Science" and "Nature". In his review in "Public Understanding of Science", John Ziman called Bauer "a stalwart veteran" of science studies.
During his investigations of what constitutes pseudoscience, Bauer came to believe in the existence of the Loch Ness Monster, UFOs and other "scientific unorthodoxies". He compares the lack of acceptance of pseudoscientific beliefs by the scientific community to the persecution his family suffered at the hands of the Nazis, stating, "I guess I am kind of naturally contrary...I think you can make a pretty good case that it's not worth just accepting whatever is the standard."
Loch Ness Monster.
Bauer developed an interest in the Loch Ness Monster and based his belief in the Monster's existence on a film made by prominent "Nessie" enthusiast Tim Dinsdale. The film purportedly shows an object, commonly thought to be a boat, moving in the Scottish lake. In the 1980s, Bauer researched and wrote a book on the Loch Ness Monster and the popular fascination with it. "The Enigma of Loch Ness" was reviewed favorably in "Isis". Bauer maintains a website arguing that there is strong evidence for the existence of the monster, which he says the media have conspired to trivialize and sensationalize. During his tenure as professor at Virginia Tech, Bauer took over twenty trips to Loch Ness, searching for the monster.
In a news interview, Bauer commented on his belief in the Loch Ness Monster and how it has influenced his career: "I've been quite open about it...if I had been a biologist instead of a chemist, I couldn't have gotten away with it. People could smile and say, 'Well, he's got his hobbyhorse.'"
Immanuel Velikovsky.
In his book, "Beyond Velikovsky: The History of a Public Controversy", Henry Bauer criticizes the research of Immanuel Velikovsky, author of the pseudoscientific and pseudohistoric "New York Times" bestseller "Worlds in Collision" (1950). "Time" magazine refers to Bauer's book as "the definitive treatise debunking Immanuel Velikovsky." Bauer's book on Velikovsky was reviewed in "Science", "Nature", "ISIS", and "Journal for the History of Astronomy".
Positions.
Affirmative action and diversity programs.
Bauer says he left the Dean’s office at Virginia Tech "when political correctness arrived" in the 1980s. Bauer joined the National Association of Scholars, a politically conservative advocacy group opposing affirmative action, and started a newsletter for the group's Virginia branch. In "The Virginia Scholar," Bauer argues that the implementation of diversity programs led to a decline in academic standards. He characterizes such programs as promoting "feminoid sexists calling men sexist" and "racist black fanatics calling others racist."
Bauer opposed the formation of a police "Sensitive Crime Unit" meant to deal with sexual assault and hate crimes at Virginia Tech, suggesting that these issues were not a serious problem on campus and did not merit special attention. Bauer called the police unit a threat to free speech. He criticized Virginia Tech’s creation of a new administrative position for multicultural affairs in response to racial incidents at the university in the mid-1990s as a wasteful allocation of resources. Bauer found fault with Virginia Tech’s policy of excusing student absences for attending religious or ethnic observances. As black enrollment at Virginia Tech declined during the 1990s, Bauer stated that the University was already doing too much ("pulling out all the stops") to attract minority students, and should instead concentrate on raising academic standards.
Homosexuality.
Bauer also drew criticism for his comments on homosexuality. In his pseudonymously-written memoir "To Rise Above Principle: The Memoirs of an Unreconstructed Dean", Bauer writes, "I regard homosexuality as an aberration or illness, not as an ‘equally valid life-style’ or whatever the current euphemism is." In his book, Bauer attributes the perceived problem of homosexuality to genetic, hereditary, and environmental factors, and suggests that the free speech and other civil rights of homosexuals should be withdrawn to prevent what Bauer views as the negative effects of homosexuality from spreading. Bauer has since stated he no longer holds this view, saying he had been "wrong" about the issue and had, in particular, mistakenly relied on the "naturalistic" fallacy that reduced culture and ethics to biology. AIDSTruth.org, an AIDS information resource, notes Bauer posted the statement one day after an account of his views appeared on their website.
AIDS.
Several years after retiring from Virginia Tech, Bauer began to assert that there are "substantive grounds for doubting that HIV is the necessary and sufficient cause of AIDS and that antiretroviral treatment is unambiguously beneficial." In his 2007 book, "The Origins, Persistence, and Failings of HIV/AIDS Theory", Bauer questions whether HIV exists, claiming that HIV tests are not accurate and that AIDS death statistics are exaggerated by mainstream media, scientists and pharmaceutical companies.
Bauer’s beliefs on HIV/AIDS are rejected by the mainstream scientific community, based upon the substantial body of research confirming that HIV exists, is infectious, causes AIDS, and that HIV tests are accurate.


Yolk plug

Yolk plug is the remaining patch of endodermal cells that is created during the formation of the dorsal lip of the blastopore in the amphibian. It is a patch of large endodermal cells which remains exposed on the vegetal surface of the blastula that will eventually be internalized by epiboly.


Experimental and Applied Acarology

Experimental and Applied Acarology is a monthly peer-reviewed scientific journal covering all aspects of acarology. It was established in 1985 and is published by Springer Science+Business Media. The editor-in-chief is Maurice W. Sabelis (University of Amsterdam).
Abstracting and indexing.
The journal is abstracted and indexed in:


Licornia peltata

Licornia peltata is a species of gymnolaematan bryozoans (sea mats) first described from the Queensland coast. Originally placed in "Scrupocellaria", it has now been accepted within "Licornia".


Lochness (song)


Rhabdoderma

Rhabdoderma is an extinct genus of coelacanth fish in the class Sarcopterygii. It lived in the Carboniferous and Early Triassic, and its fossils have been found in Europe, Madagascar and North America.


Squamous part of the frontal bone

There are two surfaces of the squamous part of the frontal bone: the external surface, and the internal surface.
External surface.
The external surface is convex and usually exhibits, in the lower part of the middle line, the remains of the frontal suture; in infancy this suture divides the frontal bone into two and later fuses. A condition where fusion has not taken place, may persist throughout life and is referred to as a "metopic suture".
On either side of this suture, about 3 cm. above the supraorbital margin, is a rounded elevation, the frontal eminence (tuber frontale).
These eminences vary in size in different individuals, are occasionally unsymmetrical, and are especially prominent in young skulls; the surface of the bone above them is smooth, and covered by the galea aponeurotica.
Below the frontal eminences, and separated from them by a shallow groove, are two arched elevations, the superciliary arches; these are prominent medially, and are joined to one another by a smooth elevation named the glabella. They are larger in the male than in the female, and their degree of prominence depends to some extent on the size of the frontal air sinuses; prominent ridges are, however, occasionally associated with small air sinuses.
Beneath each superciliary arch is a curved and prominent margin, the supraorbital margin, which forms the upper boundary of the base of the orbit, and separates the squamous part from the orbital portion of the bone.
The lateral part of this margin is sharp and prominent, affording to the eye, in that situation, considerable protection from injury; the medial part is rounded.
At the junction of its medial and intermediate thirds is a notch, sometimes converted into a foramen, the supraorbital notch or foramen, which transmits the supraorbital vessels and nerve.
A small aperture in the upper part of the notch transmits a vein from the diploë to join the supraorbital vein.
The supraorbital margin ends laterally in the zygomatic process, which is strong and prominent, and articulates with the zygomatic bone.
Running upward and backward from this process is a well-marked line, the temporal line, which divides into the upper and lower temporal lines, continuous, in the articulated skull, with the corresponding lines on the parietal bone.
The area below and behind the temporal line forms the anterior part of the temporal fossa, and gives origin to the temporalis muscle.
Between the supraorbital margins the squamous part projects downward to a level below that of the zygomatic processes. It meets the nasal bone where it presents a rough, uneven serrated notch known as the nasal notch, and this articulates on either side of the middle line with the nasal bone, and laterally with the frontal process of the maxilla and with the lacrimal. This part is sometimes called the nasal part of frontal bone.
The term nasion is applied to the middle of the frontonasal suture. From the center of the notch the nasal process projects downward and forward beneath the nasal bones and frontal processes of the maxillae, and supports the bridge of the nose.
The nasal process ends below in a sharp spine, and on either side of this is a small grooved surface which enters into the formation of the roof of the corresponding nasal cavity.
The spine forms part of the septum of the nose, articulating in front with the crest of the nasal bones and behind with the perpendicular plate of the ethmoid.
Internal surface.
The internal surface of the squamous part is concave and presents in the upper part of the middle line a vertical groove, the sagittal sulcus, the edges of which unite below to form a ridge, the frontal crest; the sulcus lodges the superior sagittal sinus, while its margins and the crest afford attachment to the falx cerebri.
The crest ends below in a small notch which is converted into a foramen, the foramen cecum, by articulation with the ethmoid.
This foramen varies in size in different subjects, and is frequently impervious; when open, it transmits a vein from the nose to the superior sagittal sinus.
On either side of the middle line the bone presents depressions for the convolutions of the brain, and numerous small furrows for the anterior branches of the middle meningeal vessels.
Several small, irregular fossæ may also be seen on either side of the sagittal sulcus, for the reception of the arachnoid granulations.


Chloeia

Chloeia is a genus of marine polychaete worms.
Members of this genus are morphologically characterized by an elliptical body composed of certain number of segments, depending on the species, with external gills situated on both lateral sides of the back, each segment has a pair of them. Their number and repartition also depends on the species.
Lateral sides of the body are cover with fin, sharp and venomous whitish calcareous bristles or setae.
Adults of this genus are often colorful especially on the dorsum.
The locomotion is done by parapodia, every segment possesses a pair in bilateral position, from which are activated "paddles", one dorsally called notopodia and another one ventrally called neropodia.
Chloeia's distribution is circumtropical. Most of the known species are found in the Indian and Pacific Ocean so only few species lives in the Atlantic Ocean.
List of species.
There are 28 species in the genus "Chloeia":


Efferent arteriole

The efferent arterioles are blood vessels that are part of the urinary tract of organisms. Efferent (from Latin ex + ferre) means "outgoing", in this case meaning carrying blood out away from the glomerulus. The efferent arterioles form a convergence of the capillaries of the glomerulus, and carry blood away from the glomerulus that has already been filtered. They play an important role in maintaining the glomerular filtration rate despite fluctuations in blood pressure.
In the mammalian kidney they follow two markedly different courses, depending on the location of the glomeruli from which they arise.
In the mammalian kidney about 15% of glomeruli lie close to the boundary between the renal cortex and renal medulla and are known as juxtamedullary glomeruli. The rest are simply undifferentiated cortical glomeruli.
In undifferentiated cortical glomeruli.
The efferent arterioles of the undifferentiated cortical glomeruli are the most complex. Promptly on leaving the glomerulus they break up into capillaries and become part of a rich plexus of vessels surrounding the cortical portions of the renal tubules.
In juxtamedullary glomeruli.
The efferent arterioles of the juxtamedullary glomeruli are much different. They do break up, but they form bundles of vessels (arteriolae recti) that cross the outer zone of the medulla to perfuse the inner zone.
Vessels returning from the inner medulla (venulae recti) intersperse themselves in a highly regular fashion among the descending arteriolae recti to form a well-organized rete mirabile.
This rete is responsible for the osmotic isolation of the inner medulla from the rest of the kidney and so permits the excretion of a hypertonic urine when circumstances require. Since the rete also isolates the inner medulla from gaseous exchange, any metabolism in this area is anaerobic, and red cells, which would serve no purpose there, are ordinarily shunted from the arteriolae recti by an unknown mechanism into the capillary plexus surrounding the tubules of the outer zone of the medulla.
Blood in this plexus and returning from the inner medulla finds its way to the renal vein and the general circulation by pathways similar to those providing drainage for the rest of the cortex.
Regulation of glomerular filtration rate.
When angiotensin II levels are increased due to activation of the renin–angiotensin–aldosterone system, most of the arteries in the body experience vasoconstriction, in order to maintain adequate blood pressure. However, this reduces blood flow to the kidneys. To compensate, the efferent arterioles constrict to a greater degree than the other arteries, in response to increased levels of angiotensin II. Pressure in glomerular capillaries is therefore maintained and glomerular filtration rate remains adequate. However, in states of where angiotensin II is very high for a prolonged period of time, the colloid oncotic pressure of the capillaries will increase, counteracting the increased hydrostatic pressure from the efferent constriction. This will decrease the glomerular filtration rate, depending on the level of oncotic increase in the capillaries, resulting in a decreased filtration fraction.


Johannes Thiele (zoologist)

Karl Hermann Johannes Thiele (1 October 1860 – 5 August 1935) was a German zoologist specialized in malacology. Thiele was born in Goldap, East Prussia. His "Handbuch der systematischen Weichtierkunde" (English edition published by the Smithsonian under the title "Handbook of Systematic Malacology") is a standard work. From 1904 until his retirement in 1925 he was the curator of the malacological collection at the Museum für Naturkunde (Museum of Natural History) in Berlin.
Thiele described more than 1.500 new species of molluscs; until today their types are deposited with the Museum of Natural History in Berlin. Especially important are his works on the Mollusca of the First German Antarctica Expedition and of the German Deep Sea Expedition aboard the vessel Valdivia.
Thiele's classification of Gastropoda has been in use up to the past decade. It modified an earlier concept of Henri Milne-Edwards (1848) with three subclasses: Prosobranchia, Opisthobranchia and Pulmonata. Thiele's classification was based on overall similarity between the species. This classification has been modified over the years, one recent example being the classification of Ponder & Lindberg, 1997, based on phylogenetic arguments. He became the first to describe "Geodia exigua" in 1898.


Parenchyma

Parenchyma () is the bulk of functional substance in an animal organ or structure such as a tumour. In zoology it is the name for the tissue that fills the interior of flatworms.
Etymology.
The term "parenchyma" is New Latin from the Greek word παρέγχυμα "parenchyma" 'visceral flesh' from παρεγχεῖν "parenkhein" 'to pour in' from παρα- "para-" 'beside' + ἐν "en-" 'in' + χεῖν "khein" 'to pour'.
Originally, Erasistratus and other anatomists used it to refer to certain human tissues. Later, it was also applied to plant tissues by Nehemiah Grew.
Structure.
The parenchyma is the "functional" parts of an organ, or of a structure such as a tumour in the body. This is in contrast to the stroma, which refers to the "structural" tissue of organs or of structures, namely, the connective tissues.
Brain.
The brain parenchyma refers to the functional tissue in the brain that is made up of the two types of brain cell, neurons and glial cells. Damage or trauma to the brain parenchyma often results in a loss of cognitive ability or even death. Bleeding into the parenchyma is known as intraparenchymal hemorrhage.
Lungs.
Lung parenchyma is the substance of the lung outside of the circulatory system that is involved with gas exchange and includes the pulmonary alveoli and respiratory bronchioles,
though some authors include only the alveoli.
Liver.
The liver parenchyma is the functional tissue of the organ made up of around 80% of the liver volume as hepatocytes. The other main type of liver cells are non-parenchymal. Non-parenchymal cells constitute 40% of the total number of liver cells but only 6.5% of its volume.
Kidneys.
The renal parenchyma (of the kidney) is divided into two major structures: the outer renal cortex and the inner renal medulla. Grossly, these structures take the shape of 7 to 18 cone-shaped renal lobes, each containing renal cortex surrounding a portion of medulla called a renal pyramid.
Tumors.
The tumor parenchyma, of a solid tumour, is one of the two distinct compartments in a solid tumour. The parenchyma is made up of neoplastic cells. The other compartment is the stroma induced by the neoplastic cells, needed for nutritional support and waste removal. In many types of tumour, clusters of parenchymal cells are separated by a basal lamina that can sometimes be incomplete.
Flatworms.
Parenchyma is the tissue made up of cells and intercellular spaces that fills the interior of the body of a flatworm, which is an acoelomate. This is a spongy tissue also known as a mesenchymal tissue, in which several types of cells are lodged in their extracellular matrices. The parenchymal cells include myocytes, and many types of specialised cells. The cells are often attached to each other and also to their nearby epithelial cells mainly by gap junctions and hemidesmosomes. There is much variation in the types of cell in the parenchyma according to the species and anatomical regions. Its possible functions may include skeletal support, nutrient storage, movement, and many others.


Skeletal-muscle pump

The skeletal-muscle pump is a collection of skeletal muscles that aid the heart in the circulation of blood. It is especially important in increasing venous return to the heart, but may also play a role in arterial blood flow.
General.
The skeletal pump is vital in negating orthostatic intolerance when standing. When moving upright, the blood volume moves to the peripheral parts of the body. To combat this, the muscles involved in standing contract and help to bring venous blood volume to the heart. The pump is important in affecting the central and local supply of blood output. Venous return, cardiac output, and stroke volume were all increased during exercise experiments, as well as affecting the local muscle being used, blood volume.
Arterial blood pumping.
Between muscle relaxations, intramuscular pressure transiently returns to a level below the venous blood pressure. This allows blood from the capillary system to refill the veins until the next contraction. It is postulated that this change in pressure may be great enough to draw blood from the arterial side to the venous side. It is hypothesized that this pressure drop during rhythmic contraction actually increases blood flow through the muscle, and may be responsible for a portion of the increase in muscle blood flow immediately at the onset of activity. This explanation is attractive, because it would explain the readily observable tight coupling between muscle contraction and a rapid increase in muscle blood flow. However, recent evidence has emerged that cast doubts on this theory. Experiments have shown that a strong muscle contraction can occur without a corresponding increase in skeletal muscle blood flow. Given the proposed manner of action of the muscle pump to increase arterial blood flow, it would seem impossible for a muscle contraction and skeletal muscle hyperemia to be uncoupled. Another experiment recently was only able to find evidence that vasodilation, not the skeletal muscle pump, was responsible for maintaining proper pressure and blood return. This might have to do with the lack of rigorous physiological tests thus far used to be able to prove the pump.
Experiments have shown the use of passive leg exercises, where only vasodilation was used, was responsible for increased blood return.