Role of CD36 in Platelet Function

CD36 is a scavenger receptor expressed on a wide variety of cells including platelets. It recognizes multiple ligands, yet its function on platelets is incompletely characterized. Endothelial cell-derived microparticles (EMP) have been identified in diseases where platelet activation plays a pivotal role. Because EMP express phosphatidylserine (PS) on their surfaces, a CD36 ligand, we hypothesized that MP may bind to platelets via a PS-CD36 interaction. Human platelets were shown to bind EMP by flow cytometry and fluorescence microscopy. Binding was significantly inhibited by anti-CD36 antibody or using platelets from CD36 null donors. We observed a significant increase in the rate and extent of platelet activation and aggregation to low concentrations of ADP when preincubated with EMP. We thus propose a model where ligands such as EMPs, generated during an acute thrombotic event, could increase the thrombotic response in a CD36 dependent manner. We also showed that CD36 expression levels on platelets were highly variable and correlated well with platelet activation by oxidized LDL. Genotyping with 10 tagged SNPs revealed that the minor alleles of 3 SNPs were significantly associated with expression levels. These data suggest that the variability of CD36 expression on platelets is at least in part genetically determined and together this phenotype-genotype can affect platelet functio

Role of CD36 in Platelet Function

CD36 is a scavenger receptor expressed on a wide variety of cells including platelets. It recognizes multiple ligands, yet its function on platelets is incompletely characterized. Endothelial cell-derived microparticles (EMP) have been identified in diseases where platelet activation plays a pivotal role. Because EMP express phosphatidylserine (PS) on their surfaces, a CD36 ligand, we hypothesized that MP may bind to platelets via a PS-CD36 interaction. Human platelets were shown to bind EMP by flow cytometry and fluorescence microscopy. Binding was significantly inhibited by anti-CD36 antibody or using platelets from CD36 null donors. We observed a significant increase in the rate and extent of platelet activation and aggregation to low concentrations of ADP when preincubated with EMP. We thus propose a model where ligands such as EMPs, generated during an acute thrombotic event, could increase the thrombotic response in a CD36 dependent manner. We also showed that CD36 expression levels on platelets were highly variable and correlated well with platelet activation by oxidized LDL. Genotyping with 10 tagged SNPs revealed that the minor alleles of 3 SNPs were significantly associated with expression levels. These data suggest that the variability of CD36 expression on platelets is at least in part genetically determined and together this phenotype-genotype can affect platelet functio

Role of CD36 in Platelet Function

CD36 is a scavenger receptor expressed on a wide variety of cells including platelets. It recognizes multiple ligands, yet its function on platelets is incompletely characterized. Endothelial cell-derived microparticles (EMP) have been identified in diseases where platelet activation plays a pivotal role. Because EMP express phosphatidylserine (PS) on their surfaces, a CD36 ligand, we hypothesized that MP may bind to platelets via a PS-CD36 interaction. Human platelets were shown to bind EMP by flow cytometry and fluorescence microscopy. Binding was significantly inhibited by anti-CD36 antibody or using platelets from CD36 null donors. We observed a significant increase in the rate and extent of platelet activation and aggregation to low concentrations of ADP when preincubated with EMP. We thus propose a model where ligands such as EMPs, generated during an acute thrombotic event, could increase the thrombotic response in a CD36 dependent manner. We also showed that CD36 expression levels on platelets were highly variable and correlated well with platelet activation by oxidized LDL. Genotyping with 10 tagged SNPs revealed that the minor alleles of 3 SNPs were significantly associated with expression levels. These data suggest that the variability of CD36 expression on platelets is at least in part genetically determined and together this phenotype-genotype can affect platelet functio

Ribosome-DnaK interactions in relation to protein folding

Bacterial ribosomes or their 50S subunit can refold many unfolded proteins. The folding activity resides in domain V of 23S RNA of the 50S subunit. Here we show that ribosomes can also refold a denatured chaperone, DnaK, in vitro, and the activity may apply in the folding of nascent DnaK polypeptides in vivo. The chaperone was unusual as the native protein associated with the 50S subunit stably with a 1:1 stoichiometry in vitro. The binding site of the native protein appears to be different from the domain V of 23S RNA, the region with which denatured proteins interact. The DnaK binding influenced the protein folding activity of domain V modestly. Conversely, denatured protein binding to domain V led to dissociation of the native chaperone from the 50S subunit. DnaK thus appears to depend on ribosomes for its own folding, and upon folding, can rebind to ribosome to modulate its general protein folding activity

Role of the ribosome in protein folding

In all organisms, the ribosome synthesizes and folds full length polypeptide chains into active three-dimensional conformations. The nascent protein goes through two major interactions, first with the ribosome which synthesizes the polypeptide chain and holds it for a considerable length of time, and then with the chaperones. Some of the chaperones are found in solution as well as associated to the ribosome. A number of in vitro and in vivo experiments revealed that the nascent protein folds through specific interactions of some amino acids with the nucleotides in the peptidyl transferase center (PTC) in the large ribosomal subunit. The mechanism of this folding differs from self-folding. In this article, we highlight the folding of nascent proteins on the ribosome and the influence of chaperones etc. on protein folding

Characterization of Zebrafish von Willebrand Factor Reveals Conservation of Domain Structure, Multimerization, and Intracellular Storage

von Willebrand disease (VWD) is the most common inherited human bleeding disorder and is caused by quantitative or qualitative defects in von Willebrand factor (VWF). VWF is a secreted glycoprotein that circulates as large multimers. While reduced VWF is associated with bleeding, elevations in overall level or multimer size are implicated in thrombosis. The zebrafish is a powerful genetic model in which the hemostatic system is well conserved with mammals. The ability of this organism to generate thousands of offspring and its optical transparency make it unique and complementary to mammalian models of hemostasis. Previously, partial clones of zebrafish vwf have been identified, and some functional conservation has been demonstrated. In this paper we clone the complete zebrafish vwf cDNA and show that there is conservation of domain structure. Recombinant zebrafish Vwf forms large multimers and pseudo-Weibel-Palade bodies (WPBs) in cell culture. Larval expression is in the pharyngeal arches, yolk sac, and intestinal epithelium. These results provide a foundation for continued study of zebrafish Vwf that may further our understanding of the mechanisms of VWD

Sperm Motility Regulatory Proteins: A Tool to Enhance Sperm Quality

Sperm forward motility is an essential parameter in mammalian fertilization. Studies from our laboratory have identified and characterized a few unique sperm motility regulatory proteins/glycoproteins from the male reproductive fluids and mammalian blood serum. The purified sperm motility-initiating protein (MIP) from caprine epididymal plasma as well as the forward motility-stimulating factor (FMSF) and motility-stimulating protein (MSP) from buffalo and goat serum, respectively, have high efficacy to initiate or increase motility in nonmotile or less motile sperm. Antibody of sperm motility inhibitory factor (MIF-II) has the high potential to enhance sperm vertical velocity and forward motility by increasing intracellular cyclic adenosine monophosphate (cAMP) level. The appearance and disappearance of D-galactose–specific lectin and its receptor along the epididymis has been reported to be involved in motility regulation in spermatozoa. A novel synthetic cryopreservation method and role of lipid to protect membrane damage during cryopreservation have been demonstrated. Motility-promoting proteins may be extremely useful for improving cattle breeding and breeding of endangered species, thereby helping in enhanced production of animal products as well as in the conservation of animals. Isolated proteins and developed cryopreservation technology may also be beneficial in human infertility clinics to increase the chance of fertilization

Evaluation of some mangrove species on the nature of their reproduction along the coastal belt of the Indian Sunderbans

Reproductive biology of three dominating mangrove species Rhizophora mucronata, Ceriops decandra and Avicennia marina from the Indian Sunderbans were studied. A comparative account on all floral parts revealed that as the bud progresses to completely open, the length of androecium surpassed the length of gynoecium and the anther matured first thus showing protandrous nature and favouring cross-fertilization. A study of pollen grain viability revealed that all of them produces fairly good amounts of viable pollen grains in their natural condition. The pollens showed their maximum viability late in the morning till early noon. The stigma showed peak receptivity after three days of flower opening in C. decandra and four days of flower opening in R. mucronata and A. marina. All the species showed out-breeding mechanism of pollination. The fruit setting percentage obtained by xenogamy was the highest and autogamy failed to show any result in all the three genera. Although Ceriops decandra and Avicennia marina showed very limited fruit set with geitonogamy, these two species can be called facultative out-crossers, while Rhizophora was obligate outcrosser in nature. The study on floral structure, pollen viability along with stigma receptivity of the investigated taxa guided to maximum exploitation of reproductive behavior for rising artificial and natural plant population in addition to build up a future research strategy in ecosystem conservation

A Study to Assess the Level of Adherence to Respectful Maternity Care (RMC) and Reasons of non-adherence among Health Personnel in the Maternity Department of Selected Hospitals, West Bengal

Evidence suggests that in countries with a high maternal mortality like India, the fear of disrespect and abuse that women often encounter in facility-based maternity care is a more powerful deterrent to use of skilled care. The purpose of the study is to assess the level of adherence of health care personnel to each component of Respectful Maternity Care and also to find out the factors influencing non-adherence. A descriptive survey with non-probability purposive sampling was used. An observation checklist and both structured and unstructured interview schedule were administered on 92 health personnel to assess the level of adherence to RMC and reasons of non-adherence. Findings of the study depicts, in physical harm area, adherence among doctors, nursing personnel and Gr-D was 81.9%, 91.6%, 79.2% respectively, in the informed consent area 41.2% (doctors) and 61.1% (nursing personnel). Adherence in the area of choice and preferences was nil and in the area of confidentiality & privacy was 48.7% (doctors), 66.7% (nursing personnel) and 39.6% (Gr-Ds). Non-adherence in the area of dignity & respect was 25.6% (doctors), 18.4% (nursing personnel), 8.3% (Gr-Ds) and in the area of abandonment or denial of care 3.5% (doctors), 4.5% (nursing personnel), 43.7% (Gr-Ds). Adherence in the area of non-discriminatory care was 100% for all and 100% adherence was found in the area of detention against will among doctors and nursing personnel except among Gr-Ds (45.8%). No significant association was found between age, experiences and level of adherence of health personnel (doctor and nursing personnel) [(χ2df (1)=3.841, 0.474 & 0.287, p>0.05] respectively). No significant differences were found between level of adherence score of doctors with nursing personnel [t (78)=2.00, p>0.05]. As observed, adherence to RMC is not at the same level in each area. Least adherent areas are informed consent, choice/ preferences, privacy and detention against will among other personnel