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Biomedical subjects

R Parekh

Publications and source records attributed to R Parekh.

At least 19 recordsLinked to original sources
PubMed2004

Clinical practice guidelines for managing dyslipidemias in kidney transplant patients: a report from the Managing Dyslipidemias in Chronic Kidney Disease Work Group of the National Kidney Foundation Kidney Disease Outcomes Quality Initiative.

The incidence of cardiovascular disease (CVD) is very high in patients with chronic kidney (CKD) disease and in kidney transplant recipients. Indeed, available evidence for these patients suggests that the 10-year cumulative risk of coronary heart disease is at least 20%, or roughly equivalent to the risk seen in patients with previous CVD. Recently, the National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (K/DOQI) published guidelines for the diagnosis and treatment of dyslipidemias in patients with CKD, including transplant patients. It was the conclusion of this Work Group that the National Cholesterol Education Program Guidelines are generally applicable to patients with CKD, but that there are significant differences in the approach and treatment of dyslipidemias in patients with CKD compared with the general population. In the present document we present the guidelines generated by this workgroup as they apply to kidney transplant recipients. Evidence from the general population indicates that treatment of dyslipidemias reduces CVD, and evidence in kidney transplant patients suggests that judicious treatment can be safe and effective in improving dyslipidemias. Dyslipidemias are very common in CKD and in transplant patients. However, until recently there have been no adequately powered, randomized, controlled trials examining the effects of dyslipidemia treatment on CVD in patients with CKD. Since completion of the K/DOQI guidelines on dyslipidemia in CKD, the results of the Assessment of Lescol in Renal Transplantation (ALERT) Study have been presented and published. Based on information from randomized trials conducted in the general population and the single study conducted in kidney transplant patients, these guidelines, which are a modified version of the K/DOQI dyslipidemia guidelines, were developed to aid clinicians in the management of dyslipidemias in kidney transplant patients. These guidelines are divided into four sections. The first section (Introduction) provides the rationale for the guidelines, and describes the target population, scope, intended users, and methods. The second section presents guidelines on the assessment of dyslipidemias (guidelines 1-3), while the third section offers guidelines for the treatment of dyslipidemias (guidelines 4-5). The key guideline statements are supported mainly by data from studies in the general population, but there is an urgent need for additional studies in CKD and in transplant patients. Therefore, the last section outlines recommendations for research.

Adolescent↗
PubMed2004

Undertreatment of hyperlipidemia in a cohort of United States kidney dialysis patients.

BACKGROUND: Application of national guidelines regarding cardiovascular disease risk reduction to kidney dialysis patients is complicated by the conflicting observations that dialysis patients have a high risk of atherosclerotic cardiovascular disease (ASCVD), but dialysis patients with higher serum cholesterol have lower mortality rates. Actual treatment patterns of hyperlipidemia are not well studied. METHODS: We assessed the prevalence, treatment and control of hyperlipidemia in this high-risk patient population from 1995 - 1998. We measured low-density lipoprotein cholesterol, treatment with a lipid-lowering agent, and prevalence of hyperlipidemia as defined by the National Cholesterol Education Program (NCEP), Adult Treatment Panel (ATP) II guidelines in 812 incident hemodialysis (HD), and peritoneal dialysis (PD) patients from dialysis clinics in 19 states throughout the United States. RESULTS: Hyperlipidemia was present in 40% of HD and 62% of PD patients. Among subjects with hyperlipidemia, 67% of HD and 63% of PD patients were untreated and only 22% of HD and 14% of PD patients were treated and controlled. Those who entered the study in 1997 or 1998, those with diabetes, males and Caucasians were more likely to be treated and controlled, whereas subjects on PD and those with ASCVD were less likely to be treated and controlled. CONCLUSION: These data suggest that high rates of undertreatment exist in the United States ESRD dialysis population. Whether improved rates of treatment will result in decreased cardiovascular disease events needs to be tested in randomized clinical trials.

Cardiovascular Diseases↗
PubMed2003

hAG-2 and hAG-3, human homologues of genes involved in differentiation, are associated with oestrogen receptor-positive breast tumours and interact with metastasis gene C4.4a and dystroglycan.

hAG-2 and hAG-3 are recently discovered human homologues of the secreted Xenopus laevis proteins XAG-1/2 (AGR-1/2) that are expressed in the cement gland, an ectodermal organ in the head associated with anteroposterior fate determination during early development. Although the roles of hAG-2 and hAG-3 in mammalian cells are unknown, both proteins share a high degree of protein sequence homology and lie adjacent to one another on chromosome 7p21. hAG-2 mRNA expression has previously been demonstrated in oestrogen receptor (ER)-positive cell lines. In this study, we have used real-time quantitative RT - PCR analysis and immunohistochemistry on tissue microarrays to demonstrate concordant expression of hAG-2 and hAG-3 mRNA and protein in breast tumour tissues. Tumour expression of both genes correlated with OR (hAG2, P=0.0002; hAG-3, P=0.0012), and inversely correlated with epidermal growth factor receptor (EGFR) (P=0.003). Yeast two-hybrid cloning identified metastasis-associated GPI-anchored C4.4a protein and extracellular alpha-dystroglycan (DAG-1) as binding partners for both hAG-2 and hAG-3, which if replicated in clinical oncology would demonstrate a potential role in tumour metastasis through the regulation of receptor adhesion and functioning. hAG-2 and hAG-3 may therefore serve as useful molecular markers and/or potential therapeutic targets for hormone-responsive breast tumours.

Amino Acid Sequence↗
PubMed2001

Proteomic comparison of human and great ape blood plasma reveals conserved glycosylation and differences in thyroid hormone metabolism.

Most blood plasma proteins are glycosylated. These glycoproteins typically carry sialic acid-bearing sugar chains, which can modify the observed molecular weights and isoelectric points of those proteins during electrophoretic analyses. To explore changes in protein expression and glycosylation that occurred during great ape and human evolution, we subjected multiple blood plasma samples from all these species to high-resolution proteomic analysis. We found very few species-specific differences, indicating a remarkable degree of conservation of plasma protein expression and glycosylation during approximately 12 million years of evolution. A few lineage-specific differences in protein migration were noted among the great apes. The only obvious differences between humans and all great apes were an apparent decrease in transthyretin (prealbumin) and a change in haptoglobin isoforms (the latter was predictable from prior genetic studies). Quantitative studies of transthyretin in samples of blood plasma (synthesized primarily by the liver) and of cerebrospinal fluid (synthesized locally by the choroid plexus of the brain) confirmed approximately 2-fold higher levels in chimpanzees compared to humans. Since transthyretin binds thyroid hormones, we next compared plasma thyroid hormone parameters between humans and chimpanzees. The results indicate significant differences in the status of thyroid hormone metabolism, which represent the first known endocrine difference between these species. Notably, thyroid hormones are known to play major roles in the development, differentiation, and metabolism of many organs and tissues, including the brain and the cranium. Also, transthyretin is known to be the major carrier of thyroid hormone in the cerebrospinal fluid, likely regulating delivery of this hormone to the brain. A potential secondary difference in retinoid (vitamin A) metabolism is also noted. The implications of these findings for explaining unique features of human evolution are discussed.

Animals↗
PubMed1999

Proteomic definition of normal human luminal and myoepithelial breast cells purified from reduction mammoplasties.

Normal human luminal and myoepithelial breast cells separately purified from a set of 10 reduction mammoplasties by using a double antibody magnetic affinity cell sorting and Dynabead immunomagnetic technique were used in two-dimensional gel proteome studies. A total of 43,302 proteins were detected across the 20 samples, and a master image for each cell type comprising a total of 1,738 unique proteins was derived. Differential analysis identified 170 proteins that were elevated 2-fold or more between the two breast cell types, and 51 of these were annotated by tandem mass spectrometry. Muscle-specific enzyme isoforms and contractile intermediate filaments including tropomyosin and smooth muscle (SM22) alpha protein were detected in the myoepithelial cells, and a large number of cytokeratin subclasses and isoforms characteristic of luminal cells were detected in this cell type. A further 134 nondifferentially regulated proteins were also annotated from the two breast cell types, making this the most extensive study to date of the protein expression map of the normal human breast and the basis for future studies of purified breast cancer cells.

Adult↗
PubMed1999

Proteomics: a major new technology for the drug discovery process.

Proteomics is a new enabling technology that is being integrated into the drug discovery process. This will facilitate the systematic analysis of proteins across any biological system or disease, forwarding new targets and information on mode of action, toxicology and surrogate markers. Proteomics is highly complementary to genomic approaches in the drug discovery process and, for the first time, offers scientists the ability to integrate information from the genome, expressed mRNAs, their respective proteins and subcellular localization. It is expected that this will lead to important new insights into disease mechanisms and improved drug discovery strategies to produce novel therapeutics.

Journal Article↗
PubMed1999

Glycan composition of serum alpha-fetoprotein in patients with hepatocellular carcinoma and non-seminomatous germ cell tumour.

Although estimation of serum alpha-fetoprotein (AFP) is widely used in the diagnosis of hepatocellular carcinoma (HCC) and non-seminomatous germ cell tumours (NSGCT), the clinical usefulness of this test is limited by a low specificity. However, there exist glycoforms of AFP which may be more specific for particular tumours. Previously, detailed analysis has been prevented by the low levels of AFP in human serum. We report here the application of fluorescence labelling, sequential exoglycosidase digestion, high-performance liquid chromatography and matrix-assisted laser desorption ionization in time-of-flight mass spectrometry, to determine the glycan structures of purified serum AFP from patients with HCC and NSGCT. Eleven major glycans were found, of which seven were N-linked, and four were O-linked, to the protein backbone. The structure of the N-linked glycans (all of bi-antennary complex-type with varying degrees of sialylation, fucosylation and galactosylation) were consistent with those previously reported. The O-linked glycans (three mucin O-GalNAc type glycans with variable degrees of sialylation, one O-HexNAc monosaccharide glycan) have not previously been reported. The finding of mucin O-GalNAc type glycans was supported by the prediction of potential O-GalNAc glycosylation sites on the protein backbone by analysis of the AFP structure by molecular modelling. With knowledge of these structures it may be possible to develop more specific assays for the detection of HCC and NSGCT.

Amino Acid Sequence↗
PubMed1998

Occupational workload of fisherwomen in India.

A group of 60 fisherwomen, aged 20 to 50 yrs., were studied to evaluate their occupational workloads. Of the eight activities involved in fish handling, only four, viz., sorting, washing, drying, and selling, which are most frequently carried out by the fisherwomen, were selected. The heart rate responses and rating of perceived exertion (RPE) were used as measures of occupational workload. Based on the findings, the occupational workload could be classified as "moderately heavy". A significant influence of age and body weight on the physiological workload was observed, being negatively correlated with age and positively with weight.

Adult↗
PubMed1996

Multimode high-performance liquid chromatography of fluorescently labeled oligosaccharides from glycoproteins.

A polymeric, secondary amine stationary phase was used to develop a method for the separation of 2-aminobenzamide (AB)-labeled neutral and anionic oligosaccharides from glycoproteins. Sequential hydrophilic interaction liquid and anion exchange chromatography were performed in the same chromatographic analysis (multimode HPLC) and unambiguous separation between neutral and anionic oligosaccharides was accomplished. Improved resolution was also achieved. The oligomannosidic-type structures from bovine ribonuclease B (Man4GlcNAc-AB-Man9GlcNAc-AB) were separated not only by size, but also by the branch location of terminal Manalpha(1 --> 2)-linked residues. Sialylated lactosamine-type oligosaccharides from human alpha1 acid glycoprotein were resolved according to charge, Fuc content, and the number of Galbeta(1 --> 4)Galbeta(1 --> 3) repeats. The minor fucosylated and polylactosamine species were well separated from the major sialylated tetra-antennary oligosaccharides. Volatile mobile phases were used to minimize sample handling for matrix assisted laser desorption mass spectrometric analysis of peak fractions. Novel polylactosamine structures (3-5 repeats) from alpha1-acid glycoprotein were deduced from the molecular weight analysis. Multimode HPLC should prove useful for preparing low pmol quantities of fluorescently labeled oligosaccharides with fewer steps and minimal sample handling for mass spectrometric analysis, important requisites for structural studies of sample-limited glycoproteins.

Animals↗
PubMed1996

Inhibition of myogenesis in mouse C2 cells by double-stranded phosphorothioate oligodeoxynucleotides containing mef-1 sequence.

Phosphorothioate oligonucleotides containing the muscle creatinine kinase enhancer sequence (mef-1) and a mutant of the enhancer sequence (mmef-1) were tested for their ability to block muscle differentiation in mouse C2 cells in culture. Maximum inhibition of fusion of myoblasts was observed at 10 microM concentration of mef-1 oligomer. No appreciable inhibition of fusion with the mmef-1 oligomer at the same concentration was observed. Synthesis of myogenin, muscle creatinine kinase, and myosin heavy chain polypeptides were reduced in mef-1 oligomer-treated cells. In contrast, no significant reduction in the synthesis of these polypeptides in mmef-1-treated cells was detected. The overall protein synthesis was not affected. These results suggest that muscle differentiation may be disrupted by competition of the oligomer with the endogenous promoter for specific transcription factor(s).

Actins↗
PubMed1995

Multicopy overexpression of bovine pancreatic trypsin inhibitor saturates the protein folding and secretory capacity of Saccharomyces cerevisiae.

Bovine pancreatic trypsin inhibitor (BPTI) was expressed and secreted from a synthetic gene as a model system for the study of protein folding and secretion in Saccharomyces cerevisiae. The efficiency of different leader sequences in directing BPTI secretion was examined, and up to 11 micrograms/ml of active BPTI was secreted. In some fusion constructs, inefficient proteolytic processing by Kex2p, Ste13p, and signal peptidase were observed immediately adjacent to the BPTI N terminus. Insertion of dipeptide spacers improved endoproteolytic processing substantially but the level of secretion was unchanged. Overexpression from a 2-microns multicopy vector results in essentially unchanged BPTI secretion as compared to expression from a single copy centromere vector. BPTI expressed from a multicopy vector accumulates intracellularly in an unfolded form, indicating that available secretory chaperones and foldases can be saturated by increasing the rate of BPTI synthesis.

Amino Acid Sequence↗
PubMed1995

Lectin-carbohydrate interactions in disease. T-cell recognition of IgA and IgD; mannose binding protein recognition of IgG0.

Two disease associated lectin-carbohydrate interactions have been studied. (1) A T-cell surface lectin which binds IgA1 and IgD is expressed on CD4+ and CD8+ T-lymphocytes in a number of diseases including systemic lupus erythematosus, rheumatoid arthritis (RA), Behcet's disease and IgA nephropathy. We have demonstrated that calcium independent binding to this receptor is mediated by the O-linked disaccharide Gal beta 3GalNAc which is associated with the hinge regions of both IgA1 and IgD. (2) In rheumatoid arthritis the proportion of IgG0 glycoform populations lacking terminal galactose increases. We have shown that terminal GlcNAc residues on oligosaccharides in the Fc region of IgG0 can bind to the C-type lectin, serum mannose binding protein, and thus activate the classical complement pathway. This provides a mechanism of activation of the complement system not available to the other classes of IgG glycoforms.

Carbohydrate Metabolism↗
PubMed1993

Use of hydrazine to release in intact and unreduced form both N- and O-linked oligosaccharides from glycoproteins.

The use of hydrazine to release unreduced N- and O-linked oligosaccharides from glycoproteins has been investigated using several "standard" glycoproteins of previously defined glycosylation. It is shown that hydrazinolysis can be used to release intact N- and O-linked oligosaccharides in an unreduced form. The release of O-linked oligosaccharides occurs with a lower temperature dependence than the release of N-linked oligosaccharides, and the kinetic parameters governing release of oligosaccharides from these standard glycoproteins have been determined. These parameters allow a definition of reaction conditions under which anhydrous hydrazinolysis can be used to selectively release O-linked oligosaccharides (60 degrees C, 5 h) or release both N- and O-linked oligosaccharides (95 degrees C, 4 h) in high yield (> 85%) from all glycoproteins investigated (n = 11). Under these reaction conditions, the recovered N- and O-linked oligosaccharides are structurally intact (as judged by 600-MHz 1H-NMR, laser-desorption mass spectrometry, HPAEC-PAD, gel filtration, and glycosidase digestion), with the possible exception of certain N- and O-acyl substituents of sialic acid. This use of mild hydrazinolysis therefore allows both the simultaneous and sequential chemical release from glycoproteins of O- and N-linked oligosaccharides in their intact unreduced form.

Animals↗
PubMed1993

Effect of culture conditions on IgM antibody structure, pharmacokinetics and activity.

Culture conditions affect the binding activity, charge heterogeneity, conformational stability, glycosylation, and pharmacokinetics of human monoclonal IgM HMAB-10058. The 10058 human/human/murine trioma was grown in serum-free airlift suspension culture, hollow fiber perfusion culture, or in nude mouse ascites. The ascites-produced antibody showed reduced conformational stability, greater charge and glycoform heterogeneity, and a lower average degree of sialylation than the in vitro culture-produced material. Mean residence time after IV injection in rats was approximately 80-fold greater for the ascites culture-produced material, but specific binding activity was less than 5% of that for the airlift-produced material. In vitro culture in serum-supplemented media (in a hollow fiber perfusion reactor or in shake-flasks) resulted in antibody with pharmacokinetics intermediate between the serum-free airlift and ascites-produced materials. Incubation of airlift-produced antibody in ascites fluid also resulted in material with intermediate pharmacokinetics. Conclusions regarding the effect of culture conditions on antibody product cannot be generalized, as in vitro-produced antibody derived from two related cell lines (HMAB-10233 and HMAB-10390) had long mean residence times similar to that of ascites-produced HMAB-10058.

Animals↗