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Biomedical subjects

A Chaudhuri

Publications and source records attributed to A Chaudhuri.

At least 127 records · Page 7Linked to original sources
PubMed1995

The coding sequence of Duffy blood group gene in humans and simians: restriction fragment length polymorphism, antibody and malarial parasite specificities, and expression in nonerythroid tissues in Duffy-negative individuals.

The coding and untranslated flanking sequences of Duffy gene (FY) in humans and simians are in a single exon. The difference between the two codominant alleles, FY*A and FY*B, is a single change at nucleotide 306: guanidine is in FY*A and adenine is in FY*B. This produces a codon change that subsequently modifies the amino acid at position 43 of gpFy, the major subunit of the Duffy blood group protein complex. The glycine at this position in antigen Fya exchanges with aspartic acid in antigen Fyb. The guanidine at nucleotide 306 creates an additional Ban I restriction site in FY*A. Ban I digestion of DNA-PCR amplified products of FY*B and FY*A yields three and four fragments, respectively. Restriction fragment length polymorphism (RFLP) studies show that Fy(a+b-) and Fy(a-b+) whites are FY homozygous, that most Fy(a-b-) blacks have FY*B, and most Fy(a+b-) blacks are FY*A/FY*B heterozygous. In the black population a silent FY*B is very common, but a silent FY*A has not been found yet. On RNA blot analysis, the gpFy cDNA clone detected mRNA in the lung, spleen, and colon but not in the bone marrow of Duffy-negative individuals. Therefore, there is no null phenotype in Fy(a-b-) blacks. The gpFy homology between human and chimpanzee is 99% with a single residue change at position 116 (valine to isoleucine), whereas a 94% homology is found in squirrel and rhesus monkeys, and there is a 93% homology in aotus monkey when compared with humans. The N-terminal exocellular domain of simian gpFy helps to identify a set of amino acids critical for antibody and malarial parasite specificities.

Alleles↗
PubMed1995

Effects of prostatectomy on testicular androgenesis and serum levels of gonadotropins in mature albino rats.

The effects of prostatectomy on testicular steroidogenic enzymes, and on serum levels of gonadotropins, prolactin, and testosterone were studied. Adult male rats were prostatectomized and sacrificed after 14 and 21 days. There was augmentation of both delta 5-3 beta-hydroxysteroid dehydrogenase (delta 5-3 beta-HSD) and 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) activities in the testes along with increased levels of FSH, prolactin, and testosterone in the serum, while no changes were observed in serum levels of LH. Hence it may be concluded that the prostate gland has an inhibitory effect on testicular androgenesis and can exert some influence in the regulation of FSH and prolactin secretion.

17-Hydroxysteroid Dehydrogenases↗
PubMed1995

Duffy and receptors for P. vivax and chemotactic peptides.

The Duffy blood group system consists of two principal antigens, Fya and Fyb produced by FY*A and FY*B co-dominant alleles. Antisera, anti-Fya and anti-Fyb, define four phenotypes: Fy(a+b-), Fy(a-b+), Fy(a+b+) and Fy(a-b-). Neither antiserum agglutinates Fy(a-b-) cells, the predominant phenotype in Blacks. Outside the Black population, Fy(a-b-) phenotype is very rare. Duffy antigens appear to be multimeric erythrocyte-membrane proteins composed of different subunits. A glycoprotein of 35-45 kDa, gp-Fy, is the major subunit of the complex and has antigenic determinants defined by Duffy antibodies. The protein consists of 337 amino acid residues with a M(r) of 35,733, the same as deglycosylated gp-Fy. The hydropathy map predicts an exocellular N-terminal domain of 64 residues, nine transmembrane alpha-helices, three short protruding hydrophilic loops and an endocellular C-terminal domain of 23 residues. Duffy specific transcript, a approximately 1.3 kb mRNA, is produced by the bone marrow of Duffy-positive individuals, but it is not produced by the bone marrow of Duffy-negative individuals. The same size mRNA is produced in many tissues of Duffy-positive individuals. The same tissues of Duffy-negative individuals also synthesize the same size mRNA and the same gp-Fy as that of Duffy-positive individuals. There is not, therefore, Duffy null phenotype in the Black population. The difference between FY*A and FY*B alleles is a single nucleotide change at position 306; guanine is in FY*A, and adenine is in FY*B.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Optimal treatment of erectile failure in patients with diabetes.

Erectile failure, although a common problem in male diabetic patients, is one of the most neglected complications of diabetes. The availability of drugs like alprostadil (prostaglandin E1; PGE1) and papaverine for intracavernosal injection and the development of vacuum tumescence devices, while making therapy simple, have also reduced the necessity for specialised investigations. In the past 10 years, alprostadil has been shown to be the safest and the most effective of the intracavernosal self-injection treatments of erectile dysfunction. Vacuum tumescence devices are an acceptable noninvasive alternative in those who fail to achieve a satisfactory response to self-injection. Surgical techniques are being improved every day, and revascularisation procedures and prosthetic implants are available to couples in specialised centres. At present, systemic drug therapy has been largely ineffective for treatment in diabetic patients but progress is being made in this field. Whatever the option, involvement of the partner in decision making is of major importance for the treatment to be successful, and psychosexual counselling is a useful adjunct to medical or surgical therapy.

Antihypertensive Agents↗
PubMed1994

Expression of the Duffy antigen in K562 cells. Evidence that it is the human erythrocyte chemokine receptor.

The human malarial parasite Plasmodium vivax invades erythrocytes by binding to a cell surface protein identified as the Duffy blood group antigen. The molecular properties of the Duffy antigen, which was recently cloned, are very similar to those of a chemokine binding protein known as the human erythrocyte chemokine receptor. This has led to the suggestion that these two molecules are the same protein. To further investigate the suspected double identity of the Duffy antigen we have transfected it into a human erythroleukemic cell line, K562. Cells stably expressing the Duffy antigen were isolated and used to characterize the protein. K562 cells transfected with the Duffy antigen displayed specific 125I-melanoma growth-stimulating activity (MGSA) binding while mock transfected cells did not. Comparison of 125I-MGSA binding to the Duffy antigen and the human erythrocyte chemokine receptor showed that the specific 125I-MGSA binding to both proteins was displaced by excess unlabeled MGSA, interleukin-8, RANTES, monocyte chemotactic peptide-1, and platelet factor 4, but not by macrophage inflammatory protein-1 alpha or -1 beta. Scatchard analysis of competition binding studies with these unlabeled chemokines revealed high affinity binding to the Duffy antigen with KD binding values of 24 +/- 4.9, 20 +/- 4.7, 41.9 +/- 12.8, and 33.9 +/- 7 nM for MGSA, interleukin-8, RANTES, and monocyte chemotactic peptide-1, respectively. A monoclonal antibody, Fy6, to the Duffy antigen inhibited 125I-MGSA binding to K562 cells expressing the Duffy antigen. Cell membranes from K562 cells permanently expressing the Duffy antigen were chemically cross-linked with 125I-MGSA. SDS-polyacrylamide gel electrophoresis analysis of the cross-linked products showed covalent incorporation of radiolabeled MGSA into a protein of molecular mass 47 kDa, and cross-linking was inhibited in the presence of unlabeled MGSA. These studies provide evidence that the Duffy blood group antigen is the same protein as the human erythrocyte chemokine receptor.

Amino Acid Sequence↗
PubMed1994

L-thyroxine (T4) elevates the free amino acid pool of haemolymph plasma of tasar silkworm, Antheraea mylitta drury (Lepidoptera: Saturniidae).

Concentration of free amino acids (FAA) in the haemolymph plasma of male and female tasar silkworm, A. mylitta, during fifth larval instar were determined by amino acid analyzer after administration of vertebrate thyroxine (T4). Twenty FAA have been identified in haemolymph plasma in both sexes, out of which ten were found to be predominating. Treatment with anabolic doses of thyroxine (0.5 and 1.0 micrograms/g) were able to enhance the titre of all the individual FAA which has been also reflected in the total concentrations. A specific pattern of variations in plasma FAA recorded during 5th larval instar, was not altered by the administered thyroxine. Our results thus indicate that T4 has a controlling influence on the FAA profiles of silkworm as observed in other biochemical parameters of the insect.

Aging↗
PubMed1994

The effect of aspirin on neurodeficit and platelet aggregability in acute ischemic cerebral strokes.

We examined the role of aspirin in modifying platelet aggregability (PA) and neurodeficit (ND) in patients presenting within 48 hours of acute ischemic cerebral strokes of the carotid territory. 28 adult patients were studied at baseline and after 7 days of treatment with a single daily dose of aspirin 325mg (group A, n = 12) and 160 mg (Group B, n = 16). We also evaluated the neurologic outcome at the beginning and at the end of 7 days using a scoring system. There was no significant difference in the ND scores and in vitro PA between these two groups. PA, as measured in vitro, does not appear to have any significant role as a predictor of neurologic outcome in acute ischemic strokes. The change in ND scores of patients with ischemic cerebral strokes treated acutely with aspirin was not significant upto first 7 days therapy.

Adult↗
PubMed1993

Cloning of glycoprotein D cDNA, which encodes the major subunit of the Duffy blood group system and the receptor for the Plasmodium vivax malaria parasite.

cDNA clones encoding the major subunit of the Duffy blood group were isolated from a human bone marrow cDNA library using a PCR-amplified DNA fragment encoding an internal peptide sequence of glycoprotein D (gpD) protein. The open reading frame of the 1267-bp cDNA clone indicated that gpD protein was composed of 338 amino acids, predicting a M(r) of 35,733, which was the same as a deglycosylated gpD protein. Portions of the predicted amino acid sequence, matched with six CNBr/pepsin peptides obtained from affinity-purified gpD protein. In ELISA analysis, an anti-Duffy murine monoclonal antibody reacted with a synthetic peptide deduced from the cDNA clone. Hydropathy analysis suggested the presence of 9 membrane-spanning alpha-helices. In bone marrow RNA blot analysis, the gpD cDNA detected a 1.27-kb mRNA in Duffy-positive but not in Duffy-negative individuals. It also identified the same size mRNA in adult kidney, adult spleen, and fetal liver; in brain, it detected a prominent 8.5-kb and a minor 2.2-kb mRNA. In Southern blot analysis, gpD cDNA identified a single gene in Duffy-positive and -negative individuals. Duffy-negative individuals, therefore, have the gpD gene, but it is not expressed in bone marrow. The same or a similar gene is active in adult kidney, adult spleen, and fetal liver of Duffy-positive individuals. Whether this is true in Duffy-negative individuals remains to be demonstrated. A GenBank sequence search yielded a significant protein sequence homology to human and rabbit interleukin-8 receptors.

Amino Acid Sequence↗
PubMed1993

Activity-dependent expression of the transcription factor Zif268 reveals ocular dominance columns in monkey visual cortex.

The visualization of neuronal populations activated by sensory stimulation has been approached using a number of different methodologies. Recent developments in our understanding of transcription factors have provided a new window for observing neural activity. We have found that the transcription factor Zif268 is expressed throughout the visual cortex of the monkey at high basal levels and that monocular visual deprivation produces dramatic changes in its levels revealing ocular dominance columns in striate cortex with as little as 2 h of selective exposure. These results show that immunodetection for Zif268 may be used for labelling activated neuronal populations in the monkey with several key advantages over prior techniques.

Animals↗
PubMed1993

Histopathological and immunological studies in a cohort of balanitis xerotica obliterans.

Balanitis xerotica obliterans consisting of 52 cases had been studied in the present series. This disease entity is an insidious sclerosing disease of unknown aetiology, affecting mainly the skin and mucous membrane of glans, prepuce and sometimes the fossa navicularis urethrae or even terminal urethra. Atrophic white patches on external genitalia and obstructive uropathy are two common presenting features. It has been classified as local form of lichen sclerosus et atrophicus. Poor local hygiene, circumcision and association of auto-immune diseases like vitiligo are responsible as suggested in this study. Routine tests detected associated cystitis in 8 cases, haematuria in 4 cases, non-reactive VDRL in all cases and impaired glucose tolerance in 5 cases. Immunoglobulin profile (39 cases) showed altered pattern, suggesting some chronic antigenic stimulation. Out of 33 cases where biopsy done, histologically proved typical balanitis xerotica obliterans was found in 19 cases. Malignant change was noted in one case only. Circumcision and dilatation offered temporary relief.

Adolescent↗
PubMed1992

Substrate specificity of the isoprenylated protein endoprotease.

Proteins containing a CAAX motif at their carboxyl termini are subject to isoprenylation at the cysteine residue. Proteolytic trimming of isoprenylated proteins is essential in the activation of these proteins. A microsomal endopeptidase activity has been identified which cleaves all-trans farnesylated cysteine containing tetrapeptides between the modified residue and the adjacent amino acid to liberate the modified cysteine residue and an intact tripeptide. Structure/activity studies are reported here on this endopeptidase activity which are consistent with the premise that this protease is identical to the one normally involved in the cellular isoprenylation pathway. The protease only processes peptides which possess an isoprenyl moiety. Within the isoprenyl series, the enzyme hydrolyzes all-trans-farnesyl-, all-trans-geranylgeranyl-, and geranyl-containing peptides. The protease also recognizes the AAX sequence, because the protease behaves either stereospecifically or stereoselectively with respect to the individual amino acids of the tripeptide. The enzyme only measurably hydrolyzes isoprenylated peptides possessing L-amino acids at C and A. On the other hand, there is a small but measurable hydrolysis of isoprenylated peptides containing a D-amino acid at X.

Amino Acid Sequence↗
PubMed1992

Heterochromatic Fusion Nystagmus: its use in estimating chromatic equiluminance in humans and monkeys.

The use of chromatic patterns that are equated for luminance has become increasingly popular in psychophysical and neurophysiological studies of visual processing. The currently available techniques for equating different colors for brightness rely upon human reports of perceptual events that are reduced at some luminance ratio. We report here the results of a study using a technique we have recently developed that produces a vivid and compelling motion percept only at isoluminance. That is, unlike previous methods, this technique relies upon a perceptual event (motion) that actually becomes more salient at isoluminance. We also observed that the optokinesis generated by the moving pattern mirrors the perceptual reports at all luminance ratios. If used in this manner, the technique can provide an estimate of chromatic isoluminance in a variety of species and can be used to corroborate a human subject's perceptual experience.

Animals↗
PubMed1992

The inequality of medical expenditures for several years in a healthy, nonelderly population.

Previous studies have shown that the distribution of annual medical expenditures for a population is very unequal and remains so for periods of more than 1 year. The authors use a better measure of inequality, the Gini coefficient, to test its persistence for longer periods. This measure is applied to data collected from the Rand Health Insurance Experiment. The experiment enrolled a nonelderly population typical of those covered by employer health plans for periods up to 5 years. The distributions of annual expenditures for this population are highly unequal, in line with previous studies. Inequality declines substantially when longer periods are considered.

Adolescent↗