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Biomedical subjects

A Bhattacharyya

Publications and source records attributed to A Bhattacharyya.

At least 127 records · Page 7Linked to original sources
PubMed1993

Clonal chromosome abnormalities in human breast carcinomas. I. Twenty-eight cases with primary disease.

Cytogenetic analysis was performed on a selected series of short-term cultures of primary breast carcinomas from 28 patients. All patients had histopathologically confirmed malignancies, with the majority (25/28 cases) demonstrating infiltrating ductal carcinoma. All 28 cases evidenced clonal chromosome abnormalities, with 10/28 displaying only numeric aberrations, whereas 18/28 displayed clonal structural alterations. In near-diploid tumors the most common numeric changes were -17 and -19. However, trisomy 7 was the only numeric change in two near-diploid tumors. Structural chromosome alterations were primarily isochromosomes, apparent terminal deletions, and unbalanced non-reciprocal translocations. Chromosomes I (10/18-56%) and 6 (8/18-44%) were most frequently altered in this series. Breakpoints of clonal structural abnormalities were shown to cluster to several chromosome segments, including 1p22-q11, 3p11, 6p11-13, 7p11-q11, 8p11-q11, and 19q13. Analysis of the gain or loss of specific chromosome segments revealed that the most consistent tendency was over-representation of 1q, 3q, and 6p.

Adenocarcinoma, Mucinous↗
PubMed1993

Adolescent pregnancy in Grenada.

A retrospective review of adolescent deliveries (maternal age range: 12-19 years) at the maternity unit of the main General Hospital, Grenada, was undertaken for the years 1987 and 1988 using the delivery room register and hospital medical records. These mothers were compared with women who delivered during the same period but were aged between 20 and 30 years. Of the 3203 deliveries which occurred during the study period, 613 (20%) involved adolescents, giving a prevalence rate of one in five pregnancies. chi 2 and Fisher's exact test analyses revealed that pregnancies occurring in younger adolescents (age less than 16 years, n = 58) carried an increased risk of preterm labour, operative delivery, prematurity, small-for gestational age infants, asphyxia and perinatal mortality when compared with the 'optimum reproductive age group'. Older adolescents (16-19 years, n = 555) had a higher risk of pregnancy induced hypertension but otherwise compared well with the optimal reproductive age group. Adolescent pregnancy is very prevalent in Grenada and the reproductive outcome for young adolescents < 16 years of age is relatively poor.

Adolescent↗
PubMed1992

Kinking of RNA helices by bulged bases, and the structure of the human immunodeficiency virus transactivator response element.

We have used gel electrophoresis to show that the pyrimidine bulge of the HIV-1 TAR sequence causes a local bending of the helical axis. The TAR bulge caused a retardation in electrophoretic mobility in polyacrylamide gels. When this was placed adjacent to an additional bulged sequence in a linear RNA fragment, the mobility of the molecule varied sinusoidally with the spacing between the two bulges. Electrophoretic mobilities suggested that the TAR sequence context of the pyrimidine bulge causes a greater degree of axial kinking than in an equivalent randomly chosen sequence. Experiments in which an A5 bulge was progressively opposed by adenine bases inserted in the opposite strand showed that even a single opposed adenine markedly reduced electrophoretic mobility, i.e. axial bending, and two adenine bases reduced the mobility virtually to that of a normal duplex. We suggest that the pronounced kinking resulting from an unopposed bulge provides a particularly recognizable feature in RNA, and that this is the basis of the interaction between the HIV Tat protein and the TAR sequence.

Base Sequence↗
PubMed1992

S100 is present in developing chicken neurons and Schwann cells and promotes motor neuron survival in vivo.

We used polyclonal antisera recognizing S100, a small acidic protein highly enriched in nervous tissue, to stain sections of embryonic chicken lumbosacral spinal cord and hindlimb. S100 immunoreactivity was detected in developing sensory neurons of the dorsal root ganglia (DRG) and motor neurons of the ventral spinal cord as early as embryonic day (E) 5, and staining persisted through hatching. In contrast, expression of S100 first became apparent in Schwann cells at E13, just before myelination, and was not detected in developing skin or muscle. Since S100 beta was present in motor and sensory neurons and is known to promote neuronal survival and neurite extension in vitro (Winningham-Major, Staecker, Barger, Coats, and Van Eldik, 1989), we tested the ability of S100 to promote neuron survival in an in ovo survival assay. Addition of S100 to chick embryos in ovo during the period of naturally occurring motor neuron cell death resulted in a significant increase in motor neuron survival, but had no effect on the in vivo survival of sensory neurons in the DRG. The findings that S100 is present in spinal motor neurons and that the addition of S100 enhances the survival of these cells in vivo are consistent with the possibility that S100 may act as a naturally occurring neuron survival factor during development.

Animals↗
PubMed1991

Model for the interaction of DNA junctions and resolving enzymes.

Four-way DNA junctions are thought to be important intermediates in a number of recombination processes. Resolution of these junctions occurs by cleavage of two strands of DNA to generate two duplex molecules. The interaction between DNA junctions and resolving enzymes appears to be largely structure-specific, reflecting a molecular recognition on a significant scale. We propose a working model for this interaction that takes account of the present state of knowledge of the structure of the DNA junction, and the substrate requirements of the enzymes. We note that three different enzymes introduce cleavages at phosphodiester bonds that are presented on one side of the molecule, suggesting that the enzymes selectively interact with this face of the junction. By forcing a junction of constant sequence to adopt one or other of the two possible antiparallel isomers, we show that the junction is cleaved in such a way as to suggest a constant mode of interaction with the protein that is dependent on structure rather than sequence. We propose that the feature that is recognized is a mutual inclination of two DNA helices at approximately 120 degrees. We show that a number of DNA substrates that contain similar inclined helices, such as a three-way junction, bulged duplexes and a duplex that is curved because of repeated runs of oligoadenine sequences, are each cleaved by phage T4 endonuclease VII. This mode of DNA-protein interaction could be significant in either recombination or DNA repair processes.

Animals↗
PubMed1991

A fluorescence spectroscopic study of glutaminyl-tRNA synthetase from Escherichia coli and its implications for the enzyme mechanism.

Interaction between Escherichia coli glutaminyl-tRNA synthetase (GlnRS) and its substrates have been studied by fluorescence quenching. In the absence of other substrates, glutamine, tRNA(Gln) and ATP bind with dissociation constants of 460, 0.22 and 180 microM, respectively. The presence of other substrates has either no effect or, at best a weak effect, on binding of ligands. Attempts to isolate enzyme-bound aminoacyl adenylate did not succeed. Binding of the phosphodiester, 5'-(methyl)adenosine monophosphate (MeAMP), to GlnRS was studied by fluorescence quenching and radioactive-ligand binding. tRNA also only has a weak effect on phosphodiester binding. Selectively pyrene-labeled GlnRS was used to obtain shape and size information for free GlnRS. A comparison with the GlnRS shape in the GlnRS/tRNA(Gln) crystal structure indicates that no major change in shape and size occurs upon tRNA(Gln) binding to GlnRS. 5,5'-Bis(8-anilino-1-naphthalene sulfonate) (bis-ANS), a non-covalent fluorescent probe, was also used to probe for conformational changes in GlnRS. This probe also indicated that no major conformational change occurs upon tRNA(Gln) binding. We conclude that lack of tRNA-independent pyrophosphate-exchange activity in this enzyme is not a result of either lack of glutamine or ATP binding in the absence of tRNA, or formation of aminoacyl adenylate and slow release of pyrophosphate. A conformational change is implied upon tRNA binding, which promotes pyrophosphate exchange. Fluorescence studies indicate that this conformational change must be limited and local in nature.

Adenosine Monophosphate↗
PubMed1991

Requirement of an extracellular energy substrate for the guinea pig sperm acrosome reaction induced by calcium ionophore.

It is well established that calcium ionophore A 23187 induces acrosome reaction (AcR) of uncapacitated spermatozoa in the presence of extracellular Ca2+ ions. In the present study, we have investigated how extracellular energy substrates (glucose, pyruvate, and lactate) affect the ionophore-induced AcR of guinea pig spermatozoa. It was found that 0.3 microM concentration of A 23187 had the maximum effect to initiate AcR of guinea pig spermatozoa. Virtually no spermatozoa underwent their AcR when incubated in substrate-free modified Tyrode's medium containing 0.3 microM A 23187 and 2 mM Ca2+. At least one exogenous substrate is essential for the ionophore-induced AcR of spermatozoa. As for efficacy of the substrates, lactate was more effective than pyruvate and glucose. However, a better result was observed when lactate was added along with pyruvate. Malonate inhibited the ionophore-induced AcR but not the hyperactivated motility of spermatozoa. The mitochondrial electron transport chain blockers rotenone, antimycin, and oligomycin failed to inhibit AcR, although in the presence of these blockers spermatozoa were unable to show hyperactivated motility. These results suggest that the mitochondrial citric acid cycle, not the electron transport chain, is probably the energy source for ionophore-induced AcR of guinea pig spermatozoa.

Acrosome↗
PubMed1991

Quantitative analysis of portal tract infiltrate allows for accurate determination of hepatic allograft rejection.

Changes in the qualitative character of the portal tract infiltrate of hepatic allografts can influence the diagnosis of acute rejection. Since qualitative data rely on subjective findings, the aim of this study was to perform a quantitative analysis of portal tract infiltrates to improve the accuracy of the diagnosis of acute rejection. A total of 431 serial hepatic biopsies in 58 consecutive adult patients were obtained. The average number of eosinophils, neutrophils, and lymphocytes in each portal tract were counted. The area of each portal tract was determined using an optical micrometer. Rejection was confirmed by an independent investigator using both clinical and histologic criteria. Using a backward stepwise logistic regression analysis, we found that eosinophils were the only variable predictive of rejection. Using this model, the probability of having rejection on a single biopsy can be determined with greater than 90% accuracy.

Biopsy↗
PubMed1991

P0 is an early marker of the Schwann cell lineage in chickens.

We have generated a monoclonal antibody, termed 1E8, that is specific for myelinating and nonmyelinating Schwann cells in mature chickens. 1E8 first stains cells at the edge of the neural crest; later, cells located between the neural tube and somites and in the sclerotome are immunopositive. Double labeling with HNK-1 indicates that these 1E8-positive cells represent a subset of neural crest cells in the ventral migratory pathways. 1E8-positive cells are later associated with the dorsal and ventral roots and with extending nerve trunks. In Western blots, 1E8 reacts with proteins comigrating with P0. Immunodepletion experiments establish that all P0 molecules carry the 1E8 determinant. The developmental distribution of P0, as determined by 1E8 immunoreactivity, differs from that reported for P0 in mammals and suggests that, in chicken, P0 is an early marker for the Schwann cell lineage.

Animals↗
PubMed1991

Morphometric inflammatory cell analysis of human liver allograft biopsies.

To quantitate the inflammatory cell response within the portal tracts of liver allografts during acute rejection, we retrospectively and in a blinded fashion reviewed 431 biweekly, protocol, core allograft biopsies in 58 consecutive adult recipients. Following the determination of the cross-sectional area of each portal tract, the number of eosinophils, neutrophils, and lymphocytes therein was tabulated. The average number, percentage, and density of each type of portal inflammatory cell were calculated for each biopsy. Each biopsy was prospectively and independently classified as either associated (REJ+) or not associated (REJ-) with acute rejection. Acute rejection consisted of simultaneous allograft dysfunction and qualitative pathologic findings of acute rejection. Biopsies obtained during periods of normal allograft function or during episodes of dysfunction due to other causes were classified as not associated with rejection (REJ-). Ninety biopsies were classified as associated with acute rejection (REJ+) while 241 biopsies were classified as not associated with acute rejection (REJ-). In general, the average portal-tract number, percentage, and density of all inflammatory cells were significantly increased in biopsies associated with acute rejection. In contrast, only the portal-tract eosinophil values were consistently predictive of acute rejection following receiver-operating characteristic curve analysis (sensitivity = 82-86%, specificity = 91-92%). This quantitative method of allograft assessment appears to improve the objectivity of the serial biopsy protocol. By using this method, we found the eosinophil's appearance within the portal tracts to be a dependable indicator of acute rejection.

Adult↗