Search PubMed⌕ Search

Biomedical subjects

A Bhattacharyya

Publications and source records attributed to A Bhattacharyya.

At least 145 records · Page 8Linked to original sources
PubMed1991

Eosinophil cationic protein's role in human hepatic allograft rejection.

Although it is known that eosinophils consistently infiltrate rejecting human liver allografts, their function is unknown. Infiltrating eosinophils can release a cytotoxic substance, eosinophil cationic protein. Furthermore, eosinophil cationic protein may be identified in biopsy specimens using immunoperoxidase staining of an eosinophil cationic protein-specific monoclonal antibody. To study a possible effector role of eosinophils in rejecting liver allografts, 38 serial allograft biopsy specimens from 12 patients with acute rejection, 54 biopsy specimens from 11 patients with allograft dysfunction caused by other causes and 22 biopsy specimens from 8 patients without allograft dysfunction were stained for extracellular eosinophil cationic protein. In addition, the absolute blood eosinophil counts and the portal tract eosinophil percent of the total number of portal tract inflammatory cells were tabulated in these patients until 30 days after transplantation. The blood absolute eosinophil count, portal tract eosinophil percent and incidence of positive extracellular eosinophil cationic protein staining were significantly increased in patients with rejection compared with patients with dysfunction from other causes (p less than 0.05 to 0.005, t test). Furthermore, each of these parameters predicted rejection with excellent sensitivity (75% to 92%) and specificity (91% to 100%). Of patients with rejection, 59% had significant elevation of all three parameters before or during rejection, and 92% had at least two parameters elevated. Conversely, of the patients with dysfunction from other causes, 0% had elevations of any parameter. The recognized cytotoxic properties of eosinophil cationic protein and its almost exclusive presence, along with eosinophils in the blood and allograft biopsy specimens of patients during acute rejection, support the role of the eosinophil as an effector cell in tissue injury during acute liver allograft rejection.

Blood Proteins↗
PubMed1990

RNA bulges and the helical periodicity of double-stranded RNA.

RNA molecules typically exhibit extensive secondary structure, including double-stranded duplex, hairpins, internal loops, bulged bases and pseudoknotted structures (reviewed in refs 3 and 4). This is intimately connected with biological function, including splicing reactions and ribozyme activity. The formation of RNA-DNA hybrids is important in the transcription of DNA, reverse transcription of viral RNA, and DNA replication. Bulged bases in RNA helices are potentially significant in RNA folding and in providing sites for specific protein-RNA interactions, as illustrated by TFIIIA of Xenopus and the coat protein of phage R17. Most information about the structure of RNA derives from fibre diffraction or crystallography of natural molecules, notably transfer RNA, but until recently there have been few systematic studies of RNA structure using designed sequences. We have used gel electrophoresis to investigate the properties of bulged bases in both RNA and RNA-DNA depending on the number and types of bases in the bulge and its position in the fragment. By varying the spacing between two bulge-induced kinks, we have measured the periodicity of RNA and RNA-DNA helices in solution.

Base Sequence↗
PubMed1990

Biochemical studies of liver & liver microsomes in envenomated rats.

Some biochemical parameters of liver and liver microsomes were studied in albino rats following administration of cobra and viper venoms at dose of 2 mg/kg body weight. The total protein content in cobra venom treated (CVT) animals and DNA and RNA contents of liver and liver microsomes were almost unaltered in both the venom treated animals while total protein content was significantly reduced in viper venom treated (VVT) animals. Alkaline and acid phosphatases activities of whole liver showed significant increase in both the venom treated animals whereas the rise in cholinesterase activity in CVT animals was not significant. Lactic acid content was significantly higher in CVT animals compared to either VVT animals or controls. The glycolytic enzymes viz., aldolase, phosphohexose isomerase and lactate dehydrogenase measured in hepatic microsomal fraction were significantly reduced while alanine and aspartate aminotransferases and gamma-glutamyl transpeptidase activities of liver microsomes were significantly elevated in both the venom treated animals compared to controls.

Animals↗
PubMed1990

Hepatic low density lipoprotein receptors, HMG-CoA reductase, and plasma lipids and apolipoproteins in high- and low-responding rhesus monkeys: effect of cholestyramine treatment.

Plasma lipids and apolipoproteins, and hepatic LDL receptor and HMG-CoA reductase activities in biopsy samples were measured in high- and low-responding rhesus monkeys maintained on a cholesterol-rich and regular diets. The effect of a 30-day cholestyramine treatment on the above parameters under both dietary conditions was also determined. On the cholesterol-rich diet the high-responders, when compared to the low-responders, had several-fold increased plasma cholesterol and apoB concentrations and significantly lower HDL apoA-I and cholesterol concentrations. Hepatic LDL receptor and HMG-CoA reductase activities were not detectable in the high-responders, while the low-responders expressed a reduced number of LDL receptors of normal affinity. Administration of cholestyramine resulted in a rapid induction of the hepatic LDL receptors in the high-responders and a small additional increase in the low-responders. Cholestyramine treatment also stimulated the expression of the hepatic HMG-CoA reductase in both groups of monkeys. These changes were accompanied by a dramatic drop in plasma cholesterol and apoB concentrations in the high-responders and, to a lesser extent, in the low-responders. Plasma HDL concentrations in the high-responders rose to levels higher than those seen in the low-responders. The affinity and receptor number were similar in both groups of monkeys on the control diet, but the low-responders had significantly higher HMG-CoA reductase activities. Administration of cholestyramine during the control diet had a small but significant additional effect on the hepatic LDL receptors of the low-responders but not of the high-responders.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Single base mismatches in DNA. Long- and short-range structure probed by analysis of axis trajectory and local chemical reactivity.

We have devised a procedure to generate any single base mismatch in a constant sequence context, and have studied these from two points of view. (1) We have examined electrophoretic mobility of 458 base-pair fragments containing approximately centrally located single mismatches, in polyacrylamide gels, compared to fully matched DNA fragments. We found that no single mismatch caused a significant perturbation of gel mobility, and we conclude that all the mismatches may be accommodated within a helical geometry such that there is no alteration of the path of the helix axis in a straight DNA molecule. (2) We have studied all the single mismatches with respect to reactivity to a number of chemical probes. We found that: (a) No mispaired adenine bases are reactive to diethyl pyrocarbonate and are therefore not simply unpaired such that N-7 is exposed. (b) A number of mispaired thymine bases are reactive to osmium tetroxide, and cytosine bases to hydroxylamine. (c) Where crystal or nuclear magnetic resonance structures are available, the reactivity correlates with exposure of the pyrimidine 5,6 double bonds to attack in the major groove as a result of wobble base-pair formation. This is particularly clear for G.T and I.T base-pairs. (d) Reactivity of bases in mismatched pairs can be dependent on sequence context. (e) Reactivity of the C.C mismatch to hydroxylamine is suppressed at low pH, suggesting that a rearrangement of base-pairing occurs on protonation. The results overall are consistent with the formation of stacked intrahelical base-pairs wherever possible, resulting in no global distortion of the DNA structure, but specific enhancement of chemical reactivity in some cases.

Base Composition↗
PubMed1989

The contrasting structures of mismatched DNA sequences containing looped-out bases (bulges) and multiple mismatches (bubbles).

We have studied the structure and reactivities of two kinds of mismatched DNA sequences--unopposed bases, or bulges, and multiple mismatched pairs of bases. These were generated in a constant sequence environment, in relatively long DNA fragments, using a technique based on heteroduplex formation between sequences cloned into single-stranded M13 phage. The mismatched sequences were studied from two points of view, viz 1. The mobility of the fragments on gel electrophoresis in polyacrylamide was studied in order to examine possible bending of the DNA due to the presence of the mismatch defect. Such bending would constitute a global effect on the conformation of the molecule. 2. Sequences in and around the mismatches were studied using enzyme and chemical probes of DNA structure. This would reveal more local structural effects of the mismatched sequences. We observed that the structures of the bulges and the multiple mismatches appear to be fundamentally different. The bulged sequences exhibited a large gel retardation, consistent with a significant bending of the DNA at the bulge, and whose magnitude depends on the number of mismatched bases. The larger bulges were sensitive to cleavage by single-strand specific nucleases, and modified by diethyl pyrocarbonate (adenines) or osmium tetroxide (thymines) in a non-uniform way, suggesting that the bulges have a precise structure that leads to exposure of some, but not all, of the bases. In contrast the multiple mismatches ('bubbles') cause very much less bending of the DNA fragment in which they occur, and uniform patterns of chemical reactivity along the length of the mismatched sequences, suggesting a less well defined, and possibly flexible, structure. The precise structure of the bulges suggests that such features may be especially significant for recognition by proteins.

Base Composition↗
PubMed1989

Calcium uptake by bovine epididymal spermatozoa is regulated by the redox state of the mitochondrial pyridine nucleotides.

Immature caput epididymal sperm accumulate calcium from exogenous sources at a rate 2- to 4-fold greater than mature caudal sperm. Calcium accumulation by these cells, however, is maximal in the presence of lactate as external substrate. This stimulation of calcium uptake by optimum levels of lactate (0.8-1.0 mM) is about 5-fold in caput and 2-fold in caudal sperm compared to values observed with glucose as substrate. Calcium accumulation by intact sperm is almost entirely mitochondrial as evidenced by the inhibition of uptake by rotenone, antimycin, and ruthenium red. The differences in the ability of the various substrates in sustaining calcium uptake appeared to be related to their ability to generate NADH (nicotinamide adenine dinucleotide). Previous reports have documented that mitochondrial calcium accumulation in several somatic cells is regulated by the oxidation state of mitochondrial NADH. A similar situation obtains for bovine epididymal sperm since calcium uptake sustained by site III oxidation of ascorbate in the presence of tetramethyl phenylenediamine and rotenone was also stimulated by NADH-producing substrates, including lactate, and inhibited by substrates generating NAD+ (nicotinamide adenine dinucleotide, oxidized form). Further, calcium uptake by digitonin-permeabilized sperm in the presence of succinate was stimulated when NADH oxidation was inhibited by rotenone. The compounds alpha-keto butyric, valeric, and caproic acids, which generate NAD+, inhibited the maximal calcium uptake observed in the presence of succinate and rotenone, and the hydroxy acids lactate and beta-hydroxybutyrate reversed this inhibition. These results document the regulation of sperm calcium accumulation by the physiological substrate lactate, emphasize the importance of mitochondria in the accumulation of calcium by bovine epididymal sperm, and suggest that the mitochondrial location of the isozyme LDH-X in mammalian sperm may be involved in the regulation of calcium accumulation.

3-Hydroxybutyric Acid↗
PubMed1989

Annual transmission potential of bancroftian filariasis in an urban and a rural area of West Bengal, India.

The annual transmission potential of Wuchereria bancrofti was calculated from the number of infective larvae found in the number of Culex quinquefasciatus expected to bite an individual exposed 24 hr a day for a year in Calcutta and in a rural (Memari) area. In Calcutta, an average of 151 mosquitoes/night/person were collected; it was calculated that 55,028 mosquitoes could bite a person per year, including an average of 177 infective mosquitoes containing 319 infective larvae of W. bancrofti. At Memari, an average of 284 mosquitoes/night/person were collected; here with the resulting calculation was that 103,718 mosquitoes could bite a person per year, including an average of 137 infective mosquitoes containing 223 infective larvae. The annual transmission potential was higher in the urban area than that in the rural area. Annual transmission potential is useful knowledge in the epidemiological assessment of transmission dynamics for the formulation of control strategies.

Animals↗
PubMed1988

Acrosome-reacted guinea pig spermatozoa become fusion competent in the presence of extracellular potassium ions.

Guinea pig spermatozoa are able to undergo capacitation and the acrosome reaction in a K+-free (-deficient) medium. However, they are unable to fuse with eggs unless they are exposed to a millimolar concentration of extracellular K+ during or after the acrosome reaction. Apparently, the plasma membrane over the equatorial segment gains the ability to fuse with eggs in the presence of K+ during and/or after the acrosome reaction. Once it becomes fusible, the membrane retains its fusibility even in a K+-deficient medium. Rb+ is almost as effective as K+ in rendering the sperm membrane fusible. Li+ and Cs+ are less effective. The molecular mechanism by which K+ renders acrosome-reacted spermatozoa fusion competent is unknown, but it may involve K+-mediated efflux of H+ from the spermatozoa.

Acrosome↗
PubMed1988

Synthetic organic pH buffers can support fertilization of guinea pig eggs, but not as efficiently as bicarbonate buffer.

Bicarbonate ions (HCO3-) in the medium are not absolutely essential for the fertilization of guinea pig eggs. However, fertilization takes place most efficiently in HCO3- -buffered medium. Capacitation, the acrosome reaction, and zona penetration by spermatozoa can occur in HCO3- -free media with synthetic organic buffers (i.e., MOPS, TES, HEPES, Tris, and TAPSO) but not as efficiently as in the HCO3- -buffered medium. It appears that HCO3- functions as more than just a pH-buffering molecule.

Animals↗