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Biomedical subjects

S Bhattacharyya

Publications and source records attributed to S Bhattacharyya.

At least 91 records · Page 5Linked to original sources
PubMed1995

Murine polyomavirus and simian virus 40 large T antigens produce different structural alterations in viral origin DNA.

Murine polyomavirus (Py) and simian virus (SV40) encode homologous large T antigens (T Ags) and also have comparable sequence motifs in their core replication origins. While the ability of SV40 T Ag to produce specific distortions within the SV40 core replication origin (ori) in a nucleotide-dependent fashion has been well documented, little is known about related effects of Py T Ag on Py ori DNA. Therefore, we have examined viral origin DNA binding in the presence of nucleotide and the resulting structural changes induced by Py and SV40 T Ags by DNase I footprinting and KMnO4 modification assays. The structural changes in the Py ori induced by Py T Ag included sites within both the A/T and early side of the core origin region, consistent with what has been shown for SV40. Interestingly, however, Py T Ag also produced sites of distortion within the center of the origin palindrome and at several sites within both the early and late regions that flank the core ori. Thus, Py T Ag produces a more extensive and substantially different pattern of KMnO4 modification sites than does SV40 T Ag. We also observed that both T Ags incompletely protected and distorted the reciprocal ori region. Therefore, significant differences in the interactions of Py and SV40 T Ags with ori DNA may account for the failure of each T Ag to support replication of the reciprocal ori DNA in permissive cell extracts.

Animals↗
PubMed1995

Demographic history of India and mtDNA-sequence diversity.

The demographic history of India was examined by comparing mtDNA sequences obtained from members of three culturally divergent Indian subpopulations (endogamous caste groups). While an inferred tree revealed some clustering according to caste affiliation, there was no clear separation into three genetically distinct groups along caste lines. Comparison of pairwise nucleotide difference distributions, however, did indicate a difference in growth patterns between two of the castes. The Brahmin population appears to have undergone either a rapid expansion or steady growth. The low-ranking Mukri caste, however, may have either maintained a roughly constant population size or undergone multiple bottlenecks during that period. Comparison of the Indian sequences to those obtained from other populations, using a tree, revealed that the Indian sequences, along with all other non-African samples, form a starlike cluster. This cluster may represent a major expansion, possibly originating in southern Asia, taking place at some point after modern humans initially left Africa.

Base Sequence↗
PubMed1993

Medical audit of community screening for undescended testes in Halton District.

OBJECTIVES: To evaluate the quality of screening in the community for undescended testis and to determine the percentage of boys referred for surgery before their second birthday. DESIGN: Population-based retrospective study of hospital and community clinic records of boys resident in Halton Health District who underwent surgery for undescended testicle during 1987-89. SETTING: Community Child Health Clinics. Medical Records Department of referral hospitals surrounding Halton district. RESULTS: During 1987-89, 76 boys from Halton district underwent surgery for undescended testis in the neighbouring hospitals: 64 (84%) of these boys had attended at least one screening examination in the community clinics; 12 (16%) did not attend any. Among the 64 who attended 18 (28%) were not considered to have undescended testis. Of the 30 boys diagnosed to have undescended testis after school entry, six were diagnosed incidentally in hospital and 24 were detected by general practitioners and School Medical Service. The age range for surgical referral varied from six months to 12.5 years. The percentage of boys referred for surgery before their second birthday was only 13%. CONCLUSION: Many cryptorchid boys were not picked up in community screening and many of these did not receive early surgery. This audit report suggested the following recommendations: (a) increased awareness of the condition amongst doctors and health visitors performing screening examination; (b) early surgical referral. These recommendations have been implemented in the district. Our further plan is to repeat the audit in three years to assess changes.

Child, Preschool↗
PubMed1993

The replication functions of polyomavirus large tumor antigen are regulated by phosphorylation.

Polyomavirus (Py) large T antigen (T Ag) contains two clusters of phosphorylation sites within the amino-terminal half of the protein. To characterize possible regulatory effects of phosphorylation on viral DNA replication, Py T Ag was treated with calf intestinal alkaline phosphatase (CIAP). Incubation of the protein with a range of phosphatase concentrations caused progressive loss of phosphate without affecting its stability. Treatment with smaller quantities of CIAP stimulated the ability of the viral protein to mediate replication of constructs containing the viral replication origin, while higher concentrations of CIAP caused a marked diminution of this replication function. Several biochemical activities of Py T Ag were examined after CIAP treatment. Py T Ag DNA unwinding and nonspecific DNA binding were only slightly affected by dephosphorylation. However, as determined by DNase I footprinting experiments, treatment with smaller amounts of CIAP stimulated specific binding to the Py replication origin by Py T Ag, while treatment with larger amounts of CIAP caused marked inhibition of origin-specific binding by the viral protein. Phosphotryptic maps of Py T Ag before or after treatment with CIAP revealed changes in individual phosphopeptides that were uniquely associated with either the stimulation or the inhibition of replication. Our data therefore suggest that Py T Ag is regulated by both repressing and activating phosphates.

Alkaline Phosphatase↗
PubMed1992

Regulation of progesterone secretion in human syncytiotrophoblast in culture by human chorionic gonadotropin.

In the present investigation we sought to define the specific sites in the pathway of placental progesterone biosynthesis that underlie the action of human chorionic gonadotropin (hCG). When the cells were challenged with dibutryl cAMP (dbcAMP), forskolin or isobutylmethylxanthine, they produced significantly higher amounts of progesterone which in the presence of the hCG antibody was reduced to the level of the control set of cells. Trophoblast cells cultured in serum free medium with 25-hydroxycholesterol (25-OHC) produced increased amounts of progesterone. In the presence of hCG antibody at a concentration which neutralized the secreted hCG, the steroid production was completely blocked, even when the 25-OHC was added to the medium. Also, direct quantitation of the cytochrome P450 SCC enzyme in the absence of hCG indicated a significant decrease. The exogenous addition of low density lipoproteins (LDL) increased the progesterone secretion by the trophoblast cells in culture. Neutralization of hCG by the antibodies, however, drastically reduced the LDL induced progesterone secretion, which was restored by the addition of dbcAMP to the medium. Based on these findings, we suggest a stimulatory effect of hCG on normal trophoblast cells at the level of LDL utilization and cytochrome P450 SCC enzyme. Since dbcAMP could mimic these actions of hCG, the data suggest a possible autocrine/paracrine role of hCG on the trophoblast cells. An additive effect of hCG and cAMP on progesterone secretion observed in our studies, indicate that apart from hCG, adenylate cyclase activity may also be regulated by other factors.

1-Methyl-3-isobutylxanthine↗
PubMed1990

A plasma-membrane associated ATPase from the acidophilic bacterium Acidiphilium cryptum.

A membrane-bound ATPase of Acidiphilium cryptum, an acidophilic bacterium of mine origin, has been studied. The enzyme has a pH optimum of 8.4 Mg2+ is required for its activity and could be replaced by Mn2+, but not by Ca2+. The enzyme shows a strong preference for ATP as substrate, with the apparent Km of about 0.2 mM. Sulphite ion significantly stimulated the enzyme activity. N,N'-Dicyclohexylcarbodiimide, oligomycin, and azide strongly inhibited the enzyme, whereas vanadate was without effect, suggesting that the A. cryptum ATPase might be of F0F1 type.

Adenosine Triphosphatases↗
PubMed1989

Cardiac nociceptors and ischemia: role of sympathetic afferents in cat.

In total, 86 units were recorded from T2 and T3 left thoracic rami of cat. These receptors were located on the circumflex coronary artery, anterior descending coronary artery, and its adjacent myocardial regions. The conduction velocity of these fibres was in the range of "C" (0.5 to 1.8 m/s) and "A delta" (5.96 to 17 m/s) fibres. Out of these 86 units, only 28 units were activated by coronary occlusion. The average resting frequency of the spontaneous unit was 0.8 +/- 0.06 impulses/s which increased to 35 +/- 4.8 impulses/s on mechanical probing. In order to examine whether the units sensitive to coronary occlusion were also responsive to algesic agents, some of these units were studied applying lactic acid, bradykinin, prostaglandins, and nicotine. It was observed that these ischemia-sensitive units are also sensitive to lactic acid (10 units), bradykinin (16 units), prostaglandins (12 units), and nicotine (15 units). These ischemia-sensitive units are presumably nociceptors and activated by algestic agents that cause cardiac ischemic pain.

Adrenergic Fibers↗
PubMed1988

Induction of tumor associated macrophage-mediated lysis of autologous tumor cells by lectins.

Lectin dependent cell mediated cytotoxicity (LDCC) to autologous tumor cells (ATC) by the tumor associated macrophages (TAM) was studied by 4 h 51Cr release assays at early and late stages of growth of a murine transplantable ascites tumor, S-180, in presence of different concentrations of wheat germ agglutinin (WGA) and Concanavalin A (Con A). Induction of LDCC by the unstimulated resident macrophages (RM) to S-180 tumor cells was also assayed. Both WGA and Con A induced significant tumoricidal activity in the TAM at different states of activation and in RM in a dose-dependent manner, the activated TAM showing expression of cytotoxicity with the lowest doses of the lectins used. Addition of N-acetylglucosamine (NAcGle) or D-mannose (D-man) in the assay completely inhibited LDCC induced by WGA and Con A, respectively. Effector-target contact alone not sufficient for inducing lysis in LDCC was evident from the observations that low doses of the lectins augmented target binding by the inactivated TAM and RM with no subsequent cytolysis.

Animals↗
PubMed1987

Inhibition by monosaccharides of tumor associated macrophages mediated antibody dependent cell cytotoxicity to autologous tumor cells.

A number of mono- and oligosaccharides are known to inhibit direct contact mediated cytotoxicity of natural killer cells, cytotoxic T lymphocytes and macrophages. In antibody dependent cell mediated cytotoxicity (ADCC), where antibody molecules mediate target recognition, binding and lysis, the role of cell surface carbohydrates is not clearly defined. In the present paper the effects of D-mannose (D-man), N-acetylglucosamine (N-AcGlc), N-acetylgalactosamine (N-AcGal) and glucose on binding and lytic events of ADCC by the tumor associated macrophages (TAM) to autologous tumor cells (ATC) were studied. The TAM were isolated on day 3 of growth of a transplantable ascites tumor--S-180, in Swiss mice. D-man, N-AcGlc and N-AcGal when added to the assay partially inhibited ADCC at 15 mM but at 25 and 40 mM totally abrogated ADCC. Glucose marginally enhanced ADCC at 25 mM but at other concentrations partial inhibition of ADCC occurred. Preincubation of TAM with 25 mM of D-man, N--AcGlc and N-AcGal resulted in total abrogation of ADCC with significant reduction in their binding of ATC, whereas, pretreatment of ATC with the sugars produced 30-40% inhibition of lysis with marginal reduction in target binding. The inhibitory effects of D-man, N-AcGlc and N-AcGal were also observed on ADCC mediated by the peritoneal resident macrophages (RM) of Swiss mice. "Lectin-like" receptors were postulated to be present on the surface of TAM which were involved in ADCC and were inhibitable by sugars.

Acetylgalactosamine↗
PubMed1986

Tumor associated macrophage mediated lysis of autologous tumor cells.

Lysis of autologous tumor cells (ATC) mediated by the tumor associated macrophages (TAM) was studied by 4 h 51Cr-release assay at different days of growth of a transplantable ascites tumor, S-180, inoculated in adult male Swiss mice. The ATC were coated with serum of tumor bearing mice. On day 3 after tumor inoculation the TAM mediated a remarkable lysis of the tumor serum coated ATC. With advancement of tumor growth the cytolysis by TAM decreased gradually to the basal level at day 10 and totally abrogated at day 12. Also the binding of the tumor serum coated ATC by TAM varied at different days of tumor growth. At early phases of tumor growth high lytic activity of the TAM was correlated with augmented target binding. The observed lysis may be considered as antibody dependent cell mediated cytotoxicity (ADCC) extended by the TAM, since presence of specific tumor antibodies were demonstrated in the tumor serum used for coating ATC. No significant lysis was recorded when the ATC was coated with normal serum or used as such for direct lysis by the TAM. In vitro treatment of the TAM with suitable doses of Levamisole and Polyionosinic-polycyticyclic acid further augmented the TAM mediated high level of ADCC at day 3 with no change in its binding of ATC. The immunopotentiators enhanced both ADCC and target binding ability of the functionally depressed TAM at day 10.

Animals↗
PubMed1986

Phagocytic activity of the tumor associated macrophages in relation to tumor growth: modulation with levamisole.

The phagocytic activity of the tumor associate macrophages isolated at different days of the growth of a murine transplantable ascites tumor was assessed by measuring the engulfment of Na2 51CrO4 labeled antibody coated sheep erythrocytes. Binding of the targets by the macrophages was also assessed. It was observed that, excepting the day 3, till day 7 of tumor growth the phagocytic activity of the tumor associated macrophages was very high as compared to that of resident macrophages of normal mice. Augmented target binding by the macrophages was recorded till day 7. Levamisole was observed to augment phagocytosis and target binding by the macrophages but a differential requirement as regard to the dose of Levamisole was noted for modulation of phagocytosis and target binding by the tumor associated macrophages at early and advanced stages of the tumor growth.

Animals↗
PubMed1982

Visceral receptors and their afferents in the caudal mesenteric nerve of the duck.

1. The behaviour and reactivities of visceral receptors to different mechanical and chemical stimuli in simple unit preparations from the caudal mesenteric nerve of adult ducks were studied to examine the physiological roles of such receptors. 2. In total, 83 single unit activities were recorded from the caudal mesenteric nerve. 3. Receptors were grouped according to their locations in different layers of the rectum as (i) over the branching points of the blood vessel or in the serosal layer, (ii) in the muscle layer or (iii) in the mucous membrane of the rectum. 4. All the receptors, both spontaneous and non-spontaneous, responded to mechanical probing. Receptors of the muscle layer responded to distension also and showed a slowly-adapting nature. Most of the receptors of the other two groups were of the rapidly-adapting type. 5. Conduction velocity ranged from 0.76 to 34.6 m/s. 6. Sympathetic afferent fibres from the hind gut ascend along the intestinal nerve and join the caudal mesenteric nerve via the colonic ganglion.

Animals↗