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Biomedical subjects

A K Pal

Publications and source records attributed to A K Pal.

At least 37 records · Page 2Linked to original sources
PubMed1999

Antiovulatory faculty of the flower of Malvaviscus conzattii.

The methanol extract of the flowers of Malvaviscus conzattii was orally administered in cycling unilaterally ovariectomized (ULO) rats at a dose level of 1 g/kg body wt/day for one or two cycles. The effect of the extract on the length of the cycle and ULO-induced compensatory ovulation and hypertrophy of the remaining ovary was assessed on the first oestrus following completion of treatment. Although no adverse influence was observed on either of the parameters, the cycle length was significantly prolonged and both the compensatory phenomena underwent significant inhibition after treatment of the extract for two consecutive cycles. In another experiment, the extract was found to be ineffective in preventing exogenous gonadotropin(s)-induced ovulation in immature and sub-adult rats. It is, therefore, suggested that the extract might have interfered with the synthesis and/or release of gonadotropin(s) from the pituitary while the ovarian utilization of gonadotropin(s) remained unaffected. The LD50 of the extract was found to be 20 g/kg body wt.

Animals↗
PubMed1999

Effect of pelvic endometrial implants on overall reproductive functions of female rats.

The effects of pelvic endometrial implants on the overall reproductive potential of female rats were investigated. After homologous transplantation in the peritoneum, the ectopic endometrium developed into highly vascularized nodes that gradually increased in mass until the 9th week postsurgery and then plateaued. In the presence of these implants, overall reproductive function was adversely affected. The effect was of greatest magnitude during 50-70 days posttransplantation. As compared with values in corresponding controls, ovulation was reduced by 43% (6 of 14) (p < 0.05), mating rate was reduced by 44% (12 of 27) (p < 0.025), and premature termination of pregnancy occurred in 34% (5 of 15) of rats. Wastage of pregnancy, which included complete termination or reduction of fetal number, occurred during the postimplantation course of gestation. Furthermore, 100% of the rats with transplants failed to respond to the copulomimetic stimulation for the induction of pseudopregnancy (p < 0.01, compared with corresponding controls). However, on exposure to vasectomized males, 46% (6 of 13) of these rats exhibited development of pseudopregnancy (p < 0.05, compared with corresponding group receiving copulomimetic stimulation). Increased rate of mating failure and differential pseudopregnancy rates after copulomimetic and natural cervical stimulation suggest that the rats with endometrial explants possibly had an absence or a short appearance of behavioral estrus. Hormonal assessment during the preovulatory phase showed a tendency toward lower mean levels of preovulatory estradiol and significantly lower LH (p < 0.01) and progesterone (p < 0.01) concentrations. The adversely affected reproductive functions may be a secondary consequence of these altered endocrine milieus.

Abortion, Spontaneous↗
PubMed1998

The role of nitric oxide in the process of implantation in rats.

Nitric oxide (NO) plays an important role in cell signalling in many physiological systems, including reproduction. During pregnancy, oestrogen modulates uterine NO generation, and NO may play an intermediary role in the oestrogen-mediated effects on the uterus. Since oestrogen is actively involved in inducing endometrial receptivity to support the process of implantation, the role of NO in the process of implantation in rats was investigated. N omega-nitro-L-arginine methyl ester (L-NAME), an inhibitor of NO synthase (NOS), was administered in utero with or without sodium nitroprusside (SNP), a generator of NO, on different days during the preimplantation phase of gestation. The status of gestation in respect of implantation failure, endometrial receptivity and embryo development were assessed. L-NAME was administered at various doses (2-5 mg per uterine horn) and on different days of pregnancy (days 2-6 of pregnancy) to optimize the pregnancy terminating dose (absence of implantation site on day 8 of pregnancy) and the effective day of treatment. L-NAME led to failure of implantation when administered at 2.5 mg per uterine horn on day 3 of pregnancy. The characteristic preimplantation permeability changes in the uterus were significantly attenuated and embryo growth was retarded. The L-NAME-mediated effects were significantly reversed when SNP (100 micrograms) was co-administered with L-NAME. These findings suggest a role for NO in the process of implantation. The possible mechanism by which inhibition of the NO-NOS system may interfere with implantation is discussed.

Animals↗
PubMed1997

Animal experimentation with tooth derived calcium hydroxyapatite based composites as bone-graft substitute biomaterials.

Calcium Hydroxyapatite (HA) has now been clinically accepted as one of the most important alloplastic bonegraft substitute in the management of oral surgical procedures including periodontal bony defects. HA can be synthetically prepared or derived from natural sources. Among the natural sources bovine bone is common but human source is also used. Of late Calcium Hydroxyapatite has been derived from extracted human tooth source. The present study involves the experiments using different varieties of HA in conjunction with chitosan, a binder, to know it's unique biological behaviour of bone bonding. The experiment was designed using 12(Twelve) New Zealand white rabbits on transcortical drilled hole tibial model and the observation was made under optical and scanning electron microscope. Result showed the osteoconductive and bioactive nature of tooth derived HA and biocompatibility of chitosan. The clinical problem of handling the particulate form of HA can be overcome by using chitosan which when mix with HA can stabilize the particle in surgical sites. This has tremendous clinical applications in dental regenerative surgery.

Animals↗
PubMed1994

The energy cost of metalliferous mining operations in relation to the aerobic capacity of Indian miners.

Mining in India is still relatively unmechanized, and in the hot, humid, and noisy environment with uncomfortable postures, many work operations impose a considerable physiological strain. The physical characteristics, including aerobic capacities, of 54 workers in an Indian metalliferous mine have been studied, and their energy expenditures measured during long periods of work in different tasks. The mean VO2max was 2.32 +/- 0.6 l/min and the mean body mass was 60 +/- 4 kg. Averaged energy expenditures for different tasks ranged between 9.4 and 22.8 kJ/min and were usually more than 33% of the workers' maximal work capacity. Recommendations about reducing the stress of mining work are made.

Anthropometry↗
PubMed1994

Preferential accumulation of putative "dics" under non-selective conditions during in vivo progression of a murine ascites sarcoma.

The occurrence and accumulation of dicentric marker (dic) chromosomes with terminal centromeres have been documented in a murine ascites sarcoma cell line (S180) during in vivo progression of the tumour for many years. Initially, in 1975, the cell line had only one such "dic" but currently the predominant clone is represented by three such "dics". Moreover, the emergence of a new sub-clone with four dicentric markers has recently been recorded. The possible significance of the preferential accumulation of "dics" in the cell line is discussed.

Animals↗
PubMed1993

Induction of SOS like responses by nitrofurantoin in Vibrio cholerae el tor cells.

Treatment of Vibrio cholerae el tor strain SLH22(J) with nitrofurantoin induced dose-dependent prophage 'kappa', the maximum induction being 6-fold the spontaneous induction level. UV-inactivated 'kappa' phages were Weigle reactivated, the maximum Weigle factor being 1.8 and 2.0 respectively in nitrofurantoin and UV pretreated el tor strain H218 Smr. Nitrofurantoin treatment also caused significant filamentation of the el tor strain H218 Smr and mutation of these cells from ampicillin sensitivity to ampicillin resistance. The levels of the four SOS-like responses induced by this drug were low but significant.

Bacteriophages↗
PubMed1993

Electron microscopic study of phages and aberrant structures produced by induction of prophage kappa in Vibrio cholerae el tor cells.

Prophage kappa in V. cholerae el tor strain SLH22(J) could be induced spontaneously or by treatment with nitrofurantoin, though the efficiency of induction was very low (not more than 0.8%). V. cholerae el tor cells were found to release many different aberrant structures of the temperate phage, kappa. These aberrant structures were characterized by density gradient centrifugation and electron microscopy.

Bacteriophages↗
PubMed1993

Induction of prophage lambda by nitrofurantoin and its modulation by butylated hydroxytoluene, sodium arsenite and alpha tocopherol.

Nitrofurantoin induced prophage-lambda in E. coli K12 strain GY5027(lambda) in a dose dependent manner, the maximum induction being 10-fold the spontaneous induction level and the maximum efficiency of induction 74%. The lever extract used as a metabolizing mixture enhanced the induction level significantly. Chloramphenicol at a concentration of 20 micrograms/ml inhibited the prophage induction by nitrofurantoin, indicating that the induction required concomitant protein synthesis. Butylated hydroxytoluene(BHT) and sodium arsenite enhanced the nitrofurantoin induced prophage-lambda induction in E. coli GY 5027(lambda) cells in a dose dependent manner. The maximum modulations in induction level (I/Io) were achieved with 100 micrograms/ml BHT and 250 micrograms/ml sodium arsenite corresponding to a nitrofurantoin concentration of 15 micrograms/ml and were found significant on statistical analysis. alpha-tocopherol, however, did not produce any effect on the prophage-lambda induction by nitrofurantoin.

Arsenic↗
PubMed1992

On the induction of umu gene expression in Salmonella typhimurium strain TA1535/pSK1002 by some nitrofurans.

Several nitrofurans were found to induce umu gene expression in Salmonella typhimurium TA1535/pSK1002 as defined on the basis of at least a 2-fold increase of beta-galactosidase activity over the background level. beta-Galactosidase activity increased with increasing concentrations of the chemical, attained a maximum at a concentration which was different for different nitrofurans used, and then gradually decreased with a further increase of the nitrofuran concentration. The umu gene expression test revealed that the genotoxic activity was highest for furazolidone and lowest for 5-nitro-2-furaldehyde.

Azides↗
PubMed1992

Effect of RMI 12,936, an antiprogestational steroid on decidual cell reaction and embryos in rat.

Subcutaneous administration of RMI 12,936 at a dose level of 2 mg/rat on day 5 of unilaterally pregnant rat having trauma-induced decidual cell reaction (DCR) in the contralateral uterine horn, suppresses DCR, induces resorption of implanted embryos and leads to decrease in the plasma level of progesterone. Progesterone replacement (D 5-8) in this situation reverses DCR suppressive effect of RMI 12,936 but fails to prevent resorption of implanted embryos. It is concluded that possibly the drug simultaneously exerts embryotoxic as well as luteolytic effects, but these effects are independent.

Androstenols↗
PubMed1992

Cervix tumour cell line established from tumour after long term passages as heterotransplant in nude mice.

One human cancer of the uterine cervix xenograft was established in tissue culture only after repeated passages in nude mice suggesting that with the repeated passages in nude mice, tumour cells acquire some properties which allow them to grow in vitro. Attempts to establish cell line tumours from earlier passages were not successful. The established cell line is tumourigenic. On inoculation of cultured cells in nude mice tumour take was found to be 100%. Karyotypic analysis revealed human origin.

Animals↗
PubMed1990

Microstructure and growth of ZnTe films.

The microstructure and growth of ZnTe films deposited onto glass and freshly cleaved NaCl substrates are carefully studied by a TEM. Effect of different stimulator on the grain growth is also described.

Tellurium↗
PubMed1990

DNA damage and prophage induction and toxicity of nitrofurantoin in Escherichia coli and Vibrio cholerae cells.

Repair-deficient and repair-proficient strains of E. coli K12 were sensitive to nitrofurantoin treatment to varying degrees with the double mutant strain (uvrA 6, recA 13) being most sensitive. Ultraviolet absorption data and thermal chromatography through a hydroxyapatite column revealed that nitrofurantoin treatment of V. cholerae strain OGAWA 154 produced a maximal amount of 55% reversibly bihelical DNA at a nitrofurantoin dose of 120 micrograms/ml/h, which indicated the formation of inter-strand cross-links in DNA. Nitrofurantoin also produced prophage-lambda induction in E. coli K12 strain GY 5027: envA, uvrB, ampA 1, strA (lambda), in a dose-dependent manner, the maximum induction being highly significant (P less than 0.001). Previously published mutation data coupled with the prophage induction data presented here suggest that the genotoxic properties of nitrofurantoin are mediated through the SOS pathway.

Bacteriophage lambda↗