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Biomedical subjects

J S Gupta

Publications and source records attributed to J S Gupta.

At least 19 recordsLinked to original sources
PubMed1989

A novel primase-free form of murine DNA polymerase alpha induced by infection with minute virus of mice.

Two species of DNA polymerase alpha free of primase activity were identified in extracts of Ehrlich mouse cells that had been infected with minute virus of mice. Primase-free forms of DNA polymerase alpha eluted with 150 and 180 mM NaCl during ion-exchange chromatography on DEAE-cellulose columns, exhibited sedimentation coefficients of 11 S and 8.2 S, respectively, and were inhibited by aphidicolin, N2-(p-n-butylphenyl)-9-(2-deoxy-beta-D-ribofuranosyl)guanine 5'-triphosphate, and 2-(p-n-butylanilino)-9-(2-deoxy-beta-D-ribofuranosyl)adenine 5'-triphosphate. The ratio of primase-free DNA polymerase alpha to the DNA polymerase alpha-primase complex increased from 1.5 to greater than 100 during the course of infection, and free primase was produced during the MVM replicative cycle.

Animals↗
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↗
PubMed1989

Effect of clomiphene on nuclear estrogen receptor of the fallopian tube during ovum transport in rabbits.

The effect of clomiphene on nuclear estrogen receptors of the Fallopian tube during ovum transport in the rabbit has been studied. Nuclear binding capacity was observed in ampulla (A), ampullary-isthmic junction (AIJ), isthmus (I), uterine-isthmic junction (UIJ) and uterus (U). Receptor concentration decreased in all segments of the tube after administration of clomiphene in mated animals. The bindings are of high affinity and low capacity. Important alterations were observed during transport when compared to that of 14, 24, 34, 48, 72, 144 and 168 hr post-coitum (p.c). At 24 hr p.c binding increased only in I and decreased in A and AIJ. Retention of eggs at I at 24 hr p.c showed as increase in binding at I. Egg transport was accelerated and eggs reached prematurely in the uterus due to the influence of clomiphene. Binding in I remained constant from 48 hr p.c to 144 hr p.c but concurrently the binding level increased in U from 34 hr p.c. The elevation of nuclear estrogen receptor level was maximum at 24 hr p.c which coincided with increased plasma estrogen level. The result of such study showed that clomiphene depleted nuclear estrogen receptor complex in the fallopian tube before transfer to the uterus. Further, observation indicated that clomiphene acted directly on the rate of egg transport because of the variations in estrogen receptors during different time periods. Thus, clomiphene reduced the quantity of estrogen receptor i.e., insensitiveness to estrogen. The variations in estrogen binding to its receptor and plasma level at different post-coital periods are modulated by clomiphene resulting in the acceleration of egg transport and prevention of pregnancy.

Animals↗
PubMed1987

Effect of tamoxifen on cytosolic estrogen receptor in the different parts of fallopian tube and uterus during ovum transport.

The effect of tamoxifen (ICI-46474) (alpha-[4-(beta-N-dimethylamino ethoxy)-phenyl]alpha'-ethyl trans stilbene on estrogen cytosolic receptor was observed in different parts of fallopian tube and uterus of rabbits during ovum transport. Tubal segments viz. ampulla (A), ampullary isthmic junction (AIJ), isthmus (I), uterine isthmic junction (UIJ) and uterus (U) were studied during the passage of ovum. Significant differences were observed in normal, drug treated and pregnant animals at 14, 24, 34, 48, 72, 144 and 168 h. In treated animals during 14 h post-coitum (p.c.) to 34 h p.c. the ampullary cytosol receptor concentration increased and suddenly decreased at 48 h p.c. whereas from 72 h p.c. to 144 h p.c. it increased gradually. Tamoxifen accelerated the rate of egg transport decreasing tubal cytosolic receptors at 48 h p.c. However, beyond 48 h p.c. receptors increased till 144 h p.c. Results suggest that tamoxifen modulated tubal cytosolic estrogen receptors during egg transport and prevents pregnancy.

Animals↗
PubMed1977

Prediction of maximal aerobic power in man.

A general prediction formula has been derived for predicting maximal aerobic power (VO2 max) based on nonlinear relationship between aerobic stress and cardiorespiratory strains imposed on the subject during submaximal exercise on bicycle ergometer. The validity of the prediction formula has been tested for the data consisting of 135 observations on 45 moderately active young subjects who were asked to exercise on the bicycle ergometer at three submaximal and one maximal work rate. It has been found that product moment correlations of aerobic stress with respiratory strain and cardiac strain expressed logarithmically were 0.7651 and 0.7457 respectively. These correlations were significant (P less than 0.001). The multiple correlation between observed and estimated aerobic stress expressed logarithmically in terms of cardiorespiratory strains was 0.8142 which was significant (P less than 0.001). There is a significant improvement in multiple correlation from the product moment correlations of aerobic stress with either of two strains expressed logarithmically. It has been conclusively established that combined index of cardioresiratory strains will be better predictor of aerobic stress than either respiratory or cardiac strain alone as commonly employed by several workers.

Aerobiosis↗
PubMed1977

Does "blastocyst estrogen" initiate implantation?

Fertilized eggs were incubated for 2 hours in a medium containing estradiol-17beta and then transferred into the uteri of day 5 pseudopregnant rats. These eggs, but not estrogen-free control eggs, induced a local increase in capillary permeability. We suggest that the blastocyst factor which induces the local increase in capillary permeability during early pregnancy is estrogen synthesized by the blastocyst.

Animals↗
PubMed1977

Evidence that "embryonic estrogen" is a factor which controls the development of the mouse preimplantation embryo.

4- to 8-cell mouse PIE's (preimplantation embryos) were cultured in vitro for 48 hr in media containing various concentrations of the anti-estrogen CI-628. Graded effects of the various concentrations were observed with the highest concentration (1.5 microng/ml) being 100% effective in blocking development to the blastocyst stage. The deleterious effects of the drug were prevented to some extent by including estradiol-17beta in the medium. Our interpretation is that the effect of CI-628 was due to its anti-estrogenic properties. If this interpretation is correct, then the results support our hypothesis that the development of mouse PIE's depends upon estrogen which originates in the PIE.

Animals↗
PubMed1976

Leucyl naphthylamidase activity in pigeon and toad testes under various experimental conditions.

The activity pattern and functional significance of leucyl naphthylamidase (LNase) in the pigeon testis under different hormonal and photoperiod conditions as well as in the testes of short- and long-term HCG-treated toads have been studied histochemically. In both the species, the enzyme activity was present in the maturing spermatids and those embedded in the Sertoli cell components, the mature spermatozoa released in the lumen being devoid of any LNase activity. In pigeon, the stimulation of spermatogenic process was associated with enhanced activity of the enzyme, whereas arrest of spermatogenesis showed little or no activity. In toad, short-term HCG treatment caused mild stimulation of spermiation resulting in sperm release from the Sertoli cells and this was accompanied by moderate decrease in LNase activity. The long-term HCG treatment produced an enhanced stimulation of spermiogenesis and spermiation processes resulting in almost total disappearance of LNase activity. The above observations suggest that the enzyme in the testes of both species is related to spermiogenesis and/or spermiation events of spermatogenesis.

Animals↗
PubMed1975

Steroidogenesis in rabbit preimplantation embryos.

Rabbit preimplantation embryos were flushed from the reproductive tract at 24 hr (1- to 2-cell stage), 48 hr (morula), 72 hr (morula), 96 hr (blastocyst), 120 hr (blastocyst), and 144 hr (blastocyst) post coitum. At 168 hr (early postimplantation period), gestation sacs were excised, frozen, and sectioned in a cryostat. Delta5-3beta-Hydroxysteroid dehydrogenase [3(or 17)beta-hydroxysteroid:NAD(P) oxidoreductase, EC 1.1.1.51] activity was determined histochemically in whole preimplantation embryos and in sectioned postimplantation embryos. 3beta-Hydroxysteroid dehydrogenase activity began at 48 hr and was sustained through the late blastocyst stage (144 hr), with the exception of a brief drop, possibly cessation, of activity at 72 hr. There was no activity at 168 hr. Since 3 beta-hydroxysteroid dehydrogenase is a key enzyme in the metabolism of steroid hormones, its presence is strong evidence for steroidogenesis. Only 144-hr preimplantation embryos were used to determine 17 beta-hydroxysteroid dehydrogenase (estradiol-17beta:NAD 17-oxidoreductase, EC 1.1.1.62) activity, which was present, suggesting synthesis of estrogen. By means of radioimmunoassay, 144-hr preimplantation embryos were found to contain estradiol-17beta. Other authors have shown that rabbit blastocysts contain progesterone and other steroids, and these embryos can synthesize steroids from non-steroid and steroid precursors. Therefore, our results plus those of others prove that rabbit preimplantation embryos synthesize steroid hormones. Our present and previous results (with rats, hamsters, and mice) suggest that the steroid hormones synthesized by the embryo are critical for preimplantation embryogenesis and for implantation of the lbastocyst.

Animals↗
PubMed1975

Changes in exercise heart rate in lowlanders after prolonged stay at high altitude (4000 m).

Studies were conducted on cardiac frequency during submaximal and maximal work on 26 sea-level residents prior to transfer to and during stay at high altitude for 1, 10, and 20 months. Maximal O2 uptake and performance in a 1.6 km run were observed. Results indicated a significant drop in Vo2 after arrival at altitude followed by recovery with further stay. The mean maximum heart rate decreased to 182.8 beats/min after 1 month at high altitude from a seal-level mean value of 188.4 beats/min. It increased to 199.2 beats/min and decreased to 185.6 beats/min after 10 and 20 months, respectively. Heart rate, during submaximal work requiring 1.0 and 1.5 102/min, indicated the highest rate after 1 month at altitude and decreased with prolonged stay, but remained higher than the sea-level value. These changes were compared with the high-altitude native residents.

Acclimatization↗