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Biomedical subjects

S Batra

Publications and source records attributed to S Batra.

At least 163 records · Page 9Linked to original sources
PubMed1987

Source of calcium for contractions induced by depolarization and muscarinic receptor stimulation in rabbit urinary bladder.

Omission of calcium or the inclusion of lanthanum in the bathing medium resulted in an almost complete inhibition of contractile responses induced by either K+ depolarization or carbachol in strips of rabbit urinary bladder. D-600 inhibited K+-induced contractions significantly more than carbachol-induced responses. The influx of 45Ca into cells was stimulated both by K+ depolarization and carbachol. Over a 2-min period the increase in 45Ca influx induced by high K+ and carbachol was 98 and 65%, respectively. Both lanthanum and D-600 blocked 45Ca influx stimulated by either K+ depolarization or carbachol. The inhibition of 45Ca influx by these calcium-channel blocking agents, particularly by D-600, was dependent on the length of exposure. Application of carbachol during 45Ca efflux in pre-loaded muscle strips had no effect on the rate of 45Ca efflux. These results indicate that the contractile responses of the urinary bladder to depolarization and to carbachol are highly dependent on an extracellular source of calcium.

Animals↗
PubMed1987

Possible reflection of intracellular calcium binding in the divergent pattern of relaxation in rat and rabbit uterus.

The mechanical responses to potassium of the rabbit and rat uterus were different. The force of a potassium-induced contracture showed a rapid decline in the rabbit uterus, whereas it was fully maintained for a long period in the rat uterus. The increase in 45Ca influx following exposure to high KCl was substantial and similar (0.3 mmol kg-1) in both rat and rabbit uterus. Calcium uptake in post nuclear supernatant (PNS) from the rat myometrium was significantly lower than that from the rabbit myometrium in both the rate and capacity of uptake. This uptake was reduced to about 10% in the presence of sodium azide in PNS from both rat and rabbit myometria. Both the rate and capacity of calcium uptake by mitochondria isolated from PNS of rat myometrium were considerably lower than that by rabbit myometrial mitochondria. Microsomes isolated from rat and rabbit PNS had very low capacity for calcium uptake compared with mitochondria. No difference was found in the rate or the capacity of uptake between the rat and the rabbit myometrial microsomes. The data support the argument for a role of mitochondria in myometrial relaxation and further provide evidence for a considerable species difference in calcium uptake by myometrial mitochondria.

Animals↗
PubMed1987

Nuclear estrogen receptors in human uterine arteries.

Specific binding of estradiol was measured in both cytoplasmic and nuclear fractions of uterine arteries obtained from ten women (39-52 years of age) undergoing hysterectomy. Seven patients were menstruating regularly and three were perimenopausal. Whereas nuclear receptors could be quantified in all ten tissues, cytoplasmic receptors were detected only in four. The mean receptor concentrations in the nuclear and cytosolic fractions were similar (31-42 fmol/mg protein), and the apparent dissociation constant of the receptor from all tissues was 1-2 nM. There was no relationship between the age and nuclear receptor concentration, but there was a tendency towards a negative correlation between the plasma progesterone:estradiol ratio and receptor levels. The presence of estrogen receptor in the nuclear fraction and its absence in the cytoplasm may warrant modification of the classical two-step model for steroid hormone action.

Adult↗
PubMed1987

Subcellular distribution of [3H]oestradiol-17 beta and salt resistance of nuclear oestrogen complexes in the rat uterus after in-vivo administration of [3H]oestradiol-17 beta.

The distribution of injected [3H]oestradiol-17 beta into nuclear and post-nuclear fractions as well as resistance to KCl (0.6 mol/l) extraction of nuclear oestrogen-binding sites in the rat uterus were studied. Both ovariectomized untreated and oestrogen-treated rats were used. One hour after injection of [3H]oestradiol into ovariectomized rats, 373 and 195 fmol/100 mg uterus were recovered in the nuclear and post-nuclear fractions respectively. About 17% of the nuclear-associated [3H]oestradiol was resistant to KCl extraction. After 18 h, the amount of [3H]oestradiol decreased to about 30% of that found after 1 h, and about 23% of nuclear complex remained resistant to extraction. In cardiac tissue, practically no [3H]oestradiol accumulated in the nuclear fractions and the amount recovered in post-nuclear fractions was about one-third of that in the uterine post-nuclear fractions. In the ovariectomized oestrogen-treated rats the distribution of [3H]oestradiol in nuclear and post-nuclear fractions was very similar and the proportion of the total nuclear fraction inextractable by KCl slightly higher (26%) than in untreated rats. After 18 h, while measurable amounts of [3H]oestradiol were found in post-nuclear fractions, no radioactivity was detected in the nuclear fraction. The results demonstrate the existence of salt-resistant nuclear oestrogen-binding sites in the mature ovariectomized rat uterus in vivo. Further, oestrogenization of ovariectomized rats did not significantly influence the amount or proportion of salt-resistant nuclear sites.

Animals↗
PubMed1987

Modulation by continuous oestrogen treatment and by progesterone of oestrogen receptors in the rabbit uterus.

The effect of continuous oestrogen treatment on uterine weight, and on cytoplasmic and nuclear oestrogen receptors was examined in rabbits. Modulation of the effects of oestrogen by progesterone was also studied. Uterine weight increased successively after exposure to oestrogen from 1 to 6 days. The concentration of both cytosolic and nuclear oestrogen receptors decreased in almost parallel fashion, however, irrespective of whether it was expressed per microgram protein or microgram DNA. Treatment with progesterone 5 days after oestrogenization caused no significant change in uterine weight at first. The oestrogen receptor concentration in both cytosolic and nuclear fractions decreased after 1 day but increased again after 3 days of progesterone treatment. The results indicated that there is a reduction in the actual concentration of oestrogen receptors in both cytosolic and nuclear fractions after continuous oestrogen treatment. The antagonism by progesterone of the effects produced by oestrogen appears to be transitory in nature, at least in the rabbit uterus.

Animals↗
PubMed1986

Effect of estrogen and progesterone treatment on calcium uptake by the myometrium and smooth muscle of the lower urinary tract.

In order to elucidate the mechanisms by which estrogen treatment increases uterine contractility, the effect of estrogen on Ca uptake was measured in the isolated rabbit uterus as well as in the urethra and urinary bladder. Estrogen treatment more than doubled the amount of cellular Ca uptake in the uterus during both rest and potassium-induced depolarization. Combined estrogen and progesterone treatment had a similar effect to estrogen alone. In both urinary bladder and the urethra, treatment with estrogen alone, or estrogen combined with progesterone had no effect on Ca uptake. Cellular Ca uptake was higher in uteri of rabbits subjected to progesterone withdrawal than in those that were under progesterone dominance. It is concluded that estrogen-induced increase in Ca entry into the uterine smooth muscle cells is a likely mechanism underlying increased uterine contractility. Since this effect of estrogen was not antagonized by progesterone, it may not strictly rely on the genomic action of estrogen. The increase in cellular calcium following progesterone withdrawal could be one of the mechanisms for the evolution of myometrial activity at parturition.

Animals↗
PubMed1986

Use of 3H-QNB in the isolation of plasma membrane from smooth muscle of the urinary bladder: effect of oxalate on calcium uptake by the membrane fractions.

Specific binding of tritiated quinuclidinyl benzilate (3H-QNB) to surface membrane muscarinic receptors was utilized to identify plasma membrane (PM) fractions from smooth muscle of the rabbit urinary bladder. Accumulation of 3H-QNB in the PM fraction was 4-5-fold higher than that in fractions of endoplasmic reticulum (EM) or mitochondria (M). A similar pattern of distribution was found for 5'-nucleotidase. 3H-QNB binding therefore appears to be a suitable marker for plasma membrane of the urinary bladder. Data on ATP-dependent calcium uptake by PM and ER fractions showed that oxalate highly potentiated calcium uptake by both fractions and consequently this feature cannot be used to identify ER fractions specifically.

Animals↗
PubMed1986

Effect of oxytocin on calcium influx and efflux in the rat myometrium.

45Ca was used to investigate the effect of oxytocin on calcium movements in uterine smooth muscle from estrogenized rats. Upon exposure to oxytocin the influx of 45Ca in myometrial strips increased rapidly. After 2 min of incubation with oxytocin (1 microM) there was a 30% increase over the control. Prolonged stimulation with oxytocin caused no further accumulation of 45Ca. The amount of Ca gained following oxytocin stimulation could be removed by washing with a lanthanum solution. The rate of 45Ca efflux from preloaded tissues was substantially increased by oxytocin. In the absence of external Ca, the stimulation of 45Ca efflux by oxytocin was much reduced. The data indicate that oxytocin-induced contraction of the myometrium is largely dependent on the influx of extracellular calcium. Oxytocin appears to be capable of releasing small amounts of calcium from intracellular storage sites. The data also provide evidence against the inhibition by oxytocin of the calcium extrusion pump.

Animals↗
PubMed1986

Binding affinities of four tricyclic antidepressive drugs to muscarinic cholinergic receptors in human parotid gland.

The binding kinetics of tritiated quinuclidinyl benzilate (QNB) were studied in membrane preparations from human parotid and rabbit submandibular glands. Inhibition of 3H-QNB was then used to compare the anticholinergic activity of lofepramine, desipramine, imipramine and amitriptyline for muscarinic receptor in the salivary glands. The apparent dissociation constant (KD) for 3H-QNB binding in human parotid and rabbit submandibular gland was 33 and 61 pM and the Bmax value 507 and 169 f mol/mg protein, respectively. The mean values for the inhibition constant (Ki) for lofepramine, desipramine, imipramine and amitriptyline in human parotid gland were 285, 135, 102 and 13 nM, respectively. Very similar values were obtained for the rabbit submandibular gland. The binding affinity of tricyclic antidepressants for muscarinic cholinergic receptor sites in human parotid gland closely paralleled clinical data on the inhibition of salivary flow by these drugs.

Animals↗
PubMed1986

Increases in blood flow of the female rabbit urethra following low dose estrogens.

The effects of low doses (0.05 to 20 micrograms./kg.) of estradiol-17 beta (E2) and estriol (E3) on blood perfusion in the genitourinary tissues were examined two and 24 hours after an intra-arterial injection into rabbits. Whereas 0.05 microgram./kg. E2 or E3 caused no detectable change, 0.5 microgram./kg. of either E2 or E3 markedly increased blood flow measured after two hours in urethra, vagina and uterus. No significant increase in the blood flow in the urinary bladder or the ureters was observed. With 20 micrograms./kg. E2 or E3 a much greater increase (10 to 25-fold) in the blood flow in the urethra, vagina and uterus was observed after two hours. At this time a small increase (about two-fold) could also be measured in urinary bladder and ureters. Twenty-four hours after this treatment (20 micrograms./kg. E2 or E3), the blood flow in the urinary organs was not significantly different from the pretreatment values but it was still significantly elevated in uterus and vagina. These data show that the blood flow in the female urethra is just as sensitive to low doses of estrogens as uterus and vagina. Both E2 and E3 seem to be equally effective in increasing blood perfusion in the urogenital tissues.

Animals↗
PubMed1986

Identification and characterization of muscarinic cholinergic receptors in the isolated plasma membranes and intact tissue of the urinary bladder.

The binding characteristics of 3H-quinuclidinyl benzilate (QNB) to strips of intact tissue and to isolated plasma membrane fraction (PM) from rabbit urinary bladder were studied. QNB binding to both preparations was of high affinity and low capacity. The equilibrium dissociation constants (KD) for binding to tissue strips and PM were 2.2 and 0.045 nM respectively. Muscarinic antagonists inhibited QNB binding more effectively than agonists. Ca-antagonist D-600, but not nifedipine caused an inhibition of QNB binding to PM. Vanadate, ouabain or N-ethylmelaimide had no significant effect on QNB binding. In contrast to the binding in PM, binding in the intact tissue was reduced by K-depolarization.

Animals↗
PubMed1985

Progesterone receptors in human vaginal tissue.

Specific progesterone receptors were measured in both cytoplasmic and nuclear fractions of vaginal tissues obtained from 17 women between 33 and 53 years in age. Whereas nuclear receptors could be measured in 11 of 17 tissues examined, cytoplasmic receptors were detected in only four. The distribution of receptor-positive tissues was similar in the follicular and luteal phases and no significant difference was observed in the nuclear receptor concentration in the two phases. The receptor concentration from all tissues examined ranged from 31 to 105 pmol/mg of protein and the apparent dissociation constant was 1 to 2 nmol/L. The presence of progesterone receptors in the nuclear fraction and their absence in the cytoplasm raise questions about the authenticity of the classical two-step model for steroid hormone action.

Adult↗
PubMed1985

Characterization of [3H]-nitrendipine binding to uterine smooth muscle plasma membrane and its relevance to inhibition of calcium entry.

Specific, high affinity (KD = 164 pM) binding of the Ca channel inhibitor [3H]-nitrendipine was identified in plasma membrane-enriched fractions from the rat myometrium. Although dihydropyridines effectively competed for [3H]-nitrendipine binding sites, both verapamil and D600 were poor competitors. Diltiazem (10 microM) increased [3H]-nitrendipine binding by about 40%, but had no effect on binding affinity. Among several other drugs tested, diethylstilboestrol (DES) caused a considerable inhibition of binding, with an IC50 value of 4 microM. Both La3+ and EDTA (or EGTA) inhibited binding. The inhibition by the latter could be overcome by the addition of Ca2+ or Mg2+. A clear relationship was found between [3H]-nitrendipine binding and 5-nucleotidase activity in the various subcellular fractions. Data on K+-stimulated Ca2+ influx in the intact uterine strips showed a good agreement between the inhibition by both nitrendipine and DES of stimulated Ca influx and their inhibitory effect on [3H]-nitrendipine binding to plasma membrane. This type of correlation was lacking in the case of D600. These results suggest that Ca channels in the myometrial membrane possess multiple sites at which different drugs can act to block these channels.

Animals↗
PubMed1985

Effect of oestrogen and progesterone on the blood flow in the lower urinary tract of the rabbit.

The effects of oestrogen and of oestrogen combined with progesterone were examined on the fractional distribution of cardiac output (blood flow) in the genitourinary tissues of the female rabbit. Oestradiol treatment significantly increased blood perfusion in the uterus, vagina and urethra but caused no change in the perfusion of the urinary bladder or the kidneys. The wet weight of the uterus and vagina increased significantly and in the urethra there was a tendency to weight gain following oestradiol treatment. Progesterone treatment following oestrogen appeared to reduce the effect of oestrogen on both perfusion and weight gain.

Animals↗
PubMed1984

Binding of estradiol-17 beta and estriol in cytosolic and nuclear fractions from urogenital tissues.

This report describes the measurement and partial characterization of the specific binding of estradiol (E2) and estriol (E3) in the cytosols and nuclear fractions from uterus, vagina, urethra and urinary bladder of the rabbit. Fractions from uterine and vaginal tissues showed the highest binding with both E2 and E3 approx 300 fmol/mg protein. The levels of specifically bound E3 were about 70% of the corresponding values for E2. In the sedimentation analysis the cytosolic receptors for both E2 and E3 exhibited 2 major forms, 3 S and 8 S, in addition to the heavy aggregates. Sephacryl S-200 chromatography showed major and minor components corresponding to mol. wt of 250.000 and 20.000-40.000 respectively. No noteworthy differences in the cytosolic receptors from different tissues could be observed in the above analyses. Whereas the uterine nuclear E2 receptor sedimented at 4.3 S the vaginal receptor distributed in two peaks, 2.5 S and 4.3 S. The receptor from both urethra and urinary bladder sedimented at 2.5 S. Nuclear E3 receptor, however, showed a major peak at 3.5 S in all cases. Some differences in tissue nuclear receptor were also observed in their chromatographic behaviour. The results confirm the existence of estrogen receptor in both urethra and urinary bladder, and the data of the limited physiochemical analysis indicate that the receptors in these tissues are essentially similar to those in the uterus or vagina.

Animals↗
PubMed1984

Effect of estradiol and estriol treatment on vaginal estrogen receptors in the ovariectomized rabbit.

Wet weight of the vagina increased by more than two-fold following treatment of the ovariectomized rabbits daily for 7 days with 100 micrograms/kg estradiol-17 beta or estriol. The concentration of estrogen receptors expressed on the basis of milligrams of protein in both the cytosolic and nuclear fractions decreased significantly after treatment with estradiol or estriol. The data reinforce the view that estriol given in low doses over a long period of time has as good an effect as estradiol on the vagina, and its use might be safer with respect to the effect on endometrial proliferation.

Animals↗