Changes in CD38 expression and ADP-ribosyl cyclase activity in rat myometrium during pregnancy: influence of sex steroid hormones

Cyclic ADP-ribose (cADPR), synthesized by CD38, regulates intracellular calcium in uterine smooth muscle. CD38 is a transmembrane protein that has both ADP-ribosyl cyclase and cADPR hydrolase enzyme activities involved in cADPR metabolism. CD38 expression and its enzyme activities in uterine smooth muscle are regulated by estrogen. In the present study, we examined CD38 expression, its enzyme activities, and cADPR levels in myometrium obtained from rats at 14-17 days of gestation (preterm) and at parturition (term). CD38 expression, ADP-ribosyl cyclase activity, and cADPR levels were higher in uterine tissues obtained from term rats compared with that of preterm rats, while activity of cADPR hydrolase did not significantly change. In an effort to address whether changes in estrogen: progesterone ratio that occur during pregnancy account for the observed effects on CD38 expression and function, we determined the effect of different doses of progesterone in the presence of estrogen on CD38 expression and its enzyme activities in uterine smooth muscle obtained from ovariectomized rats. In myometrium obtained from ovariectomized rats, estrogen administration caused increased CD38 protein expression and ADP-ribosyl cyclase activity. The estrogen-induced increases in CD38 expression and ADP-ribosyl cyclase activity were inhibited by simultaneous administration of 10 or 20 mg of progesterone. These results indicate that the estrogen:progesterone ratio determines CD38 expression and ADP-ribosyl cyclase activity. These changes in CD38/cADPR pathway may contribute to increased uterine motility and onset of labor.     

Changes in the 17 beta-hydroxysteroid dehydrogenase activity of mouse blastocysts during delayed implantation

The rate of estrone (E1)----estradiol-17 beta (E2) or E2----E1 conversion catalyzed by 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) activity was determined for each mouse embryo in modified F-10 medium containing 0.95 microM 3H-E1 or 3H-E2. During delayed implantation, the E1----E2 conversion rate was decreased (p less than 0.005) from 5.69 +/- 0.34 fmol/h/blastocyst on Day 5 to 3.50 +/- 0.46 fmol/h/blastocyst on Day 9, whereas E2----E1 was increased (p less than 0.005) from 7.44 +/- 1.08 to 18.60 +/- 2.04 fmol/h/blastocyst. After estrogen injection, the Day 9 implanting blastocyst showed an increase (p less than 0.005) in E1----E2 conversion to 9.05 +/- 0.64 fmol/h/blastocyst but a slight, insignificant decrease in E2----E1 conversion to 14.2 +/- 1.82 fmol/h/blastocyst. A similar trend was also observed in Day 5 implanting blastocysts when compared to Day 5 delayed blastocysts. Thus, 17 beta-HSD activity in delayed blastocysts favors E2----E1 over E1----E2 conversion in a ratio of 5:1. After estrogen induction of implantation, the E1----E2 conversion rate is stimulated and the ratio of E2----E1 to E1----E2 rate is decreased to 1.5:1. The results suggest that 17 beta-HSD activity may be involved in blastocyst implantation.     

Changes in the ultrastructure of rat hepatocyte nucleoli during bilateral adrenalectomy and after administration of cortisol

Nucleolar ultrastructure of the rat hepatocytes after bilateral adrenalectomy and cortisol stimulation has been studied by the electron-microscopic method Traits of nucleolar inactivation (a decrease of granular component enlargement of fibrillar centres, condensation of peri- and intranucleolar chromatin, etc.) are observed in hepatocyte nucleoli 5 days after adrenalectomy. Cortisol stimulation of hepatocytes of the adrenalectomized rats leads to nucleolar activation (4h, 5h, 8h after the hormone injection). Adrenalectomy with following cortisol injection is a useful model to study inactivation and activation of ribosomal genes in the target cells.     

Piglets born after non-surgical deep intrauterine transfer of vitrified blastocysts in gilts

The aims of this study were: (1) to evaluate the effect of the number of previous estrus of recipient gilts on effectiveness of intrauterine insertion of a flexible catheter designed for non-surgical deep intrauterine catheterization during diestrus in pigs; and (2) to determine the farrowing rate and the litter size after non-surgical deep intrauterine embryo transfer (ET) of porcine blastocysts vitrified by the open pulled straw (OPS) method. In experiment 1, 27 large white hyperprolific gilts (LWh) with 2-6 previous estrus were used. Intrauterine insertions of the flexible catheter were carried out at day 5.5-6 of the estrous cycle (D0=onset of estrus). During insertions, no or only moderate reactions were observed in 88.9% of gilts and was not related (P >0.05) to the number of estrus prior to the insertion periods. The number of the estrus had a significant effect (P <0.05) on the difficulties found during the procedure. In the 100% of gilts with two estrus (N=6) it was not possible to insert the flexible catheter through the cervix. In gilts with three or more estrus, it was possible to pass the cervix and to progress along a uterine horn in 80.9% of the cases. In 86.7% of the gilts, the tip of the flexible catheter achieved the second or third quarter of the uterine horn. In experiment 2, following non-surgical deep intrauterine transfer of 20 vitrified/warmed blastocysts, 9 Meishan recipients (42.9%) farrowed an average of 5.4 +/- 0.8 piglets (range 3-9) of which 0.6 +/- 0.3 piglets (range 0-2) were born dead. In conclusion, this study shows that it is possible to obtain birth of piglets following non-surgical deep intrauterine embryo transfer (ET) of vitrified/warmed blastocysts. Non-surgical deep intrauterine ET and OPS vitrification methods are promising procedures to be used together for the introduction of new genetic material in a farm.     

Changes in isoproterenol-stimulated adenylate cyclase activity in rat testicular tissue during cryptorchidism and after orchidopexy

Cryptorchidism was associated with increased responsiveness of the isoproterenol-sensitive adenylate cyclase in membrane particles from rat testis. Abdominal testes from uni- and bilaterally cryptorchid rats showed the same activities. The change in isoproterenol-responsive adenylate cyclase was independent of the age at which the animals were made cryptorchid. The isoproterenol response was maximal 3-4 weeks after the rats were made cryptorchid. By 2-3 months after orchidopexy the isoproterenol response in the rat testis had decreased to normal control values.     

Changes in rat hypothalamo-neurohypophyseal system after repeated ethanol administration]

The histochemical, immunohistological and histoenzymatic study of the hypothalamo-neurohypophysial system of the rat shows that chronic ethanol administration induces: a temporary blockage of vasopressin synthesis, a vasoconstriction of the neurohypophysial capillaries, a dendritic storage of immunoreactive vasopressin. In our experimental conditions, a long ethanol treatment disturbs the balance between vasopressin synthesis and release.     

Slow elimination of a prazosin metabolite compared to prazosin kinetics after its intravenous administration to rabbits

Serum concentration profiles of prazosin and its metabolite 2-(1-piperazinyl)-4-amine-6,7-dimethoxyquinazoline after intravenous bolus administration to rabbits (0.5 mg/kg) were shown to be biphasic. Rapid decline related to distribution was followed by a terminal slope lasting for up to 24 hours. Prazosin level in this phase decreased, its elimination half-life being about 9 hours, while the metabolite serum level was almost constant between 4 and 24 hours and averaged 0.9 mumol/l. This is in keeping with the earlier suggested extremely low elimination rate of this metabolite. Enterohepatic recirculation may account for this phenomenon, as well as a significant rise in the metabolite serum concentration I hour after the injection.     

Electrical coupling in rat myometrium during pregnancy.

Gap junctions were found in rat myometrium only during parturition of abortion. A comparison was made between the values of the length constants obtained from longitudinally cut strips of rat myometrium at the midterm stage of pregnancy and during parturition. No significant difference was found between these values. No significant difference was found between length constants measured in myometrium from rats near term (22 days) and those during parturition, or between midterm myometrium and myometrium taken from animals aborting at midterm following ovariectomy. It was concluded that the appearance of gap junctions in parturient myometrium does not alter the spread of passive current in the longitudinal axis of the cells in these tissues. It is suggested that gap junctions are not required for spread of passive current, and that other structures may provide an alternate path.     

Changes in activity and intra-acinar distribution of glucose-6-phosphate dehydrogenase and malic enzyme during pregnancy in rat liver

Summary Using techniques of microdissection and microassay as well as qualitative histochemistry the activity and intra-acinar distribution of G6PDH and ME were studied on selected days of pregnancy in the rat. Both enzymes show distinct fluctuations during the course of pregnancy in keeping with changes in hepatic lipogenesis. Marked increases in activity are seen as early as the 4th day, while highest values are attained on day 20, with a predominant perivenous induction. On day 22, just before parturition a sharp decrease of both enzyme activities with a flattening of the periportal/perivenous gradient was detected. G6PDH shows proportionally considerably larger increases and more distinct changes in zonation. The perivenous fluctuations in G6PDH activity of late gestation are supposed to be caused primarily by insulin. Although estrogen is known to induce both enzymes, the temporal changes in enzyme activity in pregnancy cannot be related to the action of estrogen alone. The changes in enzyme activity, however, correspond well to those of progesterone, and although no direct action of progesterone on these enzymes has yet been proposed, further work on its effects on enzyme activity and distribution is indicated.     

Changes in the activity of adenylate- and guanylate cyclase in different rat tissues after chronic administration of ACTH or cortisol

The state of adenylate and guanylate cyclases in the adrenals, suprarenal fat and ventricular myocardium of the rat was studied under conditions of chronic administration of ACTH or cortisol. By the end of ACTH injections the weight of the adrenals and the DNA content in them increased 6 and 3 times, respectively; both parameters showed a gradual increase. The corticosteroid level in the blood changed throughout the experiment. The changes in the DNA content in the adrenals and in the corticosteroid level in the blood were oppositely directed. This was paralleled with cyclic changes in the basal and stimulated activities of adenylate and guanylate cyclases occurring with a periodicity of 15 days. The peaks of the cyclase activity preceded the increase in the DNA content. Similar cyclic changes in the enzyme activity were observed in the adipose tissue and myocardium. It was supposed that periodic changes in the cyclase activity are the main prerequisites for the growth and replication of cells under conditions of changed hormonal status of the organism.     

Changes in activity and intra-acinar distribution of glucose-6-phosphate dehydrogenase and malic enzyme during pregnancy in rat liver

Using techniques of microdissection and microassay as well as qualitative histochemistry the activity and intra-acinar distribution of G6PDH and ME were studied on selected days of pregnancy in the rat. Both enzymes show distinct fluctuations during the course of pregnancy in keeping with changes in hepatic lipogenesis. Marked increases in activity are seen as early as the 4th day, while highest values are attained on day 20, with a predominant perivenous induction. On day 22, just before parturition a sharp decrease of both enzyme activities with a flattening of the periportal/perivenous gradient was detected. G6PDH shows proportionally considerably larger increases and more distinct changes in zonation. The perivenous fluctuations in G6PDH activity of late gestation are supposed to be caused primarily by insulin. Although estrogen is known to induce both enzymes, the temporal changes in enzyme activity in pregnancy cannot be related to the action of estrogen alone. The changes in enzyme activity, however, correspond well to those of progesterone, and although no direct action of progesterone on these enzymes has yet been proposed, further work on its effects on enzyme activity and distribution is indicated.     

Changes in the activity of rat cortical and hippocampal neurones after the iontophoretic administration of beta-endorphin, glutamate and GABA

The effect of microiontophoretically administered beta-endorphin on the activity of 62 cortical and hippocampal neurones was studied in acute experiments on 14 rats. The effectiveness of beta-endorphin was first of all verified in the isolated guinea pig ileum, the mouse was deferens and in a study if its analgetic and catatonic effect in rats. Beta-endorphin only mildly depressed the spontaneous activity of cortical neurones, but markedly inhibited the activity stimulated by the microiontophoretic administration of glutamate. In the hippocampus, beta-endorphin stimulated the activity of all the studied neurones when only low ejection currents were used and activation persisted for 1-4 min after terminating administration. With higher ejection currents, the discharge frequency rose enormously and not even GABA blocked this effect. The excitatory effect of beta-endorphin on the hippocampal neurones may possibly be the basis of the epileptogenic action of this substance.