Sexual differentiation of the neuronal plasma membrane: neonatal levels of sex steroids modulate the number of exo-endocytotic images in the developing rat arcuate neurons

Exo-endocytotic images and intramembrane protein particles (IMP) were quantitatively assessed in freeze-fracture replicas from the plasma membrane of arcuate neurons of rats aged 0 (newborns), 10, 20 and 100 days postpartum. Membranes contained significantly (P less than 0.02) more IMPs in females than in males. Exo-endocytotic images were increased in newborn and 10-day-old males when compared to adult males or to developing females (48 +/- 6 vs 6 +/- 1 images/100 micron 2 in 10-day-old male and female rats, respectively). Androgenization of females with a single injection of testosterone propionate on the day of birth resulted in an increased number of exo-endocytotic images in developing animals (75 +/- 9 images/100 micron 2, 10-day-old rats) and in the abolishment of the sex differences in the number of IMPs.

Estrogen hydroxylase activity in the human placenta at term

Placental estrogen hydroxylase (EH) enzyme activity was measured at term using the catechol-O-methyl transferase coupled method in normal and high risk conditions. The identity and ratio of products formed during incubation of microsomes as analysed by high performance liquid chromatography in chronic hypertension, toxemia and diabetes mellitus was not different from controls. The mean enzymatic activity was also not different among the conditions studied as expressed mean +/- SE pmol/min/mg, protein: chronic hypertension (7.8 +/- 1), toxemia (8 +/- 1.6), diabetes mellitus (6.1 +/- 0.9) and controls (8.3 +/- 1.5). The cofactor dependence of EH was studied showing that NADPH is a better substrate for the enzyme than NADH.

Immunocytochemical localization of angiotensin II immunoreactivity and demonstration of angiotensin II binding in the rat ovary

The cellular localization of angiotensin II immunoreactivity and the presence of angiotensin II binding in rat ovaries were studied. Angiotensin II immunohistochemical staining was demonstrated throughout the corpora lutea of gonadotropin-stimulated immature rats and pseudopregnant adult rats, as well as in some stromal and thecal cells surrounding large antral follicles. No immunostaining was observed in granulosa cells of preantral or antral rat follicles or in ovaries from unstimulated immature rats. With in vitro autoradiography, specific, saralasin-suppressible 125I-angiotensin II binding was demonstrated in normal cycling rat ovaries: diestrus greater than proestrus greater than estrus. The combined findings of angiotensin II immunostaining in ovarian follicles and corpora lutea and of cycle-related angiotensin II binding support the hypothesis of a functional role for the ovarian renin-angiotensin system.

Blockage of ovulation by an angiotensin antagonist

Angiotensin II (Ang II) is present in high concentrations in preovulatory follicular fluid, and ovarian follicular cells have specific Ang II receptors. To investigate the possible direct involvement of Ang II in ovulation the specific receptor antagonist of Ang II, saralasin, was administered by intraperitoneal injection to immature rats in which follide development and ovulation had been induced with pregnant mare serum gonadotrophin (PMSG) and human chorionic gonadotrophin (hCG), respectively. Saralasin halved the number of oocytes found in the fallopian tubes 17 to 20 hours after administration of hCG. The antiovulatory effect was observed when saralasin was given 1 hour before hCG or 1 or 3 hours after hCG but not when given 5 hours after hCG. Simultaneous administration of Ang II reversed the saralasin blockage of ovulation. These results indicate a direct, obligate role for Ang II in ovulation and raise the possibility of contraceptive and profertility applications for agonists or antagonists of the renin-angiotensin system that are aimed at the ovulatory process.

Neuronal membrane remodelling during the oestrus cycle: a freeze-fracture study in the arcuate nucleus of the rat hypothalamus

Freeze-fracture methodology was used to study the organization of the neuronal plasma membrane in the rat arcuate nucleus, an oestrogen sensitive area of the hypothalamus. The quantitative evaluation of freeze-fracture replicas of the perikarya, dendritic shafts and dendritic spines revealed that the numerical density of intramembranous particles varied during the ovarian cycle. The number of small (less than 10 nm) particles was decreased, and the number of large (greater than 10 nm) particles was increased, in the P-face of the perikaryal plasma membranes in prooestrus and oestrus when compared to dioestrus. This change was associated with a significant increase in the number of exo-endocytotic images in the perikaryal plasma membrane in prooestrus. Changes in intramembranous particles during the ovarian cycle were not detected in arcuate nucleus dendritic shafts and dendritic spines.

Immunohistochemical evidence for synaptic connections between pro-opiomelanocortin-immunoreactive axons and LH-RH neurons in the preoptic area of the rat

Connections between adrenocorticotropic hormone (ACTH)-immunoreactive neurons in the arcuate nucleus and the preoptic area were studied in the female rat. ACTH-immunopositive terminals were observed in the medial preoptic area in contact with dendritic shafts, while in the ventrolateral preoptic area the majority of ACTH-immunoreactive synapses were found on dendritic spines. Double-label electron microscopic immunocytochemistry using peroxidase and avidin-ferritin as contrasting electron-dense markers revealed numerous synaptic contacts between ACTH-immunopositive boutons and luteinizing hormone-releasing hormone (LH-RH)-immunoreactive dendritic shafts in the medial preoptic area. Following injection of horseradish peroxidase (HRP) into the medial preoptic area, retrogradely HRP-labeled perikarya were observed throughout the arcuate nucleus. Double-staining experiments revealed that a proportion of these retrogradely labeled cells, in the ventromedial arcuate nucleus, are also immunoreactive for ACTH. These results suggest that pro-opiomelanocortin peptide-producing neurons in the ventromedial arcuate nucleus project to the medial preoptic area. Some of these neurons establish direct synaptic contacts with LH-RH-immunoreactive cells.

Clinical significance of liver dysfunction in pregnancy-induced hypertension

Hepatic dysfunction is one of the frequent manifestations of multisystemic involvement in preeclampsia. This study was conducted to establish the impact of liver dysfunction on maternal and neonatal outcome in women with pregnancy-induced hypertension (PIH). The prevalence of liver dysfunction as determined by an elevated serum glutamic oxalacetic transaminase (SGOT) concentration was 21% in a population of 355 patients with PIH. Liver dysfunction was associated with the presence of severe hypertension, proteinuria, a lower platelet count, and renal compromise (elevated blood urea nitrogen, creatinine, and uric acid serum concentrations). Abdominal pain was also associated with an SGOT elevation. Liver dysfunction was associated with intrauterine growth retardation and prematurity. Furthermore, the association with these neonatal complications was independent from the severity of the hypertension and the presence of proteinuria. Thus, we conclude that liver dysfunction is a frequent complication of PIH and that it is an independent risk factor for maternal and perinatal complications.

Catechol-o-methyl transferase activity in the human term placenta

Catechol-O-methyltransferase (COMT) characteristics and activity were studied using radioenzymatic techniques in placentas from normal and high-risk patients at term. The affinity of the catechol estrogen 20-hydroxyestrone (2OHE1), Km = 5 microM, for the enzyme was found to be at least 90-fold higher than that of the catecholamines norepinephrine, epinephrine, and dopamine (450, 490, and 850 microM, respectively). The product formed after incubation of placental cytosol with tritiated 20HE1 was identified as being exclusively (3H) 2-methoxyestrone, by use of high-performance liquid chromatography. Placental COMT activity after normal spontaneous delivery was no different from that obtained after elective cesarean section (270 +/- 20 versus 275 +/- 27, expressed as mean +/- SE activity nanomoles of 2-methoxyestrone formed per hour/mg protein). Placental COMT activity at term in women with hypertension (toxemia [T] or chronic hypertension [CHBP]) was significantly lower than in control subjects (284 +/- 27 versus 183 +/- 26; P less than 0.05). No significant differences in enzyme activity were found between T and CHBP (175 +/- 37 versus 210 +/- 32, P = NS). There were also no differences in COMT activity of diabetic classes A-R (White classification), fetal distress (with or without acidosis), and controls. The possible interference of antihypertensive drugs used by the patients in the study on COMT activity was assessed. Incubations of healthy placental cytosol with hydralazine, methyldopa, and Mg++ in their estimated plasma therapeutic concentrations had no effect on placental COMT activity. The present study suggests that placental COMT activity is low in patients with hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)

Follicular development is impaired by inhibitors of serine proteases in the rat

Serine proteases such as plasminogen activators are produced by granulosa cells both in vivo and in vitro and have been implicated in the process of ovulation. For a study of potential roles of serine proteases in early follicular development, immature rats were injected with pregnant mare serum gonadotropin, followed 2 hours later by laparotomy and injection of the serine protease inhibitors benzamidine and epsilon-aminocaproic acid into the bursa of one ovary. As a control, saline solution was injected into the contralateral bursa. Animals were put to death 48 hours after injection of serine protease inhibitors, and three to five randomly selected longitudinal sections were evaluated by computerized morphometry. The area occupied by antral follicles relative to the total cross-sectional area of each section was computed. Resultant ratios from serine protease inhibitor-treated ovaries were compared with those from contralateral control ovaries. Ninety-three percent of serine protease inhibitor-treated ovaries showed a reduction in antral follicular size when compared with corresponding control ovaries, which is indicative of inhibitory effects of serine protease inhibitor treatment on folliculogenesis. To further investigate this effect, ovulation was induced by human chorionic gonadotropin administration 48 hours after pregnant mare serum gonadotropin and 46 hours after serine protease inhibitor or saline solution treatment. Animals were put to death 20 hours later and the number of oocytes ovulated into oviducts was determined. Oviducts from serine protease inhibitor-treated ovaries contained 51% fewer oocytes than their control counterparts. Artifacts of surgical stress or vascular diffusion of serine protease inhibitor from treated to control sides were ruled out by appropriate control experiments. We conclude that early serine protease inhibitor treatment of pregnant mare serum gonadotropin-stimulated rat ovaries impairs folliculogenesis. Thus, in addition to involvement in ovulation, serine proteases appear to play important roles throughout follicular development.

Immunocytochemical evidence for direct synaptic connections between corticotrophin-releasing factor (CRF) and gonadotrophin-releasing hormone (GnRH)-containing neurons in the preoptic area of the rat

Electron microscopic double-label immunostaining with peroxidase and avidin-ferritin was used to study connections between corticotrophin-releasing factor (CRF) and gonadotrophin-releasing hormone (GnRH) immunoreactive elements in the medial preoptic area of the rat. Synaptic contacts were observed between CRF-immunoreactive axon terminals and the dendrites of GnRH-immunopositive neurons. These results suggest that the inhibitory effects of stress-induced CRF release on reproductive function may involve a direct CRF input to the GnRH-producing cells.

The cellular effects of estrogens on neuroendocrine tissues

Estrogen action on sensitive neurons in the rat diencephalon has been studied by morphologic techniques; evidence of estrogen action at every level is presented, including tracts, cells, circuitry and subcellular organelles. The demonstration in the arcuate nucleus of estrogen-induced synaptic remodelling, estrogen-induced postsynaptic membrane phenotypes, changes in intracellular membranes and rapid estrogen actions on neuronal endo-exocytosis indicates that cellular estrogen actions may underlie the neuronal control of reproduction.

Hormonal regulation of K+-channel messenger RNA in rat myometrium during oestrus cycle and in pregnancy

The dramatic enhancement of smooth-muscle excitability in the uterus which occurs at oestrus and at term in pregnant rats is closely related to increased blood oestrogen concentrations. How oestrogen alters the electrical properties of myometrial cells is unclear, although electrical coupling between cells has been shown to increase. Many examples are known of changes in cellular excitability involving modification of existing ion channels by second-messenger pathways. Steroid hormones, in contrast, are generally thought to influence cellular processes mainly through effects on gene expression, inducing the synthesis of new proteins. Previous work, using an oocyte translation system, has shown that a very slowly activating, voltage-dependent K+ current can be expressed from the poly(A)+ RNA of oestrogen-treated rat uteri. We report here that the messenger RNA species producing this channel is rapidly and reversibly induced in the presence of oestrogen, as shown by the appearance and disappearance of this mRNA during the oestrous cycle, its emergence at the end of pregnancy, and its presence or absence following hormonal treatments. These results suggest that oestrogen controls the expression of a voltage-dependent ion channel in uterine smooth muscle cells.

Estrogen-induced synaptic remodelling in adult rat brain is accompanied by the reorganization of neuronal membranes

Adult cycling female rats were injected with estradiol valerate (2 mg/100 g body wt.), a treatment which has previously been shown to result in synaptic remodelling in the arcuate nucleus and constant vaginal estrus. During the 32 weeks following estrogen treatment, arcuate nucleus neuronal plasma membranes were quantitatively assessed for intramembrane particle (IMP) number and size using freeze-fracture techniques. Neuronal membranes from untreated cycling females, females injected with oil and untreated males were also studied. Untreated rats had dimorphic sexual phenotypes in membrane organization; female rats had more IMP than males, mainly due to greater numbers of small (less than 10 nm) particles. These sex differences were observed in perikarya and dendritic shafts, but not in dendritic spines. Following estrogen treatment the density of IMP in membranes from females decreased. The IMP changes were found only in neuronal perikarya and dendritic shafts, not in dendritic spines, and were mainly due to a massive decrease in the number of small (less than 10 nm) IMP which was only partially offset by an increase in the number of large (greater than or equal to 10 nm) IMP. Thus, by 32 weeks after estradiol valerate treatment, the number and size of IMP in neuronal membranes from females were not different from those seen in normal males. These results strengthen the idea that estradiol may affect the turnover of certain neuronal membrane components in sex-steroid sensitive areas of the brain.

Immunohistochemical localization of aromatase cytochrome P-450 and estradiol dehydrogenase in the syncytiotrophoblast of the human placenta

Immunohistochemistry employing immunoglobulin G fractions raised against aromatase cytochrome P-450 and antiserum against 17 beta-estradiol dehydrogenase was used to localize these two steroid-converting enzymes in the human placenta. Immunostaining for both enzymes was found exclusively in the syncytiotrophoblast, while the underlying cytotrophoblast and the villus core did not stain. Ultrastructural examination of aromatase cytochrome P-450- and 17 beta-estradiol dehydrogenase-labeled sections disclosed immunoreactive product in the membranes of the endoplasmic reticulum; the nucleus, mitochondria, Golgi apparatus, and secretory granules were free of staining. These findings suggest that the syncytiotrophoblast is actively involved in the synthesis and metabolism of estrogens and in their role in placental endocrine function.

Estrogen formation in the mammalian brain: possible role of aromatase in sexual differentiation of the hippocampus and neocortex

Recent studies suggest that sex differences in cognitive function may involve effects of circulating androgens on the developing cerebral cortex and hippocampus. The mechanism of these effects is not understood. In rhesus monkeys, aromatase activity is present in the hippocampus and several areas of the cerebral cortex during late fetal and early postnatal life. Similarly, work in rats and mice indicates that the hippocampus and cerebral cortex may be capable of estrogen biosynthesis during early development. These results are consistent with the hypothesis that the actions of androgens on the developing cerebral cortex and hippocampus may involve local estrogen-mediated effects similar to those responsible for differentiation of the hypothalamic mechanisms controlling reproductive function.

Aromatase activity in human ovarian cancer

Eighty-four tumor samples from 70 women with primary ovarian cancer were assayed for cytosol estrogen (ERc) and progestin (PRc) receptor concentrations and aromatase activity. In addition, 22 of the tumors were studied for their response to the aromatase inhibitor, 4-OH-androstenedione, in a soft agar clonogenic cell assay system. Although aromatase activity was detected in almost all of the primary tumors, this enzyme was barely detectable in the majority of metastatic tumor samples. There was no significant correlation between aromatase activity and either the ERc or PRc content of the tumors, or tumor grade. Of 12 tumors grown successfully in the soft agar culture system, only 1 showed a substantial (greater than 50%) reduction in colony-forming efficiency after exposure to the aromatase inhibitor. These results suggest that local estrogen biosynthesis probably does not play an important role in the majority of epithelial ovarian tumors. However, there may be a small subset of estrogen receptor-positive tumors in which aromatase could provide a local growth stimulus.

Metabolism and binding of androgens in the spinal cord of the rat

The binding of [3H]androgens and estrogens, and the metabolism of [3H]androgens, were studied in the spinal cord of the adult rat. High-affinity, specific binding sites for [3H]testosterone and [3H]estradiol were detected in cytosol fractions from the spinal cords of castrate animals. Equilibrium dissociation constants for reaction of these sites with their respective ligands were similar to those of androgen and estrogen receptors from other regions of the central nervous system. Nuclear binding of [3H]estradiol was observed in the spinal cord 1 h after intravenous administration of the isotope. Likewise, exchange assay demonstrated the presence of high-affinity androgen binding sites in spinal cord nuclei from orchidectomized, testosterone propionate treated animals. 5 alpha-Reductase activity in homogenates of the spinal cord was relatively high, approximately 3 times that in the pooled hypothalamus, preoptic area, septum and amygdala. However, in contrast to the latter brain regions, estrogen formation was not detectable in spinal cord tissue. No sex differences were observed in the metabolism of [3H]testosterone by spinal cord homogenates. These results confirm the presence of androgen and estrogen receptors in the rat spinal cord. The lack of detectable aromatase activity in the spinal cord is consistent with the hypothesis that the effects of circulating testosterone on spinal reflex function are mediated primarily through the androgen receptor system.

In situ hybridization identifies renin mRNA in the rat corpus luteum

All components of the renin-angiotensin system (RAS), including angiotensinogen messenger RNA (mRNA), renin-like activity (RLA), renin mRNA, angiotensin II (A II) immunoreactivity and angiotensin converting enzyme, have been found in the whole rat ovary and A II receptors have recently been localized to ovarian follicles. Our study was designed to test further which part of the ovary can produce renin. Renin mRNA was detected in the gonadotropin-stimulated rat's corpus luteum using in situ hybridization histochemistry techniques. No positive signal was detected in theca or granulosa cells. These results indicate ovarian renin gene expression in rat luteal cells, where the renin molecule is probably produced, and support our concept of an intrinsic ovarian RAS.

Nuclear pores in rat hypothalamic arcuate neurons: sex differences and changes during the oestrous cycle

The numerical density of nuclear pores was assessed on freeze-fracture replicas of hypothalamic arcuate neurons from adult male and female rats. In females the nuclear pore density fluctuated during the oestrous cycle and was higher in oestrus than in pro-oestrus, metoestrus and dioestrus. Nuclear pore density in males and in metoestrus and dioestrus females was similar. The nuclear pore density in male rats was significantly less than that in oestrus and pro-oestrus females. The variation of the number of pores per unit nuclear volume and the total number of pores per nucleus was similar to the variation of the numerical density of nuclear pores. These results provide morphological evidence of cyclic changes in neuronal nucleocytoplasmic traffic during the ovarian cycle.

Intraovarian markers of follicular and oocyte maturation

The use of ovulation induction for multiple follicular growth in in vitro fertilization (IVF) has introduced the problem of follicular asynchrony. As a consequence of the asynchrony, the parameters most commonly used by IVF groups to assess follicular and oocyte quality within those follicles are not sufficiently sensitive or specific. Thus, each follicle must be considered separately, and specific markers of follicular and/or oocyte maturation must be sought from within the follicle. In this review we analyze previous reports of potential markers of follicular and oocyte maturation. In regards to the follicular fluid constituents, the level of estradiol in follicular fluid correlates with fertilization and pregnancy in stimulated cycles. Other steroids are only helpful when specific stimulation protocols are used. The level of some follicular proteins such as alpha-1-antitrypsin and fibrinogen also correlates with fertilization and pregnancy outcome. Cyclic AMP levels in follicular fluid are significantly reduced in follicles leading to conception. Regulators of oocyte maturation, such as the Oocyte Maturation Inhibitor (OMI) or the Meiosis Inducing Substance (MIS) have also been correlated with IVF outcome, but their exact structure remains still unknown. In addition, other sophisticated parameters, such as chemotactic activity of human leukocytes, or simple methods, such as the presence of intrafollicular echoes, have also been used as successful markers in predicting IVF outcome.

A hypothesis concerning the general basis of organogenetic congenital anomalies

Evidence supports the idea that it is the degree of metabolic imbalance present in diabetic gravid women during the period of organogenesis that accounts for organogenetic congenital defects. In light of the proved and inferred metabolic instability occurring during early pregnancy, we propose that metabolic imbalances may occur that result in organogenetic congenital defects in offspring of apparently normal gravid women.

Insulin specific binding sites in the myometrium of pregnant rats

Insulin (INS) specific binding sites were detected in the myometrium of pregnant rats. The apparent equilibrium dissociation constants for the higher and lower affinity INS binding components were 0.01 X 10(-9) M and 2.5 X 10(-9) M, respectively. During the latter half of pregnancy INS binding increased gradually and peaked on the day of parturition (159.9 +/- 19.8, 196.3 +/- 24.6, 254.7 +/- 36.8, and 272.6 +/- 29.1 and femtomolars per mg protein, mean +/- SEM on days 15, 20, 21, and 22 of gestation, respectively). The pattern of increased INS binding paralleled the prepartum increase in myometrial cell nuclear estrogen receptors as well as myometrial glycogen levels. In contrast, low INS binding was associated with elevated cell nuclear progestin receptor levels, on day 15 and immediately postpartum. These results suggest that, during the latter half of pregnancy, myometrial INS binding capacity and glycogen concentration gradually increase. Since INS receptor levels begin to increase in parallel with increasing nuclear estrogen receptors, INS receptor synthesis may be under estrogen control.

A study of cytoplasmic and nuclear estrogen and progestin receptors in gynecologic neoplasms

A rapid method for simultaneous preparation of cytosol and nuclear estrogen (E) and progestin (P) receptors and their in vitro determination is described. The method was applied to several uterine or ovarian surgical specimens to evaluate their steroid hormone "dependence". The results suggest that low cytoplasmic E receptor levels (ERc) are associated with higher nuclear E receptor (ERn) levels but no apparent correlation was observed between PRc and ERn levels. The method appeared to be suitable for screening steroid hormone receptor content in tumor tissues and may provide better estimation of steroid dependence since both cytoplasmic and nuclear compartments can be studied simultaneously.