The effect of hybridization on local magnetic interactions at highly diluted Ce ions in tetragonal intermetallic compounds RERh2Si2 (RE=Ce, Pr, Nd, Gd, Tb, Dy).

The contribution of the 4f electron to the local magnetic field at highly diluted Ce atoms in RERh(2)Si(2) (RE = Ce, Pr, Nd, Gd, Tb, Dy) has been investigated as a function of temperature through the measurement of the magnetic hyperfine field in (140)Ce nuclei by time differential perturbed gamma-gamma angular correlation spectroscopy. Samples of the studied compounds were characterized by x-ray diffraction and zero-field resistance to determine the crystal structure and transport properties. DC magnetic susceptibility was measured for NdRh(2)Si(2). It was observed that the variation of the magnetic hyperfine field with temperature follows the expected behaviour for the host magnetization, with the exception of GdRh(2)Si(2), which showed a strong deviation from such a behaviour. It is shown that the hybridization of the d band of the host with the f band of the Ce impurity, which is stronger in GdRh(2)Si(2) than in other compounds, is responsible for the observed deviation from the expected temperature dependence of the hyperfine field. The origin of this stronger hybridization is ascribed to the relatively small magnetic anisotropy observed in GdRh(2)Si(2) when compared with the other compounds of the series, as shown by resistance measurements.

Galanin regulation of LH release in male rats.

The present study examines the role of cerebroventricular administered (IIIrd ventricle) galanin on LHRH and LH release in adult and immature male rats. In both age groups, galanin stimulated LHRH synthesis and release from the hypothalamus, leading to a higher release of pituitary LH which in turn increased plasma LH levels. Galantide, a galanin receptor blocker, on the other hand, drastically reduced hypothalamic LHRH and plasma LH while increasing pituitary LH. In vitro incubation of anterior pituitary cells with galanin followed by LHRH resulted in increased release of pituitary LH but not by galanin alone. Galantide exhibited no such effect either alone or with LHRH. These results indicate that galanin is an important regulator for both hypothalamic LHRH and hypophysial LH and its role is independent of age in the case of male rats.

Galanin stimulates hCG induced testicular steroidogenesis in adult but not in immature male rats.

The present study was undertaken to understand the role of galanin on testosterone secretion. Leydig cells from adult (60-80 days old) and immature (21-30 days old) rat testis were incubated with galanin (100 nM), galantide (100 nM) and Human Chorionic Gonadotropin (hCG, 25 I.U.) alone or in combinations and testosterone release was measured. It was observed that in adults, galanin failed to alter the basal testosterone release from the dispersed Leydig cells but potentiated the hCG induced testosterone release significantly. While galantide, prevented this galanin potentiating effect, but it did not alter the hCG alone induced testosterone release. On the other hand, the Leydig cells obtained from immature male rats were sensitive to hCG alone but not to galanin or galantide, both of which failed to alter the hCG induced testosterone release from these cells. Based on these results it can be postulated that galanin's role at the level of the male gonad is age dependent since its potentiating effects on hCG induced testosterone release were visible only in the adult and not in the immature male rats.

GABAergic neurons in prepositus hypoglossi regulate REM sleep by its action on locus coeruleus in freely moving rats.

GABA in locus coeruleus modulates REM sleep. Apart from the presence of interneurons, locus coeruleus also receives GABAergic inputs from prepositus hypoglossi in the medulla, where the presence of REM-ON-like neurons have been reported. Therefore, it was hypothesized that GABAergic projections from prepositus hypoglossi to locus coeruleus may modulate REM sleep. The experiments were conducted on chronic rats prepared for recording EEG, EOG, and EMG in freely moving conditions. Bipolar stimulating electrodes were implanted in prepositus hypoglossi bilaterally, while chemitrodes were implanted bilaterally in locus coeruleus. The prepositus hypoglossi were bilaterally stimulated (3 Hz, 250 microsec, 100 microA) for 8 h in the presence and absence of picrotoxin (0.25 microg/250 nl) microinjection bilaterally in locus coeruleus, followed by poststimulation recording for 4 h. It was observed that stimulation of prepositus hypoglossi alone significantly increased REM sleep primarily by increasing the REM sleep duration per episode. However, when it was stimulated in the presence of picrotoxin in LC, REM sleep decreased, predominantly due to decreased REM sleep duration per episode. The results of this study suggest that GABAergic inputs from prepositus hypoglossi act on locus coeruleus and regulate REM sleep, possibly by inhibition of REM-OFF neurons.

Interactions between cholinergic and GABAergic neurotransmitters in and around the locus coeruleus for the induction and maintenance of rapid eye movement sleep in rats.

The noradrenergic "REM-off" neurons in the locus coeruleus cease firing, whereas some cholinergic and non-cholinergic "REM-on" neurons increase firing during rapid eye movement sleep. A reciprocal interaction between these neurons was proposed. However, acetylcholine did not inhibit neurons in the locus coeruleus. Nevertheless, since GABA levels increase during rapid eye movement sleep and picrotoxin injections into the locus coeruleus reduced rapid eye movement sleep, it was hypothesized that GABA in the locus coeruleus might play an intermediary inhibitory role for rapid eye movement sleep regulation. Therefore, the effects of GABA or carbachol (a mixed cholinergic agonist receptor) alone, as well as an agonist of one in presence of an antagonist of the other, in the locus coeruleus were investigated on sleep-wakefulness and rapid eye movement sleep. The cholinergic agonist carbachol increased, while the muscarinic antagonist receptor scopolamine decreased, the frequency of induction of rapid eye movement sleep per hour. In contrast, GABA and picrotoxin increased and decreased, respectively, the duration of rapid eye movement sleep per episode. However, when carbachol was injected in the presence of picrotoxin or GABA was injected in the presence of scopolamine, the effect of GABA or picrotoxin was dominant. Microinjection of both scopolamine and picrotoxin in combination reduced both the frequency of initiation as well as the duration per episode of rapid eye movement sleep. From these results we suggest that in the locus coeruleus cholinergic input modulates the frequency of induction of rapid eye movement sleep and this action is mediated through GABA interneurons, whereas the length of rapid eye movement sleep per episode is maintained by the presence of an optimum level of GABA. A model of neural connections for initiation and maintenance of rapid eye movement sleep is proposed and discussed.

GABA in locus coeruleus regulates spontaneous rapid eye movement sleep by acting on GABAA receptors in freely moving rats.

The aminergic neurons in the locus coeruleus are known to cease firing during rapid eye movement sleep. Since electrical stimulation of locus coeruleus reduced, while carbachol stimulation increased rapid eye movement sleep and gamma-aminobutyric acid (GABA) neurons as well as terminals are present in the locus coeruleus, we hypothesized that GABA may be involved for cessation of locus coeruleus neuronal firing during rapid eye movement sleep. Under surgical anaesthesia male Wistar rats (250-300 g) with bilateral guide cannulae targeting locus coeruleus were prepared for chronic sleep-wakefulness recording. Electroencephalogram (EEG), electrooculogram (EOG), electromyogram (EMG) were recorded in normal, after 250 nl saline and after picrotoxin (250 ng in 250 nl) injection bilaterally into the locus coeruleus. The results showed that mean duration per episode of rapid eye movement sleep was significantly reduced, although its frequency of generation/h was not significantly affected. This study suggests that GABA in locus coeruleus is involved in tonic regulation of rapid eye movement sleep and the action is mediated through GABAA receptor.

Effect of beta-endorphin and naloxone on rat testicular steroidogenesis.

With a view to examine the possibility of a direct role of opioids in the regulation of testicular steroidogenesis, the following in vivo and in vitro experiments were conducted in male rats of different age groups. Intratesticular (i.t.) injections of beta-endorphin (beta-EP) and its antagonist naloxone (nal) were given bilaterally to adult (80-100 days), peripubertal (40 days) and juvenile (20 days) rats and blood was collected at different time intervals up to 90 min and assayed for testosterone (T). beta-EP suppressed T levels in all age groups of rats while naloxone stimulated T secretion only in adult rats. In another experiment, adult rats were also injected with 60 IU of hCG (sc) after 30 min. of beta-EP/nal treatment. Naloxone induced a greater rise in T in the presence of hCG while beta-EP blocked the hCG induced rise in testosterone. In the in vitro sets of experiments, isolated interstitial cells from testes of adult, 40 and 20 days old rats were incubated for 4 hr with hCG (25 IU), beta-EP (0.5ng) and nal (5.0ng) alone or in combinations. Naloxone alone was ineffective although it significantly enhanced hCG stimulated T release. beta-EP decreased both basal and hCG stimulated T release. Based on these results we postulate that opioids may influence steroidogenesis possibly by altering the response of interstitial cells to LH.

Effects of anti-estrogens on early pregnancy in guinea pigs.

OBJECTIVE: To compare effects of various anti-estrogens on early pregnancy. METHODS: Fifty regularly cycling guinea pigs were divided into five groups (five animals/group), of which three groups received 3 mg/kg body weight Nafoxidine, Centchroman, or Tamoxifen, respectively, on the 1st, 2nd, or 3rd day of pregnancy. The rest of the animals were kept as controls, and received either saline or propylene glycol. Autopsies were done on the 8th day of pregnancy in all the groups. Presence or absence of implantation sites was observed by using a stereomicroscope. Plasma levels of 17 beta-estradiol and progesterone and their receptors, as well as enzyme levels in the uterine tissue, were estimated. RESULTS: During normal early pregnancy there was an increase in the concentration of peripheral plasma levels of steroid hormones with respect to enzyme and steroid hormone receptor levels in the uterus. Administration of anti-estrogens showed a decreased trend in all the variables studied, especially in the tamoxifen-treated animals. CONCLUSIONS: The results of the study suggest that anti-estrogens, if administered during early pregnancy, can prevent the process of ovum implantation in this species.

Photoperiodic regulation of follicle-stimulating hormone binding to gonads and of plasma gonadotropin concentrations in Indian weaver birds.

Previous studies showed that changes of gonadal weight and of follicle-stimulating hormone (FSH) receptor number in response to fluctuations in natural environmental conditions are smaller in female than in male Indian weaver bird (Ploceus phillippinus). Therefore, we studied whether the response to artificial photoperiodic changes differs between the sexes. Birds were transferred to short-day (SD) photoperiods during the breeding phase (June). Other birds were subjected to long-day (LD) photoperiods during the nonbreeding phase (December). Exposure to SD for 10 weeks induced a marked testicular weight decrease. Similarly, FSH binding per unit testicular weight as well as per two testes decreased after SD exposure. The influence of photoperiodic manipulations on the ovarian weight was much smaller than that on the testicular weight. SD exposure did not alter FSH binding either per unit ovarian weight or per ovary. Plasma gonadotropin concentration significantly decreased in both sexes subjected to SD environment. On the other hand, exposure to LD significantly increased testicular weight. LD exposure slightly increased ovarian weight, but the increase was statistically not significant. FSH binding per unit testicular weight markedly increased 10 weeks after transfer to LD. The total FSH binding per two testes showed a parallel change with the testicular weight. However, there was no significant increase in FSH binding per unit ovarian weight during 10 weeks of LD exposure. Although LD exposure for 10 weeks significantly increased the total FSH binding per ovary, the rate of increase was much smaller than that in the testes. The plasma gonadotropin level in both sexes was increased by LD exposure. Scatchard plot analyses of FSH binding indicated that FSH binding changes were due to changes in binding site number. These results suggest that photoperiod regulates FSH receptor numbers particularly in the testis. Such an effect is manifested by marked changes in the testicular weight under different photoperiodic conditions in the subtropical bird.

Annual changes in the binding of follicle-stimulating hormone to gonads and plasma gonadotropin concentrations in Indian weaver birds inhabiting the subtropical zone.

In birds, annual changes in gonadal weight are much more pronounced in the male than in the female. To analyze the mechanism inducing such a sex difference in the gonadal responsiveness to natural environmental conditions, we measured annual changes in the binding of follicle-stimulating hormone (FSH) to the gonads and the plasma gonadotropin concentration in adult Indian weaver birds inhabiting the subtropical zone. The binding of FSH was highly specific for mammalian FSHs and located primarily in the gonad. The testicular weight and FSH binding showed marked changes during the annual breeding cycle. The testicular weight was maximal in the breeding phase (June, 1987) and minimal in the nonbreeding phase (December, 1987). FSH binding per unit testicular weight was greatest in the nonbreeding phase, while the total FSH binding per two testes was maximal in the breeding phase and minimal in the regressive phase (October, 1987). In contrast, the changes in the ovarian weight and FSH binding to the ovary were less pronounced than those in the testis. Although FSH binding per unit ovarian weight showed a peak in the nonbreeding phase, there was no significant change in the total FSH binding per ovary during the year, indicating the presence of a clear sex difference in the total FSH binding. Scatchard plot analyses of the binding suggested that the dissociation constant (Kd) ranged from 0.35 to 1.53 nM regardless of sex and season and that the changes in FSH binding were due to changes in the number of binding sites. Plasma FSH and luteinizing hormone (LH) levels markedly changed during the year in both sexes. Both FSH and LH levels were maximal in the breeding phase and minimal in the nonbreeding phase regardless of sex, although the rate of change in either hormone tended to be greater in the male than in the female.

Changes in the levels of protein and steroid hormones in the plasma and steroid hormone receptors in the uterus of normal cycling guinea pigs.

This study deals with the estrous cycle of guinea pigs in relation to sexual behavior, uterine weight, levels of gonadotropins, steroid hormones, and steroid hormone receptors in the uterus. The guinea pigs in this study showed cyclic changes in various reproductive functions broadly similar to other laboratory species studied. The increase in the uterine weight coincided with high concentration of steroid hormones (estradiol and progesterone) secreted during proestrus and estrus. The elevated levels of steroid hormone receptor concentrations in the uterus during these periods also confirm the role of these hormones. The rise in progesterone level from day 14 of the cycle was associated with lordosis and its related behavior. It was noted that the "estrus behavior" is the most accurate external marker for ovulation and sexual receptivity to males. It was also observed that there is an association between follicle-stimulating hormone and luteinizing hormone during the preovulatory period that was not demonstrated in previous studies.

Properties of follicle-stimulating hormone receptors and changes during annual breeding cycle in the testis of short-tailed bandicoot rat, Nesokia indica.

Some properties and seasonal changes of follicle-stimulating hormone (FSH) receptors in the testis of short-tailed bandicoot rat, Nesokia indica, were studied. The binding of FSH was highly specific for mammalian FSHs and located primarily in the testis. The Scatchard plot analyses of the binding of FSH to the testicular preparations of N. indica showed straight lines similar to those of albino Wistar rats, suggesting the presence of a single class of FSH-binding sites. The mean dissociation constants (Kds) for FSH receptors of N. indica were 1.416 (0.964-2.667, 95% confidence interval) nM in December, 1986; 1.348 (0.885-2.849) nM in April, 1987; and 3.039 (1.678-16.127) nM in August to October, 1987. No significant differences were found among the three groups, but they were all significantly greater than those in Wistar rats. The FSH binding per unit weight of tissue during non-breeding phase (June, 1987) was lower than those during other phases (December, 1986; April and August-October, 1987). Calculated numbers of FSH-binding sites showed no statistically significant differences among the latter three phases. In June preparations the number of binding sites was not determined due to their extremely low binding capacity.

Anti-inflammatory and analgesic properties of four amino-acids.

Orally administered L-isoleucine, DL-isoleucine and L-leucine exhibited anti-inflammatory activity in many test models of inflammation except formaldehyde-induced inflammation. L-beta-phenylalanine inhibited carrageenan-induced oedema only. L-isoleucine also exhibited prolonged analgesic effect while DL-isoleucine had a short lasting effect. The amino-acids produced no gastric ulceration or overt acute toxicity in doses which effectively suppress inflammation. Anti-inflammatory activity seems to be related with interference with the action and/or synthesis of prostaglandins and deserves further intensive study.

Developmental changes in the response of male and female rat pituitary to LH-RH in vitro.

Changes in the binding of 125I-LH-RH and the sensitivity of male and female rat pituitary of LH-RH were measured in vitro from the 5th to 60th day of age. Pituitaries of all the age groups were responsive to LH-RH. Two phases of pituitary sensitivity to LH-RH could be detected in both the male and female rat. The first phase or the period of low sensitivity extended up to the day 14, while the second one or the period of high sensitivity started from the day 15 onwards. During the second period the sensitivity of female pituitary to LH-RH was significantly higher than that of male one. In the female pituitary the changes in the sensitivity to LH-RH were parallel to changes in 125I-LH-RH binding. However, in the male pituitary 125I-LH-RH binding was higher while the sensitivity of pituitary to LH-RH was compatively lower than in the female rat. It is postulated that two different types of receptors may be involved in the stimulation of LH-RH induced LH release from the male and female pituitary.

Correlation of hypothalamic LHRH, pituitary LH and plasma LH in developing rats.

Hypothalamic LHRH, pituitary LH and plasma LH levels were measured in rats of both sexes from day 5-60 after birth. The content of hypothalamic LHRH was very high in one-week-old male and female rats. It declined gradually till day 17 in the female rat and sharply on day 10 in the male rat. Subsequently the content of hypothalamic LHRH increased and showed peak values on day 25 in the female rat and on day 45 in the male rat. It decreased markedly at respective times of puberty in both sexes (day 37 in the female rat and day 52-60 in the male rat). Results of the study suggest that maturation of hypothalamo-hypophyseal-axis proceeds in three distinct stages. Observations on days 17, 25 and 37 in the female rat and on days 5, 7, 10 and 22 in the male rat clearly show an inverse relationship between hypothalamic LHRH and plasma LH and a parallel relationship between pituitary and plasma LH. Marked decline in the content of hypothalamic LHRH at respective times of puberty in both sexes indicates that the release of threshold levels of LHRH from the hypothalamus may apparently be the event initiating the pubertal changes in rat.

Effect of estradiol & testosterone on the pituitary prolactin levels in developing male & female rats.

PIP: Testosterone priopionate (TP) or estradiol-17 beta (E2) were injected into male and female rats from day of birth to 15 days of age to determine the effect of these steroids on the pituitary prolactin (PRL) level in developing rats. Animals were autopsied on Days 5, 7, 10, 14, 17, 22, 25, 30, 37, 45, 52, and 60 and pituitary PRL estimated by radioimmunoassay. Neonatal administration of TP or E2 markedly increased PRL content in male rats. The peak of PRL was advanced to Days 14 and 23, respectively, in E2- and TP-treated groups. The content of pituitary PRL declined sharply and values increased again by Day 52 in TP-treated rats and Day 37 in E2-treated rats. In the female rat both the steroids advanced the time of PRL peak. Peaks were observed on Days 22 and 30, respectively. Although PRL content declined following these peaks, values remained at a significantly higher level than normal. These results suggest that mechanisms controlling the PRL secretion are functional during the neonatal period. It is also suggested that TP acts to increase PRL levels by 1st being converted to E2.^ieng

Effect of neonatal testosterone and oestradiol treatment on the development of the hypothalamo-hypophysial axis in the female rat.

The hypothalamic LH-RH content and the concentrations of pituitary and plasma LH were measured at various ages in female rats treated daily with 10 micrograms testosterone propionate or 10 micrograms oestradiol-17beta from birth to Day 15. Persistent vaginal oestrus was induced in all the treated rats. Both hormones significantly reduced the hypothalamic LH-RH content and pituitary and plasma LH concentrations. Hypothalamic LH-RH increased after cessation of treatment but pituitary LH did not return to normal levels. Plasma LH levels were significantly lower than those in control rats. It is concluded that testosterone propionate and oestradiol-17beta (1) have a direct negative feed-back influence on the hypothalamus in the neonatal female rat; (2) alter the normal pattern of plasma and pituitary LH in developing female rats; (3) prevent the cyclic secretion of plasma LH after maturity; and (4) probably cause a chronic impairment in the release of LH-RH.