Comparison of the effects of N-methyl-DL-aspartic acid on gonadotropin and prolactin secretion in anestrous mares and mares exhibiting estrous cycles during anestrus

Frequency of sugar feeding and blood feeding can have an impact on the infection by and transmission of malaria parasites. Data presented here indicate that frequent blood feeding has a deleterious effect on infection by malaria parasites in Aedes aegypti. In addition, mosquitoes that do not blood feed, but instead feed on sugar alone after an infected blood meal, have a higher rate of parasite transmission than mosquitoes fed additional blood meals.     

A study of spatial parameters encoded during exploration in hamsters.

In two experiments the exploratory reactions of hamsters to various rearrangements of familiar objects were examined. During two sessions, the subjects were allowed to explore a circular, open field containing four different objects. During a third test session, one or several objects were displaced, changing the shape and/or the size of the area defined by the object set. Significant reexploration was found when the change brought about during the test session affected the geometrical relations between the objects or when an object was removed. In contrast, changes that did not modify the geometrical configuration of the arrangement of the objects, but only modified the distance of one object to another, did not elicit any reexploration. Additionally, it was found that selective reexploration of the actually displaced objects occurred only when the change removed this object a certain distance from the others. These results are discussed in terms of stimulus complexity and more generally with regard to the spatial parameters that are selected, processed, and stored during exploration. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comparative study of anxiogenic effects of fluoroquinolones in rats

It is well known that the removal of a fixation point prior to the presentation of a peripheral target dramatically reduces saccadic reaction time (SRT). This effect has become known as the "gap effect". The present study examined several detailed kinematic variables to determine whether the removal of the fixation point also affects the manner in which saccades are produced. The findings indicate that saccades that were initiated after the removal of the fixation point had higher average velocities and reached greater peak velocities, accelerations, and decelerations than did saccades produced in the presence of the fixation point. The results suggest that the removal of the fixation point may affect the force-time curves of saccades in addition to affecting the time needed to initiate the saccades.     

Pulsatile release of LH and secretion of ovarian steroids in sheep during the luteal phase of the estrous cycle

The concentration of LH and progesterone in jugular venous plasma and the secretion of steroids by the ovary were measured every 10 minutes for 2 hours on days 12, 14, and 16 of the estrous cycle in 5 ewes with utero-ovarian autotransplants. A pulse of LH occurred about once every 2 hours, when the concentration rose from a basal level of 0.57 +/- 0.08 ng/ml to a peak of 2.97 +/- 0.57 ng/ml. Within 5 minutes of the pulse of LH, the secretion of estradiol (an exclusive product of the follicle) rose rapidly from a basal level of 0.75 +/- 0.12 ng/min to reach a peak value of 2.16 +/- 0.33 ng/min in about 30 minutes. In contrast, the secretion of progesterone from the corpus luteum, and the concentration of progesterone in the peripheral plasma changed very little following the pulse of LH. The secretion of androstenedione, which arises from the follicle and corpus luteum, increased from 3.03 +/-0.75 ng/min to 7.85 +/- 1.78 ng/min by 30 minutes after the pulse of LH. These findings indicate that the follicle, and possibly the stroma, respond rapidly to episodic fluctuations in the concentration of LH and are probably involved in the negative feedback loop between the ovary and the hypothalamic pituitary system. The fluctuations in the secretion of progesterone from the corpus luteum, on the other hand, are unrelated to pulses of LH.     

Tonic support of luteinizing hormone secretion by adrenal progesterone in the ovariectomized monkey replaced with midfollicular phase levels of estradiol

Although it is known that progesterone facilitates the estradiol-induced gonadotropin surge at midcycle, its effect on LH secretion at other times of the follicular phase remains to be investigated. In this study, we investigate the role of progesterone on tonic LH secretion in the ovariectomized primate replaced with estradiol at levels representative of the follicular phase. The experiments were performed in nine ovariectomized rhesus monkeys, either unreplaced with estradiol or after a 5-day estradiol therapy to mimic early follicular (10-36 pg/mL; low dose) and midfollicular (medium dose; 40-75 pg/mL) concentrations. We used two antiprogesterone compounds, RU-486 (5 mg) and ORG-31806 (1 mg), to antagonize endogenous progesterone activity and studied their acute effects on LH secretion in each group. LH concentrations were measured at 15-min intervals for a 3-h baseline period and during a 5-h period after antagonist administration. LH concentrations remained unchanged after either antiprogesterone compound or diluent (ethanol) administration in the estrogen-unreplaced monkeys or after low dose estradiol replacement. However, both antiprogesterone compounds significantly decreased LH secretion in monkeys pretreated with the medium dose of estradiol; by 5 h, the mean (+/-SE) areas under the LH curve were 54.8 +/- 4.1% and 64.0 +/- 4.2% after RU-486 and ORG-31806, respectively (P < 0.05 vs. unreplaced and low dose estrogen-replaced groups). To exclude the possibility that the LH response reflects an agonist action of the progesterone antagonist, LH responses to progesterone infusions (at three doses to reproduce preovulatory, luteal, and pharmacological levels) were also examined in monkeys pretreated with midfollicular levels of estradiol. In none of these was there a decrease in LH; rather, progesterone infusions resulted in an increase in LH secretion in all three groups (to 115-194% of baseline in seven of eight monkeys). Finally, we determined that at the dose used in our protocol, neither of the two progesterone antagonists was able to prevent dexamethasone-induced cortisol suppression, thus excluding the possibility that results after progesterone antagonist administration may reflect a putative antiglucocorticoid activity of these compounds. When the doses of the antiprogesterone compounds were increased 6 times, only RU-486 counteracted the effect of dexamethasone on cortisol. In summary, our data indicate support by progesterone of tonic LH secretion in the nonhuman primate under estrogenic conditions similar to the midfollicular phase of the menstrual cycle. Significantly, because the experiments were performed in ovariectomized monkeys, and endogenous progesterone was most probably of adrenal origin, the data also demonstrate a role of the hypothalamo-pituitary-adrenal axis in support of gonadotropin secretion.     

Bovine endometrial retinol-binding protein secretion, messenger ribonucleic acid expression, and cellular localization during the estrous cycle and early pregnancy

OBJECTIVES: We assessed the safety and efficacy of stent placement in patients with poorly controlled hypertension and renal artery stenoses, which are difficult to treat with balloon angioplasty alone. BACKGROUND: Preliminary experience with stent placement suggests improved results over balloon angioplasty alone in patients with atherosclerotic renal artery stenosis. METHODS: Balloon-expandable stents were placed in 100 consecutive patients (133 renal arteries) with hypertension and renal artery stenosis. Sixty-seven of the patients had unilateral renal artery stenosis treated and 33 had bilateral renal artery stenoses treated with stents placed in both renal arteries. RESULTS: Angiographic success, as determined by quantitative angiography, was obtained in 132 (99%) of 133 lesions. Early clinical success was achieved in 76% of the patients. Six months after stent placement, the systolic blood pressure was reduced from 173 +/- 25 to 147 +/- 23 mm Hg (p < 0.001); the diastolic pressure from 88 +/- 17 to 76 +/- 12 mm Hg (p < 0.001); and the mean number of antihypertensive medications per patient from 2.6 +/- 1 to 2.0 +/- 0.9 (p < 0.001). Angiographic follow-up at a mean of 8.7 +/- 5.0 months in 67 patients revealed restenosis (>50% diameter narrowing) in 15 (19%) of 80 stented vessels. CONCLUSIONS: Renal artery stenting is an effective treatment for renovascular hypertension, with a low angiographic restenosis rate. Stent placement appears to be a very attractive therapy in patients with lesions difficult to treat with balloon angioplasty such as renal aorto-ostial lesions and restenotic lesions, as well as after a suboptimal balloon angioplasty result.     

Simple extraction and enzyme immunoassays for estrogen and progesterone metabolites in the feces of Macaca fascicularis during non-conceptive and conceptive ovarian cycles

A simple method for extracting ovarian steroids from feces is presented, together with enzyme immunoassay systems for measuring estrogen and progesterone metabolites. Small amounts of feces were combined in a 1:10 proportion with a modified phosphate buffer, shaken for 24 h, centrifuged, and decanted; the supernatant was directly measured for estrogen and progesterone metabolites by enzyme immunoassays. Serum estradiol and progesterone profiles were compared to urinary and fecal profiles in the same animals to determine the degree to which each reflected the ovarian events detectable in serum. The correlation coefficients for the relationship between serum, urinary, and fecal hormones for individual animal cycles were found to be statistically significant in every case but one, where the relationship between serum estradiol and urinary estrone conjugates was not significant. Urinary and fecal measurements were used to determine whether estrogen and progesterone metabolism and excretion varied within and between animals. Variation in unconjugated estrogen and progesterone metabolites was observed in the follicular phase, the luteal phase, and early pregnancy.     

The localization of aldosterone-producing adenoma on computed tomography--a comparative study with adrenal scintigraphy and plasma aldosterone concentration in the adrenal or renal vein

The evaluation of computed tomography (CT) for detecting aldosterone-producing adenoma in primary aldosteronism was performed by comparison with adrenal scintiscan; determination of aldosterone in adrenal or renal veins, retroperitoneal pneumography and adrenal venography was reliable for diagnosis of adrenal tumors in pheochromocytoma or Cushing's syndrome, but not so effective for small adenoma of primary aldosteronism. An abdominal CT scan was performed on six patients with primary aldosteronism, one with idiopathic hyperaldosteronism and one with glucocorticoid responsive hyperaldosteronism; in an attempt to evaluate the utility of this noninvasive procedure. Diagnosis of hyperaldosteronism was made by demonstrating the elevated plasma aldosterone concentration and aldosterone secretion rate, normal excretion rate of urinary 17-OHCS and 17-KS, and low plasma renin activity. The CT scan correctly predicted unilateral adrenal adenoma in all the patients with primary aldosteronism of which the findings were identical to those demonstrated by surgery. The diameter of these tumors ranged from 10 X 7 X 6 to 19 X 17 X 14 mm. Also the CT scan in idiopathic hyperaldosteronism and glucocorticoid responsive hyperaldosteronism showed bilateral adrenal hyperplasia and bilateral normal adrenal glands, respectively. The pathological findings in these two cases disclosed the adrenal hyperplasia of zona glomerulosa and adrenal hyperplasia of zona subglomerulosa accompanied by a normal thickness of the adrenal gland, respectively. The precision of the CT scan, adrenal scintigraphy and determination of plasma aldosterone in the adrenal or renal veins were almost equal to the diagnosis of the localization of adrenal adenoma. It is concluded that the CT scan is a noninvasive and most useful method for the localization of aldosterone-producing adenoma and helpful in distinguishing adrenal adenoma from adrenal hyperplasia.     

Medial amygdaloid lesions and the regulation of sociosexual behavioral patterns across the estrous cycle in female golden hamsters.

Two experiments were conducted to examine the behavioral effects of medial amygdaloid (M) lesions during the estrous cycle in female golden hamsters. In Experiment 1, males were paired with gonadally intact M-lesioned, sham-operated, or ovariectomized M-lesioned females and tested in large enclosures. Medial amygdaloid lesions reduced, significantly, the occurrence of precopulatory biting attack and vaginal scent-marking behavior in females. In contrast, M lesions produced a significant increase in the duration of copulation. Mating behavior was also observed for a brief period of time in 1 M-lesioned female during the diestrus period and in 2 ovariectomized animals. After copulation, M-lesioned females attacked their mating partner less frequently than did sham-lesioned animals, which suggests that M lesions may modulate the reduction of both pre- and postcopulatory aggressive behavior by common processes. The attenuation in aggressive responsiveness was further documented in Experiment 2, which shows that during intrasexual fights, M-lesioned females exhibited significantly fewer offensive agonistic responses than did sham-operated opponents. Collectively, the results demonstrate that M lesions produce significant alterations in both social and sexual response patterns and suggest that M may be a neural component of a forebrain inhibitory system regulating the display of feminine copulatory behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Allopregnanolone concentration in hippocampus of prepubertal rats and female rats throughout estrous cycle

Hippocampus plays an important role in cognition, neuroendocrine function and sexual behaviour. Changes of hippocampal neuropeptide and neurotransmitter concentrations are associated to behavioural changes occurring throughout reproductive life. The present study focused the attention on the presence of a neurosteroid, 5 alpha-pregnan-3 alpha-ol-20-one (termed allopregnanolone) in hippocampus. In particular, hippocampal allopregnanolone concentration in male and female prepubertal rats and in female rats throughout estrous cycle were evaluated. Hippocampal extracts were eluted on high pressure liquid chromatography and allopregnanolone concentration was measured by radioimmunoassay. Prepubertal male and female rats (15 days old) showed highest values which significantly decreased with advancing age (25 and 60 days) (p < 0.01); the lowest hippocampal concentration of allopregnanolone was found in adult rats. Female rats on proestrus morning and afternoon showed an hippocampal allopregnanolone concentration significantly higher than on diestrus or on estrus (p < 0.01), while rats on estrus showed hippocampal allopregnanolone concentration significantly lower than during other days of estrus cycle (p < 0.01). These data indicate differences in hippocampal concentration of allopregnanolone between prepubertal and adult rats and throughout estrous cycle in female rats. This finding suggest a putative role of neurosteroids in the modulation of behavioral changes occurring throughout reproductive life.     

Effect of progesterone on prostaglandin F2 alpha secretion and outcome of pregnancy during cloprostenol-induced abortion in mares

OBJECTIVES: To determine the role of progesterone in the regulation of endogenous prostaglandin F2 alpha (PGF2 alpha) secretion during cloprostenol-induced abortion and to investigate use of progestins to prevent prostaglandin-associated abortion. ANIMALS: 16 pregnant mares. PROCEDURE: To induce abortion, cloprostenol (250 micrograms/d) was administered daily until fetal expulsion or for up to 5 days. In experiment 1, 8 mares, 98 to 153 days' pregnant, received progesterone (300 mg/d) at 24-hour intervals for 5 days, starting 18 hours after the first cloprostenol administration. In experiment 2, 8 mares, 93 to 115 days' pregnant, received altrenogest (44 mg/d) at 24-hour intervals, starting 12 hours after the first cloprostenol administration. Historic control mares, 82 to 102 days' pregnant, received cloprostenol (250 micrograms/d) daily until fetal expulsion. RESULTS: In control mares, fetal expulsion occurred after 2 to 3 cloprostenol administrations and was associated with significant increases in PGF2 alpha secretion. Abortion did not occur in 5 of 8 progesterone-treated mares and 8 of 8 altrenogest-treated mares, and endogenous PGF2 alpha secretion was inhibited, compared with values in aborting mares. CONCLUSION: Circulating progestogen concentrations may have a role in the outcome of pregnancy during prostaglandin-induced abortion. Altered prostaglandin secretion may be a reflection of a direct effect of progesterone or may be caused by the abortion process. CLINICAL RELEVANCE: Progestogens might be useful for prevention of abortion in mares in which pregnancy is at risk owing to diseases that are associated with excess prostaglandin secretion.     

A comparative study of gastric motility and secretion after stimulation by 2-deoxy-D-glucose in dogs (author''s transl)

The pathogenesis of Parker's Rat Coronavirus (PRCV) was studied in axenic CD rats. Three to four 9 to 10 week old rats were euthanized daily for eight days after intranasal inoculation. Rats remained free of clinical disease. Virus was recovered from the nasopharynx and trachea after twenty-four hours and from the lung by day three but was not detected in respiratory tract after seven days. Viral antigen was detected by indirect immunofluorescence in the mucosal epithelium of upper respiratory tract and in pulmonary alveolar septae from day two to six postinoculation. Acute rhinitis developed by day two and was associated with mild focal necrosis of respiratory mucosal epithelium. Mild nonsuppurative tracheitis and multifocal interstitial pneumonia appeared by day five and persisted through day eight. Dacryoadenitis did not occur, sialoadenitis was detected in only three rats and virus was recovered from only one submaxillary salivary gland. This experiment indicates that PRCV can be a primary pathogen for the respiratory system of adult rats. In contrast to sialodacryoadenitis (SDA) virus the tropism of PRCV for salivary and lacrimal glands is low.     

The negative feedback actions of progesterone on gonadotropin-releasing hormone secretion are transduced by the classical progesterone receptor

Progesterone (P) powerfully inhibits gonadotropin-releasing hormone (GnRH) secretion in ewes, as in other species, but the neural mechanisms underlying this effect remain poorly understood. Using an estrogen (E)-free ovine model, we investigated the immediate GnRH and luteinizing hormone (LH) response to acute manipulations of circulating P concentrations and whether this response was mediated by the nuclear P receptor. Simultaneous hypophyseal portal and jugular blood samples were collected over 36 hr: 0-12 hr, in the presence of exogenous P (P treatment begun 8 days earlier); 12-24 hr, P implant removed; 24-36 hr, P implant reinserted. P removal caused a significant rapid increase in the GnRH pulse frequency, which was detectable within two pulses (175 min). P insertion suppressed the GnRH pulse frequency even faster: the effect detectable within one pulse (49 min). LH pulsatility was modulated identically. The next two experiments demonstrated that these effects of P are mediated by the nuclear P receptor since intracerebroventricularly infused P suppressed LH release but 3alpha-hydroxy-5alpha-pregnan-20-one, which operates through the type A gamma-aminobutyric acid receptor, was without effect and pretreatment with the P-receptor antagonist RU486 blocked the ability of P to inhibit LH. Our final study showed that P exerts its acute suppression of GnRH through an E-dependent system because the effects of P on LH secretion, lost after long-term E deprivation, are restored after 2 weeks of E treatment. Thus we demonstrate that P acutely inhibits GnRH through an E-dependent nuclear P-receptor system.     

Regulation of prolactin secretion by adrenal steroids in oestrogen-treated ovariectomized rats: participation of endogenous opioid peptides

The purpose of the present study was to determine whether glucocorticoid inhibition of prolactin (PRL) release in oestrogen-treated ovariectomized (OVX) rats is mediated by endogenous opioid peptides (EOPs). All the animals were OVX and given oestradiol benzoate (OB, 20 microg/rat, s.c.) 2 weeks later (day 0). On day 3 they received vehicle, mifepristone (MIF, 10 mg/kg, s.c.) or hydrocortisone (HYD, 2 mg/rat, s.c.), in combination with the opioid antagonist naloxone (NAL, 2 mg/kg, i.p.) or vehicle. Serum PRL concentration was then measured by RIA at 13.00 and 18.00 hr, to include assessment of diurnal variation of PRL secretion. At 13.00 hr either MIF or NAL alone increased PRL secretion with no additional effect when NAL was combined with MIF. HYD had no significant inhibitory effect, but NAL with HYD increased PRL secretion. At 18.00 hr serum PRL concentration was higher than at 13.00 hr, and not affected significantly by MIF or NAL alone, although PRL secretion was increased by treatment with both. HYD inhibited PRL secretion and this inhibition was prevented by NAL. In a second experiment to distinguish antiglucocorticoid and antiprogesterone effects of MIF, we administered progesterone (2 mg/rat, s.c.) or a specific progesterone antiserum. In contrast with MIF, the progesterone antibody had no effect on PRL secretion at 13.00 hr, nor on the stimulation by NAL, while progesterone (unlike HYD) increased PRL secretion and NAL attenuated this response; this was opposite to the effect of NAL with HYD. Similarly, at 18.00 hr the interaction of MIF and NAL was not explained by antagonism of progesterone. Together, these results indicate inhibition of PRL by glucocorticoids but not progesterone, mediated in part by EOPs. At 18.00 hr endogenous glucocorticoids do not regulate oestrogen-stimulated PRL release, although HYD is inhibitory through EOPs.     

Effects of estrogen and progesterone on the escalation of cocaine self-administration in female rats during extended access.

Estrogen increases and progesterone decreases the acquisition and reinstatement of cocaine-seeking behavior in female rats. Here estrogen and progesterone were studied for their effects on the escalation of cocaine self-administration in female rats. The rats received ovariectomy (OVX) or sham (SH) surgery and were treated with estradiol benzoate (0.05 mg/kg sc) and/or progesterone (0.5 mg/kg) or vehicle (indicated by E, P, and V), resulting in 5 groups: SH+V, SH+P, OVX+V, OVX+E, OVX+E+P. Rats self-administered intravenous cocaine (0.4 mg/kg) under a fixed ratio 1 (FR 1) schedule during 2-hr sessions and were then given 6-hr sessions (long access; LgA) (FR 1) for 21 days. After LgA, self-administration was reassessed with 2-hr sessions under the FR 1 and a progressive ratio schedule with 4 cocaine doses. There were no differences among the 5 groups in cocaine self-administration during initial 2-hr sessions. During LgA, the SH+V, OVX+E, and OVX+V groups escalated their cocaine self-administration, whereas the OVX+E+P and SH+P groups did not. Estradiol increased escalation in the OVX+E group compared with the OVX+V group, and progesterone (SH+P) reduced escalation compared with the SH+V group. When estrogen and progesterone were both administered in OVX rats (OVX+E+P), escalation was significantly lower than in the OVX+E group. Cocaine infusions during the 2-hr sessions were significantly higher after escalation than before in all groups except the progesterone-treated groups (SH+P and OVX+E+P). Estrogen promoted and progesterone inhibited escalation of cocaine self-administration, illustrating the importance of female gonadal hormones in drug-seeking behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Concentration of monoamines and activity of several enzymes in the arcuate nucleus of the hypothalamus in young and aging rats during the estrous cycle

The arcuate nucleus (AN) and the median eminence (ME) of the hypothalamus were investigated in young and ageing female rats. During the estral cycle (EC) the monoamine (MA) content, the monoaminoxidase (MAO), NADP and NAD-diaphorase activities were determined in the AN, and the MA content and the activity of alkaline phosphatase (AP) -- in the ME. In young rats in the proestrus-estrus there was an increase in the activity of the NADP and NAD-diaphorase and of the MA content, but a decrease of the MAO activity. This indicated an intensified function of the nucleus at these stages of the EC. Accumulation of the MA in the ME was noted in the diestrus, while in the proestrus their concentration sharply fell; on the other hand, the activity of the AP was considerably increased. In the ageing rats the dynamics of the indices under study during the EC were largely unchanged. However, the functional activity of the AN proved to increase, and in the ME and elevation of the MA concentration and disturbance of its release from the nerve terminals was seen.