摘要:

A threshold value for inhibition of ovulation with estrogen via the systemic circulation was determined in the hamster to be less than that provided by the lumen of 22 gauge hypodermic tubing (450 µm ID). By the use of 30 gauge tubing (150 µm ID) the neural region in and about the arcuate nucleus was found to be the most sensitive to estrogen for inhibition of ovulation. Use of empty tube implants or testosterone-containing tubes did not inhibit ovulation, indicating that the response was specific for estroge

ISSN:0028-3835    

DOI:10.1159/000122165

出版商:S. Karger AG    

年代:1973

数据来源: Karger

摘要:

The effects of surgical isolation of the medial basal hypothalamus (MBH) on growth were studied in adult female rats. Isolation of MBH caused a gradual increase in naso-anal (N-A) length. N-A length was significantly increased 92 days after surgery and the augmented rate of growth continued until autopsy at 139 days. The increase in N-A length was accompanied by a marked gain in body weight and by conspicuous obesity. Non-stress and stress levels of plasma growth hormone (GH) were determined by radio-immunoassay at 7–11 weeks after surgery. Rats with MBH isolation had circulating non-stress levels of GH that were approximately 6 times higher than those of controls (p < 0.01) at both 7 and 11 weeks. Whereas intact controls demonstrated a marked decrease in GH levels following ether stress, those with MBH isolation showed variable responses: some demonstrated normal decreases; others showed no responses; while yet another group showed marked increases. These results confirm and extend prior findings and suggest that the MBH receives neural connections that normally inhibit growth and plasma GH level

ISSN:0028-3835    

DOI:10.1159/000122230

出版商:S. Karger AG    

年代:1973

数据来源: Karger

摘要:

24-hour urine collections were made in normally cycling and pregnant adult female rhesus monkeys. Volume and osmolality were measured and the antidiuretic hormone (ADH) excretion was determined by a radioimmuno-assay of extracted urine. No differences were found between pre- and post-ovulatory animals and between nonpregnant and pregnant animals. Mean urinary ADH excretion in nonpregnant monkeys was 4.06 ± 0.82 mU/24 h. The concentration of ADH in the urine of the monkey is similar to that in the urine of the normal human. ADH can be readily detected in the urine of the monkey. Measurement by radioimmunoassay may provide a means of directly assessing neurohypophysial function in these animals

ISSN:0028-3835    

DOI:10.1159/000122166

出版商:S. Karger AG    

年代:1973

数据来源: Karger

摘要:

The pituitary-adrenal system plays an important role in the initiation and maintenance of lactation in rats, with the suckling stimulus itself inducing the release of ACTH. The recent finding of a reduced plasma corticosterone response to a variety of noxious stimuli during lactation led us to further investigate the activity of this system in lactating (L) rats, compared with post-parturient non-lactating ontrols (NL). Plasma and adrenal corticosterone and plasma ACTH were measured, the latter with a mouse bioassay. Over a 24 h period (12 L:12 D), basal concentrations of plasma corticosterone were elevated in L females, only at those times when the NL basal concentrations were at the trough in the diurnal cycle. At all times, the plasma corticosterone increase 15 min after ether was significantly lower (by a mean of 55 %) in L rats than in NL rats. The elevations in plasma corticosterone after ether were higher for all rats during the day. The night-day difference in response to ether was greater in L rats than in NL rats. Although morning basal levels were not significantly elevated in L females deprived of their litters for 24 h, in these females, as in continually lactating rats, stress concentrations of plasma ACTH (2–4 min after ether) were one third that of the NL controls. Finally, after dexamethasone treatment, the corticosterone output to exogenous ACTH was lower in the plasma and higher in the adrenal in L rats. Thus, pituitary-adrenal activity is altered in a variety of ways during lactatio

ISSN:0028-3835    

DOI:10.1159/000122167

出版商:S. Karger AG    

年代:1973

数据来源: Karger

摘要:

The effect of pinealectomy or constant light on hamster ovulatory and body weight responses was examined. When lights were on from 5 a.m. to 7 p.m., the critical period for phenobarbital (PB) blockade of ovulation was centered around 1.45 p.m. Constant light (LL) rendered the critical period unpredictable, but it remained unchanged after pinealectomy. Those LL animals which were not blocked by PB provided significantly fewer ova than did animals from the pinealectomized, sham-operated or intact groups. LL induced significant weight gain relative to intact controls within one estrous cycle, and the difference persisted throughout the experiment. There were no body weight differences between the sham-operated and pinealectomized groups.

ISSN:0028-3835    

DOI:10.1159/000122168

出版商:S. Karger AG    

年代:1973

数据来源: Karger

摘要:

In response to ether or electric shock, plasma corticosterone concentrations in weanling and adult rats rose to equivalent levels by 15 min, but then diverged, with the weanlings showing a later peak and a slower return to resting levels. An interpretation of this effect, in terms of an immature feedback mechanism in weanling rats, was supported by an experiment in which pretreatment with peripherally injected dexamethasone completely blocked a plasma corticosterone increase, in response to an ether and blood sampling stress in adults, but only partially reduced this response in weanlings. The failure of basal hypothalamic implants of corticoids to differentiate between ages in their ability to inhibit this stress response supported the suggestion of extra-hypothalamic inhibitory systems as the loci of the deficit in weanlings.

ISSN:0028-3835    

DOI:10.1159/000122169

出版商:S. Karger AG    

年代:1973

数据来源: Karger

摘要:

The capacity for and mechanism of transport of thyroxine (T4) by the median eminence has been examined in vivo. Following an intravenous injection of 125I-thyroxine, the median eminence accumulates more hormone than either the anterior or posterior pituitary, although it does not achieve a tissue:plasma ratio greater than 1. The uptake of T4 by the median eminence is greater than normal in rats treated with methimazole and in animals (normal or hypophysectomized) treated with exogenous TSH. In reserpine-treated animals, the uptake of T4 by the median eminence is reduced. Following the infusion of T4 into the lateral ventricle, a 5-fold greater uptake is seen in the median eminence; thyroxine accumulates in the anterior pituitary and achieves a tissue:plasma ratio 2.5 times greater than when the hormone is administered intravenously. When ouabain is infused intravenously immediately before the T4, uptake of the hormone by the median eminence and delivery to the anterior pituitary are both markedly reduced. Autoradiographic studies also reveal the high accumulation of thyroxine in the median eminence; the grain concentration in this tissue was greater than any other region of the basal hypothalamus. Grain localization clearly associates thyroxine with ependyma of the median eminence.

ISSN:0028-3835    

DOI:10.1159/000122170

出版商:S. Karger AG    

年代:1973

数据来源: Karger

ISSN:0028-3835    

DOI:10.1159/000122171

出版商:S. Karger AG    

年代:1973

数据来源: Karger