A puberty-related attenuation of opiate peptide-induced inhibition of LH secretion

The long-acting synthetic enkephalin FK 33-824 (FK) potently inhibits LH secretion in gonadectomized prepubertal male and female rats. The effect is reversible by coinjection of naloxone. We have observed an age-related decrease in the ability of FK to reduce LH secretion in the 48 h post-gonadectomized rat. Thus, the IC50 values (i.e. the dose required to give 50% reduction in LH levels) for 12, 23 and 33-day old female rats were 0.03, 0.04 and 0.17 mg/kg BW, respectively. The figures for pre- and post-pubertal male rats (ages 26 and 70 days) were 0.25 and 0.89 mg/kg BW, respectively. This attenuation of opiate-induced inhibition of LH release may provide a neurochemical basis for the well-described shift in sensitivity of gonadal steroid feedback which occurs with the approach of puberty.

Neuroendocrine control of ovarian autografts

At 24 days of age, either one or both ovaries of female rats were removed and transplanted subcutaneously on their respective side. Relative to sham operated rats, endocrine effects of the ovarian grafts were as follows: 1) Animals with ovarian grafts showed an advancement of puberty, 2) rats with bilateral grafts showed more 5 day estrous cycles and higher FSH levels, 3) hemi-ovariectomy of animals with bilateral grafts produced a greater increase in both LH and FSH 6-8 hr post-surgery in contrast to controls which only showed an increase in serum FSH levels, 4) weights of the bilateral grafts were comparable to intact ovaries, but the unilateral grafts were small and comparable to their original size at the time of transplantation (the intact ovary showing compensatory hypertrophy), 5) both control and bilateral ovarian graft groups showed ovarian compensatory hypertrophy, 6) removal of the small unilateral ovarian graft had no detectable endocrine effect on the remaining intact ovary which had already undergone compensatory hypertrophy, 7) removal of the intact ovary of rats with a unilateral graft produced a remarkable increase in the weight of the remaining small autograft such that these animals had the largest remaining gonad as well as higher uterine weights than controls. Thus, although ovarian autografts appear to function similar to in situ glands, the alterations in puberty, estrous cycles, FSH and LH levels and uterine weights suggest that endocrine control mechanisms are altered in rats with ovarian grafts.

Development of a quotidian increase in pituitary responsiveness to GnRH in prepubertal female rats

Pituitaries from immature male and female rats (5, 13, 21, 27 and 30 days of age) were removed at 08:00 or 16:00 h and stimulated with GnRH in vitro. In female rats more LH was released from pituitaries taken at 16:00 h than at 08:00 h on Days 21, 27 and 30, but not on Days 5 and 13. There were no differences in male rats in responsiveness of pituitaries taken at these two times. The ability of GnRH to induce release of more LH in the late afternoon may help to synchronize hormone output to coincide with first ovulation.

Hyperparathyroidism: experiences with treated and untreated patients

During a seven-year period, after the introduction of parathyroid hormone assays, 113 patients with primary hyperparathyroidism were seen at an Australian teaching hospital. In 68, parathyroidectomy was followed by normalization of serum calcium levels. Fifteen patients (six referred from other units) remained hypercalcaemic after their initial neck exploration. Thirty patients with biochemical changes indicative of primary hyperparathyroidism were not referred for surgery, mainly because of old age or lack of symptoms. Those patients who were not submitted to surgery, and those who had undergone unsuccessful neck explorations, were observed (while hypercalcaemic) for a mean period of three years. During the period of observation, no deterioration occurred in the clinical or biochemical status of these patients. It is proposed that patients with non-symptomatic primary hyperparathyroidism may be managed by clinical observation, rather than by immediate parathyroidectomy.

A simple, inexpensive filtration device suitable for neurotransmitter receptor binding studies in brain tissue

We describe the construction and use of an inexpensive filtration manifold suitable for radioligand binding assays. Experiments with [3H]flunitrazepam indicate that the binding data for benzodiazepine receptors in rat brain homogenate are almost indistinguishable from those obtained with a commercially available manifold.

Transpubertal modulation of pituitary and testicular function in the ob/ob mouse

We have investigated developmental, transpubertal, changes in the responsiveness to stimulation of pituitary gland and testes from the male ob/ob mouse. These organs were removed from ob/ob mice at 33 and 90 days after birth and stimulated with GnRH and LH, respectively, in vitro. Pituitary glands from lean mice released significantly more LH than those from ob/ob mice at both ages. In contrast, FSH release was higher in young ob/ob mice but not significantly different at 90 days when compared with lean controls. LH-stimulated testes revealed that although the young ob/ob testes released significantly less testosterone (T) than lean controls, the response became normal after the time of expected puberty. The production of 5 alpha-androstane-3 alpha, 17 beta-diol (DIOL), although reduced at both ages in ob/ob mice, declined transpubertally in both lean and ob/ob mice. As a result, the ratio of T:DIOL which normally becomes much greater than 1 with the advent of puberty, also increases to greater than 1 in the ob/ob males, suggesting that sexual maturation of testicular androgen biosynthesis is approximately normal. We conclude that the differences in pituitary and testicular response to stimulation could arise from a defect in the ability of the pituitary gland to release gonadotrophins.

Circadian surges of LH in the ovariectomised rat occur coincident with enhanced pituitary responsiveness to GnRH

Experiments are described in which we have investigated the responsiveness to GnRH of pituitary glands obtained from ovariectomised rats in which LH surges were induced by steroid priming (a) by estrogen implants and (b) by estrogen-progesterone injections. These treatments generate LH surges late in the light phase. Stimulation with GnRH in vitro revealed a large increase in responsiveness coincident with the surge of LH. We suggest that this effect is mediated through a self-priming effect of GnRH and that this in vitro technique may be used to detect hypothalamic release of GnRH.

Vitamin D metabolites and their relationship to azotaemic osteodystrophy

Bone biopsies were performed and serum concentrations of vitamin D metabolites were measured in twenty-four patients with chronic renal failure. The concentrations of three metabolites--25-dihydroxyvitamin D (25-OHD), 24,25-dihydroxyvitamin D (24,25-OH2D) and 1,25-dihydroxyvitamin D (1,25-OH2D)--were significantly lower in uraemic than in normal sera. There was a positive correlation between serum 24,25-OH2D and serum 25-OHD, whereas serum 1,25-OH2D values, which were independent of those of the other vitamin D metabolites, were negatively correlated with serum creatinine and serum inorganic phosphate. The two major skeletal lesions, osteomalacia and parathyroid osteopathy, while coexisting in many patients, varied independently in relation to their severity and were correlated with different vitamin D metabolites. The severity of osteomalacia was negatively correlated with the serum concentrations of 25-OHD and 24,25-OH2D while th severity of parathyroid osteopathy was negatively correlated with serum 1,25-OH2D values. To our knowledge these are the first systematic studies correlating skeletal histology with dihydroxylated vitamin D metabolites in renal failure in man.

An unexpected increase in pituitary sensitivity to gonadotrophin releasing hormone after treatment with porcine follicular fluid (inhibin) in immature hemicastrate rats

Porcine follicular fluid (PFF) contains a factor (inhibin or folliculostatin) which is reported to selectively inhibit the secretion of follicle-stimulating hormone (FSH) from the anterior pituitary gland. Chronic treatment of hemicastrate immature rats with PFF is able to partially inhibit the FSH-mediated hypertrophy of the remaining testis. However, the pituitaries from PFF-treated rats are paradoxically very sensitive to stimulation with gonadotrophin-releasing hormone (GnRH) and secrete significantly more FSH than control glands. Furthermore, this increased sensitivity results in a large increase in luteinizing hormone (LH) secretion. These observations suggest that under certain circumstances PFF is not selective for FSH and that it surprisingly stimulates rather than inhibits gonadotrophin secretion.

Some factors determining prognosis in young people with severe head injuries

Eighty-four patients under the age of 40 were rehabilitated after severe head injuries. All had been unconscious for at least 24 hours, and 35 were unconscious for more than four weeks. The mean length of treatment was 30.2 weeks. Seventy were discharged home, 13 remained in hospital, and one died. Seventy-two of the patients were followed up nine months to 15 years after the injury. Twenty-eight were working, 27 were at home but not working, 13 were in hospital, and four were dead. Prolonged unconsciousness, extensive neurological damage, and severe mental changes were found to be the main factors adversely affecting the prognosis; an inadequate family background and cerebral hypoxia were also considered to have an influence.

Paget's disease of bone and hyperparathyroidism: coincidence or causal relationship?

We studied 173 patients with Paget's disease and 105 patients with hyperparathyroidism. Nine patients were found to have both disorders.