The effects of caffeine on the ultrastructure and mitochondrial function of the embryonic chick heart.

Results from this study indicate that caffeine (at an embryotoxic dose equal to the LD40 administered to 3-day chick embryos produced both ultrastructural and functional abnormalities in embryonic cardiac mitochondria. The principal effects of caffeine on the ultrastructure of embryonic myocardial cells were clearly suggestive of cellular injury and included: (1) a marked disruption of mitochondrial cristae with formation of intramitochondrial myelin-like figures and (2) intracellular edema. A biochemical analysis of mitochondrial function revealed that caffeine inhibited the capacity of mitochondria to oxidize succinate. However, when pyruvate and malate were employed as substrates for isolated mitochondria, caffeine did not significantly alter mitochondrial function. Interference with embryonic cardiac mitochondrial succinate oxidation and/or fragmentation of mitochondrial membranes are suggested as possible events in the pathogenesis of caffeine-induced cardiac cell injury which, in turn, may lead to the embryonic death of the chick.

Effects of POCA on metabolism and function in the ischemic rat heart.

Sodium 2-[5-(4-chlorophenyl)-pentyl]-oxirane-2-carboxylate (POCA) inhibits carnitine palmityltransferase I and fatty acid oxidation. The effects of POCA on cardiac function and on tissue levels of carnitine and coenzyme A esters were studied in the isolated rat heart subjected to 90 minutes of ischemia with and without 15 minutes of reperfusion. The perfusion medium contained 1.2 mM palmitate and 5.5 mM glucose plus or minus 0.5 mM POCA. This compound prevented accumulation of long-chain acylcarnitine and coenzyme A esters during ischemia and significantly improved the recovery of cardiac output after ischemia and reperfusion. Short-chain acylcarnitine levels were increased during ischemia by POCA. No effects were noted on tissue ATP and lactate levels. POCA may protect the ischemic heart by preventing accumulation of these toxic metabolites and by stimulating glucose utilization during ischemia.

Developmental changes in the luteinizing hormone secretory pattern in peripubertal female rhesus monkeys: comparisons between gonadally intact and ovariectomized animals.

Developmental changes in LH release patterns were observed longitudinally in female rhesus monkeys at 10-65 months of age. The average ages of menarche and first ovulation in this experiment (n = 14) were 31.1 +/- 2.6 and 47.0 +/- 2.6 months (mean +/- SE), respectively. To assess the ovarian influence on developmental changes in LH, data were simultaneously obtained from neonatally ovariectomized animals at similar ages. The estimation of circulating LH was made with RIA as well as biological assay. During the prepubertal period (10-20 months of age), basal LH was very low, and there was no circadian fluctuation of LH in gonadally intact monkeys. During the early pubertal stage (20-30 months of age), before menarche, basal LH levels started to increase, and a circadian LH rhythm (nocturnal increases) appeared. At the midpubertal stage (30-50 months of age), a period between menarche and first ovulation, basal LH levels further increased, and the circadian LH rhythm was maximal. At the late pubertal stage (50-60 months of age), a period after the first ovulation during which the animals were not able to reproduce fully as adults, basal LH declined, and the circadian rhythm diminished. Similar but more exaggerated developmental changes in basal LH and the circadian fluctuation of LH were observed in females ovariectomized neonatally. Basal LH levels at 10-20 months were as low as those in intact animals with no circadian rhythm present. During the early pubertal period, a circadian fluctuation appeared at the time when a slight increase in the basal LH level occurred. Furthermore, the amplitude of circadian fluctuation (the difference between morning and evening LH values) increased linearly with the increase in basal LH during the midpubertal stage. These LH parameters in ovariectomized animals reached their peaks at 40-44 months, an age before the first ovulation in intact animals. As basal LH levels declined during the late pubertal stage to postpubertal stage, circadian fluctuation disappeared. The results suggest that the increase in LH output and concomitant circadian fluctuations occur in close association with the pubertal process, and this change in LH release is not dependent on the presence of the ovary. Therefore, we suggest that alteration of the LHRH release pattern during maturation, as reflected by LH release, rather than resetting of the gonadostat, is the key factor involved in the mechanism of the onset of puberty.

Posterior hypothalamic lesions advance the onset of puberty in the female rhesus monkey.

The effects of experimental lesions in the posterior hypothalamus and the anterior hypothalamus on menarche and first ovulation were examined in nonhuman primates. With the aid of x-ray ventriculography, bilateral lesions were made by passing a radiofrequency current through a thermister electrode in the posterior hypothalamus (n = 7) or the anterior hypothalamus (n = 6) of female rhesus monkeys at 18 months of age. Four animals that received sham lesions as well as four normal females of a similar age served as controls. All animals were caged individually and examined daily for vaginal bleeding and sex skin color change. Developmental changes in gonadotropins, ovarian steroids, body weight, and nipple size were monitored throughout the experiments. The time of first ovulation was determined by laparoscopic observation of the newly formed corpus luteum and by the level of circulating progesterone. Histological examination confirmed that the bilateral lesions in the hypothalamus were approximately 2-3 mm in diameter and overlapped midline. Primary sites of posterior hypothalamic lesions included the premamillary area and the posterior nucleus, while the infundibular nucleus and the median eminence were entirely spared. The posterior lesions encroached upon the mamillary nuclei caudally in most cases and upon the ventromedial nucleus rostrally in some cases. Primary sites of anterior hypothalamic lesions included the medial preoptic area, the periventricular preoptic nucleus, and the anterior hypothalamic nucleus. Partial lesions of the diagonal bundle of Broca, the medial preoptic nucleus, and the paraventricular nucleus were also detected. Posterior hypothalamic lesions advanced the ages at menarche (22.2 +/- 1.3 months; P less than 0.001) and first ovulation (40.7 +/- 2.7 months; P less than 0.05) compared to those of control animals (menarche, 30.3 +/- 3.1; first ovulation, 51.2 +/- 3.3 months). The body weight at menarche of these lesioned animals (2.62 +/- 0.11 kg) was smaller (P less than 0.05) than that of controls (3.14 +/- 0.20 kg), but the body weight at first ovulation of lesioned animals (4.36 +/- 0.28 kg) was not different from that of controls (4.57 +/- 0.13 kg). Hormonal and physical changes during maturation, i.e. an increase in circulating estradiol and growth in nipple size before menarche and first ovulation, occurred earlier in the lesioned animals and the growth spurt before first ovulation not only began earlier but also attained mature levels several months earlier than that in control animals.(ABSTRACT TRUNCATED AT 400 WORDS)

Rat mammary carcinoma regressions during suppression of serum growth hormone and prolactin.

Female rats bearing N-nitrosomethylurea-induced mammary carcinomas were treated with pergolide mesylate to suppress serum prolactin. The drug was given alone, or with somatostatin, 20 micrograms/hr delivered by osmotic minipump for 7 days to suppress serum growth hormone. Tumour regressions did not occur with pergolide alone, but did so promptly in all of 5 rats when growth hormone levels were also suppressed by somatostatin. A potent long-acting agonistic analogue of somatostatin, L362,823 produced similar tumour regressions at a dose of 5 micrograms/hr when given with pergolide, but was ineffective alone. This dose completely prevented the episodic release of pituitary growth hormone.

Influence of prolactin and growth hormone on rat mammary tumors induced by N-nitrosomethylurea.

The effects of hypophysectomy and prolactin-suppressing drugs on the growth of mammary tumors induced in Sprague-Dawley rats by N-nitrosomethylurea and dimethylbenz(a)anthracene were compared. The influence of ovine prolactin and growth hormone administration on N-nitrosomethylurea-induced tumors was also studied in hypophysectomized animals. After hypophysectomy, all 13 tumors induced in 13 rats by N-nitrosomethylurea underwent regression, as did ten of 12 induced by dimethylbenz(a)anthracene. There were no new tumors. Pergolide mesylate, a long-acting ergoline derivative, was given in a dose of 80 micrograms twice daily by s.c. injection for 28 days. Only three of 12 N-nitrosomethylurea-induced tumors regressed, while four became static. However, only two new tumors developed in the 12 pergolide-treated rats, compared to 11 in the 12 untreated controls. Bromocriptine mesylate, at ten times the pergolide dose, was even less effective; one of 16 tumors regressed, two became static, and eight new tumors appeared in the 16 rats. In contrast, eight of 12 dimethylbenz(a)anthracene-induced tumors regressed during pergolide therapy, two became static, and there was only one new tumor among the 12 rats. Prolactin, 1 mg twice daily for 7 days by s.c. injection, was given to another eight rats bearing 11 N-nitrosomethylurea-induced tumors, commencing 7 days after hypophysectomy. Regression of five tumors borne by four rats was reversed but resumed when treatment was stopped. Regression of five tumors in the other four animals was arrested without regrowth; the sixth became inpalpable. All of these six grew rapidly when growth hormone, 2 mg twice daily, was administered in addition to prolactin.