Recombinant human growth hormone enhances tibial growth in peripubertal female rats but not in males

OBJECTIVE: A novel non-invasive technique termed microknemometry, which allows daily leg length measurement, was used to investigate the growth promoting effect of growth hormone (GH) on peripubertal rats. We compared the effect of different patterns of recombinant human (rh) GH administration to peripubertal male rats with the effect produced by two daily administrations of the same amount of rhGH to peripubertal female rats or adult male rats. Another group of peripubertal male rats was also submitted to a 3-day period of starvation, in order to study catch-up growth during refeeding and to determine whether this process could be stimulated by exogenous GH administration. RESULTS: GH treatment was unable to stimulate tibial growth or weight gain in peripubertal males, whereas a clear growth promoting effect was observed in female rats and also in adult male rats. Starvation caused a dramatic body weight loss, and a reduction in tibial growth rate. Peripubertal male rats gained body weight faster than unstarved animals during refeeding, although recovery was not complete after nine days. Tibial growth, however, was resumed at the same speed as in normally fed males. This means that no catch-up effect was observed after refeeding in animals either with or without GH treatment. CONCLUSIONS: During peripuberty, normal male rats grow at a maximal speed that cannot be further increased by exogenous GH treatment, whereas age-matched female rats or older males grow at a slower rate than peripubertal males. Thus, exogenous rhGH administration is capable of enhancing growth velocity.     

Estradiol alters Fos-immunoreactivity in the hippocampus and dorsal striatum during place and response learning in middle-aged but not young adult female rats

Evidence from lesion and inactivation studies suggests that the hippocampus (HPC) and dorsal striatum compete for control over navigation behavior, and there is some evidence in males that the structure with greater relative activation controls behavior. Estradiol has been shown to enhance HPC-dependent place learning and impair dorsal striatum-dependent response learning in female rats, possibly by increasing hippocampal activation and/or decreasing striatal activation. We used Fos-immunoreactivity (Fos-IR) to examine the activation of several subregions of the HPC and striatum in ovariectomized female rats with or without estradiol replacement 30 min after place or response learning. In 4-month-old rats, neither task nor estradiol increased Fos-IR above explore control levels in any subregion analyzed, even though estradiol impaired response learning. In 12-month-old rats, estradiol increased Fos-IR in the dentate gyrus, dorsal medial striatum, and dorsal lateral striatum in place task learners, while the absence of estradiol increased Fos-IR in these regions in response task learners. However, learning rate was not affected by estradiol in either task. We also included a group of long-term ovariectomized 12-month-old rats that displayed impaired place learning and altered Fos-IR in CA1 of the HPC. These results suggest that task-specific effects of estradiol on hippocampal and striatal activation emerge across age but that relative hippocampal and striatal activation are not related to learning rate during spatial navigation learning.     

Effect of ovariectomy and hormone replacement therapy on small artery biomechanics in angiotensin-induced hypertension in rats

OBJECTIVES: To test the effects of chronic angiotensin II administration on blood pressure and small artery biomechanics in the female sex hormone-depleted state (proposed to increase cardiovascular vulnerability) and with hormone replacement. DESIGN: Biomechanical properties of saphenous artery segments from ovariectomized (n = 10), ovariectomized + chronically angiotensin II infused-(n = 10), and ovariectomized + chronically angiotensin II-infused + sex hormone-replaced (n = 10) rats were studied. METHODS: Surgical ovariectomy was performed. Osmotic minipumps were used for chronic angiotensin II infusion (100 ng/min per kg). For hormone replacement therapy, oestradiol-propionate, 450 microg/kg for 7 days + medroxyprogesterone-acetate, 15 mg/kg for 14 days were given, intramuscularly. After 4 weeks, cylindrical segments of the saphenous artery were prepared and subjected to in-vitro microarteriographic measurements. Pressure-diameter curves (0-200 mmHg) were recorded in Krebs-Ringer solution, with smooth muscle contracted (norepinephrine, 16 micromol/l) and with relaxed (papaverine, 28 micromol/l). RESULTS: Chronic angiotensin II infusion significantly reduced the inner radius (at 100 mmHg: 298 +/- 17 microm versus 347 +/- 7 microm, P< 0.001), while wall-thickness did not change. Hormone replacement restored the morphological radius (333 +/- 7 microm). Angiotensin II infusion slightly increased the full contraction range of the segments (defined as the percentage difference between fully contracted and fully relaxed diameters), which was further significantly increased by hormone replacement (39 +/- 4%, 46 +/- 8%, 62 +/- 7% at 100 mmHg, in the three groups, respectively; P < 0.05). Despite unaltered stiffness in relaxed state, elastic moduli computed for the contracted segments decreased after hormone replacement. CONCLUSIONS: These observations give further experimental support to the hypothesis that sex hormone replacement might be useful in preventing the development and/or stabilization of postmenopausal hypertension, as well as in treating existing disease.     

Transient changes in the in vitro activity of the luteinizing hormone-releasing hormone pulse generator after ovariectomy in rats

We examined in vitro LHRH release as a function of time after ovariectomy (OVX). Adult female rats (diestrous day 1 and 11-16, 61-68, and more than 120 days post-OVX) were decapitated, and the suprachiasmatic-medial preoptic area-medial basal hypothalamus was removed and superfused in vitro. There was a statistically significant (P less than 0.05) 2-fold decrease in mean in vitro LHRH release 11-16 days post-OVX that returned to levels observed in diestrous day 1 females 60 days post-OVX. LHRH cycle amplitudes of 11- to 16-day ovariectomized rats were reduced and significantly lower (P less than 0.05) than those of more than 120-day ovariectomized rats. These results indicate a complex relationship between ovarian steroid hormone removal and LHRH pulse generator function that is only revealed after direct measurement of LHRH release.     

Severe regurgitation immediately after replacement of a dysfunctional bioprosthesis in the mitral valve position

Severe regurgitation immediately after replacement of a cardiac valve with a mechanical prosthesis or a bioprosthesis is a rare occurrence. Such, however, was the case in the patient described.     

Prepubertal reduction of the ovarian follicle population by combined LH-releasing hormone antagonist treatment and unilateral ovariectomy influences follicle characteristics but not the ovulation rate at first oestrus.

The effect on first ovulation of the massive reduction of the total pool of ovarian follicles during the infantile and late juvenile period was studied in rats. Treatment with an LH-releasing hormone antagonist (LHRH-A) during infancy (5 mg/kg body weight on days 6, 9, 12 and 15 of life) was combined with unilateral ovariectomy performed on either day 15 (early ULO) or 2-5 days before the expected day of first ovulation (late ULO). Rats were killed on the day of first or second oestrus, when blood was collected and the (remaining) ovaries were prepared for differential counting of follicles and corpora lutea. In addition, blood was sampled 8 h after ULO and the ovaries studied histologically in the group of rats which were unilaterally ovariectomized 2-5 days before first ovulation. The time of first ovulation was not influenced by treatment with LHRH-A, early or late ULO, or a combination of LHRH-A treatment and ULO. Ovulation rate after LHRH-A treatment was decreased, but was still within the normal range in intact rats and in early ULO rats compared with saline-treated controls. Serum FSH concentrations 8 h after ULO performed 2-5 days before first ovulation were similar in saline- and LHRH-A-treated rats (845 +/- 59 and 801 +/- 99 (S.E.M.) micrograms/l respectively) and had increased compared with intact controls (216 +/- 15 micrograms/l). Treatment with LHRH-A resulted in a reduction of more than 50% in healthy and atretic follicles, and late ULO reduced the number of healthy follicles even further.(ABSTRACT TRUNCATED AT 250 WORDS)     

Identification of a prodromal period in Crohn's disease but not ulcerative colitis

OBJECTIVES: Irritable bowel syndrome, a common gastrointestinal diagnosis, has not been clearly studied in inflammatory bowel disease. Some of the residual symptoms in subjects treated with Crohn's disease and ulcerative colitis are thought to be related to irritable bowel syndrome. The aims of this study were 1) to describe the duration and nature of complaints before the diagnosis of Crohn's disease and ulcerative colitis (prodromal period), and 2) to determine the role of IBS in this prodromal period. METHODS: A total of 66 patients with confirmed inflammatory bowel disease were enrolled in the study. The subjects received a questionnaire to ascertain the nature and duration of symptoms preceding the diagnosis of Crohn's disease or ulcerative colitis, including features described under the Rome criteria for irritable bowel syndrome. RESULTS: Of the 66 subjects analyzed, 45 had Crohn's disease and 21 had ulcerative colitis. The prodromal period was 7.7 +/- 10.7 yr for Crohn's disease and 1.2 +/- 1.8 yr for ulcerative colitis (p < 0.05). Once patients meeting the Rome criteria for irritable bowel syndrome during the prodrome were excluded, the duration of the prodromal period (non-IBS) for ulcerative colitis dropped to 0.8 +/- 1.3 yr compared to 6.9 +/- 9.8 yr in the Crohn's disease group (p < 0.05). The symptoms of the non-IBS prodrome in subjects with Crohn's disease were bloating, diarrhea, stomach pain, heartburn, fever, weight loss, and fatigue. Further analysis demonstrated that subjects whose Crohn's disease initially began as colonic disease had a longer prodrome than with small bowel. In the non-IBS Crohn's group, there was also a correlation between the age at the time of diagnosis and the duration of prodrome (r = 0.67, p < 0.0001). CONCLUSIONS: There is a significant prodromal period before the time of diagnosis of Crohn's disease that is not found in ulcerative colitis even after exclusion of subjects with IBS.     

Methylprednisolone does not inhibit the release of growth hormone after intravenous injection of a novel growth hormone secretagogue in rats

The present study was undertaken to study the growth hormone-releasing properties and growth-promoting effect of a GH secretagogue ipamorelin (IPA) in rats given the synthetic glucocorticoid methylprednisolone (MP).In a first experiment, rats received either saline or MP (5.0 mg/kg) for 8 days. Treatment with MP significantly (P< 0.001) decreased body weight gain, but the acute response to either IPA or growth hormone releasing hormone (GHRH) in terms of plasma GH was not changed.In a second experiment, venous catheters were surgically implanted. On the next day, rats were randomly allocated to receive saline alone, MP alone (5.0 mg/kg) or MP plus IPA in doses of 0.4 or 1.6 mg/kg/day for 10 days. IPA was administered intravenously four times a day.MP treatment significantly (P< 0.05) retarded recovery from surgery in terms of body weight. Thus, saline treated animals lost 4.0 +/- 3.5 g over the entire experimental period, whereas animals receiving MP lost 13. 6 +/- 2.9 g. When IPA was given together with MP, losses in body weight were significantly (P< 0.05) reduced to 2.3 +/- 2.0 and 1.6 +/- 2.0 g in animals given the high and low dose of IPA, respectively. In parallel with this IGF-I levels increased.In conclusion, this work shows that MP does not disrupt the response of the GH-IGF-I axis to an exogenous stimulus like IPA, and repeated stimulation leads to increases in IGF-I and of body weight gain.     

Food restriction enhances endogenous and corticotropin-induced plasma elevations of free but not total corticosterone throughout life in rats

Chronic food restriction (FR), which retards many aging processes, enhances the endogenous diurnal peak of plasma total corticosterone (B) in young rats. Although the FR-dependent enhancement of total B disappears in aged rats, increased levels of the bioavailable fraction, free B, appear to be maintained. In young rats, we previously found that the FR-induced increase in the diurnal peak of total B is associated with increased adrenal response to corticotropin, also known as adrenocorticotropic hormone (ACTH). Here we show that the FR-enhanced adrenal response of total B to ACTH disappears with age but that the enhanced response of free B is maintained. We measured the endogenous diurnal peak and the response to ACTH of total and free B in 10-, 16-, and 22-month-old ad-libitum fed and FR male Fischer 344 rats in the afternoon, when plasma B peaks. At 10 and 16 months, FR rats showed enhanced total plasma B responses to ACTH relative to ad-libitum fed rats, but not at 22 months. By contrast, the response of free B to ACTH was enhanced by FR at all ages. The effect of FR on patterns of endogenous total and free diurnal B in these three age groups paralleled the ACTH-response data. The enhanced adrenocortical response of FR rats to ACTH does not reflect an increased expression of ACTH-receptor (ACTH-R) mRNA, because ACTH-R mRNA/microg adrenal RNA and ACTH-R mRNA/mg adrenal weight did not differ between ad-libitum fed and FR rats at any age.     

Persistent changes in somatostatin and neuropeptide Y mRNA levels but not in growth hormone-releasing hormone mRNA levels in adult rats after intrauterine growth retardation

A reduction in the availability of oxygen and nutrients across the placenta in the last trimester of pregnancy may lead to intrauterine growth retardation (IUGR) which, in turn, may cause a persistent postnatal growth failure. However, it is unknown whether this persistent growth retardation is centrally mediated through alterations in the components of the growth hormone (GH)-axis. We tested the hypothesis that alterations in the development of the central components of the GH-axis contribute to the persistent growth failure observed after experimentally induced IUGR or early postnatal food restriction (FR) in the rat. Using semi-quantitative in situ hybridization, we compared somatostatin (SS), GH-releasing hormone (GHRH) and neuropeptide Y (NPY) mRNA levels in adult rats experimentally subjected to IUGR or FR. We report that IUGR increased the expression of SS mRNA in the periventricular nucleus (PeN) of adult male and female rats by 128% and 153% respectively, did not alter the expression of GHRH mRNA in the arcuate nucleus (ARC) and decreased the NPY mRNA expression in the ARC by 73% in males and 61% in females, whereas in the FR group no changes in the expression of these mRNAs were observed. These data show that the timing of malnutrition or the presence of the placenta is important for the long-term alterations since the effects only occurred in the prenatally induced growth retardation and not in the early postnatally induced growth retardation group.     

Perinatal food deprivation induces marked alterations of the hypothalamo-pituitary-adrenal axis in 8-month-old male rats both under basal conditions and after a dehydration period

Dehydration is a classic homeostatic stressor in rats that leads to a series of endocrine responses including stimulation of the hypothalamo-pituitary-adrenal (HPA) axis. During the last decade, it has been well established that perinatal food restriction is associated with the onset of diseases in adults. Our previous demonstration of long-term alterations in HPA axis activity in both basal conditions and after a 72-hour dehydration period in 4-month-old rats exposed to a 50% maternal food restriction (FR50) in late gestation and lactation prompted us to investigate whether such perinatal undernutrition further affects HPA axis activity in mature animals. As previously described in 4-month-old rats under basal conditions, 8-month-old FR50 rats showed reduced body weight and an enhanced ratio between mineralocorticoid receptor (MR) and glucocorticoid receptor (GR) mRNA levels in the hippocampus, as well as increased pro-opiomelanocortin (POMC) mRNA levels in the adenohypophysis. In addition, numerous additional alterations appeared in mature rats. In the hypothalamus, levels of vasopressin (VP) mRNAs were increased both in the paraventricular nucleus (PVN) and in the supraoptic nucleus (SON). In the adenohypophysis, GR and prohormone-convertase 2 (PC2) mRNA levels were significantly increased, whereas prohormone-convertase 1 (PC1) mRNA was not affected by maternal undernutrition. Interestingly, undernourished animals exhibited high plasma levels of total and free corticosterone in spite of normal corticotropin (ACTH) levels, an indication that HPA basal activity is enhanced by maternal undernutrition in 8-month-old animals. Dehydration for 72 h induced a rise in ACTH plasma levels, but did not modify total and free corticosterone plasma levels in 8-month-old FR50 animals. In the adenopituitary, POMC mRNA levels were decreased after dehydration but PC1 mRNA levels were unaffected. The present study indicates that maternal food restriction during the perinatal period dramatically affects the activity of the HPA axis until the age of 8 months. We speculate that higher basal HPA activity and an inadequate HPA response after dehydration in mature animals may contribute to diseases such as hypertension, known to develop with aging in perinatally growth-restricted rats.