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PubMed1987

Effects of castration or testosterone implants upon pituitary function in hypogonadal mice bearing normal foetal preoptic area grafts.

Grafts of normal mouse preoptic area (POA) tissue into the third ventricle of gonadotrophin-releasing hormone (GnRH)-deficient hypogonadal (hpg) mice resulted in an elevation of pituitary GnRH receptors, an increased synthesis of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) by the pituitary gland, an elevation of gonadal LH receptors and in the stimulation of steroidogenesis and spermatogenesis in the testis. In normal mice both castration or the subcutaneous implantation of testosterone capsules for 10 days reduced GnRH receptors, pituitary LH and FSH content, and the latter treatment also caused a 50% reduction in testicular LH receptors. In hpg mice bearing POA grafts testosterone implants failed to affect any of the above parameters, and castration failed to affect pituitary gonadotrophin hormone content, although there was a slight reduction in pituitary GnRH receptors after castration. These experiments suggest that neither the pituitary gonadotroph, nor the GnRH neurone represent major sites for the direct negative feedback of testosterone upon gonadotrophic hormone secretion in male mice.

Animals↗
PubMed1989

The effect of castration on calcitonin gene-related peptide in spinal motor neurons.

The spinal nucleus of the bulbocavernosus (SNB) is a sexually dimorphic nucleus of about 200 androgen-accumulating motor neurons in lumbar segments 5 and 6 of the rat spinal cord. In the present work we have used immunohistochemistry to investigate the change in calcitonin gene-related peptide-like immunoreactivity (CGRP-LI) in these motor neurons induced by long-term castration. CGRP-LI was found in the cell bodies of the SNB motor neurons and in thin varicose fibers coursing through the nucleus. In the intact animals 48.4 +/- 3.9% (n = 8) of the SNB neurons were CGRP-LI positive while in the castrates this ratio increased to 80.0 +/- 1.7% (n = 9, p less than 0.001). Animals castrated for 4 weeks and then implanted with testosterone-containing Silastic capsules for an additional 4 weeks had the same percentage of CGRP-LI-containing SNB motor neurons as intact animals. These results demonstrate that a reduction in circulating testosterone levels increases the number of SNB motor neurons that express CGRP-LI implying that androgen stimulation inhibits the expression of CGRP-LI in SNB motor neurons.

Animals↗
PubMed1989

Circadian rhythm of oxytocin in the cerebrospinal fluid of rhesus and cynomolgus monkeys: effects of castration and adrenalectomy and presence of a caudal-rostral gradient.

Oxytocin and vasopressin (AVP) were previously reported to have a diurnal rhythm in cerebrospinal fluid (CSF) collected from the cervical cistern of chaired, intact male rhesus monkeys. In the present study, we continuously sampled CSF from temporary indwelling catheters placed in the spinal subarachnoid space of unanesthetized monkeys maintained on tether and swivel systems. CSF was collected from intact and castrate female rhesus monkeys and intact female and castrate, adrenalectomized male cynomolgus monkeys to determine if oxytocin and AVP rhythms are expressed in spinal subarachnoid CSF, if the magnitude of the CSF rhythm displays a rostral-caudal gradient, and if the rhythm is present in adrenalectomized and castrate monkeys, or is specific to the sex or species of macaque. Monkeys, maintained on a 12-hour light/dark cycle with lights on from 06.00 to 18.00 h, had 19-gauge epidural catheters introduced at the L4-L5 intervertebral space and advanced cephalad in the subarachnoid space. The proximal end of the catheter was connected to a peristaltic pump for continuous removal of CSF (0.5 ml/h) and hourly CSF samples were radioimmunoassayed for oxytocin and AVP. For rostral-caudal studies, the distal tip of the catheter was repositioned every few days to collect CSF from 3 levels of the spinal subarachnoid space: C5-6, T5-6, T12-L1. Each animal had a diurnal CSF oxytocin rhythm with peak and trough oxytocin levels during early light and dark periods, respectively. The magnitude of the oxytocin rhythm differed among animals, but was consistent in an animal from day to day.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenalectomy↗
PubMed1988

Dichloromethylene biphosphonate retards femoral expansion in normal and castrated adult male rats.

This study reports the effects of dichloromethylene biphosphonate (Cl2MBP), an inhibitor of bone remodeling, on femoral expansion in four groups of adult male rats; (1) sham-operated controls; (2) sham operated + injections of Cl2MBP; (3) castrated (osteoporotic), and (4) castrated + injections of Cl2MBP. After controlling for body weight, analyses of covariance revealed significant differences in total femoral width between animals that had received Cl2MBP and those that had not. The results indicated that Cl2MBP treatment retarded femoral expansion in both castrated and normal adult male rats.

Animals↗
PubMed1993

Morphometric and stereological study of the glandular epithelium of the seminal vesicle of castrated guinea pigs treated with 17 beta-oestradiol benzoate.

Morphometric and stereological data are presented showing that the average thickness of the glandular epithelium (including secretory and basal cells together with intercellular spaces) of the seminal vesicle of the guinea pig increased significantly after oestradiol administration when compared with castrated controls. The increase in thickness was accompanied by a significant increase in the volume density of intercellular spaces. There were significant decreases in volume, surface and numerical densities of the secretory cell nuclei with respect to the glandular epithelium. The increase in the volume and surface densities of the secretory cell nuclei with respect to the average secretory cell was due to the significant increase in the average volume of the secretory cell. The increase in the mean volume of secretory cells was the result of a significant increase in the average cytoplasmic volume. In comparison with castrated controls, the structural data of cytoplasmic organelles also showed significant increases in total volume and surface area of granular endoplasmic reticulum per average secretory cell following oestradiol administration. This was accompanied by a significant increase in the total volume of Golgi cisternae per cell. The increase in the cytoplasmic volume of secretory cells after oestradiol treatment may be the result of an increase in number of organelles responsible for protein synthesis. The present study has provided quantitative evidence that the secretory function of the seminal vesicle of castrated guinea pigs may have been stimulated after oestradiol administration, which cannot be easily detected in a qualitative manner.

Animals↗
PubMed1994

Intracellular gonadotropin-releasing hormone immunoreactivity in gonadotrophs of intact or castrated male rats: semiquantitative estimation of testosterone and GnRH antagonist treatment.

Changes in intracellular gonadotropin-releasing hormone (GnRH) immunoreactivity (GnRH-IR) in pituitary gonadotrophs were assessed by the use of a semiquantitative immunocytochemical method in male rats undergoing various manipulations known to greatly modify gonadotropin secretion. In basal conditions, immunoreactive GnRH was localized in the cytoplasmic matrix, the secretory granules and the nucleus of these cells. Following intravenous stimulation with GnRH (100 ng i.v.), the GnRH-IR increased rapidly in all these three subcellular compartments, peaking at 15 min. In untreated, long-term castrated rats, GnRH-IR increased both in the basal state and after administration of GnRH. Injection of the castrated rats with testosterone propionate reduced the observed GnRH-IR to the level observed in intact rats. Acute or chronic treatment of castrated rats with a potent GnRH antagonist rendered GnRH-IR completely undetectable in all the three previously positive subcellular compartments of gonadotrophs, and GnRH-IR did not reappear after stimulation with GnRH. In sum, the fact that modifications of GnRH immunoreactivity are observed in rat gonadotrophs: (1) confirms the GnRH internalization process; (2) suggests different sites of action for GnRH within the cell, and (3) demonstrates rapid clearance of intracellular GnRH after stimulation.

Animals↗
PubMed1994

Testosterone eliminates the attenuating effect of castration on the progressive glomerular injury in hypercholesterolemic male Imai rats.

Hypercholesterolemic Imai rats, especially males, spontaneously develop proteinuria and glomerulosclerosis. We have shown that castration attenuated the progression of glomerular injury in male Imai rats. The present study was designed to investigate whether the attenuating effect of castration on glomerulosclerosis is eliminated by administration of testosterone. Testosterone propionate (TP) eliminated the attenuating effect of castration on the progression of glomerular injury by significantly and dose dependently increasing proteinuria and enhancing glomerular sclerosis. TP at 1 mg failed to reverse glomerulosclerosis to the control levels, despite a dose of TP sufficient to restore urinary protein excretion, serom testosterone level and glomerular growth. The results indicated that besides testosterone other sex-related hormones may be involved in the development of glomerulosclerosis in male Imai rats.

Aging↗
PubMed1988

Castration and erection. An animal study.

Castrated dogs (n = 3) need a much higher threshold level of energy to induce erection by electrical stimulation of the cavernous nerve than noncastrated animals (n = 24). In addition the resulting quality of erection, measured as maximal intracavernous pressure (pCC) versus peak systolic blood pressure (BP), was weaker in castrated dogs (pCC = 57% of BP on average) than in noncastrated dogs (pCC = 80% of BP on average). A high venous outflow from the corpora cavernosa in castrated dogs can also explain the shorter duration of erection. This experimental model excludes the interference of subjective factors, such as erotic stimuli and libido on erection, and it seems that androgen deficiency has a direct effect on the neurophysiology of the erectile tissues resulting in a higher tonus of the detumescence factors, which can be explained by an incomplete relaxation of the sinusoidal smooth muscle.

Androgens↗
PubMed1995

A randomised comparison of monotherapy with Casodex 50 mg daily and castration in the treatment of metastatic prostate carcinoma. Casodex Study Group.

Casodex (Bicalutamide, ICI 176,334) is a potent, non-steroidal, selective anti-androgen with a long half-life allowing once-daily oral administration. In this randomised, open, multicentre study, Casodex 50 mg monotherapy was compared with castration (medical, using goserelin acetate, [Zoladex], or surgical) in 245 patients with advanced prostate cancer. Primary end-points were time to treatment failure, time to objective progression and survival. Subjective responses, quality of life and tolerability were also evaluated. There was no significant difference between the groups in terms of objective progression or subjective responses. Treatment failed in 59 of 119 patients (50%) randomised to Casodex and in 61 of 126 patients (48%) randomised to castration (no statistically significant difference). An updated analysis showed that survival was similar in the two groups. Casodex was well tolerated with a low incidence of diarrhoea and sexual dysfunction. On the basis of this study, Casodex monotherapy is an effective alternative to castration in the treatment of metastatic prostate cancer.

Aged↗
PubMed1993

Circannual rhythms in starlings: response of castrated birds to 12-hr days depends on photoperiodic history.

The annual cycle of reproductive function in starlings (Sturnus vulgaris) is driven by seasonal changes in daylength and consists of a 6-month period of photosensitivity, culminating in maximal gonadal development, followed by a 6-month period of photorefractoriness. If male starlings are held under a constant photoperiod of 12 hr of light per day (LD 12:12), some individuals show circannual rhythms of testicular size. Do these rhythms consist of alternating periods of photosensitivity and photorefractoriness, and does the response depend on whether daylength is increased or decreased to 12 hr? Castrated starlings were transferred from natural short days in January (LD 9.5:14.5) to LD 12:12. Plasma LH decreased and then remained low for 2.5 years. Most birds molted, some twice. Other castrated birds were transferred from long days in August (LD 16:8) to LD 12:12. Plasma LH increased and then remained high for 15 months. None of these birds molted. Young starlings were exposed to LD 12:12 throughout incubation and thereafter. Plasma LH remained low until birds were 13 months old. All of these birds molted. These results demonstrate, first, that castrated starlings show no evidence of alternating periods of photosensitivity and photorefractoriness under LD 12:12; and second, that LD 12:12 can be perceived as a long day or a short day depending on photoperiodic history, and that young birds with no experience of any other daylength perceive LD 12:12 as a long day.

Animals↗
PubMed1977

The interaction of the photoperiod and testosterone in regulating serum gonadotropin levels in castrated male hamsters.

Castrated adult male golden hamsters maintained on either a stimulatory (LD 14:10) or a nonstimulatory (LD 6:18 ) light cycle for 10 weeks following surgery were implanted sc with empty or testosterone-filled Silastic capsules of various lengths. Capsules which maintained circulating androgen levels between 0.5 and 1.7 ng/ml reduced serum levels of LH and FSH in castrated animals exposed to LD 6:18 but not in animals maintained on LD 14:10. When serum androgen levels were maintained at about 3 ng/ml, serum gonadotropin levels were reduced 30--35-fold in nonphotostimulated hamsters but only 2--3-fold in photostimulated animals. Maintenance of serum androgen levels at 14--17 ng/ml induced a maximum decrease in serum LH and FSH in animals exposed to either photoperiod. These results indicate that exposure to short days for 10 weeks renders the hypothalamic-hypophyseal axis of the castrate hamster extremely sensitive to the negative feedback effect of testosterone. This alteration in steroid feedback sensitivity may be one way in which the photoperiod acts to alter neuroendocrine-gonadal activity in seasonally breeding animals.

Androgens↗
PubMed1989

Thyrotropin-releasing hormone (TRH)-Gly conversion to TRH in rat ventral prostate is inhibited by castration and aging.

TRH levels in rat prostate are very high in the 2-month-old rat and decline at least 90% during the next 2 yr. This decline in prostatic TRH levels with aging may be a significant factor in benign prostatic hypertrophy in man and other animals. Because prostatic TRH correlates positively with serum testosterone and negatively with serum thyroid hormone levels, we have examined the possibility that the age-related decline in prostatic TRH is hormonally regulated. TRH and a TRH precursor peptide, TRH-Gly (pGlu-His-Pro-Gly), were measured in ventral prostates from 2-, 5-, and 18-month-old Fisher 344 male rats using a combination of HPLC and specific RIAs for TRH and TRH-Gly. Similar measurements were made in a group of 2-month-old Sprague-Dawley rats which were castrated, sham castrated, or left untreated for 3 or 7 days before death. Aging and castration resulted in a significant decrease in the absolute TRH concentration as well as the TRH/TRH-Gly ratio, but no significant change was observed in TRH-Gly levels. The serum testosterone concentration did not change with aging, but serum T4 levels fell significantly. Because testosterone levels do not change during the first 18 months of life in most rat strains, and hypothyroidism in young animals is associated with a significant increase in prostate TRH and TRH-Gly levels, we conclude that the aging-related decline in prostate TRH biosynthesis is not the result of a hypogonadal state.

Aging↗
PubMed1990

Gonadotropin-releasing hormone (GnRH) agonists and GnRH antagonists do not alter endogenous GnRH secretion in short-term castrated rams.

The administration of GnRH agonists and antagonists suppresses pituitary LH secretion. However little is known about their effects on endogenous GnRH secretion. To determine if GnRH analogs act on GnRH secretion through a short or ultrashort loop feedback mechanism, experiments were performed to analyze GnRH secretion in hypophyseal portal blood of conscious short-term castrated rams under both agonist or antagonist treatment. In Study 1, six rams were castrated and surgically prepared for portal blood collection on day -7. Portal and peripheral blood were collected simultaneously every 10 min for 14-15 h on day 0. Five hours after the beginning of the portal blood collection, animals were injected im with 5 mg potent GnRH antagonist (Nal-Glu). In Study 2, six rams were treated daily from day -11 to day 0 with the GnRH agonist D-Trp6 GnRH (0.5 mg im). Castration and surgical preparation for portal blood collection were performed on day -7. On day 0 portal and peripheral blood were collected simultaneously every 10 min for 10-11 h. In both studies, to determine whether an increase in GnRH concentration in hypophyseal portal blood can overcome the inhibitory effect of the GnRH analogs, between 5 and 5.5 h after the injection of the analogs, endogenous GnRH secretion was stimulated by Naloxone administration (3 x 100 mg, iv, at 30-min intervals) followed by a bolus of exogenous GnRH (2 x 10 micrograms, iv at 30-min intervals). In Study 1, Nal-Glu administration led to a rapid cessation of pulsatile LH secretion for the duration of blood collection while GnRH pulse frequency and amplitude were not affected. GnRH and LH pulse frequency before and after Nal-Glu administration were, 6.2 +/- 0.6 vs. 5.7 +/- 0.8 (NS) and 5.3 +/- 0.3 vs. 0.3 +/- 0.2 pulses/6 h (P less than 0.001) respectively. In Study 2, peripheral LH secretion was completely suppressed while GnRH secretion (portal blood) remained pulsatile. GnRH pulses frequency and pulse amplitude were 4.3 +/- 0.3 pulses/6 h and 43.0 +/- 4.7 pg/ml, respectively. In both experiments, neither stimulation of endogenous GnRH secretion by naloxone nor administration of exogenous GnRH allowed reinitiation of LH secretion. However, additional studies in two animals of each treatment group (study-III) showed that this was clearly a dose related effect in antagonist treated but not in agonist-treated animals since higher doses of exogenous GnRH (i.e. 100 micrograms or 1000 micrograms) can increase significantly LH levels.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Influence of castration, alone or combined with thymectomy, on the development of diabetes in the nonobese diabetic mouse.

The nonobese diabetic (NOD) mouse is a recognized model for studying immunologically-mediated insulin-dependent diabetes mellitus. The disease appears with a greater preponderance in females than in males. Castration at weaning led to a significant increase in the prevalence of diabetes in NOD males, whereas a tendency to a decreased prevalence was observed in NOD females. Castration combined with thymectomy was found to further increase the prevalence of diabetes in NOD males, whereas in females castration reversed the effect of thymectomy. These results on changes in diabetes prevalence were corroborated by the degree of lymphocytic infiltration directed toward the pancreatic islets of Langerhans. Taken together these results indicate a direct relationship between the endocrine and immune systems, whereby orchidectomy has a deleterious effect on the immunopathogenesis of diabetes. In addition, we examined whether the distribution of lymphocyte subpopulations, mitogen reactivity, lymphokine production, and in vivo response to a thymus-dependent antigen, such as sheer red blood cell, were dependent or independent of the sex steroid environment.

Animals↗
PubMed1995

Expression of gonadotropin-releasing hormone (GnRH) receptor gene is altered by GnRH agonist desensitization in a manner similar to that of gonadotropin beta-subunit genes in normal and castrated rat pituitary.

It was previously established that the administration of a potent GnRH agonist such as triptorelin (D-Trp6-GnRH) induced desensitization of pituitary gonadotropic cells, resulting in decreased expression of gonadotropin beta-subunit genes and the suppression of LH and FSH synthesis and release. Binding of GnRH to the pituitary is also affected by agonist treatment. To examine the desensitizing effects of GnRH agonist on the expression of the pituitary GnRH receptor (GnRH-R) gene, male rats were given triptorelin (long-acting formulation, 300 micrograms/kg), and levels of GnRH-R messenger RNA (mRNA) were determined by Northern and dot blot hybridization to a 32P-labeled rat complementary DNA probe. Abundances of gonadotropin alpha-subunit, LH beta, and FSH beta mRNAs were examined in parallel, using appropriate probes. A rapid time-dependent decrease in the level of GnRH-R mRNA was observed in rats after triptorelin administration. A minimum residual level of mRNA, in the range of 20-25% of the initial value, was attained as early as 5 h after treatment. Levels further stabilized to 25-30% after a small transient increase to 45% on day 5. A single injection was effective for at least 30 days, after which GnRH-R mRNA levels slowly returned to normal, suggesting a progressive abolition of agonist effects. A concomitant acute depletion of mRNA levels was observed for LH beta and FSH beta (50% decrease in about 48 and 3 h, respectively), whereas the alpha-subunit message increased (rapidly reaching a level 1.8-fold that in control rats after 1-2 days). Castration induced a 3.8-fold elevation in the amounts of GnRH-R mRNA after 3 weeks, whereas alpha, LH beta, and FSH beta mRNAs increased by 6.2-, 7.9-, and 4.2-fold, respectively, compared to corresponding values in intact animals. Administration of the GnRH agonist readily prevented, for as long as 3 weeks, the stimulatory effects of castration on the GnRH-R mRNA and mRNAs for the beta-subunit of gonadotropins, but not for the alpha mRNA, which remained at a high level. When triptorelin was administered 3 weeks postoperatively, the castration-induced increase in LH beta and FSH beta was totally abolished, and no significant effect was noted on alpha-subunit mRNA. In conclusion, these data demonstrate that expression of the GnRH-R gene is subject to regulation and depends on GnRH stimulation, in a manner that indicates susceptibility to desensitizing action by the long-acting GnRH analog, triptorelin.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1996

Telomerase is activated in the prostate and seminal vesicles of the castrated rat.

Telomeres, the repetitive non-coding DNA sequences found at the ends of all eukaryotic chromosomes, shorten with each cell division. It has been proposed that telomere shortening may be the counting element of a mitotic clock that keeps track of cell divisions; with shortening to a critical length acting as a senescence signal underlying cellular aging. The enzyme telomerase functions to maintain telomere length, thus allowing unlimited cell division, and has been associated with cellular immortalization and cancer. Stem cells have large, perhaps unlimited, replicative capacities. Since these cells are potentially immortal, we reasoned that they might posses active telomerase. We therefore assayed for telomerase activity in the stem cell enriched pools of the androgen-depleted sex accessory tissues in the castrated male rat. Following castration, the ventral prostate and seminal vesicles of the rat involute, losing approximately 90% of their cells by 21 days. These residual glands persist, and are enriched for stem cells, being capable of fully regenerating these glands if testosterone is re-introduced into the animal. We assayed telomerase activity in extracts from normal, involuted, and regenerating ventral prostate and seminal vesicles. Normal glands were found to be telomerase negative, whereas telomerase activity appeared as these glands involuted following castration. Conversely, telomerase activity disappeared during testosterone-induced regeneration of these residual glands. These results provide strong evidence for the ability of androgen to negatively-regulate telomerase activity in stem cell populations of the rat ventral prostate and seminal vesicles. and represent the first in vivo model system for the modulation of telomerase activity.

Animals↗
PubMed1998

Testosterone stimulates angiogenesis and vascular regrowth in the ventral prostate in castrated adult rats.

The castration-induced regression and testosterone stimulated regrowth of the vasculature in the rat ventral prostate lobe were studied using stereological techniques. Seven days after castration, the endothelial cell proliferation rate (bromodeoxyuridine labeling index); the total weights of blood vessel walls, blood vessel lumina, endothelial cells, glandular epithelial cells; and total organ weight were all decreased. Within 2 days after sc treatment with testosterone, the total weights of blood vessel walls, endothelial cells, and vascular lumina, as well as the endothelial cell proliferation rate, were all normalized. In contrast to the rapid response of the vasculature, the total weight of glandular epithelium and total organ weight were not normalized during the 4 days of testosterone treatment. Growth of the vasculature apparently precedes growth of the glandular epithelium. The testosterone- dependent factors stimulating the vasculature are unknown, but factors derived from epithelial cells, mast cells (which accumulate in the prostate during the first day of testosterone treatment), and tissue macrophages could all be involved. Castration-induced regression and testosterone-stimulated regrowth of the prostatic vasculature can be used as an experimental model to study factors regulating angiogenesis and organ growth in the prostate.

Animals↗
PubMed2000

Molecular cloning of growth hormone-releasing hormone/pituitary adenylyl cyclase-activating polypeptide in the frog Xenopus laevis: brain distribution and regulation after castration.

Pituitary adenylyl cyclase-activating peptide (PACAP) appears to regulate several neuroendocrine functions in the frog, but its messenger RNA (mRNA) structure and brain distribution are unknown. To understand the potential role of PACAP in the male frog hypothalamic-pituitary-gonadal axis, we cloned the frog Xenopus laevis PACAP mRNA and determined its distribution in the brain. We then analyzed the castration-induced alterations of mRNA expression for PACAP and its selective type I receptor (PAC1) in the hypothalamic anterior preoptic area, a region known to regulate reproductive function. The PACAP mRNA encodes a peptide precursor predicted to give rise to both GH-releasing hormone and PACAP. The deduced peptide sequence of PACAP-38 was nearly identical to that of human PACAP with one amino acid substitution. Abundant PACAP mRNA was detected in the brain, but not several other tissues, including the testis. In situ hybridization revealed strong expression of the PACAP gene in the dorsal pallium, ventral hypothalamus, and nuclei of cerebellum. PACAP mRNA signals were weak to moderate in the hypothalamic anterior preoptic area and were absent in the pituitary. Castration induced an increase in the expression of PACAP and PAC1 receptor mRNAs in the hypothalamic anterior preoptic area after 3 days. Replacement with testosterone prevented the castration-induced changes. These results provide a molecular basis for studying the physiological functions of PACAP in frog brain and suggest that PACAP may be involved in the feedback regulation of hypothalamic-pituitary-gonadal axis.

Amino Acid Sequence↗