Intact Research Articles

Effects of Neuropeptide Y on the in vitro Release of Gonadotropin-Releasing Hormone, Luteinizing Hormone, and Beta-Endorphin and Pituitary Responsiveness to Gonadotropin-Releasing Hormone in Female Macaques

The objectives of these studies were to examine the release of gonadotropin-releasing hormone (GnRH) and beta-endorphin-like activity (beta-EP) from macaque hypothalami, and the release of luteinizing hormone (LH) and GnRH-induced LH from macaque anterior pituitaries in response to neuropeptide Y (NPY) treatment. Anterior hypothalamic (AH) and mediobasal hypothalamic (MBH) blocks of tissues and the adenohypophysis were bisected along the midline into two equal-sized fragments. Fragments were superfused with medium for 3 h, followed by 3 h of either NPY (80 nM) or medium alone. In a separate experiment, adenohypophyseal (AP) fragments were superfused in accordance with the same protocol (3 h medium - 3 h NPY or medium) except that exogenous GnRH (352 nM) was added for 30 min at the beginning of hour 3 and again at the beginning of hour 6. Immunoactive GnRH, beta-EP, and LH levels were measured in superfusate samples (400 microliters) collected at 10-min intervals. GnRH levels rose within 20-30 min of initiation of NPY treatment, and elevated GnRH release was sustained for the duration of NPY exposure of both AH and MBH fragments from ovarian intact (INT) rhesus (Macaca mulatta: n = 8; p less than 0.05) or Japanese (Macaca fascicularis; n = 4; p less than 0.01) macaques. NPY treatment had no effect on either AH or MBH fragments isolated from ovariectomized (OVX) rhesus macaques (n = 4 for AH, and n = 5 for MBH). In AP fragments isolated from INT rhesus macaques (n = 8), NPY stimulated LH release within 1 h of treatment (p less than 0.05), whereas NPY had no effect on pituitaries from OVX animals (n = 4).(ABSTRACT TRUNCATED AT 250 WORDS)

Increased Bioactivity of Serum Follicle-Stimulating Hormone, but Not Luteinizing Hormone, Following Hemicastration in Ram Lambs1

This study evaluated the short-term effects of hemicastration on levels of bioactive (bio-) and immunoactive (immuno-) FSH and LH in 3.5-mo-old ram lambs. Biological activities of FSH and LH were determined using in vitro rat granulosa cell aromatase and mouse Leydig cell testosterone assays, respectively. Four rams each were either hemicastrated (HC) or left intact (INT) and blood samples were collected over a 2-wk period. In HC rams, serum bio- and immuno-FSH concentrations increased several fold within 5-8 h after surgery and remained elevated over INT controls for 7 and 14 days, respectively. The increase in bio-FSH was greater than that for immuno-FSH, resulting in an increase in the ratio of biological to immunological activity (B/I ratio) through Day 7. Neither immuno-FSH, bio-FSH, nor the B/I ratios varied throughout the 2-wk study in INT rams. In contrast to FSH, serum concentrations of immuno- and bio-LH and the B/I ratios were similar between HC and INT rams. For both gonadotropins, biological activity was positively correlated to immunological activity. These results demonstrate that (1) immuno- and bio-FSH concentrations are elevated after hemicastration; (2) the FSH biopotency (B/I ratio) also is increased, at least temporarily; and (3), despite these changes in FSH production, neither immuno- nor bio-LH secretion is altered by hemicastration.

Growth, carcass composition and serum hormone responses to photoperiod and ovariectomy in heifers

ABSTRACTTo determine effects of photoperiod and ovaries and their interactions on live-weight (LW) gain, carcass composition, growth hormone (GH), insulin (INS) and prolactin (PRL), crossbred beef heifers were utilized. Heifers (no. = 70) were blocked by LW and assigned to a pre-treatment slaughter group for estimation of initial carcass composition or to treatments in a 2 × 2 factorial experiment (no. = 14 per treatment). Main effects were: photoperiod (8 h light (L): 16 h dark (D) v. 16L: 8D) and ovaries (intact (INT) v. ovariectomized (OVX)). Heifers were given a maize-based mixed diet (115 g protein and 11·5 MJ metabolizable energy per kg dry matter) ad libitum once per day at 07.30 h. On days 64 and 138, blood samples were taken every 30 min for 10 h from five heifers in each treatment. On day 144 treated heifers were slaughtered. Relative to OVX heifers, INT heifers had greater (P < 0·01) average LW gain (1·03 v. 1·17 kg/day), carcass weight (252 v. 270 kg) and carcass protein accretion rates (68 v. 82 g/day) but carcass fat accretion was not affected (P < 0·l; 381 v. 399 g/day). Compared with 8L: 16D, exposure to 16L: 8D non-significantly increased LW gain more in OVX heifers (16 kg) than in INT heifers (3 kg). Photoperiod did not significantly influence weight or composition of the carcass. There was no significant interaction between photoperiod and ovaries on carcass composition. Across all heifers GH declined (P < 0·05) and INS and PRL increased (P < 0·05) from day 64 to 138. Compared with 8L: 16D, exposure to 16L: 8D increased PRL on day 64 (P < 0·05; 13·4 v. 28·5 u.g/1) and decreased INS averaged across days 64 and 138 (P = 0·l; 0·71 v. 0·55 u/l) but had no effect on GH. GH, INS and PRL did not differ between INT and OVX heifers. It is concluded that ovariectomy of heifers reduces LW gains, carcass weights and accretion of protein, and that exposure to 16L: 8D partially prevents the loss in LW gain.

Direct effect of CNS on insulin hypersecretion in obese Zucker rats: involvement of vagus nerve.

It is hypothesized that the vagus nerve makes a major contribution to pancreatic insulin hypersecretion in the genetically obese rat (fa/fa) via direct pancreatic innervation. An in situ brain-pancreas perfusion model with intact pancreatic central nervous system (CNS) innervation was used in these studies. The dynamics of insulin secretion in response to a 40-min glucose stimulus (200 mg/dl) was investigated in CNS intact (INT), bilateral cervical vagotomized (VGX), and CNS functionally ablated (ABL) 11- to 12-wk-old homozygous lean (Fa/Fa) and obese (fa/fa) female Zucker rats. The overall pattern of insulin secretory dynamics from obese and lean rats was similar. However, insulin released during the entire 40-min perfusion period by pancreata from obese rats was significantly greater than in lean rats. In lean rats, there was no significant difference in insulin secretion from pancreata of CNS-INT, VGX, and ABL rats. In obese rats, CNS-INT pancreata secreted almost twice as much insulin as pancreata from obese ABL rats and four times as much insulin as CNS-INT lean rats. This demonstrates that hypersecretion of insulin in obese Zucker rats is comprised of a significant direct CNS component. Although vagotomy had little effect on CNS-INT lean rats, it reversed the CNS component of hypersecretion present in CNS-INT obese rats. Because insulin secretion in CNS-INT obese rats was lowered by vagotomy to that equivalent to values of CNS-ABL obese rats, this demonstrates a significant contribution by the parasympathetic nervous system to the hyperinsulinemia seen in the Zucker obese rat that is attributed to direct parasympathetic innervation of the pancreas.

Castration and testosterone effects on endogenous and somatocrinin-induced growth hormone release in intact and castrated male pigs

Growth hormone (GH) release is influenced mainly by two hypothalamic factors, growth hormone-releasing factor (GRF) and somatostatin and is modulated by other hormones such as gonadal steroids. The objective of this study was to determine if castration (CA) and exogenous testosterone (TE) affect endogenous and GRF-induced GH release. Purebred Yorkshire male pigs (n=32) were assigned to one of the following treatments: T1:CA; T2:CA±TE; T3: intact (IN); T4: IN±TE, in a 2 × 2 factorial design. Piglets were castrated at 3 days of age. Testosterone propionate (1.0 mg/kg) in sesame oil (2 ml) or sesame oil alone was injected sc SID during a 10-day period before each sampling day at 9, 15 and 21 weeks of age. Jugular blood samples were collected for a 6-hr period preceding and following iv injection of hGRF(1–29)NH 2 (10μg/kg). These procedures were repeated at 9, 15 and 21 weeks of age. The overall mean GH levels and the area under thr GH peaks before and after GRF stimulation were lower (P<.05) in castrated animals than in intact animals. Testosterone treatment increased (P<.05) circulating TE levels and increased the amplitude of the endogenous GH peaks but did not affect (P>.05) the GRF-induced GH release. Increasing age produced a marked reduction of the amplitude of the GH peaks, the area under the GH peaks, the baseline mean and the overall mean GH levels during the 6-hr period preceding GRF injection. The present data support the hypothesis that castration in pigs reduces circulating and GRF-induced GH release. Exogenous testosterone for 10 days did not stimulate endogenous or GRF-induced GH release with the exception of the amplitude of the endogenous GH peaks.

Short-term pituitary-testicular responses of prepubertal ram lambs to hemicastration.

To examine the short-term effects of hemicastration on pituitary-gonadal responses, 12 ram lambs were anesthetized and hemicastrated at 4 mo of age and killed (n = 4) at 2 (HC2), 7 (HC7), or 14 (HC14) days following surgery. Four intact (INT) rams were killed 14 days following anesthesia. Testis and pituitary weights were similar between HC and INT rams. Serum follicle-stimulating hormone (FSH) in HC rams increased within 6 h, peaked at 12 h, and remained elevated above INT levels throughout the study. Overall mean serum testosterone levels in HC rams were lower than in INT rams for the first 48 h, but were similar by 3 days post-surgery. Pulsatile luteinizing hormone (LH) and testosterone secretion was suppressed for the first 9.5 h following anesthesia and/or surgery in both HC and INT animals. A single LH pulse and succeeding testosterone pulse occurred in 10/12 HC and 4/4 INT rams between 10 and 14 h post-surgery, both of which were lower in amplitude in HC than INT animals. However, on Day 7, pulsatile secretory patterns of LH and testosterone were similar, suggesting compensatory androgen secretion had occurred in HC rams. Pituitary LH content was unaffected by hemicastration. In contrast, pituitary FSH content was greater in HC7 and HC14 compared to HC2 and INT animals. Pituitary gonadotropin hormone-releasing hormone (GnRH) receptor concentrations were similar in INT, HC7, and HC14 rams, but were slightly reduced in HC2 rams. Neither testicular LH nor FSH receptor concentrations were altered by hemicastration at any time.(ABSTRACT TRUNCATED AT 250 WORDS)

Transdiaphragmatic pressure and rib motion in area of apposition during paralysis.

Changes in pleural surface pressure in area of apposition of diaphragm to rib cage (delta Ppl,ap), changes in abdominal pressure (delta Pab), and redial displacement of the 11th rib have been recorded in anesthetized, paralyzed dogs during lung inflation or deflation. Above functional residual capacity (FRC) changes in transdiaphragmatic pressure in area of apposition (delta Pdi,ap) were essentially nil in intact (INT) dogs either in lateral or supine posture, and in partially eviscerated (EVS) dogs in lateral posture, either in the 10th or 11th intercostal space. Below FRC delta Pdi,ap could be positive (INT lateral and EVS), nil (EVS), or negative (INT supine and EVS); it could be different in the 10th and 11th intercostal spaces. Hence, with stretched (like with contracted) diaphragm, delta Ppl,ap measured at one site often differs from delta Pab and is not representative of average pressure acting on area of apposition. With volume increase above FRC, the 11th rib moved slightly in and then out in EVS and linearly out in INT. With volume decrease below FRC it moved out progressively in EVS, and it moved in and eventually reversed in INT. In paralyzed dogs in lateral posture the factor having the greatest influence on displacement of the abdominal rib cage is Pab. Mechanical linkage with pulmonary rib cage becomes relevant at large volume, whereas insertional traction of diaphragm becomes relevant at low volume.

Hormonal specificity and activation of social behavior in male red-winged blackbirds

Five groups of male red-winged blackbirds were observed 12 times over 14 days in an aviary setting. An estradiol-treated female was present during the last two observations of each group. Each group of males consisted of a castrated (CA) and an intact (IN) control and six castrated males given one of the following hormone treatments: the aromatizable androgens, testosterone (T) and androstenedione (AE); the nonaromatizable androgens, 5α-dihydrotestosterone (DHT), and androsterone (AN); the estrogen, estradiol (E); or a combination of E + DHT. Castration significantly reduced the frequency of singing and three common vocalizations, chucks, checks, and ips, below the levels shown by IN males. Only hormone treatments which provided both androgenic and estrogenic metabolites (A + E = T, AE, E + DHT) restored normal levels of these behaviors in castrated males. Endocrine status also modulated epaulet display. IN and A + E males were more likely than other males to keep their epaulets constantly exposed. The frequency of sidling and supplanting also varied significantly across hormone-treatment groups, with A + E males showing higher frequencies of these behaviors than other males. T was clearly the most effective hormone treatment in activating hormone-sensitive behaviors in this species. Hormone treatment was more important than size or plumage pattern in determining the outcome of aggressive interactions. In some groups, the dominant male clearly inhibited the performance of hormone-sensitive behaviors by other males. Among A + E males, the frequency of higher intensity song spread displays was highly correlated with the frequency of high-intensity aggressive behaviors and negatively correlated with the tendency to withdraw from other males. Patterns of correlations among behaviors suggest that some calls are more hormone dependent than others, and thus may serve different signal functions.

Autoradiographic analysis of hepatocytes in mirex-induced adaptive liver growth.

The relationships between [3H]thymidine incorporation into hepatocyte nuclei, cell enlargement, and mitotic index were studied in intact (INT) and adrenalectomized (ADX) mirex-dosed rats. In INT mirex-dosed rats the sequence of events included the following: a biphasic response in nuclear labeling of mononuclear hepatocytes with peaks at 48 and 66 h postmirex dose, a peak in mitotic activity 66 h postmirex dose, and a significant increase in binuclear hepatocyte size 48 h postmirex dose. In ADX mirex-dosed rats the sequence of events included the following: a biphasic response in nuclear labeling of mononuclear hepatocytes with peaks at 24 and 48 h postmirex dose, a peak in mitotic activity 60 h postmirex dose, and a marginal increase in binuclear hepatocyte size 48 h postmirex dose. Corticosterone supplements to ADX mirex-dosed rats significantly reduced nuclear labeling of the mononuclear hepatocytes and increased the size of binuclear hepatocytes to that observed in INT mirex-dosed rats. This study demonstrates that adaptive liver growth consists of a hyperplastic response that involves mononuclear hepatocytes and a hypertrophic response that involves binuclear hepatocytes. Both responses appear to be modulated by corticosterone.

Lack of neural control of atrial natriuretic peptide release in conscious dogs

To determine whether or not cardiac nerves control the release of atrial natriuretic polypeptide (ANP), we examined the effects of intrapericardial cardiac denervation on circulating ANP in conscious dogs. Base-line level of circulating ANP in six cardiac-denervated (CD) dogs (191 +/- 24 pg/ml) was not significantly different from that in seven intact (INT) dogs (196 +/- 18 pg/ml). Three percent dextran-40 in saline (18 ml/kg, 20% of estimated blood volume) was infused over 5 min, and the elevated left atrial pressure (LAP; approximately 8 mmHg) was maintained by supplemental infusion over 40 min. The increase in circulating ANP after infusion in the CD dogs (462 +/- 61 pg/ml) was not significantly different from that in the INT dogs (435 +/- 73 pg/ml). The regression line relating circulating ANP (normalized with regard to the control value) with the change in LAP in the INT dogs was not significantly different from that in the CD dogs. These results suggest that the cardiac nerves do not control the tonic release of ANP or the volume expansion-induced release of ANP.

Effect of exogenous factors on prececal nutrient and amino acid reabsorption, ascertained in swine with ileorectal anastomoses. 1. Effect of the degree of grinding up of grain

Pigs fitted with ileo-rectal anastomoses (IRA) and in parallel experiments intact (INT) pigs were used to estimate the influence of the different grinding fineness of barley and wheat (coarse, medium, fine) on the apparent and true precaecal and total digestibility resp. absorption of various N free and N containing nutrients, among them crude protein and the indispensable and dispensable amino acids. Coarse grinding (25 ... 50% of the particles greater than 2 mm) resulted in significantly lower digestibility values than medium and fine grinding--with more striking differences in barley than in wheat. Precaecally most nutrients and amino acids are distinctly less digestible than at the end of the total tract. The precaecal lysine absorption determined with IRA pigs is remarkably low. The results are discussed. In order to attain a good utilization of the protein contained in cereals grains should be ground in hammermills with maximal sieve meshes of 3 mm. It is proposed to tabulate crude protein and amino acids in future on the basis of a standardized true precaecal digestibility resp. absorption.

Regional circulatory responses to head-out water immersion in conscious dogs.

We determined the regional blood flow responses to head-out water immersion (WI) in intact (INT) and cardiac-denervated (CD) conscious dogs. Immersing dogs in thermoneutral water (37 degrees C) in the quadruped position for 100 min resulted in significant increases in cardiac output (Qco) above control values by 38.7% in the INT dogs and 39.2% in the CD dogs (P less than 0.01). Arterial pressure increased by 32 and 34.7% in the INT and CD groups, respectively, during WI, with no significant changes occurring in the calculated total peripheral resistance. Regional blood flow responses were measured with 15-microns radiolabeled microspheres. Flows in the INT and CD groups increased significantly to the heart (40, 38%), skin (93, 96%), fat (79, 83%), diaphragm (44, 48%), and intercostal muscles (58, 55%), whereas there were no changes in renal cortical blood flows during WI. Total brain blood flows did not change significantly on immersion; however, blood flows in both INT and CD animals were increased to the cerebellum (19, 22%), but a significant decrease in pituitary flow (52%) was observed only in the CD group during WI. Gastrointestinal tissue flows increased only during early WI in both INT (45%) and CD (47%) animals. However, blood flows to the skeletal muscles increased only during late WI in the INT (53%) and CD (47%) groups. There were no significant differences between the INT and CD groups. Rectal temperatures and systemic O2 consumption (VO2) were unchanged during WI in both groups of animals. These observations indicate that WI leads to a sustained elevation of Qco accompanied by selective increases in regional tissue perfusion that may be accounted for in some tissues by an increase in metabolic demand or by local heating responses and produces a time-dependent redistribution of blood flow away from the gastrointestinal tissues toward skeletal muscle tissues, which may be due to a partial uncoupling of the normal Q/VO2 relationship. This may be caused by thermal or central neurohumoral mechanisms. These regional circulatory responses are not dependent on the presence of the cardiac nerves.

Role of cardiac nerves in response to head-out water immersion in conscious dogs.

The circulatory, renal, and hormonal responses during 100 min of thermoneutral (37 degrees C) head-out water immersion (WI) were investigated in conscious intact (INT) and cardiac-denervated (CD) dogs. In the INT group, both left and right atrial and aortic transmural distending pressures and left ventricular contractile performance (LV dP/dtmax) increased, and total peripheral resistance remained unchanged. Cardiac output (QCO) increased in association with an increase in heart rate and LV dP/dtmax. Urine flow (V), sodium excretion (UNaV), and osmolal clearance (Cosmol) all increased, whereas glomerular filtration rate, as indicated by creatinine clearance (CCr), remained constant. The diuresis and natriuresis occurred in the absence of any significant changes in plasma levels of antidiuretic hormone (ADH), aldosterone, or plasma renin activity. The CD animals showed a similar hemodynamic response except that the increase in QCO was now associated with an increase in stroke volume and no change in heart rate or LV dP/dtmax. Although the increase in V was similar in both magnitude and time course of the INT animals, there was no significant change in UNaV. Thus there is a striking change in the character of the response of the denervated group in that the natriuresis is abolished and, instead, a water diuresis occurred. Free water clearance increased, but no significant changes in Cosmol or CCr were observed. In addition plasma ADH levels significantly declined during WI in the CD group. These data indicate that cardiac receptors are important in determining the nature of the renal response to WI.

NEONATAL PULMONARY VASCULTURE: RECOVERY FROM POSITIVE END—EXPIRATORY PRESSURE (PEEP) IN IMPACT AND ISOLATED LUNGS

Unilateral PEEP (UPEEP) reduces ipsilateral pulmonary blood flow (PBF) in the intact (INT) newborn lamb. On cessation of UPEEP, ipsilateral PBF returns slowly to baseline. Intact and isolated lungs of 9 infant lambs were studied to examine the mechanism of this vascular hysteresis. Flow probes were placed on R and L pumonary arteries (PA) of 4 infant lambs. R and L lungs were intubated endobronchially and synchronously ventilated (Siemens-Elena Servo 900C). UPEEP was applied to the L lung for 4 min, abruptly discontinued and recovery of L lung blood flow (LPBF) followed for 4 min (11 trials). LPA was then occluded (LOC) for 4 min using a balloon catheter and recovery of LPBF on deflation followed for 4 min (11 trials). Recovery of PA pressure (P) after stopping PEEP was studied in 5 infant lambs after median sternotomy. Isolated in situ perfused lungs (ISO) were prepared; pulmonary vasculature paralysed; and recovery of PAP on cessation of PEEP studied. In the INT, on cessation of UPEEP, airway and vascular pressures, lung volumes, and RPBF returned to baseline within 10 sec but LPBF recovered slowly. LPBF returned promptly to baseline after balloon deflation and PAP recovered promptly after stopping PEEP in ISO after paralysis of pulmonary vasomotion. These data suggest that lung distension has a direct effect on pulmonary vascular tone in the intact infant lamb.

Inhibition of hypothalamic gonadotropin-releasing hormone release by endogenous opioid peptides in the female rabbit.

Recent evidence suggests that the endogenous opioid peptides (EOPs) inhibit luteinizing hormone (LH) and follicle-stimulating hormone (FSH) by suppression of hypothalamic gonadotropin-releasing hormone (GnRH) release, and that the feedback inhibition by EOPs is influenced by ovarian steroids. In the present studies, intact (INT) and ovariectomized (OVX) adult female rabbits were fitted with femoral vein catheters and mediobasal hypothalamic (MBH) push-pull perfusion (PPP) cannulae. One week after brain cannulation, does were subjected to 6 h of PPP and sequential blood sampling. In experiment I, INT (n = 6) and OVX (n = 5) does were infused intravenously with saline for 4 h followed by 2 h of infusion of the opiate antagonist naloxone (NAL; 10 micrograms/min/kg) while the MBH was simultaneously perfused with media. In experiment II, INT (n = 5) and OVX (n = 5) does were perfused with media for 4 h followed by 2 h of intrahypothalamic (IHP) NAL perfusion (0.2 microgram/min). The GnRH in push-pull perfusates and LH and FSH in plasma samples collected at 10-min intervals were measured by specific radioimmunoassays. In INT does, neither intravenous infusion nor IHP perfusion of NAL altered pulsatile parameters of GnRH or LH release. In contrast, both intravenous and IHP NAL administration stimulated GnRH and LH release within 30-50 min in OVX does by marked increases in both GnRH and LH pulse amplitudes. Neither route of NAL administration affected FSH secretion in any of the treatment groups. We conclude that EOPs are involved in the inhibition of hypothalamic GnRH secretion in OVX does; the feedback inhibition by ovarian steroids on the hypothalamic-pituitary axis in the rabbit is sufficient to compromise the effects of EOPs, and under these experimental conditions, the hypothalamic mechanisms which regulate the secretion of pituitary LH and FSH may be independent.

Serum follicle stimulating hormone, luteinizing hormone, and testosterone in sexually stimulated intact and unilaterally castrated rams

Ten two-year-old intact (IN) and unilaterally castrated (UC) Targhee rams were exposed to an estrogenized ewe each week from June to October. Each week the rams were subjectively evaluated for libido (10 for high interest and 1 for no interest). Semen was collected from all cooperating rams and evaluated for volume, concentration, and motility. Every 2 wk, blood samples were obtained at −30 and 0 min before and 30 and 60 min after ewe access. Serum was harvested; follicle stimulating hormone (FSH), luteinizing hormone (LH), and testosterone concentrations were quantified by radioimmunoassay (RIA). Week 5 of ewe access was assigned as Week 1. Libido scores rose from a low on Week 1, with eight rams ejaculating, to a high on Week 12, with all rams ejaculating (Week 1, 5.0 ± 1.0; Week 12, 10.0 ± 0.0). The product of testis length and width was significantly greater in UC compared with IN rams (88.4 ± 1.4 versus 73.2 ± 1.0 cm 2, respectively). Serum FSH concentrations (ng/ml) were greater (P < 0.05) in UC than IN rams and dropped over the experimental period. Serum LH concentrations (ng/ml) were significantly greater in UC compared with IN rams. This difference was more pronounced in Weeks 1 and 3 compared with Weeks 11 and 13. Serum testosterone concentrations (ng/ml) were similar in UC and IN rams throughout the experiment. In conclusion, serum testosterone was not altered in UC rams; however, serum FSH and LH concentrations were increased in UC rams. Unilateral castration did not enhance the normal changes in semen quantity and quality in the rams from July to October.

Effects of unilateral castration on serum luteinizing hormone, follicle stimulating hormone, and testosterone concentrations in one-, two-, and three-year-old stallions

The endocrine control of compensatory hypertrophy was investigated in 12 Morgan stallions, four each at one, two and three years of age. Half were assigned to be unilaterally castrated (UC) in January and half to remain intact (IN). Nine blood samples were taken from each stallion at half-hour intervals 30, 90, and 150 d after unilateral castration for radioimmunoassay of serum concentrations of luteinizing hormone (LH), follicle stimulating hormone (FSH), and testosterone. Mean serum LH concentration was greater (P<0.06) in UC than IN stallions; however, the difference was greatest at 30 d and least at 150 d. Serum LH was greater (P<0.01) in two- and three-year-olds than in one-year-olds. The mean log 10 for serum FSH concentration was greater (P<0.06) in UC than IN stallions. Mean serum testosterone concentrations were similar in UC and IN stallions for all sample days, suggesting that the single testes of the UC stallions produced as much testosterone as the two testes of the IN stallions. Two- and three-year-old stallions had greater (P<0.01) serum testosterone than one-year-old stallions. Unilateral castration of stallions was associated with a significant increase in serum LH and FSH concentrations and, perhaps, higher intratesticular testosterone, which may explain, in part, the compensatory hypertrophy noted in the remaining testis.

Effects of unilateral castration on morphologic characteristics of the testis in one-, two-, and three-year-old stallions

The effects of unilateral castration on testicular compensatory hypertrophy were measured in 12 Morgan stallions, four each at one, two, and three years of age. They were randomized within age to intact (IN) or unilaterally castrated (UC) groups. Allotment and surgery were in January 1983 and total castration was in June 1983, 150 d after unilateral castration. Testis weight increased linearly with age (P < 0.01) and was increased by unilateral castration (P < 0.07). Epididymal weight also increased linearly with age (P < 0.05) and was heavier in UC animals (P = 0.15). Tubule diameter (P < 0.10) and epithelial height (P < 0.03) were greater in UC than in IN stallions. In conclusion, testes of stallions underwent compensatory hypertrophy after unilateral castration.

Estradiol increases somatomedin-C concentrations in adolescent rhesus macaques (Macaca mulatta).

Estradiol (E2) may enhance somatomedin-C (Sm-C) secretion during puberty in female rhesus monkeys. The present study evaluated the importance of age and acute changes in E2 on Sm-C secretion. Intact (INT) females at their first ovulation (age 3.5 yr; n = 6) had higher levels of Sm-C across the ovulatory cycle than did intact adults (ADT) (n = 5). Levels of Sm-C were similar for both groups during the follicular and luteal phases despite higher follicular phase levels of E2. Young, ovariectomized, E2-treated (E2OVX) females (age 3.5 yr; n = 5; E2 = 50 pg/ml) had higher basal levels of Sm-C than did either age-matched ovariectomized (OVX) females (n = 3), ovariectomized adults (OXA), or E2-treated ovariectomized adults (E2A) (E2 = 100 pg/ml). When ovariectomized groups were given E2 to induce ovulatory increases, no changes in serum Sm-C occurred. Comparisons among age-mates revealed that basal levels of Sm-C were similar between INT and E2OVX, yet these levels were higher than those for OVX. Sm-C levels were similar among all adult groups. Serum growth hormone (GH) was highest in E2OVX, next highest in INT and OVX, and lowest in all adults. Higher Sm-C levels in young animals are, thus, related to these age differences in GH concentrations and are further enhanced by basal levels of E2 and not by acute changes in this steroid. Low Sm-C secretion in adults is associated with low GH levels. Thus, the facilitory effect of basal E2 on Sm-C release is observed during conditions when basal GH levels are elevated, a situation normally limited to adolescence.

An Economic Analysis of Performance Data from Toe-Clipped Laying Hens Housed at Variable Stocking Densities

Data from a previously reported study investigating the interaction of toe-clipping and stocking density on laying-hen performance were subjected to economic analyses to determine optimal profit-producing combinations of these two management practices. In three separate trials, toe-clipped (TC) and intact (IN) pullets were examined at caging densities of either 4 (465 cm2/ hen) or 5 (372 cm2/hen) birds per cage. In each trial, beginning at 22 wk of age, hen production performance (hen-day egg production, hen-housed egg production, feed consumption, body weight, and mortality) was assessed for 12 28-day periods of lay. Performance criteria were averaged over all trials and used to determine per cage returns ($) above feed and pullet rearing costs (irrespective of fixed costs) and per cage profits (gross returns minus total costs) for the four treatment combinations. Economic analyses were also adjusted for hatchery toe-clipping costs. Profits (or losses) from each toe treatment stocking-density combination were calculated under variable egg and feed prices.At a blended egg price of $.35/doz, all cage systems lost money. Housing hens TC, 5/cage, yielded the greatest profits or least losses in 76% of the toe treatment stocking-density combinations studied. Economic returns were greatest for TC hens, 5/cage, at an egg price of $.55/doz when feed costs ranged from $140 to $230/ton and at egg prices higher than $.55/doz, regardless of feed prices. However, when these price combinations exist, housing hens IN, 4/cage is more profitable than housing hens TC, 4/cage.Reducing hen density to 4/cage resulted in less losses at the very low egg price of $.35/doz and at the very high feed price of $260/ton when coupled with an egg price of $.55/doz. Under these price combinations, housing hens TC was economically better than IN, except at the very low feed and egg prices of $140/ton and $.35/doz, respectively, where IN hens, 4/cage, resulted in the least losses.