Skin shop: A new model for high-volume skin cancer care.

INTRODUCTION: Non-melanoma skin cancer incidence is increasing in New Zealand. Increased cost of care has led to service pressure and a review of models of care. A high-volume skin surgery service at Waikato Hospital has been developed to reduce service costs. This study examines the oncological safety of the new model. METHODS: Prospective data for all skin lesions excised were collected from December 2014 to December 2016. Primary outcomes were rate of complete excision, rate of incomplete excision and rate of narrow excision. RESULTS: A total of 2076 lesions were excised: 92% were complete, 4.2% were narrow and 3.2% were incomplete. CONCLUSION: The rate of narrow and incomplete excisions was low in a service delivered by supervised surgical registrars. The Skin Shop model is safe, inexpensive and suitable for adaptation to safely reduce the cost of skin cancer surgery.

Nuclear cyclophilins affect spliceosome assembly and function in vitro.

Cyclophilins are ubiquitously expressed proteins that bind to prolines and can catalyse cis/trans isomerization of proline residues. There are 17 annotated members of the cyclophilin family in humans, ubiquitously expressed and localized variously to the cytoplasm, nucleus or mitochondria. Surprisingly, all eight of the nuclear localized cyclophilins are found associated with spliceosomal complexes. However, their particular functions within this context are unknown. We have therefore adapted three established assays for in vitro pre-mRNA splicing to probe the functional roles of nuclear cyclophilins in the context of the human spliceosome. We find that four of the eight spliceosom-associated cyclophilins exert strong effects on splicing in vitro. These effects are dose-dependent and, remarkably, uniquely characteristic of each cyclophilin. Using both qualitative and quantitative means, we show that at least half of the nuclear cyclophilins can act as regulatory factors of spliceosome function in vitro. The present work provides the first quantifiable evidence that nuclear cyclophilins are splicing factors and provides a novel approach for future work into small molecule-based modulation of pre-mRNA splicing.

Dietary restriction reduces the rate of estradiol clearance in sheep (Ovis aries).

Three experiments were designed to test the effect of dietary restriction on clearance of 17beta-estradiol (E(2)) in sheep. A preliminary experiment examined the effect of a 4-d fast on the rate of E(2) clearance in wethers. The second experiment tested the hypothesis that either long-term restriction (7 wk) or a 5-d fast would increase steroid-binding capacity of serum by increasing the concentration of sex hormone-binding globulin (SHBG) in the blood of ovariectomized ewes. In Exp. 3, we hypothesized that nutrition-dependent regulation of E(2) clearance by the liver would result in divergence in biliary extraction of E(2) in fed and fasted wethers receiving comparable levels of exogenous E(2). A marked difference in E(2) clearance between fed and fasted wethers was noted in the preliminary study. Relative to ad libitumfed wethers, a 4-d fast decreased E(2) clearance by 52%. Serum concentrations of SHBG were increased in long-term energy-restricted and fasted ewes, relative to the concentration in maintenancefed ewes (P = 0.015). Furthermore, a 5-d fast nearly doubled serum steroid-binding capacity in wethers. The E(2) concentration in bile was 2 times greater in fasted than in fed wethers. This fasting-dependent increase in biliary E(2) may be reflective of the increased serum E(2) in fasted animals, because each 1 pg/mL increase in serum E(2) increased bile E(2) by 0.86 +/- 0.12 pg/mL, independent of nutrition (P = 0.002). Our results demonstrate that the rate of clearance of E(2) is decreased during nutritional restriction. Additionally, these data indicate that altered SHBG expression, enterohepatic recirculation, or both are involved in the decreased E(2) clearance during dietary restriction.

Estimation and prediction with HIV-treatment interruption data.

We consider longitudinal clinical data for HIV patients undergoing treatment interruptions. We use a nonlinear dynamical mathematical model in attempts to fit individual patient data. A statistically-based censored data method is combined with inverse problem techniques to estimate dynamic parameters. The predictive capabilities of this approach are demonstrated by comparing simulations based on estimation of parameters using only half of the longitudinal observations to the full longitudinal data sets.

Using specific antisera to neutralize ACTH in sturgeon: a method for manipulating the interrenal response during stress.

Interrenal function and the magnitude of the stress response were assessed in green sturgeon (Acipenser medirostris) passively immunized with antisera directed against adrenocorticotropic hormone (ACTH). The nucleotide sequence encoding ACTH was determined using reverse transcriptase polymerase chain reaction (RT-PCR). We identified two isoforms of ACTH that differ at a single site (position 26) in the 39 AA peptide. Both forms of green sturgeon ACTH (gsACTH1-39) display 100% homology with both sequences of white sturgeon ACTH (wsACTH1-39). The N-terminal portion of gsACTH also shares absolute identity with the comparable portion of human ACTH (hACTH). However, we identified considerable sequence divergence in the C-terminal domain between gsACTH and hACTH. Species-specific anti-ACTH sera were generated by vaccinating sheep against the C-terminal portion of gsACTH (gsACTH26-39). The peptide was covalently linked to a carrier protein (keyhole-limpet-hemocyanin [KLH]) to further enhance its immunogenicity. The anti-gsACTH sera recognized gsACTH1-39 and the immunogenic peptide (gsACTH26-39), but did not interact with hACTH1-39. To assess the impact of the antisera, fish were passively immunized with anti-gsACTH26-39 sera or anti-KLH sera and challenged with a hACTH1-39 injection on day 1 followed by a 1-min air emersion stressor on day 2. The magnitude and duration of the secretory response induced by hACTH did not differ (P > .05) between groups. Conversely, the magnitude of cortisol secretion induced by air emersion was significantly attenuated (P < .05) in fish passively immunized against gsACTH26-39. Collectively, these data demonstrate that the targeted antisera used in this study can discriminate between mammalian and green sturgeon ACTH and moderate the in vivo response to a stressor.

Population dynamics models in plant-insect herbivore-pesticide interactions.

We consider several population dynamics models in investigating data from controlled experiments with aphids in broccoli patches surrounded by different margin types (bare or weedy ground) and three levels of insecticide spray (no, light, or heavy spray). We carry out parameter estimation computations along with statistical analysis to compare autonomous versus non-autonomous model dynamics. We conclude with a brief discussion of some not-so-subtle pitfalls that can arise when using quantitative measures of model fit-to-data to make biological inferences as well as offer a positive example of how one might combine a priori biological hypothesis and intuition with rather sophisticated (from a field biology viewpoint) mathematical methodologies to suggest synergisms.

Dynamic multidrug therapies for hiv: optimal and sti control approaches.

We formulate a dynamic mathematical model that describes the interaction of the immune system with the human immunodeficiency virus (HIV) and that permits drug "cocktail " therapies. We derive HIV therapeutic strategies by formulating and analyzing an optimal control problem using two types of dynamic treatments representing reverse transcriptase (RT) in hibitors and protease inhibitors (PIs). Continuous optimal therapies are found by solving the corresponding optimality systems. In addition, using ideas from dynamic programming, we formulate and derive suboptimal structured treatment interruptions (STI)in antiviral therapy that include drug-free periods of immune-mediated control of HIV. Our numerical results support a scenario in which STI therapies can lead to long-term control of HIV by the immune response system after discontinuation of therapy.

Effect of duration of infusion of stress-like concentrations of cortisol on follicular development and the preovulatory surge of LH in sheep.

Stress-like levels of cortisol suppress follicular growth and development and block or delay the preovulatory surge of LH when cortisol is continuously administered during the late luteal and early follicular phases of the ovine oestrous cycle. We postulated that cortisol infusion of shorter duration would have a similar effect. To test this hypothesis the oestrous cycles of mature ewes were synchronized using progestin-treated vaginal pessaries. Ewes were randomly assigned to one of four treatment groups. Animals received cortisol (0.1mg/kg/h; n=8) or vehicle alone (n=8) beginning 5 days before, and continuing for 5 days after, pessary removal (PR). Additional groups received cortisol only during the 5 days period before (n=7), or the 5 days period after (n=8), PR. Continuous delivery of cortisol established stable serum concentrations of cortisol of 72.0+/-2.5ng/ml within 6h of initiation of infusion. Serum concentrations of oestradiol increased progressively during the period after PR in control animals receiving vehicle alone and the preovulatory surge of LH was evident in all control animals (eight of eight) 55.5+/-5.0h after PR. In contrast, follicular development and the preovulatory surge of LH were evident during the period of cortisol infusion in only one of eight animals receiving stress-like levels of cortisol over the entire 10-day infusion period. Similarly, neither follicular development nor surge-like secretion of LH were evident during the infusion period in animals (zero of eight) receiving cortisol during the 5-day period after PR. This cortisol-dependent suppression of ovarian activity in sheep receiving stress-like levels of cortisol during the 5 days after PR was temporary and follicular development, the ovulatory surge of LH, and subsequent luteal function were evident in six of eight ewes after cessation of cortisol delivery. Similarly, follicular development and the preovulatory surge of LH were noted within 5 days after PR in four of seven ewes receiving cortisol only during the 5-day period prior to PR. Collectively, these data indicate that stress-like levels of cortisol reduce fertility of sheep by suppressing follicular development and the preovulatory surge of LH. Additionally, cortisol delivery during the follicular phase has a more profound suppressive effect on follicular development than cortisol administration during the luteal phase.

Effect of stress-like concentrations of cortisol on the feedback potency of oestradiol in orchidectomized sheep.

The effect of stress-like concentrations of cortisol on oestradiol-induced change in LH secretion and GnRH receptor expression was evaluated in orchidectomized sheep (wethers). Twenty-four wethers were assigned at random to one of the four treatment groups in a 2x2 factorial design (n=6 wethers/group). Wethers received cortisol (90 microg/kg/h; groups 2 and 4) or a comparable volume of cortisol delivery vehicle (groups 1 and 3) by continuous infusion for 48 h. During the final 24 h of infusion, wethers received oestradiol (6 ng/kg/h; groups 3 and 4) or oestradiol delivery vehicle (groups 1 and 2). The pattern of LH secretion was assessed during a 3-h period of intensive blood collection beginning 21 h after initiation of oestradiol infusion. Although neither cortisol nor oestradiol alone affected (P>0.05) mean serum concentration of LH or LH pulse frequency, serum LH and the frequency of secretory episodes of LH were significantly reduced (P<0.05) in wethers receiving cortisol and oestradiol in combination. Anterior pituitary tissue was collected at the end of the infusion period. Oestradiol increased (P<0.05) tissue concentrations of GnRH receptor and GnRH receptor mRNA. Although cortisol alone did not affect (P>0.05) basal concentrations of receptor or receptor mRNA, the magnitude of oestradiol-induced increase in GnRH receptor and GnRH receptor mRNA was significantly reduced in wethers receiving cortisol and oestradiol concurrently. Conversely, steady-state concentrations of mRNA encoding the LHbeta and FSHbeta subunits were increased (P<0.05) in wethers receiving cortisol. These observations demonstrate that stress-like concentrations of cortisol act in concert with oestradiol to suppress LH secretion. In addition, cortisol blocks oestradiol-dependent increase in pituitary tissue concentrations of GnRH receptor and GnRH receptor mRNA.

Development of the ventilatory response to hypoxia in Swiss CD-1 mice.

We examined developmental changes in breathing pattern and the ventilatory response to hypoxia (7.4% O(2)) in unanesthetized Swiss CD-1 mice ranging in age from postnatal day 0 to 42 (P(0)-P(42)) using head-out plethysmography. The breathing pattern of P(0) mice was unstable. Apneas were frequent at P(0) (occupying 29 +/- 6% of total time) but rare by P(3) (5 +/- 2% of total time). Tidal volume increased in proportion to body mass ( approximately 10-13 ml/kg), but increases in respiratory frequency (f) (55 +/- 7, 130 +/- 13, and 207 +/- 20 cycles/min for P(0), P(3), and P(42), respectively) were responsible for developmental increases in minute ventilation (690 +/- 90, 1,530 +/- 250, and 2,170 +/- 430 ml. min(-1). kg(-1) for P(0), P(3), and P(42), respectively). Between P(0) and P(3), increases in f were mediated by reductions in apnea and inspiratory and expiratory times; beyond P(3), increases were due to reductions in expiratory time. Mice of all ages showed a biphasic hypoxic ventilatory response, which differed in two respects from the response typical of most mammals. First, the initial hyperpnea, which was greatest in mature animals, decreased developmentally from a maximum, relative to control, of 2.58 +/- 0.29 in P(0) mice to 1. 32 +/- 0.09 in P(42) mice. Second, whereas ventilation typically falls to or below control in most neonatal mammals, ventilation remained elevated relative to control throughout the hypoxic exposure in P(0) (1.73 +/- 0.31), P(3) (1.64 +/- 0.29), and P(9) (1. 34 +/- 0.17) mice but not in P(19) or P(42) mice.

Effect of stress-like concentrations of cortisol on gonadotroph function in orchidectomized sheep.

The effect of stress-like concentrations of cortisol (C) on the feedback potency of estradiol (E2) was assessed using 32 orchidectomized sheep (wethers) assigned at random to 1 of 4 treatment groups in a 2 x 2 factorial design. Wethers received C (3. 6 mg/50 kg per hour; groups 2 and 4) or a comparable volume of C delivery vehicle (groups 1 and 3) as a continuous infusion for 7 days. During the final 48 h of infusion, wethers received E2 (0.3 microg/50 kg/h; groups 3 and 4) or E2 delivery vehicle (groups 1 and 2). The pattern of LH secretion was assessed during a 4-h period of intensive blood collection beginning 44 h after initiation of E2 infusion. Gonadotroph responsiveness (LH secretion induced by GnRH challenge [500 ng, i.v.]) was determined 48 h after E2 delivery was begun. Although the frequency of secretory episodes of LH was not affected (p > 0.05) by infusion of C or E2 alone, LH pulse frequency was significantly decreased in wethers receiving C and E2 in combination. In contrast, neither the magnitude of basal gonadotroph responsiveness nor the extent of E2-dependent augmentation of responsiveness was significantly affected by stress-like concentrations of C. In a second experiment, the effect of C on the magnitude of E2-induced increase in pituitary concentration of GnRH receptor and GnRH receptor mRNA was assessed using 32 additional wethers. Continuous infusion of E2 for 48 h increased (p < 0.05) tissue concentrations of GnRH receptor and GnRH receptor mRNA. Concurrent delivery of C did not affect (p > 0.05) E2-induced increase in GnRH receptor mRNA but significantly reduced the magnitude of the E2-dependent increase in pituitary concentration of GnRH receptor. Collectively, these data indicate that stress-like concentrations of C enhance the negative feedback potency of E2 and reduce estrogen-dependent augmentation of the concentration of GnRH receptor in pituitary tissue.

Effect of stress-like concentrations of cortisol on estradiol-dependent expression of gonadotropin-releasing hormone receptor in orchidectomized sheep.

The effect of stress-like concentrations of cortisol (C) on estrogen-dependent expression of GnRH receptor was evaluated using orchidectomized sheep (wethers; n = 6 animals per group). C (5.0 mg/50 kg per hour; groups 1-4) or a comparable volume of vehicle (groups 5-8) was delivered by continuous infusion for 48 h. During the final 24 h of infusion, animals received concurrent infusion of estradiol (E2) at rates of 0 (groups 1 and 5), 0.5 (groups 2 and 6), 2.0 (groups 3 and 7), or 8.0 (groups 4 and 8) microg/50 kg per hour. Pituitary tissue was collected at the end of infusion. Although C did not affect (p > 0.05) the basal concentration of GnRH receptor or GnRH receptor mRNA, it reduced (p < 0.05) the increase in receptor and receptor mRNA induced by concurrent administration of 0. 5 microg E2/50 kg per hour. In contrast, the increase in GnRH receptor expression induced by higher levels of estrogen stimulation was not affected (p > 0.05) by concurrent administration of C. The effect of C on the temporal pattern of E2-dependent increase in GnRH receptor expression was assessed using wethers receiving E2 (0.5 microg/50 kg per hour) by continuous infusion for 0 (groups 1 and 5), 24 (groups 2 and 6), 48 (groups 3 and 7), or 72 h (groups 4 and 8). Animals received C (5.0 mg/50 kg per hour; groups 1-4) or vehicle (groups 5-8) beginning 24 h before, and continuing throughout, the E2 delivery period. Stress-like concentrations of C reduced (p < 0. 05) the increase in GnRH receptor and receptor mRNA induced after 24 h of E2 stimulation. However, the suppressive effect of C was transient, and tissue levels of GnRH receptor and receptor mRNA were comparable after 72 h of E2 infusion in animals receiving C or vehicle alone. Collectively these observations demonstrate that C suppresses estrogen-dependent increase in tissue concentrations of GnRH receptor and receptor mRNA. However, this effect of C is transient and not evident in animals receiving moderate to high levels of estrogen stimulation. This transient suppression of GnRH receptor expression may account, at least in part, for the anti-gonadal effect of glucocorticoids.

Moderate and severe nutrient restriction has divergent effects on gonadotroph function in orchidectomized sheep.

The effect of plane of nutrition and estradiol (E2) on pituitary concentrations of GnRH receptor and GnRH receptor mRNA was assessed in orchidectomized sheep (wethers). As detailed in the companion paper, 36 wethers were fed to gain, maintain, or lose body weight. Six animals from each feeding group received E2 (0.31 microg E2/50 kg per h) or vehicle during Days 51-54 of controlled feeding. Anterior pituitary tissue was collected at the end of infusion. Both moderate and severe nutrient restriction increased (p < 0.05) tissue concentrations of FSH and FSHbeta mRNA. Conversely, concentrations of GnRH receptor and receptor mRNA were not affected (p > 0.05) by plane of nutrition. Estradiol increased (p < 0.05) GnRH receptor and receptor mRNA in wethers fed to gain or maintain weight. However, this E2-induced response was not evident in wethers subject to severe nutrient restriction. These data demonstrate that severe, but not moderate, nutrient restriction suppresses E2-induced augmentation of tissue concentrations of GnRH receptor and GnRH receptor mRNA. Collectively, the data presented here and in the companion paper suggest that severe nutrient restriction leads to physiologic changes that render the hypothalamus increasingly sensitive to estrogenic stimulation, while the pituitary is made less responsive to steroidal inputs.

Depression and life satisfaction in aging polio survivors versus age-matched controls: relation to postpolio syndrome, family functioning, and attitude toward disability.

OBJECTIVE: To compare depressive symptoms and life satisfaction in aging polio survivors with age-matched controls and to relate these outcomes to scores to psychosocial and disability-related variables. DESIGN: A planned medical, functional, and psychosocial study with multivariate analyses. SETTING: A large, urban rehabilitation center. PARTICIPANTS: A volunteer sample of 121 polio survivors and an age-matched control group of 60 people with similar sociodemographic backgrounds. MAIN OUTCOMES: Depression as measured by the Geriatric Depression Scale and an 11-item life satisfaction scale. RESULTS: The prevalence of depressive disorders was not significantly different in the two groups, although the postpolio group tended to have more symptomatology and an overall depressive disorder prevalence of 28%. Some life satisfaction scale scores were significantly lower in the postpolio group, especially those concerned with health. People with postpolio syndrome scored significantly higher on depression scales and lower on some life satisfaction scales than people with a history of polio but without postpolio syndrome. Several psychosocial variables, most notably family functioning and attitude toward disability, helped to mediate this effect. Among people with significant depression, there was little, evidence of adequate treatment in the community. CONCLUSIONS: Postpolio by itself does not relate to higher depression scores or lower life satisfaction. Postpolio syndrome has some relation to depression, but family functioning and attitude toward disability are more important. There is a need for better community-based psychological services.

Concentration of gonadotropin-releasing hormone receptor messenger ribonucleic acid in pituitary tissue of orchidectomized sheep: effect of passive immunization against gonadotropin-releasing hormone.

The effect of immunoneutralization of gonadotropin-releasing hormone (GnRH) on LH secretion and concentrations of GnRH receptor, GnRH receptor mRNA, and gonadotropin subunit mRNA in pituitary tissue of orchidectomized sheep (wethers) was assessed. Thirty-six wethers were assigned at random to one of six treatment groups (six wethers per group). Thirty wethers (groups 2 to 6) received 200 ml, (i.v.) of anti-GnRH antisera at passive immunization (PI). Anterior pituitary tissue was collected .5, 1, 2, 4, or 8 d after PI from wethers in groups 2 to 6, respectively. Pituitary tissue was also collected from unimmunized wethers (Group 1). Intravenous administration of anti-GnRH sera increased anti-GnRH activity to 69.1 +/- 7% (percentage of total 125I-labeled GnRH bound by a 1:1,000 serum:GEL-PBS dilution) within 1 h of PI. Anti-GnRH activity declined gradually during the period after PI, and 8 d after PI anti-GnRH activity was 57.2 +/- 1.7%. Serum concentration of LH was significantly reduced, relative to the pretreatment (16.1 +/- 1.8 ng/mL) level, within 4 h (7.6 +/- 1.5 ng/mL) of PI, and the LH level was 10% of the pretreatment concentration 8 d after PI (1.6 +/- 0.2 ng/mL). Steady-state concentration of GnRH receptor mRNA decreased progressively during the period after PI and was significantly reduced, relative to the level in unimmunized control wethers (.44 +/- .03 pg/micron total RNA) d after PI. Tissue concentrations of GnRH receptor and mRNA for the alpha, LH alpha, and FISH beta subunits were also reduced (P < .05) by PI. These data indicate that maintenance of steady-state concentrations of GnRH receptor and GnRH receptor mRNA requires continued GnRH stimulation.

Concentration of GnRH receptor and GnRH receptor mRNA in pituitary tissue of orchidectomized sheep: effect of oestradiol, progesterone, and progesterone withdrawal.

The effect of progesterone (P4) and P4 withdrawal on oestradiol (E2)-induced change in gonadotrope responsiveness (GR) and concentration of GnRH receptor and GnRH receptor mRNA in pituitary tissue of orchidectomized sheep (wethers) was determined. Thirty wethers were assigned at random to one of six treatment groups (n = 5 animals/group). Wethers received E2 (2 micrograms/h; groups 2, 4, and 6) in 10% ethanol-saline (vehicle), or vehicle alone (groups 1, 3, and 5), as a continuous infusion for 24 h beginning 7 days after insertion (s.c.) of blank (groups 1 and 2) or P4-containing (groups 3-6) implants. The effect of P4 withdrawal was assessed by removing P4-containing implants at the beginning of vehicle (group 5) or E2 (group 6) infusion. Gonadotrope responsiveness (increase in serum LH induced by 500 ng GnRH, i.v.) was assessed at the end of infusion. In a companion study, anterior pituitary tissue was collected at the end of the 24-h infusion period. Infusion of E2 increased (P < 0.05) GR relative to GR noted in control wethers receiving vehicle alone. The magnitude of E2-induced augmentation of GR was not affected by concurrent administration of P4 or P4 withdrawal. Pituitary tissue concentrations of GnRH receptor and GnRH receptor mRNA were significantly reduced in wethers implanted with P4. This P4-induced decrease in tissue concentration of GnRH receptor and GnRH receptor mRNA was not reversed during the 24-h period after P4 withdrawal. Steady-state concentrations of GnRH receptor and GnRH receptor mRNA were significantly increased by E2. However, the magnitude of oestrogen-induced increase in tissue concentrations of GnRH receptor mRNA was not significantly affected by P4 or P4 withdrawal. Conversely, concurrent progestin stimulation potentiated the E2-induced augmentation of tissue concentrations of GnRH receptor. However, this P4-induced potentiation of the oestrogenic response was not evident 24 h after removal of the P4-containing implants. Steady-state concentrations of mRNA encoding the LH beta and FSH beta subunits were reduced (P < 0.05) by P4. Infusion of E2 had a similar affect. These data indicate that prolonged progestin stimulation leads to a decrease in tissue concentrations of GnRH receptor and GnRH receptor mRNA. This P4-induced suppression of GnRH receptor activity is not reversed within 24 h of P4 withdrawal. In addition, the increase n steady-state concentrations of GnRH receptor and GnRH receptor mRNA induced by E2 is not compromised by concurrent progestin stimulation.

Effect of oestradiol on mRNA encoding GnRH receptor in pituitary tissue of orchidectomized sheep passively immunized against GnRH.

The effect of oestradiol on tissue concentrations of GnRH receptor and mRNA encoding GnRH receptor was assessed in orchidectomized sheep (wethers) made deficient in GnRH by passive immunization. Wethers were assigned to one of four groups (n = 6 animals per group). Animals in groups 2 and 4 received ovine anti-GnRH sera (200 ml; i.v.) at passive immunization, while antisera against the carrier protein was administered to wethers in groups 1 and 3. Oestradiol was delivered as a continuous infusion (2 micrograms h-1) to wethers in groups 1 and 2. Animals in groups 3 and 4 were infused with vehicle alone. Anterior pituitary tissue was collected at the end of the 48 h infusion. Anti-GnRH sera induced a rapid reduction in the serum concentration of LH. Continuous delivery of oestradiol resulted in a twofold increase (P < 0.05) in tissue concentration of GnRH receptor. This oestradiol-induced response was manifest even in wethers in which endogenous GnRH had been neutralized by passive immunization. Conversely, infusion of oestradiol increased (P < 0.05), and intravenous administration of anti-GnRH sera decreased (P < 0.05), concentrations of mRNA encoding GnRH receptor in pituitary tissue. When delivered in combination, anti-GnRH sera reduced (P < 0.05), but did not eliminate, the oestradiol-induced augmentation of steady-state concentrations of mRNA encoding GnRH receptor. These data demonstrate that the basal concentration of mRNA encoding GnRH receptor is dependent on continued GnRH stimulation. In contrast, the oestradiol-induced increase in steady-state concentration of mRNA encoding GnRH receptor is manifest even in the absence of GnRH.

Gonadotrope responsiveness in orchidectomized sheep: effect of duration of a simulated follicular phase.

The effect of duration of a simulated follicular phase on gonadotrope responsiveness was assessed in orchidectomized sheep (wethers). The oestrogenic and hypothalamic inputs characteristic of the ovine follicular phase were simulated by continuous infusion of oestradiol (5 micrograms h-1 in 10% (v/v) ethanol saline) and circhoral delivery of GnRH (200 ng per hourly pulse) for 0, 6, 12, 24, 48 or 96 h (n = 6 wethers per group). Responsiveness increased (P < 0.05) with increasing duration of simulated follicular phase. In a second experiment, responsiveness was assessed 96 h after initiation of infusion of oestradiol in wethers receiving hourly pulses of GnRH or saline. Concurrent administration of GnRH reduced (P < 0.05) the magnitude of the oestradiol-induced increase in gonadotrope responsiveness. In a companion study, anterior pituitary tissue was collected 96 h after the start of infusion of oestradiol and circhoral delivery of GnRH or saline. Pituitary stores of LH and tissue concentrations of GnRH receptor and mRNA encoding the GnRH receptor were increased (P < 0.05) by oestradiol infusion. The magnitude of these oestradiol-induced responses was not affected (P > 0.05) by concurrent GnRH treatment. Tissue concentrations of FSH and mRNA encoding the FSH beta subunit were decreased (P < 0.05) by oestradiol infusion. This suppressive effect of oestradiol was not reversed by GnRH. These results indicate that oestradiol stimulation, but not concurrent delivery of GnRH, is essential for full expression of surge-like secretion of LH. In addition, the oestradiol-induced increase in gonadotrope responsiveness during the simulated follicular phase is sustained throughout the period of oestradiol delivery.

Testes function and feedlot performance of bulls actively immunized against gonadotropin-releasing hormone: effect of age at immunization.

Testes function, feedlot performance, and carcass traits were evaluated in bulls actively immunized against gonadotropin-releasing hormone (GnRH) at different ages. Bull calves were randomly assigned to one of seven treatment groups (n = 15 calves/group). Calves were unimmunized (Group 1), immunized at 1.5, 4, 7, or 12 mo of age with a GnRH-keyhole limpet hemocyanin (KLH) conjugate (Groups 2 to 5, respectively), or castrated at 4 mo of age (Groups 6 and 7). Immunized bulls did not receive a secondary, or booster, immunization. Calves in group 6 received Synovex-C at castration and Synovex-S at weaning and feedlot entry. Anti-GnRH titer was evident at slaughter in all immunized bulls. However, the final immune response of bulls immunized at 1.5 mo was significantly lower than the response of bulls immunized at later stages of development. Final scrotal circumference and testis weight in bulls immunized at 4, 7, or 12 mo of age were significantly reduced relative to unimmunized bulls. The final live weight, feedlot gain, and carcass weight of immunized and unimmunized bulls did not differ (P > .05) from the same parameters in steers implanted with Synovex. Longissimus muscle area, marbling score, and backfat thickness did not differ between immunized and unimmunized bulls. The sex class score of the carcasses of immunized bulls did not differ from the score of steer carcasses. In contrast, a significantly higher proportion of carcasses from unimmunized bulls graded as bullock carcasses. Taken together, these data indicate that a single immunization against GnRH at 4 to 12 mo of age results in significant attenuation of testicular growth in bulls. These data also demonstrate that immunization against GnRH reduces the masculinity of carcasses from bulls, but does not affect feedlot performance, longissimus muscle area, marbling score, or backfat thickness. These results suggest that single immunization with the GnRH-KLH conjugate may have practical utility as a noninvasive alternative to surgical castration in management of beef cattle.

Concentrations of gonadotropin-releasing hormone (GnRH) receptor messenger ribonucleic acid in pituitary tissue of orchidectomized sheep: effect of estradiol and GnRH.

The effects of estradiol (E2) and E2 withdrawal on tissue concentrations of GnRH receptor mRNA were assessed in orchidectomized sheep (wethers). Wethers received E2 (in 20% ethanol-saline [vehicle]) by continuous infusion at rates of 0.31, 1.25, 5, or 20 micrograms/h (n = 12 animals per group). Control animals received vehicle alone. Anterior pituitary tissue was collected at the end of the 48-h infusion period. Steady-state levels of GnRH receptor mRNA were quantified by solution hybridization. Tissue levels of mRNA were significantly increased above control levels (0.5 +/- 0.1 pg/microgram RNA) by E2 infusion at 1.25 micrograms/h (1.4 +/- 0.2 pg/microgram RNA). Maximal tissue concentrations of GnRH receptor mRNA were induced by E2 delivery at 5 micrograms/h (2.4 +/- 0.3 pg/micrograms RNA). In a second study, wethers (n = 6 animals per group) received 5 micrograms E2/h for 24 h. Pituitary tissue was collected at the end of the infusion period or at 12, 24, or 48 h after cessation of E2 delivery. Infusion of E2 induced a 6-fold increase in GnRH receptor mRNA (0.4 +/- 0.1 and 2.9 +/- 0.6 pg/micrograms RNA in control and E2-treated groups, respectively). Cessation of E2 delivery resulted in rapid reduction in steady-state levels of GnRH receptor mRNA. Tissue concentrations of receptor mRNA returned to pretreatment levels within 12 h of E2 withdrawal (0.6 +/- 0.1 pg/microgram RNA). In a third study, the concentration of GnRH receptor mRNA was determined in pituitary tissue collected during preovulatory surge-like secretion induced in E2-infused wethers by episodic delivery of high-amplitude GnRH (1600 ng GnRH per hourly pulse). Estradiol (5 micrograms/ml in 10% ethanol-saline) was delivered as a continuous infusion. Episodic delivery of GnRH was initiated 24 h after E2 infusion was begun, and concurrent administration of E2 and episodic GnRH was continued to slaughter. Anterior pituitary tissue was collected at 0, 3, 6, 12, or 24 h after beginning circhoral delivery of GnRH (n = 6 wethers per group). As noted above, continuous infusion of E2 for 24 h significantly increased tissue concentrations of GnRH receptor mRNA. However, steady-state levels of GnRH receptor mRNA were returned to pretreatment levels after 3 h of circhoral delivery of GnRH (0.4 +/- 0.1 pg/microgram RNA). Taken together, these data demonstrate that physiological concentrations of E2 increase steady-state levels of GnRH receptor mRNA in a dose-dependent manner. In addition, continued estrogenic support is required to maintain enhanced tissue concentrations of GnRH receptor mRNA. Finally, high-amplitude GnRH stimulation induces down-regulation of tissue levels of GnRH receptor mRNA. These data suggest that the dynamic changes in tissue concentrations of GnRH receptor mRNA during the periovulatory period may be due to the inductive effects of gonadal steroids from the developing follicle and to the combined suppressive effects of the increased GnRH stimulation and E2 withdrawal that are associated with the gonadotropin surge.