Lamprey GnRH‐III Releases Luteinizing Hormone but not Follicle Stimulating Hormone in Pigs

The effect of exogenous administration of lamprey GnRH‐III (IGnRH‐III) on gonadotropin secretion was evaluated in pigs. Six crossbred barrows (82.4 ± 3.5 kg body weight) were assigned randomly to a replicated 3 × 3 Latin square design to evaluate the effect of 0.1, 1.0 or 10.0 μg/kg body weight of exogenous IGnRH‐III on LH and FSH secretion. To facilitate blood collection and infusion of IGnRH‐III, barrows were catheterized in the jugular vein 1 day before initiation of experiments. Blood samples were taken at 10‐min intervals for 6 h, starting 2 h before treatments were applied. Relative concentrations of LH and FSH were calculated by obtaining the ratio of the average concentration of each hormone 2 h after infusion divided by the average concentration during the 2 h before infusion. Relative concentrations of FSH after IGnRH‐III infusion did not influence mean concentration of FSH at any of the doses; yet 10.0 μg/kg body weight had a significant effect on LH secretion (p < 0.01). Relative concentrations of LH averaged 1.2, 1.0 and 3.0 ng/ml (for doses of 0.1, 1.0 and 10.0 μg/kg body weight of IGnRH‐III respectively). Only a dose of 10 μg/kg body weight elicited a significant LH increase that was associated with exogenous IGnRH‐III infusion. We conclude that IGnRH‐III is a weak GnRH agonist and at high doses, IGnRH‐III has the ability to release LH but not FSH in barrows.     

Complex interplay between intrinsic and extrinsic drivers of long-term survival trends in southern elephant seals

Background  

Determining the relative contribution of intrinsic and extrinsic factors to fluctuations in population size, trends and demographic composition is analytically complex. It is often only possible to examine the combined effects of these factors through measurements made over long periods, spanning an array of population densities or levels of food availability. Using age-structured mark-recapture models and datasets spanning five decades (1950–1999), and two periods of differing relative population density, we estimated age-specific probabilities of survival and examined the combined effects of population density and environmental conditions on juvenile survival of southern elephant seals at Macquarie Island.     

Hemodynamic effects of sevoflurane in spontaneously breathing cats

Sevoflurane has recently been introduced in feline anesthesia. However, its cardiovascular effects have not, to our knowledge, been reported in this species. Six healthy cats, aged 1.81 ± 0.31 years (mean ± SEM) and weighing 3.47 ± 0.11 kg, were studied. Anesthesia was induced and maintained with sevoflurane in oxygen. Body temperature was maintained between 38.5 and 39.55 °C. After instrumentation, end‐tidal sevoflurane concentration was randomly set at 1.25, 1.5, and 1.75 times the individual minimum alveolar concentration (MAC), determined in a previous study, according to a Latin Square Design. Thirty minutes of stabilization was allowed after each change of concentration. ECG and heart rate, systemic and pulmonary arterial pressures, central venous pressure (CVP), and core body temperature were continuously monitored and recorded. Inspired and end‐tidal oxygen, carbon dioxide, and sevoflurane concentrations were measured using a Raman spectrometer, calibrated every 80 minutes with three calibration gases of known sevoflurane concentration (1, 2, and 5%). Moreover, at selected times, pulmonary artery occlusion pressure and cardiac output (thermodilution) were measured, and arterial and mixed venous blood samples were collected for pH and blood gas analysis, hemoglobin concentration, hemoglobin oxygen saturation, packed cell volume (PCV) and total protein determination, and lactate concentration measurement. Cardiac index (CI), stroke index (SI), systemic and pulmonary vascular resistance indices, rate‐pressure product, left and right ventricular stroke work indices (LVSWI and RVSWI, respectively), arterial and mixed venous oxygen contents, oxygen delivery, oxygen consumption, and oxygen utilization ratio were calculated. Data were analyzed by a Repeated Measure Latin Square Design followed by a Tukey's test for 2 × 2 comparisons. Arterial pH significantly decreased from 7.40 ± 0.05 to 7.29 ± 0.07 with the administration of increasing concentrations of sevoflurane. Similarly, LVSWI decreased from 3.72 ± 0.60 to 2.60 ± 0.46 g m^?2. Mean arterial pressure, PaO₂, mixed venous pH, CI, SI, and oxygen delivery tended to decrease dose‐dependently, whereas CVP, PaCO₂, Pv CO₂, PCV, and arterial and mixed venous hemoglobin concentrations tended to increase dose‐dependently with the administration of sevoflurane. However, these trends did not reach statistical significance, possibly because of the limited number of animals studied. Sevoflurane seemed to induce dose‐dependent cardiovascular depression in cats.     

Transduction and Transplantation of Spermatogonia into the Testis of Ram Lambs through the Extra-testicular Rete

Spermatogonial transplantation will provide a new way to study spermatogenesis in domestic animals, disseminate male genetics and produce transgenic animals, if efficiency can be improved. We evaluated a 'surgical' method for transplanting donor cells into testes of ram lambs, where the head of the epididymis is reflected, and a catheter introduced into the extra-testicular rete testis. We also tested transduction of ram spermatogonia with a lentiviral (LV) vector as a means to identify permanent colonization, and introduce genes into donor cells. Eight ram lambs, 11- to 13-week olds, were the recipients: in five, spermatogonia were injected into one testis, and the contralateral testis was an un-manipulated control: in two, spermatogonia were injected into one testis and the contralateral was sham-injected: in one, both testes were injected. Six lambs received spermatogonia labelled with a cell-tracking dye and these were collected 1 or 2 weeks after transplantation; three lambs received spermatogonia transduced with a LV vector driving the expression of enhanced Green Fluorescence Protein and these were collected after 2 months. Donor cells were detected by immunohistochemistry in tubules of seven of nine recipient testes. Approximately 22% of tubule cross-sections contained donor cells immediately after transplantation, and 0.2% contained virally transduced cells 2 months after transplantation. The onset of spermatogenesis was delayed, and there were lesions in both injected and sham-injected testes. Despite the effects of the surgery, elongated spermatids were present in one recipient testis 2 months after surgery. The results suggest that, after modifying the surgical and transduction techniques, this approach will be a means to produce good colonization by donor spermatogonia in sheep testes.     

Spectroscopic Observation of the Formyl Cation in a Condensed Phase

The formyl cation, HCO+, has long been believed to be an important intermediate in the chemistry of carbon monoxide (CO) in acidic environments, but its spectroscopic observation in solution has been elusive. This species was generated by the reaction of CO with the liquid superacid hydrofluoric acid-antimony pentafluoride (HF-SbF5) under pressure and was observed by nuclear magnetic resonance and infrared spectroscopy. Equilibria between CO in the gas phase, CO dissolved in HF-SbF5, the SbF5 adduct of formyl fluoride, and HCO+ associated with several equilibrating anions of the type [SbxF5x+1]- are proposed to describe the system.     

A monolithic photovoltaic-photoelectrochemical device for hydrogen production via water splitting

Direct water electrolysis was achieved with a novel, integrated, monolithic photoelectrochemical-photovoltaic design. This photoelectrochemical cell, which is voltage biased with an integrated photovoltaic device, splits water directly upon illumination; light is the only energy input. The hydrogen production efficiency of this system, based on the short-circuit current and the lower heating value of hydrogen, is 12.4 percent.     

α‐6 Integrin Expression in Bovine Spermatogonial Cells Purified by Discontinuous Percoll Density Gradient

The study of spermatogonial stem cells (SSCs) provides a model to better understand adult stem cell biology. Besides the biomedical potential to perform studies of infertility in many species, SSCs hold a promising application at animal transgenesis. Because stem cells are thought to be associated with basement membranes, expression of α‐6 integrin has been investigated as a marker of type A spermatogonial cells, which are considered SSCs because of their undifferentiated status and self‐renewal ability. In this manner, the aim of this study was to isolate type A SSCs from adult bulls by a two‐step enzymatic procedure followed by a discontinuous Percoll density gradient purification and verify the expression of α‐6 integrin by flow cytometry and real‐time RT‐PCR before and after Percoll purification. Spermatogonial cells were successfully obtained using the two‐step enzymatic digestion. An average of 1 × 10⁵ viable cells per gram of testis was isolated. However, the discontinuous Percoll did not purify isolated cells regarding α‐6 integrin expression. Flow cytometry analysis demonstrated no differences in the α‐6 integrin expression between cell samples before and after Percoll purification (p = 0.5636). The same was observed in the real‐time PCR analysis (p > 0.05). In addition to α‐6 integrin, the expression of GFRa‐1 and PGP9.5, known bovine SSCs markers, was detected in all samples studied. Considering that Percoll can reduce cell viability, it is possible to conclude that Percoll density gradient is not suitable to purify bovine SSC, according to α‐6 integrin expression.     

Effects of methadone on the minimum alveolar concentration of isoflurane in dogs

ObjectiveTo investigate the effects of methadone on the minimum alveolar concentration of isoflurane (ISO_MAC) in dogs.Study designProspective, randomized cross-over experimental study.AnimalsSix adult mongrel dogs, four males and two females, weighing 22.8 ± 6.6 kg.MethodsAnimals were anesthetized with isoflurane and mechanically ventilated on three separate days, at least 1 week apart. Core temperature was maintained between 37.5 and 38.5 °C during ISO_MAC determinations. On each study day, ISO_MAC was determined using electrical stimulation of the antebrachium (50 V, 50 Hz, 10 mseconds) at 2.5 and 5 hours after intravenous injection of physiological saline (control) or one of two doses of methadone (0.5 or 1.0 mg kg^?1).ResultsMean (±SD) ISO_MAC in the control treatment was 1.19 ± 0.15% and 1.18 ± 0.15% at 2.5 and 5 hours, respectively. The 1.0 mg kg^?1 dose of methadone reduced ISO_MAC by 48% (2.5 hours) and by 30% (5 hours), whereas the 0.5 mg kg^?1 dose caused smaller reductions in ISO_MAC (35% and 15% reductions at 2.5 and 5 hours, respectively). Both doses of methadone decreased heart rate (HR), but the 1.0 mg kg^?1 dose was associated with greater negative chronotropic actions (HR 37% lower than control) and mild metabolic acidosis at 2.5 hours. Mean arterial pressure increased in the MET1.0 treatment (13% higher than control) at 2.5 hours.Conclusions and clinical relevanceMethadone reduces ISO_MAC in a dose-related fashion and this effect is lessened over time. Although the isoflurane sparing effect of the 0.5 mg kg^?1 dose of methadone was smaller in comparison to the 1.0 mg kg^?1 dose, the lower dose is recommended for clinical use because it results in less evidence of cardiovascular impairment.