Effect of ejaculation frequency and season on donkey jack semen

Semen characteristics of first and second successive ejaculates from 6 jacks were evaluated weekly for 12 mo. The semen was collected at 4-h intervals, using an artificial vagina with a female in either natural or induced estrus. The statistical analysis was done by factorial delineation 2 x 2 in randomized blocks. Due to some ejaculation failures, the data had to be divided into 2 Groups (A and B) for statistical analysis: Group A - ejaculates preceded by 2 ejaculates in the previous week and Group B - ejaculates preceded by only 1 ejaculate in the previous week. If no statistical difference was observed between the groups in a given parameter, the data was grouped together. Semen characteristics for the first and second ejaculates, respectively, showed the following mean +/- SEM: gel-free semen volume 29.2 +/- 2.2 and 31.7 +/- 2.2 ml; progressive motility 71.0 +/- 1.6 and 72.9 +/- 1.6%; sperm vigor 3.8 +/- 0.1 and 4.1 +/- 0.1; live spermatozoa for Group A 82.6 +/- 2.1 and 82.3 +/- 2.1%, and for Group B 84.6 +/- 1.4 and 86.6 +/- 1.4%; total number of spermatozoa for Group A 10.6 +/- 0.8 x 10(9) and 5.8 +/- 0.8 x 10(9), and for Group B 13.3 +/- 1.2 x 10(9) and 9.6 +/- 1.2 x 10(9); head abnormalities for Group A 1.2 +/- 0.3 and 1.4 +/- 0.3%, and for Group B 1.6 +/- 0.3 and 1.9 +/- 0.3%; mid piece abnormalities 7.7 +/- 0.7 and 6.1 +/- 0.7%; tail abnormalities 7.3 +/- 0.7 and 6.8 +/- 0.7%; pH 7.6 +/- 0.0 and 7.6 +/- 0.0. Significant differences (P < 0.05) were observed between the animals for all sperm characteristics except for sperm vigor. The means for the first and second ejaculates were significantly different (P < 0.05) for the total number of spermatozoa in all the animals, while the percentage of mid piece abnormalities was significantly different in only 1 jack. Seasonal effects on sperm parameters were observed only for semen pH.     

Sexual behavior and ejaculate characteristics in Pêga donkeys (Equus asinus) mounting estrous horse mares (Equus caballus)

The objectives were to (i) characterize sexual behavior of donkey stallions (jacks; Equus asinus) during on-farm semen collection using estrous horse mares (mares; Equus caballus); (ii) compare behavior of young (less experienced) versus older (more experienced) jacks; (iii) determine whether semen suitable for artificial insemination (AI) could be collected using mares; and (iv) determine the suitability of using mares in field collection of semen from jacks. Six Pêga jacks (3.5 to 16 yr old), previously conditioned to breed mares, were used. Mount mares were confirmed in estrus by a teaser horse stallion (stallion) and a jack. Semen was collected with an artificial vagina, at intervals of 48 to 72 h (180 collections). The mean ± SD (young [3.5 yr] vs. old [14 to 16 yr]) were Flehmen response frequency, 7.4 ± 5.8 (8.1 ± 3.0 vs. 7.0 ± 2.0); number of mounts without erection, 1.1 ± 1.3 (2.1 ± 1.4 vs. 1.2 ± 0.4, P < 0.05); latency from first exposure to mare to full erection on the ejaculatory mount, 18.3 ± 17.7 min (25.3 ± 21.3 vs. 12.2 ± 6.2, P < 0.05); latency from erection to insertion, 5.1 ± 3.5 sec (5.3 ± 3.8 vs. 4.8 ± 3.2); and duration of copulation from insertion to dismount after ejaculation, 25.4 ± 7.8 sec (22.1 ± 2.9 vs. 28.1 ± 9.3). In all jacks, sexual behavior was generally normal, with the notable absence of open mouth behavior. Mare estrous behavior was markedly less intense than that in the presence of a stallion and usually absent. Semen characteristics were gel free volume, 47.3 ± 28.7 mL; gel volume, 71.8 ± 54.8 mL; total motility, 84.3 ± 6.0%; progressive motility, 74.3 ± 74.5%; sperm vigor, 3.9 ± 0.5 (scale 1 to 5); sperm concentration, 253 × 10⁶ cells/mL; and total number of sperm, 10.3 × 10⁹ cells. Copulation duration was significantly correlated with gel free volume (r = 0.9) and gel volume (r = 0.7). We concluded that (i) the sexual behavior of jacks during semen collection using mares was similar to that reported for natural mating to jennies, (ii) precopulatory and copulatory behavior for the young (less experienced) jacks and older (more experienced) jacks were generally similar (except number of mounts without erection and latency to full erection); (iii) semen obtained using mares as stimulus and mount females was similar to that reported with estrous jennies; and (iv) semen collection from previously conditioned jacks, using estrous mares, was appropriate for field collection of semen.     

The flehmen response of bulls and cows

The response of dairy bulls to the urine of cows in various stages of the reproductive cycle was quantified by presenting 200 ml of urine in a stainless steel bowl to the stanchioned bulls for 10 min. Estrous mucus was also presented in the same manner. Sniffs, nose licks and flehmen responses were recorded. Of 15 bulls tested only 7, or 47%, met the criteria of two flehmens in response to estrous urine. Among these bulls, the rate of flehmen was higher to estrous urine 6.1 +/- 1 flehmen/10 min) than to nonestrous urine (3.5 +/- 0.6 flehmen/10 in, paired t = 3.1, P < 0.03). Flehmen duration was also longer in response to estrous urine (6.4 +/- 0.4 sec) than to nonestrous urine (5.7 +/- 0.4 sec, t = 2.65, P < 0.03). There were no significant differences between the sniff frequencies and durations or in the number of licks to estrous and diestrous urine. There were significantly more flehmen responses to estrous urine (7 +/- 1.4 10 min ) than to mucus (2.25 +/- 0.9 10 min , t = 4.75, P < 0.01). The response to water (0.6 +/- 0.3 10 min ) was not different from that to mucus (t = 2.37, P < 0.10). The spontaneous flehmen rate of dairy bulls in their home stalls was 3.2 +/- 0.7 24 h . Although estrous cows did not exhibit flehmen frequently, they did sniff bull urine more frequently (3.6 +/- 0.6 10 min ) than nonestrous cows (1.8 +/- 0.3 10 min , t = 2.4, P < 0.03).     

High-resolution X-ray computed tomography scanning of primate copulatory plugs

In this study, high-resolution computed tomography X-ray scanning was used to scan ring-tailed lemur (Lemur catta) copulatory plugs. This method produced accurate measures of plug volume and surface area, but was not useful for visualizing plug internal structure. Copulatory plug size was of interest because it may relate to male fertilization success. Copulatory plugs form from coagulated ejaculate, and are routinely displaced in this species by the penis of a subsequent mate during copulation (Parga [2003] Int. J. Primatol. 24:889-899). Because one potential function of these plugs may be to preclude or delay other males' successful insemination of females, we tested the hypothesis that larger plugs are more difficult for subsequent males to displace. Plugs were collected opportunistically upon displacement during data collection on L. catta mating behavior on St. Catherines Island, Georgia (USA) during two subsequent breeding seasons. Copulatory plugs exhibited a wide range of volumes: 1,758-5,013.6 mm3 (n = 9). Intraindividual differences in plug volume were sometimes greater than interindividual differences. Contrary to predictions, larger plugs were not more time-consuming for males to displace via penile intromission during copulation. Nor were plugs with longer vaginal residence times notably smaller than plugs with shorter residence times, as might be expected if plugs disintegrate while releasing sperm (Asdell [1946] Patterns of Mammalian Reproduction; Ithaca: Comstock). We found a significant inverse correlation between number of copulatory mounts leading to ejaculation and copulatory plug volume. This may indicate that if males are sufficiently sexually aroused to reach ejaculation in fewer mounts, they tend to produce ejaculates of greater volume.     

Cholesterol-to-phospholipid ratio in whole sperm and seminal plasma from fertile stallions and stallions with unexplained subfertility

Semen samples were collected from six fertile stallions and seven stallions with unexplained infertility. Percentages of motile sperm (77.5 +/- 11.3 versus 67.5 +/- 12.2, P = 0.2), and progressively motile sperm (70.8 +/- 13.6 versus 60.7 +/- 14.0, P = 0.2) were similar between fertile and subfertile stallions, respectively. Morphologic characteristics in ejaculates of control and affected stallions (% normal: 60.2 +/- 18.2 versus 52.9 +/- 11.3, P = 0.4; % abnormal heads 7.3 +/- 4.8 versus 12.1 +/- 5.0, P = 0.11; and % abnormal acrosomes 1.6 +/- 2.1 versus 3.0 +/- 3.4, P = 0.4) did not differ. After incubation with the calcium ionophore A23187, acrosome reaction rate of sperm from fertile stallions was 96 +/- 2.8% whereas only 2.9 +/- 2.5% of sperm from stallions with unexplained subfertility had acrosome reacted (P < 0.001). Molar amounts of cholesterol and phospholipid in whole sperm and seminal plasma did not differ (P > 0.1) between fertile and subfertile stallions. However, the molar ratio of cholesterol-to-phospholipid was 2.5 times greater in the seminal plasma (P = 0.09) and 1.9 times greater (P = 0.009) in whole sperm of subfertile stallions compared to fertile stallions.     

Characteristics of the motor and genital copulatory responses of the male hamster

The temporal and dynamic characteristics (duration, frequency, rhythmicity, and vigor) of pelvic thrusting displayed by 17 male golden hamsters during their copulatory behavioral responses: mounts, intromissions, ejaculations, and long intromissions, as well as their temporal correlation with the genital contacts established by intravaginal penile insertion, were studied by an accelerometric and polygraphic technique. Pelvic thrusting in all copulatory behavioral responses appeared as series or trains of rhythmical, synchronic, vigorous movements. The various pelvic thrusting trains lasted around 1 s on average, but those of mounts were significantly longer than the trains displayed in the other behavioral responses. The frequencies of pelvic thrusting were similar in all responses (around 15 thrusts per s) excepting mounts which had lower values. In intromission, ejaculation, and long intromission responses, when penile insertion occurred, pelvic thrusting either was interrupted or showed changes in its characteristics: penile insertion was related to a period without thrusting in intromissions, to a series of intravaginal thrusting of higher frequency (16.4 thrusts per s) and lower vigor in ejaculations, and to a prolonged period of 6 to 25 s of slow intravaginal pelvic thrusting (1–2 thrusts per s) in long intromissions. Penile insertion lasted longer in ejaculations than in intromissions and it was significantly shorter in both of these responses than in long intromissions. These results provide information about some dynamic aspects of sexual behavior in hamsters, as well as a temporal correlation between the motor and genital components of this behavior.     

Influence of alpha-tocopherol on prostacyclin synthesis by rat's arterial and myometrial tissues

Influence of alpha-tocopherol on PGI2 synthesis by rat arterial and myometrial tissues was investigated using a rat platelet antiaggregatory bioassay. Chronic administration of alpha-tocopherol to female rats (10 mg kg-1 day-1 s.c. for 14 days) significantly increased ex-vivo PGI2 synthesis by the arterial tissue from 12.7 +/- 0.3 (control, mean +/- s.e.m) to 17.2 +/- 0.4 ng PGI2 mg-1 wet tissue and by the myometrial tissue (in proestrus) from 1.1 +/- 0.07 (control) to 1.85 +/- 0.1 ng PGI2 mg-1 wet tissue (P less than 0.05, n = 6). alpha-tocopherol (5 mg kg-1 day-1 for 14 days) did not stimulate PGI2 to any significant level. Pretreatment of male rat arterial tissue with alpha-tocopherol (0.02, 0.1 or 0.2 mM) in vitro increased PGI2 synthesis in a dose-dependent manner. At a dose of 0.2 mM it increased PGI2 synthesis from 13.70 +/- 0.70 (control) to 22.6 +/- 1.4 ng PGI2 mg-1 wet tissue (P less than 0.1, n = 6). Pre-treatment of 14-day pregnant rat myometrium with alpha-tocopherol 0.2 and 0.4 mM significantly increased PGI2 synthesis from 1.2 +/- 0.06 (control) to 1.90 +/- 0.12 and 2.1 +/- 0.1 ng PGI2 mg-1 wet tissue, respectively (P less than 0.05, n = 6). The results indicate that the ability of alpha-tocopherol to stimulate PGI2 synthesis may partly contribute towards better understanding of the mechanisms that underly the protective effect of alpha-tocopherol against experimentally induced decreases in coronary flow and intravascular coagulations in some mammals. Furthermore adequate intake of alpha-tocopherol during pregnancy may enhance uterine blood flow and ensure adequate foetal nutrition.     

Relationships between seminal vesicle size and copulatory activity in bulls

Two experiments were designed to investigate the hypothesis that dimensions of the seminal vesicle are positively correlated with copulatory behavior in bulls. In Experiment 1, thirty Santa Gertrudis bulls (16.5 mo old) were used to study the relationship between copulatory activity and seminal vesicle length and width (palpation per rectum), seminal vesicle thickness (ultrasonography), and volume. The bulls showed a low level of copulatory activity (6.0+/-1.5, 0.8+/-0.3 and 0.3+/-0.1 for mean number of mounts, intromissions and ejaculations, respectively) in 2 tests. The mean number of mounts but not the mean number of intromissions or ejaculations differed (P<0.01) among bulls. No significant correlations were found between seminal vesicle size and any of the variables of sexual behavior. In Experiment 2, 16 beef bulls (18 mo old) were used to study the relationship between copulatory activity and seminal vesicle length (palpation) or dorso-ventral thickness (ultrasonography). Differences were detected (P<0.01) among bulls in mean number of mounts, intromissions and ejaculations achieved in 2 serving capacity tests. No significant correlations were found between copulatory activity and seminal vesicle length or thickness. These data do not support the hypothesis of a positive relationship between seminal vesicle length or thickness with copulatory activity, even for bulls with marked diffences in intensity of sexual behavior.     

Nitric oxide modulates renal sensory nerve fibers by mechanisms related to substance P receptor activation

Nerve terminals containing neuronal nitric oxide synthase (nNOS) are localized in the renal pelvic wall where the sensory nerves containing substance P and calcitonin gene-related peptide (CGRP) are found. We examined whether nNOS is colocalized with substance P and CGRP. All renal pelvic nerve fibers that contained nNOS-like immunoreactivity (-LI) also contained substance P-LI and CGRP-LI. In anesthetized rats, renal pelvic perfusion with the nNOS inhibitor S-methyl-L-thiocitrulline (L-SMTC, 20 microM) prolonged the afferent renal nerve activity (ARNA) response to a 3-min period of increased renal pelvic pressure from 5 +/- 0.4 to 21 +/- 2 min (P < 0.01, n = 14). The magnitude of the ARNA response was unaffected by L-SMTC. Similar effects were produced by N(omega)-nitro-L-arginine methyl ester (L-NAME) but not D-NAME. Increasing renal pelvic pressure produced similar increases in renal pelvic release of substance P before and during L-SMTC, from 5.9 +/- 1.4 to 13.6 +/- 4.2 pg/min before and from 4.9 +/- to 12.6 +/- 2.7 pg/min during L-SMTC. L-SMTC also prolonged the ARNA response to renal pelvic perfusion with substance P (3 microM) from 1.2 +/- 0.2 to 5.6 +/- 1.1 min (P < 0.01, n = 9) without affecting the magnitude of the ARNA response. In conclusion: activation of NO may function as an inhibitory neurotransmitter regulating the activation of renal mechanosensory nerve fibers by mechanisms related to activation of substance P receptors.     

Occurrence of flehmen in male buffaloes (Bubalus bubalis) with special reference to estrus

Pheromonal cues present in the urine and vaginal mucus during the estrus period elicit courtship behaviour in mammals including the characteristic flehmen behaviour. In the present study, the flehmen behaviour was assessed in male buffaloes by exposing them to heifers for three consecutive estrous cycles. Behavioural observations revealed that the bulls sniffed the female's external genitalia, responded to the chemical signal(s) and exhibited the flehmen behaviour similar to those reported in other ungulates. The flehmen behaviour was recorded daily during 15-min contact with females for three consecutive estrous cycles. Out of 180 observations during five days estrus periods (-3 to +1 days) which included high frequency of flehmen behaviour and out of 637 observations with or without flehmen behaviour during diestrus periods, the bull displayed 365 and 441 flehmen behaviour, respectively. Average numbers of all (2.03 +/- 0.66) and repeated flehmen (1.05 +/- 0.64) behaviour during estrus periods were significantly higher than those of diestrus periods of all (0.69 +/- 0.25) and repeated flehmen (0.11 +/- 0.10). The statistical significance was higher (P < 0.001) in repeated flehmen behaviour of estrus as compared to that in diestrus. In case of all flehmen behaviour, the statistical significance was higher (P < 0.01) in estrus when compared to that in diestrus. The occurrence of flehmen behaviour in male buffaloes clearly indicates that the specific pheromonal compound(s) present in the urine/vaginal mucus during estrus significantly influence the flehmen behaviour.     

Copulatory behavior in relation to anatomical characteristics of three macaques

Anatomy of copulatory organs and patterns of copulatory behavior were studied in three species of Macaca. The copulatory behavior of the rhesus monkey (M. mulatta) and crab-eating macaque (M. fascicularis) were similar. Mounting time was longer in stump-tailed macaque (M. arctoides) (48 seconds) than in the rhesus monkey or crab-eating macaque (8.5 seconds). Species differences were correlated with anatomical differences in the female and male reproductive organs. In the stump-tailed macaque the male has a relatively long penis, and the female has an elaborate vestibular colliculus in the vestibule. Both rhesus and crab-eating macaques have a short penis, and the female has no vestibular colliculus. Under scanning electron microscope, cone-like projections (3–4 mm) were observed on the surface of the glans and corpus penis of M. arctoides. In M. fascicularis shorter projections (0.05–0.1 mm) were observed on the glans penis but not the corpus penis.     

Deterioration of male sexual behavior in rats by the new prolactin-secreting tumor 7315b

The effects of hyperprolactinemia on male copulatory behavior in adult male and female rats were studied. Hyperprolactinemia was induced by the transplantable purely prolactin-secreting tumor 7315b. Male rats were castrated and received testosterone-filled capsules of different sizes which induced normal and subnormal testosterone levels. After sexual training the rats of the experimental groups were inoculated with tumor 7315b. Three weeks after tumor-inoculation high prolactin levels (2000-30000 ng/ml) were found. During this hyperprolactinemia ejaculation latency increased significantly, while the mount frequency and intromission frequency remained unchanged. Only 9 out of 22 rats ejaculated 19 days after inoculation. Moreover, it appeared that the inhibitory effect of the tumor was as strong in the presence of normal (2.33 +/- 0.07 ng/ml) as in the presence of low (0.35 +/- 0.01 ng/ml) testosterone levels. The inhibitory effect of tumor 7315b on copulatory behavior was not influenced by adrenalectomy. In gonadectomized female rats bearing testosterone-filled capsules tumor 7315b induced prolactin levels of about 2000 ng/ml and an almost complete cessation of mounts and intromission patterns 4 weeks after tumor-inoculation. It was concluded that tumor 7315b causes a strong inhibitory effect on male copulatory behavior in male and female rats and that this effect is not influenced by the presence of normal or low testosterone levels or removal of the adrenals, suggesting a direct effect of prolactin on brain functions.     

Sex-based transmural differences in cardiac repolarization and ionic-current properties in canine left ventricles

The female sex is associated with longer electrocardiographic QT intervals and increased proarrhythmic risks of QT-prolonging drugs. This study examined the hypothesis that sex differences in repolarization may be associated with differential transmural ion-current distribution. Whole cell patch-clamp and current-clamp were used to study ionic currents and action potentials (APs) in isolated canine left ventricular cells from epicardium, midmyocardium, and endocardium. No sex differences in AP duration (APD) were found in cells from epicardium versus endocardium. In midmyocardium, APD was significantly longer in female dogs (e.g., at 1 Hz, female vs. male: 288 +/- 21 vs. 237 +/- 8 ms; P < 0.05), resulting in greater transmural APD heterogeneity in females. No sex differences in inward rectifier K+ current (I(K1)) were observed. Transient outward K+ current (I(to)) densities in epicardium and midmyocardium also showed no sex differences. In endocardium, female dogs had significantly smaller I(to) (e.g., at +30 mV, female vs. male: 2.5 +/- 0.2 vs. 3.5 +/- 0.3 pA/pF; P < 0.05). Rapid delayed-rectifier K+ current (I(Kr)) density and activation voltage-dependence showed no sex differences. Female dogs had significantly larger slow delayed-rectifier K+ current (I(Ks)) in epicardium and endocardium (e.g., at +40 mV; tail densities, female vs. male; epicardium: 1.3 +/- 0.1 vs. 0.8 +/- 0.1 pA/pF; P < 0.001; endocardium: 1.2 +/- 0.1 vs. 0.7 +/- 0.1 pA/pF; P < 0.05), but there were no sex differences in midmyocardial I(Ks). Female dogs had larger L-type Ca2+ current (I(Ca,L)) densities in all layers than male dogs (e.g., at -20 mV, female vs. male, epicardium: -4.2 +/- 0.4 vs. -3.2 +/- 0.2 pA/pF; midmyocardium: -4.5 +/- 0.5 vs. -3.3 +/- 0.3 pA/pF; endocarium: -4.5 +/- 0.4 vs. -3.2 +/- 0.3 pA/pF; P < 0.05 for each). We conclude that there are sex-based transmural differences in ionic currents that may underlie sex differences in transmural cardiac repolarization.     

Effect of early and late exposure to estrual ewes on ram sexual performance classifications

This study was conducted to determine whether exposure of ram lambs to estrual ewes during their first autumn and again as adults just before serving capacity tests (SCT) affected the outcome of the sexual performance tests. Treatments were either early exposure of Polypay ram lambs (i.e., 7-8-mo-old rams with ewes for 17 d [n=30] or no early exposure [n=30]), and late exposure (i.e., 16-19-mo-old rams with estrual ewes for 3 d) or no exposure to estrual ewes in a 2x2 factorial arrangement. Three serving capacity tests were conducted immediately after the early exposure period for individual ram lambs that were exposed to ewes early. Three sham sexual performance tests (i.e., four ram lambs placed in test pens for 30-min without ewes) were conducted with ram lambs that were not exposed to ewes early. All rams were evaluated during nine 30-min serving capacity tests over a 2-mo period at 16-19 mo of age to determine sexual performance. Prior to serving capacity tests, one half of the rams from each early exposure treatment were exposed to estrual-induced ewes for 3 d. Specific sexual behaviors (e.g., sniffs, flehmens, foreleg kicks, vocalizations, mount attempts, mounts, and ejaculations) were recorded during serving capacity tests. Number of sniffs, flehmens, foreleg kicks, vocalizations, and mount attempts were summed without estimating the value of importance and analyzed as courtship behaviors. Sexual performance data were analyzed with Mixed model procedures for repeated measures. During serving capacity tests, the early exposed rams exhibited more courtships (40.3+/-8.0 versus 23.4+/-4.6; P<0.05; LSM+/-estimated SE), mounts (11.3+/-1.0 versus 7.7+/-0.9; P<0.01), and ejaculations (3.3+/-0.2 or 2.4+/-0.2; P<0.01) than rams not exposed to ewes as ram lambs, respectively. We conclude that early exposure of 7-8-mo-old ram lambs to estrual ewes improves sexual performance in serving capacity tests at 16-19 mo of age in most rams whereas, late exposure to estrual ewes for 3 d prior to serving capacity tests did not improve sexual performance scores.     

Mechanisms of blood pressure regulation that differ in men repeatedly exposed to high-G acceleration

The purpose of this study was to test the hypothesis that repeated exposure to high acceleration (G) would be associated with enhanced functions of specific mechanisms of blood pressure regulation. We measured heart rate (HR), stroke volume (SV), cardiac output (), mean arterial blood pressure, central venous pressure, forearm and leg vascular resistance, catecholamines, and changes in leg volume (%DeltaLV) during various protocols of lower body negative pressure (LBNP), carotid stimulation, and infusions of adrenoreceptor agonists in 10 males after three training sessions on different days over a period of 5-7 days using a human centrifuge (G trained). These responses were compared with the same measurements in 10 males who were matched for height, weight, and fitness but did not undergo G training (controls). Compared with the control group, G-trained subjects demonstrated greater R-R interval response to equal carotid baroreceptor stimulation (7.3 +/- 1.2 vs. 3.9 +/- 0.4 ms/mmHg, P = 0.02), less vasoconstriction to equal low-pressure baroreceptor stimulation (-1.4 +/- 0.2 vs. -2.6 +/- 0.3 U/mmHg, P = 0.01), and higher HR (-1.2 +/- 0.2 vs. -0.5 +/- 0.1 beats. min(-1). mmHg(-1), P = 0.01) and alpha-adrenoreceptor response (32.8 +/- 3.4 vs. 19.5 +/- 4.7 U/mmHg, P = 0.04) to equal dose of phenylephrine. During graded LBNP, G-trained subjects had less decline in and SV, %DeltaLV, and elevation in thoracic impedance. G-trained subjects also had greater total blood (6,497 +/- 496 vs. 5,438 +/- 228 ml, P = 0.07) and erythrocyte (3,110 +/- 364 vs. 2,310 +/- 96 ml, P = 0.06) volumes. These results support the hypothesis that exposure to repeated high G is associated with increased capacities of mechanisms that underlie blood pressure regulation.     

Effect of semen collection practices on sperm characteristics before and after storage and on fertility of stallions

This study analyzed effects of different methods and intervals of semen collection on the quantity and quality of fresh, cool-stored, and frozen-thawed sperm and fertility of AI stallions. In Experiment 1, ejaculates were obtained from six stallions (72 ejaculates per stallion) using fractionated versus non-fractionated semen collection techniques. Initial sperm quality of the first three jets of the ejaculate was not different from that of total ejaculates. Centrifugation of sperm-rich fractions before freezing improved post-thaw motility and sperm membrane integrity when compared to non-centrifuged sperm-rich fractions or non-fractionated centrifuged ejaculates (P<0.05). In Experiment 2, semen from four stallions (60-70 ejaculates per stallion) was collected either once daily or two times 1h apart every 48 h. The first ejaculates of double collections had significantly higher sperm concentrations, percentages of progressively motile sperm (PMS) after storage for 24h at 5 degrees C and lower percentages of midpiece alterations than single daily ejaculates. Semen collected once daily showed significantly lower values of live sperm after freezing and thawing than the first ejaculate of two ejaculates collected 1h apart every 48 h. In Experiment 3, semen was collected from 36 stallions (> or =12 ejaculates per stallion) during the non-breeding season and the time to ejaculation and the number of mounts was recorded. When time to ejaculation and the number of mounts increased, volume and total sperm count (TSC) also increased (P<0.05), whereas a decrease was observed in sperm concentration, percentage of PMS after storage for 24 h at 5 degrees C, percentage of membrane-intact sperm in fresh semen (P<0.05) as well as motility and percentage of membrane-intact sperm of frozen-thawed sperm (P<0.05). In Experiment 4, AI data of 71 stallions were retrospectively analyzed for the effect of number of mounts per ejaculation and frequency, time interval of semen collections on pregnancy, and foaling rates (FRs) of mares. Semen volume increased, but sperm concentration and percentage of PMS after 24-h cool-storage decreased with increasing number of mounts on the phantom (P<0.05). A statistically significant inter-relationship was demonstrated between frequency and interval of semen collection and FR. Mares inseminated with stallions from which semen was collected frequently (> or =1 on an average per day) showed significantly higher FRs than mares inseminated with semen from stallions with a daily collection frequency of 0.5-1 or <0.5. FR of mares inseminated with stallions having 0.5-1 days between semen collections was significantly better than FR of mares that were inseminated with stallions having semen collection intervals of 1-1.5 days or >2.5 days.     

Vildagliptin in drug-na?ve patients with type 2 diabetes: a 24-week, double-blind, randomized, placebo-controlled, multiple-dose study.

This 24-week double-blind, randomized, multicenter, placebo-controlled, parallel-group study was performed in 632 drug-na?ve patients with type 2 diabetes to assess efficacy and tolerability of vildagliptin (50 mg qd, 50 mg bid, or 100 mg qd). HbA1c decreased modestly in patients receiving placebo (Delta=-0.3+/-0.1%) and to a significantly greater extent in patients receiving vildagliptin 50 mg qd (Delta=-0.8+/-0 .1%), 50 mg bid (Delta=-0.8+/-0.1%), or 100 mg qd (Delta=-0.9+/-0.1%, p<0.01 for all groups VS. placebo) from an average baseline of 8.4%. In patients diagnosed >or=3 months before enrollment, HbA1c increased with placebo (Delta=+0.2+/-0.2%) and between-treatment differences (vildagliptin-placebo) were -0.8+/-0.2% (p<0.001), -0.7+/-0.2% (p=0.003), and -0.9+/-0.2% (p<0.001) with vildagliptin 50 mg qd, 50 mg bid, and 100 mg qd, respectively. There was no apparent dose-response in the overall population; however, in patients with high baseline HbA1c, there were greater reductions with either 100 mg dose regimen (Delta=-1.3+/-0.2% and -1.4+/-0.2%) compared to 50 mg qd (Delta=-0.8+/-0.1%). Body weight decreased modestly in all groups (by 0.3 to 1.8 kg). The incidence of adverse events was similar across all groups and 相似文献   

Androgen regulation of the motor copulatory pattern in the male New Zealand white rabbit

The effect of castration and testosterone propionate (TP) treatment on the motor copulatory pattern was studied by an accelerometric technique in five sexually experienced New Zealand white male rabbits. This technique permits the oscillographic recording of thrusting frequency, rhythmicity, and amplitude of the pelvic movements occurring during copulation. Castration resulted in a marked decrease in sexual activity in all rabbits. Mounting, including occasional intromissions, was retained by four of the rabbits for periods ranging from 2 to 15 weeks. Castration did not affect mount duration, but decreased strength and frequency of pelvic thrusting. Diminution in the frequency of pelvic thrusting was mainly due to intercalation of pauses within the mounting trains. The change in the rhythm of pelvic thrusting was related to the failure of most mounts performed by castrated rabbits to stimulate lordosis in the female. Testosterone propionate (TP, 10 mg daily for 15 days) restored mounting activity and increased strength and frequency of pelvic thrusting in all rabbits. It is concluded that TP, besides stimulating sexual motivation, regulates the vigor and rhythm of pelvic movements during copulation in the rabbit.     

Sexual behavior of stallions during in-hand natural service and semen collection: an observation in French studs.

The sexual behavior of 42 stallions from French national and private studs was examined in two contexts: semen collection for artificial insemination (AI) and in-hand natural service (NS). Each stallion was observed twice in the same context. Erection and ejaculation latencies, the number of mounts leading to ejaculation, dismount latency and total breeding time were measured and compared between AI and NS. Mount without erection was rare (6/83 observations). Erection latency was 89+/-11s, and was not different between NS (62+/-22s) and AI (100+/-13s, P=0.128). Stallions ejaculated after either one mount (62/83 observations), or two (11/83 observations) or three mounts (10/83 observations). Ejaculation latency was 85+/-15s (84+/-19 in AI and 86+/-28 in NS). If 1st mount did not lead to ejaculation, then ejaculation latency increased several fold following the 2nd mount during both AI and NS. The results provide reference measures for semen collection in French studs. Difference in erection latency between AI and NS, although not statistically significant, may reflect different contributions of excitatory inputs from the brain and the genital area to the activation of spinal networks controlling erection. In contrast, lack of difference in ejaculation latency between AI and NS suggests that the spinal network that controls ejaculation follows a more rigid motor pattern.     

Relaxin-induced changes in renal sodium excretion in the anesthetized male rat

Pregnancy is associated with profound changes in renal hemodynamics and electrolyte handling. Relaxin, a hormone secreted by the corpus luteum, has been shown to induce pregnancy-like increases in renal blood flow and glomerular filtration rate (GFR) and alter osmoregulation in nonpregnant female and male rats. However, its effects on renal electrolyte handling are unknown. Accordingly, the influence of short (2 h)- and long-term (7 day) infusion of relaxin on renal function was determined in the male rat. Short term infusion of recombinant human relaxin (rhRLX) at 4 microg.h(-1).100 g body wt(-1) induced a significant increase in effective renal blood flow (ERBF) within 45 min, which peaked at 2 h of infusion (vehicle, n = 6, 2.1 +/- 0.4 vs. rhRLX, n = 7, 8.1 +/- 1.1 ml.min(-1).100 g body wt(-1), P < 0.01). GFR and urinary excretion of electrolytes were unaffected. After a 7-day infusion of rhRLX at 4 microg/h, ERBF (1.4 +/- 0.2 vs. 2.5 +/- 0.4 ml.min(-1).100 g body wt(-1), P < 0.05), urine flow rate (3.1 +/- 0.3 vs. 4.3 +/- 0.4 microl.min(-1).100 g body wt(-1), P < 0.05) and urinary sodium excretion (0.8 +/- 0.1 vs. 1.2 +/- 0.1 micromol.min(-1).100 g body wt(-1), P < 0.05) were significantly higher; plasma osmolality and sodium concentrations were lower in rhRLX-treated rats. These data show that long-term relaxin infusion induces a natriuresis and diuresis in the male rat. The mechanisms involved are unclear, but they do not involve changes in plasma aldosterone or atrial natriuretic peptide concentrations.