The use of steroid hormones in superovulation of Nelore donors at different stages of estrous cycle

The objective of the present study was to evaluate the superovulatory response and ova/embryo recovery from Nelore donors following treatment with a controlled internal drug releasing device and estradiol benzoate (CIDR-B program) at different stages of the estrous cycle. The control group (TI; n=40) received a standard superovulation protocol with females of this group being between days 9 and 12 of the estrous cycle (estrus = day 0). The donors that received a CIDR-B program containing 1.9 g progesterone and an intramuscular injection of estradiol benzoate (2 mg) were at day 0 (TII; n=30), between days 2 and 6 (TIII; n=30), days 7 and 12 (TIV; n=30), days 13 and 16 (TV; n=30) and days 17 and 20 (TVI; n=30) of the estrous cycle. Superovulation was induced with 400 IU of p-FSH, divided into eight decreasing doses (80/80; 60/60; 40/40; 20/20) at intervals of 12h. The donors received PGF2alpha (Cloprostenol) 48 h after beginning the treatment and CIDRs were removed 12h later. Artificial inseminations (AI) were performed 12 and 22 h after the initiation of estrus and embryos were collected 7 days after AI. The mean numbers (+/-S.E.M.) of total ova and embryos, viable (transferable) and degenerated embryos were 14.2+/-11.3, 7.4+/-6.9 and 3.2+/-3.5 (TI), 13.3+/-10.4, 7.1+/-6.2 and 3.3+/-4.3 (TII), 13.5+/-7.0, 8.1+/-6.7 and 2.3+/-3.0 (TIII), 17.4+/-9.9, 9.4+/-6.9 and 4.0+/-4.4 (TIV), 16.9+/-8.8, 9.8+/-8.1 and 2.7+/-2.5 (TV) and 13.0+/-7.8, 7.2+/-6.9 and 2.3+/-2.5 (TVI), with no significant differences (P>/=0.05) among groups. Pregnancy rates of 67.1% (TI; n=86/128), 60.8% (TII; n=59/97), 62.5% (TIII; n=73/115), 64.1% (TIV; n=84/131), 72.3% (TV; n=81/112) and 60.6% (TVI; n=63/104) were obtained with embryos transferred from these collections and did not differ significantly (P>/=0.05) among groups. The results of the present study allow us to conclude that a combination of steroid hormones may be used prior to superovulation in Nelore donors, at any stage of the estrous cycle without affecting the efficiency of embryo transfer programs.     

Pancreas preservation with TP-IV: a hyperosmolar colloid solution

This study compares the efficacy of a new hyperosmolar colloid solution (TP-IV) with Euro-Collins solution for long-term (72 hr) hypothermic storage of canine pancreas autografts. Four experimental recipient groups and their survival (30-day study period) results were as follows: Gr. I (n = 6) pancreatectomized controls, without autotransplant (X +/- SD = 5.83 +/- 3.06 days); Gr. II (n = 6) fresh nonpreserved autografts (X +/- SD = 23.83 +/- 10.12 days, 5 of 6 greater than 30 days); and Gr. III (n = 7) and Gr. IV (n = 5) receiving pancreas autografts stored at 4 degrees C for 72 hr in either Euro-Collins or TP-IV, respectively (Gr. III, 13.85 +/- 9.04 days; Gr. IV, 21.2 +/- 12.37 days). The results appear to indicate that TP-IV is superior to Euro-Collins solution for 72-hr hypothermic storage of pancreas grafts. In fact, survival in the TP-IV-presented group was comparable to that of fresh, non-preserved autografts.     

Reproductive inhibition in the Cape porcupine, Hystrix africaeaustralis

Sexually mature female Cape porcupines kept under natural conditions of illumination and temperature did not conceive while housed within their natal groups. Before removal from their natal groups the sexually mature offspring copulated and experienced cyclic ovarian activity, but conception occurred only 70-120 days after dispersal. Mean oestrous cycle length of these females (36.9 +/- 11.5 days; n = 34) was similar to that of breeding females (33.0 +/- 11.64 days; n = 16), but mean peak plasma progesterone concentration (6.45 +/- 6.03 ng/ml; n = 34) was significantly (P less than 0.01) lower than that of cyclic breeding females (13.58 +/- 6.98 ng/ml; n = 16). Mean progesterone concentration at oestrus in non-breeding females (0.72 +/- 0.45 ng/ml; n = 34) was also significantly (P less than 0.01) lower than that of non-pregnant breeding females (4.21 +/- 2.44 ng/ml; n = 16). Reproductive inhibition within natal groups, in which only one female reproduces, therefore cannot be ascribed to a failure to copulate, but may be due to some factor inhibiting full expression of luteal activity or affecting ovulation.     

Reproduction in captive female Cape porcupines (Hystrix africaeaustralis)

Captive females attained sexual maturity at an age of 9-16 months and conceived for the first time when 10-25 months old. Adult females were polyoestrous but did not cycle while lactating or when isolated from males. The length of the cycle varied from 17 to 42 days (mean +/- s.d. 31.2 +/- 6.5 days; n = 43) and females experienced 3-7 sterile cycles before conceiving. Pregnancy lasted for 93-94 days (93.5 +/- 0.6 days; N = 4) and litter intervals varied from 296 to 500 days (385 +/- 60.4; n = 10). Litter size varied from 1 to 3 (1.5 +/- 0.66; n = 165) and the well-developed precocial young weighed 300-440 g (351 +/- 47.4 g; n = 19) at birth. Captive females reproduced throughout the year with most litters (78.7%; n = 165) being produced between August and March.     

Hindlimb unloading induces a collagen isoform shift in the soleus muscle of the rat

To determine whether hindlimb unloading (HU) alters the extracellular matrix of skeletal muscle, male Sprague-Dawley rats were subjected to 0 (n = 11), 1 (n = 11), 14 (n = 13), or 28 (n = 11) days of unloading. Remodeling of the soleus and plantaris muscles was examined biochemically for collagen abundance via measurement of hydroxyproline, and the percentage of cross-sectional area of collagen was determined histologically with picrosirius red staining. Total hydroxyproline content in the soleus and plantaris muscles was unaltered by HU at any time point. However, the relative proportions of type I collagen in the soleus muscle decreased relative to control (Con) with 14 and 28 days HU (Con 68 +/- 5%; 14 days HU 53 +/- 4%; 28 days HU 53 +/- 7%). Correspondingly, type III collagen increased in soleus muscle with 14 and 28 days HU (Con 32 +/- 5%; 14 days HU 47 +/- 4%; 28 days HU 48 +/- 7%). The proportion of type I muscle fibers in soleus muscle was diminished with HU (Con 96 +/- 2%; 14 days HU 86 +/- 1%; 28 days HU 83 +/- 1%), and the proportion of hybrid type I/IIB fibers increased (Con 0%; 14 days HU 8 +/- 2%; 28 days HU 14 +/- 2%). HU had no effect on the proportion of type I and III collagen or muscle fiber composition in plantaris muscle. The data demonstrate that HU induces a shift in the relative proportion of collagen isoform (type I to III) in the antigravity soleus muscle, which occurs concomitantly with a slow-to-fast myofiber transformation.     

Physiological changes in androgen plasma levels with elapsing of time from castration in adult male rats

In the present study we investigated in adult male rats the effects of castration on Dehydroepiandrosterone (DHEA), Androstenedione (delta 4), Testosterone (T) and Dihydrotestosterone (DHT) plasma levels: five days (group II), seven weeks (group III) and eleven weeks (group IV) after orchiectomy. The same hormone assays were performed in rats approximately 60 days of age which underwent a sham-operation for orchiectomy (group I). Our data show that five days following orchiectomy (group II) delta 4, T and DHT were decreased with respect to sham-operated rats. (Group I: delta 4: 83.3 +/- 14.9 (SEM) ng/dl (n = 12); T: 435.32 +/- 51.45 (n = 12); DHT: 51.47 +/- 6.54 (n = 12); Group II: delta 4: 44.81 +/- 6.09 (n = 12) P = 0.05; T: 25.54 +/- 2.88 (n = 12) P less than 0.01; DHT: 12.9 +/- 2.51 (n = 12) P less than 0.01). Seven weeks afterwards T and DHT remained significantly lower (group III: T: 54.37 +/- 12.21, n = 16) (P less than 0.01; DHT: 33.22 +/- 4.49 (n = 16) P less than 0.01) while eleven weeks after all steroids were significantly decreased with respect to the values observed in sham-operated rats. (Group IV) delta 4: 32.01 +/- 5.7 (n = 10) P less than 0.01: T: 27.29 +/- 7.05 (n = 10) P less than 0.01; DHT: 29.03: 5.34 (n = 10) P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Stimulation of vascular Na-K pump with subpressor angiotensin II in rats.

The effect of subpressor doses of angiotensin II (ANG II) on vascular Na-K pump activity and Na-H exchange, two transmembrane signals of trophic stimulation of vascular muscle, was investigated. Male Sprague-Dawley rats (350-400 g) were given subpressor doses of ANG II by osmotic minipump intraperitoneally for 24 hr or 7-10 days. Control rats received sham procedure/vehicle infusion. Na-K pump activity (86Rb uptake), total and intracellular (Li exchange at 4 degrees C) Na content, and amiloride-sensitive and -insensitive Na uptake of aortas were measured ex vivo. Ouabain-sensitive 86Rb uptake of aortas of rats receiving 80-100, 160-180, and 240-260 ng/kg.min-1 of ANG II for 24 hr was 26.6 +/- 3.5, 28.8 +/- 3.4, and 29.1 +/- 2.6 nmol/mg dry wt.15 min-1 (mean +/- SD, n = 7-12), respectively, compared with 25.2 +/- 3.8 in controls (n = 23, P less than 0.01). These increases were maintained at 7-10 days. After 24 hr and 7-10 days of ANG II treatment, the total Na content of aortas was increased by 9.2% (P less than 0.01) and 7.6% (P less than 0.02), respectively, without a change in intracellular Na content, indicating accumulation of excess extracellular Na. Total and amiloride-sensitive Na uptake of the aorta was unchanged after 24 hr or 7-10 days of ANG II administration. The dry weight of anatomically defined segments of the aorta was 40 +/- 3.8 mg/kg body wt (n = 25) after 24 hr and 42 +/- 4.4 (n = 20) after 7-10 days of ANG II administration, compared with 37 +/- 4.8 (n = 15, P less than 0.05) and 37 +/- 4.9 (n = 17, P less than 0.01) in appropriate controls. Increased Na-K pump activity may signal the onset of trophic stimulation of vascular muscle by ANG II.     

Synchronisation of ovarian follicular waves in the dromedary camel (Camelus dromedarius)

This study was designed to compare the efficacy of various treatments intended to synchronise follicular wave cycles in dromedary camels by removing the existing follicle of unknown size and replacing it with a follicle capable of ovulating at a known time. Camels were randomly assigned to one of five groups and treated with either (1) 5mg oestradiol benzoate (i.m.) and 100mg progesterone (i.m.; E/P, n=15), (2) 20 icrog GnRH analogue, buserelin (i.m.; GnRH, n=15), (3) 20 microg buserelin (i.m.) on Day 0 (T=0) and 500 microg prostaglandin on Day T+7 (GnRH/PG n=15), (4) transvaginal ultrasound-guided follicle ablation of all follicles > or =0.5 cm (ABL, n=15) or (5) 5 ml saline (i.m; Controls n=15). All camels were subsequently injected with 20 microg buserelin 14 days after the first treatment was given. The ovarian response was monitored daily by transrectal ultrasonography and the intervals from treatment to follicular wave emergence and also the day on which the new dominant follicle reached 1.3 cm was recorded. Amongst the treatment groups the mean interval from treatment to new follicle wave emergence and treatment to time taken for the new dominant follicle to reach 1.3 cm in diameter was shortest in the ABL group (2.3+/-0.5 days and 8.8+/-1.1 days respectively, P=0.044) and longest in the E/P group (6.4+/-0.8 days and 12.2+/-1.0 days respectively, P<0.001) whereas the GnRH and GnRH/PG groups were intermediate (3.0+/-0.5 days and 11.1+/-0.8 days GnRH; and 4.5+/-0.5 days and 10.7+/-0.7 days GnRH/PG). A total of 11/15 camels in both the GnRH and GnRH/PG groups had dominant follicles between 1.3 and 1.9 cm 14 days post treatment, of which 21 of the 22 follicles ovulated after GnRH injection on T+14. The ABL, E/P and control groups however, showed greater variability in follicle size with less camels having dominant follicles between 1.3 and 1.9 cm than the GnRH and GnRH/PG groups and more in the > or =2.0 cm or follicle regressing groups, therefore fewer of these camels ovulated (ABL n=7; E/P n=9; Control n=6) after GnRH injection on Day T+14. In conclusion, two GnRH injections 14 days apart or two GnRH injections 14 days apart and PG on Day 7 after the first GnRH were the most effective methods to synchronise ovulation rate in dromedary camels at a fixed time interval of 14 days after treatment.     

Changing responsiveness to growth hormone releasing factor in the perinatal sheep

Synthetic human pancreatic growth hormone releasing factor 1-44-amide was administered (8 micrograms/kg iv bolus) to chronically catheterised fetal sheep between 77 and 135 days of gestation and to infant sheep. At all ages human pancreatic growth hormone releasing factor induced a significant growth hormone response. In fetuses less than 120 days the integrated growth hormone response to human pancreatic growth hormone releasing factor (n = 5) was 250 +/- (SE) 50 ng X hr X ml-1 compared (p less than 0.001) to -22.8 +/- 8.6 ng X hr X ml-1 in saline treated controls (n = 7). In fetuses older than 120 days (n = 5), the response to human pancreatic growth hormone releasing factor was 110.8 +/- 15.6 ng X hr X ml-1 compared to -12.0 +/- 17.6 ng X hr X ml-1 in saline treated controls (n = 4 p less than 0.001). In 4 infant lambs (4-12 days) the response to human pancreatic growth hormone releasing factor (56.5 +/- 14.5 ng X hr X ml-1) was greater than in 6 control injected lambs (0.95 +/- 1.5 ng X hr X ml-1). The magnitude of the response to growth releasing factor decreased progressively with increasing postconceptual age (r = -0.80, p less than 0.001). These observations demonstrate that the fetal somatotrope can respond to exogenous growth releasing factor from at least 77 days of gestation. The progressive decrease in responsiveness may reflect the gradual development of somatostatin mediated inhibitory control or altered responsiveness of the somatotrope.     

The effect of prolonged hypobaric hypoxia on growth of fetal sheep

The effect of prolonged hypobaric hypoxia on fetal sheep was studied. Pregnant ewes were subjected to an atmospheric pressure of 429 torr from 30 days to 135 days gestation (long-term study). Average fetal weight for the hypoxaemic group (3.35 +/- 0.53 kg; n = 4; mean +/- SD) was significantly lower than for the controls (4.23 +/- 0.29 kg; n = 7; P less than 0.05). A short-term study was undertaken with fetuses (n = 8) which were catheterized at 110 days gestation and whose dams were subjected to hypobaric hypoxia from 120 to 141 days gestation. The mean carotid PO2 of fetuses in the hypoxic group was 12.7 +/- 0.7 torr compared to 22.7 +/- 0.7 torr for the control group (n = 9; P less than 0.001) throughout the period of treatment. Fetal arterial oxygen content fell from 6.5 +/- 1.7 to 4.9 +/- 0.4 ml/dl (P less than 0.05), but rose to control values after 7 days due to an increase in fetal haemoglobin concentration (9.6 +/- 1.1 to 13.0 +/- 1.9 g/dl, P less than 0.001) and packed cell volume (33 +/- 3 to 45 +/- 4%, P less than 0.001). In the hypoxaemic fetuses, pH fell initially from 7.34 +/- 0.02 to 7.28 +/- 0.03 (P less than 0.05) and then recovered to 7.32 +/- 0.03 within 24 h. Mean fetal weight of the short-term hypoxic group was 3.46 +/- 0.72 kg compared to 4.15 +/- 0.51 for the control group (P less than 0.05). Both long- and short-term hypoxia produced a similar reduction in fetal body weight. The adrenal glands were significantly heavier in the hypoxic fetuses than in controls. Placental weight was not effected by hypoxia, but exposure from 30 days gestation reduced the average size of cotyledons (P less than 0.05). It is concluded that the fetal sheep increases its ability to acquire and transport oxygen in response to chronic hypoxia, but this compensation is not sufficient to prevent growth retardation or changes to the pattern of tissue growth.     

Artificial insemination with frozen semen in dogs: a retrospective study of 10 years using a non-surgical approach

From 1994 to 2003, a total of 526 bitches of 99 different breeds were artificially inseminated in 685 estrus cycles with domestic (n = 353) or imported (n = 332) frozen-thawed semen from 368 males. The overall whelping rate was 73.1% and mean (+/- S.E.M.) litter size 5.7 +/- 0.1 pups. The whelping rate was higher after intrauterine insemination (75.0%; n = 665) than after intravaginal insemination (10.0%, n = 20; P < 0.05). Insemination at the optimal time resulted in a higher whelping rate (78%, n = 559; P < 0.01) and larger litter size (5.8 +/- 0.2; P < 0.05) than inseminations performed late or too late (55.7% and 4.5 +/- 0.5, n = 61). Two inseminations (n = 384) yielded a higher whelping rate (P < 0.05) and mean litter size (P < 0.01) than one insemination (n = 241), 78.1% and 6.0 +/- 0.2 and 70.5% and 5.1 +/- 0.2, respectively. For inseminations performed at the optimal time, however, the whelping rate was not significantly different for bitches inseminated twice (79.3%, n = 358) versus once (76.8%, n = 168), but the litter size was larger (6.0 +/- 0.2 and 5.3 +/- 0.3). Semen classified as of poor quality (progressive motility < 50% or percentage abnormal sperm > 20%) resulted in a lower whelping rate (P < 0.01) than semen classified as of good quality (progressive motility > or = 50% and percentage abnormal sperm < or = 20%), 61 and 77%, respectively. Small breeds (n = 50) had a smaller litter size (3.9 +/- 0.3; P < 0.01) than larger breeds (medium [5.7 +/- 0.3, n = 94], large [5.9 +/- 0.2, n = 295] or giant breeds [6.1 +/- 0.5, n = 62] [P < 0.01]). Bitches older than 6 years had a lower whelping rate (68.2%) than younger ones (77.0%; P < 0.05). The duration of pregnancy was longer (P < 0.01) for bitches with a litter size of < 3 pups (61.7 +/- 0. 4 days, n = 30) than for bitches with larger litters (60.5 +/- 0.1 days, n = 177). These results show the potential of transcervical intrauterine insemination for routine artificial insemination in dogs. The results with frozen semen inseminations were optimised by inseminating bitches < or = 6 years old 2 and 3 days after ovulation with semen of good quality from males < or = 8 years old.     

Effects of maturity of the potential ovulatory follicle on induction of oestrus and ovulation in cattle with oestradiol benzoate

The effect of maturity of the dominant follicle (DF) on the capacity of oestradiol benzoate (ODB) to induce oestrus and ovulation was examined in cattle. In experiment 1, 31 prepubertal heifers each received an intravaginal progesterone insert (IPI) and 1mg ODB i.m./500kg BW (ODB1). Daily ovarian ultrasonography detected emergence of a new follicular wave 3.1+/-0.1 days after ODB1. The IPI was removed when newly emerged DF were "young" (1.3+/-0.1 days after emergence; YDF; n=15) or "mature" (4.2+/-0.1 days; MDF; n=16), and 24h later, heifers received 0.75mg ODB/500kg BW (ODB2; n=16) or no further treatment (NoODB2; n=15). Most of the heifers receiving ODB2 were observed in oestrus (15/16) and ovulated (12/16), as compared to 0/15 and 1/15 in the NoODB2 group, respectively (P<0.01). In experiment 2, 32 heifers received ODB1 on day 6 of the oestrous cycle, and new follicular wave emergence was detected 3.2+/-0.1 days later. Heifers received an injection of prostaglandin-F2alpha (PGF) when the DF was young (1.1+/-0.1 days after emergence; YDF; n=16) or mature (4 days; MDF; n=16), and then ODB2 24h later or no further treatment (NoODB2). The interval from PGF to oestrus was greater (P<0.01) in the YDF-NoODB2 (70+/-3.9h) as compared to MDF-NoODB2 group (57+/-1.8h). Inclusion of ODB2 reduced (P<0.01) this interval to 47.0+/-0.7h without regard to the maturity of the DF (maturityxODB2, P<0.05) and also reduced (P<0.05) the interval to ovulation. In experiment 3, 21 suckling anoestrous cows received an IPI and ODB1 at 29.3+/-1.7 days postpartum. The IPI were removed either 1 day (YDF; n=9) or 3.9+/-0.1 days (MDF; n=9) after emergence of a new follicular wave and every cow received ODB2. Oestrus was subsequently detected in all but one animal. Ovulation of the newly emerged DF was detected within 48h of ODB2 in nine of nine cows of the MDF group, and in four of nine of the YDF group (P<0.05). During the subsequent ovulatory cycle, luteal size and plasma concentrations of progesterone were greater (P<0.01) in the MDF group compared to the YDF group. We conclude that behavioural oestrus is readily induced by 0.75mg ODB i.m./500kg BW. Maturity of the DF appeared to have little influence on the ability of the DF to ovulate in heifers. In contrast, young DF in lactating anoestrous cows were less likely to respond to the ovulatory cue provided, and luteal development was compromised in those that did ovulate.     

Comparison of molecular and biological characteristics of a modified live porcine reproductive and respiratory syndrome virus (PRRSV) vaccine (ingelvac PRRS MLV), the parent strain of the vaccine (ATCC VR2332), ATCC VR2385, and two recent field isolates of PRRSV

The objectives of this study were to compare the molecular and biological characteristics of recent porcine reproductive and respiratory syndrome virus (PRRSV) field isolates to those of a modified live virus (MLV) PRRS vaccine and its parent strain. One hundred seventeen, 4-week-old pigs were randomly assigned to six groups. Group 1 (n = 20) served as sham-inoculated negative controls, group 2 (n = 19) was inoculated with Ingelvac PRRS MLV vaccine, group 3 (n = 20) was inoculated with the parent strain of the vaccine (ATCC VR2332), group 4 (n = 19) was inoculated with vaccine-like PRRSV field isolate 98-38803, group 5 (n = 19) was inoculated with PRRSV field isolate 98-37120, and group 6 (n = 20) was inoculated with known high-virulence PRRSV isolate ATCC VR2385. The levels of severity of gross lung lesions (0 to 100%) among the groups were significantly different at both 10 (P < 0.0001) and 28 days postinoculation (p.i.) (P = 0.002). At 10 days p.i., VR2332 (26.5% +/- 4.64%) and VR2385 (36.4% +/- 6.51%) induced gross lesions of significantly greater severity than 98-38803 (0.0% +/- 0.0%), 98-37120 (0.8% +/- 0.42%), Ingelvac PRRS MLV (0.9% +/- 0.46%), and negative controls (2.3% +/- 1.26%). At 28 days p.i., 98-37120 (17.2% +/- 6.51%) induced gross lesions of significantly greater severity than any of the other viruses. Analyses of the microscopic-interstitial-pneumonia-lesion scores (0 to 6) revealed that VR2332 (2.9 +/- 0.23) and VR2385 (3.1 +/- 0.35) induced significantly more severe lesions at 10 days p.i. At 28 days p.i., VR2385 (2.5 +/- 0.27), VR2332 (2.3 +/- 0.21), 98-38803 (2.6 +/- 0.29), and 98-37120 (3.0 +/- 0.41) induced significantly more severe lesions than Ingelvac PRRS MLV (0.7 +/- 0.17) and controls (0.7 +/- 0.15). The molecular analyses and biological characterizations suggest that the vaccine-like isolate 98-38803 (99.5% amino acid homology based on the ORF5 gene) induces microscopic pneumonia lesions similar in type to, but different in severity and time of onset from, those observed with virulent strains VR2385 and the parent strain of the vaccine. Our data strongly suggest that isolate 98-38803 is a derivative of Ingelvac PRRS MLV and that the isolate is pneumovirulent.     

Transmembrane electrical characteristics of cultured human skeletal muscle cells

Skeletal muscle explants from normal subjects were established from biopsy material on collagen. Cellular outgrowth appeared within 3-4 days, and fusion of myoblasts was observed in 5-10 days. Multinucleated myotubes were impaled under high optical magnification, at 37 degrees C, with conventional glass microelectrodes. The mean resting potential was -44.4 mV +/- 2.4 (n = 399); -33 +/- 2.3 mV at 9 days (n = 10) vs -48 +/- 2.5 mV (n = 15) at 27 days. The average input resistance (Rin) was 9.7 M omega (n = 83). Action potentials could be elicited by electrical stimulation and had a mean amplitude of 55.9 +/- 2.1 mV with a mean maximum rate of rise (Vmax) of 72.1 +/- 7.5 V/s. The mean overshoot was 13.9 +/- 2.3 mV, and the action potential duration determined at 50% of repolarization (APD50) was 8.0 msec (n = 7). The resting membrane potential showed a depolarization of 23 mV/decade for extracellular potassium ion concentration ([K]o) between 4.5-100 mM. Thus, we have established the normal resting potential and maximum rate of rise of the action potential for human myotubes in culture. We have shown that the values for these are less than those previously reported in cultured avian and rodent cells. In addition, we have shown that the response in our system of the resting potential to change in extracellular potassium concentration is blunted compared to studies using isolated muscle, suggesting an increase in ratio of sodium to potassium permeability. Cultured human muscle cells depolarized in the presence of ouabain.     

Seasonal effects on the endocrine pattern of semi-captive female Asian elephants (Elephas maximus): timing of the anovulatory luteinizing hormone surge determines the length of the estrous cycle

Better breeding strategies for captive Asian elephants in range countries are needed to increase populations; this requires a thorough understanding of their reproductive physiology and factors affecting ovarian activity. Weekly blood samples were collected for 3.9 years from 22 semi-captive female Asian elephants in Thai elephant camps to characterize LH and progestin patterns throughout the estrous cycle. The duration of the estrous cycle was 14.6+/-0.2 weeks (mean+/-S.E.M.; n=71), with follicular and luteal phases of 6.1+/-0.2 and 8.5+/-0.2 weeks, respectively. Season had no significant effect on the overall length of the estrous cycle. However, follicular and luteal phase lengths varied among seasons and were negatively correlated (r=-0.658; P<0.01). During the follicular phase, the interval between the decrease in progestin concentrations to baseline and the anovulatory LH (anLH) surge varied in duration (average 25.9+/-2.0 days, range 7-41, n=23), and was longer in the rainy season (33.4+/-1.8 days, n=10) than in both the winter (22.2+/-4.5 days, n=5; P<0.05) and summer (18.9+/-2.6 days, n=8; P<0.05). By contrast, the interval between the anLH and ovulatory LH (ovLH) surge was more consistent (19.0+/-0.1 days, range 18-20, n=14). Thus, seasonal variation in estrous cycle characteristics were mediated by endocrine events during the early follicular phase, specifically related to timing of the anLH surge. Overall reproductive hormone patterns in Thai camp elephants were not markedly different from those in western zoos. However, this study was the first to more closely examine how timing of the LH surges impacted estrous cycle length in Asian elephants. These findings, and the ability to monitor reproductive hormones in range countries (and potentially in the field), should improve breeding management of captive and semi-wild elephants.     

Reproductive refractoriness in the Welsh Mountain ewe induced by a short photoperiod can be overridden by exposure to a shorter photoperiod

The objectives were to determine if relative lengths of photoperiods that induce reproductive cycles in ewes affect the length of the subsequent breeding season, if duration of the refractoriness that terminates breeding is affected by photoperiod length, and if the resulting refractoriness to an inductive photoperiod is absolute. Groups of Welsh Mountain ewes were exposed to either 12L:12D (n = 12) or 8L:16D (n = 6) photoperiods beginning at the summer solstice when daylengths reach a maximum of 17.5 h at Bristol, England. A control group (n = 10) was exposed to natural daylengths. Ovarian cycles in the controls, as judged by monitored plasma progesterone levels, commenced in early October, about 1 mo later (p less than 0.001 in both cases) than in sheep exposed to 12L:12D or 8L:16D. The advancement in cycle onset was similar under 12L:12D and 8L:16D (69 +/- 2 and 77 +/- 4 days after the summer solstice compared with 102 +/- 2 days in the controls). Duration of the breeding season (100 +/- 4 days) in ewes exposed to 12L:12D was significantly shorter (p less than 0.001 in both cases) than in ewes exposed to natural daylengths or 8L:16D (153 +/- 3 and 133 +/- 5 days, respectively). Approximately 70 days after the ending of ovulatory cycles in the 12L:12D group, half of the animals (n = 6) were transferred to 8L:16D. This treatment greatly (p less than 0.001) reduced the duration of anestrus and cycles began again 62 +/- 4 days after transfer to 8L:16D, or about 90 days earlier than in ewes (n = 6) remaining in 12L:12D.(ABSTRACT TRUNCATED AT 250 WORDS)     

Synchronization of follicular wave emergence prior to superovulation in Bactrian camel (Camelus bactrianus)

This study was conducted to synchronize follicle wave emergence prior to superovulation using either GnRH or progestogen treatments, in Bactrian camels. GnRH group camels (n=5) received 20 microg of the GnRH analogue Buserelin on Days -18 and -4 of the experiment (initiation of superovulation=Day 0). Camels in the progestogen group (n=5) received two consecutive treatments of progestogens, 7 days apart, on Days -14 and -8 of the experiment. On each occasion, each female received three norgestomet implants and 200mg progesterone (i.m.) and all implants were removed 14 days after the first progestogen treatment coinciding with Day -1 of superovulation. A combination of eCG and FSH was used to induce superovulation and the growth of all subsequent follicles and CLs were monitored daily by ultrasonography. Following the first GnRH injection, mature follicles ovulated within 1-2 days, and a new follicle wave emerged after 3+/-0.77 days. At the time of the second GnRH injection, a mature follicle (15.6+/-0.97 mm) ovulated and a new follicular wave emerged between 1 and 2 days after GnRH injection. Growing follicles at the time of the first progestogen treatment became either atretic (n=1) or persistent (n=4) and a new follicle wave (n=3) emerged 3-6 days later. At the initiation of superovulation, the diameters of the largest follicle in GnRH and progestogen groups were 7.4+/-0.59 and 20.5+/-2.26 mm, respectively but after superovulation and mating there was no significant differences in the number of unovulated follicles or CLs between groups. In conclusion, two GnRH injections, 14 days apart, may be used to synchronize follicle wave emergence in Bactrian camel.     

Luteal function after intrauterine infusion of recombinant bovine interferon-alpha I1 into postpartum beef cows expected to have short or normal luteal phases.

This study was conducted to determine whether intrauterine infusion of recombinant bovine interferon-alpha I1 (rboIFN-alpha I1), which has 70% sequence identity to bovine trophoblast protein-1, will prevent regression of corpora lutea anticipated to have a short lifespan. Twenty-six beef cows in good body condition were allotted to four treatment groups at parturition in a 2 x 2 factorial design. Treatments were: group 1, saline; group 2, rboIFN-alpha I1; group 3, norgestomet-saline; and group 4, norgestomet-rboIFN-alpha I1. Norgestomet implants were inserted on days 21-24 postpartum and removed 9 days later (before injection of human chorionic gonadotrophin (hCG)). Ovulation was induced 30 to 33 days postpartum with 5000 or 10,000 iu hCG. Groups 1 (n = 7) and 3 (n = 5) were given intrauterine infusions (rectocervical approach) twice daily with saline on days 1-12 or 13-24 after hCG injection, respectively. Cows allotted to groups 2 (n = 8) and 4 (n = 6) were given intrauterine infusions (rectocervical approach) of 2 mg rboIFN-alpha I1 twice daily on days 1-12 or 13-24 after hCG injection, respectively. Treatment with both norgestomet and rboIFN-alpha I1 delayed (P less than 0.01) luteolysis. Lengths of luteal phases (days; mean +/- SEM) were 8.4 +/- 0.7 (group 1, saline), 14.1 +/- 1.0 (group 2, rboIFN-alpha I1), 18.6 +/- 1.3 (group 3, norgestomet-saline) and 20.8 +/- 1.2 (group 4, norgestomet-rboIFN-alpha I1). Concentration of progesterone in serum was similar among all groups the first 6 days following hCG-induced ovulation, but differed (P less than 0.01) thereafter.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of dietary intake on pattern of growth of dominant follicles during the oestrous cycle in beef heifers

Friesian x Hereford heifers (n = 19; mean +/- s.e.m. body weight (BW) = 375 +/- 5 kg) were used in a randomized incomplete block design. Heifers were fed 0.7 (n = 7; L), 1.1 (n = 7; M) or 1.8% (n = 5; G) of BW in dry matter (DM)/day for 10 weeks. Ovaries were examined by ultrasound, for one oestrous cycle, from week 5 of treatment. Maximum diameter of dominant follicles was smaller (P less than 0.05) in L (11.8 +/- 0.1 mm) than in M (13.7 +/- 0.2 mm) or G (13.2 +/- 0.3 mm) heifers. Growth rate (mm/day) of dominant follicles during the oestrous cycle was not affected (P greater than 0.05) by dietary intake. Persistence of dominant follicles was shorter (P less than 0.05) in L (9.8 +/- 0.2 days) than in M (11.9 +/- 0.3 days) or G (12.7 +/- 0.4 days) heifers. Three dominant follicles were identified during the oestrous cycle of 5 of 7 L, 3 of 7 M and 1 of 5 G heifers (P less than 0.10); 2 dominant follicles were identified in the remaining heifers (n = 2 of 7, 4 of 7 and 4 of 5, respectively). Length of the luteal phase and luteal-phase concentrations of progesterone were not affected (P greater than 0.05) by treatment. Low dietary intake reduced the diameter and persistence of dominant follicles during the oestrous cycle of beef heifers and tended to increase the proportion of oestrous cycles with 3 dominant follicles.     

Oxidative stress in very low birth weight infants as measured by urinary 8-OHdG

Very low birth weight (VLBW) infants can be subjected to oxidative stress in the course of intensive care. We measured 8-hydroxydeoxyguanosine (8-OHdG), a biomarker of oxidative stress, and estimated the degree of oxidative stress in such infants. We also examined if the administered oxygen was related to oxidative stress. Urine samples of 50 Japanese VLBW infants [birth weights: 956.3+/-277.6g, and gestational ages: 28.0+/-2.6 weeks (mean +/- SD)] were collected on various postnatal days and 8-OHdG levels were determined using an ELISA kit. Sixteen term infants served as normal controls. As body weights at sampling increased, the average levels of urinary 8-OHdG decreased. 8-Hydroxydeoxyguanosine levels were: infants under 1000g, 29.5+/-16.4 micromol/mol creatinine (n = 24); 1000-1500g, 23.8+/-14.9 (n = 12); over 1500g, 16.1+/-8.5 (n = 14); and control, 10.9+/-7.2 (n = 16). Significant differences were found between <1000g group and > or = 1500g group (p = 0.0030), <1000g group and control (p < 0.0001), and 1000-1500g group and control (p = 0.0108). Also as postconceptional age at sampling increased, the average levels of 8-OHdG decreased. 8-Hydroxydeoxyguanosine levels were: infants before 252 days (36 weeks) of postconception: 27.4+/-15.5 micromol/mol creatinine (n = 34); after 252 days, 18.2+/-12.5 (n = 16). Differences between <252 days group and control (p < 0.0001), and <252 days group and > or = 252 days groups (p = 0.0253) were statistically significant. Among the three groups based on ambient oxygen concentration (21%, 22-29%, and > or = 30%) there was no significant difference (p = 0.417). The more premature the infants were, the more intense was the oxidative stress, hence, it is the prematurity rather than the administered oxygen which causes oxidative stress in VLBW infants. Drury et al. ["Urinary 8-hydroxydeoxyguanosine in infants and children" Free Radic. Res. 28 (1998) 423-4281 measured urinary 8-OHdG of 28 infants (24-40 weeks gestation) and found no gestation or birthweight related differences. This discrepancy seemed to be because of difference in birth weights and sampling period of the subjects.