Conception risk of beef cattle after fixed-time artificial insemination using either SexedUltra™ 4M sex-sorted semen or conventional semen.

The objective of this study was to compare conception rates of female beef cattle inseminated at a fixed-time with either conventional (CON) or SexedUltra™ sex-sorted (SU) semen. Treatments included CON or SU with two sires represented within each treatment. Cows (n = 316) and heifers (n = 78) from six locations were randomly assigned treatment. Ovulation was synchronized in all females using the industry-standard 7-d CO-Synch + controlled internal drug release (CIDR) protocol (100 µg GnRH + CIDR [1.38 g progesterone] on d 0, 25 mg PGF2α at CIDR removal on d 7, and 100 µg GnRH on d 10, 54 h (heifers) or 60 h (cows) after CIDR removal). Estrotect™ estrous detection aids were applied at CIDR removal and patch activation was recorded at insemination. Animals were assumed estrual if greater than 50% of the patch coating was removed. The results from this study indicated no main effects of treatment (P = 0.82), sire (P = 0.64), or age (P=0.8) on AI conception rates. Additionally, there were not significant interactions between sire and treatment (P=0.19) or age and treatment (P=0.29). There was however, a significant (P=0.0005) effect of estrous expression on conception rates. Conception rate for estrual females (62.8%) was greater (p=0.0001) than non-estrual females (38.7%) at FTAI regardless of treatment. Furthermore, the conception rates were similar (P = 0.61) between conventional (61.9%) and sex-sorted semen (63.8%) when estrus was expressed prior to FTAI. Larger studies are warranted to determine appropriate timing of insemination with sex-sorted semen in FTAI protocols to maximize pregnancy potential.

A transcriptomal analysis of bovine oviductal epithelial cells collected during the follicular phase versus the luteal phase of the estrous cycle.

BACKGROUND: Reproductive success depends on a functional oviduct for gamete storage, maturation, fertilization, and early embryonic development. The ovarian-derived steroids estrogen and progesterone are key regulators of oviductal function. The objective of this study was to investigate luteal and follicular phase-specific oviductal epithelial cell function by using microarray-based transcriptional profiling, to increase our understanding of mRNAs regulating epithelial cell processes, and to identify novel genes and biochemical pathways that may be found to affect fertility in the future. METHODS: Six normally cycling Angus heifers were assigned to either luteal phase (LP, n = 3) or follicular phase (FP, n = 3) treatment groups. Heifers in the LP group were killed between day 11 and 12 after estrus. Heifers in the FP group were treated with 25 mg PGF2α (Lutalyse, Pfizer, NY) at 8 pm on day 6 after estrus and killed 36 h later. Transcriptional profiling by microarray and confirmation of selected mRNAs by real-time RT-PCR analyses was performed using total RNA from epithelial cells isolated from sections of the ampulla and isthmus collected from LP and FP treatment groups. Differentially expressed genes were subjected to gene ontology classification and bioinformatic pathway analyses. RESULTS: Statistical one-way ANOVA using Benjamini-hochberg multiple testing correction for false discovery rate (FDR) and pairwise comparison of epithelial cells in the ampulla of FP versus LP groups revealed 972 and 597 transcripts up- and down-regulated, respectively (P < 0.05). Within epithelial cells of the isthmus in FP versus LP groups, 946 and 817 transcripts were up- and down-regulated, respectively (P < 0.05). Up-regulated genes from both ampulla and isthmus were found to be largely involved in cholesterol biosynthesis and cell cycle pathways, while down-regulated genes were found in numerous inflammatory response pathways. CONCLUSIONS: Microarray-based transcriptional profiling revealed phase of the cycle-dependent changes in the expression of mRNA within the epithelium of the oviducts' ampulla and isthmus.

The normal mammary microenvironment suppresses the tumorigenic phenotype of mouse mammary tumor virus-neu-transformed mammary tumor cells.

The microenvironment of the mammary gland has been shown to exert a deterministic control over cells from different normal organs during murine mammary gland regeneration in transplantation studies. When mouse mammary tumor virus (MMTV)-neu-induced tumor cells were mixed with normal mammary epithelial cells (MECs) in a dilution series and inoculated into epithelium-free mammary fat pads, they were redirected to non-carcinogenic cell fates by interaction with untransformed MECs during regenerative growth. In the presence of non-transformed MECs (50:1), tumor cells interacted with MECs to generate functional chimeric outgrowths. When injected alone, tumor cells invariably produced tumors. Here, the normal microenvironment redirects MMTV-neu-transformed tumorigenic cells to participate in the regeneration of a normal, functional mammary gland. In addition, the redirected tumor cells show the capacity to differentiate into normal mammary cell types, including luminal, myoepithelial and secretory. The results indicate that signals emanating from a normal mammary microenvironment, comprised of stromal, epithelial and host-mediated signals, combine to suppress the cancer phenotype during glandular regeneration. Clarification of these signals offers improved therapeutic possibilities for the control of mammary cancer growth.

Effect of a single injection of progesterone on ovarian follicular cysts in lactating dairy cows.

The objective of this experiment was to evaluate the effect of a single injection of progesterone on the lifespan of ovarian follicular cysts and to examine the fate of follicles that mature following treatment. Lactating Holstein and Jersey cows with ovarian follicular cysts were identified by rectal palpation. The ovaries of cystic cows were then examined by transrectal ultrasonography three times weekly to monitor formation of new follicular cysts. Cows with newly formed follicular cysts were treated either with a single injection of progesterone (200 mg, IM, n = 11) or corn oil vehicle (n = 7). Venous blood samples were collected daily for quantification of progesterone. Blood sampling and ultrasonography continued until ovulation or a new follicular cyst formed. Treatment reduced the lifespan of the cyst by 12 days, from 29.8 +/- 2.3 days in control cows to 17.2 +/- 1.8 days in progesterone-treated cows (P = 0.01). Progesterone treatment also tended to alter the frequency of subsequent follicular events. Ovulation occurred in 4/11 cows that were treated with progesterone whereas none of the vehicle treated cows ovulated (P = 0.07). In conclusion, a single injection of 200mg of progesterone, administered early in the life of an ovarian follicular cyst, shortened its lifespan and in some cases was followed by ovulation of a new follicle.

Effects of sequential or group exposure to unrestrained estrual females on expression of sexual behavior in sexually experienced beef bulls.

We tested the hypothesis that expression of sexual behavior in bulls is affected by the manner in which they are exposed to unrestrained, sexually receptive females. Twelve Angus bulls were used in a crossover design involving two treatments, each tested four times for a total of eight tests for each bull. Sexual interactions were quantified for each of four, 30-min periods under the following treatments: 1) exposure to each of four estrual females in sequence (SEQ); or 2) exposure to four estrual females as a group (GRP). Bulls were blocked into three testing groups, the order of which was stratified across eight test days. The order in which bulls were tested on a particular day had no effect on bulls' expression of mount interactions, or flehmen responses, suggesting that each group of bulls had similar sexual motivation at the beginning of each test. However, the bull testing order x treatment x time interaction influenced mounting interval (P = 0.08), copulation frequency (P <0.05), and copulation success ratio (P <0.05). When bulls were in GRP and tested first on test days, more (P <0.05) copulations were distributed to the first three females encountered compared with either the fourth female (P <0.05) or to each of the other females in SEQ (P <0.05). During later tests, other bulls in GRP were not able to copulate as frequently (P <0.05) with each female, displayed lower (P <0.05) copulation success ratios, and were allowed copulations by fewer (P <0.05) females during each 30-min test. When bulls were in SEQ, they displayed similar numbers of copulations regardless of the order in which they were tested, and had stable mounting intervals; however, copulation success ratio decreased (P <0.05) more rapidly during subsequent tests. Flehmen responses were initially displayed more frequently (P <0.05) when bulls were in GRP, but this effect diminished during subsequent 30-min tests. In conclusion, exposure of bulls to GRP induced greater sexual responsiveness than SEQ; however, this effect was due to enhanced sexual activity during the early stages of sexual encounters and with females that were not recently mated. Interestingly, bulls seem to repeatedly copulate with each individual female until, apparently, female sexual receptivity became attenuated. Thereafter, recently mated females allowed fewer episodes of repeated copulations, but they did not completely cease copulating with novel bulls.

Effects of novel females and stage of the estrous cycle on sexual behavior in mature beef bulls.

The objective of this experiment was to determine the effects of unrestrained females on sexual behavior of bulls. Twelve Angus bulls were used in three Latin square replicates where sexual interactions between one bull and one female were quantified for each of four 60-min tests (T1, T2, T3, and T4, respectively). All bulls received the following treatments: 1) exposure to four estrual females in sequence (A-B-C-D); 2) exposure to two estrual females in alternating sequence (E-F-E-F); 3) exposure repeatedly to one estrual female (G-G-G-G); and 4) exposure repeatedly to one diestrous female (CON). During T1, mount interactions, mounts with intromission and mounting intervals were similar when bulls were in A-B-C-D, E-F-E-F, or G-G-G-G. Fewer mount interactions, no mounts with intromission, and increased mounting intervals (P < 0.05) occurred in CON. During T2, there were more mount interactions, more mounts with intromission, and decreased mounting intervals (P < 0.05) when bulls were in A-B-C-D or E-F-E-F compared with when they were in G-G-G-G or CON. More mount interactions (P < 0.05) occurred in G-G-G-G compared with CON, but mounts with intromission and mounting intervals did not differ. During T3, more mount interactions (P < 0.05) occurred in G-G-G-G than in CON; otherwise, sexual behaviors were similar among treatments. Mounting intervals during T3 were similar among A-B-C-D, E-F-E-F, and G-G-G-G, but were all decreased (P < 0.05) compared with CON. During T4, more mount interactions, more mounts with intromission, and decreased mounting intervals (P < 0.05) occurred when bulls were in A-B-C-D compared with other treatments. Mount interactions were similar when bulls were in E-F-E-F, G-G-G-G, or CON; however, more (P < 0.05) mounts with intromission occurred when bulls were in E-F-E-F compared with G-G-G-G or CON. Mounting intervals during T4 were decreased (P < 0.05) in E-F-E-F compared with the CON treatment, whereas in G-G-G-G, they were intermediate. Mounts without intromission were not affected by female novelty or receptivity, but novel females induced more flehmen responses. In conclusion, novel, females, overall, enhanced sexual activity of bulls; however, bull sexual responses diminished after 2 h, even when a novel female was presented. Estrual females that were repeatedly paired with bulls displayed diminished sexual receptivity, but if mated females were rested for 60 min, they allowed further copulation from familiar bulls that were not sexually sated.

Effect of supplemental nutrient source on heifer growth and reproductive performance, and on utilization of corn silage-based diets by beef steers.

Two experiments were conducted to determine effects of oilseeds or soybean hulls on growth and reproductive performance of heifers and utilization of corn silage diets by growing beef cattle. In Exp. 1, 96 beef heifers (249 kg of BW) were used in a randomized complete block design. Treatments were as follows: 1) corn and soybean meal (CON) at 56% of the DMI; 2) whole linted cottonseed at 15% of the DMI (COT); 3) whole raw soybeans at 15% of the DMI (SB); or 4) pelleted soyhulls at 30% of the DMI (SH). Diets were formulated to be isonitrogenous (13.8% CP) and fed to achieve target weights equal to 65% of expected mature BW at the time of AI. Estrus was synchronized and heifers were inseminated by AI in response to detected estrus. Because the energy value for SH was underestimated, cumulative ADG for SH (1.03 kg/d) was greater (P < or = 0.03) than for CON (0.89 kg/d), COT (0.87 kg/d), or SB (0.86 kg/d). Treatment did not affect (P > 0.10) the proportion of pubertal heifers at the beginning of the breeding season: CON (60%), COT (53%), SB (69%), SH (71%), or first-service conception rates: CON (37%); COT (38%); SB (57%); SH (42%). In Exp. 2, crossbred steers (387 kg) were used in a 6 x 6 Latin square design to evaluate the effects of supplemental nutrient source on utilization of corn silage diets. Treatments included diets used in Exp. 1, plus a negative control (soybean meal at 10% of the DMI; SIL) and whole raw soybeans at 25% of the DMI (SB25). Diets were formulated to be isonitrogenous (13.8% CP) except SB25 (17% CP), and were fed twice daily at 1.8 x NEm. Oilseed inclusion decreased (P < 0.10) acetate:propionate ratios and (P < 0.10) apparent ruminal OM and ruminal and total tract NDF digestibilities. The CON and SH diets had the greatest (P < 0.10) total-tract OM digestibilities. Microbial efficiencies were greatest (P < 0.10), and long chain fatty acid flow to the duodenum increased (P < 0.10) with oilseeds. Biohydrogenation averaged 90.4% and increased slightly (P < 0.10) when oilseeds were added to the diet. Adding oilseeds or soybean hulls to corn silage-based diets did not affect reproductive performance of heifers. Although oilseed additions increased total fatty acid flow to the duodenum, a high degree of biohydrogenation occurred, greatly increasing C18:0, with only marginal increases in unsaturated fatty acid flow. Depending on diet and feeding conditions, inclusion of whole oilseeds may not be an effective means of increasing linoleic acid supply for ruminant animals.

Development of a progestin-based estrus synchronization program: I. Reproductive response of cows fed melengestrol acetate for 20 days with an injection of progesterone.

We designed two experiments to determine the efficacy of an estrus control system in cows that combined long-term progestin exposure (20 d) with an acute increase in progesterone concentration. In Exp. 1, cows (n = 30) were fed either melengestrol acetate (MGA; .5 mg x cow(-1) x d(-1)) or ground ear corn (MGA carrier) for 20 d. On d -15 (last day of MGA feeding = d 0), cows were administered 25 mg of PGF2alpha to regress the corpus luteum (CL) and establish an environment conducive to the development of persistent follicles. To synchronously regress persistent follicles, cows fed MGA (n = 15) were injected with 200 mg of progesterone on d -2 (MGA-P), and the cows fed the MGA carrier were not treated (CONT; n = 15). Cows in the CONT group were artificially inseminated 12 h after detection of spontaneous estrus from d -20 to d 8. Estrus was observed, and all cows in the MGA-P group were artificially inseminated during the period of estrus synchronization (SYNC; d 1 to 8). No difference in conception rate was observed between treatments. In Exp. 2, postpartum cows (n = 113) received either the MGA-P (n = 56) or CONT (n = 57) treatment. More (P < .05) cows were observed in estrus during SYNC in the MGA-P (50%) than in the CONT (28%) group. Of the cows in the MGA-P group that were not observed in estrus during SYNC, 50% were in estrus for the first time 23 to 29 d after MGA withdrawal (SYNC2), suggesting that these cows ovulated without observable estrus during SYNC. Estrus was observed for the first time during SYNC2 in more (P < .05) cows in the MGA-P (25%) than in the CONT (7%) group. Conception rate at the synchronized estrus, pregnancy rate, and interval to first service and pregnancy were similar between treatments. We conclude that administration of MGA-P results in the synchronization and(or) induction of a fertile estrus in cows.

Development of a progestin-based estrus synchronization program: II. Reproductive response of cows fed melengestrol acetate for 14 days with injections of progesterone and prostaglandin F2alpha.

We tested the efficacy of an estrus control system designed to provide optimal control of follicular development. In Exp. 1, postpartum cows (n = 133) and yearling heifers (n = 57) were fed either .5 mg x female(-1) x d(-1) of melengestrol acetate (MGA) or the carrier for MGA from d -13 to d 0 (d 0 = last day of MGA feeding). All females received 25 mg of PGF2alpha (i.m.) on d -13 and 0. On d -6, cows and heifers fed MGA were administered an i.m. injection of progesterone (200 mg; MGA/P4), and those fed the corn carrier (2XPGF2alpha) received no progesterone. Beginning on d 1, females were bred by AI from d 1 to at least d 5. During the estrus synchronization period (d 1 to d 5), more (P < .05) postpartum cows were observed in estrus (70.1 vs 42.4%), the timing of estrus was more (P < .05) precise, conception rate was similar, and pregnancy rate was higher (P < .05) in the MGA/P4 than in the 2XPGF2alpha treatment. More (P < .05) cows that were anestrous at the beginning of the breeding season were in estrus during the synchronization period in the MGA/P4 (55.8%) than in the 2XPGF2alpha (28.6%) treatment. In heifers, estrus was synchronized in over 90% of females, and neither conception nor pregnancy rate during the synchronization period differed between treatments. In Exp. 2, postpartum cows (n = 122) and heifers (n = 84) received treatments (MGA/P4 or 2XPGF2alpha) as described for Exp. 1 with one exception. In the MGA/ P4 treatment, progesterone was administered on d -7 rather than d -6. Females were bred by AI from d 1 to 5. The estrus response and conception rate during the synchronization period did not differ between treatments for either cows or heifers. We conclude that the progestin-based estrous synchronization system used in this study effectively synchronized an estrus of normal fertility in cyclic cows and induced a majority of anestrous cows to reinitiate estrous cycles.

Effect of induced alkalosis on exhaustive leg press performance.

PURPOSE: Fifteen males were studied before, during, and in recovery from exhaustive resistance exercise 105 min after ingesting 0.3 g.kg-1 of either a placebo (white flour) or sodium bicarbonate (NaHCO3). METHODS: The exercise consisted of five maximal sets on a leg press machine, The load was adjusted to maintain the number of repetitions per set for each subject at approximately 12 repetitions. A significant (P < 0.05) increase in pH (7.40 to 7.47), oxygenated base excess (OxyBE) (-1.3 to 4.0 mEq.L-1), and bicarbonate concentration ([HCO3-]) (22.8 to 27.4 mM) was achieved before exercise with the ingestion of NaHCO3. RESULTS: The exercise protocol produced significant changes in acid base status consistent with metabolic acidosis for both trials (pH sets 1-5: placebo, 7.4 to 7.26; NaHCO3, 7.47 to 7.33), (OxyBE sets 1-5: placebo, -1.3 to -12.3 mEq.L-1; NaHCO3, 4.0 to -6.9 mEq.L-1) and ([HCO3-] sets 1-5: placebo, 22.9 to 14.0 mM; NaHCO3, 27.4 to 17.6 mM). After every set; pH, OxyBE, and [HCO3-] were significantly higher in the NaHCO3 trial. Blood lactate concentration ([La-]) significantly increased throughout exercise for both trials ([La-] sets 1-5: placebo, 4.6 to 11.3 mM; NaHCO3, 4.8 to 13.4 mM). After sets 4 and 5, blood [La-] was significantly higher in the NaHCO3 trial. Bicarbonate ingestion did not improve performance (total repetitions: NaHCO3 = 59 +/- 3; placebo = 60 +/- 2). CONCLUSIONS: This may be a result of a lower demand on the whole body metabolic system in comparison with that for other modes of exercise in which ergogenic effects have been found.

Duration of treatment with progesterone and regression of persistent ovarian follicles in cattle.

The objective of the present study was to determine the duration of elevated concentrations of progesterone necessary to induce atresia of persistent ovarian follicles. Heifers were administered 25 mg of PGF2alpha on d 6 and 7 (d 0 = d of synchronized estrus) and a norgestomet implant from d 6 to 14. Ovaries were monitored by ultrasonography, and blood samples were collected on d 3, 5, 7, 9, 11, and 12 and daily from d 14 until ovulation. On d 12, heifers received either two progesterone-releasing intravaginal devices (PRID) for 6 h (6-h; n = 5), two PRID for 24 h (24-h; n = 5), or no treatment (CON; n = 5). Blood samples were collected at 15-min intervals from h -6 to 30 (PRID insertion = h 0) and analyzed for concentrations of LH. Characteristics of LH secretion were determined for consecutive 6-h periods (Period 0 to 5). Hourly blood samples, collected from h 0 to 29, were analyzed for concentrations of 17beta-estradiol (estradiol) and progesterone. The dominant ovarian follicles present on d 7 increased in size to 15.4+/-.3 mm on d 12 ("persistent follicle"). Following removal of the PRID and norgestomet implants, atresia of persistent follicles and ovulation of new follicles were induced in one of five and in four of five heifers in the 6-h and 24-h treatments, respectively. Persistent follicles ovulated after withdrawal of norgestomet in all other heifers. Concentrations of progesterone were increased from h 1 to 7 in the 6-h and h 1 to 26 in the 24-h treatment. Frequency of LH pulses was reduced (P < .05) during Periods 1 to 2 in the 6-h and Periods 1 to 5 in the 24-h treatment relative to the CON treatment. By h 10, concentrations of estradiol in the 6-h and 24-h treatments were lower (P < . 05) than in the CON treatment. This suppression continued through h 29 in the 24-h treatment (P < .05), whereas concentrations in the 6-h treatment were intermediate to those of the CON and 24-h treatments after h 14. Suppression of pulsatile LH release and estradiol secretion was evident with 6 and 24 h of treatment with progesterone, but only the 24-h treatment induced atresia of persistent follicles in a majority of the heifers.

Progestin-induced puberty and secretion of luteinizing hormone in heifers.

Two experiments were designed to investigate the endocrine mechanisms by which progestin administration induces puberty in heifers. In experiment 1, prepubertal heifers were randomly assigned by age to receive either a single norgestomet implant for 10 days (NORG; n = 15) or to serve as unimplanted controls (CONT; n = 14). Serial blood samples were obtained on Days -0.5, 8.5, and 10.5 (Day 1 = day of implant insertion) and were analyzed for concentrations of LH. On days 9 and 11, 4 heifers in each treatment were slaughtered, and the reproductive tracts were obtained. Weekly progesterone analyses were performed to estimate the day of puberty in heifers not slaughtered. Puberty was induced in 6 of 7 heifers in the NORG treatment, resulting in an earlier (p < 0.05) day of puberty in the NORG than in the CONT treatment. The frequency of LH pulses was higher (p < 0.05) on Days 8.5 and 10.5 in the NORG as compared to the CONT treatment. Although no difference (p > 0.10) was observed between treatments in follicular development, uterine weight was greater (p < 0.05) in NORG than in CONT heifers on Day 11. In experiment 2, prepubertal heifers (n = 47) were administered either 1 (1NORG; n = 16), 3(3NORG; n = 16), or 0 (CONT; n = 15) norgestomet implants for 10 days, and serial blood samples were obtained as described for experiment 1. Transrectal ultrasonography was used to determine the diameter of the largest follicle on Day 9. Plasma samples were obtained after each serial sample collection period and were analyzed for estradiol concentrations. Puberty was induced in 75% (12 of 16) and 81% (13 of 16) of heifers in the 1NORG treatments, respectively. Four heifers in the 1NORG treatment, from which serial blood samples were collected, ovulated before removal of the progestin implant, and the LH data for this treatment were deleted. In the 3NORG treatment, LH pulse frequency was suppressed (p < 0.05) on Day 8.5, but was greater (p < 0.05) 12 h after removal of the progestin (Day 10.5) than in the CONT treatment. We conclude that progestin administration hastens puberty by increasing LH secretion after progestin withdrawal and propose that progestin administration induces puberty by accelerating the peripubertal decrease of estradiol negative feedback on LH secretion.

Effects of hyperoxia and caffeine on the expression of fragile site at Xq27.3.

To enhance the cytogenetic expression of the fragile X chromosome, we studied the effects of hyperoxia and caffeine on the induction of fragile Xq27.3. A lymphoblastoid cell line (GM 06912) derived from a fragile X male proband was cultured in RPMI 1640 containing 16% dialyzed fetal calf serum. The cells were synchronously subjected to one of 3 different atmospheric oxygen tensions (21%, 21.3 kPa, normoxic; 40%, 40.5 kPa, hyperoxic; or 60%, 60.8 kPa, hyperoxic) during the last 24 hours of the 72 hour culture, immediately after the addition of 2'-deoxy-5-fluorouridine (FUdR) at 25 ng/ml. To study the enhancing effect of caffeine, with or without hyperoxia, a second set of cultures was additionally subjected to caffeine (2.5 mM) during the last 6 hours of the culture. When the fragility of hyperoxic cells (38.1 kPa dissolved oxygen) was compared to that of normoxic control cells (13.3 kPa dissolved oxygen), the difference was significant (P < 0.05). These data suggest that there is a mean increase in the fragile Xq27.3 expressivity as the dissolved oxygen tension increases. Additionally, we observed that caffeine, with or without hyperoxia, significantly (P < 0.05) suppressed the expression of the fragile X site in this lymphoblastoid cell line.

Visual performance with the Aviator Night Vision Imaging System (ANVIS) at a simulated altitude of 4300 meters.

This study determined if visual performance with Aviator Night Vision Imaging System (ANVIS) was degraded by the degree of hypoxia experienced at the maximum flight altitude currently authorized (U.S. Army regulations) without supplemental oxygen. Visual acuity and contrast sensitivity with ANVIS were tested under simulated starlight and full moonlight illumination in a hypobaric chamber: at ground level (93 m), 5 min and 30 min after ascent to 4300 m, and 10 min after return to ground level. Visual acuity was significantly (p < 0.05) degraded by a small amount (0.05 log minimal angle resolvable) after 30 min at 4300 m. Contrast sensitivity was not significantly degraded at any time. No significant difference between males (n = 11) and females (n = 6) on any measure of visual performance was detected. Females did have a significantly lower percent oxygen saturation of hemoglobin compared with males at altitude (72% versus 80% after 30 min). The results suggests that visual acuity ANVIS is degraded slightly after 30 min of exposure to 4300 m, although less than what would be expected with unaided night vision under these conditions.

Successful negotiations. Develop your personal strategy for negotiating.

Successful managers are successful negotiators. This article addresses how to develop a negotiation strategy that fits an individual manager's personality and objectives. The authors provide 12 rules aimed at developing that personal strategy and also define the elements of power, skill, and timing, and their relevance to the negotiating process.

Acute progesterone administration regresses persistent dominant follicles and improves fertility of cattle in which estrus was synchronized with melengestrol acetate.

Experiments were conducted to determine whether acute progesterone administration would regress persistent follicles and improve fertility in heifers and postpartum cows fed melengestrol acetate (MGA). In Exp. 1, heifers (n = 13) were fed MGA for 11 d (1st d of MGA = d 1). Prostaglandin F2 alpha (PGF2 alpha) was administered to heifers on d 2 to regress the corpus luteum (CL). On d 9, heifers were randomly assigned to receive an injection of either 200 mg of progesterone (PROG) or no hormone (vehicle; VEH). Neither growth of the persistent follicle nor plasma estradiol concentrations were altered by administration of VEH, and the persistent follicle ovulated after cessation of MGA feeding. Administration of PROG regressed the persistent follicle, reduced (P < .05) systemic estradiol concentrations, and resulted in ovulation of a newly recruited follicle. In Exp. 2, heifers were fed MGA for 14 d and were administered either PROG (n = 30) or VEH (n = 31) on d 12. When the CL was absent on d 12, synchronization conception rate (SCR) and pregnancy rate (PR) were greater (P < .05) for heifers administered PROG than for those administered VEH. Neither SCR nor PR were different among treatments when the CL was present on d 12. In Exp. 3, cows (n = 49) were fed MGA for 14 d and were administered either PROG or VEH on d 12. In cows lacking a CL (n = 32), administration of PROG increased (P < .05) SCR, but not PR. We conclude that acute PROG administration induces turnover of persistent follicles and may increase fertility when estrus is synchronized with MGA.

Space shuttle flight (STS-45) of L8 myoblast cells results in the isolation of a nonfusing cell line variant.

Myoblast cell cultures have been widely employed in conventional (1g) studies of biological processes because characteristics of intact muscle can be readily observed in these cultured cells. We decided to investigate the effects of spaceflight on muscle by utilizing a well characterized myoblast cell line (L8 rat myoblasts) as cultured in the recently designed Space Tissue Loss Flight Module "A" (STL-A). The STL-A is a "state of the art," compact, fully contained, automated cell culture apparatus which replaces a single mid-deck locker on the Space Shuttle. The L8 cells were successfully flown in the STL-A on the Space Shuttle STS-45 mission. Upon return to earth, reculturing of these spaceflown L8 cells (L8SF) resulted in their unexpected failure to fuse and differentiate into myotubes. This inability of the L8SF cells to fuse was found to be a permanent phenotypic alteration. Scanning electron microscopic examination of L8SF cells growing at 1g on fibronectin-coated polypropylene fibers exhibited a strikingly different morphology as compared to control cells. In addition to their failure to fuse into myotubes, L8SF cells also piled up on top of each other. When assayed in fusion-promoting soft agar, L8SF cells gave rise to substantially more and larger colonies than did either preflight (L8AT) or ground control (L8GC) cells. All data to this point indicate that flying L8 rat myoblasts on the Space Shuttle for a duration of 7-10 d at subconfluent densities results in several permanent phenotypic alterations in these cells.

Luteal maintenance during early pregnancy in the pig: role for prostaglandin E2.

We previously demonstrated that prostaglandin E2 (PGE) directly inhibits prostaglandin F2 alpha (PGF)-induced regression of individual pig corpora lutea (CL) in a dose dependent manner. The present experiments were conducted to 1) characterize and compare uterine secretion of PGE and PGF during the estrous cycle and early pregnancy and 2) evaluate the local effect of the conceptus on uterine prostaglandin secretion and associated CL function in unilaterally pregnant pigs. In Experiment 1, utero-ovarian venous blood samples were collected from two nonpregnant and two pregnant gilts at 3-h intervals from day 10 through 16 (first day of estrus or mating = day 0) for quantitation of uterine PGE and PGF secretion. In Experiment 2, gilts (n = 4) were made unilaterally pregnant on day 2, and utero-ovarian venous catheters were placed bilaterally to determine if differences in PGE and/or PGF secretion might account for the known luteotrophic/antiluteolytic effect of the gravid uterine horn on the CL of the ipsilateral ovary. During the estrous cycle (Experiment 1), pulsatile secretion of PGF increased markedly on day 13 and continued to increase through day 16. PGE secretion also increased from day 13 to 16 of the estrous cycle; however, concentrations of PGE remained at least 3-fold lower than those of PGF. In contrast to changes in non-mated gilts, prostaglandin secretion in mated gilts peaked earlier (day 11-12), with PGE predominating. Thereafter, both PGE and PGF secretion declined to basal levels where they remained through day 16 of pregnancy. During unilateral pregnancy (Experiment 2), PGF concentration in nongravid and gravid horns was similar (P > 0.8). In contrast, PGE concentrations were greater (P < 0.06) in utero-ovarian venous blood draining the gravid uterine horn. This increase in PGE was associated with enhanced CL function on the ipsilateral ovary as evidenced by an elevated progesterone content and concentration as well as increased CL weights. These data are consistent with a role for conceptus-associated increases in uterine PGE secretion in the local stimulation of luteal function during early pregnancy in the pig.

Evaluation of antimicrobials combined with hyperbaric oxygen in a mouse model of clostridial myonecrosis.

The efficacy of hyperbaric oxygen (HBO) alone and in combination with several antimicrobial agents was evaluated in a lethal model of gas gangrene in mice. Intraperitoneal administration of penicillin, imipenem, clindamycin, or metronidazole immediately followed inoculation of > 10(9) CFU of Clostridium perfringens type A in mice. Mice treated with hyperbaric oxygen were exposed twice a day to 100% oxygen at 303 kilopascals (kPa) pressure for 90 minutes. The total exposure time to HBO for surviving animals was 9 hours. Control (saline-injected) mice treated with HBO alone did not have an enhanced survival rate when compared with mice exposed to air at ambient pressure. Survival of infected mice treated with either clindamycin or metronidazole was significantly longer than that of groups treated with penicillin or imipenem (p < 0.05). Hyperbaric oxygen alone or in combination with the four antimicrobial agents evaluated did not statistically improve survival of mice infected with a lethal dose of C. perfringens.

Hyperbaric hyperoxia enhances the lethal effects of amphotericin B in Leishmania braziliensis panamensis.

Leishmania braziliensis panamensis promastigotes were exposed in vitro to amphotericin B (AmB), menadione, or phenazine methosulfate under normoxic conditions. Promastigotes were also exposed to hyperoxia alone (100% O2 at total pressures of 101.3 or 253.3 kPa), or combined with drugs. After incubation for 24 h at 27 degrees C, viable promastigotes were stained with fluorescein diacetate and counted using epifluorescence microscopy. Hyperbaric hyperoxia alone (PO2 = 229.3 kPa) was as effective as AmB alone (0.2 microM); both reduced the number of viable promastigotes to approximately 13% of the original inoculum. In addition, AmB in a hyperbaric hyperoxic environment killed more promastigotes (97% of the original inoculum) than AmB in normoxic (PO2 = 21.1 kPa) or hyperoxic conditions (PO2 = 91.7 kPa). Finally, AmB in hyperbaric hyperoxia killed significantly more (75%) promastigotes than hyperbaric hyperoxia alone. High oxygen tensions did not significantly alter the lethal effects of either menadione or phenazine methosulfate. In conclusion, the lethal effects of low dose AmB in Leishmania promastigotes were augmented by hyperbaric hyperoxia in vitro, but only at oxygen doses too high to be tolerated by human patients.