[Protective role of glutathione in buck semen cryopreservation]

The aim of this study was to determine the effect of low levels of glutathione on post-thawed buck sperm quality. In this experiment, different concentrations of glutathione [0 [LG-0], 0.5 [LG-0.5], 1 [LG-1], 1.5 [LG-1.5], and 2 [LG-2] mM] were added in a soybean lecithin-based extender. A total of 16 ejaculates from four bucks were collected and pooled. Each pooled sample was divided into five equal parts and each part was diluted by one of the above mentioned groups. After freeze-thawing process, motility and velocity, plasma membrane integrity and functionality, and apoptosis features of spermatozoa were evaluated. The results of this experiment showed that total motility [50.75 +/- 2.33], plasma membrane integrity [55.75 +/- 3.01] and functionality [46.75 +/- 2.79] were higher in LG-1 extender compared to other extenders [P<0.05]. The percentage of live spermatozoa [53.23 +/- 3.26] was higher in LG-1 extender compared to other extenders, with the exception of LG-1.5 extender [P<0.05]. Also, the percentage of late apoptotic spermatozoa [21.33 +/- 1.63] was lower in LG-1 extender compared to other extenders [P<0.05]. In conclusion, our results showed that GL-1 extender resulted in higher post-thawed buck sperm quality compared to other extenders.

effect of all-trans retinol on in vitro mouse embryo's developmental competence

All-trans retinol is a biological antioxidant scavenging the ROS in the cell culture. This study was conducted to investigate the effect of all-trans retinol in fertilization and culture medium on mouse embryo's developmental competence. This study was designed into two experiments. In the first experiment, in vitro mature oocytes were co-cultured with sperm in fertilization medium containing different concentrations of all-trans retinol [0, 1, 5, and 10 micro M]. After fertilization, zygotes in each group were separately cultured in CZB culture medium for 5 days to the blastocyst stage. In the second experiment, in vitro produced zygotes were cultured in CZB culture medium containing different concentrations of all-trans retinol [0, 1, 5, and 10 micro M] for 5 days to the blastocyst stage. In the first experiment, the blastocyst formation rate significantly increased by 5 micro M in all-trans retinol, which was more than those of the other groups. Also, percentage of grade one embryos was significantly higher in the presence of 5 micro M all-trans retinol than those in the presence of 0 and 1 micro M all-trans retinol. In the second experiment, different concentrations of all-trans retinol could not alter blastocyst formation rate; however, the percentage of grade one embryo was higher in the presence of 10 micro M all-trans retinol than that of the control group. These results showed that supplementation of fertilization medium with 5 micro M alltrans retinol could improve mouse embryo's development and morphology. On the other hand, supplementation of embryo culture medium can improve mouse embryo morphology without any effect on embryo developmental competence

[Effects of feeding frequency on carcass characteristics and plasma leptin and insulin concentrations in fattening calves]

Increased feeding frequency improve bioenergetics efficiency in lactating cows; however, there is little information about its effect on fattening animals. Twelve Holstein bull calves were allotted to two groups to determine the effect of feeding frequency on body weight, carcass quality and hormonal profiles. Control group was fed twice a day and treated group was fed six times a day by a standard diet for eight months. Body weight was recorded at 3 weeks interval. Blood samples were collected one hour after feeding at four hours intervals during 24 hours at the end of experiment. Calves were slaughtered and carcass characteristics were measured. Plasma leptin concentrations were higher [p<0.01] in treated group than those in control group. Plasma insulin concentrations were lower [p<0.01] in treated group than those in control group. Internal fat content and depth of subcutaneous fat were [p<0.05] higher in control group than those in treated group. It can be concluded that feeding frequency for growing Holstein calves resulted in decreased fat reservoirs and this effect may be mediated by plasma leptin and insulin changes

Changes in the plasma concentrations of thyroid hormones in ewes and the effect of intravenous injection of leptin on their levels

The aim of this study was to determine changes in the concentration of leptin and thyroid hormone in energyrestricted ewes and effect of leptin injection on thyroid hormone level. In the first experiment, 28 ewes were assigned to two groups [n = 14]. Ewes were fed by a ration that provided 60% or 100% of maintenance energy requirements during 71 days. Blood samples were collected and body weight [BW] and body condition score [BCS] were determined. In the second experiment, 6 energy-restricted ewes from the first experiment were selected and assigned to two groups [n = 3]. Ewes were fed a ration that provided 60% of maintenance energy requirements and injected by 1 or 4 micro leptin/Kg BW. Blood samples were taken and BW and BCS were determined. In the first experiment, concentrations of leptin, T[3] and T[4], BW and BCS were decreased in energyrestricted ewes [p < 0.01]. In the second experiment, concentration of T[3], T[4] and leptin were increased by leptin injection [p < 0.01]. The results suggested leptin injection may restore thyroid hormone secretion to normal levels in energy-restricted ewes

[ effect of L-tryptophan on growth hormone and thyroid hormones secretion in growing lambs]

Survey on effects of serotonin agonist on the plasma concentrations of growth hormone [GH] and thyroid hormones [T[3] and T[4]; TH]. Repeated measures [GLM] were used. Twenty Kurdish lambs 3-4 months old. Animals were randomly divided into four groups. The first group [control] received 2 ml normal saline. The second, third and fourth groups received 120, 240 and 480 mg/kg body weight L-tryptophan through jugular vein, respectively. blood samples were collected in three periods including before [days 1, 4, 5 and 6], during [days 7, 8, 9, 10, 11, 12, 13, 14, 15, 18, 22, 26, 30 and 34] and after [days 36, 37 and 38] injections. Plasma concentrations of these hormones in unextracted samples were analyzed by radioimmunoassay kit [Tabeshyarnoor kits company, Tehran, Iran]. Injection of serotonin agonist increased mean plasma concentration [MPC] of GH [P<0.01]. There are no significant differences in MPC of GH within the treated groups. Effects of blood sampling times, period [before, during, after injection] and their interaction with treatment on MPC of GH were significant[ P<0.01]. MPC of TH [T[3] and T[4]] in all of the treated groups was significantly increased compare with control one [P<0.01]. There are no significant differences in MPC of TH within the treated groups. Effects of blood sampling times and period [before, during and after injection] and also their interactive effects with treatment were significant. According to statistical analysis of data we can suggest that serotonin agonist stimulates GH and TH secretion simultaneously

[ Effect of successive injections of naloxone on gonadotrophins secretion in ewe in nonbreeding season]

Objective: Determination of the Naloxone opioid antagonist effect on the LH and FSH secretion in ewe in non-breeding season

Design: Repeted measures

Animals: Six zandi breed ewes with average [ +/- SE] of weight and age, 42.4 ±4.2 and 760±8 respectively and all of ewes had one birth

Procedure: Ewes were recieved five injections of 0.5 or 0.2 mg naloxone/kg BW and followed by injection of 1 1 g gonadorelin /kg BW. Blood samples were collected every 15 minutes for 4 hours before injections until 4 hours after injections of naloxone and every 15 minutes for 1 hours after injection of gonadroline

Statistical analysis: Analysis of variation

Results: Mean plasma LH concentrations had been significantly increased in both groups after naloxone injections. LH pulses frequencies in both groups significantly increased after naloxone injections. Naloxone failed to alter pulsatile LH amplitudes in both groups. LH base concentrations increased in both groups after injections of naloxone but it was not significant. Also mean plasma LH concentrations had been significantly increased after gonadorelin injection. Mean plasma FSH concentrations, pulsatile frequencies, amplitudes and base concentrations of FSH did not change significantly

Clinical Implications: The results of this study indicate that the opioids may affect on LH pattern secretion in the ewes in nonbreeding season, but the effect of opioid on FSH secretion is not observed