Changes in serum testosterone and anti-Müllerian hormone concentration in bulls undergoing scrotal insulation.

While changes in semen quality after heat stress are well characterized in the bull, changes in endocrine function have not been critically evaluated. It was hypothesized here that scrotal insulation results in alterations in Sertoli cell and Leydig cell function, as measured by changes in serum testosterone and anti-Müllerian hormone (AMH) concentration. Scrotal insulation bags were placed in 10 bulls for 8 d. Blood was collected on days -22 and -2, and weekly from days 5 to 96 (day 0 = first day of scrotal insulation) for measurement of serum concentration of AMH and testosterone using ELISA. The concentration of AMH decreased on day 5, followed by an increase on day 54 (P = 0.014). When AMH concentration was normalized to pre-insulation values, the percent increase in serum concentration of AMH was significant between days 26 and 54, with another peak at 75 d (P = 0.031). The serum concentration of testosterone (P = 0.0001) and the percentage of change in testosterone concentration (P < 0.0001) increased on day 5, followed by a decrease from days 33 to 96. Scrotal insulation was associated with Sertoli and Leydig cell dysfunction, as measured by serum testosterone and AMH concentration. The persistently low concentration of testosterone at the end of the study suggests a long term effect of scrotal insulation on Leydig cell function.

Sperm-bound antisperm antibodies prevent capacitation of bovine spermatozoa.

It was hypothesized here that sperm-bound antisperm antibodies (ASAs) impair the ability of bovine spermatozoa to undergo capacitation, bind to the zona pellucida, and complete the acrosome reaction. The effect of ASA binding on these functions was evaluated in frozen/thawed spermatozoa from four bulls before and after induction of ASAs. Ejaculates were divided into ASA negative (<10% immunoglobulin [Ig]G- and IgA-bound spermatozoa) or ASA positive (≥20% IgG and/or IgA-bound spermatozoa). The percentage of capacitated (Merocyanine 540 positive) live spermatozoa in response to heparin was lower in ASA-positive than ASA-negative ejaculates (P < 0.0001). Treatment with heparin resulted in a higher percentage of capacitated spermatozoa compared with control treatments in ASA-negative but not ASA-positive ejaculates. The percentage of capacitated spermatozoa after heparin treatment was negatively correlated with IgA (P = 0.02, R2 = -0.48) but not IgG binding. Sperm binding to the zona pellucida was lower in IgA-positive (six spermatozoa/oocyte; 3-10 spermatozoa/oocyte) than IgA-negative ejaculates (seven spermatozoa/oocyte; 4-13 spermatozoa/oocyte) (P = 0.019). Zona binding was negatively correlated with the percentage of IgA-bound spermatozoa (P = 0.04; R2 = -0.24) but not IgG-bound spermatozoa. The percentage of acrosome-reacted spermatozoa was higher in calcium ionophore A23187-treated than control aliquots in both ASA-negative and ASA-positive ejaculates (P < 0.0001). However, the percentage of acrosome-reacted spermatozoa did not differ between ASA-positive and ASA-negative samples, and no correlation was identified with IgG or IgA binding. It was concluded that sperm-bound IgA affected the ability of bovine spermatozoa to undergo capacitation. ASAs inhibited the changes in plasma membrane fluidity associated with capacitation and binding of spermatozoa to the zona pellucida.

Limits on gravitational-wave emission from selected pulsars using LIGO data.

We place direct upper limits on the amplitude of gravitational waves from 28 isolated radio pulsars by a coherent multidetector analysis of the data collected during the second science run of the LIGO interferometric detectors. These are the first direct upper limits for 26 of the 28 pulsars. We use coordinated radio observations for the first time to build radio-guided phase templates for the expected gravitational-wave signals. The unprecedented sensitivity of the detectors allows us to set strain upper limits as low as a few times 10(-24). These strain limits translate into limits on the equatorial ellipticities of the pulsars, which are smaller than 10(-5) for the four closest pulsars.