Duration of spermatogenesis and daily sperm production in the jaguar (Panthera onca).

The jaguar, like most wild felids, is an endangered species. Since there are few data regarding reproductive biology for this species, our main goal was to investigate basic aspects of the testis and spermatogenesis. Four adult male jaguars were utilized; to determine the duration of spermatogenesis, two animals received an intratesticular injection of H(3)-thymidine. Mean (+/-SEM) testis weight and the gonadosomatic index were 17.7+/-2.2g and 0.05+/-0.01%, respectively, whereas the seminiferous tubules and the Leydig cells volume density were 74.7+/-3.8 and 16.7+/-1.6%. Eight stages of spermatogenesis were characterized, according to the tubular morphology system and acrosome development. Each spermatogenic cycle and the entire spermatogenic process (based on 4.5 cycles) lasted approximately 12.8+/-0.01 and 57.7+/-0.07 d. The number of Sertoli and Leydig cells per gram of testis was 29+/-4 x 10(6) and 107+/-12 x 10(6). Based on the number of round spermatids per pachytene spermatocyte (2.8+/-0.3:1; meiotic index); significant cell loss (30%) occurred during the two meiotic divisions. There were approximately eight spermatids for each Sertoli cell (Sertoli cell efficiency), whereas the daily sperm production per gram of testis was 16.9+/-1.2 x 10(6). We expect that in the near future, the knowledge obtained in the present investigation will facilitate, utilizing germ cell transplantation, preservation of the germinal epithelium and the ability to generate sperm from jaguars in testes of domestic cats.

Estimation of the lactate threshold using bioelectrical impedance spectroscopy: a new noninvasive method.

Bioelectrical Impedance Spectroscopy (BIS) is a noninvasive technology with potential application to study exercise physiology as body composition and estimation of maximal oxygen uptake. The aim of the study was to compare the power at lactate threshold (WLT) obtained using blood lactate concentration (BLC) with the power at lactate threshold from BIS (WBT). Fifty physical education students, 35 men and 15 women (age: 24.1 +/- 5.5 years; height: 168.6 +/- 24.6 cm; weight: 70.1 +/- 9.8 kg), undergoing incremental cycle ergometer test (ICET) have participated of the study. Significant correlations (p<0.05) for Pearson coefficient were found between the two methods (r = 0.96) and standard error of estimate (SEE)=5.6 W. The mean value showed 66.7+/- 20.3 W and 66.7+/- 21.1 W between the invasive technique (WLT) and noninvasive technique (WBT), respectively. The results of this study suggest that BIS, when applied with the ICET, is a valid method to estimate the power at LT.