Search

Bos taurus indicusfemales provide a greater in vivooocyte recovery (2-4 times more) in comparision with Bos taurus taurus. This aspect has strongly contributed for the success of the embryo industry in Brazil. Little information is available to explain this difference. Our objective was to test the hypothesis that the difference in oocyte yield is a result of higher numbers of preantral follicles in the ovaries of B. indicusfemales. Ovaries (n= 44) of fetuses aging from 180 to 240 days and of heifers from 20 and 24 months were collected from Bos taurus indicus(Nelore) and Bos taurus taurus(Aberdeen Angus) females at a slaughterhouse. Fetal age was estimated from the crown-rump length (Evans HE and Sack WO 1973 Anat. Hist. Embryol. 2, 11-45). Ovaries from Nelore fetuses (n= 10) and heifers (n= 12) and Aberdeen Angus fetuses (n= 10) and heifers (n= 12) were cut longitudinally into two halves, fixed in Bouin''s solution, and processed for histological evaluation. The ovarian halves were dehydrated in alcohol, cleared with xylene, embbebed in paraffin, and serially sectioned at 7 μm. Every 120th section was mounted and stained with periodic acid Schiff and hematoxylin. The number of preantral follicles was estimated through the counting of follicles in each section using the nucleus of the oocyte as a marker and a correction factor (Gougeon A and Chainy GBN 1987 J. Reprod. Fertil. 81, 433-442). Only 1 ovary per female was analyzed. Preantral follicles were classified according to the developmental stage as primordial (1 layer of flattened granulosa cells surrounding the oocyte), primary (1 layer of cuboidal granulosa cells), or secondary (2 or more layers of cuboidal granulosa cells), and as normal or degenerated according to their morphological appearance. The number of preantral follicles was not normally distributed and was compared using the Mann-Whitney test. There was no difference (P> 0.05) between the average number of preantral follicles in the ovaries of Bos indicusand Bos taurusfemales. The average number of preantral follicles per female was 143 929 ± 253 (mean ± SD) and 285 155 ± 570 for Bos taurusand Bos indicusfetuses, respectively, and 76 851 ± 280 and 109 673 ± 293 for Bos taurus andBos indicus heifers (P> 0.05), respectively. A large variation in numbers of preantral follicles was observed among individuals within the same category and between breeds. Our results suggest that there might be differences in mechanisms controlling follicle development after the preantral stage accounting for the greater oocyte yield from Bos indicusfemales. This work was supported by grants from the Universidad Nacional del Litoral (CAI+D program), Universidad Nacional de Lomas de Zamora, the Argentine National Agency for the Promotion of Science and Technology (ANPCyT), and the Argentine National Council for Science and Technology (CONICET). [ABSTRACT FROM AUTHOR]

The development of culture systems to support the initiation of growth of primordial follicles is important to the study of the factors that control the earliest stages of folliculogenesis. The aims of the present study were to investigate the effects of α-tocopherol on survival, activation, and growth of cattle preantral follicles using histological and immunohistochemistry proliferating cell nuclear antigen (PCNA) studies. The ovarian cortex was divided into small fragments; one fragment was immediately fixed in Bouin (control). The other fragments were cultured for 2, 4, 6, or 8 d in culture plates with Minimum Essential Medium supplemented with insulin-transferrin-selenium (ITS), pyruvate, glutamine, hypoxanthine, BSA, and antibiotics (MEM+); and MEM+ plus α-tocopherol (5, 25, 50, 100, or 200 ng mL-1). Preantral follicles were classified according to their developmental stage (primordial, intermediate, primary, or secondary) and on the basis of morphological features (normal or degenerated). Pair-wise comparisons were done using Tukey''s procedure. Chi-square test was used to compare the percentage of follicles with PCNA-positive granulosa cells. All analyses were done with the SAS software (SAS Institute, Cary, NC, USA), and P< 0.05 was considered significant. The results showed that, compared with non-cultured cortical tissue (Day 0), the culture of ovarian tissue significantly reduced (P< 0.05) the percentage of normal follicles in all media tested, except for tissue cultured in the presence of 200 ng mL-1of a-tocopherol. Furthermore, in all media tested, the percentage of primordial follicles was significantly reduced (P< 0.05), with a concomitant increase in the percentage of developing follicles. The highest percentage of secondary follicles was observed after 6 days of culture in MEM plus 200 ng mL-1of a-tocopherol. The PCNA analysis confirmed the viability of follicles cultured with 200 ng mL-1of a-tocopherol after 6 d. After 8 days of in vitroculture, we observed severe follicular degeneration in all media tested, suggesting that other supplements are recommended for longer periods of culture. In conclusion, the results of the present study indicate that 200 ng mL-1of a-tocopherol maintains the survival of cattle preantral follicles and promotes activation of primordial follicles after 6 days of in vitroculture. Financial support: L. A. Lisboa is a recipient of CAPES support; E. R. Andrade and A. A. Alfieri are recipients of PRODOC/CAPES fellowships. [ABSTRACT FROM AUTHOR]

The mechanisms that regulate the gradual exit of ovarian follicles from the nongrowing, primordial pool are poorly understood. The objective of this study was to evaluate the effects of adding ascorbic acid to the media for in vitroculture of cattle ovarian fragments and to determine the effects of this addition on the growth activation and viability of preantral follicles. The ovarian cortex was divided into small fragments; 1 fragment was immediately fixed in Bouin''s solution (control). The other fragments were cultured for 2, 4, 6, or 8 days on culture plates in minimum essential medium (MEM) supplemented with insulin-transferrin-selenium (ITS), pyruvate, glutamine, hypoxantine, BSA, and antibiotics (MEM+) or in MEM+ plus ascorbic acid (5, 25, 50, 100, or 200 μg mL-1). Ovarian tissue was processed for classical histology, TEM, and immunohistochemical demonstration of proliferating cell nuclear antigen (PCNA). Preantral follicles were classified according to their development stage (primordial, intermediate, primary, and secondary) and on the basis of morphological features (normal or degenerated). Pair-wise comparisons were done using Tukey''s procedure. Chi-square test was used to compare percentages of follicles with PCNA-positive granulosa cells. All analyses were done with Statistical Analysis System (SAS Institute, Cary, NC, USA); P≤ 0.05 was considered significant. Compared with control fragments, the percentage of primordial follicles was reduced (P≤ 0.05) and the percentage of growing follicles was increased (P≤ 0.05) in cultured cortical fragments, independent of the tested medium or incubation time. Furthermore, compared with control tissue, culture of ovarian cortex for 8 days reduced the percentages of healthy, viable follicles (P≤0.05), but not when cultures were supplemented with 25, 50, and 100 μg mL-1of ascorbic acid. Ultrastructural and immunohistochemical analysis of ovarian cortical fragments cultured for 8 days, however, showed the integrity and viability of follicles only when fragments were cultured in the presence of 50 μg mL-1of ascorbic acid. In conclusion, this study demonstrated that addition of ascorbic acid to MEM at a concentration of 50 μg mL-1not only stimulates the activation and subsequent growth of cattle primordial follicles that are cultured in vitrofor 8 days but also safeguards the viability of these preantral follicles. E. R. Andrade and A. A. Alfieri are recipients of the PRODOC/CAPES fellowship. [ABSTRACT FROM AUTHOR]

Forest soils have a large capacity of stocking and cycling carbon, incorporated by organic matter and evaded by roots and soil microbiota as CO2. Soil respiration can indicate ecosystem processes, but little is known about the successional, seasonal and diurnal variation in CO2 flux. This study presents estimations of soil CO2 efflux in a seasonal Atlantic forest fragment (FF) and an adjacent 15 years-old restoration site (RS), in two seasons (winter-dry and summer-rainy), during 24-hour periods, in southern Brazil. Measurements were performed with an infrared gas analyser at 2-hour intervals. Respiration rates were 50% higher in the rainy season, both in FF (261, against 135 mg m-2 s-1 in the dry season) and RS (237 and 127 mg m-2 s-1), indicating that higher humidity and temperature promoted higher soil biota activity. The soil respiration was higher at FF only in the dry season, revealing that this environment may be less sensitive to water limitation. Greater overnight respiration was observed in the dry season for both sites, likely reflecting more intense microbial metabolism at night in this season. There was no rainy season diurnal variation. Seasonal and daily variation suggests that soil respiration in the RS is more sensitive to warmer and dryer conditions. [ABSTRACT FROM AUTHOR]

The number of oocytes recovered from Bos taurus indicus females subjected to ovum pick-up averaged two to four times greater compared to Bos taurus taurus females. The objective of the present study was to test the hypothesis that this difference in oocyte yield was due to more preantral follicles in the ovaries of Bos indicus females. Ovaries (n = 64) from Nelore (Bos indicus) fetuses (n = 10), heifers (n = 12), and cows (n = 10), and Aberdeen Angus (Bos taurus) fetuses (n = 10), heifers (n = 12), and cows (n = 10) were cut longitudinally into halves, fixed, and processed for histological evaluation. The number of preantral follicles was estimated by counting them in each histological section, using the oocyte nucleus as a marker and employing a correction factor. The average number of preantral follicles in the ovaries of Bos indicus vs Bos taurus was (mean ± SD) 143,929 ± 64,028 vs 285,155 ± 325,195 for fetuses, 76,851 ± 78,605 vs 109,673 ± 86,078 for heifers, and 39,438 ± 31,017 vs 89,577 ± 86,315 for cows (P > 0.05). The number of preantral follicles varied greatly among individual animals within the same category, as well as between breeds. In conclusion, we inferred that the higher oocyte yield from Bos indicus females was not due to a greater ovarian reserve of preantral follicles. Therefore, mechanisms controlling follicle development after the preantral stage likely accounted for differences between Bos indicus and Bos taurus females in number of oocytes retrieved at ovum pick-up., (Copyright © 2011 Elsevier Inc. All rights reserved.)