Nelson Martínez

PGA1-induced apoptosis involves specific activation of H-Ras and N-Ras in cellular endomembranes.

The cyclopentenone prostaglandin A1 (PGA1) is an inducer of cell death in cancer cells. However, the mechanism that initiates this cytotoxic response remains elusive. Here we report that PGA1 triggers apoptosis by a process that entails the specific activation of H- and N-Ras isoforms, leading to caspase activation. Cells without H- and N-Ras did not undergo apoptosis upon PGA1 treatment; in these cells, the cellular demise was rescued by overexpression of either H-Ras or N-Ras. Consistently, the mutant H-Ras-C118S, defective for binding PGA1, did not produce cell death. Molecular analysis revealed a key role for the RAF-MEK-ERK signaling pathway in the apoptotic process through the induction of calpain activity and caspase-12 cleavage. We propose that PGA1 evokes a specific physiological cell death program, through H- and N-Ras, but not K-Ras, activation at endomembranes. Our results highlight a novel mechanism that may be of potential interest for tumor treatment.

Non-genetic factors affecting calving interval and weaning weight in a buffalo herd located in flooded savannas, Cojedes state, Venezuela

Abstract The objective of the research work was to characterize a buffalo herd in flooded conditions in Cojedes state, Venezuela, being evaluated the calving distribution (CD), calving interval (CI) and weaning weight (WW). Birth and productive records from Hato La Soledad were used to determine monthly frequencies of calving (n=2106), calving interval (n=936) and weaning weight (n=1683). The statistical analysis included year (CY) and calving season (CS), sex of calf (SC), age of cow (AC) and interactions for CI, including additionally age to weaning for WW. Results showed significant differences (P≤0.05) in CD between years associated with year-on-year changes in climatic factors and progressive stabilization of the herd. CI averaged 473.9±3.0 days ( X – ± S.E.), with a significant effect of calving month (P≤0.05). CI in the herd showed an elevated percentage (75.6%) of buffalo cows with CI lower than 400 days. The effect of age at calving was not significant doubt to the fact that the herd was young. WW averaged 130.4±1.9 kg with age to weaning of 238.7±3.2 days, with significant effect of year and calving month, and age to weaning, with a daily gain of 128 g. The results showed the productive and reproductive potential of the buffalo in tropical conditions.

Survival analysis in a buffalo herd located in well drained savannas,Guárico State, Venezuela

Abstract The main objective was to identify animal outlets and to estimate survival curves based on 1198 records of birth, mortality and sales from Hato Barrancas, located in well drained savannas, Guárico State, Venezuela. Chi square test was used to find differences between years and sexes. Calving season, sex and breed were used as sources of variation to monitor survival. The data analysis involved Kaplan-Meier methodology, and Log-rank and Wilcoxon test to compare sources of variation. Sample was analyzed within four periods: calving to weaning; calving to 730 days old, weaning to 730 days old and calving to seven years old. Mortality until weaning was 10.1% and Murrah breed shows 59.38% higher than Mediterranean; while males were 147.7% superior to female. Period between weaning to 730 days old, showed an outlet highly affected by calving during rainy season (24.77%); where Murrah breed showed more outlet (61%) than Mediterranean. Differences by sex were 317% with males showing higher outlet. Period comprised within weaning to 730 days old reveals a 22.91% outlet, where animals calved in rainy season were 95.23% higher than those calved in dry season. Murrah breed had 105% superior outlet than Mediterranean. Finally, for period between calving and seven years old animals the outlet observed for females was 45.79%.

Non-genetic factors affecting calving interval and weaning weight in a buffalo herd located in well drained savannas, Guárico state, Venezuela

Abstract The main focus of this research was to evaluate non-genetic factors affecting calving interval (CI) and weaning weight (WW) on a buffalo herd located in well drained savannas of Guárico state, Venezuela. The study involved records (1997-2001) related to monthly frequency of calving (n=486); calving interval (n=365) and weaning weight (n=376). Data analysis included year and calving season, calf sex, cow age and the interactions for CI. For WW, age at weaning was also included in the statistical analysis. Results revealed significant differences for calving distribution per year (P≤0.05) associated with year-on-year climatic factor changes and progressive herd stabilization. CI averaged 378 ± 1.8 (X – ± S.E.) days, with a coefficient of variation (CV) of 7.3% and a significant effect of calving month (P ≤ 0.05). CI frequency distribution for herd showed 75% cows lower than 400 days. Female age at calving was not significant (linear or quadratic) due it was a young herd, with less than 2.6% animals older than 11 years. WW averaged 130.4±1.9 kg and CV of 24.4%; age to weaning 238.7±3.2 days, with calving month and age to weaning showing significant effect, while the weight average daily gain was 128g per animal. These findings suggest buffalo’s productive and reproductive potential under tropical conditions.