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Rangel-Negrin A.,University of Veracruz | Flores-Escobar E.,University of Barcelona | Chavira R.,Institute Ciencias Medicas y Nutricion Salvador Zubiran | Canales-Espinosa D.,University of Veracruz | Dias P.A.D.,University of Veracruz
Primates | Year: 2014

The measurement of hormones in fecal samples allows for the noninvasive assessment of the endocrine status of free-ranging primates. However, procedures and techniques for hormone analysis in feces must be validated, both analytically and physiologically. Few studies have addressed the endocrinology of black howler monkeys (Alouatta pigra). Due to its conservation status, direct handling of individuals from this species and invasive sample collection are highly regulated, and therefore traditional methods for the validation of hormone assays, such as pharmacological challenges, are not allowed. As a consequence, sometimes studies of the fecal hormones of free-ranging black howler monkeys do not report physiological validations and therefore the biological reliability of such measurements cannot be assessed. In order to stimulate future research with this species, the present study aimed at providing methodological bases for fecal endocrine monitoring. Specifically, we compared the validity of two immunoassays (radioimmunoassays, RIA; solid-phase chemiluminescent enzyme immunoassay, SPCEI) performed with commercial kits to measure cortisol, testosterone, estradiol, and progesterone; and demonstrate how the physiological functions of these steroid hormones can be determined through non-pharmacological validations. We found no differences between the analytical validity of RIA and SPCEI assays to measure cortisol and testosterone, whereas for estradiol and progesterone RIA showed better results. Concerning the physiological validation of our assays, we demonstrated that: (1) comparisons between pre- and post-stress situations may be used to assess cortisol response, (2) comparisons between females and males may be used to assess variation in testosterone levels, and (3) comparisons between pregnant and non-pregnant females may be used to determine variation in estradiol and progesterone activity. The analytical and physiological validations that we performed demonstrate that there are currently commercial kits that allow for correct endocrine monitoring of this species, and that there are non-pharmacological alternatives to assess the biological validity of hormone measurements. © 2014, Japan Monkey Centre and Springer Japan. Source

Aguilar-Melo A.R.,National Autonomous University of Mexico | Andresen E.,National Autonomous University of Mexico | Cristobal-Azkarate J.,University of Cambridge | Arroyo-Rodriguez V.,National Autonomous University of Mexico | And 5 more authors.
American Journal of Primatology | Year: 2013

Animals' responses to potentially threatening factors can provide important information for their conservation. Group size and human presence are potentially threatening factors to primates inhabiting small reserves used for recreation. We tested these hypotheses by evaluating behavioral and physiological responses in two groups of mantled howler monkeys (Alouatta palliata mexicana) at the "Centro Ecológico y Recreativo El Zapotal", a recreational forest reserve and zoo located in the Mexican state of Chiapas. Both groups presented fission-fusion dynamics, splitting into foraging subgroups which varied in size among, but not within days. Neither subgroup size nor number of people had an effect on fecal cortisol. Out of 16 behavioral response variables tested, the studied factors had effects on six: four were affected by subgroup size and two were affected by number of people. With increasing subgroup size, monkeys increased daily path lengths, rested less, increased foraging effort, and used more plant individuals for feeding. As the number of people increased, monkeys spent more time in lower-quality habitat, and less time engaged in social interactions. Although fecal cortisol levels were not affected by the factors studied, one of the monkey groups had almost twice the level of cortisol compared to the other group. The group with higher cortisol levels also spent significantly more time in the lower-quality habitat, compared to the other group. Our results suggest that particular behavioral adjustments might allow howler monkeys at El Zapotal to avoid physiological stress due to subgroup size and number of people. However, the fact that one of the monkey groups is showing increased cortisol levels may be interpreted as a warning sign, indicating that an adjustment threshold is being reached, at least for part of the howler monkey population in this forest fragment. © 2013 Wiley Periodicals, Inc. Source

Rangel-Negrin A.,University of Barcelona | Dias P.A.D.,University of Veracruz | Chavira R.,Institute Ciencias Medicas y Nutricion Salvador Zubiran | Canales-Espinosa D.,University of Veracruz
Hormones and Behavior | Year: 2011

The influence of social factors on the modulation of male testosterone levels has been demonstrated among several vertebrate species. In addition to sexual activity, parental care and reproductive competition affect testosterone secretion. We examined variations in testosterone levels among male black howlers (Alouatta pigra) in various social contexts. Fecal samples were collected from nine males living in five different groups in the Mexican state of Campeche. The potential for intragroup and extragroup competition varied among the groups. The number of resident males living in the groups was the only variable that significantly explained variations in testosterone levels. Males living in unimale groups had higher testosterone levels; the highest testosterone levels were recorded for males that had experienced a shift from multimale to unimale group compositions. In this species, the probability of being challenged by extragroup males and evicted from the group during immigration events increases when males live in unimale groups. Therefore, our results suggest that male black howlers respond to competition for group membership by increasing their testosterone levels. In this context, testosterone secretion represents an anticipatory response to reproductive conflicts. Therefore, although males living in unimale groups have exclusive access to females, they face higher physiological costs associated with sustaining high testosterone levels for extended time periods. © 2010 Elsevier Inc. Source

Hernandez I.V.,Institute Medicina Tropical Pedro Kouri | Ernesto Montoro Cardoso C.,Institute Medicina Tropical Pedro Kouri | Hernandez-Pando R.,Institute Ciencias Medicas y Nutricion Salvador Zubiran
Revista Cubana de Medicina Tropical | Year: 2012

Introduction: development of new antituberculosis vaccines requires the characterization of the cell-mediated immune responses induced by mycobacterial antigens. Objective: to determine the immunogenic potential of 'Mycobacterium habana' TMC-5135 when using subcutaneous vaccine in Balb/c mice. Methods: in this study, Balb/c mice were inoculated subcutaneously with live 'Mycobacterium habana' TMC-5135. The production of IFN gamma in cell suspensions obtained from the lungs, the spleen and the lymph nodes after stimulation with mycobacterial antigens Ag85b or culture filtrate antigens (CFA) was recorded. Results: the production of IFN gamma after stimulation with CFA and Ag85b was higher in mice vaccinated with 'M. habana' than in animals immunized with BCG. Conclusions: these results encourage new research on 'M. habana' as vaccinal candidate against tuberculosis. Source

Dunn J.C.,University of Cambridge | Cristobal-Azkarate J.,University of Cambridge | Schulte-Herbruggen B.,Cambridge Assessment | Chavira R.,Institute Ciencias Medicas y Nutricion Salvador Zubiran | Vea J.J.,University of Barcelona
International Journal of Primatology | Year: 2013

Environmental stressors impact physiology in many animal species. Accordingly, the monitoring of fecal glucocorticoid metabolites (fGCM) has been increasingly used to evaluate the physiological costs of habitat disturbance on wild animal populations, providing a powerful tool for conservation and management. Several studies have suggested that primates in forest fragments have higher fGCM levels than those in continuous forests, yet the proximate causes of fGCM variation remain to be identified. In previous studies of Mexican howlers (Alouatta palliata mexicana) in Los Tuxtlas, Mexico, we found that individuals living in a smaller and more disturbed forest fragment consumed significantly less fruit and had a significantly higher feeding effort than those living in a bigger, more conserved forest fragment. Here, we aimed to examine the effects of fruit consumption and travel time on fGCM levels in the same two groups of howlers, during three sampling sessions that differed markedly in fruit availability. We found that fGCM levels (N = 202 fecal samples) were higher in the howler group living in the smaller forest fragment and varied seasonally in both focal groups, being lowest when fruit consumption was highest. However, our results suggest that travel time is the main factor predicting fGCM levels in howlers, and that although fruit consumption may be negatively related to fGCM levels, this relationship is probably mediated by the strong effect that fruit consumption has on travel time. Our results provide important insight into the proximate causes of fGCM variation in primates in fragments and highlight the potential conservation significance of studies showing that habitat loss and transformation can lead to increases in travel time in wild primates. © 2013 Springer Science+Business Media New York. Source

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