RESUMEN
The wild South American camelids developed a strategy of seasonal reproduction during spring and summer with singleton birth. The photoperiod is one of the factors that may modulate this seasonality where light would be translated into a hormonal signal. This study evaluated the influence of changes in daily light intensity on melatonin concentration in captive guanacos under a long-day photoperiod (16 hr light/8 hr dark; 33 '28'S). Mean melatonin concentration was 28.3 ± 20.3 pg/ml, with a maximum of 52.14 ± 17.19 pg/ml at 23:30 and minimum of 14.29 ± 6.64 pg/ml at 08:30 (p < .001). There was a negative association between light intensity and melatonin concentration (r = -0.57; p < .001). The results indicate that guanacos respond to variation in daily environmental light with a hormonal response and point to a circannual rhythm as a function of the photoperiod.
Asunto(s)
Camélidos del Nuevo Mundo/fisiología , Melatonina/metabolismo , Luz Solar , Animales , Chile , Ritmo Circadiano/fisiología , Femenino , Fotoperiodo , Estaciones del AñoRESUMEN
This study evaluated ovarian activity in late gestation and post-partum in guanacos in captivity. Follicular dynamics was monitored every second day from 40 days before and other 40 after delivery by transrectal sonography and by plasma steroids concentrations. Seven out of eight (87.5%) of gestating females presented ovarian follicular activity under progesterone levels >3 nmol/l with maximum follicular size of 8.42 ± 0.83 mm from days 23 to 1 before delivery. After delivery, all females have follicular wave development from day 0 to 38, with larger follicular size and longer follicular wave phases and interwave interval when compared with pre-partum data. During post-partum period, there was a close relationship between follicle size and estradiol-17ß concentration, with r = 0.69 at the beginning of growth phase and r = 0.86 in association with the largest dominant follicle. Plasma estradiol-17ß concentration varied from 11.92 to 198.55 pmol/l. Plasma estrone sulfate, free estrone and progesterone returned to baseline concentrations during peripartal period and remained basal thereafter. The results described follicular activity during late gestation and early post-partum period. These findings provide relevant information to understand physiological changes occurring during this reproductive key period in seasonal breeders with long gestation duration as New and Old World camelids.
Asunto(s)
Camélidos del Nuevo Mundo/fisiología , Edad Gestacional , Folículo Ovárico/fisiología , Animales , Estradiol/sangre , Estrona/análogos & derivados , Estrona/sangre , Femenino , Folículo Ovárico/diagnóstico por imagen , Periodo Posparto , Embarazo , Progesterona/sangre , UltrasonografíaRESUMEN
Se propone evaluar los cambios reproductivos en ratones sometidos a hipoxia-normoxia simulando condiciones laborales de la faena minera en el norte de Chile. Se estudió hipoxia hipobárica en cámara hipobárica, simulando 4.100 msnm, en tres grupos experimentales y un grupo control (500 msnm, altura promedio de Santiago), estando cada grupo integrado por seis animales. Ratones (Mus musculus) machos adultos fueron sometidos a regímenes de hipoxia (H)-normoxia (N) los siguientes días: 4H; 8H y 4H-4N-4H (4x4x4) y el grupo control en normoxia continua. Se evaluaron: hematocrito, peso testicular y epididimario, y recuento espermático total en testículo y cauda epididimaria. El peso testicular disminuye a los ocho días de exposición hipóxica hipobárica y se recupera con intervalos de cuatro días de normoxia, al igual que el recuento de espermatozoides en cauda; sin embargo, este valor permanece bajo ocho días post-hipoxia. La producción espermática permanece baja en todos los grupos experimentales. Dado que la alternancia 4x4x4 días se utiliza como régimen habitual de trabajo en las faenas mineras chilenas, es imprescindible estudiar los efectos de la altura sobre la fertilidad humana en estas condiciones.