ABSTRACT
In Northern Patagonia, the mating season starts on March 15th, when rams are submitted to summer temperatures. Exposure of rams to heat stress increases the prevalence of microscopic damage to spermatozoa, morphological abnormalities, and reductions in fertility. This study assesses the adaptive capabilities of six unshorn and six shorn Australian Merino rams, half of which were treated in a heat chamber for eight hours for five days, gradually reaching a temperature of up to 40 °C. Microscopic damage, abnormalities and ultramicroscopic alterations of the plasma membrane and the acrosome of sperm head were analysed. There were significant differences in the percentage of tailless spermatozoa and proximal cytoplasmic droplets between post-treatment periods. Temperature primarily affected the shorn rams and the sperm heads during spermiogenesis. Submicroscopic alterations were observed when the plasma membrane was present in the anterior segment. These alterations can be intact, waved, or dilated. When the plasma membrane was absent, the acrosome might be intact, dilated, and waved. In addition, the outer acrosomal membrane may completely lose its contents or have a nude nucleus. The plasma membrane assumes a waved shape as a result of the effect of temperature on the epididymis. According to this study, the tailless head, proximal cytoplasmic droplets, and the ultramicroscopic categories studied were robust indicators of semen heat stress. After ten weeks, the sperm head recovered its normal shape. Unshorn rams are better adapted to summer heat stress than shorn ones. Microscopy and transmission electron microscopy alterations have been shown to be excellent indicators of thermal stress in Australian Merino rams and may be useful tools to help sheep farmers choose when to begin the mating season, which will vary depending on the environmental conditions of the summer.(AU)
Na Patagônia Norte, os ovinos têm sua estação de acasalamento iniciada em 15 de março, portanto, ficam sujeitos às temperaturas do verão. A exposição de carneiros a estresse térmico aumenta a prevalência de danos microscópicos e anomalias morfológicas nos espermatozoides, que implica uma redução na fertilidade. Este trabalho avaliou a capacidade adaptativa de carneiros Merino Australiano com lã (N = 6) e tosquiados (N = 6): metade ficou ao ar livre e outra metade foi mantida em uma câmara climática por oito horas, durante cinco dias, chegando gradualmente a uma temperatura máxima de 40 °C. Foram analisados danos microscópicos, anormalidades e alterações ultramicroscópicas da membrana plasmática e do acrossoma da cabeça dos espermatozoides. Os resultados microscópicos confirmaram a existência de diferença significativa na porcentagem de espermatozoides sem cauda e com gota citoplasmática proximal, entre os ejaculados pós-tratamento. A temperatura afetou os carneiros tosquiados, principalmente a cabeça de seus espermatozoides, durante a espermatogênese. Alterações submicroscópicas foram observados na membrana plasmática quando ela estava presente no segmento anterior: quando não intacta, ficava ondulada ou dilatada. Quando a membrana plasmática estava ausente, o acrossoma podia se apresentar ondulado ou dilatado. Além disso, sob efeito do calor, a membrana acrossomal externa pode perder completamente seu conteúdo ou apresentar núcleo desnudo. A membrana plasmática assume uma forma ondulada pelo efeito da temperatura no epidídimo. Depois de dez semanas, a cabeça dos espermatozoides recuperou sua forma normal. Como demonstrado neste estudo, a cabeça sem cauda, as gotas citoplasmáticas proximais e as categorias ultramicroscópicas estudadas são indicadores do efeito do estresse térmico no sêmen, e os carneiros com maior cobertura de lã se adaptam melhor ao estresse por calor. Alterações de microscopia e de microscopia eletrônica de transmissão têm se mostrado excelentes indicadores de estresse por calor em carneiros Merino Australiano e podem ser ferramentas úteis para ajudar criadores de ovelhas a escolher quando começar a época de acasalamento, o que irá variar de acordo com as condições ambientais do verão.(AU)
Subject(s)
Animals , Male , Sperm Head/ultrastructure , Acrosome/ultrastructure , Sheep/physiology , Cell Membrane/ultrastructure , Heat Stress Disorders/complications , Teratozoospermia/diagnostic imaging , Argentina , Sperm Tail/ultrastructure , SpermatogenesisABSTRACT
During normal spermatogenesis, most of the round spermatid’s cytoplasm was phagocytosed as ‘residual bodies’ by the Sertoli cell at spermiogenesis, and only a small cytoplasmic residue i.e. ‘cytoplasmic droplet’ remains applied to the elongated spermatid after release from the germinal epithelium. A characteristic morphological change on spermatozoa during epididymal transit was the caudal migration of the cytoplasmic droplet away from the neck via the principal piece, however, while studying the Cyclophosphamide (CPA) induced sperm morphological changes from the cauda epididymis in male Wistar rat, Rattus norvegicus using phase contrast microscope it was noticed that the sub-chronic and acute doses of CPA caused retention of cytoplasmic droplet on the mid-piece. Thus from the foregoing it was concluded that beside CPA being an inhibitor of spermatogenesis, it also interferes with the maturation of spermatozoa by the retention of cytoplasmic droplet perhaps due to alteration in epididymal secretory and absorptive functions thus leading to infertility.
ABSTRACT
El objetivo del presente estudio fue evaluar la integridad acrosomal, funcionalidad bioquímica de la membrana espermática y las relaciones entre éstas en machos con y sin persistencia de gotas citoplásmicas (PGC). Se usaron 254 eyaculados de 48 cerdos reproductores entre ocho y 48 meses de edad clasificados como jóvenes (<1 año), maduros (entre uno y tres años) y viejos (>3 años). Los datos fueron evaluados mediante análisis de varianza para medidas repetidas en un mismo individuo (efecto aleatorio). Se evaluó el efecto de procedencia (efecto bloque) y grupo etáreo sobre: PGC, integridad acrosomal, funcionalidad de membrana, proporción de espermatozoides vivos y con gotas citoplásmicas (GC). Además se evaluó el efecto de PGC sobre la integridad acrosomal y la funcionalidad de membrana. La presentación de PGC fue menor en cerdos reproductores jóvenes (37 ± 6 por ciento) que en los maduros (52 ± 5 por ciento; P=0,05) y los viejos (85 ± 13 por ciento; P<0,01). La diferencia en PGC entre machos maduros y viejos fue significativa (P=0,05). Los machos viejos presentaron mayor proporción de células con GC que los jóvenes (34,6 ± 4,8 vs. 19,7 ± 2.3 por ciento, respectivamente; P=0,01), mientras que los maduros no fueron diferentes de ninguno de los dos (23,5 ± 2,1 por ciento). Los cerdos reproductores que no presentaron PGC obtuvieron mayores valores de acrosoma intacto que los que presentaron PGC (86,5 ± 1,2 vs. 80,2 ± 1,1 por ciento, respectivamente; P<0,01). Los defectos de la integridad acrosomal presentaron correlaciones significativas con defectos espermáticos asociados a GC (entre -0,20 y -0,36; P<0,05). Este estudio indica que cerdos reproductores mayores de tres años presentan con mayor frecuencia eyaculados de baja calidad espermática. Los resultados además sugieren que los defectos de membrana y morfológicos tienden a presentarse conjuntamente en un eyaculado, señalando la necesidad de construir un índice de calidad seminal multifactorial...
The goal of this study was to evaluate the acrosomal integrity, biochemical functionality of the sperm membrane, and the relationship between them in boars with and without persistence of cytoplasmic droplets (PGC). It were used 254 ejaculates from 48 boars between eight and 48 months of age that were classified as young (<1 year), mature (1 to 3 years), and old (>3 years). Data were analyzed using analysis of variance for repeated measurements in the same individual (random effect). The effect of source (block effect) and age group on PGC, acrosomal integrity, membrane function, and proportion of live and with cytoplasmic droplets sperm cells were evaluated. The effect of PGC on acrosomal integrity and membrane function was also tested. Presence of PGC was lower in young (37 ± 6 percent) than mature (52 ± 5 percent; P=0.05) and old (85 ± 13 percent; P<0.01) boars. The difference in PGC between mature and old boars was significant (P=0.05). Old boars showed a higher proportion of cells with GC than young ones (34.6 ± 4.8 vs. 19.7 ± 2.3 percent, respectively; P=0.01), while mature boars were no different from the other two groups (23.5 ± 2.1 percent). Boars that did not show PGC had a higher proportion of intact acrosomes than those with PGC (86.5 ± 1.2 vs. 80.2 ± 1.1 percent, respectively; P<0.01). Defects in acrosomal integrity were significantly correlated with sperm defects associated to GC (between -0.20 y -0.36; P<0.05). These results suggest that membrane and morphologic defects tend to occur together in the same ejaculate, pointing out the need to build a multifactor seminal quality index that can be used as decision criterion in the swine industry.