Disruption of bovine sperm functions in the presence of aplastic midpiece defect.

BACKGROUND: Bulls are of great importance in the productive chain and for this reason they should have a good semen quality. There is no doubt that sperm morphology is very important to bull fertility, although little is known about how exactly the abnormal morphologies may affect sperm functions. OBJECTIVES: To detail the morphological description of the aplastic midpiece defect (AMD), as well as to understand its consequences for male fertility based on membrane and acrosome status, mitochondrial membrane potential and DNA integrity parameters. MATERIALS AND METHODS: The bulls were divided into two groups: control, consisting of satisfactory potential breeders (n = 3); and AMD, consisting of unsatisfactory potential breeders with a high percentage of AMD (n = 3). Bulls were evaluated by the breeding soundness evaluation; five ejaculates were collected from each animal and analyzed by flow cytometry. RESULTS: Spermatozoa from AMD group exhibited lower sperm motility and vigor (p < 0.05). In addition, it also exhibited lower mitochondrial membrane potential (p < 0.05), a higher percentage of spermatozoa with DNA fragmentation (p < 0.05), lower acrosome and plasma membrane integrity (p < 0.05), and higher lipid bilayer sperm membrane disorganization (p < 0.05) in comparison with control bulls. DISCUSSION: These findings may be due to oxidative stress and a reduction of the energy production capacity in addition to an alteration in the structural composition of the sperm cell. Moreover, semen with a high percentage of AMD may also be undergoing apoptosis. CONCLUSION: Bulls with a high percentage of AMD in their semen are not suitable for reproduction. Furthermore, it suggests there is a putative genetic basis for this sperm defect.

Testosterone serum profile, semen characteristics and testicular biometry of Mangalarga Marchador stallions in a tropical environment.

This study was conducted to characterize the daily profile of testosterone secretion and its mean concentrations in the four seasons as well as to evaluate the semen characteristics and testicular biometry of Mangalarga Marchador stallions throughout the year in a tropical region. Three stallions were submitted to semen collections and evaluation of testicular biometry every 14 days along a year. Blood samples were collected once at the middle of each season, in a 20-min interval during 24 hr in order to evaluate the testosterone secretion profiles among seasons. Testosterone concentrations along the day were higher at the beginning of the afternoon (from 12:00 to 15:00 hr), but a circadian secretion was not clearly observed. Mean testosterone concentrations did not differ among seasons (p > .05), but a pattern of secretion along the day showed variations with higher concentrations in the afternoon during the winter. Ejaculate volume was higher during summer; however, sperm motility decreased in summer and spring. Total sperm in ejaculate, sperm morphology and testicular biometry kept constant along the year showing no differences among the seasons. The results demonstrated that in a tropical region, reproductive aspects of stallions did not show a clearly defined seasonal variation, and months of autumn and winter were not unsuitable for reproduction of the males.

Uso de colesterol carreado por ciclodextrina na criopreservação de sêmen / Use of cholesterol loaded cyclodextrin for semen criopreservation

Os efeitos deletérios causados às células espermáticas pela criopreservação ocorrem por esseprocedimento alterar a arquitetura estrutural da membrana plasmática, prejudicando a sobrevivência espermáticapós-descongelamento. Em razão disso, novas estratégias têm sido pesquisadas a fim de minimizar os danoscelulares inerentes ao choque térmico ocasionado no processamento do sêmen, entre as quais a incorporação docolesterol à membrana plasmática por ciclodextrina. Trata-se de uma técnica alternativa e que vem apresentando,in vitro, resultados promissores para ejaculados com baixa viabilidade pós-descongelamento devido amodificações na fluidez e na permeabilidade da membrana plasmática, incrementando a tolerância aos choquestérmico e osmótico. Porém, as taxas de prenhez obtidas a campo ainda se apresentam insatisfatórias,possivelmente em razão de alguma interferência da alta proporção de colesterol sobre o processo fisiológico decapacitação espermática e de reação acrossomal, fundamentais para a ocorrência de fertilização. Na presenterevisão, serão abordados aspectos relacionados ao uso de ciclodextrinas como carreadoras de colesterolpreviamente ao congelamento de sêmen.(AU)

The deleterious effects of seminal cryopreservation on sperm cells alter the structural architecture ofthe plasma membranedecreasing the survival of the sperm after thawing. As a result, new strategies have beenresearched in order to minimize the cell damage related to the thermal shock of semen processing, such ascholesterol-loaded cyclodextrins. This is an alternative technique that has shown,in vitro, promising results forejaculated with low viability after thawing due to the modifications on the fluidity and permeability of theplasma membrane, increasing the tolerance to thermal and osmotic shock. However, the pregnancy rates at thefield remain unsatisfactory, possibly due to some interference of high proportion of cholesterol on thephysiological process of sperm capacitation and acrosome reaction, essential for the occurrence of fertilization.This review will discuss some aspects related to the use of cyclodextrins as cholesterol carriers previously tosemen cryopreservation process.(AU)

Uso de colesterol carreado por ciclodextrina na criopreservação de sêmen / Use of cholesterol loaded cyclodextrin for semen criopreservation

Os efeitos deletérios causados às células espermáticas pela criopreservação ocorrem por esseprocedimento alterar a arquitetura estrutural da membrana plasmática, prejudicando a sobrevivência espermáticapós-descongelamento. Em razão disso, novas estratégias têm sido pesquisadas a fim de minimizar os danoscelulares inerentes ao choque térmico ocasionado no processamento do sêmen, entre as quais a incorporação docolesterol à membrana plasmática por ciclodextrina. Trata-se de uma técnica alternativa e que vem apresentando,in vitro, resultados promissores para ejaculados com baixa viabilidade pós-descongelamento devido amodificações na fluidez e na permeabilidade da membrana plasmática, incrementando a tolerância aos choquestérmico e osmótico. Porém, as taxas de prenhez obtidas a campo ainda se apresentam insatisfatórias,possivelmente em razão de alguma interferência da alta proporção de colesterol sobre o processo fisiológico decapacitação espermática e de reação acrossomal, fundamentais para a ocorrência de fertilização. Na presenterevisão, serão abordados aspectos relacionados ao uso de ciclodextrinas como carreadoras de colesterolpreviamente ao congelamento de sêmen.

The deleterious effects of seminal cryopreservation on sperm cells alter the structural architecture ofthe plasma membranedecreasing the survival of the sperm after thawing. As a result, new strategies have beenresearched in order to minimize the cell damage related to the thermal shock of semen processing, such ascholesterol-loaded cyclodextrins. This is an alternative technique that has shown,in vitro, promising results forejaculated with low viability after thawing due to the modifications on the fluidity and permeability of theplasma membrane, increasing the tolerance to thermal and osmotic shock. However, the pregnancy rates at thefield remain unsatisfactory, possibly due to some interference of high proportion of cholesterol on thephysiological process of sperm capacitation and acrosome reaction, essential for the occurrence of fertilization.This review will discuss some aspects related to the use of cyclodextrins as cholesterol carriers previously tosemen cryopreservation process.