Studies have reported the importance of mitochondria in sperm functionality. However, for some species, the glycolytic pathway appears to be as important as oxidative phosphorylation in ATP synthesis and sperm kinetics. These mechanisms have not been fully elucidated for bovine spermatozoa. Therefore, the aim of this study was to evaluate the role of mitochondria and the glycolytic pathway in ATP synthesis, sperm movement patterns, and oxidative homeostasis of epididymal spermatozoa in bovine specimens. We observed that mitochondrial uncoupling with protonophores significantly reduced ATP levels. However, these levels were reestablished after stimulation of the glycolytic pathway. We verified the same pattern of results for sperm kinetic variables and the production of reactive oxygen species (ROS). Thus, we suggest that, after its appropriate stimulation, the glycolytic pathway is capable of maintaining ATP levels, sperm kinetic patterns, and oxidative balance of bovine epididymal spermatozoa submitted to mitochondrial uncoupling.

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Studies have demonstrated the importance of mitochondria to sperm functionality, as the main source of ATP for cellular homoeostasis and motility. However, the role of mitochondria on sperm metabolism is still controversial. Studies indicate that, for some species, glycolysis may be the main mechanism for sperm energy production. For ram sperm, such pathway is not clear. Thus, we evaluated ram sperm in response to mitochondrial uncoupling and glycolysis inhibition aiming to assess the importance of each pathway for sperm functionality. Statistical analysis was performed by the SAS System for Windows, using the General Linear Model Procedure. Data were tested for residue normality and variance homogeneity. A p < .05 was considered significant. Groups treated with the mitochondrial uncoupler Carbonyl cyanide 3 chlorophenylhydrazone (CCCP) showed a decrease in the percentage of cells with low mitochondrial activity and high mitochondrial membrane potential. We also observed that the highest CCCP concentration promotes a decrease in sperm susceptibility to lipid peroxidation. Regardless the lack of effect of CCCP on total motility, this substance induced significant alterations on sperm kinetics. Besides the interference of CCCP on spermatic movement patterns, it was also possible to observe such an effect in samples treated with the inhibitor of glycolysis (2-deoxy-d-glucose, DOG). Furthermore, treatment with DOG also led to a dose-dependent increase in sperm susceptibility to lipid peroxidation. Based on our results, we suggest that the glycolysis appears to be as important as oxidative phosphorylation for ovine sperm kinetics as this mechanism is capable of maintaining full motility when most of the cells have a low mitochondrial membrane potential. Furthermore, we found that changes in the glycolytic pathway trough glycolysis inhibition are likely involved in mitochondrial dysfunction and sperm oxidative unbalance.

ContentsThe fatty acid composition of the sperm membrane is an important factor involved in the overall sperm quality, including motility. However, in the canine species, the exact composition of the plasma membrane is still unknown. Therefore, the purpose of this study was to evaluate the plasma membrane lipid composition of motile sperm cells and to compare it with asthenospermic samples, as an attempt to determine possible involvements of membrane lipids in dog sperm cell motility. The sperm-rich fraction of ten mature dogs was collected, and samples were subjected to density gradient centrifugation by Percoll ® , in order to separate motile and asthenospermic samples.Processed semen samples were evaluated for sperm motility, plasma and acrosome membrane integrity, mitochondrial activity and susceptibility to oxidative stress. Lipid plasma membrane composition was identified by mass spectrometry (MALDI-MS).The motile sperm samples presented the following phospholipids in a high frequency in the plasma membrane: phosphatidylcholine 38:4 (composed of stearic and arachidonic fatty acids), phosphatidylcholine 36:1 (stearic and oleic fatty acids), phosphatidylethanolamine 34:4 (myristic and arachidonic fatty acids), glycerophosphatidic acid 36:4 (palmitic and arachidonic fatty acids), phosphatidylcholine 40:4 plasmanyl and phosphatidylcholine 40:5 plasmenyl. Furthermore, no lipid markers were found in the asthenospermic samples. Results also indicate that differences on plasma membrane composition between motile and asthenospermic samples are crucial factors for determining sperm motility, sperm functionality and susceptibility to oxidative stress. In conclusion, plasma membrane lipid composition varies considerable between motile and asthenospermic samples. Therefore, lipid markers of sperm motility can be considered, such as phosphatidylcholine, phosphatidylethanolamine, phosphatidylcholine plasmanyl, phosphatidylcholine plasmenyl and phosphatidic acid.

Contents Among the modifications that occur during the neonatal period, pulmonary development is the most critical. The neonate's lungs must be able to perform adequate gas exchange, which was previously accomplished by the placenta. Neonatal respiratory distress syndrome is defined as insufficient surfactant production or pulmonary structural immaturity and is specifically relevant to preterm newborns. Prenatal maternal betamethasone treatment of bitches at 55 days of gestation leads to structural changes in the neonatal lung parenchyma and consequently an improvement in the preterm neonatal respiratory condition, but not to an increase in pulmonary surfactant production. Parturition represents an important challenge to neonatal adaptation, as the uterine and abdominal contractions during labour provoke intermittent hypoxia. Immediately after birth, puppies present venous mixed acidosis (low blood pH and high dioxide carbon saturation) and low but satisfactory Apgar scores. Thus, the combination of physiological hypoxia during birth and the initial effort of filling the pulmonary alveoli with oxygen results in anaerobiosis. As a neonatal adaptation follow‐up, the Apgar analysis indicates a tachypnoea response after 1 h of life, which leads to a shift in the blood acid–base status to metabolic acidosis. One hour is sufficient for canine neonates to achieve an ideal Apgar score; however, a haemogasometric imbalance persists. Dystocia promotes a long‐lasting bradycardia effect, slows down Apgar score progression and aggravates metabolic acidosis and stress. The latest data reinforce the need to accurately intervene during canine parturition and offer adequate medical treatment to puppies that underwent a pathological labour.

Semen cryopreservation is an essential biotechnology in canine reproduction and during the cryopreservation process commonly egg yolk are used. The discrepancy in the egg yolk composition and the potential risk of disease dissemination are obstacles for semen exportation and use. Therefore, studies aiming to substitute egg yolk are extremely important. In this context, soy lecithin contains a low-density lipoprotein fraction, is an interesting alternative. Thus, the objective of this study was to compare extenders based on soy lecithin (several concentrations and forms) with egg yolk during the cryopreservation process of dog sperm. For this purpose, we used twelve dogs. Semen was evaluated at different time points (after refrigeration, glycerolization, and thawing), by motility analysis (CASA) and functional tests (e.g., membrane integrity-eosin/nigrosin, acrosome integrity-fast green/Bengal rose, mitochondrial activity-3'3 diaminobenzidine, Chromatin susceptibility to acid-induced denaturation-SCSA, and susceptibility to oxidative stress-thiobarbituric acid reactive substances). The results indicated that egg yolk and lower concentrations of lecithin had similar effects on mitochondrial activity and motility. Thus, soy lecithin is a potentially viable alternative to egg yolk for the cryopreservation of dog semen.

IIPontos críticos no manejo pré-abate de frango de corte: jejum, captura, carregamento, transporte e tempo de espera no abatedouro

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