Autophagy is a degradative mechanism involved in the recycling and turnover of cytoplasmic constituents from eukaryotic cells. This phenomenon of autophagy has been observed in neurons from patients with Parkinson's disease (PD), suggesting a functional role for autophagy in neuronal cell death. On the other hand, it has been demonstrated that exposure to pesticides can be a risk factor in the incidence of PD. In this sense, paraquat (PQ) (1,1'-dimethyl-4,4'-bipyridinium dichloride), a widely used herbicide that is structurally similar to the known dopaminergic neurotoxicant MPP(+) (1-methyl-4-phenyl-pyridine), has been suggested as a potential etiologic factor for the development of PD. The current study shows, for the first time, that low concentrations of PQ induce several characteristics of autophagy in human neuroblastoma SH-SY5Y cells. In this way, PQ induced the accumulation of autophagic vacuoles (AVs) in the cytoplasm and the recruitment of a LC3-GFP fusion protein to AVs. Furthermore, the cells treated with PQ showed an increase of the long-lived protein degradation which is blocked in the presence of the autophagy inhibitor 3-methyladenine and regulated by the mammalian target of rapamycin (mTOR) signaling. Finally, the cells succumbed to cell death with hallmarks of apoptosis such as phosphatidylserine exposure, caspase activation, and chromatin condensation. While caspase inhibition retarded cell death, autophagy inhibition accelerated the apoptotic cell death induced by PQ. Altogether, these findings show the relationship between autophagy and apoptotic cell death in human neuroblastoma cells treated with PQ.

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A 2-step clustering procedure, using indexes derived from principal component analysis, was used to disclose sperm subpopulations within the canine ejaculate and its relationship to sperm cryoresistance. Semen from 4 dogs was frozen-thawed by a standard protocol: before freezing, computer-assisted sperm analysis of motility and morphometry were performed; after thawing, motility analysis was performed again; and cryoresistance was estimated as the percent changes in progressive motility and sperm velocities after thawing. We used indexes derived from principal component analysis (sperm velocity index [SVI] and sperm motility index [SMI]) and the SPSS 2-step cluster method to disclose sperm subpopulations. The 2-step clustering procedure revealed the existence of 6 subpopulations. Subpopulations 4 and 6 were characterized by high values of both SVI (.200 arbitrary units) and SMI (.90 arbitrary units), subpopulations 2 and 3 were characterized by medium values (SVI 100 to 130; and SMI 30 to 40), and subpopulations 1 and 5 were characterized by low values (SVI , 100; SMI , 30). The distribution of sperm subpopulations was completely different among dogs. Four sperm subpopulations based in morphometric parameters of the sperm head and midpiece were revealed. Models including SVI and SMI indexes explained curvilinear velocity (R 2 5 0.997; P , .001), straight-line velocity (R 2 5 0.98; P , .001), and average velocity (R 2 5 0.99; P , .0001) postthaw.