Compartmentalization of small ruminant lentivirus between blood and colostrum in infected goats

The compartmentalization of small ruminant lentivirus (SRLV) subtype A (Maedi-Visna virus) and B (caprine arthritis-encephalitis virus) variants was analyzed in colostrum and peripheral blood mononuclear cells of four naturally infected goats. Sequence analysis of DNA and RNA encompassing the V4-V5 env regions showed a differential distribution of SRLV variants between the two compartments. Tissue-specific compartmentalization was demonstrated by phylogenetic analysis in three of the four cases. In these animals colostrum proviral sequences were clustered relative to the blood viral sequences. In one goat, the blood and colostrum-derived provirus sequences were intermingled, suggesting trafficking of virus between the two tissues or mirroring a recent infection. Surprisingly, the pattern of free virus variants in the colostrum of all animals corresponded only partially to that of the proviral form, suggesting that free viruses might not derive from infected colostral cells. The compartmentalization of SRLV between peripheral blood and colostrum indicates that lactogenic transmission may involve specific viruses not present in the proviral populations circulating in the blood.

Visual vector inversion during memory antisaccades--a TMS study

In the memory antisaccade task, subjects are instructed to look at an imaginary point precisely at the opposite side of a peripheral visual stimulus presented short time previously. To perform this task accurately, the visual vector, i.e., the distance between a central fixation point and the peripheral stimulus, must be inverted from one visual hemifield to the other. Recent data in humans and monkeys suggest that the posterior parietal cortex (PPC) might be critically involved in the process of visual vector inversion. In the present study, we investigated the temporal dynamics of visual vector inversion in the human PPC by using transcranial magnetic stimulation (TMS). In six healthy subjects, single pulse TMS was applied over the right PPC during a memory antisaccade task at four different time intervals: 100 ms, 217 ms, 333 ms, or 450 ms after target onset. The results indicate that for rightward antisaccades, i.e., when the visual target was presented in the left screen-half, TMS had a significant effect on saccade gain when applied 100 ms after target onset, but not later. For leftward antisaccades, i.e., when the visual target was presented in the right screen-half, a significant TMS effect on gain was found for the 333 ms and 450 ms conditions, but not for the earlier ones. This double dissociation of saccade gain suggests that the initial process of vector inversion can be disrupted 100 ms after onset of the visual stimulus and that TMS interfered with motor saccade planning based on an inversed vector signal at 333 ms and 450 ms after stimulus onset.