Assaying for structural variation in the parvovirus capsid and its role in infection.

The capsid of canine parvovirus (CPV) was assayed for susceptibility to proteases and for structural variation. The natural cleavage of VP2 to VP3 in CPV full (DNA containing) particles recovered from tissue culture occurred within the sequence Arg-Asn-Glu-Arg Ala-Thr. Trypsin, chymotrypsin, bromelain, and cathepsin B all cleaved >90% of the VP2 to VP3 in full but not in empty capsids and did not digest the capsid further. Digestion with proteinase K, Pronase, papain, or subtilisin cleaved the VP2 to VP3 and also cleaved at additional internal sites, causing particle disintegration and protein degradation. Several partial digestion products produced by proteinase K or subtilisin were approximately 31-32.5 kDa, indicating cleavage within loop 3 of the capsid protein as well as other sites. Protease treatment of capsids at pH 5.5 or 7.5 did not significantly alter their susceptibility to digestion. The isoelectric point of CPV empty capsids was pH 5.3, and full capsids were 0.3 pH more acidic, but after proteolysis of VP2 to VP3, the pI of the full capsids became the same as that of the empty capsids. Antibodies against various capsid protein sequences showed the amino termini of most VP2 molecules were on the outside of full but not empty particles, that the VP1-unique sequence was internal, and that the capsid could be disintegrated by heat or urea treatment to expose the internal sequences. Capsids added to cells were localized within the cell cytoplasm in vesicles that appeared to be lysosomes. Microinjected capsids remained primarily in the cytoplasm, although a small proportion was observed to be in the nucleus after 2 h. After CPV capsids labeled with [35S]methionine were bound to cells at 0 degrees C and the cells warmed, little cleavage of VP1 or VP2 was observed even after prolonged incubation. Inoculation of cells with virus in the presence of proteinase inhibitors did not significantly reduce the infection.

Case report: neurochemical, physiological, and behavioral effects of bright light therapy on a cortically blind patient.

The present study evaluated the effects of bright light therapy on a patient with cortical blindness. Behavioral indices of functioning included the appraisal of mood, fatigue, appetite and orientation. Physiological measures assessed were blood pressure and temperature. Blood serum samples were analyzed for 5-HIAA and norepinephrine (NE). For the control and follow-up, the patient was exposed to 30 minutes of red light (300-lux), and thirty minutes of white light (10,000-lux) was used for treatment. High-pressure liquid chromatography analyses of blood serum samples revealed no change in serotonin (5-HT). However, an increase in blood NE was indicated following light treatment (red light: 12.7 ng/ml, white light: 43.5 ng/ml and, red light: 27.5 ng/ml). Analysis of data revealed significant differences in baseline and treatment scores for 4 of the outcome measures.