Dynamics of conditioned reflex reorganization in the human visual system

The dymamics of absolute and relative changes in the brightness thresholds of letters recognition was studied in 21 subjects, under conditions of dark adaptation and molecular observation, before and after pairing of one of the letters with electrocutaneous stimulation of the index finger during one session. Isolated electrocutaneous stimulation was applied on the 10th or 35th day after the session. It has been found that after pairings the relative threshold of recognition of the letter previously paired with electrical stimuli (i.e. the threshold in relation to recognition thresholds for the other letters) becomes for three to three and a half hours significantly lower than the initial one. Then there sharply sets in a phase of threshold elevation. Both in the case of double and multiple tests, this phase persists for not less than 35 days. Following an isolated electrical stimulation, a momentary significant lowering of the threshold sets in only for the letter which was paired with it in the first sessions.     

Prevalence of seropositive reactions to Brucella canis in a limited survey of domestic cats

The prevalence of Brucella canis agglutinins was determined in 170 cats (114 from animal shelters in California and 56 from an animal hospital in Texas). Seropositive reactions in the cats from animal shelters were 5.3, 11.4, and 0%, respectively, the the rapid slide agglutination test, salt 2-mercaptoethanol tube agglutination test, salt 2-mercaptoethanol tube agglutination test, and brucellosis card test. For hospitalized cats, the respective percentages were 7.1, 8.9, and 0%. One (0.9%) of 114 cats from the animal shelters and 5 (8.9%) of 56 hospitalized cats were seropositive by the salt 2-mercaptoethanol tube agglutination test at titers greater than or equal to 1:200. Isolation of bacteria was not attempted; thus, the findings of this study may need cautious interpretation.     

Release of O-sulfate groups under mild acid hydrolysis conditions used for estimation of N-sulfate content

The treatment of chondroitin sulfate isolated from cultured B16 mouse melanoma cells with 0.04 M HCl at 100 degrees C for 90 min released up to 45% of O-sulfate residues as free inorganic sulfate. In addition to the release of inorganic sulfate, extensive degradation of this polysaccharide as well as of cartilage chondroitin sulfate, pig rib cartilage proteoglycan, heparin and hyaluronic acid was also evident under these conditions. The above hydrolysis conditions are used for characterizing 35S-labeled heparan sulfates synthesized by cultured cells and to calculate ratio of N- and O-sulfates in these molecules. Our results suggest that caution is necessary in interpreting the results of mild acid hydrolysis of glycosaminoglycans.