Putative 51,000-Mr protein marker for postsynaptic densities is virtually absent in cerebellum

Cerebrum and cerebellum contain numerous asymmetric synapses characterized by the presence of a postsynaptic thickening prominently stained by phosphotungstic acid and other electron-dense stains suitable for electron microscopy. A 51,000-Mr protein, copurified in postsynaptic density-enriched fractions from cerebrum, is considered to be a well established marker for the postsynaptic density. On the basis of two criteria, our studies demonstrate that the 51,000-Mr protein marker for postsynaptic densities is virtually absent in cerebellum, First, it is present in negligible amounts in deoxycholate-insoluble fractions from cerebellum but abundant in parallel fractions from cerebrum. Secondly, the 51,000-Mr protein, which binds 125I-calmodulin after SDS PAGE is readily visualized in membrane samples from cerebrum but is virtually undetectable in cerebellar samples. It is apparent that these results require reexamination of the role of the 51,000-Mr protein in postsynaptic density structures.

Monoclonal antibodies selective for Drosophila melanogaster choline acetyltransferase

The newly developed monoclonal antibody technology was applied to the production of antibodies selective for Drosophila melanogaster choline acetyltransferase (EC 2.3.1.6). Two stable cell lines, 1C8 and 1G4, were isolated from NS-1/spleen cell hybrids by employing a choline acetyltransferase enzyme activity-screening method. Both cell lines were cloned twice and were maintained in continuous culture and as ascites tumors. Purified antibody was isolated from ascites fluids by pH elution after adsorption to Protein A-Sepharose. Both antibodies eluted from the Protein A-Sepharose as a single subclass, IgG1, and directly inhibited choline acetyltransferase activity. Scatchard analysis of titration data for choline acetyltransferase antibody-enzyme interaction generated linear curves for both antibodies: KA for 1C8 was 2.77 X 10(7) M-1 and KA for 1G4 was 0.78 X 10(7) M-1. Inclusion of the choline acetyltransferase substrate acetyl-CoA at 10 times the KM in the antibody-enzyme reaction mixture substantially reduced the level of inhibition observed with both antibodies; choline, however, exhibited no protective effect. Neither antibody reacted with choline acetyltransferase-containing extracts of vertebrates or other insect neural tissues. We conclude that the two antibodies are nonidentical, monoclonal, and highly selective for D. melanogaster choline acetyltransferase, both reacting at or near the acetyl-CoA binding region of the enzyme-active site.

Practical application of synthetic A and B blood group immunoadsorbents

The effectiveness of synthetic blood group A and B immunoadsorbents in removing anti-A and anti-B from human sera was evaluated. The sera contained specific alloantibodies and were destined for use as diagnostic reagents. Both Synsorb-A(TM) and Synsorb-B(TM) removed all saline anti-A or anti-B activity from 20 sera tested. All trace of anti-A activity detectable by the indirect antiglobulin test was removed from only 20% of sera; anti-B with similar reactivity was removed from 66% of sera. Specific (wanted) alloantibody titres were reduced by synsorb-A in 60% of sera, but were unaffected by Synsorb-B. Despite these shortcomings, such immunoadsorbents are of value particularly when cells of appropriate phenotype are unavailable for absorptions.

Streptococcal pharyngitis: diagnosis by gram stain

Group A beta-hemolytic streptococci were isolated from 49 (10.4%) of 472 patients with pharyngitis. Throat culture results, interpreted by five observers of varying experience, showed the mean sensitivity, specificity, and predictive value of a positive Gram-stained smear of pharyngeal secretions as 73%, 96%, and 71%. Assignment to a high-risk group by clinical algorithm gave sensitivity, specificity, and predictive value of only 45%, 83%, and 23%. The Gram-stained smear is the most accurate method of early diagnosis of streptococcal pharyngitis.