Effect of adapting target size on the gain of the surround response mechanism in X- and Y-cells in cat retina

Summary The adaptation field of the surround mechanism of X and Y retinal ganglion cells in the cat was assessed with variable size, unmodulated adapting spots. Both an on-inhibition measure and an off-discharge measure of surround gain was used. Results suggest that the surround mechanism in Y-cells is strongest in the receptive field middle but weak or nonexistent in the middle of X-cell receptive fields.Acknowledgment. This research was supported by Public Health Service grant No. EY 00701.     

Genetic analysis of modifier variability inDrosophila subobscura

Summary The previously detected modifier variability acting on the expression of the Bare (Ba) locus inDrosophila subobscura is demonstrated to be due to polygenes situated along the chromosome O. From crosses between isogenic lines of high and low modifier effect we ascertained the presence of approximately 5 modifier loci.We are grateful to Dr M. Green for valuable comments on the experimental design used in this paper.     

Clindamycin and lincomycin alter miniature endplate current decay.

Antibiotic-induced muscle paralysis has frequently been found in both experimental animals and man with three distinct classes of antibiotic: (1) streptomycin and related aminoglycoside compounds, (2) polymyxins and (3) tetracyclines. Recently lincomycin and its chemical congener, clindamycin, have been reported to produce muscle paralysis which has different characteristics from those seen with other classes of antibiotic. Although closely related in chemical structure, lincomycin and clindamycin also seem to produce muscle paralysis by different mechanisms. Clindamycin is considered to exert a direct depressant action on muscle contractility whereas the action of lincomycin is considered to be primarily a depression of neuromuscular transmission. We report here that each of these antibiotics had a significant but different influence on endplate channel behaviour. Clindamycin increased the rate of miniature endplate current (m.e.p.c.) decay and reduced its voltage sensitivity without altering its exponential nature. Lincomycin split m.e.p.c. decay into an initial rapid phase followed by a prolonged phase.     

Blood-brain barrier damage and prolonged cerebral hyperemia following changes in cerebral perfusion pressure; an experimental EEG study

Résumé En expérimentant sur le chien, l'on peut produire des lésions de la barrière hémo-encéphalique aussi bien en diminuant qu'en élevant la pression de perfusion cérébrale. Ainsi l'administration d'un produit épileptogène tel que la Pénicilline déclenche des crises comitiales alors que celle-ci est normalement arrêtée par la barrière hémoencéphalique lorsque cette dernière est intacte. En clinique, des cas d'épilepsie de même mécanisme ont été demontrés.