Pyrrolo[2,3-d]pyrimidines containing an extended 5-substituent as potent and selective inhibitors of lck I.

Pyrrolo[2,3-d]pyrimidines containing a 5-(4-phenoxyphenyl) substituent are potent and selective inhibitors of Ick in vitro; some compounds are selective for lck over src. Data are shown for two compounds demonstrating that they are potent and selective inhibitors of IL2 production in cells.

The free energies for mutating S27 and W79 to alanine in streptavidin and its biotin complex: the relative size of polar and nonpolar free energies on biotin binding.

We have carried out calculations on the relative free energy of binding of biotin and its S27A and W79A mutants to streptavidin. Consistent with earlier suggestions by Miyamoto and Kollman from free energy component analysis and recent experiments by Stayton and coworkers, the reduction in binding strength by the W79A mutant is significantly larger than that of the S27A mutant. Proteins 1999;36:471-473.

Nerve terminal damage by beta-bungarotoxin: its clinical significance.

We report here original data on the biological basis of prolonged neuromuscular paralysis caused by the toxic phospholipase A2 beta-bungarotoxin. Electron microscopy and immunocytochemical labeling with anti-synaptophysin and anti-neurofilament have been used to show that the early onset of paralysis is associated with the depletion of synaptic vesicles from the motor nerve terminals of skeletal muscle and that this is followed by the destruction of the motor nerve terminal and the degeneration of the cytoskeleton of the intramuscular axons. The postjunctional architecture of the junctions were unaffected and the binding of fluorescein-isothiocyanate-conjugated alpha-bungarotoxin to acetylcholine receptor was not apparently affected by exposure to beta-bungarotoxin. The re-innervation of the muscle fiber was associated by extensive pre- and post-terminal sprouting at 3 to 5 days but was stable by 7 days. Extensive collateral innervation of adjacent muscle fibers was a significant feature of the re-innervated neuromuscular junctions. These findings suggest that the prolonged and severe paralysis seen in victims of envenoming bites by kraits (elapid snakes of the genus Bungarus) and other related snakes of the family Elapidae is caused by the depletion of synaptic vesicles from motor nerve terminals and the degeneration of the motor nerve terminal and intramuscular axons.

Myotoxic activity of the toxic phospholipase, notexin, from the venom of the Australian tiger snake.

Notexin is a neurotoxic and myotoxic phospholipase A2 derived from the venom of the Australian tiger snake, Notechis scutatus. Though the phospholipase activity has been implicated in the toxicity of notexin, little is understood of its site and mode of action. In this study we investigated the myotoxicity of notexin on the skeletal muscle of the rat. Using immunogold labeling both in vivo and in vitro, we demonstrated that notexin bound exclusively to the sarcolemma. At the early stages when notexin was injected into the muscle there was no evidence of internalization, though at more advanced degeneration when muscle fibers were necrotic, the toxin was able to penetrate the interior of the fibers to exhibit nonspecific labeling. We also showed the toxin was able to bind to glycolytic muscle fibers, which are known to be resistant to the myotoxic effects of notexin. Electron microscopy confirmed the localization of the binding site to the sarcolemma. Scanning electron microscopy showed that the primary pathological changes associated with exposure to notexin were the appearance of areas of hypercontraction along the muscle fibers associated with small lesions in the sarcolemma. At more advanced stages large tears appeared in the sarcolemma between adjacent areas of hypercontraction, revealing apparently intact myofibrils below. We conclude that the sarcolemma is the binding site for the toxin. We propose that the hydrolytic activity causes the appearance of small lesions in the membrane, the loss of ion gradients, and hypercontraction. The weakened area between sites of hypercontraction is then ruptured, leading ultimately to the degeneration of the muscle fibers.

Visibility of red and green electroluminescent diodes for color-anomalous observers.

This report identifies and characterizes those segments of the population for whom the visibility of electroluminescent diodes is significantly abnormal. Red- and green-emitting GaP and red-emitting GaAsP diodes are considered explicitly. It is concluded that the most important classes of anomalous and dichromatic observers are the protanopes and protanomalous, for whom the brightness of red electroluminescent diodes is substantially reduced from that perceived by normal observers. Protanopes and protanomalous observers occur at the rate of about one in fifty in the male population. They possess approximately 14% of the normal photopic sensitivity when viewing red-emitting GaP diodes and about 10% when viewing red-emitting GaAsP diodes. No classes of anomalous or dichromatic observers have been found to experience significantly decreased visibility for green GaP diodes.