Augmentation of human and rat lenticular glutathione in vitro by prodrugs of gamma-L-glutamyl-L-cysteine

A marked age-related decrease in glutathione (GSH) levels as well as depression of gamma-glutamylcysteine synthetase activity are factors that are believed to render the aged lens more susceptible to oxidative stress and, therefore, to cataractogenesis. Providing gamma-L-glutamyl-L-cysteine, the dipeptide precursor of GSH, would effectively bypass the compromised first step in its biosynthesis and should protect the lens from GSH depletion. Accordingly, some bioreversible sulfhydryl-, amino-, and C-terminal carboxyl-protected prodrug forms of this dipeptide were prepared. Sulfhydryl protection was in the form of an acetyl thioester, while the carboxyl group was protected as the ethyl ester. These prodrugs were evaluated for their GSH-enhancing activity in cultured human and rat lenses in vitro using an assay that measured the incorporation of [14C]glycine into lens GSH. Ethyl S-acetyl-gamma-L-glutamyl-L-cysteinate (2) raised GSH levels in human lenses by 25% and in rat lenses by >150%. These data suggest that 2 may have potential as an anticataract agent since ethyl gamma-L-glutamyl-L-cysteinate (1a), the des-S-acetyl analog of 2, had been shown (by others) to protect against experimental rodent cataracts. GSH augmentation by 1a was 2% in human lenses and 25% in rat lenses, considerably less than that shown by 2.     

Therapist responsiveness to client interpersonal styles during time-limited treatments for depression

A 4-kb DNA segment of Tenebrio molitor (Insecta, Coleoptera) genomic DNA containing two larval-pupal cuticular genes has been cloned and sequenced. These genes, transcribed in opposite directions, are related in DNA sequence and the proteins encoded are very similar. Each of them contains a single intron located inside the sequence encoding the signal peptide, and a conserved sequence at -200 bp from the mRNA start position. These similarities in sequence suggest that these genes have evolved by duplication followed by diversification and that they are members of a family of genes with a common ancestry. They are the first example of clustered genes in Tenebrio molitor.     

Some potential applications for intercalation compounds of graphite with high electrical conductivity

Intercalation compounds of graphite of the acceptor type have potential engineering applications because of their attractive electrical conductivity properties. Two kinds of applications are considered in this paper. The first concerns a composite, formed by enclosing an intercalation compound synthesized from high quality crystalline graphite in a matrix of copper. With this form of composite it is found that there are both intrinsic and extrinsic advantages pertaining to the use of a material that has a conductivity higher than and a density lower than that of copper. The second form is a composite compound of intercalated graphite fibers contained in a matrix of epoxy. Extraordinary advantages in this case result from the fact that while intercalation of the fibers produces an order of magnitude increase in their electrical conductivity, when these fibers are incorporated into an epoxy matrix, the composite conductivity is increased by two orders of magnitude over its pristine fiber counterpart. It is projected that these desirable electrical conductivity characteristics portend large scale uses for the acceptor compounds of graphite as substitutes for the present standard conductors, and as a way of upgrading the performance of carbon/graphite materials.     

Sequential switch of biomineral crystal morphology using trivalent ions

Many biominerals are laminated such that crystal shape or habit changes from layer to layer thus yielding exquisitely designed composite materials with tightly controlled properties. Although lamination in biominerals is usually performed using peptides and proteins, here we introduce a new strategy by which sequential addition or depletion of inorganic trivalent ions in a supersaturated solution can be used to switch the surface morphology of calcium oxalate monohydrate (COM) back and forth, resulting in either the growth of flat crystalline sheets or of nanostructures oriented perpendicular to the surface. We propose that the occupation of a Ca(2+) site by Eu(3+) ion switches the orientation of the COM unit cell. The need to compensate the third charge forces coordination of Eu(3+) to an additional oxalate ion ((-)OOC-COO(-)) in an orientation that is not compatible with the initial unit cell. This mechanism of switching the orientation of the unit cell is unique, as it does not involve the use of expensive and thermally labile biomolecules. Suggestions of how to extend this strategy to engineer non-biological nanocomposites are given.     

Postural changes in plasma renin activity and responses to vasoactive drugs in a case of Shy-Drager syndrome

A male aged 47 years with gross autonomic insufficiency as part of the Shy-Drager syndrome is described. He did not sweat normally when warmed, and his circulatory responses to mental arithmetic, the Valsalva manoeuvre, and head-up tilt were abnormal indicating severe sympathetic failure. During head-up tilt there was a rise in plasma renin activity and plasma aldosterone. It is argued that plasma renin activity is not dependent on sympathetic nervous activity and may be mediated by renal baroreceptors. These rises may help sustain the blood pressure in such patients during repeated head-up tilts. Infusions of L-noradrenaline and angiotension produced greater hypertension, and injections of isoprenaline greater hypotension than in controls. Although it is difficult to exclude the possibility that one factor in this may be hypersensitivity of receptors in blood vessel walls, the principal factor is likely to be the absence of those baroreflexes of which the efferent pathways are in the sympathetic nervous system.