13C NMR analysis of methionine sulfoxide in protein.

The 13C epsilon NMR signal of methionine sulfoxide is 22.6 ppm downfield from that of methionine. This affords a method by which the extent of methionine oxidation can be determined in intact protein. We demonstrate the utility of this approach with beta-galactosidase enriched with 13C in its methionine methyls.     

Variance Component Analysis of Allozyme Frequency Data from Eastern Populations of DROSOPHILA MELANOGASTER

Gene frequency variation at eight polymorphic allozyme loci in Drosophila melanogaster populations in North Carollina and the east coast of the United States were analyzed utilizing the variance component estimation procedures suggested by Cockerham (1969, 1973). These variance components were used to estimate correlations of genes within small geographic regions. The average (over loci) correlation between genes in the same individual within subpopulations was estimated to be 0.033. That between genes in the same subpopulation in different individuals was estimated to be very small, although significantly different from zero. The macrogeographic variation measured by the correlation of genes sampled from the same local region was large for some loci and smaller for others. this variation was also analyzed by correlation with latitude and longitude. Several previously recognized clines were identified as were several new clines.--These results were interpreted as indicating either some degree of nonrandom mating and local breeding unit isolation or a low frequency of null alleles. The geographic and temporal variation has no simple interpretation.     

Amphetamine-induced release of dopamine from the substantia nigra in vitro

Incubation of chopped tissue from the substantia nigra of the rat brain with d-amphetamine resulted in a significant release of [³H]dopamine into the incubation medium. This effect was observed with both exogenous [³H]dopamine previously taken up by the tissue and [³H]dopamine endogenously synthesized from L-[3,5-³H]tyrosine. The observed release was greater in magnitude when the apparent conversion of released dopamine to 3-methoxytyramine was taken into account. The relevance of the present results to the previously postulated self-inhibition by dopaminergic neurons of the substantia nigra pars compacta is discussed. The present data also provide support for the concept that catechol-O-methyltransferase (E.C.2.1.1.6.) is located primarily extraneuronally in brain.     

Silicon in rat liver organelles: Electron probe microanalysis

Summary Electron probe microanalysis of unfixed freeze-substituted rat liver tissue embedded in Spurr's low viscosity epoxy resin demonstrated the occurrence of Si as well as P, S, and Cl in the nucleus, nucleolus, mitochondria, and rough endoplasmic reticulum. Chemical analysis confirmed that the Si in the organelles did not originate from instrumental contaminants. This suggests that Si may be involved in the biochemistry of these subcellular organelles.Supported by Grant GM-08229-12-13 from the National Institutes of Health, USPHS.We are grateful to the Kevex Corporation and Mr. Glenn W. Meyer, Sales Engineer, for the use of the Kevex X-ray spectrometer; we wish to thank as well the Perkin-Elmer Corporation and their Western Branch Manager, Mr. Michael E. Mullen and Senior Microscopist, Mr. Minoru Shinorhara, for use of and assistance with the Hitachi HU 12 A transmission electron microscope. We also wish to acknowledge Mary Louise Chiappino for her technical assistance in preparing the thin sections, the final micrographs and the X-ray photographs, and Darlene Lum for technical assistance in the laboratory.