Non-canonical Targets of HIF1a Impair Oligodendrocyte Progenitor Cell Function

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Electron Spin Resonance Analysis of the Nitroxide Spin Label 2,2,6,6-Tetramethylpiperidone-N-Oxyl (Tempone) in Single Crystals of the Reduced Tempone Matrix

The nitroxide spin label Tempone (2,2,6,6-tetramethylpiperidone-N-oxyl) can be reduced with ascorbic acid to give a nonparamagnetic species. Single crystals of reduced Tempone serve as a suitable host matrix to orient trace quantities of Tempone for ESR analysis. In these crystals the majority of the Tempone molecules are well-oriented, but a smaller fraction of the molecules tumble freely to give an isotropic electron spin resonance (ESR) spectrum. ESR transitions for the oriented molecules are saturated at much lower microwave power levels than for the tumbling molecules. For the oriented molecules, an analysis of the anisotropy of the spectroscopic splitting factor (g) gives principal values of g₁ = 2.0094, g₂ = 2.0061, g₃ = 2.0021. The hyperfine coupling tensor is nearly axially symmetric, with principal values (in gauss) of A₁ = 6.5, A₂ = 6.7, A₃ = 33.0. Within experimental error, the principal axis systems for the g tensor and the hyperfine tensor are identical. Comparison of the average values of g and A with the isotropic values of these parameters for Tempone in solvents of different polarity suggests a method for choosing the most appropriate tensor elements to be used for spin label experiments in various solvent systems.     

Evolutionary relations between subtypes of telomere-associated repeats inChironomus

Summary Telomere-associated DNA inChironomus pallidivittatus contains tandemly repeated 340-bp units. We show that they are distributed among several subtypes of which we have characterized two, M1 and D1, with regard to base sequence, homogeneity, and intertelomeric distribution. Each subpopulation is highly homogeneous and the two subtypes have identical consensus sequences throughout 90% of their lengths. In the remaining part the homology is only about 60%. Each subpopulation has its specific intertelomeric distribution and there is no difference in the degree of homogenization within and between telomeres. The repeat unit contains two pairs of subrepeats embedded in linker DNA. This provides a model that makes it possible to relate the two subtypes to each other with regard to evolutionary history. The difference between the two subtypes is due to mutations that have occurred in only one of them, D1, resulting in a decreased similarity between one of its pairs of subrepeats. This type of repeat unit is therefore believed to be derived from the other, M1. The local decrease in similarity between M1 and D1 suggests that homogenization between them occurs by gene conversion.     

OPERATIONS UPON THE AGED

From the point of view of the surgeon, as repeatedly emphasized in the surgical literature, the mortality rate for operations upon old persons is only slightly higher for elective surgical operations than for the same operations on younger persons when proper preoperative and postoperative precautions are taken. However, the mortality rate for emergency operations is much higher in old persons than in younger ones. Many surgeons believe, therefore, that disease for which operation is otherwise indicated should be treated surgically irrespective of the age of the patient per se.The authors'' experience with operations upon old persons at the San Francisco Hospital accords with these conclusions.