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Item does not contain fulltext, In mammalian spermatozoa, most but not all of the genome is densely packaged by protamines. Here we reveal the molecular logic underlying the retention of nucleosomes in mouse spermatozoa, which contain only 1% residual histones. We observe high enrichment throughout the genome of nucleosomes at CpG-rich sequences that lack DNA methylation. Residual nucleosomes are largely composed of the histone H3.3 variant and are trimethylated at Lys4 of histone H3 (H3K4me3). Canonical H3.1 and H3.2 histones are also enriched at CpG-rich promoters marked by Polycomb-mediated H3K27me3, a modification predictive of gene repression in preimplantation embryos. Histone variant-specific nucleosome retention in sperm is strongly associated with nucleosome turnover in round spermatids. Our data show evolutionary conservation of the basic principles of nucleosome retention in mouse and human sperm, supporting a model of epigenetic inheritance by nucleosomes between generations.

The infrared spectrum of polystyrene has been obtained in the region of 70 cm.???1 to 3200 cm.???1 . These data, plus Raman scattering data from the literature, are used to make a complete assignment of the normal modes of the polystyrene molecule. The benzene ring modes have been analyzed in detail in terms of C 2 v symmetry, and a set of normal vibrations has been proposed. On the basis of previous analyses of the benzene and monosubstituted benzenes, and a study of the combination bands, it has been possible to make a fairly satisfactory assignment of all of the benzene ring fundamentals. Assignments of the CH 2, CH, and skeletal modes are made on the basis of previous studies of spectra of high polymers. The interpretation of the spectrum is in agreement with other evidence that the chain configuration is a random one, i.e., that the polymer is amorphous.

A mathematical model is developed which describes the dynamic characteristics of gas bubbles in subcutaneous tissues. Consideration is given to both inert and reacting gases. The effects of blood perfusion (or oxygen consumption in the tissue in dead animals), diffusion of the dissolved gases, a creep process occuring in the tissue, and thermodynamic behavior of the gases in the cavity on the dissolution of the gas bubbles are taken into account. The stress-strain relation of the tissues in creep is described by the standard linear model of viscoelasticity. The theoretical analysis is presented in three categories: (i) tissue creep controlled, (ii) mass transfer controlled and (iii) the intermediate case where both mechanisms are of comparable importance. A close agreement is obtained between the theoretical predictions and the existing experimental data for subcutaneous inert gas pockets in air breathing rats.

Infrared spectra of polyethylene terephthalate and three of its deuterated analogs have been obtained in the region of 70 to 3600 cm-1, polarized spectra having been obtained down to 330 cm-1. On the basis of analysis of the predicted spectrum, and with the aid of data from benzene and substituted benzenes, a complete assignment of the spectrum has been made. This assignment suggests a modification of the proposed chain structure of this polymer. It also leads to the conclusion that the changes in the spectrum which occur upon crystallization of the polymer are not associated with different isomeric forms of the ---OCH2CH2O--- portion of the chain, but rather with changes in the symmetry and resonance characteristics of the substituted benzenoid ring frame-work.