Neurospora crassa mutants deficient in asparagine synthetase

Neurospora crassa mutants deficient in asparagine synthetase were selected by using the procedure of inositol-less death. Complementation tests among the 100 mutants isolated suggested that their alterations were genetically allelic. Recombination analysis with strain S1007t, an asparagine auxotroph, indicated that the mutations were located near or within the asn gene on linkage group V. In vitro assays with a heterokaryon indicated that the mutation was dominant. Thermal instability of cell extracts from temperature-sensitive strains in an in vitro asparagine synthetase assay determined that the mutations were in the structural gene(s) for asparagine synthetase.     

Genetic Analysis of Murine Arylsulfatase C and Steroid Sulfatase

SWR/J mice possess two- to threefold higher 4-methylumbelliferyl sulfate (4MUS), dehydroepiandrosterone sulfate (DHEAS) and estrone sulfate (E1S) sulfatase activities in liver and kidney extracts than do A/J mice. These interstrain activity differences are maintained throughout the 6- to 45-day postnatal period. Characteristics of the hepatic activities of SWR/J mice suggest that all three activities reside in the same enzyme. Biochemical properties of the SWR/J and A/J enzyme were not significantly different. Expression of hepatic enzyme activity is subject to regulation by an autosomal locus possessing two alleles with additive effects. Postnuclear E1S- and DHEAS-sulfatase activities are primarily microsomal. Although postnuclear hepatic 4MUS-sulfatase activity is predominantly microsomal, renal activity is primarily nonmicrosomal. Only that portion of 4MUS-sulfatase occurring in cell membranes appears capable of hydrolyzing E1S and DHEAS. The hepatic- and renal-specific subcellular distributions of 4MUS-sulfatase activity may reflect tissue differences in enzyme processing. Renal 4MUS-sulfatase activity is also controlled by an autosomal gene with two alleles having additive effects. Positive correlation between hepatic and renal 4MUS-sulfatase activities indicates that both activities are most likely influenced by the same gene.     

Imminent oocyte exhaustion and reduced follicular recruitment mark the transition to acyclicity in aging C57BL/6J mice

Quantitative cytological analyses of aging C57BL/6J mouse ovaries revealed that the populations of primordial and growing follicles were nearly exhausted by 13-14 months, the average age of ovulatory failure. Anovulatory animals of this age had, on the average, half the follicle number of their counterparts which were still ovulating. This result suggests that follicular depletion is a factor which contributes to the loss of ovarian cyclicity during aging. However, the considerable overlap of follicle number between the two groups suggests that other, possibly extraovarian, factors also influence the loss of ovulatory function. Although the numbers of follicles recruited for growth was much lower in ovaries from old cycling animals, the number of ova shed cyclically was generally within the range of younger individuals. The observed reduction in incidence of morphological atresia among medium-sized follicles may explain how ovulatory constancy is maintained virtually throughout the cyclical life of the ovary.     

Ultrastructural localization of zinc in rat exocrine pancreas by autoradiography

Summary ⁶⁵Zn was infused at a constant rate for 10 days into a rat. Glutaraldehyde fixed, Epon-araldite embedded ultrathin sections of pancreatic tissue were coated with Ilford L4 emulsion and at 211 days exposure were developed. Silver grains were found over the zymogen granules and over the rough endoplasmic reticulum of exocrine cells. Islet tissue was not observed in these studies. The failure of other zinc localization methods to demonstrate zinc in acinar tissue is discussed as are some of the pitfalls of the autoradiographic method and suggestions for future improvement.Published with the approval of the Director of the Wisconsin Agricultural Experiment Station, Madison. Supported in part by USPHS Research Grant AM-05606 from the Nat. Institute of Arthritis and Metabolic Diseases.Supported by an NIH post-doctoral fellowship.     

The Physician and Industry

Many employers are interested in helping their employees improve and maintain health through a program of preventive medicine designed to supplement health services which already exist in the community. The objectives of such a health program can be attained only through team work between physicians, both within and outside industry. Such specific objectives as the development of measures for the maintenance and improvement of health and the prevention of disease; the provision of readily available diagnostic, treatment and counselling services; the rehabilitation of disabled employees; and the effective administration of sick-benefit plans require the closest communication and co-operation among the occupational health service, the private physician, and other health and welfare agencies. Only by such liaison can the maximum benefits of both preventive and curative medicine be extended to the employee—in his best interest as well as that of the community and the employer.