Effect of the Jimpy Mutation on Expression of Myelin Proteins in Heterozygous and Hemizygous Mouse Brain

The levels of myelin basic protein, proteolipid protein, and 2',3'-cyclic nucleotide 3'-phosphohydrolase (EC 3.1.4.37) in cerebral hemispheres of wild-type, heterozygous jp/+, and hemizygous jp/Y mice of different ages were determined by radioimmunoassay and immunoblotting. In jp/Y brain the level of myelin basic protein was 8% that of wild-type at all ages. All forms of the protein were reduced although the 21.5K Mr form was relatively spared at early ages compared to the 18.5K, 17K, and 14K Mr forms. The level of 2',3'-cyclic nucleotide 3'-phosphohydrolase was 8% that of wild-type at all ages, and proteolipid protein was undetectable at any age. These results are consistent with the hypothesis that the jimpy mutation blocks myelin morphogenesis subsequent to incorporation of 21.5K Mr myelin basic protein but prior to incorporation of proteolipid protein. In jp/+ brain the levels of the three proteins were reduced commensurately to 60-70% those of wild-type. The deficit was apparent as early as 10 days after birth and remained proportionately constant throughout development. These results suggest that in jp/+ mice, X-chromosome inactivation produces a mosaic population of functionally wild-type and functionally jimpy oligodendrocytes. The former elaborate normal amounts of myelin but do not completely compensate for the myelin deficit due to the latter.     

Regulation of prostaglandin biosynthesis by human ovarian follicular fluid: a mechanism for ovulation?

We have studied the effect of human ovarian follicular fluid on PG production by bovine seminal vesicles in vitro and found that hFF1 contains a factor of high molecular weight (Mr greater than 30,000) which inhibits PG synthase in a dose-dependent manner. Exposure of this substance to protease activity produced a factor of lower molecular weight (Mr less than 1000) which stimulated PG synthase activity. If this is true of ovarian follicles in vivo, it is possible that increased follicular protease activity stimulates PG synthesis at the time of ovulation.     

Vitamin A deprivation selectively lowers uridine nucleotide pools in cultured sertoli cells

The effects of retinoid addition of vitamin A-depleted (UV-irradiated) culture medium on uridine metabolism in cultured Sertoli cells have been studied. After vitamin A depletion, a consistent 2- to 4-fold enhancement of [3H]uridine incorporation into RNA was observed. Several lines of evidence indicate that this enhancement is the result of an increase in the specific activity of the uridine-labeled precursors of RNA. Although vitamin A depletion did not affect either uridine uptake or alter cellular RNA content, a 5-fold increase in the specific activity of UMP was found in vitamin A-depleted cells. This increase results because the cellular content of uracil nucleosides plus nucleotides is selectively lowered in vitamin A-depleted cells. The decreased content of uridine derivatives could be accounted for by a 45-57% decrease in the activity of glutamine-dependent carbamylphosphate synthetase in vitamin A-depleted cells. The effects of vitamin A deprivation on uridine incorporation, as well as carbamylphosphate synthetase activity, could be completely restored to or above control values by supplementing vitamin A-depleted cell culture medium with either retinol or retinoic acid. This effect of vitamin A depletion appears to be highly specific. Under the same conditions, no gross alteration in either the pattern or extent of synthesis of cellular or secreted proteins, glycoproteins, glycosaminoglycans, and lipids was observed. In addition, vitamin A depletion/repletion had no effect on the growth rate or morphology of the cells.     

Progenitors of oligodendrocytes: Limiting dilution analysis in fetal rat brain culture

In this paper, we describe the use of a combination of cell culture techniques and limiting dilution analysis to determine the number of oligodendrocyte progenitor cells and the oligodendrocyte clone size in primary dispersed cultures of 20- to 21-day-old fetal rat brain. Single-cell suspensions (1,2,3 × 10⁶ cells/ml) were plated in either microwell or 100 mm dishes. After 22 days in culture the number of differentiated oligodendrocytes was ascertained by determining the amount of myelin basic protein by radioimmunoassay. The total amount of myelin basic protein was the same in the two types of dish, indicating that proliferation and differentiation were unaffected when oligodendrocytes were grown in microwells. The fraction (F₀) of microwells containing no oligodendrocytes was determined at each cell dilution. F₀ decreased exponentially with increasing total cell concentration. The linearity of the plot of ln F₀ versus cell number indicates that the number of oligodendrocyte progenitor cells is limiting. From the equation describing the Poisson distribution of progenitor cells in microwells we calculated that, at the time of plating, primary cultures of fetal rat brain contain one oligodendrocyte progenitor cell per 1.3 × 10⁵ brain cells, or a total population of 300–500 progenitor cells per brain. The mean oligodendrocyte clone size was determined to be approximately 825 at 22 days and close to 2000 by 35 days in culture. Therefore, each progenitor cell must undergo approximately 11 divisions, on the average, during postnatal development.     

Association of newly synthesized major fl coat protein with infected host cell inner membrane

The bacteriophage fl major coat protein becomes associated with the host cell inner membrane very shortly after it is synthesized. Pulse-chase experiments suggest that the virus is never stably associated with the host cell outer membrane; we propose that it passes directly from the inner membrane to the growth medium.     

Clinical Trial of Lincomycin Hydrochloride in Reiter's Disease

A double-blind trial comparing lincomycin hydrochloride (Mycivin) and placebo in 22 patients with Reiter''s disease showed no significant difference in clinical or laboratory findings between the two groups. It is concluded that lincomycin hydrochloride is no more effective than placebo in the treatment of Reiter''s disease.     

An easy screening assay for the enzymes of the Entner-Doudoroff pathway

An easy and quick assay is described for the semiquantitative determination of the key enzymes of the Enter-Doudoroff pathway: gluconate-6-phosphate dehydrase and 2-keto-3-deoxygluconate-6-phosphate aldolase. It is a micro-method, based on the thin-layer chromatographical identification of the reaction products after incubation of cell-free extracts with both substrates.It is suitable for screening a large number of organisms.     

Studies on the metabolism ofAcetobacter peroxydans

Summary Some physiological and biochemical properties of several strains ofAcetobacter peroxydans have been studied. Their morphology, the aspects of growth on beer-gelatine slants and the colony type are described. The cells are catalase negative and acid resistant. The temperature optimum is 20–25°C. They grow readily on ethanol and on lactate, or on yeast extract alone, but not on carbohydrates and derivatives. They do not consume or oxidize glucose or gluconate. They are overoxidizers. None of these strains was able to grow as hydrogen bacteria. Resting cells oxidize lactate, pyruvate, ethanol, acetate, some Krebs cycle intermediates and several alcohols. Cell-free extracts oxidize glucose-6-phosphate, 6-phosphogluconate and ribose-5-phosphate in suitable conditions. These results favour the taxonomic position of this species as a member of the genusAcetobacter. The results are discussed.