Age-related changes in central nervous system enkephalins and substance P

Concentrations of substance P and met- and leu-enkephalins were measured by radioimmunoassay in discrete rat brain nuclei of young (4–5 months) and old (24–26 months) rats. The substance P content of n. anterior (hypothalami), n. ventromedialis, n. premamillaris ventralis, n. interstitialis striae terminalis, n. entopeduncularis and n. dorsalis raphes is reduced in old rats. The met-enkephalin content is decreased in n. suprachiasmaticus, n. arcuatus and n. premamillaris ventralis while the leu-enkephalin content of n. preopticus medialis, n. suprachiasmaticus, n. paraventricularis, n. ventromedialis and n. premamillaris ventralis is decreased in old rats.     

Serum lipoproteins and albumin in the lecithin: Cholesterol acyltransferase reaction

The unique features of pig ovarian follicular fluids, i.e., presence of high density lipoprotein (HDL) only and lecithin: cholesterol acyltransferase (EC 2.3.1.43; LCAT) activity, provides a good model to study the effect of serum lipoproteins and serum albumin on the LCAT reaction. $\text{In}\text{vitro}$ cholesterol esterification is enhanced when very low density lipoprotein (VLDL) and low density lipoprotein (LDL) fractions are added, but is inhibited when one or the other of these lipoproteins is absent. High concentrations of HDL₂ result in decreased activation which can be compensated for by the addition of the VLDL-LDL mixture. These findings suggest that the rate of cholesterol esterification in ovarian follicular fluid may be enhanced by providing the exogenous VLDL and LDL as the recipients of HDL-cholesteryl ester. The inhibition of LCAT activity caused by free fatty acid and lysophosphatidylcholine can be partially reversed by the addition of serum albumin, suggesting that serum albumin may regulate the LCAT reaction.     

Specific progesterone receptors in dimethylbenzanthracene (DMBA)-induced mammary tumors.

Properties of a progesterone receptor present in the cytosol (105,000 xg supernatant) of dimethylbenzanthracene (DMBA)-induced mammary tumors were studied using the highly potent progestin [3H]R 5020 (17, 21-dimethyl-19-nor-pregna-4, 9-diene-3,20-dione). As shown by sucrose gradient analysis, specific binding of [3H] R 5020 is associated with components migrating at 7-8S and 4S. Low affinity binding of the synthetic progestin is eliminated by treatment with dextran-coated charcoal. [3H] R 5020 binding is highly progestin-specific since it is easily displaced by unlabelled norgestrel, R 5020 and progesterone while estradiol-17beta, dihydrotestosterone, testosterone, testosterone and diethylstilbestrol have much lower activity. Dexamethasone and cortisol have little, if any, effect on [3H] R 5020 binding.     

Rapid and efficient separation and identification of the two molecular forms of human adenosine deaminase by thin-layer gel filtration chromatography

Two molecular forms of adenosine deaminase have been found in human tissues. The column gel filtration method has been used for the separation of the two enzyme forms. Routine separation and analysis of the enzyme forms based on the molecular size difference can be achieved by thin-layer gel filtration on Sephadex G-200 superfine gel. The thin-layer method has been found to be more rapid and efficient than the column method. Enzymes in crude preparations can be studied effectively with the thin-layer method.     

Intracellular localization of GDP-l-fucose: Glycoprotein and CMP-sialic acid: Apolipoprotein glycosyltransferases in rat and pork livers

A GDP-l-fucose:glycoprotein fucosyltransferase which transfers l-fucose to terminal β-N-acetyl-d-glucosaminyl residues of sialidase-, β-galactosidase-treated α₁-acid glycoprotein and a CMP-sialic acid:glycoprotein sialyltransferase acting on sialidase-treated apolipoprotein-Ala₁ from human very low density lipoprotein have been shown to be concentrated in rat liver Golgi apparatus preparations at enrichments of 40- and 45-fold, respectively, and in pork liver Golgi-rich fractions at enrichments of 35- and 20-fold, respectively. A second fucosyltransferase acting on sialidase-treated α₁-acid glycopretein was absent from rat liver and was enriched only 13-fold in a pork liver Golgi-rich fraction. The smooth-surfaced microsome fraction was the only other rat liver subcellular fraction with appreciable levels of the GDP-l-fucose: β-N-acetyl-d-glucosaminide fucosyltransferase and the lipoprotein sialyltransferase (enrichments of 2.6- and 5.2-fold, respectivley). This enrichment could not be attributed to the plasma membrane content of the smooth microsome fraction since plasma membrane fractions from rat liver were shown to have relatively low concentrations of these two transferases (enrichments of 0.3 or less). Rat liver plasma membrane was also shown to have similarly low relative specific activities for three other glycosyltransferases (sialyl-, galactosyl-, and N-acetylglucosaminyl-). The accurate determination of the glycosyltransferase activities of the plasma membrane fraction required the use of relatively low concentrations of plasma membrane and relatively high concentrations of nucleotide-sugars in order to avoid interference by the high nucleotide-sugar pyrophosphatase and hydrolase activities of this fraction.     

HIV Sexual Transmission Is Predominantly Driven by Single Individuals Rather than Discordant Couples: A Model-Based Approach

Understanding the relative contribution to HIV transmission from different social groups is important for public-health policy. Information about the importance of stable serodiscordant couples (when one partner is infected but not the other) relative to contacts outside of stable partnerships in spreading disease can aid in designing and targeting interventions. However, the overall importance of within-couple transmission, and the determinants and correlates of this importance, are not well understood. Here, we explore how mechanistic factors – like partnership dynamics and rates of extra-couple transmission – affect various routes of transmission, using a compartmental model with parameters based on estimates from Sub-Saharan Africa. Under our assumptions, when sampling model parameters within a realistic range, we find that infection of uncoupled individuals is usually the predominant route (median 0.62, 2.5%–97.5% quantiles: 0.26–0.88), while transmission within discordant couples is usually important, but rarely represents the majority of transmissions (median 0.33, 2.5%–97.5% quantiles: 0.10–0.67). We find a strong correlation between long-term HIV prevalence and the contact rate of uncoupled individuals, implying that this rate may be a key driver of HIV prevalence. For a given level of prevalence, we find a negative correlation between the proportion of discordant couples and the within-couple transmission rate, indicating that low discordance in a population may reflect a relatively high rate of within-couple transmission. Transmission within or outside couples and among uncoupled individuals are all likely to be important in sustaining heterosexual HIV transmission in Sub-Saharan Africa. Hence, intervention policies should be broadly targeted when practical.