Glutathione-related inhibition of prostaglandin metabolism

Placental homogenates contain a heat-stable, dialyzable fraction which specifically inhibits two placental enzymes, both of which possess 15-hydroxyprostaglandin dehydrogenase and 9-ketoprostaglandin reductase activities. The inhibition of the two enzymes is the same. The inhibitor has been resolved into two components by gel filtration on a column of Sephadex LH-20. The component which eluted first has been identified as oxidized glutathione (GSSG), the other as a glutathione-containing material (GSX). Inhibition of the 15-hydroxyprostaglandin dehydrogenase activity is competitive with respect to the prostaglandin substrate (K_i^GSSG = 26 μM, K_i^GSX = 1.4 μM). Inhibition of the 9-ketoprostaglandin reductase activity is also competitive with respect to the prostaglandin substrate (K_i^GSSG = 68 μM). The most effective inhibitor of the 15-hydroxyprostaglandin dehydrogenase is the prostaglandin A₁-glutathione adduct (K_i = 0.27 μM). This compound is not a substrate for oxidation of the 15-hydroxyl group but it is the best substrate found to date for reduction of the 9-keto function.     

Versatile Method for Evaluating a Cell Culture by Various Morphological Techniques

Cellulose acetate is a versatile material for evaluating cells grown under identical conditions by various morphological techniques. This inexpensive material is transparent, easily cut to size and shape, nontoxic to cell cultures, and resistant to most chemicals used in histochemistry and in scanning and transmission electron microscopy. Samples may be obtained during and after the culture process. Cellulose acetate slides can be mounted directly over glass slides for direct observation and are easily peeled off plastic blocks for electron microscopy, leaving the cells behind. Relative disadvantages include its autofluorescence and a tendency to soften in strong acids or pure solutions of organic solvents such as xylene and propylene oxide.     

Stereospecific activity of 1-O-alkyl-2-O-acetyl-sn-glycero-3-phosphocholine and comparison of analogs in the degranulation of platelets and neutrophils

1-O-Hexadecyl-2-O-acetyl-$\text{sn}$-glycero-3-phosphocholine (platelet activating factor) stimulated the degranulation of rabbit platelets and human neutrophils, whereas the enantiomer, 3-O-hexadecyl-2-O-acetyl-$\text{sn}$-glycero-1-phosphocholine, was inactive. The analogs compared had the following relative potencies in degranulating platelets and neutrophils: 1-O-hexadecyl-2-O-acetyl-$\text{sn}$-glycero-3-phosphocholine > 1-O-hexadecyl-2-O-ethyl-$\text{sn}$-glycero-3-phosphocholine >$\text{rac}$-1-O-octadecyl-2-O-ethylglycero-3-phosphocholine = 1-O-hexadecyl-2-O-methyl-$\text{sn}$-glycero-3-phosphocholine >$\text{rac}$-1-O-dodecyl-2-O-ethyl-glycero-3-phosphocholine. The deacetylated compound, 1-O-hexadecyl-2-lyso-$\text{sn}$-glycero-3-phosphocholine, and 1-O-hexadecyl-2,2-dimethylpropanediol-3-phosphocholine were inactive. The active analogs selectively desensitized the response to each other in the neutrophils. It is suggested that these compounds may activate cells through interaction with a stereospecific receptor.     

Citric acid production from glucose. II. Growth and excretion kinetics in a trickleflow fermentor

The growth and citric acid production kinetics of Saccharomycopsis lipolytica on glucose is investigated in a trickle-flow fermentor. Liquid hold-up and oxygen-transfer coefficient in the reactor column filled with cylindrical wood chips have been determined and found in agreement with chemical engineering correlations. Citric acid production starts at the end of the growth phase and proceeds at a constant specific rate of 0.025 hr^?1for about 80 hr. The fermentor can then be regenerated by addition of ammonia, which induces new growth and excretion phases. Comparing the metabolic behavior of free and immobilized cells, two main kinetic differences are observed. First, the growth phase is linear with the bound cells instead of exponential in the stirred fermentor. Second, in the trickle-bed fermentor acid productivity and oxygen acid yield are reduced by 30%. Oxygen diffusional limitations, mainly in the biomass film, and alterations in bound cell metabolism are shown to be responsible of the kinetic modifications. Simple modelizations of oxygen diffusion effects are also presented to support the interpretation of the experimental data.     

Chronic Hepatitis Associated with Drug Abuse: Significance of Hepatitis B Virus

One hundred and seventy-seven former heroin addicts, consisting of 85 who were newly admitted to a methadone maintenance program and 92 who had received methadone for a mean period of 30 months, were prospectively studied for up to 2 years in order to determine: (1) the effect of heroin withdrawal on the hepatic abnormalities, and (2) the incidence of HBsAg, anti-HBs, and anti-HCc as indices of the frequency of hepatitis B virus infection. Our study indicates that (1) hepatic abnormalities persist when heroin is discontinued and are not temporally related to drug and/or needle usage, and (2) that 71% of subjects had either HBsAg or anti-HBs; anti-HBc was tested for in 16 patients and was present in 100%, although 9 of the 16 were both HBsAg- and anti-HBs-negative. This study suggests that hepatitis B is largely responsible for the liver dysfunction. It is proposed that an abnormality in immune function, induced by heroin, is responsible for the high incidence of chronic hepatitis. Attention is drawn to the similarity between former drug addicts and hemophiliacs, since both develop chronic hepatitis in spite of anti-HBs in the serum.