Immunoregulatory functions of paf-acether. VI. Dual effect on human B cell proliferation

The role of paf-acether (paf), a phospholipid cytokine, in the modulation of human B cell function was investigated. Paf, from 1×10⁻⁵ M to 10⁻⁶ M, decreased B cell proliferation induced by both phorbol myristate acetate (PMA) and anti-IgM antibodies (anti-IgM Ab). By contrast, 1×10⁻⁷ M to 1×10⁻⁹ M paf enhanced PMA triggered, but not anti-IgM triggered B cell proliferation. B cell proliferation was modulated between 24 and 72 hr of culture indicating that the effect of paf did not merely reflect a shift in proliferation kinetics. Interestingly, paf also enhanced the spontaneous proliferation of a Burkitt lymphoma-derived B cell line, Raji, which suggests that paf can directly act on B cells. The modulatory effect of paf on peripheral blood B cells was independent of PMA concentration, yet the effect on Raji cells was dependent upon cell density. The data suggest that paf is a potent modulator of B cell function, and may be involved in the control of humoral immune response. Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989.     

Preparation of optically active poly β-propiolactones

Racemic -methyl--n-propyl--propiolactone is readily polymerized with zinc and cadmium chiral glycolates leading to optically active polyesters. The stereoelectivities observed are lower than for oxiranes and thiiranes with the same initiator system. A value of rotatory power for pure enantiomer _o, is deduced from NMR measurements in the presence of chiral solvent. The structure of polymers is discussed on the basis of NMR results.     

Poly(vinyl) chloroformate and derivatives

Poly(vinyl chloroformates) of high molecular weight have been successfully modified by amines and by KCN. Poly (vinyl carbonates) have been prepared by polymerization of phenyl vinyl carbonate.     

Pitch-coke interactions

Penetration of molten pitch into a coke bed is correlated with thermodynamic properties of pitch and of pitch-coke interfaces, as well as with the rheology of the liquid. A review of the possible relation between the above properties and the molecular properties of the pitch is presented.     

Application of a counter-current gaseous diffusion model to the oxidation of hafnium carbide at 1200 to 1530°C

A counter-current gaseous diffusion model is presented to describe the oxidation of hafnium carbide between 1200 and 1530°C. The model separates the porous hafnia scale into two gas diffusion regions separated by a flame front, where O ₂ and CO react to form CO ₂.In the outer region, O ₂ and CO ₂ counter-diffuse; in the inner region, CO ₂ and CO counter-diffuse. The concentration gradients of each gaseous specie in the pores of the hafnia are determined and the rate of oxidation is calculated. A porosity of 2% and a pore radius of 0.01 m are representative of the values observed in hafnia during the early stages of HfC oxidation. These values lead to predictions of parabolic rate constants that are close to those measured by thermogravimetric analysis. In addition, the predicted and measured parabolic rate constants are shown to have the same dependence upon temperature and oxygen partial pressure.     

Mixing in the transition flow regime with helical ribbon agitators

The effects of the non-Newtonian properties on the effective deformation rate, mixing and circulation times and flow behaviour have been investigated in the transition flow regime of mixing systems. Based on the equivalent Couette flow, three models are proposed and are shown to predict similar and drastic increases of the effective deformation rate with the impeller rotational speed in the transition regime. The predictions are shown to fit very well data obtained for various non-Newtonian fluids mixed with helical ribbon agitators, and with literature data for anchor, blade turbine and flat disc agitators. The elasticity along with shear-thinning properties appear to have slight effects on the dimensionless mixing and circulation times in the transition regime, whereas their effects in the laminar regime are quite drastic, as reported by others.     

A new short-path distillation system applied to the reduction of cholesterol in butter and lard

A molecular distillation plant, built particularly to increase the separation efficiency and to obtain safer working conditions, was tested to remove cholesterol from anhydrous butter and lard. A preliminary experiment was carried out with butter to evaluate the fractionation obtained at temperatures between 190 and 250°C and residual pressures between 10⁻³ and 10⁻⁴ torr. A second experiment was carried out at 185°C and at the maximum operational vacuum, evaluating the fractionation achieved within a time scale between 30 and 180 min. Cholesterol was almost completely removed during the second hour with minimal loss of low-molecular weight triglycerides. An experiment was carried out with lard at 250°C and maximum achievable operational vacuum (10⁻⁴ Torr), lasting approximately 6 h, and cholesterol was removed almost completely during the second hour without significant modifications in the triglyceride composition. This situation remained constant throughout the duration of the test.     

Effect of dietary n−3 and n−6 polyunsaturated fatty acids on lipid-metabolizing enzymes in obese rat liver

This study was designed to examine whether n−3 and n−6 polyunsaturated fatty acids at a very low dietary level (about 0.2%) would alter liver activities in respect to fatty acid oxidation. Obese Zucker rats were used because of their low level of fatty acid oxidation, which would make increases easier to detect. Zucker rats were fed diets containing different oil mixtures (5%, w/w) with the same ratio of n−6/n−3 fatty acids supplied either as fish oil or arachidonic acid concentrate. Decreased hepatic triacylglycerol levels were observed only with the diet containing fish oil. In mitochondrial outer membranes, which support carnitine palmitoyltransferase I activity, cholesterol content was similar for all diets, while the percentage of 22∶6n−3 and 20∶4n−6 in phospholipids was enhanced about by 6 and 3% with the diets containing fish oil and arachidonic acid, respectively. With the fish oil diet, the only difference found in activities related to fatty acid oxidation was the lower sensitivity of carnitine palmitoyltransferase I to malonyl-CoA inhibition. With the diet containing arachidonic acid, peroxisomal fatty acid oxidation and carnitine palmitoyltransferase I activity were markedly depressed. Compared with the control diet, the diets enriched in fish oil and in arachidonic acid gave rise to a higher specific activity of aryl-ester hydrolase in microsomal fractions. We suggest that slight changes in composition of n−3 or n−6 polyunsaturated fatty acids in mitochondrial outer membranes may alter carnitine palmitoyltransferase I activity.     

Hydrolysis of biliary phospholipids in the upper small intestine of the chick

Chick endogenous phospholipids were doubly labeled by an intravenous injection of [³²P] phosphate and [1-¹⁴C] oleic acid, and the free fatty acid and phospholipid fraction of gall bladder bile and in contents of upper small intestine were analyzed 4 days later. There was evidence of hydrolysis of biliary phosphatidylcholine to lysophosphatidylcholine in the duodenum and jejunum, but this did not account for the pronounced increase in the¹⁴C radioactivity of the free fatty acids relative to the³²P phospholipid radioactivity between bile and upper intestinal segments. It is suggested that phosphatidylcholine is largely absorbed in the duodenum of the chick while the remainder is progressively hydrolyzed and absorbed.     

Sitona lineatus Host-Plant Odors and Their Components: Effect on Locomotor Behavior and Peripheral Sensitivity Variations

Adult Sitona lineatus L., (Coleoptera: Curculionidae) feed on the leaves of various species of leguminous plants, and females lay in the vicinity of pea plants, the roots of which are eaten by the larvae. A study of the volatiles from several legumes and of the response of S. lineatus individuals to these substances was undertaken using two complementary techniques: behavioral, to study the locomotory orientation; and electrophysiological, using electroantennography (EAG). Four volatile compounds, cis-3-hexen-1-ol, 2-hexenal, cis-3-hexen-1-yl acetate, and 3-octanone, were identified from pea, vetch, clover, and lucerne, by coupled gas chromatography–mass spectrometry (GC-MS) and coupled gas chromatography–infrared spectrometry (GC-IR). After emergence from July to mid-November, the imago display high response to the odor of pea and some other leguminous plants. A second period of enhanced sensitivity was observed during crop colonization from March to May. High EAG response to pea odor and cis-3-hexen-1-yl acetate was correlated with periods of enhanced locomotory orientation during these months. Experimental results indicate that cis-3-hexen-1-yl acetate could play a key role in discriminating pea among other acceptable leguminous species.