J. Brian Mudd

Malaria Infection (Plasmodium lophurae): Changes in Free Amino Acids

The course of infection of the avian malaria Plasmodium lophurae in the duckling is characterized by striking increase in the intraerythrocytic free amino acid pool. The quality and quantity of this change result from the presence of the parasite and for the most part reflect the free amino acid pool of the growing plasmodium. No significant changes in the free amino acids in plasma were noted during infection.

Lipid phase separations and intramembranous particle movements in the yeast tonoplast

The tonoplast of Saccharomyces cerevisiae contains regions depleted of intramembranous particles as the cells enter stationary phase. Freeze-fracture studies on intact cells from this growth stage show that a dispersed particle distribution predominates if the cell temperature is raised to 40 degrees C but that particle-depleted areas prevail at or below the cell growth temperature of 30 degrees C. Tonoplasts of isolated vacuoles also contain particle-depleted regions. Differential thermal analysis of lipids extracted from isolated vacuoles show an endothermic transition which encompasses the cell growth temperature. These results suggest that the tonoplast at this stage contains patches of gel-phase lipid and that these patches correspond to the intramembranous particle-depleted areas of the freeze-fractured tonoplast.

Incorporaion of 1c-amino-acids by malaria (plasmodium lophurae): II. Migration and incorporation of amino-acids

Abstract 1. 1. The avian malaria. Plasmodium lophurae, malaria-infected erythrocytes, and normal duck erythrocytes suspended in a protein-free medium resembling the in vivo environmental milieu showed 4 patterns of accumulation of radioactive amino-acids. 2. 2. In vitro, malaria parasites were capable of utilizing exogenously supplied amino-acids for the synthesis of parasite proteins. The protein synthetic activity found for the malariainfected cell could, in general, be represented as the sum of the activities of the uninfected cell and that of the free parasite. 3. 3. A hypothesis is presented which proposes that the rate of amino-acid incorporation by the parasite depends on three factors: (a) the free amino-acid levels, (e) the rate of amino-acid entry, and (c) the abundance of the amino-acid in the protein being synthesized.

Inhibition by ozone of the acylation of glycerol 3-phosphate in mitochondria and microsomes from rat lung

Abstract The synthesis of lipids from [U- 14 C]glycerol 3-phosphate by mitochondrial or microsomal fractions from rat lung was inhibited by ozone. The susceptible reaction was the first acylation of glycerol 3-phosphate. Enzymes unaffected by the ozone exposure included: acyl-CoA thioesterase, acyl-CoA thiokinase, acyl-CoA:acylglycerol 3-phosphate acyltransferase, acyl-CoA:diacylglycerol acyltransferase, and acyl-CoA:acylglycerophosphocholine acyltransferase. The effect of ozone on lipid synthesis is closely comparable to the inhibition by N -ethylmaleimide suggesting that the effect of ozone is the oxidation of enzyme sulfhydryl groups. There was no indication of lipid oxidation caused by ozone and no indication of the production of a stable toxic compound.

[32] Phosphatidylglycerol synthesis in chloroplast membranes

Publisher Summary This chapter describes methods for the interpretation of phosphatidylglycerol (PG) synthesis in the chloroplast. The PG from plant material has a unique characteristic in the presence of trans-3-hexadecenoic acid at the sn-2 position of the molecule. Although PG is found in the mitochondria and the endoplasmic reticulum of higher plants, the PG of the plastids contains the trans-3-hexadecenoic acid. The synthesis of PG from acetate or G-3-P by isolated chloroplasts is stimulated by illumination of the chloroplasts. Breakage of the chloroplasts by osmotic shock eliminated the synthesis of PG. G-3-P is acylated using acyl-ACP in the stroma. This reaction is specific for the sn -1 position, and in the cases so far described is very specific for oleyl-ACP. The second acylation takes place in the inner envelope membrane and is specific for palmitoyl-ACP. The product, 1-oleoyl-2-palmitoyl-sn-G-3-P, is the precursor of PG. Fatty acid analysis of PG from isolated chloroplasts reflects this pathway of synthesis.