Histochemical observations on the exoerythrocytic malaria parasite Plasmodium berghei in rat liver

Enzyme histochemical methods were performed on sporozoite infected liver tissue of rats in order to gain insight into the nutrition and metabolism of exoerythrocytic forms of Plasmodium berghei. The following enzymes were demonstrated in the hepatocytic stages of the parasites, obtained 41 and 48 h after inoculation of sporozoites: acid phosphatase, cytochrome oxidase, NADH-tetrazolium reductase, succinate dehydrogenase, NAD+ and NADP+ dependent isocitrate dehydrogenase, NADP+-dependent malate dehydrogenase, lactate dehydrogenases, 6-phosphogluconate dehydrogenase and glucose-6-phosphate dehydrogenases and alpha-glycerol-phosphate dehydrogenase. The results suggest that a conventional Embden-Meyerhoff pathway, pentose phosphate pathway and Krebs' citric acid cycle may in part be present in these exoerythrocytic parasites. Alkaline phosphatase, nucleoside polyphosphatase, 5' nucleotidase, glucose-6-phosphatase, alpha-glucan phosphorylase, NAD+ dependent malate dehydrogenase, amino-peptidase M and non-specific esterases were not detected by our techniques in the parasite. The enzyme distribution of this intrahepatocytic malaria parasite revealed by histochemistry is compared with the enzyme distribution in the other phases of the parasite's life cycle.     

Comparative effects of meal timing on circadian rhythms of plasma insulin and skin surface temperature in non-human primates

Circadian rhythms of plasma immunoreactive insulin and skin surface temperature were demonstrated in a group of African green vervets. Alteration in the timing of a single daily meal of fixed calorie content resulted in an acrophase shift of plasma immunoreactive insulin for the group of animals and in an acrophase shift of skin surface temperature in 7 or the 8 animals studied. The acrophase shift of skin surface temperature was considerably less then the shift of acrophase of plasma immunoreactive insulin, which closely approximated the shift in meal timing. The results of this study are compared with results of similar studies in human beings.     

Role of the Sarcoplasmic Reticulum Ca2+-ATPase on Heat Production and Thermogenesis

The sarcoplasmic reticulum of skeletal muscle retains a membrane bound Ca²⁺-ATPase which is able to interconvert different forms of energy. A part of the chemical energy released during ATP hydrolysis is converted into heat and in the bibliography it is assumed that the amount of heat produced during the hydrolysis of an ATP molecule is always the same, as if the energy released during ATP cleavage were divided in two non-interchangeable parts: one would be converted into heat, and the other used for Ca²⁺ transport. Data obtained in our laboratory during the past three years indicate that the amount of heat released during the hydrolysis of ATP may vary between 7 and 32 kcal/mol depending on whether or not a transmembrane Ca²⁺ gradient is formed across the sarcoplasmic reticulum membrane. Drugs such as heparin and dimethyl sulfoxide are able to modify the fraction of the chemical energy released during ATP hydrolysis which is used for Ca²⁺ transport and the fraction which is dissipated in the surrounding medium as heat.     

Plasmodium falciparum: studies on mature exoerythrocytic forms in the liver of the chimpanzee, Pan troglodytes

Mature exoerythrocytic forms (EEF) of Plasmodium falciparum from the chimpanzee were examined by light- and transmission electron microscopy from a liver biopsy taken on Day 6 after sporozoite inoculation. Infectivity of the sporozoites obtained from whole mosquitoes which were membrane fed on cultured gametocytes was about 4-6%. In comparison, salivary gland sporozoites added to human hepatocytes in vitro had only a developmental percentage of 0.02 to 0.05% at Day 5. The EEF found in the liver biopsy were not all at the same stage of development. Immature compact parasites were seen simultaneously with stages with fully formed merozoites, indicating a rapid final maturation or asynchrony. At Day 7.5, large numbers of rings were already seen in the peripheral blood, indicating a duration of the liver development of P. falciparum in the chimpanzee of about 5.5-6 days. The process of merogony at the fine structural level was comparable to that described for rodent and other primate parasites in vivo. Compared to the fine structure of EEF in vitro in cultured human hepatocytes, the parasites described here were much more advanced in development. There appeared to be some cell infiltration with collagen deposition around the intracellular parasite; however, no marked degeneration of EEF was observed.