Liver involvement in acute mammalian malaria with special reference to Plasmodium knowlesi malaria

Gregarine attachment organelles — structure and permeability of an interspecific cell junction

The junction between the gregarine trophozoiteNematocystis magnaSchmidt and an epithelial cell of its earthworm hostLumbricus terrestrisMuller consists of an extensive folding and meshing of the single trilaminar membrane bounding the host cell and the complex folded multilaminar limiting membrane of the trophozoite. They are separated by a structureless intercellular region of some 50 nm in width. Specialized communicating regions or permeable elements were not observed. Transport of a radioactive label across non-junctional and junctional membranes was demonstrated by using tritiated glucose. The attachment organelle of the trophozoite is shown to be capable of allowing metabolites to pass into the cell directly from the host tissue.

Role of complement components in the susceptibility to Plasmodium berghei infection among inbred strains of mice

Inbred strains of mice, sensitive and resistant to Plasmodium berghei infections, including a complement deficient strain were infected with P. berghei. Daily levels of parasitaemia were determined and serum levels of complement components (C3 and C5) measured by standard haemolytic assay. Serum levels of C3 and C5 were depressed in all strains of mice infected with P. berghei. There was no difference in the infectivity and course of P. berghei infection in the co-isogenic C5 deficient and non-deficient strains. The significance of these observations is discussed.

Alterations in thyroid iodine release and the peripheral metabolism of thyroxine during acute falciparum malaria in man

Previous studies of thyroid function during various infections have yielded conflicting results, but most have suggested an acceleration of peripheral thyroxine (T(4)) turnover during the acute infectious illness. In the present studies, thyroid function was examined by a method allowing simultaneous analysis of both endogenous thyroidal release and peripheral T(4) disposal in normal volunteers after induction of acute falciparum malaria. Subjects received iodide-(125)I, followed in 5-7 days by (131)I-T(4) intravenously. 4 days later, infection was induced by the injection of parasitized red blood cells. Bidaily measurements of serum protein-bound (125)I and protein-bound (131)I, and urinary (125)I and (131)I, together with frequent estimates of serum (127)I-T(4) (Murphy-Pattee) and free T(4) (FT(4)), were made during a control period, during acute illness, and during convalescence. Alterations in the peripheral metabolism of (131)I-T(4) during infection included significant decreases in the fractional disappearance rate for T(4) [(k)], and in the clearance and daily disposal of T(4), all of which returned to control values during convalescence. Total serum (127)I-T(4) increased late in the infected period to become greater during convalescence than either before or during infection, while FT(4) did not increase significantly until convalescence. An analysis of serum (131)I-T(4)/(127)I-T(4) and (131)I-T(4)/PB(125)I ratios confirmed these observations. The slope with time of ratios for urinary (125)I/(131)I, a reflection of thyroidal iodine release, was decreased during infection, but rebounded to control values during the convalescent period. The observed increments in serum (127)I-T(4) concentration in the convalescent phase may reflect in part the slowing of (k), but together with the rising ratios of urine (125)I/(131)I suggests enhanced thyroidal T(4) secretion immediately after the acute illness. Thus, with malarial infection, there appears to be an initial depression followed by a rebound in rates of thyroidal iodine release. In contradistinction to other infections, fractional turnover and daily disposal of hormone is decreased in malaria, perhaps due to hepatic dysfunction and the consequent impairment in cellular deiodinative processes.