Experimental infections of simians with human malaria: attempts to infect Callithrix penicillata with Plasmodium falciparum

After reviewing the use of non-human primates of the Old and New Worlds for human malaria research, we concluded that another experimental animal which is easily available to use and possible to rear indoors is needed. Thus, we studied the susceptibility of the marmoset Callithrix penicillata to Plasmodium falciparum erythrocytic infections. The marmosets received various P. falciparum human isolates, directly from a patient and from continuous cultures. The Palo Alto strain, which has been adapted to the night monkey Aotus trivirgatus and further maintained in the squirrel monkey Saimiri sciureus was also used. In a total of 20 marmosets we performed 31 inoculations, with 10(5) to 10(9) parasites, intraperitoneally, intracardiacly or intravenously. Blood samples from each animal were examined daily up to day 90 post-inoculation. None of the intact marmosets developed patent infections. Four out of 19 C. penicillata, previously splenectomized, showed circulating parasites for up to five days after intravenous inoculation with the Palo Alto strain, becoming negative thereafter. Neither the addition to the simian diet of p-aminobenzoic acid, essential for the parasite metabolism, nor drug-immunosuppression, improved the marmoset susceptibility to P. falciparum.     

Copepods of the Juréia ecological reserve,state of São Paulo,Brazil. II. The genera Hesperocyclops,Muscocyclops, and Bryocyclops (Cyclopoida,Cyclopidae)

Cyclopid copepods collected mainly in aquatic microcosms and semiterrestrial habitats in the Juréia Ecological Reserve are studied. Hesperocyclops herbsti and Bryocyclops campaneri are described as new species and their taxonomical relationships discussed. Females of Muscocyclops operculatus (Chappuis) are redescribed and the males described for the first time. An emended diagnosis for Muscocyclops is proposed.     

Voltage-dependent activation and inactivation of calcium channels in PC12 cells. Correlation with neurotransmitter release

The existence and mechanisms of inactivation of voltage-gated Ca2+ channels are important, but still debatable, physiological problems. By using the Ca2+ indicators quin2 and fura-2, we demonstrate that in PC12 cells voltage-gated Ca2+ channels undergo inactivation dependent on both voltage and [Ca2+]i. Inactivation, however, is never complete and a small number of channels remains open during prolonged depolarization, explaining the steady state elevation of [Ca2+]i observed in cells depolarized with high KCl. A close parallel exists between Ca2+ channel inactivation and the transient nature of neurotransmitter release: secretion is rapidly stimulated during the first 30 s of depolarization, when a transient overshoot in [Ca2+]i can be demonstrated, while it is negligible during the following period, despite the persistence of an elevated [Ca2+]i; predepolarization in Ca2+-free medium and subsequent addition of Ca2+ (a condition which allows the development of the voltage inactivation) abolishes the fast phase of secretion, while not modifying the steady state [Ca2+]i eventually attained; and increases in the intracellular Ca2+ buffering decreases the amplitude of the fast secretion phase induced by KCl without altering the steady state [Ca2+]i. We suggest that localized [Ca2+]i gradients form close to the plasma membrane shortly after depolarization and that the [Ca2+]i reached in these regions is the relevant parameter in the regulation of secretion.     

Fura-2 secretion and sequestration in macrophages. A blocker of organic anion transport reveals that these processes occur via a membrane transport system for organic anions

Fura-2, loaded into J774.2 macrophages as the acetoxymethyl ester, is sequestered into intracellular vacuoles within 90 min after the beginning of the loading at 37 degrees C. The dye is also efficiently secreted from the cells. Sequestration and secretion of fura-2 reduce the accuracy of measurements of cytosolic free Ca2+ concentration in this cell line. Fura-2 is also sequestered and secreted by J774.2 when the dye is loaded into the cytoplasm as the pentapotassium salt by reversible permeabilization of the plasma membrane. Regardless of the mechanism by which fura-2 is loaded into the cytoplasm, both sequestration and secretion are prevented by 2.5 mM probenecid, a blocker of organic anion transport. Probenecid has no effect on resting or stimulated cytosolic free Ca2+ levels or on FcR-mediated phagocytosis. These findings suggest that macrophages express a transport mechanism for the anionic form of fura-2. This transport system is responsible for the clearance of fura-2 from the cytoplasm of this cell type. Furthermore we suggest that use of probenecid to block secretion and intracellular sequestration of fura-2 may overcome problems arising in the application of this Ca2+ indicator to macrophages and perhaps to other cell types.     

Occurrence of enteroviruses in marine sediment along the coast of Barcelona, Spain

A survey of the occurrence of enteroviruses in marine sediment was undertaken in an area receiving polluted effluents. Enteroviruses were detected in 21 out of 38 samples (55%). Viruses were found as far as 5 km from the shoreline and at a depth of 82 m. Multiple correlations between enteroviruses and bacteria, detected in the same samples, were computed. No correlation could be demonstrated between virus numbers and any other parameter in sediment samples collected south of Barcelona. This lack of correlation is probably due to the different decay rates shown by bacteria and viruses. In contrast, the cases where pollution resulted from a more recent deposition, as in sediment samples collected north of Barcelona, enterovirus levels were correlated with fecal streptococci levels.     

Cyclic AMP inhibition of phosphoinositide turnover in human neutrophils

The effect of increased intracellular levels of cyclic AMP on phosphoinositide metabolism was studied in human neutrophils stimulated with fMet-Leu-Phe. Intracellular cyclic AMP was raised by preincubation either with dibutyryl cyclic AMP and theophylline or with prostaglandin E1. Concentrations of dibutyryl cyclic AMP and theophylline fully inhibitory for the metabolic responses inhibited phosphoinositide breakdown and phosphatidic acid formation to a large extent. The accumulation of the water-soluble inositol phosphates was also measured. In agreement with the data obtained on the phospholipids, inositol phosphate generation was found to be severely, though not completely, reduced. Treatment with dibutyryl cyclic AMP and theophylline also inhibited resynthesis of membrane inositol lipids. Treatment with prostaglandin E1 had a similar, though less, marked effect on inositol lipid turnover, which was parallel with a smaller inhibition of metabolic responses. We therefore suggest that the elevation of intracellular cyclic AMP mainly affects neutrophil responses by inhibiting the phosphoinositide cycle.     

Two major classes of mitogen-reactive B lymphocytes defined by life span

The relative numbers of short- and long-lived mitogen-reactive B cells in the peripheral pool were evaluated by studying the decay of lipopolysaccharide (LPS)-reactive B lymphocytes in LPS nonresponder, histocompatible hosts for periods of up to 3 wk after cell transfer. The results obtained demonstrate the existence of two major classes of mitogen-reactive B cells defined by life span. The "short-lived" cell component comprises about 80 to 90% of the reactive cells and decays with a life expectancy of 18 to 24 hr. The long-lived cell component, with life expectancies of 10 to 20 days, comprises about 10 to 20% of the reactive cells and is preferentially enriched in circulating B cells. The present ratio for short- and long-lived B cells implies a highly dynamic state for the immune system which must be advantageous in the selection of available repertoires.     

Life span of B lymphocytes: the experimental basis for conflicting results

Recent claims have challenged the view that most peripheral, mature B cells are long-lived, and propose rates of peripheral decay that are compatible with bone marrow production. This disagreement can only reflect differences in the protocols and methods used to measure peripheral lymphocyte life spans. We have now assessed toxic or other nonselective effects of hydroxyurea treatment on the survival and migration of peripheral, noncycling cells, as well as possible reasons for exaggerated decays of LPS-reactive B cells transferred to LPS nonresponder hosts, the two methods leading to conclusions of short life spans. We also studied general effects on cell survival introduced by either repeated [3H]thymidine injections or the stress associated with surgery, thoracic duct cannulation in particular--methods with which the notion of long life spans had been established. The results failed to show toxic or nonselective effects of hydroxyurea treatments and artificial decays of LPS-reactive cells in adoptive hosts. In contrast, the present experiments demonstrate that both the stress associated with surgery and repeated [3H] thymidine administration profoundly deplete a pool of short-lived B cells, consequently selecting for an apparent higher proportion of long-lived cells.     

Principal-components analysis of Brazilian Indian anthropometric data

Analysis of nine characteristics on 1,205 males and 932 females from 12 tribes or groups of tribes indicated a poor relationship between morphology and language, as well as moderate agreement with the variability expected considering geography only. Two samples in the Xingu area studied during an interval of half a century (1897-1947) showed remarkable similarity. The conformity of the Caingang morphology with those of other tribes and the distinctiveness of the Xavante and Tenetehara has been amply confirmed.