Gentamicin and amikacin repress the growth of Plasmodium falciparum in culture, probably by inhibiting a parasite acid phospholipase

Human erythrocytes were loaded with either gentamicin or amikacin and subsequently infected with the human malarial parasite Plasmodium falciparum and grown in culture. Parasite invasion of erythrocytes was unaffected by the drugs, but subsequent development was retarded. The digestion of host cell cytosol in ring-stage parasites was inhibited by the drugs. A substantial acid, Ca2+-independent phospholipase activity could be monitored in parasite cytosol and was found to be inhibited by the drugs. These results imply that phospholipases are involved in the feeding mechanism of the parasite and that gentamicin and amikacin exert their inhibitory activity by affecting these enzymes.     

Pendelluft flow in symmetric airway bifurcations.

We propose a mathematical model for pendelluft flow in a single airway bifurcation. The model is motivated by an apparatus used in an experimental study of the pendelluft by Ultman et al. (1988). We derive differential equations governing the fluid flow, which directly connect physiological parameters to the variables determining the pendelluft; this approach allows us to include nonlinearity in the model. If nonlinearity is neglected, our model is identical to the R-I-C circuits used by previous investigators. If nonlinearity is retained, we show that pendelluft can occur even in perfectly symmetric airway bifurcations. For the specific apparatus used in the experiments of High et al. (1991), we demonstrate that two qualitatively different pendelluft flows can occur in the system.     

Sequence analysis of a 101-kilobase plasmid required for agar degradation by a Microscilla isolate.

An agar-degrading marine bacterium identified as a Microscilla species was isolated from coastal California marine sediment. This organism harbored a single 101-kb circular DNA plasmid designated pSD15. The complete nucleotide sequence of pSD15 was obtained, and sequence analysis indicated a number of genes putatively encoding a variety of enzymes involved in polysaccharide utilization. The most striking feature was the occurrence of five putative agarase genes. Loss of the plasmid, which occurred at a surprisingly high frequency, was associated with loss of agarase activity, supporting the sequence analysis results.     

Protective reaction of the myocardium in poisoning

Intensive synthesis of collagen-like substance was revealed in the rabbit myocardium during experimental diphtheria intoxication. It was more marked in the right ventricle 24 hours after the injection of diphtheria toxin. Since similar changes (the substance was mainly formed around blood vessels) have been observed in other cases of toxic myocardial alterations (i.e. ethanol intoxication, injection of pharmacological agents, etc.), it can be assumed that it is a standard protective reaction of the altered heart to the penetration of toxic agents from the blood into the myocardial tissue.     

High Altitude Frogs (Rana kukonoris) Adopt a Diversified Bethedging Strategy in the Face of Environmental Unpredictability

Environmental unpredictability can influence strategies of maternal investment among eggs within a clutch. Models predict that breeding females should adopt a diversified bet-hedging strategy in unpredictable environments, but empirical field evidence from Asia is scarce. Here we tested this hypothesis by exploring spatial patterns in egg size along an altitudinal gradient in a frog species(Rana kukunoris) inhabiting the Tibetan Plateau. Within-clutch variability in egg size increased as the environment became variable(e.g., lower mean monthly temperature and mean monthly rainfall at higher altitudes), and populations in environments with more unpredictable rainfall produced eggs that were smaller and more variable in size. We provide support for a diversified bet-hedging strategy in high-altitude environments, which experience dynamic weather patterns and therefore are of unpredictable environmental quality. This strategy may be an adaptive response to lower environmental quality and higher unpredictable environmental variance. Such a strategy should increase the likelihood of breeding success and maximize maternal lifetime fitness by producing offspring that are adapted to current environmental conditions. We speculate that in high-altitude environments prone to physical disturbance, breeding females are unable to consistently produce the optimal egg size due to physiological constraints imposed by environmental conditions(e.g., duration of the active season, food availability). Species and populations whose breeding strategies are adapted to cope with uncertain environmental conditions by adjusting offspring size and therefore quality show a remarkable degree of ability to cope with future climatic changes.