In vitro modification of Candida albicans invasiveness

Candida albicans produces germ-tubes (GT) when it is incubated in animal or human serum. This dimorphism is responsible for its invasive ability.The purpose of the present paper is (1) to evaluate the ability of rat peritoneal macrophages to inhibit GT production of ingested Candida albicans, obtained from immunized rats and then activated in vitro with Candida-induced lymphokines; (2) to determinate any possible alteration of phagocytic and candidacidal activities.The phagocytes were obtained from rats immunized with viable C. albicans. Some of them were exposed to Candida-induced lymphokines in order to activate the macrophages in vitro. The monolayers of activated, immune and normal macrophages were infected with a C. albicans suspension during 4 hr.Activated macrophages presented not only the highest phagocytic and candidacidal activities but a noticeable inhibition of GT formation and incremented candidacidal activity.     

Sensory projections to the nucleus basalis prosencephali of the pigeon

Summary The afferent pathways to the nucleus basalis prosencephali of the pigeon were studied by use of the horseradish peroxidase (HRP) technique. It was confirmed that this nucleus receives a direct pathway from the nucleus sensorius principalis nervi trigemini and that, as in the starling, it receives a direct input from the nucleus lemnisci lateralis, pars ventralis, an auditory relay. Totally novel is the finding that the nucleus basalis prosencephali is the target of a direct pathway originating in the medullary nucleus vestibularis superior. All three pathways bypass the thalamus. From within the telencephalon the nucleus basalis prosencephali also receives fibres from the tuberculum olfactorium and the peri-ectostriatal belt, suggestive of olfactory and visual input. Marked cell bodies were also found in the neostriatum frontolaterale. It is assumed that these arose from HRP uptake by axons of the tractus fronto-archistriatalis that course through the nucleus basalis prosencephali to the anterodorsal archistriatum. Marked fibres and bouton-like formations were observed in the latter structure. The afferents to the nucleus basalis prosencephali are discussed in conjunction with the probable role of the nucleus as a sensorimotor coordinator of the pecking/feeding behaviour of the pigeon.     

Feedback inhibition of homoserine dehydrogenase and threonine deaminase in the genusBifidobacterium

Feedback inhibition of crude and purified extracts of homoserine dehydrogenase and threonine deaminase activities in the genusBifidobacterium was studied. Homoserine dehydrogenase was partially or completely inhibited byl-threonine, and a marked inhibitory effect byl-isoleucine on threonine deaminase was observed. In the speciesBifidobacterium cuniculi high levels ofl-valine reversed the inhibitory effect ofl-isoleucine. The -aminobutyric acid-resistant mutant Ru 326/106 of the speciesB. ruminale, overproducer ofl-isoleucine, had a derepressed homoserine dehydrogenase and a lesser feedback inhibition byl-threonine. Homoserine dehydrogenase appeared to be in bifids specifically NAD dependent. The regulatory mechanisms of aspartate family amino acid biosynthesis in bifidobacteria was discussed.     

Monoclonal antibodies to neurospora adenylate cyclase

A monoclonal antibody against $\text{Neurospora}$ soluble adenylate cyclase was obtained. The antibody inhibits cyclase activities from several lower eucaryotic organisms but not activities associated to testicular cytosol or turkey erythrocyte membranes.     

NADPH/NADP+ ratio: regulatory implications in yeast glyoxylic acid cycle

Summary The utilization by yeast of two carbon sources is carried out through the operation of the glyoxylic acid cycle. Kinetic data from the isocitrate transforming enzymes suggest that the flow of isocitrate through the glyoxylic acid cycle depends upon the inhibition of the isocitrate decarboxylating enzymes. Both isocitrate dehydrogenases are inhibited by a mixture of glyoxylate + oxaloacetate, but for the reasons described in the text we consider that this inhibition is of no physiological significance. On the other hand, we have found that NADPH is a competitive inhibitor of NADP-isocitrate dehydrogenase with respect to NADP⁺, with a K_I similar to its K_M. It also produces an additive effect on the NADH-produced inhibition of NAD-isocitrate dehydrogenase. We propose NADPH as the compound that channels the utilization of isocitrate into the glyoxylic acid cycle. This is supported by the finding of an increased NADPH/NADP⁺ ratio in acetate grown yeast with respect to glucose grown cells.     

Mode of Action of Pesticin

The mode of action of pesticin, a bacteriocin produced by many strains of Pasturella pestis, was studied. Pesticin action on macromolecular synthesis of a sensitive strain of Escherichia coli, strain , was found to have features similar to those of colicin E2-317 acting on the same strain. After exposure to pesticin, deoxyribonucleic acid synthesis was arrested and ribonucleic acid was degraded, but little effect was observed on protein synthesis. Pesticin, like colicin E2-317, induced lysogenic E. coli (P1), but, unlike the colicin, was active in the presence of dinitrophenol. Trypsin was found to reverse pesticin action up to 15 min after its addition at 40 C to E. coli . Pesticin action was studied on three sensitive bacterial strains, P. pestis 2C, P. pseudotuberculosis, and E. coli strain , which vary widely in their optimal growth temperature. P. pestis grows best at 29 C, P. pseudotuberculosis at 37 C, and E. coli at 40 C. It was found that pesticin action on all three strains was optimal at 40 C. Whereas the titer of pesticin was the same on all three strains when determined on agar, E. coli was the most sensitive to pesticin action in broth. No action of pesticin in broth on P. pseudotuberculosis was observed unless Ca ions were added. The effect was not immediate; that is, the cells had to be grown in a medium containing Ca⁺⁺ before they displayed sensitivity to pesticin.