Presence of <Emphasis Type="Italic">C. albidus</Emphasis>, <Emphasis Type="Italic">C. laurentii</Emphasis> and <Emphasis Type="Italic">C. uniguttulatus</Emphasis> in Crop and Droppings of Pigeon Lofts (<Emphasis Type="Italic">Columba livia</Emphasis>)

Columba livia is an important reservoir and carrier of Cryptococcus neoformans, Cryptococcus uniguttulatus, Cryptococcus laurentii and Cryptococcus albidus. Upper digestive tract of this species is also known as a habitat for Cryptococcus neoformans. Given the increasing clinical interest of this microorganism, 331 swabs from crop and 174 dropping samples from pigeon lofts in Grand Canary Island have been studied. The obtained results show an extensive presence samples 81 positive (24.47%) of Cryptococcus spp. in analysed crops: 32 (9.66%) for C. neoformans, 24 (7.2%) for C. uniguttulatus, 23 (6.9%) for C. albidus and 2 (0.6%) for C. laurentii. In the same way, Cryptococcus spp was also isolated in 82 (47.13%), dropping samples: C. neoformans in 59 (33.9%), C. uniguttulatus, in 9 (5.17%), C. laurentii in 8 (4.59%) and C. albidus in 6 (3.44%) of the investigated samples, respectively. The cryptococcosis produced by species of cryptococci other than C. neoformans has become more important during the last decade, supporting the study on the role of pigeon in the epidemiology of this disease.     

Fickean and Non-Fickean Water Desorption During Vacuum Drying of <Emphasis Type="Italic">L. bulgaricus</Emphasis>

The recovery of Lactobacillus bulgaricus was studied in correlation to the kinetics of cell drying. When bacteria were dehydrated at 30 °C, either in the presence or the absence of sucrose, the drying kinetics corresponds to a Fickean diffusion in correspondence with a short lag time. In contrast, when the bacteria were dehydrated at 70 °C in the absence of sugar, the kinetics corresponds to an anomalous diffusion, and the lag time is four to five times higher than that at 30 °C. However, when drying at 70 °C was carried out in the presence of sucrose, drying kinetics turned into a Fickean process parallel to a substantial decrease in the lag time. The pattern of water desorption was correlated with the critical water activity. When the drying kinetics corresponds to a Fickean diffusion, the lag time started to increase at 0.7 water activity, but when the cells were dried at 70 °C, the damage started at 0.5 water activity. This observation indicates that the drying rate affects the pattern of water desorption, and it can change the value of critical water activity. These results put into relevance that the cell recovery is due to the drying history and that the recovery increase produced by sucrose can be related to the maintenance of kinetic barriers for water desorption.     

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.     

Effect of Ca2+, peroxides, SH reagents, phosphate and aging on the permeability of mitochondrial membranes

The mechanism by which a number of agents such as hydroperoxides, inorganic phosphate, azodicarboxylic acid bis(dimethylamide) (diamide), 2-methyl-1,4-naphthoquinone (menadione) and aging, induce Ca2+ release from rat liver mitochondria has been analyzed by following Ca2+ fluxes in parallel with K+ fluxes, matrix swelling and triphenylmethylphosphonium fluxes (as an index of transmembrane potential). Addition of hydroperoxides causes a cycle of Ca2+ efflux and reuptake and an almost parallel cycle of delta psi depression. The hydroperoxide-induced delta psi depression is biphasic. The first phase is rapid and insensitive to ATP and is presumably due to activation of the transhydrogenase reaction during the metabolization of the hydroperoxides. The second phase is slow and markedly inhibited by ATP and presumably linked to the activation of a Ca2+-dependent reaction. The slow phase of delta psi depression is paralleled by matrix K+ release and mitochondrial swelling. Nupercaine and ATP reduce or abolish also K+ release and swelling. Inorganic phosphate, diamide, menadione or aging also cause a process of Ca2+ efflux which is paralleled by a slow delta psi depression, K+ release and swelling. All these processes are reduced or abolished by Nupercaine and ATP. The slow delta psi depression following addition of hydroperoxide and diamide is largely reversible at low Ca2+ concentration but tends to become irreversible at high Ca2+ concentration. The delta psi depression increases with the increase of hydroperoxide, diamide and menadione concentration, but is irreversible only in the latter case. Addition of ruthenium red before the hydroperoxides reduces the extent of the slow but not of the rapid phase of delta psi depression. Addition of ruthenium red after the hydroperoxides results in a slow increase of delta psi. Such an effect differs from the rapid increase of delta psi due to ruthenium-red-induced inhibition of Ca2+ cycling in A23187-supplemented mitochondria. Metabolization of hydroperoxides and diamide is accompanied by a cycle of reversible pyridine nucleotide oxidation. Above certain hydroperoxide and diamide concentrations the pyridine nucleotide oxidation becomes irreversible. Addition of menadione results always in an irreversible nucleotide oxidation. The kinetic correlation between Ca2+ efflux and delta psi decline suggests that hydroperoxides, diamide, menadione, inorganic phosphate and aging cause, in the presence of Ca2+, an increase of the permeability for protons of the inner mitochondrial membrane. This is followed by Ca2+ efflux through a pathway which is not the H+/Ca2+ exchange.     

BCL-2-Related Protein Expression in Apoptosis: Oxidative Stress Versus Serum Deprivation in PC12 Cells

Abstract: Expression of the BCL-2 protein family members, BAX, BAK, BAD, BCL-xL, BCL-xS, and BCL-2, was measured (by western blotting using specific antibodies) in PC12 cells before and during apoptosis induced by either H₂O₂ treatment or by serum deprivation and during rescue from apoptosis by nerve growth factor (NGF). H₂O₂-induced apoptosis, as measured by DNA fragmentation, caused: (a) a dose-dependent increase in BAX, (b) a dose-independent increase in BAK, and (c) a dose-dependent inhibition of BAD expression. By comparison, apoptosis induced by serum deprivation resulted in a time-dependent decrease in both BAX and BAK, along with a dramatic and sudden decrease in BAD expression. However, when PC12 cells were incubated in an apoptosis-sparing medium (i.e., NGF-supplemented serum-free medium), both BAX and BAK were increased significantly, whereas BAD expression remained inhibited. BCL-xL expression was increased by H₂O₂ but unaffected by serum deprivation or long-term NGF treatment. Neither BCL-2 nor BCL-xS expression could be detected in PC12 cells under the experimental conditions tested. Our results show that the expression of BAX, BAK, BAD, and BCL-xL is altered in a stimulus-dependent manner but cannot be used to define whether a cell will undergo or survive apoptosis. The similarity between changes in expression of BCL-2-related proteins induced by H₂O₂ exposure and NGF rescue could reflect activation in part of a common antioxidant pathway.