Inhibition of Neutrophil Superoxide Secretion By of Preservative, Methylhydroxybenzoate: Effects Mediated By Perturbation of Intracellular Ca2+?

The preservative, methylhydroxybenzoate inhibited O₂^- secretion from human neutrophils activated by both the chemotactic peptide fMet-Leu-Phe and phorbol myristate acetate (PMA): the low level of oxidant secretion activated by the ionophore A23187 was similarly reduced in preservative-treated suspensions. Oxidant secretion was similarly reduced in fMet-Leu-Phe and A23187 treated suspensions in which intracellular Ca²⁺ was buffered by loading with Quin-2, indicating that methylhydroxybenzoate may exert its effects by perturbation of intracellular Ca²⁺ -dependent processes. Methylhydroxybenzoate could mimic EGTA in preventing the Ca²⁺ dependent enhancement of trypsin activity and could also bind this cation in experiments using a Ca²⁺ electrode, although the preservative bound Ca²⁺ more slowly and had a lower affinity than EGTA. These data indicate that methylhydroxybenzoate may exert its effects on neutrophils by perturbation of Ca²⁺-dependent activation pathways and this phenomenon may also explain its other known pharmacological effects. Furthermore, these observations provide an insight into the mechanisms by which intracellular Ca²⁺ may regulate oxidant secretion.     

Copper uptake by whole cells and protoplasts of a wild-type and copper-resistant strain of Saccharomyces cerevisiae

Abstract A stable copper-resistant mutant of Saccharomyces cerevisiae took up less copper than the wild-type. The use of protoplasts showed that the decreased uptake depended on changed membrane transport properties and not on alterations in the cell wall.     

The effect of exogenously-supplied nucleosides and nucleotides and the involvement of adenosine 3':5'-cyclic monophosphate (cyclic AMP) in the yeast mycelium transition of Ceratocystis (= Ophiostoma) ulmi

The yeast-mycelium transition of Ceratocystis (= Ophiostoma) ulmi (NRRL 6404) was induced by exogenously-supplied nucleosides and nucleotides in defined liquid media. During the yeast-mycelium transition, intracellular adenosine 3':5'-cyclic monophosphate (cAMP) levels increased and maximum levels coincided with maximum germination. This, coupled with findings that the cAMP phosphodiesterase inhibitors, theophylline and caffeine, also induced germination and elevated levels of intracellular cAMP, indicated the involvement of cAMP in the regulation of the yeast-mycelium transition.     

Natural abundance 13C-nuclear magnetic resonance spectroscopic analysis of acyclic polyol and trehalose accumulation by several yeast species in response to salt stress

Analysis of seventeen yeast strains by 13C-NMR spectroscopy has confirmed the significance of glycerol as the sole osmoregulatory solute under salt-stressed conditions, and has shown arabitol to be present in most of the osmotolerant species. Ribitol was detected in some species, including Debaryomyces hansenii, although ribitol accumulation did not correlate with the osmotic pressure of the medium. Relative amounts of arabitol and ribitol decreased in relation to glycerol when the external osmotic pressure was increased. Trehalose was present during exponential growth of some species.     

Treatment of Schistosoma mansoni infection with rhesus monkey stromata: two unsuccessful attempts

Independent series of experiments have failed to confirm the reported schistosomicidal effect of injections of rhesus monkey stromata and other erythrocyte preparations in infected mice (Cox &; Oliver-Gonzalez, 1970). It is suggested that the most likely explanation of the original findings is accidental contamination of the erythrocyte preparations with bacteria known to kill adult schistosomes in vivo.     

Rock phosphate solubilization by abiotic and fungal-produced oxalic acid: reaction parameters and bioleaching potential

Oxalic acid-producing fungi play an important role in biogeochemical transformations of rocks and minerals and possess biotechnological potential for extraction of valuable elements from primary or waste ores and other solid matrices. This research investigates the extraction of phosphate from rock phosphate (RP) by oxalic acid. Reaction parameters were derived using pure oxalic acid solutions to solubilize RP. It was found that the oxalic acid concentration was the main factor driving reaction kinetics. Excess oxalic acid could retard the reaction due to calcium oxalate encrustation on RP surfaces. However, complete P extraction was reached at stoichiometric proportions of apatite and oxalic acid. This reaction reached completion after 168 h, although most of the P (up to 75%) was released in less than 1 h. Most of the Ca released from the apatite formed sparingly soluble calcium oxalate minerals, with a predominance of whewellite over weddellite. Bioleaching of RP employing biomass-free spent culture filtrates containing oxalic acid (100 mM) produced by Aspergillus niger extracted ~ 74% of the P contained in the RP. These findings contribute to a better understanding of the reaction between apatite and oxalic acid and provide insights for potential applications of this process for biotechnological production of phosphate fertilizer.