Adenosine 5'-triphosphate synthesis induced by urea hydrolysis in Ureaplasma urealyticum.

Although considerable attention has been devoted to the urea-hydrolyzing activity of Ureaplasma urealyticum, there is as yet no firmly established function for this enzyme. Present results support the idea that its activity generates a chemical gradient across the membrane which drives adenosine 5'-triphosphate synthesis through a chemiosmotic type of mechanism.     

Role in hemolysis of the interaction of tellurium compounds with glutathione

We have shown that tellurite and tellurate require the interaction with reduced glutathione (GSH) to hemolyze human erythrocytes. The study of the nature of this interaction is the main object of this paper. The degree of hemolysis was determined by the method of Angelone. The addition of extracellular 1 mM GSH or cysteine increased the rate of hemolysis. Concanavalin A (0.3 mg/mL) and/or 4 mg/mL adenosine did not affect the hemolysis by 0.1 mM tellurite. One tenth to 1 mM 4-acetamido-4′-isothiocyanostilbene-2,2′-disulfonate (SITS) inhibited this hemolysis by 60–100%. Millimolar GSH released this inhibition. Incubation of 0.1 mM tellurite with 1 mM GSH for 90 min at 37°C, produced a hemolytic agent when prepared and tested under nitrogen, but one that was not active when prepared in air. The hemolysis byp-hydroxymercuribenzoate orp-hydroxymercuriphenylsulfonate did not involve GSH. Scanning electron micrographs showed a sphero-echinocyte transformation, in the pre-hemolytic stage, with all the agents tested. The rate of penetration of tellurite plays a role in determining the rate of hemolysis, as shown by the effect of SITS. The release by GSH of the inhibition by SITS poses questions concerning the site of action and cell membrane penetration of the hemolytic agent. Telluride or some intermediate in the interaction of GSH with tellurite is the actual hemolytic agent.     

Further studies on polyploid amphibians

The manner in which centromere regions of mitotic chromosomes are distributed with respect to the age of their DNA was studied. Cells of the Indian deer, Muntiacus muntjak, were grown in the presence of bromodeoxyuridine (BrdU) for two generations and stained with the fluorescent dye Hoechst 33258. Chromatids containing granddaughter DNA appear dim when compared with those containing grandparental DNA. The frequencies of the various anaphase patterns of bright and dim centromere regions were binomially distributed, indicating random distribution of chromatids with respect to the age of their DNA templates.     

Biosynthesis of saturated and unsaturated fatty acids by a T-strain mycoplasma (Ureaplasma).

A human T mycoplasma (Ureaplasma urealyticum) incorporated radioactivity into its lipids from [1-14C]acetate in the growth medium. Methanolysis of the lipids showed the label to be confined almost entirely to the methyl esters of the fatty acids. About 80% of the label was associated with the methyl esters of the saturated fatty acids, and the rest was found in the unsaturated methyl ester fraction. Gas-liquid chromatography of the saturated methyl esters showed the label to be present in the peaks of palmitate, myristate, and stearate, whereas in the unsaturated methyl ester fraction most of the radioactivity emerged in the peak of palmitoleate. The addition of either oleic or palmitic acid to the growth medium markedly decreased the organisms' incorporation of radioactivity from acetate. It is concluded that the T mycoplasma strain is capable of de novo synthesis of both saturated and unsaturated fatty acids, in this respect differing from all of the Mycoplasma and Acholeplasma strains investigated to date.     

The Rab11-family interacting proteins reveal selective interaction of mammalian recycling endosomes with the Toxoplasma parasitophorous vacuole in a Rab11- and Arf6-dependent manner

After mammalian cell invasion, the parasite Toxoplasma multiplies in a self-made membrane-bound compartment, the parasitophorous vacuole (PV). We previously showed that Toxoplasma interacts with many host cell organelles, especially from recycling pathways, and sequestrates Rab11A and Rab11B vesicles into the PV. Here, we examine the specificity of host Rab11 vesicle interaction with the PV by focusing on the recruitment of subpopulations of Rab11 vesicles characterized by different effectors, for example, Rab11-family interacting roteins (FIPs) or Arf6. Our quantitative microscopic analysis illustrates the presence of intra-PV vesicles with FIPs from class I (FIP1C, FIP2, FIP5) and class II (FIP3, FIP4) but to various degrees. The intra-PV delivery of vesicles with class I, but not class II, FIPs is dependent on Rab11 binding. Cell depletion of Rab11A results in a significant decrease in intra-PV FIP5, but not FIP3 vesicles. Class II FIPs also bind to Arf6, and we observe vesicles associated with FIP3-Rab11A or FIP3-Arf6 complexes concomitantly within the PV. Abolishing FIP3 binding to both Rab11 and Arf6 reduces the number of intra-PV FIP3 vesicles. These data point to a selective process of mammalian Rab11 vesicle recognition and scavenging mediated by Toxoplasma, suggesting that specific parasite PV proteins may be involved in these processes.     

Uridine enhances the cytotoxic effect of D-glucosamine in rat C6 glioma cells

This paper studies the influence of uridine on the effects exerted by D-glucosamine in rat C6 glioma cells. 2 mM uridine increased markedly both the cytotoxic effect of the aminosugar and the inhibition of thymidine incorporation into acid-insoluble fraction. Furthermore the complete resumption of the capacity to incorporate either 3H-thymidine or 3H-mannose which was observed after the removal of the aminosugar, was impeded when the cells were treated contemporaneously with D-glucosamine and uridine. An exposure for 4 hr to 20 mM glucosamine alone enhanced about 15-fold the cellular pool of UDP-N-acetylhexosamines; the addition of 2 mM uridine intensified the expansion of this pool, which became about 35-fold the control value. The findings suggest a connection between the accumulation of UDP-N-acetylhexosamines in the cells and the appearance of D-glucosamine cytotoxicity.     

Bacillus subtilis as a host for mosquitocidal toxins production

Aedes albopictus transmits several arboviral infections. In the absence of vaccines, control of mosquito populations is the only strategy to prevent vector-borne diseases. As part of the search for novel, biological and environmentally friendly strategies for vector control, the isolation of new bacterial species with mosquitocidal activity represents a promising approach. However, new bacterial isolates may be difficult to grow and genetically manipulate. To overcome these limits, here we set up a system allowing the expression of mosquitocidal bacterial toxins in the well-known genetic background of Bacillus subtilis. As a proof of this concept, the ability of B. subtilis to express individual or combinations of toxins of Bacillus thuringiensis israelensis (Bti) was studied. Different expression systems in which toxin gene expression was driven by IPTG-inducible, auto-inducible or toxin gene-specific promoters were developed. The larvicidal activity of the resulting B. subtilis strains against second-instar Ae. albopictus larvae allowed studying the activity of individual toxins or the synergistic interaction among Cry and Cyt toxins. The expression systems here presented lay the foundation for a better improved system to be used in the future to characterize the larvicidal activity of toxin genes from new environmental isolates.