Antimicrobial and antiviral activities of an actinomycete (Streptomyces sp.) isolated from a Brazilian tropical forest soil

A promising producer of bioactive compounds isolated from a Brazilian tropical soil was tested for its range of antimicrobial activities. Strain 606, classified as Streptomyces sp., could not be identified up to species level, suggesting a possible new taxon. The supernatant and 10 extracts and fractions, obtained by extraction and chromatographic techniques, presented antimicrobial activity using antibiograms. The methanolic fraction was highly active against pathogenic bacteria, phytopathogenic fungi and the human pathogenic yeast Candida albicans. It also possessed high antiviral activity inhibiting the propagation of an acyclovir-resistant herpes simplex virus type 1 strain on HEp-2 cells at non-cytotoxic concentration. The strong cytotoxic effect suggests an antitumour action. This revised version was published online in August 2006 with corrections to the Cover Date.     

The effects of insulin on choline kinase activity in cultured rat liver cells

The effect of insulin on phosphatidylcholine biosynthesis in cultured rat liver cells was assessed by measuring changes in the activity of the first enzyme in the choline pathway of phosphatidylcholine biosynthesis, choline kinase (ATP: cholinephosphortransferase, EC 2.7.1.32), in the presence or absence of the hormone. Choline kinase specific activity in liver cells incubated for 18 hours in the presence of 10^?7M insulin increased two-fold from 3.4 ± 0.3 nmoles phosphorylcholine formed/min/mg protein to 7.5 ± 0.6 nmoles/min/mg protein. This effect was dose dependent and reversed by the addition of actinomycin D and cycloheximide. It is concluded that the increase in specific activity is due to synthesis of new enzyme rather than activation of existing enzyme.     

The influence of hypomagnesemia on erythrocyte antioxidant enzyme defence system in mice

The effect of magnesium deficiency on antioxidant defence system was studied in RBC of mice suffering from hypomagnesemia. The animals were kept for 8, 15 and 22 days on magnesium-deficient diet with consequent reduction of magnesium level in plasma by 38% at the first 8 days and by 64% after 22 days of experiment. The activities of the most important antioxidant enzymes, catalase, glutathione peroxidase, superoxide dismutase, glutathione reductase, glutahione S-transferase were assayed in hemolysates. The level of reduced glutathione in erythrocytes was measured as well. Apart from catalase, the activities of antioxidant enzymes were decreasing. The activity of superoxide dismutase decreased gradually during the experiment and on the 15th and 22nd day of experiment was significantly (P<0,05) lowered by 30 and 32% respectively. The catalase activity was increased on each point of the experiment with the peak value up to 149% on 15th day, and by 32% on 22nd day. Glutathione peroxidase activity was insignificantly reduced. The reduction of Glutatione reductase and Glutathione S-transferase activities by 24 and 21%, respectively, were observed after 8 days of the experiment with a further downward tendency. The reduced glutathione was significantly depleted after 8 days by 33% and was kept on that level in the course of the study. These findings support previous reports on the hypomagnesemia – induced alteration in endogenous enzyme antioxidant defences and glutathione redox cycle of mice.     

Correlation of conformational changes in the acrosome stabilizing factor (ASF) with its biological activity

The rabbit Acrosome Stabilizing Factor (ASF) is a glycoprotein synthesized in the corpus epididymis that reversibly decapacitates sperm. The effects of altering the conformation of ASF were evaluated by using a competitive enzyme-linked immunoabsorption assay (ELISA) with monoclonal antibodies that recognized either sequential or conformational determinants and/or an in vivo decapacitation assay. Heat denaturation (80 degrees C for 30 min) of affinity-purified ASF resulted in destruction of its native conformation concurrent with its loss of biological activity. Acid pH treatment of ASF also resulted in a conformational change in ASF, which caused a shift from the dimeric form (MW = 260,000) to the monomeric form (MW = 130,000). This manipulation allowed the biological activity of the monomeric form of ASF to be assayed separately from the dimer. The monomer was found to be biologically inactive. Proteolysis with trypsin or Staphylococcus-V8 treatment resulted in loss of the native conformation of the molecule, but Staphylococcus-V8 did not destroy the sequential determinant recognized in this analysis. This work indicates that conformation of the ASF macromolecule is important for its biological activity, and also provides a rapid means to evaluate potential decapacitation activity of purified ASF.     

Human glucose-6-phosphate dehydrogenase gene carried on a yeast artificial chromosome encodes active enzyme in monkey cells

Yeast artificial chromosomes (YACs) permit the cloning of large tracts of human DNA. A YAC containing the human glucose-6-phosphate dehydrogenase gene is shown to encode active enzyme, supporting the inference that the YAC conserves the structure of the genomic DNA.     

The influence of sucrose, 2,4-D,and kinetin on the growth,fine structure,and lignin content of cultured sycamore cells

Summary When suspensions of sycamore cells are cultured in a synthetic medium containing 1.0 mg/l 2,4-D and 0.25 mg/l kinetin, maximum cell yield is obtained with an initial concentration of 6 per cent sucrose. There is a progressive increase in dry weight per cell, decline in extractive-free weight as a percentage of cell dry weight and increase in lignin content per cell as the initial sucrose concentration is increased from 1 per cent to 15 per cent. The percentage of lignin in the extractive-free cell residue is further enhanced by increasing the level of 2,4-D to 10 mg/l or by growing the cells in an auxin-free medium containing 10 mg/l kinetin.When the cell suspensions are treated with phloroglucinol/HCl it is found that only a proportion of the cells contain lignin, that this lignin occurs in the protoplasts and in plates between the cells, and that lignin is present in the culture medium.Electron micrographs confirmed the absence of any secondary wall such as is characteristic of tracheary elements. Cells cultured in the presence of 6 per cent sucrose or higher levels showed numerous amyloplasts and frequently the presence of electron opaque material. This occurs in the irregular but not frequent wall thickenings, as droplets in the vacuoles and as amorphous sheets between the cells. Pictures showing such electron opaque droplets clustered on the inner face of the tonoplasts suggest that this material is formed in the cytoplasm and released into the vacuoles. In addition these cells are characterised by the presence of fine electron opaque granular material in their vacuoles and external to their protoplasts. Cultures richest in lignin showed the highest content of electron opaque globules in, and amorphous sheets between, the cells and it is suggested that these correspond to lignin or a lignin-hemicellulose complex. In the presence of 15 per cent sucrose many cells showing breakdown of organised structure were observed; they were characterised by the persistence of mitochondria and particularly of the amyloplasts and by their high content of the electron opaque material equated with lignin. This material was also present in the dead cells.     

A pattern recognition machine

Summary A new probabilistic learning machine for pattern recognition is described. The machine operates on the basis of random criteria obtained from special pseudorandom generators. The input, particularly versatile due to the use of an image dissector, allows a random scan for which normal television storage pick-up tubes are not suitable. The computation data section, completely automatic, uses two ferrite core memories with a capacity of 64,000 bits. Consequently it is possible to obtain very quick recognizing cycles for a maximum of 16 classes of 256 learning examples each. Preliminary experiments are reported, some of which, like the recognition of meteorological events by the analysis of absolute baric topography maps, could already be suitable for practical application of the machine.This work was supported by Consiglio Nazionale delle Ricerche (C.N.R.) through the Gruppo Nazionale Cibernetica (G.N.C.).