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.     

Structure–antimicrobial activity of some natural isocoumarins and their analogues

Three naturally occurring isocoumarins (paepalantine, paepalantine 9-O-beta-D-glucopyranoside and paepalantine 9-O-beta-D-allopyranosyl(1 --> 6) glucopyranoside) and two semi-synthetic analogues, 9,10-acylated compound and 9-OH-10-methylated compound, structurally similar to paepalantine, were evaluated for antimicrobial activity using a spectrophotometric microdilution technique. The paepalantine was active against S. aureus, S. epidermidis, and E. faecalis while the other four compounds proved ineffective against all microorganisms tested at concentrations of 500 microg/ml. Variations in phenolic substitution at OH-9 and/or OH-10 in the paepalantine molecule resulted in compounds without antimicrobial activity. A combination of structural features, two phenolic groups as cathecolic system, forms an oxygenated system arrangement that may reflect the potentially antimicrobial properties of paepalantine.     

Kawasaki disease,or mucocutaneous lymph node syndrome: report of seven cases in North America.

The clinical and laboratory findings in seven children with Kawasaki disease are reviewed. Four of the patients had the more complicated course that has characterized the cases diagnosed in North America. This suggests that the benign forms are often mistaken for other febrile illnesses. The patients were two girls and five boys ranging in age from 4 months to 7 years; six were Caucasian and one was a North American Indian. Fever, redness of the oral mucosa, an erythematous or scarlatiniform rash and cervical adenopathy were seen in all; six patients had the characteristic fingertip desquamation and nonexudative conjunctivitis. Cardiac involvement occurred in four patients, two of whom had coronary artery aneurysm or thrombosis. Arthritis or arthralgia was seen in six patients, and aseptic meningitis occurred in four. Of the three patients with jaundice two underwent laparotomy and excision of a hydropic gallbladder; one of them died from Klebsiella pneumoniae sepsis and disseminated intravascular coagulopathy.     

Enhancement of metabolic rates of yeast flocculent cells through the use of polymeric additives

The influence of several polymeric additives on specific glucose uptake rate of flocs of a S. cerevisiae strain — S. cerevisiae NRRLY 265 was studied. A special continuous membrane microreactor was used to measure glucose uptake on the presence of calcium and of the tested additives — two cationic polymers — bis(polyoxyethylene-bis(amine)) 20,000 and BPA 1,000 and one anionic polymer — Magna Floc LT25.An increase on glucose uptake rate was always observed when comparing with calcium bound flocs. For bis(polyoxyethylene-bis(amine)) 20,000 the increase was only 19% but for BPA 1,000 a value of more than 50% was observed. For Magna Floc LT25 a two fold increase was measured.The determination of floc size and porosity in the presence of the additives indicated that, on the basis of these parameters, it was not possible to explain the observed glucose uptake rates. The floc porosites in additive bound flocs were similar and 10% larger than for calcium bound flocs and glucose uptake rate was larger for the largest flocs — Magna Floc LT25 bound flocs were the largest followed by BPA 1,000, bis(polyoxyethylene-bis(amine)) 20,000 and calcium bound flocs. These values disagree with what should be expected in diffusion controlled processes.The calculation of intercellular floc distance indicated that polymeric additives act on the reduction of diffusional limitations by increasing the available flux area for glucose inside the flocs. By analysing different kinds of packings, it was also observed that the packing arrangement for yeast cells in flocs is close to the cubic packing. The simulation of this arrangement for the obtained floc sizes confirmed that the 10% increase in floc porosity is sufficient to explain the increase in the available flux area.     

Towards the mechanism and comparative effect of diphenyl diselenide, diphenyl ditelluride and ebselen under various pathophysiological conditions in rat's kidney preparation

As an extension of our previous work we not only evaluated the relationship between acidosis and lipid peroxidation in rat's kidney homogenate, but also determined for the first time the potential anti-oxidant activity of diphenyl diselenide, diphenyl ditelluride and ebselen at a range of pH values (7.4–5.4). Because of the pH dependency of iron redox cycling, pH and iron need to be well controlled and for the reason we tested a number of pH values (from 7.4 to 5.4) to get a closer idea about the role of iron under various pathological conditions. Acidosis increased rate of lipid peroxidation in the absence Fe (II) in kidney homogenates especially at pH 5.4. This higher extent of lipid peroxidation can be explained by; the mobilized iron which may come from reserves where it is weakly bound. Addition of iron (Fe) chelator desferoxamine (DFO) to reaction medium completely inhibited the peroxidation processes at all studied pH values including acidic values (5.8–5.4). In the presence of Fe (II) acidosis also enhanced detrimental effect of Fe (II) especially at pH (6.4–5.4). Diphenyl diselenide significantly protected lipid peroxidation at all studied pH values, while ebselen offered only a small statistically non-significant protection. The highest anti-oxidant potency was observed for diphenyl ditelluride. These differences in potencies were explained by the mode of action of these compounds using their catalytic anti-oxidant cycles. However, changing the pH of the reaction medium did not alter the anti-oxidant activity of the tested compounds. This study provides evidence for acidosis catalyzed oxidative stress in kidney homogenate and for the first time anti-oxidant potential of diphenyl diselenide and diphenyl ditelluride not only at physiological pH but also at a range of acidic values.     

A split-pot experiment with sorghum to test a root water uptake partitioning model

Correct modeling of root water uptake partitioning over depth is an important issue in hydrological and crop growth models. Recently a physically based model to describe root water uptake was developed at single root scale and upscaled to the root system scale considering a homogeneous distribution of roots per soil layer. Root water uptake partitioning is calculated over soil layers or compartments as a function of respective soil hydraulic conditions, specifically the soil matric flux potential, root characteristics and a root system efficiency factor to compensate for within-layer root system heterogeneities. The performance of this model was tested in an experiment performed in two-compartment split-pot lysimeters with sorghum plants. The compartments were submitted to different irrigation cycles resulting in contrasting water contents over time. The root system efficiency factor was determined to be about 0.05. Release of water from roots to soil was predicted and observed on several occasions during the experiment; however, model predictions suggested root water release to occur more often and at a higher rate than observed. This may be due to not considering internal root system resistances, thus overestimating the ease with which roots can act as conductors of water. Excluding these erroneous predictions from the dataset, statistical indices show model performance to be of good quality.