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 excavations of La Isabela,the first European city of the New World

In the present note the author presents history of the discovery and of the status of the excavation of the site La Isabela, the first settlement planned by Columbus in the New World during his second trip to America in the summer of 1493.     

The roles of autophosphorylation and phosphorylation in the life of osteopontin

Osteopotin is a secreted glycosylated phosphoprotein found in bone and other normal and malignant tissues. Osteopontin can be autophosphorylated on tyrosine residues and can also be phosphorylated on serine and threonine residues by several protein kinases. Autophosphorylation of osteopontin may generate sites for specific interactions with other proteins on the cell surface and/or within the extracelluar matrix. These interactions of osteopontin are thought to be essential for bone mineralization and function. The polyaspartic acid motif of osteopontin, in combination with neighboring sequences that include serine residues phosphorylated by protein kinases, could fold and assemble into a molecular structure that participates in the mineralization of the bone matrix.     

Quantitative autoradiographic localization of neuropeptide Y (NPY) binding sites in rat posterior pituitary lobe

1. We have localized and quantified neuropeptide Y (NPY) binding sites in the rat pituitary gland after incubation of tissue sections in the presence of 125I-Bolton-Hunter NPY followed by autoradiography, computerized microdensitometry, and comparison to 125I-standards. 2. In the rat, NPY binding sites are localized exclusively to the part of the posterior pituitary lobe closer to the pituitary stalk. No NPY binding sites could be found in the intermediate or the anterior pituitary lobes. 3. Our results suggest a role for NPY in the regulation of pituitary function and, in particular, that of the neural lobe.     

Urinary excretion of digoxin-like immunoreactive factor and arginine-vasopressin in rats after several osmotic loads

Urinary digoxin-like immunoreactive factor (DLIF), arginine-vasopressin (AVP) and other urinary parameters were investigated under normal conditions and after the i.p. injection of the following solutions: distilled water, isotonic and hypertonic NaCl, NaHCO3, KCl and urea, at a rate of 3 ml/100 g body weight. The measurement of digoxin-like immunoreactivity by two different radioimmunoassays showed that DLIF was stimulated by all volume loads regardless of the presence or absence of osmolar compounds. This dissociation between DLIF and urinary sodium excretion suggests that DLIF may not constitute the natriuretic hormone. Moreover, a dissociation between DLIF and AVP excretion also were found, which speaks against the hypothesis of a common mechanism of stimulation for both substances.     

Peripheral benzodiazepine binding sites in kidney: modifications by diabetes insipidus

Using [3H] diazepam as ligand, it is possible to distinguish neuronal binding sites from those present on glial elements and in peripheral tissues (non-neuronal). The function of the "non-neuronal" binding sites is still obscure. Preliminary data showed a distribution of [3H] diazepam binding sites in kidney that could suggest a localization along the renal tubules. This is the site at which a renal peptide, arginine-vasopressin (AVP) is supposed to act. In an attempt to examine the function of these "non-neuronal" sites, we studied the [3H] diazepam binding in kidney of Brattleboro rats which lack AVP and present the symptoms of diabetes insipidus. The homozygous Brattleboro rats showed an increase in the apparent number of benzodiazepine binding sites (Bmax) compared to Long-Evans control rats. Replacement of AVP in these animals results in a reversal of the electrolyte alterations of diabetes insipidus and in an increase of the affinity of the [3H] diazepam binding. These findings may indicate a possible relationship between benzodiazepine binding sites and vasopressin action in kidney and may support receptor function of these "non-neuronal" binding sites.     

Increased atrial natriuretic peptide (6-33) binding sites in the subfornical organ of water deprived and Brattleboro rats

Binding sites for rat atrial natriuretic peptide (6-33) (ANP) were quantitated in the subfornical organ of chronically dehydrated homozygous Brattleboro rats unable to synthesize vasopressin; heterozygous Brattleboro rats, their controls, Long Evans rats and Long Evans rats after 4 days of water deprivation. Brain sections were incubated in the presence of 125I-ANP and the results analyzed by autoradiography coupled to computerized microdensitometry and comparison to 125I-standards. Brattleboro rats and water deprived Long Evans rats presented a higher number of ANP binding sites than their normally hydrated controls. Our results suggest a role of ANP binding sites in the subfornical organ in the central regulation of fluid balance and vasopressin secretion.     

Localization of atrial natriuretic peptide, ANP-(99-126) binding sites in the rat thymus and spleen with quantitative autoradiography

Binding sites for atrial natriuretic peptide, ANP-(99-126) were studied in lymphoid organs of the rat with quantitative autoradiography. Tissue sections were incubated in the presence of 0.13 nM 125I-ANP-(99-126) followed by autoradiography using [3H]-Ultrofilm, and the results were analyzed by computerized densitometry and comparison to 125I-standards. Specific ANP binding sites were localized in the medulla and the cortex of the rat thymus and in the white pulp of the rat spleen, with apparent binding sites concentrations of 93, 65, and 126 fmol/mg protein, respectively. The presence of ANP binding sites in areas related to the maturation and function of lymphocytes, and to the production of thymic hormones, suggests the possibility of a role of circulating ANP in the modulation of the immune response.