PROLACTIN INDUCES MATURATION OF GLUCOSE SENSING MECHANISMS IN CULTURED NEONATAL RAT ISLETS

The effects of PRL treatment on insulin content and secretion, and Rb-86 and Ca-45 fluxes from neonatal rat islets maintained in culture for 7-9 days were studied. PRL treatment enhanced islet insulin content by 40% and enhanced early insulin secretion evoked by 16.7 mm glucose. Insulin release stimulated by oxotremorine-M, a muscarinic agonist, in the presence of glucose (8.3 or 16.7 mm) was unchanged by PRL treatment. However, PRL treatment potentiated phorbol 12,13-dibutyrate-stimulated insulin secretion in the presence of the above glucose concentrations. PRL treatment potentiated the reduction in Rb-86 efflux induced by glucose or tolbutamide and enhanced the increase in Rb-86 efflux evoked by diazoxide. PRL treatment slightly potentiated the increment in Ca-45 uptake induced by high concentrations of K+, but failed to affect the increment evoked by 16.7 mm glucose. Since glucose-induced Ca-45 uptake was not affected by PRL, we suggest that the enhancement in first phase insulin secretion evoked by glucose in the PRL-treated islets occurs at a step in the secretory process that may involve protein kinase-C. These data further support observations that PRL treatment increases islet sensitivity to glucose.

Testing transposable elements as genetic drive mechanisms using Drosophila P element constructs as a model system

The use of transposable elements (TEs) as genetic drive mechanisms was explored using Drosophila melanogaster as a model system. Alternative strategies, employing autonomous and nonautonomous P element constructs were compared for their efficiency in driving the ry(+) allele into populations homozygous for a ry(-) allele at the genomic rosy locus. Transformed flies were introduced at 1%, 5%, and 10% starting frequencies to establish a series of populations that were monitored over the course of 40 generations, using both phenotypic and molecular assays. The transposon-borne ry(+) marker allele spread rapidly in almost all populations when introduced at 5% and 10% seed frequencies, but 1% introductions frequently failed to become established. A similar initial rapid increase in frequency of the ry(+) transposon occurred in several control populations lacking a source of transposase. Constructs carrying ry(+) markers also increased to moderate frequencies in the absence of selection on the marker. The results of Southern and in situ hybridization studies indicated a strong inverse relationship between the degree of conservation of construct integrity and transposition frequency. These finding have relevance to possible future applications of transposons as genetic drive mechanisms.

Lateral parabrachial nucleus serotonergic mechanisms and salt appetite induced by sodium depletion

This study investigated the effects of bilateral injections of a serotonin (5-HT) receptor agonist into the lateral parabrachial nucleus (LPBN) on the intake of NaCl and water induced by 24-h water deprivation or by sodium depletion followed by 24 h of sodium deprivation (injection of the diuretic furosemide plus 24 h of sodium-deficient diet). Rats had stainless steel cannulas implanted bilaterally into the LPBN. Bilateral LPBN injections of the serotonergic 5-HT1/2 receptor antagonist methysergide (4 mu g/200 nl at each site) increased hypertonic NaCl intake when tested 24 h after sodium depletion and after 24 h of water deprivation. Water intake also increased after bilateral injections of methysergide into the LPBN. In contrast, the intake of a palatable solution (0.06 M sucrose) under body fluid-replete conditions was not changed after bilateral LPBN methysergide injections. The results show that serotonergic mechanisms in the LPBN modulate water and sodium intake induced by volume depletion and sodium loss. The finding that sucrose intake was not affected by LPBN serotonergic blockade suggests that the effects of the methysergide treatment on the intakes of water and NaCl are not due to a mechanism producing a nonspecific enhancement of all ingestive behaviors.

Drosophila melanogaster P transposable elements: mechanisms of transposition and regulation

The molecular mechanisms that control P element transposition and determine its tissue specificity remain incompletely understood, although much information has been compiled about this element in the last decade. This review summarizes the currently available information about P element transposition, P-M hybrid dysgenesis and P cytotype features, P element-encoded repressors, and regulation of transposition.

Serotonergic mechanisms on breathing modulation in the rat locus coeruleus

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Chlorophyll fluorescence as a marker for herbicide mechanisms of action

Photosynthesis is the single most important source of 02 and organic chemical energy necessary to support all non-autotrophic life forms. Plants compartmentalize this elaborate biochemical process within chloroplasts in order to safely harness the power of solar energy and convert it into usable chemical units. Stresses (biotic or abiotic) that challenge the integrity of the plant cell are likely to affect photosynthesis and alter chlorophyll fluorescence. A simple three-step assay was developed to test selected herbicides representative of the known herbicide mechanisms of action and a number of natural phytotoxins to determine their effect on photosynthesis as measured by chlorophyll fluorescence. The most active compounds were those interacting directly with photosynthesis (inhibitors of photosystem I and II), those inhibiting carotenoid synthesis, and those with mechanisms of action generating reactive oxygen species and lipid peroxidation (uncouplers and inhibitors of protoporphyrinogen oxidase). Other active compounds targeted lipids (very-long-chain fatty acid synthase and removal of cuticular waxes). Therefore, induced chlorophyll fluorescence is a good biomarker to help identify certain herbicide modes of action and their dependence on light for bioactivity. Published by Elsevier B.V.

Photocatalytic decomposition of methylene blue via Fenton mechanisms by silicon wafer doped with Au and Cu: a theoretical and experimental study

In this work, we studied the photocatalytic and the structural aspects of silicon wafers doped with Au and Cu submitted to thermal treatment. The materials were obtained by deposition of metals on Si using the sputtering method followed by fast heating method. The photocatalyst materials were characterized by synchrotron-grazing incidence X-ray fluorescence, ultraviolet-visible spectroscopy, X-ray diffraction, and assays of H(2)O(2) degradation. The doping process decreases the optical band gap of materials and the doping with Au causes structural changes. The best photocatalytic activity was found for thermally treated material doped with Au. Theoretical calculations at density functional theory level are in agreement with the experimental data.