Morphological study of the spermatogenesis in the teleost Piaractus mesopotamicus

The spermatogenesis of Piaractus mesopotamicus was investigated under light and transmission electron microscopy. The specimens were captured from their natural environment (Rio Miranda and Rio Aquidauana, Pantanal Matogrossense, Brazil) during April and September. The results were compared with the spermatogenic data of specimens under captivity condition. In both conditions, P mesopotamicus presented the typical spermatogenesis pattern of the teleost fishes, showing no significative differences. The spermatozoon was classified as type 1, which has a globular head without acrosome, a short middle piece and a long tail constituted only by the flagellum. This type of spermatozoon is considered the basic type in fishes.

Spermatogenesis and karyotypes of three species of water striders (Gerridae, Heteroptera).

Although they are of economic importance, there have been few cytogenetic studies of the Gerridae (Heteroptera) in Brazil. We examined spermatogenesis (meiosis and spermiogenesis) and nucleolar behavior in three species of the family Gerridae. Brachymetra albinerva and Halobatopsis platensis were found to have a chromosome complement of 2n = 25 (24A + X0) and Cylindrostethus palmaris 2n = 29 (28A + X0) chromosomes. Fifteen individuals of these species were collected from the reservoir of São José do Rio Preto, SP, using screens and were transported in pots containing water to the laboratory, where cytogenetic preparations were made. The polyploidy nuclei are formed by several heteropyknotic regions; cells in meiotic prophase have a heteropyknotic region that is probably the sex chromosome, and the chromosomes from chiasmata. The spermatids are rounded and have a heteropyknotic region at the periphery of the nucleus; the sperm head is small, with a long tail. Silver impregnation of meiotic cells showed one or more disorganized bodies around the perichromosomal sheath. The round spermatids had two bodies next to each other, but these were elongated; one of the bodies remained in the head and the other migrated to the initial part of the tail at the end of spermagenesis, when the staining was no longer evident. The meiotic cells appear during spermatogenesis and have very similar silver-impregnation patterns in different species of Heteroptera.

História natural das serpentes dos gêneros Echinanthera e Taeniophallus (Echinantherini)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Análise das estratégias comunicacionais de grifes de luxo na Internet

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

Continuum resonances with shielded Coulomb-like potential and Efimov effect

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

Photo luminescence: A probe for short, medium and long-range self-organization order in ZrTiO4 oxide

Photoluminescent disordered ZrTiO4 powders were obtained by the polymeric precursor soft-chemical method. This oxide system (ordered and disordered) was characterized by photoluminescence, Raman spectroscopy, X-ray diffraction, differential scanning calorimetry and UV vis absorption experiments. The UV absorption tail formation in the disordered oxides was related to the diminution of optical band gap. In the disordered phase, this oxide displayed broad band photoluminescence caused by change in coordination number of titanium and zirconium with oxygen atoms. The gap decreased from 3.09 eV in crystalline oxide to 2.16 eV in disordered oxide. The crystalline oxide presented an orthorhombic alpha-PbO2-type structure in which Zr4+ and Ti4+ were randomly distributed in octahedral coordination polyhedra with oxygen atoms. The amorphous-crystalline transition occurred at almost 700 degrees C, at which point the photoluminescence vanished. The Raman peak at close to 80-200 cm(-1) indicated the presence of locally ordered Ti-O-n and Zr-O-n polyhedra in disordered photoluminescent oxides. (c) 2006 Elsevier B.V. All rights reserved.

Long-term nitric oxide inhibition and chronotropic responses in rat isolated right atria

The long-term administration of nitric oxide synthesis inhibitors induces arterial hypertension accompanied by left ventricular hypertrophy and myocardial ischemic lesions. Because the enhancement of sympathetic drive has been implicated in these phenomena, the current study was performed to determine the potency of β-adrenoceptor agonists and muscarinic agonists on the spontaneous rate of isolated right atria from rats given long-term treatment with the nitric oxide inhibitor N(ω)-nitro-L-arginine methyl ester (L-NAME). Atrial lesions induced by long-term treatment with L-NAME were also evaluated. Long-term L-NAME treatment caused a time-dependent, significant (P<0.05) increase in tail-cuff pressure compared with control animals. Our results showed that the potency of isoproterenol, norepinephrine, carbachol, and pilocarpine in isolated right atria from rats given long-term treatment with L-NAME for 7, 15, 30, and 60 days was not affected as compared with control animals. Addition of L-NAME in vitro (100 μmol/L) affected neither basal rate nor chronotropic response for isoproterenol and norepinephrine in rat heart. Stereological analysis of the right atria at 15 and 30 days revealed a significant increase on amount of fibrous tissues in L-NAME- treated groups (27±2.3% and 28±1.3% for 15 and 30 days, respectively; P<0.05) as compared with the control group (22±1.1%). Our results indicate that nitric oxide does not to interfere with β-adrenoceptor-mediated and muscarinic receptor-mediated chronotropic responses.