Presence of calcium in oocytes of the diplopod Rhinocricus padbergi Verhoeff (Spirobolida, Rhinocricidae)

In diplopods, the presence of calcium-containing structures seems to be a common finding in some species, with its formation being similar to that observed for other intracellular mineralization systems. In the present study, using histochemistry and transmission electron microscopy, a large amount of calcium was observed in the oocytes of Rhinocricus padbergi. Calcium was detected in both less and well developed oocytes, i.e., the occurrence of calcium coincided with the beginning of vitellogenesis. Calcium was observed as fine granulation distributed within the cytoplasm or deposited in spherical structures apparently formed by overlapping calcium layers. Some authors have suggested that these structures represent a type of reserve used for the calcification of the embryo exoskeleton, whereas others believe that calcium inclusions are a mechanism of organism detoxification as a result of excess calcium ingested by animals during soil turnover. We suggest in this paper that the first hypothesis could be occurring in R. padbergi since at the juvenile stages of the individuals the uptake of calcium is low and because the oocyte is a specialized cell not associated with detoxification.

Crystal structure of piratoxin-I: A calcium-independent, myotoxic phospholipase A(2)-homologue from Bothrops pirajai venom

The crystal structure of Piratoxin-I (PrTX-I) a Lys49 homologue isolated from the venom of Bothrops pirajai has been determined and refined at 2.8 Angstrom to a crystallographic residual of 19.7% (R-free = 29.7%). Amino-acid sequence differences between catalytically active phospholipases and PrTX-I in the putative Ca2+-binding loop, specifically the substitutions Tyr28-->Asn, Gly32-->Leu and Asp49-->Lys, result in an altered conformation of this loop, the analysis of the position of the E-amino group of Lys49 in the PrTX-I structure indicates that it fills the site normally occupied by the calcium ion in the catalytically active phospholipases, In contrast to the homologous monomeric Lys49 variant from Agkistrodon piscivorus piscivorus (App), PrTX-I is present as a dimer in the crystalline state, as observed in the structures of myotoxin II from Bothrops asper and Bothropstoxin I from Bothrops jararacussu. The two molecules in the asymmetric unit in the crystal structure of PrTX-I are related by a nearly perfect two-fold symmetry axis, yet the dimeric structure is radically different from the dimeric structure of the phospholipase from Crotalus atrox. In the C. atrox structure the dimer interface occludes the active sites, whereas in the PrTX-I structure they are exposed to solvent, (C) 1998 Elsevier B.V. Ltd. All rights reserved.

In vitro effects of calcium hydroxide and polymyxin B on endotoxins in root canals

Objectives. To evaluate the effects of intracanal medicaments on endotoxins in root canals.Methods. Seventy-five freshly extracted maxillary incisors were used in this study. The crowns of teeth were sectioned near the CEJ in order to standardize the root length to 14 mm. The root canals were instrumented to an apical size #50 file and irrigated with 1% sodium hypochlorite solution and sterilized with 60 Co gamma irradiation. Standardized suspension containing Escherichia coli endotoxin was inoculated into the 60 root canals. The specimens were randomly assigned to 5 groups (n=15), according to the intracanal medicament used: (G1) calcium hydroxide; (G2) polymyxin B; (0) combination neomycin-potymyxin B-hydrocortisone; (G4) positive control (no intracanal medicament); (G5) negative control (no endotoxin and no intracanal medicament). After 7 days, the detoxification of endotoxin was evaluated by Limulus lysate assay and antibody production in B-tymphocytes culture.Results. Groups 1, 2 and 5 presented the best results by Limulus lysate and were significantly different to groups 3 and 4 (p<0.05). Stimulation of antibodies production in cell culture by groups 1 and 6 was smaller and statistically different than groups 2, 3, 4 and 5 (p<0.05). Groups 2 and 5 induced a small increase in the antibodies production in relation to the groups 1 and 6. Groups 3 and 4 induced a significant increase of antibodies production (p<0.05).Conclusions. The calcium hydroxide and polymyxin B intracanal medicaments detoxified endotoxin in root canals and altered the properties of LPS to stimulate the antibody production by B-Lymphocytes. The combination neomycin-polymyxin B-hydrocortisone did not detoxified endotoxin. (C) 2004 Elsevier Ltd. All rights reserved.

Subcutaneous tissue reaction to castor oil bean and calcium hydroxide in rats

Castor oil bean cement (COB) is a new material that has been used as an endodontic sealer, and is a candidate material for direct pulp capping. Objective: The purpose of this study was to evaluate the biocompatibility of a new formulation of COB compared to calcium hydroxide cement (CH) and a control group without any material, in the subcutaneous tissue of rats. Material and Methods: The materials were prepared, packed into polyethylene tubes, and implanted in the rat dorsal subcutaneous tissue. Animals were sacrificed at the 7th and 50th days after implantation. A quantitative analysis of inflammatory cells was performed and data were subjected to ANOVA and Tukey's tests at 5% significance level. Results: Comparing the mean number of inflammatory cells between the two experimental groups (COB and CH) and the control group, statistically significant difference (p=0.0001) was observed at 7 and 50 days. There were no significant differences (p=0.111) between tissue reaction to CH (382 inflammatory cells) and COB (330 inflammatory cells) after 7 days. After 50 days, significantly more inflammatory cells (p=0.02) were observed in the CH group (404 inflammatory cells) than in the COB group (177 inflammatory cells). Conclusions: These results demonstrate that the COB cement induces less inflammatory response within long periods.

Effect of low-calcium diet and grind diet on bone turnover of ovariectomized female rats

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

Effects of experimental osteoporosis and low calcium intake on postextraction sockets of rats

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Calcium sulfate and PTFE nonporous barrier for regeneration of experimental bone defects

The aim of the study was to evaluate the possibility to obtain guided bone regeneration with two types of physical barriers (calcium sulfate and PTFE nonporous barrier) in surgical defects created in rat parietal bones. In the right parietal bone the calcium sulfate barrier filled out the whole defect and in the left parietal bone the barrier of PTFE was positioned in the floor and externally to the surgical defect. After 7, 14, 30 and 45 days four animals were sacrificed in each period and the bone containing the defects were submitted to the microscopic analysis. The results of the study revealed that the PTFE barrier was more effective for bone regeneration in shallow transcortical defects compared to the calcium sulfate. However, additional experiments are necessary to determine if calcium sulfate would be successful in other bone defects types or the use of the material under another consistence could complement the results obtained in this work.

Electrical conductivity of silicate glasses with tetravalent cations substituting Si

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

Functional Characterization of an Aspergillus fumigatus Calcium Transporter (PmcA) that Is Essential for Fungal Infection

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

Synthesis of chitosan/hydroxyapatite membranes coated with hydroxycarbonate apatite for guided tissue regeneration purposes

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Size distributions of fine silicate and other particles in Masaya's volcanic plume

Direct-sampling and remote-sensing measurements were made at the crater rim of Masaya volcano (Nicaragua) to sample the aerosol plume emanating from the active vent. We report the first measurements of the size distribution of fine silicate particles (d <10 mu m) in Masaya's plume, by automated scanning electron microscopy (QEMSCAN) analysis of a particle filter. The particle size distribution was approximately lognormal with modal d similar to 1.15 mu m. The majority of these particles were found to be spherical. These particles are interpreted to be droplets of quenched magma produced by a spattering process. Compositional analyses confirm earlier reports that the fine silicate particles show a range of compositions between that of the degassing magma and nearly pure silica and that the extent of compositional variability decreases with increasing particle size. These results indicate that fine silicate particles are altered owing to reactions with acidic droplets in the plume. The emission flux of fine silicate particles was estimated as similar to 10(11) s(-1), equivalent to similar to 55 kg d(-1). Sun photometry, aerosol spectrometry, and thermal precipitation were used to determine the overall particle size distribution of the plume (0.01 < d(mu m) < 10). Sun photometry and aerosol spectrometry measurements indicate the presence of a large number of particles (assumed to be aqueous) with d similar to 1 mu m. Aerosol spectrometry measurements further show an increase in particle size as the nighttime approached. The emission flux of particles from Masaya was estimated as similar to 10(17) s(-1), equivalent to similar to 5.5 Mg d(-1) where d < 4 mu m.

Direct determination of calcium in milk by atomic absorption spectrometry using flow-injection analysis

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

Role of intermediary cells in Peltodon radicans (Lamiaceae) in the transfer of calcium and formation of calcium oxalate crystals

Com o objetivo de estudar a relação entre cristais de oxalato de cálcio e floema, fragmentos de folhas de Peltodon radicans foram fixados e processados, segundo métodos usuais, para estudos ao microscópio de luz e eletrônico de transmissão. Observou-se que os cristais ocorrem nas células da bainha do feixe, lateralmente em relação ao floema. Células intermediárias estabelecem conexão entre elemento crivado e células da bainha, portadoras de cristais, com crescimento intrusivo entre estas. Íons cálcio são abundantes no citoplasma das células da bainha que contém cristais de oxalato de cálcio. Nas células intermediárias a detecção ultra-citoquímica de cálcio também apresentou resultados positivos, enquanto nos elementos crivados a presença deste íon não foi constatada. Há, portanto, um gradiente crescente de concentração de cálcio dos elementos crivados para as células da bainha. Assim, formulamos a hipótese de que a formação de cristais de oxalato de cálcio tem, em P. radicans, o objetivo de controlar os níveis de cálcio citossólico nos elementos crivados.

Reversion by calcium of a yeast-like development to the original filamentous form, of the 10V10 5-fluorocytosine-sensitive mutant of Aspergillus niger

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Calcium in pre-laying and laying rations on the performance and quality of laying hens' eggshell

O ensaio experimental objetivou avaliação do efeito de diferentes níveis de cálcio (Ca) nas rações de pré-postura e postura sobre o desempenho e qualidade dos ovos de poedeiras comerciais. Foram alojadas 256 frangas da linhagem Hisex Brown com 16 semanas de idade em galpão convencional de postura. O delineamento experimental foi inteiramente casualizado em arranjo fatorial 4 x 2 (4 níveis de cálcio - 0,8; 1,3; 1,8 e 2,3% na pré-postura e 2 níveis de cálcio - 2,5 e 3,5% na postura), totalizando oito tratamentos com quatro repetições de oito aves por unidade experimental. Iniciou-se com a ração de pré-postura às 16 semanas de idade das aves, sendo que a mesma foi fornecida até as aves atingiram 18 semanas de idade, quando então, iniciou-se com a ração de postura. Foram avaliadas durante quatro ciclos de 28 dias as seguintes variáveis: produção e peso dos ovos, consumo de ração, conversão alimentar, massa de ovos e qualidade da casca dos ovos. Através dos resultados obtidos pode-se concluir que um bom desempenho foi obtido com 0,8% de cálcio na fase de pré-postura. Na fase de postura o nível de 3,5% de cálcio promoveu maior peso de ovo e melhor qualidade de casca.