Effect of the temperature on the TMOS sono-hydrolysis and a study of the structure of the resulting aged sonogels

The effect of temperature on the oxalic acid catalyzed sono-hydrolysis of tetramethoxysilane (TMOS) was studied by means of a heat flux calorimetric method. The activation energy of the process was measured as (24.5 +/- 0.8) kJ/mol in the temperature range between 10 and 50 degreesC. The structural characteristics of the resulting sonogels, after long period of aging in saturated conditions, were studied by means of small angle X-ray scattering. The structure can be described as formed by similar to2.7 nm mean size mass fractal-like aggregates (clusters) of primary silica particles of similar to0.3 nm mean size, all imbibed in a liquid phase. The average mass fractal dimension of the clusters was found to be 2.58. The primary particle density was estimated as 2.23 g/cm(3), in good agreement with the value frequently quoted for fused silica. The volume fraction of the clusters, in the saturated sonogels was estimated as about 28%. The moment in which the meniscus of the liquid phase penetrates into the clusters under rapid evaporation process has been detected by an inflection in the first derivative of the curve of weight loss in a simple thermogravimetric test. (C) 2003 Elsevier B.V. All rights reserved.

MODEL FOR ASYMPTOTIC D-STATE PARAMETERS OF LIGHT-NUCLEI - APPLICATION TO HE-4

A simple method for calculating the asymptotic D-state observables for light nuclei is suggested. The method exploits the dominant clusters of the light nuclei. The method is applied to calculate the He-4 asymptotic D to S normalization ratio rho(alpha) and the closely related D-state parameter D2alpha. The study predicts a correlation between D2alpha and B(alpha), and between rho(alpha) and B(alpha), where B(alpha) is the binding energy of He-4. The present study yields rho(alpha) congruent-to -0.14 and D2alpha congruent-to -0.12 fm2 consistent with the correct experimental eta(d) and the binding energies of the deuteron, triton, and the alpha particle, where eta(d) is the deuteron D-state to S-state normalization ratio.

SAXS study of gelation, aging and drying of silica-polypropyleneglycol hybrid materials

New silica-polypropyleneglycol ormosils (organically modified silicates) with covalent bends between the organic (polymer) and inorganic (silica) phases have been prepared by the sol-gel process. Their structural evolution during sol formation, sol-gel transition, gel aging and drying has been studied in situ by small-angle X-ray scattering (SAXS). The experimental SAXS curves corresponding to sols and gels exhibit features expected from fractal objects. Clusters of size around 55 Angstrom with an initial fractal dimension D = 2.4 are formed in the sol. They are constituted of small primary silica particles chemically crosslinked at the end of the polymer chains. A strong liquid-like spatial correlation between the silica particles develops during drying due to the shrinkage of the polymeric network induced by water and ethanol evaporation. The continuous increase in SAXS intensity during drying, while the interparticle distance remains constant, is a consequence of the progressive growth of the dry fraction of the total volume. After drying, the gel structure consists of a rather compact arrangement of silica particles embedded in the polypropyleneglycol matrix.

Use of strontium for bovine oocyte activation

Strontium efficiently activates mouse oocytes, however, there is limited information on its use in cattle. Thus, the objective of this study was to establish a suitable protocol for activating bovine oocyte with strontium. For pronuclear development, the absence of calcium and magnesium in the activation medium (TALP) with 10 and 50mM strontium (34.4 and 53.1%, respectively) was superior to the complete TALP (6.5 and 19.4%, respectively). In all activation media, better results were observed with 25 and 50 mM strontium (21.9-53.1 and 19.4-53.1%, respectively). Incubation for 4 h promoted similar results in all strontium concentrations. However, strontium at 15, 20, and 25 mM for 6 and 8 h (40.7, 46.7, and 48.3%, and 29.3, 48.3, and 40.7%, respectively) were superior to control (15.5 and 10%, respectively). After in vitro maturation for 26 h, strontium (S; 20 mM in Ca2+ and Mg2+-free TALP for 6 h), ionomycin + strontium (IS), and strontium + ionomycin (SI) (60, 63.3, and 65%, respectively) were similar in pronuclear development and superior to ionomycin (I; 5 mu M for 5 min; 36.7%). In treatments S and I, only 1 PN zygotes were observed. In treatment S, most of them had 1 and 2 PB (35.7 and 60.7%, respectively), and in treatment I, 0, 1, and 2 PB (14.3, 57.1, and 28.6%, respectively). Most of the zygotes in treatment IS and SI were 1 PN 2 PB (77.4 and 61.6%, respectively). The number of oocytes with clusters of cortical granules was similar in all treated groups (11-29%). Cortical granule exocytosis in treatment IS (68%) was similar to S (54%) and superior to 1, SI, and control (27, 45, and 5.0%, respectively). Cleavage and blastocyst rates were similar for S, I, IS, and SI treatments (61.7-76.7, and 8.3-13.3%, respectively) and the same was observed for ICM, TE, and total cell number, and ICM/total cell ratio (22-25, 64-69, and 86-95, and 0.26-0.27). In conclusion, strontium may be efficiently applied for bovine oocyte activation at 20 mM in Ca2+-and Mg2+-free TALP medium for 6 h.

Alcohol effects on the principal and clear cells of the caput epididymis of albino rats

Ultrastructural observations of principal cells of the epithelium lining of the proximal caput epididymis in experimental alcoholic albino rats at 180 days of treatment showed pyknotic nuclei, ill-defined cellular organelles and clusters of electrondense bodies, perhaps lysosomes. It was also verified for a progressive accumulation of lipid droplets initially in the basal and perinuclear cytoplasm and finally in the apical cytoplasm of principal cells at 60, 120 and 180 days of experimentation, respectively. The clear cells of alcoholic rats at 180 days showed the cytoplasm totally filled with lipid droplets. These findings were taken comparatively with the morphological features of the same epididymal cells in control (normal) rats.

Apoptosis in the epithelial cells of the rests of Malassez of the periodontium of rat molars

Background and Objectives: Epithelial rests of Malassez are clusters of cells derived from Hertwig's root sheath that remain in the periodontal ligament throughout life. Although it is known that the cells of Malassez proliferate, there are no studies showing that they undergo programmed cell death, i.e. apoptosis. In most tissues, proliferation is balanced by apoptosis. Thus we examined regions of the periodontium of young and adult rat molars in the hope of detecting apoptosis.Methods: Wistar rats aged 29, 45 and 120 days were killed with chloral hydrate (600 mg/kg). Fragments containing maxillary molars were removed and fixed in formaldehyde, decalcified, and embedded in paraffin and glycol methacrylate. Sections were stained with hematoxylin/eosin and the Terminal deoxynucleotidyl transferase-mediated dUTP Nick End Labeling (TUNEL) method for detection of apoptosis. Specimens were also fixed in glutaraldehyde-formaldehyde, decalcified and processed for transmission electron microscopy.Results: Epithelial rests of Malassez containing round/ovoid basophilic dense bodies and TUNEL-positive structures were found in all specimens examined. Ultrastructural examination revealed that some cells of Malassez contained masses of condensed peripheral chromatin and a shrunken cytoplasm exhibiting intact organelles - images typical of apoptosis. Moreover, round/ovoid electron-opaque structures appeared to be in the process of being engulfed by neighboring epithelial cells of Malassez.Conclusions: Our results demonstrate that epithelial cells of Malassez's rests undergo apoptosis in the developing and adult periodontium. Apoptosis may, together with proliferation, be part of the mechanism of turnover/remodelling of the cells of Malassez.

Ferritin in iron containing granules from the fat body of the honeybees Apis mellifera and Scaptotrigona postica

It is already known that the behaviour of the honeybee Apis mellifera is influenced by the Earth's magnetic field. Recently it has been proposed that iron-rich granules found inside the fat body cells of this honeybee had small magnetite crystals that were responsible for this behaviour. In the present work, we studied the iron containing granules from queens of two species of honeybees (A. mellifera and Scaptotrigona postica) by electron microscopy methods in order to clarify this point. The granules were found inside rough endoplasmic reticulum cisternae. Energy dispersive X-ray analysis of granules from A. mellifera showed the presence of iron, phosphorus and calcium. The same analysis performed on the granules of S. postica also indicated the presence of these elements along with the additional element magnesium. The granules of A. mellifera were composed of apoferritin-like particles in the periphery while in the core, clusters of organised particles resembling holoferritin were seen. The larger and more mineralised granules of S. postica presented structures resembling ferritin cores in the periphery, and smaller electron dense particles inside the bulk. Electron spectroscopic images of the granules from A. mellifera showed that iron, oxygen and phosphorus were co-localised in the ferritin-like deposits. These results indicate that the iron-rich granules of these honeybees are formed by accumulation of ferritin and its degraded forms together with elements present inside the rough endoplasmic reticulum, such as phosphorus, calcium and magnesium. It is suggested that the high level of phosphate in the milieu would prevent the crystallisation of iron oxides in these structures, making very unlikely their participation in magnetoreception mechanisms. They are most probably involved in iron homeostasis. (C) 2001 Elsevier B.V. Ltd. All rights reserved.

Coffee leaf scorch caused by a strain of Xylella fastidiosa from citrus

Citrus variegated chlorosis (CVC) and coffee leaf scorch (CLS) are two economically important diseases in Brazil caused by the bacterium Xylella fastidiosa. Strains of the bacterium isolated from the two plant hosts are very closely related, and the two diseases share sharpshooter insect vectors. In order to determine if citrus strains of X. fastidiosa could infect coffee and induce CLS disease, plant inoculations were performed. Plants of coffee, Coffea arabica 'Mundo Novo', grafted on Coffea canephora var, robusta 'Apuatao 2258' were mechanically inoculated with triply cloned strains of X. fastidiosa isolated from diseased coffee and citrus. Three months postinoculation, 5 of the 10 plants inoculated with CLS-X. fastidiosa and 1 of the 10 plants inoculated with CVC-X. fastidiosa gave positive enzyme-linked immunosorbent assay (ELISA) and/or polymerase chain reaction (PCR). Eight months postinoculation, another six plants inoculated with CVC-X. fastidiosa gave positive PCR results. The two X. fastidiosa strains were isolated from the inoculated plants and showed the same characteristics as the original clones by microscopy, ELISA, and PCR. None of the plants inoculated with sterile periwinkle wilt (PW) medium as controls gave positive reactions in diagnostic tests, and none developed disease symptoms. Six months postinoculation, seven plants inoculated with CLS-X. fastidiosn and eight inoculated with CVC-X. fastidiosa began to develop characteristic CLS symptoms, including apical and marginal leaf scorch, defoliation, and reductions of internode length, leaf size, and plant height, terminal clusters of small chlorotic and deformed leaves, and lateral shoot dieback. We have demonstrated that X, fastidiosa from citrus plants is pathogenic for coffee plants. This has important consequences for the management of CLS disease and has implications for the origin of citrus variegated chlorosis disease.

High hydrostatic pressure processing on microstructure of probiotic low-fat yogurt

The effect of milk processing on the microstructure of probiotic low-fat yogurt was studied. Skim milk fortified with skim milk powder was subjected to three treatments prior to innoculation: thermal treatment at 85 degrees C for 30 min, high hydrostatic pressure at 676 MPa for 5 min, and combined treatments of high hydrostatic pressure (HHP) and heat. The processed milk was then fermented by using two different starter cultures containing Streptococcus thermophilus, Lactobacillus delbrueckii ssp. bulgaricus, Lactobacillus acidophilus, and Bifidobacterium longum. The microstructure of heat-treated milk yogurt had fewer interconnected chains of irregularly shaped casein micelles, forming a network that enclosed the void spaces. on the other hand, microstructure of HHP yogurt had more interconnected clusters of densely aggregated protein of reduced particle size, with an appearance more spherical in shape, exhibiting a smoother more regular surface and presenting more uniform size distribution. The combined HHP and heat milk treatments led to compact yogurt gels with increasingly larger casein micelle clusters interspaced by void spaces, and exhibited a high degree of cross-linking. The rounded micelles tended to fuse and form small irregular aggregates in association with clumps of dense amorphous material, which resulted in improved gel texture and viscosity. (C) 2007 Elsevier Ltd. All rights reserved.

Cataract Remains an Important Cause of Blindness in Campinas, Brazil

Objective: To estimate the prevalence of blindness in the elderly population of Campinas, Brazil, and to describe the coverage and quality of cataract surgery services in the area. Methods: A brief assessment of cataract surgery services (using the RACSS (Rapid Assessment of Cataract Surgical Services Method) was conducted using random cluster sampling, with a sample composed of 60 clusters of 40 people aged 50 years or older. Visual acuity (VA) was measured and the lens status observed by direct visual ophthalmoscopy. From the selected sample of 2,400 subjects, 92.67% were examined. Results: Blindness (VA 3/60 with available correction) was found in 1.98 % (2.03 % among male subjects, and 1.94 % among female subjects). The prevalence of blindness varied with age, from 0.2%, in the group from 50 to 54 years, to 7.2% in those above 80. Cataract was the main cause of blindness (40.2%) followed by suspected posterior segment disorders (18.2%), diabetic retinopathy (15.9%), and glaucoma (11.4%). The cataract surgical coverage was of 93% (VA 3/60) and 82.18% when the criterion was VA 6/60 in the best eye. The main reasons the subjects did not receive surgical treatment were: fear of undergoing surgery, 11.1%; lack of awareness about the condition, 16.7%; waiting for maturity, 16.7%; and contraindication to surgery, 44.4%. Conclusion: Cataract is the major cause of blindness in Campinas. Education on eye diseases, their prevention and treatment must become part of the city's public healthcare policies.

Comparative phylogeography of Trypanosoma cruzi TCIIc: New hosts, association with terrestrial ecotopes, and spatial clustering

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Histochemical study of muscle fiber types in Synbranchus marmoratus Bloch, 1795

The myotomal muscle of Synbranchus marmoratus was investigated using histochemical and immunohistochemical reactions. This musculature is composed of a superficial red compartment, uniformly distributed around the trunk circumferentially and also in the lateral line. The red compartment fibers are small in diameter and have an oxidative metabolism, a high rate of glycogen and a negative reaction to alkaline and acid myofibrillar ATPase (mATPase). The white muscle forms the bulk of the muscle mass. Its fibers are large in diameter and have a glycolytic metabolism, a negative reaction to glycogen, a strong reaction to alkaline mATPase and a negative reaction to acid mATPase. Between these two compartments there is an intermediate layer of fibers presenting a mosaic metabolism pattern with a high rate of glycogen. These fibers stained moderately for alkaline and acid m-ATPase. Several clusters of red muscles were observed inside the white muscle. Each cluster is composed of three fiber types, with a predominance of red and intermediate fibers. Reactivity to anti-MHC BA-D5 was positive only in the intermediate fibers. Reactivity to anti-MHC SC-71 was negative in all fiber types.

Interaction of the nonionic surfactant C12E8 with high molar mass poly(ethylene oxide) studied by dynamic light scattering and fluorescence quenching methods

Dynamic light scattering has been used to investigate ternary aqueous solutions of n-dodecyl octaoxyethylene glycol monoetber (C12E8) with high molar mass poly(ethylene oxide) (PEO). The measurements were made at 20 °C, always below the cloud point temperature (Tc) of the mixed solutions. The relaxation time distributions are bimodal at higher PEO and surfactant concentrations, owing to the preacute of free surfactant micelles, which coexist with the slower component, representing the polymer coil/micellar cluster comptex. As the surfactant concentration is increased, the apparent hydrodynamic radius (RH) of the coil becomes progressively larger. It is suggested that the complex structure consists of clusters of micelles sited within the polymer coil, as previously concluded for the PEO-C12E8-water system. However. C12E8 interacts less strongly than C12E8 with PEO; at low concentrations of surfactant the complex does not contribute significantly to the total scattered intensity. The perturbation of the PEO coil radius with C12E8 is also smaller than that in the C12E8 system. The addition of PEO strongly decreases the clouding temperature of the system, as previously observed for C12E8/PEO mixtures in solution Addition of PEO up to 0.2% to C12E8 (10 wt %) solutions doss not alter the aggregation number (Nagg) of the micelles probably because the surfactant monomers are equally partitioned as bound and unbound micelles. The critical micelle concentration (cmc), obtained from the I1/I3 ratio (a measure of the dependence of the vibronic band intensities on the pyrene probe environment), does not change when PEO is added, suggesting that for neutral polymer/surfactant systems the trends in Nagg and the cmc do not unambiguously reflect the strength of interaction.

Genetic variation between several species of sections Extranervosae, Caulorrhizae, Heteranthae, and Triseminatae (genus Arachis) estimated by DNA polymorphism

Genetic variation within and among accessions of the genus Arachis representing sections Extranervosae, Caulorrhizae, Heteranthae, and Triseminatae was evaluated using RFLP and RAPD markers. RAPD markers revealed a higher level of genetic diversity than did RFLP markers, both within and among the species evaluated. Phenograms based on various band-matching algorithms revealed three major clusters of similarity among the sections evaluated. The first group included the species from section Extranervosae, the second group consisted of sections Triseminatae, Caulorrhizae, and Heteranthae, and the third group consisted of one accession of Arachis hypogaea, which had been included as a representative of section Arachis. The phenograms obtained from the RAPD and RFLP data were similar but not identical. Arachis pietrarellii, assayed only by RAPD, showed a high degree of genetic similarity with Arachis villosulicarpa. This observation supported the hypothesis that these two species are closely related. It was also shown that accession V 7786, previously considered to be Arachis sp. aff. pietrarellii, and assayed using both RFLPs and RAPDs, was possibly a new species from section Extranervosae, but very distinct from A. pietrarellii.

RAPD analysis in the Neotropical fish Brycon lundii: Genetic diversity and its implications for the conservation of the species

Random amplified polymorphic DNA (RAPD) technique was used to examine the genetic variability on an endangered Neotropical fish species, Brycon lundii, collected on two regions with distinct environmental conditions in the São Francisco River (Brazil), downstream from a hydroelectric station. Using decamer oligonucleotides as single primers in Polymerase Chain Reaction (PCR), genetic similarity index, mean allele frequency and mean heterozigosity were estimated, revealing variations between samples from the two regions. Moreover, a fragment of about 1200 base pairs was found in 100% of the examined animals collected at the region closer to the hydroelectric dam, while its frequency was much lower (27.3%) within the sample from the second collecting site, 30 km downstream from the dam, indicating a possible correlation between genetic variation and geographical area. A dendogram representing the relationships among genotypes was obtained, demonstrating at least two major clusters of animals. Based on the data, a model of population structuring in Brycon lundii is suggested. The described approach holds great promise for further analyses and gives support to biodiversity maintenance and recovery efforts of B. lundii.