traG Gene Is Conserved across Mesorhizobium spp. Able to Nodulate the Same Host Plant and Expressed in Response to Root Exudates.

Evidences for an involvement of the bacterial type IV secretion system (T4SS) in the symbiotic relationship between rhizobia and legumes have been pointed out by several recent studies. However, information regarding this secretion system in Mesorhizobium is still very scarce. The aim of the present study was to investigate the phylogeny and expression of the traG gene, which encodes a substrate receptor of the T4SS. In addition, the occurrence and genomic context of this and other T4SS genes, namely, genes from tra/trb and virB/virD4 complexes, were also analyzed in order to unveil the structural and functional organization of T4SS in mesorhizobia. The location of the T4SS genes in the symbiotic region of the analyzed rhizobial genomes, along with the traG phylogeny, suggests that T4SS genes could be horizontally transferred together with the symbiosis genes. Regarding the T4SS structural organization in Mesorhizobium, the virB/virD4 genes were absent in all chickpea (Cicer arietinum L.) microsymbionts and in the Lotus symbiont Mesorhizobium japonicum MAFF303099T. Interestingly, the presence of genes belonging to another secretion system (T3SS) was restricted to these strains lacking the virB/virD4 genes. The traG gene expression was detected in M. mediterraneum Ca36T and M. ciceri LMS-1 strains when exposed to chickpea root exudates and also in the early nodules formed by M. mediterraneum Ca36T, but not in older nodules. This study contributes to a better understanding of the importance of T4SS in mutualistic symbiotic bacteria.

Analysis of the Mechanical Behavior and Surface Rugosity of Different Dental Die Materials.

AIM: This work evaluated the mechanical and surface behavior of different die materials. The studied materials are polyurethane resin Exakto-Form (Bredent), Gypsum type IV, Fuji Rock EP (Gc), and Durone (Dentsply). MATERIALS AND METHODS: Two metallic matrices molded in polyvinyl siloxane provided 30 cylindrical test specimens for the diametral compression test and 30 hemispherical test specimens for the surface rugosity test. The cylindrical test specimens were submitted to tests of diametral compression strength using a DL2000 universal assay machine, with a load cell of 2000 Kgf and constant speed of 1 mm/min connected to the software. Kruskal-Wallis and Dunn's nonparametric tests were used to analyze the results. The hemispheres were submitted to the surface rugosity assay using a SJ201-P rugosimeter with a sensitivity of 300 µm, speed of 0.5 mm/s, and cut-off of 0.8 mm, and the readings were taken on the convex surface of the test specimens and metallic matrix. Results were analyzed using with Fisher's least significant differences test (LSD) and Dunnett's test. RESULTS: Kruskal-Wallis test showed significant difference between die materials for diametral compression strength (P = 0.002). Dunn's test showed significantly higher values for modified polyurethane resin (Exakto-Form). The gypsum type IV, which did not significantly differ regarding diametral compression strength, showed 34.0% (Durone) and 42.7% (Fuji Rock) lower values in comparison to Exakto-Form. CONCLUSION: Within the parameters adopted in this study, it is possible to conclude that Exakto-Form polyurethane resin showed higher resistance to compression and was closer to the metallic matrix rugosity, and, along with the gypsum type IV Durone, showed better reproducibility of details relative to the Fuji Rock.

The impact of agricultural soil erosion on the global carbon cycle.

Agricultural soil erosion is thought to perturb the global carbon cycle, but estimates of its effect range from a source of 1 petagram per year(-1) to a sink of the same magnitude. By using caesium-137 and carbon inventory measurements from a large-scale survey, we found consistent evidence for an erosion-induced sink of atmospheric carbon equivalent to approximately 26% of the carbon transported by erosion. Based on this relationship, we estimated a global carbon sink of 0.12 (range 0.06 to 0.27) petagrams of carbon per year(-1) resulting from erosion in the world's agricultural landscapes. Our analysis directly challenges the view that agricultural erosion represents an important source or sink for atmospheric CO2.

Behavior of collagen extracellular liver matrix during regenerative growth after partial hepatectomy or after stimulation by exogenous hepatotrophic factors. Study in rats.

During regeneration after partial hepatectomy, the hepatic parenchyma grows by reproducing its histological elements at different rates. The hepatic cells grow more rapidly and the collagen components of the extracellular matrix more slowly. This report studies the behavior of liver tissue collagen in intact livers, increased in size by stimulation with exogenous hepatotrophic factors, comparing them to regenerated livers after hepatectomy. The series consists of a group of rats (n = 4), seven days after 70% hepatectomy, with an average growth of the residual liver mass of 71.55% and another group (n = 4), seven days after stimulation of the intact livers with an average growth of 121.05%. The exogenous hepatotrophic factors administered intraperitoneally (portal) included glucose, amino acids, insulin, glucagon and triiodothyronine. The hepatic collagen content was compared by studying slides stained with Picrossirius and examined with an optical microscope attached to a computer with an image analyzing program. The hepatic collagen was reduced from 2.07% +/- 0.13 to 1.14 +/- 0.08 (a difference of 44.57%; P < 0.001) after hepatectomy and from 1.98% +/- 0.19 to 1.24% +/- 0.07 (difference of 37.46%; P < 0.01) after exogenous hepatotrophic factors stimulation. It was concluded that the production of collagen in hepatic growth initiating with intact livers stimulated by exogenous hepatotrophic factors, occurs with a time difference similarly to what is observed after 70% hepatectomy.

Enhancement of liver size by stimulation of intact rat liver with exogenous hepatotrophic factors.

In mammals, liver size is related to animal body weight at the 2.5 to 3% proportion, a ratio mediated by the afflux of hepatotrophic factors. Formulas capable of modifying this ratio have been developed in previous studies on the rat, with enhancement of liver size brought about by intraperitoneal (portal) infusion of exogenous factors such as glucose, amino acids, insulin, glucagon, vitamins, electrolytes, and triiodothyronine. However, the efficacy of these formulations was accompanied by increased animal mortality (PARRA et al.). The present study, which was carried out with small methodological modifications on a larger number of rats using daily intraperitoneal injections of a solution of exogenous hepatotrophic factors (40 ml/kg) for seven days, confirms the previous findings, with a 114.16 +/- 7.90% enhancement of liver size beyond the expected value for the body weight of the animal. However, the problem of animal mortality was not fully resolved.

Reduction of liver mass due to malnutrition in rats. Correlation with emaciation of animals and size of organs not inserted in the portal system.

We studied the effects of protein-energy malnutrition on the liver morphology of rats as compared to animal emaciation and to reduction in size of the organs not irrigated by splanchnic blood such as kidneys and spleen. The animals were divided into two groups, one of them fed ad libitum rate (N = 10) and the other (N = 14) receiving water but no food for 7 days, and the changes in animal weight, liver, kidney and spleen mass were determined. DNA and the protein/DNA ratio, as well as hepatocyte size, were determined in liver tissue. The liver decreased in mass (27.14%) at a significantly higher proportion (p < 0.05) when compared to body emaciation (19.22%). Similar to the reduction in body weight, the masses of kidneys and spleen were reduced by 18.68% and 24.28%, respectively. The reduction in liver mass occurred due to hypoplasia and atrophy, i.e., a decrease in hepatocyte number and size, respectively. We conclude that there is a preferential consumption of liver protein in protein-energy malnutrition which is suggested to result from the additive action of the effects of overall consumption of organic reserves due to malnutrition proper and to the reduction of the hepatotrophic stimulus.

Oxamniquine: a labeling procedure with technetium-99m and a biodistribution study in mice.

Oxamniquine (OXY), a tetrahydroquinoline derivative, is used as an antischistosomal drug and generally has been labeled with carbon-14 and tritium. We decided instead to label it with technetium-99 (99mTc). In order to determine the optimal conditions, different concentrations of this drug were incubated with various stannous chloride solutions. We then added 99mTc, and chromatography was performed using 0.9% NaCl solution, acetone and 1.2N HCl as the mobile phase. Using a solution of 1.0 mg/mL stannous chloride and 0.5 mg/mL oxamniquine, over 94% of the radioactivity bound to oxamniquine (99mTc-OXY). In the biodistribution study, 99mTc-OXY was administered in mice intramuscularly, orally and intravenously. When the intramuscular route was used, the main uptake (after 30 minutes) of the labeled drug was in the kidneys, liver and intestines; after 240 minutes the labeled drug was still found in the liver and kidneys, but at increased levels in the intestines. It was also present in the faeces. When the oral route was employed, labeled OXY was mainly found in the stomach after 30 minutes, but there was a decrease after 240 minutes. During this period radioactivity increased in the intestines. When the intravenous route was employed the labeled OXY was found in the liver and spleen. The radioactivity decreased with time in these organs. Using infected animals, radioactivity was found in isolated worms.

[Humoral immunity and the argon-laser]. / L'immunité humorale et argon-laser.

We have done two argon-laser iridotomies 24 and 72 hours before cataract surgery, to study ocular inflammation. We have taken aqueous samples to study IgA, IgG, C3 and AAT by laser immunonephelometry. All the proteins raised in the first 24 hours (P less than or equal to 0.01) except IgA in aqueous humor, taken with control levels, but only AAT (P less than or equal to 0.05), albumine at 72 hours (P less than or equal to 0.01) in aqueous humor. We tried to understand the observed gap by immunomodulation of released mediators.

Aortofemoral bypass grafts: safety of percutaneous puncture.

To assess the safety of percutaneous puncture for the angiographic study of aortofemoral bypass grafts, we reviewed the medical records of 58 patients who underwent a total of 86 graft punctures. Short- and long-term follow-up revealed that in 83 punctures there were no complications. In three instances (3.5%) there was acute thrombosis of the punctured limb of the graft. This complication may have expedited but did not substantially alter the surgical plans of managing the underlying clinical problem. Although the incidence of complications of direct graft puncture is higher than that associated with puncture of native vessels, alternative approaches are also associated with complications, many of which may be more serious. Therefore, for angiographic studies of patients with aortofemoral bypass grafts, we favor the direct percutaneous puncture provided that enough time has elapsed from surgery.