Effects of sucrose on the extracellular matrix of plaque-like biofilm formed in vivo, studied by proteomic analysis.

Previous studies have shown that sucrose promotes changes in the composition of the extracellular matrix (ECM) of plaque-like biofilm (PLB), but its effect on protein expression has not been studied in vivo. Therefore, the protein compositions of ECM of PLB formed with and without sucrose exposure were analyzed by two-dimensional gel electrophoresis and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). For this purpose, a crossover study was conducted during two phases of 14 days each, during which a volunteer wore a palatal appliance containing eight enamel blocks for PLB accumulation. In each phase, a 20% sucrose solution or distilled and deionized water (control) were extraorally dripped onto the blocks 8x/day. On the 14th day, the PLB were collected, the ECM proteins were extracted, separated by two-dimensional gel electrophoresis, digested by in-gel trypsin and MALDI-TOF MS analyzed. In the ECM of PLB formed under sucrose exposure, the following changes compared with the control PLB were observed: (1) the presence of upregulated proteins that may be involved in bacterial response to environmental changes induced by sucrose and (2) the absence of calcium-binding proteins that may partly explain the low inorganic concentration found in ECM of PLB formed under sucrose exposure. The findings showing that sucrose affected the ECM protein composition of PLB in vivo provide further insight into the unique cariogenic properties of this dietary carbohydrate.

The role of sucrose in cariogenic dental biofilm formation--new insight.

Dental caries is a biofilm-dependent oral disease, and fermentable dietary carbohydrates are the key environmental factors involved in its initiation and development. However, among the carbohydrates, sucrose is considered the most cariogenic, because, in addition to being fermented by oral bacteria, it is a substrate for the synthesis of extracellular (EPS) and intracellular (IPS) polysaccharides. Therefore, while the low pH environment triggers the shift of the resident plaque microflora to a more cariogenic one, EPS promote changes in the composition of the biofilms' matrix. Furthermore, it has recently been shown that the biofilm formed in the presence of sucrose presents low concentrations of Ca, P(i), and F, which are critical ions involved in de- and remineralization of enamel and dentin in the oral environment. Thus, the aim of this review is to explore the broad role of sucrose in the cariogenicity of biofilms, and to present a new insight into its influence on the pathogenesis of dental caries.

Assessment of water systems for contaminants from domestic and industrial sewages.

The State of Minas Gerais represents one of Brazil's most outstanding mining resources. The contamination of river water from kaolin processing activities may be harmful to people in the way of slow but chronic poisoning. On the other hand, the discharge of untreated or inadequately treated domestic sewage into aquatic environments can also cause deleterious effects to the health. However, no reliable figures are available for pollutant occurrences in river water. This draws attention to the very precarious situation that exists with respect to pollution by organic and inorganic toxic wastes, especially with respect to humans and fauna in all its expressions. Thus, with the purpose of establishing a preliminary report to trace out industrialisation outcomes, samples of river water, vegetation and fish were collected and analysed to detect pollutant inputs. The concentration of metals was determined in suspended particle, vegetation and fish, while those of nitrite, nitrate, phosphate and chloride were determined in river water samples. The concentration of dissolved oxygen (DO) was measured in river water at the time of collection. Chemical oxygen demand (COD) and biochemical oxygen demand (BOD) were also determined. Metal inputs in the samples analysed appeared to be related to effluent discharges into the rivers. The suspended particles showed high concentrations (in mg kg(-1)) of zinc (62 600) and aluminium (559 000), while vegetation samples collected near rivers were heavily contaminated with iron (7680). The fishes examined were contaminated with chromium (1.5 mg kg(-1)). In general, the concentrations of nitrite, nitrate, chloride, phosphate and BOD in river water were lower than the maximum values established by the Brazilian Environmental Standards.

[Leprosy surgery in a bush hospital in Africa: experience in Madagascar]. / La chirurgie de la lèpre dans un hôpital de brousse en Afrique: expérience à Madagascar.

We report our experience of leprosy surgery in terms of feasibility and efficacy in a small hospital of bush in Madagascar during the period of September 1989 to January 1993. Operations of neurolysis, corrections of claw hands by the techniques of Lasso-Zancolli or Van Droogenbroeck, arthrodesis, resections and amputations have been performed. Our results suggest that at least a part of these surgical procedures may be performed by a non specialized medical team, taught on the premises. Thus, the cost of treatment will be low and accessible to more leprosy patients.

The soybean cultivar specificity gene nolX is present, expressed in a nodD-dependent manner, and of symbiotic significance in cultivar-nonspecific strains of Rhizobium (Sinorhizobium) fredii.

Rhizobium (now Sinorhizobium) fredii is a symbiotic nitrogen-fixing bacterium that can nodulate soybean in a cultivar-specific manner. This process is governed by a set of negatively acting nodulation genes termed nolXWBTUV. These genes prevent R. fredii strain USDA257 from infecting soybean cultivars such as McCall, but they do not block nodulation of cultivar Peking. R. fredii strain USDA191 contains DNA sequences that hybridize to nolXWBTUV, yet it forms normal nitrogen-fixing nodules on both McCall and Peking soybean. These sequences were isolated and their structure and function examined in comparison to nolXWBTUV of strain USDA257. Restriction maps of the two loci are identical, as is a 2-4 kb DNA sequence that corresponds to nolX and its promoter region. Expression of nolX by strain USDA191 is flavonoid-dependent in culture and readily detectable in nodules. The gene is not inducible in a mutant of strain USDA191 that lacks the regulatory nodD1 gene, and its expression is greatly attenuated in a nodD2 mutant. nolX is also present and flavonoid-inducible in HH103, a second R. fredii strain that nodulates McCall soybean normally. Inactivation of nolX in strain HH103, USDA191 or USDA257 leads to retardation of initial nodulation rates on soybean cultivars such as Peking and to acquisition of the capacity to form nitrogen-fixing nodules on two species of Erythrina. nolX is thus of symbiotic significance in all three strains, even though it regulates soybean cultivar specificity only in strain USDA257.

Proteins from cells of Rhizobium fredii bind to DNA sequences precedingnolX, a flavonoid-inducible nod gene that is not associated with a nod box.

Rhizobium fredii strains USDA257 and USDA191 both contain a set of nodulation genes termed nolXWBTUV. In the USDA257 background, nolX prevents infection of soybean cultivars such as McCall, and in both backgrounds, it blocks nodulation of Erythrina spp. We report here that expression of nolX is differentially responsive to a panel of flavonoids, and that the most potent inducers are also the most active inducers of nodC, a conventional, nod box-associated gene. Cell-free protein extracts from uninduced and flavonoid-induced cells of strains USDA191 and USDA257 retard the electrophoretic mobility of DNA sequences that lie upstream of nolX. Binding is dependent both on nodD1 and nodD2, and it is abolished by the presence of a double-stranded, 23-bp oligonucleotide that lies within a 114-bp TaqI/SacII restriction fragment. This oligomer has significant sequence homology to A3, a putative negative regulatory element from R.leguminosarum bv. viciae. Deletion of the A3-homologous sequences elevates the basal and flavonoid-inducible expression of nolX by about 50%.