Implementação da técnica de difração de elétrons de baixa energia

The purpose of this study is to describe the implementation of the Low Energy Electron Diffaction (LEED) technique in the Laboratory of Magnetic Nanostructures and Semiconductors of the Department of Theoretical and Experimental Physics of the Universidade Federal do Rio Grande do Norte (UFRN), Natal, Brazil. During this work experimental apparatus were implemented for a complete LEED set-up. A new vacuum system was also set up. This was composed of a mechanical pump, turbomolecular pump and ionic pump for ultra-high vacuum and their respective pressure measurement sensors (Pirani gauge for low vacuum measures and the wide range gauge -WRG); ion cannon maintenance, which is basically mini-sputtering, whose function is sample cleaning; and set-up, maintenance and handling of the quadrupole mass spectrometer, whose main purpose is to investigate gas contamination inside the ultra-high vacuum chamber. It should be pointed out that the main contribution of this Master's thesis was the set-up of the sample heating system; that is, a new sample holder. In addition to the function of sample holder and heater, it was necessary to implement the function of sustaining the ultra-high vacuum environment. This set of actions is essential for the complete functioning of the LEED technique

Estudo integrado do potencial fitorremediador da Eichhornia crassipes em ambientes naturais e sua utilização para obtenção de extratos proteicos

This study aimed to analyze the phytoremediation potential of Eichhornia crassipes in natural environments, optimize the extraction process of crude protein from plant tissue and, obtain and characterize this process in order to determine its viability of use instead of the protein sources of animal and/or human feed. For this, it has been determined in Apodi/Mossoró river water the concentration of ammonium ions, nitrite, nitrate, calcium, magnesium, potassium, iron, copper, manganese, zinc, nickel, cobalt, sodium, aluminum, cádmium, lead, and total chromium; It was determined in plant tissue of aquatic macrophytes of Eichhornia crassipes species present in Apodi/Mossoró River the moisture content, ash, calcium, magnesium, potassium, iron, copper, manganese, zinc, nickel, cobalt, sodium, aluminum, cadmium, lead, total chromium, total nitrogen and crude protein. It was also determined the translocation factor and bioaccumulation of all the quantified elements; It was developed and optimized the extraction procedure of crude protein based on the isoelectric method and a factorial design 24 with repetition; It was extracted and characterized the extract obtained by determining the moisture content, ash, magnesium, potassium, iron, copper, manganese, zinc, nickel, cobalt, sodium, cadmium, total nitrogen and crude protein. And finally, it was also characterized the protein extract using Thermogravimetric Analysis (TG), Derived Thermogravimetric (DTG), Differential Scanning Calorimetry (DSC), Infrared Spectroscopy (FT-IR) and jelly-like electrophoresis of polyacrylamide (SDS -PAGE) to assess the their molecular weights/mass. Thus, from the results obtained for the translocation and bioaccumulation factors was found that the same can be used as phytoremediation agent in natural environments of all quantified elements. It was also found that the developed method of extraction and protein precipitation was satisfactory for the purpose of the work, which gave the best conditions of extraction and precipitation of proteins as: pH extraction equal to 13.0, extraction temperature equals 60 ° C, reaction time equals to 30 minutes, and pH precipitation equals to 4.0. As for the extract obtained, the total nitrogen and crude protein were quantified higher than those found in the plant, increasing the crude protein content approximately 116.88% in relation to the quantified contente in the vegetal tissue of macrophyte. The levels of nickel and cadmium were the unique that were found below the detection limit of used the equipment. The electrophoretic analysis allowed us to observe that the protein extract obtained is composed of low polypeptide chains by the molecular and phytochelatins, with 6 and 15 kDa bands. Analysis of TG, DTG, DSC and FT-IR showed similarities in protein content of the obtained extracts based on different collection points and 9 parts of the plant under study, as well as commercial soy protein and casein. Finally, based on all these findings, it was concluded that the obtained extract in this work can be used instead of the protein sources of animal feed should, before that, test its digestibility. As human supplementation, it is necessary to conduct more tests associated with the optimization process in the sense of removing undesirable components and constant monitoring of the water body and the raw material used

Expressão heteróloga de biossurfactantes identificados em bibliotecas metagenômicas

The microorganisms have a vast genetic diversity and they are present throughout the biosphere, however, only about 1% of the species can be cultivated by traditional cultivation techniques. Within this diversity there is a huge pool genetic and biological being explored. The metagenomics has enabled direct access to microbial genome derived from environmental samples using independent methods of cultivation. The methodology enables to obtain functional information about the proteins, as well as identify potential products with biotechnological interest and new industrially exploitable biological resources, such as new solutions to environmental impacts. Oil-contaminated areas are characterized by a large accumulation of hydrocarbons and surfactants may be used for bioremediation. Thus, the metagenomic approach was used in this study in order to select genes involved in the degradation and hydrocarbon emulsification. In a previous work, the environmental DNA (eDNA) was extracted from soil samples collected from two different areas (Caatinga and Saline River) of Rio Grande do Norte (Brazil), the metagenomic libraries were constructed and functionally analyzed. The clone able to degrade the oil was evaluated for the ability to synthesize biosurfactants. The sequence analysis revealed an ORF with 897 bp, 298 amino acids and a protein with around 34 kDa. The search for homology in GenBank revealed sequence similarity with a hypothetical protein of representatives Halobacteriaceae family, who were recently shown as strains producing biosurfactants. The presence of the inserted coding sequence and the acquired phenotype was confirmed. Primers were designed and the ORF amplified by PCR. The ORF was subcloned into pETDuet-1 expression vector for subsequent purification of the protein of interest containing a histidine tail. The tests performed to confirm the biosurfactant activity and the ability of hydrocarbon degradation showed positive results. The immunodetection test (western blot) using the monoclonal AntiHis® confirmed the presence of the environmental protein. This study was the first to report a possible protein with biosurfactant activity obtained from a metagenomic approach

Quintosana e seus derivados conjugados com ácido gálico: avaliação de seu potencial antioxidante e de interferência na formação de cristais de oxalato de cálcio

Chitin is the second most abundant polysaccharide in nature and its derivative chitosan has been widely studied due to its unique chemical and pharmacological properties. However, studies show that when this molecule is used as food, drug, etc. it tends to accumulate in renal tissue and promotes an increase in calcium excretion. Nevertheless, the effect of chitosan on the formation of calcium oxalate (OxCa) crystals has never been evaluated. The formation of kidney stones (urolithiasis) is the disease that most often affects the kidneys and the urinary system. In addition, this is a disease with high prevalence and recurrence. Many molecules with antioxidant activity have been shown to decrease the potential for in vitro OxCa crystals formation. Thus, the aim of this study was to evaluate the effect of low molecular weight chitosan and its derivatives conjugated to gallic acid (AG) as antioxidant and inhibitor of OxCa crystals formation. The physico-chemical analysis confirmed the identity of chitosan. This molecule was subjected to five antioxidant tests and showed an excellent copper chelating activity. However, chitosan did not show other significant antioxidant activity. When chitosan was subjected to in vitro crystal formation tests, it increased the number of OxCa monohydrate crystals, modified the morphology of the crystals, modified the proportions between populations of crystals in solution and increased the zeta potential of these crystals formed. Four molecules of chitosan conjugated with GA were obtained. The physico-chemical analysis confirmed that chitosan and AG were covalently bonded. However, the amount of GA liked to chitosan did not increase even when 10 times more GA was used in experiment. When these derivatives were subjected to antioxidant tests, all chitosan conjugates showed higher antioxidant potential than their precursors. However, they showed different activity between them, which indicating that the position where AG is conjugated is an important factor for chitosan-GA activity. When conjugated chitosans were submitted to in vitro crystal formation tests, a reduction in the crystals number was observed when compared with those formed in the presence of unconjugated chitosan. Chitosan has a strong capacity for inducing OxCa monohydrate crystal formation, as well as modify their morphology and zeta potential. Over all, the process of conjugating AG to chitosan led to an increase in antioxidant potential of this molecule and was also able to decrease its capacity of inducing in vitro crystal formation

Homogalactanas sulfatadas da alga Codium isthmocladum com atividade anticoagulante

Since the first description of sulfated polysaccharides from seaweeds, the biological activities of these compounds have been evaluated under different aspects and experimental procedures. Among the broad biological activities presented by seaweed polysaccharides, anticoagulant action appears as a promising function. In this present study we have obtained sulfated polysaccharides from the green seaweed Codium isthmocladium by proteolytic digestion, followed by separation into five fractions (0.3, 0.5, 0.7, 0.9 and 1.2) by sequential acetone precipitation. The chemical analyses have demonstrated that all fractions are composed mainly by sulfated polysaccharides. The anticoagulant activity of these fractions was determined by activated partial thromboplastin time (aPTT) and prothrombin time test (PT) using citrate normal human plasma. None fraction has shown anticoagulant activity by PT test. Furthermore, all of them have shown anticoagulant activity by aPTT test. These results indicated that the molecular targets of these sulfated polysaccharides are mainly in the intrinsic via of the coagulation cascade. Agarose gel electrophoresis in 1,3-diaminopropane acetate buffer, pH 9.0, stained with 0.1% toluidine blue showed the presence of two or three bands in several fractions while the fraction 0.9 showed a single spot. By anion exchange chromatography, the acid polysaccharides from the 0.9 acetone fraction were separated into two new fractions eluted respectively with 2.0 and 3.0 M NaCl. These compounds showed a molecular weight of 6.4 and 7.4 kDa respectively. Chemical analyses and infrared spectroscopy showed that Gal 1 and Gal 2 are sulfated homogalactans and differ one from the other in degree and localization of sulfate groups. aPPT test demonstrated that fractions 2,0 and 3,0M (Gal1 and Gal 2, respectively) have anticoagulant activity. This is the first time that anticoagulant sulfated homogalatans have been isolated from green algae. To prolong the coagulation time to double the baseline value in the aPTT, the required amount of sulfated galactan 1 (6,3mg) was similar to low molecular heparin Clexane®, whereas only 0,7mg of sulfated galactan 2 was needed to obtain the same effect. Sulfated galactan 2 in high doses (250mg) induces platelet aggregation. These results suggest that these galactans from C. isthmocladum have a potential application as an anticoagulant drug

Caracterização parcial e atividades farmacológicas do extrato rico em polissacarídeos sulfatatos da angiosperma marinha Halodule wrightii

Sulfated polysaccharides (PS) are biomolecules with a great biotechnological potential. There are few data about PS from high plants. In addition, pharmacological activities of PS from plants have not been carrying out. The aim of this work was extract PS from the angiosperm Halodule wrightii and study their anticoagulant and antioxidant activities. Histological analysis showed the presence of the PS manly in the roots. A polysaccharide-rich extract was obtained from H. wrightii by proteolysis followed by methanol and TCA precipitation. Chemical, infra-red analysis and agarose gel electrophoresis in 1.3 diaminopropane acetate buffer confirmed the presence of sulfated polysaccharides made by glucose, galactose, xylose and sulfate residues in the proportion 1: 0,9: 1: 1. In addition polyacrilamide electrophoresis have shown that extract is mainly compose by 11kDa sulfated polysaccharides. Pharmacological analysis have shown total antioxidant capacity (CAT) that resulted in 15,21 μg for equivalent of ascorbic acid, scavenging activity of the DPPH radical with 41,36 % of scavenging, activity of reducing power with the maximum of 0,290 nm (50 % of vitamin C activity) and scavenging activity superoxide radical (O2-) with a maximum of 32,23 %. Chelating activity of metal less than 4% and scavenging activity of the radical hydroxyl (OH-) less than 2%. Time of activated partial tromboplastin (aPTT) doubling the time of coagulation from 20μg of and protrombin time (PT) was not present. The data indicate that PS from Halodule wrightii could be considered for future applications in medicine, food production or cosmetic industry

Caracterização parcial e atividades farmacológicas do extrato rico em polissacarídeos sulfatados da angiosperma marinha Halodule wrightii

Sulfated polysaccharides (PS) are biomolecules with a great biotechnological potential. There are few data about PS from high plants. In addition, pharmacological activities of PS from plants have not been carrying out. The aim of this work was extract PS from the angiosperm Halodule wrightii and study their anticoagulant and antioxidant activities. Histological analysis showed the presence of the PS manly in the roots. A polysaccharide-rich extract was obtained from H. wrightii by proteolysis followed by methanol and TCA precipitation. Chemical, infra-red analysis and agarose gel electrophoresis in 1.3 diaminopropane acetate buffer confirmed the presence of sulfated polysaccharides made by glucose, galactose, xylose and sulfate residues in the proportion 1: 0,9: 1: 1. In addition polyacrilamide electrophoresis have shown that extract is mainly compose by 11kDa sulfated polysaccharides. Pharmacological analysis have shown total antioxidant capacity (CAT) that resulted in 15,21 μg for equivalent of ascorbic acid, scavenging activity of the DPPH radical with 41,36 % of scavenging, activity of reducing power with the maximum of 0,290 nm (50 % of vitamin C activity) and scavenging activity superoxide radical (O2-) with a maximum of 32,23 %. Chelating activity of metal less than 4% and scavenging activity of the radical hydroxyl (OH-) less than 2%. Time of activated partial tromboplastin (aPTT) doubling the time of coagulation from 20μg of and protrombin time (PT) was not present. The data indicate that PS from Halodule wrightii could be considered for future applications in medicine, food production or cosmetic industry

Avaliação do potencial antioxidante e antiinflamatório de galactomanana do fungo Tyllopiillus ballllouiii.

Polymers of mushroom cellular wall are recognized for presenting a lot of biological activities such as anti-inflammatory, antioxidant and anti-tumoral action. Polysaccharides from mushrooms of different molecular mass obtained mushrooms can activate leucocytes, stimulate fagocitic, citotoxic and antimicrobial activity including oxygen reactive species production. In this study were investigated chemical characteristics, in vitro antioxidant activity and anti-inflammatory action in an acute inflammation model of the polysaccharides extracted from Tylopilus ballouii. Results showed that were mainly extracted polysaccharides and that it primarily consisted of mannose and galactose with variable amounts of xylose and fucose. Infrared analysis showed a possible interation between this polysaccharides and proteins. In addition, molecular mass was about 140KDa. Antioxidant activity was tested by superoxide and hydroxyl radical scavenging assay, total antioxidant activity and lipid peroxidation assay. For superoxide and hydroxyl radical generation inhibition, polysaccharides have an IC50 of 2.36 and 0.36 mg/mL, respectively. Lipid peroxidation assay results showed that polysaccharides from Tylopilus ballouii present an IC50 of 3.42 mg/mL. Futhermore, anti-inflammatory assay showed that polysaccharides cause an paw edema decreasing in 32.8, 42 and 56% in 30, 50 and 70 mg/Kg dose, respectively. Thus, these results can indicate a possible use for these polysaccharides from Tylopilus ballouii as an anti-inflammatory and antioxidant.

Atividades anticoagulante e antioxidante de extratos brutos ricos em polissacarídeos sulfatados das macroalgas marinhas marrons Canistrocarpus cervicornis, Dictyota mertensii e Dictyopteris delicatula e de Heterofucanas de Canistrocarpus cervicornis

In the present study, extracts rich-sulfated polysaccharides were obtained from three different species of Dictyotales (a class of brown macroalgae): Canistrocarpus cervicornis, Dictyota mertensii and Dictyopteris delicatula and their anticoagulant and antioxidant activities were evaluated. All extracts showed anticoagulant activity on aPTT assay, but not on PT assay. Extracts also exhibited total antioxidant activity, superoxide radical scavenging capacity and ferric chelating property. The extract from C. cervicornis showed the best results and was choose to have their sulfated polysaccharides fractioned and subsequently analysed. Thus, six fractions (CC-0.3, CC-0.5, CC-0.7, CC-1.0, CC-1.2 and CC-2.0) were obtained by proteolysis followed by sequential acetone precipitation. Agarose gel eletrophoresis stained with blue toluidine, confirmed the presence of sulfated polysaccharides in all fractions. Chemical analyses showed that all fractions presented heterofucans mainly constitued by fucose, galactose, glucuronic acid and sulfate. Any fraction changed the PT. However, all fractions were able to double the aPTT on a dose-dependent manner. CC- 0.3, CC-0.5, CC-0.7 and CC-1.0 needed only 0.100 mg/mL to double the aPTT, result only 1.25 times higher than the Clexane® (0.080 mg/mL), a commercial low molecular heparin. The heterofucans presented appreciable total antioxidant capacity, low capacity on scavenging hydroxyl radical and good efficiency on scavenging superoxide radicals (except CC-1.0). CC-1.2 showed 43.1 % on superoxide radical scavenging. This result was higher than that showed by the same concentration of gallic acid (41.8 %), a known antioxidant. Furthermore, the heterofucans showed excelent activity on ferrous chelating activity (except CC-0.3). CC-0.5, CC-0.7 and CC-1.0 showed the highest activities with 47.0 % of ferrous chelating activity, a result 2.0 times lesser than that exhibited by the same concentration of EDTA. These results clearly indicated the beneficial effects of heterofucans extracted from C. cervicornis as potential anticoagulant and antioxidant agents. However additional steps of purification, structural studies, besides in vivo experiments are needed for these fucans may be used as therapeutic agents

Tratamentos de fibras de carnaúba [copernicia prunífera (miller) h. e. moore] para o desenvolvimento de compósito biodegradável com matriz de polihidroxibutirato

The use of raw materials from renewable sources for production of materials has been the subject of several studies and researches, because of its potential to substitute petrochemical-based materials. The addition of natural fibers to polymers represents an alternative in the partial or total replacement of glass fibers in composites. In this work, carnauba leaf fibers were used in the production of biodegradable composites with polyhydroxybutyrate (PHB) matrix. To improve the interfacial properties fiber / matrix were studied four chemical treatments to the fibers..The effect of the different chemical treatments on the morphological, physical, chemical and mechanical properties of the fibers and composites were investigated by scanning electron microscopy (SEM), infrared spectroscopy, X-ray diffraction, tensile and flexural tests, dynamic mechanical analysis (DMA), thermogravimetry (TGA) and diferential scanning calorimetry (DSC). The results of tensile tests indicated an increase in tensile strength of the composites after the chemical treatment of the fibers, with best results for the hydrogen peroxide treated fibers, even though the tensile strength of fibers was slightly reduced. This suggests a better interaction fiber/matrix which was also observed by SEM fractographs. The glass transition temperature (Tg) was reduced for all composites compared to the pure polymer which can be attributed to the absorption of solvents, moisture and other low molecular weight molecules by the fibers

Reciclagem química de Polietileno utilizando Sílica Mesoporosa tipo SBA-15 avalizada por Termogravimetriae Espectrometria de Massas

The chemical recycling of polyolefins has been the focus of increasing attention owing potential application as a fuel and as source chemicals. The use of plastic waste contributes to the solution of pollution problems.The use of catalysts can enhance the thermal degradation of synthetic polymers, which may be avaliated by Themogravimetry (TG) and mass spectrometry (MS) combined techniques. This work aims to propose alternatives to the chemistry recycling of low-density polyethylene (LDPE) on mesoporous silica type SBA-15 and AlSBA-15.The mesoporous materials type SBA-15 and AlSBA-15 were synthesized through the hydrothermal method starting from TEOS, pseudobohemite, cloridric acid HCl and water. As structure template was used Pluronic P123. The syntheses were accomplished during the period of three days. The best calcination conditions for removal of the organic template (P123) were optimized by thermal analysis (TG/DTG) and through analyses of Xray diffraction (XRD), infrared spectroscopy (FT-IR), nitrogen adsorption and scanning electron microscopy (SEM) was verified that as much the hydrothermal synthesis method as the calcination by TG were promising for the production of mesoporous materials with high degree of hexagonal ordination. The general analysis of the method of Analog Scan was performed at 10oC/min to 500 oC to avoid deterioration of capillary with very high temperatures. Thus, with the results, we observed signs mass/charge more evident and, using the MID method, was obtained curve of evolution of these signals. The addition of catalysis produced a decrease in temperature of polymer degradation proportional to the acidity of the catalyst. The results showed that the mesoporous materials contributed to the formation of compounds of lower molecular weight and higher value in the process of catalytic degradation of LDPE, representing an alternative to chemical recycling of solid waste

Atividades Biológicas De Xilana De Sabugo De Milho

The corn cob is an agricultural by-product still little used, this in part due to the low knowledge of the biotechnological potential of their molecules. Xylan from corn cobs (XSM) is a polysaccharide present in greater quantity in the structure of plant and its biotechnology potential is little known. This study aimed to the extraction, chemical characterization and evaluation of biological activities of xylan from corn cobs. To this end, corncobs were cleaned, cut, dried and crushed, resulting in flour. This was subjected to a methodology that combines the use of alkaline conditions with waves of ultrasound. After methanol precipitation, centrifugation and drying was obtained a yield of 40% (g/g flour). Chemical analysis indicated a high percentage of polysaccharides in the sample (60%) and low contamination by protein (0.4%) and phenolic compounds (> 0.01%). Analysis of monosaccharide composition indicated the presence of xylose:glucose:arabinose:galactose:mannose:glucuronic acid in a molar ratio 50:20:15:10:2.5:2.5. The presence of xylan in the sample was confirmed by nuclear magnetic resonance (¹H and ¹³C) and infrared spectroscopy (IR). Tests were conducted to evaluate the antioxidant potential of XSM. This showed a total antioxidant capacity of 48.45 EAA/g sample. However, did not show scavenging activity of superoxide and hydroxyl radical and also reducing power. But, showing a high capacity chelating iron ions with 70% with about 2 mg/mL. The ability to XSM to influence cell proliferation in culture was also evaluated. This polymer did not influence the proliferation of normal fibroblast cells (3T3), however, decreased the rate of proliferation of tumor cells (HeLa) in a dose-dependent, reaching an inhibition of about 50% with a concentration around 2 mg/mL. Analyzing proteins related to cell death, by immunoblotting, XSM increases the amount of Bax, Bcl-2 decrease, increase cytochrome c and AIF, and reduce pro-caspase-3, indicating the induction of cell death induced apoptosis dependent and independent of caspase. XSM did not show anticoagulant activity in the PT test. However, the test of activated partial thromboplastin time (aPTT), XSM increased clotting time at about 5 times with 600 μg of sample compared with the negative control. The presence of sulfate on the XSM was discarded by agarose gel electrophoresis and IR. After carboxyl-reduction of XSM the anticoagulant activity decreased dramatically. The data of this study demonstrate that XSM has potential as antioxidant, antiproliferative and anticoagulant compound. Future studies to characterize these activities of XSM will help to increase knowledge about this molecule extracted from corn and allow their use in functional foods, pharmaceuticals and chemical industries.

Filogenia molecular de fungos gasteroides das ordens Phallales e Geastrales (Phallomycetidae)

Gasteroids fungi are characterized by the basidiospores maturation inside the basidioma, from which spores liberation occurs in a passive manner. These fungi were once seen as a well definite class of Basidiomycota, but nowadays they are considered an artificial assemblage, because the organisms have independent evolutionary histories forming a polyphyletic group with a vast morphological variety. Despite their diversity, studies with this group in the tropics are incipient, and the phylogenetic relationships of the species from temperate climate remain unknown. Thus, this work aimed to elucidate the phylogenetic relationships of gasteroids fungi from the Geastrales and Phallales orders, with the inclusion of tropical and temperate species, and with these analyses suggest a systematic position of species like Aseroë floriformis and Phallus roseus, as well as to verify if the lignicolous habit can indicate parental relationship in the Geastrum genus. For this, basidiomata were collected at Atlantic rain forest areas, during the rainy season, and the specimen identification followed specific literature for gasteroid fungi. The phylogenetic analyses were performed with Maximum Parsimony and Bayesian Analysis, making use of RPB2 and 28S nuclear genes and atp6 mitochondrial gene. It could be observed on the Phallales dendogram, that Aseroë floriformis did not cluster with A. rubra, and that it has an anterior divergence from all others species of the family Clathraceae used in this analysis, assuming a basal position in the clade. Phallus roseus, which once was recognized as Itajahya, has previous divergence from the group formed by Phallus species. At the Geastrales dendogram, in the group corresponding to Geastrum genus, it could be observed that species with lignicolous habitat clustered in a clade with high support values. So, the results suggest the creation of a new genus to accommodate A. floriformis, and the revalidation of Itajahya, as well as it can be affirmed that the lignicolous habitat on the Geastrum genus in fact indicates parental relationships, and that it has arised only once at the evolutionary history of the genus

Excesso de peso em região do nordeste brasileiro: contraste entre escolares de rede pública e privada de ensino

The prevalence of obesity has been increased in the last three decades. It is already considered as epidemic by the World Health Organization and reaches around 300 million people worldwide. The weight gain in all ages is related to a sedentary way of life and hyper caloric food ingestion at the modern society. Obesity is a chronic disease and leads to high blood pressure, diabetes, cardiovascular diseases and cancer. The aim of this study was to evaluate the prevalence of weight excess among student in Natal schools and to analyze its association with age, gender, school category and geographic localization in city zones. This was a transversal study which enrolled 1927 children. 1084 of these were between 6 and 8 years-old (group 1) and 843 were 9 to 10 years-old (group 2). 895 of the total children studied in private schools and 1032 studied in public schools. 33,6% of the students had body mass index equal or above the 85th percentile and were considered as having weight excess. There was no statistical difference in this prevalence considering neither gender nor age. The weight excess prevalence in private schools was 54,5% and in public ones was 15,6% (p<0,01; OR=6,49). Weight excess was also more prevalent in the south and east city zones (41,3%) which have better quality of life index than in the north and west zones (28,4%) (p<0,01). In conclusion, the weight excess prevalence among students is found to be high in Natal and programs of intervention and prevention of obesity are necessary. The higher prevalence in private schools as in the wealthier city zones reflects the link between obesity and high socioeconomic level found in countries in developing. This was an interdisciplinary work with participation of epidemiology, child nutrition and pediatric endocrinology following the recommendations and principles of the Post graduation Program in Health Sciences of the Federal University of Rio Grande do Norte

Desmame em recém-nascidos de muito baixo peso ao nascer no primeiro retorno ambulatorial após a alta hospitalar

Investigate intrahospital and neonatal determinants associated to the weaning of very low birth weight (VLBW) infants. Methods: 119 VLBW (<1500g) infants 81 were monitored from July 2005 through August 2006, from birth to the first ambulatory visit after maternity discharge. This maternity unit uses the Kangaroo Method and the Baby Friendly Hospital Initiative. Results: Out of 119 VLBW infants monitored until discharge, 88 (75%) returned to the facility, 22 (25%) were on exclusive breastfeeding (EB) and 66 (75%) were weaned (partial breastfeeding or formula feeding). Univariate analysis found an association between weaning and lower birth weight, longer stays in the NICU and longer hospitalization times, in addition to more prolonged enteral feeding and birth weight recovery period. Logistic regression showed length of NICU stay as being the main determinant of weaning. Conclusion: The negative repercussion on EB of an extended stay in the NICU is a significant challenge for health professionals to provide more adequate nutrition to VLBW infants