Qualidade e valor nutritivo de silagens de capim-marandu (B. brizantha cv. Marandu) produzidas com aditivos ou forragem emurchecida

Avaliaram-se a qualidade e o valor nutritivo de silagens de capim-marandu produzidas com polpa cítrica (PC) peletizada, com aditivo enzimático-bacteriano (ABE) ou com forragem emuchercida (E): T1 - forragem sem tratamento (controle); T2 - 10% de polpa cítrica peletizada (PC); T3 - aditivo enzimático bacteriano (AEB - SIL-ALL-C4 da Alltech), à base de 5 g/L de água/t de forragem; T4 - forragem picada grosseiramente emurchecida por 4 horas ao sol. O capim foi colhido aos 60 dias de rebrota (24% MS). Para avaliar o consumo e a digestibilidade das silagens, foram utilizados 16 novilhos mestiços com 200 kg de PV, que receberam, além das silagens, 1,0 kg de concentrado/animal/dia. O AEB não afetou a composição da silagem, mas a PC e o E aumentaram o teor de MS de 24% para 31 e 48%, respectivamente, e reduziram o pH e os teores de N-NH3 das silagens, que foram, respectivamente, de 4,17 e 4,58 e 6,78 e 7,99% NT. A PC diminuiu os teores de FDN e FDA em 12 e 4 unidades percentuais. O consumo de MS da silagem produzida com capim emurchecido foi superior (111,8 g MS/PV0,75) ao das silagens controle ou com AEB, mas não diferiu do obtido para a silagem com PC, que também não diferiu das demais. Os tratamentos não afetaram a digestibilidade, cujas médias para MS, PB, CT, FDN, FDA e NDT foram 67,0; 65,4; 68,8; 63,0; 62,5; e 65,6%, respectivamente. A PC e o E reduziram a proteólise e estimularam o consumo. A PC, o E e o AEB não melhoraram o valor nutritivo da silagem de capim-marandu colhido com 24% MS.

Effect of anaerobic digestion and initial pH on metal bioleaching from sewage sludge

The effects of anaerobic digestion and initial pH on the bioleaching of metals from sewage sludge were investigated in shake flask experiments. A strain of Acidithiobacillus thiooxidans was employed in the assays using secondary and anaerobic sludges, which resulted in similar solubilization yields of the metals chromium, copper, lead, nickel, and zinc for both the sludges investigated. The effect of initial pH (7.0 and 4.0) on metal bioleaching was assayed by using the anaerobic sludge inoculated with indigenous sulfur-oxidizing thiobacilli. Although the time required to reach the end of the experiment (final pH close to 1.0) was shortened at initial pH of 4.0, final metal solubilization was not significantly different for both initial pH values, resulting in higher solubilization yields for copper, nickel, and zinc (higher than 80%). Chromium and lead presented solubilization yields close to 50%. The results obtained in this work showed that the metal bioleaching process can be applied to sewage sludge regardless of the type of sludge and without the requirement of pH adjustment.

Preparation of SnO2 supported membranes with ultrafine pores

The colloidal route of the sol-gel process was used to prepare supported SnO2 membranes. The influence of the sol and monoelectrolyte concentrations on the formation of the gel layer by sol-casting on the top of macroporous alpha-Al2O3 support was described. The stability of the colloidal suspension as a function of the concentrations was analyzed from creep-recovery measurements. The calcined supported membranes were characterized by nitrogen adsorption-desorption isotherms and scanning electron microscopy. The set of results show that homogeneous membrane layers containing the smallest quantity of cracks are formed in a critical interval of sol (1.01 less than or equal to[SnO2]less than or equal to 1.4 M) and electrolyte (2.O less than or equal to[Cl-]less than or equal to 4.0 mM) concentrations. The samples prepared from concentrated suspensions present a lot of interconnected cracks which favors the peeling of the coated layer. The membranes have pores of average diameter of about 1 nm.

Determination of Cd(II) and Cd-metallothioneins in biological extracts using baker's yeast and inductively coupled plasma optical emission spectrometry

The use of Saccharomyces cerevisiae as a sorbent material to separate Cd(II) and Cd-metallothionein complex (Cd-MT) has been explored. Solid-liquid phase extractions were carried out in batch mode and the main parameters of the process (pH, temperature, time of incubation, amount of biomass and analyte) were evaluated. Under optimized conditions, the yeast quantitatively retain (94 +/- 5%) the Cd(II) while 97 +/- 2% of the Cd-MT remain in the supernatant. on base of the findings of this study, a simple method is proposed to determine Cd(II) and Cd-MT in cytosols extracted from mouse kidney and crab hepatopancreas. Inductively coupled plasma optical emission spectrometry was used to quantify the analytes in solid and liquid phase. Determination of Cd in the solid phase was carried out by introducing a slurry of the yeast (0.0625 g/10 mL) directly to the inductively coupled plasma optical emission spectrometer. Mixed standards solutions, which also have been submitted to the extraction procedure, were used to quantify the analytes in the samples. Thus, matrix effects due to nebulization of the slurry were overcame. Limits of detection (3 sigma) for Cd(II) and Cd-MT were 1.5 and 1.2 mu g L-1, respectively. Relative standard deviations of signals were 4.2% for measurements in the slurry of solid phase and 2.1% for measurements in the liquid phase. Recoveries of the analytes in cytosol samples were between 76 and 114%. The concentrations of Cd(II) (2.4 +/- 0.5 mu g L-1) and Cd-MT (3.0 +/- 0.5 mu g L-1) found by using the proposed approach were close to those found by tangential-flow ultrafiltration technique (2.6 +/- 0.7 mu g L-1 for Cd(II) and 3.7 +/- 1.7 mu g L-1 for Cd-MT).

A 4.2 kDa synthetic peptide as a potential probe to evaluate the antibacterial activity of coumarin drugs

The coumarin antibiotics are potent inhibitors of DNA replication whose target is the enzyme DNA gyrase, an ATP-dependent bacterial type II topoisomerase. The coumarin drugs inhibit gyrase action by competitive binding to the ATP-binding site of DNA gyrase B protein. The production of new biologically active products has stimulated additional studies on coumarin-gyrase interactions. In this regard, a 4.2 kDa peptide mimic of DNA gyrase B protein from Escherichia coli has been designed and synthesized. The peptide sequence includes the natural fragment 131-146 (coumarin resistance-determining region) and a segment containing the gyrase-DNA interaction region (positions 753-770). The peptide mimic binds to novobiocin (K-a = 1.4 +/- 0.3 x 10(5) m(-1)), plasmid (K-a = 1.6 +/- 0.5 x 10(6) m(-1)) and ATP (K-a = 1.9 f 0.4 x 10(3) m(-1)), results previously found with the intact B protein. on the other hand, the binding to novobiocin was reduced when a mutation of Arg-136 to Leu-136 was introduced, a change previously found in the DNA gyrase B protein from several coumarin-resistant clinical isolates of Escherichia coLi. In contrast, the binding to plasmid and to ATP was not altered. These results suggest that synthetic peptides designed in a similar way to that described here could be used as mimics of DNA gyrase in studies which seek a better understanding of the ATP, as well as coumarin, binding to the gyrase and also the mechanism of action of this class of antibacterial drugs. Copyright (C) 2004 European Peptide Society and John Wiley Sons, Ltd.

Study on the initial stages of water corrosion of fluorozirconate glasses

The surface corrosion process associated with the hydrolysis of fluorozirconate glass, ZBLAN (53ZrF(4), 20BaF(2), 20NaF, 4LaF(2), 3AlF(3)) was investigated using X-ray photoelectron spectroscopy (XPS), grazing-incidence small angle X-ray scattering (GISAXS), X-ray reflectivity (XRR) and scanning electron microscopy (SEM). After a short exposure period (25 min) of the glass surface to deionized water the XPS data indicate an increase of the oxygen content accompanied by a decrease of fluorine concentration. The analysis of the chemical bonding structure identified the predominant surface reaction products as zirconium hydroxyfluoride and oxyfluoride species. The second most abundant glass component, bariumfluoride, remains almost unaffected by oxygen, while sodium fluoride is completely removed from the attacked surface region. The detected structural and compositional changes are related to the selective dissolution of the glass components leading to the formation of a new surface phase. This process is accompanied by a visible surface roughening caused by reprecipitated species, observed by SEM. The modification of the glass surface is responsible for an increase of the GISAXS intensity. The scattering was attributed to nanovoids formed at the surface region of the glass with an average size of 2.4 +/- 0.05 nm. (C) 2004 Elsevier B.V. All rights reserved.

A nonisothermal study of the kinetics of the nanoporosity elimination in sonogels-derived silica xerogels

A nonisothermal study of the kinetics of the nanoporosity elimination in monolithic silica xerogels, prepared from acid and ultrasound catalyzed hydrolysis of tetraethylortosilicate (TEOS), has been carried out by means of in situ linear shrinkage measurements performed with different heating rates. The study could be applied up to almost alpha similar to 0.6 of the volume fraction alpha of eliminated pores. The activation energy was found increasing from about 3.2 x 10(2) kJ/mol for alpha similar to 0.06 up to about 4.4 x 10(2) kJ/mol for alpha. similar to 0.44. The sintering process accompanying the nanopore elimination in this set of xerogels is in agreement with a viscous flux sintering process with the hydroxyl content diminishing with the volume fraction of eliminated pores. All the volume fraction of eliminated pores versus temperature (T) curves can be matched onto a unique curve with an appropriate rescaling of the T axis, independent of the heating rate. This scaling property suggests that the path of sintering seems the same, regardless of the heating rate; the difference is that the rate is faster at higher temperature.

Kinetic of thermal decomposition of residues from different kinds of composting

Non-isothermal kinetic parameters regarding to the thermal decomposition of the ligninocellulosic fraction present in compost from urban solid residues (USR) obtained through stack covered (SC) with composted material, comes from the usine in composing of Araraquara city, São Paulo state, Brazil, and from stack containing academic restaurant organic solid residues (SAR). The samples were periodically revolved round 132 days of composting.Results from TG, DTG and DSC curves obtained on inert atmosphere indicated that the lignocellulosic fraction present, despite the slow degradation during the composting process, is thermally less stable than other substances originated during that process. The lignocellulosic fraction decomposition, between 200 and 400degreesC, were kinetically evaluated through non-isothermal methods of analysis.By using the Flynn-Wall and Ozawa isoconversional method, the medium activation energy, E-a, and pre-exponential factor, IgA, were 283.0+/-4.6, 257.6+/-1.3 U mol(-1) and 25.4+/-0.8, 23.2+/-0.2 min(-1),to the SC and SAR, respectively, at 95% confidence level.From E-a, and IgA values and DSC curves, Malek procedure could be applied, Suggesting that the SB (Sestik-Berggren) kinetic model is suitable for the first thermal decomposition step.

Improvement of the chemical resistance of zirconium fluoride glasses coated with a Tiron (R) modified tin oxide layer prepared by the sol-gel process

In order to improve the chemical resistance of zirconium fluoride glass a protective transparent SnO2 layer was deposited by the solgel dip-coating process in the presence of Tiron (R) as particle surface modifier agent. After water immersion for different periods of time, both coated and non-coated fluoride glasses were analyzed by scanning electron microscopy, mass loss evaluation, infrared spectroscopy and X-ray photoelectron spectroscopy. In contrast to the effects occurring for non-coated glass, where the surface undergoes a rapid selective dissolution of the most soluble species, the results for the SnO2-coated glass showed that the filling of the film nanopores by dissolved glass material results in a hermetic barrier protecting the glass surface. The selective glass dissolution was confirmed by liquid chromatography measurements of the etching solution after each exposure time. (c) 2006 Elsevier B.V. All rights reserved.

Development of a voltammetric sensor for chromium(VI) determination in wastewater sample

Screen-printed carbon electrode (SPCE) modified with poly-L-histidine film can be successfully applied for chromium(VI) determination based on its pre-concentration. Optimum adherence and stability of the POIY-L-histidine film was obtained by direct addition of PH solution 1% (w/v) on the electrode surface, followed by heating at 80 degrees C during 5 min. Linear response range, sensitivity and limit of detection were 0. 1-150 [mu mol L-1, 4. 13 LA mu mol L` and 0.046 mu mol L-1. The repeatability of the proposed sensor, evaluated in terms of relative standard deviation, was measured as 3.2% for 10 experiments in 40 mu mol L-1 using the same electrode and 4.0% using screen-printed electrode as disposable sensor, respectively. The voltammetric sensor was applied to determination of Cr(VI) and indirect determination of Cr(III) in wastewater samples previously treated by a leather dyeing industry and the average recovery for these samples was around 97%. (C) 2006 Elsevier B.V. All rights reserved.

Determination of low-aliphatic aldehydes indoors by micellar electrokinetic chromatography using sample dissolution manipulation for signal enhancement

This work describes a novel approach for the analysis of selected aldehydes (formaldehyde, acetaldehyde, propionaldehyde, and acrolein) and acetone in environmental samples using micellar electrokinetic chromatography (MEKC). The method is based on the reaction of carbonyl compounds with 3-methyl-2-benzothiazoline hydrazone (MBTH) that gives an azine intermediate with maximum absorbance at 216 nm. A systematic evaluation of sample dissolution medium was conducted as a means to enhancing sensitivity. In the best condition, samples were dissolved in 0.030 mol.L-1 tetraborate solution. This condition presented enhancement factors in the range of 35-54 for the aldehydes under investigation, computed as the improvement of the concentration limits of detection (LODs) with reference to the sample dissolved in pure water. The running buffer was 0.020 mol.L-1 tetraborate, pH 9.3, containing 0.050 mol-L-1 sodium dodecyly sulfate (SIDS). The overall methodology presented several advantages over established methods for aldehydes. Worthy mentioning that MBTH is available in high purity degree, dispensing laborious reagent purification procedures. A few method validation parameters were determined revealing good migration time repeatability (< 2.5% coefficient of variation, CV) and area repeatability (< 4% CV), excellent linearity (20-120 mug/L, r > 0.995) and adequate sensitivity for environmental applications. The LODs with respect to each single aldehyde were in the range of 0.54-4.0 mug.L-1 and 11 mug.L-1 for acetone. The methodology was applied to the determination of aldehydes indoors. Samples were collected in an impinger flask containing 0.05% MBTH solution, at a flow rate of 0.80 L.min(-1), during 2.5 h, at different times during the day. The most abundant carbonyls in the samples were acetone, followed by formaldehyde and acetaldehyde, with estimate peak concentrations of 452, 5.2 and 2.2 ppbv, respectively.

XPS study on water corrosion of fluorzirconate glasses and their protection by a layer of surface modified tin dioxide nanoparticles

The surface corrosion process associated with the hydrolysis of fluorozirconate glass, Z-BLAN (53ZrF(4), 20BaF(2), 20NaF, 4LaF(2), 3AlF(3)), and the corrosion protection efficiency of a nanocrystalline transparent SnO2 layer were investigated by X-ray photoelectron spectroscopy. The tin oxide film was deposited by the sol-gel dip-coating process in the presence of Tiron(R) as particle surface modifier agent. The chemical bonding structure and composition of the surface region of coated and non-coated ZBLAN were studied before water contact and after different immersion periods (5-30 min). In contrast to the effects occurring for non-coated glass, where the surface undergoes a rapid selective dissolution of the most soluble species inducing the formation of a new surface phase consisting of stable zirconium oxyfluoride, barium fluoride and lanthanum fluoride species, the results for the SnO2-coated glass showed that the hydrolytic attack induces a filling of the film nanopores by dissolved glass material and the formation of tin oxylluoride and zirconium oxyfluoride species. This process results in a modified film, which acts as a hermetic diffusion barrier protecting efficiently the glass surface. (C) 2006 Elsevier B.V. All rights reserved.

AGE-RELATED-CHANGES OF GLUTATHIONE CONTENT, GLUTATHIONE-REDUCTASE AND GLUTATHIONE-PEROXIDASE ACTIVITY OF HUMAN ERYTHROCYTES

1. In order to investigate the effect of aging on the erythrocyte glutathione system, total glutathione (GSH), glutathione reductase (GSH-red) and glutathione peroxidase (GSH-px) levels were measured in erythrocytes from 33 young (mean age = 30.5 +/- 9.7 years) and 28 aged (mean age = 68.9 +/- 11.4 years) healthy individuals.2. GSH was 3.5 +/- 1.8-mu-M/g Hb for the young group, a value significantly greater (P < 0.01) than 2.3 +/- 0.9-mu-M/g Hb found for the aged group. Similarly, GSH-red activity, 5.5 +/- 1.8 IU/g Hb, was higher (P < 0.05) for the young group than 3.4 +/- 0.9 IU/g Hb found for the aged group. The GSH-px activity levels for the young group, 21.1 +/- 5.9 IU/g Hb, were significantly greater (P < 0.01) than 12.0 +/- 3.3 IU/g Hb for the aged group. The lower activity detected in the aged group for all of these parameters of the glutathione redox system was not related to low levels of hematocrit or hemoglobin.3. There was no statistical difference in the activation coefficient (AC) of reductase (+FAD/-FAD) between groups, which seems to indicate that the lower activity of glutathione reductase observed in the aged group was not due to riboflavin deficiency.4. Additional information is required to determine the mechanisms controlling the glutathione redox system and its role in the aging process.

Spermatogenic cycle length and spermatogenic efficiency in the gerbil (Meriones unguiculatus)

The gerbil (Meriones unguiculatus) is a rodent native of the and regions of Mongolia and China. Because the gerbil can be easily bred in laboratory conditions, this species has been largely used as an experimental model in biomedical research. However, there is still little information concerning the testis structure and function in the gerbil. In this regard, we performed a detailed morphofunctional analysis of the gerbil testis and estimated the spermatogenic cycle length utilizing H-3-thymidine as a marker for germ cell progression during their evolution through the spermatogenic process. The stage frequencies of the XII stages characterized according to the acrosome formation and development were (I-XII) 13.8, 10.1, 8.1, 7.8, 4.0, 11.2, 7.5, 7.1, 5.9, 7.6, 8.1, and 8.9. The mean duration of each seminiferous epithelium cycle was determined to be 10.6 +/- 1.0 days and the total duration of spermatogenesis, based on 4.5 cycles, was approximately 47.5 days. The volume density of tubular and interstitial compartments was approximately 92% and 8%, respectively. Based on the volume occupied by seminiferous tubules in the testis and the tubular diameter, about 9 and 18 m of seminiferous tubules were found per testis and per gram of testis, respectively. Twelve primary spermatocytes were formed from each type A1 spermatogonia. The meiotic index was 2.8, indicating that 30% of cell loss occurs during meiosis. The number of Leydig and Sertoli cells per gram of the testis was 28 million and each Sertoli cell was able to support approximately 13 spermatids. The daily sperm production per gram of testis (spermatogenic efficiency) was 33 million. Taken together, these data indicate that, mainly due to the high seminiferous tubule volume density and Sertoli cell support capacity for germ cells, the gerbil presents high spermatogenic efficiency compared with other mammalian species already investigated. The data obtained in the present study might provide the basis for future research involving the reproductive biology in this species.

Determination of 2,4-dichlorophenoxyacetic acid and its major transformation product in soil samples by liquid chromatographic analysis

The 2,4-dichlorophenoxyacetic acid (2,4-D) is one of the most applied herbicides around the world to control broad leave herbs in many crops: In this study, a method was developed for simultaneous extraction and determination of 2,4D and its major transformation product, i.e., the 2,4-dichlorophenol (2,4-DCP), in soil samples. The herbicide and its degradation product were extracted twice from soil samples, after acidification, by dichloromethane on ultrasound system for 1 h. Both extracts were combined and filtrated in qualitative filter paper and Celitee. The total extract was concentrated in rotatory evaporator, dried under N-2 and finally dissolved in 1 ml of methanol. High Performance Liquid Chromatography with UV detection at 230 nm was used for analysis. Recoveries were obtained from soil samples fortified at 0.1, 1.0, 2.0, 3.0 and 4.0 mg kg(-1) levels and the results varied from 85 to 111% (for 2,4-D) and from 95 to 98% (for 2,4-DCP). For both compounds, the limits of quantification were 0.1 mg kg(-1), which were the loss level at which the accuracy and the precision were studied. Nevertheless, the limits of detection, calculated by considering the blank standard deviation and the minimum concentration level, were 0.03 and 0.02 mg kg for 2,4-D and 2,4-DCP, respectively. This proposed method was applied to soil samples of eucalyptus crops, which was previously treated with the herbicide. Despite that, neither 2,4-D nor its degradation product were detected 30 days after the herbicide application. (C) 2003 Elsevier B.V. B.V. All rights reserved.