Mesoscale plasticity anisotropy at the earliest stages of cavitation-erosion damage of a high nitrogen austenitic stainless steel

A high nitrogen austenitic stainless steel (0.9wt% N) and an ordinary 304 austenitic stainless steel were submitted to cavitation-erosion tests in a vibratory apparatus operating at a frequency of 20 kHz. The high nitrogen stainless steel was obtained by high temperature gas nitriding a 1-mm thick strip of an UNS 31803 duplex stainless steel. The 304 austenitic stainless steel was used for comparison purposes. The specimens were characterized by scanning electron microscopy and Electron Back Scatter Diffraction. The surface of the cavitation damaged specimens was analyzed trying to find out the regions where cavitation damage occurred preferentially. The distribution of sites where cavitation inception occurred was extremely heterogeneous, concentrating basically at (i) slip lines inside some grains and (ii) Sigma-3 coincidence site lattice (CSL) boundaries (twin boundaries). Furthermore, it was observed that the CE damage spread faster inside those grains which were more susceptible to damage incubation. The damage heterogeneity was addressed to plasticity anisotropy. Grains in which the crystallographic orientation leads to high resolved shear stress show intense damage at slip lines. Grain boundaries between grains with large differences in resolved shear stress where also intensely damaged. The relationship between crystallite orientation distributions, plasticity anisotropy and CE damage mechanisms are discussed. (C) 2009 Elsevier B.V. All rights reserved.

Evaluation of plaque composition by intravascular ultrasound ""virtual histology"": the impact of dense calcium on the measurement of necrotic tissue

Aims: We aimed to evaluate if the co-localisation of calcium and necrosis in intravascular ultrasound virtual histology (IVUS-VH) is due to artefact, and whether this effect can be mathematically estimated. Methods and results: We hypothesised that, in case calcium induces an artefactual coding of necrosis, any addition in calcium content would generate an artificial increment in the necrotic tissue. Stent struts were used to simulate the ""added calcium"". The change in the amount and in the spatial localisation of necrotic tissue was evaluated before and after stenting (n=17 coronary lesions) by means of a especially developed imaging software. The area of ""calcium"" increased from a median of 0.04 mm(2) at baseline to 0.76 mm(2) after stenting (p<0.01). In parallel the median necrotic content increased from 0.19 mm(2) to 0.59 mm(2) (p<0.01). The ""added"" calcium strongly predicted a proportional increase in necrosis-coded tissue in the areas surrounding the calcium-like spots (model R(2)=0.70; p<0.001). Conclusions: Artificial addition of calcium-like elements to the atherosclerotic plaque led to an increase in necrotic tissue in virtual histology that is probably artefactual. The overestimation of necrotic tissue by calcium strictly followed a linear pattern, indicating that it may be amenable to mathematical correction.

A new approach to heart valve tissue engineering: mimicking the heart ventricle with a ventricular assist device in a novel bioreactor

The `biomimetic` approach to tissue engineering usually involves the use of a bioreactor mimicking physiological parameters whilst supplying nutrients to the developing tissue. Here we present a new heart valve bioreactor, having as its centrepiece a ventricular assist device (VAD), which exposes the cell-scaffold constructs to a wider array of mechanical forces. The pump of the VAD has two chambers: a blood and a pneumatic chamber, separated by an elastic membrane. Pulsatile air-pressure is generated by a piston-type actuator and delivered to the pneumatic chamber, ejecting the fluid in the blood chamber. Subsequently, applied vacuum to the pneumatic chamber causes the blood chamber to fill. A mechanical heart valve was placed in the VAD`s inflow position. The tissue engineered (TE) valve was placed in the outflow position. The VAD was coupled in series with a Windkessel compliance chamber, variable throttle and reservoir, connected by silicone tubings. The reservoir sat on an elevated platform, allowing adjustment of ventricular preload between 0 and 11 mmHg. To allow for sterile gaseous exchange between the circuit interior and exterior, a 0.2 mu m filter was placed at the reservoir. Pressure and flow were registered downstream of the TE valve. The circuit was filled with culture medium and fitted in a standard 5% CO(2) incubator set at 37 degrees C. Pressure and flow waveforms were similar to those obtained under physiological conditions for the pulmonary circulation. The `cardiomimetic` approach presented here represents a new perspective to conventional biomimetic approaches in TE, with potential advantages. Copyright (C) 2010 John Wiley & Sons, Ltd.

Correlation Between Autofluorescence Intensity and Tumor Area in Mice Bearing Renal Cell Carcinoma

Protoporphyrin IX (PpIX) is a porphyrin derivative that is accumulated in cancerous tissue in consequence of the tumor-specific metabolic alterations. The aim of this study was to evaluate the accumulation of PpIX in mice bearing renal cell carcinoma by spectroscopy analysis. A total of 24 male Balb/c mice, 6 weeks old, were divided into six groups: Normal (without inoculation of tumor cells) and 4, 8, 13, 16, and 20 days after inoculation of tumor cells. The orthotopic tumor model of renal cancer was used. Murine renal cell carcinoma (Renca cells) were inoculated into the subcapsular space of the kidney. Normal and tumor-bearing kidneys in different progression stages were removed and analyzed by ex-vivo spectroscopy and by microscopy, for tumor histometric analysis. Emission spectra were obtained by exciting the samples at 405 nm. Significant differences between normal and tumor-bearing kidneys in autofluorescence shape occurred in the 600-700 nm spectral region. A good correlation was found between emission band intensity at 635 nm and the tumor area.

Double generalized linear model for tissue culture proportion data: a Bayesian perspective

Joint generalized linear models and double generalized linear models (DGLMs) were designed to model outcomes for which the variability can be explained using factors and/or covariates. When such factors operate, the usual normal regression models, which inherently exhibit constant variance, will under-represent variation in the data and hence may lead to erroneous inferences. For count and proportion data, such noise factors can generate a so-called overdispersion effect, and the use of binomial and Poisson models underestimates the variability and, consequently, incorrectly indicate significant effects. In this manuscript, we propose a DGLM from a Bayesian perspective, focusing on the case of proportion data, where the overdispersion can be modeled using a random effect that depends on some noise factors. The posterior joint density function was sampled using Monte Carlo Markov Chain algorithms, allowing inferences over the model parameters. An application to a data set on apple tissue culture is presented, for which it is shown that the Bayesian approach is quite feasible, even when limited prior information is available, thereby generating valuable insight for the researcher about its experimental results.

Chitinase and peroxidase activity in different stages of eucalypt leaves after inoculation with Puccinia psidii and acibenzolar-S-metil

Chitinase and peroxidase activity in different stages of eucalypt leaves after inoculation with Puccinia psidii and acibenzolar-S-metil To elucidate some biochemical processes during infection in the pathosystem Puccinia psidii x eucalyptus, the defense metabolism in different-stage leaves was compared between rust-resistant and susceptible clones, respectively. In addition, chitinase and peroxidase activities were assayed. Each treatment consisted of 4 replicates, in a completely randomized design: 2 clones, inoculated and not inoculated with P. psidii; sprayed with acibenzolar-S-methyl (ASM) and distilled water; and represented by the 1(st) leaf pair (size equivalent to 1/5 total leaf development), 2(nd) pair (2/5 total development), and 4(th) pair (4/5 total leaf length). Leaves were harvested in 4 periods: 0, 24, 72 and 96 hours after inoculation. Results indicated that ASM treatment or P. psidii action led to higher chitinase and peroxidase activity level but did not alter the expression of these activities in developed leaves (4(th) pair) during the experiment. Alterations in enzyme levels after inoculation were only observed in developing leaves (1(st) and 2(nd) pairs), which suggests that the response to infection was concomitant to chitinase and peroxidase synthesis. The highest increases in enzymatic activities were observed in resistant clones at 72 hours after inoculation and in susceptible ones previously treated with ASM and later inoculated with the pathogen.

Prepenetration Stages of Guignardia psidii in Guava: Effects of Temperature, Wetness Duration and Fruit Age

This study examined the effects of temperature and wetness duration in vitro and in vivo as well as the effects of fruit age on germination and appressoria formation by conidia of Guignardia psidii, the causal agent of black spot disease in guava fruit. The temperatures tested for in vitro and in vivo experiments were 10, 15, 20, 25, 30, 35 and 40 degrees C. The wetness periods studied were 6, 12, 24, 36 and 48 h in vitro and 6, 12 and 24 h in vivo. Fruit 10, 35, 60, 85 and 110-days old were inoculated and maintained at 25 degrees C, with a wetness period of 24 h. Temperature and wetness duration affected the variables evaluated in vitro and in vivo. All variables reached their maximum values at between 25 and 30 degrees C with a wetness duration of 24 h in vivo and 48 h in vitro. These conditions resulted in 31.3% conidia germination, 33.6% appressoria formation and 32.5% appressoria melanization in vitro, and 50.4% conidia germination and 9.5% appressoria formation in vivo. Fruit age also influenced these factors. As fruit age increased, conidia germination and appressoria formation gradually increased. Conidia germination and appressoria formation were 10.8% and 2.3%, respectively, in 10-day-old fruits. In 110-day-old fruits, conidia germination and appressoria formation were 42.5% and 23.2% respectively.

Incidence of black spot in citrus fruits from different processing stages in packinghouses and from Sao Paulo`s wholesale market

The purposes of this work were a) to evaluate citrus black spot (CBS) incidence in `Valencia` oranges and `Murcott` tangors aimed at the export market, and in Pera`, `Lima` and `Natal` oranges, and `Murcott` tangors, aimed at the domestic market after different processing stages in packinghouses in 2004/05 and 2005/06; b) to evaluate CBS incidence in Pera` and `Lima` oranges and `Murcott` tangors sold at Ceagesp-SP, the biggest wholesale market in the State of Sao Paulo, in 2006. Citrus fruits were collected at the packinghouse, on their arrival, after pre-washing and de-greening, from the packing table, from the pallet and at Ceagesp. They were stored for 14 to 21 days at 25 degrees C and 85-90% RH. The incidence of CBS was visually evaluated after one day and at the end of the storage period. CBS incidence in fruits aimed at the export market decreased, with values under 2.0% on arrival and no CBS symptoms observed on fruits from the pallet. The average incidence of CBS in `Pera`, `Lima` and `Natal` oranges, and `Murcott` tangors in the packinghouse aimed at the domestic market were 64.1, 39.0, 32.1 and 19.3%, respectively, after one day of storage, then remaining constant in all processing stages. The incidence of CBS in Ceagesp fruits was low in winter months and increased in the spring. The increase in disease incidence during the storage period (21 days) was not significant in collected fruits.

Peach brown rot incidence related to pathogen infection at different stages of fruit development in an organic peach production system

Brown rot, caused by Monilinia fructicola, is the most widespread disease for organic peach production systems in Brazil. The objective of this study was to determine the favorable periods for latent infection by M. fructicola in organic systems. The field experiment was carried out during 2006, 2007 and 2008 using the cultivar Aurora. After thinning fruits were bagged using white paraffin bags, and the treatments were performed by removing the bags and exposing the fruit for four days to the natural infection during each of seven fruit stages from pit hardening to harvest. Throughout the entire growing season, the conidial density and the weather variables were measured and related to the disease incidence using multiple regression analyses. At the fourth day after harvest in each season, the cumulative disease incidence was assessed, and it ranged from 40 to 98%. The incidence of brown rot on fruit that were exposed during the embryo growing stage was lower than that of unbagged fruit throughout the entire season in 2006 and 2008. The relative humidity and the conidia density were significantly correlated to disease incidence. Based on our results, M. fructicola can infect peaches during any stage of fruit development, and control of the disease must be revised to account for organic peach production systems. (C) 2011 Elsevier Ltd. All rights reserved.

Methylation patterns revealed by MSAP profiling in genetically stable somatic embryogenic cultures of Ocotea catharinensis (Lauraceae)

Ocotea catharinensis is a rare tree species indigenous to the Atlantic rainforest of South America. In spite of its value as a hardwood species, it is in danger of extinction. The species erratically produces seeds showing irregular flowering and slow growth. Therefore, plants are not easily replaced. Tissue culture-based techniques are commonly used for obtaining living material for tree propagation and in vitro preservation. Therefore, a high-frequency somatic embryogenic system was developed for the species. In the present work, the genetic fidelity of cell aggregates and somatic embryos at various stages of in vitro development of O. catharinensis was investigated using RAPD and AFLP markers. Both analyses confirmed the absence of genetic variation in all developmental stages of O. catharinensis embryogenic cultures, verifying that the in vitro system is genetically stable. The cultures were also analyzed for their methylation profiles at 5`-CCGG-3` sites by identifying methylation-sensitive amplification polymorphisms. Some of these markers differentiated cell aggregates from embryo bodies. The sequencing of ten MSAP markers revealed that four sequences showed significant similarity to genes encoding plant proteins. Particularly, the predicted amino acid sequence of the fragment designated as OcEaggHMttc155 was similar to the enzyme 1-aminocyclopropane-1-carboxylate oxidase (ACO), which is involved in the biosynthesis of ethylene, and its expression was reported to occur from the beginning to the intermediate stages of plant embryo development. Here, we suggest that this enzyme is possibly involved in the control of the earliest stages of somatic embryogenesis of O. catharinensis, and an approach to study ACO expression during somatic embryogenesis is proposed.

Silicon distribution and accumulation in shoot tissue of the tropical forage grass Brachiaria brizantha

Silicon (Si) accumulation in organs and cells is one of the most prominent characteristics of plants of the family Poaceae. Many species from this family are used as forage plants for animal feeding. The present study investigates in Brachiaria brizantha (Hochst. ex A. Rich.) Stapf. cv. Marandu: (1) the dry matter production and Si content in shoot due to soil Si fertilizations; (2) the Si distribution among shoot parts; and (3) the silica deposition and localization in leaves. Plants of B. brizantha cv. Marandu were grown under contrasting Si supplies in soil and nutrient solution. Silica deposition and distribution in grass leaf blades were observed using light microscope and scanning electron microscope equipped with an energy dispersive X-ray spectrometer (SEM-EDXS). Silicon concentration in the B. brizantha shoot increased according to the Si supply. Silicon in grass leaves decreased following the order: mature leaf blades > recently expanded leaf blades > non-expanded leaf blades. Silicon accumulates mainly on the upper (adaxial) epidermis of the grass leaf blades and, especially, on the bulliform cells. The Si distribution on adaxial leaf blade surface is non uniform and reflects a silica deposition exclusively on the cell wall of bulliform cells.

SacRALF1, a peptide signal from the grass sugarcane (Saccharum spp.), is potentially involved in the regulation of tissue expansion

Rapid alkalinization factor (RALF) is part of a growing family of small peptides with hormone characteristics in plants. Initially isolated from leaves of tobacco plants, RALF peptides can be found throughout the plant kingdom and they are expressed ubiquitously in plants. We took advantage of the small gene family size of RALF genes in sugarcane and the ordered cellular growth of the grass sugarcane leaves to gain information about the function of RALF peptides in plants. Here we report the isolation of two RALF peptides from leaves of sugarcane plants using the alkalinization assay. SacRALF1 was the most abundant and, when added to culture media, inhibited growth of microcalli derived from cell suspension cultures at concentrations as low as 0.1 mu M. Microcalli exposed to exogenous SacRALF1 for 5 days showed a reduced number of elongated cells. Only four copies of SacRALF genes were found in sugarcane plants. All four SacRALF genes are highly expressed in young and expanding leaves and show a low or undetectable level of expression in expanded leaves. In half-emerged leaf blades, SacRALF transcripts were found at high levels at the basal portion of the leaf and at low levels at the apical portion. Gene expression analyzes localize SacRALF genes in elongation zones of roots and leaves. Mature leaves, which are devoid of expanding cells, do not show considerable expression of SacRALF genes. Our findings are consistent with SacRALF genes playing a role in plant development potentially regulating tissue expansion.

Micronutrient dynamics in the forest biomass in succession stages of a seasonal deciduous forest, RS, Brazil

There is a great need of research to assess the behavior of micronutrients in natural forests of southern Brazil. Do to this need, the objective of this work was to study the levels and amounts of micronutrients in forest above ground biomass of the forest, in a comparative way, in two secondary succession stages (SSS) in a Seasonal Deciduous Forest in Rio Grande do Sul, Brazil. The SSS had enjoyed 35 and 55 years of regeneration since the end of agricultural use, respectively for initial secondary forest (ISF) and late secondary forest (LSF). The above-ground biomass was collected and separated into vegetative strata and these in fractions, thereafter chemically analyzed for the levels of B, Fe, Zn, Mn and Cu. Leaf fractions of arboreal, shrubs and herbaceous strata showed the highest levels for most nutrients. Only the levels of iron and manganese were higher in the bark fraction, for both sucession stages. In the LSF, the herbaceous stratum also showed high levels of Fe. The average levels of micronutrients showed differences between the two sucession stages only in relation to Fe and Mn, with higher levels in LSF biomass. The amount of nutrients stored was always higher in LSF, because of the largest biomass and the higher levels of Fe and Mn in the biomass of this SSS. The quantitative order of nutrient storage in biomass was Fe> Mn> Zn> B> Cu.

Hydrolysis Influence on Phytochemical Composition, Antioxidant Activity, Plasma Concentration, and Tissue Distribution of Hydroethanolic Ilex paraguariensis Extract Components

The infusion of aerial parts of Ilex paraguariensis is widely consumed. Its antioxidant activity suggests an important role of this plant in the treatment/prevention of oxidative stress related diseases. Plant extract active compounds are frequently found in esterified form that may be poorly absorbed. Hydrolysis of the extract is a possible approach to increase its bioavailability. The aim of this study was to perform a phytochemical analysis and evaluate in rats the plasma concentration and tissue distribution of antioxidant compounds in the hydroethanolic extract of Ilex paraguariensis, before and after enzymatic hydrolysis. Both extracts presented high antioxidant activity and phenolic content. Rats given single or repeated doses of the hydrolyzed extract showed increased plasma antioxidant activity and higher plasma levels of caffeic acid. However, no changes of endogenous antioxidants were observed. In conclusion, hydrolysis of the extract of Ilex paraguariensis is a strategy to improve its bioavailability and in vivo antioxidant activity.

Care during freeze-drying of bovine pericardium tissue to be used as a biomaterial: A comparative study

Bovine pericardium (BP) tissue is widely used in the manufacture of bioprosthetics. The effects of freeze-drying on the BP tissue have been studied by some researchers in order to decrease their cytotoxicity due to preservation in formaldehyde solution, and to increase the lifetime of the product in storage. This study was undertaken in order to study the effect of freeze-drying in the structure of BP. To perform this study BP samples were freeze-dried in two different types of freeze-dryers available in our laboratory: a laboratory freeze-dryer, in which it was not possible to control parameters and a pilot freeze-dryer, wherein all parameters during freezing and drying were controlled. After freeze-drying processes, samples were analyzed by SEM, Raman spectroscopy, tensile strength, water uptake tests and TEM. In summary, it has been demonstrated that damages occur in collagen fibers by the loss of bulk water of collagen structure implicating in a drastic decreasing of BP mechanical properties due to its structural alterations. Moreover, it was proven that the collagen fibrils suffered breakage at some points, which can be attributed to the uncontrolled parameters during drying. (C) 2011 Elsevier Inc. All rights reserved.