Extracellular matrix microarrays to study inductive signaling for endoderm specification

During tissue development, stem and progenitor cells are faced with fate decisions coordinated by microenvironmental cues. Although insights have been gained from in vitro and in vivo studies, the role of the microenvironment remains poorly understood due to the inability to systematically explore combinations of stimuli at a large scale. To overcome such restrictions, we implemented an extracellular matrix (ECM) array platform that facilitates the study of 741 distinct combinations of 38 different ECM components in a systematic, unbiased and high-throughput manner. Using embryonic stem cells as a model system, we derived definitive endoderm progenitors and applied them to the array platform to study the influence of ECM, including the interactions of ECM with growth factor signaling, on the specification of definitive endoderm cells towards the liver and pancreas fates. We identified ECM combinations that influence endoderm fate decisions towards these lineages, and demonstrated the utility of this platform for studying ECM-mediated modifications to signal activation during liver specification. In particular, defined combinations of fibronectin and laminin isoforms, as well as combinations of distinct collagen subtypes, were shown to influence SMAD pathway activation and the degree of hepatic differentiation. Overall, our systematic high-throughput approach suggests that ECM components of the microenvironment have modulatory effects on endoderm differentiation, including effects on lineage fate choice and cell adhesion and survival during the differentiation process. This platform represents a robust tool for analyzing effects of ECM composition towards the continued improvement of stem cell differentiation protocols and further elucidation of tissue development processes.

STATEMENT OF SIGNIFICANCE

Cellular microarrays can provide the capability to perform high-throughput investigations into the role of microenvironmental signals in a variety of cell functions. This study demonstrates the utility of a high-throughput cellular microarray approach for analyzing the effects of extracellular matrix (ECM) in liver and pancreas differentiation of endoderm progenitor cells. Despite an appreciation that ECM is likely involved in these processes, the influence of ECM, particularly combinations of matrix proteins, had not been systematically explored. In addition to the identification of relevant ECM compositions, this study illustrates the capability of the cellular microarray platform to be integrated with a diverse range of cell fate measurements, which could be broadly applied towards the investigation of cell fate regulation in other tissue development and disease contexts.

Magnetoresistive chip cytometer

Although conventional state-of-the-art flow cytometry systems provide rapid and reliable analytical capacities, they are bulky, expensive and complex. To overcome these drawbacks modern flow cytometers have been developed with enhanced portability for on-site measurements. Unlike external fluorescent/optical detectors, magnetoresistive sensors are micro-fabricated, can be integrated within microfluidic channels, and can detect magnetically labelled cells. This work describes the real-time detection of single magnetically labelled cells with a magnetoresistive based cell cytometer. For Kg1-a cells magnetically labelled with 50 nm CD34 microbeads (Milteny) flowing through a 150 μm wide, 14 μm high microchannel, with speeds around 1 cm s(-1), bipolar signals with an average amplitude of 10-20 μV were observed corresponding to cell events. The number of cells counted by the spin valve cytometer has been compared with that obtained with a hemocytometer. Both methods agree within the respective error bars.

Cluster of Candida parapsilosis primary bloodstream infection in a neonatal intensive care unit

Candida parapsilosis is an increasingly important bloodstream pathogen in neonatal intensive care units (NICU). We investigated a cluster of bloodstream infections in a NICU to determine whether nosocomial transmission occurred. During a 3-day period, 3 premature infants hospitalized in the same unit presented with sepsis caused by C. parapsilosis. Electrophoretic karyotype of the organisms was performed by using pulsed field gel electrophoresis in a countour-clamped homogeneous electric field system. The isolate from 1 newborn could not be typed, and the isolates from the remaining 2 infants had identical patterns. All 3 cases are described. We conclude that nosocomial transmission of C. parapsilosis occurred and that neonates under intensive care may represent a risk group for this pathogen.

The molluscicidal activity of the latex of Euphorbia splendens var. hislopii on Melanoides tuberculata (Thiaridae), a snail associated with habitats of Biomphalaria glabrata (Planorbidae)

The use of the latex of Euphorbia splendens var. hislopii was considered as an effective control method for Biomphalaria glabrata in Sumidouro, Rio de Janeiro. However, the appearance and expansion of the snail Melanoides tuberculata since August 1997, with the concomitant reduction of the population of B. glabrata suggest that competitive exclusion might be taking place. Depending on the susceptibility of the thiarid to the E. splendens toxin, the natural control that is occurring could be interrupted by the employment of the latex if the planorbid were less susceptible to the toxin. The aim of this study is to investigate the molluscicidal activity of the latex on M. tuberculata. We used 420 M. tuberculata, from Sumidouro. Fourteen different latex concentrations were tested using World Health Organization general methodology. Probit analysis was used for LD90 and LD50 determination. The LD50 was 3.57 mg/l and LD90 was 6.22 mg/l. At the highest concentration (10 mg/l) there was no survival. No significant differences among replicas (chi2 = 8.31; gl = 13; p > 0.05) were found. The LD90 dose for M. tuberculata was 13.8 times greater than that for B. glabrata, so that the molluscicide in the presence of the thiarid may have a synergic effect on reduction of Biomphalaria populations.

Determination of Cu, Pb, Cd, and Zn in river sediment extracts by sequential injection anodic stripping voltammetry with thin mercury film electrode

Determination of Cu, Pb, Cd and Zn was performed in sediment extracts obtained according to the three steps sequential extraction procedure proposed by the European Community Standards, Measurements and Testing Program. The metal content was determined by anodic stripping voltammetry with a thin mercury film electrode controlled by a sequential injection (SIA) system. The proposed method improved the reproducibility of conventional anodic stripping voltammetry, as well as the sample throughput, allowing analysis of 30 to 45 samples per hour. The influence of flow rate and sample volume was studied to achieve an adequate sensitivity for the leachate studied. No interferences due to adsorption of organic matter, colloids, or complexes with slow rate of dissociation were observed. The intermetallic formation of Cu-Zn was avoided by forming the mercury film in presence of Ga(III) ions in the SIA system, resulting in low consumption of reagent in comparison to flow injection or continuous flow systems. Results were in good agreement with those obtained by Induced Coupled Plasma - Atomic Emission Spectroscopy (ICP-AES).

[Nongovernmental organizations and AIDS, social intervention, and new ties in social solidarity]

Starting with a brief contextual analysis of the social scenario in which the AIDS epidemic is occurring in Brazil, the article focuses on the formation of the country's first nongovernmental organizations in the struggle against AIDS. There are peculiarities to AIDS NGOs to the extent that they display an ambivalence between the characteristics of a professional institution and a lobbying group, apart from the fact that dealing with sexuality and death breaks down the line between the public and the private spheres. The case in point is the Grupo Pela Vidda (For Life Group) in Rio de Janeiro, which seeks to represent the enhancement of a group of individuals and the principle of universality. The study supports the hypothesis that AIDS NGOs renew ties of social solidarity through the relationships established between various researchers involved in this sector and other NGOs with governmental spheres.

[Neuro-AIDS]

The human immunodeficiency virus (HIV) type 1 is the retrovirus which is responsible for the human immunodeficiency syndrome (AIDS) described in infancy in 1983. It is the most serious disorder caused by HIV, by a neurotropic virus, and is particularly severe in infancy. In children infected by vertical transmission of HIV, there is a shorter clinical latent period than in adults, and more viraemia than in children over the age of three months infected by blood transfusion. The neurological disorder caused by HIV is a complex clinical syndrome in which there may be varying degrees of retardation of cognition, movement or behaviour. A growing number of HIV+ children are being followed-up in the Hospital de Clinicas de Porto Alegre (HCPA) to treat the neuropsychomotor development and the presence of neurological behaviour in these children. The neurological, analytical (laboratory), electro-encephalographic and tomographic changes seen in a sample of 344 HIV+ children were studied. Analysis of these results showed a significant difference between affected and non-affected children. Encephalopathy occurred in 36% of the cases, being progressive in 29% and static in 17%. There was a relationship between neurological involvement at the first consultation and progress to encephalopathy. The RDNPM showed a tendency towards encephalopathy, usually between 1 and 5 years of age, which might also be the first sign of the disease. We found a significant relationship between being infected and having alterations not seen in cerebrospinal fluid, EEG, TCC and neurological progress.

Schistosomiasis in a low prevalence area: incomplete urbanization increasing risk of infection in Paracambi, RJ, Brazil

The risk of schistosomiasis infection and heavy infection in the locality of Sabugo was evaluated in relation to housing in areas with different urbanization development and to residential supply with snail-infested water. Critical sanitary conditions were found in areas of incomplete urbanization, where healthy water supply sources were scarce, and draining of sewage, without previous treatment, was made directly to the water-bodies used for domestic and leisure activities, despite being Biomphalaria tenagophila snail breeding-places. Stool examinations (Kato-Katz and Lutz methods) showed prevalence of 2.9% mean intensity of 79 eggs per gram of stool and 47% of positive cases presenting intense infection. The use of snail-contaminated water for domestic purposes was considered a risk factor for infection. It is concluded that incomplete urbanization would facilitate transmission, probably enhancing the intensity of infection and that a low prevalence could hide a highly focal transmission. The relevance of these facts upon the efficiency of epidemiologic study methods and disease control planning are then discussed.

[AIDS in childhood: basic guidance for attending]

The pandemic expansion of AIDS demands that all health care staff and institutions are prepared to diagnose and control this disease. The HIV virus destroys the immune response and causes a series of other organ and system dysfunctions, leading to diverse clinical manifestations. This article reviews the pathophysiology, clinical manifestations, diagnosis, treatment and prevention of HIV infection. The role of the health care worker as an educator is also reviewed.

Aorticopulmonary septal defect coexisting with ventricular septal defect

Three cases, in each of which an aorticopulmonary septal defect (AP window) coexisted with a ventricular septal defect, are described. In two the ventricular septal defect was of the usual variety, and in one it was part of the tetralogy of Fallot.

The patients presented as examples of congestive cardiac failure with a large left-to-right shunt in infancy. Aortography was the most reliable method for identification of the AP window when a ventricular septal defect was associated. Associated features included a right aortic arch with mirror image branching in the first case and tetralogy of Fallot with muscular subaortic stenosis in the third case. In the case with the tetralogy of Fallot, the effects of pulmonary stenosis were masked by the left-to-right shunt through the AP window.