Retroviral display of antibody fragments; interdomain spacing strongly influences vector infectivity

Five different single-chain antibody fragments (scFv) against human cell-surface antigens were displayed on murine ecotropic retroviral vectors by fusing them to the Moloney SU envelope glycoprotein. The spacing between the scFv and the SU glycoprotein was varied by fusing the scFv to residue +7 or to residue +1 of Moloney SU and by inserting linker sequences of different lengths between the domains. All of the chimeric envelopes were efficiently incorporated into vector particles and could bind to human cells through their displayed antibody fragments, but did not infect them. The spacing between the scFvs and the SU glycoproteins had no significant effect on the efficiency of envelope expression or viral incorporation and did not affect the binding properties of the chimeric envelopes, nor did it influence the efficiency of targeted gene delivery to human cells by scFv-displaying vectors. However, on murine fibroblasts the infectivity of vectors incorporating the chimeric envelopes was strongly influenced by the length of the interdomain spacer. The titers were very low when the single-chain antibodies were fused through a tripeptide linker to SU residue +7 and were greatly enhanced (up to 10(5)-fold) when they were fused to SU residue +1 through a heptapeptide linker. These results point to the importance of steric interactions between the domains of chimeric envelope glycoproteins and may have implications for retroviral vector design for human gene therapy.     

Shunting neural network photodetector arrays in analog CMOS

This paper describes a custom analog CMOS photodetector array IC that exploits nonlinear lateral inhibition to achieve dynamic range compression, edge enhancement, and adaptation to mean input intensity. The neural net array architecture, characterized by nearest-neighbor connections and multiplicative cell interaction, is modeled after biological vision systems. The fabricated IC successfully implements a portion of the compact and powerful nonlinear signal processing performed in the outer layers of the vertebrate retina. Measured results are presented for an optical input intensity range of nearly six decades. A scanning architecture that allows for preferential directional sensitivity is also demonstrated. Measured data agree well with models created using a spreadsheet program     

The performance of foliage mass and crown radius models in forming the input of a forest reflectance model: A test on forest growth sample plots and Landsat 7 ETM+ images

Several published foliage mass and crown radius regression models were tested on the preparation of the input for the reflectance model of Kuusk and Nilson [Kuusk, A. and Nilson, T. (2000), A directional multispectral forest reflectance model. Remote Sensing of Environment, 72(2):244–252.] for 246 forest growth sample plots in Estonia. In each test, foliage mass and crown radius for trees in the sample plots were predicted with a particular pair of allometric regression models. The forest reflectance model was then run using the estimated foliage mass and crown radius values. Reflectance factors were simulated and compared with the reflectance values obtained from three atmospherically corrected Landsat 7 Enhanced Thematic Mapper (ETM+) scenes. The statistics of linear regression between the simulated and measured reflectance factors were used to assess the performance of foliage and crown radius models. The hypothesis was that the best allometric regression models should provide the best fit in reflectance. The strongest correlation between the simulated and measured reflectance factors was found in the short-wave infrared band (ETM + 5) for all the images. The highest R² = 0.71 was observed in Picea abies dominated stands. No excellent combination of foliage mass and crown radius functions was found, but the ranking based on determination coefficients showed that some linear crown radius models are not applicable to our data. Processing of raster images, reflectance measurement for small sample plots, usage of tree-species-specific fixed parameters (specific leaf area, etc.), and the ignored influence of phenology introduced additional variation into the relationships between simulated and measured reflectance factors. Further studies are needed, but these preliminary results demonstrate that the proposed method could serve as an effective way of testing the performance of foliage mass and canopy cover regressions.     

Variability for oil and fatty acid composition in castorbean varieties

Thirty-six castorbean varieties were surveyed for oil and fatty acid composition, in order to determine variability of these seed compounds. A large variability of seed oil percentage was observed, ranging from 39.6 to 59.5%. Concerning the fatty acids, little variability was observed for ricinoleic acid, which was the most abundant in the oil, ranging from 83.65 to 90.00%. The other fatty acids appeared in small concentrations and showed a small range: 0.87 to 2.35, 0.68 to 1.84, 2.96 to 5.64, 3.19 to 5.98, and 0.34 to 0.91%, for palmitic, stearic, oleic, linoleic, and linolenic acid, respectively. Non-significant correlations were observed between fatty acids and seed oil percentage. However, significant correlations were observed among fatty acid concentrations: positive and negative ones. These significant correlations could be associated with the biosynthetic pathways of the fatty acids, which are not fully elucidated. They suggest, however, that selection for a particular fatty acid will tend to increase those positively correlated, and decrease those negative ones. Selection and plant breeding techniques could then be applied to modify the oil content of the castorbean seeds, considering the variability observed. For the fatty acid composition, however, the variability was not large enough to make substantial changes in their concentrations by selection procedures. More varieties should be surveyed to find out if such variability is available.     

An Historical Perspective on the Administration of Water in Brazil

Abstract

This article focuses on two instruments of water resources management—charging for water and reallocation of water use through a water market. Charging for water in nature has been practiced for centuries in some cases. On the other hand, a culture of free access to water was dominant in most countries during ancient times. An historical review of the charging of water and its administration is presented. The article covers the time of ancient Rome to the present. A current example is the model practiced in the semi-arid region of Ceará State in northeast Brazil. Regarding water use reallocation by a water market, as an alternative to improve water efficiency, the experience presented comes from the south of Ceará State one century ago. Based on past experience, the article then presents a model to implement a water market bounded in space to an irrigation district, and in time to periods of water deficit in reservoirs. Six prerequisites of market-based transfers of water are analyzed, and it is shown that in the proposed model they can be addressed.     

Corrosion resistance of anodic oxides on the Ti-50Zr and Ti-13Nb-13Zr alloys

Electrochemical analyses on the biocompatible alloys Ti-50Zr and Ti-13Nb-13Zr, as-cast and heat-treated, in distinct electrolytes (simulating or not physiological media: pH 7, Ringer, PBS, phosphate buffer and Na₂SO₄ solutions; pH 1, H₂SO₄, HNO₃, CH₃SO₃H, HClO₄ and H₃PO₄ solutions) are reported. Analyses of the open-circuit potential values indicated that either as-cast or heat-treated samples of both alloys present the same tendency to spontaneously form an oxide film on their surfaces and that the oxide grown in the Na₂SO₄ solution presents better protection characteristics than those formed in the phosphate buffer, Ringer and PBS solutions, in this order. Cyclic voltammograms obtained in the Ringer and PBS solutions showed that the Ti-13Nb-13Zr alloy does not transpassivate up to potentials of 8 V (versus SCE), while the Ti-50Zr alloy presents corrosion at potentials lower than 2 V (versus SCE), indicating that this alloy is less resistant to corrosion in solutions simulating physiological conditions. The obtained pit potential values showed that the heat treatment has very little influence on the corrosion behavior of the alloys. Finally, both alloys did not present transpassivation at potentials up to 8 V (versus SCE) in the H₂SO₄, HNO₃, CH₃SO₃H and H₃PO₄ solutions; however, when immersed in the HClO₄ solution the Ti-50Zr alloy underwent pit corrosion while the Ti-13Nb-13Zr alloy remained corrosion resistant in this potential range.     

Cholesterol and fatty acids profile of Brazilian commercial chicken giblets

This study was carried out to determine the chemical composition, cholesterol contents and fatty acids profile of Brazilian commercial chicken giblets. The analysis were performed in gizzard, liver and heart in natura and also in cooked gizzard, fried liver and roasted heart. Fat and cholesterol contents ranged from 0.88% and 72.68 mg/100 g, in cooked gizzard, to 22.19% and 213.18 mg/100 g, in roasted heart. As the fat content gets higher, so does the cholesterol content. Palmitic (C16:0) and stearic acids (C18:0) were the predominant saturated fatty acids (SFA). The C16:0 ranged from 6.39% in cooked gizzard to 18.51% in fried liver. The C18:0 level ranged from 6.62% in roasted heart to 19.19% in cooked gizzard. Linoleic acid (C18:2 omega 6) was the predominant polyunsaturated fatty acid (PUFA). The data revealed that the three different analysed giblets presented a good PUFA/SFA ratio, with values of 1.11, 1.14 and 1.40 for cooked gizzard, fried liver and roasted heart, respectively.     

Impact of understory vegetation on forest canopy reflectance and remotely sensed LAI estimates

Forest leaf area index (LAI), is an important variable in carbon balance models. However, understory vegetation is a recognized problem that limits the accuracy of satellite-estimated forest LAI. A canopy reflectance model was used to investigate the impact of the understory vegetation on LAI estimated from reflectance values estimated from satellite sensor data. Reflectance spectra were produced by the model using detailed field data as input, i.e. forest LAI, tree structural parameters, and the composition, distribution and reflectance of the forest floor. Common deciduous and coniferous forest types in southern Sweden were investigated. A negative linear relationship (r² = 0.6) was observed between field estimated LAI and the degree of understory vegetation, and the results indicated better agreement when coniferous and deciduous stands were analysed separately. The simulated spectra verified that the impact of the understory on the reflected signal from the top of the canopy is important; the reflectance values varying by up to ± 18% in the red and up to ± 10% in the near infra-red region of the spectra due to the understory. In order to predict the variation in LAI due to the understory vegetation, model inversions were performed where the input spectra were changed between the minimum, average and maximum reflectance values obtained from the forward runs. The resulting variation in LAI was found to be 1.6 units on average. The LAI of the understory could be predicted indirectly from simple stand data on forest characteristics, i.e. from allometric estimates, as an initial step in the process of estimating LAI. It is suggested here that compensation for the effect of the understory would improve the accuracy in the estimates of canopy LAI considerably.     

Functional analysis of the placenta-specific enhancer of the human glycoprotein hormone alpha subunit gene. Emergence of a new element

Placental expression of the alpha subunit gene of the human glycoprotein hormones requires a multicomponent enhancer composed of tandem cAMP-response elements and an adjacent upstream regulatory element. Based on recent studies indicating that the upstream regulatory element includes binding sites for more than one protein, we investigated how functional activity correlated with these binding sites. Through extensive replacement mutagenesis of the native promoter regulatory region, we provide the first functional map of the upstream regulatory element. Within this region, we find that distinct proteins interact with three overlapping binding sites. While each site is functionally significant, no single site is essential or displays clear dominance. This is surprising since one of the sites binds a placenta-specific protein that heretofore has been regarded as essential for activity of the human alpha subunit placenta-specific enhancer. Consequently, our refined functional map of the upstream regulatory element reveals a complex combinatorial code that directs expression of the human alpha subunit gene to placenta.