Racial differences in lens opacities: the Salisbury Eye Evaluation (SEE) project

Stable clones of neural stem cells (NSCs) have been isolated from the human fetal telencephalon. These self-renewing clones give rise to all fundamental neural lineages in vitro. Following transplantation into germinal zones of the newborn mouse brain they participate in aspects of normal development, including migration along established migratory pathways to disseminated central nervous system regions, differentiation into multiple developmentally and regionally appropriate cell types, and nondisruptive interspersion with host progenitors and their progeny. These human NSCs can be genetically engineered and are capable of expressing foreign transgenes in vivo. Supporting their gene therapy potential, secretory products from NSCs can correct a prototypical genetic metabolic defect in neurons and glia in vitro. The human NSCs can also replace specific deficient neuronal populations. Cryopreservable human NSCs may be propagated by both epigenetic and genetic means that are comparably safe and effective. By analogy to rodent NSCs, these observations may allow the development of NSC transplantation for a range of disorders.     

Symbolic convolution

An implementation of convolution using a symbolic mathematics software package is described. The emphasis is on the internal data structure needed to represent signals that are defined piecewise over disjoint intervals. Then the overlap-add form of convolution is used to produce the convolution of signals that are the sum of piecewise segments. A working implementation has been completed for both discrete-time and continous-time convolution. Several examples are shown to illustrate the results and to suggest ways in which this sort of software might be useful for classroom presentations     

Evaluation of alternative materials handling systems

This paper addresses the development of a simulation model to assist in the selection of a new materials handling system for the service and repair group of a major electronics company.     

Financial effect of clinical decisions: case study of a dialysis center

This paper explores, in the isolated guinea-pig ileum, the effects of temperature on the acute development of opioid dependence and on the precipitation of the abstinence response, using as reference the effect of temperature on the response to a standard nicotine concentration. Additionally, the influence of temperature on acute morphine neurodepression was examined. Three experimental groups were included. In the first, the bath temperature was adjusted and maintained along the experimental session (2.5 h) at one of the following values: 28, 32, 36 or 40 degrees C. In the second, the different values of bath temperature were applied only during the period of morphine exposure before testing the abstinence response at 36 degrees C. In the third, all segments were initially incubated at 36 degrees C for 1 h, and afterwards, abstinence and the nicotine response were elicited at the different temperatures mentioned. In all the series, a single challenge naloxone dose (3.1, 10, 31, 100, 316, 1000 or 3160 nM) was administered after 1h of morphine and complete naloxone concentration-response curves were obtained. The abstinence response was expressed as a percentage of the nicotine reference response. All segments showed robust nicotine responses at all the experimental protocols tested indicating that, at the temperature range studied, the contractile mechanisms were impaired. This study showed that changes in bath temperature modify the magnitude of acute morphine neurodepression, and of the abstinence response but did no affect the development of acute opioid dependence. These data, along with several lines of evidence, strongly suggest that acute neurodepression, the development of opiate dependence and antagonist-precipitated abstinence are separable. Results are discussed on the basis of drug-receptor interactions.     

Genetic variation and prediction of additive and nonadditive genetic effects for six carcass traits in an Angus-Brahman multibreed herd

Estimates of covariances and sire expected progeny differences of additive and nonadditive genetic effects for six carcass traits were obtained using records from 486 straightbred and crossbred steers from 121 sires born between 1989 and 1995 in the Angus-Brahman multibreed herd of the University of Florida. Steers were slaughtered at a similar carcass composition end point. Covariances were estimated by REML procedures, using a generalized expectation-maximization algorithm applied to multibreed populations. Straightbred and crossbred estimates of heritabilities and additive genetic correlations were within ranges found in the literature for steers slaughtered on an age- or weight-constant basis for hot carcass weight, longissimus muscle area, and shear force but equal to or less than the lower bound of these ranges for fat-related traits. Maximum values of interactibilities (i.e., ratios of nonadditive variances to phenotypic variances in the F1) and nonadditive genetic correlations were smaller than heritabilities and additive genetic correlations in straightbreds and crossbred groups. Sire additive and total direct genetic predictions for longissimus muscle area, marbling, and shear force tended to decrease with the fraction of Brahman alleles, whereas those for hot carcass weight and fat thickness over the longissimus were higher, and those for kidney fat were lower in straightbreds and F1 than in other crossbred groups. Nonadditive genetic predictions were similar across sire groups of all Angus and Brahman fractions. These results suggest that slaughtering steers on a similar carcass composition basis reduces variability of fat-related traits while retaining variability for non-fat-related traits comparable to slaughtering steers on a similar age or weight basis. Selection for carcass traits within desirable (narrow) ranges and slaughter of steers at similar compositional end point seems to be a good combination to help produce meat products of consistent quality.     

Cellular retinaldehyde-binding protein ligand interactions. Gln-210 and Lys-221 are in the retinoid binding pocket

Cellular retinaldehyde-binding protein (CRALBP) carries 11-cis-retinal and/or 11-cis-retinol as endogenous ligands in the retinal pigment epithelium (RPE) and Müller cells of the retina and has been linked with autosomal recessive retinitis pigmentosa. Ligand interactions determine the physiological role of CRALBP in the RPE where the protein is thought to function as a substrate carrier for 11-cis-retinol dehydrogenase in the synthesis of 11-cis-retinal for visual pigment regeneration. However, CRALBP is also present in optic nerve and brain where its natural ligand and function are not yet known. We have characterized the interactions of retinoids with native bovine CRALBP, human recombinant CRALBP (rCRALBP) and five mutant rCRALBPs. Efforts to trap and/or identify a Schiff base in the dark, under a variety of reducing, denaturing, and pH conditions were unsuccessful, suggesting the lack of covalent interactions between CRALBP and retinoid. Buried and solvent-exposed lysine residues were identified in bovine CRALBP by reductive methylation of the holoprotein followed by denaturation and reaction with [3H]acetic anhydride. Radioactive lysine residues were identified by Edman degradation and electrospray mass spectrometry following proteolysis and purification of modified peptides. Human rCRALBP mutants K152A, K221A, and K294A were prepared to investigate possible retinoid interactions with buried or partially buried lysines. Two other rCRALBP mutants, I162V and Q210R, were also prepared to identify substitutions altering the retinoid binding properties of a random mutant. The structures of all the mutants were verified by amino acid and mass spectral analyses and retinoid binding properties evaluated by UV-visible and fluorescence spectroscopy. All of the mutants bound 11-cis-retinal essentially like the wild type protein, indicating that the proteins were not grossly misfolded. Three of the mutants bound 9-cis-retinal like the wild type protein; however, Q210R and K221A bound less than stoichiometric amounts of the 9-cis-isomer and exhibited lower affinity for this retinoid relative to wild type rCRALBP. Residues Gln-210 and Lys-221 are located within a region of CRALBP exhibiting sequence homology with the ligand binding cavity of yeast phosphatidylinositol-transfer protein. The data implicate Gln-210 and Lys-221 as components of the CRALBP retinoid binding cavity and are discussed in the context of ligand interactions in structurally or functionally related proteins with known crystallographic structures.     

Cloning and overexpression in Escherichia coli of the gene encoding citrate synthase from the hyperthermophilic Archaeon Sulfolobus solfataricus

A transurethral resection of the prostate is a good operation to relieve bladder outflow obstruction and has a low incidence of complications. However, recent work suggests that many men with symptoms may not require an operation, and it can probably be delayed in a majority for many years. This may be particularly important in old and frail patients. Many men with outflow obstruction have irritative symptoms such as urgency, frequency and nocturia; these could be treated with anticholinergics, provided they have normal flow rates and small or absent residual urine volumes. Pharmacological treatment to relieve outflow obstruction is disappointing. There may be some benefit from alpha-adrenoreceptor antagonists, but the place for 5 alpha-reductase inhibitors is still unsure. All drugs have side effects which are unacceptable in patients who are not bothered by their urinary symptoms and can wait for active treatment.     

Influence of rib spacing in proton-exchange membrane electrode assemblies

A two-dimensional design analysis of a membrane-electrode assembly for a proton-exchange membrane fuel cell is presented. Specifically, the ribs of the bipolar plates restrict the access of fuel and oxidant gases to the catalyst layer. The expected change in cell performance that results from the partial blocking of the substrate layer is studied by numerical simulation of the oxygen electrode and the membrane separator. The effects of rib sizing and the thickness of the gas-diffusion electrode on the current and water distributions within the cell are presented. For all of the cases considered, the two-dimensional effect only slightly alters the half-cell potential for a given applied current but has a significant influence on water management. Concentrated solution theory with variable transport properties is used in the membrane electrolyte to solve for the electrical potential and local water content. The Stefan-Maxwell equations are used in the gas-diffusion electrode to determine the local mole fractions of nitrogen, oxygen and water vapour. A control-volume formulation is used for the resolution of the coupled nonlinear differential equations. One advantage of the control-volume approach over finite-difference methods is the relative ease in which internal boundary points in fuel-cell and battery models are handled. This and other advantages are briefly discussed.     

An integrated approach to facility location problems

An integrated analysis approach to facility location problems is described. The approach is based on integrating analytical location models and a multicriteria decision model.