Skin surface lipids of the dog

The skin surface lipid of the dog has been reported to contain a high proportion of diol diesters having a lower mobility on thin layer chromatography than diesters from other species in spite of containing similar fatty acid and diol components. In the present study, dog skin surface lipid was separated by preparative thin layer chromatography into sterol esters (42%), wax diesters (32%), free sterols (9%), polar lipids (7%), and unidentified components (10%). The diesters contained 1,2-diols, each esterified with one long chain fatty acid and one isovaleric acid moiety. The diols were principally branched chain C₂₁ and C₂₂ compounds while the long chain fatty acids esterified with them were mainly C₂₀ and C₂₁ branched compounds. The fatty acids from the sterol esters were mostly saturated, branched chain C₁₉ to C₂₃, together with 7% of straight chain monoenoic acids, principally C₂₁ and C₂₂. There were only trace amounts of free sterols other than cholesterol, while the esterified sterols contained 96% cholesterol and 4% lathosterol.     

Multichanneled finite-conjugate imaging

Multichanneled imaging systems rely on nonredundant images recorded by an array of low-resolution imagers to enable construction of a high-resolution image. We show how the varying degree of redundancy associated with imaging throughout the imaged volume effects image quality. Using ray-traced image simulations and a metric used as a proxy for human perception, we show that robust recovery of high-resolution images can be obtained by avoiding excessive redundancy and that this is a felicitous consequence of typical manufacturing tolerances.     

Environmental factors influencing microcystin distribution and concentration in the Midwestern United States

During May–September 2000–2001, physicochemical data were collected from 241 lakes in Missouri, Iowa, northeastern Kansas, and southern Minnesota U.S.A., to determine the environmental variables associated with high concentrations of the cyanobacterial hepatotoxin microcystin (MC). The study region represents a south–north latitudinal gradient in increasing trophic status, with total phosphorus (TP) and total nitrogen (TN) values ranging between 2–995 and 90–15870 μg/L, respectively. Particulate MC values, measured by ELISA, ranged from undetectable to 4500 ng/L and increased with increasing latitude. Despite latitudinal trends, environmental variables explained <50% of the variation in MC values. Inspection of MC–TN and MC–Secchi bivariate plots revealed distinctly nonlinear trends, suggesting optima for maximum MC values. Nonlinear interval maxima regression indicated that MC–TN maxima were characterized by a unimodal curve, with maximal (>2000 ng/L) MC values occurring between 1500 and 4000 μg/L TN. Above 8000 μg/L TN all MC values were <150 ng/L. MC–Secchi maxima were characterized by exponential decline, with maximal MC values occurring at Secchi depths <2.5 m. The development of empirical relationships between environmental variables and MC values is critical to effective lake management and minimization of human health risks associated with the toxin. This study indicates MC values are linked to the physicochemical environment; however, the relationships are not traditional linear models.     

Forecasting the effects of polluting discharges on natural waters—II

A brief account is given of the present state of development of methods for forecasting the effects of pollution on estuaries and coastal waters. In the case of vertically homogeneous estuaries the concentration of given pollutants at a chosen state of tide and given freshwater flow can be determined by means of a one‐dimensional steady‐state mathematical model in which use is made of observations of the distribution of salinity to calculate the rate of dispersion of the pollutants. An example is given of the application of such a model to the prediction of the concentration of dissolved oxygen, ammonia and oxidized nitrogen in the Thames Estuary. This type of approach has been extended to allow approximate estimates to be made of the variation of concentration of pollutants during a tidal cycle, and of the steady‐state concentrations in vertically stratified estuaries. A somewhat different type of model is used for predicting the effects of polluting discharges on coastal waters and in this case dispersion characteristics are determined with the aid of radio isotopes. An example is given of the application of one type of model to the prediction of the contamination of coastal waters by coliform bacteria resulting from discharge of sewage from a submerged pipeline.     

Freezing in sealed capillaries for preparation of frozen hydratedsections

We have investigated the freezing of specimens in a confined volume for preparation of vitreous samples for cryosectioning. With 15% dextran as a cryoprotectant, a sample sealed in a copper tube begins to freeze into crystalline ice when plunged into liquid ethane. Crystallization rapidly causes an increase in the pressure to the point that much of the sample freezes in a vitreous state. We used synchrotron X‐ray diffraction of samples frozen with various amounts of dextran to characterize the ice phases and crystal orientation, providing insights on the freezing process. We have characterized cryosections obtained from these samples to explore the optimum amount of cryoprotectant. Images of cryosectioned bacteria frozen with various levels of cryoprotectant illustrate effects of cryoprotectant concentration.     

Defective calcium binding to fibrillin-1: consequence of an N2144S change for fibrillin-1 structure and function

Fibrillin-1 is a major structural component of 10-12 nm connective tissue microfibrils and has a modular organisation that includes 43 calcium binding epidermal growth factor-like (cbEGF) domains and seven transforming growth factor beta-binding protein-like (TB) domains. Mutations in the fibrillin-1 (FBN1) gene cause the Marfan syndrome (MFS) and related connective tissue disorders. We have previously investigated an N2144S change, identified in a MFS patient, which removes one of the key calcium binding ligands within cbEGF domain 32. In this study the structural consequences of the N2144S amino acid change for the folding and calcium binding properties of mutant and wild-type TB6-cbEGF32 and cbEGF32-33 domain pairs have been analysed by nuclear magnetic resonance. The presence of an N2144S substitution does not alter the native fold of either the TB6 domain, or cbEGF domains 32 and 33. Comparison of calcium dissociation constants measured for the wild-type and mutant pairs shows that: (i) the affinity of cbEGF32 is weakly enhanced by N-terminal linkage of TB6 relative to cbEGF32 in isolation; (ii) the affinity of cbEGF32 is approximately ninefold decreased by the N2144S substitution in the TB-cbEGF pair; and (iii) reduced affinity of cbEGF32 does not result in lower affinity of cbEGF33 for calcium. Together, these data suggest that the TB6-cbEGF32 linkage is flexible and the structural effect of the mutation is localised to the interdomain linkage. We have also investigated the effect of defective calcium binding to cbEGF32 on fibrillin-1 produced by N2144S MFS fibroblasts. 35S-pulse-chase analysis shows that the N2144S substitution does not detectably affect fibrillin-1 biosynthesis, rate of secretion or processing. Deposition of reducible fibrillin-1 into the extracellular matrix was also unaffected. The implications of these results for the assembly and properties of the microfibril are discussed.     

Rafting the rapids: Occupational hazards, rewards, and coping strategies of psychotherapists.

In today's market, clinical practitioners have complex and demanding jobs. This survey study identified contemporary occupational hazards, rewards, and coping strategies of 208 psychotherapists and the interrelationships among these variables. Unexpected post hoc gender differences revealed that female therapists reported significantly more rewards and coping strategies than men. Suggestions are offered for how practitioners can promote their own job satisfaction. Implications for supervisors and trainers of psychotherapists are also discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Navigating the nuances: A matrix of considerations for ethical-legal dilemmas.

At one time or another, we all have encountered cases with serious ethical and legal implications. How can we know that we have thoroughly explored every facet of these dilemmas? The authors present a 7-category matrix of the following considerations: moral principles and personal values, clinical and cultural considerations, ethics codes, agency or employer policies, statutes, rules and regulations, and case law. Two clinical examples illustrate the usefulness of this multidimensional framework for professional psychologists. Implications and applications for practitioners and ethics educators are also discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)