Analysis of a BrdU-sensitive site in the cactus mouse (Peromyscus eremicus): chromosomal breakage and sister-chromatid exchange

When the thymidine analog BrdU was incorporated into the DNA of a fibroblast cell line derived from the cactus mouse Peromyscus eremicus, a chromosome region with an increased frequency of gaps and breaks was observed. Nearly a third of the chromatid aberrations found at this site were associated with a sister-chromatid exchange (SCE) although this chromosome region showed no increase in sister-chromatid exchange in the absence of a gap or break. SCEs were significantly decreased in the remainder of the chromosome arm when it contained an aberration at the unstable site. This BrdU-sensitive region, unlike others reported, was found not to be late-replicating. — In this chromosome complement, the frequency of sisterchromatid exchange in C-band positive regions was significantly lower than that in C-band negative regions.     

Enhanced rate of ethanol production from D-xylose using recycled or immobilized cells ofPachysolen tannophilus

Summary Enhanced rates of ethanol production byPachysolen tannophilus from D-xylose were obtained by performing the fermentation with recycled cells in suspension culture or immobilized in a Ca-alginate gel. Fermentation under these conditions did not require aeration. Increasing temperature from 30 to 37°C enhanced the amount of ethanol produced in 24 hours from the recycled or the immobilized cells.Issued as National Research Council of Canada Publication Number 19475.     

A radiochemical assay for N-acetyl-L-aspartate amidohydrolase (EC 3.5.1.15) and its occurrence in the tissues of the chicken

A simple and rapid radiochemical method for the determination of N-acetyl-L-aspartic acid amidohydrolase (EC 3.5.1.15) activity using ion exchange chromatography has been developed. The activity of this enzyme in the developing brain and some non-nervous tissues of the chicken has been determined. No activity of the enzyme could be detected in the brains of chick embroys prior to 14 days of gestation; activities gradually increased thereafter to adult levels which are about 60% of that found in the adult rat. In non-nervous system tissues of the adult chicken, activities varied from high levels in the kidney to low levels in heart and breast muscle. Treatment of the homogenates of the adult tissues with a detergent significantly increased the enzyme activity, suggesting that a portion of the enzyme is membrane bound.     

Respiration and carbohydrate energy metabolism of the lung-dwelling parasite Rhabdias bufonis (Nematoda: Rhabdiasoidea)

An investigation of the carbohydrate energy metabolism of Rhabdias bufonis, the lung-dwelling nematode parasite of the African toad, Bufo regularis, indicates that the nematode stores very little glycogen (0.137 +/- 0.003% on a fresh weight basis) but does utilize oxygen in vitro. The intracellular distribution and high levels of activity observed for the enzymes phosphoenolpyruvate carboxykinase, pyruvate kinase, lactate dehydrogenase, malate dehydrogenase, malic enzyme and fumarate reductase suggest two alternative pathways of carbohydrate energy metabolism.     

Fermentation of D-xylose, xylitol, and D-xylulose by yeasts

Fifteen yeasts which can assimilate D-xylose were examined for the ability to convert this pentose to ethanol. In six of the seven genera investigated the conversion was enhanced when air had access to the medium. Therefore, the ability to convert D-xylose to ethanol under these conditions is probably common among yeasts. Growth under the same conditions on xylitol, a putative catabolite of D-xylose, led to only traces of ethanol. The effects of growth on another putative catabolite, D-xylose, were complex, but some of the strains which were among the better producers of ethanol from D-xylose produced less from D-xylulose.     

Online control of evaluation algorithms of the image applied to identification of deglutition function]

Comprehensive software and hardware have been developed for the processing of biosignals. Such automatic signal processing, however not only has advantages, but also drawbacks. The question as to the reliability of the evaluation algorithm arises when the signal is modified, in the presence of interindividual differences, and in particular when noise is superimposed. This is of great interest for long-term recording when the original signal can no longer be inspected visually. The aim of our work was to display the signals on the screen of a monitor simultaneously with lines marking the points (start, end, extreme value, etc.) processed by the specific signal processing algorithm. The program package permits the on-line recording and monitoring of signals, the parallel processing and marking of detected events on the monitor, as well as storage of the parameters extracted. It is a very effective tool for developing, improving and monitoring of algorithms and their efficiency for signal processing.     

Structure of the smooth muscle myosin light-chain kinase calmodulin-binding domain peptide bound to calmodulin

The interaction between the peptide corresponding to the calmodulin-binding domain of the smooth muscle myosin light-chain kinase and (Ca2+)4-calmodulin has been studied by multinuclear and multidimensional nuclear magnetic resonance methods. The study was facilitated by the use of 15N-labeled peptide in conjunction with 15N-edited and 15N-correlated 1H spectroscopy. The peptide forms a 1:1 complex with calcium-saturated calmodulin which is in slow exchange with free peptide. The 1H and 15N resonances of the bound have been assigned. An extensive set of structural constraints for the bound peptide has been assembled from the analysis of nuclear Overhauser effects and three-bond coupling constants. The backbone conformation of the bound peptide has been determined using these constraints by use of distance geometry and related computational methods. The backbone conformation of the peptide has been determined to high precision and is generally indicative of helical secondary structure. Nonhelical backbone conformations are seen in the middle and at the C-terminal end of the bound peptide. These studies provide the first direct confirmation of the amphiphilic helix model for the structure of peptides bound to calcium-saturated calmodulin.     

An analog of ACTH/MSH (4–9), ORG-2766, reduces cerebral uptake of morphine

The uptake of morphine was significantly reduced in most regions of the brains of conscious, unrestrained rats within 10 minutes after treatment with an analog of ACTH/MSH (4–9), ORG-2766. The effect was most obvious in regions with significant densities of enkephalin receptors, namely basal ganglia, hippocampus and cortex. The results explain, in part, how some fragments and analogs of ACTH/MSH may antagonize behavioral actions of morphine, even though some of these peptides lack significant opiate receptor binding properties. We believe that this effect of ORG-2766 is related to an action on the permeability characteristics of the brain microvasculature. The underlying mechanism is unknown.