Cohesive properties of axenically grown cells of the slime mould Dictyostelium discoideum

It has been found that Dictyostelium discoideum cells from the exponential growth phase of axenically grown cultures are cohesive, whereas those from stationary phase are not. These differences in cohesiveness are seen in phosphate buffer and in axenic medium. Stationary phase medium inhibits the aggregation of log phase cells; stationary phase cells inoculated into freshly prepared medium regain their cohesiveness. Stationary phase medium may contain an inhibitor of cell cohesion. pH differences between the two types of medium are not entirely responsible for loss of cohesiveness.     

Effect of triton X-100 on ultrastructure,reactivation, and motility characteristics of ram spermatozoa

For optimal extraction and reactivation of ram sperm, glutamate, dithiothreitol, magnesium, and cyclic AMP were required in a medium of pH 7.9. On extraction with 0.01 % Triton X-100, ram sperm were only partially demembranated, and extensive areas of plasma membrane remained intact especially in the midpiece region. Treatment with 0.1% Triton X-100 removed all plasma membranes and extracted the mitochondrial membrane and matrix. In the absence of ATP, 16.6% ± 0.4 of the partially demembranated sperm were motile, but sperm extracted with 0.1% Triton X-100 were completely immotile. On adding ATP partially demembranated sperm reactivated better (81.6% ± 2.8) than sperm completely demembranated in 0.1 % Triton X-100 (39.5% ± 4.6). The release of intracellular LDH rose linearly with increasing concentrations of the detergent from 0.01 to 0.05%, at which it plateaued. There was a significant increase in beat frequency and forward velocity of partially demembranated sperm when treated with ATP. Partially demembranated sperm had intact mitochondria that presumably were still able to produce ATP, although the spermatozoan movement was stimulated by exogenous ATP.     

Effect of Intraluminal pH on the Absorption of Pteroylmonoglutamic Acid

The administration of pteroylmonoglutamic acid and either sodium bicarbonate or phenytoin sodium in normal subjects and epileptics results in lower serum levels of folic acid than when administered alone. Bicarbonate administration was shown to produce a more alkaline pH in the jejunum, while an alkaline pH was found in some epileptics on phenytoin therapy. The physicochemical mechanisms whereby folic acid absorption is reduced in an alkaline medium are considered, and the implications on folate absorption in other disease states are discussed. The mechanism by which phenytoin sodium alters the intrajejunal milieu is obscure.     

The use of cross prediction methods in a practical potato breeding programme

Summary Most previous studies on cross prediction methods have examined relatively few crosses, particularly in relation to the numbers involved in most breeding programmes. In this paper the feasibility of using cross prediction methods was examined in a practical potato (Solanum tuberosum) breeding scheme by the analyses of progeny from 52 crosses. The variate considered was breeder's preference, a visual assessment made of the harvested tubers to estimate their commercial potential. The results showed that it was possible to identify the superior crosses. Cross prediction based simply on the mean preference scores, averaged over scorers and clones within progenies, estimated on seedlings or first clonal year plants, provided the best estimate of a progeny's performance in the third clonal generation. Predictions based on the expected proportion of clones that would transgress a given target value also provided a good indication of a progeny's potential. The poorest prediction was obtained by using the observed frequency of desirable clones in a progeny sample. The implications for potato breeding are discussed.     

Vitamin D status and determinants of deficiency in non-supplemented athletes during the winter months in Tunisia

Recent reports suggest that hypovitaminosis D in athletes is as common as in the general population. This study was devised to examine vitamin D status and determinants of deficiency in athletes living in a sunny country (Tunisia). One hundred and fifty national elite athletes, training outdoors (n = 83) or indoors (n = 67), were enrolled from January to February 2012. Plasma 25-hydroxyvitamin D was measured by radioimmunoassay. Concentrations were between 50 and 75 nmol · l^-1 in 21.3% of participants, between 25 and 50 nmol · l^-1 in 55.3% of participants and <25 nmol · l^-1 in 14.7% of participants. The concentrations were significantly lower in indoor athletes than outdoor athletes (36.2±19.0 nmol · l^-1 vs. 49.1±19.2 nmol · l^-1; p < 0.001). In multivariate analysis, vitamin D deficiency (25-hydroxyvitamin D <50 nmol · l^-1) was associated with indoor sports [multi-adjusted odds ratio (95% confidence interval), 5.03 (1.64-15.4); p = 0.005], female gender [3.72 (1.44-9.65); p = 0.007] and age < 18 years [2.40 (1.01-5.85); p = 0.05]. Athletes living in sun-rich environments are exposed to a high risk of vitamin D inadequacy. Given the importance of vitamin D in health and athletic ability, targeting sufficient levels of plasma 25-hydroxyvitamin D in athletes is well justified.     

Solution of linear one-dimensional diffusion equations

The paper introduces a basic mathematical form, which is characteristic of a number of linear one-dimensional diffusion equations with coefficients being represented as simple polynomials in the spatial coordinate. A number of particular diffusion equations are introduced and their corresponding exact mathematical solutions are obtained.