Effects of Osmotic Shock on Some Membrane-regulated Events of Oat Coleoptile Cells

Oat coleoptile sections (Avena sativa L. cv. "Garry") were osmotically shocked with 0.5 m mannitol followed by 1 mm Na-phosphate (pH 6.4) at 4 C. This treatment reduced uptake of alpha-aminoisobutyric acid, 3-o-methyl glucose, and leucine by 75 to 90% but inhibited (36)Cl(-) uptake only 30%. Some recovery was observed 1 to 3 hours later. Respiration rates were unaffected by osmotic shock and protein synthesis was reduced 11%.Osmotic shock also stimulated efflux of alpha-aminoisobutyric acid and K(+) and led to an increase in conductivity of the solution bathing shocked sections. The transmembrane electropotential of 75% of the shocked cells fell to -20 mv to -45 mv compared with the majority of unshocked cells at -80 mv to -120 mv.We concluded that osmotic shock selectively modifies the plasma membrane. The inhibitions of uptake could be due to removal of specific components of the plasma membrane and/or to the lowered electropotential.     

Mechanochemical coupling in spin-labeled, active, isometric muscle

Observed effects of inorganic phosphate (P(i)) on active isometric muscle may provide the answer to one of the fundamental questions in muscle biophysics: how are the free energies of the chemical species in the myosin-catalyzed ATP hydrolysis (ATPase) reaction coupled to muscle force?. Pflugers Arch. 414:73-81) showed that active, isometric muscle force varies logarithmically with [P(i)]. Here, by simultaneously measuring electron paramagnetic resonance and the force of spin-labeled muscle fibers, we show that, in active, isometric muscle, the fraction of myosin heads in any given biochemical state is independent of both [P(i)] and force. These direct observations of mechanochemical coupling in muscle are immediately described by a muscle equation of state containing muscle force as a state variable. These results challenge the conventional assumption mechanochemical coupling is localized to individual myosin heads in muscle.     

Real-time imaging of the dynamics of secretory granules in growth cones

Secretory granules containing a hybrid protein consisting of the regulated secretory protein tissue plasminogen activator and an enhanced form of green fluorescent protein were tracked at high spatial resolution in growth cones of differentiated PC12 cells. Tracking shows that granules, unlike synaptic vesicles, generally are mobile in growth cones. Quantitative analysis of trajectories generated by granules revealed two dominant modes of motion: diffusive and directed. Diffusive motion was observed primarily in central and peripheral parts of growth cones, where most granules diffused two to four orders of magnitude more slowly than comparably sized spheres in dilute solution. Directed motion was observed primarily in proximal parts of growth cones, where a subset of granules underwent rapid, directed motion at average speeds comparable to those observed for granules in neurites. This high-resolution view of the dynamics of secretory granules in growth cones provides insight into granule organization and release at nerve terminals. In particular, the mobility of granules suggests that granules, unlike synaptic vesicles, are not tethered stably to cytoskeletal structures in nerve terminals. Moreover, the slow diffusive nature of this mobility suggests that secretory responses involving centrally distributed granules in growth cones will occur slowly, on a time scale of minutes or longer.     

Impact modeling of gymnastic back-handsprings and dive-rolls in children

This study was to determine estimates of the stiffness and damping properties of the wrist, and shoulder in children by examining wrist impacts on the outstretched hand in selected gymnastic activities. The influence of age, mass, and wrist and torso impact velocity on the stiffness and damping properties were also examined. Fourteen young gymnasts (ages 8 to 15 yrs) were videotaped while performing back-handspring trials or dive-rolls. Kinematic and ground reaction analysis provided input for computer simulation of the body as a rheological model with appropriate stiffness and damping. A significant positive linear relationship was obtained between wrist damping in dive rolls and age, mass, and wrist and torso impact velocity, while shoulder damping in the back-handsprings had a significant positive linear relationship with body mass. This new information on stiffness and damping at the shoulder and the wrist in children enables realistic mathematical modeling of children's physical responses to hand impact in falls. This is significant because modeling studies can now be used as an alternative to epidemiological studies to evaluate measures aimed at reducing injuries in gymnastics and other activities involving impact to the upper extremity.     

Spermatogenesis in Bclw-deficient mice.

Bclw is a death-protecting member of the Bcl2 family of apoptosis-regulating proteins. Mice that are mutant for Bclw display progressive and nearly complete testicular degeneration. We performed a morphometric evaluation of testicular histopathology in Bclw-deficient male mice between 9 days postnatal (p9) through 1 yr of age. Germ cell loss began by p22, with only few germ cells remaining beyond 7 mo of age. A complete block to elongated spermatid development at step 13 occurred during the first wave of spermatogenesis, whereas other types of germ cells were lost sporadically. Depletion of Sertoli cells commenced between p20 and p23 and continued until 1 yr of age, when few, if any, Sertoli cells remained. Mitochondria appeared to be swollen and the cytoplasm dense by electron microscopy, but degenerating Bclw-deficient Sertoli cells failed to display classical features of apoptosis, such as chromatin condensation and nuclear fragmentation. Macrophages entered seminiferous tubules and formed foreign-body giant cells that engulfed and phagocytosed the degenerated Sertoli cells. Leydig cell hyperplasia was evident between 3 and 5 mo of age. However, beginning at 7 mo of age, Leydig cells underwent apoptosis, with dead cells being phagocytosed by macrophages. The aforementioned cell losses culminated in a testis-containing vasculature, intertubular phagocytic cells, and peritubular cell "ghosts." An RNA in situ hybridization study indicates that Bclw is expressed in Sertoli cells in the adult mouse testis. Consequently, the diploid germ cell death may be an indirect effect of defective Sertoli cell function. Western analysis was used to confirm that Bclw is not expressed in spermatids; thus, loss of this cell type most likely results from defective Sertoli cell function. Because Bclw does not appear to be expressed in Leydig cells, loss of Leydig cells in Bclw-deficient mice may result from depletion of Sertoli cells. Bclw-deficient mice serve as a unique model to study homeostasis of cell populations in the testis.     

A limited survey of aflatoxins and fumonisins in retail maizebased products in the UK using immunoassay detection

A total of 27 maize-based products destined for human consumption were collected from retail outlets within the city of Glasgow in the UK and were analysed for the presence of aflatoxins using immunoaftinity column chromatography with fluorescence detection and for fumonisins by competitive ELISA. Aflatoxins were detected at a trace level below 4 in eight (30%) of the 27 samples tested, no sample contained aflatoxins at a high level although one sample of sweetcorn did contain aflatoxins at a level of 5-10 Fumonisins were detected in eight (30%) of the samples at levels from 1 to 8mgkg^-1 and a further eight samples contained fumonisin at a level below 1 mgkg^-1 but above the detectable level. The highest concentration of fumonisins was found in a sample of fine corn meal at 8-12mgkg^-1.     

Partial protein domains: evolutionary insights and bioinformatics challenges

Protein domains are generally thought to correspond to units of evolution. New research raises questions about how such domains are defined with bioinformatics tools and sheds light on how evolution has enabled partial domains to be viable.With the rapid expansion in the number of determined protein sequences - over 92 million in UniProt in March 2015 - an ever-increasing number of biologists are using bioinformatics tools for annotation of these sequences. One widely used strategy is to identify occurrences of Pfam families within the sequence of interest [1]. A Pfam family is a multiple sequence alignment of the occurrences of a particular domain both in different species and in different regions of the same protein. The concept underpinning Pfam is that proteins typically comprise one or more domains (regions), each of which is an evolutionary unit that generally has a well-defined biological function. A significant sequence similarity between a query protein and a Pfam family provides the basis for annotations. Two recent articles [2,3] in Genome Biology evaluate the implications of having the query sequence only matching part of a Pfam family, which is an intriguing finding, given that a Pfam family is considered to be an evolutionary unit.     

The evolutionary emergence of stochastic phenotype switching in bacteria

Stochastic phenotype switching - or bet hedging - is a pervasive feature of living systems and common in bacteria that experience fluctuating (unpredictable) environmental conditions. Under such conditions, the capacity to generate variable offspring spreads the risk of being maladapted in the present environment, against offspring likely to have some chance of survival in the future. While a rich subject for theoretical studies, little is known about the selective causes responsible for the evolutionary emergence of stochastic phenotype switching. Here we review recent work - both theoretical and experimental - that sheds light on ecological factors that favour switching types over non-switching types. Of particular relevance is an experiment that provided evidence for an adaptive origin of stochastic phenotype switching by subjecting bacterial populations to a selective regime that mimicked essential features of the host immune response. Central to the emergence of switching types was frequent imposition of 'exclusion rules' and 'population bottlenecks' - two complementary faces of frequency dependent selection. While features of the immune response, exclusion rules and bottlenecks are likely to operate in many natural environments. Together these factors define a set of selective conditions relevant to the evolution of stochastic switching, including antigenic variation and bacterial persistence.     

Scats and den contents as indicators of the diet of stoats (Mustela erminea) in the Tasman Valley,South Canterbury,New Zealand

Stoats are significant predators of native fauna in New Zealand. They occur in many habitat types and consume a wide range of prey. The diet of stoats in the Tasman River, South Canterbury, was studied by analysis of scats and den contents. Analysis of 206 scats showed that stoats ate mainly lagomorphs, birds and invertebrates. Minor components included mice, lizards, fish and hedgehogs. Stoats ate more birds in spring than in autumn, and female stoats ate more invertebrates than did males. The contents of 219 dens collected in the same area at the same time provided further information. Birds and lagomorphs occurred at high frequency in dens, and other components were minor. Remains in dens were larger than in scats and allowed identification of many more prey items to species level. Den contents revealed a potentially substantial impact of stoats on threatened shorebirds locally; this impact was not detected by analysis of scats.     

Genetic variability and population structure in Sapindus emarginatus Vahl from India

Sapindus emarginatus is an economically important tropical tree species sparsely distributed in different geographical provinces like Gangetic Plains, Western Ghats, and Deccan Plateau in India. In the present paper estimation of genetic variability within and among 41 accessions representing five populations was carried out using 3 single primer amplification reaction (SPAR) methods viz. RAPD, DAMD and ISSR. The cumulative data analysis was carried out for all three SPAR methods, and showed 82.32% polymorphism across all the accessions of S. emarginatus. Jaccard's similarity values among 41 accessions ranged from 0.15 to 0.49 with an average value of 0.37. The intra-population genetic diversity revealed highest values of Nei's genetic diversity (0.19,) Shannon information index (0.29) and polymorphic loci (55.18%), among the accessions of Gujarat (GJ) population, while the corresponding lowest values were (0.10), (0.15) and (26.40%) respectively among the accessions of Rajasthan (RJ) population. The maximum inter-population average genetic distance (0.20) was between Karnataka (KA) and RJ, while the corresponding least genetic distance (0.06) was between Allahabad (AL) and Varanasi (VS) populations. The analysis of molecular variance (AMOVA) revealed maximum percentage of variation among individuals of populations (72%) followed by 16% among regions and 12% among populations. Principal coordinate analysis (PCA) of cumulative data also supported the clustering pattern in the UPGMA dendrogram. These results suggest that genetic diversity is corroborating with the geographical diversity. Mantel's test was performed which revealed a highly significant correlation between cumulative vs RAPD, and showed the maximum (0.93) correlation coefficient, followed by cumulative vs ISSR (0.78) and cumulative vs DAMD (0.91) respectively, and this clearly indicates that the SPAR methods (RAPD, DAMD and ISSR) are sufficiently informative and are suitable to analyze the genetic variability within and among the populations of S. emarginatus.