Composite analysis of black duck breeding population surveys in eastern North America

Waterfowl are monitored in eastern Canada and the northeastern United States with 2 surveys: a transect survey from fixed-wing aircraft and a plot survey conducted from helicopters. The surveys vary in extent, but overlap exists in a core area of 9 strata covering portions of all provinces from Ontario east to Newfoundland. We estimated population change for American black ducks (Anas rubripes) and mallards (Anas platyrhynchos) from these surveys using a log-linear hierarchical model that accommodates differences in sample design and visibility associated with these survey methods. Using a combined analysis of the surveys based on total indicated birds, we estimate the American black duck population to be 901,700 (95% CI: 715,200–1,274,000) in 2011, with 526,900 (95% CI: 357,500–852,300) mallards in the surveyed area. Precision of estimates varies widely by species and region, with transect surveys providing less precise results than plot surveys for black ducks in areas of overlap. The combined survey analysis for black ducks in the eastern survey region produced estimates with an average yearly coefficient of variation (CV) of 12.1% for the entire area and an average CV of 6.9% in the plot survey area. Mallards, which had a more limited distribution in the region, had an average yearly CV of 22.1% over the entire region, and an average CV of 27.7% in the plot survey area. Hierarchical models provide a rich framework for analyzing and combining results from complex survey designs, providing useful spatial and temporal information on population size and change in these economically important species. © 2012 The Wildlife Society.     

Distribution of zooplankton associated with the Endeavour Ridge Hydrothermal Plume

Enhanced zooplankton biomass was found in shallow (<900 m)and deep (>900 m) net samples collected over the EndeavourRidge hydrothermal plume in 1991 and 1992. This enhanced biomasswas manifest in considerably higher abundance values for mostspecies in proximity to the vent field compared with abundancevalues from net samples collected 10–50 km off-axis. Thespecies most enriched in abundance by the hydrothermal plumewere those normally found in the mid-depth scattering layerat 400–900 m depth. These mid-depth animals were alsothe dominant fauna in the deep scattering layers that overliethe hydrothermal plume at depths of 1200–1900 m near themain vent field. The abundance and biomass dominants were specieswith pronounced ontogenetic migration patterns, and their associatedpredators. The abundance of many typically deep species wasalso enhanced over the main vent field. Faimal compositionsof net samples were compared using a similarity measure andaverage linkage rule. Deep fauna in proximity to the vent fieldbut not associated with scattering layers (Group 1), were similarto deep fauna 10–50 km off axis. The fauna of the deepscattering layer over the vent field (Group 2) was most similarto surface and mid- depth scattering layer fauna found withina 50km radius of the vent field. Statistical tests of linkagesobtained using a bootstrap method indicate that the abundanceand taxonomic composition of the two faunal groups were significantlydistinct in 1992, but not in 1991. We conclude that there wasconsiderable infiltration of shallow fauna into the deep scatteringlayers within 2–3 km of the main vent field, less extensiveinfiltration 10–15 km to the noilh and south of the ventfield in 1991, and insignificant infiltration at stations 50kmto the west of the vent field in 1992. A bootstrap analysiscomparing the faunal composition of nets towed above 900 m depthshowed that shallow fauna were not significantly distinct betweenthe two sampling years or up to 50 km away from the vent field.     

Identification of cDNAs encoding isoprenylated proteins

Isoprenylated proteins are involved in signal transduction, control of cell growth and differentiation, organization of the nuclear lamina and cytoskeleton, and vesicle sorting. The isoprenoid moiety facilitates the interaction of these proteins with membranes and/or other proteins. However, many isoprenylated proteins remain unidentified. A method is described for identifying novel and known cDNAs encoding isoprenylated proteins. Sufficient details of the screening procedure are given so that this method may be easily used to identify cDNAs encoding other covalently modified proteins or proteins possessing high affinity ligand binding sites.     

Patterns of cell division and interkinetic nuclear migration in the chick embryo hindbrain.

Early in its development, the chick embryo hindbrain manifests an axial series of bulges, termed rhombomeres. Rhombomeres are units of cell lineage restriction, and both they and their intervening boundaries form a series that reiterates various features of neuronal differentiation, cytoarchitecture, and molecular character. The segmented nature of hindbrain morphology and cellular development may be related to early patterns of cell division. These were explored by labeling with BrdU to reveal S-phase nuclei, and staining with basic fuchsin to visualise mitotic cells. Whereas within rhombomeres, S-phase nuclei were located predominantly toward the pial surface of the neuroepithelium, at rhombomere boundaries S-phase nuclei were significantly closer to the ventricular surface. The density of mitotic figures was greater toward the centres of rhombomeres than in boundary regions. Mitotic cells did not show any consistent bias in the orientation of division, either in the centres of rhombomeres, or near boundaries. Our results are consistent with the idea that rhombomeres are centres of cell proliferation, while boundaries contain populations of relatively static cells with reduced rates of cell division.     

Effects of electrically induced fatigue on the twitch and tetanus of paralyzed soleus muscle in humans

Shields, Richard K., Laura Frey Law, Brenda Reiling, KellySass, and Jason Wilwert. Effects of electrically induced fatigueon the twitch and tetanus of paralyzed soleus muscle in humans.J. Appl. Physiol. 82(5):1499-1507, 1997.We analyzed the twitch and summated torque(tetanus) during repetitive activation and recovery of the human soleusmuscle in individuals with spinal cord injury. Thirteen individualswith complete paralysis (9 chronic, 4 acute) had the tibial nerveactivated every 1,500 ms with a 20-Hz train (7 stimuli) for 300 ms anda single pulse at 1,100 ms. The stimulation protocol lasted 3 min andincluded 120 twitches and 120 tetani. Minimal changes were found forthe acute group. The chronic group showed a significant reduction inthe torque and a significant slowing of the contractile speeds of boththe twitch and tetanus. The decrease in the peak twitch torque was significantly greater than the decrease in the peak tetanus torque early during the fatigue protocol for the chronic group. The twitch time to peak and half relaxation time were prolonged during fatigue, which was associated with improved fusion of the tetanus torque. At theend of the fatigue protocol, the decrease in the peak twitch torque wasnot significantly different from the decrease in the peak tetanustorque. After 5 min of rest, the contractile speeds recovered causingthe tetanus to become unfused, but the tetanus torque became lessdepressed than the twitch torque. The differential responses for thetwitch and the tetanus suggest an interplay between optimal fusioncreated from contractile speed slowing and excitation contractioncoupling compromise. These issues make the optimal design of functionalelectrical stimulation systems a formidable task.

     

Ischemia dysregulates DNA methyltransferases and p16INK4a methylation in human colorectal cancer cells

Epigenetic modifications are involved in the initiation and progression of cancer. Expression patterns and activity of DNA methyltransferases (DNMTs) are strictly controlled in normal cells; however, regulation of these enzymes is lost in cancer cells due to unknown reasons. Cancer therapies which target DNMTs are promising treatments of hematologic cancers, but they lack effectiveness in solid tumors. Solid tumors exhibit areas of hypoxia and hypoglycaemia due to their irregular and dysfunctional vasculature, and we previously showed that hypoxia reduces global DNA methylation. Colorectal carcinoma (CRC) cells (HCT116 and 379.2; p53^+/+ and p53^-/-, respectively) were subjected to ischemia (hypoxia and hypoglycaemia) in vitro and levels of DNMTs were assessed. We found a significant decrease in mRNA for DNMT1, DNMT3a and DNMT3b, and similar reductions in DNMT1 and DNMT3a protein levels were detected by western blotting. In addition, total activity levels of DNMTs (as measured by an ELISA-based DNMT activity assay) were reduced in cells exposed to hypoxic and hypoglycaemic conditions. Immunofluorescence of HCT116 tumor xenografts demonstrated an inverse relationship between ischemia (as revealed by carbonic anhydrase IX staining) and DNMT1 protein. Bisulfite sequencing of the proximal promoter region of p16^INK4a showed a decrease in 5-methylcytosine following in vitro exposure to ischemia. These studies provide evidence for the downregulation of DNMTs and modulation of methylation patterns by hypoxia and hypoglycaemia in human CRC cells, both in vitro and in vivo. Our findings suggest that ischemia, either intrinsic or induced through the use of anti-angiogenic drugs, may influence epigenetic patterning and hence tumor progression.Key words: DNA methylation, DNA methyltransferases, colorectal carcinoma, ischemia, p53, hypoxia, hypoglycaemia     

A temporal comparison of a benthic infaunal community southwest of St. Lawrence Island, Bering Sea between 2006 and 1970–1974

Benthic infaunal biomass and abundance may be changing in Bering Sea communities. This study compared benthic infaunal biomass, abundance, and community composition southwest of St. Lawrence Island in an important forage area for benthic-feeding birds and mammals between 1970–1974 and 2006. Invertebrate biomass and abundance were significantly greater in 2006 than in 1970–1974 primarily due to high nuculid (Bivalvia) biomass and abundance that contributed 13.2% (biomass) and 8.5% (abundance) to differences in community structure between the sampling periods. This is in contrast to St. Lawrence Island Polynya studies conducted in the 1980s and 1990s that documented decreases in benthic biomass and abundance. Spatial scale of sampling, selective predation, a strong recruitment event, and/or sampling design may account for the difference in trends among the studies.     

Nonlinear regulation of unitary synaptic signals by CaV(2.3) voltage-sensitive calcium channels located in dendritic spines

The roles of voltage-sensitive sodium (Na) and calcium (Ca) channels located on dendrites and spines in regulating synaptic signals are largely unknown. Here we use 2-photon glutamate uncaging to stimulate individual spines while monitoring uncaging-evoked excitatory postsynaptic potentials (uEPSPs) and Ca transients. We find that, in CA1 pyramidal neurons in acute mouse hippocampal slices, CaV(2.3) voltage-sensitive Ca channels (VSCCs) are found selectively on spines and act locally to dampen uncaging-evoked Ca transients and somatic potentials. These effects are mediated by a regulatory loop that requires opening of CaV(2.3) channels, voltage-gated Na channels, small conductance Ca-activated potassium (SK) channels, and NMDA receptors. Ca influx through CaV(2.3) VSCCs selectively activates SK channels, revealing the presence of functional Ca microdomains within the spine. Our results suggest that synaptic strength can be modulated by mechanisms that regulate voltage-gated conductances within the spine but do not alter the properties or numbers of synaptic glutamate receptors.     

A defect in synapsis causes male sterility in a T-DNA-tagged Arabidopsis thaliana mutant

Fluorescence microscopy was used to study meiosis in microsporocytes from wild-type Arabidopsis thaliana and a T-DNA-tagged meiotic mutant. Techniques for visualizing chromosomes and β-tubulin in other plant species were evaluated and modified in order to develop a method for analyzing meiosis in A. thaliana anthers. Like most dicots, A. thaliana microsporocytes undergo simultaneous cytokinesis in which both meiotic divisions are completed prior to cytokinesis. However, two unique events were observed in wild-type A. thaliana that have not been reported in other angiosperms: (1) polarization of the microsporocyte cytoskeleton during prophase I prior to nuclear envelope breakdown, and (2) extensive depolymerization of microtubules just prior to metaphase II. The first observation could have implications regarding a previously uncharacterized mechanism for determining the axis of the metaphase I spindle during microsporogenesis. The second observation is peculiar since microtubules are known to be involved in chromosome alignment in other species; possible explanations will be discussed. A T-DNA-tagged meiotic mutant of A. thaliana ( syn1 ), which had previously been shown to produce abnormal microspores with variable DNA content, was also cytologically characterized. The first observable defect occurs in microsporocytes at telophase I, where some chromosomes are scattered throughout the cytoplasm, usually attached to stray microtubules. Subsequent developmental stages are affected, leading to complete male sterility. Based on similarities to synaptic mutants that have been described in other species, it is suggested that this mutant is defective in synaptonemal complex formation and/or cohesion between sister chromatids.