Crenation and cupping of the red cell: A new theoretical approach. Part II. Cupping

Typical, axisymmetrical cup shaped cells have been carefully measured and the shapes analyzed mathematically. The results show that the strain energy of a cup shaped cell is always higher than that of a biconcave cell except when the two layers of the membrane involved in resistance to bending are free to slide over one another. This is true whether intrinsic curvature of the membrane is positive, negative or zero. If the two layers can slide over one another, the cup shape becomes the lower energy form. Shear resistance, if appreciable, must cause the cup cell to buckle. Photomicrographs of cup shaped cells show buckled configurations characteristic of those of a partly deflated thin-walled rubber ball, which is a similar object having a low ratio of bending/shear strength.In light of these findings, the cup shape of the red cell can no longer be considered as evidence of intrinsic membrane curvature of opposite sign to that of the crenated cell, but appears to indicate a phase change either in the hydrophobic interior of the bimolecular membrane or in some equivalent interface.     

Bubble splitting in bifurcating tubes: a model study of cardiovascular gas emboli transport.

The transport of long gas bubbles, suspended in liquid, through symmetric bifurcations, is investigated experimentally and theoretically as a model of cardiovascular gas bubble transport in air embolism and gas embolotherapy. The relevant dimensionless parameters in the models match the corresponding values for arteries and arterioles. The effects of roll angle (the angle the plane of the bifurcation makes with the horizontal), capillary number (a dimensionless indicator of flow), and bubble volume (or length) on the splitting of bubbles as they pass through the bifurcation are examined. Splitting is observed to be more homogenous at higher capillary numbers and lower roll angles. It is shown that, at nonzero roll angles, there is a critical value of the capillary number below which the bubbles do not split and are transported entirely into the upper branch. The value of the critical capillary number increases with roll angle and parent tube diameter. A unique bubble motion is observed at the critical capillary number and for slightly slower flows: the bubble begins to split, the meniscus in the lower branch then moves backward, and finally the entire bubble enters the upper branch. These findings suggest that, in large vessels, emboli tend to be transported upward unless flow is unusually strong but that a more homogeneous distribution of emboli occurs in smaller vessels. This corresponds to previous observations that air emboli tend to lodge in the upper regions of the lungs and suggests that relatively uniform infarction of tumors by gas embolotherapy may be possible.     

Metapopulation extinction risk is increased by environmental stochasticity and assemblage complexity

Extinction risk is a key area of investigation for contemporary ecologists and conservation biologists. Practical conservation efforts for vulnerable species can be considerably enhanced by thoroughly understanding the ecological processes that interact to determine species persistence or extinction. Theory has highlighted the importance of both extrinsic environmental factors and intrinsic demographic processes. In laboratory microcosms, single-species single-habitat patch experimental designs have been widely used to validate the theoretical prediction that environmental heterogeneity can increase extinction risk. Here, we develop on this theme by testing the effects of fluctuating resource levels in experimental multispecies metapopulations. We compare a three-species host-parasitoid assemblage that exhibits apparent competition to the individual pairwise, host-parasitoid interactions. Existing theory is broadly supported for two-species assemblages: environmental stochasticity reduces trophic interaction persistence time, while metapopulation structure increases persistence time. However, with increasing assemblage complexity, the effects of trophic interactions mask environmental impacts and persistence time is further reduced, regardless of resource renewal regime. We relate our findings to recent theory, highlighting the importance of taking into account both intrinsic and extrinsic factors, over a range of spatial scales, in order to understand resource-consumer dynamics.     

An Experimental Evaluation of Different Methods of Restoring Phyllospadix torreyi (Surfgrass)

The surfgrass Phyllospadix torreyi is an abundant seagrass found on rocky exposed shores of the Pacific coast of North America. In southern California surfgrass populations are adversely affected by a range of natural events and anthropogenic activities. Few attempts have been made to develop restoration methods for surfgrass, and none have investigated the efficacy of using different life stages. We evaluated several techniques for restoration in intertidal and subtidal habitats using: (1) laboratory‐reared seedlings transplanted to the field (2) sprigs (short lengths of rhizome containing a few shoots) transplanted from undisturbed populations, and (3) plugs (a cohesive clump of shoots and rhizomes) transplanted from undisturbed populations. We calculated the net change in the aerial coverage of surfgrass after 6 months, taking into account the recovery or additional losses from the donor population, and amount of effort involved in transplanting. Transplanted seedlings survived poorly and had minimal rhizome growth at both the intertidal and the subtidal sites, yet the individuals that did survive showed a 275% increase in leaf number. Survivorship of transplanted plugs was high in both habitats; however, physical disturbances to the donor populations exacerbated damage sustained at the time of collecting, yielding a substantial net loss in surfgrass. Sprigs transplanted to the subtidal had higher survivorship (71 versus 48%) and a greater increase in the aerial coverage of rhizome (86 versus 42%) than those transplanted to the intertidal. Of the three techniques, transplanted sprigs had the greatest overall increase in aerial coverage per unit effort, suggesting that this method may be the most effective approach for restoring P. torreyi.     

Distribution and abundance of coral plankton

High densities of eggs and larvae of scleractinian corals were found in plankton samples after mass, multi-specific spawnings on inshore high island fringing reefs in the central Great Barrier Reef region. Immediately after spawning, vertical stratification was observed with eggs concentrated on the surface. Larvae were found to be distributed vertically and horizontally within 12 hours of spawning. Larval development over the subsequent 6–7 days was associated with an increase in the length/width ratios of larvae and their volumes. Influxes of mature larvae onto the study reef were observed 3–6 days after spawning. The relative success of the sampling in relation to other reports in the literature, and the future for more informed work on the larval ecology of corals are discussed.     

A Few-Polyhedra Mutant and Wild-Type Nucleopolyhedrovirus Remain as a Stable Polymorphism during Serial Coinfection in Trichoplusia ni

Few-polyhedra (FP) mutants of nucleopolyhedroviruses (NPVs) are a well-known phenomenon during serial passage of virus in cell culture. Under these circumstances such mutants produce low yields of occlusion bodies (OBs) and poorly occlude virions, but they are selected for through advantageous rates of budded virus replication. Spontaneous insertion of transposable elements originating from host cell DNA into the viral fp25 gene has been shown to be a common cause of the phenotype. A model of NPV population genetics predicts that mutants with these characteristics might persist within stable polymorphisms in viral populations during serial passage of virus in vivo. However, this hypothesis was previously untested, and FP mutants have not been recovered from field isolates of NPVs. We isolated and characterized an FP mutant that arose during routine passage of Autographa californica multinucleocapsid NPV (AcMNPV) in cell culture and identified a transposable element within the fp25 gene. We tracked the fates of coinfecting wild-type and FP mutant AcMNPV strains through serial passage in fifth-instar Trichoplusia ni larvae. The levels of both strains remained stable during successive rounds of infection. We applied the data obtained to a model of NPV population genetics in order to derive the frequency distribution of the multiplicity of cell infection in infected insects and estimated that 4.3 baculovirus genomes per OB-producing cell would account for this equilibrium.     

Classifying genotypic data from plant breeding trials: a preliminary investigation using repeated checks

Summary Several subjective choices must be made when classifying genotypes based on data from plant breeding trials. One choice involves the method used to weight the contribution each environment makes to the classification. A second involves the use of either genotype-means for each environment or genotypevalues for each block, i.e., considering each block to be a different environment. Another involves whether environments (or blocks) in which genotypes are nonsignificantly different should be included or excluded from such classifications. An alternative to the use of raw or standardized data, is proposed in which each environment is weighted by a discrimination index (DI) that is based on the concept of repeatability. In this study the effect of three weighting methods (raw, standardized and DI), the choice of using environments or blocks, and the choice of including or excluding environments or blocks in which genotypic effects were not significant, were considered in factorial combination to give 12 options. A data set comprised of five check cultivars each repeated six times in each of three blocks at six environments was used. The effect of these options on the ability of a hierarchical clustering technique to correctly classify the repeats into five groups, each consisting of all the six repeats of a particular check cultivar, was investigated. It was found that the DI weighting method generally led to better recovery of the known structure. Using block data rather than environmental data also improved structure recovery for each of the three weighting methods. The exclusive use of environments in which genotypic effects were significant decreased structure recovery while the contrary generally occurred for blocks. The best structure recovery was obtained from the DI weighting applied to blocks (whether genotypes were significant or not).     

Post-construction avian mortality monitoring at Project West Wind

Abstract

Post-construction avifauna investigations were undertaken at Project West Wind, Meridian Energy Limited's 62-turbine wind farm on the Wellington south coast. These investigations were required in accordance with the resource consent conditions to quantify the level of avian mortalities occurring at the wind farm, particularly in regard to New Zealand falcon (Falco novaeseelandiae), kākā (Nestor meridionalis) and kererū (Hemiphaga novaeseelandiae). This is the first comprehensive study at a New Zealand operating wind farm. The methods included three field components necessary to calculate annual estimates of mortalities across the wind farm site: routine turbine searches; carcass detection trials; and carcass removal trials. Results from years 1 and 2 of a three-year programme are presented. To date, mortalities have been recorded for 17 taxa at 18 of the 24 study turbines. There have been no recorded mortalities of falcon, kākā or kererū. Australasian harrier (Circus approximans) has been the species for which the most mortalities have been recorded. Overall estimated annual mortality rates for years 1 and 2 were calculated to be approximately six and five birds per turbine respectively.     

Effect of lipid supplements on the production and glycosylation of recombinant interferon-γ expressed in CHO cells

The effects of lipids on the glycosylation of recombinant human interferon- expressed in a Chinese Hamster Ovary cell line were investigated in batch culture. Lipids form an essential part of the N-glycosylation pathway, and have been shown to improve cell viability. In control (serum-free) medium the proportion of fully-glycosylated interferon- deteriorated reproducibly with time in batch culture, but the lipoprotein supplement ExCyte was shown to minimise this trend. Partially substituting the bovine serum albumin content of the medium with a fatty-acid free preparation also improved interferon- glycosylation, possibly indicating that oxidised lipids carried on Cohn fraction V albumin may damage the glycosylation process.Abbreviations BSA bovine serum albumin - CHO chinese hamster ovary - DHFR dihydrofolate reductase - FCS foetal calf serum - IFN- human interferon-gamma - q _IFN specific interferon production rate - specific growth rate - 2N doubly-gycosylated - 1N singly-glycosylated - ON non-glycosylated     

Combining data in phylogenetic analysis

Systematists have access to multiple sources of character information in phylogenetic analysis. For example, it is not unusual to have nucleotide sequences from several different genes, or to have molecular and morphological data. How should diverse data be analyzed in phylogenetic analysis? Several methods have been proposed for the treatment of partitioned data: the total evidence, separate analysis, and conditional combination approaches. Here, we review some of the advantages and disadvantages of the different approaches, with special concentration on which methods help us to discern the evolutionary process and provide the most accurate estimates of phylogeny.