Interactions of Vesicular Stomatitis Virus Structural Proteins with HeLa Plasma Membranes

THE processes whereby nucleoprotein core particles of certain animal viruses become enveloped by and bud off from host cell membranes can be studied by preparing membrane^1,2 or “sedimentable”³ fractions from infected cells and examining them for the presence of virus proteins. We find that similar experiments designed to monitor assembly of vesicular stoma-titus virus (VSV) at sites along the plasma membranes of HeLa cells are best interpreted after first investigating the possibility that virus proteins adsorb to plasma membranes during cell fractionation and membrane isolation. In this report, we show that at 0° C the membrane protein of VSV, among other virus proteins, adsorbs to plasma membranes isolated from uninfected HeLa cells. With appropriate pulse-chase experiments, however, we are able to demonstrate the progressive association, in vivo, of VSV core protein with plasma membranes of infected HeLa cells.     

Physical and Serologic Properties of an Antigen Prepared from Erythrocytes of Horses with Acute Babesiosis*

SYNOPSIS. By means of precipitation with protamine sulfate, a soluble antigen (PS) was obtained from erythrocytes of horses with acute babesiosis due to Babesia caballi and B. equi. This antigen reacted in gel diffusion tests with sera from horses recovered from acute babesiosis. The PS antigen was found to be muco-protein, susceptible to destruction by trypsin and taka-diastase. Analysis of the antigen by paper electrophoresis revealed 2 components which were not present in similar preparations made from erythrocytes of Babesia-free horses. When the PS antigen was heated in boiling water for 30 minutes, a serologically inactive precipitate was formed; however, the supernate remained serologically active and was termed boiled PS (BPS) antigen. This antigen was polysaccharide in nature; its serologic activity was destroyed by taka-diastase. In gel diffusion tests with sera of recovered horses, the PS antigen formed 2 lines of precipitation which coalesced in a single line formed between these sera and the BPS antigen. Both PS and BPS antigens reacted with sera of horses recovered from acute babesiosis in the gel-diffusion test, but not with sera of dogs and rats recovered from acute infection with Babesia canis and Babesia rodhaini, respectively. The serologic specificity of these antigens suggests that they might have application in the serodiagnosis of inapparent Babesia infections of equine animals.     

The Role of Extracellular Ca2+ in the Activation of Pectinaria Oocytes

Several events are associated with fertilization in oocytes. Two such events are an increase in cytoplasmic Ca²⁺ concentration and the resumption of meiosis. Oocytes of the marine annelid, Pectinaria gouldii , are in metaphase I arrest when they are spawned. In this report we investigate the relationship between Ca²⁺ and resumption of meiosis in this species. Meiosis in unfertilized oocytes could be re-initiated with the divalent cation ionophore, A23187. Oocytes in Ca²⁺ free sea water, however, did not resume meiosis in the presence of the ionophore. Furthermore, it was observed that Ca²⁺ must be present for at least 15 min following ionophore treatment for meiosis to resume. These results suggest that extracellular Ca²⁺ is required for the re-initiation of meiosis in this species.     

Growth patterns of a stream vertebrate differ between urban and forested catchments

1. Urban development results in the decline of amphibian density and species richness. A logical next step towards understanding why urbanisation negatively impacts amphibians is to track species‐specific demographic responses to urbanisation. 2. We monitored growth of two‐lined salamander (Eurycea cirrigera Green) larvae over two complete cohorts (2006 and 2007) in nine western Georgia, U.S.A. streams. 3. We found that salamanders in streams surrounded by urbanised and developing catchments hatched at the same size as their reference‐stream counterparts, but achieved larger sizes within the first few months of growth. We evaluated the effect of four variables that correlate with the urban‐forest gradient and found that elevated temperatures in the urban environment, coupled with decreased intraspecific competition because of lower survivorship in these same habitats, were two of the most likely explanations for increased growth rates. 4. Such an increase in growth of surviving larvae may maintain population viability in urban areas where it has been shown survival is difficult because of increased in‐channel flow during flood events. Because larvae that do survive in urban streams undergo metamorphosis at large sizes, they may recoup a component of fitness (i.e. increased adult survivorship and reproduction) through growth.     

Cougar Kill Rate and Prey Composition in a Multiprey System

Abstract: Assessing the impact of large carnivores on ungulate prey has been challenging in part because even basic components of predation are difficult to measure. For cougars (Puma concolor), limited field data are available concerning fundamental aspects of predation, such as kill rate, or the influence of season, cougar demography, or prey vulnerability on predation, leading to uncertainty over how best to predict or interpret cougar-ungulate dynamics. Global Positioning System (GPS) telemetry used to locate predation events in the field is an efficient way to monitor large numbers of cougars over long periods in all seasons. We applied GPS telemetry techniques combined with occasional snow-tracking to locate 1,509 predation events for 53 marked and an unknown number of unmarked cougars and amassed 9,543 days of continuous predation monitoring for a subset of 42 GPS-collared cougars in west-central Alberta, Canada. Cougars killed ungulates at rates near the upper end of the previously recorded range, and demography substantially influenced annual kill rate in terms of both number of ungulates (subad F [SAF] = 24, subad M [SAM] = 31, ad M = 35, ad F = 42, ad F with kittens <6 months = 47, ad F with kittens <6 months = 67) and kg of prey (SAF = 1,441, SAM = 2,051, ad M = 4,708, ad F = 2,423, ad F with kittens <6 months = 2,794, ad F with kittens >6 months = 4,280). Demography also influenced prey composition; adult females subsisted primarily on deer (Odocoileus spp.), whereas adult males killed more large ungulates (e.g., moose [Alces alces]), and subadults incorporated the highest proportion of nonungulate prey. Predation patterns varied by season and cougars killed ungulates 1.5 times more frequently in summer when juveniles dominated the diet. Higher kill rate in summer appeared to be driven primarily by greater vulnerability of juvenile prey and secondarily by reduced handling time for smaller prey. Moreover, in accordance with predictions of the reproductive vulnerability hypothesis, female ungulates made up a higher proportion of cougar diet in spring just prior to and during the birthing period, whereas the proportion of males increased dramatically in autumn during the rut, supporting the notion that prey vulnerability influences cougar predation. Our results have implications for the impact cougars have on ungulate populations and have application for using cougar harvest to manage ungulates.     

Rapid Homogenization of Multiple Sources: Genetic Structure of a Recolonizing Population of Fishers

Abstract: Fishers (Martes pennanti) were extirpated from much of southern Ontario, Canada, prior to the 1950s. We hypothesised that the recent recolonization of this area originated from an expansion of the population in Algonquin Provincial Park, which historically served as a refuge for fishers. To test this hypothesis, we created a sampling lattice to encompass Algonquin and the surrounding area, and we collected contemporaneous DNA samples. We sampled fishers from each of 35 sites and genotyped them at 16 microsatellite loci. Using a Bayesian assignment approach, with no a priori geographic information, we inferred 5 discrete genetic populations and used genetic population assignment as a means to cluster sites together. We concluded that the Algonquin Park fisher population has not been a substantial source for recolonization and expansion, which has instead occurred from a number of remnant populations within Ontario, Quebec, and most recently from the Adirondacks in New York, USA. The genetic structure among sampling sites across the entire area revealed a pattern of isolation-by-distance (IBD). However, an examination of the distribution of genetic structure (F_ST/1^- F_ST) at different distances showed higher rates of gene flow than predicted under a strict IBD model at small distances (40 km) within clusters and at larger distances up to 100 km among clusters. This pattern of genetic structure suggests increased migration and gene flow among expanding reproductive fronts.     

Stand selection by birds in Scots pinewoods in Scotland: the need for more old-growth pinewood

A study at Abernethy Forest, Scotland, examined stand selection by some of the birds of conservation concern that inhabit pinewoods. Abernethy Forest was ideally suited for the study because all four main stand types of forest development (stand initiation, stem exclusion, understorey reinitiation and old-growth) were represented. Capercaillies Tetrao urogallus (both males and females) and crossbills Loxia spp. preferred old-growth pinewood in winter, and Redstarts Phoenicurus phoenicurus and Tree Pipits Anthus trivialis preferred old-growth in summer. Great Spotted Woodpecker Dendrocopos major selected snags in old-growth to excavate nest and roost sites. In winter, Crested Tits Parus cristatus had a weak selection for old-growth stands and Bullfinches Pyrrhula pyrrhula preferred stands at initiation. Possible reasons for these preferences are put forward. Although the area of conifer woodland in Scotland is 888 000 ha, it largely comprises North American species destined to be cut before reaching old-growth. Old-growth pinewood in Scotland is largely confined to the fragments of ancient native pinewood, amounting to only 16 000 ha. To conserve some pinewood birds of conservation concern, a mechanism to allow more Scots Pine Pinus sylvestris woods to reach and remain in an old-growth state needs to be pursued.     

Climate‐driven increases in storm frequency simplify kelp forest food webs

Climate models predict a dramatic increase in the annual frequency and severity of extreme weather events during the next century. Here we show that increases in the annual frequency of severe storms lead to a decrease in the diversity and complexity of food webs of giant kelp forests, one of the most productive habitats on Earth. We demonstrate this by linking natural variation in storms with measured changes in kelp forest food web structure in the Santa Barbara Channel using structural equation modeling (SEM). We then match predictions from statistical models to results from a multiyear kelp removal experiment designed to simulate frequent large storms. Both SEM models and experiments agree: if large storms remain at their current annual frequency (roughly one major kelp‐removing storm every 3.5 years), periodic storms help maintain the complexity of kelp forest food webs. However, if large storms increase in annual frequency and begin to occur year after year, kelp forest food webs become less diverse and complex as species go locally extinct. The loss of complexity occurs primarily due to decreases in the diversity and complexity of higher trophic levels. Our findings demonstrate that shifts in climate‐driven disturbances that affect foundation species are likely to have impacts that cascade through entire ecosystems.