bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Real-Time PCR for Detection of the
tcdC
Gene with Four Toxin Immunoassays and Culture in Diagnosis of
Clostridium difficile
Infection
Authors: Sloan Lynne M. , Duresko Brian J. , Gustafson Daniel R. , Rosenblatt Jon E.
Published: April 2008

We have developed a rapid real-time PCR method using fluorescence resonance energy transfer probes and the LightCycler (Roche Diagnostics), which will detect the presence of the
tcdC
gene of
Clostridium difficile
in stool samples. Our PCR method also will identify the presence of base pair deletions, one of which (18 bp) has been associated with the “epidemic” toxin-hyperproducing strains. We compared the results of this PCR with those of three
C. difficile
toxin-detecting enzyme immunoassays (EIAs), an EIA for the detection of glutamate dehydrogenase (GDH), and culture of
C. difficile
. A total of 200 stool specimens were studied by the methods under comparison.
C. difficile
was isolated from 49 specimens by culture, and 44 of these were confirmed as containing one of the genes associated with toxin production (“toxigenic culture”). Using toxigenic culture as the “gold standard”, the sensitivities, specificities, and positive and negative predictive values, respectively, of the assays were 48%, 98%, 88%, and 87% for the Premier toxin A and B test; 48%, 99%, 91%, and 87% for the ImmunoCard toxin A & B test; 48%, 84%, 46%, and 85% for the Xpect
C. difficile
toxin A/B test; 32%, 100%, 100%, and 84% for the Triage
C. difficile
panel (for toxin A); and 86%, 97%, 90%, and 96% for the LightCycler PCR. Thus, in comparison to the sensitivity of toxigenic culture, the sensitivities of the toxin immunoassays were unacceptably low, while the LightCycler real-time PCR assay for the detection of the
tcdC
gene of
C. difficile
is sensitive and specific.
Occurrence of Norovirus Infections Unrelated to Norovirus Outbreaks in an Asymptomatic Food Handler Population
Authors: Okabayashi Tamaki , Yokota Shin-ichi , Ohkoshi Yasuo , Ohuchi Hironori , Yoshida Yasuhiro , Kikuchi Masayuki , Yano Koichi , Fujii Nobuhiro
Published: April 2008

Norovirus (NV) is the most common causative agent of nonbacterial gastroenteritis. Reports of surveillance of NV in facilities that reported outbreaks are frequently found in publications, but reports of that in facilities without outbreaks are not found. We investigated the molecular epidemiology of NV isolates derived from asymptomatic food handlers working at a nonoutbreak food catering facility in Hokkaido, Japan, from February to March in 2005 and January to February in 2006 by RNA polymerase gene sequencing. Approximately 12% (20/159) of the samples were positive for genogroup II (GII; 10.1% in 2005 and 14.2% in 2006). The GI genotypes were not detected. The data from the phylogenetic analysis indicated that, among the 20 strains detected, 13 strains were GII/genotype 2 (GII/2), two were GII/3, three were GII/8, and two were GII/12. GII/4, which has been found most frequently in recent outbreaks worldwide, including Japan, was not detected. We found that one individual was coinfected with two genotypes, GII/2 and GII/12. This is the first report of the detection of NV genotypes in asymptomatic food handlers working at a nonoutbreak facility. The excretion of NV from healthy individuals may be an infection source of NV outbreaks as well as other food-borne diseases.
Two Cases of Keratitis and Corneal Ulcers Caused by
Burkholderia gladioli
Authors: Lestin Franka , Kraak Robert , Podbielski Andreas
Published: April 2008

We report two cases of protracted keratitis complicated by corneal ulcer.
Burkholderia gladioli
, primarily known as a plant pathogen, was cultured from corneal swabs. The epithelial defects healed after extended adequate antibiotic therapy. Despite identical patterns of both strains in restriction fragment length polymorphism analysis, a common infection source was not detectable.
Virus-Specific Interleukin-17-Producing CD4
+
T Cells Are Detectable in Early Human Immunodeficiency Virus Type 1 Infection
Authors: Yue Feng Yun , Merchant Asad , Kovacs Colin M. , Loutfy Mona , Persad Desmond , Ostrowski Mario A.
Published: April 2008

T
H
-17 cells have been shown to play a role in bacterial defense, acute inflammation, and autoimmunity. We examined the role of interleukin 17 (IL-17) production in human immunodeficiency virus type 1 (HIV-1) infection. Both HIV-1- and cytomegalovirus (CMV)-specific IL-17-producing CD4
+
T cells were detectable in early HIV-1 infection but were reduced to nondetectable levels in chronic and nonprogressive HIV-1 infection. IL-17-producing CMV-specific cells were not detected in blood from HIV-1-uninfected normal volunteers. Virus-specific T
H
-17 cells could coexpress other cytokines and could express CCR4 or CXCR3. Although the etiology of these cells has yet to be established, we propose that microbial translocation may induce them.
Link Between Long-Term Variability in Upwelling and Fish Production in the Northeast Pacific Ocean
Authors: Ware Daniel M. , Thomson Richard E.
Published: April 2008

The biomass of pelagic fish in the Coastal Upwelling Domain off the west coast of North America decreased by a factor of 5 in the first half of this century. We assemble several physical and biological time series spanning this period to determine what may have caused this decline in productivity. Based on an observed link between time series of the coastal wind and primary production, we conclude that there was a strong relaxation in wind-induced upwelling and primary production between 1916 and 1942 off southern California. The fact that the individual biomasses of the dominant pelagic fish species tend to rise and fall in phase through the sediment record off southern California is consistent with our belief that these species are responding to a long-period (40–60 yr) oscillation in primary and secondary production, which, in turn, is being forced by a long-period oscillation in wind-induced upwelling. Our extended sardine recruitment time series indicates that there is a nonlinear relationship between Pacific sardine (Sardinops sagax) recruitment and upwelling and suggests that optimal recruitment occurs when the wind speed during the first few months of life averages 7–8 m/s.
Multivariate Description of Pacific Herring (Clupea harengus pallasi) Stocks from Size and Age Information
Authors: Schweigert J. F.
Published: April 2008

Fisheries management must trade off biological conciseness with institutional and practical constraints, which may preclude separate management of all genetic stock units but should ensure long-term survival of such components in each area. The technique described here, while unable to explicitly identify genetic differences, is applicable to other species and would be particularly valuable for preliminary studies where limited resources preclude the use of expensive and analytically more complex techniques such as morphometric and meristic or electrophoretic analyses which are more suitable for that task. The method developed in this study involves the application of discriminant function and canonical variates analysis to information on size and age structure of Pacific herring (Clupea harengus pallasi) from samples representing the seven major migratory populations and other spawning aggregations in six geographical regions of coastal British Columbia. Results of the analysis quantify the separation of stocks of herring between geographical regions, and at a finer spatial scale, within all regions. Generally, one or more migratory stocks occurred together with minor stocks in each geographical region.
Spawning by Hatchery-Origin Lake Trout (Salvelinus namaycush) in Lake Ontario: Data from Egg Collections, Substrate Analysis, and Diver Observations
Authors: Marsden J. Ellen , Krueger Charles C.
Published: April 2008

Three techniques were used to find evidence of reproductive activity by stocked lake trout (Salvelinus namaycush) on Stony Island reef in Lake Ontario from 1986 to 1990. In the fall, egg nets and traps were deployed on different substrate types, and in the spring, fry traps were used to capture newly emergent fry. Fry were only captured in an area approximately 50 by 10 m at the north end of the eastern edge of the reef. Eggs were only captured in nets and traps deployed near this area, or in nets and traps which moved over this area during storms and came to rest at the base of the reef. The area of Stony Island reef actually used by lake trout for egg deposition appeared to be extremely limited relative to the entire reef. This area was characterized by large cobble substrate with minimal infilling by sand and fines. Thus, hatchery-origin lake trout appeared to recognize substrate appropriate for successful egg incubation.
Abundance, Growth, and Production Estimation of the Blue Mussel Mytilus edulis on Moored Navigation Buoys in the Estuary and Northwestern Gulf of St. Lawrence
Authors: Ardisson P.-L. , Bourget E.
Published: April 2008

Production of Mytilus edulis was estimated from measurements of recruitment, growth, and abundances. The study is based on (1) yearly samplings carried out between 1975 and 1985 on 161 navigation buoys moored each year in the Estuary and Gulf of St. Lawrence and (2) monthly production estimates in a reference region in 1987. The relationships between production and maximum size, biomass, mean weight per individual, and abundance were calculated for this reference region. Maximum size and biomass were the parameters best reflecting production. Abundance and production estimates showed that the Gaspé Peninsula and the western North Shore zones were the most productive ones. The density-dependent mortality of individuals in crowded even-aged populations (self-thinning) was studied in the baie de Gaspé, the region showing the highest abundance and growth rate of Mytilus in the system. The slope of this relationship varied depending on initial density and age classes considered. These results, when compared with the theoretical value of the self-thinning model, suggest that the biomass observed on the buoys and the production estimates derived from them correspond to near-maximal values
Does Tagging and Handling Affect the Growth of Northern Fur Seal Pups (Callorhinus ursinus)?
Authors: Trites Andrew W.
Published: April 2008

From 1957 to 1966, samples of tagged and marked northern fur seal pups (Callorhinus ursinus) consistently weighed less than untagged and unmarked pups on the Pribilof Islands, Alaska. At the time, it was concluded that tagging and handling had caused a loss of weight and had slowed the normal rate of pup growth. In re-evaluating the data from this time period, it seems that tagged pups grew at the same rate as untagged pups, but were smaller at the time of tagging than average size pups. The growth curve for tagged pups appears to lag behind that of untagged pups, suggesting that tagged pups were born later in the breeding season and were more susceptible to being captured and tagged than older and heavier pups.
Lactation in the Ringed Seal (Phoca hispida)
Authors: Hammill M. O. , Lydersen C. , Ryg M. , Smith T. G.
Published: April 2008

Length of lactation, pup growth rate, and female weight loss in ringed seals (Phoca hispida) were estimated using cross-sectional data from the Canadian and Norwegian Arctic. At birth the pups had a standard length of 63.4 cm (SE = 1.3, N = 11) and weighed 5.4 kg (SE = 0.4, N = 6). Weaning occurred approximately 39 d (range 36–41 d) after birth at an estimated length of 88.4 cm (SE = 0.65, N = 96) and an estimated weight of 22.1 kg, resulting in an increase in length of 0.64 cm∙d−1 and a weight change of 0.43 kg∙d−1. Regression of female weight on the number of days after the nominal date of birth for each region indicated that the postpartum female weighed 81.2 kg and lost 0.64 kg∙d−1 (95% CI = ±0.20). During lactation, female weight declined by an estimated 32%, with much of the loss occurring from the blubber. Analyses of stomachs indicated that ringed seals supplemented stored energy reserves by feeding during lactation.
Biotic Responses along the Recovery Gradient of a Regulated Stream
Authors: Voelz Neal J. , Ward J. V.
Published: April 2008

Samples were collected year-round over a 1-yr period at six sites located downstream from a reservoir with a hypolimnetic release on the upper Colorado River to examine the longitudinal patterns of macroinvertebrates along an environmental gradient induced by river regulation. The impoundment had only minimal effects on river chemistry, and chemical variables did not exhibit a distinct downstream gradient. Macroinvertebrate density was highest at sites near the Granby Reservoir dam, but diversity increased with distance from the impoundment. A percentage similarity matrix identified two areas of rapid transition in macroinvertebrate assemblages along the regulated river gradient. Detrended correspondence analyses (DCA) showed a sequential faunal gradient with the most rapid change occurring within the first 3.0 km below the impoundment. Detrended canonical correspondence analysis (DCCA) suggested that downstream decreases in periphyton standing crop and minimum temperatures and downstream increases in most food resources and maximum temperatures were major variables structuring faunal assemblages. The results of this study, when compared with research conducted in free-flowing and other impounded rivers, indicated the predictability of some longitudinal patterns and the recovery potential of regulated lotic systems.
Temperature-Dependent Maximum Daily Consumption of Juvenile Salmonids by Northern Squawfish (Ptychocheilus oregonensis) from the Columbia River
Authors: Vigg Steven , Burley Craig C.
Published: April 2008

Maximum daily consumption rate (Cmax as ration or number) of northern squawfish (Ptychocheilus oregonensis) from the Columbia River increased exponentially as a function of temperature. Predator weight did not explain a significant independent proportion of variation in Cmax. The mean maximum daily ration, determined from replicate ad libitum feeding on juvenile Pacific salmon (Oncorhynchus spp.), was 0.47, 0.70, 3.39, and 4.50 cg∙g−1 at 8.0, 12.5, 17.0, and 21.5 °C, respectively. The corresponding mean daily number eaten was 0.50, 1.17, 4.25, and 7.01 prey per predator at the four increasing temperatures. To quantify the temperature-dependent consumption relation, replicate Cmax data within the preferred temperature range were fitted to exponential and exponential sigmoid models. On the basis of a knowledge of thermal relations of northern squawfish, we combined hypothetical Cmax data at temperature extremes with our mean experimental results to fit an algorithm suitable for use in simulation modeling. Both the generalized gamma and biological-rate (Thornton and Lessem. 1978. Trans. Am. Fish. Soc. 107: 284–287) algorithms were suitable to describe a hypothetical temperature–Cmax model over the entire environmental temperature range of 0–27 °C observed in the Columbia River.
A Brief Review of the International Council for the Exploration of the Sea (ICES) on the Occasion of the Formation of the North Pacific Marine Science Organization
Authors: Stewart James E.
Published: April 2008

Elements of the first 90 years of the North Atlantic organization the International Council for the Exploration of the Sea (ICES) have been examined to illustrate its functions and some of its achievements. The 17-nation Council, founded in 1902 to deal with overfishing in northern European marine areas, now represents countries on both sides of the Atlantic. Its mandate is to promote marine science and provide advice on the rational use of marine living resources. To accomplish this it stimulates and coordinates cooperative research programmes in the biology of marine, anadromous, and catadromous species, mariculture, fisheries assessment, pollution, and physical and chemical oceanography.
Spatial distribution of ecologically applicable climatic statistics in Michigan
Authors: Denton Shirley R. , Barnes Burton V.
Published: April 2008

The paper addresses the problem of selecting appropriate climatic variables from readily available weather data for use in studies of species ranges and ecosystem site classification. Principal component variables and more traditional climatic variables such as heat sums are presented. To facilitate comparison of spatially distributed variables, a procedure is described for estimation of climatic statistics for areas between weather stations. The procedure is objective and provides a measure of its error. Like any regression procedure, it improves with availability of more data. Extension of climatic statistics to a 5 × 5 km grid covering the state of Michigan was used to create contour maps for a number of climatic statistics with potential relevance for plant growth. In addition, a large number of climatic statistics were summarized using principal component analysis. Separate analyses were made for winter temperature and precipitation, growing season temperature, growing season precipitation, and a combination of variables possibly related to stressful conditions. There was a high degree of correlation among many of the statistics. The correlations were due to global climatic controls and to moderation due to the Great Lakes. Principal component variables successfully presented major climatic trends. However, for ecological use they appeared to offer few advantages over more traditional climatic statistics.
Changes in loblolly pine root growth potential from September to April
Authors: DeWald Laura E. , Feret Peter P.
Published: April 2008

Loblolly pine (Pinustaeda L.) 1 + 0 seedlings were periodically hand lifted from a Virginia nursery to determine how root growth potential (RGP) varied between September and April. Several seedling characteristics, RGP, and shoot phenology were recorded for each lift date in 1983–1984 and 1984–1985. An attempt was made to relate RGP variation to changes in the nursery environment and to shoot phenology. Root growth potential variation was consistent between years and was more closely related to shoot phenological changes than to short-term environmental changes. During the development of dormancy, RGP was low, RGP increased when shoot activity resumed during the RGP tests (late winter, early spring), and declined as active shoot elongation began in the nursery. When RGP was low, elongation of existing lateral roots primarily contributed to the new root systems, but as seedling metabolism increased in the late winter, new root initiation also contributed to new root systems. Absolute differences in RGP between years may be related to the fibrosity of seedling root systems.
Growth and nutrition of containerized Pinusresinosa at exponentially increasing nutrient additions
Authors: Timmer V. R. , Armstrong G.
Published: April 2008

Containerized red pine (Pinusresinosa Ait.) seedlings were reared on different fertility regimes that compared conventional applications of a recommended 39 mg N per seedling as a complete nutrient solution (175 mg N•L−1) with more frequent applications of an equal, one-half, or one-quarter amount of nutrients delivered at exponentially increasing solution concentrations over the same time period. Height growth, dry matter production, and root development at the end of the greenhouse rotation was significantly greater for seedlings receiving nutrients at exponentially rather than constantly increasing rates, although shoot growth among the three exponential treatments did not differ significantly. The increased yield was attributed to improved seedling nutrition as fertilizer addition rates better matched exponential growth development and nutrient consumption of the plants. The results indicate that superior seedlings can be grown successfully at low concentrations of nutrient solution, applying only one-quarter of the fertilizer dose conventionally used for container stock production.
Geographical variation in wood properties of Larixlaricina juvenile wood in northern Ontario
Authors: Yang K. C. , Hazenberg G.
Published: April 2008

Growth rate, latewood ratio, specific gravity, and tracheid length of Larixlaricina (Du Roi) K. Koch juvenile wood were studied with two 12-mm increment cores extracted at breast height from 240 healthy trees from 12 locations at a range in latitude from 46 to 56° N in northern Ontario. Ten trees were selected from each stand and two stands were chosen from each location. Univariate analyses of variance indicated that growth rate and latewood of juvenile wood varied significantly in various locations, stands, and trees at the α = 0.01 level of significance. Growth rate of juvenile wood decreased from a lower latitude to a higher latitude, whereas latewood ratios displayed a reverse trend, i.e., a higher latewood ratio was found at a higher latitude. Specific gravity of juvenile wood varied significantly in individual trees. Tracheid length varied significantly among locations, stands, and trees. The overall average growth rate, tracheid length, and specific gravity are 1.29 mm per ring, 2.10 mm, and 0.43, respectively. An unexpected relationship was found between growth rate and tracheid length. Growth rate of juvenile wood has a positive relationship with tracheid length and an inverse relationship with specific gravity.
A comparative analysis of the reduced major axis technique of fitting lines to bivariate data
Authors: Leduc Daniel J.
Published: April 2008

There are many ways of estimating the parameters of an equation to represent the relationship between two variables. While least-squares regression is generally acknowledged to be the best method to use when estimating the conditional mean of one variable given a fixed value for another, it is not usually an appropriate method to use when your primary interest is in the values of the equation parameters themselves (functional relations). In this case there are many other techniques (Bartlett's three-group method, Schnute's trend line, the general structural relationship, major axis regression, and reduced major axis) that may provide better estimates of these values. When all of the above techniques are compared, it is found that reduced major axis is often the most applicable because of its desirable properties and ease of estimation.
Throughfall chemistry in a red maple provenance plantation sprayed with "acid rain"
Authors: Schier George A.
Published: April 2008

Trees of three red maple (Acerrubrum L.) seed sources in a plantation were sprayed with simulated acid rain [Formula: see text] at pH 5.2, 4.2, and 3.2 on five dates (May to September) and throughfall chemistry was monitored. All pH treatments produced throughfall that was less acid than the spray solution. Ca, K, Mg, and Fe were evident in throughfall on more than one date; concentrations generally were at their lowest levels in the spring, reaching a peak in mid to late summer. Na, Zn, and B were detectable only in September. Concentrations of all mineral elements in throughfall, except K, increased with increasing acidity of the spray solution. On most dates K showed little sensitivity to spray pH, but on the August application date K concentrations were significantly higher at pH 5.2 and 4.2 than at 3.2. There were small but significant differences among provenances in concentrations of Ca, Fe, and Zn in throughfall. Concentrations of mineral elements in throughfall resulting from simulated acid rain were similar to concentrations of elements in throughfall resulting from natural precipitation of comparable pH and time.
Wood density of natural white spruce populations in Quebec
Authors: Corriveau A. , Beaulieu J. , Mothe F.
Published: April 2008

During genetic sampling of white spruce in 1984, increment cores were taken from 80 populations in order to study wood density variation within species in natural Quebec forests. Results show that wood density differences exist between populations and that wood density is negatively correlated with the width of the growth rings; however, some trees and some populations exhibit both high wood density and rapid growth. A moderate positive link was found between juvenile and mature wood densities at both the individual and population levels. Therefore, breeding programs for the improvement of wood density could be based on selections made on juvenile wood.
Development of cherrybark oak and sweet gum in mixed, even-aged bottomland stands in central Mississippi, U.S.A.
Authors: Clatterbuck Wayne K. , Hodges John D.
Published: April 2008

Development of even-aged mixed cherrybark oak (Quercusfalcata var. pagodifolia Ell.) and sweet gum (Liquidambarstyraciflua L.) stands was examined over a range of stand densities and ages in minor river bottoms of central Mississippi, U.S.A. Two stand development patterns were documented based on average spacing between dominant and codominant trees during the pole stage of development: a "restricted" pattern and an "unrestricted" pattern. The restricted pattern occurred at average spacings of less than 5.5 m. Here cherrybark oak was initially shorter than sweet gum but was able to outgrow and stratify above sweet gum when the stand was 20 to 25 years of age. Dominant and codominant cherrybark oaks averaged 61 cm in diameter, 34 m in height, and had 15 m of merchantable height at 58 years. The unrestricted pattern was found where cherrybark oak was either a few years older than sweet gum or was essentially open grown, with dominant and codominant trees of either species being more than 5.5 m apart. The unrestricted pattern resulted in cherrybark oak attaining less than 8 m of clear merchantable length and diameters of 56 cm in 40 years. The spacing of interacting trees appears to be responsible for the differences between the two development patterns in the timing and rate of cherrybark oak crown expansion, diameter growth, and length of the merchantable bole.
Decline in long-term growth trends of white oak
Authors: Phipps Richard L. , Whiton John C.
Published: April 2008

White oak (Quercusalba L.) tree-ring collections from 89 locations throughout much of its range, from Connecticut to North Carolina to Iowa, were examined for evidence of growth decline initiated in the 1950's. The expected trend of annual basal area increments, based on pre-1950 growth, appears to be linear, with the slope varying among collections relative to site quality. Growth decline, defined as departure of actual growth below that expected, was identified in 40 of 60 collections judged to have not been affected by local site histories. The percentage of collections showing decline was essentially the same in the Northeast, the Midwest, and the Southeast. Onset of decline began during a relatively narrow time window from the mid-1950's to the early 1960's. Since then the growth trend has been linear and appears unrelated to changes in regional sulfur and nitrogen oxide emissions. It is postulated that events or conditions, unique to the 1950's, initiated a growth rate change in about two thirds of the white oak stands examined. Initiation of the decline appears to be unrelated to tree age, geographic location, site quality, climatic trends, or regional emissions of sulfur and nitrogen oxides.
Wound response of loblolly and shortleaf pine attacked or reattacked by Dendroctonusfrontalis Zimmermann (Coleoptera: Scolytidae) or its fungal associate, Ceratocystisminor (Hedgecock) Hunt
Authors: Cook Stephen P. , Hain Fred P.
Published: April 2008

Loblolly, Pinustaeda L., and shortleaf, Pinusechinata Mill., pines respond to attack by the southern pine beetle (SPB), Dendroctonusfrontalis Zimmermann, or invasion by the SPB fungal associate, Ceratocystisminor (Hedgecock) Hunt, by forming a necrotic lesion around the wound site. This response was compared between trees that had no known prior experience with SPB or C. minor (naive trees) and trees that had been exposed to SPB or C. minor the previous year (experienced trees). No significant differences were observed in the average length of the lesions between experienced and naive trees in either pine species. However, the experienced loblolly pines had higher concentrations of inner bark monoterpenes than did the naive loblolly pines and the experienced shortleaf pines had a significantly different inner bark monoterpene composition compared with naive shortleaf pines during the June sample period. The monoterpene composition in unwounded tissue of experienced shortleaf pine closely resembled the observed monoterpene composition of lesion tissue at this time. The observed differences in inner bark monoterpenes following fungal or beetle exposure could render the trees less susceptible to later bark beetle attack for a period of time following the initial exposure.
Embryo growth in Alaskan white spruce seeds
Authors: Zasada John C.
Published: April 2008

Embryo development in white spruce seeds was studied in five stands in interior Alaska. Cones and seeds were collected at 10- to 14-day intervals starting in mid-July and continuing until just before seed dispersal began. Significant differences were found in embryo development between stands, between trees within stands, and between cones within trees. The four stands at lower elevations produced seeds that had embryos filling 95% or more of the embryo cavity; this percentage was significantly higher than the highest elevation stand where embryos filled about 75% of the embryo cavity at the end of the growing season. Relative cotyledon length was generally greater than 25% in the lower elevation stands and slightly less than 20% in the high elevation stand. Although seed collection can be started when embryos fill 75% of the embryo cavity, the results of this and other studies suggest that collecting seeds when embryos are more mature will result in better quality seeds. Air and soil temperatures and soil moisture levels associated with embryo development are presented.
Adaptive variation in cold hardiness of eastern larch, Larixlaricina, in northern Ontario
Authors: Joyce D. G.
Published: April 2008

Adaptive differentiation in cold hardiness of Larixlaricina (DuRoi) K. Koch from 66 populations, primarily from northern Ontario, was studied using laboratory freezing tests. Population differentiation was greatest before the first frost. However, relative hardiness of populations before and after the first frost were strongly correlated. Hardiness was related to latitude, longitude, and elevation of population origins. Multiple regression analyses accounted for 74% of the variance among population means. Population differentiation was detected across relatively small geographic and elevational intervals. Consequently, in order to limit maladaptation, transfer of plant material in artificial reforestation should be carefully controlled.
Influence of seral stage and season on leaf chemistry of southeastern Alaska deer forage
Authors: Horne Beatrice Van , Hanley Thomas A. , Cates Rex G. , McKendrick Jay D. , Horner John D.
Published: April 2008

The relationships between seral stage and nutrient and organic composition of five plant species used as forage by Sitka black-tailed deer were investigated in hemlock–spruce forest in southeastern Alaska. One shrub, three forbs, and one conifer species were collected during May, July, and October to ascertain differences among seral stands in seasonal patterns of nutrient levels, in vitro dry matter digestibility, astringency, and the concentrations of phenolics, terpenes, total nonstructural carbohydrates, and cyanide. In the shrub and forbs, concentrations of N, P, and K tended to be higher in leaves from forested than from open clear-cut areas, and higher in May than in July and October. These nutrients tended to covary in an opposite manner to Ca, Mg, and Na and in a similar manner to the trace elements Cu, Zn, Mn, and Fe, although these patterns were inconsistent. In these species there was also a general pattern of higher levels of total nonstructural carbohydrates, astringency, and phenolics in the three young open stands than in the shaded forest understories of the two oldest stands. Dry matter digestibility did not differ across stands but did vary seasonally. The among-stand differences in foliage chemical composition may have resulted from differences in the availability of light. While seral stage affected both the inorganic and organic quality of understory forage species, the combined results suggest that the impact on N economy of deer is greater than that on their energy economy.
Geographic variation of black spruce tested in the Maritimes
Authors: Park Y. S. , Fowler D. P.
Published: April 2008

Range-wide provenance tests of black spruce (Piceamariana (Mill.) B.S.P.) established at 10 locations in the Maritime provinces were evaluated. Based on the 14-year data, the genetic variation in the species is predominantly clinal. The magnitude of provenance × location interactions is moderately large, and stability of provenances varies widely. Trees of Maritime origin generally performed well, suggesting that there is little advantage in going outside the region to obtain black spruce seed. Seed transfer recommendations are summarized, and three overlapping breeding zones are delineated for the Maritime provinces.
Foliar nutrient variation and sampling intensity for Acerrubrum trees
Authors: Erdmann Gayne G. , Crow Thomas R. , Rauscher H. Michael
Published: April 2008

Concentrations of N, P, K, Ca, and Mg were determined for red maple (Acerrubrum L.) foliage sampled during mid to late August. Samples of mature leaves were collected from the upper, middle, and lower crown on the north and south sides of 22 dominant and codominant red maple trees growing in 51- to 58-year-old even-aged stands on a good site (SI50 = 21.6 m) and a poor site (SI50 = 13.6 m) in northern Michigan. Although individual trees differed greatly in concentrations of all elements, trees growing on the good site had significantly higher foliar concentrations of P, Ca, and Mg than trees on the poor site. Concentrations of N and K were similar for both sites. Concentrations of N, P, K, and Ca also differed significantly with crown position, but no difference in concentration for any element was found with crown direction. The sample-size requirements are given for each element at a selected level of accuracy.
A rapid method for detecting cold injury in conifer seedling root systems
Authors: Ritchie Gary A.
Published: April 2008

A method is described for rapidly determining the extent of cold injury to Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) seedling root systems. It is based upon pressure:volume theory but short-cuts the tedious pressure:volume method. Injured root systems were brought to full hydration, then weighed and placed into a pressure chamber. A pressure of 1.5 MPa was applied for a 5-min period, then the root system was removed from the chamber and reweighed. The percent weight loss was then calculated. Percent weight loss was closely related to degree of low temperature exposure in Douglas-fir seedling roots. Percent weight loss values were near 5 in uninjured controls, whereas freeze-injured seedlings had percent weight loss values of 7 or greater. Percent weight loss values measured on seedlings just before planting were closely correlated with seedling vigor and mortality 3 months following planting in both a field test and a greenhouse pot trial.
Espèces biologiques d'armillaire dans les érablières dépérissantes du sud-est du Québec
Authors: Sabourin M. , Dessureault M. , Bérubé J. A.
Published: April 2008

Biological species of the Armillaria complex present in declining sugar maple stands in southeastern Quebec were identified by pairing monosporous isolates with known tester strains. Armillariaostoyae (I), A. gemina (II), A. calvescens (III), and A. sinapina (V) were collected. Armillariacalvescens was the most frequent species and was found in almost all the stands sampled. The presence of various Armillaria species was not correlated with either the severity of decline of the stands or the health of the hosts with which they were associated, suggesting that none of the species present in sugar maple stands is particularly responsible for their decline. However, the role of A. calvescens and the factors that favor its development warrant further investigations because this species appears to be found almost exclusively on maple trees.
Foliar injury and growth response of red spruce to sulfate and nitrate acidic mist
Authors: Jacobson Jay S. , Heller Laurence I. , Yamada Karen E. , Osmeloski Joseph F. , Bethard Twylene , Lassoie James P.
Published: April 2008

Seedlings of red spruce (Picearubens Sarg.) were exposed repeatedly, either in the field or in the greenhouse, to sulfuric acid mist, nitric acid mist (with or without ammonium ions), or a combination of sulfuric and nitric acid mist (with or without ammonium ions) for 10 to 39% of the time over periods of 6 to 19 weeks. Sulfuric acid mist produced visible foliar injury after repeated overnight exposures to pH 3 or less. Foliar symptoms were significantly less or absent after exposures to nitric acid or combined sulphuric–nitric acid mist at the same pH values. Abscission of needles during the subsequent winter also was increased by sulfuric acid mist. Intermittent exposures that contained fewer hours of treatment with acidic mist and longer drying periods than continuous exposures caused greater amounts of foliar injury. Wind during the drying periods enhanced foliar injury, especially with sulfuric acid mist. Significant reductions in shoot elongation occurred with sulfuric acid mist in those experiments where seedlings continued to grow throughout the treatment period. Different provenances responded similarly to acidic mist. The results indicate that red spruce is particularly vulnerable to injury from acidic mist when sulfate concentrations are high and when mist exposures are intermittent with repeated periods of drying of liquid on foliage.
The effect of self-, cross-, and no pollination on ovule, embryo, seed, and cone development in western red cedar (Thujaplicata)
Authors: Owens John N. , Colangeli Anna M. , Morris Sheila J.
Published: April 2008

The effects of self-, cross-, and no pollination on cone size, filled seed, pollination efficiency, ovule development, and seed efficiency were tested on rooted ramets of six western red cedar (Thujaplicata Donn) clones. To fully develop, ovules must be pollinated with viable pollen and cones must have a minimum of one developing seed. The seed potential was constant among clones and not affected by pollination. The greatest loss of potential seed resulted from a failure of ovules to be pollinated, followed closely by the low percent viability of pollen. Unpollinated ovules aborted at the megaspore or free-nuclear stages. Pollinated ovules may abort at any stage of development, but it was most common during the long free nuclear stage. Selfing had a limited effect on postzygotic loss owing to embryo abortion or on seed set. Western red cedar is well adapted for a high degree of selfing. Clonal differences occurred in seed efficiency and stages at wich seed losses were most commun. Seed set in western red cedar may be increased if cones on female parents having a history of high seed efficiency are pollinated several times within a 1 week peak pollination period with abundant pollen of known high percent viability. Potential seed losses are discussed with reference to pollination and ovule development.
Asynchronous breeding in the socially monogamous prairie vole
Authors: Wolff Jerry O. , Ophir Alexander G. , Phelps Steven M.
Published: April 2008

At least two hypotheses have been proposed for why animals should breed synchronously: (1) to swamp predators and reduce the probability of offspring being killed and (2) to promote monogamy when paternal care is important for offspring survival. Thus prey and monogamous species are likely candidates for synchronous breeding. We conducted an experiment to determine if a prey species, the monogamously breeding prairie vole ( Microtus ochrogaster (Wagner, 1842)), breeds synchronously. We conducted eight replicates in which we placed six nulliparous females and six adult males in semi-natural enclosures for 18–21 days to determine if they bred synchronously. The time of conception ranged from 2 to 18 days within replicates with no indication of breeding synchrony within any of the populations. Thus neither predator avoidance nor paternal care models were supported for prairie voles. We conclude that rodents in general are not good models for breeding synchrony and that females use alternative mating tactics to enhance their lifetime reproductive success. We discuss our results in the context of the prairie vole mating system.
Positive relationship between non-native and native squirrels in an urban landscape
Authors: Gonzales E. K. , Wiersma Y. F. , Maher A. I. , Nudds T. D.
Published: April 2008

Paradoxically, non-native species sometimes displace native species that appear to be well adapted to local landscapes. That many landscapes have been altered by humans, creating habitat suitable for non-native species, helps explain this apparent paradox. We asked whether the abundance of native Douglas ( Tamiasciurus douglasii (Bachman, 1839)) and northern flying ( Glaucomys sabrinus (Shaw, 1801)) squirrels was best explained by the abundance of non-native eastern grey squirrels ( Sciurus carolinensis Gmelin, 1788), the proportion of urban development, or both using available squirrel abundance data from wildlife shelters and land-use maps. There was no evidence that non-native squirrels replaced native squirrels given that their abundances were positively related, whereas native squirrels varied negatively with the amount of development. The best model explaining variation in the abundance of Douglas and northern flying squirrels incorporated both eastern grey squirrels and development, which is consistent with the hypothesis that regional declines in native squirrels are more likely to be predicated by the alteration of native conifer habitats by humans independent of the effects of non-native squirrels.
Extreme suppression of aboveground activity by a food-storing hibernator, the eastern chipmunk (Tamias striatus)
Authors: Munro D. , Thomas D. W. , Humphries M. M.
Published: April 2008

Eastern chipmunks ( Tamias striatus (L., 1758)) capitalize on pulsed production of storable seed from masting trees by accumulating large, long-term larder hoards in their burrow. Since this species does not accumulate fat, hoarded food is the sole source of energy used during hibernation and inactive periods. Because hoards can be very large, they offer chipmunks the possibility of forgoing aboveground foraging when seeds or nuts are not abundant on the forest floor. Here, we present evidence that at least 82 chipmunks in two different populations interrupted aboveground activity for 9–11 months when mast was not available. A large hoard of American beech ( Fagus grandifolia Ehrh.) nuts established during the preceding year appeared to allow these chipmunks to cease foraging for almost a full year when food availability was particularly low. This extended period of inactivity is among the longest reported for a hibernating mammal, and demonstrates complex interactions between past, current, and future resource availability in shaping the seasonal activity patterns of food-storing hibernators.
Caution on isotopic model use for analyses of consumer diet
Authors: Caut Stéphane , Angulo Elena , Courchamp Franck
Published: April 2008

Isotopic models are increasingly used to determine the relative contribution of different food sources to an animal’s diet. However, these models are based on restrictive assumptions and provide estimates rather than exact values of contributions to consumer diet. The sources of inaccuracies in isotopic models are not well understood and laboratory experiments may be useful to evaluate model performance. In this paper we assess the accuracy of the three main isotopic models in controlled laboratory experiments, involving a breed of Norway rats ( Rattus norvegicus (Berkenhout, 1769)), in which the isotopic values of resources are known. At the same time, we measure errors resulting from the use of fixed or specific discrimination factor values for each resource and tissue. We show that the results of the three main isotopic models deviate considerably from the correct values in some cases. Estimations obtained using specific discrimination factors (corresponding to each experimental diet and tissue) were more accurate than those obtained using fixed discrimination factors (obtained from the literature). In addition, estimations varied depending on the tissue used, with the liver giving more accurate results than muscle or hair. We discuss the assumptions and limitations of isotopic models and highlight the importance of taking these assumptions into account when the most accurate results are sought. Finally, we propose some recommendations for the correct use of isotopic models, emphasizing the need to use specific discrimination factors for each species, tissue, and diet isotopic value.
Drosophila parasitoid–host interactions: vibrotaxis and ovipositor searching from the host's perspective
Authors: Sokolowski Marla B. , Turlings Ted C. J.
Published: April 2008

Two strains of Drosophila differing in host movement were simultaneously offered to a female parasitoid of either Leptopilina heterotoma or Asobara tabida. The number of encounters with the moving and nonmoving host strains was independent of larval movement forL. heterotoma whereas a highly significant effect of movement was found for A. tabida. This increased encounter rate of A. tabida with moving larvae resulted from the interaction of this parasitoid's searching strategy (vibrotaxis) and the polymorphic behaviour of the hosts. We conclude that differences in searching mode of two parasitoids of Drosophila larvae, A. tabida and L. heterotoma, can influence individual host susceptibility.
Hepatic metallothionein mRNA in the winter flounder (Pseudopleuronectes americanus)
Authors: Chan King Ming , Davidson William S. , Fletcher Garth L.
Published: April 2008

Analysis of polyadenylated mRNA directed cell-free translation products by polyacrylamide gel electrophoresis under native and denaturing conditions showed that hepatic mRNA from cadmium-injected flounder translated to yield metallothionein. Metallothionein was not detected in the translation products of mRNA isolated from livers of saline-treated (control) flounder. The metallothionein mRNA was purified on sucrose gradients and found to have a sedimentation coefficient of 9S.
Chemosensory detection of predators by coho salmon (Oncorhynchus kisutch): behavioural reaction and the physiological stress response
Authors: Rehnberg Bradley G. , Schreck Carl B.
Published: April 2008

Behavioral and physiological reactions were examined in juvenile coho salmon (Oncorhynchus kisutch) before and after the chemodetection of alarm substance and chemical stimuli released from predators and nonpredators. Chemical stimulus from northern squawfish (Ptychocheilus oregonensis) was avoided in a two-choice Y trough, whereas stimulus from the largescale sucker (Catostomus macrocheilus) was not. Paradoxically, both stimuli induced a stress response as indicated by elevations in plasma Cortisol and glucose. Plasma thyroxine was not a sensitive indicator of stress. Extracts from the broken skin of squawfish or suckers induced a physiological stress response, thereby raising the possibility of a nonostariophysan fish recognizing an ostariophysan alarm substance. Rinses from human skin or L-serine were behaviorally avoided, but neither stimulus induced physiological stress responses. A conclusion from these results is that behavioral and physiological reactions to chemical stimuli from predators do not necessarily co-occur. These data also suggest that fright is not necessarily a sufficient condition for inducing a stress response of the general adaptation syndrome type in fish.