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1.
The activity of 5′-nucleotidase and ouabain-sensitive Na/K ATPase was determined in seven different mouse melanoma cell lines. Ouabain-sensitive Na/K ATPase activity was found in NP40-treated cell homogenates of all cell lines. However, 5′-nucleotidase activity was found in only one mouse melanoma cell line—JB/RH. The absence of expression of 5′-nucleotidase activity in the other six cell lines is not associated with pigmentation in melanoma cells, nor is the gene switched off in all transformed melanocytes of C57BL/6 origin.  相似文献   
2.
Abstract The dung beetle genus Phanaeus as currently recognized by Edmonds (1994) consists of 51 species placed in 13 species groups and two subgenera. Here, I examine the phylogeny and biogeography of this genus by analysing the mitochondrial cytochrome oxidase subunit I (530 bp), nuclear large subunit ribosomal RNA (28S, D2 region), and 67 morphological characters for 28 species of Phanaeus. Both maximum parsimony and Bayesian analyses from the combined data yielded well‐resolved trees, although low bootstrap and posterior probability support were found for basal nodes. The phylogenetic hypotheses presented here suggest that the subgenera Phanaeus s.str. and Notiophanaeus should each be elevated to the status of full genus. With the exception of the eucraniine outgroups, the paleano species group of the genus Phanaeus is recovered as sister to all other taxa, including the outgroups Oxysternon, Sulcophanaeus and Coprophanaeus. High bootstrap values and posterior probabilities supported the species groups endymion, tridens and vindex. Biogeographical analyses suggest an ancestral distribution for Phanaeus in the Andes in South America, although numerous dispersal events evidently have produced a complicated biogeographical history.  相似文献   
3.
Colonizing species are predicted to suffer from reductions in genetic diversity during founding events. Although there is no unique mode of reproduction that is characteristic of successful plant colonizers, many of them are predominantly self-fertilizing or apomictic species, and almost all outcrossing colonizers are self-compatible. Carduus acanthoides comprises a species of disturbed habitats with wind-dispersed seeds that colonizes open spaces of various sizes. Population genetic diversity was expressed by assessing patterns of variation at nine putatively neutral allozyme loci within and among 20 natural populations in its native distribution range in the Czech Republic. Overall, C. acanthoides displayed high levels of genetic diversity compared to other herbaceous plants. The percentage of polymorphic loci was 84.5, with values of 2.37, 0.330, and 0.364 for the mean number of alleles per polymorphic locus ( A ), observed heterozygosity ( H o), and expected heterozygosity ( H e), respectively. There was only weak evidence of inbreeding within populations ( f  = 0.097) and very low genetic differentiation among populations ( θ  = 0.085). Analyses of the data provide strong evidence for isolation-by-distance for the whole study area. Even the colonizing species, C. acanthoides , currently supports a substantial amount of allozyme variation at both the species and population levels.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 596–607.  相似文献   
4.
ABSTRACT The hairy woodpecker (Picoides villosus) is a keystone species in forest ecosystems of Washington, USA, providing nesting and roosting cavities for many species of wildlife. Therefore, management practices that promote healthy populations of this bird will help to conserve cavity-nesting communities as a whole. The objective of this study was to determine patterns in forest type and landscape use by hairy woodpeckers, and thus, provide landscape-level recommendations to forest managers. We documented the ranging patterns and habitat use of 23 hairy woodpeckers on the Olympic Peninsula using radiotelemetry and a Geographic Information System analysis. Use patterns of stand age, type, and size, as well as distance-from-edge analyses revealed that the hairy woodpecker is a relative generalist in its use of the managed forest landscape. However, certain features, such as older stands with large trees, were used more heavily by nesting pairs. Hairy woodpeckers used 61–80-year forest stands significantly (P < 0.05) more than expected relative to their availability within the birds' home ranges. We also documented significant underuse of 6–10-year and 11–20-year stands, whereas the birds used 41–60-year stands, >80-year stands, and clear-cuts (< 5 yr) equivalent to their availability. We suggest that hairy woodpeckers select older stands with larger, dying trees for foraging, but also use clear-cuts proportionally due to the residual snags, decaying trees, and remnant dead wood available. Higher use (P < 0.001) by hairy woodpeckers of small forest patches (0–5 ha) and intermediate-sized stands (5–30 ha) than large patches (>30 ha) may be a result of the older, higher-quality habitat available in small stands in the managed forest landscape. We recommend that land managers interested in maintaining healthy managed forest ecosystems with a full complement of cavity-using species in forests of western Washington and northwestern Oregon maintain a landscape mosaic with approximately 45% of the landscape in stands >40 years, and >30% of the landscape in stands >60 years.  相似文献   
5.
Microbial characteristics of soils on a latitudinal transect in Siberia   总被引:2,自引:0,他引:2  
Soil microbial properties were studied from localities on a transect along the Yenisei River, Central Siberia. The 1000 km‐long transect, from 56°N to 68°N, passed through tundra, taiga and pine forest characteristic of Northern Russia. Soil microbial properties were characterized by dehydrogenase activity, microbial biomass, composition of microbial community (PLFAs), respiration rates, denitrification and N mineralization rates. Relationships between vegetation, latitude, soil quality (pH, texture), soil organic carbon (SOC) and the microbial properties were examined using multivariate analysis. In addition, the temperature responses of microbial growth (net growth rate) and activity (soil respiration rate) were tested by laboratory experiments. The major conclusions of the study are as follows: 1. Multivariate analysis of the data revealed significant differences in microbial activity. SOC clay content was positively related to clay content. Soil texture and SOC exhibited the dominant effect on soil microbial parameters, while the vegetation and climatic effects (expressed as a function of latitude) were weaker but still significant. The effect of vegetation cover is linked to SOC quality, which can control soil microbial activity. 2. When compared to fine‐textured soils, coarse‐textured soils have (i) proportionally more SOC bound in microbial biomass, which might result in higher susceptibility of SOC transformation to fluctuation of environmental factors, and (ii) low mineralization potential, but with a substantial part of the consumed C being transformed to microbial products. 3. The soil microbial community from the northernmost study region located within the permafrost zone appears to be adapted to cold conditions. As a result, microbial net growth rate became negative when temperature rose above 5 °C and C mineralization then exceeded C accumulation.  相似文献   
6.
SYNOPSIS. The genie control of the development of neural morphologyand specific neural connections is little known, primarily becauseof a paucity of neurological mutants in animal models suitablefor experimental manipulation. However, by using cell markers—suchas tetraploidy, a large cell marker whose development is describedhere—the development of single retinal cells in tetraploidembryos, the growth of marked polyclones in chimeric eyes, andthe central connections of various chimeric eyes have been analyzedto identify the strategies used in molding eye morphology andestablishing precise central connections. Theoretical modelsand computer simulations were used to draw inferences aboutthe information used to accomplish the identified strategies.This analysis resulted in predictions about the sorts of mutantgenes which might be found to affect neural ontogeny.  相似文献   
7.
1. We investigated the effects of two features of leaf‐pack habitat structure (i.e. mass of a leaf pack and surface area of leaves comprising a leaf pack) and fish predation on colonisation of shredders and leaf breakdown rates in a coldwater stream. Packs were constructed of red maple (Acer rubrum) leaves. 2. A 2 × 3 × 3 factorial experiment was used to manipulate fish predation (exclusion and control cage), leaf‐pack mass (1, 3 and 5 g dry mass) and leaf surface area (small: approx. 17.9 cm2, medium: approx. 34.6 cm2, large: approx. 65.6 cm2). Exclusion cages had mesh on all sides, whereas control cages lacked mesh on two sides to provide access to fish. 3. Common shredders were Gammarus pseudolimnaeus, Pycnopsyche and Lepidostoma. Shredder biomass per leaf pack increased with the mass of a leaf pack (P < 0.001), but biomass per unit mass of leaf pack did not differ with leaf‐pack mass (P = 0.506). Shredder densities did not respond to the exclusion of fish (P > 0.7) or leaf surface area (P > 0.7), and interactions among treatment factors were not significant (P > 0.2). 4. Breakdown rates were lower for leaf packs comprised of small leaves (P < 0.001) and leaf packs with high mass (P = 0.001). Excluding fish did not significantly affect leaf breakdown rates (P = 0.293), and interactions among treatment factors were not significant (P > 0.3). Breakdown rates were highest when packs consisted of few leaves (i.e. leaf packs with large leaves and low mass) and were colonised by many shredders. 5. Fish predation was not an important factor controlling shredder densities in leaf packs over the spatiotemporal scale of our experiment. Nevertheless, we found shredder colonisation was proportional to leaf‐pack mass and breakdown rates were affected by leaf‐pack size (i.e. number of leaves in a pack). We suspect that fragmentation is the primary mechanism causing the breakdown rates to be dependent on leaf‐pack size.  相似文献   
8.
The objective of this investigation was to compare two sampling methods (expectoration and ingestion) of single component water solutions (sweet—5% sucrose, sour—0.006% citric acid, bitter—0.027% caffeine, salty—0.325% sodium chloride) using time-intensity (T-I) evaluations. Analysis of variance was used to evaluate significant differences. There were subject inconsistencies for the recording times (RT) of sucrose, caffeine and sodium chloride tastes among the sampling methods. No panel differences were found for citric acid duration (RT) between ingested or expectorated samples. Individual contradictions for amplitude sucrose and sodium chloride mixtures were apparent however, the panel demonstrated no differences among the amplitude means between the sampling methods for citric acid and caffeine solutions. Aftertastes for ingested sodium chloride solutions were significantly (P < 0.01) greater than for expectorated samples whereas sampling techniques had no effect upon caffeine aftertastes. Individual contradictions were apparent for citric acid and sucrose aftertastes between the sampling methods.  相似文献   
9.
I isolated the first set of polymorphic microsatellite markers from the house finch, Carpodacus mexicanus, a well‐studied North American bird species, as part of an effort to compare levels of genetic diversity in introduced and native populations. Here, I describe eight independently assorting microsatellite loci screened for polymorphism using 40 house finches. Polymorphism levels ranged from six to 14 alleles (mean = 10.6), making these markers a powerful tool for paternity and population level analyses of this widely distributed North American species.  相似文献   
10.
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