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251.
Energy dynamics in the C4 species dominated montane subtropical grassland at Nilgiri Biosphere Reserve, the Western Ghats, India 下载免费PDF全文
The energy dynamics in Thiashola grassland, a montane subtropical vegetation in Nilgiri Biosphere Reserve, the Western Ghats, India is studied for a period of one year. The study revealed that the energy content in unit biomass of C3 and C4 species has not varied significantly. However, the C4 species in total due to higher net primary production, entrapped 8.5 times greater solar energy (28.82 kcal/m2/day) than that of their C3 counterparts. Of the total energy fixed, the C3 and C4 species, respectively channeled 4.07 kcal/m2/day and 13.3 kcal/m2/day to the aboveground standing live compartment. The transfer rate of energy to standing dead compartment from standing live part were 3.22 kcal/m2/day and 10.36 kcal/m2/day for C3 and C4 species, respectively and both the C3 and C4 together transferred 4.81 kcal/m2/day of energy from standing dead to litter compartment. The total dissipation of energy from the system is determined to be 4401.11 kcal/m2/yr and the surplus quantity of 38.37% of energy is accumulated in the aboveground parts of both C3 and C4 species which indicates the availability of substantial amount of energetic fodder to the wild herbivores in the Thiashola grassland. 相似文献
252.
To counter antibiotic-resistant bacteria, we screened the Kitasato Institute for Life Sciences Chemical Library with bacterial quinol oxidase, which does not exist in the mitochondrial respiratory chain. We identified five prenylphenols, LL-Z1272β, γ, δ, ? and ζ, as new inhibitors for the Escherichia coli cytochrome bd. We found that these compounds also inhibited the E. coli bo-type ubiquinol oxidase and trypanosome alternative oxidase, although these three oxidases are structurally unrelated. LL-Z1272β and ? (dechlorinated derivatives) were more active against cytochrome bd while LL-Z1272γ, δ, and ζ (chlorinated derivatives) were potent inhibitors of cytochrome bo and trypanosome alternative oxidase. Thus prenylphenols are useful for the selective inhibition of quinol oxidases and for understanding the molecular mechanisms of respiratory quinol oxidases as a probe for the quinol oxidation site. Since quinol oxidases are absent from mammalian mitochondria, LL-Z1272β and δ, which are less toxic to human cells, could be used as lead compounds for development of novel chemotherapeutic agents against pathogenic bacteria and African trypanosomiasis. 相似文献
253.
S.?A.?KaschulaEmail author W.?E.?Twine M.?C.?Scholes 《Human ecology: an interdisciplinary journal》2005,33(3):387-418
The limitations of Community Based Natural Resource Management (CBNRM) with respect to the difficulties of comparing local versus scientific knowledge categories within a bounded definition of ‘community’ were investigated by means of a study exploring local indigenous knowledge pertaining to harvesting technique, and the impact of soil and species type on the post-harvest coppice response of popular savanna fuelwood species, among rural inhabitants of the Bushbuckridge region of the Limpopo Province, South Africa. Soils and plants were evaluated chiefly in terms of their perceived ability to retain precipitation, making rainfall a driving force in local understanding of environmental productivity. Some indigenous knowledge showed an agreement with biological data, but overall the variability in responses, as well as the diverse scales at which indigenous and scientific knowledge is directed, were too great to allow for simplistic parallels between local ecological indices to be made. Indigenous environmental knowledge was underscored by the perceived symbolic link between environmental and social degradation. It is recommended that environmental managers incorporate indigenous knowledge as a component of a systems-level approach to natural resource management, where biological, cultural, economic, and symbolic aspects of natural resource use are nested within a broader ecosocial system. This approach to indigenous knowledge is offered as an alternative to the simple scientific evaluation that so often characterizes environmental management. 相似文献
254.
It has been proposed that variation in calpain 10 (CAPN10) contributes to the risk of type 2 diabetes (T2D). A previous survey of CAPN10 in ethnically diverse populations revealed an intronic region with a significant excess of polymorphism levels relative to inter-species sequence divergence, suggesting that this region was the target of long-standing balancing selection. Based on the thrifty genotype hypothesis, variation that increases risk to T2D in contemporary humans at one time conferred a survival advantage in ancestral populations. Thus, the signature of positive natural selection in a T2D candidate gene could identify a genomic region containing variation that influences disease susceptibility. Here, we investigate this hypothesis by re-sequencing the CAPN10 region with unusual polymorphism levels in T2D cases and controls (n=91) from a Mexican American (MA) population, and by using networks to infer the evolutionary relationships between the major haplotypes. Haplotype tag SNPs (htSNPs) were then selected in each population sample and in MA cases and controls. By placing the htSNPs on the haplotype network, we investigate how cross-population differences in CAPN10 genetic architecture may affect the detection of the disease association. Interestingly, despite the small scale of our case-control study, we observe a nearly significant signal of association between T2D and variation in the putative target of balancing selection. Finally, we use phylogenetic shadowing across 10 primate species to search for conserved non-coding elements that may affect the expression and function of CAPN10. These elements are postulated to be the targets of long-standing balancing selection. 相似文献
255.
To investigate natural killer (NK) and lymphokine-activated killer (LAK) cell functions from 10 healthy dogs and 29 dogs with a variety of spontaneous neoplasms, large granular lymphocytes (LGLs) from blood samples were separated by a 58.5% Percoll density gradient. LGLs were stimulated with a low dose of recombinant human interleukin 2 (rhIL-2) for 7 days. Cytotoxicity of effector cells against the susceptible CTAC cell line was measured before and after stimulation. Compared with those before stimulation, the percentage of LGLs after stimulation with rhIL-2 was found to be significantly increased (P<0.01) in both dogs with tumors and controls. However, the increase was significantly higher in control animals, indicating a defect in proliferation ability of NK cells in canine tumor patients. After stimulation with rhIL-2, lymphokine-activated killer (LAK) cell activity in dogs with tumors was significantly lower (P<0.01) when compared with controls. Reduced cytotoxicity of rhIL-2–activated NK cells in dogs with tumors seems to be attributable to the presence of a diminished proliferative capacity of NK cells and a decreased ability of LAK cells to lyse target cells. Further knowledge of the precise function of IL-2–activated NK cells in dogs with tumors may help to optimize new and therapeutically beneficial treatment strategies in canine and human cancer patients. Our findings suggest that the dog could also serve as a relevant large animal model for cancer immunotherapy with IL-2. 相似文献
256.
Ishiguro H Kishimoto T Furuya M Nagai Y Watanabe T Ishikura H 《Cancer immunology, immunotherapy : CII》2005,54(12):1191-1199
Tumor-derived cytokines, such as interleukin (IL)-6, function in the context of tumor-to-host interactions, and their functions in immune-compromised hosts need to be addressed in the light of ever- increasing number of patients under immunosuppression. We studied the effects, in immune-comprised animals, of tumor-derived IL-6 on tumor growth using an experimental tumor vaccination model. Murine mammary carcinoma FM3A clone 25 (CL25) cells, which neither produce IL-6 nor express IL-6 receptors, were used. cDNA for murine IL-6 (mIL-6) was introduced to the CL25 cells, resulting in a high-producer (mIL-6H) clone. In the severe combined immune-deficient (SCID) mice, the inoculation 3 weeks earlier of mIL-6H to a dorsal flank site suppressed the growth of the CL25 cells at the opposite flank site; a tumor-derived IL-6-mediated vaccination effect occurred. In the T-cell-deficient nude mice, the inoculations 4 weeks earlier of mIL-6H suppressed the growth of CL25, but the simultaneous inoculation of these transfectants did not affect the growth of CL25. Reducing the number of inoculated transfectants or a shorter vaccination period obscured the suppressive effect. The amounts of circulating tumor-reactive immunoglobulin did not correlate with the suppressive effect. The subcutaneous injection of the anti-CD40 antibody generated a further suppression of tumor growth in the mIL-6H-inoculated, but not in the mock-inoculated, T-cell-deficient mice. In the immune-competent hosts, a suppressive effect was not observed. Natural killer (NK) activity was augmented in the spleen of mIL-6H-inoculated scid mice. This study indicated a possible vaccination effect with tumor-derived IL-6 in immune-compromised hosts. 相似文献
257.
Inspired by the evolution of antibiotic resistance in bacteria, we have developed a model that examines the evolution of "producers" (who secrete a substance that breaks down antibiotics) and non-producers. In a previous study, we found that frequency-dependent selection could favor an intermediate frequency of producers in a single, large population. Here we develop a metapopulation model that examines the evolution of producers and non-producers. Our results indicate that in a metapopulation with many groups, each of size N, the equilibrial frequency of producers decreases with group size. Even when N is high (e.g. 150 individuals/group), however, a significant frequency of producers is still predicted. We also found that the equilibrial frequency of producers increases as the minimum numbers of producers necessary to provide protection to non-producers increases. Lastly, increasing the benefit/cost ratio (b/c) for producers increases their equilibrial frequency. 相似文献
258.
The study of essential oils obtained from Coridothymus capitatus and Satureja thymbra collected from different natural habitat types of 11 NATURA 2000 sites scattered all over Crete has shown that they are characterized either by a high amount of carvacrol (up to 75.7%) or thymol (up to 65.6%) or by a more or less equal amount of the two phenols. The results of a discriminant analysis with predefined groups the natural habitat types wherefrom the plants were collected have shown that the oils of both species collected from the dry dwarf-shrub formations of the lowland have a high carvacrol content whereas those collected from the more mesic timber or highland formations have a high thymol content. Furthermore, the results of this study introduce the use of natural habitat unit as a tool for the assessment of essential oil variation. 相似文献
259.
Major histocompatibility complex (MHC) class II genes are usually among the most polymorphic in vertebrate genomes because
of their critical role (antigen presentation) in immune response. Prior to this study, the MHC was poorly characterized in
tiger salamanders (Ambystoma tigrinum), but the congeneric axolotl (Ambystoma mexicanum) is thought to have an unusual MHC. Most notably, axolotl class II genes lack allelic variation and possess a splice variant
without a full peptide binding region (PBR). The axolotl is considered immunodeficient, but it is unclear how or to what extent
MHC genetics and immunodeficiency are interrelated. To study the evolution of MHC genes in urodele amphibians, we describe
for the first time an expressed polymorphic class II gene in wild tiger salamanders. We sequenced the PBR of a class II gene
from wild A. tigrinum (n=33) and identified nine distinct alleles. Observed heterozygosity was 73%, and there were a total of 46 polymorphic sites,
most of which correspond to amino acid positions that bind peptides. Patterns of nucleotide substitutions exhibit the signature
of diversifying selection, but no recombination was detected. Not surprisingly, transspecies evolution of tiger salamander
and axolotl class II alleles was apparent. We have no direct data on the immunodeficiency of tiger salamanders, but the levels
of polymorphism in our study population should suffice to bind a variety of foreign peptides (unlike axolotls). Our tiger
salamander data suggest that the monomorphism and immunodeficiencies associated with axolotl class II genes is a relict of
their unique historical demography, not their phylogenetic legacy.
Electronic supplementary material Electronic supplementary material is available for this article at and accessible for authorised users. 相似文献
260.
The present state of knowledge in the chemistry of mandragora plant is reviewed. Isolations and identifications of the compounds were done from all parts of this plant. Up-to-date more than 80 substances were identified in different species of the genus Mandragora. 相似文献