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31.
The process of ageing is associated with increased susceptibility to infection. Phagocytes form the primary defence mechanism against infecting microorganisms, but the influence of ageing on phagocyte function remains controversial. In this study we have applied a microtitre plate phagocyte chemiluminescence (CL) assay suitable for clinical use to compare phagocyte oxidative metabolism in younger healthy subjects (age 20–60 years) and healthy older (60–70 years) subjects. Polymorphonuclear leukocytes (PMNL) and monocytes were stimulated using phorbol myristate acetate (PMA), serum opsonized zymosan (SOZ), and non-opsonized zymosan (ZYM) in the presence of both lucigenin and luminol. Monocytes showed a higher luminolenhanced CL response to PMA in males compared with females in the younger age group. No PMNL differences were observed between the sexes. Although no difference were found in relation to age when cells were stimulated with PMA and SOZ, significantly lower background (unstimulated) CL was obtained from PMNL with luminol. PMNL luminol-enhanced CL responses were also lower in response to ZYM. The findings suggest a reduced response of PMNL from older subjects to minimal stimulation. This could be related to abnormalities in the triggering of the respiratory burst or myeloperoxidase release due to ageing. The influence of age and sex should be taken into account in clinical studies of phagocyte CL. 相似文献
32.
Paola A Gilardoni Stefan Schuck Ruth Jüngling Björn Rotter Ian T Baldwin Gustavo Bonaventure 《BMC plant biology》2010,10(1):66
Background
Plants trigger and tailor defense responses after perception of the oral secretions (OS) of attacking specialist lepidopteran larvae. Fatty acid-amino acid conjugates (FACs) in the OS of the Manduca sexta larvae are necessary and sufficient to elicit the herbivory-specific responses in Nicotiana attenuata, an annual wild tobacco species. How FACs are perceived and activate signal transduction mechanisms is unknown. 相似文献33.
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36.
Evaluating Hypotheses on the Evolution of Helping Behaviour in the Bell Miner (Manorina melanophrys)
In an analysis of the pattern of helping at the nest in bell miners (Manorina melanophrys), Clarke (1989) examined five hypotheses that could explain the evolution of helping behaviour in this species. We applaud the attempt by Clarke to consider many different hypotheses, but believe that more careful formulation of the hypotheses, more appropriate statistical analyses, and eventual experimental testing are required before his conclusions can be accepted. 相似文献
37.
Ian D. Hodkinson Jeremy M. Bird Jane K. Hill Robert Baxter . 《Ecological Entomology》2001,26(4):376-387
1. Salix lapponum host plants at an upper altitudinal site differed significantly in size, structural density, phenology, growth performance, and spatial isolation from those growing at a lower site. 2. Plant differences were paralleled by significant differences in psyllid population density and phenology parameters, with psyllid population density, percentage of catkins occupied, and phenological development relatively lower or retarded at the upper site. Population densities at the upper site, nevertheless, remained high. 3. Plant measurements were good predictors of insect density, often explaining up to 73% of the variance in abundance among plants at a given site. 4. Sets of four plant characters identified by best subsets regression were better predictors of psyllid density and development than single factors, although differences were often not great and the combinations of characters selected by multiple regression sometimes differed from the best single predictors. 5. Best single predictors of psyllid density on catkins were measurements of plant size, particularly height, length, and basal stem diameter. Shoot density and catkin phenology were occasionally important but plant isolation and prior growth performance were less important. 6. By contrast with density, age structure of the psyllid population was predicted best from plant phenological measurements, notably catkin phenology. 相似文献
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39.
Michael L. Roderick Ian R. Noble Shane W. Cridland 《Global Ecology and Biogeography》1999,8(6):501-508
In this paper we test a method to estimate the tree and grass vegetation cover over Australia from satellite-derived normalized difference vegetation index (NDVI) time series (monthly 1981–91, ≈5 km pixels) observations. The evergreen cover is assumed to track along the base of the NDVI time series, which is assumed to be equivalent to the woody vegetation cover. The base of the NDVI time series is estimated using modifications to a classical econometric model (i.e. time series is the sum of trend, seasonal and random components). Estimates of the average evergreen component during 1982–85 and 1986–89 were generally consistent with known vegetation distributions. Changes in evergreen cover were largely restricted to the south-west and south-east of Australia. Those changes were largely the result of differences in rainfall between the two periods. The proposed method for estimating woody vegetation cover is found to be generally robust. However, there are some regions where the grass (or pasture) is mostly evergreen. Some possible refinements are proposed to handle such cases. 相似文献
40.
The present study characterizes four potentially informative polymorphic bands of 5.2, 2.3, 1.9, and 1.2 kb, detected by Southern blot hybridization of Eco RI digests of human DNA using HK101/80 (an immunoglobulin V
I probe). These restriction fragment length polymorphisms (RFLP) show Mendelian segregation and they are linked to each other and to Km(1), the allotypic marker on the kappa constant region. There is strong linkage disequilibrium between the 2.3 and 1.2 kb polymorphisms. A 0.7 kb Pst I polymorphic band and a 2.9 kb Sac I polymorphic band were also identified; the latter may reflect a region of tandem repeats in the V
region. No bands representing the alternative forms of any of the polymorphic restriction sites were identified. This implies either that genes are missing from the V
repertoire or that such bands are hidden because of comigration of fragments due to conservation of restriction sites. Evidence for comigration of fragments was obtained from independent V
clones and suggests that dark bands on Southern blots of Pst I digests must often represent several superimposed genes which have conserved restriction sites. The demonstration of RFLP within the V region provides circumstantial evidence for polymorphic variation in the repertoire of V
structural genes. The RFLP reported here should be useful as genetic markers in future studies on the immune response and disease susceptibility in man. 相似文献