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21.
MANUEL B. CRESPO SEGUNDO RÍOS JOSÉ L. VIVERO JOSEFA PRADOS ESTEBAN HERNÁNDEZ-BERMEJO M. DOLORES LLEDÓ 《Botanical journal of the Linnean Society. Linnean Society of London》2005,149(1):121-128
Vella castrilensis sp. nov. is described from the high mountains of Granada and Jaén provinces (south-eastern Iberian Peninsula), where it grows on calcareous soils. It is a hexaploid (2 n = 68) spineless dwarf shrub, woody at the base, with oblong-lanceolate, entire to shallowly dentate leaves and fruit with an acute tongue-shaped stylar segment and strongly reticulate-nerved valves. The characteristic unique combination of vegetative, karyological and reproductive features of V. castrilensis is not present in any described taxon of the genus, and warrants recognition at the species rank. Affinities and differences with other related taxa are discussed. Phylogenetic, biogeographical, bioclimatic, ecological data and conservation proposals are also reported. © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 149 , 121–128. 相似文献
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Alekseeva LP Mazrukho BL Chemisova OS Sal'nikova OI Markina OV Lobanov VV 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》2002,(4):25-29
The epitope composition of O-polysaccharides in the lipopolysaccharide (LPS) of V. cholerae, serogroup O139, isolated from clinical material and water of surface reservoirs was analyzed with the use of monoclonal antibodies. The analysis demonstrated that these O-polysaccharides were similar in their structure and chemical composition. In LPS of V. cholerae O139 clinical strains O-polysaccharide determinants occurred more often. Among V. cholerae isolated from water strains on whose surface individual epitopes of O-polysaccharide occurred less frequently or were absent appeared to be more numerous. A decrease in the concentration of microbial cells in the process of their testing by immunological methods led to increased percent of negative reactions with specific antibodies. Some V. cholerae O139 strains isolated from water were similar in the epitope composition of their O-polysaccharide and binding activity to cultures isolated from humans. As indicated by the results of these studies, cholera vibrios Bengal and vibrios isolated from river water on the territory of Russia had quantitative differences due to a higher level of the production of O-polysaccharide determinants and their occurrence in V. cholerae of serogroup O139. 相似文献
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1. The coexistence of Bosmina and Ceriodaphnia was studied in relation to phytoplankton succession in a small lake (Laguna Ezquerra) in the araucanian region of Argentina. 2. The study involved field sampling and single species cultures of each of the two cladocerans in lake water under laboratory conditions. 3. Ceriodaphnia showed a unimodal cycle while Bosmina had a bimodal pattern during 4 months of coexistence. Ceriodaphnia exhibited a direct relationship between clutch size and biovolume of edible algae, whereas Bosmina's fecundity was related to the density of flagellates. 4. We found that the fecundity of these species responded differently to laboratory and field conditions. The fecundity of Ceriodaphnia followed the same pattern in both the field and laboratory, whereas Bosmina showed higher fecundity values in laboratory experiments. 5. Our results are in good agreement with predictions derived from Northern Hemisphere studies, indicating that food-limited populations of daphnids and Bosmina can coexist for extended periods in spatially homogeneous environments. 6. The variation in food availability, measured as biovolume of edible algae, determines the loss of Ceriodaphnia and the persistence of Bosmina. 相似文献
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M. REDONDO-NIETO A. R. WILMOT A. EL-HAMDAOUI I. BONILLA & L. BOLAÑOS 《Plant, cell & environment》2003,26(11):1905-1915
Because boron (B) and calcium (Ca2+) seem to have a strong effect on legume nodulation and nitrogen fixation, rhizobial symbiosis with leguminous plants, grown under varying concentrations of both nutrients, was investigated. The study of early pre‐infection events included the capacity of root exudates to induce nod genes, and the degree of adsorption of bacteria to the root surface. Both phenomena were inhibited by B deficiency, and increased by addition of Ca2+, resulting in an increase of the number of nodules. The infection and invasion steps were investigated by fluorescence microscopy in pea nodules harbouring a Rhizobium leguminosarum strain that constitutively expresses green fluorescent protein. High Ca2+ enhanced cell and tissue invasion by Rhizobium, which was highly inhibited after B deficiency. This was combined with an increased B concentration in nodules of plants grown on B‐free medium and supplemented with high Ca2+ concentrations, and that can be attributed to an increased B import to the nodules. Histological examination of indeterminate (pea) and determinate (bean) nodules showed an altered nodule anatomy at low B content of the tissue. The moderate increase in nodular B due to additional Ca2+ was not sufficient to prevent the abnormal cell wall structure and the aberrant distribution of pectin polysaccharides in B‐deficient treatments. Overall results indicate that the development of the symbiosis depends of the concentration of B and Ca2+, and that both nutrients are essential for nodule structure and function. 相似文献
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1. Specialisation in dispersal by alate aphids often imposes constraints on other functions, particularly a reduction in fecundity due to wing development. Short‐distance flight from patches of high population density to uninfested plants may provide temporary predator‐free space, compensating for low fecundity. However, this theoretical prediction has not been explored experimentally. 2. To test this hypothesis, a field cage experiment was conducted in which Aphis glycines populations initiated with controlled proportions of apterous and alate individuals were exposed to predation, while predator‐free space was accessible only through flight. It was predicted that an investment in alate individuals would benefit a population under predation, regardless of associated costs to fecundity. 3. As expected, a strong trade‐off was observed between fecundity and wing development. However, populations initiated with a fixed proportion of alate and apterous individuals showed no reductions in final population size compared with populations initiated with apterous individuals exclusively. Moreover, the initial presence of alate individuals in the populations increased aphid prevalence (i.e. proportion of plants colonised). Similarly, both increased population size and prevalence were observed when predator‐free space was accessible through flight, as opposed to when it was inaccessible. 4. These results show that despite high costs to fecundity, an investment in alate individuals is neither beneficial nor detrimental to population size when predator‐free space is accessible, but increases aphid prevalence. It is concluded that prevalence might provide an ecological advantage important enough to warrant the production of alate morphs under intense predation. 相似文献
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Modulatory effects of interferon‐γ and interleukin‐4 on cellular immune responses against Hypoderma lineatum antigens
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E. CABANELAS C. M. L
PEZ P. DÍAZ A. PREZ ‐CREO P. MORRONDO P. DÍEZ ‐BA
OS R. PANADERO 《Medical and veterinary entomology》2016,30(4):439-443
This study investigates the in vitro modulatory effects of interferon‐γ (IFN‐γ) and interleukin‐4 (IL‐4) on both proliferative bovine T cell responses and IL‐10 production induced by different antigens [crude larval extract and the purified fractions hypodermin A, B and C (HyA, HyB, HyC)] obtained from first instars of Hypoderma lineatum (Diptera: Oestridae), alone or in the presence of the mitogen concanavalin A. Incubation with the different parasitic antigens resulted in significant inhibition of T cell proliferation and IL‐10 production, which, in general, did not revert after the addition of IFN‐γ and IL‐4. In the absence of antigens, IL‐4 induced significant inhibition of mitogen‐induced T cell responses. Exogenous IFN‐γ exhibited an inhibitory effect on cell proliferation in the presence of the purified fractions HyB and HyC. These in vitro data suggest that far from neutralizing the effects of larval antigens, the addition of IFN‐γ potentiates their anti‐proliferative activity; by contrast, IL‐4 had no consistent effects on proliferative responses to Hypoderma. IL‐4 provoked an increment of IL‐10 levels in supernatants of HyB‐stimulated cells. In conclusion, exogenous IFN‐γ and IL‐4 were unable to counteract the suppressor effects of H. lineatum antigens. 相似文献
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Abstract: A revision of thelodont scales from the Lower Devonian of the Iberian Chains enables their grouping into two taxa: Turinia pagei and T. nachoi sp. nov. These taxa are clearly distinguishable by morphological and histological features; they also have a different stratigraphic range ( T. pagei is restricted to Lochkovian strata, whereas T. nachoi sp. nov. occurs within lower–middle Pragian rocks). The new species is represented by head, transitional (cephalopectoral) and trunk scales. 相似文献
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Growth of oral Streptococcus species and Actinomyces viscosus in human saliva. 总被引:4,自引:1,他引:3
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Microorganisms in dental plaque live in constant association with saliva. The role of saliva in the adherence of bacteria to the teeth and the antibacterial properties of saliva have been well investigated; less interest has been shown in the possible role of saliva as a substrate for oral microorganisms. In this study it was shown that saliva can serve as a growth medium for oral Streptococcus spp. and Actinomyces viscosus. The cell production of these organisms on saliva was carbohydrate limited. The doubling times for growth on glucose-supplemented saliva (4 to 5 mmol/liter) ranged from 1.6 to 4.0 h. The availability of carbohydrate sources for the oral microflora is discussed in relation to microbial growth in the oral cavity. 相似文献
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A. EL-HAMDAOUI M. REDONDO-NIETO R. RIVILLA I. BONILLA & L. BOLAÑOS 《Plant, cell & environment》2003,26(7):1003-1011
The effects of modifying boron (B) and calcium (Ca2+) concentrations on the establishment and development of rhizobial symbiosis in Pisum sativum plants grown under salt stress were investigated. Salinity almost completely inhibited the nodulation of pea plants by Rhizobium leguminosarum bv. viciae 3841. This effect was prevented by addition of Ca2+ during plant growth. The capacity of root exudates derived from salt‐treated plants to induce Rhizobium nod genes was not significantly decreased. However, bacterial adsorption to roots was highly inhibited in plants grown with 75 mM NaCl. Moreover, R. leguminosarum 3841 did not grow in minimal media containing such salt concentration. High Ca2+ levels enhanced both rhizobial growth and adsorption to roots, and increased nodule number in the presence of high salt. Nevertheless, the nodules developed were not functional unless the B concentration was also increased. Because B has a strong effect on infection and cell invasion, these processes were investigated by fluorescence microscopy in pea nodules harbouring a R. leguminosarum strain that expresses green fluorescent protein. Salt‐stressed plants had empty nodules and only those treated with high B and high Ca2+ developed infection threads and exhibited enhanced cell and tissue invasion by Rhizobium. Overall, the results indicate that Ca2+ promotes nodulation and B nodule development leading to an increase of salt tolerance of nodulated legumes. 相似文献