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排序方式: 共有125条查询结果,搜索用时 31 毫秒
81.
Jan Mees Nancy Fockedey Ann Dewicke Colin R. Janssen Jean-Claude Sorbe 《Aquatic Ecology》1995,29(2):161-166
Intersexuality in the mysidNeomysis integer is described from samples collected in the Elbe (north Germany), Eems-Dollard (north Netherlands), Westerschelde (south-west
Netherlands) and Gironde (southwest France) estuaries. Individuals which had an irregularly shaped or nearly symmetrically
rounded telson, rather than a typically truncated one, were also recorded from the four populations studied. A culture experiment
with damaged specimens revealed that all types of abnormal telson morphology found in the field can result from regeneration
of damaged parts. It is concluded that both intersexuality and aberrant telson morphology are widespread phenomena among estuarineN. integer populations. Both abnormalities seem to be rare in the other common mysid species in the study area: only one intersexualGastrosaccus spinifer and oneSchistomysis kervillei with an aberrant telson were recorded. 相似文献
82.
23 hybridomas secreting monoclonal antibodies against human 2 , the fast-acting inhibitor of plasmin present in plasma, have been produced by the cell-fusion technique. Isotyping of the monoclonal antibodies has revealed that 14 monoclonal antibodies belong to the class IgG1, 6 to the class IgG2a, and 3 to the class tgG2b. All light chains belong to the group. The specificity and relative avidity of these monoclonals have been determined Using an indirect enzyme-linked immunosorbent assay. 13 monoclonals exhibit a relatively high avidity for 2 , 5 are of intermediate avidity, and 5 of low avidity. The epitope specificity of these 23 rnonoclonal antibodies, originating from a single mouse, have been examined in inhibition experiments. A group of 10 monoclonal antibodies exhibit a very similar inhibition pattern. Partial inhibition effects displayed by 10 other antibodies define partially overlapping antigenic regions. The binding of these antibodies seems to produce a conformational change in the 2 molecule, reducing the binding of two other antibodies. The last antibody defines an independent epitope. 相似文献
83.
Anti-CD3 antibodies induce T cells from unprimed animals to secrete IL-4 both in vitro and in vivo 总被引:3,自引:0,他引:3
V Flamand D Abramowicz M Goldman C Biernaux G Huez J Urbain M Moser O Leo 《Journal of immunology (Baltimore, Md. : 1950)》1990,144(8):2875-2882
Recently, functional heterogeneity among Th cells has been recognized. Based on pattern of lymphokine secretion, two mutually exclusive subsets of CD4+ cells have been defined and designated Th1 (secreting IL-2 and IFN-gamma) and Th2 (secreting IL-4 and IL-5). Identification of these subsets was mostly based on the study of long term cultured T cell lines and clones, and little is known about the Th heterogeneity in vivo. In particular, it has been suggested that IL-4 producing cells cannot be detected in vivo or in primary stimulations in vitro unless responder cells had been previously primed. Our data however, indicate that anti-CD3 mediated stimulation can induce T cells isolated from unprimed animals to IL-4 production. An assay system based on the ability of IL-4 to increase Ia expression of B cells present in the environment of activated T cells was found to be more sensitive than detection of secreted IL-4 in the supernatant by conventional bioassays and was used to study IL-4 production by unprimed lymphocytes polyclonally stimulated in vivo and in vitro by anti-CD3 mAb. The results obtained indicate that CD4+ CD8- T cells able to produce IL-4 upon receptor-specific stimulation exist in the preimmune pool of adult animals. Remarkably, these cells can also be stimulated in vivo by treating animals with anti-CD3 mAb, as indicated by the in vivo induction of IL-4 specific mRNA and hyper-Ia expression on B cells. These results indicate that the inability to detect IL-4 in primary cultures is not due to different activation requirements of Th2 cells but may simply result from their lower frequency in unprimed animals. 相似文献
84.
The effect of a 4 hr upright posture on serum potassium (SK) levels was investigated in a certain group of hospitalized renal patients with selective hypoaldosteronism and in healthy subjects. Significant (p less than 0.001) postural increase in SK (0.4 MMol/L) was found only in the 3 young patients with chronic glomerulonephritis and hypoaldosteronism who presented with hyperkalemia (5.84 +/- 0.13 mMol/L) as outpatients, but showed a marked improvement toward normokalemia (4.95 +/- 0.13 mMol/L; p less than 0.001) within the hospital without any specific treatment. In healthy persons in the fastqng condition the influence of the upright position of short duration (45 min) was also studied on SK and a very small but significant increase (0.15 mMol/L) was found. It was concluded: 1. the postural SK INCREASE MAY OFFER AN--AT LEAST PARTIAL--EXPLANTATION FOR THE "OUTPATIENT HYPERKALEMIA", 2. The normal activity of renin-angiotensinaldosterone system may play a role in the counteraction of the trend for SK rise in the upright posture. 相似文献
85.
Summary For a general multiple loop feedback inhibition system in which the end product can inhibit any or all of the intermediate reactions it is shown that biologically significant behaviour is always confined to a bounded region of reaction space containing a unique equilibrium. By explicit construction of a Liapunov function for the general n dimensional differential equation it is shown that some values of reaction parameters cause the concentration vector to approach the equilibrium asymptotically for all physically realizable initial conditions. As the parameter values change, periodic solutions can appear within the bounded region. Some information about these periodic solutions can be obtained from the Hopf bifurcation theorem. Alternatively, if specific parameter values are known a numerical method can be used to find periodic solutions and determine their stability by locating a zero of the displacement map. The single loop Goodwin oscillator is analysed in detail. The methods are then used to treat an oscillator with two feedback loops and it is found that oscillations are possible even if both Hill coefficients are equal to one. 相似文献
86.
Higher-order thalamic nuclei receive input from both the cerebral cortex and prethalamic sensory pathways. However, at rest these nuclei appear silent due to inhibitory input from extrathalamic regions, and it has therefore remained unclear how sensory gating of these nuclei takes place. In the rodent, the ventral division of the zona incerta (ZIv) serves as a relay station within the paralemniscal thalamocortical projection pathway for whisker-driven motor activity. Most, perhaps all, ZIv neurons are GABAergic, and recent studies have shown that these cells participate in a feedforward inhibitory circuit that blocks sensory transmission in the thalamus. The present study provides evidence that the stimulation of the vibrissa motor cortex suppresses vibrissal responses in ZIv via an intra-incertal GABAergic circuit. These results provide support for the proposal that sensory transmission operates via a top-down disinhibitory mechanism that is contingent on motor activity. 相似文献
87.
The sharing of amino acid short spans by ancestrally unrelated proteins may be the result of ubiquitous alpha and beta secondary structures 总被引:1,自引:0,他引:1
Short homologies are often found when genetically unrelated proteins are compared but it is not known whether the rate at which they occur is or not above randomness. Comparing 190 pairs of unrelated proteins enable us to show that the frequency at which pairs of unrelated proteins share little spans of amino acids is compatible with chance.However, it appears that those short homologies are mainly located within protein subregions of identical secondary structure: the frequency at which pairs of unrelated proteins exhibit related spans of amino acids inside subregions of identical secondary structure is far above randomness. Those data suggest that the sharing of related spans of amino acids by genetically unrelated proteins could result from structural constraints imposed by the α or β secondary structures. 相似文献
88.
89.
Mucosa‐associated biohydrogenating microbes protect the simulated colon microbiome from stress associated with high concentrations of poly‐unsaturated fat
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Rosemarie De Weirdt Emma Hernandez‐Sanabria Veerle Fievez Eva Mees Annelies Geirnaert Florence Van Herreweghen Ramiro Vilchez‐Vargas Pieter Van den Abbeele Ruy Jauregui Dietmar H. Pieper Bruno Vlaeminck Tom Van de Wiele 《Environmental microbiology》2017,19(2):722-739
Polyunsaturated fatty acids (PUFAs) may affect colon microbiome homeostasis by exerting (specific) antimicrobial effects and/or interfering with mucosal biofilm formation at the gut mucosal interface. We used standardized batch incubations and the Mucosal‐Simulator of the Human Microbial Intestinal Ecosystem (M‐SHIME) to show the in vitro luminal and mucosal effects of the main PUFA in the Western diet, linoleic acid (LA). High concentrations of LA were found to decrease butyrate production and Faecalibacterium prausnitzii numbers dependent on LA biohydrogenation to vaccenic acid (VA) and stearic acid (SA). In faecal batch incubations, LA biohydrogenation and butyrate production were positively correlated and SA did not inhibit butyrate production. In the M‐SHIME, addition of a mucosal environment stimulated biohydrogenation to SA and protected F. prausnitzii from inhibition by LA. This was probably due to the preference of two biohydrogenating genera Roseburia and Pseudobutyrivibrio for the mucosal niche. Co‐culture batch incubations using Roseburia hominis and F. prausnitzii validated these observations. Correlations networks further uncovered the central role of Roseburia and Pseudobutyrivibrio in protecting luminal and mucosal SHIME microbiota from LA‐induced stress. Our results confirm how cross‐shielding interactions provide resilience to the microbiome and demonstrate the importance of biohydrogenating, mucosal bacteria for recovery from LA stress. 相似文献
90.
Olivier Hamerlynck Kris Hostens Renato V. Arellano Jan Mees Paul A. Van Damme 《Aquatic Ecology》1993,27(2-4):343-358
During 1989 monthly beam trawl samples were collected at 48 stations in the Dutch Delta. The annual mean densities of the demersal fishes and mobile epibenthic invertebrates at these stations were calculated. These data were then subjected to multivariate statistical techniques for an analysis of the spatial structure of the communities found and to study the relationship between these communities and their environment. The present study confirms the results of HENDERSON (1989) that, given a fairly limited number of environmental variables, mainly salinity and exposure/substratum type, quite accurate predictions of the type of community expected at a certain site can be made. The explicit inclusion of epibenthic invertebrates, a dominant group in most assemblages, in studies mainly targeted at demersal fishes, is strongly recommended. In the Dutch Delta rich and varied communities exist in the Voordelta. A number of groups, such as salmonids, anadromous species and starfish, expected in the westerschelde are absent or extremely rare probably as a consequence of pollution stress. The Oosterschelde is relatively poor in density terms but has a highly diverse epibenthic fauna dominated by fishes. 相似文献