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1.
An epizootic characterized by birth of calves severly ataxic and blind were encountered in 3 herds 7–8 months after outbreaks of bovine virus diarrhoea. Serological and virological investigations indicated introduction of bovine viral diarrhoea virus (BVDV) into previously virus-free herds, followed by transplacental virus infection of the fetuses of cows in the first trimester. Clinical, pathological, serological, and microbiological examinations were performed on 10 calves. Pathological findings included microcephaly and cerebellar hypoplasia, ocular malformations, and thymic hypoplasia. BVDV was isolated from tissue and blood of 7 calves, and 4 calves, 1 of which had not received colostrum, had virus-specific neutralizing antibodies.This is the first report on natural occurrence of congenital bovine infection with BVDV among Danish cattle herds resulting in abortion and birth of calves with severe debilitating congenital anomalies. It draws attention to the importance of this virus for bovines of all age groups.  相似文献   
2.
The serological and virological results of an experimental infection of bovine fetuses with bovine viral diarrhea virus are presented. Four fetuses, 120-165 days gestational age, were inoculated in utero with a second passage virus strain. Two fetuses received a sham-inoculum. A humoral immune response in the virus-inoculated fetuses, was demonstrated three weeks later. In three fetuses only IgM and IgG1 were detectable. The serum from the fourth fetus also contained IgG2 and IgA. Bovine viral diarrhea virus-neutralizing antibodies were detected in two fetuses. These two fetuses inoculated at 135-150 days gestational age, represent the youngest reported bovids, giving a specific response in three weeks following an experimental infection with bovine viral diarrhea virus. The fetal sera did not contain heat-labile factors, which could mediate the neutralization. The virus was not reisolated from any of the fetuses, but viral antigen was nevertheless demonstrated by immunocytochemical methods in sections of several of the fetal organs, primarily lymphoid tissues.  相似文献   
3.
Cachectin/tumor necrosis factor-alpha (TNF), a protein produced by macrophages upon stimulation, has been implicated as an important mediator of inflammatory processes and of clinical manifestations in chronic infectious diseases. In order to study further the potential role of TNF in infectious diseases, a homologous system was employed in which recombinant Escherichia coli (E. coli) derived bovine TNF (rBoTNF) was injected in cattle, either as a single bolus or in a repetitive treatment-regime. No clinical signs were observed, although changes occurred in hematologic and immunologic parameters when less than 0.5 mg of TNF/100 kg body weight was administered twice daily for 18 days. Prolonged treatment with 0.05-0.5 mg/100 kg induced histologic but no gross changes in the kidneys and liver. When doses were increased above 0.5 mg/100 kg, depression, anorexia, cachexia, and diarrhea appeared rapidly. Pathologic changes were apparent in various tissues including liver, kidneys, and lymphoid organs; body fat depots were depleted. Most of these changes appeared to be reversible; return to normal tissue-morphology occurred within 3 weeks of withdrawal of rBoTNF. The clinical and pathologic changes induced by prolonged rBoTNF administration resembled those observed in some chronic parasitic and viral infections of cattle in which macrophage-activation characteristically occur. Our finding may be relevant to the elucidation of the pathogenesis of these and other chronic infections.  相似文献   
4.
The phenotypic identity of mononuclear leukocytes in skin and digestive tract of bovine viral diarrhea virus (BVDV)-infected animals was examined using sensitive single and double labeling immunocytochemical techniques. Occurrence and distribution of B lymphocytes, T lymphocytes of either the helper (BoT4) or suppressor/cytotoxic (BoT8) subsets, and macrophages (M phi) were examined. No differences were found in the skin and digestive tract of persistently infected clinically healthy calves and uninfected controls, despite widespread virus-antigen presence in keratinocytes (stratum basale and stratum spinosum) of skin and upper digestive tract, in dermal/subepithelial macrophages (M phi), in gut-epithelial cells, and in lymphocytes and M phi/monocytes of blood and lymphoid tissues of the former group. M phi and Langerhans cells (LC) were the prevailing leukocyte types in the keratinized epithelia and subepithelial connective tissues, with occasional T lymphocytes (mostly intraepithelially located and of the BoT8 phenotype). No B cells were seen. Some infiltrating leukocytes also contained virus antigen. In animals succumbing to mucosal disease (MD), hyper- and parakeratotic changes, as well as necrotizing epithelial lesions, were accompanied by massive infiltration in dermis and epithelium of major histocompatibility complex (MHC) class II antigen positive cells (M phi and LC), some T lymphocytes (predominantly BoT8 positive cells), and, only rarely, B cells. M phi also predominated in lamina propria of the gastrointestinal tract. Findings suggest that M phi activation is an important aspect of MD pathogenesis. In contrast, the contention that T lymphocytes may play a major role could not be substantiated.  相似文献   
5.
Interleukin-2 (IL-2) treatment of cells and generation of non-major histocompatibility complex (MHC)-restricted cytotoxic cells from peripheral blood mononuclear leukocytes (PBML) was studied. Effector-target conjugate assays demonstrated that bovine PBML bound but did not lyse K562, HL60S and HL60R cells unless activated with IL-2. The magnitude of IL-2-activated killing of tumor cells as well as the magnitude of antibody-dependent cellular cytotoxicity depended on the IL-2 concentration. A short treatment (12-18 h) of effector cells with IL-2 was sufficient for development of cytotoxic activity. Withdrawal of IL-2 from the culture resulted in a reduction of cytotoxic activity that could be restored by further addition of IL-2. Cytotoxic activity of IL-2-activated populations obtained after nylon wool or Sephadex G-10 passage, and Percoll gradient centrifugation of PBML suggests that lymphokine-activated killer (LAK) cell activity in PBML is mainly mediated by a non-adherent lymphocyte lacking markers for B-cells. Positive and negative selection experiments using cell sorting confirmed these findings and demonstrated that the cell responsible for LAK cell activity in cattle belongs to a non-monocyte, non-B, CD2+ lymphocyte population. Furthermore, cytotoxic activity could not be generated in CD2+ populations enriched for cells expressing molecules equivalent to human and murine CD4 and CD8. These findings suggest that effector cells mediating non MHC-restricted cytotoxicity in cattle prevail in a population bearing a CD2+, CD4-, CD8- phenotype and that this population depends on the continuous presence of IL-2 for optimal cytotoxic function.  相似文献   
6.
The effect of an infection with bovine viral diarrhea virus on fetal bovine tissues as well as the tissue-localization of viral antigen are described. Four bovine fetuses, 120-165 days of gestation, were inoculated in utero with a second passage virus strain. Lymphoid tissues were studied by light and electron microscopy. The infection induced precocious development of the secondary lymphoid organs. Characteristic changes were seen in postcapillary venules, cells of the mononuclear phagocyte system and lymphoid follicles. In all four fetuses the thymus was hypoplastic. In three fetuses this implicated a morphological immaturity, but no actual pathological alterations. In the fourth fetus, the hypoplasia was caused by necrosis and depletion of lymphocytes, attended by infiltration of macrophages. Histopathological changes were also noted in the cerebellum of three fetuses, consisting of necrosis in and depletion of the external germ layer and in the skin and mucous membranes of all four fetuses. The viral antigen was present in cells of the mononuclear phagocyte system, primarily in the lymphoid tissues. The infection was further demonstrated in the affected cerebelli.  相似文献   
7.
Human modification of forest habitats is a major component of global environmental change. Even areas that remain predominantly forested may be changed considerably by human alteration of historical disturbance regimes. To better understand human influences on the abundance and pattern of forest habitats, we studied forest land cover change from 1936 to 1996 in a 25000 km2 landscape in the Oregon (USA) Coast Range. We integrated historical forest survey data and maps from 1936 with satellite imagery and GIS data from 1996 to quantify changes in major forest cover types. Change in the total area of closed-canopy forests was relatively minor, decreasing from 68% of the landscape in 1936 to 65% in 1996. In contrast, large-conifer forests decreased from 42% in 1936 to 17% in 1996, whereas small-conifer forests increased from 21% of the landscape in 1936 to 39% in 1996. Linear regression models were used to predict changes in the proportion of large conifer forest as a function of socioeconomic and environmental variables at scales of subbasins (mean size = 1964 km2, n=13), watersheds (mean size = 302 km2, n=83), and subwatersheds (mean size = 18 km2, n=1325). The proportion of land in private ownership was the strongest predictor at all three spatial scales (partial R2 values 0.57–0.76). The amounts of variation explained by other independent variables were comparatively minor. Results corroborate the hypothesis that differing management regimes on private and public ownerships have led to different pathways of landscape change. Furthermore, these distinctive trajectories are consistent over a broad domain of spatial scales.  相似文献   
8.
In vitro treatment of bovine peripheral blood mononuclear leukocytes, polymorphonuclear neutrophilic granulocytes and alveolar macrophages with recombinant bovine interferons -alpha 1 1, -beta 2 or -gamma induced an immediate increase in the intracellular level of 2'-5' oligoadenylate synthetase activity. The induction was dose-dependent, with interferon -alpha 1 1 and -beta 2 being more potent than interferon-gamma. Maximal levels were reached within 10-12 h with IFN-alpha 1 1, which corresponded well with findings in vivo. In contrast to what has been found in nonlymphoid bovine cells, tumour necrosis factor-alpha did not potentiate the induction of 2-5A synthetase by interferons, neither did it by itself induce the enzyme.  相似文献   
9.
An isolated outbreak of the emerging forest disease sudden oak death was discovered in Oregon forests in 2001. Despite considerable control efforts, disease continues to spread from the introduction site due to slow and incomplete detection and eradication. Annual field surveys and laboratory tests between 2001 and 2009 confirmed a total of 802 infested locations. Here, we apply two invasive species distribution models (iSDMs) of sudden oak death establishment and spread risk to target early detection and control further disease spread in Oregon forests. The goal was to develop (1) a model of potential distribution that estimates the level and spatial variability of disease establishment and spread risk for western Oregon, and (2) a model of actual distribution that quantifies the relative likelihood of current invasion in the quarantine area. Our predictions were based on four groups of primary parameters that vary in space and time: climate conditions, topographical factors, abundance and susceptibility of host vegetation, and dispersal pressure. First, we used multi-criteria evaluation to identify large-scale areas at potential risk of infection. We mapped and ranked host abundance and susceptibility using geospatial vegetation data developed with gradient nearest neighbor imputation. The host vegetation and climate variables were parameterized in accordance to their epidemiological importance and the final appraisal scores were summarized by month to represent a cumulative spread risk index, standardized as five categories from very low to very high risk. Second, using the field data for calibration we applied the machine-learning method, maximum entropy, to predict the actual distribution of the sudden oak death epidemic. The dispersal pressure incorporated in the statistical model estimates the force of invasion at all susceptible locations, allowing us to quantify the relative likelihood of current disease incidence rather than its potential distribution. Our predictions show that 65 km2 of forested land was invaded by 2009, but further disease spread threatens more than 2100 km2 of forests across the western region of Oregon (very high and high risk). Areas at greatest risk of disease spread are concentrated in the southwest region of Oregon where the highest densities of susceptible host species exist. This research identifies high priority locations for early detection and invasion control and illustrates how iSDMs can be used to analyze the actual versus potential distribution of emerging infectious disease in a complex, heterogeneous ecosystem.  相似文献   
10.
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