首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   66篇
  免费   3篇
林业   1篇
农学   3篇
  21篇
农作物   3篇
水产渔业   4篇
畜牧兽医   36篇
植物保护   1篇
  2020年   2篇
  2019年   2篇
  2018年   2篇
  2016年   1篇
  2015年   2篇
  2014年   4篇
  2013年   3篇
  2012年   6篇
  2011年   5篇
  2010年   2篇
  2009年   5篇
  2008年   3篇
  2007年   2篇
  2006年   4篇
  2005年   3篇
  2004年   4篇
  2003年   1篇
  2002年   3篇
  2000年   2篇
  1999年   3篇
  1998年   1篇
  1997年   1篇
  1995年   1篇
  1990年   1篇
  1988年   1篇
  1983年   1篇
  1982年   2篇
  1980年   1篇
  1955年   1篇
排序方式: 共有69条查询结果,搜索用时 109 毫秒
61.

Background

Acute phase proteins haptoglobin (Hp), serum amyloid A (SAA) and lipopolysaccharide binding protein (LBP) have suggested to be suitable inflammatory markers for bovine mastitis. The aim of the study was to investigate acute phase markers along with clinical parameters in two consecutive intramammary challenges with Escherichia coli and to evaluate the possible carry-over effect when same animals are used in an experimental model.

Methods

Mastitis was induced with a dose of 1500 cfu of E. coli in one quarter of six cows and inoculation repeated in another quarter after an interval of 14 days. Concentrations of acute phase proteins haptoglobin (Hp), serum amyloid A (SAA) and lipopolysaccharide binding protein (LBP) were determined in serum and milk.

Results

In both challenges all cows became infected and developed clinical mastitis within 12 hours of inoculation. Clinical disease and acute phase response was generally milder in the second challenge. Concentrations of SAA in milk started to increase 12 hours after inoculation and peaked at 60 hours after the first challenge and at 44 hours after the second challenge. Concentrations of SAA in serum increased more slowly and peaked at the same times as in milk; concentrations in serum were about one third of those in milk. Hp started to increase in milk similarly and peaked at 36–44 hours. In serum, the concentration of Hp peaked at 60–68 hours and was twice as high as in milk. LBP concentrations in milk and serum started to increase after 12 hours and peaked at 36 hours, being higher in milk. The concentrations of acute phase proteins in serum and milk in the E. coli infection model were much higher than those recorded in experiments using Gram-positive pathogens, indicating the severe inflammation induced by E. coli.

Conclusion

Acute phase proteins would be useful parameters as mastitis indicators and to assess the severity of mastitis. If repeated experimental intramammary induction of the same animals with E. coli is used in cross-over studies, the interval between challenges should be longer than 2 weeks, due to the carry-over effect from the first infection.  相似文献   
62.
The study was undertaken to determine how equine red blood cells (RBCs) survive in storage bags designed for use with human RBCs. Separated RBCs were stored in a routine manner for 35 days and examined every 7 days for storage lesions. Measured parameters included haematology, haemolysis, pH, potassium, lactate, adenosine triphosphate (ATP) and 2,3-diphosphoglycerate (2,3-DPG). All tests were performed in vitro. Haematology did not change significantly. Haemolysis increased during storage but did not exceed human limits. pH and 2,3-DPG decreased, while lactate, potassium and ATP increased. RBCs deteriorated somewhat during storage, but when compared with human in vitro parameters, remained suitable for transfusion. It is concluded that equine erythrocytes can be stored for at least 35 days before transfusion.  相似文献   
63.

Background

The purpose of this study was to develop and validate an analytical method to determine the presence of hyaluronic acid derived disaccharides in equine synovial fluid.

Findings

A high-performance liquid chromatography method for the determination of hyaluronic acid derived unsaturated disaccharides in equine synovial fluid was developed and validated. The method is based on the measurement of unsaturated disaccharides released by digestion of linear hyaluronic acid molecules. The method showed linearity (r2 = 0.996) over the full working concentration range 0.89-30 mg/l. Relative standard deviation of intra- and inter-day precision ranged from of 4.3-6.7% and 7.1-7.8% respectively. The detection limit was 0.3 mg/l corresponding to 20 mg/l in synovial fluid. Accuracy of the assay was 97-103%. This method was evaluated by determining the concentration of unsaturated disaccharides from hyaluronic acid in synovial fluid of horses with lameness in the metacarpo-/metatarsophalangeal joint localized with positive response to intra-articular anesthesia.

Conclusions

The described method is valid for determination of hyaluronic acid derived disaccharides in equine synovial fluid. This method was applied to a larger research project dealing with a new form of intra-articular therapy in horses with arthritic diseases.  相似文献   
64.
A cross-over study was conducted to investigate the effect of intramammarily infused lipopolysaccharide (LPS) on the acute phase reaction in early (EL) and in late (LL) lactation. Nine cows received intramammary injections of 100 microg of Escherichia coli 0111:B4 LPS during EL and LL. The severity of each cows systemic and local signs and change in milk appearance were recorded and scored throughout the experiment. Systemic and local signs were found to be more serious in EL cows. Tumor necrosis factor alpha (TNF alpha) was detected in milk but not in serum. Serum amyloid A (SAA) concentrations increased both in serum and in milk. The milk TNF alpha concentrations peaked at 8 h post-challenge (PC). SAA concentrations started to increase at 8 h PC, and peak concentrations were seen at 32 and 48 h PC in milk and serum, respectively. The milk TNF alpha and SAA seemed to be correlated, being on average higher in EL. Serum SAA concentration was not correlated with milk TNF alpha or SAA, nor with the severity of local or systemic signs, but was correlated with changes in milk appearance.  相似文献   
65.
The effect of catalase on the toxicity of cadmium (Cd) in Cd-resistant Staphylococcus aureus 3719+ and its plasmid-negative Cd-sensitive variant 3719– was studied. Catalase on a solid medium increased the recovery of Gd-stressed S. aureus 3719– cells, and the addition of catalase into a liquid growth medium resulted in a shortened lag phase of growth especially in S. aureus 3719–. The catalase activity of S. aureus 3719+ cell suspensions was greater than the corresponding activity of S. aureus 3719– cell suspensions. Cd did not influence the activity of beef liver catalase or the catalase production of the bacterial cells.Catalase reduced the toxicity of Cd especially for S. aureus 3719–. The greater catalase production of S. aureus 3719+ might be one factor in its resistance against the toxic effects of Cd. It is suggested that Cd together with hydrogen peroxide may induce oxidative damage to cells if there is not sufficient catalase available to decompose all the hydrogen peroxide formed.  相似文献   
66.
Summary Transgenic barley plants (Hordeum vulgare L. cv. Kymppi) were obtained by particle bombardment of various tissues. Immature embryos and microspore-derived cultures were bombarded with gold particles coated with plasmid DNA carrying the gene coding for neomycin phosphotransferase II (NPTII), together with plasmid DNA containing the gene for -glucuronidase (GUS).Bombarded immature embryos were grown to plants without selection and NPTII activity was screened in small plantlets. One plant proved to be transgenic (T0). This chimeric plant passed the transferred nptII gene to its T1 progeny. The presence of the nptII gene was demonstrated by the PCR technique and enzyme activity was analyzed by an NPTII gel assay. Four T0 spikes and 15 T1 offspring were transgenic. The integration and inheritance was confirmed by Southern blot hybridization. Transgenic T2 and T3 plants were produced by isolating embryos from green grains of transgenic T1 and T2 plants, respectively and growing them to plants. After selfing, the ratio of transgenic to non-transgenic T2 offspring was shown to follow the rule of Mendelian inheritance. The general performance of transgenic plants was normal and no reduction in fertility was observed.Microspore-derived cultures were bombarded one and four weeks after microspore isolation. After bombardment, cultures were grown either with or without antibiotic selection (geneticin R or kanamycin). When cultures were grown without selection and regenerated plants were transferred to kanamycin selection in rooting phase, one out of a total of about 1500 plants survived. This plant both carried and expressed the transferred nptII gene. The integration was confirmed by Southern blot hybridization. This plant was not fertile.  相似文献   
67.
Coagulase-negative staphylococci-emerging mastitis pathogens   总被引:3,自引:0,他引:3  
Coagulase-negative staphylococci (CNS) have become the most common bovine mastitis isolate in many countries and could therefore be described as emerging mastitis pathogens. The prevalence of CNS mastitis is higher in primiparous cows than in older cows. CNS are not as pathogenic as the other principal mastitis pathogens and infection mostly remains subclinical. However, CNS can cause persistent infections, which result in increased milk somatic cell count (SCC) and decreased milk quality. CNS infection can damage udder tissue and lead to decreased milk production. Staphylococcus simulans and Staphylococcus chromogenes are currently the predominant CNS species in bovine mastitis. S. chromogenes is the major CNS species affecting nulliparous and primiparous cows whereas S. simulans has been isolated more frequently from older cows. Multiparous cows generally become infected with CNS during later lactation whereas primiparous cows develop infection before or shortly after calving. CNS mastitis is not a therapeutic problem as cure rates after antimicrobial treatment are usually high. Based on current knowledge, it is difficult to determine whether CNS species behave as contagious or environmental pathogens. Control measures against contagious mastitis pathogens, such as post-milking teat disinfection, reduce CNS infections in the herd. Phenotypic methods for identification of CNS are not sufficiently reliable, and molecular methods may soon replace them. Knowledge of the CNS species involved in bovine mastitis is limited. The dairy industry would benefit from more research on the epidemiology of CNS mastitis and more reliable methods for species identification.  相似文献   
68.
Indicators of inflammation in the diagnosis of mastitis   总被引:18,自引:0,他引:18  
Mastitis affects the quality of milk and is a potential health risk for the other cows. In a well managed dairy herd, in addition to clinical mastitis, subclinical mastitis should be efficiently detected. Bacteriological sampling is not feasible as a routine test to identify subclinical mastitis, and indirect tests of mastitis are more suitable for selecting cows with intramammary infections for subsequent bacteriological sampling. Mastitis affects the composition of milk, and the degree of changes depends on the infecting agent and the inflammatory response. Indicators of inflammation in the milk which can be determined using rapid, reliable and easy routine techniques, can be used for the early detection of mastitis. The measuring of the somatic cell count in milk is the standard method, but the analysis technique is problematic for routine use in herds. The most promising parameters for monitoring subclinical mastitis are milk N-acetyl-beta-D-glucosaminidase activity, lactose, and electrical conductivity along with some other indicators such as optical and milk flow measurements, preferably with an inter-quarter evaluation included in the test. Acute phase proteins, haptoglobin and serum amyloid A, are also potential candidates for mastitis monitoring. New mastitis detection systems which can be adapted into on-line use are urgently needed, since dairy units are growing bigger and automatic milking systems are being taken into use.  相似文献   
69.
The specialized crayfish parasite Aphanomyces astaci causes the devastating crayfish plague in European crayfish. Even though A. astaci sporulation has been thoroughly studied under pure culture conditions, little is known about the sporulation dynamic from its live host. Our purpose was to investigate the A. astaci spore dynamic in its native parasite-host relationship by monitoring the sporulation from carrier crayfish into the ambient water using agent specific qPCR. American signal crayfish (Pacifastacus leniusculus) with known positive carrier status were housed individually and communally in two experimental set-ups using multiple replicates and different temperatures. Water samples were collected weekly, and spore numbers were quantified. We demonstrate here that live latent carrier crayfish continuously released a moderate number of A. astaci spores (~2700 spores per crayfish/week) in the absence of death and moulting events. In contrast, a pronounced sporulation increase was seen already one week prior to death in moribund crayfish, suggesting a crayfish plague-like condition developing in weakened or stressed individuals. Significantly more spores were produced at 18°C compared to 4°C, while a negative correlation was detected between spore numbers and temperatures rising from 17 to 23°C. This study is the first attempt to quantify the spore release from carrier crayfish on the basis of qPCR applied on water samples, and demonstrate that the approach successfully unravel A. astaci sporulation patterns. The results emphasize that carrier crayfish pose a constant infection risk to highly susceptible crayfish species regardless of crayfish life cycle state.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号