Selection of amino acid sequences in the beta chain of the T cell antigen receptor   总被引：29，自引：0，他引：29  

S M Hedrick  I Engel  D L McElligott  P J Fink  M L Hsu  D Hansburg  L A Matis 《Science (New York, N.Y.)》1988,239(4847):1541-1544

The induction of an immune response in mammals is initiated by specifically reactive T lymphocytes. The specificity of the reaction is mediated by a complex receptor, part of which is highly variable in sequence and analogous to immunoglobulin heavy- and light-chain variable domains. The functional specificity of the T cell antigen receptor is, however, markedly different from immunoglobulins in that it mediates cell-cell interactions via the simultaneous recognition of foreign antigens and major histocompatibility complex-encoded molecules expressed on the surface of various lymphoid and nonlymphoid cells. The relation between the structure of the receptor and its functional specificity was investigated by analyzing the primary sequences of the receptors expressed by a series of T lymphocyte clones specific for a model antigen, pigeon cytochrome c. Within this set of T lymphocyte clones there was a striking selection for amino acid sequences in the receptor beta-chain in the region analogous to the third complementarity-determining region of immunoglobulins. Thus, despite the functional differences between T cell antigen receptors and immunoglobulin molecules, analogous regions appear to be important in determining ligand specificity.  相似文献   

Prevalence and clonal diversity of Campylobacter jejuni from dairy farms and urban sources     

B Adhikari  JH Connolly  P Madie  PR Davies 《New Zealand veterinary journal》2013,61(6):378-383

AIM: To investigate the role of free-living animals such as spar- rows, rodents and flies as potential reservoirs of Campylobacter spp on a dairy farm, and to assess the genetic diversity among Campylobacter isolates from the farm and an urban source.

METHODS: A total of 290 samples (bovine, passerine and ro- dent faeces, and whole flies) were collected from a large com- mercial dairy farm in the Manawatu district in New Zealand, and from faeces from urban sparrows in a nearby city. Other samples collected from the dairy farm included five from silage, two from aprons worn by workers during milking, two from workers' boots and two from water in troughs in a paddock. Isolates of thermophilic Campylobacter spp were identified mor- phologically and phenotypically and further characterised mo- lecularly using pulsed-field gel electrophoresis (PFGE) and the restriction enzyme SmaI.

RESULTS: Campylobacter jejuni was the only Campylobacter species isolated from all samples. The highest prevalence was found in faeces from dairy cows (54%), followed by faeces from sparrows from the urban area (40%) and the farm (38%), and from rodents (11%) and whole flies (9%). Other samples from the farm environment such as silage, trough water, and work- ers' aprons and boots were also positive for C. jejuni. Of the 22 restriction patterns obtained, seven were common to more than one source.

CONCLUSIONS: Cattle, sparrows, rodents and flies are po- tential reservoirs of C. jejuni on dairy farms. Identical clones of C. jejuni carried by cattle, sparrows, flies and rodents prob- ably indicate a common source of infection. The high level of asymptomatic carriage of C. jejuni by healthy dairy cows could be sufficient to maintain infections within the dairy farm sur- roundings via environmental contamination.  相似文献   

Effect of setting a maximum milking time,from peak lactation,on production,milking time and udder health     

JG Jago  JE McGowan  JH Williamson 《New Zealand veterinary journal》2013,61(5):246-252

Abstract

AIM: To examine the effect of setting a maximum milking time, from peak lactation until drying-off, on production, duration of milking, and udder health of dairy cows.

METHODS: Forty cows were assigned in twin-pairs to be either milked until cups were removed at a milk flow-rate threshold of 0.35 kg/minute (Control), or until cups were removed at a milk flow-rate threshold of 0.35 kg/minute, or maximum time, whichever came first (MaxT). The maximum time was set by determining the milking time of the 70th percentile cow when ranked from fastest to slowest, irrespective of yield. The milking routine was typical of that practised on dairy farms in New Zealand, and involved no pre-milking preparation. The study began at peak lactation (68 (SD 7) days in milk; DIM) and continued for 26 weeks. Duration of milking and milk yield were measured for each milking. Composition of milk was determined from weekly herd tests, and milk quality from fortnightly somatic cell counts (SCC). Completeness of milking and teat condition were assessed during the study. The bacterial status of quarter milk samples was determined at the beginning and end of the study, and all treated cases of clinical mastitis recorded. ANOVA was used to examine the effect of treatment group on variables of interest.

RESULTS: Total milk, fat and protein yields during the study period did not differ between treatments. On average, 30.3% of the morning and 27.6% of the afternoon milkings of MaxT cows reached the maximum time at which cups were removed, and were therefore shortened. While the average milking time of the slowest-milking cow was longer for the Control compared with MaxT group in Weeks 1–18, the average milking time did not differ between treatments. There was no difference in overall SCC, and the incidence of clinical mastitis, or the percentage of infected quarters at drying-off, was similar for the MaxT and Control cows.

CONCLUSION: The results show that setting a maximum milking time can reduce the milking time of slower-milking cows in a herd without compromising overall herd production and udder health.

CLINICAL RELEVANCE: Although the numbers of cows in the study were small there was no evidence of a major increase in SCC, or subclinical or clinical mastitis when a maximum milking time was set for slower-milking cows.  相似文献   

Rapid vacuolar sequestration: the horseweed glyphosate resistance mechanism     

Xia Ge  D André d'Avignon  Joseph JH Ackerman  R Douglas Sammons 《Pest management science》2010,66(4):345-348

BACKGROUND: Glyphosate‐resistant (GR) weed species are now found with increasing frequency and threaten the critically important GR weed management system. RESULTS: The reported ³¹P NMR experiments on glyphosate‐sensitive (S) and glyphosate‐resistant (R) horseweed, Conyza canadensis (L.) Cronq., show significantly more accumulation of glyphosate within the R biotype vacuole. CONCLUSIONS: Selective sequestration of glyphosate into the vacuole confers the observed horseweed resistance to glyphosate. This observation represents the first clear evidence for the glyphosate resistance mechanism in C. canadensis. Copyright © 2010 Society of Chemical Industry  相似文献   

Sorption of As(V) by Goethite Particles and Study of Their Flocculation     

Matis  K. A.  Zouboulis  A. I.  Zamboulis  D.  Valtadorou  A. V. 《Water, air, and soil pollution》1999,111(1-4):297-316

Arsenate oxyanions were removed from aqueous solutions by sorption onto synthetic goethite, which was applied as fine particulate suspension during laboratory experiments. The main parameters affecting this treatment process were investigated, namely the concentrations of goethite and of arsenic(V), contact time, temperature, solution pH values and ionic strength variations, and typical adsorption isotherms were calculated. The study of flocculation of goethite particulates in bench scale was subsequently carried out in presence of pentavalent arsenic (being a toxic pollutant), by applying an appropriate optical technique. The flocculation dynamics of dispersed goethite particles was examined, complemented by turbidity and electrophoretic mobility measurements.  相似文献   

High-Tc superconductors in the two-dimensional limit:     

JH Choy  SJ Kwon  GS Park 《Science (New York, N.Y.)》1998,280(5369):1589-1592

The free modulation of interlayer distance in a layered high-transition temperature (high-Tc) superconductor is of crucial importance not only for the study of the superconducting mechanism but also for the practical application of high-Tc superconducting materials. Two-dimensional (2D) superconductors were achieved by intercalating a long-chain organic compound into bismuth-based high-Tc cuprates. Although the intercalation of the organic chain increased the interlayer distance remarkably, to tens of angstroms, the superconducting transition temperature of the intercalate was nearly the same as that of the pristine material, suggesting the 2D nature of the high-Tc superconductivity.  相似文献   

Rupert Paul Herd     

JH Arundel 《Australian veterinary journal》1999,77(12):803-803

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Amoebic meningoencephalitis in a young grey kangaroo (Macropus giganteus)     

JH NORTON  WJ HARTLEY 《Australian veterinary journal》1993,70(11):421-421

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Evaluation of protein-A gold labelling with Dirofilaria immitis antigen coated nitrocelluslose for the detection of anti-heartworm antibody in dogs     

JH TARISH  RB ATWELL 《Australian veterinary journal》1989,66(9):295-296

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Infiltrating Foxp3+ Regulatory T cells and Histopathological Features in Canine Classical and Spermatocytic Seminomas     

JH Kim  SK Chon  KS Im  NH Kim  KW Cho  JH Sur 《Reproduction in domestic animals》2013,48(2):218-222

In humans, regulatory T (T reg) cells are known to play a critical role in both the regulation of immune homoeostasis and the progression of cancer. However, there is little information about the identification, characterization and the function of T reg cells in canine tumours. We identified T reg cells in 28 canine seminoma samples using a Forkhead box P3 (Foxp3) antibody and investigated the relationship between T reg cell infiltration and histopathological features of classical and spermatocytic seminomas (SE and SS, respectively). The Foxp3 protein showed nuclear immunostaining in infiltrating lymphocytes, and Foxp3+ cells were diffused or focally distributed in seminoma tissues. Foxp3+ cells were frequently present in the SS histotype, in seminomas that showed no evidence of tumour cell invasion into the vessels and in seminomas showing a diffuse growth pattern with three cell types. Neither the SE/SS histotype nor the histopathological features of the tumour correlated with Foxp3+ cell counts. These results indicate that Foxp3+ T reg cells may be associated with a less malignant histological phenotype or may not play a critical role in the immune response of canine seminomas. Moreover, Foxp3+ T reg cells may be associated with SS seminoma, but further studies, involving a larger number of samples, are required to better understand whether these cells play a critical role in the immune response in canine seminomas. This is the first report to demonstrate the characteristics of T reg cell infiltration in canine seminoma.  相似文献