Experimental infection of cats (Felis catus) with Tritrichomonas foetus isolated from cattle     

Stockdale HD  Dillon AR  Newton JC  Bird RC  Bondurant RH  Deinnocentes P  Barney S  Bulter J  Land T  Spencer JA  Lindsay DS  Blagburn BL 《Veterinary parasitology》2008,154(1-2):156-161

Tritrichomonas foetus is recognized as the causative agent of venereal trichomoniasis in cattle. It is characterized by embryonic and early fetal death and post-coital pyometra, and feline trichomoniasis, manifest as chronic, large bowel diarrhea. Many of the infected cats are less than 2 years old and specific routes of transmission remain unknown. We recently demonstrated that feline isolates of T. foetus can successfully infect heifers, resulting in pathologic changes similar, but not identical to those previously reported as representative of bovine trichomoniasis. In this study, we experimentally infected six cats less than 1 year of age with a bovine (D-1) isolate of T. foetus and one cat with a feline (AUTf-1) isolate of T. foetus. Within 2 weeks, the cat infected with the feline (AUTf-1) isolate was culture positive for trichomonads in weekly fecal samples. At the end of 5 weeks, only one cat infected with the bovine (D-1) isolate was fecal culture positive for trichomonads. At necropsy, the intestine of each cat was removed and divided into five sections (ileum, cecum, anterior, medial and posterior colon). Contents from each section were collected and cultured. The cat infected with the feline (AUTf-1) isolate was culture positive in the ileum, cecum, medial and posterior colon. Two cats infected with the bovine (D-1) isolate were culture positive in the cecum only. Additionally, each intestinal section was submitted to a pathologist for histopathological examination. The combined results indicate that there are demonstrable differences between the feline (AUTf-1) and bovine (D-1) isolates regarding their infectivity in cats.  相似文献   

Pathology of naturally occurring bovine tuberculosis in England and Wales   总被引：3，自引：0，他引：3  

Liebana E  Johnson L  Gough J  Durr P  Jahans K  Clifton-Hadley R  Spencer Y  Hewinson RG  Downs SH 《Veterinary journal (London, England : 1997)》2008,176(3):354-360

The aim of this study was to obtain a contemporary data set of pathology in tuberculin reactor and in-contact cattle in England and Wales. Four hundred animals (200 reactors and 200 in-contacts) from 242 farms located in 14 counties in Western England and Wales were examined. The mean number of lymph nodes (LNs) with tuberculosis (TB)-like lesions per TB-confirmed animal was 1.7 in reactors and 1.5 in in-contact animals. Tuberculous lesions in both reactor and in-contact animals were most commonly observed in the LNs of the thorax, followed by the head and abdomen, particularly the mediastinal, retropharyngeal and tracheobronchial LNs. Twenty-five reactors had macroscopic lesions in the palatine tonsils. Among TB-confirmed cattle, 27% of reactors and 9% of in-contact animals had gross TB-like lesions in the lungs, particularly in the caudal lobes. Gross lesions that were not TB-confirmed were parasitic granulomas (45%), bacterial or mycotic club-forming pyogranulomas (27%) and bacterial abscesses (23%). Diagnostic sensitivity was maximised when bacteriology and histopathology were used concurrently. Stage IV granulomas, alone or in combination with other stages, constituted 63% of lesions, while 16% of lesions were stage I/II granulomas. Caseous necrosis and calcification were common features of the granulomas encountered in natural Mycobacterium bovis infections, even with pathology limited to a small number of sites. Granulomas often covered large areas of histological sections and typically contained only small numbers of acid fast bacilli.  相似文献   

Histological observations of bovine tuberculosis in lung and lymph node tissues from British deer     

Johnson LK  Liebana E  Nunez A  Spencer Y  Clifton-Hadley R  Jahans K  Ward A  Barlow A  Delahay R 《Veterinary journal (London, England : 1997)》2008,175(3):409-412

Deer are recognized as hosts of Mycobacterium bovis and assessing the role of wild cervids in perpetuating tuberculosis among cattle has motivated extensive research on several continents. In this paper, the histopathology of lymph node and lung tuberculous granulomas in M. bovis positive British deer is presented. The overall aim was to seek further insights into the potential for onward transmission from infected deer to other species, including cattle. Samples were obtained from an extensive survey of wild mammals in South-West England and from statutory tuberculosis surveillance. M. bovis culture-positive samples were characterised microscopically as to their stage of lesion advancement, number of acid-fast bacilli and granuloma encapsulation. Seventy percent of the deer developed granulomas containing far greater numbers of M. bovis bacilli than typically reported in cattle. Red and fallow deer had the largest number of poorly encapsulated granulomas often containing many hundreds of bacilli. The results are consistent with infected wild British deer being a potential source of environmental contamination and onward transmission to other species. However, further work on levels of bacillary shedding is required before this can be confirmed.  相似文献   

Effects of ultraviolet radiation on the growth and morphology of Hymenolepis microstoma (Cestoda)     

J H Butler  F H Whittaker  H T Spencer 《Folia parasitologica》1972,19(2):113-120

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Photoemission evidence for a remnant fermi surface and a d-wave-like dispersion in insulating Ca2CuO2Cl2     

F Ronning  C Kim  DL Feng  DS Marshall  AG Loeser  LL Miller  JN Eckstein  I Bozovic  Z Shen 《Science (New York, N.Y.)》1998,282(5396):2067-2072

An angle-resolved photoemission study is reported on Ca2CuO2Cl2, a parent compound of high-Tc superconductors. Analysis of the electron occupation probability, n(k), from the spectra shows a steep drop in spectral intensity across a contour that is close to the Fermi surface predicted by the band calculation. This analysis reveals a Fermi surface remnant, even though Ca2CuO2Cl2 is a Mott insulator. The lowest energy peak exhibits a dispersion with approximately the &cjs3539;coskxa - coskya&cjs3539; form along this remnant Fermi surface. Together with the data from Dy-doped Bi2Sr2CaCu2O8+delta, these results suggest that this d-wave-like dispersion of the insulator is the underlying reason for the pseudo gap in the underdoped regime.  相似文献   

In search of the first flower: A jurassic angiosperm, archaefructus, from northeast china   总被引：1，自引：0，他引：1  

G Sun  DL Dilcher  S Zheng  Z Zhou 《Science (New York, N.Y.)》1998,282(5394):1692-1695

Angiosperm fruiting axes were discovered from the Upper Jurassic of China. Angiosperms are defined by carpels enclosing ovules, a character demonstrated in this fossil. This feature is lacking in other fossils reported to be earliest angiosperms. The fruits are small follicles formed from conduplicate carpels helically arranged. Adaxial elongate stigmatic crests are conspicuous on each carpel. The basal one-third of the axes bore deciduous organs of uncertain affinities. No scars of subtending floral organs are present to define the individual fertile parts as floral units, but the leaf-like structures subtending each axis define them as flowers. These fruiting axes have primitive characters and characters not considered primitive.  相似文献   

Forest fires: An example of self-organized critical behavior   总被引：1，自引：0，他引：1  

BD Malamud  G Morein  DL Turcotte 《Science (New York, N.Y.)》1998,281(5384):1840-1842

Despite the many complexities concerning their initiation and propagation, forest fires exhibit power-law frequency-area statistics over many orders of magnitude. A simple forest fire model, which is an example of self-organized criticality, exhibits similar behavior. One practical implication of this result is that the frequency-area distribution of small and medium fires can be used to quantify the risk of large fires, as is routinely done for earthquakes.  相似文献   

Compensation of horizontal temperature and salinity gradients in the ocean mixed layer   总被引：1，自引：0，他引：1  

DL Rudnick  R Ferrari 《Science (New York, N.Y.)》1999,283(5401):526-529

Establishment of the temperature-salinity relationship in the ocean has concerned oceanographers for decades because of its importance for understanding ocean circulation. High-resolution measurements in the ocean mixed layer are used to show that temperature and salinity gradients on horizontal scales of 20 meters to 10 kilometers tend to compensate in their effect on density. These observations support the notion of a horizontal mixing in the mixed layer that depends on density gradient.  相似文献   

Limaria hians (Mollusca: Limacea): a neglected reef‐forming keystone species     

J.M. Hall‐Spencer  P.G. Moore 《水产资源保护:海洋与淡水生态系统》2000,10(4):267-277

1. The case is made for recognition of the marine bivalve Limaria hians as a reef‐forming species, which plays a key architectural role in certain benthic communities around the United Kingdom and Ireland. 2. This species uses byssal threads to construct nests that can coalesce to form reefs that cover hectares of seabed, contain multiple conspecifics and bind sediment. In so doing, L. hians modifies physical, chemical and biological processes at the sediment–water interface. 3. Such nests support a high diversity of associated organisms in coarse‐grade sediments (19 species of algae and 265 species of invertebrates from six discrete nests in Loch Fyne are reported on), although the biological interactions between species both inside and outside this assemblage (e.g. predatory cod) are unknown. 4. Being insubstantial, labyrinthine structures situated on the sediment surface, Limaria nests are sensitive to mechanical impacts, such as those caused by moorings, hydraulic dredging for infaunal bivalves and scallop dredging. 5. At appropriate sites, the status of L. hians can contribute a useful indication of disturbance on coarse‐grade sediments. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

Impact of Spodoptera frugiperda neonate pretreatment conditions on Vip3Aa19 insecticidal protein activity and laboratory bioassay variation          下载免费PDF全文

Karen F Da Silva  Terence A Spencer  Carolina Camargo Gil  Blair D Siegfried  Frederick S Walters 《Pest management science》2016,72(4):837-844

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