Immunosuppressive effect of Trypanosoma congolense and Trypanosoma vivax on the secondary immune response of cattle to Mycoplasma mycoides subsp mycoides.     

F R Rurangirwa  H Tabel  G Losos  W N Masiga  P Mwambu 《Research in veterinary science》1978,25(3):395-397

Trypanosoma congolense and T vivax infections in cattle were shown to have a suppressive effect on the secondary humoral immune response to M mycoides. The trypanosome infections caused an involution of the thymus. The secondary response was biphasic in nature and was unrelated to infection with trypanosomes.  相似文献   

An Outbreak of Meningitis in Swine Caused by Haemophilus Species of Bacterium          下载免费PDF全文

Radostits OM  Ruhnke HL  Losos GJ 《The Canadian veterinary journal. La revue veterinaire canadienne》1963,4(10):265-270

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微量Bradford法测定提纯禽结核菌素蛋白含量   总被引：4，自引：0，他引：4  

程君生  毛开荣  丁家波  蒋玉文 《中国兽药杂志》2007,41(6):9-11

研究用96孔微量板Bradford法测定提纯禽结核菌素蛋白含量。通过不同浓度的待测禽结核菌素与考马斯亮蓝G-250溶液混合后，在595nm光波下测定各孔样品的OD值。微量Bradford法检测禽结核菌素的线性范围是50—1000μg／mL，相关系数为0．999，最低定量限为50μg／mL。试验用3支禽结核菌素国际参照品，分别配制成125、250、500μg／mL三种不同浓度，每支每种浓度测定4次，计算实际测得的蛋白质浓度。结果显示，批内相对标准偏差为1．6％～4．4％；批间相对标准偏差0．7％-2．2％。研究结果表明微量Bradford法可作为测定禽结核菌素蛋白含量的一种方法。  相似文献   

Absence of host proteins from the surface of Trypanosoma vivax of cattle     

H. Tabel  G.J. Losos 《Veterinary parasitology》1980,7(4):297-303

Trypanosoma vivax (EATRO 1721) organisms were isolated by DEAE-cellulose chromatography from blood of an experimentally infected calf. Attempts to agglutinate the purified trypanosomes with a rabbit antiserum against whole bovine serum or antisera monospecific for bovine IgG1, IgG2, IgM, complement component C3 or albumin were unsuccessful. The trypanosomes, however, were agglutinated by immune sera of four different calves chronically infected with T. vivax (EATRO 1721). It was concluded that T. vivax organisms purified by DEAE-cellulose chromatography from blood of cattle do not have bovine serum proteins on their surface.  相似文献   

Design of Nonionic Surfactants for Supercritical Carbon Dioxide     

JB McClain  DE Betts  DA Canelas  ET Samulski  JM DeSimone  JD Londono  HD Cochran  GD Wignall  D Chillura-Martino  R Triolo 《Science (New York, N.Y.)》1996,274(5295):2049-2052

Interfacially active block copolymer amphiphiles have been synthesized and their self-assembly into micelles in supercritical carbon dioxide (CO2) has been demonstrated with small-angle neutron scattering (SANS). These materials establish the design criteria for molecularly engineered surfactants that can stabilize and disperse otherwise insoluble matter into a CO2 continuous phase. Polystyrene-b-poly(1,1-dihydroperfluorooctyl acrylate) copolymers self-assembled into polydisperse core-shell-type micelles as a result of the disparate solubility characteristics of the different block segments in CO2. These nonionic surfactants for CO2 were shown by SANS to be capable of emulsifying up to 20 percent by weight of a CO2-insoluble hydrocarbon into CO2. This result demonstrates the efficacy of surfactant-modified CO2 in reducing the large volumes of organic and halogenated solvent waste streams released into our environment by solvent-intensive manufacturing and process industries.  相似文献   

Island biogeography of populations: an introduced species transforms survival patterns     

Schoener TW  Losos JB  Spiller DA 《Science (New York, N.Y.)》2005,310(5755):1807-1809

Population phenomena, which provide much of the underlying basis for the theoretical structure of island biogeography, have received little direct study. We determined a key population trait-survival-in the Bahamian lizard Anolis sagrei on islands with an experimentally introduced predatory lizard and on neighboring unmanipulated islands. On unmanipulated islands, survival declined with several variables, most notably vegetation height: The island with the shortest vegetation had nearly the highest survival recorded for any lizard. On islands with the introduced predator, which forages mostly on the ground, A. sagrei shifted to taller vegetation; unlike on unmanipulated islands, its survival was very low on islands with the shortest vegetation but was higher on the others. Thus, species introduction radically changed a resident species' relation of survival to a key island-biogeographical variable.  相似文献   

Unusual ovarian activity in a mare preceding the development of an ovarian granulosa cell tumour   总被引：1，自引：0，他引：1  

CHOPIN JB  CHOPIN LK  KNOTT LM  DE KRETSER DM  DOWSETT KF 《Australian veterinary journal》2002,80(1):32-36

An 8-year-old mare, with a foal at foot, was inseminated on foal heat with frozen semen, with the resultant pregnancy lost between days 34 and 41. The right ovary developed a large anovulatory follicle that was non-responsive to multiple doses of ovulating agents. The follicle eventually appeared to luteinise, although plasma progesterone concentrations did not reflect this. Another follicle developed, responded to GnRH and resulted in a pregnancy from frozen semen that went to term with a healthy foal. When the mare was examined after foaling, the structure on the right ovary appeared to be a granulosa cell tumour; the left ovary was smaller than normal and non-functional. Surgical removal of the right ovary before increasing photoperiod resulted in a return to function of the left ovary and a pregnancy to frozen semen on the second cycle following removal. Figures showing concentrations of inhibin, progesterone, androstenedione, oestradiol and testosterone are presented for this entire period. Unusual ovarian activity in the mare might be a prelude to the development of a granulosa cell tumour.  相似文献   

Induction of testicular degeneration in bulls by isoimmunization   总被引：2，自引：0，他引：2  

G J Losos  A J Winter  K McEntee 《American journal of veterinary research》1968,29(12):2295-2306

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Contingency and determinism in replicated adaptive radiations of island lizards   总被引：2，自引：0，他引：2  

JB Losos  TR Jackman  A Larson  K Queiroz  L Rodriguez-Schettino 《Science (New York, N.Y.)》1998,279(5359):2115-2118

The vagaries of history lead to the prediction that repeated instances of evolutionary diversification will lead to disparate outcomes even if starting conditions are similar. We tested this proposition by examining the evolutionary radiation of Anolis lizards on the four islands of the Greater Antilles. Morphometric analyses indicate that the same set of habitat specialists, termed ecomorphs, occurs on all four islands. Although these similar assemblages could result from a single evolutionary origin of each ecomorph, followed by dispersal or vicariance, phylogenetic analysis indicates that the ecomorphs originated independently on each island. Thus, adaptive radiation in similar environments can overcome historical contingencies to produce strikingly similar evolutionary outcomes.  相似文献   

Nonrandom processes maintain diversity in tropical forests     

Wills C  Harms KE  Condit R  King D  Thompson J  He F  Muller-Landau HC  Ashton P  Losos E  Comita L  Hubbell S  Lafrankie J  Bunyavejchewin S  Dattaraja HS  Davies S  Esufali S  Foster R  Gunatilleke N  Gunatilleke S  Hall P  Itoh A  John R  Kiratiprayoon S  de Lao SL  Massa M  Nath C  Noor MN  Kassim AR  Sukumar R  Suresh HS  Sun IF  Tan S  Yamakura T  Zimmerman J 《Science (New York, N.Y.)》2006,311(5760):527-531

An ecological community's species diversity tends to erode through time as a result of stochastic extinction, competitive exclusion, and unstable host-enemy dynamics. This erosion of diversity can be prevented over the short term if recruits are highly diverse as a result of preferential recruitment of rare species or, alternatively, if rare species survive preferentially, which increases diversity as the ages of the individuals increase. Here, we present census data from seven New and Old World tropical forest dynamics plots that all show the latter pattern. Within local areas, the trees that survived were as a group more diverse than those that were recruited or those that died. The larger (and therefore on average older) survivors were more diverse within local areas than the smaller survivors. When species were rare in a local area, they had a higher survival rate than when they were common, resulting in enrichment for rare species and increasing diversity with age and size class in these complex ecosystems.  相似文献