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  • 1
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: A cluster of eight genes, vbsGSO, vbsADL, vbsC and vbsP, are involved in the synthesis of vicibactin, a cyclic, trihydroxamate siderophore made by the symbiotic bacterium Rhizobium leguminosarum. None of these vbs genes was required for symbiotic N2 fixation on peas or Vicia. Transcription of vbsC, vbsGSO and vbsADL (but not vbsP) was enhanced by growth in low levels of Fe. Transcription of vbsGSO and vbsADL, but not vbsP or vbsC, required the closely linked gene rpoI, which encodes an ECF σ factor of RNA polymerase. Transfer of the cloned vbs genes, plus rpoI, to Rhodobacter, Paracoccus and Sinorhizobium conferred the ability to make vicibactin on these other genera. We present a biochemical genetic model of vicibactin synthesis, which accommodates the phenotypes of different vbs mutants and the homologies of the vbs gene products. In this model, VbsS, which is similar to many non-ribosomal peptide synthetase multienzymes, has a central role. It is proposed that VbsS activates L-N5-hydroxyornithine via covalent attachment as an acyl thioester to a peptidyl carrier protein domain. Subsequent VbsA-catalysed acylation of the hydroxyornithine, followed by VbsL-mediated epimerization and acetylation catalysed by VbsC, yields the vicibactin subunit, which is then trimerized and cyclized by the thioesterase domain of VbsS to give the completed siderophore.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Biochimica et Biophysica Acta (BBA)/General Subjects 673 (1981), S. 435-442 
    ISSN: 0304-4165
    Keywords: (Rat lymph) ; Colchicine treatment ; Sialyltransferase
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Biochimica et Biophysica Acta (BBA)/General Subjects 673 (1981), S. 435-442 
    ISSN: 0304-4165
    Keywords: (Rat lymph) ; Colchicine treatment ; Sialyltransferase
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Agriculture and human values 12 (1995), S. 95-106 
    ISSN: 1572-8366
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Tick and tick-borne diseases, especially East Coast fever, caused byTheileria parva, are amongst the most important factors limiting cattle production in Eastern, Central, and Southern Africa. In the past, they have been controlled mainly by the use of acaricides to kill ticks. Immunization has been shown to be an effective alternative method of control of tick-borne diseases in limited field trials. A development program has been initiated to produce vaccines and implement immunization on a wide scale in the region in a sustainable manner as part of an integrated tick and tickborne disease control program. The consequent reduction in cattle mortality is expected to have far-reaching benefits for the region.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    World journal of urology 14 (1996), S. 124-130 
    ISSN: 1433-8726
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Metastasis is the cascade of events involved in the transition of a malignancy from a localized tumor to the establishment of a distant foci. In this review we define the known stages and the factors involved. The multiplicity of steps involved allows many opportunities for therapeutic intervention. Current research has focused on interruption of a step or a series of steps to limit the spread of cancer. With emphasis on the urologic malignancies, we outline the research thus far accomplished in the field of metastasis.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Educational studies in mathematics 14 (1983), S. 73-85 
    ISSN: 1573-0816
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract This study reports the development and use of a taxonomy for describing the way distance students plant their work and use course materials to complete mathematics exercises. A taxonomy of 12 component procedures of cognitive operations was developed from a set of propositions about problem-solving. Two undergraduate students of mathematics and one graduate thought aloud as they completed an exercise using standard course materials under distance study conditions. The verbal protocols of the students' problem-solving processes and use of course materials were described and compared using the taxonomy. The two undergraduates centred on single aspects of the problem. They used examples rather than conceptual information presented in the written materials. The graduate made greater use of theories and definitions, but like the undergraduates, neglected the expository material. No student planned the work. The data are discussed in terms of the usefulness of a taxonomic description of thinking-aloud data for course designers and mathematics teachers.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Tropical animal health and production 14 (1982), S. 127-140 
    ISSN: 1573-7438
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé Une souche pathogène et quatre souches bovines bénignes deTheileria d'Afrique australe, toutes transmises parRhipicephalus appendiculatus ont été comparées entre elles, puis avec des souches de bovins et de buffles du complexe deT. parva de l'Afrique australe et orientale et enfin avec des souches bovines deT. taurotragi de Tanzanie considérées comme originaires de l'Elan du Cap. Les critères utilisés ont été d'ordre parasitologique, clinique, sérologique avec recherche des caractères d'immunité-croisée. Les sourches bénignes sont similaires àT. taurotragi. La sérologie a suggéreré queT. taurotragi est également infectieuse chez le mouton. La souche pathogène appartient au complexe deT. parva ; ce complexe consiste en une série de types présentant divers comportements depuis le typelawrencei du buffle causant l'affection “Corridor”, et le typebovis cause de la theileriose maligne de Rhodésie jusqu'au type “parva” cause de l'East Coast Fever classique. 7 passages bétail-tique d'une souche de typebovis n'ont pas réussi à la transformer en typeparva. 4 espèces de Theileries bovines sont maintenant connues en Afrique australe :T. parva (typeslawrencei etbovis) etT. taurotragi toutes deux transmises parR. appendiculatus, T. mutans etT. velifera avec toutes deuxAmblyomma spp. comme vecteurs.
    Abstract: Resumen Se compararon 5 cepas deTheileria del sur de Africa, 1 patógena y 4 benignas, todas transmitidas porRhipicephalus appendiculatus, entre si y también con cepas derivadas de bovinos y búfalos, del complejoT. parva, del sur y este de Africa, y con cepas bovinas deT. taurotragi de Tanzania derivadas de antílope eland. Los criterios de evaluación utilizados fueron parasitológico, clínico, serológico, utilizando también los caracteres de inmunidad cruzada. Las cepas benignas son similares aT. taurotragi de bovinos. Las pruebas serológicas indicaron que esta última es también infectiva para ovejas. Las cepas patógenas pertenecen al complejoT. parva; este último consiste de un rango de tipos con diferente comportamiento que van desde el tipolawrencei (búfalo) que causa la enfermedad Corridor, a través del tipobovis que causa la theileriosis maligna de Rodesia, hasta el tipoparva que causa la típica Fiebre de la Costa Este. Siete pasajes a través de bovinos y garrapatas de un tipobovis, no produjo transformación alguna al tipoparva. Se conocen entonces 4 especies deTheileriae bovina en el sur de Africa :T. parva (tiposlawrencei ybovis) yT. taurotragi, ambas transmitidas porR. appendiculatus, yT. mutans yT. velifera, ambas transmitidas porAmblyomma spp.
    Notes: Summary One pathogenic and 4 mild bovineTheileria strains from southern Africa, all transmitted byRhipicephalus appendiculatus, were compared amongst themselves as well as to bovine and buffalo strains of theT. parva complex from eastern and southern Africa and to bovine strains ofT. taurotragi from Tanzania considered to be derived from eland antelope. Criteria used were parasitological, clinical, serological and cross-immunity characters. The mild strains are similar to bovineT. taurotragi. Serological evidence suggested thatT. taurotragi is also infective to sheep. The pathogenic strain belongs to theT. parva complex; the latter consists of a series of types with different behaviour ranging from thelawrencei-type (of buffalo) causing Corridor disease, through thebovis-type causing Rhodesian malignant theileriosis to theparva-type causing classical East Coat fever. Seven cattle-tick passages of abovis-type strain did not result in transformation into aparva-type. Four species of bovineTheileriae are now known to occur in southern Africa:T. parva (lawrencei- andbovis-types) andT. taurotragi, both transmitted byR. appendiculatus, andT. mutans andT. velifera both withAmblyomma spp. as vectors.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Tropical animal health and production 15 (1983), S. 39-42 
    ISSN: 1573-7438
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé La transmission expérimentale deTheileria parva parva chez les bovins parRhipicephalus zambeziensis a été démontrée expérimentalement à partir de la nymphe jusqu'au stade adulte, celle deTheileria parva lawrencei, Theileria parva bovis etTheileria taurotragi à partir de la larve jusqu'au stade nymphal et à partir de la nymphe jusqu'au stade adulte. Au cours d'un seul essai la tique n'a pas réussi à transmettreTheileria mutans. Cette tique se révèle être un vecteur deT. parva lawrencei sur le terrain au Zimbabwe.
    Abstract: Resumen Se domostro experimentalmente la transmisión deTheileria parva parva en bovinos, teniendo como vector el estado de ninfa a adulto deRhipicephalus zambesis, como tambien la transmisión deTheileria parva lawrencei; Theileria parva bovis y Theileria taurotragi de larva a ninfa y ninfa a adulto. En un ensayo aislado, la garrapata no transmitióTheileria mutans. Se crée que la garrapata es el vector deTheileria parva lawrencei en condiciones de campo, en Zimbabwe.
    Notes: Summary Rhipicephalus zambeziensis was shown experimentally to transmitTheileria parva parva in cattle from nymph to adult andTheileria parva lawrencei, Theileria parva bovis andTheileria taurotragi from larva to nymph and nymph to adult. In a single trial the tick failed to transmitTheileria mutans. The tick is believed to be a vector ofT. parva lawrencei in the field in Zimbabwe.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Tropical animal health and production 15 (1983), S. 87-94 
    ISSN: 1573-7438
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé Une enquête sur l'incidence des anticorps deBabesia bigemina etBabesia bovis chez des veaux âgés de l à 3 ans dans 274 localités du Zimbabwe a révélé queB. bigemina était présente dans tout le pays avec pour vecteur principalBoophilus decoloratus. La répartition deB. bovis suivait de près celle de son vecteurBoophilus microplus qui est limité à la partie est du pays. La stabilité enzootique pourB. bigemina a été notée dans la plupart des régions d'élevage traditionnel où le traitement des bovins par bains détiqueurs a été interrompu depuis plusieurs années; mais elle était moins courante dans les fermes industrielles où ces bains sont pratiqués régulièrement. La stabilité enzootique pourB. bovis était réduite à quelques localités des régions d'élevage traditionnel et le parasite était rare dans les fermes industrielles.
    Abstract: Resumen Se llevó a cabo un estudio de a incidencia de anticuerpos deBabesia bigemina yBabesia bovis, en terneros en edades comprendidas entre uno y tres años, en 274 localidades de Zimbabwe. Los resultados revelaron, queB. bigemina existe en todo el pais conjuntamente con su vector principal,Boophilus decoloratus. La distribuición deB. bovis siguió aquélla de su vectorBoophilus microplus, el cual existe únicamente en la parte oriental del pais. La estabilidad enzoótica deB. bigemina fué notoria en la mayoria de regiones en donde los baños garrapaticidas habían sido interrumpidos por varios años. En las regiones en donde se practicaban baños regulares en fincas comerciales, ésta fué menos manifiesta. La estabilidad enzoòtica deB. bovis estuvo restringida a unas pocas localidades de pastoreo comunal y la presencia de parásitos fué rara en fincas o hatos comerciales.
    Notes: Summary A survey on the incidence of antibodies toBabesia bigemina andBabesia bovis in one to three year old calves at 274 localities in Zimbabwe revealed thatB. bigemina occurred throughout the country together with its main vector,Boophilus decoloratus. The distribution ofB. bovis followed closely that of its vectorBoophilus microplus which is limited to the eastern part of the country. Enzootic stability forB. bigemina was recorded in most of the communal tribal areas where regular dipping of cattle had been interrupted for several years but was less common on commercial farms where regular dipping is practised. Enzootic stability forB. bovis was restricted to a few localities in communal areas and the parasite was rare on commercial farms.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Tropical animal health and production 16 (1984), S. 63-70 
    ISSN: 1573-7438
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé Une enquête sur l'incidence des anticorps dus àAnaplasma marginale chez des veaux de un à trois ans a été effectuée au Zimbabwe en utilisant le test d'agglutination en tube capillaire. Les anticorps ont été décelés dans tous les cas sauf un des 118 lots de sérum recueillis dans les différentes localités du pays. Il n'y a eu aucune relation apparente entre la fréquence de l'apparition de réactions sérologiques positives, qui était semblable dans les régions d'élevage industriel et d'élevage villageois et l'incidence d'anaplasmose clinique. Cependant les effectifs les plus élevés de bovins positifs ont été généralement localisés dans les régions les plus fortement infestées par les tiques. Il semblerait que les ongulés sauvages agissent comme réservoirs de l'infection puisque des anticorps àA. marginale ont été décelés dans des sérums de buffles (Syncerus caffer) et d'impalas (Aepyceros melampus).
    Abstract: Resumen Se llevo a cabo un estudio de la prevalencia de anaplasmosis (Anaplasma marginale) en Zimbabwe, utilizando la prueba de aglutinación en tubos capilares. Se detectaron anticuerpos en todos, menos en un grupo, de 118 muestras de suero colectadas en diferentes localidades através del país. No hubo correlación entre reactores positivos de áreas de pastoreo comerciales y comunales, y casos de anaplasmosis clínica. Sinembargo, el número más alto de reactores correspondió, al área de pastoreo más infestada de garrapatas. Hubo evidencia, que animales salvajes de pezuña endida, servian posiblemente de portadores de la infección, debido a que se encontraron anticuerpos deA. marginale en suero de búfalos (Syncerus caffer) e impala (Aepyceros melampus).
    Notes: Summary A survey on the incidence of antibodies toAnaplasma marginale in one- to three-year-old cattle was carried out in Zimbabwe using the capillary tube agglutination test. Antibodies were detected in all but one of 118 batches of sera collected from different localities throughout the country. There was no clear relationship between the frequency of occurrence of positive serological reactors, which was similar in both commercial and communal farming areas, and the incidence of clinical anaplasmosis. However, the highest numbers of cattle exhibiting positive reactions were generally recorded from the areas that were most heavily tick infested. There was evidence that wild ungulates may serve as reservoirs of infection as antibodies toA. marginale were detected in sera from buffalo (Syncerus caffer) and impala (Aepyceros melampus).
    Type of Medium: Electronic Resource
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