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At least 919 records · Page 51Linked to original sources
PubMed1983

Infection of mammalian cells with Theileria species.

Experiments were carried out to determine the susceptibility of mammalian cells to infection with different species of Theileria in vitro. Sporozoites of Theileria parva (parva), Theileria parva (lawrencei) and Theileria taurotragi were isolated from Rhipicephalus appendiculatus ticks by grinding infected ticks in medium, filtering the suspension and concentrating by centrifugation. The sporozoites were used in attempts to infect in vitro peripheral blood leucocytes harvested from 16 different mammalian species which included 12 species of Bovidae from 6 different sub-families. The technique was shown to be both sensitive and reproducible. The sporozoites of T. parva (parva) infected and transformed cells from 2 species of the sub-family Bovinae, the two cattle types and African buffalo. Theileria parva (lawrencei) infected and transformed cells from the two cattle types, African buffalo and Defassa waterbuck. Theileria taurotragi sporozoites infected in vitro cells from 11 different species of Bovidae which were members of 6 sub-families; Bovinae, Tragelaphinae, Reduncinae, Alcelaphinae, Antilopinae and Caprinae. Transformed lymphoblastoid cell lines were established from 7 of the species infected. Sporozoite attachment and infection was not observed with non-susceptible bovid host cells, nor were any of the non-bovid leucocytes infected by the parasites. The host range observed in this study corresponded to the known host range in vivo.

Animals↗
PubMed2005

Phylogeny of Trypanosoma ( Megatrypanum ) theileri and related trypanosomes reveals lineages of isolates associated with artiodactyl hosts diverging on SSU and ITS ribosomal sequences.

SSU ribosomal sequences of trypanosomes from Brazilian cattle and water buffalo were used to infer phylogenetic relationships between non-pathogenic T. theileri and allied species parasitic in artiodactyls. T. theileri trypanosomes from distinct geographical regions in Brazil and from other countries were tightly clustered into the 'clade T. theileri' distant from the 'T. brucei clade' of pathogenic parasites of artiodactyls, and also distinct from trypanosomes of other mammals. The existence of this monophyletic assemblage (T. theileri clade) composed only by isolates from artiodactyl species justifies the continued recognition of the subgenus T. (Megatrypanum) with T. theileri as its type species. Phylogenies based on SSU and ITS1 ribosomal sequences produced the same branching pattern with isolates from different mammalian hosts clustered in 5 lineages: A, related to water buffalo; B, C and D, to cattle; E, to fallow deer. The pattern of host specificity allied to some congruence between host and parasite phylogenies suggested association of these trypanosomes with their respective hosts. Segregation of cattle isolates into three lineages revealed an overall geographical structure. Moreover, positioning of trypanosomes infecting tabanids in the T. theileri clade is consistent with the role of these flies as important vectors of these trypanosomes.

Animals↗
PubMed1988

The distribution of African swine fever virus isolated from Ornithodoros moubata in Zambia.

African swine fever (ASF) has been reported in the Eastern Province of Zambia since 1912 and is now considered to be enzootic there. A survey of the distribution of ASF virus in Zambia was carried out by virus isolation from Ornithodoros moubata ticks collected from animal burrows in National Parks and Game Management Areas in northern, eastern, central and southern Zambia. ASF virus was isolated from ticks in all areas examined. The prevalence of infection in O. moubata was between 0.4% in South Luangwa National Park and 5.1% in Livingstone Game Park and mean infectious virus titres ranged from 10(3.4) HAD50/tick in Kakumbe Game Management Area to 10(5.9) HAD50/tick in Chunga and Nalusanga Game Management Areas. The prevalence of infection in adult ticks was between 4.7% and 5.3% in all areas examined except Sumbu National Park and Livingstone Game Park, where the prevalence was 15.1% and 13.2% respectively in adult ticks. The ratio of infected females to males for all the infected adult ticks in all areas of Zambia was 3.2:1.

African Swine Fever↗
PubMed1991

A sensitive method for isolating Fusobacterium necrophorum from faeces.

The isolation of Fusobacterium necrophorum present in small numbers in heavily contaminated material such as faeces or soil is hampered by the lack of an efficient selective medium and by the high minimum infective dose of the organism. A sensitive method for the detection and isolation of faecal strains of F. necrophorum type A was based on the subcutaneous injection of faeces, suspended (5% w/v) in broth culture of Actinomyces (Corynebacterium) pyogenes or Staphylococcus aureus to increase fusobacterial infectivity, into mice pretreated with clostridial antitoxins. When necrobacillosis developed F. necrophorum was identified microscopically in tissue from the advancing edge of the lesion and isolated on a partly selective medium. The enhancement of fusobacterial infectivity produced by A. pyogenes and by S. aureus was high, but the latter was slightly the more efficient, enabling as few as 80 F. necrophorum organisms/g of faeces to be detected. Use of the method showed that 3 of 16 wallabies had F. necrophorum in their faeces at the time of examination. Numerous epidemiological applications are suggested.

Animals↗
PubMed1993

The role of wild animals, other than buffalo, in the current epidemiology of foot-and-mouth disease in Zimbabwe.

Between 1989 and 1992, 7970 wild ungulates, comprising 14 different species, were tested for antibodies to types SAT 1, SAT 2 and SAT 3 foot-and-mouth disease (FMD) virus. Of these 1.2% were found to be positive and these included impala (Aepyceros melampus), eland (Taurotragus oryx), waterbuck (Kobus ellipsiprymnus) and sable (Hippotragus niger). All the positive animals were either from the wildlife areas where buffalo (Syncerus caffer) occur or from ranches where clinical FMD had occurred in cattle. The role of these animal species in the current epidemiology of FMD in Zimbabwe is discussed.

Animals↗
PubMedDate not supplied

The horizontal cells of artiodactyl retinae: a comparison with Cajal's descriptions.

The morphology of horizontal cells in ox, sheep, and pig retinae as observed after Lucifer Yellow injections are described and compared with the descriptions of Golgi-stained cells by Ramón y Cajal (1893). Horizontal cells in the retinae of less domesticated species, wild pig, fallow and sika deer, mouflon, and aurochs were also examined. All these retinae have two types of horizontal cell; their morphologies are in common, although with some familial differences. Their basic appearance is as Cajal described; except in one important respect, a single axon-like process could not be identified on the external horizontal cells. It is concluded that external horizontal cells of artiodactyls correspond to the axonless (A-type) cells of other mammals. Cajal's internal horizontal cells have a single axon which contacts rods. This type corresponds to the B-type cells of other mammalian retinae. Artiodactyl A- and B-type horizontal cells differ from those of many other mammals in that the B-type dendritic tree is robust and the A-type dendritic tree is delicate. Historically, this morphological difference between orders of mammals has led to some confusion. The comparisons presented here suggest that the morphological types of primate horizontal cells can be integrated into a general mammalian classification.

Animals↗
PubMed2002

Sexual segregation in ungulates: a comparative test of three hypotheses.

In most social ungulate species, males are larger than females and the sexes live in separate groups outside the breeding season. It is important for our understanding of the evolution of sociality to find out why sexual segregation is so widespread not only in ungulates but also in other mammals. Sexual body size dimorphism was proposed as a central factor in the evolution of sexual segregation in ungulates. We tested three hypotheses put forward to explain sexual segregation: the predation-risk, the forage-selection, and the activity budget hypothesis. We included in our analyses ungulate species ranging from non-dimorphic to extremely dimorphic in body size. We observed oryx, zebra, bighorn sheep and ibex in the field and relied on literature data for 31 additional species. The predation-risk hypothesis predicts that females will use relatively predator-safe habitats, while males are predicted to use habitats with higher predation risk but better food quality. Out of 24 studies on different species of ungulates, females and their offspring chose poorer quality but safer habitat in only eight cases. The forage-selection hypothesis predicts that females would select habitat based on food quality, while males should prefer high forage biomass. In fact, females selected higher quality food in only six out of 18 studies where males and females segregated, in eight studies there was no difference in forage quality and in four studies males were in better quality habitat. The activity budget hypothesis predicts that with increasing dimorphism in body size males and females will increasingly differ in the time spent in different activities. Differences in activity budgets would make it difficult for males and females to stay in mixed-sex groups due to increased costs of synchrony to maintain group cohesion. The predictions of the activity budget hypothesis were confirmed in most cases (22 out of 23 studies). The heavier males were compared to females, the more time females spent foraging compared to males. The bigger the dimorphism in body mass, the more males spent time walking compared to females. Lactating females spent more time foraging than did non-lactating females or males. Whether species were mainly bulk or intermediate feeders did not affect sexual differences in time spent foraging. We conclude that sexual differences in activity budgets are most likely driving sexual segregation and that sexual differences in predation risk or forage selection are additive factors.

Animals↗
PubMed1998

Origin of the catalytic activity of bovine seminal ribonuclease against double-stranded RNA.

Bovine seminal ribonuclease (RNase) binds, melts, and (in the case of RNA) catalyzes the hydrolysis of double-stranded nucleic acid 30-fold better under physiological conditions than its pancreatic homologue, the well-known RNase A. Reported here are site-directed mutagenesis experiments that identify the sequence determinants of this enhanced catalytic activity. These experiments have been guided in part by experimental reconstructions of ancestral RNases from extinct organisms that were intermediates in the evolution of the RNase superfamily. It is shown that the enhanced interactions between bovine seminal RNase and double-stranded nucleic acid do not arise from the increased number of basic residues carried by the seminal enzyme. Rather, a combination of a dimeric structure and the introduction of two glycine residues at positions 38 and 111 on the periphery of the active site confers the full catalytic activity of bovine seminal RNase against duplex RNA. A structural model is presented to explain these data, the use of evolutionary reconstructions to guide protein engineering experiments is discussed, and a new variant of RNase A, A(Q28L K31C S32C D38G E111G), which contains all of the elements identified in these experiments as being important for duplex activity, is prepared. This is the most powerful catalyst within this subfamily yet observed, some 46-fold more active against duplex RNA than RNase A.

Amino Acid Substitution↗
PubMed1999

CAG repeats in various organisms studied by Southern blot analysis.

A 90-nucleotide (CAG)30, single-stranded DNA was used to probe Southern blots in order to indicate the quantity and distribution of long CAG repeats in selected genomes. Bovine and rat genomes were found to contain a particularly high content of CAG repeats, while the repeats were comparatively rare in the human genome. A particularly strong signal in the bovine genome was due to a CAG repeat associated with the 1.709 satellite. A similar element was found in goat and musk, but not in the other artiodactyls tested, suggesting that this particular CAG repeat developed some 10-20 million years ago within a 3.8-kb unit presently belonging to the satellite element and that this unit has later multiplied in the genome. Single-copy repeats could be discerned in yeast, but not in mammals. Thus the probe did not detect specific repeats in patients with CAG repeat diseases.

Animals↗
PubMed2003

Molecular epidemiology of SAT3-type foot-and-mouth disease.

VP1 gene nucleotide sequences of 51 SAT3-type foot-and-mouth disease (FMD) viruses from seven southern and eastern African countries were used to infer a gene phylogeny. Results obtained by phylogenetic analysis of the homologous 405 nt region corresponding to the C-terminal 128 amino acids of 1D and adjacent 7 amino acids of 2A indicate that there are six distinct virus lineages evolving independently in different geographical localities in accordance with the FMD topotype concept. Topotypes I-IV occur in southern Africa, whilst topotypes V and VI are unique to East Africa. Viruses of different topotypes differ from each other at 20% or more of the nucleotide sites, specified in this study. Despite the limited geographical distribution of this serotype, the level of intratypic variation is intermediate between that of SAT1 and SAT2, both of which are widely distributed in sub-Saharan Africa. Within SAT3, 37.3% and 47.4% of sites were completely conserved on nucleotide and amino acid levels, respectively. The locality-specific grouping of viruses permits accurate determination of the sources of outbreaks, whilst the high levels of variation within the immunodominant 1D protein has implications for the control of the disease through vaccination.

Africa, Eastern↗