Biomedical subjects

A C Marriott

Publications and source records attributed to A C Marriott.

24 records · Page 2Linked to original sources

PubMed1991

Dissemination, replication, and trans-stadial persistence of Dugbe virus (Nairovirus, Bunyaviridae) in the tick vector Amblyomma variegatum.

The dissemination and replication of Dugbe (DUG) virus and its tissue tropisms in the tick vector Amblyomma variegatum were examined by immunohistochemical analysis using specific antibody, in situ hybridization with a viral-complementary riboprobe, and infectivity assays of dissected tissues. Dugbe virus was localized in both unfed and feeding adults inoculated as nymphs or orally infected by capillary feeding, and in nymphs infected by capillary feeding. In non-feeding ticks, the main sites of DUG virus replication were the epidermis, hemocytes associated with loose connective tissue, and a small number of phagocytic digestive cells in the gut lumen. Virus infectivity in the hemolymph was associated entirely with hemocytes. Dugbe viral antigen or infectivity was not detected in the salivary glands until after the start of feeding. Viral titers in the salivary glands of feeding ticks were about ten-fold higher than in gut, ovary, or loose connective tissue. The level of infection decreased during molting and increased during feeding. Viral particles and pathologic effects were not detected in infected ticks. The primary site of trans-stadial persistence of DUG virus is the hemocytes. Tick hemocytes and other motile cells may be important in the transmission of persistent virus infection from one cell or organ to another by diapedesis.

Animals↗

PubMed1990

Coding strategy of the S RNA segment of Dugbe virus (Nairovirus; Bunyaviridae).

The S RNA segment of Dugbe (DUG) virus (Nairovirus; Bunyaviridae) was sequenced from three overlapping cDNA clones and by primer extension. The S RNA is 1712 nucleotides in length and contains one large open reading frame (ORF) of 1326 nucleotides coding for a 49.4-kDa protein on viral complementary (vc) RNA. This protein in size corresponds to the DUG nucleocapsid (N) protein (P. Cash, 1985, J. Gen. Virol. 66, 141-148). The 49.4-kDa product was expressed as a fusion protein with beta-galactosidase in Escherichia coli cells and confirmed as DUG N protein by Western blotting with DUG N-specific monoclonal antibody. An additional ORF of 150 nucleotides coding for a possible 5.9-kDa protein is present in the +1 reading frame, 3' to the N protein ORF on vcRNA. DUG S segment mRNA was found to be essentially full length. No evidence was obtained for the existence of a smaller mRNA species that could code for a 5.9-kDa protein. Comparisons of the DUG S RNA sequence and predicted N protein amino acid sequence, with the respective sequences of snowshoe hare, La Crosse (bunyaviruses), Punta Toro, Sandfly fever Sicilian (phleboviruses), and Hantaan (hantavirus) viruses, failed to detect any sequence similarity, although the genomic structure of DUG S RNA is similar to that of the S RNA segment of Hantaan (HTN) virus.

Amino Acid Sequence↗

PubMed1990

Detection of an arbovirus in an invertebrate and a vertebrate host using the polymerase chain reaction.

The ability of the polymerase chain reaction (PCR) to diagnose an arboviral infection in an arthropod vector or a mammalian host was examined. Dugbe (DUG) viral RNA was detected in RNA extracts from infected tissue samples by reverse transcription and enzymatic amplification of the resulting cDNA using Taq DNA polymerase, followed by characterisation of the amplified product by agarose gel electrophoresis or dot-blot hybridisation. Viral RNA was detected in the organs and haemolymph of infected Amblyomma variegatum ticks, and in the brain and blood of infected mice. The PCR technique was found to be as sensitive as a plaque assay for detecting DUG virus, but not as sensitive as intracerebral inoculation of mice. The sensitivity of the technique was greatest using crude RNA extracts combined with dot-blot analysis of the resulting PCR products using a DUG specific cDNA probe. A result was obtained within 48 h using PCR whereas biological assays took at least 8 days to diagnose the virus infection.

Animals↗

PubMed1990

RNA probes detect nucleotide sequence homology between members of two different nairovirus serogroups.

Cloned cDNA derived from the small (S) and medium (M) genomic RNA segments of Dugbe (DUG) virus, isolate ArD44313, a member of the Nairobi sheep disease (NSD) serogroup of nairoviruses (family, Bunyaviridae) was used to prepare 32P-labelled DNA and RNA probes. The S and M segments of six isolates of DUG virus all hybridised to both DNA and RNA probes, although the M segment of isolate KT281/75 reacted only weakly. Of nine other nairoviruses tested, representing all the six other serogroups within the Nairovirus genus, none hybridised to the DNA probes. However, under conditions of low stringency, the DUG S and M RNA probes hybridised to the respective S and M segments of Ganjam (GAN) virus (another member of the NSD serogroup). The DUG S RNA probe also hybridised to the S segments of Crimean-Congo haemorrhagic fever (CCHF) virus and Hazara (HAZ) virus (members of the CCHF serogroup). The indicated sequence relationships between DUG, GAN, CCHF and HAZ viruses show that the NSD serogroup is more closely related to members of the CCHF serogroup than it is to nairoviruses of the other five serogroups.

Animals↗

PubMed1989

The S RNA segment of Sandfly Fever Sicilian virus: evidence for an ambisense genome.

The complete nucleotide sequence of the S RNA segment of Sandfly Fever Sicilian (SFS) virus (Phlebovirus, Bunyaviridae) was determined from overlapping cDNA clones and by primer extension. The RNA is 1746 nucleotides in length and has two large open reading frames (ORF), one of which (24.8 kDa) is viral-complementary in sense, and the other (30.4 kDa) is in the viral sense. This ambisense genome arrangement has been seen in another member of the Phlebovirus genus, Punta Toro (PT) virus (T. Ihara, H. Akashi, and D. H. L. Bishop, 1984, Virology 136, 293-306), but not in representatives of either the Bunyavirus or Hantavirus genera of the Bunyaviridae. Comparison of the predicted amino acid sequences for SFS virus with the recognized products of PT S RNA (T. Ihara, Y. Matsuura, and D. H. L. Bishop, 1985, Virology 147, 317-325; H. A. Overton, T. Ihara, and D. H. L. Bishop, 1987, Virology 157, 338-350) indicated that the 24.8-kDa ORF encodes the nucleoprotein (N) of SFS virus, and the 30.4-kDa ORF codes for a nonstructural protein (NSs). Subgenomic messenger RNAs, from which these two proteins are presumably translated, were detected in virus-infected cells.

Amino Acid Sequence↗

PubMed1984

Mitochondrial DNA in Fusarium oxysporum is a 46.5 kilobase pair circular molecule.

Purified mitochondria were obtained from the phytopathogenic fungus Fusarium oxysporum f. sp. lycopersici by mechanical disruption of protoplasts, followed by differential and density gradient centrifugation. DNA, extracted from the mitochondria, was shown by electron microscopy and restriction endonuclease analysis to be a 46.5 kilobase pair circular molecule.

Base Composition↗