Biomedical subjects

I D Marshall

Publications and source records attributed to I D Marshall.

At least 37 records · Page 2Linked to original sources

PubMed1980

Arboviruses of coastal south-eastern Australia.

During investigations of epidemic polyarthritis at Nelson Bay, New South Wales, 12 strains of Ross River virus, the causative agent, were recovered from pools of mosquitoes. In addition, the mosquito pools yielded 9 strains of the flavivirus Edge Hill, 4 strains of a bunyavirus, Gan Gan, 1 strain of an orbivirus Tilligerry, and 1 strain of an ungrouped probable arbovirus, Yacaaba. The latter 3 viruses were found to be antigenically distinct from previously recorded arboviruses. A case of epidemic polyarthritis probably contracted at Bawley Point, approximately 400 kilometres south of Nelson Bay on the south coast of New South Wales, is recorded. Mosquitoes collected in the nearby Termeil State Forest one year later yielded a strain of Ross River virus and 5 strains of a previously undescribed ungrouped togavirus, Termeil. The extent of arboviral activity in temperate coastal areas of south-eastern Australia was unexpected.

Animals↗

PubMed1980

Bunyaviridae.

The family Bunyaviridae comprises over 200 viruses (serotypes, subtypes, and varieties) that infect vertebrates and/or invertebrates. Four genera of viruses have been defined (Bunyavirus, Nairovirus, Phlebovirus, and Uukuvirus). The main characteristics of the member viruses are: (i) the virus particles are for the most part uniformly spherical, 80-110 nm in diameter, and possess a unit membrane envelope from which protrude polypeptide spikes 5-10nm long; (ii) the viruses have three helical nucleocapsids, often in the form of supercoiled circles, each consisting of a single species of single-stranded RNA, major nucleocapsid polypeptide, N, and at least in some cases minor amounts of a large polypeptide which may be a transcriptase component; (iii) the genome is composed of three species of RNA (L, large; M, medium; and S, small), organized in end-hydrogen bonded circular structures; (iv) most viruses have three major virion polypeptides (N, and two surface polypeptides, designated G1 and G2); (v) for at least some member viruses, the virions have been shown to contain an RNA-directed RNA polymerase, believed to be responsible for the synthesis of viral complementary mRNA, so that bunyaviruses are considered to be negative-stranded viruses; (vi) at least some bunyaviruses are capable of heterologous virus genome segment reassortment and can form recombinant viruses at high or low frequency; (vii) viruses appear to mature primarily at smooth membrane surfaces and accumulate in Golgi vesicles and saccules, or nearby; (viii) transovarial, venereal and/or transstadial transmission in arthropods has been shown to occur for some members of the family.

Bunyaviridae↗

PubMed1979

Cross-reactive cytotoxic T cells to alphavirus infection.

Secondary Tc cells immune to alphaviruses (BEB, SIN and SFV) cross-react between serologically defined subgroups at the level of target lysis and at the level of induction of response. Despite this apparently complete Tc cell cross-reactivity between BEB, SIN and SFV, antisera raised against BEB and SIN showed virus specificity in their ability to block Tc cell-mediated lysis of alphavirus-infected targets. This result suggests that Tc cells recognize the same viral antigen molecule as antibodies, but with less specificity. Other possible interpretations are discussed.

Animals↗

PubMed1977

Antigenically distinct strains of Ross River virus from north Queensland and coastal New South Wales.

Ross River virus strains recovered from north Queensland and the central coast of New South Wales can be clearly discriminated by the use of a short incubation haemagglutination inhibition test. Antigenic homology of strains within these regions and heterology between the regions seem unaffected by time, passage history, adaptation to laboratory mice and the nature of the original source material yielding the strains. It is concluded that the two antigenic types are enzootic to their respective regions and that they have evolved in isolation from a common ancestral virus. A short incubation complement fixation test was found to be more sensitive than the haemagglutination inhibition test in attempts to characterize the virus type inducing convalescent antibody in humans and horses.

Animals↗

PubMed1977

Association of Australian arboviruses with nervous disease in horses.

An outbreak of Murray Valley encephalitis (MVE) occurred in New South Wales during the first five months of 1974. Specimens from 52 horses with nervous disease collected January to May 1974 were examined histopathological or virologically. Although MVE virus was not isolated, 13 horses had serological evidence of recent infection with MVE virus. Another 4 horses had evidence of recent infection with Ross River virus. Two animals had histological evidence of viral infection of the central nervous system. Attempts to experimentally infect 2 horses with a low dose of MVE virus were not successful by intravenous, intramuscular and subcutaneous routes.

Animals↗

PubMed1977

Investigations of reasons for the avirulence of the A7 strain of Semliki Forest virus in adult mice.

A strain of Semliki Forest virus (A7) which is avirulent in adult mice killed baby mice in a similar manner to strain V13 which was also virulent for adult mice. In the muscle and brains of baby mice A7 and V13 replicated and produced haemagglutinating activity similarly. Our previous suggestion that defective interfering particles were present in the brains of A7-infected adult mice appears not to be so. The interference formerly detected was due to an inhibitor present in brain tissue of adult and baby mice both normal and infected. Homogenates of A7-infected adult brain produced normal RNA species in BHK cells and not those characteristic of defective interfering particles. Organ culture experiments indicated that avirulence of A7 was not due to lack of release of virus from infected adult brain cells. Also, A7 as well as V13 was detected and was probably replicating in all parts of the brain and spinal cord that were sectioned and examined. Evidence is presented that suggests that the reason for the avirulence of A7 for adult mice compared with its virulence for baby mice may relate to a lower ability to replicate in brain tissue per se rather than to interaction with host defence mechanisms.

Age Factors↗

PubMed1976

The responses of the popliteal lymph node of the sheep to Ross River and Kunjin viruses.

The responses of popliteal lymph nodes of sheep to Ross River virus (RRV) or Kunjin virus (KV) have been studied by monitoring the cell populations, virus titre, antibody titre and plaque-forming cell (PFC) content of the efferent lymph. In a typical primary response to subcutaneous inoculation in the lower hind limb of either RRV or KV, the flow rate of lymph increased slightly. Increased cell concentrations in the lymph following inoculation caused the hourly cell outputs to rise 5.3- to 10.1-fold above pre-challenge levels. High cell outputs were sustained at greater than 3-fold above pre-challenge figures for up to 10 days. The increased number of large, blastic lymphocytes ranged from 4.0- to 14.9-fold; the increase in these cells usually followed the rise in total number of lymphocytes by 24 to 48 h and remained at greater than 3-fold higher levels for up to 12 days. Ross River virus was recovered in the efferent lymph for at least 36 h after inoculation. Sudden disappearance of the virus from the lymph was correlated with the onset of significant haemagglutination-inhibition antibody titres by 3 to 4 days after infection. In the efferent lymph, PFC were detected 5 to 7 days after primary or secondary inoculation of KV or RRV when lymphocytes were incubated with specific haemagglutinin-coated goose erythrocytes and guinea-pig complement. Antibody levels in the lymph were persistent while the occurrence of PFC was transient.

Animals↗

PubMed1975

Adaptation studies with Ross River virus: laboratory mice and cell cultures.

Ross River virus, an Australian group A arbovirus, was adapted by serial passage to cell cultures and to day old mice. The results of titrations in mice of different ages allowed the comparison of virulence between different stocks. Passage in cell cultures depressed the virulence of virus while passage in mice raised the level of virulence. Clones of original virus populations revealed heterogeneity with respect to virulence but none of the 41 clones was as highly virulent as virus passed 10 times in mice. Clones selected in sequence during serial passage in mice indicated that adaptation proceeded by the overgrowth of variants of increasingly higher virulence, and that clones from relatively hhighly passaged s strains were still heterogeneous in virulence.

Adaptation, Biological↗

PubMed1975

Adaptation studies with Ross River virus: retention of field level virulence.

Two field strains of Ross River virus (RRV) which differed in virulence for laboratory mice were maintained without detectable change in virulence when passaged alternately in Aedes aegypti mosquitoes and newborn mice. No biological mechanism or selection pressure was identified to explain this suppression of the usual change to higher virulence observed when RRV is passed serially in infant mice. The maintenance of initial virulence by alternating passages appears to be related to the fact that A. aegypti can be infected only if fed on mice during the period of peak viraemia and that at this time a sub-population of higher virulence may not be present in high enough infectivity to be represented in the mosquito's blood meal.

Adaptation, Biological↗

PubMed1973