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G J Atkins

Publications and source records attributed to G J Atkins.

87 records · Page 5Linked to original sources
PubMed1979

Virulence of temperature-sensitive mutants of Sindbis virus in neonatal mice.

The virulence in neonatal mice of temperature-sensitive (ts) mutants of Sindbis virus was determined by measurements of mean survival time and 50% lethal dose after intracerebral injection. For 11 ts mutants, mean survival time was determined by the ribonucleic acid (RNA) phenotype, RNA+ mutants killing the mice sooner than RNA- mutants for the same titer of virus injected. Mortality caused by seven ts mutants was, with one exception, correlated with the proportion of revertants recovered after death. A82, a presumed double mutant showing low reversion, showed no detectable lethality. The pathogenicity of this mutant could be detected by inhibition of weight gain, which was proportional to the titer of virus injected. A low-level persistence, independent of the titer injected, occurred up to 7 days after injection. This was followed by complete clearance. It is concluded that the virulence of Sindbis virus may be considerably altered by mutation, and that this is related to events occurring at the cellular level.

Animals↗
PubMed1978

Regulation of the synthesis of Sindbis virus-specified RNA: role of the virion core protein.

Cells infected with seven different RNA+ mutants of Sindbis virus were found to accumulate a virus-specified polypeptide of mol. wt. 144000 (p144) during incubation at the non-permissive temperature, while at the same time synthesis of the virus structural proteins was drastically reduced. Mapping of the tryptic peptides of p144 showed that it contained the amino acid sequences of all the virus structural proteins. At the non-permissive temperature cells infected with the same seven mutants (out of 28 examined) also showed increased synthesis of 26S RNA, the mRNA for the virus structural proteins, relative to 42S RNA, and the virus genome, compared with infections by wild-type virus. We propose that both these phenotypic effects are the results of a single mutational step and that the primary defect in the processing of the virus structural protein precursor induces the relatively increased rate of synthesis of structural protein mRNA. Temperature-shift experiments with mutant-infected cells showed that p144 itself is not the agent of this effect. The failure of exposure to zinc ions to alter the RNA ratio in wild-type virus-infected cells suggested that the virus envelope proteins are not involved either, since their synthesis is preferentially inhibited under these circumstances. It is possible that it is the failure to synthesize the proper quantity of core protein in the mutant-infected cells which causes the shift of RNA synthesis in favour of structural protein mRNA.

Culture Techniques↗
PubMed1976

The induction of interferon by temperature-sensitive mutants of Sindbis virus: its relationship to double-stranded RNA synthesis and cytopathic effect.

Sindbis virus strain AR339 induces interferon by 3 h after infection at 39 degrees C and by 8 h after infection at 30 degrees C. The time course of interferon induction between 4 and 9 h after infection at the restrictive temperature (39 degrees C) was measured for 24 temperature-sensitive (ts) mutants, all of which induced interferon by 16 h after infection. Mutants showing total RNA synthesis at 39 degrees C greater than 10% of the wild-type level induced interferon with kinetics similar to the wild-type. Of those mutants showing 1 to 10% of the wild-type level of RNA synthesis at 39 degrees C, four induced interferon with kinetics similar to the wild type, whereas six showed a lag in induction. Nine mutants, showing 0 to 5% of the wild-type level of RNA synthesis at 39 degrees C, and the wild type, were examined for single and double-stranded RNA synthesis at 30 and 39 degrees C, using a combination of lithium chloride precipitation and CF11 cellulose chromatography. Six of these mutants showed a lag in interferon induction at 30 degrees C, while three showed no lag. For all nine mutants, double-stranded RNA synthesis at 39 degrees C was undetectable, although easily detectable for the wild type. Both the wild type and the mutants synthesized double-stranded RNA at 30 degrees C. For all mutants, time of interferon induction at 39 degrees C was correlated with c.p.e. as measured by trypan blue uptake 30 h after infection. The mutant F104, showing undetectable RNA synthesis and a long lag in interferon induction at 39 degrees C, was examined for interferon induction in a temperature shift system. Only 1/2 h at 30 degrees C, before a shift to 39 degrees C, was required for interferon to be induced with wil-type kinetics, and this was correlated with an increased c.p.e. 30 h after infection. Increased RNA synthesis and infectious virus production were detectable at 30 degrees C after an initial hour at 30 degrees C. It is concluded that, for interferon to be induced with normal kinetics, early virus functions are required, but that normal levels of double-stranded RNA synthesis are not necessary. The events which lead to interferon induction also lead to visible c.p.e.

Cell Line↗
PubMed1973

Some bacteriophages active against Rhizobium trifolii strain W19.

Fourteen soil bacteriophages active against Rhizobium trifolii W19 have been studied which fall into four structural groups. Group 1 phages have contractile tails. Some particles show double base plates to which at least three spikes are attached, and fibers are attached to the base plates. Group 2 phages also have contractile tails. At least five spikes are attached to the base plate, and there are spherical bodies adjacent to the tail, at the ends of fibers attached to the tail base. Group 3 phages have contractile tails, but are larger than phages of groups 1 and 2. The end of the tail has a complex structure. Group 4 phages have long, noncontractile tails. Phages c and I of group 1 and phages a and e of group 2 were chosen for further study. Single-step growth curves were plotted, and absorption constants were measured. The classification into groups was confirmed by using antiserum inactivation. Susceptibility of phage-resistant mutants of R. trifolii W19 to these bacteriophages was determined.

Adsorption↗
PubMed1973

Isolation and preliminary characterization of temperature-sensitive mutants of rhizobiophage c.

By using mutagenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine, 150 temperature-sensitive mutants of rhizobiophage c were isolated. All were able to form plaques at 14 C but not at 29 C. They were classified into 21 complementation groups. Representative temperature-sensitive mutants from each complementation group were analyzed with regard to gene function. The approximate time of expression of the genes defined by the mutants was measured by temperature-shift experiments. Most genes began to be expressed at 4.0 to 7.5 h after infection at 14 C. Four genes were found which were expressed 2.5 to 3.5 h after infection. Some mutants showed no DNA synthesis at 29 C; some showed a delay in lysis. Some produced apparently normal particles after infection and lysis at 29 C; others produced various types of defective particles. Some mutants showing no DNA synthesis at 29 C nevertheless caused lysis at the normal time together with the production of phage structural components. Representative mutants from each complementation group were mapped by using two-factor crosses. A preliminary genetic map of phage c was constructed from the data.

Bacteriophages↗
PubMedDate not supplied

Transient virus infection and multiple sclerosis.

Multiple sclerosis (MS) is a chronic, demyelinating disease of the CNS in which autoimmunity to myelin plays a role in pathogenesis. The epidemiology of MS indicates that it may be triggered by a virus infection before the age of adolescence, but attempts to associate a specific virus with MS have produced equivocal results. Many studies of the aetiology of MS have postulated that a persistent virus infection is involved, but transient virus infection may provide a plausible alternative mechanism that could explain many of the inconsistencies in MS research. The most studied animal model of MS is chronic relapsing experimental autoimmune encephalomyelitis (CREAE), which is induced in susceptible animals following injection of myelin components. While CREAE cannot provide information on the initiating factor for MS, it may mimic disease processes occurring after an initial trigger that may involve transient virus infection. The disease process may comprise separate triggering and relapse phases. The triggering phase may involve sensitisation to myelin antigens as a result of damage to oligodendrocytes or molecular mimicry. The relapse phase could be similar to CREAE, or alternatively relapses may be induced by further transient virus infections which may not involve infection of the CNS, but which may involve the recrudescence of anti-myelin autoimmunity. Although current vaccines have a high degree of biosafety, it is suggested that the measles-mumps-rubella vaccine in particular could be modified to obviate any possibility of triggering anti-myelin autoimmunity.

Animals↗
PubMedDate not supplied

Colocalisation of human immunodeficiency virus and human cytomegalovirus infection in brain autopsy tissue from AIDS patients.

We have examined 26 human AIDS brains obtained at post mortem for infection by human immunodeficiency virus (HIV) and human cytomegalovirus (HCMV), and for dual infection of cells by both viruses. The techniques used were enzyme-linked immunocytochemistry for HCMV and in situ hybridisation using a cDNA probe for HIV. Using these techniques, HCMV infection was detected in 14 brains, HIV infection in 14 brains, and coinfection with HIV and HCMV in 7 brains. Four case of dual HIV/HCMV infection were found where no colocalisation could be detected. In randomly chosen dually infected areas 19.2% of infected cells were coinfected with both viruses. Although cells identified morphologically as macrophages were the most common infected cell type, astrocytes and neurons were both singly and doubly infected with HIV and HCMV. Complete clinical data were available for 4 of the 7 cases with coinfection and each had AIDS dementia complex.

AIDS-Related Opportunistic Infections↗
PubMedDate not supplied

Morphometric analysis of growth retardation in fetal lambs following experimental infection of pregnant ewes with border disease virus.

The onset of growth retardation was investigated in fetal lambs following experimental infection of pregnant ewes with Border Disease virus (BDV) on day 53 of pregnancy. Fetuses from control and infected ewes were harvested at weekly intervals between day 60 and day 95 of gestation and morphometric studies were completed on tibial radiographs and tibial growth cartilage metaphyseal junctions. Mean tibial areas were significantly reduced (P < 0.01) in fetuses from infected ewes at 35 and 42 days after infection and growth cartilage metaphyseal junctions were less mature in fetuses from infected ewes at 42 days after infection. Positive immunostaining for BDV antigen was demonstrated in the brains of all fetuses from infected ewes between 14 and 42 days after infection. Attempts to demonstrate BDV antigen in bone proved unsuccessful. It is concluded that intrauterine growth retardation is an early manifestation of BDV infection in lambs and that the process is initiated shortly following infection of the fetus.

Animals↗
PubMedDate not supplied

The pathogenicity of louping ill virus for mice and lambs.

Mice and lambs were infected with the LI/I, LI/31 or MA54 strain of louping ill virus (LIV) to provide information relevant to testing the efficacy and biosafety of a new generation of flavivirus vaccines based on a Semliki Forest virus (SFV) vector. Whereas clinical signs and neuropathological lesions were consistently severe in mice, the majority of lambs showed lesions of moderate severity and only lambs with severe lesions were clinically affected. For both species, dispersal of viral antigen occurred along neuronal cell processes, and neuronal degeneration and death were confirmed as central events after infection with LIV. In contrast to lambs, in which most lesions remained localized, mice showed widely dispersed lesions which were associated with less intense leucocytic infiltrates. Among the infiltrating cells, histiocytes predominated and apoptotic forms were prominent in severely affected animals. The intranasal route of infection provided an efficient avenue for entry of LIV into the brain and resulted in lesions which were more severe than those produced by subcutaneous or intraperitoneal inoculation.

Animals↗
PubMedDate not supplied

Expression of defensin antimicrobial peptides in the peritoneal cavity of patients on peritoneal dialysis.

OBJECTIVE: To investigate the expression and regulation of defensins in the peritoneal cavity of peritoneal dialysis (PD) patients. DESIGN: The presence of defensins in the peritoneal cavity was assessed using reverse transcription polymerase chain reaction (RT-PCR). In vivo defensin expression was analyzed in human peritoneal membrane biopsies and in peritoneal cavity leukocytes isolated from spent dialysate. Defensin expression in vitro was assessed in cultured human peritoneal mesothelial cells (HPMC) and confirmed with PCR Southern blot and DNA sequencing. The effect of tumor necrosis factor alpha (TNFalpha) and epidermal growth factor (EGF) on beta2 defensin expression in HPMC was analyzed by Northern blot analysis and RT-PCR respectively. RESULTS: Both alpha and beta classes of defensins are expressed in the peritoneal cavity of PD patients. Messenger RNA for the alpha-defensin human neutrophil peptide 3 and for beta-defensin-1 (hbetaD-1) were found in preparations containing predominantly peritoneal leukocytes, whereas beta-defensin-2 (hbetaD-2) is expressed by HPMC. HPMC isolated from different individuals displayed variability in both basal hbetaD-2 expression and in response to stimulation by TNFalpha. Conversely, EGF consistently downregulated the level of hbetaD-2 message in HPMC. CONCLUSION: Alpha- and beta-defensins are expressed in the peritoneal cavity, and hbetaD-2 is the main defensin present in the peritoneal membrane. Variable levels of expression of hbetaD-2 by mesothelial cells were seen, with evidence of regulation by cytokines and growth factors. This provides evidence for a previously unknown mechanism of innate immunity at that site.

Base Sequence↗