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T Whistler

Publications and source records attributed to T Whistler.

15 recordsLinked to original sources
PubMed1997

Rapid identification of measles virus strains by the heteroduplex mobility assay.

The continued endemic presence of measles virus (MV), and the large number of isolates which are made in South Africa each year, demanded the use of a rapid and reliable pre-screening technique to select isolates for molecular epidemiological studies by sequence analysis. The heteroduplex mobility assay (HMA) was used to genetically characterize 47 MV isolates collected from three different provinces in South Africa, made between 1986 and 1995. The carboxyl-terminal 590 nt of the nucleocapsid (N) gene--the most variable region of the genome--was amplified by polymerase chain reaction (PCR) and subsequently subjected to HMA analysis for initial genotyping. The results showed three different patterns of heteroduplex formation by gel electrophoresis, representing two distinct wild-type lineages and one group of vaccine-like viruses. Comparison of HMA results with phylogenetic analysis of sequence data for several of the South African MV strains showed a complete correlation of results. The HMA proved to be a useful tool for screening MV isolates for use in molecular epidemiological studies.

DNA, Viral↗
PubMed1997

A rapid culture assay for examining measles virus infections from urine specimens.

BACKGROUND: Large numbers of measles virus (MV) specimens are processed in our laboratory each year as part of a molecular epidemiological study of MV in South Africa. The development of a sensitive, rapid virus isolation system is needed to cope with the number of specimens processed. OBJECTIVES: A comparison was made of centrifugation-enhanced shell vial culture and standard tissue culture using B95a cells for the isolation of MV from throat swabs and urine. STUDY DESIGN: The rapid method was initially evaluated using Schwarz vaccine virus and then compared to standard culture using throat swab specimens. RESULTS: The shell via assay proved to be ten times more sensitive than standard culture in the initial evaluation. Of 43 throat swab specimens, 37 (86%) were positive and 6 (14%) negative in standard culture using B95a cells. The specimens were removed after adsorption in standard culture, frozen and then used in the shell vial assay. It was found that 16/27 were positive in the shell vial assay (24 of these 27 being positive in standard culture,) and 8 negative and 8 specimens gave an indeterminate result. For the 45 urine specimens used in the shell vial assay, 71% were positive, 11% negative and 18% gave an indeterminate result, due to too few cells being present for antigen determination by indirect fluorescent antibody assay. Results were obtained in 4 days, as opposed to the average of 14 days for confirmed isolation in standard culture. CONCLUSION: Rapid culture substantially reduced total test time, was less labour-intensive and was as sensitive as standard culture for the isolation of measles virus from clinical specimens.

Cell Culture Techniques↗
PubMed1997

Sequence analysis of the nucleocapsid gene of measles virus isolates from South Africa identifies a new genotype.

Sequence analysis was performed on 20 measles virus (MV) isolates from South Africa, five of which were obtained between 1986 and 1989 and 15 isolates collected during the 1994/95 measles season. A 590 bp fragment of the carboxyl terminus of the nucleocapsid (N) was amplified by PCR and subjected to sequence and phylogenetic analysis. Comparison of the South African MV strains with those previously described revealed that at least two distinct groups of wild-type (wt) MV exist, one of which has been circulating since 1986. The major genotype (I) was represented by the more recent isolates which showed three characteristic amino acid substitutions. Furthermore, three vaccine-like viruses with sequences very similar to the Edmonston wt strain were identified. Phylogenetic analysis of 100 MV strains allowed the assignment of new definitions for MV genotypes and subgroups. Employing these definitions, the majority of South African isolates analysed here formed a new genotype.

Amino Acid Sequence↗
PubMed1996

Generation of defective interfering particles by two vaccine strains of measles virus.

A systematic study was made to measure the generation of defective interfering particles upon up to 13 serial passages of two measles vaccine strains, Edmonston and Edmonston-Zagreb, through either simian (Vero) or human (WI-38) cell lines. Results for the Vero cell passage were nearly identical for both viruses. Infectivity titers dropped by nearly 8 logs to undetectable levels at passage 4 and cycled between maximum and minimum levels every 4 passages. Samples with the lowest infectivity titers produced the greatest reduction in titer of standard virus and contained an approximately 900-nucleotide subgenomic RNA for the Edmonston strain and two subgenomic RNAs of 4300 and 3000 nucleotides for the Edmonston-Zagreb vaccine strain. A defective interfering RNA-specific reverse transcription-polymerase chain reaction (RT-PCR) detected subgenomic RNAs at all passage levels. In contrast, samples obtained after passage of these viruses in WI-38 did not reduce the yield of standard virus and did not contain subgenomic RNAs in both Northern blot and RT-PCR assays. These results clearly show that cell type rather than virus strain affects defective interfering particle generation for measles virus.

Animals↗
PubMed1992

Antigenic and genetic characterization of the haemagglutinins of recent cocirculating strains of influenza B virus.

The antigenic and genetic characteristics of the haemagglutinins of influenza type B viruses isolated since 1988 during periods of both widespread activity (1990/1991) and sporadic activity (1989/1990) were examined using microneutralization tests and direct RNA sequencing. During 1989/1990, influenza B viruses representative of two distinct lineages antigenically and genetically related to either B/Victoria/2/87 or B/Yamagata/16/88 were isolated, and a minor drift variant of B/Yamagata/16/88, B/Hong Kong/22/89, was identified. In 1990/1991, B/Hong Kong/22/89- or B/Yamagata/16/88-like viruses accounted for the majority of the influenza virus isolates in most countries. Sequence analysis of the HA1 domains of representative viruses confirmed the continued existence of two main lineages among recent strains of influenza B virus and identified unique amino acid changes that could account for the altered antigenic reactivity of some variants. Sequence analysis of the HA2 domains of some of the recent influenza B viruses allowed for a comparison of the evolutionary rates and patterns between the HA1 and HA2 domains.

Amino Acid Sequence↗
PubMed1991

Teratogenicity of the Palyam serogroup orbiviruses in the embryonated chicken egg model.

Embryonated chicken eggs were used as a model for assessing the teratogenic potential of several Palyam serogroup orbiviruses. Infection of 4-day-old embryonated chicken eggs via the yolk sac with eight of the viruses resulted in deaths or congenital deformities which included retarded development, arthrogryposis and reduced feathering. Statistical analysis showed that the viruses could be divided into three groups: those that caused death (Gweru virus isolates 866/77 and 1726/76; and Apies River virus), those that caused deaths only when large amounts of virus were inoculated (Gweru isolate AR11869 and Marondera virus) and those that caused death and deformities (Abadina, Kasba, Nyabira, Petevo and Vellore viruses). Differences in pathogenic potential were noted between isolates identified as the same serotype by serological tests.

Animals↗
PubMed1990

Proteins of Palyam serogroup viruses.

The replication and polypeptide synthesis of Abadina virus, a member of the Palyam serogroup of orbiviruses, was studied. The first virus-specified proteins could be demonstrated 2 to 4 h post-infection (p.i.) by immunoprecipitation. The rate of synthesis increased rapidly until 12 h p.i. after which it remained fairly constant until 18 h p.i. when it began to decline. Host cell protein synthesis shutoff was incomplete. Twelve virus-induced polypeptides were identified in infected cell lysates, ranging in Mr from 36K to 143K. Three small polypeptides (Mr 15K to 20K) identified in homologous immunoprecipitation studies are also thought to be virus-specified. Nine structural proteins were identified, four being major components of the purified virion. Partial proteolysis was used to demonstrate homology between some proteins. Pulse-chase experiments provided no evidence for a precursor-product relationship between any of the Abadina virus proteins. A non-structural protein was found to be phosphorylated.

Animals↗
PubMed1989

Characterization of Palyam serogroup orbiviruses isolated in South Africa and serologic evidence for their widespread distribution in the country.

The finding that there had been multiple isolations of Palyam serogroup orbiviruses from aborted cattle fetuses in neighbouring Zimbabwe, suggested that there was a need to investigate the possible occurrence of the viruses in South Africa. Unidentified viruses isolated in South Africa, which had been in storage, were examined. Four viruses which had been isolated from Culicoides midges collected at various sites in the years from 1969 to 1977, were identified as three strains of Gweru virus and one of the Nyabira virus (Palyam group serotypes originally described from Zimbabwe). A fifth virus, isolated in 1967 from the blood of a cow with mild fever, was found to be a distinct new member of the Vellore antigenic complex of the Palyam serogroup and was named Apies River virus. Sera from 476 cattle, 150 sheep, 24 goats and 78 humans from 10 farms were tested for neutralizing antibodies to the above three serotypes of virus plus Abadina and Marondera serotypes. Only 1 of 100 cattle sera from two farms in the southern coastal area had antibody, but elsewhere there was a high prevalence of antibody with 254 (53%) of all cattle exhibiting activity for one or more of the five serotypes of virus tested. Only 6 (4%) sheep, 3 (12.5%) goats and 11 (14%) humans had antibody.

Animals↗
PubMed1988

Characterization of potentially foetotropic Palyam serogroup orbiviruses isolated in Zimbabwe.

Twelve Palyam serogroup orbiviruses isolated in Zimbabwe from aborted cattle foetuses, plus one isolated from the visceral organs of a cow and another from vulture faeces, were examined in comparison with known members of the serogroup by complement fixation, indirect immunofluorescence, fluorescent focus reduction neutralization tests and PAGE of the segmented, dsRNA genomes. The viruses were indistinguishable from known members of the serogroup by complement fixation and indirect immunofluorescence, but two novel viruses, for which the names Gweru and Marondera are proposed, and two previously described viruses, Nyabira and Abadina, were identified by neutralization tests. The dsRNA profiles of Abadina serotype isolates differed from that of the Abadina prototype virus, indicating that different electropherotypes may occur within serotypes.

Animals↗
PubMed1988

Autosomal recessive distal myopathy.

Five patients with an autosomally recessively transmitted distal myopathy were investigated. Of these, three belonged to a single sibship. Studies included electromyography, histological examination of muscle tissue, histochemical, electron microscopical, and biochemical analyses. One of the cases resembled the Nonaka form while the others were regarded as expressions of the commoner variety of recessive distal dystrophy.

Adult↗
PubMed1987

Diagonal Z-lines: an unexplained electron microscopic finding.

A patient suffering with myasthenia gravis was subjected to muscle biopsy of the deltoid and subsequently of the pectoralis muscle. Electron microscopic examination of the muscles revealed the scattered presence of Z-lines that were curiously orientated diagonally across the I band. This appears to be a coincidental finding, the significance of which is unknown and unreported at this time.

Adult↗
PubMed1986

Peptide mapping of the group-specific antigens from the Australian bluetongue virus (BTV-20) and serotypes from southern Africa and North America.

The Australian bluetongue virus (BTV-20) was compared with six serotypes isolated in southern Africa and North America by peptide mapping of the virus proteins with group antigen properties. The p7 group antigens from each of the seven serotypes analysed did not have identical primary structures and a comparison of shared and unique tryptic peptides has been used as a means of estimating virus relationships. Whereas serological studies have suggested that BTV-20 is closely related to BTV serotypes 4 and 17, comparative peptide mapping of p7 indicates a different set of relationships with viruses from both southern Africa and North America. In contrast with cross-immune precipitation results, peptide mapping of p3 suggest that this protein is not a group specific antigen.

Antigens, Viral↗
PubMed1986

No abnormal low molecular weight proteins identified in human malignant hyperthermic muscle.

There is no single, simple diagnostic test available to enable identification of malignant hyperthermia (MH) susceptible individuals. Recently, two novel low-molecular-weight proteins (15,000 daltons and 13,500 daltons) that were not present in normal muscle were identified in MH muscle and it was felt that this might eventually be of assistance in diagnosing MH. The authors of this report have been unable to verify these results. Polyacrylamide gel electrophoresis of the soluble proteins from muscle of four MH-susceptible and four normal individuals showed no differences in the electrophoretic fractionation patterns. Therefore, the authors conclude that the differences in protein composition previously reported in MH muscle are not characteristic of this syndrome.

Biopsy↗
PubMed1986

Acid maltase deficiency: a case study and review of the pathophysiological changes and proposed therapeutic measures.

An adult patient with lysosomal acid alpha-glucosidase deficiency was fully investigated, and then placed on various forms of therapy with favourable response to a high protein, low carbohydrate diet. The rationale for the employment of this therapy, the problem of acid maltase deficiency and the relationship to weakness and glycogenosome formation with accumulation or otherwise of glycogen within the muscle fibres is discussed.

Adult↗