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Biomedical subjects

D J MacKenzie

Publications and source records attributed to D J MacKenzie.

10 recordsLinked to original sources
PubMed1990

Transgenic Nicotiana debneyii expressing viral coat protein are resistant to potato virus S infection.

The coat protein gene from potato virus S (PVS) was introduced into Nicotiana debneyii by leaf disc transformation using Agrobacterium tumefaciens. Transgenic plants expressing the viral coat protein were highly resistant to subsequent infection by the ME strain of PVS as indicated by an absence of symptom development and a lack of accumulation of virus in both the inoculated and upper leaves. As in reported experiments with plants expressing potato virus X coat protein, plants expressing PVS coat protein were also protected from inoculation with PVS RNA. These results provide further evidence that coat protein-mediated protection for these two groups of viruses, which share similar genome organizations, may involve inhibition of some early event in infection other than or in addition to virus uncoating.

Capsid↗
PubMed1989

Organization and interviral homologies of the 3'-terminal portion of potato virus S RNA.

The sequence of 3553 nucleotides corresponding to the 3'-terminal region of potato virus S (PVS) has been determined from cloned cDNA. The sequence obtained contains six open reading frames (ORFs) encoding proteins of Mr 10,734, Mr 32,515, Mr 7,222, Mr 11,802, Mr 25,092 and at least Mr 41,052. The sequence of the 33K ORF has been confirmed to be that of the viral coat protein gene. The nucleotide sequence of this ORF was obtained from plasmids which were isolated by colony hybridization with a specific monoclonal antibody to PVS, and the expression of coat protein fusion products was verified by Western blots of bacterial cell lystates. The deduced amino acid sequence of a 70 amino acid portion from the central region of the PVS coat protein was 59% identical to the analogous region of potato virus X. In addition, the 7K, 12K and 25K ORFs displayed significant sequence homology with the similarly sized ORFs from a number of potexviruses. The partial 41K ORF product was homologous with the C-terminal portion of the viral replicase proteins of potato virus X and white clover mosaic virus.

Amino Acid Sequence↗
PubMed1988

Duration discrimination of speech and tonal complex stimuli by normally hearing and hearing-impaired listeners.

The ability to discriminate changes in the length of vowels and tonal complexes (filled intervals) and in the duration of closure in stop consonants and gaps in tonal complexes (unfilled intervals) was studied in three normally hearing and seven severely hearing-impaired listeners. The speech stimuli consisted of the vowels (i, I, u, U, a, A) and the consonants (p, t, k), and the tonal complexes consisted of digitally generated sinusoids at 0.5, 1, and 2 kHz. The signals were presented at conversational levels for each listener group, and a 3IFC adaptive procedure was used to estimate difference limens (DLs). The DLs for speech were similar to those for tonal complex stimuli in both the filled and unfilled conditions. Both normally and impaired-hearing listeners demonstrated greater acuity for changes in the duration of filled than unfilled intervals. Mean thresholds for filled intervals obtained from normally hearing listeners were smaller than those obtained from hearing-impaired listeners. For unfilled intervals, however, the difference between listener groups was not significant. A few hearing-impaired listeners demonstrated temporal acuity comparable to that of normally hearing listeners for several listening conditions. Implications of these results are discussed with regard to speech perception in normally and impaired-hearing individuals.

Adult↗
PubMed1980

Subacute sclerosing panencephalitis (SSPE) in southern Africa. Recent additions to the SSPE Registry.

Subacute sclerosing panencephalitis can no longer be regarded as a rare disease in all parts of southern Africa. Information derived from a third postal survey added to that from our own experience in Cape Town has brought to light 116 cases; 61 of the patients came from the Cape Province, 40 from the Transvaal and the remaining 15 from the other regions. This unequal distribution and the high prevalence in the Coloured community are important factors in any attempt to understand the epidemiology and the pathogenesis of this serious complication of measles.

Adolescent↗
PubMed1975

Crisis therapy.

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Crisis Intervention↗
PubMedDate not supplied

Resistance to tomato spotted wilt virus infection in transgenic tobacco expressing the viral nucleocapsid gene.

A recombinant plasmid containing the entire tomato spotted with virus (TSWV) nucleocapsid gene, with the exception of nucleotide encoding three N-terminal amino acids, was isolated by screening a complementary DNA library, prepared against random primed viral RNA, using a specific monoclonal antibody. The insert contained in plasmid pTSW1 was repaired and amplified by polymerase chain reaction, and the complete nucleocapsid protein gene was introduced into Nicotiana tabacum 'Samsun' by leaf disk transformation using Agrobacterium tumefaciens. Transgenic plants expressing the viral nucleocapsid protein were resistant to subsequent infection following mechanical inoculation with TSWV as indicated by a lack of systemic symptoms and little or no systemic accumulation of virus as determined by double antibody sandwich enzyme-liked immunosorbent assay. These results further extend the applicability of coat protein-mediated resistance, as previously demonstrated for a number of simple plant viruses composed of a positive-sense RNA genome encapsidated with a single species of coat protein, to a membrane-encapsidated, multi-component, negative-sense RNA virus.

Base Sequence↗