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Biomedical subjects

J Duncan

Publications and source records attributed to J Duncan.

At least 109 records · Page 6Linked to original sources
PubMed1990

Sequence requirements for DNA rearrangements induced by the terminal repeat of herpes simplex virus type 1 KOS DNA.

We investigated the sequence requirements for the site-specific DNA cleavages and recombinational genome isomerization events driven by the terminal repeat or a sequence of herpes simplex virus type 1 KOS DNA by inserting a series of mutated a sequences into the thymidine kinase locus in the intact viral genome. Our results indicate that sequences located at both extremities of the a sequence contribute to these events. Deletions entering from the Ub side of the a sequence progressively reduced the frequency of DNA rearrangements, and further deletion of the internal DR2 repeat array had an additional inhibitory effect. This deletion series allowed us to map the pac1 site-specific DNA cleavage signal specifying the S-terminal cleavage to a sequence that is conserved among herpesvirus genomes. Constructs lacking this signal were unable to directly specify the S-terminal cleavage event but retained a reduced ability to give rise to S termini following recombination with intact a sequences. Deletions entering from the Uc side demonstrated that the copy of direct repeat 1 located adjacent to the Uc region plays an important role in the DNA rearrangements induced by the a sequence: mutants lacking this sequence displayed a reduced frequency of novel terminal and recombinational inversion fragments, and further deletions of the Uc region had a relatively minor additional effect. By using a construct in which site-specific cleavage was directed to heterologous DNA sequences, we found that the recombination events leading to genome segment inversion did not occur at the sites of DNA cleavage used by the cleavage-packaging machinery. This observation, coupled with the finding that completely nonoverlapping portions of the a sequence retained detectable recombinational activity, suggests that inter-a recombination does not occur by cleavage-ligation at a single specific site in herpes simplex virus type 1 strain KOS. The mutational sensitivity of the extremities of the a sequence leads us to hypothesize that the site-specific DNA breaks induced by the cleavage-packaging system stimulate the initiation of recombination.

Animals↗
PubMed1989

Clinical assessment of a new breath-actuated inhaler.

Up to 50 per cent of patients cannot use a conventional metered-dose inhaler (MDI) efficiently and therefore obtain less than optimum benefit. Seventy adults with no previous experience of inhalers were asked to demonstrate their inhaler techniques after reading written instructions for an MDI and for a new breath-actuated inhaler. The breath-actuated inhaler was found to be easier to use and was preferred to the MDI.

Adult↗
PubMed1989

Toxicity of IL-2 and Corynebacterium parvum following direct intracranial injection.

The toxicity of IL-2 and/or C. Parvum when injected directly into the mouse brain was examined by survival and histopathology using different numbers of injections, different doses of IL-2, different solvents for the IL-2, and different doses and routes of administration of C. Parvum. Two injections was found significantly to increase mortality (19%) over a single injection (4%). Mortality from two injections of 30,000 U (23%) or 60,000 U (20%) was higher than from two injections of 15,000 U (12%). The mortality from two injections with normal saline as solvent was much higher (29%) than from two injections with sterile water (19%) or D5W (9%). Two injections of IL-2 given simultaneously with C. Parvum showed a much higher mortality (26%) than other doses and routes of C. Parvum administration. Mice dying acutely (6-24 days) of toxicity showed an extensive mononuclear infiltrate at the site of injection. The brains of surviving mice (sacrificed at 30 days) showed a mild residual mononuclear cell infiltrate with the exception of mice which had received IL-2 and C. Parvum simultaneously. Brains from this latter group had an extensive residual mononuclear cell infiltrate.

Animals↗
PubMed1989

Boundary conditions on parallel processing in human vision.

A new theory of visual search is tested experimentally with simple colour patches. The essential element of this new theory is that, whatever the search materials, efficiency increases continuously with (i) decreasing similarity between targets and nontargets, and (ii) increasing similarity between one nontarget and another. Control of 'attention' (access to visual short-term memory) is seen as a competitive interaction between display elements, and the theory shows how stimulus similarities influence the outcome of this competition. One alternative view is that parallel visual processes are limited to local mismatch detection. Search is parallel if the target forms a break in an otherwise homogeneous field, but is serial when absolute stimulus identification is required. It is shown, however, that even colour identification can be parallel, providing targets and nontargets are sufficiently dissimilar. A second alternative view is that search for simple features is parallel whereas search for conjunctions is serial. Conjunction search, however, has a characteristic similarity structure: different kinds of nontarget each share one relevant attribute with the target, but none with one another. When this structure is mimicked in search for colour patches, correspondingly poor performance is obtained.

Adult↗
PubMed1989

Long-term storage of eggs of Simulium ornatum.

A method for the storage of non-diapausing eggs of Simulium ornatum Meigen has been developed. High survival rates for 5-6 months depend on the age of eggs when placed at reduced temperature. A period of precooling or conditioning is required for 28 days before storage of the eggs at 1 degree C with lowering of oxygen partial pressure. Induced quiescence does not appear to affect development from egg to adult.

Animals↗
PubMed1989

The molluscicidal properties of Ambrosia maritima L. (Compositae). 4. Temporal and spatial distribution of Biomphalaria alexandrina in Egyptian village irrigation systems with reference to schistosomiasis transmission control.

Data on the temporal and spatial distribution of Biomphalaria alexandrina were collected throughout one year in two village irrigation systems near Alexandria, Egypt. Snails bearing Schistosoma mansoni cercariae were found from May to December but about 80% of annual transmission potential was confined from June to August. Although snail infection rates were generally 0-2%, higher rates were recorded and tended to be associated with smaller number snail collections. Infected snails were found in most canal and drain types and were judged to be present across most of the irrigated area of each village. In view of the dispersed nature of both infected snails and human-water contact in the area, it is suggested that schistosomiasis transmission is more widespread than focal. Effective transmission control using molluscicides should therefore require application to all village irrigation water-courses. The difficulties these various findings might impose on the use of commercial molluscicides are discussed and some possible advantages of the alternative plant molluscicide, Ambrosia maritima are noted.

Animals↗
PubMed1988

Molluscicide resistance and a field test kit.

Molluscicide resistance literature is reviewed. Alterations in tolerance have been recorded in some laboratory experiments and field surveys but not others. Resistance, as the failure to control a natural snail population, has not been reported. A kit is described for measuring molluscicide susceptibility of snails. A microlitre delivery device is used to prepare molluscicide solutions. Trials have shown that the kit can be used successfully in the field.

Animals↗
PubMed1987

Human immunodeficiency virus infection in two cohorts of homosexual men: neutralising sera and association of anti-gag antibody with prognosis.

Sequential sera from 48 subjects infected with human immunodeficiency virus type I (HIV-I) were examined over 36 months for the presence of neutralising antibodies, and for specific anti-gag (p24) and anti-env (gp41) antibodies to HIV-I. Results were interpreted in terms of clinical outcome during the period 1982/3 to 1985/6. HIV-I-infected subjects who remained symptom-free, by comparison with those who manifested AIDS or AIDS-related complex (ARC), had a significantly higher titre of anti-p24 antibodies throughout the 3 years, as measured by competitive enzyme-linked immunosorbent assay and radioimmunoprecipitation. The symptomless subjects also showed a trend towards an increasing neutralising antibody titre with time. There was no relation between anti-gp41 titre and clinical outcome, nor an independent relation between anti-p24 and neutralising titre. A lower or falling titre of anti-p24 antibody was associated significantly with clinical progression, up to 27 months before development of AIDS/ARC.

AIDS-Related Complex↗
PubMed1987

Effects of discrimination training on reading improvement among adults.

This study examined the effects of discrimination training on improving reading skills for young adults. 90 college students (M age = 26.2 yr.), who were identified as low achievers with below average reading skills, were randomly assigned to one of three training conditions: the General Discrimination Group, the Reading Discrimination Group, and the Study Skills Group. Following 10 days of training, the subjects were tested on a standard reading achievement test, a problem-solving test, and a measure of cognitive style. Minimal differences between the pre- and posttraining scores for all three training conditions were noted. These findings contrast with developmental research that has indicated the importance of discrimination ability and suggest distinctive problems of adults with poor reading skills.

Achievement↗
PubMed1987

The molluscicidal properties of Ambrosia maritima L. (Compositae). 3. A comparative field trial using dry and freshly-harvested plant material.

A comparative trial of freshly-harvested and dry forms of the plant molluscicide, Ambrosia maritima is described. The plant was grown near Alexandria, Egypt and gave a weight ratio of 4:1 for fresh: dry, mature plants. Applications of plant material were made to irrigation watercourses at dosage levels of 560 mg . l-1 fresh and 70 and 140 mg . l-1 dry in May and 280 mg . l-1 fresh and 70 mg . l-1 dry in June. Snail numbers were reduced to low levels after two weeks in all treatments. Statistically significant differences could not be detected between the molluscicidal effects of fresh and dry material or their use in May and June. The cultivated plant has a similar order of activity to that collected from the wild. The snail number reduction was maintained to the end of the year in all treatments. This confirms an earlier finding that a correctly-timed, single application of the plant is capable of controlling snails throughout the entire schistosomiasis transmission season in Lower Egypt.

Animals↗