Search PubMed⌕ Search

Biomedical subjects

D Willits

Publications and source records attributed to D Willits.

5 recordsLinked to original sources
PubMed2003

Effects of the cowpea chlorotic mottle bromovirus beta-hexamer structure on virion assembly.

The X-ray crystal structure of Cowpea chlorotic mottle bromovirus (CCMV) revealed a unique tubular structure formed by the interaction of the N-termini from six coat protein subunits at each three-fold axis of the assembled virion. This structure, termed the beta-hexamer, consists of six short beta-strands. The beta-hexamer was postulated to play a critical role in the assembly and stability of the virion by stabilizing hexameric capsomers. Mutational analyses of the beta-hexamer structure, utilizing both in vitro and in vivo assembly assays, demonstrate that this structure is not required for virion formation devoid of nucleic acids in vitro or for RNA-containing virions in vivo. However, the beta-hexamer structure does contribute to virion stability in vitro and modulates disease expression in vivo. These results support a model for CCMV assembly through pentamer intermediates.

Base Sequence↗
PubMed2001

Viruses from extreme thermal environments.

Viruses of extreme thermophiles are of great interest because they serve as model systems for understanding the biochemistry and molecular biology required for life at high temperatures. In this work, we report the discovery, isolation, and preliminary characterization of viruses and virus-like particles from extreme thermal acidic environments (70-92 degrees C, pH 1.0-4.5) found in Yellowstone National Park. Six unique particle morphologies were found in Sulfolobus enrichment cultures. Three of the particle morphologies are similar to viruses previously isolated from Sulfolobus species from Iceland and/or Japan. Sequence analysis of their viral genomes suggests that they are related to the Icelandic and Japanese isolates. In addition, three virus particle morphologies that had not been previously observed from thermal environments were found. These viruses appear to be completely novel in nature.

Archaeal Viruses↗
PubMed2000

Validation of a questionnaire measuring patient satisfaction with general practitioner services.

BACKGROUND: In order that patient satisfaction may be assessed in a meaningful way, measures that are valid and reliable are required. This study was undertaken to assess the construct validity and internal reliability of the previously developed Patient Satisfaction Questionnaire (PSQ). METHOD: A total of 1390 patients from five practices in the North of England, the Midlands, and Scotland completed the questionnaire. Responses were checked for construct validity (including confirmatory factor analysis to check the factor structure of the scale) and internal reliability. RESULTS: Confirmatory factor analysis showed that items loaded on the appropriate factors in a five factor model (doctors, nurses, access, appointments, and facilities). Scores on the specific subscales showed highly significant positive correlations with general satisfaction subscale scores suggesting construct validity. Also, the prediction (derived from past research) that older people would be more satisfied with the service was borne out by the results (F (4, 1312) = 57.10; p < 0.0001), providing further construct validation. The five specific subscales (doctors, nurses, access, appointments, and facilities), the general satisfaction subscale, and the questionnaire as a whole were found to have high internal reliability (Cronbach's alpha = 0.74-0.95). CONCLUSION: The results suggest that the PSQ is a valid and internally reliable tool for assessing patient satisfaction with general practitioner services.

Factor Analysis, Statistical↗
PubMed1995

Development of a questionnaire to measure patients' satisfaction with general practitioners' services.

BACKGROUND: It is now a requirement that patients' satisfaction with the services obtained from their general practitioner should be surveyed. AIM: The aim of the study was to produce a reliable and valid multidimensional patient satisfaction questionnaire that could be used in general practice. METHOD: Items were originally derived from patients' responses to open-ended questions. The resulting 148-item Likert-scale questionnaire was completed by 1193 patients. General satisfaction items were removed from the set, and responses to remaining items underwent factor analysis. Subscales were produced from items representing each factor. Reliability and validity of each subscale were examined. RESULTS: Five subscales with a total of 40 items resulted from the factor analysis: doctors, access, nurses, appointments and facilities. Each subscale was internally reliable (Cronbach's alpha coefficient between 0.73 and 0.95), and initial tests of validity suggested that all subscales were valid. CONCLUSION: The study has resulted in a 40-item scale that has been found to be reliable and valid after initial tests. Further work to test the reliability and validity of the final version of the patient satisfaction questionnaire is described.

Adolescent↗