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Biomedical subjects

R I Evans

Publications and source records attributed to R I Evans.

At least 19 recordsLinked to original sources
PubMed2000

Mechanism of action of pulsed high electric field (PHEF) on the membranes of food-poisoning bacteria is an 'all-or-nothing' effect.

Salmonella typhimurium (CRA 1005) was more sensitive than Listeria monocytogenes (NCTC 11994) to pulsed high electric field (PHEF) treatment in distilled water (10, 15 and 20 kV/cm), 10 mM tris-maleate buffer pH 7.4 (15 kV/cm) and model beef broth (0.75% w/v: 15 kV/cm). Sublethal injury could not be detected using a selective medium plating technique, indicating that bacterial inactivation by PHEF may be an 'all-or-nothing' event. PHEF-induced membrane permeabilization resulted in increased UV-leakage and a decreased ability of L. monocytogenes to maintain a pH gradient.

Cell Membrane↗
PubMed2000

Psychosocial determinants of the onset and escalation of smoking: cross-sectional and prospective findings in multiethnic middle school samples.

PURPOSE: To investigate a broad range of social influence-related and global determinants of smoking to aid in the design of comprehensive multiethnic interventions by testing the most important factors of initiation and escalation of smoking across various subgroups. METHODS: Cross-sectional (N = 2546) and cohort (N = 736) samples of multiethnic middle school students near a large Southwestern metropolis were surveyed through self-report questionnaires. The confidential questionnaires included information on demographics, risk factors, and smoking behavior and were administered in class by trained data collectors. Multivariable logistic regression analysis was used to examine the statistical significance and strength of the factors. RESULTS: Those lower in self-esteem and higher in social assertiveness appeared to be most at risk for the onset of smoking, whereas those low in optimism appeared to be the most at risk for the escalation of smoking. Attitudes, friends' norms, parents' norms, perceived behavioral control, and perceived prevalence were consistent predictors of all smoking status outcomes. CONCLUSIONS: The behavioral-specific determinants of smoking appear to be important predictors of smoking status outcomes in all demographic subgroups. The relationships of the global determinants were more dependent on the smoking outcome variable and subgroup examined. The findings may serve to help facilitate the targeting of comprehensive interventions aimed at reducing adolescent smoking in multiethnic and ethnic group-specific populations.

Adolescent↗
PubMed2000

The relationship between psychosocial factors and condom use among African-American adolescents.

The present investigation explored the relationship between psychosocial factors and condom use by African-American adolescents. Two hundred twenty-nine males, aged 14 to 19 years, responded to a health behavior survey that gathered information on demographics, HIV knowledge, perceived certainty of future condom use, present and past use of condoms, and intention to use condoms in the next six months. Several psychological variables, including sexual self-efficacy and self-esteem, were also measured. It was found that the majority of participants were sexually active by age 13, had four or more lifetime sexual partners, and were using condoms regularly. Multiple linear regression analysis indicated that sexual self-efficacy predicted perceived certainty of condom use. In addition, self-esteem and sexual self-efficacy predicted intention to use condoms. These findings highlight the need to develop HIV prevention curricula for African-American male adolescents that not only emphasize the potential risks associated with having multiple sexual partners, but also include components to enhance self-worth and sexual self-efficacy.

Adolescent↗
PubMed2000

Invasive cervical resorption--a periodontist's perspective.

Invasive cervical resorption (ICR) is a relatively uncommon, insidious, resorptive lesion starting subgingivally at the cervical root surface of a tooth. ICR is of uncertain aetiology, although damage to the cervical periodontal attachment to the tooth appears to be a prerequisite. For the most part the lesion is asymptomatic so early detection can be difficult. Nevertheless, if less than a third of the root of the tooth is affected by an ICR lesion treatment of the resorptive tissue using the chemical escharotic agent trichloracetic acid, with or without surgical access, followed by curettage of the lesion and restoration of the defect with glass ionomer cement, is generally successful.

Caustics↗
PubMed1998

The effect of growth temperature on the phospholipid and fatty acyl compositions of non-proteolytic Clostridium botulinum.

A non-proteolytic strain of Clostridium botulinum (NCIB 4270) was found to have a complex lipid composition, comprising five major phosphorus-containing lipids: phosphatidylethanolamine (PE), phosphatidylglycerol (PG), diphosphatidylglycerol (DPG), phosphatidylserine (PS) and a glycophospholipid of unknown structure (GPL), in order of abundance. Changing the growth temperature did not alter the lipid composition either qualitatively or quantitatively. The main fatty acyl components of the lipids are 14:0, 16:0 and 16:1. When the growth temperature was lowered from 37 to 8 degrees C, there was an increase in 14:0 from 16.4 to 37.5%, an increase in 16:1 from 10.5 to 22.5%, and a decrease in the proportion of 16:0 from 40.3 to 19.1%. There was also a decrease in the proportion of cyclopropane fatty acids (15:0cyc and 17:0cyc) from 7.3 to 0.5%, and in the equivalent chain length of the total fatty acids from 15.9 to 15.3 as the temperature was lowered. The same temperature-dependent changes occurred in the five major lipid classes examined. Despite reports of the presence of plasmalogenic forms of phospholipids (i.e. those lipids which have the acyl chain in the sn-1 position replaced by an alk-1-enyl group) in some Clostridium spp., none were detected in C. botulinum NCIB 4270 using either commercially available spray reagents or by gas-liquid chromatographic analysis of the products or acid methanolysis of total lipid extracts. It is concluded that non-proteolytic C. botulinum lacks plasmalogens, typical of other clostridia, in its membranes and instead modulates its fatty acid composition in response to temperature changes in a manner that is typical of other (non-clostridial) bacteria.

Chromatography, Gas↗
PubMed1998

Survey of injuries among West End performers.

OBJECTIVES: To obtain more information about injuries of West End performers. METHODS: A retrospective survey of 269 performers appearing in 20 West End productions (12 dramas and eight musicals). RESULTS: In current productions, 46% of all performers sustained at least one injury for an average of 0.87 injuries per performer. Lower extremity injuries were the most common for dancers (52.2% of injuries) and actors (43.2%) with neck and back injuries the second most common. Sprains and strains were the most common diagnoses. 61% of performers thought that their injuries were preventable. Most performers consulted nonphysician healthcare providers. Factors significantly influencing the risk of injuries for performers include female sex, a history of previous injuries, missed performances due to previous injuries, more physically demanding roles, and performing on raked (angled) stages. CONCLUSION: West End performers commonly sustain injuries. Although primary prevention of most theatrical injuries is not possible, modification of raked stages may reduce the incidence. This study may be helpful to the growing number of healthcare providers who practice performing arts medicine and may stimulate additional concern and research in the medical and theatrical communities about the performance injuries of professionals, amateurs, and theatrical students worldwide.

Accidents, Occupational↗
PubMed1997

The germinability of spores of a psychrotolerant, non-proteolytic strain of Clostridium botulinum is influenced by their formation and storage temperature.

The formation and storage temperatures of Clostridium botulinum spores are shown to influence their subsequent ability to germinate. Spores were formed at 10 degrees, 20 degrees, 30 degrees and 37 degrees C and following harvest were stored as aqueous suspensions at 20 degrees C (ambient temperature), 4 degrees C (refrigerated) or -20 degrees C (frozen) for periods of up to 1 month. The spores formed at 20 degrees C germinated most rapidly and to the greatest extent. When the spores were germinated immediately after harvest (fresh), there was no difference in the germinability of those spores formed at 20 degrees or 30 degrees C, whether or not they had been heat-shocked before use. However, following storage overnight or longer, differences in the relative germinabilities of the different spore samples were seen. Spores which had been stored at ambient temperature overnight germinated significantly faster and to a greater extent than did those which had been stored for up to 1 month. Similar differences were also observed between spores germinated fresh and those stored overnight, when the spores were stored refrigerated or frozen. Germinability was also influenced by the temperature of storage, since there were differences between spores formed at the same temperature but stored at different temperatures for the same period of time: for example, when spores which had been formed at 20 degrees C were germinated at 10 degrees C following a heat-shock, those which had been stored at ambient temperature germinated faster and to a greater extent than did those which had been stored refrigerated or frozen. It is concluded that there is a complex interaction between formation, storage and germination temperatures, which determines spore germinability. The fact that the changes are time-dependent and can occur in the frozen state is taken to mean that they are physico-chemical rather than metabolic. It is also significant in relation to refrigerated foods which are at risk from Cl. botulinum in that changes which occur during cool or frozen storage can enhance the germinability of spores if the temperature rises above that of chill cabinets.

Clostridium botulinum↗
PubMed1996

Craniotomy guidance using a stereo-video-based tracking system.

In open intracranial neurosurgery, it is desirable to minimize exposure and to approach the target in the most accurate way possible. The VISLAN system described here employs a completely passive hand-held locator which is tracked by a video system and does not require a mechanical linkage nor cables. The system also tracks easily recognizable, constant, anatomical landmarks of the patient. By this means the initial registration of pre-operative imaging and the detection of, and correction for, patient movement can be accomplished. High-resolution MRI segmented interactively is used to define external surface and brain anatomy. Thus, a pre-operative patient representation (POPR) is planned. During the surgical procedure the patient's head is illuminated by structured light and stereo-video pictures obtained from two television cameras mounted above the head. The system is calibrated and registered with the POPR using a chamfered matching algorithm. The locator is also tracked in space by the video system, and its tip position shown in relation to the POPR on the video monitor.

Craniotomy↗
PubMed1996

A survey of injuries among Broadway performers.

To obtain more information about injuries of Broadway performers, 313 performers appearing in 23 Broadway companies were surveyed. The percentage of performers injured was 55.5%, with a mean of 1.08 injuries performer. Lower extremity injuries were the most common. Sixty-two percent of performers believed that their injuries were preventable. As this study reports factors that significantly increase the risk of injury for dancers and actors, it may help to heighten concern with reducing the incidence of injuries to professional performers, theatrical students, and nonprofessionals worldwide.

Accidents, Occupational↗
PubMed1994

Intraclass correlation among common measures of adolescent smoking: estimates, correlates, and applications in smoking prevention studies.

Most adolescent smoking prevention studies employ designs in which classrooms, schools, school districts, or sometimes whole communities are assigned to treatment conditions while observations are made on individual students. The critical design feature in such community trials is the nesting of intact social groups within treatment conditions. This combination requires that the treatment effect be assessed against the between-group variance; unfortunately, that variance is usually larger than for randomly constituted groups and its precision is usually less than that for the within-group variance. These factors often combine to reduce power so that it is almost impossible to detect important treatment effects in an otherwise well designed and properly executed study. To address these problems, investigators need good estimates of the intraclass correlation for the variables of interest, which together with the number of observations per unit determine the magnitude of the extra variation in the nested design. The purpose of this paper is to describe the methods and results from a study designed to generate estimates of intraclass correlation for common outcomes in adolescent smoking prevention studies and to discuss the use of these estimates in the planning of new studies.

Adolescent↗
PubMed1994

The physician survey on the post-concussion and whiplash syndromes.

BACKGROUND: The post-concussion syndrome (PCS) and whiplash syndrome (WS) have been controversial topics among physicians for many decades. There is little information available on the opinions and practices of physicians. METHODS: In June of 1992, we performed a national survey by mail of the four physician groups most commonly treating these problems. The number of respondents and response rates were as follows: family physicians, 118, 16%; neurologists, 100, 21%; neurosurgeons, 97, 23%; orthopedists, 82, 13%. The survey instrument contained items on demographics, definitions, causation, prognosis, medico-legal aspects, testing, and treatment. RESULTS: Only a minority of respondents believe that PCS and WS are clearly defined syndromes. A substantial minority report that psychogenic and litigation factors are most responsible for the conditions. Most of the physicians believe that PCS and WS have a 3-6 month recovery time. A significant minority concur that symptoms of the two syndromes resolve when litigation is settled. Most of the physicians order tests to rule out pathology although a minority order tests to reassure patients or because of litigation concerns. Only a minority of respondents believe that effective treatments are available. Not surprisingly, a multitude of conventional and unconventional treatments are sometimes recommended. CONCLUSIONS: Many aspects of PCS and WS are controversial among treating physicians. This controversy can have a profound impact on the quality and cost of patient care. Ongoing research is required to discover more effective treatments for mild brain injury and chronic pain.

Brain Concussion↗
PubMed1992

Diagnostic accuracy and observer performance in the diagnosis of abnormalities in the anterior maxilla: a comparison of panoramic with intraoral radiography.

An investigation was undertaken to assess the reliability of radiographic diagnosis of abnormalities of orthodontic significance in the anterior region of the maxilla from intraoral and dental panoramic tomograph (DPT) views. DPT films of 200 patients were scrutinised by two observers on two separate occasions, who also examined intraoral radiographs of the same patients. Sixty-three of these patients were selected because they had previously been diagnosed as presenting with a defined abnormality of orthodontic relevance, such as supernumerary teeth, absent incisors, etc. The remaining cases had been assessed as depicting normal radiographic appearances. Each radiograph was allocated a unique, randomly selected code number as the only means of identification. It was not possible for the observers to match the DPT to the corresponding intraoral films, and this information was only available to the principal investigator (JWF). Both observers were asked to record the presence or otherwise of any abnormalities at each observation of each radiograph, and to record their findings. The overall level of diagnostic accuracy and reproducibility was fairly high, and in general terms the DPT views were as reliable as the intraoral films with regard to the detection of abnormalities; however, there were significant differences between the observers. It was concluded that in many instances supplementary intraoral films would not contribute any additional information compared to the DPT and that selection criteria should be defined for the former.

Chi-Square Distribution↗
PubMed1991

Quality assurance. A project on patient waiting times at appointment in an orthodontic department.

A quality assurance project to establish patient waiting time at appointments was undertaken over a four-week period during the spring of 1989. The Orthodontic Department was selected as one of two departments in the Birmingham General Hospital/Birmingham Dental Hospital unit site that was to participate in the programme initiated at the District Health Authority management level. Patient waiting periods for a total of 142 clinical sessions were assessed. Fifty per cent of patients were kept waiting and 50 per cent were seen either earlier or at their appointed time. The mean period of time that patients were kept waiting past their appointment time was 9.4 min (+/- 10.9). On clinics for which patients arrived late the mean time that they were kept waiting increased to a mean of 18.9 min (+/- 9.1). Data from 92 patient questionnaires established that they considered a reasonable mean time of waiting to be 16.1 min (+/- 7.9). Five recommendations were proposed as a result of this quality assurance initiative and their implementation is discussed.

Appointments and Schedules↗
PubMed1989

Formative evaluation in school-based health promotion investigations.

This article is intended for behavioral and biomedical researchers who have become involved increasingly in health promotion research in social settings. It describes how researchers may more precisely plan and profit from employing formative evaluation, which is too frequently more casually undertaken than is summative evaluation. Formative evaluation includes responses from the student subjects of such programs and school administrative and instructional staff, as well as other elements unique to the school setting such as existing curricula and the logistics of time and space. In order to tailor such programs to the unique properties of the school setting, a continual feedback loop should be in place. Such loops can channel both quantitative and qualitative data to the researcher to assist in adapting projects to changing conditions during the course of their implementation. This article presents a case history of the application of formative evaluation drawn from a health promotion project conducted by the authors. It includes as background for this case history, definitions of formative evaluation and an analysis of its costs.

Adolescent↗
PubMed1989

Smoking.

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Forecasting↗