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J Stevens

Publications and source records attributed to J Stevens.

At least 91 records · Page 5Linked to original sources
PubMed2000

Impact of age on associations between weight and mortality.

The effect of age on the weight associated with the lowest mortality and the effect of age on the mortality risk associated with obesity are issues fraught with methodologic complexities. Current evidence supports the notion that the body mass index associated with the lowest mortality falls within the range of 18.5 to 24.9 in men and women between the ages of 30 and 74. The impact of age on the mortality risk associated with obesity changes with age, however, and the direction of the trend depends upon the measure used.

Adult↗
PubMed2000

Pattern of premature degenerative changes of the cervical spine in patients with spasmodic torticollis and the impact on the outcome of selective peripheral denervation.

OBJECTIVES: To characterise the pattern of and risk factors for degenerative changes of the cervical spine in patients with spasmodic torticollis and to assess whether these changes affect outcome after selective peripheral denervation. METHODS: Preoperative CT of the upper cervical spine of 34 patients with spasmodic torticollis referred for surgery were reviewed by two radiologists blinded to the clinical findings. Degenerative changes were assessed for each joint separately and rated as absent, minimal, moderate, or severe. Patients were clinically assessed before surgery and 3 months postoperatively by an independent examiner using standardised clinical rating scales. For comparison of means a t test was carried out. To determine whether an association exists between the side of degenerative changes and type of spasmodic torticollis a chi(2) test was used. Changes in severity, disability, and pain before and after surgery were calculated using a Wilcoxon matched pairs signed ranks test. RESULTS: Fourteen out of 34 patients had moderate or severe degenerative changes. They were predominantly found at the C2/C3 and C3/C4 level and were significantly more likely to occur on the side of the main direction of the spasmodic torticollis (p = 0.015). There was no significant difference in age, sex, duration of torticollis, overall severity, degree of disability, or pain between the group with either no or minimal changes and the group with moderate or severe changes. However, in the second group the duration of inadequate treatment was longer (10.1 v 4.8 years; p=0.009), head mobility was more restricted (p = 0.015), and head tremor was more severe (p = 0.01). At 3 months postoperatively, patients with n or minimal degenerative changes showed a significant improvement in pain and severity whereas no difference was found in those with moderate or severe changes. CONCLUSIONS: Patients with spasmodic torticollis have an increased risk of developing premature degenerative changes of the upper cervical spine that tend to be on the side towards which the head is turned or tilted and compromise outcome after surgery. Effective early treatment of spasmodic torticollis with botulinum toxin seems to have a protective effect. Patients with spasmodic torticollis and restricted head mobility who do not adequately respond to treatment should undergo imaging of the upper cervical spine. Patients with imaging evidence of moderate or severe degenerative changes seem to respond poorly to selective peripheral denervation.

Adult↗
PubMed1999

Annual deaths attributable to obesity in the United States.

CONTEXT: Obesity is a major health problem in the United States, but the number of obesity-attributable deaths has not been rigorously estimated. OBJECTIVE: To estimate the number of deaths, annually, attributable to obesity among US adults. DESIGN: Data from 5 prospective cohort studies (the Alameda Community Health Study, the Framingham Heart Study, the Tecumseh Community Health Study, the American Cancer Society Cancer Prevention Study I, and the National Health and Nutrition Examination Survey I Epidemiologic Follow-up Study) and 1 published study (the Nurses' Health Study) in conjunction with 1991 national statistics on body mass index distributions, population size, and overall deaths. SUBJECTS: Adults, 18 years or older in 1991, classified by body mass index (kg/m2) as overweight (25-30), obese (30-35), and severely obese (>35). MAIN OUTCOME MEASURE: Relative hazard ratio (HR) of death for obese or overweight persons. RESULTS: The estimated number of annual deaths attributable to obesity varied with the cohort used to calculate the HRs, but findings were consistent overall. More than 80% of the estimated obesity-attributable deaths occurred among individuals with a body mass index of more than 30 kg/m2. When HRs were estimated for all eligible subjects from all 6 studies, the mean estimate of deaths attributable to obesity in the United States was 280184 (range, 236111-341153). Hazard ratios also were calculated from data for nonsmokers or never-smokers only. When these HRs were applied to the entire population (assuming the HR applied to all individuals), the mean estimate for obesity-attributable death was 324 940 (range, 262541-383410). CONCLUSIONS: The estimated number of annual deaths attributable to obesity among US adults is approximately 280000 based on HRs from all subjects and 325000 based on HRs from only nonsmokers and never-smokers.

Adult↗
PubMed1999

Consequences of the use of different measures of effect to determine the impact of age on the association between obesity and mortality.

The impact of using different measures of the effect of obesity on mortality across age groups has not been explored. The authors examined this issue by using mortality data from 62,116 men and 262,965 women in the Cancer Prevention Study-I (1960-1972). Measures of effect were calculated separately, by decade of age, for five groups of participants aged 30-79 years. The rate ratio associated with obesity declined with age, from 2.60 (men) and 1.99 (women) for participants aged 30-39 years to 1.24 (men) and 1.15 (women) for those aged 70-79 years. In contrast, the rate differences between obese and reference-weight participants increased with age, from 201 (men) and 112 (women) deaths per 100,000 person-years for those in the youngest decade to 1,379 (men) and 626 (women) deaths per 100,000 person-years for those in the oldest decade. The years of life lost attributable to obesity tended to increase with age but declined for those in the oldest decade. The rate advancement period declined with decade of age. Standardization of estimates to a population changed some age-associated trends. The direction of trends varied regarding the effect of obesity on mortality across age groups, depending on the measure of effect used.

Adult↗
PubMed1999

High performance DNA sequencing, and the detection of mutations and polymorphisms, on the Clipper sequencer.

The Visible Genetics Clipper sequencer is a new platform for automated DNA sequencing which employs disposable MicroCel cassettes and 50 microm thick polyacrylamide gels. Two DNA ladders can be analyzed simultaneously in each of 16 lanes on a gel, after labeling with far-red absorbing dyes such as Cy5 and Cy5.5. This allows a simultaneous bidirectional sequencing of four templates. We have evaluated the Clipper sequencer, by cycle-sequencing of an M13 single-stranded DNA standard, and by coupled amplification and sequencing (CLIP) of reverse-transcribed human immunodeficiency virus (HIV-1) RNA standards and clinical patient samples. (i) Limitations of instrument. We have examined basic instrument parameters such as detector stability, background, digital sampling rate, and gain. With proper usage, the optical and electronic subsystems of the Clipper sequencer do not limit the data collection or sequence-determination processes. (ii) Limitations of gel performance. We have also examined the physics of DNA band separation on 50 microm thick MicroCel gels. We routinely obtain well-resolved sequence which can be base-called with 98.5% accuracy to position approximately 450 on an 11 cm gel, and to position approximately 900 on a 25 cm gel. Resolution on 5 and 11 cm gels ultimately is limited by a sharp decrease in spacing between adjacent bands, in the biased reptation separation regime. Fick's (thermal) diffusion appears to be of minor importance on 6 cm or 11 cm gels, but becomes an additional resolution-limiting factor on 25 cm gels. (iii) Limitations of enzymology. Template quality, primer nesting, choice of DNA polymerase, and choice between dye primers and dye terminators are key determinants of the ability to detect mutations and polymorphisms on the Clipper sequencer, as on other DNA sequencers. When CLIP is used with dye-labeled primers and a DNA polymerase of the F667Y, delta(5'--> 3' exo) class, we can routinely detect single-nucleotide mutations and polymorphisms over the 0.35-0.65 heterozygosity range. We present an example of detecting therapeutically relevant mutations in a clinical HIV-1 RNA isolate.

Bacteriophage M13↗
PubMed1999

Weight-related attitudes and behaviors in fourth grade American Indian children.

OBJECTIVE: American Indian children have a high prevalence of obesity, yet little is known about weight-related attitudes and the prevalence of dieting in this population. This study assessed weight concerns, body size perceptions, weight reduction attempts, and weight loss methods in fourth grade American Indian children. RESEARCH METHODS AND PROCEDURES: Participants (n = 304) attended one of eight schools in the Pathways Feasibility Study. Question and answer choices were read to children by trained staff, and children marked their own answers. RESULTS: Thirty-eight percent of the children reported that they had tried to lose weight. The most common strategy for weight reduction was exercising more. Girls were more likely than boys to be dissatisfied with their body size (48% of girls vs. 34% of boys desired a slimmer body size; 22% of girls vs. 15% of boys desired a larger body size; p<0.001). Children who had tried to lose weight were more likely to indicate that the size they most desired and the most healthy size were smaller than their perceived size (p<0.001). Children who reported trying to lose weight were also more likely to want to be skinnier and to be unhappy about their weight than were children who did not report trying to lose weight (p<0.001 for both). DISCUSSION: We conclude that weight loss attempts and weight-related concerns are prevalent in American Indian children at a young age.

Arizona↗
PubMed1999

Genetic exchange in the trypanosomatidae.

The only trypanosomatid so far proved to undergo genetic exchange is Trypanosoma brucei, for which hybrid production after co-transmission of different parental strains through the tsetse fly vector has been demonstrated experimentally. Analogous mating experiments have been attempted with other Trypanosoma and Leishmania species, so far without success. However, natural Leishmania hybrids, with a combination of the molecular characters of two sympatric species, have been described amongst both New and Old World isolates. Typical homozygotic and heterozygotic banding patterns for isoenzyme and deoxyribonucleic acid markers have also been demonstrated amongst naturally-occurring T. cruzi isolates. The mechanism of genetic exchange in T. brucei remains unclear, although it appears to be a true sexual process involving meiosis. However, no haploid stage has been observed, and intermediates in the process are still a matter for conjecture. The frequency of sex in trypanosomes in nature is also a matter for speculation and controversy, with conflicting results arising from population genetics analysis. Experimental findings for T. brucei are discussed in the first section of this review, together with laboratory evidence of genetic exchange in other species. The second section covers population genetics analysis of the large body of data from field isolates of Leishmania and Trypanosoma species. The final discussion attempts to put the evidence from experimental and population genetics into its biological context.

Animals↗
PubMed1999

Development of a questionnaire to assess knowledge, attitudes, and behaviors in American Indian children.

One aim of the Pathways study is to improve the knowledge, attitudes, and behaviors of American Indian children in grades 3-5 regarding physical activity and diet in. This article describes the development of a culturally sensitive, age-appropriate questionnaire to assess these variables. The questionnaire was designed to be administered in the classroom in two 30-min sessions. Questions were developed to assess 4 key areas: physical activity, diet, weight-related attitudes, and cultural identity. Potential questions were written after review of relevant literature and existing questionnaires. Numerous and extensive revisions were made in response to input from structured, semistructured, and informal data collection. Questions were pretested in 32 children in grades 3-5 by using semistructured interviews. Test-retest reliability and the internal consistency of scales were examined in 371 fourth-grade children and subsequently in 145 fourth-grade children. Questions were reviewed by American Indians from the communities involved in the Pathways study several times during the developmental process. The process described here serves as one model for the development of a culturally appropriate tool to assess knowledge, attitudes, and behaviors in American Indian children.

Asian People↗
PubMed1999

Portion-size estimation training in second- and third-grade American Indian children.

Training in portion-size estimation is known to improve the accuracy of dietary self-reporting in adults, but there is no comparable evidence for children. To obtain this information, we studied 110 second- and third-grade American Indian schoolchildren (34 control subjects were not trained), testing the hypotheses that a 45-min portion-size estimation training session would reduce children's food quantity estimation error, and that the improvement would be dependent on food type, measurement type, or both. Training was a hands-on, 4-step estimation and measurement skill-building process. Mixed linear models (using logarithmic-transformed data) were used to evaluate within- and between-group differences from pre- to posttest. Test scores were calculated as percentage estimation errors by difference and absolute value methods. Mean within-group estimation error decreased significantly (P<0.05) from pre- to posttest for 7 of 12 foods (trained group) by both calculation methods, plus 3 additional foods by the difference method and one additional food by the absolute value method. Significant (P<0.05) between-group differences occurred for 3 foods, reflecting a greater decrease in estimation error for the trained group. Improvement was greatest for solid foods estimated by dimensions (P>0.05) or in cups (P<0.05), for liquids estimated by volume or by label reading (P<0.001), and for one amorphous food estimated in cups (P<0.01). Despite these significant improvements in estimation ability, the error for several foods remained >100% of the true quantity, indicating that more than one training session would be necessary to further increase dietary reporting accuracy.

Asian People↗
PubMed1999

Emergency cranial computed tomography in the management of acute febrile encephalopathy in children.

OBJECTIVE: Evaluation of the influence of emergency cranial computed tomography on the management of acute febrile encephalopathy in children. METHODS: A retrospective study in children with acute febrile encephalopathy who underwent emergency cranial computed tomography within 12 hours of admission to the paediatric intensive care unit. All scans were evaluated by two independent radiologists. RESULTS: Thirty nine children were included. Fourteen scans were abnormal and two had clinically insignificant incidental findings. Four children with focal neurological signs had scans demonstrating extra-axial collections. None required neurosurgical intervention. Clinically, raised intracranial pressure was present in 10 patients. Only five had cerebral oedema on computed tomography; these five children died. Emergency cranial computed tomography influenced subsequent management in no child without focal neurological signs and in only one child with focal neurology. CONCLUSION: Emergency cranial computed tomography in acute febrile encephalopathy in children without focal neurological signs has little influence on subsequent management. Where cranial computed tomography is thought to be necessary, it should be carried out when the child's clinical condition has been stabilised.

Adolescent↗
PubMed1999

Spontaneous intralesional haemorrhage in dysembryoplastic neuroepithelial tumours: a series of five cases.

Five patients with dysembryoplastic neuroepithelial tumour (DNT) showing extensive secondary haemorrhage, a finding not previously associated with these neoplasms, are described. The clinical presentations, neuroimaging findings, and histopathological features of these patients are reviewed. One patient, a previously asymptomatic 12 year old girl, presented with an acute intracerebral haemorrhage into a DNT. A further four young adults with histories of intractable partial and generalised seizures dating from childhood showed significant chronic haemorrhages within DNT, the MRI appearances in one patient giving a false impression of a cavernoma. Histopathology disclosed vascular abnormalities within these tumours which, together with other factors discussed, may have predisposed these tumours to haemorrhage.

Brain Neoplasms↗
PubMed1999

Unilateral focal lesions in the rostrolateral medulla influence chemosensitivity and breathing measured during wakefulness, sleep, and exercise.

OBJECTIVES: The rostrolateral medulla (RLM) has been identified in animals as an important site of chemosensitivity; in humans such site(s) have not been defined. The aim of this study was to investigate the physiological implications of unilateral lesions in the lower brainstem on the control of breathing. METHODS: In 15 patients breathing was measured awake at rest, asleep, during exercise, and during CO(2) stimulation. The lesions were located clinically and by MRI; in nine patients they involved the RLM (RLM group), in six they were in the pons, cerebellum, or medial medulla (Non-RLM group). All RLM group patients, and three non-RLM group patients had ipsilateral Horner's syndrome. RESULTS: Six of the RLM group had a ventilatory sensitivity to inhaled CO(2) (V/P(ET) CO(2)) below normal (group A: V/P(ET) CO(2), mean, 0.87; range 0.3-1.4 l. min(-1)/mm Hg). It was normal in all of the non-RLM group (group B: V/P(ET) CO(2), mean, 3.0; range, 2.6-3.9 min(-1)/mmHg). There was no significant difference in breathing between groups during relaxed wakefulness (V, group A: 7.44 (SD 2.5) l.min(-1); group B: 6.02 (SD 1.3) l.min(-1); P(ET) CO(2), group A: 41.0 (SD 4.2) mm g; group B: 38.3 (SD2.0) mm Hg) or during exercise (V/VO(2): group A: 21 (SD 6. 0) l.min(-1)/l.min(-1); group B: 24 (SD 7.3) l.min(-1)/l.min(-1)). During sleep, all group A had fragmented sleep compared with only one patient in group B (group A: arousals, range 13 to > 60 events/hour); moreover, in group A there was a high incidence of obstructive sleep apnoea associated with hypoxaemia. CONCLUSION: Patients with unilateral RLM lesions require monitoring during sleep to diagnose any sleep apnoea. The finding that unilateral RLM lesions reduce ventilatory sensitivity to inhaled CO(2) is consistent with animal studies. The reduced chemosensitivity had a minimal effect on breathing awake at rest or during exercise.

Adult↗