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Biomedical subjects

M Ball

Publications and source records attributed to M Ball.

At least 37 records · Page 2Linked to original sources
PubMed1999

Effects of overlapping parametric resonances on the particle diffusion process.

The evolution of the beam distribution in a double-rf system with a phase modulation on either the primary or secondary rf cavity was measured. We find that the particle diffusion process obeys the Einstein relation if the phase space becomes globally chaotic. When dominant parametric resonances still exist in the phase space, particles stream along the separatrices of the dominant resonance, and the beam width exhibits characteristic oscillatory structure. The particle-tracking simulations for the double-rf system are employed to reveal the essential diffusion mechanism. Coherent octupolar motion has been observed in the bunch beam excitation. The evolution of the longitudinal phase space in the octupole mode is displayed.

Journal Article↗
PubMed1999

Lipoprotein(a), essential fatty acid status and lipoprotein lipids in female Australian vegetarians.

In the present study we investigated serum lipoprotein(a) [Lp(a)] levels, plasma lipids, the serum phospholipid polyunsaturated fatty acid profile and correlates of serum Lp(a) in healthy free-living female vegetarians (n=50) and omnivores (n=24) to assess differences which may have implications for cardiovascular risk. Dietary saturated fat and total plasma cholesterol were significantly lower in the vegetarians compared with omnivores. The mean serum Lp(a) concentration was lower in the vegetarians (171 mg/l) than in the omnivores (247 mg/l). The serum Lp(a) concentration was significantly negatively correlated with carbohydrate intake (as % of energy), and positively correlated with plasma total cholesterol. Compared with the omnivores, the vegetarians had significantly lower concentrations of 20:3,n-6, 20:4,n-6, 22:5,n-6, 20:5,n-3, 22:6,n-3 and total n-6 and n-3 polyunsaturated fatty acids, and a lower n-3/n-6 polyunsaturated fatty acid ratio, in serum phospholipids. Lower concentrations of plasma total cholesterol, serum phospholipid total fatty acids, total saturated fatty acids and arachidonic acid, and a tendency towards a lower serum Lp(a) concentration, in vegetarians may have beneficial effects on cardiovascular disease risk. However, the decreased concentration of serum phospholipid n-3 polyunsaturated fatty acids may potentially promote thrombotic risk. Based on the present data, it would seem appropriate for omnivores to reduce their dietary intake of total fat and saturated fat in order to decrease their plasma cholesterol, and vegetarians should perhaps increase their dietary intake of n-3 polyunsaturated fatty acids, and thus improve the balance of n-3/n-6, in order to reduce any thrombotic tendency that might increase their generally low risk of cardiovascular disease.

Adult↗
PubMed1998

[Fixation disparity with the Pola pointing test: not representative for eye position under natural viewing conditions].

BACKGROUND: According to certain findings obtained with the Zeiss Polatest, H.J. Haase defined a "Fixation Disparity Type One". In this diagnosis, the "Zeigertest" is particularly important. The Zeigertest consists of a central ring presented to both eyes for fixation, a vertical clock hand presented to the right eye and two markings at the six and twelve o'clock positions presented to the left eye. All parts are surrounded by a binocularly visible frame. Subjects with a "Fixation Disparity Type One" see a misalignment between the clock hand and the peripheral markings. We investigated (1) whether the perceived misalignment correlated with an objective deviation of the eyes from orthovergence and (2) whether subjects with a "Fixation Disparity Type One" had a deviation of the eyes from orthovergence when looking at a natural, i.e., fully fusionable object. SUBJECTS AND METHODS: Out of 303 medical students, 10 subjects with a "Fixation Disparity Type One" were selected and asked to indicate the perceived alignment or misalignment in the Zeigertest with a laser pointer. Two subjects without fixation disparity served as controls. The position of both eyes was recorded using the search coil technique. One of the 10 subjects with "Fixation Disparity Type One" had to be excluded due to excessive blinking. Experiment 1: In the beginning all parts of the Zeigertest were presented to both eyes (natural viewing condition). Then, the object for one of the eyes was switched off leaving the frame as the only fusional stimulus. The outcome variable was a refixation movement of the other eye. This experiment is similar to the unilateral cover test. Experiment 2: In the beginning all parts of the Zeigertest were presented to both eyes (natural viewing condition). Then, the original Zeigertest was switched on (clock hand presented only to the right eye, peripheral markings only to the left eye). The outcome variable was a change of vergence. RESULTS: Experiment 1: A significant refixation movement did not occur in any of the subjects. Experiment 2. In all 9 subjects with "Fixation Disparity Type One" the vergence changed significantly between 2.4 and 14.9 arcmin. The change of vergence correlated significantly with the angle of the perceived misalignment between clock hand and peripheral markings. CONCLUSION: A fixation disparity ascertained at the Zeigertest does not indicate a fixation disparity under natural viewing conditions.

Adult↗
PubMed1998

Transformation of health care through innovative use of information technology: challenges for health and medical informatics education.

Information storage and processing continues to become increasingly important for health care, and offers enormous potential to be realised in the delivery of health care. Therefore, it is imperative that all health care professionals should learn skills and gain knowledge in the field of health informatics, or medical informatics, respectively. Working Group 1, Health and Medical Informatics Education, of the International Medical Informatics Association (IMIA WG1) seeks to advance the knowledge of how these skills are taught in courses for the various health care professions around the world, and includes physicians, nurses, administrators, and specialists in medical informatics. IMIA WG1 held its 6th International Conference on Health and Medical Education in Newcastle, Australia, in August 1997. The theme of the conference was 'Transformation of Healthcare through Innovative Use of Information Technology'. This special issue of the International Journal of Medical Informatics on Health and Medical Informatics Education contains selected papers presented at the conference. In addition to the central topic, Educating Health Care Professionals in Medical Informatics the topics telematics, distance education and computer based training were also discussed at the conference.

Health Occupations↗
PubMed1997

Volume loss of the hippocampus and temporal lobe in healthy elderly persons destined to develop dementia.

OBJECTIVE: To determine initial locus and rate of degeneration of temporal lobe structures (total lobe, hippocampus and parahippocampus) in preclinical dementia. BACKGROUND: Postmortem studies suggest that the earliest changes in Alzheimer's disease are neurofibrillary tangle formation in hippocampus and adjacent cortex. MRI volume analysis of temporal lobe structures over time in subjects prior to developing dementia may allow the identification of when these processes begin, the rate they develop, and which areas are key to symptom development. METHODS: 30 nondemented (NoD), healthy, elderly individuals enrolled in a prospective study of healthy aging evaluated annually over a mean of 42 months. Twelve subjects with subsequent cognitive decline were assigned to the preclinical dementia group (PreD). All 120 annual MRI studies analyzed by volumetric techniques assessed group differences in temporal lobe volumes and rates of brain loss. RESULTS: NoD as well as PreD subjects had significant, time-dependent decreases in hippocampal and parahippocampal volume. Rates of volume loss between the groups did not significantly differ. PreD cases had significantly smaller hippocampi when asymptomatic. Parahippocampal volume did not differ between PreD and NoD cases. Significant time-dependent temporal lobe atrophy was present only in PreD. CONCLUSIONS: Hippocampal and parahippocampal atrophy occurs at a similar rate regardless of diagnostic group. Those who develop dementia may have smaller hippocampi to begin with, but become symptomatic because of accelerated loss of temporal lobe volume. Temporal lobe volume loss may mark the beginning of the disease process within six years prior to dementia onset.

Aged↗
PubMed1997

Vegetarian, vegan or meat eater. The pros and the cons.

This article discusses the potential health benefits of a vegetarian diet, while highlighting some potential problems that may occur if such a dietary regimen is adopted, particularly in certain groups. It emphasises the importance of health professionals contributing to people's knowledge of nutrition in order to allow them to choose a healthy diet, whether they are vegetarian or meat eaters.

Diet, Vegetarian↗
PubMed1996

Decrease in milk and blood dioxin levels over two years in a mother nursing twins: estimates of decreased maternal and increased infant dioxin body burden from nursing.

This study addresses the issue of breast-feeding and its reduction of maternal dioxin body burden. Nursing is also a source of infant dioxin exposure. This study extends our previous efforts to investigate a nursing mother's milk and blood dioxin levels. We report polychlorinated dibenzo-p-dioxin (PCDD) and polychlorinated dibenzofuran (PCDF) dioxin toxic equivalents (TEQs) in milk (M) and blood (B) both before and also after two years of nursing twins to be 16.9 ppt (M), 14.9 ppt (B), and 3.1 ppt (M) and 4.9 ppt (B), respectively. The ratios of measured congeners comparing milk to whole blood from a nursing mother taken initially and after two years of nursing vary from 0.36 to 8.40 in 1992 and 0.17 to 1.0 in 1994. The mother's body burden was initially calculated to be 329 ng TEQ from milk levels and 291 ng TEQ from blood levels using samples taken in February 1992 and decreased to 60.1 ng TEQ from milk and 96 ng TEQ from measured blood using samples collected in December 1994. We calculate that the excretion of dioxin TEQ by the mother through breast-feeding is 269 ng TEQ, which is similar to the 303 ng TEQ estimated total dioxin intake by the twins over two years. The average daily dioxin intake from nursing is 66 pg TEQ/kg-BW/day for each twin over the two years.

Benzofurans↗
PubMed1996

Concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans in human placental and fetal tissues from the U.S. and in placentas from Yu-Cheng exposed mothers.

We report the concentrations of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) found in human placentas and fetal tissue from the U.S. and in placentas from Yu-Cheng mothers. In placental material from sources in the U.S. we found concentrations, expressed as dioxin toxic equivalence (TEQ) values and on a lipid basis, between 8.4 and 17.6 ng/kg. In a pooled sample of fetal tissue (8-14 week) the concentration, 5.3 ng/kg, was somewhat smaller. In placental material from Taiwanese Yu-Cheng subjects much higher concentrations were found, in the range 610 to 9010 TEQ ng/kg, again on a lipid basis.

Benzofurans↗
PubMed1995

Individual variation in plasma cholesterol response to dietary saturated fat.

OBJECTIVE: To determine the extent to which plasma lipid concentrations of individuals are consistently sensitive to changes in saturated fats; to examine whether groups that consistently have large or small responses can be defined; and to identify factors which predict response of lipids to dietary change. DESIGN: A double crossover design in which two diets (S, providing 21% energy from saturated fat, and P, providing 10%) were followed for periods of six weeks in the sequence SPSP or PSPS. SETTING: 67 free living subjects, total cholesterol 5.5-7.9 mmol/l. MAIN OUTCOME MEASURES: Relation of cholesterol responses to repeated dietary changes and of potential predictors and cholesterol response. RESULTS: Similar average changes in cholesterol mask a wide range of individual responses. Response was not related to compliance. In all participants the change in cholesterol observed when the nature of dietary fat was changed on the two crossovers was correlated (r = 0.31, P = 0.01); the degree of correlation between the two sets of responses was greater in the 46 consistent responders than in the 21 variable responders (r = 0.71 v r = 0.21). Mean differences in cholesterol between diet S and diet P during the two crossovers were 1.16 (SD 0.35) mmol/l and 0.95 (0.26) mmol/l for consistent hyperresponders and 0.18 (0.26) mmol/l and 0.18 (0.25) mmol/l for consistent minimal responders. In consistent responders, changes in total cholesterol in response to increasing saturated fats correlated with baseline cholesteryl ester transfer activity (r = 0.32, P = 0.03); total cholesterol (r = 0.37, P = 0.01); triglycerides (r = 0.30, P = 0.04); and apolipoprotein B (r = 0.54, P = 0.01). CONCLUSIONS: There is a degree of consistency in cholesterol response to instructions to change dietary fat which is not explained by dietary compliance, and there are groups of consistent hyperresponders and minimal responders within a population of hypercholesterolaemic individuals. Several factors predicting response have been identified. These results have relevance to dietary approaches aimed at reducing the lipoprotein mediated risk of coronary heart disease.

Adult↗
PubMed1995

Dioxin concentrations in the blood of workers at municipal waste incinerators.

OBJECTIVES: Increased concentrations of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzo-furans (PCDFs) in pooled blood samples from workers at municipal waste incinerators have been reported. This study was undertaken to confirm these results in individual blood samples from potentially exposed and unexposed workers at municipal waste incinerators compared with matched unexposed controls and compared with concentrations in the slag and fly ash from the municipal waste incinerators. METHODS: Concentrations of PCDDs and PCDFs were determined in the blood of 10 workers from an old municipal waste incinerator without adequate pollution controls, 11 workers from a newer incinerator with modern pollution controls, and 25 controls from the general population group matched for age (+/- 10 years), sex, and race, and in the slag and fly ash from the older incinerator. RESULTS: Significant increases of certain PCDDs and PCDFs were found in the blood of the workers from the older incinerator compared with the controls as follows: octaCDD (1051 (438) v 637 (344), P < 0.001), hexaCDF (52.3 (28.7) v 30.2 (18.2), P < 0.01), heptaCDF (43.9 (30.4) v 22.7 (12.4), P < 0.001), total PCDDs (1262 (484) v 825 (454), P < 0.001), total PCDFs (133.0 (68.1) v 93.7 (36.7), P < 0.05), and total PCDD/Fs (1395 (537) v 918 (437), P < 0.001). The workers from the older incinerator with the greatest exposure were found to have the most significant increases of the blood PCDDs and PCDFs, and the pattern of increased PCDD and PCDF congeners in the blood corresponded to the pattern in the incinerator slag and ash. No significant differences were found between the blood concentrations of the workers at the newer incinerator and the controls. CONCLUSION: Occupational exposure to slag and fly ash from municipal waste incinerators may increase the blood concentrations of PCDDs and PCDFs. Modern pollution control technology in new incinerators may be able to minimise potential exposure to slag and fly ash and thus the absorption of PCDDs and PCDFs from this source.

Adult↗
PubMed1995

Investigation of benefits and costs of an ophthalmic outreach clinic in general practice.

BACKGROUND: With the advent of general practitioner fundholding, there has been growth in outreach clinics covering many specialties. The benefits and costs of this model of service provision are unclear. AIM: A pilot study aimed to evaluate an outreach model of ophthalmic care in terms of its impact on general practitioners, their use of secondary ophthalmology services, patients' views, and costs. METHOD: A prospective study, from April 1992 to March 1993, of the introduction of an ophthalmic outreach service in 17 general practices in London was undertaken. An ophthalmic outreach team, comprising an ophthalmic medical practitioner and an ophthalmic nurse, held clinics in the practices once a month. Referral rates to Edgware General Hospital ophthalmology outpatient department over one year from the study practices were compared with those from 17 control practices. General practitioners' assessments of the scheme and its impact on their knowledge and practice of ophthalmology were sought through a postal survey of all partners and interviews with one partner in each practice. Patient surveys were conducted using self-administered structured questionnaires. A costings exercise compared the outreach model with the conventional hospital ophthalmology outpatient clinic. RESULTS: Of 1309 patients seen by the outreach team in the study practices, 480 (37%) were referred to the ophthalmology outpatient department. The annual referral rate to this department from control practices was 9.5 per 10,000 registered patients compared with 3.8 per 10,000 registered patients from study practices. A total of 1187 patients were referred to the outpatient department from control practices. An increase in knowledge of ophthalmology was reported by 18 of 47 general practitioners (38%). Nineteen (40%) of 47 general practitioners took advantage of the opportunity for inservice training with the outreach team; they were more likely to change their routine practice for ophthalmic care or referral criteria for patients with cataracts or diabetes than those who did not attend for inservice training. The outreach scheme was popular with patients, for whom ease of access and familiarity of surroundings were major advantages. The cost per patient seen in the outreach clinics (48.09 pounds) was about three times the cost per patient seen in the outpatient department (15.71 pounds). CONCLUSION: The model of ophthalmic outreach care in this pilot study was popular with patients and general practitioners and appeared to act as an effective filter of demand for care in the hospital setting. However, the educational impact of the scheme was limited. Although the unit costs (per patient) of the outreach scheme compared unfavourably with those of conventional outpatient treatment, potential health gains from this more accessible model of care require further exploration.

Ambulatory Care Facilities↗