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Biomedical subjects

M Ball

Publications and source records attributed to M Ball.

At least 19 recordsLinked to original sources
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↗
PubMed1994

Characterization of a single glycosylated asparagine site on a glycopeptide using solid-phase Edman degradation.

The characterization of site-specific glycosylation is traditionally dependent on the availability of suitable proteolytic cleavage sites between each glycosylated residue, so that peptides containing individual glycosylation sites are recovered. In the case of heavily glycosylated domains such as the O-glycosylated mucins, which have no available protease sites, this approach is not possible. Here we introduce a new method to gain site-specific compositional data on the oligosaccharides attached to a single amino acid. Using a model glycopeptide from a mutant human albumin Casebrook, glycosylated PTH-Asn was recovered after sequential solid-phase Edman degradation, subjected to acid hydrolysis and the sugars were identified by high performance anion exchange chromatography with pulsed amperometric detection. The PTH-Asn(Sac) derivative was further characterized by ionspray mass spectrometry. Comparison between an endoproteinase Glu-C glycopeptide and a tryptic glycopeptide showed that the oligosaccharide attached to Asn494 was stable after at least 10 cycles of Edman degradation.

Amino Acid Sequence↗
PubMed1994

Metabolic effects of alterations in meal frequency in hypercholesterolaemic individuals.

It has been suggested that the metabolic consequences of a given diet may depend in part on the frequency with which meals are eaten. To investigate the effects of meal frequency on plasma lipid metabolism, 16 free-living hypercholesterolaemic men and women consumed their usual diet as 3 or 9 meals/day in random order for 4 weeks. Dietary macronutrient intake and body weight remained similar on the 2 regimens. Fasting plasma lipids were measured after 2, 3 and 4 weeks on each regimen and there were no significant differences in the fasting concentrations of plasma total, LDL, and HDL cholesterol, triglycerides, apolipoprotein A-I and B and the ratio of total: LDL and LDL:HDL cholesterol (HDL-C) on the two diets. The mean (+/- S.D.) fasting total cholesterol was 6.73 +/- 0.74 and 6.81 +/- 0.88 mmol/l on 3 and 9 meals/day, respectively and LDL-C was 4.77 +/- 0.66 and 4.87 +/- 0.78 mmol/l, respectively. There was also no significant variation in the response of plasma triglycerides or serum insulin to a high fat meal following a 3 week adaptation to regimens of 3 and 9 meals/day. Finally the 24 h urinary output of C-peptide was similar on each diet. The consumption of isoenergetic diets as 3 and 9 meals/day did not influence fasting plasma lipid levels, C-peptide excretion or the plasma triglyceride response to a high fat meal of a group of free living hypercholesterolaemic subjects.

Adult↗
PubMed1994

The effect of dietary fat content on plasma noncholesterol sterol concentrations in patients with familial hypercholesterolemia treated with simvastatin.

The effects of a low-fat, low-cholesterol diet (LFD) or a higher-fat, higher-cholesterol diet (HFD) on plasma concentrations of lipids, lipoproteins, lathosterol (an index of cholesterol synthesis rate), and plant sterols were determined in 19 patients with familial hypercholesterolemia (FH) treated with simvastatin. The study followed a randomized crossover design including two 8-week diet periods. The LFD significantly decreased plasma lathosterol (-22%), cholesterol (-6%), low-density lipoprotein (LDL) cholesterol (-6%), and high-density lipoprotein (HDL) cholesterol (-7%) levels compared with the HFD. Decreases in plasma lathosterol and LDL cholesterol concentrations in patients during the LFD were significantly correlated (r = .522, n = 19, P < .05). These results suggest that a LFD may enhance the decrease in cholesterol synthesis induced by simvastatin treatment, and in this way might contribute to the decrease in plasma cholesterol levels when the fat content of the diet is reduced in simvastatin-treated FH patients.

Adult↗
PubMed1994

Chlorinated dioxins and dibenzofurans in human tissue from general populations: a selective review.

During the past decade a considerable amount of data has been generated concerning polychlorinated dibenzodioxin (PCDD) and polychlorinated dibenzofuran (PCDF) levels in humans from many geographical locations. To organize these data in a useful fashion for environmental purposes and for consideration of human toxicity, selected portions of our data are presented in a somewhat atypical fashion, by percentage contribution of individual congeners to total PCDD/Fs in human tissue, and to the total dioxin equivalents (TEq). This is done to better characterize congener contributions from environmental contamination in various geographical regions at this time and health-related levels. To present the findings in a global perspective, data from widely different locations are presented including the United States, Germany, Vietnam, the former Soviet Union, Thailand, Cambodia, China, South Africa, and Guam.

Adipose Tissue↗
PubMed1993

Avidin-biotin based electrochemical immunoassay for thyrotropin.

A two site electrochemical enzyme immunoassay for thyrotropin (TSH) has been developed. This assay is based on the use of an immobilized capture antibody and a biotinylated second antibody. Detection is achieved via avidin labelled with alkaline phosphatase. The substrate 1-naphthyl phosphate was used and the product 1-naphthol was detected at disposable screen-printed carbon 8-electrode combs using specially designed instrumentation.

Alkaline Phosphatase↗
PubMed1993

Increasing calcium intake in women on a low-fat diet.

Dietary advice to reduce the risk of coronary heart disease (CHD) is aimed at reducing saturated fat intake, especially in people with hyperlipidaemia. Dairy products contribute a considerable proportion of the fat intake of many people's diet in New Zealand, and are thus often reduced. However, dairy products provide about 60% of the dietary calcium. This study investigated the calcium intake of 50 women aged 40-65 years on fat-reduced diets. The effect of giving standardized information on the importance of calcium intake, and on ways to increase this, was assessed by a repeat dietary analysis 3 months later. The mean (SD) calcium intake was initially 696 (245) mg per day; below that recommended for post-menopausal women. The mean percentage energy from fat and saturated fat was 28.5% and 9.6%, respectively. Three months later, after the specific advice on calcium, the mean calcium intake was significantly higher at 938 (317) mg per day, with 88% having increased their intake, yet the intake of energy, fat and saturated fat were unchanged. This was mainly achieved by increased use of low-fat dairy products. Specific advice about calcium should be given to women commencing lipid-lowering diets in order to attain recommended intakes and to reduce the risk of osteoporosis, as well as CHD.

Adult↗
PubMed1992

Androgenic-anabolic steroid abuse and platelet aggregation: a pilot study in weight lifters.

The abuse of anabolic-androgenic steroids by athletes has recently been associated with the development of myocardial infarction and stroke. Because platelets play a pathogenic role in these disorders, the authors hypothesized that androgenic steroid abuse among weight lifters was associated with increased platelet aggregation as measured in vitro. Twenty-eight study participants were recruited. Twelve denied current androgen use. However, 8 of these 12 tested positive for urinary androgens. Nonsignificant trends toward increased platelet counts and increased platelet aggregation to adenosine diphosphate were noted when androgen users were compared to nonusers. However, when stratified by age, older (greater than 22 years) androgen users required lower concentrations of collagen to produce 50% aggregation of test platelets than did younger (less than or equal to 22 years) androgen users (1.47 versus 3.35 micrograms/ml; p = .01). Further subgroup analysis revealed nonsignificant trends toward increased adenosine diphosphate-induced aggregability and nonsignificant trends in the platelet count in older weight lifters. Subsequent studies using collagen threshold aggregometry revealed no age-dependent effect in 17 other men (aged 18 to 46 years) not specifically selected for activity (r = .17). This study suggests an association between androgen use, age, and increased platelet sensitivity to collagen in weight lifters and may be helpful in explaining recent thrombotic disease in androgen users. It additionally calls into question the validity of subjective reporting when assessing androgen use among weight lifters.

Adolescent↗