International Commission for Protection Against Environmental Mutagens and Carcinogens. Genetic risk extrapolation from animal data to human disease. A Taskgroup Report. No. 00105

This report describes a model for producing quantitative genetic risk assessments for human populations. The model is patterned after current methods used in cancer risk analysis. The risk to humans is expressed as the number of additional dominant genetic diseases added to the existing genetic burden, in the offspring of the exposed individuals.

Plasma nitrate concentration and urinary nitrate excretion in patients with gastroenteritis

The concentration of nitrate (the stable oxidation product of nitric oxide) in plasma and its excretion in urine was measured in 20 patients with a diagnosis of gastroenteritis. On day 1 of the illness plasma nitrate concentration was significantly elevated compared with a healthy control population (92.7 +/- 17.0 mumol/l vs. 33.1 +/- 1.6 mumol/l; P < 0.001) and continued to be elevated on days 2 and 3. Urinary nitrate excretion was also elevated. The plasma nitrate concentration correlated with disease severity as assessed by stool frequency and plasma urea concentration. Plasma nitrate concentration may be a sensitive and clinically useful indicator of severity of gastroenteritis.

The short-time effect of latanoprost on the intraocular pressure in normal pressure glaucoma

Latanoprost, a prostaglandin analogue, was given topically to 20 patients with normal pressure glaucoma in a double masked randomized study. Either latanoprost 0.006% or placebo (vehicle) was administered twice a day for 14 days. Latanoprost caused a statistically significant (p < 0.001) reduction in intraocular pressure from a diurnal baseline level of 16.8 to 14.3 mmHg, as measured on day 14. Latanoprost was well tolerated.

The importance of self-efficacy as a mediating variable between learning environments and achievement

The purpose of this research was to investigate the extent to which self-efficacy acts as a mediating variable between the learning environment and achievement. Seven year 5 classes (N = 179 students aged 9 to 10 years) were allocated randomly to cooperative, competitive or individualistic environments for twice-weekly social studies lessons, changing environments after five weeks. Data collected on self-efficacy and achievement in weeks 5 and 10 indicated that co-operative environments led to higher self-efficacy and achievement as well as more appropriate behaviour. The performance of particular tasks under competition appears to be enhanced when students have previously worked co-operatively, but may be difficult to sustain as self-efficacy and behaviour standards decline.

Corynebacterium afermentans subsp. lipophilum: multiple abscess formation in brain and liver

Corynebacterium afermentans, a species recently identified, has previously been isolated from human blood cultures. We report the case of a previously healthy 39-year-old man who developed a brain abscess and a liver abscess due to Corynebacterium afermentans subsp. lipophilum. The liver abscess penetrated through the diaphragm to cause pleural effusion and periostitis of the ribs. We believe this is the first reported case of disseminated infection with abscess formation due to this organism.

Private money and public health. Managing the risks

Private capital can now be invested in the NHS. This new market freedom needs to be balanced against a backdrop of public accountability. Brian Salter and Glenn Douglas explain.

Costing shared care

Growing interest in shared health care schemes over the last decade has received additional impetus with the introduction of GP fund holding and the internal market in health care provision. Ken Buckingham and colleagues report on the relative costs of such a scheme for asthma in comparison with the costs of conventional outpatient care. Data was collected during a randomised controlled trial of shared or integrated care for patients with chronic asthma, who had been referred to a hospital outpatient clinic.

Integrated care for patients with asthma: views of general practitioners

BACKGROUND

In 1989, a shared or integrated care scheme was developed for hospital outpatients with asthma, using the computerized patient record system of Grampian Health Board, Scotland. Patients with asthma attending hospital clinics were entered into this scheme and were invited to attend their general practitioner instead of an outpatient clinic for review of their asthma. Three-monthly questionnaires covering clinical aspects of asthma were sent to these patients and their general practitioners; the latter then returned them to the specialist. Patients could be recalled to the hospital clinic if either the general practitioner or consultant felt this was necessary and all patients were reviewed after one year by the specialist. The success of integrated care for patients with asthma relies on the cooperation of general practitioners.

AIM

The aim of this study was to investigate how this scheme worked in general practice, and general practitioners' perceptions of it, in order to identify factors that enhance or inhibit integrated care for patients with asthma in general practice.

METHOD

A qualitative survey was carried out with a random, stratified sample of 38 of the 317 general practitioners in the region. Semi-structured interviews were designed to elicit general practitioners' accounts of their operation of integrated care and their attitudes towards the scheme.

RESULTS

General practitioners perceived the scheme to have several advantages: the continuity and quality of care provided was improved; and the transmission of information between general practitioner and specialist was enhanced. Regular general practitioner reviews, instigated by standard letters generated by computer, were favoured as being clearly structured. Concerns were raised about the processing of paperwork, and the possibility that unnecessary reviews might be generated.

CONCLUSION

Integrated care for asthma patients is an acceptable management option among general practitioners.

The effect of cognitive style and mode of presentation on learning performance

The effect of text-plus-text versus text-plus-picture computer presentation conditions, and the students' cognitive styles, on learning performance was investigated. In the text-plus-text condition, the learning material content described the working of car braking systems. The text-plus-picture condition consisted of text with additional pictorial information. Fifty-nine 15-16-year-old students in a secondary school were randomly assigned, within sexes, to one of the conditions. Having worked through the computer presented material, they were given a post-test overall learning performance. Immediately following this, they did the Cognitive Styles Analysis (CSA) (Riding, 1991) which measures an individual's position on two cognitive style dimensions; Verbal-Imagery and Wholist-Analytic. It was found that the Verbal-Imagery cognitive style and presentation condition interacted in their effect on overall learning performance (p < .05). In the text-plus-picture condition Imagers were superior to Verbalisers, while the text-plus-text condition Verbalisers did better than Imagers. It was also observed that Imagers used more diagrams to illustrate their answers than Verbalisers. The results are discussed in terms of their implications for instruction.

Social effects of wheeze in childhood: a 25 year follow up

OBJECTIVES

To determine the outcome of childhood wheeze in terms of education, employment, housing, and social class.

DESIGN

25 year follow up study.

SETTING

Community study based at the department of thoracic medicine, Aberdeen Royal Infirmary.

PARTICIPANTS

Three groups of subjects who had been identified in a random community survey in 1964: those who had had asthma in childhood (n = 97), those who had wheezed only in the presence of upper respiratory tract infections (n = 132), and a comparison group who had had no respiratory symptoms as children (n = 131). Subjects were aged 34 to 40 years at the time of the current study.

MAIN OUTCOME MEASURES

Interview and questionnaire data on education, employment, housing and social class, ventilatory function, and peak flow rate.

RESULTS

Pulmonary function testing showed that only the "asthmatic" group had airways obstruction; this group showed greater peak flow variation than the "wheezy" group, which did not differ from the comparison group. The asthmatic subjects were more likely to have experienced respiratory problems during their school years and associated with their work. Despite these problems, educational attainment, employment, housing, and eventual social class were similar for all three groups.

CONCLUSION

Childhood wheeze did not adversely affect education, employment, housing, or social class in this population.

Overview, conclusions, and recommendations of the IPCS collaborative study on complex mixtures

The International Programme on Chemical Safety (IPCS) sponsored an international collaborative study to examine the variability associated with the extraction and bioassay of standard reference materials (SRMs) that are complex environmental mixtures provided by the U.S. National Institute of Standards and Technology (NIST). The study was also intended to evaluate the feasibility of establishing bioassay reference values and ranges for the SRMs. Twenty laboratories from North America, Europe, and Japan participated in the study. As part of the mandatory core protocol, each laboratory extracted the organic material from two particulate samples and bioassayed these extracts. A coal tar polycyclic aromatic hydrocarbon (PAH) solution and two mutagenic control compounds were also subjected to bioassay without prior extraction by the participating laboratories. The bioassay used was the Salmonella/microsomal plate incorporation assay. For the optional portion of the study, a laboratory was free to use the SRMs for any type of exploratory research. The primary purpose of the required portion of the study was to estimate the intra- and inter-laboratory variability in mutagenic potencies of the test materials and to determine whether or not the NIST mixtures could be used as reference materials by others performing the Salmonella assay. Repeatability (intra-laboratory variance) of the bioassay results ranged from 16% to 88% depending on the SRM and the bioassay conditions (tester strain and metabolic activation), whereas reproducibility (inter-laboratory variance) ranged from 33% to 152%. Between-laboratory variability was the main source of variation accounting for approximately 55-95% of the total variation for the three environmental samples. Variation in the mutagenic potency of the control compounds was comparable, with the exception of 1-nitropyrene for which the reproducibility ranged from 127% to 132%. In summary, NIST SRMs provided useful materials for an international inter-laboratory study of complex mixtures. By establishing both intra- and inter-laboratory variance for the mutagenicity results for these materials, the usefulness of these SRMs as reference materials for the Salmonella bioassay was established, critical procedures within the bioassay protocol were identified, and recommendations for future efforts were delineated.

Results of the IPCS collaborative study on complex mixtures

The International Programme on Chemical Safety (IPCS) sponsored a collaborative study to examine the intra- and inter-laboratory variation associated with the preparation and bioassay of complex chemical mixtures. The mixtures selected were National Institute of Standards and Technology (NIST) Standard Reference Materials (SRMs). 20 laboratories worldwide participated in the collaborative trial. The participating laboratories extracted the organic portion of two particulate samples--an air-particulate sample and a diesel-particulate sample--and bioassayed the extracts. The laboratories simultaneously bioassayed a NIST-prepared extract of coal tar and two control compounds (benzo[a]pyrene, and 1-nitropyrene). The bioassay method used was the Salmonella/mammalian microsome plate-incorporation test using strains TA98 and TA100. Study design also allowed for a comparison of sonication and Soxhlet extraction techniques. The mean extractable masses for the air particles and diesel particles were approximately 5% and 17.5%, respectively. The particulate samples were mutagenic in both strains with and without activation in all 20 laboratories. For TA100 the with and without activation slope values for the air particulate were 162 and 137 revertants per mg particles, respectively. For TA98 the respective diesel slope values were 268 and 269. The mutagenicity slope values for the diesel particles ranged from 3090 (TA98, +S9) to 6697 (TA100, +S9) revertants per mg particles. The coal tar solution was negative for both strains when exogenous activation was not used but was mutagenic in both strains with exogenous activation. The benzo[a]pyrene and 1-nitropyrene were used as positive controls and gave results consistent with the literature. This paper provides a complete summary of the data collected during the collaborative study. Companion papers provide further analysis and interpretation of the results.

Characteristics of the normal central visual field measured with resolution perimetry

The ring perimeter is an innovative device that measures the resolution threshold at 50 locations in the central visual field in approximately 6 min. This study was undertaken to define the characteristics of the resolution visual field in normal eyes using this instrument and to check the repeatability of the measurement. A total of 114 perimetrically naive, normal subjects aged from 20 to 79 years were prospectively enrolled; 55 randomly chosen subjects were tested twice, with a rest period of less than or equal to 60 s elapsing between examinations. The resolution threshold increased towards the periphery in all subjects. A small but significant decline in sensitivity occurred with age; this loss was greatest in the inner part of the field. Variability in threshold between subjects was not found to increase towards the periphery or in the upper field as compared with the lower. The field was highly repeatable when reexamined in the same subject. This study defines the resolution visual field in normal subjects, along with its inter- and intra-observer variability, and gives age-corrected predictive confidence intervals for each location of the field using the ring perimeter.

A comparison of chromosomal aberrations induced by in vivo radiotherapy in human sperm and lymphocytes

Chromosomal aberrations in human sperm and lymphocytes were compared before and after in vivo radiation treatment of 13 cancer patients. The times of analyses after radiotherapy (RT) were 1, 3, 12, 24, 36, 48 and 60 months. The median total radiation dose was 30 Gy and the testicular dose varied from 0.4 to 5.0 Gy. Human sperm chromosome complements were analysed after fusion with golden hamster eggs. There were no abnormalities in sperm or lymphocytes before RT. Following RT there was an increase in the frequency of numerical and structural chromosomal abnormalities in both lymphocytes and sperm. For structural abnormalities there were more rejoined lesions (dicentrics, rings) in lymphocytes and more unrejoined lesions (chromosome breaks, fragments) in sperm. After RT there was a dramatic increase in the frequency of chromosomal abnormalities in lymphocytes: at 1 mo. the frequency was 42%, at 3 mo. 25%, at 12 mo. 14%, at 24 mo. 11%, at 36 mo. 9%, at 48 mo. 7% and at 6 mo. 4%. Since the majority of men were azoospermic after RT, there is little data on sperm chromosome complements before the analyses performed at 24 mo. post-RT. At 24 mo. the frequency of abnormalities was 13%, followed by 21% at 36 mo., 12% at 48 mo. and 22% at 60 mo. Thus it appears that the frequency of lymphocyte chromosomal abnormalities had an initial marked increase after RT followed by a gradual decrease with time whereas the frequency of sperm chromosomal abnormalities was elevated when sperm production recovered and remained elevated from 24 to 60 mo. post-RT. This difference in the effect of time makes it very difficult to compare abnormality rates in lymphocytes and sperm and to use analysis of induced damage in somatic cells as surrogates for germ cells since the ratio between sperm and lymphocytes varied from 1:1 (at 24 mo. post-RT) to 5:1 (at 60 mo. post-RT).

Thyroid function and endocrine abnormalities in elderly patients with severe chronic obstructive lung disease

Serum pituitary and thyroid hormones, testosterone, and the response of pituitary hormones to thyrotrophin releasing hormone were measured in 20 inpatients (mean age 68, range 42-81 years) with severe chronic obstructive lung disease and in 15 control convalescent inpatients (mean age 73, range 57-83 years) who had normal respiratory function. No significant differences were found in total and free thyroid hormone concentrations and basal concentrations of thyrotrophin, growth hormone, and prolactin; and their increments after injection of thyrotrophin releasing hormone were similar in patients with chronic obstructive lung disease, and control patients. Three patients with chronic obstructive lung disease, however, had no thyrotrophin responses to thyrotrophin releasing hormone. In men, low testosterone concentrations were found both in patients with chronic obstructive lung disease and in controls. Luteinising hormone concentrations were higher in men with chronic obstructive lung disease (p less than 0.02), whereas concentrations of follicle stimulating hormone in the two groups were not significantly different. There was no significant correlation between arterial blood gas tensions and these hormone measurements. General effects of age and illness may be more important than direct effects of hypoxia in determining hypothalamic-pituitary function in elderly patients with chronic obstructive lung disease.