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Biomedical subjects

M Dickson

Publications and source records attributed to M Dickson.

At least 37 records · Page 2Linked to original sources
PubMed1995

Childhood leukaemia and non-Hodgkin's lymphoma near large rural construction sites, with a comparison with Sellafield nuclear site.

OBJECTIVE: To determine whether population mixing produced by large, non-nuclear construction projects in rural areas is associated with an increase in childhood leukaemia and non-Hodgkin's lymphoma. DESIGN: A study of the incidence of leukaemia and non-Hodgkin's lymphoma among children living near large construction projects in Britain since 1945, situated more than 20 km from a population centre, involving a workforce of more than 1000, and built over three or more calendar years. For periods before 1962 mortality was studied. SETTING: Areas within 10 km of relevant sites, and the highland counties of Scotland with many hydroelectric schemes. SUBJECTS: Children aged under 15. RESULTS: A 37% excess of leukaemia and non-Hodgkin's lymphoma at 0-14 years of age was recorded during construction and the following calendar year. The excesses were greater at times when construction workers and operating staff overlapped (72%), particularly in areas of relatively high social class. For several sites the excesses were similar to or greater than that near the nuclear site of Sellafield (67%), which is distinctive in its large workforce with many construction workers. Seascale, near Sellafield, with a ninefold increase had an unusually high proportion of residents in social class I. The only study parish of comparable social class also showed a significant excess, with a confidence interval that included the Seascale excess. CONCLUSION: The findings support the infection hypothesis and reinforce the view that the excess of childhood leukaemia and non-Hodgkin's lymphoma near Sellafield has a similar explanation.

Adolescent↗
PubMed1994

Long-term neoplasia risk after azathioprine treatment in inflammatory bowel disease.

The incidence of various cancers, especially non-Hodgkin lymphoma (NHL), is higher among patients who receive azathioprine for immunosuppression after organ transplants than in the general population. We have studied the risk of neoplasia after azathioprine in 755 patients treated for inflammatory bowel disease. The patients received 2 mg/kg daily for a median of 12.5 months (range 2 days to 15 years) between 1962 and 1991; median follow-up was 9 years (range 2 weeks to 29 years). Overall there was no significant excess of cancer: 31 azathioprine-treated patients developed cancer before age 85 compared with 24.3 expected from rates in the general population (observed/expected ratio 1.27, p = 0.186). There was a difference in the frequency of colorectal (13) and anal (2) carcinomas (expected 2.27; ratio 6.7, p = 0.00001); these tumours are recognised complications of chronic inflammatory bowel disease. There were 2 cases of invasive cervical cancer (expected 0.5), but no case of NHL. Among patients with extensive chronic ulcerative colitis there was no difference in cancer frequency between 86 who had received azathioprine and 180 matched patients who had never received it. Thus, azathioprine treatment does not substantially increase the risk of cancer in inflammatory bowel disease.

Adenocarcinoma↗
PubMed1993

Incidence of non-driving excitation of Ia afferents during ramp frequency stimulation of static gamma-axons in cat hindlimbs.

1. The aim of this investigation was to identify static gamma-axons which do not drive any Ia afferents at any stimulus frequency in any spindle which they supply, and to determine their occurrence in various hindlimb muscles (peroneus tertius, brevis, longus and tenuissimus). 2. Ia responses to static gamma stimulation were classified as 'non-driven' when the discharge did not follow the stimulation frequency, or its subharmonics, at any time during a linear increase in stimulus frequency up to 150 Hz lasting 2-3 s, and when tested at two muscle lengths--except in the tenuissimus muscle. In almost all experiments, cross-correlograms were used in addition to evaluate the percentage of these 'non-driven' responses in which a time-locking of discharge to stimulus pulses was obscured by irregularity of the Ia discharge. 3. In 104 spindles, out of 347 responses to stimulation of single static gamma-axons 332 (93%) could be characterized, and of these, 57% (183) were of the non-driven type. The mean number of static gamma effects characterized per spindle was 4.1 (fourteen experiments). In the large majority of spindles (79%, 82 out of 104) at least one response was of the non-driven type. 4. Of the static gamma-axons studied 16% were called 'non driving' ('ndr' gamma s-axons) because they elicited non-driven effects, and since they had the same qualitative effect consistently in all spindles whose discharge was modulated by stimulating them they were called specific 'ndr' axons. If axons with non-driven effects, but acting on one spindle were included in the 'non-driving' category the proportion was 23%. Of spindles tested 63% were innervated by at least one 'ndr' axon. 5. Absence of Ia driving during ramp frequency stimulation of gamma s-axons has been equated with selective bag2 contraction. All the non-driven responses identified in this study cannot be attributed to exclusive bag2 involvement because the total number of 'ndr' responses was too high. In fact, in the isolated spindle preparation bag2 and chain co-contraction were shown to elicit non-driven responses, so chain contraction is not detected reliably in all experimental conditions. Possibly chain fibre contraction is sometimes too weak to dominate the response, or can be of a non-driving character.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

A controlled trial of home-based acute psychiatric services. II: Treatment patterns and costs.

Treatment records of 94 patients treated in an experimental home-based psychiatric service and 78 control patients in standard care were collected over one year. There was a substantial reduction in in-patient care in the experimental group, both in terms of proportion admitted and duration of admissions, despite similar out-patient and general practice care. The total treatment costs were significantly larger (> 50%) for standard care when controlled for by diagnostic grouping. Costs were further examined by including all specialist psychiatric care, and by excluding patients with primary diagnoses of brain damage or alcoholism. Sensitivity analysis explored the effects of increasing the cost of home visits. The relative cost effectiveness of the experimental service persisted. Clinical and social outcome was similar in control and experimental groups.

Adolescent↗
PubMed1992

Elevated levels of endotoxin, oxygen-derived free radicals, and cytokines during extracorporeal membrane oxygenation.

It has been demonstrated that the initiation of extracorporeal membrane oxygenation (ECMO) is associated with an increase in the circulating plasma levels of inflammatory mediators. We have expanded the study of these substances to include measurements of complement activation, prostaglandin production, endotoxin appearance, oxygen-derived free radical generation, and cytokine release before, during, and after ECMO. A reproducible second phase of complement activity and prostaglandin synthesis was associated with the appearance of detectable circulating endotoxin (0.04 U/mL pre-ECMO to 0.07 U/mL at 36 hours, P less than .05). Oxygen-derived free radical activity also increased (2 ng/mL to 3 ng/mL at 36 hours, P less than .05), as did plasma levels of tumor necrosis factor (40 pg/mL to 70 pg/mL at 36 hours, nonsurvivor group: P less than .05). Interleukin-1 was elevated above normal, but there were no significant variations noted during the time period studied. Small amounts of interleukin-6 were also detected in the occasional patient. None of these mediators differed significantly between survivors and nonsurvivors. These data indicate that ECMO is associated with a previously undescribed, endotoxin-related, generalized inflammatory state after 36 hours of support. The pulmonary, renal, and cardiac dysfunctions documented with prolonged bypass can all be related to a classic sepsis syndrome.

Endotoxins↗
PubMed1991

Managing common oral problems: some considerations.

In the absence of early interventions, incipient dental problems can progress to destructive and even fatal outcomes. It is particularly important that primary health personnel correctly diagnose a presenting condition and provide care as early as possible. Some considerations are presented to assist in recognizing and managing common mouth problems.

Developing Countries↗
PubMed1990

A useful technique for closure of pulmonary lacerations.

Methods of closing lung tissue with stapling devices or simple sutures are usually adequate. In some patients lung tissue is so friable that reinforcement of the sutures with tissue flaps is beneficial. Felt bolsters or pledgets can also be used as we describe.

Humans↗
PubMed1989

Fusimotor mechanisms determining the afferent output of muscle spindles.

There is both direct and indirect evidence that stretch activation occurs in the dynamic bag1 fibres of the mammalian muscle spindle and that it is responsible for maintaining the high sensitivity of primary sensory endings in stretches great enough to break the resting actomyosin bonds responsible for the short-range stiffness of muscle fibres. However the direct observations of dynamic bag1 fibre behaviour during stretching were made on damaged fibres and during very slow stretches. Preliminary results of experiments employing faster stretches of intact muscle spindles are reported here. An image processing system is being developed to automate and facilitate analysis of sarcomere movements during stretch, release and activation of intrafusal fibres. Unequivocal evidence confirming the development of stretch activation has not yet been found. Boyd (1986a) believed that static bag2 and chain fibres are controlled by separate populations of static gamma motoneurones, while accepting that there is some degree of common innervation. His evidence and the functional implications are discussed.

Animals↗
PubMed1987

Appropriate dental training.

Primary dental health care has emerged as an important concept, particularly in the poor countries of the world, where dentistry as currently practised has not proved capable of controlling oral disease. Training for primary dental health care provision must be shaped to meet the specific needs of countries and communities. It demands a reorientation of those objectives which are conventional in dental teaching and the development of new attitudes on the part of teachers. Training must aim at self-development in which the ability to achieve simple goals is to the fore. The formulation of plans, the activities which result from them and the evaluation of their effects must be central to the teaching philosophy. Training must aim to develop competency in individual workers. This can best be generated by the use of field exercises. Teachers must not just deliver packages of information but they should develop a climate favourable to self-learning and use resources in a manner which allow students to recognise their own growth and development. Appropriate methods for achieving these goals are reviewed.

Community Dentistry↗
PubMed1985

Interhospital variations in hospital pharmacy markups.

The relationship between pharmacy pricing policies and overall hospital objectives was analyzed for 64 South Carolina hospitals in 1980. Using published hospital data, a linear regression model was developed to test the relationship between a pricing variable (the charge-to-cost ratio for each pharmacy) and five independent variables: demand (defined as hospital occupancy rate), industry structure (defined as affiliation or nonaffiliation with a multihospital system), level of hospital use by Medicare and Medicaid patients (defined as the proportion of hospital admissions for which reimbursement was based on costs), the contribution of nonoperating revenue, or subsidization (defined as the proportion of hospital nonoperating revenue to total expenses), and the contribution of operating revenues of departments other than pharmacy (defined as the proportion of non-pharmacy charges to total charges). In these predominantly nonprofit hospitals, the mean (+/- standard deviation) pharmacy markup was 1.99 +/- 0.49, with considerable inter-hospital variation. The level of hospital use by Medicare and Medicaid patients had the greatest influence on variation in markup, indicating that hospitals were responding to cost-based payer reimbursement practices by raising charges in areas with a high cost base, such as pharmacy. Nonoperating revenue and operating revenue of departments other than pharmacy also were significantly related to the charge-to-cost ratio. The relationship between the charge-to-cost ratio and either occupancy rate or affiliation with a multihospital system was not significant. The hospitals studied set pharmacy revenues to contribute to overall target income, but pharmacy prices were not set to achieve maximum profits by responding to changes in demand.

Costs and Cost Analysis↗