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Biomedical subjects

A Marsden

Publications and source records attributed to A Marsden.

At least 19 recordsLinked to original sources
PubMed2002

Flexible tubular replicas of abdominal aortic aneurysms.

The aim of this study was to manufacture life-size, flexible, tubular replicas of human abdominal aortic aneurysms and the associated vasculature, suitable for use in a training simulator for endovascular procedures. Selective laser sintering was used to create a geometrically correct master model for each of ten anatomical variations. The masters were used to generate flexible latex replicas. The use of the replicas in the training simulator was demonstrated. In total ten silicone rubber models were produced. When connected into the training simulator and perfused at arterial pressure it was possible to deploy an endovascular stent under fluoroscopic control and to perform angiography. The study has shown that conventional rapid prototyping technology can be used to manufacture flexible, radiolucent replicas which provide a realistic training environment for endovascular procedures.

Angiography, Digital Subtraction↗
PubMed1995

Problems with registration of cutaneous malignant melanoma in England.

The aim of the study was to assess the completeness and accuracy of cancer registration for cutaneous malignant melanoma. The study was conducted in seven health districts in England and one health board in Scotland from 1987 to 1989 with a total resident population of 3.6 million. Records from pigmented lesion clinics and pathology laboratories collected during the Cancer Research Campaign's health education programme to promote the early detection of melanoma were matched with cancer registrations from a total of five regional cancer registries. In England 74% out of a total of 642 cases of invasive malignant melanomas (ICD 172) and 44% out of a total of 155 in situ melanomas (ICD 232) had been registered compared with 96% and 100% respectively in Scotland. A significantly higher proportion of late-stage cases was found among registered than among non-registered cases in England (P < 0.001). In all registries the majority of superficial spreading in situ melanomas were miscoded as invasive cases. The annual incidence of invasive malignant melanoma in the English study areas was found to be seven per 100,000 in men and 11 per 100,000 in women, similar to that reported in Scotland. The registries are best at recording thick or late-stage melanomas. As the skin cancer target for Health of the Nation depends on monitoring trends in the incidence of malignant melanoma, future improved ascertainment of cases and changes in the type of cases being registered must be taken into account.

England↗
PubMed1995

Cancer Research Campaign health education programme to promote the early detection of cutaneous malignant melanoma. I. Work-load and referral patterns.

From 1987 to 1989 a campaign to promote the early detection of cutaneous malignant melanoma was conducted in the areas of seven health authorities in England and Scotland (total population 3.6 million). Data were collected on 17,155 patients attending pigmented lesion clinics (PLCs) in each study area during the campaign. After a dramatic rise in PLC referral rates in the first month of the campaign the average monthly referral rate among the target population in the study period settled to an average of 13 per 10(5), a twofold increase compared with the pre-campaign period. Over 85% of patients at all PLCs were seen within 4 weeks of referral from their general practitioners. The melanoma to non-melanoma detection ratio was (1:33). The organization of future early detection initiatives needs careful review and planning, in order to improve their effectiveness in all sections of the population, and to enable health services to cope with the increased work-load.

Adult↗
PubMed1995

Cancer Research Campaign health education programme to promote the early detection of cutaneous malignant melanoma. II. Characteristics and incidence of melanoma.

The effect on the detection and characteristics of melanoma, resulting from the Cancer Research Campaign's health education programme to promote the early detection of melanoma in the general population, was studied from 1987 to 1989. The seven study areas in England and Scotland yield a target population of 3.6 million. Data were collected from local clinic-based registers, pathology laboratories, and the cancer registries. The average annual incidence rates of melanoma were seven and 12 per 10(5) in males and females, respectively, age-standardized to England and Wales, 1988. These rates are similar to the national figures for Scotland, where there is a national melanoma register, but higher than those reported by the English and Welsh cancer registries. The incidence was significantly higher in females than males (P < 0.001), and increased with age. Fifty-three per cent and 65% of cases in males and females, respectively, were thin (Breslow thickness < or = 1.5 mm), similar to the national figures from Scotland. No significant decrease in the incidence of late-stage tumours was found in either sex as a result of the campaign. Because of difficulties with ascertainment of cases in England, the main evaluation will focus on future trends in mortality rates for melanoma.

Adult↗
PubMed1994

Cutaneous manifestations of long-term hydroxyurea therapy.

Skin changes associated with long term hydroxyurea therapy have only rarely been reported and are not widely known. This report concerns a patient in whom extensive and debilitating skin changes developed secondary to hydroxyurea therapy. In addition to previously reported manifestations such as ichthyosis, a dermatomyositis-like eruption on the dorsal hands, facial erythema and accelerated development of premalignant and malignant skin lesions, the patient developed an erosive eruption on the glans penis. He also developed a rapidly enlarging viral wart which clinically resembled a squamous cell carcinoma and histologically showed marked cytological atypia. It is possible that hydroxyurea caused accelerated photoageing and also contributed to the rapid growth of the viral wart and the atypical histological features. The time course of the clinical changes suggests that they result from direct toxicity of hydroxyurea on the basal layer of the epidermis and mucosal surfaces.

Drug Eruptions↗
PubMed1993

The effect of using different reference dates for control exposure measurement on relative risk estimates in a case-control study.

In case-control studies in which case and control enrollment periods are not identical, exposure status for time-dependent variables is often measured relative to a reference date. Using data from a case-control study of the relation between cervical cancer and oral contraceptive (OC) use in which control enrollment began 6 months after the end of case enrollment, we evaluated the effect on odds ratios from using five different reference dates to determine the controls' exposure status. The choice of reference date had little effect on the odds ratios in this study. Reference dates for time-dependent exposure variables should be considered carefully in studies when case and control enrollment periods are not identical.

Carcinoma in Situ↗
PubMed1993

Cell proliferation in the liver and thyroid of C57Bl/10J mice after dietary administration of chlordane.

Chlordane is a polychlorinated hydrocarbon that causes liver enlargement and induces mixed-function oxidases similar to those induced by phenobarbitone in the mouse. We have assessed the hepatocarcinogenicity (after 2 years) and the time course (over 6 months) of liver and thyroid cell proliferation in C57Bl/10J mice exposed to chlordane at 50 ppm in the diet, using the same batch of food for both carcinogenicity and cell proliferation studies. In the bioassay, 15/39 survivors had hepatocellular adenomas and a further 5/59 had carcinomas, compared with less than 5% incidence of primary hepatic tumors in concurrent controls. Among unscheduled deaths, 1/40 adenomas and 2/40 carcinomas were recorded. There were no macroscopically observed thyroid lesions. In the proliferation study, mice were killed on days 4, 5, 8, 15, 29, 99, and 190 after the start of dosing. Withdrawal groups were included from days 29 to 99 and from days 190 to 247. Replicating cells were labeled via bromodeoxyuridine delivered by osmotic minipump for 3 days before necropsy. In the thyroid, the peak labeling index (LI) was seen on day 5 (LI = 5.99 +/- 2.90% versus 1.00 +/- 20% in controls), while in the liver the peak was on day 8 (9.0 +/- 1.6% versus 0.5 +/- 0.4% in controls). Both organs had an elevated LI for the first month of dosing, but while the thyroid follicular LI was similar to control at 99 and 190 days, the liver LI was significantly elevated at all time points except in the withdrawal groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenoma, Liver Cell↗
PubMed1992

Netilmycin and vancomycin in the treatment of peritonitis in CAPD patients.

This study was undertaken to evaluate: 1. The efficacy of netilmycin and vancomycin as combined first line antimicrobial regime, compared to cefuroxime, in the treatment of peritonitis. 2. To measure the levels of netilmycin and vancomycin in the serum and dialysate. 3. To report on the use of this combination over a one year period and compare it with that of cefuroxime used during the previous one year.

Adult↗
PubMed1990

The expert system approach to predicting protein structure.

Prediction of protein structure is an open-ended problem. Since an approach from first principles cannot be taken in reasonable computer time, short-cuts using further data are necessary. Such data include information about the specific protein in question, and information in databases which are about proteins in general. Is it possible to write a general, flexible 'superalgorithm' which would suit most circumstances? If so, it would seem likely to overcome one of the most understated but nonetheless greatest difficulties associated with molecular modelling and computer-aided drug design--reproducibility. To this end, a 'polymorphic programming environment' has been developed which represents both an expert system and a high-level language for theoretical chemists and molecular biologists. This language is GLOBAL (Ball et al., 1990). In a series of earlier studies, and more recently by means of GLOBAL itself, the nature of reproducibility and its rather surprising limits have been explored, and in general the current status and future potential of protein modelling have been examined.

Expert Systems↗
PubMed1988

Chronic bullous dermatosis of childhood persisting into adulthood.

Chronic bullous dermatosis of childhood (CBDC) is an autoimmune, subepidermal bullous disease that, in the majority of patients, remits before the onset of puberty. The disease does not always pursue a benign course, however. We cared for a patient in whom the condition persisted well beyond puberty without clinical or immunologic remission.

Child, Preschool↗
PubMed1987

Effects of constant environmental temperatures on the performance of laying pullets.

1. Two experiments are described in which laying pullets maintained at constant temperatures were fed a range of diets with a view to defining optimum combinations of temperature and nutrient intake. 2. In the first experiment, all combinations of 6 temperatures (15 degrees, 18 degrees, 21 degrees, 24 degrees, 27 degrees and 30 degrees C) 9 diets (three protein concentrations and three energy contents) and two stocks were tested for 34 weeks using 4320 pullets. In experiment 2, all combinations of three rearing temperatures, three laying temperatures (18 degrees, 22.5 degrees and 27 degrees C) three diets (protein concentration) and two stocks were tested for 61 weeks using 2160 pullets. 3. As anticipated, higher dietary protein concentrations were needed to maintain egg output at higher temperatures. If diets suplying adequate amino acid intakes were provided, egg output was unaffected by temperatures in the range 15 degrees to 27 degrees C although, at the highest temperature, egg weight was slightly reduced and rate of lay (particularly in the later part of the laying year) was increased. At 30 degrees C, egg output was depressed whichever diet was fed. 4. Dietary energy content had small but significant effects on egg weight and egg output but did not interact with temperature. It was not possible to maintain egg weight or egg output at 30 degrees C by feeding a high energy, high protein diet. 5. Estimated heat output of the birds increased during the course of the experiment at the lower temperatures but decreased with time at 30 degrees C. Feather loss occurred earlier at the lower temperatures and this is interpreted as an effect of temperature on the timing of the annual moult, which also accounts for the better persistency of lay observed at 27 degrees C.

Animals↗
PubMed1987

Quantitative review of the effects of environmental temperature on food intake, egg output and energy balance in laying pullets.

1. Data from 30 published experiments have been analysed to examine the relationships between environmental temperature and the long-term, adapted responses of laying pullets, measured as metabolisable energy intake, egg output and body weight change. Heat production was also estimated indirectly from the other three variables. 2. The majority of experiments employed White Leghorns, but there were 8 large trials in which brown crossbred pullets had been compared directly with White Leghorns. These trials were used to estimate differences in energy intake and heat output between brown and white birds. 3. A total of over 26,000 birds was involved in the analysis. Individual trials varied in scale from 9 birds to 2,280 birds per treatment and in duration from 8 to 61 weeks. The constant temperatures investigated ranged from 10 degrees C to 34 degrees C, but there were no data for brown pullets beyond 30 degrees C. 4. The relationship between temperature and metabolisable energy intake is curvilinear, with food intake declining more steeply as ambient temperature approaches body temperature. Adapted heat production per bird is also a curvilinear function of temperature, tending towards a value of zero when extrapolated to the point at which ambient temperature equals normal body temperature. However no satisfactory data are available for fully adapted responses in the range 34 to 42 degrees C because egg production declines continuously when these temperatures are maintained for long periods. 5. When energy intake and heat output are expressed as functions of metabolic body size (kg 0.75) they can be represented as linear functions of temperature within the range 15 to 30 degrees C, but the slope must change outside this range. 6. It is calculated that the energy available for production is at a maximum at 23 degrees C for brown birds and at 24 degrees C for White Leghorns. Gross energetic efficiency is at a maximum at 30 degrees C, but egg output is reduced at this temperature. The optimum operating temperature for laying houses will depend upon the local cost of modifying ambient temperature and on the cost of supplying diets of appropriate protein content.

Animals↗
PubMed1986

Calculation of the conformation of glycosphingolipids. 1. Beta-D-glucosyl-N-(2-D-hydroxyoctadecanoyl)-D-dihydrosphingosine (glucosyl-ceramide) and alpha-D-N-acetylneuraminyl-(2----3)-beta-D-galactose.

The conformation of a glucosyl-ceramide, beta-D-galactosyl-N-(2-D-hydroxyoctadecanoyl)-D-dihydrosphingos in e, and of the disaccharide, N-acetylneuraminyl-galactose have been predicted by energy minimization techniques including an orbital force field approach. The predictions have been shown to be in excellent agreement with the results of X-ray single crystal analysis and structures postulated from nuclear magnetic resonance methods and have confirmed the utility of the computational approach to the study of glycosphingolipids.

Carbohydrate Conformation↗