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Biomedical subjects

J Sneddon

Publications and source records attributed to J Sneddon.

At least 19 recordsLinked to original sources
PubMed2004

A descriptive study of urban rabies during the civil war in Sierra Leone: 1995-2001.

A study was conducted to assess the effects of the breakdown in internal infrastructure on the incidence of canine-transmitted human rabies in urban areas of Sierra Leone during the course of the civil war between 1995 and 2001. Data from provincial hospitals in the Western Area and Southern Province indicated that there was a significant increase in the incidence of canine-transmitted urban human rabies chi2 = 39.63, p < 0.0001, particularly among children chi2 = 23.73, p < 0.0001, over the course of the war. In the Western Area in 2001, towards the end of the war, there was a significant increase in adult cases, which was reflected in the observed versus the expected chi2 ratio (70 versus 53). Interview-based questionnaire surveys in Freetown administered between 2001 and 2002 indicated that dogs were commonly kept for security reasons, and were largely unrestrained and unlicensed, regardless of the socioeconomic status of the owner. Virtually all dogs were unvaccinated and were mainly living in close proximity with humans. This study indicated that there is an urgent requirement for appropriate mass rabies vaccination campaigns for pet dogs and for campaigns to manipulate the urban habitat to control free-roaming and wandering but owned dog populations in Freetown and other urban areas in the provinces of Sierra Leone. Interview-based questionnaires administered in three districts of Freetown indicated a relatively high degree of uniformity in dog husbandry and veterinary care habits across a wide range of socioeconomic status categories in dog owners.

Adolescent↗
PubMed2001

Manganese species migration in soil at the Sabine National Wildlife Refuge, Louisiana.

A modified sequential extraction procedure was employed to speciate the chemical forms of Mn in sediment using flame atomic absorption spectrophotometry. Concentrations were determined in five different fractions for each sample (Mn in the exchangeable form, bound to carbonates, bound to Mn/Fe oxides, bound to organic matter and in the residual form). The determinations were made for sediments obtained from the Sabine National Wildlife Refuge while a marshland reclamation project was being conducted. Sediment samples were taken from Ship Channel dredge spoils (thought to be contaminated), an old reclamation site, a new reclamation site and a reference site. The results indicated that the Ship Channel sediments were not contaminated, but revealed an Mn "pumping" model, which proposes that additional Mn added to a similar site is concentrated near the surface soil layers by environmental conditions, which may be a cause of the observed slow recovery of vegetation at one of the more recently developed sites.

Conservation of Natural Resources↗
PubMed1997

Control of infection: a survey of general medical practices.

BACKGROUND: The aims of the study were (1) to assess current infection control practice within general medical practices and establish a base line; (2) to identify potential infection control problems; (3) to assess the need for local infection control guidelines or standards related to general medical practice; (4) to assess the need for educational provision. METHODS: A survey was carried out, using questionnaire and structured interviews, of all general practices (92) within a Health Board area with a patient population of 561,300. RESULTS: Forty two (46 per cent) practices participated, serving 67 per cent of the patient population. Only three (7 per cent) practices had written infection control policies and only six (14 per cent) provided training on the subject. Thirty (71 per cent) practices had autoclaves; however, performance monitoring was poor. The majority of high-risk instruments were adequately decontaminated; of the medium-risk instruments, the auriscope speculum was the item most frequently inadequately treated [36 practices (88 per cent)]. Deficiencies were identified in treatment of blood spillage, and protective clothing provision was variable. The majority, 40 (95 per cent) practices, had systems to deal with clinical waste; however, only two (5 per cent) reported use of BS7320 sharps containers on domiciliary visits. Despite the recognized dangers, 23 (55 per cent) practices resheathed needles and only six (14 per cent) had first aid guidance for needlestick injuries. Only eight (19 per cent) practices knew and recorded staff immunity to hepatitis B following vaccination. CONCLUSIONS: Some deficiencies in infection control practice were identified and the need for policy guidance and staff training was highlighted.

Family Practice↗
PubMed1995

Frameshift mutation in codon 176 of the p53 gene in rat esophageal epithelial cells transformed by benzo[a]pyrene dihydrodiol.

Mutations in the p53 tumor suppressor gene have been associated with exposure to environmental chemical carcinogens. Cultured rat esophageal epithelial cells were transformed in vitro by treatment with benzo[a]pyrene dihydrodiol (BP-DHD). A BP-DHD-transformed cell line and control cell lines were analyzed for mutations in the p53 gene and in the Ha-ras gene by single-strand conformation polymorphism analysis of polymerase chain reaction-amplified products and direct DNA sequencing. The deletion of one cytosine in codons 174-176 (TGCCCCCAC-->TGCCCCAC) of the p53 gene was found only in the BP-DHD-transformed cell line. The BP-DHD-transformed cells were highly invasive and tumorigenic when transplanted into syngeneic rats, whereas control lines either were nontumorigenic or formed epithelial cysts. BP-DHD-transformed cells and control lines were negative for mutations in the Ha-ras gene. Our results suggest that the tumorigenic potential of the BP-DHD-transformed cell line is associated with a frameshift mutation in codon 176 of the p53 gene but not with mutations in the Ha-ras gene. The G/C-rich codons 174-176 in the rat p53 gene may be specific targets for BP-DHD.

Animals↗
PubMed1994

Effect of subcutaneous nicotine injections of EEG alpha frequency in non-smokers: a placebo-controlled pilot study.

The effect of two subcutaneous injections of 0.6 mg nicotine, administered 40 min apart, was compared with placebo in four non-smoking subjects in a counter-balanced double-blind crossover design. The nicotine injections produced mean peak plasma nicotine concentrations of 5.3 ng/ml 10 min after the first injection and 8.5 ng/ml 10 min after the second injection. The nicotine injections produced an increase in mean dominant alpha frequency on the electroencephalogram (EEG) which was 2 Hz greater than the effect of placebo (P = 0.049) and also produced a heart-rate boost which was 8 beats per minute greater than that produced by placebo (P = 0.022). These effects on dominant alpha frequency and heart rate were most apparent in the 10 min following each nicotine injection. The increase in dominant alpha frequency found in non-smokers in this study was similar to that following nicotine inhalation in abstinent smokers in previous studies, and suggests that this is a primary effect of nicotine, rather than simply a reversal of withdrawal-induced EEG slowing.

Adult↗
PubMed1994

Decreased heart rate variability in survivors of sudden cardiac death not associated with coronary artery disease.

BACKGROUND: Although heart rate variability has already been studied in survivors of sudden cardiac death secondary to coronary artery disease, an assessment of heart rate variability in survivors of sudden cardiac death not associated with coronary artery disease has not been made. METHODS: 10 patients with aborted sudden cardiac death not associated with coronary artery disease (seven patients with primary ventricular fibrillation and three with unclassified mild cardiomyopathy) underwent two channel 24 hour Holter monitoring in a drug free state. All subjects were in sinus rhythm and had normal atrioventricular conduction and normal cardiac function. Spectral heart rate variability was analysed on a Holter analysis system and was expressed as total (0.01-1.00 Hz), low (0.04-0.15 Hz) and high (0.15-0.40 Hz) frequency components for each hour. Heart rate variability index was calculated for the 24 hour periods. 10 age and sex matched healthy subjects were taken as a control group. RESULTS: The spectral heart rate variability over 24 hours was significantly lower in survivors of sudden cardiac death than in controls (total 38(15) v 48(14) ms; low, 25(11) v 32(13) ms; and high, 13(8) v 18(8) ms; p < 0.05 for all comparisons). The differences in the ratio of low/high (2.19(0.76) v 1.98(0.50), p = 0.132), mean heart rate (77(12) v 69(12) beats/min, p = 0.070), and heart rate variability index (38(12) v 44(16), p = 0.287) over 24 hours between survivors of sudden cardiac death and controls did not reach significance. Comparisons of the hourly heart rate variability over the 24 hour period between the two groups showed that the differences in all components of heart rate variability, low/high ratio and mean heart rate were highly significant. Furthermore, there was no significant difference in the maximum hourly heart rate variability over the 24 hour period. The minimum hourly heart rate variability was, however, significantly lower in survivors of sudden cardiac death than in controls (total, 20(8) v 28(4) ms; low, 12(6) v 17(3) ms; high, 6(2) v 8(2) ms; p < 0.05 for all comparisons). CONCLUSIONS: These findings suggest that there is abnormal autonomic influence on the heart in patients without coronary artery disease at risk of sudden cardiac death. Hourly analysis of heart rate variability throughout the 24 hour period may provide additional information important in the identification of high risk patients.

Adolescent↗
PubMed1993

Influence of thrombolytic therapy on the evolution of baroreflex sensitivity after myocardial infarction.

Depressed baroreceptor sensitivity (BRS) has been associated with an increased risk of ventricular arrhythmias and sudden cardiac death after myocardial infarction, but the influence of thrombolytic therapy on BRS has not been examined. To determine the effect of thrombolytic therapy on the evolution of BRS after myocardial infarction, BRS was assessed at 6 days, 6 weeks, and 3 months in 76 patients, 53 (70%) of whom had received thrombolytic therapy. The mean age (57 vs 57 years), sites of infarction, and the proportion of patients taking beta-blockers (68% vs 52%) did not differ between patients who did and those who did not receive thrombolytic therapy. There was no difference in predischarge mean left ventricular ejection fractions (42% vs 46%) between the two groups of patients, but mean baseline BRS was 9.2 (0.8) msec/mm Hg in patients who were treated with thrombolysis and 5.9 (1.3) msec/mm Hg in those who were not (p = 0.03). At 6 weeks the corresponding values were 9.7 (1.1) and 11.1 (2.8) msec/mm Hg (p = 0.6) and at 3 months 9.1 (1.0) and 6.5 (1.1) msec/mm Hg (p = 0.07). At baseline 13% of patients who were treated with thrombolysis and 13% of those who were not had BRS < 3.0 msec/mm Hg, but at 3 months 9% of patients who were treated with thrombolytic agents compared with 17% of those who had BRS < 3.0 msec/mm Hg. In conclusion, early after myocardial infarction mean BRS was higher in patients treated with thrombolysis compared with nontreated patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1990

Measurement of activity of urea resistant neutrophil alkaline phosphatase as an antenatal screening test for Down's syndrome.

OBJECTIVE: To investigate the value of measuring maternal urea resistant neutrophil alkaline phosphatase activity as an antenatal screening test for Down's syndrome. DESIGN: Case-control study of blood samples collected at nine to 27 weeks of pregnancy. SETTING: Antenatal clinics in London and Oxford. PATIENTS: 72 Women whose fetuses had been diagnosed by amniocentesis or chorionic villus sampling as having Down's syndrome and 156 women whose fetuses did not have the syndrome. Only singleton pregnancies were studied. MAIN OUTCOME MEASURE: Activity of urea resistant neutrophil alkaline phosphatase measured cytochemically. RESULTS: The median enzyme activity in the index patients was 1.65 times the expected median for the controls at the same duration of pregnancy (p less than 0.0001; 95% confidence interval 1.56 to 1.74). A cut off value that identified the 5% of control patients with the highest activities yielded a rate of detection of Down's syndrome of 79% (95% confidence interval 70 to 89%). CONCLUSION: Activity of urea resistant neutrophil alkaline phosphatase is an effective maternal blood marker for Down's syndrome. Its use in antenatal screening could lead to a substantial improvement in the detection of this disorder. Before introducing the test into routine medical practice it will have to be automated so that it can be used on a large scale and is less subjective.

Adult↗
PubMed1990

Determination of subnanogram per cubic meter concentrations of metals in the air of a trace metal clean room by impaction graphite furnace atomic absorption and laser excited atomic fluorescence spectrometry.

Air, drawn by vacuum through a jet, was impacted against the inside surface of an atomic absorption graphite electrothermal atomizer (ETA). The amounts of the particles thus collected were determined at the ng m-3 level by graphite furnace atomic absorption or at the pg m-3 level by laser excited atomic fluorescence. The overall reproducibility of two sets of measurements, made 7 months apart, was 23%, with no significant difference between the two sets of data, based on Student's "t" test at the 95% confidence level. Short-term reproducibility varied from 13% to 34% depending upon the air concentration of the metal. The method shows promise for monitoring long-term effectiveness of the filtering systems in trace metal clean rooms. It was not possible to test for accuracy, due to the low concentrations involved, but accuracy was expected to be within a factor of 2 or 3 of the actual value, based on theoretical aspects of impaction.

Air↗
PubMed1987

Action of di- and tri-valent cations on calcium-activated K+-efflux in rat erythrocytes.

Isolated rat erythrocytes were labelled with [86Rb] as a tracer for intracellular K+. It was demonstrated that rat erythrocytes possess a Ca2+-mediated K+-efflux mechanism similar to that reported for human erythrocytes. This model was used to investigate the interactions of di- and tri-valent cations on potassium [86Rb] permeability in intact cells. Low concentrations of Ag2+ and Hg2+ haemolysed erythrocytes and Pb2+ produced a selective increase in [86Rb] efflux which became self-inhibitory at concentrations above 100 microM. The effects of Pb2+ were potentiated by A23187. Ni2+, Cu2+, Co2+, Zn2+, Fe2+, Mn2+, Y2+ and Ba2+ did not initiate [86Rb] efflux, even in the presence of 0.5 microM A23187 and at concentrations as high as 1 mM. All of these cations, except Ba2+, were potent inhibitors of [86Rb] efflux evoked by 50 microM Ca2+ + 0.5 microM A23187. The lanthanides Tb3+, Gd3+, Eu3+, Sm3+ and La3+ increased [86Rb] efflux at low concentrations in the presence of A23187, but were self inhibitory at higher concentrations. They also inhibited Ca2+-mediated [86Rb]-efflux. It is concluded that the effectiveness of a cation in activating [86Rb] efflux is, in part, related to its non-hydrated crystalline ionic radius, and that the site of activation may only accommodate ionic radii between 0.95 and 1.00 A.

Animals↗
PubMed1980

Myasthenia gravis: a study of social, medical, and emotional problems in 26 patients.

26 patients with proven myasthenia gravis were asked how they overcame the social, medical, and emotional problems of their illness, with special reference to weakness caused by emotional stress, especially anger. They knew that stress made them weak but they resented being told they were neurotic. A third of the patients had initially been given a psychiatric diagnosis because physical signs fluctuated so much that there were often no abnormalities on examination, especially in the morning. Many emphasised problems of communication caused by difficulties with speech and facial expression. Patients who sought treatment for other medical problems often knew more about their myasthenia, its treatment, and complications than the doctors and were resentful because the doctors did not believe them.

Adaptation, Psychological↗
PubMed1980

Myasthenia gravis--the difficult diagnosis.

Twenty-six patients with proven myasthenia gravis were interviewed to assess the length of time between onset of symptoms, presentation to the general practitioner and diagnosis. In one third the initial diagnosis was psychiatric and the average time between presentation and correct diagnosis was 2.8 years for men, 1.2 years for premenopausal women and three weeks for postmenopausal women. Diagnosis could have been made much earlier if doctors had been familiar with early symptoms in this relatively rare disease. Symptoms and signs fluctuated and were at times absent, especially in the mornings.

Adult↗