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Biomedical subjects

N John

Publications and source records attributed to N John.

9 recordsLinked to original sources
PubMed2005

Drowning of babies in bath seats: do they provide false reassurance?

AIMS: To investigate the problem of children drowning in bath seats by examining case reports, by looking at the epidemiology of bath drowning in children under two years of age and by reviewing the literature. METHODS: We describe two babies: one who drowned and one nearly drowned in the bath whilst in a bath seat. We examined the RoSPA/RLSS UK database of cases of children under two years drowning in the bath for the years 1989-2003. Cases are ascertained through a press cutting system. We conducted an all language literature search of original articles, references, textbooks and conference abstracts 1951-October 2004 in 11 standard databases. RESULTS: The two cases illustrate how parents can have a false sense of security with bath seats. We found six cases of babies under two years drowning in the UK associated with bath seats in the time period 1989-2003. They were all boys: five of the six were under one year of age. This compared with 47 children of similar age drowning in the bath not associated with a bath seat. The literature is sparse with only four papers since 1966. DISCUSSION: A baby drowning after being placed in a bath seats is a rare but definite cause of death. Bath seats appear to give a false sense of security (even if not encouraged by the manufacturers). It is unclear whether putting a baby in a bath seat represents an increased risk of drowning compared with a baby without a seat. Without knowing the numbers of mothers that use bath seats it is difficult to come to firm conclusions on the risks to babies. New research is needed to clarify this issue. Whether in a seat or not it is clear that the main risk to babies in the bath is being left unsupervised.

Drowning↗
PubMed2005

Current estimates of blindness in India.

BACKGROUND: Evidence based planning has been the hallmark of the blindness control programme in India. A nationwide survey was undertaken in 1999-2001 to document the magnitude and causes of blindness. METHODS: One district each in 15 populous states was covered. 25 clusters were randomly selected in each district and all individuals aged 50 years and above were enumerated. Presenting and best corrected vision was recorded using retroilluminated logMAR tumbling E charts and detailed eye examination was offered. RESULTS: The response rate was 89.3%. Presenting vision <6/60, in the better eye, was observed in 8.5% (95% CI: 8.1 to 8.9). Age, sex, residence, literacy, and working status were associated with blindness. The highest risk was among those aged 70+ and the illiterate. Cataract was responsible for 62.4% of bilateral blindness. Prevalence of cataract blindness was 5.3% (95% CI: 4.97 to 5.62). Reduction in blindness prevalence among people aged 50 years and above was observed compared to earlier studies. CONCLUSION: Blindness control efforts seem to have played a part in arresting the increasing prevalence of blindness in India and there is hope that the goals of the "Vision 2020--right to sight" initiative can be achieved if there is strong political will and prioritised action.

Age Distribution↗
PubMed1998

Growth factor protection against cytokine-induced apoptosis in neonatal rat islets of Langerhans: role of Fas.

Treatment of neonatal rat islets of Langerhans with combined cytokines (interleukin-1beta 10(-10) M, tumour necrosis factor-alpha 10(-10) M, interferon-gamma 5 U/ml) led to extensive cell death, which was potentiated by Fas activation with the anti-Fas cytolytic antibody JO2. Pre-treatment with insulin (25 ng/ml) or insulin-like growth factor-1 (10(-8)M) gave only partial protection against cell killing, but prevented the Fas-mediated component. In the absence of cytokine treatment, Fas-mediated killing was not observed.

Animals↗
PubMed1998

Effectiveness of fixed minidose warfarin in the prevention of thromboembolism and vascular death in nonrheumatic atrial fibrillation.

Adjusted-dose warfarin is effective for stroke prevention in patients with nonrheumatic atrial fibrillation (AF), but the risk of bleeding is high, especially among the elderly. Fixed minidose warfarin is effective in preventing venous thromboembolism with low risk of bleeding and no need for frequent clinical monitoring. Patients > 60 years with nonrheumatic AF were randomized in an open-labeled trial to receive fixed minidose warfarin (1.25 mg/day) or standard adjusted-dose warfarin (International Normalized Ratio [INR] between 2.0 and 3.0). Primary outcome events were ischemic stroke, peripheral or visceral embolism, cerebral or fatal bleeding, and vascular death. Secondary end points were major bleeding, myocardial infarction, and death. This study was discontinued before completion in light of publication of the Stroke Prevention in Atrial Fibrillation III trial, which indicated that low-intensity fixed-dose warfarin treatment (i.e., INR < 1.5) was insufficient for stroke prevention in high-risk patients with nonrheumatic AF. From a total of 1,209 considered patients, 303 were randomized to be studied (150 in the minidose group and 153 in the adjusted-dose group). Mean follow-up was 14.5 months. The rate of cumulative primary events was 11.1% (95% confidence intervals [CI] 4.0 to 18.2) in the fixed minidose group and 6.1% (95% CI 1.1 to 11.1) in the adjusted-dose group (p = 0.29). The rate of ischemic stroke was significantly higher in the minidose group (3.7% vs 0% per year, p = 0.025). Major bleedings were more frequent in standard treatment group (2.6% vs 1% per year, p = 0.19). Most thromboembolic complications occurred at INRs < 1.2, whereas the majority of hemorrhages occurred at INRs > 3.0. No significant difference in primary outcome events was observed in the abbreviated study. However, the significantly increased occurrence of ischemic stroke in the fixed minidose warfarin group suggests that this regimen does not protect patients with nonrheumatic AF.

Aged↗
PubMed1997

Insulin-like growth factor I reverses interleukin-1beta inhibition of insulin secretion, induction of nitric oxide synthase and cytokine-mediated apoptosis in rat islets of Langerhans.

We have previously observed that treatment of rat islets of Langerhans with interleukin-1beta for 12 h results in nitric oxide-dependent inhibition of insulin secretion, while 48 h treatment increased rates of islet cell death by apoptosis. Here, we demonstrate that interleukin-1beta-mediated nitric oxide formation and inhibition of insulin secretion are significantly reduced by 24 h pretreatment of rat islets of Langerhans with insulin-like growth factor I (IGF-I). IGF-I decreased cytokine induction of nitric oxide synthase in islets. Use of an arginine analogue in culture or IGF-I pretreatment of islets were also effective in protecting islets against cytokine-mediated apoptotic cell death. We conclude that IGF-I antagonises inhibitory and cytotoxic effects of cytokines in rat islets.

Animals↗
PubMed1997

Transforming growth factor beta 1 prevents cytokine-mediated inhibitory effects and induction of nitric oxide synthase in the RINm5F insulin-containing beta-cell line.

The aim of this study was to examine if the growth factor, transforming growth factor beta 1 (TGF beta 1), could prevent induction of nitric oxide synthase and cytokine-mediated inhibitory effects in the insulin-containing, clonal beta cell line RINm5F. Treatment of RINm5F cells for 24 h with interleukin-1 beta (IL-1 beta) (100 pM) induced expression of nitric oxide synthase and inhibited glyceraldehyde-stimulated insulin secretion. Combinations of IL-1 beta (100 pM), tumour necrosis factor-alpha (100 pM) and interferon-gamma (100 pM) reduced RINm5F cell viability (determined by the 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium (MTT) reduction assay) and de novo protein synthesis, as measured by incorporation of radiolabelled amino acids into perchloric acid-precipitable protein. Pretreatment of RINm5F cells with TGF beta 1 (10 pM) for 18 or 24 h, prior to the addition of either IL-1 beta or combined cytokines, prevented cytokine-induced inhibition of insulin secretion, protein synthesis and the loss of cell viability. TGF beta 1 pretreatment inhibited cytokine-induced expression and activity of nitric oxide synthase in RINm5F cells as determined by Western blotting and by cytosolic conversion of radiolabelled arginine into labelled citrulline and nitric oxide. Chemically generated superoxide also induced expression of nitric oxide synthase possibly due to direct activation of the nuclear transcription factor NF kappa B, an effect prevented by both an antioxidant and TGF beta 1 pretreatment. In conclusion, the mechanism of action of TGF beta 1 in blocking cytokine inhibitory effects was by preventing induction of nitric oxide synthase.

Animals↗
PubMed1986

Rhythm and conduction disturbances in isolated, congenitally corrected transposition of the great arteries.

The incidence and types of rhythm and conduction disturbances in 11 male and 6 female patients with congenitally corrected transposition of the great arteries and no other intrinsic complicating anomalies were studied. Patient age ranged from 5 to 54 years; follow-up ranged from 5 to 37 years. Surface electrocardiograms were recorded in each patient; 15 also underwent 24-hour Holter monitoring and 10 underwent electrophysiologic study. The conduction system of a 54-year-old woman who died suddenly, with complete atrioventricular (AV) block since age 30 years, was studied by serial histologic sections. Fifteen patients were asymptomatic and 2 reported repeated episodes of palpitation since childhood. Ten patients presented with a normal PR interval and 2 with first-degree AV block (12%). Five patients had complete AV block (29%), but none had had it at birth; first- and second-degree AV block preceded complete AV block in 2 patients. The morphologic pattern and duration of QRS suggested a junctional rhythm in 4 patients and an idioventricular pacemaker in 1 patient. Electrophysiologic studies confirmed that the complete AV block site was supra-Hisian in 2 patients and proximal to the His bundle bifurcation in 1 patient. However, histologic investigation disclosed fibrosis and disruption of the proximal nonbifurcating His bundle in the patient who died suddenly. In 2 patients with recurrent supraventricular tachycardia, electrophysiologic studies suggested reentry through James fibers (or dual AV nodal pathway) in 1 and the presence of a left lateral accessory AV pathway in the other. Holter monitoring showed a high incidence of ventricular arrhythmias.

Adolescent↗
PubMed1986

Ventricular development and function in complete transposition: angiocardiographic evaluation.

We studied 50 left ventricular cineangiograms and 41 right ventricular cineangiograms of 40 patients with usual atrial arrangement (situs solitus) together with concordant atrioventricular and discordant ventriculo-arterial connexions (complete transposition), catheterized between 1 day and 12 months of age. Our purpose was to evaluate ventricular development and function. The patients were subdivided on the basis of associated lesions into groups with intact ventricular septum; with ventricular septal defect; with ventricular septal defect together with pulmonary stenosis and with pulmonary stenosis in isolation. Each group was further separated according to age into those patients below and above 60 days. Ventricular volumes, ejection fraction and the ratio between systolic pressure and end-systolic volume were evaluated for both ventricles. The left ventricular mass, stress, and the ratio of stress to end-systolic volume were also calculated. A volume overload leads to increased left ventricular volume even at birth. With an intact ventricular septum, the left ventricle in patients with complete transposition is normal at birth and also during the first weeks of life. Myocardial mass, however, does not increase proportionately with increase in volume as the patient grows and it remains inadequate by the age of one year. The left ventricular mass is also inadequate in patients with associated anomalies when the left ventricular pressure is less than 60 mm Hg. Moreover, the left ventricle in presence of an intact ventricular septum presents a decrease in contractility during the first year of life despite the finding of a satisfactory arterial oxygen saturation. The right ventricle has a normal volume at birth which increases during the first year due to a greater diastolic filling following atrial septostomy. We noted a progressive decrease in ejection fraction, however, which is related to various factors including a reduction in contractility.

Angiocardiography↗