Search PubMed⌕ Search

Biomedical subjects

N Evans

Publications and source records attributed to N Evans.

At least 91 records · Page 5Linked to original sources
PubMed1996

Early ductal shunting and intraventricular haemorrhage in ventilated preterm infants.

AIM: To establish if there is an association between early cardiovascular adaptation and intraventricular haemorrhage (IVH). METHODS: One hundred and seventeen ventilated preterm infants (mean gestational age 27 weeks, mean birthweight 993 g) were studied echocardiographically within the first 36 hours. Measurements included right (RVO) and left ventricular outputs (LVO), ductus arteriosus (PDA) and atrial shunt diameter using colour Doppler and pulsed Doppler direction and velocity of both shunts. Clinical variables collected over the first 24 hours included use of antenatal steroids, respiratory severity, and mean blood pressure. Cerebral ultrasound scans were reported by a radiologist blinded to clinical and echocardiographic data. RESULTS: Antenatal steroids (two doses) had been given to 73% of the 86 infants with no IVH compared with 48% of the 21 infants with grades 1 and 2 IVH, and just 10% of 10 babies with grades 3 and 4 (P < 0.05). Both groups with IVH had significantly larger PDA diameters than the group with no IVH. Infants with grades 3 and 4 IVH had significantly lower RVO than the other infants. These differences were more pronounced when only infants with definite late IVH were analysed. Logistic regression analysis showed lack of antenatal steroids and larger PDA diameters were significantly associated with any grade of IVH and lack of antenatal steroids; lower RVO was significantly associated with grades 3 and 4 IVH. CONCLUSIONS: Larger early PDA shunts, lower RVO, and lack of antenatal steroids were significantly associated with IVH.

Adrenal Cortex Hormones↗
PubMed1996

Incidence of hibernating myocardium after acute myocardial infarction treated with thrombolysis.

OBJECTIVE: To establish the incidence of hibernating myocardium after myocardial infarction treated with thrombolysis and to observe differences in the clinical outcome between patients with and without hibernating tissue. METHODS: 41 patients underwent gated positron emission tomography with 18-fluorodeoxyglucose and 13N-ammonia at a median of eight days after first myocardial infarction. RESULTS: All 41 subjects had a matched perfusion-metabolism deficit in the region of myocardium indicated as the site of infarction by an electrocardiograph; 32 patients (78%) had scans which also showed at least one area of reduced blood flow and contraction with a concomitant increase in glucose uptake, representing hibernating myocardium. Patients were followed up at a median of six months: all 41 were alive and none had sustained a further infarct or cardiac arrhythmia; 17 subjects with hibernating tissue (53.1%) and two without (25%) reported chest pain after myocardial infarction. CONCLUSIONS: Hibernating myocardium is relatively common shortly after myocardial infarction treated with thrombolysis. It does not influence mortality or the incidence of postinfarction chest pain.

Aged↗
PubMed1996

Limbic dysfunction in schizophrenia and mania. A study using 18F-labelled fluorodeoxyglucose and positron emission tomography.

BACKGROUND: Diagnostic classes (derived from CATEGO) can be correlated with regional brain metabolism in patients with major psychiatric disorders. METHOD: Seventeen patients with schizophrenia, 15 with mania, 10 with depression and 10 healthy Volunteers were examined with positron emission tomography (PET) and 18F-labelled fluorodeoxyglucose, as a marker for glucose metabolism. The number of possible comparisons of regions of interest was reduced by principal-components analysis, and differences in factor scores were determined between diagnostic groups. RESULTS: Four independent factors, representing distributed brain systems, emerged: an anterior-posterior (1), a left-right temporal (2), a temporofrontal (3), and a mediofrontal (4) system, of which (1), (2) and (3) were abnormal in schizophrenia, (1) and (2) in mania, and (1) in depression. CONCLUSIONS: Abnormal patterns of metabolism could be detected, in decreasing order, in schizophrenia, mania and depression. Some of these abnormalities are likely to be due to medication, but others will be associated with structural or functional abnormalities of the frontolimbic system in the diagnostic groups.

Adult↗
PubMed1995

Influence of tobacco marketing and exposure to smokers on adolescent susceptibility to smoking.

BACKGROUND: Today the uptake of smoking is primarily an adolescent pursuit. Awareness of tobacco advertising and promotion is high, and evidence suggests that it plays a role in adolescent smoking uptake. PURPOSE: We evaluated the influence of tobacco advertising and promotion and exposure to smokers on never-smoking adolescents' susceptibility to smoking. METHODS: We used data on 3536 adolescent never smokers (those who had never even puffed on a cigarette) from the 1993 California Tobacco Survey. That survey questioned adolescents about smoking history and inclinations. For this analysis, we defined as susceptible to smoking those never smokers who said on the survey that they could not rule out independently deciding to try a cigarette soon or smoking one offered by a friend. Also for this analysis, we devised two indices: 1) a 5-point index of an individual's receptivity to tobacco advertising as determined by the number of positive responses to five survey items (recognition of advertising messages, having a favorite advertisement, naming a brand he/she might buy, owning a tobacco-related promotional item, and willingness to use a tobacco-related promotional item) and 2) an index classifying an individual's reported exposure to family and peer smoking into one of four levels. Using logistic regression, we assessed the independent importance of our indices in predicting susceptibility to smoking after adjustment for sociodemographic variables, including age, sex, and race/ethnicity, and for perceived school performance. Tests of statistical significance were two-sided. RESULTS: Receptivity to tobacco advertising and exposure to smokers were independently associated with susceptibility to smoking, but the relationship appeared stronger for receptivity to advertising. Adolescents exposed to family members and peers (n = 489) who smoked were 1.89 (95% confidence interval [CI] = 1.30-2.74) times as likely to be susceptible, whereas adolescents who scored 4 or more on the Index of Receptivity to Tobacco Marketing (n = 361) were 3.91 (95% CI = 2.38-6.42) times as likely to be susceptible as those who scored 0. Even adolescents who scored 2 (n = 1090) were 2.03 (95% CI = 1.31-3.15) times as likely to be susceptible. There was no interaction effect between score on the Index of Receptivity to Tobacco Marketing and exposure to smokers. CONCLUSION: Our results support the hypothesis that tobacco marketing may be a stronger current influence in encouraging adolescents to initiate the smoking uptake process than exposure to peer or family smokers or sociodemographic variables including perceived school performance.

Adolescent↗
PubMed1995

Distal gangrene in a polycythemic recipient fetus in twin-twin transfusion.

BACKGROUND: Gangrene of an extremity in a twin pregnancy has been attributed to the release of thromboplastin from a dead fetus or to a combination of polycythemia and anomalous vasculature. It has not been described in a situation where both twins survived. CASE: In a pregnancy complicated by twin-twin transfusion syndrome and managed with repeated amniocenteses, both twins survived. The recipient twin had necrosis of the left lower leg, which had appeared in the antenatal period and was associated with polycythemia, but not anomalous vasculature. CONCLUSION: Antenatally, polycythemia alone may cause necrosis of an extremity. Necrosis could be detected with ultrasound examination and may be an additional argument for laser photocoagulation of the chorioangiopagus.

Adult↗
PubMed1995

Signal changes in the intervertebral discs on MRI of the thoracolumbar spine in ankylosing spondylitis.

Contrary to standard teaching in magnetic resonance imaging (MRI), recent reports have documented calcification appearing as areas of increased signal intensity (SI) on T1-weighted images. Intervertebral disc calcification is a frequent finding on radiographs in chronic ankylosing spondylitis (AS). This study was performed to investigate the appearance of variable degrees of disc calcification in MRI. Thirty-six patients with AS of variable duration underwent an MRI scan of the thoraco-lumbar spine and the MR appearances, particularly of the discs, were compared with plain radiographs. Increased SI of the discs on T1-weighted images were found in 17 of 36 patients, occurring over a range of disc levels, and correlating with disc calcification on the radiographs in 78% of cases. This group tended to be older and have a longer duration of disease than those with normal appearing discs. Four different patterns of increased signal within the discs termed Type A (marginal), Type B (annular), Type C (central) and Type D (solid) were identified. In those with less than six discs involved Type A was the most common pattern. In those with more than six discs involved Type D was the most common pattern, suggesting a progression of disc involvement with more advanced disease. Although these findings will not affect the management of the disease, they do highlight the recently described phenomenon of calcification appearing as increased SI on T1-weighted images, likely to be related to the surface area of the calcium crystal. This should lead to the consideration of calcium in the differential diagnosis of increased SI on T1-weighted images. End-plate marrow changes were a relatively frequent finding in this study but did not correlate with the signal changes seen within the discs; in a number of cases they related to variable degrees of bony bridging.

Adult↗
PubMed1995

Early echocardiographic prediction of symptomatic patent ductus arteriosus in preterm infants undergoing mechanical ventilation.

OBJECTIVE: To identify early echocardiographic markers allowing prediction of subsequent symptomatic patent ductus arteriosus (PDA). METHODS: One hundred sixteen preterm infants ( < 1500 gm) requiring mechanical ventilation underwent echocardiography at a mean postnatal age of 19 hours (range, 7 to 31 hours). Four potential markers were studied: the left atrial to aortic root ratio, pulsed Doppler signal within the course of the duct (ductal diameter), and the direction of postductal aortic diastolic flow. Subsequent ductal closure or significant patency (if suspected clinically) was confirmed echocardiographically. RESULTS: A significant PDA developed in 42 infants (36%). Ductal diameter was the most accurate echocardiographic marker in predicting subsequent significant most accurate echocardiographic marker in predicting subsequent significant PDA. With a ductal diameter of 1.5 mm or greater there were 34 true-positive, 11 false-positive, 63 true-negative, and 8 false-negative results, giving a positive likelihood ratio of 5.5 and a negative likelihood ratio of 0.22 for prediction of development of a PDA requiring treatment. The sensitivity was 81% and the specificity was 85%. Only one infant older than 28 weeks of gestational age had a significant PDA, and limiting the analysis to infants younger than 29 weeks of gestation further improved the predictive accuracy of ductal diameter. The positive likelihood ratio was 8.1 and the negative likelihood ratio was 0.19, with a sensitivity of 83% and a specificity of 90%. CONCLUSION: Color Doppler measurement of the internal ductal diameter allows early prediction of significant PDA in preterm infants.

Ductus Arteriosus↗
PubMed1995

Characterisation of the binding of [3H]WAY-100635, a novel 5-hydroxytryptamine1A receptor antagonist, to rat brain.

The specific binding of [3H]WAY-100635 (N-[2-[4-(2-[O-methyl-3H]methoxyphenyl)-1-piperazinyl]ethyl]-N- 2-pyridinyl) cyclohexane carboxamide trihydrochloride) to rat hippocampal membrane preparations was time, temperature, and tissue concentration dependent. The rates of [3H]WAY-100635 association (k+1 = 0.069 +/- 0.015 nM-1 min-1) and dissociation (k-1 = 0.023 +/- 0.001 min-1) followed monoexponential kinetics. Saturation binding isotherms of [3H]WAY-100635 exhibited a single class of recognition site with an affinity of 0.37 +/- 0.051 nM and a maximal binding capacity (Bmax) of 312 +/- 12 fmol/mg of protein. The maximal number of binding sites labelled by [3H]WAY-100635 was approximately 36% higher compared with that of 8-hydroxy-2-(di-n-[3H]-propylamino) tetralin ([3H]8-OH-DPAT). The binding affinity of [3H]WAY-100635 was significantly lowered by the divalent cations CaCl2 (2.5-fold; p < 0.02) and MnCl2 (3.6-fold; p < 0.05), with no effect on Bmax. Guanyl nucleotides failed to influence the KD and Bmax parameters of [3H]WAY-100635 binding to 5-HT1A receptors. The pharmacological binding profile of [3H]WAY-100635 was closely correlated with that of [3H]8-OH-DPAT, which is consistent with the labelling of 5-hydroxytryptamine1A (5-HT1A) sites in rat hippocampus. [3H]WAY-100635 competition curves with 5-HT1A agonists and partial agonists were best resolved into high- and low-affinity binding components, whereas antagonists were best described by a one-site binding model. In the presence of 50 microM guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S), competition curves for the antagonists remained unaltered, whereas the agonist and partial agonist curves were shifted to the right, reflecting an influence of G protein coupling on agonist versus antagonist binding to the 5-HT1A receptor. However, a residual (16 +/- 2%) high-affinity agonist binding component was still apparent in the presence of GTP gamma S, indicating the existence of GTP-insensitive sites.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1995

Upper and lower gastrointestinal complications with dexamethasone despite H2 antagonists.

OBJECTIVE: To describe three preterm babies who developed gastrointestinal complications during treatment with dexamethasone for chronic lung disease, during a 10 month period. METHODOLOGY: Case reports in a tertiary neonatal intensive care unit. RESULTS: All three babies had received intravenous cimetidine since the commencement of steroid therapy, and developed gastrointestinal complications. There was no evidence of necrotizing enterocolitis in either of the two babies with gastrointestinal perforation. This is the first report of lower gastrointestinal complications associated with dexamethasone therapy. CONCLUSION: Recommendation of concomitant use of H2 antagonists with steroid therapy may be premature, and requires testing with a randomized controlled trial.

Cimetidine↗
PubMed1995

Sciatica in degenerative spondylolisthesis of the lumbar spine.

Intraspinal synovial cysts are an uncommon but well recognised cause of backache and sciatica, and should be considered in patients, in particular with degenerative spondylolisthesis, who are symptomatic. MRI is the initial investigation of choice. If there is any doubt as to the diagnosis, CT with or without facet joint arthrography is helpful.

Female↗
PubMed1995

Longitudinal changes in the diameter of the ductus arteriosus in ventilated preterm infants: correlation with respiratory outcomes.

This study aimed to examine the early natural history of ductal shunting in ventilated preterm infants (< 1500 g) and to document the association between this shunting and respiratory outcomes. The size of the ductal shunt was assessed in 48 infants using serial echocardiographic measurement of colour Doppler internal ductal diameter and pulsed Doppler postductal aortic diastolic flow (PADF). At all postnatal ages, normal antegrade PADF was invariably seen when the ductal diameter was 1.5 mm or less, and was usually abnormal (absent or retrograde) when more than 1.5 mm. Longitudinal progress of ductal diameter fell into three groups: (i) asymptomatic spontaneous closure (n = 31)--in 20 of these infants closure occurred within 48 hours; (ii) symptomatic PDA which enlarged after a postnatal constriction (n = 9); and (iii) symptomatic PDA that showed minimal postnatal constriction (n = 8). Infants in group 2 were significantly less mature and had PDAs which became symptomatic significantly later than those in group 3. Logistic regression showed that ductal shunting had a significant correlation with mean oxygenation index over the first five days but not with ventilator or oxygen days. Gestation had the most significant association with the latter two variables, with atrial shunting also being related to days in oxygen. The preterm duct displays a wide spectrum of postnatal constrictive activity. Symptomatic PDAs usually showed slower early postnatal constriction. Ductal shunting independently related to short term but not long term respiratory outcomes.

Diastole↗
PubMed1995

Adolescents' perceptions of their peers' health norms.

OBJECTIVES: The purpose of this study was to determine the relative importance adolescents place on preventive health behaviors. METHODS: Data were from a survey of California adolescents (n = 5040). Respondents were asked how important it was to their peers to avoid drugs, marijuana, cigarettes, heavy drinking, and drinking and driving and to maintain seat belt use, fitness, weight control, and healthy eating habits. Results were compared with data from a similar national survey (n = 6126). RESULTS: California teenagers perceived that their peers gave top priority to weight control: 85% of California teenagers believed that weight control was of high concern to girls in their age group. Avoiding drugs, not drinking and driving, and maintaining fitness ranked in the top five behaviors. The lowest ranked health behaviors were seat belt use, heavy drinking, and, last, eating healthily. In the national survey, healthy eating also ranked last. Although not identical in rank, teenage priorities for other health behaviors were consistent with the California results. CONCLUSION: Efforts are needed to bring adolescent health norms more into line with the objective risks of their health choices during this critical period of socialization.

Adolescent↗