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Biomedical subjects

K Brown

Publications and source records attributed to K Brown.

At least 37 records · Page 2Linked to original sources
PubMed2004

Evaluation of advanced neonatal nurse practitioners: confidential enquiry into the management of sentinel cases.

OBJECTIVE: To evaluate the quality of the neonatal care delivered by an advanced neonatal nurse practitioner led service at Ashington Hospital, Northumberland. SETTING: Maternity service with no resident paediatric medical input. DESIGN: Comparison of quality measures on sentinel cases with five comparator hospitals using modified confidential enquiry. RESULTS: On six out of seven dimensions, the neonatal nurse practitioner service performed better than the average of the five comparator hospitals, and overall ranked second. CONCLUSION: Good quality neonatal care can be delivered by advanced neonatal nurse practitioners alone, without the support of resident junior paediatricians.

Clinical Competence↗
PubMed2004

Abnormal cognitive function in treated congenital hypopituitarism.

AIMS: To assess cognitive function in school age children with congenital pituitary hormone deficiency (PHD). METHODS: Ten children with PHD (aged 6.0-15.6 years, mean 11.5 years) and sibling controls (aged 8.7-14.9 years, mean 12.1 years) were assessed using the Wechsler Intelligence Scale for Children (WISC-III UK). RESULTS: The patients' full scale IQ scores were all below average (mean 75, 95% CI 70-80), but were not significantly different to those of sibling controls (mean 82, 95% CI 75-89). There was no difference in verbal IQ between patients and siblings, but performance IQ was significantly reduced (mean 75, 95% CI 68-82 in patients; mean 88, 95% CI 80-96 in sibling controls). The reduced performance IQ reflected a poorer performance in tasks assessing perceptual organisational skills. CONCLUSIONS: Data suggest that children with PHD have an IQ that is below average when compared to the population norm and a reduced performance IQ when compared to sibling controls. This may reflect abnormal brain development or could be linked to the impact of hypoglycaemia or low thyroxine concentrations in early life. This information is of value when counselling parents and planning a child's care and education, although further, more extensive studies of patients and siblings are required.

Adolescent↗
PubMed2004

Open lung biopsy in neonatal and paediatric patients referred for extracorporeal membrane oxygenation (ECMO).

BACKGROUND: This study was undertaken to determine the usefulness, safety, and most appropriate timing of open lung biopsy in infants and children considered for and on extracorporeal membrane oxygenation (ECMO) for respiratory failure. METHODS: A retrospective review of children referred for consideration of and placed on ECMO in our institution in the period 1996-2002. RESULTS: 506 patients were referred, 15 (3%) of whom underwent antemortem open lung biopsy (eight neonatal, four paediatric, and three cardiac patients). In the neonatal group open lung biopsy contributed to clinical decision making in all patients. Four neonates had a fatal lung dysplasia (three alveolar capillary dysplasia and one surfactant protein B deficiency) and treatment was withdrawn. Of the other four neonates, two had pulmonary hypoplasia, one had pulmonary lymphangiectasia, and one had meconium aspiration with mild barotrauma. Treatment was continued in these four patients and two survived. In the paediatric group the biopsies were of clinical relevance in two infants with pertussis who had lung infarction on biopsy in whom treatment was withdrawn. In the other two paediatric patients the biopsies were equivocal, treatment was continued, but both patients died. In the cardiac group, who presented perioperatively with pulmonary hypertension, the biopsies excluded a fatal lung dysplasia and severe pulmonary vascular disease but all three infants died. One patient had non-fatal bleeding complications. CONCLUSION: Open lung biopsy is clinically most useful when performed to diagnose fatal lung dysplasias in neonates and to confirm the presence of viable lung tissue in patients with acute lung injury due to pertussis infection.

Biopsy↗
PubMed2003

A disturbance of nonlinear interdependence in scalp EEG of subjects with first episode schizophrenia.

It has been proposed that schizophrenia arises through a disturbance of coupling between large-scale cortical systems. This "disconnection hypothesis" is tested by applying a measure of dynamical interdependence to scalp EEG data. EEG data were collected from 40 subjects with a first episode of schizophrenia and 40 matched healthy controls. An algorithm for the detection of dynamical interdependence was applied to six pairs of bipolar electrodes in each subject. The topographic organization of the interdependence was calculated and served as the principle measure of cortical integration. The rate of occurrence of dynamical interdependence did not statistically differ between subject groups at any of the sites. However, the topography across the scalp was significantly different between the two groups. Specifically, nonlinear interdependence tended to occur in larger concurrent "clusters" across the scalp in schizophrenia than in the healthy subjects. This disturbance was reflected most strongly in left intrahemispheric coupling and did not differ significantly according to symptomatology. Medication dose and subject arousal were not observed to be confounding factors. The study of dynamical interdependence in scalp EEG data does not support a straightforward interpretation of the disconnection hypothesis-that there is a decrease in the strength of functional coupling between adjacent cortical regions. Rather, it suggests a dysregulation in the organization of dynamical interactions across supraregional brain systems.

Adolescent↗
PubMed2003

Practical problems with the collection and interpretation of serial quality of life assessments in patients with malignant glioma.

OBJECTIVES: To assess the problems involved with the collection and interpretation of serial collected health related quality of life assessments in patients with malignant glioma. PATIENTS AND METHODS: One-hundred and fifty nine patients with malignant glioma from three Scottish neurosurgical centres in whom assessments of performance status, neurological impairment, mood, and quality of life had been recorded over a 6-month period were prospectively identified. The amount of missing data and the reasons for missing data were assessed. Characteristics of patients that were fully compliant with serial assessments were then compared with those that were not. RESULTS: Compliance with serial assessments (both patient and observer reported) was poor, dropping to less than 50% at 6 months. Observer reported measures showed a similar pattern of decline as patient reported measures. The largest single cause of missing data (approximately 70%) was due to administrative failure. Compliant patients were found to have a significantly greater probability of survival compared to non-compliant patients and were also found to be younger and fitter relative to the rest of the study population. CONCLUSIONS: Studies utilising quality of life outcomes should give early consideration to minimising avoidable sources of missing data and recording the reasons for non-compliance. Quality of life studies basing conclusions on a complete case analysis should be wary of possible bias.

Bias↗
PubMed2002

Dose-related neurocognitive effects of marijuana use.

BACKGROUND: Although about 7 million people in the US population use marijuana at least weekly, there is a paucity of scientific data on persistent neurocognitive effects of marijuana use. OBJECTIVE: To determine if neurocognitive deficits persist in 28-day abstinent heavy marijuana users and if these deficits are dose-related to the number of marijuana joints smoked per week. METHODS: A battery of neurocognitive tests was given to 28-day abstinent heavy marijuana abusers. RESULTS: As joints smoked per week increased, performance decreased on tests measuring memory, executive functioning, psychomotor speed, and manual dexterity. When dividing the group into light, middle, and heavy user groups, the heavy group performed significantly below the light group on 5 of 35 measures and the size of the effect ranged from 3.00 to 4.20 SD units. Duration of use had little effect on neurocognitive performance. CONCLUSIONS: Very heavy use of marijuana is associated with persistent decrements in neurocognitive performance even after 28 days of abstinence. It is unclear if these decrements will resolve with continued abstinence or become progressively worse with continued heavy marijuana use.

Adolescent↗
PubMed2002

The vibrational mode structure of a golf ball.

In this paper, we report the discrete frequencies at which golf balls can vibrate, the mode patterns of these vibrations and how these modes can be excited. There are two broad classes of modes: those that radiate sound waves and those that do not. Both silent and acoustic modes are excited by tangential (i.e. spin-producing) impact forces; only acoustic modes are excited by radial impact forces. Exact analytical results for a homogeneous ball core are compared with finite element numerical results for both a core and a model two-piece ball. Correspondences are readily established for the important low-frequency modes, and the good agreement suggests the validity of these results for real golf balls. The results potentially provide the basis for a rapid, simple and non-destructive method of measuring the effective high-frequency elastic shear modulae of balls (and ball cores) as well as a method for 'tuning' the performance of balls for specific clubs. Some of these aspects are explored further in our companion paper in this issue.

Golf↗
PubMed2001

Decreased focal adhesion kinase suppresses papilloma formation during experimental mouse skin carcinogenesis.

Although focal adhesion kinase (FAK) is elevated in epithelial cancers, it is not known whether FAK expression influences tumor development in vivo. We found that fak +/- heterozygous mice display reduced 7,12-dimethylbenz[a]anthracene-induced papilloma formation that correlates with reduced FAK protein expression in the skin. However, the frequency of malignant conversion of papillomas into carcinomas is indistinguishable in fak +/- mice and their wild-type fak +/+ littermates, most likely because papilloma FAK protein expression is elevated to wild-type levels. We also found that keratinocyte FAK protein expression is important for cellular responses downstream of ras in vitro (monitored by extracellular signal-regulated kinase activation after integrin engagement). Because 7,12-dimethylbenz[a]anthracene induces an activating mutation of H-ras, this provides one possible explanation for suppression of papilloma formation when FAK protein is limiting.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed2001

The bioaccumulation of cadmium by the Blue Swimmer Crab Portunus pelagicus L.

The Blue Swimmer Crab (Portunus pelagicus) accumulates only cadmium in the hepatopancreas after being presented elevated levels of the metals Cd, Cu, Zn, As, Fe and Al via a food source, the mussel Trychomya hirsuta. Over 8 weeks, crabs were fed a controlled diet to determine the accumulation of metals. Significant (P = 0.05) Cd accumulation was detected after 4 weeks of feeding. Food mussels were sourced from either 'contaminated' or 'uncontaminated' sites. Mussels from uncontaminated sites had an average Cd level of 0.07 microg/g wet weight and contaminated mussels had an average of 5.2 microg/g wet weight. The usefulness of presenting metals in this way to assess potential bioaccumulators is further considered against other presentation methods.

Animals↗
PubMed2001

Domain swing upon His to Ala mutation in nitrite reductase of Pseudomonas aeruginosa.

The nitrite reductase (NIR) from Pseudomonas aeruginosa (NIR-Pa) is a soluble enzyme catalysing the reduction of nitrite (NO2(-)) to nitric oxide (NO). The enzyme is a 120 kDa homodimer, in which the monomers carry a c-heme domain and a d(1)-heme domain. The structures of the enzyme in both the oxidised and reduced state were solved previously and indicate His327 and His369 as putative catalytic residues. The kinetic characterisation of site-directed mutants has shown that the substitution of either one of these two His with Ala dramatically reduces the physiologically relevant reactivity towards nitrite, leaving the reactivity towards oxygen unaffected. The three-dimensional structures of P. aeruginosa NIR mutant H327A, and H369A in complex with NO have been solved by multiple wavelength anomalous dispersion (MAD), using the iron anomalous signal, and molecular replacement techniques. In both refined crystal structures the c-heme domain, whilst preserving its classical c-type cytochrome fold, has undergone a 60 degrees rigid-body rotation around an axis parallel with the pseudo 8-fold axis of the beta-propeller, and passing through residue Gln115. Even though the distance between the Fe ions of the c and d(1)-heme remains 21 A, the edge-to-edge distance between the two hemes has increased by 5 A. Furthermore the distal side of the d(1)-heme pocket appears to have undergone structural re-arrangement and Tyr10 has moved out of the active site. In the H369A-NO complex, the position and orientation of NO is significantly different from that of the NO bound to the reduced wild-type structure. Our results provide insight into the flexibility of the enzyme and the distinction between nitrite and oxidase reduction mechanisms. Moreover they demonstrate that the two histidine residues play a crucial role in the physiological activity of nitrite reduction, ligand binding and in the structural organisation of nitrite reductase from P. aeruginosa.

Alanine↗
PubMed2001

Idiopathic pulmonary fibrosis: relationship between histopathologic features and mortality.

It is hypothesized that the extent and severity of fibrosis and cellularity found on lung biopsy determine the prognosis and response to therapy in idiopathic pulmonary fibrosis (IPF). The objective of this study was to determine which histopathologic features predict survival in IPF. We prospectively studied 87 patients with usual interstitial pneumonia (UIP) confirmed by surgical lung biopsy. Four pathologists independently graded the extent and severity of specific histopathologic features. We used Cox proportional-hazards models to assess the effect of histopathologic patterns on patients' survival. The effects of age, sex, and smoking were also included in the analysis. Sixty-three patients died during the 17-yr study period. Survival was longer in subjects with lesser degrees of granulation/connective tissue deposition (fibroblastic foci). The degree of alveolar space cellularity, alveolar wall fibrosis, and cellularity did not affect survival. A history of cigarette smoking, the level of dyspnea, and the degree of lung stiffness at presentation were also shown to be independent factors predicting survival. The extent of fibroblastic foci present on lung biopsy predicts survival in IPF. These findings support the hypothesis that the critical pathway to end-stage fibrosis is not "alveolitis" but rather the ongoing epithelial damage and repair process associated with persistent fibroblastic proliferation. Controlling these processes, rather than stopping inflammation, appears most important in preventing progressive disease and the fatal outcome common in IPF.

Adult↗