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Biomedical subjects

C Hall

Publications and source records attributed to C Hall.

At least 127 records · Page 7Linked to original sources
PubMed1998

Properties of adenosine monophosphate deaminase of Candida albicans.

Adenosine monophosphate deaminase (AMPD; EC 3.5.4.6) catalyses the hydrolysis of adenosine monophosphate (AMP) to commensurate amounts of inosine monophosphate (IMP) and ammonia. The production of AMP deaminase in Candida albicans was measured in Lee's medium grown cultures. The highest AMPD activity was observed at 24 h of growth. The enzyme had an optimum pH and temperature at 6-7 and 28 degrees C, respectively. This enzyme was inhibited under iron-limited growth conditions as well as by protease inhibitors. The AMPD of C. albicans showed a moderate increase in activity when cultures were grown in the presence of the divalent cations Mg2+, Ca2+, and Zn2+. Moreover, ADP, ATP, adenine, adenosine, deoxyribose and hypoxanthine increased the enzyme activity. Cultures grown in trypticase soy broth exhibited maximum AMPD activity compared with those grown in Sabouraud dextrose broth or Lee's medium.

AMP Deaminase↗
PubMed1998

Alterations in classical cadherins associated with progression in ulcerative and Crohn's colitis.

Human colitis is a condition associated with a spectrum of altered morphologic changes and cellular adhesion. The role of cadherins, which are powerful morphoregulatory cell adhesion molecules, in colitis is provocative and as yet unknown. Herein, we present results that suggest a strong correlation between the deregulation of two cadherin molecules, E- and P-cadherins, and the progression of human colitis. We examined the expression and structural integrity of E- and P-cadherins in inflamed, dysplastic, or neoplastic human ulcerative colitis (UC) (n=58), human Crohn's colitis (n = 30), and normal tissue (n = 20) to assess cadherin function in normal and abnormal epithelium. E-cadherin is strongly expressed in normal colorectal epithelium, whereas in left-sided UC it is either down-regulated or has a single-base pair mutation in exon 4 resulting in an amino acid alteration (6 of 58 UC cases). By contrast, P-cadherin is dramatically up-regulated in both Crohn's disease and ulcerative colitis and especially in dysplastic ulcerative tissue. In vitro transfected SW-480 colorectal cells containing E-cadherin mutations identical to those in vivo were associated with increased spontaneous disaggregation compared with cells transfected with wild-type E-cadherin. Based on this evidence, we hypothesize that a small subset of colorectal cells expressing mutant E-cadherin are associated with widespread ulceration, whereas those expressing P-cadherin are associated with a rapidly dividing immature phenotype that includes dysplasia. The differential expression of mutated and wild-type cadherins examined herein are associated with a broad spectrum of abnormal epithelial phenotypes, lymphocyte integrin binding, and resistance to denudation, as is seen in the colitis adenocarcinoma sequence.

Adult↗
PubMed1997

Paradoxical relationship between N-terminal proatrial natriuretic peptide and filling pressure in adults with cyanotic congenital heart disease.

BACKGROUND: Many adults with cyanotic congenital heart disease are characterized by reduced ventricular filling pressures and decreased systemic oxygen transport. Data from animals suggest that hypoxia can induce synthesis and secretion of atrial natriuretic peptide. METHODS AND RESULTS: We measured plasma N-terminal (1-98) proatrial natriuretic peptide (proANP) in 26 cyanotic adults and 28 noncyanotic control subjects. Resting arterial oxygen saturation was significantly lower and hemoglobin concentration and hematocrit significantly greater in cyanotic patients than in control subjects (82+/-6 versus 96+/-3%, 19.7+/-2.2 versus 14.7+/-2.1 g/dL, and 59.0+/-8.5% versus 44.3+/-5.2%, respectively, P<.0001 in all cases). Four cyanotic patients had evidence of iron deficiency. Plasma proANP levels were elevated in cyanotic patients compared with control subjects (1828+/-1147 versus 689+/-343 pmol/L, P<.0001). Comparison of resting arterial oxygen saturation and proANP levels demonstrated an inverse linear relationship between the two measures (r=-.70, P<.0001). There was a significant linear relationship between both hemoglobin concentration and hematocrit and proANP levels as well (r=.53, P=.0003 and r=.48, P=.002, respectively). Cyanotic patients had lower mean right atrial pressures than the control subjects (4+/-3 versus 7+/-2 mm Hg, P=.005), and there were inverse logarithmic relationships between proANP levels and systemic cardiac index (r=-.82, P=.0002), systemic oxygen transport (r=-.68, P=.005), and mixed venous oxygen saturation (r=-.79, P<.0001). CONCLUSIONS: Adults with cyanotic congenital heart disease are characterized by increased levels of plasma proANP. The increased atrial natriuretic peptide most likely results in extracellular and plasma volume depletion and reduced systemic oxygen transport. Measures designed to increase ventricular filling may improve quality of life of these patients.

Adolescent↗
PubMed1997

Cortical cell loss in asymptomatic cats experimentally infected with feline immunodeficiency virus.

Specific pathogen-free cats experimentally infected with feline immunodeficiency virus (FIV) were used to evaluate the development of central nervous system changes during the asymptomatic stages of viral infection. The brains of asyptomatic cats were examined at postinoculation times ranging from 8 weeks to 3 years for changes in neuron density, glutamate receptor density, and synaptophysin immunoreactivity. At 2-3 years postinoculation a small decrease in neuronal density was found in layers 2-3 and layer 5 of the frontal cortex (-14.4%), parietal cortex (-18.1%), and striatum (-29.5%). The only other indications of pathology within these regions were a mild diffuse astrogliosis, occasional microglial nodules, and the accumulation of satellite cells around selected neurons. An average loss of large neurons of 56-68% was seen in the cortex of four random source cats euthanized with AIDS. These values contrasted with the absence of any significant cell loss in FIV-infected cats 18 weeks after inoculation or FIV-negative controls. The loss of neurons in the asymptomatic cats showed a significant positive correlation with a decrease in the blood CD4:CD8 ratios. Morphometric evaluation of synaptic terminal densities immunocytochemically stained with synaptophysin revealed a significant increase in the asymptomatic cats at 2-3 years postinoculation that correlated negatively with the CD4:CD8 ratios. Random source AIDS cats showed a 34% decrease in synaptophysin-immunoreactive profiles. Glutamate binding in the cortex did not change significantly in the asymptomatic cats (4-7% decline). Thus, experimentally infected specific pathogen-free cats show a loss of cortical neurons similar to what has been observed in postmortem studies of humans infected with HIV. The detection of neuronal loss during the asymptomatic stage of disease and the correlation with the peripheral CD4:CD8 cell ratios indicate that neurodegeneration may progress in parallel with peripheral disease.

Animals↗
PubMed1997

The cervical spine in Crouzon syndrome.

STUDY DESIGN: All cervical spine radiographs of 44 patients with Crouzon syndrome treated at Great Ormond Street Hospital during the past 10 years were studied. OBJECTIVES: To assess the incidence and pattern of cervical spine abnormalities of patients with a confirmed diagnosis of Crouzon syndrome, but particularly regarding progressive fusion. SUMMARY OF BACKGROUND DATA: Previous studies into the cervical spine anomalies in those with Crouzon syndrome have shown an increased incidence of congenital abnormalities compared with the normal population. There is some suggestion from previous studies that cervical spine fusions are progressive in nature. METHODS: All radiographs were reviewed by the craniofacial team, along with a single pediatric radiologist with experience in assessment of skeletal dysplasias. RESULTS: Radiologic abnormalities included "butterfly" vertebrae and fusions of the bodies and the posterior elements. Evidence of fusion was present in eight of 44 (18%) of patients. C2-C3 and C5-C6 were almost equally affected. Block fusions involving multiple vertebrae were seen. Analysis of sequential studies in 16 patients showed evidence of progression in five. CONCLUSIONS: These results reveal an incidence of fusions that is lower than reported previously. There is radiologic evidence from serial studies that the fusions are progressive, and because these patients are children, the fusion process may not be complete, which may account for the lower incidence of fusions than in previous studies. The pattern of fusions is different from that in earlier studies, which may be a result of the method of diagnosis because this population is less likely to include atypical forms of other syndromes (which have a higher incidence of cervical fusions, particularly at C2-C3). Regarding other congenital anomalies, it appears that butterfly vertebrae are especially prevalent in association with Crouzon syndrome.

Cervical Vertebrae↗
PubMed1997

Validation of Portable Ergonomic Observation (PEO) method using optoelectronic and video recordings.

The validity of the 'Portable Ergonomic Observation' method (PEO) was investigated against posture measurements based on continuous optoelectronic and video recordings made simultaneously with the observation. Work postures and actions during different frequently changing tasks were analyzed using both methods. In general, a high agreement between measured and observed data was achieved for the duration of clearly identifiable sustained postures and actions (such as repetitive movements of hands when typing), as well as for the frequency of clearly distinguishable actions (such as lifts). The agreement between observations and measurements was low for neck postures. In dynamic tasks the agreement was generally low. This was probably because of high levels of simultaneous information for the observer. No improvement in the agreement between measured and observed events could be achieved by leaving parts of the PEO categories unobserved at a time. Playback of video tapes to observe each category separately would increase the reliability of the observations but at the expense of increased time for the analysis.

Ergonomics↗
PubMed1997

Neuroperceptual differences in consonant and vowel discrimination: as revealed by direct cortical electrical interference.

The effects of direct cortical electrical interference on consonant and vowel discrimination were investigated in five patients with implanted subdural electrode arrays. Without electrical interference, patients performance discriminating consonants and vowels was intact. With electrical interference, consonant discrimination was impaired at one electrode site in each patient on the superior temporal gyrus of the lateral left perisylvian cortex. Conversely, vowel and tone discrimination remained relatively intact when tested with electrical interference at the same site. Analysis of patients' consonant discrimination errors revealed that neither differences in acoustic temporal structure nor syllable position fully account for the consonant-vowel perceptual dissociations elicited. Our data suggest that at the cortical level consonant and vowel perception are intrinsically distinct perceptual phenomena. The selective impairment of consonant, but not vowel, discrimination further suggests that consonant and vowel perception are distinguished by differences in relative dependence on the functional--perhaps integrative--resources of the left lateral superior temporal gyrus.

Adolescent↗
PubMed1997

Effects of angiotensin II receptor blockade on N-terminal proatrial natriuretic factor plasma levels in chronic heart failure.

BACKGROUND: Plasma N-terminal proatrial natriuretic factor (N-terminal proANF) has been shown to reflect intraatrial pressures in heart failure patients, and may be used as a biochemical parameter of atrial pressures. It is still unclear how treatment of heart failure influences the relationship between hemodynamic parameters and plasma levels of N-terminal proANF. METHODS AND RESULTS: This double-blind, placebo-controlled study investigated whether 12 weeks of treatment with the angiotensin II receptor blocker losartan influenced N-terminal proANF plasma levels in 129 chronic heart failure patients. After 12 weeks of treatment, N-terminal proANF level was increased in patients given placebo by 344 +/- 1126 pmol/L, whereas in patients given 50 mg losartan, the levels had decreased by 251 +/- 886 pmol/L (P < .01 vs placebo). The change in N-terminal proANF correlated significantly with the corresponding change in pulmonary capillary wedge pressure (r = .53, P < .001). CONCLUSION: The correlation between N-terminal proANF plasma levels and pulmonary capillary wedge pressure at baseline, as well as the correlation between the changes in these parameters during treatment, suggests that plasma N-terminal proANF may be used to monitor effects on left ventricular filling pressures in patients treated with losartan.

Aged↗
PubMed1997

Plasma N-terminal atrial natriuretic factor: a predictor of survival in patients with congestive heart failure.

BACKGROUND: Congestive heart failure results in biatrial stretch, which stimulates myocyte release of atrial natriuretic factor (1-126). The N-terminal fragment, proatrial natriuretic factor(1-98), (proANF), is released on an equimolar basis with the C-terminal (99-126) active hormone and may be assayed simply because of prolonged in vitro stability. Proatrial natriuretic factor has been shown to be predictive of clinical status in patients with congestive heart failure. This retrospective analysis was undertaken to evaluate the relationship between N-terminal atrial natriuretic factor(1-98) and survival in patients with stable congestive heart failure. METHODS AND RESULTS: Proatrial natriuretic factor was sampled from 316 patients (mean age, 68 (+/-) 11 years; 71% men) recruited from an outpatient heart failure clinic. The mean ejection fraction was 34 (+/-) 13%. Seventy-three deaths were registered during the period of data collection (42 months). Deaths per proANF quartile (n = 79) were as follows: 2 (2.5%) in quartile I. 13 (16.5%) in quartile II, 21 (26.6%) in quartile III, and 37 (46.8%) in quartile IV. The odds ratio estimates for death adjusted for age and sex were 7.6, 13.9, and 33.9 for the second, third, and fourth quartiles, respectively. Survival curves constructed according to proANF quartiles demonstrate significant differences in mortality rates. The correlation with death was greater for proANF as compared with left ventricular end-diastolic diameter (P < .001), systolic pulmonary artery pressure (P < .005), or ejection fraction (P < .05). CONCLUSION: These data indicate that the concentration of proANF is related to prognosis in patients with heart failure and that moderate elevation is associated with markedly decreased survival. Analysis should be of practical value in the assessment of prognosis in this heterogeneous population.

Adolescent↗
PubMed1997

Consumption of non-steroidal anti-inflammatory drugs and the development of functional renal impairment in elderly subjects. Results of a case-control study.

AIMS: The aim of the present study was to explore the level of risk associated with community use of non-steroidal anti-inflammatory drugs (NSAIDs). METHODS: We carried out a matched case-control study of the relationship between recent use of NSAIDs and the presence of functional renal impairment present at the time of hospitalisation with a range of clinical problems. Cases (n = 110) were consecutive patients admitted acutely to hospital who had serum creatinine levels greater than or equal to 0.15 mmol l(-1) , which improved by 20% or more within the next 14 days, or prior to discharge from hospital. Controls (n= 189) were subjects of the same sex and age (to within 5 years) as the cases, who were admitted to the same hospital, who had normal serum creatinine levels (<0.12 mmol l(-1) throughout their hospital stay. Information on a number of study factors, including recent use of aspirin and other NSAIDs, was obtained by structured interview. RESULTS: Overall, there was a weak association between consumption of NSAIDs (including non-prophylactic aspirin) and the development of functional renal impairment-adjusted odds ratios (OR) with use of NSAIDs in the previous week or in the previous month: OR 1.5 (95% CI 0.80, 2.9) and 1.8 (95% CI 0.97, 3.4) respectively. In subjects with a previous history of renal disease the adjusted OR was 6.6 (0.75, 57.8) and in those with a history of gout or hyperuricaemia the OR was 7.2 (1.3, 40.2). There was a weak positive relationship between the dose of drug consumed in the previous week and the odds of functional renal impairment. The relationship between risk and published figures for drug half-lives (t1/2) was stronger. The odds ratio increased from 1.2 (95% CI 0.61, 2.4) with a t1/2 < or = 4 h, to 4.8 (1.5, 15.8) with a t1/2 of < or = 12 h (P=0.012, test for trend). This relationship remained statistically significant after adjustment for a number of clinical variables and the dose of drug ingested. CONCLUSIONS: NSAIDs are an important cause of functional renal impairment in subjects with renal disease or a history of gout or hyperuricemia. The half-life of the drug is more important than the ingested dose in determining the risk of this outcome. Long half-life drugs should be avoided in individuals who are at risk of developing renal impairment.

Aged↗
PubMed1997

Atrial natriuretic peptides predict mortality in the elderly.

OBJECTIVES: To ascertain whether atrial natriuretic peptides could be used as prospective and independent predictors of total mortality in an elderly population. DESIGN: Atrial natriuretic peptides, ANP(1-98) and ANP(99-126), were measured in 541 subjects from the 85-year-old population of Gothenburg, Sweden. Before the study cardiovascular disorders such as congestive heart failure, ischaemic heart disease, hypertension and atrial fibrillation were defined. Total mortality was recorded during the prospective 60-month follow-up period. SETTING: Individuals aged 85 years from the population of Gothenburg, Sweden, were visited once at home and made one visit to Vasa Hospital. MAIN OUTCOME MEASURES: Sixty-month mortality in relation to circulating concentrations of atrial natriuretic peptides. RESULTS: Circulating concentrations of ANP(1-98) and ANP(99-126) were significantly correlated with 60-month mortality in the total study population (ANP(1-98), P < 0.001: ANP(99-126), P < 0.01). In subjects with cardiovascular disorders, 60-month mortality was significantly correlated with increased concentrations of ANP(1-98) (P < 0.01) and ANP(99-126) (P < 0.05). In subjects with no defined cardiovascular disorder, 60-month mortality was significantly correlated with increased ANP(1-98) concentrations (P < 0.01). CONCLUSIONS: In the elderly population, atrial peptides predict mortality in subjects with defined cardiovascular disorders as well as in the total population and may predict future cardiovascular disorder.

Aged↗
PubMed1997

Recalling demonstrated and guided movements using imaginary and verbal rehearsal strategies.

This study investigated the recall of movement patterns presented either by demonstration or guided movement with vision eliminated. Participants were instructed to rehearse and remember each of the 12 patterns using one of four strategies: imagery, verbal labeling, imagery and verbal labeling, or no rehearsal strategy (i.e., control condition). Recall was better for patterns that were demonstrated than for those presented via guided movement. In addition, more patterns were remembered if a combination of imagery and verbal labeling were employed as a rehearsal strategy compared to using imagery alone. These results are discussed using Annett's (1994) model showing the relationships between action, language, and imagination in the acquisition of motor skills.

Analysis of Variance↗
PubMed1997

Gas exchange and neurohumoral response to exercise: influence of the exercise protocol.

Maximal oxygen uptake varies with the exercise protocol, but the extent to which hormonal and metabolic responses to exercise are influenced by the exercise protocol has not been precisely defined. Twelve healthy subjects underwent maximal exercise testing using two incremental bicycle tests with individualized, identical work rate increments between 40 and 70 W. One protocol employed a 1-min and the other a 3-min duration per stage. Expiratory gas and venous blood were sampled at regular intervals for metabolic and hormonal analysis. Exercise duration for the 1-min and 3-min protocols was 6.0 +/- 0.1 and 14.3 +/- 0.3 min, respectively (P < 0.001). Significantly higher values were observed for peak VO2 and maximal ventilation during the 3-min protocol compared with the 1-min protocol (41.1 +/- 1.8 vs 38.3 +/- 1.6 ml.kg-1.min-1, P < 0.001; and 104.9 +/- 8.0 vs 97.2 + 5.7 l.min-1, P < 0.05, for peak VO2 and peak ventilation, respectively). However, the maximal workload achieved was higher during the 1-min versus the 3-min protocol (330 + 24 vs 280 + 21 W, P < 0.01). No differences were observed for maximal heart rate or blood pressure, whereas maximal plasma lactate was roughly twice as high during the 3-min compared with the 1-min protocol (7.5 +/- 0.8 vs 3.8 +/- 0.5 mmol.l-1, P < 0.001). Norepinephrine, epinephrine, dopamine, and growth hormone levels were generally higher throughout exercise during the 3-min compared with the 1-min protocol. When expressed as a percentage of peak VO2, however, differences in catecholamine levels were not observed. Endothelin levels did not change. We conclude that the exercise protocol profoundly influences exercise capacity as well as the metabolic and hormonal response to exercise and should be considered when using these variables to evaluate an intervention.

Adult↗
PubMed1997

The effects of human relations training on reported teacher stress, pupil control ideology and locus of control.

BACKGROUND: This study presents the reported outcomes of a two-year, part-time Masters' programme in human relations using an experiential learning methodology based mainly on humanistic psychological theory. AIMS: The following hypotheses were examined. That as a result of the two-year programme: the experience of reported stress would be reduced; reported attitudes to student classroom control would shift from custodial to humanistic; there would be an increase in reports from participants of a sense of control over their lives; changes of behaviour in work, social settings and at home related to these three variables would be reported. SAMPLE: Involved in the study were 42 experienced teachers. These included 32 women and 10 men, with an average age of 35, who worked in a wide range of educational institutions. Their learning style preferences were also considered as independent variables. A control group of 42 was established with similar demographic characteristics. METHODS: Prior to the course, the experimental group and the control group were given the Maslach Burnout Inventory and the Pupil Control Ideology Form. In the early stages of the course, the experimental group completed the Kolb Learning Style Inventory and an informal measure of locus of control which was repeated at the end of the first year of the course. A sample of 32 from the experimental group were given semi-structured interviews relating to changes in their professional and personal lives. RESULTS: The results indicated that, following the training, there was a reduction in reported stress, indications of a more humanistic orientation towards pupil control and an increase in a sense of an internal locus of control. The quantitative data were confirmed by qualitative data generated from semi-structured interviews, which involved substantial reports of applications of the training in their professional and personal lives. CONCLUSION: These results provide support for including experiential human relations training as part of both the in-service and initial teacher training programmes.

Adult↗