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Biomedical subjects

J E O'Connell

Publications and source records attributed to J E O'Connell.

At least 19 recordsLinked to original sources
PubMed2003

Association behavior of beta-casein.

The association behavior of beta-casein, a protein with a distinct amphipathic character, was studied. beta-Casein exhibits markedly temperature-dependent association behavior; at low temperatures (<10-15 degrees C), monomers predominate, but as the temperature is increased, monomers associate, via hydrophobic bonding, into micelles. beta-Casein micelles have a hydrodynamic radius of approximately 12 nm, a radius of gyration of approximately 8.3 nm, and an interaction radius of approximately 15 nm. These data are fully consistent with a previous fluffy particle. The association behavior of beta-casein is also strongly affected by concentration and solvent quality. At low concentrations beta-casein exhibits a critical micelle concentration (CMC) of approximately 0.05%, w/v, at 40 degrees C. In the presence of 6 M urea the temperature dependence of beta-casein's association behavior is eliminated, leaving monomers predominantly. Temperature-dependent transformations in micelle morphology can be explained by changes in solvent quality, i.e., the temperature-protein hydrophobicity and temperature-voluminosity profiles of beta-casein. The results obtained are consistent with the shell model as developed by Kegeles, in which a distribution of micelle sizes is formed. They contrast with the traditional description of the micellization of beta-casein by a two-state model or by the closed-association model, i.e., monomers if micelles.

Caseins↗
PubMed2002

Beta blockers in older persons with heart failure: tolerability and impact on quality of life.

OBJECTIVE: To determine tolerability and symptom changes associated with the introduction of bisoprolol treatment in older patients with heart failure. DESIGN: Prospective observational cohort study. SETTING: Geriatric medicine outpatient department of a university hospital. PATIENTS: 51 patients (mean age 78 years, range 70-89 years) with stable symptomatic heart failure caused by left ventricular systolic dysfunction. INTERVENTIONS: Bisoprolol tablets, 1.25-10.0 mg. MAIN OUTCOME MEASURES: Tolerability; changes in symptoms and exercise tolerance. RESULTS: 69% of patients tolerated bisoprolol. Mean tolerated dose was 7.6 mg. There was no change in symptoms or exercise capacity in those who tolerated bisoprolol. Perceived health status and symptoms of anxiety and depression improved during the titration period. CONCLUSIONS: The rate of withdrawal from bisoprolol treatment in older patients with congestive heart failure was twice that previously reported in younger patients. The mean tolerated dose was similar to that found in trials reporting clinical efficacy. There was no evidence of a negative impact on symptoms or exercise capacity in patients who tolerated bisoprolol.

Adrenergic beta-Agonists↗
PubMed2001

Effect of beta-lactoglobulin and precipitation of calcium phosphate on the thermal coagulation of milk.

The effect of beta-lactoglobulin and heat-induced precipitation of calcium phosphate on the pH dependence and mechanism of thermal coagulation of milk throughout the pH range 6.3-7.3 was studied using serum protein-free milk and sodium caseinate as models for micellar and non-micellar milk protein systems respectively. It appears that the specific effect of beta-lactoglobulin at the pH of maximum stability may be related to its ability to chelate calcium. The effect of beta-lactoglobulin at the pH of minimum stability does not appear to be directly related to heat-induced dissociation of K-casein or micellar integrity but may be due to its ability to sensitize casein micelles to heat-induced precipitation of calcium phosphate, by increasing micellar hydrophobicity. The extent of heat-induced precipitation of calcium phosphate, as a function of pH, is an inverse reflection of the pH dependence of heat stability. Micellar integrity appears to play a critical role in the heat stability of milk but for reasons not previously appreciated.

Animals↗
PubMed2001

Ethanol-dependent heat-induced dissociation of casein micelles.

The dissociation of casein micelles when heated to approximately 65 degrees C in the presence of ethanol [1:1 mixture (v/v) of milk and 65% (w/w) aqueous ethanol] was investigated using L* values and transmission measurements. Mixtures of milk and ethanol became transparent on heating, which suggests dissociation of casein micelles. Results of experiments using confocal laser scanning microscopy, light scattering (static and dynamic), and dialysis to examine the changes of milk during heating in the presence of ethanol supported the assertion that such treatments result in dissociation of casein micelles, as did studies of model beta-casein micellar systems.

Animals↗
PubMed2001

Mechanism for the ethanol-dependent heat-induced dissociation of casein micelles.

An explanation as to how casein micelles dissociate when heated in the presence of ethanol is presented. Dissociation of casein micelles in milk-ethanol mixtures was studied using (1)H NMR, and the effects of addition of CaCl(2), NaCl, or EDTA or alteration of milk pH on this dissociation were studied. It is proposed that at low temperatures, ethanol reduces the solvent quality of milk serum, but above a critical temperature (approximately 30 degrees C in a 35% ethanol solution), ethanol enhances solvent quality and dissociates the casein micelles. Ethanol reduced protein hydrophobicity and increased the pK(a) value of phosphoserine, effects that are likely to be significant in the dissociating effect of ethanol at elevated temperatures.

Animals↗
PubMed2001

Blood pressure response to glucose potassium insulin therapy in patients with acute stroke with mild to moderate hyperglycaemia.

Insulin is neuroprotective in animal stroke models but its effects in acute stroke in humans are unknown. The Glucose Insulin in Stroke Trial (GIST-UK) is a randomised controlled trial investigating the benefits of maintaining euglycaemia in hyperglycaemic patients with acute stroke. Data are reported from a GIST-UK substudy which sought to determine the influence of glucose potassium insulin (GKI) infusion on blood pressure in acute stroke. All adult patients admitted to hospital with acute stroke with hyperglycaemia (plasma glucose 6.1-17 mmol/l) were potentially eligible. Randomised patients received either a GKI infusion (500 ml 10% glucose, 20 mmol potassium chloride, 16 units of insulin) or control therapy with 154 mmol/l (0.9%) saline at 100 ml/h for 24 hours. BM test strip glucose monitoring was performed 2 hourly, blood pressure monitoring 4 hourly, and plasma glucose sampling 8 hourly. Insulin concentration in the GKI infusate was altered according to test strip values to maintain test strip values between 4-7 mmol/l in the GKI group. Neurological impairment was determined using the European stroke scale (ESS). 145 patients were studied (73 GKI, 72 control). Mean systolic blood pressure was significantly lower during GKI infusion between 4 hours and 24 hours except at 8 hours. Median total ESS scores improved significantly between admission and day 7 in the GKI group (p<0.001) although there was no significant difference in total ESS score between groups at day 7. The significant reduction of systolic blood pressure in acute stroke associated with GKI therapy was not associated with neurological deterioration and may have been beneficial.

Adult↗
PubMed2001

Short communication: influence of transglutaminase on the heat stability of milk.

Skim milk powders were prepared from control and transglutaminase-treated skimmed milk. The heat stability of reconstituted transglutaminase-treated skimmed milk (9.0% total solids) was markedly increased in the pH region of minimum stability (pH 6.8 to 7.1) compared with control milk, while the heat stability of reconstituted concentrated transglutaminase-treated skimmed milk (22.5% total solids) increased progressively as a function of pH relative to control milk. The effect of transglutaminase treatment on the heat stability of skimmed milk may have commercial applications, but extensive research is necessary to gain a better understanding of the mechanism by which transglutaminase improves heat stability.

Animals↗
PubMed2000

The Comorbidity Symptom Scale: a combined disease inventory and assessment of symptom severity.

OBJECTIVES: To develop and evaluate a scale to quantify the presence and severity of symptoms arising from comorbid diseases in older people. DESIGN: A validation cohort study of hospital inpatients and outpatients aged 65 years and older. SETTING: A Hospital and community in Northeast England. PARTICIPANTS: Development of the Comorbidity Symptom Scale-Convenience sample of 50 hospital inpatients and outpatients aged 65 years and older. Evaluation of the Comorbidity Symptom Scale- Convenience sample of 183 patients aged 65 years and older either awaiting cataract surgery or attending a geriatric day hospital. MEASUREMENTS: For development of the Comorbidity Symptom Scale, 22 comorbid conditions were identified and incorporated into a questionnaire (the CmSS). Evaluation of the Comorbidity Symptom Scale-Assessments included the CmSS, activities of daily living, perceived health status, and anxiety and depression. RESULTS: A 23-item scale was developed. Reliability of the CmSS was demonstrated by a test-retest correlation coefficient for the total instrument score of r = 0. 87 (P < .001). The CmSS scores correlated with assessments of activities of daily living, perceived health status, and anxiety and depression. CONCLUSIONS: The CmSS is a simple interviewer-administered tool for use in older people and provides an objective measure of the presence of comorbid disease and the patient's perception of severity of associated symptoms.

Activities of Daily Living↗
PubMed2000

The two-stage coagulation of milk proteins in the minimum of the heat coagulation time-pH profile of milk: effect of casein micelle size.

Milks with casein micelles larger or smaller than control milk were prepared by differential centrifugation. The heat stability of these modified milks increased markedly throughout the pH range 6.4 to 7.1 with decreasing casein micelle size. Within the region of the minimum in the heat coagulation time-pH profile, the control milk coagulated by a two-stage process, but the modified milks, because of their narrower casein micelle size distribution, coagulated by a single-stage process at the pH of minimum stability. The content of kappa-CN and protein hydration increased as the size of the casein micelles decreased, and the level of glycosylation of kappa-CN and protein surface hydrophobicity increased as a function of micelle size. The effect of casein micelle size on the heat stability of milk is likely to be related to changes in the above physico-chemical properties.

Animals↗
PubMed2000

Heat stability of buttermilk.

Buttermilk prepared on a laboratory scale from raw cream, or on a commercial scale from flash-pasteurized cream (90 degrees C for 1 to 2 s), exhibited a type B heat coagulation time-pH profile (i.e., stability increased as a function of pH). The high heat stability of buttermilk in the pH range of the minimum of a type A milk (pH approximately 6.8 to 7.0) appears to be related to differences in the serum phase constituents (i.e., a low calcium and beta-Lg concentration and a high nonmicellar kappa-CN content).

Animals↗
PubMed1999

Measuring visual symptoms in British cataract patients: the cataract symptom scale.

AIMS: To develop and validate a scale for the measurement of visual symptoms and functional disability due to cataract in older UK residents. METHODS: In depth semistructured interviews were undertaken with 44 consecutive patients awaiting cataract surgery. Patients were asked to describe visual symptoms and problems with social functioning which were then incorporated into a questionnaire, the cataract symptom scale (CSS). The CSS was further examined in a cohort of 118 consecutive cataract patients awaiting surgery. Further assessments in these patients included visual acuity, visual function using an existing scale (the VF-14), activities of daily living, perceived health status, anxiety and depression, and a global assessment of how much patients felt their visual symptoms affected their daily life. RESULTS: A 15 item scale was derived which was simple to administer to older patients and had a high internal consistency. The test-retest correlation coefficient for the total instrument score was r = 0.91 (p<0.0001). The CSS correlated well with the VF-14 and to a lesser extent with visual acuity in the better eye, activities of daily living, perceived health status, anxiety and depression, and the patients' global assessment of visual symptoms. CONCLUSION: The CSS provides information regarding the symptomatic and functional status of older cataract patients resident in the UK which cannot be obtained by measurement of visual acuity alone.

Activities of Daily Living↗