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Biomedical subjects

M O'Brien

Publications and source records attributed to M O'Brien.

At least 343 records · Page 19Linked to original sources
PubMed1976

Modification of the regulatory properties of pyruvate kinase of Neurospora by growth at elevated temperatures.

Pyruvate kinase (EC 2.7.1.40) was isolated from Neurospora crassa mycelium grown at 28 degrees C (PK-28) and at 42 degrees C (PK-42). The regulatory properties, particularly the response towards the allosteric effector fructose 1,6-diphosphate (FDP), was different in the two enzymes. PK-28 showed an activation by FDP but PK-42, under comparable conditions, appeared to be activated by low concentrations of FDP and inhibited by higher ones. For PK-28, complex formation with FDP results in a lowering of the isoelectric point from 6.40 to 5.50, representing the pI of the unliganded enzyme and that of the complex, respectively. In contrast to this, PK-42 exhibits a weak binding to FDP as suggested by a lack of decrease in the isoelectric point on treatment with comparable concentrations of FDP. Studies with quenching of aromatic residue fluorescence of PK-28 and PK-42, following binding of FDP, indicate that although this ligand binds to both types of enzymes the affinity for the two is vastly different. Dissociation constants of 9.3 muM and 0.1 mM were calculated for the binding of FDP to PK-28 and PK-42, respectively. It is concluded that growth at elevated temperatures induced a conformational change in the pyruvate kinase leading to partial desensitization of the allosteric site. The nature of the factor(s) responsible for this change is not understood at present.

Allosteric Regulation↗
PubMed1975

Automated spectrophotometric assay of cefazolin.

An automated, stability-indicating, UV spectrophotometric assay for cefazolin is presented. The method employs a reaction with hydroxylamine and derives its stability-indicating power through comparison of reacted and unreacted aliquots of the sample. A double-probe sampling procedure is used. Good agreement with microbiological assays is obtained, and the coefficient of variation is about 1%.

Autoanalysis↗
PubMedDate not supplied

Exercise and osteoporosis.

Osteoporosis is a systemic skeletal disease characterised by low bone density and micro architectural deterioration of bone tissue with a consequent increase in bone fragility and susceptibility to fracture. It is a silent disease. It is the result of the negative balance between bone formation and bone resorption, i.e. more bone is lost than is formed. It is the most common bone disease worldwide and is now a major health problem. Bones require a normal level of systemic hormones, adequate caloric intake, particularly protein, calcium and vitamin D and regular weight-bearing exercise throughout life. A large bone mass early in life protects against osteoporosis. Peak bone mass is determined by sex, heredity family history, race, diet and exercise. Sixty per cent of bone growth occurs during adolescence. Moderate exercise protects against osteoporosis, but too little or excessive exercise may cause osteoporosis.

Bone Density↗
PubMedDate not supplied

Vitamin D intake and status in Irish elderly women and adolescent girls.

AIM: To assess vitamin D status during summer and winter in Irish girls and elderly women, and to estimate vitamin D intake in these two age-groups. METHODS: Ambulatory free-living, elderly Irish women (aged 70-76 years; n = 43) and girls (aged 11-13 years; n = 17) were recruited. Fasting serums were collected during August/ September 2002 and February/March 2003 and analysed for 25 (OH) D by HPLC. RESULTS: Mean daily intakes of vitamin D were 4.6 microg and 2.1 microg in elderly women and girls, respectively. Serum 25 (OH) D was significantly lower (P<0.001) during winter than summer in both age-groups. Eight (20%) and one (during late summer) and sixteen (37.2%) and eight (47%) (during late winter) of the elderly women and girls, respectively, had inadequate vitamin D status (serum 25 (OH) D <40 nmol/l). CONCLUSION: Inadequate vitamin D status during winter time is quite common in elderly women and adolescent girls in Ireland.

Adolescent↗
PubMedDate not supplied

Prevalence of obstructive airflow limitation in Irish collegiate athletes.

BACKGROUND: Asthma prevalence in athletes is variable, depending on the sport and training conditions. AIMS: To investigate the prevalence of obstructive airflow limitation, asthma control and lung volume differences in a control group and five groups of collegiate athletes--outdoor field, indoor court, endurance, combat sports and swimming. METHODS: Three hundred and five athletes completed a respiratory questionnaire and performed spirometry during normal training conditions, to determine FEV1, FVC and PEFR pre- and at 5, 10 and 15 minutes post-exercise. Between and within group analysis was carried out using single factor and repeated measures ANOVA. RESULTS: Previous diagnosis of asthma was reported by 24%, outdoor field sports 4.9%, indoor court sports 2.3%, endurance events 2.6%, combat sports 3%, swimming 6.9% and controls 4.3%. Mean FEV1 and FVC data, expressed as percentage of predicted, were greatest in swimming and lowest in controls. Swimming showed a significant rise in FEV1 post-exercise, indoor court and endurance sports demonstrated no change and outdoor field, combat and control groups showed a fall in FEV1 post-exercise. CONCLUSION: Warm humid training conditions appear protective against exercise-induced asthma. The greatest reductions in lung volumes occurred following high intensity exercise under cool conditions in the poorly aerobically conditioned.

Adult↗
PubMedDate not supplied

Analysis of an escalating sequence of problem behaviors: a case study.

This case study focused on a student with severe disabilities who displayed multiple problem behaviors that fit a pattern of behavioral escalation. Analysis of the pattern in which problem behaviors occurred within instructional sessions, and comparisons of conditional rates of occurrence for specific behaviors to overall base rates of occurrence, indicated that the student's problem behaviors did represent a behavioral sequence. Functional assessment led to the hypothesis that the use of rule statements by the teacher was related to the occurrence and escalation of the problem behaviors. An ABAB reversal design showed that eliminating the use of rule statements was an effective instructional intervention for decreasing the rate of the student's problem behaviors. Independent ratings of the physical effort required for specific problem behaviors in the sequence suggested that response effort may be one variable underlying the pattern of responding within a behavioral sequence. Implications are offered for our theoretical understanding of complex patterns of problem behaviors and for future research and clinical intervention.

Adult↗
PubMedDate not supplied

Anti-Kell (K1) in idiopathic thrombocytopenic purpura.

A transiently occurring anti-Kell antibody was observed in a 2 1/2-year-old child who had idiopathic thrombocytopenic purpura after recovery from an upper respiratory tract infection. The antibody was probably of the IgM class. There was no history of prior blood transfusion.

Agglutination Tests↗