Energy cost for the proper ionization of active site residues in 6-phosphogluconate dehydrogenase from T. brucei.

The catalytic mechanism of 6-phosphogluconate dehydrogenase requires the inversion of a Lys/Glu couple from its natural ionization state. The pKa of these residues in free and substrate bound enzymes has been determined measuring by ITC the proton release/uptake induced by substrate binding at different pH values. Wt 6-phosphogluconate dehydrogenase from Trypanosoma brucei and two active site enzyme mutants, K185H and E192Q were investigated. Substrate binding was accompanied by proton release and was dependent on the ionization of a group with pKa 7.07 which was absent in the E192Q mutant. Kinetic data highlighted two pKa, 7.17 and 9.64, in the enzyme-substrate complex, the latter being absent in the E192Q mutant, suggesting that the substrate binding shifts Glu192 pKa from 7.07 to 9.64. A comparison of wt and E192Q mutant appears to show that the substrate binding shifts Lys185 pKa from 9.9 to 7.17. By comparing differences in proton release and the binding enthalpy of wt and mutant enzymes, the enthalpic cost of the change in the protonation state of Lys185 and Glu192 was estimated at ≈6.1kcal/mol. The change in protonation state of Lys185 and Glu192 has little effect on Gibbs free energy, 240-325cal/mol. However proton balance evidences the dissociation of other group(s) that can be collectively described by a single pKa shift from 9.1 to 7.54. This further change in ionization state of the enzyme causes an increase of free energy with a total cost of 1.2-2.3kcal/mol to set the enzyme into a catalytically competent form.

Canine mitral valve size as measured by computed tomography.

OBJECTIVE: To measure the mitral annulus in dogs. Our hypothesis was that mitral measurement would be possible and consistent among observers using CT. SAMPLE: Thoracic CT scans of dogs without known heart disease. PROCEDURES: Five trained investigators measured 4 aspects of the mitral valve and the fourth thoracic vertebrae (T4) length using multiplanar reformatting tools. Ten randomly chosen animals were measured by all investigators to determine interobserver reliability. RESULTS: There were 233 CT scans eligible for inclusion. Dogs weighed 2 to 96 kg (mean, 28.1 kg), with a variety of breeds represented. Golden Retrievers (n = 28) and Labrador Retrievers (n = 37) were overrepresented. The intraclass correlations were all greater than 0.9, showing excellent agreement between observers. The means and SDs of each measurement were as follows: trigone-to-trigone distance, 17.2 ± 4.7 mm; the remaining circumference, 79.0 ± 17.5 mm; commissure-to-commissure distance, 30.8 ± 6.5 mm; septal leaflet-to-lateral leaflet distance, 26.3 ± 6.0 mm; T4 length, 16.9 ± 3.1 mm; and the total circumference normalized by T4, 5.7 ± 0.7 mm. CLINICAL RELEVANCE: This study provides information that may help in the development of future treatment for mitral valve dysfunction and subsequent annular enlargement.

Coping with a chronic disease.

Interviews were conducted with 55 experienced patients with insulin-dependent diabetes with the aim of identifying strategies for coping with diabetes. This study was based on a health-oriented approach known as Antonovsky's salutogenic model, which conceptualizes the person as being actively involved in maintaining biological, psychological, and social homeostasis. All patients had developed some strategy for maintaining biological balance. Twenty-two also had strategies for coping both psychologically and socially with the disease. The remaining 33 patients had developed either a psychological or a social strategy in addition to their biological strategies. The results indicate that it is important for the patient's well-being and self-esteem to establish all three coping strategies--biological, psychological, and social. The diabetes care team could be a valuable resource for the patient in this respect.

Metabolic control, residual insulin secretion and self-care behaviours in a defined group of patients with type 1 diabetes.

A population of 185 type 1 diabetes patients (insulin-dependent, IDDM), 25-45 years old, was studied retro- and prospectively over a 9-year period with the aim of analysing background factors of importance for the ability to perform adequate self-care. Expressed as mean HbA1c, the metabolic control was slightly improved at the end of the study, when the insulin schedule had been changed in 60% of the patients to multidose treatment. The degree of metabolic control remained constant over the years. The impact of residual insulin secretion, measured as 24-hour urinary C peptide, was low. Patients with less good metabolic control often had a poor educational background and made less use of self-monitoring of blood glucose (SMBG); they also experienced difficulties with SMBG. The applied knowledge of diabetes also differed between groups with good and poor control. Subjectively, most patients considered their metabolic control to be good, irrespective of the HbA1c values. When asked about their own diabetes complications, their answers were often discrepant from the medical records. Patients with particularly "good" or "poor" metabolic control were on the whole less satisfied with the education and information received than those with intermediate blood glucose regulation. Development of strategies for individually adjusted education seems important.

The patient's experience of diabetes and its treatment: construction of an attitude scale by a semantic differential technique.

An instrument for measuring attitudes towards diabetes and self-care was constructed by a semantic differential technique. The instrument contained nine adjective pairs. Factor analysis classified these into four factors: self-esteem/autonomy, object evaluation, quality of life supporting factor and self-strength/vulnerability. The reliability coefficient of test-retest by 28 nurses/nurse tutors was 0.93. Fifty diabetic patients completed the attitude scale for testing the validity of the instrument. Male patients had a more positive attitude towards diabetes than females. Those who had had diabetes for less than 10 years were more positive than those with a longer duration of the disease. A higher degree of education, well-performed self-monitoring of blood glucose and achievement of good metabolic control were all associated with a more negative attitude towards diabetes. A group of nurses/nurse tutors who also completed the attitude scale had a more negative attitude towards diabetes than the investigated groups of patients.

Health and unhealth in chronic disease.

When health is defined from a holistic view, traditional measures of control in diabetes, such as analysis of blood glucose or HbA1c, are of limited use as indicators of health and unhealth. On the other hand, evaluation of attitudes and certain personality variables might provide guidance both in discovering unhealth and in creating individual self-care programmes for its treatment. In the present study the subjective experience of health and unhealth was studied in a defined population of patients with insulin dependent diabetes mellitus (IDDM). The patients could be divided into three categories: a) those not abandoning important goals because of their diabetes, b) "adapted abandoners" and, c) those abandoning vital aspects of life. On the basis of the findings, the question of how "problem patients" can be identified and treated is discussed.