PubMed Health⌕ Search

Biomedical subjects

D A Mason

Publications and source records attributed to D A Mason.

At least 19 recordsLinked to original sources
PubMed1999

A gain-of-function polymorphism in a G-protein coupling domain of the human beta1-adrenergic receptor.

The beta1-adrenergic receptor (beta1AR) is a key cell surface signaling protein expressed in the heart and other organs that mediates the actions of catecholamines of the sympathetic nervous system. A polymorphism in the intracellular cytoplasmic tail near the seventh transmembrane-spanning segment of the human beta1AR has been identified in a cohort of normal individuals. At amino acid position 389, Gly or Arg can be found (allele frequencies 0.26 and 0. 74, respectively), the former previously considered as the human wild-type beta1AR. Using site-directed mutagenesis to mimic the two variants, CHW-1102 cells were permanently transfected to express the Gly-389 and Arg-389 receptors. In functional studies with matched expression, the Arg-389 receptors had slightly higher basal levels of adenylyl cyclase activities (10.7 +/- 1.2 versus 6.1 +/- 0.4 pmol/min/mg). However, maximal isoproterenol-stimulated levels were markedly higher for the Arg-389 as compared to the Gly-389 receptor (63.3 +/- 6.1 versus 20.9 +/- 2.0 pmol/min/mg). Agonist-promoted [35S]guanosine 5'-O-(thiotriphosphate) binding was also increased with the Arg-389 receptor consistent with enhanced coupling to Gs and increased adenylyl cyclase activation. In agonist competition studies carried out in the absence of guanosine 5'-(beta, gamma-imido)triphosphate, high affinity binding could not be resolved with the Gly-389 receptor, whereas Arg-389 displayed an accumulation of the agonist high affinity receptor complex (RH = 26%). Taken together, these data indicate that this polymorphic variation of the human beta1AR results in alterations of receptor-Gs interaction with functional signal transduction consequences, consistent with its localization in a putative G-protein binding domain. The genetic variation of beta1AR at this locus may be the basis of interindividual differences in pathophysiologic characteristics or in the response to therapeutic betaAR agonists and antagonists in cardiovascular and other diseases.

Adenylyl Cyclases↗
PubMed1997

Motivational interviewing to improve adherence to a behavioral weight-control program for older obese women with NIDDM. A pilot study.

OBJECTIVE: The aim of this randomized pilot study was to examine whether the addition of motivational interviewing strategies to a behavioral obesity intervention enhances adherence and glucose control in older obese women with NIDDM. RESEARCH DESIGN AND METHODS: Twenty-two older obese women (41% black) with NIDDM were randomly assigned to 1) a standard 16-week group behavioral weight-control program that provided instruction in diet, exercise, and behavioral modification or 2) the same group behavioral program with three individualized motivational interviewing sessions added. RESULTS: The motivational group attended significantly more group meetings (13.3 vs. 8.9), completed significantly more food diaries (15.2 vs. 10.1), and recorded blood glucose significantly more often (46.0 vs. 32.2 days) than the standard group. Further, participants in the motivational group had significantly better glucose control post-treatment (9.8 vs. 10.8%). Although both groups demonstrated significant weight loss, no differences were apparent between groups. CONCLUSIONS: These results suggest that augmenting a standard behavioral treatment program for obese women with NIDDM with a motivational interviewing component may significantly enhance adherence to program recommendations and glycemic control. Preliminary data warrant further investigation with larger samples and a longer follow-up.

Behavior Therapy↗
PubMed1994

Symptoms from impacted wisdom teeth.

A study of patients referred for wisdom teeth removal was carried out, to investigate symptoms prior to consultation and during the period on the waiting list for surgery. The reasons for treatment of asymptomatic wisdom teeth were investigated. Pain was the main indication for surgery in 73.7% of patients waiting for consultation. 168 patients waiting for consultation consumed a total of 271 courses of antibiotics, averaging 1.6 courses of antibiotics per patient. The antibiotic consumption increased to an average of 2.5 courses per patient in 94 patients waiting for operation. 67 out of 423 patients had an average of three lost working days due to symptoms from wisdom teeth. The long waiting list for consultation and treatment added further to the discomfort. The extent of symptoms from wisdom teeth may be underestimated.

Absenteeism↗
PubMed1992

Flexible-geometry conformational energy maps for the amino acid residue preceding a proline.

Previously calculated conformational energy maps suggest that the alpha-helical conformation for the residue preceding a proline is disfavored relative to the extended conformation by more than 7 kcal/mol. In known protein structures this conformation is observed, however, to occur for about 9% of all prolines. In addition, introduction or removal of prolines at theoretically unfavorable positions in proteins and peptides can have modest effects on stability and structure. To investigate the discrepancy between calculation and experiment, we have determined how the conformation of the proline affects the calculated energy. We have also explored the effect of bond length and bond angle relaxation on the conformational energy map. The conformational energy of the preceding residue is found to be unaffected by the conformation of the proline, but the effect of allowing covalent bond relaxation is dramatic. If bond lengths and angles, and dihedral angles within the pyrrolidine ring, are allowed to relax, a calculated energy difference between the alpha and beta conformations of 1.1 kcal/mol is obtained, in reasonable agreement with experiment. The detailed shape of the calculated energy surface is also in excellent agreement with the observed conformational distributions in known protein structures.

Amino Acid Sequence↗
PubMed1991

Analysis and predictors of pulmonary vascular resistance after cardiac transplantation.

Elevated pulmonary vascular resistance is a known risk factor for early death from acute right ventricular failure after orthotopic cardiac transplantation. Patients in whom the elevated pulmonary vascular resistance is due primarily to increased left atrial pressure ("reactive") frequently have normalization of resistance after transplantation, but few studies have detailed the time course and magnitude of these changes. To analyze the response of pulmonary vascular resistance to cardiac transplantation, we analyzed data from 4353 right heart catheterizations on all 182 patients undergoing cardiac transplantation between 1981 and Jan. 1, 1990. Before transplantation 18% of patients had a pulmonary vascular resistance greater than 4 WU, 16% had a pulmonary artery systolic pressure greater than 60 mm Hg, and 16% had a transpulmonary gradient greater than 14 mm Hg. In the overall group of patients, pulmonary vascular resistance (mean value 2.63 WU), transpulmonary gradient (mean value 9.9 mm Hg), and pulmonary artery systolic pressure (mean value 48.0 mm Hg) were normalized within 1 week of cardiac transplantation. In patients with a high preoperative pulmonary vascular resistance (greater than or equal to 4 WU), the resistance fell promptly within 1 week of transplantation but continued to be slightly elevated throughout the period of follow-up. By multiple regression analysis, pulmonary vascular resistance at 1 week and 1 year after transplantation was significantly correlated with the pretransplantation resistance. Pulmonary vascular resistance anytime after transplantation was related to preoperative resistance, body surface area, and pulmonary artery diastolic pressure. Inferences: (1) As a group, cardiac transplant recipients have a normal pulmonary vascular resistance, transpulmonary gradient, and pulmonary artery systolic pressure within 1 week after transplantation with little change thereafter for at least several years. (2) Patients with reversible elevation of pulmonary vascular resistance before cardiac transplantation typically have a reactive and a fixed component. Cardiac transplantation relieves the reactive but not the fixed component. As a result, pulmonary vascular resistance early (within 1 week) and late after transplantation will have fallen but not completely normalized.

Cardiac Catheterization↗
PubMed1988

Lingual nerve damage following lower third molar surgery.

A prospective study was carried out on the effects of surgical, operator, and anatomical variables on the incidence and duration of lingual dysaesthesia after the surgical removal of impacted lower third molars under general anaesthesia. The predictive value of the area of sensory loss in relation to recovery was also studied. 120 instances of dysaesthesia occurred following 1040 operations in 602 patients, an overall incidence of 11.5%. The effects of 22 possible causative factors, analysed initially by the X2 test, are recorded. Since factors may not be independent, the results were then subjected to logit analysis, revealing highly significant effects from depth of impaction, removal of overhanging distal bone, lingual flap elevation, and operating time. Neither individual operators nor operator seniority had significant effects on the incidence. 6 cases of dysaesthesia failed to recover within 6 months. Where the area of sensory loss was incomplete, recovery occurred within 6 months in all cases.

Adolescent↗
PubMed1985

Muscular and intraocular pressure responses among ocular-hypertensive subjects: is there a rationale for biofeedback?

Several animal and human investigations have indicated that intraocular pressure (IOP) levels may be associated with extreme drug-induced changes in the extraocular muscles. Further, recent data suggest that, among individuals with normal IOP level, moderate increases in facial muscle (EMG) activity around the eye while the eye is open are associated with increases in IOP. To investigate further the relationship between facial EMG activity and IOP levels and to examine a group of individuals with elevated IOP levels, subjects were recruited from outpatients at an optometry clinic. Three groups of subjects were selected: a group of ocular hypertensive subjects who showed elevated pressures at the optometry clinic and upon the day of testing, a group of labile ocular hypertensive subjects who evinced elevated pressures during their visit to the optometry clinic but lower pressures on the day of testing, and a group of normal IOP subjects who showed normal pressures both during their optometry clinic visit and on the day of testing. To investigate anxiety differences, subjects were administered the State-Trait Anxiety Inventory, but subsequent analysis revealed no group differences. To evaluate the role of stress upon muscle (EMG) functioning around the eye, subjects were subjected to imagery and standardized mental arithmetic stressors; analyses of these results also revealed no significant group differences. Finally, subjects were given EMG biofeedback for muscle activity around the eye while IOP was assessed during five alternating periods in which they made decreases and increases in EMG activity. Results revealed significant group, period, and group by period interaction effects. The pattern of results is interpreted as implicating EMG activity in IOP fluctuations; the implications of these data for potential biofeedback and stress management treatments are discussed.

Adult↗
PubMed1985

Dental and facial injuries following sports accidents: a study of 130 patients.

Details of injuries to the face and teeth have been collected over a five-year period. One hundred and thirty patients were seen with injuries resulting from 21 different sports. Estimates of the numbers of people playing various team sports in the Bradford area suggest that the incidence of facial injuries is most common in rugby, followed by soccer and cricket. Miniature motor cycling and horse-riding are the most dangerous individual sports. The ages of injured patients varied widely in different sports, but the severity of injuries sustained is less than those due to other causes.

Adolescent↗
PubMed1984

Facial fractures--the results of a prospective four-year-study.

A prospective four-year-study of 945 fractures of the facial skeleton is presented. Details of facial trauma were collected in patients referred from the Bradford and Airedale Districts of West Yorkshire, England, an area with a population slightly in excess of half a million. Statistical analysis shows variations from previously published papers, the male to female ratio being under 2.6:1, with an average of 1.15 fractures per patient. A relatively high incidence of sports fractures is reported but the number of industrial accidents is surprisingly low. The majority of patients seen were in their third decade, the mean age being just over 25 years. The analysis also reveals that a high percentage of fractures were treated conservatively.

Adolescent↗