Biomedical subjects
Publications and source records attributed to R I Brown.
Angioplasty of right internal mammary artery grafts may present problems because of the variable origin of the mammary artery and its angulation from the subclavian artery. We report a case of successful angioplasty using a custom designed guide catheter, after failed attempts using conventional guide catheters.
Attempted coronary angioplasty of a right coronary artery sub-total occlusion was unsuccessful due to failure to cross the lesion with the dilatation catheter. Both fixed-wire and over-the-wire systems were tried. Coronary rotational ablation was successful in reducing the stenosis and allowing successful angioplasty.
We report our initial experience using the Double Marker ACX II for intracoronary stent deployment in 22 patients, 10 of whom were elective stents and 12 of whom were stented for complications following failed coronary angioplasty. The overall success rate was 95 percent. This dilatation catheter offers advantages which include accurate stent deployment with a double marker system, the option of using a delivery sheath, and the ability to deliver multiple stents with the same balloon catheter.
Abrupt closure of a dominant right coronary artery occurred in a patient 1 h post coronary angioplasty. Angiography revealed a long spiral dissection involving the mid to distal segment of the right coronary artery. Four intracoronary balloon expandable stents were deployed to 'tack up' the dissection and recanalize the occluded artery. Six month follow-up angiography revealed continued patency of the stented segment. Balloon expandable stents may be an effective alternative to coronary bypass surgery in the treatment of acute closure following coronary angioplasty.
The governing equations defining the separation of blood in continuous flow centrifuges are derived using an empirical model for the viscosity of blood. The effects of fluid shear on the separation process are addressed and further models are developed to permit estimations of shear rate during centrifugation. Simplified predictive equations for species specific separations are developed. Contributions due to shear enhanced diffusion are addressed and found to be negligible at the discontinuous interface between cells and plasma. Experimental results from an investigational centrifuge are presented and compared with theoretical predictions. The role of rouleaux formation in conventional centrifuges is discussed and known centrifugal separation characteristics are explained. The viscosity of blood is related to that for suspensions of rigid particles and an equation for the hydraulic permeability of red blood cell suspensions is derived.
Retrospective and prospective studies of a total sample of 232 attenders at groups of Gamblers Anonymous suggest that total abstinence from gambling was maintained by 8% of all comers at one year from first attendance and by 7% at two years.
Cognitive-behavioral models of behavioral reversions or relapses in the addictions are inevitably incomplete because they miss affective and decision-making factors in the relapse process. They over-emphasize the importance of external "relapse-provoking" situations and under-value or ignore important intrapersonal determining processes. A theoretical model of an affective/decision-making factor in reversions or relapses, derived from studies in the role of arousal in gambling addictions, is developed and applied to addictions in general. Some of the implications of this model for the further classification and study of behavioral reversions are explored, and the options for testing it empirically are outlined.
Successful percutaneous transluminal coronary angioplasty is achieved by fracture of the atheromatous plaque and perhaps dilatation of the arterial walls to increase the luminal diameter of the artery. Because this "controlled" injury stimulates platelet adhesion on the subendothelial matrix, the use of dextran-40 in addition to heparin has been advocated. The overall incidence of Dextran-induced anaphylactoid reactions at our institution was 0.6% and of severe life-threatening reactions, 0.2%. With the recent doubts cast on the efficacy of dextran-40, the question arises regarding its routine use in PTCA.
The existence and importance of excitement in gambling, the effects of runs of wins and losses on gambling behaviour and the relationships of both with sensation-seeking were investigated using samples of students and experienced gamblers in real and artificial gambling situations. Heart-rate increases, gambling behaviour and events such as 'stake decision time' were recorded as subjects played blackjack. Significant differences between real and artificial casinos were found for mean heart-rate increases over base-lines, for gambling behaviour and in the relationships between sensation-seeking, arousal and gambling in the two conditions. Doubt is cast on laboratory gambling as a valid analogue of the real gambling situation. Sensation-seeking and arousal are discussed briefly in relation to explanations of gambling.
Measures of cognitive, verbal, and functional performance obtained at widely separated time periods were examined for adults with Down syndrome. Comparisons of first and last test profiles for Raven Coloured Progressive Matrices, Peabody Picture Vocabulary Test, and Adaptive Functioning Index (Social Education) Test all demonstrated significant increases over a mean time span of 5 years. These increases could not be attributed to year of entry into program, history of institutionalization, or age of the individuals. The findings indicate that mental development of adults with Down syndrome continues well into the third and fourth decade of life.
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