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Biomedical subjects

C Breckenridge

Publications and source records attributed to C Breckenridge.

13 recordsLinked to original sources
PubMed2001

New wheelie aid for wheelchairs: controlled trial of safety and efficacy.

OBJECTIVE: To test hypotheses that people learning to perform aided wheelies (AW) with a new self-deploying wheelie aid (WA) (1) are safer than those who use the conventional wheelie (CW), (2) are more successful at learning the skills, (3) learn more quickly, and (4) find such skills less difficult. DESIGN: Randomized, controlled study. SETTING: Wheelchair obstacle course. PARTICIPANTS: Forty-two subjects (12 wheelchair users, 30 able-bodied) randomly assigned to the CW (n = 23) or AW (n = 19) groups. INTERVENTIONS: We performed static tests on a WA-modified wheelchair occupied by a test dummy. We also attempted to teach each subject to perform a set of 14 wheelie-related skills. MAIN OUTCOME MEASURES: Visual analog scale (VAS) of safety, percentage of subjects able to learn the skills, the time required, and subjective difficulty scores (from 1 for "very easy" to 5 for "very difficult"). RESULTS: Up to 11.2 degrees of antitip-device stability was available without the WA extending beyond the rearmost aspect of the rear wheel in the resting position. For the CW and AW groups, the mean +/- standard deviation VAS safety scores were 43% +/- 27% and 98% +/- 2% (p <.0001), respectively; the overall success rates were 93% and 96% (p =.079), respectively; the mean times required to learn a skill (in 5-min increments) were 1.56 +/- 1.08 minutes and.72 +/-.35 minutes (p =.002), respectively; and the mean difficulty scores were 2.94 +/-.38 and 2.23 +/-.34 (p <.0001), respectively. CONCLUSIONS: The new WA provides stability and wheelie-like function without interfering with maneuverability. Although both groups were equally successful, learning to perform AWs is safer, faster, and less difficult than learning CWs.

Equipment Design↗
PubMed1995

Comparison of Lp(a) concentrations and some potential effects in hemodialysis, CAPD, transplantation, and control groups, and review of the literature.

Apolipoprotein (a)-Lp(a)-is reported to be an independent risk factor for coronary artery disease and for hemodialysis (HD) access occlusion. Homology with plasminogen may predispose to thrombosis. High concentrations usually have been reported in patients on HD and on continuous ambulatory peritoneal dialysis (CAPD), but near-normal values in many kidney transplants (TP). We used Pharmacia immunoradiometric assay in 52 patients on HD, 58 on CAPD, 94 after TP, and 56 controls. The Lp(a) mean levels for CAPD, HD, TP, and control groups were 738, 647, 348, and 368 U/l and the medians were 542, 537, 96 and 143 U/l, respectively. The means and medians for CAPD and HD were significantly greater than those for TP and controls (p < 0.003 for means and < 0.005 for medians). We found no significant difference between: (1) Lp(a) means or medians comparing HD and CAPD or TP and controls; (2) Lp(a) means for the 33 patients with insulin-dependent diabetes mellitus and the 171 without; (3) number of occlusions of HD fistulae or grafts in patients with high Lp(a) values and without; (4) mean Lp(a) for CAPD patients on gemfibrozil and also for TP patients on 3-hydroxy-methylglutaryl coenzyme 1 reductase inhibitors, or diet alone, before and after treatment, and (5) mean Lp(a) values for HD and CAPD patients with and without myocardial infarction. Lp(a) did not correlate significantly with fractional shortening or left ventricular end systolic or diastolic diameter by echocardiogram or with ejection fraction. For TP patients, Lp(a) and serum creatinine correlated (p = 0.004), and mean Lp(a) for 71 TP on ciclosporin A exceeded that for the other 23 patients (p < 0.03). Lp(a) fell in 13 of 14 patients after TP (mean fall 77%). The dominant Apo(a) isoform in 10 of 13 patients on CAPD or HD with high Lp(a) values was the equivalent of S2 (Utermann). Lp(a) in HD or CAPD is often elevated and regulated by both genetic and renal failure factors, but falls after TP with return of renal function and mainly genetic regulation. Lp(a) was not a risk factor for coronary artery disease in HD or CAPD patients and did not fall significantly with two drugs or diet.

Adolescent↗
PubMed1986

A subchronic inhalation toxicity study of a Matacil formulation in the albino rat.

The subchronic toxicity of a new formulation of Matacil (aminocarb) was assessed by exposing male and female Sprague-Dawley rats via a nose-only technique to a respirable (2.0- to 4.1-microns diameter) aerosol at chamber concentrations of 22.5, 45, and 90 micrograms of insecticide/liter of air for 2 hr/day for 30 consecutive days. Control groups were exposed to a vehicle aerosol or to room air. Randomly selected rats of each group were bled after 8, 15, and 30 days of treatment, and after a 30-day recovery period. Routine clinical laboratory investigations (hematology, blood chemistry, and urinalysis) were conducted during treatment. Other parameters measured included body weight, feed intake, plasma, red blood cell count, brain cholinesterase activity, and hepatic and renal carboxylesterase activities. Organ weights were recorded at necropsy and routine histopathological evaluation was performed. Mild muscle tremors were observed occasionally in the intermediate- and high-dose groups. Treated females, but not males, demonstrated a dose-dependent inhibition of cholinesterase activity, though within treatment groups, there were no differences associated with the number of days of treatment. Enzyme values had returned to baseline levels by 30 days post-treatment. Hepatic carboxylesterase activity was significantly reduced only in male rats at the highest dose. Lung weights were increased in vehicle and Matacil-treated groups. Histological studies indicated that these changes were a nonspecific tissue response to a heavy burden of an oil-based irritant, which was partially resolved by 30 days post-treatment. The results showed that, at the concentrations tested, the formulation produced little or no acute symptoms and minimal long-term sequellae.

Acetylcholinesterase↗
PubMed1978

Multi-laboratory comparison of three heparin-Mn2+ precipitation procedures for estimating cholesterol in high-density lipoprotein.

Plasma high-density lipoprotein is commonly estimated by measuring the cholesterol remaining in plasma supernatant solutions after other lipoproteins, which contain apolipoprotein B, are precipitated with heparin and Mn2+. The method (method I) now in use by the Lipid Research Clinics, in which Mn2+ is at 46 mmol/liter final concentration, is reasonably accurate, but precipitation and sedimentation of lipoproteins other than high-density lipoproteins is often incomplete. We evaluated two modifications of method I. In method II, the Mn2+ concentration was doubled; the second modification (method III) included the increased Mn2+ concentration in a combined heparin Mn2+ reagent, decreased sample volume (2 ml), and a shorter incubation time (10 min at room temperature). The percentages of samples with turbid supernates (i.e., incomplete sedimentation) by methods I, II, and III were 9, 3, and 2%, respectively. Among non-turbid supernates, the percentages of samples containing measurable apolipoprotein B (incomplete precipitation) were 79, 19, and 16%, respectively. We conclude that method III is the most convenient and accurate of the three procedures.

Chemical Precipitation↗
PubMed1978

Some preliminary observations on the effects of kola nut on the cardiovascular system.

The prevalence of kola nut chewing and the effects attributed to it are briefly reviewed. Except for a generalisation that its effects are probably due to its caffeine content, no attempts have been made to quantify its specific actions. Preliminary observations on the cardiovascular system of the cat show that aqueous extracts of the nut evoke a dose dependent differential response - the 8 - 9% hypertensive effect of 0.01 ug - 1mg/ml doses contrasting with the 18--71% hypotensive response of 10--1000mgs/ml doses. Adrenergic receptor blockade showed no significant alteration of the response. With larger doses a bradycardia developed and cardiac arrythmias were observed as a terminal event. These results are compatible with the action of xanthines on the heart and peripheral vasculature. The possible role of the habitually chewed kola nut in the pathophysiology of cardiovascular disease and its implications have been briefly discussed.

Animals↗
PubMedDate not supplied

Six month inhalation studies of pirbuterol acetate aerosol in the beagle dog and squirrel monkey.

Groups of Beagle dogs and Squirrel monkeys were exposed to aerosols of pirbuterol acetate, a new bronchodilator at doses of 0, 200, 400 and 800 micrograms of pirbuterol/kg body weight daily for 6 months. Each group consisted of 4 dogs or 6 monkeys per sex. Dogs were exposed by face mask and monkeys were exposed by head only in a manifold. Plasma drug concentrations indicated that expected levels of drug exposure were achieved in both species. No significant alterations were revealed in physical appearance and body weights, hematological and blood biochemical analyses, urinalyses, ophthalmoscopy, assessment of cardiovascular status, pulmonary function or gross and histopathology. Examination of the respiratory tract showed no morphological changes that could be attributed to pirbuterol acetate inhalation.

Aerosols↗