Biomedical subjects
A Page
Publications and source records attributed to A Page.
Alterations in femoral and acetabular bone strains immediately following cementless total hip arthroplasty: an in vitro canine study.
Alterations in strain patterns in both the femur and acetabulum of the dog, due to cementless total hip arthroplasty (THA), were evaluated by monitoring cortical bone strains before and immediately following implantation of components, using an accurate in vitro jig, simulating the loading of the canine hip in vivo. Femoral arthroplasty with straight stem, canal-filling, femoral components, made of titanium-based alloy, led to a statistically significant reduction of proximal femoral bone strains, with proximal medical compressive strains reduced, on average, to only 22% of intact strain magnitude (p less than 0.01), even though the prostheses contained collars and were not fixed with cement. Strain alterations on the acetabulum, following cementless THA, were more complex and variable. Laterally, a significant decrease (p less than 0.01) in periacetabular strains to between 20 and 60% of the intact state was observed, while medial wall strains varied inconsistently after arthroplasty. These strain alterations reflect major changes in mechanical loading of both the femur and acetabulum immediately following cementless THA, using components similar to those used clinically in humans. Major reductions in strains on the proximal femur occurred with cementless femoral components, while the change in strains on the acetabulum were variable, and could be a result of variations in fit and placement of components inherent even in well-controlled implantation techniques. The physiologic in vitro loading of the canine femur with the pelvis, used to obtain these data, can be applied to future investigations exploring stress transfer around uncemented components and the relationship of stress transfer to morphological changes of bone, in the canine model.
A chest radiograph scoring system to predict chronic oxygen dependency in low birth weight infants.
The usefulness of a chest radiograph scoring system to predict chronic oxygen dependency (oxygen dependency at 36 weeks post conceptual age) was determined in 40 infants with a median gestational age 27 weeks (range 24-32 weeks). The scoring system assessed the appearance of the preterm infant's chest radiograph taken at one month of age, and graded the radiograph according to lung volume, the presence of opacification, cystic elements and interstitial change (maximum score 24). Infants who were chronically oxygen dependent had significantly higher scores (median 9, range 7-20) than those not oxygen dependent (median 3, range 0-13, P less than 0.01). All nine chronically oxygen dependent infants had a score greater than 6, in comparison with only two of 31 infants not chronically oxygen dependent (P less than 0.01). A chest radiograph score of 6 thus had a sensitivity of 100% and specificity of 93.5% in predicting chronic oxygen dependency.
Purification and characterisation of cysteine proteinases from human osteoclastomas.
Explore the source record for details and available documents.
Cardiac changes in experimental hyperthyroidism in dogs.
Injection of triiodothyronine (T3) (1 mg/kg per day subcutaneously for 14 days) to 10 healthy dogs produced a hyperthyroid state characterised by high serum T3 concentrations, hypokalaemia, hyperactivity, loss of weight, diarrhoea and thirst. Electrocardiographic measurements showed that these dogs had an increase in heart rate of 63 +/- 11 beats/min with a significantly increased T wave amplitude without changes in R wave amplitude. Echocardiographic measurements showed no changes in fractional shortening and no evidence of ventricular hypertrophy, in contrast to reports in humans, cats and rats. However, the smooth muscle of the coronary arteries was markedly hypertrophied, which may cause a decrease in myocardial perfusion.
Chest radiograph scoring system for use in pre-term infants.
A scoring system to characterize the pre-term infant's chest radiograph appearance has been evaluated. Chest radiographs taken at 1 month of age in 20 infants (median gestational age 27 weeks) were scored according to abnormalities of lung volume, presence of opacification, interstitial changes and cystic elements (maximum score 17). The median score was 4 (range 1-14); the highest scores were for the only infants with cystic elements and/or interstitial changes on their chest radiographs. The scoring system documented accurately the severity of neonatal respiratory distress; the highest scores occurred in those infants requiring the most prolonged respiratory support, i.e. ventilated beyond 1 week of age (p less than 0.01) and oxygen-dependent beyond 1 month (p less than 0.01). It was also a useful predictor of chronic respiratory problems, with an 88% sensitivity in the detection of infants with the most severe lung function abnormalities at 6 months of age.
[Muckle-Welles syndrome (urticaria, deafness and amyloidosis). A new familial case].
Explore the source record for details and available documents.
A second look at the effects of supportive follow-up on smoking cessation.
In 1982 a report in CMAJ (1982; 126: 127-129) indicated that the addition of supportive follow-up appointments in a family practice increased the 6-month cigarette abstinence rate from 12% to 23%. We reanalysed the data by means of recognized standards for treatment success and found little evidence that the treatment had any reliable effect on attempts to quit that lasted at least 3 months: 8.5% and 4.8% of the groups with and without supportive follow-up respectively abstained for more than 3 months. We discuss a problem of the experimental design (longer evaluative follow-up for the control group than for the treatment group) and cost-benefit issues.
A non-linear regression program in BASIC for estimating Km and Vmax.
This paper gives a program in BASIC for calculating the kinetic parameters Km and Vmax for an enzyme reaction from a set of paired values of reaction velocity at given substrate concentrations. An initial estimate of the two parameters is made using a weighted linear regression, these values are then used in an iterative process to fit the data to the Michaelis-Menten equation and give final values of Km and Vmax with their associated standard errors.
A reappraisal of the relationship between arachnoid cysts of the middle fossa and chronic subdural haematoma.
It has been increasingly recognised that patients with arachnoid cysts of the middle fossa appear more susceptible to the development of subdural haematomas. Seven patients with arachnoid cysts of the middle fossa and associated subdural haematomas are presented. Intra-cystic haemorrhage, masking the presence of an arachnoid cyst on computed tomography (CT) is highlighted. Repeat of CT scanning in young patients with subdural haematomas in the absence of severe trauma is recommended. Two theories are proposed to account for the observed susceptibility to the development of subdural haematomas in these patients.
Simple system for portable positive end-expiratory pressure.
Explore the source record for details and available documents.
[Obstructive cardiomyopathy of the left ventricle: prolonged treatment using beta-blockers. Haemodynamic, cineangiocardiographic and echographic study (author's transl)].
Explore the source record for details and available documents.
[Intravenous trinitroglycerin in the treatment of pre-infarction syndrome. Preliminary results (author's transl)].
Intravenous trinitroglycerine (IV TNT) was used in 17 patients with myocardial pre-infarction syndrome defined by the presence of prolonged spontaneous attacks of attacks of angina, with electrocardiographic changes, persisting despite medical treatment with beta-blockers and oral nitrite derivatives. Seven patients had chronic angina, 7 had angina of recent onset and 3 patients had early post-infarction angina. IV TNT was used for 3 to 11 days at a mean dose of 40 micrograms/mn in 11 patients and 8 micrograms/mn in 6 patients. In the latter, cardiac output and pulmonary pressures were measured. IV TNT made it possible to decrease or stop angina attacks in all the patients except one. There was no significant variation in heart rate and mean blood pressure fell by 8 mmHg (p < 0.001). Cardiac index was maintained despite a fall in capillary pressure of 4.1 mmHg (p < 0.01). Coronary arteriography was performed in 16 cases, with circulatory assistance in 4 patients. Thirteen patients were treated by surgical revascularisation, with two operative deaths. IV TNT appeared to be effective and well tolerated treatment in these particularly severe forms of unstable angina.
[Antiarrhythmic action of disopyramide: a study of plasma levels].
The action of dysopyramide was studied in 13 patients, 11 with ventricular and 2 with supraventricular arrhythmias. The drug was given parenterally at first and then by mouth. The patients were monitored with an arrhythmia counter and the plasma levels of disopyramide measured throughout the treatment period. The plasma level was stable at about 4 micrograms/ml during the different phases. Toxic levels of 10 microgram/ml were observed in 1 patient in renal failure. The antiarrhythmic action was very effective (70% success), especially on the ventricular arrhythmias. Two of the four patients who failed to respond to treatment had low, non-therapeutic plasma levels. The dosage should be adapted with respect to the patient's weight and renal function.
[Hemodynamic effects of mexiletine].
The haemodynamic changes caused by intravenous mexiletine were studied in 12 patients. Initially the drug was given rapidly at the rate of 3 mg/kg/min for 10 minutes and then slowly at a rate of 0,06 mg/kg/min for 30 minutes. The plasma Mexiletine level measured after 20 minutes was used to divide the series of patients into two groups: in Group A the level was over 0,7 g/ml (0,961 +/- 0,109 microgram/ml) whilst in Group B the level was only 0,547 +/- 0,101 microgram/ml. The mean aortic pressure, heart rate and left ventricular end diastolic volume did not vary significantly in the two groups. The left ventricular end diastolic pressure rose, and the cardiac index and the ejection fraction fell in Group A. The indices of left ventricular contractility fell in all patients of the start of the injection. This depression only persisted to the end of the injection in Group A. Mexiteline did not cause significant changes in post extrasystolic potentialisation in the 5 cases in which this phenomenon was studied.
[Hemodynamic effects of oral dihydralazine and sublingual isosorbide dinitrate, alone and in combination in chronic heart failure].
Explore the source record for details and available documents.
[Importance of sequential atrioventricular pacing in obstructive myocardiopathy with atrioventricular block].
A case of atrioventricular block (AVB) complicating hypertrophic obstructive cardiomyopathy is reported and analysed with respect to the results of cardiac catheterisation. The installation of 2nd degree AVB was associated with an increase of the intraventricular pressure gradient from 36 to 128 mmHg. This aggravation was related to the lenghtening of diastole which lowered the aortic diastolic pressure and allowed a more forceful ventricular contraction with a reduction in the calibre of the intraventricular stenosis. The sudden lenghtening of diastole also led to an increased contractility of the following systole. In complete AVB the increased gradient was related to a reduction in ventricular volume secondary to the loss of atrial systole. The 33 mmHg pressure gradient disappeared when spontaneous atrial systole or an atrial systole provoked by sequential atrioventricular pacing preceded ventricular contraction. Sequential atrioventricular pacing would seem to be the most appropriate pacing technique in hypertrophic obstructive cardiomyopathy complicated by complete AVB.