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Biomedical subjects

D A Mary

Publications and source records attributed to D A Mary.

At least 19 recordsLinked to original sources
PubMed1992

Indices for detection of changes in cardiorespiratory fitness during exercise training in man.

A decrease in the elevation of the linear relation of heart rate on oxygen consumption (HR/VO2) throughout submaximal exercise testing has previously been used in individuals as an index of improvement in cardiorespiratory fitness after a moderate intensity training programme. In the present investigation, changes in HR/VO2 elevation and its variability were quantified and compared with those of other similar indices. These comprised changes in the level of oxygen consumption or heart rate attained at respiratory exchange ratio (R) of unity (VO2/R=1 or HR/R=1. In a first trial in six healthy volunteers, the decrease in HR/VO2 elevation caused by 16 weeks of training significantly exceeded measurement variability, and was associated with increases and decreases respectively in VO2/R=1 and HR/R=1. In a second trial in eight healthy volunteers, the three indices were obtained at four stages during the course of the 16 weeks of training, to grade the improvement in fitness. There were progressive changes in the three indices, the magnitude of which was greatest in the case of the HR/VO2 index. The findings make it possible quantitatively to obtain a graded measure of improvement in fitness during exercise training as indicated by the magnitude of decreases in HR/VO2 elevation.

Adult↗
PubMed1992

Haemodynamic effects of distension of the descending colon in anaesthetized dogs.

1. This study was undertaken to determine whether distension of the descending colon in anaesthetized dogs reflexly affects the heart rate, arterial blood pressure or the left ventricular inotropic state. 2. Experiments were performed on twenty-six dogs, which were anaesthetized with sodium pentobarbitone and artificially ventilated. A segment of the distal descending colon was isolated and was distended with warm Ringer solution at a steady intraluminal pressure. 3. In each animal, distension of the colon caused an increase in heart rate and aortic blood pressure. The response of an increase in heart rate was augmented by preventing changes in aortic blood pressure, and was graded in seven dogs by step increments in the distending pressure. In the same animals, distension of the colon always caused a small increase in left ventricular (dP/dt)max at constant heart rate and aortic blood pressure. 4. In four of the twenty-six dogs, cutting the pelvic nerves did not abolish the observed responses to the distension. In seven of the twenty-six dogs, which included the four animals with sectioned pelvic nerves, cutting the hypogastric nerves completely abolished all the observed responses. 5. In thirteen of the twenty-six dogs, propranolol or bretylium tosylate completely abolished the reflex increases in heart rate and left ventricular (dP/dt)max, and phentolamine or bretylium tosylate abolished the reflex increase in aortic blood pressure. 6. These results showed that distension of the colon reflexly increased the heart rate, arterial blood pressure and left ventricular inotropic state. These reflex responses were mediated by sympathetic effects and their afferent limb involved the hypogastric nerves.

Animals↗
PubMed1992

Efferent limb of the coronary vasoconstrictor reflex elicited by distension of the descending colon in anesthetized dogs.

Distension of the descending colon elicits reflex coronary vasoconstriction. To study the efferent branch of this reflex, experiments were performed on 5 dogs anesthetized with pentobarbitone. A pouch was formed from the distal 15 cm of the descending colon and distended at constant pressure (54 +/- 8.9 mmHg) with warm Ringer solution from a pressurized bottle. During distensions of the colon, arterial blood pressure and heart rate were kept constant by the withdrawal of blood and pacing of the heart, respectively. Experiments were performed before and after intravenous bretylium tosylate (10 mg/kg), a compound which prevents the outflow of catecholamines from the sympathetic postganglionic neurons. Before chemical sympathectomy, colon distension at constant heart rate and blood pressure caused a decrease in mean coronary blood flow by 7 +/- 3.3% (mean +/- SD, p less than 0.0005). This response was abolished after the administration of bretylium (-0.07 +/- 0.95%, p greater than 0.40). We conclude that the efferent branch of the reflex coronary vasoconstriction elicited by colon distension is through sympathetic nerves.

Animals↗
PubMed1991

The effect of distension of the urinary bladder on coronary blood flow in anesthetized dogs.

To determine whether distension of the urinary bladder reflexly affects coronary blood flow, experiments were performed in eleven dogs anaesthetized with sodium pentobarbitone. Both ureters were cannulated and the urinary bladder was distended with warm Ringer solution at a steady intravesical pressure. Arterial blood pressure was prevented from changing by a pressurized reservoir of warm Ringer solution connected to the femoral arteries. Coronary blood flow was measured with an electromagnetic flowmeter positioned around the origin of the left circumflex coronary artery. When the reflex increase in heart rate was prevented by atrial pacing in seven dogs, distension of the urinary bladder always caused a decrease in mean coronary blood flow. Similar results were obtained in all eleven dogs after administration of propranolol. The decrease in mean coronary blood flow was significantly reduced by atropine or bilateral cervical vagotomy, and was abolished by bretylium tosylate. The results showed that distension of the urinary bladder reflexly decreased mean coronary blood flow, a response involving efferent cardiac vagal and sympathetic pathways.

Animals↗
PubMed1991

The efferent mechanisms of reflex hemodynamic responses to distension of the descending colon in anesthetized dogs.

We have recently shown that distension of the descending colon in anesthetized dogs causes reflex increases in heart rate, aortic blood pressure and the maximal rate of rise of left ventricular pressure, involving afferent pathways in the hypogastric nerves. In this study we have examined the efferent mechanisms involved in those responses. The descending colon was distended using Ringer solution at constant pressure in 13 anesthetized dogs. As previously shown, distension of the colon caused an increase in aortic blood pressure, heart rate and the maximal rate of rise of left ventricular pressure. The increase in the aortic blood pressure was abolished by either bretylium tosylate or phentolamine. Propranolol or bretylium tosylate abolished the increases in heart rate when changes in the aortic blood pressure were prevented, and abolished the increases in the maximal rate of rise of left ventricular pressure when the increases in heart rate were also prevented. These results indicate that the reflex increases in heart rate, arterial blood pressure and the maximal rate of rise of left ventricular pressure involved efferent sympathetic pathways.

Animals↗
PubMed1979

Diagnostic value of routine exercise testing in hospital patients with angina pectoris.

A group of patients with angina pectoris were investigated prospectively using a simple and well-recognised exercise test protocol, and S-T segment displacements during exercise were correlated with the results of coronary arteriography. Definitive exercise results in 100 patients correlated well with findings on coronary angiograms: 69 out of 70 patients with positive exercise test results had significant coronary disease on angiography, while 23 out of 30 with negative exercise test results had no significant coronary disease. In six patients a period of physical training changed indeterminate initial tests to definitive ones after the training. These results show that the use of a widely available exercise test and a light physical training programme, with rigid adherence to the protocol, can reduce the overall demand on coronary arteriography.

Adult↗
PubMed1979

Echocardiographic pattern of posterior mitral valve leaflet movement after mitral valve repair.

The pattern of movement of the posterior leaflet at the time of opening of the stenosed mitral valve has been described as either anterior or posterior in direction. In 32 patients who underwent mitral annuloplasty, the anatomical features of the mitral apparatus were correlated with the postoperative echocardiographic pattern of movements of the posterior leaflet. Anterior movement of the posterior leaflet was associated with extensive disease of this leaflet, and posterior movement with minimal disease. No relation was found between valve orifice or anterior leaflet mobility and the pattern of movement of the posterior leaflet.

Adult↗
PubMed1979

Scanning esophageal impedance probe for measurement of luminal cross section.

A scanning esophageal probe for measuring luminal cross section is described. Current is injected into electrode assemblies so that a variable voltage output directly proportional to interelectrode impedance and inversely proportional to cross-sectional area of the medium around the electrodes may be measured. The device is capable of measuring the cross section of glass cylinders. It was used in one esophagus to measure the cross-sectional area of different sizes of swallowed bolus. The probe offers a safe and repeatable method of studying dynamic changes in luminal dimensions of the esophagus.

Electrodes↗
PubMed1977

Sequential hemodynamic studies in patients having aortic valve replacement with the Ionescu-Shiley pericardial xenograft.

Sequential hemodynamic studies were performed in 13 patients having aortic valve replacement with glutaraldehyde-stabilized pericardial xenografts. The investigation done preoperatively was repeated twice in all patients at mean intervals of 9.9 and 42.2 months following valve replacement. Annulus diameters of the valves were 19, 23, and 25 mm. Between the preoperative and the first postoperative investigation there was a significant increase in cardiac index (p less than 0.05) and a significant reduction in both pulmonary wedge and left ventricular end-diastolic pressures (p less than 0.01). At the first postoperative study the mean ejection systolic gradient across the three sizes of aortic pericardial xenograft was 7, 15.7, and 8.4 mm Hg at rest and 10, 19.6, and 13.7 mm Hg on exercise, respectively. The corresponding surface areas of the three valve sizes were 1.1, 1.5, and 1.62 cm2 at rest and 1.4, 2.1, and 2.03 cm2 on exercise. There was no significant change in any of these measurements between the first and the second postoperative study. The results have shown considerable postoperative hemodynamic improvement, insignificant transvalvular pressure gradients, and maintenance of the functional integrity of the pericardial xenograft up to 56 months following valve insertion.

Adult↗
PubMed1977

Atrial receptors in the dog and rabbit.

1. Action potentials were recorded from slips of the cervical vagi in anaesthetized dogs and rabbits. Single functional units with atrial patterns of discharge (Paintal Type A, B and intermediate) were obtained and then attempts were made to alter (i.e. convert) their patterns of discharge. Finally the points of origin of these action potentials were located.2. Thirty unselected units were investigated in thirty dogs. Twenty-seven of these were located in the endocardium of the vein-atrial system and the ratio of the type A, type B and intermediate type receptors was 1:16:10; three units were located elsewhere in the chest. Conversion of the pattern of discharge was achieved in twenty of the twenty-seven units; conversion was achieved in the single type A unit.3. In a second series of experiments in dogs, eight Paintal Type A units were selectively studied in fifteen animals. Four of these were located in the endocardium and all were converted. The remaining four were located outside the endocardium and conversion could not be achieved in two of these. Thus in the entire investigation, the ;type A' units which could not be converted were all located at sites other than the atrial endocardium.4. In the corresponding unselected study in the rabbit, eleven units were studied in eleven animals. Nine of these units were located in the atrial endocardium and the ratio of the type A, type B and intermediate type receptors was 2:1:6. Conversion was achieved in both type A units, the sole type B unit and two of the intermediate units. One of the two units found outside the atrial endocardium was a ;type A' unit and could not be converted.5. The present investigation has shown that the atrial receptors with a Paintal Type A pattern of discharge are relatively rare in both dogs and rabbits. Conversion of the pattern of discharge is a relatively common phenomenon. Evidence for the proposition that there is one basic type of atrial receptor whose pattern of discharge is determined by its precise location in the vein-atrial system is discussed.

Action Potentials↗
PubMed1977

Heart valve replacement with the Ionescu-Shiley pericardial xenograft.

Between March, 1971, and September, 1975, glutaraldehyde-stabilized pericardial xenografts were used for single valve replacement in.212 patients (142 aortic, 67 mitral, and three tricuspid). The 195 operative survivors were observed for a total of 5,926 months over a period 6 to 61 months (mean 30). actuarial analysis of late results indicates an expected survival rate at 5 years of 92.3 per cent for patients with aortic and 91.1 per cent for patients with valve replacement. The rate of systemic embolism has been 0.62 episodes per 100 patient years for the aortic and 2.48 episodes per 100 patient years for the mitral group in the absence of anticoagulant treatment. All six emboli occurred early postoperatively, were trivial or mild, and left no sequelae. Symptomatically, 96.7 per cent of patients are now in Class I and 3.3 per cent in Class II (N.Y.H.A.). Maintenance of structural and functional integrity of the glutaraldehyde-stabilized pericardial zenograft was demonstrated by histologic and hemodynamic investigations. Catheterization showed substantial circulatory improvement in both patients with aortic and those with mitral replacement. The transaortic gradients were negligible (8 mm. Hg at rest and 17.5 mm. Hg during exercise). The available indicates that results of valve replacement withpericardial xenografts. Over this period of follow-up, compare very favorably with those obtained with other available prostheses and tissue valves.

Adolescent↗
PubMed1976

The effect of premarin on blood loss attending open heart surgery.

Premarin was administered prophylactically to every other patient in a series of 148 consecutive cases of open intracardiac surgery. Of these, 132 patients were matched to analyse the results of Premarin administration and postoperative blood loss. There were 67 patients who were given Premarin and 65 who did not receive this drug; both groups were identical in respect of age and sex. Matching was undertaken according to history of previous cardiac operations and anticoagulation, type of valve surgery or repair of congenital anomaly, duration of perfusion, platelet count and the use of fresh blood and epsilon-aminocaproic acid in the postoperative period. The prophylactic use of Premarin was not associated with a reduction in postoperative bleeding.

Adolescent↗