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Biomedical subjects

B Haider

Publications and source records attributed to B Haider.

At least 19 recordsLinked to original sources
PubMed1996

Myocardial infarction postpartum in patients taking bromocriptine for the prevention of breast engorgement.

Three cases of myocardial infarction (MI) in women taking bromocriptine for milk suppression are presented. The incidents occurred in 1993 and 1994, the last only two weeks before the withdrawal of the drug from the American market as a drug suitable for ablactation. In one patient, the MI presented on the 12 day postpartum and was accompanied by signs and symptoms reminiscent to ergotism. Another mother suffered MI, accompanied by hypertension, six days after a vaginal delivery complicated by postpartum haemorrhage. The third patient began to take bromocriptine more than 2 weeks postpartum and died suddenly 24 days after her childbirth. To the knowledge of the authors, these are the 12th to 14th literary reports describing an apparent association between the use of bromocriptine for ablactation and the occurrence of MI in the puerperium.

Adult↗
PubMed1995

A double chamber system for producing constant radon concentration.

An experimental arrangement of a radon chamber with an intrinsic constancy of the relative radon concentration is described. The system consists of a reference chamber and an auxiliary storage chamber. The only active device is a timer-controlled pump or valve which feeds radon gas from the storage into the reference chamber. The switching pattern of the timer is extracted from model calculations and theoretically performs an exact compensation of the radon loss by radioactive decay. If the calculations are done in real time and online, every known external event influencing the radon concentration can be compensated. This paper presents a simple timer circuit and a computer code which generates the timer program. The influence of the air flow stability and the leakage of the chambers are discussed. It is planned to apply this theoretical approach to provide a constant radon gas concentration for an actual chamber.

Calibration↗
PubMed1994

Diabetic cardiomyopathy: experimental and clinical observations.

Heart failure, arrhythmia, or chest pain can be a consequence of diabetes independent of coronary disease or hypertension. Diastolic myocardial dysfunction is common, contributing to the high mortality during acute infarction. The authors discuss diabetic cardiomyopathy and its management.

Angina Pectoris↗
PubMed1990

Efficacy and safety of combinations of nitrendipine, atenolol, and hydrochlorothiazide in black hypertensive patients.

Twenty-four black hypertensive patients were studied in a randomized, double-blind trial of combinations of nitrendipine, atenolol, and hydrochlorothiazide. After six weeks, blood pressure was normalized in all three treatment groups, i.e. diastolic blood pressure less than 95 mmHg and a decline in diastolic blood pressure of at least 5 mmHg from baseline. The drug combinations containing hydrochlorothiazide were associated with higher incidence of metabolic abnormalities, especially hypokalaemia and hyperuricaemia.

Atenolol↗
PubMed1989

Effects of diabetes on myocardial perfusion in the atherosclerotic monkey.

We examined the influence of diabetes on the severity of coronary atherosclerosis, as judged by coronary morphometric and blood flow studies. Cynomolgus monkeys were fed a coconut-peanut oil mixture plus cholesterol to induce the plaque lesions of atherosclerosis in nondiabetic (group 2) and diabetic monkeys (group 3). Group 1 consisted of chow-fed controls. After 18 months of hypercholesterolemia, the animals were anesthetized to assess myocardial blood flow, by use of radioactive microspheres. Transmural and inner/outer wall flow ratios were normal in the two lipid-fed groups in the basal state. Vasodilation after adenosine (0.45 mg/kg/min IV) elicited a more than threefold rise of transmural blood flow in group 1, and a significantly reduced increment in groups 2 and 3. The blood flow ratio was not different from unity in group 1 but declined to 0.69 +/- 0.03 in group 2 and 0.69 +/- 0.06 in group 3, with similar decrements of heart rate and aortic pressure. In contrast to results in group 1, left ventricular filling pressure rose and velocity of contractile elements declined to a similar extent in groups 2 and 3 after adenosine, consistent with myocardial ischemia. Morphometric measurements as well as chemical analyses were performed on the three major coronary arteries. The degree of intimal thickening and increase of cholesterol and collagen content were comparable in groups 2 and 3. Thus, in this model the plaque lesions of atherosclerosis did not appear to be intensified by diabetes. Moreover, the responses to adenosine in terms of myocardial underperfusion and mechanical dysfunction were comparable in the two experimental groups.

Adenosine↗
PubMed1986

Metabolic fate of inhaled Co aerosols in beagle dogs.

Lung retention of 57Co in dogs after the inhalation of physically and chemically uniform particles of Co compounds was similar, indicating little biological variability. The retention of Co oxide particles ranging from 0.3 micron to 2.7 micron geometric diameter, however, depended markedly on their physicochemical parameters. Measuring the retention by a gamma camera, and analyzing excreta and blood samples enabled the distinction of different clearance pathways from the lungs particularly with the use of results of some metabolic studies. Particle dissolution was the predominant clearance pathway. Particle dissolution half-times ranged from 6 to 80 d proportional to the size of the particles. Organ analysis yielded information on the fate of the long-term burden of Co in the lungs and other organs. A fraction less than 10% of the initial lung burden was retained in the lungs of all dogs with a biological half-time of 400 d presumably after being transformed into a nonparticulate state. There were cellular structures in the tracheobronchial tree which accumulated Co significantly. These studies on dogs suggest the dose after human exposure to well-defined Co aerosols can be accurately estimated. Whereas risk assessment after the exposure to undefined aerosols containing radionuclides of Co will mostly be impossible because retention varies widely with the varying physicochemical properties of the aerosol particles.

Administration, Inhalation↗
PubMed1986

Arrhythmia susceptibility and myocardial composition in diabetes. Influence of physical conditioning.

Abnormal myocardial composition in diabetes mellitus has been described, but the effects on ventricular vulnerability have not been defined. We have assessed the susceptibility to arrhythmias in a canine model after 1 yr of mild diabetes induced by alloxan. Since physical conditioning can affect metabolic abnormalities in diabetes, this intervention has also been evaluated. Group 1 served as controls and groups 3 and 4 were diabetic. Animals in the latter group as well as nondiabetic controls of group 2 were exercised on a treadmill for the last 8 mo of the experiment. After 1 yr, anesthesia was induced with chloralose for vulnerability studies. The ventricular fibrillation threshold of 24.4 +/- 1.9 mA in group 3 was significantly less than in normals (45.1 +/- 2.2). Spontaneous arrhythmias were also more prevalent in diabetics during acute ischemia (group 3-A). Increased ventricular vulnerability after epinephrine infusion was present in the sedentary diabetes despite normal ventricular function responsiveness. In a superfused preparation of myocardium, resting membrane potential and action potential amplitude were normal in diabetics, and beta-adrenergic stimulation shortened repolarization more than in controls. Myocardial collagen concentrations, which included an interfibrillar distribution on morphologic examination, were increased in group 3. In the trained diabetics of group 4 the basal vulnerability thresholds and responses to epinephrine were normal. While myocardial collagen levels were normal, cholesterol and triglyceride increments persisted. Thus, in mild experimental diabetes, enhanced susceptibility to arrhythmias exists; this susceptibility may be based on a combination of nonhomogenous collagen accumulation affecting local conduction and increased electrophysiologic sensitivity to catecholamines.

Action Potentials↗
PubMed1985

Total and regional lung retention of monodisperse cobalt compound aerosols after a single inhalation.

After a single short term inhalation of monodisperse cobalt compound aerosols with preselected physical and chemical parameters the long term retention in beagle dogs is determined measuring their radioactive Co-57 label by a gamma camera. Additionally the major clearance pathways are estimated by excretion analyses. The biological variability of the lung retention is small but it depends clearly on the physiochemical properties of the inhaled aerosol particles. The predominant clearance mechanism in the lung is a moderate dissolution process depending on the specific surface area of the particles. So cobalt oxide particles with an adjustable solubility in the lung can be used for studies of distinct dissolution processes in the lung. Using a gamma camera the dynamics of particle accumulation in the tracheobronchial lymph nodes and the subsequent clearance are analysed on single dogs.

Aerosols↗
PubMed1984

Effects of beta-adrenergic inhibition on scar formation after myocardial infarction.

In view of clinical interest in the efficacy of beta-adrenergic blockade during acute myocardial infarction (AMI), we have determined the long-term effect of therapy on scar formation after experimental myocardial ischemia. Intact anesthetized dogs underwent acute occlusion of the left anterior descending coronary artery, by means of a balloon catheter, which permitted monitoring of the aortic-peripheral coronary artery pressure gradient during the 4-hour period of balloon inflation. Practolol administration was begun 15 minutes after the onset of ischemia in group A. Control animals (group B) received procainamide to approximate the antiarrhythmic action of beta blockade. Only group A exhibited significant reduction in the ST segments during acute ischemia. Chronic therapy was maintained for 1 month and the mature scar formed in the myocardium was assessed after 4 months. The extent of subendocardial scar was similar in both groups but subepicardial scar formation was significantly less in group A. There was also a significant decrease in the percentage of total myocardium involved with scar in this treatment group. Although thinning of the left ventricular wall was similar for both groups in the central scar region, this process was significantly reduced at the lateral margin in group A. Thus, specific beta-receptor blockade during acute myocardial ischemia and sustained during the repair process can result in a reduced quantity and altered distribution of mature scar.

Adrenergic beta-Antagonists↗
PubMed1983

Intra-aortic balloon counterpulsation in an experimental model of myocardial infarction.

The efficacy of intra-aortic balloon counterpulsation for heart failure during acute myocardial infarction has been controversial, and early intervention has been suggested as crucial. We have examined this type of therapy in the intact anesthetized dog during complete occlusion of the proximal left anterior descending coronary artery with a balloon-tipped catheter. Group 1 (n = 8) represented untreated animals undergoing four hours of ischemia. Group 2 (n = 7) consisted of animals undergoing counterpulsation with an intra-aortic balloon after 15 minutes of ischemia. Initially, stroke volume and the mean rate of left ventricular fiber shortening were similarly diminished in both groups, while filling pressure rose proportionately. After four hours, the mean rate of fiber shortening, stroke volume, and left ventricular filling pressure rose to a greater extent in untreated compared to treated animals (p less than 0.01). The degree of swelling in ischemic tissue and the number of sites with ST-segment elevation and their sums were comparable in the two groups. Thus, intra-aortic counterpulsation applied early in the course of ischemia can improve global left ventricular dysfunction without affecting the extent of myocardial injury.

Animals↗
PubMed1983

Emetine-induced cardiomyopathy in rabbits.

A correlative electrocardiographic and ultrastructural study of myocardium in rabbits, administered 1 mg/kg of emetine hydrochloride intramuscularly for 5 successive days of a week over 2 to 4 week period, was conducted. The study revealed electrocardiographic changes and a spectrum of ultrastructural lesions involving myocardial cells and interstitial neural elements. The severity of these lesions was related to the cumulative dose of the drug. Myocardial cell lesions were characterized by fatty infiltration, increase in glycogen content, myofibrillolysis, focal cytoplasmic degeneration, contraction-band necrosis and intercalated disc disjunction, herniation and fragmentation of the close junction (nexus). Neural lesions included mesaxonal and axonal myelinoid bodies and alterations in dense-core vesicles of biogenic amine containing cells. Atrial myocardial lesions were relatively fewer and less severe than those in the ventricular myocardium. The myocardial cell and neural lesions may be inter-related and underlie the pathogenesis of emetine-induced cardiomyopathy.

Animals↗
PubMed1981

Myocardial composition and function in diabetes. The effects of chronic insulin use.

This study was undertaken in an animal model of mild diabetes to determine if provision of chronic insulin replacement during postprandial hyperglycemia may modify the abnormalities of myocardium. Group 1 served as controls with normal glucose tolerance by intravenous testing. Two additional groups were made diabetic with low doses of alloxan. Diabetic animals of Group 2 were untreated (n = 6). Group 3 animals (n = 6) received regular insulin daily to reduce postprandial hyperglycemia. After one year with maintained body weight, the animals were studied in the intact anesthetized state using the indicator dilution technique for left ventricular volume determinations. Basal left ventricular function and contractility were similar to normals in both diabetic groups. During intraventricular infusion of saline, end-diastolic pressure rose to higher levels in untreated diabetes (14.8 +/- 2 mm Hg) than normals (8.8 +/- 0.84), despite similar basal levels. Insulin treatment was associated with higher filling pressures than in group 1 as well as reduced end-diastolic volume response. Collagen concentrations were enhanced an average of 50% in layers from the inner to outer myocardium in both untreated and treated diabetics, associated with sodium and water accumulation. Since hypertrophy was not present, the diminished compliance appeared related to increased collagen levels. On electron microscopy, the subcellular organelles of the cardiac cell appeared normal in both diabetic groups. Thus, collagen accumulation and abnormal myocardial function in this model of diabetes is not affected by control of postprandial hyperglycemia, but a potential role for sustained hormone replacement is not excluded.

Animals↗
PubMed1981

Ethanol abuse and heart disease.

The toxic effects of chronic ethanol abuse on cerebral and hepatic function have long been recognized. The role of ethanol abuse as an etiologic factor in heart disease is less clear and is often attributed to coexistent malnutrition. However, malnutrition has been dissociated from ethanol use in many patients with congestive cardiomyopathy. Studies in various animals provide major support for the role of ethanol as a toxic agent when used in large amounts for a prolonged period. Abnormalities that result from ethanol in test animals include depression of left ventricular performance and metabolic and morphologic changes that parallel the changes in human alcoholics with subclinical mechanical dysfunction of the heart, such as symptomatic cardiac arrhythmias, particularly during intensive alcohol ingestion. What causes the progression to heart failure or arrhythmias is not known, but several factors may be involved. These include, particularly in males, the cumulative effects of ethanol alone or after intensified drinking episodes, excessive exposure to trace metals or superimposed infection. The low prevalence of clinical nutritional deficiency in patients with alcoholic cardiomyopathy and the apparent infrequency of heart failure in patients with cirrhosis or neuropathy supports the view that the cardiac abnormality is often not dependent on malnutrition. Clinical data indicate that the cessation of alcohol intake may reverse the disease or interrupt its progression in many patients. However, the pathogenetic process may continued unabated in some who become abstinent.

Alcoholism↗
PubMed1981

Depression of myocardial function during acute pancreatitis.

The left ventricular function of 24 patients with acute pancreatitis was studied noninvasively using systolic time intervals. Seven of the 24 patients were reevaluated 4-40 days following the onset of acute symptoms. During the acute phase the PEP/LVET ratio was significantly prolonged to 0.470 +/- 0.031 and later declined to 0.376 +/- 0.017 (P less than 0.01). The convalescent value is similar to the low grade abnormality found in noncardiac alcoholics without pancreatitis (0.381 vs 0.312 in age-matched normals). Since serum electrolytes were normal, serum cardiac isoenzymes were not elevated and there was no evidence of volume depletion in the initial stages, the transient cardiac depression produced by acute pancreatitis may be mediated by the postulated myocardial depressant factor from the pancreas.

Acute Disease↗