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Biomedical subjects

H Atlan

Publications and source records attributed to H Atlan.

At least 55 records · Page 3Linked to original sources
PubMed1984

Ouabain-resistant Na+, K+ transport system in mouse NIH 3T3 cells.

It is shown that the ouabain-resistant (OR) furosemide-sensitive K+(Rb+) transport system performs a net efflux of K+ in growing mouse 3T3 cells. This conclusion is based on the finding that under the same assay conditions the furosemide-sensitive K+(Rb+) efflux was found to be two- to threefold higher than the ouabain-resistant furosemide-sensitive K+(Rb+) influx. The ouabain-resistant furosemide-sensitive influxes of both 22Na and 86Rb appear to be Cl- dependent, and the data are consistent with coupled unidirectional furosemide-sensitive influxes of Na+, K+ and Cl- with a ratio of 1:1:2. However, the net efflux of K+ performed by this transport system cannot be coupled to a ouabain-resistant net efflux of Na+ since the unidirectional ouabain-resistant efflux of Na+ was found to be negligible under physiological conditions. This latter conclusion was based on the fact that practically all the Na+ efflux appears to be ouabain-sensitive and sufficient to balance the Na+ influx under such steady-state conditions. Therefore, it is suggested that the ouabain-resistant furosemide-sensitive transport system in growing cells performs a facilitated diffusion of K+ and Na+, driven by their respective concentration gradients: a net K+ efflux and a net Na+ influx.

Animals↗
PubMed1984

Left ventricular function during asynchronous ventricular pacing: a radionuclide study.

This study was undertaken to assess ventricular volumes and function by radionuclide angiography during asynchronous ventricular pacing in a group of 22 patients who needed an artificial pacemaker. 14 had ischaemic heart disease and 8 had primary disturbances of conduction of the impulse-forming system. The transition from sinus to a paced rhythm or increasing the pacing rate had little effect on patients with primary conduction disturbances. In contrast, in patients with ischaemic heart disease, the transition to a paced rhythm decreased significantly left ventricular end-diastolic (15.3 +/- 4.7%) and stroke (26.3 +/- 4%) volumes, ejection fraction (9.0 +/- 4.4%), and cardiac output (21.0 +/- 3.9%). Pacing at a progressively increasing heart rate showed that each patient had an optimal rate of pacing.

Aged↗
PubMed1983

Probabilistic automata as a model for epigenesis of cellular networks.

Probabilistic automata are compared with deterministic ones in simulations of growing networks made of dividing interconnected cells. On examples of chains, wheels and tree-like structures made of large numbers of cells it is shown that the number of necessary states in the initial generating cell automaton is reduced drastically when the automaton is probabilistic rather than deterministic. Since the price being paid is a decrease in the accuracy of the generated network, conditions under which reasonable compromises can be achieved are studied. They depend on the degree of redundancy of the final network (defined from the complexity of a deterministic automaton capable of generating it with maximum accuracy), on the "entropy" of the generating probabilistic automaton, and on the effects of different inputs on its transition probabilities (as measured by its "'capacity" in the sense of Shannon's information theory). The results are used to discuss and make more precise the notion of biological specificity. It is suggested that the weak metaphor of a genetic program, classically used to account for the role of DNA in specific genetic determinations, is replaced by that of inputs to biochemical probabilistic automata.

Biological Evolution↗
PubMed1983

Atrial pacing thallium scintigraphy in the evaluation of coronary artery disease.

A study was undertaken to examine the value of rapid atrial pacing and thallium-201 scintigraphy in the evaluation of ischemic heart disease. Ten subjects with angiographically normal coronary arteries and 31 patients with coronary artery disease were studied. Six of these patients were studied after coronary artery bypass surgery. Coronary ischemia or infarction could be diagnosed from the ECG alone (rest and atrial pacing) in 87% of the patients with a greater than or equal to 50% narrowing of a coronary artery. The ECG and scintiscan (at rest and pacing) together had a sensitivity of 100%. The ECG could not identify the site of stress-induced ischemia. Rapid atrial pacing with scintigraphy identified 91% of those patients with a right coronary artery narrowing (greater than 50%), 85% with a narrowing of the left anterior descending coronary artery, but only 33% with a narrowing of the circumflex coronary artery. The scintiscan correctly identified 40% of arteries with a 50 to 89% narrowing, 75% with a 90 to 99% narrowing and 88% with a complete obstruction. The scintiscan predicted single- and double-vessel disease, but underestimated the number of vessels involved in patients with triple-vessel disease. This technique was also useful in assessing the patency of implanted coronary artery bypass grafts. Rapid atrial pacing is a simple and safe method of inducing ischemia, while thallium scintigraphy shows the site, extent and severity of coronary artery disease.

Adult↗
PubMed1983

Nuclear left ventriculography at rest and during atrial pacing in the evaluation of coronary artery disease.

This study was undertaken to examine the value of rapid atrial pacing (RAP) combined with left-ventricular nuclear (LVN) angiography in the diagnosis of ischemic heart disease. It included 32 patients: 12 normal subjects and 20 with clinical coronary artery disease (CAD) and greater than 50% narrowing of a coronary artery (significant CAD). The ECG and an LVN angiogram (LVNA) were recorded at rest and during graded RAP. In the normal subjects, left-ventricular wall motion was normal at rest and during atrial pacing, but a wall motion abnormality (WMA) appeared in one subject. Left-ventricular ejection fraction (EF) did not change significantly. In the 20 patients with significant CAD, the diagnostic sensitivity of the ECG during RAP was 100% and 90% for the nuclear angiogram (presence or appearance of WMA at rest and during RAP). The mean EF in this group decreased from 0.38 to 0.31. WMA on the LVNA was present in 79% of patients with significant left-anterior descending, in 44% of those with right, and in 33% of those with circumflex coronary artery disease. WMA (at rest or on pacing) occurred in 17% of patients with 50 to 89% narrowing of an artery, in 50% with 90 to 99% narrowing and in 68% with total obstructions. The LVNA (rest and/or RAP) identified patients with significant single-vessel disease, but underestimated the extent of double-and triple-vessel disease. The LVNA at rest and during atrial pacing was an excellent method of evaluating significant coronary artery disease.

Adult↗
PubMed1982

Differentiation between serum stimulation of ouabain-resistant and sensitive Rb influx in quiescent NIH 3T3 cells.

The addition of serum to quiescent NIH 3T3 mouse cell cultures resulted in a 10- to 20-fold increase of Rb influx which was resistant to ouabain, and only a three- to fourfold activation of ouabain-sensitive Rb influx. Stimulation of the ouabain-resistant Rb influx following serum addition reached its maximum within 2 min. The stimulation of ouabain-resistant Rb influx was a result of Vm increase while the Km for Rb was unchanged. Ouabain-resistant Rb influx, after serum addition, was resistant to amiloride and sensitive to ethacrynic acid. Replacing chloride in the medium by NO3-, CO3- and CH3COO- resulted in a drastic decrease in the ouabain-resistant Rb influx. It appeared, therefore, that the ouabain-resistant Rb influx in NIH 3T3 cells was Cl--dependent.

Animals↗
PubMed1981

The use of thallium 201 myocardial imaging to exclude myocardial infarction after dissection in congenital coarctation of the aorta.

The use of a mobile gamma camera with thallium 201 myocardial imaging is described to exclude myocardial infarction in a patient admitted to the coronary care unit in shock and with clinical, enzyme, and ECG changes consistent with infarction. The patient suffered from acute aortic dissection associated with congenital coarctation of the aorta. The myocardial scan excluded transmural myocardial injury.

Adult↗
PubMed1981

Diagnosis of coronary artery disease by multigated radionuclide angiography during right atrial pacing.

Right atrial pacing in conjunction with radionuclide angiography was used as a method to augment gradually myocardial oxygen demand in seven normal subjects and 11 patients with angiographically documented coronary artery disease (CAD). In five of the seven normal subjects the ECG during atrial pacing was normal and falsely pathologic in the two others; in all seven the ejection fraction (64 +/- 8 percent) did not change during the pacing. The atrial pacing was positive in seven of the eleven patients with CAD and falsely negative in four. In comparison, nine of these patients had more than 15 percent reduction in ejection fraction, while only two were regarded as negative. A maximal decrease of 31 percent in the average ejection fraction was observed in CAD patients at a pacing rate of 160/min. Wall motion pattern remained normal in all seven normal subjects, while new wall motion abnormalities developed during the atrial pacing in nine of the 11 CAD patients. We concluded that changes in ejection fraction induced by atrial pacing are sensitive indicators of myocardial ischemia. In patients with CAD, ejection fraction falls during pacing compared with normal subjects in whom ejection fraction remains unchanged.

Adult↗
PubMed1980

Cinderella--a clinical nuclear medicine retrieval and filing on-line stand-alone system for patient data.

We describe a microcomputer-based, stand-alone, on-line scheduling data entry and retrieval clinical data base system, specially tailored for a nuclear medicine department. It includes provision for free format clinical diagnostics text answers to each radioisotope scan. Such a system is currently installed at the Department of Medical Biophysics and Nuclear Medicine at the Hadassah University Hospital, and handles all the patient tests performed in this department. We feel that the design of an independent microprocessor-based system customized for one's department needs has indeed improved the quality of the clinical services, both in ensuring that the patient records are kept up-to-date and complete, and in providing, through fast interactive retrieval transactions, immediate answers for a given patient status.

Information Systems↗
PubMed1980

Evaluation of myocardial perfusion by thallium-201 imaging at rest and during exercise. Comparison with ECG stress testing.

In order to assess the accuracy of thallium-201 cardiac imaging at rest or during exercise in detecting permanent or transient myocardial damage, we studied 49 patients with angiographically documented coronary disease (31 with previous myocardial infarction) and 29 patients with normal coronary arteries. The resting thallium scan was significantly more accurate in detecting previous myocardial infarction (31 patients) than the resting ECG (22 patients) (P < 0.01). The combination of thallium imaging and ECG stress testing revealed reversible myocardial ischemia in 41 of the 49 patients (84%), compared with 28 of 49 (57%) detected by ECG stress testing alone (P < 0.01). Thallium imaging was more accurate in ruling out coronary disease (26 of 29 patients, 90%) than ECG stress testing (19 of 29 patients, 65%) (P < 0.05). In patients with previous myocardial infarction, thallium imaging alone or in combination with ECG stress testing was not significantly more sensitive than ECG stress testing alone.

Coronary Circulation↗
PubMed1979

Carcinoma of the bronchus with atypical presentation: report of a case.

A 64-year-old man presented with dysphagia due to obstruction of lower third of the esophagus. Esophagoscopy showed narrowing of the esophagus with normal mucosa. Chest X rays were normal, but on lung scan there was no perfusion of the left lung. That patient died of aspiration and on post mortem a carcinoma of the bronchus with abscess formation and perforation into the esophagus was found.

Bronchial Neoplasms↗