Search PubMed⌕ Search

Biomedical subjects

H Atlan

Publications and source records attributed to H Atlan.

At least 73 records · Page 4Linked to original sources
PubMed1979

Radionuclide assessment of aortocoronary bypass surgery.

Rest and exercise thallium 201 myocardial scintigraphy and multiple gated radionuclide angiography were correlated with the results of clinical status, exercise electrocardiography, coronary arteriography, and contrast left ventriculography in a series of 12 prospectively studied consecutive patients before and after aortocoronary bypass operation. Patients were divided into two groups based on a comparison between preoperative and postoperative 201T1 scintigrams. Group 1 (6 patients) demonstrated improved or normal postoperative perfusion scintigrams and excellent correlation between the site of a patent graft and the improvement in myocardial perfusion on the postoperative exercise scintigrams. Regional wall motion remained normal in 3 patients and improved in 3. In Group 2 (6 patients) the postoperative 201T1 scintigrams were unchanged or worse. Each patient demonstrated graft occlusion, graft stenosis, distal disease, or a perioperative myocardial infarction. No improvement in regional wall motion occurred in 4 of these 6 patients. Neither the symptomatic response to aortocoronary bypass operation nor the response to exercise testing successfully predicted graft patency.

Adult↗
PubMed1979

[Study of muscle hemodynamics during exercise: Physiological and pathological variations in Xe 133 elimination: A new method of interpretation (author's transl)].

Muscle blood flow measurements are of physiological (and pathological) significance only during effort. For this reason, the authors used Xe 133, which has been known since 1964, to measure regional muscle blood flow after its injection into the muscle, to quantify results during effort (pedalling). Effort is controlled by two measurable parameters: the weight lifted by the pedal and the frequency of movements. Curves showing the reduction in intramuscular Xe 133 levels cannot be mathematically formulated. It is easy, however, to measure their areas and thus define a mean elimination time (Tm) between times T1 and T2, beginning and end of effort, corresponding to activities A1 and A2 such that: formula: (see text). Normal Tm value, measured in 58 normal subjects with variable frequencies and weights lifted is: Tm = 1.70 +/- 0.38 min. The values in 70 patients with arteritis were significantly longer and can be greater than 3.5 min. This objective test could be of value in quintifying the effects of so-called vasodilators, both in patients with arteritis and venous insufficiency.

Humans↗
PubMed1975

Interaction between membrane properties and proteins synthesis in reticulocytes - a two step inhibition of protein synthesis by valinomycin.

In this work we consider the differential effect of Valinomycin used at different concentrations both on the protein synthesis of reticulocytes and on 42K exchange. We demonstrate that there is a two step action of this antibiotic. At 10(-6)M and below the drug has no effect on the 42K exchange, but it stops, however reversibly, protein synthesis. At 10(-5)M the drug has a very sharp action on the 42K exchange and stops protein synthesis in an irreversible way. Ribosomal population checked by two ways, sucrose gradient and direct counting on E.M. sections shows that at low concentrations of Valinomycin (10(-8)M to 10(-6)M) there is no breakdown of the polysomes which can be detected by either one of these methods. On the contrary, after short incubation with 10(-5)M of Valinomycin the breakdown of ribosomes is very clear, as evidenced by sucrose gradient analysis. By direct ribosomes clusters counting on E.M. sections this breakdown is seen only after long incubation.

Animals↗
PubMed1975

[Variability of cultures and genetic variability].

Cultural selection is defined as a modification in gene frequency distributions within a population under the effects of socio-cultural factors. The conditions are examined which determine the efficiency of such a selection mechanism as a driving force for the evolution of the genetic pool of a social group in a state of relative isolation. The possible effect of the cultural variation on the genetic variation of the human species is discussed.

Culture↗
PubMedDate not supplied

A mathematical analysis of the mortality kinetics of Drosophila melanogaster exposed to gamma radiation.

A mathematical model with nonlinear time-varying characteristics has been developed which describes the relationship between the kinetics of natural aging and radiation-induced delayed mortality. Based on this model, it appears that there is an immediate effect of radiation which is continuously, but nonlinearly, increasing in severity. Two phases appear in this variation, corresponding to the two phases (plateau and dying phase) of the mortality curves for control populations. Accordingly, S/E (survival time post-irradiation/further expectation of life) can best be interpreted as an increasing function during the plateau phase of normal mortality curves, which levels off during the ensuing dying phase.

Aging↗
PubMedDate not supplied

Effects of temperature on the life span, vitality and fine structure of Drosophila melanogaster.

The effects of temperature on the aging process have been investigated in approximately 3500 imagoes of male Drosophila melanogaster (Oregon R), with focus on the following parameters: mortality, O2 utilization, vitality (as expressed by negative geotaxis and mating) and fine structural alterations in the abdominal organs and brain. The data on mortality kinetics of flies maintained continuously at 18 degrees, 21 degrees, 27 degrees or 30 degrees C or exposed in succession to 21 degrees and 27 degrees C or vice versa support the concept that life span is temperature dependent. Moreover, these data, together with the increased O2 utilization and accelerated loss of vitality at 21 degrees C as compared with 18 degrees C, suggest that, in agreement with the rate-of-living theory proposed by Alpatov and Pearl in 1929, the flies are living faster at the higher temperature. Fine structural aging changes, like ribosomal loss in the Malpighian tubules and lipofuscin-ceroid accumulation in the midgut cells, seem to be more intense at 27 degrees and at 29 degrees C than at 21 degrees C. Also, the low vitality exhibited through their lives by flies kept at previous exposure through many generations) to 21 degrees C. Flies maintained at 29 degrees C showed a striking degeneration of the brain with an almost complete loss of the cytoplasmic organelles of the nerve cells. This electron microscopic finding lends support to the view that nervous tissue injury (perhaps induced by thermal denaturation of membrane lipoproteins) may play a crucial role in life shortening induced by relatively high temperatures.

Animals↗
PubMedDate not supplied

Thermodynamics of aging in Drosophila melanogaster.

The data on mortality kinetics and decline in functions reported in the preceding article are used to calculate temperature coefficients for the aging process(es) in Drosophila. Different values are found, according to the model chosen to account for the mortality kinetics. The respective implications of three equally suitable models are discussed. Thus, organization parameters on two different levels can be identified: rates of changes assumed to occur at the elementary molecular level, and redundancy factors at a more integrated level. Their temperature coefficients are compared with those of protein denaturations and lipid peroxidation pigment accumulation. It is suggested that elementary molecular processes responsible for aging can indeed be protein denaturations, whereas the known lipid peroxidation pigment accumulation is more likely to be a secondary effect, resulting from a failure of the overall cellular organization at a more integrated, supramolecular, level.

Aging↗