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Biomedical subjects

G Nicolas

Publications and source records attributed to G Nicolas.

At least 91 records · Page 5Linked to original sources
PubMed1982

Ultrastructure of scales in a teleost (Carassius auratus L.) after use of rapid freeze-fixation and freeze-substitution.

New data on the ultrastructural features of the elasmoid scales of Carassius auratus have been obtained by use of rapid freezing with subsequent freeze-substitution in anhydrous solvents. These are compared with the results obtained using conventional aqueous fixatives. The external layer of the scales is composed of randomly oriented collagen fibres. In the first stages of mineralization, mineral deposits are located in the interfibrillary substance where dense granules appear to be active sites of mineralization. Spheritic mineralization occurs in this layer. The fibrillary plate is composed of two kinds of collagen fibres. Most of them are organized in lamellae forming the "plywood-like structure". They are thicker than the so-called "TC fibres", which are oriented from the basal part towards the superficial layer. These TC fibres are involved in the first stages of mineral deposition in the fibrillary plate where inotropic mineralization occurs. The mineral phase is almost always located in the interfibrillary matrix in both layers of the elasmoid scale. In this respect, teleost scales differ from those described so far in other lower vertebrates.

Animals↗
PubMed1982

[Complications of myocardial infarction between the 2d and 4th week].

The complications of myocardial infarction after transfer from the Coronary Care Unit on the 6th day were analysed bu a retrospective study of 3,460 computerised case reports (1973-1980). The mortality rate was 6% (1/3 of hospital deaths) in the period from the 7th day to discharge from hospital (14th to 30th day). Cardiac arrest as not uncommon (20% of all cardiac arrests) but the prognosis was better thn during the initial phase (p less than 0.05) as the mechanism was more commonly ventricular fibrillation or tachycardia (p less than 0.05). This series was compared with a similar population from 1970-1973; an improvement was observed in global hospital mortality (27% previously compared to 17%, in the study series, p less than 0.001). As the population were comparable, this phenomenon seems to be related to better treatment of shock and cardiac failure and the advances in cardiac surgery during the initial phase of infarction. Thd commonest mechanical complication was ventricular aneurysm; its occurrence does not influence the vital prognosis during this period. The incidence of cardiac arrest and death due to cardiac failure is not negligible after the first week of myocardial infarction. Therefore, we do not believe that the hospital period should be reduced after myocardial infarction. Special training of the nursing staff is essential for the successful treatment of these complications. The global prognosis could be improved by the rehabilitation of digitalis therapy and the introduction of new sympathomimetic amines in the acute phase of myocardial infarction.

Adult↗
PubMed1981

[Ethical problems posed by protocols of studies of anti-arrhythmia agents].

Clinical trials of new drugs cannot be considered to be free of risk. Guide lines have been laid down to guarantee the objectivity and quality of the scientific study carried out by the clinical experts charged with the trial. The French Medical Code of Ethics and the recommendations on medical ethics of the World Health Association (Helsinki 1964; Tokyo 1975) aim to guarantee that all therapeutic clinical trials are useful in themselves, that the interests of the individual patient pass before those of society, and, finally, that all trials are carried out with the free and informed consent of patients. Sometimes the licitness of a therapeutic trial may be unclear, exceptions to the rule of informed consent may be necessary, and the nature of surveillance during the testing of potential risks may be difficult to determine. In these cases it is of the utmost value that the proposed trial be submitted to an ethical committee provided that its composition guarantees the competence of its opinions from the technical, ethical and judicial points of view.

Anti-Arrhythmia Agents↗
PubMed1981

Reference values for ionized, complexed, and protein-bound plasma magnesium in men and women.

Of the three magnesium fractions in plasma, free ionized magnesium (Mg2+) has the greatest biological activity. Accordingly, information concerning this form in plasma is of cardinal importance to investigations in biometry and human pathology. For this reason, we developed an indirect assay for ionized magnesium in which Mg2+ is determined as the difference between ultrafiltrable magnesium, as measured in plasma water after ultracentrifugation, and complexed magnesium, as obtained after fixation of the ionized and protein-bound magnesium on Amberlite IR-120(H) cation-exchange resin. All magnesium assays were performed by atomic absorption spectrometry. We used this methodology to compare ionized, complexed, and protein-bound plasma magnesium in 34 normal men and 12 normal women. Sex-related differences between the values for these fractions were not significant. Interesting preliminary results for cases of myocardial infarction prompt us to continue our investigations concerning these three states of plasma magnesium in cardiac pathology.

Adult↗
PubMed1980

Intercellular junctions in the adrenal medulla: a comparative freeze-fracture study.

Observations of freeze-fractured specimens revealed that intercellular junctions in adrenal medulla are different in nature and number according to species. Only gap junctions of diverse size exhibiting characteristic loop-like configurations were found in hamster chromaffin cells. In addition to such gap junctions, polymorphic focal tight junctions occasionally combined with particle clusters or small gap junctions were found in guinea-pig. So far, no intercellular junctions were found in rat. Discussion is focused on the possible function of these junctions, in keeping with their presumably high lability.

Adrenal Medulla↗
PubMed1980

Modifications of the envelope of Chlamydia psittaci during its developmental cycle: freeze-fracture study of complementary replicas.

Examination of complementary replicas obtained by freeze-fracture of Chlamydia psittaci revealed, at the level of the plasma membrane, a progressive differentiation of "crate-like formations," which likely correspond to transmembranal pores. Recognition of "early" and "late" stages observed in the intermediate bodies permitted detailed study of the developmental cycle of this chlamydia.

Cell Cycle↗
PubMed1980

[Exercise testing in probable primary hypokinetic cardiomyopathies].

50 patients with primary congestive cardiomyopathy underwent one or several exercise tests at yearly intervals in order to evaluate exercise capacity and to assess the prognosis. Three parameters were studied: the workload, the elevation of the systolic blood pressure (SBP) on exercise and the appearance of premature ventricular beats (PVB) on exercise or during the recovery phase. The results show that when the work loads > 120 watts, an elevation of SBP greater than or equal to 50 mmHg and the appearance of less than 3 PVB per minute were compatible with a moderate degree of physical exertion. On the other hand these same poor prognostic factors were associated with a higher mortality rate after 20 months follow-up.

Adult↗
PubMed1980

Concentrations of magnesium, calcium, potassium, and sodium in human heart muscle after acute myocardial infarction.

Atomic absorption spectrometry was used to measure magnesium, calcium, and sodium, and emission spectrometry to measure potassium, in myocardium (left and right ventricles) of 26 control subjects who died of acute trauma. Results were expressed in mumol/g of proteins. Mg/Ca and K/Na ratios were also determined. The same measurements were made in 24 patients who died from acute myocardial infarction. Samples were also taken from the necrotic area. Mg/Ca and K/Na ratios were significantly higher in the left ventricle of both populations, thus providing evidence of anatomical and physiological differences between the two ventricles. As a result of cytolysis and anoxia, the Mg/Ca ratio was very significantly inverted, and the K/Na ratio very significantly smaller, for samples from the necrotic area. In these clinical conditions arrhythmias could certainly be considered likely, and there is reason to believe that magnesium depletion may be a cause of arrhythmias.

Adolescent↗
PubMed1980

[Ethical and legal problems of medical responsibility in drug trials (author's transl)].

Trials of new drugs are not without risk. Standards have been laid down ensuring the objectivity and quality of the scientific studies of investigators involved in the clinical trial. Article 19 of the French Medical Code of Ethics and the recommendations on medical ethics formulated by the World Medical Association (Helsinki, 1964; and Tokyo, 1975) are designed to ensure that clinical trials on human subjects are of benefit to the subjects themselves, that the interests of the individual are placed before those of society, and, finally, that the trials are conducted with the informed consent of the subjects. In the case of injury sustained by a subject as a result of a clinical trial, the question arises as to the legal liability of the investigator. Possible grounds for malpractice include absence of licitness of the trial, lack of informed consent and negligence or irresponsibility in the conduct of the trial. In certain cases it is difficult to determine the licitness of a clinical trial; exceptions to the rule of informed consent may appear necessary; and it is sometimes difficult to ensure adequate control and evaluation of potential risks of a trial. Hence the need to submit such cases to an ethical committee, provided its members are so chosen as to guarantee the technical and legal competence of its pronouncements.

Clinical Trials as Topic↗
PubMed1979

[Is the process of localized lysosomal exocytosis responsible for the cytolytic action of killer T-lymphocytes?].

In this paper, we formulate the hypothesis that in the process of target cell lysis a lysosomal enzyme regurgitation, performed by killer cells at the level of the target effector junction, accounts for the target lesion which precedes the lysis (lethal hit). This process of exocytosis, similar to the one described previously in polymorphonuclear neutrophils is supported by cytological studies performed directly on identified killers isolated by micromanipulation. Light and electron microscopy observations confirm a previous report which describes the effector cells rich in lysosomal bodies. In addition, when a killer cell is associated with a target cell to form a conjugate, lysosomes are concentrated near the cell junction and, after incubation at 37 degrees C, acid phosphatases may be detected at the junction. Lysosomal enzyme exocytosis explains why target lysis needs an effector target binding to occur and also the other conditions required for any exocytosis process such as Ca++ in the medium, integrity of the microtubular apparatus, a low level of cyclic AMP and energy dependancy.

Acid Phosphatase↗
PubMed1979

[Coronary lesions due to aortic valve disease. I -- Occurrence and clinical prognosis].

A multicentre retrospective study of 467 cases of operated aortic valve disease was undertaken to define the indications of coronary arteriography in the pre-operative work-up. Significant coronary artery disease was present in 15% of all cases or, more precisely, in 17% of cases with angina and in 8% when investigation was only routine. Coronary artery disease was more frequent in males, in patients with clinical or electrical evidence of previous myocardial infarction, in patients with ST-T wave changes, and when angina was severe (more than one attack per day). None of these factors was specific. It is therefore difficult to limit coronary arteriography to these patients or there would be a risk of missing significant lesions in a small number of cases. It is important to give the surgeon all the necessary information before aortic valve replacement and so coronary arteriography should be widely practiced in this context. However exceptions may be made for young patients and also those in congestive cardiac failure in whom coronary arteriography represents an unnecessary risk before surgery.

Aortic Valve Insufficiency↗
PubMed1978

[Accidental intoxication with aconitine (author's transl)].

Involuntary ingestion of 3 mg of aconitine induces in a young woman multifocal extrasystoles and alternating periods of sinusal rhythm and junctional arrhythmia. The rhythmogenetic abnormalities disappear spontaneously within two hours. The physiopathology of arrhymias due to aconitine is discussed.

Aconitine↗