Dependence of Tc on the physical parameters in single-layered copper oxides.
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Journal Article↗
Biomedical subjects
P Germain
Publications and source records attributed to P Germain.
Muscle strength during bedrest with and without muscle exercise as a countermeasure.
Bedrest is known to be a useful experimental model for simulating weightlessness and studying its effects on human skeletal muscle activity. We therefore conducted a study in which 12 healthy male subjects underwent 28 days of continuous exposure to 6 degrees head-down bedrest. Our main objective was to test a set of preventive countermeasures for maintaining the stability of the human body. Of the subjects 6 performed deadlifts in the supine position for 30 to 45 min each day. The isometric actions were performed for 5-30 s at 90, 120 and 150 degrees knee angles and isokinetic training at speeds of 30 and 180 degrees.s-1. In vivo quadriceps muscle strength was measured under controlled experimental conditions with a commercial dynamometer. The hypothesis that intense daily isometric and isokinetic leg exercise and lower body negative pressure (LBNP) might serve to maintain muscle strength under conditions of weightlessness was tested. Of the subjects 6, who did not perform any exercise, served as the control population under conditions of simulated weightlessness. The results showed that a significant reduction (P < or = 0.0001) in the muscle force [-10.3 (SD 6.7%)] occurred in the control group whereas no significant changes were observed in the trained group [+3.9 (6.8%)]. From these studies we conclude that intense muscle training and LBNP constitute efficient countermeasures to compensate for the biomechanical effects of weightlessness on human lower limbs and to limit other factors such as cardiovascular deconditioning.
Adult↗
Glycerol effect on spiramycin production and valine catabolism in Streptomyces ambofaciens.
Spiramycin production by Streptomyces ambofaciens in a chemically defined medium, with valine as nitrogen source, was controlled by the nature and the concentration of the carbon source. The production of this antibiotic was better in dextrins than in glycerol-containing medium. The negative effect of glycerol could be attributed in part to an excess of energy and a high specific growth rate. The intracellular ATP content, at the start of spiramycin production, was twofold higher in glycerol than in dextrin-containing medium. Increasing the initial concentrations of glycerol led to an increase in the specific growth rate and a drop in spiramycin production. Comparison between glycerol and a protein synthesis inhibitor effects and the use of resting cell systems (RCS) proved that glycerol exerted both inhibitory and repressive actions on spiramycin production independently from the growth. At the enzymatic level, glycerol interfered with valine catabolism by repressing partially valine dehydrogenase (VDH) and alpha-ketoisovalerate dehydrogenase (KIVDH), generator of spiramycin aglycone precursors.
Amino Acid Oxidoreductases↗
Prognostic factors of chronic heart failure in NYHA class II or III: value of invasive exercise haemodynamic data.
UNLABELLED: Various parameters have been found useful for establishing the prognosis of patients with chronic heart failure, in particular haemodynamic parameters measured at rest. However, few studies deal with the prognostic value of invasive exercise haemodynamic parameters in such patients. Our aim was to test the value of such parameters to assess the prognosis of patients with chronic heart failure in functional class II or III of the New York Heart Association. METHODS: Between December 1990 and June 1993, 50 patients fulfilled the criteria for inclusion in the study. The average age and ejection fraction of the population were 54 +/- 2 years and 20 +/- 0.5% respectively. All patients were examined clinically; their invasive haemodynamic parameters were measured at rest and during exercise, and their exercise peak VO2, validated by reaching the anaerobic threshold, was determined. They were followed up for 21.2 +/- 1.17 months (ranges 3-26 months). The assessment criteria employed were mortality and the occurrence of major events (heart failure, pulmonary oedema or severe ventricular arrhythmia). RESULTS: The population consisted of 32 men and 18 women. No gender-related differences were found. Two groups could be distinguished in terms of prognosis: G1: n = 31 living patients with no events, and G2: n = 19 deceased or with major events. G1 and G2 were comparable with regard to age, sex ratio and ejection fraction. Several of the 52 parameters tested were different in the two groups, in particular peak VO2, exercise duration, the workload developed during the cardiopulmonary test and all the invasive exercise haemodynamic parameters except heart rate (P < 0.0001). Haemodynamic parameters at rest had no prognostic value in this series. The ROC curves, the survival curves and the Cox analysis showed that exercise cardiac power output, exercise left ventricular work indices and exercise peak VO2 were the most useful factors for assessing the prognosis of patients with NYHA II or III chronic heart failure. An exercise cardiac power output < 2 watts accurately identified those patients with a short-term poor prognosis, and exercise peak VO2 was almost as accurate. To a lesser extent, the NYHA functional class was also an independent prognostic parameter during multivariate analysis. In conclusion, it appears that invasive haemodynamic parameters are best for determining the prognosis of patients with chronic heart failure. Peak VO2 can, however, be as useful. Moreover this is an easily obtainable non-invasive parameter, which makes it more useful in the evaluation and the follow up of such patients.
Adolescent↗
Regulation of valine catabolism by ammonium in Streptomyces ambofaciens, producer of spiramycin.
In Streptomyces ambofaciens, valine favored spiramycin biosynthesis by supplying aglycone precursors. The kinetics of valine consumption and isobutyrate production showed that isobutyrate accumulated in the cell during the growth phase, was excreted in the stationary phase, and then was reassimilated during spiramycin production. When valine was in excess, its deamination led to high ammonium excretion and to a significant drop in spiramycin production. We demonstrated that ammonium ions were the cause of the negative effect. Addition of a chelator agent, Ca3(PO4)2, improved spiramycin production by sixfold. In contrast, addition of ammonium, between 0 and 48 h, severely reduced spiramycin production. The negative effect of ammonium was reversed by addition of a catabolic intermediate of valine, isobutyrate. In addition to stimulating the specific growth rate, ammonium ions slowed down valine catabolism: the specific valine uptake rate, excretion, and reassimilation of isobutyrate were lowered by the pulse of ammonium. Our study showed that in addition to valine dehydrogenase, which provided the nitrogen necessary to the cell, ammonium ions repressed ketoisovalerate dehydrogenase, which introduced valine as carbon, energy, and aglycone precursor sources. However, valine dehydrogenase and ketoisovalerate dehydrogenase did not constitute the principal enzymatic targets of the negative effect of ammonium in spiramycin production.
2-Oxoisovalerate Dehydrogenase (Acylating)↗
[4-year mortality of heart failure with intact systolic function: a retrospective studies].
Heart failure with normal systolic function has been recognised in 30-40% of patients investigated for congestive heart failure. The authors undertook a retrospective study of global and cardiovascular mortality at 4 years in two groups of patients with a history of congestive heart failure documented by equilibrium angioscintigraphy: group I (n = 109) with poor left ventricular systolic function (EF = 26 +/- 9%) and group II (n = 40) with normal systolic function (EF = 58 +/- 8%). The 4 year cardiovascular mortality was less in group II (21.6% vs 49%; p < 0.004) whereas the global mortality was comparable in the two groups. The only discriminating parameters for cardiovascular mortality between the two groups were age of more than 60 years and values of diastolic blood pressure exceeding 90 mmHg which were associated with a higher mortality in the group with normal systolic function. These results indicate a better prognosis in terms of cardiovascular mortality from congestive heart failure in patients with normal systolic function compared with those with poor systolic function.
Aged↗
Internalization and biological effects of serum albumin in the breast cancer MCF-7 and MDA-MB 231 cells.
We show that albumin is internalized by human breast cancer cells (MDA-MB 231 and MCF-7) in culture by using confocal laser scanning microscopy. Moreover, albumin has an effect on the level of radioactivity incorporated when the cells are incubated with radioactive estradiol, and it is necessary to observe the mitogenic effect of estradiol towards the MCF-7 cells. This finding opens some possibilities regarding the internalization mechanisms and fate (degradation, recycling) of albumin as well as the role played by this protein in the intracellular metabolism of estradiol and in the intra-extracellular traffic of estradiol and its metabolites.
Biological Transport, Active↗
Exercise peak VO2 determination in chronic heart failure: is it still of value?
The prognostic value of exercise peak VO2 is still controversial. We therefore prospectively studied 75 patients in New York Heart Association functional class II or III with chronic heart failure stabilized by drug treatment. The patients (mean age of 58 +/- 10 years) were submitted to a clinical examination, a radionuclide determination of left ventricular ejection fraction, and a haemodynamic study at rest (right side catheterization); their plasma sodium, plasma creatinine and blood urea nitrogen levels were measured in addition to exercise peak VO2. An exercise peak VO2 threshold value of 14 ml.kg-1.min-1 was used to define two groups: GI (23 patients), with an exercise peak VO2 < or = 14 ml.kg-1.min-1 and G2 (52 patients) with an exercise peak VO2 > 14 m.kg-1.min-1. G1 and G2 were comparable in terms of age, heart rate, left ventricular ejection fraction, cardiac index and mean arterial pressure. Apart from exercise peak VO2, G1 and G2 also showed differences in right and left ventricular filling pressures, plasma sodium, plasma creatinine, blood urea nitrogen levels and exercise duration (all P < 0.01). Moreover the prognosis was worse in G1 than in G2: nine deaths vs 0, and seven major events--major events being defined as pulmonary oedema, hospitalization for heart failure, or severe ventricular arrhythmias--vs three (P < 0.001). A sub-group analysis (deceased patients, living patients with and without major events) was performed. Out of 20 clinical and paraclinical parameters, exercise peak VO2 proved to have the greatest prognostic value.(ABSTRACT TRUNCATED AT 250 WORDS)
Aged↗
Relationship between valine, fatty acids, and spiramycin biosynthesis in Streptomyces ambofaciens.
Spiramycin biosynthesis in Streptomyces ambofaciens was stimulated in the presence of valine or by sequential addition of some short-chain fatty acids to a culture medium containing an ammonium salt as source of nitrogen. Acetate kinase and acetyl-CoA carboxylase, enzymes that catalysed the formation of precursors of spiramycin biosynthesis (acetyl-CoA and malonyl-CoA), were detected during the active growth and antibiotic production phases. In this latter phase a higher level of acetyl-CoA carboxylase activity was observed with valine (1.02 mumol.min-1.mg protein-1) than with ammonium (0.05 mumol.min-1.mg protein-1) as nitrogen source, while the evolution and the level of acetate kinase activity were the same in both media. Successive addition of acetate and isobutyrate stimulated highly and weakly the acetyl-CoA carboxylase and acetate kinase activity, respectively.
Acetate Kinase↗
Chemical behaviour of three radionuclides (cesium, americium and technetium) and their uptake at the cytosolic level in aquatic organisms.
In previous papers, we observed that there were great differences in the subcellular accumulation and elimination of 137Cs, 99Tc and 241Am in different marine animals. In this study, we analysed and compared the behaviour of these radionuclides at the cytosolic level. We found great similarities in the cytosolic distribution of a given radionuclide in the various organisms studied. The chemical characteristics of the radionuclides seem to play a major role in the biochemical affinity and metabolic behaviour in different aquatic organisms.
Americium↗
Biodynamic study of americium-241 accumulation in the cytosol of the hepatopancreas of the lobster Homarus gammarus.
In the lobster, most of the radionuclides ingested with contaminated food are concentrated in the digestive gland. Americium-241 accumulation in the hepatopancreas of the lobster was studied during the digestive cycle. Fractionations of cytosols at different times after ingestion of radioactive preys were performed by gel permeation chromatography to determine the distribution of 241Am in the different macromolecular components. 241Am was associated with ferritin during the whole digestive cycle. This observation suggests a correlation between 241Am distribution pathways and iron metabolism. The distribution of 241Am present in the other cytosolic proteins followed two major steps of accumulation which may be correlated to the evolution of the two main cellular types playing an important role in the digestive cycle (B and R type cells).
Americium↗
Biopsy and quantitative hepatobiliary scintigraphy in the evaluation of liver transplantation.
METHODS: Hepatobiliary scintigraphy with technetium-99m-mebrofenin including a first-pass study of 60 two-sec images and a functional phase of 40 one-min images was performed in 26 patients (42.5 +/- 12.5 yr) in the early postoperative period (9.1 +/- 4.3 days) after liver grafting. Needle biopsy was carried out within a mean of 0.5 +/- 2.2 days of the scintigraphy study. Considering only rejection and cholestasis, biopsy results were used to classify the patients in three groups: control group I (11 patients) with minimal lesions, group II (9 patients) with moderate histologic modifications, and group III (6 patients) with severe dysfunction showing important structural changes. First-pass time-activity curves were used to calculate arterial (alpha-A) and portal (alpha-P) angles as well as a portal perfusion index. Functional time-activity curves were used to define two blood retention indices (BRI1 and BRI2) and two liver uptake indices (LUI1 and LUI2). Excretion was not quantified. RESULTS: Simple linear regression analysis showed a significant correlation between portal perfusion index and BRI1 (p < 0.05, r = -0.43) and BRI2 (p = 0.01, r = -0.53). The validity of the histologic classification was assessed by the existence of significantly different (p < 0.05) mean values for alpha-P, portal perfusion index and LUI1 in the three groups. All other indices could distinguish significantly between groups I and II. Furthermore, arterial angle alpha-A allowed differentiation of group II from group III but not group I from group II; on the contrary, LUI2 and BRI1 distinguished group I from group II but not group II from group III. CONCLUSION: This study demonstrated a close correlation between early biopsy results and perfusion indices in patients with a liver graft as well as uptake parameters determined by hepatobiliary scintigraphy.
Adult↗
Pre- and post-operative MRI study of an aneurysm of the right brachiocephalic artery with tracheal compression.
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Aneurysm↗
[Left ventricular filling in young insulin-dependent diabetics].
Left ventricular function indices were measured by pulsed Doppler-echocardiography in 17 young patients (mean age: 25 +/- 5) with insulin-dependent diabetes and 17 controls (identical mean age: 25 +/- 5) free of heart disease. All subjects had normal left ventricular systolic function. Twenty three per cent of diabetics showed a left ventricular filling anomaly on the basis of at least two abnormal indices. Isovolumic relaxation time was significantly prolonged in diabetics as compared with normal individuals (83 +/- 7 v. 68 +/- 9 ms, p < 0.00015). Half-pressure time was also prolonged in the patients (46 +/- 9 v. 38 +/- 6 ms, p < 0.01), the same applying to rapid filling deceleration time (158 +/- 32 v. 136 +/- 29 ms, p < 0.05). Peak rapid filling rate, the proportion of total filling accounted for by rapid filling, peak atrial systole velocity and the atrial contribution to total filling did not differ between the diabetics and controls. Systolic blood pressure was significantly higher in diabetics as compared with controls (124 +/- 8 v. 114 +/- 10 mmHg, p = 0.007), although remaining within normal limits. This would not, however, explain the differences seen between the 2 groups regarding left ventricular profile. The filling anomalies reported here were not correlated with the duration of diabetes nor with other parameters such as glycosylated hemoglobin or 24-hour microalbuminuria. Our results suggest that approximately 20 p. cent of young diabetics have sub-clinical left ventricular anomalies.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Distribution of [241Am] in hepato-pancreatic nuclear proteins of the lobster (Homarus gammarus).
Recent studies on the bio-accumulation of transuranic elements in marine invertebrates have demonstrated an intracellular concentration of radionuclides in the digestive gland. The present investigation aims to establish the distribution of [241Am] within the different structures of the cell nucleus. Lobsters were experimentally contaminated through feeding and then killed. The nuclei of hepato-pancreatic cells were isolated, purified and dissociated. The different protein categories were separated in media of increasing ionic strength. The distribution of americium in this material yielded results showing a preferential fixation onto the structural proteins of the nuclear matrix. The radiological consequences of such an affinity are discussed in terms of the life-times of the ligands concerned.
Americium↗
[Dynamic cartography of flow patterns by cine-MRI. Presentation of the technique and preliminary results for major vessels].
The authors report the principles, experimental evaluation and clinical approach of a method for dynamic imaging of flow patterns by NMRI, based upon the phase modulation technique. The imaging method is based upon gradient echo, functioning in "cine" and "flow compensated" mode. Modifications in this sequence enable attribution to the moving spins phase of a value which is considered to be proportional to the flow rate. A map of rates is then obtained from the phase image. Calibration of this sequence in vitro has shown excellent correlations between flow rate and the phase information thus obtained: r always > 0.98 for rates up to m/s. The first results obtained in vivo for the thoracic and abdominal aorta, in 11 control subjects, show that the technique is suitable for the study of pulsatile blood flow, providing very detailed information concerning the spatial distribution of flow rates. Mean flow in the suprarenal abdominal aorta (4.6 +/- 1.6 l/min) is 32% greater than that in the inferior vena cava (3.1 +/- 1 l/min), corresponding to an estimation of portal vein flow of 1.5 l/min. Practical limitations related to the use of a resistive magnet are nevertheless stressed and the authors list the technical aspects necessary for the better clinical utilisation of this non-invasive flowmetric technique. A review of the current literature forms the basis for an assessment of the potential importance of dynamic and quantitative NMRI of flow patterns in the cardiovascular area.
Aorta↗
[Use of diode laser in transcleral retinal photocoagulation].
Transscleral retinal photocoagulation using a diode laser emitting infrared radiation (810 nm) was performed on 8 rabbits. Examination was performed at 2 days, one month and three months after photocoagulation. The retinal burns were examined by light and electron microscopy and were found to be similar to those produced by argon and krypton photocoagulations. Histopathologic evaluation of the lesions demonstrated an intact sclera overlying the chorioretinal lesions. The results of the present experimental study support the hypothesis that transsccleral retinal photocoagulation using diode laser in selected indications may be a valuable alternative to cryotreatment and diathermy in the human eye. The absence of scleral damage and pigmented epithelium cell dispersion as well as the decreased break down of the blood ocular barrier after transscleral diode laser photocoagulation are the main advantages of the technique as compared to transscleral diathermy and cryotreatment.
Animals↗
Systematic study of light-induced effects in hydrogenated amorphous silicon.
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