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Biomedical subjects

F Lefebvre

Publications and source records attributed to F Lefebvre.

At least 73 records · Page 4Linked to original sources
PubMed1987

A new reconstituted connective tissue matrix: preparation, biochemical, structural and mechanical studies.

A fibrinogen derivative generated by thrombin was reacted with elastin to yield a new addition product or adduct between the two proteins. Addition of fibronectin, and then of collagen, did not interfere with the basic elastin-fibrinogen reaction and conferred the qualities of an artificial connective tissue to the product. Biochemical, structural and biomechanical aspects of the new matrix were studied. Aprotinin, heparin, thiomersal, and thiourea did not inhibit the main reaction; indeed, some of these ingredients improved the matrix cohesion. Scanning electron microscopy showed the genesis of a true network whose meshes were more reticulated by the addition of thiourea. Biomechanical studies, i.e., strength and elasticity showed the thiourea matrix to be the strongest. These intrinsic properties suggest the product could have biological and clinical applications.

Biocompatible Materials↗
PubMed1987

Adduct formation between soluble fibrin monomers and elastin.

Monomers of fibrin generated from fibrinogen by thrombin reacted with elastin to give a new addition product or adduct. The adduct formation results from a covalent bond between both proteins, formation of which is dependent on elastin, fibrinogen and Ca2+ concentrations; but, Factor XIIIa did not intervene. Addition of fibronectin, together with fibrinogen, as cold insoluble proteins from human plasma, and of soluble collagen from rat tail tendon did not inhibit the first reaction. This enabled us to elaborate a new artificial connective matrix.

Animals↗
PubMed1986

Inhibition of human pancreatic elastase II activity on human aortic elastin by human alpha 2-macroglobulin.

Human alpha 2-macroglobulin-human pancreatic elastase II binding were investigated using a homologous substrate, human aortic elastin, in order to test the enzymatic activity. We demonstrated that two moles of alpha 2-M are required to inhibit one mole of HPEII when the enzyme is added to a mixture of elastin and alpha 2-M. In addition, when the elastase-alpha 2-M complex is prepared under some circumstances, it exhibits an elastinolytic activity.

Aorta↗
PubMed1986

Soluble fibrinogen derivatives generated by thrombin: affinity for elastin.

When human citrated plasma is dialysed against a phosphate buffer containing Ca++, citrate anions are removed, thrombin is generated and soluble fibrinogen derivatives (fibrin monomers and/or soluble fibrin polymers) are formed. These derivatives are able to combine with human or bovine elastin to form a very stable addition product or adduct. The formation of the adduct is dependent on time, Ca++ and thrombin concentrations.

Animals↗
PubMed1985

Magnesium enhances human pancreatic elastase digestion of 125I-labeled elastin.

The effect of some divalent cations, especially Mg++, on elastinolysis by porcine or human pancreatic elastase has been determined using 125Iodine-labeled elastin as substrate. Elastin degradation was significantly increased in the presence of 10(-3) M Mg++. If elastin was pre-incubated with 0.5 (w/v) Triton, there was a further increase in elastinolysis to 2.6 times the original rate.

Animals↗
PubMed1984

Human alpha 1-antitrypsin genetic polymorphism: PI N subtypes.

Three new genetic variants (PI types) of alpha 1-antitrypsin are described. They have been compared to previously described phenotypes by several techniques including narrow pH range isoelectric focusing in ultrathin polyacrylamide gels. In this system, the relevant alpha 1-antitrypsin gel bands, identified by crossed immunoelectrophoresis, focused between PI M2, the most cathodal PI M subtype, and PI P BUD, the most anodal PI P subtype. They were therefore considered to be PI N subtypes. Two of them, PI N GRO and PI N YER, could not be separated by isoelectric focusing, but gave a different pattern in agarose gel electrophoresis. None of the new alleles seemed to be associated with disease. The high resolving power of isoelectric focusing is emphasized with respect to the information it may provide concerning amino acid substitutions, while the use of other techniques proved to be of utmost importance in the differentiation of other variants showing similar isoelectric points.

Electrophoresis, Agar Gel↗
PubMed1984

Purification of human alpha 1 antiprotease-pancreatic elastase complex. Interaction with homologous elastin.

A human alpha 1-antiprotease (alpha 1.AP)-human pancreatic elastase ( HPE11 ) complex was isolated from plasma, or prepared from commercial alpha 1.AP. The complex was identified and isolated by affinity chromatography, using Concanavalin A or IgG anti-elastase as ligands, in association with Sephacryl gel filtration. The alpha 1.AP- HPE11 complex was shown to bind with aorta and with purified aortic elastin. In both cases, the complex exhibited elastinolytic activity.

Aorta↗
PubMed1983

Myosin polymorphism in muscles of the toadfish, Opsanus tau.

The superfast swimbladder muscle of Opsanus tau differs from the corresponding fast skeletal muscle not only by its greater sarcoplasmic reticulum and parvalbumin content but also by a genuine myosin LC2. The study of light chains has been extended here to other striated muscles. Myosins from fast (trunk muscle), superfast (swimbladder muscle), slow (lateral-line muscle) and cardiac (ventricle muscle) were compared, using one- and two-dimensional polyacrylamide gel electrophoresis. The results showed that the light chains all appear distinct in isoelectric point and molecular weight, except for the two LC1 and two LC3 from fast and superfast muscles. Striated muscles from the toadfish Opsanus tau exhibited at least four isoenzymic forms of the myosin, related to the light chains and corresponding to different physiological properties.

Air Sacs↗
PubMed1983

[Complexes of "pancreatic elastase-seric inhibitors" in swine: their behavior in the presence of homologous aortic elastin].

The present paper deals with the particular behavior of the complexes formed between pancreatic elastase and seric inhibitors in the Pig, when they were set in contact with homologous elastin. The previously known values of dissociation constants of alpha 1-antiprotease-elastase and alpha 2-macroglobulin-elastase complexes indicated they were very stable and almost irreversible. Nevertheless, our results suggest that, when the overall complexes between porcine pancreatic elastase and seric inhibitors were isolated in non drastic conditions, they might develop an elastolytic activity against elastin fibers. This result is important as regards atherosclerosis--in Human--where a destruction of elastin is involved at a early stage of the disease.

Animals↗
PubMed1983

[Demonstration of elastinolytic activity in blood or plasma].

The complexes between "elastases" and their seric inhibitors (a. 1. AP and a2. M) which could be formed in the blood, are exhibited in vitro: after incubation of serum or plasma with 125iodine labelled elastin at pH = 6, followed by extensive washing, pH was increased from 6 to 8.6: labelled peptides are released in supernatant.

Animals↗
PubMed1982

Early discharge of low birthweight infants.

A study was conducted to see if the discharge weight of preterm infants born at less than or equal to 2000 g could safely be reduced. A study group (21 infants) was discharged 'early' at a mean weight of 2010 g (1890-2190) provided there were no medical problems, weight gain was adequate, temperature control in room air was stable, all feedings were by breast, and the mother was ready to have the baby home. A control group (17 infants) was discharged at a mean weight of 2261 g (2200-2400). The duration of time in hospital for the 'early' group was shortened by 11.6 days. At expected date of delivery the weight of infants in each group was similar (3095 +/- 403 compared with 3146 +/- 453 g); length, head circumference, and haemoglobin concentration in each group were similar too. There was no morbidity or mortality in either group. Early discharge did not affect mothering confidence. This study shows that low birthweight infants can be discharged early (at 2000 +/- 100 g) provided appropriate criteria are met, home conditions are adequate, and follow-up is available.

Female↗
PubMed1981

Genetic variations of serum alpha-1-antitrypsin (Pi types) in Normans. Common Pi M subtypes and new phenotypes.

The results of Pi typing by high resolution isoelectric focusing on 1,030 Normans from the area of Rouen (France) is reported. The frequency of the three common subtypes of Pi M is given and new variants partly described. Pi gene frequencies are compared to previously obtained data and results from other countries. The application of high resolution isoelectric focusing to the Pi system is discussed together with the advantages it provides in the knowledge of alpha-1-antitrypsin genetic polymorphism.

Female↗
PubMed1981

A specific one step method for the isolation of pancreatic elastase; its use to characterize aortic elastase.

Elastase was purified from an acetone-ether powder of porcine pancreas by a one step affinity chromatography procedure on IgG-Sepharose 4B. The IgG was derived from a rabbit immunized with porcine pancreatic elastase and was itself isolated by affinity chromatography on elastase immobilized on the same matrix. The column was calibrated with a known elastase preparation under standardized conditions. Direct isolation of elastase from pancreatic extracts yielded approximately 90 mg from two pancreas. The enzymatic activity and electrophoretic migration in SDS-polyacrylamide gel of the purified elastase were equal to those of the purest commercially available enzymes. Application of this method to aorta of young pigs suggests the presence of active elastase in the aorta.

Animals↗
PubMed1980

[Anti-elastase of human pancreas: preparation and biological interest].

The present paper deals with the use of a new technique in type II human pancreatic elastase studies based on the use of a reversible immune-adsorbent which provides a unique specificity. According to the type of ligand linked on activated Sepharose, the elastase or its antibody in Rabbit could be obtained, in very pure form, in a one step process. The anti-human pancreatic elastase II, which specifically inhibits the enzyme, may be used in therapy whenever the elastase-inhibitor system becomes unbalanced.

Animals↗
PubMed1980

The effects of various warming up intensities and durations during a short maximal anaerobic exercise.

In the literature, few experiments deal with the study of warming up before short exercises. The present paper investigates the influence of different warming up procedures on a short maximal anaerobic exercise leading to exhaustion in 1 min or less. Performance, heart rate, oxygen consumption, and lactic acid level are measured. The performance is improved when light warming up (30% VO2 max) is used just before the criterion exercise, while it is impaired with a more strenuous warming up (70% VO2 max). After light warming up, heart rate and oxygen consumption are slightly higher during the criterion exercise as compared with the values without warming up. Warming up itself does not lead to an increase in lactic acid level. When a resting period is introduced between warming up and exercise, no modification occurs whatever the warming up intensity, and no important variation of the physiological measures are observed in this case.

Adult↗
PubMed1979

Synthesis of highly diversified carrier ampholytes. Evaluation of the resolving power of isoelectric focusing in the Pi system (alpha-1-antitrypsin genetic polymorphism).

The use of condensing reagents such as epoxypropanol, diepoxyoctane, acrylamide and N,N'-methylenebisacrylamide in the synthesis of carrier ampholytes increased the diversity of amphoteric components. The quality of these synthetic carrier ampholytes has been tested in the separation of variants of alpha-1-anti-trypsin, a genetic polymorphism called the Pi system. A resolving power of the order of 0.005 pH unit was obtained.

Ampholyte Mixtures↗