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Biomedical subjects

M Maillard

Publications and source records attributed to M Maillard.

At least 55 records · Page 3Linked to original sources
PubMed1985

Twisted architectures in cell-free assembled collagen gels: study of collagen substrates used for cultures.

Reprecipitated fibrils from collagen solutions assemble into aggregates often showing a remarkable twisted structure. We first observed these aggregates in collagen gels prepared to facilitate culture of epithelial cells. We verified that these structures form in the absence of cells and correspond to a process of self-assembly. Studies on reconstructed fibrils of collagen are generally based on the examination of thin specimens mounted onto coated grids prepared for electron microscopy. We rather applied the classical methods of fixation, embedding and ultramicrotomy, which allowed us to analyze the structure of these aggregates, several microns in diameter. Our gels were prepared from 2.5 mg/ml tropocollagen solutions usually chosen for cell and organ cultures. The time required to obtain twisted architectures, in these aggregates, depends on temperature and the presence of factors such as fetal calf serum proteins. Twist is observed at two different levels of organization. Microfibrils are gathered into twisted bundles which condense into cross-striated fibrils. These fibrils themselves aggregate and show a mutual twist whose orientation is left-handed as is the twist observed within each microfibril bundle. Several models of these architectures are presented. Planar twist, cylindrical twist and toroidal twist are described and their relation to the structure of certain liquid crystals is considered. Examples of orthogonal packing also have been observed. These structures obtained in vitro are very close to patterns already described in vivo in numerous collagen matrices.

Animals↗
PubMed1982

Studies on a highly active anticoagulant fraction of high molecular weight isolated from porcine sodium heparin.

We have studied heparin fractionation using gel filtration and ion-exchange chromatographic methods. The starting material was commercial grade porcine mucosal sodium heparin (PSH). The fractionation was monitored employing synthetic substrates for assaying both antithrombin (with H-D-Phe-Pip-Arg-pNA ; S-2238) and anti-FXa (with Bz-Ileu-Glu-Gly-Arg-pNA ; S-2222) activities. The resulting fractions were evaluated in different amidolytic and coagulation methods used to determine heparin potency by comparison with PSH. By gel filtration of PSH on Ultrogel Aca 54, both strong anti-FXa and antithrombin activities were associated with the fractions eluted in the high molecular weight range (MW congruent to 20 x 10(3)). These fractions also had potent anticoagulant action when assayed by conventional clotting methods. PSH was also subjected to fractionation by an ion-exchange technique (DEAE-Sephacel) with increasing salt molarity. The patterns for antithrombin and anti-FXa activities were again closely related, if not identical. Four fractions were usually distinguished, with respectively negligible, intermediate, high and very high activities when compared to PSH. The very highly active fraction (HAF), approximately 15% by weight, was eluted at high salt molarity (greater than 0.8 M NaCl). On a weight basis its anticoagulant activity was congruent to 2-3 times that of PSH as determined by amidolytic as well as clotting methods. Intravenous injection of HAF to rabbits and dogs (1.0 and 2.5 mg/kg) produced a much stronger anticoagulant response than PSH, also showing an effect which persisted for a longer duration.

Animals↗
PubMed1980

Energetic metabolism of leukocytes. XI. Presence and function of creatine kinase in leukocytes.

Creatine kinase activity could be demonstrated in the cytosol of macrophages and polymorphonuclear leukocytes from guinea pig peritoneal exudates, in circulating mononuclear cells of blood donors and of a preleukemic patient, but not in human circulating polymorphonuclear cells. According to immunoinhibition assays most of the creatine kinase activity of human monocytes (preleukemic patient) and lymphocytes can be assigned to the MM and BB isoenzymes, respectively. Both isoenzymes have been observed in human lymphocytes by electrophoresis; with the help of the same procedure the predominance of creatine kinase BB has been demonstrated in the cells of guinea pig peritoneal exudates. The possible function of creatine kinase in leukocytes is discussed.

Animals↗
PubMed1979

[Acquired von Willebrand's syndrome associated with malignant lymphoma].

The sudden development of multiple bleeding episodes in a 63-year-old patient with malignant lymphoma was shown to be due to the presence of an acquired von Willebrand syndrome, characterized by a prolonged bleeding time and low levels of the factors VIII: C, VIIR:Ag and VIII:Rcof. Crossed immunoelectrophoresis demonstrated diminution of the factor VIII portion with least anodic mobility. Mixing experiments of the patient's and normal plasma revealed a weak (T/2: 4.5 hours) inhibitory activity against the factors VIII:C, VIIIR:Ag and VIII:Rcof. After infusion of 800 units of cryoprecipitate there was rapid destruction (T/2: less than 1 hour) of infused factors VIII: C and VIIIR:Ag and no correction of the bleeding time. Chemotherapy resulted in disappearance of the lymphoma and the hemostatic defect, and its discontinuation in their reappearance. The weak inhibitory activity of the patient's plasma does not fully account for the factor VIII levels observed and other pathophysiological mechanisms, such as adsorption of factor VIII to the malignant lymphocytes, must be considered.

Antigens↗
PubMed1977

The energy metabolism of the leukocyte. IX. Changes in the concentration of the coenzymes NAD, NADH, NADP, and NADPH in polymorphonuclear leukocytes during phagocytosis of Staphylococcus albus and due to the action of phospholipase C.

The determination of the coenzymes NAD+, NADH, NADP+ and NADPH, by the use of a method of enzymatic cycling, demonstrates that the enzymes responsible for the stimulations found during the phagocytosis of Staphylococcus albus are NADH and NADPH oxidase of human leukocytes and NADPH oxidase in the case of guinea pig leukocytes. The effects of serum, of the bacterial strain used and of phospholipase C are also discussed.

Animals↗
PubMed1977

Leucocyte energy metabolism. VII. Respiratory chain enzymes, oxygen consumption and oxidative phosphorylation of mitochondria isolated from leucocytes.

A new method for the destruction of cell membrane with heparin and for the subsequent isolation of mitochondria from different types of leucocytes (polymorphonuclear leucocytes (PMN) and lymphocytes of human blood, PMN and macrophages of guinea pig peritoneal exudates) is presented. This method is less traumatic to the mitochondria than the usual mechanical procedures. The activites of several enzymes of the respiratory chain were estimated. Oxygen consumption was measured with oxyhaemoglobin as oxygen donor and reaction rate indicator. The integrity of the mitochodria can be demonstrated by the determination of the acceptor control index; the existence of a coupled phosphorylation of ADP to the respiration is clearly demonstrated in all type of cells studied; the ADP/O ratios with several substrates, near to the theoretical values, could be estimated in mitochondria preparation of lymphocytes (normal and leukaemic) and of macrophages. The highest oxidative ratios were found in leukaemic cells.

Animals↗