[Amyloidosis, protein conformation dynamics and neurologic diseases]. / Amylose, dynamique conformationnelle des protéines et maladies neurologiques.

The abnormal protein which accumulates in the extracellular space in the central nervous system in Alzheimer's disease and prion diseases could result from similar mechanisms. Many studies have demonstrated that the abnormal protein is resistant to proteolytic agents. This resistance is correlated with a modification in the conformation of the protein, inverting the ratio of alpha and beta helix structures. This change in conformation could be the cause of the central nervous system lesions. The mechanism of the modification in conformation could be related to a process of hydrophobisation of the protein resulting from mutation. A hydrophilic amino acid would be replaced by a hydrophobic amino acid or in sporadic forms, modifications in the environment of the peptide may lead to physical and chemical aggressions. Hydrophobisation of the two proteins could later lead to formation of polymers and then insoluble aggregates with the physical and chemical characteristics of the amyloid substance. Polymerisation could be triggered by the formation of protein dimers which would be, in one case, an endogenous protein, PrP, and in the other exogenous proteins coming from the environment.

Condensable chemical vapors for sterilization of freeze dryers.

Sterilization of freeze dryers is usually performed by subjecting them to saturated steam under pressure by steam (121 degrees C, 2 bar a., 30 minutes). In order to avoid such stressful conditions, another process was designed on the basis of a strong oxidizing mixture of condensable chemical vapors, consisting of ozone and hydrogen peroxide in acidic conditions. This process works at sub-zero temperatures up to 30 degrees C and under negative pressure. 10(6), inoculum of standard biological indicators as well as wild types of bioburden were easely sterilized from 2 minutes up to 10 minutes. Other parameters were studied, in order to optimize the main process conditions: temperature, pressure, concentration of chemicals, type of micro-organisms and their environmental surroundings.

Liquid pasteurization of an immunoglobulin preparation without stabilizer: effects on its biological and biochemical properties.

Intravenous immunoglobulins (IVIg) purified by cold ethanol fractionation have a very good safety record with regard to the transmission of many viruses. However, a few cases of non-A-non-B hepatitis have been described after intravenous injection of some immunoglobulin preparations. To ensure even higher safety for our IVIg, an additional virus inactivation step, based on pasteurization, was developed. The heating of aqueous IVIg was performed without stabilizer, and at a very low salt concentration (< 1 mM) at acidic pH. No generation of polymer was detected after pasteurization and a significant decrease in the proportion of dimers was observed. Analysis of the secondary structure by circular dichroism showed a very slight change in the secondary structure. The biological properties of the Fc region as well as the Fab region were not affected by the pasteurization. Our method has several advantages: (1) improvement of viral safety; (2) there is no need to add stabilizer which may stabilize viral particles, and (3) the absence of any hypotensive effect and low anticomplementary activity indicates a good clinical tolerance of IgG preparation.

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.

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.

[Histopathology of microsurgical arterial repair. Use of fibrin cryoprecipitates]. / Histopathologie de la réparation artérielle microchirurgicale. Apport des cryoprécipités fibrineux.

The increasing practice of small arteries anastomosis especially in neurosurgery entails improvements in suture techniques. Classical suture is slow and needs a prolonged clamping. The stitches are responsible for severe necrotic lesions in the arterial wall. A biological glue made of cryoprecipitated human fibrinogen, factor XIII and fibronectin, locally activated by thrombin, is tested here on rabbit's common carotid. The application of the glue on intact or sectioned arteries appears innocuous, notably with regard to its thrombogenic potential. Comparison of classical sutures and sutures with glue and a greatly reduced number of stitches shows histological results of equivalent quality. At the early stages, the fibrin glue doesn't exceed in volume the usual perianastomotic hematoma. It is completely resorbed within two weeks. Later the scar is thinner than after classical suture, although no ruptures or aneurysms were observed. This method shortens the surgical procedure, with presumed benefit for the drained territories. It diminishes the lesions caused by the stitches. Moreover it allows an easy application of an arterial patch on the sectioned vessel: a comparative series with sutured patches shows on the contrary poor results. Although aggresive for the tissues, a minimal number of stitches remains necessary: it is actually the only available means of correctly positioning the anastomosis area.

Chemical contaminants in human serum albumin: presence of glucose and ethanol in freeze-dried or ultrafiltered products.

Glucose and Ethanol are determined in final Human Serum Albumin solutions, obtained by two different processes: freeze-drying (FD) and ultrafiltration (UF). The elimination rate for glucose is higher than that for ethanol in case of ultrafiltration. The concentration of both "contaminants" seems to be much lower by UF than by FD. From these data arises the question of a limit-value for fractionating agents, in the final product. In the case of FD process, as the reagents remain in the product final, they all must be strongly controlled. As a large part of small molecules can be eliminated by UF process, it permits to seek new reagents for protein separation.

HBs antigen in human plasma fractions.

Therapeutic fractions were obtained by fractionating human plasma containing HBs antigen, by the Cohn ethanol technique modified by Nitschmann. Plasmas with various HBs antigen titers were selected. The antigen was sought in each fraction by the techniques of counterelectrophoresis and radioimmunological detection in liquid phase. With the exception of very pure albumins, all fractions were found to contain the HBs antigen, though in variable proportions. A technique for the purification of albumin, applicable on an industrial scale, is proposed. It makes it possible to obtain an albumin fraction in which the HBs antigen cannot be detected by the most sensitive techniques, even starting with a plasma which is very rich in HBs antigen (titer 1/64 by counterelectrophoresis).