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Biomedical subjects

M Grandgeorge

Publications and source records attributed to M Grandgeorge.

25 records · Page 2Linked to original sources
PubMed1991

Importance of purification on transfusional efficacy of hemoglobin solutions.

It has only been realized quite recently how important is the purification of hemoglobin solution for use in transfusion and several techniques have been published. We used ion exchange chromatography with which the main "contaminants" (glycoproteins, enzymes, phospholipids) are absorbed by the gel, whereas hemoglobin is not retained. The solutions studied here are non-modified hemoglobin and its homologue pyridoxylated hemoglobin (PLP-Hb). Physico-chemical analyses, usually undertaken to characterize hemoglobin solutions, show no difference before and after purification, except that the enzymatic activity almost disappears. In order to appreciate the benefits of purification, total exchange transfusions were carried out on rats. Without reperfusion, purification of the hemoglobin solution allowed a significantly longer survival time which was even more significant with PLP-Hb solution. Urinary loss did not seem to be affected by purification. With reperfusion in order to compensate these renal losses, PLP-Hb solutions gave survival times up to three days. However, the inevitable death of the animals poses the problem of instability of these purified solutions following enzyme loss.

Animals↗
PubMed1990

Increased biological activity of a recombinant factor IX variant carrying alanine at position +1.

In attempts to improve the post-translational modification and processing of recombinant factor IX (FIX) we have altered the cDNA sequence encoding pre-pro-FIX using site-directed mutagenesis and have expressed the variant cDNAs in BHK21 cells using a vaccinia-virus-derived vector. We find that substitution of the tyrosine residue at +1 for an alanine increases the biological activity of the recombinant molecules 2-fold. On the other hand, substitution of the proline at -3 for a valine results in no significant change to the specific activity of the protein. Other alterations to the N-terminus of the FIX proteins, in attempts to mimic other vitamin-K-dependent proteins, result in the failure to produce a secreted polypeptide. N-terminal sequence analysis of purified recombinant molecules reveals a correlation between specific activity and the efficiency of correct pro-sequence cleavage. gamma-Carboxylation analysis of purified recombinant proteins indicates that each molecule including unmutated FIX is completely gamma-carboxylated in this system. Thus the observed increase in biological activity of FIX variants containing an alanine at position +1 is not due to increased gamma-carboxylation but, at least in part, to more efficient pro-peptide cleavage.

Alanine↗
PubMed1989

Inactivation of the human immunodeficiency viruses (HIV-1 and HIV-2) during the manufacturing of placental albumin and gammaglobulins.

A laboratory study was undertaken to verify the elimination and/or inactivation of the human immunodeficiency viruses HIV-1 and HIV-2 during the manufacture of placental albumin and the gammaglobulins Gamma 16 and Veinoglobuline. Nine steps of the process were selected for study. Samples of current production batches were taken at these different stages and a known quantity of virus was added. Each sample was then processed according to the production schedule for the corresponding step, and the residual viral activity was measured. In eight of nine steps, a complete viral clearance was achieved. Estimation of the cumulative infectivity reduction due to these nine steps is in the following range: greater than 12 to 16 log10 HIV-1 and greater than 17 to 19 log10 HIV-2 for Gamma 16, greater than 9 to 13 log10 HIV-1 and greater than 13 to 15 log10 HIV-2 for Veinoglobuline, and greater than 19.7 log10 HIV-1 and greater than 24 log10 HIV-2 for albumin. As many other purification steps were not included in this study, the real infectivity reduction capacity for the whole process probably exceeds these values. Nevertheless, the levels of inactivation measured clearly document a rigorous fractionation process that has a high assurance of killing or eliminating all contaminating virus.

Cytotoxicity Tests, Immunologic↗
PubMed1976

[Partial purification and study of gamma-glutamyl transpeptidase from sheep cerebral capillaries].

Gamma-glutamyl transpeptidase was purified 53 times from Sheep brain cortex capillaries. On gel filtration it appears homogeneous with a M.W. = 350 000. The enzyme is likely a glycoprotein, the properties of which are close to hog kidney gamma-glutamyl transpeptidase ; gamma-glutamyl aminoacid formation is assayed electrophoretically. The results obtained using several aminoacids are in favour of the existence of different units, specific of each group of aminoacids ; together with the data from structural analogs, they support the hypothesis that gamma-glutamyl transpeptidase participates in aminoacid transport accross blood brain barrier.

Amino Acids↗
PubMedDate not supplied

Preparation of unaltered hemoglobin from human placentas for possible use in blood substitutes.

Hemoglobin extracted from human placentas could be used as the basis of blood substitutes provided it could be prepared on a large scale with appropriate oxygen-binding properties. Unfortunately, the industrial conditions under which it is extracted, produce hemoglobin with high oxygen affinity and which is no longer influenced by the classical effectors. These characteristics were shown to be caused by a degradation of the alpha-chain brought about by an arginine carboxypeptidase present in the placental tissues and leading to the disappearance of the C-terminal arginine residue. This carboxypeptidase which is released from the tissues during the process of crushing the frozen placentas, degrades the protein during the chromatographic purification procedure. The addition of an inhibitor of this carboxypeptidase (for example, arginine) as soon as the placentas are thawed and during the chromatographic process, makes it possible to obtain placental hemoglobin with oxygen-binding properties quite similar to those of HbA prepared from peripheral venous blood.

Adult↗