PubMed Health⌕ Search

Biomedical subjects

R Mage

Publications and source records attributed to R Mage.

At least 37 records · Page 2Linked to original sources
PubMed1993

[Islet of Langerhans transplantation in humans].

Islet of Langerhans transplantation is an alternative to whole pancreas transplantation for type I diabetic patients, in whom exogenous insulin therapy has not prevented the occurrence of systemic complications. Thanks to a new isolation technique of human islets, 45 patients have been transplanted worldwide since 1988, of whom only 7 have become totally insulin-independent. Rejection and quality of the islet preparations are problems which remain to be solved. Autotransplantation of islets has been proposed in patients undergoing a pancreatectomy for benign disease. The present report concerns two of our patients who had a pancreatectomy with islet autotransplantation. Both patients are insulin-independent 3 and 11 months postoperatively, with satisfactory metabolic tests. Islet autotransplantation can be proposed when pancreatectomy for non-malignant disease is performed. This method may prevent the development of insulin-dependent diabetes, known to be particularly labile. Because of the sophisticated technical procedures required, human islet isolation is at present only performed in a small number of medical centers and still is in the field of medical experimentation.

Adult↗
PubMed1993

[Transplantation of islets of Langerhans in man].

Islet of Langerhans transplantation is an alternative to whole pancreas transplantation for type I diabetic patients, in whom exogenous insulin therapy has not prevented the occurrence of systemic complications. Thanks to a new isolation technique of human islets, 45 patients have been transplanted worldwide since 1988, of whom only 7 have become totally insulin-independent. Rejection and quality of the islet preparations are problems which remain to be solved. Autotransplantation of islets has been proposed in patients undergoing a pancreatectomy for benign disease. The present report concerns two of our patients who had a pancreatectomy with islet autotransplantation. Both patients are insulin-independent 3 and 11 months postoperatively, with satisfactory metabolic tests. Islet autotransplantation can be proposed when pancreatectomy for non-malignant disease is performed. This method may prevent the development of insulin-dependent diabetes, known to be particularly labile. Because of the sophisticated technical procedures required, human islet isolation is at present only performed in a small number of medical centers and still is in the field of medical experimentation.

Adult↗
PubMed1987

A cluster of rabbit T-cell beta-chain variable region genes.

A genomic Eco RI DNA fragment of 4291 base pairs contains three V beta genes (V44T0, V44T1, and V44T2), each represented as only a single copy in the haploid genome of the rabbit. These V beta do not appear to be pseudogenes; all three can be found on approximately 1.3 kb (mature size) transcripts in thymus RNA, although they do not contain classical upstream promoter sequences. V beta T0 and T1 exhibit high DNA sequence homologies with mouse V beta 10 and V beta 1 genes, respectively (approximately 81 and 73%). In the mouse, the two genes are also closely linked. Rabbit V beta gene T2 resembles mouse V beta 11 and human YT35 DNA sequences but the homologies are lower (approximately 63%). The deduced protein sequences of the rabbit and mouse gene pairs are also conserved and ratios of replacement changes to silent base changes are low, suggesting that there has been selection for conservation of certain portions of the protein sequences. In contrast, the DNA and deduced protein sequences of the adjacent closely linked rabbit V beta genes are remarkably different from each other (approximately 54-65% DNA; approximately 33-55% protein homologies). These facts suggest early duplication of V beta genes and evolutionary conservation of certain members.

Amino Acid Sequence↗
PubMed1986

Anti-hapten IgG antibodies bound to cell surface hapten: anti-IgG antibody prevents dissociation as measured with fluid phase hapten.

We investigated the dissociation by fluid phase hapten of IgG antibodies bound to cell surface hapten in the presence and absence of anti-IgG antibodies. Dissociation was quantitated with fluid phase hapten, preventing reassociation of the anti-hapten antibodies. More than 90% of the anti-hapten IgG alone was prevented from reassociation by low concentrations of fluid phase hapten (nanogram to microgram range). In contrast, no dissociation of some IgG-anti-IgG complexes could be measured even at 24 hr incubation in the presence of very large excess of fluid phase hapten (100 mg/ml). We excluded aggregate formation between anti-hapten antibodies due to cross-linking by anti-antibodies as a cause for decreased dissociability by 1) performing the experiments in large excess of anti-antibody, 2) showing that the phenomenon was independent of anti-hapten antibody density, 3) showing that decreased dissociation also occurred at 4 degrees C, and 4) showing that aggregation by protein A did induce decreased dissociability, albeit three orders of magnitude lower than the anti-antibody. It was concluded that anti-antibody directly affected the "avidity" of cell hapten bound anti-hapten IgG in an unknown manner.

Animals↗
PubMed1983

Use of Trypanosoma equiperdum infected rabbits as a source of splenic mRNA; construction of cDNA clones and identification of a rabbit mu heavy chain clone.

Rabbits were infected by Trypanosoma equiperdum and the splenic mRNA was isolated. In vitro translation of this RNA and immunoprecipitation with anti-light chain, anti-heavy chain, anti-mu and anti-VH antibodies demonstrated that T. equiperdum infection elicits large quantities of splenic mRNA encoding mu and kappa chains. The mu and gamma heavy chains and the kappa light chains synthesized in the cell-free translation system were specifically immunoprecipitated by antisera to heavy chain VHa and light chain kappa b allotypes. In vitro labeling of spleen cells from trypanosome-infected animals demonstrated that the biosynthetically labeled IgM has a mu chain of higher molecular weight than the mu chain synthesized by in vitro translation, a difference that is largely abolished when cellular glycosylation is blocked with the antibiotic tunicamycin. Enrichment for heavy chain or light chain mRNA was achieved by fractionating mRNA from trypanosome-infected animals on a sucrose gradient. cDNA clones carrying mu heavy chain sequences were produced using a 'one tube' protocol and identified by cross species hybridization and hybridization selection. Infection of rabbits with T. equiperdum followed by sucrose gradient enrichment of splenic mRNA has provided sufficient quantities of mRNA encoding mu heavy chain suitable for cDNA cloning.

Animals↗
PubMed1982

Messenger RNA from allotype-defined rabbits directing the cell-free synthesis of immunoglobulin heavy and light chains.

In vitro synthesis studies were performed utilizing polyA(+)-RNA and lymphocytes from the spleens of rabbits hyperimmunized with Micrococcus luteus or Streptococcus pneumoniae (type III). PolyA(+)-RNA isolated after 4 M guanidinium thiocyanate extraction and oligo(dT)-selection appeared to be undegraded on CH3HgOH-agarose gel electrophoresis and demonstrated biological activity when translated in a rabbit reticulocyte cell-free system. The electrophoretic patterns of the specifically immunoprecipitated cell-free products were compared with those of Nonidet-P40 extracts (lysates) and secretions (supernatants) from rabbit spleen lymphocyte cultures and serum proteins. Kappa light chains with specific b allotypes, as well as immunoglobulin heavy chains, were identified. The efficient translation of mRNA of defined allotypes was a necessary prerequisite for production of characterized cDNA clones and identification of genomic sequences for rabbit immunoglobulin heavy and light chains.

Animals↗
PubMed1982

Construction of a partial rabbit spleen cDNA library and identification of immunoglobulin clones.

A partial cDNA library was constructed from total poly A(+)-RNA isolated from the spleen of a rabbit (kappa allotype b5; heavy chain allotypes a3d12e15) that had been hyperimmunized with Streptococcus pneumoniae (type III). In spite of the absence of either specific DNA probes for rabbit immunoglobulin (Ig) sequences or cross-hybridizing mouse Ig DNA probes, recombinant clones containing cDNA sequences of rabbit gamma heavy chain and kappa light chains were identified by a combination of screening techniques: (a) colony hybridization using labeled mRNA; (b) mRNA hybridization selection and translation and (c) hybridization to electrophoretically fractionated poly A(+)-RNA ("Northern" analysis). Sequencing of three kappa light chain recombinant DNA sequences, including part of the 3' untranslated (UT) region, has confirmed the fact that recombinant DNA for kappa light chain mRNA has been identified. An unexpectedly high degree of homology between the 3' UT region sequence of this DNA from a rabbit of b5 allotype and the published 3' UT sequence from a b4 rabbit was found. It appears that 3' UT sequences from b4 and b5 alleles have diverged less than the coding sequences for the constant regions. The functional significance of this conservation of 3' UT sequences remains to be elucidated.

Animals↗
PubMed1977

A screening assay for rapid and quantitative measurement of immunoglobulins and anti-immunoglobulins in unknown sera.

A radioimmunoassay which can measure serum levels of antibody and antigen when both species are immuloglobulins (Igs) is described. The technique is based on competition between insolubilized Ig (bound to Sepharose) and serum Ig for radiolabeled Ig. For measurement of anti-Ig antibodies, labeled Ig antigen is added to a mixture of antibody-Sepharose and unknown or standard antibody solution. For measurement of antigen, labeled, purified antibody is added to a mixture of antigen-Sepharose and unknown or standard antigen solution. Although both assays can detect either Ig antigen or Ig antibody in a given unknown, the antibody assay requires 10-20 times as much antigen as antibody to achieve the same degree of inhibition, and the antigen assay is 100 times more sensitive for antigen than for antibody. By titrating the same unknown in both assays, one can determine whether inhibitory activity is due to antigen or antibody. The routine assay readily detects 1 microgram/ml of antibody or of antigen. A modified assay was also developed which detects levels of antibody as low as 5-10 ng/ml. The technique is simple and allows rapid screening of hundreds of serum samples in a short period of time. The assay can also be modified for measurement of anti-idiotype antibodies.

Animals↗