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Biomedical subjects

R Alejandro

Publications and source records attributed to R Alejandro.

At least 55 records · Page 3Linked to original sources
PubMed1996

Expression of a specific subset of CD44 variant transcripts in NOD pancreatic islets.

Adhesion of lymphocytes to the endothelial venules inside the islets of Langerhans seems to initiate the infiltration of islets in NOD mice. An overexpression of the lymphocyte surface molecule CD44 in infiltrated NOD islets compared with peripheral blood lymphocytes was recently reported. The CD44 protein family includes a variety of molecules generated by alternative RNA splicing from 10 variant exons (v1-v10). By using reverse transcriptase-polymerase chain reaction followed by Southern blotting and hybridization to exon-specific cDNA probes, we investigated the expression of CD44 isoforms in highly purified islets of Langerhans from 4- and 10-week-old NOD mice. At least six CD44 isoforms were strongly overexpressed in NOD islets at 4 and 10 weeks when compared with age-matched BALB/c islets. Controls in different tissues indicate that these variants are specifically increased in the islets from the NOD strain. Islets from the NOD-scid/scid strain also expressed these variant exons. Splenocytes from BALB/c did not express CD44 isoforms, whereas splenocytes from 4-week-old NOD mice did express CD44 variants. Treatment with inflammatory mediators induced new isoforms; however, these transcripts have a different variant exon composition from that found in NOD mice islets. These results suggest that some isoforms are expressed very early in the development of insulitis by a component of the NOD islet itself and underscore a possible role of CD44 in islet infiltration.

Animals↗
PubMed1995

Long-term (> 3-year) insulin independence in a patient with pancreatic islet cell transplantation following upper abdominal exenteration and liver replacement for fibrolamellar hepatocellular carcinoma.

In the University of Pittsburgh experience, the most successful setting for human islet allografts is in patients undergoing upper abdominal exenteration with total pancreatectomy and liver transplantation for the indication of malignancy (cluster). In this group of patients 6/11 were insulin-independent for long periods. We report herein the metabolic course or the longest survivor (> 3 years). This patient has been free of exogenous insulin since the third postoperative month and has sustained her body weight without total parenteral nutrition since the 4th postoperative month. The patient has some postprandial hyperglycemia but average capillary glucoses are near-normal to normal as are glycosylated hemoglobin values. The clearance of glucose during the administration of an intravenous glucose load has been well preserved and is currently normal. C-peptide stimulates significantly in response to intravenously injected glucose. The absolute levels of stimulation during the test have declined possibly related to improvements in renal function, decreased immunosuppression or the natural history of cells transplanted into the portal site. The kinetics of the C-peptide response to intravenously injected glucose shows a persistent abnormality of first-phase insulin release and a prolonged second phase release. Basal glucagon levels are low but stimulate to a mixed meal. This patient's results demonstrate long-term function of islet cells from a single donor transplanted into the portal vein using FK506 as an immunosuppressant agent.

Abdominal Neoplasms↗
PubMed1995

The influence of donor specific vertebral body derived bone marrow cell infusion on canine islet allograft survival without irradiation conditioning of the recipient.

In recent studies in rodents, it was shown, that donor specific tolerance towards islet allografts without irradiation therapy of the recipient is induced by bone marrow cell infusion in combination with temporary immunosuppression. In the present study, the effect of donor specific bone marrow cell (DBMC) infusion at the time of intrahepatic islet allotransplantation without irradiation conditioning of the recipient was investigated in the canine model, paralleling ongoing clinical trials. It was observed, that unfractionated bone marrow cells given simultaneous to islet allografts led to higher frequencies of rejection periods and decreased islet allograft survival, when administered to recipients immunosuppressed with Cyclosporine A only. In contrast, an additional short inductive treatment of the recipient with an anti-dog-T-lymphocyte monoclonal antibody (5G2) abrogated the enhanced immunogenicity of the unfractionated bone marrow preparation, prolonging islet allograft survival with no rejection episodes observed during the immunosuppressive treatment with Cyclosporine. The composition of bone marrow cells might have contributed to the higher immunogenicity, since the percentage of MHC-class II antigen bearing cells is similar to man, but significantly higher than compared to rodents. It is therefore suggested, that further studies should encompass both timing of bone marrow cell infusion, appropriate immunosuppression and strategies to functionally inactivate mature MHC-class-II positive cells prior to DBMC infusion.

Animals↗
PubMed1995

Transplantation of islets of Langerhans in patients with insulin-dependent diabetes mellitus.

From 1974 to December, 1992, as reported by the International Islet Transplant Registry, there have been 175 adult islet allografts worldwide. Ninety-eight of these transplants have been performed since 1989. Eleven patients with Type I diabetes mellitus who have received islet allografts since 1989 have achieved insulin-independence for variable periods of time. As of June, 1993, four patients remain insulin-independent (from > 127 to > 326 days). Insulin-independence after human islet cell transplantation is not yet a consistent achievement. Several key issues in pancreas procurement, islet cell isolation, islet preservation, islet engraftment and the prevention of islet allograft rejection still need to be addressed. The expansion of current clinical trials should be limited to patients who are taking or who require immunosuppressive drugs for other reasons (kidney or liver transplant recipient) since the risks of chronic immunosuppression probably outweight the risks from chronic diabetes, although as we are able to induce a more specific state of immunosuppression this rationale may become debatable.

Animals↗