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Biomedical subjects

R Alejandro

Publications and source records attributed to R Alejandro.

At least 109 records · Page 6Linked to original sources
PubMed1990

Pancreatic islet transplantation after upper abdominal exenteration and liver replacement.

Nine patients who became diabetic after upper-abdominal exenteration and liver transplantation were given pancreatic islet-cell grafts obtained from the liver donor (eight cases), a third-party donor (one), or both (four). Two patients were diabetic when they died of infections after 48 and 109 days, as was a third patient who died of tumour recurrence after 178 days. The other 6 are alive 101-186 days postoperatively, and five are insulin-free or on insulin only during night-time parenteral alimentation. C-peptide increased 1.7 to 3.3 fold in response to intravenous glucose in these five patients who have had glycosylated haemoglobin in the high normal range. However, the kinetics of the C-peptide responses to intravenous glucose in all eight patients tested revealed an absent first-phase release and a delayed peak response consistent with transplantation and/or engraftment of a suboptimal islet cell mass. The longest survivor, who requires neither parenteral alimentation nor insulin, is the first unequivocal example of successful clinical islet-cell transplantation.

Abdomen↗
PubMed1990

Isolation of pancreatic islets from dogs. Semiautomated purification on albumin gradients.

We describe a procedure for the isolation of large numbers of canine pancreatic islets with a high level of purity. The method utilizes enzymatic and mechanical disruption of the pancreas, followed by islet purification on discontinuous density gradients of bovine serum albumin. Purification has been semiautomated through use of the Cobe 2991 cell processor. Islet preparations have a purity of 86.5% and contain 36.8 microliters of endocrine tissue. Islets isolated by this procedure are functionally intact, and restore fasting euglycemia following autotransplantation.

Animals↗
PubMed1990

Ultraviolet light immunomodulation of canine islets for prolongation of allograft survival.

Ultraviolet (UV) light treatment of donor islets has been shown to be effective for the prolongation of islet allograft survival in rodent models. This study evaluated UV as an immunomodulator of canine islets. The effects of UV irradiation on islet secretory function in vitro revealed a trend of increasing basal insulin release with increasing doses of UV and a corresponding significant decrease in glucose-mediated insulin release (expressed as percentage of basal fractional insulin release) beginning at UV light exposures of 200-300 J/m2 (n = 3, P less than 0.05). Proliferative responses to UV-irradiated allogeneic peripheral blood leukocytes and islets were significantly decreased by 53-112% (P less than 0.05) in 27 of 29 mixed-lymphocyte cultures and by 35-74% (P less than 0.05) in 4 of 5 mixed-lymphocyte islet culture experiments, respectively, beginning at 200-600 J/m2. Autotransplantation of nonirradiated (n = 8) and irradiated islets (600 J/m2, n = 6) resulted in a 1-mo graft survival rate of 75% for the control group and 50% for the irradiated group. Allotransplantation of irradiated islets (600 J/m2) into either nonimmunosuppressed recipients (1 donor to 1 recipient, n = 8) or recipients of subimmunosuppressive doses of cyclosporin (2 donors to 1 recipient, n = 4) resulted in 100% rejection by day 10. In contrast, when islets were cultured for 24 h postirradiation and transplanted into cyclosporin-treated pancreatectomized recipients (2 donors to 1 recipient), 3 of 7 grafts were prolonged beyond day 10 to days 16, 26, and greater than 100.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Experience with islet immunoalteration in dogs: in vitro and in vivo studies.

In an attempt to prolong canine islet allograft survival, in the presence of minimal or no recipient immunosupression, two methods of islet immunoalteration were utilized prior to transplantation. With or without administration of subimmunosuppressive doses of cyclosporin A (CSA) to recipients, treatment of islets with anti-class II monoclonal antibody (moab) and complement (C) resulted in prolongation of allograft survival when treatment was combined with a culture period of 7 days. Transplantation of ultraviolet light (UV) irradiated, 24 hour cultured islets into recipients of subimmunosuppressive doses of CSA also resulted in modest prolongation of allograft survival.

Animals↗
PubMed1989

Immunochemical studies of DNA polymerase delta: relationships with DNA polymerase alpha.

A panel of murine hybridoma cell lines which produce antibodies against polypeptides present in human placental DNA polymerase delta preparations was developed. Eight of these antibodies were characterized by virtue of their ability to inhibit DNA polymerase delta activity and immunoblot the 170-kDa catalytic polypeptide. Six of these eight antibodies inhibit DNA polymerase delta but not DNA polymerase alpha, showing that the two proteins are distinct. However, the other two monoclonal antibodies inhibited both DNA polymerase delta and alpha activities, providing the first evidence that these two proteins have a structural relationship. In addition to antibodies against the catalytic polypeptide we also identified 11 antibodies which recognize 120-, 100-, 88-, 75-, 62-, 36-, and 22-kDa polypeptides in DNA polymerase delta preparations, suggesting that these proteins might be part of a replication complex. The antibody to the 36-kDa polypeptide was shown to be directed against proliferating cell nuclear antigen/cyclin. These antibodies should prove useful for studies aimed at distinguishing between DNA polymerases alpha and delta and for the investigation of the functional roles of DNA polymerase delta polypeptides.

Animals↗
PubMed1989

Effects of cyclosporin on insulin and C-peptide secretion in healthy beagles.

Plasma glucose, C-peptide, and insulin responses to intravenous glucose (intravenous glucose tolerance test [IVGTT], 0.5 g/kg), glucagon (1 mg i.v.), and oral glucose (oral glucose tolerance test [OGTT], 1 g/kg) were assessed in six normal beagles before, during, and 1 and 4 mo after the administration of cyclosporin A (CsA) in doses previously shown to be required for uniform prevention of canine islet-allograft rejection (20 mg/kg; mean trough radioimmunoassay serum levels greater than or equal to 500 ng/ml). Insulin secretion in response to intravenous glucose and glucagon was significantly inhibited during the administration of CsA (areas under insulin-response curves, pmol.min-1.L-1; IVGTT, pre-CsA, 11,127 +/- 1285; during CsA, 5954 +/- 1147, P less than .05; glucagon tolerance test, pre-CsA, 18,617 +/- 2807; during CsA, 4401 +/- 486, P less than .05 vs. pretreatment levels). These secretory defects persisted 4 mo after CsA was discontinued (IVGTT, 4358 +/- 659; glucagon tolerance test, 10,567 +/- 2479, P less than .05). C-peptide responses paralleled these changes. Plasma glucose disposal in response to these secretagogues, however, returned to normal 1 mo after discontinuation of CsA. In contrast to the findings for IVGTT and glucagon, insulin-response curves to OGTT were not statistically different during CsA administration. We conclude that, although glucose disappearance rates are normal after discontinuation of the CsA administration, CsA causes irreversible impairment in islet secretory responses detectable with IVGTT and glucagon but not with OGTT. These results suggest that short-term CsA in doses required to prevent islet-allograft rejection in dogs can result in permanent loss of functionally competent beta-cells.

Animals↗
PubMed1988

Advances in canine diabetes mellitus research: etiopathology and results of islet transplantation.

Histopathologic and immunocytochemical alterations in the pancreas of 18 dogs with spontaneous diabetes mellitus were evaluated. In 5 of 18 dogs (28%), extensive pancreatic damage appeared to be responsible for the development of diabetes mellitus. In the other 13 dogs, there was substantial reduction in the number of well-granulated beta cells, but the number of well-granulated alpha and delta cells was normal in 70% and 85% of the dogs, respectively. Also, insulitis lesions composed of infiltrating mononuclear cells, predominantly lymphocytes, were observed in 6 of 13 dogs (46%), but evidence of islet-directed humoral autoimmunity was not detected. Each pancreas had dense Ia (class II antigen) expression on ductal epithelia but not on islet endocrine cells. The importance of the insulitis lesions and class II antigen expression on ductal epithelial cells remains unclear. Of the 18 dogs, 8 received multidonor intrahepatic islet allografts. Allograft rejection was prevented by administration of cyclosporin. Five dogs were administered cyclosporin continuously. One dog with an allograft failed to sustain euglycemia at 231 days after transplantation, and one dog with fasting euglycemia died of pneumonia at 186 days after transplantation. In the other dogs, euglycemia was sustained for periods that ranged from 253 to 716 days.

Animals↗
PubMed1988

Effects of in vitro and in vivo anticanine T lymphocyte and anticanine class II-specific monoclonal antibodies in the beagle.

Two murine anticanine lymphocyte monoclonal antibodies, designated T83 and B1F6, were assessed for (1) in vitro antiepitope activity to circulating lymphocyte subsets, their functional effects on lymphoproliferative assays and binding specificities to diverse cell suspensions and tissue sections; (2) in vivo effects after administration on cells expressing the target epitopes, lymphoproliferation, and allograft survival; and (3) the host immune response to the injected murine immunoglobulins. The monoclonal antibody T83 (IgG3) appeared to be specific for a T cell subset with an up-regulating function on lymphoproliferation. It caused a profound depletion of cells with the appropriate epitope after intravenous administration but it bound to lymphocyte membrane epitopes on some cells in peripheral blood that did not become depleted and putatively caused other modulating effects on lymphocyte function. The monoclonal antibody B1F6 (IgG2a, previously described) was immunologically specific in vitro for cells expressing class II major histocompatibility complex antigens. In the dog, this also consisted of 50% of T lymphocytes. After intravenous administration, there were functional effects similar to those of T83. A modest prolongation of survival of renal allografts was observed when both mAbs were used as the sole immunosuppressive agent. These studies also demonstrated the occurrence of natural canine antimurine IgG antibodies. Administration of either monoclonal antibody was followed by a rapid increase in the concentration of the antimouse antibody(s). We postulate that the presence of canine natural antimouse IgG markedly influenced the biologic effects of in vivo administered monoclonals.

Animals↗
PubMed1988

Natural history of multiple intrahepatic canine islet allografts during and following administration of cyclosporine.

Cyclosporine (CsA) prevented acute rejection of intrahepatic canine islet allografts (IHIA) in 5/5 pancreatectomized dogs. Normal fasting blood glucose levels were sustained in these dogs for 210 +/- 78 days (mean +/- SEM) following withdrawal of CsA. We tested whether combining islets from more than one pancreas would improve function and prolong islet allograft survival during and following administration of CsA. Areas under the glucose disappearance (GDA) and C-peptide response (CPA) curves following i.v. glucose (0.5 g/kg), 1 month posttransplant were not significantly different using islets from 1 or 2 pancreases, whereas GDA and CPA approached normal if islet yields from 3 or more pancreases were combined. Mean islet allograft survival following interruption of CsA decreased with an increase in the number of donor pancreases (one: 210 +/- 78 days, vs. two: 113 +/- 23 days, vs. greater than 2: 57 +/- 5 days). These studies demonstrate that: (1) IHIA uniformly resulted in fasting euglycemia in 36 of 38 diabetic dogs treated with CsA; (2) normal i.v. glucose metabolism required the combined islet yield of 3 or more donor pancreases, suggesting that a substantial number of intrahepatic islet cells are functionally lost despite effective CsA-induced immunosuppression; (3) use of multiple donors to accumulate an increased mass of islets may immunologically compromise allograft survival following discontinuation of CsA (these experiments, however, do not exclude a direct relationship between the duration of CsA therapy and the duration of immune unresponsiveness following interruption of CsA in multidonor islet allografts as an independent variable); and (4) unmodified islets obtained from multiple donors seem to require continuous immunosuppression to prevent rejection.

Animals↗
PubMed1987

Effect of anti-Ia antibodies, culture, and cyclosporin on prolongation of canine islet allograft survival.

Evidence in rodents suggests that islet pretreatment to reduce islet immunogenicity will also require some form of immunosuppression of the recipient for islet allograft acceptance in highly reactive donor-recipient pairs. We attempted to ascertain whether outbred dogs would also require treatment of both donor islets and the recipient to prolong islet allograft survival. Untreated canine islets are uniformly rejected in 6-10 days in beagles. Tissue culture alone, at 37 degrees C for 7 days, or treatment of freshly prepared islets with anti-Ia monoclonal antibodies (MoAbs) (B1F6 + 7.2) did not prolong canine islet allograft survival. Treatment of culture-maintained canine islets with anti-Ia MoAbs plus complement resulted in prolongation of islet allograft survival for 188 and 368 days in two of seven pancreatectomized nonimmunosuppressed beagles. The administration of low doses of cyclosporin A (CsA) intramuscularly, to recipients of untreated canine islet allografts had no effect on graft survival. By contrast, six of nine CsA-treated recipients of islets that were also treated with anti-Ia MoAbs (B1F6 + 7.2) plus complement showed prolongation of graft survival. Euglycemia was sustained for 19, 34, 89, and 300 days after the CsA was discontinued (day 30) in four of these animals. Two animals had unstable grafts from the beginning that failed 23 and 29 days after transplantation. Our results indicate that simple maneuvers like short-term tissue culture at 37 degrees C and treatment of freshly isolated islets with anti-Ia MoAbs and complement are inadequate to prevent rejection in outbred pancreatectomized beagles.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗