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G L Warnock

Publications and source records attributed to G L Warnock.

At least 73 records · Page 4Linked to original sources
PubMed1993

The effect of cryopreservation on the survival and MHC antigen expression of murine islet allografts.

Cryopreservation is an effective method of islet storage that can facilitate clinical trials of islet transplantation. In the present study we examined the effect of cryopreservation on the survival of islet allografts and the quantity of islet MHC antigen expression. Islets isolated from CBA/J (H-2k) mice were transplanted into streptozotocin-induced diabetic BALB/c (H-2d) mice treated with or without antilymphocyte serum (ALS). Frozen/thawed (F/T) grafts were cooled slowly to -40 degrees C, stored at -196 degrees C, and thawed rapidly. Fresh and F/T isograft controls reversed diabetes promptly and maintained normoglycemia > 100 days. Allografts of fresh and F/T islets induced normoglycemia initially, but graft failure ensued at 18.2 +/- 1.5 and 16.4 +/- 1.9 days, respectively. ALS treatment prolonged allograft survival significantly to 35.3 +/- 3.9 and 37.5 +/- 6.3 days for fresh and F/T islets, respectively. Following cryopreservation, the quantity of class I antigen expression was reduced by 40%, while the quantity of class II expression was variable. These data indicate that murine islet MHC class I expression is reduced after cryopreservation. This decrease was not associated with altered survival of allogeneic grafts.

Animals↗
PubMed1993

Survival and function of purified islets in the omental pouch site of outbred dogs.

The aims of this study were to devise an omental pouch site for islet implantation in a preclinical large animal and to compare the function of islets engrafted to this site with islets implanted into the spleen. Highly purified islets were isolated from outbred mongrel dogs, then grafted into totally pancreatectomized outbred recipients. Autografts of islets were implanted into a greater omental pouch (group [gp] 1, n = 12) or into the spleen by venous reflux (gp 2, n = 12). Allografts of single donor islets were implanted into the omental pouch (gp 3) of dogs that received CsA (n = 9) or untreated controls (n = 3). The threshold islet mass that consistently reversed diabetes in gp 1 was 10 microliters/kg, which exceeded by 2.5-fold that required in gp 2. Normoglycemia was induced and maintained for 2 months in 6 gp 1 and 8 gp 2 dogs. At IVGTT, the K value (decline in glucose, %/min) was 1.3 +/- 0.4 in gp 1 versus 1.5 +/- 0.2 in gp 2 (P > 0.2). Peripheral venous insulin levels were significantly lower (P < 0.01) in gp 1. Omentectomy (gp 1) or splenectomy (gp 2) induced prompt hyperglycemia. All gp 3 dogs (received > 10 microliters/kg) were initially normoglycemic: grafts of untreated controls failed at 4.2 +/- 1.8 days. In 1 CsA-treated dog the graft failed for technical reasons; normoglycemia persisted in the other 8 for 10, 15, and 21 days, and in 5 instances for > 30 days. When CsA therapy was stopped at 30 days, normoglycemia persisted for 34 +/- 9.5 days. We conclude that purified islets restore normoglycemia after implantation into the omental pouch of diabetic dogs. Compared with intrasplenic islet implantation, an increased graft volume is required and insulin levels are lower.

Animals↗
PubMed1992

Long-term follow-up after transplantation of insulin-producing pancreatic islets into patients with type 1 (insulin-dependent) diabetes mellitus.

Purified human islets and a kidney from the same donor were transplanted into four patients with Type 1 (insulin-dependent) diabetes mellitus. Two of the patients received additional islets that were isolated from multiple donors, cryopreserved, and stored in a tissue bank. The islets were embolized into the liver via the portal vein. Immunosuppression was induced with antilymphocyte globulin and maintained with azathioprine, prednisone and cyclosporine. In the first two patients, fasting serum C-peptide rose to levels of 0.5-2.0 ng/ml during the first 4-8 weeks and mixed meal feeding elicited increases to 2-3 ng/ml. C-peptide secretion persisted for 8 months, but at progressively lower levels and insulin therapy could not be withdrawn. In the next two patients who received cryopreserved islets in addition to fresh islets, serum C-peptide levels (fasting/post-meal) rose to 4-7 ng/ml and serum glucose was more stable, allowing withdrawal of insulin therapy after 69 days in one patient, and reduced insulin doses in the other. The insulin-independent patient has maintained normal fasting glucose, glycosylated haemoglobin, and oral glucose tolerance at 1 year following cessation of daily insulin therapy. Episodes of renal graft rejection occurred in three patients, including the insulin-independent patient. High-dose steroid therapy reversed the rejection in all instances, with apparent preservation of C-peptide secretion. These data show that transplantation of purified freshly-prepared and cryopreserved islets into Type 1 diabetic patients results in prolonged insulin secretion, and that sufficient function could be provided in one patient to sustain euglycaemia in the absence of insulin therapy at 1 year of follow-up.

Adult↗
PubMed1992

Prevention of recurrence of IDDM in islet-transplanted diabetic NOD mice by adjuvant immunotherapy.

Insulin-dependent diabetes mellitus (IDDM) involves the destruction of the insulin-producing cells in the islets of Langerhans. One possible cure is by transplanting the islet cells; however, transplanted islets, even between identical twins, are subject to autoimmune destruction by the disease process, resulting in diabetes recurrence. We recently reported that complete Freund's adjuvant (CFA), an immunomodulating agent, prevented development of autoimmune diabetes in the NOD mouse. In this study, we evaluated adjuvant therapy in prevention of autoimmune destruction and rejection of transplanted islets in diabetic NOD mice. After transplantation, untreated syngeneic islet recipients (n = 16) initially became normoglycemic and then hyperglycemic, with a median survival time (MST) of the graft of 17 days. When CFA was administered at the time of transplantation, 11 of 13 CFA-treated syngeneic islet recipients remained normoglycemic long term (greater than 100 days) with an MST greater than 107 days. Ten of 11 mice maintained indefinite normoglycemia until the conclusion of follow-up (101 to 172 days). When adjuvant therapy was used in conjunction with allogeneic islet transplantation, graft survival was not extended, with MST being similar to the untreated allogeneic islet recipients (12 [n = 5] and 13 [n = 5] days, respectively). The extended acceptance of second syngeneic islet grafts by CFA-treated mice indicates that the persistent autoimmunity against the transplanted islets can be reversed in the diabetic NOD mice after CFA treatment.

Animals↗
PubMed1991

Normoglycaemia after transplantation of freshly isolated and cryopreserved pancreatic islets in type 1 (insulin-dependent) diabetes mellitus.

Purified islets of Langerhans and a kidney were transplanted into a 36-year-old patient who suffered from renal failure secondary to a 25 year history of Type 1 (insulin-dependent) diabetes mellitus. The islet graft contained 243,000 fresh islets (mean islet diameter 150 microns) that were syngeneic with the kidney graft and 368000 cryopreserved islets that had been collected from four other donors. The total of 10,000 islets/kg body weight was infused into the liver via the umbilical vein. Immunosuppression was induced with antilymphocyte globulin and maintained with prednisone, cyclosporine and azathioprine. Serum C-peptide levels (ng/ml) during fasting and after standard mixed meal feeding (Sustacal) were less than 0.12 preoperatively. Postoperatively, insulin secretion was restored: fasting C-peptide rose during the first 4 weeks to levels of 4 to 5 and Sustacal elicited a further rise to 6 to 7. Transplant renal function was stable. Daily fasting glucose (mmol/l, mean +/- SD) was 5.6 +/- 1 and 5.3 +/- 0.6 during the first and second months respectively and post-Sustacal glucose was 5.7 +/- 0.8. Exogenous insulin therapy was progressively withdrawn and stopped during the ninth week. Thereafter, fasting glucose was 4.7 +/- 0.5, 24 h mean glucose was 6.6 +/- 0.5, and normoglycaemia was maintained after Sustacal. These data show that this mass of freshly isolated and cryopreserved islets from multiple donors provided sustained function (3 months) that reversed insulin-dependence in an immunosuppressed Type 1 diabetic patient treated with simultaneous islet-kidney transplantation.

Adult↗
PubMed1991

Transplantation of purified frozen/thawed canine pancreatic islet allografts with cyclosporine.

We studied the survival of defined volumes of highly purified frozen/thawed islets transplanted into the spleen of 4 groups of apancreatic mongrel dogs (total, 21), with or without cyclosporine from day -4 to day 30: group 1 (controls), without CsA, autograft of mean (+/- SE) islet volume 5 +/- 1 microliters/kg body weight; group 2, single-donor allograft, and group 3, multiple-donor allograft (both, 6 +/- 1 microliters/kg), both with CsA; and group 4, large-volume multiple-donor allograft (24 +/- 1 microliters/kg) with CsA. Grafts were cooled slowly to -40 degrees C, stored at -196 degrees C, and thawed rapidly. The CsA dose was adjusted to maintain whole-blood trough values of 600-800 micrograms/L, and allograft recipients manifesting early hyperglycemia were given insulin to maintain plasma glucose concentration below 150 mg/dl. In group 1, two dogs died early (graft failure in 1, intussusception in 1), but the remaining five were normoglycemic at 30 days. In groups 2 and 3, hyperglycemia ensued from about day 2.5, but 4 of 5 grafts in group 2 and all grafts in group 3 secreted insulin into the splenic vein at 30 days. In group 4, normoglycemia ensued within 24 hr of transplantation and was maintained in all 6 dogs for 30 days; the grafts failed 15 +/- 2 days after CsA was stopped. The data demonstrate prolonged function of purified frozen/thawed islets after transplantation into these outbred dogs but indicate a need for a greater volume of allogeneic islets from multiple donors than of autologous islets to achieve normoglycemia.

Animals↗