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Biomedical subjects

P E Lacy

Publications and source records attributed to P E Lacy.

At least 19 recordsLinked to original sources
PubMed1992

A T-cell dormant state in the autoimmune process of nonobese diabetic mice treated with complete Freund's adjuvant.

Three experimental manipulations showed the suppressive effect of injection of complete Freund's adjuvant (CFA) in the diabetic state of nonobese diabetic (NOD) mice. (i) Diabetes was inhibited in young NOD mice injected with the adjuvant. (ii) Recurrence of diabetes in mice transplanted with pancreatic islets was also inhibited when the recipients were injected with CFA. (iii) Injection of spleen lymphocytes from diabetic mice into male NOD mice transferred the diabetic state, but this transfer was markedly suppressed when the recipients were treated with CFA. In all three cases the spleen cells from the normoglycemic mice treated with CFA induced diabetes when transferred into NOD male mice. CFA, therefore, induces a state of T-cell dormancy, in which the islets are no longer subject to an immune attack.

Adjuvants, Immunologic↗
PubMed1992

Beneficial effect of syngeneic pancreatic islet transplantation on liver atrophy and hepatocellular function after portacaval shunt.

BACKGROUND: Hepatic insufficiency, which continues to be a source of morbidity after portacaval shunt (PCS), can be prevented by syngeneic pancreatic islet transplantation into the portal vein before PCS. This study investigated the ability of syngeneic pancreatic islet transplantation after PCS to prevent hepatic atrophy and rescue hepatocellular function. METHODS: Approximately 1200 to 1400 syngeneic rat pancreatic islets were transplanted through a heparinized catheter into the left lobes of the liver 3, 7, and 21 days after end-to-side PCS. Normal rats received no treatment, and PCS control rats received PCS only, without islet transplantation. Hepatocellular function (caffeine clearance) and hepatic blood flow (indocyanine green clearance) were analyzed at 42 and 49 days after PCS. On day 51 after PCS, the left and right lobes of the liver were divided, weighed, and sectioned for histologic studies. RESULTS: Caffeine clearance in the animals at 3 days (p less than 0.05) and at 7 days (p less than 0.05) after end-to-side PCS was significantly improved versus control PCS animals, indicating that hepatocellular function could be rescued after creation of a PCS. Indocyanine green clearance of all groups with PCS was significantly (p less than 0.001) decreased versus normal animals, showing that hepatic blood flow was uniformly decreased by PCS in all groups. The weight of the transplanted left lobes was significantly greater than the untransplanted right lobes of the groups at 3 days (p less than 0.01) and at 7 days (p less than 0.05) after end-to-side PCS compared with control animals, indicating that liver atrophy was prevented in the islet-transplanted lobes but not in those lobes without a transplant. CONCLUSIONS: Islet transplantation early after PCS can prevent liver atrophy and significantly improve hepatocellular function.

Animals↗
PubMed1991

Maintenance of normoglycemia in diabetic mice by subcutaneous xenografts of encapsulated islets.

The goal of islet transplantation in human diabetes is to maintain the islet grafts in the recipients without the use of immunosuppression. One approach is to encapsulate the donor islets in permselective membranes. Hollow fibers fabricated from an acrylic copolymer were used to encapsulate small numbers of rat islets that were immobilized in an alginate hydrogel for transplantation in diabetic mice. The fibers were biocompatible, prevented rejection, and maintained normoglycemia when transplanted intraperitoneally; hyperglycemia returned when the fibers were removed at 60 days. Normoglycemia was also maintained by subcutaneous implants that had an appropriately constructed outer surface on the fibers.

Acrylic Resins↗
PubMed1991

Results of our first nine intraportal islet allografts in type 1, insulin-dependent diabetic patients.

With the first demonstration of insulin independence following intraportal islet transplantation into a patient with type 1 diabetes, a new era of clinical islet transplantation will begin. This report provides our initial experience of clinical islet transplantation with a total of nine consecutive portal vein islet transplants in seven diabetic recipients. The first three transplants were done in nonrenal failure diabetics (NRFI) using 6319 +/- 2173 islets/kg body weight with islets processed from single pancreas and cultured for 7 days at 24 degrees C. Prednisone, azathioprine, and cyclosporine were initiated prior to transplant. While all three recipients demonstrated C-peptide function posttransplant, all three rejected their grafts at 2 weeks. Five days of OKT3 treatment failed to recover more than 10% of their rejecting islet grafts. The studies were then shifted to established kidney transplant recipients (EKI) maintaining their basal immunosuppression while adding 7 days of Minnesota antilymphoblast globulin (MALG) to the recipient using islets from single donor pancreas that had been cultured for 7 days at 24 degrees C. There were an average of 6161 +/- 911 islets transplanted intraportally into three EKI recipients. All three had C-peptide response from the transplant, but none achieved insulin independence. While the first patient rejected his graft at 2 weeks, two recipients demonstrated long-term islet function up to 10 months posttransplant. Sustacal challenge testing demonstrated C-peptide responsiveness, but in a delayed pattern suggesting insufficient islet mass had been transplanted. The next three kidney transplant recipients received islets from more than one donor pancreas averaging 13,916 +/- 556 islets/kg body weight. The first of these was the first to achieve insulin independence from 10 to day 25 posttransplant when she appeared to have a rejection episode. The second and third recipients were retransplanted with islets from multiple donors having achieved partial islet function from single pancreas donor. The first patient on triple immunosuppression is demonstrating long-term partial function at 184 days but is not insulin independent. The third patient on prednisone and azathioprine received one half his islets after 7-day culture and the other half after 7-day culture combined with cryopreservation. He is continuing to demonstrate insulin independence for 154 days post-transplant with a glycated hemoglobin value of 5.6%. Sustacal challenge data demonstrate a total stimulated C-peptide response of 155 rhomol/ml at 4 months post-transplant compared with 148 +/- 12 rhomol/ml for normal controls (NC) and 425 rhomol/ml for nondiabetic, established kidney transplant recipients on triple immunosuppression.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1991

Automated large-scale isolation, in vitro function and xenotransplantation of porcine islets of Langerhans.

To evaluate the potential of utilizing porcine islet tissue as an alternative to human islet tissue for transplantation, we developed a method for the isolation of large amounts of highly purified porcine islets, and assessed the in vitro and in vivo function of the isolated islets after 1, 4, and 7 days of culture. The pancreatic duct of the splenic lobe was cannulated and distended by injection of Hanks' balanced salt solution containing 1.5 mg/ml collagenase. The pancreas was then processed by a modification of the automated digestion-filtration method developed in this laboratory, and with purification accomplished by Euro-Ficoll gradients (dialyzed Ficoll in Eurocollins solution), consisting of two layers of 1.108 and 1.091 g/cm3 density, topped with a layer of HBSS. The postpurification yield was 5203 +/- 645 (mean +/- SEM) islets per gram of pancreas with a number of islet equivalents (IE) per gram pancreas (islet equivalence: 150-microns-sized islets) of 3551 +/- 305, and a volume of 6.27 +/- 1.7 mm3 islet tissue per gram of pancreas. The islet purity exceeded 90%. Overnight-cultured, perifused porcine islets released 53.1 +/- 8.2 pM insulin/200 IE at 3.3 mM glucose, and 114.9 +/- 25.4 pM insulin/200 IE at 16.7 mM glucose (P less than 0.001 vs. basal output). When theophylline was added, insulin secretion increased to 264.2 +/- 63.2 pM/200 IE (P less than 0.001 vs. basal secretion and P less than 0.005 vs. secretion at 16.7 mM glucose). After 4 days of culture, the islets still responded to secretagogues. The functional integrity of the isolated islets was confirmed by reversal of diabetes in aL3T4 antibody-treated C57B/B6 diabetic mice: normoglycemia was promptly restored by transplanting 1000 overnight- or 7-day-cultured (24 degrees C) islets under the kidney capsule. These results suggest that continued improvements of porcine islet isolation and culture could permit the use of porcine islets in immunoalteration and immunoisolation studies that may lead to eventual human transplantation.

Animals↗
PubMed1991

No evidence for serological autoimmunity to islet cell heat shock proteins in insulin dependent diabetes.

Recent studies in nonobese diabetic mice have implicated the autoimmune destruction of pancreatic islet cells with immunity to a beta cell protein cross-reactive to Mycobacterium tuberculosis heat shock protein 65 (hsp 65). Therefore, our studies examined serological immunity to islet cell hsp in humans with insulin-dependent diabetes (IDD). Heat shock of human islet cells in vitro markedly increased the synthesis of proteins of 72,000, 75,000, and 90,000 Mr. No autoantibodies reactive to these hsp, nor to the constituently expressed islet cell hsp 65 protein (identified as 60,000 Mr) were observed in IDD patients. The islet cell 64,000-Mr autoantigen and hsp 65 proteins were physiologically and immunocompetitively distinct. These experiments do not support the hypothesis that IDD in humans is associated with autoimmunity to islet cell heat shock proteins.

Adolescent↗
PubMed1991

Macrophage-specific chemotactic lipid release by in vivo streptozocin-administered mouse islets.

The development of insulitis in animal models of immune-mediated diabetes mellitus is preceded by an influx of macrophages into the islets. In this study, ICR mice were given four 30-mg/kg doses of streptozocin over 36 h to induce insulitis. The islets were subsequently isolated and cultured in suspension. A macrophage-specific islet infiltration was observed within 48 h of the first drug injection. Concurrent with this leukocyte influx, enhanced in vitro release of a macrophage-specific chemotactic lipid by islets from streptozotocin-administered animals was observed. By chromatographic analysis, the islet-derived chemotactic factor appears to resemble a moderately polar complex lipid that is distinct from previously characterized lipid chemoattractants. Secretion of the factor is not dependent on cyclooxygenase activity. Identification of this lipid may provide important insights into the etiology of insulin-dependent diabetes mellitus and other autoimmune diseases.

Animals↗
PubMed1991

Production of marked prolongation of islet xenograft survival (rat to mouse) by local release of mouse and rat antilymphocyte sera at transplant site.

Polymer rods impregnated with lyophilized particles of mouse (M) or rat (R) antilymphocyte serum (ALS) were placed adjacent to rat islet xenografts transplanted beneath the kidney capsule of diabetic mice. Insertion of rods containing only MALS or RALS had no effect on the survival time of the rat islet xenografts. In contrast, the insertion of both MALS and RALS rods with the graft produced a marked prolongation of islet xenograft survival (mean survival time greater than 55.5 +/- 10.9 days) compared with controls (14.7 +/- 2.5 days). One recipient was still normoglycemic at 100 days, and removal of the graft returned the animal to a diabetic state. The islet graft had a normal degree of beta-granulation, and a slight fibrotic reaction was present around the rods. The effect of the rods in prolonging survival of the xenografts resulted from a local slow release of MALS and RALS, because implantation of the MALS and RALS rods in the right kidney and the islets in the left kidney had no effect on prolonging islet xenograft survival. These findings indicate that local immunosuppression produced marked prolongation of rat islet xenograft survival in mice. This raises the possibility of using polymer rods for the local slow release of monoclonal antibodies to lymphokines and other agents for prevention of rejection of islet allografts and xenografts and to determine the effect of lymphokines in vivo on islet function.

Animals↗
PubMed1991

Expression of functional human Epstein-Barr virus/C3d receptor ([CR2] CD21) on insulinoma cell line. Induction of tumor rejection but not diabetes in syngeneic rats.

We stably expressed human complement receptor 2 ([CR2] CD21 C3d/Epstein-Barr virus [EBV] receptor) on the rat insulinoma cell line RINm5F with a recombinant retroviral vector. CR2-expressing RINm5F cells secreted 78-33% less insulin than parental cells or cells transduced with an antisense vector and could be infected with high-titer EBV. We tested whether human CR2 expression on RINm5F cells would affect tumorigenesis after transplantation to syngeneic New England Deaconess Hospital rats. Non-CR2-expressing antisense-transduced RINm5F cells rapidly grew tumors and caused hypoglycemia, hyperinsulinemia, and the death of the animals after 15.7 +/- 0.7 days. CR2-expressing RINm5F cells were infiltrated by mononuclear cells at an early stage and eventually caused noninfiltrated tumors and the death of the animals after 33.0 +/- 0.4 days. These tumors were CR2- and are believed to have arisen from a minor CR2- population of tumor cells. The pancreatic islets were histologically normal at all time points. We conclude that expression of a xenoantigen on a rat insulinoma cell line induces an immune response in syngeneic rats but does not result in breakage of tolerance to parental or revertant cells.

Animals↗