Search

Background It has been proposed that islet transplants comprised primarily of small rather than large islets may provide better graft function, due to their lower susceptibility to hypoxic damage. Our aim was to determine whether islet size correlated with in vivo graft function in islet transplant recipients with C peptide negative type 1 diabetes when islets have undergone pre-transplant islet culture. Methods Human pancreatic islets were isolated, cultured for 24hours and infused by standardised protocols. 90 min-stimulated C-peptide concentrations were determined during a standard meal tolerance test 3 months post-transplant. The islet isolation index (IEq/islet number) was determined immediately after isolation and again before transplantation (after tissue culture). This was correlated with patient insulin requirement or stimulated C-peptide. Results Changes in insulin requirement did not significantly correlate with islet isolation index. Stimulated C-peptide correlated weakly with IEq at isolation (p=0.40) and significantly with IEq at transplantation (p=0.018). Stimulated C-peptide correlated with islet number at isolation (p=0.013) and more strongly with the islet number at transplantation (p=0.001). In contrast, the correlation of stimulated C-peptide and islet isolation index was weaker (p=0.018) and this was poorer at transplantation (p=0.034). Using linear regression, the strongest association with graft function was islet number (r=0.722, p=0.001). Islet size was not related to graft function after adjusting for islet volume or number. Conclusion These data show no clear correlation between islet isolation index and graft function; both small and large islets are suitable for transplantation provided the islets have survived a short culture period post-isolation.

BACKGROUND AND AIMS: Elevated free fatty acid (FFA) levels are believed to be one of the major contributing factors in the pathogenesis of type 2 diabetes. FFAs enhance peripheral insulin resistance, promote beta-cell dysfunction, and trigger beta-cell death. The purpose of this study was to investigate whether the lipoapoptotic effect of FFAs is determined by the degree of saturation and the chain length, and which pathways might be involved. MATERIAL AND METHODS: After incubation of RIN1046-38 rat insulinoma cells and primary human islet cells with different FFAs, apoptosis was assessed by flow cytometry (sub-G1-DNA formation) and TUNEL assay, respectively. Intracellular distribution of protein kinase C-delta (PKC-delta) was determined by confocal laser microscopy. RESULTS: In RIN1046-38 cells, the sub-G1 fraction increased 40-fold over basal (0.5% to approximately 20%) after treatment with the saturated FFAs palmitate and stearate (1 mM, 24 h), while the monounsaturated FFAs palmitoleate and oleate as well as the polyunsaturated FFA linoleate had no proapoptotic effect. Unsaturated FFAs even more prevented palmitate- and stearate-induced apoptosis completely. Furthermore, these results could be confirmed in primary beta-cells of human islets. Investigating potential underlying signaling pathways, it was found that only the saturated FFAs were able to induce nuclear translocation of PKC-delta. CONCLUSIONS: FFAs exert different effects on beta-cell survival. Saturated FFAs turned out to be pro-apoptotic, whereas unsaturated FFAs protected from saturated FFA-induced apoptosis. Furthermore, our data suggest an involvement of PKC-delta in apoptosis induced by saturated FFAs.

BACKGROUND: Clinical and experimental data indicate that early failure of intraportally grafted islets is caused by inflammation including secretion of cytokines and nitric oxide. Direct inducible nitric oxide synthase suppression may avoid detrimental effects associated with steroid administration. We compared the efficiency of selective and unselective inducible nitric oxide synthase inhibitors with dexamethasone to suppress nitric oxide generation after intraportal islet xenotransplantation into nude rats. METHODS: Nonfasting serum glucose levels were daily evaluated after intraportal transplantation of 4000 freshly isolated pig islets into diabetic nude rats (85 mg/kg streptozotocin) either sham-treated with saline (n=21) or continuously infused for 7 days with L-NG-monomethyl-arginine (n=7), S-methyl-isothiourea (n=15), or S-(2-aminoethyl)-isothiourea (n=19) in a dosage of 240, 100, or 50 mg/kg/day, respectively. Dexamethasone was injected i.p. twice as a daily bolus of 20 mg/kg (n=10) starting 1 day pretransplant. The nitrate/nitrite serum level was quantified colorimetrically 0, 24, and 48 hr posttransplant. RESULTS: Saline treatment partially resulted in graft function (4/21) throughout the observation period (21 days). L-NG-monomethyl-arginine-treated rats showed sustained hyperglycemia (0/7) not different from diabetic controls. Normoglycemia was observed after treatment with dexamethasone (6/10, P

For more than a decade Liberase HI was commonly used as the standard enzyme blend for clinical human islet isolation until enforced replacement by collagenase NB1 (NB1). This change resulted initially in a reduction in islet isolation outcome and transplant activities worldwide. This retrospective study was initiated to compare the efficiency of NB1 premium grade with Liberase in 197 human islet isolations. All pancreata were processed between January 2006 and June 2008 utilizing the same procedures for isolation and quality assessment except the administration of preselected lots of either Liberase ( n = 101) or NB1 ( n = 96). Utilizing Liberase, significantly more digested tissue and purified islet yield was produced compared to NB1. In contrast, the use of NB1 was associated with significantly higher purity and glucose stimulation index during dynamic perifusion. The expression of proinflammatory markers was almost identical except tissue factor expression, which was higher after utilization of Liberase. No difference was found in the percentage of pancreata fulfilling the criteria for clinical islet transplantation. The results suggest that Liberase is more efficient for pancreas dissociation than collagenase NB1 but seems to be more harmful to exocrine cells and islet tissue.

24th European Photovoltaic Solar Energy Conference, 21-25 September 2009, Hamburg, Germany; 106-110, Auburn University is working in conjunction with ENTECH, Inc. to perform a “direct drive” experiment using a high-voltage (600 Voc) ENTECH SunLine concentrator array that has multijunction solar cells coupled to a Russian T-100 Hall Effect Thruster. This may well be the first time a Hall thruster has been run directly from III-V-based multi-junction solar cells and at this high voltage. This paper will discuss the set-up and testing results. Testing will include the addition of SLA hardware in a vacuum chamber to measure plume impingement effects at various positions relative to the exhaust axis of the thruster. The goal of this task was t o define the most meaningful combined high voltage SLA concentrator array and Hall-effect thruster demonstration tests relevant to solar electric propulsion to test SLA reliability and provide information to help advance the SLAs qualification level. This is the next step under a Phase II STTR with NASA Glenn Research Center for the development of Stretched Lens Array hardware for Solar Electric Propulsion missions and is being performed at Auburn Universitys Space Research Institute. The ENTECH SunLine triple-junction concentrator array is very similar to the SLA design.