Biomedical subjects

K Federlin

Publications and source records attributed to K Federlin.

At least 73 records · Page 4Linked to original sources

PubMed1995

Body mass index of pancreatic donors: a decisive factor for human islet isolation.

Despite improvements in islet isolation techniques, islet transplantation remains unpredictable as a method for reliably rendering human type I diabetic recipients normoglycemic. Advances in immunosuppression to prevent primary nonfunction, to promote engraftment and to prevent rejection should improve success rates. However, factors influencing the isolation process remain incompletely defined. During our experience, the donor's nutritional status as well as other donor characteristics were noted to be associated with islet isolation success. Thus, in this study, we tried to clarify whether the body mass index of the human pancreatic donor affects islet isolation yield and viability. In lean donors we found significantly lower islet yields in comparison with normal and obese donors and a significantly lower islet viability compared to obese donors. Obese donor islets had a significantly higher insulin secretory capacity than lean and normal donor islets. In summary, islet yield and viability were improved selecting pancreata from obese donors associated with a BMI > 24 for islet preparation. We hypothesize that, on the one hand, the increased distribution of fat in pancreata of obese donors possibly can facilitate the release of islets during the collagenase digestion, and, on the other hand, pancreata of obese donors contain more islets than pancreata of lean donors. These data underline the decisive influence of the pancreas donor's body mass index on successful human islet isolation. The body mass index should be noted as a potential predictor of success of islet preparations.

Body Mass Index↗

PubMed1995

Activation of human complement by collagenase and ficoll.

Collagenase and ficoll are standard chemicals used for isolation and purification of pancreatic islets. The capacity of these substances to activate human complement was tested by incubation for 45 min at 37 degrees C with fresh or liquid nitrogen-stored human plasma from normal blood donors. Complement-split products were then determined by sensitive enzyme immunoassays from QUIDEL. Collagenase activates both the classical and the alternative pathway, whereas Ficoll activates the alternative pathway only. When present in islet preparations used for islet transplantation, these substances may induce local inflammatory reactions compromising islet viability and engraftment.

Cell Separation↗

PubMed1995

Comparison of the survival of fresh or cultured pancreatic islets, pseudoislets and single cells following allotransplantation beneath the kidney capsule in non-immunosuppressed diabetic rats.

The purpose of the present study was to examine the effect of culture pretreatment and islet structure on transplantation survival time. Donors for islet isolation were highly inbred male Lewis rats (RT 1(1)). Production of single cells was performed by using EDTA and Trypsin. Pseudo-islets were produced by culturing single cell suspensions at 37 degrees C for 12-14 days. Recipients were BDE rats (RT 1u), made diabetic by streptozotocin injection. 1000-1200 islets (or corresponding amount of single cells or pseudoislets) were transplanted to the subcapsular renal space. Five groups were transplanted. Group 1 (n = 5) received freshly isolated islets of Langerhans. Group 2 (n = 7) received single cells, produced from freshly isolated islets. In group III (n = 7) pseudoislets were transplanted. The animals of group IV received 37 degrees C cultured islets (12-14 days), while group V received single cells consisting of 12-14 day cultured islets at 37 degrees C. The median survival times were: gr. I 7 d.; gr. II 5 d.; gr. III 120 d.; gr. IV 11 d.; gr. V 9 d.. Group III showed a prolongation of allograft survival that was statistically significant compared to all other groups. 4 from 7 animals showed a long-term acceptance. It can be concluded that neither culturing islets at 37 degrees C nor producing single cells achieves long-term acceptance. Transplanting pseudoislets resulted in a long-term acceptance of allograft, without immunosuppression of the host. Three factors may be responsible for this success: Firstly, a reduced number of class-II-antigen positive cells, secondly, metabolic state of rest, and thirdly, the transplantation site.

Animals↗

PubMed1995

Pancreatic islet xenografts at two different transplantation sites (renal subcapsular versus intraportal): comparison of graft survival and morphology.

Our primary objective in this study was to determine the effect of two different transplantation sites (renal capsule vs. portal vein) on islet xenograft survival and graft morphology. 59 chemically induced diabetic C57BL/6J mice were transplanted either intraportally (n = 30) or under the left renal capsule (n = 29) receiving 300-350 either freshly isolated or culture pretreated (37 degrees C or 22 degrees C) Lewis rat islets without any immunosuppressive therapy. Histology was performed by immunohistochemical staining to examine the morphologic pattern after rejection or after post-transplant normoglycemia for more than 120 days. Life table analysis revealed a significant (p < 0.001) prolongation of xenograft survival using the renal capsule as transplantation site. 75% graft rejection occurred 56 days after transplantation when the renal capsule was used, compared to 19.5 days intraportal. The intriguing finding was that graft morphology was different depending on the transplantation site. After transplantation under the renal capsule we observed predominantly a more periinsular infiltration with focal aggregates of mononuclear cells at the periphery of the graft. This pattern was more consistent with a non-destructive type of insulitis. In contrast, we found direct infiltration of the transplanted islets following intraportal transplantation reflecting a more destructive type of insulitis. In summary, we could demonstrate a significant prolongation of islet xenograft survival by using the renal capsule as transplantation site in contrast to intraportal transplantation. The morphological pattern possibly indicates two different mechanisms of rejection depending on the transplantation site.

Animals↗

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

Different toxic effects of hydrogen peroxide, nitric oxide, and superoxide on human, pig, and rat islets of Langerhans.

Susceptibility of islet cells to damage by hydrogen peroxide, superoxide, and nitric oxide was determined on islets isolated from humans, pigs, and rats. Islets were incubated for 20 hr at 37 degrees C with different concentrations of hydrogen peroxide, hypoxanthine/xanthine oxidase, or nitroprusside sodium, respectively. Islet cell damage was then measured as trypan blue-uptake. Rat islets showed a higher sensitivity than human or pig islets to damage by reactive oxygen species or nitric oxide. These results indicate that pig islets may be a more suitable model than rat islets to study inflammatory islet cell damage in diabetes and clinical islet transplantation.

Animals↗

PubMed1995

Islet transplantation in immunoseparating membranes for treatment of insulin-dependent diabetes mellitus.

Despite remarkable progress in treatment life expectancy of insulin-dependent diabetics is limited by the onset of life threatening complications. These could be avoided by an optimized glucose hemeostasis only as it has been shown by experimental islet transplantation. Successful transplantation of islets encapsulated in immunoseparating membranes (bioartificial pancreas) would circumvent problems of islet availability and rejection. In this article macro- and microencapsulation as the two major principles are evaluated. Present limitations are discussed under technical and immunological aspects and directions for future research are addressed. Progress in the development of immunoseparating membranes and devices for treatment of insulin-dependend diabetes and finally their clinical introduction will permit the application of this technology in other endocrine deficiency syndromes.

Animals↗

PubMed1995

Evaluation of the effect of microencapsulation and immuno-modulation on islet immunogenicity in vitro.

The complexity of the transplantation model in microencapsulated islet transplantation suggests the use of an in vitro model for the analysis of the effect of encapsulation and graft pretreatment on islet immunogenicity. In this study, the mixed lymphocyte islet culture is applied to islets encapsulated in barium alginate beads, showing a significant reduction of the cellular response compared with non-encapsulated islets. Moreover, the effect of low-temperature culture as the immuno modulatory principle is shown on encapsulated and non-encapsulated islets. The data suggest that encapsulation reduces but not totally impedes the immunological interaction between the encapsulated tissue and the surrounding immune cells and that the stimulatory potency of the encapsulated islet may be modified by immuno-altering pretreatment.

Adjuvants, Immunologic↗

PubMed1995

The effects of glucagon-like peptide-I (GLP-I) on hormone secretion from isolated human pancreatic islets.

Glucagon-like peptide-I (GLP-I) is a potent incretin hormone that is now considered as a new therapeutic tool in the treatment of diabetes mellitus. In this study we characterized the effects of GLP-I on peptide hormone release from isolated human pancreatic islets. GLP-I stimulated insulin release in the presence of 10 mM glucose (2.8 mM glucose, 100%; 10 mM glucose, 166%; 10 mM glucose + 10 nM GLP-I, 222%) but had only a weak insulinotropic effect (128%) at 2.8 mM glucose. Glucagon release was inhibited by 10 mM glucose (2.8 mM glucose, 100%; 10 mM glucose, 72%) and by 10 nM GLP-I at 2.8 mM glucose (67%). Somatostatin secretion was increased by 10 mM glucose (2.8 mM glucose, 100%; 10 mM glucose, 166%). GLP-I stimulated somatostatin release in the presence of 2.8 mM glucose (172%). Pancreatic polypeptide (PP) secretion was enhanced by 10 mM glucose (2.8 mM glucose, 100%; 10 mM glucose, 236%). GLP-I induced PP release only in the presence of 2.8 mM glucose (184%).

Culture Techniques↗

PubMed1995

Analysis of proteins that interact with the IL-2 regulatory region in patients with rheumatic diseases.

In order to investigate transcriptional regulation of lymphokine genes in rheumatic diseases, peripheral blood mononuclear cells from patients with systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and systemic sclerosis (SSc) were analysed for expression of DNA-binding proteins. Nuclear extracts prepared from unstimulated and mitogen-activated cells were studied for their ability to bind to 32P-labelled oligonucleotides containing the AP-1, NF-AT, NF-B and CD28RC sites of the IL-2 promoter. Using gel mobility-shift assay, detection of protein binding to the AP-1 site was reduced in SLE compared with controls. NF-AT binding activity was enhanced in all groups of patients, and was associated with measures of disease activity in RA. In addition, SSc patients showed increased NF-kappa B binding activity. Altered patterns of DNA-binding proteins suggest disturbed intracellular signalling which may contribute to abnormal lymphokine production in rheumatic diseases.

Adult↗

PubMed1995

Evidence of impaired cartilage/bone turnover in patients with active ankylosing spondylitis.

OBJECTIVES: To compare serum markers of bone formation with the urinary excretion of pyridinium crosslinks (PYR) as a possible measure of bone and cartilage degradation which would detect changes in bone metabolism in patients with ankylosing spondylitis (AS) and to relate them to influences of inflammatory disease activity, and to treatment. METHODS: In 62 patients with AS, serum osteocalcin, alkaline phosphatase (ALP), and skeletal ALP isoenzyme levels were evaluated concurrently in comparison with urinary excretion of pyridinium cross links and were compared with values in 50 healthy controls. RESULTS: Osteocalcin concentrations in AS patients were in the middle normal range (3.5 (SD 1.2) ng/ml) and did not differ significantly from those in control subjects (4.2 (1.3) ng/ml); the same was true for ALP and skeletal ALP isoenzyme fraction (AS: ALP 149 (50.3) U/l, skeletal ALP 12.8 (4.1) micrograms/l; controls: ALP 133 (25.2) U/l, skeletal ALP 11.9 (4.3) micrograms/l). The urinary levels of PYR in AS (51.2 (25.2) nmol PYR/mmol creatinine) were significantly increased compared with controls (33.9 (12.4) nmol PYR/mmol creatinine (p < 0.001)). In the AS group there was a positive correlation between urinary excretion of PYR and inflammatory disease activity (erythrocyte sedimentation rate (ESR)) (r = 0.6, p < 0.0001) and C reactive protein (CRP) (r = 0.3, p = 0.02), but no significant correlation was found with ESR, CRP, and markers of bone formation. CONCLUSIONS: Bone metabolism in patients with AS is characterised by normal bone formation and enhanced cartilage/bone degradation, suggesting that impaired bone turnover is pronounced in active disease. The results clearly indicate that this comparison can be used to demonstrate impairment of cartilage/bone metabolism which correlates with disease activity. The data obtained further emphasise the importance of measuring both serum variables and urinary excretion of PYR crosslinks to obtain adequate evaluation of cartilage/bone metabolism in patients with AS.

Adult↗

PubMed1995

[Combined liver-islet transplantation after epigastric exenteration in carcinoma of Vater's ampulla].

A 44 year old female underwent an upper abdominal exenteration because of an adenocarcinoma of the pancreas with liver metastases (T1 N1 M1). Reconstruction was performed by orthotopic liver transplantation and intraportal islet transplantation. Due to initial non function of the first liver graft, a second liver transplantation was performed. Thereafter, the patient received 375,000 islet equivalents of the primary liver donor in addition to 295,400 islet equivalents of another donor. Six months postoperatively, the patient is off insulin except irregular injections of 4-6 units of insulin to protect her from hyperglycemia after lunch. CT scans of the liver do not show any signs of tumor recurrence. Upper abdominal exenteration with consecutive islet transplantation offers a good method of reconstruction after radical surgery in the upper abdomen. The oncological aspects of the procedure have to be further investigated.

Adenocarcinoma↗

PubMed1995

[Therapeutic complications from insulin antibodies--two case reports].

Immunological complications of insulin therapy are extremely rare, since highly purified insulins, especially human semi- or biosynthetic insulin preparations became available for treatment of diabetes mellitus. Insulin antibodies of the immunoglobulin G or immunoglobulin E class can develop in 10-60%, however, in low titers in patients treated exclusively with human insulin. In rare cases these antibodies assume clinical significance, if the antigenic potential of the insulin used is high enough and if genetic predisposition exists. Two case reports presented here confirm this concept.

Aged↗

PubMed1995