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Biomedical subjects

H Jahr

Publications and source records attributed to H Jahr.

At least 37 records · Page 2Linked to original sources
PubMed1999

Isokinetic gradient centrifugation prolongs survival of pig islets xenografted into mice.

Highly purified porcine islets were prepared by isokinetic gradients performed subsequently to isopycnic gradients. This additional purification step separates ductal, vascular, and lymphoid tissue effectively from endocrine tissue. Although ductal, vascular, and lymphoid tissue comprises only a minor contamination of the islet suspensions, a significant prolongation of the survival of porcine islets xenografted into streptozotocin diabetic C57BL/6 mice can be achieved by the elimination of the non-endocrine tissue. Rejection after islet transplantation is delayed from 2.2+/-0.4 days (n=27) to 13.1+/-2.1 days (n=36), respectively, when conventionally purified and highly purified islets are compared. Irrespective of the purification state, pretreatment of islets by low temperature culture had no effect on xenograft survival.

Animals↗
PubMed1998

[Graft rejection in experimental xenogenic transplantation of isolated islands of Langerhans of the pig].

Prevention of the occurrence of diabetes-specific vascular complications is the final aim of clinical islet transplantation. Pancreatic islets isolated from adult pigs may be a suitable tissue source to transplant a large number of type 1 diabetic patients. Acute cellular rejection may be finally overcome by clinically applicable protocols for tolerance induction. However, primary nonfunction of the graft, as regularly observed in the porcine islet-to-rat xenotransplantation model, may be an additional problem. In this paper, species-specific inflammatory and immunological mechanisms are discussed which prevent early porcine islet graft function in rats but not in mice.

Adult↗
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

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

Amyloid fibril composition and transthyretin gene structure in senile systemic amyloidosis.

BACKGROUND: In many different forms of amyloidosis, transthyretin (TTR) comprises the major amyloid fibril protein. In the familial forms, various TTR mutations are linked to disease. This study was designed to characterize the components of the TTR-derived amyloid fibril protein in senile systemic amyloidosis and to determine whether any mutation in the TTR gene was present. EXPERIMENTAL DESIGN: Heart tissues from two patients with advanced senile systemic amyloidosis were studied. Amyloid fibrils were extracted and the amyloid fibril protein purified. The relationship between full-length and fragmented TTR and the amino acid sequence of the TTR were determined. The TTR gene was studied by single-strand conformation polymorphism analysis or direct sequencing. RESULTS: In both cases, the amyloid deposits contained full-length TTR and a complex mixture of TTR fragments. The fragments, most of which had their N-termini at positions 46-52, predominated. No amino acid substitution was identified. The N-terminal fragment (1-45) was not identified in either patient. In each case, the four exons of the TTR gene were of normal sequence. CONCLUSIONS: In familial amyloidosis resulting from deposition of TTR Met 30 (Swedish-type familial amyloidosis), full-length TTR molecules (some mutant) usually predominate, and TTR fragments lacking three of the eight beta-strands (nonmutant) form a major part of the fibril in senile systemic amyloidosis. This may indicate a difference in the fibrillogenesis between these two forms of TTR-derived amyloidosis. We propose that the name senile systemic amyloidosis be used only for normal-sequence TTR amyloidosis occurring in advanced age.

Aged↗
PubMed1991

Influence of albumin-bound bilirubin on the antibody-dependent cellular cytotoxicity of human cells in vitro.

In neonatal hyperbilirubinaemia the distribution of unconjugated bilirubin (BR) between albumin and cellular binding determines its toxicity. The relationship between the ratio of BR/albumin and the impairment of cellular functions was studied employing a system of antibody-dependent cellular cytotoxicity (ADCC) with erythrocytes as target cells. The cytotoxic activity of peripheral blood monocytes, lymphocytes and granulocytes is inhibited in a concentration-related manner depending on the molar ratio BR/albumin. The occupation of albumin binding sites by BR is related to the extent of inhibition of ADCC activity suggesting that there is a competition between albumin and cellular binding sites for free bilirubin. This competition is governed by the respective affinity and concentration of the binding sites. Bilirubin binding to the cellular (silent) membrane receptors leads to the chain of events resulting in impairment of cellular functions, i.e. ADCC.

Adult↗