Biomedical subjects

Richard Olsson

Publications and source records attributed to Richard Olsson.

4 recordsLinked to original sources

PubMed2003

[Severe vascular dysfunction shown in transplanted islets].

Despite recent advances in clinical islet transplantation, a surprisingly large number of islets (approximately 1 million) are still required to obtain insulin independence in type 1 diabetes. The reasons for this are obscure and likely multifactorial. One explanation may be disturbances in engraftment of the transplanted islets, i.e. the adaptation of the islet transplant to its new surroundings with regard to e.g. revascularization and blood perfusion. Endogenous islets have a dense glomerular-like angioarchitecture. Transplantation of isolated islets causes a disruption of their vascular connections, making the islets dependent on the formation of new blood vessels for optimal function. Evidence from experimental islet transplantation indicates an insufficient revascularization of transplanted islets with subsequent chronically decreased blood perfusion and oxygen tension, which has metabolic consequences within the tissue.

Animals↗

PubMed2002

Prostaglandin E2 induces vasodilation and pruritus, but no protein extravasation in atopic dermatitis and controls.

BACKGROUND: Prostaglandin E(2) (PGE(2)) has well-established vasodilatory effects, whereas its effects on protein extravasation and its sensory effects are less clear. OBJECTIVE: Vasoactive effects of PGE(2) were correlated to its ability to evoke pain or itch in healthy volunteers and patients with atopic dermatitis (AD). METHODS: Intradermal microdialysis was used to apply PGE(2) (10(-8)-10(-4) M) via microdialysis capillaries in 8 patients and 8 controls. Large pore size membranes (3000 kd) enabled simultaneous analysis of protein extravasation. Itch and pain sensations were measured psychophysically, and superficial blood flow was measured by laser Doppler imaging. RESULTS: PGE(2) dose dependently provoked intense local vasodilation, weak pruritus, and pain, but no protein extravasation. No differences were found between patients with AD and controls for any parameter. CONCLUSION: We conclude that PGE(2) is a potent vasodilator and a weak pruritic agent in normal skin and in patients with AD, but does not provoke increased protein extravasation.

Adult↗

PubMed2002

Microdialysis measurements demonstrate a shift to nonoxidative glucose metabolism in rat pancreatic islets transplanted beneath the renal capsule.

BACKGROUND: We aimed to use microdialysis to assess, for the first time, the internal milieu of pancreatic islet grafts. METHODS: One month after transplantation, microdialysis probes were inserted into syngeneic rat islet transplants (500-700 islets) placed beneath the renal capsule of nondiabetic or diabetic recipients. The number of grafted islets was purposely chosen not to cure the diabetic recipients. RESULTS: During an intravenous glucose challenge, insulin concentrations increased in parallel in serum and in the graft interstitium of nondiabetic animals suggesting the existence of a functionally well-established vascularization. Diabetic recipients had both a lower serum and dialysate insulin concentration than normoglycemic animals. The lactate/pyruvate ratios were determined in the dialysates as a measure of the degree of anaerobic metabolism in the islet grafts. Lactate/pyruvate ratios were between 50 and 100 in grafts of both nondiabetic and diabetic recipients, and they almost doubled in response to the intravenous glucose challenge in the grafts of nondiabetic recipients. In comparison, lactate/pyruvate ratios were approximately 12 in the medium of cultured islets incubated at low glucose (5.6 mmol/L) or high glucose (16.7 mmol/L) concentrations. CONCLUSIONS: The microdialysis technique has proven to be a valuable tool for evaluating the internal environment of islet transplants. Moreover, the high lactate/pyruvate ratio suggests that islet grafts have an increased anaerobic glucose metabolism.

Animals↗

PubMed2002

Glucose-induced islet blood flow increase in rats: interaction between nervous and metabolic mediators.

This study investigated the mechanisms for glucose-induced islet blood flow increase in rats. The effects of adenosine, adenosine receptor antagonists, and vagotomy on islet blood flow were evaluated with a microsphere technique. Vagotomy prevented the islet blood flow increase expected 3, 10, and 20 min after injection of glucose, whereas theophylline (a nonspecific adenosine receptor antagonist) prevented the islet blood flow increase from occurring 10 and 20 min after glucose administration. Administration of selective adenosine receptor antagonists suggested that the response to theophylline was mediated by A1 receptors. Exogenous administration of adenosine did not affect islet blood flow, but local accumulation of adenosine, induced by the adenosine uptake inhibitor dipyridamole, caused a doubling of islet blood flow. In conclusion, the increased islet blood flow seen 3 min after induction of hyperglycemia is caused by the vagal nerve, whereas the increase in islet blood perfusion seen at 10 and 20 min after glucose administration is caused by both the vagal nerve and adenosine.

Adenosine↗