Biomedical subjects

Per-Ola Carlsson

Publications and source records attributed to Per-Ola Carlsson.

39 records · Page 3Linked to original sources

PubMed2002

Multiple injections of coloured microspheres for islet blood flow measurements in anaesthetised rats: influence of microsphere size.

We investigated if coloured microspheres could be used for repeated measurements of pancreatic islet blood flow in rats. An initial injection of 1.0-1.5 x 10(5) microspheres (black colour), with a size of 10 or 15 microm, was made into the ascending aorta, while an arterial reference sample was collected from the femoral artery. Twelve min later, 1 ml of saline or 30% D-glucose was injected intravenously. Three min after this injection a second injection of 10- or 15-microm microspheres (green colour) was given. The animals were then killed, and the pancreas and adrenals were removed and samples (150-200 mg) were secured from the duodenum, ileum, colon, right kidney and liver. The microsphere contents were determined with the aid of a freeze-thawing technique and blood flow values were calculated. Our results suggest that 10-microm microspheres, but not 15-microm microspheres, provide reproducible islet and total pancreatic blood flow measurements when repeatedly injected. Values for the blood flow to the intestines, kidney and liver were less sensitive to the size of the microspheres. We conclude that repeated administration of 15-microm microspheres induces a high risk for erroneous islet and total pancreatic blood flow measurements, whereas two such measurements can be performed if 10-microm microspheres are used.

Animals↗

PubMed2002

Oxygen tension and blood flow in relation to revascularization in transplanted adult and fetal rat pancreatic islets.

We have previously recorded a decreased oxygen tension and blood flow in syngeneically transplanted rat pancreatic islets. The present study related measurements of oxygen tension and blood flow to the vascular density in such grafts implanted beneath the renal capsule. We also evaluated whether transplanted fetal islets are better revascularized than adult islets, and if the degree of revascularization is directly related to the islet vascular endothelial growth factor (VEGF) production. Tissue pO2 was measured using Clark microelectrodes, whereas islet graft blood flow was measured with laser-Doppler flowmetry. The vascular density of endogenous and transplanted islets was quantified in histological specimens stained with the lectin Bandeiraea simplicifolia (BS-1). Tissue pO2 in the transplanted adult and fetal islet grafts was similar and markedly lower than in the endogenous islets. The blood perfusion of both the adult and fetal islet grafts was 60-65% of that in the renal cortex. Administration of D-glucose did not affect tissue pO2 in either the endogenous or transplanted islets, nor graft blood perfusion. The number of capillaries found in the transplanted adult and fetal islets was similar and markedly lower than in endogenous islets. However, in the connective tissue stroma, which constituted approximately 20% of all islet grafts, the vascular density was higher than in the corresponding endocrine parts of these grafts. Incubated adult islets released higher amounts of VEGF than fetal islets. In conclusion, the previously described low oxygen tension of syngeneically transplanted adult rat islets is related to a low vascular density. Similar low oxygen tension and vascular density are seen in grafted fetal islets. The amount of VEGF production does not correlate to the degree of revascularization of the grafts.

Age Factors↗

PubMedDate not supplied

Differentiating between effects of streptozotocin per se and subsequent hyperglycemia on renal function and metabolism in the streptozotocin-diabetic rat model.

BACKGROUND: The animal model with streptozotocin (STZ)-induced diabetes mellitus is associated with progressive renal disturbances. The aim of this study was to differentiate between toxic effects of STZ and the effect of hyperglycemia. Previous studies have been limited to investigating the influence of STZ on glomerular filtration rate (GFR), albuminuria and renal morphology. The present study presents a new approach when transplanting beta-cells to cure the STZ-treated animals and extends the evaluation to include both renal function and oxygen metabolism. METHODS: Animals were allocated to three groups: control animals, STZ-diabetic animals and animals rendered diabetic with an injection of STZ, followed by immediate syngeneic transplantation of approximately 1000 pancreatic islets into the splenic parenchyma. This latter procedure reversed the hyperglycemia induced by STZ. Renal function was evaluated from GFR and urinary albumin and protein leakage, while regional renal blood flow was determined using a laser-Doppler technique and oxygen tension measured with Clark-type electrodes. RESULTS: In diabetic animals, GFR increased, renal oxygen tension decreased and renal hypertrophy occurred, along with urinary leakage of protein, including albumin. Early transplantation of pancreatic islets to STZ-treated animals prevented the development of all these changes, except for proteinuria. However, an analysis of urinary protein content revealed that albuminuria was preventable by islet transplantation. CONCLUSIONS: We conclude that the urinary protein leakage in this animal model is at least partly due to direct toxic effects of STZ, whereas the other renal changes investigated in this study are due to the long-term diabetic condition.

Animals↗