Hyaluronidase treatment of graft pancreatitis in rats: marked effects on the blood perfusion of the transplanted pancreas.

Hyaluronan is known to accumulate in tissues during inflammatory diseases associated with graft implantation and rejection of organ allografts. The aim was to evaluate whether hyaluronidase treatment affected hyaluronan content and blood perfusion in graft pancreatitis. Syngeneic rat pancreatic-duodenal transplantations were performed. Two days later blood flow measurements were made with a microsphere technique in both grafted and endogenous pancreas in animals treated with daily injections of vehicle or hyaluronidase (20.000 U/kg). Non-transplanted rats served as controls. Also, samples for analysis of hyaluronan and water content were taken. The hyaluronan content of the pancreatic graft was increased after transplantation. Hyaluronidase treatment markedly reduced total pancreatic and islet blood flow in both grafted and endogenous pancreas, whereas duodenum blood flow was unaffected. No blood flow effects were seen in non-transplanted control rats. Hyaluronan content was increased in the grafted pancreas, but hyaluronidase treatment decreased it to levels comparable to those of the endogenous gland. There were no differences in hyaluronan content in the endogenous pancreases of transplanted and non-transplanted rats. Graft pancreatitis after rat pancreas transplantation is associated with an increased hyaluronan content, which can be reduced by treatment with hyaluronidase. Hyaluronidase treatment of the graft recipients effected a 50% reduction in total pancreatic and islet blood flow in the graft, as well as in the endogenous pancreas. The functional importance of this is at present unknown.

Pancreatic islet blood flow during euglycaemic, hyperinsulinaemic clamp in anaesthetized rats.

AIMS: Previous studies have demonstrated that pancreatic islet blood flow is crucially dependent on blood glucose concentration. Thus, hyperglycaemia increases and hypoglycaemia decreases islet blood perfusion, by a combination of nervous and metabolic signals. The aim of the present study was to evaluate if hyperinsulinaemia, without associated hypoglycaemia, affects islet blood flow. METHODS: Thiobutabarbital-anaesthetized Wistar-Furth rats were subjected to an euglycaemic, hyperinsulinaemic clamp, that is they were infused for 60 min with either saline, insulin (18 mU kg(-1) min(-1)), glucose (27 mg kg(-1) min(-1)) or both glucose and insulin. This was followed by islet blood flow measurements with a microsphere technique. RESULTS: Animals receiving only glucose doubled their blood glucose and serum insulin concentrations, whereas rats receiving only insulin had blood glucose concentrations <2 mmol L(-1) and a 10-fold increase in serum insulin concentrations. Animals given simultaneous glucose and insulin had normal blood glucose concentrations but a 10-fold increase in serum insulin concentrations. Total pancreatic blood flow was unaffected in all animals. Islet blood flow was increased in hyperglycaemic and decreased in hypoglycaemic rats compared with control rats. Islet blood flow did not differ between clamped and control rats. CONCLUSIONS: Serum insulin concentration per se does not affect islet blood flow, whereas the ambient blood glucose concentration is of major importance in this context.

Carbon monoxide and pancreatic islet blood flow in the rat: inhibition of haem oxygenase does not affect islet blood perfusion.

OBJECTIVE: To determine whether carbon monoxide, a known gaseous vasorelaxator, affects pancreatic islet blood flow in rats. MATERIAL AND METHODS: Sprague-Dawley rats were anaesthetized with thiobutabarbital and injected intravenously with the haem oxygenase inhibitor tin-protoporphyrin IX dichloride (SnPP; 4, 10 or 20 mg/kg body-weight). After 15 min, blood flow measurements were performed using a microsphere technique. RESULTS: There was a slight increase in mean arterial blood pressure with the highest dose of SnPP. No effects on total pancreatic, islet, duodenal, colonic, renal or adrenal blood flow were seen with any of the applied doses. CONCLUSIONS: The findings of this study suggest that the haem oxygenase-carbon monoxide system is likely to be of limited importance in the regulation of blood perfusion to the pancreas, the islets of Langerhans or any of the other studied organs.

A perfusion protocol for highly efficient transduction of intact pancreatic islets of Langerhans.

AIMS/HYPOTHESIS: Successful gene transfer to pancreatic islets might be a powerful tool for dissecting the biological pathways involved in the functional impairment and destruction of beta cells in type 1 diabetes. In the long run, such an approach may also prove useful for promoting islet graft survival after transplantation in diabetic patients. However, efficient genetic modification of primary insulin-producing cells is limited by the specific compact structure of the pancreatic islet. We present here a whole-pancreas perfusion-based transduction procedure for genetic modification of intact pancreatic islets. MATERIALS AND METHODS: We used flow cytometry analysis and confocal microscopy to evaluate the efficiency of in vitro and perfusion-based transduction protocols that use adenoviral and lentiviral vectors expressing green fluorescent protein. Islet cell viability was assessed by fluorescence microscopy and beta cell function was determined via glucose-stimulated insulin secretion. RESULTS: In intact rat and human pancreatic islets, adenoviral and lentiviral vectors mediated gene transfer to about 30% of cells, but they did not reach the inner cellular mass within the islet core. Using the whole-pancreas perfusion protocol, we demonstrate that at least in rodent models the centrally located insulin-producing cells can be transduced with high efficiency, while preserving the structural integrity of the islet. Moreover, islet cell viability and function are not impaired by this procedure. CONCLUSIONS/INTERPRETATION: These results support the view that perfusion-based transduction protocols may significantly improve the yield of successfully engineered primary insulin-producing cells for diabetes research.

Neuronal nitric oxide synthase and splanchnic blood flow in anaesthetized rats.

AIMS: To evaluate to what extent the neuronal form of constitutive nitric oxide synthase (nNOS) contributes to the blood perfusion of splanchnic organs, including the islets of Langerhans. METHODS: The nNOS inhibitor 7-nitroindazole (300 mg kg(-1) i.p.) was administered to anaesthetized Sprague-Dawley rats, some of which were pre-treated with the ganglionic blocker hexamethonium (20 mg kg(-1) i.v.) The blood perfusion of the splanchnic organs, including the pancreatic islets was then measured with a microsphere technique. RESULTS: Nitroindazole decreased total pancreatic, duodenal and renal blood flow, whereas pancreatic islet, colonic and adrenal blood flows were unchanged. A slight increase in mean arterial blood pressure was seen after nitroindazole treatment. Nitroindazole did not affect blood glucose or serum insulin concentrations. In separate experiments, hexamethonium affected none of the studied blood flow values, suggesting that the effects of nNOS-inhibition were not mediated from the nervous system. CONCLUSION: Nitric oxide derived from the activity of nNOS contributes to the blood perfusion in the upper portions of the gastrointestinal tract, viz. the parts supplied by the cranial mesenteric artery, and the kidneys, whilst no effects are seen on colonic or adrenal blood flow. Pancreatic islet blood flow was unaffected by nNOS inhibition, thereby suggesting that NO derived from the other isoforms of NOS maintains the high basal islet blood perfusion.

Pancreatic islet blood flow during pregnancy in the rat: an increased islet mass is associated with decreased islet blood flow.

Increased blood perfusion of pancreatic islets is seen during various conditions of increased demand for insulin secretion. Pregnancy confers an increased need for insulin secretion, met by increased islet mass and volume as well as a decreased threshold for glucose-induced insulin secretion. In the present study, whole pancreatic and islet blood flow were studied with a microsphere technique in Wistar rats on days 15, 18 and 20 of pregnancy and days 2 and 7 post-partum. There were no changes in total pancreatic blood flow during pregnancy and the first post-partum week. Total blood perfusion through islet tissue expressed as flow per weight of whole pancreas was higher at day 15 of pregnancy. When islet blood flow was expressed per gram of islet tissue there was a decrease at day 18 of pregnancy. This decrease of islet blood flow was concomitant to a short-lived increase of the islet mass at the end of pregnancy. We conclude that upregulation of insulin output during late pregnancy does not specifically include increased net blood perfusion through the islets. One possible reason for this might be lack of synchronization between the proliferation of endocrine cells and angiogenesis, resulting in a relative decrease in islet vascular density in the islets.

Capillary blood pressure in the endocrine and exocrine parenchyma of rat pancreas transplants.

BACKGROUND: Transplantation of isolated organs or cells leads to a functional denervation of the organ, which may cause a hyperperfusion of blood. The current study evaluated to what extent blood perfusion and capillary blood pressures were affected in the transplanted rat pancreas. METHODS: Inbred, male Wistar-Furth rats underwent transplantation with a syngeneic pancreaticoduodenal graft. Four weeks later, blood flow to the native and transplanted pancreases was measured with a microsphere technique. Capillary pressures were measured by direct micropuncture technique. RESULTS: An increased islet blood flow was consistently observed in the transplanted pancreas as compared with the native organ, while whole pancreatic and duodenal blood flow was similar in the native and transplanted organs. The capillary pressure was twice as high in the exocrine pancreas (6-7 mm Hg) of both the native and transplanted glands when compared with that of the islets (approximately 3 mm Hg). There were no differences in the capillary pressures in either the islets or exocrine gland when native and transplanted pancreases were compared. CONCLUSIONS: We conclude that the transplanted whole pancreas retains a low islet capillary blood pressure after transplantation despite having a higher islet blood perfusion.

Coping with diagnosis related groups. The changing role of the nursing home.

In an attempt to document the changing role of a specific nursing home in the delivery of medical care since the initiation of diagnosis related groups (DRGs), we studied 100 consecutive patients initially admitted to the Veterans Administration Medical Center-Milwaukee Nursing Home Care Unit (NHCU) during the first 23 weeks of 1986 (post-DRGs). Patient characteristics, reason for NHCU admission, and patients' final disposition were determined and compared with those of consecutive patients admitted to the same facility during an identical time period in 1983 (pre-DRGs). More than seven times as many patients were admitted in 1986, and prior to NHCU admission the acute care hospital stay was significantly shorter in 1986 (22 vs 60 days). Whereas in 1983, most patients (94%) were admitted to the NHCU for long-term care placement, in 1986, the majority of patients (64%) were admitted for continuation of therapy started in the acute care hospital. In 1983 only two patients (9%) required hospital readmission within ten days of NHCU admission, compared with 22 (22%) of the patients in 1986. At the termination of the study period, none of the 31 patients admitted to the NHCU in 1983 had been discharged; in comparison, 33% of the patients in 1986 were discharged home. We conclude that in 1986 certain nursing homes drastically changed their role in the delivery of medical care, and are now functioning as extensions of acute care hospitals. Such a role is advantageous in allowing patients to be quickly discharged from the acute care hospital; however, the changing role presents new problems and challenges.