Kaj Fält

Prostacyclin is Produced from Endothelial Cell-seeded Grafts: an Experimental Study in Sheep*

Endothelial cell seeding might be of value in reducing the thrombogenicity of small-diameter vascular grafts. We investigated the capacity of endothelial cell-seeded grafts to produce prostacyclin and compared this with that of the unseeded graft as well as the native artery. Twelve sheep were operated on with carotid interposition of externally supported knitted dacron grafts. On one side of the neck the graft was seeded with endothelial cells, enzymatically harvested from the left jugular vein. After 3 weeks, three out of 12 seeded grafts, and one out of 12 unseeded grafts were occluded (N.S.). After excision, the grafts were mounted and perfused ex vivo for five 15-min periods. During the last period, arachidonic acid (4 micrograms/ml) was added to the perfusate. The resected carotid artery was used as a control. Prostacyclin was determined as the stable degradation product 6-keto-PGF1 alpha using radio-immunoassay, and expressed as pg mm-2 luminal surface. The native artery had a significantly higher release of prostacyclin than the seeded graft, which in turn had a significantly higher release than the unseeded graft. Histological examination showed weakly positive staining for factor VIII-related antigen on the luminal surface of seeded grafts. Scanning electron microscopy showed endothelial cells with typical endothelial tufts and was evaluated blindly from 10 areas of each graft. The extent of endothelial cell coverage was evaluated and scored from 0 to 2.5. The median score for the unseeded grafts was 0.3 and for the seeded grafts 1.5 (p = 0.008). Prostacyclin production was higher in seeded than unseeded grafts, but did not influence patency in this model.

Vessel repair after balloon angioplasty: Morphological appearance and prostacyclin synthesising capacity

Immediately after balloon dilatation of the rabbit aorta the release of prostacyclin is diminished. In this study the morphological appearance and time course for recovery of prostacyclin production after balloon dilatation have been investigated. Healthy rabbit aortas were analysed 1 h (n = 12), 1 week (n = 13) and 1 month (n = 13) after angioplasty. The production of prostacyclin, from dilated and non-dilated aortic segments, was recorded in a perfusion system. Prostacyclin was measured as its stable degradation product 6-keto-PGF1 alpha. Scanning electron microscopy and light microscopy were used to analyse the type of cells present at the luminal surfaces of the segments. When endothelial cells were found their degree of coverage was also estimated. One hour after balloon dilatation there was a lower production of prostacyclin from the angioplasty segments than from controls. Also, the response to added arachidonic acid (AA) was lower in the angioplasty segments. No endothelial cells were present in the angioplasty segments. After 1 week there was no difference in the basic production of prostacyclin but there was still a lower response from angioplasty segments to the addition of AA. The inner surfaces of the angioplasty segments were covered by three to five layers of smooth muscle cells (SMC). After 1 month, there was no difference in either the basic production or after the addition of AA between control and angioplasty segments. The angioplasty segments were covered with a multilayer of SMC. The control segments had an almost complete cover of endothelial cells at every time interval after angioplasty.(ABSTRACT TRUNCATED AT 250 WORDS)

Neuron-specific enolase (NSE) as a neuroendocrine cell marker in the human fetal pancreas

Using the PAP technique, we investigated the presence of neuron-specific enolase in the human fetal pancreas of 10, 12, and 14 weeks of gestational age. Neuron-specific enolase is present in the islet cells in the 10th week. Positive cells are situated mainly in duct epithelium. The number of cells with a positive reaction increases from the 12th to the 14th week. In the 14th week, they are clustered either near the ducts or between the acini. The numbers and localizations of the cells correspond to those obtained in previous studies with 4 basic islet cell types in the same material. The present results are a further proof that islet cells are biologically active during early fetal development.

Islet cell antibody reactivity with human fetal pancreatic islets

To evaluate the possibility of autoimmune processes against pancreatic islets in fetal life, we tested islet cell antibody (ICA) reactivity with 14 fetal pancreata obtained after abortion at the 15th up to the 19th week of gestation. Pancreatic islets positive for a monoclonal proinsulin antibody but non-reactive with ICA negative control serum were found in 9/14 pancreata and all (9/9) of them showed a positive reaction with the ICA standard. It is concluded that ICA reactivity may be detected in fetal human pancreata. Further studies on fetal islet cell antibody reactivity in the development of insulin dependent diabetes mellitus (IDDM) are warranted.

Influence of prostanoids on gastrointestinal mucosal injury in experimental septic shock

Capillary stasis and mucosal injury in the stomach and small intestine were studied in septic shocked pigs. Septicemia was induced by live E. coli i.v. in 28 animals. Additionally, five animals were infused with Ringers solution and served as sham controls. The 28 E. coli‐infused animals were pretreated with either a cyclooxygenase inhibitor –indomethacin, n = 6, a thromboxane (TxA2)‐synthetase inhibitor –UK 38 485 alone, n = 6, or combined with a serotonin‐antagonist – ketanserin, n = 9. Seven E. coli‐infused animals were left untreated and served as septic controls. The sham controls were hemodynamically stable and had normal histological findings. All bacteria‐infused animals exhibited signs of septic shock with pronounced hemodynamic reactions. Attenuation of the bacteria‐induced increase in pulmonary arterial blood pressure was found in all pretreated animals but most pronounced in the indomethacin‐pretreated group which also showed protection against gastric mucosal injury and capillary stasis. TxA2‐inhibited animals had aggravated capillary stasis and mucosal injuries. It is concluded that gastric mucosal damage could be modified by drugs influencing the prostanoid system. The “cytoprotective” effect of prostaglandins seem to be of minor importance for the prevention of the gastro‐intestinal mucosal injury seen in some series.

Immunohistochemical investigations of β-endorphin in human pancreatic islets

The PAP technique was used to examine adult human pancreata (corpus) immunohistochemically for the presence of beta-endorphin containing cells. These cells were found to account for 4.8% of the islet cells. They are irregularly distributed within the islets, where they occur singly or in groups of 3 to 5 cells between the acini (0.4% of the parenchyma). Investigations designed to detect the simultaneous presence of beta-endorphin and somatostatin or glucagon revealed that beta-endorphin occurs in somatostatin cells (1.0% of the islet parenchyma). This is the 1st proof that these 2 hormones appear together. The simultaneous presence of beta-endorphin and glucagon in the same cell was also observed in 0.9% of the islet parenchyma. Earlier studies undertaken by us have shown that beta-endorphin is synthetized in the islets of Langerhans. Possible functions of beta-endorphin in the islets are discussed.

Augmentation of streptozotocin-induced hyperglycemia in mice by prior treatment with complete freund’s adjuvant

SummaryThe effect of complete Freund’s adjuvant (CFA), in combination with streptozotocin (STZ), on pancreatic insulin content, plasma glucose, and pancreatic histopathology were studied in male Balb/c mice. One injection of CFA, followed 24 h later by a single dose of 100 mg/kg of STZ (group I), produced a 92% (p<0.01) reduction in pancreatic insulin, a 54% (p<0.01) increase in glucagon content, and severe hyperglycemia. The depletion of pancreatic insulin was associated with degranulation, necrosis of beta cells, and reduction of the apparent islet size. Focal pancreatitis, without apparent islet inflammation, occurred in all animals in this group. After treatment with STZ alone (group II), pancreatic insulin content decreased 73% (p<0.01), whereas plasma glucose levels, even though being in the hyperglycemic range, were significantly lower (p<0.02) than the mice in group I. Although pyknotic and hypertrophic cell nuclei could be observed in several islets of mice from group II, major histopathological changes, such as pancreatitis and extensive beta cell necrosis seen in group I, were absent. The results show that in the Balb/c mouse strain, a nonspecific insult by CFA prior to a cell-specific cytotoxic insult markedly enhanced destruction of beta cells and the development of hyperglycemia.

β-Endorphin-immunoreactive cells in the human fetal pancreas

This investigation has been carried out on 50 samples of fetal pancreata from the 10th to the 32nd week of gestation using the PAP technique. beta-Endorphin-reactive cells were morphometrically recorded by means of the point-counting method. beta-Endorphin reactivity occurred for the first time during the 15th week. During further development, beta-endorphin cells were found inside and outside the islets. From the 18th to 23rd week, these cells were primarily localized in the islet periphery. From the 24th week, they rearranged and occurred in irregular positions mixed with other islet cells. This rearrangement took place with a 4 week delay compared with the basic cell types of the islet organ. The extrainsular portion of these cells in the exocrine parenchyma varied between 0.3% in the 27th week and up to 10% in the 22nd week. Concerning the adult human pancreas, it has been suggested whether beta-endorphin cells may be a 6th basic cell type of the islet organ. Previous studies on the coexistence of somatostatin, glucagon and beta-endorphin in the same islet cell and the morphometric analysis would support this assumption. Biochemical examinations indicate that beta-endorphin is a modulator of insulin, glucagon, and somatostatin secretion in the islet organ. This is supported by the fact that beta-endorphin cells have extended cell bodies which is typical of cells with paracrine function.

Secretory State and Acute Gastric Mucosal Injury in Sepsis

Cats were subjected to a standardized 3-h septicemia by intravenous infusion of live Escherichia coli in an LD50 dose. The effect of pentagastrin stimulation on the development of gastric mucosal injury was studied. There was no hemodynamic difference between the series during septicemia. Thus, pentagastrin did not induce increased gastric blood flow during the period of E. coli infusion. Intraluminal gastric pH was lower in the series given pentagastrin during the last 2 h of septicemia. Nevertheless, the extent of gastric mucosal injury was similar in the two groups, whereas the depth of injury was, if anything, less pronounced in the pentagastrin-stimulated group.

Early Indicators of Allograft Rejection in a Porcine Pancreatic Transplantation Model

Urine cytology and blood lymphocyte blastogenesis were evaluated as indicators of allograft rejection in a porcine pancreatic transplantation model. The percentage of activated lymphocytes and/or blasts was significantly increased during the rejection phase. Positive cytology was present in all rejection episodes. An increased thymidine uptake of blood lymphocytes and a decreased uridine/thymidine uptake quotient were seen prior to the onset of rejection. The reported dissociation of anionic and cationic trypsin levels in serum and urine after transplantation was not seen after simple urinary diversion of the pancreatic juice. This supports the hypothesis that a decreased synthesis of cationic trypsinogen compared with anionic trypsinogen occurs after porcine pancreatic transplantation.