Biomedical subjects
Publications and source records attributed to C Tagesson.
Two man-made mineral fibres, rockwool and glasswool, were found to mediate hydroxylation of deoxyguanosine and calf thymus DNA to form the DNA adduct 8-hydroxy-2'-deoxyguanosine. The modification of the nucleoside is probably mediated by hydroxyl radicals and may play a role in fibre-induced carcinogenesis.
Plasma malondialdehyde (MDA) was evaluated as an index of lipid peroxidation in 20 patients with small intestinal obstruction, with or without strangulation. The gut proved to be strangulated in nine cases--irreversibly in five and reversibly in four--while 11 patients had simple obstruction. The MDA levels in these cases were compared with values obtained from 29 healthy control subjects. The mean MDA level in the control group was 2.3 +/- 0.7 (range 1.5-4.0) mumol/l. In the patients with strangulation obstruction the MDA concentration was 6.7 +/- 1.6 mumol/l, and in those with simple obstruction it was 2.9 +/- 0.5 mumol/l. The difference between the MDA level in strangulation and in the other investigated groups was statistically significant. Values above 4 mumol/l were found in all the patients with intestinal strangulation, whereas those with simple obstruction had lower values. The heightened MDA level in patients with intestinal strangulation may be used for diagnostic purposes.
The influence of ischaemia and revascularisation on lipid peroxidation and phospholipid metabolism in the rat small intestinal mucosa was investigated. Two hours of total ischaemia followed by five minutes of revascularisation caused not only accumulation of malondialdehyde in the mucosa, but also increased activity of phospholipase A2, decreased activity of lysophospholipase, and increased ratio between lysophosphatidylcholine and phosphatidylcholine. Pretreatment with the phospholipase A2 inhibitor, quinacrine, prevented the increases in mucosal phospholipase A2 activity and lysophosphatidylcholine/phosphatidylcholine ratio after ischaemia and morphological examinations revealed that the mucosa was then also protected against ischaemic injury. These findings point to the possibility that activation of phospholipase A2 and accumulation of lysophosphoglycerides could be involved in mediating the mucosal injury caused by small intestinal ischaemia.
We have studied the development of phospholipase A2 (PLA2) and lysophosphatidylcholine (lysoPC)-metabolising enzyme activities in the neonatal rat intestine and its relation to the intestinal permeability of macromolecules. The permeability was determined by feeding young rats a mixture of bovine serum albumin, bovine immunoglobulin G and fluorescein-isothiocyanate-conjugated dextran 70,000, and analysing the serum concentrations after six hours. The animals were then killed and the intestinal mucosa was homogenised and assessed for PLA2 and lysoPC-metabolising enzyme activities. The intestine was 'open' to the macromolecules in 14 day old animals, but 'closed' in 22 and 32 day old animals and in 14 day old rats treated with cortisone acetate on day 10, 11, and 12 postpartum. The activity of PLA2 (at pH 6 and 2 mM Ca2+) was higher in 32, 22, and cortisone treated 14 day old animals, than in untreated, 14 day old animals. Incubation of 14C-acyl-lysoPC with mucosa from 14 day old rats did not change the radioactivity pattern as shown by thin layer chromatography, whereas after incubation with mucosa from 22 or 32 day old animals all the radiolabel was found in free 14C-fatty acid and in 14C-phosphatidylcholine. These findings indicate that mucosal PLA2 activity increases during intestinal maturation and that the mucosa acquires the ability to acylate and deacylate lysoPC when it is 'closed' to macromolecules.
Phospholipase A2 (PLA2) activity was measured and partially characterized in prostasomes isolated from human seminal plasma. The results show high PLA2 activity in seminal plasma with a threefold enrichment in the isolated prostasomes. Highest activity was found at pH 8.0 and 10.5, and there was an absolute requirement for calcium with almost total inhibition of PLA2 activity in the presence of 1 mM EDTA. Analysis with two-dimensional gel electrophoresis of prostasome material revealed a complex protein pattern with most of the proteins in the molecular weight interval of 10,000-90,000 daltons. The possible role of PLA2 in prostasomes is discussed.
We have developed a simple experimental model for studying reversible intestinal ischemia. The model is based on tenting the mesenteric vessels (artery and vein) to a tied loop of the small bowel in rat and, after a certain time, lowering them down again. Total and partial ischemia (created by tenting 2 and 1 cm, respectively) were demonstrated by laser Doppler flowmetry, as was the revascularization obtained after bringing the vessels down again. Alterations in mucosal permeability after ischemia were determined by depositing fluorescent dextran 3000 in the tied loop and measuring its concentration in the portal blood, and mucosal damage due to ischemia was assessed by measuring the activity of N-acetyl-beta-glucosaminidase, a lysosomal enzyme, in the gut lumen. There was a significant increase in the intestinal permeability to dextran 3000 after total ischemia for 10 min or more, and the permeability was directly related to the duration of the ischemia. After the intestine had been subjected to total ischemia for 30 min or more, the activity of N-acetyl-beta-glucosaminidase in the luminal contents was significantly increased. The permeability after partial ischemia for 30 min was less than that after total ischemia for 30 min. After total ischemia for 10 min followed by revascularization for 30 or 60 min, the permeability did not differ from that in animals not subjected to ischemia. It is concluded that this simple model may be used to study reversible small intestinal ischemia and factors that influence mucosal permeability.
Gastrointestinal absorption of orally administered polyethyleneglycols in the 634-1294 dalton range (PEG 1000) was investigated in 44 patients with ileocaecal Crohn's disease and in 24 healthy controls. Absorption of PEG was inversely proportional to molecular weight in both groups. In the Crohn patients the absorption of all tested molecular weights of PEG was significantly less than in the controls. In Crohn's disease there was also less of selectivity of the mucosal barrier against the larger molecules. The state of the distal ileum--acutely inflamed, in remission or post-resection did not influence absorption. Decreased PEG absorption in ileocaecal Crohn's disease probably reflects an abnormality of jejunal mucosal permeability. The observations support the concept that Crohn's disease is a diffuse lesion, affecting the whole gastrointestinal tract. The nondependence of the abnormality on the severity of distal inflammatory changes or on previous resection suggests that abnormal jejunal permeability may be a primary expression of Crohn's disease.
The influence of lysophosphatidylcholine (LPC), taurocholate (TC), and taurodeoxycholate (TDC) on gastric mucosal permeability was studied in a rat experimental model, with different-sized polyethylene glycols (PEGs) in the 722-1206-dalton range as permeability markers. Gastric mucosal morphology was also studied by transmission electron microscopy. We found that 2.5 mM and 5 mM LPC and TDC, but not TC, caused an increase in the passage of PEGs across the gastric mucosa. LPC altered the permeability significantly more than did TDC. Morphologically damaged intercellular microvillous structures could be seen after LPC treatment, whereas no obvious changes could be seen after TC or TDC treatment. These findings indicate that LPC and TDC may damage the gastric mucosa and enable permeation of molecules in the 722-1206-dalton range. Molecules within this range could potentially be toxic or antigenic, and this therefore represents an aspect of interest in the pathology of enterogastric reflux. Furthermore, the results indicate that dihydroxy secondary bile acids (TDC) have a more pronounced effect on gastric mucosal permeability than trihydroxy primary bile acids (TC).
The influence of lysophosphatidylcholine (lysoPC), taurodeoxycholate (TDC), and taurochenodeoxycholate (TCDC) on the permeability properties of the ischaemic small-intestinal mucosa was investigated. We first studied the effect of ischaemia alone, then of lysoPC, TDC, or TCDC alone, and finally of ischaemia together with lysoPC, TDC, or TCDC on the permeability to sodium fluorescein in a ligated loop of the distal ileum in the rat. Longer periods of ischaemia alone (10 min or more) caused increased permeability, as did high concentrations (10 mM) of any of the agents. Low concentrations (1 mM) of lysoPC alone did not alter the gut permeability, but it significantly potentiated the increased permeability caused by 30 min of ischaemia. In contrast, 1 mM TDC or TCDC did not influence the permeability after 30 min of ischaemia. These findings imply that the ischaemic small intestine may be damaged by small amounts of lysoPC, with increased absorption of potentially pathogenic compounds as a possible consequence. They also point to the possibility that endogenously formed lysoPC may play a role in the mucosal damage and the increased permeability that occurs after small-intestinal ischaemia.
We have studied the influence of lysolecithin on mucosal permeability to different-sized molecules in the distal part of the ileum. Using a rat experimental model, we determined the intestinal permeability to ethylene glycol (62 dalton), different-sized polyethylene glycols (634- to 1206-dalton PEGs), and dextran 3000, in the absence and presence of lysolecithin. We also examined the morphology of the ileal mucosa and determined the activity of brush border enzymes after deposition of lysolecithin in the gut lumen. We found that lysolecithin did not affect the absorption of ethylene glycol and had no influence on the activities of the enzymes. In contrast, lysolecithin enhanced the desquamation of enterocytes at the villous tips and increased the permeability to 634- to 1206-dalton PEGs and dextran 3000. These findings indicate that lysolecithin may facilitate the uptake of larger, potentially antigenic and toxic molecules in the distal ileum, although the underlying epithelial desquamation might have little or no influence on the absorption of small compounds.
Multiple biopsy specimens were taken from the duodenal cap and/or from the descending part of the duodenum in patients admitted for routine upper endoscopy, to determine the degree of variation in disaccharidase activity. Four specimens were taken from each site and assayed in pairs. The mean coefficients of variation (CV) of enzymatic activities between duplicate measurements in the same pair of specimens were less than 3.5% and between two pairs of biopsies about 30%. The large variation in disaccharidase activity between assays performed on simultaneously biopsied specimens from the same area of the bulb and the descending part of the duodenum in the same individual implies that single values for enzyme activity must be interpreted with caution.
The effects of lysophosphatidylcholine (lysoPC) on airway and capillary permeability in the isolated perfused rat lung were investigated. We determined the influence of lysoPC on the passage of different-sized (326-722 dalton) polyethylene glycols (PEGs), both from the airways to the pulmonary circulation and from the pulmonary circulation into the lung. We found that 1 mM lysoPC increased the overall passage of PEGs from the airways to the pulmonary circulation, and that 80 microM lysoPC increased the overall passage from the circulation into the lung. In both cases, the passage of the larger (502-722 dalton) PEGs increased more than the passage of the smaller (326-458 dalton) PEGs. We also found that the presence of lysoPC in the circulation increased the pulmonary arterial pressure, whereas deposition of lysoPC in the trachea did not. The pressure increase was blocked by indomethacine, BW755C, and quinacrine, inhibitors of arachidonic acid metabolism. These findings suggest that higher concentrations of lysoPC increase the airway permeability to larger molecules, and that lower concentrations of lysoPC increase the capillary permeability. The increase in capillary permeability may be due to a rise in capillary pressure mediated by arachidonic acid metabolites. The possibility that formation and accumulation of lysoPC is of importance for mediating inflammatory reactions in the lung is inferred.
The influence of lysophosphatidylcholine (LPC) on the permeability to different sized molecules in the stomach has been studied. Using a rat experimental model, we determined the gastric permeability to sodium fluorescein (molecular weight 376 dalton) and to fluorescein-labeled dextran 3000 (molecular weight 3000 dalton) in the absence or presence of LPC. We also examined the influence of LPC on the morphology of the gastric mucosa using light microscopy, scanning electron microscopy and transmission electron microscopy. We found that 10 mM LPC increased the gastric permeability to both sodium fluorescein and to dextran 3000. Moreover, by transmission electron microscopy, damaged microvillous structures could be seen after LPC treatment. Light microscopy and scanning electron microscopy showed no difference between LPC-treated rats and controls. These findings indicate that LPC, a naturally occurring component in duodenal juice, may damage the gastric mucosa and increase the stomach permeability to larger, potentially pathogenic molecules.
The influence of lysophosphatidylcholine (LPC) on macromolecular permeability in the distal ileum has been studied. Using a rat experimental model, we determined the intestinal permeability to different sized dextrans (3000-70 000 daltons) and bovine serum albumin (BSA) in the absence and presence of LPC. We also examined the morphology of the ileal mucosa after deposition of LPC in the gut lumen, and determined N-acetyl-beta-glucosaminidase, 5'-nucleotidase, and alkaline phosphatase activities in suspensions of isolated mucosal cells and different concentrations of LPC. We found that 20 mM LPC damaged the ileal mucosa and that it increased its permeability to all the molecules investigated. Moreover, mixtures of mucosal cells and 0.01-1 mM LPC showed increased N-acetyl-beta-glucosaminidase activity: the higher the LPC concentration, the higher the enzyme activity. These findings indicate that LPC, a naturally occurring surfactant in the intestine, might damage mucosal cells and release lysosomal enzyme activity, and that higher LPC concentrations may impair the mucosal barrier function and increase the gut permeability to macromolecules such as proteins. This could have relevance to the development of various disease states, in which increased intestinal absorption of macromolecules is of importance.
A simple experimental model was used to study the influence of organic solvents and solvent mixtures on the integrity of biological membranes. Radiolabelled membranes were prepared biosynthetically by growing Escherichia coli in the presence of 14C-oleic acid; the bulk of the radioactivity was incorporated into 14C-phosphatidylethanolamine, the predominant phospholipid species in E coli membranes. The radiolabelled bacteria were incubated at 37 degrees C in the presence of solvent, and the mixture filtrated through a Millipore 0.45 micron filter. This filtration retained radiolabel associated with the bacteria, and only radiolabel released as a result of solvent action was allowed through the filter. The radioactivity in the filtrate was then counted and expressed as a percentage of the total radioactivity. Results showed that aliphatic alcohols released membrane constituents in relation to their hydrocarbon chain length (1-propanol greater than 2-propanol greater than ethanol greater than methanol); the effects of aliphatic alcohols were potentiated by acetone, ethyl methyl ketone, ethylene glycol, and N,N'-dimethylformamide, and the effects of ethanol were potentiated by 1-butanol, benzyl alcohol, and ethylacetate. These findings point to the possibility that certain mixtures of organic solvents are more damaging to membranes than the components of the mixture would indicate, and suggest that the experimental model used might help in showing mixtures that are particularly harmful.
The effects of colostrum and constituents/factors in colostrum which may influence intestinal macromolecular transmission in the newborn preclosure pig were investigated. Unsuckled piglets were given, by use of a stomach tube, bovine serum albumin (BSA) and fluorescein-isothiocyanate (FITC)-labelled dextran 70,000 (FITC-D) as markers together with colostrum or the factors under study. The serum levels of BSA and FITC-D 4 h after feeding were then determined as a measure of the transfer. It was found that the two colostrums tested, bovine and especially porcine, markedly enhanced the transmission of both BSA and FITC-D. Furthermore, increasing amounts of the model proteins, BSA and bovine IgG (50-200 mg/ml), significantly increased the transfer of FITC-D, whereas unlabelled dextran 70,000 given in similar amounts did not. Proteinase inhibitors obtained from sow colostrum or soy bean also enhanced the transmission of both BSA and FITC-D while the inactive inhibitors, given as trypsin-inhibitor complexes, had no effect. On the other hand, addition of a proteinase, porcine trypsin, significantly decreased the transmission of FITC-D. These findings indicate that the intestinal transmission of macromolecules in the preclosure piglet is governed by the amount of protein available in the intestine. Therefore, feeding colostrum with a high protein content and proteinase inhibitors is likely to favour efficient intestinal transmission, although other colostrum factors may also be of importance.
A rapid and simple procedure has been used to determine phospholipase A2 activity (EC 3.1.1.4) in rat ileal mucosa. We used 14C-oleate-labeled Escherichia coli as substrate for the phospholipase activity and a 0.45-micron Millipore filter to separate the product of hydrolysis--the 14C-oleic acid--from the unhydrolyzed substrate. The phospholipase A2 activity was optimal at pH 9.8 and at 2 mM Ca2+, but another peak of activity appeared at pH 7.2. In addition, cell fractionation revealed yet another phospholipase A2 activity at pH 5.0 in the absence of Ca2+. These findings suggest the presence of more than one phospholipase A2 in the ileal mucosa and points to the possible use of a simple procedure for studying their distribution and properties.
In Crohn's disease there are changes in the ultrastructure of the intestinal epithelium, not only in the inflammatory tissue but also in non-ulcerated areas and in non-involved resection margins. Vitamin A is known to influence the metabolism and differentiation of epithelial tissue and has also been reported to normalize the number of stools after ileocaecal resection for Crohn's disease. We gave vitamin A (150 000 U daily) for 2 weeks to 8 patients with severe but not acute Crohn's disease. Various clinical parameters and the mucosal permeability to different-sized polyethyleneglycols were investigated before and after the administration of vitamin A. Disappointingly, no patient derived any benefit from the vitamin A ingestion as regards subjective manifestations, clinical signs, or mucosal permeability. However, some patients with Crohn's disease have low plasma concentrations of vitamin A and should be offered replacement therapy.