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Biomedical subjects

J Lauronen

Publications and source records attributed to J Lauronen.

13 recordsLinked to original sources
PubMed1999

Synchronous ileal autotransplantation impairs adaptation of remaining gut in pigs with proximal small bowel resection.

This study investigates the effects of ileal autotransplantation on morphology, crypt cell proliferation, and brush border disaccharidases of the remaining jejunoileum and colon in growing pigs with 75% proximal small bowel resection. Resection was performed on 30 pigs, of which 15 underwent an autotransplantation of the remaining ileum. The autotransplanted pigs showed reduced weight gain and remnant ileal length when compared to the resected controls. In the autotransplanted pigs, small bowel diameter and weight, mucosal weight and protein content, villus height and surface area, crypt depth, and the number of proliferating crypt cells were reduced similarly both in the intact jejunum and in the autotransplanted ileal remnant. Autotransplantation also decreased the number of proliferative crypt cells of the colon. Specific activities of maltase and sucrase tended to increase in the autotransplanted ileal remnant, whereas the total enzyme activities decreased. These results suggest that ileal autotransplantation disturbs postresectional adaptation of the remaining gut.

Adaptation, Physiological↗
PubMed1998

Absorption, excretion, and distribution of plant sterols after proximal gut resection and autotransplantation of porcine ileum.

Contribution of different gut segments to plant sterol absorption, adaptation of plant sterol absorption after partial small bowel resection, and effects of gut transplantation (necessitates extrinsic autonomic denervation and lymphatic disruption) on plant sterol biodynamics are unclear. We studied the consequences of massive proximal small bowel resection and autotransplantation of the remaining ileum on the adaptive absorption and biodynamics of plant sterols. Dietary, fecal, biliary, hepatic and plasma plant sterols, fecal elimination and absorption of cholesterol, small bowel morphology, and intestinal transit were determined before (n = 5) and at 4, 8, and 14 wk after resection of the proximal 75% of the jejunoileum (n = 15) and autotransplantation of the remaining ileum (n = 15) or transection (n = 5). Proximal gut resection significantly reduced cholesterol absorption efficiency; percentage absorption and biliary secretion of plant sterols; plasma, biliary and hepatic campesterol-to-cholesterol proportions; and sitosterol proportions in plasma and bile. Autotransplantation of the remaining ileum further significantly decreased cholesterol absorption efficiency; percentage absorption and biliary secretion of campesterol; campesterol proportions in plasma, bile and liver; and plasma proportions of sitosterol while increasing fecal excretion of neutral and acidic steroids. Plasma proportions of the two plant sterols, but absorption of just campesterol, were gradually improved with increasing cholesterol absorption and villus height after proximal gut resection; the same result was observed to a lesser degree after ileal autotransplantation. In addition, significant positive correlations were found between percentage cholesterol and campesterol absorption and the plasma plant sterol proportions in both proximal resection groups, between campesterol absorption and ileal villus height in the resection group, and between campesterol absorption and intestinal transit time in the autotransplantation group. In conclusion, plasma campesterol and sitosterol closely reflect absorption of cholesterol and plant sterols from intact and autotransplanted ileum during adaptation to proximal gut resection. A loss of proximal gut absorptive surface impairs cholesterol and campesterol absorption more than sitosterol absorption, the latter being apparently less dependent on available jejunal villus surface area.

Animals↗
PubMed1998

Nerve terminals containing neuropeptides decrease in number after massive proximal small bowel resection in the piglet.

The aim of this study was to evaluate possible changes in the neuropeptide innervation pattern of the remaining porcine ileum following 75% proximal resection of the small intestine. Three-month-old piglets were operated on and two months postoperatively full-thickness specimens of the proximal part of the distal ileum wall were taken. Age-matched 3- and 5-month-old unoperated piglets were used as controls. The number and intensity of VIP-, galanin-, enkephalin-, substance P-, and somatostatin-containing nerve fibers were estimated in sections processed for immunofluorescence microscopy and subjected to quantitative scoring. The VIP-, galanin-, and enkephalin-immunoreactive fibers of the circular muscle layer and villi were also quantitated by computer-assisted morphometry. The number and intensity of VIP-immunoreactive fibers in the mucosa and circular muscle layer markedly decreased after resection as compared to 3-month-old and 5-month-old controls (P < 0.05). The galanin immunoreactivity index decreased significantly after resection in the circular muscle layer as compared to both control groups (P < 0.05). The increase in the number of enkephalin-immunoreactive nerve fibers that normally occurred from 3 to 5 months of age was inhibited by the resection. We were not able to see any differences in somatostatin or substance P immunoreactivity between the groups. The results suggest that massive resection induces significant changes in the neuropeptide-containing innervation of the remaining small intestine. These findings are compatible with altered motor activity and mucosa function in the remain intestine.

Adaptation, Physiological↗
PubMed1998

Intestinal adaptation after massive proximal small-bowel resection in the pig.

BACKGROUND: Small-intestinal adaptation to resection has been extensively studied in rats. The present study investigates morphology, crypt cell proliferation, and disaccharidase activities of the remaining small intestine and colon after 75% proximal resection of porcine small intestine. METHODS: Specimens were obtained from the proximal jejunum, middle and distal ileum, and proximal colon preoperatively (n = 5) and 14 weeks after small-bowel transection (n = 5) or resection (n = 5). Proliferation was analyzed immunohistochemically with the Ki-67 antigen MIB-1. Disaccharidase activities were determined in accordance with the method of Dahlqvist. RESULTS: In addition to macroscopic enlargement, resection markedly increased the villi and crypts of the remaining small bowel. Crypt cell proliferation decreased with advancing age after transection but remained at the preoperative level after resection. Specific, but not total, activities of maltase and sucrase in the mid-ileum decreased after resection. CONCLUSION: Small-intestinal adaptation in the pig involves macroscopic enlargement and a prompt increase in villus size, which is associated with high crypt cell proliferation.

Animals↗
PubMed1997

L-selectin ligands in rat high endothelium: multivalent sialyl Lewis x glycans are high-affinity inhibitors of lymphocyte adhesion.

Lymphocyte homing is initiated by their tethering to and rolling on the high endothelium and is followed by extravasation into the lymph nodes. We show here that glycosylated cell adhesion molecule-1 (GlyCAM-1), CD34, and sialyl Lewis x (sLex) are present on rat lymph node high endothelium analyzed by using monoclonal antibodies. alpha (1,3)fucosyltransferase VII (Fuc-TVII), the last enzyme involved in the synthesis of the sLex sequence is also expressed on the rat lymph node high endothelium. We have synthesized a family of sLex-decorated oligosaccharide structures and used them to inhibit lymphocyte binding to high endothelium in the Stamper-Woodruff assay. Monovalent sLex, branched di- and tetravalent sLex, as well as a linear tetravalent sLex significantly reduce lymphocyte binding to endothelium. The branched and linear forms of tetravalent sLex were clearly superior inhibitors of the L-selectin-dependent lymphocyte adhesion, with IC50 values in low nanomolar range. In contrast, the fucose-free analogs having the same charge and approximately the same size as the corresponding sLex glycans had no effect on lymphocyte binding and served as negative controls. Taken together, these data show the crucial importance of sLex in the endothelial ligands for L-selectin. Furthermore, we suggest that L-selectin acts as an oligomer on the lymphocyte surface as it binds multivalent sLex glycans.

Animals↗
PubMed1997

Value of mucosal biopsies in the monitoring of acute small bowel rejection.

The value of mucosal biopsies in evaluating small bowel rejection is controversial. In this study, the value of mucosal biopsies was estimated in unmodified porcine small bowel rejection. Ten animals received the distal half of the small bowel as a heterotopic loop (Thiry-Vella loop). The allografts were followed by proximally and distally harvested full-thickness and mucosal biopsies every other day, starting from the 3rd day and continuing until the grafts became necrotic. The histological parameters in both types of biopsies were semiquantitatively scored from 0 to 3 and compared with each other. The difference in mean values on the subsequent days was not remarkable, the results favoring slightly higher values in full-thickness than in mucosal biopsies. Our results suggest that multiple mucosal biopsies are adequate in monitoring morphological changes of small bowel grafts during rejection and that the proximal and distal ileum are similarly affected by acute rejection.

Acute Disease↗
PubMed1997

Adaptive lipid metabolism after ileal autotransplantation in pigs with proximal gut resection.

BACKGROUND: Transplantation of the small intestine impairs intestinal absorptive function, but the adaptive response of a segmental graft is unknown. The aim of this study was to investigate the effects of ileal autotransplantation on the adaptive absorption and metabolism of lipids in pigs that had undergone proximal gut resection. METHODS: Serum lipids, plasma vitamins A and E, absorption and excretion of cholesterol, bile acids and fat, plasma cholesterol precursor and plant sterol proportions to cholesterol (respective markers of cholesterol synthesis and absorption), enteric structure, and transit were determined 4, 8, and 14 weeks after 75% proximal resection with (n = 15) or without (n = 15) autotransplantation of the remaining ileum. RESULTS: As compared with pigs that underwent proximal gut resection, the additional autotransplantation reduced the adaptive increase in total serum and high-density lipoprotein cholesterol, plasma plant sterol proportions and vitamin E concentrations, cholesterol and fat absorption efficiency, and villus height (p < 0.05 for all) during the 14 postoperative weeks and resulted in increases of up to 4.6, 2.7, 1.3, and 2.1 times the plasma cholesterol precursors (p < 0.005), fecal excretion of bile acids (p < 0.0005), neutral steroids (p < 0.005), and net elimination of cholesterol (p < 0.0005), respectively. Cholesterol and fat absorption and plasma plant sterols were significantly enhanced between 8 and 14 weeks after autotransplantation (p < 0.05, p < 0.005, and p < 0.05, respectively), whereas fecal elimination of cholesterol remained increased until the end of the follow-up. CONCLUSIONS: Autotransplantation of the ileum in pigs that have undergone proximal small bowel resection disturbs the adaptive absorption of cholesterol, bile acids, fat, and fat-soluble vitamins, resulting, through increased fecal elimination of cholesterol, in decreased serum cholesterol despite a marked compensatory increase in cholesterol synthesis.

Animals↗
PubMed1997

How to diagnose chronic rejection. A study in porcine intestinal allografts.

Porcine small bowel allografts were followed for 18 weeks during immunosuppression with cyclosporine-A (CyA), azatioprine and prednisone. The mucosal alterations noted at the 12th week were epithelial vacuolation and loss of Goblet cells. Moderate infiltration of inflammatory cells, mainly lymphocytes, was found in the lamina propria. In addition, a few grafts exhibited oedema and fibrosis. Vessels already showed endothelial swelling and intimal proliferation at the 12th week. In the submucosa, the infiltration of inflammatory cells was not present till the 18th week. Further changes in the mucosa at the 18th week were the blunting of villi, cuboidal epithelium, crypt abscesses and epithelial atrophy. The histological alterations of mucosa and lamina propria existing in the full thickness biopsies were mostly also detectable in mucosal biopsies, provided that multiple biopsies were taken. Thus these parameters analyzed from mucosal biopsy material are suitable for the diagnosis and monitoring of chronic small bowel rejection. In autopsy, the most prominent features were in the mesenterial arteries: intimal proliferation, vasculitis, proliferation of media and endothelial alterations. The activity of the mucosal disaccharidases maltase and sucrase remained near the initial level till the 12th week and had decreased markedly by the 18th week.

Abscess↗
PubMed1996

Brush border enzymes in evaluation of acute small bowel rejection.

The change in activity of three disaccharidase enzymes (maltase, sucrase and lactase) was determined according to the method of Dahlqvist during acute rejection in non-immunosuppressed piglet small bowel grafts. In addition, two brush border enzymes, lactase and aminopeptidase, were stained with monoclonal antibodies. Diminishing disaccharidase activity was an early event during rejection. Diminution began 2 days before distinct morphological changes were seen in the mucosal biopsies. Evaluation of disaccharidase activity can thus be used as a confirmatory method in detecting rejection. Reduction in immunohistological staining of lactase and aminopeptidase with monoclonal antibodies and changes in mucosal morphology were observed to progress simultaneously.

Animals↗
PubMed1996

Adaptation of cholesterol absorption after proximal resection of porcine small intestine.

Cholesterol absorption occurs primarily in the upper small intestine. Our aim was to assess absorption of cholesterol during ileal adaptation after proximal small intestinal resection. In vivo absorption and elimination of cholesterol, plasma cholesterol, cholesterol precursors, and plant sterols were related to intestinal morphology and transit 4 (n = 5), 8 (n = 5), and 14 (n = 5) weeks after a 75% proximal resection of porcine small intestine, and compared to preoperative (n = 5) and transected (n = 5) control animals. Fractional cholesterol absorption, the daily amount of cholesterol absorbed, plasma cholesterol, and plant sterol to cholesterol proportions were significantly (P < 0.05 or less) decreased, whereas fecal loss of cholesterol as neutral steroids, less so as bile acids, plasma cholesterol precursor proportions, and ileal mass and villus height were significantly increased (P < 0.05 or less) after 8 weeks of the resection. Cholesterol absorption efficiency, decreased by the resection, was gradually increased from 5.4 +/- 2.2 to 26.9 +/- 3.9% during the 14 postoperative weeks (P < 0.0001) simultaneously with a 46% increase in villus height compared with transection (P < 0.0001), but absorption remained still below control levels (80.4 +/- 2.5%, P < 0.0001). In resected and control animals, villus height correlated positively with cholesterol absorption efficiency (r = 0.85, P < 0.0001; r = 0.76, P = 0.01) and plasma plant sterol proportions (r = 0.94-0.95, P < 0.0001; r = 0.78-0.85, P < 0.008), respectively. In conclusion, after massive proximal small bowel resection, adaptation of intestinal cholesterol absorption efficiency occurs in the distal ileum closely parlleling villus hypertrophy.

Adaptation, Physiological↗
PubMedDate not supplied

Brush cytology in the course of acute small bowel allograft rejection.

OBJECTIVE: To examine the changes in brush cytology during acute small bowel allograft rejection and to evaluate the usefulness of cytology in detecting acute rejection. STUDY DESIGN: Heterotopic porcine small bowel allografts were followed by brush cytology and full-thickness biopsies during unmodified rejection. RESULTS: The most prominent changes in cell differential counts were an increase in the proportion of granulocytes and decrease in the proportion of epithelial cells. In brushed epithelial fragments, infiltration of granulocytes and acidophilia increased, and cell cohesion was gradually lost with the degeneration of nuclei and necrosis of epithelium. The cell differential count was compared to the histologic acute rejection index, which was created on the basis of five semiquantitatively evaluated histologic parameters. The sensitivity of cell differentiation in detecting histologically moderate or severe rejection was 87% (13 of 15 cases) and the specificity 76% (5 false positives in 21 negative cases). CONCLUSION: Suspicion of acute rejection can be assessed with reasonable reliability by cytology, but it cannot be detected earlier than by histology. Brush cytology complements mucosal biopsies in the evaluation of rejection and, as a rapid and cost-effective method, may even partly replace them. It may also prove valuable in detecting opportunistic bowel infections in immunosuppressed patients.

Animals↗