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Biomedical subjects

T Landsverk

Publications and source records attributed to T Landsverk.

At least 73 records · Page 4Linked to original sources
PubMed1988

Importance of carbonic anhydrase for canalicular and ductular choleresis in the pig.

To assess the importance of carbonic anhydrase (CA) for canalicular and ductular choleresis, the effect of acetazolamide on bile secretion was measured in three experimental groups of anaesthetized pigs. CA activity in liver homogenate was 46 (43-54) U g-1 wet weight, 150 mg kg-1 b.w. acetazolamide completely abolished the CA activity. Acetazolamide reduced bile HCO3- secretion in six secretin infused, bile-acid depleted pigs by 67 (58-71)% at arterial pH 7.41 (7.38-7.46). By contrast, acetazolamide did not affect HCO3- secretion in six Na-taurocholate (TCA) infused pigs in the absence of secretin stimulation. Acetazolamide reduced ursodeoxycholic-acid- (UDCA) dependent HCO3- secretion by 24 (11-38)% in six other pigs in the absence of secretin stimulation. Histochemical examination using modifications of Hansson's method showed strong reaction in bile ductules and weaker reaction in peripheral zones of liver lobules. Because acetazolamide impairs HCO3- secretion from cells sustaining high rates of H+/HCO3- transport, it is suggested that high rates of H+/HCO3- transport are confined to bile ductules under conditions of secretin- and UDCA-induced choleresis.

Acetazolamide↗
PubMed1987

The follicle-associated epithelium of the ileal Peyer's patch in ruminants is distinguished by its shedding of 50 nm particles.

Significant differences were found between the follicle-associated epithelial cells (FAE) covering the domes of the jejunal and ileal Peyer's patches (PP) in calves. Whereas the FAE of the jejunal PP had scattered membraneous (M) cells among absorptive epithelial cells, the FAE of the ileal PP constituted a homogeneous population of cells different from both absorptive cells and M cells. The FAE of the ileal PP had short microvilli or folds, cytoplasmic vesicles and vacuoles containing acid phosphatase. Fifty nanometer membrane-bounded particles were found in lacunae extending from the lateral cell border. These particles appeared to have been shed from the FAE. Finger-like projections, rich in microfilaments, extended into the lacunae. M cells had short, sparse microvilli, many vesicles, few lysosomal structures, and they enfolded groups of mononuclear leucocytes. Transcytosis of macromolecular tracers occurred in both M cells and in the FAE of the ileal PP, though the uptake was greater in the latter. The 50 nm particles were also found between cells in the lymphoid tissue underneath the FAE of the ileal PP. The FAE of PP in pre- and post-natal lambs from 115 days of gestation and onwards, and goat kids, showed similar structural features.

Animals↗
PubMed1987

Carbonic anhydrase--a marker for particles shed from the epithelium to the lymphoid follicles of the ileal Peyer's patch in goat kids and lambs.

Carbonic anhydrase (CA) was found to be a marker for 50 nanometer membrane-bounded particles shed from the lateral cell border of follicle-associated epithelial cells (FAE) in the ileal Peyer's patch (PP) of pre- and post-natal lambs and goat kids. The CA-positive particles seemed to filter into the underlying lymphoid tissue where they formed part of the matrix embedding the cells of the follicle centre.

Animals↗
PubMed1987

Localization of K-NPPase and Li+ secretion in the exocrine pancreas of the pig.

To study the mode of transepithelial Na+ transport into pancreatic ducts during secretin-dependent NaHCO3 secretion, Na, K-ATPase was first localized within the exocrine pancreas of the pig using a cytochemical reaction for K-dependent p-nitrophenylphosphatase (K-NPPase). K-NPPase staining was confined to the lateral cell membrane bordering the intercellular spaces between ductal cells, negating the possibility of primary active, transcellular Na+ transport into pancreatic ducts. To assess how transepithelial Na+ transport may be coupled to HCO-3 secretion, net flux of Li+ into pancreatic juice was measured following intravenous systemic Li+ loading of 12 secretin infused, anaesthetized pigs. At plasma Li+ 32 (23-35) mmol l-1, Li+ displaced Na+ as accompanying cation to secreted HCO-3, and Li+/Na+ in pancreatic juice matched Li+/Na+ in arterial plasma. During superimposed inhibition of pancreatic water flux by hyperglycaemia, Li+ and Na+ were both transported against a transepithelial concentration gradient. Li+ reduced pancreatic HCO-3 secretion rate by 14 (-2 to -20)%, as well as Na,K-ATPase activity in a separate in vitro assay. The finding that Li+ substituted for Na+ in the secretion even during reduced osmotic water flow suggests that Na+ and Li+ are transported together with secreted HCO-3 into pancreatic juice by an electrogenic mechanism in addition to solvent drag and diffusion.

4-Nitrophenylphosphatase↗
PubMed1987

Ultrastructure of pancreatic duct cells at secretory rest and during secretin-dependent NaHCO3 secretion.

The study was undertaken to identify possible ultrastructural changes occurring in pancreatic duct cells in relation to secretin-dependent NaHCO3 secretion, Pancreatic biopsies were obtained for examination, following in situ glutaraldehyde fixation from four groups of anaesthetized, young pigs. In the resting state, pancreatic duct cell cytoplasm was found to contain multiple vesicles of approximately 0.2 micron diameter. Elevation of systemic arterial PCO2 to 11.1 (10.6-11.6) kPa increased the number of vesicles per unit volume of resting cells by approximately 250%. During secretin-dependent NaHCO3 secretion, the duct cell cytoplasm was devoid of vesicles. Following cessation of secretin-dependent NaHCO3 secretion, cytoplasmic vesicles reappeared. The observed changes in the population of cytoplasmic vesicles in pancreatic duct cells may be causally related to the exocrine secretion of NaHCO3.

Animals↗
PubMed1987

Cryptosporidiosis and the follicle-associated epithelium over the ileal Peyer's patch in calves.

Three calves were studied in stages of spontaneous cryptosporidial infection with particular reference to the relation of the cryptosporidia to the follicle-associated epithelium (FAE) over the ileal Peyer's patch (IPP). In early infection scanning electron microscopy and streptavidin immunoperoxidase staining showed marked predilection of cryptosporidia for the FAE. Cryptosporidial antigen was also found in subepithelial tissue, both in the domes over the IPP and in villi, apparently in macrophages, where the parasites seemed to be progressively degraded. The FAE showed long tightly spaced microvilli, replacing normal low folds and protrusions, particularly in late infection. Endocytosis of indian ink was restricted to the cell periphery in late infection, contrasting the normal, more even distribution of endocytosis in the FAE apical cytoplasm. Few parasites were seen in the intestinal mucosa at this stage. At convalescence the FAE was normal, but all stages of infection were characterised by elongation of microvilli in absorptive cells.

Animals↗
PubMed1986

Histochemical distribution of potassium-dependent p-nitrophenylphosphatase in the calf intestine.

Potassium-dependent p-nitrophenylphosphatase was demonstrated, using the lead citrate method of Mayahara et al. (1980), in frozen sections of calf intestine fixed in formalin-calcium. The calcium chloride included in the fixative was shown to improve the localization of the reaction markedly. The phosphatase activity observed in the basolateral cell borders of the surface epithelium in the small intestine and colon was reduced by 10 mM ouabain and by substitution of sodium ions for potassium ions, confirming that the reaction was representative for the second step in the Na+/K+-ATPase complex. The intensity of the basolateral enzyme reaction was in the order: colon greater than duodenum, proximal jejunum greater than ileum greater than middle and distal jejunum. The crypts reacted weakly. A reaction in the brush border of the proximal jejunum and duodenum and a granular reaction in the supranuclear cytoplasm of the epithelial cells was not influenced by ouabain. The staining pattern for the potassium-dependent phosphatase differed from that of alkaline phosphatase and Mg2+-dependent ATPase, which gave a reaction that was restricted to the brush border.

4-Nitrophenylphosphatase↗
PubMed1986

Histochemical localization of carbonic anhydrase in the pig's exocrine pancreas.

Carbonic anhydrase is essential for the pancreatic secretion of NaHCO3. To localize the distribution of carbonic anhydrase in the exocrine gland and, hence, identify the potential cellular source of secreted NaHCO3, histochemical staining of carbonic anhydrase was carried out on pancreatic biopsies obtained from six pigs at both supramaximal intravenous secretin stimulation and at secretory rest. Tissue staining, using Hansson's technique, revealed a strong staining both in membranes and cytoplasm in the duct cells and a weaker cytoplasmic staining in the acinar cells. Staining reaction was abolished by 10(-5) mol l-1 acetazolamide. Duct cells, accordingly, seem to be responsible for NaHCO3 secretion, while acinar cells appear unlikely to contribute substantially to NaHCO3 secretion.

Acetazolamide↗
PubMed1986

Distribution of T and B lymphocytes in jejunal and ileocaecal Peyer's patches of lambs.

Jejunal (JPPs) and ileocaecal (IPP) Peyer's patches in lambs were studied by employing the indirect and the avidin-biotin-peroxidase methods, using antibodies to sheep IgM and thymocytes. Thymocyte sera absorbed with IPP germinal centre cells showed specificity for T cells in the thymus, lymph nodes and Peyer's patches. Whereas JPPs had large interfollicular T cell areas, IPP mainly contained B cells, although small triangular T cell areas were found at the apex of the follicles. Some T cells were also found in the dome and corona region of JPPs and IPP. While germinal centres of JPPs had about 40 per cent of IgM-positive cells, IPP germinal centres contained about 80 per cent of such cells. Negative or weak IgM-positive cells were seen in the peripheral zone of IPP germinal centres, contrasting with surface IgM-positive cells in the central zone, and indicating a centripetal migration of maturing lymphocytes.

Animals↗
PubMed1984

Studies on hydragogue drugs: light and electron microscopic examination of the isolated rat colonic mucosa exposed to deoxycholic acid and synthetic surfactants.

Sacs of the stripped and everted, isolated descending rat colon were incubated for 2 hours in presence of the following surfactants at the mucosal side: Dodecylsulphate (DDS), dioctylsulphosuccinate (DOSS), cetrimonium bromide (CTMAB), Triton X100 and deoxycholic acid (DOC). After tissue fixation, the sacs were processed for light microscopy (LM) and for scanning (SEM) and transmission (TEM) electron microscopy. All three methods revealed that DOSS (1.3 X 10(-4) and 2.6 X 10(-4) mol/l, CTMAB (5 X 10(-5) and 1 X 10(-4) ) and Triton (2 X 10(-5), 5 X 10(-5) and 1 X 10(-4) ) caused only minor or moderate changes compared to parallel controls, as did also DDS at 1 X 10(-5) and 2 X 10(-5) mol/l. DDS at 2 X 10(-4) and 4 X 10(-4) mol/l and DOC at 1.5 X 10(-4) and 3 X 10(-4) mol/l caused more prominent changes. LM showed swollen, vacuolated cells with pycnotic nuclei; many of these cells seemed to be extruded. According to SEM, cells thus affected were most abundantly localized to the normal extrusion zone at the borders of the crypt-surface epithelial cell units. DOC tended to cause a more generalized affection within the units than DDS. In spite of these deleterious effects, gaps corresponding to missing epithelial cells were not observed. TEM indicated the mechanism responsible for restoration of epithelial continuity in spite of extensive cell loss: The remaining epithelial cells seemed to flatten out and re-establish cell-to-cell contact by pseudopod formation along the basement lamina. This repair mechanism seemed to operate at a rapid rate; however, incomplete closure of cellular gaps i.e. small denuded parts of the basement lamina were occasionally observed. The results of this study are discussed in relation to a functional study under identical experimental conditions (Gastroenterol. Clin. Biol. 1981, 5, 124), in which these surfactants caused a significant alteration of normal colonic transport function.

Animals↗
PubMed1984

Is the ileo-caecal Peyer's patch in ruminants a mammalian "bursa-equivalent"?

The ileo-caecal Peyer's patch (IPP) in young ruminants shows prenatal maturation and involution in young age, mainly like the thymus (1, 7, 8). In an examination of three-week-old calves IPP had features compatible with an essentially thymus-independent, primary function, different from that of jejunal patches. Features of IPP included very high lymphoblastic activity despite scarcity of coronal cells and few high endothelial venules in the interfollicular tissue.

Animals↗
PubMed1984

Intestinal lymphangiectasia in the Lundehund. Scanning electron microscopy of intestinal mucosa.

Intestinal lymphangiectasia of obscure etiology is frequent among Norwegian Lundehunds ("puffin-dog"). A study of three Lundehunds with typical symptoms, including wasting, diarrhea and ascites, revealed segmental distention of lymphatics resembling primary lymphangiectasia in man. Atrophy, fusion and balloon-like swelling of villi with occasional rupture of lacteals were seen. Subepithelial fluid accumulation caused bulging of the epithelium. Microvilli showed partial or complete atrophy. The protein loss in the Lundehund enteropathy may be due to rupture of lacteals, increased paracellular permeability, caused by enhanced hydrostatic tissue pressure, and decreased absorption through a malformed brush border.

Animals↗
PubMed1981

Encephalitozoonosis in the blue fox--morphological identification of the parasite.

Microsporidian organisms causing great losses among young blue foxes (alopex lagopus) were isolated and propagated in monolayer cell cultures and examined by transmission- and scanning electron microscopy. The parasite was found to fulfil the criteria set up for the genus Encephalitozoon and the ultrastructural findings indicated that the parasite was morphologically identical to Encephalitozoon cuniculi previously isolated from some other mammalian species. Terminal vesicles on the extruded polar filaments seen on scanning electron micrographs were discussed to be similar formation as described for the microsporidian Nosema michaelis.

Animals↗