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Biomedical subjects

K M Madsen

Publications and source records attributed to K M Madsen.

At least 55 records · Page 3Linked to original sources
PubMed1991

Postprandial gastro-oesophageal reflux demonstrated by radiology.

An investigation to detect food-stimulated gastro-oesophageal (GE) reflux was carried out in 54 consecutive fasting patients, 35 of whom experienced reflux while 19 did not. All patients then received a standard meal (566 kcal), and the investigation was repeated 1 h later. Out of the 35 with GE reflux in the fasting state, 33 also had GE reflux in the postprandial state, and 17 of the 19 patients with no GE reflux while fasting also had none in the postprandial state. It is concluded that the radiological method can identify most patients in whom food-stimulated GE reflux could be of clinical significance.

Administration, Oral↗
PubMed1990

H-K-ATPase immunoreactivity in cortical and outer medullary collecting duct.

Biochemical and physiologic studies in individual segments of the cortical collecting duct (CCD) and outer medullary collecting duct (OMCD) have provided evidence for the presence of an H-K-ATPase which is involved in the reabsorption of potassium in exchange for protons. The present study was designed to determine the cellular distribution of H-K-ATPase immunoreactivity in the CCD and OMCD of the rat and rabbit using mouse monoclonal antibodies against hog gastric H-K-ATPase. Kidneys of normal rats and rabbits were preserved for light microscopic immunohistochemistry and embedded in paraffin. Sections were incubated with the primary antibody followed by the avidin-biotin-horseradish peroxidase procedure. Sections incubated without primary antibody or with a non-specific mouse Ig served as controls. Light microscopy revealed diffuse cytoplasmic staining indicating H-K-ATPase immunoreactivity in intercalated cells in the CCD and OMCD in both rat and rabbit. In all segments studied except the rat CCD, the percentage of H-K-ATPase immunoreactive cells corresponded to the percentage of intercalated cells. In the rat CCD only 23% of the cells were reactive with H-K-ATPase antibodies, which is less than the percentage of intercalated cells in this region. It is possible that only type A intercalated cells possess H-K-ATPase immunoreactivity or that some intercalated cells did not have sufficient activity to be detected by our method. These results demonstrate H-K-ATPase immunoreactivity in the intercalated cells of the CCD and OMCD of rat and rabbit, suggesting that these cells are involved in potassium reabsorption in exchange for proton secretion in the mammalian collecting duct.

Adenosine Triphosphatases↗
PubMed1990

Ultrastructural localization of carbonic anhydrase II in subpopulations of intercalated cells of the rat kidney.

At least two configurations of intercalated cells, type A and type B, are present in the cortical collecting duct. Intercalated cells are rich in carbonic anhydrase. However, it is not known whether there are differences in the level and subcellular distribution of this enzyme between type A and type B intercalated cells. The purpose of this study was to determine the relative content and intracellular distribution of carbonic anhydrase II in the various subpopulations of intercalated cells in the rat collecting duct. A rabbit polyclonal antibody directed against mouse erythrocyte carbonic anhydrase II was employed to localize carbonic anhydrase, II by light and electron microscopy by an indirect immunoperoxidase method. A Western immunoblot analysis of homogenates of rat kidney cortex and medulla with the carbonic anhydrase II antibody revealed a single polypeptide band at 29 kDa corresponding to the molecular size of carbonic anhydrase II. By both light and electron microscopy, carbonic anhydrase II immunoreactivity was present in all intercalated cells but the intensity of staining was much greater in type A than in type B cells. In addition, immunostaining in type A cells was especially pronounced in the apical cytoplasm and apical microprojections whereas in type B cells, immunostaining was more diffuse throughout the cytoplasm. A third configuration of intercalated cell with diffuse immunostaining for carbonic anhydrase II was occasionally observed in the connecting segment. Very weak immunostaining was present in principal cells, whereas connecting tubule cells and inner medullary collecting duct cells were negative for carbonic anhydrase II.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

[Tuberculous cysts of the mediastinum].

A 71-year-old woman was admitted to the hospital with polycystic deformations in the left pulmonary hilus in the mediastinum, found in a routine chest X-ray. The patient had earlier been treated for pulmonary tuberculosis. Mediastinotomia was performed and thin-walled cysts with a creamy type of pus were found. Microbiological examinations revealed evidence of tubercle bacilli. Medical treatment for tuberculosis was begun, which led to recovery with regression of the cysts.

Aged↗
PubMed1989

Immunocytochemical localization of intracellular acidic compartments: rat proximal nephron.

There is evidence that components of the endosomal-lysosomal system of most cells have an acidic interior. The weak base, N-(3-[(2,4-dinitrophenyl)amino]propyl)-N-(3-aminopropyl)methylamine dihydrochloride (DAMP) has been shown to accumulate in acidic compartments in cultured cells and in isolated perfused proximal tubules. We infused DAMP intravascularly in vivo and used colloidal gold immunocytochemistry to identify acidic compartments in cells of the rat glomerulus and proximal tubule. Sprague-Dawley rats were infused intra-arterially with DAMP. The kidneys were fixed by intravascular perfusion with 1% glutaraldehyde and embedded in Lowicryl K4M. Sections were exposed to a mouse anti-dinitrophenol (DNP) monoclonal antibody that cross-reacts with DAMP, followed by gold-conjugated goat anti-mouse immunoglobulin G. Transmission electron microscopy revealed positive labeling of the lysosome-like structures of the various cells of the glomerulus and lysosomes, endosomes, and numerous endocytic vesicles of all segments of the proximal tubule. We conclude that 1) DAMP can be used in vivo to identify acidic compartments in the kidney and 2) lysosomes, endosomes, and many endocytic vesicles of the rat proximal tubule as well as lysosome-like structures in cells of the glomerulus have an acidic interior.

Acids↗
PubMed1989

Morphologic heterogeneity along the rat inner medullary collecting duct.

The qualitative and quantitative morphologic features of the cells lining the inner medullary collecting duct (IMCD) in the outer (IMCD1), middle (IMCD2) and inner (IMCD3) segments were investigated. Kidneys of male rats were fixed by in vivo vascular perfusion with glutaraldehyde and processed for light microscopy and scanning and transmission electron microscopy. The IMCD1 consisted of both principal cells and intercalated cells similar to those present in the outer medullary collecting duct. The principal cells were covered with small microvilli and a single cilium. Most of the IMCD2 and the entire IMCD3 contained one cell type (IMCD cell). When compared with the principal cells, the IMCD cells were taller, had fewer basal infoldings and a lighter staining cytoplasm containing numerous free ribosomes and small electron-dense cytoplasmic bodies in the basal region. The luminal surface was covered with prominent microvilli, but had no cilia. Morphometric analysis demonstrated that the surface density of apical and basal plasma membranes decreased from IMCD1 to IMCD3. However, because of an overall increase in tubule volume from IMCD1 to IMCD3, there were no significant differences in the absolute area of apical or basal membranes between the three segments. In contrast, the absolute area of lateral membranes increased significantly from IMCD1 to IMCD3. This study demonstrates that the IMCD1 consists of principal cells and intercalated cells similar to those in the outer medullary collecting duct, whereas the cells in most of the IMCD2 and the entire IMCD3 appear to represent a distinct and separate cell type which we choose to call the IMCD cell. Thus, both morphologic and functional heterogeneity appear to exist along the IMCD.

Animals↗
PubMed1988

Relationship between structure and function in distal tubule and collecting duct.

The relationship between structure and function in the distal tubule and collecting duct has been studied with morphologic and physiologic techniques, including morphometric analysis, to identify functionally distinct cell populations. The distal tubule, including the thick ascending limb (TAL) and the distal convoluted tubule (DCT), is involved in active reabsorption of sodium chloride. It is characterized by extensive invaginations of the basolateral plasma membrane, numerous mitochondria, and high Na-K-ATPase activity, features characteristic for an epithelium involved in active transport. Between the distal tubule and the collecting duct is a transition region, the connecting segment or the connecting tubule (CNT), which exhibits species differences with respect to both structure and function. The collecting duct includes the cortical (CCD), the outer medullary (OMCD), and the inner medullary (IMCD) collecting ducts. Principal cells are present throughout the collecting duct, whereas intercalated cells are located mainly in the CCD and OMCD. Morphometric analysis combined with micropuncture and microperfusion studies has provided evidence that the CNT and principal cells are responsible for potassium secretion in the connecting segment and the CCD. The OMCD is a main site of hydrogen ion secretion, and morphometric studies have provided evidence that the intercalated cells in this segment secrete hydrogen ion at least in the rat. Two configurations of intercalated cells exist in the CCD--a type A and a type B. The A cells are similar in ultrastructure to the intercalated cells in the OMCD and are believed to be involved in hydrogen ion secretion. The function of the B cells remains to be established. The inner two-thirds of the IMCD corresponds to the papillary collecting duct, which has a high permeability to urea. The relationship between structure and function in the IMCD has not been studied in detail. This review emphasizes the role of morphometric analysis in establishing the relationship between structure and function in the distal nephron.

Animals↗
PubMed1988

Immunocytochemical localization of band 3 protein in the rat collecting duct.

Band 3 protein is the major anion transport protein of the erythrocyte cell membrane where it catalyzes the exchange of HCO3- for Cl-. There is evidence that band 3 protein is present in the collecting duct of both the rat and rabbit kidney. We used colloidal-gold immunocytochemistry to determine the ultrastructural location of band 3 protein in the rat cortical (CCD) and outer medullary collecting ducts (OMCD). Kidneys of normal Sprague-Dawley rats were fixed by intravascular perfusion with 1% glutaraldehyde and embedded in Lowicryl K4M. Two polyclonal antibodies raised in rabbits were used as the primary antibody in separate experiments, one against the 43-kDa fragment of the cytoplasmic domain of human erythrocyte band 3 protein and the other against rat erythrocyte band 3 protein. This was followed by exposure to gold-conjugated goat anti-rabbit immunoglobulin G. Transmission electron microscopy revealed gold particles along the basal and lateral plasma membranes of all intercalated cells of the OMCD. In the CCD, the basal and lateral plasma membranes of the type A intercalated cells only were labeled with gold particles. The type B intercalated cells and principal cells were devoid of gold particles, as were all cells of the proximal tubule, the distal convoluted tubule, and the thick ascending limb of the loop of Henle. We conclude that a Cl(-)-HCO3- transporter is present in the basal and lateral plasma membranes of the intercalated cells in the OMCD and the type A intercalated cells in the CCD. These findings provide further evidence that these intercalated cells are involved in H+ secretion in the OMCD and CCD of the rat. We have no evidence for the presence of band 3 protein in the type B intercalated cells of the CCD, which supports the hypothesis that type B cells are functionally and structurally distinct from type A cells.

Animals↗
PubMed1988

Axial heterogeneity in the handling of albumin by the rabbit proximal tubule.

Morphologic and physiologic studies have established that filtered proteins are absorbed in the proximal tubule by endocytosis and transported to the lysosomes for degradation. The tubular absorption, hydrolysis and accumulation of albumin were examined in all three segments of the rabbit proximal tubule. S1, S2 and S3 segments were dissected and perfused in vitro with tritiated albumin at a physiologic concentration of 0.0364 mg/ml, and with [14C]inulin to determine fluid reabsorption. In addition, the three segments were fixed for ultrastructural examination after perfusion under conditions similar to those in the physiologic studies. The fluid reabsorption was similar in S1 and S2 but lower in S3. Albumin absorption was unexpectedly similar in the three segments. A lower percentage of absorbed albumin was hydrolyzed in the S3 segment compared with the earlier segments. The values were 70 +/- 15%, 61 +/- 11%, and 30 +/- 4% for S1, S2, and S3, respectively. The cellular accumulation of protein was highest in the S3 segment. The ultrastructure of the three segments was similar to that described in in vivo preserved kidneys, and no abnormalities were observed in the endocytic-lysosomal compartment. These results reveal axial heterogeneity in the hydrolysis of absorbed albumin by the rabbit proximal tubule and suggest that under normal physiologic conditions the S3 segment has a lower lysosomal proteolytic activity. Although the S3 segment maintains a high capacity for protein absorption, the earlier proximal segments likely have a greater role in protein degradation.

Absorption↗
PubMed1987

Intercalated cells of the rat inner medullary collecting duct.

There is increasing evidence of acidification along the entire mammalian collecting duct including the inner medullary collecting duct (IMCD). Recent studies have provided morphologic evidence that the intercalated cells are involved in hydrogen ion secretion in the cortical and outer medullary collecting duct of the rat. In the present study we performed a quantitative and qualitative morphologic examination of the intercalated cells in the IMCD of the rat and compared the results to observations obtained from intercalated cells in the collecting duct in the inner stripe of the outer medulla (OMCDi). Kidneys of male rats were preserved by in vivo perfusion with glutaraldehyde and processed for morphologic evaluation. With light microscopy and scanning electron microscopy intercalated cells were found in the outer third of the IMCD (IMCD1) and accounted for 10% of the total cell population. They were absent in the terminal two-thirds of the IMCD. Examination of the intercalated cells using transmission electron microscopy revealed striking similarities between the cells of the IMCD1 and those in the OMCDi. In addition, no differences were found in the surface densities of the apical or basolateral plasma membranes or the volume densities of the mitochondria of the intercalated cells in the two regions. In light of the morphologic similarity with the intercalated cells of the OMCDi that are believed to be involved in hydrogen ion secretion, it is likely that the intercalated cells of the IMCD1 are also involved in the acidification of tubular fluid.

Animals↗
PubMed1987

Effect of acute respiratory acidosis on two populations of intercalated cells in rat cortical collecting duct.

Recent studies suggest the presence of two populations of intercalated cells in the rabbit cortical collecting duct (CCD), one involved with hydrogen ion secretion and another that may play a role in bicarbonate secretion. The purpose of this study was to determine whether two populations of intercalated cells are present in the rat CCD and to establish their response to acute respiratory acidosis. Rats were studied during normal acid-base conditions and after 4-5 h of respiratory acidosis. In all animals light microscopy and transmission and scanning electron microscopy revealed two configurations of intercalated cells, type A with an extensive apical tubulovesicular membrane compartment and prominent surface microprojections and type B with a well-developed vesicular compartment and short sparse surface microprojections. By transmission electron microscopy, studs were present on the cytoplasmic face of the apical plasmalemma and tubulovesicular profiles of A cells. In respiratory acidosis there was a striking increase in apical microprojections and in the surface density of the apical membrane of type A cells similar to the response observed previously in intercalated cells in the outer medullary collecting duct (OMCD) studied under the same physiological conditions. No changes were observed in type B cells. Scanning electron microscopy revealed no change in the relative number of type A and type B cells in respiratory acidosis. We conclude that two distinct populations of intercalated cells exist in the rat CCD: type A, which resembles the intercalated cells in the OMCD, and type B. The response of type A cells to acute respiratory acidosis and the similarity between these cells and intercalated cells in the OMCD, which are believed to secrete hydrogen ion, suggest that the type A cells are involved in hydrogen ion secretion in the CCD.

Acidosis, Respiratory↗
PubMed1987

Lysosome distribution and cathepsin B and L activity along the rabbit proximal tubule.

The lysosomal-vacuolar system in the proximal tubule is responsible for reabsorption and degradation of proteins from the glomerular filtrate. In this study we mapped the activity of the lysosomal proteinases, cathepsins B and L, along the rabbit proximal tubule and compared cathepsin activities with the volume of lysosomes and endocytic vacuoles in the three segments of the proximal tubule. Individual tubules were dissected and assayed fluorometrically using two synthetic substrates, one specific for cathepsin B and a second for cathepsins B and L. The distribution of cathepsin activity along the proximal tubule was the same with each substrate, but there was a two- to threefold difference in the level of activity when expressed per millimeter of tubule. Enzyme activities were high in the initial 4-5 mm corresponding to the S1 segment and decreased in the pars recta to approximately 20% of the S1 value. Morphometric analysis revealed that the volumes of lysosomes and endocytic vacuoles per millimeter of tubule were significantly greater in the S1 segment than in the S2 and S3 segments. These findings suggest that the main site of protein degradation in the rabbit kidney under normal conditions is the initial 4-5 mm of the proximal tubule which corresponds to the S1 segment and is known to be a major site of protein reabsorption.

Animals↗
PubMed1986

Structural-functional relationships along the distal nephron.

The distal tubule, which includes the thick ascending limb (TAL), the macula densa, and the distal convoluted tubule (DCT), and the collecting duct are structurally heterogeneous, thus reflecting the functional heterogeneity that is also present. As the TAL ascends from medulla to cortex, the surface area of the apical plasma membrane increases while that of the basolateral membrane decreases. The structure of the DCT resembles that of the medullary TAL. An excellent correlation exists between structure, Na-K-ATPase activity, and NaCl reabsorptive capacity in the distal tubule. The collecting duct is subdivided into the initial collecting tubule (ICT), and cortical (CCD), outer medullary (OMCD), and inner medullary (IMCD) collecting ducts. Between the distal tubule and the collecting duct is a transition region termed the connecting segment or connecting tubule (CNT). Considerable structural heterogeneity exists along the collecting duct within the two major cell populations, the intercalated cells and the principal cells. In the CNT, the ICT, and the CCD, potassium loading and mineralocorticoids stimulate Na-K-ATPase activity and cause proliferation of the basolateral membrane of CNT cells and principal cells, thus identifying the cells responsible for mineralocorticoid-stimulated potassium secretion in these regions. Finally, at least two morphologically distinct populations of intercalated cells exist, types A and B. In the rat, type A predominates in the CNT and the OMCD and is believed to be responsible for H+ secretion, at least in the OMCD. Type B predominates in the CCD, where it may be involved in bicarbonate secretion.

Animals↗
PubMed1985

Inhibition of protein reabsorption in the renal proximal tubule by basic amino acids.

The effects of basic and neutral amino acids on the reabsorption of 125I-lysozyme by the renal proximal tubule were examined in rats. In whole animal experiments control animals were given an intravenous (i.v.) injection of 125I-lysozyme alone while experimental animals received an i.v. injection of either a basic or a neutral amino acid prior to the injection of 125I-lysozyme. In control animals the renal content of 125I-lysozyme 30 min after injection was 35% of the injected dose. After injection of basic amino acids there was a significant decrease in the renal uptake of lysozyme. There was no effect of neutral amino acids on the reabsorption of lysozyme. In microperfusion experiments proximal convoluted tubules were perfused in vivo for 3 min with a solution containing 125I-lysozyme and either lysine or alanine. In tubules perfused with lysine there was a significant decrease in the reabsorption of lysozyme, whereas alanine had no effect on lysozyme uptake. Electron microscope autoradiography revealed that lysozyme was located in endocytic vesicles and lysosomes in both experimental groups. However, the autoradiographic grain density was significantly decreased in tubules perfused with lysine as compared with those perfused with alanine. These findings demonstrate that basic amino acids inhibit the reabsorption of the cationic protein lysozyme by the proximal tubule cells.

Absorption↗
PubMed1985

Structure-function relationships in H+-secreting epithelia.

Stimulation or inhibition of H+ secretion has been associated with characteristic ultrastructural changes in various epithelial cells, including the parietal cell of the gastric mucosa, the carbonic anhydrase (CA)-rich cell of the turtle urinary bladder, and the intercalated (I) cell of the mammalian collecting duct. An electroneutral potassium-activated H+-ATPase is responsible for H+ secretion in the stomach, whereas acidification in the turtle bladder and the mammalian collecting duct is mediated by an electrogenic H+-translocating ATPase. Despite these differences, the parietal cell, the CA-rich cell, and the I cell have several morphological features in common. They are rich in mitochondria, contain numerous tubulovesicular membrane structures in the apical region of the cell, and possess a variable number of microprojections on the luminal surface. After stimulation of H+ secretion there is a significant increase in the surface area of the apical membrane concomitant with a decrease in the tubulovesicular membrane compartment in these cells, as revealed by morphometric analysis. These findings suggest that membrane (possibly containing an H+ pump) is being transferred from the tubulovesicular compartment to the apical plasma membrane on stimulation of H+ secretion. A hypothesis of membrane recycling is proposed to account for the observed morphological changes.

Amphibians↗