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H Jessen

Publications and source records attributed to H Jessen.

At least 37 records · Page 2Linked to original sources
PubMed1991

Na(+)- and H(+)-gradient-dependent transport of alpha-aminoisobutyrate by luminal membrane vesicles from rabbit proximal tubule.

1. The characteristics of renal transport of alpha-aminoisobutyrate (AIB) by luminal membrane vesicles isolated from either the proximal convoluted part (pars convoluta) or the proximal straight part (pars recta) of rabbit proximal tubule were investigated. 2. Transport of AIB in vesicles from pars convoluta was mediated by both Na(+)-dependent and Na(+)-independent systems, which in the presence of an inwardly directed H+ gradient can drive the uphill transport of AIB into these vesicles. 3. By contrast, in luminal membrane vesicles from pars recta, transient accumulation of AIB was only dependent on Na+. Lowering pH without a H+ gradient (pHi = pH0 = 5.5) completely abolished the Na(+)-dependent transient accumulation of AIB in these vesicle preparations. 4. Attempts to determine the stoichiometry of both the Na(+)-AIB and H(+)-AIB transporters located in these two segments of proximal tubule suggested that one Na+ and one H+ ion may be involved in the transport of AIB. 5. Sodium-dependent uptake of AIB in vesicles from pars convoluta was competitively inhibited by L-serine and L-phenylalanine, whereas the presence of L-proline, L-alanine and glycine had no significant effect. By contrast, the H(+)-gradient-dependent uptake of AIB was drastically reduced (30% of the control value) by L-proline, L-alanine and glycine, while L-serine and L-phenylalanine had no significant effect. 6. On the other hand, pars recta vesicles exhibited a different transport specificity. L-Phenylalanine, L-serine, L-alanine and glycine, but not L-proline competitively inhibited the uptake of AIB, providing evidence for the existence of a common transport system for AIB, L-phenylalanine, L-serine, L-alanine and glycine in this segment of rabbit proximal tubule.

Amiloride↗
PubMed1991

Interstitial cells of Cajal and Auerbach's plexus. A scanning electron microscopical study of guinea-pig small intestine.

Interstitial cells of Cajal (ICC) appear to be involved in the regulation of intestinal motility, probably as pacemaker cells. We investigated the complex organization of ICC associated with Auerbach's plexus of guinea-pig small intestine in the scanning electron microscope. The plexus was exposed by microdissection of zinc iodide/osmic acid stained tissue. After separation of the muscle layers by microdissection alone, the exposed Auerbach's plexus was seen to be covered by a smooth mat of reticular fibrils, thin enough to allow the detailed examination of the intact nerve plexus and interstitial tissue. ICC were distinguished as small, ovoid cell bodies from which 2-5 long, branching, roughly cylindrical processes emerge, associating to form a complex network. Characteristically, ICC processes participated in the formation of small bundles along their course, individual processes passing from one bundle to another. Cell bodies and processes of ICC were intimately associated with tertiary nerves of Auerbach's plexus. Axons were identified and distinguished these from ICC processes by their varicose structure and by th smaller diameters as compared with ICC processes. We found no single axons in our material. The characteristic morphology of ICC clearly distinguished these as a separate cell population different from neurons, glial cells, fibroblasts, and smooth muscle cells. After removal of the mat of reticular fibrils by chemical digestion the detailed organization of the interstitial tissue was preserved. Macrophage-like cells were previously demonstrated by other techniques to constitute a constant and rather dense population of cells in the studied location. As an indication that we preserve the full complement of interstitial cells by our technique, these macrophage-like cells wer for the first time identified in material processed for scanning electron microscopy. The cells had characteristically irregular cell surfaces with short, veil-like, folded extensions intertwined between the other cells in the interstices. Our study establishes an improved correlation between results obtained by the application of scanning electron microscopy to dissected tissue and results from light and transmission electron microscopy of the intact tissue.

Animals↗
PubMed1990

Proton gradient-dependent renal transport of glycine: evidence for vesicle studies.

The characteristics of renal transport of glycine by luminal membrane vesicles isolated from either proximal convoluted part (pars convoluta) or proximal straight part (pars recta) of rabbit proximal tubule were investigated. In vesicles from pars convoluta two transport systems have been characterized: a Na(+)-dependent system with intermediate affinity (half-saturation 3.64 mM) and a Na(+)-independent system that, in the presence of H+ gradient (extravesicular greater than intravesicular), can accelerate the transport of glycine into these vesicles. This is the first demonstration of H(+)-glycine cotransport across the luminal membrane of rabbit kidney proximal convoluted tubule. By contrast, in membrane vesicles from pars recta, transport of glycine was strictly dependent on Na+ and occurred via a dual transport system, namely a high-affinity (half-saturation 0.34 mM) and a low-affinity system (half-saturation 8.56 mM). The demonstration of competition between the H(+)-gradient dependent uptake of glycine, L-alanine, and L-proline, but insignificant inhibition with L-phenylalanine in vesicles from pars convoluta suggests that glycine, L-proline, and L-alanine probably share a common proton gradient-dependent transport system. In vesicles from pars recta, the Na(+)-dependent uptake of glycine was inhibited by low concentrations of L-alanine and L-phenylalanine, whereas addition of L-proline to the incubation medium did not significantly alter the uptake of glycine, suggesting that the Na(+)-dependent high-affinity system for glycine located in pars recta is shared with the high-affinity L-alanine and L-phenylalanine but not L-proline transport system.

Amino Acids↗
PubMed1989

Electrogenic uptake of D-imino acids by luminal membrane vesicles from rabbit kidney proximal tubule.

Some characteristics of electrogenic uptake of D-proline and hydroxy-D-proline by luminal membrane vesicles isolated either from pars convoluta or from pars recta of rabbit proximal tubule were indirectly studied by the spectrophotometric method. In vesicles from pars convoluta, the uptake of D-imino acids was mediated by both Na+-dependent and Na+-independent, but electrogenic processes. Indirect evidence for coupling between D-imino acids and H+ fluxes was obtained by the following observations: (1) Addition of the H+ ionophore (FCCP) to the vesicle-dye (3,3'-diethyloxadicarbocyanine iodide) suspension completely abolished the Na+-independent electrogenic uptake of D-proline and hydroxy-D-proline by membrane vesicles from pars convoluta. (2) Addition of a relatively low concentration of D-proline in the incubation system decreased the H+-gradient dependent renal uptake of radioactive L-proline to approx. 60% of the control value. By contrast, the uptake of D-proline in vesicles from pars recta was strictly Na+-dependent, since no transient depolarization of membrane vesicles was ever observed in the absence of Na+. A comparison between the transport characteristics of D-imino acids and their naturally occurring L-isomers indicated that these compounds probably share common transport systems located along the proximal tubule of rabbit kidney.

Animals↗
PubMed1989

Demonstration of H+- and Na+-coupled co-transport of beta-alanine by luminal membrane vesicles of rabbit proximal tubule.

1. The characteristics of renal transport of beta-alanine by luminal membrane vesicles isolated from either the proximal convoluted part (pars convoluta) or the proximal straight part (pars recta) of rabbit proximal tubule were investigated. 2. In vesicles from pars convoluta two transport systems have been characterized: (1) a Na+-dependent system with intermediate affinity (half-saturation 2.7 mM), and (2) a Na+-independent system, which in the presence of a H+ gradient (extravesicular greater than intravesicular) can drive the uphill transport of beta-alanine into these vesicles. This is the first demonstration of H+-beta-alanine co-transport across luminal membrane of rabbit kidney proximal convoluted tubule. 3. By contrast, in membrane vesicles from pars recta, transport of beta-alanine was strictly dependent on Na+ and occurred via a dual transport system, namely a high-affinity (half-saturation 0.16 mM) and a low-affinity system (half-saturation 9.3 mM). 4. The demonstration of competition between the Na+-gradient-dependent uptake of beta-alanine and taurine, without appreciable inhibition by alpha-amino acids in vesicles from pars convoluta as well as from pars recta, strongly suggests that the luminal membrane of proximal tubule has transport systems for the reabsorption of beta-amino acids which are distinct from alpha-amino acid transport systems.

Alanine↗
PubMed1988

Energetics of renal Na+ and H+/L-alanine co-transport systems.

The stoichiometric properties of Na+- and H+-dependent L-alanine transporters recently identified in luminal-membrane vesicles prepared from proximal convoluted tubules (pars convoluta) and proximal straight tubules (pars recta) of rabbit kidney were studied. We provide indirect evidence suggesting that one Na+ and one H+ ion are co-transported with the L-alanine molecule via Na+-dependent and H+-dependent transport systems located in vesicles from pars convoluta. Furthermore, our experimental data suggest that both the high-affinity and the low-affinity Na+-dependent L-alanine transport systems of pars recta vesicles operate with a 1:1 stoichiometry.

Alanine↗
PubMed1988

Characteristics of D-alanine transport by luminal membrane vesicles from pars convoluta and pars recta of rabbit proximal tubule.

Uptake of D-alanine against a concentration gradient has been shown to occur with isolated luminal-membrane vesicles from pars convoluta or pars recta of rabbit proximal tubule. Renal D-alanine transport systems, displaying the following characteristics, were shown: (1) In vesicles from pars convoluta, the uptake of D-alanine was mediated by both Na+-dependent and Na+-independent transport processes. It was found that an inwardly directed H+-gradient could drive the transport of D-alanine into the vesicles both in the presence and absence of Na+. Thus, in addition to Na+, the transport of D-alanine is influenced by the H+-gradient. (2) In vesicles from pars recta, the transient accumulation of D-alanine was strictly dependent on Na+, since no 'overshoot' was ever observed in the absence of Na+. Although the Na+-dependent uptake of D-alanine was stimulated at acid pH, H+ did not substitute for Na+, as it apparently does in pars convoluta, but instead potentiated the Na+ effect. (3) Addition of L-alanine to vesicle preparations, both from pars convoluta and from pars recta, specifically inhibited renal uptake of D-alanine. A comparison between the transport characteristics of D- and L-alanine indicated that these two isomers of alanine probably share common transport systems located along the proximal tubule of rabbit kidney.

Alanine↗
PubMed1988

Mechanism of transport of L-alanine by luminal-membrane vesicles from pars recta of rabbit proximal tubule.

The characteristics of renal transport of L-alanine by luminal-membrane vesicles from proximal straight tubules (pars recta) of rabbit kidney were investigated. The following picture emerges from transport studies. Two electrogenic and Na+ requiring systems confined to this region of the nephron exist for the transport of L-alanine. In addition to Na+, the transport of L-alanine was influenced by H+. However, H+ does not substitute for Na+, but instead potentiates the Na+ effect. Modification of histidyl residues of the intact luminal-membrane vesicles by diethylpyrocarbonate (DEP), completely abolished the transient renal accumulation of L-alanine. Substrate and Na+-protection experiments suggest that histidyl residues may be at or close to the active site of the L-alanine transporter in membrane vesicles from pars recta.

Alanine↗
PubMed1986

Selective binding of colloidal gold-protein conjugates to epidermal phosphorus-rich keratohyaline granules and cornified cells.

Colloidal gold solutions conjugated with staphylococcal protein A (SpA) are widely used in high-resolution immunocytochemical studies to visualize antibodies bound at antigenic sites. Here we report that colloidal gold solutions conjugated with SpA, bovine serum albumin (BSA), or gelatin bind selectively to structures in glutaraldehyde-fixed, plastic-embedded epidermis of rabbit, mouse, and human. Two types of keratohyaline granules are present in epidermis, a phosphorus-rich (PR) and a sulphur-rich (SR) type. The PR keratohyaline granules were strongly labeled with gold particles, whereas SR keratohyaline granules or other structures in the living cells of epidermis were unlabeled. The PR keratohyaline granules are assumed to be precursors of the matrix protein of cornified cells, and intense gold labeling occurred over the lower layer of cornified cells (i.e., stratum lucidum). More superficial cornified cells were weakly labeled or unlabeled. The gold labeling pattern was identical whether SpA, BSA, or gelatin was used to stabilize the colloidal gold solution. The mechanism of binding of protein-conjugated gold to PR keratohyaline granules and matrix protein of cornified cells is not clear. It is speculated that the charged gold particles are not completely coated by the stabilizing protein, allowing for an electrostatic interaction with charged proteins in sections of cells.

Animals↗
PubMed1986

Morphological features of established cultures of human squamous lung carcinoma cells and the cellular distribution of tumor-specific glycoproteins.

Phenotypic characteristics of a cloned cell line, RH-SLC-L11, established from a human squamous lung carcinoma, were studied. The line has maintained its morphologically characteristic growth pattern for over 3 years. Settling cells exhibited extensive surface blebbing during spreading and established small cell islands that eventually expanded by mitosis to confluent cultures. Cell islands and confluent cultures presented three cell types: (i) small, polygonal cells, (ii) polygonal cells of intermediary size and (iii) very large, extremely flattened, degenerating cells. Mitotic activity was present predominantly in type (i) and the sequence (i)--(iii) is presumed to represent the lines' cycle. Previous work has demonstrated that the SLC-L11 line releases tumor-associated glycoproteins and glycolipids. These could be identified with a murine Mab (43-9F). The specific epitope was determined by carbohydrate residues and was shown to have growth factor-like properties. Mab 43-9F bound heterogeneously to the surface of SLC-L11 cells: Most large cells were unreactive while both type (i) and (ii) cells showed conspicuous differences in immunostaining intensity. Immunocytochemical analysis also indicated redistribution, shedding and internalization of antigen-Mab complexes, which may have significant impact on the use of the epitope as tumor marker in diagnosis and therapy. No definite clue was obtained as to the release of the antigenic carbohydrate epitope itself.

Antibodies, Monoclonal↗
PubMed1986

Non-specific binding of protein-stabilized gold sols as a source of error in immunocytochemistry.

The observation that protein-A conjugated gold sols bound to fibronectin-collagen (FNC) fibres in human fibroblast cultures prompted a series of studies on the binding of gold particles stabilized in various ways (Staphylococcal protein A, bovine serum albumin, avidin, streptavidin, gelatin, hemoglobin, polyethylene glycol (MW 20 000), methylcellulose and the nonionic detergent Tween 20) to cell and tissue components, to protein dot blots and SDS-PAGE blots on nitrocellulose paper. We found that binding of gold particles to certain cell and tissue components and to various immobilized proteins did occur irrespective of the stabilizing agent. We argue that, albeit gold sols are stabilized against salt coagulation by adsorption of proteins and other stabilizing agents, "naked areas" are (constantly or intermittently) present on particle surfaces, available for interaction with cell and tissue components that have a high electrostatic affinity for the charged gold surface under prevailing experimental conditions. Non-specific binding may be reduced or abolished by competing proteins (i.e. proteins with a higher affinity for gold than any component in the object studied) provided the proteins and the gold conjugate are present concomitantly during incubation. We found gelatin (Bloom number 60-100) to be an effective competitive protein probably due to its high affinity for gold over a wide pH range. Further, gelatin did not appreciably inhibit the specific interaction in dot blots between SpA and IgG except at very low IgG concentrations. A protocol for the use of gold-protein conjugates to circumvent the hazards of unspecific gold binding is suggested.

Cell Line↗
PubMed1976

Sulphure in epidermal keratohyalin granules: a quantitative assay by x-ray microanalysis.

The elemental composition of different types of keratohyalin granules from the epidermis of newborn and adult rats was studied by means of an EMMA-4 analytical electron microscope, equipped with an energy-dispersive X-ray spectrometer. An absolute quantitation of the sulphur concentration in keratohyalin granules was performed. The results demonstrate that epidermal keratohyalin granules are chemically heterogeneous. A type of keratohyalin granule present in the nuclei and cytoplasm of epidermal cells from both newborn and adult rats - termed single granules - is rich in sulphur, having a content of 2-5-3-6%. Other types of keratohyalin granules, which differ in newborn and adult rats, contain a sulphur-poor component; they often have a sulphur-rich component as well. The sulphur-poor keratohyalin contains 0-6-0-9% sulphur. It is suggested that the sulphur-rich keratohyalin granules are the source of the peripheral envelope protein of cornified cells.

Animals↗