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Biomedical subjects

U Walter

Publications and source records attributed to U Walter.

At least 181 records · Page 10Linked to original sources
PubMed1986

[Histological, ultrastructural and topochemical studies on the brood care of Symphysodon aequifasciatus Pellegrin 1903].

In the period of brood care, the epidermis of the genus Symphysodon has a trophical function. Compartment-like filament-containing surface layer cells and secretocytes of different degree of maturity are the first nourishment for the young larvae. Because of the modifications on the outer surface, the larvae are able to take in epidermal nourishment. Epibiotical bacteria on the epidermis of the adults and other epibiotical organisms are found in the intestine of the larvae.

Animals↗
PubMed1985

Purification and characterization of hormone-regulated isoforms of the regulatory subunit of type II cAMP-dependent protein kinase from rat ovaries.

The regulatory subunit (R-II) of cAMP-dependent protein kinase type II is induced in rat ovarian granulosa cells by the synergistic actions of estradiol and follicle-stimulating hormone. The R-II from rat ovaries was compared with R-II from rat heart, rat brain, bovine heart, and bovine brain using immunological methods, 8-N3[32P]cAMP photoaffinity labeling and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Three isoforms of R-II were identified in rat ovarian cell extract (R-II54 Mr = 54,000, R-II52 Mr = 52,000, R-II51 Mr = 51,000), two isoforms of R-II in rat brain cell extract (Mr = 54,000, Mr = 52,000), and one isoform of R-II in rat heart cell extract (Mr = 54,000). Rat ovarian R-II54, heart R-II, and brain R-II (Mr = 54,000) were recognized by antiserum against rat heart R-II, whereas rat ovarian R-II52/R-II51 and rat brain R-II (Mr = 52,000) were not. In contrast, an antiserum raised against bovine heart R-II recognized all three isoforms of ovarian R-II as well as the lower molecular weight form of rat brain R-II. Ovarian types R-II52 and R-II51 but not R-II54 were increased selectively in granulosa cells by estradiol and follicle-stimulating hormone. In addition: 1) ovarian R-II52/51 subunits were purified to homogeneity and shown to recombine with C subunit from bovine heart to form a cAMP-dependent protein kinase; 2) pure R-II52/51 were not interconvertible to a higher molecular weight form by C subunit-dependent phosphorylation; 3) pure rat heart R-II (Mr = 54,000) and ovarian R-II52/51 exhibited distinct differences based on one- and two-dimensional peptide mapping; and 4) by two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis pure R-II52/51 were resolved as three (rather than two) isoelectric variants which were clearly different from pure rat heart R-II54. Thus, the hormone-regulated form of R-II in rat ovarian granulosa cells appears to represent a gene product distinct from R-II54 in rat heart.

Affinity Labels↗
PubMed1985

Selective increase of R-I subunit of cyclic AMP-dependent protein kinase in glia-rich primary cultures upon treatment with dibutyryl cyclic AMP.

Levels of cyclic GMP-dependent protein kinase and of the subunits (R-I, R-II and C) of cyclic AMP-dependent protein kinase were determined in two types of neural primary cell cultures that were either treated or not treated with dibutyryl cyclic AMP. Astroglia-rich cell cultures from newborn rat brain responded to exposure to dibutyryl cyclic AMP by a 2-3-fold increase in the level of R-I subunit, as demonstrated by two radioimmunological procedures, while the levels of the other subunits (R-II and C) and of cyclic GMP-dependent protein kinase remained unaffected. In contrast, neuron-rich cell cultures from embryonic rat brain did not display such a change in the level of R-I subunit. Thus, the elevation in the level of R-I elicited by dibutyryl cyclic AMP in normal non-malignant neural cells in culture was restricted to glial rather than neuronal cells.

Animals↗
PubMed1985

Pharmacokinetics of the loop diuretic piretanide in renal failure.

Piretanide 60 mg was administered intravenously over 30 min to 15 men with different degrees of renal failure. The mean piretanide serum concentration at the end of the infusion period was 5.72 +/- 1.51 micrograms/ml. Serum piretanide concentration-time curves declined biexponentially and 24 hours after medication the serum level had fallen to less than twice the detection limit. The terminal half-life ranged from 1.63 to 3.44 h. A relationship to creatinine clearance was not demonstrable. The mean metabolic clearance of piretanide was 107.7 +/- 47.6 ml/min/1.73 m2 body surface area and was the same as that reported for healthy subjects. The renal clearance of piretanide ranged from 3.33 to 43.9 ml/min/1.73 m2 body surface area and very closely correlated with the creatinine clearance (p less than 0.01). Its renal clearance depended principally on active secretion of the drug into the tubule, and glomerular filtration appeared unimportant. There was a close relationship between the amount of piretanide excreted in the urine and the creatinine clearance. Because the diuretic effect of piretanide depends on the concentration of the drug in the tubule, the observed correlation might be of use in evaluating the appropriate dosage of piretanide in patients with renal failure. The present data suggest that single daily doses of piretanide will not result in accumulation, even when high doses are administered to patients with advanced renal failure.

Adult↗
PubMed1985

Evidence for a Na-K-ATPase-inhibitor in erythrocytes of patients with essential hypertension.

ATPase activities were determined in haemolysed and dialysed erythrocytes and in haemoglobin-free membranes of twenty patients with essential hypertension and twenty normotensive controls. Ouabain-sensitive ATPase (Na-K-ATPase) activity of haemolysate but not that of membranes was decreased in hypertensives whereas ouabain-insensitive ATPase (Mg-ATPase + some residual Ca-ATPase) activity was increased in both enzyme preparations when measurements were preformed in the absence of Ca2+-chelating substances. In haemolysed erythrocytes ouabain-sensitivity as a percentage of total ATPase activity was a good discriminator between both groups and may be a possible marker for essential hypertension. The decreased activity of Na-K-ATPase in haemolysate is apparently due to a non dialysable inhibitor of Na-K-ATPase which is either tightly bound to the erythrocyte membrane or dissolved in the cytoplasm. Following haemolysis with subsequent centrifugation the Na-K-ATPase inhibitor is removed, at least in part, and thus differences in Na-K-ATPase activity demonstrable in haemolysed and dialysed erythrocytes are no longer apparent in haemoglobin-free membranes.

Adolescent↗
PubMed1985

Determination of cyclic AMP-dependent protein kinase subunits by an immunoassay reveals a different subcellular distribution of the enzyme in rat parotid than does determination of the enzyme activity.

The distribution of cyclic cAMP-dependent protein kinase in subcellular fractions of rat parotid was determined by two independent biochemical methods, measurement of kinase catalytic activity or by quantitation of the catalytic and regulatory subunits in an enzyme-linked immunosorbent assay using monospecific antibodies. The major amount (85%) of the catalytic activity was found associated with the 100,000 g soluble fraction, whereas only 1/3 of the total catalytic subunit was demonstrated in the soluble fraction by the immunoassay. The immunoassay results furthermore indicated that approximately 50% of the total cellular protein kinase was associated with the extranuclear particulate fraction and that the predominant form of the kinase in the particulate fractions was the type II isoenzyme. The reasons for the differences in the distribution of the protein kinase demonstrated by the two methods were examined. Incomplete extraction of membrane-bound protein kinase and the influence of membrane localized ATPases on activity measurements were, at least in part, responsible for the low percentage of kinase activity measured in the particulate fractions. These results emphasize that the precise quantitation of protein kinase subunits merits investigation by more than one method. For the parotid, the finding that approximately 2/3 of the total catalytic subunit may be particulate associated provides additional evidence that cyclic AMP could be involved in membrane mechanisms of hormone-regulated secretion.

Adenosine Triphosphatases↗
PubMed1984

Bradykinin regulates the level of guanosine 3',5'-cyclic monophosphate (cyclic GMP) in neural cell lines.

The nonapeptide, bradykinin, elevated the level of cyclic GMP in two neural cell lines, neuroblastoma X glioma hybrid cells (clone 108CC15) and glioma cells (clone C6-4-2). In the hybrid cells the half-maximal stimulation occurred at 0.1 nM and the maximum was reached at 10 nM bradykinin. As soon as 30 s after the addition of bradykinin to the cultured cells, the intracellular concentration of cyclic GMP had increased maximally. The subsequent decline to the original level proceeded more slowly and lasted around 10 min. Hybrid cells incubated for 10 min in the presence of bradykinin and washed thereafter, did not respond at all to a subsequent 1 min challenge incubation with bradykinin. This nearly complete desensitization lasted for a period of 20 min. One hour after removal of bradykinin the original response to the peptide was restored. Modified and partial sequences of bradykinin were also investigated for their ability to induce the cyclic GMP response in the hybrid cells. Removal of amino acids from either terminus of bradykinin led to an almost complete loss of activity. The data are discussed with respect to our previous observation that bradykinin causes a slow hyperpolarization response in these cell lines and that on prolonged exposure to the peptide the membrane potential response of the cells is lost due to desensitization.

Animals↗
PubMed1984

Anatomy of cerebellar Purkinje cells in the rat determined by a specific immunohistochemical marker.

In the present study we have used guanosine 3':5'-phosphate-dependent protein kinase antiserum, a specific immunohistochemical marker for cerebellar Purkinje cells, [ Lohmann , Walter, Miller, Greengard and De Camilli (1981) Proc. natn . Acad. Sci. U.S.A. 78, 653-657], to carry out a detailed analysis of the architecture and projections of Purkinje cells in the adult rat. We have obtained a novel view of aspects of Purkinje cell morphology that were already known and, in addition, we have provided some new information, in particular on the targets of Purkinje cell axons and their pattern of innervation, and on the morphology and course of Purkinje cell axons. Furthermore, we have found a few cells positive for guanosine 3':5' phosphate-dependent protein kinase which are very similar morphologically to Purkinje cells but are located outside of the cerebellar cortex. A unique feature of Purkinje cells is their peculiar monoplanar shape. Not only do their dendritic arbors lie in planes perpendicular to the major axis of the folia, but their axons, including the collaterals, also travel roughly in the same planes. Thus, Purkinje cells can be imagined as lying in longitudinal sheets radiating from the deep cerebellar nuclei. In these sheets, Purkinje cell axons originating from cells located at different rostrocaudal levels of the cortex converge towards the deep cerebellar nuclei without intersecting each other. It is as a result of this precise organization that Purkinje cell axons reach the deep cerebellar nuclei with a mediolateral and rostrocaudal topology that closely reflects the position of their parent cells in the cerebellar cortex. In the subcortical rays of white matter, Purkinje cell axons are interspersed with other axons, being excluded only from longitudinal strips which correspond to the cerebellar raphes . Upon converging towards the deep cerebellar nuclei they segregate into tracts of white matter that alternate with tracts of white matter from which they are excluded. The great majority of Purkinje cell axons terminate in the deep cerebellar nuclei. Recurrent collaterals terminate in close proximity to the Purkinje cell layer. Dense innervation by these axons is found around large interneurons ( Lugaro and Golgi cells) and around the Purkinje cell pinceaux . No direct input of recurrent collaterals to Purkinje cell somata is evident in immunostained material. A substantial number of Purkinje cell axons continue beyond the cerebellar nuclei to innervate nearby regions in the brain stem.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1984

High-affinity binding of the regulatory subunit (RII) of cAMP-dependent protein kinase to microtubule-associated and other cellular proteins.

Interaction of the regulatory subunit of the type II cAMP-dependent protein kinase (RII) with tissue-specific cellular binding proteins has been demonstrated by two independent methods. Complexes of RII and its binding proteins were isolated on a cAMP analog-Sepharose affinity column, eluted from the column, and analyzed by sodium dodecyl sulfate/polyacrylamide gel electrophoresis. Alternatively, nitrocellulose blots made from polyacrylamide gels containing samples of tissue extracts or affinity column eluates were treated with sequential overlays of RII, monospecific antibody, and radioiodinated protein A. In bovine cerebrum, specific high-affinity interactions between RII and several binding proteins, including major proteins of 300, 80, and 68 kDa, were recognized by the two methods. The 300-kDa and 68-kDa proteins were identified as microtubule-associated protein 2 (300 kDa) and a protein of lower molecular weight (68 kDa) that copurifies with it. The additional major binding protein of 80 kDa requires further characterization. In addition, several binding proteins distinct from those observed in bovine cerebrum were found in bovine heart. Many of the RII binding proteins from brain and heart served to differing extents as substrates for the purified catalytic subunit of cAMP-dependent protein kinase. One hypothesis of the significance of the protein kinase regulatory subunit interaction with cellular binding proteins is that this may control the protein kinase holoenzyme localization and, thereby, define the substrate targets most accessible for phosphorylation by the activated protein kinase catalytic subunit. Alternatively, RII binding to a variety of cellular proteins might regulate their function--i.e., RII could be a regulator for multiple proteins in addition to the catalytic subunit of the cAMP-dependent protein kinase.

Animals↗
PubMed1984

Adenosine 3',5'-monophosphate-dependent protein kinase and granulosa cell responsiveness to gonadotropins.

The mechanisms by which estradiol enhances the actions of FSH (and cAMP), including the induction of LH receptors in rat ovarian granulosa cells, remain unclear. These studies were conducted to determine the extent to which changes in the activity, content, or intracellular distribution of the catalytic subunit of cAMP-dependent protein kinase might be altered in granulosa cells as a consequence of estradiol, FSH, and hCG administration in vivo. Dose-dependent stimulation of protein kinase activity (measured by histone phosphorylation in the presence of [gamma 32P]ATP and cAMP) demonstrated that the EC50 for cAMP was consistently 20 X 10(-8) M in cytosols prepared from granulosa cells of hypophysectomized rats before and after treatment with estradiol alone or estradiol and FSH. However, estradiol alone caused a 1.5 to 2.0-fold increase in the total amount of enzyme activity. When the cytosol content of the catalytic subunit (C) was quantitated directly, using immunoblotting procedures, the amount of C was 40 pmol/mg protein in all tissues, regardless of hormone treatments in vivo. When the content of RII, the regulatory subunit of type II cAMP-dependent protein kinase, was measured by similar immunoblotting procedures, a 10-fold increase was observed in granulosa cells exposed to both estradiol and FSH compared to that in cells exposed to estradiol alone. Greater than 80% of the intracellular content of both C and RII was present in the cytosol fraction (30,000 X g supernatant) rather than in the particulate nuclear fraction (30,000 X g pellet) of granulosa cells. This distribution of subunits was not altered by rapidly elevating intracellular concentrations of cAMP in vivo with 10 IU hCG, iv. We conclude that the catalytic subunit of protein kinase is a constitutive component of granulosa cells and that the sensitivity of the enzyme for cAMP is not affected by hormones or by a 10-fold increase in RII. Thus, the ability of estradiol to enhance FSH and cAMP action in granulosa cells appears to come primarily from the induction of specific substrates for the enzyme and a small increase in the catalytic activity but not from a change in the content of the catalytic subunit.

Animals↗
PubMed1983

Dibutyryl cAMP treatment of neuroblastoma-glioma hybrid cells results in selective increase in cAMP-receptor protein (R-I) as measured by monospecific antibodies.

The absolute levels of cAMP-dependent protein kinase (cAMP-dPK) subunits (R-I, R-II and C) and cGMP-dependent protein kinase (cGMP-dPK) holoenzyme were studied in neuroblastoma-glioma hybrid cells before and after dibutyryl-cAMP (Bt2cAMP) treatment which results in differentiation of these cells. The levels were determined by two different techniques utilizing antibodies which had been raised against each individual purified protein kinase subunit (or the holoenzyme in the case of the cGMP-dPK). Electrophoretic transfer of samples from SDS-polyacrylamide gels to nitrocellulose paper, followed by immunolabeling of protein kinase subunits with their respective antibodies and [125I]Protein A, demonstrated the monospecific nature of the antibodies, and a selective, several-fold increase in the R-I subunit in Bt2cAMP-treated cells, with no change in the level of R-II or C subunits. A simple enzyme-linked immunosorbent assay (ELISA) capable of measuring nanogram amounts of the various subunits confirmed the selective increase in the R-I subunit. ELISA assay results also indicated that the R-I subunits present before and after Bt2cAMP treatment are antigenically homologous. In conclusion, the specific, sensitive immunological methods described here demonstrate the capacity of neuroblastoma-glioma hybrid cells to regulate separately the levels of the two distinct subunits (R-I and C) of the Type I cAMP-dPK.

Animals↗
PubMed1983

Red blood cell sodium transport and phosphate release in uremia.

Red blood cell (RBC) phosphate release was linear for more than 1 h and dependent on the intracellular hydrolysis of organic phosphate esters. In uremics on chronic hemodialysis total phosphate release was significantly increased suggesting an elevated RBC energy metabolism. Ouabain-sensitive phosphate release, however, was decreased. For RBCs of controls and uremic subjects approximately 80% of inorganic phosphate liberated within the cell was recycled. Thus, RBC phosphate release represents 20% of intracellular phosphate ester metabolism. In uremia active electrolyte transport was diminished, suggesting an impaired Na-K-ATPase activity. It resulted in an increased RBC sodium and a decreased potassium concentration. The positive correlation between ouabain-sensitive rate constant for sodium efflux and ouabain-sensitive RBC phosphate release indicates that ouabain inhibition of phosphate elimination might be related to Na-K-ATPase. In RBCs of uremic subjects almost 4% of the increased energy metabolism was needed for active electrolyte transport mechanisms, in control RBCs 12% was required.

Biological Transport, Active↗
PubMed1983

Recent results of the German Thorotrast study--dose relevant physical and biological properties of Thorotrast equivalent colloids.

As a prerequisite for quantifying the non-radiation effect of Thorotrast, nonradioactive and radioactive aquasols with identical physicochemical properties and with biophysical behavior comparable to that of Thorotrast were developed and produced for a second long-term animal experiment. Comparative investigations with hafnium and zirconium (zirconotrast) dioxide aquasols showed the latter to be most appropriate considering the size of both the dispersoids and the aggregates in the liver tissue. The average particle diameters of ThO2, ZrO2 and HfO2 proved to be values of 9.3 nm, 15 nm and 45 nm, respectively. The size of the aggregates shows a slight dependence on the applied amount but no dependence on the duration of body burden of the colloid. The aggregate diameters in the 600 microliters group turned out to be 9.6 microns, 14.4 microns and 5.3 microns, respectively. Radioactive zirconotrast was prepared by radiochemical incorporation of 230Th and 228Th at dose rates which produce accumulated doses in the liver of rats equivalent to those of commercial 230Th enriched Thorotrast after 1.5 yr. Five different colloids were prepared with alpha-energy emission rates increased by factors of 1, 2.5, 5, 10 and 25 compared to Thorotrast and then injected into rats.

Animals↗