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Biomedical subjects

T Takuma

Publications and source records attributed to T Takuma.

At least 55 records · Page 3Linked to original sources
PubMed1987

Effects of sodium ions and monensin on amylase secretion from rat parotid cells.

The role of sodium ions in amylase secretion from rat parotid cells was studied using various Na+-free media and monensin. In a sucrose medium, amylase secretion was not stimulated by isoproterenol but was significantly stimulated by dibutyryl cAMP. In choline chloride and LiCl media, both isoproterenol and dibutyryl cAMP clearly evoked amylase release. Monensin itself elicited amylase secretion slightly, but significantly inhibited the secretion stimulated by isoproterenol or dibutyryl cAMP. The inhibitory effect of monensin was detectable even in choline chloride, LiCl and KCl media. These results indicate that sodium ions are not essential for amylase secretion from rat parotid cells and that the inhibitory effect of monensin is independent of influx of sodium ions or efflux of potassium ions.

Amylases↗
PubMed1987

Synergism of tumor necrosis factor and interferon-gamma in induction of differentiation of human myeloblastic leukemic ML-1 cells.

Natural or recombinant human tumor necrosis factor (TNF) induced NBT-reducing activity of ML-1 cells in a dose-dependent manner. Interferon-gamma (IFN-gamma) induced NBT-reducing activity only marginally. However, when IFN-gamma was combined with TNF, induction of NBT-reducing activity was remarkably increased. IFN-alpha or -beta had almost no effect on the induction of NBT-reducing activity of ML-1 cells, either alone or in combination with TNF. Treatment with both TNF and IFN-gamma synergistically enhanced morphological changes, growth inhibition and activity of Fc receptors, and NBT reduction in ML-1 cells, but not phagocytic activity. The TNF treated cells were classified as macrophage-like by morphology, and by lineage-specific alpha-naphthyl acetate esterase stain. The results indicate that combinations of TNF and IFN-gamma act synergistically in the induction of differentiation of human myeloblastic ML-1 cells.

Cell Differentiation↗
PubMed1987

Renal effects of synthetic rat-atrial natriuretic peptide in nephron-reduced rats with nephrotoxic nephritis.

Following nephron reduction by means of five--sixths nephrectomy (Nx), nephritis was induced in rats by injection of nephrotoxic serum (NTS). A continuous intravenous infusion of synthetic rat--atrial natriuretic peptide (r-ANP) at 2.5 micrograms/min for produced remarkable diuresis and natriuresis in these rats. Furthermore, inulin clearance, para-amino-hippuric acid clearance and filtration fraction increased in spite of the reduction of mean arterial pressure during the infusion of r-ANP. It was therefore evident that diuresis and natriuresis were mediated by a direct action of r-ANP in the kidney. We observed that r-ANP was a diuretic, natriuretic and hypotensive agent but at a higher dosage in Nx rats with NTN.

Animals↗
PubMed1986

ATP-dependent calcium transport in rat parotid basolateral membrane vesicles. Modulation by agents which elevate cyclic AMP.

ATP-dependent Ca2+ transport was studied in basolateral membrane vesicles prepared from rat parotid gland slices incubated without or with agents which increase cyclic AMP. Isoproterenol (10(-5) M), forskolin (2 X 10(-6) M) and 8-bromocyclic AMP (2 X 10(-3) M) all increased ATP-dependent 45Ca2+ uptake 1.5- to 3-fold. The effect of isoproterenol was concentration-dependent and blocked by the beta-adrenergic antagonist propranolol. Enhanced uptake did not appear an artifact of vesicle preparation as apparent vesicle sidedness, 45Ca2+ efflux rates, specific activity of marker enzymes and equilibrium Ca2+ content were identical in vesicle preparations from control and 8-bromocyclic AMP-treated slices. Kinetic studies showed the ATP-dependent Ca2+ transport system in vesicles from 8-bromocyclic AMP-treated slices displayed a approximately 50% increase in Vmax and in Km Ca2+, compared to controls. The data suggest that physiological secretory stimuli to rat parotid acinar cells, which involve cyclic AMP, result in a readjustment of the basolateral membrane ATP-dependent Ca2+ pump.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1986

Does cyclic AMP mobilize Ca2+ for amylase secretion from rat parotid cells?

Both dibutyryl cAMP and carbachol stimulated amylase released from rat parotid cells incubated in Ca2+-free medium containing 1 mM EGTA. Cells preincubated with 10 microM carbachol in Ca2+-free, 1 mM EGTA medium for 15 min lost responsiveness to carbachol, but maintained responsiveness to dibutyryl cAMP. Dibutyryl cAMP still evoked amylase release from cells preincubated with 1 microM ionophore A23187 and 1 mM EGTA for 20 min. Although carbachol stimulated net efflux of 45Ca from cells preequilibrated with 45Ca for 30 min, dibutyryl cAMP did not elicit any apparent changes in the cellular 45Ca level. Inositol trisphosphate, but not cAMP, evoked 45Ca release from saponin-permeabilized cells. These results suggest that cAMP does not mobilize calcium for amylase release from rat parotid cells.

Amylases↗
PubMed1986

Phorbol ester stimulates amylase secretion from rat parotid cells.

Phorbol myristate acetate (PMA), a potent activator of Ca2+- and phospholipid-dependent protein kinase (protein kinase C), evoked amylase release from rat parotid cells. In dose-response studies, PMA stimulated amylase release independently of db-cAMP, but potentiated the effect of carbachol. PMA and A23187, a Ca2+ ionophore, synergistically increased amylase release. The maximum effect of carbachol was further enhanced by PMA but not by A23187, suggesting that protein kinase C is not fully activated by the muscarinic-cholinergic agonist under the condition where calcium is fully utilized for amylase secretion.

Amylases↗
PubMed1986

Chlorpromazine inhibition of muscarinic-cholinergic responses in the rat parotid gland.

The ability of chlorpromazine (CPZ) to inhibit muscarinic-cholinergic secretory events was studied in vitro in rat parotid acinar cells. CPZ inhibited carbachol-induced amylase release in a dose-dependent fashion but had no effect on that elicited by isoproterenol. The inhibition of parotid protein synthesis induced by carbachol, but not that induced by A23187, was blocked by CPZ. CPZ exhibited a dose-dependent inhibition of [3H] quinuclidinyl benzilate (QNB) binding to muscarinic receptors, and altered the KD of the receptor for the ligand. These results are consistent with an ability of CPZ to inhibit muscarinic-cholinergic-induced salivary secretion by complex interference with receptor binding. In addition, CPZ may block parotid-muscarinic responses by impeding a post-receptor signaling step which is proximal to Ca2+ mobilization.

Amylases↗
PubMed1985

Calcium transport mechanisms in basolateral plasma membrane-enriched vesicles from rat parotid gland.

Ca2+ transport was studied by using basolateral plasma membrane vesicles from rat parotid gland prepared by a Percoll gradient centrifugation method. In these membrane vesicles, there were two Ca2+ transport systems; Na+/Ca2+ exchange and ATP-dependent Ca2+ transport. An outwardly directed Na+ gradient increased Ca2+ uptake. Ca2+ efflux from Ca2+-preloaded vesicles was stimulated by an inwardly directed Na+ gradient. However, Na+/Ca2+ exchange did not show any 'uphill' transport of Ca2+ against its own gradient. ATP-dependent Ca2+ transport exhibited 'uphill' transport. An inwardly directed Na+ gradient also decreased Ca2+ accumulation by ATP-dependent Ca2+ uptake. The inhibition of Ca2+ accumulation was proportional to the external Na+ level. Na+/Ca2+ exchange was inhibited by monensin, tetracaine and chlorpromazine, whereas ATP-dependent Ca2+ transport was inhibited by orthovanadate, tetracaine and chlorpromazine. Oligomycin had no effect on either system. These results suggest that in the parotid gland cellular free Ca2+ is extruded mainly by an ATP-dependent Ca2+ transport system, and Na+/Ca2+ exchange may modify the efficacy of that system.

Adenosine Triphosphate↗
PubMed1985

Na+-dependent transport of alpha-aminoisobutyrate in isolated basolateral membrane vesicles from rat parotid glands.

Basolateral plasma membranes were prepared from rat parotid gland after centrifugation in a self-orienting Percoll gradient. K+-dependent phosphatase [Na+ + K+)-ATPase), a marker enzyme for basolateral membranes, was enriched 10-fold from tissue homogenates. Using this preparation, the transport of alpha-aminoisobutyrate was studied. The uptake of alpha-aminoisobutyrate was Na+-dependent, osmotically sensitive, and temperature-dependent. In the presence of a Na+ gradient between the extra- and intravesicular solutions, vesicles showed an 'overshoot' accumulation of alpha-aminoisobutyrate. Sodium-dependent alpha-aminoisobutyrate uptake was saturable, exhibiting an apparent Km of 1.28 +/- 0.35 mM and Vmax of 780 +/- 170 pmol/min per mg protein. alpha-Aminoisobutyrate transport was inhibited considerably by monensin, but incubating with ouabain was without effect. These results suggest that basolateral membrane vesicles, which possess an active amino acid transport system (system A), can be prepared from the rat parotid gland.

Aminoisobutyric Acids↗
PubMed1985

Regulation of functional mRNA levels for trypsin-like esteroproteases by 5 alpha-dihydrotestosterone and triiodothyronine in mouse submandibular salivary gland.

The effects of 5 alpha-dihydrotestosterone and triiodothyronine on the levels of mRNA for trypsin-like esteroproteases in the submandibular glands of young female mice were examined using a translation system in a reticulocyte lysate. Immunoprecipitation of the trypsin-like esteroproteases synthesized in vitro gave almost the same isozyme profile as that of enzymes synthesized in vivo on isoelectric focusing in acrylamide gel containing 8 M urea. Although 5 alpha-dihydrotestosterone and triiodothyronine induced the enzyme activity 3-5 times, these hormones increased their functional mRNA levels only 45-70 per cent. These results suggest that there is little if any post-translational processing of esteroproteases and that hormones increase both the amount of mRNA and the efficacy of its translation.

Animals↗
PubMed1985

Metabolic conversion of alpha-keto valine to valine in patients with chronic renal failure.

Change in the metabolic conversion rate of alpha-keto valine to valine following oral administration of the analog of the essential amino acid (0.1 g/kgB.W.) is studied in six patients with chronic renal failure and five control subjects under low protein, low and normal energy intake diets. Diet I is composed of 105 kj (25 kcal)/kgB.W. energy and 0.6 g/kgB.W. protein, whereas Diet II is composed of 165 kj (40 kcal)/kgB.W. with the same amount of protein intake. As a result, an increase in plasma keto valine concentration is observed immediately after oral administration, followed by an increase in plasma valine concentration, implying that metabolic conversion of alpha-keto valine to valine occurs within a small amount of time. In addition, the conversion rate appears to be accelerated under Diet II. It is therefore suggested that reutilization of urea nitrogen with the ketoanalog under the low protein diet seems to be promoted under adequate energy intake.

Administration, Oral↗