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Y Shidoji

Publications and source records attributed to Y Shidoji.

At least 37 records · Page 2Linked to original sources
PubMed1993

The clearance rate of chylomicron retinyl ester from plasma can be used to distinguish rats with cirrhosis from those with portacaval shunt.

Effects of carbon tetrachloride treatment and portacaval shunt surgery on exogenous chylomicron retinyl ester clearance from rat plasma were analyzed assuming three-compartment model kinetics. In rats with cirrhosis and in those with Eck fistulas, the relative pool size of compartment 2 decreased (0.20 and 0.36, respectively) compared with controls (0.82). The relative mass of compartment 3 significantly increased in rats with cirrhosis (1.55) or Eck fistula (0.19) compared with control rats (0.11). The cirrhotic and Eck fistula groups were indistinguishable on the basis of these parameters and on the basis of indocyanine green test values. However, the cirrhosis and Eck fistula groups differed clearly from each other with respect to fractional efflux rate constants (l2, l3), where the constant l2 is from compartment 2 and the l3 is from compartment 3. Both values decreased in cirrhotic rats, suggesting that the hepatic uptake of chylomicron retinyl esters was impaired by carbon tetrachloride. On the other hand, Eck fistula rats did experience dramatic increases in l3, implying that the hepatic uptake of chylomicron retinyl esters from compartment 3 was enhanced by portacaval shunting. Elevation of the plasma estrogen level observed in Eck fistula rats may be responsible for the induction of low-density lipoprotein receptors on hepatocytes and for the subsequent enhancement of l3. These results suggest that a three-compartment model of plasma retinyl ester disappearance kinetics gives important quantitative information about hepatic function. Clinical application of the chylomicron retinyl ester clearance test is discussed for estimating hepatic function reserves and for differential diagnosis of portal hypertension.

Animals↗
PubMed1988

[Small intestinal alkaline phosphatase activity and changes induced by cysteamine administration in fecal excretions of male Wistar rats].

Alkaline phosphatase (ALP) activity in fecal excretions was measured in male Wistar rats. Total daily ALP activity in fecal extracts was 133.1 +/- 21.2 mumoles/min per rat weighing approximately 150 g. We found that 63.7% of the fecal ALP activity was inhibited by 30 mM L-phenylalanine (L-Phe), a specific inhibitor for intestinal ALP. As body weight increased from 150 g to 300 g, total daily ALP activity in fecal extracts decreased rapidly to 33.7 +/- 6.08 mumoles/min/rat. However, the percentage of L-Phe-sensitive ALP to total enzyme activity was less variable (40-65%) in the growing rats. Cysteamine-HCl, an ulcerogenic drug, was injected subcutaneously to adult rats (300 g b. w) at a dosage of 400 mg/kg. b. w. Daily excretion of L-Phe-sensitive ALP in fecal extracts decreased to one-third 2 days after injection. Afterwards, a steep and transient increase in the enzyme activity was detected in fecal extracts between days 4 and 7 after injection. ALP activity in fecal excretions may be a clinical indicator of duodenal mucosal damage.

Alkaline Phosphatase↗
PubMed1988

Minerals and vitamin-A status in relation to gustatory functions for salt in healthy female college students.

Twenty-five healthy female college students were studied for the gustatory function tests for salt (NaCl) and some selected biochemical parameters including plasma retinol and plasma retinol-binding protein (PRBP). Plasma zinc (PZn) and retinol levels were comparable with those of good responders in tests of discrimination between two levels of NaCl in the previous report, but PRBP was lower in the present subjects. From the results of correlation analysis and stepwise multiple regression analysis, the individual student's discriminability of NaCl concentrations was related to the parameters regarding metabolic status of calcium (Ca), magnesium (Mg), sodium (Na), and selenium (Se). The detection threshold of NaCl concentration ranged from 1 to 60 mmol/liter and was related to PRBP. Plasma Zn was significantly positively correlated with both plasma retinol and PRBP, but significantly negatively correlated only for the detection threshold of NaCl concentration. On the basis of these results, the importance of vitamin-A nutrition and the relation of minerals such as Na, Ca, Mg, and Zn to the gustatory functions of NaCl was confirmed and a possible participation of Se to the functions was suggested.

Adult↗
PubMed1986

Multiple form of L-phenylalanine sensitive alkaline phosphatase in rat fecal extracts.

Alkaline phosphatase activity was detected in fecal extracts of male rats. 58% of the total enzyme activity was inhibited by 30 mM L-phenylalanine, which is an inhibitor specific for intestinal alkaline phosphatase. L-Phenylalanine sensitive alkaline phosphatase in the fecal extracts revealed multiple peaks on DEAE-Sephadex A-25 ion exchange column with a linear gradient of NaCl. It is discussed that a part of the fecal alkaline phosphatase might be a set of catabolites of the intestinal enzyme.

Alkaline Phosphatase↗
PubMed1985

Interrelationship of some selected nutritional parameters relevant to taste for salt in a group of college-aged women.

Students in a women's college were investigated for taste acuity for salt, discrimination of salt concentrations in food, and anthropometrical (the body mass index, and systolic and diastolic blood pressures) and biochemical nutritional parameters (blood hemoglobin, plasma zinc, plasma copper, plasma vitamin A, plasma retinol-binding protein, urinary sodium, urinary potassium, urinary magnesium, urinary calcium and urinary zinc). Among 95 students who participated in the test for discrimination of salt concentrations, which was repeated 6 times with 5 different test samples, only 43 (45.3%) committed no mistakes. The detection threshold for taste of salt was significantly associated with neither the discriminability of salt concentrations nor any biochemical parameters. Levels of plasma zinc (PZn), urinary zinc (UZn) and plasma vitamin A (VA) were lower in the present subjects than in those reported previously. The rate of correct discrimination (RCD) was significantly correlated with PZn and VA positively, and with urinary sodium (UNa) and urinary potassium (UK) negatively. In the factor analysis to investigate the interrelationship of nutritional parameters, 6 factors with significance were extracted, among which factors 3 and 4 were related to RCD. Factor 3 had large loadings on VA, plasma retinol-binding protein (RBP) and RCD, and factor 4 was positively loaded on UNa and UK and negatively on UZn and RCD. In the stepwise multiple regression analysis (RCD being the dependent variable), significant independent variables selected were VA, UK, PZn, systolic blood pressure and UNa. From these results, the college-aged women's failure in discriminating salt concentrations in food was likely to be related to vitamin A inadequacy, mild Zn deficiency and excessive intakes of Na and K.

Adolescent↗
PubMed1984

Mode of rat cecal enlargement induced by a short-term feeding on glucomannan.

The increase in wet weight of rat cecum was evident at 16 hr of glucomannan ingestion and continued until 184 hr (the longest period observed in this experiment), reaching about 2.5-fold. The ratios of total protein/DNA and RNA/DNA were both always higher in cecum of rats fed glucomannan than the control group (0 hr). During the initial 40 hr, no significant change in total DNA content was observed with the increase in total protein and RNA. Furthermore, the incorporation rate of [3H]thymidine in cecal DNA was even lower in the glucomannan feeding than the control (0 hr) during the initial 40 hr. After 88 hr of the experiment, however, a significant increase in the synthetic rate of DNA was found as well as [14C]leucine incorporation into total protein. It was discussed that a hypertrophic change in rat cecum was initially induced by glucomannan ingestion and was followed by hyperplastic growth under continuous exposure of glucomannan.

Animals↗
PubMed1983

Retinyl phosphate mannose synthesis in rat liver membranes. Phospholipase sensitivity and phospholipid requirement.

A remarkable and immediate decrease in GDP-mannose:retinyl phosphate mannosyltransferase activity was found on pre-incubation of rat liver postnuclear membranes with phospholipase A2 or phospholipase C. Under the same conditions of pre-incubation (1 min at 37 degrees C) trypsin did not affect the enzyme activity, whereas pre-incubation for 30 min with trypsin and Pronase abolished enzyme activity. The lipid extract of untreated rat liver membranes partially restored enzyme activity after phospholipase treatment. Sphingomyelin was as active as the endogenous lipids. Other phospholipids were less active in the following order: phosphatidylcholine greater than phosphatidylethanolamine greater than phosphatidylinositol = phosphatidylserine. Dolichyl phosphate mannose synthesis was inhibited less (33%) by phospholipase C than was Ret-P-Man synthesis (98.5%) under identical conditions of incubation, which included 0.025% Triton. However, retinyl phosphate mannose synthesis by purified endoplasmic reticulum was found to be resistant to phospholipase C. Mixing experiments failed to demonstrate an inhibitory effect of the phospholipase-treated postnuclear membrane fraction on the synthetic activity of the endoplasmic reticulum, thus excluding the release of an inhibitory factor from the postnuclear membranes.

Animals↗
PubMed1983

Interactions between retinyl phosphate and bivalent cations.

In the presence of Mn(II) ions, the u.v. absorption spectrum of retinyl phosphate (Ret-P) solubilized in Triton X-100 micelles, phosphatidylcholine liposomes or rat liver microsomes exhibited a shift from the maximum of 330 nm to 287 nm. The effect of Mn(II) was reversed by adding EDTA or phosphate buffer. The same spectral change was found in the presence of poly-L-lysine in place of Mn(II) ions. The e.s.r. spectrum of Mn(II) in the presence or in the absence of Ret-P clearly showed that approx. 75% of the initial concentration of Mn(II) ions is bound to Ret-P when the molar ratio of Ret-P to Mn(II) ions is 4:1; no such binding occurred in the presence of retinol or retinoic acid. The appearance of two isosbestic points at 303 and 368 nm, in the presence of Mn(II) ions, suggests the existence of an equilibrium between an Mn(II)-bound monomer and an Mn(II)-bound dimer of Ret-P in Triton X-100 micelles. The same effect on the u.v.-absorption spectrum of Ret-P was also induced by Co(II), Cr(II), Zn(II) and Fe(II), but not by Mg2+ or Cu(II). The formation of the 'metachromatic complex' between Ret-P and Mn(II) or Co(II) inhibited the synthesis of retinyl phosphate mannose (Ret-P-Man) from exogenous and endogenous Ret-P and guanosine diphosphate [14C]mannose when bovine serum albumin was added after the metal ion. However, the order of addition did not influence Ret-P-Man synthesis in incubations containing MgCl2, which does not form the metachromatic complex with Ret-P. These results suggest that the bioavailability of proteins, polyamines and metal ions may control the extent to which Ret-P can be mannosylated in the intact membrane.

Animals↗
PubMed1983

Mannosyl carrier functions of retinyl phosphate and dolichyl phosphate in rat liver endoplasmic reticulum.

Of the subcellular fractions of rat liver the endoplasmic reticulum was the most active in GDP-mannose: retinyl phosphate mannosyl-transfer activity. The synthesis of retinyl phosphate mannose reached a maximum at 20-30 min of incubation and declined at later times. Retinyl phosphate mannose and dolichyl phosphate mannose from endogenous retinyl phosphate and dolichyl phosphate could also be assayed in the endoplasmic reticulum. About 1.8 ng (5 pmol) of endogenous retinyl phosphate was mannosylated per mg of endoplasmic reticulum protein (15 min at 37 degrees C, in the presence of 5 mM-MnCl2), and about 0.15 ng (0.41 pmol) of endogenous retinyl phosphate was mannosylated with Golgi-apparatus membranes. About 20 ng (13.4 pmol) of endogenous dolichyl phosphate was mannosylated in endoplasmic reticulum and 4.5 ng (3 pmol) in Golgi apparatus under these conditions. Endoplasmic reticulum, but not Golgi-apparatus membranes, catalysed significant transfer of [14C]mannose to endogenous acceptor proteins in the presence of exogenous retinyl phosphate. Mannosylation of endogenous acceptors in the presence of exogenous dolichyl phosphate required the presence of Triton X-100 and could not be detected when dolichyl phosphate was solubilized in liposomes. Dolichyl phosphate mainly stimulated the incorporation of mannose into the lipid-oligosaccharide-containing fraction, whereas retinyl phosphate transferred mannose directly to protein.

Animals↗
PubMed1982

The polyenic system of retinyl phosphate is required for its mannosyl donor activity but not for acceptor activity.

We investigated whether the polyenic and allylic phosphate systems of retinyl phosphate are essential for its mannosyl acceptor and donor activities in rat liver postnuclear membranes. Perhydromonoeneretinyl phosphate, a compound without growth-promoting activity in vitamin A-deficient animals, was prepared by catalytic hydrogenation of retinol and phosphorylation. Perhydromonoeneretinyl phosphate mannose synthesis from GDP-mannose showed continued accumulation for at least 60 min, while retinyl phosphate mannose synthesis showed a maximum at 20-30 min and then declined. Moreover, only retinyl phosphate stimulated transfer of mannose from GDP-mannose to endogenous proteins, which were separated by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. Thus, hydrogenation of side-chain double bonds in retinyl phosphate impaired only slightly its mannosyl acceptor activity, but caused loss of mannosyl donor activity.

Animals↗
PubMed1982

Synthesis of retinyl phosphate mannose and dolichyl phosphate mannose from endogenous and exogenous retinyl phosphate and dolichyl phosphate in microsomal fraction. Specific decrease in endogenous retinyl phosphate mannose synthesis in vitamin A deficiency.

Rat liver microsomal fraction synthesized Ret-P-Man (retinyl phosphate mannose) and Dol-P-Man (dolichyl phosphate mannose) from endogenous Ret-P (retinyl phosphate) and Dol-P (dolichyl phosphate). Ret-P-Man synthesis displayed an absolute requirement for a bivalent cation, and also Dol-P-Man synthesis was stimulated by bivalent metal ions. Mn2+ and Co2+ were the most active, with maximum synthesis of Ret-P-Man occurring at 5-10 mM: Mg2+ was also active, but at higher concentrations. At 5mM-Mn2+ the amount of endogenous Ret-P mannosylated in incubation mixtures containing 5 microM-GDP-mannose in 15 min at 37 degrees C was approx. 3 pmol/mg of protein. In the same assays about 7-10 pmol of endogenous Dol-P was mannosylated. Bivalentcation requirement for Ret-P-Man synthesis from exogenous Ret-P showed maximum synthesis at 2.5 mM-Mn2+ or -Co2+. In addition to Ret-P-Man and Dol-P-Man, a mannolipid co-chromatographing with undecaprenyl phosphate mannose was detected. Triton X-100 (0.5%) abolished Ret-P-Man synthesis from endogenous Ret-P and caused a 99% inhibition of Ret-P-Man synthesis from exogenous Ret-P. The presence of detergent (0.5%) also inhibited Dol-P-Man synthesis from endogenous Dol-P and altered the requirement for Mn2+. Microsomal fraction from Syrian golden hamsters was also active in Ret-P-Man and Dol-P-Man synthesis from endogenous Ret-P and Dol-P. At 5 mM-Mn2+ about 2.5 pmol of endogenous Ret-P and 3.7 pmol of endogenous Dol-P were mannosylated from GDP-mannose per mg of protein in 15 min at 37 degrees C. On the other hand, microsomal fraction from vitamin A-deficient hamsters contained 1.2 pmol of Ret-P and 14.1 pmol of Dol-P available for mannosylation. Since GDP-mannose: Ret-P and GDP-mannose: Dol-P mannosyltransferase activities were not affected, depletion of vitamin A must affect Ret-P and Dol-P pools in opposite ways.

Animals↗
PubMed1981

Rat liver microsomes catalyse mannosyl transfer from GDP-D-mannose to retinyl phosphate with high efficiency in the absence of detergents.

In the absence of detergent, the transfer of mannose from GDP-mannose to rat liver microsomal vesicles was highly stimulated by exogenous retinyl phosphate in incubations containing bovine serum albumin, as measured in a filter binding assay. Under these conditions 65% of mannose 6-phosphatase activity was latent. The transfer process was linear with time up to 5min and with protein concentration up to 1.5mg/0.2ml. It was also temperature-dependent. The microsomal uptake of mannose was highly dependent on retinyl phosphate and was saturable against increasing amounts of retinyl phosphate, a concentration of 15mum giving half-maximal transfer. The uptake system was also saturated by increasing concentrations of GDP-mannose, with an apparent K(m) of 18mum. Neither exogenous dolichyl phosphate nor non-phosphorylated retinoids were active in this process in the absence of detergent. Phosphatidylethanolamine and synthetic dipalmitoylglycerophosphocholine were also without activity. Several water-soluble organic phosphates (1.5mm), such as phenyl phosphate, 4-nitrophenyl phosphate, phosphoserine and phosphocholine, did not inhibit the retinyl phosphate-stimulated mannosyl transfer to microsomes. This mannosyl-transfer activity was highest in microsomes and marginal in mitochondria, plasma and nuclear membranes. It was specific for mannose residues from GDP-mannose and did not occur with UDP-[(3)H]galactose, UDP- or GDP-[(14)C]glucose, UDP-N-acetyl[(14)C]-glucosamine and UDP-N-acetyl[(14)C]galactosamine, all at 24mum. The mannosyl transfer was inhibited 85% by 3mm-EDTA and 93% by 0.8mm-amphomycin. At 2min, 90% of the radioactivity retained on the filter could be extracted with chloroform/methanol (2:1, v/v) and mainly co-migrated with retinyl phosphate mannose by t.l.c. This mannolipid was shown to bind to immunoglobulin G fraction of anti-(vitamin A) serum and was displaced by a large excess of retinoic acid, thus confirming the presence of the beta-ionone ring in the mannolipid. The amount of retinyl phosphate mannose formed in the bovine serum albumin/retinyl phosphate incubation is about 100-fold greater than in incubations containing 0.5% Triton X-100. In contrast with the lack of activity as a mannosyl acceptor for exogenous dolichyl phosphate in the present assay system, endogenous dolichyl phosphate clearly functions as an acceptor. Moreover in the same incubations a mannolipid with chromatographic properties of retinyl phosphate mannose was also synthesized from endogenous lipid acceptor. The biosynthesis of this mannolipid (retinyl phosphate mannose) was optimal at MnCl(2) concentrations between 5 and 10mm and could not be detected below 0.6mm-MnCl(2), when synthesis of dolichyl phosphate mannose from endogenous dolichyl phosphate was about 80% of optimal synthesis. Under optimal conditions (5mm-MnCl(2)) endogenous retinyl phosphate mannose represented about 20% of dolichyl phosphate mannose at 15min of incubation at 37 degrees C.

Animals↗
PubMed1981

Recent studies on the involvement of retinyl phosphate as a carrier of mannose in biological membranes.

Rat liver microsomes synthesized [14C]mannosylretinylphosphate and dolichyl [14C]mannosylphosphate from guanosinedisphosphate [14C]mannose, retinylphosphate and dolichylphosphate. Two distinct enzyme activities were shown to be responsible for the biosynthesis of the two mannolipids. A higher affinity mannosyl transferase (EA I), responsible for dolichylmannosylphosphate synthesis, displayed a Km for GDP-mannose of 1.7 microM; while a lower affinity enzyme (EA II), responsible for mannosylretinylphosphate synthesis, displayed a Km for GDP-mannose of 12.5 microM. These Km values were unaffected by the addition of either dolichylphosphate for EA II, or retinylphosphate for EA I. The same Km values were found before and after solubilization of the enzyme activity with 1% Triton X-100. Differential solubilization of EA I and EA II was demonstrated, utilizing different concentrations of Triton X-100. Triple-labeled mannosylretinylphosphate was prepared from [3H]retinylphosphate, retinyl[32P]phosphate and GDP-[14C]mannose from incubations containing rat liver microsomes. This compound was shown to donate [14C]mannose to endogenous acceptors of rat liver microsomes.

Animals↗
PubMed1981

A new aspect on the mechanism of intestinal cholesterol absorption in rat.

In order to study the mechanism of intestinal cholesterol absorption, the relationship between the amount of cholesterol administered and the rate of absorption was investigated by the dual isotope plasma ratio method in vivo and the ligated-loop method in situ. The energy requirement of cholesterol absorption was also observed by means of the ligated-loop method. The results obtained are summarized below. 1) Tri-phase absorption was observed by the dual isotope plasma ratio method. When less than 300 microgram of cholesterol was administered, absorption increased linearly, with the coefficient of absorption being more than 80%. When the amount administered was between 300 and 500 microgram, the absorption was constant. With the administration of more than 500 microgram, absorption increased linearly, but the coefficient of absorption decreased to approximately 55%. 2) With the ligated-loop method, a second saturation profile was obtained when between 250 and 400 microgram of cholesterol was administered to a segment. When 50 to 250 microgram of cholesterol were administered, absorption increased in proportion to the increase in cholesterol dosage. 3) The mucosal uptake of cholesterol decreased to 40-60% of the control with the addition of metabolic inhibitors such as NaN3, KCN, 2,4-DNP and ouabain, whereas the uptake of palmitate showed no significant decrease. In addition, the uptake of cholesterol decreased remarkably to 25% of the control with the lowering of body temperature from 37 degrees C to 27 C. These results suggest the existence of an active transport system which has a limited capacity for cholesterol absorption and which requires energy for its operation in the physiological state.

Animals↗
PubMed1980

Inhibition of beta-sitosterol on intestinal cholesterol absorption in rat using in vivo dual isotope ratio method.

The inhibitory effects of beta-sitosterol on intestinal cholesterol absorption were studied by means of a dual isotope plasma ratio method (in vivo), which is a new technique for the measurement of cholesterol absorption, as well as a ligated-loop method (in situ). The results obtained were as follows: 1. The absorption of beta-sitosterol itself was significantly less than cholesterol. Cholesterol was selectively absorbed from rat intestine. 2. When 100 to 1,000 microgram of beta-sitosterol were added to the dose solution containing 10 microgram of cholesterol, cholesterol absorption by the in vivo experiment decreased with the increae of additional beta-sitosterol. 3. A similar inhibitory effect of beta-sitosterol was observed by the in situ ligated-loop method. These results suggest that beta-sitosterol actually inhibits cholesterol absorption in the physiological state of an animal.

Animals↗