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Biomedical subjects

M Inui

Publications and source records attributed to M Inui.

At least 145 records · Page 8Linked to original sources
PubMed1988

Positive influence of dietary deoxycholic acid on development of pre-neoplastic lesions initiated by N-methyl-N-nitrosourea in rat liver.

The effect of deoxycholic acid (DCA) treatment subsequent to initiation of F344 male rats with N-methyl-N-nitrosourea (MNU), a wide spectrum carcinogen inducing tumors in many organs, was investigated. Rats were initially given four doses of MNU (50 mg/kg) i.p. within a 2-week period combined with a two-thirds partial hepatectomy performed at day 7 and then placed on basal diet containing DCA at concentrations of 0.313, 0.125, 0.050 and 0.020% for 21 weeks prior to final sacrifice. All organs studied were carefully examined histologically and histochemically for development of neoplastic and pre-neoplastic lesions. DCA enhanced the induction of glutathione S-transferase positive (GST-P+) liver cell foci in a dose-related manner. Furthermore groups of rats given DCA without prior MNU administration also developed dose-dependent numbers of pre-neoplastic liver lesions. In addition, increased numbers of small intestine tumors were apparent in DCA-treated animals although the difference was not significant. Induction of tumors in the thyroids, Zymbal glands, skin and peripheral nerves was not affected. The results indicate that DCA is a strong promoter of hepatocarcinogenesis with possible complete carcinogenicity in the liver and promotion potential for tumor development in the small intestine.

Animals↗
PubMed1988

Regulation of muscle contraction and relaxation in heart.

The calcium uptake and release machinery in heart SR have been characterized: (1) The calcium pump membrane is involved in energized Ca2+ uptake enabling muscle to relax. The calcium pump protein (CPP) in heart SR is modulated by protein kinase phosphorylation of phospholamban lowering the KCa2+. We conclude that in the membrane, phospholamban elevates KCa2+ of calcium pump protein. Phosphorylation of phospholamban attenuates the influence of phospholamban. In the limit, the intrinsic KCa2+ of calcium pump protein in heart and skeletal muscle are approximately the same. (2) The junctional face membrane is involved in calcium release which triggers muscle contraction. Ryanodine is a specific modulator of the Ca2+ release channels of SR which are involved in excitation-contraction coupling. The ryanodine receptor has been isolated, found to be equivalent to the feet structures, and on reconstitution into bilayers, identified as the calcium release channel of SR. The calcium release channel of SR is closed by ruthenium red and Mg2+ and opened by Ca2+ and ATP and low ryanodine concentration. The calcium release channel of SR is not effected by drugs such as nitrendipine, diltiazem and D-600 which modulate the slow inward Ca2+ channel of the plasmalemma/transverse tubule. (3) The calcium release channels from heart and skeletal muscle SR are similar but not identical (Table IV). Important differences distinguish the calcium release machinery in heart from that of skeletal muscle. 1. In heart there are two sources of calcium fluxes: a) extracellular Ca2+ enters via the plasmalemma slow inward calcium current; and b) "Ca2+ induced Ca2+ release" from SR. In skeletal muscle, SR is the single main source of calcium which enters via "Depolarization induced calcium release". 2. The calcium release channel from heart SR has a lower Mr approximately 340,000 vs 360,000 for skeletal muscle. 3. Ryanodine binding in cardiac SR is distinct from that in skeletal muscle (Fig. 7). 4. The isolated calcium release channel from heart SR is more sensitive to Ca2+ for calcium release (Hymel et al. 1988c). Significant progress has been achieved in identifying the calcium release channel of SR in heart and skeletal muscle. The focus of excitation-contraction coupling now shifts to defining the precise nature of the coupling of excitation to contraction.

Animals↗
PubMed1987

The major metabolite of doxorubicin is a potent inhibitor of membrane-associated ion pumps. A correlative study of cardiac muscle with isolated membrane fractions.

Doxorubicin (adriamycin) is a highly effective cancer chemotherapeutic drug but its clinical utility is limited by its cardiotoxicity. Doxorubicinol, the major metabolite of doxorubicin, is up to 10 times more potent than doxorubicin at inhibiting isometric contraction of the papillary muscle isolated from the right ventricle of rabbit heart. Doxorubicinol also increases resting tension of isolated cardiac muscle indicative of incomplete relaxation between contractions, a characteristic of doxorubicinol but not of doxorubicin. This study assesses the effect(s) of doxorubicinol on a variety of ion pumps which may explain, in part, the action of the metabolite in the intact muscle. We find the doxorubicinol is a potent inhibitor (IC50 less than 5 micrograms/ml) of calcium-stimulated ATPase activity of sarcoplasmic reticulum from canine heart and rabbit skeletal muscle. At comparable levels, doxorubicinol is also a potent inhibitor of (Na + K)-ATPase of cardiac sarcolemma and the Mg-dependent ATPase activity referable to the F0F1 proton pump of mitochondria. For each of these ion pumps, doxorubicinol is at least 80 times more potent an inhibitor than doxorubicin. Doxorubicinol, between 10 and 50 micrograms/ml, increases resting tension up to 4-fold in isolated papillary muscles cyclically contracting at 30 times/min. Resting stress is relatively insensitive to doxorubicin. Thus, doxorubicinol is a potent inhibitor of several key cationic pumps that directly or indirectly regulate cell calcium and inhibits relaxation in the isolated fiber preparation. These observations add a new dimension to understanding the cardiotoxicity of doxorubicin.

5'-Nucleotidase↗
PubMed1987

Isolation of the ryanodine receptor from cardiac sarcoplasmic reticulum and identity with the feet structures.

Ryanodine, a highly toxic alkaloid, reacts specifically with the Ca2+ release channels which are localized in the terminal cisternae of sarcoplasmic reticulum (SR). In this study, the ryanodine receptor from cardiac SR has been purified, characterized, and compared with that of skeletal muscle SR. The ryanodine receptor was solubilized with 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS) in the presence of phospholipids. Purification was performed by sequential affinity chromatography followed by gel permeation chromatography in the presence of CHAPS and phospholipids. The enrichment of the receptor from cardiac microsomes was about 110-fold. The purified receptor contained a major polypeptide band of Mr 340,000 with a minor band of Mr 300,000 (absorbance ratio 100/8) on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Electron microscopy of the purified receptor from heart showed square structures of 222 +/- 21 A/side, which is the unique characteristic of feet structures of junctional face membrane of terminal cisternae of SR. Recently, we isolated the ryanodine receptor from skeletal muscle (Inui, M., Saito, A., and Fleischer, S. (1987) J. Biol. Chem. 262, 1740-1747). The ryanodine receptors from heart and skeletal muscle have similar characteristics in terms of protein composition, morphology, chromatographic behavior, and Ca2+, salt, and phospholipid dependence of ryanodine binding. However, there are distinct differences: 1) the Mr of the receptor is slightly larger for skeletal muscle (Mr approximately 360,000); 2) the purified receptor from heart contains two different affinities for ryanodine binding with Kd values in the nanomolar and micromolar ranges, contrasting with that of skeletal muscle SR which shows only the high affinity binding; 3) the affinity of the purified cardiac receptor for ryanodine was 4-5-fold higher than that of skeletal muscle, measured under identical conditions. The greater sensitivity in ryanodine in intact heart can be directly explained by the tighter binding of the ryanodine receptor from heart. The present study suggests that basically similar machinery (the ryanodine receptor and foot structure) is involved in triggering Ca2+ release from cardiac and skeletal muscle SR, albeit there are distinct differences in the sensitivity to ryanodine and other ligands in heart versus skeletal muscle.

Animals↗
PubMed1987

Purification of the ryanodine receptor and identity with feet structures of junctional terminal cisternae of sarcoplasmic reticulum from fast skeletal muscle.

The ryanodine receptor has been purified from junctional terminal cisternae of fast skeletal muscle sarcoplasmic reticulum (SR). The ryanodine receptor was solubilized with 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS) and stabilized by addition of phospholipids. The solubilized receptor showed the same [3H]ryanodine binding properties as the original SR vesicles in terms of affinity, Ca2+ dependence, and salt dependence. Purification of the ryanodine receptor was performed by sequential column chromatography on heparin-agarose and hydroxylapatite in the presence of CHAPS. The purified receptor bound 393 +/- 65 pmol of ryanodine/mg of protein (mean +/- S.E., n = 5). The purified receptor showed three bands on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with Mr of 360,000, 330,000, and 175,000. Densitometry indicates that these are present in the ratio of 2/1/1, suggesting a monomer Mr of 1.225 X 10(6) and supported by gel exclusion chromatography in CHAPS. Electron microscopy of the purified preparation showed the square shape of 210 A characteristic of and comparable in size and shape to the feet structures of junctional terminal cisternae of SR, indicating that ryanodine binds directly to the feet structures. From the ryanodine binding data, the stoichiometry between ryanodine binding sites to the number of feet structures is estimated to be about 2. Since the ryanodine receptor is coupled to Ca2+ gating, the present finding suggests that the ryanodine receptor and Ca2+ release channel represent a functional unit, the structural unit being the foot structure which, in situ, is junctionally associated with the transverse tubules. It is across this triad junction that the signal for Ca2+ release is expressed. Thus, the foot structure appears to directly respond to the signal from transverse tubules, causing the release of Ca2+ from the junctional face membrane of the terminal cisternae of SR.

Animals↗
PubMed1986

The nature of the modulation of Ca2+ transport as studied by reconstitution of cardiac sarcoplasmic reticulum.

Membrane vesicles capable of energized Ca2+ pumping have been reconstituted from cardiac sarcoplasmic reticulum (SR). Cardiac SR was solubilized with Triton X-100 in a detergent to protein weight ratio of 0.8, and membranous vesicles were reconstituted by removal of detergent with Bio-Beads SM-2 (a neutral porous styrene-divinylbenzene copolymer). The reconstituted vesicles exhibited ATP-dependent oxalate-facilitated Ca2+ accumulation with rates and efficiency comparable to the best reconstituted skeletal muscle preparation (Ca2+-loading rate = 1.65 +/- 0.31 mumol mg-1 min-1, Ca2+-activated ATPase activity = 2.39 +/- 0.25 mumol mg-1 min-1, efficiency (Ca2+/ATP) = 0.69 +/- 0.09). Phospholamban in the reconstituted vesicles was phosphorylated with added catalytic subunit of cAMP-dependent protein kinase to almost the same extent as that in original vesicles. However, phosphorylation of phospholamban had no effect on the Ca2+ accumulation of the reconstituted vesicles. This is to be contrasted with a decrease in the half-maximal concentration of Ca2+ for Ca2+ accumulation (KCa) in the original vesicles from 1.35 +/- 0.08 microM to 0.75 +/- 0.12 microM by cAMP-dependent phosphorylation of phospholamban. On the other hand KCa for the reconstituted vesicles was about 0.5 microM and remained unchanged by phosphorylation, indicating that the Ca2+ pump in the reconstituted vesicles is already fully activated. These results suggest that in normal cardiac SR, phospholamban in the dephosphorylated state acts as a suppressor of the Ca2+ pump and that phosphorylation of phospholamban serves to reverse the suppression.

Animals↗
PubMed1986

Histological development of intervertebral disc herniation.

Sagittal and horizontal sections of 257 intervertebral discs obtained at autopsy and material obtained from 441 operations for herniation of a disc were examined histologically. In the material that was taken at autopsy, myxomatous degeneration of the annulus fibrosus increased in proportion to the age of the subject. The bundles in the internal layer of the annulus fibrosus reversed their usual direction and showed myxomatous degeneration, sometimes resulting in posterior and anterior convex bulging in the internal layer of the anterior and posterior parts of the annulus fibrosus, respectively. When material from a disc was surgically removed as a single free fragment (as in a complete extrusion or a sequestration type of herniation), annulus fibrosus with myxomatous degeneration was found in most material, while the nucleus pulposus rarely was. These results suggest that, from the standpoint of pathomechanism, a protrusion type of herniation of the annulus fibrosus exists in which only the annulus fibrosus is protruded due to reversal of the bundles of the annulus fibrosus, without involvement of the nucleus pulposus. This type of herniation would be a separate entity from the protrusion type of herniation of the nucleus pulposus that occurs when the nucleus pulposus is protruded through a fissure in the annulus fibrosus.

Adult↗
PubMed1986

Generalized granulomatous arteritis with aortic dissection.

A 56 year-old Japanese woman died suddenly after complaining of abdominal pain. Autopsy revealed typical aortic dissection with cardiac tamponade. Histologically, generalized granulomatosis with giant cells resembling sarcoidosis was found. The aorta was most strikingly affected so that granulomatous aortitis was regarded as the cause of the aortic dissection.

Aorta↗
PubMed1985

Purification and characterization of phospholamban from canine cardiac sarcoplasmic reticulum.

Phospholamban, a putative regulator of the Ca2+-dependent ATPase of cardiac sarcoplasmic reticulum (SR), was purified from canine cardiac SR membranes. Cardiac SR was extracted with deoxycholate and fractionated with ammonium sulfate followed by gel permeation high performance liquid chromatography in the presence of the nonionic detergent, octa-ethylene glycol mono-n-dodecyl ether (C12E8), and KI. Further purification was achieved with CM-Sepharose CL 6B column chromatography in the presence of C12E8. The purified phospholamban showed a single band of 22,000 daltons on neutral sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (Weber, K., and Osborn, M. (1969) J. Biol. Chem. 244, 4406-4412) and 27,000 daltons on alkaline SDS gels (Laemmli, U. K. (1970) Nature (Lond.) 227, 680-685). Boiling of phospholamban in 2% SDS produced total conversion into the lower molecular weight component on SDS gels (11,000 on Laemmli gel and 10,500 on Weber and Osborn gel). The apparent molecular weight of phospholamban on SDS gels was slightly increased by cAMP-dependent phosphorylation. The extent of phosphorylation catalyzed by cAMP-dependent protein kinase in the purified phospholamban preparations was about 42 nmol of phosphate/mg of protein when the protein concentration was determined by the method of Lowry et al. (Lowry, O. H., Rosebrough, N. J., Farr, A. L., and Randall, R. J. (1951) J. Biol. Chem. 193, 265-275), or 138 nmol/mg of protein based on the protein concentration estimated by the dye absorption method. Rabbit antisera were prepared against purified phospholamban. The obtained antisera were found to bind to purified phospholamban as well as that in cardiac SR. No reaction was detected in fast skeletal muscle SR by immunofluorescent staining of Western blots. The present preparation of purified phospholamban and the antisera should facilitate further understanding of the regulatory action of phospholamban on the calcium pump ATPase.

Animals↗
PubMed1985

The adreno-sympathetic system, the genetic predisposition to hypertension, and stress.

The blood pressure, heart rate, and plasma catecholamine (CA) response to standing and mental stresses were studied in 14 normotensive subjects with normotensive parents (PNT group), 14 normotensive subjects with hypertensive parent(s) (PHT group), and eight borderline hypertensive patients (BHT group). Mean basal plasma norepinephrine (NE) concentration in BHT group (302 +/- 94 pg/ml) and PHT group (289 +/- 167 pg/ml) were significantly higher than in PNT group (205 +/- 76 pg/ml). Significant differences in the mean basal plasma epinephrine (E) were found only between the PNT and BHT groups (22 +/- 12 vs 43 +/- 18 pg/ml, p less than 0.01). Both plasma NE and E increased significantly on standing in all groups. With mental stress, plasma E increased significantly, though plasma NE did not change significantly in all three groups. The mean changes in blood pressure, heart rate, and plasma CA in response to standing and mental stresses were not different in the three groups. However, a higher incidence (50%) of high blood pressure responders (greater than or equal to 20 mmHg in systolic blood pressure) to mental stress was found in the PHT group compared with PNT (14%) and BHT (12%). The high responders in the PHT group had significantly higher mean plasma E concentrations throughout the experiment. Also, their increases in plasma NE and E in response to mental stress were higher than those of the low responders. The results indicate that genetic predisposition to hypertension plays a significant role in determining plasma catecholamine levels and the responsiveness to stress, especially to mental stress.

Adolescent↗
PubMed1985

Tay-Sachs disease associated with precocious puberty.

A girl with Tay-Sachs disease developed enlargement of the mammary glands at the age of 4 years and menstruation at the age of 6 years. It was demonstrated that the precocious puberty in this patient was due to the hypersecretion of gonadotropins.

Child↗
PubMed1985

Development of quantitative analysis of plasma thromboxane B2 by gas chromatography-mass spectrometry.

In order to diagnose patients in thrombotic state, it is quite important to detect increased concentration of plasma thromboxane B2 (TXB2), a stable catabolite of TXA2. To determine plasma TXB2 levels with high sensitivity and selectivity, we employed gas chromatography-mass spectrometry (GC/MS). The trimethylsilyl (TMS) ether derivatives conventionally employed in GC/MS analysis of prostanoids are not suitable for quantitation of plasma prostanoids, because the mass spectra are deficient in ions with high intensity in the high mass range and TMS ether derivatives are sensitive to moisture. To solve these problems we employed tert-butyldimethylsilyl (t-BDMS) ether derivatives, based on the observation that t-BDMS ether derivatives afforded abundant ions at [M-57]+ and showed good hydrolytic stability. The reaction conditions of tert-butyldimethylsilylation were also examined to optimize the selected ion monitoring response. The t-BDMS ether derivatives of prostanoids were successfully analyzed with a short capillary column with a relatively large diameter, with maintaining good separation. In conjunction with the use of reversed-phase high performance liquid chromatography as purification procedure, a sensitive and reproducible stable isotope dilution assay of plasma TXB2 was developed. The values obtained by this method correlated well with those obtained by the radioimmunoassay we have developed.

6-Ketoprostaglandin F1 alpha↗
PubMed1984

Energy level in large intestinal mucosa in patients with ulcerative colitis.

In 7 patients with ulcerative colitis, the energy level in the large intestinal mucosa was investigated. ATP and energy charge in the intestinal mucosa in ulcerative colitis showed lower levels than those of control subjects. Therefore, energy-deficit may exist in the large intestinal mucosa in ulcerative colitis.

Adenine Nucleotides↗
PubMed1984

[Effect of obstructive jaundice on acute gastric ulceration viewed from gastric mucosal energy metabolism in rats].

The mechanism of acute gastric ulceration in rats with obstructive jaundice was investigated in terms of the changes in the gastric mucosal energy metabolism. Rats were divided into 4 groups as follows: control, vagotomized, jaundiced, and jaundiced and vagotomized group. The water immersion and restraint procedures were performed and the ulcer index was calculated. The change of energy metabolism in the gastric mucosa of corpus and antrum was clarified by measuring ATP and energy charge. The following results were obtained: Vagotomized group showed significant decreased ulcer index, however, the gastric mucosal energy metabolism were unchanged compared to the control group after stress. Jaundiced group showed significant higher ulcer index, and the early, significant depression of the gastric mucosal energy metabolism compared to the control group. Jaundiced and vagotomized group showed significant improvement of ulcer index and gastric mucosal energy metabolism compared to the jaundiced group. The gastric energy metabolism of the corpus revealed more prominent depression than that of the antrum in jaundiced group, and jaundiced and vagotomized group. These data suggested that the deterioration of the gastric mucosal energy metabolism after stress was enhanced under the condition of obstructive jaundice and these results were improved by vagotomy.

Acute Disease↗
PubMed1983

Caldesmon, a calmodulin-binding, F actin-interacting protein, is present in aorta, uterus and platelets.

Caldesmon, a protein originally found in chicken gizzard, was concluded also to be present in bovine aorta, uterus, and human platelets by demonstration of a protein with the following properties: (a) Ca2+-dependent calmodulin-binding; (b) binding to F actin in such way that the binding was broken on Ca2+-dependent binding of calmodulin; (c) cross-reactivity in immune blotting procedures with affinity-purified antibody against gizzard caldesmon; (d) similar subunit Mr-values on SDS-gel to those of gizzard caldesmon. Like gizzard caldesmon, platelet caldesmon was composed of two polypeptide bands of Mr 150 000 and 147 000, but caldesmon in aorta and uterus gave a single band of Mr 150 000. A polypeptide of Mr 165 000 that was immunologically distinct from caldesmon but, like caldesmon, bound to calmodulin and F actin in a flip-flop fashion, was also demonstrated in aorta and uterus.

Animals↗