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Biomedical subjects

U Murakami

Publications and source records attributed to U Murakami.

At least 19 recordsLinked to original sources
PubMed1990

Antihypertensive effect of tryptic hydrolysate of milk casein in spontaneously hypertensive rats.

1. Repeated oral administrations of tryptic hydrolysate of bovine milk casein (CEI) showed antihypertensive effect in spontaneously hypertensive rats. 2. Single oral administration of CEI antagonized the pressor response to angiotensin I. 3. Bovine milk casein hydrolysate inhibited the angiotensin I-converting enzyme (ACE) activity. Three peptides with ACE-inhibiting activity were isolated from CEI. 4. It is suggested that ACE-inhibiting peptides in the tryptic hydrolysate milk casein are absorbed from the intestinal tract and produce an antihypertensive effect.

Administration, Oral↗
PubMed1987

Coexistence of fast and slow myosin isozymes in human external urethral sphincter. A preliminary report.

Human external urethral sphincter muscle was isolated for biochemical research. Myosin samples were prepared and pyrophosphate gel electrophoresis and two-dimensional electrophoresis were performed. Assignment in pyrophosphate gel of myosin isozymes of human external urethral sphincter was carried out by making comparisons with those from human rectus abdominis muscle. Myosin light chains in human external urethral sphincter were identified using two-dimensional electrophoresis. Human external urethral sphincter, similar to other voluntary muscles, is composed of fast and slow twitch muscle fibers, since fast and slow myosin components were shown in both pyrophosphate gel and two-dimensional electrophoretograms.

Electrophoresis↗
PubMed1986

The fiber type of the rabbits' striated external urethral sphincter: electrophoretic analysis of myosin.

The fiber type of the rabbits' external urethral sphincter was investigated with O'Farrell's 2-dimensional electrophoresis of constituent proteins of glycerinated muscle, peptide mapping of myosin heavy chains and non-denaturing pyrophosphate gel electrophoresis of myosin. It was determined as fast type by all three methods. The relative proportions of muscle fibers which were estimated from myosin light chain contents were 88 per cent fast type and 12 per cent slow type. On the basis of the results presented, it was shown to be fast twitch muscle, but not identical to the psoas muscle.

Animals↗
PubMed1985

Contents of myofibrillar proteins in cardiac, skeletal, and smooth muscles.

The in situ contents of myosin, actin, alpha-actinin, tropomyosin, troponin, desmin were estimated in dog cardiac, rabbit skeletal, and chicken smooth muscles. Whole muscle tissues were dissolved with 8 M guanidine hydrochloride and subjected to two-dimensional gel electrophoresis, which is a nonequilibrium pH gradient electrophoresis (Murakami, U. & Uchida, K. (1984) J. Biochem. 95, 1577-1584) with some modification. The amount of protein in a spot on a slab gel was determined by quantification of the extracted dye. Dye binding capacity of individual myofibrillar proteins was determined by using the purified protein. Myosin contents were 82 +/- 7 pmol/mg wet weight in cardiac muscle, 105 +/- 10 pmol/mg wet weight in skeletal muscle, and 45 +/- 4 pmol/mg wet weight in smooth muscle. Actin contents were 339 +/- 15 pmol/mg wet weight in cardiac muscle, 625 +/- 27 pmol/mg wet weight in skeletal muscle, and 742 +/- 13 pmol/mg wet weight in smooth muscle. The subunit stoichiometry of myosin in the three types of muscles was two heavy chains and four light chains, and there was one light chain 2 for every heavy chain. The molar ratio of actin to tropomyosin was 7/1 in the three types of muscles. Striking differences were seen in the molar ratio of myosin to actin: 1.0/4.1 in cardiac muscle, 1.0/6.0 in skeletal muscle, and 1.0/16.5 in smooth muscle.

Actinin↗
PubMed1984

Electrophoretic and ultrastructural analysis of the rabbit's striated external urethral sphincter.

The male rabbit's external urethral sphincter was investigated with O'Farrell's 2-dimensional electrophoretic analysis of myosin light chains and electron microscopy. Its pattern of myosin light chains was different from that of the soleus (predominantly slow twitch muscle) but was very similar to that of the psoas (predominantly fast twitch muscle). Ultrastructurally it was shown to be red muscle resembling the soleus. Therefore the fiber type of the rabbit's external urethral sphincter was determined to be the red (fast) type.

Animals↗
PubMed1984

Two-dimensional electrophoresis of troponin complex with nonequilibrium pH gradient-sodium dodecyl sulfate polyacrylamide slab gel.

A two-dimensional electrophoresis procedure for the separation and analysis of troponin subunits is described in which the protein solution supplemented with 50 mM each of both glutamic and aspartic acids is subjected to nonequilibrium pH gradient electrophoresis in the first dimension. Complete dissolution and gelation of the sample with agarose are essential for analysis of constituent proteins of cardiac myofibrils. Electrophoresis in the first dimension gel is carried out for a relatively short time, 2-3 h. In combination with sodium dodecyl sulfate slab gel electrophoresis (second dimension), three subunits, troponin T, troponin I, and troponin C, of dog cardiac troponin-tropomyosin complex and myofibrils can be simultaneously analyzed quantitatively on a slab gel. The contents of troponin and tropomyosin of cardiac myofibrils were 275 +/- 34 pmol/mg of myofibrillar protein. The molar ratio of troponin T, troponin I, troponin C, and tropomyosin was close to 1 : 1 : 1 : 1 in troponin-tropomyosin complex and myofibrils.

Animals↗
PubMed1980

Temporal and spatial patterns of Purkinje cell formation in the mouse cerebellum.

In an attempt to determine the time of origin and the final localization of Purkinje cells in the cerebellum, pregnant mice were injected with tritiated thymidine successively, four to six times daily, beginning on either day 10, 11, 12, 12.5, 13, or 14 of gestation, considering 6 a.m. on the day when vaginal plugs were found as day 0. Offspring were killed at 30 days of age, and serial sagittal sections of the cerebellum were prepared for autoradiography. Labeled and unlabeled Purkinje cells in the various regions of the cerebellum were counted, and unlabeled ones were considered to be formed earlier than the initiation of the injections. In the medial level of the vermis, the majority of the Purkinje cell population was formed on day 12 of gestation and a few on day 13, whereas the cells in the paravermian and hemispheric portions were formed on days 11 and 12. Thus, a slight lateromedial gradient of the time of Purkinje cell origin was demonstrated. Purkinje cells that were formed after day 12.5 were distributed more in the vermis than in the hemisphere, more in the ventral region of the vermis (lingula, ventral lobule of lobulus centralis, and nodulus) than in the dorsal region (culmen, declive, tuber, pyramis, and uvula), and deep in the vermian fissures, rather than on the surface of the lobules. These findings suggest that postnatally, early maturing regions of the cerebellum may have received many of the later formed Purkinje cells.

Animals↗
PubMed1980

Ultrastructural alteration of rat cardiac myofibrils caused by a myosin-cleaving protease.

Incubation of rat cardiac myofibrils with a myosin-cleaving protease in the presence of EDTA at 25 degrees C caused removal of Z- and M-lines, accompanied by myofibril fragmentation. When rat cardiac muscle I-Z-I brushes were subjected to proteolysis, the protein. Ca2+ was not required for the ultrastructural alterations of myofibrils caused by the protease action.

Animals↗
PubMed1979

Degradation of rat cardiac myofibrils and myofibrillar proteins by a myosin-cleaving protease.

The degradation of rat cardiac myofibrils and their constituent proteins with a myosin-cleaving protease was studied. Electrophoretograms of the digestion products of myofibrils showed that myosin,M-protein, C-protein, and troponin were degraded, but actin and tropomyosin were not. Degradation of these constituents resulted in losses of the Mg2+-ATPase activity and its Ca2+-sensitivity of myofibrils. Incubation of myofibrils with the protease induced the release of alpha-actinin without degradation. Susceptibilities of myosin, actin, troponin, and alpha-actinin purified from rat and pig hearts to the protease were essentially identical to those of the assembled forms in myofibrils. Although the purified tropomyosin was readily degraded into five fragments with the protease, the tropomyosin assembled in myofibrils and actin-tropomyosin complex were insusceptible to the protease. Digestion of myosin in the filamentous state with the protease resulted in the disappearance of myosin heavy chain and light chain 2, producing two fragments having molecular weights of 130,000 and 94,000 which originated from the degradation of heavy chain. The Ca2+- and EDTA-ATPase activities of the degradation products remained unchanged during incubation for 22 h. The actin-activated ATPase activity of myosin was reduced by 30% during incubation for 6 h, and recovered to the original level on adding actin to give a ratio of actin to myosin of 2:1. The pH optima for degradation of myosin in the soluble and filamentous states were 8.5 and 7.0, respectively. The results indicate that cardiac myosin in the filamentous state was more readily degraded with the protease than the myosin in the soluble state.

Actinin↗
PubMed1979

Two types of congenital hydrocephalus induced in rats by X-irradiation in utero: electron microscopic study on the telencephalic wall.

Stage-specific incidences of congenital hydrocephalus induced by X-irradiation of pregnant rats showed a bimodal distribution. At a dose level of 200 R, 100% hydrocephalic offspring were obtained by irradiation at embryonic days 11 and 14. When pregnant rats were subjected to 200 R X-irradiation at embryonic day 11, numerous ventricular cells of the telencephalic wall of the embryo became necrotic during the first 2 hours post-irradiation, but the paraventricular cell-to-cell interconnexions made up of zonulae adhaerentes were less affected. Mitosis took place in the surviving paraventricular surface cells throughout subsequent development. The full-term fetus exhibited little change in the cytoarchitectural arrangement of neural cells and neuropils, although it was only about half the thickness of the untreated control. After 200 R X-irradiation at embryonic day 14, most of the ventricular cells became necrotic within 6 hours. The paraventricular cell-to-cell interconnexions were completely destroyed, and never repaired in subsequent development. Mitosis took place either freely in cell clusters, or in rosettes which formed randomly in the telencephalic wall between 48 and 72 hours post-irradiation. The resulting telencephalic wall of the full-term fetus was also about half the thickness of the control. In the outer part of the tissue, the cortical plate made up of differentiating neuroblasts was hypoplastic, but the inner half was filled with numerous heterotopic masses of pleomorphic cells and bundles of primitive axons. The ependymal layer at the paraventricular surface was never formed. Whether the paraventricular zonulae adhaerentes were destroyed or not by X-irradiation was considered to be an important factor in the determination of the subsequent cytoarchitectural organization of the telencephalic wall.

Animals↗
PubMed1978

Purification and characterization of a myosin-cleaving protease from rat heart myofibrils.

A proteolytic enzyme, which causes the limited degradation of cardiac myosin, was purified from rat heart myofibrils. The purified enzyme (a myosin-cleaving protease) was apparently homogeneous by polyacrylamide gel electrophoresis in the presence and absence of sodium dodecyl sulfate. Autolysis of the purified enzyme was observed at neutral pH without high concentration of CaCl2. The molecular weight was estimated to be 26 000-27 000. The enzyme was active against casein, N-acetyl-L-tyrosine ethyl ester and N-glutaryl-L-phenylalanine-4-nitroanilide (Glu-Phe-NAn), but less active with N-benzoyl-DL-arginine-4-nitroanilide. Optimum pH values for the enzyme were 9.0 for casein and 8.4 for Glu-Phe-NAn. Caseinolytic activity of the enzyme was completely inhibited with phenylmethylsulfonyl fluoride and diisopropylphosphofluoride and partially inhibited with L-1-tosyl-L-phenylalanine chloromethyl ketone (Tos-PheCH2Cl) and soybean trypsin inhibitor. Tos-LysCH2Cl had no effect. Sulfhydryl reagents, metal-chelating agents and metal ions except for Zn2+ had little or no effect on the activity. Degradation of cardiac myosin with the enzyme produced two fragments having molecular weights of 130 000 and 94 000, accompanied by the disappearance of myosin heavy chain and light chain 2. Myosin degradation with the enzyme was more restrictive than with chymotrypsin.

Animals↗
PubMed1978

Teratogenic effect of N-methyl-N'-nitro-N-nitrosoguanidine in mice.

The teratogenic effect on the mouse fetus of a potently mutagenic and carcinogenic agent, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), was studied. Pregnant mice were injected on one of gestation days 7-12 with an intraperitoneal dose of 40, 60 or 80 mg/kg of MNNG, and fetuses were examined on day 18 of gestation. Various malformations affecting the brain, face, vertebra, rib and limb appeared in high frequency. Brain malformations were the most predominant; hydrocephalus, hydromicrocephaly and microcephaly appeared in sequence with developmental stages of treatment, although exencephaly occurred infrequently. Cleft palate, sometimes associated with microglossia and micrognathia, and vertebral anomalies including tail defect were observed following almost every gestation-day treatment. Long-bone defects of fore- and hindlimbs were also predominant. Polydactyly, ectrodactyly and microdactyly frequently occurred together in the fore- or hindlimbs or both in sequence with treatment stages. Ectrodactyly and microdactyly appeared with greater frequency on the left than on the right in both fore- and hindlimbs, but polydactyly and long-bone defects appeared bilaterally.

Abnormalities, Drug-Induced↗
PubMed1977

Studies on the catalytic action of poly-alpha-amino acids. VII. Stereospecificity in the enzyme-like hydrolysis of benzoyl-L-(D)-arginine-p-nitroanilides by copoly (Cys, Glu).

The substrate specificity in the hydrolysis of L-, DL-, and D-BAPA (benzoylarginine-p-nitro-anilide) by copoly (L-Cys, L-Glu) and copoly (D-Cys, D-Glu) was studied, and enzyme-like stereospecific hydrolyses by poly-alpha-amino acids were identified for the first time. The L-type copolymer hydrolyzed L-BAPA faster than D-BAPA and the rates (v) of BAPA hydrolyses by L-type copolymer were found to be in the order vL greater than vDL greater than vD. On the other hand, the D-type copolymer hydrolysed D-BAPA faster than L-BAPA and the rates of BAPA hydrolyses by D-type copolymer were in the order vD greater than vDL greater than vL. In all cases, the reaction followed Michaelis-Menten kinetics when the substrate concentration was corrected, and the optimum conditions of the reaction were pH 6.0 and 40 degrees. The activity appeared after a certain amount of BAPA had combined with the polymer. D- and L-substrates combine competitively with the polymer and the different rates of hydrolysis are presumably due to the different substrate configurations in relation to the conformation of the active site in the polymer. The polymer shows activity near the range of random coil conformation, where some alpha-helical conformation is still present. Only some of the cysteine residues in the copolymer are involved in the hydrolytic activity.

Arginine↗