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T Sawamura

Publications and source records attributed to T Sawamura.

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

Structure-activity relationships of endothelin: importance of the C-terminal moiety.

The vasoconstrictor activities of various forms of derivatives of endothelin (ET) were characterized in vitro by measuring the contraction of porcine coronary artery strips. The removal of the C-terminal Trp21 reduced the molar potency of the peptide by nearly 3 orders of magnitude. The removal of amino acid residues from the C-terminus of ET(1-20) further attenuated the activity. Replacement of Trp21 with D-Trp, reduction and carboxamidomethylation of the four Cys residues, or cleavage at Lys9 by lysyl endopeptidase all lowered the potency approximately 200 fold. While both native ET and [D-Trp21]ET induced a very slow and sustained vasoconstriction, the other derivatives of ET listed above showed a much more rapid kinetics of vasoconstriction. These results indicate that the C-terminal Trp of ET is especially important for the potent and extremely long-lasting vasoconstrictor activity characteristic to ET.

Animals↗
PubMed1988

[Surgical managements of massive involvement of small bowel and of short gut syndrome].

Despite the recent advent of total parenteral nutrition (TPN), the long-term survival of the patients with short gut syndrome is not satisfactory with complications of catheter-related sepsis and cholestasis. The causes of short gut syndrome in pediatric surgery are multiple intestinal atresias, necrotizing enterocolitis (NEC), and midgut volvulus. For the multiple atresias, multiple anastomosis without resection has been successfully undertaken to avoid developing short gut syndrome for the last 17 years. For the massive involvement of the intestines due to NEC or volvulus, high jejunostomy and peritoneal drainage with TPN support have been tried for the last two patients and successfully weaned from the TPN within two months after closure of jejunostomy. However, in case 2 malabsorption has been persistent presumably due to a severe degree of mucosal damage occurring in the remaining intestines. Whether this eventually gets back to the normal or not is unknown. For the patients with short gut syndrome, small bowel reversal procedure was successfully done and now doing well 10 years after surgery. This paper reports details of these 3 cases.

Enterocolitis, Pseudomembranous↗
PubMed1986

Three molecular forms of a rat asialoglycoprotein receptor.

It has been reported that a rat asialoglycoprotein receptor is composed of three polypeptide chains with molecular masses of 43, 54, and 64 kilodaltons (43, 54, and 64-Kd forms) and that the first has a different primary structure from the latter two forms. Incorporation of [3H]leucine into these forms showed that no precursor-product relationship is found between the 54-Kd and 64-Kd forms. The half-life of the 43-Kd form (25 h) was shorter than those of the 54-Kd and 64-Kd forms (66 and 70 h, respectively). Glycopeptides of the three forms were prepared from rat livers previously labeled in vivo with [3H]glucosamine. Gel filtration analysis of the glycopeptides before and after endo H treatment revealed that they were all resistant to endo H. Alkali treatment did not change the elution position appreciately. These results indicate that the three molecular forms contained only complex oligosaccharide chains. The receptor was prepared from rat livers previously treated with tunicamycin in vivo and subjected to SDS-PAGE. A distinct band with a molecular mass of 33 Kd was observed. The receptor was also immunoprecipitated from rat hepatocytes in primary culture previously labeled with [35S]methionine and analysed by SDS-PAGE and fluorography. In addition to the major 43-Kd form, a band with a molecular mass of 41 Kd was found and tunicamycin treatment gave rise to a 33-Kd component, which is in good agreement with the receptor purified from tunicamycin treated rats. It is suggested that the 43-Kd form is synthesized as a 33 Kd polypeptide, cotranslationally glycosylated to form the 41 Kd component and then processed to the final 43-Kd form. We also think that the 43-Kd form could bind to asialoorosomucoid-Sepharose 4B without its carbohydrate chains.

Animals↗
PubMed1986

Use of a gated counting method for radiation monitoring at a 45-MeV electron LINAC facility.

A fixed-point radiation monitoring system based on the gated counting method, which was previously reported by us, was constructed for a 45-MeV electron LINAC facility. It was tested under different beam intensities of the accelerator both at the current and repetition rates. It showed excellent dynamic response (from 2.5 X 10(-11) to 1.0 X 10(-8) Sv h-1) to the intensity variation of the radiation source. It was demonstrated that the system was very useful in monitoring an extremely low-level radiation from a pulsed source.

Electrons↗
PubMed1985

Phosphorylation of the rat hepatocyte asialoglycoprotein receptor.

Phosphorylation of asialoglycoprotein receptor was investigated by using rat hepatocytes. Analysis of the purified receptor by SDS-PAGE and autoradiogram revealed that the 64 and 54 Kd polypeptides of the receptor were phosphorylated but the 43 Kd one was not and that phosphorylation took place at the cell surface. These results are compatible with the fact that the 64 and 54 Kd species exist predominantly at the cell surface. The sites of phosphorylation were identified as Ser and Thr with no detectable radioactivity in phosphotyrosine.

Amino Acids↗
PubMed1985

Clinical application of the measurement of serum asialoglycoproteins to estimate residual liver function in patients with chronic liver diseases with or without hepatocellular carcinoma.

The correlation between the amount of asialoglycoproteins and results of conventional liver function tests was studied in patients with chronic liver diseases, with or without hepatocellular carcinoma. The objective was to determine the clinical significance of the measurement of levels of serum asialoglycoproteins. The levels were elevated in accordance with the progress of liver diseases, and correlated with the decrease in albumin content, cholinesterase activity, the ratio of esterified cholesterol to total cholesterol and to the increase of indocyanine green retention at 15 min (p less than 0.001). There was no correlation with values of glutamic oxaloacetic and pyruvic transaminases. The amount of serum asialoglycoproteins also correlated with survival time in fatal cases of cirrhosis and/or hepatocellular carcinoma. Bilirubin and bile acids did not interfere with the measurement of serum asialoglycoproteins in cases of hyperbilirubinemia. Serum asialoglycoprotein levels are a good indicator of hepatic functional reserve in patients with chronic liver diseases, with or without hepatocellular carcinoma.

Asialoglycoproteins↗
PubMed1985

Intracellular transport of a newly synthesized asialoglycoprotein receptor in rat liver.

Intracellular transport of a newly synthesized asialoglycoprotein receptor was studied biochemically using a monospecific antibody for the receptor. Pulse-labeling by intravenous injection of [3H]leucine and pulse-chasing after 10 min by cycloheximide injection resulted in the maximal labeling of the receptor in the rough microsomes at 15 min, in the smooth microsomes and the heavy Golgi subfraction (GF3) at 25 min and in the intermediate plus light Golgi subfraction (GF1+2) at 30 min. By 60 min, the labeling in GF1+2 had decreased and leveled off. In the plasma membrane fraction, the labeled receptor first appeared at 20 min, increased rapidly and also reached a constant level at 40-60 min. Intracellular movement of the newly synthesized receptor in the GF1+2 and plasma membrane fractions was also investigated by purifying the receptor protein from the GF1+2 and plasma membrane fractions by affinity chromatography. It was revealed that the specific radioactivities of the receptor in the two fractions become equilibrated after 60-120 min. The receptor of the various membrane fractions was also pulse-labeled in vivo for 20 min simultaneously with [3H]glucosamine and [14C]leucine, and pulse-chased for the following 40 min. After pulse-labeling for 20 min, the ratio of the radioactivity of [3H]glucosamine or [3H]sialic acid to [14C]leucine of the receptor from the rough and smooth microsomes, and GF3, GF2, and GF1 increased in that order. That of the receptor from the plasma membrane fraction was infinitely higher, because, while a significant amount of 3H-radioactivity was incorporated into the receptor in the Golgi apparatus, only a negligible amount of 14C-radioactivity was incorporated into the same receptor in the plasma membrane due to the delay in the arrival of [14C]leucine labeled receptor to the plasma membrane. After chasing for 40 min, however, the same radioactivity ratios of the GF1 and plasma membrane fractions approached each other. All these results strongly suggest that the distribution of the newly synthesized receptor becomes rapidly equilibrated between the trans-Golgi components and plasma membranes probably by repeated recycling of the receptor protein between the two membranes.

Animals↗
PubMed1985

Release of hepatic mitochondrial ornithine transcarbamylase into the circulation in D-galactosamine-treated rats. Identification of serum ornithine transcarbamylase as the intact form of the mitochondrial enzyme.

A single injection of D-galactosamine into rats caused acute liver cell injury, and the activity of ornithine transcarbamylase in the serum increased about 600-fold as compared with that in the normal serum. Some properties of the serum enzyme from galactosamine-treated rats have been studied together with those of the mitochondrial enzyme in liver. Both the enzyme activities gave similar pH profiles, showing an optimum of pH 8.5. Apparent Km values of the serum enzyme for ornithine under the standard conditions at pH 7.4 and pH 7.7 were 1.59 mM and 0.94 mM, respectively, and those of the mitochondrial enzyme were 1.69 mM and 0.97 mM, respectively. The Km value of the serum enzyme for carbamyl phosphate was 0.34 mM, which is similar to that of the mitochondrial enzyme. The mitochondrial enzyme was purified 78-fold to homogeneity with a 45% yield by ammonium sulfate fractionation, heat treatment, 2nd ammonium sulfate fractionation, and phenyl-Sepharose CL-4B and CM-Sephadex C-50 column chromatographies. The specific activity of the purified enzyme was 282 mumol of citrulline formed per mg of protein per min at 37 degrees C. The mitochondrial and serum enzymes have a molecular weight of 115,000 as determined by Sephacryl S-300 gel filtration. Antibody specific for the mitochondrial enzyme was raised, and the immunological properties of the serum enzyme were examined. In immunoinhibition experiments, a decrease of the serum enzyme activity as well as the mitochondrial enzyme was observed on increasing the amount of the antibody.

Animals↗
PubMed1985

Measurement of radiation leaked from a 45-MeV linear accelerator facility by gated counting.

By the gated counting method that had been developed by the authors the spatial dose distributions at the boundary and inside of a 45-MeV electron linear accelerator (linac) facility were obtained using a NaI(Tl) scintillation probe and a counting system. Both distributions of pulse height and radiation propagation time were also measured. At the facility boundary, dose rates measured ranged from 0.16 microR hr-1 to 0.86 microR hr-1, which were less than one-tenth the natural background. At measurement in the linac control room, two different leakage sources, one originating at and around the accelerator and the other at a microwave power system, were discriminated by measuring pulse height and time distributions simultaneously.

Environmental Exposure↗
PubMed1985

The effect of galactosamine on rat liver cytochrome P-450 activities.

The effect of galactosamine on hepatic drug metabolizing activities was examined in rats. In the microsomal fraction, the contents of cytochrome P-450 (P-450) and cytochrome b5 (b5) and the activity of NADPH-cytochrome c reductase (reductase) were examined for 7 days after galactosamine administration. In addition, substrate metabolizing activities in damaged microsomes were examined using four substrates: aminopyrine, aniline, benzo(a)pyrene (B(a)P) and 7-ethoxycoumarine (7-EC). The contents of P-450 and b5 and the activity of reductase showed a minimal value after 3 days of galactosamine administration and then gradually increased, reaching to the control level after 7 days. All four substrate metabolizing activities showed a similar response as the content of P-450, but the decrement among the four activities was not uniform. The activities of B(a)P hydroxylation and 7-EC deethylation were more impared than those of aminopyrine demethylation and aniline hydroxylation. This nonuniformity was clear on the activity based on P-450. This result suggested that galactosamine disturbed the population of multiple P-450 subtypes, and each P-450 subtype was damaged to the various extent by galactosamine administration.

Alanine Transaminase↗
PubMed1984

Glycosylation of a receptor specific for asialoglycoproteins in rat liver.

Glycosylation of a rat receptor specific for asialoglycoproteins was investigated in vivo by using monospecific antibody. After intravenous injection of [3H]mannose, the receptor protein was immunoprecipitated from various subcellular fractions and the glycopeptide and oligosaccharide chains of the protein were prepared by treatment with pronase and endo-beta-N-acetylglucosaminidase H. The glycopeptides thus prepared from the rough and smooth microsomes and Golgi heavy fraction (GF3) were all sensitive to endo H and most of the endo H-sensitive oligosaccharides were eluted at the position considered to correspond to Man8GlcNAc on high-resolution Bio-Gel chromatography. Endo H-resistant forms were first detected in the Golgi intermediate fraction (GF2) and significantly in the light Golgi fraction (GF1), suggesting the formation of the complex-type oligosaccharide chains in the latter fraction. This view was also supported by the almost exclusive addition of the terminal sugars such as N-acetylglucosamine, galactose, and sialic acid in GF1. These results suggest that the major form of the oligosaccharide chains from the endoplasmic reticulum to the Golgi apparatus is Man8GlcNAc2 and that the processing of these large mannosyloligosaccharide chains and subsequent addition of terminal sugars to them are performed successively in the trans-Golgi region.

Animals↗
PubMed1984

Topology of asialoglycoprotein receptor in rat liver subcellular fractions: a ferritin immunoelectron microscopic study.

Direct ferritin immunoelectron microscopy was used to visualize the asialoglycoprotein receptor in various rat liver subcellular fractions. The cytoplasmic surfaces of cytoplasmic organelles such as the rough and smooth microsomes, Golgi cisternae and lysosomes showed hardly any ferritin label exception for the slight labeling of secretory granules found mainly in the light Golgi fraction (GF1). Occasionally, however, open membrane sheet structures, smooth vesicular or tubular structures heavily labeled with ferritin, were present in all these subcellular fractions. These structures probably correspond to fragmented sinusoidal or lateral hepatocyte plasma membranes recovered to these subcellular fractions. When the limiting membranes of the secretion granules were partially broken by mechanical force, a number of ferritin particles frequently were seen attached in large clusters to the luminal surface of the membrane, the cytoplasmic surface of the corresponding domain being slightly labeled. These observations are strong evidence that the receptor protein is never translocated vertically throughout the intracellular transport from ER to plasma membrane via Golgi apparatus and from plasma membrane back to trans-Golgi elements and also in lysosomes, always exposing the major antigenic sites to the luminal or extracellular surface and the minor counterparts to the cytoplasmic surface of the membranes. The receptor protein also is suggested to be concentrated in clusters on the luminal surface of secretion granules when they form on the trans-side of the Golgi apparatus.

Animals↗