Search PubMed⌕ Search

Biomedical subjects

T Kawamoto

Publications and source records attributed to T Kawamoto.

At least 289 records · Page 16Linked to original sources
PubMed1988

Central projection of proprioceptive afferents arising from maxillo-facial regions in some animals studied by HRP-labeling technique.

20 ICR mice (adult females) were used for analyzing the axonal projection of the trigeminal mesencephalic tract neurons and 10 Japanese shrew-moles for analyzing that of the snout proprioceptive neurons. The HRP-labeled axons were found to be ipsilaterally terminated in the trigeminal motor nucleus, supratrigeminal nucleus and trigeminal main and spinal tract nuclei, lateral pontine-medullary reticular formation, vagal dorsal motor and hypoglossal nuclei and the lamina V of the C2 spinal cord segments. No HRP-labeled axons were found in the facial and solitary nuclei and the cerebellum. Also, the functional localization of the trigeminal mesencephalic tract neurons was analyzed with the retrograde tracers of fluorescent compounds injected into the jaw-closing muscles having spindles. The fluorescent-labeled neurons were found to be intermingled throughout the nucleus and clustered at the caudal level of the nucleus. Also, double or triple fluorescent-labeled neurons were not observed in the nucleus. The HRP-labeled axon bundle of the facial proprioceptive neurons are divided rostro-caudally into the shorter ascending and the longer descending roots, both running closely dorsal to the trigeminal spinal tract nucleus. The ascending root lies adjacently dorsal to the spinal tract nucleus, giving off the terminal fibers to it, to the wider area of the dorso-medial pontine nuclei and finally to the cerebellar nuclei. At the level of the facial inner genu, it turns medially to meet the facial nerve root, giving off the terminal fibers to the facial motor nucleus and to the raphe nuclei and to the opposite nuclei bilaterally. The HRP-labeled descending root takes the course caudally at least down to the C3 segment of the spinal cord, giving off the terminal fibers to the spinal tract nucleus, the nuclei of the IXth, Xth and XIIth cranial nerves and the pontine-medullary reticular formation. In the spinal cord, it descends bilaterally through the posterior fascicles, giving off the terminal fibers to the dorsal and ventral horns.

Afferent Pathways↗
PubMed1987

Intestinal absorption of trichloroethylene in dogs.

In order to examine the intestinal absorption of trichloroethylene (TRI), we developed the intestinal circulation system of dogs and administered TRI solution at three concentrations (0.1, 0.25 and 0.5%) to the three parts of the intestinal tract (jejunum, ileum, and colon) of the operated dogs. We measured TRI and its metabolites, free-trichloroethanol, trichloroacetic acid, and conjugated trichloroethanol, in serum or blood, urine, bile and circulating solutions. The absorption rates of TRI from the intestine were 50-70% of the administered volume of TRI 2 hr after administration in all groups, and all parts of intestine readily absorbed TRI. Moreover, there were no significant differences in the absorption rates of TRI and water between the jejunum and ileum, and ileum and colon, respectively. The excretion rates of TRI and its metabolites in urine and bile were very low (0.1-0.4%) compared with the volume of absorbed TRI from the intestine 2 hr after administration in all groups. The high degree of absorption of TRI should be considered when threshold limits for TRI in the drinking water, the surface water, and the ground water are established.

Animals↗
PubMed1987

The cholecystohepatic circulation of trichloroethylene and its metabolites in dogs.

In order to examine the cholecystohepatic circulation of trichloroethylene (TRI) and its metabolites, we injected the gallbladder with TRI and its metabolites, i.e. chloral hydrate (CH), free-trichloroethanol (F-TCE), trichloroacetic acid (TCA) and conjugated-trichloroethanol (Conj-TCE), using anesthetized dogs. The absorption rates of water from the gallbladder were 25-30% 2 h after administration for all substances. The absorption rates of substances were 65-70% in the CH, F-TCE and TRI groups, and 40-50% in the Conj-TCE and TCA groups 2 h after the administration. Conj-TCE in the blood absorbed from the gallbladder has a tendency to be directly transported to the venous system rather than to be taken into hepatocytes in the liver. All of the administered substances, in particular, F-TCE might be metabolized to other substances in the gallbladder.

Absorption↗
PubMed1987

Alteration of chloral hydrate metabolism in rats with carbon tetrachloride-induced liver damage.

The metabolism of chloral hydrate (CH) was investigated in the isolated perfused rat liver system. The experiments were performed on rats that were administered carbon tetrachloride (CCl4) subcutaneously for 15 weeks to induce chronic liver damage and on untreated rats. Clearance of CH from the perfusion system was lower in damaged liver than in control liver. In both groups, 50-70% of the added CH was excreted into perfusate as trichloroethanol (TCE) and trichloroacetic acid (TCA) within 120 min. The TCE/TCA ratio was 1:1.3 in the control group compared to 2:1 in the damaged liver group. The findings suggest that CH metabolism in the liver is affected by chronic damage.

Animals↗
PubMed1987

Biliary excretion of apolipoprotein B by the isolated perfused rat liver. Relationship to receptor-mediated uptake of human low-density lipoprotein and biliary lipid secretion.

Since we previously reported that apolipoproteins, the lipid transport proteins of lipoproteins, are present in human bile, we tested the hypothesis that apolipoproteins in bile are derived from circulating lipoproteins and that they are involved in the biliary excretion of lipids. We perfused isolated rat livers with lipoprotein-free solutions and collected bile before and after addition of human low and high density lipoproteins. When human low density lipoprotein was added to solutions perfusing livers isolated from rats previously treated with ethinyl estradiol, a hormone that increases receptor-mediated uptake of low density lipoproteins by hepatocytes, the concentrations in bile of cholesterol and phospholipid, but not bile acids, increased by approximately 25% together with the appearance of small amounts (approximately 1% of the amount perfused) of a metabolized form of human apolipoprotein B in bile. Acetylation of low density lipoprotein, a procedure that prevents this lipoprotein from binding to its receptor on hepatocytes, both abolished the appearance of immunoreactive apolipoprotein B in bile and blocked the increase in biliary cholesterol and phospholipid concentrations. Whereas the addition of a high density lipoprotein to solutions perfusing isolated livers of normal rats was associated with the appearance of small amounts (approximately 1% of the amount perfused) of apolipoproteins A-I and A-II in bile, there were no accompanying changes in the concentrations of biliary lipids. These results suggest that apolipoproteins or their fragments in bile are derived from circulating lipoproteins; in the case of apolipoprotein B, biliary excretion is dependent upon receptor-mediated uptake of low density lipoprotein by the hepatocyte. Our data are also consistent with the hypothesis that certain apolipoproteins may be involved in biliary lipid secretion, although in an as yet unclear manner.

Animals↗
PubMed1987

Preoperative left ventricular function: minimal requirement for successful late results of valve replacement for aortic regurgitation.

Postoperative survival and left ventricular function were studied in 62 patients who underwent aortic valve replacement for isolated, chronic aortic regurgitation between 1978 and 1985. The average follow-up period was 3.8 years. There were three in-hospital and six late deaths. Five (56%) of the nine postoperative deaths were of cardiac-related causes. The mean 7 year survival rate was 83 +/- 5%. Preoperative left ventricular end-systolic volume index was the most important indicator (p less than 0.001) for subsequent cardiac death. The 6.5 year survival rate was 92 +/- 4% for patients with an end-systolic volume index less than 200 ml/m2 compared with 51 +/- 16% for those whose index was greater than 200 ml/m2. None of the 48 patients with an end-systolic volume index less than 200 ml/m2 died of cardiac-related causes. Twenty-three of the 48 patients with an end-systolic volume index less than 200 ml/m2 (Group 1) and 6 of the 12 patients with a higher index (Group 2) underwent repeat catheterization 26 months postoperatively. Preoperative afterload, assessed by end-systolic wall stress, was elevated in both groups, but decreased postoperatively, becoming identical to the afterload in 20 normal control subjects. Although the preoperative ejection fraction was depressed in both groups, the great majority of patients in Group 1, compared with none in Group 2, exhibited normal ejection fraction postoperatively. Thus, in patients who recently underwent surgery for aortic regurgitation, satisfactory late results in both long-term survival and reversal of left ventricular dysfunction were obtained when the preoperative end-systolic volume index was less than 200 ml/m2.

Adolescent↗
PubMed1987

Tyrosine-specific dephosphorylation-phosphorylation with alkaline phosphatases and epidermal growth factor receptor kinase as evidenced by 31P NMR spectroscopy.

The dephosphorylation of phospho-amino acids with alkaline phosphatase (AlPase) from calf intestine or Escherichia coli and the phosphorylation of bovine serum albumin (BSA) with epidermal growth factor (EGF) receptor kinase from human A431 epidermoid carcinoma cells were investigated by 31P NMR spectroscopy. The initial rates of the dephosphorylation of phospho-tyrosine (P-Tyr) and phosphoserine (P-Ser) with AlPase were essentially the same in the one-substrate system. In the two-substrate system (P-Tyr plus P-Ser), however, the ratio of the initial rate for P-Tyr vs. P-Ser was 2.4 to 4.5 depending on the buffer and pH conditions employed. This substantiates for the first time the specificity of AlPases to P-Tyr over P-Ser at the free amino acid level. In the stationary phase of the overall process, the dephosphorylation of P-Ser became slow compared to that of P-Tyr in the one-substrate system. The decrease in the rate for P-Ser was further pronounced in the two-substrate system. For this remarkable effect, the rephosphorylation of serine was responsible, as demonstrated in the reaction mixture containing serine, Pi, and AlPase. BSA phosphorylated by EGF receptor kinase exhibited sharp 31P resonances around 0 ppm at neutral pH, far distant from the peak positions (4.9 ppm) of histone H1 phosphorylated by cAMP-dependent protein kinase. These NMR data are directed evidence that BSA was phosphorylated exclusively at the tyrosyl residues, whereas the phosphorylation of histone H1 was at the seryl residues.

Alkaline Phosphatase↗
PubMed1987

Electron microscopic evidence for epidermal growth factor receptor (EGF-R)-like immunoreactivity associated with the basolateral surface of gastric parietal cells.

Epidermal growth factor (EGF), in addition to its effects on cell growth, has a suppressive effect on gastric hydrochloride secretion. We recently demonstrated EGF-receptor (EGF-R)-like immunoreactivity on human gastric parietal cells by light microscopy. To reveal further the localization of this reaction an immuno-electron microscopical study was performed. 528IgG, an anti-EGF-R murine monoclonal antibody and a polyclonal anti-EGF antibody were employed for immunostaining using the avidin-biotin method. Positive reaction against 528IgG was shown mostly on the outer membrane of parietal cells, except in the apical portion. No reaction was observed on most of the intracytoplasmic membranes including intracellular canaliculi, endoplasmic reticulum and other membranous components. In the basillar portion, the 528IgG-positive parietal cell membrane formed labyrinthine interdigitations. No reaction against anti-EGF was demonstrated in any of the gastric mucosal cells, although a reaction was clearly shown on salivary gland cells. These findings suggest a blood-mediated direct action of EGF on parietal cells.

Cell Membrane↗
PubMed1987

Purification and properties of calmodulin-lysine N-methyltransferase from rat brain cytosol.

A S-adenosylmethionine:protein-lysine N-methyltransferase (EC 2.1.1.43) has been purified from rat brain cytosol 7,080-fold with a yield of 8%, using octopus calmodulin as a substrate. It contains a lysine residue that is not fully methylated. The enzyme was purified by ammonium sulfate fractionation, Sephacryl S-200 gel filtration, and phosphocellulose and octopus calmodulin-Sepharose affinity chromatographies. Among protein substrates, it was highly specific toward octupus calmodulin. The Km values for octopus calmodulin and S-adenosyl-L-methionine were found to be 2.2 X 10(-8) M and 0.8 X 10(-6) M, respectively. The molecular weight was estimated to be 57,000 by gel filtration and the pH optimum was between 7.5 and 8.5. The enzyme was stimulated in the presence of 10(-7) M Mn2+ and 10(-4) M Ca2+. HPLC of the acid hydrolysate of methyl-3H-labeled calmodulin showed the formation of epsilon-N-mono, epsilon-N-di, and epsilon-N-trimethyllysine. Reverse-phase HPLC of tryptic peptides of the methyl-3H-labeled calmodulin demonstrated that the labeled N-methyllysine lies in the 107-126 peptide. These findings suggest that this enzyme methylated a specific lysine residue of octopus calmodulin.

Animals↗
PubMed1987

The metabolite ratio as a function of chloral hydrate dose and intracellular redox state in the perfused rat liver.

Chloral hydrate (CH), an intermediate metabolite of trichloroethylene, is reduced to trichloroethanol (TCE) by alcohol dehydrogenase and aldehyde reductase, and is also oxidized to trichloroacetic acid (TCA) by the nicotinamide adenine dinucleotide (NAD)-dependent enzyme, CH dehydrogenase. Alcohol dehydrogenase requires reduced NAD (NADH), aldehyde reductase requires reduced nicotinamide adenine dinucleotide phosphate (NADPH) and CH dehydrogenase requires NAD to complete the reaction. It is unclear which reaction is predominant at the physiological redox level in intact liver cells. To study this question, we perfused the livers of well-fed rats with Krebs-Ringer buffer solution containing 0.1 mM pyruvate/1.0 mM lactate. The levels of TCE and TCA in the effluent were measured by gas chromatography, and the fluorescence of reduced pyridine nucleotides was measured with a surface fluorometer. When a low concentration (below 0.25 mM) of CH was administered, more TCA than TCE was produced. When a high concentration of CH was administered (over 0.5 mM), TCE production was greater. Reduced pyridine nucleotides decreased inversely with the CH concentration. Even at low CH concentrations, pyridine nucleotides were not reduced. When 10 mM lactate was added to the perfusate in order to reduce the pyridine nucleotides in the liver cells, the TCE/TCA ratio increased. On the other hand, the TCE/TCA ratio tended to fall following the addition of 5.0 mM pyruvate. In conclusion, the TCE/TCA ratio was altered according to the concentration of CH, and to the redox level of pyridine nucleotides in the liver.

Animals↗
PubMed1987

Extrahepatic metabolism of chloral hydrate, trichloroethanol and trichloroacetic acid in dogs.

To examine the details concerning that part of TRI metabolism which was carried out by the extrahepatic organs, we studied the extrahepatic metabolism of chloral hydrate (CH), free-trichloroethanol (F-TCE) and trichloroacetic acid (TCA) using a method developed in our laboratory. Bypass and non-bypass dogs were given CH, F-TCE and TCA, and we compared the concentrations these substances and their metabolites in the serum and urine of the two groups of animals. In the bypass dogs, F-TCE, TCA and conjugated-trichloroethanol (Conj-TCE) appeared in the blood and urine 30 min. after the CH administration, and TCA and Conj-TCE appeared 30 min. after the F-TCE. All levels of administered substance were higher in bypass dogs than in non-bypass dogs, and the compounds were metabolized in small amounts in the extrahepatic organs compared with the liver. Therefore, administered substances remained at high levels in the serum and were excreted in large amounts in the urine in the form of unchanged substances. The metabolized percentage volumes of CH to TCA in the bypass dogs were 10-20%, and those of F-TCE to TCA were very small, while these percentage values of CH to F-TCE were the same or slightly smaller, respectively. Moreover, trichloroethylene (TRI) acts to decrease the leukocyte count in the blood, but the TRI metabolites described above do not have this function.

Animals↗
PubMed1987

The metabolism of trichloroethylene and its metabolites in the perfused liver.

The metabolism of trichloroethylene (TRI) and its metabolites, chloral hydrate (CH), trichloroethanol (free-TCE) and trichloroacetic acid (TCA), were examined in the isolated perfused rat liver, to clarify the role of the liver in the metabolism of TRI. TRI was rapidly converted to TCE and TCA by the perfused liver. TCA was produced from TRI about 2.5 times greater than was total-TCE. CH was metabolized to TCE and TCA immediately. TCA was also a dominant metabolite of CH over total-TCE. TCE(free type) was speedily conjugated by the liver. A portion of TCE was converted to TCA. Less than 10% of these metabolites produced by the liver were excreted into the bile. Most of them appeared in the perfusate.

Animals↗