Sliding wear of various composite resins and bovine enamel.
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Animals↗
Biomedical subjects
M Fujioka
Publications and source records attributed to M Fujioka.
[The influence of palatal plate thickness on functional mandibular movement].
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Denture Bases↗
[Studies on physical properties of light cured veneer resin].
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Chemical Phenomena↗
Nephrotoxicity of ferric nitrilotriacetate. An electron-microscopic and metabolic study.
Repeated intraperitoneal injections of ferric nitrilotriacetate (Fe-NTA) induce nephrotoxic features such as proximal tubular necrosis and renal failure, an unexpected phenomenon for a ferric compound. The mechanism of Fe-NTA toxicity was investigated by electron microscopy and respiration studies of renal cortical mitochondria in rats. Four hours after a single intraperitoneal injection of Fe-NTA, 5 mg iron/kg body wt, loss of microvilli, increased number of cytoplasmic vacuoles, electron-dense cytoplasmic deposits, mitochondrial swelling, karyorrhexis, and rupture of cytoplasmic membrane were observed in proximal tubular epithelia. At 24 hours, an increased number of cells had become necrotic. Polarographic studies of mitochondria from renal cortex 4 hours after Fe-NTA treatment showed a significant decrease in State 3 respiration and DNP-uncoupled respiration, whereas little change was observed in State 4 respiration and ADP/O.
Acid Phosphatase↗
Chemical modification of S-adenosylhomocysteinase by a water-soluble carbodiimide.
S-Adenosylhomocysteinase (EC 3.3.1.1) from rat liver is inactivated by 1-cyclohexyl-3-(2-morpholinoethyl)carbodiimide metho-p-toluenesulfonate (CMC) in a pseudo-first-order fashion. The rate of inactivation is linearly related to the concentration of the reagent, and a second-order rate constant of 4.94 +/- 0.27 M-1 min-1 is obtained at pH 5.5 and 25 degrees C. The inactivation does not involve change in the quaternary structure of the enzyme nor modification or release of the enzyme-bound NAD. Lack of modification at tyrosine, serine, cysteine, histidine, and lysine residues and the fact that the inactivation is favored at low pH suggest that the inactivation is caused by the modification of a carboxyl group. Statistical analysis of the relationship between the residual enzyme activity and the extent of modification, and comparison of the number of residues modified in the presence and absence of the substrate adenosine show that, among four reactive residues per enzyme subunit, only one residue which reacts more rapidly with the reagent than the rest is critical for activity. The CMC-modified enzyme binds adenosine and S-adenosylhomocysteine and is able to oxidize the 3' hydroxyl of these substrates, but apparently fails to catalyze the abstraction of the 4' proton of adenosine.
Adenosylhomocysteinase↗
S-Adenosylhomocysteinase from rat liver. Evidence for structurally identical and catalytically equivalent subunits.
Lines of evidence are presented which indicate that rat liver S-adenosylhomocysteinase consists of four identical or nearly identical subunits. Cross-linking of the enzyme with dimethyl suberimidate followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis yields four distinct protein bands with molecular weights of 47,000, 93,000, 145,000, and 190,000. The molecular weight of the largest protein is in excellent agreement with that of the native enzyme. Carboxypeptidase A liberates 4 mol of COOH-terminal tyrosine/mol of enzyme, and the number of arginine-containing peptides in a tryptic digest of the enzyme is one-fourth of that arginine residues present in the enzyme. The enzyme reversibly binds 4 mol of the substrate adenosine in a noninteracting manner, and the binding is associated with the reduction of 3.2 mol of enzyme-bound NAD+. However, in the presence of dithiothreitol, the same compound causes a time-dependent irreversible loss of enzyme activity concomitant with the formation of 3.6 mol of enzyme-bound NADH/mol of enzyme. Studies with adenine-labeled adenosine shows that radioactivity corresponding to 3.8 mol of substrate is tightly bound to the inactivated enzyme. Since the inactivation is apparently the consequence of reaction of dithiothreitol with an enzyme-bound intermediate as revealed by the kinetics of inactivation, these results support the conclusion that the four subunits of rat liver S-adenosylhomocysteinase are functionally equivalent.
Adenosine↗
Determination of testosterone propionate in human plasma by gas chromatography-mass spectrometry.
A specific, sensitive and accurate quantitative analysis of testosterone propionate in human plasma was developed using gas chromatography-mass spectrometry-selected-ion monitoring. For the calculation of testosterone propionate in plasma, peak height ratios were measured by selected-ion monitoring performed on the molecular ions of the trifluoroacetyl derivative of testosterone propionate (m/z 440) and testosterone propionate-19,19,19-d3 (m/z 443). The sensitivity of the method was judged from the lower limit of the detection of the mass spectrometer which was at 20 pg. The inter-assay coefficients of variation and relative error at a concentration of 1.31 ng/ml of plasma were 5.47% and -2.3%, respectively. The method described was applied to the determination of plasma concentrations of testosterone propionate-19,19,19-d3 following an intramuscular dose of testosterone propionate-19,19,19-d3 in a healthy male volunteer.
Adult↗
Effects of amosulalol on the electrical responses of guinea-pig vascular smooth muscle to adrenoceptor activation.
The effects of amosulalol, a newly synthesized sulphonamide-substituted phenylethylamine derivative, on electrical responses of smooth muscle cells of the guinea-pig vascular tissues to noradrenaline, isoprenaline and perivascular nerve stimulation were investigated. Amosulalol (10(-10) -10(-5)M) did not alter the resting membrane potential of smooth muscle cells of the mesenteric artery, the mesenteric vein, the main pulmonary artery and the portal vein. In the mesenteric artery, main pulmonary artery and portal vein, but not in the mesenteric vein, membrane depolarizations produced by noradrenaline were antagonized by amosulalol. In the portal vein, membrane hyperpolarizations produced by isoprenaline were antagonized by amosulalol. In the mesenteric artery, amosulalol (over 10(-6)M) enhanced the amplitude of excitatory junction potentials (e.j.ps) produced by perivascular nerve stimulation. Amosulalol antagonized the noradrenaline-induced decrease in the e.j.p. amplitude; this effect was much weaker than that of phentolamine. Amosulalol also antagonized the isoprenaline-induced enhancement of the e.j.p. amplitude. In the mesenteric vein, the slow depolarizations produced by perivascular nerve stimulation were depressed by amosulalol (over 10(-6)M), but the effect was much weaker than that of prazosin, yohimbine or phentolamine. Actions of amosulalol on electrical properties of vascular tissues can be summarized as follows: amosulalol blocks alpha 1- and beta-adrenoceptors. It also blocks alpha 2-adrenoceptors, though weakly.
Animals↗
Congenital anorectal anomaly: CT evaluation.
Anorectal anomalies were evaluated by computed tomography (CT) scanning in 23 patients. CT scans showed clearly the anatomy of the anal sphincter muscles in relation to the intestine and the amount of muscle mass present. These findings correlated well with the results of direct visualization and electromyograms in patients who underwent surgery. The information revealed by CT scans is considered important in preoperative planning for surgical repair and in predicting a patient's prognosis. In cases of postoperative incontinence, CT scans demonstrated the location of the pulled-through intestine, including whether it had been correctly placed in the levator sling. Where the intestine was outside the levator sling, CT scans could be used in considerations of further surgery.
Anal Canal↗
Connections of the fronto-parietal operculum and the postcentral gyrus with the posterior ventral thalamic nucleus, especially its medial nucleus, in monkeys.
In 22 crab-eating monkeys (Macaca irus), either lesions or HRP injections were made in the frontol parietal operculum and, for the purpose of contrast, in the postcentral gyrus to observe their fiber connectionl with the posterior ventral nucleus (VP). The exposed opercular part, reported to consist of areas 3b, 1, and 2 showed scanty fiber connections with VP. The buried parietal operculum had connections with the media (VPM) and lateral (VPL) nuclei of VP, corresponding to the second somatic sensory cortex (SII). This cortica area was connected, in VPM, to its ventromedial part, while the base of the postcentral gyrus, the ordinary face area of SI, was connected to its lateral-most part. This suggests that the ventromedial part of VPM is more intimately related to SII, and its lateral-most part to SI. In contrast, the SI and SII areas of VPL overlapped more extensively with each other. The cortical area which received fibers from the parvocellular part of VPM (VPMpc) lay in the frontal operculum, especially in its buried part. This area extended caudally beyond the precentral dimple and included areas 1 and 2 of the buried frontal operculum, indicating that its posterior extent was wider than the pure taste cortical area. Spinothalamic terminations in VPL and the PO nuclear group were discussed in relation to cortical connections of these thalamic nuclei. It was suggested that spinothalamic input could be relayed to both postcentral and opercular cortices. The relation of the spinothalamic input to the PO group appeared to be minor.
Animals↗
Eperisone, an antispastic agent, possesses vasodilating actions on the guinea-pig basilar artery.
The effects of eperisone, an antispasmodic, on the electrical and mechanical properties of smooth muscle cells of the guinea-pig basilar artery were investigated. Eperisone (below 50 microM) did not modify the membrane potential, membrane resistance, excitatory junction potential evoked by perivascular nerve stimulation or the K- and 5-hydroxytryptamine-induced depolarizations. However, in concentrations over 10 microM, this agent reversibly blocked the spontaneously generated and evoked action potentials in the presence of 5 to 8 mM tetraethylammonium. The contractions evoked by high concentrations of K, 5-hydroxytryptamine or direct muscle stimulation in the presence of tetraethylammonium were dose dependently inhibited by eperisone, in concentrations over 1 microM. In Ca-free 2 mM ethylene glycol bis(beta-aminoethyl ether)-N,N'-tetraacetic acid-containing solution, 5-hydroxytryptamine produced only a single contraction. Eperisone inhibited this contraction to the same extent as that observed in the presence of Ca. These results indicate that eperisone possesses the property of a Ca antagonist on smooth muscle tissues of the guinea-pig basilar artery, in addition to the action of antispastic agent, i.e., this agent blocks the voltage-dependent influx of Ca at the smooth muscle membrane, but not at the nerve terminals, and inhibits the action of Ca in cells through inhibition of the contractile protein.
Animals↗
Snare applying the Ti-Ni shape memory alloy for nasal polypotomy and tonsillectomy.
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Humans↗
Molecular cloning of cDNA for rat glycine methyltransferase.
Using a highly purified preparation of glycine methyltransferase mRNA, double-stranded cDNA was synthesized and inserted into the PstI site of pBR322. The resulting recombinant DNA was used to transform E. coli X 1776 by conventional methods. Among tetracycline-resistant transformants, a number of colonies were found to contain cDNA sequence for glycine methyltransferase as examined by hybrid-selected translation. A restriction endonuclease cleavage map was constructed covering about 720 base pairs. With the cDNA as the probe, the content of the glycine methyltransferase mRNA was quantitated in various rat tissues and was found to be proportional to the specific enzyme activity.
Animals↗
5'-[p-(Fluorosulfonyl)benzoyl]adenosine-mediated inactivation of S-adenosylhomocysteinase.
Rat liver S-adenosylhomocysteinase (EC 3.3.1.1) is inactivated by 5'-[p-(fluorosulfonyl)benzoyl]adenosine following pseudo-first-order kinetics. A plot of the apparent first-order rate constant for inactivation vs. the 5'-[p-(fluorosulfonyl)benzoyl]adenosine concentration exhibits a hyperbolic curve indicative of the formation of a reversible enzyme-reagent complex prior to the inactivation. Values of 71.0 +/- 7.7 microM and 0.14 +/- 0.01 min-1 are estimated for Kd and k, respectively, at pH 8.25 and 25 degrees C. The substrate adenosine and a competitive inhibitor adenine completely protect the enzyme against inactivation. Values of dissociation constant for these ligands calculated from the protection experiments agree well with those obtained by other means, indicating that 5'-[p-(fluorosulfonyl)benzoyl]adenosine competes with these ligands for the same binding site. The inactivation is not reversed by dialysis against phosphate buffer or tris(hydroxymethyl)aminomethane hydrochloride buffer, but a full enzyme activity is regained by treatment with dithiothreitol. The inactivation is not accompanied by covalent attachment of the reagent but is correlated with the loss of two sulfhydryl groups per enzyme subunit. Thus, the inactivation appears to result from a reagent-mediated formation of a disulfide between two cysteine residues in close proximity. The 5'-[p-(fluorosulfonyl)benzoyl]adenosine-modified enzyme which is not capable of catalyzing the overall reaction can still catalyze the partial reactions such as the oxidation of the 3'-hydroxyl and the abstraction of the 4'-proton of adenosine.
Adenosine↗
Chemical mechanism of saccharopine dehydrogenase (NAD+, L-lysine-forming) as deduced from initial rate pH studies.
The variation of kinetic parameters with pH has been determined so as to gain insight into the chemical mechanism of the saccharopine dehydrogenase (NAD+,L-lysine-forming)-catalyzed reaction. In the direction of reductive condensation of lysine and alpha-ketoglutarate (reverse reaction), the V/K profile for lysine shows a group with a pK of 6.3 must be unprotonated and a group with a pK of 8.0 must be protonated for activity. Similar pK's are obtained in the pKi profile for ornithine, which acts as a linear competitive inhibitor with respect to lysine. Temperature and solvent perturbation studies show that these groups are probably histidines. The V/K profile for alpha-ketoglutarate reveals a single group with pK = 8.4 (probably lysine) that must be protonated. It is proposed that one of the histidines is involved in the binding of the epsilon-amino group of the substrate lysine and the positively charged lysine residue hydrogen bonds to the carbonyl oxygen of alpha-ketoglutarate. In the direction of saccharopine cleavage, the V/K profile for saccharopine shows that two groups with pK values of 6.0 and 7.1, possibly a histidine and lysine, must be unprotonated for its reaction with the enzyme X NAD+ complex. The log V-pH plots for the forward and reverse reactions both show sigmoidal curves. At low pH, the activity is lower for the forward reaction, and is higher for the reverse reaction. The ionization of a single group appears to be responsible for the change in activity. A tentative scheme for the chemical reaction is presented.
Chemical Phenomena↗
Spectrophotometric studies of the interaction of S-adenosylhomocysteinase with adenosine, adenine and cordycepin.
The spectral changes observed on interaction of S-adenosylhomocysteinase with adenine and cordycepin are approximated by the addition of dimethylsulfoxide to the aqueous solutions of these compounds, but not by protonation of the compounds. Although adenosine when bound to the enzyme undergoes partial reactions, it gives a spectral change similar to those obtained with adenine and cordycepin, except for the occurrence of a peak at 327 nm due to the reduction of the enzyme-bound NAD. From these results, it is suggested that S-adenosylhomocysteinase binds the nucleoside substrates mainly through hydrophobic interactions.
Adenine↗
Cystic meconium peritonitis: ultrasonographic features.
Meconium peritonitis occasionally occurs as a localized, encysted collection of meconium ranging from a few centimeters in size to huge cysts occupying most of the abdominal cavity. The cyst wall consists of fibrous granulation tissue and the cyst may contain only meconium or may also encase loops of bowel. Gas within the cyst indicates persistent communication between the perforated bowel and the cyst cavity; if the perforation seals over in utero the cyst remains gasless. Calcification is a variable finding. Sonography in two neonates with cystic meconium peritonitis showed well-defined, echogenic masses, one of which contained calcifications and was detected in utero.
Adolescent↗
Lack of a causal relationship between the vasodilator effect of papaverine and cyclic AMP production in the dog basilar artery.
The effects of papaverine and isoprenaline on smooth muscle cells of the dog basilar artery were investigated using radioimmunoassay, electrophysiological and isometric tension recording methods. For comparative purposes, the actions of these drugs on the guinea-pig basilar artery were also examined. Papaverine and isoprenaline (1 microM and 10 microM) increased the amount of cyclic AMP in both dog and guinea-pig basilar arteries. Papaverine (up to 100 microM) and isoprenaline (up to 1 microM) had no effect on the membrane potential and membrane resistance measured by recording the amplitudes of the electrotonic potentials in smooth muscle cells of the dog and guinea-pig basilar arteries. The action potential evoked by outward current pulses after pretreatment with tetraethylammonium chloride (5-10 mM) was inhibited by papaverine (greater than 1 microM) but not by isoprenaline (up to 10 microM) in smooth muscle cells of the dog and guinea-pig basilar arteries. In the dog basilar artery, papaverine (greater than 1 microM) consistently inhibited the contractions evoked by excess concentrations of [K]o (greater than 20.2 mM) or 5-hydroxytryptamine (10 nM-10 microM), dose-dependently. Isoprenaline (1 microM) had only slight effects on the contraction evoked by low concentrations of 5-hydroxytryptamine (10 nM). In the Ca2+-free solution containing EGTA (2 mM), the contraction evoked by 5-hydroxytryptamine (10 microM) or caffeine (10 mM) was dose-dependently inhibited by papaverine (greater than 1 microM). However, isoprenaline (1 microM) had no effect on these contractions. These results indicate that the vasodilator actions of papaverine on the dog basilar artery are mainly due to inhibition of the voltage-dependent influx of Ca2+ and also to inhibition of the receptor-activated release of Ca2+ stored in the cell. Since isoprenaline increased the cyclic AMP to the same extent as papaverine but had no effect on the electrical and mechanical responses, the inhibitory actions of papaverine on this tissue may not be causally related to the increased levels of cyclic AMP induced by inhibition of phosphodiesterase.
Animals↗