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Biomedical subjects

N Yagi

Publications and source records attributed to N Yagi.

At least 19 recordsLinked to original sources
PubMed1992

Effects of N-ethylmaleimide on the structure of skinned frog skeletal muscles.

The effects of N-ethylmaleimide (NEM) and other sulfhydryl modifiers on the structure of skinned frog skeletal muscles were studied using the X-ray diffraction technique. In sartorius muscle with full overlap between the thick and thin filaments, 0.1-1.0 mM NEM changed the intensity ratio of the (1,0) and (1,1) equatorial reflections from 4.35 to 0.72, and the (1,0) spacing of the hexagonal filament lattice from 40.4 to 41.4 nm. The axial X-ray diffraction pattern showed weak myosin layer-lines after the NEM treatment but enhancement of the actin layer-lines was not observed. In overstretched semitendinosus muscle, NEM did not affect the equatorial spacing but the myosin layer-lines were weakened. These results indicate that modification of myosin by NEM destroys the helical arrangement of myosin heads around the shaft of the thick filament and that when thin filaments are available, myosin heads move towards, and possibly bind to them. This binding is different from that in rigor since the 'ladder-like' appearance of the higher actin layer-lines, which is typical of patterns from rigor muscles, was not observed. On removal of ATP after the NEM treatment, the diffraction pattern showed features characteristic of that from normal rigor muscles but no tension was produced. The pattern showed well-defined samplings on layer-lines in the small-angle region, indicating the presence of an extensive lattice order and exact axial alignment of the filaments. The first actin layer-line did not show samplings from the superlattice of the thick filaments, which are observed on the myosin layer-lines in patterns from resting muscles.(ABSTRACT TRUNCATED AT 250 WORDS)

Actin Cytoskeleton↗
PubMed1992

Effects of 2,3-butanedione monoxime on contraction of frog skeletal muscles: an X-ray diffraction study.

We studied the effects of BDM (2,3-butanedione monoxime) on the tetanic contraction of frog skeletal muscles using an X-ray diffraction technique. BDM significantly increased the resting equatorial intensity ratio (I1,0/I1,1). In sartorius muscle, 3 mM BDM suppressed tetanic tension by 40-70% whereas the equatorial intensity ratio, which is 2.6 at rest, decreased to 0.75 during tetanus, close to the value in normal contraction (about 0.50). BDM (3 mM) reduced the intensity increase of the 5.1-nm layer-line to 41%, that of the 5.9-nm layer-line to 24%, and the intensity decrease of the second myosin meridional reflection (at 1/21.5 nm-1) at 81%. In overstretched semitendinosus muscle, 3 mM BDM did not significantly reduce the intensity increase of the second actin layer-line during activation, suggesting that enough calcium is released to activate the regulatory system and the regulatory proteins are intact. These results indicate that BDM suppresses tetanic tension by mainly inhibiting actin-myosin interaction. It has a smaller effect on the equatorial reflections and myosin layer-lines than on the actin layer-lines, suggesting that BDM-influenced myosin heads may bind to actin without following the symmetry of the actin helix.

Actin Cytoskeleton↗
PubMed1992

Age-related changes of the branched-chain fatty acid concentration in rat skin surface lipid.

1. Age-related change of the branched-chain fatty acid distribution in rat skin surface lipid was studied for 24 months. 2. The proportion of even carbon number iso-acid increased from infancy to month 5 and thereafter decreased with advancing age toward senescence. 3. Concentration of odd carbon number iso-acid depicted a similar shape of time course, but with a lesser magnitude and a peak value at month 1. 4. Anteiso- fatty acid reached the plateau level at month 5 and remained roughly constant through maturity to senescence.

Aging↗
PubMed1992

Effects of the Fab fragment of digoxin antibody on the natriuresis and increase in blood pressure induced by intracerebroventricular infusion of hypertonic saline solution in rats.

1. The effects of intravenous injection of Fab fragments of anti-digoxin IgG (Digibind) on the changes in blood pressure, urine volume and urinary sodium excretion after intracerebroventricular infusion of artificial cerebrospinal fluid with normal or high sodium concentration were examined in anaesthetized rats. 2. The biological efficacy of Digibind was confirmed by experiments in vitro and in vivo, which showed that pretreatment with Digibind completely abolished or significantly attenuated the aortic contractile response or pressor response to digoxin in guinea-pigs. 3. Infusion of high-sodium cerebrospinal fluid, but not normal-sodium cerebrospinal fluid, into the lateral brain ventricle of rats caused marked increases in blood pressure, urine volume and urinary sodium excretion. 4. Digibind did not significantly affect the increases in blood pressure, urine volume and urinary sodium excretion caused by intracerebroventricular infusion of high-sodium cerebrospinal fluid. 5. Digoxin-like immunoreactive factor may play a minor role, if any, in central nervous system-induced natriuresis in rats.

Animals↗
PubMed1992

Nasal absorption of digoxin in rats.

The nasal administration of digoxin was studied in rats and compared to intravenous, intraduodenal and rectal administration of the drug. The results indicated that the plasma level of digoxin after nasal administration was comparable to the level after intravenous injection. Administration by the intraduodenal and rectal routes resulted in considerably lower plasma levels. These data reveal that digoxin absorption across the nasal membranes is a reasonable approach. In the in situ nasal and intestinal perfusion experiments, digoxin disappeared from the perfusate following the apparent first-order kinetics. The nasal and intestinal absorption rate of digoxin was reduced by an increase in the perfusion volume. The plot of absorption rate constant against 1/volume resulted in a straight line, suggesting that digoxin is absorbed from nasal mucosa by a passive diffusion process.

Absorption↗
PubMed1991

Structure of the SPXX motif.

To understand the structure of the DNA-binding SPXX motif, an analysis of Ser1-Pro2-X3-X4 and Thr1-Pro2-X3-X4 structures observed in proteins is presented. About half (43-46%) of the (S or T) PXX sequences fold into a beta-turn of type (I) or one of a few closely related turn structures. The turn structure has either or both of two compatible hydrogen bonds, one between CO of (Ser or Thr) and NH of X4 (a standard beta-turn type), and the other between OH of (Ser or Thr) and NH of X3 (which we name the sigma type). Within the beta-turn of the TPXX sequence, another type of hydrogen bond (which we name the tau type) occurs between OH of Thr and NH of X4 with the frequency of 72%. These observations support a previous proposal that the (S or T) PXX sequences of DNA-binding proteins fold into a compact beta-turn stabilized by a side-chain-main-chain interaction, which may be suitable to fit into the groove of DNA.

Amino Acid Sequence↗
PubMed1991

Digoxin-like immunoreactivity: is it still worth measuring?

On the assumption that digoxin-like immunoreactivity may represent digitalis-like sodium pump inhibitors in the mammalian body, many investigators have used radioimmunoassay for digoxin to monitor such factors during the past decade. The presence of digoxin-like immunoreactivity has been confirmed by numerous studies using biochemical, immunological or morphological methods. Very recently, ouabain or a very similar substance, which did not cross-react with antidigoxin antibodies, was identified from the human plasma as the long-sought sodium pump inhibitor. However, it is yet to be determined whether sodium pump inhibitory activity in the circulation results from one substance or several. Some researchers still insist on the possible physiological roles of digoxin-like immunoreactivity which may or may not be related to the regulation of sodium pump. These issues are critically reviewed in this article.

Animals↗
PubMed1991

Intensification of the first actin layer-line during contraction of frog skeletal muscle.

The peak position of the first myosin layer-line in frog skeletal muscle shifts towards the higher angle during contraction. An analysis showed that the observed axial intensity profile of the first myosin layer-line is fitted well by summation of two layer-lines at 1/43.0 and 1/36.0 nm-1. The former corresponds to the first myosin layer-line, and the latter to the first actin layer-line whose intensity the analysis shows to increase in 0.03-0.08 nm-1 but to decrease in 0.08-0.14 nm-1 during contraction.

Actins↗
PubMed1991

Cross-bridge movement in fast and slow skeletal muscles of the chick.

1. Fast (posterior latissimus dorsi, PLD) and slow (anterior latissimus dorsi, ALD) muscles of the chick were studied by time-resolved X-ray diffraction using a synchrotron radiation source. 2. In both muscles and at both 20 and 30 degrees C, intensities of the X-ray equatorial reflections changed faster than tension at the beginning of tetanus. When the intensity change was converted into the mass transfer from the thick to the thin filament, the difference between the half-rise times of the transfer and tension development at 20 degrees C was 140 ms in ALD and 37 ms in PLD. At 30 degrees C it was 110 ms and 10-20 ms for ALD and PLD respectively. 3. These results indicate that in the early stage of contraction, some of the myosin heads in the vicinity of the thin filament are developing little or no tension, and suggest that the fast and slow muscles differ in the transition rate of myosin heads from the state of attachment with low tension to that with high tension.

Actins↗
PubMed1991

Binding characteristics of [3H]ketanserin for serotonin-2 receptor in the rabbit platelet.

The present study was designed to examine 1) the properties of [3H]ketanserin binding to serotonin-2 (5HT2)-serotonergic receptors in the rabbit platelet membranes, 2) displacement affinities of various chemicals and 3) difference of the affinities between their chemicals and new agents, MCI-9042 and M-1. The plots of specific binding obtained from the Scatchard analysis using [3H]ketanserin for the platelet membranes were monophasic when the non-specific binding was determined by the use of 0.1 mM serotonin (5HT), and the Kd and Bmax values were 3.93 +/- 0.41 nM and 1.19 +/- 0.20 pmol/mg protein, respectively. The displacement potencies of chemicals which were serotonin receptor-, dopamine receptor-, histamine receptor-, and alpha-adrenoceptor-related agents were characterized by [3H]ketanserin binding to 5HT2-serotonergic receptor. The pKi values of a new antiplatelet agent, MCI-9042, and its metabolite, M-1, were 7.19 and 7.59, respectively and these values were lower than those of ketanserin and pirenperone but higher than those of methysergide, cinanserin and cyproheptadine. The affinities of ketanserin for 5HT2-receptors in the rabbit platelet were similar to those for 5HT2-receptors previously identified in the rat frontal lobe and in canine aorta, but cinancerin was selective to 5HT2-receptors in the rat frontal lobe and in canine aorta, prazosin was selective to 5HT2-receptor in the rabbit platelet, and MCI-9042 and M-1 had the same affinities to the receptors in the rat frontal lobe and in the rabbit platelet.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

[Studies on ouinolone antibiotics. II. Synthesis and antibacterial activity of 7-aminoalkoxy-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxoquinoline-3 -carbo xylic acids and their derivatives].

7-Aminoalkoxy-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxoquinoline-3- carboxylic acid and their derivatives were synthesized and their antibacterial activities were evaluated. Among them, compounds having an alkyl group at alpha-position of the amino group were found to have in vitro and in vivo antibacterial activity comparable to that of ciprofloxacin. Structure-activity relationship of these compounds was also stated.

4-Quinolones↗
PubMed1991

[Effect of inclusion complexation of decanoic acid with alpha-cyclodextrin on rectal absorption of cefmetazole sodium suppository in rabbits].

Inclusion complex of decanoic acid (DA) with alpha-cyclodextrin (alpha-CyD) was prepared as an additive of cefmetazole sodium (CMZ) suppository and rectally administered to rabbits. The resulting complexation was examined by the phase solubility method, differential scanning calorimetry (DSC) and X-ray diffractometry. Plasma concentration and AUC of CMZ after rectal administration of a suppository containing DA/alpha-CyD complex to rabbits increased more significantly than those with none additive.

Adjuvants, Pharmaceutic↗
PubMed1991

[Studies on quinolone antibiotics. III. Synthesis and antibacterial activity of 5-amino-7-(2-aminoalkoxy)-1-cyclopropyl-6-fluoro-1,4- dihydro-4-oxoquinoline-3-carboxylic acid and their derivatives].

5-Amino-7-(2-aminoalkoxy)-1-cyclopropyl-6-fluoro-1,4-dihydro-4- oxoquinoline-3-carboxylic acid and their derivatives (10, 11) were prepared and their antibacterial activities were evaluated. As a result of in vitro antibacterial screening, the compounds having mono- or di-methyl (11d, e) group at alpha-position of amino group were most effective among the 7-aminoalkoxy derivatives. Structure-activity relationship of these compounds is also discussed.

Anti-Infective Agents↗
PubMed1990

Viscosity of effusion in the middle ear and eustachian tube in patients with otitis media with effusion.

The viscosity of middle ear effusion (MEE) in the tympanic cavity and in the bony portion of the eustachian tube (ET) was compared in 11 specimens (10 patients) with otitis media with effusion (OME). Twenty microliters of effusion from the bony portion of the ET was sampled through myringotomy on the anterosuperior quadrant of the tympanic membrane with a micro-syringe with a curved needle. MEE in the hypotympanum was also sampled by separately puncturing the posteroinferior quadrant of the tympanic membrane. Using the microviscometer developed by one of the authors, the relative viscosity of these effusions were measured, and their natural logarithmic values were compared between the two sites mentioned above in each patient by obtaining their ratios (ET/ME). Effusion was found to have a significantly higher viscosity in the bony portion of the ET than in the hypotympanum (paired t-test: t = 3.859, p less than 0.01). In two patients with OME (serous mastoiditis) due to radiation to the temporal region, the ratios of the viscosity were comparatively small. On the other hand, excluding these two patients with serous mastoiditis mentioned above, the ratios were highest in two patients with a history of more than 60 days of hearing loss. These results were considered to be a clue to the possibility that viscous effusion aggravates ET function as a result of OME.

Adult↗
PubMed1990

Specific binding of [3H]pyrilamine to histamine H1 receptors in guinea pig brain in vivo: determination of binding parameters by a kinetic four-compartment model.

The binding of [3H]pyrilamine, a selective ligand of histamine H1 receptors, to guinea pig brain in vivo was compared with its binding to a brain homogenate. The pharmacological properties (regional distribution, saturability, and stereoselectivity) of the [3H]pyrilamine binding in vivo were similar to those of the in vitro binding to brain homogenate. A dynamic four-compartment model was proposed for the analysis of the kinetics of [3H]pyrilamine binding in vivo. The receptor constants in vivo were determined by a computer-fitting method after correcting the radioactivity of arterial plasma and brain for the presence of radioactive metabolites. The in vivo association and dissociation were 213 and 42 times, respectively, slower than those of in vitro binding at 37 degrees C. A possible mechanism for slow association and dissociation in vivo is discussed.

Aminopyridines↗
PubMed1990

Studies on antiallergic agents. I. Synthesis and antiallergic activity of novel pyrazine derivatives.

Various pyrazine derivatives were synthesized and their antiallergic activity was examined. The inhibitory activity on allergic histamine release of the compounds bearing a 5-tetrazolyl group was more potent than that of the corresponding carboxyl derivatives. The introduction of -CONH- or -NHCO- between the pyrazine ring and the 5-tetrazolyl group as a spacer greatly enhanced the activity. N-(1H-Tetrazol-5-yl)-2-pyrazinecarboxamide (I-3) was estimated to exhibit nearly the same potency as disodium cromoglycate (DSCG). The structure-activity relationship among various derivatives modified by introducing some substituents onto the 3-, 5- or 6-position of the pyrazine ring of I-3 was investigated. The activity remained unchanged or was reduced when such substituents as methyl, chloro, methoxy, methylamino and dimethylamino were introduced at the 3- or 5-position. In contrast, 6-substitution with various alkylamino groups more or less increased the activity. Among them, the 6-dimethylamino (I-17c) and 6-(1-pyrrolidinyl) (I-34) derivative were proved to be most potent. The IC50 values (concentration which produces 50% inhibition of the allergic histamine release) of I-17c and I-34 were determined to be 4.7 x 10(-10) and 4.6 x 10(-10) M, respectively. These two compounds produced a potent inhibitory activity on passive cutaneous anaphylaxis (PCA) in rat, not only by the intravenous route (ED50 = 0.0096 mg/kg for both compounds) but also by the oral route (ED50 = 0.19 and 0.18 mg/kg, respectively). On the other hand, when the pyrazine ring of some representative compounds was replaced with a pyridine ring, the inhibitory activity on histamine release was significantly reduced.

Animals↗