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Biomedical subjects

N Noguchi

Publications and source records attributed to N Noguchi.

At least 145 records · Page 8Linked to original sources
PubMed1991

UGA can be decoded as tryptophan at low efficiency in Bacillus subtilis.

Replacement of cat-86 codon 7 or 144 with the UGA codon permitted the gene to confer chloramphenicol resistance in wild-type Bacillus subtilis. UAA replacements of the same codons resulted in a chloramphenicol-sensitive phenotype in wild-type B. subtilis and a chloramphenicol-resistant phenotype in suppressor-positive strains. N-terminal sequencing showed that UGA at codon 7 was decoded as tryptophan in wild-type cells, at an efficiency of about 6%.

Bacillus subtilis↗
PubMed1991

Delayed cardiac tamponade and hemothorax induced by an acupuncture needle.

We report a 52-year-old man who presented with cardiac tamponade a few years after accidental breakage of an acupuncture needle that had not been removed. Thoracotomy showed a hemopericardium with penetration of the pulmonary artery by the very fine needle which was barely detected on the chest roentgenogram. This lesion was not suspected on the basis of roentgenography, two-dimensional echocardiography, or computed tomography, but was detected by the presence of other thick needles in the neck, chest and abdomen. This case showed a possible threat of 'stealthy' and migrating foreign bodies, such as very fine acupuncture needles.

Acupuncture Therapy↗
PubMed1991

Cooperative enhancement of hyaluronic acid synthesis by combined use of IGF-I and EGF, and inhibition by tyrosine kinase inhibitor genistein, in cultured mesothelial cells from rabbit pericardial cavity.

We examined the combined effects of IGF-I and EGF on hyaluronic acid synthesis using cultured pericardial mesothelial cells from rabbit pericardial cavity. Combined exposure of pericardial cells to IGF-I and EGF cooperatively increased hyaluronic acid synthesis and the level of hyaluronic acid synthase activity over that seen with or without IGF-I or EGF alone, but did not significantly stimulate the sulfated glycosaminoglycan synthesis. Increase in the level of hyaluronic acid synthesis and hyaluronic acid synthase activity induced by these growth factors was blocked after pretreatment with a tyrosine-specific protein kinase inhibitor, genistein. Genistein had no direct inhibitory effect on hyaluronic acid synthase activity. These results suggest that cooperative enhancement of hyaluronic acid synthesis induced by combined use of IGF-I and EGF could be mediated by a receptor tyrosine kinase-involved transmembrane signaling process that is responsive to IGF-I and EGF.

Animals↗
PubMed1991

Bunazosin, an alpha-adrenoceptor antagonist, blocks calcium current in guinea-pig ventricular myocytes.

1. Effect of bunazosin, an alpha 1-adrenoceptor antagonist, upon the slow inward Ca2+ current (ICa) was studied in single ventricular myocytes of the guinea-pig using a whole-cell patch-clamp technique. 2. Bunazosin (10-100 microM) decreased ICa in a concentration-dependent manner with an IC50 of 60 microM during depolarization to + 10 mV from the holding potential of -40 mV. 3. As for the inactivation process of ICa, the steady-state inactivation (f infinity) curve was shifted toward more negative potentials from -12 mV to -17 mV and -21 mV at f infinity = 0.5, by 30 microM and 70 microM bunazosin. 4. Inhibition of ICa by the compound (10 microM) was also dependent on stimulation frequency, with greater block induced at 2 Hz (50%) than at 0.33 Hz (13%). 5. It is concluded that bunazosin possesses a direct Ca2+ channel-blocking (class 4) action in a rate-dependent fashion.

Adrenergic alpha-Antagonists↗
PubMed1990

Bunazosin induces use-dependent slowing of conduction in guinea-pig ventricular myocardium.

The use-dependent effects of bunazosin on the maximal rate of rise (Vmax) of the action potential and conduction velocity were studied in isolated papillary muscles of guinea-pig. Standard microelectrode techniques were used to monitor the conduction and action potential of the muscles. In the presence of 30 microM bunazosin, the time constants for the start of the use-dependent inhibition of Vmax during a 0.2, 1, 2 and 3 Hz stimulation were (means +/- S.E.M. in s) 30.9 +/- 8.0, 15.0 +/- 1.6, 7.4 +/- 0.9 and 3.9 +/- 0.7 (n = 4) and those for conduction velocity were 17.3 +/- 2.3, 17.3 +/- 5.2, 6.5 +/- 0.9 and 3.4 +/- 0.2, respectively. These results showed that in the cardiac ventricular muscle of the guinea-pigs, bunazosin produces use-dependent changes in conduction velocity with onset kinetics comparable to those measured simultaneously using Vmax. The characteristics of the use-dependent inhibition of conduction velocity induced by bunazosin are similar to those found with slow kinetic drugs such as disopyramide rather than with fast ones.

Action Potentials↗
PubMed1990

An electrophysiological study of 9-amino-1,2,3,4-tetrahydroacridine (THA) on sino-atrial node preparations of rabbits.

1. The electrophysiological effect of 9-amino-1,2,3,4-tetrahydroacridine (THA) on the rabbit sino-atrial node was studied using double-microelectrode voltage clamp methods. 2. THA (above 10 microM) caused statistically significant decreases in the maximum rate of rise, the action potential amplitude, the rate of diastolic depolarization, and increases in the spontaneous cycle length, the action potential duration at 50% repolarization. 3. On the current systems, THA obviously depressed the time-dependent outward K+ current. The compound also decreased the slow inward Ca2+ current and the hyperpolarization-activated inward current. 4. These findings indicate that THA exerts an inhibitory action on the automaticity of sino-atrial node via effects on both outward and inward current systems.

Action Potentials↗
PubMed1990

Use-dependent effects of pirmenol on Vmax and conduction in guinea-pig ventricular myocardium.

1. The use-dependent effects of pirmenol, a new antiarrhythmic drug, on the maximal rate of rise (Vmax) of the action potential, conduction velocity, and their corresponding recovery kinetics were studied in isolated papillary muscles of guinea-pig. Standard microelectrode techniques were used to monitor the conduction and action potential characteristics of the muscles. 2. Pirmenol decreased Vmax and the overshoot of action potentials in a dose-dependent fashion. Also, doses of pirmenol greater than 1 mM abolished the generation of action potentials. Low concentrations of pirmenol (3 and 10 microM) prolonged the action potential duration, while concentrations greater than 0.1 mM shortened it markedly. 3. The resting block of Vmax in the presence of 10 and 30 microM pirmenol was 9.48 +/- 3.12 and 20.36 +/- 3.61%, and that of conduction velocity 2.87 +/- 1.52 and 6.58 +/- 2.09%, respectively. 4. The degree of use-dependent block induced by 10 and 30 microM pirmenol during 0.2, 1, 2 and 3 Hz stimulations was dose- and rate-dependent. 5. In the presence of 30 microM pirmenol, mean values of time constants for the onset of the use-dependent inhibition of Vmax and conduction velocity during a 2 Hz stimulation were 1.32 +/- 0.15 and 1.28 +/- 0.09 s, respectively. The recovery time constants averaged 15.83 +/- 2.14 (for Vmax) and 27.80 +/- 8.74 (for conduction velocity) s in the presence of 30 microM pirmenol. 6. These results showed that the characteristics of the use-dependent inhibition of Vmax and conduction velocity induced by pirmenol are similar to those of slow kinetic drugs such as disopyramide rather than of fast ones.

Action Potentials↗
PubMed1990

Initial accumulation of paraquat in the heart leading to acute death.

When a large amount of paraquat (364 mg/kg) which caused death in several hours was orally ingested in rats, the herbicide concentration in blood continued to increase until the animal died. Furthermore, there was a correlation between the paraquat concentration in the blood, heart, liver and adrenal gland and the survival time. While the paraquat concentration in the heart had the most evident correlation in those tissues (r = -0.962), there was no correlation between the paraquat concentration and survival time in the lung or kidney. ECG of the rats which died in the early stages showed severe damage in the heart. It was found by histopathological studies that edema, congestion and hemorrhage occurred in the myocardium of rats that had died shortly after administration of a large amount of paraquat (364 mg/kg). These results suggest that a rapid accumulation of paraquat into the heart in the early stages may play an important role in the cause of acute death.

Animals↗
PubMed1989

Effect of chlordane on hepatic mitochondrial respiration.

In order to clarify the cytotoxicity of chlordane, an industrial product used as an insecticide, its effect on oxidative phosphorylation in rat hepatic mitochondria was studied. The respiration rate, RCI and ADP/O ratios were inhibited by chlordane-related compounds; the degree of inhibition was in the descending order of trans-chlordane, cis-chlordane, heptachlor and heptachlorepoxide. Of the indices indicating various respiratory activities, state 3 respiration was the most sensitively inhibited by these compounds, suggesting that they inhibit energy transfer. However, electron transport was inhibited also by high concentrations of chlordane constituents. The inhibitory effect of the chlordane constituents on respiratory activity varied depending on the species of respiratory substrate, suggesting site-specificity of these compounds. The release of K+ ions paralleled the results of the respiratory activity study. Heptachlorepoxide, a metabolic product of heptachlor, had less effect on mitochondria than heptachlor.

Animals↗
PubMed1987

Complete nucleotide sequence of pTZ12, a chloramphenicol-resistance plasmid of Bacillus subtilis.

The complete nucleotide sequence of pTZ12, a chloramphenicol-resistance (CmR) plasmid (2517 bp) derived from Corynebacterium xerosis plasmid pTZ10, has been determined after propagation in Bacillus subtilis. The nucleotide sequence of pTZ12 suggests that a recombination event may have occurred naturally within the open reading frames for the Rep protein of pT181 (or a pT181-like plasmid) and pC221 (or a pC221-like plasmid).

Amino Acid Sequence↗
PubMed1986

Large myelinated club endings on the Mauthner cell in the goldfish. A study with thin sectioning and freeze-fracturing.

Thin sectioning and freeze-fracturing have revealed the distribution of gap junctions and chemical synapses in the synaptic interface of the large myelinated club endings on the lateral dendrite of the goldfish Mauthner cell. In 12 samples of club endings fractured completely or nearly completely, the apposed synaptic membrane area averaged 39.090 microns2, of which 16.6% was occupied by gap junctions and about 4 to 5% by the active zones of chemical synapses. The numerical profile density (number per unit area of the synaptic membrane) of gap junctions varied greatly, from 1.78 to 6.30, and was mostly in inverse proportion to their size. The chemical synapses were located mainly in two places: in the circumferential rim of the synaptic membrane next to the widened extracellular space, and in the margins of intraterminal invaginations of the synaptic cleft. The axoplasm of the preterminal axon, just after losing its myelin sheath, was filled with microtubules, among which neurofilaments gathered into many small bundles. The correlation between the areas of gap junctions and the chemical synapses and the amplitude of the excitatory postsynaptic potentials (EPSP) is discussed.

Animals↗
PubMed1985

Synthesis and structure-activity relationships of 2-azetidinone-1-sulfonic acid derivatives with a heteroatom-bound substituent at the 4-position.

The synthesis and antibacterial activity of 3-[(Z)-2-alkoxyimino-2-(2-aminothiazol-4-yl)-acetamido] -2-azetidinone-1-sulfonic acid derivatives with a heteroatom-bound substituent at the 4-position are described. The effect of various 4-substituents on the antibacterial activity was examined. Some of these compounds showed excellent antibacterial activity especially against Gram-negative bacteria, including beta-lactamase-producing strains.

Anti-Bacterial Agents↗