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Biomedical subjects

T Asakawa

Publications and source records attributed to T Asakawa.

At least 91 records · Page 5Linked to original sources
PubMed1990

ADP-ribosylation of myelin basic protein by cholera toxin.

Cholera toxin ADP-ribosylates four types of myelin basic proteins (MBPs) of Mr 14,000, 17,500, 19,000 and 22,000 in rat brain myelin. On an analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, MBP underwent mono- and multi-(ADP-ribosyl)ation by cholera toxin and thus modified MBP migrated on the gel as several discrete protein bands, the molecular masses of which were apparently larger by 500-2000 daltons than that of the corresponding untreated MBP. On average, 1.1 mol of ADP-ribosyl residue was incorporated into 1 mol of MBP. Four types of purified MBPs were also ADP-ribosylated by cholera toxin dependent on GTP and the protein factor for the ADP-ribosylation. The results show evidence that MBP is one of major and specific substrates of cholera toxin in brain membranes.

Brain↗
PubMed1990

Two isoforms of regulatory light chain of abalone smooth muscle myosin.

Abalone myosin contains two kinds of light chain, regulatory light chain (LC2) and essential light chain (LC1) according to SDS-PAGE. Three distinct light chain bands were observed on polyacrylamide gel electrophoresis of purified abalone myosin in the presence of urea (urea-PAGE). The slower two components showed had mobility on SDS-PAGE and they also showed regulatory activity as the regulatory light chain. They were termed LC2-a and LC2-b in order of increasing mobility on urea-PAGE and isolated by DE-32 ion exchange column chromatography in the presence 8 M urea. The ratio of LC2-a and LC2-b in the central portion of adductor muscle of abalone (LC2-a: LC2-b = 7:3) was different from that (1:1) in the peripheral portion. These results suggest that the two light chains are isoforms of the regulatory light chain. The amino acid compositions of LC2-a and LC2-b were very similar to each other except for the Cys content. The UV absorption spectra were also quite similar, as were the UV difference absorption spectra induced by Ca2+. Phosphorylation was not detectable with the myosin light chain kinase of chicken gizzard. The Ca2+ concentration dependencies of Mg-ATPase activity of LC2-a or LC2-b hybridized abalone myosin (a-myosin, b-myosin) were similar to each other in the absence of rabbit F-actin, but differed in the presence of actin. The b-myosin had a higher maximum value of actomyosin ATPase activity and a lower apparent binding constant of actin and myosin than a-myosin.(ABSTRACT TRUNCATED AT 250 WORDS)

Actins↗
PubMed1990

Improvement of the frequency responses in an ambulatory ECG system by the natural observation method.

The ambulatory ECG system has been used not only in detecting arrhythmia but also in the diagnosis of myocardial ischemia. Therefore, it is necessary to reproduce ECG waveforms as accurately as possible. However, ambulatory ECG waveforms which are in clinical use are apt to be distorted because the frequency responses do not satisfy the AHA (American Heart Association) recommendation which is well accepted as the standard of the conventional ECG system. An improvement of frequency response is reported here using a compensation circuit, whose theory is based on the natural observation method. Since our system is adjusted with square waveforms and composed of a simple analog circuit, it can be compensated easily in real time. In this paper, our newly developed system and various improved ECG signals are presented and compared with conventional ECG signals. As a result, we could obtain less distorted waveforms than from commercially available devices. This new approach enables us to obtain diagnostic information of the distortion-free ST segment in ECG waveforms.

Arrhythmias, Cardiac↗
PubMed1989

Is extensive lymphadenectomy necessary for surgical treatment of intramucosal carcinoma of the stomach?

This study was undertaken to elucidate those histological and gross features associated with gastric carcinoma that can be adequately treated by gastrectomy with less aggressive lymphadenectomy. The frequency of metastasis to the lymph nodes was analyzed in 514 cases of resected, solitary, gastric carcinomas. The frequency of metastasis to the lymph nodes increased in proportion to the increase in the extent of penetration by the cancer into the gastric wall. Lymph nodes were not involved in cases of intramucosal carcinoma of the intestinal type, by Laurén's histological classification. By contrast, metastasis to the lymph nodes was observed in cases of intramucosal carcinoma of the diffuse type, by Laurén's classification. We conclude that extensive lymphadenectomy is not mandatory for patients with intramucosal carcinoma of the stomach of the protruded type, since the lymph nodes do not become involved in this type of gastric carcinoma.

Adenocarcinoma↗
PubMed1988

Preparation of subfragment-1 from abalone smooth muscle myosin.

Myosin subfragment-1 (S1), which has one heavy chain (HC) (93 kDa) and two light chains (LC1 and LC2), was prepared by papain digestion of myosin from abalone-smooth muscle in the presence of Ca2+. The Ca-sensitivity of abalone S1 itself was not lost completely (about 30%). The tryptic digestion of S1 showed that in the presence of EDTA, S1 HC was split into 68, 55, and 23 kDa fragments, as in the presence of Ca2+, but 23 kDa was further degraded into 19 kDa. In contrast to the result in the presence of Ca2+, LCs disappeared in the early stage of reaction and Ca-ATPase activity decreased rapidly to about 70% of that of intact S1. This rapid decrease of Ca-ATPase activity seemed to be accompanied with the digestion of LCs. Therefore, LCs contribute to the protection of 23 kDa fragment from further digestion, to the maintenance of Ca-ATPase activity by stabilizing the structure of S1 to some extent in the presence of Ca2+. Since F-actin suppressed the cleavage of S1 HC to 68 and 23 kDa during tryptic digestion, it might be that 23 and 68 kDa corresponded to 20 kDa (C-terminal fragment) and to 50 + 25 kDa (N-terminal fragment) of skeletal myosin S1, respectively.

Actins↗
PubMed1988

The chromosomal normality of in vitro-fertilized rabbit oocytes.

The chromosomal normality of rabbit oocytes fertilized in vitro was examined. Ovum donors were superovulated with pregnant mare's serum gonadotropin and human chorionic gonadotropin (hCG). Follicular oocytes were collected laparoscopically 9-10 h after hCG treatment and incubated in vitro with spermatozoa capacitated in vivo. Of 267 aspirated oocytes, 191 (71.4%) were fertilized in vitro and developed to the 2- to 8-cell stage 24-48 h after insemination. In the chromosomal studies, 121 (63.4%) were examined. Of these, 94 (77.7%) had a normal diploid complement of chromosomes (2n = 44) and 6 (5%) showed aneuploidy. Of the remaining 21, 20 were triploid and one was tetraploid. The incidence of triploid oocytes after in vitro fertilization was higher than the rate in vivo (16.5% vs. 9.0%, respectively). These triploid oocytes were suspected to be the result of polyspermic fertilization in vitro. In addition, at the Metaphase II stage, 62 (89.9%) of 69 induced, preovulatory oocytes had a normal number of chromosomes.

Animals↗
PubMed1988

[Basic and clinical studies on ceftriaxone in perinatal infections].

Basic and clinical investigations were conducted on ceftriaxone (CTRX), a cephem antibiotic with a wide antibacterial spectrum and with especially high activity against Gram-negative bacteria. The results obtained are summarized as follows: 1. CTRX, following intravenous drip infusion of 1 g, had a serum half-life of 5.8 hours, which is longer than that of any other existing cephem antibiotics. 2. The level of CTRX in the umbilical cord serum 6 hours after intravenous drip infusion of 1 g was at a satisfactory level, 15 micrograms/ml. 3. The CTRX was remarkably effective or effective in 9 cases, and the activity was high even in cases where penicillin or other third-generation cephems were ineffective. These results seem to indicate that CTRX may be effective in perinatal and intrauterine fetal infections.

Adult↗
PubMed1987

Non-invasive assessment of the age related changes in stiffness of major branches of the human arteries.

The static mechanical properties of major branches of the human arteries (common carotid artery, abdominal aorta, femoral artery, and brachial artery) were studied in 39 subjects, aged 6-81 years, using an ultrasonic phase locked echo tracking system that allows continuous transcutaneous measurement of the diameter of the artery. The stiffness indices were calculated from the relation between systemic blood pressure and arterial diameter. With advancing age there was a significant increase in the diameter of all arteries with a reduction in percentage change in diameter. The stiffness index increased with age in all arteries; however, in the brachial and femoral arteries there was considerable variation in the individual values for a given age. The age associated increase in stiffness was statistically significant only in the common carotid artery and the abdominal aorta. Although the mechanical properties of the peripheral arteries were significantly influenced by the measuring environment, the calculated stiffness indices were less vulnerable to these stimuli in the central arteries. These results indicate that the stiffness indices of the peripheral muscular arteries are modified appreciably by vasoactive stimuli and that the mechanical properties of the deeper elastic arteries provide sufficiently reliable information about changes caused by aging and arteriosclerosis. The new ultrasonic method used appears to be suitable for this analysis.

Adolescent↗
PubMed1987

Effects of nipradilol, a new beta-adrenoceptor blocking agent with vasodilating properties, on transmural energy metabolism in the underperfused canine heart.

Effects of nipradilol on hemodynamics and transmural energy metabolism of underperfused (ischemic) canine hearts were investigated. The ischemic heart was prepared by constricting a tube connecting the circumflex coronary artery with the carotid artery for 10 min so that the perfusion pressure (CPP) was reduced to 30 mmHg. The reduction in CPP resulted in decreases in coronary blood flow (CBF) by 70%, regional myocardial contractile force (MCF) by 30%, myocardial ATP contents by 32% (inner layer)-22% (outer) and creatine phosphate by 75% (inner)-60% (outer). Increases in the left ventricular end diastolic pressure (LVEDP) by 4.8 mmHg, myocardial inorganic phosphate contents by 1.9 times (inner)-1.3 (outer) and lactate by 4.3 times (inner)-2.4 (outer) were also observed. In dogs with normal hearts, an infusion of nipradilol (10 micrograms/kg/min, i.v., for 15 min) decreased CPP by 25%, CBF by 40%, cardiac effort index by 45% and MCF by 30 to 40%, and it slightly increased LVEDP without affecting myocardial high-energy phosphate and lactate levels. In ischemic hearts, nipradilol infusion starting 5 min before ischemia attenuated the ischemia-induced elevation of LVEDP to 1.8 mmHg, and the ischemia-induced changes in high-energy phosphate contents to 1/2 (inner)-1/3 (outer) and changes in lactate to 1/6 (inner)-1/10 (outer). These results indicate that nipradilol improves the ischemic derangement of both transmural energy metabolism and hemodynamics.

Adrenergic beta-Antagonists↗
PubMed1987

[Clinical studies on cefuzonam in the field of obstetrics and gynecology].

Cefuzonam (CZON, L-105), a cephem type antibiotic, was clinically studied in the field of obstetrics and gynecology. The results are summarized as follows: CZON 1-2 g was administered by injection twice daily to 11 cases of infections (4 of endometritis, 2 of pyometra, 3 of adnexitis and peritonitis, 1 of abdominal abscess, and 1 of puerperal fever). Clinical efficacy was excellent in 2 cases and good in 9 cases, with a very high overall efficacy rate of 100%. Slight elevations of GOT and GPT in 1 case were noted in clinical laboratory tests. No side effects attributable to the drug were noted. CZON is considered to be a useful drug for obstetric and gynecological infections.

Adult↗
PubMed1986

Inhibition of catalytic unit of adenylate cyclase and activation of GTPase of Ni protein by beta gamma-subunits of GTP-binding proteins.

A protein factor which inhibited adenylate cyclase was purified to apparent homogeneity from rat brain and identified as the beta gamma-subunits of the GTP-binding regulatory proteins of adenylate cyclase. (i) The beta gamma-subunits (protein factor) inhibited the partially purified catalytic unit of adenylate cyclase in the presence of an activator, forskolin or the stimulative regulatory protein (Ns), to 60 and 40% of the control, respectively; inhibition of the catalytic unit in the presence of forskolin required no guanine nucleotides. (ii) The subunits enhanced the GTPase activity of the purified alpha-subunit of the inhibitory regulatory protein (Ni alpha) 3.8-fold. (iii) The subunits stimulated ADP-ribosylation of Ni alpha catalyzed by islet-activating protein (pertussis toxin). ADP-ribosylation had no effect on the GTPase activity of Ni alpha in the presence of the beta gamma-subunits. The results suggest that direct inhibition of the catalytic unit by the beta gamma-subunits liberated from Ni is essential for the receptor-mediated inhibition of adenylate cyclase.

Adenosine Diphosphate Ribose↗
PubMed1984

GTPase activity associates with the inhibitory GTP-binding regulatory component of adenylate cyclase purified from rat brain.

The inhibitory regulatory component of adenylate cyclase (Ni) was highly purified from rat brain synaptic membranes. A low Km GTPase activity was always associated with Ni through the purification, and the recovery of GTPase activity correlated well with that of Ni. Purified Ni was hardly ADP-ribosylated by islet-activating protein (IAP). A heat-labile factor in the fraction of the stimulative regulatory component (Ns) restored ADP-ribosylation and also activated the GTPase about 2-fold. NaF which was reported to interact with Ni markedly reduced GTPase activity. The purified Ni fraction inhibited adenylate cyclase only in the presence of a heat-stable factor found in the partially purified regulatory component. GTPase and inhibitory activities were weak in myelin which contained only a small amount of Ni. These findings support the view that GTPase activity is an intrinsic activity of Ni and some factors are necessary for the function of Ni.

Adenosine Diphosphate Ribose↗
PubMed1983

Inhibitory effect of MgATP on the release of regulatory light chain from scallop myosin and light chain composition of scallop myosin hybridized with abalone light chain 2 at 30 degrees C.

The experimental conditions for release of the regulatory light chain (RLC) of scallop myosin at 30 degrees C were studied. Substantially all RLC was released from myosin by incubation for 5 min in medium containing buffer and KCl. This release of RLC was inhibited strongly by Ca2+, while the effect of Mg2+ was about 10,000 times weaker than that of Ca2+. Even in the absence of Ca2+, MgATP and MgADP inhibited the release of RLC, while the protective effect of AMPPNP was negligible. Other Mg nucleotides also showed some protective effect, though appreciably less than MgATP. The incubation of scallop myosin with abalone regulatory light chain (LC2) at 30 degrees C for 5 min produced a hybrid myosin. In the presence of 5 mM MgCl2, 1 of the 2 mol of RLC per mol of scallop myosin was exchanged with 1 mol of LC2. In the presence of Ca2+ or MgATP, myosin bound 1 extra mole of LC2 besides the 2 mol each of SH-LC and RLC.

Adenosine Triphosphate↗
PubMed1983

Evidence for the presence of GTP-dependent regulatory component of adenylate cyclase in myelin from rat brain.

A GTP-dependent regulatory component of adenylate cyclase was found in myelin from rat brain. The fraction solubilized from myelin contained a component that reconstituted guanine nucleotide-responsive adenylate cyclase activity when combined with the catalytic unit of adenylate cyclase prepared from rat brain. Purified myelin demonstrated little adenylate cyclase activity, even in the presence of F- or Mn2+. The reconstituted activity was dependent on the amount of the solubilized myelin fraction and required the presence of 5'-guanylylimidodiphosphate, a hydrolysis-resistant analog of GTP. The elution pattern of the component solubilized from myelin in gel filtration was very similar to that of a GTP-dependent regulatory component from synaptic plasma membranes. The content of the regulatory component-like activity in myelin was estimated to be 50-60% of that in synaptic plasma membranes. Cholera toxin ADP-ribosylated proteins having molecular weights of 48,000, 38,000, 23,000, 20,000, and 15,000 and other minor peptides in myelin, some of which were also present in synaptic plasma membranes. We conclude that myelin contained a GTP-dependent regulatory component of adenylate cyclase despite the apparent lack of adenylate cyclase activity in myelin.

Adenosine Diphosphate Ribose↗
PubMed1983

Effects of pentobarbital anesthesia on the plasma catecholamines and renin activity as reflected in the hemodynamic changes in dogs.

Correlation between hemodynamic changes and plasma catecholamines or renin activity were studied in dogs anesthetized with pentobarbital, 30 mg/kg, i.v. Pentobarbital increased heart rate in all cases regardless of changes in plasma catecholamines, and the increase was not depressed fully by propranolol. Blood pressure (BP) showed a transient decline just after pentobarbital injection and then elevated gradually to one of three levels 30-60 min after anesthesia. In low (62 +/- 4 mmHg, Mean +/- S.E.) and very high BP (169 +/- 7 mmHg), plasma norepinephrine (NE) showed low (305 +/- 55 leads to 89 +/- 22 pg/ml) and high levels (296 +/- 54 leads to 372 +/- 106 pg/ml), respectively, which probably reflect the neurosympathetic activities. In moderately high BP (112 +/- 4 mmHg), however, the hypertension did not necessarily reflect changes in plasma NE. When the level before anesthesia was 108-164 pg/ml, plasma NE increased, whereas it decreased when the level was 182-374 pg/ml. In either case, the level was fixed within 117-182 (154 +/- 6) pg/ml. Plasma renin activity increased after anesthesia and maintained for at least 2 hr. However, the increase were observed regardless of the BP level, and moderately high BP was not depressed by an angiotensin II antagonist. Participation of angiotensin in these sustained BP cases seems unlikely. Plasma epinephrine reflecting adrenal-medullary activity was decreased markedly in all cases, and the low level lasted for at least 2 hr. Changes in plasma dopamine are related to those in plasma NE, and the origin seems to be the same.

Anesthesia, General↗