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T Yamagata

Publications and source records attributed to T Yamagata.

At least 163 records · Page 9Linked to original sources
PubMed1995

Relationships between morphometric and mitochondrial DNA differentiation in laboratory strains of musk shrews (Suncus murinus).

Morphometric differentiation among six strains of musk shrews (Suncus murinus) originating in Bangladesh (BAN), Sri Lanka (SRI), and four Japanese areas, Nagasaki (NAG), Okinawa Island (OKI), Tokunoshima Island (TKU), and Taramajima Island (TR), was examined by use of skull and external measurements. These data were compared with mitochondrial DNA (mtDNA) differentiation previously reported. Significant sexual dimorphism was observed in all morphometric characters of the six strains, except for two characters in the TR strain. The six strains were clearly grouped by principal component analysis into three body-size types: large BAN shrews, intermediate SRI shrews, and small Japanese shrews. By canonical discriminant analysis, the NAG strain was further distinct from the other three Japanese strains despite their apparent similarities in external morphology, and was characterized by having the most unusual shape in the six strains. No individuals were misclassified as to their geographic origin for both sexes of the six strains. The morphometric differentiation pattern based on only the first canonical variate, extracting an overall size factor, was concordant with the mtDNA differentiation pattern (rss = 0.944, P < 0.001 in males and rss = 0.930, P < 0.001 in females). In contrast, the morphometric differentiation pattern estimated from the second to the fifth canonical variates, representing shape factors, was apparently discordant with the mtDNA differentiation pattern (rss = 0.467, P > 0.05 in both sexes). It was previously reported that a partial premating reproductive isolation mechanism is caused by the difference in body size between mating pairs. Thus, body size may be a factor useful for understanding the mechanisms of population differentiation in this species.

Animals↗
PubMed1995

The role of the left atrial appendage. A volume loading study in open-chest dogs.

Although the left atrial appendage has a quite unique structure, its function remains unclear. To clarify the function of the left atrial appendage, changes in its anteroposterior, transverse and longitudinal dimensions, and in the anteroposterior dimension of the left atrial body were measured by a sonomicrometer during volume loading in open chest dogs. In the control state, fractional shortening of the transverse dimension of the appendage was greater than that of the atrial body. After dextran infusion, each dimension of the appendage and body, measured just before atrial contraction, increased curvilinearly. The percent increase in appendage dimensions was greater than that of the atrial body dimension (p < 0.05). Systolic shortenings of the appendage increased until mean left atrial pressure reached approximately 15 mmHg but after further pressure elevation, it decreased. In postmortem isolated hearts, the appendage volume was 17.2 +/- 4.4% of the whole left atrial volume. These findings indicate that the appendage has a considerable volume with a greater compliance and assists left ventricular filling during atrial contraction by a Frank-Starling mechanism.

Animals↗
PubMed1995

Effects of heart rate on left atrial contractile performance and left ventricular filling during atrial systole in dogs.

Left ventricular (LV) diastolic filling and left atrial (LA) contribution have been investigated in patients with heart disease. However, many of these studies were not conducted at a constant heart rate, and the effects of heart rate remain unclear. The purpose of this study was to clarify the effects of the heart rate on left atrial contractile performance and left ventricular filling during atrial systole. The changes in LA and LV dimensions and pulmonary venous (PV) flow were determined in 9 open-chest dogs by a sonomicrometer and an electromagnetic flowmeter. With a stepwise decrease in the pacing rate from 110 beats/minute to 70 beats/minute, the LA dimension just before atrial contraction increased from 21.4 +/- 0.6 mm to 23.1 +/- 0.7 mm (p < 0.01), and the LA systolic shortening increased from 1.6 +/- 0.1 mm to 2.1 +/- 0.1 mm (p < 0.01). However, the calculated LV filling volume during atrial systole decreased from 1.9 +/- 0.3 ml to 1.4 +/- 0.2 ml (p < 0.01). The PV flow during atrial systole was directed toward the LA, and the LA influx volume from PV decreased from 0.6 +/- 0.1 ml to 0.2 +/- 0.04 ml (p < 0.01). With a decrease in the pacing rate, the LA Frank-Starling mechanism operated. However, LV filling during atrial systole decreased because of the decrease in PV flow to the LV via the LA. Thus, LA contractile performance cannot always be evaluated from LV filling.

Animals↗
PubMed1995

[Vein patch angioplasty for coronary revascularization to ischemic heart disease: report of two cases].

Two cases of vein patch angioplasty for ischemic heart disease were presented. The first case (59-year-old female) admitted to our hospital because of posterolateral infarction. Preoperative coronary angiogram (CAG) showed stenosis of 4-PD of RCA, proximal LAD and distal LCX. The second case (62-year-old male) admitted for operation of abdominal aortic aneurysm. Preoperative CAG showed stenosis of proximal RCA and mid LAD. Stenosis of 4-PD and proximal RCA was relieved by patch angioplasty using saphenous vein graft and coronary artery bypass to LAD was performed by left internal thoracic artery graft. Both cases showed successful enlargement of RCA stenosis and good graft patency at the postoperative CAG. Vein patch angioplasty is thought to be an alternative method for coronary revascularization to ischemic heart disease.

Female↗
PubMed1995

[Two patients with far advanced gastric cancer responding to combination chemotherapy with 5-FU and CDDP].

Combination chemotherapy with 5-FU and CDDP was given to two patients with far advanced gastric cancer. One patient was associated with metastases of lung, liver, pancreas and Virchow and periaortic lymph nodes, and the other was associated with metastases of periaortic lymph nodes and malignant ascitis. The regimen consisted of 5-FU 1,000 mg/m2 (day 1-5, continuous infusion) and CDDP 100 mg/m2 (day 3, 1 hr drip infusion). The interval was from the 6th to the 21st day. The response to chemotherapy showed shrinking of primary gastric lesions and metastases of liver, pancreas and periaortic lymph nodes, and disappearance of Virchow lymph nodes and malignant ascitis. Adverse reactions were thrombocytopenia (Grade 4), leukocytopenia (Grade 3), stomatitis (Grade 1, 3), vomiting (Grade 1, 2) and peripheral neuropathy (Grade 3). This therapy is thought to be effective against far advanced gastric cancer.

Adenocarcinoma↗
PubMed1994

Endoglycoceramidase treatment inhibits synchronous oscillations of intracellular Ca2+ in cultured cortical neurons.

Gangliosides are major components of nerve cell membranes and are especially rich in synaptic areas. In order to evaluate the role of endogenous gangliosides in synapse formation, endoglycoceramidase (EGCase) was used to remove oligosaccharides of gangliosides from the cell surface. We have reported previously that synapse formation between cultured rat cerebral cortical neurons can be estimated by the synchronous oscillation of synaptic activity monitored by fura-2 calcium imaging. Continuous application of endoglycoceramidase (EGCase) together with its activator protein dose-dependently decreased the frequency of synchronous oscillations without any morphological changes in neurons and their neurites. The result suggests that oligosaccharides liberated from glycosphingolipids on cultured cortical cell surface with EGCase are important for synapse formation between cortical neurons.

Animals↗
PubMed1994

Changes of the expression and distribution of retinoic acid receptors during neurogenesis in mouse embryos.

The expression and distribution of three retinoic acid receptors, alpha, beta, and gamma, were investigated in the CNS of mouse embryos during development. mRNAs and protein of RAR-beta that were expressed in the spinal cord of the 12.5-day mouse embryo decreased during development but they were not decreased in the brain. The RAR-beta-positive cells were already present in the ventral region of the spinal cord of 10.5-day mouse embryos, gradually appeared in the dorsal region during development and then disappeared from the spinal cord after birth. In the brain, RAR-beta-positive cells were detected in the mesencephalon and rhombencephalon but not in the telencephalon of the 12.5-day mouse embryos. RAR-beta-positive cells were present in the hippocampus and cingulum but not in the neocortex of 14.5-day mouse embryos. Most neurons in the hippocampus of 16.5-day mouse embryos and the cortex of newborn mice were RAR-beta-positive. In the spinal cord, RAR-alpha mRNAs and proteins also decreased during development but more gradually than RAR-beta mRNAs and proteins. During development, the distributions of RAR-alpha and -beta in the spinal cord and brain did not differ substantially. The main difference was the appearance of a subtypes of RAR-alpha, a 52-kDa protein, in the brain of newborn mice. On the other hand, RAR-gamma proteins were only faintly detected in the spinal cord and the brain of the mice during the embryonal stages but these increased after birth. The distribution of RAR-alpha- or -beta-positive cells were consistent with the neurogenesis during development in the spinal cord and brain.

Amino Acid Sequence↗
PubMed1994

Differential effect of pharmacological autonomic blockade on some electrophysiological properties of the human ventricle and atrium.

OBJECTIVE: This study investigated the dominance of each limb of the autonomic nervous system and tested sympathetic-vagal interactions in the human ventricle and atrium after administration of propranolol and atropine. PATIENTS AND METHODS: The 90% monophasic action potential duration (MAPD90) and the effective refractory period (ERP) at the right ventricular apex (RV) and the right lateral atrium (RA) were measured in 14 patients. The MAPD90 was measured during constant RV and RA pacing (cycle length 600 ms) and the ERP was measured at a driven cycle length of 600 ms. Electrophysiological variables were measured during a control period, after propranolol (0.15 mg/kg loading dose followed by 0.1 mg/min infusion), and after autonomic blockade (atropine 0.04 mg/kg). RESULTS: Both RV MAPD90 and RV ERP increased after propranolol (RV MAPD90 from 268 (26) ms to 275 (26) ms, p < 0.005; RV ERP from 252 (25) ms to 258 (26) ms, p < 0.0005) and then decreased to below the control values after autonomic blockade (RV MAPD90 256 (24) ms; RV ERP 239 (25) ms, p < 0.0005 v propranolol, p < 0.0005 v control). In contrast, both RA MAPD90 and RA ERP increased after propranolol (RA MAPD90 from 242 (19) ms to 260 (19) ms; RA ERP from 216 (21) ms to 230 (18) ms, p < 0.0005), and then increased slightly more after autonomic blockade (RA MAPD90 265 (16) ms, p = 0.09; RA ERP 235 (16) ms, p = 0.07), thus remaining above control values (p < 0.0005). CONCLUSIONS: The results indicate (a) that in the human ventricle vagal stimulation and sympathetic beta stimulation are antagonistic and that direct vagal stimulation predominates over beta stimulation, with sympathetic-vagal interaction being minimal and (b) that in the human atrium vagal stimulation and beta stimulation are synergistic and beta stimulation predominates over vagal stimulation, with direct vagal stimulation having a minimal effect.

Action Potentials↗
PubMed1994

Diuretic effects of KW-3902, a novel adenosine A1-receptor antagonist, in anesthetized dogs.

The effects of intravenous infusion of KW-3902 (8-(noradamantan-3-yl)-1,3-dipropylxanthine), a novel adenosine A1-receptor antagonist, on urine volume, urinary excretion of electrolytes and renal hemodynamics were examined in anesthetized dogs. KW-3902 at 10 and 30 micrograms/kg/min for 20 min inhibited the decline of renal blood flow induced by intrarenal arterial injection of adenosine (0.5-2.0 micrograms). KW-3902 at these doses produced significant increases in urine volume and sodium excretion with little change in potassium excretion. The diuretic effect of KW-3902 at 30 micrograms/kg/min for 20 min continued for longer than 1 h even after discontinuation of the KW-3902 infusion. KW-3902 did not affect creatinine clearance, renal blood flow, arterial blood pressure or heart rate. Furosemide at 10 micrograms/kg/min for 20 min brought about significant increases in urine volume and excretion of sodium and potassium. The diuresis and saliuresis induced by furosemide continued for only 40 min after discontinuation of the drug infusion. Trichlormethiazide at 3 micrograms/kg/min for 20 min also provoked increases in urine volume and sodium excretion, but did not affect potassium excretion. The diuretic and natriuretic effect of trichlormethiazide gradually disappeared after discontinuation of the drug infusion. The present study in anesthetized dogs suggests that KW-3902, an adenosine A1-receptor antagonist, produces diuresis and natriuresis but not kaliuresis and that the diuresis and natriuresis are caused in large part by the inhibition of sodium reabsorption at tubular sites.

Anesthesia↗
PubMed1994

The role of the accessory pathway in the onset of atrial fibrillation in Wolff-Parkinson-White syndrome--electrophysiological examination before and after surgical ablation.

To determine the role of the accessory pathway in the pathogenesis of atrial fibrillation, we compared electrophysiological findings in 17 patients (44.7 +/- 10.2 years) with a history of atrial fibrillation before and after surgical ablation of the accessory pathway. The PA interval was shortened, and the atrial refractory periods and the potential minimal wavelength of an atrial impulse (FRPA/PA) were significantly increased, after surgery. Fragmented atrial activity (an increase of 150% or more in the duration of the high right atrial electrogram) was observed in 80% of the patients before surgery and in 25% after surgery. Its zone was significantly decreased after surgery. Repetitive atrial firing was defined as the occurrence of 3 or more successive atrial electrograms induced by a premature stimulation. This was observed in 60% of the patients before surgery, but in none after surgery. Atrial fibrillation was induced in 16 patients during the preoperative study, but in only 1 patient postoperatively. In conclusion, these results suggest that accessory pathways affect atrial vulnerability and play an important role in the onset of atrial fibrillation in WPW syndrome.

Adult↗
PubMed1994

Topographical anatomy of the internal mammary lymphatics in the superior mediastinum and anterior mediastinal lymph nodes.

The lymphatics lying along the internal thoracic artery and vein, which are termed the "internal mammary lymphatics" (IML), were minutely dissected in 134 adult cadavers (80 males and 54 females, aged 27-94 years) in order to clarify the configuration of IML in the superior mediastinum. On the right side, IML frequently terminated at the brachiocephalic angle (BA) nodes and often at the nodes situated at an intermediate position between the internal thoracic artery and vein. By way of these nodes, IML communicated with regional lymphatics of the lung and esophagus. Moreover, IML joined the right superficial bronchomediastinal trunks. On the left side, IML consistently terminated at a superficial group of aortic arch nodes, termed the "superior phrenic nodes", lying along the left phrenic nerve and lying medially to the internal thoracic vein and inferiorly to the left brachiocephalic vein. At and around these nodes, IML joined drainage routes from the so-called Botallo's nodes, which received the left lung lymphatics. The efferents of the superior phrenic nodes formed the left superior bronchomediastinal trunks, and passed deeply to the left brachiocephalic vein and on the subclavian artery toward the left venous angle region. Consequently, IML formed common drainage routes with the drainage routes from the lung and esophagus in the superior mediastinum. A transverse communicating route of IMLs via the retromanubrial nodes, lying inferior to or along the left brachiocephalic vein, was often observed. On the right side, the communicating route terminated at the BA nodes or the nodes situated at an intermediate position between the internal thoracic artery and vein. On the left side, the route consistently terminated at the superior phrenic nodes. In addition to the communicating route described above, we identified (1) a direct and superficial transverse communicating route, and (2) a deep transverse communicating route. The former route was composed of fasciculated large collecting vessels directly connecting the BA nodes to the left venous angle region, lying superficial to the left brachiocephalic vein. The latter route was composed of several large collecting vessels, crossing the brachiocephalic and left common carotid arteries superficially, and merging into the left phrenic nodes directly or occasionally via the pretracheal nodes. These results suggested that IMLs of both sides can closely communicate with each other in the superior mediastinum.

Adult↗
PubMed1994

Repulsive contribution of surface sialic acid residues to cell adhesion to substratum.

Roles of surface sialic acid residues in cell adhesion to substratum were investigated in model systems to clarify their contribution to intercellular interactions. Treatment of cells of a fibroblastic cell line, Swiss 3T3, an epithelial cell line, TES-1, and a T lymphoma cell line, BW5147, with a sialylated oligosaccharide binding lectin enhanced adhesion to plastic plates irrespective of the cell lineage. This enhancement was inhibited by the addition of sialyl lactose. Digestion of the cells with sialidase or endoglycoceramidase also augmented adhesion. On the other hand, adhesion was reduced by pre-coating plastic plates with gangliosides but not with desialylated gangliosides. These findings suggest that sialic acid residues exposed to cell surfaces negatively regulate cell adhesiveness.

3T3 Cells↗
PubMed1993

Specific hydrolysis of intact erythrocyte cell-surface glycosphingolipids by endoglycoceramidase. Lack of modulation of erythrocyte glucose transporter by endogenous glycosphingolipids.

This study represents the specific hydrolysis of cell-surface glycosphingolipids (GSLs) of intact cells by endoglycoceramidase (EGCase; EC.3.2.1.123) which cleaves the linkage between oligosaccharides and ceramides of various GSLs. After a 2-h incubation of horse intact erythrocytes with 20 mU EGCase II in the presence of activator at 37 degrees C, 68% of the N-glycolylneuraminic-acid-containing ganglioside GM3(NeuGc) and 70% of 4-O-acetyl GM3(NeuGc) were found to be hydrolyzed without hemolysis, accompanied by a corresponding increase in ceramide but not sphingosine or N,N-dimethylsphingosine. No hydrolysis was observed for sphingomyelin, phosphatidylcholine, phosphatidylethanolamine, cholesterol or membrane proteins. The decrease in immunoreactivity with GMR8 antibody, specific to NeuGc alpha 2,3Gal- of GM3(NeuGc), corresponded to that of cell-surface GM3(NeuGc) by the enzyme, and almost no immunoreactivity was found when 70% of the GM3(NeuGc) was hydrolyzed. Besides the cell-surface GM3(NeuGc) of horse erythrocytes, Gg3Cer of guinea pig, GM3(NeuAc) and LcCer of human, and bovine and rabbit erythrocyte IV3Gal alpha-nLc4Cer were found to be efficiently hydrolyzed by EGCase II even when present in intact cells, while human erythrocyte Gb4Cer is quite resistant to hydrolysis by the enzyme on the cell surface as well as in detergent micelles. Glucose incorporation via the glucose transporter in erythrocytes was not affected at all by the specific and exhaustive hydrolysis of cell-surface GSLs by EGCase II. This result strongly suggested that glucose transporter function was not directly modulated by endogenous GSLs. In summary, this paper demonstrates that, together with the assistance of activator protein, EGCase II will become a powerful tool for selectively removing sugar chains from cell-surface GSLs without damaging other cell membrane components, and will be useful for describing the biological functions of endogenous GSLs.

Animals↗
PubMed1993

Kinetics of endoglycoceramidase action toward cell-surface glycosphingolipids of erythrocytes.

As shown in the preceding paper [Ito, M., Ikegami, Y., Tai, T. & Yamagata, T. (1993) Eur. J. Biochem. 218, 637-643], endoglycoceramidase (EGCase; EC.3.2.1.123) was found to hydrolyze the cell-surface glycosphingolipids (GSLs) of erythrocytes without any damage to other cell membrane components. This paper represents the kinetics of EGCase action toward cell-surface GSLs of erythrocytes. Without activator or detergents, cell-surface GSLs were found to be hydrolyzed by EGCase II very slowly at pH 7.0. The initial reaction velocity of EGCase II under this condition was 0.038 pmol.min-1.mU-1 for horse erythrocyte cell-surface GM3 and 0.032 pmol.min-1.mU-1 for guinea pig erythrocyte cell-surface Gg3Cer. The addition of activator protein (60 microM), which stimulates EGCase II in the absence of detergents, increased the initial reaction velocity of the enzyme 616-fold for cell-surface GM3 and 468-fold for Gg3Cer, while no increased hemolysis was observed with the addition of activator. However, even in the presence of the activator, the cell-surface GSLs were very resistant to hydrolysis by EGCase II compared to GSL vesicles (or micelles) under same conditions. In contrast to the activator, Triton X-100 (0.4%, mass/vol.) not only stimulated the enzyme activity but also solubilized erythrocyte GSLs into detergent micelles, inducing further increment of the enzyme reaction velocity. The apparent Km and Vmax values of EGCase II were calculated from the Lineweaver-Burk plot as 47 microM and 35 pmol min-1 mU-1 for horse erythrocyte cell-surface GM3 and 44 microM and 27 pmol.min-1.mU-1 for guinea pig erythrocyte cell-surface Gg3Cer, at pH 7.0 in the presence of activator at a concentration of 60 microM.

Animals↗
PubMed1993

Abnormal systolic blood pressure response during exercise recovery in patients with angina pectoris.

OBJECTIVES: This study was conducted to clarify the mechanisms of the abnormal systolic blood pressure response after exercise in patients with angina pectoris. BACKGROUND: An abnormal systolic blood pressure response in patients with angina pectoris has been observed not only during exercise but also during the recovery period after exercise. However, the mechanisms of this abnormal response during recovery have not been elucidated. METHODS: Thirty-five patients with angina pectoris and 17 control subjects underwent bicycle ergometric studies after insertion of a Swan-Ganz catheter. RESULTS: In control subjects, all hemodynamic variables decreased rapidly after exercise. In 7 of the 35 patients, systolic blood pressure increased after exercise. The patients with angina were classified into two groups. In group I (17 patients), changes in systolic blood pressure during recovery were smaller than those in control subjects. In group II (18 patients) recovery of systolic blood pressure was normal. Changes in stroke index from rest to peak exercise were smaller in group I than in group II. Stroke index in both patient groups increased paradoxically during recovery. The increase in systemic vascular resistance index during recovery and the ratio of plasma norepinephrine concentration to cumulative work load were greater in group I than in group II. CONCLUSIONS: An abnormal systolic blood pressure response after physical exercise in patients with angina pectoris is indicative of severe myocardial ischemia during exercise and may be caused by an increase in stroke volume due to recovery from myocardial ischemia and increased systemic vascular resistance secondary to exaggerated sympathetic nervous activity.

Adult↗
PubMed1993

Retention of hamster oolemma fusibility with spermatozoa after various enzyme treatments: a search for the molecules involved in sperm-egg fusion.

The plasma membrane (oolemma) of the hamster egg retains the ability to fuse with spermatozoa even after exhaustive treatment with proteases and glycosidases. In contrast, when mouse oolemma is treated with proteases, the ability of eggs to fuse with spermatozoa is reduced. In the present study, similar treatments effective in reducing fusibility in the mouse were reexamined in the hamster. Of the several enzymes and treatments tested, only trypsin in Ca(2+)-free medium significantly reduced the hamster oolemma's ability to fuse with spermatozoa. This is suggestive of a cadherin-like system of binding and fusion. When hamster oolemmae were treated with the same protease regimen that reduced fusibility of mouse oolemma for mouse spermatozoa, heterologous fusion of hamster oolemmae with mouse spermatozoa was reduced, without affecting the fusion of these oolemmae with hamster spermatozoa. These data suggest that a protease-sensitive oolemma molecule is of critical importance for mouse sperm-oolemma fusion but not for hamster sperm-oolemma fusion.

Animals↗