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Biomedical subjects

K Machii

Publications and source records attributed to K Machii.

At least 37 records · Page 2Linked to original sources
PubMed1996

Maintenance of pluripotency in mouse embryonic stem cells persistently infected with murine coronavirus.

A persistently coronavirus-infected embryonic stem (ES) cell line A3/MHV was established by infecting an ES cell line, A3-1, with mouse hepatitis virus type-2. Although almost all A3/MHV cells were found infected, both A3/MHV and A3-1 cells expressed comparable levels of cell surface differentiation markers. In addition, A3/MHV cells retained the ability to form embryoid bodies. These results suggest that persistent coronavirus infection does not affect the differentiation of ES cells.

Animals↗
PubMed1996

Characterization of T cells expanded in vivo during primary mouse hepatitis virus infection in mice.

After intraperitoneal infection with mouse hepatitis virus, strain JHM (JHMV), JHMV replicated in the spleen of C57BL/6 mice for a few days but cleared within a week. The acute viral clearance coincided with moderate expansion of CD8+T cells and modest expansion of CD4+T cells, and was impaired moderately in mice depleted of CD8+T cells and completely in mice depleted of both CD4+ and CD8+T cell subsets. Flow cytometric analysis showed that expression of cell surface markers on the spleen T cells changed during JHMV infection. CD8+T cells expressing increased amounts of CD11a, CD43, CD44 and CD49d, and those expressing decreased levels of T cell receptor alpha beta, CD8, CD45RB and L-selectin were expanded in the spleen after JHMV infection. However, they did not express CD11b, CD25 or NK1.1. They used highly heterogenous V beta chains for their T cell receptors. In addition to CD11ahighCD8+T cells, CD11ahighCD4+T cells were detected transiently after JHMV infection. The virus-specific cytotoxic T lymphocyte (CTL) activity was observed in both CD4+ and CD8+ spleen T cells from mice 7 days post-infection. The present study shows the dynamics of CD8+ and CD4+T cells in the spleen during JHMV infection in mice and suggests that CD11ahighT cells may be involved in JHMV clearance in vivo because their appearance was temporally correlated with T cell-mediated viral clearance in vivo and antiviral CTL activity in vitro.

Animals↗
PubMed1996

Generation of antiviral CD11ahigh T cells in CD4+ T cell-depleted mice and adult thymectomized mice after mouse hepatitis virus infection.

The mechanism of CD11ahighCD8+ T cell induction after mouse hepatitis virus infection, which has been suggested to play a key role in the elimination of infectious virus from the spleen in C57BL/6 mice, was studied. In CD4+ T cell-depleted mice, CD11ahighCD8+ T cells were induced in the spleen and spleen cells showed virus-specific cytotoxic T lymphocyte activity after mouse hepatitis virus infection. The same results were obtained in adult thymectomized mice. These results indicate that CD11ahighCD8+ T cells can be generated after mouse hepatitis virus infection in the absence of either CD4+ T cells or the thymus.

Aging↗
PubMed1996

Role of CD4+ and CD8+ T cells in mouse hepatitis virus infection in mice.

Viral growth and histopathological changes in the liver after intraperitoneal infection with mouse hepatitis virus, strain JHM were compared among normal C57BL/6 mice, those depleted of CD4+ T cells, CD8+ T cells and both T cell subsets. Viral growth in mice depleted of CD4+ T cells increased slightly, but pathological changes resembled those in normal mice. In contrast, the hepatitis was exacerbated in mice depleted of CD8+ T cells and those depleted of both T cell subsets. These results suggest that CD8+ T cells play a key role although both T cell subsets are involved in protection against mouse hepatitis virus infection in mice.

Animals↗
PubMed1995

[A case report of pyomyositis--early diagnosis and follow-up by MRI].

We report a rare case of pyomyositis in a 28-year-old Japanese woman who was not immunocompromised. She was admitted because of high fever, sore throat, and severe tenderness and swelling of the right calf. Redness, swelling, and tenderness indicated presence of acute inflammation in the calf. CT of the lower extremities demonstrated low density areas in the right soleus muscle and surrounding fascia with marked swelling, which were of high signal on T2 weighted images of MRI. There was no finding of abscess formation. A tentative clinical diagnosis of acute pyomyositis was made, and antibiotics therapy with a combination of fosfomycin and sulbactam/cefoperazone was started although the arterial blood culture was negative for bacteria. Associated acute tonsilitis was the most probable focus of pyomyositis. Antibiotics relieved her symptoms, and the inflammation subsided in several weeks. No surgical procedure was necessary. MRI taken tree weeks after the onset demonstrated abscess formation between the soleus and gastrocnemius muscles. Slight high intensity indicating scar formation remained in the area of the former abscess six weeks after the onset. MRI was very useful not only in making the early diagnosis but also in the follow-up of pyomyositis.

Adult↗
PubMed1994

[123I-IMP SPECT findings of visual perseveration in a patient with old hemorrhage in the right occipital lobe].

We report a case of visual presevertation in a 67-year-old man. He had been well until 66 years of age when he had brain hemorrhage in the right occipital lobe. After an operation for removal of the hematoma, visual hallucination occurred and persisted for about 6 months. One year and a half later, he had a convulsive seizure and diphenylhydantoin was started. During the two weeks following the convulsion, he several times experienced episodes of visual preservation, visual hallucination and metamorphopsia. MRI revealed an old hemorrhage in the right occipital lobe. 123I-IMP SPECT demonstrated increase of cerebral blood flow of the right medial occipital lobe one day after the episode of visual perseveration and decrease about three weeks after the episode. The mechanism which causes visual perseveration still remains to be clarified. The findings of 123I-IMP SPECT of the present case suggest that visual perseveration may be generated by postictal transient functional excitation of the right occipital lobe.

Aged↗
PubMed1993

Vascular relaxing mechanism of denopamine in isolated canine coronary, femoral, mesenteric, and renal arteries.

We investigated the mechanism of vascular relaxation produced by denopamine (deno), an oral positive inotropic agent that has selective beta 1-adrenergic action. Deno concentration-dependently (0.1 microM-30 microM) relaxed ring segments of canine femoral, mesenteric, and renal arteries which were partially precontracted with 1 micron phenylephrine or norepinephrine, but did not relax those precontracted with 5 microM prostaglandin F2 alpha or 40 mM K+. The relaxation was not significantly inhibited by pretreatment with 10 microM propranolol or metoprolol. Deno produced a parallel rightward shift in concentration-response curves to phenylephrine in femoral and renal arteries. The Schild plot yielded linear regressions of slopes of 1.301 +/- 0.106 and 0.823 +/- 0.122, respectively, which were not significantly different from unity. The pA2 values of Deno against phenylephrine in femoral and renal arteries were 5.41 +/- 0.03 and 5.76 +/- 0.06, respectively. On the other hand, Deno concentration-dependently (10 nM-10 microM) relaxed ring segments of canine coronary arteries which were partially precontracted with 5 microM prostaglandin F2 alpha. The relaxation was significantly inhibited by pretreatment with 10 microM metoprolol. In conclusion, vascular smooth muscle relaxation by Deno was mediated through beta 1-adrenergic action in canine coronary arteries and through the blocking effect of alpha-adrenoceptors in canine femoral, mesenteric, and renal arteries.

Adrenergic beta-Agonists↗
PubMed1993

Effects of rHuEPO therapy on exercise capacity in hemodialysis patients with coronary artery disease.

We investigated the effects of recombinant human erythropoietin (rHuEPO) therapy on exercise capacity by symptom-limited maximal treadmill exercise testing in 9 patients with coronary artery disease who were receiving maintenance hemodialysis. The initial hemoglobin concentration of 7.9 +/- 0.7 g/dl, (mean +/- S.D.) rose to 10.4 +/- 1.1 g/dl, (p < 0.01) after three months of rHuEPO therapy. The partial correction of renal anemia resulted in a significant increase in exercise duration (from 278 +/- 84 sec to 384 +/- 74 sec, p < 0.01) and maximum pressure-rate product (from 228.3 +/- 50.3 mmHg.bpm/10(2) to 262.8 +/- 40.4 mmHg.bpm/10(2), p < 0.01). The maximum exercise-induced ST segment depression significantly decreased after treatment (from 1.3 +/- 0.5 mm to 0.5 +/- 0.5 mm, p < 0.05). These results suggest that the improvement in maximum coronary oxygen supply exceeded the increased maximum myocardial oxygen requirements after the partial correction of renal anemia by rHuEPO therapy in hemodialysis patients with coronary artery disease.

Adult↗
PubMed1993

[Evaluation of left ventricular systolic function by pulsed Doppler echocardiography in patients with acute myocardial infarction].

Left ventricular systolic function in patients with acute myocardial infarction was assessed by Doppler echocardiographic measurement of left ventricular ejection flow velocity and maximum acceleration in 20 patients with initial acute anteroseptal myocardial infarction (group A) and 15 age-matched normal subjects. All patients underwent emergency reperfusion therapy by direct percutaneous transluminal coronary angioplasty (direct PTCA). Pulsed Doppler echocardiograms were obtained from sample volume immediately below the aortic valve in the apical long-axis view. Three parameters, peak velocity, ratio of acceleration time to ejection time (AT/ET) and maximum acceleration, were measured by the Doppler analysis program. Changes in the 3 parameters from the day of admission to the 3rd post-admission day were also observed in 15 patients. Although no significant difference was observed in AT/ET in the 2 groups, peak velocity and maximum acceleration in the patient group were significantly lower than those in the normal group (peak velocity: 90.8 +/- 13.1 vs 99.4 +/- 9.7 cm/sec, p < 0.05, maximum acceleration: 2,692.4 +/- 604.5 vs 3,410.2 +/- 712.5 cm/sec2, p < 0.01, respectively). Between the admission and 3rd day, peak velocity and AT/ET did not change significantly, but maximum acceleration increased significantly (2,720.5 +/- 676.7, 1st day vs 3,313.9 +/- 947.5 cm/sec2, 3rd day, p < 0.05). These results indicate that the maximum acceleration measured by pulsed Doppler echocardiography is useful for assessing global left ventricular systolic function in acute myocardial infarction. Direct PTCA results in improved ventricular systolic function on the 3rd post-operative day.

Adult↗
PubMed1993

[Effect of physical exercise training on graft patency after aortocoronary bypass grafting].

This study evaluated the effect of physical exercise training on graft patency after aortocoronary bypass grafting (ACBG). Patients who underwent ACBG were randomized into the training (17 patients, 43 grafts) and nontraining groups (18 patients, 45 grafts). Tissue plasminogen activator (TPA) antigen, TPA activity, plasminogen activator inhibitor-1 (PAI-1) antigen and PAI-1 activity as fibrinolysis variables, and an angiographic study were performed 2 and 26 weeks after ACBG. Plasma TPA activity increased significantly in the training group, but not in the nontraining group after 24 weeks of training. Plasma PAI-1 antigen and activity decreased significantly in the training group, while PAI-1 levels remained unchanged in the nontraining group. Grafts were patent in 93% (40 of 43) of the training group and 76% (34 of 45) of the nontraining group (p < 0.05). A high plasma concentration of PAI-1 may interfere with the natural thrombolytic process. Exercise training can decrease PAI-1 levels and increase TPA activity after ACBG. Improved fibrinolysis obtained by exercise training may have beneficial effects on graft patency.

Adult↗
PubMed1993

Fatal spontaneous pneumocystosis in nude rats.

Spontaneously generated fatal pneumocystosis was found in a congenitally athymic nude (rnu/rnu) rat colony. Severe pulmonary pneumocystosis was seen in rnu/rnu rats, and 10(7) to 10(8) cysts per lung were detected. No histologic changes were seen nor were Pneumocystis carinii organisms detected in heterozygous rnu/+ rats. Indirect immunofluorescence revealed strong reactivity in the sera from rnu/+ rats with rat-P. carinii cysts (originated from Wistar strain), compared with mouse- or human P. carinii cysts. The cysts isolated from rnu/rnu rats reacted strongly with antirat-P. carinii rat serum in comparison with antimouse-P. carinii rabbit serum and serum from a human with pneumocystosis. Immunoblotting studies using rat-P. carinii antigen showed that 116-kDa antigen reacted with the antirat-P. carinii serum and sera from rnu/+ rats but not with the antimouse-P. carinii serum and the serum from a human with pneumocystosis, whereas 52-kDa antigens of rat-P. carinii were recognized by all the anti-P. carinii sera tested. On the basis of our findings, the outbreak was caused by the P. carinii indigenous to the rat.

Animals↗
PubMed1992

Granulocyte-colony stimulating factor stimulates immunoreactive endothelin-1 release from cultured bovine endothelial cells.

We examined the effect of human recombinant granulocyte-colony stimulating factor (G-CSF) on the release of immunoreactive endothelin-1 (ET-1) from cultured bovine vascular endothelial cells. G-CSF dose dependently (10(-8)-10(-6) M) increased the release of immunoreactive ET-1 as a function of time under a serum-free condition. Coaddition of G-CSF and thrombin induced an additive effect on immunoreactive ET-1 release. Neither Ca2+ channel antagonist nor cyclooxygenase inhibitor affected immunoreactive ET-1 release stimulated by G-CSF. These results suggest that G-CSF, in addition to its effect on granulocyte progenitors, has a direct effect on vascular endothelium to induce the release of immunoreactive ET-1.

Animals↗
PubMed1992

Endothelin-1- and endothelin-3-induced vasorelaxation via common generation of endothelium-derived nitric oxide.

The vasorelaxant effects by endothelin-1 (ET-1) and endothelin-3 (ET-3), and their mechanisms of action were studied in isolated porcine pulmonary arterial strips. ET-1 and ET-3 dose-dependently (10(-9) - 10(-8) M) relaxed vascular strips precontracted with norepinephrine only in the presence of endothelium. The maximal vasorelaxant effect by ET-1 was about 70% of that by ET-3. The ET-1- and ET-3- induced vasorelaxation was blocked by NG-nitro-L-arginine, an inhibitor of nitric oxide synthesis, and methylene blue, an inhibitor of soluble guanylate cyclase. The present data suggest that vascular smooth muscle relaxation induced by ET-1 and ET-3 is mainly ascribed to synthesis and release of nitric oxide from L-arginine in endothelium.

Animals↗
PubMed1992

Preventive effect of exercise training on recurrent stenosis after percutaneous transluminal coronary angioplasty (PTCA).

The purpose of this study is to evaluate whether exercise training for 12 weeks prevents the development of restenosis after percutaneous transluminal coronary angioplasty (PTCA). Symptom-limited treadmill exercise with thallium-201 myocardial single photon emission computed tomography (SPECT) was performed one and 13 weeks after PTCA in 18 patients with exercise training and in 20 patients without. For quantitative analysis, the average count of region of interest in the hypoperfused area on the polar map was calculated. A percentage T1 uptake was determined by dividing average count of the hypoperfused area by that of a normal reference area at an initial image (%IU) and a delayed image (%DU). A percentage redistribution (%RD) was obtained by subtracting %IU from %DU as the parameter of residual ischemia in the hypoperfused area. Total treadmill exercise duration and maximal pressure rate product 13 weeks after PTCA increased significantly (p less than 0.01) in the trained group, whereas there was no significant change in the untrained group. %DU increased significantly (p less than 0.01) in the trained group, whereas there was no significant change in the untrained group. %RD decreased significantly (p less than 0.01) in the trained group, whereas there was no significant changes in the untrained group. The restenosis rates at the third month after PTCA was 17% (3/18) in the trained group and 40% (8/20) in the untrained group. These findings suggest that in patients with coronary artery disease exercise training improves myocardial perfusion by preventing the progression of coronary artery stenosis after PTCA.

Aged↗
PubMed1992

[Effects of exercise training on restoration of residual myocardial ischemia after percutaneous transluminal coronary angioplasty].

The effects of exercise training on the restoration of hibernating myocardium after percutaneous transluminal coronary angioplasty (PTCA) were evaluated. Symptom-limited treadmill exercise with thallium-201 myocardial single photon emission CT (SPECT) was performed at one and 13 weeks after PTCA in 15 patients with training and in 15 control patients without training who had no restenosis on repeat angiography. For quantitative analysis, counts for the regions of interest (ROI) were calculated in the hypoperfused area on the polar map. Percent T1 uptake was determined by dividing counts of the hypoperfused area by counts of a normal reference area on the initial image (%IU) and delayed image (%DU). The difference between %DU and %IU, defined as percent redistribution (%RD), was a parameter of residual ischemia in the hypoperfused area. %DU increased significantly in the trained group (65 +/- 11 to 73 +/- 9.3%, p < 0.01) and in the untrained group (66 +/- 14 to 70 +/- 15%, p < 0.05). %RD decreased significantly in the trained group (6.3 +/- 3.2 to 2.8 +/- 2.3%, p < 0.01); whereas, there was no significant change in the untrained group (6.1 +/- 2.8 to 5.2 +/- 3.8%). These findings suggest that, after successful PTCA, exercise training helps alleviate myocardial ischemia, probably by fostering the promoting effects which restore the hibernating myocardium.

Aged↗
PubMed1992

[An experimental study of determining the appropriate frequency of radiofrequency catheter ablation in vitro and in vivo for ventricular tachycardias].

The purpose of this study was to examine the appropriate frequency of radiofrequency catheter ablation (RFA) for ventricular tachycardia. Radiofrequency energy generated by a device in which the frequency could be changed, was delivered from an electrode catheter with an electrode tip-width of 4 mm. RFA was performed for 10 seconds with 20W (50V x 0.4A) using 7 different frequencies from 10 to 500 kHz on ventricular myocardium in vitro and in anesthetized dogs. The ablated lesion was significantly larger with RFA of 200-300 kHz in both surface area and depth (p less than 0.05). The appearance of ventricular arrhythmia during RFA increased as the frequency decreased, and one dog applied with RFA of 100 kHz had spontaneous ventricular fibrillation resulting in death. All dogs with frequency less than 100 kHz had a muscle cramp during RFA. We conclude that appropriate frequency seems to be 200-300 kHz to obtain a large ablated lesion, and a frequency higher than 300 kHz seems suitable to avoid arrhythmia. We also conclude that a frequency under 100 kHz should not be used.

Animals↗