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Biomedical subjects

K Imataka

Publications and source records attributed to K Imataka.

At least 37 records · Page 2Linked to original sources
PubMed1990

Expression of major histocompatibility complex class I antigen in murine ventricular myocytes infected with Coxsackievirus B3.

Evidence has accumulated that T cell-mediated autoimmunity plays an important role in the pathogenesis of viral myocarditis. T lymphocytes are known to recognize antigen-presenting cells, such as virus-infected cells, being restricted by syngeneic major histocompatibility complex (MHC) antigens. To clarify in more detail the immunological mechanisms involved, we induced acute viral myocarditis in C3H/He mouse ventricles with coxsackievirus B3 (CVB3) and examined, by immunofluorescence, the expression of MHC class I and II antigens, previously reported not to be expressed by normal cardiac myocytes. Furthermore, to confirm the expression of MHC class I (H-2Kk) antigens at the cellular level, we treated cultured cardiac myocytes with interferon gamma and examined the antigen expression by immunofluorescence and Northern blot hybridization, using an antisense RNA probe for MHC messenger RNA. Our observations demonstrated 1) CVB3-induced myocarditis resulted in the enhanced expression of MHC class I (H-2Kk) gene product on the surface of cardiac myocytes but low or undetectable levels of MHC class II or H-2Dk gene products, and moderate focal transient (days 5-7) expression of both MHC class I (Kk + Dk) region gene products and MHC class II antigens were induced on capillary endothelial cells; 2) murine fetal cardiac myocytes cultured in vitro in the presence of interferon gamma similarly were shown to express marked levels of MHC class I (H-2Kk) but low to undetectable levels of the H-2Dk gene product; however, weak to moderate MHC Class II antigens were expressed by these cultured myocytes; and 3) the expression of MHC antigens in cardiac myocytes was modulated at the transcriptional level.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Intracranial metastasis of a spinal cord astrocytoma--case report.

The authors report a case of cerebral metastasis from a spinal cord astrocytoma. The first metastatic tumor was controlled by radiation therapy. A second metastatic brain tumor was detected 2 years later, but attempts to control it through subtotal removal and chemotherapy failed. Metastasis from a spinal cord tumor to the brain is a rare event.

Astrocytoma↗
PubMed1990

[Establishment of permanent atrial fibrillation and time course of the amplitude of the f wave].

Atrial fibrillation is one of the arrhythmias that increase with increasing age. In this study we compared transition intervals from sinus rhythm to permanent atrial fibrillation and the time course of the f wave amplitude immediately after the transition between 32 younger (less than 65 years) and 44 elderly patients (greater than or equal to 65 years) in whom transition from sinus rhythm to permanent atrial fibrillation was confirmed on serial ECG recordings. Each group was classified into three categories according their underlying diseases: hypertensive heart disease, valvular disease, and lone atrial fibrillation. In patients with hypertensive heart disease or lone atrial fibrillation, there was no significant difference in the transition intervals between the younger and the elderly groups. In both groups the transition intervals were significantly (p less than 0.05) longer in patients with lone atrial fibrillation than those in patients with hypertensive heart disease (44.6 vs. 12.5 months in younger and 26.8 vs. 12.9 months in elderly). A significant positive correlation (r = 0.58, p less than 0.01) was observed between the final P wave and the initial f wave amplitude on establishment of permanent atrial fibrillation in all patients. In the younger group, the initial f wave amplitude of patients with valvular disease (0.27 +/- 0.04 mV, mean +/- SE) was significantly larger than those of patients with hypertensive heart disease (0.15 +/- 0.03 mV, p less than 0.05) and of patients with lone atrial fibrillation (0.16 +/- 0.01 mV, p less than 0.05). The f wave amplitude of valvular disease was significantly decreased after 1 year (0.22 +/- 0.03 mV, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

[Peculiar mitral periannular cardiac muscle lesion in rabbits with experimentally-induced mitral regurgitation by vagus stimulation: investigation of a collagen increase and a myosin heavy chain isozyme change].

A peculiar mitral periannular cardiac muscle lesion was developed in rabbits with experimentally-induced mitral regurgitation by vagus stimulation. We investigated the cardiac muscle lesion of mitral regurgitation rabbits (MR group, N = 30) using pathohistological, immunohistochemical and biochemical methods. Control group consisted of 21 non-treated rabbits. The periannular cardiac muscle lesion in the MR group was characterized by swelling and increased stiffness of the muscle which were observed as swelling and degeneration of the myocardial cells and interstitial fibrosis on the microscopic observation, and increase in the amount and dimension of collagen tendon, strands, and struts on the scanning electron microscopic study. Hydroxyproline content of the periannular cardiac muscle lesion in the MR group was significantly abundant compared with that in the control group (10.5 +/- 1.6 vs 7.8 +/- 0.9 mg/g.wet wt, mean +/- SD, p less than 0.01) and that of the cardiac muscle in the left ventricular free wall in the MR group (10.5 +/- 1.6 vs 7.1 +/- 0.9, p less than 0.01). Furthermore, the immunohistochemical study clearly indicated that the increased collagen in the periannular cardiac muscle lesion in the MR group was type III collagen. A significant myosin heavy chain isozyme change from V1 myosin to V3 myosin on pyrophosphate gel electrophoresis was observed at the periannular cardiac muscle lesion in the MR group compared with that in the control group (%V1: %V3, 4.2: 92.7 vs 15.4: 74.7, p less than 0.01) and that of the cardiac muscle in the left ventricular free wall in the MR group (4.2: 92.7 vs 14.1: 75.4, p less than 0.01). These results suggested that the mitral periannular cardiac muscle in experimental mitral regurgitation rabbits induced by vagus stimulation suffers a strong mechanical load compared with the cardiac muscle in the left ventricular free wall.

Animals↗
PubMed1990

[The predictive factors for cerebral infarction in patients with non-rheumatic atrial fibrillation].

To investigate possible factors predicting cerebral infarction (CI) in patients with non-rheumatic atrial fibrillation, we reviewed the clinical records of 79 patients in whom conversion from sinus rhythm to persistent atrial fibrillation was confirmed by serial electrocardiographic tracings. The patients averaged 68.4 years in age and their average observation period after transition to persistent atrial fibrillation was 4.1 years. During the observation period, 20 patients developed CI. CI occurred in 10 of 22 patients with hypertensive heart disease, but in only three of 30 patients with lone atrial fibrillation and the difference was statistically significant (p less than 0.01). We compared demographic and pathophysiologic factors recorded at the onset of fixed atrial fibrillation between groups with and without CI. There were no significant differences in age, sex, smoking habits, diabetic complications and serum cholesterol level, but hematocrit level was significantly higher in patients with CI than in those without CI (45.3 +/- 3.2% vs 42.3 +/- 4.4%, p less than 0.01). The cardiothoracic ratio was not significantly different, but echocardiographic left atrial dimension was significantly greater in patients with CI than in those without CI (43.7 +/- 3.3 mm vs 38.6 +/- 5.8 mm, p less than 0.01). The left ventricular ejection fraction was significantly lower in patients with CI than in those without CI (62.2 +/- 16.6% vs 72.9 +/- 8.2%, p less than 0.05) and congestive heart failure was significantly more frequent in patients with CI than in those without CI (40.0% vs 13.6%, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1989

Hydroxyproline in all parts of the rabbit heart in hypertension and in its reversal.

To investigate the response of cardiac collagen to arterial hypertension and its reversal, we measured the hydroxyproline concentration in all parts of the rabbit heart in three groups: a chronic hypertension group (n = 11), a reversal group (n = 9) and an age-matched control group (n = 10). Left ventricular overload was produced by one-kidney, one-clip Goldblatt hypertension and its reversal was produced by clip release. The wet weight of every part of the left side of the heart was increased by hypertension and all parts except for the papillary muscles showed regression with reversal. However, the response of collagen was quite different among the various parts of the heart. The wet weights of the left atrium, left ventricular free wall, interventricular septum, and anterior and posterior papillary muscle in the hypertension group were 144 (P less than 0.01), 140 (P less than 0.01), 134 (P less than 0.01), 144 (P less than 0.01) and 129% (P less than 0.01), respectively, and those in the reversal group were 92, 113 (P less than 0.05), 107 (P less than 0.05), 142 (P less than 0.05) and 126% (P less than 0.05) of those in the control group, respectively. Hydroxyproline concentrations in the respective parts in the hypertension group were 79 (P less than 0.05), 91, 98, 121 (P less than 0.05) and 120% (P less than 0.05) and those in the reversal group were 86, 93, 94, 107 and 110% of those in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Age-related reduction in the number of rabbit erythrocyte Na, K-ATPase.

The number of Na, K-ATPase units, assessed by [3H]-ouabain binding assay, was significantly less in erythrocytes from 17 mature (30-week) rabbits than in those from 17 young (16-week) ones (0.179 +/- 0.010 vs. 0.263 +/- 0.014 pmol/10(9) cells, p less than 0.01). Consistent with this finding, the erythrocyte sodium concentration was significantly higher in mature rabbits as compared with young animals (17.1 +/- 1.30 vs. 10.8 +/- 0.68 mmol/liter, p less than 0.01). When the assays were repeated in 8 of the young rabbits 8 weeks after the initial determination, both variables were found to be similar to the levels from mature animals. The data suggest that the activity of erythrocyte sodium pump declines with aging or growth of donor rabbits, as a result of a reduction in the number of Na, K-ATPase units.

Aging↗
PubMed1989

[Production of experimental infective endocarditis in rabbit mitral valve prolapse induced by vagus stimulation].

An experimental model of bacterial endocarditis was developed in rabbits with mitral valve prolapse which was induced by vagus stimulation. Endocarditis was produced by injecting bacteria including pseudomonas pseudoalkaligenes (pathogenic for rabbits) and streptococcus viridans taken from human beings. Both bacteria induced bacterial endocarditis with high incidence, which was augmented by higher dose or earlier administration of bacterial after producing mitral valve prolapse. Similarly, verruca was produced more frequently by higher dose of bacteria or earlier administration of bacteria. The present data are similar to those of human beings, so that it is helpful to a study of bacterial endocarditis in a clinical setting.

Animals↗
PubMed1988

Relationship between plasma levels of atrial natriuretic peptide and cyclic guanosine monophosphate in patients with heart diseases.

The relation of plasma levels of atrial natriuretic peptide (ANP) to those of cyclic 3', 5'-guanosine monophosphate (cGMP) was studied in 43 patients with various heart diseases. Plasma levels of both ANP and cGMP were significantly (p less than 0.001) elevated in 34 patients with chronic heart diseases, and a significant positive correlation was observed between the two variables (r = 0.706, p less than 0.01). Clinical improvement of congestive heart failure resulted in a concomitant decrease in plasma ANP and cGMP levels in 6 patients. In 3 patients with paroxysmal atrial fibrillation, plasma levels of ANP and cGMP increased markedly during arrhythmia. These results indicate that increased circulating ANP may stimulate cGMP production in target cells, which in turn raises plasma levels of cGMP in humans.

Aged↗
PubMed1988

Hematocrit increase by mental stress in hypertensive patients.

Hematocrit (Hct) changes during mental stress were studied in 21 patients with mild hypertension. A 10 min arithmetic stress test increased blood pressure from 129 +/- 2/80 +/- 2 mmHg (mean +/- SEM) to 167 +/- 5/98 +/- 3 mmHg, and heart rate from 64 +/- 2 to 81 +/- 3 (p less than 0.001). Concomitantly, a significant (p less than 0.001) increase in Hct was observed (from 41.5 +/- 0.7% to 42.2 +/- 0.8%), and increments of Hct (-0.1% to 2.2%) were significantly (r = 0.61, p less than 0.01) correlated with those of systolic blood pressure. Plasma levels of norepinephrine (NE), epinephrine (E) and atrial natriuretic peptide (ANP) also showed a significant increase after mental stress. All these changes disappeared after a 60 min recovery period. The results suggest that mental stress increases Hct promptly, which may be due to concomitant increases in plasma NE, E and ANP levels. Hct elevation resulting from mental stress may be clinically relevant, at least, in hypertensive patients who are at risk of occlusive vascular diseases.

Adult↗
PubMed1988

Effects of monotherapy and withdrawal of antihypertensive drugs in the treatment of hypertension.

The final number of antihypertensive drugs used in the long-term treatment of a given patient is not always predictable at the start of therapy. By reviewing clinical records, we retrospectively examined the relationship between pretreatment blood pressure and the final number of drugs administered in 282 patients with mild to moderate hypertension who had been treated for 5 years or more (average 9.7 years). After years of treatment approximately one third and one half of 137 patients with a pretreatment diastolic blood pressure of between 90 and 104 mmHg were well controlled with combined therapy and monotherapy, respectively. The drugs had been withdrawn in the remaining 17% for 12 months or more. Lower pretreatment systolic blood pressure and lower pretreatment QRS voltage were signs favorable for withdrawal of the drugs. Combined therapy was required in more than half the patients with higher pretreatment diastolic blood pressure.

Adult↗
PubMed1988

[Assessment of tissue and intracellular pH following cold-induced vasogenic brain edema--in vitro and in vivo study].

Acid-base balance is closely related to the brain function and various methods have been applied to estimate the intracellular, extracellular or tissue pH. Umbelliferone, a fluorescent pH indicator, has been used to study either intracellular or tissue pH. In the present study, umbelliferone was used for histochemically estimating the tissue pH in the rat brain. The pH nomograms were made from the difference between fluorescent intensities at 450 nm on both excitations at 370 nm and 340 nm at different tissue water contents and different umbelliferone concentrations. Linear correlations were noted under each condition but 0.125% w/v umbelliferone provided the best estimation of tissue pH because of the least influence of water contents. Using this concentration of umbelliferone, a histochemical study was done to estimate the sequential changes in tissue pH following cold-induced vasogenic brain edema in rats. The results revealed a clear delineation of brain edema and the mild alkalosis in the edematous tissue, which probably reflects the pH of leaked plasma fluid. While the pH in the cortex around the lesion was neutral in the histochemical study, it was acidic in the in vivo study. This discrepancy is probably due to the former indicating the tissue pH while the latter the intracellular pH. Thus, the alkalosis in the edema fluid and the intracellular acidosis in the cortex around the lesion were noted in the cold-induced vasogenic edema.

Acid-Base Equilibrium↗