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Biomedical subjects

K Hirosawa

Publications and source records attributed to K Hirosawa.

At least 55 records · Page 3Linked to original sources
PubMed1990

Analysis of photoreceptor membrane turnover in a Drosophila visual mutant, rdgA, by electron microscope autoradiography.

A Drosophila visual mutant, rdgA, has photoreceptor cells whose rhabdomeres degenerate in several days after eclosion. Incorporations of 3H-amino acids, and 3H-mannose and 3H-glucosamine residues into the photoreceptive membranes were studied in newly emerged rdgA mutant flies by electron microscope autoradiography. The amount of 3H-amino acids incorporated in rdgA rhabdomeres at 3 hr after the injection was about 50%, and that of 3H-sugar residues was about 20% of normal. Together with our previous finding that degradative activity is low in rdgA cell bodies at this time, these data indicate that the supply of photoreceptive membrane proteins is defective in rdgA.

Amino Acids↗
PubMed1989

Structure of the subrhabdomeric cisternae in the photoreceptor cells of Drosophila melanogaster.

The structure of subrhabdomeric cisternae (SRC) and related structures in the photoreceptor cells (retinular cells) of Drosophila melanogaster in normal flies and visual mutants were compared by electron microscopic observation of semithin sections of osmium-impregnated specimens. The three-dimensional organization of SRC and the other cell organelles was demonstrated by stereoscopy. Both light- and dark-adapted normal retinular cells contained elaborate networks of anastomosing tubules of SRC immediately beneath the rhabdomeres. Tubules connecting the SRC and rough endoplasmic reticulum were frequently seen. The SRC were absent from the retinular cells of rdgAKS60 whose rhabdomeres degenerate gradually after eclosion. Instead, numerous smooth vesicles were observed in the subrhabdomeric regions. In rdgBEE170, in which rhabdomere degeneration is light dependent, the SRC appeared normal in the dark-adapted flies. But their SRC gradually disintegrated after exposure to light. In norpASB37, whose rhabdomeres are small but do not degenerate, SRC appeared normal. These results suggest that the SRC is a significant structure for the maintenance of the structure of photoreceptive membrane in the retinular cells of Drosophila.

Animals↗
PubMed1989

Morphological observations of the apical surface of chick retinal pigment epithelium.

Chick embryonic retina was examined in order to investigate morphological changes of the apical portion of retinal pigment epithelial (RPE) cells. Whole retina and RPE sheets were observed by fluorescence microscopy (rhodamine-phalloidin preparation) and transmission electron microscopy. Photoreceptor cells had no inner and outer segments on the 8th day in ovo. The inner segments have been formed on the 15th day and the outer segments on the 19th day. RPE sheets had short and blunt apical processes on the 8th day, elongated and slender ones on the 15th day, and well-developed and melanin-containing processes on the 19th day. RPE of the 19th day had numerous bundles of actin filaments associated with melanin pigments in the basal portion of the apical processes and in the apical cytoplasm. In rhodamine-phalloidin preparations, intense fluorescence was localized in the RPE apical processes and cytoplasm on the 19th day. We concluded that RPE apical processes develop in accordance with the photoreceptor development.

Actins↗
PubMed1989

Uptake of retinol by cultured fibroblasts.

Cultured fibroblasts of adult rats were used to determine whether they could take in retinol administered to the culture medium at physiological concentration. After the administration of retinol, cells were observed with a phase-contrast fluorescence light microscope (LM) and a transmission electron microscope (TEM). Retinol and retinyl fatty acyl esters (RFAE) stored in the cells were analyzed with high-performance liquid chromatography (HPLC). It was revealed that these fibroblasts could take in retinol in the medium at a concentration of 1 x 10(-7) M and store it in lipid droplets in the cytoplasm as retinyl palmitate and other RFAE.

Animals↗
PubMed1989

Severity of cardiac failure from the standpoint of pulmonary circulation: studies centered on distribution of pulmonary perfusion.

In a normal man sitting upright, pulmonary perfusion is several times greater in the lower lung zone than in the upper zone. This pattern may sometimes be reversed in patients with cardiac disease. Tc99m-macro-aggregated albumin pulmonary perfusion images were computerized to isocounts area images (digital perfusion images; DPI). DPI were applied to various types of cardiac disease and patterns of DPI were divided into 4 classes according to amount of nonperfused pulmonary vascular bed. C-0; normal perfusion. C-1; decrease of nonperfused pulmonary vascular bed. C-2; disappearance of nonperfused pulmonary vascular bed. C-3; decrease of pulmonary vascular bed. In 71 patients with mitral stenosis relationships between pulmonary hemodynamics during exercise and distribution of pulmonary perfusion were studied, i.e. at rest (n = 71, mean pulmonary arterial pressure; 23 mmHg-cardiac index; 2.4 L/m) and during exercise C-0 (n = 13, 41 mmHg-5.4 L/m), C-1 (n = 17, 52 mmHg-5.2 L/m), C-2 (n = 27, 52 mmHg-4.5 L/m) and C-3 (n = 14, 65 mmHg-3.6 L/m) respectively. In patients with congestive heart failure cardiac status was classified to 4 classes according to ejection fraction and DPI. Patients with EF less than 30% and DPI more than C-2 showed high morbidity and mortality (two years mortality 47%; 27/40). Pulmonary venous pressure increases to maintain the cardiac index (Starling's law) in cases of decline in cardiac function or mitral stenosis. It was shown that increases in pulmonary venous pressure cause changes in distribution of pulmonary perfusion, which in turn works to depress the cardiac index. A decline in cardiac function and changes in the distribution of pulmonary perfusion coexist, mediated by pulmonary venous pressure and cardiac index. The distribution of pulmonary perfusion reflects the severity of cardiac failure itself, so by using DPI the severity of cardiac failure can be easily evaluated.

Blood Pressure↗
PubMed1989

Mechanism and prediction of sudden cardiac death in arrhythmia patients using electrophysiological studies.

Thirty nine cases, in which sudden cardiac death (SCD) was suspected, were studied to evaluate the mechanism and the prediction of SCD in arrhythmia-patients using electrophysiological studies (EPS). The 39 cases (28 male and 11 female) were located by surveying 2098 patients who underwent EPS for the evaluation of arrhythmias. Age at time of EPS ranged from 4 to 86 years, average 50.5 years. Time from EPS to death was 2 to 163 months, average 27.9 months. Underlying heart disease was: dilated cardiomyopathy in 11, old myocardial infarction in 5, ischemic heart disease in 5, hypertensive heart disease in 5, valvular heart disease in 3, hypertrophic cardiomyopathy in 2, arrhythmogenic right ventricular dysplasia in 1, myocarditis in 1, sarcoidosis in 1, cor pulmonale in 1, and no obvious heart disease in 4. Fifteen had a permanent pacemaker implanted. SCD in cases without a permanent pacemaker (24 cases): 2 had chronic complete A-V block (one BH block, one HV block), 1 had advanced A-V block (HV block), 3 had bundle branch block with first degree HV block, 9 had ventricular tachycardia (VT), 3 had sick sinus syndrome (SSS), 3 had paroxysmal atrial flutter, 1 had WPW syndrome and paroxysmal atrial fibrillation, 1 had paroxysmal atrial tachycardia, and 3 had premature ventricular beats and first degree HV block. SCD in cases with permanent pacemaker (15 cases): 5 had SSS, and 10 had A-V block. In 3 of the 5 with SSS and 7 of the 10 with A-V block, VT was found before pacemaker implantation. In our study, brady and tachyarrhythmias coexisted in 25 cases (64%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

Quick-freeze, deep-etch visualization of the nuclear pore complex.

We have visualized the nuclear pore complex (NPCx) three-dimensionally by quick-freeze, deep etching and suggest that NPCx is composed of four rings and associated filaments. The rings were located at the cytoplasmic side, at the nucleoplasmic side, and at the pore waist as well. Some of the filaments emanated toward the cytoplasm, some sprawled over the cytoplasmic face of the nuclear membrane, and some intervened the rings. The emanating filaments were considered to be vimentin filaments judging from the replica and thin-sectioned image.

Freeze Etching↗
PubMed1989

Retinol transport in cultured fat-storing cells of rat liver. Quantitative analysis by anchored cell analysis and sorting system.

It is difficult to study the mechanism of specific transport of vitamin A in fat-storing cells (FSC) in vivo. In this study, transport of vitamin A added to the medium was quantitatively analyzed in cultured FSCs by means of the spontaneous fluorescence emitted by vitamin A. By density-gradient centrifugation with 38% Percoll, an FSC-rich fraction was separated from normal rat liver cells. The FSCs were observed to retain cytoplasmic fat droplets even on days 3 and 4 of culture. The FSCs containing fat droplets were selected for this experiment by checking their emission of vitamin A fluorescence. To analyze the vitamin A content of isolated cells, we employed a newly developed anchored cell analysis and sorting system (ACAS 470), which provides fluorescence analysis and sorting of adherent cells under the phase contrast microscope by utilizing a laser with its irradiation range narrowed to 1 micron. Vitamin A fluorescence was detectable by this system even in the cultured FSCs. After 24 hours of culture of FSCs in medium with 1 x 10(-6) M vitamin A added, the strength of fluorescence per FSC was 24.3 +/- 11.2 x 10(5)/cell for control, 61.5 +/- 17.6 x 10(5)/cell for retinyl acetate, 26.0 +/- 12.6 x 10(5)/cell for retinyl palmitate, and 59.0 +/- 15.1 x 10(5)/cell for retinol. Thus, retinol and retinyl acetate were transferred to FSCs in significant amounts without the participation of retinol-binding protein. Furthermore, an extended examination was made of the mechanism of the retinol transport observed in this study. Transport was never inhibited by the presence of vitamin E or azide. Retinol may be transferred by passive transport attributable to the concentration gradient rather than by active transport or through cell membrane damage by retinol itself. There was a tendency for inhibition of the transport of retinol into the cells in fetal calf serum. This inhibition may have occurred because the retinol-binding protein or other serum proteins had decreased the concentration of free retinol.

Animals↗
PubMed1989

[Estimation of regional myocardial sympathetic neuronal function with I-123 metaiodobenzylguanidine (MIBG) myocardial images in patients with cardiomyopathy].

I-123 Metaiodobenzylguanidine (MIBG) is taken up by myocardial sympathetic neuronal endings. Sympathetic neuronal function in 10 patients with cardiomyopathy under stable state were studied by using MIBG and Tl-201 (Tl) SPECT images with 50% cut off level. For myocardial imaging MIBG and Tl were simultaneously injected and collected (dual injection and dual collection mode; Dd mode). Four hours delayed images were also collected. Three types of abnormal findings were noted in MIBG images in combination with Tl images. 1) Enhancement of regional MIBG washout with otherwise normal MIBG and Tl uptake in infero-lateral wall were noted in 5 patients with history of congestive heart failure (Pathophysiologically acceleration of regional sympathetic neuronal function was suspected. Mean washout ratio is 63 +/- 7% vs. 45 +/- 10% in normal region). 2) In 3 patients with dilated cardiomyopathy increase of MIBG/Tl (M/T) ratio was noted in basal septal wall (Sympathetic neuronal function is abnormally accelerated in the region with depressed coronary perfusion. Exaltation of regional sympathetic neuronal function was suspected. Mean M/T ratio is 1.6. Tentative normal range is from 0.8 to 1.20). 3) In 2 patients with dilated cardiomyopathy under severe congestive heart failure defects of MIBG uptake with normal Tl uptake were noted (Sympathetic neuronal function was depleted in spite of normal coronary perfusion. Depletion of myocardial catecolamine was suspected. M/T ratio is 0.75 and 0.7 respectively). Heterogeneous abnormality of sympathetic neuronal function was noted in MIBG images. This findings corresponded to report about heterogeneous myocardial catecholamine concentrations in hearts of recipients of transplantation.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Iodobenzylguanidine↗
PubMed1988

Structure of retinular cells in a Drosophila melanogaster visual mutant, rdgA, at early stages of degeneration.

A Drosophila visual mutant rdgA has photoreceptive cells which degenerate gradually after eclosion. Fine structure of the retinular cells of rdgAKS60 and rdgAKO14 was studied during early stages of degeneration to determine the initial morphological defects. The retinular cells of these two alleles showed the following structural abnormality within 1 day after eclosion: (1) rhabdomeres were small and irregular in shape; (2) cisternae of the rough endoplasmic reticulum were more numerous than those in normal retinular cells; (3) submicrovillar cisternae were absent; and (4) lysosomes were fewer than normal. Three-dimensional reconstruction of serial sections of the ommatidia showed that the degeneration of mutant rhabdomeres proceeds more rapidly in regions remote from the nuclei. These results suggest that the process of turnover of rhabdomeric microvilli is abnormal in rdgA. We also confirmed an increase of lysosomes and destruction of cellular organelles, as reported by previous investigators at more advanced stages of degeneration.

Animals↗
PubMed1988

Immunohistocytochemical localization of alpha human atrial natriuretic peptide in human atrium obtained from endomyocardial biopsy and cardiac surgery.

To demonstrate the localization of atrial natriuretic peptide (ANP), we were able to apply the indirect and avidin-biotin peroxidase complex (ABC) methods for immunohistocytochemical analysis on sections with routine fixation and embedding for conventional histopathological and ultrastructural examinations. Human right and/or left atrial myocardial specimens were obtained at cardiac surgery (n = 12) or by right atrial endomyocardial biopsy, employing Konno's catheter bioptome (n = 30). In both specimens, ANP-like immunoreactivity was observed mainly around the nuclei and in specific granules in atrial myocytes. These new techniques are, therefore, considered to be useful for clinical analysis employing minute human atrial specimens in various heart diseases.

Atrial Natriuretic Factor↗
PubMed1988

An integrated study employing histopathological, immunohistocytochemical and radioimmunoassay analyses of atrial natriuretic peptide in the right and left atria in patients with mitral valve disease.

To clarify the production mechanism of atrial natriuretic peptide (ANP) in right (RA) and left atria (LA) in mitral valve disease, histopathological and immunohistocytochemical analyses were performed and ANP levels were investigated by radioimmunoassay (RIA) in 28 patients. Atrial tissues were obtained during mitral valve replacement. ANP-like immunoreactivity of the myocytes applied by the avidin-biotin peroxidase complex method was observed around the nuclei of the atrial myocytes. Electronmicroscopically, immunoreactivity was observed in atrial specific granules. Light-microscopically determined intensity of the immunoreactivity was classified into 4 grades and the intensity in 100 myocytes was expressed by adding the scores of each myocyte. Mean right atrial pressure was positively correlated with the activity score in RA (r = 0.80). Pulmonary capillary wedge pressure was not correlated with the score in LA. The score in RA was significantly higher than that in LA. The ANP level in RA investigated by RIA was also higher than that in LA. Histopathological findings such as myocyte hypertrophy, degeneration and interstitial fibrosis were more severe in LA than in RA. In conclusion, longstanding atrial overloading, especially in LA, caused severe pathological damage, resulting in a smaller production of ANP. Much more ANP may be produced from RA in long-standing mitral valve disease.

Adult↗
PubMed1988

Clinical significance of Vanghan Williams classification for treatment of ventricular tachycardia: study of class IA and IB antiarrhythmic agents.

UNLABELLED: Ninety-eight cases of ventricular tachycardia (VT) were studied using clinical electrophysiological (EP)-pharmacological assessment to compare the efficacy of class IA (disopyramide-DP, procainamide-PA) and class IB (mexiletine-Mex, Lidocaine-Lid, aprindine-AP) agents available in Japan, and to evaluate the clinical significance of class subdivisions for the treatment of VT. In assessing the efficacy of drugs, we evaluated their ability to prevent and terminate induced sustained VT as well as their ability to suppress spontaneous premature ventricular beats (VPB). I. EP properties: DP significantly extended QTc, ERPRV, and the coupling interval by which VT or repetitive ventricular response (RVR) was induced. On the other hand, Mex and AP had no effect. Although no significant extension of QRS width was found, the significant extension of the interval from extrastimulus to the first induced VT or RVR complex by the three drugs indicates that all have suppressive effects on conduction velocity within the reentry circuit. II. CLINICAL SIGNIFICANCE: Correspondence of preventive effects was 67% for DP and PA (class IA), 54% for Mex and Lid (class IB), 55% for DP and Mex, 27% for AP and Mex, and 25% for AP and DP. Correspondence of terminating effect was 85% for DP and PA, 80% for DP and AP, 77% for DP and Mex, 75% for Mex and Lid, and 63% for Mex and AP. For suppression of spontaneous VPB's, correspondence rate was 100% for DP and PA, 39% for DP and Mex, 64% for Mex and Lid, 61% for Mex and AP, and 69% for DP and AP.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1988

Surgical and medical treatments of true and dissecting aortic aneurysm in cases over 65 years old.

Ninety-one patients with true and dissecting aortic aneurysm were reviewed. They ranged in age from 65 to 87 years (mean 71 years). Forty-eight patients were diagnosed with abdominal aortic aneurysm, 21 patients with thoracic aortic aneurysm and 22 patients with dissecting aortic aneurysm. They were divided into 2 categories, surgical group and non-surgical, and the prognoses of the 2 groups were compared. The average age of surgically treated cases was significantly younger than that of non-surgical cases. This study suggests that elective operation should be considered for abdominal aortic aneurysms because of the high risk of late rupture. In older patients with thoracic aortic aneurysm, the prognosis was better in surgically treated patients than in those not treated. However, the surgical mortality rate of elective operation was high. The surgical mortality rate of older patients with dissecting aortic aneurysm was not satisfactory, and medical treatment which decreases blood pressure should be considered first. All patients classified as Stanford type A should be operated on if possible.

Age Factors↗