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Biomedical subjects

K Takata

Publications and source records attributed to K Takata.

At least 145 records · Page 8Linked to original sources
PubMed1992

Involvement of actin filaments in mouse testicular cord organization in vivo and in vitro.

Involvement of actin filaments in mouse fetal testicular differentiation was examined in vivo and in vitro. During testicular cord formation in vivo, actin filaments accumulated in the basal cytoplasm of Sertoli cells. Addition of cytochalasin D (CD) to organ cultures of undifferentiated gonadal primordia significantly inhibited testicular cord formation. In brief, treatment with 25 ng/ml CD induced the formation of slender testicular cords, and treatment with 50 ng/ml largely inhibited cord formation in the explants. However, development and growth of the testicular parenchyma and Leydig cell differentiation occurred in the presence of CD. By electron microscopic and immunohistochemical examinations, it became clear that CD also affected formation of the basal lamina and accumulation of vimentin filaments in Sertoli cells. On the other hand, treatment with colcemid at 12.5 or 15 ng/ml prevented growth of the testicular parenchyma and development of interstitial regions. Interestingly, testicular cords formed under this condition. These results indicate that the basal actin filaments of Sertoli cells may play an important role in testicular cord formation, especially Sertoli cell polarization. Cell mitosis and/or microtubules, on the other hand, may not be directly involved in this process.

Actins↗
PubMed1992

Human lumbar vertebrae. Quantitative three-dimensional anatomy.

This study details the quantitative three-dimensional surface anatomy of human lumbar vertebrae based on a study of 60 vertebrae. The two lower vertebrae (L4 and L5) appeared to be transitional toward the sacral region, whereas the upper two vertebrae (L1 and L2) were transitional toward the thoracic region. Means and standard errors of the means for linear, angular, and area dimensions of vertebral bodies, spinal canal, pedicle, pars interarticularis, spinous and transverse processes were obtained for all lumbar vertebrae. This information provides a better understanding of the spine, and allows for a more precise clinical diagnosis and surgical management of spinal problems. The information is also necessary for constructing accurate mathematical models of the human spine.

Cadaver↗
PubMed1992

[A case of the emergency salvage from the thrombotic occlusion of the Fontan conduit in tricuspid atresia].

The thrombotic occlusion of the Fontan conduit is one of the most fatal complications after Fontan procedure. Its survival case by the successful emergency surgery is reported. A 17-year-old male who had undergone Fontan procedure three years before for tricuspid atresia, using the expanded PTFE graft of 19 mm in internal diameter, had several episodes of palpitation due to probable paroxysmal atrial fibrillation. He suddenly complained chest oppression feeling and suffered paroxysmal atrial tachycardia following after atrial fibrillation. The radionuclide angiocardiography was performed immediately, which revealed clearly that the Fontan conduit had occluded by the thromboembolism in spite of the prophylactic anticoagulant therapy. Then the emergency surgery was performed successfully, in which the occluded Fontan conduit was replaced with another expanded PTFE graft of 20 mm in internal diameter under the extracorporeal circulation. It seemed that the inducement of this thrombotic occlusion of the Fontan conduit was paroxysmal atrial fibrillation. We emphasize the importance of the prevention of arrhythmias in the postoperative care of the Fontan procedure. Additionally we do emphasize the usefulness of the radionuclide angiocardiography which is available and non-invasive. Especially, first-pass study is much informative to elucidate the circulatory states in the cardiac anomalies.

Adolescent↗
PubMed1992

Ultracytochemical localization of the erythrocyte/HepG2-type glucose transporter (GLUT1) in cells of the blood-retinal barrier in the rat.

The blood-retinal barrier is part of the blood-ocular barrier. Retinal pigment epithelial cells connected by tight junctions serve as an outer blood-retinal barrier, and the nonfenestrated endothelial cells of blood vessels sealed by tight junctions serve as an inner blood-retinal barrier. Using antibodies specific for the erythrocyte/HepG2-type glucose transporter (GLUT1), one isoform of facilitated-diffusion glucose transporters, it was found, by ultrastructural cytochemical examination, that GLUT1 in the rat was localized at both the apical and basolateral plasma membranes of retinal pigment epithelial cells. The fenestrated endothelial cells of the underlying choriocapillaries were negative for GLUT1. In the inner retina, GLUT1 was found at both the luminal and contraluminal plasma membranes of endothelial cells. These observations show that GLUT1 is concentrated at the critical plasma membranes of the blood-retinal barrier and may serve as the machinery for glucose transport across the barrier.

Animals↗
PubMed1991

The role of N-glycosylation of GLUT1 for glucose transport activity.

To elucidate a functional role of N-glycosylation in glucose transporters, we introduced oligonucleotide-directed mutagenesis in GLUT1 cDNA to remove the possible site for N-linked glycosylation. The wild-type and the mutated GLUT1 cDNAs which induced a mutation of Asn at residue 45 to Asp, Tyr, or Gln were transfected and stably expressed into Chinese hamster ovary cells. The expressed wild-type and the mutated GLUT1 was demonstrated to be a broad band of a 45-60-kDa form and a sharp band of a 38-kDa form on Western blot analysis, respectively, indicating no glycosylation in the mutated GLUT1. Although the cell surface labeling of the glucose transporters demonstrated the presence of the glycosylation-defective glucose transporters on the cells surface, photoaffinity labeling of glycosylation-defective GLUT1 with [3H] cytochalasin B and a photoreactive mannose derivative, [3H]2-N-4-(1-azi-2,2,2,trifluoroethyl)benzoyl-1,3-bis(D-mannos+ ++-4-yloxy)-2- propylamine in the membranes was observed to be 40-70 and 15-30% of that of the wild-type GLUT1, respectively. The kinetic study of 2-deoxyglucose uptake revealed that the glycosylation-defective GLUT1 had a 2-2.5-fold greater Km value for 2-deoxyglucose uptake compared with the wild-type GLUT1. These observations strongly suggest that 1) N-glycosylation of GLUT1 glucose transporter is only on Asn 45 and 2) N-glycosylation plays an important role in maintaining a structure of glucose transporter with high affinity for glucose, thus, with high transport activity.

Affinity Labels↗
PubMed1991

Production of hepatitis B virion-like particles in yeast.

We constructed a yeast strain that simultaneously expresses four genes encoding the major S, middle S, large S hepatitis B viral envelope proteins and the core protein under the control of the yeast glyceraldehyde-3-phosphate dehydrogenase promoter and terminator. The lysate from this cell line, examined by immunological, physicochemical methods and electron microscopy, was found to contain spherical particles with a diameter of about 40 nm and a density of 1.25 g/ml. These particles reacted with anti-envelope antibodies, but not with anti-core antibodies. However, core antigenicity appeared upon treatment with 3% Nonidet P-40 that eliminates an outer envelope. These observations suggest production of a virion-like complex structure, or at least its DNA-less analog, consisting of core particle enveloped by antibody-reactive envelope. Such a structure was made only when all the four gene products were synthesized in a yeast cell. This system may be useful for the study of virus structure and assembly, and for improved vaccine development.

Blotting, Western↗
PubMed1991

Accuracy of assessment of cardiac vagal tone by heart rate variability in normal subjects.

The correlations of 11 indexes of heart rate variability were examined with pharmacologically determined cardiac vagal tone in 15 normal subjects at supine rest. After sympathetic influences by intravenous propranolol were eliminated, RR interval variability was measured for 10 minutes under controlled respiration (0.25 Hz), and cardiac vagal tone was determined as the decrease in mean RR interval following complete vagal blockade with atropine. Time domain indexes (standard deviation, coefficient of variance and mean successive difference) correlated strongly with vagal tone (r = 0.87, 0.81 and 0.92, respectively; p less than 0.001 for all). The same was true for frequency domain indexes for the high-frequency (0.25 Hz) component calculated both by autoregressive spectrum analysis (square root of power and coefficient of component variance) and by fast Fourier transform (mean amplitude) (r = 0.91, 0.85 and 0.86, respectively; p less than 0.0001 for all). However, frequency domain indexes for the low-frequency spectral component (0.03 to 0.15 Hz) correlated less strongly (r = 0.69, 0.55 and 0.70, respectively), and the fraction of power [power/(total power greater than 0.03 Hz)] of both components showed no correlation. Principal component analysis showed that the first 6 indexes with strong correlations contained solely the first principal component closely related to vagal tone, whereas the remaining 5 indexes also contained the second component unrelated to vagal tone. These results indicate that most of the time and frequency domain analyses in use provides an accurate and common measure of cardiac vagal tone at rest.

Adult↗
PubMed1991

Effect of tunicamycin, an inhibitor of protein glycosylation, on testicular cord organization in fetal mouse gonadal explants in vitro.

The effect of tunicamycin (TM) on testicular cord organization in the fetal mouse was examined in vitro at light and electron microscopic levels, with special reference to the glycoprotein functions during Sertoli cell differentiation. In testicular explants treated with TM, testicular cord organization was inhibited. TM treatment affected basal lamina formation by Sertoli cells, resulting in a discontinuous basal lamina or none at all in certain areas. The disorganized Sertoli cells were amorphous in shape, exhibited poor epithelial polarity, and were irregularly arranged in the testicular parenchyma. Extracellular matrix and collagen fibers were often observed in the intercellular spaces between the disorganized Sertoli cells. Lectin histochemical observation revealed that the number of wheat germ agglutinin binding sites on the plasma membrane and basal lamina of disorganized Sertoli cells was significantly decreased by TM treatment. However, junctions were normally observed in the plasma membrane between disorganized Sertoli cells. Leydig cells showed a normal differentiation in the testicular parenchyma in the presence of TM. These observations suggest that basal lamina formation of Sertoli cells and/or the expression of their cell surface glycoconjugates may be crucial for the establishment of Sertoli cell polarity and/or the Sertoli-Sertoli cell interactions required for proper testicular cord formation. Sertoli cell organization into testicular cords and Leydig cell differentiation may be controlled by different regulatory mechanisms.

Animals↗
PubMed1991

Severity of coronary atherosclerosis correlates with the respiratory component of heart rate variability.

Decreased vagal activity is frequently observed in coronary artery disease, but the mechanism of this association is unknown. We investigated cardiac autonomic function by relating heart rate spectral components to clinical and angiographic findings in 80 patients who were undergoing coronary angiography. The age- and sex-adjusted magnitude of the respiratory spectral component, which is an index of cardiac vagal tone, showed a significant negative correlation with the extent of coronary atheromatosis (r = -0.43, p less than 0.0001) and a less significant negative correlation with the severity of coronary stenosis (r = -0.30, p = 0.0070). These relationships were independent of previous myocardial infarction and of left ventricular function. Stepwise regression analysis showed that the respiratory spectral component contributed to atheromatosis independently of established coronary risk factors (partial R2 = 9.4%, p = 0.002), but not to stenosis. Our results support the hypothesis that decreased cardiac vagal activity is associated with an increased risk of coronary atherosclerosis.

Adult↗
PubMed1991

Cervical human vertebrae. Quantitative three-dimensional anatomy of the middle and lower regions.

In this study, the three-dimensional quantitative anatomy of middle and lower cervical vertebrae was determined. The three-dimensional coordinates of various marked points on the surface of the vertebra were measured with a specially designed morphometer instrument. From these coordinates, linear dimensions, angulations, and areas of surfaces and cross-sections of most vertebral components were calculated. The results showed two distinct transition regions: 1) toward the thoracic spine by the wider C7 vertebra but narrower spinal canal; and 2) toward the upper cervical region with the larger pedicle and spinous process of C2. Based on the study of 72 human cervical vertebrae, mean and standard error of the mean values of some clinically important dimensions of vertebral body, spinal canal, pedicles, transverse processes, spinous process, and uncovertebral joints are given for C2-C7 vertebrae. The areas of the end plates, spinal canal, and pedicles were modeled by elliptical and triangular shapes, and results were compared with the actual measurements.

Anthropometry↗
PubMed1991

Thoracic human vertebrae. Quantitative three-dimensional anatomy.

This study details the quantitative three-dimensional surface anatomy of thoracic vertebrae based on a study of 144 vertebrae. The thoracic spine was found to have three distinct regions: upper, middle, and lower segments. The two end segments appear to be transitional zones toward cervical and lumbar regions. The middle zone (T3 to T9) is of utmost importance due to the presence of the combination of narrow spinal canal and critical vascular supply. Means and standard errors of the means for linear, angular, and area dimensions of vertebral bodies, spinal canal, pedicle, pars articularis, spinous and transverse processes, and rib articulations are provided for all thoracic vertebrae. This information is necessary for constructing accurate mathematical models of the human spine. It will also provide a better understanding of the spine, and allow for a more precise clinical and surgical management of spinal problems.

Anthropometry↗
PubMed1991

Localization of Na(+)-dependent active type and erythrocyte/HepG2-type glucose transporters in rat kidney: immunofluorescence and immunogold study.

Glucose is actively taken up from the glomerular filtrate into the tubule cells by the Na(+)-dependent active glucose transporter (GT), and passively crosses the basolateral membrane via facilitated diffusion GT. With the use of antibodies directed against two types of GTs, we show the immunocytochemical localization of the Na(+)-dependent active GT (SGLT1) and the erythrocyte/HepG2-type facilitated diffusion GT (GLUT1). For light microscopic observation, frozen sections were stained by the rhodamine labeling method. Counterstaining with fluorescein-phalloidin and 4,6-diamidino-2-phenylindole dihydrochloride (DAPI) was employed to facilitate cell type identification. Immunogold staining was carried out on ultra-thin frozen sections for electron microscopy. The antibody to SGLT1 reacted with a 77 KD protein in immunoblotting of a kidney lysate. By immunocytochemistry, SGLT1 was localized in the microvillous plasma membrane in the apical brush borders of the cells of all three proximal tubule segments (S1, S2, and S3). The antibodies to GLUT1, a member of the facilitated diffusion GT family, were raised against human erythrocyte GT or synthetic oligopeptides derived from HepG2 GT, which reacted with a 48 KD protein in immunoblotting of the kidney lysate. GLUT1 was found at the basolateral plasma membranes of S3 proximal tubule cells, cells of the thick limb of Henle's loop, and collecting duct cells. Combined with known physiological data, our findings suggest that SGLT1 in the apical plasma membrane of the proximal tubule cells is responsible for the Na(+)-dependent active reabsorption of glucose from the glomerular filtrate. GLUT1 in the basolateral plasma membrane of S3 cells may transport reabsorbed glucose to the blood vessels. GLUT1 in the basolateral plasma membranes of cells of the thick limb of Henle's loop and of the collecting duct, on the other hand, may nourish these metabolically active cells by facilitating the diffusion of extracellular glucose provided from blood through the basolateral side of the cells.

Animals↗
PubMed1991

An improved fixation method for transmission electron microscopy for the histological study of the lens.

An improved fixation technique for transmission electron microscopic observation that enables good fixation of all areas of the rat lens was devised. Immersion fixation with 0.1 M phosphate-buffered 1.25% glutaraldehyde at 4 degrees C for 12 hours followed by postosmication produced good results for all areas of the lens--anterior, equatorial, and posterior zones. The technique was particularly suitable for maintenance of the shape of the lens since practically no irregularity, vacuolar degeneration, or expansion of the intercellular spaces was noted. This technique, which requires only a relatively short time, was also useful for the detection of early ultrastructural changes associated with cataract in spontaneously diabetic WBN/Kob rats. We anticipate that our procedure will be widely applied.

Animals↗
PubMed1991

[Distribution of glycoconjugates in gerbil hippocampal neurons--histochemical study with lectins].

Paraffin-embedded sections of gerbil hippocampus were made and stained by use of lectins with different sugar specificities: Concanavalin A (Con A), wheat germ agglutinin (WGA), Ricinus communis agglutinin (RCA), Phaseolus vulgaris agglutinin (PHA-E), peanut agglutinin (PNA), soybean agglutinin (SBA), and Vicia villosa agglutinin (VVA) to investigate the distribution of glycoconjugates in this brain region. Nuclear membranes of all the neurons in the hippocampus were positively stained with Con A and PHA-E, whereas WGA revealed definite staining of cell membranes. Endothelial cells of blood vessels were intensely positive to RCA, suggesting its usefulness as a marker of endothelial cells. With SBA and VVA, a few neurons in Ammon's horn were positively stained, while no positive cells were observed in the dentate gyrus. CA2 and the medial part of the CA1 were also positive bilaterally with SBA and VVA. Some neurons in Ammon's horn and dentate gyrus were selectively stained on the surface of their cell bodies with PNA. The present results show that lectins used distinguish different subpopulations of hippocampal neurons, indicating a new possible classification of hippocampal neurons based on their differences in glycoconjugates.

Animals↗
PubMed1991

Ultracytochemical localization of the erythrocyte/HepG2-type glucose transporter (GLUT1) in the ciliary body and iris of the rat eye.

Aqueous humor, with its unique low concentration of proteins, is produced by the ciliary body and isolated by the blood-aqueous barrier from the body fluid. Glucose in aqueous humor is a major source of nutrients for lens and corneal cells, and is maintained near the plasma level, suggesting a specific glucose transport mechanism in the blood-aqueous barrier. Using antibodies against erythrocyte/HepG2-type glucose transporter (GLUT1), one isoform of the facilitated diffusion glucose transporters, the authors found immunocytochemically that GLUT1 localizes in the epithelial cells of ciliary body and iris. GLUT1 is also found in the endothelial cells of blood vessels in the iris, whereas no labeling is seen in the blood vessels in the ciliary body. In the ciliary body epithelium, the plasma membranes of both the pigmented epithelial (PE) and nonpigmented epithelial (NPE) cells are positive for GLUT1. By the colloidal gold particle counting, the basal infoldings of PE cells show approximately two-fold denser labeling than those of NPE cells. Since PE and NPE cells make up a functional syncytium with numerous gap junctions, the authors suggest that glucose transport in the ciliary body occurs in this manner: glucose diffuses out from blood vessels through the pores of fenestrated endothelial cells, is transported into PE cells by GLUT1 in their plasma membrane, enters NPE cells through gap junctions connecting PE and NPE cells, and is finally transported into the aqueous humor by GLUT1 of NPE cells. The higher density of GLUT1 in PE cells may account for the consumption of glucose by PE and NPE cells in addition to the transepithelial transport.

Animals↗
PubMed1990

Erythrocyte/HepG2-type glucose transporter is concentrated in cells of blood-tissue barriers.

In search of possible diverse roles of glucose transporters (GT's), we examined whether any GT's are present in blood-tissue barriers where selective flow of glucose from blood to tissue cells is critically important. We found in rat that the erythrocyte/HepG2-type GT is localized in all the limiting plasma membranes known to serve as blood-tissue barriers, whether the barriers are endothelial type (brain, iris, inner retina, peripheral nerve) or epithelial type (choroid plexus, ciliary body, outer retina, peripheral nerve, placenta), except for plasma membranes in testis and thymus where no appreciable amount of the GT was found. The erythrocyte/HepG2-type GT may play a vital role for the entry of glucose into these firmly guarded tissues.

Actins↗