Biomedical subjects

Masahiro Yamaguchi

Publications and source records attributed to Masahiro Yamaguchi.

14 recordsLinked to original sources

PubMed2003

Decrease in expression of alpha 5 beta 1 integrin during neuronal differentiation of cortical progenitor cells.

Neuronal differentiation of embryonic neural progenitor cells is regulated by both intrinsic and extrinsic signals. Since dynamic changes in cell shape typify neuronal differentiation, cell adhesion molecules could be relevant to this process. Although it has been reported that fibronectin-integrin interactions are important for the proliferation of neural progenitor cells, little is known about the contribution of integrins to neuronal differentiation. In order to address this shortfall, we examined integrin expression on cortical progenitor cells by using immunohistochemistry and FACS analysis of cells in which GFP expression was driven by regulatory (promoter) regions of the nestin gene (nestin-GFP(+)). We here report that high levels of nestin promoter activity correlated with high expression levels of alpha(5)beta(1) integrin (alpha(5)beta(1)(high) cells). FACS analysis of nestin-GFP(+) cortical cells revealed an additional subpopulation with reduced expression of alpha(5)beta(1) integrin (alpha(5)beta(1)(low) cells). The size of the alpha(5)beta(1)(low) subpopulation increased during cortical development. To investigate the correlation between integrin and neuronal differentiation, nestin-GFP(+) cortical progenitor cells were sorted into alpha(5)beta(1)(high) or alpha(5)beta(1)(low) populations, and each potential to differentiate was analyzed. We show that the nestin-GFP(+) alpha(5)beta(1)(high) population corresponded to broadly multipotential neural progenitor cells, whereas nestin-GFP(+) alpha(5)beta(1)(low) cells appeared to be committed to a neuronal fate. These findings suggest that alpha(5)beta(1) expression on cortical progenitor cells is developmentally regulated and its downregulation is involved in the process of neuronal differentiation.

Animals↗

PubMed2003

Distorted odor maps in the olfactory bulb of semaphorin 3A-deficient mice.

Semaphorin 3A (Sema3A) repels growing olfactory axons that express neuropilin-1 (NP-1), a receptor for Sema3A. The Sema3A-mediated axon guidance seems to be essential for the formation of the glomerular sensory map in the olfactory bulb (OB). To understand whether and how Sema3A is involved in sensory map formation, we examined the glomerular map in the OB of adult Sema3A-deficient mice. In wild-type mice, NP-1-positive glomeruli form the lateral and medial bands and avoid the anteromedial and ventral regions of the OB. In the Sema3A-deficient OB, NP-1-positive glomeruli spread over the entire OB, and we consistently found the ectopic arrangement of NP-1-positive glomeruli in the anteromedial and ventral regions. In addition, a specific subset of NP-1-negative and olfactory cell adhesion molecule-positive glomeruli, especially those in the anteromedial region, disappeared from the mutant OB. These results show a critical role for Sema3A in the spatial arrangement of glomeruli in the OB. Optical imaging from the dorsal OB showed that the distorted glomerular map conserved molecular-feature domains. However, the positions of the domains were shifted, which suggests a secondary rearrangement of the glomerular map in the Sema3A-deficient OB.

Animals↗

PubMed2003

Vascular endothelial growth factor in children with congenital heart disease.

BACKGROUND: Children with cyanotic congenital heart disease may experience the development of abnormal vessels that become a source of significant morbidity. Abnormal vessel proliferation in these children may take several forms, including systemic-to-pulmonary collateral arteries, systemic-to-pulmonary venous collaterals, systemic venous collateral channels after bidirectional cavopulmonary anastomosis, and pulmonary arteriovenous malformations. However, no entity responsible for these abnormalities has been identified yet. This study determined whether children with cyanotic congenital heart disease have elevated serum levels of vascular endothelial growth factor (VEGF) and whether elevated VEGF correlated with these abnormal vessels. METHODS: Mean systemic room air oxygen saturation (SpO2), blood cell counts (RBC), and serum VEGF levels were measured preoperatively. Samples were obtained from 61 children with acyanotic heart disease (group N) and 102 children with cyanotic heart disease (group C) before cardiac surgery. Postoperative catheterization was performed 1-month after the operation to evaluate the abnormal vessels in group C. RESULTS: The VEGF level was significantly elevated in group C (355.0 +/- 287.1 pg/mL) compared with group N (203.0 +/- 221.6 pg/mL; p < 0.001). VEGF levels in patients with a single ventricle associated with asplenia syndrome (n = 7) in group C were significantly elevated (711.9 +/- 443.5 pg/mL) compared with other patients. There was no significant correlation between VEGF level and SpO2 or RBC. Abnormal vessels were diagnosed in 19.6% (20/102) patients in group C. There was no difference in VEGF levels between the patients with abnormal vessels (336.8 +/- 182.5 pg/mL) and the patients without abnormal vessels (359.1 +/- 306.8 pg/mL). CONCLUSIONS: Children with cyanotic heart disease have elevated systemic levels of VEGF, especially in those patients with a single ventricle associated with asplenia syndrome. There was no significant relationship in VEGF levels between the patients with abnormal vessels and without these vessels.

Adolescent↗

PubMed2003

Cardioprotective effects and the mechanisms of terminal warm blood cardioplegia in pediatric cardiac surgery.

OBJECTIVES: Terminal warm blood cardioplegia has been shown to enhance myocardial protection in adult patients. However, the cardioprotective effects and the mechanisms of terminal warm blood cardioplegia in pediatric heart surgery were still unknown. METHODS: One hundred three consecutive patients were prospectively randomized to one of two groups. In the control group (n = 52), myocardial protection was achieved with intermittent hyperkalemic cold blood cardioplegia and topical cardiac cooling. In the terminal warm blood cardioplegia group (n = 51), this was supplemented with terminal warm blood cardioplegia before the aorta was declamped. Arterial and coronary sinus blood samples were analyzed to determine myocardial energy metabolism and tissue injury. RESULTS: There were no significant differences between the two groups in age (5.5 +/- 0.6 years in the control group vs 5.6 +/- 0.5 years in the terminal warm blood cardioplegia group), body weight (17.2 +/- 1.4 kg in the control group vs 19.8 +/- 1.7 kg in the terminal warm blood cardioplegia group), percentage of cyanotic heart diseases (50% in the control group vs 51% in the terminal warm blood cardioplegia group), number of patients who required right ventriculotomy (33% in the control group vs 39% in the terminal warm blood cardioplegia group), cardiopulmonary bypass time (194 +/- 12.1 minutes in the control group vs 177 +/- 8.6 minutes in the terminal warm blood cardioplegia group), aortic crossclamp time (83.3 +/- 5.9 minutes in the control group vs 82.3 +/- 5 minutes in the terminal warm blood cardioplegia group), lowest rectal temperature (27.4 +/- 0.3 degrees C in the control group vs 28.1 +/- 0.3 degrees C in the terminal warm blood cardioplegia group), and myocardial temperature (9.6 +/- 0.6 degrees C in the control group vs 9.6 +/- 0.7 degrees C in the terminal warm blood cardioplegia group). Spontaneous defibrillation occurred after reperfusion in 80% in the terminal warm blood cardioplegia group, which was significantly (P <.05) higher than the control group (62%). The lactate extraction rate at 60 minutes of reperfusion was significantly (P <.05) higher in the terminal warm blood cardioplegia group (9.0 +/- 2.8%) than the control group (-3.3 +/- 2.4%). The postreperfusion values of cardiac troponin T (7.4 +/- 0.6 ng/mL vs 11.2 +/- 1.0 ng/mL at 6 hours; 4.6 +/- 0.6 ng/mL vs 9.3 +/- 1.6 ng/mL at 18 hours) and heart-type fatty acid binding protein (137 +/- 28 ng/mL vs 240 +/- 30 ng/mL at 2 hours; 88 +/- 19 ng/mL vs 162 +/- 26 ng/mL at 3 hours) were significantly (P <.05 vs the control group) lower in the terminal warm blood cardioplegia group. CONCLUSION: Terminal warm blood cardioplegia enhances myocardial protection in pediatric cardiac surgery by an improvement in aerobic energy metabolism and a reduction of myocardial injury or necrosis.

Adolescent↗

PubMed2003

Subpopulation of nestin-expressing progenitor cells in the adult murine hippocampus shows electrophysiological and morphological characteristics of astrocytes.

Based on the expression of glial fibrillary acidic protein (GFAP), a recent hypothesis considered stem or progenitor cells in the adult hippocampus to be a type of astrocyte. In a complementary approach, we used transgenic mice expressing green fluorescent protein (GFP) under the promoter for nestin, an intermediate filament present in progenitor cells, to demonstrate astrocytic features in nestin-GFP-positive cells. Morphologically, two subpopulations of nestin-GFP-positive cells were distinguishable; one had an elaborate tree of processes in the granule cell layer and expression of GFAP (but not of S100beta, another astrocytic marker). Electron microscopy revealed vascular end feet of nestin-positive cells, further supporting astrocytic differentiation. Electrophysiological examination of nestin-GFP-positive cells on acutely isolated hippocampal slices showed passive current characteristics of astrocytes in one subset of cells. Among the nestin-GFP-expressing cells with lacking astrocytic features, two cell types could be identified electrophysiologically: cells with delayed-rectifying potassium currents and a very small number of cells with sodium currents, potentially representing signs of the earliest steps of neuronal differentiation.

Age Factors↗

PubMed2003

Surgical management of trabecular ventricular septal defects: the sandwich technique.

BACKGROUND: Surgical closure of trabecular ventricular septal defects is difficult and often unsuccessful. OBJECTIVE: We performed closure of trabecular ventricular septal defects by sandwiching the septum between 2 polyester felt patches placed in the left ventricle and right ventricle without ventriculotomy. METHODS: Eleven patients (7 boys and 4 girls) underwent a sandwiching closure at a mean age of 4.7 years (range, 0.4-9.7 years) and a mean weight of 16.7 kg (range, 4.6-52 kg). Associated cardiac malformations were present in 9 of the 11 patients. Seven patients had undergone previous operations. The trabecular ventricular septal defects are exposed through the tricuspid valve and also from the left ventricular side through a coexisting large perimembranous ventricular septal defect or through the mitral valve through an interatrial septostomy. Two forceps, one each from the right and left ventricular side, lead a 3F Nelaton catheter through the trabecular defect. An oversized circular polyester felt patch mounted on a 3-0 Nespolen suture attached to the Nelaton catheter is then passed into the left ventricle. The suture ends are then passed through a slightly smaller polyester felt patch on the right ventricular side of the septum. The Nespolen suture is then tied, thereby sandwiching the septum between the 2 patches. RESULTS: Time required for the procedure was less than 20 minutes in each case. There were no hospital deaths, and the postoperative course was uneventful in all patients. There was no residual shunt in 3 patients, and a minimal residual shunt was observed in 5 patients. Mild residual shunt was observed in 3 patients. Cardiac catheterization was performed 1 month postoperatively in 8 patients in whom residual shunt was noted on echocardiography. Five of 8 patients had a minimal residual shunt (pulmonary blood flow/systemic blood flow ratio = 1.0). Three patients had a residual shunt (pulmonary blood flow/systemic blood flow ratio = 2.0, 1.6, and 1.2). The patient with a pulmonary blood flow/systemic blood flow ratio of 2.0 had a "Swiss cheese" ventricular septal defect, and a residual shunt remained around the patch. However, the residual shunt decreased to a pulmonary blood flow/systemic blood flow ratio of 1.6 at examination 16 months postoperatively. Echocardiography showed that the residual shunt had also decreased in another 2 patients. CONCLUSIONS: We conclude that the sandwich technique is safe and easy. Even in cases with a residual shunt present, the shunt is expected to decrease as time passes. Further experience and longer follow-up of these patients are necessary to conclude whether this technique is applicable to neonates and young infants.

Blood Flow Velocity↗

PubMed2003

Early determination and long-term persistence of adult-generated new neurons in the hippocampus of mice.

New neurons are continually generated in the adult hippocampus, but the important question, whether adult neurogenesis is transient or leads to the lasting presence of new neurons, has not yet been answered. Dividing cells were labeled with bromodeoxyuridine (BrdU) and were investigated by means of immunofluorescence and confocal microscopy at several time-points 1 day to 11 months thereafter. BrdU-labeled neurons remained stable in number and in their relative position in the granule cell layer over at least 11 months. This finding implies that the addition of new neurons is not transient and that their final number and localization are determined early. By contrast, expression of immature markers beta-III-tubulin and doublecortin in BrdU-labeled cells, peaked early after division and was not detectable after 4 weeks. In transgenic mice expressing enhanced green fluorescent protein under the nestin promoter none of the BrdU/nestin-positive cells early after division expressed the mature marker NeuN, confirming that no dividing neurons were detected. These new data suggest that new neurons are recruited early from the pool of proliferating progenitor cells and lead to a lasting effect of adult neurogenesis.

Animals↗

PubMed2003

N-cadherin mediates retinal lamination, maintenance of forebrain compartments and patterning of retinal neurites.

The complex, yet highly ordered and predictable, structure of the neural retina is one of the most conserved features of the vertebrate central nervous system. In all vertebrate classes, retinal neurons are organized into laminae with each neuronal class adopting specific morphologies and patterns of connectivity. Using genetic analyses in zebrafish, we demonstrate that N-cadherin (Ncad) has several distinct and crucial functions during the establishment of retinal organization. Although the location of cell division is disorganized in embryos with reduced or no Ncad function, different classes of retinal neurons are generated. However, these neurons fail to organize into correct laminae, most probably owing to compromised adhesion between retinal cells. In addition, amacrine cells exhibit exuberant and misdirected outgrowth of neurites that contributes to severe disorganization of the inner plexiform layer. Retinal ganglion cells also exhibit defects in process outgrowth, with axons exhibiting fasciculation defects and adopting incorrect ipsilateral trajectories. At least some of these defects are likely to be due to a failure to maintain compartment boundaries between eye, optic nerve and brain. Although in vitro studies have implicated Fgf receptors in modulating the axon outgrowth promoting properties of Ncad, most aspects of the Ncad mutant phenotype are not phenocopied by treatments that block Fgf receptor function.

Adherens Junctions↗

PubMed2002

Nonlinear estimation of spectral reflectance based on Gaussian mixture distribution for color image reproduction.

Nonlinear estimation method of spectral reflectance from camera responses is proposed. The proposed method minimizes the mean square error of spectral reflectance when the reflectance can be regarded as a random sequence of Gaussian mixture distribution. In computer simulations, 168 samples of spectral reflectance from a color chart are estimated from their image signals obtained by three- and six-band cameras. It is confirmed that the proposed method improves the accuracy in comparison with the conventional Wiener estimation method.

Journal Article↗

PubMed2002

Grouping and representation of odorant receptors in domains of the olfactory bulb sensory map.

Individual glomeruli in the mammalian main olfactory bulb represent a single or at most a few types of odorant receptors. Thus the physical arrangement of glomeruli at the surface of the olfactory bulb can be viewed as a sensory map representing approximately 1,000 types of odorant receptors. This review summarizes the recent advance of the knowledge regarding the spatial organization of the sensory map in the main olfactory bulb. Recent studies show that individual olfactory bulbs contain dual sensory maps, one in the lateral hemisphere and the other in the medial hemisphere of the bulb. The tracings of selective subsets of olfactory axons to their target glomeruli in the olfactory bulb show that glomeruli are parceled into large zones or bands. The spatial arrangement of these zones and bands are stereotypical and conserved across individual mice. Optical imaging studies show that glomeruli in the most rostrodosal zone, zone I, are further parceled into smaller functional domains, and suggest that odorant receptors having a common or similar molecular feature receptive site are grouped together and represented by glomeruli within the functional domain. The possible relation between the functional domain organization and the subjectively perceived odor quality (olfactory submodality) is reviewed.

Axons↗

PubMed2002

Effects of modified ultrafiltration on coagulation factors in pediatric cardiac surgery.

PURPOSE: Modified ultrafiltration (MUF) after cardiopulmonary bypass (CPB) in children has been reported to reduce the need for postoperative blood transfusion and minimize postoperative blood loss. This study was undertaken to quantify the effects of MUF on coagulation factors in pediatric patients. METHODS: Seven children scheduled to undergo open-heart surgery for congenital heart defects were studied. CPB circuits were primed with crystalloid solutions and no blood transfusions were performed. Hematocrit, platelet count, total plasma proteins, albumin, fibrinogen, prothrombin, factor VII, factor IX, and factor X were measured preoperatively, at the termination of cardiopulmonary bypass, and at the end of modified ultrafiltration. RESULTS: MUF was associated with significant (P < 0.05) increases in hematocrit (17.6% +/- 1.6% to 21.6% +/- 2.4%), platelet count 11.1 +/- 2.5 to 12.8 +/- 2.4 x 10(4)/mm3), total plasma proteins (2.7 +/- 0.3 to 3.4 +/- 0.4 g/dl), and albumin (1.6 +/- 0.2 to 2.1 +/- 0.2 g/dl). Fibrinogen, prothrombin, and factor VII also increased significantly (P < 0.05) during MUF, but factor IX and factor X did not change. CONCLUSION: We conclude that MUF attenuates the dilutional coagulopathy that occurs during CPB in children. There were slight improvements in the coagulation factors when MUF was employed.

Blood Coagulation Factors↗

PubMed2002

Anomalous origin of the left coronary artery from the pulmonary artery A case using the autologous pulmonary arterial wall graft.

A 10-year-old girl with anomalous origin of the left coronary artery from the pulmonary artery underwent a two coronary system reconstruction with a new technique. Her left coronary artery was stenotic next to its origin and had a severe adhesion with the aorta. We made a bypass grafting between the aorta and the left coronary artery with a roll shaped transected main pulmonary arterial wall graft. The postoperative angiogram showed a good patency of a reconstructed left coronary artery. This technique is considered useful surgical option for bypass grafting to the left coronary artery when the left coronary artery has an obstructive lesion or a difficulty to dissect and mobilize.

Blood Vessel Prosthesis Implantation↗

PubMed2002

Fast determination method of cerebral metabolic rate images of glucose using dynamic PET data.

Measurement of the rate constant parameters of the tracer 18F-FDG, used with positron emission tomography (PET) to determine the cerebral metabolic rate of glucose (CMRGlc), can provide a clear understanding of the physiological processes in the human brain. At present, the methods that are widely used to obtain CMRGlc, such as nonlinear least squares (NLS), first require the reconstruction of a time sequence of images. The reconstruction of these images requires a large amount of computation, especially in 3D Depth-of Interaction PET (DOI-PET), and the nonlinear based methods also require a large amount of computation. In this paper, we propose a fast parametric image reconstruction method for 18F-FDG dynamic PET studies. In our method a deconvolving process is first employed on the time sequential projection data to remove the effect of the measured plasma time activity. The deconvolved terms are integrated over three different time intervals and the parameters for determining CMRGlc can be obtained analytically. Our method requires only three reconstructing processes and reduces the computational demand to estimate CMRGlc. The algorithm performance is evaluated using a digital phantom and a clinical data set and the results show that the proposed method produces images with the same or better quality as the images from the NLS method, with much less computation compared to the NLS method.

Algorithms↗

PubMed2001

[Algebraic 2D PET image reconstruction using depth-of-interaction information]

Recently a high-performance PET scanner, which measures depth-of-interaction (DOI) information, is being developed for molecular imaging. DOI measurement of multi-layered thin crystals can improve spatial resolution and scanner sensitivity simultaneously. In this paper, we apply an algebraic image reconstruction method to 2-dimensional (2D) DOI-PET scanners using accurate system modeling, in order to evaluate the effects of using DOI information on PET image quality. Algebraic image reconstruction methods have been successfully used to improve PET image quality, compared with the conventional filtered backprojection method. The proposed method is applied to simulated data for a small 2D DOI-PET scanner. The results show that accurate system modeling improves spatial resolution without noise emphasis, and that DOI information improves uniformity of spatial resolution.

Journal Article↗