Biomedical subjects

Y Wakabayashi

Publications and source records attributed to Y Wakabayashi.

At least 19 recordsLinked to original sources

PubMed2006

Intrinsic colossal magnetoresistance effect in thin-film Pr0.5Sr0.5MnO3 through dimensionality switching.

A homogeneous colossal magnetoresistance (CMR) effect at low temperatures has been found in a thin-film perovskite manganite Pr0.5Sr0.5MnO3. The transition is driven not by the spin alignment as in usual CMR in bulk samples but by the localization-delocalization transition switched by the change in the effective dimensionality. Two-dimensional (x2-y2)-orbital ordering enhanced by the substrate strain is essential for the stabilization of the insulating localized state, which is on the verge of the first-order transition to the three-dimensional metallic ferromangetic state.

Journal Article↗

PubMed2006

Novel orbital ordering induced by anisotropic stress in a manganite thin film.

A novel structure of orbital ordering is found in a Nd0.5Sr0.5MnO3 thin film, which exhibits a clear first-order transition, by synchrotron x-ray diffraction measurements. Lattice parameters vary drastically at the metal-insulator transition at 170 K (= T(MI)), and superlattice reflections appear below 140 K (= T(CO)). The electronic structure between T(MI) and T(CO) is identified as A-type antiferromagnetic with a d(x2-y2) ferro-orbital ordering. The new type of antiferro-orbital ordering characterized by the wave vector (1/4 1/4 1/2) in cubic notation emerges below T(CO). The accommodation of the large lattice distortion at the first-order phase transition and the appearance of the novel orbital ordering are brought about by the anisotropy in the substrate, a new parameter for the phase control.

Journal Article↗

PubMed2006

Long-term outcome of renal transplantation in focal glomerulosclerosis.

INTRODUCTION: Focal segmental glomerulosclerosis (FSGS) has a tendency to recur frequently after kidney transplantation. We evaluated 12 cases to examine the incidence and long-term outcomes of recurrent FSGS. MATERIALS AND METHODS: Twelve patients with renal failure caused by FSGS received kidney allografts from living related donors. Tacrolimus or cyclosporine was used in combination with prednisolone and azathioprine or mycophenolate mofetil. RESULTS: The mean graft survival was 87.4 +/- 46.8 months. The graft survival rates in FSGS recipients were at 1 year, 100%; 5 years, 79.6%; 10 years, 68.2%. Two out of four recipients experienced graft loss due to chronic rejection. The other two out of four recipients with graft loss displayed severe proteinuria diagnosed as recurrence of FSGS. To treat recurrent FSGS, plasma exchange was partially effective to reduce proteinuria. CONCLUSION: Our incidence of recurrent FSGS is 16.7% with graft survivals at 5 and 10 years of 79.6% and 68.2%, respectively. The recurrence of FSGS happened after scheduled reductions in immunosuppressants. Careful observation is required with maintenance of immunosuppression in these patients.

Biopsy↗

PubMed2005

p53 prevents maturation of T cell development to the immature CD4-CD8+ stage in Bcl11b-/- mice.

Signaling pathways such as the pre-TCR and Wnt pathways regulate alpha/beta T cell differentiation in thymus. Mice lacking an essential component of the pre-TCR exhibit arrest at the (CD4(-)CD8(-)) (CD44(-)CD25(+)) stage (DN3) of thymocyte development, and introduction of p53 deficiency into those mice abrogates this arrest, resulting in transition to the (CD4(+)CD8(+)) double-positive (DP) stage. This paper examines the effect of inactivation of p53 on thymocyte development in Bcl11b(-/-) mice that exhibit arrest at the DN3 or (CD4(-)CD8(+)) immature single-positive (ISP) stage. No DP thymocytes were detected in thymocytes of adoptive transfer experiments in scid mice that were derived from p53(-/-)Bcl11b(-/-) precursors but ISP thymocytes increased in the proportion and in the cell number approximately three times higher than those from Bcl11b(-/-) precursors. Consistently, the level of apoptosis decreased to the level of wild-type precursors. These results suggest that inactivation of p53 is sufficient for DN3 thymocytes to differentiate into the ISP, but not to DP, stage of thymocyte development in Bcl11b(-/-) mice. This provides evidence for a novel p53-mediated checkpoint that regulates the transition from the DN3 to ISP stage of thymocyte development.

Animals↗

PubMed2005

Therapeutic drug monitoring of mycophenolic acid in renal transplant recipients.

Immunosuppressive regimens including mycophenolate mofetil (MMF, Cellcept) were used in a renal transplant transplant program since May 2000 including 67 patients in whom it was the primary drug. Acute rejection (AR) occurred in 9 cases (13%) with 1-year graft survival rate of 96.8%. Pharmacokinetic (PK) studies of mycophenolic acid (MPA) were performed in 46 recent patients (total, 127 times). There was no correlation between dose (mg/kg) and blood concentration (AUC0-9: r2= 0.27). AUC0-9 was well correlated with AUC0-4 (r2= 0.91), but not with a single timepoint concentration. MPA AUC0-9 level was significantly higher among the AR-negative group (n = 33; 34.2 +/- 16.8 ng.hr/mL) compared with AR-positive group (n = 3; 28.2 +/- 1.9 ng.hr/mL; P = .04085) over the 2 weeks after transplantation. MPA AUC0-9 level was higher among the adverse event (AE-positive) group (n = 15; 39.2 +/- 22.8 ng.hr/mL) compared with the negative group (n = 21; 30.1 +/- 8.0 ng.hr/mL; P = .08772) within 2 weeks after transplantation. These results suggest the necessity of measuring AUC for therapeutic drug monitoring (TDM) of MMF-containing immunosuppressive therapy. The possible target level of MPA AUC0-9 would be approximately 30 ng.hr/mL using the present immunosuppressive regimen.

Adolescent↗

PubMed2005

Twenty-five-year survival of living related kidney transplants: thirty-five years' experience.

AIM: Although better graft survival in patients treated with CsA has been obtained, chronic rejection continues to be a common complication in renal transplantation. In this study, we examined the graft survivals and complications among renal transplant patients followed for more than 25 years. METHODS: Between April 1970 and April 1979, 110 consecutive renal transplantations from living donors were performed in 110 patients. There were 83 men and 27 women of mean age of 27 +/- 7.0 years. A combination of azathioprine (AZ) and prednisolone (PSL) was used for the initial immunosuppressive therapy in all patients. RESULTS: Over 25 years postoperatively, 41 patients died with or without a functioning graft due to complications including infections and malignancies. Therefore, the 25-year patient survival was 62.5% and 34 patients returned to hemodialysis, yielding an actual 25-year graft survival of 36/110 (32.1%). The longest surviving graft is 30 years and 2 months. The main causes of death were infectious disease and malignancy; 73% of graft loss was due to chronic rejection. Mean serum creatinine of the patient with functioning grafts over 25 years is 1.2 mg/dL; 75% of patients displayed a value under 1.5 mg/dL. The mean dosage of Az was 52.3 mg/d and PSL was 5.6 mg/d.

Adult↗

PubMed2005

Renovascular reconstruction of grafts with renal artery variations in living kidney transplantation.

INTRODUCTION: The shortage of grafts in living kidney transplantation has forced the use of marginal grafts with arterial disease or grafts with multiple renal arteries (MRA). We reviewed the outcomes of transplants using allografts with MRA procured by open donor nephrectomy and report two cases requiring vascular reconstruction. PATIENTS AND METHODS: We reviewed 31 cases where renovascular reconstruction of an MRA graft was performed. A ex vivo pantaloon (side-to-side) anastomosis to create a common channel was performed in 24 cases including two cases of renal artery aneurysms in the grafts, where vascular reconstruction was performed in the same fashion after resection of the aneurysm. In four cases, an accessory artery was anastomosed sequentially after revasculization of the main artery. In three cases of grafts with multiple renal arteries, multiple anastomoses were done in situ after various ex vivo renovascular reconstructions. RESULTS: Twenty one MRA grafts including grafts with a renal aneurysm are functioning well for a mean follow-up 135 months. The graft survival rate was 71.0% at 5 years after transplantation and 67.7% at 10 years. The donors whose grafts had a renal aneurysm were also well and normotensive with normal renal function at present. Ten grafts failed mainly due to chronic allograft nephropathy. CONCLUSION: MRA grafts procured by open nephrectomy, including those with renal artery aneurysms, were engrafted successfully by applying appropriate renovascular surgery. The use of those grafts was safe for both the recipient and the donor.

Anastomosis, Surgical↗

PubMed2004

Recurrence of focal glomerulosclerosis in post-renal transplant recipients: report of two cases.

INTRODUCTION: Focal segmental glomerulosclerosis (FGS) has a tendency to recur frequently after kidney transplantation. To evaluate the incidence and outcome of recurrence of FGS, we report 2 cases of recurrence. PATIENTS: Among 12 patients with renal failure caused by biopsy-proved FGS who received kidney allografts from living related donors, 2 experienced recurrent FGS. CASE REPORTS: Case 1 was a 28-year-old man who received a renal transplant from his mother. The recurrence of FGS happened just after the scheduled reduction in immunosuppressants at 36 months after the transplantation. He developed subsequently end-stage renal failure (ESRD) 50 months after transplantation. Case 2 was a 22-year-old man who received a renal transplant from this ABO disparate mother. A few days after renal transplantation, he displayed a severe nephrotic syndrome due to recurrent FGS, reaching ESRD at 23 months. To treat recurrent FGS, plasma exchange was partially effective, reducing the proteinuria but not stopping the progression of disease. DISCUSSION: Two recipients with severe proteinuria were diagnosed as having recurrent FGS. The incidence of recurrent FGS was 16.7% with 5-year and 10-year graft survival rates among recipients with ESRD caused by FGS of 79.6% and 68.2%, respectively. The incidence and graft survival rates were better than those expected based upon previous reports. Once the recurrence occurred, it was difficult to halt the progression of disease. Effective prevention of FGS and careful observations with maintained of immunosuppression are necessary in these patients.

Adult↗

PubMed2003

Simple techniques for atraumatic peritoneal dissection from the abdominal wall and for preventing peritoneal injury during trocar placement under retroperitoneoscopy.

PURPOSE: Inadvertent peritoneal tearing causes pneumoperitoneum and makes retroperitoneal laparoscopic procedures technically more difficult. We describe some simple techniques of atraumatic peritoneal dissection and the prevention of peritoneal injury during trocar placement under retroperitoneoscopic guidance. MATERIALS AND METHODS: After balloon dilation and the establishment of pneumoretroperitoneum a laparoscopic swab stick was used for peritoneal dissection from the abdominal wall under retroperitoneoscopic guidance. Exploratory puncture using a Cathelin (Terumo, Tokyo, Japan) needle was performed before trocar placement in close proximity to the lateral peritoneal reflection. RESULTS: We applied this technique in our last 10 consecutive retroperitoneal laparoscopic procedures. No peritoneal rents occurred during dissection of the lateral peritoneal reflection or trocar insertion. CONCLUSIONS: The laparoscopic swab stick technique described facilitates atraumatic peritoneal dissection as well as creation of an adequate working space. Exploratory puncture using a Cathelin needle is useful for preventing inadvertent peritoneal injury during trocar placement.

Abdominal Wall↗

PubMed2003

Plasma urea-cycle-related amino acids, ammonium levels, and urinary orotic acid excretion in short-bowel patients managed with an oral diet.

BACKGROUND AND AIMS: The small intestine contains several enzymes involved in arginine synthesis and converts glutamine to citrulline, the major compound for endogenous arginine synthesis. This study was conducted to assess the plasma status of urea-cycle intermediates and orotic urinary excretion in short-bowel patients. METHODS: Thirteen stable short-bowel syndrome patients (7 men; 60.2+/-15.2 years) were studied. Patients were divided into moderately resected (Group A; n=6) and severely resected (Group B; n=7) according to their remnant bowel length (Group A: 61-150 cm; Group B: < or =60 cm). All subjects were consuming an oral diet plus dietetic supplements. Plasma urea-cycle amino acids, ammonium and urinary orotic acid were determined. RESULTS: Plasma glutamine levels were significantly higher in both patient groups than in the control group (P<0.001). Regarding citrulline, Group B levels were significantly lower vs. controls (P<0.001). Comparisons between patient groups showed higher arginine in Group A (P<0.05) and non-statistically lower citrulline in Group B. Blood ammonium and orotic urinary excretion were normal. CONCLUSIONS: Although plasma citrulline and glutamine alterations were found, patients showed no hyperammonemia or orotic aciduria, which suggests a certain degree of adaptation in arginine and related amino acid metabolism, when an adequate dietary supply of arginine is provided.

Adult↗

PubMed2002

Development of growth-associated protein-43 and neurotrophin receptor immunoreactivities in the rat urinary bladder.

Little is known about how the prenatal innervation of the urinary bladder develops. The objective of this study was to define the timing and pattern of innervation of the developing rat bladder using growth-associated protein-43 (GAP-43) immunohistochemistry. In addition, we examined the development of two different classes of transmembrane receptor proteins, the Trk family of tyrosine kinases and neurotrophin receptor p75 immunoreactivities. GAP-43-positive nerves were first detected in the bladder at embryonic day (E) 16. They were growing rapidly to the bladder dome and covered the whole bladder by E18. The density of GAP-43-containing nerves increased in the muscle layer by postnatal day (P) 0. Both Trk receptor-positive and p75 neurotrophin receptor-positive fibers were also first seen at E16. The number of Trk immunoreactive nerves reached a peak at E18, and then decreased over the following days. In contrast, p75-labeled fibers were abundant at E18-P14. There were few GAP-43 or neurotrophin receptor-positive fibers in the adult. GAP-43 immunohistochemistry provided us with a picture of innervation in the developing rat bladder. Furthermore, the demonstration of neurotrophin receptors positive fibers in the prenatal and early postnatal bladders suggests that neurotrophins may contribute to the development of the peripheral nervous system in the urinary bladder.

Animals↗

PubMed2001

Genetic loci controlling susceptibility to gamma-ray-induced thymic lymphoma.

BALB/c is a susceptible strain for the development of gamma-ray induced mouse thymic lymphoma whereas MSM shows resistance. Association analysis of 220 backcross mice between the two strains using 67 markers was carried out to identify loci involved in the control of susceptibility. The genotype of mice with lymphoma showed excess heterozygosity relative to MSM homozygosity at D2Mit15 and D4Mit12 and was skewed toward MSM-derived alleles at D5Mit5. The P values in Mantel-Cox test were 0.0048 (D2Mit15), 0.0034 (D4Mit12) and 0.0048 (D5Mit5), suggesting association at the three loci in the susceptibility. Cooperative effect on lymphomagenesis was also observed among the three loci. To obtain independent evidence for linkage at D4Mit12, we made partially congenic mice in which a D4Mit12 region in BALB/c was replaced by MSM-derived homolog. Examination for the lymphoma susceptibility in 78 progeny of the congenic mice confirmed the effect of the locus near D4Mit12 (P=0.0037). The result, together with the linkage analysis, shows that the locus near D4Mit12 is regarded as a confirmed linkage but the other two loci as marginally suggestive.

Alleles↗

PubMed2001

"Devil's staircase"-type phase transition in NaV2O5 under high pressure.

The "devil's staircase"-type phase transition in the quarter-filled spin-ladder compound NaV2O5 has been discovered at low temperature and high pressure by synchrotron radiation x-ray diffraction. A large number of transitions are found to successively take place among higher-order commensurate phases with 2a x 2b x zc type superstructures. The observed temperature and pressure dependence of modulation wave number q(c), defined by 1/z, is well reproduced by the axial next nearest neighbor Ising model. The q(c) is suggested to reflect atomic displacements presumably coupled with charge ordering in this system.

Journal Article↗

PubMed2001

Functional recovery and regeneration of descending tracts in rats after spinal cord transection in infancy.

STUDY DESIGN: The functional recovery of rats that underwent spinal cord transection in infancy was evaluated by multimodal examination (functional tests, electrophysiologic evaluation, tract-tracing) to determine the basis for the recovery. OBJECTIVES: To determine whether the hind limb function in rats that underwent spinal cord transection in infancy is regained completely, which descending tracts regenerate after the transection, and whether the functional recovery is correlated with axonal reconnection. SUMMARY OF BACKGROUND DATA: It is widely accepted that a newborn rat recovers its hind limb function after spinal cord transection even without any specific treatments. This functional recovery might be attributed to possible regeneration of some descending pathways, although there is a counterargument that well-trained spinal cord reflexes may bring about functional compensation. METHODS: The thoracic spinal cord of infant rats was completely transected at Th10 when they were 2 weeks of age. Multimodal functional tests and electrophysiologic studies were performed 5 weeks later. Some recovered rats (i.e., those able to walk after the transection) underwent spinal cord retransection, with subsequent reevaluation of locomotion and muscle-evoked potentials. At 6 weeks after the initial transection, tract-tracing studies were performed in some animals. RESULTS: A motor performance score detected the functional differences between the control and the recovered rats. Muscle-evoked potentials of hind limbs after electrical stimulation to the brain were recorded in some of the recovered rats, but never in the unrecovered rats. Moreover, the muscle-evoked potentials of the recovered rats disappeared after spinal cord retransection that resulted in loss of voluntary movement. Morphologic studies in two rats provided evidence that reconnection of rubrospinal, vestibulospinal, and reticulospinal tracts had occurred, whereas corticospinal regeneration was not detected. CONCLUSIONS: It can be concluded that the hind limb function of rats that underwent spinal cord transection in infancy was partially regained; that axonal regeneration of the rubrospinal, vestibulospinal, or reticulospinal tracts was demonstrated, whereas the reconnection of the corticospinal tract was not observed; and that the axonal regeneration of these tracts is involved in the functional recovery.

Animals↗

PubMed2001

A point mutation in a cadherin gene, Cdh23, causes deafness in a novel mutant, Waltzer mouse niigata.

A novel mouse model for human nonsyndromic hearing loss, Waltzer niigata (v(ngt)), is found and subjected to positional cloning analysis. Genome-wide scan of 1648 backcross mice maps v(ngt) to the D10Mit258 locus near Waltzer (v). Recombination breakpoints are positioned on a physical map consisting of 13 BACs relative to the flanking markers in the vicinity of v(ngt). Allelism test done in parallel shows that v(ngt) and v are allelic. Sequence analysis reveals one-base deletion in the cDNA encoding a cadherin-related protein, Cdh23, mutation of which is recently reported in v mutants. The frame-shift change, producing a truncated protein of 51 amino acids, is ascribed to a base-substitution of G to A in the acceptor site of splicing junction which is predicted to cause one-base shift of the splicing position.

Animals↗

PubMed2001

Dopamine and serotonin uptake inhibitors on the release of dopamine and serotonin in the nucleus accumbens of young and aged rats.

Nucleus accumbens (ACC) of young (4 months old) and aged (24 months old) Wistar rats were perfused with dopamine (DA) uptake blocker, cocaine, or the serotonin (5-HT) selective reuptake inhibitor, fluoxetine, through the microdialysis probe membrane, used to assess the dopamine transporter (DAT) or serotonin transporter (SERT) modulation. The basal extracellular DA release in the ACC was significantly lower in aged rats than young rats. Analysis of DA and 5-HT concentrations in the ACC with increased positive GFAP revealed that DA and DOPAC levels of aged rats were decreased to 55 and 60% of those in young rats, respectively. After co-perfusion with cocaine, both DA and 5-HT releases in the ACC were increased in the young and aged groups. However, the magnitude of the increased DA release was lower in aged rats than young rats. Co-perfusion with fluoxetine showed lower magnitude of the increased DA release in aged rats. It appears that the DAT and SERT system responds initially to ACC cell loss with age, and that especially ACC DAT in the aged rat is more degenerative compared with the young rats. These findings suggest that the serotonergic system with SERT in the remaining ACC neurons show an early adaptive response and resistance to the normal aging and maintain the multiple regulatory system in the ACC despite neural loss since the dopaminergic neurons in the aged animals are vulnerable to aging.

Aging↗

PubMed2001

Vascular endothelial growth factor secreted by replicating hepatocytes induces sinusoidal endothelial cell proliferation during regeneration after partial hepatectomy in rats.

BACKGROUND: The aim of this study was to investigate regulatory mechanisms of sinusoidal endothelial cell (SEC) proliferation after hepatectomy in rats. METHODS: We investigated expressions of vascular endothelial cell growth factor (VEGF) and its receptors, flt-1 and KDR/flk-1, in regenerating liver after 70% hepatectomy. Proliferation of both hepatocytes and SECs was also monitored by evaluating the proliferating cell nuclear antigen (PCNA) labeling index. Furthermore, VEGF production by cultured hepatocytes isolated at different times after hepatectomy was measured in vitro. RESULTS: The expression of VEGF mRNA was increased markedly between 48 and 72 h after hepatectomy, and thereafter decreasing gradually. The immunohistochemical staining revealed that expression of VEGF started to increase 24 h after hepatectomy, with a peak at 72 h, and the majority of the VEGF-positive cells were hepatocytes located in periportal areas. Meanwhile, expression of flt-1 and KDR/flk-1 was observed along the sinusoids even before hepatectomy, but was increased between 72 and 120 h. Furthermore, VEGF production by cultured hepatocytes isolated 72 h after hepatectomy was significantly increased. The PCNA labeling index of the SECs exhibited a delayed and slower regenerative response in comparison to the hepatocytes, reaching a peak at 72 h. CONCLUSIONS: These data strongly suggest that VEGF secreted by proliferating hepatocytes may represent an important stimulator of SEC proliferation.

Animals↗

PubMed2001

Presence of a nucleus or nucleus-deriving factors is indispensable for the formation of the spindle, the diastema and the cleavage furrow in the blastomere of the Xenopus embryo.

The present study examines the indispensability of a nucleus or nucleus-deriving factors in the induction of cleavage in Xenopus eggs by testing cleavage in Xenopus eggs fertilized with ultraviolet (UV)-damaged sperm and deprived of the female nucleus. These eggs, which contain only one UV-damaged nucleus with one set of centrioles, undergo unique cleavages. Cleavage takes place in only one of the two blastomeres formed by the immediately preceding cleavage. Histologically, only one nucleus, which does not appear to be organized into typical chromosomes, is found in one of the two blastomeres formed by the immediately preceding cleavage. The typical bipolar spindle and the diastema, or a slit of astral rays, are formed in the blastomere that contains the nucleus. By contrast, only asters lacking the spindle and the diastema are formed in the remaining blastomeres, which do not contain a nucleus. The same results are obtained in eggs that contain two UV-damaged nuclei with one set of centrioles. In these eggs, cleavage appears to occur in one or two blastomeres that contain either or both of the nuclei and one bipolar spindle. In eggs that contain one intact and one UV-damaged nuclei, cleavage takes place quite normally with each blastomere containing one nucleus or one set of chromosomes as well as one bipolar spindle. Thus, there is a very close correlation between the presence of a nucleus and the formation of the mitotic spindle, the diastema and the cleavage furrow in the blastomeres of Xenopus embryos. We conclude that the presence of a nucleus or nucleus-deriving factors is indispensable for the formation of the bipolar spindle, the diastema and the cleavage furrow in the blastomeres of the Xenopus embryos.

Animals↗