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Biomedical subjects

K Niwa

Publications and source records attributed to K Niwa.

At least 19 recordsLinked to original sources
PubMed2006

Electron microscopic investigation on the osteogenesis at titanium implant/bone marrow interface under masticatory loading.

Electron microscopic investigation on osteogenetic process at the implant surface of threadless rod-type titanium implants with different surface roughness of Ra 0.4 +/- 0.01 microm, Sm 2.6 +/- 0.3 microm and Ra 2.0 +/- 0.12 microm, Sm 36 +/- 9.1 microm was performed at the early stage of 21 and 42 days post implantation into the jawbones of four beagles under the load bearing condition of functional mastication. The implant surfaces were covered with a blood clot and haematopoietic stem cells (HSC) including phagocytic monocytes immediately after the implantation. Successively, osteogenic stem cells (OSC) migrated from cortical and/or trabecular endosteum to the HSC-layer on the implant surface. The new bone formation at the implant/bone marrow interface was developed by collaboration of osteomediator cells (OMC) differentiated from monocytes of HSC and osteoblast phenotype cells of OSC derived from endosteum of cortical bone and/or trabecular. The new bone layer at the implant surface consisted of two layers, solution-mediated calcification layer of pseudo bone and cell (osteoblast) -mediated calcification layer of true bone. The pseudo bone was produced by solution-mediated calcification of OMC- and HSC-remnants near by the implant surface. The bone healing process at the implant/bone marrow interface depended upon two factors; the migration of OSC from cortical and/or trabecular endosteum to the implant surface and the healing potentiality. Topographic dependency upon the bone healing potential at implant/bone marrow interface was not confirmed in this experiment under the load bearing condition of functional mastication.

Animals↗
PubMed2006

The right ventricle in congenital heart disease.

In patients with congenital heart disease the right ventricle (RV) may support the pulmonary (subpulmonary RV) or the systemic circulation (systemic RV). During the last 50 years evidence is accumulating that RV dysfunction develops in many of these patients and leads to considerable morbidity and mortality. Therefore RV function in certain groups of congenital heart disease patients needs close surveillance and timely and appropriate intervention to optimise outcomes. Despite major progress being made, assessing the RV either in the subpulmonary or the systemic circulation remains challenging, often requiring a multi-imaging approach and expertise (echocardiography, magnetic resonance imaging, nuclear and occasionally invasive assessment with angiography). This review discusses the implications of volume and pressure loading of the RV in the context of congenital heart disease and describes the most relevant imaging modalities for monitoring RV function.

Echocardiography↗
PubMed2005

Outcome of fertility-preserving treatment in young women with endometrial carcinomas.

OBJECTIVE: To evaluate the outcome of conservative treatment of young women with endometrial cancer. DESIGN: Observational study. SETTING: Gifu University Hospital, Japan from 1988 to 2002. POPULATION: Twelve women with endometrial cancer, FIGO IA estimated by MRI under 35 years. METHODS: Patients were treated with medroxyprogestreone acetate (400-600 mg/day) for 6-10 months, with endometrial curettage performed every four weeks. MAIN OUTCOME MEASURES: Response to therapy, pregnancies and reoccurrence of disease during follow up over a 30-month period. RESULTS: All cases had pathological complete remissions within 6-10 months. Seven of 10 wishing to have babies conceived, and five of them were delivered of full-term babies. Eight of nine cases receiving long term follow up (over 30 months) developed recurrent disease, with four opting for hysterectomy. No patient developed distant metastases or had disease-related death. CONCLUSION: Conservative therapy is feasible in carefully selected young women with endometrial cancer. Recurrence rates were high during long term observation even after pathological complete remissions. Therefore, close follow up is recommended.

Adenocarcinoma↗
PubMed2005

Infective endocarditis in congenital heart disease: Japanese national collaboration study.

OBJECTIVE: To provide pure cohorts of paediatric and adult patients with congenital heart disease (CHD) and infective endocarditis (IE) for making future guidelines. DESIGN: Japanese nationwide survey. SETTING: 66 Japanese institutions. PATIENTS: 170 children, mean (SD) age 7.4 (5.7) years (range 14 days to 17 years), and 69 adults, age 32.5 (14.1) years (range 18-69) who developed IE between 1997 and 2001 (one in 240 admissions with CHD). MAIN OUTCOME MEASURES: Clinical presentation of IE. RESULTS: 119 patients including 88 with cyanotic CHD had previous cardiac surgery. Procedures preceding IE were dental (12%) followed by cardiovascular surgery (8%). Sites of infection were left sided in 46% and right sided in 51%. Vegetation with diameter of 11 mm was documented in 151 (63%). Frequent complications were embolic events (stroke 11%, other emboli 20%) and cardiac failure (23%). The most common microorganisms were streptococci (50%) and staphylococci (37%) with methicillin resistant Staphylococcus aureus in 7.5%. Empirical treatments were penicillins (alone or with other antibiotics 57%) followed by cephems (22%) and vancomycin (11%). Surgery during active IE was common (26%), with vegetation (45%) and heart failure (29%) as the most frequent indications. Mortality was 8.8%: 8.0% among patients who received medical treatment alone and 11.1% among those with active IE who underwent surgery. The causes of death (n = 21) were surgery (7), infection (7), cardiac failure (6), and renal failure (1). CONCLUSIONS: Because of a recent increase in the incidence of IE and high mortality and complication rate, it is mandatory to establish well formulated recommendations for management of IE in paediatric and adult patients with CHD based on a large cohort. Results of this nationwide multicentre database should be helpful in establishing guidelines.

Adolescent↗
PubMed2004

In vitro study on bone formation and surface topography from the standpoint of biomechanics.

Effect of surface topography upon cell-adhesion, -orientation and -differentiation was investigated by in vitro study on cellular responses to titanium substratum with different surface roughness. Cell-shape, -function and -differentiation depending upon the surface topography were clarified by use of bone formative group cells (BFGCs) derived from bone marrow of beagle's femur. BFGCs consisted of hematopoietic stem cells (HSC) and osteogenetic stem cells (OSC). Cell differentiation of BFGCs was expressed and promoted by structural changes of cytoskeleton, and cell-organella, which was caused by mechanical stress with cytoplasmic stretching of cell adhesions to the substratum. Phagocytic monocytes of HSC differentiated to osteomediator cells (OMC) by cytoplasmic stretching with cell adhesion to the substratum. The OMC mediated and promoted cell differentiation from OSC to osteoblast through osteoblastic phenotype cell (OBC) by cell-aggregation of nodules with "pile up" phenomenon of OBC onto OMC. The osteogenesis might be performed by coupling work of both cells, OMC originated from monocyte of HSC and OBC originated from OSC, which were explained by SEM, TEM and fluorescent probe investigation on BFGCs on the test plate of cp titanium plates with different topographies. This osteogenetic process was proved by investigating cell proliferation, DNA contents, cell-adhesion, alkaline phosphatase activity and osteocalcine productivity for cells on the titanium plates with different topographies. The study showed increased osteogenic effects for cells cultured on Ti with increased surface roughness. Possible mechanisms were discussed from a biomechanical perspective.

Animals↗
PubMed2004

Nitric oxide regulates the levels of cGMP accumulation in the cricket brain.

Cricket brains were incubated in a saline containing nitric oxide (NO)-donor and phosphodiesterase inhibitor IBMX, which could activate soluble guanylate cyclase (sGC) to increase cGMP levels in the targets of NO. The increase of cGMP was detected by immunohistochemistry and enzyme linked immunosorbent assay. NO-induced cGMP immunohistochemistry revealed that many cell bodies of cricket brain showed cGMP immunoreactivity when preparations were treated with a saline containing 10 mM NO-donor SNP and phosphodiesterase inhibitor IBMX, but only a few cell bodies showed immunoreactivity when preparations were incubated without NO-donor. The concentration of cGMP in cricket brains were then measured by using cGMP-specific enzyme linked immunosorbent assay. Cricket brains were treated with a saline containing 1 microM of NO-donor NOR3 and 1 mM IBMX. The cGMP levels in the brain were increased about 75% compared to control preparations that was treated with a cricket saline containing IBMX. The level of cGMP decreased about 40% when preparations were incubated NOR3 saline containing sGC inhibitor ODQ. These results indicate that NO activates sGC and increases the levels of cGMP in particular neurons of the cricket brain and that the level of cGMP would be kept a particular level, which might regulate synaptic efficacy in the neurotransmission.

1-Methyl-3-isobutylxanthine↗
PubMed2004

Soybean isoflavones inhibit estrogen-stimulated gene expression in mouse uteri.

This study was performed to examine the inhibitory effects of soybean isoflavones on estrogen-stimulated gene expression of the uteri in ovarectomized mice. Especially when compared with the inhibitory effect of genistein and daidzein as aglycosides described in our previous report, subcutaneous administration of the glycoside genistin significantly decreased the levels of estradiol-17beta (E2)-induced expressions of c-jun, interleukin (IL)-1alpha and tumor necrosis factor (TNF)-alpha mRNAs (p < 0.005, p < 0.05 and p < 0.05, respectively) and seemingly proteins in the mice uteri, whereas the glycoside daidzin weakly inhibited E2-stimulated expressions of c-fos and IL-1alpha. Both genistin and daidzin seemed to have a weaker inhibitory effect than that of genistein and daidzein on the expression of estrogen-stimulated genes. It is suggested that those glycosides are naturally derived and generally absorbed from plant foods and might prevent E2-related endometrial carcinogenesis.

Animals↗
PubMed2003

Vitrification of rat embryos at various developmental stages.

The effect of developmental stage on the survival of cryopreserved rat embryos was examined. Wistar rat embryos at various developmental stages were vitrified by a 1-step method with EFS40, an ethylene glycol-based solution, or by a 2-step method with EFS20 and EFS40. After warming, the survival of the embryos was assessed by their morphology, their ability to develop to blastocysts (or expanded blastocysts for blastocysts) in culture, or their ability to develop to term after transfer. Most (91-100%) of the embryos recovered after vitrification were morphologically normal in all developmental stages. However, the developmental ability of 1-cell embryos was quite low; exposing them to EFS40 for just 0.5 min decreased the in vitro survival rate from 76 to 9%. The survival rates of 2-cell embryos and blastocysts, both in vitro and in vivo, were significantly higher with a 2-step vitrification process than with a 1-step vitrification process. Very high in vitro survival rates (94-100%) were obtained in 4- to 8-cell embryos and morulae in the 1-step method. Although survival rates in vivo of 4-cell (40%) and 8-cell (4%) embryos vitrified by the 1-step method were comparatively low, the values were similar to those obtained in non-vitrified fresh embryos. When morulae vitrified by the 1-step method were transferred to recipients, the in vivo survival rate (61%) was high, and not significantly different from that of fresh embryos (70%). These results show that rat embryos at the 2-cell to blastocyst stages can be vitrified with EFS40, and that the morula stage is the most feasible stage for embryo cryopreservation in this species.

Animals↗
PubMed2003

Development of rat oocytes following intracytoplasmic injection of sperm heads isolated from testicular and epididymal spermatozoa.

The possibility of obtaining normal development of rat oocytes following intracytoplasmic injection of rat sperm heads, obtained by sonicating spermatozoa from testes and epididymides, was evaluated. Irrespective of the source of spermatozoa, sperm heads were successfully injected into approximately 45% of oocytes used; after 9-12h of culture, approximately 55% of injected oocytes still had normal morphology. Of the oocytes injected with testicular sperm heads 45% were activated, with a female pronucleus and a second polar body, but significantly more oocytes (approximately 68%) injected with caput and cauda epididymal sperm heads were activated. Male pronuclear formation was observed in 67-84% of the activated oocytes, with no difference in the proportions among the different sources of sperm heads. When zygotes showing two pronuclei and a second polar body at 10h after injection were cultured in conditions that support development of 1-cell embryos produced in vivo, no embryos derived from testicular sperm heads developed to blastocysts after 120 h of culture. Development of embryos derived from cauda sperm heads was significantly higher at all points of assessment, while embryos from caput sperm showed an intermediate degree of development, compared with embryos from testicular spermatozoa. However, similar proportions (2-4%) of 1-cell embryos derived from all three groups of sperm heads developed into normal offspring after transfer to foster mothers; of the limited number of offspring tested, all were fertile. These results demonstrate that sperm heads from all sources tested are similar in their ability to contribute to full development of normal, fertile offspring.

Animals↗
PubMed2003

Reversible changes in protein phosphorylation during germinal vesicle breakdown and pronuclear formation in bovine oocytes in vitro.

This study examined the event of protein phosphorylation in bovine oocytes during germinal vesicle breakdown (GVBD) and formation of pronuclei following fertilisation in vitro. Immature oocytes were obtained from abattoir materials and cultured in vitro. The oocytes were labelled with [32P]orthophosphate at 3 h intervals from 0 to 12 h following maturation in culture or from 3 to 18 h following insemination. One-dimensional gel electrophoresis indicated that levels of protein phosphorylation are low prior to GVBD. However, the levels of protein phosphorylation at approximately 40 kDa, 27 kDa, 23 kDa and 18 kDa increased substantially following GVBD and then decreased gradually as maturation in culture progressed. In contrast, the levels of protein phosphorylation increased gradually in the oocytes following pronucleus formation. Further, two-dimensional gel electrophoresis indicated that the protein at approximately 18 kDa reversibly changed in the oocytes during maturation and fertilisation. These results indicate that the reversible changes of this phosphoprotein may be related to either cell cycle transition or pronucleus formation during maturation and fertilisation in bovine oocytes.

Animals↗
PubMed2003

Contrast-enhanced transabdominal ultrasonography in the diagnosis of pancreatic mass lesions.

PURPOSE: In this study, we evaluated the diagnostic usefulness of contrast-enhanced transabdominal ultrasonography (CE-US) in pancreatic mass lesions that could be detected by US. MATERIAL AND METHODS: CE-US was performed in 37 patients with various pancreatic mass lesions to evaluate the characteristic vascular findings. RESULTS: Pancreatic tubular adenocarcinoma showed negative enhancement pattern in 16 cases and a slight spotty enhancement pattern in 5 cases. Poorly differentiated adenocarcinoma showed slight homogeneous enhancement pattern in 1 case and acinar cell carcinoma was expressed as a heterogeneous enhancement pattern in 3 cases on CE-US. Endocrine cell tumor had a strong homogeneous enhancement pattern in 3 cases, a strong central enhancement in 1 case and a strong peripheral enhancement in 2 cases. Pseudotumorous pancreatitis showed an iso-enhancement pattern in 6 cases. CONCLUSION: CE-US is useful in evaluating the vascularity of the lesions in various pancreatic mass lesions in real-time images, and may be useful for the differential diagnosis of pancreatic mass lesions.

Abdomen↗
PubMed2002

Capacitation status and in vitro fertility of boar spermatozoa: effects of seminal plasma, cumulus-oocyte-complexes-conditioned medium and hyaluronan.

In the present study, the effects of seminal plasma (SP), cumulus-oocyte-complexes (COCs) conditioned medium (CCM) and hyaluronan (HA) on functional changes and in vitro fertilizing ability of porcine spermatozoa were examined. In in vitro fertilization (IVF) experiments, 10% (v/v) of exogenous SP in the fertilization medium prevented sperm penetration (using fresh-extended and frozen-thawed ejaculated spermatozoa). Analysis of frozen-thawed CCM revealed a HA content to levels of 30 ng/mL per incubated COC. Presence of frozen-thawed CCM did not, however, prove effective to increase (furthermore decreasing) oocyte penetration in vitro, and neither did supplementation with exogenous HA at the same concentration as that present in the CCM (secreted by COCs). Analysis of sperm capacitation using the chlortetracycline (CTC) assay showed that frozen-thawed CCM had no elevating effect on 'B-pattern' spermatozoa (implying capacitation-like changes) and that addition of 10% (v/v) SP held spermatozoa in the 'F-pattern' (intact) status. Dose of 500 microg/mL HA and freshly prepared CCM increased, however, the frequency of capacitated spermatozoa (B-pattern) without resulting in increased rates of 'AR-pattern' (acrosome-reacted) spermatozoa, compared with controls. The present results confirm the decapacitating effect of SP and suggest capacitating actions of HA (dose-related) and CCM (freshly prepared) on boar spermatozoa in vitro. The unclear effects of frozen-thawed CCM and a low dose of HA on penetration rates of boar spermatozoa call for further researches of their function in vivo.

Animals↗
PubMed2001

Cell proliferation in cancer prevention; effects of preventive agents on estrogen-related endometrial carcinogenesis model and on an in vitro model in human colorectal cells.

Proto-oncogenes such as c-fos, c-jun and c-myc are known to relate to cell proliferation and differentiation. Some oriental herbal medicines like Glycyrrhizae radix or Juzen-taiho-to were found to suppress estradiol-17 beta (E2)-induced expression of c-fos/jun in uterine corpus and inhibited N-methyl-N-nitrosourea and E2-induced endometrial carcinogenesis in mice. It is suggested that the effects of such oriental drugs are exerted probably through suppression of estrogen-induced c-fos/jun expression and they are promising preventing agents for endometrial cancers. In the combined in vitro assay for cell proliferation (MTS assay) and apoptosis (DNA fragmentation) in human colorectal cancer cells (Colo 320), a number of naturally occurring chemopreventive agents such as curcumin, quercetin, auraptene, 1'-acetoxychavicol acetate (ACA) and indole-3-carbinol were shown to generate apoptosis as well as to inhibit cell proliferation. The results suggest a mode of action of these chemopreventive agents and also imply that such in vitro short term assay is useful for detection of new agents for cancer prevention.

Adenocarcinoma↗
PubMed2001

Alleviation of myocardial ischemia after Kawasaki disease by heparin and exercise therapy.

BACKGROUND: Heparin promotes angiogenesis. We evaluated the effects of combined treatment with heparin and exercise on myocardial ischemia in the chronic stage of Kawasaki disease. METHODS AND RESULTS: This study was conducted in 7 patients (aged 6 to 19 years) who had a totally occluded coronary artery and stress-induced myocardial ischemia in the collateral-dependent areas. Twice-daily exercise using a bicycle ergometer was performed with increments of 0.5 W/kg every 3 minutes up to maximal exertion for 10 days. Heparin, which immediately increased circulating hepatocyte growth factor, was given intravenously 10 minutes before each exercise period. Newly developed myocardial infarction, ventricular tachyarrhythmia, anginal attack, or hemorrhagic complication was not observed in any patient. Dipyridamole-loading single photon emission computed tomography documented improved myocardial perfusion in the collateral-dependent areas and a significant reduction in total defect scores in all patients after the completion of 20 sessions (P=0.01). In control patients who did not receive the heparin-exercise therapy, however, stress defect scores remained unchanged (n=1) or increased (n=2) during follow-up. Computerized quantitative coronary angiography provided evidence that the heparin-exercise therapy increased the diameter of the occluded artery to which collaterals terminated (P=0.001) but not that of the reference artery with which collaterals were not connected (P=0.96). CONCLUSIONS: The findings suggest that a series of heparin and exercise treatments over 10 days may have a dramatic effect on the alleviation of myocardial ischemia in collateral-dependent regions. This may be a safe, noninvasive revascularization therapy for patients with coronary artery occlusion in the chronic stage of Kawasaki disease.

Adolescent↗
PubMed2001

Impact of pulmonary valve replacement on arrhythmia propensity late after repair of tetralogy of Fallot.

BACKGROUND: Chronic pulmonary regurgitation after repair of tetralogy of Fallot (TOF) may lead to right ventricular dilatation, which may be accompanied by ventricular tachycardia and sudden death. We aimed to examine the effects of pulmonary valve replacement (PVR) on (1) certain electrocardiographic markers predictive of monomorphic ventricular arrhythmia and sudden death and (2) sustained atrial flutter/fibrillation and monomorphic ventricular tachycardia. METHODS AND RESULTS: We studied 70 patients who underwent PVR for pulmonary regurgitation and/or right ventricular outflow tract obstruction late after repair of TOF. Maximum QRS duration and QT dispersion were measured from standard ECGs before PVR and at the latest follow-up. Arrhythmia was defined as sustained atrial flutter/fibrillation or sustained monomorphic ventricular tachycardia. Concomitant intraoperative electrophysiological mapping and/or cryoablation were performed in 9 patients (60%) with preexisting ventricular tachycardia and 6 patients (50%) with preexisting atrial flutter. QRS duration remained unchanged in the study group (P=0.46), but it was significantly prolonged (P<0.001) in a comparable group of patients with repaired TOF who did not undergo PVR. At a mean follow-up of 4.7 years, the incidence of ventricular tachycardia diminished from 22% to 9% (P<0.001), and atrial flutter/fibrillation decreased from 17% to 12% (P=0.32). Intraoperative ablation prevented recurrence of preexisting tachyarrhythmia (0 of 15 patients). CONCLUSIONS: PVR in patients with previous TOF repair and chronic pulmonary regurgitation leads to stabilization of QRS duration and, in conjunction with intraoperative cryoablation, to a decrease in the incidence of preexisting atrial and ventricular tachyarrhythmia. When applicable, this combined approach should be used in patients late after repair of TOF.

Adolescent↗
PubMed2001

Cyclooxygenase-1 participates in selected vasodilator responses of the cerebral circulation.

Cyclooxygenase (COX) is a prostanoid-synthesizing enzyme present in 2 isoforms: COX-1 and COX-2. Although it has long been hypothesized that prostanoids participate in cerebrovascular regulation, the lack of adequate pharmacological tools has led to conflicting results and has not permitted investigators to define the relative contribution of COX-1 and COX-2. We used the COX-1 inhibitor SC-560 and COX-1-null (COX-1(-/-)) mice to investigate whether COX-1 plays a role in cerebrovascular regulation. Mice were anesthetized (urethane and chloralose) and equipped with a cranial window. Cerebral blood flow (CBF) was measured by laser Doppler flowmetry or by the (14)C-iodoantipyrine technique with quantitative autoradiography. In wild-type mice, SC-560 (25 micromol/L) reduced resting CBF by 21+/-4% and attenuated the CBF increase produced by topical application of bradykinin (-59%) or calcium ionophore A23187 (-49%) and by systemic hypercapnia (-58%) (P<0.05 to 0.01). However, SC-560 did not reduce responses to acetylcholine or the increase in somatosensory cortex blood flow produced by vibrissal stimulation. In COX-1(-/-) mice, resting CBF assessed by (14)C-iodoantipyrine was reduced (-13% to -20%) in cerebral cortex and other telencephalic regions (P<0.05). The CBF increase produced by bradykinin, A23187, and hypercapnia, but not acetylcholine or vibrissal stimulation, were attenuated (P<0.05 to 0.01). The free radical scavenger superoxide dismutase attenuated responses to bradykinin and A23187 in wild-type mice but not in COX-1(-/-) mice, suggesting that COX-1 is the source of the reactive oxygen species known to mediate these responses. The data provide evidence for a critical role of COX-1 in maintaining resting vascular tone and in selected vasodilator responses of the cerebral microcirculation.

Acetylcholine↗
PubMed2001

Fertile and diploid nuclear transplants derived from embryonic cells of a small laboratory fish, medaka (Oryzias latipes).

Fertile and diploid nuclear transplants were successfully generated by using embryonic cells as donors in a small laboratory fish, medaka (Oryzias latipes). Embryonic cell nuclei from transgenic fish carrying the green fluorescent protein (GFP) gene were transplanted into unfertilized eggs enucleated by x-ray irradiation. In this study, 1 out of 588 eggs transplanted in the first experiment and 5 out of 298 eggs transplanted in the second experiment reached the adult stage. All of these nuclear transplants were fertile and diploid, and the natural and GFP markers of the donor nuclei were transmitted to the F(1) and F(2) offspring in a Mendelian fashion. This systematic study proves the feasibility of generating nuclear transplants by using embryonic cells from fish as donors, and it is supported by convincing evidence.

Animals↗