Biomedical subjects

Y Okamura

Publications and source records attributed to Y Okamura.

At least 109 records · Page 6Linked to original sources

PubMed1994

[Combined coronary artery bypass grafting and choledocholithotomy--a report of two cases].

A 74-year-old man and a 66-year-old woman were diagnosed as angina pectoris with choledocholithiasis. Combined coronary artery bypass grafting and choledocholithotomy were performed successfully in the two cases. For the prevention of cardiac complications and mediastinal infection, coronary artery bypass grafting was performed prior to choledocholithotomy. However, skin incisions were different in both cases. In the case with the biliary tract infection, both two surgical procedure were performed through a single skin incision in order to prepare the gastroepiploic artery as a graft. The combined operation is considered to be useful in selected cases with ischemic heart disease and choledocholithiasis.

Aged↗

PubMed1993

The ascidian embryo as a prototype of vertebrate neurogenesis.

Ascidian tadpole larvae, composed of only about 2500 cells, have a primitive nervous system which is derived from the neural plate. The stereotyped cell cleavage pattern and well characterized cell lineage in these animals allow the isolation and culture of identified blastomeres in variable combinations. Ascidian embryos express cell-type-specific markers corresponding to their cell fates, even when cultured under cleavage-arrest by cytochalasin B. This system provides us with a unique opportunity to study the roles of cell lineage and cell contact in early neuronal differentiation in the absence of events associated with complex morphogenesis. In addition, the isolated, cleavage-arrested blastomeres are ideally suited to electrical recording, permitting the use of ionic channels as specific markers for differentiation. In the cleavage-arrested embryos, suppression of one type of K+ channel, and induction of two types of Na+ channels, occur following cell contact with the vegetal blastomere. The combination of molecular and electrophysiological analyses on this simple animal system may provide insights into the nature of the cell interactions important in early neurogenesis, both in ascidians and in vertebrates.

Animals↗

PubMed1993

Neural induction suppresses early expression of the inward-rectifier K+ channel in the ascidian blastomere.

1. Early expression of ion channels following neural induction was examined in isolated, cleavage-arrested blastomeres from the ascidian embryo using a two-electrode voltage clamp. Currents were recorded from the isolated, cleavage-arrested blastomere, a4-2, after treatment with serine protease, subtilisin, which induces neural differentiation as consistently as cell contact. 2. The inward-rectifier K+ current increased at the late gastrula stage shortly after the sensitive period for neural induction both in the induced (protease-treated) and uninduced cells. Ca2+ channels, characteristic of epidermal-type differentiation, and delayed-rectifier K+ channels and differentiated-type Na+ channels, characteristic of neural-type differentiation appeared much later than the inward-rectifier K+ channels, at a time corresponding to the tail bud stage of the intact embryo. 3. When cells were treated with subtilisin during the critical period for neural induction, the increase in the inward-rectifier K+ current from the late gastrula stage to the neurula stage was about three times smaller (3.67 +/- 1.74 nA, mean +/- S.D., n = 14) than in untreated cells (11.25 +/- 3.10 nA, n = 26). The same changes in the inward-rectifier K+ channel were also observed in a4 2 blastomeres which were induced by cell contact with an A4-1 blastomere. However, when cells were treated with subtilisin after the critical period for neural induction, the amplitude of the inward-rectifier K+ current was the same as in untreated cells. Thus the expressed level of the inward-rectifier K+ channel was linked to the determination of neural or epidermal cell types. 4. There was no significant difference in the input capacitance of induced and uninduced cells, indicating that the difference in the amplitude of the inward-rectifier K+ currents derived from a difference in the channel density rather than a difference in cell surface area. 5. The expression of the inward-rectifier K+ channel at the late gastrula stage was sensitive to alpha-amanitin, a highly specific transcription inhibitor. In both induced and uninduced cells, injection of alpha-amanitin at the 32-cell stage reduced the current density of the inward-rectifier K+ channel to about 2 nA/nF, corresponding to 13% of that recorded from uninjected cells. By contrast, the expression of the fast-inactivating-type Na+ current, which transiently increased along with the inward-rectifier K+ channel, was resistant to alpha-amanitin injection. 6. The dose of alpha-amanitin injected was controlled by monitoring co-injected fluorescent dye, fura-2.(ABSTRACT TRUNCATED AT 400 WORDS)

Amanitins↗

PubMed1993

Lymphoplasmacytic lymphoma in a stallion.

Lymphoplasmacytic lymphoma found in a 6-year-old Anglo-Arabian stallion was investigated histologically, immunohistochemically and ultrastructurally. The animal showed a large mediastinal mass and generalized lymph node involvement. The neoplastic cells were in various differentiation stages of small lymphocyte, centrocyte, centroblast, immunoblast and plasma cell. Some neoplastic cells showed positive cytoplasmic reactivity for mu and lambda chains. There were well developed rough endoplasmic reticulum (RER) and Golgi complexes in plasmacytoid cells, and slightly developed RER or a few long strands of RER in medium-sized to large lymphoid cells. These findings suggest that this neoplasm is of B-cell origin.

Animals↗

PubMed1993

[A case report of graft replacement of the ascending and transverse aorta without homologous red blood cell transfusion].

A 28-year-old man of DeBakey type I dissecting aneurysm was received graft replacement of the ascending and transverse aorta under the deep hypothermic circulatory arrest and continuous retrograde cerebral perfusion for cerebral protection during circulatory arrest. From 3 weeks before operation, autologous blood was collected from the patient with the intravenous administration of a recombinant human erythropoietin (rHuEPO) and was subsequently used in the operation. As result, the graft replacement of the ascending and transverse aorta was performed without homologous red blood cell transfusion and postoperative neurological complications. We believe autologous blood transfusion with rHuEPO and circulatory arrest with CRCP contributes operations of aortic aneurysms without homologous blood transfusion.

Adult↗

PubMed1993

[Cardiac hemangioma of the interventricular septum and right ventricle: a case report].

A 52-year-old man who had been pointed out cardiac tumor on echocardiography, CT, MRI and coronary angiography was admitted to our hospital. He was asymptomatic. The surgical excision of the tumor was performed under extracorporal circulation and the postoperative period was free of event. It was not certain whether it originated from interventricular septum or right ventricle. The histology was mixed hemangioma composed of capillary and cavernous type.

Heart Neoplasms↗

PubMed1993

[Recent advances in the molecular biology of voltage-sensitive Na+ channels].

Na+ channels play a crucial role in generating action potentials in neurones and other excitable cells. alpha-subunits, composed of four homologous repeats, are responsible for most of the Na+ channel properties. The combination of molecular biology with electro-physiological tools has proved useful for understanding the molecular mechanism of the channel function. Activation, inactivation and ion permeation occur, based on Segment 4, III-IV linker, the region intervened by Segment 5 and 6, respectively. Mutations in a human skeletal muscle Na+ channel gene cause heritable muscle disorders, hyperkalemic periodic paralysis and paramyotonica congenita. Future directions in Na+ channel studies may include gene regulation of the Na+ channel related to neural cell fate and subcellular localization of channel molecules concurrent with plasticity or development.

Action Potentials↗

PubMed1993

[A case of modified Fontan procedure for SLL single ventricular heart with bicaval total occlusion].

We successfully performed a modified Fontan procedure and bidirectional Glenn shunt for a 6-year-old boy with single ventricular heart (SLL). After the operation, the patient suffered from a severe pneumonia, so intravenous catheter had to be inserted for a long time. Post operative angiography revealed bicaval total occlusion. But, inspite of these several complications, this patient is doing well. We believe that if bilateral SVC without communication exist on such a candidate for the Fontan type procedure, LSVC should be anastomosed to PA. The bidirectional Glenn shunt will contribute to save a life of the patient when the systemic venous route was occluded. In addition, the anticoagulation therapy should be taken for the patients underwent the Fontan type procedure.

Child↗

PubMed1992

[Double valve replacement for secondary atrioventricular regurgitation due to dilated cardiomyopathy--a case report].

A successful surgical case of double valve replacement for a patient with dilated cardiomyopathy was performed. A 45-year-old man was admitted to our hospital with paroxysmal atrial fibrillation and congestive heart failure. Echo cardiogram and cineangiography showed dilatation and decreased contraction of the left ventricle. A diagnosis of dilated cardiomyopathy was established since neither coronary artery disease nor valvular disease were observed. He was treated with medication of diuretics and pacemaker implantation. However, mitral and tricuspid regurgitation occurred and progressed 7 years later. Since then, he repeated admission and discharge against the strong medication. He became medically uncontrollable at the age of 58. Because of this, surgical treatment had to be considered. Double valve replacement for mitral and tricuspid valve was performed on September, 1989. Avoidance of cardiopulmonary bypass was only possible with the aid of catecholamine. Poor left ventricular function and pleural effusion frequently shown on chest X-ray film complicated the postoperative course. And with hospital treatment, he discharged three months after the operation. He has been doing well without any significant complaint during the past two years and cardiomegaly has been decreasing as well.

Cardiomyopathy, Dilated↗

PubMed1992

[Comparative studies of various conduits for myocardial revascularization with Kawasaki disease].

Between October 1976 and December 1991, 36 patients with Kawasaki disease underwent coronary bypass surgery. Comparisons were made from the postoperative morphologic condition of 4 conduits; saphenous vein graft (SVG n = 27), left internal thoracic artery (LITA n = 22), right internal thoracic artery (RITA n = 5) and gastroepiploic artery (GEA n = 8). The patency rate of arterial grafts was 100% at 1 month after surgery, and kept as high as 94.7% at 1-3 years after surgery. On the other hand, the patency rate of SVG was 90% at 1 month, but decreased to 52% at 1-3 years postoperatively. Arterial grafts sometimes showed string sign at 1 month after surgery, but the length and the diameter increased during 1 year after surgery. The internal thoracic artery showed superior flow potential compared with GEA. Thus, the internal thoracic artery is the first choice and GEA is the second as the graft material with Kawasaki disease. Long-term result of SVG was very poor, so coronary revascularization only by the arterial grafts is recommended.

Adolescent↗

PubMed1992

[Study on the pharmacokinetics of cefepime (I)].

The pharmacokinetics of 14C-cefepime dihydrochloride (14C-CFPM), were studied in rats upon both single and repeated intravenous administration. 1. Blood level of radioactivity was 59.27 micrograms eq./ml at 5 minutes after single intravenous administration at a dose of 20 mg/kg, and declined biexponentially thereafter. The values of AUC and T 1/2 were 70.1 micrograms eq..hr/ml and 38.0 hours, respectively. 2. Blood level of radioactivity was 59.41 micrograms eq./ml at 5 minutes after administration on the 7th day of repeated intravenous administration at a daily dose of 20 mg/kg, and declined more slowly as compared to the case of single administration. The values of AUC and T 1/2 after repeated administration were 159.7 micrograms eq..hr/ml and 44.5 hours, respectively. 3. Urinary and fecal excretion rates after single administration were 93.3% and 3.3%, respectively. 4. Urinary and fecal excretion rates were almost constant throughout the repeated administration; 88.4-90.7% and 2.3-3.7%, respectively. 5. 14C-CFPM distributed rapidly to the whole body except to the central nervous system. Although the radioactivity was removed rapidly from tissues, high levels of radioactivity remained in the kidney and the spleen as compared to other tissues. 6. Tissue concentrations of radioactivity at 5 minutes after the final dose of repeated administration were about the same as those after single administration but they declined more slowly than those after single administration. High levels of radioactivity were found in the kidney and the spleen as were found upon single administration. The ratios of these levels between repeated and single dosing were 4.3 and 2.6 for kidney and spleen, respectively. 7. Data obtained with autoradiograms of the whole body were consistent with measured tissue distribution obtained in both cases of single and repeated administration.

Animals↗

PubMed1992

[Study on the pharmacokinetics of cefepime (II)].

The pharmacokinetics of 14C-cefepime dihydrochloride (14C-CFPM), was studied in dogs after single intravenous administration at a dose of 20 mg/kg. Protein binding was also investigated both in vitro and in vivo. 1. Blood level of radioactivity was 83.53 microns eq./ml at 5 minutes after single intravenous administration and declined biexponentially thereafter. The values of AUC and T1/2 were 229 microns eq.(.)hr/ml and 90 hours, respectively. 2. Urinary and fecal excretion rates were 95.1% and 2.7%, respectively. 3. The in vitro protein binding at 1 to 100 microns/ml of drug concentration was 7.9 to 12.7% in rat, 12.4 to 18.6% in human, and 12.5 to 14.5% in dog. In vivo protein binding, which increased with time after administration, was 10.8 to 92.9% in rat and 17.5 to 64.9% in dog at 5 minutes to 6 hours.

Animals↗

PubMed1992

[An emergency surgical case of double aortic arch with hemoptysis].

A 78-year-old man was admitted because of hemoptysis. CT and aortogram revealed double aortic arch. Bronchofiberscopy revealed intratracheal hemorrhage which was associated with right aortic arch. An emergency operation was performed to prevent massive intra-tracheal bleeding. The patient underwent ligation of the right aortic arch through median sternotomy. After operation, hemoptysis disappeared and the postoperative course was uneventful. Surgical cases of double aortic arch are rare, especially with critical hemoptysis in aged patients.

Aged↗

PubMed1992

[Intra-arterial infusion chemotherapy in locally recurrent breast cancer].

Intra-arterial infusion chemotherapy (IA) using implantable reservoir was performed in four locally recurrent breast cancers. The regimen consisted of several cycles of induction (1 cycle, 90-150mg: EPI) and the following maintenance infusion. The results were as follows. (1) D.F.I. of all cases were short and pre-treatment of 3 cases was not effective. (2) Clinical response was 2 CR and 1 MR. We confirmed that IA was an effective treatment for not only locally recurrence but also disseminated foci. (3) In 3 out of the four cases there was reduction of severe arm swelling. These findings suggested that IA using implantable reservoir was useful for the treatment of locally recurrent breast cancer in terms of anti-cancer effect and improved QOL.

Adult↗

PubMed1992

[A case report of thrombosed Björk-Shiley valve in aortic position diagnosed using transtelephone PCG monitoring].

We report a successful elective re-AVR and MVR 10 years after AVR with aortic root enlargement and OMC. The patient was a 41-year-old woman. The diagnosis of thrombosed Björk-Shiley (B-S) valve was first suspected by transtelephone PCG monitoring and reconfirmed by the frequency analysis of prosthetic valve sounds and the aortography preoperatively. The thrombosis was 15 x 8 x 6.5 mm in size and located at the minor orifice of B-S valve, extending to the strut. The transtelephone PCG was useful in analyzing prosthetic valve sounds for patients especially living away from the hospital.

Adult↗

PubMed1991

Spatial-temporal appearance of developing immunoreactive TRH neurons in the neuroepithelial wall of the diencephalon.

Using an anti-pro-thyrotrophic hormone-releasing hormone (TRH) serum for immunohistochemical analysis, we examined the ontogenesis of TRH-producing neurons in the rat diencephalon, and distinguished three waves in the neurogenesis corresponding to the time and place of their origin. The first wave started on day 12.5 of embryonic age (E12.5); the neurons appeared within the neuroepithelium in both the anterior and posterior walls of the optic recess. These cells then migrated anteriorly into the marginal layer of the developing preoptic area (group 1 cells) and posteriorly into the hypothalamus (group 2 cells). The second and third waves occurred on E13.5-14.5 and E16.5-17.5, respectively. We named the cells that appeared in the neuroepithelium of the anterior portion of the hypothalamus as group 3 and 5 cells, and those in the posterior portion as group 4 and 6 cells. Group 1 and 3 cells generated the lateral and medial preoptic TRH neurons, and group 2 and 4 cells generated the cells in the lateral hypothalamic nucleus. Group 6 cells were involved in the development of the dorso-medial hypothalamic nucleus. Group 5 cells gave rise to the hypophysiotrophic secretory neurons in the parvocellular paraventricular nucleus. The cells derived from each cell group showed distinct morphological characteristics. These findings suggest that the ventricular wall of the hypothalamus is protomapped in a spatial-temporal manner to generate TRH neurons with distinct functional properties.

Amino Acid Sequence↗

PubMed1991

Anti-bilirubin monoclonal antibody. III. Preparation and properties of monoclonal antibodies to unconjugated bilirubin-IX alpha.

Anti-bilirubin-IX alpha monoclonal antibodies exclusively specific for unconjugated bilirubin-IX alpha are prepared and characterized. Using modified MBS (metamaleimidobenzoyl-N-hydroxysuccinimide ester) method, bilirubin-IX alpha was covalently coupled to bovine serum albumin (BSA) retaining its intramolecular hydrogen bonds as well as three-dimensional structure. Somatic cell fusion was performed between murine spleen cells immunized with the bilirubin-IX alpha-BSA and murine myeloma P3-X63-Ag8-U1 cells. After screening assay, 58 clones were identified which were producing antibodies not to albumin nor MBS, but to haptenic bilirubin-IX alpha. In inhibition analysis, the antibodies in the culture supernatant reacted only with bilirubin-IX alpha to a varying degree, but did not react with conjugated bilirubin-IX alpha, including bilirubin-IX alpha monoglucuronide, bilirubin-IX alpha diglucuronide, and ditauronic bilirubin-IX alpha.

Animals↗

PubMed1991

Further evidence of the presence of rat embryonic hypothalamic factors that induce the differentiation of gonadotrophic hormone-releasing hormone-containing secretory neurons.

We examined the presence of factor(s) in the embryonic medial basal hypothalamus (MBH) that may influence nasal placode (NAP)-derived luteinizing hormone-releasing hormone (LHRH) neurons in determining their secretory phenotype. In this study, we performed organotypic culture and transplantation of the NAP from 12.5-day-old embryos of rats and vomeronasal organ (VNO) from 14.5-day-old embryos. Surgical operations, however, were performed on 16.5-day-old embryos. The NAP and VNO were cultured singly or with the MBH obtained from the embryos of the same age and, further, in a medium with a nerve growth factor or fibroblast growth factors. Although LHRH neurons were derived from the NAP and VNO in all the cultures, judging from numbers and cellular morphologies, the MBH was most effective. The VNO was transplanted into the third ventricle of adult female rats singly or with the cerebral cortex, the mesencephalon-myelencephalon complex, or the MBH from 14.5-day-old embryos. All the grafts gave rise to LHRH neurons, but the number of the neurons was far greater in the grafts cotransplanted with the MBH, in which the neurons projected long processes to blood capillaries and formed neurovascular complexes, the feature of which may suggest the occurrence of the secretory activity in the fibers. The animals were examined 5 days after the surgical operations. In rhinoectomized embryos, LHRH neurons were distributed throughout the brain in the same pattern as found in intact rats, showing normal cellular morphology. In the encephalectomized rats, immunoreactive LHRH cells were present only in the terminal ganglia. These findings indicate that the embryonal MBH has a factor (s) that is essential to the development of secretory LHRH neurons.

Animals↗