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Biomedical subjects

N Koyama

Publications and source records attributed to N Koyama.

At least 109 records · Page 6Linked to original sources
PubMed1995

In vitro fertilization and development of immature and mature bovine oocytes cryopreserved by ethylene glycol with sucrose.

Immature and mature bovine oocytes were frozen slowly in 1.8 M ethylene glycol (EG) with different concentrations of sucrose (0, 0.1, and 0.2 M). After thawing and dilution of the cryoprotectant by a one-step procedure, the survival of the oocytes was assessed morphologically and also by in vitro fertilization and culture. Sucrose had no effect on the survival and fertilization rates of frozen-thawed oocytes. However, higher cleavage rates of frozen-thawed immature oocytes were obtained with 0.2 M sucrose used in combination with EG. Moreover, none of the immature oocytes frozen in EG without sucrose developed into blastocysts, but about 1% of immature oocytes frozen with sucrose developed into blastocysts. The cleavage rates of mature oocytes frozen in EG were significantly lower with sucrose than without sucrose. However, no significant difference was observed in the development to blastocysts. Transfer of four blastocysts derived from frozen-thawed immature oocytes into two recipient heifers resulted in one pregnancy.

Animals↗
PubMed1995

Relationship between functional levels and movement in tetraplegic patients. A retrospective study.

The aim of the present study was to set targets for each spinal lesion level after determining the relationship between the spinal lesion level and movement abilities in patients with tetraplegia following injury to the cervical cord. A total of 109 patients, 96 men and 13 women were included in the study. We mainly examined locomotion and transfer capabilities according to Zancolli's classification. The results of this study showed that 50% of the patients classified as C6A, 75% of C6B1 and 96% of the patients classified C6B2 accomplished bed transfer. The number of patients who could manage toilet transfer was 53% in the group classified as C6B1 and 85% in group C6B2. These results suggest that achievement of those classified as C6B2 is a clue to the assumption that the patient will achieve toilet transfer capability and can perform ADL independently.

Activities of Daily Living↗
PubMed1995

The effects of clonidine and tizanidine on responses of nociceptive neurons in nucleus ventralis posterolateralis of the cat thalamus.

The effects of intravenous clonidine and tizanidine on nociceptive neurons in the nucleus ventralis posterolateralis (VPL) of the thalamus, a key station in the lateral system of ascending pain pathways, were evaluated in urethane-chloralose anesthetized cats. Intravenous clonidine and tizanidine produced a dose-dependent (5 and 10 micrograms/kg, and 25 and 50 micrograms/kg, respectively) suppression of responses of nociceptive specific (NS) and wide dynamic range (WDR) neurons in the VPL to high threshold splanchnic input. In contrast, the responses of both NS and WDR units to electrical stimulation of spinothalamic tract fibers in the ventrolateral funiculus (VLF) were little affected. We conclude that a site of suppressive action of the alpha 2-adrenoceptor agonists, as observed in nociceptive VPL neurons, is at the level of the spinal dorsal horn rather than in the VPL itself.

Adrenergic alpha-Agonists↗
PubMed1995

Mechanism of angiogenic effects of saponin from ginseng Radix rubra in human umbilical vein endothelial cells.

1. The effects of saponin from Ginseng Radix rubra on angiogenesis (tube formation) and its key steps (protease secretion, proliferation and migration) in human umbilical vein endothelial cells (HUVEC) were examined to elucidate the mechanism of the tissue repairing effects of Ginseng Radix rubra. The effect on a wound healing model was also studied. 2. Tube formation was measured by an in vitro system. The activity and immunoreactivity of tissue-type plasminogen activator (tPA) as a protease for angiogenesis and the immunoreactivity of its inhibitor, plasminogen activator inhibitor-1 (PAI-1), were measured in conditioned medium of HUVEC stimulated for 24 h with saponin. Cell proliferation was measured by counting the cell numbers at 2-7 days after seeding. Migration was measured by Boyden's chamber method. The effect on wound healing was studied in the skin of diabetic rats. 3. Saponin at 10-100 micrograms ml-1 significantly stimulated tube formation by HUVEC in a dose-dependent manner. Saponin in a similar concentration-range increased the secretion of tPA from HUVEC as estimated by immunoreactivity and enzyme activity. On the other hand, PAI-1 immunoreactivity was slightly increased at 10 micrograms ml-1 of saponin, but then was significantly decreased at 50 and 100 micrograms ml-1. Cell proliferation was only slightly enhanced by 1-100 micrograms ml-1 of saponin, but migration was significantly enhanced by 10-100 micrograms ml-1 in a dose-dependent manner. Moreover, saponin stimulated wound healing with enhanced angiogenesis in vivo. 4. These results indicate that saponin stimulates tube formation mainly by modifying the balance of protease/protease inhibitor secretion from HUVEC and enhancing the migration of HUVEC, and that it is effective in vivo.

Animals↗
PubMed1995

Morphology and biodegradability of a binary blend of poly((R)-3-hydroxybutyric acid) and poly((R,S)-lactic acid).

The miscibility, morphology, and biodegradability of a binary blend of bacterial poly((R)-3-hydroxybutyric acid)(P((R)-3HB);Mn = 300,000) with atactic poly((R,S)-lactic acid)(P((R,S)-LA);Mn = 9,000) were studied by means of differential scanning calorimetry, optical microscopy, scanning electron microscopy, and hydrolysis with an without enzyme. Differential scanning calorimetry revealed that a P((R)-3HB)-P((R,S)-LA) blend had a single glass-transition temperature for all proportions of the components. The spherulites of P((R)-3HB) were volume filled in the blend films, indicating the inclusion of amorphous P((R,S)-LA) within the spherulites. The spherulitic growth rate decreased with an increase in the content of P((R,S)-LA). These results indicate that the P((R)-3HB)-P((R,S)-LA) blend is miscible in the melt and in the amorphous state. The enzymatic hydrolysis of P((R)-3HB)-P((R,S)-LA) blend films was carried out at 37 degrees C for 19 h in 0.1 M potassium phosphate buffer (pH 7.4) with an extracellular poly(hydroxybutyrate) depolymerase from Alcaligenes faecalis T1. The rate of enzymatic surface erosion decreased with increasing P((R,S)-LA) content in the blend films. The simple hydrolysis of P((R)-3HB)-P((R,S)-LA) blend films without enzyme was also conducted at 37 degrees C in a 0.01 M potassium phosphate buffer (pH 7.4) for 150 days. The hydrolytic scission of P((R)-3HB) polymer chains was accelerated by blending with P((R,S)-LA). However, the rate of enzymatic hydrolysis was much faster than the rate of nonenzymatic hydrolysis.

Alcaligenes↗
PubMed1995

Effects of beta-1 integrins in the process of implantation.

The expression and function of beta 1 integrins on human decidual cells were investigated. Flow cytometric analysis revealed that the cultured decidual cells expressed a high level of the beta 1 subunit on the cell surface. Mouse blastocysts attached to and spread onto cultured human decidual cells. Attachment of the blastocysts was a necessary prerequisite for the further outgrowth of trophoblasts. The addition of a monoclonal antibody recognizing the beta 1 subunit to the cultured decidual cells did not affect the rates of hatching and attachment of blastocysts. The outgrowth of embryos on decidual cells was inhibited by the addition of the anti-beta 1-subunit antibody in a dose-dependent manner. Furthermore, exposure of decidual cells to the anti-beta 1-subunit antibody significantly inhibited the extent of outgrowth of trophoblasts, implying that blastocyst attachment and outgrowth is mediated by different mechanisms. These observations suggest that beta 1 integrins on decidual cells may be involved in the process of blastocyst development and differentiation after attachment.

Antibodies, Monoclonal↗
PubMed1995

Differential inhibitory mechanisms in VPL versus intralaminar nociceptive neurons of the cat: I. Effects of periaqueductal gray stimulation.

Nociceptive thalamic units receiving afferent input from the greater splanchnic nerve (SPL) were recorded from the nucleus ventralis posterolatealis (VPL) and intralaminar nuclei in urethane-chloralose anesthetized cats. The effects of stimulating the periaqueductal gray (PAG), or the nucleus raphe dorsalis (NRD) on responses of nociceptive thalamic units were investigated. Forty-eight nociceptive specific (NS) and 20 wide dynamic range (WDR) units with SPL input were found in the shell region of the caudal VPL. Following electrical stimulation of either the ventral PAG or the NRD, responses to SPL input were inhibited in all NS and WDR units tested. Responses of these units to electrical stimulation of spinothalamic tract fibers in the ventrolateral funiculus (VLF) were also inhibited following the PAG/NRD stimulation. These results suggest that PAG/NRD stimulation-produced inhibition of both NS and WDR units may be partially mediated by an ascending antinociceptive mechanism. Intralaminar nociceptive units with SPL input were found in the nuclei centralis lateralis (CL), paracentralis (Pc), and parafascicularis (Pf). The effects of conditioning electrical stimulation of either the ventral PAG or the NRD on responses of intralaminar nociceptive units were studied. Of 113 intralaminar nociceptive units studied, 68 units were unaffected, 23 units were excited and 22 units were inhibited following the conditioning stimulation. In the units in which responses to SPL stimulation were inhibited, responses elicited by electrical stimulation of the mesencephalic reticular formation (MRF) were also inhibited. These data suggest that although there is an ascending inhibitory pathway from PAG/NRD to intralaminar nuclei, this system is far less potent compared with the ascending inhibitory system acting upon the VPL.

Afferent Pathways↗
PubMed1995

Differential inhibitory mechanisms in VPL versus intralaminar nociceptive neurons of the cat: II. Effects of systemic morphine and CCK.

In urethane-chloralose anesthetized cats, the effects of intravenous morphine on responses of thalamic nociceptive units were studied. In both nociceptive specific (NS) and wide dynamic range (WDR) units recorded from the nucleus ventralis posterolateralis (VPL), intravenous morphine suppressed unit responses to the greater splanchnic nerve (SPL) stimulation, but had little effect on responses to stimulation of spinothalamic tract fibers in the ventrolateral funiculus. In nociceptive units recorded from nuclei centralis lateralis (CL) and parafascicularis (Pf) of the intralaminar nuclei, intravenous morphine suppressed responses to stimulation of the mesencephalic reticular formation as well as to SPL stimulation. Intravenous cholecystokinin (CCK) antagonized the suppressive action of morphine on responses of VPL units, but did not antagonize the suppressive action of morphine on responses of intralaminar units. The results suggest that intravenous morphine inhibits synaptic transmission of nociceptive impulses in the intralaminar nuclei as well as in the spinal cord, but not in the VPL, and that CCK antagonizes the antinociceptive action of morphine in the spinal cord, but not in the intralaminar nuclei.

Animals↗
PubMed1995

[A successful surgical replacement for mitral regurgitation after cardiac arrest due to widely ruptured chordae tendineae].

A 47-year-old woman, who has mitral regurgitation previously diagnosed in another hospital, was transferred to our intensive care unit for acute congestive heart failure. Just after admission, her respiratory state became worse and she suddenly fell into cardiac arrest. Five minutes later she recovered through cardiopulmonary resuscitation. The pulmonary artery pressure, however, which reached 85/43 mmHg with a Swan-Ganz catheter, had been exceeding systemic pressure. On echocardiography ruptured chordae tendineae of the mitral anterior leaflet was most suspected. Five days after the intensive treatment with a use of IABP, we operated upon her. On the operative findings most rough zone chordae of both leaflets including two strut chordae were ruptured with severe prolapsing. Thus we chose prosthetic valve replacement rather than mitral valve repair. We replaced the mitral valve with a Carbomedix 25 mm. Postoperatively the mean pulmonary artery pressure remained still high as 40 mmHg. With a continuous intravenous administration of prostaglandin E1, the pulmonary artery pressure became lower gradually. The patient was able to wean from respirator on the 18th postoperative day. The patient was discharged on the 49th postoperative day. The mitral valve removed at operation showed myxomatous degeneration and idiopathic ruptured chordae tendineae on the pathological examination. In summary a 47-year-old woman underwent mitral valve replacement 5 days after cardiac arrest from acute severe mitral regurgitation due to widely ruptured chordae tendineae of both leaflets. She survived the operation and got well. The mitral valve showed myxomatous degeneration on pathological examination.

Chordae Tendineae↗
PubMed1994

A novel procedure for the preparation of biologically active recombinant peptides using a cyanylation reaction.

A cysteine specific cleavage reaction was used for the preparation of biologically active peptides from recombinant fusion proteins. The fusion protein through cysteine was prepared by a recombinant DNA technology and then treated with cyanylating reagents such as 2-nitro-5-thiocyanatobenzoic acid (NTCB) and 1-cyano-4-(dimethylamino) pyridinium tetrafluoroborate (DMAP-CN) to release the desired product. As an example, we have selected a glucagon-like peptide 1 (7-37) (termed insulinotropin). We constructed an expression vector for a fusion protein in which insulinotropin and human basic fibroblast growth factor (hbFGF) mutein (abbreviated as CS 23) are connected by cysteine and then expressed it in Escherichia coli cells. The fusion protein, after refolding, was purified by heparin affinity chromatography, since CS23 has a strong affinity for heparin. The affinity-purified fusion protein was treated with NTCB or DMAP-CN to give crude insulinotropin, which was then purified by reversed phase (rp) high-performance liquid chromatography (HPLC). From various criteria such as amino acid analysis, amino acid sequence and the biological activity, the purified material obtained was found to be methionylated insulinotropin (Met-insulinotropin) with full activity. The specificity and simplicity of the present method make it versatile and convenient for the preparation of biologically active peptides.

Amino Acid Sequence↗
PubMed1994

Migratory and proliferative effect of platelet-derived growth factor in rabbit retinal endothelial cells: evidence of an autocrine pathway of platelet-derived growth factor.

Angiogenesis is a crucial event in the progression of diabetic retinopathy. Migration and proliferation of endothelial cells (EC) are important steps in angiogenesis and are caused by angiogenic factors such as basic fibroblast growth factor (bFGF). In this work, capillary EC were isolated from rabbit retinal tissues and rabbit retinal EC (RREC) were found to secrete a migration factor for RREC in conditioned medium (CM). The activity was inhibited by an anti-platelet-derived growth factor (PDGF) antibody, but not by an anti-bFGF antibody. We also found that RREC showed a migratory response to PDGF. The response was induced by PDGF-BB and PDGF-AB dose dependently, but not by PDGF-AA, indicating that it was mediated by PDGF-beta receptor-dependent pathways, and that the PDGF-like factor was PDGF-BB or -AB. In addition, PDGF-BB induced the proliferation of RREC as well as bFGF. These data indicate that RREC have an autocrine pathway of PDGF by the secretion of and the response to PDGF. PDGF may play significant parts in angiogenesis in the progression of diabetic retinopathy.

Animals↗
PubMed1994

Effects of quality and developmental stage on the survival of IVF-derived bovine blastocysts cultured in vitro after freezing and thawing.

Factors affecting viability of IVF-derived bovine blastocysts after freezing and thawing were investigated. A total of 1,101 ova matured and fertilized in vitro were cultured under 2 different conditions, 1) in TCM-199 on granulosa cell monolayers at 5% CO(2) in air and 2) in synthetic oviduct fluid (SOF) medium without somatic cell support at 5% CO(2), 5% O(2), 90% N(2). All blastocysts that developed from the 2 different culture systems were individually classified into 4 grades of embryo quality and were then frozen by conventional slow freezing. Developmental rates of the IVF-derived ova to blastocysts and the survival rates of the frozen-thawed blastocysts were not different between the SOF medium (16 and 49%) and the co-culture system (13 and 61%, respectively). Survival of frozen-thawed blastocysts was affected by embryo quality in both the SOF and co-culture systems (P<0.001). Blastocysts produced in vitro were also individually classified into 3 developmental stages and were then cultured for 3 d in the co-culture system with granulosa cells after freezing and thawing. There was a difference in the survival rate of frozen-thawed embryos between blastocyst developmental stages (early vs mid, P<0.05; mid vs expanded, P<0.01; early vs expanded, P<0.001). The post-thawing survival rate of blastocysts frozen at Day 7 (62%) of culture was higher compared with that of Day 8 (45%), but there was no difference in survival rate between Day 7 and 8 of culture. The results indicate that the quality and developmental stage of blastocysts are important factors influencing their survival after freezing and thawing.

Journal Article↗
PubMed1994

Neuropathology of infant with Pena-Shokeir I syndrome.

In an infant with clinical features of Pena-Shokeir I syndrome, who survived for 182 days, neuropathologic examination revealed little myelination in peripheral nerves with group atrophy of muscle fibers, dysplasia of inferior olivary and dentate nuclei, and leptomeningeal heterotopia. Congenital peripheral neuropathy associated with minor brain anomalies is characteristic in this patient, and may cause absence of fetal movements leading to ankylosis of multiple joints, absence of breathing in association with pulmonary hypoplasia, absence of swallowing causing polyhydramnios, and absence of movements of facial muscles causing craniofacial anomalies.

Abnormalities, Multiple↗
PubMed1994

Effect of surfactant lavage in a rabbit model of meconium aspiration syndrome.

Meconium aspiration syndrome (MAS) is a frequent cause of respiratory distress in neonates. Recent reports have suggested that surfactant dysfunction contributes to the pathophysiology of MAS and surfactant therapy improves oxygenation of infants with MAS. We evaluated the effect of bronchial lavage with surfactant solution in a rabbit model of meconium aspiration. All animals were given 5 mL/kg of a 20% slurry of human meconium into the endotracheal tube and mechanically ventilated. The animals were then divided into saline lavage (n = 5) or surfactant lavage (n = 5). Lavage was performed an hour after meconium instillation. After the lavage the total amount of meconium recovered was measured. Blood gas was monitored during the experiment. The amount of meconium recovered by saline lavage was 14%, and by surfactant lavage was 57%. The surfactant group had a significant improvement in gas exchange, whereas the saline group had no improvement. It was concluded that the lavage with surfactant solution effectively washed out meconium and improved gas exchange in rabbit model of MAS.

Animals↗
PubMed1994

Different functions of the platelet-derived growth factor-alpha and -beta receptors for the migration and proliferation of cultured baboon smooth muscle cells.

Migration of medial smooth muscle cells (SMCs) and their proliferation in the intima contribute to thickening of injured and atherosclerotic vessels. These events have been proposed to be regulated in part by platelet-derived growth factor (PDGF). Two separate PDGF receptors have been identified, PDGF-R alpha and PDGF-R beta. To study the functions of PDGF-R alpha and PDGF-R beta in vascular SMCs, neutralizing monoclonal antibodies (mAbs) specific for each of the two receptors were used. These antibodies allowed us to evaluate the role of each receptor for PDGF-induced proliferation and migration of cultured baboon SMCs. Both PDGF-AA and PDGF-BB stimulated SMC growth, with PDGF-BB being more potent than PDGF-AA. Studies with anti-PDGF-R alpha and anti-PDGF-R beta mAbs revealed that both PDGF receptors promoted the stimulatory signals for proliferation. In contrast, PDGF-BB stimulated SMC migration, whereas PDGF-AA had no stimulatory activity on its own. Additionally, PDGF-AA was able to suppress migration induced by PDGF-BB or fibronectin in modified Boyden's chamber assay. When PDGF-BB-induced migration was separated into chemotactic and chemokinetic activities, only the chemotactic component was inhibited by PDGF-AA. The suppression of SMC migration by PDGF-AA was eliminated by anti-PDGF-R alpha mAb. In addition, PDGF-BB, in the presence of anti-PDGF-R beta, bound only to PDGF-R alpha and caused suppression of SMC migration induced by fibronectin. These results suggest that when activated by ligand binding, both PDGF-R alpha and PDGF-R beta stimulate proliferation. In contrast, only activation of PDGF-R beta stimulates migration, whereas ligand binding to PDGF-R alpha leads to inhibition of cell migration. These observations provide support for the conclusion that PDGF-R alpha and PDGF-R beta may play different roles in SMC function and may be involved in different regulatory mechanisms during vascular remodeling.

Animals↗
PubMed1994

Gonadotropin stimulates ovarian renin-angiotensin system in the rabbit.

The present study was undertaken to assess the role of ovarian renin-angiotensin system (RAS) in the preovulatory cascade induced by gonadotropin exposure. In the in vitro perfused rabbit ovaries, exposure to human chorionic gonadotropin (hCG) enhanced the secretion rate of angiotensin II (Ang II) within 1 h. The secretion rate reached maximal levels at 6 h and then declined thereafter. The intrafollicular Ang II content and renin-like activity were also significantly increased at 2 and 4 h after exposure to hCG, compared with control ovaries perfused with medium alone. The level of intrafollicular Ang II after hCG exposure significantly exceeded the concentration of Ang II in an equivalent volume of plasma. The addition of 1 microM captopril to the perfusate significantly inhibited the secretion rate of Ang II stimulated by hCG; however, captopril affected neither the ovulatory efficiency nor prostaglandin production in ovaries treated with hCG. Captopril significantly inhibited the resumption of meiosis in the ovulated ova and follicular oocytes stimulated by hCG. The administration of 100 micrograms Ang II at 2-h intervals to the perfusate reversed the inhibitory effects of captopril on hCG-induced oocyte maturation. In conclusion, these data indicate that gonadotropin stimulates renin-like activity and Ang II production in the rabbit ovary. Ovarian renin-angiotensin system may play an important role in the process of oocyte maturation after exposure to gonadotropin.

Angiotensin II↗
PubMed1994

Evaluation of the efficacy of nicorandil in patients with ischemic heart disease by exercise Tl-201 myocardial SPECT.

The effect of nicorandil on myocardial perfusion in ischemic heart disease was studied using exercise-load Tl-201 myocardial SPECT (Ex-SPECT). ExSPECT was carried out in 12 patients with previous myocardial infarction (OMI) and 9 with angina pectoris (AP) before and after administration of nicorandil 15 mg/day, for three or more weeks; %Tl uptake and the washout rate in infarcted or ischemic areas were calculated from short axial images using the Bull's eye method. In the OMI group, %Tl uptake and washout rates in the infarction areas improved significantly from 52.4% and 0.25 before nicorandil to 60.4% and 0.38 after nicorandil. In the AP group, too, %Tl uptake and washout rates showed a significant improvement from 56.9% and 0.10 before to 69.1% and 0.33 after administration of nicorandil. Six subjects who had not received the drug, and who showed negative washout rates, had high improvement rates when nicorandil was administered, suggesting that the drug could increase myocardial perfusion during exercise loading as well as suppressing coronary spasm. Ex-SPECT was carried out in 4 subjects before and after the administration of nicarandil and after subsequent surgical treatment (PTCA or CABG) and the effects of the two therapies were compared. The washout rate was improved from 0.01 to 0.34 by the administration of nicorandil, and a notable increase in coronary artery blood flow was achieved compared to the level after surgical treatment, i.e. 0.50. It is concluded that normal dosages of nicorandil have a powerful direct effect of dilating the coronary arteries without any influence on preload or afterload.

Adult↗