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Biomedical subjects

K Koyano

Publications and source records attributed to K Koyano.

At least 73 records · Page 4Linked to original sources
PubMed1989

Microvascular anastomosis using a new diode laser system with a contact probe.

The aim of the present study was to demonstrate the usefulness of our newly produced diode laser device (an 830-nm output of 190 mW CW) for microvascular end-to-end anastomoses. In the device, diode laser energy is delivered to a contact ceramic tip with a 200-microns diameter output end. Its wavelength is 830 nm and its power 60 mW. This device is small (30 x 25 x 10 cm), lightweight (gross weight 3kg), and easy to manipulate. Compared with conventional microvascular suture anastomosis (CMSA), the time required for the laser-assisted vascular anastomoses (LAVA) was reduced by almost half. Anastomosed portions of both methods were examined 1, 2, 4, 12, and 24 weeks later for patency and aneurysm formation. The patency rate and incidence of aneurysmal formation were the same in both groups. Histological examination revealed that LAVA is superior to CMSA in the smoothness of the inner surface, less inflammatory reaction, and normal collagen and elastic reorientation. The tensile strength and bursting pressure measured immediately after anastomosis demonstrated no significant difference between the two groups. It was concluded that this diode laser contact method may be clinically useful for microvascular surgery.

Anastomosis, Surgical↗
PubMed1989

[Geometrical investigation on mechanism and movement of Gysi Simplex OU articulator].

Gysi Simplex OU articulator was constructed by modifying Gysi Simplex 1914, and has been used for students' practice of complete denture construction at 18 Japanese dental schools. Therefore, the mechanism and movement of the articulator should be explained and understood clearly from the educational standpoint of view. In this study, the movement was analyzed by geometrical drawing after Ishiwara-Suetsugu's simplified method. The following results were obtained: 1. Sagittal inclination of incisal guidance acted as an important role for location and inclination of lateral axis. 2. Accessory working condylar guide, which is located behind the condyle post, is another important mechanism as one of determinants of the movement. 3. The lateral wall of balancing condylar guide should be forced to touch always the balancing condyle. 4. It was clarified that the movement of Gysi Simplex OU followed the Gysi's axis theory.

Dental Articulators↗
PubMed1989

[Movement analysis of Gysi Simplex OU articulator. 1. Rotational point and lateral axis].

Several researches have been reported on the mechanism and movement of Gysi Simplex OU articulator. And it was clarified logically by geometrical drawing method that the movement of the articulator followed the Gysi's axis theory. But no study reported about the movement of the articulator by measuring it. Therefore, the authors measured the movement of the articulator with Kyushu University 3-D movement analyzing system, and compared it with the results obtained from geometrical drawing method which we reported previously. The following results were obtained: 1. The rotational point exists actually at the same position where we analyzed by geometrical drawing method. 2. Lateral axis is constructed by joining the rotational points at various height. 3. The inclination of lateral axis changes by sagittal inclination of incisal guidance. As the results, we clarified that the movement of Gysi Simplex OU followed the Gysi's axis theory.

Dental Articulators↗
PubMed1988

Selective stripping operation based on Doppler ultrasonic findings for primary varicose veins of the lower extremities.

In 337 limbs (208 patients) with primary varicose veins, Doppler ultrasound was used to detect reverse flow in the saphenous veins caused by manual compression of the calf. According to the extent of reverse flow in the saphenous trunks, varicosities of the long saphenous vein were classified into five types and the short saphenous vein, into four types. Two hundred five (66.3%) of 309 limbs with varicosities of the long saphenous vein had reverse flow in the entire saphenous trunk from the groin to the ankle. In varicosities of the short saphenous vein, 37 (52.9%) of 70 limbs showed reverse flow from the popliteal fossa to the ankle. The other limbs demonstrated reverse flow only in some segments of the saphenous veins. On the basis of these Doppler ultrasonic findings, selective stripping operations were performed on 80 limbs, in which only the segments with venous reverse flow were selectively removed. Postoperative plethysmographic measurement of the venous reflux volume and follow-up studies showed that results of the selective stripping operations were as satisfactory as those of the standard stripping operations (189 limbs) in which the entire saphenous vein was removed. Furthermore, the selective stripping operation was advantageous in reducing the incidence of nerve injury.

Blood Flow Velocity↗
PubMed1987

Effects of synthetic omega-conotoxin on synaptic transmission.

The effects of chemically synthesized omega-conotoxin GVIA (a neurotoxic peptide from Conus geographus) on synaptic transmission at the bullfrog sympathetic ganglion, frog neuromuscular junction and electric organ of the ray, Narke japonica, were studied. The synthetic toxin irreversibly suppressed synaptic transmission at these synapses by arresting the release of transmission from the nerve terminals without showing postsynaptic effects. This action of the toxin was effectively antagonized by high concentrations of extracellular Ca2+. The synthetic toxin irreversibly blocked the Ca2+-dependent action potential of bullfrog sympathetic ganglion cells. These results suggest that omega-conotoxin GVIA blocks synaptic transmission by interfering with the Ca2+ influx through the voltage-sensitive Ca2+ channel of the nerve terminal. These results indicate that the chemically synthesized omega-conotoxin GVIA acts exactly like the natural omega-conotoxin GVIA. Thus, the synthetic toxin can be used in place of the natural toxin as a useful probe for the voltage-sensitive Ca2+ channel in the nervous system.

Action Potentials↗
PubMed1986

Binding of omega-conotoxin to receptor sites associated with the voltage-sensitive calcium channel.

The binding of radioiodinated omega-conotoxin GVIA, a probable Ca channel antagonist, to synaptic plasma membranes of rat brain was examined. Two kinds of specific binding sites were found with apparent dissociation constants of 10 pM and 0.5 nM and maximum binding capacities of 0.5 and 3.4 pmol/mg prot., respectively. The binding of the toxin was not affected by high concentrations of Ca antagonists or an agonist, indicating distinct binding sites of the toxin from those of these drugs. Divalent and trivalent metal ions strongly inhibited the binding. The order of their inhibitory potencies was similar to that for inhibition of the Ca current through certain Ca channels. These results suggest that the binding sites of omega-conotoxin GVIA are functionally related to the Ca2+-binding site postulated to be in the pore of the Ca channel.

Animals↗
PubMed1986

Differential effects of apamin on Ca2+-dependent K+ currents in bullfrog sympathetic ganglion cells.

In B-type neurones of bullfrog sympathetic ganglia, apamin (10 nM) suppressed the Ca2+-dependent K+ current (IAH) involved in the afterhyperpolarization of an action potential, while it did not affect the Ca2+-dependent K+ current (Ic) underlying the spike repolarization. IAH was further separated into two exponential components which were differentially affected by apamin, voltage and alterations in Ca2+ influx, suggesting the existence of 3 different types of Ca2+-dependent K+ channel in bullfrog sympathetic neurones.

Action Potentials↗
PubMed1985

Pharmacological evidence for two types of Ca2+-dependent K+-conductance in bullfrog sympathetic ganglion cells.

The effect of apamin, a bee venom toxin, on the action potential and the spike after hyperpolarization was studied in bullfrog sympathetic ganglion cells. Apamin reduced the duration of the afterhyperpolarization but did not affect the maximum rates of rise and fall of Na+- and Ca2+-dependent action potentials. In the presence of apamin and Co2+, the maximum rate of fall of the action potential was decreased, and the spike duration was prolonged. These results suggest that at least two types of Ca2+-dependent K+-conductance co-exist in bullfrog sympathetic ganglion cells.

Action Potentials↗
PubMed1985

Long-term potentiation of transmitter release induced by repetitive presynaptic activities in bull-frog sympathetic ganglia.

Long-lasting potentiation of transmitter release induced by repetitive presynaptic activities in bull-frog sympathetic ganglia was studied by recording intracellularly fast excitatory post-synaptic potentials (fast e.p.s.p.s.). Following a brief period of post-tetanic potentiation or depression (less than 10 min), the amplitude of the fast e.p.s.p. was potentiated for a period between several tens of minutes and more than 2 h in response to tetanic stimulation of the preganglionic nerve in twenty-one out of twenty-eight cells. Quantal analysis revealed that this long-term potentiation of the fast e.p.s.p. (l.t.p.) was accompanied by an increase in quantal content m (in nine out of twenty-one cells), quantal size (four cells) or both (eight cells). The increased quantal content (presynaptic l.t.p.) declined exponentially (ten cells) or decayed gradually to a certain enhanced level which lasted several hours. In contrast, the increased quantal size grew with a relatively long latency (10-25 min) and remained relatively constant for at least 2 h. The magnitude of presynaptic l.t.p. increased with increased duration of the presynaptic tetanus (33 Hz) from 2 to 5 s. No l.t.p. was elicited by a 1-s tetanus, whereas the time course appears to be independent of the tetanus duration and the magnitude of l.t.p. There was a positive correlation between the magnitude of presynaptic l.t.p. and the pre-tetanic quantal content up to m = 3, but the former deviated from linear regression when the value of the latter exceeded 3. No l.t.p. occurred when quantal content was less than 0.5. A tetanus (33 Hz, 10 s) applied in Ca2+-free solution elicited no presynaptic l.t.p., while the same tetanus in normal Ringer solution produced a large presynaptic l.t.p. Presynaptic l.t.p. was enhanced in magnitude at low temperature (8-10 degrees C). These results demonstrate the existence of a use-dependent, long-term potentiation of transmitter release in bull-frog sympathetic ganglia. Several possible mechanisms are discussed in terms of Ca2+-buffering mechanisms of the presynaptic nerve terminals.

Action Potentials↗
PubMed1981

Postoperative assessment of arterial reconstructive surgery using Doppler flow detection.

The ankle systolic pressure was measured by the Doppler flow detector during the postoperative course after arterial reconstructive surgery in 61 limbs. The ankle systolic pressure was expressed as a pressure index (PI). There were 2 patterns in the recovery of PI after successful reconstructions. In one of these patterns, PI returned to the normal level within 24 hours. The other group represented a delayed recovery of PI. A comparative study between these 2 groups indicated that the delay in the recovery of PI may be chiefly related to a poor distal run-off. There was no relationship between the recovery pattern of PI and the late patency of reconstructed arteries. On the other hand, follow-up examination by means of the ankle pressure measurement was useful to detect new occurrences of stenotic lesions in the postoperative period.

Adolescent↗
PubMed1980

Synthesis and immunological activity of 5,6,6a,8,9,11a-hexahydronaphth[1',2':4,5]imidazo[2,1-b]thiazoles and 5,6,6a,9,10,11a-hexahydroanaphth[2',1':4,5]imidazo[2,1-b]thiazoles.

A series of 5,6,6a,8,9,11a-hexahydroanaphth[1',2':4,5]imidazo[2,q-b]thiazoles (17 and 20) and 5,6,6a,9,10,11a-hexahydronaphth[2',1':4,5]imidazo[2,1-b]thiazoles has been synthesized with cis- and/or trans-1,2-diamino-1,2,3,4-tetrahydronaphthalenes as the key intermediates and subsequently evaluated for immunological activity (effects on antibody formation and delayed-type hypersensitivity reaction). Among the compounds tested trans-5,6,6a,8,9,11a-hexahydronaphth[1',2':4,5]imidazo[2,1-b]thiazole (trans-17a) and (+/-)-5,6,6a beta,8,9,11a alpha-hexahydro-8 beta-hydroxy-9 beta-methyl-8 alpha-phenylnaphth[1',2':4,5]imidazo[2,1-b]thiazole (20a) showed the largest immunological activity in mice with a magnitude comparable to that of levamisole and were found to be considerably less toxic than levamisole in acute toxicological study. The structures of 18a and 20a were determined by X-ray crystallography.

Adjuvants, Immunologic↗
PubMed1977

Protracted oral chemotherapy with fluorinated pyrimidines as an adjuvant to surgical treatment for stomach cancer.

Studies of oral chemotherapy of 5-fluroruracil (5-FU) combined with FT-207, a furanyl analog of 5-FU, as an adjuvant to surgical treatment of stomach cancer have been performed since 1970 in the first department of surgery of Chiba University, Japan. These studies were performed on 107 patients with curative stomach cancer and 22 patients with non-curative stomach cancer. These patients received consecutively 3.5mg/kg/day of 5-FU and 8mg/kg/day of FT-207 for 24 to 36 months and were compared with control patients who had undergone only surgical treatment. A significant higher survival was observed in the curatively resected patients receiving oral 5-FU and FT-207, as compared to the control group. Studies on non-curative stomach cancer patients treated with the same dose schedule gave encouraging results. Because of the limited number of patients treated in this study, the drawing of reliable conclusions must wait the results of further studies.

Administration, Oral↗
PubMed1976

A study of survival in patients with stomach cancer treated by a combination of preoperative intra-arterial infusion therapy and surgery.

Since 1968, there have been 62 patients with stomach cancer seen in the First Department of Surgery of Chiba University. Treatment consisted of preoperative intra-arterial chemotherapy and surgery. The chemotherapy entailed continuous infusion for 15 to 20 hours. The survival rates were analyzed with particular emphasis on the degree of serosal invasion of the stomach. The overall survivals at the end of 3 years were 54.2% for the treated patients, and 37.1% for the controls: and at the end of 5 years, 33.3% of the treated patients were living as compared to 29.7% of the control patients. In patients without serosal invasion, the survival rates were higher for those treated than for the controls for the first 2 years. At the end of 3 years, the 39 patients treated for serosal invasion had a survival rate of 46.8% vs. 29% in the controls: and at 5 years, 32.2% of the treated patients vs. 23.7% in the controls. The survival rates for the treated patients with cancerous infiltration of other organs were about the same as those for the corresponding control patients.

Adult↗
PubMed1976

Effect of N1-(2'-tetrahydrofuryl)-5-fluorouracil and 5-fluorouracil on nucleic acid and protein biosyntheses in Ehrlich ascites cells.

N1-(2'-Tetrahydrofuryl)-5-fluorouracil (FT-207) is a derivative of 5-fluorouracil (5-FU) and has been accepted as a new chemotherapeutic drug. The inhibitory effects of FT-207 and 5-FU on nucleic acid and protein biosyntheses in Ehrlich ascites cells were compared. Both drugs markedly inhibited the incorporation in vivo of the labeled precursors into nucleic acid and protein. The inhibitory effect of FT-207 on DNA and RNA synthesis lasted for a long period of time. Two hr after administration of 5-FU (250 mug/g body weight), the absolute size of uracil pool of liver increased by at least 50%. However, in an in vitro study, FT-207 at a concentration of 60 mug/ml produced no effect on the incorporation of precursors into DNA and RNA of Ehrlich ascites cells 3 hr incubation. If 5-FU was added to Ehrlich ascites cell suspension simultaneously with [5-3H]uridine, the incorporation of the labeled precursor into RNA increased by 30 to 50%.

Animals↗