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Biomedical subjects

K Koyano

Publications and source records attributed to K Koyano.

At least 55 records · Page 3Linked to original sources
PubMed1995

Electromyographic signal changes during exercise in human chronic jaw-muscle pain.

Twelve individuals (2 males, 10 females) with chronic masticatory muscle pain and 11 individuals (2 males, 9 females) without, had their bite force and surface electromyography from the right and left superficial masseter and anterior temporalis muscles recorded before, during and after a 30-s sustained submaximal clenching task. This task was performed at 50% of the force level of each subject's maximum voluntary contraction (MVC) for 30 s. Brief (3 s) 50% MVC efforts were recorded at 15-s intervals, three times before and six times after the sustained clench. Each subject performed this pattern of activities three times with a 15-min rest between each trial. The centre frequency (CF) of the electromyographic power spectrum was calculated by fast Fourier transformations. The mean CF at the end of the 30-s clench and the rate of change at the CF during the clenching task were analysed between groups, sides and muscles. The data indicated that the masseter CF decreased at a significantly faster rate for the first clenching trial in the muscle-pain group. Conversely, the rate of change of the temporalis CF did not significantly differ for the two groups during the three clenching trials. By the third trial the CF of the exercised masseter in the non-pain group exhibited a similar rate of change to that in the pain group. This suggests that both repeated exercise and the presence of chronic inflammation increase the rate of change of the electromyographic signal of the contracting masseter. The mechanism underlying this increased change is unknown.

Adult↗
PubMed1995

Functional masticatory evaluation in hemifacial microsomia.

The features of hemifacial microsomia with unilateral condylar hypoplasia in a 9-year-old female patient were analysed in a multidisciplinary fashion. Cephalometric roentgenograms revealed malformation of the mandible, with the right condylar process being smaller than the left. In addition, the right maxillary alveolar process was underdeveloped. Closed view radiography with oblique lateral transcranial projection (by modified Schüller's method) of the temporomandibular joint revealed an anterior dislocation of the condyle on the unaffected side. Computed tomography (CT) of the masticatory muscles demonstrated that the medial pterygoid muscle on the affected side, unlike the other muscles, was larger than that on the unaffected side. The surface electromyographic activities of the temporal and masseter muscles and reduction of the maximum bite force on the affected side during clenching corresponded with the CT findings. The hypertrophy of the medial pterygoid muscle on the affected side was considered likely to be a compensatory adjustment to keep the mandible centred. A three-dimensional study of the movement of the mandible revealed that the condyle on the affected side moved vertically and that the rotational centre was located antero-inferior to the condylar process during maximum jaw opening and closing movements. These findings suggested lack of articular guidance. Moreover, the unaffected condylar process showed considerable backward movement during retrusion and ipsilateral excursion of the mandible. The mandibular head on the unaffected side showed obvious protraction during all jaw movements, which might have induced the overgrowth of the condylar head on the unaffected side in this growing child.

Alveolar Process↗
PubMed1995

Comparative stress analyses of fixed free-end osseointegrated prostheses using the finite element method.

We investigated the designs of osseointegrated prostheses in cases of free-end partial edentulism using comparative stress analyses interpreted with the two-dimensional finite element method. Seven free-end fixed osseointegrated prosthesis models with various connection designs (i.e., rigidly connected to an abutment tooth, not connected to an abutment tooth, connected to an abutment tooth with a non-rigid attachment) were studied. The stress values of the seven models loaded with vertical force were analyzed. When the prosthesis was not connected to natural abutment tooth but was supported instead by two free-standing implant abutments, lowest levels of stress in bone were noted. On the other hand, non-rigid attachments, when incorporated into a prosthesis, did not significantly reduce the level of stress in bone.

Alveolar Process↗
PubMed1994

The role of arachidonic acid metabolism in somatostatin and substance P effects on inward rectifier K conductance in rat brain neurons.

Somatostatin enhances an inward rectifier K conductance in cultured locus coeruleus neurons, while substance P reduces an inward rectifier K conductance in cultured nucleus basalis and locus coeruleus neurons. The role of arachidonic acid metabolites in these responses was studied. The somatostatin-induced response was reduced by phospholipase A2 inhibitors, non-specific lipoxygenase inhibitors and specific 5-lipoxygenase inhibitors. A cyclooxygenase inhibitor and a 12-lipoxygenase inhibitor had no effect. 5(S)-HPETE occasionally increased the K conductance, but failed to occlude the somatostatin response. The substance P response was suppressed by a 5-lipoxygenase inhibitor but not by a 12-lipoxygenase inhibitor. These results suggest that the 5-lipoxygenase pathway is not a specific messenger of either one of these responses, but that it plays a more general role in maintaining or enhancing the effectiveness of both somatostatin and substance P responses.

Animals↗
PubMed1993

Two signal transduction mechanisms of substance P-induced depolarization in locus coeruleus neurons.

Effects of substance P on cultured neurons of the locus coeruleus of the rat were studied using the whole-cell patch clamp technique. In some cells substance P produced a decrease in a K conductance which showed an inwardly rectifying property. In other cells substance P produced an initial inward current which was accompanied by a conductance increase. The rest of the cells showed responses which were mixtures of the above two responses. The measurement of the reversal potential of the initial inward current after suppressing the voltage-gated Ca and K conductances suggests that it is caused by an increase in a non-selective ionic conductance. In cells loaded with 260 microM GTP gamma S, application of substance P produced an irreversible reduction of the K conductance, while the initial inward current could still be recorded, suggesting that the former is mediated by a G protein, whereas the latter may be activated by a different signal transduction mechanism. The initial inward current was not eliminated by external application of high concentrations of tetrodotoxin, d-tubocurarine or amiloride. Nor was it affected by the intracellular application of cyclic GMP or cyclic AMP.

Amiloride↗
PubMed1993

The coexistence of abdominal aortic aneurysm and early gastric cancer: report of three cases.

The surgical approach for patients with abdominal aortic aneurysm (AAA) and coexistent abdominal malignancy remains controversial. We report herein three cases of coincident AAA and early gastric cancer, all of whom were treated by a two-stage operation and underwent curative surgery for their gastric cancer. The principles of our surgical approach are as follows: (1) the lesion which requires urgent surgery should be operated on first, and if both lesions show absolute indications, a one-stage surgical procedure should then be performed; (2) a two-stage surgical procedure in which aneurysmectomy is performed first should be undertaken when no absolute indications for urgent surgery exist for either lesion; (3) a one-stage surgical procedure should only be performed when surgery on one lesion makes the other lesion highly dangerous; and (4) in patients with a poor prognosis because of far advanced cancer in whom the AAA shows no sign of rupturing, only a gastrectomy should be performed.

Aged↗
PubMed1993

Oral motor disorders in humans.

Motor disorders affecting the orofacial musculature include bruxism, chronic orofacial muscle pain affecting the jaw and neck muscles and the involuntary waking period disorders such as orofacial dyskinesia, oral mandibular dystonia, tremor and others. Research at UCLA has touched these and many other areas. Current results have indicated the usefulness of contingent afferent electrical stimulation of the lip to control bruxism; provided information regarding the fatigue, endurance and recovery faculties of the protrusive jaw muscles; explored the issue of chronic muscle hyperactivity inducing headache pain; and worked with botulin toxin as a method to treat orofacial dystonia and dyskinesia.

Bruxism↗
PubMed1992

Extension incision for renal carcinoma including invaded vena cava and right lobe of liver.

We report on a thirty-five-year-old woman with renal cell carcinoma who successfully underwent right radical nephrectomy and extended right hepatic lobectomy with resection and reconstruction of inferior vena cava (IVC). A temporary bypass was placed between the infrarenal IVC and right atrium using a heparin-coated synthetic tube. The tumor was resected en bloc including right kidney, adrenal gland, hepatic lobe, and IVC. The IVC was reconstructed using an expanded polytetrafluoroethylene (EPTFE) graft. Her postoperative course was uneventful with no signs of recurrence four years after surgery.

Adult↗
PubMed1992

A patch-clamp study on the muscarine-sensitive potassium channel in bullfrog sympathetic ganglion cells.

1. A voltage-independent K+ channel was characterized and effects of muscarine were studied in cultured bullfrog sympathetic ganglion cells using the cell-attached patch-clamp configuration. 2. Three types of single-channel current were recorded from 2- to 10-day-old cultured cells in the presence of tetraethylammonium (2-20 mM), tetrodotoxin (1-2 microM), Cd2+ (0.1 mM) and apamin (20 nM). 3. The most frequently observed channel was a voltage-independent K+ channel which was open at the resting membrane potential and had a conductance of 52.6, 78.9 and 114.9 pS at a [K+]o of 2, 40 and 100 mM, respectively. This channel was designated background K+ channel. 4. Two other channel types were observed less frequently. One had a conductance of 26 pS (external K+, 118 mM) and a long open time of several seconds at the resting membrane potential. The second channel had a smaller conductance (20 pS) and displayed a voltage-dependent activation. 5. The open probability of the background K+ channel varied between patches, ranging from 0.0005 to 0.486. The open time distribution was fitted by a single exponential with a time constant of 0.51 ms. Both of these parameters were independent of the membrane potential. The closed time distribution consisted of at least four exponentials having time constants of 0.17, 3.7, 120 ms and several seconds. 6. Muscarine (10-20 microM) applied to the membrane outside the patch pipette reversibly enhanced the activity of the background K+ channel. This effect was associated with an increase in the open probability, which resulted from an increase in the mean open time concomitant with a decrease in the mean closed time. Muscarine did not change the single-channel conductance of this channel. 7. The effects of muscarine were blocked by atropine (1 microM). 8. It is concluded that there exists a muscarine-sensitive, voltage-independent K+ channel in cultured bullfrog ganglion cells. This K+ channel appears to contribute to the generation of the resting membrane potential and underlie the slow inhibitory postsynaptic potential of these neurones in situ.

Animals↗
PubMed1992

[The comparison of postoperative multiple organ failure with arterial disease to that with gastrointestinal cancer].

The clinical features of 22 postoperative multiple organ failure (MOF) patients, comprised of 8 with arterial disease (A-MOF) and 14 with gastrointestinal cancer (G-MOF), were investigated. Differences in the operative time, blood loss, and mortality were not significant. The initial organ impaired was the lungs in 78.6% of G-MOF patients and the heart or kidneys in all A-MOF patients. Infection developed in over 80% of both groups. In many A-MOF patients, the pneumonia or septicemia developed secondary to organ failure, while intraabdominal infection triggered respiratory failure in many G-MOF patients. Our organisms in infected specimens and their antibiotic sensitivities was valuable for the early administration of effective antibiotics. Upper gastrointestinal tract bleeding was important in the prognosis of both groups and occurred more frequently in A-MOF than in G-MOF patients. Consumption coagulopathy in A-MOF patients and DIC induced by infection in G-MOF patients mainly caused such bleeding. Preoperative administration of heparin was effective in improving coagulopathy. Furthermore, measurement of intramural pH with tonometer in the stomach and gastric irrigation with oxygenated perfluorochemicals were effective in the prediction and prevention of gastrointestinal bleeding.

Aged↗
PubMed1992

[Principle of treatment of intermittent claudication due to arteriosclerosis obliterans--reconstruction or conservative treatment].

MATERIALS AND METHODS: Two hundred and one patients of arteriosclerosis obliterans (ASO) with intermittent claudication (IC) were studied. Improvement of IC, score of return to social life, change of life condition and prognosis were compared between the two groups of reconstructive and conservative treatment. RESULTS: Improvement of IC was seen in 88.0% of the patients in the group of reconstruction and only 30.4% in the conservative treatment group. In the reconstructive group, the score of return to social life improved from 2.10 to 1.31 and the score of life condition also improved from 2.71 to 1.66. However in the conservative treatment group these score showed no significant improvement. Moreover the long term mortality rate was lower in the treatment group of reconstruction. CONCLUSION: The arterial reconstruction for IC is significant for improving the quality of life and exerts a favorable effect on life prognosis.

Aged↗
PubMed1991

A muscarine-activated voltage-independent K+ channel in cultured bullfrog sympathetic neurones.

In cultured bullfrog sympathetic neurones, cell-attached patch clamp revealed a voltage-independent K+ channel having a conductance of 46-113 pS at an external K+ of 2-120 mM. Muscarine (10-20 microM), applied to the cell membrane outside a recording pipette, increased its open probability and mean open time in an atropine-sensitive manner. This muscarine-activated K+ channel could underlie some of the muscarinic inhibitory postsynaptic potentials in both central and peripheral nervous systems.

Animals↗
PubMed1991

Free radical injury in skeletal muscle ischemia and reperfusion.

This study was made in a canine isolated gracilis muscle model to measure directly the free radicals, to predict the severity of ischemia and reperfusion injury of the skeletal muscle by measuring its surface pH (mspH), and to determine the effect of Coenzyme Q10 (CoQ10) in reducing the extent of muscle injury. Animals were divided into three groups: group A (control, n = 10), group B (untreated, n = 10), and group C (CoQ10 treated, n = 10). In both groups B and C, 5 hr ischemia followed by 40 min of reperfusion was made. Free radicals were measured directly by electron spin resonance spectrometer (ESR) and mspH was measured using a pH microprobe. Serum creatine phosphokinase (CPK) was estimated before ischemia, 5 and 30 min after reperfusion. The extent of muscle injury was evaluated morphologically by Evan's blue dye exclusion test. ESR intensity in group B was 0.55 +/- 0.19 and decreased to 0.30 +/- 0.04 in group C (P less than 0.01). Rate of recovery of mspH was higher in group C (7.16 +/- 0.06) compared to group B (6.88 +/- 0.11, P less than 0.01) and CPK in group C was less (847 +/- 381 IU/liter) than in group B (1356 +/- 519 IU/liter, P less than 0.05) after 30 min of reperfusion. In group C the morphological muscle injury was less (37.8 +/- 5%) compared to group B (56.7 +/- 3.6%, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Structure of N-gamma-L-glutamyl-L-cysteine ethyl ester monohydrate.

C10H18N2O5S.H2O, Mr = 296.39, monoclinic, P2(1), a = 19.600 (1), b = 7.480 (1), c = 5.061 (1) A, beta = 94.74 (1) degree, V = 739.445 (1) A3, Z = 2, Dm = 1.31, Dx = 1.331 g cm-3, Cu K alpha, lambda = 1.54178 A, mu = 21.4 cm-1, F(000) = 316, room temperature, R = 0.057 for 1263 reflections. The molecule adopts an extended form. The molecules are arranged so as to form double molecular sheets parallel to the bc plane through some hydrogen bonds.

Dipeptides↗
PubMed1990

Hepatic vein reconstruction for preserving remnant liver function.

Hepatic malignancies often infiltrate to the major hepatic vein. Recently, we performed hepatic resection combined with hepatic vein reconstruction for preserving remnant liver function in three such patients. One patient had a saphenous vein graft. Postoperative liver function of the patients who underwent hepatic vein reconstruction was compared with those of eight patients who underwent hepatic resection of segments VII and VIII. The right hepatic vein in four of them was resected and in the remaining four was preserved by skeletalization using an ultrasonic aspirator. Although four patients with right hepatic vein resection showed severe lowering of liver function after surgery, the postoperative course of patients with preservation or reconstruction of the right hepatic vein maintained good liver function. Liver regeneration of three patients with hepatic vein reconstruction was good on computed tomography. Besides this report, to our knowledge, there is no other report of hepatic vein reconstruction for preserving the remnant liver function. Problems with hepatic resection combined with hepatic vein reconstruction are discussed. We conclude that hepatic vein reconstruction is one of the means for extending indication of the malignant tumor resection of the liver.

Adult↗