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Biomedical subjects

J Koyama

Publications and source records attributed to J Koyama.

At least 19 recordsLinked to original sources
PubMed2003

Functionally essential neuronal population of the facial motor nucleus.

Cranial nerve impairment is one of the more serious complications in neurosurgery. Nevertheless, the important question of how many neurons are required for cranial nerve functions remains unanswered. The VIIth cranial nerve (facial nerve) in mice was subjected to graded crush injuries. After assessment of the facial function, the number of uninjured, healthy facial motor neurons was quantified with a retrograde neuronal tracer. We report that normal facial function is preserved if intact neurons account for more than 56% of the control value, while complete facial paralysis occurs if intact neurons are reduced to less than 32% of the control value.

Animals↗
PubMed2003

Great potentiality of neonatal facial motor neurons for neural plasticity as determined by functionally essential neuronal population.

The present study was undertaken to determine the neuronal population essential for normal and minimal facial function of young adult rats that had received various degrees of crush injuries to the facial nerve in the neonatal period. Using a neuronal tracer, it was found in young adult rats receiving neonatal injuries that the minimum number of tracer-labeled facial motor neurons necessary for normal facial function corresponded to 13-14% of the neurons (2540+/-64) of the age-matched control animals, whereas the minimum number of neurons necessary for minimal facial function corresponded to 5%. On the other hand, the minimum numbers of tracer-labeled facial motor neurons necessary for normal and minimal facial function of young adult rats that received various degrees of crush injuries corresponded to 61 and 27-30%, respectively, of the neurons (2540+/-64) of the uninjured control animals. These results indicate that the facial function of animals with nerves crushed at the neonatal stage can be adequately maintained by a very small population of neurons, implying a great potential of neonatal neurons for neural plasticity.

Animals↗
PubMed2003

Regenerative process of the facial nerve: rate of regeneration of fibers and their bifurcations.

After the main trunk of the mouse facial nerve was injured by crushing, a fiber tracing method was used to quantify the facial motor neurons that extended regenerating nerve fibers to the specific site of the facial nerve branch. The total number of motor neurons retrogradely labeled with a fluorescent tracer, Fluoro-Gold (FG), were 0 on postsurgical days (PSDs) 1 and 2, 75+/-25 on PSD3, 264+/-21 on PSD4, 378+/-19 on PSD6, 428+/-19 on PSD8, 491+/-13 on PSD12 and 532+/-15 on PSD16. Assuming that the FG-positive neurons (535+/-11) of the control mice represent 100%, the FG-labeled neurons accounted for 0, 14, 49, 71, 80, 92 and 99% on the corresponding days. Two different fluorescent tracers were applied to the different facial nerve branches 16 days after facial nerve injuries. Double-labeled neurons were consistently found in the nerve-crushed facial nucleus (3.2%), and their number increased in the nerve-transected facial nucleus (12.2%). The present study indicates that the regenerating facial nerve consists of heterogeneous nerve fibers with varying growth rates and that excessive axonal branching occurs more frequently in the nerve-transected than in the nerve-crushed injuries.

Animals↗
PubMed2002

Periosteal osteosarcoma of the mandible.

We report a rare case of periosteal osteosarcoma of the mandible in a 15-year-old girl. Extension of the tumour into the bone marrow by way of the periodontal ligament is demonstrated.

Adolescent↗
PubMed2001

Accumulative characteristics of pesticide residues in organs of bivalves (Anodonta woodiana and Corbicula leana) under natural conditions.

Accumulative characteristics of pesticide residues in the gill, midgut gland, gonad, and the remaining tissues of the bivalve mollusks Anodonta woodiana and Corbicula leana were examined during the rice planting seasons of 1992 and 1994. Although seven pesticides, except thiobencarb, were accumulated all at ppb levels in the midgut gland (liver) and gonad of both bivalves during their application period, thiobencarb was accumulated in C. leana at extremely high levels of 15.70 microg g(-1) in 1992 and 12.45 microg g(-1) in 1994 in the midgut gland and 15.80 microg g(-1) in 1992 and 16.40 microg g(-1) in 1994 in the gonad, respectively. These levels were about 100 times higher than those in A. woodiana. Thiobencarb and molinate in A. woodiana and chlornitrofen (CNP) and molinate in C. leana remained in the gonad and midgut gland longer than in the gill and remaining tissues, while thiobencarb in organs of C. leana remained at ppm levels until the end of the experiments. The present study suggests that these interspecies differences can be attributed to differences between the two species in their ability to eliminate pesticides.

Animals↗
PubMed2001

Influence of organic solvents on the growth of marine microalgae.

Ninety-six-hour toxicity tests of five organic solvents (methanol, ethanol, acetone, N,N-dimethylformamide [DMF], and dimethyl sulfoxide [DMSO]) on nine species of marine microalgae (Bacillariophyceae; Skeletonema costatum, and Chaetoceros calcitrans, Prasinophyceae; Tetraselmis tetrathele, Haptophyceae; Isochrysis galbana and Pavlova lutheri, Dinophyceae; Prorocentrum minimum, Raphidophyceae; Heterosigma akashiwo, Euglenophyceae; Eutreptiella sp., Chlorophyceae; Dunaliella tertiolecta) were conducted. For D. tertiolecta, T. tetrathele, I. galbana, and P. lutheri, methanol was the least toxic solvent. For S. costatum, C. calcitrans and Eutreptiella sp., DMSO was the least toxic solvent. For Heterosigma akashiwo, DMF was the least toxic solvent. In general, solvent toxicity was ethanol > methanol or acetone > DMF > DMSO. In relation to sensitivity of the microalgae to solvents, D. tertiolecta and T. tetrathele were lower in sensitivity, and Eutreptiella sp. and H. akashiwo were higher in sensitivity than the other species. The no observed effect concentration (NOEC) of acetone, DMF, and DMSO were higher than for ethanol and methanol. Acetone, DMF, and DMSO were suitable for carrier solvents used in toxicity test of water-insoluble chemicals. Excellent regression between logEC(50) and logNOEC was obtained (logNOEC = 1.09 x logEC(50) - 0.84, R(2) = 0.91). This equation indicated that higher toxicity was higher application factor (EC(50)/NOEC) than lower toxicity. All application factors were higher than 0.1.

Dose-Response Relationship, Drug↗
PubMed2001

Bianthraquinones from Cassia siamea.

The isolation of two bianthraquinones, 1,1',3,8,8'-pentahydroxy-3',6-dimethyl[2,2'-bianthracene]-9,9',10,10'-tetrone and 7-chloro-1,1',6,8,8'-pentahydroxy-3,3'-dimethyl[2,2'-bianthracene]-9,9',10,10'-tetrone, from the root bark of Cassia siamea is reported. The structures were established by analysis of spectroscopic data and 7-chloro-1,1',6,8,8'-pentahydroxy-3,3'-dimethyl[2,2'-bianthracene]-9,9',10,10'-tetrone was determined on the direct comparison with synthetic compound.

Anthraquinones↗
PubMed2001

Microvolt T wave alternans in human cardiac hypertrophy: electrical instability and abnormal myocardial arrangement.

INTRODUCTION: Although T wave alternans (TWA) is a promising risk marker for myocardial electrical instability, it remains unclear how the presence of TWA is related to myocardial damage. METHODS AND RESULTS: TWA was measured in 28 patients with hypertrophic cardiomyopathy (HCM), 29 patients with hypertensive left ventricular hypertrophy (HLVH), and 15 normal volunteers using a CH2000 system. The amplitude of TWA (Valt) was measured at the lead with the maximum amplitude. Cardiac biopsy was performed in 12 HCM patients, who were divided into two groups (severe and mild) based on histologic findings of myocardial disarray and fibrosis. TWA was positive (Valt > 1.9 microV) in 61% of HCM and 31% of HLVH, despite a nearly identical left ventricular mass index (176 +/- 65 g/m2 vs 175 +/- 39 g/m2). Valt at heart rate = 110 beats/min was significantly greater in HCM with severe disarray and fibrosis than in HCM with mild disarray and in HLVH. CONCLUSION: In HCM patients, a positive TWA test probably is related to abnormal myocardial arrangement (disarray) and/or fibrosis, and it may reflect electrical instability of the myocardium.

Aged↗
PubMed2001

Apoptosis and epithelial phagocytosis in mitomycin C-treated human pulmonary adenocarcinoma A549 cells.

Fate of human cancer cells damaged by mitomycin C was investigated by electron microscopy. In a monolayer culture of pulmonary adenocarcinoma A549 cells, the antitumor drug mitomycin C induced dilation of the smooth endoplasmic reticulum and Golgi apparatus. Simultaneously, the myelin figures, autophagosomes and dense tonofilament bundles were formed in the cytosol. Nuclear changes also included nucleolar condensation, as well as the disappearance of the karyosomes and thinned marginal heterochromatins. These nuclei came to be rigid and densely chromatic, finally resulting in apoptosis. There was no alteration in the mitochondria or rough endoplasmic reticulum. Meanwhile, some remaining intact A549 cells extended their cytoplasm toward detached cells and engulfed them. These results indicate that mitomycin C induces apoptosis in A549 cells and concurrently stimulates epithelial phagocytotic activity against their own damaged cells.

Adenocarcinoma↗
PubMed2001

Cerebral vasoreactivity and internal carotid artery flow help to identify patients at risk for hyperperfusion after carotid endarterectomy.

BACKGROUND AND PURPOSE: Hyperperfusion syndrome is a rare but potentially devastating complication after carotid endarterectomy (CEA). The aim of this study was to investigate whether preoperative measurement of cerebral vasoreactivity (CVR) and intraoperative measurement of internal carotid artery (ICA) flow could identify patients at risk for hyperperfusion after CEA. METHODS: For 26 patients with unilateral ICA stenosis >/=70%, cerebral blood flow (CBF) and CVR were investigated before and 1 month after CEA, with resting and acetazolamide-challenge single-photon emission CT. CBF on the first postoperative day was also measured. ICA flow was measured before and after reconstruction by electromagnetic flowmeter during surgery. RESULTS: Ipsilateral CBF on the first postoperative day significantly increased relatively (56.6+/-53.2%) as well as absolutely (37.9+/-8.8 to 57.7+/-18.0 mL/100 g per minute) in the reduced CVR group (CVR <12%) but not in the normal CVR group (CVR >/=12%) (10.3+/-15.5% and 40.6+/-7.9 to 43.9+/-5.7 mL/100 g per minute, respectively). One month later, this difference almost disappeared. Two patients showed ipsilateral CBF increase of >/=100%. A significant association of intracerebral steal with hyperperfusion (CBF increase >/=100%) on the first postoperative day was also observed. ICA flow increase after reconstruction significantly correlated with CBF increase on the first postoperative day in the reduced CVR group but not in the normal CVR group. The threshold of ICA flow increase for hyperperfusion was estimated to be 330 mL/min in the reduced CVR group. CONCLUSIONS: Single-photon emission CT with acetazolamide challenge and ICA flow measurement during surgery could identify patients at risk for hyperperfusion after CEA, in whom careful monitoring and control of blood pressure should be initiated even intraoperatively.

Acetazolamide↗
PubMed2001

Correlation with redox potentials and inhibitory effects on Epstein-Barr virus activation of azaanthraquinones.

The redox potentials have been determined for nine azaanthraquinones in phosphate buffer at pH 7.2 by means of cyclic voltammetry. A definite correlation has been found between the redox potentials and the inhibitory effects of the azaanthraquinones on Epstein-Barr virus early antigen (EBV-EA) activation. It has further been shown that the correlation can be made better by introducing an electronic property, i.e., the atomic charge at O11 as an additional parameter.

Anthraquinones↗
PubMed2001

Emotional stress-induced 'ampulla cardiomyopathy': discrepancy between the metabolic and sympathetic innervation imaging performed during the recovery course.

Four patients had the clinical features of 'ampulla cardiomyopathy', consisting of acute-onset transient left ventricular apical akinesis with basal normokinesis, normal coronary angiogram, ST-segment elevation and subsequent giant T wave inversion, which mimicked acute coronary syndrome, the onset of which occurred shortly after extreme mental stress. Myocardial necrosis was minimal, although 2 patients showed elevated serum catecholamine levels in the acute phase. Each patient underwent serial cardiac radionuclide single-photon emission computed tomography of myocardial functional sympathetic innervation, fatty acid metabolism and perfusion using I-123-metaiodobenzyl-guanidine (MIBG), I-123-beta-metyl-iodophenyl pentadecanoic acid (BMIPP) and thallium-201 (201Tl), respectively. In the acute phase, MIBG and BMIPP imaging showed an uptake defect in the apical region, whereas 201Tl uptake was mildly decreased. When assessed semi-quantitatively, the MIBG images had higher defect scores from the acute phase throughout the year of observation compared with BMIPP, and 201Tl. These observations suggest that the primary cause of ampulla cardiomyopathy is related to a disturbance of the cardiac sympathetic innervation.

3-Iodobenzylguanidine↗
PubMed2001

An 80-year-old mitochondrial disease patient with A3243G tRNA(Leu(UUR)) gene presenting cardiac dysfunction as the main symptom.

MELAS is characterized by mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes, but cardiac involvement also frequently occurs. An 80-year-old female patient had been suffering from insulin-dependent diabetes mellitus and neurosensory hearing loss. At the age of 79 she suffered metabolic acidosis with persistent drowsiness and was subsequently found to have severe cardiac dysfunction. Muscle biopsy disclosed the presence of abnormal mitochondria, and the MELAS gene mutation (A3243G of the tRNA(Leu(UUR))) was demonstrated. It is noteworthy that this mitochondrial disease patient has survived until a great age, which shows the wide clinical spectrum of MELAS, especially in the age of onset.

Aged↗
PubMed2001

The accuracy of sonography for evaluation of internal derangement of the temporomandibular joint in asymptomatic elementary school children: comparison with MR and CT.

BACKGROUND AND PURPOSE: In order to clarify the incidence and evolution of disk displacement in the temporomandibular joint (TMJ) in children, we performed a longitudinal analysis in 18 subjects. Some investigators have suggested that sonography can provide information about the articular disk position of the TMJ. The purpose of this study was to determine the diagnostic accuracy of sonography for revealing internal derangement of the TMJ in elementary school children compared with our standard of reference, MR imaging and helical CT. METHODS: Eighteen children were examined using both sonography and MR imaging or helical CT or both. The sonographically revealed distance between the articular capsule and the lateral surface of the mandibular condyle was measured and compared with that obtained by MR or helical CT scanning. RESULTS: Compared with our MR/CT standard of reference, sonography revealed a sensitivity of 83%, a specificity of 96%, and an accuracy of 92% for identifying disk displacement (defined as a distance of 4 mm or more between the articular capsule and the lateral surface of the mandibular condyle). CONCLUSION: Although sonography's sensitivity, specificity, and accuracy for the diagnosis of disk displacement were slightly inferior to those of MR or helical CT, we assert it is a useful imaging method for longitudinal investigations of a large group of elementary school children. Internal derangement of the TMJ should be suspected if sonography reveals a distance between the articular capsule and the lateral surface of the mandibular condyle of 4 mm or more.

Child↗
PubMed2001

[A giant thrombosed aneurysm of the anterior communicating artery which developed 18 years after clipping: a case report].

A 64-year-old man, who had undergone clipping surgery 18 years before for a ruptured anterior communicating artery (ACoA) aneurysm, presented with mild aphasia. A computerized tomography (CT) scan showed a subcortical hemorrhage in the left temporal lobe, and a high density large mass at the ACoA. Neuro-imaging study revealed a giant thrombosed ACoA aneurysm. Thrombectomy and neck clipping were successfully performed, using the interhemispheric approach. The patient was discharged without additional neurological deficits. A long-term follow-up study is thus considered necessary after neck clipping of a ruptured aneurysm.

Humans↗
PubMed2000

Relation between vascular morphologic changes during stent implantation and the magnitude of in-stent neointimal hyperplasia.

Intimal hyperplasia usually occurs after balloon overstretch injury or wire coil stimuli to coronary arteries. We examined whether the degree of vessel wall stretch during coronary stent placement could predict the amount of in-stent neointimal hyperplasia after a 6-month follow-up. Serial (preintervention, postballooning, poststent implantation, and a follow-up after 6 months) intravascular ultrasound (IVUS) was used to study 457 consecutive cross-sectional areas in 28 patients. IVUS imaging, using a motorized pullback system at 0.5 mm/s, allowed 1-mm axial increment measurements of the total vascular, stent, and lumen cross-sectional areas. The mean total vascular area changed from 10.89 +/- 2.50 mm2 before to 11.27 +/- 2.49 mm2 after ballooning, to 12.80 +/- 2.59 mm2 after stenting, and to 12.58 +/- 2.41 mm2 at follow-up (p < 0.0001). The mean lumen area changed from 3.36 +/- 1.95 mm2 before to 4.21 +/- 1.65 mm2 after ballooning, to 5.16 +/- 1.09 mm2 after stenting, and to 3.57 +/- 1.23 mm2 at follow-up (p < 0.0001). The mean stent area decreased from 5.25 +/- 1.17 mm2 after stenting to 5.09 +/- 0.90 mm2 at follow-up (p < 0.0001). Stepwise logistic regression analysis showed that delta total vascular area (after stent implantation - before intervention) was a strong predictor of the amount of intimal hyperplasia (r = 0.57, p < 0.0001). Vascular overstretch caused by the stenting procedure promotes intimal hyperplasia in proportion to the degree of sectional vascular stretch.

Aged↗