Biomedical subjects

N Yokota

Publications and source records attributed to N Yokota.

At least 37 records · Page 2Linked to original sources

PubMed2000

Intracerebral hemorrhage from a ruptured pseudoaneurysm after STA-MCA anastomosis--case report.

A 43-year-old hypertensive male developed a pseudoaneurysm at the site of a superficial temporal artery (STA)-middle cerebral artery (MCA) anastomosis, causing massive intracerebral hemorrhage 5 years after the operation. He first experienced repeated transient ischemic attacks, and cerebral angiography disclosed complete occlusion in the cervical portion of the left internal carotid artery. STA-MCA anastomosis was performed, and the ischemic attacks stopped. Postoperative angiography confirmed patency of the anastomosis and good filling of the cortical branches of the left MCA. Five years after surgery, the patient suffered sudden onset of generalized convulsions and consciousness disturbance. Computed tomography disclosed a massive intracerebral hemorrhage in the left frontoparietal region, and angiography revealed an aneurysmal dilatation at the site of the anastomosis that was not seen before. Emergency evacuation of the hematoma and clipping of the aneurysmal dilatation were performed. The patient recovered well and became ambulatory. Histological examination of the surgical specimen showed collagen tissue, indicating a pseudoaneurysm. Patients who undergo STA-MCA anastomosis, especially hypertensive patients, should be followed up by repeated magnetic resonance angiography to confirm the patency of the anastomosis and cerebral perfusion, and to detect the formation of pseudoaneurysms at the anastomosis site, which can cause fatal bleeding.

Adult↗

PubMed2000

In vitro antifungal activity of a novel lipopeptide antifungal agent, FK463, against various fungal pathogens.

The antifungal activities of FK463 against various pathogenic fungi were tested by standard broth microdilution methods, and compared with the activities of five currently available antifungal agents; viz., fluconazole (FLCZ), itraconazole, miconazole, amphotericin B and flucytosine. Fourteen clinical isolates of Candida albicans categorized as FLCZ susceptible, FLCZ susceptible-dose dependent and FLCZ resistant were similarly susceptible to FK463 with geometric (GM) MIC values of 0.010, 0.011 and 0.015 microg/ml, respectively. All of 17 clinical isolates of Aspergillus fumigatus were inhibited by FK463 at 0.0078 microg/ml or lower concentrations. The antifungal activity of FK463 against a wider range of medically important yeasts and filamentous fungi were studied using stock fungal strains. While Cryptococcus, Trichosporon, Fusarium, Pseudallescheria and Alternaria species or zygomycetes were scarcely or not inhibited by 16 microg/ml of FK463, two Candida species (C. albicans, C. glabrata), as well as all species of Aspergillus, Paecilomyces and Penicillium, were highly susceptible with GM-MICs of < or = 0.008 microg/ml. The other fungal species including several non-albicans Candida were less susceptible with GM-MICs ranging between 0.016 and 2 microg/ml. MICs of the reference drugs were within the range thus previously reported. These results suggest that FK463 be of use in the treatment of serious fungal infections.

Antifungal Agents↗

PubMed2000

Angiographically demonstrated coronary collaterals predict residual viable myocardium in patients with chronic myocardial infarction: a regional metabolic study.

Angiographical demonstration of coronary collateral circulation may suggest the presence of residual viable myocardium. The development of coronary collaterals was judged according to Rentrop's classification in 37 patients with old anteroseptal myocardial infarction and 13 control patients with chest pain syndrome. The subjects with myocardial infarction were divided into 2 groups: 17 patients with the main branch of the left coronary artery clearly identified by collateral blood flow from the contralateral coronary artery [Coll(+)group, male/female 10/7, mean age 56.6 years]and 20 patients with obscure coronary trunk [Coll(-)group, male/female 16/4, mean age 54.9 years]. Thallium-201 myocardial scintigraphy and examination of local myocardial metabolism were carried out by measuring the flux of lactic acid under dipyridamole infusion load. Coronary stenosis of 99% or total occlusion was found in only 5 of 20 patients (25%)in the Coll(-)group but in 16 of 17 patients(94%)in the Coll(+)group(p < 0.001). Redistribution of myocardial scintigraphy was found in 11 of 15 patients(73%)in the Coll(+)group, but only 3 of 18 patients (17%)in the Coll(-)group(p < 0.01). The myocardial lactic acid extraction rate was--13.2 +/- 17.0% in the Coll(+)group, but 9.1 +/- 13.2% in the Coll(-)group(p < 0.001). These results suggest that coronary collateral may contribute to minimizing the infarct area and to prediction of the presence of viable myocardium.

Adult↗

PubMed2000

[Prolactinoma in a child showing high MIB-1 labeling index: a case report].

We report a very rare case of a prolactin secreting pituitary tumor (prolactinoma) which occurred in a 12-year-old boy. The tumor showed an extremely high MIB-1 index. The clinical implication in the postoperative management of childhood prolactinoma is discussed. The patient showed right third nerve palsy, and MRI revealed a pituitary tumor invading the right cavernous sinus. Preoperative hormonal evaluation showed a very high prolactin level (2800 ng/ml). The patient underwent transsphenoidal surgery, and the third nerve palsy disappeared just after the procedure. MIB-1 index obtained by using immunostaining was 18.9%. Postoperative prolactin level remained high (2200 ng/ml), and the patient was treated with 10 mg/day of bromocriptine. Prolactinomas in children with high MIB-1 index show resistance to treatment with bromocriptine. In the postoperative management of a childhood prolactinoma, it should be considered how to control sufficiently high serum prolactin level to expect sexual development while preserving other normal residual pituitary functions. If control with bromocriptine, fails radiation treatment should be adopted with careful observation of the increase in height and the progress of sexual development of the patient.

Bromocriptine↗

PubMed2000

[A case of multiple sclerosis with hypothalamic amenorrhea].

We present a 31-year-old woman of multiple sclerosis. At age 28, she was admitted with complaints of echolalia and a gradual onset of weakness affecting the right upper and bilateral lower limbs. Brain MRI showed high intensity areas in the bilateral frontal gyri, lobuli paracentralis, and left anterior thalamus. Although she had been in remission for 3 years, she developed dysesthesia of left upper and lower limbs. Cervical T2 weighted MRI showed a new high signal intensity lesion in the spinal cord from the C2 to C3 level. The combination of the cerebral, thalamic and spinal cord lesions with remission and excerbations allowed the diagnosis of clinically MS to be made. She suffered amenorrhea from the onset of her illness. Serum prolactin was within the normal range. The LH and FSH basal secretions were decreased and there were low delayed secretions of LH and FSH after intravenous injection of 100 micrograms LHRH. We consider that her amenorrhea was caused by the hypothalamic lesion, supported by MR findings of dilatation of the third ventricle.

Adult↗

PubMed1999

Characterization of the LolA-LolB system as the general lipoprotein localization mechanism of Escherichia coli.

The major outer membrane lipoprotein (Lpp) of Escherichia coli requires LolA for its release from the cytoplasmic membrane, and LolB for its localization to the outer membrane. We examined the significance of the LolA-LolB system as to the outer membrane localization of other lipoproteins. All lipoproteins possessing an outer membrane-directed signal at the N-terminal second position were efficiently released from the inner membrane in the presence of LolA. Some lipoproteins were released in the absence of externally added LolA, albeit at a slower rate and to a lesser extent. This LolA-independent release was also strictly dependent on the outer membrane sorting signal. A lipoprotein-LolA complex was formed when the release took place in the presence of LolA, whereas lipoproteins released in the absence of LolA existed as heterogeneous complexes, suggesting that the release and the formation of a complex with LolA are distinct events. The release of LolB, an outer membrane lipoprotein functioning as the receptor for a lipoprotein-LolA complex, occurred with a trace amount of LolA, and therefore was extremely efficient. The LolA-dependent release of lipoproteins was found to be crucial for the specific incorporation of lipoproteins into the outer membrane, whereas lipoproteins released in the absence of LolA were nonspecifically and inefficiently incorporated into the membrane. The outer membrane incorporation of lipoproteins including LolB per se was dependent on LolB in the outer membrane. From these results, we conclude that lipoproteins in E. coli generally utilize the LolA-LolB system for efficient release from the inner membrane and specific localization to the outer membrane.

Bacterial Outer Membrane Proteins↗

PubMed1999

High cervical disc lesions in elderly patients--presentation and surgical approach.

The incidence of high cervical disc lesions is extremely rare, and the mechanism of their development is unclear. We report these three cases, and discuss the possible mechanisms. We also describe surgical strategies for these lesions. The first and second cases were an 82-year-old male and an 84-year-old male with retro-odontoid disc hernia. The third was an 83-year-old female with a herniated disc at C2/C3. To investigate Aetiological mechanisms of these lesions, we examined the findings on cervical images in extension and flexion, and compared the results in a younger than 80-year-old group and an older than 80-year-old group. The patients underwent surgery via a posterolateral intradural approach. Wide laminectomy and incision of the dentate ligaments enabled access to the ventral space of the upper cervical spinal canal and sufficient decompression. All patients became ambulatory postoperatively without special fixation of the cervical spine. In the younger group, the level mostly loaded during cervical movement was C5/6, however, the levels in the older group were C2/3 and C3/4. In elderly patients, less mobilization of the middle and/or lower cervical spine due to spondylotic change causes overloading at higher levels resulting in high cervical disc lesions. Retro-odontoid disc lesions can be caused by a herniated disc at C2/C3, which migrates upward. Regarding surgical strategy, the posterolateral intradural approach is less invasive and more advantageous for these lesions.

Aged↗

PubMed1999

Plasma and urine levels of adrenomedullin and proadrenomedullin N-terminal 20 peptide in chronic glomerulonephritis.

Proadrenomedullin N-terminal 20 peptide (PAMP) is a novel hypotensive peptide present in the precursor of adrenomedullin (AM), a vasodilative and natriuretic peptide. We examined the plasma and urinary levels of these peptides in patients with chronic glomerulonephritis (CGN). The mean plasma AM concentration of the patients with CGN did not differ from that of control subjects (4.17 +/- 0.17 v 3.87 +/- 0.21 fmol/mL, respectively), whereas urinary AM excretion was significantly less in the patients with CGN (5.96 +/- 0.95 v control, 8.93 +/- 1.02 fmol/mg of creatinine; P < 0.05). Plasma concentrations and urinary excretion of PAMP were significantly less for the patients with CGN compared with control subjects (0.91 +/- 0.08 v 1.23 +/- 0.20 fmol/mL; P < 0.05 and 25.0 +/- 3.0 v 35.0 +/- 3.6 fmol/mg of creatinine, respectively; P < 0. 05). The plasma AM concentration was negatively correlated with plasma renin activity (r = -0.58; P < 0.01) and aldosterone concentration (r = -0.40; P < 0.05). Urinary excretions of AM and PAMP showed significant correlations with urine excretion of sodium (r = 0.39; P < 0.05 and r = 0.49; P < 0.01, respectively). These findings suggest that AM and PAMP may have roles in the regulation of sodium in patients with CGN.

Adrenomedullin↗

PubMed1999

A case of nocturnal polyuria in olivopontocerebellar atrophy.

We report a case of olivopontocerebellar atrophy without sleep apnea syndrome who presented nocturnal polyuria. It is considered that a disturbance in the circadian rhythm for arginine vasopressin secretion due to degeneration of suprachiasmatic nuclei and marked increase in the secretion of atrial natriuretic peptide due to abnormal diurnal variation in blood pressure may be involved in the mechanism of nocturnal polyuria.

Arginine Vasopressin↗

PubMed1999

Disappearance of rhythmic involuntary movements during sleep in a case of olivopontocerebellar atrophy.

We report on a 54-year-old woman with an 8 or so year history of olivopontocerebellar atrophy associated with the rhythmic involuntary movements of the left upper and lower limbs, and cervical region. Surface electromyogram of the left upper limb revealed rhythmicity (about 3 Hz) and reciprocity between antagonistic muscles, which disappeared on polysomnography at all sleep stages including rapid eye movement sleep without atonia. These were characterized by the co-existence of rhythmic skeletal myoclonus and parkinsonian tremor. These findings suggest that a disturbance of the striatonigral system as well as the dentato-rubro-olivary circuit may be involved in these movements. It also seems that their fate is dependent on the level of wakefulness and that the ascending reticular activating system also plays a role in the development of these movements.

Cerebellar Nuclei↗

PubMed1999

Effect of simvastatin on proliferative nephritis and cell-cycle protein expression.

BACKGROUND: Mesangial cell proliferation is important in subsequent mesangial matrix expansion in glomerular injury. Therefore, the regulation of mesangial cell proliferation may be critical in the treatment of glomerulonephritis. Inhibition of 3-hydro-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibits the production of mevalonate and has been shown to suppress proliferation in many cell types, including mesangial cells in vitro. It is expected that HMG-CoA reductase inhibitor may suppress mesangial cell proliferation and subsequent progression of glomerulonephritis. Recently, the tight relationship between cell-cycle regulatory protein expression and mesangial cell proliferation in experimental glomerulonephritis was demonstrated. The aim of the present study is to examine the effect of simvastatin, one of the HMG-CoA reductase inhibitors, on the glomerular cell proliferation and on the expression of CDK2 or p27Kip1 in mesangial cells in experimental glomerulonephritis in vivo. METHODS: The effect of simvastatin on a rat mesangial proliferative glomerulonephritis induced by antithymocyte antibody (anti-Thy 1.1 GN) was studied. Administration of simvastatin or vehicle (for control GN) were started from two days before disease induction, and was continued to the day of nephrectomy. Nephrectomy was done at days 0, 2, 4, 7, 12 and 20 after disease induction. Immunohistochemistry for proliferating cells, macrophages, alpha-smooth muscle actin, type IV collagen and PDGF-B chain was performed, respectively, in addition to conventional periodic-acid Schiff staining. Double immunostaining for CDK2/OX-7 or p27Kip1/OX-7 was also done, respectively. RESULTS: There was no difference in the degree of the initial injuries between simvastatin-treated and control GN rats. The most pronounced feature of simvastatin-treated GN was the suppression of the early glomerular cell proliferation (about 70% of proliferation was suppressed at day 4). At day 4, alpha-smooth muscle actin expression was also decreased in simvastatin-treated GN rats. Inhibition of macrophage recruitment into glomeruli by simvastatin was also a prominent feature (about 30% decrease in the number of glomerular macrophages at day 2). Simvastatin significantly suppressed subsequent mesangial matrix expansion and type IV collagen accumulation in glomeruli. Although it might simply reflect the reduction in mesangial cells, glomerular PDGF-B chain expression was reduced. There was no significant difference in plasma lipids levels at day 2 and day 4. In vehicle-treated GN rats, the number of CDK2+/OX-7+ cells (CDK2-expressed mesangial cells) in glomeruli increased significantly from day 4 to day 7. Although simvastatin suppressed mesangial cell proliferation, the increase in the number of glomerular CDK2+/OX-7+ cells was also attenuated by simvastatin treatment. There was no difference in the number of p27Kip1+/OX-7+ cells (p27Kip1-expressed mesangial cells) in the glomerulus between vehicle-treated and simvastatin-treated GN rats. CONCLUSION: Simvastatin suppressed mesangial cell proliferation and subsequent matrix expansion, and macrophage infiltration into glomeruli in anti-Thy 1.1 GN rats. The antiproliferative effect of simvastatin in this model was also associated with the reduction of CDK2 expression in mesangial cells.

Animals↗

PubMed1999

Primary intraorbital ectopic meningioma.

We report a case of intraorbital meningioma. Operative findings and histopathological examination revealed the tumoc to be meningothelial meningloma and to be located entirely outside the optic dura. This case demonstrates the occurrence of primary intraorbital ectopic meningioma, and the tumor was removed through a modified Dolenc approach. The primary intraorbital ectopic meningioma is discussed and the surgical approach to the orbital apex region is reviewed.

Case Reports↗

PubMed1999

Intraoperative evoked facial muscle responses and recovery process of the facial nerve in acoustic neuroma surgery.

The prognostic value of intraoperative evoked facial muscle responses (EFMR) was studied and correlated with the recovery process of the facial nerve during a follow-up period of 18 months. The patients were classified into four groups according to EFMR amplitudes, group A (150 microV or greater, 190.8, SD28.9 microV, n = 24), group B (100-149 microV, 125.7, SD14.3 microV, n = 14), group C (50-99 microV, 79.0, SD17.0 microV, n = 13) and group D (less than 50 microV, 22.1, SD13.3 microV, n = 15). Significant improved facial function appeared at 3 months after the operation in group A, at 6 months in group B, at 9 months in group C and at 12 months in group D. The early postoperative facial function and facial outcome of groups A and B were significantly better than those of groups C and D. Our data revealed that the intraoperative EFMR amplitudes have more prognostic value in predicting the recovery process of the nerve than functional outcome.

Analysis of Variance↗

PubMed1999

Aneurysm of persistent primitive hypoglossal artery.

A patient with a ruptured intracranial aneurysm of the right persistent primitive hypoglossal artery is described. Clipping of the aneurysmal neck was achieved by a far lateral approach together with drilling of the jugular tubercle, and it was concluded that this approach should be followed for safe and complete clipping.

Aneurysm, Ruptured↗

PubMed1999

Expression of bcl-2 and bax in glomerular disease.

Bcl-2 may account in part for the maintenance of hypercellularity in human glomerular diseases through preventing cell death and by counteracting bax which may be expressed to regulate excessive proliferation. This process is associated with the effect of PDGF B-chain expression. Bax expression may be important in the cell loss leading to glomerulosclerosis and TGF-beta1 participates in this process by increasing bax expression. Thus, the balance of bcl-2/bax expression may be critical in the course of human glomerular diseases.

Animals↗

PubMed1999

Visual evoked oscillatory responses of the human optic tract.

Optic tract oscillatory responses directly recorded during posteroventral pallidotomy were investigated to reveal their features with respect to extracranially recorded visual oscillations and to clarify their contributions to scalp-recorded or far-field visual evoked potentials. Oscillatory responses of the optic tract consisting of early and subsequent late oscillations were recorded in all patients. Early oscillations consist of five negative and positive peaks, and late oscillations consist of two to four negative and positive peaks. The frequency of the first peak of early oscillations (103.0+/-9.2 Hz, n = 14) was significantly lower than that of others (t test, P<0.006), but there were no significant differences among other peaks (t test, P>0.4). This difference was not observed among peaks of late oscillations (t test, P>0.3). As a whole, the frequency of early oscillations (123.9+/-16.7 Hz, n = 70) was significantly higher than that of late oscillations (66.3+/-13.7 Hz, n = 41) (t test, P = 0.0001). Intracerebral recording of the optic responses with the same band filter of scalp-recorded visual evoked potentials (10 Hz to 1 KHz) showed prominent negative (No) and positive (Po) waves, whereas responses obtained over the scalp at Oz and Cz consisted of negative (NI), positive (PI), negative (NII), and positive (PII) waves. Comparisons between No and PI and Po and NII showed overall phase reversal relations between them, but there were significantly different peak latencies between them (t test, P<0.001) except that between Po (116.7+/-11.7 msec, n = 5) and NII of Cz recording (118.4+/-9.4 msec, n = 5) (t test, P<0.3). Our study in conjunction with other studies on visual oscillations revealed that a relatively constant frequency of oscillations is traveling in the subcortical visual system and is probably playing an important role in generating stationary or fixed peaks of the far-field potentials of visual evoked potentials.

Evoked Potentials, Visual↗

PubMed1999

Visual evoked potentials during posteroventral pallidotomy for Parkinson's disease.

OBJECTIVE: To examine the efficacy of intracerebral recording of visual evoked potentials (VEPs) during posteroventral pallidotomy comparing macro- and microelectrode stimulation. MATERIALS AND METHODS: The optic tract was identified by intracerebral recording of VEPs in 16 patients. Electrical stimulation through a lesioning electrode (macroelectrode stimulation: biphasic wave, 50 Hz, 0.2 ms, 0-6 V) and a microelectrode (microelectrode stimulation: impedance of 1 M(omega) at 300 Hz, biphasic pulse, 300 Hz, 0.2 ms, 10-50 microA) was delivered to assess visual responses. RESULTS: VEPs were recorded in every patient from 18.0+/-3.3 mm (n = 14) to 22.8+/-3.4 mm (n = 14) in the mediolateral direction. The mean amplitude at this midpoint (57.7+/-15.4 microV, n = 35) was significantly higher than other amplitudes (t test, P < 0.05). Significant increment of amplitudes appeared at 4 mm (64.3+/-18.5 microV, n = 16) below the initial target along trajectories that pass close to the midpoint of the optic tract. The distance from the initial target to the dorsal surface of the optic tract along these trajectories ranged from 3 to 6 mm, with a mean of 5.0+/-0.7 mm (n = 16), whereas adjusted distances perpendicular to the intercommissural plane ranged from 1.3 to 4.1 mm, with a mean of 3.0+/-0.7 mm (n = 16) below, and the distance from the optic tract to the intercommissural plane ranged from 6.3 to 8.7 mm, with a mean of 7.5+/-0.7 mm (n = 16). Macroelectrode stimulation evoked visual responses at various sites in the pallidal region, totaling 27 sites in 11 of 16 patients (68.7%). Microelectrode stimulation evoked responses at only five sites in 3 of 13 patients (23.1 %), within a very limited area 4 to 7 mm below the target where the electrode was very close to the optic tract. Physiological targeting of VEPs necessitated change of the initial target in 13 of 16 patients (81.2%). CONCLUSION: VEPs of prominent oscillatory potentials with high amplitudes indicate the location of the optic tract, which allows easy identification of the optic tract and facilitates neurophysiological targeting of the globus pallidus internus in conjunction with microelectrode recording.

Aged↗

PubMed1999

Subthalamic nucleus stimulation for gait disturbance in Parkinson's disease.

OBJECTIVE: A preliminary study of subthalamic nucleus (STN) stimulation was performed to determine its applicability for the treatment of gait and postural disturbances in Parkinson's disease. METHODS: Five Parkinson's disease patients with freezing gait and postural instability were selected for this study. Their ages ranged from 60 to 73 years (mean+/-standard deviation, 65.6+/-4.8 years). Semi-microelectrode recording was used to identify the STN and to place a chronic electrical stimulation electrode within the right STN in all patients. The Unified Parkinson's Disease Rating Scale and the modified Hoehn and Yahr Staging Scale were used to assess patients in on- and off-drug conditions before surgery and 3 months after surgery. RESULTS: The scores on the Hoehn and Yahr Staging Scale and the total Unified Parkinson's Disease Rating Scale for akinesia (P < 0.05), gait (P < 0.05), and gait and posture (P < 0.01) in off-drug on-stimulation conditions significantly improved over the preoperative and postoperative off-drug off-stimulation conditions (analysis of variance [ANOVA], P < 0.01). Improvement over the preoperative scores was 24% on the Hoehn and Yahr Staging Scale, 43.6% on the total Unified Parkinson's Disease Rating Scale, 33.4% for akinesia, 36.6% for gait, and 38.7% for gait and posture. However, stimulation in the on-drug phase did not show a significant difference compared with pre- and postoperative conditions (ANOVA, P > 0.05). Comparisons between preoperative on-drug and postoperative off-drug on-stimulation conditions revealed that there were no significant differences in the scores, except for gait (ANOVA, P < 0.05). The scores on subscales for falling, freezing, walking, and gait in off-drug on-stimulation conditions were significantly improved over the scores for preoperative and postoperative off-stimulation (ANOVA, P < 0.05), but the score for postural stability remained unchanged. CONCLUSION: Our findings showed that STN stimulation effectively alleviates freezing gait and improves walking to its status during the preoperative on-drug phase and can be applied for treatment of Parkinson's disease patients with these symptoms.

Aged↗