Biomedical subjects

Y Yoshimoto

Publications and source records attributed to Y Yoshimoto.

At least 55 records · Page 3Linked to original sources

PubMed1997

Intraparenchymal metastatic tumor with periventricular dissemination--case report.

A 50-year-old male presented with a rare intraparenchymal metastatic tumor spreading through the periventricular tissue. Magnetic resonance (MR) imaging demonstrated the tumor as a heterogeneous low-intensity area on T1-weighted images with enhancement by gadolinium-diethylenetriaminepenta-acetic acid, and as a heterogeneous high- or isointensity area on T2-weighted images. Histological examination of a biopsy sample showed adenocarcinoma. This MR imaging appearance is typical of malignant glioma. The differential diagnosis of tumor in the cerebral parenchyma with ventricular dissemination should include both primary and secondary intracranial malignant tumors. MR imaging is useful in the diagnosis of such tumors, but the final diagnosis should be based on either tissue biopsy or cytological examination of the cerebrospinal fluid.

Brain Neoplasms↗

PubMed1997

Correlation between venous stump pressure and brain damage after cortical vein occlusion: an experimental study.

A canine model of cortical vein occlusion was used to evaluate whether data obtained from monitoring venous stump pressure could help predict cerebral infarction after venous obstruction. Following bilateral parasagittal craniotomy, the cortical vein in each hemisphere was temporarily occluded and the increase in pressure was directly measured. Permanent venous obstruction was subsequently produced, and parenchymal brain damage 24 hours later was classified as: Stage 0, no parenchymal damage; Stage I, mild edema; Stage II, moderate parenchymal edema and/or ischemic changes in neurons; and Stage III, moderate-to-severe hemorrhage. The histological stages correlated closely with the rise in venous pressure: mean pressure increases (+/- standard deviation) were 5.5 +/- 2.9 mm Hg in hemispheres graded as Stage 0 (12 hemispheres), 7.7 +/- 3.2 mm Hg in those graded as Stage I (five), 11.2 +/- 4.1 mm Hg in those classed as Stage II (five), and 16.4 +/- 5 in those categorized as Stage III (seven). There were significant differences between Stages 0 and II (p < 0.01) and between Stages 0 and III (p < 0.001). Disruption of the blood-brain barrier as indicated by extravasation of Evans blue dye correlated well with the pressure increment. These results may indicate the threshold for injury after cortical venous occlusion. Venous stump pressure measurements obtained during a test occlusion may be a useful adjunct in predicting brain damage and may be helpful for intraoperative vessel selection for venous resection.

Animals↗

PubMed1997

Cancer mortality among atomic bomb survivors exposed in utero or as young children, October 1950-May 1992.

Cancer mortality for the period from October 1950 through May 1992 was analyzed in atomic bomb survivors exposed in utero. Risk estimates for this group were also compared to those for survivors who were less than 6 years old at the time of exposure. The cohorts studied include 807 in utero survivors and 5,545 persons exposed during childhood with all members of both groups having estimated doses of at least 0.01 Sv. The comparison group includes 10,453 persons with little (<0.01 Sv) or no exposure. Analyses were limited mainly to cancer deaths occurring between the ages of 17 and 46. Only 10 cancer deaths were observed among persons exposed in utero. However, there is a significant dose response with an estimate of excess relative risk per sievert (ERR/Sv) of 2.1 (90% confidence interval of 0.2 to 6.0). This estimate does not differ significantly from that for survivors exposed during the first 5 years of life. The cancer deaths among those exposed in utero involved leukemia (2), female-specific organs (3) and digestive organs (5). Nine deaths occurred in females, where the excess risk for all solid cancers has a 90% confidence interval on the ERR/Sv of 1.6 to 17. Significant risks were found for cancers of the digestive system [90% confidence interval (CI) on the ERR/Sv of 0.7 to 20] and for female-specific cancers (90% CI on the ERR/Sv of 0.7 to 42). These risks do not differ significantly from those seen in females exposed as children. There were no deaths from solid cancer in men exposed in utero. The ERR/Sv has an upper 95% confidence bound of 2.5 which does not differ from that for exposed children, where the upper 95% confidence bound is 1.5. The sexes differ even when female-specific cancers are excluded from the comparison. Although there were only two leukemia deaths among those exposed in utero, the leukemia death rate for this group is higher than that in the comparison group (P = 0.054) with an exposure effect that is about half the magnitude and not significantly different from that seen after childhood exposure (P = 0.103). However, there is no evidence of a dose response among those exposed in utero because no high-dose leukemia deaths were observed, a result that differs considerably from that for those exposed as children. There is a need for caution in the interpretation of these data. First, the number of cancer deaths is small; second, there is unexplained significant difference in the mortality from solid cancer between the sexes; and third, the excess of leukemia in those exposed in utero is not reflected in an increasing dose response.

Adult↗

PubMed1996

G protein-gated K+ channel (GIRK1) protein is expressed presynaptically in the paraventricular nucleus of the hypothalamus.

We prepared a specific antibody against GIRK1, the major subunit of the G protein-gated K+ (KG) channel. Immunohistochemical study revealed that GIRK1 immunoreactivity was detected in the presynaptic, but not in the postsynaptic, region in the paraventricular nucleus of the rat hypothalamus (PVN). Therefore, activation of the KG channel may underlie presynaptic inhibition of neurotransmitter release by various agonists, such as dopamine, noradrenaline, opioids, and histamine, in PVN.

Adenosine↗

PubMed1996

Cerebral aneurysms unrelated to arterial bifurcations.

The majority of saccular cerebral aneurysms arise at arterial branchings; those arising elsewhere are rare. Among 557 saccular cerebral aneurysms surgically treated between 1983 and 1994, 29 (5.2%) were unrelated to arterial divisions. These cases were retrospectively analysed. The ages of the subjects ranged from 6 to 80 years (mean 57); 17 (59%) were female, and 12 (41%) male. Twenty-four (83%) presented with subarachnoid haemorrhage. Seventeen (59%) had a history of hypertension, and ten (34%) had multiple cerebral aneurysms. The most common site was the internal carotid artery (45%), followed by the middle cerebral artery (28%), the vertebrobasilar arteries (17%), and the anterior cerebral artery (10%). The aneurysms were classified in relation to arterial curvature into three groups: dorsal curvature (41%), ventral curvature (10%) and non-curvature (49%). During surgery, sclerotic changes were noted in the arterial wall adjacent to the aneurysms in 14 patients (48%). Five cases (17%) had small thin walled (blister-like) aneurysms, four of which ruptured during surgery resulting in poor clinical outcomes. We suggest that arteriosclerotic changes in the arterial wall, carotid siphon, and/or local haemodynamic forces are important factors in the development of this type of aneurysms. At surgery, one should bear in mind the possibility of sclerotic or blister-like aneurysms which require special attention to deal with them.

Adult↗

PubMed1996

Impaired calcium regulation of smooth muscle during chronic vasospasm following subarachnoid hemorrhage.

The intracellular calcium level was determined in the canine basilar artery to investigate whether Ca2+ regulation of its smooth muscle is altered during chronic vasospasm following subarachnoid hemorrhage. A double-hemorrhage model was used. The occurrence of vasospasm was confirmed angiographically 7 days after initial hemorrhage. The intracellular calcium concentration ([Ca2+]i) of smooth muscle was measured using Fura-2. Fluorescence to excitation at 340 and 356 nm was monitored and the ration R340/356 was used as the indicator of [Ca2+]i. When the extracellular calcium concentration ([Ca2+]e) was increased from pCa 8 to 2, [Ca2+]i also increased. In the spastic arteries, the [Ca2+]e - [Ca2+]i curve was elevated as compared with the normal arteries. Treatment with ionomycin elevated the curve in the normal group, but it had little effect in the spastic arteries. Values of [Ca2+]i, calculated in multiples of Kd, were greater in the spastic arteries. Diltiazem (10(-5) mol/L) partially suppressed the augmented [Ca2+]i signal in the spastic arteries, whereas it did not affect the curve in the control group. These results indicate that the calcium regulation of smooth muscle is impaired after subarachnoid hemorrhage, which may contribute to the pathogenesis of chronic vasospasm.

Animals↗

PubMed1996

8-Bromo-cAMP inhibits glucose transport activity in mouse placental cells in culture.

Glucose plays an important role in fetal development and energy metabolism. Facilitative glucose transporter-1 (GLUT1) has been found in placenta. However, little is known about GLUT1 modulation in placental cells. To examine changes in mouse placental GLUT1 levels caused by 8-bromo-cAMP, we performed 2-deoxyglucose uptake experiments, Northern blot analysis and immunoblot analysis using a primary mouse placental cell culture. Immunohistochemical analysis showed that GLUT1 was localized to the ectoplacental cone and the labyrinth zone of mouse placentas on days 7 and 11 of pregnancy respectively. Treatment of mouse placental cells with 250 mumol/l 8-bromo-cAMP resulted in a significant (P < 0.01) decrease in glucose uptake on days 2-5 of culture. The inhibitory effect of 8-bromo-cAMP on glucose uptake was concentration-dependent. Glucose uptake was also inhibited by 100 micrograms/l cholera toxin and by 0.1 mmol/l forskolin. Northern blot and immunoblot analysis revealed that both GLUT1 mRNA and protein levels were also decreased by 8-bromo-cAMP. These findings suggest that 8-bromo-cAMP inhibits glucose transport activity in mouse placental cells in culture.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed1996

Bridged craniotomy for stable fixation of a bone flap. Technical note.

Postoperative depression of the bone flap is a common and bothersome problem in craniotomies. In this paper, a simple technique to avoid this deformity is described. The key to this technique is to leave uncut a part of each osteotomy approximately 5 mm in width as a "bridge" to the bone flap, which is then subsequently cut with the aid of a chisel. This technique provides stable fixation of the bone flap and satisfactory cosmetic results with little additional operating time.

Craniotomy↗

PubMed1996

[Clinical investigations of five patients with intracranial lesions presenting tinnitus].

We investigated 5 patients with intracranial lesions. The initial complaint was tinnitus with normal hearing or sight sensorineural hearing loss. The lesions were 2 cerebello-pontine angle meningiomas, 1 cerebello-pontine angle epidermoid cyst, 1 supratentorial falx meningioma and 1 dural arteriovenous malformation at the temporal bone. Because of pulsatile or severe persistent tinnitus, we performed CT and MRI to determine the presence of intracranial lesions. Some patients had an episode of cerebral infarction and the complaint of headache or head heaviness. Quantitative measurement of tinnitus showed a low-frequency character in a pitch-match examination and moderate loudness in loudness balance. In the patients with falx meningioma and dural arteriovenous malformation, the tinnitus character was pulsatile and abnormal blood flow might have affected the peripheral auditory system. On the other hand, in the patients with a cerebello-pontine angle tumor, the tinnitus character was non-pulsatile and compression on the central auditory system by the tumor might have caused the tinnitus.

Adult↗

PubMed1996

Localization of human placental glucose transporter 1 during pregnancy. An immunohistochemical study.

To elucidate the potential roles of glucose transporter 1 (GLUT1) in human placenta during pregnancy, we examined the localization of GLUT1 in human placenta at various stages by immunohistochemistry with an anti-GLUT1 antibody by use of both light and electron microscopy. Specific staining for GLUT1 was localized on the apical brush border and along the basal plasma membrane of the syncytiotrophoblasts. The staining at the apical side was more intense than that at the basal side during the early stages of gestation. In later gestational stages, however, the staining pattern at the apical side became blurred and the staining intensity at the basal side increased. The cytotrophoblasts, seen embedded in the basal part of the syncytiotrophoblasts, seemed to show immunoreactivity for GLUT1 along the plasma membranes at the light-microscopic level. However, immuno-electron microscopic analysis with either pre- or post-embedding methods revealed that specific staining for GLUT1 was hardly observed on the cytotrophoblasts, but the cytotrophoblasts were often surrounded by immunoreactive processes of syncytiotrophoblasts. The blood capillaries and erythrocytes in the stroma of placental villi were always immunoreactive for GLUT1 throughout pregnancy. These findings suggest that GLUT1 may play a vital role in human pregnancy.

Capillaries↗

PubMed1996

[Ruptured peripheral lenticulostriate artery aneurysm in a child: case report].

We report a 12-year-old with intracerebral hematoma and subarachnoid hemorrhage secondary to the rupture of a peripheral lenticulostriate artery aneurysm. We carried out proximal clipping of the lateral lenticulostriate artery at the middle cerebral artery following six days of continuous ventricular drainage for acute hydrocephalus. Postoperative angiography confirmed the obliteration of the aneurysm. The girl was discharged without any neurologic deficits. To our knowledge, this is a first reported case in the literature of a ruptured peripheral lenticulostriate artery aneurysm in childhood. The pathogenesis of such an aneurysm and the treatment modalities are discussed.

Aneurysm, Ruptured↗

PubMed1996

[Increased urinary iron excretion rate in patients with non-insulin dependent diabetes mellitus].

Urinary iron excretion rate(u-FeER, microgram/min) in urine at night time from 58 patients with non-insulin dependent diabetes mellitus and 8 controls was measured by atomic absorption. The patients were divided into three groups according to urinary albumin excretion rate(u-AER), namely, Group I(n = 44): less than 20 micrograms/min of u-AER; Group II(n = 9): 20 < or = u-AER < 200 micrograms/min; Group III(n = 5): more than 200 micrograms/min of u-AER. The u-FeER in group III(56.3 +/- 14.8 ng/min, mean +/- SEM) was significantly higher than that in controls (4.0 +/- 1.6ng/min), group I(8.3 +/- 1.6 ng/min) and group II(18.5 +/- 6.5ng/min). The increase of u-FeER in group III indicates that urinary iron may at least partly play a role in development of diabetic nephropathy.

Adult↗

PubMed1995

Expression and localization of glucose transporter 1 (GLUT1) in the rat oviduct: a possible supplier of glucose to embryo during early embryonic development.

The oviduct fluid mainly derived from the oviduct epithelium is reported to provide the environment necessary for embryonic development. To elucidate the origin of glucose in the oviduct fluid, we examined the expression and localization of glucose transporter 1 (GLUT1) in the rat oviduct by Northern blot analysis, immunoblot analysis and immunohistochemistry using both light and electron microscopy. Northern blot and immunoblot analyses both showed the presence of the GLUT1 mRNA and protein. Specific staining for GLUT1 was observed in the ampulla and the isthmus, but only slightly in the fimbria and the utero-tubal junction. Staining was confined to the luminal surface of the epithelial mucosa. Immunoelectron microscopic analysis revealed that GLUT1 was observed only on the surface of the microvilli in non ciliated secretory cells, but not in ciliated cells. These findings suggest that GLUT1 plays an important role in the glucose transfer from the oviduct epithelium into the lumen and in maintaining the adequate glucose concentration of the oviduct fluid for embryonic development in rat oviduct.

Animals↗

PubMed1995

Astrocytes retrovirally transduced with BDNF elicit behavioral improvement in a rat model of Parkinson's disease.

Neurotrophic factors that improve the survival of specific neuronal types during development and after exposure to various neuronal insults hold potential for treatment of neurodegenerative diseases. In particular, brain-derived neurotrophic factor (BDNF) has been shown to exert trophic and protective effects on dopaminergic neurons, the cell type known to degenerate in Parkinson's disease. To determine whether increased levels of biologically produced BDNF affect the function or regeneration of damaged dopaminergic neurons, the effects of grafting astrocytes transduced with the human BDNF gene into the striatum of the partially lesioned hemiparkinsonian rat were examined. Replication deficient retroviruses carrying either human prepro-BDNF or human alkaline phosphatase (AP) cDNA were used to transduce primary type 1 astrocytes purified from neonatal rat cortex. In vitro, BDNF mRNA was expressed by BDNF transduced astrocytes (BDNF astrocytes), but not control AP transduced astrocytes (AP astrocytes), as determined by reverse transcription polymerase chain reaction (RT-PCR). The modified astrocytes were injected into the right striatum 15 days after partial lesioning of the right substantia nigra with 6-hydroxydopamine. Transplantation of BDNF astrocytes, but not AP astrocytes, significantly attenuated amphetamine-induced rotation by 45% 32 days after grafting. Apomorphine-induced rotation increased over time in both groups, but was not significantly different in the BDNF-treated group. The modified BDNF astrocytes survived well with non-invasive growth in the brain for up to 42 days. Although BDNF mRNA positive cells were not detected within the graft site using in situ hybridization, alkaline phosphatase immunoreactive (IR) cells were present in control graft sites suggesting that the retroviral construct continued to be expressed at 42 days. Analysis of the density of tyrosine hydroxylase (TH)-IR fibers showed no effect of BDNF on TH-IR fiber density in the striatum on the lesioned side. These findings suggest that ex vivo gene therapy with BDNF ameliorates parkinsonian symptoms through a mechanism(s) other than one involving an effect of BDNF on regeneration or sprouting from dopaminergic neurons.

Amphetamine↗

PubMed1995

Ca2+ channel activities in the limb bud of early embryonic chick.

Ca2+ channel activities were recorded in the limb bud of embryonic day 4 chick with Ca2+ sensitive fluorescence (Fura-2) measurements and patch clamp techniques. Rises in intracellular Ca2+ concentrations were evoked by depolarization with the application of 100 mM K+ and this Ca2+ response was abolished by removing extracellular Ca2+. The Ca2+ response was blocked by 10 microM nifedipine and enhanced by 5 microM Bay K 8644. Long-lasting inward currents were revealed by whole-cell patch clamp recordings from dissociated cells of the limb bud. The inward current was also blocked by 10 microM nifedipine. Our study suggested the presence of L-type Ca2+ channels in the limb bud cells.

Animals↗

PubMed1995

Superficial temporal artery--middle cerebral artery anastomosis for acute cerebral ischemia: the effect of small augmentation of blood flow.

In order to evaluate the effectiveness of acute cerebral revascularisation, we conducted a review of 70 patients with acute arterial occlusion or severe stenosis. Of these, 35 underwent emergency superficial temporal artery--middle cerebral artery (STA-MCA) anastomosis (surgical group) and the other 35 were treated conservatively (non-surgical group) at different times. Statistical analysis indicated that the two groups were homogeneous for the prognostic indicators. Seven days after admission, neurological symptoms and signs improved in 43% of patients in the surgical group and in 29% of the non-surgical group, however, this difference was not significant. The ratios of independent life at 3 months were 51% and 31%, respectively (not significant). Subgroup analyses indicated that final outcomes for patients with mild to moderate paresis on admission were significantly better in the surgical group than in the non-surgical group (94% vs. 53%, p < 0.01). The ratios of haemorrhagic infarction, neurological worsening, and mortality were comparable between the two groups. Time of ischaemia is a less important factor in the criteria for surgical selection. Acute revascularisation in selected patients does improve a natural course and could be a therapeutic option for acute cerebral ischaemia.

Adult↗

PubMed1995

Encircling method of trigeminal nerve decompression for neuralgia caused by tortuous vertebrobasilar artery: technical note.

BACKGROUND: Surgical treatment of trigeminal neuralgia caused by dolichoectatic vertebrobasilar artery presents a difficult problem because of the immobility and the stiffness of the atherosclerotic vessel walls. METHODS AND RESULTS: A patient with trigeminal neuralgia was treated by a new method of vascular decompression. Preoperative studies demonstrated a dolichoectatic vertebrobasilar artery, and compression of the trigeminal nerve by the artery was confirmed during surgery. The fifth nerve was mobilized away from the artery using a ring-shaped piece of silicone rubber. Postoperatively, the facial pain completely resolved without complication. CONCLUSIONS: Trigeminal neuralgia due to nerve compression by tortuous vertebrobasilar artery was successfully treated by an encircling method of vascular decompression.

Aged↗

PubMed1995

Michaelis-Menten analysis of immobilized enzyme by affinity capillary electrophoresis.

Michaelis constant of enzymatic reaction was evaluated by affinity capillary electrophoresis using beta-galactosidase as a model enzyme and o- and p-isomers of nitrophenyl-beta-galactoside as substrates. The enzyme was immobilized on the inner surface of a fused-silica capillary by the covalent bonding through a bridging group, and the substrates were introduced into the capillary. The reaction products migrated electrophoretically toward the detection side (anodic side), while the unreacted substrates moved toward the injection side (cathodic side) on a slow electroosmotic flow generated by the weak negative charge of the immobilized enzyme. The initial velocity of the enzymatic reaction was estimated from the peak height of the product, and the Michaelis constant was calculated according to Lineweaver-Burk equation. The results (Km, 2.34 mM for o-isomer and 1.09 mM for p-isomer) were reproducible (RSD < 11.8%, n = 5). Although the estimated Michaelis constants were larger than the reported values measured in homogeneous solution, the ratio of the Michaelis constants of o-/p-isomers was in good agreement with the literature value. The present method required as low as a few microgram amount of enzyme and nanogram amount of substrate which is far smaller than those required in a conventional affinity HPLC.

Amides↗