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S Nakasu

Publications and source records attributed to S Nakasu.

At least 55 records · Page 3Linked to original sources
PubMed1992

Structure of the ColE1 DNA molecule before segregation to daughter molecules.

The segregation of daughter DNA molecules at the end stage of replication of plasmid ColE1 was examined. When circular ColE1 DNA replicates in a cell extract at a high KCl concentration (140 mM), a unique class of molecules accumulates. When the molecule is cleaved by a restriction enzyme that cuts the ColE1 DNA at a single site, an X-shaped molecule in which two linear components are held together around the origin of DNA replication is made. For a large fraction of these molecules, the 5' end of the leading strand remains at the origin and the 3' end of the strand is about 30 nucleotides upstream of the origin. The 3' end of the lagging strand is located at the terH site (17 nucleotides upstream of the origin) and the 5' end of the strand is a few hundred nucleotides upstream of the terH site. Thus the parental strands of the molecule intertwine with each other only once. When the KCl concentration is lowered to 70 mM, practically all of these molecules are converted to daughter circular monomers or to catenanes consisting of two singly interlocked circular units.

Bacterial Proteins↗
PubMed1992

[Cystic falx meningioma: report of a case with difficulty in radiologic diagnosis].

A case of cystic falx meningioma in the frontal region in which preoperative neuroradiologic diagnosis was difficult is reported. This 33-year-old man had suffered from epileptic seizures three times in one month. Physical and neurological examinations on admission were normal. A cystic mass with a small nodule was found on CT in the frontal region. Thin wall was enhanced smoothly and the nodule attached to the falx was enhanced heterogeneously. The mass was considered to be an extra-axial lesion on MRI. The right anterior falcine artery seemed to feed the mass. Bifrontal craniotomy was performed. Cyst was evacuated, and a soft reddish mass was subtotally removed. Cyst fluid was yellowish and protein content was 3.5 g/dl. Histopathological diagnosis was a meningotheliomatous meningioma and tumor cells were present also in the thin cyst wall. At the second operation the mass was completely removed, cyst wall inclusive. When we encounter a cystic mass in the sites of predilection of meningiomas, we have to consider the possibility of a cystic meningioma. If the mass has meningeal vascularization, a correct diagnosis is not difficult. Taking the location of the mass into consideration, an accurate interpretation of CT and MRI findings indicating extra-axial nature of the mass is indispensable.

Adult↗
PubMed1992

Craniosynostosis in association with medulloblastoma.

A case of a 13-month-old boy with craniosynostosis associated with medulloblastoma was presented. Sagittal suture was prematurely closed, and coronal and lambdoid sutures were widely separated. A large infiltrative tumor in the midcerebellar region was partially removed and treated by irradiation and chemotherapy. A review of the current literature failed to reveal a similar report.

Cerebellar Neoplasms↗
PubMed1992

Intramedullary subependymoma with neurofibromatosis--report of two cases.

Two cases of subependymoma in the cervical spinal cord associated with stigmata of neurofibromatosis are reported. Magnetic resonance (MR) imaging showed one tumor with a sharp margin, which was well-demarcated intraoperatively and was totally removed. MR imaging showed the other tumor with an irregular margin, which was partly invasive at operation. Subependymomas are rare in the spinal cord and these are the first reported associations with neurofibromatosis.

Adolescent↗
PubMed1992

[Outcome of patients with primary malignant lymphoma of the brain; relationship to the nucleolar organizer region].

Twelve cases of primary malignant lymphoma of the central nervous system had been treated since April, 1979 to August, 1990. Radiation therapy was completed in ten of them without adjuvant chemotherapy, and the other two patients expired before or during radiation therapy. In spite of good response to the radiation therapy, five of the ten patients died within 2 years. Three cases are alive after more than 5 years, and there has been no recurrence. In eight cases, the number of the argyrophilic proteins of the nucleolar organizer regions (AgNORs) was counted in the formalin-fixed paraffin embedded sections. In those cases with an AgNOR number of 4.0 or higher, prognosis was significantly worse than in the others. AgNOR number may be used as one of the reliable factors in the prognosis of primary malignant lymphoma of the central nervous system.

Adult↗
PubMed1991

Diploic meningioma contiguous to a contralateral parasagittal meningioma: CT and MR features.

A patient with a diploic meningioma is presented. Computed tomography (CT) scan revealed an intradiploic tumor which seemed contiguous at a point to a contralateral, recurrent parasagittal meningioma. On CT, density of the diploic meningioma was similar to that of the parasagittal meningioma, but the contrast study showed that the former enhanced much less than the latter. Magnetic resonance (MR) imaging demonstrated that the diploic tumor was heterogeneous and much less enhanced with Gadolinium-DTPA (Gd-DTPA) than the parasagittal meningioma on T1-weighted image, although they were very similar in signal intensities on T2-weighted and proton density-weighted MR images without Gd-DTPA. Reasons for such marked differences in enhancement patterns are discussed.

Female↗
PubMed1991

Primary carcinoma of the choroid plexus in the lateral ventricle.

Primary carcinomas of the choroid plexus are rare and occur more frequently in children than in adults. They have been posing a problem in their differential diagnosis from benign papilloma of the choroid plexus, ependymoma, and metastatic tumors of extracranial origin. A case of a 31-year-old woman with primary carcinoma of the choroid plexus in the trigone is reported. Electron microscopic and immunohistochemical studies are helpful, but not decisive yet, to reach the diagnosis. The literature is reviewed.

Adult↗
PubMed1990

Periventricular spread of malignant lymphoma: report of two cases.

Two cases of intracranial malignant lymphoma with an atypical feature on CT scan are reported. Both patients presented subacute progressive dementia. CT scan showed high density lesion extending all the way along the ventricular wall, which was homogeneously enhanced and resembled severe ventriculitis. Differential diagnosis on CT scan is discussed.

Aged↗
PubMed1990

Central neurocytoma: report of a case.

Central neurocytoma is a rare intraventricular tumor recently accepted as a clinicopathological entity. A 21-year-old female was admitted with three-year history of episodic headaches and vomiting, and with rapid deterioration of her left vision over two weeks prior to admission. Computed tomography (CT) scan revealed a marked hydrocephalus and an isodense, mildly enhancing mass in the left lateral ventricle. On magnetic resonance imaging (MRI) scan, T1-weighted images revealed an intraventricular mass of slightly high intensity signal, which contained areas of low intensity signal representing multiple intratumoral cysts. The tumor showed a minimal enhancement with Gd-DTPA. A diagnosis of central neurocytoma was confirmed by an electron-microscopic study of a surgical specimen; there were numerous neuronal cell processes containing microtubules and dense-core vesicles, and a few small intercellular junctions were also identified.

Adult↗
PubMed1990

[Meningiomas in the elderly: analysis of 34 patients].

We have operated on 82 patients with intracranial meningiomas in the past 10 years. They ranged in age from 6 to 80 (mean 56.3), 59 patients were female and 23 were male. Thirty-four patients were 60 years of age or older. Of 82 patients, follow-up examination was possible in 71, with a mean follow-up period of 3 10/12 years. Pattern of clinical onset, location of tumors, and histology were compared among groups of approximately 59 years, 60-69 years, and 70 years approximately in age. Of 71 followed-up patients, 11 (15.5%) had expired. Operative mortality in patients aged 60 or older in this series, however, was low at 2.9%.

Aged↗
PubMed1990

[Pituitary adenoma associated with neurofibromatosis: case report].

A case of pituitary adenoma associated with multiple neurinomas in the central nervous system was presented. A 52-year-old man was referred to us for surgical treatment of an intradural extramedullary cervical cord tumor. He had been operated on for a cauda equina tumor when he was 43 years old, and again for a glossopharyngeal neurinoma at 49 years of age. His brother expired in childhood, and had multiple subcutaneous nodules. The patient had been complaining of left leg pain, left shoulder pain, and hypesthesia of the right leg and foot. Examination showed 6th cervical nerve root sign. MRI revealed a well-circumscribed extramedullary tumor at the C5 level, and, in addition, incidentally showed an intra- and supra-sellar tumor which was isointensity on T1 weighted and high intensity on T2 weighted images. Myelography showed multiple extramedullary tumors in the lumbar region. Endocrinological study revealed an increased serum prolactin level (818.0ng/ml). The patient had neither café au lait spots nor subcutaneous nodules. A neurinoma of C6 root was totally removed and chromophobe pituitary adenoma was partially removed through a transsphenoidal approach. Neurofibromatosis is known to be associated with many kinds of tumors in the central nervous system. They are usually neurinomas, meningiomas or gliomas, and association of pituitary adenomas has been reported in only three cases, one of which being a prolactin secreting adenoma. Coexistence of multiple primary brain tumors has been also reported apart from phakomatosis. The most common combination is association of glioma and meningioma, and it is probably incidental coexistence due to their high frequency.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenoma, Chromophobe↗
PubMed1990

[Radiological features of primary central nervous system lymphoma].

Radiological features of 12 cases of primary malignant lymphoma of the central nervous system with histological confirmation were reviewed. Ten patients had primary intracranial lymphoma, and two spinal. Angiography yielded no specific findings. CT appearances varied widely. Any positive relationships were not found between histologic types of tumors and patterns of contrast enhancement in the present cases as well as in those reported previously. Gd-DTPA was used in two patients. All lymphomas showed low to isointensity signals on T1-WI and high signal intensities on rho-WI and T2-WI. Although MRI gave no additional informations to those on CT with regard to the differential diagnosis, it proved to be a very accurate, non-invasive method of providing better delineation of tumor on multiplanar basis. Use of Gd-DTPA improved quality of T1-WI by markedly enhancing the tumor. It is generally difficult to distinguish primary from secondary spinal lymphoma, but two spinal epidural lymphomas in the present series were considered primary, as we could detect no other lesion elsewhere in the body. We expect that MR imaging would lead to an improvement in the detection of lesion in the paravertebral area.

Adult↗
PubMed1990

Rathke's cleft cyst: computed tomographic scan and magnetic resonance imaging.

Three patients with histologically proved Rathke's cleft cysts (RCCs) were evaluated with magnetic resonance imaging (MRI) and computed tomographic (CT) scan. Thirteen cases reported in the previous literature were also reviewed to evaluate the MRI features of RCCs and to compare them with CT features. The RCCs had various patterns of signal intensities on T 1-weighted and T 2-weighted MRI. The cysts were well-circumscribed and mainly in the sella turcica extending to the suprasellar cistern with minimal mass effect. Ten of sixteen cases had homogeneous cysts, and six had heterogeneous cysts. The CT scans showed the cysts as low or isodensity, well-demarcated lesions in the sella, that did not enhance with a few exceptions in which a thin ring enhancement was seen. MRI is superior to CT in the evaluation of the RCC, and is particularly useful in surgical planning, although MRI has a limitation on the specific, analytic description of the cyst contents.

Cysts↗
PubMed1990

Interface between the meningioma and the brain on magnetic resonance imaging.

Magnetic resonance imaging of 31 meningiomas in 29 patients was retrospectively reviewed and compared with pathologic specimens in 25 tumors to investigate how magnetic resonance imaging could delineate a tumor-brain interface. The thick, collagenous connective tissue, which was seen around four tumors, was shown as a low signal intensity rim on both a T1-weighted image and a T2-weighted image. A rim of low signal intensity on a T1-weighted image and high signal intensity on a T2-weighted image most likely represented cerebrospinal fluid space: this finding was seen around eight tumors. No distinct rim could be identified in five tumors. Of these five, two tumors grew invasively into the brain. Although mixed features predominated in meningiomas, magnetic resonance imaging could well delineate a tumor-brain relationship in most of the cases.

Adult↗
PubMed1990

Cerebral hemodynamics in patients with normal pressure hydrocephalus: correlation between cerebral circulation time and dementia.

Regional cerebral blood flow and regional cerebral circulation time were measured in 13 demented patients with chronic hydrocephalus, mostly normal pressure hydrocephalus. The average hemispheric, frontal, and temporal cerebral blood flows were significantly reduced. The average regional cerebral circulation time values were significantly prolonged in the frontal, temporal, and thalamic regions, most markedly in the frontal white matter, where periventricular lucency was observed on computed tomography. Clinical improvement was obtained in all patients after operation. While postoperative regional cerebral blood flow values did not change compared with preoperative ones, postoperative regional cerebral circulation time values were significantly reduced in all the regions measured, and most markedly in the frontal white matter. The present results suggest that microcirculation in the frontal lobe is closely correlated with dementia in association with pressure exerted on the nerve fibers in the frontal white matter in patients with normal pressure hydrocephalus.

Aged↗
PubMed1989

[Pneumothorax, subcutaneous emphysema and mediastinal emphysema in transnasally intubated patients].

A 41-year-old woman was admitted to our clinic because of an acute subdural hematoma. After an emergency operation her neurological status improved with an increase in the Glasgow Coma Scale score from 6 to 11. On the second postoperative day she developed frequent episodes of clonic convulsive seizures localized in the face and the left upper extremity, and her level of consciousness deteriorated. Next day she was transnasally intubated for respiratory management, but no mechanical ventilation was required. While she was undergoing the CT scanning 5 days after intubation, respiratory arrest and cyanosis developed all of a sudden, and her face and neck became swollen. The chest x-ray revealed a marked subcutaneous emphysema, mediastinal emphysema and bilateral pneumothorax. CT at that time showed a diffuse low density area in the right hemisphere, and a marked midline shift returned. She did not regain consciousness and died 12 days after the incident. At autopsy an ulcer was observed in the wall of the trachea, where the tip or the cuff of the transnasal tracheal tube was supposed to be present. No perforation, however, was there. Case 2: A 75-year-old woman was admitted to our hospital because of SAH. In hospital course she was also transnasally intubated and required no mechanical ventilation. When she was undergoing the CT scanning 3 days after intubation, she developed subcutaneous and mediastinal emphysema similarly to case 1. Although it is reported to be not a rare complication in patients on a mechanical ventilator, subcutaneous emphysema or pneumothorax is extremely rare in those intubated patients with spontaneous respiration. The mechanism of these complications in these cases is briefly discussed.

Adult↗
PubMed1989

Structural changes in positively and negatively supercoiled DNA.

The effect of superhelical constraint on the structure of covalently closed circular DNA (cccDNA; pBR322) with positive and negative writhe (superturn) has been investigated as a function of decreasing and increasing specific linking difference (mean superhelical density sigma). At low and moderate negative superhelical densities sigma, the overall average structure is maintained in an unwound B-form slightly modified. The overwound cccDNAs with positive writhe differ from those with negative writhe by an absence of cruciform structure. At high negative densities of supercoiling different changes involving the reversal of twist handedness are shown to lead to the formation of DNA segments in a conformation identical to the left-handed component of form V DNA.

Circular Dichroism↗