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Biomedical subjects

S Nakasu

Publications and source records attributed to S Nakasu.

At least 73 records · Page 4Linked to original sources
PubMed1989

[Angiographically occult vascular malformations in the posterior fossa].

Three cases of spontaneous intraparenchymal hemorrhage in the posterior fossa were operated upon, and the diagnosis of thrombosed vascular malformation was histologically confirmed in two of them. So-called "angiographically occult" vascular malformations often present characteristic magnetic resonance (MR) images, namely, iso- to high intensity signal core surrounded by a low intensity signal rim or area on both T1 and T2 weighted images. Such findings are thought to indicate that subacute and chronic intraparenchymal hematoma has a relatively short T1 and long T2 relaxation times, resulting in an area of relatively increased signal intensity, and that hemosiderin deposits apparently decrease T2 relaxation time by paramagnetic effect. Most such lesions do not show significant perifocal edema. Occasionally, however, perifocal edema may be seen as in our Case 3, and the differential diagnosis from the tumor, particularly bleeding tumor, may become difficult even with the recent technical standards of high resolution CT and MRI. Reasons responsible for non-visualization of such vascular malformations at angiography are discussed. Small size of the lesion, slow blood flow through it, compression by adjacent clot or gliotic scar, spontaneous or secondary thrombosis with hyalin degeneration, and destruction at its rupture are possible factors.

Adult↗
PubMed1989

Interface between the meningioma and the brain.

Though meningiomas are usually well demarcated from the brain, their interfaces with the brain take various forms. Based on 27 nonoperated supratentorial meningiomas from autopsies, the interfaces were classified into four types, that is, smooth, lobular, finger-like expansion, and invasive. Relationships between the types of interfaces and the so-called capsule of the tumor and subarachnoid vessels are discussed. Additionally, three surgical cases which showed more or less the invasive form are presented with neuroradiological findings.

Adult↗
PubMed1989

Pituitary adenoma with multiple ciliated cysts: transitional cell tumor?

The case of a prolactin-secreting pituitary tumor with multiple cyst formation is described. Ultrastructurally, the cyst-lining cells were ciliated and closely resembled those of Rathke's cleft cyst but contained secretory granules, and no basal lamina formation was seen between the adenoma cells and the lining cells. Immunohistochemical study revealed that the adenoma cells consisted of both prolactin-secreting cells and growth hormone-secreting cells. The lining cells were immunoreactive with the antiserum to cytokeratin. No S-100 protein-positive cells were seen. The origin of this tumor is discussed.

Adult↗
PubMed1988

[Clinical evaluation of subarachnoid hemorrhage of unknown etiology].

This study concerns 16 cases with spontaneous subarachnoid hemorrhage (SAH) of unknown etiology experienced in our department during a period from September 1979 through August 1986. SAH was confirmed by computed tomographic scanning (CT) or lumbar puncture. All cases were studied by four or three-vessel study. In the case of three-vessel study, adequate opacification of the posterior inferior cerebellar artery contralateral to the injected vertebral artery was considered as a necessary condition. Panangiography was repeated in all patients one to two weeks after the initial study and was negative. The severity of SAH in these patients on admission was relatively mild (Hunt and Kosnik grade I + II = 75%), and the degree of subarachnoid bleeding on CT was also mild. Medium to long-term outcome was excellent or good in 81% of cases, and none of them experienced rebleeding. Only one patient died of severe vasospasm on the 20th hospital day, but no aneurysm was found at autopsy. Illustrative 3 patients in whom the cause of SAH had been finally found was briefly reported. In the first patient, SAH was secondary to a paraventricular cryptic angioma. In the second patient, a microaneurysm had been concealed at the initial angiography by the parent arteries or intra-aneurysmal clot. In the third case of a fusiform aneurysm of the vertebral artery, the aneurysm proximal to the posterior inferior cerebellar artery could not be found at the first three-vessel angiography. Importance of CT and the necessity of repeat panangiography including magnification or oblique views so as not to over-look the causative vascular abnormalities were emphasized.

Adult↗
PubMed1987

Intrinsic DNA-dependent ATPase activity of reverse gyrase.

Reverse gyrase is a type I DNA topoisomerase that promotes positive supercoiling of closed-circular double-stranded DNA through an ATP-dependent reaction, and it was purified from an archaebacterium, Sulfolobus. When ATP is replaced by UTP, GTP, or CTP, this enzyme just relaxes the negatively supercoiled closed-circular double-stranded DNA. We found that reverse gyrase hydrolyzes ATP through a double-stranded DNA-dependent reaction. The superhelicity of the DNA did not affect the ATPase activity. However, reverse gyrase does not hydrolyze UTP, GTP, or CTP. Therefore, any of the four nucleotide 5'-triphosphates acts as an effector for the topoisomerase activity of reverse gyrase, but only ATP supports the positive supercoiling of closed-circular double-stranded DNA, through the energy released on its hydrolysis. Single-stranded DNA was a much more potent cofactor for the ATPase activity of the enzyme than double-stranded DNA, and it acted as a potent inhibitor for the topoisomerase activity on double-stranded DNA. These results indicate that reverse gyrase has higher affinity to single-stranded DNA than to double-stranded DNA, which suggests a cellular function of the enzyme.

Adenosine Triphosphatases↗
PubMed1987

Incidental meningiomas in autopsy study.

Two hundred thirty-one cases of incidental meningiomas found at autopsy at the Montefiore Medical Center during the period from 1950 to 1982 were reviewed. The prevalence of incidental meningiomas increased with age, and was highest in people 80 years of age or older. The male to female ratio was 1 to 3. The relative size of the tumors also increased with age. Multiple meningiomas were found in 8.2% of the cases; none of them had stigmata of neurofibromatosis.

Adult↗
PubMed1987

[Oligodendroglioma of the lateral ventricle--report of 2 cases and a review].

Oligodendrogliomas rarely grow primarily in the ventricles. When compared to more common hemispheric counterparts, such intraventricular oligodendrogliomas, or oligodendrogliomas of the midline group (Martin), present distinct clinical features, namely, (1) they occur in the younger age, (2) an interval between clinical onset and diagnosis or operation is shorter, and (3) initial symptoms are most often limited to those of increased intracranial pressure, although the patient may occasionally present mild organic dementia, callosal disconnection syndrome, and/or mild gait ataxia. Two cases of oligodendroglioma primarily involving the lateral ventricle are reported in female patients, aged 29 and 19, respectively, with sole complaints of an increased intracranial pressure. Magnetic resonance imaging proved to be most useful as a radiologic diagnostic procedure. The tumor was radically removed via a para-falcine transcallosal approach without causing any persistent neurological deficits. Merit and demerit of the approach are briefly discussed.

Adult↗
PubMed1986

Bacteriophage T3 gene 8 product oligomer structure.

The structure of the connector of bacteriophage T3 (built up by the product of gene 8) has been studied in two dimensions by combined use of translational and rotational image filtering procedures applied to tetragonal ordered aggregates of the former oligomers. This analysis, performed up to 1/1.6 nm-1 resolution, has revealed the existence of a 12-fold symmetry in the outermost region of the specimen (mainly between radii 5.2 and 6.7 nm), a 6-fold one in the inner region (between radii 1.7 and 3.2 nm), and a hole in its center. These features are very similar to the ones described for the connectors of other phages, such as T4, lambda, and phi 29, thus suggesting a common mechanism for the functions carried out by this viral region.

Fourier Analysis↗
PubMed1986

[Multifocal glioma of the brain--an autopsy case].

This is an autopsy case report of a 76 year old woman with multifocal glioblastoma multiforme. CT scan revealed three separate mass lesions in the left temporal lobe, left parietal lobe and right fronto-parietal lobes. CT-guided needle biopsy of the right fronto-parietal mass revealed glioblastoma multiforme. At autopsy, serial horizontal sections of the brain confirmed the CT scan findings and demonstrated extension of the tumor in the left parietal lobe to the subarachnoid space. The lesion in the right fronto-parietal region infiltrated a large area and was not demarcated. Microscopic examination of all three lesions revealed glioblastoma multiforme. The left temporal lobe tumor consisted of gemistocytic astrocytes predominantly. Reaction of the tumor to glial fibrillary acid protein (GFAP) antibody ranged from markedly positive in the gemistocytic astrocytes to negative in the anaplastic cells. The reported incidence of multifocal glioma is about 2-10%. The main pathophysiologic mechanisms invoked for this phenomenon are simultaneous neoplastic transformation and seeding from one tumor. The pathophysiology of this particular case is discussed in reference to the differences in the histopathology of the 3 separate foci of glioblastoma multiforme.

Aged↗
PubMed1985

Reverse gyrase; ATP-dependent type I topoisomerase from Sulfolobus.

Reverse gyrase, a topoisomerase which introduces positive superhelical turns into DNA, has been purified from Sulfolobus to near homogeneity. It is a single polypeptide with a mol. wt. of 120 000 as determined by denaturing gel electrophoresis. Contrary to a previous report, it is a type I topoisomerase as judged by the linking-number change of closed circular DNA topoisomer. Unlike other known type I topoisomerases, ATP or dATP is required for introducing positive superhelical turns. In order to relax negatively supercoiled DNA, other nucleotide triphosphates (XTP) are also effective with low efficiency. In the absence of either XTP or divalent cations, the enzyme introduces nicks into closed circular DNA when the reaction is stopped by SDS. This suggests that reverse gyrase cuts one of the two strands of DNA in the course of its enzymatic reaction.

Journal Article↗