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Biomedical subjects

K Takemoto

Publications and source records attributed to K Takemoto.

At least 73 records · Page 4Linked to original sources
PubMed1990

Watersoluble synthetic nucleic acid analogs--polyethyleneimine derivatives containing nucleic acid bases--conformation and interactionwith nucleic acids.

Water soluble polyethyleneimine derivatives containing nucleic acid bases were found to interact with polynucleotides, DNA, RNA. The conformational change by formation of complex was observed by CD spectra and was discussed with the hypochromicity in UV spectra. The rates of interactions between nucleic acid bases in polymers were slow as shown by UV spectra, but the conformational changes of the polynucleotides were fast as shown by CD spectra. In the case of the uracil derivative (PEI-Hse-Ura), high value of CD spectra [theta] 2.80 = -8.0 x 10(-4) for the complex with DNA might be caused by psi type conformation of DNA.

Circular Dichroism↗
PubMed1990

[A well-differentiated hepatocellular carcinoma within adenomatous hyperplasia].

A 37-year-old male was admitted to hospital for jaundice and ascites. An ultrasonogram revealed a hypoechoic mass located in the right anterior inferior segment. A needle specimen of the liver was taken, and its biopsy led to a histological diagnosis of a hepatocellular carcinoma. The patient subsequently underwent an operation wherein it was found that the resected tumor that was taken was not clearly demarcated from the cirrhotic parenchyma. The histological diagnosis was an adenomatous hyperplasia. In a portion of this adenomatous hyperplasia, highly consistent hepatic cells and pseudogland formations were seen, confirming the diagnosis of a well-differentiated hepatocellular carcinoma within an adenomatous hyperplasia.

Adult↗
PubMed1990

[A case of bilateral adrenal myelolipoma].

We reported a case of bilateral adrenal myelolipoma. Low height, obesity and and elevation of 17-KS were found in this case. Tumors were hypovascular adrenal masses with low attenuation numbers on CT. MRI was useful in demonstrating the relation of tumors to adjacent organs. It should be considered that, although very rare, bilateral myelolipoma is possible.

Adrenal Gland Neoplasms↗
PubMed1990

[MR images of gliomas].

MR images of 55 gliomas (23 malignant gliomas, 16 Grade I-II astrocytomas, 7 oligodendrogliomas, 5 pontine gliomas, 2 central neurocytomas and 2 ependymomas) were reviewed. Histological diagnosis was obtained in all of these gliomas. Morphologic appearance and signal intensities of each glioma were evaluated on T1 and T2 weighted images. Nearly isointensity areas which correspond to enhanced areas on CT scans were observed in all malignant gliomas, and 19 of 23 malignant gliomas (83%) showed heterogeneous intensities on MR images. On the other hand, 12 of 16 benign astrocytomas (75%), 5 of 7 oligodendrogliomas (71%) and all of 5 pontine gliomas showed homogeneous intensities. All of central neurocytomas and ependymomas were shown as a solid tumor with cysts and heterogeneous intensities. In conclusion, although MR images without Gd-DTPA seemed not to be superior to contrast CT in differentiating malignant gliomas from benign one, it appears significant to know some tissue characteristics on MR images of gliomas in differentiating from the other brain tumors.

Adolescent↗
PubMed1989

[MR images of wallerian degeneration--relation between the time and MR findings of wallerian degeneration].

On magnetic resonance (MR) images, wallerian degeneration of the pyramidal tract can be demonstrated as an abnormal intensity showing prolonged T1 and T2 relaxation times corresponding to the corticospinal tract, and/or as shrinkage of the ipsilateral cerebral peduncle and pons. We evaluated 150 cases with supratentorial cerebrovascular accident (CVA) and found the above findings in 35 patients (hematoma 21, infarction 14). The time interval between the ictus of CVA and manifestation of wallerian degeneration on MR images was evaluated. In all 35 cases the foci of CVA located at or extended into the motor cortex, the corona radiata of the pyramidal tract or the posterior limb of the internal capsule. Abnormal signal intensity appeared as early as 5 weeks after ictus and was observed in all 17 cases after 10 weeks. Ipsilateral shrinkage of the cerebral peduncle and the pons has appeared 13 months after ictus. MR appears to be the most useful modality for early detection of waller degeneration.

Cerebrovascular Disorders↗
PubMed1989

Analyses of transplacentally induced sister chromatid exchanges and micronuclei in mouse fetal liver cells following maternal exposure to cigarette smoke.

The effect of maternal exposure to cigarette smoke on the fetus was studied by analyses of sister chromatid exchange (SCE) and formation of micronuclei with fetal liver cells. Fetal tissues were obtained from pregnant ICR/Jcl mice at the 16th day of gestation. Mice were exposed to mainstream or sidestream cigarette smoke with or without passage through filter (gas phase smoke or whole smoke). Each stream of smoke was used for three exposure schedules, i.e., short-term (two exposures at 15th and 16th day of gestation), long-term (exposure started at 4 wk before mating and stopped at 16th day of gestation), and prepregnant term (exposed for 4 wk before mating). The number of SCEs of fetal liver cells was significantly increased in all exposed groups. In the mainstream experiments, the long-term group showed a significant increase in the number of SCEs in comparison with that in the short-term group. Exposure to sidestream smoke increased the number of SCEs more than in groups exposed to mainstream smoke. This tendency was also recognized in the experiments with filtered smoke. On the contrary, no significant changes were observed by the micronucleus test. The transplacental genotoxic effect of maternally inhaled cigarette smoke was accurately detected by analysis of SCEs with fetal liver cells.

Animals↗
PubMed1989

Induction of squamous metaplasia, dysplasia and carcinoma in situ of the mouse tracheal mucosa by inhalation of sodium chloride mist following subcutaneous injection of 4-nitroquinoline 1-oxide.

Squamous metaplasia, dysplasia and carcinoma in situ (CIS) were induced in the ICR/Jcl mouse tracheal mucosa by exposure to a mist of 5% NaCl solution following single subcutaneous injection of 4-nitroquinoline 1-oxide (4-NQO). Either subcutaneous injection of 4-NQO or NaCl inhalation alone did not cause any marked change in the tracheal mucosa. The NaCl inhalation is considered to have promotion-like action on the mouse tracheal mucosa after administration of 4-NQO injection.

4-Nitroquinoline-1-oxide↗
PubMed1989

[Intrahepatic portal vein aneurysm: report of two cases].

We present two cases of intrahepatic portal vein aneurysm. The lesions were seen as low density mass on precontrast CT, hypoechoic mass with connecting vascular structures on ultrasonogram and dilatated branch of portal vein on MRI. Definite diagnosis were obtained by arteriogram. Only 15 cases of portal vein aneurysm were reported in Japan up to now in the literature.

Aged↗
PubMed1988

Hemolytic activity of a cyclic peptide Ro09-0198 isolated from Streptoverticillium.

Ro09-0198, a cyclic peptide isolated from culture filtrates of Streptoverticillium griseoverticillatum, induced lysis of erythrocytes. Preincubation of the peptide with phosphatidylethanolamine reduced the hemolytic activity, whereas other phospholipids present in erythrocytes in nature had no effect. A study of the structural requirements on phosphatidylethanolamine necessary for interaction with the peptide indicates that Ro09-0198 recognizes strictly a particular chemical structure of phosphatidylethanolamine: dialkylphosphoethanolamine as well as 1-acylglycerophosphoethanolamine showed the same inhibitory effect on hemolysis induced by Ro09-0198 as diacylphosphatidylethanolamine, whereas phosphoethanolamine gave no inhibitory effect. Neither phosphatidyl-N-monomethylethanolamine nor alkylphosphopropanolamine had an inhibitory effect. Consequently, the hydrophobic chain is necessary for the interaction and the phosphoethanolamine moiety is exactly recognized by the peptide. Ro-09-0198-induced hemolysis was temperature-dependent and the sensitivity of hemolysis differed greatly among animal species.

Actinomycetales↗
PubMed1988

Interaction of a cyclic peptide, Ro09-0198, with phosphatidylethanolamine in liposomal membranes.

Ro09-0198 is a cyclic peptide isolated from Streptoverticillium griseoverticillatum. This peptide caused permeability increase and aggregation of liposomes containing phosphatidylethanolamine. Liposomes containing phosphatidylserine, phosphatidylinositol or cardiolipin instead of phosphatidylethanolamine were, however, not appreciably reactive with the peptide. Among the structural analogs of phosphatidylethanolamine, dialkylphosphatidylethanolamine and 1-acylglycerophosphoethanolamine incorporated into liposomes could interact with Ro09-0198 to cause a permeability increase, whereas liposomes consisting of alkylphosphoethanolamine or phosphatidyl-N-monomethylethanolamine were insensitive to the peptide. These findings indicate that a glycerol backbone and a primary amino group of phosphatidylethanolamine are necessary for interaction with Ro09-0198 to cause membrane damage. Ro09-0198 induced a selective permeability change on liposomes. Glucose and umbelliferyl phosphate were effluxed significantly, but sucrose was only slightly permeable and inulin could not be released. Consequently, the permeability increase induced by Ro09-0198 is rather specific to molecules smaller than sucrose. Line broadening of electron spin resonance signals of spin-labeled phosphatidylethanolamine was observed upon treatment of liposomes with Ro09-0198. It was suggested from these results that Ro09-0198 can alter the physical organization of phosphatidylethanolamine in membranes, thus providing a basis for changes in membrane permeability.

Actinomycetales↗
PubMed1988

MR imaging of intraspinal tumors--capability in histological differentiation and compartmentalization of extramedullary tumors.

Magnetic resonance (MR) images of 29 consecutive patients with intraspinal neoplasms (9 intramedullary tumors, 20 extramedullary tumors) were reviewed to evaluate the utility of MR imaging in distinguishing the intraspinal compartmental localisation and signal characteristics of each lesion. Compartment and histology of all neoplasms were surgically proven. MR correctly assigned one of three compartments to all lesions, 9 intramedullary, 14 intradural extramedullary (6 schwannomas, 3 neurofibromas, 5 meningiomas), and 6 extradural (3 schwannomas, 1 meningioma, 1 cavernous hemangioma, 1 metastatic renal cell carcinoma). All intramedullary tumors showed swelling of the spinal cord itself. In all five extradural tumors a low intensity band was visualized between the spinal cord and tumor. On the other hand, a low intensity band was demonstrated in no cases with intradural tumors. Visualization of this low intensity band is important in differentiating extradural from intradural-extramedullary lesions. We call this low intensity band, "the extradural sign". Signal intensity of intradural tumors varied with histology. In extramedullary tumors, signal intensity of schwannomas was similar to that of the cerebrospinal fluid (CSF) both on T1 weighted (inversion recovery) and T2 weighted spin echo (SE) images. On the other hand, meningiomas tended to be isointense to the spinal cord on both T1 and T2 weighted SE images. We found relatively reliable signal characteristics to discriminate meningioma from schwannoma.

Astrocytoma↗
PubMed1988

Magnetic resonance images of tuberous sclerosis. Further observations and clinical correlations.

The cerebral lesions in tuberous sclerosis are of three kinds: subependymal nodules, cortical tubers, and cluster of heterotopic cells in the white matter. Understanding of these hamartomas is still incomplete even with modern imaging modalities. Magnetic resonance (MR) images of ten patients with tuberous sclerosis were reviewed and compared to computed tomographic (CT) scans and to the clinical severity of the disease. T2 weighted spin echo (TR = 1800, TE = 120) images and inversion recovery (TR = 2100, TI = 500-600, TE = 40) images were obtained at the same axial planes. Periventricular nodules were better seen, because of their calcifications, with CT than with MR imaging. They were demonstrated as iso- to low intensity depending on the amount of calcification on T2 weighted images, and as a similar intensity to the white matter on IR images. Small peripheral lesions in the hemispheres, which were only occasionally seen as small low density areas on CT scans, were well demonstrated on MR images. These foci were hyperintense on T2 weighted images, and hypointense on IR images. Exact location of these was not in the cortex, but in the subcortical white matter. The findings indicate that these foci represent the pathologically well known demyelinating foci, which are commonly present under the cortical tuber, but may be independent of them. Cortical tubers were not confidently identified, which suggested that they might have similar intensity to the cortical gray matter.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1988

Nucleic acid analogs for high performance liquid chromatography.

HPLC resins containing nucleic acid base derivatives were successfully prepared. These resins were found to give excellent complementary separation of nucleic acid base derivatives, nucleosides, nucleotides, and oligonucleotides. These resins may be useful for separation of components of nucleic acids and polynucleotides as a specific separation system, while ion-exchange and reverse-phase systems are non-specific separation systems.

Chromatography, High Pressure Liquid↗