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Biomedical subjects

R Kuroda

Publications and source records attributed to R Kuroda.

At least 145 records · Page 8Linked to original sources
PubMed1982

X-ray crystallographic analysis of 3-(2'-phenyl-2,4'-bithiazole-4-carboxamido) propyldimethylsulphonium iodide, an analogue of the DNA-binding portion of bleomycin A2.

The crystal and molecular structure of the title compound, an analogue of the DNA binding region of bleomycin A2, has been determined by X-ray crystallography. All the three independent molecules in an asymmetric unit are approximately planar with fully extended side chains. A computer graphics model-building study has shown that the phenyl group and the second thiazole ring can be intercalated between the base pairs of the double-stranded deoxydinucleoside phosphate d(CpG), and also that the sulphonium cation can interact with a backbone phosphate group. This model is in accord with NMR spectral data.

Bleomycin↗
PubMed1982

Relation of cytoplasmic calcium to contractility in Physarum polycephalum.

In a dumbbell-shaped plasmodium of Physarum polycephalum showing active shuttle streaming Ca was precipitated with potassium pyroantimonate (K[Sb(OH)6]), and the distribution of Ca between the cytoplasm and cellular organelles, especially vacuoles, was examined by electron microscopy. The contracting half-mass, where many empty vacuoles were present, was rich in the small Ca precipitates located in the cytoplasm. The relaxing half-mass, where many Ca-containing vacuoles were present, was poor in the cytoplasmic Ca precipitates. One half-mass of a dumbbell-shaped plasmodium was treated with Ca ionophore, X-537A, and its effect on the motive force for endoplasmic streaming and the distribution of Ca was investigated. The motive force was increased by X-537A, but the period of shuttle streaming was not changed. X-537A also induced a significant increase in the number of the cytoplasmic Ca precipitates in the X-537A-treated contracting half-mass, so that the asymmetry of the distribution of cytoplasmic Ca precipitates was enhanced. A large portion of the vacuoles were empty in the contracting half-mass, and Ca-containing in the relaxing one as in the case of the untreated plasmodium.

Calcium↗
PubMed1982

Molecular structure of (+/-)-7,8,9,10-tetrahydroxy-7,8,9,10-tetrahydrobenzo(a)pyrene determined by x-ray crystallography.

The molecular structure of a tetrahydrotetrol that is formed by hydrolysis of (+/-)-7 alpha, 8 beta-dihydroxy-9 beta, 10 beta-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene, has been determined by X-ray crystallographic methods. The relative orientations of the four hydroxyl groups of the racemic tetrahydrotetrol (7 alpha, 8 beta, 9 beta, 10 alpha) indicate that the tetrahydrotetrol was formed by the trans opening of the epoxide ring of the diol-oxide. The hydroxyl groups at positions 7 and 8 adopt a diequatorial conformation, while those at positions 9 and 10 adopt a diaxial conformation. Several other geometric features are discussed.

Benzopyrenes↗
PubMed1981

Origin of the membrane potential in plasmodial droplets of Physarum polycephalum. Evidence for an electrogenic pump.

Spherical droplets, derived from Physarum plasmodia by incubation in 10 mM caffeine, seemed to be an excellent system for electrophysiological studies because they were large (less than or equal to 300 micrometer in diameter) and because they tolerated intracellular electrodes filled with 3 M KCl and 10 mM EDTA for a few hours. Intact plasmodia, by contrast, gave valid records for only a few minutes. Under standard conditions ([K+]o = 1 mM, [Na+]o = 5 mM, [Ca++]0 = 0.5 mM, [Mg++]o = 2 mM, and [Cl-]o = 6 mM at pH 7.0), the potential difference across droplet membranes was -80 to -120mV, interior negative. The membrane potential was only slightly sensitive to concentration changes for the above-mentioned ions, and was far negative to the equilibrium diffusion potentials calculated from the known internal contents of K, Na, Ca, Mg, and CL (29.4, 1.6, 3.7, 6.5, and 27.8 mmol/kg, respectively). Variations of external pH did have a strong influence on the membrane potential, yielding a slope of 59 mV/pH between pH 6.5 and 5.5. In this pH range, however, the equilibrium potential for H+ (assuming 6.2 less than or equal to pHi less than or equal to 7.0) was greater than 75 mV positive to the observed membrane potential. Membrane potential was directly responsive to metabolic events, being lowered by potassium cyanide, and by cooling from 25 to 12 degrees C. This ensemble of results strongly indicates that the major component of membrane potential in plasmodial droplets of Physarum is generated by an electrogenic ion pump, probably one extruding H+ ions.

Antimetabolites↗
PubMed1980

Subjective visual symptoms and electroencephalographic analysis before and after removal of occipital falx meningioma.

A 41-year-old patient underwent surgery for the partial removal of a posterior falx meningioma, which invaded deeply into both occipital lobes. After surgery, the patient complained of marked metamorphopsia, colored photopsia, afterimage and loss of stereopsia. The relationships between these symptoms and features of the VEP and EEG power spectra (both under resting and photic driving conditions) were investigated. Marked photopsia on the 4th postoperative day was accompanied by EEG features indicating asynchronous excitation of injured cortical cells, while the presence of a strong afterimage on days 17 through 24 coincided with indications of an apparent refractoriness in cortical activation.

Adult↗
PubMed1980

Calcium accumulation in vacuoles of Physarum polycephalum following starvation.

The plasmodium of Physarum polycephalum contained 15.3 mmol Ca/kg fresh weight of sample, 11.8 mmol Mg/kg, 24.5 mmol K/kg and 1.4 mmol Na/kg. When the plasmodium was starved of food, the Ca content increased gradually up to 71.9 mmol/kg during 5 days of starvation. The concentration of other elements changed only slightly. The endoplasm contained 23.0 mmol Ca/kg, 12.6 mmol Mg/kg, 26.6 mmol K/kg and 1.7 mmol Na/kg, but these contents changed only slightly during starvation. The Ca, Mg, K and Na contents of the slime and the soluble fraction were also determined. In order to clarify where the accumulated Ca was localized, Ca in the plasmodium was precipitated with potassium pyroantimonate and examined by electron microscopy. In the starved plasmodium, the vacuoles which contained the electron-opaque precipitates and were located in the ectoplasm increased in number, compared with the unstarved plasmodium. At the same time the large electron-opaque granules in the extracellular slime increased in number. The electron-opaque precipitates were identified as Ca pyroantimonate by its susceptibility to removal by chelation with ethyleneglycol bis (beta-aminoethyl ether) N, N, N', N'-tetraacetic acid (EGTA) and X-ray microprobe analysis.

Calcium↗
PubMed1979

9-beta-D-Arabinofuranosyl-8-n-butylaminoadenine, a C-8 substituted nucleoside in the anti conformation. Crystallographic and NMR studies.

The protein NMR spectrum of 9-beta-D-arabinofuranosyl-8-n-butylaminoadenine shows an unusually low-field 5'-hydroxyl proton resonance, which has been interpreted in terms of an anti glycosidic conformation together with an 05' ... N8 intramolecular hydrogen bond. Confirmatory evidence for this was obtained by an X-ray crystallographic study; in the crystal, the glycosidic angle chi is 52.7 degrees and the sugar pucker is C3' endo-C4' exo.

Butylamines↗
PubMed1977

The distribution of degenerating axons after small lesions in the intact and isolated visual cortex of the cat.

The extent of the spread of axonal degeneration was investigated in the visual cortex of the cat after making small lesions restricted to the grey matter. Two series of experiments were undertaken. In the first, normal adult cats were used, and in the second, the cortex of the postlateral gyrus was isolated from its extrinsic afferents by surgical undercutting 3 months before making the lesions. The results were similar in the two series in most respects. 1. Horizontal fibres extended in considerable numbers for some 500 micrometer from the lesion, mainly in layers I, III/IV and V, a few reaching 2/3 mm. These fibres were better seen in the intact than in the isolated cortex. Their spread was usually asymmetrical, being greater posteromedially than anterolaterally. 2. Oblique axons ran downwards from the middle layers into layers V and VI, or upwards into layers I and II. 3. Axons arising from layers II to VI descended vertically into the white matter. Degeneration patterns after lesions in areas 17 and 18 were compared.

Afferent Pathways↗
PubMed1977

[Clinical study on penetration of antibiotics into cerebrospinal fluid (second report),-Study on intravenous administration of sodium cephalothin with mannitol solution (author's transl)].

Penetration of Sodium Cephalothin (CET) into CSF follwing intravenous administration was studied in 23 patients with intracranial diseases excluding inflammation and severe subarachnoid hemorrhage. 1) After intravenous injection of 2 g of CET, ventricular CSF was obtained in 4 cases. All these 4 cases showed CET concentration in CSF to be below 0.1 mcg/ml. 2) After intravenous injection of 2 g of CET, lumbar CSF was obtained in 6 cases. In two cases out of these 6 cases, CET concentration in CSF was higher than 0.7 mcg/ml. 3) In 13 cases 2 g of CET with 200ml of 20% Mannitol was injected intravenously and lumbar CSF was examined. CET concentrations in CSF between 0.7 mcg/ml and 6.0 mcg/ml were observed in 9 cases of this group. 4) According to the results it is strongly suggested that the administration of Monnitol and CET is very effective for penetration of CET into CSF.

Adolescent↗