Biomedical subjects

R Kuroda

Publications and source records attributed to R Kuroda.

At least 109 records · Page 6Linked to original sources

PubMed1992

Functional changes in thalamic relay neurons after focal cerebral infarct: a study of unit recordings from VPL neurons after MCA occlusion in rats.

We evaluated neuronal and histological changes of thalamic neurons 1, 4, 7, and 14 days after middle cerebral artery (MCA) occlusion in rats. After the somatosensory evoked potentials (SEPs) were measured from the cerebral cortex, the thalamic relay neuronal activities were recorded with a glass microelectrode following repetitive electrical stimulation of the contralateral forepaw at frequencies ranging from 1 to 50 Hz. In approximately 95% of the occluded rats, the ipsilateral somatosensory cortex and/or the subcortical somatosensory pathway developed infarct, resulting in SEP loss. We evaluated unit data from rats with abolished SEPs. The average firing rate of the nucleus ventralis posterolateralis (VPL) neurons in response to 25 stimulations at 30 Hz was significantly reduced to 0.1 spike/stimulus 1 day after MCA occlusion. In sham-operated rats, the same stimulation produced 0.7 spike/stimulus. The firing rate recovered to 0.4 spike/stimulus at 30-Hz stimulation 4 and 7 days after occlusion. This was followed by resuppression (0.1 spike/stimulus) 14 days after occlusion. Histological study revealed some abnormal neurons in the ipsilateral thalamus 7 days after occlusion. We were unable to find normal-shaped neurons in the VPL 14 days after occlusion. The present study demonstrates that cortical infarct produces functional and morphologic changes that gradually and progressively affect the ipsilateral thalamus, although incomplete transient recovery of somatosensory transmission may occur.

Animals↗

PubMed1992

Detection and partial purification of ischaemia-related neurotrophic activity in the periinfarcted brain tissue.

In the rat model of middle cerebral artery (MCA) occlusion, axons originating from the ipsilateral cortical and thalamic neurons are injured by ischaemia. The cortical neurons survive thereafter without retrograde degeneration, but thalamic neurons slowly die because of retrograde degeneration. The fate of these two neurons is remarkably different and may be related to neurotrophic activity induced by ischaemia. We detected ischaemia-related neurotrophic activity, and partially purified the factor. Tissue samples were obtained from the cortex adjacent to the infarction and contralateral corresponding site at 4, 8 and 12 days after occlusion of the MCA. They were homogenated with a culture medium and ultracentrifuged. The supernatant was obtained and used for neurotrophic assay. Foetal cortical neurons were obtained from 17 days rat embryo and cultured. Neurotrophic activity was assayed by applying tissue extract to the culture medium. Application of periischaemic cortical extract obtained at 8 and 12 days after ischaemia improved neuronal survival by 50% and 200% as compared to contralateral cortical extract, respectively. The activity was not detectable at 4 days after ischaemia. The neurotrophic activity disappeared by heating the extract at 90 degrees C for 10 min. We fractionated the extract by saturated ammonium sulphate precipitation, followed by gel-filtered with Superose 12 column. The neurotrophic activity was detected in the precipitation of 30 to 60% saturation fraction of ammonium sulphate. With gel-filtration we separated neurotrophic activity in several fractions, which included marker proteins of 8, 22 and 30 kilodaltons. The activities were only detected in the lesioned side but not in the contralateral side.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

A case of glomerular lipidosis accompanied by familial combined hyperlipidemia and panhypopituitarism.

This is a report of a case of glomerular lipidosis with familial combined hyperlipidemia and panhypopituitarism. A 60-yr-old woman was admitted for evaluation of hyponatremia. Administration of hydrocortisone normalized the level of serum Na. A pituitary hormone-stimulating test and brain computed tomography revealed panhypopituitarism with an empty sella. Glucocorticoid deficiency due to secondary hypoaldosteronism was thought to have caused the Na loss. She had been treated for thyroid dysfunction and hyperlipidemia with replacement of thyroid hormone and a lipid-lowering drug. Hyperlipidemia changed from type V into IIa in 4 yr. Furthermore, one of her brothers and one of her sons were suspected to have type IV hyperlipidemia. Familial combined hyperlipidemia accompanied by secondary hypothyroidism was thought to have increased the levels of both total cholesterol and triglyceride. Two renal biopsies in 3 yr showed lipid deposits in the mesangial cells and indicated a positive correlation between the levels of serum lipids and lipid deposits in glomeruli, which suggested an important role of abnormal lipid metabolism in the progression of glomerular lipidosis.

Empty Sella Syndrome↗

PubMed1992

Origin of sequence specific cleavage of DNA by bleomycins.

A new DNA photocleaving agent which contains bleomycin A2's DNA binding portion and its mono- and terthiazole analogues have been designed and synthesized, and their DNA binding mode and cleavage base specificity have been studied. The photoactive p-nitrobenzoyl group attached at the end of molecules cleaves DNA on UV irradiation. All the oligo-thiazole compounds exhibited high sequence specificity in DNA scission. The bithiazole derivative did not cleave DNA at or near 5'-GpT-3' or 5'-GpC-3' as expected from widely believed DNA binding mechanism of the antibiotics.

Bleomycin↗

PubMed1992

[The analysis of nuclear organizer regions of astrocytomas with various histologic malignancies].

Nucleolar organizer regions (NORs) correspond to the loops of DNA which encode the ribosomal RNA. Acid proteins related to NORs can be stained by the silver colloidal technique (AgNORs). Since the configurations of AgNORs may be related to the protein metabolism or the proliferative activity of the cell, we tried to evaluate the corelationship between the morphology of AgNOR and the histologic malignancy in astrocytic tumors. For the quantitative evaluation the histographic pattern of AgNORs was analysed. Twenty-seven surgical specimens of astrocytomas (astrocytoma; 7 Cases, anaplastic astrocytoma; 9 cases, glioblastoma; 11 cases) were examined. The average of the means of AgNOR count in astrocytoma, anaplastic astrocytoma, glioblastoma were 1.68, 1.85 and 2.76 respectively. The averages of standard deviations (S. D.) of AgNOR count were 0.87, 1.03 and 1.26, respectively. In those tumors, the AgNOR histograms were flattered and the means and S. D. increased significantly as the malignancy increased. We speculate that the increased number and variations of AgNOR count could be a reflection of phenotypic alterations of astrocytoma cells such as cellular anaplasia and pleomorphism.

Astrocytoma↗

PubMed1991

Photocleavage of DNA by the p-nitrobenzoyl group covalently linked to proflavine.

We have synthesized two novel DNA photocleaving agents,3,6-diamino-10-[6-(4-nitrobenzoyloxy)hexyl]acridinium chloride and 3,6-diamino-10-[6-(4-nitrobenzamido)-hexyl]acridinium chloride, and studied their DNA binding mode and cleavage properties. These compounds contain the photoactive p-nitrobenzoyl group attached to proflavine via an amide or ester linker group and a polymethylene chain. Spectroscopic and viscometric studies have shown that the compounds bind DNA by an intercalative mode. The presence of covalently-bonded intercalator is essential for the UV (310 nm) induced DNA scission. Above a critical ratio, an increase in the relative concentration of compound to DNA did not induce further cleavage. The cleavage efficiency was dependent on the type of linker group. These results are discussed in regard to possible mechanisms for photoinduced DNA breakage.

DNA↗

PubMed1991

Structure of 4-(3-chlorophenyl)thiosemicarbazide.

C7H8ClN3S, Mr = 201.67, monoclinic, P21/c, a = 6.914 (5), b = 4.304 (4), c = 30.306 (3) A, beta = 94.66 (3) degrees, V = 899.0 (1) A3, Z = 4, Dm = 1.54, Dx = 1.490 Mg m-3, lambda (Cu K alpha) = 1.5418 A, mu = 5.54 mm-1, F(000) = 416, T = 298 K, final R = 0.048 for 1219 observed reflections. The S and terminal hydrazinic N atoms are in a trans conformation. As a result of the sigma-electron-withdrawing effect of the Cl atom at the meta position in the phenyl ring with respect to the thiosemicarbazide chain, the net negative charge on the terminal N atom decreases compared to the p-chloro and p-methoxy derivatives. The antibacterial activity of the compound is also lowered.

Chemical Phenomena↗

PubMed1991

Location of a DBS-electrode in lateral thalamus for deafferentation pain. An autopsy case report.

Pain relief was obtainable when deep brain stimulation was tried in the sensory thalamic nucleus in a patient with deaffereantation pain to cervical myelopathy. The electrode was histologically verified in post-mortem examination after 20 months and the localization of contact points of the implanted electrode was estimated. The cathode appeared to have been placed in the region from Vim to the rostral border of Vci while the anode was in the medical lemniscus region. Stimulation of the Vim nucleus might have had a pain relieving effects because no facial paraesthesiae was evoked by stimulation. The implanted electrode caused only minor histological changes.

Afferent Pathways↗

PubMed1991

Influence of dopamine on cerebral blood flow, and metabolism for oxygen and glucose under barbiturate administration in cats.

The effect of dopamine during barbiturate therapy was investigated in 29 cats including 5 sham-operated cats. According to Kiersey's classification of electro-encephalographic patterns, physiological variables, cerebral metabolic rates for oxygen and glucose, cerebral blood flow (CBF), and intracranial pressure (ICP), etc. were evaluated in each electro-encephalographic pattern. Oxygen-glucose index was calculated and used as an indicator for aerobic or anaerobic metabolism of glucose. Group 1 (12 cats), to which only thiamylal was administered, maintained aerobic glycolysis due to a parallel reduction of cerebral metabolic rates for oxygen and glucose (about half of the initial value at Kiersey's fifth pattern) in spite of reduction of CBF and mean arterial blood pressure (MABP). Group 2 (12 cats), to which dopamine was administered in addition to thiamylal due to a reduction of MABP, showed anaerobic glycolysis though MABP and CBF were maintained. These findings are ascribed to an increase of cerebral metabolic rate for glucose up to 130% of the initial value though cerebral metabolic rate for oxygen decreased down to half of the initial value: The beneficial effect of barbiturate on cerebral metabolism was reduced by use of dopamine. ICP was reduced in both groups. Our result indicates that administration of extracellular fluid may be preferable for treatment of hypotension during barbiturate therapy than dopamine medication.

Animals↗

PubMed1991

Cholinergic deafferentation after focal cerebral infarct in rats.

BACKGROUND AND PURPOSE: For a better understanding of neuronal network disturbances after stroke, we investigated the changes in the cholinergic system after experimental focal infarct. METHODS: We quantitatively evaluated the highly sensitive acetylcholinesterase histochemistry and local glucose utilization 7 days after left middle cerebral artery occlusion in Wistar rats. RESULTS: In all rats with occlusion, the ipsilateral frontal cortex and the nucleus basalis Meynert developed no infarct, whereas the subcortical striatum did. In the frontal cortex on the occlusion side, the acetylcholinesterase-positive fiber density was significantly (p less than 0.05) reduced; a computer-assisted image-analyzing system quantified approximately 1.0 m/mm3 brain cortex acetylcholinesterase-positive fibers in the ipsilateral frontal cortex layers II-IV and approximately 9.7 m/mm3 brain cortex acetylcholinesterase-positive fibers in the contralateral frontal cortex layers II-IV. Local glucose utilization was also significantly (p less than 0.05) decreased in the ipsilateral frontal cortex compared to the contralateral side and sham-operated animals. CONCLUSIONS: These results suggest that functional disturbances and disruption of the cholinergic pathway between the frontal cortex and the nucleus basalis Meynert occur after middle cerebral artery occlusion in rats.

Acetylcholinesterase↗

PubMed1990

DNA binding and intercalation by novel porphyrins: role of charge and substituents probed by DNase I footprinting and topoisomerase I unwinding.

Porphyrins carrying four charged sidechains, e.g., meso-tetrakis[4-N-methylpyridiniumyl]- and meso-tetrakis[4-N-(2-hydroxyethyl)pyridiniumyl]-porphyrin, bound and intercalated similarly into DNA as measured by helix stabilization and DNA unwinding studies in the presence of DNA topoisomerase I. Despite their different bulky sidechains, these complexes gave essentially identical DNase I footprinting patterns. In contrast, tetrasubstituted porphyrins carrying three phenyl rings and a single positively charged pyridiniumyl sidechain did not intercalate and exhibited little affinity for DNA. Thus, the presence of charged sidechains on the porphyrin rather than their identity appears to be critical for efficient DNA intercalation. The results are discussed in regard to current models for the porphyrin-DNA intercalation complex.

Base Sequence↗

PubMed1990

Conformational effects of nucleotide exchange in ras p21 proteins as studied by fluorescence spectroscopy.

The intrinsic fluorescence properties of the oncogene protein p21N-ras,p21H-ras and one of its transforming mutants, p21N-ras (Val12), have been investigated. A mutant containing a single tryptophan at position 28 in p21H-ras (Trp28) has been specifically engineered to provide a probe of protein conformation on nucleotide binding. The proteins produced essentially similar circular dichroism spectra typical of alpha/beta proteins. A decrease in the intensity of the fluorescence emission spectrum due to tyrosine occurred on GDP/GTP nucleotide exchange in the native and mutant proteins. Selective excitation of the single tryptophan in p21 produced a decrease in fluorescence intensity which was accompanied by a blue shift in the wavelength of maximum emission on nucleotide exchange. A reduction in the residual Mg2+ ion concentration enhanced this effect.

Circular Dichroism↗

PubMed1990

Clinical experience of intraorbital optic nerve sheath meningioma--report of eight cases.

Eight cases of primary optic nerve sheath meningioma were treated between 1980 and 1988. Five were females aged 37-61 years. The other three were two boys, one with neurofibromatosis, and an old male aged 71 years. They were first seen by the ophthalmologist with complaints of unilateral progressive visual loss or proptosis. Although blindness of the affected eye mainly occurred between 1 month and 3 years after the initial symptoms, the diagnosis tended to be made late in the adult cases. Intracranial extension was demonstrated in four of the six adult cases when contralateral visual loss or disturbance of consciousness presented. Larger intraorbital meningiomas were easily diagnosed by a combination of computed tomographic (CT) scanning, magnetic resonance (MR) imaging, and carotid angiography. MR imaging provided clear delineation of the optic nerve and its course through the tumor, and perioptic meningioma could be diagnosed. However, it was difficult to make a diagnosis without biopsy at the early stage, for example, when just the enlargement of the optic nerve was demonstrated by CT or MR imaging. Tumor removal was performed when blindness developed after definitive diagnosis by biopsy, intracranial extension was demonstrated, and advanced proptosis presented. The transcranial supraorbital approach or transcranial transorbital approach with resection of the supraorbital rim was used for these large intraorbital meningiomas. From our clinical experience, early diagnosis and early treatment should be emphasized.

Adult↗

PubMed1989

Structures of three DNA cross-linking agents, ethane-1,2-di(methylsulfonate), propane-1,3-di(methylsulfonate) and n-butane-1,4-di(methylsulfonate).

(I): C4H10O6S2, Mr = 218.25, P2(1)/c, a = 7.2611 (9), b = 5.8726 (4), c = 10.6628 (19) A, beta = 103.95 (1) degree, V = 441.3 (2) A3, Z = 2, Dm = 1.65, Dx = 1.642 Mg m-3, lambda(Cu K alpha) = 1.54184 A, mu = 5.43 mm-1, F(000) = 228, R = 0.0336 and wR = 0.0346 for 745 unique reflections with F greater than or equal to 3 sigma (F), T = 298 K. (II): C5H12O6S2, Mr = 232.28, P2(1)/c, a = 11.030 (1), b = 8.452 (1), c = 11.162 (1) A, beta = 104.65 (1) degree, V = 1006.8 (3) A3, Z = 4, Dm 1.54, Dx = 1.532 Mg m-3, lambda(Cu K alpha) = 1.54184 A, mu = 4.79 mm-1, F(000) = 488, R = 0.0418 and wR = 0.0430 for 1666 unique reflections with F greater than or equal to 3 sigma(F), T = 298 K. (III): C6H14O6S2, Mr = 246.30, P1, a = 5.6147 (9), b = 6.8343 (6), c = 7.5434 (6) A, alpha = 110.61 (1), beta = 92.08 (1), gamma = 76.15 (1) degree, V = 262.7 (3) A3, Z = 1, Dm = 1.56, Dx = 1.557 Mg m-3, lambda(Cu K alpha) = 1.54184 A, mu = 4.79 mm-1, F(000) = 130, R = 0.0397 and wR = 0.0425 for 907 unique reflections with F greater than or equal to 3 sigma(F), T = 298 K. All three compounds have a common conformation in the C.O.SO2.CH3 part of the molecules due to weak O...H interactions. Compounds (I) and (III) have a trans conformation about the central C--C bond, whereas (II) is cis.

Busulfan↗

PubMed1989

Isolation and characterization of the diastereoisomers of a series of phosphate-ethylated dinucleoside monophosphates.

Internucleotide phosphate esterification is a common reaction of many potent carcinogenic alkylating agents. It can give rise to two stereochemically distinct molecules about a triesterified phosphorus atom. The eight individual diastereoisomers derived from phosphate ethylation of d-ApT, d-CpT, d-GpT, and d-TpT were prepared from o-chlorophenyl phosphotriester intermediates and isolated by reverse-phase HPLC. Each pair of isomers, together with its parent analog, was examined by variable temperature circular dichroism. The results are interpreted in terms of secondary structure changes from which the absolute configurations of the ethylated phosphate groups can be inferred. These configurational assignments were confirmed by 31P NMR.

Chromatography, High Pressure Liquid↗

PubMed1989

Cloning and characterization of a DNA gyrase A gene from Escherichia coli that confers clinical resistance to 4-quinolones.

Nalidixic acid, enoxacin, and other antibacterial 4-quinolones inhibit DNA gyrase activity by interrupting DNA breakage and reunion by A subunits of the A2B2 gyrase complex. Despite their clinical importance, the mode of quinolone action and mechanisms of resistance are poorly understood at the molecular level. Using a DNA fragment enrichment procedure, we isolated the gyrA gene from a uropathogenic Escherichia coli strain that encodes a gyrase A protein cross-resistant to a variety of quinolones. When complemented with gyrase B subunit, the purified A protein reconstituted DNA supercoiling activity approximately 100-fold more resistant to inhibition by enoxacin than the susceptible enzyme and failed to mediate quinolone-dependent DNA cleavage. Nucleotide sequence analysis revealed that the gene differed at 58 nucleotide positions compared with the K-12 gyrA sequence. The 875-amino-acid residue-resistant gyrase A protein differed at three positions from its wild-type E. coli K-12 counterpart: tryptophan, glutamate, and serine replaced serine, aspartate, and alanine residues at positions 83, 678, and 828, respectively. By genetic analysis of chimeric gyrA genes in a gyrA(Ts) background, we showed that the Ser-83----Trp mutation in the gyrase A protein was solely responsible for high-level bacterial resistance to nalidixic acid and fluoroquinolones.

4-Quinolones↗

PubMed1989

Neuronal network disturbance after focal ischemia in rats.

We studied functional disturbances following left middle cerebral artery occlusion in rats. Neuronal function was evaluated by [14C]2-deoxyglucose autoradiography 1 day after occlusion. We analyzed the mechanisms of change in glucose utilization outside the infarct using Fink-Heimer silver impregnation, axonal transport of wheat germ agglutinin-conjugated-horseradish peroxidase, and succinate dehydrogenase histochemistry. One day after occlusion, glucose utilization was remarkably reduced in the areas surrounding the infarct. There were many silver grains indicating degeneration of the synaptic terminals in the cortical areas surrounding the infarct and the ipsilateral cingulate cortex. Moreover, in the left thalamus where the left middle cerebral artery supplied no blood, glucose utilization significantly decreased compared with sham-operated rats. In the left thalamus, massive silver staining of degenerated synaptic terminals and decreases in succinate dehydrogenase activity were observed 4 and 5 days after occlusion. The absence of succinate dehydrogenase staining may reflect early changes in retrograde degeneration of thalamic neurons after ischemic injury of the thalamocortical pathway. Terminal degeneration even affected areas remote from the infarct: there were silver grains in the contralateral hemisphere transcallosally connected to the infarct and in the ipsilateral substantia nigra. Axonal transport study showed disruption of the corticospinal tract by subcortical ischemia; the transcallosal pathways in the cortex surrounding the infarct were preserved. The relation between neural function and the neuronal network in the area surrounding the focal cerebral infarct is discussed with regard to ischemic penumbra and diaschisis.

Animals↗

PubMed1989

Regional cerebral blood flow in the persistent vegetative state.

Regional cerebral blood flow (CBF) in eight patients in a persistent vegetative state was measured and compared with that in five healthy volunteers. The patients were classified into three groups: Group 1 (locked-in syndrome) consisted of a single patient, Group 2 (typical vegetative state) of five patients, and Group 3 (prolonged coma) of two patients. CBF was measured early after onset by single photon emission computed tomography with 123I-N-isopropyl-p-iodo-amphetamine and/or 99mTc-hexamethyl-propyleneamine oxime. The regions of interest (ROIs) were the bilateral frontal, temporal, parietal, occipital, and cerebellar areas and basal ganglia. The values obtained in these areas were averaged, and the ratio for each ROI [(the value in the ROI/the mean value) x 100] was calculated. "Hyperfrontal distribution" of CBF was found to be rare in both the normal condition and the vegetative state. Higher CBF values were noted in the left than in the right frontal area in four of the five volunteers but in only four of the eight patients. CBF distribution in the frontal lobe was characteristic for each group: Group 1 showed high CBF bilaterally, although the elevation was statistically significant only on the right side, and Group 3 exhibited significantly low values. In Group 2, CBF was variable but, for the most part, within normal limits. Awareness was closely correlated with frontal lobe function and alteration of CBF in the frontal region.

Adult↗