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Biomedical subjects

M Kotera

Publications and source records attributed to M Kotera.

14 recordsLinked to original sources
PubMed2001

Translesional synthesis on DNA templates containing the 2'-deoxyribonolactone lesion.

A site-specifically modified oligonucleotide containing a single 2'-deoxyribonolactone lesion was used as a template for primer extension reactions catalyzed by M-MuLV reverse transcriptase (RT) and by the Klenow fragments of Escherichia coli DNA polymerase proficient (KF exo(+)) or deficient (KF exo(-)) in exonuclease activity. Analysis of the extension products in the presence of the four dNTPs or of a single dNTP showed that the M-MuLV RT was completely blocked and did not incorporate any dNMP opposite 2'-deoxyribonolactone. KF exo(-) preferentially incorporated nucleotides opposite the lesion following the frequency order dAMP > dGMP >> dTMP approximately dCMP and thus appeared to obey the 'A rule' for preferential incorporation as has been shown previously for the 2'-deoxyribose abasic site. In the sequence context examined, the primer extension by KF exo(-) appeared to be less efficient when dAMP was positioned opposite the lesion as compared with dTMP or dGMP. These two nucleotides promoted a more efficient polymerization accompanied by nucleotide deletion through misalignment incorporations. We therefore predict that the sequence context may strongly influence the translesional synthesis by KF exo(-) and thus the miscoding and mutational potential of the 2'-deoxyribonolactone in E.coli.

Base Sequence↗
PubMed2000

The 7-nitroindole nucleoside as a photochemical precursor of 2'-deoxyribonolactone: access to DNA fragments containing this oxidative abasic lesion.

On the basis of molecular modeling studies, the 7-nitroindole nucleoside 1 was selected as a suitable photochemical precursor for photochemical generation of the C1' deoxyribosyl radical under irradiation, which led to 2'-deoxyribonolactone. The nitro-indole nucleoside derivatives 1a and 1b were prepared and their conformation was determined by X-ray crystallography and NMR spectroscopy. The photoreaction of these nucleosides gave the corresponding deoxyribonolactone derivatives efficiently, with release of 7-nitrosoindole. This reaction was successfully applied to synthesis of oligonucleotides containing the deoxyribonolactone lesion.

Journal Article↗
PubMed1999

2'-deoxyribonolactone lesion in DNA: refined solution structure determined by nuclear magnetic resonance and molecular modeling.

The solution conformation of the DNA duplex d(C1G2C3A4C5L6C7A8C9G10C11).d(G12C13G14T15G16T17G18T19G20C21G22 ) containing the 2'-deoxyribonolactone lesion (L6) in the middle of the sequence has been investigated by NMR spectroscopy and restrained molecular dynamics calculations. Interproton distances have been obtained by complete relaxation matrix analysis of the NOESY cross-peak intensities. These distances, along with torsion angles for sugar rings and additional data derived from canonical A- and B-DNA, have been used for structure refinement by restrained molecular dynamics (rMD). Six rMD simulations have been carried out starting from both regular A- and B-DNA forms. The pairwise rms deviations calculated for each refined structure are <1 A, indicating convergence to essentially the same geometry. The accuracy of the rMD structures has been assessed by complete relaxation matrix back-calculation. The average sixth-root residual index (Rx = 0.052 +/- 0.003) indicated that a good fit between experimental and calculated NOESY spectra has been achieved. Detailed analysis revealed a right-handed DNA conformation for the duplex in which both the T17 nucleotide opposite the abasic site and the lactone ring are located inside the helix. No kinking is observed for this molecule, even at the abasic site step. This structure is compared to that of the oligonucleotide with the identical sequence containing the stable tetrahydrofuran abasic site analogue that we reported previously [Coppel, Y., Berthet, N., Coulombeau, C., Coulombeau, Ce., Garcia, J., and Lhomme, J. (1997) Biochemistry 36, 4817-4830].

Base Sequence↗
PubMed1994

Improvement of left unilateral spatial neglect in a line extension task.

Patients with left unilateral spatial neglect following lesions that mainly involved the right parietal lobe performed a line extension task, extending a horizontal line leftward to double its original length. We examined line extension performances in the left and right hemispaces, as well as in the midline, to assess whether spatial conditions affected these performances. Whatever the severity of neglect found in the line bisection test, the line extension performances of the patients were almost accurate and comparable with those of normal controls across the three spatial conditions. The neglect patients executed movements in or toward the contralesional space as the task oriented their attention sufficiently to the left. The results suggest that the motor component, ie, directional hypokinesia, has little part in left unilateral spatial neglect due to right parietal lesions.

Adult↗
PubMed1994

[Visual memory in a case of topographical disorientation].

A 67-year-old, right-handed man was admitted to our hospital because of restricted field of vision. Neurological examination revealed left upper quadrantanopsia on confrontation. Axial and coronal T2 weighted MR images showed an increased signal intensity lesion that involved the right fusiform and lingual gyri. A small lesion was also noted in the white matter of the left cuneate gyrus. He was unable to describe the ground plan of his house or the well-known route he lived. No signs of unilateral spatial neglect, prosopangnosia, apraxia, and aphasia were found in specific tests. Wechsler Adult Intelligence Scale showed verbal IQ 126 and performance IQ 92. However, he scored poorly in the Benton Visual Retention Test (5 correct immediate recalls from 10 items). Recall from memory of Rey-Osterrieth's complex figure was severely impaired. Visual recall subtest of the Wechsler Memory Scale-Revised (WMS-R) scored 30 points when performed immediately, but zero after a 30 minutes delay. Visual paired associates learning from the WMS-R was also severely impaired. These findings suggest that visual memory is one of the important factors in the pathogenesis of topographical disorientation of this patient.

Aged↗
PubMed1992

[An autopsied case of Parkinson's disease manifesting Shy-Drager syndrome].

We report an autopsied case of Parkinson's disease manifesting Shy-Drager syndrome. At the age of 63 years, the patient noticed an onset of progressive orthostatic dizziness, which was followed by constipation, dysuria, and sexual impotence. When he was 66 years old, syncopal attack for a few minutes, tremor in the bilateral hands, and memory disturbance developed. On admission, his blood pressure was 142/72 mmHg in supine position, which fell to 58/42 mmHg on standing with appropriate increase of heart rate. Neurological examination revealed hallucination, memory disturbance, masked face, muscular rigidity, bradykinesia, mild postural tremor, and autonomic dysfunction including severe orthostatic hypotension, hypohydrosis, constipation, dysuria, and sexual impotence. Electroencephalogram showed diffuse slowing. Brain CT demonstrated absence of severe atrophy of the cerebellum, and brain stem. Pharmacological study revealed denervation hypersensitivity to the intravenously administrated noradrenaline. A diagnosis of Shy-Drager syndrome was made, and he was treated with anti parkinsonian drugs. However, no improvement was observed in his clinical symptoms. Seven months later, he died of pneumonia. Neuropathological examination revealed marked neuronal cell loss and gliosis in the substantia nigra and locus ceruleus. Lewy bodies were seen in those pigmented nuclei, dorsal vagal nucleus, hypothalamus and nucleus basalis of Meynert. No abnormality was found in the intermediolateral nucleus of the spinal cord. This is the first report on a Japanese patient who presented clinically Shy-Drager syndrome and pathologically typical Parkinson's disease. In this patient, from the pharmacological and pathological findings, sympathetic ganglia were supposed to be the responsible lesion for orthostatic hypotension.

Aged↗
PubMedDate not supplied

Labeling during cleavage of nucleic acids for their detection on DNA chips.

A new and efficient strategy for labeling of nucleic acids prior to their hybridization on high density DNA chip has been developed. Our approach which combines the fragmentation and the labeling is based on the reactivity of the terminal phosphates of cleaved DNA and RNA fragments with a reporter molecule bearing aryldiazomethane group.

DNA↗
PubMedDate not supplied

Universal labeling chemistry for nucleic acid detection on DNA-arrays.

We show here a new and efficient aqueous chemistry for labeling of any class of nucleic acids for their detection on DNA chip. The labels contain a diazo function as reactive moiety and biotin as detectable unit. The highly selective reaction of diazo group on the phosphate does not disrupt base pairing recognition and hybridization specificity.

Azo Compounds↗