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Biomedical subjects

M Ohno

Publications and source records attributed to M Ohno.

At least 505 records · Page 28Linked to original sources
PubMed1987

High-performance liquid chromatography of N-terminal tyrosine-containing oligopeptides by pre-column fluorescence derivatization with hydroxylamine, cobalt (II) and borate reagents.

A pre-column fluorescence derivatization method is described for the high-performance liquid chromatographic determination of N-terminal tyrosine-containing oligopeptides involving methionine-enkephalin and leucine-enkephalin. The peptides are converted into fluorescent derivatives by heating in a weakly alkaline medium (pH 8.5) containing hydroxylamine, cobalt(II) ion and borate. The derivatives are separated on a reversed-phase column (TSKgel ODS-120T) by gradient elution of acetonitrile in a mobile phase containing borate buffer (pH 8.5) and tetra-n-butylammonium chloride, and then determined by fluorimetry. The derivatization provides a single fluorescent product for each N-terminal tyrosine-containing oligopeptide, but does not allow the production of fluorescent derivatives for peptides having no tyrosyl residue at the N-terminal. The method is selective and sensitive; the lower limits of detection for the N-terminal tyrosine-containing oligopeptides tested were 140-310 fmol per 100 microliters injected.

Boric Acids↗
PubMed1987

On-line post-column fluorescence detection for N-terminal tyrosine-containing peptides in high-performance liquid chromatography.

A detection system based on on-line post-column fluorescence derivatization is described for the determination of N-terminal tyrosine-containing peptides by reversed-phase high-performance liquid chromatography. The peptides are automatically converted into fluorescent derivatives by reaction with hydroxylamine, cobalt (II) and borate after peptide separation on a reversed-phase column (TSKgel ODS-120T) followed by passage through an ultraviolet absorbance detector. The reaction system permits the fluorescence detection at 435 nm (emission) with excitation at 335 nm for N-terminal tyrosine-containing synthetic peptides in as little as picomole amounts. The facile fluorescence detection of N-terminal tyrosine-containing fragments produced from methionine-enkephalin by enzymatic degradation using a rat brain homogenate was achieved by comparison with the ultraviolet absorption detection at 215 nm.

Animals↗
PubMed1987

High production of type VI collagen in multiple fibromatosis with multiple articular dysplasia.

A patient with multiple fibromatosis occurring at the sites of multiple cartilagenous dysplasia was described. Collagen types solubilized with pepsin from the fibromatous tissue were fractionated by a different salt concentration and analyzed by SDS-polyacrylamide gel electrophoresis, which indicated that the tissue produces predominantly "short-chain" collagen. Western blotting of the subunits indicated a cross reaction with antisera of the type VI collagen. The results of rotatory shadowing electron microscopy confirmed the characteristic short-chain structure.

Amino Acids↗
PubMed1987

Clonidine attenuates wet-dog shaking induced by hippocampal stimulation in rats.

The effect of an alpha 2-adrenoceptor agonist, clonidine on wet-dog shaking (WDS; also, WDS = wet-dog shakes) induced by electrical stimulation of the hippocampus was investigated. Clonidine (0.01-0.32 mg/kg i.p.) inhibited the appearance of WDS in a dose-dependent manner without showing any effect on hippocampal afterdischarge. Although clonidine has been reported to inhibit the activity not only of noradrenergic but also of serotonergic neurons, a 5-hydroxytryptamine (5-HT) antagonist, cinanserin at doses up to 32 mg/kg had no significant effect on hippocampal stimulation-induced WDS. Therefore, a possible anti-5-HT action of clonidine in the inhibition of WDS can be excluded. The WDS inhibition produced by clonidine was blocked significantly by pretreatment of the rats with an alpha 2-adrenoceptor antagonist, yohimbine, but not with a narcotic antagonist, naloxone. The present results suggest that a central noradrenergic function may be involved in WDS induced by hippocampal stimulation.

Animals↗
PubMed1987

On-line post-column fluorescence derivatization of arginine-containing peptides in high-performance liquid chromatography.

A selective detection system based on on-line post-column fluorescence derivatization is described for the analysis of arginine-containing peptides by high-performance liquid chromatography. The peptides are automatically converted into fluorescent derivatives with benzoin, a fluorogenic reagent for guanidino compounds, after separation on a reversed-phase column (TSKgel ODS-120T) and detection in an ultraviolet absorption detector. The system permits fluorescence detection at 435 nm emission with irradiation at 325 nm for arginine-containing peptides in as little as picomole amounts. The chromatogram obtained with fluorescence detection only shows peaks corresponding to arginine-containing peptides. The facile detection of arginine-containing fragments in the tryptic digest of beta-melanocyte stimulating hormone as a model compound could be achieved by comparison with a chromatogram obtained with ultraviolet absorption detection at 215 nm.

Arginine↗
PubMed1987

The effect of kappa-opioid agonist U-50, 488H on wet-dog shaking behavior induced by hippocampal stimulation in rats.

The effect of a selective kappa-opioid agonist, U-50, 488H, on wet-dog shaking (WDS) induced by hippocampal stimulation was investigated and compared with that produced by morphine. U-50, 488H, as well as morphine, inhibited the appearance of WDS in a dose-dependent manner. U-50, 488H was approximately three times more potent than morphine in this effect. Neither drug showed any effect on hippocampal afterdischarge. The inhibition of WDS produced by U-50, 488H was blocked significantly by a kappa-opioid antagonist, MR-2266, but not by naloxone. On the other hand, the inhibitory effect of morphine was completely antagonized by both MR-2266 and naloxone. The present results strongly suggest that not only mu-but also kappa-opioid receptors are involved in the appearance of WDS induced by hippocampal stimulation.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1987

Response properties and visual receptive fields of climbing and mossy fibers terminating in the flocculus of the monkey.

Response properties and visual receptive fields of climbing fibers and mossy fibers terminating in the cerebellar flocculus were studied in monkeys trained to fixate a stationary visual target. Among a total of 429 climbing fiber-related units (climbing fibers and complex spikes of Purkinje cells), 20 (4.9%) showed cyclic modulations in firing in response to sinusoidal retinal-slip velocities. Their receptive fields always included the fovea. Among 485 mossy fibers, 64 (13%) responded to the visual stimulation. Of the 64 visually responsive mossy fiber units, 39 (61%) responded exclusively to the retinal-slip velocity (visual mossy fibers and the remaining 25 mossy fibers (39%) responded also to the eye and head velocities (visuomotor mossy fibers). Receptive fields for 17 visual mossy fibers (17/39 or 44%) were within 10 degrees of fixation and those for 22 others (56%) were in the periphery. Receptive fields for all 25 visuomotor mossy fibers were in the periphery. Each mossy fiber unit had a unique velocity-tuning curve and, therefore, the response patterns of individual mossy fibers were different depending on the range of their velocity sensitivity and on the retinal-slip velocity applied.

Action Potentials↗
PubMed1987

Influences of electrical lesions of the dopaminergic system on morphine- and U-50,488H-induced analgesia in rats.

The effects of electrical lesions of brain areas containing dopamine cell bodies and terminals on morphine analgesia were investigated and compared with those of a selective kappa-opioid agonist, U-50,488H. The analgesic effect of morphine 10 mg/kg IP was potentiated significantly in substantia nigra (SN)- or caudate-putamen-lesioned rats, but not by ventral tegmental area (VTA) or nucleus accumbens lesions. However, electrical lesions of neither SN nor VTA affected the analgesic activity of U-50,488H 32 mg/kg IP. Although the tolerance to morphine analgesia developed in all four of the lesioned groups as well as in sham-lesioned rats, a significant analgesic effect in the SN-lesioned group prevailed during chronic treatment for 14 days as compared with that of sham-lesioned rats. From these results, it is suggested that morphine analgesia is potentiated by dysfunction of the nigro-striatal dopaminergic system, but not by that of the mesolimbic dopaminergic system, the central dopaminergic system is not involved in the appearance of U-50,488H analgesia and is not basically related to the development of tolerance to morphine analgesia.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1987

Preferential excision of the 5' proximal intron from mRNA precursors with two introns as mediated by the cap structure.

We have studied the effect of the 5' cap structure on the splicing of precursor mRNAs containing three exons and two introns within a single molecule in a HeLa nuclear extract. When a precursor mRNA was capped, the upstream intron was spliced out more efficiently than the downstream intron. The differential splicing reactions of the two introns are not due to differences in the intrinsic efficiency of splicing of each intron, since the preferential excision of the upstream intron was also observed when the positions of the two introns relative to the cap structure were reversed. When uncapped precursor mRNA was used as substrate, the downstream intron was spliced out appreciably, but splicing of the upstream intron was greatly reduced. Preincubation of the extract with cap analogues inhibited splicing of the upstream intron but not the downstream intron. Thus, the cap structure exerts its effect primarily on the 5' proximal intron.

HeLa Cells↗