Biomedical subjects

Shinichi Tatsumi

Publications and source records attributed to Shinichi Tatsumi.

5 recordsLinked to original sources

PubMed2005

Rho-kinase mediates spinal nitric oxide formation by prostaglandin E2 via EP3 subtype.

Prostaglandin E2 (PGE2), the principal pro-inflammatory prostanoid, is known to play versatile roles in pain transmission via four PGE receptor subtypes, EP1-EP4. We recently demonstrated that continuous production of nitric oxide (NO) by neuronal NO synthase (nNOS) following phosphorylation of myristoylated alanine-rich C-kinase substrate (MARCKS) and NMDA receptor NR2B subunits is essential for neuropathic pain. These phosphorylation and nNOS activity visualized by NADPH-diaphorase histochemistry were blocked by indomethacin, a PG synthesis inhibitor. To clarify the interaction between cyclooxygenase and nNOS pathways in the spinal cord, we examined the effect of EP subtype-selective agonists on NO production. NO formation was stimulated in the spinal superficial layer by EP1, EP3, and EP4 agonists. While the EP1- and the EP4-stimulated NO formation was markedly blocked by MK-801, an NMDA receptor antagonist, the EP3-stimulated one was completely inhibited by H-1152, a Rho-kinase inhibitor. Phosphorylation of MARCKS and NADPH-diaphorase activity stimulated by the EP3 agonist were also blocked by H-1152. These results suggest that PGE2 stimulates NO formation by Rho-kinase via EP3, a mechanism(s) different from EP1 and EP4.

Animals↗

PubMed2004

Analgesic effect of extracts of Chinese medicinal herbs Moutan cortex and Coicis semen on neuropathic pain in mice.

Neuropathic pain arising from peripheral nerve injury is a clinical disorder characterized by a combination of spontaneous pain, hyperalgesia and tactile pain (allodynia), and remains a significant clinical problem since it is often poorly relieved by conventional analgesics. To seek an analgesic compound(s) in Chinese herbs, we examined the effect of seven Chinese herbs that are routinely prescribed for pain management in two neuropathic pain models: allodynia induced by intrathecal administration of prostaglandin F2alpha (PGF2alpha) and by selective L5 spinal nerve transection. The extracts of Moutan cortex and Coicis semen dose-dependently alleviated the PGF2alpha-induced allodynia by oral administration 1 h before intrathecal injection of PGF2alpha. When orally administrated every day for 7 days, these extracts attenuated neuropathic pain in the ipsilateral side, but not in the contralateral side, day 7 after L5 spinal nerve transection. The increase in NADPH diaphorase activity in the spinal cord associated with neuropathic pain was also blocked by these extracts. These results suggest that Moutan cortex and Coicis semen contain substances effective in neuropathic pain.

Anesthesia↗

PubMed2004

Characterization of N-methyl-D-aspartate receptor subunits responsible for postoperative pain.

N-methyl-D-aspartate (NMDA) receptors have been suggested to be critical for the development of central sensitization, which may amplify postoperative pain. NMDA receptors are formed by GluRzeta (NR1) with any one of four GluRvarepsilon1-4 (NR2A-D) subunits. To clarify the involvement of NMDA receptors in postoperative pain, we examined the effect of the GluRepsilon2-selective antagonist (1S,2S)-1-(4-hydroxyphenyl)-2-(4-hydroxy-4-phenyl piperidino)-1-propanol (CP-101,606) on postoperative pain caused by plantar incision. We also applied the postoperative pain model to GluRepsilon1 and GluRepsilon4 knockout mice. CP-101,606 administered intrathecally 30 min prior to incision significantly increased mechanical withdrawal thresholds 2 h and 1-3 days after surgery and reduced postoperative pain dose-dependently. Neither GluRvarepsilon1 nor GluRepsilon4 knockout mice showed a difference in withdrawal thresholds as compared with wild-type mice. Pretreatment with CP-101,606 did not produce an additive analgesic effect in the mice. These results demonstrate that GluRepsilon2-containing NMDA receptors are involved in postoperative pain and that CP-101,606 may be effective in reducing it.

Animals↗

PubMed2004

Sample enrichment by using monolithic precolumns in microcolumn liquid chromatography.

An on-line sample enrichment system was designed using monolithic precolumns in microcolumn LC. The monolithic ODS capillary columns were prepared via in situ sol-gel processes. The enrichment efficiency of the monolithic columns was tested by using phthalates as the analytes. The relative standard deviations (n = 6) for the retention time, peak area and peak height were between 0.4 and 1.2%, 0.9 and 5.5% and 0.4 and 3.9%, respectively. The system was linear (R2 > 0.99) within the working sample concentration and sample volume ranges. Comparing to 0.2 microl injection with a typical sample injector, the theoretical plate number of a same separation column was increased by 3-6-fold when the precolumn unit was used for sample injection. The recoveries of the analytes were between 88 and 120%, and the sample volume that could be injected into the system was increased up to 5000-fold. The limits of detection were improved by more than 2000-fold and were between 0.21 and 0.87 ng ml(-1) even with a UV absorbance detector. This system was applied to the determination of phthalates contained in laboratory distilled water and tap water samples.

Chromatography, Liquid↗

PubMed2003

Split flow and bypass flow systems for monolithic capillary columns in liquid chromatography.

Split flow and bypass flow systems were assembled using Nano Y Connectors with low dead volume commercially available for capillary liquid chromatography (LC). The split ratio could be controlled by changing the dimension of restriction tubing and applied back pressure to the restriction tubing. The split flow system allowed us to use valve injectors and pumps commercially available for capillary LC. The reproducibility of the present split flow system was acceptable. The relative standard deviation for six successive measurements was 0.4% for the retention time, whereas that for the peak height and peak area was 1-3% depending on the analytes. The bypass flow system uses two Nano Y Connectors, where the eluent split at the first Nano Y Connector, which is located in the inlet of the separation column, is merged again into the effluent from the column at the second Nano Y Connector. The bypass flow system could avoid on-column detection and allowed us to use flow cells, leading to an approximate three times improvement in signal-to-noise. The present flow systems were evaluated by using aromatic hydrocarbons and alkylbenzenes as test analytes.

Chromatography, Liquid↗