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T Ren

Publications and source records attributed to T Ren.

60 records · Page 4Linked to original sources
PubMed1993

Betahistine-induced vascular effects in the rat cochlea.

Betahistine (BH) has been used widely to treat cochlear disorders, such as tinnitus and Meniere's disease. The mechanism of action of BH in the cochlea is assumed to be based on its histamine-like effect on H1 receptors in the cochlear vasculature, leading to an increased cochlear blood flow (CBF). Recently it has been shown that BH can strongly affect H3 heteroreceptors (a novel histamine receptor subclass) in the periphery, via an autonomic ligand. This mechanism may also contribute to the BH effects on CBF. This study was to validate BH effects in the cochlear vasculature and to investigate the possible mechanisms of action of this drug in the inner ear vasculature. We assessed the effects of BH on CBF with the laser Doppler flowmeter in 23 rats and concluded that BH affects vascular conductivity in the cochlea in a dose-dependent fashion; betahistine diffuses through the round window, but does not have access to vascular receptors or ligands once in the labyrinthine fluids; and the H1 receptors mediate the systemic and peripheral vascular effects of BH, whereas the cochlear effect involves cholinergic receptors.

Animals↗
PubMed1992

Induction of c-fos immunostaining in the rat brain after the systemic administration of nicotine.

To search for evidence of altered neuronal gene expression in response to exposure to the highly addictive drug nicotine, rat brains were examined by immunocytochemistry for the fos protein after the systemic administration of nicotine. The drug was administered as an IV infusion over 1 h At a dose of 2 mg/kg, the most dramatic nicotine-induced fos nuclear immunostaining was seen in central visual pathways, including the superficial superior colliculus and the medial terminal nu. of the accessory optic tract, in the interpeduncular nu. Notably, many regions with high levels of nicotine binding sites, including the medial habenula, thalamus, substantia nigra, and ventral tegmental area, failed to express the c-fos gene with this schedule of nicotine administration. A minimal increase in fos immunostaining was seen after a nicotine dose of 0.5 mg/kg, with a much greater response after 1 or 2 mg/kg. The response was seen as soon as 60 min after the beginning of the infusion, was maximal at 2-3 h, and declined thereafter. c-fos expression was substantially attenuated in the superficial gray layer of superior colliculus, medial terminal nucleus of the accessory optic tract, and the interpeduncular nucleus by pretreatment with the centrally acting nicotine antagonist mecamylamine, 5 mg/kg IP, but not with the peripherally acting antagonist hexamethonium, 4 mg/kg IP. These observations identify a subset of central nervous system neurons that respond to nicotine with altered expression of the immediate early gene c-fos. These neurons presumably undergo long-term changes in gene expression as a result of acute exposure to high doses of nicotine.

Animals↗
PubMed1992

Dispersion of Small Ceramic Particles (Al(2)O(3)) with Azotobacter vinelandii.

The high surface charge of small ceramic particles such as alumina particles prevents them from dispersing evenly in aqueous suspensions and forming high-density compacts. However, suspensions of 400-nm-diameter alumina particles treated with alginate from the bacterium Azotobacter vinelandii were well dispersed. The alginate bound firmly to the particle surface and could not be removed by repeated washing with distilled water (2.82 mg of the bacterial alginate adsorbed to 1 g of the alumina particles). Furthermore, A. vinelandii grew and produced alginate in the presence of up to 15% (vol/vol) alumina particles. These results suggest that an in situ process using this bacterium to coat ceramic particles with alginate might be developed. In in situ processing experiments, the particle-packing densities were significantly increased and the viscosities of 5 and 10% (vol/vol) suspensions were reduced 4- and 60-fold, respectively, over those of controls. The bacteria were readily removed from the alumina particles by washing.

Journal Article↗
PubMed1989

[Determination of lactate dehydrogenase isozymes in the cochleae of guinea pigs].

The isozymes of lactate dehydrogenase (LDH) in perilymph and homogenates from vascular stria, Corti's organ, and vestibular membrane of healthy guinea pigs were determined with the micro-homogenate electrophoresis technique. The results were compared with those in serum and cerebrospinal fluid. It was found that electrophoretogram of individual homogenate or perilymph, which showed the isozymes of LDH, had a special pattern different from that in the serum. The factors which might affect LDH in perilymph had been discussed.

Animals↗