Biomedical subjects

S Ohnuma

Publications and source records attributed to S Ohnuma.

44 records · Page 3Linked to original sources

PubMed1992

Chain length distribution of the products formed in solanesyl diphosphate synthase reaction.

Factors that affect the termination of isoprenoid chain elongation catalyzed by prenyltransferase were investigated. The chain-length distribution of reaction products of solanesyl diphosphate synthase [EC 2.5.1.11] homogeneously purified from Micrococcus luteus changed dramatically according to the concentration of the complex formed between isopentenyl diphosphate and Mg2+ (IPP-Mg) in the reaction mixture. However, the concentration of the complex between farnesyl diphosphate and Mg2+ (FPP-Mg), the priming substrate for this synthase, did not affect the product distribution, provided that the concentration of IPP-Mg was maintained at a certain level. Thus, the level of IPP-Mg is decisive in affecting the chain length distribution of the products of the prenyltransferase reaction, and the Mg(2+)-dependent variability of product specificity so far observed can now be understood in terms of the effect of IPP-Mg concentration.

Alkyl and Aryl Transferases↗

PubMed1991

Purification of solanesyl-diphosphate synthase from Micrococcus luteus. A new class of prenyltransferase.

The activity of solanesyl-diphosphate synthase from Micrococcus luteus is stimulated by a high molecular mass fraction (HMF) which is separated from cell-free extracts of the same bacterium by DEAE-Toyopearl chromatography followed by Sephadex G-100 chromatography. By employing HMF in the assay procedure, solanesyl-diphosphate synthase was able to be purified to homogeneity and was found to be a homodimer with a monomeric molecular mass of 34 kDa. In contrast to hexaprenyl- and heptaprenyl-diphosphate synthases, which are composed of two easily dissociable components that are inactive unless combined, the homogeneously purified solanesyl-diphosphate synthase itself showed a catalytic activity, though weak, catalyzing the synthesis of both (all-E)-nonaprenyl-(solanesyl-) and (all-E)-octaprenyl diphosphate. HMF does not affect the stability of solanesyl-diphosphate synthase or Km values for isopentenyl diphosphate and farnesyl diphosphate, but it markedly increases Vmax values in a time-dependent manner. Several lines of evidence indicate that HMF contains a factor which binds to polyprenyl products and removes them out of the active site of enzyme to facilitate and maintain the turnover of catalysis.

Alkyl and Aryl Transferases↗

PubMed1990

[Statistical studies of student clinical practice. 1. Clinical practice of operative dentistry from 1983 to 1989].

Clinical practice has been assigned as a final and very important aspect of study and practice of dental education. In our university, the students are exposed the clinical practice from the latter term of fifth year. This report investigated the protocols of clinical cases from the first to the seventh class of graduates. The results obtained were as follows: 1) The graduates of first class averaged 9 clinical cases. This decreased with the years and the fourth class averaged 5.5 cases. From the sixth class simulator training and mutual practice among the students was introduced and the total average of seventh class was 5.1 cases. 2) The dental practice centers on restoration and 20 percent of all cases were amalgam fillings from the first to four the class. However this decreased from the fifth class and does not take place at present. Composite resin restorations increased. Cast restorations occupied 20 percent of all cases and the proportion hasn't changed. 3) Clinical cases of graduates of fifth class who were first to include treatment between students averaged 7 cases. Mutual treatment practice is useful because of the increase exposure to clinical practice.

Clinical Clerkship↗

PubMed1990

[A study for non-asbestos casting liners. An experimental study of the adaptability of MOD casting to die].

Asbestos liners for investment metal casting has frequently been used in dental laboratory work. In recent years, the dangerous properties of asbestos to the human body were reported in Europe and the United States, and casting liners without asbestos were developed and marketed by many manufacturers. These are so-called non-asbestos liners. This study evaluated the adaptability of MOD inlay castings to dies using 8 kinds of commercial non-asbestos liners of ADA standard No. 2 specifications. The results were as follows; Single and double layers of Casting ribbon, New Asbestos Ribon, Shofu experimental, and KAOLIN showed good adaptation. Shofu experimental with a single layer showed the best marginal adaptation (10 microns). OVAL LINERS and CASTING LINERS with single layer showed good adaptation, but with double layers the adaptation was poor. In FLASK LINER, the double layer showed better adaptation than that with a single layer. Most non-asbestos liners used in this study are adequate in useful to MOD inlay castings.

Asbestos↗

PubMed1989

Kinetic studies on the prenyl chain elongation by undecaprenyl diphosphate synthase with artificial substrate homologues.

In the undecaprenyl diphosphate synthase reaction, an allylic substrate homologue, (2Z,6E,10E)-4-methyl-geranylgeranyl diphosphate was found to be a potent competitive inhibitor against the allylic primer, (2Z,6E,10E)-geranylgeranyl diphosphate. On the other hand, it acted as a strong noncompetitive inhibitor against isopentenyl diphosphate. On the basis of these facts, the topology of the substrate-binding sites as well as the reason why the synthase reaction with (E)-3-methyl-3-pentenyl diphosphate always stops completely at the first stage of condensation, yielding an allylic diphosphate with a methyl group at the 4-position, are discussed.

Alkyl and Aryl Transferases↗

PubMedDate not supplied

Alpha 2-adrenoceptor activity induces the antidepressant-like glycolipid in mouse forced swimming.

Antidepressants show an antidepressive-like behavioral effect on mouse forced swimming via induction of GalNAc alpha 1-3GalNAc-lipid. In order to detect the mechanisms of the neuron receptor activities on the effect, the glycolipid reactivities in the serum induced by tandospirone, a specific 5-HT1A receptor agonist, and clonidine, a specific alpha 2-adrenoceptor agonist, were investigated. Both of these agonists showed dose-dependent behavioral effects which were decreased by pretreatment with yohimbine, a specific alpha 2-adrenoceptor antagonist. The glycolipid reactivities corresponded with the effects. These present findings strongly suggest that alpha 2-adrenoceptor activity in the brain mediates the induction of the antidepressant glycolipid in the forced swimming test.

Adrenergic alpha-Agonists↗

PubMedDate not supplied

Behavioral effect of herbal glycoside in the forced swimming test.

We investigated the behavioral effects of Chinese herbal medicines in the forced swimming test. One of these medicines, Kami-shoyo-san, induced an antidepressive climbing behavior in mice. An effective substance detected to be an O-linked glycoside with the sugar chain structure GalNAc alpha 1-3GalNAc was separated. The behavioral effect was dose-dependently decreased by the dopamine 2 antagonist sulpiride, but not by the dopamine 1 antagonist SCH-233960. Investigated Chinese herbal medicines, including Kami-shoyo-san, have been used for human depression. These facts suggest that glycoside is one of the antidepressant-like substances of Chinese herbal medicines.

Animals↗

PubMedDate not supplied

A glycoside of Nicotina tabacum affects mouse dopaminergic behavior.

Climbing in the forced swimming test is considered a dopaminergic-specific behavior. A substance of Nicotina tabacum affecting dopamine neuronal activity was investigated using the mouse behavioral system. The substance was found to be a glycoside with the peripheral sugar chain structures Fuc alpha 1-2Gal, Gal beta 1-4GlcNAc and GalNAc alpha 1-3GalNAc and with basic polymannoses. The glycoside dose-dependently increased behavior via D2 neuronal activity, but not D1 activity. This suggests that smoking can affect human brain function not only via the nicotinic cholinergic neuron, but also via the D2 neuron.

Animals↗