Biomedical subjects

T T Nakashima

Publications and source records attributed to T T Nakashima.

4 recordsLinked to original sources

PubMed2000

Chronic lithium and sodium valproate both decrease the concentration of myo-inositol and increase the concentration of inositol monophosphates in rat brain.

One of the mechanisms underlying lithium's efficacy as a mood stabilizer in bipolar disorder has been proposed to be via its effects on the phosphoinositol cycle (PI-cycle), where it is an inhibitor of the enzyme converting inositol monophosphates to myo-inositol. In contrast, sodium valproate, another commonly used mood stabilizer, appears to have no direct effects on this enzyme and was thus believed to have a different mechanism of action. In the present study, high resolution nuclear magnetic resonance (NMR) spectroscopy was used to study the chronic effects of both lithium and sodium valproate on the concentrations of myo-inositol and inositol monophosphates in rat brain. As predicted, lithium-treated rats exhibited a significant increase in the concentration of inositol monophosphates and a significant decrease in myo-inositol concentration compared to saline-treated controls. However, unexpectedly, sodium valproate administration produced exactly the same results as lithium administration. These novel findings suggest that both lithium and sodium valproate may share a common mechanism of action in the treatment of bipolar disorder via actions on the PI-cycle.

Animals↗

PubMed1998

Information from the water stripe in TOCSY experiments on systems with exchangeable protons.

The water "stripes" of the TOCSY maps of aqueous solutions of sucrose, of a 15-aminoacid peptide, and of several of the constituent aminoacids are shown to contain correlations at the resonance frequencies of protons which are scalar coupled to OH or NH protons which exchange with the solvent. Theoretical analysis of chemical exchange during the spin-lock period in TOCSY elucidates the origin of these correlations, and shows that their intensities vary with the duration of the spin-lock period and with the exchange rate.

Amino Acids↗

PubMed1997

Three-dimensional structure of leucocin A in trifluoroethanol and dodecylphosphocholine micelles: spatial location of residues critical for biological activity in type IIa bacteriocins from lactic acid bacteria.

The first three-dimensional structure of a type IIa bacteriocin from lactic acid bacteria is reported. Complete 1H resonance assignments of leucocin A, a 37 amino acid antimicrobial peptide isolated from the lactic acid bacterium Leuconostoc gelidum UAL187, were determined in 90% trifluoroethanol (TFE)-water and in aqueous dodecylphosphocholine (DPC) micelles (1:40 ratio of leucocin A:DPC) using two-dimensional NMR techniques (e.g., DQF-COSY, TOCSY, NOESY). Circular dichroism spectra, NMR chemical shift indices, amide hydrogen exchange rates, and long-range nuclear Overhauser effects indicate that leucocin A adopts a reasonably well defined structure in both TFE and DPC micelle environments but exists as a random coil in water or aqueous DMSO. Distance geometry and simulated annealing calculations were employed to generate structures for leucocin A in both lipophilic media. While some differences were noted between the structures calculated for the two different solvent systems, in both, the region encompassing residues 17-31 assumes an essentially identical amphiphilic alpha-helix conformation. A three-strand antiparallel beta-sheet domain (residues 2-16), anchored by the disulfide bridge, is also observed in both media. In TFE, these two regions have a more defined relationship relative to each other, while, in DPC micelles, the C-terminus is folded back onto the alpha-helix. The implications of these structural features with regard to the antimicrobial mechanism of action and target recognition are discussed.

Amino Acid Sequence↗

PubMed1984

Synthesis of 1,2,3,4-tetra-O-acetyl-5-deoxy-5-C-[(R) and (S) -methoxyphosphinyl]-alpha- and -beta-D-ribopyranoses.

Treatment of methyl 5-deoxy-5-C-( diethoxyphosphinyl )-2,3-O-isopropylidene-beta-D- ri bofuranoside with sodium dihydrobis (2- methoxyethoxy ) aluminate , followed by hydrogen peroxide, mineral acid, and hydrogen peroxide, gave 5-deoxy-5-C-( hydroxyphosphinyl )-alpha,beta-D- ribopyranoses in 40-45% overall yield. The structures of these sugar analogs were effectively established on the basis of the mass and 400-MHz, 1H-n.m.r. spectra of the title compounds, derived by treatment with diazomethane and then acetic anhydride in pyridine.

Deoxyribose↗