Quantum chemical studies for oxidation of morpholine by Cytochrome P450

Since morpholine oxidation has recently been shown to involve Cytochrome P450, the study on its mechanism at molecular level using quantum chemical calculations for the model of cytochrome active site is reported here. The reaction pathway is investigated for two electronic states, the doublet and the quartet, by means of density functional theory. The results show that morpholine hydroxylation occurs through hydrogen atom abstraction and rebound mechanism. However, in the low spin state, the reaction is concerted and hydrogen atom abstraction yields directly ferric-hydroxy morpholine complex without a distinct rebound step while in quartet state the reaction is stepwise. The presence of nitrogen in a morpholine heterocycle is postulated to greatly facilitate hydrogen abstraction. The hydroxylated product undergoes intramolecular hydrogen atom transfer from hydroxy group to nitrogen, leading to the cleavage of the C-N bond and the formation of 2-(2-aminoethoxy) acetaldehyde. The cleavage of the C-N bond is indicated as the rate-determining step for the studied reaction. The assistance of explicit water molecule is shown to lower the energy barrier for the C-N bond cleavage in enzymatic environment whereas solvent effects mimicked by COSMO solvent model have minor influence on relative energies along the pathway.     

Resting potential of the mouse neuroblastoma cells: I. The presence of K+ channels activated at high K+ concentration but closed at low K+ concentration including the physiological concentration

The effects of changes in extracellular K⁺ concentration ([K⁺]_o) on the resting membrane potential, the input resistance and ⁸⁶Rb efflux (as a marker of K⁺ efflux) were examined with use of the cultured mouse neuroblastoma cells (N-18 clone). The results obtained are as follows. (1) The membrane potential was depolarized, with an increase in [K⁺]_o at concentrations above 10–20 mM at a rate of 55–58 mV per 10-fold change in [K⁺]_o, but practically unchanged with varying [K⁺]_o below this concentration. (2) Above the critical [K⁺]_o of 10–20 mM, the input membrane resistance decreased sharply by a factor of $\text{1}\text{4}\text{?}\text{1}\text{5}$ with an increase in [K⁺]_o. A similar decrease in the resistance occurred even under the conditions that the membrane potential was held at control level (about ?55 mV) by a steady-state current passage. (3) Elimination of Na⁺ and Cl^? from the external solution brought about practically no change in the membrane potential. (4) A fractional escape rate of ⁸⁶Rb from N-18 cells remained constant at relatively low level (0.125%/min on average) in the low [K⁺]_o range, but increased sharply with increasing [K⁺]_o above 15 mM (e.g., approx. 3.4- and 4.5-fold at 30 and 100 mM [K⁺]_o, respectively). (5) The high K⁺-induced ⁸⁶Rb efflux was not practically inhibited by 1 mM tetraethylammonium or 0.1 mM 4-aminopyridine, indicating that the K⁺ channels activated by an elevation of [K⁺]_o are not the delayed (voltage-dependent) K⁺ channels. The present results favoured the conclusion that N-18 cells carry K⁺ channels which open at high [K⁺]_o but are closed at low [K⁺]_o including the physiological range for the mouse neuroblastoma cells (around 5.4 mM). This conclusion leads to the notion that in the mouse neuroblastoma N-18 cells the K⁺ permeability does not mainly contribute to determining the resting membrane potential under physiological conditions.     

Identification of a hormonal basis for gallbladder filling

The cycle of gallbladder filling and emptying controls the flow of bile into the intestine for digestion. Here we show that fibroblast growth factor-15, a hormone made by the distal small intestine in response to bile acids, is required for gallbladder filling. These studies demonstrate that gallbladder filling is actively regulated by an endocrine pathway and suggest a postprandial timing mechanism that controls gallbladder motility.     

Physicochemical studies of taste reception. V. Suppressive effect of salts on sugar response of the frog

The model membrane composed of a Millipore filter paper and the total lipids from bovine tongue epithelium or phosphatidylcholine from egg yolk simulated well the water response of a living taste cell. The water response observed with the model membrane adapted to various salt solutions was interpreted in terms of changes in electric potential at the membrane-solution interface, i.e. the water response was attributed to the e.m.f. change produced by diffusion of the electrolytes dissolved in (or adsorbed on) the membrane surface into the bulk solution.The water response of the frog tongue was also investigated by measuring the neural response of the glossopharyngeal nerve. The results obtained were consistent with the mechanism proposed in the present paper. The response of the frog to Ca²⁺ was examined under the condition where the water response was suppressed, and it was concluded that the water response of the frog is different from the response to Ca²⁺.     

Involvement of Growth-Associated Protein-43 with Irreversible Neurite Outgrowth by Dibutyryl Cyclic AMP and Phorbol Ester in NG108–15 Cells

Simultaneous treatment with 12-O-tetradecanoylphorbol 13-acetate (TPA) and dibutyryl cyclic AMP (diBu-cAMP) for 72 h induced neurites in NG108-15 cells significantly longer than treatment with each alone. Treatment for 72 h with both drugs induced irreversible neurite extension and a decline in protein kinase C activity, although neurites extended by diBu-cAMP alone disappeared after the withdrawal of the drug. The expression of growth-associated protein-43 (GAP-43) mRNA was also observed by a combined application of TPA and diBu-cAMP. The increased level of GAP-43 mRNA induced by treatment with both drugs for 72 h was maintained at least 24 h after withdrawal of the drugs. In cells transfected with GAP-43 cDNA, neurites induced by treatment with diBu-cAMP alone for 72 h were maintained at least 48 h after removal of the drugs. These results suggest that GAP-43 could be involved in the maintenance of elongated neurites and that a decline in protein kinase C activity may be involved in the accumulation of GAP-43.     

A novel neuroprotective agent with antioxidant and nitric oxide synthase inhibitory action

N^α-vanillyl-N^ω-nitroarginine (N ? 1) that combines the active functions of natural antioxidant and nitric oxide synthase inhibitor was developed for its neuroprotective properties. N ? 1 exhibited protective effects against hydrogen peroxide-induced cell damage and the inhibitory effect on nitric oxide ‘NO’ production induced by calcium ionophore in NG 108-15 cells. N ? 1 inhibited the constitutive NOS isolated from rat cerebellar in a greater extent than constitutive NOS from human endothelial cells. Low binding energy ( ? 10.2 kcal/mol) obtained from docking N ? 1 to nNOS supported the additional mode of action of N ? 1 as an nNOS inhibitor. The in vivo neuroprotective effect on kainic acid-induced nitric oxide production and neuronal cell death in rat brain was investigated via microdialysis. Rats were injected intra-peritonially with N ? 1 at 75 μmol/kg before kainic acid injection (10 mg/kg). The significant suppression effect on kainic acid-induced NO and significant increase in surviving cells were observed in the hippocampus at 40 min after the induction.     

Dropped head syndrome due to myogenic atrophy --- a case report of surgical treatment

Osteoid osteoma of the spine is a relatively rare bone-forming tumor. Pain that is worse at night and relieved by aspirin and muscle contracture are the most characteristic symptoms of spinal osteoid osteoma. Although radicular pain occasionally occurs in spinal osteoid osteoma, spinal cord and nerve root compression is absent in most cases. Although radicular pain appears to be associated with tumorous inflammation, there have been no presentations of histological findings of inflammation around the nerve root. We present here two rare cases of spinal osteoid osteoma causing radiculopathy and the first histological evidence of tumorous inflammation as a cause of radiculopathy in osteoid osteoma near the intervertebral foramen.