The role of polypyrrole as charge transfer mediator and immobilization matrix for d-fructose dehydrogenase in a fructose sensor

A fructose dehydrogenase (FDH) modified electrode is produced by the electroadsorption of a layer of FDH on a platinum electrode followed by the electropolymerization of a polypyrrole (PPy) film around and over the enzyme. This immobilizes and stabilizes the enzyme as well as providing an electron transfer pathway to the electrode. The amperometric response to fructose and the enzymatic activity are measured as a function of PPy film thickness. The electrode is shown to have a maximum response at a PPy thickness of approximately the thickness of the enzyme layer. A measure of the electrode efficiency is also obtained, this is the amperometric response to fructose as a percentage of that expected on the basis of the enzyme activity. The functioning of the electrode is also dependent on the counter-ion used for PPy polymerization. This is shown to be mainly related to the nucleation and growth of the PPy film in the interfacial region.     

Basic steroid saponins from aerial parts of Fritillaria Thunbergii

From the aerial parts of Fritillaria thunbergii, three glycosidal Solanum alkaloids (basic steroid saponins) were isolated together with minor     

Mechanism of Photoregulated Carotenogenesis in Rhodotorula minuta IV. Effect of Light on the Production of Ergosterol and Phytoene and on the Composition of Carotenoid Pigments

The effect of light on the production of ergosterol and phytoeneand on the composition of carotenoids in Rhodotorula minutawas studied to determine which part of the pathway of carotenoidsynthesis regulated by light. The ergosterol content in the cells was in the range of 3.4–3.6mg/g dry cells regardless of the presence or absence of illuminationand the light intensity. The phytoene production in the cellswas markedly stimulated by light and was dependent on the lightintensity according to the amount of carotenoid pigments produced.In addition, the ratio of phytoene to carotenoid was in therange of 0.36–0.44, regardless of the presence or absenceof illumination and the light intensity. The fact that the ratio of carotenoid fractionated on the basisof the functional group involved in each carotenoid to the totalamount of carotenoid was almost constant regardless of the lightintensity suggested that the composition of the carotenoidssynthesized in the cells is not affected by light. It was deduced from these results that light induced the productionof enzyme(s) required for phytoene biosynthesis in Rhodotorulaminuta. (Received November 7, 1981; Accepted March 19, 1982)     

Determination of serum unconjugated estrone, estradiol-17β and estriol during pregnancy by selected ion monitoring

A simple, rapid and highly specific method by selected ion monitoring (SIM), using 9α,11α-[²H₂]estrone, [2,4-²H₂]estradiol-17β and 2,4-[²H₂]estriol as internal standards, was developed for the determination of serum estrogens during pregnancy. Serum samples were submitted to a simple extraction procedure and were analysed after formation of the trifluoroacetic anhydride derivative. The inter-assay coefficients of variation for estrone, estradiol-17β and estriol were 3.73%, 3.42% and 3.49%, respectively. The results obtained by SIM were compared with analysis performed using radioimmunoassay.     

Kinetcs and decay of fumarase activity of immobilized Brevibacterium ammoniagenes cells for continuous production of L-malic acid

The kinetics of the reversible fumarase reaction of immobilized Brevibacterium ammoniagenes cells and the decay behavior of enzyme activity were investigated in a plug flow system. The time course of the reaction in the immobilized cell column was well explained by the time-conversion equation including the apparent kinetic constants of the immobilized cell enzyme. The decay rate of fumarase activity was faster in the upper sections of the column (inlet side of the substrate solution) compared with the lower sections when 1M sodium fumarate (pH 7.0) was continuously passed through the column at 37°C. It was shown that the decay rate of the fumarase activity in the immobilized cell column depends on the flow rate of the substrate solution. The effect of flow rate on the decay rate of enzyme activity was considered to be related to the rate of contamination of enzyme with poisonous substances derived from the substrate solution or to the rate of leakage of enzyme stabilizers and/or enzyme itself from the immobilized cells.     

Effects of Hypoxia on the Activity of the Dopaminergic Neuron System in the Rat Striatum as Studied by In Vivo Brain Microdialysis

The purpose of the present study is to clarify the effects of hypoxia on the activity of the dopaminergic neurons in the brain and its mechanism of action. For this purpose, the effects of hypoxia on the extracellular levels of 3,4-dihy-droxyphenylethylamine (dopamine) were examined in the rat Striatum using in vivo brain microdialysis in the presence or absence of pretreatment with either tetrodotoxin (a blocker of voltage-dependent sodium channels) or nomifensine (a blocker of dopamine reuptake). Exposure to various degrees of hypoxia (15, 10, and 8% O₂ in N₂) increased dopamine levels in striatal dialysates to 200, 400, and 1,100%, respectively, of the control value. On reoxygenation, dopamine levels in the dialysates rapidly returned to the control level. Reexposure to hypoxia increased the dopamine levels to the same extent as during the first exposure. After addition of tetrodotoxin (40 mUM) to the perfusion fluid or pretreatment with nomifensine (100 mg/kg, i.p.), exposure to hypoxia no longer increased the dopamine levels. These results suggest that although hypoxia induces an increase in the extracellular dopamine levels (hence, an apparent increase in the activity of the dopaminergic neurons), this increase is not the result of an increase in dopamine release itself, but rather the result of inhibition of the dopamine reuptake mechanism.     

Comparison of cytochrome P-450 species which catalyze the hydroxylations of the aromatic ring of estradiol and estradiol 17-sulfate

For identification of microsomal cytochrome P-450 (P-450) enzymes which catalyze 2- or 4-hydroxylations of estrogens in the rat liver, estradiol (E₂) and estradiol 17-sulfate (E₂-17-S) were selected as the substrates and incubated with various kinds of purified P-450 enzymes: PB-1, PB-2, PB-4 and PB-5 obtained from phenobarbital-treated male rats (Sprague-Dawley); MC-1 and MC-5 from 3-methylcholanthrene-treated male rats; and UT-1, UT-2, UT-4 and UT-5 from untreated animals. The reactions were carried out under the P-450-reconstructed system, and the resulting products were determined by HPLC using electrochemical detection. All the enzymes tested were shown to have varying degrees of catalytic activities for 2-hydroxylation of the two substrates; UT-1 and UT-2 had the highest activity. Of the induced P-450 enzymes, PB-2 and MC-1 showed fairly high catalytic activity for 4-hydroxylation of E₂. The P-450 enzymes obtained from the untreated male rats, especially UT-4, showed the highest catalytic activity for 4-hydroxylation of the two substrates. From these results and also from kinetic experiments, the P-450 enzymes which catalyze 2- and 4-hydroxylations of estrogen were considered to be different species. A part of E₂ was converted to such metabolites as estrone and those having a hydroxyl group at positions 6β, 15 or 16, each production of which was estimated to be catalyzed by single or multiple P-450s.     

Stimulatory Effects of Exogenous Thyroid Hormone and Growth Hormone on sn-Glycerol-3-Phosphate Dehydrogenase Activity in the Genetic-Hypothyroid Mutant Mouse Cerebellum: Restricted to the Second 20 Days of Postnatal Life

We recently reported that by postnatal day 40 the activity of sn-glycerol-3-phosphate dehydrogenase (GPDH) was significantly depressed in the cerebellum of genetic-hypothyroid mutant mice. This mutant mouse-GPDH combination was used in the present study to define the critical time period during which thyroid hormone (T4) and growth hormone (GH) are essential for maturation of Bergmann glial cells. Our findings are that (a) induction of GPDH activity in the Bergmann glial cell is dependent on T4, (b) T4 is most effective when administered during the second 20 days of postnatal life, (c) the effect of GH on GPDH activity is complementary to or synergistic with that of T4, and (d) Bergmann glial cells and radial glial fibers of the mutant mice contain immunoreactive GPDH following various hormonal treatments. These results suggest that T4 is indispensable for the maturation of Bergmann glial cells.