Pteridine-metabolizing enzymes of Macaca fascicularis

1. The crab-eating monkey (Macaca fascicularis) has been studied for enzymes which react in the biosynthesis of pteridine cofactor of phenylalanine hydroxylase: 2. Rather high activity of sepiapterin reductase (EC 1.1.1.153)(0.130 mumol) and measurable activity of dihydrofolate reductase (EC 1.5.1.3)(0.039 mumol), (in amount of substrate reduced/hr/mg protein at 37 degrees C) were found in the crude extract from the liver. 3. Sepiapterin reductase was observed, in blood, only in the erythrocytes while dihydrofolate reductase was observed both in erythrocytes and leucocytes. 4. Activity of pteridine cofactor of phenylalanine hydroxylase was detected in the extract of the liver. 5. Sepiapterin reductase was partially purified from the liver, and was studied in the mol. wt, coenzyme-requirement, pH optimum, KmS and inhibitors.

The effect on photosynthetic electron transport of temperature-dependent changes in the fluidity of the thylakoid membrane in a thermophilic blue-green alga

Various electron transport reactions in cell or isolated thylakoid membranes of the thermophilic blue-green alga, Synechococcus sp. were measured at different temperatures between 72 and 3 degrees C. They are classified into two groups with respect to their temperature dependency. The first group involves cytochrome 553 photooxidation, methyl viologen photoreduction with reduced 2,6-dichlorophenolindophenol as electron donor and 3-(3',4'-dichlorophenyl)-1,1-dimethylurea-resistant ferricyanide photoreduction determined in the presence or absence of silicomolybdate. The Arrhenius plot of these reactions showed a single straight line with the activation energy of about 10 kcal/mol throughout wide temperature ranges studied. Methyl viologen photoreduction with water as electron donor, reduction of flash-oxidized cytochrome 553, ferricyanide photoreduction and photosynthetic O2 evolution form the second group. Their arrhenius plots are characterized by discontinuities or breaks at about 30 and 10 degrees C, which respectively correspond to the upper and lower boundaries of the lateral phase separation of the membrane lipids. The first group reactions represent short spans of electron transport which are mediated either by Photosystem I or Photosystem II alone and not related to plastoquinone, whereas all the reactions of the second group involve plastoquinone. It is concluded therefore that the membrane fluidity affect electron transport specifically at the region of plastoquinone. It is proposed that the reaction center chlorophyll-protein complexes of both Photosystems I and II are closely associated with related electron carrier proteins to form functional supramolecular assemblies so that electron transfer within such a cluster of proteins proceeds independently of the phase changes in the membrane lipids. On the other hand, the role of plastoquinone as a mobile electron carrier mediating electron transfer from the protein assembly of Photosystem II to that of Photosystem I through the fluid hydrophobic matrix of the membranes is highly sensitive to the physical state of the membrane lipids.

Thermal properties of NADP:ferredoxin oxidoreductase and ferredoxin isolated from a thermophilic blue-green alga

NADP:ferredoxin oxidoreductase (EC. 1.6.7.1.) isolated from a thermophilic blue-green alga, Synechococcus sp., was stable at temperatures up to 65°C. The diaphorase and cytochrome c reductase activities of the enzyme were low at 25°C but increased with elevated temperature to reach a maximum at about 60°C. The pH-profile of the diaphorase activity showed a peak at pH 9.0 at 55°C, whereas the activity was largely independent of pH at 25°C. High concentrations of NaCl suppressed activity at both high and low temperatures. In the cytochrome c reductase activity catalyzed by the enzyme, ferredoxin served as an electron carrier in a temperature-insensitive manner over a wide range of temperature. The results support the view that the optimum and the upper limiting temperatures for photosynthesis in this alga are related to thermal properties of proteins.

Plastoquinone as a common link between photosynthesis and respiration in a blue-green alga

The role of plastoquinone in a thermophilic blue-green alga, Shynechococcus sp., was studied by measuring reduction kinetics of cytochrome 553 which was oxidized with red flash preferentially exciting photosystem I. Sensitivity of the cytochrome reduction to DBMIB Abbreviations: DCMU = 3-(3,4-dichlorophenyl)-1,1-dimethylurea; DBMIB = 2,5-dib romo-3-methyl-6-isopropyl-p-benzoquinone; HOQNO = 2-n-heptyl-4-hydroxyquinoline-N-oxide indicates that cytochrome 553 accepts electrons from reduced plastoquinone. Plastoquinone is in turn reduced in cells without electrons from photosystem II, since DCMU Abbreviations: DCMU = 3-(3,4-dichlorophenyl)-1,1-dimethylurea; DBMIB = 2,5-dib romo-3-methyl-6-isopropyl-p-benzoquinone; HOQNO = 2-n-heptyl-4-hydroxyquinoline-N-oxide , which inhibited methyl viologen photoreduction more strongly than DBMIB, failed to affect the cytochrome reduction. Participation of cyclic electron transport around photosystem I in cytochrome reduction in the presence of DCMU was excluded, because methyl viologen and antimycin A had no effect on the cytochrome kinetics. On the other hand, electron donation from endogenous substrates to plastoquinone was suggested from decreases in rate of the cytochrome reduction by dark starvation of cells and also from restoration of fast reduction kinetics by the addition of exogenous substrates to or by reillumination of starved cells.KCN, which completely suppressed respiratory O2-uptake, induced a marked acceleration of the cytochrome reduction in starved cells. The poison was less or not effective in stimulating the cytochrome reduction in more extensively starved or reilluminated cells.Results indicate that plastoquinone is functioning not only in the photosynthetic but also in the respiratory electron transport chain, thereby forming a common link between the two energy conservation systems of the blue-green alga.

Dihydropteridine reductase and tetrahydropterin in Crithidia fasciculata cells

Dihydropteridine reductase was found in extracts of Crithidia fasciculata and was demonstrated by the fact that the enzyme required both quinonoid-dihydropterin and NADH as substrates. 7,8-Dihydropterin and dihydrofolate failed to serve as substrates; tetrahydropterin was formed as the reaction product. The molecular weight of the enzyme was estimated to be about 55 000 by Sephadex G-100 gel filtration. NADH was more effective than NADPH as substrate for the enzyme. Tetrahydropterin (1.35 nmol tetrahydrobiopterin equivalents/g cells) was also detected in C. fasciculata.

A study on tension signs in lumbar disc hernia

The laminae were removed from the lower lumbar spines of five cadavers within four hours of death. A short length of rubber tube was inserted between the nerve roots and the lumbar disc and the tension monitored using semiconductor pressure transducers. The angulatory stresses exerted on the lumbar nerve roots during tension sign tests were found to correspond to clinical experience.

Two electrogenic mechanisms contributing to the 560 nm absorption changes in intact Bryopsis chloroplasts

Light -induced absorbance changes at 560 nm in dark-adapted intact chloroplasts of the green alga, Bryopsis maxima were studied in the time range of 200 ms. The initial rise of the 560 nm signals consists of two major components which are both electrochromic absorbance changes of the carotenoids, siponein and/or siphonaxanthin, but different in mechanisms of the field formation. The first component (component S) is related to electron transport since it was sensitive to 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) and 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB) and showed at light-intensity dependence similar to that of electron transport in chloroplasts. In the presence of DCMU, component S could be restored on addition of proton-transporting electron donors such as reduced 2.6-dichlorophenol indophenol and phenazine methosulfate, but not on addition of N,N,N',N'-tetramethyl-p-phenylenediamine which does not carry protons with electrons (Trebst, A. (1974) Annu. Rev. Plant Physiol. 25, 423--458). We propose that component S is due to the electric field set up by the proton translocation across the thylakoid membrane. The second component (component R) was resistant to DCMU and DBMIB. The light-intensity dependency of component R was similar to that of cytochrome f photooxidation which showed saturation at a relatively low light intensity. The magnitude of component R was markedly reduced by phenylmercuric acetate, suggesting the participation of ferredoxin and ferredoxin-NADP oxidoreductase in the mechanism of the field formation responsible for this component. In the presence of DCMU and phenylmercuric acetate, time courses of the 560 nm changes paralleled those of cytochrome f changes. These results indicate that component R is due to the electric field formed between oxidized cytochrome f and other intersystem electron carriers located in the inner part of the thylakoid membrane and reduced electron acceptors of Photosystem I situated on the membrane surface. The complex natures of the 560 nm changes, as well as the contributions of Photosystems I and II to the absorbance changes, are explained in terms of the two electrogenic mechanisms.

Endoscopic studies on the minute structures of colonic mucosa in the follow-up observation of ulcerative colitis

Thirty cases of ulcerative colitis were examined endoscopically by means of magnifying colonoscope with dye spraying method (the combined method), and their minute mucosal structures were classified into four categories endoscopically, which correlated well with the histological findings. By this procedure, it was easy to detect the subsidence of inflammation of the mucosa in the quiescent phase or to reveal the active inflammatory involvement of the bowel. Moreover, inspecting the minute changes of the colonic mucosa detected by the combined method, remission was more correctly decided and rigid control is contributing to the decrease in the recent rate of recurrence of ulcerative colitis.

On the dye spraying method in colonofiberscopy

Dye spraying method was applied in colonofiberscopy; 111 cases of normal colonic mucosa and 26 cases of ulcerative colitis were examined by this method. Using indigocarmine in this method, we could recognize the fine mucosal changes more easily and clearly and get better information for differential diagnosis. Furthermore, the degree of staining of the mucosa by methylene blue, one of the ultra vital staining dye, is different according to the stage of the inflammatory process of colonic mucosa itself in ulcerative colitis. Namely the stainability of the colonic mucosa is corresponding to the healing process of the disease.