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Biomedical subjects

K Yagi

Publications and source records attributed to K Yagi.

At least 649 records · Page 36Linked to original sources
PubMed1980

Pulse fluorimetry of N-(1-pyrenesulfonyl)dipalmitoyl-L-alpha-phosphatidylethanolamine in concanavalin A-stimulated human lymphocytes.

Human peripheral lymphocytes were cultured with a fluorescent probe, N-(1-pyrenesulfonyl)dipalmitoyl-L-alpha-phosphatidylethanolamine, and with concanavalin A. Fluorescence microscopic observations revealed that in lymphoblasts, pyrenesulfonyl dye was distributed mainly in vacuoles whereas in normal cells cultured without concanavalin A the dye was distributed exclusively in plasma membranes. The fluorescence spectra of the pyrenesulfonyl group incorporated into the cells exhibited two emission maxima, band A (monomer fluorescence of the pyrenesulfonyl group at about 400 nm) and band B (dimer fluorescence of the dye at about 500 nm). The values of the fluorescence lifetime measured at bands A and B indicated that in the absence of concanavalin A, the environment surrounding the pyrenesulfonyl group at the lipid/water interface became more hydrophilic with cultivation time. Concanavalin A made the environment of the interface more hydrophobic than that of lymphocytes cultured without concanavalin A. Fluorescence polarization measured at band A revealed that the mobility of pyrenesulfonyl monomers at the aqueous interface of the membranes was reduced upon concanavalin A stimulation.

Cell Membrane↗
PubMed1980

L-gulonolactone oxidase activity and vitamin C status in riboflavin-deficient rats.

The effect of riboflavin deficiency on the activity of L-gulonolactone oxidase [L-gulono-gamma-lactone: oxygen 2-oxidoreductase, EC 1.1.3.8] and on vitamin C status was studied. A marked decrease in the specific activity of L-gulonolactone oxidase was observed in the liver microsomes isolated from riboflavin-deficient rats: the specific activity was approx. one-third of that in the microsomes isolated from control rats. The L-ascorbic acid content in the liver of the riboflavin-deficient rats was approx. one-half of that in the liver of the control rats. It seems that the rate of production of L-ascorbic acid in the riboflavin-deficient rats is limited by the decreased level of L-gulonolactone oxidase activity. Immunotitration using rabbit antiserum directed to L-gulonolactone oxidase revealed that a substantial amount of an inactive form of this enzyme is present in the liver microsomes of the riboflavin-deficient rats. L-Gulonolactone oxidase activity in the microsomes of these rats increased by approx. 35% upon addition of FAD, but it was slightly decreased by the addition of FMN or riboflavin. These results indicate that the liver microsomes of the riboflavin-deficient rats contain a protein which exhibits L-gulonolactone oxidase activity upon addition of Fad.

Animals↗
PubMed1980

Picosecond fluorescence lifetime of the coenzyme of D-amino acid oxidase.

Conformational difference surrounding the coenzyme, FAD, of D-amino acid oxidase (D-amino-acid:O2 oxidoreductase (deaminating), EC 1.4.3.3) between its monomeric and dimeric forms were examined by observing fluorescence of FAD. The fluorescence lifetimes of the coenzyme was measured directly with a mode-locked Nd:YAG laser and a streak camera in picosecond region. The values of lifetime of FAD fluorescence in the monomer and dimer were 130 +/- 20 ps and 40 +/- 10 ps, respectively. The relative quantum yield of the fluorescence of FAD combined with the protein to that of free FAD depended on the concentration of the enzyme; it was higher at lower concentration. Comparing the lifetime with relative quantum yield of FAD combined with the protein, it is concluded that the fluorescence is quenched mostly by a dynamic process. These results indicate that the distance between the isoalloxazine nucleus and a quencher is nearer in the dimer than in the monomer.

D-Amino-Acid Oxidase↗
PubMed1980

Effect of hydrogen bonding on electronic spectra and reactivity of flavins.

Riboflavin tetrabutyrate undergoes characteristic spectral changes, in both the first and second absorption band regions, upon hydrogen bonding with trichloroacetic acid of trifluoroacetic acid. On the basis of the calculated electron densities, hydrogen bonding at the heteroatoms of the isoalloxazine nucleus is considered to occur with increasing concentrations of the proton donor, first at N(1), then at O(12), O(14), and N(3)H, and finally at N(5). The idea that the major effect of the hydrogen bonding at the N(1), N(3)H, and oxygen atoms of the flavin nucleus is to facilitate the electrophilicity of the N(5) position, which was predicted by molecular orbital calculations, was supported by the observation that the hydrogen-bonded flavin in its triplet state abstracts hydrogen from the donor N-benzyl-n,n'-dimethylethylenediamine at a faster rate than do the non-hydrogen-bonded species in CCI4. The implications of the present study in the spectroscopic and catalytic properties of flavoproteins are briefly discussed.

Hydrogen Bonding↗
PubMed1980

Oxidation by superoxide of tocopherols dispersed in aqueous media with deoxycholate.

alpha-Tocopherol dispersed in aqueous media with deoxycholate was found to be oxidized, at a physiological pH, by a xanthine-xanthine oxidase system. This reaction was completely inhibited by the addition of superoxide dismutase, whereas catalase and mannitol (scavenger of hydroxyl radical) did not affect the reaction. This finding indicates that the oxidation of alpha-tocopherol is caused by O2. The reaction product formed was identified as 8 alpha-hydroxy-alpha-tocopherone by thin-layer chromatography and ultraviolet spectroscopy. The product was found to change spontaneously to alpha-tocopherol quinone. beta-, gamma-, and delta-tocopherol dispersed with deoxycholate also reacted with O2. The reaction of tocopherols dispersed in the micellar form may be considered as a model of in vivo reaction of tocopherols, since tocopherols are present in tissues largely in the membranes, where O2 is known to be generated.

Ascorbic Acid↗
PubMed1980

Stimulation-dependent changes in synaptic effects on unit activity of medial preoptic nucleus neurones in rats.

Stimulation-dependent changes in synaptic effects were observed in medial preoptic nucleus neurones during stimulation of the amygdala or pyriform cortex in anaesthetized female rats. The changes occurred after 35--240 triple pulse stimuli repeated at 0.89 Hz. Median eminence stimulation did not produce any synaptic change. These data show the existence of synaptic plasticity in the neural pathway from the amygdala and pyriform cortex to the medial preoptic nucleus.

Amygdala↗
PubMed1980

Calmodulins from muscles of marine invertebrates, scallop and sea anemone.

Invertebrate calmodulins of the sea anemone and scallop muscle were isolated and their properties were compared with those of vertebrate calmodulins from rabbit muscle and pig brain. The molecular weights estimated by SDS-polyacrylamide gel electrophoresis were similar to the molecular weight (16,500) of the vertebrate calmodulins. Every calmodulin contained 1 mol each of trimethyllysine and histidine, and high contents of acidic amino acids. The marine invertebrate calmodulins contained only one tyrosine in contrast to two tyrosines in the vertebrate ones. As a result, the UV absorption spectra were clearly different. The Ca2+-induced difference UV absorption spectra of the invertebrate calmodulins were indistinguishable from those of the vertebrate ones in spite of the difference in tyrosine contents. In tryptic peptide maps of invertebrate calmodulins, a few spots different from those of vertebrate calmodulins were observed in the basic and acidic peptide regions. The calmodulins of invertebrate muscles and that of rabbit skeletal muscle were almost indistinguishable in terms of the activation profile of rabbit skeletal myosin light chain kinase.

Amino Acids↗
PubMed1980

Localization of g2 light chain in the link between the heads and tail of cardiac myosin.

Cardiac myosin liberated 1.99 mol of acetate per mol after acid hydrolysis. The myosin subfragment-1, which cannot bind g2 light chain, liberated 0.85-1.16 mol of acetate per mol. On the other hand, negligible amounts of acetate could be detected from g1 and g2 light chains. The acetates, which were measured by a microenzymic method, were derived from the acetylated N-terminal of the heavy chain. It was concluded that g2 light chain is bound to the C-terminal region of subfragment-1, which is the link between the heads and tail of myosin.

Acetates↗
PubMed1980

The apparent binding constants of Ca2+ to EGTA and heavy meromyosin.

The apparent binding constant (K E app) of EGTA to Ca2+ was determined using a color indicator, murexide, or a Ca2+-selective electrode in the pH range between 6.5 and 7.5, at 5 degrees C and at 20 degrees C. K E app values obtained at two different temperatures (5 degrees C and 20 degrees C) were essentially the same when measured at the same pH. However, K E app depended markedly on pH. In the presence of 0.1 M KCl and 20 mM MOPS-KOH buffer (pH 6.8), K E app was 6.3 X 10(5) M-1. The absolute binding constant (K) was calculated as 10(10.48). Addition of 10 mM MgCl2 did not change the K E app. The binding of Ca2+ to heavy meromyosin was studied in 0.1 M KCl and 20 mM MOPS-KOH buffer (pH 7.2), at 5 degrees C. The binding constant and maximum binding number (mol/mol) were obtained as 1.8 X 10(6) M-1 and 1.4, respectively.

Animals↗
PubMed1980

A tautology in the classification of generalized non-convulsive epileptic seizures.

Five patients with the Lennox-Gastaut syndrome who have shown generalized nonconvulsive seizures were presented. The seizure manifestations which occurred spontaneously were documented by simultaneous recording and analyzed in terms of clinical and electroencephalographic correlates. According to the diagnostic criteria of the International Classification, it was possible, on the one hand, to regard them as "atypical complex absences" in which the impairment of consciousness is accompanied by other symptoms, which tend to dominate the clinical picture. They were: hypotonic, hypertonic, myoclonic and akinetic components, respectively. On the other hand, if we give a special weight to the accompanying symptoms, it is entirely possible that they are at the same time diagnosed atonic, axial tonic, bilateral myoclonic and akinetic seizures. The initial impairment of consciousness is common to all the seizure manifestations, and the ictal and interictal EEG expressions are not of diagnostic significance. A question arises as to whether two different nomenclatures were arbitrarily given to a unique ictal manifestation or not as far as the generalized non-convulsive seizures were concerned.

Adolescent↗
PubMed1980

Amygdala neurones: converging synaptic inputs produced by median eminence and medial preoptic area stimulations in rats.

1. Amygdaloid afferent inputs from the median eminence and the medial preoptic area were studied electrophysiologically in urethane-anaesthetized female rats.2. Stimulation of the surface of the median eminence produced orthodromic responses in about 80% of the forty-seven amygdala units tested and about 65% of the responsive cells showed an excitation.3. Stimulation of the ipsilateral medial preoptic area orthodromically excited seventeen and inhibited twenty of the forty-nine units tested.4. Stimulation of the contralateral medial preoptic area evoked orthodromic excitation in nine and inhibition in three of the twenty-two units tested. These stimuli were ineffective for producing antidromically conducted impulses in the tested units.5. Sixteen of the thirty amygdala units tested for responses to both median eminence and ipsilateral medial preoptic area stimulation responded orthodromically with either excitation or inhibition. The latency of the response to median eminence stimulation was approximately equal to that of the response to ipsilateral preoptic area stimulation in four of these sixteen units.6. A characteristic bursting discharge was observed in eleven amygdala units during and after ipsilateral preoptic area stimulation. A transitory inhibition was evoked simultaneously with the bursting discharge in some units. Seven of the eleven units were also tested for median eminence stimulation, and a transitory excitation was observed in each of these units.7. These results suggest the existence of converging synaptic inputs both from tuberoinfundibular neurones and the ipsilateral medial preoptic area to certain amygdala neurones. They also demonstrate the existence of a specific neural pathway mediating a characteristic self-sustained bursting discharge in some amygdala neurones after such stimulation.

Afferent Pathways↗