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Biomedical subjects

S Itoh

Publications and source records attributed to S Itoh.

At least 19 recordsLinked to original sources
PubMed1979

Postnatal development of uridine diphosphate glucuronyltransferase activity towards bilirubin and 2-aminophenol in human liver.

UDP-glucuronyltransferase activities towards 2-aminophenol and bilirubin were studied in a total of 70 human subjects, including premature and full-term newborn babies, infants, children and adults. These two activities have been reported in rat to develop latefoetally and neonatally respectively, but in man they both develop neonatally. There is a linear relationship between the logarithm of each liver transferase activity and the logarithm of the number of days after birth during the first 3 months of life, after which each activity remains constant.

Adult↗
PubMed1979

Surface potential and reaction of membrane-bound electron transfer components. I. Reaction of P-700 in sonicated chloroplasts with redox reagents.

Salt- or pH-induced change of the rate of reduction of the photoxidized membrane bound electron transfer components, P-700, by ionic and nonionic reductants added in the outer medium was studied in sonicated chloroplasts. The rate with the negatively charged reductants increased with the increase of salt concentration at a neutral pH or with the decrease of medium pH. Salts of divalent cations were much more effective than those of monovalent cations. A trivalent cation was even more effective. The rate with a nonionic reductant was little affected by salts. The change of the reduction rate was analysed using the Guoy-Chapman theory, which explains the change of reduction rate by the changes of activities of ionic reductants at the charged membrane surface where the reaction takes place. This analysis gave more useful parameters and explained more satisfactorily the case with high-valence cation salts than the Brönsted type analysis. The values for the surface charge density and the surface potential of the membrane surface in the vicinity of P-700 estimated from the analysis were lower than those estimated for the surface in the vicinity of Photosystem II primary acceptor, suggesting the heterogeneity of the thylakoid surface. The salt-induced surface potential change was shown to affect the activation energy of the reaction between P-700 and the ionic reagent.

Chlorophyll↗
PubMed1979

Surface potential and reaction of the membrane-bound electron transfer components. II. Integrity of the chloroplast membrane and reaction of P-700.

Electrostatic characteristics of the membrane in the vicinity of P-700 were estimated by analyzing the salt and detergent effects on its reaction rate with ionic reagents using the Gouy-Chapman diffuse double layer theory in various preparations of chloroplasts. Upon disruption of thylakoid membranes by sonic treatment or by treatment with digitonin, the reaction rate markedly increased, while the estimated surface charge density became smaller. It was concluded that the membrane surface which determines the reaction rate between P-700 and the ionic reagents changed as the disruption of thylakoid structure. The outer thylakoid surface had more negative charges than the inner one. Changes in the electrical potential profile across the thylakoid membrane during the illumination were also discussed from these results.

Ascorbic Acid↗
PubMed1979

A high potential acceptor for photosystem II.

The effects of ferricyanide on Photosystem II reactions have been investigated by measurements of microsecond and millisecond prompt fluorescence and microsecond-delayed fluorescence in dark-adapted chloroplasts: (1) Titrations using ferri-ferrocyanide mixtures on: (a) the fast phase of the increase in fluorescence yield observed during a xenon flash, and (b) the normalised area above the millisecond fluorescence induction curve for chloroplasts inhibited by DCMU, showed a pH dependent mid point potential of 400 mV at pH 7.0 which varied by approx. -60 mV/pH unit between pH 6 and 8.5. (2) A saturating laser flash induced a fluorescence increase (as monitored by a weak measuring beam) of only 50% of that reached following a second flash in chloroplasts preincubated with ferricyanide and inhibited by 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) prior to illumination. In the absence of ferricyanide, the fluorescence level reached after a single flash was initially close to that measured after a second flash (although the level subsequently declined). (3) The initial amplitude of the microsecond-delayed fluorescence excited by a single laser flash was diminished in chloroplasts dark-adapted with ferricyanide. In the presence of DCMU and ferricyanide, the amplitude was also diminished for the first flash of a series, but subsequently enhanced above the level obtained in chloroplasts in the presence of DCMU alone. (4) The above effects were not seen if DCMU was added to the chloroplasts before ferricyanide, or if the period of incubation with ferricyanide was much less than 4 min. (5) These results suggested the presence of a second acceptor Q2, with Em7 = 400 mV and n = 1, before the DCMU block in Photosystem II. There is 0.35--1 equivalent of the acceptor per reaction centre, and its reduction occurs within less than 5 mus. The role of the acceptor in double turnovers of the photochemistry during a single flash and its likely operating redox potential are discussed.

Chloroplasts↗
PubMed1979

Effects of pH on reactions on the donor side of photosystem II.

The effects of pH on the increase of fluorescence yield measured in the microsecond range, and on the microsecond delayed fluorescence have been studied in dark adapted chloroplasts as a function of flash number. (1) At pH 7, the amplitude of the fast-phase of the microsecond fluorescence yield rise oscillated as a function of flash number with period 4 and with maxima on flashes 1 and 5, and minima on flashes 3 and 7. The damped oscillations were apparent over the range between 6 and 8, although the absolute amplitude of the fast phase was diminished at the lower end of the range. At pH 4, there was no fast phase in the rise and, at pH 9, an enhanced fast-phase occurred only for the first flash. (2) The decay of microsecond delayed fluorescence was described by the sum of exponentials with half-times of 10--15 mus and 40--50 mus. Over the pH range 6- less than 8, the extrapolated initial amplitude and the proportion of the change due to the faster component showed oscillations which were opposite in phase to those observed for the prompt fluorescence yield rise; the slower component showed weaker oscillations of the same phase. At pH 4, there were no oscillations and the slow phase predominated. At pH 9, the delayed fluorescence intensity was diminished on the first flash, and high on subsequent flashes. (3) The results are interpreted in terms of a model in which protons are released during all transitions of the S-states with the exception of S1 leads to S2, and in which ther are two sites of inhibition on the donor side of the photo-system at extreme pH values. At pH 4, electron donation to P+ occurs with a half-time approx. 135 mus, either by a back reaction from Q-, or from D; electron transport is interrupted between Z1 and P. At pH 9, electron transport is inhibited between Z1 and Z2; rapid re-reduction of P+ by Z1 occurs after 1 flash, and on subsequent flashes electrons from D, an alternative donor reduce P+. The location of the positive charge on states S2 and S3 is discussed.

Chloroplasts↗
PubMed1979

Effect of surface potential on the intramembrane electrical field measured with carotenoid spectral shift in chromatophores from Rhodopseudomonas sphaeroides.

Changes in the surface potential, the electrical potential difference between the membrane surface and the bulk aqueous phase were measured with the carotenoid spectral shift which indicates the change of electrical field in the membrane. Chromatophores were prepared from a non-sulfur purple bacterium, Rhodopseudomonas sphaeroides, in a low-salt buffer. Surface potential was changed by addition of salt or by pH jump as predicted by the Gouy-Chapman diffuse double layer theory. When a salf was added at neutral pH, the shift of carotenoid spectrum to shorter wavelength, corresponding to an increase in electrical potential at the outside surface, was observed. The salts of divalent cations (MgSO4, MgCl-2, CaCl2) were effective at concentrations lower than those of monovalent cation salts (NACl, KCl, Na2SO4) by a factor of about 50. Among the salts of monoor divalent cation used, little ionic species-dependent difference was observed in the low-concentration range except that due to the valence of cations. The pH dependence of the salt-induced carotenoid change was explained in terms of the change in surface charge density, which was about 0 at pH 5--5.5 and had negative values at higher pH values. The dependence of the pH jump-induced absorbance change on the salt concentration was also consistent with the change in the charge density. The surface potential change by the salt addition, which was calibrated by H+ diffusion potential, was about 90 mV at the maximum. From the difference between the effective concentrations with salts of mono- and divalent cations at pH 7.8, the surface charge density of (-1.9 +/- 0.5) . 10(-3) elementary charge per A2, and the surface potential of about -100 mV in the presence of about 0.1 mM divalent cation of 5 mM monovalent cation were calculated.

Bacterial Chromatophores↗
PubMed1979

Isolation and characterization of stable hybrid mRNA molecules transcribed from ribosomal protein promoters in E. coli.

The promoters from the str and spc operons of ribosomal proteins from E. coli were inserted into the Hind II cleavage site of mini-Col E1 (pVH51) plasmid. For both promoters, strains with the hybrid plasmid accumulated a small RNA species not present in strains carrying the vector. These RNAs were analyzed by RNA sequencing techniques and compared to DNA sequences. In both cases, synthesis of the new RNA species is initiated by the cloned r protein promoter at the site predicted by previous in vitro experiments. The RNAs extend across the Hind II site used for cloning and terminate specifically in the vector sequences. The termination site was localized to six consecutive thymine nucleotides preceded by a sequence with dyad symmetry. We found that the RNA from the str promoter was 205 (+/- 3) nucleotides long and that from the spc promoter was 177 (+/- 3) nucleotides long. These "hybrid mRNAs" are much more stable than ordinary mRNA. The str hybrid mRNA has a half-life of about 8 min, and the spc hybrid mRNA has a half-life of about 18 min at 37 degrees C. These hybrid mRNAs provide an in vivo system with which to examine directly the discrete transcription products from ribosomal protein promoters, and to study promoter function and mRNA metabolism in vivo.

Bacterial Proteins↗
PubMed1979

Suppressive effect of pentagastrin on pituitary-adrenocortical secretion.

The effect of pentagastrin on the pituitary-adrenocortical secretion was examined in male rats. In the morning the intraperitoneal injection of this peptide produced a slight, but significant, decrease in the plasma corticosterone levels, but it had no effect on the evening rise due to circadian periodicity and the stress-induced elevation of the plasma corticosterone level. Following intracerebroventricular administration of pentagastrin, plasma corticosterone tended to decrease and in in vitro incubation of rat pituitary tissue the addition of pentagastrin elicited a suppressive effect on the ACTH release from the tissue into the medium. It was suggested that gastrin-like peptide might control the secretion of ACTH.

Adrenocorticotropic Hormone↗
PubMed1979

Study on trace impurity elements in highly purified iron and aluminum by neutron activation analysis.

Activation analysis was carried out on the purified iron and aluminum to study the behavior of trace impurities on purification process, and to estimate the purity of the purified samples. Thermal neutrons with high Cd ratio through D2O column or graphite column were used for the activation of samples to reduce the interference effects by fast neutrons, the reactions, (n, p) or (n, a), from matrix elements. On the zone refined aluminum, the segregation of impurity elements was cleary observed. In the case of iron, decrease of impurity content was confirmed on superposing the various purification processes.

Aluminum↗
PubMed1979

Five patients with nonalcoholic diabetic cirrhosis.

Five nonalcoholic diabetic women were clinically and histologically verified as having micronodular cirrhosis. In this series all the patients were over 50 years of age, and showed obesity, hyperglycemia, enlarged liver and mild abnormalities of liver function tests. The histological findings differed from hepatitic cirrhosis. In two patients serial biopsies confirmed development of cirrhosis from centrilobular necrosis.

Aged↗
PubMed1978

Membrane surface potential and the reactivity of the system II primary electron acceptor to charged electron carriers in the medium.

A hypothesis is proposed to explain the changes in the apparent rate constant for the reaction between the primary electron acceptor of System II situated in the thylakoid membrane and the artificial electron acceptors added in the medium. Dark oxidation rate of the primary acceptor by artificial electron acceptors was monitored by measuring the induction of chlorophyll fluorescence in the presence of an electron transport inhibitor, 3-(3',4'-dichlorophenyl)-1,1-dimethylurea, in spinach chloroplasts. The apparent rate constant for the oxidation changed widely when the medium pH or salt concentrations were varied, or ionic detergents were added. The change was quantitatively ascribed (1) to the change in the local concentration of electron acceptors at the thylakoid surface due to the electrical potential difference between the surface and the bulk aqueous phase (Gouy-Chapman diffuse double layer theory) and (2) to the situation whereby the apparent rate constant is determined with respect to concentration in the bulk phase. Values for the surface potential in the vicinity of System II were estimated from the change in the apparent rate constant under various conditions. The results closely agreed with those obtained previously from the rate constant of the dark step of the System II-dependent Hill reaction with ferricyanide (Itoh, S. (1978) Plant Cell Physiol. 19, 149--166). Application of the hypothesis to various reactions between the added ionic reagents and the endogenous components in the membrane or between the endogenous components situated in different parts of the membrane is discussed.

Chloroplasts↗
PubMed1978

[Postnatal development of adrenocortical circadian rhythm in neonatally cortisol- and estriol-treated rats (author's transl)].

The effect of a single neonatal administration of cortisol and estriol on the development of the adrenocortical circadian rhythm was investigated in immature rats. In normal control rats of both sexes, the plasma corticosterone rhythm was discernible on day 21. In male rats the adult pattern was observed on day 28, but in females as the plasma corticosterone level elevated progressively during puberty, the rhythm increased in amplitude and the adult pattern was established at 8 weeks of age. In neonatally cortisol-treated rats, the plasma corticosterone rhythm appeared at 4 weeks of age, but the plasma level was significantly lower than that of the controls until 6 weeks and attained a level similar to the controls at 8 weeks. Neonatally estriol-treated rats exhibited the rhythm as early as 2 weeks of age, but this was temporary. It disappeared at 3 weeks and reappeared a 4 weeks. Although 5-week-old males showed normal rhythm as seen in the controls, in females the plasma corticosterone level remained low for weeks and approached the control level at 8 weeks of age. The development of circadian periodicity of adrenal corticosterone content almost paralleled that of plasma corticosterone not only in the controls but also in steroid-treated groups, but the rhythm was occasionally equivocal. In neonatally estriol-treated rats, stress response of plasma and adrenal corticosterone to ether was similar to that of the controls, but the response to exposure to a strange environment was significantly small.

Adrenal Cortex↗