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Biomedical subjects

M Kitajima

Publications and source records attributed to M Kitajima.

At least 397 records · Page 22Linked to original sources
PubMed1981

Plasma glucose concentrations of whole blood, as determined with a multilayer-film analytical element.

A new type of multilayer film analytical element--consisting of a spreading layer, a blocking layer, an enzymic reagent layer, and a transparent layer--has been developed for blood glucose determination. After a spot of whole blood is dropped on the film, the plasma glucose concentration is determined in 6 min without further manipulations. Precise measurement of sample volume spotted on the film is not necessary for good results, nor is knowledge of the hematocrit in the range 10-46%. The minimum concentration of glucose detectable by this method is 100 mg/L. The coefficients of variation, within-run and between-run, were all less than 2.5% for 800-4000 mg/L glucose concentrations. Macromolecules and hydrophobic substances in blood did not interfere. This method seems suitable for emergency use, especially.

Blood Glucose↗
PubMed1978

Gastric mucosal lesions after burn injury: relationship to H+ back-diffusion and the microcirculation.

Rats were subjected to a 30% body surface area full-thickness burn. Two hours after injury, 93% of animals had gastric mucosal erosions. At 5 hours this increased to 100%, but at 24 and 72 hours, lesions were fewer and less severe. Histologic study suggested that lesions noted at 24 and 72 hours represented erosions formed earlier. No mucosal abnormalities were noted in control rats. A causal relationship between mucosal ischemia and the development of erosions is suggested by the presence of A-V shunts at 2 and 5 hours only. Significant increases in H+ back-diffusion and protein leakage into the gastric lumen at 2 and 5 hours also implicated changed mucosal permeability in the etiology of erosions. The return of H+ back-diffusion to control values at 24 and 72 hours, when lesions were still present, appears to contradict the theory that permeability changes are secondary to erosion formation.

Animals↗
PubMed1976

Microencapsulation of chloroplast particles.

Chloroplast and photosystem I particles were encapsulated in small spheres (about 20 mum diameter) with an artificial membrane built up by cross-linking amino groups of protamine with toluenediisocyanate. The artificial membrane was permeable to small substrate and product molecules but not to soluble proteins. Photosystem I activity was retained by the encapsulated chloroplast particles. Washed photosystem I particles were encapsulated with the soluble proteins, ferredoxin, and ferredoxin-NADP oxidoreductase, and the microcapsules photoreduced NADP using ascorbate plus dichlorophenolindophenol as the electron donor. The photosystem I particles were also encapsulated with hydrogenase from Chromatium and a very low rate of photoevolution of hydrogen was obtained. The results show that chloroplast membrane fragments can be encapsulated with soluble proteins that couple transfer reactions to the primary photochemical apparatus.

Journal Article↗
PubMed1975

Excitation spectra for photosystem I and photosystem II in chloroplasts and the spectral characteristics of the distributions of quanta between the two photosystems.

The parameters listed in the title were determined within the context of a model for the photochemical apparatus of photosynthesis. The fluorescence of variable yield at 750 nm at -196 degrees C is due to energy transfer from Photosystem II to Photosystem I. Fluorescence excitation spectra were measured at -196 degrees C at the minimum, FO, level and the maximum, FM, level of the emission at 750 nm. The difference spectrum, FM-FO, which represents the excitation spectrum for FV is presented as a pure Photosystem II excitation spectrum. This spectrum shows a maximum at 677 nm, attributable to the antenna chlorophyll a of Photosystem II units, with a shoulder at 670 nm and a smaller maximum at 650 nm, presumably due to chlorophyll a and chlorophyll b of the light-harvesting chlorophyll complex. Fluoresence at the FO level at 750 nm can be considered in two parts; one part due to the fraction of absorbed quanta, alpha, which excites Photosystem I more-or-less directly and another part due to energy transfer from Photosystem II to Photosystem I. The latter contribution can be estimated from the ratio of FO/FV measured at 692 nm and the extent of FV at 750 nm. According to this procedure the excitation spectrum of Photosystem I at -196 degrees C was determined by subtracting 1/3 of the excitation spectrum of FV at 750 nm from the excitation spectrum of FO at 750 nm. The spectrum shows a relatively sharp maximum at 681 nm due to the antenna chlorophyll a of Photosystem I units with probably some energy transfer from the light-harvesting chlorophyll complex. The wavelength dependence of alpha was determined from fluorescence measurements at 692 and 750 nm at -196 degrees C. Alpha is constant to within a few percent from 400 to 680 nm, the maximum deviation being at 515 nm where alpha shows a broad maximum increasing from 0.30 to 0.34. At wavelengths between 680 and 700 nm, alpha increases to unity as Photosystem I becomes the dominant absorber in the photochemical apparatus.

Chloroplasts↗
PubMed1975

Energy transfer between photosystem II and photosystem I in chloroplasts.

A model for the photochemical apparatus of photosynthesis is presented which accounts for the fluorescence properties of Photosystem II and Photosystem I as well as energy transfer between the two photosystems. The model was tested by measuring at - 196 degrees C fluorescence induction curves at 690 and 730 nm in the absence and presence of 5mMMgCl2 which presumably changes the distrubution of excitation energy between the two photosystems. The equations describing the fluorescence properties involve terms for the distribution of absorbed quanta, alpha, being the fraction distributed to Photosystem I, and beta, the fraction to Photosystem II to Photosystem I, KT(II yields I). The data, analyzed within the context of the model, permit a direct comparison of alpha and kt(II yields I) in the absence (minus) and presence (+) of Mg-2+ :alpha minus/alpha-+ equals 1.2 and k-minus t)II yields I)/K-+T(II yields I) equal to 1.9. If the criterion that alpha + beta equal to 1 is applied absolute values can be calculated: in the presence of Mg-2+, alpha-+ equal to 0.27 and the yield of energy transfer, phi-+ t(II yields I) varied the presence of Mg-2+, alpha-+ equal to 0.27 and the yield of energy transfer, phi-+ t(II yields I) varied from 0.065 when the Photosystem II reaction centers were all open to 0.23 when they were closed. In the absence of Mg-2+, alpha-minus equal to 0.32 and phi t(II yields I) varied from 0.12 to 0.28. The data were also analyzed assuming that two types of energy transfer could be distinguished; a transfer from the light-harvesting chlorophyll of Photosystem II to Photosystem I, kt(II yields I), and a transfer from the reaction centers of Photosystem II to Photosystem I, kt(II yields I). In that case alpha-minus/alpha+ equal to 1.3, k-minus t(II yields I)/k+ t(II yields I)equal to 1.3 and k-minus t(II yields I) equal to 3.0. It was concluded, however, that both of these types of energy transfer are different manifestations of a single energy transfer process.

Chloroplasts↗
PubMed1975

Quenching of chlorophyll fluorescence and primary photochemistry in chloroplasts by dibromothymoquinone.

The quenching action of dibromothymoquinone on fluorescence and on primary photochemistry was examined in chloroplasts at minus 196 degrees C. Both the initial (F0) and final (FM) levels of fluorescence as well as the fluorescence of variable yield (FV equals FM minus FO) were quenched at minus 196 degrees C to a degree which depended on the concentration of dibromothymoquinone added prior to freezing. The initial rate of photoreduction of C-550 at minus 196 degrees C, which was assumed to be proportional to maximum yield for primary photochemistry, phipo, was also decreased in the presence of dibromothymoquinone. Simple theory predicts that the ratio FV/FM should equal phipo. Excellent agreement was found in a comparison of relative values of phipo with relative values of FV/FM at various degrees of quenching by dibromothymoquinone. These results are taken to indicate that FO and FV are the same type of fluorescence, both emanating from the bulk chlorophyll of Photosystem II. Dibromothymoquinone appears to create quenching centers in the bulk chlorophyll of Photosystem II which compete with the reaction centers for excitation energy. The rate constant for the quenching of excitation energy by dibromothymoquinone is directly proportional to the concentration of the quencher. Rate constants for the de-excitation of excited chlorophyll molecules by fluorescence, kF, by nonradiative decay processes, kD, by photochemistry, kP, and by the specific quenching of dibromothymoquinone, kQ, were calculated assuming the absolute yield of fluorescence at FO to be either 0.02 or 0.05.

Bromine↗
PubMed1975

Fluorescence quenching in photosystem II of chloroplasts.

A simple photochemical model for the photosynthetic units of Photosystem II based on first-order rate constants for de-excitation of excited chlorophyll molecules is presented in the form of equations which predict the yields of fluorescence (i.e. at the FO level, at the maximal FM level and the fluorescence of variable yield, FV equals FM minus FO). Two types of quenching mechanisms are recognized: (1) increasing nonradiative decay processes in the bulk chlorophyll by creating quenching centers which complete with the reaction centers for the excitation energy (this mechanism quenches both FO and FV) and (2) increasing nonradiative decay of the excited reaction center chlorophyll (this mechanism quenches FV but not FO). Quenching in the bulk chlorophyll preserves the relationship that Fv/FM is equal to the maximum yield of photochemistry; quenching at the reaction center chlorophyll decreases FV/FM substantially (since FV is quenched specifically) but may have very little effect on the yield of photochemistry. Estimates are made of the relative magnitudes of the rate constants for de-excitation of the excited reaction center chlorophyll by photochemistry, kp, by nonradiative decay processes, kd, and by energy transfer back to the bulk chlorophyll, kt. Fluorescence is assumed to emanate only from the bulk chlorophyll. Energy transfer from Photosystem II to Photosystem I may occur from either the excited bulk chlorophyll or from the excited reaction center chlorophyll. The model is valid for any degree of energy transfer between Photosystem II units.

Bromine↗