PubMed Health⌕ Search

Biomedical subjects

K Shimazaki

Publications and source records attributed to K Shimazaki.

At least 127 records · Page 7Linked to original sources
PubMed1989

Calvin-Benson Cycle Enzymes in Guard-Cell Protoplasts from Vicia faba L: Implications for the Greater Utilization of Phosphoglycerate/Dihydroxyacetone Phosphate Shuttle between Chloroplasts and the Cytosol.

Activities of Calvin-Benson cycle enzymes were found in protoplasts of guard cells from Vicia faba L. The activities of NADP-glyceraldehyde-3-phosphate dehydrogenase (NADP-GAPD) and ribulose-1,5-bisphosphate carboxylase (RuBPC) were 2670 and 52 micromoles per milligrams chlorophyll per hour, respectively. Activities of NADP-GAPD and RuBPC in guard cells were increased by red light illumination, and the light activations were inhibited completely by 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), an inhibitor of photosystem II. Enzymes related to the Calvin-Benson cycle such as 3-phosphoglycerate kinase (PGAK), triose phosphate (TP) isomerase, and fructose-1,6-bisphosphatase (FBPase) were shown to be present in guard-cell chloroplasts. From these results, we conclude that the photosynthetic carbon reduction pathway is present in guard-cell chloroplasts of Vicia faba. We compared these enzyme activities in guard cells with those in mesophyll cells. The activities of NADP-GAPD and PGAK were more than several-fold higher and that of TP isomerase was much higher in guard-cell chloroplasts than in mesophyll chloroplasts. In contrast, activities of RuBPC and FBPase were estimated to be roughly half of those in mesophyll chloroplasts. High activities of PGAK, NAD-GAPD, and TP isomerase were found in fractions enriched in cytosol of guard cells. Illumination of guard-cell protoplasts with red light increased the cellular ATP/ADP ratio from 5 to 14. These results support the interpretation that guard cells utilize a shuttle system (e.g. phosphoglycerate [PGA]/dihydroxyacetone phosphate [DHAP] shuttle) for an indirect transfer of ATP and reducing equivalents from chloroplasts to the cytosol.

Journal Article↗
PubMed1989

Ribulosebisphosphate carboxylase activity and photosynthetic o(2) evolution rate in vicia guard-cell protoplasts.

Activities of ribulose-1,5-bisphosphate carboxylase and rates of photosynthetic O(2) evolution were measured in guard-cell and mesophyll protoplasts from Vicia faba. The ribulose-1,5-bisphosphate carboxylase activity of guard-cell protoplasts was 30% of that of mesophyll protoplasts; however, the O(2) evolution rate was 3 times higher in guard-cell protoplasts than in mesophyll protoplasts on a chlorophyll basis. When the dark-adapted, guard-cell protoplasts were illuminated by red light, O(2) was evolved with an induction period, which became shorter when the protoplasts were reilluminated. High activity of irreversible NADP-glyceraldehyde-3-phosphate dehyrogenase was found in guard-cell protoplasts. Several lines of evidence revealed that there was virtually no contamination by mesophyll cells in guard-cell preparations. These results indicate that guard cells fix CO(2) photosynthetically and imply that the cells utilize a considerable proportion of reducing equivalents from water for reactions other than CO(2) fixation.

Journal Article↗
PubMed1989

Soluble complex formation of bovine immunoglobulin G2 with staphylococcal protein A studied by gel filtration chromatography.

The binding property of bovine IgG2 to staphylococcal Protein A was investigated by the methods of gel filtration chromatography and affinity chromatography. High performance gel filtration chromatography was carried out using TSK gel G3000SW and G2000SW columns, and immobilized Protein A column was used for affinity chromatography. Although bovine IgG2 did not form any precipitin lines with Protein A by double diffusion method on agar gel, IgG2 could bind to immobilized Protein A column. Moreover, by gel filtration chromatography, peaks of the complex between bovine IgG2 and Protein A were observed in addition to the IgG2 monomer peak. Thus, it is concluded that bovine IgG2 interacts with staphylococcal Protein A and forms "soluble complexes". Carbethoxylated IgG2 lost its affinity to Protein A indicating that histidyl residues in IgG2 is essential for the binding to Protein A.

Animals↗
PubMed1989

[Three cases of pernicious anemia complicated with chronic thyroiditis--the evaluations of immunological abnormalities].

We reported 3 patients with pernicious anemia associated with chronic thyroiditis and evaluated their immunological abnormalities in this paper. Two patients were females and another was male. They were all advanced in age. Levels of gammaglobulin including IgG was elevated in patients' sera. Values of complement components were within normal ranges. Although organ specific autoantibodies against intrinsic factors, parietal cells and thyroidal tissue antigens were detected, organ non-specific autoantibodies such as anti-DNA and/or anti-ENA antibodies were negative in the patients' sera. Percentage of T cells in peripheral blood remained within normal ranges. However, ratio of helper T/suppressor T cells was reduced considering patients' age. Moreover, Mantoux tests were negative in all of three patients. These results suggested that impaired cellular immunity, particularly imbalance of T cell subsets, caused by senescence, simultaneously induced pernicious anemia and chronic thyroiditis in these patients.

Aged↗
PubMed1988

An autoradiographic study of binding of iodinated spider toxin to lobster muscle.

Distribution of the binding sites of Joro spider toxin (JSTX), a specific inhibitor of the glutamate receptors in the crustacean neuromuscular synapse, was studied by using autoradiography. JSTX was synthesized and made radioactive by conjugation with iodine-125. 125I-JSTX irreversibly blocked the excitatory postsynaptic potentials of the lobster neuromuscular synapse in a similar manner as the natural spider toxin. Light microscopic autoradiography of 125I-JSTX treated muscle showed sporadic aggregates of reduced silver grains on the surface of muscles. Electron microscopy of adjoining ultrathin sections revealed that these spots corresponded to the fraction of sarcolemma apposed to axonal terminals with or without synaptic junctional profiles. This finding gives morphological support to the formulation that JSTX binds to the glutamate receptor-ion channel molecules.

Animals↗
PubMed1988

Color development upon reaction of ferric ion with the toxin JSTX, a glutamate receptor blocker present in the venom gland of the spider Nephila clavata (Joro spider).

A spider toxin, JSTX, derived from Nephila clavata, which blocks glutamate receptor was found to react with Fe3+. Mechanism of the coloration may be chelate formation since the green color completely faded upon the addition of EDTA. The colored JSTX significantly lost its neurophysiological activity. This unique coloration may be useful for not only detecting specific blockers of the glutamate receptor in spider venom but also for characterizing the glutamate receptor.

Animals↗
PubMed1988

Response of spinach and kidney bean plants to nitrogen dioxide.

Different responses of spinach and kidney bean plants to various concentrations of NO(2) in the light and in the dark were shown. Spinach is more resistant than NO(2) than kidney bean. It is not only due to its greater tolerance to NO(2)(-) accumulated in leaves, but also to its stronger ability to metabolize NO(2)(-). The injury of spinach induced by the exposure to high concentration NO(2) in the light was not caused by the accumulation of NO(2)(-), but concerned the large amount of accumulated NH(3). The primary causes of NH(3) accumulation were that the activity of nitrite reductase was not affected by the fumigation on the one hand, and the activities of glutamine synthetase and glutamate synthase were inhibited on the other.

Journal Article↗
PubMed1988

Calcium-binding lysozymes.

It was found that pigeon lysozyme binds one calcium ion, as does equine lysozyme. The protein was eluted with equimolar calcium ions from a Bio-Gel P-60 column. The binding constants of equine and pigeon lysozymes were determined to be 2 x 10(6) and 1.6 x 10(7) M-1, respectively, in 0.1 M KCl at pH 7.1 and 20 degrees C. During evolution the gene of calcium-binding lysozyme is deduced to be separated from that of non-calcium-binding lysozyme by gene duplication before splitting of avian and mammalian lineages, from their amino-acid sequences. It is assumed that the alpha-lactalbumin might have evolved from calcium-binding lysozyme.

Animals↗
PubMed1987

The calcium-binding property of equine lysozyme.

It was found that equine lysozyme binds one Ca2+. It was eluted with equimolar Ca2+ from a Bio-Gel P-4 column. Human lysozyme did not behave similarly. Equine lysozyme is concluded to be a calcium metallo-protein like alpha-lactalbumin, which is a homologue of hen egg white lysozyme.

Animals↗
PubMed1987

Experimental study on the repair of full thickness articular cartilage defects: effects of varying periods of continuous passive motion, cage activity, and immobilization.

In order to clarify the dose/response characteristics of continuous passive motion (CPM), the repair response of full thickness articular cartilage defects was studied in a rabbit model. The following combinations of CPM and immobilization (Imm) were utilized: CPM, 24 h/day; CPM, 8 h/day and Imm, 16 h/day; CPM, 2 h/day and Imm 22 h/day; Imm 24 h/day; and normal cage activity. These regimens were used only in the initial week and then all rabbits were permitted to move freely in their cages, except for a sixth Imm-CPM group that was kept immobilized in the initial week and then CPM 24 h/day for another week. The CPM 24 h/day and the CPM 8 h/day groups (groups 1 and 4, respectively) showed better repair than the other groups, i.e., better surface congruity, larger positive Safranin-O staining area, and greater number of chondrocytes in the repair tissue. The CPM 2 h/day group (group 3), however, showed only slightly better repair than the Imm group (group 4). The CPM following immobilization was not effective to overcome the harmful effect of immobilization. We conclude that in the present model, CPM for 8 or 24 h/day is effective for adequate cartilage repair even with some component of immobilization. Its application should be at least 8 h/day. On the contrary, if CPM is delayed for a week following immobilization, the effect of CPM on cartilage will be reduced.

Animals↗
PubMed1987

Dumbbell-shaped spinal extradural hemangioma.

A case of recurrent extradural cavernous hemangioma is presented. In contrast to secondary extension of a vertebral hemangioma to the epidural space, pure epidural hemangioma is rare. The location of this case was at the level of the 7th thoracic vertebra, and the tumor showed unusual dumbbell-like growth through an intervertebral foramen. The rarity of these lesions, as well as their clinical and radiological features, the diagnostic procedure, and the treatment are discussed.

Hemangioma, Cavernous↗
PubMed1987

Red Light-Dependent CO(2) Uptake and Oxygen Evolution in Guard Cell Protoplasts of Vicia faba L.: Evidence for Photosynthetic CO(2) Fixation.

Suspensions of dark-adapted guard cell protoplasts of Vicia faba L. alkalinized their medium in response to irradiation with red light. The alkalinization peaked within about 50 minutes and reached steady state shortly thereafter. Simultaneous measurements of O(2) concentrations and medium pH showed that oxygen evolved in parallel with the red light-induced alkalinization. When the protoplasts were returned to darkness, they acidified their medium and consumed oxygen. Both oxygen evolution and medium alkalinization were inhibited by 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). In photosynthetically competent preparations, light-dependent medium alkalinization is diagnostic for photosynthetic carbon fixation, indicating that guard cell chloroplasts have that capacity. The striking contrast between the responses of guard cell protoplasts to red light, which induces alkalinization, and that to blue light, which activates proton extrusion, suggests that proton pumping and photosynthesis in guard cells are regulated by light quality.

Journal Article↗
PubMed1987

Image analysis of chlorophyll fluorescence transients for diagnosing the photosynthetic system of attached leaves.

A new image instrumentation system for quantitative analysis of the rapid change in intensity of chlorophyll fluorescence during dark-light transition (CFI, chlorophyll fluorescence induction), which is a sensitive indicator of the various reactions of photosynthesis, was developed and its performance was evaluated. This system made it possible to resolve CFI at any small leaf area (about 1 square millimeter) of a whole leaf when the plant was illuminated by blue-green light at more than 50 micromoles photons per square meter per second. In order to test the usefulness of this system, we applied it to analyze the effect of SO(2) on photosynthetic apparatus in attached sunflower leaves. Dynamic CFI imaging over the whole single leaf, where there was no visible injury, indicated not only the local changes in photosynthetic activity but also the site of inhibition in photosynthetic electron transport system in chloroplasts. The new instrumentation system will be useful for the analytical diagnosis of various stress-actions on plants in situ.

Journal Article↗