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Biomedical subjects

T Yagi

Publications and source records attributed to T Yagi.

At least 541 records · Page 30Linked to original sources
PubMed1988

Involvement of prostaglandin E-like material in the purgative action of rhein anthrone, the intraluminal active metabolite of sennosides A and B in mice.

Intracaecal administration of rhein anthrone, the intraluminally active metabolite of sennosides A and B, to mice quickly induced severe diarrhoea. Pretreatment with the prostaglandin (PG) biosynthesis inhibitor, indomethacin, and PGE2 antagonist, SC-19220, prevented the onset of diarrhoea induced by rhein anthrone, but the PGE2 antagonist polyphoretin phosphate (PPP) showed only a weak inhibitory effect. Rhein anthrone stimulated the production of PGE-like material only in the colon and its large intestinal propulsive activity was depressed by indomethacin and SC-19220, but not by PPP which suggests that the release of PGE-like material has some role in its purgative action.

Animals↗
PubMed1988

The axon terminal of goldfish retinal horizontal cells: a low membrane conductance measured in solitary preparations and its implication to the signal conduction from the soma.

1. Mechanical dissociation of the enzyme-treated goldfish retina yielded somata and axon terminals of horizontal cells. The membrane properties of these solitary axon terminals were investigated using the whole-cell patch-clamp technique. 2. Axon terminals had a large input resistance, comparable to the seal resistance (approximately 30 G omega). Most axon terminals (greater than 80%) showed a nearly linear current-voltage relation between -60 and +10 mV, where the slope conductance was as small as 5 muS/cm2. Some axon terminals showed a shallow negative slope conductance in the same potential range. 3. The membrane current consisted of two components: transient and sustained. The transient component was carried by sodium ions, and the sustained component was a mixture of calcium and potassium currents. The sodium current (INa) was activated by depolarization of beyond -45 mV and was maximal (approximately 60 pA) at -10 mV. It was blocked by 5 microM tetrodotoxin and disappeared in Na+-free medium. The maximum amplitude of INa was less than 10% of INa of the soma. 4. A small calcium current (less than 6 pA) was isolated in a small proportion of cells, with an amplitude approximately 5% of the calcium current evoked in the soma under the identical recording conditions. 5. A small amount of potassium current through the anomalous rectifier was induced in the axon terminal when the membrane potential was below -60 mV. Its conductance was 15-20 muS/cm2, only 1/20 of the estimate in the soma. Other types of potassium currents were not detected. 6. It is concluded that the soma and the axon terminal have a similar set of membrane currents, but the specific membrane conductance of the axon terminal is extremely low. The signal conductivity from soma to axon terminal was assessed using a passive cable model together with numerical values obtained from the present experiments. Although the membrane conductance of the connecting axon was not measurable directly, the calculation strongly suggests that low conductance of the axon terminal membrane minimizes the leakage of signals arriving electrotonically through the thin connecting axon, even if the membrane conductance of the axon was overestimated as being identical to the soma membrane. 7. These results can explain why light-evoked responses recorded from the axon terminal are similar in amplitude as well as in waveform to those recorded from the soma, despite the lack of direct inputs from photoreceptors.

Animals↗
PubMed1988

Histochemical demonstration of carbonic anhydrase activity in the odontogenic cells of the rat incisor.

Aldehyde-fixed, EDTA-demineralized frozen sections of the rat maxillary incisor were histochemically stained for carbonic anhydrase activity, by use of Hansson's method. Intense staining was observed in the odontoblasts, all types of epithelial cells of enamel organ in the maturation zone, cementoblasts, and the cells of the lingual dental sac. Less intense but consistent staining was observed in all types of epithelial cells of odontogenic origin directly facing the pulp and pulp cells adjacent to the odontoblast cell layer in the apical part of the pulp, and was considered due to the carbonic anhydrase-catalyzed reaction. Staining of these cells was completely inhibited by heat pretreatment (120 degrees C, 30 min), 10(-6) mol/L acetazolamide in the incubation medium, incubation by continuous immersion under the liquid surface, and omission of the substrate, NaHCO3. The dentin also exhibited heavy staining which was inhibited by the heat pre-treatment. However, this dentinal staining resisted the inhibition by 10(-3) mol/L acetazolamide and was not inhibited by incubation by continuous immersion or incubation without the substrate NaHCO3. The dentinal staining was thus judged to have been due to non-enzymatic cobalt precipitation.

Animals↗
PubMed1988

Neurotological findings in Bell's palsy and Hunt's syndrome.

Neurotological findings were analysed in 23 patients with Bell's palsy and in 25 patients with Hunt's syndrome. The incidence and extent of the auditory and vestibular pathology was high in Hunt's syndrome. Although patients had no subjective symptoms related to the auditory and/or vestibular pathology in the Bell's palsy cases, about one-third of the patients showed abnormal findings upon neurotological examination. Differentiating these two diseases is therefore considered difficult by means of neurotological examination in the same way as by serological testing as has been reported by other investigators.

Audiometry, Pure-Tone↗
PubMed1988

The evaluation of glucagon infusion algorithms for a counterregulatory system in artificial endocrine pancreas.

As counterregulatory system of artificial endocrine pancreas, glucagon infusion algorithm has been developed and its usefulness has been examined in pancreatectomized dogs and a pancreatectomized diabetic patient. Glucagon infusion rate (G1nIR(t)) was determined depending on proportional plus derivative action to blood glucose concentration (BG(t] with the time delay (tau) to start infusion as follows. G1nIR(t) = Gp(BGp- BG(t-tau)) + Gd(-dBG(t-tau)) + Gc where BGp is the projected value of blood glucose concentration, Gp, and Gd are the coefficients and Gc is the constant for basal glucagon supplement. Glucagon infusions based only on proportional action (Gp/Gd/Gc/tau) = (0.2/0/0.4/10 or 0.4/0/0.4/10) failed in simulating the pattern of blood glucose or glucagon response seen in normal dogs. Glucagon infusion based on proportional plus derivative action (Gp/Gd/Gc/tau = 0.2/0.4/0.4/10) successfully mimicked the pattern of blood glucose concentration and plasma glucagon profile seen in normal dogs. This glucagon infusion algorithm has been applied to control insulin-induced hypoglycemia in a pancreatectomized patient with the same infusion parameters. Hypoglycemia was recovered to normoglycemia in 80 min and the plasma glucagon patterns showed no significant difference from those in healthy volunteers. These data indicate that glucagon infusion algorithm thus developed is effective to render hypoglycemia to normoglycemia and mimic plasma glucagon response seen in normal subjects.

Algorithms↗
PubMed1988

[Efficacy and problems of radio- and chemo-combination therapy for malignant bone tumors].

In this study we reviewed cases of osteosarcoma, malignant lymphoma of bone and Ewing's sarcoma. Historically, osteosarcoma was unresponsive to chemotherapy. Most patients were treated by radiation or amputation alone and 80% of them died from pulmonary metastasis within 2 years. Five-year survival rate was 13%. Introduction of ADM, HD-MTX and CDDP improved dramatically the prognosis of these cases. Five-year survival rate was 60%. On the other hand, 11 cases of malignant lymphoma of bone and 4 cases of Ewing's sarcoma were treated by radiation with no local recurrence. VEPA or CHOP chemotherapy was used for the former with a five-year survival rate of 45%. For the latter, T-11 protocol (Rosen) was applied, and all patients survive with no metastasis. Other organ injuries circulatory disturbance, bone necrosis and growth-disturbance of bone in radiotherapy, myocardiopathy caused by ADM and renal toxicity of CDDP are all problematic.

Adolescent↗
PubMed1988

Electron microscopic observations on the fate of hypertrophic chondrocytes in condylar cartilage of rat mandible.

The present study focused on the hypertrophic cell zone and the adjacent region of primary spongiosa in the mandibular condylar cartilage in growing rats (3 to 7 weeks old). In this cartilage, chondrocytes were not arranged in columns, and there was no clear distinction between longitudinal and transverse septum. The hypertrophic chondrocytes were not surrounded entirely by calcified matrix, and capillaries were in close contact with cartilage cells. The staining intensity of the pericellular matrix decreased in the lower hypertrophic cell zone in comparison with that in the upper part of the hypertrophic cell zone. Electron microscopic examinations indicated that the lowest hypertrophic cells contained lysosomes and pinocytotic vesicles. Some hypertrophic chondrocytes appeared to have been released from their lacunae and were observed in the region of the primary spongiosa. Hence it is suggested that the lowest hypertrophic chondrocytes in the rat mandibular condyle do not die but are released from their lacunae into the bone marrow. Further study is needed to determine whether or not these cells do indeed become osteoblasts and/or chondroclasts.

Animals↗
PubMed1987

EPR characterization of the iron-sulfur clusters in the NADH: ubiquinone oxidoreductase segment of the respiratory chain in Paracoccus denitrificans.

The physicochemical properties of the iron-sulfur clusters present in the NADH:ubiquinone oxidoreductase of Paracoccus denitrificans have been examined in the cytoplasmic membrane particles by redox potentiometry and EPR spectroscopy. Analogous to the iron-sulfur clusters present in the mitochondrial NADH: ubiquinone oxidoreductase, we have found two binuclear and three tetranuclear EPR detectable iron-sulfur clusters, namely, N-1a, N-1b, N-2, N-3, and N-4. In the bacterial system, the two binuclear clusters differ in line shape and in Em values; the cluster with more rhombic symmetry (gx,y,z = 1.918, 1.937, 2.029) has the Em7.0 value of -150 while the almost axial one (gx,y,z = 1.929, 1.941, 2.019) has Em7.0 of -270 mV. The Em of the former cluster is pH dependent (-60 mV/pH) as in the case of mammalian N-1a while the latter is pH independent as is the mammalian cluster N-1b. The pH-dependent P. denitrificans [2Fe-2S] cluster, which we have labeled N-1a, has an Em7.0 as high as that of N-2, in contrast to the mammalian N-1a. Thus N-1a is reducible with a physiological reductant, NADH in this bacterial system. The Em of the cluster N-2 is also pH dependent (Em7.0 = -130 mV) with a pK value near 7.7. The Em values of all other clusters exhibit no pH dependence as in the case of their mammalian counterparts. We have found that the cluster N-1a is the most labile component among the five iron-sulfur clusters and may give rise to variable relative spin concentrations and extremely low Em values due to the facile modifications of the microenvironment of the cluster. The P. denitrificans NADH:ubiquinone oxidoreductase provides a unique and useful site I model system where redox composition is similar to the mitochondrial enzyme but with fewer numbers of polypeptides (Yagi, T. (1986) Arch. Biochem. Biophys. 250, 302-311).

Animals↗
PubMed1987

Inhibition of NADH-ubiquinone reductase activity by N,N'-dicyclohexylcarbodiimide and correlation of this inhibition with the occurrence of energy-coupling site 1 in various organisms.

The NADH-ubiquinone reductase activity of the respiratory chains of several organisms was inhibited by the carboxyl-modifying reagent N,N'-dicyclohexylcarbodiimide (DCCD). This inhibition correlated with the presence of an energy-transducing site in this segment of the respiratory chain. Where the NADH-quinone reductase segment involved an energy-coupling site (e.g., in bovine heart and rat liver mitochondria, and in Paracoccus denitrificans, Escherichia coli, and Thermus thermophilus HB-8 membranes), DCCD acted as an inhibitor of ubiquinone reduction by NADH. By contrast, where energy-coupling site 1 was absent (e.g., in Saccharomyces cerevisiae mitochondria and Bacillus subtilis membranes), there was no inhibition of NADH-ubiquinone reductase activity by DCCD. In the bovine and P. denitrificans systems, DCCD inhibition was pseudo first order with respect to incubation time, and reaction order with respect to inhibitor concentration was close to unity, indicating that inhibition resulted from the binding of one inhibitor molecule per active unit of NADH-ubiquinone reductase. In the bovine NADH-ubiquinone reductase complex (complex I), [14C]DCCD was preferentially incorporated into two subunits of molecular weight 49,000 and 29,000. The time course of labeling of the 29,000 molecular weight subunit with [14C]DCCD paralleled the time course of inhibition of NADH-ubiquinone reductase activity.

Animals↗
PubMed1987

Single crystals of hydrogenase from Desulfovibrio vulgaris Miyazaki F.

The hydrogenase solubilized from the particulate fraction from Desulfovibrio vulgaris Miyazaki F (IAM 12604) has been crystallized. Although the solubilized hydrogenase purified by the previous method (Yagi, T., Kimura, K., Daidoji, H., Sakai, F., Tamura, S., and Inokuchi, H. (1976) J. Biochem. (Tokyo) 79,661-671) revealed a single band upon disc electrophoresis, it could not be crystallized. The apparently homogeneous hydrogenase has been separated into three components of similar molecular weights by high performance liquid chromatography on DEAE-Toyopearl. Each hydrogenase component was successfully crystallized by means of the vapor diffusion method with polyethylene glycol or 2-methyl-2,4-pentanediol as a precipitating agent. Seeding procedure is necessary to grow an x-ray grade crystal. Preliminary x-ray experiments reveal that crystals grown from one component are in space group of P2(1)2(1)2(1) with a = 102.1(1), b = 126.8 (3), and c = 66.9(1) A. The unit cell volume of 8.66 X 10(5) A3 suggests that it contains one molecule/asymmetric unit (Vm = 2.43). The crystals grown from another component are in the same space group with a = 99.6(1), b = 126.8(3), c = 66.9(1) A, and the unit cell volume is 8.45 X 10(5) A3 (Vm = 2.37). The crystals diffract more than 2.5 A and are suitable for complete crystal analysis. Up to 4 A resolution native data have been collected on a diffractometer.

Chromatography, High Pressure Liquid↗