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T Asakura

Publications and source records attributed to T Asakura.

At least 19 recordsLinked to original sources
PubMed1992

Histochemical demonstration of NADPH-diaphorase activity, a marker for nitric oxide synthase, in neurons of the rat pancreas.

To clarify the role of nitric oxide (NO) in the pancreas, we histochemically investigated NADPH-diaphorase, a marker for NO synthase, in the rat pancreas. NADPH-diaphorase activity was localized in the neurons and endothelium of vessels. The nerve fibers with NADPH-diaphorase activity were observed in both the exocrine and the endocrine pancreas associated chiefly with the vascular systems. Most nerve cell bodies (98.5%) within the pancreatic parenchyma showed strong activity for this enzyme. These results suggest that NO may participate in the hemodynamic control of the pancreas and in the neuronal regulation of pancreatic exocrine and endocrine functions.

Amino Acid Oxidoreductases↗
PubMed1992

A method for the calculation of protein alpha-CH chemical shifts.

The chemical shifts of C(alpha)H protons have been calculated for 9 proteins, based on coordinates taken from high-resolution crystal structures. Chemical shifts were calculated using ring-current shifts, shifts arising from magnetic anisotropies of bonds, and shifts arising from the polarizing effect of polar atoms on the C(alpha)H bond. The parameters used were refined iteratively to give the best fit to (experimental-random coil) shifts over the set of 9 proteins. A further small correction was made to the averaged Gly C(alpha)H shift. The calculated shifts match observed shifts with correlation coefficients varying between 0.45 and 0.86, with a standard deviation of about 0.3 ppm. The differences between calculated and observed shifts have been studied in detail, including an analysis of different crystal structures of the same protein, and indicate that most of the differences can be accounted for by small differences between the structure in solution and in the crystal. Calculations using NMR-derived structures give a poor fit. The calculations reproduce the experimentally observed differences between chemical shifts for C(alpha)H in alpha-helix and beta-sheet. Most of the differentiation in secondary-structure-dependent shifts arises from electric field effects, although magnetic anisotropy also makes a large contribution to the net shift. Applications of the calculations to assignment (including stereospecific assignment) and structure determination are discussed.

Carbon↗
PubMed1992

Cytochrome P450-mediated prostaglandin omega/omega-1 hydroxylase activities in porcine ciliary body epithelial cells.

The ocular hypotensive effect of topically applied prostaglandins (PGs) is well documented. Although PGs introduced in the posterior chamber accumulate in the anterior tissues (e.g. iris/ciliary complex), little is known about the metabolism of PGs by these tissues. We have recently found that non-pigmented epithelial (NPE) cells and pigmented epithelial (PE) cells are readily separated from porcine ciliary body and cytochrome P450-dependent xenobiotic metabolism is considerably higher in NPE cells than in PE cells. We have therefore investigated in this study the cytochrome P450-mediated PG omega/omega-1 hydroxylase activities of porcine ciliary epithelial cells. The NPE cells show about three times higher activities than do PE cells; the NPE cells, in fact, demonstrate the highest PG omega/omega-1 hydroxylase activities among different ocular tissues. Both omega and omega-1 hydroxylases show broad substrate specificities and hydroxylate PGA1, A2, E1, E2, and lauric acid. The omega/omega-1 hydroxylase activities of NPE and PE, as determined with PGA2 and lauric acid as substrates, are enhanced or induced by treatment of primary cultures of the individual epithelial cells with clofibrate, both activities reaching maximum levels within 48 hr of induction. The induced activities are inhibited almost completely by cycloheximide and actinomycin D. The omega/omega-1 hydroxylase activities of both NPE and PE cells require NADPH and molecular oxygen, are associated with the microsomal fraction, respond to inducers such as clofibrate, and are inhibited by metyrapone and SKF525 A (inhibitors of P450 enzymes). These results support the suggestion that PG omega/omega-1 hydroxylations by NPE and PE are cytochrome P450-mediated reactions.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Effect of local tumor removal and retained oncolysate on lung metastasis.

We reported earlier that oncolysate retained in the excision wound of a local tumor inhibits growth of remote tumor in the rat. We further studied this effect on pulmonary metastasis. C57BL/6 mice were given B16 melanoma F10 cells subcutaneously into the gluteal area (Day 0) and then intravenously on Day 10. On Day 14, mice were divided into four groups. Group 1 received a sham operation and no further treatment. Tumors were excised in the remaining mice. Group 2 received tumor excision alone. Groups 3 and 4 received injections of freeze-lysed tumor cells (TC) and lysate modified (PTC) with a hapten, L-phenylalanine mustard (PhM), respectively, into excision wounds. On Day 24, metastases were assessed by determining metastatic burden. Average diameters of excised tumors in repeated experiments ranged from 8.7 to 10.9 mm. In repeat experiments, pulmonary metastatic burden increased by as much as 52 to 181% in the tumor excised group (Group 2) in comparison with those receiving sham surgery (Group 1). However, metastatic burden was always reduced in Group 3. An even greater reduction was seen in Group 4. To study the possible involvement of macrophages, the production of prostaglandin-E2 (PGE2) and cytotoxicity of macrophages in these animals were examined. It was found that tumor excision enhanced PGE2 production by macrophages and suppressed their cytotoxicity, while TC inoculation prevented both of these changes. An even greater prevention was observed with PTC inoculation. These results indicate an association among macrophage cytotoxicity, PGE2 production of macrophages, and metastasis. In order to clarify the mechanism for these reactions, we did experiments using adherent splenic macrophages from the four groups of animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Coexistence of extracranial internal carotid artery aneurysm and multiple intracranial aneurysms--case report.

A rare case of extracranial internal carotid artery (ICA) aneurysm coexisting with intracranial multiple aneurysms in a 64-year-old female is reported. The three intracranial aneurysms were clipped uneventfully by two-stage craniotomies. The extracranial ICA aneurysm at the infratemporal region was excised through a high cervical route and ICA was reconstructed by an end-to-end direct anastomosis. Ours is the first case reported of extra- and intracranial aneurysms surgically treated successfully.

Aneurysm↗
PubMed1992

Traumatic internal carotid artery occlusion--case report.

A 20-year-old male was admitted comatose immediately after a motorcycle accident. Initial computed tomography demonstrated traumatic subarachnoid hemorrhage, and the diagnosis of traumatic internal carotid artery occlusion was established by angiography. Conservative management improved his symptoms, but eventually he died from delayed traumatic apoplexy. Traumatic internal carotid artery occlusion is relatively rare, but is serious and requires early diagnosis and treatment. For patients with severe head trauma and vascular occlusion, anticoagulants are contraindicated, and frequent follow-up angiography is recommended.

Adult↗
PubMed1992

[Transcranial magnetic stimulation of the facial nerve].

It was the object of the present study to determine whether transcranial facial nerve stimulation using a magnetic coil can be clinically applicable, and to find the site where the facial nerve is best stimulated. A magnetic coil was placed over the parieto-occipital skull of the subjects for stimulation, and the facial nerve was electrically stimulated in its intracranial and peripheral courses. Then an electromyogram was recorded from the nasalis muscle of the face on the stimulated side. In 9 healthy volunteers, 18 facial nerves received magnetic and electric stimuli in the peripheral region, and the actual site of stimulation was estimated from the conduction velocity of the nerve. The conduction velocity was 56.6 +/- 4.8 m/s, and the latency between CMAPs for electric at the magnetic stimuli to the posterior tragus was 1.23 +/- 0.21 ms. Therefore, the position stimulated by magnetic coil was estimated to be 70.0 +/- 11.4 mm central to the posterior tragus, i.e., near the root exit zone. In two patients undergoing surgery in the cerebellopontine angle, transcranial magnetic stimulation and electrical stimulation of the intracranial facial nerve were compared intraoperatively. The CMAP produced by transcranial magnetic stimulation coincided closely with that produced by direct electrical stimulation of the root exit zone. Thus, the facial nerve was stimulated at the root exit zone, and this method could be expected to be useful for evaluation of disorders of the intracranial facial nerve.

Adult↗
PubMed1992

[Problems and prevention in using arterial grafts for coronary artery bypass grafting].

The arterial graft has proved to be superior to the saphenous vein graft for coronary bypass grafting (CABG), because of its excellent long-term patency. However, there mains controversial on the choice of the arterial grafts. Six hundreds and twenty seven patients who had CABG using both arterial grafts and saphenous vein grafts, operated upon over 11-years period between 1980 and 1991, have been analysed. Some disadvantages and complications associated with the use of arterial grafts were demonstrated in our series. We discussed, the flow capacity, myocardial protection and postoperative complications in using arterial grafts for CABG.

Aged↗
PubMed1979

Formation of nuclei during delay time prior to aggregation of deoxyhemoglobin S in concentrated phosphate buffer.

The delay time prior to aggregation of deoxyhemoglobin S was found to be shortened significantly if monomeric deoxyhemoglobin S was added near the end of the expected delay time. This suggests the formation of a preaggregation complex of deoxyhemoglobin S, probably so-called "nuclei", near the end of the delay time. In fact, the molecular weight of deoxyhemoglobin S as measured by a low angle laser light scattering photometer increased exponentially during the delay time prior to the visible aggregation of deoxyhemoglobin S. These results support the nucleation-controlled aggregation mechanism for the aggregation of deoxyhemoglobin S in concentrated phosphate buffer.

Biopolymers↗
PubMed1979

The solubility of sickle and non-sickle hemoglobins in concentrated phosphate buffer.

A new turbidimetric method for the direct measurement of the solubility of oxy- and deoxyhemoglobins (Hb) in concentrated phosphate buffer has been established. The principle of the method is the formation of a homogeneous emulsion when hemoglobin is introduced in concentrated phosphate buffer. The solubility of the oxy and deoxy forms of Hb A, Hb S, Hb C, Hb F, and Hb CHarlem (beta 6Glu leads to Val, beta 73Asp leads to Asn) has been studied. The solubility of deoxy-Hb S was the lowest and the solubility curve was broader than those of the other hemoglobins indicating that the aggregates of deoxy Hb S require more water to be dissolved. The solubility of oxy- and deoxyhemoglobins depends on temperature and pH. The solubility of hemoglobins is increased as the temperature is lowered and the pH is raised. The pH dependency of the solubility of deoxy-Hb S in high phosphate buffer was opposite to that of the minimum gelling concentration of deoxy-Hb S. The order of the solubility of Hb CHarlem, Hb FS, Hb AS, Hb CS, and Hb S in concentrated phosphate buffer corresponds to the order of minimum gelling concentration of these hemoglobins or hemoglobin mixtures. Solubility studies of a 1:1 mixture of deoxy-Hb A and deoxy-Hb S show that deoxy-Hb A aggregates in 2.42 M phosphate buffer in which pure deoxy-Hb A is totally soluble. This result indicates that deoxy-Hb S interacts with deoxy-Hb A and decreases its solubility.

Buffers↗
PubMed1979

Use of heme spin-labeling to probe heme environments of alpha and beta chains of hemoglobin.

A spin label attached to a propionic acid group of the heme has been used to probe the heme environment of the alpha and beta chains of hemoglobin in both the subunit and tetrameric forms. The electron paramagnetic resonance (EPR) studies of hemoglobin hybrids in which the spin label is attached to either the alpha- or beta-heme (alpha2SLbeta 2 or alpha2beta2SL) and spin-labeled isolated chains (alphaSL and betaSL) show that: 1) alpha- and beta-hemes have different environments in the tetrameric forms of oxy-, deoxy-, and methemoglobins as well as in isolated single chains; 2) when isolated subunits associate to form hemoglobin tetramers, the environment of the alpha-heme changes more drastically than that of the beta-heme; 3) upon deoxygenation of hemoglobin, the structure in the vicinity of the alpha-heme changes more drastically than that of the beta-heme; and 4) upon the addition of organic phosphates to methemoglobin, the change in the spin state of the heme irons mainly arises from beta-heme. The results demonstrate conclusively that the alpha and the beta subunits of hemoglobin are structurally nonequivalent as are their structural changes as the result of ligation. The relationship of EPR spectrum and structure of hemoglobin is discussed.

Electron Spin Resonance Spectroscopy↗
PubMed1979

Spin-label studies of membrane-associated denatured hemoglobin in normal and sickle cells.

A maleimide spin label (N-(1-oxyl-2,2,5,5-tetramethylpyrrolidinyl)-maleimide) was reacted with oxyhemoglobin-free cell stromata of normal and sickle cells. The EPR spectrum of spin-labeled red cell membranes showed that the spin labels are attached to at least two different binding sites. There was a major signal, A, which characterized a strongly immobilized environment and a minor signal, B, which characterized a weakly immobilized environment. Quantitative EPR measurements using equal amounts of Hb AA and Hb SS red blood cells demonstrated that Hb SS red cell membranes had an approximately four times higher EPR signal intensity than Hb AA red cell membranes ((7.98 +/- 1.14 . 10(5) and (2.2 +/- 1.2) . 10(5) spin labels/cell, respectively). Moreover, the ratio of signal intensities A and B are different in these cells. Comparative spectrophotometric studies of membrane-associated denatured hemoglobins of Hb AA and Hb SS red cell membranes suggested that the EPR signal A is derived from spin labels attached to membrane-associated denatured hemoglobin, while signal B is mainly from spin labels attached to membranes. The combination of EPR spectrum of Hb AA membranes pretreated with N-ethylmaleimide and that of spin-labeled precipitated hemoglobin further strengthened this conclusion.

Anemia, Sickle Cell↗
PubMed1979

Oxygen dissociation curves in children with anemia and malignant disease.

Two automatic apparatuses utilizing a dual wavelength spectrophotometer were used to perform oxygen dissociation curves on microsamples of blood. The method provides a complete print-out of an oxygen dissociation curve in 15--20 min and the P50 vlues obtained in normal individuals agree closely with those obtained by classical methods. These apparatuses were used to measure oxygen affinity, ie P50, in anemic children with malignant disease prior to treatment and in children undergoing therapy. Red cell 2,3-DPG levels were also measured. In patients with anemia at the time of diagnosis and prior to therapy, the P50 values and 2,3-DPG levels were elevated as is usual in other types of anemia. However, when oxygen affinity and 2,3-DPG levels were measured in anemic patients receiving treatment, three types of response to anemia were noted: 1) increased P50 and 2,3-DPG; 2) normal or low P50 and 2,3-DPG, and; 3) normal or low P50 with increased 2,3-DPG. Patients who adapted poorly to anemia during treatment had usually received prior intensive chemotherapy and transfusion therapy, and their pattern of red cell glycolytic intermediates was consistent with a red cell population with an increased cell age. The failure of some patients to respond to anemia with a decrease in oxygen affinity has implications in regards to the hemoglobin level at which they should be transfused.

Adult↗
PubMed1979

Blood flow velocity in pulmonary microvessels of bullfrog.

Flow velocity in the pulmonary microvessels of the exposed lung of bullfrogs was measured by means of a laser Doppler microscope of an oblique backward mode, together with a signal-analyzing system having a time sharing circuit triggered by the R-wave of the ECG. By these means, measurements of the changes of flow velocity contour in the cardiac cycle were made. Flow velocity was clearly pulsatile in response to cardiac cycles in all microvessels including capillaries. Flow velocities in the arteriole and venule consistently decreased for a short period after the R-wave (84 +/- 33 msec (mean +/- SD) in the arteriole and 130 +/- 31 msec in the venule, respectively) and rapidly increased up to a maximicronm value. The mean flow velocities in arterioles (diameter 50 +/- 17 micron) and venules (39 +/- 9 micronm) were 2.29 +/- 0.32 and 2.30 +/- 0.27 mm/sec. The amplitudes of pulsatile flow in these vessels were 0.83 +/- 0.31 and 0.63 +/- 0.16 mm/sec, respectively. In the capillary the times from the R-wave to the minimicronm and maximum values were variable. In some cases the velocity gradually increased without first decreasing and the increase sharply accelerated a certain time after the R-wave. The mean velocity in the pulmonary capillary and the amplitude of the pulsatile flow ere 1.78 +/- 0.31 and 0.37 +/- 0.12 mm/sec, resepctively. The ratios of the pulsatile amplitude to the mean velocity in the pulmonary capillary, venule and arteriole averaged 0.21, and 0.36, respectively.

Animals↗
PubMed1979

Automated method for determination of oxygen equilibrium curves of red cell suspensions under controlled buffer conditions and its clinical applications.

The accurate determination of the oxygen equilibrium curve (OEC) of whole blood or red cell suspensions requires special considerations to avoid the secondary effects due to lactate formation, removal of carbon dioxide, use of anticoagulants, etc. An automated apparatus has been constructed that can record the whole OEC of red cells within 20 min. The instrument also can be used to record the OEC of hemolysate. The pH, temperature, and PO2 are monitored constantly during the measurement. Using this instrument, the effects of pH, temperature, carbon dioxide, anticoagulants, and buffers on the OEC of normal fresh blood have been investigated. The OEC of normal blood, blood containing abnormal hemoglobin, or enzyme, were determined. The results were compared with those obtained using commercial OEC apparatuses.

Autoanalysis↗