Biomedical subjects

Y Amemiya

Publications and source records attributed to Y Amemiya.

At least 19 recordsLinked to original sources

PubMed1992

Purification and initial characterization of the proteasome from the higher plant Spinacia oleracea.

The proteasome (multicatalytic protease complex), a high molecular weight protein complex, has been purified from spinach leaves by successive chromatography on DEAE-cellulose, Bio-Gel A-1.5m, DEAE-TOYOPEARL 650C, and DEAE-5PW. The molecular mass was estimated to be 850 kDa by gel filtration. Polyacrylamide gel electrophoresis of the proteasome gave a single protein band under nondenaturing conditions and at least 10 bands in the range of 21-32 kDa in the presence of sodium dodecyl sulfate. By electron microscopy after negative staining with uranyl acetate, the proteasome from spinach appeared as symmetrical ring-shaped particles. The substrate specificity of proteasomes indicates that they contain at least three types of activity, namely, chymotrypsin-like, Staphylococcus aureus V8 protease-like, and trypsin-like activities. The former two activities were enhanced by poly-L-lysine or sodium dodecyl sulfate. Moreover, we examined the immunological reactivities of proteasomes from various eukaryotes. As a result, cross-immunoreactivities of some subunits were observed. These properties of the proteasome are similar to those of proteasomes isolated from various other eukaryotic sources.

Amino Acid Sequence↗

PubMed1992

Small-angle synchrotron x-ray scattering reveals distinct shape changes of the myosin head during hydrolysis of ATP.

In the energy transduction of muscle contraction, it is important to know the nature and extent of conformational changes of the head portion of the myosin molecules. In the presence of magnesium adenosine triphosphate (MgATP), fairly large conformational changes of the myosin head [subfragment-1 (S1)] in solution were observed by small-angle x-ray scattering with the use of synchrotron radiation as an intense and stable x-ray source. The presence of MgATP reduced the radius of gyration of the molecule by about 3 angstrom units and the maximum chord length by about 10 angstroms, showing that the shape of S1 becomes more compact or round during hydrolysis of MgATP. Comparison with various nucleotide-bound S1 complexes that correspond to the known intermediate states during ATP hydrolysis indicates that the shape of S1 in a key intermediate state, S1-bound adenosine diphosphate (ADP) and phosphate [S1**.ADP.P(i)], differs significantly from the shape in the other intermediate states of the S1 adenosine triphosphatase cycle as well as that of nucleotide-free S1.

Adenosine Triphosphate↗

PubMed1992

Clinicopathologic and therapeutic aspects of angioimmunoblastic lymphadenopathy-related lesions.

The clinicopathologic features of 14 patients with angioimmunoblastic lymphadenopathy (AIL)-related lesions were analyzed. Lymph node biopsy specimens from all the patients showed a diffuse obliteration of lymph node architecture, prominent vascular proliferation, a polymorphous cellular infiltrate, including immunoblasts, and varying degrees of clear cell proliferation. The patients were eight males and six females, with a median age of 58.5 years. All but one were in an advanced stage at the time of diagnosis. Bone marrow involvement was observed in eight patients. Thirteen patients had a negative serologic reaction for antibody to human T-cell leukemia virus type I (HTLV-I), and one patient was considered to be a HTLV-I carrier. Polyclonal hypergamma-globulinemia was observed in 6 patients, and 6 of the 12 patients showed elevated IgE levels. Immunophenotyping of the involved lymph nodes revealed a preponderance of T-cells in all the patients. Eleven of these patients showed a predominance of CD4+ over CD8+ T-cells, and only one patient showed a predominance of CD8+ over CD4+ T-cells. Two of five patients whose gene analysis was carried out showed clonal rearrangement of the T-cell receptor beta chain gene without rearrangement of the immunoglobulin heavy chain genes. Twelve patients received doxorubicin-containing combination chemotherapy; of these, 7 patients achieved complete response, and the other 5 had partial response. Nine patients are still alive with a median follow-up period of 21 months, and five patients died during the follow-up period. Progression to high-grade T-cell lymphoma with systemic infiltration was ascertained in two of three cases for which autopsy was performed. From our experience, we recommend doxorubicin-containing combination chemotherapy as initial therapy for AIL-related lesions.

Aged↗

PubMed1992

Synthesis and alpha-adrenergic activities of 2- and 4-substituted imidazoline and imidazole analogues.

Seven analogues of medetomidine and naphazoline were synthesized and evaluated for their alpha 1 (aorta) and alpha 2 (platelet) activities. The analogues were composed of 2- and 4-substituted imidazoles and imidazolines attached through a methylene bridge to either the 1- or 2-naphthalene ring system. In general the 1-naphthalene analogues were the most potent inhibitors of epinephrine-induced platelet aggregation. Of considerable interest was the fact that the 1-naphthalene analogues (2, 5-7) were partial agonists while the 2-naphthalene analogues (3, 8, 9) were antagonists in an alpha 1-adrenergic system (aorta). Thus, appropriately substituted naphthalene analogues of medetomidine and naphthazoline provide a spectrum of alpha 1-agonist, alpha 1-antagonist, and alpha 2-antagonist activity.

Adrenergic alpha-Agonists↗

PubMed1992

Reactivity profiles of leukemic myeloblasts with monoclonal antibodies directed to sialosyl-Le(x) and other lacto-series type 2 chain antigens:absence of reactivity with normal hematopoietic progenitor cells.

We investigated the expression profiles of lacto-series type 2 antigens in hematopoietic cells and their progenitors, in comparison with leukemic leukocytes. Reactivity profiles of various anti-type 2 chain monoclonal antibodies (MoAbs) with leukemic blasts from 12 patients with acute myeloblastic leukemia (AML) and those from two patients with acute unclassified leukemia (AUL) show that anti-sialosyl-Le(x) MoAb SNH3 reacted strongly with greater than 95% of leukemic blast leukocyte populations from all patients (14 of 14). Another anti-sialosyl-Le(x) MoAb, FH6, showed less reactivity than SNH3 (12 of 14 patients), while anti-Le(y) MoAb AH6 showed reactivity with only 8 of 14 patients. On the other hand, none of the anti-type 2 chain MoAbs reacted with CD34+ normal adult bone marrow (BM) mononuclear cells obtained independently from three healthy volunteers. MoAb SNH3, but not FH6 or AH6, showed complement-mediated cytotoxicity to leukemic blasts from these patients, as well as to myelogenous leukemia cell line HL60. Colony-forming unit granulocyte-macrophage (CFU-GM), but not burst-forming unit-erythroid (BFU-E), was incompletely inhibited by treatment of normal BM mononuclear cells with SNH3 and complement. The absence of type 2 chain antigen expression in hematopoietic progenitor cells and in in vitro hematopoietic colonies (CFU-GM and BFU-E) strongly suggests that application of anti-carbohydrate MoAbs, particularly anti-sialosyl-Le(x) could be useful for elimination of leukemic myeloblasts infiltrating in BM, for purging of leukemic blasts in BM, and for facilitation of autologous BM transplantation.

Antibodies, Monoclonal↗

PubMed1992

Effects of 2,3-butanedione monoxime on contraction of frog skeletal muscles: an X-ray diffraction study.

We studied the effects of BDM (2,3-butanedione monoxime) on the tetanic contraction of frog skeletal muscles using an X-ray diffraction technique. BDM significantly increased the resting equatorial intensity ratio (I1,0/I1,1). In sartorius muscle, 3 mM BDM suppressed tetanic tension by 40-70% whereas the equatorial intensity ratio, which is 2.6 at rest, decreased to 0.75 during tetanus, close to the value in normal contraction (about 0.50). BDM (3 mM) reduced the intensity increase of the 5.1-nm layer-line to 41%, that of the 5.9-nm layer-line to 24%, and the intensity decrease of the second myosin meridional reflection (at 1/21.5 nm-1) at 81%. In overstretched semitendinosus muscle, 3 mM BDM did not significantly reduce the intensity increase of the second actin layer-line during activation, suggesting that enough calcium is released to activate the regulatory system and the regulatory proteins are intact. These results indicate that BDM suppresses tetanic tension by mainly inhibiting actin-myosin interaction. It has a smaller effect on the equatorial reflections and myosin layer-lines than on the actin layer-lines, suggesting that BDM-influenced myosin heads may bind to actin without following the symmetry of the actin helix.

Actin Cytoskeleton↗

PubMed1992

Postoperative death of a patient in apparent remission of malignant lymphoma after dissection for squamous cell carcinoma.

A 67-year-old man in apparent remission of malignant lymphoma had squamous cell carcinoma of the left buccal mucosa. The patient underwent partial resection of the mandible, including the excision of the tumor. During the fourth postoperative night the patient suddenly became febrile and had a spiking fever for the next 5 days. His general condition deteriorated afterward, and acute aggravation of malignant lymphoma was suspected. On day 16 disseminated intravascular coagulation was indicated by a decreased platelet count of 3.8 x 10(4), a tendency toward bleeding, and multiple organ failure. The patient died 18 days postoperatively. We alert anesthesiologists and surgeons that surgically treating patients with malignant lymphoma who are receiving immunosuppressive drugs is precarious even though their disease is considered to be in apparent remission.

Aged↗

PubMed1992

Practical application of meridian acupuncture treatment for trigeminal neuralgia.

This report evaluates the effect of meridian acupuncture treatment on trigeminal neuralgia. Ten patients aged 26 to 67 years (mean 55.4 years) who visited the outpatient Dental Anesthesiology Clinic at Tsurumi University Dental Hospital from 1985 to 1990 were studied. Five of the patients suffered from idiopathic and five from symptomatic trigeminal neuralgia. The patients underwent meridian treatment by acupuncture alone or acupuncture combined with moxibustion. The acupuncture method used was primarily basic treatment employing only needles without electrical stimulation. Meridian acupuncture treatments were repeated from two to four times a month. Five patients were restored to a pain-free state. The other five patients noted a decrease in pain, but with some level of pain remaining (significant pain in one patient). It is concluded that meridian acupuncture treatment is useful and can be one therapeutic approach in the management of trigeminal neuralgia.

Acupuncture Therapy↗

PubMed1991

Crystallographic characterization by X-ray diffraction of the M-intermediate from the photo-cycle of bacteriorhodopsin at room temperature.

The structure of the M-intermediate appearing in the photo-cycle of bacteriorhodopsin was studied with X-ray diffraction techniques at room temperature. The lifetime of the M-intermediate was prolonged by treatment with an arginine solution at alkaline pH (Nakasako et al., FEBS Lett. 254, 211-214). The diffraction profile of membranes which had accumulated the M-intermediate had small but significant differences in the intensities of Bragg reflections and the lattice constant in comparison with that of membranes having trans-bacteriorhodopsin. Diffraction intensities were carefully evaluated and the structural changes during the formation of the intermediate were evaluated with difference Fourier analysis. We could find structural changes around helices G and B.

Bacteriorhodopsins↗

PubMed1991

Interstitial hyperthermia of malignant brain tumors by implant heating system: clinical experience.

An implant heating system using a ferromagnetic implant with low Curie temperature has been developed for treating human brain tumors. Safe and repeated hyperthermia was possible over periods averaging ten weeks in 23 out of 25 patients with malignant brain tumors without development of major side effects. Evaluation of the effects of this new treatment is still preliminary. Overall response rate was 34.8%. However, five of thirteen cases of malignant glioma and two of five cases of brain metastasis were responded well to interstitial hyperthermia given with or without irradiation. Pathological findings common to the treated tumors were circumscribed, ellipsoid shape of coagulation necrosis around the implant. Degeneration of tumor cells, hemorrhage, vascular stasis and thrombosis were found adjacent to the necrosis. In the future, a combination of interstitial hyperthermia with brachytherapy and chemotherapy may offer improved local control of brain tumor.

Brain Neoplasms↗

PubMed1991

Structure-activity studies of new imidazolines on adrenoceptors of rat aorta and human platelets.

Potencies of new aromatic substituted fluoro or iodo analogues of catecholimidazolines on functional responses in rat aorta (alpha 1) and platelets (alpha 2) were quantified. (1) When compared either on the basis of EC50 or the dissociation constant (KA), 5-fluorocatecholimidazoline was as potent as the reference alpha 1-adrenoceptor agonist, phenylephrine in the vascular tissue. The maximum contraction of aorta produced by the fluoro analogue was, however, 17% higher than that of phenylephrine. The time required for 1/2 relaxation of the tissue after 5-fluoro hydroxy imidazoline was at least twice as long as that of the phenylephrine. The catechol moiety as well as fluorine substitution at the critical 5-position of the aromatic ring is essential for higher alpha 1 adrenoceptor-mediated potency. (2) As compared to the fluoro analogues, the adrenoceptor-mediated potencies of iodo-analogues were relatively weak on vascular tissue. Naphazoline and its analogues were partial agonists on vascular tissue with dissociation constants which ranged from 110 to 2600 nmol/l. (3) Imidazole analogues were generally less potent agonist than the imidazolines by one order of magnitude. (4) The vacular effects of all agonists were competitively blocked by prazosin with KB values which ranged from 0.04 to 0.48 nmol/l. Since the variation in KB values were within normal limits, the action of new imidazolines on rat aorta appears to be mediated mainly by the activation of the alpha 1-adrenoceptor. Prazosin 10 nmol/l abolished the vascular response of some partial agonists. This indicates a slightly different mode of interaction of agonists with the transduction process. (5) Carbon 4-substituted imidazolines produced little or no alpha 1 adrenoceptor-mediated intrinsic activity, but competitive receptor blocking potency was comparable to that of phentolamine. (6) Medetomidine was a partial agonist on the rat aorta with a KA of 260 nmol/l. When investigated as a blocker, the KB of medetomidine against phenylephrine was approximately 5600 nmol/l. The variation in the latter value was high. (7) In acetylsalicylic acid-treated human platelets, the alpha 2-adrenoceptor-mediated aggregatory effect of all fluoro analogues was weak. Iodo or naphazoline analogues did not initiate platelet aggregation but blocked the aggregation induced by epinephrine. The affinity of naphazoline for the alpha 2-adrenoceptor was 1100 nmol/l. The IC50 of medetomidine for platelet anti-aggregatory effect was 3300 nmol/l, which compares favorably with other imidazoline type of blockers of platelet aggregation. (8) Sympathomimetic vasoconstrictor actions and platelet aggregation effects of these compounds can be dissociated.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1991

Dynamic X-ray diffraction of skeletal muscle contraction: structural change of actin filaments.

The X-ray diffraction pattern recorded during contraction shows that the force generation of a muscle proceeds upon interaction of the actin and myosin heads in the incommensurate structural framework of the thin and thick filaments. In this molecular framework the binding of myosin heads to actin filaments is thought to occur on a random basis. Such an actomyosin structure would not produce constructive interference between scattered X-rays from the bound heads and the thin filaments. The characteristic intensity changes of the thin filament layer lines that occur during contraction suggest strongly that the actin structure is varied by interaction with the myosin heads, in a manner that is quite different from that in the rigor state. Variability of the time courses of the intensity changes of the various layer lines indicates that structural change within the thin filament does not take place uniformly and that some different structural processes are involved during contraction At the plateau of isometric contraction, the thin filament structure as a whole assumes a more four-stranded nature due to the changes in the actin structure and tropomyosin position. Our present results imply that the changes of actin structure induced by interaction with myosin heads would be responsible for the regulation as well as force generation in muscle contraction.

Actins↗

PubMed1991

X-ray studies of thin filaments in a tonically contracting molluscan smooth muscle.

In the X-ray pattern of the ABRM, layer lines from the thin filaments can be clearly observed not only at the small angles but also at the medium angles up to 0.145 A-1, and the layer lines are changed in intensity in the tonically contracting state in both the small and medium angle regions. Because tropomyosin does not contribute significantly to the layer lines except the three near the equator, it is suggested that structural change of actin occurs in the tonically contracting state. The intensity profiles of the layer lines with the 0th Bessel order corresponding to the axial periods 27.9, 13.8, 9.3, and 6.9 A indicate axial staggering of the inner and outer domains of actin by about 1/3 of the axial period of actin, and the presence of a small mass on the shoulder of the outer domain at a distance of 50 A from the filament axis. The difference Patterson functions calculated from the intensities of the four layer lines with the 0th Bessel order suggest that peptide chains are oriented perpendicularly to the filament axis in the actin molecules. The peptide chain direction is presumably tilted against the filament axis in the outer part of actin as a result of structural change by tonic contraction.

Acetylcholine↗

PubMed1991

Changes in the X-ray diffraction pattern from rigor muscles by application of external length changes.

The effect of external force on the X-ray pattern from frog muscles in rigor was studied by a time-resolved diffraction technique. When sinusoidal length changes (1.5-3% of the muscle length, 5 Hz) were applied to the muscle, the 14.3 nm intensity decreased during the releasing phase and increased during the stretching phase. The intensity ratio of the equatorial 1.0 and 1.1 reflections did not change, nor were there any appreciable intensity changes in the 5.9 nm and 5.1 nm reflections during the length change. Experiments were also done with the relaxed muscles and no change was seen in any reflection, indicating that the rigor linkages are needed to produce the 14.3 nm intensity change. Thus the distinct effect of the length change was detected only on the 14.3 nm reflection. These results suggest no large conformational changes are induced in both the distal part of the myosin head attached to actin and the actin filament during the oscillation. It is therefore most probable that the proximal portion of myosin heads including S-2 contributes to the intensity change in response to the length change (see, also ref. 21). When the muscle was stretched beyond the filament overlap, the 14.3 nm intensity change was suppressed to less than 50% of that of the slack length. It was also found that the tension change delayed the intensity change during the length oscillation. However, this delay of the tension change as observed in the muscle at the slack length was lacking in the overstretched muscle, indicating that the 14.3 nm intensity change may arise partly from a portion other than the crossbridges.

Animals↗

PubMed1991

Imaging plate and its application to X-ray diffraction of muscle.

The excellent performance of the IP as an integrating X-ray area detector makes it well suited to X-ray diffraction and scattering experiments using synchrotron radiation. The IP is particularly useful for biological specimens for which the shortest exposure time or the smallest amount of X-ray dose possible is required. It is also useful for time-resolved measurements of an X-ray diffraction pattern, to complement its uses in static measurements. A combination of two powerful tools, synchrotron radiation and imaging plates, has mutually enhanced the potentials of both. The IP may replace conventional X-ray film and some other X-ray detectors which have been conventionally used in many of the application fields of synchrotron radiation. As examples, it has recently proved to be very promising in experiments of X-ray diffraction under high pressure and high temperature (12) DEXAFS and X-ray diffuse scattering. X-ray microscopy will also benefit from the IP when the spatial resolution is improved to a few tens of microns in FWHM. When more intense X-rays are available from insertion devices installed in planned 6-8 GeV storage rings, the IP system will play a more important role as one of the best X-ray area detectors because of its high DQE and the lack of any instantaneous count-rate limitations.

Animals↗

PubMed1991

Time-resolved synchrotron X-ray diffraction studies of a single frog skeletal muscle fiber. Time courses of intensity changes of the equatorial reflections and intracellular Ca2+ transients.

Time-resolved X-ray equatorial diffraction studies on a single frog skeletal muscle fiber were performed with a 10 ms time resolution using synchrotron radiation in order to compare the time courses of the molecular changes of contractile proteins and the intracellular Ca2+ transient during an isometric twitch contraction at 2.7 degrees C. Measurements of the Ca2+ transient using aequorin as an intracellular Ca2+ indicator were conducted separately just before and after the X-ray experiments under very similar experimental conditions. The results, which showed a similar time course of tension to that observed in the X-ray experiment, were compared with the aequorin light signal, tension and the intensity changes of the 1,0 and 1,1 equatorial reflections. No appreciable change in both reflection spacings indicated that the effect of internal shortening of the muscle was minimized during contraction. The intensity change of the equatorial reflections generally occurred after the aequorin light signal. In the rising phase, the time course of increase in the 1,1 intensity paralleled that of the rise of the light signal and the intensity peak occurred 20-30 ms after the peak of the light signal. The decrease in the 1,0 intensity showed a time course similar to that of tension and the intensity minimum roughly coincided with the tension peak, coming at 80-90 ms and about 60 ms after the peaks of the light signal and the 1,1 intensity change, respectively. In the relaxation phase, the 1,1 intensity seemed to fall rapidly just before the tension peak and then returned to the original level in parallel with the decay of tension. The 1,0 intensity returned more slowly than the tension relaxation. Thus, the change of the 1,1 intensity was faster than that of the 1,0 intensity in both the rising and relaxation phases. When the measured aequorin light signal was corrected for the kinetic delay of the aequorin reaction with a first-order rate constant of either 50 or 17 s-1, the peak of the corrected light signal preceded that of the measured one by approx. 30 ms. Thus, the peak of the Ca2+ transient appeared earlier than the peaks of the 1,1 and 1,0 intensity changes by 50-60 and 110-120 ms, respectively. The time lag between the extent of structural change and the Ca2+ transient is discussed in relation to the double-headed attachment of a cross-bridge to actin.

Aequorin↗

PubMed1991

Long-term bone marrow failure accompanied by skin pigmentation.

A rare case of long-term bone marrow failure with skin pigmentation is presented. The patient was a female with a long history of anemia and skin pigmentation since childhood, although she had no malformations nor chromosomal abnormalities. Hematological improvement has been maintained by the administration of prednisolone. This case may differ from other disorders known as congenital aplastic anemia.

Addison Disease↗

PubMed1991

[Multiple myeloma with hemolytic anemia and thrombocytopenia].

We report a 59 year old female patient who was diagnosed as having IgG kappa myeloma with hemolytic anemia and thrombocytopenia simultaneously. Although M-protein was suspected to contribute to the hemolysis, the IgG purified from the patient's serum did not bind to red blood cells. Therefore, massive non-specific binding of M-protein to blood cells might contribute to high levels of red blood cell-associated IgG and platelet-associated IgG in the patient.

Anemia, Hemolytic↗