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Biomedical subjects

K Imada

Publications and source records attributed to K Imada.

72 records · Page 4Linked to original sources
PubMed1992

Pseudo-high affinity interleukin 2 (IL-2) receptor lacks the third component that is essential for functional IL-2 binding and signaling.

Functional studies of the interleukin 2 receptor (IL-2R) of two (ED515-D and Kit225) IL-2-dependent and three (ED515-I, 3T3-alpha beta 11, and Hut102) IL-2-independent cell lines were done. All of these cell lines appeared to express high as well as low affinity IL-2R. However, ED515-I and 3T3-alpha beta 11, which expressed the IL-2R beta chain, did not bind IL-2 at all when IL-2 binding to their IL-2R alpha chain was blocked with anti-Tac monoclonal antibody, whereas the intermediate affinity binding in ED515-D, Kit225, and Hut102 cells remained. We tentatively called the high affinity IL-2R of the former cells pseudo-high affinity IL-2R. The dissociation constant of pseudo-high affinity IL-2R was higher than that of ordinary high affinity IL-2R. Internalization of cell-bound 125I-IL-2 into ED515-I and 3T3-alpha beta 11 cells was less efficient than that into ED515-D cells. The addition of IL-2 neither promoted cell growth nor upregulated IL-2R alpha chain expression in ED515-I and 3T3-alpha beta 11 cells. Furthermore, tyrosine phosphorylation of the cellular proteins (p120, p98, p96, p54, and p38) was induced or enhanced in response to the addition of IL-2 in ED515-D and Kit225 cells, but not in the cell lines expressing pseudo-high affinity IL-2R. Finally, 125I-IL-2 crosslinking followed by SDS-PAGE analysis showed an 80-kD band corresponding to p65 + IL-2, in addition to bands corresponding to IL-2R alpha and beta chain + IL-2 in cells bearing ordinary high affinity IL-2R but not in cells with pseudo-high affinity IL-2R. Taken together, we consider that another protein whose molecular mass is approximately 65 kD is functionally important in IL-2 binding and subsequent signal transduction and may be the third component of IL-2R.

3T3 Cells↗
PubMed1992

Interleukin-2 (IL-2) induces erythroid differentiation and tyrosine phosphorylation in ELM-I-1 cells transfected with a human IL-2 receptor beta chain cDNA.

The molecular mechanism of erythroid differentiation has been still ill-defined. In this study, we introduced a human interleukin-2 receptor (IL-2R) beta chain cDNA into ELM-I-1 cells which differentiated into hemoglobin-positive cells in the presence of erythropoietin (Epo), and established the transformant which expressed IL-2R beta chain. In this transformant, we revealed that IL-2 induced erythroid differentiation and the same pattern of tyrosine phosphorylation as Epo. These data suggest that tyrosine phosphorylation is involved in signal transduction pathway of erythroid differentiation. It is also implicated that the Epo and IL-2 receptor system share a common signal transduction pathway.

Animals↗
PubMed1992

The third molecule associated with interleukin 2 receptor alpha and beta chain.

It is known that the affinity cross-linking study of the human high-affinity Interleukin 2 (IL-2) receptor reveals triplet bands consisting of 70 kDa alpha chain(Tac)-IL-2 and the 90/80 kDa doublet. We found the cell lines lacking the lower band of the doublet in spite of the expression of both alpha and beta chains. No IL-2 binding was detectable in the presence of anti-Tac antibody in these cells. Immunoprecipitation from the cell extract of [125 I] IL-2-cross-linked T cells with anti-beta chain polyclonal IgG detected the upper band, but not lower band of the doublet. These data suggest that the lower band of the doublet represents an unknown IL-2-binding protein (p65) distinct from the beta chain and this molecule may be involved in the intermediate-affinity IL-2 binding together with the beta chain.

3T3 Cells↗
PubMed1992

Crystallization and preliminary X-ray studies of a Bacillus subtilis and Thermus thermophilus HB8 chimeric 3-isopropylmalate dehydrogenase and thermostable mutants of it.

A new type of chimeric 3-isopropylmalate dehydrogenase (2T2M6T) was produced by expressing the fused gene of Bacillus subtilis and Thermus thermophilus. The enzyme shows heat stability intermediate between those of the parents. The crystal of the enzyme belongs to the space group of P3(2)21, with cell dimensions of a = b = 78.9 A and c = 158.9 A. Two thermostable mutants of the chimeric enzyme were prepared by site-directed mutagenesis and then crystallized.

3-Isopropylmalate Dehydrogenase↗
PubMed1992

Extraperitoneal anterolateral discectomy for lumbar disc herniation: indications, techniques, and time-related clinical results.

We analyzed 80 consecutive cases of lumbar disc herniation who underwent an extraperitoneal anterolateral discectomy according to clinical and radiologic parameters. The average follow-up period was 5 1/2 years (range, 1-10 years). The results of 71 patients (89%) were satisfactory through the mid- and long-term follow-up periods, although a very slight decrease in subjective/objective scores and ADL score was found. Satisfactory results were obtained for adolescent and younger male adults and in isolated central or centrolateral herniations with a broad base. From an analysis of the nine reoperated cases, we determined that the contraindications of this technique are a sequestrated or extruded nucleus pulposus and disc protrusion accompanied by posterior dislocation of a vertebral edge fragment. The relative indications include a small, hard posterolateral herniation located just beneath the nerve roots, double-level herniation, disc herniation accompanied by narrow spinal canal, and bulged disc in elder patients. The absolute indications for this surgery are a centrally or centrolaterally protruded disc with a relatively broad base of herniation at single-disc level that is not accompanied by spinal stenosis in adolescent and younger male adults.

Adolescent↗
PubMed1991

Three-dimensional structure of a highly thermostable enzyme, 3-isopropylmalate dehydrogenase of Thermus thermophilus at 2.2 A resolution.

The three-dimensional structure of the highly thermostable 3-isopropylmalate dehydrogenase (IPMDH) from Thermus thermophilus has been determined by the multiple isomorphous replacement method and refined to 2.2 A resolution. The final R-factor is 0.185 for 20,307 reflections. The crystal asymmetric unit has one subunit consisting of 345 amino acid residues. The polypeptide chain of this subunit is folded into two domains (first and second domains) with parallel alpha/beta motifs. The domains are similar in their conformations and folding topologies, but differ from those of the NAD-binding domains of such well-known enzymes as the alcohol and lactate dehydrogenases. A beta-strand that is a part of the long arm-like polypeptide protruding from the second domain comes into contact with another subunit and contributes to the formation of an isologous dimer with a crystallographic 2-fold symmetry. Close subunit contacts are also present at two alpha-helices in the second domain. These helices strongly interact hydrophobically with the corresponding helices of the other subunit to form a hydrophobic core at the center of the dimer. Two large pockets that exist between the first domain of one subunit and the second domain of the other include the amino acid residues responsible for substrate binding. These results indicate that the dimeric form is essential for the IPMDH to express enzymatic activity and that the close subunit contact at the hydrophobic core is important for the thermal stability of the enzyme.

3-Isopropylmalate Dehydrogenase↗
PubMed1991

Crystallization and preliminary X-ray studies of a Bacillus subtilis and Thermus thermophilus HB8 chimeric 3-isopropylmalate dehydrogenase.

A chimeric gene was constructed by fusing the Bacillus subtilis and Thermus thermophilus genes coding for 3-isopropylmalate dehydrogenase, and expressed in Escherichia coli. The chimeric enzyme was crystallized in a size suitable for X-ray structure analysis. The crystal has a space group of P3(1)21 or P3(2)21, a = b = 77.1 A and c = 158.3 A, which is isomorphous with that of the native enzyme from T. thermophilus.

3-Isopropylmalate Dehydrogenase↗
PubMed1991

Immunoadsorption with PH-350: as a beneficial therapy for acute Guillain-Barre syndrome.

The subjects here were patients (two males and a female) with the severe acute Guillain-Barre Syndrome admitted to our hospital between September 1987 and December 1988. One case was treated with a double filtration plasmapheresis and two cases were with a immunoadsorption. Of the two extracorponeal thrapeutical methods, the clinical efficacies seemed not to be different however biochemical and serological laboratory data showed prominent differences. For instance the large molecular substances in blood; immunoglobulins, coagulating factors and albumin were reduced in plasma levels by the double filtration plasmapheresis, but not or less by the immunoadsorption. Considering the expectable side effects of the two methods, it may say that the immunoadsorption should be applied as a beneficial extracorponeal method for the acute Guillain-Barre Syndrome.

Acute Disease↗
PubMed1989

[General pharmacological studies on 5,8,11,14,17-eicosapentaenoic acid ethyl ester (EPA-E)].

EPA-E, even at 3,000 mg/kg, p.o., did not affect the general behaviors, spontaneous locomotor activities, pentobarbital hypnosis and body temperature; and it did not elicit anticonvulsant, analgesic and muscle relaxant actions. It had no influence on spontaneous EEG activities, even at 3,000 mg/kg, i.d. EPA-E at concentrations up to 10(-4) M, did not affect the tonus or agonist-induced contraction of the isolated ileum, trachea, fundus and vas deferens. EPA-E had no influence on the spontaneous movement of isolated ileum or uterus. EPA-E did not affect the nictitating membrane contraction and intestinal propulsive motility, and it did not damage gastric mucosa nor elicit antiulcer action. EPA-E at 1,000 mg/kg were without effect on gastric secretory volume (SV), total acidity (TA) and pepsin activities (PA). However, EPA-E at 3,000 mg/kg significantly decreased SV and TA without significantly decreasing PA. EPA-E caused no changes in the respiration, blood pressure, heart rate and ECG at the doses up to 3,000 mg/kg; and it did not affect the heart rate and contractile force on the isolated atria at concentrations up to 10(-4) M. The intracutaneous injection of 2.0% EPA-E produced neither anesthetic nor irritative action. EPA-E did not elicit hemolytic action at 10(-4) M. EPA-E, even at 3,000 mg/kg, did not affect the neuro-muscular transmission, urine volume, urinary excretion of electrolytes and carrageenin edema. These results suggested that EPA-E has no noticeable effects on the central nervous, autonomic nervous, respiratory and cardiovascular systems and so on.

Animals↗
PubMed1985

Isolation and structure of a minor metabolite of pyridoxine in seedlings of Pisum sativum L.

A new derivative of pyridoxine was formed from PN in seedlings of podded pea, Pisum sativum L. cv. Kinusaya, together with 5'-O-(beta-D-glucopyranosyl)pyridoxine and 5'-O-[6-O-(3-hydroxy-3-methyl-4-carboxybutanoyl)-beta-D-glucopyran osyl] pyridoxine. The compound was isolated and identified as 5'-O-(6-O-malonyl-beta-D-glucopyranosyl)pyridoxine.

Chromatography, Ion Exchange↗
PubMed1980

Conformation of crystalline type III pneumococcal polysaccharide.

The conformation of crystalline Type III pneumococcal polysaccharide, poly[(1 yields 3)-beta-D-GlcpA-(1 yields 4)-beta-D-Glcp], has been studied by X-ray diffraction and stereochemical analysis. The X-ray pattern, recorded at 80% relative humidity, led to a trigonal unit-cell, with alpha = beta = 1.028 nm, c = 2.77 nm, and gamma = 120 degrees. Meridional reflections on the third and the sixth layer-lines show that the chain consists of a three-fold helix, with a repeat of 0.923 nm. Conformational analysis, by the virtual-bond method, shows that one right-handed and two left-handed helices are equally favorable, on the basis of energies of isolated chains. Packing of the three helix models in the unit cell, by contact-distance criteria, ruled out the possibility of the right-handed helical conformation. One of the left-handed helices has intramolecular hydrogen-bonds O-3'...O-5 and O-2...O-6' between the residues in the (1 yields 4) linkage, and O-4'...O-5 between those in the (1 yields 3) linkage. In the other left-handed helix, the O-4'...O-5 hydrogen bond is replaced by an O-2...O-2' hydrogen bond. The choice between the two left-handed helix models is inhibited by the paucity of X-ray intensity data.

Carbohydrate Conformation↗
PubMedDate not supplied

The Jak-STAT pathway.

A variety of important cellular functions are regulated by cytokines. The Jak-STAT pathway is one of the important signaling pathways downstream of cytokine receptors. Following binding of a ligand to its cognate receptor, receptor-associated Jaks are activated. STAT proteins are then in turn activated by tyrosine phosphorylation by Jak kinases, allowing their dimerization and subsequent translocation into the nucleus, where they modulate expression of target genes. Indispensable functions of Jaks and STATs in cytokine signaling in vivo have been revealed through knockout mouse studies. Moreover, the recent discovery of the CIS/SOCS/JAB/SSI family of inhibitors has contributed to understanding how this pathway is negatively regulated.

Animals↗
PubMedDate not supplied

Mixed venous oxygen saturation as a promising parameter for physiologic control of total artificial heart.

Mixed venous oxygen saturation (SvO2) has been proposed as one of the suitable parameters for physiologic control of a total artificial heart (TAH). To establish the practical application of SvO2, we investigated the response of cardiac output (CO) and SvO2 to step-loaded exercise. A normal calf was surgically equipped with an ultrasonic flowmeter probe and an oximetry catheter in the pulmonary artery to measure CO and SvO2, respectively. Three stage step treadmill exercise tests (1, 2, and 4 km/h) were performed three times. While CO increased from 8.9 L/min at preexercise level to 9.7, 10.2 and 11.4 L/min at 1, 2, and 4 km/h, respectively, SvO2 decreased from 59.6% to 56.8, 55.3, and 52.2%, respectively. There existed a linear correlation between the magnitude of changes in CO and SvO2. CO and SvO2 exhibited a similar course of change, expressing an inverted exponential curve. The time constant of SvO2 was from 19 to 35 seconds, whereas that of CO was from 21 to 39 seconds. We conclude that SvO2 changes in close association with CO during exercise and has good potential to be a parameter for physiologic control of a TAH, by reflecting the recipient's CO demand without conspicuous time delay.

Animals↗