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Biomedical subjects

T Kusama

Publications and source records attributed to T Kusama.

At least 55 records · Page 3Linked to original sources
PubMed1995

Effects of ET antagonists (PD143296 and PD145065) on contractions in guinea pig hilar bronchus induced by endothelin-1 and its related peptide.

ETs-induced contractions were resistant to ET(A)-selective antagonists and believed to be mediated by activation of ETB receptors in guinea pig bronchus. In the present study, the effects of the ET antagonists, PD143296 (Ac-D-Phe-L-Leu-L-Phe-L-Ile-L-Ile-L-Trp.2Na) and PD145065 (Ac-[(R)-2-10, 11-dihydro-5H-dibenzo[a, d]cyclohepten-5-yl]Gly)-L-Leu-L-Asp-L-Ile-L-Ile- L-Trp.2Na), on contractions induced by ET-1, ET-3, sarafotoxin S6c (STXc), and IRL1620 in the isolated hilar bronchus of the guinea pig were investigated. An ETA/B nonselective antagonist, PD145065 antagonized contractions induced by ET-1, ET-3, STXc, and IRL1620. Its antagonistic activity against ET-1, with pKB of 5.77 +/- 0.02 (n = 16, 3-10 microM), was significantly lower than that against ET-3, with pKB of 6.18 +/- 0.02 (n = 12, 3-10 microM), STXc, with pKB of 5.97 +/- 0.01 (n = 14, 3-10 microM), and IRL1620, with pKB of 6.80 +/- 0.04 (n = 14, 0.3-1 microM). Conversely, although a putative ETB-selective antagonist, PD143296 (10 microM) slightly but significantly antagonized the concentration-response curve of IRL1620 (pKB = 5.28 +/- 0.14, n = 6), it had no effect on ET-1-,ET-3-, or STXc-induced contractions. These results suggest that ETs possibly activate ETB2 or an atypical ETB receptor subtype in guinea pig hilar bronchus.

Animals↗
PubMed1994

Mutagenesis of the GABA rho 1 receptor alters agonist affinity and channel gating.

Seventeen site-directed mutations were constructed in the GABA rho 1 receptor with the aim of finding agonist binding domains common to rho 1 and rho 2 receptors but distinct from those identified in members of the family of homologous, ligand gated ion channels. Mutated cDNAs were expressed in Xenopus oocytes and tested by voltage clamp experiments. Five of the mutations abolished responsiveness to GABA. Mutation Q189H, in the conserved cysteine loop, diminished apparent GABA affinity to about 1/10 of wild type values in a manner consistent with decreased allosteric cooperativity among agonist recognition sites. Mutation R316A, located in the extracellular loop between transmembrane domains II and III, increased the Hill coefficient to 3.9 in a fashion consistent with enhanced open probability of a receptor multimer.

Amino Acid Sequence↗
PubMed1994

The significance of the hydrophilic backbone and the hydrophobic fatty acid regions of lipid A for macrophage binding and cytokine induction.

Natural partial structures of lipopolysaccharide (LPS) as well as synthetic analogues and derivatives of lipid A were compared with respect to inhibit the binding of 125I-labelled Re-chemotype LPS to mouse macrophage-like J774.1 cells and to induce cytokine-release in J774.1 cells. LPS, synthetic Escherichia coli-type lipid A (compound 506) and tetraacyl precursor Ia (compound 406) inhibited the binding of 125I-LPS to macrophage-like J774.1 cells and induced the release of tumor necrosis factor alpha (TNF alpha) and interleukin 6 (IL-6). Deacylated R-chemotype LPS preparations were completely inactive in inhibiting binding and in inducing cytokine-release. Among tetraacyl compounds, the inhibition-capacity of LPS-binding was in decreasing order: PE-4 (alpha-phosphonooxyethyl analogue of 406) > 406 >> 404 (4'-monophosphoryl partial structure of 406) > 405 (1-monophosphoryl partial structure of 406). In the case of hexaacyl preparations, compounds 506, PE-1 (alpha-phosphonooxyethyl analogue of 506) and PE-2 (differing from PE-1 in having 14:0 at positions 2 and 3 of the reducing GlcN) inhibited LPS-binding and induced cytokine release equally well, whereas preparation PE-3 (differing from PE-2 in containing a beta-phosphonooxyethyl group) showed a substantially lower capacity in binding-inhibition and cytokine-induction. The conclusion is that chemical changes in the hydrophilic lipid A backbone reduce the capacity of lipid A to bind to cells, whereas the number of fatty acids determines the capacity of lipid A to activate cells. These results indicate that the bisphosphorylated hexosamine backbone of lipid A is essential for specific binding of LPS to macrophages and that the acylation pattern plays a critical role for LPS-promoted cell activation, i.e. cytokine induction.

Acylation↗
PubMed1994

Monte Carlo simulation of DNA strand breaks induced by monoenergetic electrons using higher-order structure models of DNA.

A new theoretical model for estimating yield of initial DNA strand break induced by several monoenergetic electrons is presented. It is based on the Monte Carlo track structure simulation and on new DNA structure models (one turn of double-strand DNA, nucleosome, solenoid), and links physical and chemical stages of radiation action. Direct and indirect effects are strictly distinguished. Some results of calculations indicated: (1) the number of single strand breaks per nucleus (6 microns in diameter) per Gy in pure water was about 10 times that in a cell environment (OH radical life time is assumed to be 8.7 ns). This is due to the difference in the time-dependent variation in the total number of the OH radical; and (2) the contribution of indirect effects to total damage decreased as the order of the DNA target model structure used in the stimulation increased (e.g. a one-turn model of double-strand DNA, approximately 98.4%; but the 30-nm solenoid model, approximately 86.1%). This was due to the protective effect of histone protein against OH radical attack. Double-strand breaks were scored if two single-strand breaks were located on the same base pair. The present study indicated that the information from morphological and biochemical examinations of the cell environment must be considered more carefully with computer simulation.

Computer Graphics↗
PubMed1993

GABA rho 2 receptor pharmacological profile: GABA recognition site similarities to rho 1.

The rho 2 receptor for gamma-aminobutyric acid (GABA) induces GABA-gated currents when expressed as a homooligomer in Xenopus oocytes. rho 2 responses display pharmacological profiles similar to those of expressed rho 1 receptors, although responses were slower, most agonists were more potent at rho 2 and Im values for the partial agonist imidazole-4-acetic acid were 7-fold higher. Amino acids important for most aspects of GABA agonist ligand recognition may not be among those that differ between rho 1 and rho 2, including the 20% amino acid difference in the N-terminal region.

Animals↗
PubMed1993

Pharmacology of GABA rho 1 and GABA alpha/beta receptors expressed in Xenopus oocytes and COS cells.

1. The rho 1 protein, which we previously cloned from retina, assembles as a homooligomer that transduces the binding of gamma-aminobutyric acid (GABA) into robust chloride currents. However, its insensitivity to bicuculline, pentobarbitone and benzodiazepines, all potent agents at typical GABAA receptors, suggested that it may react atypically to other GABA agonists and antagonists. 2. cDNAs for the rho 1 and the alpha 5 beta 1 receptors for GABA were expressed as homo- and heterooligomers, respectively, in Xenopus oocytes. The selectivities of the respective receptors for various agonists were investigated using concentration-response experiments in voltage clamped cells. 3. The most potent agonists at the rho 1 receptor were trans-4-aminocrotonic acid (TACA) > GABA > muscimol; at the alpha 5 beta 1 receptor the rank order was muscimol > GABA > 4,5,6,7-tetrahydroisoxazole[4,5-c]pyridine-3-ol (THIP). The most specific agonists were cis-(2-(aminomethyl)-cyclopropyl-carboxylic acid (CAMP) and THIP for the rho 1 and the alpha 5 beta 1 receptors, respectively. 4. Comparing GABA, TACA and cis-aminocrotonic acid (CACA) at rho 1 receptors expressed in COS cells gave results almost indistinguishable from those found at oocytes; the pharmacology of rho 1 seems independent of the expression system. 5. Agonists THIP, piperidine-4-sulphonic acid (P4S), and isoguvacine, whose C-C-C-N chains are constrained by rings into a folded conformation and were potent at the alpha 5 beta 1 receptor, were among the weakest at the rho 1 receptor. However CACA and CAMP, which align better with the extended than the folded conformation, were weakest at the alpha 5 beta 1 receptor but moderately potent at the pl receptor. These findings suggest that the rho l receptor recognizes agonists in the extended conformation, in contrast to GABAA receptors, which are believed to recognize agonists in the partially folded conformation.6. In contrast to the alpha 5 beta 1 receptor, gradations in maximum responses were apparent in the rho l receptor,suggesting various degrees of partial agonism. In particular, imidazole-4-acetic acid (I4AA), whose maximum response was only 3% of GABA's maximum, had an apparent Kd for activating the rho l receptor of 16 microM; but it had an apparent Kd for competitively blocking the receptor of 0.64 microM. This difference suggests that steric constraints in the activated (open channel) receptor are tighter than in the resting receptor.7. Hill coefficients approached 2 at the rho l receptor, but were closer to unity at the alpha 5 beta 1 receptor. Thus,the rho l receptor displayed higher cooperativity.8. Unlike typical GABAA receptors, the rho l receptor was insensitive to the competitive antagonists bicuculline, SR95531, securinine, and (+)-tubocurarine.

Animals↗
PubMed1993

[Estimations of organ dose and health risk of the mass chest X-ray examinations in children].

In Japan, mass chest X-ray examinations are mandated by law for schoolchildren and students. Recently, questions of the justification of such X-ray examination have arisen. In this study the absorbed doses of each organ, and the health detriments from the mass chest X-ray examinations to schoolchildren and students were estimated. The doses of organs were measured by the TLDs (Mg2SiO4), slab phantom, and anthropomorphic phantom. The probability of fatal cancer, and the resultant reduction in life expectancy induced by mass chest X-ray examinations were calculated by the multiplicative risk projection model of the ICRP-1990. The absorbed doses of lung, thyroid glands, esophagus, stomach, breast, and red bone marrow in first-year elementary schoolchildren were 90, 30, 90, 60, 90, and 30 muGy, respectively, and the doses in ovaries and testes were almost nil. Each organ dose of first-year students of junior high school was about 1.5 times that for elementary schoolchildren. The total radiation-induced lifetime cancer risk of schoolchildren and students was from 0.3 x 10(-5) to 0.9 x 10(-5) per person by the multiplicative risk projection model of the ICRP-1990 and a factor of 2 for the DDREF (dose and dose rate effectiveness factor). The reduction in life expectancy by radiation induced fatal cancer was from 15 x 10(-5) years to 50 x 10(-5) years per person. The results of this study suggest that subjects of mass chest X-ray examinations should be carefully selected from the viewpoint of radiation protection.

Adolescent↗
PubMed1992

Significant antitumor effect of a synthetic lipid A analogue, DT-5461, on murine syngeneic tumor models.

The antitumor effect of a synthetic lipid A analogue, DT-5461, was investigated using syngeneic tumor models in mice. Intravenous injection of DT-5461 into mice transplanted with solid tumors of MethA fibrosarcoma, MH134 hepatoma, MM46 mammary carcinoma, Lewis lung carcinoma (3LL), and colon adenocarcinomas 26 and 38 resulted in significant reductions in the weight of all tumors except Colon 26, with marked hemorrhagic necrosis of tumor tissues. Efficacy was almost equal to that of an Escherichia coli-type synthetic lipid A (compound 506), and also to those of some chemotherapeutics including Adriamycin, mitomycin C, fluorouracil and cisplatin. Furthermore, DT-5461 was more effective than other immunotherapeutics, including picibanil (OK-432) and lentinan. However, its antitumor effects were inferior to those of Adriamycin or OK-432 against the malignant ascites caused by intraperitoneal inoculation with MethA or with MH134 cells; life span was not prolonged by either intraperitoneal or intravenous administration. In addition, although DT-5461 showed direct inhibitory effects on the in vitro growth of MethA or MH134, these were much weaker than those of Adriamycin. These findings clearly indicated that DT-5461 with systemic administration is a highly effective antitumor agent on solid tumors, and suggest that the antitumor effect of DT-5461 with potent necrotizing activity might derive from indirect mechanisms related to the activation of host immune systems and not to the weak direct cytotoxicity.

Animals↗
PubMed1992

Contractile response of guinea pig ileum by repetitive application of morphine.

1. The repetitive application of morphine gradually induced a contracture in the isolated guinea pig ileum. 2. The optimum conditions for induction of the contracture were as follows: the concentration, incubation time and washout time of morphine were 1 or 10 microM, 2 and 3 min, respectively. 3. Preincubation with naloxone or TTX blocked this morphine-induced contracture. 4. Among twitch-inhibiting drugs, only clonidine induced a contracture similar to that induced by morphine, while tetrodotoxin (TTX) and adenosine did not. 5. The contracture was also observed in the longitudinal muscle-myenteric plexus preparations. 6. These findings indicate that morphine has a dual inhibitory and excitatory action on the guinea pig ileum and that its repetitive application preferentially diminish the inhibitory one.

Animals↗
PubMed1992

Modulation of endotoxin-induced monokine release in human monocytes by lipid A partial structures that inhibit binding of 125I-lipopolysaccharide.

We have previously shown that the synthetic tetraacyl precursor Ia (compound 406, LA-14-PP, or lipid IVa) was not able to induce the production of tumor necrosis factor, interleukin-1, and interleukin-6 in human monocytes but strongly antagonized lipopolysaccharide (LPS)-induced formation of these monokines. This inhibition was detectable at the level of mRNA production. To achieve a better understanding of molecular basis of this inhibition, we investigated whether lipid A precursor Ia (LA-14-PP), Escherichia coli-type lipid A (LA-15-PP), Chromobacterium violaceum-type lipid A (LA-22-PP), and synthetic lipid A partial structures and analogs (LA-23-PP, LA-24-PP, and PE-4) were able to influence the binding of 125I-LPS to human monocytes and compared this inhibitory activity with the agonistic and antagonistic action in the induction of monokines in human monocytes. 125I-LPS (20 ng per well) was added to human monocytes in the presence or absence of unlabeled rough Re mutant-derived LPS (Re-LPS) or lipid A compounds, and specific LPS binding was determined after 7 h. This binding was found to be dependent on CD14 as shown by the use of an anti-CD14 monoclonal antibody. Compound LA-14-PP was found to inhibit the binding of 125I-LPS to the cells in a similar dose-response to that of unlabeled LPS. This shows that the inhibitory capacity on LPS binding does not correlate with the monokine-inducing capacity because Re-LPS is active in inducing tumor necrosis factor, interleukin-1, and interleukin-6, while LA-14-PP is not. The strong capacity of LA-14-PP to inhibit 125I-LPS binding, however, correlates with the strong inhibitory capacity of this compound on LPS-induced monokine production. Compounds LA-15-PP, LA-23-PP, and LA-24-PP were active in the inhibition of 125I-LPS binding but were 5- to 10-fold weaker than Re-LPS and LA-14-PP. Of all lipid A structures tested, compound LA-22-PP expressed the weakest inhibitory capacity on LPS binding. These compounds showed again that the activity of binding inhibition does not correlate with the monokine-inducing capacity. We assume that the inhibitory effects of lipid A partial structures on LPS-induced monokine production have their origin in a competitive inhibition between LPS and the lipid A partial structures for the same binding site on the cell membrane.

Antigens, CD↗
PubMed1992

Biological activity of synthetic phosphonooxyethyl analogs of lipid A and lipid A partial structures.

We investigated the biological activity of four new synthetic analogs of lipid A, termed PE-1, PE-2, PE-3, and PE-4. All compounds contain an alpha-oxyethyl-linked (-O-CH2-CH2-) phosphoryl group in position 1 of the reducing glucosaminyl residue (GlcN I) of lipid A. PE-1 is a hexaacylated analog of Escherichia coli lipid A (compound 506). PE-2 differs from PE-1 in carrying two myristic acid residues at GlcN I. PE-3 has the same acylation pattern as PE-2, but GlcN I is present in the beta anomeric form. Finally, PE-4 represents an analog of tetraacyl precursor Ia (compound 406). Structure-activity relationships of these compounds were determined by measuring their capacity to induce tumor necrosis factor alpha, interleukin 1, and interleukin 6 release by human mononuclear cells and to cause mitogenicity of murine spleen cells. The results show that replacement of the glycosidic phosphoryl residue by a phosphonooxyethyl group had no substantial effect on the biological activity of compounds. However, the anomeric configuration of GlcN I was found to be of great biological relevance, as, in general, the alpha anomer (PE-2) expressed high activity, and the beta anomer (PE-3) expressed low mediator-inducing and mitogenic activity. The absence of the 3-hydroxyl groups within the acyl residues at GlcN I in PE-2 was found to only slightly affect the induction of monokines in human mononuclear cells compared with that of PE-1 or lipid A (506). These stable 1-phosphonooxyethyl analogs of lipid A may be candidates in the development of immunomodulators for the treatment of systemic endotoxicosis.

Animals↗
PubMed1992

Zinc triflate-promoted glycosidation: synthesis of lipid A disaccharide intermediates.

Zinc triflate was found to be superior to the heavy metal salts as a promoter in the Koenigs-Knorr type glycosidation reaction in the synthesis of lipid A disaccharide intermediates. It readily promoted the reaction of a complex glycosyl bromide with a reducing sugar moiety and gave the disaccharide with beta-selectivity in good yield. This method would be suitable for the bulk preparation of lipid A disaccharide intermediates.

Carbohydrate Sequence↗
PubMed1991

Synthesis and biological activities of analogs of a lipid A biosynthetic precursor: 1-O-phosphonooxyethyl-4'-O-phosphono-disaccharides with (R)-3-hydroxytetradecanoyl or tetradecanoyl groups at positions 2, 3, 2' and 3'.

Two novel analogs of a biosynthetic precursor of lipid A (2) were synthesized. The one analog (3) has acyl groups identical to those of 2, and the other (4) has tetradecanoyl groups in place of the (R)-3-hydroxytetradecanoyl groups of 2. Both 3 and 4 possess an alpha-glycosidically-bound phosphonooxyethyl group in place of the alpha-glycosyl phosphate group of 2. Compounds 3 and 4 exhibited definite antitumor activity against Meth A fibrosarcoma and low toxicity in rabbits, as the original compound 2 does. The replacement of the hydroxytetradecanoyl groups with tetradecanoyl groups barely affected the antitumor activity, but slightly enhanced the toxicity in rabbits.

Animals↗
PubMed1991

Synthesis and biological activities of lipid A analogs: modification of a glycosidically bound group with chemically stable polar acidic groups and lipophilic groups on the disaccharide backbone with tetradecanoyl or N-dodecanoylglycyl groups.

Six novel lipid A analogs were synthesized. The first two analogs, 4 and 5, have an alpha-glycosidically bound carboxymethyl or 1,3-dicarboxyisopropyl group on the disaccharide backbone with four tetradecanoyl groups. The next three analogs, 6, 7 and 8, have two or four N-dodecanoylglycyl groups on the 1-alpha-O-phosphonooxyethylated disaccharide backbone. Analog 6 bears N-dodecanoylglycyl groups on the hydroxyl functions at positions 3 and 3', and tetradecanoyl groups on the amino functions at positions 2 and 2'. Analog 7 is a 2, 3, 2' and 3'-tetrakis(N-dodecanoylglycyl) derivative, and analog 8 resembles compound 6, but the binding of the N-dodecanoylglycyl and tetradecanoyl groups at positions 2, 2' and 3, 3' are reversed. The third analog, 9, has the same acyl group configuration as compound 6, but has a 1,3-dicarboxyisopropyl group at position C-1. Compounds 4 and 5 exhibited definite antitumor activity against Meth A fibrosarcoma, indicating that the phosphate group at the C-1 position in lipid A could be replaced by the carboxylic acid without reducing the antitumor activity. In rabbits, compounds 6 and 9 exhibited potent antitumor activity, but their toxicity was extremely low. On the other hand, compounds 7 and 8 showed no antitumor activity. The levels of antitumor activity of 6 and 9 were similar to those of the natural-type lipid A. The antitumor activities of analogs with a N-dodecanoylglycyl group on the disaccharide backbone depended on the connecting sites of the acyl groups.

Animals↗
PubMed1991

Withdrawal like responses of rat hippocampal slices following brief exposure to morphine.

An acutely acquired dependence was investigated in rat hippocampal slices after brief exposure to morphine. Morphine augmented the population spike amplitude. Naloxone not only reversed the augmentation but decreased the amplitude to a level below that of the control. The inhibitory effect of naloxone correlated with the period of preincubation with morphine. These results suggested that the decreased response may indicate the withdrawal state acquired in vitro.

Animals↗
PubMed1990

Synthesis and antitumor activity of lipid A analogs having a phosphonooxyethyl group with alpha- or beta-configuration at position 1.

Three novel lipid A analogs, which have an alpha- or beta-glycosidically bound phosphonooxyethyl group instead of the alpha-glycosyl phosphate group of natural lipid A, were synthesized. The first analog (2) had an alpha-phosphonooxyethyl group on the identical acylated disaccharide 4'-phosphate structure found in natural lipid A (from Escherichia coli) and hence differed from the latter only in the nature of the acidic group at position 1. The second one (3) had tetradecanoyl groups in place of the two (R)-3-hydroxytetradecanoyl groups bound to the 2- and 3-hydroxyl function of 2, retaining the alpha-phosphonooxyethyl group. The structure of the third analog (4) was the same as that of 3 except that the phosphonooxyethyl group of the former was beta-oriented. Compounds 2 and 3 exhibited potent activity against Meth A at the same level as natural lipid A, whereas 4 showed less activity. This fact revealed that the glycosidic phosphate is not a prerequisite for the antitumor activity of lipopolysaccharide. It can be replaced with a phosphonooxyethyl group without any loss of activity provided that the alpha-anomeric configuration at C-1 is retained. The replacement of the hydroxytetradecanoyl groups with tetradecanoyl groups does not change the activity either.

Animals↗
PubMed1989

The immunopotentiating property of lipophilic muramyl dipeptide and its molecular state in liposomal membranes: plaque-forming cell responses and ESR studies.

The immunopotentiating property of spin-labeled lipophilic muramyl dipeptide (SL-MDP) in liposomes was studied as to the plaque-forming cell (PFC) response to glycophorin, as an antigen, in membranes. The effect of SL-MDP depended on the densities of both SL-MDP itself and the antigen. The addition of the optimal amount of SL-MDP to liposomes containing a low density (0.016 mol%) of the antigen increased the PFC response by three times, whereas the presence of SL-MDP in optimal antigen density (0.032 0.127 mol%) membranes was rather inhibitory. In these liposomes, the amounts and molecular states of SL-MDP were determined from ESR spectra and are discussed in connection with its immunopotentiating property.

Acetylmuramyl-Alanyl-Isoglutamine↗