PubMed Health⌕ Search

Biomedical subjects

J Imai

Publications and source records attributed to J Imai.

At least 109 records · Page 6Linked to original sources
PubMed1984

Chemical synthesis and biological activities of partially inosine-substituted 2',5'-oligoadenylates: functional discrimination of three adenine amino groups on 2-5A for the binding to and activation of 2-5A-dependent endonuclease.

Binding and activation efficacies to the 2-5A-dependent endonucease by chemically synthesized partially inosine-substituted 2-5A analogs, namely, pppI2'p5'A2'p5'A, pppA2'p5'I2'p5'A and pppA2'p5'A2'p5'I were compared with that of native 2-5A in mouse L cell and human lymphoblastoid cell extracts. The results obtained in this study indicated that the first adenine amino group from the 5' terminus of 2-5A molecule plays critical role in binding to the endonuclease, whereas the third adenine amino group has a function for the activation of this enzyme.

Adenine Nucleotides↗
PubMed1983

A sensitive immunoenzymometric assay for 2',5'-oligoadenylate. Detection of elevated 2',5'-oligoadenylate synthetase in human peripheral mononuclear cells.

A competition immunoenzymometric assay for 2',5'-oligoadenylate was developed and employed to measure the interferon-inducible enzyme 2',5'-oligoadenylate synthetase in cell extracts. Microtiter plates coated with a novel conjugate of p5'A2'p5'A2'p5'A and N-(2-aminoethyl)-carbamylmethylated-Ficoll (AECM-Ficoll) bound rabbit polyclonal or mouse monoclonal antibody directed against 2',5'-oligoadenylate. Binding was inhibited by soluble 2',5'-oligoadenylate. Estimates of 2',5'-oligoadenylate concentrations based on inhibition of antibody binding compared favorably with those obtained using a protein synthesis inhibition assay. Low concentrations of 2',5'-oligoadenylate synthesized in vitro by extracts of human peripheral mononuclear cells were conveniently estimated using less than or equal to 10(6) cells. Virtually identical results were obtained when either total extract or synthetase bound to poly(I) . poly(C)-agarose was used for the in vitro incubation. When peripheral mononuclear cells were incubated in vitro with interferon, the normally low levels of 2',5'-oligo(A) synthetase rose dramatically. The assay was employed to measure synthetase levels in peripheral mononuclear cells isolated from patients with systemic lupus erythematosus. Some of these patients were found to have elevated levels of 2',5'-oligoadenylate synthetase.

2',5'-Oligoadenylate Synthetase↗
PubMed1983

Biological activities of phosphodiester linkage isomers of 2-5A.

To determine the relative importance of the 2',5'-phosphodiester bond of 2-5A in its binding to and activation of the 2-5A-dependent ribonuclease (RNase L, RNase F), a number of phosphodiester linkage isomers of 2-5A were prepared. These isomers were obtained either by lead ion-catalyzed polymerization of adenosine 5'-phosphorimidazolidate or by T4 polynucleotide kinase-catalyzed 5'-phosphorylation of adenylyl(3' leads to 5')adenylyl(3' leads to 5')adenosine followed by reaction of the corresponding phosphorimidazolidates with tri(n-butylammonium)pyrophosphate. The following 2-5A isomers thus were prepared: ppp5'A2'p5'A3'p5'A, ppp5'A3'p5'A2'p5'A, ppp5'A3'p5'A3'p5'A("3-5A"), ppp5'A2'p5'A3'p5'A2'p5'A,and ppp5'A3'p5'A2'p5'-A2'p5'A. The ability of these isomeric 2-5As to interact with the 2-5A-dependent endonuclease was ascertained by three different criteria: (i) ability to prevent the protein synthesis inhibitory effects of 2-5A, (ii) activity as an inhibitor of translation in encephalomyocarditis RNA-programmed L cell extracts, and (iii) ability to prevent binding of the radiolabeled probe, ppp5'A2'p5'A2'p5'A2'p5'A3'[32P]p5'Cp, to the endonuclease of L cell extracts. In certain experiments, degradation of oligonucleotide was minimized or eliminated by altering assay conditions, providing alternate phosphodiesterase substrates, or by using purified endoribonuclease of Ehrlich ascites cells. By all criteria, replacement of 2',5'-bond by a 3',5'-bond led to a substantial decrease in biological activity. Generally, replacement of just one 2',5'-phosphodiester bond with a 3',5'-linkage led to at least a one order of magnitude loss of activity. In accord with this trend, ppp5'A3'p5'A3'p5'A(3-5A) was greater than 10,000 less active than 2-5A in binding to the endonuclease or as an inhibitor of protein synthesis.

Adenine Nucleotides↗
PubMed1983

Epstein-Barr virus-specific antibodies in patients with adult T-cell leukemia (ATL) and healthy ATL virus-carriers.

Antibodies to Epstein-Barr virus (EBV)-capsid antigen (VCA), early antigen (EA) and EBV-associated nuclear antigen (EBNA) in the sera of 103 patients with adult T-cell leukemia (ATL) and the sera of 243 age- and sex-matched healthy adults, namely 99 anti-ATLA-positive (antibodies to ATL virus-associated antigen) and 144 anti-ATLA-negative individuals, were determined by indirect immunofluorescence. The anti-VCA titers in the sera from ATL patients were within the range observed in healthy controls. Anti-EA was found in 27% of the sera from ATL patients, but in only 8% of the sera from anti-ATLA-negative healthy controls. Antibodies to EBNA, which were present in almost all healthy adults, were not found in 30% of the sera from ATL patients. Of the sera of anti-ATLA-positive healthy adult donors 11% were negative for EBNA antibody. These results suggest that functional impairment of the T-cell system in most ATL patients, and also to a lesser extent in anti-ATLA-positive adults who might be healthy ATLV-carriers, may cause an unusual immune response of antibodies to EBV-associated antigens.

Adult↗
PubMed1983

Assay of 2',5'-oligoadenylate phosphodiesterase activity in mouse L-cell extracts.

A rapid and convenient assay for adenylyl(2' leads to 5')adenosine(A2'p5'A) or adenylyl(3' leads to 5')adenosine(A3'p5'A) phosphodiesterase activities is described. The dinucleotides A3'p5'A and A2'p5'A were labeled to a high specific activity by means of a catalytic-exchange procedure. Degradation studies of each of these labeled dinucleotides showed an asymmetrical distribution of label between the two adenine bases. Enzymatic degradation of [3H]A3'p5'A or [3H]A2'p5'A could be quantitated by first digesting the reaction products with bacterial alkaline phosphatase and then adding a slurry of DEAE-Sephadex. Under conditions described, adenosine did not adsorb to the resin, whereas dinucleotides as well as AMP did adsorb. As a consequence, when liquid scintillation fluid was added to the DEAE-Sephadex reaction mixture slurry, the radioactivity of the dinucleotides and AMP was severely quenched. This permitted a direct estimation of the amount of adenosine liberated during the phosphodiesterase degradation and subsequent alkaline phosphatase digestion. This method was applied to the measurement of A2'p5'A degrading activities in extracts of mouse L cells. Extracts from control mouse L cells were as active in degrading A2'p5'A as extracts from interferon pretreated cells.

Adenosine Monophosphate↗
PubMed1983

Cordycepin analogues of 2-5A and its derivatives. Chemical synthesis and biological activity.

Cordycepin (3'-deoxyadenosine) analogues of 2-5A were prepared by dicyclohexylcarbodiimide-induced polymerization of cordycepin 5'-monophosphate. A series of oligomers of the general formula p5'(3'dA)-2'[p5'(3'dA)]n (n = 1-5) was obtained. Cordycepin trimer 5'-monophosphate (n = 2) and cordycepin tetramer 5'-monophosphate (n = 3) were converted to the corresponding 5'-di- and triphosphates via the phosphorimidazolide method. Confirmation of assigned structures was provided through enzyme digestions, 1H and 31P NMR, and comparison with material which was synthesized by a completely independent route. Neither the cordycepin trimer triphosphate, ppp5'(3'dA)-2'p5'(3'dA)2'p5'(3'dA), nor the cordycepin tetramer triphosphate, ppp5'(3'dA)2'p5'(3'dA)2'p5'(3'dA)2'p5'-(3'dA), were inhibitors of translation in cell-free extracts of mouse L-cells programmed with encephalomyocarditis virus. In rabbit reticulocyte lysates, the cordycepin trimer triphosphate was devoid of activity, whereas the cordycepin tetramer triphosphate had approximately 1/100th the activity of 2-5A tetramer triphosphate, ppp5'A2'p5'A2'p5'A2'p5'A. Even though the cordycepin analogues were unable to activate the 2-5A-dependent endoribonuclease, they were able to bind to the endonuclease, thereby antagonizing the translational inhibitory effects of 2-5A. Thus, replacement of the 3'-hydroxyl groups of all the ribose moieties of 2-5A results in an analogue which can bind to the 2-5A-dependent endoribonuclease but is incapable of activating the enzyme. The 3'-hydroxyl groups of 2-5A, therefore, are critical for activation of the 2-5A-dependent endonuclease.

Animals↗
PubMed1983

Intestinal absorption of dl-alpha-tocopherol from bile salts and polysorbate 80 micellar solutions in rat.

The intestinal absorption of dl-alpha-tocopherol (VE) from various micellar solutions was studied by the in situ recirculating perfusion in rat small intestine. The perfused micellar solutions of VE were formed by sodium taurocholate (STC), sodium taurodeoxycholate (STDC) or polysorbate 80 (PS-80). The absorption ratio of VE was STC greater than STDC greater than PS-80 micellar solutions. The addition of egg lecithin (PC) to all micellar solutions caused the decrease of the absorption. The absorption ratio did not necessarily have a simple correlation with the VE solubilization in these micellar solutions. And it was also found that the absorption ratio correlated with the micellar size and with net water flux in the intestinal lumen.

Animals↗
PubMed1982

Chemical modification potentiates the biological activities of 2-5A and its congeners.

Chemical modification of p5'A2'(p5'A2')np5'A by a periodate oxidation/Schiff base formation/borohydride reduction cycle gave a series of 2-5A analogues in which the ribose of the 2'-terminal nucleotide was transformed to an N-substituted morpholine (azahexapyranose). 2',5'-Oligoriboadenylate 5'-monophosphates bearing this modification were 5-10 times more potent as antagonists of the action of 2-5A or poly(I).poly(C) than was unmodified p5'A2'p5'A2'p5'A. Application of this modification to the tetramer triphosphate ppp5'A2'p5'A2'p5'A2'p5'A resulted in an analogue with 10 times the activity of ppp5'A2'p5'A2'p5'A (2-5A trimer triphosphate) as an inhibitor of protein synthesis or activator of the 2-5A-dependent endoribonuclease. This activator of the 2-5A-dependent endoribonuclease. This new 2-5A analogue, the most potent 2-5A derivative reported to date, inhibited translation in extracts of mouse L-cells programmed with encephalomyocarditis virus RNA at a concentration of 10(-10) M (concentration for half-maximal inhibition). All such N-substituted morpholine modified 2',5'-oligoriboadenylates were found to be extremely resistant to degradation by L-cell extracts under conditions where unmodified 2-5A or its derivatives were quickly destroyed. These data demonstrate the necessity for an intact terminal ribose ring for the action of the 2-5A phosphodiesterase. Thus, extensive chemical modification of 2' terminus of 2-5A may be possible without adversely affecting its biological activity while endowing it with other favorable properties such as resistance to degradation.

Adenine Nucleotides↗
PubMed1982

Electrocardiographic abnormalities in Syrian golden hamsters with coxsackievirus B1 myocarditis.

Serial electrocardiograms of acute viral myocarditis were recorded from Syrian golden hamsters inoculated with Coxsackievirus B1 (CVB1). Various electrocardiographic abnormalities similar to those reported in human viral myocarditis were observed. The reciprocal ST displacement and/or T wave flattening were most frequently found, and were detected in 80% of the animals. Occasionally, other abnormalities such as atrioventricular (AV) block, left bundle branch block (LBBB) pattern or extrasystoles were recorded. A histopathological examination disclosed the most prominent lesions of myocarditis in the endocardial third of the myocardium, particularly in the interventricular septum. These lesions were more widespread in the left ventricule than in the right. A close correlation between the electrocardiographic manifestations and distribution of the lesions in the myocardium was observed. Since electrocardiography is widely used in clinical medicine, its application to experimental viral myocarditis will promote the study of viral myocarditis and the analysis of myocardial fibrosis as its sequelae.

Animals↗
PubMed1982

Oligonucleotide structural features involved in binding to and activation of the 2-5A-dependent endoribonuclease of L cells.

Several analogues of 2-5A were prepared and evaluated for their ability to bind to and/or activate the 2-5A dependent endonuclease from murine L cells. Replacement of one of the two 2',5'-phosphodiester bonds of ppp5'A2'p5'A2'p5'A with 3',5'-phosphodiester bonds gave analogues 40-50 X less active than 2-5A in binding to or activation of the 2-5A-activated endonuclease whereas replacement of both 2',5'-linkages with 3',5'-linkage resulted in a compound (3-5A) which was 10,000 X less effective in binding to the endonuclease and devoid of activity as an inhibitor of protein synthesis. The sequence of periodate oxidation/Schiff base formation/borohydride reduction gave a derivative of ppp5'A2'p5'A2'p5'A2'p5'A in which the 2'-terminal ribose was replaced with a N-hexyl morpholine ring. This material was 10 X more active than 2-5A an a inhibitor of translation. One possible explanation for this increased activity is that the 2'-terminally modified oligomer is resistant to degradation by the 2',5'-phosphodiesterase responsible for the degradation of 2-5A in cell extracts.

Adenine Nucleotides↗
PubMed1981

5'-O-Monophosphoryladenylyl(2' goes to 5')adenylyl(2' goes to 5')adenosine is an antagonist of the action of 5'-O-triphosphoryladenylyl-(2' goes to 5')adenylyl(2' goes to 5')adenosine and double-stranded RNA.

5'-O-Monophosphoryladenylyl(2' goes to 5')adenylyl-(2' goes to 5')adenosine [(2' goes to 5')(pA)3] antagonizes the protein synthesis inhibitory effects of 5'-O-triphosphoryladenylyl-(2' goes to 5')adenylyl(2' goes to 5')adenosine by preventing activation of the (2' goes to 5')oligo(a)-activated ribonuclease which degrades mRNA. The oligoribonucleotide (2' goes to 5')(pA)3 also antagonizes the translational inhibitory capacity of poly(I).poly(C) in extracts of interferon-treated L cells, suggesting that (2' goes to 5')oligo(A) is the primary mediator of the protein synthesis inhibitory effects of poly(I).poly(C) in this cell-free system.

Adenine Nucleotides↗
PubMed1980

Structure-activity relationships for the inhibition of formation of acid-fastness im mycobacterial organisms by coumarins and cinnamates.

The relationships between the structure and inhibitory activity against the formation of acid-fastness in mycobacterial organisms were investigated in naturally occurring or synthetic coumarins and cinnamates. The presence of an OH-group at C7 in the coumarin nucleus proved to be essential for the inhibitory activity. Likewise, the presence of a para-OH-group in cinnamates is also essential. Reduction of a conjugated alpha, beta-double bond in both series resulted in a decrease of the ininhibitory activity. Shortening of the side chain of cinnamates resulted in total loss of the activity. The grouping -C-C-CO2R appeared to be necessary for retaining the inhibitory activity.

Acids↗