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PubMed1978

[Inhibition of the process of sugar transport stimulation in the frog sartorius muscles by amines and amides].

In the experiments on isolated frog sartorius muscles, amines and amides were found to inhibit the process of stimulation of D-xylose transport induced by insulin, 2,4-dinitrophenol or potassium contracture. The inhibitory action was produced by urea, acetamide, guanidine, NH4Cl, mono-, di- and trimethyl- or ethylamines, some diamines (all the substances being, applied in the concentration range equal to 100 mM). The similar effect was obtained when cystamine (20 mM), tryptamine, 5-methoxytryptamine (2 mM) and adenine, adenosine, guanosine (1-10 mM) were used. There was no inhibitory effect of acetone, glycerol, tetraethylammonium, propilamine, butylamine, aminoacids, spermine, spermidine, ATP, AMP or cAMP. It has been suggested that the inhibitory substances may interact by producing hydrogen bonds from NH-groups with the neutrally or negatively charged groups at the external surface of the muscle membrane in the region with a slow hydrophobicity. As a result, no structural changes required for activation of the sugar transport system occur in the membrane.

Amides↗
PubMed1983

Reversal of the reaction catalyzed by glyoxalase I. Calculation of the equilibrium constant for the enzymatic reaction.

Glyoxalase I catalyzes the formation of S-D-lactoyl-glutathione via the hemimercaptal adduct of methylglyoxal and glutathione. This enzymatic reaction, which has been considered virtually irreversible, was found to be reversible under such conditions that glutathione liberated from the thiolester was trapped. The reverse reaction could be monitored spectrophotometrically by use of 5,5'-dithiobis-(2-nitrobenzoate). In addition to 5,5'-dithiobis-(2-nitrobenzoate), 2,2'-dithiobispyridine and cystamine were used to promote the reverse reaction. S-D-Lactoylglutathione did not hydrolyze in the presence of glyoxalase I under the conditions investigated, as shown by its stability in the absence of thioltrapping agents. Proof of the reversal of the reaction was obtained by demonstrating the formation of stoichiometric amounts of methylglyoxal and glutathione from S-D-lactoylglutathione. Catalysis of the reverse reaction was dependent upon the presence of a bivalent metal ion in the active site of the enzyme. Apoenzyme, obtained by removal of the essential Zn2+ from the active site, did not catalyze the reverse reaction, but catalytic activity was restored by addition of Zn2+, Mg2+, Mn2+, or Co2+. The reverse reaction was also catalyzed by glyoxalase I from yeast. Linear competitive inhibition (Ki = 0.64 mM) was obtained with 5,5'-dithiobis-(2-nitrobenzoate), which necessitated correction of the apparent kinetic parameters of the reverse reaction. The corrected values for the reverse reaction catalyzed by glyoxalase I from human erythrocytes with S-D-lactoylglutathione as substrate were kcat = 3.6 s-1 and Km = 1.9 mM. Combination of these values with the corresponding parameters for the forward reaction allowed calculation, through the Haldane relation, of the equilibrium constant, Keq = 1.1 X 10(4), for the isomerization between the hemimercaptal of methylglyoxal and glutathione and S-D-lactoylglutathione. The strong reversible competitive inhibitor of the forward reaction, S-p-bromobenzylglutathione, also inhibited the reverse reaction competitively (Ki = 0.38 microM).

Disulfides↗
PubMed1981

Selective proteolysis of abnormal proteins of shortened chain length in rabbit reticulocytes.

Proteolysis of certain shortened globin chains can proceed in cell-free extracts of rabbit reticulocytes in the absence of ATP. Proteolysis of amino acid analogue-induced abnormal globin chains of normal chain length may be stimulated by ATP, however. The ATP independent degradation of globin cyanogen bromide-peptides appears to require the presence of free, unblocked amino groups in the substrate, has a pH optimum of 7.8 and is inhibited by phenanthroline, cobalt and zinc ions, N-ethylmaleimide and cystamine.

Adenosine Triphosphate↗
PubMed1982

The biosynthesis of rat serum albumin. In vivo studies on the formation of the disulfide bonds.

In order to learn at what stage the disulfide bonds of albumin are formed during its biosynthesis, we perfused rat livers with iodoacetamide and then isolated the intracellular precursor, proalbumin, from organelles known to be in the pathway of albumin synthesis and secretion. The alkylated cysteines in proalbumin were determined as a measure of its thiol groups in vivo. Proalbumin of smooth microsomes was found to contain a single thiol, which is proposed to be the noncoupling cysteine occurring residue 34 in circulating albumin. Proalbumin in rough microsomes contained an average of two cysteines; the additional cysteine thiol was largely situated in the COOH-terminal region and disappeared rapidly after blocking albumin synthesis with cycloheximide. In nascent chains of proalbumin, about 45% of the cysteine + cystine was in the thiol form. From these findings we propose that disulfide bond formation begins while the nascent chain is still attached to the ribosome and proceeds in an NH2 to COOH direction. The disulfide bonding apparently is completed into the endoplasmic reticulum. Possible intermediates in the process such as mixed disulfide forms of proalbumin with glutathione or cystamine were not detected. We suggest that cysteine-34 does not participate in disulfide bonding because the NH2 terminus of proalbumin remains loosely bound to the membrane, attached by a hydrophobic segment of the chain at residues 21-27.

Animals↗
PubMedDate not supplied

Detection of covalently bound halothane metabolites in the hypoxic rat model for halothane hepatotoxicity.

Using a non-radiometric technique, halothane metabolites have been shown to covalently bind to rat hepatic tissue with the production of a lesion. The conditions required for optimizing the lesion (hypoxia and biotransformation enzyme induction) also optimizes the binding of fluorinated halothane residues to hepatic tissue. The maximal binding of fluorinated halothane residues to the liver of rats precedes the development of the hepatic lesion. Female rats, which are resistant to the halothane initiated lesion, have one-third as much covalently bound halothane residue. Biotransformation inhibitors (SKF-525A, metyrapone), which inhibited lesion formation, also inhibit the covalent binding of halothane to hepatic tissue. Cystamine and cysteine, sulfhydryl agents which can inhibit hepatic lesion development when administered four hr after halothane exposure, also suppressed the amount of halothane metabolites covalently bound to hepatic tissue. Using this non-radioactive method for measuring the covalent binding of halothane to hepatic tissue, it appears that the bioactivation of halothane was a necessary event for the appearance of a halothane initiated hepatic lesion.

Animals↗
PubMed1980

Synthesis of gamma-L-glutamyl-taurine.

Glu(Tau), a bioactive substance previously isolated from the protein free aqueous extract of bovine parathyroid powder, has been synthesized. The intermediate derivative Z-Glu(Tau)-OBzl was prepared in three different ways from Z-Glu-OBzl and (1) cystamine by using the mixed anhydride method followed by oxidation, (2) Tau by the active ester procedure via Z-Glu-(ONp)-OBzl, (3) Tau applying mixed anhydride coupling. The protecting groups were removed by hydrogenolysis.

Animals↗
PubMed1995

[Bis((2,4-dioxo-1,2,3,4-tetrahydroquinazolin-3-yl)alkyl)disulfane and 3-(mercaptoalkyl)quinazolin-2,4(1H,3H)-dione: synthesis by ring transformation and antiviral activity. 42. Heterocyclic azines with heteroatoms in the 1- and 3- positions].

Reaction of N-(sulfonyloxy)phtalimide derivatives 1, 2, with cystamine and homocystamine, respectively, affords bis[2,4-dioxol-1,2,3,4-tetra-hydroquinazolin-3-yl)alkyl] disulfanes [sequence: see text] 3, which could be reduced to 3-(mercaptoalkyl)quinazoline-2,4(1H,3H)-diones. 5. (3-(2-Mercaptoethyl)quinazoline-2,4(1H,3H)-dione (5a) was also obtained in a one-pot reaction from 1 or 2 and cysteamine. 2-Ethoxy-4H-3,1-benzoxazin-4-ones 4a-c were converted with cysteamine to 3-(mercaptoethyl)quinazoline-2,4-diones 5a-c by a new ringtransformation reaction. 3-(2-Mercaptoethyl)quinazoline-2,4(1H,3H)dione (5a) and the corresponding disulfane 3a were evaluated for antiviral activity in vitro. Compounds 3a and 5a showed significant antiviral activity against some DNA- and RNA-viruses (vaccinia-, herpes simplex virus type 1; influenza A virus) at concentrations that were nontoxic to the host cell cultures.

Animals↗
PubMedDate not supplied

[The effect of different classes of radioprotectors on the survival of mice irradiated at a wide range of doses].

In experiments with mice three kinds of dose dependence of radioprotection efficiency were shown for different radioprotectors. Maximum protection was revealed in the ranges of LD70-100/30 for naphthyzin and cystamine, LD50-70/30 for thymogen and lymphokinin, LD70/30 for prodigiosan and polyribonate. The necessity of research of preparations which increase radioresistance in the wide range of doses is pointed. The problem of improved criteria for radioprotector selection is discussed.

Animals↗
PubMed1975

[Chromosome aberrations in the cells of monkeys that have undergone acute irradiation with the use of chemical protection].

The rate and type of chromosomal aberrations in the bone marrow cells and circulating lymphocytes of the gamma-irradiated monkeys prophylactically treated with cystamine and mexamine 5-10 minutes before the irradiation was studied. The number of chromosomal aberrations 9-10 years after the gamma-irradiation (600-650 r) of the protected monkeys was similar to that in the animals irradiated without protection. Symmetrical chromosomal changes were most freuqent in all the monkeys long after the irradition, including the animals treated with radioprotectors.

5-Methoxytryptamine↗
PubMedDate not supplied

Synthesis of selenocystathionamine and preliminary data on its oxidation by diamineoxidase.

Details are reported for the synthesis of selenocystathionamine, the 2-aminoethyl, 3-aminopropyl selenide, NH2CH2CH2-Se-CH2CH2CH2NH2. Paper and ion exchange chromatographic behaviour of the compound has been investigated. By automated ion exchange chromatography on a sulfonated resin selenocystathionamine may be easily differentiated from cystathionamine, cystamine and selenocystamine. It has been shown that selenocystathionamine is oxidatively deaminated by pig kidney diamineoxidase. Preliminary data indicate that the first product of the reaction is a cyclized aminoaldehyde which then undergoes further degradation.

Amine Oxidase (Copper-Containing)↗
PubMed1993

The inhibition of bovine serum amine oxidase by cysteamine.

Bovine serum amine oxidase (BSAO) is inhibited by cysteamine, while cystamine is a good substrate. The activity of BSAO is not restored following removal of excess cysteamine by N-ethylmaleimide, by iodoacetate or by filtration through a G-25 Sephadex column.

Animals↗
PubMed1993

The gamma subunit of the Escherichia coli F1-ATPase can be cross-linked near the glycine-rich loop region of a beta subunit when ADP + Mg2+ occupies catalytic sites but not when ATP + Mg2+ is bound.

A mutant of the Escherichia coli F1-ATPase, gamma S8C, has been reacted with a novel bifunctional reagent, N-maleimido-N'-(4-azido-2,3,5,6-tetrafluorobenzamido) cystamine (TFPAM-SS1). Modification of Cys-8 via the maleimide, followed by photolysis to convert the azido group to a reactive nitrene, led to cross-linking of the gamma subunit to a beta subunit. When this cross-linking was conducted with ADP + Mg2+ in catalytic sites, the predominant cross-linked product had a M(r) of 108,000. If cross-linking was done with uncleaved ATP + Mg2+ in catalytic sites, cross-linked products of 102,000 and 84,000 were formed. Cross-linking under both conditions led to inhibition of ATPase activity. TFPAM-SS1 could be cleaved by using reducing agents to break the disulfide bond that links the malemide and tetrafluorophenylazide moieties. Cleavage of this disulfide bond after formation of 102,000 and 84,000 species led to full recovery of ATPase activity. When the 108-kDa cross-linked product was cleaved, full activity was not restored, presumably because of insertion of the tetrafluorophenylazide into a functionally important site on the beta subunit. After cleavage of the disulfide bond, the free thiols could be reacted with [14C]N-ethylmaleimide, thereby radioactively tagging the sites of insertion of the tetrafluorophenylnitrene moiety. In this way, the site of cross-linking from Cys-8 of gamma to the beta subunit in the presence of ADP + Mg2+ was localized to within the sequence Val 145-Lys-155, which contains the glycine-rich loop. This loop region is a part of the catalytic site of the enzyme.

Adenosine Diphosphate↗
PubMedDate not supplied

[A new method for the comparative quantitative assessment of a radiomodifying effect].

A new criterion for the quantitative estimation of a radioprotective effect (radioprotector efficiency) is suggested. This is an integral index of protection. Biologically, this is an estimation of a proportion of animals survived, the survival rate in the experimental and control groups of exposed objects in the studied dose range. The methods of assessing the criterion, and its advantages over the commonly used dose reduction factor (DRF) are described. The efficiency of Cystamine, Naphthysin, Indralin, Thymogen, Lymphokinin, Prodigiosan, and Polyribonate are considered using the suggested criterion. A new method of a comparative estimation of the radioprotective effect is suggested.

Animals↗
PubMed1997

Programmed cell death of Mycobacterium avium serovar 4-infected human macrophages prevents the mycobacteria from spreading and induces mycobacterial growth inhibition by freshly added, uninfected macrophages.

Mycobacterium avium, an opportunistic pathogen in AIDS patients, replicates in human macrophages (Mphi) and induces programmed cell death (PCD). In this study we examine the effect of freshly added, uninfected Mphi on M. avium growth in apoptotic Mphi cultures. Incubation of uninfected autologous Mphi with apoptotic Mphi infected with M. avium for 6 h results in 90% inhibition of bacterial growth. The uninfected Mphi adhere to M. avium-infected apoptotic, but not to nonapoptotic M. avium-infected Mphi, suggesting a specific interaction between apoptotic and nonapoptotic Mphi. PCD of the host Mphi also prevents the release of intracellular components and the spread of the mycobacterial infection. Once the apoptotic infected Mphi reach the necrotic stage, mycobacteria and other intracellular material are released; the latter suffice to support extracellular mycobacterial replication. Necrosis of M. avium-infected Mphi is significantly augmented by the transglutaminase inhibitors dansyl-cadaverine and cystamine, indicating that apoptosis of Mphi is dependent on the extent of cross-linking of cell proteins by transglutaminases. Consequently, transglutaminase inhibitors accelerate the release of mycobacteria and intracellular components from the infected Mphi into the medium. These findings indicate that PCD of M. avium-infected Mphi is an important defense mechanism, preventing the spread of infection by sequestering the mycobacteria and by contributing to their demise by activation of newly recruited uninfected Mphi.

Apoptosis↗
PubMedDate not supplied

[The anti-ulcer action of zinc sulfate in models of acute and chronic ulcerogenesis in the rat duodenum].

The 5-day pretreatment of rats with zinc sulfate (50 or 150 mg/kg/day per os) significantly reduce the rate, the number, and area of cystamine-induced duodenal lesions in rats. Pretreatment with zinc sulfate in a dose of 15 mg/kg/day over a 5-day period or single administration of zinc sulfate (50 mg/kg) did not markedly reduce the above-mentioned lesion parameters. The administration of zinc sulfate (50 or 150 mg/kg/day per os) during 7 days results in a dose-dependent, significant decrease in the area of chronic acetate-induced gastric and duodenal lesions in rats. The results of clinical and experimental study indicate that zinc-containing compounds can be successfully used both for prophylaxis and treatment of duodenal ulcer.

Acetic Acid↗
PubMedDate not supplied

[Effect of a number of sulfur-containing radioprotective agents on the evacuatory function of the stomach in mice].

Tests staged on mongrel albino mice demonstrated that sulphur-containing radioprotectors used in doses two orders below those exercising a radioprotective action with their peroral administration are apt to significantly modify the evacuative function of the stomach. This properties of the sulphur-containing radioprotectors depends upon their chemical structure. A particularly strong influence on the evacuative function of the stomach in mice exerts cystamine dichlorohydrate, aminoalkylamino-alkylthiophosphates and mercaptoamidines. This property is less pronounced in cystaphos and cysteamine chlorhydrate. The least effect on the delayed evacuation was found in cysteamine bitartrate and in the disodium salt-4, 4(1)-trithiobis (butane-sulphonate). These data allow it to explain the specificity of the toxic and radioprotective action produced by diverse drugs with their peroral administration.

Animals↗
PubMed1997

[The effect of intracellular protease inhibitors on DNA synthesis in fibroblasts from the NIH 3T3 mouse strain].

The enhancement of catabolic reactions of cell macromolecules, primarily proteins, raises the question about the role of active proteolysis and particular kinds of proteases in the process leading to cell proliferation retardation. The application of highly specific inhibitors of intracellular proteases helps to answer this question even in part. It has been shown that a short-term (2-6 h) treatment of resting cells of line NIH 3T3 with inhibitors of lysosomal cysteinous proteases--cystatine or leupeptin, as well as with inhibitors of non-lysosomal Ca(2+)-activated cystein proteases--L-cystamine and L-cystin--enhances the cell proliferative response on the serum and even stimulates tritiated thymidine incorporation in the cells cultured in the medium with a low (0.2%) serum content. Unlike, the treatment of resting cells with the lysosomotropic agent chloroquin, known to shut down all lysosomal hydrolases, reduces the cell proliferative response of the serum. In the experiments of fusing the resting and stimulated cells, it was found that the pretreatment of the former with inhibitors of lysosomal proteases enhanced the index of labeled nuclei in the latter, while observed in dikaryons, compared to the control, although failed to remove totally the effect of DNA synthesis inhibition in heterokaryons (Setkov et al., 1984; Setkov, Kazakov, 1989). A conclusion is made that the short-term metabolic shift in resting cells towards anabolism may result in that resting cells commit a cycle, and that an enhanced activity of cystein proteases is one of specific metabolic processes in resting cells leading to proliferation retardation.

3T3 Cells↗