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PubMed1972

Thio reduction of human 2 -macroglobulin. The subunit structure.

1. Human alpha(2)-macroglobulin was prepared from a fraction obtained during the large-scale separation of normal human plasma proteins for clinical use. 2. Sedimentation-equilibrium measurements indicated a molecular weight of 725000. A value of 18.1S was obtained for s(0) (20,w). 3. The dissociation that occurs in the pH range 4.5-2.5 and in the region of neutrality in urea-containing solutions is consistent with a dimeric structure of the molecule. 4. The effects of the thiol reagents mercaptoethanol, mercaptoethylamine and N-acetylcysteine were investigated over a range of experimental conditions. Distinct components having sedimentation coefficients of 15, 12 and 8.5S were identified. 5. Conditions were found under which limited reduction with thiol liberated a subunit with a molecular weight approximately one-quarter of that of the intact molecule. This subunit retains the serological specificity of the whole molecule.

Acetylcysteine↗

PubMed1996

Thiols, recA induction and radiosensitivity in Escherichia coli.

Induction by gamma-radiation, UV radiation or hydroxyurea of RecA gene product synthesis in Escherichia coli, monitored as beta-D-galactosidase in recA-lacZ fusion strains, was shown to be inhibited if 2-mercaptoethylamine (MEA) was added before treatment with the inducing agents. If cysteine (Cys) at low concentrations was added at the same time as MEA it counteracted the action of MEA. The effect of MEA may be described as a competitive inhibition of an inducing or conducting effect of Cys. In E. coli GE499 (uvrA+), complete inhibition by 30-mmol dm-3 MEA of recA induction was associated with about five times higher radio-resistence. Both of these effects of MEA were completely reversed by 0.3-mmol dm-3 Cys. As shown in parallel experiments with E. coli GE500 (uvrA-), these effects of MEA and Cys were shown to be independent of excision-repair proficiency. Treatment of bacteria with MEA and/or Cys was shown not to lead to increased intracellular concentrations of these thiols. Instead, treatment with them appeared to provoke conspicuous increases in glutathione levels, which are, however, probably not directly involved in the studied action of MEA and Cys.

Cysteine↗

PubMed1975

An in vitro and in vivo investigation of the phototoxic effect and its amelioration with radioprotective compounds.

Electron spin resonance spectroscopy has been used to demonstrate that the phototoxic antimalarial drug, 6,8-dichloro-2-phenyl-a-2-piperidnylquinolinemethanol (WR 7930), when irradiated with long-wave ultraviolet (UV) light (lambda greater than 320 nm) while held in a glassy matrix at 73 degrees K, enters a triplet state and releases hydrogen atoms in its environment. The steady-state concentration of triplet WR 7930 molecules and of hydrogen atoms is reduced 2 to 3 times when mercaptoethylamine (MEA) is also present in the UV-irradiated glass. Organosulfur radicals form on MEA while hydrogen atoms and triplet-state molecules are reduced in number. Hydrogen atoms and triplet WR 7930 molecules are considered as mediators of the phototoxicity of the antimalarial drug. Thus, hydrogen atom scavanging and chemical quenching of the triplet state are possible mechanisms by which protection against phototoxic effects could be gained. Protection is demonstrated in mice receiving 20 mg per kg WR 7930 intraperitoneally and exposed to long-wave UV for 20 hr when the radioprotective aminothiol-forming compound, 2-(3-aminopropylamino) ethyl dihydrogen phosphorothioate (WR 2721), is administered at 400 mg per kg immediately before irradiation. When no protective drug is administered concurrently, WR 7930 administration results in intense erythema, edema, and eventual necrosis of ear tissues.

Animals↗

PubMed1976

Respiratory activity as a determinant of radiation survival response.

Respiration is depressed in irradiated bacteria reaching a minimum level in most strains at 1-3 h after exposure when incubated in growth medium. Since a delay in response is observed, direct action on respiratory enzymes is unlikely. The dosage response of respiration varies widely in the strains studied with Do's from 15 kR for Escherichia coli BS-1 to 1200 kR for Micrococcus radiodurans. All strains exhibit two-component dosage-response curves. Escherichia coli BS-1 uniquely possesses a positive-sloped second component suggesting a major disruption of respiratory control. A relationship exists between the responses of respiration and survival to a 50-kR exposure in the strains studied. When E. coli B/r is grown in 0.4% glucose reaching a pH of 5.3, a condition known to increase radiation survival considerably, a large increase in radioresistance of respiration is found. 2-Mercaptoethylamine (MEA), a radioprotective agent, also produces proportionate radioprotection of respiration and survival. In M. radiodurans protection is afforded to respiration at doses which produce no measurable effect on survival. These facts suggest that respiration is a major factor in influencing cell survival and may be the principal mechanism through which chemical agents modify radiation response.

Dose-Response Relationship, Radiation↗

PubMed1977

Effect of the radioprotective drugs MEA, DMSO, and WR-2721 on tumor control and skin tolerance in the rat.

Mercaptoethylamine (MEA), dimethylsulfoxide (DMSO), and S-2-(3-aminopropylamino)ethylphosphorothioate (WR-2721) were tested for their protective effects against single and fractionated doses of 250 kv X-rays. Acute and late skin reactions and control of the BA-1112 rhabdomyosarcoma were examined in protected and unprotected WAG/Rij rats. All drugs protected skin in both single and fractionated treatment regimens, with MEA giving the most protection and DMSO the least. DMSO and WR-2721 protected tumors against single doses of radiation, and all three drugs tested protected tumors against fractionated irradiation. As a result, only single-fraction treatments of MEA-protected animals showed therapeutically favorable differential protection.

Amifostine↗

PubMed1988

Cistiside-M, a new protective agent.

The toxicological and radiopharmacological properties of the agent Cistiside-M (2-mercaptoethylamine adenosine-5-phosphate) were investigated on male mice, lines C57Bl and H. The compound was administered intraperitoneally in doses from 1000 to 125 mg/kg, 15 min prior to lethal gamma-irradiation using a 137Cs source in the 6 to 15 Gy range. The radioprotective effect was assessed by the integral indices of 30-day survival, mean survival time, coefficient of protection alpha, S30 and the dose-reduction factor (DRF). The compound was characterized by low toxicity and good antiradiation effect in a wide dose range. Maximum degree of radioprotection (75% survival) was established when the agent was administered in a dose of 1000 mg/kg. DRF was 1.6. The dose of 250 mg/kg was interesting--with 50% survival rate and increase of the therapeutic index to 5.6. The low toxicity and the considerable radioprotective effect of the compound are due to its complex structure.

Adenosine Monophosphate↗

PubMed1973

Metabolism of cholesteryl palmitate by rat brain in vitro; formation of cholesterol epoxides and cholestane-3beta,5alpha,6beta-triol.

Incubation of [4-(14)C]cholesteryl palmitate with the 12,000 g supernatant fraction of adult rat brain fortified with an NADPH-generating system and beta-mercaptoethylamine resulted in formation (2-5%) of more polar metabolites characterized as a mixture of cholesterol-5,6-epoxides. Under extended incubation conditions, cholestane-3beta-5alpha-6beta-triol was isolated as the major end product of the incubations. Free [4-(14)C]cholesterol incubated under similar conditions was not oxidized, whereas oxidation of [4-(14)C]cholesteryl palmitate appeared to be dependent upon hydrolysis of the ester by the rat brain microsomal subcellular fraction. Elimination of the NADPH-generating system or the addition of EDTA to the incubation mixture inhibited epoxide formation, suggesting that the products are derived from an NADPH-dependent enzymatic lipoperoxidation mechanism. The in vitro conversion of [4-(14)C]cholesterol-5alpha,6alpha-epoxide to cholestane-3beta,5alpha,6beta-triol was also demonstrated in rat brain subcellular fractions in the absence of added cofactors.

Animals↗

PubMedDate not supplied

[Effect of MEA on DNA degradation in permeable irradiated Bac. stearothermophilus cells].

It was shown that DNA-degrading activity of permeable, intact and gamma-irradiated cells of Bac. stearothermophilus decreased under the effect of beta-mercaptoethylamine (MEA). MEA decreased also a DNAase activity, in a crude acellular extract of Bac. stearothermophilus, and activities of S1-nuclease and DNAase I. The data obtained prompt an assumption that MEA has an inhibitory action on the activity of endonucleases irrespective of their substrate specificity.

Cell Membrane Permeability↗

PubMedDate not supplied

[Effect of MEA on the accumulation of DNA breaks in Bac. stearothermophilus irradiated with gamma and ultraviolet rays and treated with nitrosomethylurea].

beta-Mercaptoethylamine (MEA) decreased the accumulation of enzymatic single- and double-strand breaks in DNA of thermophilic bacteria exposed to gamma- and UV-radiation and treated with N-nitroso-N-methylurea. The protective effect of MEA, as registered according to accumulation of single-strand and double-strand breaks in DNA of Bac. stearothermophilus immediately after irradiation and after 30 min postirradiation incubation, was similar.

Cobalt Radioisotopes↗

PubMedDate not supplied

[The role of endogenous glutathione in the action of sulfur-containing radio-protectors].

In experiments on Ehrlich ascite tumor cells, the dependence of the radioprotective effect of beta-mercaptoethylamine and beta-mercaptopropionylglycine on the initial level of endogenous glutathione was studied. A varying degree of N-ethylmaleimide induced decrease of SH-glutathione content in the cells led to either easing or elimination of the radioprotective effect of the agents under study.

Animals↗

PubMed1982

Reactions of acyl phosphates with carboxylate and thiol anions. Model reactions for CoA transferase involving anhydride formation.

Succinyl phosphate reacts rapidly with the thiol N-acetyl-beta-mercaptoethylamine (a CoA analog) to form the succinate thiol ester. This is a chemical model for the enzymic reaction of CoA transferase. It is demonstrated that: 1) the chemical reaction is stepwise, proceeding through the formation of a succinic anhydride intermediate. The rate-determining step at pH 6.6 is anhydride formation. 2) The apparent equilibrium constant for anhydride formation from succinyl phosphate is increased 6000-fold in going from pH 6.6 to 4.4. Formation of the reactive anhydride intermediate is so favorable at pH 4.4 that it accumulates in the reaction solution. 3) The rate constant for anhydride formation is accelerated 60-fold in going from pH 6.6 to 4.4 due to protonation of the phosphate moiety of succinyl phosphate, which enhances its leaving ability. 4) Anhydride formation through intramolecular reaction of the --COO- group of succinyl phosphate is accelerated greater than or equal to 10(5)-fold compared to the intermolecular reaction of 1 M acetate and acetyl phosphate. Thus, in the chemical reaction, anhydride formation can be made rapid and favorable by: 1) making the reacting groups intramolecular; and 2) catalyzing the expulsion of the leaving group. These are modes of rate acceleration that can occur in enzymic reactions. This model study provides support for a mechanism that proceeds through an anhydride intermediate in the enzymic reaction catalyzed by CoA transferase.

Acyltransferases↗

PubMedDate not supplied

[Study of the cytogenetic activity of radioprotectors in a human lymphocyte culture. II].

Action of certain radioprotectors: 2-mercaptoethylamine HCl (MEA), cysteine HCl, 2-aminoethylsothiouronium (AET), dithiol 2,3-dimercaptopropansulphate Na (unithiol), aminopropylaminoethylthiophosphoric acid (gammaphos), cystaphos and 5-metoxytriptamine (mexamine) was studied as applied to human chromosome aberrations induced with thio-TEPA. It was shown that with an increase in thioTEPA and protectors concentrations their effect grows.

5-Methoxytryptamine↗

PubMedDate not supplied

Determination of plasma total homocysteine and cysteine using HPLC with fluorescence detection and an ammonium 7-fluoro-2, 1, 3-benzoxadiazole-4-sulphonate (SBD-F) derivatization protocol optimized for antioxidant concentration, derivatization reagent concentration, temperature and matrix pH.

A sensitive HPLC-fluorescence method for determining total endogenous plasma homocysteine (Hcy), cysteine (Cys) and cysteinylglycine (Cys-Gly) following derivatization with ammonium 7-fluoro 2,1,3-benzoxadiazole-4-sulphonate (SBD-F) is described. Quantitation utilizes an internal standard, 2-mercaptoethylamine. The derivatization procedure has been optimized for concentration of SBD-F, reducing agent (tributylphosphine) and temperature. Findings indicate that values for plasma determinations vary according to the nature of the matrix in which calibration standards are made up. If quantitation is based on a peak height ratio, then standards should be made up in either pH 7.4 phosphate buffered saline or plasma taking into account the endogenous thiol concentration. These findings are based on calibration data, and 30 plasma samples quantified using thiol standards made up in plasma, pH 7.4 and pH 9.5 buffers. By defining how this matrix/pH effect influences thiol quantitation, it should be possible to make a more meaningful comparison of Hcy measurements between laboratories. The chromatographic separation was investigated at several mobile-phase pH values with the following conditions ascertained to be optimal: a mobile phase consisting of 5% (v/v) acetonitrile in 0.1 M KH2PO4, pH 2.15 was run at a flow rate of 0.5 mL/min. It was used in conjunction with a Supelco LC-18 base deactivated analytical column (150 x 4.6 cm i.d. 3 microM bonded silica). The internal standard and thiols were measured by fluorescence detection at 385 nm excitation and 515 nm emmission. Plasma levels are easily measured in a 100 microL volume. Storage for 2 months at -20 degrees C resulted in no deterioration of thiols. Furthermore, no difference in thiol levels was observed between bloods collected in lithium heparin and EDTA. Collected blood should, however, be separated as soon as possible to avoid red cell metabolism of Hcy which was observed in a case of hyperhomocysteinemia. Once derivatized, thiols are stable for at least one week at +4 degrees C.

Adolescent↗

PubMed1992

Novel and ultrasensitive noncompetitive enzyme immunoassay (hetero-two-site complex transfer enzyme immunoassay) for alpha-human atrial natriuretic peptide.

A novel and ultrasensitive noncompetitive enzyme immunoassay (hetero-two-site complex transfer enzyme immunoassay) for alpha-human atrial natriuretic peptide (alpha-hANP) in plasma is described. alpha-hANP was biotinylated using N-hydroxysuccinimidobiotin and trapped onto an anti-alpha-hANP [6-28] IgG-coated polystyrene ball. After washing, biotinylated alpha-hANP was eluted from the polystyrene ball with HCI and was reacted with 2,4-dinitrophenyl-fluorescein-bovine serum albumin-disulfide-rabbit anti-alpha-hANP [6-28] IgG conjugate. The complex formed was trapped onto (anti-2,4-dinitrophenyl group) IgG-coated polystyrene balls and, after washing, reacted with avidin-beta-D-galactosidase conjugate. The polystyrene balls were washed, and the complex of the three components was eluted with epsilon N-2, 4-dinitrophenyl-L-lysine and transferred to anti-fluorescein IgG-coated polystyrene balls. After washing, the complex was released from the polystyrene balls by reduction with 2-mercaptoethylamine and transferred to (anti-rabbit IgG) IgG-coated polystyrene balls. beta-D-Galactosidase activity bound to the last polystyrene balls was assayed by fluorometry. The detection limit of alpha-hANP [1-28] was 3 fg (1 amol)/tube. Interference by plasma proteins was eliminated by separation of peptides from proteins using a molecular sieve. The assay range of plasma alpha-hANP [1-28] was 0.04-120 ng/L, and plasma levels of hANP in healthy subjects (11-56 ng/L) were measured without concentration.

Atrial Natriuretic Factor↗

PubMed1979

1,2-Dialkyl-4-pyrazolidinethiols as potential antiradiation agents.

The reaction between 3-chloropropylene sulfide and the 1,2-dialkylhydrazines was employed to prepare a series of 1,2-dialkyl-4-pyrazolidinethiols. Evidence is presented to support the structure proposed for the product. These mercaptoheterocycles are related to the beta-mercaptoethylamines and were prepared as potential radiation protective agents. No significant activity was observed.

Animals↗

PubMed1981

Inhibition of mucopolysaccharide sulfation.

A method of measuring the inhibition of sulfation in mucopolysaccharides employed the coupled enzyme system of Wortman. This procedure utilized the phenol and mucopolysaccharide sulfotransferases of beef cornea extract. Compounds tested against this system included amino acids, salicylates, 2-mercaptoethylamine and a derivative, heterocyclic ethanethiosulfuric acids, arylsulfonamidoethanethiosulfates, and several other compounds. In general, the salicylates and thiosulfates were inhibitory, with sodiumm 2-(4-acetamidobenzenesulfonamido)-ethanethiosulfate being the most inhibitory and 2-mercaptoethylguanidine trithiocarbonic acid the second most inhibitory. Salicylamide and allopurinol, which have been employed in kidney stone therapy, were inhibitors. Kidney stones have a mucopolysaccharide sulfate matrix, which is involved in their growth.

Animals↗

PubMed2000

Synthesis of bifunctional antibodies for immunoassays.

The synthesis of bifunctional antibodies using the principle of solid-phase synthesis is described. Two Fab' fragments were chemically linked together via a bismaleimide crosslinking reagent. The F(ab')(2) fragments from intact immunoglobulin G (IgG) were prepared using an immobilized pepsin column. Goat, mouse, and human antibodies were digested completely within 4 h. The F(ab')(2) fragments thus produced did not contain any IgG impurities. Fab' fragments were produced by reducing the heavy interchain disulfide bonds using 2-mercaptoethylamine. Use of the solid-phase reactor in the preparation of the bifunctional antibodies eliminated many of the time-consuming separation steps between the fragmentation and conjugation steps. This procedure facilitates the automation of bifunctional antibody preparation and the rapid optimization of reaction conditions.

Animals↗

PubMed1989

Cytotoxicities of two disulfide-bond-linked conjugates of methotrexate with monoclonal anti-MM46 antibody.

In studies on (antitumor antibody)-drug conjugates as potential antitumor agents, the amide derivatives of methotrexate (MTX) with cysteine and with 2-mercaptoethylamine (cysteamine) (MTX-Cys and MTX-MEA, respectively) were linked via a disulfide bond with a monoclonal antibody (alpha MM46) to a mouse mammary tumor MM46 with attached 3-(2-pyridyldithio) propionyl groups to give conjugates of MTX with alpha MM46 (MTX-Cys-SS-alpha MM46 and MTX-MEA-SS-alpha MM46, respectively). These two conjugates are both linked by a disulfide bond and are very similar in structure, but MTX-MEA-SS-alpha MM46 showed only weak in vitro cytotoxicity against MM46 cells, whereas MTX-Cys-SS-alpha MM46 had strong cytotoxicity. The cytotoxicity of the latter was comparable to that of the conventional direct MTX-alpha MM46 conjugate prepared with an MTX-active ester. However, this conjugate had a greater selectivity than that of the direct conjugate, calculated as the IC50 (concentration of a conjugate by MTX equivalence required for suppression of the number of viable MM46 cells to 50% of that of the untreated control) for the corresponding nonspecific conjugate divided by the IC50 for the alpha MM46 conjugate. The inhibitory activities of MTX-Cys and MTX-MEA on dihydrofolate reductase were similar. The cytotoxicity of MTX-Cys-SS-alpha MM46 was not affected by thiamine pyrophosphate, an inhibitor of the active transport of MTX across the cell membrane, but was decreased significantly by ammonium chloride, a lysosomotropic amine. However, the cytotoxicity was decreased only to a small extent by leupeptin, an inhibitor of lysosomal cysteine proteases cathepsins B, H, and L. These results suggest that the cytotoxicity is mediated by lysosomes, and may involve lysosomal enzymes other than cathepsins B, H, and L.

Animals↗