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At least 73 records · Page 4Linked to original sources
PubMed1976

Beta-glucuronidase activity of Yoshida ascites hepatomas of different drug-sensitivity and its change after treatment of host rats with various anticancer agents.

Change in beta-glucuronidase activity of six Yoshida ascites hepatomas was examined after treatment of host rats with one of 12 anticancer agents. The hepatomas, AH-66F, AH-130, AH-109A, AH-60C, and AH-44, in decreasing order showed more or less distinct increase in beta-glucuronidase activity after treatment of the rats with Nitromin, Endoxan, 864-T, Carbazilquinone, Mitomycin-C, Toyomycin, Daunomycin, Neocarzinostatin, vincristine sulfate, 5-fluorouracil, or cytosine arabinoside only when the cytological effect was positive. Moreover, degree of the increase was generally correlated with that of cytological effect. Bleomycin was ineffective either enzymically or cytologically. AH-66 was insensitive to any of the agents tested in increasing beta-glucuronidase activity and showed only a very slight cytological response to some of the agents. Acid deoxyribonuclease behaved like beta-glucuronidase but to a lesser extent. The above order of drug sensitivity of the hepatomas was not in parallel with that of normal beta-glucuronidase level, which also did not correlate with the life span of host rats.

Animals↗
PubMed2004

Mass spectrometric investigation of noncovalent complexation between a tetratosylated resorcarene and alkyl ammonium ions.

Noncovalent complexation between tetratosylated tetraethyl resorcarene (1) and primary, secondary, and tertiary alkyl ammonium ions (mMe, dMe, tMe, mEt, dEt, tEt, dBu, and dHex) was studied by electrospray ionization Fourier transform ion cyclotron resonance (ESI-FTICR) mass spectrometry. Interactions of the noncovalent complexes were investigated by means of competition experiments, collision-induced dissociation (CID) experiments, ion-molecule reactions with tripropylamine and gas phase H/D-exchange reactions with deuteroammonia. Gas phase ion-molecule reactions gave especially valuable information about the structure and properties of the complexes. Resorcarene 1 formed relatively stable 1:1 complexes with all aliphatic alkyl ammonium ions. Steric properties of the alkyl ammonium ions and proton affinities of the conjugate amines noticeably affected the complexation properties, indicating the importance of hydrogen bonding in these complexes. According to the competition experiments, the thermodynamically most stable host-guest complexes were formed with alkyl ammonium ions that were most substituted and had the longest alkyl chains. In CID experiments, release of an intact free guest ion or dissociation of the host was observed to depend on the proton affinity of the amine and the strength of the hydrogen bond that was formed. In ion-molecule reactions with tripropylamine, a guest exchange reaction occurred with all alkyl ammonium ion complexes with reaction rates mostly dependent on the steric properties of the original guest ion. In H/D-exchange reactions the N-H hydrogen atoms of the guest ion were exchanged with deuterium, whereas the resorcinol hydrogen atoms remained unchanged.

Ions↗
PubMed1996

Development of magnetic beads for rapid and efficient metal-chelate affinity purifications.

Metal-chelate affinity chromatography offers multiple advantages for protein purification, yet existing resins make its applications to sparse, hydrophobic, or particularly labile proteins and peptides quite difficult. In this work, we have developed a simple method to covalently modify commercially available superparamagnetic beads with a six-carbon spacer and nitrilotriacetic acid to provide a novel resin for extremely rapid and efficient metal chelate affinity purifications. Further, the small size and surface chemistry of these beads provide clear improvement in applicability to small scale purifications with reduced nonspecific adsorption. These advantages have been demonstrated relative to a commercially available nickel resin.

Chromatography, Affinity↗
PubMed2001

Chloramine-T in radiolabeling techniques. IV. Penta-O-acetyl-N-chloro-N-methylglucamine as an oxidizing agent in radiolabelling techniques.

Chloramine-T (CAT) is commonly used in radiolabeling of bioactive molecules by halogenation. CAT is used to release radioactive elemental iodine by oxidation of its salts. Unfortunately, CAT is a strong oxidizing agent and can cause significant damage to peptides and proteins. This may lower the yield of the iodination reaction and may produce undesirable side products. Recently, it was found that the in situ formation of N-chlorosecondary amines, by the addition of secondary amines to CAT prior to exposure to the substrate, can reduce the oxidative damage caused by CAT. To simplify the method, we prepared penta-O-acetyl-N-chloro-N-methylglucamine (NCMGE) as a solid N-chlorosecondary amine. The chemical reactivity of NCMGE toward a model amino acid, 1-aminocyclohexane carboxylic acid, was compared with that of chloramine-T. In the presence of the model amino acid, CAT lost all its chlorine titer within 60 min while NCMGE retained 99% of its chlorine titer. NCMGE was compared to CAT for the iodination of l-tyrosine and leucine enkephalin. For both substrates, the NCMGE method produced larger or equal yields of the monoiodo and diiodo products and less decomposition. It is proposed that the method employing NCMGE to release diatomic iodine is more convenient and efficient for radiolabeling peptides and proteins than currently used methods.

Amino Acids, Cyclic↗
PubMed2003

Preparation and reactivity of O2-sulfonated diazeniumdiolates.

We report the facile preparation of O2-sulfonated diazeniumdiolates and mechanistic investigation of their reactions with representative nucleophiles. This new class of compounds extends the range of O2-substituted diazeniumdiolates available for potential applications in research and medicine.

Alkanesulfonates↗
PubMed2001

Tetrapentylammonium block of chloramine-T and veratridine modified rat brain type IIA sodium channels.

Tetrapentylammonium (TPeA) block of rat brain type IIA sodium channel alpha subunit was studied using whole cell patch clamp. Results indicate that TPeA blocks the inactivating brain sodium channel in a potential and use-dependent manner similar to that of the cardiac sodium channel. Removal of inactivation using chloramine-T (CT) unmasks a time-dependent block by TPeA consistent with slow blocking kinetics. On the other hand, no time dependence is observed when inactivation is abolished by modification with veratridine. TPeA does not bind in a potential-dependent fashion to veratridine-modified channels and does not significantly affect gating of veratridine-modified channels suggesting that high affinity binding of TPeA to the brain sodium channel is lost after veratridine modification.

Algorithms↗
PubMed1972

Increase in fibrinogen and fibrin-related antigen in human serum due to in vitro lysis of fibrin by thrombin.

In vitro lysis of fibrin, as indicated by increased fibrinogen-fibrin-related antigen (FR-antigen) in serum is usually seen when whole blood, or plasma, or highly purified fibrinogen prepared by several different procedures is clotted and kept at temperatures above 0 degrees C. This increase is both time and temperature dependent, occurs despite the addition of various plasmin and cathepsin inhibitors, and is probably caused by thrombin evolved during clotting and/or added in vitro. In these experiments, the FR-antigen was measured by a sensitive, reproducible hemagglutination inhibition immunoassay adapted to the AutoAnalyzer. Serum from whole blood contained more than serum from plasma, and fibrin rather than fibrinogen proved to be essential for the in vitro lysis. The phenomenon was also caused by Arvin or Reptilase, suggesting that splitting of one or more arginine or lysine bonds in fibrin may be at least partially responsible. To obtain minimal levels of FR-antigen (< 0.5 mug/ml), plasma is clotted for 4 hr at 0 degrees C with 1.0-5.0 U/ml thrombin, CaCl(2) (0.0125 mole/liter), and epsilon aminocaproic acid (0.05 mole/liter). Slightly higher levels, probably adequate for clinical diagnosis, are obtained by 10-30 min clotting at room temperature. Since endogenous and/or exogenous thrombin is essential for the collection of serum FR-antigen, all the FR-antigen found in normal serum probably results from an irreducible amount of in vitro lysis rather than from continuous intravascular clotting and fibrinolysis.

Aminocaproates↗
PubMed1988

Transnitrosating activity of N-nitroso-N-methyl-p-toluenesulfonamide in rats and human gastric juice.

N-nitroso-N-methyl-p-toluenesulfonamide (NMTS, diazald, CAS 80-11-5) is a widely used compound for laboratory production of diazomethane. The present results showed that the noncarcinogenic NMTS reacts as a transnitrosating agent with amino nitrogen of secondary amines and amide both in vitro (human gastric juice) and in vivo (rats) to yield N-nitroso compounds. Since all compounds formed (NMOR, NDMA, NPIP, NPZ, NMU) are known animal carcinogens, caution should be taken by users handling NMTS.

Amides↗
PubMed1980

[Histochemical changes in the neurosecretory hypothalamic nuclei as result of an intoxication with mercury compounds (author's transl)].

The effect of experimental poisoning by organic compounds, frequently used in agriculture as fungicides, on the histochemical and histoenzymic pattern of the hypothalamic neurosecretory system has been studied. The experimental rats were fed by means of a gastric tube with the following compounds: Phenylmercuryacetate, 0.1 g daily, for 10 days; Aethylmercury-p-toluenesulphanilide, 0.2 g daily, for 10 days, and Methoxyethylmercurychloride (Ceresan), 0.1 g daily, for 6 days. The histochemical and histoenzymic investigations have shown that ingestion of Phenylmercuryacetate brought about an increase in the release of antidiuretic hormone (ADH) with a concomitant enhancement of production of neurosecretory substances. The peroral administration of Aethylmercury-p-toluenesulphanilide and of Methoxyethylmercury chloride instead, resulted in the accumulation of the neurosecretion within the hypothalamic-hypophyseal system with a parallel inhibition of ADH release. The experimental poisoning of Ceresan had also a stimulatory effect on the activity of many enzymes in the neurosecretory nuclei of the rat hypothalamus. Morphological changes resulting from the experimental intoxication were only rarely observed in the neurosecretory cells of the investigated hypothalamic nuclei.

Animals↗
PubMed2004

Tosylation of endocrine-disruptive alkylphenolic compounds in a solid-phase reaction system consisting of C18-modified silica gel and aqueous buffer solution.

The tosylation reaction of endocrine-disruptive alkylphenolic compounds in a solid-phase aqueous system was investigated with the aim of developing an environment-friendly and efficient derivatization method for HPLC analyses of environmental samples. The phenols were rapidly and efficiently converted to the tosyl derivatives on a commercially available ODS solid-phase cartridge by passing an aqueous buffer solution through it. The solid-phase aqueous tosylation system has been incorporated into a preconcentration step performed by solid-phase extraction from environmental water.

Buffers↗
PubMed1989

A new assay for the determination of factor XII in plasma using a chromogenic substrate and a selective inhibitor of plasma kallikrein.

A new chromogenic assay for factor XII in plasma was designed by the use of the soluble activator Kalliplastin, the substrate H-D-HHT-Gly-Arg-pNA and a synthetic inhibitor of plasma kallikrein (Pefabloc PK). The assay was carried out in one and the same cuvette and did not require factor XII-deficient plasma. There was a good correlation between F XII coagulant and amidolytic assays.

Benzamidines↗