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At least 19 recordsLinked to original sources
PubMed1979

Effect of thiourea and substituted thioureas on dynein ATPase and on the turbidity response of Tetrahymena cilia.

The effects of thiourea and of several substituted thioureas -- phenylthiourea, alpha-naphtylthiourea, metiamide, and burimamide -- on dynein ATPase have been studied. The substituted thioureas are over 30 times more potent than thiourea in causing enhancement of 30S dynein ATPase activity and inhibition of 14S dynein ATPase activity. The effects of thiourea and phenylthiourea can be prevented by very low concentrations of beta-mercaptoethanol or dithiothreitol. Axonemal ATPase is also enhanced by the thioureas, but the reaction proceeds more slowly than for solubilized 30S dynein. Enhancement of 30S dynein ATPase by metiamide is prevented by low (approximately 1 microM) concentrations of ATP and, less effectively, by AMP-PNP, but not by AMP-PCP even though the latter is a stronger inhibitor of 30S dynein ATPase than is AMP-PNP. The thioureas inhibit the ATP-induced decrease in turbidity (measured as delta A350) of axonemal suspensions. Inhibition of the turbidity response is also prevented by low concentrations of beta-mercaptoethanol, but, in contrast to the irreversible enhancement of ATPase activity, inhibition of the turbidity response is largely reversible. The ability of 30S dynein to rebind onto twice-extracted axonemes is not changed by treatment with phenylthiourea or metiamide. These observations indicate that the thioureas react with at least two sets of SH or S--S groups on axonemes. Reaction with the group(s) on the 30S dynein causes an apparently irreversible enhancement of ATPase activity. Reaction with another group(s) causes a reversible inhibition of the turbidity response.

Adenosine Triphosphatases↗
PubMed1979

Effect of thiourea on microsomal oxidation of alcohols and associated microsomal functions.

Thiourea and diethylthiourea, two compounds which react with hydroxyl radicals, inhibited NADPH-dependent microsomal oxidation of ethanol and 1-butanol. Inhibition by both compounds was more effective in the presence of the catalase inhibitor, azide. Inhibition by thiourea was noncompetitive with respect to ethanol in the absence of azide but was competitive in the presence of azide. Urea, a compound which does not react with hydroxyl radicals or H2O2, was without effect. Thiourea had no effect on NADH- and NADH-cytochrome c reductase, NADPH oxidase, and NADH- and NADPH-dependent oxygen uptake. Thiourea inhibited the activities of aniline hydroxylase and aminopyrine demethylase. Thiourea, but no other hydroxyl radical scavengers, e.g., dimethyl sulfoxide, mannitol, and benzoate, reacted directly with H202 and decreased H2O2 accumulation in the presence of azide. Therefore the actions of thiourea are complex because it can react with both hydroxyl radicals and H2O2. Differences between the actions of thiourea and those previously reported for dimethyl sulfoxide, mannitol, and benzoate, e.g., effects on drug metabolism, effectiveness of inhibition in the absence of azide, or kinetics of the inhibition, probably reflect the fact that thiourea reacts directly with H2O2 whereas the other agents do not. The current results remain consistent with the concept that microsomal oxidation of alcohols involves interactions of the alcohols with hydroxyl radicals generated from microsomal electron transfer.

Aminopyrine N-Demethylase↗
PubMed1979

Thiourea and cyanamide as inhibitors of thyroid peroxidase: the role of iodide.

Thiourea, methylmercaptoimidazole, propylthiouracil, and thiouracil are all potent inhibitors of thyroid peroxidase (TPO)-catalyzed iodination. Unlike the cyclic thioureylenes, thiourea at 5 mM has no effect on guaiacol oxidation. If iodide is added to guaiacol assays containing thiourea, enzyme activity is lost. The latter observation may be explained as follows. In the presence of iodide, the iodinating species [TPO.Ioxid], oxidizes thiourea to formamidine disulfide. This product decomposes to cyanamide at neutral pH. We have shown cyanamide to be an inhibitor of the peroxidative and iodinating functions of TPO. Studies in rats demonstrate that doses of thiourea which completely inhibit in vivo protein-bound iodine formation have no irreversible effect on TPO, as measured by guaiacol peroxidation after removal of the thyroids. The major in vivo action of cyanamide is similar to that of thiourea. The data suggest that the primary in vivo and in vitro mode of action of thiourea is the reversible Ioxid-trapping mechanism. The anomalous inhibition of guaiacol peroxidation seen in the presence of thiourea plus iodide derives from the formation of formamide disulfide, followed by its nonenzymic decomposition to cyanamide.

Animals↗
PubMed1979

Effect of thiourea on intracranial bone tumour formation in AkR mice.

The effect of administration of thiourea (5 g/kg in diet) alone or simultaneously with thyroxine (1 mg/l in drinking water) on the frequency of hyperplastic benign osteoma of the skull was studied in AkR mice. Animals treated with both thiourea and thyroxine were in hyperthyroidism: the thyroxine dose received was higher that that required to prevent thiourea-induced thyroid gland hypertrophy. A significant increase of the intracranial bone tumour (IBT) frequency was observed both in mice treated with thiourea alone and those which received thiourea and thyroxine simultaneously. Increase of IBT frequency was not due to the antithyroid effect of thiourea but seems due to a direct toxic action of thiourea on the pituitary.

Animals↗
PubMed1976

Innate and drug-induced resistance to acute lung damage caused in rats by alpha-naphthyl thiourea (ANTU) and related compounds.

During the 3rd and 4th weeks of life rats were highly resistant to the toxic effects of alpha-naphthyl thiourea (ANTU) and of thiourea and its derivatives but toxicity developed rapidly during the following 2 weeks. Marked resistance to lung damage by toxic thioureas could be induced in older, mature rats by pretreatment with the toxic agent itself (tachyphylaxis), with other toxic and non-toxic antithyroid drugs or with iodine or iodide--even if the rats were pretreated at an early age before susceptibility to the agent developed. ANTU-tachyphylaxis was dose-dependent. Total thyroidectomy did not affect either lung damage induced by ANTU or the resistance due to tachyphylaxis or to pretreatment with iodide or the antithyroid drugs thiourea, 1-ethyl-1-phenyl thiourea or propyl thiouracil. Neither total nor medullary adrenalectomy affected ANTU toxicity. Marked resistance to ANTU-induced lung damage was induced in rats by pretreatment with either an activator (3-4 benzypyrene) or an inhibitor (SKF 525-A) of drug-metabolizine mixed-function microsomal enzyme systems; the inhibitor, sodium phenobarbitone, had no significant effect on toxicity. The sulphydryl compound, AET, induced marked resistance to ANTU; cysteine was less effective. Neither autonomic blockade with nicotine and atropine nor actinomycin D had significant effects on toxicity to ANTU. The acute pulmonary oedema induced in rats by high pressure oxygen, chemical convulsants, pressor agents and ammonium sulphate differed in many respects from that induced by toxic thioureas; it was typically haemorrhagic in nature, did not result in significant pleural effusion, did not exhibit tachyphylaxis, and was not influenced by pretreatment with iodide or derivatives of thiourea.

Age Factors↗
PubMed1978

[Structurally dependent effects of substituted thioureas on the concentration of potato virus X in Nicotiana tabacum L. "Samsun" (author's transl)].

A study has been made to investigate the effects of N-alkyl- and aryl-substituted thioureas as well as N,N'-alkyl-alkyl-, alkyl-aryl-, and aryl-aryl-substituted thioureas on the multiplication of PVX in Nicotiana tabacum L. "Samsun". The virus concentrations of the treated plants were serologically determined and compared with these of untreated controls. The weak antiphytoviral effect of nonsubstituted thiourea remained virtually unchanged in N,N'-dimethyl thiourea, and in N,N,N'-trimethyl thiourea. A stronger antiphytoviral effect was observed for N-phenyl, N',N'-pentamethylene thiourea, as well as N-methyl thiourea. All other substitutions, especially those by longer-chain substituents or by a larger number of substituents, were not found to have an influence on viral multiplication.

Chemical Phenomena↗
PubMed1979

Gas-liquid chromatographic determination of thiourea in citrus peels.

A gas-liquid chromatographic (GLC) method was developed for the detection and determination of thiourea in citrus peels. After the peel is extracted with ethyl ether, the ether extract is adsorbed on sodium sulfate together with water. Thiourea is recoverd from both the sodium sulfate and the peel residue with ethyl acetate-acetone(2+1). The extracted mixture is cleaned on an alumina column, the eluate is concentrated under vacuum, and thiourea is extracted from the concentrate with sodium carbonate solution. GLC was carried out on the prepared benzoyl derivative of thiourea. The average recoveries of thiourea from lemon peel were 85.3, 93.1, and 97.6% at the fortification levels of 1, 10, and 100 ppm, respectively. The detection limit was low as 0.08 ppm.

Chromatography, Gas↗
PubMed1978

[Structurally dependent effects of substituted thioureas on rna phage m 12 (author's transl)].

Using the agar diffusion method, thiourea as well as N-aryl-, N, N'-diaryl-, N-aryl-N'-alkyl-, N,N'-dialkyl-, and N-alkyl-substituted thiourea derivatives were examined for their effects on the system of Escherichia coli W 1665 F+/M 12. The compounds tested were found to produce more or less strongly inhibitive or promotive effects on the RNA phages and/or host bacteria. N-phenyl-N'-dibutyl thiourea, N-phenyl-N'-acetyl thiuorea, and N1,N1'-p-phenylene-bis-(N3-n-propyl thiourea) showed an intense inhibitory effect on M12. Quite obviously, the decisive intervention by these substances in the multiplication of viruses was by a replicative step subsequent to the adsorption of phages.

Coliphages↗
PubMed1977

Cyanoguanidine-thiourea equivalence in the development of the histamine H2-receptor antagonist, cimetidine.

In the histamine H2-receptor antagonist metiamide (2a) isosteric replacement of thione sulfur (=S) by carbonyl oxygen (=O) or imino nitrogen (=NH) affords the urea 2c and guanidine 2d which are antagonists of decreased potency. The guanidine is very basic and at physiological pH is completely protonated. However, introduction of strongly electronegative substituents into the guanidine group reduces basicity and gives potent H2-receptor antagonists, viz. the cyanoguanidine 2b (cimetidine, "Tagamet") and nitroguanidine 2e. A correspondence between the activity of thioureas and cyanoguanidines is demonstrated for a series of structures 1-4. The close correspondence between cyanoguanidine and thiourea in many physicochemical properties and the pharmacological equivalence of these groups in H2-receptor antagonists leads to the description of cyanoguanidine and thiourea as bioisosteres. Acid hydrolysis of the cyanoguanidine 2b yields the carbamoylguanidine 2f at ambient temperatures and the guanidine 2d at elevated temperatures. Cimetidine is slightly more active than metiamide in vivo as an inhibitor of histamine-stimulated gastric acid secretion and has clinical use in the treatment of peptic ulcer and associated gastrointestinal disorders.

Chemical Phenomena↗
PubMed1979

14C-Thiourea binding in the rat lung.

Results of the present study demonstrate that in vitro covalent binding of radioactivity from the edematogenic agent [14C] thiourea to rat lung protein can occur under aerobic and anaerobic conditions. Binding of thiourea to lung protein is associated with a reduction in glutathione. The binding of [14C] from thiourea to lung protein is temperature dependent.

Aerobiosis↗
PubMed2026

UVB photoprotection by thiourea and (thio)semicarbazone derivatives: cellular and molecular evidence.

BACKGROUND: Ultraviolet B (UVB) radiation is a major environmental stressor that contributes to oxidative stress, inflammation, DNA damage, and ultimately an increased risk of skin carcinogenesis. The development of safer, multifaceted UV filters with improved photostability and bioprotective properties remains an important research priority. Here, alkyl chain-conjugated thiourea (I-XIX) and aryl-linked (thio)semicarbazone (XX-XXV) derivatives have been systematically assessed for their photoprotective potential against UVB-induced cellular damage. METHODS: The UV absorption properties, molar absorptivity, and photostability of the test compounds were assessed through spectroscopic studies. Cytotoxicity, effective concentrations, and bioprotective effects of the compounds were evaluated using in vitro cellular methods. RESULTS: Several compounds exhibited robust UVB absorption with high molar absorptivity, particularly semicarbazone derivatives, while displaying minimal cytotoxicity to normal human dermal fibroblasts. Among the evaluated compounds, ten compounds were found to be more photostable than benzophenone (reference compound). Selected compounds significantly reduced UVB-induced intracellular reactive oxygen species and nitric oxide production, signifying effective attenuation of oxidative and nitrosative stress. In addition, compounds IV, XXI, and XXIII alleviated UVB-induced inflammatory cascades by diminishing Interleukin-1 beta (IL-1β) and Tumor Necrosis Factor alpha (TNF-α) levels. Therefore, these compounds also protected fibroblast morphology. Moreover, the same compounds protected from DNA damage by preventing UVB-induced genomic DNA fragmentation and formation of cyclobutane pyrimidine dimers. In particular, compound XXIII displayed selective UVB absorption, better photostability, low cytotoxicity, and moderate biological photoprotection (SPF 16). CONCLUSION: Together, the results suggest that thiourea and (thio)semicarbazone derivatives, notably compound XXIII, represent promising photoprotective scaffolds requiring further formulation, in vivo, permeability, phototoxicity, and safety studies to validate their potential as UV-filtering agents.

Humans↗
PubMed1979

Azethoxyl nitroxide spin labels. ESR studies involving thiourea crystals, model membrane systems and chromatophores, and chemical reduction with ascorbate and dithiothreitol.

Trans- and cis-azethoxyl nitroxides 1, 2, 3 and 4 can be trapped in the cavities of thiourea crystals. The presence of a single gauche conformation on either side of the pyrrolidine ring within the crystals was indicated by the ESR spectra. Rotation about the long molecular axis then corresponds approximately to y-axis motion of the nitroxide moiety. Proxyl nitroxides in which the nitroxide group is located on the penultimate carbon of long chain lipids can also be trapped and were shown to adopt the azethoxyl conformation in the thiourea crystals. The measured deltaA values (A parallel to - A perpendicular) of oriented egg lecithin multilayers containing trans- and cis-azethoxyl nitroxides 1 and 2 were quite small, consistent with the unique orientation of the nitroxide principal axes with respect to the long axis of the molecule. The deltaA values for a series of lipids bearing a label near the terminus of the chain were very similar to that of 1, showing that the azethoxyl conformation is likely the predominant one in these labels in orienting systems. Computer simulations of the ESR spectra of 1 and 2 in egg lecithin vesicles provided values for molecular orientation and motion parameters consistent with those expected from a consideration of molecular models in the extended (all trans) conformation. Azethoxyl nitroxides have also proven useful in the investigation of motion restricted (boundary) lipid in a lipid-protein system. Thus, the values (69 +/- 10%) for the amount of boundary lipid in the chromatophore membranes from Rhodopseudomonas sphaeroides as determined using trans- 2 and cis- 2 are in good agreement with values using 16-doxylstearic acid (64 +/- 3%). The fact that all three labels show about the same fraction of boundary lipid in this system indicates that the lipid binding sites are relatively insensitive to the geometry of the lipid chain. Also, both 1 and 2 appear to be able to detect a third lipid environment not seen with the doxyl fatty acid. The apparent fluidity of this component lies between that of boundary and bilayer lipid. The unique orientation of the nitroxide principal axes with respect to the long molecular axis in azethoxyl nitroxides 1 and 2 allows detection of hindrance to rotation about the long molecular axis, in contrast to the analogous doxyl and proxyl fatty acids. Comparative reduction studies using ascorbate and dithiothreitol indicate that azethoxyl nitroxides are slightly more resistant toward reduction than proxyl nitroxides and much more resistant than doxyl nitroxides.

Ascorbic Acid↗
PubMed1979

Thiourea reverses cross-links and restores biological activity in DNA treated with dichlorodiaminoplatinum (II).

Cis and trans dichlorodiaminoplatinum (II) compounds bind to DNA and form DNA cross-links, which are usually considered to be irreversible. Thiourea can reverse these cross-links without any apparent breakdown of the DNA. In addition, cis- and trans-Pt (II) treatment of lambda decreases its transfectivity. After suitable incubation with thiourea, full transfectivity of Pt(II)-treated lambda DNA can be restored.

Animals↗
PubMed1977

Thyroid uptake or radiophosphorus as influenced by thiourea parathormone, and ACTH in Heteropneustes fossilis.

The Indian catfish, Heteropneusted fossilis, was chemically thyroidectomized with thiourea. The uptake of radioactive phosphorus by the thyroid of these thyroidectomized fished was then studied. The effect of mammalian ACTH and parathormone on the thyroid uptake of P-32 by the treated fish was also studied. It was found that thiourea reduces the P-32 uptake considerably, whereas both the hormones, separately, elevate the P-32 levels in the thyroid to near control values.

Adrenocorticotropic Hormone↗
PubMed1979

Thiourea derivatives as specific inhibitors of picorna viruses.

30 compounds with antipicorna virus activity were selected from 173 N,N'-disubstituted thiourea derivatives. The spectrum of antiviral activity was determined in vitro using entero, FMD, rhino and EMC viruses. Structure-activity relationships were studied. Several compounds produced marked activity against coxsackie viruses A and B infection of mice and FMD infection in mice and guinea pigs. N-Phenyl-N'-3-hydroxyphenyl-thiourea (PTU-23) inhibited poliovirus production by more than 99% without influencing the FL host cell. EMC virus was readily inhibited by PTU-23 in Kreb-II cells. Virus RNA synthesis was significantly reduced. Under the effect of PTU-23 the amount of 37S ssRNA extracted from EMC virus infected cells was considerably more reduced than that of the 20S ds RNA. PTU-23 did not influence the activity of virus-induced RNA polymerase in a cell-free system.

Animals↗
PubMed1975

Influence of amino acids, thiourea and hydroquinone on cellulolytic activity in some Fusarium strains.

Studies were carried out on the influence of various amino acids: cysteine, cystine, methionine, alanine, serine, tryptophan, and of thiourea and hydroquinone on the activity of cellulase synthesized by four strains of Fusarium. It follows from the results obtained that the addition of amino acids, thiourea or hydroquinone to the culture media stimulates or inhibits the activity of the enzyme studied. The effect of this action depended both on the compound and the strain studied.

Amino Acids↗
PubMed1978

Substitution reactions of a water-soluble metalloporphyrin with azide and 1,1,3,3-tetramethyl-2-thiourea.

The substitution reactions of tetrakis-(4-N-methylpyridyl)porphinecobalt (III) (CoIIITMpyP) with azide and with 1,1,3,3-tetramethyl-2-thiourea (TMTU) have been studied as a function of pH at 25 degrees and an ionic strength of 0.5 M. The mechanistic pathway proposed for thiocyanate [1] and pyridine [2] is applicable to these ligands as well once allowance is made for two attacking forms of azide, N3- and HN3. A TMTU axial substituent has about the same influence on the rate of further ligand substitution as does SCN- and a much larger influence than does azide. Similar behavior between bound SCN- and bound TMTU is also shown in electron-transfer reactions with Ru(NH3)62+. Whereas both sulfur-containing ligands enhance the rate relative to the diaquo complex, the azide complex undergoes reduction an order of magnitude more slowly than does the diaquo complex.

Azides↗
PubMed1978

Effect of toxic thioureas on resistance of rats to growth in the lungs of intravenously and intratracheally seeded tumour cells.

Clonogenic growth (colony-forming efficiency, CFE) of i.v. injected allogeneic W256 tumour cells in the lungs was markedly enhanced by treatment of rats with alpha-naphthyl thiourea (ANTU) injected i.p. from 2 h before to 2 h after the tumour cells. ANTU specifically increases pulmonary vascular permeability in adult rats and causes acute pulmonary oedema and pleural effusion. Inhibition of drug toxicity to the lungs by tachyphylaxis, specific antimetabolites or iodides did not abolish the effect of ANTU on CFE. CFE was not increased when cells were seeded by i.v. injection the lungs affected by advanced pulmonary oedema at 6 to 24 h after treatment with drug. ANTU did not enhance growth of intratracheally injected cells. Although ANTU has no cytotoxic or immunosuppressive action, treatment of tumour-immunized rats with ANTU caused apparent "breakdown" of tumour immunity in 50% of rats, by causing growth of tumour colonies in the lungs. Possible mechanisms for the ANTU-induced decrease in innate resistance to growth of tumour in the lungs are discussed.

Adrenalectomy↗