Proton cotransport of thiourea in Chlorella fusca

Abstract Active thiourea uptake by Chlorella fusca var. vacuolata was accompanied by a simultaneous uptake of protons. The ratio of uptake of protons: uptake of thiourea was 0.92 (average of 5 experiments). The half maximal rate of proton uptake occurred at a thiourea concentration of 62 μM. Rate of thiourea uptake was highest at pH 5.5 and fell to 20% of the maximal rate as pH was increased to 8.0. It is concluded that thiourea is transported into Chlorella by a proton cotransport system similar to that known for glucose transport.     

Inhibition of mast cell leukotriene release by thiourea derivatives

Mast cell derived leukotrienes (LT's) play a vital role in pathophysiology of allergy and asthma. We synthesized various analogues of indolyl, naphthyl and phenylethyl substituted halopyridyl, thiazolyl and benzothiazolyl thioureas and examined their in vitro effects on the high affinity IgE receptor/FcERI-mediated mast cell leukotriene release. Of the 22 naphthylethyl thiourea compounds tested, there were seven active compounds and N-[1-(1-naphthyl)ethyl]-N'-[2-(ethyl-4-acetylthiazolyl)]thiourea (17 and 16) (IC(50)=0.002 microM) and N-[1-(1R)-naphthylethyl]-N'-[2-(5-methylpyridyl)]thiourea (5) (IC(50)=0.005 microM) were identified as the lead compounds. Among the 11 indolylethyl thiourea compounds tested, there were seven active compounds and the halopyridyl compounds N-[2-(3-indolylethyl)]-N'-[2-(5-chloropyridyl)]thiourea and N-[2-(3-indolylethyl)]-N'-[2-(5-bromopyridyl)]thiourea were the most active agents and inhibited the LTC(4) release with low micromolar IC(50) values of 4.9 microM and 6.1 microM, respectively. The hydroxylphenyl substituted compounds N-[2-(4-hydroxyphenyl)ethyl]-N'-[2-(5-chloropyridyl)]thiourea (IC(50)=12.6 microM), N-[2-(4-hydroxyphenyl)ethyl]-N'-[2-(5-bromopyridyl)]thiourea (IC(50)=16.8 microM) and N-[2-(4-hydroxyphenyl)ethyl]-N'-[2-(pyridyl)]thiourea (IC(50)=8.5 microM) were the most active pyridyl thiourea agents. Notably, the introduction of electron withdrawing or donating groups had a marked impact on the biological activity of these thiourea derivatives and the Hammett sigma values of their substituents were identified as predictors of their potency. In contrast, experimentally determined partition coefficient values did not correlate with the biological activity of the thiourea compounds which demonstrates that their liphophilicity is not an important factor controlling their mast cell inhibitory effects.     

Dormancy and Impotency of Cocklebur Seeds: IV. Effects of Gibberellic Acid, Benzyladenine, Thiourea, and Potassium Nitrate on the Growth of Embryonic Axis and Cotyledon Segments

Germination of nondormant but impotent small cocklebur seeds (Xanthium pennsylvanicum Wallr.) was promoted profoundly with thiourea or benzyladenine, and slightly with gibberellic acid. Gibberellic acid was ineffective in causing the germination of dormant cocklebur seeds, although thiourea and benzyladenine were effective. Experiments with excised seed pieces showed that the promotive effects of thiourea, benzyladenine, and gibberellic acid on cocklebur seed germination were associated with the enhancement of growth of seed parts; thiourea stimulated predominantly the axial growth, whereas benzyladenine stimulated predominantly the cotyledonary growth.     

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.     

Inhibition and inactivation of horseradish peroxidase by thiourea

The kinetics of horseradish peroxidase (EC 1.11.1.7)-catalyzed oxidation of o-dianisidine by hydrogen peroxide in the presence of thiourea were studied. At the first, fast step of this process thiourea acts as a competitive reversible inhibitor with respect to o-dianisidine (Ki = 0.22 mM). The formation of a thiourea-peroxidase complex was determined by the increase in the absorbance at A495 and A638 of the enzyme. The dissociation constant for the peroxidase-thiourea complex is equal to 2.0-2.7 mM. Thiourea is not a specific substrate of peroxidase during the oxidation reaction by H2O2, but is an oxidase substrate (although not a very active one) of peroxidase. The irreversible inactivation of the enzyme during its incubation with thiourea was studied. The first-order inactivation rate constant (kin) was shown to increase with a fall in the enzyme concentration. The curve of the dependence of kin on the initial concentration of thiourea shows a maximum at 5-7 mM. The enzyme inactivation is due to its modification by intermediate free radical products of thiourea oxidation. The inhibitors of the free radical reactions (o-dianisidine) protect the enzyme against inactivation. The degree of inactivation depends on concentrations and ratio of thiourea and peroxidase. A possible mechanism of peroxidase interaction with thiourea is discussed.     

Synthesis of acyl thiourea derivatives of chitosan and their antimicrobial activities in vitro

Three different acyl thiourea derivatives of chitosan (CS) were synthesized and their structures were characterized by FT-IR spectroscopy and elemental analysis. The antimicrobial behaviors of CS and its derivatives against four species of bacteria (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Sarcina) and four crop-threatening pathogenic fungi (Alternaria solani, Fusarium oxysporum f. sp. vasinfectum, Colletotrichum gloeosporioides (Penz.) Saec, and Phyllisticta zingiberi) were investigated. The results indicated that the antimicrobial activities of the acyl thiourea derivatives are much better than that of the parent CS. The minimum value of MIC and MBC of the derivatives against E. coli was 15.62 and 62.49 microg/mL, respectively. All of the acyl thiourea derivatives had a significant inhibitory effect on the fungi in concentrations of 50-500 microg/mL; the maximum inhibitory index was 66.67%. The antifungal activities of the chloracetyl thiourea derivatives of CS are noticeably higher than the acetyl and benzoyl thiourea derivatives. The degree of grafting of the acyl thiourea group in the derivatives was related to antifungal activity; higher substitution resulted in stronger antifungal activity.     

Substituted heterocyclic thiourea compounds as a new class of anti-allergic agents inhibiting IgE/Fc epsilon RI receptor mediated mast cell leukotriene release

Mast cell derived leukotrienes (LT's) play a vital role in pathophysiology of allergy and asthma. We synthesized various analogues of indolyl, naphthyl and phenylethyl substituted halopyridyl, thiazolyl and benzothiazolyl thioureas and examined their in vitro effects on the high affinity IgE receptor/Fc epsilon RI-mediated mast cell leukotriene release. Of the 22 naphthylethyl thiourea compounds tested, there were 7 active compounds and N-[1-(1-naphthyl)ethyl]-N'-[2-(ethyl-4-acetylthiazolyl)]thiourea (17 and 16) (IC(50)=0.002 microM) and N-[1-(1R)-naphthylethyl]-N'-[2-(5-methylpyridyl)]thiourea (compound 5) (IC(50)=0.005 microM) were identified as the lead compounds. Among the 11 indolylethyl thiourea compounds tested, there were seven active compounds and the halopyridyl compounds N-[2-(3-indolylethyl)]-N'-[2-(5-chloropyridyl)]thiourea (24) and N-[2-(3-indolylethyl)]-N'-[2-(5-bromopyridyl)]thiourea (25) were the most active agents and inhibited the LTC(4) release with low micromolar IC(50) values of 4.9 and 6.1 microM, respectively. The hydroxylphenyl substituted compounds N-[2-(4-hydroxyphenyl)ethyl]-N'-[2-(5-chloropyridyl)]thiourea (37; IC(50)=12.6 microM), N-[2-(4-hydroxyphenyl)ethyl]-N'-[2-(5-bromopyridyl)]thiourea (50; IC(50)=16.8 microM) and N-[2-(4-hydroxyphenyl)ethyl]-N'-[2-(pyridyl)]thiourea (35; IC(50)=8.5 microM) were the most active pyridyl thiourea agents. Notably, the introduction of electron withdrawing or donating groups had a marked impact on the biological activity of these thiourea derivatives and the Hammett sigma values of their substituents were identified as predictors of their potency. In contrast, experimentally determined partition coefficient values did not correlate with the biological activity of the thiourea compounds which demonstrates that their liphophilicity is not an important factor controlling their mast cell inhibitory effects. These results establish the substituted halopyridyl, indolyl and naphthyl thiourea compounds as a new chemical class of anti-allergic agents inhibiting IgE receptor/Fc epsilon RI-mediated mast cell LTC(4) release. Further lead optimization efforts may provide the basis for new and effective treatment as well as prevention programs for allergic asthma in clinical settings.     

Analysis of structure-activity relationships for the 'B-region' of N-(3-acyloxy-2-benzylpropyl)-N(')-[4-(methylsulfonylamino)benzyl]thiourea analogues as vanilloid receptor antagonists: discovery of an N-hydroxythiourea analogue with potent analgesic activity

The structural modifications on the B-region of the potent and high affinity vanilloid receptor (VR1) lead ligand N-(3-acyloxy-2-benzylpropyl)-N(')-[4-(methylsulfonylamino)benzyl]thiourea were investigated by the replacement of the thiourea with diverse isosteric functional groups. Structure-activity analysis indicated that the A-region in this series was the primary factor in determining the agonistic/antagonistic activities regardless of the B-region. The N(C)-hydroxy thiourea analogues (12, 13) showed excellent analgesic activities in the acetic acid writhing assay compared to the parent thiourea analogues.     

Thiourea: the antioxidant of choice for the purification of proteins from phenol-rich plant tissues

Metabisulfite, diethyldithiocarbamate, and thiourea are potent phenoloxidase inhibitors commonly used during the extraction of plant proteins. Their effects on several amino acid derivatives and peptides are reported. Important and pH-dependent changes are induced by metabisulfite in the uv-absorption spectrum of N-acetyltryptophanamide but not of N-acetyltyrosinamide. Similar spectral changes are also induced in tryptophanyl-containing peptides. Neither diethyldithiocarbamate nor thiourea modified the spectral properties of tryptophan or tyrosine. Cysteinyl groups are rapidly modified by diethyldithiocarbamate, especially in the lower pH range, but not by metabisulfite or thiourea. Diethyldithiocarbamate as well as metabisulfite interfere with cysteinyl groups. It is concluded that thiourea is the most appropriate reagent for use as a phenoloxidase inhibitor.     

Germination of Talinum triangulare L. Seeds as Affected by Various Chemical and Physical Treatments

Three-month ‘old’ and ‘fresh’ seedsof Talinum triangulare were subjected to various treatmentsto induce early and rapid germination. Scarification and activated carbon were the most effective treatmentsin improving total germination in fresh seeds, while the 3 and5 per cent thiourea treatments were most effective in improvingtotal germination in old seeds. Activated carbon, scarificationand 5 per cent thiourea treatments enhanced early germinationin both old and fresh seeds. Cumulative percentage germinationwas very high in fresh seeds after scarification or after treatmentwith activated carbon and 5 per cent thiourea, and lowest inseeds treated with 3 per cent thiourea and hot water. In oldseeds, highest cumulative percentage germination was obtainedwith 3 and 5 per cent thiourea treatments and scarification.Generally, higher germination was obtained with fresh seedsthan with old seeds. Partial seed-coat removal and treatment with 5 per cent thiouriaresulted in a higher rate of and cumulative percentage germinationcompared with seeds with the coat partially removed but nottreated with thiourea. Constantly high temperature (34 °C) increased both rateand total germination compared with seeds planted at room temperature(20–23 °C). Treatments that did not induce germinationwere 1 per cent thiourea, H₂SO₄, cold water soaking at roomtemperature, 6 per cent hydrogen peroxide and soil planting.These treatments effected less than 3 per cent germination. Talinum triangulare L, seed scarification, activated charcoal, thiourea, germination     

The effect of thiourea on ureide metabolism in Neurospora crassa

The wild-type strain of Neurospora crassa Em 5297a can utilize allantoin as a sole nitrogen source. The pathway of allantoin utilization is via its conversion into allantoic acid and urea, followed by the breakdown of urea to ammonia. This is shown by the inability of the urease-less mutant, N. crassa 1229, to grow on allantoin as a sole nitrogen source and by the formation of allantoate and urea by pre-formed mycelia of this mutant. In the wild strain (Em 5297a) thiourea is tenfold more toxic on an allantoin medium than on an inorganic nitrogen medium; allantoin as well as urea counteract thiourea toxicity in the allantoin nitrogen medium. This selective toxicity of thiourea for the mould utilizing allantoin nitrogen does not, however, result in an impairment of allantoin uptake, allantoinase activity or the formation of urea from allantoin. The only process affected by thiourea is the synthesis of urease; urea antagonizes this effect of thiourea in N. crassa.     

Inactivation of Escherichia coli glutamine synthetase by thiourea trioxide

Incubation of Escherichia coli glutamine synthetase with thiourea trioxide resulted in partial inactivation of the enzyme. This reagent specifically modifies lysine residues to form homoarginine. By amino acid analysis 2.3 ± 0.3 residues of homoarginine are produced per enzyme subunit after treatment with thiourea trioxide. Previously we determined that thiourea dioxide totally inactivated glutamine synthetase and modified both lysine and histidine residues (J. Colanduoni and J. J. Villafranca (1985) J. Biol. Chem. 260, 15,042–15,050). Thiourea trioxide reacted with the same lysine residues of glutamine synthetase as thiourea dioxide. The K_m values for the thiourea trioxide modified enzyme were determined and are 210 ± 30 μm and 10 ± 1 mm for ATP and glutamate, respectively. Both values are about threefold higher than for native enzyme assayed under the same conditions. Fluorescence titrations of native and thiourea trioxide labeled enzyme showed that ATP binding was virtually unchanged by the modification while glutamate and methionine sulfoximine bound about twofold more weakly to the modified enzyme.     

Iminothiol/thiourea tautomeric equilibrium in thiourea lipids impacts DNA compaction by inducing a cationic nucleation for complex assembly

Our research on lipidic vectors for transfection led us to develop thiourea lipids able to interact with DNA. Hence, we developed a series of lipopolythioureas based on the strong hydrogen bond donor ability of thiourea. More recently we have reported a branched hydroxylated bis-thiourea derivative with interesting transfecting properties. The last step of the syntheses involved a strong acidic condition, leading to an unstable product upon storage. Therefore we designed a new synthesis in mild acidic conditions. Though they exhibit the same mass, the lipids obtained in the two different conditions differ by their interaction with DNA. We therefore explored the physicochemical properties of these two lipids by different means that we describe in this article. In order to insure easier and reliable ¹³C-NMR studies of the thiourea group we have designed the synthesis of the corresponding ¹³C-labeled thiourea lipids. We have thus shown that when the lipid was submitted to mildly acidic medium; only the thiourea group was observed; while a thiourea/charged and/or uncharged iminothiol tautomeric equilibrium formed when the last step of the synthesis was submitted to low pH. NMR experiments showed that this tautomeric equilibrium could not form in polar solvents. However, UV experiments on the liposomal form of the lipopolythiourea showed the presence of the tautomers. Lipid/DNA interaction consequently differed according to the acidic treatment applied. Eventually, these results revealed that on this particular thiourea lipid, electrostatic interactions due to cationic thioureas are likely to be responsible for DNA compaction and that this tautomeric form of the thiourea could be stabilised by hydrogen bonds in a supramolecular assembly. Nevertheless, this does not reflect a general thiourea lipid/DNA interaction as other thiourea lipids that are able to compact DNA do not undergo an acidic treatment during the final stage of their synthesis.     

Seed Germination of Triglochin Maritima as Influenced by Salinity and Dormancy Relieving Compounds

Triglochin maritima had only 40 % germination in distilled water, but germination was substantially enhanced when seeds were exposed to ethephon, fusicoccin, proline, kinetin, and thiourea. Also, the effect of low salinity on germination was alleviated by fusicoccin, kinetin, nitrate and thiourea, whereas, the reduction in germination at high salinity was partially countered by ethephon, kinetin, thiourea and nitrate.     

Inhibiting nitrification and increasing yield of barley by band placement of thiourea with fall-applied urea

Incubation and field experiments were conducted on the influence of thiourea in inhibiting nitrification of urea N, and subsequently on reducing over-winter losses of fallapplied N. Under incubation, most of the added urea placed in bands was nitritified within five or six weeks. However, thiourea when pelleted with urea (21 urea to thiourea by weight) reduced the amount of nitrification to less than one-half during the same period.In two uncropped field experiments in an early dry fall, the application of pelleted urea+thiourea (21) in bands resulted in almost complete inhibition of nitrification of urea for four weeks. In two other uncropped field experiments begun in June with the same fertilizer in bands, half or less of applied N appeared as nitrate after eight weeks. In 10 cropped field experiments with 56 kg N ha^–1, urea+thiourea placed in bands depressed nitrification of fall-applied urea over the winter. By early May, the urea mixed into the soil in the previous fall was nearly all nitrified, while only one-half of the banded urea+thiourea was nitrified. The loss of mineral N by early May was 38% with urea mixed into the soil, but only 18% with bands of urea+thiourea.The 10 sites were cropped to spring barley. The increase in yield of grain or the increase in %N uptake from fertilier N was approximately only one-half as much with fall-applied urea mixed into the soil as compared to spring-applied urea added in the same way. Specifically, fall-applied mixed urea produced 930 kg ha^–1 less grain yield and 32% less N uptake from fertilizer N than did mixed urea in spring. On fall-application there was some benefit from banding of urea or with mixing urea+thiourea pellets into the soil, but the banding of urea+thiourea pellets gave more benefit. Among the fall applications, banded urea+thiourea pellets produced 670 kg ha^–1 more grain yield and 26% more N uptake in grain from fertilizer N than did urea mixed into the soil.     

The Effect of PCIB on the Germination and Growth of Lettuce in the Presence of Thiourea

The joint action of the anti-auxin parachlorophenoxy isobutyricacid (PCIB) and thiourea on germination and growth of lettuceseed was investigated. PCIB alone did not affect germinationor hypocotyl growth of lettuce. Root growth was stimulated byPCIB. In germination PCIB showed interaction at all the thioureaconcentrations. All thiourea concentrations reversed the stimulationof root growth caused by PCIB, except the lowest thiourea concentrationwith the highest PCIB one. In hypocotyl growth the two substances showed no interaction.These results are discussed in relation to the auxin and anti-auxineffects in germination and growth.     

Effect of Thiourea and Starvation on the Physiological and Biochemical State and the Reproductive System of Climbing Perch Anabas testudineus

Journal of Ichthyology - The effects of thiourea (keeping of fish for 32 days in 0.05% solution of thiourea) and of starvation (during 12 days) on the physiological and biochemical state and on the...     

The Action of Thiourea as a Germination Stimulator

It has been shown that thiourea is not metabolized by lettuceseeds during germination despite its stimulatory action. Thioureawas known to enter the seeds at much the same rate as water.Substitution of thiourea converted it from a stimulatory toa strongly inhibitory substance.     

Radiosensitization and radioprotection of E. coli by thiourea in nitrous oxide saturated suspensions

N2O did not modify the radiosensitivity of E. coli BH and H/r-30 strains as to colony-forming ability and DNA single-strand breaks. In N2O-saturated suspensions of E. coli, thiourea and thiosemicarbasite sensitized at low concentrations, while cysteamine and cysteine protected at all concentrations. Protection by thiourea in N2O-saturated suspensions was observed only in the frozen state. These results suggest that the conversion of e-aq to OH radicals may be responsible for sensitization and this sensitization is probably due to the thiourea and thiosemicarbasite radicals produced extracellularly.     

Influence of thiourea application on some physiological and molecular criteria of sunflower (Helianthus annuus L.) plants under conditions of heat stress

High temperature is a major factor limiting the growth of plant species during summer. Understanding the mechanisms of plant tolerance to high temperature would help in developing effective management practices and heat-tolerant cultivars through breeding or biotechnology. The present investigation was carried out to study the role of thiourea in enhancing the tolerance of sunflower plants to heat stress. Sunflower plants were subjected to temperature stress by exposing plants to 35 or 45 °C for 12 h. Two levels of thiourea (10 and 20 mM) were applied before sowing (seed treatment). The results indicated that the plants exposed to temperature stress exhibited a significant decline in growth parameters, chlorophylls, relative leaf water content, oil content, leaf nutrient status, and nitrate reductase activity. Treatment with thiourea, especially when applied at 10 mM, improved the above parameters and induced non-enzymatic and enzymatic antioxidants responsible for antioxidation. SDS-PAGE of protein revealed that high-temperature treatments alone or in combination with thiourea were associated with the disappearance of some bands or the appearance of unique ones. The result of RAPD analysis using five primers showed variable qualitative and quantitative changes. These findings confirm the effectiveness of applying thiourea on alleviating heat injuries in sunflower plants.