The Conversion of 1-(Malonylamino)cyclopropane-1-Carboxylic Acid to 1-Aminocyclopropane-1-Carboxylic Acid in Plant Tissues

Since 1-(malonylamino)cyclopropane-1-carboxylic acid (MACC), the major conjugate of 1-aminocyclopropane-1-carboxylic acid (ACC) in plant tissues, is a poor ethylene producer, it is generally thought that MACC is a biologically inactive end product of ACC. In the present study we have shown that the capability of watercress (Nasturtium officinale R. Br) stem sections and tobacco (Nicotiana tabacum L.) leaf discs to convert exogenously applied MACC to ACC increased with increasing MACC concentrations (0.2-5 millimolar) and duration (4-48 hours) of the treatment. The MACC-induced ethylene production was inhibited by CoCl₂ but not by aminoethoxyvinylglycin, suggesting that the ACC formed is derived from the MACC applied, and not from the methionine pathway. This was further confirmed by the observation that radioactive MACC released radioactive ACC and ethylene. A cell-free extract, which catalyzes the conversion of MACC to ACC, was prepared from watercress stems which were preincubated with 1 millimolar MACC for 24 hours. Neither fresh tissues nor aged tissues incubated without external MACC exhibited enzymic activity, confirming the view that the enzyme is induced by MACC. The enzyme had a K_m of 0.45 millimolar for MACC and showed maximal activity at pH 8.0 in the presence of 1 millimolar MnSO₄. The present study indicates that high MACC levels in the plant tissue can induce to some extent the capability to convert MACC to ACC.     

(Z)-4-Bromo-5-(bromomethylene)-3-methylfuran-2(5H)-one sensitizes Escherichia coli persister cells to antibiotics

Persisters are a small subpopulation of bacterial cells that are dormant and extremely tolerant to antibiotics. The intrinsic antibiotic tolerance of persisters also facilitates the development of multidrug resistance through acquired mechanisms based on drug resistance genes. In this study, we demonstrate that (Z)-4-bromo-5-(bromomethylene)-3-methylfuran-2(5H)-one (BF8) can reduce persistence during Escherichia coli growth and revert the antibiotic tolerance of its persister cells. The effects of BF8 were more profound when the pH was increased from 6 to 8.5. Although BF8 is a quorum sensing (QS) inhibitor, similar effects were observed for the wild-type E. coli RP437 and its ΔluxS mutant, suggesting that these effects did not occur solely through inhibition of AI-2-mediated QS. In addition to its effects on planktonic persisters, BF8 was also found to disperse RP437 biofilms and to render associated cells more sensitive to ofloxacin. At the doses that are effective against E. coli persister cells, BF8 appeared to be safe to the tested normal mammalian cells in vitro and exhibited no long-term cytotoxicity to normal mouse tissues in vivo. These findings broadened the activities of brominated furanones and shed new light on persister control.     

Synthesis of 2-(d-Arabino-tetra-hydroxybutyl)pyrazine-5-sulfonic Acid

An efficient method for the isolation of dihydrodipicolinate synthase (DPS)-defective threonine producers from a Br evibacterium strain with feedback-sensitive aspartokinase (AK, Ak^s) was established. After mutagenesis of a strain with AK, No. 70, mutants resistant to α-amino-β- hydroxyvaleric acid were isolated and then selected as to threonine productivity in the presence of diaminopimelic acid. DPS activity in the strains in which the threonine production was inhibited by lysine was found to be absent or reduced to less than 10 % of the level in the parent. On the other hand, the strains in which the production was not inhibited by lysine were conventional threonine producers with feedback-resistant homoserine dehydrogenases (HDs and HD^Rs) and wild type DPS. The HD activities of most of the threonine mutants were also markedly reduced. However, only one mutant lacking DPS, DK330, exhibited an HD level comparable to that in the parent and produced the largest amount of threonine among the threonine producers obtained. The formation of HD and HK in strain DK330 was hardly repressed by the addition of methionine. Under the optimum conditions, strain DK330 produced 12.4 g/1 of threonine, while a typical HD type threonine producer, BK29, produced 9.9 g/1.     

The Effects of l-Azetidine-2-Carboxylic Acid (Analogue of Proline) on Dental Cytodifferentiations in vitro

The action of t-azetidine-2-carboxylic acid (an analogue of proline) on the cytodifferentiation of odontoblasts and ameloblasts of mouse tooth buds cultivated In vitro has been studied. The results of our morphological, cytological and functional investigations suggest that the expression of differentiation of ameloblasts is partially conditioned by collagen and/or associated mucopolysaccharides contained in predentin.     

Irreversible Inhibition of Mitochondrial Complex I by 7-(2-Aminoethyl)-3,4-Dihydro-5-Hydroxy-2H-1,4-Benzothiazine-3-Carboxylic Acid (DHBT-1): A Putative Nigral Endotoxin of Relevance to Parkinson's Disease

Abstract: Based on a number of lines of evidence, we have proposed recently that a very early step in the pathogenesis of idiopathic Parkinson's disease might be elevated translocation of l -cysteine into neuromelanin-pigmented dopaminergic cell bodies in the substantia nigra. In vitro studies suggest that such an influx of l -cysteine would divert the neuromelanin pathway by scavenging dopamine-o-quinone, the proximate autoxidation product of dopamine, to give 5-S-cysteinyldopamine, which is oxidized further to 7-(2-aminoethyl)-3,4-dihydro-5-hydroxy-2H-1,4-benzothiazine-3-carboxylic acid (DHBT-1) and other cysteinyldopamines and dihydrobenzothiazines. In this study, it is demonstrated that DHBT-1 inhibits ADP-stimulated oxidation of malate and pyruvate (state 3 or complex I respiration) when incubated with intact rat brain mitochondria with an IC₅₀ of ～0.80 mM. Incubation of DHBT-1 with freeze-thawed rat brain mitochondria in both the presence and absence of KCN and/or NADH causes an irreversible, time-dependent decrease of NADH-coenzyme Q₁ reductase activity. Significantly lower concentrations of DHBT-1 are necessary to cause this effect when mitochondrial membranes are incubated in the absence of KCN and NADH. The irreversible inhibition of mitochondrial complex I caused by DHBT-1 under the latter conditions could be blocked only partially by glutathione, ascorbic acid, superoxide dismutase, or catalase. Together, these results suggest that DHBT-1 can cross the outer mitochondrial membrane and irreversibly inhibit complex I by a mechanism that is not primarily related to oxygen radical-mediated damage. Formation of DHBT-1 requires only dopamine, l -cysteine, and an oxidizing environment, conditions that may well exist in the cytoplasm of neuromelanin-pigmented dopaminergic neurons in the parkinsonian substantia nigra. The results of this study raise the possibility that DHBT-1 might be an endotoxin formed specifically in pigmented dopaminergic neurons that can contribute to irreversible damage to mitochondrial complex I and substantia nigra cell death in Parkinson's disease.     

Evidence for 1-(Malonylamino)cyclopropane-1-Carboxylic Acid Being the Major Conjugate of Aminocyclopropane-1-Carboxylic Acid in Tomato Fruit

Tomato (Lycopersicon esculentum Miller) fruit discs fed with [2,3-¹⁴C]1-aminocyclopropane-1-carboxylic acid (ACC) formed 1-malonyl-ACC (MACC) as the major conjugate of ACC in fruit throughout all ripening stages, from immature-green through the red-ripe stage. Another conjugate of ACC, γ-glutamyl-ACC (GACC), was formed only in mature-green fruit in an amount about 10% of that of MACC; conjugation of ACC into GACC was not detected in fruits at other ripening stages. No GACC formation was observed from etiolated mung bean (Vigna radiata [L.] Wilczek) hypocotyls, etiolated common vetch (Vicia sativum L.) epicotyls, or pea (Pisum sativum L.) root tips, etiolated epicotyls, and green stem tissue, where active conversion of ACC into MACC was observed. GACC was, however, formed in vitro in extracts from fruit of all ripening stages. GACC formation in an extract from red fruit at pH 7.15 was only about 3% of that at pH 8.0, the pH at which most assays were run. Our present in vivo data support the previous contention that MACC is the major conjugate of ACC in plant tissues, whereas GACC is a minor, if any, conjugate of ACC. Thus, our data do not support the proposal that GACC formation could be more important than MACC formation in tomato fruit.     

Improved Isotopic Deuterium Labeling at the Diastereotopic Methyl Group of Leucine: a Synthetic Route to (4S)- and (4R)-[5-2H1]Leucine

Two isotopomers of deuterium-labeled leucine in the diastereotopic methyl group were synthesized from inexpensively available (R)- and (S)-citronellol in a more convenient way than by previous methods.     

(5Z)-4-bromo-5-(bromomethylene)-3-butyl-2(5H)-furanone reduces corrosion from Desulfotomaculum orientis

(5Z)-4-bromo-5-(bromomethylene)-3-butyl-2(5H)-furanone (furanone) from the red marine alga Delisea pulchra was found previously to inhibit the growth, swarming and biofilm formation of Gram-positive bacteria (Ren et al., 2002, Lett Appl Microbiol 34: 293-299). In the present study, the Gram-positive sulphate-reducing bacterium (SRB), Desulfotomaculum orientis, was used to study the inhibition of mild steel corrosion due to the addition of furanone. The weight loss from batch coupon experiments incubated with 40 microg x ml(-1) furanone was reduced fivefold compared with samples that lacked furanone. Analysis of the metal surface with environmental scanning electron microscopy further confirmed the protection afforded by the addition of furanone. In agreement with the corrosion inhibition, most probable number (MPN) analysis showed that 20 and 40 microg x ml(-1) furanone inhibited 58% and 96% of the D. orientis growth respectively. Hence, furanone has the potential to inhibit microbial-induced corrosion related to Gram-positive bacteria.     

An Alternate Synthesis of 2-(4-Isobutylphenyl)-propionic Acid

2-(4-Isobutylphenyl)-propionic acid, which is known to have a high anti-inflammatory activity and has widely been used in the treatment of diseases caused by inflammation, such as rheumatism, was synthesized from methyl 3-methyl-3-(4-isobutylphenyl)-glycidate, via methyl 2-hydroxy-3-(4-isobutylphenyl)-3-butenoate (VI) in four steps.     

Differential gene expression to investigate the effect of (5Z)-4-bromo- 5-(bromomethylene)-3-butyl-2(5H)-furanone on Bacillus subtilis

(5Z)-4-Bromo-5-(bromomethylene)-3-butyl-2(5H)-furanone (furanone) from the red marine alga Delisea pulchra was found previously to inhibit the growth, swarming, and biofilm formation of gram-positive bacteria. Using the gram-positive bacterium Bacillus subtilis as a test organism, we observed cell killing by 20 microg of furanone per ml, while 5 microg of furanone per ml inhibited growth approximately twofold without killing the cells. To discover the mechanism of this inhibition on a genetic level and to investigate furanone as a novel antibiotic, full-genome DNA microarrays were used to analyze the gene expression profiles of B. subtilis grown with and without 5 microg of furanone per ml. This agent induced 92 genes more than fivefold (P < 0.05) and repressed 15 genes more than fivefold (P < 0.05). The induced genes include genes involved in stress responses (such as the class III heat shock genes clpC, clpE, and ctsR and the class I heat shock genes groES, but no class II or IV heat shock genes), fatty acid biosynthesis, lichenan degradation, transport, and metabolism, as well as 59 genes with unknown functions. The microarray results for four genes were confirmed by RNA dot blotting. Mutation of a stress response gene, clpC, caused B. subtilis to be much more sensitive to 5 microg of furanone per ml (there was no growth in 8 h, while the wild-type strain grew to the stationary phase in 8 h) and confirmed the importance of the induction of this gene as identified by the microarray analysis.     

Comparative evaluation of 2,3-bis [2-methyloxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide (XTT) and 2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2, 4-disulfophenyl)-2H-tetrazolium,monosodium salt (WST-8) rapid colorimetric assays for antimicrobial susceptibility testing of staphylococci and ESBL-producing clinical isolates

A new generation of water soluble tetrazolium salts have recently become available and in this study we compared a colorimetric assay developed using one of these salts, 2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2, 4-disulfophenyl)-2H-tetrazolium, monosodium salt (WST-8), with a previously developed 2,3-bis [2-methyloxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide (XTT) colorimetric assay to determine which agent is most suitable for use as a colorimetric indicator in susceptibility testing. The MICs of 6 antibiotics were determined for 33 staphylococci using both colorimetric assays and compared with those obtained using the British Society for Antimicrobial Chemotherapy reference broth microdilution method. Absolute categorical agreement between the reference and test methods ranged from 79% (cefuroxime) to 100% (vancomycin) for both assays. No minor or major errors occurred using either assay with very major errors ranging from zero (vancomycin) to seven (cefuroxime). Analysis of the distribution of differences in the log₂ dilution MIC results revealed overall agreement, within the accuracy limits of the standard test (± 1 log₂ dilution), using the XTT and WST-8 assays of 98% and 88%, respectively. Further studies on 31 ESBL-producing isolates were performed using the XTT method with absolute categorical agreement ranging from 87% (nitrofurantoin) to 100% (ofloxacin and meropenem). No errors were noted for either ofloxacin or meropenem with overall agreement of 91%. The data suggests that XTT is more reliable and accurate than WST-8 for use in a rapid antimicrobial susceptibility test.     

1-(4-Methane(amino)sulfonylphenyl)-3-(4-substituted-phenyl)-5-(4-trifluoromethylphenyl)-1H-2-pyrazolines/pyrazoles as potential anti-inflammatory agents

2-Pyrazolins 14a–l and pyrazoles 15a–l were designed as celecoxib analogs for the evaluation of their in vitro COX-1/COX-2 inhibitory activity and the in vivo anti-inflammatory activity. Compounds 14i, 15a, 15d and 15f were the most COX-2 selective derivatives (S.I. = 5.93, 6.08, 5.03 and 5.27 respectively) while the pyrazoline derivatives 14g and 14i exhibited the highest AI activity (ED₅₀ = 190.5 and 160.1 μmol/kg po, respectively).     

Comparative evaluation of 2,3-bis [2-methyloxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide (XTT) and 2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2, 4-disulfophenyl)-2H-tetrazolium, monosodium salt (WST-8) rapid colorimetric assays for antimicrobial susceptibility testing of staphylococci and ESBL-producing clinical isolates

A new generation of water soluble tetrazolium salts have recently become available and in this study we compared a colorimetric assay developed using one of these salts, 2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2, 4-disulfophenyl)-2H-tetrazolium, monosodium salt (WST-8), with a previously developed 2,3-bis [2-methyloxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide (XTT) colorimetric assay to determine which agent is most suitable for use as a colorimetric indicator in susceptibility testing. The MICs of 6 antibiotics were determined for 33 staphylococci using both colorimetric assays and compared with those obtained using the British Society for Antimicrobial Chemotherapy reference broth microdilution method. Absolute categorical agreement between the reference and test methods ranged from 79% (cefuroxime) to 100% (vancomycin) for both assays. No minor or major errors occurred using either assay with very major errors ranging from zero (vancomycin) to seven (cefuroxime). Analysis of the distribution of differences in the log(2) dilution MIC results revealed overall agreement, within the accuracy limits of the standard test (+/-1 log(2) dilution), using the XTT and WST-8 assays of 98% and 88%, respectively. Further studies on 31 ESBL-producing isolates were performed using the XTT method with absolute categorical agreement ranging from 87% (nitrofurantoin) to 100% (ofloxacin and meropenem). No errors were noted for either ofloxacin or meropenem with overall agreement of 91%. The data suggests that XTT is more reliable and accurate than WST-8 for use in a rapid antimicrobial susceptibility test.     

QSAR studies of N(1)-(5-chloro-2-pyridyl)-2-{[4-(alkyl methyl)benzoyl]amino}-5-chlorobenzamide analogs

Factor X(a) has materialized as a key enzyme for the intervention of blood coagulation cascade and for the development of new antithrombotic agents. It is the lone enzyme that is responsible for the production of thrombin and is therefore an attractive target for the control of thrombus formation. The biological activities (log1/IC(50)) of anthranilamide-based factor X(a) inhibitors were quantitatively analyzed in terms of physicochemical parameters by the regression analysis. Structural requirements for maximal potency were derived from the results of a quantitative structure activity relationship analysis. The leave-one-out cross-validation method was used to judge the predictive power of final equations.     

Synthesis and Structure Assignment of 1-(2-Acetoxyethoxy)methyl Derivatives of 5-Chloro-6-azauracil and 5-Bromo-6-azaisocytosine

Abstract

1-[(2-Acetoxyethoxy)methyl]-5-chloro-6-azauracil has been prepared and its unambiguous assignment of ¹H and ¹³C peaks through the ¹H-¹³C heteronuclear correlation (HETCOR) NMR experiments is described. The isosteric 1-[(2-acetoxyethoxy)methyl]-5-bromo-6-azaisocytosine has also been synthesized. The X-Ray crystallographic analysis reveals unambiguously the site of glycosylation at N¹. Deacetylation of both acyclonucleosides provided 5-chloro-1-[(2-hydroxyethoxy)methyl]-6-azauracil and 5-bromo-1-[(2-hydroxyethoxy)methyl]-6-azaisocytosine respectively. Their structures have been well established by the NMR spectra and the elemental analyses.     

Influence of 1-[(E)-2-(2-Methyl-4-Nitrophenyl)Diaz-1-enyl]Pyrrolidine-2-Carboxylic Acid and Diphenyliodonium Chloride on Ruminal Protein Metabolism and Ruminal Microorganisms

The effects of 1-[(E)-2-(2-methyl-4-nitrophenyl)diaz-1-enyl]pyrrolidine-2-carboxylic acid (LY29) and diphenyliodonium chloride (DIC) on the degradation of protein to ammonia were determined in a mixed rumen microbial population taken from sheep on a grass hay-concentrate diet. Both compounds decreased NH₃ production by inhibiting deamination of amino acids. LY29, but not DIC, inhibited growth of the high-activity ammonia-producing species, Clostridium aminophilum and Clostridium sticklandii.     

Brain Mitochondria Catalyze the Oxidation of 7-(2-Aminoethyl)-3,4-Dihydro-5-Hydroxy-2H-1,4-Benzothiazine-3-Carboxylic Acid (DHBT-1) to Intermediates that Irreversibly Inhibit Complex I and Scavenge Glutathione: Potential Relevance to the Pathogenesis of Parkinson's Disease

Abstract: We have proposed that a very early step in the pathogenesis of idiopathic Parkinson's disease is the elevated translocation of l -cysteine into neuromelanin-pigmented dopaminergic neurons in the substantia nigra. This influx of l -cysteine was proposed to divert the normal neuromelanin pathway by scavenging dopamine-o-quinone, formed by autoxidation of cytoplasmic dopamine, to give initially 5-S-cysteinyldopamine, which is further oxidized to 7 - (2 - aminoethyl) - 3,4 - dihydro - 5 - hydroxy - 2H - 1,4 - benzothiazine-3-carboxylic acid (DHBT-1). In a recent report, it was demonstrated that DHBT-1 evokes inhibition of complex I respiration when incubated with intact rat brain mitochondria and a time-dependent irreversible inhibition of NADH-coenzyme Q₁ (CoQ₁) reductase when incubated with mitochondrial membranes. In this study, it is established that the time dependence of NADH-CoQ₁ reductase inhibition reflects the oxidation of DHBT-1, catalyzed by an unknown constituent of the inner mitochondrial membrane, to an o-quinone imine intermediate that rearranges to 7-(2-aminoethyl) - 5 - hydroxy - 1,4 - benzothiazine - 3 - carboxylic acid (BT-1) and decarboxylates to 7-(2-aminoethyl)-5-hydroxy-1,4-benzothiazine (BT-2), which are further catalytically oxidized to o-quinone imine intermediates. The electrophilic o-quinone imine intermediates formed in these mitochondria-catalyzed oxidations of DHBT-1, BT-1, and BT-2 are proposed to bind covalently to key sulfhydryl residues at the complex I site, thus evoking irreversible inhibition of NADH-CoQ₁ reductase. Evidence for this mechanism derives from the fact that greater than equimolar concentrations of glutathione completely block inhibition of NADH-CoQ₁ reductase by DHBT-1, BT-1, and BT-2 by scavenging their electrophilic o-quinone imine metabolites to form glutathionyl conjugates. The results of this investigation may provide insights into the irreversible loss of glutathione and decreased mitochondrial complex I activity, which are both anatomically specific to the substantia nigra and exclusive to Parkinson's disease.     

Contrasting Effects of D- and L-(E)-4-(3-Phospiono-2- Propenyl) Piperazine-2-Carboxylic Acid as Anticonvulsants and as Inhibitors of Potassium-Evoked Increases in Hippocampal Extracellular Glutamate and Aspartate Levels in Freely Moving Rats I

Abstract: Microdialysis experiments performed in the dorsal hippocampus of freely moving rats showed that L-( E )- 4-(3-phosphono-2-propenyl) piperazine-2-carboxylic acid (L-CPPene) is 10 times as potent as D-CPPene in inhibiting potassium-induced increases in extracellular levels of aspartate and glutamate. In control experiments, two 100 m M KCI stimuli (S1 and S2) applied for 10 min each (separated by a 40-min recovery period) produced substantial (300–500%) increases in the extracellular levels of aspartate, glutamate, taurine, and GABA and a 50% decrease in the glutamine level. S2/S1 ratios in the control groups were 0.67 (aspartate), 0.78 (glutamate), 0.83 (GABA), and 0.85 (taurine). In the experimental groups, D- or L-CPPene was applied via the probe during the second potassium stimulus (S2). L-CPPene (25 or 250 μ M ) produced selective suppression of potassium-induced increases of extracellular glutamate (S2/S1 ratio: 0.25) and aspartate (S2/S1 ratio: 0.20) levels, whereas 250 μ M D-CPPene was required to inhibit the extracellular aspartate and glutamate increases. Neither enantiomer of CPPene affected the potassium-induced increases of GABA and taurine or the decrease in extracellular glutamine concentration. An addtional study comparing the anticonvulsant potencies of D- and L-CPPene was performed using audiogenic DBA/2 mice. The anticonvulsant potency of D-CPPene, as assessed against sound-induced seizures in DBA/2 mice, was an order of magnitude higher than that of L-CPPene [ED₅₀ clonic phase (intraperitoneal, 45 min): 1.64 μmol/kg and 16.8 μmol/kg, respectively]. We attribute the anticonvulsant action of D-CPPene to its antagonist action at the NMDA receptor. The selective inhibition by L-CPPene of potassium-induced increases in extracellular aspartate and glutamate levels is presumably due to an action on presynaptic glutamate receptors.