Cytokinin activity of N-phenyl-N′-(4-pyridyl)urea derivatives

We have synthesized 35 N-phenyl-N′-(4-pyridyl)urea derivatives and tested their cytokinin activity in the tobacco callus bioassay. Among them, N-phenyl-N′- (2-chloro-4-pyridyl)urea is highly active, the optimum concentration of which is lower than 4 × 10^?9 M (0.001 ppm), 3 compounds, i.e. N-(2-methylphenyl)-N′-(2-chloro-4-pyridyl)urea, N-(3-methylphenyl)-N′-(2-chloro-4-pyridyl)urea and N-(3-chlorophenyl)-N′-(2-chloro-4-pyridyl) urea are as active as N⁶-benzyladenine (concentration for optimum yield: 4.4 × 10^?8 M or 0.01 ppm), and N-phenyl-N′-(2-methyl-4-pyridyl)urea and N-(2-chlorophenyl)-N′-(2-chloro-4-pyridyl)urea are as active as N-phenyl-N′-(4-pyridyl)urea (concentration for optimum yield: 4.7 × 10^?7 M or 0.1 ppm), while the activity of the other 29 compounds are not so remarkable and 11 of them are almost or completely inactive.     

Hormonal Control of Morphogenesis in Leaf Explants of Perilla frutescens Britton var. crispa Decaisne f. viridi-crispa Makino

Leaf discs of Perilla frutescens var. crispa f. viridi-crispawere cultured on a defined medium to investigate factors influencingbud and root formation, callus induction, somatic embryogenesis,and floral bud formation. Addition of naphthalene-acetic acid(NAA) to the culture medium caused compact callus whereas 2,4-dichlorophenoxyacetic acid (2,4-D) promoted soft and friable callus formationon the surface of the explants. Benzyladenine, when appliedwith auxin, suppressed callus and root formation. Somatic embryogenesisoccurred, when the explants were first grown on nutrient mediumcontaining 2,4-D and organic elements, and then transferredto the 2,4-D free medium. Treatments with cytokinins, N-phenyl-N'-(4-pyridyl)urea and its derivatives induced bud formation. A low concentrationof NAA and naphthoxy-acetic acid promoted bud development. Occasionalfloral bud formation was observed depending on the originalleaf positions on mother plants from which the leaf discs wereexcised. A gradient of floral bud forming capacity along thestem was noted. Perilla frutescens, tissue culture, embryogenesis, morphogenesis, benzyl adenine, kinetin, naphthalene-acetic acid, naphthoxy-acetic acid, 2,4-dichlorophenoxy acetic acid, indol-3yl-acetic acid, cytokinins, auxins     

Physiological and Hormonal Factors Influencing Organogenesis in Rudbeckia bicolor Explants Cultured In vitro

Factors influencing organogenetic responses and bolting of adventitiouslyformed buds were investigated in in vitro cultured cotyledon,stem and leaf explants of Rudbeckia bicolor. Application ofnaphthaleneacetic acid (NAA) induced adventitious root formationand that of benzyladenine (BA) induced adventitious bud differentiation.When NAA at a low concentration was added together with BA,bud initiation and development were promoted further, althoughoptimal concentrations of NAA and BA varied with the kind ofexplants used. Gibberellic acid caused stem elongation of adventitiousbuds, and occasionally differentiation of floral buds on theapices of developed shoots. The action of N-phenyl-N'-(4-pyridyl)urea(4PU) and its derivative (4PU-Cl) on adventitious bud formationwas also examined. (Received August 8, 1981; Accepted November 9, 1981)     

Structural Studies of the Vacuolar H+-Pyrophosphatase: Sequence Analysis and Identification of the Residues Modified by Fluorescent Cyclohexylcarbodiimide and Maleimide

We determined the amino acid residues of the H⁺-translocatinginorganic pyrophosphatase (H⁺-PPase) of pumpkin which are covalentlylabeled by two fluorescent labeling reagents; N-cyclohexyl-.N'-[4-(dimethylamino)-     

Effects of the new plant growth retardants of quaternary ammonium iodides on gibberellin biosynthesis in Gibberella fujikuroi

The effects of twelve quaternary ammonium iodides, synthesizedas plant growth relardants, on the biosynthesis of gibberellinsin the culture of Gibberella fujikuroi were investigated. Ofthe two compounds with the strongest growth-retarding activity,N,N,N-trimethyl-1-methyl-(3',3',5'-trimethylcydohexyl)-2-propenylammonium iodide (1) was found to inhibit the biosynthesis, whileN,N,N-trimethyl-l-methyl-(3',3',5'5'- tetramethylcyclohexyl)-2-propenylammonium iodide (2) was not. The results on examination of thetwelve analogues indicate that their plant growth-retardingactivity is not related to the inhibition of gibberellin biosynthesis. (Received July 18, 1978; )     

Isolation and Identification of Diacylglyceryl-O-4'-(N,N,N-trimethyl)-homoserine from the Fern Adiantum capillus-veneris L.

Diacylglyceryl-O-4'-(N,N,N-trimethyl)-homoserine was isolatedfrom fronds of the fern Adiantum capillus-veneris L. and identifiedby chemical and spectral analyses. Positional analysis of thefatty acids by lipase treatment showed that palmitic acid wasesterified at position 1, but linoleic, linolenic and arachidonicacids at position 2 of the glycerol moiety of the lipid. Althoughthe trimethylhomoserine lipid has been found in some algal species,this is the first report that it exists in a vascular plant. (Received April 9, 1983; Accepted June 22, 1983)     

Urea derivatives on the move: cytokinin-like activity and adventitious rooting enhancement depend on chemical structure

Urea derivatives are synthetic compounds, some of which have proved to be positive regulators of cell division and differentiation. N -phenyl- N '-(2-chloro-4-pyridyl)urea (forchlorofenuron, CPPU) and N -phenyl- N '-(1,2,3-thiadiazol-5-yl)urea (thidiazuron, TDZ), well known urea cytokinin representatives, are extensively used in in vitro plant morphogenesis studies, as they show cytokinin-like activity often exceeding that of adenine compounds. In recent years, renewed interest in structure–activity relationship studies allowed identification of new urea cytokinins and other urea derivatives that specifically enhance adventitious root formation. In this review, we report the research history of urea derivatives, new insights into their biological activity, and recent progress on their mode of action.     

Synthesis of 5-(4-hydroxy-3-methylphenyl)-5-(substituted phenyl)-4, 5-dihydro-1H-1-pyrazolyl-4-pyridylmethanone derivatives with anti-viral activity

A series of N¹-nicotinoyl-3- (4-hydroxy-3-methyl phenyl)-5-(substituted phenyl)-2-pyrazolines were synthesized by the reaction between isoniazid (INH) and chalcones and were tested for their in vitro anti-viral activity. Among the compounds, the electron withdrawing group substituted analogues 5-(4-chlorophenyl)-3-(4-hydroxy-3-methylphenyl)-4, 5-dihydro-1H-1-pyrazolyl-4-pyridylmethanone (4b), 5-(2-chlorophenyl)-3-(4-hydroxy-3-methylphenyl)-4,5-dihydro-1H-1-pyrazolyl-4-pyridylmethanone (4i), 5-(4-fluorophenyl)-3-(4-hydroxy-3-methylphenyl)-4,5-dihydro-1H-1-pyrazolyl-4-pyridylmethanone (4h) and 5-(2,6-dichlorophenyl)-3-(4-hydroxy-3-methylphenyl)-4,5-dihydro-1H-1-pyrazolyl-4-pyridyl methanone (4j) were the most promising and the halogeno function appeared to be essential for antiviral activity.     

Growth of Phaseolus vulgaris on Various Nitrogen Sources: The Importance of Urease

Rhizobium-inoculatcd plants of Phaseolus vulgaris L. were grownwith different N-sources (nitrate, ammonium, urea) and differentconcentrations of urea. The distribution of growth between plantparts varied with N-sources. Nitrate and ammonium were moreinhibitory to nodulation than urea, which at 40 mol m^–3N had no effect. Urease activity varied in amount and locationover a range of urea concentrations. At higher concentrations,more urea was transported to and increased urease activity wasfound in the shoot Lower levels of activity in plants relianton N₂-fixation were consistent with a ureide-degradation pathwaynot involving urea. Moderate doses of urea could be assimilatedconcomitantly with N₂-fixation. At higher levels of appliedurea, nodulation and ureide transport to the shoots were reduced,although increased growth could not be maintained at concentrationsof applied urea greater than 6.0 mol m^–3 urea N. Key words: Phaseolus vulgaris, growth, nitrogen source, urease     

Induction of leaf abscission in cotton is a common effect of urea- and adenine-type cytokinins

Cytokinins of the urea and adenine type induced leaf abscission in young cotton (Gossypium hirsutum) plants in the following order of activity: N-phenyl-N′-1,2,3-thiadiazol-5-ylurea (thidiazuron) » N-phenyl-N′-(2-chloro-4-pyridyl)urea > isopentenyladenine ≥ 6-benzyladenine > zeatin = dihydrozeatin > kinetin. It is suggested that ethylene production is implicated in this response because it was stimulated by the compounds in cotton leaf discs with nearly the same effectiveness. Moreover, similar to thidiazuron (JC Suttle [1985] Plant Physiol 78: 272-276), isopentenyladenine-induced defoliation was inhibited by aminoethoxyvinylglycine, and the effect was restored by 1-aminocyclopropane-1-carboxylic acid.     

Progress in antischistosomal N,N′-diaryl urea SAR

N,N′-Diaryl ureas have recently emerged as a new antischistosomal chemotype. We now describe physicochemical profiling, in vitro ADME, plasma exposure, and ex vivo and in vivo activities against Schistosoma mansoni for twenty new N,N′-diaryl ureas designed primarily to increase aqueous solubility, but also to maximize structural diversity. Replacement of one of the 4-fluoro-3-trifluoromethylphenyl substructures of lead N,N′-diaryl urea 1 with azaheterocycles and benzoic acids, benzamides, or benzonitriles decreased lipophilicity, and in most cases, increased aqueous solubility. There was no clear relationship between lipophilicity and metabolic stability, although all compounds with 3-trifluoromethyl-4-pyridyl substructures were metabolically stable. N,N′-diaryl ureas containing 4-fluoro-3-trifluoromethylphenyl, 3-trifluoromethyl-4-pyridyl, 2,2-difluorobenzodioxole, or 4-benzonitrile substructures had high activity against ex vivo S. mansoni and relatively low cytotoxicity. N,N-diaryl ureas with 3-trifluoromethyl-4-pyridyl and 2,2-difluorobenzodioxole substructures had the highest exposures whereas those with 4-fluoro-3-trifluoromethylphenyl substructures had the best in vivo antischistosomal activities. There was no direct correlation between compound exposure and in vivo activity.     

Polarity of A2b adenosine receptor expression determines characteristics of receptor desensitization

It is not knownif, in polarized cells, desensitization events can be influenced by thedomain on which the receptor resides. Desensitization was induced by5'-(N-ethylcarboxamido)adenosine (NECA) and wasquantitated by measurement of short-circuit current (I_sc) in response to adenosine. NECA addedto either the apical or basolateral compartments rapidly desensitizedreceptors on these respective domains. Although apical NECA had noeffect on the basolateral receptor stimulation, basolateral NECAinduced a complete desensitization of the apical receptor. Wehypothesized that desensitization of apical receptor by basolateraldesensitization could relate to a trafficking step in which A2breceptor is first targeted basolaterally upon synthesis and transportedto the apical surface via vesicular transport/microtubules. Becausedesensitization is associated with downregulation of receptors, apicaladenosine receptor can thus be affected by basolateral desensitization. Both low temperature and nocodazole inhibited I_scinduced by apical and not basolateral adenosine. In conclusion:1) a single receptor subtype, here modeled by the A2b receptor,differentially desensitizes based on the membrane domain on which it isexpressed, 2) agonist exposure on one domain can result indesensitization of receptors on the opposite domain, 3)cross-domain desensitization can display strict polarity, and4) receptor trafficking may play a role in thecross-desensitization process.

     

Preconditioning of cortical neurons by oxygen-glucose deprivation: tolerance induction through abbreviated neurotoxic signaling

Transient exposure of rat cortical cultures to nonlethal oxygen-glucose deprivation (OGD preconditioning) induces tolerance to otherwise lethal oxygen-glucose deprivation (OGD) or N-methyl-D-aspartate 24 h later. This study evaluates the role of cytosolic and mitochondrial Ca²⁺-dependent cellular signaling. Mechanistic findings are placed in context with other models of ischemic preconditioning or known neurotoxic pathways within cortical neurons. Tolerance to otherwise lethal OGD is suppressed by performing OGD preconditioning in the presence of the broad-scope catalytic antioxidants Mn(III)tetra(4-carboxyphenyl)porphyrin (MnTBAP) or Zn(II)tetra(4-carboxyphenyl)porphyrin [Zn(II)TBAP], but not by a less active analog, Mn(III)tetra(4-sulfonatophenyl)porphyrin, or a potent superoxide scavenger, Mn(III)tetra(N-ethyl-2-pyridyl)porphyrin chloride. Inhibitors of adenosine A₁ receptors, nitric oxide synthase, mitogen-activated protein kinase, and poly(ADP-ribose) polymerase fail to suppress OGD preconditioning despite possible links with reactive oxygen species in other models of ischemic preconditioning. Preconditioning is suppressed by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), which has been ascribed elsewhere to inhibition of superoxide transport to the cytosol through mitochondrial anion channels. However, although it induces mitochondrial Ca²⁺ uptake, neuronal preconditioning is largely insensitive to mitochondrial uncoupling with carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone or 2,4-dinitrophenol. Un-couplers will prevent production of mitochondrial reactive oxygen species, implying nonmitochondrial targets by MnTBAP, Zn(II)TBAP, and DIDS. Emphasizing the importance of an increase in cytosolic Ca²⁺ during preconditioning, a Ca²⁺/calmodulin-dependent protein kinase II inhibitor, KN-62, suppresses development of subsequent tolerance. Summarizing, only those cellular transduction pathways that have the potential to be neurotoxic may be activated by preconditioning in cortical neurons. Finally, a marked decrease in extracellular glutamate is observed during otherwise lethal OGD in preconditioned cultures, suggesting that this end effector may represent a point of convergence across different preconditioning models. N-methyl-D-aspartate; Ca²⁺; antioxidants; mitochondria     

A novel one-dimensional acentric copper(I) coordination polymer with second-harmonic generation response

The reaction of N,N-(2-pyridyl)(4-pyridylmethyl)amine with [Cu(MeCN)₂(PPh₃)₂]ClO₄ in the presence of THF affords a novel one-dimensional copper(I) coordination polymer {[Cu(PPh₃)(N,N-(2-pyridyl)(4-pyridylmethyl)amine)](ClO₄)}_n (1), which crystallizes in an noncentrosymmetric space group and displays strong second-harmonic generation (SHG) response.     

Rapid Evaluation of Least-Squares and Minimum-Evolution Criteria on Phylogenetic Trees

We present fast new algorithms for evaluating trees with respectto least squares and minimum evolution (ME), the most commonlyused criteria for inferring phylogenetic trees from distancedata. The new algorithms include an optimal O(N2) time algorithmfor calculating the edge (branch or internode) lengths on atree according to ordinary or unweighted least squares (OLS);an O(N3) time algorithm for edge lengths under weighted leastsquares (WLS) including the Fitch-Margoliash method; and anoptimal O(N4) time algorithm for generalized least-squares (GLS)edge lengths (where N is the number of taxa in the tree). TheME criterion is based on the sum of edge lengths. Consequently,the edge lengths algorithms presented here lead directly toO(N2), O(N3), and O(N4) time algorithms for ME under OLS, WLS,and GLS, respectively. All of these algorithms are as fast asor faster than any of those previously published, and the algorithmsfor OLS and GLS are the fastest possible (with respect to orderof computational complexity). A major advantage of our new methodsis that they are as well adapted to multifurcating trees asthey are to binary trees. An optimal algorithm for determiningpath lengths from a tree with given edge lengths is also developed.This leads to an optimal O(N2) algorithm for OLS sums of squaresevaluation and corresponding O(N3) and O(N4) time algorithmsfor WLS and GLS sums of squares, respectively. The GLS algorithmis time-optimal if the covariance matrix is already inverted.The speed of each algorithm is assessed analytically—thespeed increases we calculate are confirmed by the dramatic speedincreases resulting from their implementation in PAUP* 4.0.The new algorithms enable far more extensive tree searches andstatistical evaluations (e.g., bootstrap, parametric bootstrap,or jackknife) in the same amount of time. Hopefully, the fastalgorithms for WLS and GLS will encourage the use of these criteriafor evaluating trees and their edge lengths (e.g., for approximatedivergence time estimates), since they should be more statisticallyefficient than OLS.     

Ubiquitination regulates the plasma membrane expression of renal UT-A urea transporters

The renal UT-A urea transporters UT-A1, UT-A2, and UT-A3 are known to play an important role in the urinary concentrating mechanism. The control of the cellular localization of UT-A transporters is therefore vital to overall renal function. In the present study, we have investigated the effect of ubiquitination on UT-A plasma membrane expression in Madin-Darby canine kidney (MDCK) cell lines expressing each of the three renal UT-A transporters. Inhibition of the ubiquitin-proteasome pathway caused an increase in basal transepithelial urea flux across MDCK-rat (r)UT-A1 and MDCK-mouse (m)UT-A2 monolayers (P < 0.01, n = 3, ANOVA) and also increased dimethyl urea-sensitive, arginine vasopressin-stimulated urea flux (P < 0.05, n = 3, ANOVA). Inhibition of the ubiquitin-proteasome pathway also increased basolateral urea flux in MDCK-mUT-A3 monolayers (P < 0.01, n = 4, ANOVA) in a concentration-dependent manner. These increases in urea flux corresponded to a significant increase in UT-A transporter expression in the plasma membrane (P < 0.05, n = 3, ANOVA). Further analysis of the MDCK-mUT-A3 cell line confirmed that vasopressin specifically increased UT-A3 expression in the plasma membrane (P < 0.05, n = 3, ANOVA). However, preliminary data suggested that vasopressin produces this effect through an alternative route to that of the ubiquitin-proteasome pathway. In conclusion, our study suggests that ubiquitination regulates the plasma membrane expression of all three major UT-A urea transporters, but that this is not the mechanism primarily used by vasopressin to produce its physiological effects. ubiquitin-proteasome pathway; urea transport; membrane localization     

The Transport and Metabolism of Urea in Chara australis: III. TWO SPECIFIC TRANSPORT SYSTEMS

Reciprocal competitive inhibition studies were used to showthat N-methyl-urea (NMU), acetamide and urea all compete forbinding to a common transport system, designated system I andthat this system is one of two specific mechanisms transportingurea in Chara. System I binds urea with a Km of about 0–3mmol m-3 and is strongly influenced by metabolic controls. SystemI is active and electrogenic and may be energized by the couplingof urea uptake to an influx of protons. This is the first reportof an electrogenic urea transport system in an alga. The secondspecific mechanism for urea transport, designated system II,binds urea with a relatively low affinity (K_m c. 7–0 mmolm-3) and does not transport NMU to a significant extent. SystemII is less subject to metabolic control than system I and, thoughit may be active, is not electrogenic. Key words: Urea, methylurea, proton cotransport, metabolic control     

Human non-secretory ribonucleases. II. Structural characterization of theN-glycans of the kidney, liver and spleen enzymes by NMR spectroscopy and electrospray mass spectrometry

The N-glylycans have been removed by peptide-N-glycosidase F(PNGase F) from purified human non-secretory RNases derivedfrom kidney, liver and spleen. The spleen RNase was purifiedby two procedures, one of which did not include the usual acidtreatment step (0.25 M H₂SO₄, 45 min, 4C), to determine ifacid treatment alters the carbohydrate moieties. TheN-glycansof the RNases were fractionated by Bio-Gel P-4 chromatographyand analysed by 600 MHz ¹H-NMR spectroscopy and electrospraymass spectrometry. All four non-secretory RNase preparationscontained the following structures: The relative amounts of the trisaccharide, pentasaccharide andhexasaccharide appeared to vary slightly in the different tissueRNases. The overall results indicate: (i) that acid treatmentduring purification does not alter the N-glycans of non-secretoryRNases; (ii) that the N-glycans from kidney, liver and spleennon-secretory RNases are very similar, if not identical, toone another, but different from the N-glycan structures reportedfor secretory RNase. N-glycans non-secretory RNases     

The role of the anionic groups in the receptor binding of interleukin-8 antagonists

Summary In an effort to determine the role of the acidic group in the receptor binding ofN-(2-hydroxy-4-nitrophenyl)-N′-(phenyl) urea, an interleukin-8B receptor antagonist, its binding and that of several analogs was measured as a function of pH. These titrations indicate that these ureas bind most strongly in their anionic form. Studies of antagonists, with different acidities, demonstrated that the greatest change in binding of each urea occurred around the pK _a of the compound being examined. The studies suggest that the increase in binding of the antagonists at higher pH is a result of the increased negative charge on the compounds rather than the effects of pH on the receptor or radioligand.     

Effect of Applied Nitrogen on N2 Fixation, Assimilation of Nitrate and Ammonia in Nodules of Field-grown Moong (Vigna radiata)

A field experiment was conducted to study the effect of nitrogenapplication at 15, 30 and 45 kg ha^–1 of urea at pre-flowering(PF) and pod initiation (PI) stages on the activity of nitrogenase(N₂ase), nitrate reductase (NR) and other related parametersin the nodules of moong (Vigna radiata). Nitrogen applied atPF or PI stage was found to be inhibitory to N₂ase and glutaminesynthetase (GS) activities except at 15 kg N ha^–1 whenapplied at PF in the case of N₂ase. At both the stages therewas increase in NR and glutamate dehydrogenase (GDH) activitieswith the application of nitrogen. Seed yield increased by 18per cent with the application of 15 kg N ha^–1 at PI stagewhereas nitrogen application at PF stage only increased strawyield significantly. Nitrate reductase, nitrogenase, nitrogen application, ammonia assimilation, Vigna radiata