RESUMO
Competition for shared resources represents a fundamental driver of biological diversity. However, the tempo and mode of phenotypic evolution in deep-time has been predominantly investigated using trait evolutionary models which assume that lineages evolve independently from each other. Consequently, the role of species interactions in driving macroevolutionary dynamics remains poorly understood. Here, we quantify the prevalence for signatures of competition between related species in the evolution of ecomorphological traits across the bird radiation. We find that mechanistic trait models accounting for the effect of species interactions on phenotypic divergence provide the best fit for the data on at least one trait axis in 27 out of 59 clades ranging between 21 and 195 species. Where it occurs, the signature of competition generally coincides with positive species diversity-dependence, driven by the accumulation of lineages with similar ecologies, and we find scarce evidence for trait-dependent or negative diversity-dependent phenotypic evolution. Overall, our results suggest that the footprint of interspecific competition is often eroded in long-term patterns of phenotypic diversification, and that other selection pressures may predominantly shape ecomorphological diversity among extant species at macroevolutionary scales.
Assuntos
Evolução Biológica , Aves , Animais , Fenótipo , FilogeniaRESUMO
Heterogeneity in rates of trait evolution is widespread, but it remains unclear which processes drive fast and slow character divergence across global radiations. Here, we test multiple hypotheses for explaining rate variation in an ecomorphological trait (beak shape) across a globally distributed group (birds). We find low support that variation in evolutionary rates of species is correlated with life history, environmental mutagenic factors, range size, number of competitors, or living on islands. Indeed, after controlling for the negative effect of species' age, 80% of variation in species-specific evolutionary rates remains unexplained. At the clade level, high evolutionary rates are associated with unusual phenotypes or high species richness. Taken together, these results imply that macroevolutionary rates of ecomorphological traits are governed by both ecological opportunity in distinct adaptive zones and niche differentiation among closely related species.
Assuntos
Evolução Biológica , Ecologia , Animais , Masculino , Fenótipo , FilogeniaRESUMO
BACKGROUND: NAD(P)H:quinone acceptor oxidoreductase (QR1) protects animal cells from the deleterious and carcinogenic effects of quinones and other electrophiles. Remarkably, the same enzyme activates cancer prodrugs that become cytotoxic only after two-electron reduction. QR1's ability to bioactivate quinones and its elevated expression in many human solid tumors makes this protein an excellent target for enzyme-directed drug development. Until now, structural analysis of the mode of binding of chemotherapeutic compounds to QR1 was based on model building using the structures of complexes with simple substrates; no structure of complexes of QR1 with chemotherapeutic prodrugs had been reported. RESULTS: Here we report the high-resolution crystal structures of complexes of QR1 with three chemotherapeutic prodrugs: RH1, a water-soluble homolog of dimethylaziridinylbenzoquinone; EO9, an aziridinylindolequinone; and ARH019, another aziridinylindolequinone. The structures, determined to resolutions of 2.0 A, 2.5 A, and 1.86 A, respectively, were refined to R values below 21% with excellent geometry. CONCLUSIONS: The structures show that compounds can bind to QR1 in more than one orientation. Surprisingly, the two aziridinylindolequinones bind to the enzyme in different orientations. The results presented here reveal two new factors that must be taken into account in the design of prodrugs targeted for activation by QR1: the enzyme binding site is highly plastic and changes to accommodate binding of different substrates, and homologous drugs with different substituents may bind to QR1 in different orientations. These structural insights provide important clues for the optimization of chemotherapeutic compounds that utilize this reductive bioactivation pathway.
Assuntos
Antineoplásicos/química , Desenho de Fármacos , Quinona Redutases/química , Quinonas/uso terapêutico , Antineoplásicos/farmacologia , Benzoquinonas/química , Sítios de Ligação , Domínio Catalítico , Cristalografia por Raios X , Humanos , Cinética , Modelos Químicos , Ligação Proteica , Quinonas/química , Proteínas Recombinantes/químicaRESUMO
The protein caldesmon, originally isolated from smooth muscle tissue where it is the most abundant calmodulin-binding protein, has since been shown to have a wide distribution in actin- and myosin- containing cells where it is localized in sub-cellular structures concerned with motility, shape changes and exo- or endo-cytosis. Caldesmon is believed to be an actin- regulatory protein, and binds with high affinity to actin or actin-tropomyosin. Caldesmon inhibits the activation by actin-tropomyosin of myosin MgATPase activity, and the inhibition can be reversed by Ca2+.calmodulin. The binding of caldesmon to smooth muscle proteins has been studied in detail, enabling a model to be constructed which could account for the observed Ca2+ regulation of smooth muscle thin filaments. The abundance of caldesmon, and the Ca2+-regulation of its activity via calmodulin, mean that it is potentially an important intracellular regulator of processes such as smooth muscle contraction, cell motility and secretion.
Assuntos
Proteínas de Ligação a Calmodulina/fisiologia , Actinas/fisiologia , Animais , Cálcio/fisiologia , Calmodulina/fisiologia , Citoesqueleto/fisiologia , Músculo Liso/fisiologia , Miosinas/fisiologia , Fosforilação , Distribuição TecidualRESUMO
Using X-ray and NMR data relating to the conformation of the antihypertensive, angiotensin-converting enzyme inhibitor, captopril, and structure--activity relationships of analogues, it has been possible to postulate with the aid of computer graphics, the orientation of the three functions, the thiol, the terminal carboxyl and the carbonyl group which are involved in binding to the enzyme. Bicyclic mimetics of captopril, with related arrays of these functions, have been designed and synthesized. Compounds with the closest approximation to the array in captopril are the most active inhibitors of angiotensin converting enzyme, in vitro.
Assuntos
Inibidores da Enzima Conversora de Angiotensina , Animais , Sítios de Ligação , Captopril/metabolismo , Computadores , Pulmão/enzimologia , Modelos Moleculares , Coelhos , Relação Estrutura-Atividade , Difração de Raios XRESUMO
Ca2+-sensitive thin filaments from vascular smooth muscle were disassembled into their constituent proteins, actin, tropomyosin and caldesmon. Caldesmon bound to both actin and to actin-tropomyosin and inhibited actin-tropomyosin activation of skeletal muscle myosin MgATPase. It also promoted the aggregation of actin or actin-tropomyosin into parallel aligned bundles. Quantitative electron microscopy measurements showed that with 1.1 microM actin-tropomyosin, 1.6 +/- 0.5% (n = 3) of the filaments were in bundles. At 0.073 microM, caldesmon inhibited MgATPase activity by 50%, whereas bundling was 3.0 +/- 1.3% (n = 4). At 0.37 microM caldesmon, MgATPase inhibition was 83% while 28.1 +/- 6.9% (n = 4) of filaments were in bundles. Experiments at 4.4 microM in which MgATPase and bundling were measured in the same samples gave similar results. Small bundles of 2-3 filaments showed the most frequent occurrence at 1.1 microM actin. At 4.4 microM actin the most common bundle size was 3-5 filaments, with the occasional occurrence of large bundles consisting of up to 120 filaments. The incidence of bundling was the same in the presence and absence of tropomyosin. Thus caldesmon can induce the formation of actin bundles but this property bears no relationship to its inhibition of MgATPase activity.
Assuntos
Actinas/metabolismo , Proteínas de Ligação a Calmodulina/fisiologia , Músculo Liso Vascular/metabolismo , Animais , Aorta/metabolismo , ATPase de Ca(2+) e Mg(2+)/antagonistas & inibidores , Ativação Enzimática , Técnicas In Vitro , Ovinos , Tropomiosina/metabolismoRESUMO
A number of analogues of the naturally occurring thiazolylindolequinone BE 10988, a reported potent inhibitor of topoisomerase II, have been prepared and evaluated. The compounds were synthesized from 4-(benzyloxy)-5-methoxy-1-methylindole by appropriate substitution at the indole 3-position followed by standard thiazole ring-forming reactions. The toxicity of these potentially bioreductively activated indolequinones was measured in Chinese hamster V79 cells under aerobic and hypoxic conditions. In addition, toxicity was measured in a human breast cancer cell line that shows amplification of the topo II alpha gene and hypersensitivity to known topo II inhibitors such as mAMSA and mitoxantrone. Using a DNA decatenation assay, a comparison was also made of the inhibitory effects of BE 10988 and mitoxantrone on topo II activity.
Assuntos
Indóis/síntese química , Indóis/farmacologia , Quinonas/síntese química , Quinonas/farmacologia , Tiazóis/síntese química , Tiazóis/farmacologia , Inibidores da Topoisomerase II , Aerobiose , Animais , Neoplasias da Mama/tratamento farmacológico , Células CHO , Hipóxia Celular , Cricetinae , Cricetulus , Avaliação Pré-Clínica de Medicamentos , Células HeLa , Humanos , Relação Estrutura-Atividade , Células Tumorais CultivadasRESUMO
A series of indolequinones bearing various functional groups has been synthesized, and the effects of substituents on the metabolism of the quinones by recombinant human NAD(P)H:quinone oxidoreductase (NQO1) were studied. Indolequinones were selected for study on the basis of the X-ray crystal structure of the human enzyme, and were designed to probe the effect of substituents particularly at N-1. Metabolism of the quinones by NQO1 revealed that, in general, compounds with electron-withdrawing groups at the indole 3-position were among the best substrates, and that groups larger than methyl at N-1 are clearly tolerated. Compounds with a leaving group at the 3-indolyl methyl position generally inactivated the enzyme. The toxicity toward human colon carcinoma cells with either no detectable activity (BE-WT) or high NQO1 activity (BE-NQ) was also studied in representative quinones. The most toxic compounds were those with a leaving group at the C-3 position; these compounds were 1.1-5.3-fold more toxic to the BE-NQ than the BE-WT cells.
Assuntos
Antineoplásicos/síntese química , Indóis/síntese química , NAD(P)H Desidrogenase (Quinona)/metabolismo , Quinonas/síntese química , Antineoplásicos/química , Antineoplásicos/farmacologia , Cromatografia Líquida de Alta Pressão , Ensaios de Seleção de Medicamentos Antitumorais , Humanos , Indóis/química , Indóis/farmacologia , Concentração Inibidora 50 , Quinonas/química , Quinonas/farmacologia , Proteínas Recombinantes/metabolismo , Relação Estrutura-Atividade , Células Tumorais CultivadasRESUMO
A series of indolequinones bearing various functional groups has been synthesized, and the effects of substituents on the metabolism of the quinones by recombinant human NAD(P)H:quinone oxidoreductase (NQO1) were studied. Thus 5-methoxyindolequinones were prepared by the Nenitzescu reaction, followed by functional group interconversions. The methoxy group was subsequently displaced by amine nucleophiles to give a series of amine-substituted quinones. Metabolism of the quinones by NQO1 revealed that, in general, compounds with electron-withdrawing groups at the indole 3-position were among the best substrates, whereas those with amine groups at the 5-position were poor substrates. Compounds with a leaving group at the 3-indolyl methyl position generally inactivated the enzyme. The toxicity toward non-small-cell lung cancer cells with either high NQO1 activity (H460) or no detectable activity (H596) was also studied in representative quinones. Compounds which were good substrates for NQO1 showed the highest selectivity between the two cell lines.
Assuntos
Antineoplásicos/síntese química , NAD(P)H Desidrogenase (Quinona)/metabolismo , Quinonas/síntese química , Antineoplásicos/química , Antineoplásicos/metabolismo , Antineoplásicos/farmacologia , Carcinoma Pulmonar de Células não Pequenas/enzimologia , Carcinoma Pulmonar de Células não Pequenas/patologia , Ensaios de Seleção de Medicamentos Antitumorais , Humanos , Concentração Inibidora 50 , Neoplasias Pulmonares/enzimologia , Neoplasias Pulmonares/patologia , Quinonas/química , Quinonas/metabolismo , Quinonas/farmacologia , Proteínas Recombinantes/metabolismo , Relação Estrutura-Atividade , Células Tumorais CultivadasRESUMO
The synthesis of the indolequinones 8 and 9 starting from methyl 4-(benzyloxy)-5-methoxy-indole-2-carboxylate (10) is described. The methoxy group in the indolequinones 1, 2, 4, 5, and 7-9 can be displaced by various nitrogen nucleophiles (ammonia, 2-methoxyethylamine, aziridine, 2-methylaziridine, pyrrolidine) in 22-88% yield. The resulting amino-substituted quinones, together with their methoxy precursors, were studied by cyclic voltammetry to determine their reduction potentials, which, in DMF solution, lie in the range -1.355 to -1.597 V (vs ferrocene). The cytotoxicity of the compounds towards aerobic and hypoxic mammalian cells was also determined; in general, under aerobic conditions, the cyclopropamitosenes are more toxic than the corresponding pyrrolo[1,2-a]indolequinones, which are in turn more toxic than the simple 1,2-dimethylindolequinones, with many of the compounds in each series showing greater toxicity toward hypoxic cells.
Assuntos
Indóis/química , Mitomicinas/síntese química , Mitomicinas/farmacologia , Quinonas/síntese química , Animais , Divisão Celular/efeitos dos fármacos , Células Cultivadas , Cricetinae , Cricetulus , Eletroquímica , Oxirredução , Quinonas/farmacologiaRESUMO
A series of indolequinones bearing a variety of leaving groups at the (indol-3-yl)methyl position was synthesized by functionalization of the corresponding 3-(hydroxymethyl)indolequinone, and the resulting compounds were evaluated in vitro as bioreductively activated cytotoxins. The elimination of a range of functional groups-carboxylate, phenol, and thiol-was demonstrated upon reductive activation under both chemical and quantitative radiolytic conditions. Only those compounds which eliminated such groups under both sets of conditions exhibited significant hypoxia selectivity, with anoxic:oxic toxicity ratios in the range 10-200. With the exception of the 3-hydroxymethyl derivative, radiolytic generation of semiquinone radicals and HPLC analysis indicated that efficient elimination of the leaving group occurred following one-electron reduction of the parent compound. The active species in leaving group elimination was predominantly the hydroquinone rather than the semiquinone radical. The resulting iminium derivative acted as an alkylating agent and was efficiently trapped by added thiol following chemical reduction and by either water or 2-propanol following radiolytic reduction. A chain reaction in the radical-initiated reduction of these indolequinones (not seen in a simpler benzoquinone) in the presence of a hydrogen donor (2-propanol) was observed. Compounds that were unsubstituted at C-2 were found to be up to 300 times more potent as cytotoxins than their 2-alkyl-substituted analogues in V79-379A cells, but with lower hypoxic cytotoxicity ratios.
Assuntos
Antineoplásicos , Indóis , Quinonas , Animais , Antineoplásicos/síntese química , Antineoplásicos/química , Antineoplásicos/farmacologia , Antineoplásicos/efeitos da radiação , Morte Celular/efeitos dos fármacos , Hipóxia Celular , Cromatografia Líquida de Alta Pressão , Cricetinae , Ensaios de Seleção de Medicamentos Antitumorais , Radicais Livres/química , Indóis/síntese química , Indóis/química , Indóis/farmacologia , Indóis/efeitos da radiação , Cinética , Oxirredução , Radiólise de Impulso , Quinonas/síntese química , Quinonas/química , Quinonas/farmacologia , Quinonas/efeitos da radiação , Relação Estrutura-Atividade , Células Tumorais CultivadasRESUMO
1 The effects of adenosine, 5'-N-ethylcarboxamidoadenosine (NECA), 2-chloroadenosine, 2-azidoadenosine, and their L-enantiomers were examined on driven left atria, trachea and transmurally stimulated ileum of the guinea-pig. 2 In each tissue the order of potency of the D-enantiomers for producing inhibitory effects was NECA greater than 2-chloroadenosine greater than 2-azidoadenosine greater than adenosine. 3 The log concentration-response curve of each agonist was shifted to the right in the presence of the P1-purinoceptor antagonist, theophylline. 4 Dipyridamole, which blocks adenosine uptake, potentiated the effects of adenosine but not those of the D-enantiomers of adenosine analogues. 5 The greater potency of the adenosine analogues therefore, is at least partly due to their resistance to tissue uptake and subsequent enzymatic destruction. 6 The L-enantiomers of adenosine and its analogues did not produce inhibitory responses in the driven left atria or transmurally stimulated ileum. At high concentrations relaxations of the tracheal muscle were obtained, with the potency series L-NECA greater than 2-chloro-L-adenosine greater than 2-azido-L-adenosine greater than L-adenosine. 7 It is concluded that the postsynaptic P1-purinoceptors in the guinea-pig atria and trachea and the presynaptic P1-purinoceptors on cholinergic nerve terminals in guinea-pig ileum are stereospecific for the D-enantiomers of adenosine and its analogues.
Assuntos
Adenosina/análogos & derivados , Adenosina/farmacologia , Azidas , Receptores de Droga/efeitos dos fármacos , 2-Cloroadenosina , Adenosina-5'-(N-etilcarboxamida) , Animais , Feminino , Cobaias , Átrios do Coração/efeitos dos fármacos , Íleo/efeitos dos fármacos , Técnicas In Vitro , Masculino , Receptores Purinérgicos , Estereoisomerismo , Teofilina/farmacologia , Traqueia/efeitos dos fármacosRESUMO
To investigate the importance of NAD(P)H:quinone oxidoreductase 1 (or DT-diaphorase; NQO1) in the bioactivation of antitumor quinones, we established a series of stably transfected cell lines derived from BE human colon adenocarcinoma cells. BE cells have no NQO1 activity due to a genetic polymorphism. The new cell lines, BE-NQ, stably express wild-type NQO1. BE-NQ7 cells expressed the highest level of NQO1 and were more susceptible [determined by the thiazolyl blue (MTT) assay] to known antitumor quinones and newer clinical candidates. Inhibition of NQO1 by pretreatment with an irreversible inhibitor, ES936 [5-methoxy-1,2-dimethyl-3-[(4-nitrophenoxy)methyl]indole-4,7-dione], protected BE-NQ7 cells from toxicity induced by streptonigrin, ES921 [5-(aziridin-1-yl)-3-(hydroxymethyl)-1,2-dimethylindole-4,7-dione], and RH1 [2,5-diaziridinyl-3-(hydroxymethyl)-6-methyl-1,4-benzoquinone]. RH1 was evaluated further by clonogenic assay for cytotoxic response and was more cytotoxic to BE-NQ7 cells than to BE cells. Cytotoxicity was abrogated by inhibition of NQO1 with ES936 pretreatment. Using a comet assay to evaluate DNA cross-linking, BE-NQ7 cells demonstrated significantly higher DNA cross-links than did BE cells in response to RH1 treatment. DNA cross-linking in BE-NQ7 cells was observed at very low concentrations of RH1 (5 nM), confirming that NQO1 activates RH1 to a potent cross-linking species. Further studies using streptonigrin, ES921, and RH1 were undertaken to analyze the relationship between NQO1 activity and quinone toxicity. Toxicity of these compounds was measured in a panel of BE-NQ cells expressing a range of NQO1 activity (23-433 nmol/min/mg). Data obtained suggest a threshold for NQO1-induced toxicity above 23 nmol/min/mg and a sharp dose-response curve between the no effect level of NQO1 (23 nmol/min/mg) and the maximal effect level (>77 nmol/min/mg). These data provide evidence that NQO1 can bioactivate antitumor quinones in this system and suggest that a threshold level of NQO1 activity is required to initiate toxic events.
Assuntos
Antineoplásicos/farmacologia , NAD(P)H Desidrogenase (Quinona)/metabolismo , Quinonas/farmacologia , Antibióticos Antineoplásicos/farmacologia , Aziridinas/farmacologia , Benzoquinonas/farmacologia , Biotransformação , Divisão Celular/efeitos dos fármacos , Interações Medicamentosas , Humanos , Concentração Inibidora 50 , NAD(P)H Desidrogenase (Quinona)/antagonistas & inibidores , Quinonas/metabolismo , Estreptonigrina/farmacologia , Transfecção , Células Tumorais CultivadasRESUMO
The inhibitory effects of adenosine, ATP, 5'-adenylyl methylene diphosphonate (beta, gamma-meATP) and adenosine 5'-alpha, beta-methylene triphosphonate (alpha, beta-meATP) were compared on the cholinergic twitch responses to transmural stimulation of the guinea-pig ileum. Adenosine, ATP and beta, gamma-meATP reduced the twitch responses in a concentration dependent manner. Theophylline antagonized and dipyridamole potentiated the inhibitory responses to adenosine, ATP and beta, gamma-meATP. Inhibitory responses to alpha, beta-meATP were usually preceded by an enhancement in twitch height. Contractions of the unstimulated ileum to alpha, beta-meATP were blocked by atropine and tetrodotoxin while those elicited by ATP were unaffected, which suggests that the initial excitatory effects of alpha, beta-meATP may be due to its ability to release ACh from cholinergic nerve terminals. Use of high pressure liquid chromatography and bioluminescence assay techniques demonstrated the ability of the tissue to degrade ATP and beta, gamma-meATP and, at a much slower rate, alpha, beta-meATP. Inhibitory responses to ATP, AMP and beta, gamma-meATP were reduced by adenosine deaminase, which also abolished responses to adenosine. 5'-AMP deaminase abolished responses to AMP and adenosine, and reduced those to ATP and beta, gamma-meATP. The results suggest that the inhibitory effect of ATP on cholinergic neurotransmission is due to its rapid breakdown to AMP or adenosine, which act on prejunctional P1-purinoceptors.
Assuntos
Fibras Colinérgicas/metabolismo , Íleo/inervação , Terminações Nervosas/metabolismo , Purinas/metabolismo , Receptores de Droga/metabolismo , Adenosina/farmacologia , Monofosfato de Adenosina/farmacologia , Trifosfato de Adenosina/análogos & derivados , Trifosfato de Adenosina/farmacologia , Animais , Biotransformação , Cobaias , Íleo/fisiologia , Técnicas In Vitro , Masculino , Contração Muscular/efeitos dos fármacos , Receptores Purinérgicos , Transmissão Sináptica/efeitos dos fármacosRESUMO
The effects of degradative enzymes and enzyme inhibitors were examined on the inhibitory actions of adenosine, AMP and ATP on atrial muscle and on the cholinergic responses of the ileum to transmural stimulation of the guinea-pig, in order to determine whether ATP responses are mediated by its breakdown products, AMP and adenosine. In both the atria and the ileum, adenosine deaminase reduced responses to ATP, although when combined with 5'-nucleotidase it had no further effect. In the atrium, the 5'-nucleotidase inhibitor, alpha,beta-methylene ADP (APCP), had no effect on its own, but prevented the potentiating effect of the adenosine deaminase inhibitor erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA) on responses to ATP. In the ileum, EHNA had no effect, but APCP potentiated responses to ATP. The enzyme 5'-AMP deaminase was shown to have a non-specific inhibitory effect on purine responses in both preparations. It is concluded for both preparations, that (1) the inhibitory responses to ATP are partly mediated by AMP and adenosine following the ectoenzymatic breakdown of ATP, and partly mediated by ATP itself, and (2) that AMP as well as adenosine can act directly on P1-purinoceptors. It is suggested that of the two breakdown products of ATP, AMP and adenosine, a larger proportion of the response is mediated by AMP in the ileum, whereas adenosine is the major mediator in the atrium.
Assuntos
Monofosfato de Adenosina/farmacologia , Trifosfato de Adenosina/farmacologia , Adenosina/farmacologia , Coração/fisiologia , Receptores de Superfície Celular/fisiologia , 5'-Nucleotidase , AMP Desaminase/farmacologia , Inibidores de Adenosina Desaminase , Trifosfato de Adenosina/metabolismo , Animais , Função Atrial , Feminino , Cobaias , Íleo/fisiologia , Masculino , Contração Muscular/efeitos dos fármacos , Contração Miocárdica/efeitos dos fármacos , Nucleotidases/antagonistas & inibidores , Receptores PurinérgicosRESUMO
8-Phenyltheophylline was more potent than theophylline in antagonizing the inhibitory effects of adenosine in guinea-pig driven left atrium, rabbit basilar artery and electrically stimulated guinea-pig ileum preparations. In guinea-pig atrium and ileum, the antagonism of adenosine responses by the methylxanthines is of a competitive nature, but in rabbit basilar artery it does not appear to be so. In all three preparations, the effects of theophylline and 8-phenyltheophylline could be reversed by washing. It is concluded that 8-phenyltheophylline is a more potent P1-purinoceptor antagonist than theophylline.
Assuntos
Adenosina/antagonistas & inibidores , Contração Muscular/efeitos dos fármacos , Receptores de Droga/efeitos dos fármacos , Teofilina/análogos & derivados , Animais , Artéria Basilar/efeitos dos fármacos , Feminino , Cobaias , Átrios do Coração/efeitos dos fármacos , Íleo/efeitos dos fármacos , Técnicas In Vitro , Masculino , Músculo Liso Vascular/efeitos dos fármacos , Contração Miocárdica/efeitos dos fármacos , Coelhos , Receptores Purinérgicos , Teofilina/farmacologiaRESUMO
Gliotoxin is a natural mycotoxin with immunosuppressive and antimicrobial activity. Inhibition of farnesyltransferase (IC50 80 microM) and geranylgeranyltransferase I (IC50 17 microM) stimulated interest in the potential antitumor activity of this epidithiodioxopiperazine. Gliotoxin inhibited proliferation of six breast cancer cell lines in culture with mean +/- SD IC50 289 +/- 328 microM (range 38-985 microM); intracellular farnesylation of Lamin B and geranylgeranylation of Rap1A were inhibited in a dose-dependent manner. In randomized controlled studies using the N-methyl-N-nitrosourea rat mammary carcinoma model, gliotoxin had pronounced antitumor activity in vitro and little systemic toxicity when administered to 10 animals at 10 mg/kg by subcutaneous injection weekly for 4 wk compared with 10 controls. Single doses up to 25 mg/kg were well tolerated. The present studies confirm that gliotoxin is a dual inhibitor of farnesyltransferase and geranylgeranyltransferase I with pronounced antitumor activity and favorable toxicity profile against breast cancer in vitro and in vivo.
Assuntos
Alquil e Aril Transferases/antagonistas & inibidores , Gliotoxina/farmacologia , Neoplasias Mamárias Experimentais/tratamento farmacológico , Animais , Divisão Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Relação Dose-Resposta a Droga , Farnesiltranstransferase , Feminino , Gliotoxina/química , Gliotoxina/uso terapêutico , Humanos , Imunossupressores/química , Imunossupressores/farmacologia , Imunossupressores/uso terapêutico , Distribuição Aleatória , Ratos , Resultado do TratamentoRESUMO
The background to bioreductive drugs based on indolequinones is surveyed, and the development of novel cyclopropamitosenes as potent anticancer agents is reviewed. Thiazolylindoles were also investigated as potential inhibitors of topoisomerase II.
Assuntos
Antineoplásicos/síntese química , Indóis/síntese química , Quinonas/síntese química , Antineoplásicos/farmacologia , Indóis/farmacologia , Pró-Fármacos/síntese química , Quinonas/farmacologiaRESUMO
Using a computer-controlled torque motor and manipulandum, 50 ms torque pulses and 70 second trains of binary pseudorandom torque disturbances were applied to the wrists of 10 adult controls and 22 patients with essential tremor in order to study the interaction between mechanically-induced stretch-reflex oscillations and essential tremor. These two oscillations were separated by applying inertial and spring loads to the wrist. There was no evidence of increased or unstable stretch-reflex activity in the essential tremor patients, and stretch-reflex latencies did not correlate with the frequency of essential tremor. Essential tremor and mechanically-induced stretch-reflex oscillations are separate phenomena capable of complex interaction.
Assuntos
Reflexo de Estiramento , Tremor/fisiopatologia , Adulto , Idoso , Eletromiografia , Humanos , Pessoa de Meia-Idade , Tempo de Reação/fisiologia , PunhoRESUMO
Xwnt-3A is a member of the Xenopus-Wnt gene family, a class of secreted, cysteine-rich proteins implicated in intercellular signaling during early development. Here we describe the full-length coding sequence of Xwnt-3A, as well as the spatial expression pattern of this Xwnt gene as determined by whole-mount in situ hybridization analysis. While Xwnt-3A shares considerable amino acid identity with both Wnt-3 (87%) and Wnt-3A (85%), its spatial expression pattern is most like that of Wnt-3A. Xwnt-3A, which is first detected at the neurula stage of development, is expressed exclusively along the dorsal midline of the developing brain and neural tube and along the dorsal surface of the otic vesicle. While the expression of Xwnt-1 extensively overlaps that of Xwnt-3A, Xwnt-1 is uniquely expressed along the midbrain/hindbrain boundary and is absent from the otic vesicle. The expression of Xwnt-3A in neural ectoderm is dependent upon neural induction as determined by experiments with recombined ectoderm and mesoderm tissue. These results suggest that Xwnt-3A may participate in patterning the central nervous system during early Xenopus development. Last, the ectopic expression of Xwnt-3A induces the formation of a secondary axis at the anterior end of the embryo.