RESUMO
Selection exerted by herbivores is a major force driving the evolution of plant defensive characters such as leaf trichomes or secondary metabolites. However, plant defense expression is highly variable among populations and identifying the sources of this variation remains a major challenge. Plant populations are often distributed across broad geographic ranges and are exposed to different herbivore communities, ranging from generalists (that feed on diverse plant species) to specialists (that feed on a restricted group of plants). We studied eight populations of the plant Datura stramonium usually eaten by specialist or generalist herbivores, in order to examine whether the pattern of phenotypic selection on secondary compounds (atropine and scopolamine) and a physical defense (trichome density) can explain geographic variation in these traits. Following co-evolutionary theory, we evaluated whether a more derived alkaloid (scopolamine) confers higher fitness benefits than its precursor (atropine), and whether this effect differs between specialist and generalist herbivores. Our results showed consistent directional selection in almost all populations and herbivores to reduce the concentration of atropine. The most derived alkaloid (scopolamine) was favored in only one of the populations, which is dominated by a generalist herbivore. In general, the patterns of selection support the existence of a selection mosaic and accounts for the positive correlation observed between atropine concentration and plant damage by herbivores recorded in previous studies.
Assuntos
Datura stramonium/fisiologia , Animais , Atropina/metabolismo , Datura stramonium/anatomia & histologia , Herbivoria , México , Fenótipo , Dispersão Vegetal , Seleção Genética , Tricomas/anatomia & histologia , Tricomas/fisiologiaRESUMO
Muscarinic receptors play an important role in secretory and vasodilator responses in rat salivary glands. Nitric oxide synthase (NOS) activity was found coupled to muscarinic receptor activation as well as to nitric oxide-mediated amylase secretion elicited by carbachol. Parotid glands presented a predominant M(3) and a minor muscarinic M(1) acetylcholine receptor population, though carbachol stimulated NOS activity only through muscarinic M(3) receptors as revealed in the presence of 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP) and pirenzepine. Amylase secretion induced by carbachol appeared to be partly mediated by nitric oxide and nitric oxide-induced signaling since N-nitro-L-arginine methyl ester (L-NAME) inhibited the effect as well as did methylene blue. A negative regulation of NOS by protein kinase C activation in the presence of a high concentration of carbachol was seen in parotid glands and this inhibition was paralleled by amylase secretion.
Assuntos
Óxido Nítrico Sintase/metabolismo , Glândula Parótida/metabolismo , Receptores Muscarínicos/metabolismo , Amilases/metabolismo , Animais , Atropina/metabolismo , Atropina/farmacologia , Ligação Competitiva , Carbacol/farmacologia , Membrana Celular/efeitos dos fármacos , Membrana Celular/metabolismo , Relação Dose-Resposta a Droga , Ativação Enzimática/efeitos dos fármacos , Inibidores Enzimáticos/farmacologia , Masculino , Antagonistas Muscarínicos/farmacologia , NG-Nitroarginina Metil Éster/farmacologia , Óxido Nítrico/metabolismo , Óxido Nítrico Sintase/antagonistas & inibidores , Glândula Parótida/efeitos dos fármacos , Piperidinas/metabolismo , Piperidinas/farmacologia , Pirenzepina/farmacologia , Quinuclidinil Benzilato/metabolismo , Quinuclidinil Benzilato/farmacologia , Ratos , Ratos Wistar , Organismos Livres de Patógenos EspecíficosRESUMO
The quenching ability of photogenerated oxidative species by some antimuscarinic drugs generically named atropines (e.g. atropine [I] eucatropine [II], homatropine [III] and scopolamine [IV]) have been investigated employing stationary photolysis, polarographic detection of dissolved oxygen, stationary and time-resolved fluorescence spectroscopy, and laser flash photolysis. Using Rose Bengal as a dye sensitiser for singlet molecular oxygen, O(2)((1)Delta(g)), generation, compounds I-IV behave as moderate chemical plus physical quenchers of the oxidative species. Correlation between kinetic and electrochemical data indicates that the process is possibly driven by a charge-transfer interaction. The situation is somewhat more complicated employing the natural pigment riboflavin (Rf) as a sensitiser. Compounds I and II complex Rf ground state, diminishing the quenching ability towards singlet and triplet excited state of the pigment. On the other hand, compounds III and IV effectively quench Rf excited states, protecting the pigment against photodegradation. Under anaerobic conditions, semireduced Rf (Rf(.-)) is formed through quenching of excited triplet Rf. Nevertheless, although Rf(.-) is a well-known generator of the reactive species superoxide radical anion by reductive quenching in the presence of oxygen, the process of O(2)((1)Delta(g)) production prevails over superoxide radical generation, due to the relatively low rate constants for the quenching of triplet Rf by the atropines (in the order of 10(7) M(-1)s(-1) for compounds III and IV) in comparison to the rate constant for the quenching by ground state oxygen, approximately two orders of magnitude higher, yielding O(2)((1)Delta(g)). Compound I is the most promising O(2)((1)Delta(g)) physical scavenger, provided that it exhibits the higher value for the overall quenching rate constant and only 11% of the quenching process leads to its own chemical damage.
Assuntos
Atropina/química , Atropina/metabolismo , Sequestradores de Radicais Livres/metabolismo , Antagonistas Muscarínicos/metabolismo , Fotólise , Estabilidade de Medicamentos , Estrutura Molecular , Antagonistas Muscarínicos/química , Fármacos Fotossensibilizantes/química , Rosa Bengala/química , Oxigênio Singlete/química , Oxigênio Singlete/metabolismo , Espectrofotometria AtômicaRESUMO
Hairy roots of Brugmansia candida that grew without agitation were obtained. Kinetics of growth and production of the tropane alkaloids scopolamine and hyoscyamine, with and without agitation, were studied. The exponential growth rate was higher in the roots that were exposed to shaking (0.13 d(-1)) than in the nonagitated ones (0.09 d(-1)). The specific production and the levels per flask of both alkaloids were enhanced without shaking. The use of these roots in large-scale productions could be economically advantageous. It remains to be seen if the data obtained in shake flasks can be extrapolated to large-scale bioreactors.
Assuntos
Atropina/metabolismo , Biotecnologia/métodos , Raízes de Plantas/crescimento & desenvolvimento , Escopolamina/metabolismo , Solanaceae/crescimento & desenvolvimento , Raízes de Plantas/citologia , Raízes de Plantas/metabolismo , Solanaceae/citologia , Solanaceae/metabolismoRESUMO
In Pseudomonas aeruginosa and Rhizobium meliloti several choline derivatives, utilized as the sole carbon and nitrogen source, increase acid phosphatase activity. The enzyme activity of both bacteria could be released into the surrounding medium by EDTA-lysozyme treatment. The R. meliloti acid phosphatase activity of crude periplasmic extracts measured with p-nitrophenylphosphate was not inhibited by the presence of 5 mM choline, betaine, trimethylammonium or phosphorylcholine. The activity could not be detected using phosphorylethanolamine or phosphorylcholine as substrates. Among several phosphoesters tested only pyridoxal-5-phosphate was hydrolyzed at a considerable rate. In 7.5% polyacrylamide slab gel electrophoresis (non-denaturing conditions) of crude extracts obtained from bacteria grown in the presence of serine, glutamate, aspartate or dimethylglycine a phosphatase activity with identical mobility could be detected with alpha-naphthylphosphate or pyridoxal-5-phosphate were used as substrates. In conclusion, although the choline metabolites are capable of increasing acid phosphatase activities in R. meliloti and in P. aeruginosa, there are two different enzymes involved, apparently in different metabolisms.
Assuntos
Fosfatase Ácida/metabolismo , Colina/farmacologia , Pseudomonas aeruginosa/enzimologia , Rhizobium/enzimologia , Atropina/metabolismo , Atropina/farmacologia , Betaína/metabolismo , Betaína/farmacologia , Colina/metabolismo , Meios de Cultura , Fosforilcolina/metabolismo , Fosforilcolina/farmacologia , Pseudomonas aeruginosa/efeitos dos fármacos , Compostos de Amônio Quaternário/metabolismo , Compostos de Amônio Quaternário/farmacologia , Rhizobium/efeitos dos fármacos , Sarcosina/análogos & derivados , Sarcosina/metabolismo , Sarcosina/farmacologiaRESUMO
Para estudiar el mecanismos de acción del AMP en el nodo A-V, se estudiaron 10 pacientes con taquicardia supraventricular por re-entrada (TVS) que incluía el nodo AV en su circuito.. El promedio de edad fue 32.8 + ou - 11.1 años. La taquicardia se indujo por estimulación auricular programada y se realizaron registros electrofisiológicos intracavitarios en todos los casos. En la primera etapa la administración de AMP suprimió la arrtmia en todos los casos en un tiempo promedio de 15.2 + ou - 2.6 seg., con una dosis de 0.095 + ou - 0.037mg/kg. En la segunda etapa la administración de atropina (0.04mg/kg.) no impidió la supresión de la arritmia. La dosis de AMP fue 0.122 + ou - 0.045mg/kg (P3NDS) y el tiempo promedio 16.2 + ou - 2.2 (p=NDS). En la tercera etapa: la administración de AMP no interrumpió la arritmia inducida bajo el efecto de atropina y aminofilina (4mg/kg) en 8 de los pacientes. En uno de los restantes la dosis necesarias fue 0.250mg/kg., y en el otro fue 0.075mg/kg. No hubo efectos colaterales graves. Se demuestra que la acción del AMP está mediada por estimulación agonista de receptores purinérgicos en el nodo AV