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1.
Arch Microbiol ; 180(6): 427-33, 2003 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-14610640

RESUMO

The effects of the Ca(2+)/H(+) exchanger A23187 and the K(+)/H(+) exchanger nigericin, the electrogenic membrane-potential depleters valinomycin and CCCP, and the calcium channel blockers ruthenium red, nifedipine, and nitrendipine on the apical growth of Phycomyces blakesleeanus were analyzed. While all of the compounds inhibited the growth of germlings in liquid medium, the Ca(2+) channel blockers were the least effective. Chitin synthesis in vivo was also sensitive to the inhibitors; here again, the calcium channel blockers were less efficient, and their effect occurred after a lag phase, in contrast to the electroneutral ionophores whose effects were immediate. The ionophores rapidly inhibited protein secretion, and reduced the number of secretory vesicles and chitosomes in the hyphal apex of P. blakesleeanus. The results suggest that not only tip-to-base calcium gradients but also transmembrane ionic gradients and membrane potential have a role in the apical growth of P. blakesleeanus. They are probably involved in the formation, migration, and/or fusion with the plasmalemma of secretory vesicles and chitosomes.


Assuntos
Bloqueadores dos Canais de Cálcio/farmacologia , Ionóforos/farmacologia , Phycomyces/efeitos dos fármacos , Phycomyces/crescimento & desenvolvimento , Calcimicina/farmacologia , Metabolismo dos Carboidratos , Carbonil Cianeto m-Clorofenil Hidrazona/farmacologia , Quitina/biossíntese , Hifas/efeitos dos fármacos , Hifas/ultraestrutura , Nifedipino/farmacologia , Nigericina/farmacologia , Nitrendipino/farmacologia , Phycomyces/metabolismo , Phycomyces/ultraestrutura , Transporte Proteico/efeitos dos fármacos , Rutênio Vermelho/farmacologia , Vesículas Secretórias/efeitos dos fármacos , Valinomicina/farmacologia , beta-Frutofuranosidase/metabolismo
2.
Antonie Van Leeuwenhoek ; 77(3): 209-14, 2000 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-15188885

RESUMO

Addition of cycloheximide rapidly inhibited protein synthesis in Phycomyces blakesleeanus. In contrast, chitin biosynthesis decreased with biphasic kinetics displaying a slow and a rapid decay phases. Electron microscopic studies revealed a decrease in the number of apical vesicles and chitosomes after cycloheximide addition; and no change in wall thickness. It is proposed that the slow phase of decay in chitin biosynthesis represents the exhaustion of the pool of chitosomes which transport the chitin synthase necessary to maintain apical wall growth; whereas the second one corresponds to inactivation of the enzyme, which is short lived in vivo. Data also rule out a change in the polarization of wall synthesis induced by cycloheximide, as suggested in other systems.


Assuntos
Quitina/biossíntese , Cicloeximida/farmacologia , Vesículas Citoplasmáticas/efeitos dos fármacos , Phycomyces/efeitos dos fármacos , Antifúngicos/farmacologia , Parede Celular/efeitos dos fármacos , Parede Celular/ultraestrutura , Quitinases/antagonistas & inibidores , Quitinases/metabolismo , Vesículas Citoplasmáticas/ultraestrutura , Proteínas Fúngicas/análise , Proteínas Fúngicas/efeitos dos fármacos , Hifas/crescimento & desenvolvimento , Hifas/metabolismo , Hifas/ultraestrutura , Cinética , Phycomyces/citologia , Phycomyces/metabolismo , Phycomyces/ultraestrutura , Inibidores da Síntese de Proteínas/farmacologia
3.
Antonie Van Leeuwenhoek ; 53(3): 171-81, 1987.
Artigo em Inglês | MEDLINE | ID: mdl-2959200

RESUMO

Stability of chitin synthetase in cell-free extracts from mycelial fungi was markedly improved by the presence of sucrose in the homogenization media. Breakage of mycelium in sucrose-containing buffer yielded enzyme preparations from which chitosomal chitin synthetase could be purified by a procedure involving ammonium sulfate precipitation, gel filtration and centrifugation in sucrose density gradients. Purified chitosomes catalyzed the synthesis of chitin microfibrils in vitro upon incubation with substrate and activators. Chitosomal chitin synthetase from the filamentous form of M. rouxii was similar to the enzyme from yeast cells, except for the poorer stability and diminished sensitivity to GlcNAc activation of the former.


Assuntos
Quitina Sintase/metabolismo , Glucosiltransferases/metabolismo , Mucor/enzimologia , Mucorales/enzimologia , Organoides/ultraestrutura , Phycomyces/enzimologia , Centrifugação com Gradiente de Concentração , Quitina Sintase/isolamento & purificação , Cromatografia em Gel , Microscopia Eletrônica , Mucor/ultraestrutura , Mucorales/ultraestrutura , Phycomyces/ultraestrutura , Sacarose/metabolismo
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