The effect of Cuscuta chinensis extract on the rabbit penile corpus cavernosum （PCC） was evaluated in the present study. Penises obtained from healthy male New Zealand white rabbits （2.5-3.0 kg） were precontracted...The effect of Cuscuta chinensis extract on the rabbit penile corpus cavernosum （PCC） was evaluated in the present study. Penises obtained from healthy male New Zealand white rabbits （2.5-3.0 kg） were precontracted with phenylephrine （Phe, 10 pmol I^-1） and then treated with various concentrations of Cuscuta chinensis extract （1, 2, 3, 4 and 5 mg ml^-1）. The change in penile tension was recorded, and cyclic nucleotides in the PCC were measured by radioimmunoassay （RIA）. The interaction between Cuscuta chinensis and sildenafil was also evaluated. The result indicated that the PCC relaxation induced by Cuscuta chinensis extract was concentration-dependent. Pre-treatment with an nitric oxide synthase （NOS） inhibitor （No〉 nitro-L-arginine-methyl ester, L-NAME）, a guanylyl cyclase inhibitor （1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-l-one, ODQ）, or a protein kinase A inhibitor （KT 5720） did not completely inhibit the relaxation. Incubation of penile cavernous tissue with the Cuscuta chinensis extract significantly increased cyclic guanosine monophosphate （cGMP） and cyclic adenosine monophosphate （cAMP） in the PCC. Moreover, the Cuscuta chinensis extract significantly enhanced sildenafil-induced PCC relaxation. In conclusion, the Cuscuta chinensis extract exerts a relaxing effect on penile cavernous tissue in part by activating the NO-cGMP pathway, and it may improve erectile dysfunction （ED）, which does not completely respond to sildenafil citrate.展开更多
The recent discovery of the Entner-Doudoroff(ED)pathway as a third glycolytic route beside Embden-Meyerhof-Parnas(EMP)and oxidative pentose phosphate(OPP)pathway in oxygenic photoautotrophs requires a revision of thei...The recent discovery of the Entner-Doudoroff(ED)pathway as a third glycolytic route beside Embden-Meyerhof-Parnas(EMP)and oxidative pentose phosphate(OPP)pathway in oxygenic photoautotrophs requires a revision of their central carbohydrate metabolism.In this study,unexpectedly,we observed that deletion of the ED pathway alone,and even more pronounced in combination with other glycolytic routes,diminished photoautotrophic growth in continuous light in the cyanobacterium Synechocystis sp.PCC 6803.Furthermore,we found that the ED pathway is required for optimal glycogen catabolism in parallel to an operating Calvin-Benson-Bassham(CBB)cycle.It is counter-intuitive that glycolytic routes,which are a reverse to the CBB cycle and do not provide any additional biosynthetic intermediates,are important under photoautotrophic conditions.However,observations on the ability to reactivate an arrested CBB cycle revealed that they form glycolytic shunts that tap the cellular carbohydrate reservoir to replenish the cycle.Taken together,our results suggest that the classical view of the CBB cycle as an autocatalytic,completely autonomous cycle that exclusively relies on its own enzymes and C02 fixation to regenerate ribulose-1,5-bisphosphate for Rubisco is an oversimplification.We propose that in common with other known autocatalytic cycles,the CBB cycle likewise relies on anaplerotic reactions to compensate for the depletion of intermediates,particularly in transition states and under fluctuating light conditions that are common in nature.展开更多
文摘The effect of Cuscuta chinensis extract on the rabbit penile corpus cavernosum （PCC） was evaluated in the present study. Penises obtained from healthy male New Zealand white rabbits （2.5-3.0 kg） were precontracted with phenylephrine （Phe, 10 pmol I^-1） and then treated with various concentrations of Cuscuta chinensis extract （1, 2, 3, 4 and 5 mg ml^-1）. The change in penile tension was recorded, and cyclic nucleotides in the PCC were measured by radioimmunoassay （RIA）. The interaction between Cuscuta chinensis and sildenafil was also evaluated. The result indicated that the PCC relaxation induced by Cuscuta chinensis extract was concentration-dependent. Pre-treatment with an nitric oxide synthase （NOS） inhibitor （No〉 nitro-L-arginine-methyl ester, L-NAME）, a guanylyl cyclase inhibitor （1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-l-one, ODQ）, or a protein kinase A inhibitor （KT 5720） did not completely inhibit the relaxation. Incubation of penile cavernous tissue with the Cuscuta chinensis extract significantly increased cyclic guanosine monophosphate （cGMP） and cyclic adenosine monophosphate （cAMP） in the PCC. Moreover, the Cuscuta chinensis extract significantly enhanced sildenafil-induced PCC relaxation. In conclusion, the Cuscuta chinensis extract exerts a relaxing effect on penile cavernous tissue in part by activating the NO-cGMP pathway, and it may improve erectile dysfunction （ED）, which does not completely respond to sildenafil citrate.
基金financed by grants from the Deutsche Forschungsgemeinschaft(GU1522/1-1,GU1522/2-1,WI1796/3-1,and FOR 2816)the Bundesministerium fur Bildung und Forschung(FP309).
文摘The recent discovery of the Entner-Doudoroff(ED)pathway as a third glycolytic route beside Embden-Meyerhof-Parnas(EMP)and oxidative pentose phosphate(OPP)pathway in oxygenic photoautotrophs requires a revision of their central carbohydrate metabolism.In this study,unexpectedly,we observed that deletion of the ED pathway alone,and even more pronounced in combination with other glycolytic routes,diminished photoautotrophic growth in continuous light in the cyanobacterium Synechocystis sp.PCC 6803.Furthermore,we found that the ED pathway is required for optimal glycogen catabolism in parallel to an operating Calvin-Benson-Bassham(CBB)cycle.It is counter-intuitive that glycolytic routes,which are a reverse to the CBB cycle and do not provide any additional biosynthetic intermediates,are important under photoautotrophic conditions.However,observations on the ability to reactivate an arrested CBB cycle revealed that they form glycolytic shunts that tap the cellular carbohydrate reservoir to replenish the cycle.Taken together,our results suggest that the classical view of the CBB cycle as an autocatalytic,completely autonomous cycle that exclusively relies on its own enzymes and C02 fixation to regenerate ribulose-1,5-bisphosphate for Rubisco is an oversimplification.We propose that in common with other known autocatalytic cycles,the CBB cycle likewise relies on anaplerotic reactions to compensate for the depletion of intermediates,particularly in transition states and under fluctuating light conditions that are common in nature.
