Starch degradation in cells is closely associated with cereal seed germination, photosynthesis in leaves, carbohydrate storage in tuber and tuberous roots, and fleshy fruit development. Based on previously reported ...Starch degradation in cells is closely associated with cereal seed germination, photosynthesis in leaves, carbohydrate storage in tuber and tuberous roots, and fleshy fruit development. Based on previously reported in vitro assays, β amylase is considered as one of the key enzymes catalyzing starch breakdown, but up to date its role in starch breakdown in living cells remains unclear because the enzyme was shown often extrachloroplastic in living cells. Recently we have shown for the first time that β_amylase is predominantly immuno_localized to plastids in living cells of developing apple fruit. But it remains to know whether this model of β_amylase compartmentation is more widespread in plant living cells. The present experiment, conducted in tuberous root of sweet potato ( Ipomea batatas Lam. cv. Xushu 18) and via immunogold electron_microscopy technique, showed that β amylase visualized by gold particles was predominantly localized in plastids especially at periphery of starch granules, but the gold particles were scarcely found in other subcellular compartments, indicating that the enzyme is subcellularly compartmented in the same zone as its starch substrates. The density of gold particles (β amylase) in plastids was increasing during growing season, but the predominantly plastid_distributed pattern of β amylase in cells was shown unchanged throughout the tuberous root development. These data prove that the enzyme is compartmented in its functional sites, and so provide evidence to support the possible widespread biological function of the enzyme in catalyzing starch breakdown in plant living cells or at least in living cells of plant storage organs.展开更多
Objective The aim of the present study is to verify the ATP-induced varied responses in isolated dorsal root ganglion （DRG） neurons of the adult rat, and investigate the modulatory effects of specific P2X receptor a...Objective The aim of the present study is to verify the ATP-induced varied responses in isolated dorsal root ganglion （DRG） neurons of the adult rat, and investigate the modulatory effects of specific P2X receptor agonist β,γ-me-ATP and protein kinase C （PKC） on P2X receptor-mediated inward current in DRG neurons. Methods Whole cell patch-clamp was employed to record the currents on acutely isolated DRG neurons in the adult rats. Results β,γ-me-ATE similar as ATE evoked 2 distinct subtypes of P2X receptor-mediated inward currents in a dose-dependent manner in DRG neurons. Activation of PKC by phorbol 12,13-dibutyrate （PDBu） significantly inhibited both subtypes of inward currents mediated by P2X receptors in a dose-dependent manner. Conclusion Activation of PKC negatively modulated the P2X receptor-mediated currents in rat DRG neurons, which may be of benefit to preventing the over-excitation of nociceptor under inflammatory or neuropathic conditions.展开更多
文摘Starch degradation in cells is closely associated with cereal seed germination, photosynthesis in leaves, carbohydrate storage in tuber and tuberous roots, and fleshy fruit development. Based on previously reported in vitro assays, β amylase is considered as one of the key enzymes catalyzing starch breakdown, but up to date its role in starch breakdown in living cells remains unclear because the enzyme was shown often extrachloroplastic in living cells. Recently we have shown for the first time that β_amylase is predominantly immuno_localized to plastids in living cells of developing apple fruit. But it remains to know whether this model of β_amylase compartmentation is more widespread in plant living cells. The present experiment, conducted in tuberous root of sweet potato ( Ipomea batatas Lam. cv. Xushu 18) and via immunogold electron_microscopy technique, showed that β amylase visualized by gold particles was predominantly localized in plastids especially at periphery of starch granules, but the gold particles were scarcely found in other subcellular compartments, indicating that the enzyme is subcellularly compartmented in the same zone as its starch substrates. The density of gold particles (β amylase) in plastids was increasing during growing season, but the predominantly plastid_distributed pattern of β amylase in cells was shown unchanged throughout the tuberous root development. These data prove that the enzyme is compartmented in its functional sites, and so provide evidence to support the possible widespread biological function of the enzyme in catalyzing starch breakdown in plant living cells or at least in living cells of plant storage organs.
基金supported by grants from the National Basic Research Development Program of China (No.2006CB500807)the National Natural Science Foundation of China (No.30600178)
文摘Objective The aim of the present study is to verify the ATP-induced varied responses in isolated dorsal root ganglion （DRG） neurons of the adult rat, and investigate the modulatory effects of specific P2X receptor agonist β,γ-me-ATP and protein kinase C （PKC） on P2X receptor-mediated inward current in DRG neurons. Methods Whole cell patch-clamp was employed to record the currents on acutely isolated DRG neurons in the adult rats. Results β,γ-me-ATE similar as ATE evoked 2 distinct subtypes of P2X receptor-mediated inward currents in a dose-dependent manner in DRG neurons. Activation of PKC by phorbol 12,13-dibutyrate （PDBu） significantly inhibited both subtypes of inward currents mediated by P2X receptors in a dose-dependent manner. Conclusion Activation of PKC negatively modulated the P2X receptor-mediated currents in rat DRG neurons, which may be of benefit to preventing the over-excitation of nociceptor under inflammatory or neuropathic conditions.
