PubMed · 14081168
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
F PASSARINO. 1963-05-10. [PROGRESS IN PEDIATRICS].. https://pubmed.ncbi.nlm.nih.gov/14081168/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
Xenopus oocyte maturation is analogous to G2/M transition and characterized by germinal vesicle breakdown (GVBD), spindle formation, activation of MPF and Mos-Xp42(Mpk1) pathways. It is accompanied prior to GVBD by a transient increase in intracellular pH. We determined that a well known acidifying compound, NH(4)Cl, delayed progesterone-induced GVBD in a dose-dependent manner. GVBD(50) was delayed up to 2.3-fold by 10 mM NH(4)Cl. Cyclin B2 phosphorylation, Cdk1 Tyr15 dephosphorylation as well as p39(Mos) accumulation, Xp42(Mpk1) and p90(Rsk) phosphorylation induced by progesterone were also delayed by incubation of oocyte in NH(4)Cl. The delay induced by NH(4)Cl was prevented by injection of MOPS buffer pH 7.7. In contrast to acidifying medium, alkalyzing treatment such as Tris buffer pH 9 injections, accelerated GVBD, MPF and Xp42(Mpk1) activation, indicating that pHi changes control early steps of G2/M dynamics. When injected in an immature recipient oocyte, egg cytoplasm triggers GVBD through MPF auto-amplification, independently of protein synthesis. In these conditions, GVBD and Xp42(Mpk1) activation were delayed by high concentration of NH(4)Cl, which never prevented or delayed MPF activation. Strickingly, NH(4)Cl strongly inhibited thiophosphorylated active MAPK-induced GVBD and MPF activation. Nevertheless, Tris pH 9 did not have any effects on egg cytoplasm- or active MAPK-induced GVBD. Taken together, our results suggest that dynamic of early events driving Xp42(Mpk1) and MPF activation induced by progesterone may be negatively or positively regulated by pH(i) changes. However Xp42(Mpk1) pathway was inhibited by acidification alone. Finally, MPF auto-amplification loop was not sensitive to pH(i) changes.
The acid-base equilibria in 5,10,15,20-tetrakis(4-sulfonatophenyl)chlorin were studied in aqueous solution and compared with the respective data for the corresponding porphyrin. The reduction of the pyrrole ring in the tetrapyrrolic macrocycle noticeably influences both free base/monoprotonated and mono-/diprotonated species equilibria. In strong acidic solutions protonation of 4-sulfonatophenyl groups takes place in addition to protonation of the macrocycle core. The photophysical properties of all ionic forms are influenced by an enhanced rate of internal S1 --> S0 conversion, leading to about 50% and 90% deactivation through this channel for the free base and diprotonated species, respectively. The enhancement of the rate of the radiationless transitions is explained by an increased conformational flexibility of the chlorin macrocycle with respect to that of a porphyrin. Structural volume change measurements with laser-induced optoacoustic spectroscopy support this explanation. The contraction upon triplet state formation of the free base is about one-half of that measured for the corresponding porphyrin. This contraction should be due to intramolecular structural rearrangements of the macrocycle to adopt a minimum energy conformation in case of the chlorin. On the contrary, for the more rigid porphyrin macrocycle the interactions of the molecule with the solvent environment play a more important role. The diprotonated forms of both porphyrin and chlorin show a high radiationless S1 --> S0 conversion rate and seem to have a similar conformational flexibility. In agreement with previous calculations, the conformational flexibility of the diprotonated forms appears to be higher than that of the free base molecule.
BACKGROUND: The aim of this prospective, single-blind study was to assess the variations in the blood levels of PaO(2), PaO(2)/FiO(2), PaCO(2), and acid-base balance of patients undergoing laryngeal microsurgery under general anesthesia using small-bore endotracheal tubes. METHODS: 25 male patients were intubated with endotracheal tubes of 5.5-mm-inner diameter and fifteen female patients were intubated with endotracheal tubes of 5-mm-inner diameter during surgery. PaO(2)/FiO(2), PaO(2), PaCO(2), percentage saturation of O(2) and HCO(3), and pH levels were monitored before surgery and at 15-min intervals during laryngeal microsurgery. Respiratory function's values (dead space, peak inspiratory pressure (PIP) and dynamic compliance) were recorded every 15 min throughout laryngeal microsurgery. RESULTS: No significant differences were observed between the pre- and intra-operative values of percentage saturation of O(2), PaO(2)/FiO(2) and HCO(3) until 120th min. There was no significant difference in respiratory function's values intraoperatively. Under anesthesia, PaO(2) levels significantly increased when compared with preoperative values. Another significant increase was observed in PaCO(2) levels after the 60th min. However, compared with preoperative values, pH levels significantly decreased under anesthesia at the 105th and 120th min. CONCLUSION: Laryngeal microsurgery under general anesthesia can be performed using small-bore endotracheal tubes. This is not likely to have any adverse effects on a patient's blood gases and acid-base balance unless the operation lasts longer than 105 min.