PubMed · 10241458
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
1978. Sprinkler systems.. https://pubmed.ncbi.nlm.nih.gov/10241458/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
Tidal fractional exhaled nitric oxide (FE(NO)) changes were investigated in healthy, unsedated infants with or without prenatal tobacco exposure. Tidal flow (V), FE(NO), and CO(2) were measured in 20 healthy, unsedated infants [age: 25-58 days, length: 56.5 +/- 2.5 (SE) cm]. NO output (VNO) was calculated (VNO = FE(NO) x V). Two approaches were used to investigate within-breath changes of FE(NO) and VNO. First, we identified phases II and III from the expiratory capnogram. Second, we divided expiration into time-based quartiles. Tidal FE(NO) (range: 14.5 +/- 1.6 to 17.6 +/- 2.1 parts/billion: quartile 4 and phase II, respectively) was not different between portions and exhibited significant negative V dependence. VNO was significantly dependent on the expiratory portion, with quartile 4 being significantly lower than the remaining expiratory portions. Infants exposed to prenatal cigarette smoke (n = 7) exhibited significantly lower FE(NO) and VNO compared with nonexposed (n = 13) infants. We conclude that tidal FE(NO) is V dependent and that VNO may be a more suitable outcome parameter in variable V conditions. Prenatal tobacco exposure resulted in a decreased FE(NO) and VNO in infants.
Hemoproteins are one of the major targets of peroxynitrite in vivo. It has been proposed that the bimolecular heme/peroxynitrite interaction results in both peroxynitrite inactivation (scavenging) and catalysis of tyrosine nitration. In this study, we used spectroscopic techniques to analyze the reaction of peroxynitrite with human methemoglobin (metHb). Although conventional differential spectroscopy did not reveal heme changes, our results suggest that, in the absence of bicarbonate, the heme in metHb reacts bimolecularly with peroxynitrite but is quickly back-reduced by the reaction products. This hypothesis is based on two indirect observations. First, metHb prevents the peroxynitrite-mediated nitration of a target dipeptide, Ala-Tyr, and second, it promotes the isomerization of peroxynitrite to nitrate. Both the scavenging and the isomerization activities of metHb were heme-dependent and inhibited by CO(2). Ferrous cytochrome c was an efficient scavenger of peroxynitrite, but in the ferric form did not show either scavenging or isomerization activities. We found no evidence of an increase in Ala-Tyr nitration with these hemoproteins. Peroxynitrite-treated metHb induced the formation of a long-lived radical assigned to tyrosine by spin-trapping studies. This radical, however, did not allow us to predict an interaction of peroxynitrite with heme. Hb was nitrated by peroxynitrite/CO(2) mainly in tyrosines beta 130, alpha 42, and alpha 140 and, to a lesser extent, alpha 24. The nitration of alpha chain tyrosines more exposed to the solvent (alpha 140 and alpha 24) was higher in CO-Hb and metHb, while nitration of alpha 42, the tyrosine nearest to the heme, was higher in oxyHb. We deduce that the heme/peroxynitrite interaction, which is inhibited in CO-Hb and metHb, affects alpha tyrosine nitration in two opposite ways, i.e., by protecting exposed residues and by promoting nitration of the residue nearest to the heme. Conversely, nitration of beta Tyr 130 was comparable in oxyHb, metHb, and CO-Hb, suggesting a mechanism involving only nitrating species formed during peroxynitrite decay.
An important adaptation to CO2-limited photosynthesis in cyanobacteria, algae and some plants was development of CO2-concentrating mechanisms (CCM). Evolution of a CCM occurred many times in flowering plants, beginning at least 15-20 million years ago, in response to atmospheric CO2 reduction, climate change, geological trends, and evolutionary diversification of species. In plants, this is achieved through a biochemical inorganic carbon pump called C4 photosynthesis, discovered 35 years ago. C4 photosynthesis is advantageous when limitations on carbon acquisition are imposed by high temperature, drought and saline conditions. It has been thought that a specialized leaf anatomy, composed of two, distinctive photosynthetic cell types (Kranz anatomy), is required for C4 photosynthesis. We provide evidence that C4 photosynthesis can function within a single photosynthetic cell in terrestrial plants. Borszczowia aralocaspica (Chenopodiaceae) has the photosynthetic features of C4 plants, yet lacks Kranz anatomy. This species accomplishes C4 photosynthesis through spatial compartmentation of photosynthetic enzymes, and by separation of two types of chloroplasts and other organelles in distinct positions within the chlorenchyma cell cytoplasm.