Analysis of gas exchange in seedlings of Acer saccharum : integration of field and laboratory studies

In the field, photosynthesis of Acer saccharum seedlings was rarely light saturated, even though light saturation occurs at about 100 μmol quanta m -2 s -1 photosynthetic photon flux density (PPFD). PPFD during more than 75% of the daylight period was 50 μmol m -2 s -1 or less. At these low PPFD's there is a marked interaction of PPFD with the initial slope (CE) of the CO 2 response. At PPFD-saturation CE was 0.018 μmol m -2 s -1 /(μl/l). The apparent quantum efficiency (incident PPFD) at saturating CO 2 was 0.05–0.08 mol/mol. and PPFD-saturated CO 2 exchange was 6–8 μmol m -2 s -1 . The ratio of internal CO 2 concentration to external ( C i / C a ) was 0.7 to 0.8 except during sunflecks when it decreased to 0.5. The decrease in C i / C a during sunflecks was the result of the slow response of stomates to increased PPFD compared to the response of net photosynthesis. An empirical model, which included the above parameters was used to simulate the measured CO 2 exchange rate for portions of two days. Parameter values for the model were determined in experiments separate from the daily time courses being sumulated. Analysis of the field data, partly through the use of simulations, indicate that the elimination of sunflecks would reduce net carbon gain by 5–10%.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47755/1/442_2004_Article_BF00378907.pd

Continuous monitoring of the bronchial epithelial lining fluid by microdialysis

<p>Abstract</p> <p>Background</p> <p>Contents of the epithelial lining fluid (ELF) of the bronchi are of central interest in lung diseases, acute lung injury and pharmacology. The most commonly used technique broncheoalveolar lavage is invasive and may cause lung injury. Microdialysis (MD) is a method for continuous sampling of extracellular molecules in the immediate surroundings of the catheter. Urea is used as an endogenous marker of dilution in samples collected from the ELF. The aim of this study was to evaluate bronchial MD as a continuous monitor of the ELF.</p> <p>Methods</p> <p>Microdialysis catheters were introduced into the right main stem bronchus and into the right subclavian artery of five anesthetized and normoventilated pigs. The flowrate was 2 μl/min and the sampling interval was 60 minutes. Lactate and fluorescein-isothiocyanate-dextran 4 kDa (FD-4) infusions were performed to obtain two levels of steady-state concentrations in blood. Accuracy was defined as [bronchial-MD] divided by [arterial-MD] in percent. Data presented as mean ± 95 percent confidence interval.</p> <p>Results</p> <p>The accuracy of bronchial MD was calculated with and without correction by the arteriobronchial urea gradient. The arteriobronchial lactate gradient was 1.2 ± 0.1 and FD-4 gradient was 4.0 ± 1.2. Accuracy of bronchial MD with a continuous lactate infusion was mean 25.5% (range 5.7–59.6%) with a coefficient of variation (CV) of 62.6%. With correction by the arteriobronchial urea gradient accuracy was mean 79.0% (57.3–108.1%) with a CV of 17.0%.</p> <p>Conclusion</p> <p>Urea as a marker of catheter functioning enhances bronchial MD and makes it useful for monitoring substantial changes in the composition of the ELF.</p

Non-invasive measurements of exhaled NO and CO associated with methacholine responses in mice

<p>Abstract</p> <p>Background</p> <p>Nitric oxide (NO) and carbon monoxide (CO) in exhaled breath are considered obtainable biomarkers of physiologic mechanisms. Therefore, obtaining their measures simply, non-invasively, and repeatedly, is of interest, and was the purpose of the current study.</p> <p>Methods</p> <p>Expired NO (E_NO) and CO (E_CO) were measured non-invasively using a gas micro-analyzer on several strains of mice (C57Bl6, IL-10^-/-, A/J, MKK3^-/-, JNK1^-/-, NOS-2^-/-and NOS-3^-/-) with and without allergic airway inflammation (AI) induced by ovalbumin systemic sensitization and aerosol challenge, compared using independent-sample t-tests between groups, and repeated measures analysis of variance (ANOVA) within groups over time of inflammation induction. E_NOand E_COwere also measured in C57Bl6 and IL-10-/- mice, ages 8–58 weeks old, the relationship of which was determined by regression analysis. S-methionyl-L-thiocitrulline (SMTC), and tin protoporphyrin (SnPP) were used to inhibit neuronal/constitutive NOS-1 and heme-oxygenase, respectively, and alter NO and CO production, respectively, as assessed by paired t-tests. Methacholine-associated airway responses (AR) were measured by the enhanced pause method, with comparisons by repeated measures ANOVA and post-hoc testing.</p> <p>Results</p> <p>E_NOwas significantly elevated in naïve IL-10^-/-(9–14 ppb) and NOS-2^-/-(16 ppb) mice as compared to others (average: 5–8 ppb), whereas E_COwas significantly higher in naïve A/J, NOS-3^-/-(3–4 ppm), and MKK3^-/-(4–5 ppm) mice, as compared to others (average: 2.5 ppm). As compared to C57Bl6 mice, AR of IL-10^-/-, JNK1^-/-, NOS-2^-/-, and NOS-3^-/-mice were decreased, whereas they were greater for A/J and MKK3^-/-mice. SMTC significantly decreased E_NOby ~30%, but did not change AR in NOS-2^-/-mice. SnPP reduced E_COin C57Bl6 and IL-10^-/-mice, and increased AR in NOS-2^-/-mice. E_NOdecreased as a function of age in IL-10^-/-mice, remaining unchanged in C57Bl6 mice.</p> <p>Conclusion</p> <p>These results are consistent with the ideas that: 1) E_NOis associated with mouse strain and knockout differences in NO production and AR, 2) alterations of E_NOand E_COcan be measured non-invasively with induction of allergic AI or inhibition of key gas-producing enzymes, and 3) alterations in AR may be dependent on the relative balance of NO and CO in the airway.</p

A Cohort Study of Serum Bilirubin Levels and Incident Non-Alcoholic Fatty Liver Disease in Middle Aged Korean Workers

BACKGROUND: Serum bilirubin may have potent antioxidant and cytoprotective effects. Serum bilirubin levels are inversely associated with several cardiovascular and metabolic endpoints, but their association with nonalcoholic fatty liver disease (NAFLD) has not been investigated except for a single cross-sectional study in a pediatric population. We assessed the prospective association between serum bilirubin concentrations (total, direct, and indirect) and the risk for NAFLD. METHODS AND FINDINGS: We performed a cohort study in 5,900 Korean men, 30 to 59 years of age, with no evidence of liver disease and no major risk factors for liver disease at baseline. Study participants were followed in annual or biennial health examinations between 2002 and 2009. The presence of fatty liver was determined at each visit by ultrasonography. We observed 1,938 incident cases of NAFLD during 28,101.8 person-years of follow-up. Increasing levels of serum direct bilirubin were progressively associated with a decreasing incidence of NAFLD. In age-adjusted models, the hazard ratio for NAFLD comparing the highest to the lowest quartile of serum direct bilirubin levels was 0.61 (95% CI 0.54-0.68). The association persisted after adjusting for multiple metabolic parameters (hazard ratio comparing the highest to the lowest quartile 0.86, 95% CI 0.76-0.98; P trend = 0.039). Neither serum total nor indirect bilirubin levels were significantly associated with the incidence of NAFLD. CONCLUSIONS: In this large prospective study, higher serum direct bilirubin levels were significantly associated with a lower risk of developing NAFLD, even adjusting for a variety of metabolic parameters. Further research is needed to elucidate the mechanisms underlying this association and to establish the role of serum direct bilirubin as a marker for NAFLD risk

Functional Induction of the Cystine-Glutamate Exchanger System Xc- Activity in SH-SY5Y Cells by Unconjugated Bilirubin

We have previously reported that exposure of SH-SY5Y neuroblastoma cells to unconjugated bilirubin (UCB) resulted in a marked up-regulation of the mRNA encoding for the Na+ -independent cystine∶glutamate exchanger System Xc− (SLC7A11 and SLC3A2 genes). In this study we demonstrate that SH-SY5Y cells treated with UCB showed a higher cystine uptake due to a significant and specific increase in the activity of System Xc−, without the contribution of the others two cystine transporters (XAG− and GGT) reported in neurons. The total intracellular glutathione content was 2 folds higher in the cells exposed to bilirubin as compared to controls, suggesting that the internalized cystine is used for gluthathione synthesis. Interestingly, these cells were significantly less sensitive to an oxidative insult induced by hydrogen peroxide. If System Xc− is silenced the protection is lost. In conclusion, these results suggest that bilirubin can modulate the gluthathione levels in neuroblastoma cells through the induction of the System Xc−, and this renders the cell less prone to oxidative damage

Garlic Accelerates Red Blood Cell Turnover and Splenic Erythropoietic Gene Expression in Mice: Evidence for Erythropoietin-Independent Erythropoiesis

Garlic (Allium sativum) has been valued in many cultures both for its health effects and as a culinary flavor enhancer. Garlic's chemical complexity is widely thought to be the source of its many health benefits, which include, but are not limited to, anti-platelet, procirculatory, anti-inflammatory, anti-apoptotic, neuro-protective, and anti-cancer effects. While a growing body of scientific evidence strongly upholds the herb's broad and potent capacity to influence health, the common mechanisms underlying these diverse effects remain disjointed and relatively poorly understood. We adopted a phenotype-driven approach to investigate the effects of garlic in a mouse model. We examined RBC indices and morphologies, spleen histochemistry, RBC half-lives and gene expression profiles, followed up by qPCR and immunoblot validation. The RBCs of garlic-fed mice register shorter half-lives than the control. But they have normal blood chemistry and RBC indices. Their spleens manifest increased heme oxygenase 1, higher levels of iron and bilirubin, and presumably higher CO, a pleiotropic gasotransmitter. Heat shock genes and those critical for erythropoiesis are elevated in spleens but not in bone marrow. The garlic-fed mice have lower plasma erythropoietin than the controls, however. Chronic exposure to CO of mice on garlic-free diet was sufficient to cause increased RBC indices but again with a lower plasma erythropoietin level than air-treated controls. Furthermore, dietary garlic supplementation and CO treatment showed additive effects on reducing plasma erythropoietin levels in mice. Thus, garlic consumption not only causes increased energy demand from the faster RBC turnover but also increases the production of CO, which in turn stimulates splenic erythropoiesis by an erythropoietin-independent mechanism, thus completing the sequence of feedback regulation for RBC metabolism. Being a pleiotropic gasotransmitter, CO may be a second messenger for garlic's other physiological effects

A Novel, “Double-Clamp” Binding Mode for Human Heme Oxygenase-1 Inhibition

The development of heme oxygenase (HO) inhibitors is critical in dissecting and understanding the HO system and for potential therapeutic applications. We have established a program to design and optimize HO inhibitors using structure-activity relationships in conjunction with X-ray crystallographic analyses. One of our previous complex crystal structures revealed a putative secondary hydrophobic binding pocket which could be exploited for a new design strategy by introducing a functional group that would fit into this potential site. To test this hypothesis and gain further insights into the structural basis of inhibitor binding, we have synthesized and characterized 1-(1H-imidazol-1-yl)-4,4-diphenyl-2-butanone (QC-308). Using a carbon monoxide (CO) formation assay on rat spleen microsomes, the compound was found to be ∼15 times more potent (IC50 = 0.27±0.07 µM) than its monophenyl analogue, which is already a potent compound in its own right (QC-65; IC50 = 4.0±1.8 µM). The crystal structure of hHO-1 with QC-308 revealed that the second phenyl group in the western region of the compound is indeed accommodated by a definitive secondary proximal hydrophobic pocket. Thus, the two phenyl moieties are each stabilized by distinct hydrophobic pockets. This “double-clamp” binding offers additional inhibitor stabilization and provides a new route for improvement of human heme oxygenase inhibitors

Heme oxygenase-1 and carbon monoxide in pulmonary medicine

Heme oxygenase-1 (HO-1), an inducible stress protein, confers cytoprotection against oxidative stress in vitro and in vivo. In addition to its physiological role in heme degradation, HO-1 may influence a number of cellular processes, including growth, inflammation, and apoptosis. By virtue of anti-inflammatory effects, HO-1 limits tissue damage in response to proinflammatory stimuli and prevents allograft rejection after transplantation. The transcriptional upregulation of HO-1 responds to many agents, such as hypoxia, bacterial lipopolysaccharide, and reactive oxygen/nitrogen species. HO-1 and its constitutively expressed isozyme, heme oxygenase-2, catalyze the rate-limiting step in the conversion of heme to its metabolites, bilirubin IXα, ferrous iron, and carbon monoxide (CO). The mechanisms by which HO-1 provides protection most likely involve its enzymatic reaction products. Remarkably, administration of CO at low concentrations can substitute for HO-1 with respect to anti-inflammatory and anti-apoptotic effects, suggesting a role for CO as a key mediator of HO-1 function. Chronic, low-level, exogenous exposure to CO from cigarette smoking contributes to the importance of CO in pulmonary medicine. The implications of the HO-1/CO system in pulmonary diseases will be discussed in this review, with an emphasis on inflammatory states