Duration Of CO2 Exposure Research Articles

Is photosynthetic enhancement sustained through three years of elevated CO2 exposure in 175-year-old Quercus robur?

Current carbon cycle models attribute rising atmospheric CO2 as the major driver of the increased terrestrial carbon sink, but with substantial uncertainties. The photosynthetic response of trees to elevated atmospheric CO2 is a necessary step, but not the only one, for sustaining the terrestrial carbon uptake, but can vary diurnally, seasonally and with duration of CO2 exposure. Hence, we sought to quantify the photosynthetic response of the canopy-dominant species, Quercus robur, in a mature deciduous forest to elevated CO2 (eCO2) (+150 μmol mol−1 CO2) over the first 3 years of a long-term free air CO2 enrichment facility at the Birmingham Institute of Forest Research in central England (BIFoR FACE). Over 3000 measurements of leaf gas exchange and related biochemical parameters were conducted in the upper canopy to assess the diurnal and seasonal responses of photosynthesis during the 2nd and 3rd year of eCO2 exposure. Measurements of photosynthetic capacity via biochemical parameters, derived from CO2 response curves, (Vcmax and Jmax) together with leaf nitrogen concentrations from the pre-treatment year to the 3rd year of eCO2 exposure, were examined. We hypothesized an initial enhancement in light-saturated net photosynthetic rates (Asat) with CO2 enrichment of ≈37% based on theory but also expected photosynthetic capacity would fall over the duration of the study. Over the 3-year period, Asat of upper-canopy leaves was 33 ± 8% higher (mean and standard error) in trees grown in eCO2 compared with ambient CO2 (aCO2), and photosynthetic enhancement decreased with decreasing light. There were no significant effects of CO2 treatment on Vcmax or Jmax, nor leaf nitrogen. Our results suggest that mature Q. robur may exhibit a sustained, positive response to eCO2 without photosynthetic downregulation, suggesting that, with adequate nutrients, there will be sustained enhancement in C assimilated by these mature trees. Further research will be required to understand the location and role of the additionally assimilated carbon.

Amniotic membrane and placental histopathological findings after open and fetoscopic prenatal neural tube defect repair

To describe and compare placental and amniotic histology in women who underwent a fetoscopic myelomeningocele repair to those who underwent an open hysterotomy myelomeningocele repair. Also, we intended to compare findings from both prenatal repair groups to age-matched control pregnant patients. Placental and membrane histopathology from 43 prenatally repaired spina bifida cases (17 fetoscopic and 26 open) and 18 healthy controls were retrospectively assessed. Quantitative assessment of histopathology included apoptosis count and maternal and fetal underperfusion scores. Qualitative assessment included the detection of pigmented macrophages and/or signs of placental/amniotic inflammation. Associations between the duration of surgery or the duration of CO2 insufflation and quantitative histological parameters were tested. Fetoscopic surgery cases did not show significant differences in any of the studied parameters when compared against controls. No differences were detected either when compared with open repaired cases, except for lower proportion of pigmented laden macrophages in the fetoscopic group (11.8% vs 61.5%, P<0.01). No associations between the duration of surgery or the duration of CO2 exposure and any of the quantitative histological parameters were detected. These preliminary results support the lack of detrimental effects of the use of heated and humidified CO2 gas for uterine insufflation to fetal membranes and placenta.

Scanning Transmission X-Ray Microscopic Study of Carbonated Calcium Silicate Hydrate

Calcium silicate hydrate (C-S-H) is the main hydration product of portland cement. Studying the structural and chemical decomposition of C-S-H after carbonation is critical for determining the durability and serviceability of concrete. Recent studies showed that the mechanical properties are likely to be enhanced when mineral admixtures and polymers are introduced. So far, no molecular-level studies have been conducted on carbonated C-S-H material to clarify these effects. In this research, scanning transmission X-ray microscopy (STXM) is used to study C-S-H modified with two organic polymers (hexadecyltrimethyl-ammonium and polyethylene glycol 200) and exposed to different reaction times with CO2. STXM uses light in the soft X-ray region where a number of atomic resonances are present. By tuning the X-ray energies to a certain absorption edge, elemental and chemical identification was performed. The energy of the X-rays was tuned to the C K-edge, Ca L2,3-edge, and Si K-edge. Detailed images were also recorded with a lateral resolution of 30 nm. Structural, elemental, and chemical heterogeneities were spatially identified. Significant differences were found in carbon spectra in the atmospheric and 48-h continuous CO2-carbonated C-S-H samples, suggesting that carbon-containing precipitates formed within a C-S-H matrix differ depending on the extent of carbonation. Si K-edge spectra suggest increased polymerization of silicates depending on the duration of CO2 exposure. This study found that the degree of silicate polymerization and the coordination environment for carbon-containing mineral phases vary with the CO2 exposure level.

The effects of duration of CO 2 insufflation and irrigation on peritoneal microcirculation assessed by free radical scavengers and total glutathion levels during operative laparoscopy

To investigate the effects of peritoneal exposure to carbon dioxide (CO2) on peritoneal microcirculation and free radical scavenger (FRS) metabolism, and its role in potential adhesion formation after operative laparoscopy. Randomized, controlled study (Canadian Task Force classification I). University-affiliated hospital. Twenty-eight women undergoing operative laparoscopy for adnexal masses. For each patient, a 1 x 1-cm sidewall peritoneal flap was excised at the end of laparoscopy and numbered randomly. Similar flaps obtained from 24 women immediately after entering the abdomen during laparotomy served as controls. Changes in glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) levels were studied in homogenized peritoneal tissues. The duration of CO2 exposure and amount of CO2 used were correlated with levels of free radical scavengers and compared with controls. Mean CO2 exposure, amount of CO2 used, and CO2 pressure (15 mm Hg) was similar between low irrigation and irrigated laparoscopy (118.3 +/- 25 and 39.2 +/- 8.81 min and 125 +/- 20 and 44.5 +/- 6.81 min, respectively). The change in FRS levels was significantly correlated with duration and amount of CO2 exposure (r = -0.92). Levels of GSH-Px, SOD, CAT, and GSH were significantly lower in the CO2 exposure group than in controls (0.57 micro mol, 1.8 ng, 48.5 micro mol, 1.5 nmol vs 0.8 micro mol, 2.6 +/- 0.4 ng, 79 micro mol, 3.6 nmol, respectively). Exposure to CO2 has adverse effects on peritoneal microcirculation and cell-protective systems, which are proposed mechanisms in adhesion formation. Avoiding long CO2 exposure and copiously irrigating the abdominal cavity throughout surgery may lessen these effects. The potential role of the peritoneal FRS system on postoperative adhesion formation and its relation to estrogen status mandates further studies.

Acetazolamide teratogenesis: association of maternal respiratory acidosis and ectrodactyly in C57BL/6J mice.

Exposure of C57BL/6J mice to CO2 during a critical period of gestation results in predominantly right-sided, postaxial, forelimb ectrodactyly in the offspring. The incidence and severity of CO2-induced limb malformations has been shown to be dependent on the concentration of inspired CO2, the developmental age of the embryo at exposure and the duration of CO2 exposure. Offspring of acetazolamide-treated C57BL/6J mice also display this highly specific form of ectrodactyly (Green et al., '73). Since the drug has been shown to elevate tissue CO2 tension (Mithoefer and Davis, '58), the teratogenic effect of acetazolamide may be related to induction of a hypercapnic embryonic environment.