Outcomes of children with constipation and autism spectrum disorder treated with antegrade continence enemas

BACKGROUND

Treatment of functional constipation (FC) in children with autism spectrum disorder (ASD) is challenging due to sensory and behavioral issues. We aimed to understand whether antegrade continence enemas (ACEs) are successful in the treatment of FC in children with ASD.

METHODS

A single-institution retrospective review was performed in children diagnosed with ASD and FC who underwent appendicostomy or cecostomy placement from 2007 to 2019. Descriptive statistics regarding soiling and complications were calculated.

RESULTS

There were 33 patients included, with a median age of 9.7 years at the time of ACE initiation. The average intelligence quotient was 63.6 (SD = 18.0, n = 12), the average behavioral adaptive score was 59.9 (SD = 11.1, n = 13), and the average total Child Behavioral Checklist score was 72.5 (SD = 7.1, n = 10). Soiling rates were significantly lower following ACE initiation (42.3% vs. 14.8%, p = 0.04). Behavioral issues only prevented 1 patient (3.0%) from proper ACE use. Eleven patients (36.6%) were able to transition to laxatives. There were significant improvements in patient-reported outcomes measures and quality of life.

CONCLUSION

Placement of an appendicostomy or cecostomy for management of FC in children with severe ASD was successful in treating constipation and improving quality of life.

Rates of Hirschsprung-Associated Enterocolitis Decrease With Increasing Child Opportunity Index

BACKGROUND

Hirschsprung-associated enterocolitis (HAEC) is the most common cause of morbidity and mortality in patients with Hirschsprung disease (HD). There is a correlation between social determinants of health (SDOH) and outcomes in children with HD. The Child Opportunity Index (COI) is a publicly available dataset that stratifies patients by address into levels of opportunity. We aimed to understand if a relationship exists between COI and HAEC.

METHODS

A single-institution, IRB-approved, retrospective cohort study was performed of children with HD. Census tract information was used to obtain COI scores, which were stratified into categories (very low, low, medium, high, very high). Subgroups with and without history of HAEC were compared.

RESULTS

The cohort had 100 patients, of which 93 had a COI score. There were 27 patients (29.0%) with HAEC. There were no differences in demographics or clinical factors, including length of aganglionic colon, operative approach, and age at pull-through. As child opportunity score increased from very low to very high, there was a statistically significant decrease in the incidence of HAEC (p = 0.04).

CONCLUSION

We demonstrate a significant association between increasing opportunity and decreasing incidence of HAEC. This suggests an opportunity for targeted intervention in populations with low opportunity.

LEVEL OF EVIDENCE

III.

IRB NUMBER

IRB14-00232.

Social Determinants of Health are Associated with Failed Bowel Management for Children with Anorectal Malformations

Introduction Children with anorectal malformations (ARMs) benefit from bowel management programs (BMPs) to manage constipation or fecal incontinence. We aimed to understand the role of social determinants of health (SDOH) in outcomes following BMPs in this population. Materials and Methods A single-institution, IRB-approved, retrospective review was performed in children with ARM who underwent BMP from 2014-2021. Clinical, surgical, and SDOH data were collected. Children were stratified as clean or not clean per Rome IV criteria at the completion of BMP. Descriptive statistics were computed. Categorical variables were analyzed via Fisher's exact tests and continuous variables with Mood's median tests. Results There were 239 patients identified who underwent BMP, with median age of 6.62 years [IQR: 4.78 - 9.83]. Of these, 81 (34%) were not clean after completing BMP. Children with prior history of antegrade enema procedures had more failure. Children who held public insurance, lived within driving distance, had unmarried parents, lived with extended family, and lacked formal support systems had a significant association with BMP failure (p<0.05 for all). Type of ARM, age at repair, type of repair, age at BMP, and type of BMP regimen were not significantly associated with failure. Conclusions There is a significant correlation of failure of BMPs with several SDOH elements in patients with ARM. Attention to SDOH may help identify high-risk patients in whom additional care may lead improved outcomes following BMP.

Validation for Abbreviated Hospital Stay in Pediatric Patients with Solid Organ Injury

BACKGROUND

In 2000, the American Pediatric Surgical Association (APSA) published guidelines for the management of pediatric solid organ injury, recommending a hospital length of stay (LOS) of grade of injury plus 1 day. Since the publication of these guidelines, several studies have suggested that it is safe to discharge patients sooner based upon hemodynamic and clinical factors. The results of several of these studies have been confounded by the existence of other injuries. The aim of this study was to examine LOS and outcomes in children with strictly isolated solid organ injuries.

MATERIALS AND METHODS

This is a 12-year retrospective review of pediatric patients with isolated trauma to the kidney, liver, or spleen to determine LOS. Patients were excluded for associated intracranial, neurologic, orthopedic, or pulmonary injuries which would impact length of stay. Documented hemodynamic parameters were reviewed as determinants of patient stability.

RESULTS

A total of 156 patients were included in the study. The projected average LOS for all patients based on the 2000 APSA guidelines would have been 3.71 ± 0.98 days. The actual average LOS for all patients 2.85 ± 3.32 days. Need for operation, ICU stay, and transfusion all contributed to increased LOS. The number of episodes of abnormal vitals positively correlated with increased LOS.

DISCUSSION

This study validates that management of isolated solid organ injuries based upon hemodynamic parameters and clinical status is safe and decreases hospital length of stay. Consistently normal vital signs indicate these children can be safely discharged sooner.

Questioning Prophylactic Antibiotic Use for Pyloromyotomy: Analysis of the Pediatric Health Information System database

BACKGROUND

Pyloromyotomy has a low rate of wound complications, yet antibiotic prophylaxis is still given. The Pediatric Health Information System (PHIS) database was queried to determine whether prophylactic antibiotics decreased wound complications.

METHODS

Records for infants with pyloric stenosis between 2016 and 2021 were extracted from the PHIS database and analyzed for demographics, comorbid conditions, and complications within 30 days of pyloromyotomy. Logistic regression was used to evaluate the effect of antibiotic prophylaxis on complications.

RESULTS

Among 14,247 infants who underwent pyloromyotomy, 29.5% had antibiotic prophylaxis. These patients were more likely to have been admitted to the NICU and have chronic conditions and prematurity (p < 0.01). Antibiotic utilization varied among hospitals from 2.3 to 58.5%. Complication rates among those who received antibiotics was 1.64% versus 1.62% for those who did not. The odds for developing complications in those who received prophylaxis compared to those who did not was 1.10, (0.73, 1.41, 95%, p = 0.93) suggesting there is no effect of antibiotics on complication rates.

CONCLUSIONS

There was a wide variation among hospitals in the usage of prophylactic antibiotics for pyloromyotomy. There was no difference in complication rates whether or not patients received antibiotics. These results suggest antibiotic prophylaxis is unnecessary for pyloromyotomy.

LEVEL OF EVIDENCE

III.

Pediatric Biliary Dyskinesia: Evaluating Predictive Factors for Successful Treatment of Biliary Dyskinesia with Laparoscopic Cholecystectomy

Biliary dyskinesia (BD) is a motility disorder of the gallbladder that can result in right upper quadrant (RUQ) pain, nausea, vomiting, and diarrhea. Cholecystectomy is considered the standard of care for BD. Up to 23 per cent of pediatric patients who undergo surgery for BD have persistent symptoms postoperatively. We performed a retrospective review to identify preoperative factors significantly associated with symptom resolution after cholecystectomy. We retrospectively reviewed pediatric patients aged 10–17 years diagnosed with BD who underwent cholecystectomy between 2006 and 2016. Patients were divided into two groups based on postoperative symptom resolution. Chi-squared and student t tests were used to compare patient groups. Two hundred and thirty-six patients were included in the study. The most common preoperative symptoms included RUQ pain (80.1%), nausea (54.2%), postprandial pain (44.5%), vomiting (32.6%), and epigastric pain (19.9%). The rate of postoperative symptom resolution was 68.6 per cent. Comparative analysis showed patients who presented with RUQ pain, nausea, postprandial pain, or constipation experienced significantly higher rates of symptom resolution postoperatively. In addition, patients with ejection fraction <35 per cent or pain reproducible with cholecystokinin were found to have significantly higher rates of symptom resolution as well. To date, it remains difficult to predict successful outcomes for pediatric patients undergoing cholecystectomy for BD. In our study, patient demographics and duration of symptoms did not affect postoperative outcomes. Pediatric patients who presented with RUQ pain, nausea, postprandial pain, constipation, an ejection fraction of <35 per cent on hepatobiliary iminodiacetic acid, or pain reproducible with cholecystokinin injection, were found to have significantly higher rates of symptom resolution.

Pediatric Biliary Dyskinesia: Evaluating Predictive Factors for Successful Treatment of Biliary Dyskinesia with Laparoscopic Cholecystectomy

Biliary dyskinesia (BD) is a motility disorder of the gallbladder that can result in right upper quadrant (RUQ) pain, nausea, vomiting, and diarrhea. Cholecystectomy is considered the standard of care for BD. Up to 23 per cent of pediatric patients who undergo surgery for BD have persistent symptoms postoperatively. We performed a retrospective review to identify preoperative factors significantly associated with symptom resolution after cholecystectomy. We retrospectively reviewed pediatric patients aged 10-17 years diagnosed with BD who underwent cholecystectomy between 2006 and 2016. Patients were divided into two groups based on postoperative symptom resolution. Chi-squared and student t tests were used to compare patient groups. Two hundred and thirty-six patients were included in the study. The most common preoperative symptoms included RUQ pain (80.1%), nausea (54.2%), postprandial pain (44.5%), vomiting (32.6%), and epigastric pain (19.9%). The rate of postoperative symptom resolution was 68.6 per cent. Comparative analysis showed patients who presented with RUQ pain, nausea, postprandial pain, or constipation experienced significantly higher rates of symptom resolution postoperatively. In addition, patients with ejection fraction <35 per cent or pain reproducible with cholecystokinin were found to have significantly higher rates of symptom resolution as well. To date, it remains difficult to predict successful outcomes for pediatric patients undergoing cholecystectomy for BD. In our study, patient demographics and duration of symptoms did not affect postoperative outcomes. Pediatric patients who presented with RUQ pain, nausea, postprandial pain, constipation, an ejection fraction of <35 per cent on hepatobiliary iminodiacetic acid, or pain reproducible with cholecystokinin injection, were found to have significantly higher rates of symptom resolution.

European and Mediterranean hydroclimate responses to tropical volcanic forcing over the last millennium

Volcanic eruptions have global climate impacts, but their effect on the hydrologic cycle is poorly understood. We use a modified version of superposed epoch analysis, an eruption year list collated from multiple datasets, and seasonal paleoclimate reconstructions (soil moisture, precipitation, geopotential heights, and temperature) to investigate volcanic forcing of spring and summer hydroclimate over Europe and the Mediterranean over the last millennium. In the western Mediterranean, wet conditions occur in the eruption year and the following 3 years. Conversely, northwestern Europe and the British Isles experience dry conditions in response to volcanic eruptions, with the largest moisture deficits in post-eruption years 2 and 3. The precipitation response occurs primarily in late spring and early summer (April-July), a pattern that strongly resembles the negative phase of the East Atlantic Pattern. Modulated by this mode of climate variability, eruptions force significant, widespread, and heterogeneous hydroclimate responses across Europe and the Mediterranean.

Light saturated RuBP oxygenation by Rubisco is a robust predictor of light inhibition of respiration in Triticum aestivum L

Plant respiratory metabolism is complicated by the fact that the rate of non-photorespiratory mitochondrial CO2 release in the light (R light) may be lower than the rate of leaf respiration in the dark (R dark). A body of work on this topic implies a linkage between light inhibition of respiration and photorespiration, although the direction of effect and underlying mechanisms remain uncertain. In this study we used a variety of short- and long-term environmental manipulations to explicitly manipulate the rate of photorespiration (νo) and quantify the effect on the inhibition of mitochondrial respiration in the light (R light:R dark). We address the following three questions: (i) will the R light:R dark ratio increase or decrease with high CO2 or low O2 and at low temperatures; (ii) does νo correlate with R light:R dark, and if so, in what way; (iii) will suppression of respiration by light (the 'Kok effect') be seen to the same extent in Zea mays, a C4 plant, and in Triticum aestivum, a C3 plant? We found that Rlight :Rdark decreased under conditions that suppressed νo in wheat, and this resulted in a positive relationship between R light:R dark and νo. Inhibition of respiration by light in C4 maize did not respond to environmental treatment, and the fixed R light:R dark (0.46-0.72) was consistent with the wheat response, assuming a νo approaching zero. The most likely mechanism to explain this finding is that R light increases (or the inhibition of respiration by light decreases) when there is an increase in photorespiration and thus an increase in the demand for TCA cycle substrates associated with the recovery of photorespiratory cycle intermediates in the peroxisome. This work is significant because it combines a comparison of C3 and C4 metabolism with a range of environmental treatments to independently suppress νo.

Demonstration of ignition radiation temperatures in indirect-drive inertial confinement fusion hohlraums

We demonstrate the hohlraum radiation temperature and symmetry required for ignition-scale inertial confinement fusion capsule implosions. Cryogenic gas-filled hohlraums with 2.2 mm-diameter capsules are heated with unprecedented laser energies of 1.2 MJ delivered by 192 ultraviolet laser beams on the National Ignition Facility. Laser backscatter measurements show that these hohlraums absorb 87% to 91% of the incident laser power resulting in peak radiation temperatures of T(RAD)=300 eV and a symmetric implosion to a 100 μm diameter hot core.

Changes in composition, structure and aboveground biomass over seventy-six years (1930-2006) in the Black Rock Forest, Hudson Highlands, southeastern New York State

We sought to quantify changes in tree species composition, forest structure and aboveground forest biomass (AGB) over 76 years (1930-2006) in the deciduous Black Rock Forest in southeastern New York, USA. We used data from periodic forest inventories, published floras and a set of eight long-term plots, along with species-specific allometric equations to estimate AGB and carbon content. Between the early 1930s and 2000, three species were extirpated from the forest (American elm (Ulmus americana L.), paper birch (Betula papyrifera Marsh.) and black spruce (Picea mariana (nigra) (Mill.) BSP)) and seven species invaded the forest (non-natives tree-of-heaven (Ailanthus altissima (Mill.) Swingle) and white poplar (Populus alba L.) and native, generally southerly distributed, southern catalpa (Catalpa bignonioides Walt.), cockspur hawthorn (Crataegus crus-galli L.), red mulberry (Morus rubra L.), eastern cottonwood (Populus deltoides Bartr.) and slippery elm (Ulmus rubra Muhl.)). Forest canopy was dominated by red oak and chestnut oak, but the understory tree community changed substantially from mixed oak-maple to red maple-black birch. Density decreased from an average of 1500 to 735 trees ha(-1), whereas basal area doubled from less than 15 m(2) ha(-1) to almost 30 m(2) ha(-1) by 2000. Forest-wide mean AGB from inventory data increased from about 71 Mg ha(-1) in 1930 to about 145 Mg ha(-1) in 1985, and mean AGB on the long-term plots increased from 75 Mg ha(-1) in 1936 to 218 Mg ha(-1) in 1998. Over 76 years, red oak (Quercus rubra L.) canopy trees stored carbon at about twice the rate of similar-sized canopy trees of other species. However, there has been a significant loss of live tree biomass as a result of canopy tree mortality since 1999. Important constraints on long-term biomass increment have included insect outbreaks and droughts.

Construction cost and invasive potential: comparing Lythrum salicaria (Lythraceae) with co-occurring native species along pond banks

Lythrum salicaria (purple loosestrife) is a nonindigenous invasive species characterized by prolific growth and abundance in marshy and riparian habitats across North America. Given its invasive success, we hypothesized this species may require less energy and/or use energy more efficiently for biomass construction than co-occurring noninvasive plant species. We measured leaf construction cost (CC), leaf mass per unit area (LMA), and leaf organic nitrogen and carbon content of L. salicaria and the five most abundant co-occurring species, Parthenocissus quinquefolia, Erigeron philadelphicus, Asclepias syriaca, Spiraea latifolia, and Solidago graminifolia, along dammed ponds in the Black Rock Forest, Cornwall, New York, USA. Lythrum salicaria, which was highly abundant (2.52 individuals/m(2)), exhibited significantly lower area-based leaf CC (44.47 ± 4.24 g glucose/m(2) leaf) than relatively less abundant species, suggesting energetics may influence its invasive success. Conversely, least abundant Solidago graminifolia (0.67 individuals/m(2)) exhibited the significantly highest leaf CC per unit leaf area (141.87 ± 39.21 g glucose/m(2) leaf). Overall, a negative correlation between species abundance and area-based leaf CC (r(2) = 0.73) indicated low energy requirements and/or high energy efficiency may influence relative abundance in the plant species studied. As it correlates with species abundance in this study, CC may be a useful tool for evaluating invasive potential.

Endothelium-mediated relaxation of porcine collateral-dependent arterioles is improved by exercise training

BACKGROUND

Endothelium-dependent modulation of coronary tone is impaired in the collateral-dependent coronary microcirculation. We used a porcine model of chronic coronary occlusion and collateral development to evaluate the hypothesis that exercise training enhances endothelium-mediated relaxation and increases endothelial nitric oxide synthase (ecNOS) mRNA levels of collateral-dependent microvasculature.

METHODS AND RESULTS

Adult female miniature swine were subjected to chronic, progressive ameroid occlusion of the proximal left circumflex coronary artery (LCx); after 2 months, animals were randomly exposed to 16-week exercise-training (EX group; treadmill running) or sedentary (SED group; cage confinement) protocols. After completion of EX or SED programs, coronary arterioles ( approximately 100 microm in diameter) were isolated from collateral-dependent LCx (distal to occlusion) and nonoccluded left anterior descending coronary artery (LAD) regions of each heart. Arterioles were studied by in vitro videomicroscopy or frozen for ecNOS mRNA analysis (RT-PCR techniques). Relaxation to the endothelium-dependent vasodilator bradykinin was decreased (P<0.05) in arterioles isolated from collateral-dependent LCx versus nonoccluded LAD regions of SED animals. Bradykinin-mediated relaxation, however, was not different in LCx versus LAD arterioles isolated from EX animals. Nitroprusside-induced relaxation was unaffected by either chronic occlusion or exercise. Importantly, ecNOS mRNA expression was significantly decreased in arterioles isolated from LCx versus LAD regions of SED animals. After training, ecNOS mRNA expression was not different between LAD and LCx arterioles.

CONCLUSIONS

These data indicate that exercise training enhances bradykinin-mediated relaxation of collateral-dependent LCx arterioles isolated after chronic coronary occlusion, most likely because of effects on ecNOS mRNA expression and increased production of NO.

Canopy position and needle age affect photosynthetic response in field-grown Pinus radiata after five years of exposure to elevated carbon dioxide partial pressure

Photosynthesis of tree seedlings is generally enhanced during short-term exposure to elevated atmospheric CO2 partial pressure, but longer-term studies often indicate some degree of photosynthetic adjustment. We present physiological and biochemical evidence to explain observed long-term photosynthetic responses to elevated CO2 partial pressure as influenced by needle age and canopy position. We grew Pinus radiata D. Don. trees in open-top chambers for 5 years in sandy soil at ambient (36 Pa) and elevated (65 Pa) CO2 partial pressures. The trees were well watered and exposed to natural light and ambient temperature. In the fourth year of CO2 exposure (fall 1997), when foliage growth had ceased for the year, photosynthetic down-regulation was observed in 1-year-old needles, but not in current-year needles, suggesting a reduction in carbohydrate sink strength as a result of increasing needle age (Turnbull et al. 1998). In 5-year-old trees (spring 1997), when foliage expansion was occurring, photosynthetic down-regulation was not observed, reflecting significantly large sinks for carbohydrates throughout the tree. Net photosynthesis was stimulated by 79% in trees growing in elevated CO2 partial pressure, but there was no significant effect on photosynthetic capacity or Rubisco activity and concentration. Current-year needles were more responsive to elevated CO2 partial pressure than 1-year-old needles, exhibiting larger relative increases in net photosynthesis to elevated CO2 partial pressure (98 versus 64%). Lower canopy and upper canopy leaves exhibited similar relative responses to growth in elevated CO2 partial pressure. However, needles in the upper canopy exhibited higher net photosynthesis, photosynthetic capacity, and Rubisco activity and concentration than needles in the lower canopy. Given that the ratio of mature to juvenile foliage mass in the canopy will increase as trees mature, we suggest that trees may become less responsive to elevated CO2 partial pressure with increasing age. We conclude that tree response to elevated CO2 partial pressure is based primarily on sink strength and not on the duration of exposure.

Responses of leaf respiration to temperature and leaf characteristics in three deciduous tree species vary with site water availability

We measured responses of leaf respiration to temperature and leaf characteristics in three deciduous tree species (Quercus rubra L., Quercus prinus L. and Acer rubrum L.) at two sites differing in water availability within a single catchment in the Black Rock Forest, New York. The response of respiration to temperature differed significantly among the species. Acer rubrum displayed the smallest increase in respiration with increasing temperature. Corresponding Q(10) values ranged from 1.5 in A. rubrum to 2.1 in Q. prinus. Dark respiration at ambient air temperatures, expressed on a leaf area basis (Rarea), did not differ significantly between species, but it was significantly lower (P < 0.01) in trees at the wetter (lower) site than at the drier (upper) site (Q. rubra: 0.8 versus 1.1 micromol m(-2) s(-1); Q. prinus: 0.95 versus 1.2 micromol m(-2) s(-1)). In contrast, when expressed on a leaf mass basis (R(mass)), respiration rates were significantly higher (P < 0.01) in A. rubrum (12.5-14.6 micromol CO(2) kg(-1) s(-1)) than in Q. rubra (8.6-9.9 micromol CO(2) kg(-1) s(-1)) and Q. prinus (9.2-10.6 micromol CO(2) kg(-1) s(-1)) at both the lower and upper sites. Respiration on a nitrogen basis (R(N)) displayed a similar response to R(mass). The consistency in R(mass) and R(N) between sites indicates a strong coupling between factors influencing respiration and those affecting leaf characteristics. Finally, the relationships between dark respiration and A(max) differed between sites. Trees at the upper site had higher rates of leaf respiration and lower A(max) than trees at the lower site. This shift in the balance of carbon gain and loss clearly limits carbon acquisition by trees at sites of low water availability, particularly in the case of A. rubrum.

Effects of elevated atmospheric CO2 concentration on leaf dark respiration of Xanthium strumarium in light and in darkness

Leaf dark respiration (R) is an important component of plant carbon balance, but the effects of rising atmospheric CO(2) on leaf R during illumination are largely unknown. We studied the effects of elevated CO(2) on leaf R in light (R(L)) and in darkness (R(D)) in Xanthium strumarium at different developmental stages. Leaf R(L) was estimated by using the Kok method, whereas leaf R(D) was measured as the rate of CO(2) efflux at zero light. Leaf R(L) and R(D) were significantly higher at elevated than at ambient CO(2) throughout the growing period. Elevated CO(2) increased the ratio of leaf R(L) to net photosynthesis at saturated light (A(max)) when plants were young and also after flowering, but the ratio of leaf R(D) to A(max) was unaffected by CO(2) levels. Leaf R(N) was significantly higher at the beginning but significantly lower at the end of the growing period in elevated CO(2)-grown plants. The ratio of leaf R(L) to R(D) was used to estimate the effect of light on leaf R during the day. We found that light inhibited leaf R at both CO(2) concentrations but to a lesser degree for elevated (17-24%) than for ambient (29-35%) CO(2)-grown plants, presumably because elevated CO(2)-grown plants had a higher demand for energy and carbon skeletons than ambient CO(2)-grown plants in light. Our results suggest that using the CO(2) efflux rate, determined by shading leaves during the day, as a measure for leaf R is likely to underestimate carbon loss from elevated CO(2)-grown plants.

Plant growth in elevated CO2 alters mitochondrial number and chloroplast fine structure

With increasing interest in the effects of elevated atmospheric CO(2) on plant growth and the global carbon balance, there is a need for greater understanding of how plants respond to variations in atmospheric partial pressure of CO(2). Our research shows that elevated CO(2) produces significant fine structural changes in major cellular organelles that appear to be an important component of the metabolic responses of plants to this global change. Nine species (representing seven plant families) in several experimental facilities with different CO(2)-dosing technologies were examined. Growth in elevated CO(2) increased numbers of mitochondria per unit cell area by 1.3-2.4 times the number in control plants grown in lower CO(2) and produced a statistically significant increase in the amount of chloroplast stroma (nonappressed) thylakoid membranes compared with those in lower CO(2) treatments. There was no observable change in size of the mitochondria. However, in contrast to the CO(2) effect on mitochondrial number, elevated CO(2) promoted a decrease in the rate of mass-based dark respiration. These changes may reflect a major shift in plant metabolism and energy balance that may help to explain enhanced plant productivity in response to elevated atmospheric CO(2) concentrations.

Exercise training improves endothelium-mediated vasorelaxation after chronic coronary occlusion

The present study evaluated combined effects of chronic coronary occlusion and exercise training on endothelial function. Gradual occlusion was produced by placement of an ameroid constrictor around the proximal left circumflex (LCX) coronary artery of female swine. Two months after placement of the ameroid, animals were restricted to their pens or exercise trained for 16 wk. Epicardial arteries (>500 microm ID) were isolated from the collateral-dependent LCX coronary artery distal to the occlusion and the nonoccluded left anterior descending (LAD) coronary artery. Bradykinin- and ADP-mediated relaxation of LCX and LAD coronary arteries was enhanced after exercise training. Inhibition of nitric oxide synthase with N(G)-nitro-L-arginine methyl ester decreased bradykinin- and ADP-mediated relaxation in LCX and LAD myocardial regions. Importantly, combined inhibition of effects of endothelium-derived hyperpolarizing factor with increased extracellular K(+) (20-30 mM) and nitric oxide synthase completely abolished coronary LAD and LCX relaxation to bradykinin. Our data indicate that exercise training improves endothelium-mediated relaxation of arteries isolated after chronic coronary artery occlusion, likely as a result of enhanced production of nitric oxide and endothelium-derived hyperpolarizing factor.

EcoCELLs: tools for mesocosm scale measurements of gas exchange

We describe the use of a unique plant growth facility, which has as its centerpiece four 'EcoCELLs', or 5x7 m mesocosms designed as open-flow, mass-balance systems for the measurement of carbon, water and trace gas fluxes. This system is unique in that it was conceived specifically to bridge the gap between measurement scales during long-term experiments examining the function and development of model ecosystems. There are several advantages to using EcoCELLs, including (i) the same theory of operation as leaf level gas exchange systems, but with continuous operation at a much larger scale; (ii) the ability to independently evaluate canopy-level and ecosystem models; (iii) simultaneous manipulation of environmental factors and measurement of system-level responses, and (iv) maximum access to, and manipulation of, a large rooting volume. In addition to discussing the theory, construction and relative merits of EcoCELLs, we describe the calibration and use of the EcoCELLs during a 'proof of concept' experiment. This experiment involved growing soybeans under two ambient CO2 concentrations (approximately 360 and 710 micromoles mol-1). During this experiment, we asked 'How accurate is the simplest model that can be used to scale from leaf-level to canopy-level responses?' in order to illustrate the utility of the EcoCELLs in validating canopy-scale models.

Plants, CO2 and photosynthesis in the 21st century

Human activity in the last 200 years has led to a marked increase in the level of CO2 in the atmosphere. Plants sense increases in CO2 levels and initially respond with an increase in photosynthetic rate, which may then slow as the plant adapts. This increase in photosynthetic rate may account in part for the 'disappearance' of an estimated 1.8 gigatons of carbon per year.

Phosphorus supply affects the photosynthetic capacity of loblolly pine grown in elevated carbon dioxide

Effects of phosphorus supply and mycorrhizal status on the response of photosynthetic capacity to elevated CO(2) were investigated in loblolly pine (Pinus taeda L.) seedlings. Seedlings were grown in greenhouses maintained at either 35.5 or 71.0 Pa CO(2) in a full factorial experiment with or without mycorrhizal inoculum (Pisolithus tinctorius (Pers.) Coker & Couch) and with an adequate or a limiting supply of phosphorus. Assimilation versus internal CO(2) partial pressure (C(i)) curves were used to estimate maximum Rubisco activity (V(c,max)), electron transport mediated ribulose 1,5-bisphosphate regeneration capacity (J(max)), phosphate regeneration capacity (PiRC) and daytime respiration rates (R(d)). Nonmycorrhizal seedlings grown with limiting phosphorus had significantly reduced V(c,max) and PiRC compared to seedlings in other treatments. Elevated CO(2) increased photosynthetic capacity in nonmycorrhizal seedlings in the low phosphorus treatment by increasing PiRC, whereas it induced phosphorus limitation in mycorrhizal seedlings in the low phosphorus treatment and did not affect the photosynthetic capacity of seedlings in the high phosphorus treatment. Despite the variety of effects on photosynthetic capacity, seedlings in the elevated CO(2) treatments had higher net assimilation rates than seedlings in the ambient CO(2) treatments. We conclude that phosphorus supply affects photosynthetic capacity during long-term exposure to elevated CO(2) through effects on Rubisco activity and ribulose 1,5-bisphosphate regeneration rates.