Increased Carbon Dioxide Levels Research Articles

Adult Identified with Congenital Central Hypoventilation Syndrome–Mutation in PHOX2b Gene and Late-Onset CHS

In light of our recent review of the genetic basis for congenital central hypoventilation syndrome (CCHS) (1), we bring to your attention a 35-year-old adult recently identified as having had late-onset CHS and the CCHS-mutation in PHOX2b. One year ago this patient presented with a history of snoring “for his whole life,” nocturnal gasping, and “stopping breathing and turning blue.” During polysomnography he had 46 obstructive events (38 hypopneas, 8 apneas), 16 central apneas, and an apnea–hypopnea index of 77 events/hour, with an SaO2 nadir of 65% in room air and 80% with supplemental oxygen. He temporarily responded to Bi-Pap with supplemental oxygen during sleep, but within 6 months was referred for uvulopalatopharyngoplasty. He was readmitted 48 hours after discharge with intermittent confusion, difficulty staying awake, and respiratory failure (awake arterial Pco2 of 73 mm Hg). His admission hematocrit was 73%, body temperature was 35.5 C, chest X-ray revealed cardiomegaly, and ECG revealed right axis deviation, enlargement, and hypertrophy. He required intubation and mechanical ventilation, then a tracheostomy; however, mechanical ventilation was discontinued. We were contacted by the family when an arterial blood gas assay upon awakening revealed a Pco2 of 129 mm Hg (pH 7.03). Because of his daughter’s diagnosis of late-onset CHS 3 years before, and documentation that she is heterozygous for the CCHS-related PHOX2b polyalanine expansion mutation, we conducted the same assay with the father’s DNA. Figure 1 demonstrates the identical mutation in the 4-year-old daughter and the father, as well as in the 2-yearold daughter, who also has alveolar hypoventilation (all three have a genotype of 20/25). In retrospect, we learned that the father uses Dexadrine to “stay on task,” has symptoms compatible with autonomic nervous system dysregulation (low body temperature, postural hypotension, pinpoint pupils minimally reactive to light, no shortness of breath despite markedly increased carbon dioxide levels), and has awakened with headaches and periods of disorientation for several years. On the basis of this remarkably late presentation of the alveolar hypoventilation component of CHS, we suggest that adult pulmonologists and intensivists consider the possibility of lateonset CHS, confirmable by PHOX2b assay, when caring for adults with hypercarbia of unknown etiology. From a scientific perspective, this case raises the possibility of a regulatory gene that modifies the expression or activity of PHOX2b, determining the severity of the autonomic dysregulation in late-onset CHS.

Possible Implications of Increased Carbon Dioxide Levels and Climate Change for Desert Ecosystems

Despite the considerable progress achieved during recent years in quantifying and modeling climatic and ecological processes caused by increasing concentrations of greenhouse gases in the atmosphere, there are still major uncertainties regarding the potential effects of increasing concentrations of either CO2 (carbon dioxide) or future climate change in arid ecosystems. General Circulation Models predict varying patterns of moister or drier conditions in deserts for the next century, but the results of climatic and ecosystem modeling in relation to deserts in a future “greenhouse effect” climate are complex and contradictory. Nevertheless, if deserts do respond more dramatically to global temperature change, as they did during the Holocene and, especially the last interglacial era (130,000 years ago), they might act as globally significant sinks of carbon into soils and vegetation. Some growth chamber experiments have indicated that increased CO2 will significantly affect desert shrubs, whereas other chamber and field experiments suggest that rising levels of atmospheric CO2 may not dramatically affect desert ecosystems, although certain individual species may be strongly favored. It is difficult to make a firm statement whether there are any valid analogs between the climate changes of the past and future climate change induced by greenhouse gases.

Development of a Cerebral Autoregulation Model for Use With Clinical Blood Flow Measurements

Cerebral autoregulation is the mechanism which controls blood flow to the brain despite variations in blood pressure. Although important this mechanism is currently not well understood, with autoregulatory failure difficult to diagnose. In this paper we develop a simple model based upon those measurements available in the clinical setting. The model can replicate previous results and is used to investigate a variety of hypothetical autoregulatory responses. Furthermore the model has been extended by including the autoregulatory vessels themselves to explain the observed influence of increased carbon dioxide levels in the blood. A focus on only those measurements which may be realistically obtained in human patients avoids the need for estimating many unknown parameters or the modelling of complex and poorly understood physiological process necessary in previous, more complicated, models.

Reduction of soil carbon formation by tropospheric ozone under increased carbon dioxide levels.

In the Northern Hemisphere, ozone levels in the troposphere have increased by 35 per cent over the past century, with detrimental impacts on forest and agricultural productivity, even when forest productivity has been stimulated by increased carbon dioxide levels. In addition to reducing productivity, increased tropospheric ozone levels could alter terrestrial carbon cycling by lowering the quantity and quality of carbon inputs to soils. However, the influence of elevated ozone levels on soil carbon formation and decomposition are unknown. Here we examine the effects of elevated ozone levels on the formation rates of total and decay-resistant acid-insoluble soil carbon under conditions of elevated carbon dioxide levels in experimental aspen (Populus tremuloides) stands and mixed aspen-birch (Betula papyrifera) stands. With ambient concentrations of ozone and carbon dioxide both raised by 50 per cent, we find that the formation rates of total and acid-insoluble soil carbon are reduced by 50 per cent relative to the amounts entering the soil when the forests were exposed to increased carbon dioxide alone. Our results suggest that, in a world with elevated atmospheric carbon dioxide concentrations, global-scale reductions in plant productivity due to elevated ozone levels will also lower soil carbon formation rates significantly.

USE OF CONTROLLED ATMOSPHERES TO ENHANCE ESSENTIAL OIL FUMIGANT TOXICITY AGAINST WESTERN FLOWER THRIPS, FRANKLINIELLA OCCIDENTALIS

The fumigant toxicity of selected essential oils was assessed against the Western Flower Thrips, Frankliniella occidentalis. Adult females and larvae were exposed to combinations of essential oil doses and increased carbon dioxide and decreased oxygen levels. Application of such combinations were found to significantly increase the fumigant toxicity against thrips. An increase in exposure time also led to an increase in mortalities in both essential oil alone and combined treatments. These results indicate that by combining applications of the essential oils with e.g. moderately increased carbon dioxide levels (2 to 10%), it may be possible to achieve toxicity levels similar to those of standard chemical fumigants.

RECENT ADVANCES IN THE POSTHARVEST PACKAGING AND HANDLING OF TROPICAL FRUIT

Several recent advances in postharvest packaging and physiology are discussed for durians, mangoes, pineapples and rambutans. Packaging had been found to control or even eliminate durian odours. Careful design of packaging (together with appropriate cool storage) reduces water loss and can greatly extend the shelf life of fresh durian. Packaging of mangoes to produce modified atmospheres (MA) was not consistently successful, unless some perforations were included. Without perforations increased decay and off-flavours were problems. MA packaging (MAP) was found to reduce chilling injury, enabling storage at lower temperatures. Pineapples were also found to respond to MAP by reducing chilling injury especially the symptoms of 'black heart'. The latest findings about physiology of rambutan colour loss or blackening are discussed, with the role of water relations in the peel found to be very important. High relative humidities and increased carbon dioxide levels reduced browning and extended storage life.

Establishing predictive indicators for the status of loaded soft tissues

Two complementary techniques were employed to assess the soft tissue response to applied pressure. The noninvasive methods involve the simultaneous measurement of the local tensions of oxygen and carbon dioxide (tcPO2 and tcPCO2) and the collection and subsequent analysis of sweat collected from the sacrum, a common site for the development of pressure sores. All tests were performed on able-bodied subjects. Results have indicated that oxygen levels (tcPO2) were lowered in soft tissues subjected to applied pressures of between 40 (5.3 kPa) and 120 mmHg (16.0 kPa). At the higher pressures, this decrease was generally associated with an increase in carbon dioxide levels (tcPCO2) well above the normal basal levels of 45 mmHg (6 kPa). There were also considerable increases, in some cases up to twofold, in the concentrations of both sweat lactate and urea at the loaded site compared with the unloaded control. By comparing selected parameters, a threshold value for loaded tcPO2 was identified, representing a reduction of ~60% from unloaded values. Above this threshold, there was a significant relationship between this parameter and the loaded/unloaded concentration ratios for both sweat metabolites. These parameters may prove useful in identifying those subjects whose soft tissue may be compromised during periods of pressure ischemia.

Stimulation of border cell production in response to increased carbon dioxide levels.

Field soil atmospheres have higher CO(2) and lower O(2) concentrations compared with ambient atmosphere, but little is known about the impact of such conditions on root exudation patterns. We used altered levels of CO(2) and O(2) relative to ambient conditions to examine the influence of the atmosphere on the production of root border cells by pea (Pisum sativum) root tips. During germination, atmospheres with high CO(2) and low O(2) inhibited root development and border cell separation in pea seedlings. Later in development, the same atmospheric composition stimulated border cell separation without significantly influencing root growth. Increased CO(2), not low O(2), was responsible for the observed stimulation of border cell number. High CO(2) apparently can override endogenous signals that regulate the number of border cells released from pea roots into the rhizosphere. The same conditions that stimulated border cell production in pea had no such effect in alfalfa (Medicago sativa).

Global Warming Is True - Isn't It?

Scientists are now sure that global warming is a real phenomenon. No ifs or buts, this is a definite statement. It’s true. Three of the past 8 years have been the hottest since at least the Middle Ages. What could be more definite? Three years in the last 500, maybe 600 years and they were all in the last decade. In the past if weather got a kick in the pants it used to be due to volcanic eruption, unusual changes in the sun-spot pattern or the now infamous El Nino behaving oddly. Now it’s us. We keep on burning things, mostly fossil fuels but also forests. This last year has been particularly bad for forest burning. Burning carbon containing material produces carbon dioxide and that is a ‘greenhouse gas’. I know that a few years ago we worried about CFCs and their effect on the ozone layer but that is another story and they no longer seem to be major players in any doomsday drama, today carbon dioxide is at the front of the stage. However, the role of carbon dioxide is not entirely clear. We know that the amount in the atmosphere has increased since the time before the Industrial Revolution. This increase is probably the most believable part of the story because we can measure the levels very accurately and have been able to do so for many years. In the pre-industrial era carbon dioxide levels were around 280 ppm, by the time of the second world war they were still only around 290 ppm but now that figure has increased to around 355 ppm. If and how this increase is responsible for and related to global warming is a difficult problem and there seems to be little consensus between the experts involved in its study. Some will say that the increased level plays a major part in the global warming that we are experiencing. Others will deny that we are experiencing global warming or if we are then the role of carbon dioxide is greatly overstated. So I should restate my opening sentence and say that some scientists are absolutely convinced that the biosphere is hotting up and that carbon dioxide is largely responsible. I am sitting on the fence. The Intergovernmental Panel on Climate Change (IPCC) has said in a report [1] that ‘carbon dioxide has been responsible for over half the enhanced greenhouse effect in the past, and is likely to remain so in the future’. The increase in carbon dioxide levels is continuing and in the future there will be a lot more. How much more depends on the credence you give to the many scenarios that have been proposed so ‘a lot more’ seems to be accurate enough as a description. Of course the problem is compounded by the fact that the relationship between carbon dioxide in the atmosphere and the mean global temperature is not, as I said earlier, a simple one. During the Cretaceous period carbon dioxide levels were in excess of 2,000 ppm and yet temperatures were little different to those today. Arguments about changes taking place in geological time have the advantage that vagueness is to a degree acceptable. A year, a century, or even a millennium are unimportant. The correct order is important; before this but after that and about the same time as are necessary and adequate. Exactly when something occurred is less so. If we go back in the time of the history of the Earth by some 3 billion years we arrive in an era when life had begun but the degree of cellular organisation had not got a long way beyond one. There may have been colonies of cells but such aggregation was probably disorganised. Most importantly for the march of evolution the biosphere was anaerobic. Oxygen, strictly dioxygen, levels were constrained to below 0.001% of the present atmo-

Petition strengthens hand of global warming sceptics

washington About 15,000 US science graduates, including 6,000 PhDs, have signed a petition that rejects the Kyoto agreement on global warming and argues that increases in carbon dioxide levels benefit Earth, according to the petition's organizers.

Effects of increasing carbon dioxide level on the regional thermal environment

In order to clarify the daily effects of increasing carbon dioxide level on the regional thermal environment, a two-dimensional numerical analysis was carried out on unsteady heat and mass-transfer. The results indicate a large surface temperature change in the nighttime and in the summer. The nighttime change is proportional to the change in infrared radiation flux from the atmosphere. An interaction between the effects of water vapor and those of carbon dioxide is found only in the daytime. When carbon dioxide is released from an urban surface, the vertical distributions of the air temperature and the pollutant concentration are affected in urban areas.

Ergebnisse der endoskopischen, retroperitonealen Adrenalektomie unter besonderer Berücksichtigung des intraoperativen Verlaufs

In 20 patients the hemodynamic and ventilatory data during endoscopic retroperitoneal adrenalectomy were checked retrospectively to analyze the hemodynamic and ventilatory effects of a pneumoretroperitoneum. After insufflation of CO2 into the retroperitoneal space we observed an increase in systolic blood pressure [median 180 mm Hg ([130-200)]. Analyzing the ventilatory parameters we noted that the minute ventilation had to be increased by a median value of 4.25 I (0.4-13) to reduce the increased carbon dioxide levels during CO2 insufflation. After insufflation of CO2 into the retroperitoneal space we observed no major complications. We therefore believe that retroperitoneal endoscopic adrenalectomy is also indicated in patients with cardiac or pulmonary diseases.

Effects of elevated pCO2 and/or osmolality on the growth and recombinant tPA production of CHO cells

Carbon dioxide is a by-product of mammalian cell metabolism that will build up in culture if it is not removed from the medium. Increased carbon dioxide levels are generally not a problem in bench-top bioreactors, but inhibitory levels can easily be reached in large-scale vessels, especially if the aeration gas is enriched in oxygen. Due to the equilibrium attained between dissolved CO2 and bicarbonate, increased pCO2 is associated with increased osmolality in bioreactors with pH control. While a few preliminary reports indicate that elevated pCO2 levels can inhibit cell growth and/or recombinant protein production, no comprehensive analysis of the interrelated effects of elevated pCO2 and osmolality has been published. We have examined the effects of 140, 195, and 250 mm Hg (187, 260, and 333 mbar, respectively) pCO2 (with and without osmolality control) on the growth of and recombinant tPA production by MT2-1-8 Chinese hamster ovary (CHO) cells. The effects of elevated osmolality were also investigated at the control pCO2 of 36 mm Hg. Elevated pCO2 at 310 mOsm/kg osmolality inhibited cell growth in a dose-dependent fashion, with a maximum decrease of 30% in the specific growth rate (μ) at 250 mm Hg. Osmolality alone had no effect on μ, but the combination of elevated pCO2 and osmolality increased the maximal reduction in μ to 45%. Elevated pCO2 at 310 mOsm/kg osmolality decreased the specific tPA production rate (qtPA) by up to 40% at 250 mm Hg. Interestingly, while increased osmolality decreased qtPA significantly at 140 mm Hg pCO2, it had no effect or even increased qtPA at 195 and 250 mm Hg. © 1996 John Wiley & Sons, Inc.

Effects of elevated pCO2 and/or osmolality on the growth and recombinant tPA production of CHO cells

Carbon dioxide is a by-product of mammalian cell metabolism that will build up in culture if it is not removed from the medium. Increased carbon dioxide levels are generally not a problem in bench-top bioreactors, but inhibitory levels can easily be reached in large-scale vessels, especially if the aeration gas is enriched in oxygen. Due to the equilibrium attained between dissolved CO(2) and bicarbonate, increased pCO(2) is associated with increased osmolality in bioreactors with pH control. While a few preliminary reports indicate that elevated pCO(2) levels can inhibit cell growth and/or recombinant protein production, no comprehensive analysis of the interrelated effects of elevated pCO(2) and osmolality has been published. We have examined the effects of 140, 195, and 250 mm Hg (187, 260, and 333 mbar, respectively) pCO(2) (with and without osmolality control) on the growth of and recombinant tPA production by MT2-1-8 Chinese hamster ovary (CHO) cells. The effects of elevated osmolality were also investigated at the control pCO(2) of 36 mm Hg. Elevated pCO(2) at 310 mOsm/kg osmolality inhibited cell growth in a dose-dependent fashion, with a maximum decrease of 30% in the specific growth rate (mu) at 250 mm Hg. Osmolality alone had no effect on mu, but the combination of elevated pCO(2) and osmolality increased the maximal reduction in mu to 45%. Elevated pCO(2) at 310 mOsm/kg osmolality decreased the specific tPA production rate (q(tPA)) by up to 40% at 250 mm Hg. Interestingly, while increased osmolality decreased q(tPA) significantly at 140 mm Hg pCO(2), it had no effect or even increased q(tPA) at 195 and 250 mm Hg. (c) 1996 John Wiley & Sons, Inc.

Comparative respiration and methane production rates in Nearctic termites

Rates of oxygen consumption and the production of carbon dioxide and methane were measured in thirteen Nearctic termite species periodically, for 48h, at 25 °C. Decreased respiration rates were observed in several species with decreasing oxygen and increasing carbon dioxide levels. Those species with apparently higher moisture requirements (i.e. subterranean termites) generally had lower respiration rates compared with the dampwood (highest rates) and dry wood (intermediate rates) termites. Termite biomass significantly influenced respiration rates, with the largest species having the highest rates. Methane production occurred in seven of the thirteen species assayed. Of these apparently methanogenic species, only one of the eleven colonies of Incisitermes minor and one of the two colonies of Prorhinotermes simplex produced methane. The generally reduced respiration rates found at lower oxygen and higher carbon dioxide levels are considered more representative of the conditions encountered in termite galleries. Bioassays conducted under more natural atmospheric conditions may be more representative of termite responses in the field.

Effects of liming on shallow acidified moorland pools: a culture and a seed bank experiment

To study the effects of liming on water chemistry and the development of aquatic macrophytes, culture experiments with Littorella uniflora (L.) Aschers. and Juncus bulbosus L. were carried out. The addition of powdered limestone to acidified moorland pools led to increased phosphate levels in the water layer and increased carbon dioxide levels in the sediment pore water and the water column; this resulted in an excessive growth of Juncus bulbosus. Similar observations were made in seed bank experiments, conducted in a greenhouse. After 2 years the abundance of J. bulbosus was very high. Littorella uniflora and Lobelia dortmanna L. germinated spontaneously and developed in mini-ecosystems with sediments from the Padvindersven and the Peetersven, respectively, two moorland pools from which these species had disappeared a few decades ago. Spontaneous germination and development of endangered soft water macrophytes only occurred on sediments after removal of the organic sapropelium layer. Therefore, this study showed that in order to restore the original water chemistry of acidified moorland pools, removal of the organic sapropelium layer is necessary, as well for improving vegetation development.

Development of o.a.s.i.s., a new automated blood culture system in which detection is based on measurement of bottle headspace pressure changes

o.a.s.i.s. (Unipath Ltd., Basingstoke, United Kingdom) is a new automated blood culture system. The metabolism of microorganisms is detected by measuring changes in the pressure of the headspace of blood culture bottles. These changes are measured by monitoring the position of a flexible sealing septum, every 5 min, with a scanning laser sensor. This noninvasive system can detect both gas absorption and production and does not rely solely on measuring increasing carbon dioxide levels. A research prototype instrument was used to carry out an evaluation of the media, the detection system, and its associated detection algorithm. In simulated blood cultures, o.a.s.i.s. supported growth and detected a range of clinical isolates. Times to positivity were significantly shorter in o.a.s.i.s. than in the BACTEC 460 system. Results of a clinical feasibility study, with a manual blood culture system as a control, confirmed that o.a.s.i.s. was able to support the growth and detection of a variety of clinically significant organisms. On the basis of these findings, full-scale comparative clinical trials of o.a.s.i.s. with other automated blood culture systems are warranted.

Implications of increased carbon dioxide levels for carbon input and turnover in soils

Implications of increased carbon dioxide levels for carbon input and turnover in soils

Global Changes and New Challenges For Civil Engineers

The world's civil engineers have designed and built a new habitat for man that has led to improved health and prosperity in virtually every country, while the momentum of continuing global changes presents a new set of challenges for civil engineers. World population is continuing to increase, primarily in the developing countries, with major growth in city populations, World food production per person is increasing, and this is also contributing to increased urbanization. Cities can be considered as productive units, and there is a widening range of opportunities for location for manufacturing. A major problem in world cities is inappropriate transport facilities with growing incompatibility between urban form and urban transport, which has a consequential impact on the economic efficiency of cities. There is a growing world demand for energy and electricity, and increasing carbon dioxide levels in the atmosphere are causing concern about climatic changes and rising average sea levels. Uranium is seen as a preferred energy source for electricity on environmental grounds. Excessive legalism in some countries, e.g., the United States, imposes additional costs on engineering and the economy.

Combined work stresses: Effect of reduced air renewal on psychological performance during 72h sustained operations

Abstract Human tolerance limits for sustained operations under the combined stress of stale air and sleep loss were studied in two groups often male volunteers over a 72 h period, with only 1h of sleep permitted after 32, 48 and 60h. The experiment investigated whether such sustained performance might be additionally influenced by mild hypoxia (15 vol% O2) together with correspondingly increased carbon dioxide levels (5 vol%). Performance on various psychological tests showed the expected decrease with increasing duration of sleep loss. However, there were no clear cut differences in performance between the control and the hypoxia groups. There were, however, more pronounced decreases with time in either group in the more complex tasks as compared to simple reaction time and vigilance tasks. Short-term memory improved probably due to learning. The missing effect of hypoxia could be attributed to a hyperventilation response in the experimental subjects and an increase in cerebral blood flow initiated by the hypercapnia.