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Oxygen Requirements (oxygen + requirement)

Distribution by Scientific Domains

Medical Sciences	66%

Selected Abstracts

Isolation and gene quantification of heterotrophic N2 -fixing bacterioplankton in the Baltic Sea

ENVIRONMENTAL MICROBIOLOGY, Issue 1 2007
Kjärstin H. Boström
Summary Cyanobacteria are regarded as the main N2 -fixing organisms in marine waters. However, recent clone libraries from various oceans show a wide distribution of the dinitrogenase reductase gene (nifH) originating from heterotrophic bacterioplankton. We isolated heterotrophic N2 -fixing bacteria from Baltic Sea bacterioplankton using low-nitrogen plates and semi-solid diazotroph medium (SSDM) tubes. Isolates were analysed for the nitrogenase (nifH) gene and active N2 fixation by nested polymerase chain reaction (PCR) and acetylene reduction respectively. A primer-probe set targeting the nifH gene from a , - proteobacterial isolate, 97% 16S rDNA similarity to Pseudomonas stutzeri, was designed for measuring in situ dynamics using quantitative real-time PCR. This nifH gene sequence was detected at two of 11 stations in a Baltic Proper transect at abundances of 3 × 104 and 0.8 × 103 copies per litre seawater respectively. Oxygen requirements of isolates were examined by cultivation in SSDM tubes where oxygen gradients were determined with microelectrodes. Growth, and thereby N2 fixation, was observed as horizontal bands formed at oxygen levels of 0,6% air saturation. The apparent microaerophilic or facultative anaerobic nature of the isolates explains why the SSDM approach is the most appropriate isolation method. Our study illustrates how combined isolation, functional analyses and in situ quantification yielded insights into the oxygen requirements of heterotrophic N2 -fixing bacterioplankton isolates, which were confirmed to be present in situ. [source]

Budesonide delivered by dosimetric jet nebulization to preterm very low birthweight infants at high risk for development of chronic lung disease

ACTA PAEDIATRICA, Issue 12 2000
B Jónsson
We investigated the effect of an aerosolized corticosteroid (budesonide) on the oxygen requirement of infants at high risk for developing chronic lung disease (CLD) in a randomized, double-blind study. The study objective was to attain a 30% decrease in FiO2 levels in the budesonide treatment group after 14 d of therapy. Thirty very low birthweight (VLBW) infants (median (range)) gestational age 26 wk (23,29) and birthweight 805 g (525,1227) were randomized. Inclusion criteria were mechanical ventilation on day 6 of life, or if extubated on nasal continuous positive airway pressure with FiO2± 0.3. The budesonide (PulmicortÔ dose was 500 ,g bid, or placebo. The aerosol was delivered with a dosimetric jet nebulizer, with variable inspiratory time and breath sensitivity. Inhalations were started on day 7 of life. Twenty-seven patients completed the study. A significant lowering of the FiO2 levels at 21 d of life was not detected. Infants who received budesonide were more often extubated during the study period (7/8 vs 2/9) and had a greater relative change from baseline in their oxygenation index (budesonide decreased 26% vs placebo increased 60%). Subsequent use of intravenous dexamethasone or inhaled budesonide in the treatment group was significantly less. All patients required O2 supplementation on day 28 of life. At 36 wk postconceptual age, 61% of infants in the budesonide group needed supplemental O2 as opposed to 79% in the placebo group. No side effects on growth or adrenal function were observed Conclusion: We conclude that inhaled budesonide aerosol via dosimetric jet nebulizer started on day 7 of life for infants at high risk for developing CLD decreases the need for mechanical ventilation similar to intravenous dexamethasone, but without significant side effects. [source]

Mycoplasma pneumonia and pulmonary embolism in a child due to acquired prothrombotic factors

PEDIATRIC PULMONOLOGY, Issue 2 2008
Sarah M.N. Brown MRCPCH
Abstract We report on a child with Mycoplasma pneumonia, who developed an unexplained new oxygen requirement. He was found to have an ileo-femoral thrombosis and an acute pulmonary embolus, with positive anti-phospholipid antibodies and acquired activated protein C resistance. These are both acquired risk factors for venous thrombosis. He was successfully anti-coagulated and well at follow-up with disappearance of the anti-phospholipid antibodies, and normalization of his activated protein C activity. Children who present with Mycoplasma infections who run an atypical course should be monitored closely for signs of thrombosis. Thrombosis formation should also be considered in those children with deteriorating respiratory status, but little change in radiographical findings. Children found to have developed thrombi should be investigated with a full thrombophilia screen to elicit both congenital and acquired risk factors, and should be anti-coagulated appropriately. Pediatr Pulmonol. 2008; 43:200,202. © 2007 Wiley-Liss, Inc. [source]

Influence of body fat distribution on oxygen uptake and pulmonary performance in morbidly obese females during exercise

RESPIROLOGY, Issue 1 2001
Jing Li
Objective: The aim of this study was to determine the effects of fat distribution on aerobic and ventilatory response to exercise testing in morbidly obese (MO) females. Methodology: The study population consisted of 164 MO females, 55% (n = 90) with upper body or abdominal adiposity (UBD), as defined by waist,hip circumference ratio (WHR) , 0.80, and 45% (n = 74) with lower body fat distribution (LBD) (WHR < 0.80). An incremental exercise testing on cycle ergometer was performed to determine the effect of exercise on oxygen consumption (V·O2), carbon dioxide production (V·CO2), minute ventilation (V·E), tidal volume ( T), respiratory rate (fb) and heart rate (HR). Results: Upper body adiposity individuals had significantly higher O2 and V·CO2 than LBD subjects (P < 0.05) from 0 watt (W) of pedalling up to their anaerobic threshold (AT) and maximal exercise. E was significantly higher in UBD subjects compared with LBD subjects, from 20 W during exercise up to AT and peak work levels (P < 0.05). Upper body adiposity group also had a significantly higher fb than the LBD group at rest, after each workload and at AT and peak exercise work rates (P < 0.05). T was lower in UBD subjects at free pedalling and up to AT and peak workload with significant difference at 60 and 80 W (P < 0.05). The anaerobic threshold, expressed as work rate, was significantly lower in the UBD subjects (P < 0.05) and peak workload achieved did not differ significantly between the two groups. Conclusions: Upper body adiposity subjects had higher oxygen requirement, more rapid and shallow breathing, higher ventilatory demand, but lower anaerobic threshold than the LBD individuals during progressive exercise. It suggests that the cardiopulmonary endurance to exercise in MO patients with upper body fat distribution is lower than in those with lower body fat distribution. [source]

Isolation and gene quantification of heterotrophic N2 -fixing bacterioplankton in the Baltic Sea

Do egg size and parental care coevolve in fishes?

JOURNAL OF FISH BIOLOGY, Issue 6 2005
N. Kolm
A phenomenon that has attracted a substantial theoretical and empirical interest is the positive relationship between egg size and the extent of parental care in fishes. Interestingly, despite the effort put into solving the causality behind this relationship over the past two decades it remains largely unsolved. Moreover, how general the positive relationship between egg size and parental care is among fishes is also poorly understood. In order to stimulate research exploring egg size and parental care variation in fishes, the potential selective forces from both natural and sexual selection on egg size and parental care are discussed. Recent empirical findings on how oxygen requirements and developmental times may differ between differently sized eggs are incorporated into a critical view of the current theory of this field. Furthermore, it is suggested that the up to now neglected effects of sexual selection, through both mate choice and sexual conflict, can have strong effects on the relationship between egg size and parental care in fishes. In light of the recent developments of comparative and experimental methods, future approaches that may improve the understanding of the relationship between egg size and care in fishes are suggested. [source]

Lung function in infants and young children with chronic lung disease of infancy: The next steps?

PEDIATRIC PULMONOLOGY, Issue 1 2007
Janet Stocks PhD
Abstract Over the past year, a series of papers have reviewed the literature concerning assessment and interpretation of lung function in infants and young children with chronic lung disease of infancy. This manuscript, which represents the final paper in that series, summarizes the findings to date and highlights key areas for future research. Despite the huge literature in this field, interpretation of results and their use in guiding clinical management are still limited by difficulties in ,normalizing data' according to body size and maturation and selection of appropriate control groups. Furthermore, sensitive tests that more closely reflect the underlying pathophysiology of ,new' bronchopulmonary dysplasia, together with simple and reliable methods of assessing lung maturity at birth and true oxygen requirements at specified time points are urgently required. Research in this field is also challenged by the need to separate the independent effects of genetic predisposition, gene,environment interactions, preterm delivery, neonatal respiratory disorders and various treatment strategies on the growing lung. The extent to which disruption of lung growth following premature exposure to the extra-uterine environment leads to an earlier or more aggravated decline in respiratory function in later adult life remains to be elucidated. Whatever its origin, given the increasing survival of smaller and more immature infants, the long term sequelae of neonatal lung disease, are likely to continue to change, requiring ongoing, carefully designed longitudinal studies. Future research strategies need to encompass a multicenter, multi-disciplinary, collaborative approach with closer links between clinicians and basic scientists, to ensure that the most relevant research questions are addressed using appropriate methodology and that findings are implemented into clinical practice in a more timely fashion. Pediatr Pulmonol. 2007; 42:3,9. © 2006 Wiley-Liss, Inc. [source]

Oxygen cost of ventilation during incremental exercise to VO2 max

RESPIROLOGY, Issue 2 2006
Chantal A. VELLA
Objective: Evidence of significant oxygen requirements for ventilation during exercise (exercise hyperpnoea) prompted the investigation into whether the oxygen cost of ventilation affects the presence of a whole-body VO2 plateau at maximal exercise. The purposes of this study were to: (i) use isocapnic hyperpnoea trials to determine the oxygen cost of ventilation (VO2VENT) across a range of ventilation (VE); (ii) determine the mean VO2VENT at maximal exercise expressed as a percentage of whole-body VO2 max; and (iii) determine if a plateau in VO2 is more evident when the VO2VENT is subtracted from whole-body VO2 at maximal exercise. Methods: A total of 21 subjects performed a VO2 max test on the cycle ergometer to determine the range of VE for each subject. From the initial VO2 max test, nine VE values across the range of VE were selected for each subject and the oxygen cost of each was measured. Results: The mean maximal VO2VENT equalled 8.8 ± 3.3% of VO2 max and ranged from 5.0% to 17.6%. VO2VENT increased exponentially with increasing VE, but there was considerable subject variability in the oxygen cost per litre of VE as VE increased. Subtracting the VO2VENT from whole-body VO2 at maximal exercise increased the detection of a plateau in VO2 at VO2 max. Conclusions: The data of the present study indicate that the VO2VENT is a significant portion of VO2 max and may be a limiting factor of maximal exercise performance in some subjects. [source]

Analysis of vascular gene expression in arthritic synovium by laser-mediated microdissection

ARTHRITIS & RHEUMATISM, Issue 4 2007
Atsushi Hashimoto
Objective In rheumatoid arthritis (RA), formation of new blood vessels is necessary to meet the nutritional and oxygen requirements of actively proliferating synovial tissue. The aim of this study was to analyze the specific synovial vascular expression profiles of several angiogenesis-related genes as well as CD82 in RA compared with osteoarthritis (OA), using laser-mediated microdissection (LMM). Methods LMM and subsequent real-time polymerase chain reaction were used in combination with immunohistochemical analysis for area-specific analysis of messenger RNA (mRNA) and protein expression of vascular endothelial growth factor (VEGF), VEGF receptor 1 (VEGFR-1), VEGFR-2, hypoxia-inducible factor 1, (HIF-1,), HIF-2,, platelet-derived growth factor receptor , (PDGFR,), PDGFR,, inhibitor of DNA binding/differentiation 2 (Id2), and CD82 in RA and OA synovial microvasculature and synovial lining. Results Expression of Id2 mRNA was significantly lower in RA synovial vessels compared with OA synovial vessels (P = 0.0011), whereas expression of VEGFR-1 was significantly higher in RA (P = 0.0433). No differences were observed for the other parameters. At the protein level, no statistically significant differences were observed for any parameter, although Id2 levels were 2.5-fold lower in RA (P = 0.0952). However, the number of synovial blood vessels and the number of VEGFR-2,expressing blood vessels were significantly higher in RA compared with OA. Conclusion Our results underscore the importance of area-specific gene expression analysis in studying the pathogenesis of RA and support LMM as a robust tool for this purpose. Of note, our results indicate that previously described differences between RA and OA in the expression of angiogenic molecules are attributable to higher total numbers of synovial and vascular cells expressing these molecules in RA rather than higher expression levels in the individual cells. [source]