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Positive Linear Correlation (positive + linear_correlation)
Selected AbstractsHypolithic community shifts occur as a result of liquid water availability along environmental gradients in China's hot and cold hyperarid desertsENVIRONMENTAL MICROBIOLOGY, Issue 2 2007Stephen B. Pointing Summary Hypolithic cyanobacterial communities occur in hot and cold hyperarid environments but the physical factors determining their diversity are not well understood. Here we report hypolithic diversity and colonization of a common quartz substrate at several hyperarid locations in the ancient deserts of north-western China, that experience varying mean annual temperature, rainfall and concomitant availability of liquid water in soil. Microscopy and enrichment culture resulted only in Chroococcidiopsis morphotypes which were ubiquitous, but community phylogenetic analysis revealed considerable cyanobacterial and heterotrophic bacterial diversity. Species Richness and Shannon's Diversity Index displayed a significant positive linear correlation with availability of liquid water but not temperature or rainfall alone. Several taxonomic groups occurred only in specific climatically defined locations, while for Chroococcidiopsis, Deinococcus and Phormidium location specific lineages within these genera were also evident. Multivariate analysis was used to illustrate pronounced community shifts due to liquid water availability, although these did not significantly affect the predicted functional relationships within any given assemblage in either hot or cold, wet or dry hyperarid deserts. This study clearly demonstrates that availability of liquid water, rather than temperature or rainfall per se is the key determinant of hypolithic diversity in hyperarid locations, and furthermore that functionally similar yet taxonomically distinct communities occur, characterized by the presence of taxa that are specific to defined levels of aridity. [source] Characteristics of microcystin production in the cell cycle of Microcystis viridisENVIRONMENTAL TOXICOLOGY, Issue 1 2004Keishi Kameyama Abstract The correlation between the content of three microcystins (types LR, RR and YR) and the cell cycle of an axenic strain of Microcystis viridis, NIES-102, was investigated under conditions of high (16 mg L,1) and low (1.0 mg L,1) nitrate (NO3 -N) concentrations. Each phase of the cell cycle was identified using a flow cytometer equipped with a 488-nm argon laser using SYTOX Green dye, which binds specifically to nucleic acids and can be exited by the wavelength (Ex/Em: 504/523 nm on DNA). Microcystin concentration showed a positive linear correlation with DNA concentration. The microcystin content of the cells changed remarkably as the cell cycle process proceeded, with maximum content in the G2/M phase and minimum content in the G0/G1 phase. Under a condition of high NO3 -N concentration, the ratio of the total content in the G0/G1 phase to that in the G2/M phase was about 6:1. In contrast, for the two batch cultures the total content was 1.3-fold greater in the G2/M phase. The compositions of the three microcystins also changed along with the cell cycle process, although there was little difference in composition that was related to NO3 -N concentration. Therefore, there were distinctive compositions specific to each phase of the cycle, and the cell cycle of the M. viridis strain was more strongly responsible for both the quantity and the types of microcystin production than was the effect of NO3 -N concentration. © 2004 Wiley Periodicals, Inc. Environ Toxicol 19: 20,25, 2004. [source] Genotypic variation in patterns of root distribution, nitrate interception and response to moisture stress of a perennial ryegrass (Lolium perenne L.) mapping populationGRASS & FORAGE SCIENCE, Issue 3 2007J. R. Crush Abstract Genotypic variation in patterns of root distribution, nitrate interception and response to moisture stress were assessed in both parents and 198 progeny of a perennial ryegrass (Lolium perenne L.) full-sibling mapping population. This was carried out in metre-deep tubes of sand culture in a glasshouse experiment. The proportion of root dry matter (DM) weight in the top 10 cm of sand ranged from 0·33 to 0·75 and values of log10(1 , K), where K is the constant for an exponential model relating root DM weight and root depth, also showed wide variation among genotypes. The proportion of a pulse of 15N recovered in whole plants ranged from 0·124 to 0·431. There was a positive linear correlation between the proportion of 15N recovered and plant total DM weight, but no relationship between nitrate interception and patterns of distribution of DM weight of roots. Some genotypes responded to moisture stress by increasing root growth, and in others root growth was inhibited. It is concluded that this below-ground variability in root variables may be an evolutionary adaptation by plant populations to survive heterogeneity in soil biotic and edaphic factors. [source] GENERATION OF BIOLUMINESCENT MORGANELLA MORGANII AND ITS POTENTIAL USAGE IN DETERMINATION OF GROWTH LIMITS AND HISTAMINE PRODUCTIONJOURNAL OF FOOD SAFETY, Issue 2 2009MEHDI ZAREI ABSTRACT A mini-Tn5 promoter probe carrying the intact lux operon of Photorhabdus luminescens (pUT mini-Tn5 luxCDABE) which allowed measurement of light output without the addition of exogenous substrate was constructed. It was used to create a pool of chromosomally lux -marked strains of Morganella morganii. Also plasmid-mediated expression of bioluminescence in M. morganii was assessed using plasmid pT7-3 luxCDABE. No significant differences in growth and histamine formation characteristics of the lux -marked strains and wild type M. morganii strain were observed. Luminescent strain of M. morganii was used in experiments in which the correlation between light output, viable cell count and histamine formation was assessed. During the exponential growth phase, a positive linear correlation was observed between these three parameters in trypticase soy broth-histidine medium at 37C. It was demonstrated that expression of bioluminescence had not had a significant effect upon both growth rate and histamine production. Thus, the measurement of bioluminescence was found to be a simple, fast and reliable method for determination of viable cell count and histamine content. PRACTICAL APPLICATIONS Constructing predictive models in microbiology requires a large number of data on desired factors. Commonly used traditional methods of counting viable cells and measuring histamine, e.g., to model the growth limits of M. morganii as a function of different intrinsic and extrinsic factors, are time consuming and laborious, and require a lot of laboratory space and materials. According to the results of this research, measurement of bioluminescence is a simple, fast and reliable method for the determination of viable cell count and histamine content during the exponential growth phase. Thus, it can be used as a labor- and material-saving selective data capture method for constructing predictive models in many different areas. [source] Absolute quantification of cerebral blood flow in normal volunteers: Correlation between Xe-133 SPECT and dynamic susceptibility contrast MRIJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 4 2007Linda Knutsson PhD Abstract Purpose To compare absolute cerebral blood flow (CBF) estimates obtained by dynamic susceptibility contrast MRI (DSC-MRI) and Xe-133 SPECT. Materials and Methods CBF was measured in 20 healthy volunteers using DSC-MRI at 3T and Xe-133 SPECT. DSC-MRI was accomplished by gradient-echo EPI and CBF was calculated using a time-shift-insensitive deconvolution algorithm and regional arterial input functions (AIFs). To improve the reproducibility of AIF registration the time integral was rescaled by use of a venous output function. In the Xe-133 SPECT experiment, Xe-133 gas was inhaled over 8 minutes and CBF was calculated using a biexponential analysis. Results The average whole-brain CBF estimates obtained by DSC-MRI and Xe-133 SPECT were 85 ± 23 mL/(min 100 g) and 40 ± 8 mL/(min 100 g), respectively (mean ± SD, n = 20). The linear CBF relationship between the two modalities showed a correlation coefficient of r = 0.76 and was described by the equation CBF(MRI) = 2.4 · CBF(Xe),7.9 (CBF in units of mL/(min 100 g)). Conclusion A reasonable positive linear correlation between MRI-based and SPECT-based CBF estimates was observed after AIF time-integral correction. The use of DSC-MRI typically results in overestimated absolute perfusion estimates and the present study indicates that this trend is further enhanced by the use of high magnetic field strength (3T). J. Magn. Reson. Imaging 2007;26:913,920. © 2007 Wiley-Liss, Inc. [source] Isoprenoid emission in trees of Quercus pubescens and Quercus ilex with lifetime exposure to naturally high CO2 environment,PLANT CELL & ENVIRONMENT, Issue 4 2004F. RAPPARINI ABSTRACT The long-term effect of elevated atmospheric CO2 on isoprenoid emissions from adult trees of two Mediterranean oak species (the monoterpene-emitting Quercus ilex L. and the isoprene-emitting Quercus pubescens Willd.) native to a high-CO2 environment was investigated. During two consecutive years, isoprenoid emission was monitored both at branch level, measuring the actual emissions under natural conditions, and at leaf level, measuring the basal emissions under the standard conditions of 30 °C and at light intensity of 1000 µmol m,2 s,1. Long-term exposure to high atmospheric levels of CO2 did not significantly affect the actual isoprenoid emissions. However, when leaves of plants grown in the control site were exposed for a short period to an elevated CO2 level by rapidly switching the CO2 concentration in the gas-exchange cuvette, both isoprene and monoterpene basal emissions were clearly inhibited. These results generally confirm the inhibitory effect of elevated CO2 on isoprenoid emission. The absence of a CO2 effect on actual emissions might indicate higher leaf temperature at elevated CO2, or an interaction with multiple stresses some of which (e.g. recurrent droughts) may compensate for the CO2 effect in Mediterranean ecosystems. Under elevated CO2, isoprene emission by Q. pubescens was also uncoupled from the previous day's air temperature. In addition, pronounced daily and seasonal variations of basal emission were observed under elevated CO2 underlining that correction factors may be necessary to improve the realistic estimation of isoprene emissions with empirical algorithms in the future. A positive linear correlation of isoprenoid emission with the photosynthetic electron transport and in particular with its calculated fraction used for isoprenoid synthesis was found. The slope of this relationship was different for isoprene and monoterpenes, but did not change when plants were grown in either ambient or elevated CO2. This suggests that physiological algorithms may usefully predict isoprenoid emission also under rising CO2 levels. [source] Significance of CT Attenuation Value in Liver Grafts Following Right Lobe Living-Donor Liver TransplantationAMERICAN JOURNAL OF TRANSPLANTATION, Issue 5 2005Taku Iida In adult living-donor liver transplantation (LDLT), the assessment of the allograft functional reserve is important for adequate graft regeneration. From March 2002 to December 2003, 30 adult recipients underwent right lobe LDLT. Mean CT attenuation values (CT-AVs) in the graft were measured on unenhanced CT for 6 months after LDLT. The histological features of the graft parenchyma were evaluated with post-operative liver biopsy specimens. Mean CT-AVs after LDLT were decreased significantly from the pre-operative values, recovered to over 60 HU within 6 months. There was a positive linear correlation between the CT-AVs and the receptor index (LHL15) in technetium-99m-diethylenetriaminepenta-acetic acid-galactosyl-human serum albumin (99mTc-GSA) liver scintigraphy (r = 0.803, p = 0.005). The recipients were divided into two groups according to the CT-AV at one post-operative week (group H; ,55HU, group L; <55HU). The low CT-AVs, under 55 HU, in group L were prolonged for 3 months compared with those in group H (p < 0.05). The 1-year cumulative survival rate was 94.7% and 45.5% in groups H and L, respectively (p = 0.014). Histological findings revealed that the parenchymal damage was severe in the grafts with low CT-AVs. The CT-AVs in the grafts may be a useful parameter for assessing the allograft functional reserve. [source] Therapeutic Effects and Anti-inflammatory Mechanisms of Heparin on Acute Lung Injury in RabbitsACADEMIC EMERGENCY MEDICINE, Issue 7 2008Meitang Wang MD Abstract Objectives:, The objectives were to investigate the potential beneficial effects and molecular mechanisms of heparin and low-molecular-weight heparin (LMWH) on acute lung injury (ALI). Methods:, Forty-eight rabbits were randomized into four groups: normal control group (Group A), lipopolysaccharide (LPS) group (Group B), LPS + heparin group (Group C), and LPS + LMWH group (Group D). The rabbit ALI model was established by intravenous (IV) injection with LPS. Alveolar,arterial O2 difference (PA-aO2), serum tumor necrosis factor , (TNF-,), circulating p38 mitogen-activated protein kinase (p38 MAPK) levels, lung nuclear factor (NF)-,B levels, and lung dry/wet (D/W) ratio were measured, and the lung injury scores were calculated. Results:, Lipopolysaccharide caused significant increases in PA-aO2, serum TNF-,, expression of p38 MAPK in polymorphonuclear neutrophils (PMNs), the lung injury scores, and nuclear factor-,B (NF-,B) activity in the lung tissue and caused a decrease in lung D/W ratio. A positive linear correlation was found between p38 MAPK and TNF-, at 1, 2, 4, and 6 hours (r = 0.68, 0.92, 0.93, and 0.93, respectively) and between NF-,B and p38 MAPK and TNF-, at 6 hours (r = 0.94 and 0.83, respectively). IV heparin or LMWH given after LPS treatment attenuated these changes in inflammatory response, oxygenation, p38 MAPK expression, and NF-,B activation. Conclusions:, The anti-inflammatory mechanisms of heparin in ALI may be inhibiting p38 MAPK and NF-,B activities, and then TNF-, overexpression, thus alleviating the inflammatory reaction. [source] Opioid switching from transdermal fentanyl to oral methadone in patients with cancer painCANCER, Issue 12 2004Miguel Angel Benítez-Rosario M.D., Ph.D. Abstract BACKGROUND Patients with cancer often are rotated from other opioids to methadone to improve the balance between analgesia and side effects. To the authors' knowledge, no clear guidelines currently exist for the safe and effective rotation from transdermal fentanyl to methadone. METHODS The authors evaluated a protocol for switching opioid from transdermal fentanyl to oral methadone in 17 patients with cancer. Reasons for switching were uncontrolled pain (41.1% of patients) and neurotoxic side effects (58.9% of patients). Methadone was initiated 8,24 hours after fentanyl withdrawal, depending on the patient's previous opioid doses (from < 100 ,g per hour to > 300 ,g per hour). The starting methadone dose was calculated according to a 2-step conversion between transdermal fentanyl:oral morphine (1:100 ratio) and oral morphine:oral methadone (5:1 ratio or 10:1 ratio). The correlation between previous fentanyl dose and the final methadone dose or the fentanyl:methadone dose ratio was assessed by means of Pearson and Spearman correlation coefficients (r), respectively. A Friedman test was used to compare pain intensity before and after the switch and the use of daily rescue doses. RESULTS Opioid rotation was fully or partially effective in 80% and 20%, respectively, of patients with somatic pain. Neuropathic pain was not affected by opioid switching. Delirium and myoclonus were reverted in 80% and 100% of patients, respectively, after opioid switching. A positive linear correlation was obtained between the fentanyl and methadone doses (Pearson r, 0.851). Previous fentanyl doses were not correlated with the final fentanyl:methadone dose ratios (Spearman r, , 0.327). CONCLUSIONS The protocol studied provided a safe approach for switching from transdermal fentanyl to oral methadone, improving the balance between analgesia and side effects in patients with cancer. Cancer 2004. © 2004 American Cancer Society. [source] Comparison of the firing patterns of human postganglionic sympathetic neurones and spinal , motoneurones during brief burstsEXPERIMENTAL PHYSIOLOGY, Issue 1 2004Vaughan G. Macefield Focal recordings from individual postganglionic sympathetic neurones in awake human subjects have revealed common firing properties. One of the most striking features is that they tend to fire only once per sympathetic burst. Why this should be so is not known, but we propose that the short duration of the burst may limit the number of times a sympathetic neurone can fire. Indeed, while the normal variation in cardiac interval and burst duration is too narrow to reveal a correlation between burst duration and the number of spikes generated, we know that spike generation is doubled when burst duration is doubled following ectopic heart beats. To test the hypothesis that the burst duration constrains the firing of individual sympathetic neurones to one per burst, we used the human skeletomotor system as a model for the sympathetic nervous system, which allowed us to vary burst duration and amplitude experimentally. Intramuscular recordings were made from 27 single motor units (, motoneurones) in the tibialis anterior or soleus muscles of seven subjects; multiunit EMG activity was recorded via surface electrodes and blood pressure was recorded continuously. Subjects were instructed to generate EMG bursts of varying amplitude in the intervals between heart beats. By constraining the firing of , motoneurones to brief (,400 ms) bursts we could emulate real sympathetic bursts. Individual motoneurones generated 0,7 spikes during the emulated sympathetic bursts, with firing patterns similar to those exhibited by real sympathetic neurones. Eleven motor units showed significant positive linear correlations between the number of spikes they generated within a burst and its amplitude, whereas for 17 motor units there were significant positive correlations between the number of spikes and burst duration. This indicates that burst duration is a major determinant of the number of times an , motoneurone will fire during a brief burst, and we suggest that the same principle may explain the firing pattern typical of human sympathetic neurones. [source] | ||||||||||||||||