Intensity gradient
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Background and Aims: The stress gradient hypothesis (SGH), the view that competition prevails in undisturbed and productive environments, and shifts to facilitation in disturbed or stressful environments, has become a central paradigm in ecology. However, an alternative view proposes that the relationship between biotic interactions and environmental severity should be unimodal instead of monotonic. Possible causes of discrepancies between these two views were examined in the high elevation desert of the arid Trans-Himalayas. Methods: A putative nurse species and its associated plant community was surveyed over its entire elevation range, spanning from alpine to desert vegetation belts. The results were analysed at the community level (vegetation cover and species richness), considering the distinction between the intensity and the importance of biotic interactions. Interactions at the species level (pairwise interactions) were also considered, i.e. the variation of biotic interactions within the niche of a species, for which the abundance (species cover) and probability of occurrence (presence/absence) for the most widespread species along the gradient were distinguished. Key Results: Overall, facilitation was infrequent in our study system; however, it was observed for the two most widespread species. At the community level, the intensity and importance of biotic interactions showed a unimodal pattern. The departure from the prediction of the SGH happened abruptly where the nurse species entered the desert vegetation belt at the lowest elevation. This abrupt shift was attributed to the turnover of species with contrasting tolerances. At the species level, however, facilitation increased consistently as the level of stress increases and individuals deviate from their optimum (increasing strain). Conclusion: While the stress gradient hypothesis was not supported along our elevation gradient at the community level, the strain gradient hypothesis, considering how species perceive the ambient level of stress and deviate from their optimum, provided a parsimonious explanation for the outcome of plant-plant interactions at both scales.
In the past two decades, supercritical fluid chromatography has evolved from a niche application to a comprehensive technology and a fully-fledged alternative to conventional high-performance liquid chromatography. In this study, we have focused on chiral separation of synthetic cathinones in gradient supercritical fluid chromatography coupled to mass spectrometry using an inverse gradient of a make-up solvent. Synthetic cathinones possess an amphetamine-like effect and, therefore, are frequently being offered on the Internet as a replacement for illicit drugs. Cathinones are chiral compounds, however, they are usually marketed and used as racemic mixtures. Since the effect of individual enantiomers can significantly vary, there is a need for the development of enantioseparation methods enabling to study the biological effects of individual enantiomers. Since cathinones are basic molecules, they are easily protonated (positively charged) under weakly acidic mobile phase conditions, which is a typical feature of supercritical mobile phases with an alcohol as an organic modifier. The positively charged species represent ideal analytes for ion exchangers, such as chiral zwitterion ion exchangers Chiralpak ZWIX (+) and Chiralpak ZWIX (-), which possess a positively and negatively charged unit in the molecular structure of the selectors. The presence of the positive charge in the selector's structure, functioning as a counter-ion for the positively charged analytes, significantly reduces the required amount of a buffer, which is plausible for hyphenation of such a separation system with mass spectrometry. For mass spectrometry hyphenated to supercritical fluid chromatography, the use of a make-up solvent is required to avoid analyte precipitation when using a low concentration of an organic co-solvent (modifier) in the super-/subcritical mobile phase. Hereby, we introduce a unique approach, which is based on the gradient introduction of the make-up to the post-column effluent. Using this approach, it is possible to keep constant the overall amount of the organic solvent (modifier and make-up) introduced into the mass spectrometer when using a gradient of the organic modifier. We show that the developed gradient elution method facilitates the chiral separation of all employed analytes, while the mobile-phase gradient compensation by the inverse make-up gradient enables their detection with high signal intensities.
- MeSH
- alkaloidy chemická syntéza chemie izolace a purifikace MeSH
- hmotnostní spektrometrie metody MeSH
- reologie * MeSH
- rozpouštědla chemie MeSH
- stereoizomerie MeSH
- superkritická fluidní chromatografie metody MeSH
- teplota MeSH
- tlak MeSH
- vysokoúčinná kapalinová chromatografie MeSH
- Publikační typ
- časopisecké články MeSH
OBJECTIVES: In the Conservative vs. Liberal Approach to Fluid Therapy of Septic Shock in Intensive Care (CLASSIC) trial, restriction of IV fluid volumes led to similar overall mortality in ICU patients with septic shock. We assessed if variation in standard IV fluid treatment intensity across sites impacted the effects of fluid restriction. DESIGN: Secondary analysis of randomized clinical trial. SETTING: ICU. PATIENTS: The CLASSIC trial enrolled adult ICU patients with septic shock. We included 1366 participants from 19 sites, representing 88% of the full trial population. All sites with greater than or equal to 15 participants in the standard-fluid group were included in this study. INTERVENTIONS: Restrictive vs. standard IV fluid therapy. MEASUREMENTS AND MAIN RESULTS: We used machine learning (eXtreme Gradient Boosting) to predict the IV fluid volumes in the first 24 hours in the standard-fluid group while accounting for participant characteristics that could contribute to treatment variations. We then classified sites into intensity subgroups based on the mean differences between predicted and administered IV fluid volumes in the first 24 hours in the standard-fluid group. We assessed the intervention effects on mortality, serious adverse events and reactions, days alive without life support, and days alive out of hospital at day 90 across these intensity subgroups, using hierarchical Bayesian models with weakly informative priors. Sensitivity analyses evaluated intervention effects separately in each site. In the standard-fluid group, the median absolute difference between administered and predicted IV fluid volumes was -118 mL (interquartile range, -1,341 to 1,731 mL; full range, -5,873 to 11,761 mL). Sites were categorized into five intensity subgroups. The absolute differences in mortality across these subgroups ranged from -2.7% point to 1.4% point. We found similar effects of restrictive vs. standard IV fluid treatment on all outcomes within the intensity subgroups. Results were similar in the sensitivity analyses. CONCLUSIONS: Among adult ICU patients with septic shock, variation in standard IV fluid volumes across sites did not substantially impact the effects of fluid restriction on outcomes after accounting for patient characteristics.
- MeSH
- jednotky intenzivní péče MeSH
- lidé středního věku MeSH
- lidé MeSH
- mortalita v nemocnicích MeSH
- péče o pacienty v kritickém stavu * metody MeSH
- senioři MeSH
- septický šok * terapie mortalita MeSH
- strojové učení MeSH
- tekutinová terapie * metody MeSH
- Check Tag
- lidé středního věku MeSH
- lidé MeSH
- mužské pohlaví MeSH
- senioři MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- multicentrická studie MeSH
- randomizované kontrolované studie MeSH
Many cushion plants ameliorate the harsh environment they inhabit in alpine ecosystems and act as nurse plants, with significantly more species growing within their canopy than outside. These facilitative interactions seem to increase with the abiotic stress, thus supporting the stress-gradient hypothesis. We tested this prediction by exploring the association pattern of vascular plants with the dominant cushion plant Thylacospermum caespitosum (Caryophyllaceae) in the arid Trans-Himalaya, where vascular plants occur at one of the highest worldwide elevational limits. We compared plant composition between 1112 pair-plots placed both inside cushions and in surrounding open areas, in communities from cold steppes to subnival zones along two elevational gradients (East Karakoram: 4850-5250 m and Little Tibet: 5350-5850 m). We used PERMANOVA to assess differences in species composition, Friedman-based permutation tests to determine individual species habitat preferences, species-area curves to assess whether interactions are size-dependent and competitive intensity and importance indices to evaluate plant-plant interactions. No indications for net facilitation were found along the elevation gradients. The open areas were not only richer in species, but not a single species preferred to grow exclusively inside cushions, while 39-60% of 56 species detected had a significant preference for the habitat outside cushions. Across the entire elevation range of T. caespitosum, the number and abundance of species were greater outside cushions, suggesting that competitive rather than facilitative interactions prevail. This was supported by lower soil nutrient contents inside cushions, indicating a resource preemption, and little thermal amelioration at the extreme end of the elevational gradient. We attribute the negative associations to competition for limited resources, a strong environmental filter in arid high-mountain environment selecting the stress-tolerant species that do not rely on help from other plants during their life cycle and to the fact the cushions do not provide a better microhabitat to grow in.
- MeSH
- biodiverzita * MeSH
- biologické modely * MeSH
- Caryophyllaceae růst a vývoj fyziologie MeSH
- chemické jevy MeSH
- druhová specificita MeSH
- fyziologický stres * MeSH
- mikroklima MeSH
- nadmořská výška * MeSH
- půda MeSH
- teplota MeSH
- vzduch MeSH
- zeměpis MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Geografické názvy
- Indie MeSH
- Tibet MeSH
BACKGROUND: Variation in usual practice in fluid trials assessing lower versus higher volumes may affect overall comparisons. To address this, we will evaluate the effects of heterogeneity in treatment intensity in the Conservative versus Liberal Approach to Fluid Therapy of Septic Shock in Intensive Care trial. This will reflect the effects of differences in site-specific intensities of standard fluid treatment due to local practice preferences while considering participant characteristics. METHODS: We will assess the effects of heterogeneity in treatment intensity across one primary (all-cause mortality) and three secondary outcomes (serious adverse events or reactions, days alive without life support and days alive out of hospital) after 90 days. We will classify sites based on the site-specific intensity of standard fluid treatment, defined as the mean differences in observed versus predicted intravenous fluid volumes in the first 24 h in the standard-fluid group while accounting for differences in participant characteristics. Predictions will be made using a machine learning model including 22 baseline predictors using the extreme gradient boosting algorithm. Subsequently, sites will be grouped into fluid treatment intensity subgroups containing at least 100 participants each. Subgroups differences will be assessed using hierarchical Bayesian regression models with weakly informative priors. We will present the full posterior distributions of relative (risk ratios and ratios of means) and absolute differences (risk differences and mean differences) in each subgroup. DISCUSSION: This study will provide data on the effects of heterogeneity in treatment intensity while accounting for patient characteristics in critically ill adult patients with septic shock. REGISTRATIONS: The European Clinical Trials Database (EudraCT): 2018-000404-42, ClinicalTrials. gov: NCT03668236.
- MeSH
- Bayesova věta MeSH
- lidé MeSH
- péče o pacienty v kritickém stavu metody MeSH
- septický šok * terapie MeSH
- strojové učení MeSH
- tekutinová terapie * metody MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
Nosocomial infections are a major cause of morbidity and mortality among neonates admitted to neonatal intensive care units (NICUs). The aim of this paper was to describe an outbreak of Escherichia coli among infants admitted to the NICU of the General Hospital "Dr. Manuel Gea Gonzalez" in May of 2008. The isolated E. coli strains were identified using standard biochemical methods. The susceptibilities of these strains were analysed by determining their minimal inhibitory concentrations. Following this, their molecular relationships to each other were assessed by pulsed field gel electrophoresis (PFGE) analysis and corroborated by serology. Twelve E. coli strains were isolated from blood, urine, or indwelling catheter samples from five cases of preterm infants within a 3-day period. Patients were admitted to the NICU of the general hospital and, during the outbreak, developed sepsis caused by E. coli. For four of the patients, the average age was 23 days, while one patient was a 3-month-old infant. Prior to sepsis, the infants had received assisted ventilation and hyperalimentation through a central venous catheter. Two profiles were observed by PFGE; profile A was identified as the outbreak's cause and an outcome of cross-infection, while profile B showed genetic differences but serologically it was identified as part of the same serotype. We conclude that E. coli colonised the patients through horizontal transmission. A focal source of the microorganism in this outbreak was not identified, but cross-transmission through handling was the most probable route.
- MeSH
- bakteriální léková rezistence MeSH
- epidemický výskyt choroby * MeSH
- Escherichia coli izolace a purifikace MeSH
- infekce spojené se zdravotní péčí epidemiologie mikrobiologie přenos MeSH
- infekce vyvolané Escherichia coli epidemiologie přenos MeSH
- jednotky intenzivní péče o novorozence * MeSH
- kojenec MeSH
- lidé MeSH
- mikrobiální testy citlivosti MeSH
- nemocnice všeobecné MeSH
- novorozenec nedonošený MeSH
- novorozenec MeSH
- pulzní gelová elektroforéza MeSH
- sepse epidemiologie mikrobiologie MeSH
- Check Tag
- kojenec MeSH
- lidé MeSH
- mužské pohlaví MeSH
- novorozenec MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Geografické názvy
- Mexiko MeSH
A model was constructed which includes electron transport (linear and cyclic and Mehler type reaction) coupled to proton translocation, counter ion movement, ATP synthesis, and Calvin-Benson cycle. The focus is on modeling of the light-induced total electric potential difference (ΔΨ) which in this model originates from the bulk phase electric potential difference (ΔΨb), the localized electric potential difference (ΔΨc), as well as the surface electric potential difference (ΔΨs). The measured dual wavelength transmittance signal (ΔA515-560nm, electrochromic shift) was used as a proxy for experimental ΔΨ. The predictions for theoretical ΔΨ vary with assumed contribution of ΔΨs, which might imply that the measured ΔA515-560nm trace on a long time scale reflects the interplay of the ΔΨ components. Simulations also show that partitioning of proton motive force (pmf) to ΔΨb and ΔpH components is sensitive to the stoichiometric ratio of H(+)/ATP, energy barrier for ATP synthesis, ionic strength, buffer capacity and light intensity. Our model shows that high buffer capacity promotes the establishment of ΔΨb, while the formation of pHi minimum is not 'dissipated' but 'postponed' until it reaches the same level as that for low buffer capacity. Under physiologically optimal conditions, the output of the model shows that at steady state in light, the ΔpH component is the main contributor to pmf to drive ATP synthesis while a low ΔΨb persists energizing the membrane. Our model predicts 11mV as the resting electric potential difference across the thylakoid membrane in dark. We suggest that the model presented in this work can be integrated as a module into a more comprehensive model of oxygenic photosynthesis.
- MeSH
- biologické modely * MeSH
- časové faktory MeSH
- koncentrace vodíkových iontů účinky záření MeSH
- listy rostlin metabolismus účinky záření MeSH
- membránové potenciály účinky záření MeSH
- počítačová simulace MeSH
- protonmotorická síla účinky záření MeSH
- protony MeSH
- pufry MeSH
- světlo * MeSH
- transport elektronů MeSH
- tylakoidy metabolismus účinky záření MeSH
- uhlík metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
OBJECTIVES: The objective of this study was to perform a multinational survey of patients' colonization by metallo-β-lactamase (MBL)-producing Enterobacteriaceae, including their molecular characterization. METHODS: Patients in 18 hospital units across Europe and Israel (n = 17 945) were screened between mid-2008 and mid-2011. MBL-producing isolates were typed by PFGE and MLST. MBL genes were amplified and sequenced within their integrons. Plasmids with MBL genes were analysed by nuclease S1 plus hybridization profiling, mating and transformation assays, and by PCR-based replicon typing. RESULTS: Ninety-one patients in nine centres (six countries), including 62 patients in two Greek ICUs, carried 94 non-duplicate MBL-producing organisms. Klebsiella pneumoniae isolates from Greece dominated (n = 57) and belonged mainly to ST147, ST36 and ST383. All but one of the isolates expressed VIM-1-type MBLs. Isolates of Greek origins produced five enzymes, including new VIM-39, encoded by class 1 integrons of four types. In-e541-like elements prevailed, comprising six variants located on IncR, IncFIIK, IncR + FIIK, IncR + A/C or non-typeable plasmids. The other group were new In4873 and In4863, being the first In416-like elements identified in Greece, which were present on IncA/C or non-typeable plasmids. Isolates from other countries produced only VIM-1 and the major integron was In916, identified in 16 organisms from France, Italy and Spain. In916 was carried by four plasmid types, including IncA/C, IncFIIK and IncHI2. Other integrons included a new element, In3103, in Spain and In110 identified only in Latvia. CONCLUSIONS: This study provided fully comparable data on the occurrence and molecular characteristics of VIM-producing Enterobacteriaceae in a group of hospital units across Europe, documenting recent changes in their epidemiology.
- MeSH
- bakteriální geny MeSH
- beta-laktamasy sekrece MeSH
- DNA bakterií chemie genetika MeSH
- Enterobacteriaceae klasifikace enzymologie genetika izolace a purifikace MeSH
- enterobakteriální infekce epidemiologie mikrobiologie MeSH
- jednotky intenzivní péče MeSH
- lidé MeSH
- molekulární epidemiologie MeSH
- multilokusová sekvenční typizace MeSH
- nemocnice MeSH
- plazmidy analýza MeSH
- polymerázová řetězová reakce MeSH
- přenašečství epidemiologie mikrobiologie MeSH
- pulzní gelová elektroforéza MeSH
- sekvenční analýza DNA MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Geografické názvy
- Evropa MeSH
The aim of this study was to compare radiosurgical treatment plan quality of a linear accelerator with Leksell Gamma Knife (LGK) for pituitary adenoma irradiation. Thirty pituitary adenoma patients were evaluated in this study. Treatment plans were prepared on LGK and stereotactic linear accelerator Varian TrueBeam STx. Volumetric Modulated Arc Therapy (VMAT) plans (21 plans with 2 coplanar arcs and 9 plans with 4 non-coplanar arcs) were calculated for linear accelerator. All the plans were evaluated in terms of conformity, selectivity, gradient index and organ at risk (OAR) sparing. VMAT produced dosimetrically comparable treatment plans to LGK regarding conformity and selectivity (New Conformity Index (NCI): 1.76 ± 0.65 for 4 arc VMAT, 2.33 ± 1,16 for 2 arc VMAT and 1.96 ± 0.71 for LGK; Selectivity Index (SI): 0.63 ± 0.16 for 4 arc VMAT, 0.51 ± 0.16 for 2 arc VMAT and 0.58 ± 0.17 for LGK). Gradient index (GI) was superior for LGK plans (GI: 2.74 ± 0.20 for LGK and 5.28 ± 2.29 for 4 arc VMAT). OAR sparing for optics, brainstem, and hypophysis was similar for both modalities while target volume coverage was maintained the same. Finally, treatment time resulted in favor of VMAT plans (in this study VMAT plans were almost 5 times faster than LGK treatment regarding beam on time). According to the results of this study stereotactic linear accelerator with VMAT treatment could be used as a reasonable alternative to LGK for pituitary adenoma radiosurgery but only if the same head fixation method accuracy and target volume delineation are maintained for both modalities.
- MeSH
- částice - urychlovače MeSH
- celková dávka radioterapie MeSH
- lidé MeSH
- nádory hypofýzy * radioterapie MeSH
- nádory mozku * chirurgie MeSH
- plánování radioterapie pomocí počítače MeSH
- radiochirurgie * MeSH
- radioterapie s modulovanou intenzitou * MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
OBJECTIVES: The aim of this study was to analyse the emergence of carbapenem resistance among hospital strains of Acinetobacter in the Czech Republic. METHODS: Acinetobacter isolates were collected prospectively in 2005-06 from 19 diagnostic laboratories. They were identified to species level by AFLP, typed using AFLP, pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing, and tested for susceptibility to 14 antimicrobials and for the presence of 20 genes associated with antimicrobial resistance. RESULTS: A total of 150 Acinetobacter isolates were obtained from 56 intensive care units of 20 hospitals in 15 cities. They were identified as Acinetobacter baumannii (n = 108) or other species. A. baumannii isolates were allocated to EU clone I (n = 5), EU clone II (n = 66) or other, mostly unique genotypes. Two-thirds of the clone II isolates had nearly identical AFLP and PFGE fingerprints. As many as 85% and 88% isolates were susceptible to meropenem and imipenem (
- MeSH
- Acinetobacter baumannii izolace a purifikace klasifikace účinky léků MeSH
- analýza polymorfismu délky amplifikovaných restrikčních fragmentů MeSH
- antibakteriální látky farmakologie MeSH
- bakteriální proteiny genetika MeSH
- beta-laktamasy genetika MeSH
- DNA bakterií genetika MeSH
- DNA fingerprinting MeSH
- genotyp MeSH
- infekce bakteriemi rodu Acinetobacter epidemiologie mikrobiologie MeSH
- infekce spojené se zdravotní péčí epidemiologie mikrobiologie MeSH
- jednotky intenzivní péče MeSH
- karbapenemy farmakologie MeSH
- lidé MeSH
- mikrobiální testy citlivosti MeSH
- mnohočetná bakteriální léková rezistence MeSH
- nemocnice MeSH
- prospektivní studie MeSH
- pulzní gelová elektroforéza MeSH
- sekvenční analýza DNA MeSH
- shluková analýza MeSH
- Check Tag
- lidé MeSH
- Geografické názvy
- Česká republika MeSH
