National strategies for knowledge translation in health policy-making: A scoping review of grey literature.

BACKGROUND AND OBJECTIVES: Without strategic actions in its support, the translation of scientific research evidence into health policy is often absent or delayed. This review systematically maps and assesses national-level strategic documents in the field of knowledge translation (KT) for health policy, and develops a practical template that can support Evidence-informed Policy Network (EVIPNet) Europe countries in producing national strategies for evidence-informed policy-making. METHODS: Websites of organizations with strategic responsibilities in KT were electronically searched, on the basis of pre-defined criteria, in July-August 2017, and an updated search was carried out in April-June 2021. We included national strategies or elements of national strategies that dealt with KT activities, as well as similar strategies of individual institutions with a national policy focus. Two reviewers screened the strategies for inclusion. Data were analysed using qualitative content analysis. RESULTS: A total of 65 unique documents were identified, of which 17 were eligible and analysed for their structure and content. Of the 17, 1 document was a national health KT action plan and 6 documents were institution-level KT strategies. The remaining 10 strategies, which were also included were 2 national health strategies, 5 national health research strategies and 3 national KT strategies (not specific to the field of health alone). In all, 13 structural elements and 7 major themes of health policy KT strategies were identified from the included documents. CONCLUSION: KT in health policy, as emerged from the national strategies that our mapping identified, is based on the production and accessibility of policy-relevant research, its packaging for policy-making and the activities related to knowledge exchange. KT strategies may play different roles in the complex and context-specific process of policy-making. Our findings show that the main ideas of health-specific evidence-informed policy literature appear in these strategies, but their effectiveness depends on the way stakeholders use them. Specific knowledge-brokering institutions and organizational capacity, advocacy about the use of evidence, and close collaboration and co-decision-making with key stakeholders are essential in furthering the policy uptake of research results.

Cost-Effectiveness Analysis of Treating Patients With NTRK-Positive Cancer With the Histology-Independent Therapy Entrectinib.

OBJECTIVES: This study tackles several challenges of evaluating histology-independent treatments using entrectinib as an example. Histology-independent treatments are provided based on genetic marker(s) of tumors, regardless of the tumor type. We evaluated the lifetime cost-effectiveness of testing all patients for NTRK fusions and treating the positive cases with entrectinib compared with no testing and standard of care (SoC) for all patients. METHODS: The health economic model consisted of a decision tree reflecting the NTRK testing phase followed by a microsimulation model reflecting treatment with either entrectinib or SoC. Efficacy of entrectinib was based on data from basket trials, whereas historical data from NTRK-negative patients were corrected for the prognostic value of NTRK fusions to model SoC. RESULTS: "Testing" (testing for NTRK fusions, with subsequent entrectinib treatment in NTRK-positive patients and SoC in NTRK-negative patients) had higher per-patient quality-adjusted life-years (QALYs) and costs than "No testing" (SoC for all patients), with a difference of 0.0043 and €732, respectively. This corresponded to an incremental cost-effectiveness ratio (ICER) of €169 957/QALY and, using a cost-effectiveness threshold of €80 000/QALY, an incremental net monetary benefit of -€388. When excluding the costs of genetic testing for NTRK fusions, the ICER was reduced to €36 290/QALY and the incremental net monetary benefit increased to €188. CONCLUSIONS: When treatment requires the identification of a genetic marker, the associated costs and effects need to be accounted for. Because of the low prevalence of NTRK fusions, the number needed-to-test to identify patients eligible for entrectinib is large. Excluding the testing phase reduces the ICER substantially.

Significant improvement in melanoma survival over the last decade: A Hungarian nationwide study between 2011 and 2019.

BACKGROUND: Recent real-world studies have reported significant improvements in the survival of malignant melanoma in the past few years, mainly as a result of modern therapies. However, long-term survival data from Central Eastern European countries such as Hungary are currently lacking. METHODS: This nationwide, retrospective study examined melanoma survival in Hungary between 2011-2019 using the databases of the National Health Insurance Fund (NHIF) and Central Statistical Office (CSO) of Hungary. Crude overall survival and age-standardized 5-year net survival as well as the association between age, sex and survival were calculated. RESULTS: Between 2011 and 2019, 22,948 newly diagnosed malignant melanoma cases were recorded in the NHIF database (47.89% male, mean age: 60.75 years (SD: ±16.39)). Five-year overall survival was 75.40% (women: 80.78%; men: 69.52%). Patients diagnosed between 2017-2019 had a 20% lower risk of mortality compared to patients diagnosed between 2011-2012 (HR 0.80, 95% CI 0.73-0.89; p < 0.0001). Age-standardized 5-year net survival rates in 2011-2014 and 2015-2019 were 90.6% and 95.8%, respectively (women: 93.1% and 98.4%, men: 87.8% and 92.7%, respectively). The highest age-standardized 5-year net survival rates were found in the 0-39 age cohort (94.6% in the 2015-2019 period). CONCLUSION: Hungary has similar melanoma survival rates to Western European countries. Based on net survival, the risk of dying of melanoma within 5 years was cut by more than half (55%) during the study period, which coincides with the successful implementation of awareness campaigns and the wide availability of modern therapies.

The Net Benefit of Personalized Medicine: A Systematic Literature Review and Regression Analysis.

OBJECTIVES: Amidst conflicting expectations about the benefits of personalized medicine (PM) and the potentially high implementation costs, we reviewed the available evidence on the cost-effectiveness of PM relative to non-PM. METHODS: We conducted a systematic literature review of economic evaluations of PM and extracted data, including incremental quality-adjusted life-years (ΔQALYs) and incremental costs (Δcosts). ΔQALYs and Δcosts were combined with estimates of national cost-effectiveness thresholds to calculate incremental net monetary benefit (ΔNMB). Regression analyses were performed with these variables as dependent variables and PM intervention characteristics as independent variables. Random intercepts were used to cluster studies according to country. RESULTS: Of 4774 studies reviewed, 128 were selected, providing cost-effectiveness data for 279 PM interventions. Most studies were set in the United States (48%) and the United Kingdom (16%) and adopted a healthcare perspective (82%). Cancer treatments (60%) and pharmaceutical interventions (72%) occurred frequently. Prognostic tests (19%) and tests to identify (non)responders (37%) were least and most common, respectively. Industry sponsorship occurred in 32%. Median ΔQALYs, Δcosts, and ΔNMB per individual were 0.03, Int$575, and Int$18, respectively. We found large heterogeneity in cost-effectiveness. Regression analysis showed that gene therapies were associated with higher ΔQALYs than other interventions. PM interventions for neoplasms brought higher ΔNMB than PM interventions for other conditions. Nonetheless, average ΔNMB in the 'neoplasm' group was found to be negative. CONCLUSIONS: PM brings improvements in health but often at a high cost, resulting in 0 to negative ΔNMB on average. Pricing policies may be needed to reduce the costs of interventions with negative ΔNMB.

Effects of fixed cutoff filtering on dark- and light-adapted ERG components and the application of variable cutoff filter.

PURPOSE: Human oscillatory potentials (OPs) are derived from dark-adapted (DA) electroretinograms (ERGs) with fixed frequency cutoff filters while light-adapted (LA) OPs are generally not isolated from ERGs. Our purpose was to analyze the effect of cutoff frequencies on DA and LA ERG components using a series of fixed and variable filters. METHODS: DA and LA ERGs were recorded from 10 healthy eyes of 10 subjects (mean age = 20.5 ± 6.7 years) following ISCEV standards. Each signal was filtered in the Fourier domain to acquire slow (a- and b-waves; below cutoff frequency) and fast (OPs; above cutoff frequency) components. Fixed cutoff frequencies ranged from 60 to 105 Hz and a variable cutoff frequency was calculated. Results were analyzed with statistical tests and specific models. RESULTS: DA ERG components were slightly influenced by the filter cutoff frequency. In contrast, fixed and variable filters significantly changed LA components: the lower the cutoff frequency the smaller the b-wave and OP3 and the higher the OP2/OP4 amplitudes. Analyzing the filter frequency limits a transition range between 68.9 Hz and 83.9 Hz was observed where amplitudes vary. CONCLUSIONS: The present report shows that DA OPs may be isolated from ERGs using filtering procedures with high-pass cutoff frequency at about 75 Hz as recommended by ISCEV. On the other hand, the spectral distribution of low-frequency and high-frequency LA ERG components may overlap. Accordingly, filtering the signal using different cutoff frequencies is not necessarily separating b-wave and OPs.

Wireless Temperature, Relative Humidity and Occupancy Monitoring System for Investigating Overheating in Buildings.

With the climate change we are experiencing today, the number and intensity of heatwaves are increasing dramatically, significantly impacting our buildings' overheating. The majority of the prefabricated concrete panel buildings in Hungary are considered outdated from an energy point of view. These buildings may be at greater risk from extreme weather events. To examine this, long-term monitoring measurements are needed. Therefore, we developed a unique, reliable, and cost-effective wireless monitoring system, which can track in real time the indoor air quality data (temperature, relative humidity, CO2) of the investigated apartment building, as well as users' habits, such as resident presence, window opening, and blind movement. The data were used to analyse and quantify the summer overheating of the dwelling and user habits. The measurements showed that the average temperature in all rooms was above 26 °C, and there were several occasions when the temperature exceeded 30 °C. Overheating in apartment buildings in summer is a significant problem that needs to be addressed. Further investigation of ventilation habits will help develop favourable ventilation strategies, and using these measurements in dynamic simulations will also help improve the models' validity for further studies.

[The role of intravenous thrombolysis before mechanical thrombectomy in the treatment of large vessel occlusion strokes]. / A mechanikus thrombectomiát megelozo intravénás thrombolysis szerepe az akut agyi nagyérelzáródások kezelésében.

BACKGROUND AND PURPOSE: The efficacy of intravenous thrombolysis (IVT) is moderate in the proximal vascular segments of intracranial arteries, as opposed to mecha-nical thrombectomy (MT). In the management of acute ischemic stroke (AIS) caused by large vessel occlusions (LVO), IVT prior to MT is highly recommended based on the latest guidelines, but the necessity of IVT has been questioned by the latest studies of the past years. The aim of our study was to investigate and compare the efficacy and safety of direct mechanical thrombectomy (dMT) and combined therapy (CT) for patients who suffered an AIS with LVO and were treated in our department. METHODS: We investigated patients with AIS caused by LVO who were admitted up to 4.5 hours after symptom onset and underwent MT in our department between November 2017 and August 2019. Patients' data were collected in our stroke register. Patients enrolled in our study were divided into two groups depending on whether dMT or CT was used. Our primary outcome was the 30- and 90- day functional outcome measured by modified Rankin Scale (mRS). Mortality at 30- and 90- day, successful recanalization rates, and symptomatic intracranial hemorrhage were considered as secondary outcomes. RESULTS: A total of 142 patients (age: 68.3 ± 12.6 years, 53.5% female) were enrolled in our study, including 81 (57.0%) dMT cases, and 61 (43.0%) patients who received CT. The vascular risk factors and comorbidities were significantly higher in the dMT-treated group. At day 30, the rate of favorable functional outcomes was 34.7% in dMT vs. 43.6% among those who received CT (p = 0.307), by day 90 this ratio changed to 40.8% vs. 46.3% (p = 0.542). Mortality rates at day 30 were 22.2% and 23.6% (p = 0.851), and at day 90 33.8% and 25.9% (p = 0.343). The rate of effective recanalization was 94.2% for dMT-treated patients and 98.0% for CT-treated patients (p = 0.318). Symptomatic intracranial hemorrhage was detected in 2.5% of dMT-treated patients and 3.4% of CT-treated group (p = 0.757). CONCLUSION: Our results suggest that CT is associated with a moderately better outcome compared to dMT. IVT prior to MT did not increase the risk of symptomatic intracranial hemorrhages.

Propagation of positioning uncertainties in near-field goniophotometers using the Monte Carlo method.

The method of near-field goniophotometry is used ever-increasingly to acquire detailed luminance information about various luminaires. It overcomes certain limitations of its predecessor, the widely used and thoroughly standardized far-field goniophotometry, and provides further opportunities to expand the scope of the measurement, but also introduces a new set of limiting factors. The aim of this paper is to examine the effect of positioning uncertainties on near-field goniophotometric measurements' results. For this, a simplified ray tracing model is constructed computable in closed form as stacked matrix equations, in order to reduce the computation time as much as possible. The model is then fed to a simulated goniophotometric measurement, loaded with various uncertainties according to the Monte Carlo method. Finally, the resulting uncertainties are derived from statistical analysis of the output in both the near and far fields. Various metrics are tested as potential criteria for acceptance, including correlation and repeated measures ANOVA tests, both faring well until the angle of incidence of the rays is below 55°, the ANOVA test being more sensitive to sampling and rejecting systems with 0.1° angular error and above, while the same results still pass the correlation test until 0.5°. Converted far-field results are compared to the standardized requirements, indicating the necessity of similar mechanical precision.

Magnetic Angular Rate and Gravity Sensor Based Supervised Learning for Positioning Tasks.

This paper deals with sensor fusion of magnetic, angular rate and gravity sensor (MARG). The main contribution of this paper is the sensor fusion performed by supervised learning, which means parallel processing of the different kinds of measured data and estimating the position in periodic and non-periodic cases. During the learning phase, the position estimated by sensor fusion is compared with position data of a motion capture system. The main challenge is avoiding the error caused by the implicit integral calculation of MARG. There are several filter based signal processing methods for disturbance and noise estimation, which are calculated for each sensor separately. These classical methods can be used for disturbance and noise reduction and extracting hidden information from it as well. This paper examines the different types of noises and proposes a machine learning-based method for calculation of position and orientation directly from nine separate sensors. This method includes the disturbance and noise reduction in addition to sensor fusion. The proposed method was validated by experiments which provided promising results on periodic and translational motion as well.

Preliminary Findings on the Optimization of Visual Performance in Patients with Age-Related Macular Degeneration Using Biofeedback Training.

Biofeedback training has been used to improve fixation stability in subjects with central vision loss, but the psychophysiological mechanisms underlying the functional improvements resulted was not reported. The aim of this study was to investigate the effects of microperimetric biofeedback training on different visual functions and self-reported quality of vision in subjects with age-related macular degeneration. This case-control study included six subjects (72.0 ± 6.1 years of age) diagnosed with age-related macular degeneration (wet or dry) with low vision (best corrected visual acuity ranging from 0.5 to 0.1 in the study eye) and five healthy volunteers (64.2 ± 3.7 years of age). Ophthalmological and functional examinations were obtained from all subjects twice with an approximately 3-month interval. Subjects with central vision loss performed 12 sessions (10 min each) of biofeedback training between the two examinations. Functional evaluation included: microperimetry, spatial luminance contrast sensitivities, color vision thresholds, visual acuity, and reading speed. Visual performance during daily activities was also assessed using a standardized questionnaire. The ratio (2nd/1st examination) of the spatial luminance contrast sensitivity at lower spatial frequencies were much higher for the training subjects compared with the controls. In addition, self-reported quality of vision improved after the training. The significant improvement of the visual function such as spatial luminance contrast sensitivity may explain the better self-reported quality of vision. Possible structural and physiological mechanisms underlying this neuromodulation are discussed.

Comparison between albino and pigmented rabbit ERGs.

BACKGROUND: Pigmented and albino rabbits are commonly used in visual research; however, the lack of pigment in the eyes may affect retinal responses. Here, we compare and describe the differences of retinal function between pigmented (English Butterfly) and albino (New Zealand) rabbits. METHODS: Electroretinograms were recorded in pigmented and albino rabbits in the dark-adapted eye, in the light-adapted eye and for four temporal frequencies in the light-adapted eye. The implicit time and amplitude of the a- and b-waves were analyzed, as well as the amplitude and phase of the first harmonic component of the photopic flicker response. RESULTS: Albino rabbits presented significantly larger amplitudes for both a- and b-waves at all intensities and frequencies. The intensity-response function of the scotopic b-wave also showed that the albino retina is more sensitive than the pigmented retina and the larger flicker amplitudes found in the albino group also revealed post-receptoral changes specifically related to cone pathways. CONCLUSIONS: The larger amplitude of albino receptoral and post-receptoral activities might be attributed to greater availability of light due to scatter and reflection at the retinal layer, and as the differences in response amplitudes between the groups increase with flicker frequency, we suggest that ON bipolar cells recover faster in the albino group, suggesting that this might be a mechanism to explain the higher temporal resolution for albinos compared to the pigmented group.

Photoreceptor-specific light adaptation of critical flicker frequency in trichromat and dichromat observers.

The silent substitution paradigm offers possibilities to investigate and compare the temporal properties of mechanisms driven by single photoreceptor types, including the critical flicker frequency (CFF), in which the state of adaptation can be kept as invariant. We have (1) measured CFFs using triple silent substitutions to isolate L-, M-, and S-cone as well as rod-driven pathways under identical mean luminances and chromaticities; (2) repeated the CFF measurements at different mean luminances in order to validate the Ferry-Porter law (stating that the relationship between CFF and the log retinal illuminance-log I-is linear); and (3) compared these CFF versus log I functions for L-, M-, S-cone-, and rod-isolating stimuli for five trichromats and four X-linked dichromats (two protanopes, two deuteranopes). We show that the effects of luminance on the CFFs with silent substitution are comparable to those measured previously with chromatic stimuli. We found that M-cone-driven CFFs are smaller in trichromats than in protanopes. Furthermore, the slopes of the M-cone-driven CFF versus log I functions are smaller in trichromats. Possibly, the lacking L-cones are replaced by M-cones in these two protanopes and the CFF depends on cone density. Furthermore, we found that in trichromats, the slopes of the CFF-log I functions are smaller for M-cone- than for L-cone-isolating stimuli. This contradicts the current interpretation of the CFF-log I functions for chromatic stimuli, which states that CFF is mediated by the most strongly modulated photoreceptor type. Thus, the larger slopes that were previously found with medium-wavelength chromatic stimuli compared with long-wavelength chromatic stimuli seem to be the result of an addition of signals from different photoreceptors and do not necessarily result from M-cones being inherently faster.

Electroretinographical determination of human color vision type.

It has been previously demonstrated that electroretinography (ERG) elicited by heterochromatically modulated stimuli can be used for objective determination of color vision type. Color vision of trichromatic, deuteranopic, and protanopic participants was psychophysically assessed by the Cambridge Color Test and confirmed genetically. ERG responses to red and green lights modulating in counterphase at 12 and 36 Hz were recorded, while the fraction of red modulation was varied. At 36 Hz (and second harmonics at 12 Hz), the responses were minimal at red fractions that differed significantly in protanopes. At 12 Hz (fundamental component), the responses of the trichromats differed significantly compared to those of the dichromats. An improved protocol shows that the three subject groups can be separated with no overlap.

Local decomposition of imaginary polarizabilities and dispersion coefficients.

We present a new way to compute the two-body contribution to the dispersion energy using ab initio theory. By combining the complex polarization propagator method and the LoProp transformation, local contributions to the Casimir-Polder interaction is obtained. The full dispersion energy in dimer systems consisting of pairs of molecules including H2, N2, CO, CH4, pyridine, and benzene is investigated, where anisotropic as well as isotropic models of dispersion are obtained using a decomposition scheme for the dipole-dipole polarizability. It is found that the local minima structure of the π-cloud stacking of the benzene dimer is underestimated by the total molecular dispersion, but is alleviated by the inclusion of atomic interactions via the decomposition scheme. The dispersion energy in the T-shaped benzene dimer system is greatly underestimated by all dispersion models, as compared to high-level quantum calculations. The generalization of the decomposition scheme to higher order multipole polarizability interactions, representing higher order dispersion coefficients, is briefly discussed. It is argued that the incorporation of atomic C6 coefficients in new atomic force fields may have important ramifications in molecular dynamics studies of biomolecular systems.

Enhancing substrate utilization and power production of a microbial fuel cell with nitrogen-doped carbon aerogel as cathode catalyst.

OBJECTIVES: Catalytic efficiency of a nitrogen-doped, mesoporous carbon aerogel cathode catalyst was investigated in a two-chambered microbial fuel cell (MFC) applying graphite felt as base material for cathode and anode, utilizing peptone as carbon source. RESULTS: This mesoporous carbon aerogel containing catalyst layer on the cathode increased the maximum power density normalized to the anode volume to 2.7 times higher compared to the maximum power density obtained applying graphite felt cathode without the catalyst layer. At high (2 and 3) cathode/anode volume ratios, maximum power density exceeded 40 W m-3. At the same time, current density and specific substrate utilization rate increased by 58% resulting in 31.9 A m-3 and 18.8 g COD m-3 h-1, respectively (normalized to anode volume). Besides the increase of the power and the rate of biodegradation, the investigated catalyst decreased the internal resistance from the range of 450-600 to 350-370 Ω. CONCLUSIONS: Although Pt/C catalyst proved to be more efficient, a considerable decrease in the material costs might be achieved by substituting it with nitrogen-doped carbon aerogel in MFCs. Such cathode still displays enhanced catalytic effect.

L-/M-cone opponency in visual evoked potentials of human cortex.

L and M cones send their signals to the cortex using two chromatic (parvocellular and blue-yellow koniocellular) and one luminance (magnocellular) pathways. These pathways contain ON and OFF subpathways that respond to excitation increments and decrements respectively. Here, we report on visually evoked potentials (VEP) recordings that reflect L- and M-cone driven increment (LI and MI) and decrement (LD and MD) activity. VEP recordings were performed on 12 trichromats and four dichromats (two protanopes and two deuteranopes). We found that the responses to LI strongly resembled those to MD, and that LD and MI responses were very similar. Moreover, the lack of a photoreceptor type (L or M) in the dichromats led to a dominance of the ON pathway of the remaining photoreceptor type. These results provide electrophysiological evidence that antagonistic L/M signal processing, already present in the retina and the lateral geniculate nucleus (LGN), is also observed at the visual cortex. These data are in agreement with results from human psychophysics where MI stimuli lead to a perceived brightness decrease whereas LI stimuli resulted in perceived brightness increases. VEP recording is a noninvasive tool that can be easily and painlessly applied. We propose that the technique may provide information in the diagnosis of color vision deficiencies.

[Model concept of the health economic evaluation of low-dose CT lung cancer screening in Hungary]. / Az alacsony dózisú CT-vel végzett tüdorákszurés magyarországi egészség-gazdaságtani elemzésének koncepcionális terve.

INTRODUCTION: Lung cancer is a rapidly progressing, often life-threatening disease that constitutes a huge societal burden. Because of the scarce resources of the Hungarian health care system, the cost-effectiveness of introducing low-dose computed tomography screening is a relevant health policy matter. AIM: The aim of this study is to design a model concept for assessing the cost-effectiveness of low-dose computed tomography lung cancer screening in Hungary, and to define the required steps for performing the analysis. METHOD: A targeted literature review was conducted to identify and synthesize the evidence on efficacy and effectiveness of screening, and results were evaluated based on adaptability to Hungarian settings. We also summarized the available Hungarian scientific evidence and reconstructed the potential patient pathways. RESULTS: In accordance with these findings, we recommend to perform the full health-economic evaluation of low-dose computed tomography lung cancer screening using a complex model structure that consists of several sub-models and is capable to follow the population at risk on life-time horizon. CONCLUSIONS: The proposed cost-effectiveness model will be suitable to provide data for further analyses that support decision-making on introducing low-dose computed tomography lung cancer screening as public health program. Orv Hetil. 2017; 158(25): 963-975.

Cost-effectiveness of a risk-based secondary screening programme of type 2 diabetes.

OBJECTIVE: The objective of this study was to develop a long-term economic model for type 2 diabetes to describe the entire spectrum of the disease over a wide range of healthcare programmes. The model evaluates a public health, risk-based screening programme in a country specific setting. METHODS: The lifespan of persons and important phases of the disease and related interventions are recorded in a Markov model, which first simulates the effect of screening, then replicates important complications of diabetes, follows the progression of individuals through physiological variables and finally calculates outcomes in monetary and naturalistic units. RESULTS: The introduction of the screening programme nearly doubled the proportion of diagnosed patients at the age of 50 and prolonged life expectancy. Three-yearly screening gained 0.0229 quality adjusted life years for an additional €83 per person compared with no screening and resulted an incremental cost-effectiveness ratio of €3630/quality adjusted life years. CONCLUSION: From the economic perspective introduction of the 3-yearly screening programme is justifiable and it provides a good value for money. Copyright © 2016 John Wiley & Sons, Ltd.

Diversity of extremophilic bacteria in the sediment of high-altitude lakes located in the mountain desert of Ojos del Salado volcano, Dry-Andes.

Ojos del Salado, the highest volcano on Earth is surrounded by a special mountain desert with extreme aridity, great daily temperature range, intense solar radiation, and permafrost from 5000 meters above sea level. Several saline lakes and permafrost derived high-altitude lakes can be found in this area, often surrounded by fumaroles and hot springs. The aim of this study was to gain information about the bacterial communities inhabiting the sediment of high-altitude lakes of the Ojos del Salado region located between 3770 and 6500 m. Altogether 11 sediment samples from 4 different altitudes were examined with 16S rRNA gene based denaturing gradient gel electrophoresis and clone libraries. Members of 17 phyla or candidate divisions were detected with the dominance of Proteobacteria, Acidobacteria, Actinobacteria and Bacteroidetes. The bacterial community composition was determined mainly by the altitude of the sampling sites; nevertheless, the extreme aridity and the active volcanism had a strong influence on it. Most of the sequences showed the highest relation to bacterial species or uncultured clones from similar extreme environments.

The influence of stimulus size on heterochromatic modulation electroretinograms.

When combined with the electroretinogram (ERG), the heterochromatic flicker photometry procedure allows an objective in vivo assessment of postreceptoral activity. Responses evoked at intermediate (approximately 12 Hz) and high (>30 Hz) temporal frequencies reflect the red-green cone opponent (possibly parvocellular) and the luminance (possibly magnocellular) responses, respectively. Previously, we found that cone-isolating stimuli at intermediate temporal frequencies elicited ERG responses with similar amplitudes and phases for different spatial arrangements of the stimuli, whereas response amplitudes at high temporal frequencies were positively correlated with stimulus size. The purpose of this study was to investigate whether the influence of stimulus size was confined to cone-isolating stimuli or whether it was a general feature of heterochromatic stimulation. Furthermore, we aimed to determine the smallest spatial extent for a significant response in the two postreceptoral mechanisms. Monocular ERGs were recorded to red-green counterphase modulated sinusoidal stimuli (mean luminance of 200 cd/m2) presented at 12 and 36 Hz at different stimulus sizes. At each stimulus condition, a series of ERGs were recorded with the red-contrast fraction (FR) [FR = CR/(CR + CR)] of the stimulus varying between 0.0 and 1.0. Response amplitudes at 36 Hz changed with FR for all subjects, exhibiting a V-shaped amplitude profile with a minimum close to the psychophysics-based isoluminance, where the ERG phase changed by 180°. As stimulus size decreased, the amplitudes to 36 Hz also decreased. In contrast, amplitudes and phases at 12 Hz generally were constant for all values of FR. These amplitudes were invariant to stimulus sizes larger than 10° but decreased with decreasing stimulus size below 10°. Phase also changed in this range. Thus, luminance pathway ERG responses (36 Hz) show direct dependency on stimulus size, whereas chromatic pathway responses (12 Hz) are independent of the stimulus size above 10°.