The aim was to investigate the effect of different speech tasks, i.e. recitation of prose (PR), alliteration (AR) and hexameter (HR) verses and a control task (mental arithmetic (MA) with voicing of ...the result on end-tidal CO2 (PETCO2), cerebral hemodynamics and oxygenation. CO2 levels in the blood are known to strongly affect cerebral blood flow. Speech changes breathing pattern and may affect CO2 levels.
Measurements were performed on 24 healthy adult volunteers during the performance of the 4 tasks. Tissue oxygen saturation (StO2) and absolute concentrations of oxyhemoglobin (O2Hb), deoxyhemoglobin (HHb) and total hemoglobin (tHb) were measured by functional near-infrared spectroscopy (fNIRS) and PETCO2 by a gas analyzer. Statistical analysis was applied to the difference between baseline before the task, 2 recitation and 5 baseline periods after the task. The 2 brain hemispheres and 4 tasks were tested separately.
A significant decrease in PETCO2 was found during all 4 tasks with the smallest decrease during the MA task. During the recitation tasks (PR, AR and HR) a statistically significant (p<0.05) decrease occurred for StO2 during PR and AR in the right prefrontal cortex (PFC) and during AR and HR in the left PFC. O2Hb decreased significantly during PR, AR and HR in both hemispheres. HHb increased significantly during the AR task in the right PFC. tHb decreased significantly during HR in the right PFC and during PR, AR and HR in the left PFC. During the MA task, StO2 increased and HHb decreased significantly during the MA task.
We conclude that changes in breathing (hyperventilation) during the tasks led to lower CO2 pressure in the blood (hypocapnia), predominantly responsible for the measured changes in cerebral hemodynamics and oxygenation. In conclusion, our findings demonstrate that PETCO2 should be monitored during functional brain studies investigating speech using neuroimaging modalities, such as fNIRS, fMRI to ensure a correct interpretation of changes in hemodynamics and oxygenation.
► Effects of PaCO2 in functional brain studies have as yet been neglected. ► PaCO2 changed significantly and substantially during speech exercises. ► Inverse changes in blood circulation and oxygenation correlated to PaCO2. ► Previously inverse fNIRS/negative BOLD signals had not been attributed to PaCO2. ► PaCO2 is still underestimated as a potential confounder in functional brain studies.
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OBJECTIVE: The expression of vascular endothelial growth factor (VEGF) is elevated in diabetic macular edema (DME). Ranibizumab binds to and inhibits multiple VEGF variants. We investigated the ...safety and efficacy of ranibizumab in DME involving the foveal center. RESEARCH DESIGN AND METHODS: This was a 12-month, multicenter, sham-controlled, double-masked study with eyes (age >18 years, type 1 or 2 diabetes, central retinal thickness CRT ≥300 μm, and best corrected visual acuity BCVA of 73-39 ETDRS letters Early Treatment Diabetic Retinopathy Study) randomly assigned to intravitreal ranibizumab (0.3 or 0.5 mg; n = 51 each) or sham (n = 49). The treatment schedule comprised three monthly injections, after which treatment could be stopped/reinitiated with an opportunity for rescue laser photocoagulation (protocol-defined criteria). After month 1, dose-doubling was permitted (protocol-defined criteria, injection volume increased from 0.05 to 0.1 ml and remained at 0.1 ml thereafter). Efficacy (BCVA and CRT) and safety were compared between pooled ranibizumab and sham arms using the full analysis set (n = 151, patients receiving ≥1 injection). RESULTS: At month 12, mean ± SD BCVA improved from baseline by 10.3 ± 9.1 letters with ranibizumab and declined by 1.4 ± 14.2 letters with sham (P < 0.0001). Mean CRT reduction was 194.2 ± 135.1 μm with ranibizumab and 48.4 ± 153.4 μm with sham (P < 0.0001). Gain of ≥10 letters BCVA from baseline occurred in 60.8% of ranibizumab and 18.4% of sham eyes (P < 0.0001). Safety data were consistent with previous studies of intravitreal ranibizumab. CONCLUSIONS: Ranibizumab is effective in improving BCVA and is well tolerated in DME. Future clinical trials are required to confirm its long-term efficacy and safety.
Males and females of nearly all animals differ in their body size, a phenomenon called sexual size dimorphism (SSD). The degree and direction of SSD vary considerably among taxa, including among ...populations within species. A considerable amount of this variation is due to sex differences in body size plasticity. We examine how variation in these sex differences is generated by exploring sex differences in plasticity in growth rate and development time and the physiological regulation of these differences (e.g., sex differences in regulation by the endocrine system). We explore adaptive hypotheses proposed to explain sex differences in plasticity, including those that predict that plasticity will be lowest for traits under strong selection (adaptive canalization) or greatest for traits under strong directional selection (condition dependence), but few studies have tested these hypotheses. Studies that combine proximate and ultimate mechanisms offer great promise for understanding variation in SSD and sex differences in body size plasticity in insects.
(Invited Article)
Sexual size dimorphism (SSD) is widespread and variable among animals. According to the differential equilibrium model, SSD in a given species is expected to result if opposing ...selection forces equilibrate differently in both sexes. Here I review the factors that affect the evolution of SSD specifically as they relate to behavior. Taking the approach that SSD results as an epiphenomenon from separate but related selection on male and female body size, the advantages and disadvantages of large size in terms of the standard components of individual fitness (mating success, fecundity, viability, growth, foraging success) are discussed to help guiding future research on the subject. This includes a discussion of intra‐SSDs. The main conclusions are: (1) Evidence for disadvantages of large body size is still sparse and requires more research. In contrast, evidence for sexual or fecundity selection favoring large body size is overwhelming, so these mechanisms do no longer require special attention, but need to be documented nonetheless to acquire a complete picture. (2) Some hypotheses suggesting that small size is favored are not well investigated at all, because they apply only to some species or restricted situations, may be difficult to study, or have simply been disregarded. Evidence for these cryptic hypotheses is best revealed using experiments under multiple environmental (food, temperature, etc.) stresses with particularly well‐suited model species. (3) The evolution of SSD ultimately depends on processes generating variation within as well as between the sexes, so studies should always investigate and report effects on both sexes separately, in addition to size‐dependent effects within each sex; within sexes the key issue is whether small individuals under, over‐ or perfectly compensate their general fitness disadvantage. (4) Tests of several hypotheses should be integrated in case studies of well‐suited model species to investigate selection on body size comprehensively. For example, all episodes of sexual selection (mate search, competition, pre‐ and post‐copulatory choice) should be addressed in conjunction. Investigations of size‐selective and sex‐dependent predation should take the viewpoint of the prey rather than the predator to permit integration of effects throughout prey ontogeny generated by various predators with differing preferences. Comparative studies should also test multiple alternative hypotheses at the same time to permit stronger inference. (5) Experimental behavioral studies of sexual and natural selection should provide selection differentials using the available standard methods. This would allow integration with phenomenological studies of selection and facilitate subsequent meta‐analyses, which are very valuable in evaluating general patterns. (6) Comparative phylogenetic studies identifying patterns and phenomenological and experimental studies of model species that investigate particular mechanisms should be integrated, so that macro‐evolutionary patterns can be linked to micro‐evolutionary processes, which is the central paradigm of evolutionary ecology. (7) A major problem is the general difficulty of separating causes generating a particular body size and SSD over evolutionary time and its consequences for behavior and ecology today, i.e. today's researchers cannot completely avoid this ‘ghost of SSD evolution past’.
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5.
Comment on Pruitt & Krauel 2010 by JEB EiC Blanckenhorn, Wolf
Journal of evolutionary biology,
December 2021, 2021-12-00, 20211201, Volume:
34, Issue:
12
Journal Article
Peer reviewed
Open access
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The evolution of the vast diversity of floral volatiles is little understood, although they serve fundamental functions, such as pollinator attraction and herbivore deterrence. Floral volatiles are ...often species specific, yet highly variable and sensitive to environmental factors. To date, nothing is known about the heritability of floral volatiles, and whether individual compounds can evolve independently or solely in concert with the whole volatile bouquet.
We conducted bi-directional artificial selection on four target floral volatiles to estimate heritability and correlated pleiotropic responses in the wild turnip (Brassica rapa).
The realized heritability of the four target volatiles ranged from 20% to 45%. The average narrow-sense heritability of all 13 analyzed floral volatiles was 18% based on parent–offspring regressions. There were pleiotropic effects of the selected floral volatile compounds on other constituents of the floral scent bouquet, on flowering time and on some morphological traits. We found that the whole floral scent bouquet changed, even when there was selection only on single compounds, with the overall phenotypic covariance being unaffected.
Our study demonstrates that floral scent can evolve rapidly under phenotypic selection, but with additional correlated responses in traits that are not direct targets of selection.
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Uncovering genetic responses to selection in wild populations typically requires tracking individuals over generations and use of animal models. Our group monitored the body size of one Swiss Yellow ...Dung Fly (Scathophaga stercoraria; Diptera: Scathophagidae) field population over 15 years, including intermittent common-garden rearing in the laboratory to assess body size with minimized environmental and maximized genetic variation. Contrary to expectations based on repeated heritability and phenotypic selection assessments over the years (reported elsewhere), field body sizes declined by >10% and common-garden laboratory sizes by >5% from 1993 to 2009. Our results confirm the temperature-size rule (smaller when warmer) and, albeit entirely correlational, could be mediated by climate change, as over this period mean temperature at the site increased by 0.5°C, although alternative systematic environmental changes cannot be entirely excluded. Monitoring genetic responses to selection in wild invertebrate populations is thus possible, though indirect, and wild populations may evolve in directions not consistent with strongly positive directional selection favoring large body size.
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Thermal performance curves (TPCs) have been estimated in multiple ectotherm species to understand their thermal plasticity and adaptation and to predict the effect of global warming. However, TPCs ...are typically assessed under constant temperature regimes, so their reliability for predicting thermal responses in the wild where temperature fluctuates diurnally and seasonally remains poorly documented.
Here, we use distant latitudinal populations of five species of sepsid flies (Diptera: Sepsidae) from the temperate region (Europe, North Africa, North America) to compare estimates derived from constant TPCs with observed development rate under fluctuating temperatures in laboratory and field conditions.
TPCs changed across gradients in that flies originating from higher latitudes showed accelerated development at higher temperatures, an adaptive response. TPCs were then used to predict development rates observed under fluctuating temperatures; these predictions were relatively accurate in the laboratory but not the field. Interestingly, the precision of TPC predictions depended not only on the resolution of temperature data, with daily and overall temperature summing performing better than hourly temperature summing, but also on the frequency of temperatures falling below the estimated critical minimum temperature. Hourly temperature resolution most strongly underestimated actual development rates, because flies apparently either did not stop growing when temperatures dropped below this threshold, or they sped up their growth when the temperature rose again, thus most severely reflecting this error.
We conclude that when flies do not encounter cold temperatures, TPC predictions based on constant temperatures can accurately reflect performance under fluctuating temperatures if adequately adjusted for nonlinearities, but when encountering cold temperatures, this method is more error‐prone.
Our study emphasizes the importance of the resolution of temperature data and cold temperatures in shaping thermal reaction norms.
Thermal performance curve (TPC) can be used to predict the response of ectotherms to thermal changes. This study, carried out on coprophagous flies, highlights the usefulness and limitations of TPC in predicting the effect of temperature fluctuations on development rate under laboratory and field conditions.
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Sexual size dimorphism (SSD) arises when the net effects of natural and sexual selection on body size differ between the sexes. Quantitative SSD variation between taxa is common, but directional ...intraspecific SSD reversals are rare. We combined micro- and macroevolutionary approaches to study geographic SSD variation in closely related black scavenger flies. Common garden experiments revealed stark intra- and interspecific variation: Sepsis biflexuosa is monomorphic across the Holarctic, while S. cynipsea (only in Europe) consistently exhibits female-biased SSD. Interestingly, S. neocynipsea displays contrasting SSD in Europe (females larger) and North America (males larger), a pattern opposite to the geographic reversal in SSD of S. punctum documented in a previous study. In accordance with the differential equilibrium model for the evolution of SSD, the intensity of sexual selection on male size varied between continents (weaker in Europe), whereas fecundity selection on female body size did not. Subsequent comparative analyses of 49 taxa documented at least six independent origins of male-biased SSD in Sepsidae, which is likely caused by sexual selection on male size and mediated by bimaturism. Therefore, reversals in SSD and the associated changes in larval development might be much more common and rapid and less constrained than currently assumed.
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In a study by Law and colleagues recently published in Neuroimage, the authors reported that wearing a surgical mask during an fMRI scan leads to a statistically significant subject-specific change ...(30%) in the baseline BOLD level in gray matter, although the response to a sensory-motor task was unaffected. An average increase in end-tidal CO2 of 7.4% was found when wearing a mask, despite little support in the literature for major effects of mask wearing on blood gas levels. We comment on these findings, point out a several relevant limitations of the study design and provide alternative interpretations of these data.
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