Maintainence of Primary Human Hepatocyte Function In Vitro by Extracellular Matrix Biologic Scaffolds

Liver disease is a leading cause of mortality in the United States. Tissue engineering and regenerative medicine (TE&RM) approaches to treating liver disease have the potential to provide temporary support with biohybrid artificial liver-assist devices or long-term therapy by replacing the diseased liver with functional tissue-engineered constructs that utilize a combination of cells, scaffolds and bioactive factors. A rate-limiting step for TE&RM technologies has been the loss of hepatocyte-specific functions in vitro after hepatocytes are isolated from their highly specialized in vivo microenvironment. The identification of a biologic substrate that can maintain a functional hepatocyte differentiation profile during in vitro culture would advance potential TE&RM therapeutic strategies. The present study is predicated upon the hypothesis that the substrate upon which hepatocytes are seeded is a critical determinant of cell phenotype and function. Biologic scaffolds composed of extracellular matrix (ECM) derived from mammalian organs have been used to maintain cell phenotype in vitro. Two studies were performed to evaluate the ability of ECM scaffolds to maintain primary human hepatocyte (PHH) phenotype in vitro. The first study evaluated the effect of ECM scaffolds derived from porcine liver (PLECM) and human liver (HLECM) upon maintainence of PHH specific functions in vitro. Cytochrome P450 activity and albumin secretion were used as indicators of hepatocyte functionality. No differences in hepatoycte-specific functions were measured when comparing PHH cultured with PLECM and HLECM. From a clinical perspective, the results are appealing because of the limited availability of human liver tissue compared to porcine liver tissue for the manufacture of ECM scaffolds.The second study cultured PHH between two layers of PLECM and compared with Matrigel double gel cultures and adsorbed type-1 collagen. Albumin secretion, hepatic transport activity and ammonia metabolism were used as markers of hepatocyte functionality. PHH cultured between two layers of porcine liver ECM had significantly higher levels of albumin secretion, hepatic transport activity, and ammonia metabolism compared to PHH cultured on collagen

Effects of collagen orientation on the medium-term fatigue response of heart valve biomaterials

Worldwide 275,000 diseased heart valves are replaced annually and approximately 50% are bioprosthetic heart valves (BHV). BHV are fabricated from biologically derived tissues chemically modified to reduce immunogenecity and improve durability. BHV are nonviable, non-renewing biomaterials that undergo progressive degenerative changes in-vivo resulting in durability issues, which can be due to both calcific and non-calcific mechanisms. In-vitro durability testing of intact valves up to 200x106 cycles is used to assess BHV durability. In-vitro durability testing confounds characterization and modeling of fatigue. Thus there is a need for elucidation of the underlying mechanisms in the BHV response to repeated cyclic loading (RCL), independent of BHV design. In this study, the effects of collagen orientation on the medium-term (up to 50x106 cycles) BHV RCL response was investigated. Glutaraldehyde treated bovine pericardium were subjected to cyclic tensile loading to stress levels of 500±50 kPa at a frequency of 22 Hz. Two specimen groups were examined, with the preferred collagen fiber direction parallel (PD) and perpendicular (XD) to the direction of loading. Small angle light scattering (SALS) was used to assess the degree of fiber reorientation of the BHV collagenous network after 0 and 50x106 cycles. After 0, 20x106 and 50x106 cycles, specimens were subjected to biaxial mechanical testing and Fourier transform IR spectroscopy (FT-IR) was performed to assess molecular level changes to collagen . In addition, and the collagen fiber crimp period was also measured. Substantial permanent set effects were observed in both groups. In the perpendicular group, the areal stretch, which is a measure of overall tissue compliance, increased significantly while in the parallel group the areal stretch decreased significantly after 50x106 cycles. After 50x106 cycles, SALS measurements revealed that in the perpendicular group, the collagenous fibers became less aligned and in the parallel group, the collagen fibers became more highly aligned. The only significant changes in collagen crimp were an increase in collage crimp period from 23.46±1.39 mm (at 0 cycles) to 28.14±0.84 mm after 20x106 cycles in the parallel group. FT-IR spectra indicated that RCL of both of the groups lead to collagen conformational changes and early denaturation after 20x106 cycles. The results of this study suggest that 1) collagen orientation plays a critical role in BHV fatigue response, and 2) chemical fixation technologies that allow greater fiber mobility under functional stresses yet without permanent set effects may yield more durable materials

Perception of Sunflecks by the UV-B Photoreceptor UV RESISTANCE LOCUS8

Sunflecks, transient patches of light that penetrate through gaps in the canopy and transiently interrupt shade, are eco-physiologically and agriculturally important sources of energy for carbon gain, but our molecular understanding of how plant organs perceive and respond to sunflecks through photoreceptors remains limited. The UV-B photoreceptor UV RESISTANCE LOCUS8 (UVR8) is a recent addition to the list of plant photosensory receptors, and we have made considerable advances in our understanding of the physiology and molecular mechanisms of action of UVR8 and its signaling pathway. However, the function of UVR8 in the natural environment is poorly understood. Here, we show that the UVR8 dimer/monomer ratio responds quantitatively and reversibly to the intensity of sunflecks that interrupt shade in the field. Sunflecks reduced hypocotyl growth and increased CHALCONE SYNTHASE (CHS) and ELONGATED HYPOCOTYL5 gene expression and CHS protein abundance in wild-type Arabidopsis (Arabidopsis thaliana) seedlings, but the uvr8 mutant was impaired in these responses. UVR8 was also required for normal nuclear dynamics of CONSTITUTIVELY PHOTOMORPHOGENIC1. We propose that UVR8 plays an important role in the plant perception of and response to sunflecks.Fil: Moriconi, Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Binkert, Melanie. Universidad de Ginebra; SuizaFil: Costigliolo Rojas, María Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Sellaro, Romina Vanesa. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Ulm, Roman. Universidad de Ginebra. Facultad de Ciencias; SuizaFil: Casal, Jorge José. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentin

When co-action eliminates the Simon effect: Disentangling the impact of co-actor' s presence and task sharing on joint-task performance.

Thisstudyaimedatassessingwhetherthemerebeliefofperformingataskwithanotherperson,whoisinchargeofthecomplementarypartofthetask,issufficientfortheso-calledjointSimoneffecttooccur.Inallthreeexperimentsofthestudy,participantssataloneinaroomandunderwenttwoconsecutiveGo/NoGotasksthatwereidenticalexceptfortheinstructions.InExperiment1,participantsperformedthetaskfirstindividually(baselinetask),andtheneitherco-actingwithanotherpersonwhorespondedfromanunknownlocationtotheNoGostimuli(jointtask)orimagingthemselvesrespondingtotheNoGostimuli(imaginativetask).Relativetothebaseline,theinstructionsoftheimaginativetaskmadetheSimoneffectoccur,whilethoseofthejointtaskwereineffectiveinelicitingtheeffect.Thisresultsuggeststhatsharingataskwithapersonwhoisknowntobeinchargeofthecomplementarytask,butisnotphysicallypresent,isnotsufficienttoinducetherepresentationofanalternativeresponseabletoproduceinterference,whichhappensinsteadwhentheinstructionsexplicitlyrequiretoimaginesucharesponse.Interestingly,weobservedthatwhentheSimoneffectwasalreadypresentinthebaselinetask(i.e.,whentheresponsealternativetotheGoresponsewasrepresentedintheindividualtaskduetonon-socialfactors),itdisappearedinthejointtask.Weproposethat,whennoinformationabouttheco-actor’spositionisavailable,thedivisionoflaborbetweentheparticipantandco-actorallowsparticipantstofilteroutthepossible(incidental)representationofthealternativeresponsefromtheirtaskrepresentation,thuseliminatingpotentialsourcesofinterference.ThisaccountissupportedbytheresultsofExperiments2and3andsuggeststhatundercertaincircumstancestask-sharingmayreducetheinterferenceproducedbytheirrelevantinformation,ratherthanincreaseit

Repression of shade-avoidance reactions by sunfleck induction of HY5 expression in Arabidopsis

The light environment provides signals that play a critical role in the control of stem growth in plants. The reduced irradiance and altered spectral composition of shade light promote stem growth compared with unfiltered sunlight. However, whereas most studies have used seedlings exposed to contrasting but constant light treatments, the natural light environment may exhibit strong fluctuations. As a result of gaps in the canopy, plants shaded by neighbours may experience sunflecks, i.e. brief periods of exposure to unfiltered sunlight. Here, we show that sunflecks are perceived by phytochromes A and B, and inhibit hypocotyl growth in Arabidopsis thaliana mainly if they occur during the final portion of the photoperiod. By using forward and reverse genetic approaches we found that ELONGATED HYPOCOTYL 5, LATE ELONGATED HYPOCOTYL, PHYTOCHROME KINASE SUBSTRATE 4 and auxin signalling are key players in this response.Fil: Sellaro, Romina Vanesa. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Yanovsky, Marcelo Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Casal, Jorge José. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentin

"Unfocus" on foc.us: Commercial tDCS headset impairs working memory

In this study, we tested whether the commercial transcranial direct current stimulation (tDCS) headset foc.us improves cognitive performance, as advertised in the media. A single-blind, sham-controlled, within-subject design was used to assess the effect of online and off-line foc.us tDCS—applied over the prefrontal cortex in healthy young volunteers (n = 24) on working memory (WM) updating and monitoring. WM updating and monitoring, as assessed by means of the N-back task, is a cognitive-control process that has been shown to benefit from interventions with CE-certified tDCS devices. For both online and off-line stimulation protocols, results showed that active stimulation with foc.us, compared to sham stimulation, significantly decreased accuracy performance in a well-established task tapping WM updating and monitoring. These results provide evidence for the important role of the scientific community in validating and testing far-reaching claims made by the brain training industry

A randomized controlled trial to test the effect of multispecies probiotics on cognitive reactivity to sad mood

AbstractBackground: Recent insights into the role of the human microbiota in cognitive and affective functioning have led to the hypothesis that probiotic supplementation may act as an adjuvant strategy to ameliorate or prevent depression. Objective: Heightened cognitive reactivity to normal, transient changes in sad mood is an established marker of vulnerability to depression and is considered an important target for interventions. The present study aimed to test if a multispecies probiotic containing Bifidobacterium bifidum W23, Bifidobacterium lactis W52, Lactobacillus acidophilus W37, Lactobacillus brevis W63, Lactobacillus casei W56, Lactobacillus salivarius W24, and Lactococcus lactis (W19 and W58) may reduce cognitive reactivity in non-depressed individuals. Design: In a triple-blind, placebo-controlled, randomized, pre- and post-intervention assessment design, 20 healthy participants without current mood disorder received a 4-week probiotic food-supplement intervention with the multispecies probiotics, while 20 control participants received an inert placebo for the same period. In the pre- and post-intervention assessment, cognitive reactivity to sad mood was assessed using the revised Leiden index of depression sensitivity scale. Results: Compared to participants who received the placebo intervention, participants who received the 4-week multispecies probiotics intervention showed a significantly reduced overall cognitive reactivity to sad mood, which was largely accounted for by reduced rumination and aggressive thoughts. Conclusion: These results provide the first evidence that the intake of probiotics may help reduce negative thoughts associated with sad mood. Probiotics supplementation warrants further research as a potential preventive strategy for depression

Hysteresis in PHYTOCHROME-INTERACTING FACTOR 4 and EARLY-FLOWERING 3 dynamics dominates warm daytime memory in Arabidopsis

Despite the identification of temperature sensors and downstream components involved in promoting stem growth by warm temperatures, when and how previous temperatures affect current plant growth remain unclear. Here we show that hypocotyl growth in Arabidopsis thaliana during the night responds not only to the current temperature but also to preceding daytime temperatures, revealing a short-term memory of previous conditions. Daytime temperature affected the levels of PHYTOCHROME-INTERACTING FACTOR 4 (PIF4) and LONG HYPOCOTYL 5 (HY5) in the nucleus during the next night. These factors jointly accounted for the observed growth kinetics, whereas nighttime memory of prior daytime temperature was impaired in pif4 and hy5 mutants. PIF4 promoter activity largely accounted for the temperature-dependent changes in PIF4 protein levels. Notably, the decrease in PIF4 promoter activity triggered by cooling required a stronger temperature shift than the increase caused by warming, representing a typical hysteretic effect; this hysteretic pattern required EARLY-FLOWERING 3 (ELF3). Warm temperatures promoted the formation of nuclear condensates of ELF3 in hypocotyl cells during the afternoon but not in the morning. These nuclear speckles showed poor sensitivity to subsequent cooling. We conclude that ELF3 achieves hysteresis and drives the PIF4 promoter into the same behavior, enabling a short-term memory of daytime temperature conditions.Fil: Murcia, Mauro Germán. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Nieto, Cristina. Consejo Superior de Investigaciones Científicas. Centro Nacional de Biotecnología; EspañaFil: Sellaro, Romina Vanesa. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Prat, Salomé. Consejo Superior de Investigaciones Científicas. Centro Nacional de Biotecnología; EspañaFil: Casal, Jorge José. Fundación Instituto Leloir; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentin

Phytochrome B dynamics departs from photoequilibrium in the field

Vegetation shade is characterized by marked decreases in the red/far‐red ratio and photosynthetic irradiance. The activity of phytochrome in the field has typically been described by its photoequilibrium, defined by the photochemical properties of the pigment in combination with the spectral distribution of the light. This approach represents an oversimplification because phytochrome B (phyB) activity depends not only on its photochemical reactions but also on its rates of synthesis, degradation, translocation to the nucleus, and thermal reversion. To account for these complex cellular reactions, we used a model to simulate phyB activity under a range of field conditions. The model provided values of phyB activity that in turn predicted hypocotyl growth in the field with reasonable accuracy. On the basis of these observations, we define two scenarios, one is under shade, in cloudy weather, at the extremes of the photoperiod or in the presence of rapid fluctuations of the light environment caused by wind‐induced movements of the foliage, where phyB activity departs from photoequilibrium and becomes affected by irradiance and temperature in addition to the spectral distribution. The other scenario is under full sunlight, where phyB activity responds mainly to the spectral distribution of the light.Fil: Sellaro, Romina Vanesa. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Smith, Robert W.. University of Agriculture Wageningen; Países BajosFil: Legris, Martina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Fleck, Christian. University of Agriculture Wageningen; Países Bajos. Eidgenössische Technische Hochschule Zürich; SuizaFil: Casal, Jorge José. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; Argentin