The redundant target paradigm and its use as a blindsight-test: A meta-analytic study.

The redundant target effect (RTE) is the well-known effect whereby a single target is detected faster when a second, redundant target is presented simultaneously. The RTE was shown in different experimental designs and applied in various clinical contexts. However, there are also studies showing non-effects or effects in the opposite direction. Our meta-analysis aims to investigate the replicability of the RTE. Herein, we focused on the clinical context within which the RTE has been applied most often and for which it gained particular prominence: The research on blindsight and other forms of residual vision in patients with damage to the neuronal visual system. The application of the RTE in clinical contexts assumes that whenever vision is present, an RTE will be found. Put differently, the RTE as a tool to uncover residual vision presumes that the RTE is a consistent feature of vision in the healthy population. We found a significant summary effect size of the RTE in healthy participants. The effect size depended on certain experimental features: task type, target configuration in the redundant condition, and how reaction times were computed in the single condition. A specific feature combination is typically used in blindsight research. Analyzing studies with this feature combination revealed a significant summary effect size in healthy participants predicting positive RTEs for future studies. A power-analysis revealed a required sample size of 14 participants to obtain an RTE with high reliability. However, the required sample size is rarely reached in blindsight research. Rather, blindsight research is mostly based on single-case studies. In summary, the RTE is a robust effect on group level but does not occur in every single individual. This means failure to obtain an RTE in a single patient should not be interpreted as evidence for the absence of residual vision in this patient.

How to test blindsight without light scatter artefacts?

light scatter artefacts are a methodological problem in testing residual visual capacities (RVCs), for instance blindsight, in patients with homonymous visual field defects (HVFDs). The term light scatter artefact describes the phenomenon that light from targets directed towards the HVFD can stray into the sighted visual field. This might enable an observer to respond correctly to information directed at her blind field despite the fact that she is unable to process that information in the blind field itself. In this manuscript, we present a review of the relevance of light scatter in visual neuroscience, discuss factors that influence the impact of light scatter and evaluate means to test for light scatter artefacts. Furthermore, we present findings from an empirical study that was aimed at developing tests for RVCs that are free of light scatter artefacts. Previous studies on light scatter only used small sample sizes and equipment that is no longer in use. Hence, their results cannot be generalized to future experiments making it necessary to run laborious light scatter tests for every new study on RVCs. To avoid this, we hereby start a pool of stimuli and paradigms which demonstrably do not elicit light scatter artefacts. To this end, we investigated 21 healthy young participants in three frequently used RVC-paradigms: (1) temporal 2AFC task, (2) movement direction discrimination, and (3) redundant target paradigm. For each paradigm, we applied the blind-spot method. But first, we had to establish that our testing paradigm was sufficiently sensitive to detect light scatter artefacts. For this, we used conditions that are known to produce strong light scatter and a paradigm that is very sensitive to such effects. Specifically, we presented white targets on a black background in a dark room. The stimuli were presented to observers' blind spot. To check for light scatter artefacts, we used a target-detection task in a temporal 2AFC format. We obtained clear light scatter artefacts. Participants produced reliably above-chance detection performance under these conditions. The other two luminance conditions, measured in an illuminated room, did not produce light scatter artefacts. Accuracy in the temporal 2AFC task was at chance level for white targets on a grey background at the blind-spot position. Additionally, black targets on a grey background avoided light scatter artefacts in all three RVC-paradigms. In future, researchers can apply these stimulus and illumination conditions when using one of the three above paradigms in their studies. Using these conditions, they will be able to avoid light scatter artefacts without having to perform their own blind-spot tests.

Groundwater Chemistry Has a Greater Influence on the Mobility of Nanoparticles Used for Remediation than the Chemical Heterogeneity of Aquifer Media.

The application of nanoscale zerovalent iron (nano-ZVI) particles for groundwater remediation has spurred research into the influence of the collector heterogeneity on the nano-ZVI mobility. The chemical heterogeneity of surfaces within aquifer media affects their surface charge distribution and their affinity for nano-ZVI. The groundwater chemistry affects the properties of both aquifer surfaces and the nano-ZVI particles. Commercial poly(acrylic acid)-coated nano-ZVI (PAA-nano-ZVI) particles were tested in column experiments using two solution chemistries and silica collectors with different degrees of chemical heterogeneity, achieved by ferrihydrite coating. A porous media filtration model was used to determine the attachment efficiency of PAA-nano-ZVI particles, and the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory was used to describe the interactions between PAA-nano-ZVI particles and the aquifer "collectors". The mobility of PAA-nano-ZVI particles suspended in ultrapure water depended on the extent of ferrihydrite coating on the collector surfaces. The mobility of PAA-nano-ZVI particles under environmentally relevant conditions was independent of the collector chemical heterogeneity. The size of PAA-nano-ZVI aggregates doubled, inducing gravitational sedimentation and possibly straining as mechanisms of particle deposition. There was no repulsive energy barrier between particles and collectors, and the DLVO theory was unable to explain the observed particle attachment. Our results suggest that the groundwater chemistry has a greater influence on the mobility of PAA-nano-ZVI particles than the collector chemical heterogeneity. A better understanding of polymer adsorption to nanoparticles and its conformation under natural groundwater conditions is needed to further elucidate nanoparticle-collector interactions.

Gaze-contingent stimulus removal leads to subsequent changes in overt attentional allocation.

Spatial neglect is a debilitating neurological disorder marked by reduced exploration of contralesional space. We developed an intervention in which eye movements to and within one half of a search display were reduced over the course of several hundred trials. The aim of this study was to determine whether this intervention had an effect on the deployment of attention of healthy participants as a first step towards application in patients. The participants carried out a visual search task during which the stimuli in one half of the search display were removed whenever the participants made eye movements towards it. The stimuli in the other half were unaffected by eye movements. Indeed, this led to a steady relative decrease in fixations within the affected half over the course of the intervention. In five experiments, the performance in different spatial attention paradigms was measured before and after this intervention. In two visual search paradigms (feature and conjunction search), exploration of the affected half decreased compared to the unaffected half. In a Posner task with exogenous cues, a partial effect of the intervention was found. However, an attempt at replicating this effect was not successful. The fifth experiment showed that performance in a line bisection paradigm was not significantly influenced by the intervention. To conclude, the intervention showed the potential to influence the behavior of healthy participants in overt attentional exploration tasks.

Optimising the transport properties and reactivity of microbially-synthesised magnetite for in situ remediation.

Engineered nanoparticles offer the potential for remediation of land and water that has been contaminated by organics and metals. Microbially synthesized nano-scale magnetite, prepared from Fe(III) oxides by subsurface Fe(III)-reducing bacteria, offers a scalable biosynthesis route to such a nano-scale remediation reagent. To underpin delivery of "bionanomagnetite" (BNM) nanomaterial during in situ treatment options, we conducted a range of batch and column experiments to assess and optimise the transport and reactivity of the particles in porous media. Collectively these experiments, which include state of the art gamma imaging of the transport of 99m Tc-labelled BNM in columns, showed that non-toxic, low cost coatings such as guar gum and salts of humic acid can be used to enhance the mobility of the nanomaterial, while maintaining reactivity against target contaminants. Furthermore, BNM reactivity can be enhanced by the addition of surface coatings of nano-Pd, extending the operational lifetime of the BNM, in the presence of a simple electron donor such as hydrogen or formate.

Effect of field site hydrogeochemical conditions on the corrosion of milled zerovalent iron particles and their dechlorination efficiency.

Milled zerovalent iron (milled ZVI) particles have been recognized as a promising agent for groundwater remediation because of (1) their high reactivity with chlorinated aliphatic hydrocarbons, organochlorine pesticides, organic dyes, and a number of inorganic contaminants, and (2) a possible greater persistance than the more extensively investigated nanoscale zerovalent iron. We have used laboratory-scale batch degradation experiments to investigate the effect that hydrogeochemical conditions have on the corrosion of milled ZVI and on its ability to degrade trichloroethene (TCE). The observed pseudo first-order degradation rate constants indicated that the degradation of TCE by milled ZVI is affected by groundwater chemistry. The apparent corrosion rates of milled ZVI particles were of the same order of magnitude for hydrogeochemical conditions representative for two contaminated field sites (133-140mmolkg-1day-1, indicating a milled ZVI life-time of 128-135days). Sulfate enhances milled ZVI reactivity by removing passivating iron oxides and hydroxides from the Fe0 surface, thus increasing the number of reactive sites available. The organic matter content of 1.69% in the aquifer material tends to suppress the formation of iron corrosion precipitates. Results from scanning electron microscopy, X-ray diffraction, and iron K-edge X-ray adsorption spectroscopy suggest that the corrosion mechanisms involve the partial dissolution of particles followed by the formation and surface precipitation of magnetite and/or maghemite. Numerical corrosion modeling revealed that fitting iron corrosion rates and hydrogen inhibitory terms to hydrogen and pH measurements in batch reactors can reduce the life-time of milled ZVI particles by a factor of 1.2 to 1.7.

Impact of Sodium Humate Coating on Collector Surfaces on Deposition of Polymer-Coated Nanoiron Particles.

The affinity between nanoscale zerovalent iron (nano-ZVI) and mineral surfaces hinders its mobility, and hence its delivery into contaminated aquifers. We have tested the hypothesis that the attachment of poly(acrylic acid)-coated nano-ZVI (PAA-nano-ZVI) to mineral surfaces could be limited by coating such surfaces with sodium (Na) humate prior to PAA-nano-ZVI injection. Na humate was expected to form a coating over favorable sites for PAA-nano-ZVI attachment and hence reduce the affinity of PAA-nano-ZVI for the collector surfaces through electrosteric repulsion between the two interpenetrating charged polymers. Column experiments demonstrated that a low concentration (10 mg/L) Na humate solution in synthetic water significantly improved the mobility of PAA-nano-ZVI within a standard sand medium. This effect was, however, reduced in more heterogeneous natural collector media from contaminated sites, as not an adequate amount of the collector sites favorable for PAA-nano-ZVI attachment within these media appear to have been screened by the Na humate. Na humate did not interact with the surfaces of acid-washed glass beads or standard Ottawa sand, which presented less surface heterogeneity. Important factors influencing the effectiveness of Na humate application in improving PAA-nano-ZVI mobility include the solution chemistry, the Na humate concentration, and the collector properties.

Agar agar-stabilized milled zerovalent iron particles for in situ groundwater remediation.

Submicron-scale milled zerovalent iron (milled ZVI) particles produced by grinding macroscopic raw materials could provide a cost-effective alternative to nanoscale zerovalent iron (nZVI) particles for in situ degradation of chlorinated aliphatic hydrocarbons in groundwater. However, the aggregation and settling of bare milled ZVI particles from suspension presents a significant obstacle to their in situ application for groundwater remediation. In our investigations we reduced the rapid aggregation and settling rate of bare milled ZVI particles from suspension by stabilization with a "green" agar agar polymer. The transport potential of stabilized milled ZVI particle suspensions in a diverse array of natural heterogeneous porous media was evaluated in a series of well-controlled laboratory column experiments. The impact of agar agar on trichloroethene (TCE) removal by milled ZVI particles was assessed in laboratory-scale batch reactors. The use of agar agar significantly enhanced the transport of milled ZVI particles in all of the investigated porous media. Reactivity tests showed that the agar agar-stabilized milled ZVI particles were reactive towards TCE, but that their reactivity was an order of magnitude less than that of bare, non-stabilized milled ZVI particles. Our results suggest that milled ZVI particles could be used as an alternative to nZVI particles as their potential for emplacement into contaminated zone, their reactivity, and expected longevity are beneficial for in situ groundwater remediation.

Mechanical fibrinogen-depletion supports heparin-free mesenchymal stem cell propagation in human platelet lysate.

BACKGROUND: Pooled human platelet lysate (pHPL) is an efficient alternative to xenogenic supplements for ex vivo expansion of mesenchymal stem cells (MSCs) in clinical studies. Currently, porcine heparin is used in pHPL-supplemented medium to prevent clotting due to plasmatic coagulation factors. We therefore searched for an efficient and reproducible medium preparation method that avoids clot formation while omitting animal-derived heparin. METHODS: We established a protocol to deplete fibrinogen by clotting of pHPL in medium, subsequent mechanical hydrogel disruption and removal of the fibrin pellet. After primary culture, bone-marrow and umbilical cord derived MSCs were tested for surface markers by flow cytometry and for trilineage differentiation capacity. Proliferation and clonogenicity were analyzed for three passages. RESULTS: The proposed clotting procedure reduced fibrinogen more than 1000-fold, while a volume recovery of 99.5 % was obtained. All MSC types were propagated in standard and fibrinogen-depleted medium. Flow cytometric phenotype profiles and adipogenic, osteogenic and chondrogenic differentiation potential in vitro were independent of MSC-source or medium type. Enhanced proliferation of MSCs was observed in the absence of fibrinogen but presence of heparin compared to standard medium. Interestingly, this proliferative response to heparin was not detected after an initial contact with fibrinogen during the isolation procedure. CONCLUSIONS: Here, we present an efficient, reproducible and economical method in compliance to good manufacturing practice for the preparation of MSC media avoiding xenogenic components and suitable for clinical studies.

Measuring the reactivity of commercially available zero-valent iron nanoparticles used for environmental remediation with iopromide.

The high specific surface area and high reactivity of nanoscale zero-valent iron (nZVI) particles have led to much research on their application to environmental remediation. The reactivity of nZVI is affected by both the water chemistry and the properties of the particular type of nZVI particle used. We have investigated the reactivity of three types of commercially available Nanofer particles (from Nanoiron, s.r.o., Czech Republic) that are currently either used in, or proposed for use in full scale environmental remediation projects. The performance of one of these, the air-stable and thus easy-to-handle Nanofer Star particle, has not previously been reported. Experiments were carried out first in batch shaking reactors in order to derive maximum reactivity rates and provide a rapid estimate of the Nanofer particle's reactivity. The experiments were performed under near-natural environmental conditions with respect to the pH value of water and solute concentrations, and results were compared with those obtained using synthetic water. Thereafter, the polyelectrolyte-coated Nanofer 25S particles (having the highest potential for transport within porous media) were chosen for the experiments in column reactors, in order to elucidate nanoparticle reactivity under a more field-site realistic setting. Iopromide was rapidly dehalogenated by the investigated nZVI particles, following pseudo-first-order reaction kinetics that was independent of the experimental conditions. The specific surface area normalized reaction rate constant (kSA) value in the batch reactors ranged between 0.12 and 0.53Lm(-2)h(-1); it was highest for the uncoated Nanofer 25 particles, followed by the polyacrylic acid-coated Nanofer 25S and air-stable Nanofer Star particles. In the batch reactors all particles were less reactive in natural water than in synthetic water. The kSA values derived from the column reactor experiments were about 1000 times lower than those from the batch reactors, ranging between 2.6×10(-4) and 5.7×10(-4)Lm(-2)h(-1). Our results revealed that the easy-to-handle and air-stable Nanofer Star particles are the least reactive of all the Nanofer products tested. The reaction kinetics predicted by column experiments were more realistic than those predicted by batch experiments and these should therefore be used when designing a full-scale field application of nanomaterials for environmental remediation.

Iron depletion with a novel apheresis system in patients with hemochromatosis.

BACKGROUND: Phlebotomy represents the standard treatment option for iron overload in hemochromatosis (HC). Recently, red blood cell (RBC) apheresis has increasingly been used to remove iron. In this study we evaluated the depletion program of the newly developed Spectra Optia device. STUDY DESIGN AND METHODS: Adult male patients (n = 11) with HC were RBC depleted with the Spectra Optia device (Terumo BCT). In total, 24 procedures were performed. A volume of 300 to 550 mL of RBCs was withdrawn per single treatment. RESULTS: No significant adverse events were recorded. A median blood volume of 857.3 ± 23.3 mL was processed. The median procedure time was 12.0 ± 0.4 minutes. The mean reduction of Hct value in each procedure was approximately 6% (Hct pre 42.6 ± 0.5% vs. Hct post 36.6 ± 0.6%) and iron removed per procedure was 405.2 ± 23.3 mg. CONCLUSION: The Spectra Optia device proved to be highly efficient in depleting RBCs in HC patients and allows for short procedure time. The Optia device can be safely used in this clinical setting. We recommend its use in case of severe iron overload if rapid iron depletion needs to be achieved and in case of cardiac compromise due to less blood volume removed.

Targeting of the hNC16A collagen domain to dendritic cells induces tolerance to human type XVII collagen.

Antibodies, specific to murine DEC205, can be used to target antigens to dendritic cells. The immunodominant domain of human type XVII collagen, hNC16A, was fused to this antibody (DEC-hNC16A) and was administered as expression plasmid by gene gun transfection with the aim of inducing tolerance to human type XVII collagen in a skin transplantation model. Mice transfected with DEC-hNC16A were challenged with skin grafts from transgenic mice engineered to express human type XVII collagen. Graft survival was either prolonged or grafts were accepted infinitely (33% and 16%, respectively) upon treatment with DEC-hNC16A while 100% of grafts were rejected in untreated controls. Graft acceptance was associated with the absence of a CD4+ infiltrate and a dense CD8+ T-cell infiltrate and was not strictly dependent on antibody production. Our results show that DEC-hNC16A targets dendritic cells in vivo leading to prolonged survival of transgenic skin grafts. This indicates that DEC205-targeting may be used for the induction of tolerance to skin antigens, which would increase the chances of successful skin gene therapy of epidermolysis bullosa patients.

Transcutaneous gene gun delivery of hNC16A Induces BPAG2-specific tolerance.

Immune recognition and rejection of tissues expressing transfected genes is a major complication of gene replacement therapy for inherited genetic disorders. Owing to the high immunogenicity of human bullous pemphigoid antigen 2 (hBPAG2), the induction and maintenance of tolerance to this neo-antigen is essential to deliver the gene product to patients with epidermolysis bullosa junctionalis. In a skin grafting mouse model, we used gene gun transfection with a construct encoding hNC16A, the immunodominant domain of hBPAG2, to induce antigen-specific immune tolerance. Eighty percent of wild-type mice transfected with hNC16A showed long-term survival of skin grafts expressing hBPAG2. Tolerance was stable and transferable by T cells but not by B cells of tolerant mice to naive hosts. A dense Foxp3(+) regulatory T-cell (T(reg)) infiltrate was noticed in grafts of tolerant mice and depletion of these cells resulted in a loss of tolerance. Taken together, we show that long-lasting hBPAG2-specific tolerance was induced with gene gun delivery of hNC16A through a T(reg)-dependent mechanism. This is of relevance to patients undergoing gene therapy and has broader implications for the treatment of antigen-specific autoimmune diseases.

HAX1 deficiency: impact on lymphopoiesis and B-cell development.

HAX1 was originally described as HS1-associated protein with a suggested function in receptor-mediated apoptotic and proliferative responses of lymphoid cells. Recent publications refer to a complex and multifunctional role of this protein. To investigate the in vivo function of HAX1 (HS1-associated protein X1) in B cells, we generated a Hax1-deficient mouse strain. Targeted deletion of Hax1 resulted in premature death around the age of 12 wk accompanied by a severe reduction of lymphocytes in spleen, thymus and bone marrow. In the bone marrow, all B-cell populations were lost comparably. In the spleen, B220(+) cells were reduced by almost 70%. However, as investigated by adoptive transfer experiments, this impairment is not exclusively B-cell intrinsic and we hypothesize that a HAX1-deficient environment cannot sufficiently provide the essential factors for proper lymphocyte development, trafficking and survival. Hax1(-/-) B cells show a significantly reduced expression of CXCR4, which might have an influence on the observed defects in B-cell development.

HPK1 associates with SKAP-HOM to negatively regulate Rap1-mediated B-lymphocyte adhesion.

BACKGROUND: Hematopoietic progenitor kinase 1 (HPK1) is a Ste20-related serine/threonine kinase activated by a range of environmental stimuli including genotoxic stress, growth factors, inflammatory cytokines and antigen receptor triggering. Being inducibly recruited to membrane-proximal signalling scaffolds to regulate NFAT, AP-1 and NFkappaB-mediated gene transcription in T-cells, the function of HPK1 in B-cells to date remains rather ill-defined. METHODOLOGY/PRINCIPAL FINDINGS: By using two loss of function models, we show that HPK1 displays a novel function in regulating B-cell integrin activity. Wehi 231 lymphoma cells lacking HPK1 after shRNA mediated knockdown exhibit increased basic activation levels of Ras-related protein 1 (Rap1), accompanied by a severe lymphocyte function-associated antigen-1 (LFA-1) dependent homotypic aggregation and increased adhesion to intercellular adhesion molecule 1 (ICAM-1). The observed phenotype of enhanced integrin activity is caused downstream of Src, by a signalling module independent of PI3K and PLC, involving HPK1, SKAP55 homologue (SKAP-HOM) and Rap1-GTP-interacting adaptor molecule (RIAM). This alters actin dynamics and renders focal adhesion kinase (FAK) constitutively phosphorylated. Bone marrow and splenic B-cell development of HPK1(-/-) mice are largely unaffected, except age-related tendencies for increased splenic cellularity and BCR downregulation. In addition, naïve splenic knockout B-cells appear hyperresponsive to a range of stimuli applied ex vivo as recently demonstrated by others for T-cells. CONCLUSIONS/SIGNIFICANCE: We therefore conclude that HPK1 exhibits a dual function in B-cells by negatively regulating integrin activity and controlling cellular activation, which makes it an interesting candidate to study in pathological settings like autoimmunity and cancer.

Targeting the extracellular membrane-proximal domain of membrane-bound IgE by passive immunization blocks IgE synthesis in vivo.

The classical allergic reaction starts seconds or minutes after Ag contact and is committed by Abs produced by a special subset of B lymphocytes. These Abs belong to the IgE subclass and are responsible for Type I hyperreactivity reactions. Treatment of allergic diseases with humanized anti-IgE Abs leads primarily to a decrease of serum IgE levels. As a consequence, the number of high-affinity IgE receptors on mast cells and basophils decreases, leading to a lower excitability of the effector cells. The biological mechanism behind anti-IgE therapy remains partly speculative; however, it is likely that these Abs also interact with membrane IgE (mIgE) on B cells and possibly interfere with IgE production. In the present work, we raised a mouse mAb directed exclusively against the extracellular membrane-proximal domain of mIgE. The interaction between the monoclonal anti-mIgE Ab and mIgE induces receptor-mediated apoptosis in vitro. Passive immunization experiments lead to a block of newly synthesized specific IgEs during a parallel application of recombinant Bet v1a, the major birch pollen allergen. The decrease of allergen-specific serum IgE might be related to tolerance-inducing mechanisms stopping mIgE-displaying B cells in their proliferation and differentiation.

HS1-associated protein X-1 interacts with membrane-bound IgE: impact on receptor-mediated internalization.

Engagement of the BCR triggers signals that control affinity maturation, memory induction, differentiation, and various other physiological processes in B cells. In previous work, we showed that truncation of the cytoplasmic tail of membrane-bound Ig (mIg)E in vivo resulted in lower serum IgE levels, decreased numbers of IgE-secreting plasma cells, and the abrogation of specific secondary responses correlating with a defect in the selection of high-affinity Abs during the germinal center reaction. We concluded that the Ag receptor is necessary at all times during Ab responses not only for the maturation process, but also for the expansion of Ag-specific B cells. Based on these results, we asked whether the cytoplasmic tail of mIgE, or specific proteins binding the cytoplasmic tail in vivo commit a signal transduction accompanying the B cell along its differentiation process. In this study, we present the identification of HS1-associated protein X-1 as a novel protein interacting with the cytoplasmic tail of mIgE. ELISA, surface plasmon resonance analysis, and coimmunoprecipitation experiments confirmed the specific interaction in vitro. In functional assays, we clearly showed that HS1-associated protein X-1 expression levels influence the efficiency of BCR-mediated Ag internalization.

Kinetic properties of cardiac myosin heavy chain isoforms in rat.

The head portion of the myosin heavy chain (MHC) is essential in force generation. As previously shown, Ca2+-activated fibres of mammalian skeletal muscle display a strong correlation between their MHC isoform complement and the kinetics of stretch activation, suggesting isoform-specific differences in kinetic properties of myosin heads. Using the same methodology on muscle strips of atria and ventricles of hyper- and hypothyroid rats, this study showed that the kinetics of cardiac alphaMHC are 3 times faster than those of cardiac betaMHC under isometric conditions and maximal Ca2+ activation. Comparison of rat heart and skeletal muscle fibres revealed that 100% alphaMHC heart muscle strips exhibited faster stretch activation kinetics (time parameter t3: 108+/-18 ms, mean+/-SD) than rat type-IIA fibres ( t3: 157+/-19 ms), but slower than type-IID fibres ( t3: 55+/-10 ms). The kinetics of 100% betaMHC heart muscle strips ( t3: 351+/-44 ms) were faster than that of type-I fibres in rat skeletal muscle ( t3: 901+/-348 ms). This difference between the two muscle types calls in question the generally accepted identity of betaMHC and MHCIbeta.