The remarkable deformability of the human red blood cell (RBC) results from the coupled dynamic response of the phospholipid bilayer and the spectrin molecular network. Here we present quantitative connections between spectrin morphology and membrane fluctuations of human RBCs by using dynamic full-field laser interferometry techniques. We present conclusive evidence that the presence of adenosine 5′-triphosphate (ATP) facilitates nonequilibrium dynamic fluctuations in the RBC membrane that are highly correlated with the biconcave shape of RBCs. Spatial analysis of the fluctuations reveals that these non-equilibrium membrane vibrations are enhanced at the scale of spectrin mesh size. Our results indicate that the dynamic remodeling of the coupled membranes powered by ATP results in non-equilibrium membrane fluctuations manifesting from both metabolic and thermal energies and also maintains the biconcave shape of RBCs.ATP | imaging technique | membrane fluctuation | RBC | spectrin A s they travel through small blood vessels and organs, RBCs undergo repeated severe deformation. The coupling and interactions between the phospholipid bilayer and the spectrin network govern the deformability of RBCs (1). The fluid-like lipid bilayer is coupled to the two-dimensional spectrin network that comprises an approximately hexagonal lattice via protein junctional complexes. The RBC membrane is remarkably soft and elastic, and thus exhibits fluctuations with amplitudes of the order of tens of nanometers. The dynamics of the RBC membrane is strongly related to the membrane structure and mechanical properties and has been explored extensively (2-6). However, experimental results available to date on RBC membrane fluctuations have provided only limited information on select regions of the cell membrane with limited spatial and/or temporal resolution (7-9). No full-field measurements of membrane fluctuations in the entire RBC arising in response to well-controlled metabolic activity have been made so far and, consequently, different techniques have led to different interpretations of the mechanistic origins of dynamic RBC membrane fluctuations with and without metabolic activity (7-9).The RBC membrane is not a static but a metabolically regulated active structure. It is known that biochemical energy controls its static and dynamic characteristics. The presence of ATP is not only crucial in maintaining the biconcave shape of the RBC membrane (10), but was also shown to increase the dynamic membrane fluctuations (7, 9). However, the regulatory mechanism of ATP in RBC membranes still remains elusive. Furthermore, these static and dynamic effects of ATP on RBC membrane fluctuations have hitherto been regarded as separate phenomena and have never been explored simultaneously.Here, we present dynamic, full-field, and quantitative measurements of ATP effects on RBC membrane morphology and fluctuations. We show that in the presence of ATP, the RBC membrane fluctuations have a non-equilibrium, metabolic component in addition to a thermal o...

The human red blood cell (RBC) membrane, a fluid lipid bilayer tethered to an elastic 2D spectrin network, provides the principal control of the cell's morphology and mechanics. These properties, in turn, influence the ability of RBCs to transport oxygen in circulation. Current mechanical measurements of RBCs rely on external loads. Here we apply a noncontact optical interferometric technique to quantify the thermal fluctuations of RBC membranes with 3 nm accuracy over a broad range of spatial and temporal frequencies. Combining this technique with a new mathematical model describing RBC membrane undulations, we measure the mechanical changes of RBCs as they undergo a transition from the normal discoid shape to the abnormal echinocyte and spherical shapes. These measurements indicate that, coincident with this morphological transition, there is a significant increase in the membrane's shear, area, and bending moduli. This mechanical transition can alter cell circulation and impede oxygen delivery. promises more sensitive probes of their structure at the nanoscale and suggests new insights into the etiology of a number of human diseases (1, 2). In the healthy individual, these cells withstand repeated, large-amplitude mechanical deformations as they circulate through the microvasculature. Certain pathological conditions such as spherocytosis, malaria, and Sickle cell disease cause changes in both the equilibrium shape and mechanics of RBCs, which impact their transport function. Here we communicate measurements of RBC mechanics that rely on unique experimental and theoretical techniques to characterize the mechanics/rheology of normal and pathological RBCs over a range of length and time scales.Lacking a 3D cytoskeleton, RBCs maintain their shape and mechanical integrity through a spectrin-dominated, triangular 2D network attached to the cytosolic side of their plasma membrane. This semiflexible filament network, along with the surface tension of the bilayer, contributes to the elastic moduli of the composite membrane (3). The fluid lipid bilayer is thought to be the principal contributor to its bending or curvature modulus. Little is known about the molecular and structural transformations that take place in the membrane and spectrin network during the cell's morphological transitions from discocyte (DC, normal shape) to echinocyte (EC, spiculated shape) to spherocyte (SC, nearly spherical) (Figs. 1 A-C), which are accompanied by changes in RBC mechanics.A number of techniques have been used to study the rheology of live cells (2). Micropipette aspiration (4), electric field deformation (5), and optical tweezers (2) provide quantitative information about the shear and bending moduli of RBC membranes in static conditions. However, dynamic, frequencydependent knowledge of RBC mechanics is currently very limited with the notable exception of ref. 6. RBC thermal fluctuations ("flickering") have been studied for more than a century (7) to better understand the interaction between the lipid bilayer and the cytoskeleto...

Brain temperature, as an independent therapeutic target variable, has received increasingly intense clinical attention. To date, brain hypothermia represents the most potent neuroprotectant in laboratory studies. Although the impact of brain temperature is prevalent in a number of common human diseases including: head trauma, stroke, multiple sclerosis, epilepsy, mood disorders, headaches, and neurodegenerative disorders, it is evident and well recognized that the therapeutic application of induced hypothermia is limited to a few highly selected clinical conditions such as cardiac arrest and hypoxic ischemic neonatal encephalopathy. Efforts to understand the fundamental aspects of brain temperature regulation are therefore critical for the development of safe, effective, and pragmatic clinical treatments for patients with brain injuries. Although centrally-mediated mechanisms to maintain a stable body temperature are relatively well established, very little is clinically known about brain temperature's spatial and temporal distribution, its physiological and pathological fluctuations, and the mechanism underlying brain thermal homeostasis. The human brain, a metabolically “expensive” organ with intense heat production, is sensitive to fluctuations in temperature with regards to its functional activity and energy efficiency. In this review, we discuss several critical aspects concerning the fundamental properties of brain temperature from a clinical perspective.

We present a new quantitative method for investigating red blood cell morphology and dynamics. The instrument integrates quantitative phase microscopy with an inverted microscope, which makes it particularly suitable for the noninvasive assessment of live erythrocytes. In particular, we demonstrate the ability of this approach to quantify noninvasively cell volume and dynamic morphology. The subnanometer path-length sensitivity at the millisecond time scales is exemplified by measuring the hemoglobin flow out of the cell during hemolysis.

Little is known regarding metacognition in individuals with autism. Specifically, it is unclear how individuals with autism think about their own mental states. The current study assessed memory awareness during a facial recognition task. High-functioning children (M=13,1 years, n=18) and adults (M=27.5 years, n =16) with autism matched with typically developing children (M =14.3 years, n =13) and adults (M =26.9 years, n=15) were tested. Children with autism demonstrated less accurate memory awareness and less reliable differentiation between their confidence ratings compared to typically developing children. Subtle impairments in memory awareness were also evident in adults with autism. Results indicate that broader metacognitive deficits may exist in individuals with autism, possibly contributing to other known impairments. Keywordsautism; face recognition; memory awareness; theory of mind; metacognition Although autism is a developmental disorder characterized by behavioral, communicative and social impairments, the majority of research on autism has focused on deficits within the social domain, including those relating to nonverbal behaviors (e.g., eye-to-eye gaze), the quality and quantity of social relationships, interpersonal sharing, and social or emotional reciprocity. Research on social deficits in individuals with autism burgeoned when children with autism were found to have impaired theory of mind, or an impaired ability to attribute mental states to others (Baron-Cohen, Leslie, & Frith;1985). Compared to typically developing children, children with autism are significantly delayed in their understanding of false-belief tasks and require a higher verbal mental age in order in order to make successful attributions about another person's mental state (Happé, 1995; Pellicano, 2007). Moreover, individuals with autism continue to have impairments in advanced tests of theory of mind into adulthood (Baron-Cohen, Jolliffe, Mortimore, & Robertson, 1997). While theory of mind continues to be the focus of much research on autism, little research has examined individuals' with autism understanding of their own mental states, or metacognition.Correspondence regarding this article should be addressed to Mark S. Strauss, Department of Psychology, University of Pittsburgh, 210 South Bouquet Street, Pittsburgh, PA 15260, strauss@pitt.edu. Metacognition can broadly be defined as one's general knowledge regarding any aspect of cognitive activity, either within oneself or within others (Lockl & Schneider, 2007). Under this definition, metacognition includes the knowledge typically described as theory of mind. However, more specifically, metacognition can be divided into two types, metacognitive knowledge of cognition and metacognitive regulation of cognition (Shraw & Moshman, 1995). Metacognitive knowledge refers to what an individual knows about cognition, including declarative knowledge (e.g., knowledge about oneself as a learner and about factors that influence performance), procedural knowledge (e.g., know...