Early cortical specialization for face-to-face communication in human infants

This study examined the brain bases of early human social cognitive abilities. Specifically, we investigated whether cortical regions implicated in adults' perception of facial communication signals are functionally active in early human development. Four-month-old infants watched two kinds of dynamic scenarios in which a face either established mutual gaze or averted its gaze, both of which were followed by an eyebrow raise with accompanying smile. Haemodynamic responses were measured by near-infrared spectroscopy, permitting spatial localization of brain activation (experiment 1), and gamma-band oscillatory brain activity was analysed from electroencephalography to provide temporal information about the underlying cortical processes (experiment 2). The results revealed that perceiving facial communication signals activates areas in the infant temporal and prefrontal cortex that correspond to the brain regions implicated in these processes in adults. In addition, mutual gaze itself, and the eyebrow raise with accompanying smile in the context of mutual gaze, produce similar cortical activations. This pattern of results suggests an early specialization of the cortical network involved in the perception of facial communication cues, which is essential for infants' interactions with, and learning from, others.     

''The surface management system'' (SuMS) database: a surface-based database to aid cortical surface reconstruction, visualization and analysis.

Surface reconstructions of the cerebral cortex are increasingly widely used in the analysis and visualization of cortical structure, function and connectivity. From a neuroinformatics perspective, dealing with surface-related data poses a number of challenges. These include the multiplicity of configurations in which surfaces are routinely viewed (e.g. inflated maps, spheres and flat maps), plus the diversity of experimental data that can be represented on any given surface. To address these challenges, we have developed a surface management system (SuMS) that allows automated storage and retrieval of complex surface-related datasets. SuMS provides a systematic framework for the classification, storage and retrieval of many types of surface-related data and associated volume data. Within this classification framework, it serves as a version-control system capable of handling large numbers of surface and volume datasets. With built-in database management system support, SuMS provides rapid search and retrieval capabilities across all the datasets, while also incorporating multiple security levels to regulate access. SuMS is implemented in Java and can be accessed via a Web interface (WebSuMS) or using downloaded client software. Thus, SuMS is well positioned to act as a multiplatform, multi-user 'surface request broker' for the neuroscience community.     

The role of the lamellar interface during torsional yielding of human cortical bone

Fragility fractures are a result of alterations in bone quantity, tissue properties, applied loads, or a combination of these factors. The current study addresses the contribution of cortical bone tissue properties to skeletal fragility by characterizing the shear damage accumulation processes which occur during torsional yielding in normal bone. Samples of human femoral cortical bone were loaded in torsion and damaged at a post-yield twist level. The number of microcracks within osteons, interstitial tissue, and along cement lines were assessed using basic fuchsin staining. Damage density measures (number of cracks/mm2) were correlated with stiffness degradation and changes in relaxation. Damaged samples exhibited a wide variation in total microcrack density, ranging from 1.1 to 43.3 cracks/mm2 with a mean density of 19.7 +/- 9.8 cracks/mm2. Lamellar interface cracks comprised more than 75% of the total damage, indicating that the lamellar interface is weak in shear and is a principal site of shear damage accumulation. Damage density was positively correlated with secant stiffness degradation, but only explained 22% of the variability in degradation. In contrast, damage density was uncorrelated with the changes in relaxation, indicating that a simple crack counting measure such as microcrack density was not an appropriate measure of relaxation degradation. Finally, a nonuniform microcrack density distribution was observed, suggesting that internal shear stresses were redistributed within the torsion samples during post-yield loading. The results suggested that the lamellar interface in human cortical bone plays an important role in torsional yielding by keeping cracks physically isolated from each other and delaying microcrack coalescence in order to postpone the inevitable formation of the fatal crack.     

Imaging of the cell surface interface using objective coupled widefield surface plasmon microscopy

We report on the development and on the first use of the widefield surface plasmon (WSPR) microscope in the examination of the cell surface interface at submicron lateral resolutions. The microscope is Kohler illuminated and uses either a 1.45 numerical aperture (NA) oil immersion lens, or a 1.65 NA oil immersion lens to excite surface plasmons at the interface between a thin gold layer and a glass or sapphire cover slip. Like all surface plasmon microscope systems the WSPR has been proven in previous studies to also be capable of nanometric z-scale resolutions. In this study we used the system to image the interface between HaCaT cells and the gold layer. Imaging was performed in air using fixed samples and the 1.45 NA objective based system and also using live cells in culture media using the 1.65 NA based system. Imaging in air enabled the visualisation of high resolution and high-contrast submicron features identified by vinculin immunostaining as component of focal contacts and focal adhesions. In comparison, imaging in fluid enabled cell surface interfacial interactions to be tracked by time-lapse video WSPR microscopy. Our results indicate that the cell surface interface and thus cell signalling mechanisms may be readily interrogated in live cells without the use of labelling techniques.     

Role of surface chemistry in protein remodeling at the cell-material interface

Background

The cell-material interaction is a complex bi-directional and dynamic process that mimics to a certain extent the natural interactions of cells with the extracellular matrix. Cells tend to adhere and rearrange adsorbed extracellular matrix (ECM) proteins on the material surface in a fibril-like pattern. Afterwards, the ECM undergoes proteolytic degradation, which is a mechanism for the removal of the excess ECM usually approximated with remodeling. ECM remodeling is a dynamic process that consists of two opposite events: assembly and degradation.

Methodology/Principal Findings

This work investigates matrix protein dynamics on mixed self-assembled monolayers (SAMs) of –OH and –CH₃ terminated alkanethiols. SAMs assembled on gold are highly ordered organic surfaces able to provide different chemical functionalities and well-controlled surface properties. Fibronectin (FN) was adsorbed on the different surfaces and quantified in terms of the adsorbed surface density, distribution and conformation. Initial cell adhesion and signaling on FN-coated SAMs were characterized via the formation of focal adhesions, integrin expression and phosphorylation of FAKs. Afterwards, the reorganization and secretion of FN was assessed. Finally, matrix degradation was followed via the expression of matrix metalloproteinases MMP2 and MMP9 and correlated with Runx2 levels. We show that matrix degradation at the cell material interface depends on surface chemistry in MMP-dependent way.

Conclusions/Significance

This work provides a broad overview of matrix remodeling at the cell-material interface, establishing correlations between surface chemistry, FN adsorption, cell adhesion and signaling, matrix reorganization and degradation. The reported findings improve our understanding of the role of surface chemistry as a key parameter in the design of new biomaterials. It demonstrates the ability of surface chemistry to direct proteolytic routes at the cell-material interface, which gains a distinct bioengineering interest as a new tool to trigger matrix degradation in different biomedical applications.     

Propagation of surface fatigue cracks in human cortical bone

An understanding of how fatigue cracks grow in bone is of importance as fatigue is thought to be the main cause of clinical stress fractures. This study presents new results on the fatigue-crack growth behavior of small surface cracks (approximately 75-1000 microm in size) in human cortical bone, and compares their growth rates with data from other published studies on the behavior of both surface cracks and many millimeter, through-thickness large cracks. Results are obtained with a cyclically loaded cantilever-beam geometry using optical microscopy to examine for crack growth after every 100-500 cycles. Based on the current and previous results, small fatigue cracks appear to become more resistant to fatigue-crack growth with crack extension, analogous to the way the fracture resistance of cortical bone increases with crack growth. Mechanistically, a theory attributing such behavior to the development of bridges in the wake of the crack with crack growth is presented. The existence of such bridges is directly confirmed using optical microscopy.     

Facilitation of reactions of cortical neurons to cortical and peripheral stimulation after tetanization of the brain surface

The electrical activity of neurons of the sensomotor cortex of an unanesthetized rabbit was investigated. Conditioning tetanization of the cortex was carried out through surface electrodes located close to the site of the lead. Test stimuli were supplied through electrodes 2.5–12 mm more caudally on the cortical surface. In addition, peripheral test stimuli were applied. Impulse reactions to previously ineffective stimuli develop after conditioning tetanization and prolonged (up to 1 min) intensification of exciting postsynaptic potentials (EPSP) to cortical and peripheral test stimuli is observed. Facilitation of the reactions is especially clear during tetanization superthreshold for evoking epileptiform afterdischarges. It continued after the conclusion of these discharges and could also be observed during tetanization subthreshold for evoking afterdischarges. The time course of the facilitation was similar to the time course of the post-tetanic intensification of reactions of single stimuli applied with the electrodes used for tetanization. An analysis of the changes in intracellular activity makes it possible to assume that the mechanism of post-tetanic potentiation (PTP) lies at the basis of the described facilitation, which is considered as the "cellular analog" of the dominant focus which develops as a result of tetanization of the cortical surface.Institute of the Brain, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 3, No. 1, pp. 3–12, January–February, 1971.     

CNV-like potentials on the cortical surface associated with conditioning in head-restrained rats

Head-restrained rats were conditioned to perform a CNV task: to press a lever in response to an imperative auditory stimulus (S2) given 1.5 sec after a warning stimulus (S1) for a drop of jelly food. With an electrode on the surface of the forelimb cortex, (1) sharp wave complexes immediately after S1 and S2, and (2) a negative slow potential (SP) between S1 and S2, on which early and late components were discernible, were recorded in association with performance of this task. With the electrode at a depth of 2 mm in the same cortical area, the corresponding field potential showed a long-lasting positive shift in addition to the components of the surface potential. These monopolar recordings were obtained with respect to a common reference at the frontal sinus. The surface-minus-depth potential (the transcortical potential), consequently, showed a surface-negative tonic wave, confirming Pirch's report (1980). During extinction of this conditioning, the SP between S1 and S2 disappeared, while the sharp waves following S1 and S2 remained with little modification, suggesting that the sharp waves are a kind of evoked potential (EP) elicited by the stimuli.Recording from 5 surface electrodes set in an array over the left hemisphere contralateral to the used forelimb during development of the conditioning revealed not only a spatial distribution of the SP but also a transition of the potentials. As the conditioning progressed, the negativity of the early SP component tended to increase, while that of the late component tended to decrease and was confined to the sensorimotor cortex. The similarities of the rat cortical surface potentials to the human and monkey CNV in their wave form and function suggests that the rat brain can produce electrical activity analogous to the human CNV.     

Three-dimensional reconstruction of the membrane skeleton at the plasma membrane interface by electron tomography

Three-dimensional images of the undercoat structure on the cytoplasmic surface of the upper cell membrane of normal rat kidney fibroblast (NRK) cells and fetal rat skin keratinocytes were reconstructed by electron tomography, with 0.85-nm-thick consecutive sections made approximately 100 nm from the cytoplasmic surface using rapidly frozen, deeply etched, platinum-replicated plasma membranes. The membrane skeleton (MSK) primarily consists of actin filaments and associated proteins. The MSK covers the entire cytoplasmic surface and is closely linked to clathrin-coated pits and caveolae. The actin filaments that are closely apposed to the cytoplasmic surface of the plasma membrane (within 10.2 nm) are likely to form the boundaries of the membrane compartments responsible for the temporary confinement of membrane molecules, thus partitioning the plasma membrane with regard to their lateral diffusion. The distribution of the MSK mesh size as determined by electron tomography and that of the compartment size as determined from high speed single-particle tracking of phospholipid diffusion agree well in both cell types, supporting the MSK fence and MSK-anchored protein picket models.     

Lipase kinetics at the triacylglycerol-water interface using surface tension measurements

Two methods, the so-called "oil drop" and "Teflon plunger" methods, were designed to monitor lipase hydrolysis of natural long-chain triacylglycerols through the variation with time of the oil-water interfacial tension. The first part of this work is devoted to the development of these two techniques using pure, well-characterized porcine pancreatic lipase. They gave linear responses with enzyme concentrations ranging from 1 x 10(-3) to 30 units x ml-1. We then applied them to a study of the optimal pH conditions for human gastric lipase which were found to range around 5, as previously observed. In the presence of variable concentrations of sodium taurodeoxycholate, these two methods also showed that human gastric lipase is active in the 8-13 dyn cm-1 range of interfacial tension. It is concluded that these two methods, based upon variations with time of the oil-water interfacial tension, constitute reliable, sensitive and convenient means of investigating lipase kinetics.     

Nutrient dynamics at the interface between surface waters and groundwaters

1. The surface water/groundwater (SW/GW) interface is a crucial control point for lateral nutrient fluxes between uplands and aquatic ecosystems and for upstream/downstream (longitudinal) processes in lotic ecosystems. 2. Hydrological and biogeochemical dynamics of the SW/GW ecotone are linked to the degree of channel constraint and the sediment characteristics of the floodplain and stream bed. 3. The availability of specific chemical forms of electron donors and electron acceptors affects the spatial distribution of biogeochemical processes at the SW/GW interface. Temporal change in discharge is also a major factor affecting the rate and extent of these processes. 4. The magnitude of SW/GW interactions in lotic ecosystems is predicted to be a major determinant of solute retention. Channel morphology, stream bed composition and discharge are predicted to be important controls on SW/GW interactions. 5. Interdisciplinary research involving hydrologists, geomorphologists, aquatic ecologists, microbial ecologists and landscape ecologists is needed to further our present understanding of this critical interface linking terrestrial and aquatic ecosystems.     

Computational modeling of seizure spread on a cortical surface

Journal of Computational Neuroscience - In the field of computational epilepsy, neural field models helped to understand some large-scale features of seizure dynamics. These insights however remain...     

Electron-dense material in the cell sall/plasma membrane interface of specialized cortical cells of peanut nodules.

The nitrogen-fixing peanut root nodules have 2-3 layers of specialized cortical cells surrounding the infected zone. These cells are morphologically distinct from the other cortical cells due to the presence of prominent amyloplasts, lipid bodies (oleosomes), large microbodies and localized pockets of electron-dense material at the plasma membrane-cell wall interface. The material is resistant to solubilization by hexane and chloroform. Electron density is enhanced by p-phenylenediamine staining and heavy metal ions such as iron, uranium and osmium. The silver proteinate staining method for suberin has shown positive results. Peroxidative activity can be demonstrated by diaminobenzidine reaction. The material appears to be proteinaceous, but could be complexed with suberin or phenolics. Although the exact nature of this material remains to be clarified, its unique position in the cells of specialized tissue of the cortex relates it to the regulation of bidirectional transport of gases and solutes during symbiosis in the root nodules.     

Amniotic membrane transplantation for ocular surface reconstruction

The purpose of this study is to analyze the clinical experience and the effect of human amniotic membrane transplantation on pterygium excision and bullous keratopathy. From January 1999 to January 2001 at University Hospital "Sestre milosrdnice" amniotic membrane transplantation was performed consecutively in 21 eyes: 11 eyes with bullous keratopathy and 10 with recurrent pterygia. In the group with bullous keratopathy epithelization took place in 19.6 days in 72.7% and the reduction of pain was satisfactory. Recurrence rate in group with recurrent pterygia was 20%. Based on the presented results it could be concluded that amniotic membrane transplantation can be considered as an effective alternative for treating severe ocular surface diseases and as an alternative for penetrating keratoplasty if there is a lack of grafts.     

Application of sterilised human amnion for reconstruction of the ocular surface

BACKGROUND: Despite improved surgical techniques and the use of new medication, healing of corneal and conjunctival defects cannot always be achieved. In this connection the clinical use of human amnion, produced by different techniques, has represented a successful alternative for the past ten years. The purpose of the present investigation was the development of a clinically secure, therapeutically efficient, and easy-to-handle (transport, storage, application) allogenic amnion transplant. PATIENTS AND METHODS: A new method for an amnion preparation, which contains a sterilisation process in peracetic acid and a drying process in a laminar flow cabinet, was developed as an alternative to previous techniques described in the literature. Amnion transplantation was used to treat 41 patients, 36 of them with corneal ulcer. Further indications for amnion transplantation were symblepharon, descemetocele, as well as dehiscence of conjunctiva after cerclage. RESULTS: Seventy-three percent of cases showed postoperative improvement evidenced by constant vision, while 15 percent showed decreased vision. CONCLUSIONS: The study confirms the observations of previous investigators who consider amnion transplantation an efficient therapeutic method for a multitude of eye diseases. The new method described in this report, guarantees patients' safety by using a validated new sterilisation process against infections that can be transmitted by human tissue. At present this method constitutes the only process available in Germany, and is approved by the Federal Institute for Drugs and Medical Products (BfArM) for the manufacture of human amnion transplants as a finished medical product.     

Role of Src-family kinases in formation of the cortical actin cap at the dorsal cell surface

Protein-tyrosine phosphorylation is regulated by protein-tyrosine kinases and protein-tyrosine phosphatases (PTPs). Src-family tyrosine kinases (SFKs) participate in the regulation of the actin cytoskeleton. Actin filaments can be accumulated in a cap at the dorsal cell surface, which is called the cortical actin cap. Here, we show that SFKs play an important role in formation of the cortical actin cap. HeLa cells normally exhibit the cortical actin cap, one of the major sites of tyrosine phosphorylation. The cortical actin cap is disrupted by SFK inhibitors or overexpression of the Lyn SH3 domain. Csk-knockout cells form the cortical actin cap when the level of tyrosine phosphorylation is increased by Na₃VO₄, a PTP inhibitor, and the formation of the cortical actin cap is inhibited by SFK inactivation with re-introduction of Csk. SYF cells lacking SFKs minimally exhibit the cortical actin cap even in the presence of Na₃VO₄, and transfection with Lyn restores the cortical actin cap in the presence of Na₃VO₄. Disruption of the cortical actin cap by dominant-negative Cdc42 causes loss of tyrosine phosphorylation at the cell top. These results suggest that SFK(s) is involved in formation of the cortical actin cap, which may serve as a platform of tyrosine phosphorylation signaling.     

Negative surface potential shift and responses of neurons and glial cells during tetanic stimulation of the cortical surface

The negative potential shift in response to tetanic stimulation of the surface of the cortex or thalamic nucleus was recorded from the cortical surface in cats lightly anesthetized with pentobarbital. Parallel intracellular recordings were obtained of activity of neurons and glial cells. Glial cells responded to this stimulation by slow depolarization, which, under certain conditions of stimulation, was followed by slow hyperpolarization; hyperpolarization shifts were observed in neurons. Depolarization and hyperpolarization of glial cells, like hyperpolarization of neurons, did not correlate in time with the development of a negative shift of the surface potential. It is postulated that this shift is a response of complex origin involving the participation not only of glial cells, but also of cortical neurons.I. S. Beritashvili Institute of Physiology, Academy of Sciences of the Georgian SSR, Tbilisi. Translated from Neirofiziologiya, Vol. 14, No. 3, pp. 248–253, May–June, 1982.