Deletion of N-terminal residues 23-88 from prion protein (PrP) abrogates the potential to rescue PrP-deficient mice from PrP-like protein/doppel-induced Neurodegeneration

Accumulating evidence has suggested that prion protein (PrP) is neuroprotective and that a PrP-like protein/Doppel (PrPLP/Dpl) is neurotoxic. A line of PrP-deficient mice, Ngsk Prnp0/0, ectopically expressing PrPLP/Dpl in neurons, exhibits late-onset ataxia because of Purkinje cell death that is prevented by a transgene encoding wild-type mouse PrP. To elucidate the mechanisms of neurodegeneration in these mice, we introduced five types of PrP transgene, namely one heterologous hamster, two mouse/hamster chimeric genes, and two mutants, each of which encoded PrP lacking residues 23-88 (MHM2.del23-88) or with E199K substitution (Mo.E199K), into Ngsk Prnp0/0 mice. Only MHM2.del23-88 failed to rescue the mice from the Purkinje cell death. The transgenic mice, MHM2.del23-88/Ngsk Prnp0/0, expressed several times more PrP than did wild-type (Prnp+/+) mice and PrPLP/Dpl at an equivalent level to Ngsk Prnp0/0 mice. Little difference was observed in the pathology and onset of ataxia between Ngsk Prnp0/0 and MHM2.del23-88/Ngsk Prnp0/0. No detergent-insoluble PrPLP/Dpl was detectable in the central nervous system of Ngsk Prnp0/0 mice even after the onset of ataxia. Our findings provide evidence that the N-terminal residues 23-88 of PrP containing the unique octapeptide-repeat region is crucial for preventing Purkinje cell death in Prnp0/0 mice expressing PrPLP/Dpl in the neuron.

Star Trek replicators and diatom nanotechnology

Diatoms are single celled algae, the 10(5)-10(6) species of which create a wide variety of three-dimensional amorphous silica shells. If we could get them to produce useful structures, perhaps by compustat selection experiments (i.e. forced evolution of development or evodevo), their exponential growth in suspension cultures could compete with the lithography techniques of present day nanotechnology, which have limited 3D capabilities. Alternatively, their fine detail could be used for templates for MEMS (micro electro mechanical systems), or their silica deposition systems isolated for guiding silica deposition. A recent paper has demonstrated that silica can be replaced atom for atom without change of shape--a step towards the Star Trek replicator.

Synergistic Action of Growth Factors and Dynamic Loading for Articular Cartilage Tissue Engineering

It has previously been demonstrated that dynamic deformational loading of chondrocyte-seeded agarose hydrogels over the course of 1 month can increase construct mechanical and biochemical properties relative to free-swelling controls. The present study examines the manner in which two mediators of matrix biosynthesis, the growth factors TGF-beta1 and IGF-I, interact with applied dynamic deformational loading. Under free-swelling conditions in control medium (C), the [proteoglycan content][collagen content][equilibrium aggregate modulus] of cell-laden (10 x 10(6) cells/mL) 2% agarose constructs reached a peak of [0.54% wet weight (ww)][0.16% ww][13.4 kPa]c, whereas the addition of TGF-beta1 or IGF-I to the control medium led to significantly higher peaks of [1.18% ww][0.97% ww][23.6 kPa](C-TGF) and [1.00% ww][0.63% ww][19.3 kPa](C-IGF), respectively, by day 28 or 35 (p<0.01). Under dynamic loading in control medium (L), the measured parameters were [1.10% ww][0.52% ww][24.5 kPa]L, and with the addition of TGF-beta1 or IGF-I to the control medium these further increased to [1.49% ww][1.07% ww][50.5 kPa](L-TGF) and [1.48% ww][0.81% ww][46.2 kPa](L-IGF), respectively (p<0.05). Immunohistochemical staining revealed that type II collagen accumulated primarily in the pericellular area under free-swelling conditions, but spanned the entire tissue in dynamically loaded constructs. Applied in concert, dynamic deformational loading and TGF-beta1 or IGF-I increased the aggregate modulus of engineered constructs by 277 or 245%, respectively, an increase greater than the sum of either stimulus applied alone. These results support the hypothesis that the combination of chemical and mechanical promoters of matrix biosynthesis can optimize the growth of tissue-engineered cartilage constructs.

Numerical modeling of pulsatile turbulent flow in stenotic vessels

Pulsatile turbulent flow in stenotic vessels has been numerically modeled using the Reynolds-averaged Navier-Stokes equation approach. The commercially available computational fluid dynamics code (CFD), FLUENT, has been used for these studies. Two different experiments were modeled involving pulsatile flow through axisymmetric stenoses. Four different turbulence models were employed to study their influence on the results. It was found that the low Reynolds number k-omega turbulence model was in much better agreement with previous experimental measurements than both the low and high Reynolds number versions of the RNG (renormalization-group theory) k-epsilon turbulence model and the standard k-epsilon model, with regard to predicting the mean flow distal to the stenosis including aspects of the vortex shedding process and the turbulent flow field. All models predicted a wall shear stress peak at the throat of the stenosis with minimum values observed distal to the stenosis where flow separation occurred.

Partitioning of individual flexible polymers into a nanoscopic protein pore

Polymer dynamics are of fundamental importance in materials science, biotechnology, and medicine. However, very little is known about the kinetics of partitioning of flexible polymer molecules into pores of nanometer dimensions. We employed electrical recording to probe the partitioning of single poly(ethylene glycol) (PEG) molecules, at concentrations near the dilute regime, into the transmembrane beta-barrel of individual protein pores formed from staphylococcal alpha-hemolysin (alphaHL). The interactions of the alpha-hemolysin pore with the PEGs (M(w) 940-6000 Da) fell into two classes: short-duration events (tau approximately 20 micro s), approximately 85% of the total, and long-duration events (tau approximately 100 micro s), approximately 15% of the total. The association rate constants (k(on)) for both classes of events were strongly dependent on polymer mass, and values of k(on) ranged over two orders of magnitude. By contrast, the dissociation rate constants (k(off)) exhibited a weak dependence on mass, suggesting that the polymer chains are largely compacted before they enter the pore, and do not decompact to a significant extent before they exit. The values of k(on) and k(off) were used to determine partition coefficients (Pi) for the PEGs between the bulk aqueous phase and the pore lumen. The low values of Pi are in keeping with a negligible interaction between the PEG chains and the interior surface of the pore, which is independent of ionic strength. For the long events, values of Pi decrease exponentially with polymer mass, according to the scaling law of Daoud and de Gennes. For PEG molecules larger than approximately 5 kDa, Pi reached a limiting value suggesting that these PEG chains cannot fit entirely into the beta-barrel.

Shrinking the biologic world--nanobiotechnologies for toxicology

Although toxicologic effects need to be considered at the organismal level, the adverse events originate from interactions and alterations at the molecular level. Cellular structures and functions can be disrupted by modifications of the nanometer structure of critical molecules; therefore, devices used to assess biologic and toxicologic processes at the nanoscale will allow important new research pursuits. In order to properly assess alterations at these dimensions, nanofabricated tools are needed to detect, separate, analyze, and manipulate cells or biologic molecules of interest. The emergence of laser tweezers, surface plasmon resonance (SPR), laser capture microdissection (LCM), atomic force microscopy (AFM), and multi-photon microscopes have allowed for these assessments. Micro- and nanobiotechnologies will further advance biologic, clinical, and toxicologic endeavors with the aid of miniaturized, more sensitive devices. Miniaturized table-top laboratory equipment incorporating additional innovative technologies can lead to new advances, including micro total analysis systems (microTAS) or "lab-on-a-chip" and "sentinel sensor" devices. This review will highlight several devices, which have been made possible by techniques originating in the microelectronics industry. These devices can be used for toxicologic assessment of cellular structures and functions, such as cellular adhesion, signal transduction, motility, deformability, metabolism, and secretion.

Micro-PET imaging and small animal models of disease

Positron emission tomography (PET) has been used clinically to measure enzyme reactions, ligand-receptor interactions, cellular metabolism and cell proliferation. Until recently, however, PET has not been suitable for small animal models because of resolution limitations. Development of micro-PET instrumentation for small animal imaging and the availability of positron-emitting tracers has made this technology accessible for the non-invasive, quantitative and repetitive imaging of biological function in living animals. The development of new probes and positron-imaging based reporter genes has extended micro-PET applications to investigations of metabolism, enzyme activity, receptor-ligand interactions, protein-protein interactions, gene expression, adoptive cell therapy and somatic gene therapy. Because small animal PET is immediately extrapolatable to the clinic, laboratory advances should rapidly be translated to clinical practice.

Hydrodynamic guiding for addressing subsets of immobilized cells and molecules in microfluidic systems

BACKGROUND

The interest in microfluidics and surface patterning is increasing as the use of these technologies in diverse biomedical applications is substantiated. Controlled molecular and cellular surface patterning is a costly and time-consuming process. Methods for keeping multiple separate experimental conditions on a patterned area are, therefore, needed to amplify the amount of biological information that can be retrieved from a patterned surface area. We describe, in three examples of biomedical applications, how this can be achieved in an open microfluidic system, by hydrodynamically guiding sample fluid over biological molecules and living cells immobilized on a surface.

RESULTS

A microfluidic format of a standard assay for cell-membrane integrity showed a fast and dose-dependent toxicity of saponin on mammalian cells. A model of the interactions of human mononuclear leukocytes and endothelial cells was established. By contrast to static adhesion assays, cell-cell adhesion in this dynamic model depended on cytokine-mediated activation of both endothelial and blood cells. The microfluidic system allowed the use of unprocessed blood as sample material, and a specific and fast immunoassay for measuring the concentration of C-reactive protein in whole blood was demonstrated.

CONCLUSION

The use of hydrodynamic guiding made multiple and dynamic experimental conditions on a small surface area possible. The ability to change the direction of flow and produce two-dimensional grids can increase the number of reactions per surface area even further. The described microfluidic system is widely applicable, and can take advantage of surfaces produced by current and future techniques for patterning in the micro- and nanometer scale.

Orientation modulation of a synthetic polypeptide in self-assembled monolayers: a TOF-SIMS study

Structure and orientation of molecules are key properties of functionalized surfaces. Using time-of-flight secondary ion mass spectrometry (TOF-SIMS), here we investigate how to modulate these parameters upon the immobilization process varying the conditions of self-assembly. The molecule of interest, a template-assembled synthetic protein (TASP), consists of a central peptide ring with orthogonally arranged residues. Thioalkane chains allow the directed self-assembly of the molecule on a gold surface; four serine residues on the opposite side of the ring can be used as anchoring sites for various functional sensing molecules. The TASP conformation and its orientation in self-assembled monolayers (SAMs) play a central role for the accessibility of these serine residues. To study the influence of the self-assembly conditions, two series of samples were prepared. Pure TASP monolayers of different surface densities are compared to mixed TASP/alkanethiol monolayers prepared by sequential adsorption varying sequence and particular incubation times as well as by coadsorption modifying incubation times and TASP/alkanethiol mass ratios. Switching the TASP orientation from a state where the molecules are lying flat on the surface to an upright orientation turned out to be possible by inserting the TASP into a preformed alkanethiol monolayer of an appropriate surface density. This study demonstrates that TOF-SIMS is an excellent tool not only to investigate the surface composition, but also the molecular structure of functionalized surfaces.

Highly sensitive fluorescence detection technology currently available for HTS

Homogeneous fluorescence methods are providing an important tool for HTS technologies. A wide range of different techniques have been established on the market, with read-outs ranging from total fluorescence intensity to statistical analysis of fluorescence fluctuations for biochemical assays or fluorescence imaging techniques for cellular systems. Each method has its own advantages and limitations, which have to be accounted for when designing a specific assay. Here, recently developed fluorescence techniques and some of their applications, with a particular focus on sensitivity, are summarized and their principles are presented.

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A picoliter 'fountain-pen' using co-axial dual pipettes

A double pipette system for local, controlled drug infusion is presented. Two concentric pipettes can be manipulated separately and pressurized independently by a designated double holder. The inner pipette is loaded with the desirable solution (drug), and functions as a source, while the outer one is a sink. This gives a flow of the solution between the two pipettes that protrudes only a small distance into the surrounding fluid and does not diffuse away. Time resolution of the infusion is highly controllable, and oscillatory flow can be generated. Three implementations of the double pipette system are demonstrated. We show that local application of neurotransmitters in neuronal networks is an efficient way of stimulating activity in the network. We then present a wet micro lithography technique using topical application of proteins onto the substrate. Finally, we show that we can localize a given drug on a small targeted part of a cell.

Fluorescence in situ hybridization: past, present and future

Fluorescence in situ hybridization (FISH), the assay of choice for localization of specific nucleic acids sequences in native context, is a 20-year-old technology that has developed continuously. Over its maturation, various methodologies and modifications have been introduced to optimize the detection of DNA and RNA. The pervasiveness of this technique is largely because of its wide variety of applications and the relative ease of implementation and performance of in situ studies. Although the basic principles of FISH have remained unchanged, high-sensitivity detection, simultaneous assay of multiple species, and automated data collection and analysis have advanced the field significantly. The introduction of FISH surpassed previously available technology to become a foremost biological assay. Key methodological advances have allowed facile preparation of low-noise hybridization probes, and technological breakthroughs now permit multi-target visualization and quantitative analysis - both factors that have made FISH accessible to all and applicable to any investigation of nucleic acids. In the future, this technique is likely to have significant further impact on live-cell imaging and on medical diagnostics.

Selective two-photon microscopy with shaped femtosecond pulses

Selective two-photon excitation of fluorescent probe molecules using phase-only modulated ultrashort 15-fs laser pulses is demonstrated. The spectral phase required to achieve the maximum contrast in the excitation of different probe molecules or identical probe molecules in different micro-chemical environments is designed according to the principles of multiphoton intrapulse interference (MII). The MII method modulates the probabilities with which specific spectral components in the excitation pulse contribute to the two-photon absorption process due to the dependence of the absorption on the power spectrum of E2(t) [1-3]. Images obtained from a number of samples using the multiphoton microscope are presented.

Skin changes following defibrillation. The effect of high voltage direct current

Previously, electrical injuries have been suggested caused only by the concomitant heat developed during the passage of an electrical current. Recent experimental studies on fully anesthetized pigs and the study of one human case have, however, shown typical electrical alterations. The purpose of the present study was further to evaluate the histology of electrically induced changes in the skin in humans. In addition, supplementary in vivo methods for evaluation of skin changes as high-frequency ultrasound and Raman spectroscopy were used. The skin of 11 patients treated with a defibrillation of the heart was examined for macroscopic changes, the skin of eight of them also for histologic changes and for changes observable via supplementary methods. Immediately and 7 days after the defibrillation, fractions of a narrow red ring were observed along the periphery of the tin-foil electrode. Epidermis showed signs previously observed following electrical influence: segmental alterations often related to the openings of sweat ducts, darkstaining or "empty" nuclei and homogeneous cytoplasm, eosinophilic or pale. Dermis did not show the specific sign of electrical influence: deposits of calcium salts on dermal fibres, neither via histologic examination nor via high-frequency ultrasonography and Raman spectroscopy. Fractions of a narrow red ring along the periphery of the electrode showing histological signs of electric influence in epidermis thus appear to be characteristic of high voltage electrical injury.

Fibronectin blocks p38 and jnk activation by cyclic strain in Caco-2 cells

Diverse repetitive forces deform the intestinal epithelium and basement membrane. Such repetitive deformation induces intestinal epithelial proliferation, differentiation, and intracellular signaling. Although at least some deformation-induced signals probably involve integrins, the matrix-dependence of these signals is poorly understood. We compared rapid strain activation of p38 and jnk in human Caco-2 intestinal epithelial cells cultured on collagen I, collagen IV, laminin, and tissue fibronectin. These signals were inhibited in cells on a fibronectin substrate, but activated by strain on collagens and laminin. Furthermore, adding 300 microg/ml plasma fibronectin (approximately the concentration found in plasma) to the culture medium inhibited strain activation of p38 and jnk in cells cultured on collagen. Since tissue and plasma fibronectin levels vary in acute or chronic inflammatory or infectious conditions, these results suggest that tissue or plasma fibronectin may modulate the intestinal epithelial response to repetitive deformation.

Growth of walled cells: from shells to vesicles

The growth of isolated walled cells is investigated. Examples of such cells range from bacteria to giant algae, and include cochlear hair, plant root hair, fungi, and yeast cells. They are modeled as elastic shells containing a liquid. Cell growth is driven by fluid pressure and is is similar to a plastic deformation of the wall. The requirement of mechanical equilibrium leads to two new scaling laws for cell size that are in quantitative agreement with the compiled biological data. Given these results, possible shapes for growing cells are computed by analogy with those of vesicle membranes.

DNA vaccines for non-infectious diseases: new treatments for tumour and allergy

The last decade of DNA vaccine research was characterised by a pioneer spirit and enormous enthusiasm, with a large number of publications demonstrating the usefulness of this approach. Unfortunately, DNA vaccines have not necessarily met the high clinical expectations and a number of complications need to be overcome. In the case of cancer and allergy, the requirements for achieving the objectives are very different. Vaccines against allergies need to suppress or alter an unwanted immune response, while a cancer DNA vaccine has to overcome tolerance and/or immune suppression and initiate a powerful immune response. This review addresses currently used general optimisation strategies for DNA vaccines such as modification of immunisation regimens, improving the delivery systems and using molecular adjuvants. In addition, cancer-specific approaches, such as the stimulation of innate and adaptive immunity with replicase-based DNA vaccines, and targeting non-tumour-associated antigens (TAAs) are discussed. Specifically for the optimisation of DNA vaccination against allergies, procedures such as allergen gene recoding, T helper (Th)1 modulation, and the creation of safe DNA vaccines by gene fragmentation, ubiquitination or using artificial hypoallergens are being analysed. These strategies, individually or in combination, hold the potential of making DNA vaccines useful for application in the clinic.

A smart microfluidic affinity chromatography matrix composed of poly(N-isopropylacrylamide)-coated beads

The efficient upstream processing of complex biological or environmental samples for subsequent biochemical analysis remains a challenge in many analytical systems. New microfluidic platforms that provide multidiagnostic capabilities on single chips face a similar challenge in getting specific analytes purified or contaminants removed in different fluid streams. Here, stimuli-responsive polymers have been used to construct "smart" beads that can be reversibly immobilized on microfluidic channel walls to capture and release targets. The 100-nm latex beads were surface-modified with the temperature-sensitive polymer poly(N-isopropylacrylamide) (PNIPAAm). At room temperature, a suspension of these beads flows through a microfluidic channel constructed of poly(ethylene terephthalate). However, when the temperature in the channel is raised above the lower critical solution temperature (LCST) of PNIPAAm, the beads aggregate and adhere to the walls of the channel. The adhered beads are stable for long durations on the channel walls (demonstrated up to 70 min) in the presence of flow. The beads were further modified with the affinity moiety biotin, which tightly binds streptavidin. The dual-modified beads were adhered to the channel walls and functioned as a chromatographic affinity separation matrix, capable of binding streptavidin that was flowed through the microfluidic channel. Upon the reverse thermal stimulation to below the PNIPAAm LCST, the beads and captured streptavidin were observed to quickly dissolve and elute from the channel walls. This temperature-responsive affinity chromatography matrix can thus be flowed into a column and aggregated via temperature change, followed by the controlled release of affinity-captured targets back into the microfluidic flow stream.

Maleic anhydride copolymers--a versatile platform for molecular biosurface engineering

A platform of thin polymer coatings was introduced for the functional modulation of immobilized bioactive molecules at solid/liquid interfaces. The approach is based on covalently attached alternating maleic acid anhydride copolymers with a variety of comonomers and extended through conversion of the anhydride moieties by hydrolysis, reaction with functional amines, and other conversions of the anhydride moieties. We demonstrate that these options permit control of the physicochemical constraints for bioactive molecules immobilized at interfaces to influence important performance characteristics of biofunctionalized materials for medical devices and molecular diagnostics. Examples concern the impact of the substrate-anchorage of fibronectin on the formation of cell-matrix adhesions, the orientation of endothelial cells according to lateral anti-adhesive micropatterns using grafted poly(ethylene oxide), and the spacer-dependent activity of immobilized synthetic thrombin inhibitors.

Effects of the local mechanical environment on vertebrate tissue differentiation during repair: does repair recapitulate development?

The local mechanical environment is a crucial factor in determining cell and tissue differentiation during vertebrate skeletal development and repair. Unlike the basic response of bone to mechanical load, as described in Wolff's law, the mechanobiological relationship between the local mechanical environment and tissue differentiation influences everything from tissue type and molecular architecture to the formation of complex joints. This study tests the hypothesis that precisely controlled mechanical loading can regulate gene expression, tissue differentiation and tissue architecture in the adult skeleton and that precise manipulation of the defect's local mechanical environment can initiate a limited recapitulation of joint tissue development. We generated tissue type predictions using finite element models (FEMs) interpreted by published mechanobiological fate maps of tissue differentiation. The experiment included a custom-designed external fixator capable of introducing daily bending, shear or a combination of bending and shear load regimens to induce precisely controlled mechanical conditions within healing femoral defects. Tissue types and ratios were characterized using histomorphometrics and molecular markers. Tissue molecular architecture was quantified using polarized light and Fourier transforms, while immunological staining and in situ hybridization were used to characterize gene expression. The finite element models predicted the differentiation of cartilage within the defects and that substantial fibrous tissues would develop along the extreme excursion peripheries in the bending group. The three experimentally induced loading regimens produced contiguous cartilage bands across all experimental defects, inhibiting bony healing. Histomorphometric analysis of the ratios of cartilage to bone in the experimental groups were not significantly different from those for the knee joint, and Fourier transform analysis determined significantly different collagen fibril angle specializations within superficial, intermediate and deep layers of all experimental cartilages (P<0.0001), approximating those for articular cartilage. All stimulations resulted in the expression of collagen type II, while the bending stimulation also resulted in the expression of the joint-determining gene GDF-5. These findings indicate that the local mechanical environment is an important regulator of gene expression, tissue differentiation and tissue architecture.

Perimeter growth of a branched structure: application to crackle sounds in the lung

We study an invasion percolation process on Cayley trees and find that the dynamics of perimeter growth is strongly dependent on the nature of the invasion process, as well as on the underlying tree structure. We apply this process to model the inflation of the lung in the airway tree, where crackling sounds are generated when airways open. We define the perimeter as the interface between the closed and opened regions of the lung. In this context we find that the distribution of time intervals between consecutive openings is a power law with an exponent beta approximately 2. We generalize the binary structure of the lung to a Cayley tree with a coordination number Z between 2 and 4. For Z=4, beta remains close to 2, while for a chain, Z=2 and beta=1, exactly. We also find a mean field solution of the model.

Force- and moment-generating capacities of muscles in the distal forelimb of the horse

A detailed musculoskeletal model of the distal equine forelimb was developed to study the influence of musculoskeletal geometry (i.e. muscle paths) and muscle physiology (i.e. force-length properties) on the force- and moment-generating capacities of muscles crossing the carpal and metacarpophalangeal joints. The distal forelimb skeleton was represented as a five degree-of-freedom kinematic linkage comprised of eight bones (humerus, radius and ulna combined, proximal carpus, distal carpus, metacarpus, proximal phalanx, intermediate phalanx and distal phalanx) and seven joints (elbow, radiocarpal, intercarpal, carpometacarpal, metacarpophalangeal (MCP), proximal interphalangeal (pastern) and distal interphalangeal (coffin)). Bone surfaces were reconstructed from computed tomography scans obtained from the left forelimb of a Thoroughbred horse. The model was actuated by nine muscle-tendon units. Each unit was represented as a three-element Hill-type muscle in series with an elastic tendon. Architectural parameters specifying the force-producing properties of each muscle-tendon unit were found by dissecting seven forelimbs from five Thoroughbred horses. Maximum isometric moments were calculated for a wide range of joint angles by fully activating the extensor and flexor muscles crossing the carpus and MCP joint. Peak isometric moments generated by the flexor muscles were an order of magnitude greater than those generated by the extensor muscles at both the carpus and the MCP joint. For each flexor muscle in the model, the shape of the maximum isometric joint moment-angle curve was dominated by the variation in muscle force. By contrast, the moment-angle curves for the muscles that extend the MCP joint were determined mainly by the variation in muscle moment arms. The suspensory and check ligaments contributed more than half of the total support moment developed about the MCP joint in the model. When combined with appropriate in vivo measurements of joint kinematics and ground-reaction forces, the model may be used to determine muscle-tendon and joint-reaction forces generated during gait.

A high-throughput quantitative multiplex kinase assay for monitoring information flow in signaling networks: application to sepsis-apoptosis

To treat complex human diseases effectively, a systems-level approach is needed to understand the interplay of environmental cues, intracellular signals, and cellular behaviors that underlie disease states. This approach requires high-throughput, multiplex techniques that measure quantitative temporal variations of multiple protein activities in the intracellular signaling network. Here, we describe a single microtiter-based format that simultaneously quantifies protein kinase activities in the phosphatidylinositol 3-kinase pathway (Akt), nuclear factor-kappaB pathway (IKK), and three core mitogen-activated protein kinase pathways (ERK, JNK1, MK2). These parallel high-throughput assays are stringently linear, redundantly specific, reproducible, and sensitive compared with classical low-throughput techniques. When applied to a model of sepsis-induced colon epithelial apoptosis, this approach identified a late phase of Akt activity as a critical mediator of cell survival that quantitatively contributed to the efficacy of insulin as an anti-apoptotic cue. Thus, sampling parallel nodes in the intracellular signaling network identified part of the molecular mechanism underlying the efficacy of insulin in the treatment of human sepsis.

Tandem isotachophoresis-zone electrophoresis via base-mediated destacking for increased detection sensitivity in microfluidic systems

Electrophoresis in microfluidic devices is becoming a useful analytical platform for a variety of biological assays. In this report, we present a method that allows for an increased sensitivity of detection of fluorescent molecules in microfluidic electrophoresis devices. This capability is provided by the implementation of a particular buffer system that is designed to initially function in an isotachophoretic (ITP) mode and, then after a controlled amount of electric current has been applied to the system, to transition to a zone electrophoretic mode. In the initial ITP mode, analytes dissolved in a large volume of injected sample are concentrated into a single narrow zone. After application of a sufficient and adjustable amount of electric current, the system switches into a zone electrophoretic mode, where the concentrated analytes are separated according to their electrophoretic mobilities. Application of this tandem ITP-zone electrophoretic strategy to the concentration, separation, and detection of fluorescent reporter molecules in a standard microfluidic device results in an approximately 50-fold increase in detection sensitivity relative to equivalent separations that are obtained with zone electrophoresis alone. Even with very long initial sample plugs (up to 3000 microm), this strategy produces electrophoretic separations with high resolutions and peak efficiencies. This strategy can be implemented to increase detection sensitivity in any standard microfluidic electrophoresis platform and does not require any specialized hardware or microchannel configurations.

Isolation of motile spermatozoa from semen samples using microfluidics

A microfluidic device was designed with two parallel laminar flow channels where non-motile spermatozoa and debris would flow along their initial streamlines and exit one outlet, whereas motile spermatozoa had an opportunity to swim into a parallel stream and exit a separate outlet. Motile sperm samples were prepared with density gradient separation (n = 5). Sperm motility was assessed the following day after exposing aliquots to polydimethylsiloxane (PDMS) used to construct the device. There was no difference in sperm motility when compared with unexposed aliquots (P > 0.05). Unprocessed semen samples (n = 10) were placed in wider channels and sperm motility and strict morphology were assessed from sorted outlets. Sperm motility increased from 44 +/- 4.5% to 98 +/- 0.4% (P < 0.05) and morphology increased from 10 +/- 1.05% to 22 +/- 3.3% (P < 0.05) following processing. Finally, density gradient prepared samples (n = 6) containing 5 x 10(6) motile spermatozoa/ml and 50 x 10(6) round immature germ cells/ml were sorted and assessed in a similar fashion. The ratio of motile spermatozoa to round immature germ cells in the wide inlet (1:10) was significantly improved in the thin outlet (33:1) (P < 0.05). This microfluidic device provides a novel method for isolating motile, morphologically normal spermatozoa from semen samples without centrifugation. This technology may prove useful in isolating motile spermatozoa from oligozoospermic samples, even with high amounts of non-motile gamete and/or non-gamete cell contamination. A movie sequence showing streaming and sorting of spermatozoa may be purchased for viewing on the internet at www.rbmonline.com/Article/847 (free to web subscribers).

Monitoring the biomechanical response of individual cells under compression: a new compression device

Skeletal muscle cells are sensitive to sustained compression, which can lead to the development of pressure sores. Although it is known that this type of tissue breakdown depends on the magnitude and duration of the applied load, the exact relationship between cell deformation and damage remains unclear. To gain more insight into this process, a method has been developed, that incorporates the use of a new loading device and confocal microscopy. The loading device is able to compress individual cells, either statically or dynamically, while measuring the resulting forces. Experiments can be performed under ideal environmental conditions, comparable with those of a CO2 incubator. First compression experiments on C2C12 mouse myoblasts showed the shape changes that cells undergo during static compression by the loading device. Calculations using the three-dimensional confocal images showed no change in volume and an increase in the surface area of the cell as a result of compression. The device presented here provides a useful way to monitor the biomechanical response of skeletal muscle cells during long-term compression experiments. Therefore it will contribute to the knowledge about strain-induced cell damage, as seen in pressure sores and other mechanically induced clinical conditions.

Long-term intermittent shear deformation improves the quality of cartilaginous tissue formed in vitro

The formation of cartilaginous tissue in vitro is a promising alternative to repair damaged articular cartilage. However, recent attempts to tissue-engineer articular cartilage that has similar properties to the native tissue have proven to be difficult. The in vitro-formed cartilaginous tissue typically has a similar proteoglycan content to native cartilage, but has a reduced collagen content and only a fraction of the mechanical properties. In this study, we investigated whether the intermittent application of cyclic shearing forces during tissue formation would improve the tissue quality. Chondrocyte cultures were stimulated at a 2% shear strain amplitude at a frequency of 1 Hz for 400 cycles every 2nd day. At one week, both collagen and proteoglycan synthesis increased (23+/-6% and 20+/-6%, respectively) over the unstimulated, static controls. At four weeks, an increased amount of tissue formed (stimulated: 1.85+/-0.08, unstimulated: 1.58+/-0.07 mg dry wt.). This tissue contained approximately 40% more collagen (stimulated: 511+/-23, unstimulated: 367+/-24 microg/construct) and 35% more proteoglycans (stimulated: 376+/-21, unstimulated: 279+/-26 microg/construct). Tissues that formed in the presence of shearing forces also displayed a 3-fold increase in compressive load-bearing capacity (stimulated: 16+/-5, unstimulated: 5+/-1 kPa max. equilibrium stress) and a 6-fold increase in stiffness (stimulated: 112+/-36, unstimulated: 20+/-6 kPa max. equilibrium modulus) compared to the static controls. These results demonstrate that intermittent application of dynamic shearing forces over a four-week period improves the quality of cartilaginous tissue formed in vitro. Interestingly, low amplitudes of shear stimulation for short periods of time (6 min of stimulation applied every 2nd day) produced these changes.

Combined in vivo confocal Raman spectroscopy and confocal microscopy of human skin

In vivo confocal Raman spectroscopy is a noninvasive optical method to obtain detailed information about the molecular composition of the skin with high spatial resolution. In vivo confocal scanning laser microscopy is an imaging modality that provides optical sections of the skin without physically dissecting the tissue. A combination of both techniques in a single instrument is described. This combination allows the skin morphology to be visualized and (subsurface) structures in the skin to be targeted for Raman measurements. Novel results are presented that show detailed in vivo concentration profiles of water and of natural moisturizing factor for the stratum corneum that are directly related to the skin architecture by in vivo cross-sectional images of the skin. Targeting of skin structures is demonstrated by recording in vivo Raman spectra of sweat ducts and sebaceous glands in situ. In vivo measurements on dermal capillaries yielded high-quality Raman spectra of blood in a completely noninvasive manner. From the results of this exploratory study we conclude that the technique presented has great potential for fundamental skin research, pharmacology (percutaneous transport), clinical dermatology, and cosmetic research, as well as for noninvasive analysis of blood analytes, including glucose.

In vivo NMR studies of the glutamate neurotransmitter flux and neuroenergetics: implications for brain function

Until very recently, non-invasive measurement of the glutamate-glutamine cycle in the intact mammalian brain had not been possible. In this review, we describe some studies that have led to quantitative assessment of the glutamate-glutamine cycle (Vcyc), as well as other important metabolic fluxes (e.g., glucose oxidation, CMRglc(ox)), with (13)C magnetic resonance spectroscopy (MRS) in vivo. These (13)C MRS studies clearly demonstrate that glutamate released from presynaptic neurons is taken up by the astrocyte for subsequent glutamine synthesis. Contrary to the earlier concept of a small, metabolically inactive neurotransmitter pool, in vivo (13)C MRS studies demonstrate that glutamate release and recycling is a major metabolic pathway that cannot be distinguished from its actions of neurotransmission. Furthermore, the in vivo (13)C MRS studies demonstrate in the rat cerebral cortex that increases in Vcyc and neuronal CMRglc(ox) are linearly related with a close to 1:1 slope. Measurements in human cerebral cortex are in agreement with this result. This relationship is consistent with more than two thirds of the energy yielded by glucose oxidation being used to support events associated with glutamate neurotransmission, and it supports a molecular model of a stoichiometric coupling between glutamate neurotransmission and functional glucose oxidation. (13)C MRS measurements of resting human cerebral cortex have found a high level of glutamate-glutamine cycling. This high resting neuronal activity, which is subtracted away in brain mapping studies by positron emission tomography (PET) and functional magnetic resonance imaging (fMRI), has significant implications for the interpretations of functional imaging data. Here we review and discuss the importance of neurotransmission and neuroenergetics as measured by (13)C MRS for understanding brain function and interpreting fMRI.

Combined effects of dynamic tissue shear deformation and insulin-like growth factor I on chondrocyte biosynthesis in cartilage explants

Biophysical forces and biochemical factors play crucial roles in the maintenance of the integrity of articular cartilage. In this study, we explored the effect of dynamic tissue shear deformation and insulin-like growth factor I (IGF-I) on matrix synthesis by chondrocytes within native cartilage explants. Dynamic tissue shear in the range of 0.5-6% strain amplitude at 0.1 Hz was applied to cartilage explants cultured in serum-free medium. Dynamic tissue shear above 1.5% strain amplitude significantly stimulated protein and proteoglycan synthesis, by maximum values of 35 and 25%, respectively, over statically held control specimens. In the absence of tissue shear, IGF-I augmented protein and proteoglycan synthesis up to twofold at IGF-I concentrations in the range of 100-300 ng/ml. When tissue shear and IGF-I stimuli were combined, matrix biosynthesis levels were significantly higher than the maximal effect caused by either stimulus alone. However, there was no significant interaction between tissue shear and IGF-I as determined by two-way ANOVA. We then quantified the effect of dynamic tissue shear on the transport of IGF-I into and within cartilage explants. [125I]IGF-I was added to the medium, and the levels of intratissue [125I]IGF-I were directly measured as a function of time over 48 h in the presence and absence of continuous dynamic shear strain. Dynamic shear did not alter the rate of uptake of [125I]IGF-I into the explants, suggesting that convective diffusion of [125I]IGF-I is negligible under the shear strain conditions used. This is in marked contrast to the enhancement of transport reported in response to uniaxial dynamic compression. Taken together, these data suggest that (1) the stimulatory effect of tissue shear is via mechanotransduction pathways and not by facilitated transport of biochemical factors and (2) chondrocytes may possess complementary signal transduction pathways for biophysical and biochemical factors leading to changes in metabolic activity.

Percutaneous cryoablation in treatment of liver cancer: a report of 31 cases

AIM

To describe the indication, efficacy and clinical significance of percutaneous cryoablation in the treatment of liver malignancy.

METHODS

Total 31 patients with histologically or clinically confirmed primary or metastatic malignancies were treated pucutaneously under ultrasound guidance using the cryocare surgical system from July 2001 to January 2002. All patients were followed up to determine the serum tumor marker, and reveal CT scans, MRI images or utra-sound images.

RESULTS

This therapy was performed in 31 patients including 26 cases with Child A liver reserve, 4 cases with Child B and 1 cases with Child C. There were 21 cases of primary liver cancer and 10 metastastic liver cancer. AFP positive small liver cancer became AFP negative in 80% patients. The rate of completely concreted necrosis in small hepatic cancer with negative AFP was 66.7%, shown by CT or MRI. The curative rate for metastasis liver cancer was 50% at CT, MRI or tumor marker level.

CONCLUSION

Percutaneous cryoablation is a kind of new palliative treatment for liver carcinoma. It is minimally invasive, safe and effective especially for patients with unresectable liver cancer.

In vitro bone formation using muscle-derived cells: a new paradigm for bone tissue engineering using polymer-bone morphogenetic protein matrices

Over 800,000 bone grafting procedures are performed in the United States annually, creating a demand for viable alternatives to autogenous bone, the grafting standard in osseous repair. The objective of this study was to examine the efficacy of a BMP-polymer matrix in inducing the expression of the osteoblastic phenotype and in vitro bone formation by muscle-derived cells. Specifically, we evaluated the ability of bone morphogenetic protein-7 (BMP-7), delivered from a poly(lactide-co-glycolide) (PLAGA) matrix, to induce the differentiation of cells derived from rabbit skeletal muscle into osteoblast-like cells and subsequently form mineralized tissue. Results confirmed that muscle-derived cells attached and proliferated on the PLAGA substrates. BMP-7 released from PLAGA induced the muscle-derived cells to increase bone marker expression and form mineralized cultures. These results demonstrate the efficacy of a BMP-polymer matrix in inducing the expression of the osteoblastic phenotype by muscle-derived cells and present a new paradigm for bone tissue engineering.

Dynamic changes of fibrin architecture during fibrin formation and intrinsic fibrinolysis of fibrin-rich clots

Clotting and fibrinolysis are initiated simultaneously in vivo, and fibrinolysis usually occurs without any individualized lysis front (intrinsic fibrinolysis). We have developed a novel model to assess whether morphological changes resulting from intrinsic fibrinolysis are similar to those previously reported at the lysis front using externally applied lytic agents. Fibrin assembly and fibrinolysis were followed in real-time by confocal microscopy using gold-labeled fibrinogen molecules. An increase in fiber absorbance (30%, p < 0.01) and a decrease in fiber diameter (60%, p < 0.01) due to the ongoing accumulation and packing of fibrin molecules were the most significant detectable features occurring during fibrin assembly. Similar features with a similar magnitude were observed during fibrin dissolution, but in the reverse order and with a 3-fold increase in duration. Then, lysing fibers were progressively transected laterally, and thinner fibers were cleaved at a 2.5-fold faster rate than thicker fibers (p < 0.001). Frayed lysing fibers were seen to interact progressively with adjoining fibers (agglomeration), leading to a 76 and 88% increase in the network pore diameter (p < 0.05) and fiber diameter (p < 0.01), respectively. At the maximum decrease in fiber absorbance (46%, p < 0.05), the network suddenly collapsed with the release of large fragments that gradually vanished. Morphological changes of fibrin that occur during intrinsic fibrinolysis are similar as those observed next to the lysis front, although they are not restricted spatially to the clot/surrounding milieu interface but are observed through the entire clot.

Ozone-induced disruptions of lung transcriptomes

We have analyzed changes in approximately 4000 lung mRNAs, with GeneChips, in mice exposed to 1 ppm O(3) for three consecutive nights (8 h per night). Differential gene expression analysis identified approximately 260 O(3) sensitive genes; approximately 80% of these were repressed and approximately 20% were induced in O(3)-exposed mice compared to the air-exposed controls. A 20-fold induction of serum amyloid A3 mRNA by O(3) suggested activation of NF-kappaB and CCAAT/enhancer binding protein-mediated pathways by inflammatory cytokines. Induction (up to 14-fold) of 12 genes that increase DNA synthesis and cell cycle progression, and increase (approximately 7-fold) in CD44 mRNA and macrophage metalloelastase suggested a state of O(3)-induced hyperplasia and lung remodeling. Several mRNAs encoding enzymes of xenobiotic metabolism and cytoskeletal functions were repressed and may suggest cytokine mediated suppression of cytochrome P450 expression and cachexia-like inflammatory state in ozone-exposed lungs. The expressions of approximately 30 genes of immune response were also repressed. Collectively this genome-wide analysis of lungs identified ozone-induced disruption of gene transcriptional profile indicative of increased cellular proliferation under suppressed immune surveillance and xenobiotic metabolism.

Feasibility, sensitivity, and reliability of laser-induced fluorescence imaging of green fluorescent protein-expressing tumors in vivo

Whole-body imaging of green fluorescent protein (GFP) can be used to test the efficiency of gene carriers for in vivo transduction. The aim of the current study was to determine the sensitivity and the accuracy of a GFP imaging procedure by in vivo investigation of GFP-expressing tumor cells. An improved method of whole-body GFP imaging made use of a laser excitation source and band-pass filters matched specifically to GFP and constitutive tissue fluorescence emission bands. Processing of the primary GFP fluorescence images acquired by the CCD camera subtracted background tissue autofluorescence. Our approach achieved 100% sensitivity and specificity for in vivo detection of 10%-transfected BxPc3 pancreatic tumor after subcutaneous grafting or orthotopical implantation in the pancreas of nude mice. It also detected less transfected tumors (i.e., 1 to 5%) but with a loss in sensitivity (50% of cases). The system was employed over a 5-week period to monitor the persistence of GFP expression in 10%-transfected BxPc3 tumors orthotopically implanted in the pancreas of two nude mice, allowing the direct visualization of tumor progression and spread. In facilitating the temporal-spatial follow-up of GFP expression in vivo, the optimized laser-induced fluorescence imaging device can support preclinical investigations of vectors for therapeutic gene transduction through regular, harmless, real-time monitoring of theirin vivo transductional efficacy and persistence.

Interaction of nitrogen monoxide with hemoglobin and the artefactual production of S-nitroso-hemoglobin

Hemoglobin (Hb) is probably the most thoroughly studied protein in the human body. However, it has recently been proposed that in addition to the well known function of dioxygen and carbon dioxide transporter, one of the main roles of hemoglobin is to store and transport nitrogen monoxide. This hypothesis is highly disputed and is in contrast to the proposal that hemoglobin serves as an NO. scavenger in the blood. In this short review, I have presented the current status of research on the much-debated mechanism of the reaction between circulating hemoglobin and NO.. Despite the fact that oxyHb is extremely rapidly oxidized by NO., under basal physiological conditions the biological activity of NO. in the blood vessels is not completely lost. It has been shown that three factors reduce the efficiency of hemoglobin to scavenge NO.: a so-called red blood cell-free zone created close to the vessel wall by intravascular flow, an undisturbed layer around the red blood cells--where the NO. concentration is much smaller than the bulk concentration--and/or the red blood cell membrane. Alternatively, it has been proposed that NO. binds to Cys beta 93 of oxyHb, is liberated after deoxygenation of Hb, and consequently allows for a more effective delivery of O2 to peripheral tissues. However, because of the extremely fast rate of the reaction between NO. and oxyHb, experiments in vitro lead to artefactual production of large amounts of S-nitroso-hemoglobin. These results, together with other data, which challenge most steps of the NO.-transporter hypothesis, are discussed.

Specificity is complex and time consuming: mutual exclusivity in tyrosine kinase-mediated signaling

Most fundamental cellular processes are transduced through tyrosine kinase (TK)-mediated pathways. For transduction without corruption, the protein-protein interactions involved have to be mutually exclusive. Many of these proteins bind via homologous domains whose binding characteristics suggest that their innate specificity is not sufficiently high to account for the integrity of signal transduction. Stimulation of TK-mediated signals is often accompanied by recruitment of a precise, multimolecular protein complex that is itself capable of imposing specificity. Furthermore, this complex provides protection against phosphatase activity, controlling the longevity of the active signaling complex, and thus influencing outcomes in subsequent downstream events.

Cell and organ printing 2: fusion of cell aggregates in three-dimensional gels

We recently developed a cell printer (Wilson and Boland, 2003) that enables us to place cells in positions that mimic their respective positions in organs. However, this technology was limited to the printing of two-dimensional (2D) tissue constructs. Here we describe the use of thermosensitive gels to generate sequential layers for cell printing. The ability to drop cells on previously printed successive layers provides a real opportunity for the realization of three-dimensional (3D) organ printing. Organ printing will allow us to print complex 3D organs with computer-controlled, exact placing of different cell types, by a process that can be completed in several minutes. To demonstrate the feasibility of this novel technology, we showed that cell aggregates can be placed in the sequential layers of 3D gels close enough for fusion to occur. We estimated the optimum minimal thickness of the gel that can be reproducibly generated by dropping the liquid at room temperature onto a heated substrate. Then we generated cell aggregates with the corresponding (to the minimal thickness of the gel) size to ensure a direct contact between printed cell aggregates during sequential printing cycles. Finally, we demonstrated that these closely-placed cell aggregates could fuse in two types of thermosensitive 3D gels. Taken together, these data strongly support the feasibility of the proposed novel organ-printing technology.