Disorder-to-order transition of long fibers contained in evaporating sessile drops

A liquid drop containing a long fiber is a complex system whose configuration is determined by an interplay of elastic stresses in the fiber and capillary forces due to the liquid. We study the morphological evolution of fibers that are much longer than the drop diameter in evaporating sessile drops. After insertion, the fibers are either found in an ordered or disordered state, with increasing disorder for increasing fiber length. Upon evaporation, the order increases, in such a way that the final configuration deposited on the solid surface is either a circle, an ellipse, or 8-shaped. The morphology of the deposit depends on the fiber length and the elastocapillary length, both non-dimensionalized with the characteristic drop size, which we classify in a morphology regime map. The disorder-to-order transition allows depositing ordered fiber structures on solid surfaces even in cases of a strongly disordered state after fiber insertion. Combined with technologies such as inkjet printing, this process could open new avenues to decorate surfaces with filamental structures whose morphology can be controlled by varying the fiber length.

SimuCell3D: three-dimensional simulation of tissue mechanics with cell polarization

The three-dimensional (3D) organization of cells determines tissue function and integrity, and changes markedly in development and disease. Cell-based simulations have long been used to define the underlying mechanical principles. However, high computational costs have so far limited simulations to either simplified cell geometries or small tissue patches. Here, we present SimuCell3D, an efficient open-source program to simulate large tissues in three dimensions with subcellular resolution, growth, proliferation, extracellular matrix, fluid cavities, nuclei and non-uniform mechanical properties, as found in polarized epithelia. Spheroids, vesicles, sheets, tubes and other tissue geometries can readily be imported from microscopy images and simulated to infer biomechanical parameters. Doing so, we show that 3D cell shapes in layered and pseudostratified epithelia are largely governed by a competition between surface tension and intercellular adhesion. SimuCell3D enables the large-scale in silico study of 3D tissue organization in development and disease at a great level of detail.

Geometric effects position renal vesicles during kidney development

During kidney development, reciprocal signaling between the epithelium and the mesenchyme coordinates nephrogenesis with branching morphogenesis of the collecting ducts. The mechanism that positions the renal vesicles, and thus the nephrons, relative to the branching ureteric buds has remained elusive. By combining computational modeling and experiments, we show that geometric effects concentrate the key regulator, WNT9b, at the junctions between parent and daughter branches where renal vesicles emerge, even when uniformly expressed in the ureteric epithelium. This curvature effect might be a general paradigm to create non-uniform signaling in development.

Geometric mapping from rectilinear material orthotropy to isotropy: Insights into plates and shells

Orthotropic shell structures are ubiquitous in biology and engineering, from bacterial cell walls to reinforced domes. We present a rescaling transformation that maps an orthotropic shallow shell to an isotropic one with a different local geometry. The mapping is applicable to any shell section for which the material orthotropy directions match the principal curvature directions, assuming the commonly used Huber form for the orthotropic shear modulus. Using the rescaling transformation, we derive exact expressions for the buckling pressure as well as the linear indentation response of orthotropic cylinders and general ellipsoids of revolution, which we verify against numerical simulations. Our analysis disentangles the separate contributions of geometric and material anisotropy to shell rigidity. In particular, we identify the geometric mean of orthotropic elastic constants as the key quantifier of material stiffness, playing a role akin to the Gaussian curvature which captures the geometric stiffness contribution. Besides providing insights into the mechanical response of orthotropic shells, our work rigorously establishes the validity of isotropic approximations to orthotropic shells and also identifies situations in which these approximations might fail.

2D effects enhance precision of gradient-based tissue patterning

Robust embryonic development requires pattern formation with high spatial accuracy. In epithelial tissues that are patterned by morphogen gradients, the emerging patterns achieve levels of precision that have recently been explained by a simple one-dimensional reaction-diffusion model with kinetic noise. Here, we show that patterning precision is even greater if transverse diffusion effects are at play in such tissues. The positional error, a measure for spatial patterning accuracy, decreases in wider tissues but then saturates beyond a width of about ten cells. This demonstrates that the precision of gradient-based patterning in two- or higher-dimensional systems can be even greater than predicted by 1D models, and further attests to the potential of noisy morphogen gradients for high-precision tissue patterning.

Impact of cell size on morphogen gradient precision

Tissue patterning during embryonic development is remarkably precise. In this paper, we numerically determine the impact of the cell diameter, gradient length, and the morphogen source on the variability of morphogen gradients. In this way, we show that the positional error increases with the gradient length relative to the size of the morphogen source, and with the square root of the cell diameter and the readout position. We provide theoretical explanations for these relationships, and show thatthey enable high patterning precision over developmental time for readouts that scale with expanding tissue domains, as observed in the Drosophila wing disc. Our analysis suggests that epithelial tissues generally achieve higher patterning precision with small cross-sectional cell areas. An extensive survey of measured apical cell areas shows that they are indeed small in developing tissues that are patterned by morphogen gradients. Enhanced precision may thus have led to the emergence of pseudostratification in epithelia, a phenomenon for which the evolutionary benefit had so far remained elusive.

Patterning precision under non-linear morphogen decay and molecular noise

Morphogen gradients can instruct cells about their position in a patterned tissue. Non-linear morphogen decay has been suggested to increase gradient precision by reducing the sensitivity to variability in the morphogen source. Here, we use cell-based simulations to quantitatively compare the positional error of gradients for linear and non-linear morphogen decay. While we confirm that non-linear decay reduces the positional error close to the source, the reduction is very small for physiological noise levels. Far from the source, the positional error is much larger for non-linear decay in tissues that pose a flux barrier to the morphogen at the boundary. In light of this new data, a physiological role of morphogen decay dynamics in patterning precision appears unlikely.

Relationship between epithelial organization and morphogen interpretation

Despite molecular noise and genetic differences between individuals, developmental outcomes are remarkably constant. Decades of research has focused on the underlying mechanisms that ensure this precision and robustness. Recent quantifications of chemical gradients and epithelial cell shapes provide novel insights into the basis of precise development. In this review, we argue that these two aspects may be linked in epithelial morphogenesis.

Hinge point emergence in mammalian spinal neurulation

Neurulation is the process in early vertebrate embryonic development during which the neural plate folds to form the neural tube. Spinal neural tube folding in the posterior neuropore changes over time, first showing a median hinge point, then both the median hinge point and dorsolateral hinge points, followed by dorsolateral hinge points only. The biomechanical mechanism of hinge point formation in the mammalian neural tube is poorly understood. Here we employ a mechanical finite element model to study neural tube formation. The computational model mimics the mammalian neural tube using microscopy data from mouse and human embryos. While intrinsic curvature at the neural plate midline has been hypothesized to drive neural tube folding, intrinsic curvature was not sufficient for tube closure in our simulations. We achieved neural tube closure with an alternative model combining mesoderm expansion, nonneural ectoderm expansion, and neural plate adhesion to the notochord. Dorsolateral hinge points emerged in simulations with low mesoderm expansion and zippering. We propose that zippering provides the biomechanical force for dorsolateral hinge point formation in settings where the neural plate lateral sides extend above the mesoderm. Together, these results provide a perspective on the biomechanical and molecular mechanism of mammalian spinal neurulation.

Large-scale orientational order in bacterial colonies during inward growth

During colony growth, complex interactions regulate the bacterial orientation, leading to the formation of large-scale ordered structures, including topological defects, microdomains, and branches. These structures may benefit bacterial strains, providing invasive advantages during colonization. Active matter dynamics of growing colonies drives the emergence of these ordered structures. However, additional biomechanical factors also play a significant role during this process. Here, we show that the velocity profile of growing colonies creates strong radial orientation during inward growth when crowded populations invade a closed area. During this process, growth geometry sets virtual confinement and dictates the velocity profile. Herein, flow-induced alignment and torque balance on the rod-shaped bacteria result in a new stable orientational equilibrium in the radial direction. Our analysis revealed that the dynamics of these radially oriented structures, also known as aster defects, depend on bacterial length and can promote the survival of the longest bacteria around localized nutritional hotspots. The present results indicate a new mechanism underlying structural order and provide mechanistic insights into the dynamics of bacterial growth on complex surfaces.

Precision of morphogen gradients in neural tube development

Morphogen gradients encode positional information during development. How high patterning precision is achieved despite natural variation in both the morphogen gradients and in the readout process, is still largely elusive. Here, we show that the positional error of gradients in the mouse neural tube has previously been overestimated, and that the reported accuracy of the central progenitor domain boundaries in the mouse neural tube can be achieved with a single gradient, rather than requiring the simultaneous readout of opposing gradients. Consistently and independently, numerical simulations based on measured molecular noise levels likewise result in lower gradient variabilities than reported. Finally, we show that the patterning mechanism yields progenitor cell numbers with even greater precision than boundary positions, as gradient amplitude changes do not affect interior progenitor domain sizes. We conclude that single gradients can yield the observed developmental precision, which provides prospects for tissue engineering.

3D cell neighbour dynamics in growing pseudostratified epithelia

During morphogenesis, epithelial sheets remodel into complex geometries. How cells dynamically organise their contact with neighbouring cells in these tightly packed tissues is poorly understood. We have used light-sheet microscopy of growing mouse embryonic lung explants, three-dimensional cell segmentation, and physical theory to unravel the principles behind 3D cell organisation in growing pseudostratified epithelia. We find that cells have highly irregular 3D shapes and exhibit numerous neighbour intercalations along the apical-basal axis as well as over time. Despite the fluidic nature, the cell packing configurations follow fundamental relationships previously described for apical epithelial layers, that is, Euler's polyhedron formula, Lewis' law, and Aboav-Weaire's law, at all times and across the entire tissue thickness. This arrangement minimises the lateral cell-cell surface energy for a given cross-sectional area variability, generated primarily by the distribution and movement of nuclei. We conclude that the complex 3D cell organisation in growing epithelia emerges from simple physical principles.

The biomechanical basis of biased epithelial tube elongation in lung and kidney development

During lung development, epithelial branches expand preferentially in a longitudinal direction. This bias in outgrowth has been linked to a bias in cell shape and in the cell division plane. How this bias arises is unknown. Here, we show that biased epithelial outgrowth occurs independent of the surrounding mesenchyme, of preferential turnover of the extracellular matrix at the bud tips and of FGF signalling. There is also no evidence for actin-rich filopodia at the bud tips. Rather, we find epithelial tubes to be collapsed during early lung and kidney development, and we observe fluid flow in the narrow tubes. By simulating the measured fluid flow inside segmented narrow epithelial tubes, we show that the shear stress levels on the apical surface are sufficient to explain the reported bias in cell shape and outgrowth. We use a cell-based vertex model to confirm that apical shear forces, unlike constricting forces, can give rise to both the observed bias in cell shapes and tube elongation. We conclude that shear stress may be a more general driver of biased tube elongation beyond its established role in angiogenesis. This article has an associated 'The people behind the papers' interview.

Collapse of Orthotropic Spherical Shells

We report on the buckling and subsequent collapse of orthotropic elastic spherical shells under volume and pressure control. Going far beyond what is known for isotropic shells, a rich morphological phase space with three distinct regimes emerges upon variation of shell slenderness and degree of orthotropy. Our extensive numerical simulations are in agreement with experiments using fabricated polymer shells. The shell buckling pathways and corresponding strain energy evolution are shown to depend strongly on material orthotropy. We find surprisingly robust orthotropic structures with strong similarities to stomatocytes and tricolpate pollen grains, suggesting that the shape of several of Nature's collapsed shells could be understood from the viewpoint of material orthotropy.

Morphogenesis of filaments growing in flexible confinements

Space-saving design is a requirement that is encountered in biological systems and the development of modern technological devices alike. Many living organisms dynamically pack their polymer chains, filaments or membranes inside deformable vesicles or soft tissue-like cell walls, chorions and buds. Surprisingly little is known about morphogenesis due to growth in flexible confinements--perhaps owing to the daunting complexity lying in the nonlinear feedback between packed material and expandable cavity. Here we show by experiments and simulations how geometric and material properties lead to a plethora of morphologies when elastic filaments are growing far beyond the equilibrium size of a flexible thin sheet they are confined in. Depending on friction, sheet flexibility and thickness, we identify four distinct morphological phases emerging from bifurcation and present the corresponding phase diagram. Four order parameters quantifying the transitions between these phases are proposed.

Susceptibility of cat fleas (Siphonaptera: Pulicidae) to fipronil and imidacloprid using adult and larval bioassays

The monitoring of the susceptibility offleas to insecticides has typically been conducted by exposing adults on treated surfaces. Other methods such as topical applications of insecticides to adults and larval bioassays on treated rearing media have been developed. Unfortunately, baseline responses of susceptible strains of cat flea, Ctenocephalides felis (Bouchè), except for imidacloprid, have not been determined for all on-animal therapies and new classes of chemistry now being used. However, the relationship between adult and larval bioassays of fleas has not been previously investigated. The adult and larval bioassays of fipronil and imidacloprid were compared for both field-collected isolates and laboratory strains. Adult topical bioassays of fipronil and imidacloprid to laboratory strains and field-collected isolates demonstrated that LD50s of fipronil and imidacloprid ranged from 0.11 to 0.40 nanograms per flea and 0.02 to 0.18 nanograms per flea, respectively. Resistance ratios for fipronil and imidacloprid ranged from 0.11 to 2.21. Based on the larval bioassay published for imidacloprid, a larval bioassay was established for fipronil and reported in this article. The ranges of the LC50s of fipronil and imidacloprid in the larval rearing media were 0.07-0.16 and 0.11-0.21 ppm, respectively. Resistance ratios for adult and larval bioassays ranged from 0.11 to 2.2 and 0.58 to 1.75, respectively. Both adult and larval bioassays provided similar patterns for fipronil and imidacloprid. Although the adult bioassays permitted a more precise dosage applied, the larval bioassays allowed for testing isolates without the need to maintain on synthetic or natural hosts.

Multifunctional flexible parylene-based intracortical microelectrodes

Delivering drugs directly to the brain tissue opens new approaches to disease treatment and improving neural interfaces. Several approaches using neural prostheses have been made to deliver drugs directly with bypassing the blood-brain barrier (BBB) [1, 2]. In this paper, we propose a new polymer-based flexible microelectrode with drug delivery capability. The probe was fabricated and tested for electrical and fluidic functionality in early stage design. In vivo chronic recording experiments succeeded in demonstrating the in vivo reliability of the probe. Successful in vivo experiments confirm the suitability of the probes as implantable chronic recording devices with robust fluid delivery function.

microRNA122-regulated transgene expression increases specificity of cardiac gene transfer upon intravenous delivery of AAV9 vectors

Adeno-associated virus (AAV) vectors with capsids of AAV serotype 9 enable an efficient transduction of the heart upon intravenous injection of adult mice but also transduce the liver. The aim of this study was to improve specificity of AAV9 vector-mediated cardiac gene transfer by microRNA (miR)-dependent control of transgene expression. We constructed plasmids and AAV vectors containing target sites (TSs) of liver-specific miR122, miR192 and miR148a in the 3' untranslated region (3'UTR) of a luciferase expression cassette. Luciferase expression was efficiently suppressed in liver cell lines expressing high levels of the corresponding miRs, whereas luciferase expression was unaffected in cardiac myocytes. Intravenous injections of AAV9 vectors bearing three repeats of miR122 TS in the 3'UTR of an enhanced green fluorescent expression (EGFP) expression cassette resulted in the absence of EGFP expression in the liver of adult mice, whereas the control vectors without miR TS displayed significant hepatic EGFP expression. EGFP expression levels in the heart, however, were comparable between miR122-regulated and control vectors. The liver-specific de-targeting in vivo using miR122 was even more efficient than transcriptional targeting with a cardiac cytomegalovirus (CMV)-enhanced myosin light chain (MLC) promoter. These data indicate that miR-regulated targeting is a powerful new tool to further improve cardiospecificity of AAV9 vectors.

Spatial steering of deep brain stimulation volumes using a novel lead design

OBJECTIVE

To investigate steering the volume of activated tissue (VTA) with deep brain stimulation (DBS) using a novel high spatial-resolution lead design.

METHODS

We examined the effect of asymmetric current-injection across the DBS-array on the VTA. These predictions were then evaluated acutely in a non-human primate implanted with the DBS-array, using motor side-effect thresholds as the metric for estimating VTA asymmetries.

RESULTS

Simulations show the DBS-array, with electrodes arranged together in a cylindrical configuration, can generate field distributions equivalent to commercial DBS leads, and these field distributions can be modulated using field-steering methods. Stimulation with implanted DBS-arrays showed directionally-selective muscle activation, presumably through spread of stimulation fields into portions of the corticospinal tract lying in the internal capsule.

CONCLUSIONS

Our computational and experimental studies demonstrate that the DBS-array is capable of spatially selective stimulation. Displacing VTAs away from the lead's axis can be achieved using a single simple and intuitive control parameter.

SIGNIFICANCE

Optimal DBS likely requires non-uniform VTAs that may differentially affect a nucleus or fiber pathway. The DBS-array allows positioning VTAs with sub-millimeter precision, which is especially relevant for those patients with DBS leads placed in sub-optimal locations. This may present clinicians with an additional degree of freedom to optimize the DBS therapy.

Coxsackievirus B3 and adenovirus infections of cardiac cells are efficiently inhibited by vector-mediated RNA interference targeting their common receptor

As coxsackievirus B3 (CoxB3) and adenoviruses may cause acute myocarditis and inflammatory cardiomyopathy, isolation of the common coxsackievirus–adenovirus-receptor (CAR) has provided an interesting new target for molecular antiviral therapy. Whereas many viruses show high mutation rates enabling them to develop escape mutants, mutations of their cellular virus receptors are far less likely. We report on antiviral efficacies of CAR gene silencing by short hairpin (sh)RNAs in the cardiac-derived HL-1 cell line and in primary neonatal rat cardiomyocytes (PNCMs). Treatment with shRNA vectors mediating RNA interference against the CAR resulted in almost complete silencing of receptor expression both in HL-1 cells and PNCMs. Whereas CAR was silenced in HL-1 cells as early as 24 h after vector treatment, its downregulation in PNCMs did not become significant before day 6. CAR knockout resulted in inhibition of CoxB3 infections by up to 97% in HL-1 cells and up to 90% in PNCMs. Adenovirus was inhibited by only 75% in HL-1 cells, but up to 92% in PNCMs. We conclude that CAR knockout by shRNA vectors is efficient against CoxB3 and adenovirus in primary cardiac cells, but the efficacy of this approach in vivo may be influenced by cell type-specific silencing kinetics in different tissues.

Highly efficient and specific modulation of cardiac calcium homeostasis by adenovector-derived short hairpin RNA targeting phospholamban

Impaired function of the phospholamban (PLB)-regulated sarcoplasmic reticulum Ca(2+) pump (SERCA2a) contributes to cardiac dysfunction in heart failure (HF). PLB downregulation may increase SERCA2a activity and improve cardiac function. Small interfering (si)RNAs mediate efficient gene silencing by RNA interference (RNAi). However, their use for in vivo gene therapy is limited by siRNA instability in plasma and tissues, and by low siRNA transfer rates into target cells. To address these problems, we developed an adenoviral vector (AdV) transcribing short hairpin (sh)RNAs against rat PLB and evaluated its potential to silence the PLB gene and to modulate SERCA2a-mediated Ca(2+) sequestration in primary neonatal rat cardiomyocytes (PNCMs). Over a period of 13 days, vector transduction resulted in stable > 99.9% ablation of PLB-mRNA at a multiplicity of infection of 100. PLB protein gradually decreased until day 7 (7+/-2% left), whereas SERCA, Na(+)/Ca(2+) exchanger (NCX1), calsequestrin and troponin I protein remained unchanged. PLB silencing was associated with a marked increase in ATP-dependent oxalate-supported Ca(2+) uptake at 0.34 microM of free Ca(2+), and rapid loss of responsiveness to protein kinase A-dependent stimulation of Ca(2+) uptake was maintained until day 7. In summary, these results indicate that AdV-derived PLB-shRNA mediates highly efficient, specific and stable PLB gene silencing and modulation of active Ca(2+) sequestration in PNCMs. The availability of the new vector now enables employment of RNAi for the treatment of HF in vivo.

An optical-optical double resonance experiment in LiH molecules: Lifetime measurements in the C state

An optical-optical double resonance sub-Doppler experiment is used to measure short nonradiative lifetimes in the C (1)Sigma(+) state of LiH. These lifetimes are expected to result from the strong electronic interaction between the C (1)Sigma(+) state and the continuum of the A (1)Sigma(+) state and to vary with the vibrational quantum number, from nanoseconds to milliseconds. The experimental setup combines a molecular beam of LiH, a first cw laser beam locked to a given A-X absorption line, and a second cw laser beam scanned over C-A absorption profiles. Analysis of these absorption profiles in terms of Voigt profiles shows that their Lorentzian components significantly vary with the vibrational quantum numbers of the C state. Nonradiative decay rates deduced this way are systematically larger than the calculated ones but their variations are similar. Coherent saturation effects cannot be invoked to explain this discrepancy.

Efficiency of the Chubon versus the QWERTY keyboard

There is little available evidence for claims of the efficiency of alternative keyboard layouts. Part of the difficulty in providing such evidence is that available research subjects typically have extensive experience with the standard keyboard, making a fair comparison of keyboard layouts difficult. The purpose of this study was to provide a true comparison of the QWERTY and Chubon keyboard layouts for individuals who type with a single digit by neutralizing prior experience through an inversion of the QWERTY keyboard. A single-subject, repeated measures design was used with a convenience sample of nine participants. Each participant began typing on a preselected keyboard and continued typing until fluency was achieved. This procedure was replicated with each keyboard layout. The words per minute typed at fluency for the Reverse QWERTY was approximately 62% of the QWERTY, indicating that the learned effect had been erased. The average typing speed of the Chubon was at least 5% higher and at most 51% higher than the Reverse QWERTY. There were no significant patterns of error. Results of this study indicate that the biomechanical layout of the Chubon is superior to that of the Reverse QWERTY and, by extension, to that of the QWERTY. Additional research is needed to expand knowledge of the effectiveness of the various alternative keyboard layouts.

[Aspects of data protection in telemedicine]

Telemedical applications like the electronic patient file, the electronic physician's letter and the electronic consultation ("Telekonsil"), the electronic prescription, the electronic patient's card (the "patient smart card") facilitate and improve the processing of sensitive medical data as well as the possibilities for using medical resources in an unusual degree and can thereby substantially contribute to the well-being of the patient. However, improving the quality of medical supply must not lead to a degradation of the patients' rights, in particular their right of self-determination. The introduction and the use of telemedical applications do not change the legal basic conditions for medical data processing. Therefore, a patient-friendly telemedicine must include data protection as well. Data protective telemedicine requires medical secrecy ensuring the patients' rights of information and transparency, correction of false and the up-to-date deletion of information that is no longer necessary, as well as secure data processing. All electronic processing of patients' data must meet the requirements of data security, i.e. the confidentiality, the integrity, the availability of the data at any time and the verifiability of the data processing have to be guaranteed. For this, electronic signatures and encodings have to be used, medical information systems have to be protected effectively against any risks resulting from open networks, particularly the Internet, and data processing has to be monitored. Electronic patient files may be open only to the treating physician and the medical assistants up to the necessary extent, ensuring the possibility of an emergency access. Any access beyond that does require the special consent of the patient. The medical secrecy has to be ensured. The electronic prescription with a documentation of the patient's medication requires the consent of the patient and must protect the rights of the physicians. In particular it has to ensure that the respective physician's prescribing behaviour cannot be stored or become known from a third party. Furthermore it has to protect the pharmacists' right to hide their turnover from other pharmacies. So-called patient smart cards require the consent of the patient. The right of the patient to keep his information secret, must be ensured with access options to the information stored on the smart card. Electronic physician's letters and socalled Telekonsile, i.e. the consultation with professional colleagues who were not involved in the patient's treatment from the beginning, require basically the agreement of the patient--if there cannot be dealt with anonymized data already from the beginning. In emergencies, after adequate consideration and weighing of values and interests, the consent of the patient can be suspected. The adherence to these boundary conditions ensures security and trustworthiness of telemedicine regarding the security of data processing as well as the rights of self-determination of all who are concerned. Data protection is also a contribution for the acceptance of these revolutionary advancements in the medical world.

Effects of angiotensin II subtype 1 receptor blockade on cardiac fibrosis and sarcoplasmic reticulum Ca2+ handling in hypertensive transgenic rats overexpressing the Ren2 gene

OBJECTIVE

We evaluated the effects of angiotensin II subtype 1 (AT1) receptor antagonism on cardiac fibrosis and sarcoplasmic (SR) Ca2+ handling in a transgenic rat model of renin-dependent left ventricular (LV) hypertrophy (LVH).

METHODS

Hypertensive transgenic rats overexpressing the Ren2 gene (TGR(mRen2)27) were treated between 10 and 30 weeks of age with the angiotensin II subtype 1 (AT1) receptor antagonist, eprosartan, in an antihypertensive (Ren2-E60, 60 mg/kg per day) and a non-antihypertensive (Ren2-E6, 6 mg/kg per day) dose applied intraperitoneally via osmotic-mini-pumps. They were compared to age-matched Ren2 and Sprague-Dawley (SD) control rats receiving 0.9% NaCl as vehicle via osmotic mini-pumps (Ren2-Vehicle, SD-Vehicle, respectively).

RESULTS

Systolic blood pressure (SBP), LV weight, LV end-diastolic pressure (LVEDP), and cardiac fibrosis were elevated in Ren2-Vehicle, while diastolic function (-dP/dt(max)) and sarcoplasmic reticulum (SR) Ca2+ uptake were decreased in Ren2-Vehicle compared to SD-Vehicle (P < 0.05, respectively). SBP was not altered in Ren2-E6, but reduced to normotensive levels in Ren2-E60 compared to Ren2-Vehicle and SD-Vehicle (P < 0.0001). In both Ren2-E6 and Ren2-E60, LV weights were reduced and LVEDP and -dP/dt(max)normalized compared to Ren2-Vehicle (P < 0.05). SR Ca2+ uptake was normalized in both Ren2-E6 and Ren2-E60. Cardiac fibrosis did not change in Ren2-E6, but perivascular LV fibrosis and hydroxyprolin content were reduced in Ren2-E60 compared to Ren2-Vehicle (P < 0.05, respectively).

CONCLUSIONS

Normalization of LV SR Ca2+ uptake is an important mechanism by which AT1 receptor antagonism improves LV diastolic dysfunction independent from a reduction of SBP and cardiac fibrosis in the TGR (mRen2)27 model.

DNA synthesis in cultured human keratinocytes and HaCaT keratinocytes is reduced by specific inhibition of dipeptidyl peptidase IV (CD26) enzymatic activity

The ectopeptidase dipeptidyl peptidase IV (DP IV, CD26, EC 3.4.14.5) is present on most mammalian cells. Using specific inhibitors of DP IV, it has been shown that this enzyme is involved in the regulation of DNA synthesis and in production of various cytokines in lymphocytes. The aim of the present work was to investigate the expression of DP IV/CD26 on human keratinocytes and to answer the question, whether the proliferation (DNA synthesis) of human keratinocytes is influenced by inhibition of the enzymatic activity of DP IV. Using flow cytometry, RT-PCR, and specific enzymatic activity assays, expression of DP IV-mRNA and CD26 antigen were shown on primary keratinocyte strains and on the HaCaT keratinocyte cell line. The synthetic DP IV inhibitors Lys[Z(NO2)]-thiazolidide and -pyrrolidide suppress the DNA-synthesis of these cells in a dose-dependent manner. These data demonstrate that CD26 is also involved in the regulation of DNA synthesis of keratinocytes and that the enzymatic activity is required for mediating these effects.

Kissing bugs (Triatoma) and the skin

Kissing bugs (Family Reduviidae) can be the source of nocturnal dermatologic wounds in the mid to southern latitudes in the United States. The insects are obligate blood feeders and though the bites may be asymptomatic, a variety of dermatologic eruptions or death from anaphylaxis can result. The various dermatologic forms of the bite can be mistaken for herpes zoster, erythema multiforme and the ubiquitous catch-all diagnoses of "spider-bite."

Sarcoplasmic reticulum function and carnitine palmitoyltransferase-1 inhibition during progression of heart failure

Failing cardiac hypertrophy is associated with an inadequate sarcoplasmic reticulum (SR) function. The hypothesis was examined that pressure overloaded hearts fail to increase SR Ca(2+) uptake rate proportionally to the hypertrophy and that carnitine palmitoyltransferase-1 inhibition by etomoxir ((+/-)-ethyl 2[6(4-chlorophenoxy)hexyl] oxirane-2-carboxylate) can counteract this process. Severe left ventricular pressure overload was induced in rats by constricting the ascending aorta for 8, 10, 14 and 28 weeks leading to cardiac hypertrophy (+62 - +103% of sham-operated rats) and pulmonary congestion. Homogenate oxalate-facilitated SR Ca(2+) uptake rate g wet wt(-1) was reduced (P<0.05) by 29.9+/-1.8% irrespective of phospholamban phosphorylation (in the presence of catalytic subunit of protein kinase A) and inhibition of SR Ca(2+) release channel by ruthenium red. SERCA2 protein level was reduced (P<0.05) by 30.4+/-0.8%. SR Ca(2+) uptake rate was inversely correlated (P<0.05) with left ventricular weight but was not affected by the occurrence of pulmonary congestion. Because SR Ca(2+) uptake rate of whole ventricles was not reduced, a hypertrophy proportional dilution of SR Ca(2+) uptake has to be inferred which precedes pulmonary congestion. Treatment with etomoxir (15 mg kg body wt(-1) day(-1) for 10 weeks) did not affect left ventricular weight but decreased (P:<0.05) the right ventricular hypertrophy related to pulmonary congestion. In parallel, SR Ca(2+) uptake rate of left ventricle and myosin isozyme V(1) were increased (P<0.05). Etomoxir represents a candidate approach for prevention of heart failure by inducing a hypertrophy proportional increase in SR Ca(2+) uptake rate.

Differential lusitropic responsiveness to beta-adrenergic stimulation in rat atrial and ventricular cardiac myocytes

Cardiac myocyte relaxation is brought about mainly through Ca2+ uptake into the sarcoplasmic reticulum (SR) by a Ca2+-ATPase isoform, SERCA2a. Its activity is modulated by another protein, phospholamban (PLB). The levels of both proteins differ in some mammals between atrial and ventricular myocardium and this may lead to differences in relaxation, especially under stimulatory conditions. At a concentration of 100 nM, the beta-adrenergic agonist isoprenaline (ISO) accelerates the relaxation of rat papillary muscle more than that of the left atria (16.4 versus 4.0% hastening of time to 50% relaxation, respectively). Ventricular myocytes were 24.7% quicker in reaching 50% of their diastolic length after contraction when treated with ISO compared to atrial myocytes, which were only 3.6% faster. Ca2+ fluorescence transients were also abbreviated in ventricular compared to atrial myocytes exposed to ISO (41.9 versus 25.2% hastening of time to 50% peak Ca2+ respectively). Ca2+ uptake into ventricular SR vesicles was increased by 13% in the presence of protein kinase A while that into atrial SR vesicles remained unaffected. Western blotting analysis revealed 23% less SERCA2a protein, but 76% more PLB in ventricular compared to atrial tissue. We conclude that the distinct levels of SERCA2a and PLB in ventricular and atrial myocardium are responsible for the differential modulation of the relaxation process arising from beta-adrenergic stimulation in single rat atrial and ventricular myocytes.

Myocardial contractility after infarction and carnitine palmitoyltransferase I inhibition in rats

Inhibition of carnitine palmitoyltransferase I with etomoxir increases sarcoplasmic reticulum Ca(2+)-transport and V(1) isomyosin expression. To test whether etomoxir attenuates contractile dysfunction after myocardial infarction, we compared the contractility of papillary muscles from etomoxir- and placebo-treated rats 6 weeks after infarction. Etomoxir induced cardiac hypertrophy in animals with small infarctions, and enhanced compensatory heart growth at large infarct size. Contractile function of papillary muscles from etomoxir-treated rats was improved particularly in animals with small infarctions. Thus, induction of mild cardiac hypertrophy by etomoxir in rats with small infarctions may be beneficial for myocardial performance.

Cardiac endothelin system impairs left ventricular function in renin-dependent hypertension via decreased sarcoplasmic reticulum Ca(2+) uptake

BACKGROUND

We evaluated the role of the cardiac endothelin (ET) system in compensated hypertensive left ventricular (LV) hypertrophy (LVH) and after the transition toward LV dysfunction.

METHODS AND RESULTS

Hypertensive transgenic rats overexpressing the Ren2 gene (Ren2 rats) were investigated between the ages of 10 and 30 weeks (Ren2-10 and Ren2-30 groups, respectively) and compared with age-matched normotensive Sprague-Dawley (SD) rats (SD-10 and SD-30 groups, respectively). Systolic blood pressure and LV weight were elevated in both Ren2 groups compared with their age-matched SD control groups (P:<0.0001). In Ren2-30 rats, LV end-diastolic pressure increased and -dP/dt(max) decreased compared with the values in SD-30 and Ren2-10 rats (P:<0.05). This was paralleled by an activation of LV mRNA expression of preproET-1 and ET-converting enzyme-1 and ET subtype A (ETA) receptor binding in Ren2-30 compared with Ren2-10 rats (P:<0.001). Cardiac fibrosis was increased and sarcoplasmic reticulum (SR) Ca(2+) reuptake was reduced in Ren2-30 compared with SD-30 and Ren2-10 rats (P:<0.05). Treatment of Ren2 rats with the selective ETA receptor antagonist Lu135252 between 10 and 30 weeks of age did not lower systolic blood pressure, heart weight, or cardiac fibrosis but completely prevented the deterioration of LV end-diastolic pressure and abolished alterations in -dP/dt(max) and SR Ca(2+) reuptake compared with no treatment in Ren2-30 and SD-30 rats (P:<0.05).

CONCLUSIONS

Activation of the cardiac ET system accounts at least in part for the LV dysfunction that gradually develops in LVH. The protective effect of ETA antagonism can be attributed to the improvement of diastolic LV function that is due to normalization of impaired SR Ca(2+) uptake.

Influence of sustained mechanical stress on Egr-1 mRNA expression in cultured human endothelial cells

Restenosis after initially successful balloon angioplasty of coronary artery stenosis remains a major problem in clinical cardiology. Previous studies have identified pathogenetic factors which trigger cell proliferation and vascular remodeling ultimately leading to restenosis. Since there is evidence that endothelial cells adjacent to the angioplasty wound area synthesize factors which may initiate this process, we investigated the effects of mechanical stimulation on endothelial gene expression in vitro and focussed on the influence of sustained mechanical stress on expression of immediate early genes which have previously been shown to be induced in the vascular wall in vivo. Primary cultured human umbilical vein endothelial cells (HUVEC) and the human endothelial cell line EA.hy 926 were plated on collagen-coated silicone membranes and subjected to constant longitudinal stress of approximately 20% for 10 min to 6 h. Total RNA was isolated and the expression of the immediate early genes c-Fos and Egr-1 was studied by Northern blot analysis. We found a rapid upregulation c-Fos and Egr-1 mRNA which started at 10 min and reached its maxima at 30 min. HUVEC lost most of their stretch response after the third passage whereas immediate early gene expression was constantly in EA.hy 926 cells. Using specific inhibitors we investigated the contribution of several signal transduction pathways to stretch-activated Egr-1 mRNA expression. We found significant suppression of stretch-induced Egr-1 mRNA expression by protein kinase C (PKC) inhibition (p < 0.05) and by calcium depletion (EA.hy 926, p < 0.05; HUVEC, p = 0.063). No effect on stretch-activated Egr-1 mRNA expression was detected by inhibition of protein kinase A, blockade of stretch-activated cation channels or inhibition of microtubule synthesis. We conclude that sustained mechanical strain induces Egr-1 mRNA expression by PKC- and calcium-dependent mechanisms.

Observer of autonomic cardiac outflow based on blind source separation of ECG parameters

We present a novel method which provides an observer of the autonomic cardiac outflow using heartbeat intervals (RR) and QT intervals. The model of the observer is inferred from qualitative physiological knowledge. It consists in a problem of blind source separation of noisy mixtures which is resolved by a simple and robust algorithm. The robustness of the algorithm has been assessed by numerical simulations in adverse noisy environments. In clinical applications, we have validated the observer on subjects exposed to experimental conditions known to elicit sympathetic or parasympathetic response.