Beating Of Cilia Research Articles

Spontaneous Synchronization of Beating Cilia: An Experimental Proof Using Vision-Based Control

This article investigates the formation of spontaneous coordination in a row of flexible 2D flaps (artificial cilia) in a chamber filled with a high viscous liquid (Re = 0.12). Each flap is driven individually to oscillate by a rotary motor with the root of the flap attached to its spindle axle. A computer-vision control loop tracks the flap tips online and toggles the axle rotation direction when the tips reach a pre-defined maximum excursion. This is a vision-controlled implementation of the so-called “geometric clutch” hypothesis. When running the control loop with the flaps in an inviscid reference situation (air), they remain in their individual phases for a long term. Then, the flaps are studied in the chamber filled with a highly viscous liquid, and the same control loop is started. The flexible flaps now undergo bending due to hydrodynamic coupling and come, after a maximum of 15 beats, into a synchronous metachronal coordination. The study proves in a macroscopic lab experiment that viscous coupling is sufficient to achieve spontaneous synchronization, even for a symmetric cilia shape and beat pattern.

Ciliary proteins Fap43 and Fap44 interact with each other and are essential for proper cilia and flagella beating

Cilia beating is powered by the inner and outer dynein arms (IDAs and ODAs). These multi-subunit macrocomplexes are arranged in two rows on each outer doublet along the entire cilium length, except its distal end. To generate cilia beating, the activity of ODAs and IDAs must be strictly regulated locally by interactions with the dynein arm-associated structures within each ciliary unit and coordinated globally in time and space between doublets and along the axoneme. Here, we provide evidence of a novel ciliary complex composed of two conserved WD-repeat proteins, Fap43p and Fap44p. This complex is adjacent to another WD-repeat protein, Fap57p, and most likely the two-headed inner dynein arm, IDA I1. Loss of either protein results in altered waveform, beat stroke and reduced swimming speed. The ciliary localization of Fap43p and Fap44p is interdependent in the ciliate Tetrahymena thermophila.

Mathematical modelling of pressure-driven micropolar biological flow due to metachronal wave propulsion of beating cilia

In this paper, we present an analytical study of pressure-driven flow of micropolar non-Newtonian physiological fluids through a channel comprising two parallel oscillating walls. The cilia are arranged at equal intervals and protrude normally from both walls of the infinitely long channel. A metachronal wave is generated due to natural beating of cilia and the direction of wave propagation is parallel to the direction of fluid flow. Appropriate expressions are presented for deformation via longitudinal and transverse velocity components induced by the ciliary beating phenomenon with cilia assumed to follow elliptic trajectories. The conservation equations for mass, longitudinal and transverse (linear) momentum and angular momentum are reduced in accordance with the long wavelength and creeping Stokesian flow approximations and then normalized with appropriate transformations. The resulting non-linear moving boundary value problem is solved analytically for constant micro-inertia density, subject to physically realistic boundary conditions. Closed-form expressions are derived for axial velocity, angular velocity, volumetric flow rate and pressure rise. The transport phenomena are shown to be dictated by several non-Newtonian parameters, including micropolar material parameter and Eringen coupling parameter, and also several geometric parameters, viz eccentricity parameter, wave number and cilia length. The influence of these parameters on streamline profiles (with a view to addressing trapping features via bolus formation and evolution), pressure gradient and other characteristics are evaluated graphically. Both axial and angular velocities are observed to be substantially modified with both micropolar rheological parameters and furthermore are significantly altered with increasing volumetric flow rate. Free pumping is also examined. An inverse relationship between pressure rise and flow rate is computed which is similar to that observed in Newtonian fluids. The study is relevant to hemodynamics in narrow capillaries and also bio-inspired micro-fluidic devices.

Physiological Study of the Neurotoxic Actions of Manganese on Dopamine Cell Signaling in Crassostrea virginica, Downstream of D2‐Like Receptor Activation

Dopamine and serotonin are important neurotransmitters in invertebrates and have been well studied in bivalves with respect to gill and heart. Lateral gill cell cilia of Crassostrea virginica are controlled by a reciprocal dopaminergic‐serotonergic innervation from their ganglia. Dopamine slows down and stops beating of gill lateral cell cilia while serotonin accelerates cilia beating rates. Previously we found that dopamine postsynaptic receptors involved in controlling gill lateral cell cilia are D2‐like (D2DR). The D2DR signaling pathway involves steps that include inhibition of adenylyl cyclase and activation of phospholipase C (PLC). While the effects of dopamine on cAMP levels in oyster gill is well known, the activation of PLC by dopamine D2DR signaling has not been well studied. PLC activation increases cellular inositol trisphosphate (IP3) and diacylglycerol (DAG). IP3 and DAG are both second messengers. IP3 binds to IP3 receptors and increase cytoplasmic calcium levels. High cytoplasmic calcium levels have been shown to slow down gill lateral cell cilia beating. DAG activates protein kinase C. Manganese is a neurotoxin causing Manganism in people, a Parkinson's‐like syndrome. The dopamine induced cilio‐inhibition of gill lateral cell cilia activity in C. virginica is disrupted by manganese. Earlier work of our lab showed the site of action of manganese is the D2DR receptor. We hypothesize IP3 and DAG would be cilio‐inhibitory but not be effected by manganese treatments. We studied this by conducting acute experiments testing the effects of IP3, a DAG analog, a DAG kinase inhibitor, and manganese on gill lateral cell cilia beating. Ciliary activity of gill lateral cells was measured by stroboscopic microscopy and expressed as beats/min ± sem. The results showed that IP3, the DAG analog and the DAG kinase inhibitor each produced a dose dependent (10−6 – 10−4 M) decrease in gill lateral cell cilia beating. Acute treatments with 500 μM of manganese did not reduce the effectiveness of IP3 and the DAG analog to reduce cilia beating. This study provides new knowledge of the physiological actions of the PLC, IP3 and DAG components of the D2DR pathway on gill lateral cell cilia of C. virginica and demonstrates that manganese did not affect those aspects of the D2DR pathway. The study also provides a foundation to further study the physiological roles of PLC in bivalve gill as well as the neurotoxic actions of manganese on the physiology of the D2‐like receptors in the gill.Support or Funding InformationSupported in part by a Carnegie Foundation award.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

A Parallel Modular Biomimetic Cilia Sorting Platform.

The aquatic unicellular organism Paramecium caudatum uses cilia to swim around its environment and to graze on food particles and bacteria. Paramecia use waves of ciliary beating for locomotion, intake of food particles and sensing. There is some evidence that Paramecia pre-sort food particles by discarding larger particles, but intake the particles matching their mouth cavity. Most prior attempts to mimic cilia-based manipulation merely mimicked the overall action rather than the beating of cilia. The majority of massive-parallel actuators are controlled by a central computer; however, a distributed control would be far more true-to-life. We propose and test a distributed parallel cilia platform where each actuating unit is autonomous, yet exchanging information with its closest neighboring units. The units are arranged in a hexagonal array. Each unit is a tileable circuit board, with a microprocessor, color-based object sensor and servo-actuated biomimetic cilia actuator. Localized synchronous communication between cilia allowed for the emergence of coordinated action, moving different colored objects together. The coordinated beating action was capable of moving objects up to 4 cm/s at its highest beating frequency; however, objects were moved at a speed proportional to the beat frequency. Using the local communication, we were able to detect the shape of objects and rotating an object using edge detection was performed; however, lateral manipulation using shape information was unsuccessful.

Microtubule-bundling protein Spef1 enables mammalian ciliary central apparatus formation.

Cilia are cellular protrusions containing nine microtubule (MT) doublets and function to propel cell movement or extracellular liquid flow through beating or sense environmental stimuli through signal transductions. Cilia require the central pair (CP) apparatus, consisting of two CP MTs covered with projections of CP proteins, for planar strokes. How the CP MTs of such '9 + 2' cilia are constructed, however, remains unknown. Here we identify Spef1, an evolutionarily conserved microtubule-bundling protein, as a core CP MT regulator in mammalian cilia. Spef1 was selectively expressed in mammalian cells with 9 + 2 cilia and specifically localized along the CP. Its depletion in multiciliated mouse ependymal cells by RNAi completely abolished the CP MTs and markedly attenuated ciliary localizations of CP proteins such as Hydin and Spag6, resulting in rotational beat of the ependymal cilia. Spef1, which binds to MTs through its N-terminal calponin-homologous domain, formed homodimers through its C-terminal coiled coil region to bundle and stabilize MTs. Disruption of either the MT-binding or the dimerization activity abolished the ability of exogenous Spef1 to restore the structure and functions of the CP apparatus. We propose that Spef1 bundles and stabilizes central MTs to enable the assembly and functions of the CP apparatus.

Role of spatial heterogeneity in the collective dynamics of cilia beating in a minimal one-dimensional model.

Cilia are elastic hairlike protuberances of the cell membrane found in various unicellular organisms and in several tissues of most living organisms. In some tissues such as the airway tissues of the lung, the coordinated beating of cilia induces a fluid flow of crucial importance as it allows the continuous cleaning of our bronchia, known as mucociliary clearance. While most of the models addressing the question of collective dynamics and metachronal wave consider homogeneous carpets of cilia, experimental observations rather show that cilia clusters are heterogeneously distributed over the tissue surface. The purpose of this paper is to investigate the role of spatial heterogeneity on the coherent beating of cilia using a very simple one-dimensional model for cilia known as the rower model. We systematically study systems consisting of a few rowers to hundreds of rowers and we investigate the conditions for the emergence of collective beating. When considering a small number of rowers, a phase drift occurs, hence, a bifurcation in beating frequency is observed as the distance between rower clusters is changed. In the case of many rowers, a distribution of frequencies is observed. We found in particular the pattern of the patchy structure that shows the best robustness in collective beating behavior, as the density of cilia is varied over a wide range.

Originator of the hormesis concept: Rudolf Virchow or Hugo Schulz.

In 2006, Henschler disputed the claim of Calabrese and Baldwin that Hugo Schulz should be considered the originator of the hormesis concept. Henschler cited an 1854 paper by Rudolf Virchow on the effects of two agents on the beating of cilia, which showed a hormetic-biphasic dose response. The interpretation of Henschler became broadly accepted over the past decade based on citations in the literature. However, a recent translation of the Virchow paper from German into English reveals that the claims of Henschler are not supported by the article.

Characterization of ecto-nucleotidases in human oviducts with an improved approach simultaneously identifying protein expression and in situ enzyme activity.

Extracellular ATP and its hydrolysis product adenosine modulate various reproductive functions such as those taking place in oviducts, including contraction, beating of cilia, and maintenance of fluid composition that, in turn, influences sperm capacitation and hyperactivation, as well as oocyte and embryo nourishing. Ecto-nucleotidases are the enzymes that regulate extracellular ATP and adenosine levels, thus playing a role in reproduction. We have optimized a convenient method for characterizing ecto-nucleotidases that simultaneously localizes the protein and its associated enzyme activity in the same tissue slice and characterizes ecto-nucleotidases in human oviducts. The technique combines immunofluorescence and in situ histochemistry, allowing precise identification of ecto-nucleotidases at a subcellular level. In oviducts, remarkably, ectonucleoside triphosphate diphosphohydrolase 2 (NTPDase2) and NTPDase3, with the ability to hydrolyze ATP to AMP, are expressed in ciliated epithelial cells but with different subcellular localization. Ecto-5'nucleotidase/CD73 is also expressed apically in ciliated cells. CD73, together with alkaline phosphatase, also expressed apically in oviductal epithelium, complete the hydrolysis sequence by dephosphorylating AMP to adenosine. The concerted action of these enzymes would contribute to the local increase of adenosine concentration necessary for sperm capacitation. The use of this method would be an asset for testing new potential therapeutic drugs with inhibitory potential, which is of great interest presently in the field of oncology and in other clinical disciplines.

Individually Controllable Magnetic Cilia: Mixing Application

This paper introduces a new design for individually controlled magnetic artificial cilia for use in fluid devices and specifically intended to improve the mixing in DNA microarray experiments. The design has been implemented using a low-cost prototype that can be fabricated using polydimethylsiloxane (PDMS) and off-the-shelf parts and achieves large cilium deflections (59% of the cilium length). The device's performance is measured via a series of mixing experiments using different actuation patterns inspired by the blinking vortex theory. The experimental results, quantified using the relative standard deviation of the color when mixing two colored inks, show that exploiting the individual control leads to faster mixing (38% reduction in mixing time) than when operating the device in a simultaneous-actuation mode with the same average cilium beat frequency. Furthermore, the experimental results show an optimal beating pattern that minimizes the mixing time. The existence and character of this optimum is predicted by simulations using a blinking-vortex approach for 2D ideal flow, suggesting that the blinking-vortex model can be used to predict the effect of parameter variation on the experimental system.

Evidence for a self-organized compliant mechanism for the spontaneous steady beating of cilia.

Cilia or eukaryotic flagella are slender 200-nm-diameter organelles that move the immersing fluid relative to a cell and sense the environment. Their core structure is nine doublet microtubules (DMTs) arranged around a central-pair. When motile, thousands of tiny motors slide the DMTs relative to each other to facilitate traveling waves of bending along the cilium's length. These motors provide the energy to change the shape of the cilium and overcome the viscous forces of moving in the surrounding fluid. In planar beating, motors walk toward where the cilium is attached to the cell body. Traveling waves are initiated by motors bending the elastic cilium back and forth, a self-organized mechanical oscillator. We found remarkably that the energy in a wave is nearly constant over a wide range of (ATP) and medium viscosities and inter-doublet springs operate only in the central and not in the basal region. Since the energy in a wave does not depend on its rate of formation, the control mechanism is likely purely mechanical. Further the torque per length generated by the motors acting on the doublets is proportional to and nearly in phase with the microtubule sliding velocity with magnitude dependent on the medium. We determined the frequency-dependent elastic moduli and strain energies of beating cilia. Incorporation of these in an energy-based model explains the beating frequency, wavelength, limiting of the wave amplitude and the overall energy of the traveling wave. Our model describes the intricacies of the basal-wave initiation as well as the traveling wave.

Comparative Study of the Response to Light on the Sensory Motor Integration of Gill Lateral Cell Cilia in Bivalve Mollusc

Most bivalves have gill lateral cell (GLC) cilia that respond to serotonin, which is cilio‐excitatory and dopamine, which is cilio‐inhibitory. Crassostrea virginica and Mytilus edulis are two well‐studied bivalves whose GLC are innervated by serotonin and dopamine nerves. The motor aspects of GLC innervation have been well studied but the sensory side to the motor response of the cilia has not. Recently we found sensory cues, such as light, algae or crab extract applied to C. virginica mantle rim initiated an integrated response via the visceral/cerebral ganglia, between mantle rim sensory tentacles and the motor response of GLC cilia. Since in invertebrates, histamine is the neurotransmitter of photoreception, we tested histamine application to mantle rim and found it elicited the same sensory‐motor response as light had, decreasing cilia beating of GLC. In this study we tested effects of shining a spotlight (11 lumen, ¼ inch diameter) on mantle rim sensory tentacles of M. edulis and found it had a cilio‐excitatory effect on GLC cilia, opposite the cilio‐inhibitory effect we previously found in C. virginica. However, since C. virginica is nocturnal and M. edulis is not, the opposite responses to light may very well represent the appropriate motor response for each bivalve. In this study we also investigated effects of light on cerebral ocelli (eyespots) in both C. virginica and M. edulis. Cerebral ocelli are located near the cerebral ganglia. They have been rarely studied beyond a few histological/anatomical reports of their existence. We hypothesize cerebral ocelli are light sensitive and involved in a histamine‐mediated sensory‐motor integration response effecting GLC cilia. To test this we used animal preparations with intact gill to cerebral/visceral ganglia innervation and a spotlight (11 lumen, ¼ inch diameter) to stimulate cerebral ocelli. We found stimulating cerebral ocelli decreased beating of GLC cilia to zero in C. virginica, but increased cilia beating in M. edulis by over 300%. Again, opposite motor responses but consistent with the motor responses we observed when light was applied to mantle rim sensory tentacles. In both animals light induced sensory‐motor integration response of GLC was lost when cerebral ocelli were excised. We also treated cerebral ocelli with the histamine H2 receptor antagonist famotidine (10−9–10−3M) before light application and it, caused a statistically significant, dose‐dependent blockage of the motor response of GLC cilia. The study shows light induced sensory‐motor integration between mantle rim sensory tentacles and GLC cilia is also present in the bivalve M. edulis, and expands the existence of this sensory‐motor response to include the light‐sensitive cerebral ocelli of both bivalves. The study adds new knowledge of the physiological role of cerebral ocelli in a class of animals where it has not been well studied and further supports the hypothesis histamine is the sensory neurotransmitter for photoreceptor cells in both cerebral ocelli and mantle rim in these bivalves.Support or Funding InformationThis work was supported by grant 690340047 of PSC‐CUNY, grant 2R25GM06003 of the Bridge Program of NIGMS and a Carnegie Foundation award.

Carbon nanotube (CNT)-suspended nanofluid analysis due to metachronal beating of cilia with entropy generation

A mathematical model is presented for the hydromagnetic wavy (sinusoidal) flow of CNT-suspended nanofluid in a flexible ciliated tube. Entropy generation analysis has been also taken into account. This study is motivated by biomagnetic transport phenomena (of relevance to drug targeting and endoscopy) and also industrial applications such as electrically conducting rheological waste conveyance and transport of corrosive magnetized nanofluids where fluid contact with machinery parts is prohibited. Such systems can be controlled effectively with applied magnetic fields which generate a Lorentzian drag force in the flow. As geometry of the problem is ciliated tube, flow equations are modeled considering cylindrical coordinates. Governing partial differential equations are simplified and converted into differential equations using non-dimensionless variables with low Reynolds number (Re ≪ 0, i.e., inertial forces are small as compared to the viscous forces) and long wavelength approximations. Mathematica software is employed to evaluate the exact solutions of velocity profile, temperature profile, axial velocity profile, pressure gradient and entropy generation number. The influence of the pertinent control parameters on velocity profiles, temperature profile, pressure rise, pressure gradient and entropy generation number are illustrated graphically. It is observed that with an increase in the Hartmann number decreases the velocity of the fluid whereas an increment in the solid nanoparticle volume fraction of the fluid increases the velocity of the fluid.

MHD convective heat transfer of nanofluids through a flexible tube with buoyancy: A study of nano-particle shape effects

This paper presents an analytical study of magnetohydrodynamics and convective heat transfer of nanofluids synthesized by three different shaped (brick, platelet and cylinder) silver (Ag) nanoparticles in water. A two-phase nanoscale formulation is adopted which is more appropriate for biophysical systems. The flow is induced by metachronal beating of cilia and the flow geometry is considered as a cylindrical tube. The analysis is carried out under the low Reynolds number and long wavelength approximations and the fluid and cilia dynamics is of the creeping type. A Lorentzian magnetic body force model is employed and magnetic induction effects are neglected. Solutions to the transformed boundary value problem are obtained via numerical integration. The influence of cilia length parameter, Hartmann (magnetic) number, heat absorption parameter, Grashof number (free convection), solid nanoparticle volume fraction, and cilia eccentricity parameter on the flow and heat transfer characteristics (including effective thermal conductivity of the nanofluid) are examined in detail. Furthermore a comparative study for different nanoparticle geometries (i.e. bricks, platelets and cylinders) is conducted. The computations show that pressure increases with enhancing the heat absorption, buoyancy force (i.e. Grashof number) and nanoparticle fraction however it reduces with increasing the magnetic field. The computations also reveal that pressure enhancement is a maximum for the platelet nano-particle case compared with the brick and cylinder nanoparticle cases. Furthermore the quantity of trapped streamlines for cylinder type nanoparticles exceeds substantially that computed for brick and platelet nanoparticles, whereas the bolus magnitude (trapped zone) for brick nanoparticles is demonstrably greater than that obtained for cylinder and platelet nanoparticles. The present model is applicable in biological and biomimetic transport phenomena exploiting magnetic nanofluids and ciliated inner tube surfaces.

Study of heat transfer on physiological driven movement with CNT nanofluids and variable viscosity

Background and objectivesWith ongoing interest in CNT nanofluids and materials in biotechnology, energy and environment, microelectronics, composite materials etc., the current investigation is carried out to analyze the effects of variable viscosity and thermal conductivity of CNT nanofluids flow driven by cilia induced movement through a circular cylindrical tube. Metachronal wave is generated by the beating of cilia and mathematically modeled as elliptical wave propagation by Blake (1971). Methods, results and conclusionsThe problem is formulated in the form of nonlinear partial differential equations, which are simplified by using the dimensional analysis to avoid the complicacy of dimensional homogeneity. Lubrication theory is employed to linearize the governing equations and it is also physically appropriate for cilia movement. Analytical solutions for velocity, temperature and pressure gradient and stream function are obtained. The analytical results are numerically simulated by using the Mathematica Software and plotted the graphs for velocity profile, temperature profile, pressure gradient and stream lines for better discussion and visualization. This model is applicable in physiological transport phenomena to explore the nanotechnology in engineering the artificial cilia and ciliated tube/pipe.

Alix-mediated assembly of the actomyosin-tight junction polarity complex preserves epithelial polarity and epithelial barrier.

Maintenance of epithelial cell polarity and epithelial barrier relies on the spatial organization of the actin cytoskeleton and proper positioning/assembly of intercellular junctions. However, how these processes are regulated is poorly understood. Here we reveal a key role for the multifunctional protein Alix in both processes. In a knockout mouse model of Alix, we identified overt structural changes in the epithelium of the choroid plexus and in the ependyma, such as asymmetrical cell shape and size, misplacement and abnormal beating of cilia, blebbing of the microvilli. These defects culminate in excessive cell extrusion, enlargement of the lateral ventricles and hydrocephalus. Mechanistically, we find that by interacting with F-actin, the Par complex and ZO-1, Alix ensures the formation and maintenance of the apically restricted actomyosin–tight junction complex. We propose that in this capacity Alix plays a role in the establishment of apical–basal polarity and in the maintenance of the epithelial barrier.

PIERCE1 is critical for specification of left-right asymmetry in mice.

The specification of left-right asymmetry of the visceral organs is precisely regulated. The earliest breakage of left-right symmetry occurs as the result of leftward flow generated by asymmetric beating of nodal cilia, which eventually induces asymmetric Nodal/Lefty/Pitx2 expression on the left side of the lateral plate mesoderm. PIERCE1 has been identified as a p53 target gene involved in the DNA damage response. In this study, we found that Pierce1-null mice exhibit severe laterality defects, including situs inversus totalis and heterotaxy with randomized situs and left and right isomerisms. The spectrum of laterality defects was closely correlated with randomized expression of Nodal and its downstream genes, Lefty1/2 and Pitx2. The phenotype of Pierce1-null mice most closely resembled that of mutant mice with impaired ciliogenesis and/or ciliary motility of the node. We also found the loss of asymmetric expression of Cerl2, the earliest flow-responding gene in the node of Pierce1-null embryos. The results suggest that Pierce1-null embryos have defects in generating a symmetry breaking signal including leftward nodal flow. This is the first report implicating a role for PIERCE1 in the symmetry-breaking step of left-right asymmetry specification.

Complement system activation contributes to the ependymal damage induced by microbial neuraminidase.

BackgroundIn the rat brain, a single intracerebroventricular injection of neuraminidase from Clostridium perfringens induces ependymal detachment and death. This injury occurs before the infiltration of inflammatory blood cells; some reports implicate the complement system as a cause of these injuries. Here, we set out to test the role of complement.MethodsThe assembly of the complement membrane attack complex on the ependymal epithelium of rats injected with neuraminidase was analyzed by immunohistochemistry. Complement activation, triggered by neuraminidase, and the participation of different activation pathways were analyzed by Western blot. In vitro studies used primary cultures of ependymal cells and explants of the septal ventricular wall. In these models, ependymal cells were exposed to neuraminidase in the presence or absence of complement, and their viability was assessed by observing beating of cilia or by trypan blue staining. The role of complement in ependymal damage induced by neuraminidase was analyzed in vivo in two rat models of complement blockade: systemic inhibition of C5 by using a function blocking antibody and testing in C6-deficient rats.ResultsThe complement membrane attack complex immunolocalized on the ependymal surface in rats injected intracerebroventricularly with neuraminidase. C3 activation fragments were found in serum and cerebrospinal fluid of rats treated with neuraminidase, suggesting that neuraminidase itself activates complement. In ventricular wall explants and isolated ependymal cells, treatment with neuraminidase alone induced ependymal cell death; however, the addition of complement caused increased cell death and disorganization of the ependymal epithelium. In rats treated with anti-C5 and in C6-deficient rats, intracerebroventricular injection of neuraminidase provoked reduced ependymal alterations compared to non-treated or control rats. Immunohistochemistry confirmed the absence of membrane attack complex on the ependymal surfaces of neuraminidase-exposed rats treated with anti-C5 or deficient in C6.ConclusionsThese results demonstrate that the complement system contributes to ependymal damage and death caused by neuraminidase. However, neuraminidase alone can induce moderate ependymal damage without the aid of complement.

Spatial differences in gene expression in the bovine oviduct.

The aim of this study was to compare the transcriptome of the oviductal isthmus of pregnant heifers with that of cyclic heifers as well as to investigate spatial differences between the transcriptome of the isthmus and ampulla of the oviduct in pregnant heifers. After synchronizing crossbred beef heifers, those in standing oestrus (=Day 0) were randomly assigned to cyclic (non-bred, n=6) or pregnant (artificially inseminated, n=11) groups. They were slaughtered on Day 3 and both oviducts from each animal were isolated and cut in half to separate ampulla and isthmus. Each portion was flushed to confirm the presence of an oocyte/embryo and was then opened longitudinally and scraped to obtain epithelial cells which were snap-frozen. Oocytes and embryos were located in the isthmus of the oviduct ipsilateral to the corpus luteum Microarray analysis of oviductal cells revealed that proximity to the corpus luteum did not affect the transcriptome of the isthmus, irrespective of pregnancy status. However, 2287 genes were differentially expressed (P<0.01) between the ampulla and isthmus of the oviduct ipsilateral to the corpus luteum in pregnant animals. Gene ontology revealed that the main biological processes overrepresented in the isthmus were synthesis of nitrogen, lipids, nucleotides, steroids and cholesterol as well as vesicle-mediated transport, cell cycle, apoptosis, endocytosis and exocytosis, whereas cell motion, motility and migration, DNA repair, calcium ion homeostasis, carbohydrate biosynthesis, and regulation of cilium movement and beat frequency were overrepresented in the ampulla. In conclusion, large differences in gene expression were observed between the isthmus and ampulla of pregnant animals at Day 3 after oestrus.

Cryo-Electron Tomography Provides a New Window into Ciliary Structure and Function

Cilia and flagella are conserved and ubiquitous eukaryotic organelles that are composed of more than 600 different proteins and have important biological roles in motility and sensation. The beating of motile cilia and flagella is driven by conformational changes of dynein motors that are coordinated by regulatory complexes. However, the mechanism(s) by which flagellar motility is generated and regulated are largely unknown. We use cryo-electron tomography, subtomogram averaging, molecular tagging and classification analyses to visualize the three-dimensional structures of intact wild-type and mutant flagella, and dissect the organization of key macromolecular complexes. We also study active (beating) flagella that were rapidly frozen to resolve the different conformations of these complexes and identify distinct conformations for different axonemal dyneins and other structures, many of which showing bend direction dependent distributions. Our comprehensive analyses combined with biochemical investigations provides a new understanding of the distinct roles played by various dyneins and regulatory complexes in the motility of cilia and flagella, and suggests critical modifications to previous hypotheses for the molecular mechanisms underlying their motility.