The axoneme, a biological template to design a swell energy recovery system.

The axonemal micro-machinery, the axial skeleton and actuator of cilia and flagella of eukaryotic cells, is able to bend and twist and generates wave trains. We already demonstrated that it can be the template to construct an active trunk robot (Cibert 2013 Bioinspir. Biomim.

Bending, twisting and beating trunk robot bioinspired from the '3 + 0' axoneme.

The axoneme is the skeleton and motor axis of flagella and cilia in eukaryotic organisms. Basically it consists of a series of longitudinal fibers (outer doublets of microtubules) that design a cylinder and whose sliding, due to the coordinated activities of dedicated molecular motors (the dynein arms), is converted into a bending because outer doublets pairs are stabilized by elastic links (the nexine molecules). In spite of these interesting mechanical properties, mechanical and robotics engineers have never considered this amazing molecular machinery as a model.

Is the curvature of the flagellum involved in the apparent cooperativity of the dynein arms along the "9+2" axoneme?

In a recent study [Cibert, 2008. Journal of Theoretical Biology 253, 74-89], by assuming that walls of microtubules are involved in cyclic compression/dilation equilibriums as a consequence of cyclic curvature of the axoneme, it was proposed that local adjustments of spatial frequencies of both dynein arms and beta-tubulin monomers facing series create propagation of joint probability waves of interaction (JPI) between these two necessary partners. Modeling the occurrence of these probable interactions along the entire length of an axoneme between each outer doublet pair (without programming any cooperative dialog between molecular complexes) and the cyclic attachment of two facing partners, we show that such constituted active couples are clustered.

Bending of the "9+2" axoneme analyzed by the finite element method.

Many data demonstrate that the regulation of the bending polarity of the "9+2" axoneme is supported by the curvature itself, making the internal constraints central in this process, adjusting either the physical characteristics of the machinery or the activity of the enzymes involved in different pathways. Among them, the very integrated Geometric Clutch model founds this regulation on the convenient adjustments of the probability of interaction between the dynein arms and the beta-tubulin monomers of the outer doublet pairs on which they walk. Taking into consideration (i) the deviated bending of the outer doublets pairs (Cibert, C.

Are the local adjustments of the relative spatial frequencies of the dynein arms and the beta-tubulin monomers involved in the regulation of the "9+2" axoneme?

The "9+2" axoneme is a highly specific cylindrical machine whose periodic bending is due to the cumulative shear of its 9 outer doublets of microtubules. Because of the discrete architecture of the tubulin monomers and the active appendices that the outer doublets carry (dynein arms, nexin links and radial spokes), this movement corresponds to the relative shear of these topological verniers, whose characteristics depend on the geometry of the wave train. When an axonemal segment bends, this induces the compressed and dilated conformations of the tubulin monomers and, consequently, the modification of the spatial frequencies of the appendages that the outer doublets carry.

Altered heterochromatin organization after perinatal exposure to zidovudine.

Background: Zidovudine (3'-azido-3'-deoxythymidine, AZT), administered to pregnant women alone or in combination with other antiretroviral drugs, greatly reduces the mother-to-child transmission of HIV-1. The potential genotoxicity of these molecules is underestimated and wide-ranging evaluation of its biological and clinical consequences is required.

Methods: We investigated the nuclear organization of constitutive heterochromatin, a major domain participating in epigenetic regulation, in uninfected infants born to HIV-1-infected mothers treated with zidovudine and/or other nucleoside reverse transcriptase inhibitors (NRTIs) during pregnancy.

Structural and immunocytochemical alterations in eye lens fiber cells from Cx46 and Cx50 knockout mice.

In the current study we describe the changes of overall organization of lens fiber cells in connexin 46 (Cx46) and connexin 50 (Cx50) knockout mice. Morphometric analyses and the application of immunocytochemical techniques revealed that in Cx46 knockout lens (Cx46 -/-), where Cx50 is expressed alone, the postnatal differentiation of secondary fiber cells proceeds faster and is characterized by an increased number of smaller fiber cells. Conversely, in Cx50 knockout mice (Cx50 -/-), the lenticular mass is considerably reduced and characterized by a small number of fiber cells added during the postnatal period.

Distinct domains of the spinal muscular atrophy protein SMN are required for targeting to Cajal bodies in mammalian cells.

Mutations of the survival motor neuron gene SMN1 cause the inherited disease spinal muscular atrophy (SMA). The ubiquitous SMN protein facilitates the biogenesis of spliceosomal small nuclear ribonucleoproteins (snRNPs). The protein is detected in the cytoplasm, nucleoplasm and enriched with snRNPs in nuclear Cajal bodies.

Oscillation modes of microtubules.

Microtubules are long, filamentous protein complexes which play a central role in several cellular physiological processes, such as cell division transport and locomotion. Their mechanical properties are extremely important since they determine the biological function. In a recently published experiment [Phys.

Geometry drives the "deviated-bending" of the bi-tubular structures of the 9 + 2 axoneme in the flagellum.

The axoneme "9 + 2" is basically a system constituted of a cylinder of 9 microtubule doublets surrounding a central pair of microtubules. These bi-tubular structures are considered as the support system of the active molecular complexes that generate and regulate the axonemal movement. Schoutens has calculated their moments of inertia [Schoutens, 1994: Journal of Theoretical Biology 171:163-177].

Initiation of gastrulation in the mouse embryo is preceded by an apparent shift in the orientation of the anterior-posterior axis.

Background: It is generally assumed that the migration of anterior visceral endoderm (AVE) cells from a distal to a proximal position at embryonic day (E)5.5 breaks the radial symmetry of the mouse embryo, marks anterior, and conditions the formation of the primitive streak on the opposite side at E6.5.

Entropy and information in flagellar axoneme cybernetics: a radial spokes integrative function.

Radial spokes and the consequences of their relationships with the central apparatus seem to play a very important role in the regulation of axonemal activity. We modeled their behavior and observed that it appears to differ in the cilium and the flagellum with respect to the development of bending as a function of time. Specifically, our calculation raises the question of the real function of the radial spokes in the regulation of the axoneme, because a given curvature of the flagellar axoneme may correspond to two opposite of their tilts.

Mitochondrial respiration and Ca2+ waves are linked during fertilization and meiosis completion.

Fertilization increases both cytosolic Ca(2+) concentration and oxygen consumption in the egg but the relationship between these two phenomena remains largely obscure. We have measured mitochondrial oxygen consumption and the mitochondrial NADH concentration on single ascidian eggs and found that they increase in phase with each series of meiotic Ca(2+) waves emitted by two pacemakers (PM1 and PM2). Oxygen consumption also increases in response to Ins(1,4,5)P(3)-induced Ca(2+) transients.

Axonemal activity relative to the 2D/3D-waveform conversion of the flagellum.

The waveform of the flagellum of the sea urchin spermatozoon is mainly planar, but its 3D-properties were evoked for dynamic reasons and described as helical. In 1975, the apparent twisting pattern of the sea urchin axoneme was described [Gibbons I. 1975.

Elastic extension and jump of the flagellar nexin links: a theoretical mechanical cycle.

The functions of the nexin links of a flagellar axoneme have not been clearly demonstrated. Taking into account both the elastic (Hookean) characteristics and the possible jump of the nexin links, we calculated the sliding to bending conversion of a theoretical model in a tip-ward direction step by step, according to the essential principles proposed by the geometric clutch hypothesis [Lindemann, 1994: J Theoret Biol 168:175-189]: the activity of the dynein arms depends on the transverse forces induced by the axonemal curvature. In our calculations, however, the transverse forces that are involved in the regulation of the activities of the dynein arms were due to the extension of the nexin links located upstream of a given abscissa.

Differential localization of arabinan and galactan side chains of rhamnogalacturonan 1 in cambial derivatives.

The development of pectin structural features during the differentiation of cambial derivatives was investigated in aspen (Populus tremula L. x P. tremuloides Michx.

Effects of osmolality, morphology perturbations and intracellular nucleotide content during the movement of sea bass (Dicentrarchus labrax) spermatozoa.

Sea bass spermatozoa are maintained immotile in the seminal fluid, but initiate swimming for 45 s at 20 degrees C, immediately after dispersion in a hyperosmotic medium (1100 mOsm kg-1). The duration of this motile period could be extended by a reduction of the amplitude of the hyperosmotic shock. Five seconds after the initiation of motility, 94.

Calculation of a Gap restoration in the membrane skeleton of the red blood cell: possible role for myosin II in local repair.

Human red blood cells contain all of the elements involved in the formation of nonmuscle actomyosin II complexes (V. M. Fowler.

The use of phosphocreatine plus ADP as energy source for motility of membrane-deprived trout spermatozoa.

Live trout spermatozoa initiate flagellar motility for a short period of time (30 s at 18 degrees C), during which their mean beat frequency (BF) decreases steadily from 60 to 20 Hz; motility then stops abruptly. When demembranated, the motility of axonemes lasts much longer, up to 20 min, with high beat frequency, provided that ATP (millimolar concentration) and cAMP (micromolar) are added. In the present paper, the motility of demembranated trout sperm was investigated in the absence of added ATP in various incubation conditions relative to other substrates.

Molecular cloning and characterization of a radial spoke head protein of sea urchin sperm axonemes: involvement of the protein in the regulation of sperm motility.

Monoclonal antibodies raised against axonemal proteins of sea urchin spermatozoa have been used to study regulatory mechanisms involved in flagellar motility. Here, we report that one of these antibodies, monoclonal antibody D-316, has an unusual perturbating effect on the motility of sea urchin sperm models; it does not affect the beat frequency, the amplitude of beating or the percentage of motile sperm models, but instead promotes a marked transformation of the flagellar beating pattern which changes from a two-dimensional to a three-dimensional type of movement. On immunoblots of axonemal proteins separated by SDS-PAGE, D-316 recognized a single polypeptide of 90 kDa.

A functional analysis of p53 during early development of Xenopus laevis.

p53 is a nuclear protein that acts like a tumor suppressor and is involved in regulation of cellular growth. In Xenopus, the p53 protein is highly expressed during oogenesis and is strictly cytoplasmic in the oocyte. We have analysed its participation in DNA replication and transcription during early development, using the egg and oocyte as model-systems.

Kinetics of protoporphyrinogen oxidase inhibition by diphenyleneiodonium derivatives.

Protoporphyrinogen oxidase, the last enzyme of the common branch of the heme and chlorophyll pathways in plants, is the molecular target of diphenyl ether-type herbicides. These compounds inhibit the enzyme competitively with respect to the tetrapyrrole substrate, protoporphyrinogen IX. We used the flavinic nature of protoporphyrinogen oxidase to investigate the reactivity of the enzyme toward the 2,2'-diphenyleneiodonium cation, a known inhibitor of several flavoproteins.

Suppressors of the vestigial mutant phenotype increase the level of expression of the gene.

Suppressor genes of the vestigial phenotype have been isolated in a wild-type population. These suppressors have an effect on different wing mutants and are allele-specific in the case of vestigial. In a vg background they produced overgrowth of the imaginal wing disc.