Model Of Axoneme Research Articles

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. 8 026006). The work presented in this paper describes how the axonemal model can also be useful to design worm shaped devices to convert swell energy into usable energy such as electricity. Using dynamic simulation we have designed three models either very close to the biological machinery or being a reasonable interpretation of its functioning principles. Their main advantage as compared with another existing device, Pelamis, is the additional twist degree-of-freedom that gives interesting properties to the system.

Sperm accessory microtubules suggest the placement of Diplura as the sister-group of Insecta s.s.

Sperm ultrastructure and spermiogenesis of the dipluran Japygidae ( Japyx solifugus, Metajapyx braueri and Occasjapyx japonicus) and Campodeidae ( Campodea sp.) were studied with the aim of looking for potential characters for the reconstruction of the phylogenetic relationships of basal hexapods. Both Japygidae and Campodeidae share a common sperm axonemal model 9 + 9 + 2, provided with nine accessory microtubules. These microtubules, however, after their formation lose the usual position around the 9 + 2 and migrate between the two mitochondria. In Japygidae, four of these microtubules are very short and were observed beneath the nucleus after negative staining and serial sections. Accessory microtubules have 13 protofilaments in their tubular wall. Diplura have a sperm morphology which is very different from that of the remaining Entognatha (Protura + Collembola). On the basis of the present results, the presence of accessory microtubules suggests that Diplura are the sister-group of the Insecta s.s.. Moreover, Japygidae and Campodeidae differ with regards to the relative position of the sperm components, the former having the axoneme starting from beneath the nucleus (above which sits the short acrosome), while the latter having a long apical acrosome and a nucleus running parallel with the proximal part of the axoneme. The present study also allowed to redescribe the male genital system of Japyx.

Elastic axonemal model: Solitary wave shapes

We introduce an elastic beam Bernoulli–Euler model for the axoneme (cytoskeletal inner core of eukaryotic cells appendages) whose dynamics is controlled by internally generated torques at the inflexion points of the beam. We calculate the geometrical and the mechanical parameters of the axoneme, and compared them with experimental data. We make predictions about nonlinear shapes, including possible solitary waves in the curvature, which can explain certain swimming patterns of the cells.

Three-dimensional reconstruction of axonemal outer dynein arms in situ by electron tomography

We present here for the first time a 3D reconstruction of in situ axonemal outer dynein arms. This reconstruction has been obtained by electron tomography applied to a series of tilted images collected from metal replicas of rapidly frozen, cryofractured, and metal-replicated sperm axonemes of the cecidomid dipteran Monarthropalpus flavus. This peculiar axonemal model consists of several microtubular laminae that proved to be particularly suitable for this type of analysis. These laminae are sufficiently planar to allow the visualization of many dynein molecules within the same fracture face, allowing us to recover a significant number of equivalent objects and to improve the signal-to-noise ratio of the reconstruction by applying advanced averaging protocols. The 3D model we obtained showed the following interesting structural features: First, each dynein arm has two head domains that are almost parallel and are obliquely oriented with respect to the longitudinal axis of microtubules. The two heads are therefore positioned at different distances from the surface of the A-tubule. Second, each head domain consists of a series of globular subdomains that are positioned on the same plane. Third, a stalk domain originates as a conical region from the proximal head and ends with a small globular domain that contacts the B-tubule. Fourth, the stem region comprises several globular subdomains and presents two distinct points of anchorage to the surface of the A-tubule. Finally, and most importantly, contrary to what has been observed in isolated dynein molecules adsorbed to flat surfaces, the stalk and the stem domains are not in the same plane as the head.

Composition and organization of tubulin isoforms reveals a variety of axonemal models.

In the flagellum of mammalian spermatozoa, glutamylated and glycylated tubulin isoforms are detected according to longitudinal gradients and preferentially in axonemal doublets 1-5-6 and 3-8, respectively. This suggested a role for these tubulin isoforms in the regulation of flagellar beating. In the present work, using antibodies directed against various tubulin isoforms and quantitative immunogold analysis, we aimed at investigating whether the particular accessibility of tubulin isoforms in the mammalian sperm flagellum is restricted to this model of axoneme surrounded with periaxonemal structures or is also displayed in naked axonemes. In rodent lung ciliated cells, all studied tubulin isoforms are uniformly distributed in all axonemal microtubules with a unique deficiency of glutamylated tubulin in the transitional region. A similar distribution of tubulin isoforms is observed in cilia of Paramecium, except for a decreasing gradient of glutamylated tubulin labeling in the proximal part of axonemal microtubules. In the sea urchin sperm flagellum, predominant labeling of tyrosinated and detyrosinated tubulin in 1-5-6 and 3-8 doublets, respectively, were observed together with decreasing proximo-distal gradients of glutamylated and polyglycylated tubulin labeling and an increasing gradient of monoglycylated tubulin labeling. In flagella of Chlamydomonas, the glutamylated and glycylated tubulin isoforms are detected at low levels. Our results show a specific composition and organization of tubulin isoforms in different models of cilia and flagella, suggesting various models of functional organization and beating regulation of the axoneme.

Composition and organization of tubulin isoforms reveals a variety of axonemal models

In the flagellum of mammalian spermatozoa, glutamylated and glycylated tubulin isoforms are detected according to longitudinal gradients and preferentially in axonemal doublets 1–5–6 and 3–8, respectively. This suggested a role for these tubulin isoforms in the regulation of flagellar beating. In the present work, using antibodies directed against various tubulin isoforms and quantitative immunogold analysis, we aimed at investigating whether the particular accessibility of tubulin isoforms in the mammalian sperm flagellum is restricted to this model of axoneme surrounded with periaxonemal structures or is also displayed in naked axonemes. In rodent lung ciliated cells, all studied tubulin isoforms are uniformly distributed in all axonemal microtubules with a unique deficiency of glutamylated tubulin in the transitional region. A similar distribution of tubulin isoforms is observed in cilia of Paramecium, except for a decreasing gradient of glutamylated tubulin labeling in the proximal part of axonemal microtubules. In the sea urchin sperm flagellum, predominant labeling of tyrosinated and detyrosinated tubulin in 1–5–6 and 3–8 doublets, respectively, were observed together with decreasing proximo-distal gradients of glutamylated and polyglycylated tubulin labeling and an increasing gradient of monoglycylated tubulin labeling. In flagella of Chlamydomonas, the glutamylated and glycylated tubulin isoforms are detected at low levels. Our results show a specific composition and organization of tubulin isoforms in different models of cilia and flagella, suggesting various models of functional organization and beating regulation of the axoneme.

Characteristics of sperm ultrastructure in the gall midges Porricondylinae (Insecta, Diptera, Cecidomyiidae), with phylogenetic considerations on the subfamily

Sperm ultrastructure was studied in ten genera of the Porricondylinae (Cecidomyiidae). Sperm structure is remarkably simplified by the absence of the acrosome and the accessory tubules, as happens in all the cecidomyiid flies. All genera of the Porricondylinae show a peculiar 9+3 axonemal model exceptDiallactes, which retains the plesiomorphic condition of a 9+2 axoneme, andWinnertzia, which appears to have secondarily acquired a 9+0 model. A cladistic analysis of relevant sperm characters (based on the axonemal model, the number of mitochondrial derivatives and the size and structure of the centriolar adjunct) was performed to infer phylogenetic relationships among six tribes of the Porricondylinae. In this cladogram, the Porricondylini are the sister group to the Asynaptini, Heteropezini and Winnertzini and these four taxa form the sister group to the Dicerurini. The tribe Diallactini are regarded as the group with the most plesiomorphic characters within the family.

A “13+0” axonemal pattern in the spermatozoon of Neocondeellum dolichotarsum (Insecta, Protura)

The new 13+0 axonemal model has been described in the proturan Neocondeellum. All the doublets are devoid of dynein arms and the spermatozoa are immotile. A protruded acrosome is evident in the mature coiled spermatozoa. On the basis of the spermatological results Protentomidae seem closely related to Acerentomidae.