Perspectives on the origin of microfilaments, microtubules, the relevant chaperonin system and cytoskeletal motors - a commentary on the spirochaete origin of flagella

The origin of cytoskeleton and the origin of relevant intracellular transportation system are big problems for understanding the emergence of eukaryotic cells. The present article summarized relevant information of evidences and molecular traces on the origin of actin, tubulin, the chaperonin system for folding them, myosins, kinesins, axonemal dyneins and cytoplasmic dyneins. On this basis the authors proposed a series of works, which should be done in the future, and indicated the ways for reaching the targets. These targets are mainly: 1) the reconstruction of evolutionary path from MreB protein of archaeal ancestor of eukaryotic cells to typical actin; 2) the finding of the MreB or MreB-related proteins in crenarchaea and using them to examine J. A. Lake's hypothesis on the origin of eukaryote from "eocytes" (crenarchaea); 3) the examinations of the existence and distribution of cytoskeleton made of MreB-related protein within coccoid archaea, especially in amoeboid archaeon Thermoplasm acidophilum; 4) using Thermoplasma as a model of archaeal ancestor of eukaryotic cells; 5) the searching for the homolog of ancestral dynein in present-day living archaea. During the writing of this article, Margulis' famous spirochaete hypothesis on the origin of flagella and cilia was unexpectedly involved and analyzed from aspects of tubulins, dyneins and spirochaetes. Actually, spirochaete cannot be reasonably assumed as the ectosymbiotic ancestor of eukaryotic flagella and cilia, since their swing depends upon large amount of bacterial flagella beneath the flexible outer wall, but not depends upon their intracellular tubules and the assumed dyneins. In this case, if they had "evolved" into cilia and lost their bacterial flagella, they would immediately become immobile! In fact, tubulin and dynein-like proteins have not been found in any spirochaete.

Swimming direction reversal of flagella through ciliary motion of mastigonemes.

Bio-inspired designs can provide an answer to engineering problems such as swimming strategies at the micron or nano-scale. Scientists are now designing artificial micro-swimmers that can mimic flagella-powered swimming of micro-organisms. In an application such as lab-on-a-chip in which micro-object manipulation in small flow geometries could be achieved by micro-swimmers, control of the swimming direction becomes an important aspect for retrieval and control of the micro-swimmer. A bio-inspired approach for swimming direction reversal (a flagellum bearing mastigonemes) can be used to design such a system and is being explored in the present work. We analyze the system using a computational framework in which the equations of solid mechanics and fluid dynamics are solved simultaneously. The fluid dynamics of Stokes flow is represented by a 2D Stokeslets approach while the solid mechanics behavior is realized using Euler-Bernoulli beam elements. The working principle of a flagellum bearing mastigonemes can be broken up into two parts: (1) the contribution of the base flagellum and (2) the contribution of mastigonemes, which act like cilia. These contributions are counteractive, and the net motion (velocity and direction) is a superposition of the two. In the present work, we also perform a dimensional analysis to understand the underlying physics associated with the system parameters such as the height of the mastigonemes, the number of mastigonemes, the flagellar wave length and amplitude, the flagellum length, and mastigonemes rigidity. Our results provide fundamental physical insight on the swimming of a flagellum with mastigonemes, and it provides guidelines for the design of artificial flagellar systems.

Nature-inspired microfluidic propulsion using magnetic actuation.

In this work we mimic the efficient propulsion mechanism of natural cilia by magnetically actuating thin films in a cyclic but non-reciprocating manner. By simultaneously solving the elastodynamic, magnetostatic, and fluid mechanics equations, we show that the amount of fluid propelled is proportional to the area swept by the cilia. By using the intricate interplay between film magnetization and applied field we are able to generate a pronounced asymmetry and associated flow. We delineate the functional response of the system in terms of three dimensionless parameters that capture the relative contribution of elastic, inertial, viscous, and magnetic forces.

Light and scanning electron microscopic study of Balantidium ctenopharyngodoni Chen, 1955 (Class : Litostomatea) from China

Redescription of Balantidium ctenopharyngodoni "Chen (Acta Hydrobiol Sin 1:123-164, 1955)", collected from the hindgut of grass carp (Ctenopharyngodon idella), especially the segment of 6-10 cm upstream from the anus, from Honghu Lake, Hubei Province, central China in November 2005, is presented in this paper to complete Chen's description at both light and scanning electron microscopic levels. Some revisions were done: the vestibulum is fairly symmetrical, with compactly arranged cilia rather than assembled membrane bordering on the left vestibular side; four contractile vacuoles actually exist in the latter body, three of which surround the posterior portion of the macronucleus, whereas the fourth lies antero-left to it. Somatic monokinetids were compared among the species of genus Balantidium. The cysts were described, and possible infection routes of B. ctenopharyngodoni were also discussed.

PRELIMINARY STUDIES ON CRYOPRESERVATION OF SYDNEY ROCK OYSTER (SACCOSTREA GLOMERATA) LARVAE

In this study several parameters critical to the success of cryopreserving Sydney rock oyster (Saccostrea glomerata) larvae were investigated. They were: (1) cryoprotectants (10% dimethyl sulfoxide and 10% propylene glycol). (2) freezing protocols (with or without the seeding step). (3) larval concentrations (1,000, 3,000, 5,000, 10,000, 30,000 individuals mL(-1)). and (4) larval ages (6, 12, 24, 48 and 96 h old). The survival rates were determined as percentages of postthaw larvae performing active movements for the 6 and 12 h larvae or active cilia movement for the 24, 48 and 96 h larvae. Analyses showed that the difference in survival rates between different age classses was significant in all the experiments conducted, with the maximum survival rate being achieved in the 24-h-old larvae the postthaw survival rates of larvae cryopreserved with 10% dimethyl sulfoxide (93.1 +/- 0.2%) were significantly higher (P < 0.001) that those with 10% propylene glycol (81.5 +/- 0.4%). Differences in postthaw survival rates between different concentrations (1,000 30,000 individuals mL(-1)) were not significant within each of the three larval age classes (6-, 12-, and 24-h-old ) used.

Kiitricha minuta n. Sp., a peculiar hypotrichous ciliate (Ciliophora, Spirotrichea) from the Yellow Sea

The morphology and infraciliature of a new ciliate, Kiitricha minuta n. sp., isolated from the Yellow Sea, were investigated using live observation and protargol impregnation. Kiitricha minuta represents a third member of the rarely known order Kiitrichida. It is unique in the subclass Hypotrichia in having many rows of small uniform cirri along the right side of the body and the dorsal kineties composed of dikinetids, most of which bear two cilia. Kiitricha minuta n. sp. is ovoid and measures about 60 x 45 mu m in vivo. It has a huge buccal cavity occupying about 80% of the body length, numerous body extrusomes, one macronucleus and two micronuclei, 27-27 adoral membranelles, 9-12 frontoventral cirral rows, a submarginal row of 7-9 cirri, 6 or 7 transverse cirri, and roughly 7-9 dorsal kineties. This new species differs distinctly from its only congener Kiitricha marina by its smaller size (60 mu m vs. 80-150 mu m), the presence of body extrusomes (vs. absent), the different macronuclear pattern (one vs. two nodules), and the lower number of frontoventral cirral rows (9-12 vs. 21-26), which terminate at the anterior two-thirds of body (vs. extend to the posterior). The new term "submarginal cirral row" is introduced to distinguish from the marginal cirral row in typical hypotrichs sensu lato. Based on our new observations and the literature, an improved diagnosis for the genus Kiitricha is provided and its phylogenetic importance is discussed.

Individuals with mutations in XPNPEP3, which encodes a mitochondrial protein, develop a nephronophthisis-like nephropathy.

The autosomal recessive kidney disease nephronophthisis (NPHP) constitutes the most frequent genetic cause of terminal renal failure in the first 3 decades of life. Ten causative genes (NPHP1-NPHP9 and NPHP11), whose products localize to the primary cilia-centrosome complex, support the unifying concept that cystic kidney diseases are "ciliopathies". Using genome-wide homozygosity mapping, we report here what we believe to be a new locus (NPHP-like 1 [NPHPL1]) for an NPHP-like nephropathy. In 2 families with an NPHP-like phenotype, we detected homozygous frameshift and splice-site mutations, respectively, in the X-prolyl aminopeptidase 3 (XPNPEP3) gene. In contrast to all known NPHP proteins, XPNPEP3 localizes to mitochondria of renal cells. However, in vivo analyses also revealed a likely cilia-related function; suppression of zebrafish xpnpep3 phenocopied the developmental phenotypes of ciliopathy morphants, and this effect was rescued by human XPNPEP3 that was devoid of a mitochondrial localization signal. Consistent with a role for XPNPEP3 in ciliary function, several ciliary cystogenic proteins were found to be XPNPEP3 substrates, for which resistance to N-terminal proline cleavage resulted in attenuated protein function in vivo in zebrafish. Our data highlight an emerging link between mitochondria and ciliary dysfunction, and suggest that further understanding the enzymatic activity and substrates of XPNPEP3 will illuminate novel cystogenic pathways.

A beta-adrenergic receptor kinase-like enzyme is involved in olfactory signal termination.

We have previously shown that second-messenger-dependent kinases (cAMP-dependent kinase, protein kinase C) in the olfactory system are essential in terminating second-messenger signaling in response to odorants. We now document that subtype 2 of the beta-adrenergic receptor kinase (beta ARK) is also involved in this process. By using subtype-specific antibodies to beta ARK-1 and beta ARK-2, we show that beta ARK-2 is preferentially expressed in the olfactory epithelium in contrast to findings in most other tissues. Heparin, an inhibitor of beta ARK, as well as anti-beta ARK-2 antibodies, (i) completely prevents the rapid decline of second-messenger signals (desensitization) that follows odorant stimulation and (ii) strongly inhibits odorant-induced phosphorylation of olfactory ciliary proteins. In contrast, beta ARK-1 antibodies are without effect. Inhibitors of protein kinase A and protein kinase C also block odorant-induced desensitization and phosphorylation. These data suggest that a sequential interplay of second-messenger-dependent and receptor-specific kinases is functionally involved in olfactory desensitization.

Ultrastructure of the excretory system of Trilocularia acanthiaevulgaris (Cestoda, Tetraphyllidea).

The fine structure of the excretory system in the juvenile (plerocercoid-like) form of Trilocularia acanthiaevulgaris is described. The flame cell bears a bunch of 50-70 cilia, which are anchored in the cytoplasm by means of basal bodies possessing striated rootlets. All the cilia in the

The role of a kinesin, KLP-20, on neural development and epidermal morphogenesis in Caenorhabditis elegans

The heterotrimeric kinesin-II motor in Caenorhabditis elegans consists of KLP-20, KLP-11, and KAP-1 subunits and broadly functions in cellular transport for the development of biological structures including cilia and axons. The results of this paper support the ubiquitous and necessary role kinesin-II motors have in development, particularly the KLP-20 microtubule-associating subunit. Mutations in klp-20 result in a variable abnormal (vab) phenotype characterized by observable epidermal defects, although the role of this gene in development and the mechanism by which the vab phenotype is produced is largely unknown. The vab phenotype is highly penetrant in the first larval stage (L1) of C. elegans, which supports that klp-20 functions in early development. Ciliated amphid sensory neurons can be stained with a fluorescent dye, DiI, to simultaneously test cilia structure and function, as well as the morphology of the amphid sensory organ. Reduced dye uptake in klp-20 mutant L1s suggests that the microtubule-based cilia are under-developed as a result of defective kinesin-II function. Consistent observations of the PLM mechanosensory neuron using the zdIs5 reporter suggest that klp-20 has an essential role in neuron development, as mutations to klp-20 result in under-developed PLM axons. Qualitative observations suggest there may be an interaction between the development of the overlying epidermis and the underlying nervous system, as a more severe vab phenotype is observed simultaneously with reduced dye uptake, and hence amphid sensory cilia under-development. Furthermore, a more severe vab phenotype manifested as large bumps on the posterior epidermis appears to be spatially correlated with PLM defects. The results presented and discussed in this paper suggest that KLP-20 has a necessary role in neurodevelopment and epidermal morphogenesis in C. elegans during embryogenesis.

Ultrastructural features of the epidermis of the planarian Artioposthia triangulata (Dendy)

The epidermis of the land planarian Arthioposthia triangulata was examined by scanning and transmission electron microscopy. This investigation revealed that the flatworm was covered entirely with cilia and was especially densely populated on the ventral surface. In all regions the epidermis consisted of a one-layered columnar epithelium resting on a prominent basement membrane, but lacking a terminal web. Various secretions were found in the epidermis together with epidermal rhabdoids. Below the basement membrane other secretory material was visible and this included the cytoplasmic lamellated granules and adenal rhabdites. The basement membrane consisted of fibrils with a beaded appearance and these were arranged parallel to the epidermal layer but did not display cross-banding. The secretory cells above and below the basement membrane were compared and their products characterized on the basis of shape, size and location. Their possible function is discussed.

A test for mucus removal in the chiton Lepidochitona cinerea (Linnaeus, 1767) (Polyplacophora: Chitonida: Ischnochitonidae)

Several methods have been proposed to ‘clean’ the soft tissues of molluscs of mucus, so that the surface cilia can be examined microscopically. We report the first empirical test of the effectiveness of methods for removing mucus in the pallial cavity surface of chitons. Three methods were compared, at several time intervals: the enzyme hyaluronidase, the mucolytic agent N-acetyl cysteine (NAC), and seawater washing via the natural action of cilia in excised tissue. Treatment in NAC for 10 min produced the best results, and we recommend this protocol as a starting point for further investigation on mucus removal in a broader suite of taxa. We present the first description of the pallial surface cilia in the chiton Lepidochitona cinerea. During the course of this study, we also determined that these chitons were frequently infested with a ciliate protozoan parasite, Trichodina sp., which have been historically reported from chitons but never studied in detail. The parasites were absent where antimucus treatments were effective, but their abundance and large size (about 30-mm diameter) in less successful treatments obscured the view of the pallial cavity surface.

A new sensory organ in "primitive" molluscs (Polyplacophora Lepidopleurida), and its context in the nervous system of chitons

Introduction: Chitons (Polyplacophora) are molluscs considered to have a simple nervous system without cephalisation. The position of the class within Mollusca is the topic of extensive debate and neuroanatomical characters can provide new sources of phylogenetic data as well as insights into the fundamental biology of the organisms. We report a new discrete anterior sensory structure in chitons, occurring throughout Lepidopleurida, the order of living chitons that retains plesiomorphic characteristics.

Results: The novel "Schwabe organ" is clearly visible on living animals as a pair of streaks of brown or purplish pigment on the roof of the pallial cavity, lateral to or partly covered by the mouth lappets. We describe the histology and ultrastructure of the anterior nervous system, including the Schwabe organ, in two lepidopleuran chitons using light and electron microscopy. The oesophageal nerve ring is greatly enlarged and displays ganglionic structure, with the neuropil surrounded by neural somata. The Schwabe organ is innervated by the lateral nerve cord, and dense bundles of nerve fibres running through the Schwabe organ epithelium are frequently surrounded by the pigment granules which characterise the organ. Basal cells projecting to the epithelial surface and cells bearing a large number of ciliary structures may be indicative of sensory function. The Schwabe organ is present in all genera within Lepidopleurida (and absent throughout Chitonida) and represents a novel anatomical synapomorphy of the clade.

Conclusions: The Schwabe organ is a pigmented sensory organ, found on the ventral surface of deep-sea and shallow water chitons; although its anatomy is well understood, its function remains unknown. The anterior commissure of the chiton oesophagial nerve ring can be considered a brain. Our thorough review of the chiton central nervous system, and particularly the sensory organs of the pallial cavity, provides a context to interpret neuroanatomical homology and assess this new sense organ.

Decision making in child protection: An international comparative study on maltreatment substantiation, risk assessment and interventions recommendations, and the role of professionals’ child welfare attitudes

Child welfare professionals regularly make crucial decisions that have a significant impact on children and their families. The present study presents the Judgments and Decision Processes in Context model (JUDPIC) and uses it to examine the relationships between three indepndent domains: case characteristic (mother’s wish with regard to removal), practitioner characteristic (child welfare attitudes), and protective system context (four countries: Israel, the Netherlands, Northern Ireland and Spain); and three dependent factors: substantiation of maltreatment, risk assessment, and intervention recommendation.
The sample consisted of 828 practitioners from four countries. Participants were presented with a vignette of a case of alleged child maltreatment and were asked to determine whether maltreatment was substantiated, assess risk and recommend an intervention using structured instruments. Participants’ child welfare attitudes were assessed.
The case characteristic of mother’s wish with regard to removal had no impact on judgments and decisions. In contrast, practitioners’ child welfare attitudes were associated with substantiation, risk assessments and recommendations. There were significant country differences on most measures.
The findings support most of the predictions derived from the JUDPIC model. The significant differences between practitioners from different countries underscore the importance of context in child protection decision making. Training should enhance practitioners’ awareness of the impact that their attitudes and the context in which they are embedded have on their judgments and decisions.