Body Column Research Articles

Specific characters of the mammoth calf (Mammuthus primigenius) from the Khroma River (Yakutia)

The exterior, skeletal morphology, and teeth of a 4- to 5-month-old woolly mammoth calf, Mammuthus primigenius Proboscidea, Elephantidae from the Khroma River (Yakutia, Russia) are described. This is the third and best preserved frozen carcass of the mammoth calves from Yakutia. The calf is male (penis available). The individual age as determined by the degree of wearing of DP2 and the beginning of wear of DP3 corresponds to the stage of transition to combined feeding (milk and vegetal forage). At the same time, formation of the cranial sutures (sutura sagittalis, fronto-temporalis, squamo-temporalis, and the suture between os occipitale superior and os occipitale inferior) testifies to an older juvenile stage. The proximal and distal epiphyses of the humerus and the distal epiphysis of the femur are represented by paired centers of ossification. A comparison of the dimensions of the head, body, and legs with the corresponding parameters of other M. primigenius calves of the same age shows the individual variability (10–15%) of these features. Although of medium size characteristic of M. primigenius calves, the described individual lacks subcutaneous fat deposits in the withers and subdermal areas of the body flanks. Death was caused by a rupture of the body and vertebral column at the level of the pectoral vertebrae 11–12. The deformation of the legs and longitudinal stretching of the soft tissues of the body caused no bone fractures (except for three ribs in the zone of the rupture). The long bones are not dislocated either in the shoulder and pelvic girdles or relative to each other. Possible causes and the timing of the death of the mammoth calves preserved in the permafrost are discussed.

Conservation of the nucleotide excision repair pathway: characterization of hydra Xeroderma Pigmentosum group F homolog.

Hydra, one of the earliest metazoans with tissue grade organization and nervous system, is an animal with a remarkable regeneration capacity and shows no signs of organismal aging. We have for the first time identified genes of the nucleotide excision repair (NER) pathway from hydra. Here we report cloning and characterization of hydra homolog of xeroderma pigmentosum group F (XPF) gene that encodes a structure-specific 5′ endonuclease which is a crucial component of NER. In silico analysis shows that hydra XPF amino acid sequence is very similar to its counterparts from other animals, especially vertebrates, and shows all features essential for its function. By in situ hybridization, we show that hydra XPF is expressed prominently in the multipotent stem cell niche in the central region of the body column. Ectoderm of the diploblastic hydra was shown to express higher levels of XPF as compared to the endoderm by semi-quantitative RT-PCR. Semi-quantitative RT-PCR analysis also demonstrated that interstitial cells, a multipotent and rapidly cycling stem cell lineage of hydra, express higher levels of XPF mRNA than other cell types. Our data show that XPF and by extension, the NER pathway is highly conserved during evolution. The prominent expression of an NER gene in interstitial cells may have implications for the lack of senescence in hydra.

The consistent, non-destructive measurement of small proteiform aquatic animals, with application to the size and growth of hydra

Hydra (Cnidaria), the basal metazoan most often studied in cellular, molecular and developmental biology, is difficult to measure because it is small, proteiform and aquatic. To facilitate broader organismal and ecological study of Hydra, we evaluated three methods, whereby a polyp’s body column can be measured by means of photomicroscopy. The volume, cylindrical surface area and surface area corrected for changes in body shape were all highly repeatable methods (r > 0.97) when shape varied little. However, shape changes altered volume and cylindrical surface area. Repeated corrected surface-area measurements of the same individuals in markedly different positions yielded standard deviations <5% of the mean measured area. This easy, non-lethal means of individual size measurement explicitly accounts for the flexible morphology of a polyp’s hydrostatic skeleton. It therefore allows for the elucidation of how growth and size vary over time, age and food intake. We found that hydra changed size dramatically from day to day, and that although the food level influenced adult size, it had little effect on the early growth of recently detached buds. Finally, we discuss ecological and biological applications of this method.

A New Species ofHydra(Cnidaria: Hydrozoa: Hydridae) and Molecular Phylogenetic Analysis of Six Congeners from China

A new species of genus Hydra (Cnidaria: Hydrozoa: Hydridae), Hydra shenzhensis sp. nov. from Guangdong Province, China, is described and illustrated. Most polyps have five tentacles. Column length reaches 11 mm when relaxed. Buds do not acquire tentacles synchronously. Stenotele is broad and pyriform in shape, 1.2 times as long as its width. Holotrichous isorhiza is asymmetrical and slender (more than 2.7 times as long as its width), with transverse and slanting coils. Atrichous isorhiza is long, resembling a melon-seed in shape. Desmoneme is asymmetrically pyriform in shape. The new species, belonging to the vulgaris group, is dioecious; sexual reproduction was found to occur mostly during November and December under conditions of dense culture or food shortage. Two to thirteen testes, cone-like shape with papilla, formed beneath the tentacles. One to three ovaries, with an egg cup, milky white in color, formed on body column. Ninety percent of individuals developed only one ovum. On a mother polyp, a fertilized ovum developed an embryonic theca covering its surface. The embryotheca is brown, with a spine-like structure, covering a layer of transparent, membrane-like material. For phylogenetic analysis, the mitochondrial cytochrome oxidase subunit I gene (COI) of six hydra species collected from China was amplified by polymerase chain reaction (PCR) and sequenced. Morphological characters in combination with molecular evidence support the hydra described here as a new species.

NF-κB is required for cnidocyte development in the sea anemone Nematostella vectensis

The sea anemone Nematostella vectensis (Nv) is a leading model organism for the phylum Cnidaria, which includes anemones, corals, jellyfishes and hydras. A defining trait across this phylum is the cnidocyte, an ectodermal cell type with a variety of functions including defense, prey capture and environmental sensing. Herein, we show that the Nv-NF-κB transcription factor and its inhibitor Nv-IκB are expressed in a subset of cnidocytes in the body column of juvenile and adult anemones. The size and distribution of the Nv-NF-κB-positive cnidocytes suggest that they are in a subtype known as basitrichous haplonema cnidocytes. Nv-NF-κB is primarily cytoplasmic in cnidocytes in juvenile and adult animals, but is nuclear when first detected in the 30-h post-fertilization embryo. Morpholino-mediated knockdown of Nv-NF-κB expression results in greatly reduced cnidocyte formation in the 5 day-old animal. Taken together, these results indicate that NF-κB plays a key role in the development of the phylum-specific cnidocyte cell type in Nematostella, likely by nuclear Nv-NF-κB-dependent activation of genes required for cnidocyte development.

Effect of Bus Skin on Rollover Crash Simulation Outcomes

AbstractAccording to the test requirements stipulated in ECE/R66 and GB/T17578-1998, a finite element model of body frame and a finite element model of body with shin for type 6120 high—bed bus were established, and then the influence of bus skin on the simulation results of rollover crash was analyzed. Bus skin was shown to have a greater influence on the deformation of the front and rear body columns in rollover crash simulation. Thus, the impact of bus skin cannot be overlooked in testing the strength of bus superstructure by the finite element analysis method.

Age differential response of Hyalella curvispina to a cadmium pulse: Influence of sediment particle size

In Argentina periurban streams frequently receive agricultural, livestock and industrial discharges. Heavy metals have been found in the water column and sediments of numerous water bodies of the pampean region, at levels above the limits established for aquatic life protection. This study aimed to evaluate the effect of a contaminant pulse of cadmium discharged into a water-sediment system of different particle sizes, by means of laboratory tests using juveniles and adults of Hyalella curvispina, a native amphipod. We found that the substrate particle size was a determining factor in the toxicity of cadmium and that the adults of H. curvispina were more sensitive than juveniles. We also observed a temporal difference between the two ages for the same type of sediment. Given the nature of the sediments of regional water bodies, it is expected that a discharge of cadmium, even at concentrations as low as those tested here, will affect the survival of native amphipods.

The head organizer in Hydra

Organizers and organizing centers play critical roles in axis formation and patterning during the early stages of embryogenesis in many bilaterians. The presence and activity of an organizer was first described in adult Hydra about 100 years ago, and in the following decades organizer regions were identified in a number of bilaterian embryos. In an adult Hydra, the cells of the body column are constantly in the mitotic cycle resulting in continuous displacement of the tissue to the extremities where it is sloughed. In this context, the head organizer located in the hypostome is continuously active sending out signals to maintain the structure and morphology of the head, body column and foot of the animal. The molecular basis of the head organizer involves the canonical Wnt pathway, which acts in a self-renewing manner to maintain itself in the context of the tissue dynamics of Hydra. During bud formation, Hydra's mode of asexual reproduction, a head organizer based on the canonical Wnt pathway is set up to initiate and control the development of a new Hydra. As this pathway plays a central role in vertebrate embryonic organizers, its presence and activity in Hydra indicate that the molecular basis of the organizer arose early in metazoan evolution.

Interstitial stem cells in Hydra: multipotency and decision-making

Interstitial stem cells in Hydra constitute a population of multipotent cells, which continuously give rise to differentiated products during the growth and budding of Hydra polyps. They also give rise to germ cells in animals undergoing sexual differentiation. Cloning experiments have shown that interstitial stem cells are multipotent. In vivo tracing of stem cell lineages has revealed that stem cells divide symmetrically to yield two stem cells or asymmetrically to yield one stem cell daughter and one daughter cell which initiates nerve or nematocyte differentiation. Following commitment, some nerve cell precursors migrate from the body column into the head or foot region, thus giving rise to the high density of nerve cells observed in these regions. Stem cell proliferation is regulated by changes in the self-renewal probability and is controlled by stem cell density. Nerve cell commitment is controlled by several peptides including the Head Activator. Factors affecting nematocyte commitment are not known, but wnt and notch signaling are both required for differentiation of committed precursors.

Transplantation analysis of developmental mechanisms in Hydra

Since the pioneering work of Ethel Browne (1909) who demonstrated for the first time the concept of organizer activity, i.e. the potency of an apical Hydra tissue to induce a secondary axis when transplanted onto a host, Hydra flourished as a fruitful model system for developmental studies. Over the next 60 years this efficient transplantation approach identified graded biological activities along the body column of Hydra named Head Acti-vation and Head Inhibition. These properties inspired theoretical modelers including Lewis Wolpert, Alfred Gierer and Hans Meinhardt to propose models for morphogenesis, respectively the positional information (1969) and reaction-diffusion (1972) models. In 1973, Tsutomu Sugiyama and Toshitaka Fujisawa initiated in Mishima a unique project to analyze the properties of Hydra strains with distinct morphological and developmental characters. To this end, they collected in several areas of Japan multiple Hydra strains that they subsequently characterized and crossed. They also established a lateral transplantation strategy that was much more powerful than the previous ones, as it combined quantitative measurements with cellular analyses thanks to the chimera procedures developed by Campbell and colleagues. In-deed this approach provided a paradigm to quantify in any morphological phenotype the Head Activation and Head Inhibition levels along the body column. In this article, I review the various strains identified by Sugiyama and colleagues, the principles and the main results deduced from the quantitative lateral transplantation strategy. In addition, I briefly discuss the relevance of this approach in the era of molecular biology.

Hydra, a model system to trace the emergence of boundaries in developing eumetazoans

In developing embryos, boundary formation between neighbouring groups of cells is essential to establish compartments which later fulfil specialized functions. The ability to form such boundaries has likely developed early in animal evolution - due to functional requirements imposed by the necessity to separate tissues which protect the animal, take up food or ensure propagation. Essential for boundary formation are local cues which may be provided by the intersection of diffusible molecules or set locally by activation of membrane-bound receptors and transcription factors. In the simple diploblastic Hydra, a representative of the basally branching metazoan Cnidaria, tissue boundaries are morphologically detectable between the body column and terminally differentiated head and foot structures. In adult polyps, these borders correspond to sharp lines of differential gene expression. They form de novo during regeneration and budding of a young polyp. Functional studies strongly suggest the involvement of FGFR/Notch signalling in the establishment of the parent-bud boundary, and it is very likely that these pathways interact with the WNT and BMP systems. How boundaries in the head and foot regions are generated is still unclear. Expression patterns of transcription factors like Cngsc, HyAlx, HyBra, HyOtx, Prdl-a, CnNK2 and Manacle show strong position dependency and may be involved in regulating gene expression on either side of the boundaries, by interpreting positional information during their formation and maintenance. Due to its simplicity, the easy accessibility to pharmacological interference and, recently, transgenesis, Hydra is an interesting prebilaterian model system to study the emergence of boundary-forming mechanisms during evolution.

Nervous systems of the sea anemone Nematostella vectensis are generated by ectoderm and endoderm and shaped by distinct mechanisms

As a sister group to Bilateria, Cnidaria is important for understanding early nervous system evolution. Here we examine neural development in the anthozoan cnidarian Nematostella vectensis in order to better understand whether similar developmental mechanisms are utilized to establish the strikingly different overall organization of bilaterian and cnidarian nervous systems. We generated a neuron-specific transgenic NvElav1 reporter line of N. vectensis and used it in combination with immunohistochemistry against neuropeptides, in situ hybridization and confocal microscopy to analyze nervous system formation in this cnidarian model organism in detail. We show that the development of neurons commences in the ectoderm during gastrulation and involves interkinetic nuclear migration. Transplantation experiments reveal that sensory and ganglion cells are autonomously generated by the ectoderm. In contrast to bilaterians, neurons are also generated throughout the endoderm during planula stages. Morpholino-mediated gene knockdown shows that the development of a subset of ectodermal neurons requires NvElav1, the ortholog to bilaterian neural elav1 genes. The orientation of ectodermal neurites changes during planula development from longitudinal (in early-born neurons) to transverse (in late-born neurons), whereas endodermal neurites can grow in both orientations at any stage. Our findings imply that elav1-dependent ectodermal neurogenesis evolved prior to the divergence of Cnidaria and Bilateria. Moreover, they suggest that, in contrast to bilaterians, almost the entire ectoderm and endoderm of the body column of Nematostella planulae have neurogenic potential and that the establishment of connectivity in its seemingly simple nervous system involves multiple neurite guidance systems.

Advanced prediction for multiple disaster sources of laneway under complicated geological conditions

The driving safety in the laneway is often controlled by multiple disaster sources which include fault fracture zone, water-bearing body, goaf and collapse column. The advanced prediction of them has become a hotspot. Based on analysis of physical characteristics of the disaster sources and comparative evaluation of accuracy of the main advanced geophysical detection methods, we proposed a comprehensive judging criterion that tectonic interface can be judged by the elastic wave energy anomaly, strata water abundance can be discriminated by apparent resistivity response difference and establish a reasonable advanced prediction system. The results show that the concealed disaster sources are detected effectively with the accuracy rate of 80% if we use advanced prediction methods of integrated geophysics combined with correction of seismic and electromagnetic parameters, moreover, applying geological data, we may then distinguish types of the disaster sources and fulfill the qualitative forecast. Therefore, the advanced prediction system pays an important referential and instructive role in laneway driving project.

Axis Formation in Hydra

A hydra has a simple structure consisting of a head, body column, and foot along a single axis called the oral-aboral axis. The tissue dynamics of a hydra consist of a steady state of production and loss of tissue involving the entire animal. Axis formation and its maintenance is controlled by the head organizer, which is located at the apex of the animal. The head organizer produces two signals, the head activator and head inhibitor, which are transmitted to, and are distributed in, descending gradients among the epithelial cells along the body column. The two gradients control axial patterning along the oral-aboral axis. In the context of the tissue dynamics of the adult hydra, these three elements controlling axis formation and axial patterning are in a steady state of production and loss. The canonical Wnt pathway plays a major role in setting up and maintaining the head organizer.

The Optimization Design of New Type F-Nail Nailing Machine

Welded structure is usually used in current nailing machines. When a nailing machine was used for a period of time, the base of the machine was deformed, so products produced with the machines become waste. The reason for these problems is that the design of window shape around the body column plate is unreasonable, so the plate often cracks. In addition, the hydraulic system in current nailing machines is unreasonable too, which makes production less efficient. Aiming the current problems of the nailing machine, finite element analysis software ANSYS is used to analysis and find the machine’s stress concentration areas. According to the analysis results, the shape and size of these areas are re-designed, which has the minimum area stress and deformation. The welded machine body is changed into a casted one, and the other modules are also re-build, all of which make the machine has longer service life. Through the process analysis, the hydraulic system is re-designed too, which improves the equipment productivity greatly.

Entre homéostasie et développement, quelles stratégies pour régénérer ?

The Hydra model system is well suited to decipher the mechanisms underlying adult regeneration, specifically those that were robust enough to be maintained across evolution. After mid-gastric bissection head regeneration in Hydra relies on apoptosis-induced compensatory proliferation via the release of Wnt3 by the apoptotic interstitial cells and activation of the β-catenin pathway in the surrounding cycling interstitial cells. As apoptosis-induced compensatory proliferation is also at work in Drosophila regenerating imaginal discs, Xenopus tadpole regenerating their tail and mice regenerating their skin or their liver, this mechanism might represent an evolutionarily-conserved way to launch a regenerative response. However after decapitation, the analysis of the activation of the canonical Wnt pathway in decapitated Hydra showed that apoptosis-induced compensatory proliferation does not take place in this context. Given that the proportion of interstitial stem cells is significantly higher in the middle part than in the upper part of the body column, this suggested that the route taken to regenerate a structure as complex as the head dramatically varies according to the homeostatic status of the tissue at the time of injury. From these observations, we propose a tri-modular model for animal regeneration where the first module or "wound healing module" is followed by a transient module named "inducing module of regeneration" that allows the recruitment of the third module named "re-development module", necessary for repatterning the missing structure. We claim that among these three modules, the inducing module of regeneration is the most drastically constrained by the homeostatic conditions of any given tissue or organ at the time of injury and therefore the most variable.

Field sensitivity distribution of macroinvertebrates for phosphorus in inland waters

The magnitude of ecological damage caused by elevated phosphorus concentrations (C(P) ) in Dutch inland waters is expressed as the fraction of disappeared macroinvertebrate genera. We used field observations of species occurrence from 1980 to 2005 that were stored in the Limnodata Neerlandica to derive the presence of 867 aquatic macroinvertebrate genera in the water column of freshwater bodies with total phosphorus (P(tot) ) concentrations ranging from 0.001 to 40 mg/L. At concentrations > 0.3 mg/L, which is considered to cause nutrient enrichment of freshwater bodies, the disappeared fraction (DF) of macroinvertebrate genera can be described as a logistic function of the C(P) : DF = 1/(1 + 4.07/C( P)¹·¹¹). The logistic function suggests that half of the macroinvertebrate genera that potentially occur in the freshwater column in the Netherlands would disappear at a C(P) = 3.5 mg/L. This field-based effect expression resembles the cumulative sensitivity distribution function for a toxic substance based on the species sensitivity distribution (SSD) concept and exposure data. Whereas an SSD for a toxic chemical is derived from laboratory sensitivity data for a small number of species, our DF is derived from field observations of many macroinvertebrate genera at numerous C(P) levels. By applying this damage function to measured phosphorus in the rivers Rhine, Meuse, and Scheldt, we found that the observed C(P) values in 1975 imply diversity losses of 15% for the Rhine and Meuse, and 20% for the Scheldt. For 2000, the calculated diversity losses are 3% (Rhine), 6% (Meuse), and 9% (Scheldt). The cumulative genera sensitivity distribution function for phosphorus from national freshwater monitoring data can be applied in various environmental screening systems, such as multistress impact assessment of surface waters, and in life cycle impact assessment of products.

Microtubules are involved in regulating body length in hydra

Little is known about how the size of an adult animal is determined and regulated. To investigate this issue in hydra, we altered the body size by surgically removing a part of the body column and/or by axial grafting, and examined changes of column length with time. When the body column was shortened it elongated and resumed the original length within 24–48 h. This increase in the body column length was not accompanied by an increase in the number of epithelial cells in the body column. Instead, each of the epithelial cells elongated longitudinally, leading to elongation of the body column. When the body column surpassed the original length, the column shortened over time. This was not accompanied by a decrease in cell number but by the shortening and thickening of the epithelial cells. TEM analysis showed that formation of microtubule arrays takes place longitudinally along the body axis in elongated cells and perpendicular to the axis in shortened cells. Treatment with a drug that degrades microtubules completely blocked changes in body length. These observations suggest that microtubules are involved in regulating the length of the hydra body column by altering the shape of the epithelial cells. We propose from these observations that hydra has a mechanism for detecting the metrical distance between the two ends of the body column.

A conserved cluster of three PRD-class homeobox genes (homeobrain, rx and orthopedia) in the Cnidaria and Protostomia

BackgroundHomeobox genes are a superclass of transcription factors with diverse developmental regulatory functions, which are found in plants, fungi and animals. In animals, several Antennapedia (ANTP)-class homeobox genes reside in extremely ancient gene clusters (for example, the Hox, ParaHox, and NKL clusters) and the evolution of these clusters has been implicated in the morphological diversification of animal bodyplans. By contrast, similarly ancient gene clusters have not been reported among the other classes of homeobox genes (that is, the LIM, POU, PRD and SIX classes).ResultsUsing a combination of in silico queries and phylogenetic analyses, we found that a cluster of three PRD-class homeobox genes (Homeobrain (hbn), Rax (rx) and Orthopedia (otp)) is present in cnidarians, insects and mollusks (a partial cluster comprising hbn and rx is present in the placozoan Trichoplax adhaerens). We failed to identify this 'HRO' cluster in deuterostomes; in fact, the Homeobrain gene appears to be missing from the chordate genomes we examined, although it is present in hemichordates and echinoderms. To illuminate the ancestral organization and function of this ancient cluster, we mapped the constituent genes against the assembled genome of a model cnidarian, the sea anemone Nematostella vectensis, and characterized their spatiotemporal expression using in situ hybridization. In N. vectensis, these genes reside in a span of 33 kb with the same gene order as previously reported in insects. Comparisons of genomic sequences and expressed sequence tags revealed the presence of alternative transcripts of Nv-otp and two highly unusual protein-coding polymorphisms in the terminal helix of the Nv-rx homeodomain. A population genetic survey revealed the Rx polymorphisms to be widespread in natural populations. During larval development, all three genes are expressed in the ectoderm, in non-overlapping territories along the oral-aboral axis, with distinct temporal expression.ConclusionWe report the first evidence for a PRD-class homeobox cluster that appears to have been conserved since the time of the cnidarian-bilaterian ancestor, and possibly even earlier, given the presence of a partial cluster in the placozoan Trichoplax. Very similar clusters comprising these three genes exist in Nematostella and diverse protostomes. Interestingly, in chordates, one member of the ancestral cluster (homeobrain) has apparently been lost, and there is no linkage between rx and orthopedia in any of the vertebrates. In Nematostella, the spatial expression of these three genes along the body column is not colinear with their physical order in the cluster but the temporal expression is, therefore, using the terminology that has been applied to the Hox cluster genes, the HRO cluster would appear to exhibit temporal but not spatial colinearity. It remains to be seen whether the mechanisms responsible for the evolutionary conservation of the HRO cluster are the same mechanisms responsible for cohesion of the Hox cluster and other ANTP-class homeobox clusters that have been widely conserved throughout animal evolution.

The designs and feasibility of clinical applications about a novel percutaneous pedicle screw system

Objective To evaluate the rationality of the designs and the feasibility of applications about a novel percutaneous pedicle screw system. Methods Six human cadaver specimens were used to simulate operative procedures with the novel percutaneous pedicle screw system (group A), and Sextant sys-tem was served as a control group (group B). Compression fractured vertebral bodies harvested from fresh calf were distracted with novel percutaneous pedicle screw system to assess the distraction function of percuta-neous system and distraction effect of modified screw. Biomechanical properties of modified screw were as-sessed according to the fixation effects of three types of screw-rod systems for fractured segment. Results The mean operation time in group A [(38.2 6.20) min] and B [(56.4 12.8) min] had significant difference (P< 0.05). The excellent and good rate of screws position was 91.7% and 95.8% in group A and B, respectively, showed no significant difference. The novel percutaneous system had a good distraction function to three kinds of screws. Modified and monoaxial screws could distract mainly the anterior column of vertebral body and there was no significant difference. However, the polyaxial screws distracted mainly middle and posterior column, the distraction effect of the anterior column was not as good as previous screws (P<0.05). There were no significant differences in flexion and extension, lateral bending and rotation of all specimens in intact and fractured. Modified and monoaxial screws could provide similar three-dimensional stabilities to fractured specimens. Polyaxial screw provided poor stability in flexion and extension compared with the two previous of screws (P<0.05). There were no significant differences in lateral and rotation stability provided by three kinds of screws. Conclusion Through using novel percutaneous pedicle screw system, modified and monoaxial screws have similar distraction effect on anterior column of vertebral body, and can provide similar three-dimen-sional stability. The novel percutaneous pedicle screw system is well-designed and feasible in clinical practice. Key words: Spine; Biomechanics; Internal fixators; Bone screws