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1.
The effects of meal size and meal type on specific dynamic action (SDA) were investigated in a large, active asteroid, the sunflower star, Pycnopodia helianthoides. When the sunflower stars were fed clam flesh totalling 5%, 10%, or 20% of their body weight there was a step-wise increase in the scope, time to peak oxygen consumption, duration of the response and total SDA. The change in the rate of oxygen consumption was slower than other organisms, and oxygen uptake remained elevated for over 12 d following consumption of the largest meal. There were also differences in the characteristics of the SDA if sunflower stars consumed a whole clam versus the shucked flesh of a clam. The time to reach peak oxygen consumption was greater for sunflower stars consuming a whole clam. This occurred because the clam had to be opened before they could digest the flesh; a smaller initial peak comprising 3.5% of the total SDA represented the energy require to open the clam valves. When the sunflower stars were fed different prey items (e.g. butter clam, purple urchin and herring) of similar wet organic mass, there was no difference in the time to peak, peak oxygen uptake or total SDA despite the fact that the prey items differed in protein, lipid and caloric content. There was an increased duration for which oxygen uptake remained elevated for sea stars that consumed the urchin meal. Five of the seven sunflower stars that consumed urchins exhibited a smaller second peak in oxygen uptake, totalling approximately 8.5% of the SDA energy budget. This likely represented the energy required to eject the urchin test from the stomach. Although the sunflower star is much larger and more active than other sea stars, it displayed similar SDA responses to other members of the Asteroidea, indicative of the low metabolic rate of this class.  相似文献   

2.
Leeuwenhoek first described polyamines in 1677, but active investigation did not begin until the 1970's. When intracellular polyamine levels are reduced by inhibitors, mutation, or transfection, severe reductions occur in cell division, cell differentiation, and cell migration. These effects are not difficult to demonstrate and measure, and all can be prevented if supplemental exogenous polyamines are supplied. However, linking the overall effects to molecular events remains to be accomplished. In this review, we discuss work (mostly from the last 10 years) that relates to cell migration. Specifically, we have discussed the biology and biochemistry of the polyamines, their transport and regulation, the structure of the cytoskeleton and the mechanics of cell movement. We have also considered four specific processes that polyamines participate in that may affect cell migration significantly. These are: 1) the regulation of intracellular Ca++ concentration by voltage-gated K+ channels, 2) the maintenance of normal RhoA levels that, with Rac, regulate the assembly of actin stress fibers, focal adhesions, and contractility, 3) the formation of ATP-Mg++-polyamine trimers that enhance the phosphorylation activity of ATP toward enzymes in specific signaling pathways and, 4) alterations in the structure of RNA that change translation initiation sites and affect the expression of proteins.  相似文献   

3.
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4.
The sea star Pisaster ochraceus is one of the more striking species on the rocky shores of the Northeast Pacific, in part due to the dramatic color polymorphism of the adults. Along the open Pacific coast, Pisaster populations are 6%-28% orange, with a small percentage of brilliant purple stars and a large percentage of reddish-brown to dull purple ones. However, populations in the San Juan Island Archipelago (Washington, USA) and the southern Strait of Georgia (British Columbia, Canada) are almost entirely brilliant purple. The factors that maintain the color polymorphism, and those that contribute to among-site variation in color frequencies, remain unknown. We examined the relationships between color frequencies and several ecological and morphological variables, and conducted a large-scale phylogeographic survey of Pisaster populations. We found very low population genetic structure, suggesting that gene flow is high and geographic variation in color frequencies is not a vestige of Pleistocene glacial refugia. Color frequencies are also unrelated to adult size and to the frequency of injury within a population. However, there are suggestive relationships between color frequency and diet, and with areas of potentially low salinity. We propose that, although the color polymorphism may have an underlying genetic component, the regional-scale variation in color frequency is ecologically controlled.  相似文献   

5.
Coelomocytes are recognized as the main cellular component of the echinoderm immune system. They are the first line of defense and their number and type can vary dramatically during infections or following injury. Sea stars have been used as a model system to study the regeneration process after autotomy or predation. In the present study we examined the cellular and biochemical responses of coelomocytes from the European sea star Asterias rubens to traumatic stress using immunochemical and biochemical approaches. In terms of trauma and post-traumatic stress period, here we consider the experimental arm amputation and the repair phase involved in the first 24 hours post-amputation, which mimicked a natural predation event. Four cell morphotypes were distinguishable in the coelomic fluid of both control and post-traumatic-stressed animals (phagocytes, amoebocytes, vibratile cells, hemocytes), but phagocytes were the major components, accounting for about 95% of the total population. Thus, the effects measured relate to the overall population of coelomocytes. A modest increase in the total number of freely circulating coelomocytes was observed 6 hours post-amputation. Interestingly, a monoclonal antibody (McAb) to a sea urchin embryo adhesion protein (toposome) cross-reacted with isolated sea star coelomocytes and stained the coelomic epithelium of control animals with an increase in trauma-stressed arms. In addition, coelomocytes from trauma-stressed animals showed a time-dependent increase in Hsp70 levels, as detected by both immunocytochemistry and immunoblotting within 24 hours after arm tip amputation, with a peak at 6 hours after amputation. Our findings indicate a clear role for coelomocytes and classic stress molecules in the post-traumatic stress associated with the early repair phase of regeneration.  相似文献   

6.
When individuals have higher evolutionary fitness because of being heterozygous at a given gene region, it is known as overdominance. Although overdominant selection could represent an important mechanism for maintaining genetic variation within species, the prevalence of this mode of selection appears to be relatively low. Identification of cases of true single‐locus heterozygote advantage are thus useful reference points in our overall understanding of how various forms of balancing selection influence and maintain genetic variation in natural populations. Here we report the apparent long‐term maintenance of diversity via overdominant selection with homozygous lethality at an elongation factor locus in the sea star Pisaster ochraceus. Observing this pattern in a gene with such major effects on protein assembly indicates that overdominant selection could be a more prevalent factor in maintaining allelic diversity in the wild than previously recognized.  相似文献   

7.
Dysferlin is a calcium-binding transmembrane protein involved in membrane fusion and membrane repair. In humans, mutations in the dysferlin gene are associated with muscular dystrophy. In this study, we isolated plasma membrane-enriched fractions from full-grown immature oocytes of the sea star, and identified dysferlin by mass spectrometry analysis. The full-length dysferlin sequence is highly conserved between human and the sea star. We learned that in the sea star Patiria miniata, dysferlin RNA and protein are expressed from oogenesis to gastrulation. Interestingly, the protein is highly enriched in the plasma membrane of oocytes. Injection of a morpholino against dysferlin leads to a decrease of endocytosis in oocytes, and to a developmental arrest during gastrulation. These results suggest that dysferlin is critical for normal endocytosis during oogenesis and for embryogenesis in the sea star and that this animal may be a useful model for studying the relationship of dysferlin structure as it relates to its function.  相似文献   

8.
The ultrastructural features of spermatogenesis were investigated in the hermaphroditic sea star Asterina minor. The primordial germ cells in the genital rachis contain small clusters of electron-dense material (nuage material) and a stack of annulate lamellae. They also have a flagellum and basal body complex situated close to the Golgi complex. After the development of the genital rachis into the ovotestis, spermatogenic cells increase in number and differentiation begins. Nuage material is observed in spermatogonia, but it gradually disappears in spermatocytes. The annulate lamellae do not exist beyond the early spermatogonial stage. By contrast, a flagellum and basal body complex are found throughout spermatogenesis. The Golgi-derived proacrosomal vesicles appear in the spermatocyte and coalesce to form an acrosomal vesicle in the early spermatid. The process of acrosome formation is as follows: (1) a lamella of endoplasmic reticulum (ER) continuous with the outer nuclear membrane encloses the posterior portion of the acrosomal vesicle; (2) the vesicle attaches to the cell membrane with its anterior portion; (3) periacrosomal material accumulates in the space between the acrosomal vesicle and the ER; (4) the nucleus proper changes its features to surround the acrosome; (5) amorphous, electron-dense material is deposited under the electron-dense disk; and (6) the nucleus forms a hollow opposite the electron-dense material.  相似文献   

9.
The effect of inhibitors of polyamine biosynthesis on the development of embryogenic cell cultures of celery (Apium graveolus L.) was studied. Several developmental stages of somatic embryos were compared for differences in the content and biosynthesis of free polyamines and for cytokinin content. Cyclohexylamine and particularly methylglyoxal bis(guanylhydrazone), inhibited both cell division and the organization of polar embryos from globular embryos. Difluoromethylornithine slightly promoted embryo development, especially cell division.The free putrescine content of globular embryos was 6-fold that of fully differentiated plantlets, and that of spermidine 2-fold. Only a slight increase in the spermine content was found with embryo development. These differences were confirmed by data from polyamine biosynthesis. Incorporation of 14C-arginine into polyamines was slightly higher than that of 14C-ornithine. Over 96% of this incorporation was detected in the putrescine fraction. Incorporation of 14C into putrescine in globular embryos was 3 to 4-fold that in fully-differentiated plantlets. Incorporation into spermidine and spermine was, however, higher in plantlets than in globular embryos.Cytokinin analysis revealed considerable differences in the biological activity between the developmental stages of embryogenesis. This could be due to endogenous cytokinins and/or BA taken up from the maintenance medium. Cytokinin levels decreased with increased embryo development. Most of the detected cytokinin-like activity co-chromatographed with BA and its metabolites. Some as yet unidentified peaks of activity were recorded in the globular embryos.The results are considered with respect to the possible participation of polyamines and cytokinins in the development of embryogenic cell cultures of celery. It is suggested that the onset of embryogenesis is characterized by a high content of putrescine and cytokinins, while a decrease in putrescine synthesis and cytokinin content, and an increase in spermidine and spermine content, accompany further embryo development and plantlet formation.Abbreviation ADC arginine decarboxylase - ODC ornithine decarboxylase - 2,4-D dichlorophenoxyacetic acid - DFMA difluoromethylarginine - DFMO difluoromethylornithine - MGBG methylglyoxal bis(guanylhydrazone) - CHA cyclohexylamine - BA benzyladenine - BAR benzyladenine riboside  相似文献   

10.
The possible role of polyamines in the development of isolated neuroblasts from the cerebral cortex of embryonic chick brain was studied by means of three enzyme activated irreversible inhibitors of ornithine decarboxylase. -Difluoromethylornithine (MDL 71782) showed no effects on development at doses which depleted dramatically neuronal putrescine and spermidine levels. In contrast, the two other inhibitors, (E)--(fluoromethy)dehydroputrescine (MDL 72197) and 6-heptyne-2,5-diamine (MDL 72175) blocked the formation of neuronal outgrowths completely at 100 M and higher concentrations. Their effects on neuronal polyamines differed at this concentration considerably. The growth inhibitory effect of the ornithine decarboxylase inhibitors was in all cases reversible: cells which were grown after 3 days of exposure to the drugs in normal medium produced neuronal networks. The presence of putrescine at 10M concentration in the culture medium prevented the growth inhibitory effect of 100 M concentrations of the drugs. This concentration of putrescine was not only capable of preventing, but also of reversing growth inhibition by the ornithine decarboxylase inhibitors. Although the cellular polyamine levels were not correlated with the morphological development of chick embryo cortical neurons, the present study leaves no doubt that putrescine plays an essential role in neuronal differentiation.  相似文献   

11.
Summary Wound healing and regeneration following amputation of arm-tips of the sea star, Leptasterias hexactis, are described using light microscopy, SEM, TEM, and [3H] thymidine autoradiography. The process can be divided into a number of stages. Initially, the wound is closed by contractions of the stump-tip. Re-epithelialization then occurs through migration of epidermal cells from adjacent areas over the wound to form a thin wound epidermis. This is converted into a thicker, permanent covering in concurrence with the onset of cell cycle activity in the wound epidermis and adjacent epidermal regions. Histolysis and phagocytosis of damaged tissues occur beneath the new epidermis and a small connective tissue scar develops at the wound site within which muscle differentiates. At this time, elevated levels of [3H]thymidine incorporation are initiated in the sub-epidermal tissues of the arm-tip. A variety of differentiated cell types enter the cell cycle including cells of the parietal peritoneum, lining of the radial water canal, and the dermis. Cell division is accompanied by the development of a small new arm-tip complete with terminal ossicle, terminal tentacle, and optic cushion. The radial water canal, radial nerve, and perivisceral coelom extend by outgrowth into this newly developing tip. Accelerated growth of the regenerate then occurs in a zone just proximal to the new tip. There is no evidence of a blastema-like mass of rapidly dividing undifferentiated cells at the tip of regenerating arms. Arm-tip regeneration in this sea star may therefore be best described as a morphallactic-like process in which a true blastema is not formed, but in which scattered cell proliferation plays an essential role.  相似文献   

12.
This work presents results of study of a peculiar form of behavior of the sea stars Asterias rubens, which can be called transient from the unconditional-reflex reaction of the standing still to action of the an outside stimulus or unfavorable environment factor to the elaborated internal inhibition of the higher animals. The experiment was based on use of the biological peculiarity of behavior of sea stars (placed in a vessel)—a congenital reflex of movement to the water surface. At repeated meeting with the unfavorable action (the water surface desalting or a tapping on the upper rays), the sea star descends to the vessel bottom, is firmly attached with ambulacral feet to the vessel wall and stops rising to the surface. This state can be disinhibited by throwing the sea star onto the bottom. After a long training (for several experimental days) the sea stars begin to crawl on the bottom without ascending to the water surface. On destruction of the nervous system intactness (two rays with the madrepore plate were cut) the reflexes of the rise to the surface and escape of the unfavorable factors are preserved, but the active cessation of the rise does not appear. The observed phenomenon is similar to the elaboration of the reflex with negative reinforcement in the higher animals, at which there occurs inhibition of the congenital reaction that is inadequate under changed environment conditions. At present, neurophysiological mechanisms of elaboration of such “forbidden” inhibition are unknown.  相似文献   

13.
In the fertilization process of sea stars, sperm is activated to go through the acrosome reaction before cell fusion. We focused on induction of the acrosome reaction as a key process in fertilization. Six species of sea stars were used in this study: Asterias amurensis, Asterias rubens, Asterias forbesi, Aphelasterias japonica, Distolasterias nipon, and Asterina pectinifera. Acrosome reaction assays indicate that the acrosome reaction can be induced across species within Asteriinae subfamily. However, cross-fertilization assays indicate that sea stars have species specificity in fertilization. Therefore, steps after the acrosome reaction are responsible for the species specificity. To explain acrosome reaction subfamily specificity at the molecular level, the sugar components of egg jelly were examined and analyzed by principal component analysis. A. amurensis and A. forbesi belong to the same induction group of the acrosome reaction. D. nipon and An. pectinifera are in a unique group. Enzyme-linked immunosorbent assays indicate that Asteriinae subfamily share a common glycan structure, the Fragment 1 of Acrosome Reaction-Inducing Substance from A. amurensis. Fragment 1 plays an important role in the subfamily specificity of acrosome reaction induction. In addition, A. amurensis sperm activating peptide was recognized by sperm from the same superorder. These results demonstrate that the specificity of acrosome reaction induction is present at the subfamily level in sea stars.  相似文献   

14.
An elastolytic protease was purified from the hepatopancreas of the sea star Patiria pectinifera with specific activity of 100 units per 1 mg of protein. The molecular mass of the enzyme was estimated to be 30 KD by SDS-polyacrylamide gel electrophoresis. The isoelectric point of the enzyme was shown to be about 7.3 by gel isoelectrofocusing. The pH-dependence of the sea star elastase activity was determined toward Z-Ala-pNA. Values of kKaT and KM were equal to 36 s-1 and 1 mM, respectively. The kinetics of the thermal denaturation of purified elastase was studied at 40 and 60 degrees C. High thermostability and high activity of star elastase permit relying upon successful application of the enzyme in production of different cell cultures.  相似文献   

15.
Kadri S  Hinman VF  Benos PV 《PloS one》2011,6(12):e29217
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16.
1. Cell-free homogenates of male and female pyloric caeca, body wall, testis and ovary were incubated with radiolabeled 3H-androstenedione. 2. Pyloric caeca had highest rates of androstenedione conversion. The predominant metabolites in the pyloric caeca were testosterone, 5 alpha-androstane-3 beta, 17 beta-diol and 5 beta-androstane-3 beta, 17 beta-diol. 3. In body wall, testicular and ovarian homogenates, androstenedione was converted primarily to testosterone and also to 5 alpha-androstanedione and epiandrosterone. 4. Qualitative and quantitative differences in androgen metabolism in somatic and germinal tissues may be related to tissue-specific regulation of cellular metabolism.  相似文献   

17.
Hepatic stellate cells represent a highly versatile cytotype that plays a significant role in liver development and differentiation, regeneration, xenobiotic response, immunoregulation, control of hepatic blood flow and inflammatory reactions. Because of the wide panel of molecular intermediates they may produce and secrete, particularly after their sustained activation in a disease state, hepatic stellate cells are definitely involved in the pathogenesis of various liver pathologies, besides the well know key role in fibrosis and extracellular matrix remodelling. In particular, they can actively contribute to the progression of hepatitis and steatohepatitis of different aetiology, and of liver carcinogenesis.  相似文献   

18.
Life history plays a critical role in governing microevolutionary processes such as gene flow and adaptation, as well as macroevolutionary processes such speciation. Here, we use multilocus phylogeographic analyses to examine a speciation event involving spectacular life-history differences between sister species of sea stars. Cryptasterina hystera has evolved a suite of derived life-history traits (including internal self-fertilization and brood protection) that differ from its sister species Cryptasterina pentagona, a gonochoric broadcast spawner. We show that these species have only been reproductively isolated for approximately 6000 years (95% highest posterior density of 905-22 628), and that this life-history change may be responsible for dramatic genetic consequences, including low nucleotide diversity, zero heterozygosity and no gene flow. The rapid divergence of these species rules out some mechanisms of isolation such as adaptation to microhabitats in sympatry, or slow divergence by genetic drift during prolonged isolation. We hypothesize that the large phenotypic differences between species relative to the short divergence time suggests that the life-history differences observed may be direct responses to disruptive selection between populations. We speculate that local environmental or demographic differences at the southern range margin are possible mechanisms of selection driving one of the fastest known marine speciation events.  相似文献   

19.
The density-dependent prophylaxis hypothesis predicts that individuals at high density will invest more resources into immune defence than individuals at lower densities as a counter-measure to density-dependent pathogen transmission rates. Evidence has been found for this hypothesis in insects, but not in a non-arthropod taxon. To investigate this hypothesis in the coral-eating crown-of-thorns sea star, Acanthaster planci, density treatments were set up over 21 days, and pathogen infection was simulated with bacterial injection. Five immune responses: amoebocyte count, amoebocyte viability, lysosomal membrane integrity, respiratory burst and peroxidase activity were all upregulated at high density. These results demonstrate that immune investment shows phenotypic plasticity with adult population density in agreement with the density-dependent prophylaxis hypothesis. Here I show that the density-dependent prophylaxis hypothesis is neither dependent on larval density nor restricted to insects, and hence may potentially have important consequences on disease dynamics in any species with widely fluctuating population densities. This is the first demonstration of the density-dependent prophylaxis hypothesis outside arthropods.  相似文献   

20.
The Wnt signaling pathway is highly conserved across metazoa and has pleiotropic functions in the development of many animals. Binding of a secreted Wnt ligand to its Frizzled (Fz) receptor activates Dishevelled, which then drives one of three major signaling cascades, canonical (β-catenin), calcium, or planar cell polarity signaling. These pathways have distinct developmental effects and function in different processes in different organisms. Here we report the expression of six wnt and three fz genes during embryogenesis of the sea star, Patiria miniata, as a first step in uncovering the roles of Wnt signaling in the development of this organism. wnt3, wnt4, wnt8, and wnt16 are expressed in nested domains in the endoderm and lateral ectoderm from blastula through late gastrula stages; wnt2 and wnt5 are expressed in the mesoderm and anterior endoderm. Expression of different fz paralogs is detected in the mesoderm; posterior endoderm and ectoderm; and anterior ectoderm. Taken together, this suggests that Wnt signaling can occur throughout most of the embryo and may therefore play multiple roles during sea star development.  相似文献   

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