Humoral responses of congenital immunity in the starfish <Emphasis Type="Italic">Asterias rubens</Emphasis>

The work presents analysis of changes of humoral protective factors in the starfish Asterias rubens in response to injection of human erythrocytes (HE). The total protein concentration and the titers of hemagglutinins and hemolysins in starfish coelomic fluid, as well as the time of human hemoglobin elimination from circulation were estimated for 6–144 h of the experiment. The hemagglutinin titer was determined in hemagglutination reactions, the hemolysin titer—in hemolysis reaction. Time of human hemoglobin elimination from coelomic fluid was determined in a color enzymatic reaction. The starfish coelomic fluid was revealed to contain soluble factors that are able to interact with antigen— antibody complexes of mammals and have an opsonizing activity. It is established that injection of HE does not change the total protein concentration per 1 ml coelomic fluid, but affects dynamics of changes of the hemagglutinins titer. Time of hemoglobin elimination from circulation does not exceed 24 h. Humoral factors of coelomic fluid of the starfish Asterias rubens play an auxiliary role in congenital immunity reactions.Translated from Zhurnal Evolyutsionnoi Biokhimii i Fiziologii, Vol. 41, No. 1, 2005, pp. 23–28.Original Russian Text Copyright © 2005 by Kudryavtsev, Dyachkov, Kazakov, Kanaikin, Kharazova, Polevshchikov.     

Steroid compounds from the Far East starfish <Emphasis Type="Italic">Pteraster obscurus</Emphasis> and the ophiura <Emphasis Type="Italic">Asteronyx loveni</Emphasis>

Seven sulfated polyhydroxysteroids were isolated from the Far East starfish Pteraster obscurus and the ophiura (snake star) Asteronyx loveni (collected in the Sea of Okhotsk) and characterized: disodium and sodium salts of (20R)-24-methyl-2β-hydroxycholesta-5,24(28)-diene-3α,21-diyl disulfate, (20R)-5α-cholestane-3β,21-diyl disulfate, (20R)-3β-hydroxy-5α-cholestan-21-yl sulfate, (20R)-cholest-5-ene-3β,21-diyl disulfate, (20R)-2β-hydroxycholest-5-ene-3α,21-diyl disulfate, (20R)-cholest-5-en-3β-yl sulfate, and (20R)-5α-cholestan-3β-yl sulfate. The first four compounds turned out to be new, whereas the others were identical to the known compounds. Structures of the isolated steroids were identified by two-dimensional NMR spectroscopy and other physicochemical methods. The compounds isolated from starfish are structurally similar to typical ophiuroid metabolites, which support the opinion of some taxonomists that starfish and ophiuroids are phylogenetically related classes.     

Development of the starfish <Emphasis Type="Italic">Asterias amurensis</Emphasis> under laboratory conditions

Under laboratory conditions the development of the starfish Asterias amurensis Lütken from Vostok Bay (Sea of Japan) was studied at 14 and 17°C. At 14°C and a salinity of 31.6–32.6, ciliated coeloblastulae hatched from egg envelopes 19 h after fertilization. At this temperature the development proceeded slowly and stopped at the stage of bipinnaria. At 17°C and normal salinity of seawater, the development of A. amurensis was successful. The swimming blastula appeared in 14 h. It took 30.5 h for the embryos to reach the gastrula stage. The larvae began swimming in a horizontal position with the apical tip ahead. The dipleurula appeared at 60 h. These larvae began feeding. At 71 h after the beginning of development, the early bipinnaria has developed. In the larva, the edged ciliated band, the preoral plate, and the anal plate were already formed. At the age of 4.2 days, the larvae reached the stage of bipinnaria and the brachiolaria stage developed by 26–28 days after fertilization. The larvae had three identical brachiolar arms with attachment papillae on their tips and an attachment disk. In 37–44 days (at 17°C) the pelagic phase of A. amurensis development was completed by the attachment of larvae to the bottom plates and termination of metamorphosis. Most likely, the specificity to a substrate is not expressed in the brachiolaria of A. amurensis. They can settle on almost any hard substrate which is coated with a bacterial film. The newly settled juvenile starfish had five well-developed arms and moved using their ambulacral podia.Original Russian Text Copyright © 2005 by Biologiya Morya, Kashenko.     

Associational resistance of fouled blue mussels (<Emphasis Type="Italic">Mytilus edulis</Emphasis>) against starfish (<Emphasis Type="Italic">Asterias rubens</Emphasis>) predation: relative importance of structural and chemical properties of the epibionts

Several epibiotic species reduce starfish (Asterias rubens) preference for the blue mussel Mytilus edulis in the Baltic. The aim of this study was to reveal whether this associational resistance was caused by structural or chemical aspects of the different epibionts. To assess structural epibiont effects, an in situ experiment was conducted with unfouled mussels and mussels equipped with artificial epibionts (dummies) exposed to natural predation by A. rubens. The chemically inert dummies closely matched the structural properties of the locally common epibionts Balanus improvisus (barnacle), Ceramium strictum (red alga), Halichondria panicea (sponge), and Laomedea flexuosa (hydrozoan). Starfish fed indiscriminately in all treatments. Chemical effects of epibionts on the attractiveness of mussels for A. rubens were investigated by incorporating freeze-dried epibionts or mussel tissue into Phytagel pellets at natural concentrations. Starfish were allowed to choose among these structurally similar but chemically different prey items in an in vitro experiment. The predators exhibited significant preferences among the food pellets, which closely matched their preferences for corresponding natural mussel–epibiont associations. Thus, chemical aspects of epibionts appear to play a larger role in this associational resistance than do structural aspects. Implications of these indirect interactions for benthic communities are discussed.Communicated by H.-D. Franke     

Soil characteristics and nitrogen resorption in Stipa krylovii native to northern China

Nitrogen (N) resorption from senescing tissues enables plants to conserve and reuse this important nutrient. As such, it is expected that plant species adapted to infertile soils could have a higher N-resorption efficiency (percentage reduction of nitrogen between green and senescing tissues) and/or higher N-resorption proficiency (absolute reduction of nitrogen in senescing tissues) than those adapted to fertile soils. To test this hypothesis, we investigated the relationships among soil characteristics (total N, nitrate-N, ammonium-N, pH and moisture) and N resorption in Stipa kryloviiRoshev., a species occurred widely in natural grasslands of northern China. N contents in green and senescing tissues were 6.7±0.1 and 3.3±0.1 mg g^–1, respectively. The mean value of N-resorption efficiency was found to be 72.1%. The N-resorption efficiency in S. kryloviiwas independent of soil characteristics. The N-resorption proficiency in S. kryloviiwas dependent on soil nitrate- and ammonium-N, but it was relatively independent of soil total N. The N-resorption proficiency was negatively correlated with soil pH and moisture. There was a positive correlation between N concentration in green tissues and resorption efficiency. However, N-resorption efficiency was not correlated significantly with N concentration in senescing tissues. These results indicate that the intraspecific variation in N resorption of Stipa kryloviiRoshev. is associated with soil regimes and that higher N resorption on N-poor soils is an adaptive strategy for S. kryloviito maximize N use under conditions of limited N supply.     

No-take reserves protect coral reefs from predatory starfish

The crown-of-thorns starfish, Acanthaster planci, is a predator of corals that is a major management issue on coral reefs [1]. It occurs throughout the Indo–Pacific and shows boom–bust population dynamics with low background densities and intermittent outbreaks. Three waves of population outbreaks have affected Australia's Great Barrier Reef (GBR) since the 1960s. The waves of outbreaks appear to start 15°S [2] and progress southward through the central GBR (Figure 1A), causing major losses of living coral on many reefs across a large area and dwarfing losses from other disturbances such as storms or coral bleaching over the same period [3]. Humans can potentially influence starfish population dynamics by exploiting predators, though evidence to date is circumstantial. Extensive surveys in the GBR Marine Park (GBRMP) show that protection from fishing affects the frequency of outbreaks: the relative frequency of outbreaks on reefs that were open to fishing was 3.75 times higher than that on no-take reefs in the mid-shelf region of the GBR, where most outbreaks occur, and seven times greater on open reefs if all reefs were included. Although exploited fishes are unlikely to prey on starfish directly, trophic cascades could favour invertebrates that prey on juvenile starfish.     

Simulation of the effects of Acanthaster planci on the population structure of massive corals in the genus Porites: evidence of population resilience?

Scleractinian corals in the genus Porites are slow growing, can live for centuries, and can attain great size. In these respects they differ from the majority of coral species, which grow faster and live for years to decades. The predatory starfish Acanthaster planci L. feeds on a wide range of coral species including Porites spp., and during outbreaks in its populations, causes high coral mortality and injury over much of the affected reefs. Because they are slow growing and because recent outbreaks of the starfish occurred only 15 years apart, it may be argued that the Porites populations on affected reefs will be sent into a period of prolonged decline. The present study uses a size stage model of the transition matrix type to predict effects of starfish outbreaks of various frequencies on Porites populations. A transition matrix characterizing the mortality and injury caused in different Porites size classes at John Brewer Reef during an outbreak year was determined from field data. Transition matrices for non-outbreak years were constructed on the basis of realistic growth rates and postulated survivorship and recruitment schedules. The medium term (100 years) effects of outbreaks were simulated by alternation of a single iteration of the outbreak matrix with many iterations of each non-outbreak matrix. By varying the interval between simulated outbreaks it was possible to define combinations of growth rate, survivorship and recruitment which were viable for various outbreak intervals. Simulations based on estimates of the initial size frequency distribution, recruitment rates and colony growth rates for the John Brewer Reef population predicted that the population would remain viable in the face of outbreaks every 15 years only if juvenile and adult survivorship were high. However, within the range of colony growth rates known to occur throughout the Great Barrier Reef and at recruitment rates of the same order as those estimated in the field population, it appears that a much wider range of survivorship schedules could lead to parity or even sustained growth in the face of outbreaks recurring at intervals of from 1 to 3 decades. It is suggested that because the key measurable parameters (initial size structure, damage characteristics, recruitment rate and growth rate) are likely to be very patchy at the scale of whole reefs, no general statement concerning the prognosis for Porites would be meaningful. However the model provides a tool by which a standardized evaluation of this type of field data may be made on a reef by reef basis.     

Osteoclast‐specific inactivation of the integrin‐linked kinase (ILK) inhibits bone resorption

Bone resorption requires the adhesion of osteoclasts to extracellular matrix (ECM) components, a process mediated by the α_vβ₃ integrin. Following engagement with the ECM, integrin receptors signal via multiple downstream effectors, including the integrin‐linked kinase (ILK). In order to characterize the physiological role of ILK in bone resorption, we generated mice with an osteoclast‐specific Ilk gene ablation by mating mice with a floxed Ilk allele with TRAP‐Cre transgenic mice. The TRAP‐Cre mice specifically excised floxed alleles in osteoclasts, as revealed by crossing them with the ROSA26R reporter strain. Osteoclast‐specific Ilk mutant mice appeared phenotypically normal, but histomorphometric analysis of the proximal tibia revealed an increase in bone volume and trabecular thickness. Osteoclast‐specific Ilk ablation was associated with an increase in osteoclastogenesis both in vitro and in vivo. However, the mutant osteoclasts displayed a decrease in resorption activity as assessed by reduced pit formation on dentin slices in vitro and decreased serum concentrations of the C‐terminal telopeptide of collagen in vivo. Interestingly, compound heterozygous mice in which one allele of Ilk and one allele of the β₃ integrin gene were inactivated (ILK^+/?; β) also had increased trabecular thickness, confirming that β₃ integrin and Ilk form part of the same genetic cascade. Our results show that ILK is important for the function, but not the differentiation, of osteoclasts. J. Cell. Biochem. 110: 960–967, 2010. © 2010 Wiley‐Liss, Inc.     

Crown-of-thorns starfish have true image forming vision

Background

Photoreceptors have evolved numerous times giving organisms the ability to detect light and respond to specific visual stimuli. Studies into the visual abilities of the Asteroidea (Echinodermata) have recently shown that species within this class have a more developed visual sense than previously thought and it has been demonstrated that starfish use visual information for orientation within their habitat. Whereas image forming eyes have been suggested for starfish, direct experimental proof of true spatial vision has not yet been obtained.

Results

The behavioural response of the coral reef inhabiting crown-of-thorns starfish (Acanthaster planci) was tested in controlled aquarium experiments using an array of stimuli to examine their visual performance. We presented starfish with various black-and-white shapes against a mid-intensity grey background, designed such that the animals would need to possess true spatial vision to detect these shapes. Starfish responded to black-and-white rectangles, but no directional response was found to black-and-white circles, despite equal areas of black and white. Additionally, we confirmed that starfish were attracted to black circles on a white background when the visual angle is larger than 14°. When changing the grey tone of the largest circle from black to white, we found responses to contrasts of 0.5 and up. The starfish were attracted to the dark area’s of the visual stimuli and were found to be both attracted and repelled by the visual targets.

Conclusions

For crown-of-thorns starfish, visual cues are essential for close range orientation towards objects, such as coral boulders, in the wild. These visually guided behaviours can be replicated in aquarium conditions. Our observation that crown-of-thorns starfish respond to black-and-white shapes on a mid-intensity grey background is the first direct proof of true spatial vision in starfish and in the phylum Echinodermata.

     

Steroid Compounds from the Far Eastern Starfish Diplopteraster multipes

Sodium salt of (20R)-3,4-dihydroxycholest-5-ene-21-yl sulfate and disodium salts of (20R)-4-hydroxycholest-5-ene-3,21-diyl disulfate, (20R)-24-methylcholest-5,24(28)-diene-3,21-diyl disulfate, (20R)-24-methyl-5-cholest-24(28)-ene-3,21-diyl disulfate, (20R)-cholest-5-ene-3,21-diyl disulfate, (20R)-5-cholestane-3,21-diyl disulfate, and (20R)-3-hydroxycholest-5-ene-2,21-diyl disulfate were isolated from the far eastern starfish Diplopteraster multipes and characterized. These compounds differ structurally from sulfated polyhydroxysteroids in other starfish species. At the same time, they are typical secondary metabolites of Ophiuroidea and have some structural features characteristic of the ophiuroid-isolated steroids, namely the 3-hydroxy (or 3-sulfoxy) and 21-sulfoxy groups. These data support the opinion of some taxonomists that starfishes and ophiuroids are phylogeneteically related classes and are closer to each other than to other classes of the Echinodermata phylum.     

<Emphasis Type="Italic">Chlamydomonas fla</Emphasis> mutants reveal a link between deflagellation and intraflagellar transport

Background

Cilia and flagella are often lost in anticipation of mitosis or in response to stress. There are two ways that a cell can lose its flagella: resorption or deflagellation. Deflagellation involves active severing of the axoneme at the base of the flagellum; this process is defective in Chlamydomonas fa mutants. In contrast, resorption has been thought to occur as a consequence of constitutive disassembly at the tip in the absence of continued assembly, which requires intraflagellar transport (IFT). Chlamydomonas fla mutants are unable to build and maintain flagella due to defects in IFT.

Results

fla10 cells, which are defective in kinesin-II, the anterograde IFT motor, resorb their flagella at the restrictive temperature (33°C), as previously reported. We find that in standard media containing ~300 microM calcium, fla10 cells lose flagella by deflagellation at 33°C. This temperature-induced deflagellation of a fla mutant is not predicted by the IFT-based model for flagellar length control. Other fla mutants behave similarly, losing their flagella by deflagellation instead of resorption, if adequate calcium is available. These data suggest a new model whereby flagellar resorption involves active disassembly at the base of the flagellum via a mechanism with components in common with the severing machinery of deflagellation. As predicted by this model, we discovered that deflagellation stimuli induce resorption if deflagellation is blocked either by mutation in a FA gene or by lack of calcium. Further support for this model comes from our discovery that fla10-fa double mutants resorb their flagella more slowly than fla10 mutants.

Conclusions

Deflagellation of the fla10 mutant at the restrictive temperature is indicative of an active disassembly signal, which can manifest as either resorption or deflagellation. We propose that when IFT is halted by either an inactivating mutation or a cellular signal, active flagellar disassembly is initiated. This active disassembly is distinct from the constitutive disassembly which plays a role in flagellar length control.

     

Spawning Inhibitor in Gonads of the Starfish,Asterina pectinifera

A biologically active substance which inhibits spawning of the starfish, Asterina pectinifera, has been isolated from gonads of the same organism and identified as l-glutamic acid.     

The small cells of coelomic fluid and coelomic epithelium isolated from starfish <Emphasis Type="Italic">Asterias rubens</Emphasis> and <Emphasis Type="Italic">Asterias amurensis</Emphasis> (Echinodermata: Asteroidea): Comparative analysis of cell morphology and proliferative activity in vivo and in vitro

Earlier we revealed the probable candidates for the role of Asteroidea stem cells in the starfish Asterias rubens L., small coelomic epithelial cells (SECs-1) with a high nuclear–cytoplasmic ratio that were able to proliferate in vivo and in vitro. To check the existence of a similar cell type in other members of Asteroidea, the small cells in suspensions of coelomic fluid (CF) and coelomic epithelium (CE) of A. amurensis were analyzed with respect to their morphology and proportion in the total cell pool. The morphology of proliferating cells and the proliferative activity of CF and CE cells in vivo and in vitro were studied. The small cells with parameters identical to those of A. rubens SECs-1, were found both in CF and CE of related species. The subpopulation of weakly attached CE cells, highly enriched with SECs-1, was detected. These cells were able to migrate from CE and to proliferate in vivo and in vitro. Additionally, large proliferating cells were described in both starfish. The dynamics of proliferative activity in primary cell cultures of these starfish had some distinctions. Moreover, for the first time, the formation of “crystals”, the potential centres of spiculogenesis, was observed in primary culture of A. amurensis CE cells. The data prove that SECs may fulfil the common functions in two members of Asteroidea.     

Responses of Embryos and Larvae of the Starfish <Emphasis Type="Italic">Asterias amurensis</Emphasis> to Changes in Temperature and Salinity

We studied the effects of different combinations of temperature (5, 10, 14, 17, 20, and 22°C) and salinity (from 32 to 8‰) on the development of the starfish Asterias amurensis Lutken from Vostok Bay, Sea of Japan. Embryonic development is the most vulnerable stage; it passes successfully at 10–17°C and the salinity range of 32 to 26‰. Blastulae are the most tolerant of changing environmental factors. They survive and develop at the temperatures of 5–17°C and in the salinity range of 32–18‰. Gastrulae and bipinnariae survive under higher temperature values and salinity from 32 to 20‰. The tolerance for decreased salinity during the process of fertilization and in the latest stage of development, the brachiolaria with the developing juvenile starfish, was confined to the salinity range of 32–22‰, which agrees with the tolerance of adult starfish Asterias amurensis. Thus, for normal development of the Amur starfish in the early stages, some particular conditions of temperature and salinity are required. This is, probably, due to adaptive capabilities of each developmental stage and the peculiarities of the ecological conditions at particular depths.     

The Reaction of the Starfish Asterias amurensisand Patiria pectinifera (Asteroidea) from Vostok Bay (Sea of Japan) to a Salinity Decrease

The reactions of the starfish Asterias amurensis and Patiria pectinifera that live in Vostok Bay at the salinity of 32–33 to a salinity decrease were studied under laboratory conditions. The lower limits of the desalination tolerance range of A. amurensis and P. pectinifera were, respectively, 24 and 20. A. amurensis proved to be less resistant to desalination. Under experimental conditions, all specimens of this species survived the salinity of 22, while those of P. pectinifera tolerated 18. At the same time, A. amurensis responded more actively than P. pectinifera to unfavorable changes in the environment. Turned to their dorsal side and exposed to a salinity of 16 to 32, the former reverted to the normal position within a shorter time than the latter. Being a more euryhaline species, P. pectinifera endured a salinity decrease to 6 or 8 over, respectively, 21 or 28 h. However, only 30–40% of all specimens could recover locomotory activity 12 or 8.5 h after being placed into water of normal salinity.     

Visual orientation by the crown-of-thorns starfish (<Emphasis Type="Italic">Acanthaster planci</Emphasis>)

Photoreception in echinoderms has been known for over 200 years, but their visual capabilities remain poorly understood. As has been reported for some asteroids, the crown-of-thorns starfish (Acanthaster planci) possess a seemingly advanced eye at the tip of each of its 7–23 arms. With such an array of eyes, the starfish can integrate a wide field of view of its surroundings. We hypothesise that, at close range, orientation and directional movements of the crown-of-thorns starfish are visually guided. In this study, the eyes and vision of A. planci were examined by means of light microscopy, electron microscopy, underwater goniometry, electroretinograms and behavioural experiments in the animals’ natural habitat. We found that only animals with intact vision could orient to a nearby coral reef, whereas blinded animals, with olfaction intact, walked in random directions. The eye had peak sensitivity in the blue part (470 nm) of the visual spectrum and a narrow, horizontal visual field of approximately 100° wide and 30° high. With approximately 250 ommatidia in each adult compound eye and average interommatidial angles of 8°, crown-of-thorns starfish have the highest spatial resolution of any starfish studied to date. In addition, they have the slowest vision of all animals examined thus far, with a flicker fusion frequency of only 0.6–0.7 Hz. This may be adaptive as fast vision is not required for the detection of stationary objects such as reefs. In short, the eyes seem optimised for detecting large, dark, stationary objects contrasted against an ocean blue background. Our results show that the visual sense of the crown-of-thorns starfish is much more elaborate than has been thus far appreciated and is essential for orientation and localisation of suitable habitats.     

Cathepsin K Activity-dependent Regulation of Osteoclast Actin Ring Formation and Bone Resorption

Cathepsin K is responsible for the degradation of type I collagen in osteoclast-mediated bone resorption. Collagen fragments are known to be biologically active in a number of cell types. Here, we investigate their potential to regulate osteoclast activity. Mature murine osteoclasts were seeded on type I collagen for actin ring assays or dentine discs for resorption assays. Cells were treated with cathepsins K-, L-, or MMP-1-predigested type I collagen or soluble bone fragments for 24 h. The presence of actin rings was determined fluorescently by staining for actin. We found that the percentage of osteoclasts displaying actin rings and the area of resorbed dentine decreased significantly on addition of cathepsin K-digested type I collagen or bone fragments, but not with cathepsin L or MMP-1 digests. Counterintuitively, actin ring formation was found to decrease in the presence of the cysteine proteinase inhibitor LHVS and in cathepsin K-deficient osteoclasts. However, cathepsin L deficiency or the general MMP inhibitor GM6001 had no effect on the presence of actin rings. Predigestion of the collagen matrix with cathepsin K, but not by cathepsin L or MMP-1 resulted in an increased actin ring presence in cathepsin K-deficient osteoclasts. These studies suggest that cathepsin K interaction with type I collagen is required for 1) the release of cryptic Arg-Gly-Asp motifs during the initial attachment of osteoclasts and 2) termination of resorption via the creation of autocrine signals originating from type I collagen degradation.Osteoclasts are monocyte-macrophage lineage-derived, large multinucleated cells. They are the major bone resorbing cells, essential for bone turnover and development. Active osteoclasts display characteristic membranes, including the ruffled border, attachment zone, and the basolateral secretory membrane. After attachment to bone, the ruffled border secretes enzymes and protons enabling the solubilization and digestion of the bone matrix. Osteoclasts express many proteases including cathepsins and matrix metalloproteases (MMPs)² (for review see Refs. 1-3). However, it is the general consensus that cathepsin K (catK) is the major bone-degrading enzyme (4-7).Rapid cytoskeletal reorganization is essential for osteoclast function and formation of the specialized membranes. Bone resorption occurs within the sealing zone, which is formed by an actin ring structure. This can be identified as a solid circular belt like formation and consists of an actin filament core surrounded by actin-binding proteins such as talin, α-actinin, and vinculin, which link matrix-recognizing integrins to the cytoskeleton (8). The ruffled border is contained within this structure. The actin ring is initiated by the formation of podosomes, which represent dot-like actin structures of small F-actin containing columns surrounded by proteins also found in focal adhesion such as vinculin and paxillin (9). It was previously thought that the sealing zone was formed by the fusion of podosomes after the osteoclast becomes activated (10, 11), but it has since been demonstrated that podosomes and the sealing zone are distinct structures (12, 13). It should be noted that bone resorption only occurs when the sealing zone is formed and the actin ring is present (14).Osteoclasts bind and interact with the bone surface through specific integrin receptors. The most abundant integrin present in osteoclasts is the αvß3 receptor also known as the vitronectin receptor (15, 16). This receptor attaches to RGD sequence containing components of the bone matrix, e.g. vitronectin, osteopontin, and type I collagen (17-19). This interaction enables the formation and regulation of the actin ring and therefore osteoclast activity (20-22). It has previously been shown that soluble RGD containing peptides added to cell supernatant are capable of inhibiting osteoclast binding and bone resorption (18, 22-24).This study investigates the effect of collagen degradation fragments on osteoclast activity. Soluble type I collagen and the bone powder of murine long bones were subjected to digestion reactions by the cysteine proteases, catK and catL, and the interstitial collagenase, MMP-1. The effect of these degradation products on osteoclasts was investigated by monitoring actin ring and resorption pit formation. We further investigated the role of cathepsins using catK- and catL-deficient mice. Finally, we looked in more detail at the effect of collagen, as a cell adhesion matrix, on osteoclast activity.     

Evolution of nutrient resorption across the herbaceous genus <Emphasis Type="Italic">Helianthus</Emphasis>

Foliar nutrient resorption is a key modulator of plant nutrient use. However, evolutionary patterns for nutrient resorption remain unclear, especially in herbs. We measured nitrogen and phosphorus resorption on preselected leaves across the Helianthus (sunflower) genus in a common garden in Athens, GA. We analyzed our data with published leaf traits and native habitat environmental data. Using phylogenetically controlled analyses, we tested if (1) nutrient resorption correlates with leaf economic, vasculature, and defense traits through evolutionary time, and (2) native habitat environment predicts nutrient resorption evolution. For Helianthus, nutrient resorption capacity is greater in resource-conservative species, as previously defined for Helianthus with a principle components analysis of leaf economic spectrum traits (photosynthetic rate, respiration rate, leaf lifespan, leaf mass per area, and green-leaf N and P concentrations). Nutrient resorption capacity also evolutionarily correlates with individual leaf economic traits, though not always as expected based on broad species surveys. Greater nutrient resorption is also positively associated with leaf chemical defenses, but not leaf vasculature or senescence rate. Finally, nitrogen resorption evolution increases with native habitat precipitation, but native habitat soil fertility does not predict nitrogen or phosphorus resorption. Our results suggest nutrient resorption evolution is more closely tied to resource economic strategy than native habitat.     

Molecular Basis of the Size Polymorphism of the First Intron of the<Emphasis Type="Italic">Adh-1</Emphasis> Gene of the Mediterranean Fruit Fly, <Emphasis Type="Italic">Ceratitis capitata</Emphasis>

The first intron of the gene encoding one of the alcohol dehydrogenase isoenzymes (ADH-1) in Ceratitis capitata is highly polymorphic in size. Five size variants of this intron were isolated from different strains and populations and characterized. Restriction map and sequence analysis showed that the intron size polymorphism is due to the presence or absence of (a) a copy of a defective mariner-like element, postdoc; (b) an 550-bp 3 indel which exhibits no similarity to any known sequence; and (c) a central duplication of 704 bp consisting of part of the 3 end of the postdoc element, the region between postdoc and the 3 indel, and the first 20 bp of the 3 indel. The homologous Adh-1 intron was amplified from the congeneric species, Ceratitis rosa, in order to obtain an outgroup for comparative and phylogenetic analyses. The C. rosa introns were polymorphic in size, ranging from about 1100 to 2000 bp, the major difference between them being the presence or absence of a mariner-like element Crmar2, unrelated to the postdoc element. Phylogenetic analysis suggests that the shorter intron variants in C. capitata may represent the ancestral form of the intron, the longest variants apparently being the most recent.     

An ultrastructural study of the dermal papulae of the starfish,Asterias rubens,with special reference to innervation of the muscles

Summary The ultrastructure of the dermal papulae of a starfish (Asterias rubens) is consistent with a respiratory function. The present study has shown no regions specialized for excretory mechanisms. The papulae consist of an outer ectodermal epithelium of sensory, support and gland cells and a small basiepithelial nerve plexus. A true basement membrane lies underneath the epithelium and regularly arranged longitudinal muscle bundles lie within the connective tissue. The coelomic cavity of the papulae is lined with ciliated endothelial cells, which overlie an irregular layer of circular muscles. A system of canals that are not lined by cells occurs at the base of the papulae with the circular muscles. The longitudinal and circular muscles show a different gross morphological arrangement and innervation. This paper proposes that there are skeletal and visceral types of smooth muscle in echinoderms and discusses this proposal at length.The author wishes to acknowledge with thanks the help of Miss Elaine Sneddon in the preparation of material for the electron microscope