Phenotypic variability, deformations and post-traumatic reactions of the stem ofEncrinus cf.liliiformis Lamarck (Crinoidea) from the Middle Triassic of Qingyan, south-western China

Well-preserved stem remains ofEncrinus cf.liliiformis Lamarck 1801 from the Upper Anisian and lowest Ladinian (Middle Triassic) of Qingyan, Guizhou Province, south-western China, are described. The characteristic morphological features of the columnals, especially the sculptural characteristics of the articular facets, vary in the different parts of the stem. Numerous fine, short, peripheral crenulae and perilumina with a tendency to pentalobate shapes in the proximal stem region change to few long, coarse crenulae and circular perilumina in the distal stem part. The holdfasts exhibit various differentiations: the basic discoid type occurs on flat surfaces, encrusting holdfasts are characteristic of irregular substrates; juvenile holdfasts often show an irregular outline, adult ones have a more even, circular shape. Some special and unusual structures allow palaeoecological interpretations: Holdfasts and stems joined by callous growth probably result from the lack of suitable hard substrates for attachment on the soft seafloor; the larvae often had to settle very closely to each other on a relatively small substrate. After breakage of stem,Encrinus was able to continue living despite the traumatic loss of its basal fixation. Broken ends underwent skeletal regeneration. Some specimens strongly suggest that juvenile individuals sometimes even were able to re-attach secondarily, e.g. by coiling around stems of other crinoids and cementing to these by callous outgrowths.     

Characterization of the Adhesive Holdfast of Marine and Freshwater Caulobacters

Caulobacters are prosthecate (stalked) bacteria that elaborate an attachment organelle called a holdfast at the tip of the cellular stalk. We examined the binding of lectins to the holdfasts of 16 marine Caulobacter strains and 10 freshwater species or strains by using a panel of fluorescein-conjugated lectins and fluorescence microscopy. The holdfasts of all the marine isolates bound to only wheat germ agglutinin (WGA) and other lectins that bind N-acetylglucosamine (GlcNac) residues. The freshwater caulobacters showed more variability in holdfast composition. Some bound only to WGA and comparable lectins as the marine strains did. Others bound additional or other lectins, and some did not bind to the lectins tested. The binding of WGA appeared to involve the regions of the holdfast involved with adhesion; a holdfast bound to WGA was significantly less adhesive to glass. Competition experiments with WGA-binding holdfasts and oligomers of GlcNac demonstrated that trimers of GlcNac (the preferred substrate for WGA binding) were more effective than dimers or monomers in preventing WGA binding to holdfasts, suggesting that stretches of contiguous GlcNac residues occur in the WGA-binding holdfasts. In addition, differences between freshwater and marine holdfasts in the strength of WGA binding were noted. The effect of a number of proteolytic and glycolytic enzymes on holdfast integrity was examined; the proteases had no effect for all caulobacters. None of the glycolytic enzymes had an effect on marine caulobacter holdfasts, but chitinase and lysozyme (both attack oligomers of GlcNac) disrupted the holdfasts of those freshwater caulobacters that bound WGA. Despite some similarity to chitin, holdfasts did not bind Calcofluor and no measurable effects on holdfast production were detectable after cell growth in the presence of diflubenzuron or polyoxin D, inhibitors of chitin synthesis in other systems. Finally, the holdfasts of all caulobacters bound to colloidal gold particles, without regard to the coating used to stabilize the gold particles. This binding was stronger or more specific than WGA binding; treatment with colloidal gold particles prevented WGA binding, but the reverse was not the case.     

Evidence for a complex life cycle and endospore formation in the attached, filamentous, segmented bacterium from murine ileum.

Light and electron microscope observations showed that the filamentous, segmented bacterium commonly found attached to the ileal epithelium of rats and mice undergoes a complex life cycle. Filaments comprising up to 90 segments were attached to the microvillous border of absorptive epithelial cells by a specialized terminal holdfast segment. Starting at the free end of the filament and progressing toward the attached end, undifferentiated segments were converted into reproductive or mother segments. Within each mother cell two new holdfast segments developed. As the holdfasts matured, their mother cells degenerated and released them into the intervillar space where they attached, grew, and divided to produce new segmented filaments. Alternately, in some filaments, newly formed but not yet released holdfasts were converted into endospores, which were released in the same manner as holdfasts, presumably to spread the bacterial colony to other members of the rodent population.     

Temporal, spatial and substrate-dependent variations of Danish hard-bottom macrofauna

Detailed knowledge of the Danish hard-bottom fauna is at present limited because of sampling problems. In this study, two different sampling units were used to yield quantitative results of the fauna on two stone reefs in Kattegat: natural holdfasts of Laminaria digitata and plastic pan-scourers imitating the holdfasts. On the two reefs a total of 135 taxa (102 species) were identified, representing 12 phyla. One species, the bryozoan Cribrilina cryptooecium, has not previously been recorded in Denmark. The fauna was characterized by a mixture of a large number of rare species, yielding high values on the Shannon-Wiener diversity index, and it showed a high degree of spatial and temporal variation. ANOSIM analyses showed a significant difference in species compositions between both sampling location, time and substrate type. The plastic pan-scourers proved to be a valuable substrate for quantitative investigations of the fauna. In contrast, the Laminaria holdfasts were too small and variable to be suitable for such studies. Electronic Publication     

Isolation and characterization of novel neutral glycolipids from Thermoplasma acidophilum.

Several novel neutral glycolipids (GL-1a, GL-1b, GL-2a, GL-2b and GL-2c) were isolated from Thermoplasma acidophilum by high-performance liquid chromatography using phenylboronic acid-silica and preparative thin-layer chromatography. The tentative structures of these lipids were characterized by the combination of gas-liquid chromatography, the methylation procedure, and (1)H-NMR and FAB-mass spectrometries. The lipophilic portion of the neutral glycolipids was composed of a simple molecular species named caldarchaeol (dibiphytanyl-diglycerol tetraether). The sugar moieties of these glycolipids were composed of gulose and glucose which formed monosaccharide residues on one side or both sides of the core lipids. Gulose was attached to the terminal glycerol OH group of the core lipid with a beta-configuration and glucose being attached with an alpha-configuration. The proposed structure of GL-1a was gulosylcaldarchaeol and that of GL-1b was glucosylcaldarchaeol. The structures of GL-2a, GL-2b, and GL-2c were the analogs of the caldarchaeol derivatives attached by a variety of gulosyl residues or glucosyl residues on both sides of the terminal OH groups.     

The effects of egg position, egg mass size, substrate and biofouling on embryo mortality in the squid Sepioteuthis australis

Using a combination of laboratory and field investigations, this study examined embryo mortality in the southern calamary Sepioteuthis australis as a function of egg mass size, the substrate upon which the mass is attached, the position of the embryo within the mass, and the degree of biofouling. Egg mass size ranged from 2 to 1,241 egg strands, however most masses consisted of 200–299 strands. Small egg masses (<300 strands) were generally attached to soft-sediment vegetation (Amphibolis antarctica, Heterozostera tasmanica, Caulerpa sp.), whereas larger masses (>300 strands) were either securely attached to robust macroalgae holdfasts (Ecklonia sp., Marcocystis pyrifera, Sargassum sp.) or unattached. Rates of embryo mortality were highly variable ranging from 2 to 25%. Both laboratory and field results indicated a positive relationship between egg mass size and embryo mortality. Larger, unattached egg masses contained twice as many dead embryos than those securely attached to a substrate. Mortality rates were significantly affected by the embryos’ relative position within the mass and were highest in embryos located near the attachment point of the egg strand, within the interior of the mass, and in close contact with the substrate. This was attributed to the inability of the embryos to respire adequately and eliminate metabolic wastes. Biofouling did not strongly influence embryo mortality, but colonisation occurred in areas conducive to growth, photosynthesis, and respiration indicating ‘healthy’ regions within the mass.     

Ediacaran macroalgal holdfasts and their evolution: a case study from China

A macroalgal holdfast (root-like structure) anchored or grown into sediments is a key trait of metaphytes and eukaryotic algae. Various patterns and taphonomic variants of congeneric holdfasts are preserved on the bedding planes of black shales of the Ediacaran Wenghui biota in South China. The macroalgal holdfast, which commonly consists of a rhizome, rhizoid and pith (perhaps mechanical tissue), can be morphologically classified into ten types within four groups of rhizomes: bare rhizome holdfasts (Grypania, Tongrenphyton and Sectoralga-type holdfasts), canopy rhizome holdfasts (Gemmaphyton, Gesinella, Discusphyton and Baculiphyca-type holdfasts), pithy rhizome holdfasts (Zhongbaodaophyton and pithy-cone-type holdfasts) and differentiated rhizome holdfasts (Wenghuiphyton-type holdfasts). Analysis of the Precambrian macroalgal record indicates that rhizomes played a more important role in the evolution of macroalgal holdfast than rhizoids. The following evolutionary stages of development of macroalgal holdfasts are proposed: (1) growth of the basal thallus into sediments (Grypania-type holdfast); (2) development of a primitive (indistinct) rhizome from the base of a stipe or thallus (Tongrenphyton-type and Sectoralga-type holdfasts); (3) growth of a distinct rhizome with rhizoid (Gemmaphyton-type, Gesinella-type and Discusphyton-type holdfasts); (4) development of a pith in the stipe (Baculiphyca-type holdfast); (5) pith extension into the rhizome (Zhongbaodaophyton-type and pithy-cone-type holdfasts); and (6) rhizome differentiation and development of a complex holdfast system (Wenghuiphyton-type holdfast).     

Theory of the kinetics of reactions catalyzed by enzymes attached to the interior surfaces of tubes

A theoretical treatment is given of the kinetics of reactions catalyzed by enzymes attached to the inner surface of a tube, through which the substrate solution passes. A utilization factor, the ratio of the actual reaction rate to that in the absence of diffusional effects, is defined. A numerical procedure is proposed and numerical and approximate solutions for the utilization factor are given for five kinetic conditions: (a) Michaelis-Menten behavior, (b) substrate inhibition, (c) product inhibition (competitive), (d) product, inhibition (non-competitive), and (e) product inhibition (anticompetitive). When the enzyme chemically attached to a tube obeys a Michaelis-Menten relationship, criteria for insignificant and significant diffusional effects are proposed.     

Radial perforations in crinoid stems from the Silurian of Gotland

Radiating intracolumnal canals are a characteristic feature of large (diameter 10 mm or more) crinoid stems from the Silurian of Gotland. They are found in nodals as well as in internodals where the columnal height exceeds one millimetre. They were formed secondarily in the median and distal portions of crinoid stems with pseudocirriferous holdfasts. Intercolumnal canals are found in the distal parts of stems with true cirri regardless of the size of the stem. It is suggested that these canals played an important role in crinoid physiology. The crinoids are believed to have sustained a large proportion of their tissues through cutaneous digestion and uptake of dissolved substances from the surrounding sea water. The intra- and intercolumnal canals increased the surface of the axial canal in relation to volume. They provided a connection between the axial canal and the surrounding sea water, thus facilitating nutrient transport to the tissues.     

Patterns of abundance and assemblage structure of epifauna inhabiting two morphologically different kelp holdfasts

The mobile fauna associated with two sympatric kelp species with different holdfast morphology (Saccorhiza polyschides and Laminaria hyperborea) was compared to test for differences in the assemblage structure of holdfast-associated mobile epifauna. A total of 24,140 epifaunal individuals were counted from 30 holdfasts of each kelp species. Overall epifaunal abundances exceeded faunal abundances previously reported from holdfasts of other kelps. Three taxonomic groups, Amphipoda, Mollusca, and Polychaeta, accounted for ca. 85% of all individuals. Total abundances increased with the amount of habitat available, quantified either as the volume or the area provided by the holdfasts. The multivariate structure of the epifaunal assemblage did not differ between holdfasts of the two kelp species. However, epifaunal assemblages responded differentially to the habitat attributes provided by each type of kelp holdfast: multivariate variation in the assemblage structure of epifauna was mostly explained by holdfast area and volume for L. hyperborea, and by the surface-to-volume ratio for S. polyschides holdfasts. Therefore, the physical attributes of biogenic habitats, here kelp holdfasts that better predict patterns in the assemblage structure of associated fauna can differ according to their different physical morphology, even though the overall assemblage structure of associated fauna was similar.     

Effect of colcemid on the radial spreading of fibroblasts in culture

Effect of colcemide upon the spreading of mouse embryo fibroblast-like cells on the substrate was studied with the aid of time-lapse microcinematography and scanning electron microscopy. On the glass, colcemide did not prevent the transition of cells into a well-attached state, however, the time needed for this transition was seen considerably increased as compared with the control cultures. Intermediate stages of spreading on flat glass had the following abnormal features in colcemide-containing medium: a) shapes of cytoplasmic outgrowths formed by the cell were altered and their distribution along the cell border appeared less regular; b) partial detachments of the attached parts of cells occurred very frequently; c) the spreading of various parts of the cells was not correlated. Possible mechanisms of colcemide action on the cell spreading are discussed, and it is suggested that intracellular structures sensitive to colcemide are essential for coordination of reactions that occur in various parts of the cell in the course of spreading.     

Gravitropic response of inflorescence stems in Arabidopsis thaliana.

We have characterized the gravitropic response of inflorescence stems in Arabidopsis thaliana. When the inflorescence stems were placed horizontally, they curved upward about 90 degrees within 90 min in darkness at 23 degrees C, exhibiting strong negative gravitropism. Decapitated stem segments (without all flowers, flower buds, and apical apices) also showed gravitropic responses when they included the elongation zone. This result indicates that the minimum elements needed for the gravitropic response exist in the decapitated inflorescence stem segments. At least the 3-min gravistimulation time was sufficient to induce the initial curvature at 23 degrees C after a lag time of about 30 min. In the gravitropic response of inflorescence stems, (a) the gravity perception site exists through the elongating zone, (b) auxin is involved in this response, (c) the gravitropic curvature was inhibited at 4 degrees C but at least the gravity perception step could occur, and (d) two curvatures could be induced in sequence at 23 degrees C by two opposite directional horizontal gravistimulations at 4 degrees C.     

Substrate-attached serum and cell proteins in adhesion of mouse fibroblasts.

The effects of serum and coatings of substrate-attached material (SAM, which remains tightly adherent to the substrate after EGTA-mediated removal of cells) on the kinetics of attachment of DNA-radiolabeled BALB/c 3T3. SV40-transformed 3T3, and concanavalin A-selected revertant cells to glass coverlips were studied. The presence of serum in the medium of attaching cells had a marked effect on (1) the initial time lag before stable attachment of cells, (2) the maximum level of attached cells, (3) the stability of attachment, and (4) pseudopodial spread of the cell over the substrate. These serum effects could be mimicked by measuring attachment in medium without serum and with use of serum-preadsorbed or 3T3 SAM-coated coverslips. Enzymatic treatment of serumpreadsorbed substrates indicated that the factor(s) in serum which affects attachment is very trypsin-sensitive. Serum preadsorption of substrates stimulated attachment of SVT2 cells in medium with serum in a manner very similar to the effects of 3T3 SAM coating, while attachment of 3T3 SAM coating, while attachment of 3T3 or revertant cells was unaffected. Slab gel electrophoretic analysis (PAGE-SDS gels) identified eight major serum proteins by Coomassie blue staining (a) which bind to the substrate in the absence of cells and (b) which persist on the substrate after growth to confluence of 3T3 or SVT2 cells; this suggests that major breakdown or serum-adsorbed components does not occur during growth of normal or transformed cells. Seven radioactive SAM proteins were detected by autoradiography in 3T3 or SVT2 SAM electropherograms -- two of which are high molecular weight components which correspond to the glucosamine-radiolabeled hyaluronate proteoglycans observed previously; the remaining five are newly-identified proteins in SAM (one of these proteins appears to be actin). 3T3 and SVT2 cells have unique proportions of these seven components. The data are consistent with the idea that normal or virus-transformed cells do not attach directly to the culture substrate, but to specific classes of substrate-adsorbed serum proteins via deposition of specific classes of cell surface proteins and polysaccharides.     

Gelatinous fibers are widespread in coiling tendrils and twining vines

Although the coiling of tendrils and the twining of vines has been investigated since Darwin's time, a full understanding of the mechanism(s) of this coiling and twining ability has not yet been obtained. In a previous study (Planta 225: 485-498), gelatinous (G) fibers in tendrils of redvine occurred concomitantly with the ability to coil, strongly indicating their role in the coiling process. In this study, tendrils and twining vines of a number of species were examined using microscopic and immunocytochemical techniques to determine if a similar presence and distribution of these fibers exists in other plant species. Tendrils that coiled in many different directions had a cylinder of cortical G fibers, similar to redvine. However, tendrils that coiled only in a single direction had gelatinous fibers only along the inner surface of the coil. In tendrils with adhesive tips, the gelatinous fibers occurred in the central/core region of the tendril. Coiling occurred later in development in these tendrils, after the adhesive pad had attached. In twining stems, G fibers were not observed during the rapid circumnutation stage, but were found at later stages when the vine's position was fixed, generally one or two nodes below the node still circumnutating. The number and extent of fiber development correlated roughly with the amount of torsion required for the vine to ascend a support. In contrast, species that use adventitious roots for climbing or were trailing/scrambling-type vines did not have G fibers. These data strongly support the concept that coiling and twining in vines is caused by the presence of G fibers.     

Studies on the mechanism of reduction of azo dye carcinogens by rat liver microsomal cytochrome P-450

This laboratory has described the azoreduction of p-dimethylaminoazobenzene (1c) by rat liver microsomal cytochrome P-450. To elucidate the mechanisms involved, the reduction of structurally related azobenzenes by hepatic microsomes was investigated. High substrate reactivity was observed for 1c, its corresponding secondary (1a) and primary (1b) amines and p-hydroxyazobenzene (1d). In contrast, only negligible rates were obtained for unsubstituted azobenzene (1g), hydrazobenzene (2g), p-isopropylazobenzene (1e) and 1f, the benzoylamide derivative of 1b. These results clearly indicate that electron-donating groups, such as hydroxyl or primary, secondary and tertiary amines, are essential for binding of azo dye carcinogens to liver microsomal cytochrome P-450 and, by implication, their enzymic reduction. No inhibition of azoreduction of 1c or 1d was obtained by addition of 1e, 1g, or 2g to the reaction mixture. In the presence of hepatic microsomes, a type I binding spectrum was obtained for 1d and type II binding spectra for 1a, 1b and 1c, the reactive azo dyes. In contrast, very weak binding was observed for the unreactive compounds 1e, 1f, 1g and 2g. Thus, there is good correlation between binding and substrate reactivity. The apparent lack of binding may explain the inability of the non-reactive compounds to inhibit azoreduction. The difference in the reduction rate observed for 1g vs. 1d suggested that hydroxylation would facilitate the reduction of an otherwise non-reactive azo dye. Support for such a mechanism was obtained in two experiments. In the first, marked facilitation of azoreduction of both the inactive compounds, 2g and 2f, was seen when they were incubated with microsomes under aerobic conditions where preliminary hydroxylation can occur. In the second, azobenzene was initially incubated aerobically with microsomes from phenobarbital- or beta-naphthoflavone-induced rats. The hydroxyazobenzene formed was then readily reduced anaerobically by microsomes from untreated rats.     

Tree stem phosphoenolpyruvate carboxylase (PEPC): lack of biochemical and localization evidence for a C4-like photosynthesis system

Here, the kinetic properties and immunolocalization of phosphoenolpyruvate carboxylase (PEPC) and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) in young stems of Fagus sylvatica were investigated. The aim of the study was to test the hypothesis that there is a C4-like photosynthesis system in the stems of this C3 tree species. The activity, optimal pH and L-malate sensitivity of PEPC, and the Michaelis-Menten constant (Km) for phosphoenolpyruvate (PEP), were measured in protein extracts from current-year stems and leaves. A gel blot experiment and immunolocalization studies were performed to examine the isozyme complexity of PEPC and the tissue distribution of PEPC and Rubisco in stems. Leaf and stem PEPCs exhibited similar, classical values characteristic of C3 PEPCs, with an optimal pH of c. 7.8, a Km for PEP of c. 0.3 mM and a IC50 for L-malate (the L-malate concentration that inhibits 50% of PEPC activity at the Km for PEP) of c. 0.1 mM. Western blot analysis showed the presence of two PEPC subunits (molecular mass c. 110 kDa) both in leaves and in stems. Immunogold labelling did not reveal any differential localization of PEPC and Rubisco, neither between nor inside cells. This study suggests that C4-type photosynthesis does not occur in stems of F. sylvatica and underlines the importance of PEPC in nonphotosynthetic carbon fixation by most stem tissues (fixation of respired CO2 and fixation via the anaplerotic pathway).     

Maplexins, new α-glucosidase inhibitors from red maple (Acer rubrum) stems

Thirteen gallic acid derivatives including five new gallotannins, named maplexins A-E, were isolated from red maple (Acer rubrum) stems. The compounds were identified by spectral analyses. The maplexins varied in number and location of galloyl groups attached to 1,5-anhydro-d-glucitol. The isolates were evaluated for α-glucosidase inhibitory and antioxidant activities. Maplexin E, the first compound identified with three galloyl groups linked to three different positions of 1,5-anhydro-d-glucitol, was 20 fold more potent than the α-glucosidase inhibitory drug, Acarbose (IC(50)=8 vs 160 μM). Structure-activity related studies suggested that both number and position of galloyls attached to 1,5-anhydro-d-glucitol were important for α-glucosidase inhibition.     

Differences in response between haploid and diploid isomorphic phases of Gracilaria verrucosa (Rhodophyta: Gigartinales) exposed to artificial environmental conditions

This study tests the responses of juvenile gametophytes and tetrasporophytes (holdfast stage) of the isomorphic alga Gracilaria verrucosa under different environmental conditions.Estimations of survival and growth of holdfasts of haploid and diploid juvenile individuals were performed in natural sea-water and artificial culture medium, and under stringent conditions using lead as a toxin and ultra violet radiation as a mutagen. Results indicate that (i) holdfasts of haploid juveniles grow better than diploids in non-optimal medium conditions; (ii) holdfasts of diploid juveniles have a better tolerance to lead than haploids; and (iii) slight advantage of holdfasts of diploid juveniles grow better than haploids under U.V. radiation.     

Metabolism of a Non-phenolic β-O-4 Lignin Substructure Model Compound by Coriolus versicolor

A non-phenolic β-O-4 lignin substructure model, 4-ethoxy-3-methoxyphenylglycerol-β-syringaldehyde ether (I), was metabolized by a ligninolytic culture of Coriolus versicolor. Based on the identification of the metabolic products (II~XI), the following reactions were found to occur in the culture; a) oxidation (III) and reduction (II) at the benzyl (Cα′) position of the substrate (I), b) β-ether cleavage to give arylglycerols (IV, V), and c) Cα-Cβ cleavage of the arylglycerols and/or arylglycerol moiety of the substrate (I). In addition, β-deoxy diol (VI) and γ-formylglycerol (VII) were obtained as degradation products from substrate (I).