Relationships between macroalgal functional form groups and substrata stability in a subtropical rocky-intertidal system

The general hypothesis that morphological, physiological, and ecological adaptations of macro algal functional-form groups can be related to the level of disturbance encountered in a natural environment was examined. Two articulated calcareous coralline algae (Amphiroa van-bosseae Lemoine, 24% cover and Corallina frondescens Post. & Rupr. 20%) and one non-articulated coralline alga (Lithophyllum sp., 16%), all late-successional predation-tolerant strategists, comprise most of the community cover on stable bedrock substrata at Punta Las Cuevitas, Sonora, Mexico. Conversely, Ulva rigida C. ag. (26% cover) and a ralfsioid crust (23%), shows to be early-successional opportunistic strategists, cover more of the disturbed boulder habitat. Porolithon sonorense Daws., a stress-tolerant strategist, is uniquely abundant on both substratum types (13% cover on boulders, 10% on bedrock). The sheet-like and filamentous algae, prevalent in the temporally unstable habitat, generally show greater productivity (>2×) than the thicker and calcareous forms conspicuous in the more constant environment. It appears that selection for delicate thalli with high productivities, as well as selection for tougher morphologies having lower photosynthetic rates due to greater proportions of structural tissues, are widespread, divergent evolutionary forces among marine algae. Experiments with captive sea urchins (Echinometra vanbrunti Agassiz), in conjunction with fish-preference data published for some of the same algae studied here, offer strong support for the functional-form model. Parrotfishes, rudderfishes, surgeonfishes, damselfishes and E. vanbrunti, in the Gulf of California, preferentially feed on delicate, early-successional, sheet-like, and filamentous algae, while rejecting or ignoring the more structured, late-successional and calcareous algae. There is no significant (P > 0.05) gradation in calorific content between the first four of the six functional groups (i.e., Sheet-, Filamentous-, Coarsely Branched- and Thick Leathery-Groups), but the mean value for these fleshy forms (2.6 kcal · g ash-free dry wt^?1) is significantly greater than that for the last two groups (0.3 kcal, Jointed Calcareous- and Crustose-Groups). The approach used in this study demonstrates a realistic technique for predicting macrophyte community composition from knowledge of the disturbance levels in a given habitat or the reverse. The form group-disturbance relationship has important implications for future biological monitoring of rocky-inter-tidal and subtidal systems.     

A murine cytotoxic T lymphocyte cell line resistant to Vicia villosa lectin is deficient in UDP-GalNAc:beta-galactose beta 1,4-N-acetylgalactosaminyltransferase

We have reported the presence of N-acetylgalactosamine linked beta 1,4 to galactose on O-linked oligosaccharides of a cloned murine cytotoxic T cell line and the absence of these residues from the O-linked structures of a Vicia villosa lectin-resistant mutant line, VV6, derived from parental B6.1.SF.1 cells (Conzelmann, A., and Kornfeld, S. (1984) J. Biol. Chem. 259, 12528-12535). This study shows that B6.1.SF.1 cells contain an enzyme which transfers N-acetylgalactosamine from UDP-GalNAc onto the O-linked tetrasaccharides of human glycophorin A, giving rise to pentasaccharides which contain beta-glycosidically linked N-acetylgalactosamine. Desialylated glycophorin was inactive as an acceptor. The enzyme also transfers N-acetylgalactosamine to the N-linked oligosaccharides of the Tamm-Horsfall glycoprotein. This glycoprotein is known to contain N-linked oligosaccharides with beta-linked N-acetylgalactosamine residues which constitute the Sda blood group determinant. This N-acetylgalactosaminyltransferase could not be detected in VV6 cells which can account for the lack of beta-linked N-acetylgalactosamine residues on its O-linked oligosaccharides. The two cell lines have comparable levels of UDP-GalNAc:apomucin N-acetylgalactosaminyltransferase, demonstrating that the enzyme deficiency in VV6 cells is selective. Both cell lines have a similar glycolipid content, with the major component being asialo-GM1. Since this glycolipid contains N-acetylgalactosamine linked beta 1,4 to galactose, it would appear that the N-acetylgalactosyltransferase involved in the biosynthesis of glycolipids is different from the UDP-GalNAc:glycoprotein N-acetylgalactosaminyltransferase. An independently derived murine CTL line also contains the UDP-GalNAc:glycoprotein N-acetylgalactosaminyltransferase, suggesting that the expression of this enzyme is a common characteristic of this type of cell line.     

Regulation of pyruvate kinase expression and growth in P-815 mastocytoma cells. II. Potential role of prostaglandins

P-815 mastocytoma cells increase the level of pyruvate kinase (PK) expression in response to chloroform-methanol extracts of conditioned media, butyrate, and dibutyryl cyclic AMP (but2cAMP) plus theophylline. The butyrate effect is indomethacin sensitive, suggesting a prostaglandin (PG) is the active signaling factor. Moreover, the chloroform-methanol extracts contain PGE2 and PGF2 alpha and additions of the latter enhance PK activity. PGE2 alone has little or no effect but acts synergistically with PGF2 alpha. These data show that PGF2 alpha can regulate PK levels. On the other hand, other factors may also be active, since the endogeneous and the but2cAMP plus theophylline effects are indomethacin insensitive. Most of the factors that increase PK activity also inhibit cellular growth; however, regulation of PK expression can be uncoupled from growth inhibition.     

The stimulation of hepatic gluconeogenesis by acetoacetate precursors. A role for the monocarboxylate translocator

The regulation of the gluconeogenic pathway from the 3-carbon precursors pyruvate, lactate, and alanine was investigated in the isolated perfused rat liver. Using pyruvate (less than 1 mM), lactate, or alanine as the gluconeogenic precursor, infusion of the acetoacetate precursors oleate, acetate, or beta-hydroxybutyrate stimulated the rate of glucose production and, in the case of pyruvate (less than 1 mM), the rate of pyruvate decarboxylation. alpha-Cyanocinnamate, an inhibitor of the monocarboxylate transporter, prevented the stimulation of pyruvate decarboxylation and glucose production due to acetate infusion. With lactate as the gluconeogenic precursor, acetate infusion in the presence of L-carnitine stimulated the rate of gluconeogenesis (100%) and ketogenesis (60%) without altering the tissue acetyl-CoA level usually considered a requisite for the stimulation of gluconeogenesis by fatty acids. Hence, our studies suggest that gluconeogenesis from pyruvate or other substrates which are converted to pyruvate prior to glucose synthesis may be limited or controlled by the rate of entry of pyruvate into the mitochondrial compartment on the monocarboxylate translocator.     

Immunoprecipitation of nonerythrocyte spectrin within live cells following microinjection of specific antibodies: relation to cytoskeletal structures

The intracellular precipitation of nonerythrocyte spectrin has been achieved by the microinjection into cells of either a monoclonal antibody (IgM) directed against the alpha chain of nonerythrocyte spectrin or an affinity-purified polyclonal antibody raised against bovine brain spectrin (fodrin). This antibody-induced precipitation of spectrin was observed in fibroblastic and epithelial cell types, including embryonic bovine tracheal fibroblasts, a bovine kidney epithelial cell line (MDBK), Hela cells, gerbil fibroma cells, and fibroblast lines of human and mouse origins. The precipitation of the spectrin was specific and two proteins with a similar distribution to the nonerythrocyte spectrin were not induced to co-precipitate in the spectrin aggregates. Comparing the two types of antibody microinjected, the affinity-purified polyclonal antibody resulted in more compact aggregates of spectrin and these were frequently aligned with microfilament bundles. The rate at which the spectrin aggregates were cleared into presumptive lysosomes varied with different cell types: in some such as the bovine kidney epithelial cells, this appeared complete within 3 h after microinjection, whereas in some of the fibroblasts the spectrin aggregates were prominent in the cytoplasm at 24 and even 48 h after microinjection. Microfilament bundles appeared unaffected by the aggregation of spectrin. We conclude that the integrity of the actin microfilament bundles does not require nonerythrocyte spectrin and that most probably these structures are linked at their termini to the membrane through proteins other than nonerythrocyte spectrin. No effect of the intracellular spectrin precipitation was observed on cell shape, or on the distribution of coated vesicles or microtubules. The aggregation of the nonerythrocyte spectrin, however, did affect the distribution of the vimentin type of intermediate filaments in most of the cell types studied. These filaments became more distorted and condensed, but generally did not collapse around the nucleus as occurs following microtubule disruption induced by colchicine treatment. The clumped intermediate filaments were frequently seen to coincide with regions of aggregated spectrin. This aggregation of intermediate filaments was not induced by microinjection of irrelevant antibodies, nor was it induced by the monoclonal antibody against spectrin in cells with which it did not cross-react.(ABSTRACT TRUNCATED AT 400 WORDS)     

Identification of coated vesicles in Saccharomyces cerevisiae

Clathrin-coated vesicles were found in yeast, Saccharomyces cerevisiae, and enriched from spheroplasts by a rapid procedure utilizing gel filtration on Sephacryl S-1000. The coated vesicles (62-nm diam) were visualized by negative stain electron microscopy and clathrin triskelions were observed by rotary shadowing. The contour length of a triskelion leg was 490 nm. Coated vesicle fractions contain a prominent band with molecular weight of approximately 185,000 when analyzed by SDS PAGE. The presence of coated vesicles in yeast cells suggests that this organism will be useful for studying the function of clathrin-coated vesicles.     

Incorporation of fluorescent gangliosides into human fibroblasts: mobility, fate, and interaction with fibronectin

Rhodamine- and fluorescein-labeled gangliosides were used as probes to investigate the distribution, dynamics, and fate of plasma membrane-bound gangliosides on cultured human fibroblasts. When sparse cultures of fibroblasts were incubated with the fluorescent ganglioside derivatives, their surfaces became highly fluorescent. The fluorescent gangliosides were taken up by the cells in a time- and temperature-dependent manner and were not removed from the cell surface by trypsin or serum. Thus, the gangliosides appeared to be stably incorporated into the lipid bilayer of the plasma membrane. Fluorescent photobleaching recovery measurements showed that the inserted gangliosides were free to diffuse in the plane of the membrane with a high diffusion coefficient of approximately 10(-8) cm2/s. When the ganglioside-treated cells were washed and incubated in fresh medium, the surface gangliosides became internalized with time, and localized in the perinuclear region of the fibroblasts. In dense cultures of fibroblasts, a large fraction of the fluorescent gangliosides were organized in a fibrillar network and were immobile on the time scale of fluorescent photobleaching recovery measurements. Using antifibronectin antibodies and indirect immunofluorescence, these gangliosides were found to co-distribute with fibrillar fibronectin. Thus, exogenous gangliosides appear to be stably inserted into the lipid bilayer of the plasma membrane and to diffuse freely in its plane as well as form a less mobile state with the fibrillar networks of fibronectin associated with the cells.     

Genetic exchange between oral streptococci during mixed growth

To determine whether oral streptococci might exchange genetic information in the oral cavity, paired transformable strains of Streptococcus mutans, Streptococcus sanguis and Streptococcus milleri were growth together. Chromosomal and plasmid-borne antibiotic resistance markers could be readily transferred from S. mutans GS-5 to S. milleri NCTC 10707 or S. sanguis Challis during mixed growth. However, no exchange from the latter two organisms to strain GS-5 could be detected under these conditions. The transfer of genetic information from S. sanguis to S. milleri was also observed.     

Actions of synthetic piperidine derivatives on an insect acetylcholine receptor/ion channel complex

The actions of synthetic piperidine derivatives on the response to ionophoretically-applied acetylcholine (ACh) have been tested on the cell body membrane of the fast coxal depressor motoneurone (F_f) of the cockroach Periplaneta americana. The cis form and the cis (80%):trans (20%) mixture of 2-methyl-6-undecyl piperidine were the most effective (the half-maximal blocking action of the mixed isomers was estimated to be 6.3 × 10^?5 M). Less potent was the cis (50%):trans (50%) mixture of 2-methyl-6-tridecyl piperidine. However, pure cis 2-methyl-6-tridecyl piperidine was even less effective than the mixed isomers, indicating that, in the case of the tridecyl derivative, the trans form was largely responsible for the block of the ACh response.Cis 2-Methyl-6-undecyl piperidine failed to inhibit the binding of N-[propionyl-³H] propionylated α-bungarotoxin to metathoracic ganglion homogenates at concentrations up to 1.0 × 10^?4 M. Also, block of ACh-induced current by 2-methyl-6-undecyl piperidine (cis 80%:trans 20%) was largely independent of membrane potential in the range ?120 mV to ?60 mV, indicating an interaction with the closed ACh receptor/ion channel complex at a site which, in the case of the cis isomer, is separate from the binding site for α-bungarotoxin.     

The functional origin of bacteriophage f1 DNA replication. Its signals and domains

The origin of DNA replication of bacteriophage f1 functions as a signal, not only for initiation of viral strand synthesis, but also for its termination. Viral (plus) strand synthesis initiates and terminates at a specific site (plus origin) that is recognized and nicked by the viral gene II protein. Mutational analysis of the 5' side (upstream) of the origin of plus strand replication of phage f1 led us to postulate the existence of a set of overlapping functional domains. These included ones for strand nicking, and initiation and termination of DNA synthesis. Mutational analysis of the 3' side (downstream) of the origin has verified the existence of these domains and determined their extent. The results indicate that the f1 "functional origin" can be divided into two domains: (1) a "core region", about 40 nucleotides long, that is absolutely required for plus strand synthesis and contains three distinct but partially overlapping signals, (a) the gene II protein recognition sequence, which is necessary both for plus strand initiation and termination, (b) the termination signal, which extends for eight more nucleotides on the 5' side of the gene II protein recognition sequence, (c) the initiation signal that extends for about ten more nucleotides on the 3' side of the gene II protein recognition sequence; (2) a "secondary region", 100 nucleotides long, required exclusively for plus strand initiation. Disruption of the secondary region does not completely abolish the functionality of the f1 origin but does drastically reduce it (1% residual biological activity). We discuss a possible explanation of the fact that this region can be interrupted (e.g. f1, M13 cloning vectors) by large insertions of foreign DNA without significantly affecting replication.