Chicken lactose lectin: Cell-to-cell or cell-to-matrix adhesion molecule?

Summary Endogenous chicken muscle lectin isolated by lactose affinity chromatography inhibits myoblast fusion. Similar lectins isolated from embryonic brain, heart, and liver and from adult intestine exhibit the same ability. Elevated levels of any of these lectins canceled the inhibitory effect. Peanut agglutinin isolated by the same procedure had no effect at any concentration tested. Concanavalin A affected fusion only at high concentrations. Muscle lectin was shown to agglutinate myoblasts in microtiter plates, whereas exogenous addition in culture inhibited alignment as seen by time lapse microcinematography. Cell-to-cell communication between lectin-treated cells was shown by nucleotide exchange, and lectin-coated culture dishes did not affect cell attachment. Our evidence shows a lack of specificity to muscle, but suggests an aggregating capacity between cells, or possibly an interaction between the cell membrane and the extracellular matrix. This study was supported by National Institutes of Health grants AM 25202 and HD 07104, The Muscular Dystrophy Association, and the Cleveland chapter of Sigma Xi.     

Life-history traits of Amur sleeper, <Emphasis Type="Italic">Perccottus glenii</Emphasis>, in the invaded Vistula River: early investment in reproduction but reduced growth rate

In recent decades, Amur sleeper is one of the most invasive fish species in Eastern and Central Europe. Generally, it is assumed that success of an invasive species can largely depend on the plasticity of its life-history traits, e.g., indicated by higher investment in reproduction in the initial stage of its invasion. On the other hand, such energy allocation to production of gonads should negatively impact somatic growth rate. The aim of this article was to explore this phenomenon in a non-native population of Amur sleeper inhabiting artificial reservoir on a large lowland river in Central Europe. Through analysis of the population age structure, sex-dependent growth rate and life-history traits we assessed investment in reproduction and its possible relationship with growth pattern as well as compared the results with literature data from native and introduced range. Samples collected monthly from April 2005 to March 2006 were used to estimate sex ratio, GSI, fecundity, eggs diameter frequency over the year, duration of spawning season, and mode of spawning. Age structure was calculated from scales and the same data were also used to back-calculate standard length (SL) at age. The population in the Włocławski Reservoir was represented by eight age groups, and its life span was one of the longest recorded both in its natural range and introduced areas. The weight–length relationship showed that the Amur sleeper grew isometrically and there was no difference between females and males. Although the Amur sleeper growth rate was relatively slow in the Włocławski Reservoir, its increment in the first year of life was comparable to that in other introduced areas and higher than in its natural range. The female age of maturation (1+) found in the reservoir was earlier than observed in its natural range as well as in most introduced areas (2+, 3+). Female length at maturation was similar to that reported elsewhere. The back-calculated standard length (SL) of females and males showed that in the first two age classes (1 and 2) males achieved larger SL than females. Meanwhile, at age 3, 4 and 5, females were larger than males but these differences were insignificant, except for class 5. For both sexes the average annual increment of SL decreased with age but in females the increment was always higher than in males (P < 0.05). The growth rate differences between females and males resulted possibly from their unequal investment in reproduction. Multiple spawning in the Włocławski Reservoir lasted from April to the end of August and was almost 3 months longer than in other regions. Thus, this higher investment in reproduction displayed by, e.g., earlier maturation of females and longer spawning season in the Włocławski Reservoir, may contribute to invasive success of Amur sleeper in newly colonized areas; however, the costs of this strategy result in slower growth in older age classes.     

Plasmon-waveguide resonance studies of ligand binding to integral proteins in membrane fragments derived from bacterial and mammalian cells

A procedure has been developed for directly depositing membrane fragments derived from bacterial cells (chromatophores from Rhodopseudomonas sphaeroides) and mammalian cells (μ-opioid receptor- and MC4 receptor-transfected human embryonic kidney (HEK) cells and rat trigeminal ganglion cells) on the silica surface of a plasmon-waveguide resonance (PWR) spectrometer. Binding of ligands (cytochrome c₂ for the chromatophores, the peptide agonists DAMGO and melanotan-II that are specific for the μ-opioid and MC4 receptors, and two nonpeptide agonists that are specific for the CB1 receptor) to these membrane fragments has been observed and characterized with high sensitivity using PWR spectral shifts. The K_D values obtained are in excellent agreement with conventional pharmacological assays and with prior PWR studies using purified receptors inserted into deposited lipid bilayer membranes. These studies provide a new tool for obtaining useful biological information about receptor-mediated processes in real biological membranes.