Sialic acid is a cell surface component of Entamoeba invadens trophozoites

The surface anionic groups of Entamoeba invadens were analysed by cell electrophoresis, by ultrastructural cytochemistry, and by identification of sialic acids using paper and gas-liquid chromatography. Binding of colloidal iron hydroxide (CIH) and of cationized ferritin (CF) particles at pH 1.8 and 7.2, respectively, was observed on the cell surface. E. invadens has a highly negative surface charge (-0.96 microns s-1 V-1 cm). Treatment of the cells with trypsin and neuraminidase significantly reduced the electrophoretic mobility by 24% and 40%, respectively. Treatment of the amoebae with neuraminidase also markedly decreased the binding of CIH to the cell surface. This finding suggests that sialic acid residues are the major anionogenic groups exposed on the surface of E. invadens. Paper and gas-liquid chromatography showed that N-acetylneuraminic acid was the only derivative characterized in E. invadens.     

To produce many small or few large eggs: a size-independent reproductive tactic of fish

Summary We demonstrate here the existence of a range of size-independent reproductive tactics in teleostean fish involving the allocation of a size-dependent reproductive effort between fecundity and egg size. Despite considerable evidence that larger eggs and the larvae hatching from them are more likely to survive than smaller ones, we found no evidence of evolutionary trends towards greater egg sizes. Fish with pelagic eggs tend to spawn many, and therefore small, eggs, whereas demersal spawners tend to produce large, and therefore few, eggs. Maximizing egg number should increase the number of eggs hatching in suitable locations in the patchy pelagic environment and, hence, increase the reproductive success of pelagic spawners. On the other hand, the reproductive success of demersal spawners, which reduce the variance in growing conditions experienced by the off spring, should be more dependent on the survival of the individual larvae, which increases as egg size increases.     

Effect of HCO - 3 concentration in the absorption solution on the energetic coupling of H+-cotransports in roots of Zea mays L.

The effect of HCO ₃ ^- on ion absorption by young corn roots was studied in conditions allowing the independent control of both the pH of uptake solution and the CO₂ partial pressure in air bubbled through the solution. The surface pH shift in the vicinity of the outer surface of the plasmalemma induced by active H⁺ excretion was estimated using the initial uptake rate of acetic acid as a pH probe (Sentenac and Grignon (1987) Plant Physiol. 84, 1367). Acetic acid and orthophosphate uptake rates and NO ₃ ^- accumulation were slowed down, while ⁸⁶Rb⁺ uptake and K⁺ accumulation rates were increased by HCO ₃ ^- . These effects were similar to those induced by 4-(2-hydroxyethyl)-1-piperazineethane sulfonic acid/2-amino-2-(hydroxymethyl)-1,3-propanediol (Hepes-Tris). They were more pronounced when the H⁺ excretion was strong, were rapidly reversible and were not additive to those of Hepes-Tris. The hypothesis is advanced that the buffering system CO₂/H₂CO₃/HCO ₃ ^- accelerated the diffusion of equivalent H⁺ inside the cell wall towards the medium. This attenuated the surface pH shift in the vicinity the plasma membrane and affected the coupling between the proton pump and cotransport systems.Abbreviations FW fresh weight - Hepes 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid - J_aa acetic acid influx - J_K ⁺ K⁺ influx - J_Pi orthophosphate influx - Mes 2-(N-morpholino)ethanesulfonic acid - pCO₂ CO₂ partial pressure - Tris 2-amino-2-(hydroxymethyl)-1,3-propanediol     

A major histocompatibility locus in fish: serological identification and segregation of transplantation antigens in the common carp (Cyprinus carpio L.)

In this study, experiments are described that were designed to investigate whether fish have an immune regulatory systems similar to the major histocompatibility complex (MHC) in higher vertebrate species. From combinations of gynogenetic carp showing either slow of fast rejection of skin transplants, the latter were chosen for alloantiserum production by hyperimmunization with peripheral blood leucocytes. The resulting alloantisera were analyzed for hemagglutinating reactivity with gynogenetic siblings and proved to be operationally monoscpecific in absorption experiments. The serologically determined carp erythrocyte specificites were shown to correspond to two codominantly expressed allelic products of a single locus and were designated K1 and K2, respectively. Flow cytometer analysis revealed that the same products are also present on leucocytes from peripheral blood, thymus, spleen, and pronephros.K1-andK2-homozygous second-generation gynogenetic siblings were used to study the histocompatibiligy nature of the K locus products. Skin transplants between K-allogeneic gynogenetic siblings were rejected significantly faster than within K-syngeneic combinations. Taken together, these data suggest that theK locus incorporates MHC class I-like characteristics.     

Aggregation and/or oxygenated products of arachidonic acid are not required for collagen-induced deacylation of phosphatidylcholine in human platelets.

In the present study the effects of collagen on platelet aggregation and arachidonic acid (AA) mobilization, specifically from phosphatidylcholine (PC), were investigated in the presence and absence of BW755C, a selective inhibitor of cyclo-oxygenase and lipoxygenases. The inhibition of cyclo-oxygenase and lipoxygenase(s) by BW755C (75 microM) resulted in severe impairment in collagen-induced platelet aggregation. In the presence of BW755C, the aggregation response amounted to 14, 26, 37 and 49% of the corresponding controls (without BW755C) at 10, 25, 50 and 100 micrograms of collagen respectively. On the contrary, the amount of AA released from PC, which ranged from 3.5 to 8.6 nmol/10(9) platelets, in response to the action of collagen (10-100 micrograms) remained unaffected by the presence of BW755C. Substantial amounts of non-esterified AA were detected in the free fatty acid fractions obtained from collagen-stimulated platelets in the presence as well as in the absence of BW755C. However, the presence of BW755C caused a greater accumulation of free AA (mass) and this ranged from 4 to 16 nmol, depending upon the amount of collagen. In addition, small increases in free stearic and oleic acids were observed in collagen-stimulated platelets as compared with unstimulated platelets. The amount of AA lost from PC represented 67, 80, 49 and 52% of the free AA obtained at 10, 25, 50 and 100 micrograms of collagen respectively. Our results adhesion of platelets to collagen fibres may be responsible for much of the AA release from PC Furthermore, these results demonstrate that aggregation and/or cyclo-oxygenase/lipoxygenase metabolites are not obligatory for the release of AA from PC in collagen-stimulated human platelets.     

Conformational changes in human serum albumin studied by fluorescence and absorption spectroscopy. Distance measurements as a function of pH and fatty acids.

pH- and fatty acid-induced conformational changes in human serum albumin were investigated by fluorescence-energy transfer, determining the distance between Trp-214 and bound bilirubin at 25 degrees C. This distance changes significantly with the pH, being 2.52 +/- 0.01 nm at pH 6, 2.31 +/- 0.04 nm at pH 9, 2.13 +/- 0.07 nm at pH 11.0 and 2.77 nm at pH 11.9. The influence of different fatty acids on the distance was also determined. At pH 7.4 medium-chain fatty acids seem to increase this distance, whereas long-chain fatty acids, at low concentrations, decrease the distance between the two chromophores. The contraction of the protein carrying long-chain saturated fatty acids is even more pronounced at pH 9.     

Tyrosination-detyrosination of tubulin and microtubules during the development of chick erythrocytes

The protein composition of nuclear matrices containing different amount of DNA was examined. It was found that, in matrices containing 2% to 80% of total DNA, the quantity of DNA-bound proteins remains relatively constant varying from 10% to 15% of total nuclear proteins. Electrophoretic patterns do not differ substantially, but autoradiograms with in vitro ¹²⁵I labelled proteins show quantitative variations in the actin content. Application of radioimmunoassay (RIA) enabled to determine the exact content of actin in GAT nuclei and nuclear matrices – 5 g/ml in nuclei, of which 50% are bound to DNA and 3001o being a component of the protein part of the nuclear matrix. These results are supported by electron microscopic data, where immunogold technique was performed on thin sections and spread material. The applied methods suggest that part of the nuclear actin is tightly bound (resistant to 2 M NaCI) to DNA and represents a component of the internal nuclear matrix.     

Preparation of megabase-sized tomato DNA and separation of large restriction fragments by field inversion gel electrophoresis (FIGE)

The Schwartz and Cantor technique for releasing and fractionating megabase-sized DNA from agarose-embedded cells is beginning to bridge the gap in resoluation between classical genetics and current molecular DNA techniques, particularly in mammalian systems. As yet no conditions have been described for preparing plant DNA that is of sufficient length to allow similar long-range restriction mapping experiments in plant systems. In this report, we describe the application of the Schwartz and Cantor technique for preparing high molecular weight DNA from embedded tomato leaf protoplasts, as well as conditions for generating and fractionating large restriction fragments, by field inversion gel electrophoresis (FIGE). The bulk of DNA released from lysed protoplasts was at least 2 Mb in size and amenable to restriction digestion as shown by hybridizing Southern blots with, among others, a probe for the Adh-2 gene of tomato. Restriction fragments as large as 700 kb were detected. Chloroplast DNA is isolated intact, amenable to restriction analysis and, in its native form, not mobile in FIGE.     

Continuous production of gibberellic acid in a fixed-bed reactor by immobilized mycelia of Gibberella fujikuroi in calcium alginate beads

Summary The continuous production of gibberellic acid with immobilized mycelia of Gibberella fujikuroi was maintained over a hundred days in a tubular fixed-bed reactor. Free mycelium at the beginning of the storage phase was harvested from G. fujikuroi shake-flask culture and was immobilized by ionotropic gelation in calcium alginate beads.The continuous recycle production system consisted of a fixed-bed reactor, a container in which the culture medium was heated, stirred and aerated, and valves for sample withdrawal or reactant addition during the first 1320 h (55 days). A two-phase continuous extractor was then added for the last 960 hours (40 days). Free and immobilized mycelium shake-flask cultures with the same strain used in the continuous culture system were also realized to compare growth, maintenance and production parameters. The results show about the same gibberellic acid productivity in both free and immobilized mycelium shakeflask cultures: 0.384 and 0.408 mgGA₃·gBiomass^-1 ·day^-1, respectively, whereas in the continuous system the gibberellic acid production is about twice as large for a similar biomass: 0.768 mgGA₃·gBiomass^-1·day^-1. Several factors affecting the overall productivity of the immobilized systems were found to be: the quality and the quantity of mycelia in the biocatalyst beads and the immobilization conditions.