Extracellular glycosaminoglycans (GAG) released by chick embryonic fibroblasts

Summary Administration of Concanavalin A (Con A) to cultured skin fibroblasts derived from chick embryos at two developmental stages produce variations in the relative concentration of individual glycosaminoglycan (GAG) secreted by the cells. This effect is different: at 7 days (increase of hyaluronic acid and dermatan sulphate and decrease of chondroitin sulphate) and at 14 days (dermatan sulphate is not detectable).All the cells bind the Con A specifically, but a different pattern of agglutination is present in fibroblasts of the two embryonic ages. Since Con A is well known to bind carbohydrate-containing surface proteins, the result suggests that the release of GAG by chick embryonic fibroblasts can be modulated by cell surface receptors.     

Fatty acid synthesis by isolated chromoplasts from the daffodil. Energy sources and distribution patterns of the acids

1. Fatty acid synthesis in isolated intact chromoplasts from [1-¹⁴C]acetate was made possible by using ATP, ADP (via adenylate kinase), and, with decreasing efficiency, UTP, CTP, and GTP as energy sources. 2. The glycolytic path from dihydroxyacetone phosphate to acetyl-CoA operates within the chromoplasts. The glycolytic intermediates, especially 2-phosphoglycerate and phosphoenolpyruvate, served as very effective energy donors for fatty acid synthesis by phosphorylating the endogenous adenine nucleotide pool. 3. In the presence of exogenous ATP or ADP, appreciable amounts of in vitro formed fatty acids were found as acyl-CoA and subsequent products, mainly phosphatidylcholine. When other energy sources were used most of the acids formed were in the free form, and to a minor extent, in the phosphatidic acid and diacylglycerol fractions. Similar results have recently been reported for spinach chloroplasts (Kleinig and Liedvogel 1979, FEBS Lett.101, 339–342).Abbreviations ATP adenosine triphosphate - ADP adenosine diphosphate - UTP uridine triphosphate - CTP cytidine triphosphate - GTP gnanosine triphosphate     

Fatty acid and glycerolipid synthesis in abscised daffodil flowers after acetate feeding

The coronae of Narcissus pseudonarcissus flowers incorporated [1-¹⁴C]acetate almost exclusively into the fatty acid moieties of glycerolipids. After a 4 h incubation, the newly synthesized acids were: stearate plus palmitate (50%); oleate (17%); linoleate (32%); and linolenate (0.5%). Phosphatidylcholine and diacylglycerol were the principal labelled lipids. In pulse experiments these acids were further desaturated, with time, to an appreciable extent and, concurrently, transferred essentially from phosphatidylcholine to diacylglycerol, diacylgalactosylglycerol, and diacylgalabiosylglycerol. The labelling of diacylgalactosylglycerol and diacylgalabiosylglycerol paralleled the appearance of linolenate. The distribution of labelled acids in phosphatidylcholine, diacylgalactosylglycerol, and diacylgalabiosylglycerol was very different. The results were compared with those obtained in vitro with isolated coronae chromoplasts and discussed in relation to current schemes of fatty acid and glycerolipid synthesis in plant cells.     

Galactolipid synthesis in chromoplasts in vitro

Isolated chromoplasts from Narcissus pseudonarcissus flowers contain: a fatty acid synthesizing system; acyl-CoA synthetase (EC 6.2.1.3); glycero-phosphate acyltransferase (EC 2.3.1.15); acylglycero-phosphate acyltransferase; phosphatidate phosphatase (EC 3.1.3.4); diacylglycerol galactosyltransferase (EC 2.4.1.46); and diacylgalactosylglycerol galactosyltransferase, i.e. all enzymatic activities necessary for the synthesis of diacylgalactosylglycerol and diacylgalabiosylglycerol from acetate, HCO _- ³ , sn-glycerol 3-phosphate, and UDP-d-galactose. Diacylgalactosylglycerol and diacylgalabiosylglycerol, however, are synthesized from these precursors to only a very low extent in an in vitro system. This is attributed to a specificity of diacylglycerol galactosyltransferase for highly unsaturated diacylglycerols. Specificities of acyltransferase reactions were also found.     

Photosensory transduction in the flagellated alga, Euglena gracilis. III. Induction of Ca2+-dependent responses by monovalent cation ionophores

(1) The effects of monovalent cation ionophores (valinomycin and gramicidin), a protonophore (nigericin) and extracellular pH change on the motility and blue light-induced photobehavior (step-down photophobic response) of Euglena were investigated. (2) Monovalent cation ionophores, but not the protonophore, can both partially suppress photobehavior and, under appropriate conditions, induce a change in flagellar activity (and thus cell movement) that appears identical to that associated with the photobehavior. (3) Valinomycin, at low extracellular KCl, delays the induction of photobehavior and also induces a light-independent elevation in the frequency of directional changes in the cells' swimming path. Both effects are suppressed by elevation in extracellular KCl. (4) Gramicidin, in the presence of the anion tetraphenylborate, suppresses photobehavior. The same combination, if applied in the presence of elevated extracellular NaCl, induces a light-independent cell tumbling and elevation in the frequency of directional changes in the cells' swimming path. The induced behavior is dependent on the extracellular Na concentration, requires the presence of extracellular Ca²⁺ and is blocked by La³⁺. (5) Photobehavior is observed over the pH range 3.5–8.2 and fluence/response relationships for photobehavior are not significantly different over the pH range 5.5–8.2. (6) The results provide a link between the previously reported effects of Ca²⁺ ionophores, and the effects of monovalent cations and monovalent cation-transport inhibitor on motility and photobehavior.     

Fulvic acid disturbs processing of procollagen II in articular cartilage of embryonic chicken and may also cause Kashin-Beck disease.

Kashin-Beck disease is an endemic osteoarthropathy in China which may lead to skeletal deformation and dwarfism. We have analysed articular cartilage from two patients and found an accumulation of the precursor molecule, pro-pN-collagen II (pN, peptide attached at the amino-terminus) which was not present in extracts of control fetal cartilage. In addition, collagen II isolated from the same tissue by limited pepsin digestion had a decreased electrophoretic mobility, increased proline hydroxylation and decreased thermal stability. Previously, a genetic defect in pro-pN-collagen-I processing has been described in calf and sheep (dermatosparaxis) and man (Ehlers-Danlos, type VII) which caused an extreme fragility of the skin [Lenaers, A., Ansay, M., Nusgens, B.V. & Lapière, C.M. (1971) Eur. J. Biochem. 23, 533-541; Helle, O. & Nes, N.J. (1972) Acta Vet. Scand. 13, 443-445; Lichtenstein, J.R., Martin, G.R., Kohn, L.D., Byers, P.H. & McKusick, V.A. (1973) Science 182, 298-300]. Accordingly, one may assume that the impaired conversion of pro-pN-collagen II to collagen II and the structural alteration of collagen II, presumably caused by fulvic acid and other environmental factors, play an important role in the pathogenesis of Kashin-Beck disease.     

A numerical taxonomic study of Propionibacterium strains from dairy sources

T.J. BRITZ AND K-H.J. RIEDEL. 1991. Phenotypic results from 81 tests conducted on 73 propionibacteria, including five type strains, 22 reference strains, unidentified propionibacteria and strains isolated from dairy sources, were analysed by numerical taxonomy. Characters giving uniform results were excluded. With the simple matching coefficient and the single linkage cluster analysis, 61 cultures were recovered in five major clusters. Final linkage of all the Propionibacterium cultures examined was at the 77% S-level. The results clearly showed that it was possible to distinguish between the 'classical' and 'cutaneous' Propionibacterium spp., corresponding with the type habitat of each group. The major 'classical' clusters were equated with the P. freudenreichii, P. thoenii, P. jensenii and P. acidipropionici species, while the only major 'cutaneous' cluster was equated with the P. acnes species. The major clusters were identified by relating them to specific type strains and by comparing phenotypic characteristics. The differentiating characteristics of each cluster were determined. The largest cluster, representing 37% of the strains, was equated with P. jensenii but contained cultures that produced an atypical brown/red pigment. These strains, although positively identified as P. jensenii , could also be identified as the 'old' P. rubrum ' species. Thus if pigmentation is used as differential characteristic two distinct groups of propionibacteria could be identified within the P. jensenii species.     

The effect of metal binding on the structure of annexin V and implications for membrane binding.

The structure of annexin V, crystallised in the presence of two calcium or barium ions for each protein molecule, was solved by molecular replacement to 0.24 nm resolution. The two metal ions are found in domains I and IV, i.e. on the same side of the channel that lies in the centre of the molecule. The structures of the barium and calcium form are extremely close, the only differences localised in the metal-binding sites that lie on the surface of the molecule. The occupancies of the metal ions, however, are lower for barium than for calcium, expressing the lower affinity of the protein for the former. The packing of the annexin molecules in the crystal asymmetric unit may represent a model for the calcium driven association of membrane-bound annexins that leads to membrane fusion.     

In vivo mechanical properties of leukocytes during adhesion to venular endothelium

Transient deformations of leukocytes (WBCs) were studied during their saltation along post-capillary venous endothelium (EC) in mesentery of the rat. During intermittent adhesion of WBCs to EC, prevailing fluid shear stresses, tau wall, resulted in a stepwise loading of the WBC upon attachment with a transient increase in length, L(t), and reduction in height, H(t). Measurements of L(t) and H(t) from frame-by-frame analysis of video recordings were modelled as the simple shear of a standard linear viscoelastic solid to facilitate calculation of the elastic (k1, k2) and viscous (mu) elements with k1 in parallel with serial elements k2 and mu. The magnitude of tau wall was determined from measurements of red cell velocity within the venule. During the spontaneous adhesion of WBCs, a value of cell viscosity (mu) of 45 Poise was determined. Stimulating adhesion by topical application of the chemoattractant FMLP resulted in a 15-fold increase of mu to 668 Poise. Transient deformations during topical application of cytochalesin B to disrupt actin fibers within the WBC, yielded a 40% reduction in k1, compared to an 80% reduction with colchicine which disrupts the microtubule structure. Thus, colchicine treated cells appear to be twice as deformable as cells treated with cytochalesin. During adhesion stimulated by the cytokine Interleukin-1, mu increased 50% without changes in k1 and k2, possibly due to slight activation of the WBC.     

Phyto- and protozooplankton biomass during austral summer in surface waters of the Weddell Sea and vicinity

Summary Phyto- and protozooplankton were sampled in the upper 10 m of the water column in austral summer during a cruise of RV Polarstern from January 6 to February 20 1985 in the eastern Bransfield Strait vicinity and in the northern, southeastern (off Vestkapp, twice: I and II) and southern Weddell Sea (Vahsel Bay across the Filchner Depression to Gould Bay). The plankton assemblages are discussed in relation to physical, chemical and biological factors in the different geographical areas in summer. Phytoplankton biomass (Phytoplankton carbon, PPC) ranged from 4–194 g carbon/l and consisted on average of 65% diatoms and 35% autotrophic flagellates. Whereas in the northwest phytoplankton assemblages were dominated by small nanoflagellates (78% of PPC), higher biomass of diatoms (54–94% of PPC) occurred at the other sampling sites. In general autotrophic flagellates and small pennate diatoms dominated at oceanic stations; in neritic areas large centric diatoms prevailed. Chlorophyll a concentrations ranged from 0.25–3.14/g chl a/l with a mean of 1.13/gmg chlorophyll a/l and an average phytoplankton carbon/chlorophyll a ratio of 39. Protozooplankton biomass (Protozooplankton carbon, PZC) ranged from 0–67 g carbon/l and consisted of 49% ciliates, 49% heterotrophic dinoflagellates and 2% tintinnids. Heterotrophic dinoflagellates were more important in the northern investigation areas (58%–84% of PZC). Ciliates dominated the protozooplankton in the southeast and south (56%–65% of PZC); higher abundances of tintinnids were observed only in the south (11% of PZC). The most remarkable feature of the surface waters was the high protozooplankton biomass: protozooplankton amounted to 25% on an average of the combined biomass of PPC plus PZC for the entire investigation period. Protozoan biomass in the southeastern and southern Weddell Sea occasionally exceeded phytoplankton biomass. Temperature, salinity, and inorganic nutrients were generally lower in the southern regions; at most of these stations a meltwater layer occurred in the upper meters of the water column. We suggest that this physical regime allows a well developed summer system with a high proportion of heterotrophic microplankton. In the eastern Bransfield Strait, in the northern Weddell Sea and close to the coast off Vestkapp (I), however, early summer conditions occurred with less protozooplankton contribution.Contribution no. 427 from the Alfred-Wegener-Institute for Polar and Marine Research