Arg-Gly-Asp (RGD) sequence conjugated in a synthetic copolymer bearing a sugar moiety for improved culture of parenchymal cells (hepatocytes)

A copolymer, including a Gly-Arg-Gly-Asp-Ser (GRGDS) sequence and sugar moieties, was synthesized for the culturing of parenchymal cells (hepatocytes). Hepatocyte cells attached to poly[N-p-vinylbenzyl-d-maltonamide-co-6-(p-vinylbenzamido)-hexanoic acid-GRGDS] [poly(VMA-co-VBRGD)]-coated dishes grew approximately 60% better than on other polymer-coated surface for 12 h. Also, about 80% greater albumin secretion (0.38 pg ml^–1) and about 70% greater urea synthesis (0.495 pg ml^–1) from hepatocytes were produced in this matrix as compared with unstimulated cells. The behaviour of hepatocytes on poly(VMA-co-VBGRGDS)-coated dishes was not distinct from those attached to a collagen. The conjugation of the adhesion molecules of the RGD peptide in the poly(VMA-co-VBGRGDS) copolymer therefore specifically interacts with integrin families on the hepatocyte cell membrane.     

Relationship between the concentration of sugars in the roots and VA mycorrhizal infection

Summary The VA-infected wheat varieties showed an increase of total (Lozano var.) and reducing (Lozano and Pane vars.) sugars in their root extracts. However, no clear relationship between sugar concentration in the root and VA mycorrhizal infection level could be established.In addition, the VA mycorrhizal hosts sorghum, alfalfa, sunflower and maize, and non-host radish and cabbage plants were tested for sugar content in their root extracts after fifteen days of growth. Sugars present in the root extracts of these plants did not seem to be a decisive factor in plant susceptibility to VA infection.     

Photoautotrophic and photomixotrophic growth of strawberry plantlets in vitro and changes in nutrient composition of the medium

Explants excised from strawberry (Fragaria x ananassa Duch.) plantlets were cultured in vitro for 21 days on half-strength MS (Murashige & Skoog 1962) basal liquid medium with 20 g l^-1 sucrose and without sugar in the vessels capped with gas permeable microporous polypropylene film. The experiments were conducted under CO₂ nonenriched (350–450 mol mol^-1 in the culture room) and CO₂ enriched (2,000 mol mol^-1 during the photoperiod in the culture room) conditions with a PPF (photosynthetic photon flux) of 200 mol m^-2 s^-1. The CO₂ concentration in the vessels decreased to approximately 200 mol mol^-1 during the photoperiod on day 21 under CO₂ nonenriched conditions. The fresh and dry weight, net photosynthetic rate (NPR) per plantlet, NPR per g leaf fresh weight, NPR per g leaf dry weight, the number of unfolded leaves, and ion uptake of PO₄ ^3-, NO₃ ^-, Ca²⁺, Mg²⁺ and K⁺ on day 21 were the greatest under photoautotrophic (no sugar in the medium) and CO₂ enriched conditions. The residual percent of PO₄ ^3- was 3% on day 21 under photoautotrophic and CO₂ enriched conditions.Abbreviations MS Murashige & Skoog (1962) basal medium composition - NPR net photosynthetic rate - PPF photosynthetic photon flux     

Effects of external NaCl on the growth of Atriplex amnicola and the ion relations and carbohydrate status of the leaves

Abstract Atriplex amnicola, was grown in nutrient solution cultures with concentrations of NaCl up to 750 mol m^?3. The growth optimum was at 25–50 mol m^?3 NaCl and growth was 10–15% of that value at 750 mol m^?3 NaCl. Sodium chloride at 200 mol m^?3 and higher reduced the rate of leaf extension and increased the time taken for a leaf to reach its maximal length. Concentrations of Na⁺, K⁺ and Mg²⁺ in leaves of different ages were investigated for plants grown at 25, 200 and 400 mol m^?3 NaCl. Although leaves of plants grown at 200 and 400 mol m^?3 NaCl had high Na⁺ concentrations at young developmental stages, much of this Na⁺ was located in the salt bladders. Leaves excluding bladders had low Na⁺ concentrations when young, but very high in Na⁺ when old. In contrast to Na⁺, K⁺ concentrations were similar in bladders and leaves excluding bladders. Concentrations of K⁺ were higher in the rapidly expanding than in the old leaves. At 400 mol m^?3 NaCl, the K⁺:Na⁺ ratios of the leaves excluding bladders were 0.4–0.6 and 0.1 for rapidly expanding and oldest leaves, respectively. The Na⁺ content in moles per leaf, excluding bladders, increased linearly with the age of the leaves; concurrent increases in succulence were closely correlated with the Na ⁺ concentration in the leaves excluding the bladders. Soluble sugars and starch in leaves, stems and buds were determined at dusk and dawn. There was a pronounced diurnal fluctation in concentrations of carbohydrates. During the night, most plant parts showed large decreases in starch and sugar. Concentrations of carbohydrates in most plant organs were similar for plants grown at 25 and 400 mol m^?3 NaCl. One notable exception was buds at dusk, where sugar and starch concentrations were 30–35% less in plants grown at 400 mol m^?3 NaCl than in plants grown at 25 mol m^?3 NaCl. The data indicate that the growth of A. amnicola at 400 mol m^?3 NaCl is not limited by the availability of photosynthate in the plant as a whole. However, there could have been a growth limitation due to inadequate organic solutes for osmotic regulation.     

Inhibition of hexose transport in the human erythrocyte by 5, 5′-dithiobis(2-nitrobenzoic acid): Role of an exofacial carrier sulfhydryl group

Summary The sulfhydryl reagent 5, 5-dithiobis (2-nitrobenzoic acid) (DTNB) was used to study the functional role of an exofacial sulfhydryl group on the human erythrocyte hexose carrier. Above 1mm DTNB rapidly inhibited erythrocyte 3-O-methylglucose influx, but only to about half of control rates. Efflux was also inhibited, but to a lesser extent. Uptake inhibition was completely reversed by incubation and washing with 10mm cysteine, whereas it was only partially reduced by washing in buffer alone, suggesting both covalent and noncovalent interactions. The covalent thiol-reversible reaction of DTNB occurred on the exofacial carrier, since (i) penetration of DTNB into cells was minimal, (ii) blockade of potential uptake via the anion transporter did not affect DTNB-induced hexose transport inhibition, and (iii) DTNB protected from transport inhibition by the impermeant sulfhydryl reagent glutathione-maleimide-I. Maltose at 120mm accelerated the covalent transport inhibition induced by DTNB, whereas 6.5 m cytochalasin B had the opposite effect, indicating under the one-site carrier model that the reactive sulfhydryl is on the outward-facing carrier but not in the substrate-binding site. In contrast to glutathione-maleimide-I, however, DTNB did not restrict the ability of the carrier to reorient inwardly, since it did not affect equilibrium cytochalasin B binding. Thus, carrier conformation determines exposure of the exofacial carrier sulfydryl, but reaction of this group may not always lock the carrier in an outward-facing conformation.     

DNA radiation damage and asymmetric somatic hybridization: Is UV a potential substitute or supplement to ionising radiation in fusion experiments?

Recent reports have revealed that the asymmetric nature of the nuclear genome of somatic hybrids, produced following the irradiation of one of the parents with X- or gamma rays, is generally much less than had been anticipated. As a consequence, we have begun to investigate whether UV radiation might be used as an alternative or indeed a supplement to the presently-used ionising radiation techniques in such experiments. Cell culture studies have revealed that UV radiation induces the desired physiological effects in sugar beet ( Beta vulgaris ) protoplasts, namely, a prevention of cell division without immediate cytotoxicity. Preliminary studies using denaturing and pulsed field gel electrophoresis have shown that UV can also induce substantial physical fragmentation of DNA. When using the same techniques, less breakdown was observed following gamma radiation. All results were highly reproducible. Such results augur well for the potential use of UV in asymmetric somatic cell fusion experiments.     

The effect of blue light on free and esterified phenolic acids in etiolated gherkin tissues

The major phenolic acid found in gherkin tissues is p-coumaric acid, although cinnamic and caffeic acids are also present; these occur both free an     

Root border cells take up and release glucose-C

BACKGROUND AND AIMS: Border cells are released from the root tips of many plant species, and can remain viable in the rhizosphere for 1 week. Whether border cells are capable of controlled glucose exchange with their environment was investigated. METHODS: Border cells were removed from Zea mays L. root tips, and immersed in (14)C-labelled D-glucose. In one experiment, the hexose transport inhibitor, phlorizin, was used to investigate active glucose uptake from a range of glucose concentrations. In another experiment, glucose efflux from border cells was monitored over time. KEY RESULTS: Glucose uptake by the border cells increased with increasing glucose concentration from 0.2 to 20 mm. At 0.2 mm glucose, uptake was mainly active, as evidenced by the approx. 60 % inhibition with phlorizin. At 2 and 20 mm glucose, however, uptake was mainly via diffusion, as phlorizin inhibition was negligible. Glucose efflux increased with time for live border cells in both 2 and 20 mm glucose. There was no clear efflux/time pattern for heat-killed border cells. CONCLUSIONS: Border cells actively take up glucose, and also release it. Under our experimental conditions, glucose uptake and efflux were of similar order of magnitude. In the rhizosphere net glucose exchange will almost certainly depend on local soil conditions.     

Liquid–liquid extraction of fermentation inhibiting compounds in lignocellulose hydrolysate

Several compounds that are formed or released during hydrolysis of lignocellulosic biomass inhibit the fermentation of the hydrolysate. The use of a liquid extractive agent is suggested as a method for removal of these fermentation inhibitors. The method can be applied before or during the fermentation. For a series of alkanes and alcohols, partition coefficients were measured at low concentrations of the inhibiting compounds furfural, hydroxymethyl furfural, vanillin, syringaldehyde, coniferyl aldehyde, acetic acid, as well as for ethanol as the fermentation product. Carbon dioxide production was measured during fermentation in the presence of each organic solvent to indicate its biocompatibility. The feasibility of extractive fermentation of hydrolysate was investigated by ethanolic glucose fermentation in synthetic medium containing several concentrations of furfural and vanillin and in the presence of decanol, oleyl alcohol and oleic acid. Volumetric ethanol productivity with 6 g/L vanillin in the medium increased twofold with 30% volume oleyl alcohol. Decanol showed interesting extractive properties for most fermentation inhibiting compounds, but it is not suitable for in situ application due to its poor biocompatibility. Biotechnol. Bioeng. 2009;102: 1354–1360. © 2008 Wiley Periodicals, Inc.