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At least 19 recordsLinked to original sources
PubMed1992

[The use of bead cellulose for controlled drug liberation. 5. Kinetics of liberation of bonded drugs from bead cellulose and bead cellulose derivatives].

Examination of in vitro liberation of prazosin hydrochloride and benzocaine from formulations of matrix type with bead cellulose and bead cellulose derivatives shows deviations from first order kinetics owing to competition of several processes: dissociation of ionic bonds or cleavage of covalent bonds between drugs and bead cellulose, pore diffusion, dissolution of the drugs and swelling of cellulose matrix. Suitable combinations of different bonded portions of the drug on bead celluloses let these complexes seem to be successful in the use for controlled and retarded liberation of drugs.

Cellulose↗
PubMed1992

[The use of bead cellulose for controlled drug liberation. 4. Binding of bead cellulose and bead cellulose-derivatives with prazosin hydrochloride and its liberation].

Pure bead cellulose and the ionic derivatives carboxymethyl and dihydrogen phosphate bead cellulose were coupled with prazosin hydrochloride. The degree of substitution achieved during loading mostly depends on the number of functional groups, what was verified by titrimetric determination of the ion exchange capacity. Because of predominant ionic binding of the protonated prazosin cation to the anionic groups of several types of bead cellulose in electrolytes containing liquids as well as in water a large amount of bonded drug is liberated considerable fast. Retardation of the liberation in comparison to the commercial product Adversuten is verified but not applicable to therapeutic use in the case of prazosin.

Cellulose↗
PubMed1975

Cellulose synthesis by Acetobacter xylinum. III. Matrix, primer and lipid requirements and heat stability of the cellulose-forming enzymes.

The addition of soluble cellodextrins of increasing size to a cell envelope preparation of Acetobacter xylinum stimulated cellulose synthesis from UDPG. This stimulation was attributed to both acceptor and activator effects. Enzymes required for cellulose synthesis were found to be heat-unstable and those required for synthesis of glycosylated lipid components from UDPG, heat-stable. Both heat-inactivated envelope fragments and supernatant fluid from whole cells were necessary for cellulose synthesis from UDPG. Cellulose was not formed from UDPG in the presence of either supernatant fluid alone or heat-inactivated envelopes alone. The combined results of this and previous studies suggest that either the cell envelope is necessary for synthesis of a more immediate precursor to cellulose than UDPG, or that the synthesis from UDPG requires a matrix. The former suggestion and its possible link with lipid intermediate involvement was strengthened by the observation of inefficient glycosylated lipid formation by a celluloseless mutant strain of A. xylinum. The possible locations of various enzyme activities required for the synthesis of the cellulose precursor are indicated and a possible microfibril nucleation process is discussed.

Cell Wall↗
PubMed1975

The site of cellulose synthesis. Hormone treatment alters the intracellular location of alkali-insoluble beta-1,4-glucan (cellulose) synthetase activities.

Membrane preparations from growing regions of 8-day old Pisum sativum epicotyls contain multiple beta-1,4-glucan (cellulose) synthetase activities (UDP- or GDP-glucose: beta-1,4-glucan-glucosyl transferase), and the levels of some of these are influenced by treatments with the growth hormone, indoleacetic acid (IAA). When membranes from control epicotyl segments (zero time) are fractionated by isopycnic sedimentation in sucrose density gradients, all of the synthetase activities are associated mainly with Golgi membrane (density 1.55 g/cm3). After decapitation and treatment of epicotyls with IAA, synthetases also appear in a smooth vesicle fraction (density 1.11 g/cm3) which is rich in endoplasmic reticulum (ER) marker enzyme. Major fractions of these synthetases are not recovered in association with plasma membrane or washed cell walls. When [14-C]sucrose is supplied in vivo to segments +/- IAA, radioactive cellulose is deposited only in the wall. Cellulose or cellodextrin precursors do not accumulate in those membranes in which synthetase activities are recovered in vitro. In experiments where tissue slices containing intact cells are supplied with [14C]sugar nucleotide in vitro, alkali-insoluble beta-1,4-glucan is synthesized (presumably outside the protoplast) at rates which greatly exceeded (20-30 times) those obtained using isolated membrane preparations. Progressive disruption of cell structure results in increasing losses of this high activity. These results are consistent with the interpretation that Golgi and ER-associated synthetases are not themselves loci for cellulose synthesis in vivo, but represent enzymes in transit to sites of action at the wall:protoplast omterface. There they operate only if integrity of cellular organization is maintained.

Cell Membrane↗
PubMed1992

Improvement of blood compatibility on cellulose dialysis membrane. I. Grafting of 2-methacryloyloxyethyl phosphorylcholine on to a cellulose membrane surface.

A methacrylate with a phospholipid polar group, 2-methacryloyloxyethyl phosphorylcholine (MPC), was grafted on cellulose membrane for haemodialysis in an aqueous medium using cerium ion (Ce4+) as an initiator. The effects of the concentrations of MPC and Ce4+, and degassing of feed solution on the grafting of MPC on the surface and the membrane properties such as permeability and mechanical strength were examined. The grafted MPC composition depended on the concentrations of both the monomer and initiator in the feed solution. When the grafted MPC distribution was controlled by the monomer concentration, the permeability of the membrane decreased with an increase in grafted MPC distribution. On the other hand, the permeability was not changed from the original membrane's value when the MPC distribution was regulated by Ce4+ concentration. The tensile strength of the membrane did not change during the grafting of MPC and this indicated that the grafting had taken place in the amorphous region of the cellulose. These results suggested that this method is a promising way to improve the blood compatibility of a cellulose membrane without having an adverse effect on the haemodialysis membrane.

Biocompatible Materials↗
PubMed1975

Cellulose synthesis by Acetobacter xylinum. II. Investigation into the relation between cellulose synthesis and cell envelope components.

Cell envelope fractions, capable of cellulose synthesis from uridine diphosphate glucose, alpha-glucose-1-phosphate, glucose-6-phosphate and glucose, have been isolated from Acetobacter xylinum suspensions and various enzymatic properties examined. Essential enzymes were found to be distributed throughout the cell envelope region, with both inner (cytoplasmic) and outer (cell wall) membranes contributing to cellulose synthesis. The central role of UDPG in cellulose synthesis was confirmed and the results indicated that the nucleoside diphosphate sugar functions solely in the cell envelope region of whole cells. A comparison of properties of the cell envelope system with those of different preparations used by other workers, suggested that the method of cell disruption may influence substrate specificity.

Cell Membrane↗
PubMed1992

Ethanol production from cellobiose, amorphous cellulose, and crystalline cellulose by recombinant Klebsiella oxytoca containing chromosomally integrated Zymomonas mobilis genes for ethanol production and plasmids expressing thermostable cellulase genes from Clostridium thermocellum.

The Zymomonas mobilis genes for ethanol production have been integrated into the chromosome of Klebsiella oxytoca M5A1. The best of these constructs, strain P2, produced ethanol efficiently from cellobiose in addition to monomeric sugars. Utilization of cellobiose and cellotriose by this strain eliminated the requirement for external beta-glucosidase and reduced the amount of commercial cellulase needed to ferment Solka Floc SW40 (primarily crystalline cellulose). The addition of plasmids encoding endoglucanases from Clostridium thermocellum resulted in the intracellular accumulation of thermostable enzymes as coproducts with ethanol during fermentation. The best of these, strain P2(pCT603T) containing celD, was used to hydrolyze amorphous cellulose to cellobiose and produce ethanol in a two-stage process. Strain P2(pCT603T) was also tested in combination with commercial cellulases. Pretreatment of Solka Floc SW40 at 60 degrees C with endoglucanase D substantially reduced the amount of commercial cellulase required to ferment Solka Floc. The stimulatory effect of the endoglucanase D pretreatment may result from the hydrolysis of amorphous regions, exposing additional sites for attack by fungal cellulases. Since endoglucanase D functions as part of a complex in C. thermocellum, it is possible that this enzyme may complex with fungal enzymes or bind cellulose to produce a more open structure for hydrolysis.

Cellobiose↗
PubMed1992

Permeability of cellulosic and non-cellulosic membranes to endotoxin subunits and cytokine production during in-vitro haemodialysis.

The possibility of endotoxin transfer across haemodialysis membranes remains a controversial issue. Additional concern has arisen because of the recent introduction in clinical practice of highly permeable, synthetic dialysis membranes and of bacteria-contaminated bicarbonate concentrate with potential short-term and long-term hazards for haemodialysis (HD) patients. Therefore, we performed experiments in an in-vitro dialysis recirculation system using three different types of HD membranes, namely standard regenerated cellulose (Cuprophan, CU), polyacrylonitrile AN-69 (PAN), and polysulphone F-60 (PS). When radiolabelled lipopolysaccharide (125I M-LPS) from E. coli, together with 10 micrograms/ml unlabelled LPS, was added to the recirculating solution in the dialysis compartment, radioactivity could be detected in the blood compartment after 15 min and increased progressively with time up to respectively 6.7% (CU), 10.3% (PAN), and 10.3% (PS) of initial activity on the dialysate side. The addition of albumin to the solution on the blood side led to a decreased permeability of radioactivity (7.3% vs 10.3%), compared to the absence of albumin (tested only for PS membrane). Furthermore, 73% of 125I M-LPS transferred across the PS membrane in the presence of albumin was TCA-precipitable. In contrast, free iodine (Na 125I) incubated in an albumin-containing solution did not precipitate with albumin after the addition of TCA (precipitation of only 0.6%). Moreover, kinetics of transmembranous transfer of Na-125I were strikingly different from that of 125I M-LPS. Analysis by the method of sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) of the blood side solution, after LPS addition in the dialysis solution and 30 min of back-filtration, revealed the presence of several silver-stainable and autoradiographic bands of low-molecular-weight range, probably LPS fragments. Finally, the presence of LPS in the dialysate compartment led to a moderate increase in interleukin 1 (IL-1) and tumour necrosis factor alpha (TNF) concentrations in plasma as well as in monocyte culture supernatants after isolation from recirculating normal human whole blood exposed to CU, PAN, or PS membrane. In conclusion, our study provides evidence for the permeation of low-molecular-weight LPS subunits across cellulosic and non-cellulosic HD membranes. The clinical significance, if any, of such a transfer has, however, still to be demonstrated.

Cellulose↗
PubMed1992

[The use of bead cellulose for controlled drug liberation. 5. Binding of benzocaine as a model drug to dialdehyde-bead cellulose and its in vitro liberation].

In the case of ionic binding of drugs to bead cellulose and its derivatives there was no pronounced retardation obvious. Because of this lack benzocaine as a model drug was covalent bound to dialdehyde bead cellulose by an azomethine bond in analogy with enzyme immobilisation methods. The rate of liberation in phosphate buffer was low and incomplete compared with the dissolution rate of pure benzocaine under the same conditions. A further decrease of liberation rate was obtained by reduction of the azomethine to the amine bond. Retardation of drug liberation strictly speaking was not achieved. The main amount of liberated drug was liberated during the first 20 min, but after 6 h the rate was still under 50% of the drug available. The physical properties of the beads like spherical shape and porosity are not significantly influenced by oxidation of cellulose and by loading with drug.

Benzocaine↗
PubMed1992

Improvement of blood compatibility on cellulose dialysis membrane. 2. Blood compatibility of phospholipid polymer grafted cellulose membrane.

The blood compatibility of a cellulose haemodialysis membrane whose surface was grafted with a methacrylate having a phospholipid polar group, 2-methacryloyloxyethyl phosphorylcholine, was evaluated with attention to platelet adhesion to the membrane surface and complement activation induced by the membrane. When the original cellulose membrane came in contact with platelet-rich plasma for 30 min, numerous platelets adhered to the surface and aggregated. On the other hand, the membrane grafted with 2-methacryloyloxyethyl phosphorylcholine effectively suppressed platelet adhesion and activation. This effect became more pronounced with increasing surface distribution. Especially, the 2-methacryloyloxyethyl phosphorylcholine grafted membranes, whose distribution exceeded 0.27, completely inhibited platelet adhesion, even when the contact time was 180 min. Moreover, the complement activation was also reduced with increased 2-methacryloyloxyethyl phosphorylcholine distribution on the surface of the membrane.

Animals↗
PubMed1976

Relation of certain infrared bands to conformational changes of cellulose and cellulose oligosaccharides.

The i.r. spectra of D-glucose and cellulose oligosaccharides up to cellopentaose have been compared with those of cellulose at various temperatures between that of liguid nitrogen and approximately 250 degrees. Significant changes in frequency and intensity of the bands at approximately 3400 cm -1 were observed. The a 1372 cm -1/a2900 cm -1 ratio for each carbohydrate studied decreased gradually as the temperature was increased above ambient. The change of the band intensities at 1429 and 893 cm -1 with temperature was also investigated. The observed spectral changes are assumed to be associated with changes of hydrogen bonding.

Cellulose↗
PubMed1992

[Comparative study of the rheological properties of artificial saliva types based on hydroxy-propyl-methyl-cellulose (methocel) and carboxy-methyl-cellulose (CMC)].

Apparent viscosity at different shear rates was measured for two types of saliva substitutes based on methocel and CMC, and was compared with that of human whole saliva. Results indicate, that fresh mixed human saliva is viscoelastic, exhibiting pseudoplasticity. Methocel containing artificial saliva and human whole saliva are similar in their rheological properties, while the preparation based on CMC is almost a Newtonian liquid. From the results it can be concluded that the saliva substitute containing 0.5% of methocel appears to be a better substitute for natural saliva than of containing CMC as far as rheological properties are concerned.

Carboxymethylcellulose Sodium↗
PubMed1992

Response surface analysis of the effects of pH and dilution rate on Ruminococcus flavefaciens FD-1 in cellulose-fed continuous culture.

The ruminal cellulolytic bacterium Ruminococcus flavefaciens FD-1 was grown in cellulose-fed continuous culture with 20 different combinations of pH and dilution rate (D); the combinations were selected according to the physiological pH range of the organism (6.0 to 7.1) and growth rate of the organism on cellulose (0.017 to 0.10 h-1). A response surface analysis was used to characterize the effects of pH and D on the extent of cellulose consumption, growth yield, soluble sugar concentration, and yields of fermentation products. The response surfaces indicate that pH and D coordinately affect cellulose digestion and growth yield in this organism. As expected, the net cellulose consumption increased with increasing D while the fraction of added cellulose that was utilized decreased with increasing D. The effect of changes in pH within the physiological range on cellulose consumption was smaller than that of changes in D. Cellulose degradation was less sensitive to low pH than to high pH. At low Ds (longer retention times), cellulose degradation did not follow first-order kinetics. This decreased rate of cellulose digestion was not due to poor mixing, limitation by other medium components, or preferential utilization of the more amorphous fraction of the cellulose. The cell yield increased from 0.13 to 0.18 mg of cells per mg of cellulose with increasing Ds from 0.02 to 0.06 h-1 and decreased when the pH was shifted from the optimum of 6.5 to 6.8. The effect of pH on cell yield increased with increasing D. The reduced cell yield at low pH appears to be due to both an increase in maintenance energy requirements and a decrease in true growth yield.

Bacteriological Techniques↗
PubMed1978

Comparison of glucocorticoid-receptor complex binding to nuclei and DNA cellulose. Evidence for different forms of interaction.

Binding of dexamethasone . receptors with isolated nuclei, DNA-cellulose and cellulose has been compared with respect to dependence on salt concentration and resistance to KCl extraction and DNAse I digestion. A solution of cytoplasmic dexamethasone . receptor complexes was prepared by the incubation of rat thymus cells with steroid at 3 degrees C and breaking the cells by hypotonic lysis. Activation of the complexes was accomplished by warming the solution at 25 degrees C for 15 min. Activation significantly increased the ability of dexamethasone . receptors to bind to nuclei and DNA-cellulose but not to cellulose. Dexamethasone-receptor complexes bound to nuclei at 3 degrees C are completely resistant to extraction with 0.1 M KCl, 76% resistant to 0.2 M KCl and 20% resistant to 0.4 M KCl. Dexamethasone . receptors bound to DNA-cellulose are 45% resistant to extraction with 0.1 M and 0.2 M KCl and 29% resistant to 0.4 M KCl extraction. Cellulose-bound dexamethasone . receptors are not resistant to any of these extractions. DNAase I treatment releases 60% of the dexamethasone . receptors bound to DNA-cellulose but only 13% of those bound to nuclei, though at least 60% of the nuclear DNA is solubilized. The presence of 0.15 M KCl decreases binding of activated dexamethasone . receptors to nuclei by 73% but to DNA-cellulose by only 17%. Pretreatment of nuclei with 0.1--0.4 M KCl reduces their capacity to bind activated dexamethasone . receptors by 90% whereas similar treatment reduces the capacity of DNA-cellulose to bind dexamethasone . receptors by only 29%. Nuclei extracted with 0.1 M KCl appear to have a limited capacity to accept dexamethasone . receptors. These studies demonstrate that binding of dexamethasone . receptors to nuclei and DNA-cellulose differs by (a) the higher resistance of nuclear complexes to KCl and DNAase I treatment; (b) the much greater sensitivity of nuclei to KCl treatment.

Cell Nucleus↗
PubMed1992

The cellulose paradox: pollutant par excellence and/or a reclaimable natural resource?

The various aspects of cellulose as a pollutant are considered in view of its lack of toxicity on the one hand and its recalcitrant durable nature on the other. The microbial degradation of cellulosics is discussed, and the contrast between its success in handling natural cellulosic wastes versus its failure to cope with man-made refuse is described. Research carried out in the past decade has demonstrated that cellulolytic organisms are provided with cell surface multifunctional multienzyme conglomerates, called cellulosomes, which are capable of solubilizing solid cellulosic substrates. The intriguing properties of such complexes include their cohesive nature, their many enzymatic components, and a characteristic glycosylated cellulose-binding, 'scaffolding' component. The latter appears to serve as a substrate-targeting carrier, which delivers the other (hydrolytic) components to the cellulose. Progress in establishing efficient model systems for in vitro solubilization of purified cellulose or natural cellulosic substrates has been achieved using purified cellulosome preparations, fortified with beta-glucosidase and pectinase. The latter enzymes were required in order to alleviate the phenomenon of product inhibition which reduces the efficiency of the free cellulosome. Such combined enzyme systems are proposed as examples of future tailor-made cellulolytic systems for the degradation of natural cellulosics.

Biodegradation, Environmental↗
PubMed1977

Purification of biologically active globin mRNA using cDNA-cellulose affinity chromatography.

A complementary DNA (cDNA) copy of mouse globin mRNA was synthesized using the RNA-dependent DNA polymerase from avian myeloblastosis virus and the oligo(dT) covalently attached to cellulose as primer. All four deoxyribonucleotide triphosphates, NaCl, the globin mRNA template, and an oligo(dT) primer were required for optimal synthesis of cDNA. By saturating the primer sites using a 3-fold excess of mRNA, sufficient concentrations of immobilized cDNA could be synthesized to allow the hybridization reactions to be performed using an excess of globin cDNA. Conditions which permitted the annealing of globin mRNA to cDNA-cellulose were selected and the sequence specificity for hybridization to cDNA-cellulose was determined using 28 S ribosomal RNA, polyadenylic acid, and mouse L-cell RNA. Both analytical and preparative applications of this chromatographic medium were explored. When radioactively labeled poly(A)-containing 9 S RNA isolated from nucleated erythroid cells was analyzed by affinity chromatography on globin cDNA-cellulose, 46 per cent of the applied radioactivity hybridized to the cDNA-cellulose column. Only 1 per cent of the labeled RNA was retained by the column during reapplication of the unbound fraction, while 96 per cent of the bound RNA reannealed to cDNA-cellulose. Hybridizations utilizing unfractionated RNA extracts from either mouse reticulocytes or nucleated erythroid cells provided a one-step purification method for globin mRNA sequences. The relative purity of the RNA isolated by cDNA-cellulose affinity chromatography was determined by hybridization kinetic analysis. The cDNA-bound fraction obtained from the unfractionated RNA of either cell type was shown to have a Crt1/2 of 2.7 x 10-3. This represents a 60-fold purification of the globin sequences present in reticulocyte polysomal RNA and a 280-fold enrichment of the globin mRNA in nucleated erythroid cells. Hybridization to cDNA-cellulose did not result in any change in the sedimentation rate of globin mRNA. Furthermore, experiments were performed which demonstrated that the globin mRNA isolated by hybridization to cDNA-cellulose retained its biological activity when assayed in a wheat germ cell-free lysate.

Animals↗
PubMed1975

Isolation of bacterial and phage proteins by homopolymer RNA-cellulose chromatography.

Nucleic acid-free extracts of Escherichia coli have been analyzed by chromatography on columns of cellulose, to which poly(A), poly(U), or poly(C) have been attached by ultraviolet irradiation. Proteins are released from the columns by stepwise elution with increasingly higher concentrations of salt, followed by washing with urea to remove very tightly bound molecules. The pattern of protein elution is reproducibly different for each of the homopolymer RNA-cellulose columns used: some proteins bind very tightly to one column, but poorly to others. Analysis by sodium dodecyl sulfate-polyacrylamide slab gel electrophoresis, by immunological cross-reactivity in double diffusion tests, and by enzymological assays, has allowed the identification of a number of these proteins. The RNA polymerase core enzyme binds to poly(C)- and to poly(U)-cellulose columns, and can be purified to 20 to 30 percent homogeneity in a single step. Ribosomal protein S1 and the termination factor rho bind very tightly to poly(C)-cellulose, and both can be purified to homogeneity rapidly, in much higher yields than previously reported. Poly(A)-cellulose chromatography allows the isolation of large amounts of an 80,000 molecular weight protein having an as yet unassigned cellular function. The host factor required for RNA phage Qbeta RNA replication in vitro can also be obtained from poly(A)-cellulose, and chromatography of extracts of phage Qbeta-infected E. coli on RNA-cellulose columns results in very rapid isolation of the Qbeta replicase enzyme. Homopolymer RNA-cellulose chromatography thus appears to be a simple, general technique, useful for the efficient isolation of a variety of RNA-binding proteins.

Bacterial Proteins↗