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At least 505 records · Page 28Linked to original sources

PubMed1972

Replication of Phi-X174 DNA by Escherichia coli polA- in vitro (Phi-X174 DNA-DNA replication-E. coli polA-).

Lysates of an Escherichia coli polA(-) strain convert single-stranded DNA from varphiX174 virus to the double-stranded replicative form with high efficiency on cellophane discs. The initiation of synthesis of the complementary strand appears to be rate limiting; once initiation occurs, the chain is propagated rapidly. Under these conditions, the unsealed replicative form accumulates and is slowly converted to the sealed form; this conversion requires the activity of the DPN-dependent DNA ligase.

Centrifugation, Density Gradient↗

PubMed1975

Chemotactic signals induce cell differentiation in Dictyostelium discoideum.

Experiments carried out with the aid of cellophane membranes demonstrate that the morphogenetic block of certain nonaggregating, "aggregateless," mutants may be overcome by diffusible factors excreted by aggregating wild-type cells. The same differentiation process into aggregation-competent cell is observed if mutant amoebae are subjected to external 3':5'-cAMP pulses imposed at 5 min intervals. Wild-type amoebae also respond to cAMP pulses, since the onset of differentiation is more precocious in pulsed than in unpulsed populations. These data suggest that chemotactic signals act as an inducer of cell differentiation.

Adenosine Monophosphate↗

PubMed1977

Phage T4-modified RNA polymerase transcribes T4 late genes in vitro.

Initiation of T4 late RNA synthesis has been achieved in an in vitro system prepared from Escherichia coli cells infected with wild-type or maturation-defective mutant T4 phage. The system uses a cellophane membrane as a mechanical support for concentrated cell lysates and for added streptolydigin-resistant RNA polymerases. Transcriptional activity and selectivity of added RNA polymerases are tested while endogenous RNA polymerase activity is inhibited by streptolydigin. T4-modified RNA polymerase is required for substantial stimulation of T4 late RNA synthesis.

Coliphages↗

PubMed1979

An oligosaccharide-containing factor that induces cell differentiation in Dictyostelium discoideum.

When Dictyostelium discoideum amoebae (strain V12 M2) are spread at high density on agar containing 1 mM cyclic AMP, essentially all the cells differentiate into stalk cells after 2-3 days. We showed previously that isolated amoebae plated at low density on agar containing cyclic AMP do not differentiate, but can be induced to do so by a layer of high density helper cells from which they are separated by a thin cellophane membrane. We now show that the high density cell population releases a dialyzable factor that, in the presence of cyclic AMP, is capable of inducing isolated amoebae to differentiate into stalk cells. Sugar inhibition, sensitivity to glycosidases, and lectin affinity suggest that the differentiation-inducing activity requires the integrity of an oligosaccharide group containing sialic acid, L-fucose, and N-acetylgalactosamine. In addition, a phosphate group appears to be necessary for biological activity.

Biological Assay↗

PubMed2003

Effects of nutrients, cell density and culture techniques on protoplast regeneration and early protonema development in a moss, Physcomitrella patens.

To regenerate auxotrophic mutants of Physcomitrella patens, two media of increasing complexity were developed. The survival rate of protoplasts was around 30% higher on full medium when compared to standard minimal medium. Protoplast survival was higher in a medium containing 2.5 mmol/L ammonium tartrate compared to a medium with 5 mmol/L of this compound. Solid medium had a positive effect on protoplast survival compared to either liquid medium or solid medium overlaid with cellophane; the maximum survival rate being 31.6%. However, the number of surviving protoplasts without any cell division during the first ten days increased on solid medium. Density and survival rate of protoplasts were positively correlated, but the formation of long protonema filaments decreased markedly. The effect of different protoplast densities could be explained partly by physiologically active compounds excreted into the medium.

Bioreactors↗

PubMed1987

A novel method of electrophoresis for the separation of individual human serum glycoproteins.

A method for the isolation of protein components by a combination of polyacrylamide gel electrophoresis and electro-extraction of slices of gel contained in cellophane dialysis tubing, using the H tube electrophoresis apparatus, is described. The method was applied to the purification of individual human serum glycoproteins. Although the glycoproteins have widely differing electrophoretic mobilities, they appeared to be antigenically interrelated judging from their complex "spurring" in Ouchterlony double gel diffusion tests.

Blood Protein Electrophoresis↗

PubMed2004

Congenital portosystemic shunts in dogs and cats.

Congenital portosystemic shunts (PPS) are abnormal vascular communications that allow blood from the intestine to bypass the liver, and are classified as intrahepatic or extrahepatic. Clinical signs are generally related to the nervous, gastrointestinal or urinary systems, and are often vague. In addition, changes present on routine blood analysis are often mild and non-specific. For this reason, alternative tests are required for a diagnosis. Diagnostic tests include serum bile-acid concentrations, ammonia tolerance test, portography, ultrasonography and/or scintigraphy. Medical therapy involves reducing absorption of encephalopathic toxins from the gastrointestinal tract and may prolong survival. Surgical therapy is aimed at attenuation of the shunting vessel and provides improved survival rates. The traditional approach has been complete or partial ligation of the shunt. More recent approaches have involved slow, progressive attenuation with ameroid constrictors or cellophane banding. Overall, prognosis following surgical therapy is good in dogs and fair in cats.

Journal Article↗

PubMed2006

Enhancement of the dissolution and permeation rates of meloxicam by formation of its freeze-dried solid dispersions in polyvinylpyrrolidone K-30.

Freeze-drying (FD) and solvent evaporation (SE) were used to prepare solid dispersions (SDs) of meloxicam (MX) in polyvinylpyrrolidone K-30 (PVP). The SDs were prepared at different ratios, namely 1:1, 1:3, and 1:5 MX:PVP weight ratio. Differential scanning calorimetry (DSC), infrared absorption spectroscopy (IR), and x-ray powder diffractometry (XPD) were utilized to characterize the physicochemical properties of the SDs. Meloxicam (MX) in the solid dispersions appeared with less crystallinity form and was present in a complete amorphous form at higher PVP ratio. Dissolution rates of MX as a pure drug, physical mixtures (PMs), and SDs indicated a marked increase of the dissolution rate of MX in presence of PVP. The increase in the dissolution rate was dependent on the ratio of PVP and the method of preparation. In addition, the permeability of the drug through standard cellophane membrane and hairless mouse skin was also evaluated. The permeation rate of MX was significantly increased in the case of SDs and was dependent on the ratio of PVP. The results were primarily due to increase wettability, the solubilization of the drug by the carrier, and formation of MX amorphous form.

Animals↗

PubMed2003

In-vitro evaluation and vaginal absorption of metronidazole suppositories in rabbits.

Vaginal suppository formulations of metronidazole were prepared using six different bases as Witepsol H15, Cremao, Ovucire WL2944, Ovucire WL3264, PEG 1500, PEG 6000. Three different dissolution methods were used to evaluate the in vitro drug release from the suppositories. The diffusion studies were performed through synthetic (cellophane) and natural membrane (rabbit vagina), but the drug did not show good permeation characteristics from natural membrane. Ovucire WL3264 suppositories of metronidazole labeled with 99mTc (Tecnetium-99m) were used for the vaginal absorption and biodistribution studies in the rabbits. Scintigraphic images were collected after vaginal administration of the labeled suppositories using SPECT gamma fitted with a low energy, high-resolution parallel hole collimator. The labeled drug showed high biodistribution in urine beside vaginal site. The results of this study suggested that the Ovucire WL3264 suppository of metronidazole prepared for vaginal infections could also be effective in the urinary infections.

Administration, Intravaginal↗

PubMed2004

Solubility enhancement of indomethacin with poly(amidoamine) dendrimers and targeting to inflammatory regions of arthritic rats.

This work includes investigation on solubility enhancement of indomethacin (IND) in the presence of poly(amidoamine) (PAMAM) dendrimers and passive targeting of the PAMAM/IND complex so formed to the inflamed regions in an animal model. The complex formation was confirmed by infrared and (1)H nuclear magnetic resonance spectroscopy methods. Solubility of IND in aqueous G4-PAMAM followed Higuchi's A(N) curve depending on pH of the solubilizing medium. The solubility was decreased upon addition of dendrimer to the IND saturated solution at various pH, indicating aggregation behavior of the PAMAM/IND complex and conforming to the Higuchi's A(N) solubility profile. The in vitro release of IND from the PAMAM/IND complex through a cellophane membrane, from a Franz diffusion cell, showed 79 +/- 3.2% drug release in 24 h. The drug release was further retarded in the presence of human serum albumin (HSA) suggesting the significance of complex HSA binding in altering in vivo behavior of the complex. Intravenous administration of the PAMAM/IND complex formulation in rats showed a two-compartment pharmacokinetic profile. Enhanced effective IND concentrations in the inflamed regions were obtained for the prolonged time period with the PAMAM/IND complex compared to the free drug in arthritic rats indicating preferred accumulation of IND to the inflamed region. The targeting efficiency of PAMAM/IND complex was 2.29 times higher compared to free drug. In contrast to the previous investigations, two interesting findings reported here are: (a) solubility behavior of IND in G4-PAMAM dendrimer deviates from linearity with increasing concentrations of dendrimer at acidic to neutral pH values and (b) inspite of lymphatic drainage, retention of PAMAM/IND complexes occurs at the inflammatory site.

Animals↗

PubMed2004

Controlled release of biomolecules from pH-sensitive network polymers prepared by radiation polymerization.

Copolymers of 2-hydroxyethyl methacrylate (HEMA) and methacrylic acid (MAA) based hydrogels containing 5 and 10% of a cross-linking agent were studied as drug delivery systems. Terephthalic acid was covalently linked with HEMA, abbreviated as CA. Radiation copolymerization of HEMA and MAA, mixed with a particulate glibenclamide with the various ratios CA as crosslinking agent were carried out at the room temperature. The structure of the CA was confirmed by FTIR, H NMR and C NMR spectroscopy. The compositions of the cross-linked three-dimensional polymers were determined by FTIR spectroscopy. Glass transition temperature (T) of the network polymers was determined calorimetrically. The hydrolysis of drug-polymer conjugates was carried out in cellophane membrane dialysis bags containing an aqueous buffer solution (pH 7.4 and pH 1) at 37 degree C. The drug-release profiles indicate that amount drug release depends on their degree of swelling and cross-linking.

Calorimetry, Differential Scanning↗

PubMedDate not supplied

Solid lipid nanoparticles bearing flurbiprofen for transdermal delivery.

Topical application of the drugs at the pathological sites offer potential advantages of delivering the drug directly to the site of action and thus producing high tissue concentrations of the drug. The solid lipid nanoparticles (SLN) bearing flurbiprofen were prepared by microemulsion method by dispersing o/w microemulsion in a cold aqueous surfactant medium under mechanical stirring. The SLN gel was prepared by adding SLN dispersion to polyacrylamide gel prepared by using polyacrylamide (0.5%), glycerol (10%), and water (69.5%). Shape and surface morphology was determined by scanning electron microscopy that revealed fairly spherical shape of the formulation. Percent drug entrapment was higher in SLN dispersion in comparison to SLN gel formulations. In vitro drug release, determined using cellophane membrane, showed that SLN dispersion exhibited higher drug release compared with SLN gel formulations. Both the SLN dispersion and SLN-gel formulation possessed a sustained drug release over a 24-hr period, but this sustained effect was more pronounced with SLN-gel formulations. The percent inhibition of edema after 8 hr was 55.51 +/- 0.26% in case of SLN-T4-gel, whereas flurbiprofen and SLN-T4 dispersion exhibited 28.81 +/- 0.46 and 31.89 +/- 0.82 inhibition of edema. The SLN-T4-gel not only decreased the inflammation to larger magnitude, but also sustained its effect.

Administration, Cutaneous↗

PubMedDate not supplied

The relation between swelling properties and cross-linking of hydrogels designed for colon-specific drug delivery.

Copolymers of 2-hydroxyethyl methacrylate (HEMA) and methacrylic acid (MAA)-based hydrogels containing 5% and 10% of a cross-linking agent were studied as drug delivery systems. Terephthalic acid was covalently linked with HEMA, abbreviated as CA (cross-linking agent). Free radical cross-linking copolymerization of HEMA and methacrylic acid (MAA) in three different molar ratios, mixed with a particulate 3, 3-azobis (6-hydroxy benzoic acid) (ABHB) as an azo derivative of 5-aminosalicylic acid with the various ratios CA as cross-linking agent were carried out with using 2, 2, Azobisisobutyronitrile as initiator at the temperature range 60-70 degrees C. The compositions of the cross-linked three-dimensional polymers were determined by FTIR spectroscopy. Glass transition temperature of the network polymers was determined calorimetrically. The hydrolysis of drug-polymer conjugates was carried out in cellophane membrane dialysis bags containing an aqueous buffer solution (pH 7.4 and pH 1) at 37 degrees C. The drug-release profiles indicate that the amount of drug release depends on its degree of swelling and cross-linking.

Azo Compounds↗

PubMedDate not supplied

Molecular and phenotypic description of the widespread root symbiont Acephala applanata gen. et sp. nov., formerly known as dark-septate endophyte type 1.

Acephala applanata gen. et sp. nov. is described. A. applanata is a dark-septate endophyte (DSE) of conifer roots and belongs to the Phialocephala fortinii species complex. Several genetic markers, including isozymes, inter-simple-sequence-repeat (ISSR) fingerprints, single-copy restriction fragment length polymorphisms (RFLP) and sequences of the internal transcribed spacers (ITS), let us unambiguously separate isolates of A. applanata from isolates of P. fortinii s.l. and other dark-septate endophytes. Alleles at four RFLP loci and two fixed nucleotides in the ITS region were diagnostic for A. applanata. One of the fixed nucleotides resulted in the addition of an Afa I restriction site. PCR amplification with primers prITS4 and the newly developed primer PF-ITS_F (ACT CTG AAT GTT AGT GAT GTC TGA GT) and restriction digestion with Afa I yielded three fragments (203 bp, 117 bp, 56 bp) in A. applanata but only two (260 bp and 117 bp) in P. fortinii s.l. Population differentiation (GST) between A. applanata and other cryptic species of P fortinii was pronounced, and the index of association (IA) did not deviate significantly from zero, showing that recombination occurs or had occurred in A. applanata. Although isolates of A. applanata never were observed to sporulate, it can be distinguished morphologically from P fortinii s.l. by the scarcity of aerial mycelium, significantly slower growth and denser mycelium on cellophane overlaid on water agar. These phenotypic characteristics, combined with diagnostic RFLP alleles and/or PCR-RFLP of the ITS fragment with the fixed Afa I restriction site, unequivocally allow identification of A. applanata.

Ascomycota↗

PubMed2000

In vitro iontophoretic release of lithium chloride and lidocaine hydrochloride from polymer electrolytes.

Ionically conducting polymers, frequently known as polymer electrolytes, are potential candidates as hosts for drugs to be delivered iontophoretically. The iontophoretic delivery of lithium or lidocaine from polymer electrolyte films through a cellophane membrane was examined using different delivery current regimes. Thin, mechanically strong, polymer electrolyte films were fabricated from poly(ethylene oxide) (PEO) with lithium chloride or lidocaine hydrochloride. Experiments showed that iontophoretic transport of both lithium chloride and lidocaine hydrochloride might be achieved from these PEO-based films. Cation transport number determinations give values for PEO-based films of about 0.4 for lithium chloride systems and 0.12 for lidocaine hydrochloride systems. The mechanism of transport from these PEO-based polymer electrolyte films allows the delivery of ionic salts such as lithium chloride and lidocaine hydrochloride to be controlled solely by current, thus providing a system that can deliver precise amounts of drug.

Anesthetics, Local↗

PubMed2001

Topical permeation characteristics of diclofenac sodium from NaCMC gels in comparison with conventional gel formulations.

Topical gel formulations of diclofenac sodium were prepared by using sodium carboxymethylcellulose (NaCMC), a low-toxicity cellulose polymer as a gel-forming material that is biocompatible and biodegradable. The influence of various formulation variables, such as initial drug concentrations and NaCMC concentration, and certain skin permeation enhancers on release characteristics of the diclofenac sodium from the prepared gels through a standard cellophane membrane was studied in comparison with four commercially available gel formulations of diclofenac sodium,. The cumulative amounts released and the apparent release rates were higher for the prepared gels in comparison with the commercial formulations. Skin permeation studies using abdominal rat skin revealed good improvement of skin permeation characteristics of diclofenac sodium using NaCMC gels as compared to the commercial gels. The cumulative amount permeated at 6 h (microg/cm2), steady-state flux Jss (microg/cm2 h), lag time tL (h), permeability coefficient kp (cm/s), partition coefficient k, and diffusion coefficient D (cm2/s) were determined for the prepared gels in comparison with the commercial gels. Skin permeation enhancers such as isopropyl alcohol (IPA), Tween 80, and alpha-tocopherol polyethylene glycol succinate (TPGS) exhibited little or no effect on the permeation characteristics of diclofenac sodium. Infrared (IR) spectrum and differential scanning calorimetry (DSC) studies on the pure diclofenac sodium, NaCMC, and their physical mixture at a 1:1 ratio revealed that there was no positive evidence for the interactions between the drug and NaCMC, indicating the compatibility of the drug and the vehicle. Based on experimental results, preparation of diclofenac sodium gels using NaCMC vehicle is promising.

Animals↗

PubMed2002

Assemblies for in vitro measurement of bioadhesive strength and retention characteristics in simulated vaginal environment.

The vaginal route of administration offers a promising option for local and systemic delivery of drugs. Conventional vaginal formulations are associated with limitations of poor retention, leakage, and messiness, thereby causing inconvenience to users. To overcome these limitations, formulations that adhere to the vaginal mucosa for a sufficient period of time need to be developed. Bioadhesion and retention are desirable characteristics of a vaginal formulation to achieve desired efficacy. These properties can be built in during formulation development by the use of bioadhesive polymers. In the present study, assemblies for in vitro measurement of bioadhesive strength and retention characteristics of vaginal formulations have been developed. A modified simulated vaginal fluid (SVFM) was used to simulate vaginal conditions for bioadhesion studies. Cellophane hydrated with SVFM and isolated sheep vaginal mucosa were used as model membranes. The bioadhesive potential of various polymers and their combinations was evaluated. Among the polymers evaluated, xanthan gum (XG), sodium alginate (SA), Polycarbophil (PC), and their combinations (XG + SA and XG + PC) were found to possess significant bioadhesive strength. In retention experiments, XG, SA, and combinations (XG + SA and XG + PC) were retained in isolated sheep vaginal tissue, while PC exhibited poor retention under experimental conditions. Based on the results of the study conducted, XG, SA, and combinations (XG + SA and XG + PC) have been proposed as potential candidates for developing bioadhesive vaginal drug delivery systems.

Acrylates↗

PubMed1968

The circumfusion system for multipurposeculture chambers. II. The protracted maintenance of differentiation of fetal and newborn mouse liver in vitro.

The circumfusion system is a complex in vitro pumping unit incorporating 12 multipurpose culture chambers through which a serum-supplemented fluid nutrient is recirculated at a rate of 4.5 ml/min per chamber. This system was used to study the differentiative responses of fetal and newborn mouse liver explants placed in the serum-free environment formed between the sheets of unperforated cellophane and cover glasses of the chambers. Hepatocytes (parenchymal cells) were discernible in 3-5 days. They retained many of their features of differentiation in the circumfusion system for more than 120 days of cultivation. The living morphological characteristics of the hepatocytes were studied by phase-contrast microscopy (direct viewing and time-lapse cinemicrography) and by special cytochemical staining. Electron micrographs were made of both fresh liver specimens and the cultured cells. Comparisons of the cultured parenchymal cells with their in vivo progenitors showed a remarkable preservation of their differentiated state.

Animals↗