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At least 721 records · Page 40Linked to original sources
PubMed1996

Physical and biological effects of a surface coating procedure on polyurethane catheters.

Central venous catheters are widely used in clinical practice; however, complications such as venous thrombosis or infection are frequent. The physical and biological effects of a coating procedure designed to improve the blood-contacting properties of polyurethane central venous catheters (CVCs) were studied. The surface atomic composition of poly(vinyl pyrrolidone) (PVP)-coated or uncoated Pellethane single lumen CVCs was characterized by electron spectroscopy for chemical analysis (ESCA), which confirmed the presence of an oxygen-rich PVP layer on the former material. Topological analysis of both single and triple lumen CVCs by scanning force microscopy (SFM) revealed a very smooth surface in PVP-coated catheters compared to the more frequent surface irregularities found either in uncoated Pellethane or in four additional randomly selected, commercially available triple lumen polyurethane CVCs. The PVP-coated Pellethane showed a strong reduction in either fibrinogen or fibronectin adsorption compared to all other PVP-free polyurethane CVCs. This decreased protein adsorption led to a proportional reduction in protein-mediated adhesion of either Staphylococcus aureus or Staphylococcus epidermidis and in the binding of a monoclonal antibody directed against the cell-binding domain of fibronectin. Increased surface smoothness and hydrophilic properties of polyurethane CVCs might decrease the risk of bacterial colonization and infection.

Adsorption↗
PubMed1979

Termination of pseudopregnancy in rats by silastic-PVP-PGF2 alpha tube.

The efficacy of a one-end or both-end open Silastic-polyvinyl-pyrrolidone (Silastic-PVP) tube containing 600 microgram prostaglandin-F2 alpha (PGF2 alpha) and placed subcutaneously on day-6 of pseudopregnancy (PSP) in the induction of premature termination of PSP was compared. A both-end open Silastic-PVP-PGF2 alpha tube was more efficacious in inducing an early termination of PSP with a mean duration of 7.8 days. By contrast, PSP females receiving a one-end open Silastic-PVP-PGF2 alpha tube showed a mean duration of PSP of 9.9 days. The shortened duration of PSP in both these treatment groups was significantly different from the control value of 13.1 days. The significant drop in progesterone (delta 4P) but rise in 20 alpha-dihydroprogesterone (20 alpha-DHP) occurred 24 hr after treatment in PSP rats treated with both-end open Silastic-PVP-PGF2 alpha tube, whereas similar changes in delta 4P and 20 alpha-DHP took place 48-72 hr after the deposition of a one-end open Silastic-PVP PGF2 alpha tube. It is concluded than an initial larger amount of circulating PGF2 alpha is needed to induce an early premature termination of PSP. The exposure of corpus luteum to a more sustained but lower level of PGF2 alpha leads to a slower response.

20-alpha-Dihydroprogesterone↗
PubMed1987

Effects of preformed proline and proline amino acid precursors (including glutamine) on collagen synthesis in human fibroblast cultures.

A technique of derivatizing proline and 4-hydroxyproline with 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole was used to measure the radioactivities, concentrations and specific activities of proline and hydroxyproline. The technique was used to study the conditions of procollagen synthesis in cultured human foreskin fibroblasts. Procollagen synthesis appeared to be independent of the proline concentration in the medium, in the presence of glutamine, when monitored by the assay of non-dialyzable hydroxyproline, but not when monitored by [14C]proline incorporation. In the absence of unlabelled proline added to labelled proline in the medium, the specific activity of the secreted procollagen did not reach a plateau over a 24-h period. When the medium was supplemented with glutamine, glutamic acid, or aspartic acid, both the radioactivity and concentration of intracellular free proline decreased. Pyrrolidone-2-carboxylic acid and ornithine both induced a slight increase in concentration of the intracellular free proline. Glutamine competed with [14C]proline for incorporation into prolyl-tRNA and procollagen, independently of free intracellular proline, and it stimulated the biosynthesis of procollagen (expressed as non-dialyzable hydroxyproline) by a factor of 2.3.

Amino Acids↗
PubMed1991

Media additives for protecting freely suspended animal cells against agitation and aeration damage.

Over the past 30 years, several different additives have been used to protect freely suspended animal cells in culture from agitation and aeration damage. These include pluronic polyols, various derivatized celluloses and starches, protein mixtures, polyvinyl-pyrrolidones, dextrans, and, more recently, polyethylene glycol (PEG) and polyvinyl alcohol. The protective mechanisms of these additives are not yet fully understood, but recent studies suggest both fluid-mechanical and biological mechanisms of protection.

Animals↗
PubMed1985

Immunological castration by a totally synthetic vaccine: modification of biological properties of LH-RH after conjugation to adjuvant-active muramyl peptide.

Recently, we demonstrated that immunological castration of male mice can be obtained by immunization with Luteinizing Hormone-Releasing Hormone (LH-RH) directly coupled to NAcMur-L-Ala-D-isoGln-L-Lys (MDP-Lys) without carrier and Freund's Complete Adjuvant (FCA) but in the presence of Polyvinyl-Pyrrolidone (PVP). In the present report, we have observed that: (a) immunization by the conjugate, LH-RH-MDP-Lys, was very effective even in absence of PVP, and this conjugate was more active than other conjugates containing MDP coupled to LH-RH fragments; (b) a strong secondary response could be observed by the administration of free LH-RH suggesting that the endogenous secretion of LH-RH might elicit a boosting effect; (c) administration of MDP-Lys coupled to LH-RH decreased the pyrogenicity of the glycopeptide; (d) such a conjugation also decreased the hormonal activity of the antigen although it enhanced its immunogenicity. These results show that a conjugate (2000 dalton) of a decapeptide hormone with a synthetic adjuvant glycopeptide can induce immunological castration in mice after administration in saline. The immunopharmacological properties of the conjugate and its conditions of efficacy suggest that such an approach could find clinical application.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1995

The specific type IV phosphodiesterase inhibitor rolipram combined with adenosine reduces tumor necrosis factor-alpha-primed neutrophil oxidative activity.

Monocytes and macrophages produce tumor necrosis factor-alpha (TNF alpha) in response to microbial products including endotoxin. TNF alpha is a potent primer of neutrophil (PMN) oxidative activity. Certain xanthine phosphodiesterase (PDE) inhibitors such as pentoxifylline have been shown to inhibit stimulated oxidative activity in PMN. In the present study, the non-xanthine PDE type IV inhibitor rolipram (4-[3'-cyclopentyloxy-4'-methoxyphenyl]-2-pyrrolidone) alone and in combination with adenosine is examined as a potential modulator of TNF alpha-primed PMN oxidative activity. Attainable in vivo concentrations of rolipram and physiological concentrations of adenosine alone and together synergistically decreased rhTNF alpha-primed suspended PMN oxidative activity stimulated by the chemoattractant f-met-leu-phe. The rolipram effect was reversible by washing, and rolipram had a comparable effect if added before or after priming, indicating that its effect was on the primed response rather than on priming per se. In addition, rolipram especially when combined with adenosine, decreased rhTNF alpha-stimulated PMN adherence to a fibrinogen-coated surface, and the oxidative burst of rhTNF alpha-stimulated adherent PMN. The specific adenosine A2a receptor agonists CGS 21680 and WRC-0474 had comparable activity to adenosine in these experiments. Adenosine (or CGS 21680) combined with rolipram synergistically increased f-met-leu-phe-stimulated PMN cAMP content. The effects of both adenosine and rolipram with adenosine could be only partly counteracted by treatment of the PMN with the protein kinase A inhibitor KT 5720, indicating that protein phosphorylation is only partially involved. Rolipram activity was about 1000 x (by molar concentration) greater than pentoxifylline in comparable assays. Thus, rolipram, especially when combined with adenosine, has potent modulating effects on PMN activation and may be useful in decreasing inflammatory tissue damage in patients with sepsis.

Adenosine↗
PubMed1985

Assay of pyroglutamyl aminopeptidase by high-performance liquid chromatography and its use in peptide sequencing.

Assay of pyroglutamyl aminopeptidase by HPLC methodology allows determination of the kinetic parameters of the enzyme for a variety of natural peptide substrates. Moreover, by this method it is possible both to evaluate the extent of the enzymatic reaction by determining the amount of pyrrolidone carboxylic acid released and to obtain the unblocked peptide for structural and functional characterization.

Amino Acid Sequence↗
PubMed1987

Pyroglutamyl N-termini of thermal polyamino acids.

It has been established indirectly that the N-termini of the thermal polyamino acids are pyroglutamic acid. This was determined by trifluoroacetic acid hydrolysis of the lactam ring followed by Dansyl labelling. The polyamino acids contained Ala, Gly, Glu, Leu, Phe, and Pro. In the experiments described here, the presence of pyroglutamic acid at the N-terminus of a polyamino acid was determined directly by the use of pyrrolidone carboxylyl peptidase. The enzyme catalyzes the removal of pyroglutamyl residues at the N-terminus of polypeptide chains. The polyamino acids used in these studies contained glutamic acid, aspartic acid, alanine, glycine, isoleucine, proline and valine. Alkaline hydrolysis was also used to determine indirectly that the N-termini of these polyamino acids are pyroglutamic acid. Another interesting finding was that many of the amino acids in the polymerization mixture were found to occur penultimate to the N-terminal amino acid. This is interpreted to mean that the diffusible fraction contains many polyamino acids.

Amino Acid Sequence↗
PubMed1992

Effects of glycine antagonists on Mg(2+)- and glycine-induced [3H]N-(1-[2-thienyl]cyclohexyl)-3,4-piperidine binding.

We investigated the effects of glycine antagonists, 3-amino-1-hydroxy-2- pyrrolidone (HA-966), 7-chlorokynurenic acid (7-Cl-KYNA), 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), 6,7-dichloro-3-hydroxy-2-quinoxalinecarboxylic acid (DHQXC), 6,7-dichloroquinoxaline-2,3-dione (DCQX), and 5-chloro-indole-2-carboxylic acid (5-Cl-I2CA), on Mg(2+)- and glycine-induced [3H]N-(1-[2-thienyl]cyclohexyl)-3,4-piperidine ([3H]TCP) binding to well-washed rat cortical membranes. Except for 5-Cl-I2CA, all the glycine antagonists completely inhibited not only glycine- but also Mg(2+)-induced [3H]TCP binding in a concentration-dependent manner. Out of all the glycine antagonists examined DHQXC most selectively inhibited Mg(2+)-induced [3H]TCP binding, while DCQX was the most selective for inhibiting glycine-induced [3H]TCP binding.

Animals↗
PubMed1981

The involvement of parenchymal, Kupffer and endothelial liver cells in the hepatic uptake of intravenously injected liposomes. Effects of lanthanum and gadolinium salts.

125I-labeled albumin or poly(vinyl pyrrolidone) encapsulated in intermediate size multilamellar or unilamellar liposomes with 30-40% of cholesterol were injected intravenously into rats. In other experiments liposomes containing phosphatidyl[Me-14C]choline was injected. 1 h after injection parenchymal or non-parenchymal cells were isolated. Non-parenchymal cells were separated by elutriation centrifugation into a Kupffer cell fraction and an endothelial cell fraction. From the measurements of radioactivities in the various cell fractions it was concluded that the liposomes are almost exclusively taken up by the Kupffer cells. Endothelial cells did not contribute at all and hepatocytes only to a very low extent to total hepatic uptake of the 125I-labels. Of the 14C-label, which orginates from the phosphatidylcholine moiety of the liposomes, much larger proportions were recovered in the hepatocytes. A time-dependence study suggested that besides the involvement of phosphatidylcholine exchange between liposomes and high density lipoprotein, a process of intercellular transfer of lipid label from Kupffer cells to the hepatocytes may be involved in this phenomenon. Lanthanum or gadolinium salts, which effectively block Kupffer cell activity, failed to accomplish an increase in the fraction of liposomal material recovered in the parenchymal cells. This is compatible with the notion that liposomes of the type used in these experiments have no, or at most very limited, access to the liver parenchyma following their intravenous administration to rats.

Animals↗
PubMed1981

In vivo fate of large unilamellar sphingomyelin-cholesterol liposomes after intraperitoneal and intravenous injection into rats.

We investigated the fate of intraperitoneally and intravenously injected reverse phase evaporation vesicles of fairly uniform size (100-200 nm) with respect to blood clearance, tissue distribution and integrity in vivo. The vesicles are composed of sphingomyelin and cholesterol in a molar ratio 3 : 2 and contain 125I-labeled poly(vinyl pyrrolidone) in the aqueous compartment. It is shown that following an intraperitoneal injection the vesicles are transported intact, and not associated with cells, from the peritoneal cavity to the blood and are subsequently taken up mainly by liver and spleen, where, particularly in liver, the phospholipid is partially metabolized. After an intraperitoneal injection the rate of vesicle-uptake by liver and spleen is reduced by a factor of 2-3 compared to the rate of vesicle-uptake by liver and spleen following an intravenous injection. The peritoneal cavity functions as a reservoir of vesicles for some hours. The rates of blood clearance and uptake of the vesicles by liver and spleen appear to be slower than that found for vesicles of different lipid composition.

Animals↗
PubMed1993

A novel rapid hybridization technique: paper chromatography hybridization assay (PACHA).

A new DNA hybridization technique, based on chromatographic migration of DNA on a nitrocellulose strip passing through an immobilized probe area, is described. The new paper chromatography hybridization assay (PACHA) is faster and simpler to use than the conventional dot hybridization assay. In this assay, an aliquot of biotinylated, PCR-amplified target DNA is applied to one end of a nitrocellulose strip. The DNA migrates to the opposite end of the strip by capillary forces and hybridizes to a specific DNA probe immobilized in a reaction zone (RZ), located in the middle of the strip. Unhybridized DNA migrates away from the RZ. The biotinylated hybrid is visualized by a color reaction employing a streptavidin-alkaline phosphatase (SA-AP) conjugate and a specific chromogenic substrate. The new PACHA technique allows for detection of as little as 1-5 pg of specific human papilloma virus 16 (HPV16) DNA in 25 min of hybridization. In this system, the hybridization efficiency is controlled by the flow velocity of the hybridization solution (HS) and by the volume of the amplified labeled DNA migrating across the immobilized probe. Glycerol (30%) or polyvinyl pyrrolidone (PVP) (1%) reduces the flow rate by a factor of 2.5-3 and increases the sensitivity of the assay by a factor of 5.2 for glycerol and 2.6 for PVP. This novel method ensures efficient hybridization to multiple probes and appears to be superior to currently available solid-phase hybridization techniques.

Base Sequence↗
PubMed1994

Denaturants or cosolvents improve the specificity of PCR amplification of a G + C-rich DNA using genetically engineered DNA polymerases.

We describe conditions that improve the specificity of amplification of a G + C-rich (57% G + C) DNA by PCR. Under standard conditions a 368-bp segment of the approx. 2.1-kb repeat unit of a satellite DNA that accounts for approx. 3% of the genome of the Bermuda land crab, Gecarcinus lateralis, was not amplified specifically. To establish optimal conditions for amplification of the segment of the G + C-rich satellite, we used two genetically engineered enzymes, AmpliTaq DNA polymerase and AmpliTaq DNA polymerase, Stoffel fragment (SF), and a number of denaturants or co-solvents. In the absence of denaturants or co-solvents, amplified products of both enzymes contained non-specific bands upon gel electrophoresis. Addition of certain denaturants or co-solvents to PCR mixtures resulted in the production of the single specific band of the expected size. Reagents that improved specificity of the amplified product were formamide, glycerol, DMSO, Tween-20 and NP-40; on the other hand, urea, ethanol and 1-methyl-2-pyrrolidone (NMP) inhibited amplification. Of the two enzymes, SF was more specific and efficient. The products of AmpliTaq DNA polymerase included one or more extra bands, even in the presence of denaturants or co-solvents, except for glycerol or DMSO.

Base Sequence↗
PubMed1990

Electron spin resonance studies of the reaction of hypochlorite with 5,5-dimethyl-1-pyrroline-N-oxide.

The reaction of hypochlorous acid with the spin trap, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) was found to yield 5,5-dimethyl-2-pyrrolidone-N-oxyl (DMPOX). In addition to DMPOX, 5,5-dimethyl-2-hydroxypyrrolidine-N-oxyl (DMPO-OH) and an unidentified chlorine-containing radical species were also observed under neutral and near-neutral conditions. Through the use of [17O]HOCl and the hydroxyl radical scavengers ethanol and formate, it was established that DMPO-OH was derived from hydration of DMPO rather than the spin-trapping of hydroxyl radical. Furthermore, kinetic studies and the incorporation of 17O showed that DMPO-OH was readily oxidized to DMPOX and that this reaction was acid and base catalyzed. Under strongly alkaline conditions, DMPOX reversibly formed another species, presumably the enolate, that had a four-line ESR signal identical to that of DMPO-OH. Eventually, carbon-centered adducts appeared whose ESR signals were consistent with the formation of DMPO condensation products.

Buffers↗
PubMed1990

Stereoselective enhancement by (R)-HA-966 of the binding of [3H]CPP to the NMDA receptor complex.

The enantiomers of the strychnine-insensitive glycine antagonist, HA-966 (1-hydroxy-3-amino-pyrrolidone-2), stereoselectively enhance binding of the N-methyl-D-aspartate (NMDA) competitive antagonist, [3H]CPP (3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid) to rat brain synaptosomal membranes. The enhancement by the more potent (R)-HA-966 is competitively inhibited by the glycine antagonist 7-chlorokynurenic acid and noncompetitively by the polyamine spermine. Thus, (R)-HA-966, apparently at the glycine site, enhances the binding of antagonist to the NMDA receptor, possibly through a mechanism partially in common with that of spermine.

Animals↗
PubMed1990

Evidence for a functional coupling of the NMDA and glycine recognition sites in synaptic plasma membranes.

Activation of the N-methyl-D-aspartate (NMDA) receptor complex is subject to modulation via interactions at a coupled [3H]glycine recognition site in rat brain synaptic plasma membranes (SPM). We examined the effect of the potent and specific glycine site antagonists, 1-hydroxy-3-amino-2-pyrrolidone (HA-966) and 1-aminocyclobutane-1-carboxylate (ACBC), on the NMDA recognition site. These glycine analogs were found to significantly stimulate the binding of the competitive NMDA antagonist, [3H]3-(2-carboxypiperazin-4-y1)propyl-1-phosphonate ([3H]CPP) in a dose-dependent fashion, whereas both compounds inhibited NMDA-specific L-[3H]glutamate (agonist) binding. Additionally, both glycine antagonists reduced the binding of [3H]1-[1-(2-thienyl)cyclohexyl]piperidine ([3H]TCP) to SPM, a functional assessment of activation of the NMDA receptor-channel complex. The glycine site agonists, glycine and serine reversed these effects in a dose-dependent manner, with the serine reversal being stereospecific for D-serine. The relative potencies of these compounds in reversing the glycine antagonist effects on the NMDA recognition site corresponded with their ability to competitively displace strychnine-insensitive [3H]glycine binding. These results provide evidence for a functional coupling between the glycine and NMDA recognition sites and further, may provide a mechanism by which compounds interacting at the glycine recognition site may modulate NMDA receptor activity.

Amino Acids↗
PubMed1992

Modulation of [3H]3-((+-)-2-carboxypiperazin-4-yl)propyl-1-phosphonic acid ([3H]CPP) binding by ligands acting at the glycine and the polyamine sites of the rat brain NMDA receptor complex.

The competitive N-methyl-D-aspartate (NMDA) receptor antagonist [3H]3-((+-)-2-carboxypiperazin-4-yl)propyl-1-phosphonic acid ([3H]CPP) interacts with two discrete binding sites, one of high- and the other of low-affinity, on rat forebrain synaptic plasma membranes. The high affinity site exhibited a Kd of 101.5 nM and a Bmax of 2.01 pmol/mg, while for the low affinity site the Kd was 4.11 microM with a Bmax of 19.7 pmol/mg. The glycine site antagonists 3-amino-1-hydroxy-2-pyrrolidone (HA-966), 1-aminocyclobutanecarboxylic acid (ACBC), the glycine site agonist 1-aminocyclopropanecarboxylic acid (ACC) and glycine itself (as well as the polyamines spermine and spermidine), enhanced [3H]CPP binding. When subjected to saturation analysis, this enhancement was found primarily to involve an increase in the affinity of the high affinity component of [3H]CPP binding. Neither of the parameters of the low affinity component of binding were affected. Although a similar enhancement was observed with the polyamines, the effects of these two classes of ligands were additive, consistent with their having actions at different recognition sites on the NMDA receptor complex.

Amino Acids↗
PubMed1995

Lyophilized aqueous based polymer matrices for transdermal delivery of captopril.

Transdermal system(s) bearing captopril were developed using a low temperature casting method and aqueous based polymers viz., eudragit RL-100 and polyvinyl pyrrolidone (PVP). The developed system(s) were subjected to an in vitro characterization study. The results were compared with the transdermal systems of the same composition prepared at room temperature. The study revealed that the system(s) prepared using the low temperature casting method performed better in comparison to those prepared at room temperature. The developed system(s) followed zero order release kinetics.

Acrylic Resins↗