Biomedical subjects

A Urtti

Publications and source records attributed to A Urtti.

At least 37 records · Page 2Linked to original sources

PubMed1999

Influence of ionic strength on drug adsorption onto and release from a poly(acrylic acid) grafted poly(vinylidene fluoride) membrane.

Ion exchange resins have several applications in pharmacy for controlled or sustained release of drugs. In the present study, effects of the ionic strengths of adsorption medium and dissolution medium on drug adsorption onto and release from a acrylic acid grafted poly(vinylidene fluoride) (PAA-PVDF) were studied. Despite their porosity, PAA-PVDF membranes act reasonable well as cation exchange membranes. It was observed, that ionic strength of adsorption medium, degree of grafting and concentration of propranolol-HCl in adsorption medium affect propranolol-HCl adsorption onto the membrane. The fluxes of smaller molecules (MW < 500) across the membrane decreased with ionic strength of buffer solution, whereas the fluxes of the large molecules (FITC-dextran, MW 4400) increased with ionic strength. Release rate of adsorbed propranolol-HCl from the membrane into phosphate buffer was greatly affected by ionic strength of adsorption medium. These results can be explained by a cation exchange process between membrane and cations present in the buffer solution and swelling behavior of the grafted PAA chains.

Acrylates↗

PubMed1999

Interactions of polymeric and liposomal gene delivery systems with extracellular glycosaminoglycans: physicochemical and transfection studies.

Complexes of DNA with cationic lipids and cationic polymers are frequently used for gene transfer. Extracellular interactions of the complexes with anionic glycosaminoglycans (GAGs) may interfere with gene transfer. Interactions of GAGs with the carrier-DNA complexes were studied using tests for DNA relaxation (ethidium bromide intercalation), DNA release (electrophoresis), and transfection (pCMVbetaGal transfer into RAA smooth muscle cells). Several cationic lipid formulations (DOTAP, DOTAP/Chol, DOTAP/DOPE, DOTMA/DOPE, DOGS) and cationic polymers (fractured dendrimer, polyethylene imines 25 kDa and 800 kDa, polylysines 20 kDa and 200 kDa) were tested. Polycations condensed DNA more effectively than the monovalent lipids. Hyaluronic acid did not release or relax DNA in any complex, but it inhibited the transfection by some polyvalent systems (PEI, dendrimers, DOGS). Gene transfer by the other carriers was not affected by hyaluronic acid. Sulfated GAGs (heparan sulfate, chondroitin sulfates B and C) completely blocked transfection, except in the case of the liposomes with DOPE. Sulfated GAGs relaxed and released DNA from some complexes, but these events were not prerequisites for the inhibition of transfection. In conclusion, polyvalent delivery systems with endosomal buffering capacity (DOGS, PEI, dendrimer) were most sensitive to the inhibitory effects of GAGs on gene transfer, while fusogenic liposomes (with DOPE) were the most resistant systems.

Animals↗

PubMed1999

The single dose pharmacokinetics and safety of deramciclane in healthy male volunteers.

The pharmacokinetics and tolerability of a new putative non-benzodiazepine type anxiolytic compound deramciclane was studied in two consecutive studies. An open dose-escalation design was used to study doses from 0.2 to 50 mg in 18 healthy male volunteers. In the second study doses from 50 to 150 mg were investigated in 14 healthy males in a double-blind, placebo-controlled, dose escalation study. Deramciclane was rapidly absorbed from the GI-tract and T(max) was 2-4 h. The elimination half-life increased from about 20 h to about 32 h with the increasing dose. Nevertheless, the AUC(0-infinity) values increased linearly within the studies over the dose ranges of 3-50 and 50-150 mg. However, the increase was more than the ratio of the dose over the total dose range of 3-150 mg. Therefore, non-linear pharmacokinetics of deramciclane at high doses cannot be excluded. N-desmethyl deramciclane, which is the active metabolite of deramciclane, was determined in plasma. C(max) was reached at about 6 h. The AUC(0-48 h) for the N-desmethyl metabolite was about one third of the AUC(0-infinity) of the parent compound and the ratio remained constant at each dose level. Deramciclane was safe, and was well tolerated at each dose level.

Adult↗

PubMed1999

Liposome-skin interactions and their effects on the skin permeation of drugs.

The aim of the study was to evaluate the interaction of phospholipid liposomes with skin and stratum corneum lipid liposomes (SCLLs). The influence of phospholipid liposomes on the skin permeability of model drugs was also studied. The transdermal flux of the drugs applied in various phospholipid containing formulations through human epidermis was studied in diffusion chambers. Liposomes in water solutions did not enhance the skin permeability of the drugs, but when ethanol (32% w/v) was present in the donor with EPC (egg yolk lecithin), permeabilities of some model drugs were substantially increased. Confocal microscopy studies revealed that EPC do not penetrate into the skin from water solutions, while from ethanol solutions, EPC penetrates deeply into the stratum corneum. Also, resonance energy transfer between different liposome compositions and the release of calcein from SCLLs showed that interactions between phospholipid liposomes and SCLLs increased with increasing ethanol concentration in the liposome solutions.

Adrenergic beta-Antagonists↗

PubMed1999

Contrasting effects of alendronate and clodronate on RAW 264 macrophages: the role of a bisphosphonate metabolite.

Clodronate (dichloromethylidene-bisphosphonate), a halogen-containing bisphosphonate, can inhibit the release of cytokines from RAW 264 macrophages and has anti-inflammatory properties in rheumatoid arthritis, whilst amino-containing bisphosphonates such as alendronate (4-amino-1-hydroxybutylidene-bisphosphonate), have pro-inflammatory properties and can cause an acute phase response. The basis for these pharmacological properties is unclear. Recently, it was demonstrated that clodronate is metabolised by certain cell lines in vitro to an analogue of ATP, whereas amino-bisphosphonates are not. We therefore investigated whether clodronate can also be metabolised by RAW 264 macrophages and whether intracellular accumulation of the metabolite (AppCCl2p) could account for the anti-inflammatory properties of clodronate. The effect of alendronate and AppCCl2p on the release of cytokines (IL-1beta, IL-6, and TNFalpha) from RAW 264 cells was compared, and the effect of the bisphosphonates and AppCCl2p on the DNA binding activities of transcription factors, NF-kappaB and AP-1, was investigated. Pretreatment of RAW 264 macrophages with alendronate augmented the LPS-stimulated release of IL-1beta and increased the binding of NF-kappaB to DNA in an electrophoretic mobility shift assay. Without LPS-induction, alendronate did not affect cytokine release or NF-kappaB binding. Clodronate was metabolised by RAW 264 cells to AppCCl2p. Like clodronate, AppCCl2p inhibited the LPS-induced release of cytokines and NO from RAW 264 macrophages. Both clodronate and its metabolite also inhibited the LPS-stimulated binding of NF-kappaB to DNA. In conclusion, these results suggest that the metabolite of clodronate may be responsible for the anti-inflammatory properties of clodronate, and that the contrasting effects of different bisphosphonates on the release of cytokines could be mediated partly through changes in the DNA binding activity of NF-kappaB.

Alendronate↗

PubMed1999

Efficient adventitial gene delivery to rabbit carotid artery with cationic polymer-plasmid complexes.

Different lipids and cationic polymers were tested in vitro for their ability to transfect rabbit aortic smooth muscle cells and human endothelial cells with lacZ marker gene. Toxicity of the complexes was evaluated with MTT assay. Selected plasmid-polymer complexes with different charge ratios were then tested for in vivo gene transfer efficiency using adventitial gene transfer by placing a silastic gene delivery reservoir (collar) around the carotid artery. Transfection efficiency was determined by X-gal staining 3 days after the gene transfer. Based on in vitro experiments, fractured polyamidoamine dendrimers and polyethylenimines (PEI) were selected for in vivo experiments. Fractured dendrimers (generation 6, +/- charge ratio of 3) had the highest in vivo gene transfer efficiency (4.4% +/- 1.7). PEI with molecular size of 25 kDa (+/- charge ratio 4) was also effective (2.8% +/- 1.8) in this model. PEI of 800 kDa showed a constant but modest gene transfer efficiency (1.8% +/- 0.1) with all charge ratios. A low level gene transfer was also detected with naked DNA (0.5% +/- 0.3). No signs of inflammation were seen in any of the study groups. We show here that in vitro cell culture experiments can be used to identify efficient in vivo gene transfer methods for arterial gene therapy, but the charge ratios for each complex must be optimized in vivo. It is concluded that fractured dendrimer and PEI are efficient gene delivery vehicles and can be used for arterial gene therapy via adventitial gene delivery route.

Animals↗

PubMed1999

Pharmacokinetics and safety of deramciclane during multiple oral dosing.

UNLABELLED: Deramciclane is a new putative non-benzodiazepine-type anxiolytic compound. It is a selective serotonin 5-HT(2A) and 5-HT(2C) receptor antagonist and has also inverse agonist properties. The aim of this study was to reveal the pharmacokinetics and tolerability of deramciclane during repeated oral dosing in healthy male volunteers. SUBJECTS, MATERIAL AND METHODS: A randomized double-blind, placebo-controlled design was used. The study had three consecutive groups that received first a single oral dose of 10, 30 and 60 mg of deramciclane followed by twice a day administration for seven days. The total number of subjects was 28. The pharmacokinetic parameters were calculated for a single dose and after repeated administration. Tolerability was assessed by monitoring safety laboratory variables, electrocardiogram, heart rate, blood pressure and adverse events. RESULTS: The steady-state was reached during the seven-day administration. The pharmacokinetics of deramciclane was dose-proportional at steady-state at each dose level. Deramciclane accumulated about three-fold during repeated administration. The relative bioavailability of deramciclane increased about 1.4-fold compared to that of a single dose at each dose level. The mean elimination half-life of deramciclane for 10, 30 and 60 mg doses prolonged from 24.3, 20.9 and 22.9 h after a single dose to 30.5, 25.6 and 28.7 h at steady-state, respectively. Only few adverse events were reported, all mild and transient in nature. The most frequently reported adverse drug reactions were tiredness and headache. There were no deramciclane-induced changes in the clinical chemistry or hematology variables, blood pressure, heart rate or in electrocardiogram. CONCLUSIONS: In conclusion, the pharmacokinetics of deramciclane is linear over the dose range of 10 - 60 mg at steady-state. The slight non-linearity within the dose levels during repeated administration of seven days was regarded as clinically irrelevant. Deramciclane was safe and well tolerated up to doses of 60 mg b.i.d. for seven days.

Administration, Oral↗

PubMed1998

Roles of acid/base nature and molecular weight in drug release from matrices of gelfoam and monoisopropyl ester of poly(vinyl methyl ether-maleic anhydride).

Ophthalmic drug inserts are usually placed in the conjunctival sac. Being in contact with the conjunctiva, they may provide means to deliver large and hydrophilic molecules, such as peptides and oligonucleotides into the eye. We evaluated Gelfoam and monoisopropyl ester of poly(vinyl methyl ether/maleic anhydride) (PVM/MA) as potential polymers for ocular inserts. Matrices were solvent cast with model drugs that had different pKa, molecular weight and hydrophilicity. Drug release from the matrices as well as charge and swelling of Gelfoam(R)-matrix were studied. The release of drugs from PVM/MA-matrices was by erosion of the polymer matrix. The molecular weight and other variants of the releasing compound did not affect their release. In Gelfoam(R)-matrices the release was diffusion controlled and it was affected by the pH of the external solution as well as the charge and molecular weight of the studied compound.

Buffers↗

PubMed1998

Lipid fusion in oligonucleotide and gene delivery with cationic lipids.

Delivery of oligonucleotides and genes to their intracellular targets is a prerequisite for their successful use in medical therapy. Cationic liposomes are among the most commonly used and promising delivery systems for oligonucleotides and genes. Lipid fusion plays an important role in the cationic liposome-mediated delivery of these compounds. Fusion is involved in the complex formation between the nucleotides and the lipids, in the interactions between extracellular materials with the complexes, as well as in the intracellular trafficking of the delivery system and its load. Since lipid fusion is such a crucial factor in polynucleotide delivery, its controlled use is important for the success in oligonucleotide and DNA delivery. In this article we are reviewing the current knowledge on lipid fusion phenomena associated with the delivery of oligonucleotides and genes.

Journal Article↗

PubMed1998

Gradient high-performance liquid chromatographic analysis of enkephalin peptides, their metabolites, and enzyme inhibitors using combined ultraviolet and electrochemical detection II. Application to ocular permeability studies in vitro.

A gradient HPLC method with combined ultraviolet (UV) and electrochemical detection (ED) was used to study the ocular permeability of [D-Ala2]-methionine enkephalinamide (MEA) in vitro. Coulometric ED was selective for MEA and its tyrosine-containing metabolites with quantitation limits between 20 and 60 nM (1.0-3.0 pmol per 50-microl injection), whereas UV detection at 205 nm allowed the determination of several aromatic metabolites and enzyme inhibitors with quantitation limits between 40 and 500 nM (2.0-25.0 pmol). This method was capable of detecting permeability of MEA and metabolite formation in the cornea and conjunctiva in vitro. Furthermore, effects of aminopeptidase inhibitor bestatin and enkephalinase inhibitor SCH 39370 on permeation and metabolism of MEA could be determined.

Aminopeptidases↗

PubMed1998

Transport of drugs across porous ion exchange membranes.

Porous ion exchange membranes have potential applications for drug delivery systems. Permeability of these membranes can be controlled by environmental factors like pH and ionic strength but also the drug properties have an important role in the permeation process. In this paper the influence of the drug charge, lipophilicity and molecular weight on the diffusional drug flux is demonstrated. The membranes under study were poly(acrylic acid) (PAA) grafted porous poly(vinylidene fluoride) (PVDF) membranes which are cation selective due to the partial ionization of carboxyl groups in grafted PAA chains. At low pH the membrane pores are open and the drugs can diffuse through the membrane quite easily. However, at pH 7 the grafted chains partially block the pores and the diffusional flux of bigger drug molecules (Mw9400) decreases five orders of magnitude and also the flux of smaller molecules is clearly reduced. When the influence of the drug charge on the diffusion of the drugs across the membranes was studied, it turned out that the PAA-PVDF membranes facilitate the transport of cationic drugs and repel anionic ones. The presented mathematical model, based on Donnan drugs equilibrium and measured transport number data, predicted the observed trends reasonably well.

Biological Transport↗

PubMed1998

Pharmacokinetics of deramciclane in dogs after single oral and intravenous dosing and multiple oral dosing.

The pharmacokinetics of a new serotonin 5-HT2 antagonist, deramciclane, was studied. Single oral doses of 1, 3, 6 and 10 mg kg(-1) and intravenous doses of 1, 3 and 6 mg kg(-1) were administered in beagle dogs. Moreover, the steady state pharmacokinetics of 1, 3 and 6 mg kg(-1) doses were studied. Deramciclane was rapidly and completely absorbed from the gastrointestinal tract. Due to a moderate first-pass metabolism the absolute bioavailability was only 45-61%. Deramciclane had a large volume of distribution (32-37 L kg(-1)) because of its lipophilic nature. Deramciclane was extensively metabolized after intravenous injection and only trace amounts of intact drug is excreted in the urine. The total body clearance decreased (from 32 to 17 L h(-1)) as the dose increased. It is suggested that the metabolic capacity was not sufficient to eliminate deramciclane in a linear manner with increasing dose. Therefore, deramciclane exhibited nonlinear pharmacokinetics as the AUC(0-infinity) increased disproportionally to the dose after both intravenous and oral dosing. Formation of the active metabolite, N-desmethyl deramciclane, was also nonlinear (p = 0.0002). At steady state deramciclane accumulated less than 2-fold during repeated administration.

Administration, Oral↗

PubMed1998

Effect of the CB1 receptor antagonist, SR141716A, on cannabinoid-induced ocular hypotension in normotensive rabbits.

The present study attempts to indirectly determine if a neuronal cannabinoid (CB1) receptor mediates the intraocular pressure (IOP) reduction effects of arachidonoyl ethanolamide (AEA), its R-alpha-isopropyl analog, and the non-classical cannabinoid, CP-55,940. A series of these cannabinoids were dissolved in an aqueous 10-20% 2-hydroxypropyl-beta-cyclodextrin (2-HP-beta-CD) solution (containing 3% polyvinyl alcohol) and administered (25-62.5 microg) unilaterally to normotensive rabbit eyes. This was repeated on animals pre-treated with a subcutaneous injection (2.5 mg/kg) of the highly specific CB1 receptor antagonist, SR 141716A, dissolved in an aqueous 42% 2-HP-beta-CD solution. AEA, its R-alpha-isopropyl analog, and CP-55,940 reduced IOP upon topical application to a greater degree than was detected in the untreated eye. This reduction was eliminated for the latter two compounds by subcutaneous (s.c.) pretreatment of the rabbits with the CB1 receptor antagonist, but the IOP properties of AEA remained unchanged. SR 141716A administered alone (s.c.), elevated the IOP of both eyes. A CB1 receptor seems involved in the IOP reduction induced by either R-alpha-isopropyl anandamide or CP-55,940. However, AEA apparently functions through a different mechanism.

Animals↗

PubMed1998

Different effects of pH on the permeation of pilocarpine and pilocarpine prodrugs across the isolated rabbit cornea.

Ocular absorption of pilocarpine and many other ophthalmic drugs can be improved by prodrug derivatization. For stability and solubility reasons basic prodrugs must be formulated at acidic pH, which may affect the corneal drug permeability. We studied the effects of pH on in vitro permeation of pilocarpine, pilocarpic acid benzyl diester prodrugs [O-propionyl (I) and O-valeryl (II)] and O,O'-(1, 4-xylylene) bispilocarpic acid diester prodrugs [O,O'-diacetyl (III), O,O'-dipropionyl (IV) and O,O'-divaleryl (V)] through albino rabbit cornea. Reversed-phase high-performance liquid chromatography was used to assay pilocarpine and its prodrugs. The permeability coefficient for pilocarpine decreased more than three times, from 2. 8x10-6 cm/s to 0.9x10-6 cm/s, when the pH was decreased from 7.65 to 5.5. At pH 7.65 permeability of pilocarpine improved several fold with delivery as prodrugs. Acidic pH (5.5, 6.0) affected to a different extent the corneal permeability of pilocarpine given as prodrugs. Consequently, the rank order of the corneal permeabilities among the compounds was different at various pH values. The effect of pH was greatest (an order of magnitude) for prodrugs with intermediate lipophilicity (I, III, IV), while pH had only minor or no effect on permeability of the most lipophilic prodrugs (II, V). In conclusion, the effect of pH on pilocarpine delivery as prodrug is dependent on prodrug structure and the advantage gained with prodrugs relative to pilocarpine is dependent on formulation pH.

Animals↗

PubMed1998

Evaluation of cytotoxicity of various ophthalmic drugs, eye drop excipients and cyclodextrins in an immortalized human corneal epithelial cell line.

PURPOSE: An immortalized human corneal epithelial cell line (HCE) was tested as a screening tool for prediction of topical ocular irritation/toxicity by pharmaceuticals METHODS: Effects of various drugs, excipients and cyclodextrins (CDs) on viability of HCE cells were evaluated using two in vitro cytotoxicity tests, 3-(4,5-dimethlthiazol-2-yl)-205-diphenyl tetrazolium bromide (MTT) dye reduction assay and propidium iodide assay. RESULTS: Mitochondrion-based MTT test was a more sensitive indicator of cytotoxicity than the plasma membrane-based propidium iodide test. The tests revealed following cytotoxic rankings for ophthalmic drugs: dipivefrin > timolol > pilocarpine approximately equal to dexamethasone; for excipients: benzalkonium chloride (BAC) > sodium edetate (NA2 EDTA)>polyvinyl alcohol (PVA) > methylparaben; and for CDs :alpha- CD > dimethyl beta-cyclodextrin (DM-beta-CD) > sulfobutyl ether beta-cyclodextrin ((SBE)7m-beta-CD approximately equal to hydroxypropyl-beta-cyclodextrin (HP-beta-CD) > lambda CD. In consideration of the in vivo clinical situation, the short exposure time (5 min) is more relevant even though toxic effects of some test substances were seen only after longer exposure time (30 and 60 min). CONCLUSIONS: Immortalized HCE cells are a promising tool for rapid cytotoxicity assays of ocular medications. The cell line is potentially useful in predicting the in vivo coreal toxicity of ocularly applied compounds.

Cell Line, Transformed↗

PubMed1998

Different absorption profiles of deramciclane in man and in dog.

We have studied the dog model for predicting the oral absorption of deramciclane, a novel anxiolytic compound, as a model acid-labile drug. The absorption profile of deramciclane was studied in man and beagle dogs after administration of conventional capsules and enteric coated tablets. Absorption in dogs pretreated with pentagastrin or saline was also studied after administration of conventional capsules. The in-vitro stability of deramciclane was determined over the pH range 1.2-6.0. The rate of degradation of deramciclane increased ten-fold as the pH was reduced from 2.1 to 1.2 (t 1/2 beta (elimination half-life) 9 h and 39 min, respectively). Deramciclane was stable at pH > or = 3. The two formulations were bioequivalent in dogs and there were no significant differences between pharmacokinetic parameters measured for dogs pretreated with pentagastrin or saline. In man the mean relative bioavailability and Cmax (peak plasma concentration) for the conventional capsules were approximately 75% and 83% of those for the enteric coated tablets (P = 0.0004 and P = 0.0031, respectively). This was probably because of degradation of deramciclane at lower pH of man's stomach compared with that of the dog. Pentagastrin was probably unsuccessful in reducing gastric pH and thus no change in absorption was observed. It is concluded that the absorption of deramciclane, and possibly other acid-labile drugs, cannot be predicted by use of the dog model.

Absorption↗

PubMed1997

Inhibitory properties of double-helix-forming circular oligonucleotides.

Several circular oligonucleotides were synthesized and characterized by electrospray ionization mass spectrometry. Experiments on termination of primer extension catalysed by DNA polymerases, Klenow fragment and Tth have demonstrated that a double helix forming circular 2'-deoxyribooligomer containing a 25mer sequence complementary to the target single-stranded DNA along with a 34mer random mismatching stretch appears to be a potent inhibitor of replication in vitro. Studies on inhibition of luciferase gene expression in a cell-free transcription-translation system have shown that a duplex forming circular 2'-deoxyribooligonucleotide containing a 25mer sequence complementary to the target mRNA and a 14mer random mismatching stretch can serve as an effective antisense compound as a standard linear complementary oligomer. Features of double helix forming circular oligonucleotides composed of 2'-deoxyribonucleosides seem to be useful for the design of new antigene and antisense agents.

Base Sequence↗

PubMed1997

Effects of topical alpha-substituted anandamides on intraocular pressure in normotensive rabbits.

PURPOSE: Anandamides have been observed to lower intraocular pressure in the rabbit eye, preceded by a period of hypertension. Amidases are thought to catabolize these compounds into their component parts, including arachidonic acid. Direct application of arachidonic acid has been observed to cause a marked rise of intraocular pressure. Thus, anandamide analogs resistant to catabolism were thought possibly devoid of this initial hypertension, and their effects on rabbit IOP investigated. METHODS: A series of chiral alpha-substituted anandamides were synthesized and studied for their effect on the intraocular pressure (IOP) of normotensive pigmented rabbits. Each test compound was dissolved in an aqueous 2-hydroxypropyl-beta-cyclodextrin solution (containing 3% polyvinyl alcohol) and administered (62.5 micrograms) unilaterally to the eye. RESULTS: The most promising compounds caused a statistically significant reduction of IOP (vs. vehicle) in the treated eyes. Of these, the R-alpha-isopropyl compound exhibited the best activity tested. Unlike the alpha-unsubstituted analogs previously studied, hypotensive effects were not preceded by an initial elevation of IOP and indomethacin pre-treatment (12.5 mg, s.c.) did not eliminate the IOP response, as demonstrated by administered R-alpha-isopropyl anandamide. CONCLUSIONS: Catabolism of alpha-unsubstituted anandamides may account for their observed intraocular hypertensive effects. The physiological mechanism by which alpha-substituted anandamides work apparently differs from that of the more easily metabolized alpha-unsubstituted compounds.

Animals↗