1.
Ackermann, Paul, et al.
(författare)
An opioid system in connective tissue : A study of Achilles tendon in the rat
2001
Ingår i: Journal of Histochemistry and Cytochemistry. - : SAGE Publications. - 0022-1554 .- 1551-5044. ; 49:11, s. 1387-1395
Tidskriftsartikel (refereegranskat) abstract
The occurrence of endogenous opioids and their receptors in rat achilles tendon was analyzed by immunohistochemistry (IHC), radioimmunoassay (RIA), and in vitro binding assays. The investigation focused on four enkephalins, dynorphin B, and nociceptin/orphanin FQ. Nerve fibers immunoreactive to all enkephalins (Met-enkephalin, Leu-enkephalin, Met-enkephalin-Arg-Gly-Lys, Met-enkephalin-Arg-Phe) were consistently found in the loose connective tissue and the paratenon, whereas dynorphin B and nociceptin/orphanin FQ could not be detected. The majority of enkephalin-positive nerve fibers exhibited varicosities predominantly seen in blood vessel walls. Measurable levels of Met-enkephalin-Arg-Phe and nociceptin/orphanin FQ were found in tendon tissue using RIA, whereas dynorphin B could not be detected. In addition to the endogenous opioids identified, delta -opioid receptors on nerve fibers were also detected by IHC. Binding assays to characterize the opioid binding sites showed that they were specific and saturable for [H-3]-naloxone (K-d 7.01 +/- 0.98 nM; B-max 23.52 +/- 2.23 fmol/mg protein). Our study demonstrates the occurrence of an opioid system in rat achilles tendon, which may be assumed to be present also in other connective tissues of the locomotor apparatus. This system may prove to be a useful target for pharmacological therapy in painful and inflammatory conditions by new drugs acting selectively in the periphery.
2.
Alterman, Mathias, et al.
(författare)
P1/P1' modified HIV protease inhibitors as tools in two new sensitive surface plasmon resonance biosensor screening assays
2001
Ingår i: European Journal of Pharmaceutical Sciences. - : Elsevier. - 0928-0987 .- 1879-0720. ; 13:2, s. 203-212
Tidskriftsartikel (refereegranskat) abstract
The commonly used HIV-1 protease assays rely on measurements of the effect of inhibitions on the hydrolysis rate of synthetic peptides. Recently an assay based on surface plasmon resonance (SPR) was introduced. We have taken advantage of the fact that the SPR signal is proportional to the mass of the analyte interacting with the immobilised molecule and developed two new improved efficient competition assay methods. Thus, high molecular weight binders were used as amplifiers of the surface plasmon resonance signal. Linkers were attached by a Heck reaction to the para-positions of the P1/P1′ benzyloxy groups of a linear C2-symmetric C-terminal duplicated inhibitor to enable (a) biotin labelling or (b) direct immobilisation of the inhibitor to the biosensor surface matrix. The interaction properties of a series of 17 structurally diverse inhibitors was assessed and compared to previously reported data. The most sensitive assay was obtained by immobilising the enzyme and amplifying the signal with an antibody, giving a detection range between 0.1 nM and 10 μM. Immobilisation of the inhibitor resulted in a stable and durable surface but a narrower detection range (1–100 nM). The two competition assays are anticipated to be very suitable for fast screening of potential HIV inhibitors.
3.
Azarbayjani, Faranak
(författare)
Common mechanism for teratogenicity of antiepileptic drugs : Drug-induced embryonic arrhythmia and hypoxia-reoxygenation damage
2001
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
The Antiepilptic drugs (AEDs) phenytoin (PHT), carbamazepine (CBZ), phenobarbital (PB), tri- and dimethadione (TMD and DMD) are known teratogens having a common malformation pattern in human and animal studies. This thesis was designed chiefly to test a hypothesis correlating the teratogenicity of these AEDs to episodes of pharmacologically induced embryonic arrhythmia and hypoxia-reoxygenation damage.Effects on the embryonic heart were studied both after maternal administration in mice and inmouse embryos cultured in vitro. Only AEDs, correlated with the same type of malformation as could be induced by episodes of interrupted oxygen supply to the embryo (e.g. cleft palate) caused concentration dependent bradycardia and arrhythmia. PHT and DMD had the highest potential and affected embryonic heart at clinically relevant concentration, followed by CBZ, TMD and PB. Valproate and vigabatrin not associated with hypoxia-related malformations caused neither arrhythmia nor severe bradycardia.The results showed that the embryonic heart is extremely susceptible to PHT and DMD onlyduring a restricted period of development, between gestational days 9-13 (weeks 5-9 of human pregnancy).An observed genetic susceptibility to react with arrhythmia at low concentrations when exposed to PHT or to external stress, could explain why A/J strain of mice is more susceptible to develop cleft palate compared to other strains. High activities of reactive oxygen species (ROS) capturing antioxidant enzymes observed in untreated A/J embryos supported this assumption. The potential to cause embryonic arrythmia by an AED was related to the potential to inhibit the rapid component of the delayed rectifier potassium channel (I kr ).A marked I kr blocking activity (70%)of DMD in voltage clamping studies was observed. The I kr inhibition occurred at similar concentrations, which causes severe arrhythmia.The idea of a relation between teratogenicity and arrhythmia, resulting in ischemia followed by reperfusion and generation of ROS was supported by mechanistic studies. Pre-treatment with the spin-trapping agent PBN, which has the capacity to capture ROS, markedly reduced the incidence of PHT and DMD-induced cleft palate. In utero exposure to teratogenic doses of DMD and PHT resulted in hemorrhages in the embryonic palatal region. The same type of haemorrhage in the palatal region precedes orofacial clefts induced by episodic hypoxia.
4.
Bouw, M. René, et al.
(författare)
Blood-brain barrier transport and brain distribution of morphine-6-glucuronide in relation to the antinociceptive effect in rats : pharmacokinetic/pharmacodynamic modelling
2001
Ingår i: British Journal of Pharmacology. - : The British Pharmacological Society. - 0007-1188 .- 1476-5381. ; 134:8, s. 1796-1804
Tidskriftsartikel (refereegranskat) abstract
1. The objective of this study was to investigate the contribution of the blood-brain barrier (BBB) transport to the delay in antinociceptive effect of morphine-6-glucuronide (M6G), and to study the equilibration of M6G in vivo across the BBB with microdialysis measuring unbound concentrations. 2. On two consecutive days, rats received an exponential infusion of M6G for 4 h aiming at a target concentration of 3000 ng ml(-1) (6.5 microM) in blood. Concentrations of unbound M6G were determined in brain extracellular fluid (ECF) and venous blood using microdialysis and in arterial blood by regular sampling. MD probes were calibrated in vivo using retrodialysis by drug prior to drug administration. 3. The half-life of M6G was 23+/-5 min in arterial blood, 26+/-10 min in venous blood and 58+/-17 min in brain ECF (P<0.05; brain vs blood). The BBB equilibration, expressed as the unbound steady-state concentration ratio, was 0.22+/-0.09, indicating active efflux in the BBB transport of M6G. A two-compartment model best described the brain distribution of M6G. The unbound volume of distribution was 0.20+/-0.02 ml g brain(-1). The concentration-antinociceptive effect relationships exhibited a clear hysteresis, resulting in an effect delay half-life of 103 min in relation to blood concentrations and a remaining effect delay half-life of 53 min in relation to brain ECF concentrations. 4. Half the effect delay of M6G can be explained by transport across the BBB, suggesting that the remaining effect delay of 53 min is a result of drug distribution within the brain tissue or rate-limiting mechanisms at the receptor level.
5.
Broussalis, Adriana M., et al.
(författare)
First cyclotide from Hybanthus (Violaceae)
2001
Ingår i: Phytochemistry. - : Elsevier. - 0031-9422 .- 1873-3700. ; 58:1, s. 47-51
Tidskriftsartikel (refereegranskat) abstract
Hypa A, a novel macrocyclic polypeptide containing 30 amino acid residues, has been isolated from the n-butanol extract of the Argentine plant Hybanthus parviflorus. The sequence, cyclo-(SCVYIPCTITALLGCSCKNKVCYNGIPCAE), was determined by automated Edman degradation, quantitative amino acid analysis and nanospray MS/MS2. Three intramolecular disulfide bridges stabilize the cyclic peptide backbone of hypa A. Using these structural features to classify the peptide as a cyclotide, we extended the distribution of that substance class to a new genus, and now propose a uniform nomenclature for cyclotides.
6.
7.
El-Seedi, Hesham R, et al.
(författare)
Ecologically active 2-octanoylcyclohexane-1,3-dione from Philodendron guttiferum
2001
Ingår i: Journal of Chemical Ecology. - 0098-0331 .- 1573-1561. ; 27:3, s. 517-521
Tidskriftsartikel (refereegranskat) abstract
The novel naturally occurring 2-octanoylcyclohexane-1,3-dione 1 was isolated in its enol form from P. guttiferum (Araceae). Its chemical ecological relevance is discussed. There was mass spectral evidence for the presence of small amounts of the homologous 2-decanoyl and 2-dodecanoyl derivatives.
8.
9.
Gordi, Toufigh
(författare)
Clinical Pharmacokinetics of the Antimalarial Artemisinin Based on Saliva Sampling
2001
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
Artemisinin is the parent compound of a novel family of antimalarials. Repetitive administrations of artemisinin to both healthy volunteers and malaria patients have been shown to result in decreased plasma concentrations of the compound, most probably due to an autoinduction of different CYP450 enzymes. The aim of this thesis was to investigate the clinical pharmacokinetics and efficacy of different dosage regimens of the drug, and study the kinetics of the enzyme induction. Moreover, the putative interaction of the compound with blood components was investigated in vitro. Artemisinin was found to distribute into red blood cells, competing with oxygen for binding to hemoglobin. The compound was stable in plasma and, in contrast to previous reports, did not bind to red blood cell membranes. To circumvent the logistical and ethical problems associated with plasma sampling, suitability of saliva as substitute was investigated. Moreover, due to the large number of collected samples, an HPLC method, enabling a direct injection of saliva and plasma samples, was developed. Saliva artemisinin concentrations were found to correlate with its unbound plasma levels, making saliva a suitable body fluid for pharmacokinetic studies of the compound. Based on saliva samples, artemisinin was shown to exhibit a dose-dependent kinetics and efficacy in malaria patients, with a possible sex-effect on the metabolism of the compound during the first treatment day. Moreover, the time-dependent kinetics of the compound was observed in both malaria patients and healthy subjects. A physiological approach was utilized to model the autoinduction in the latter group. A model with a feedback mechanism of enzymes was able to describe the data, with estimations of the half-lives of induction (3.15 hrs) and elimination of enzymes (32.9 hrs), as well as pharmacokinetic parameters of artemisinin. In conclusion, artemisinin was found to exhibit a fast induction of enzymes, with time- and dose-dependent drug kinetics and dose-dependent antimalarial efficacy.
10.
Graffner-Nordberg, Malin, et al.
(författare)
Design, Synthesis, Computational Prediction and Biological Evaluation of Ester Soft Drugs as Inhibitors of Dihydrofolate Reductase from Pneumocystis Carinii
2001
Ingår i: Journal of Medicinal Chemistry. - : American Chemical Society (ACS). - 0022-2623 .- 1520-4804. ; 44:15, s. 2391-2402
Tidskriftsartikel (refereegranskat) abstract
A series of lipophilic soft drugs structurally related to the nonclassical dihydrofolate reductase (DHFR) inhibitors trimetrexate and piritrexim have been designed, synthesized, and evaluated in DHFR assays, with special emphasis on the inhibition of P. carinii DHFR. The best inhibitors, encompassing an ester bond in the bridge connecting the two aromatic systems, were approximately 10 times less potent than trimetrexate and piritrexim. The metabolites were designed to be poor inhibitors. Furthermore, molecular dynamics simulations of three ligands in complex with DHFR from Pneumocystis carinii and from the human enzyme were conducted in order to better understand the factors determining the selectivity. A correct ranking of the relative inhibition of DHFR was achieved utilizing the linear interaction energy method. The soft drugs are intended for local administration. One representative ester was selected for a pharmacokinetic study in rats where it was found to undergo fast metabolic degradation to the predicted inactive metabolites.
