bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of an Allosteric Ternary Complex Model to the Technique of Pharmacological Resultant Analysis
Authors: Christopoulos Arthur , Mitchelson Fred
Published: April 2011

A simple ternary complex model of drug-receptor interaction has been used to extend the procedure of pharmacological resultant analysis, enabling the quantitation of interactions between allosteric modulators and orthosteric antagonists.

Equations derived in the theoretical treatment were used to analyse functional data for the interaction between the allosteric modulator gallamine and the orthosteric antagonist scopolamine, with oxotremorine as the agonist, at rat tracheal muscarinic acetylcholine receptors. Quantitative estimates of the affinity of gallamine for the allosteric site (pKZ = 4.7) and the extent of negative, heterotropic co-operativity between gallamine and scopolamine (α′ = 13.1) were obtained. Furthermore, an alternative direct, model-fitting approach, that does not rely on the determination of concentration ratios, was also developed, and yielded similar results.

It is suggested that the approach presented in this paper is useful for quantifying interactions between orthosteric antagonists and allosteric modulators, particularly when the extent of co-operativity is low or the modulators possess multiple pharmacological properties, or both.
Degradation Pathways of Ampicillin in Alkaline Solutions
Authors: Robinson-Fuentes V A , Jefferies T M , Branch S K
Published: April 2011

Ampicillin trihydrate, sodium salt, in aqueous solution has a pH of about 8. No complete degradation pathway has been proposed to explain the degradation of ampicillin under alkaline conditions and the information available explains the formation of only certain products. The present work was carried out with the aim of providing this information.

The formation of degradation products of ampicillin trihydrate, sodium salt, produced in aqueous solutions (pH 12 and 37°C) have been studied as an accelerated form of the possible degradation that may occur in aqueous solutions at pH 8. Some of the degradation products formed under these conditions were then obtained either by synthesis or by degradation of ampicillin sodium followed by isolation using semi-preparative HPLC. These compounds were characterized by 1H NMR spectroscopy.

The information obtained from the experiments by HPLC and NMR spectroscopy made it possible to propose a degradation pathway for ampicillin under the conditions described above. 5R-penicilloic acid is the first degradation product of ampicillin and subsequently undergoes epimerization at C-5 to form the 55 isomer via the imine tautomer. Mechanisms for the formation of compounds previously believed to form only under acidic conditions are proposed, i.e. ampicillin penilloic acid and 2-hydroxy-3-phenylpyrazine. The formation of ampicillin polymers was detected in dilute solutions (1% w/v) within a few hours of dissolution. The presence of ampicillin penicillenic acid and ampicillin penamaldic acid was detected by 1H NMR and their main spectroscopic features determined.
Effects of Thyrotrophin-releasing Hormone Tartrate and its Sustained Release Formulation on Cerebral Glucose Metabolism in Aged Rats
Authors: Nakayama Takahiro , Nagai Yasuo
Published: April 2011

The effects of a sustained release formulation of thyrotrophin-releasing hormone (TRH) over two weeks (TRH-SR, 10 or 50 mg kg− equivalent to 0.56 or 2.80 mg kg− free TRH, respectively) and repeated treatment with TRH tartrate (TRH-T, 0.3, 1.0 or 3.0 mg kg−, equivalent to 0.2, 0.7 or 2.0 mg kg− free TRH, respectively) on the rate of local cerebral glucose utilization (LCGU) were investigated using the quantitative autoradiographic 2-deoxy-[14C]d-glucose method in various brain regions of aged rats.

In aged rats (28 months old), the LCGU was significantly reduced as compared with young adult rats (3 months old), while treatment with TRH-SR ameliorated the reduction of the LCGU in a dose-dependent manner. The brain regions ameliorated by TRH-SR were the auditory cortex, septal nucleus, substantia nigra, cerebellar cortex and cerebellar nucleus. In contrast, once-daily repeated treatment over one week with TRH-T at a dose of 0.3 mg kg− (equivalent to 50 mg kg− of TRH-SR) had no effect on the reduced LCGU in various brain regions in aged rats (27 months old), whereas treatment with a higher dose of TRH-T (0.7 or 2.0 mg kg− free TRH) significantly ameliorated the reduction.

The comparison of the ameliorating potencies between TRH-T and TRH-SR indicated that TRH-SR had a potency about 7 times greater than TRH-T.
Nitric Oxide is a Regulator of Bone Remodelling
Authors: Chae Han-Jung , Park Rae-Kil , Chung Hun-Taeg , Kang Jang-Sook , Kim Myung-Sun , Choi Du-Young , Bang Byung-Gwan , Kim Hyung-Ryong
Published: April 2011

Nitric oxide (NO) is known to be implicated in the metabolism of bone, especially as a mediator of cytokine effects on the remodelling of bone tissue. In this study we examine whether NO affects the osteoblast activation or the osteoclast differentiation of primary mouse osteoblast-like and osteosarcoma ROS 17/2.8 cell lines.

Primary osteoblast and ROS 17/2.8 cells released NO upon stimulation of interleukin-1β, tumour necrosis factor-α, and interferon-γ. Sodium nitroprusside, a donor of nitric oxide, increased the activity of alkaline phosphatase in ROS 17/2.8 cells as well as the number of calcified nodule formations in primary mouse osteoblast-like cells. Sodium nitroprusside also completely inhibited 1α,25-(OH)2D3-induced osteoclast generation in a high concentration (100 μm). However, a low concentration of sodium nitroprusside (3–30 μm) significantly increased the generation of osteoclasts.

These results indicated that NO appears to be an important regulatory molecule in the processes of bone formation and resorption. Hence, NO may be involved in the pathogenesis of bone loss in diseases associated with cytokine activation, such as periodontal disease and rheumatoid arthritis.
Evidence for α2-Adrenoceptor Agonist Activity of Minoxidil
Authors: Sharma Nitin , Mehta Anita A , Santani Dev D , Goyal Ramesh K
Published: April 2011

The present investigation was undertaken to study the mechanism of action of minoxidil using various smooth muscle preparations.

Minoxidil (4.7 × 10−6 m to 4.7 × 10−4 m) produced a concentration-dependent inhibition of field stimulation-evoked responses in rat anococcygeus muscle and vas deferens. The inhibition produced by minoxidil was antagonized by yohimbine (2.5 × 10−7 m). Minoxidil (1.4 × 10−5 m to 4.7 × 10−4 m) also produced a concentration-dependent relaxation in oestrogen-primed potassium chloride-depolarized rat uterus. These responses were blocked not only by yohimbine but also by glibenclamide (202 × 10−8 m).

Our results suggest that minoxidil possesses α2-adrenoceptor agonist activity in addition to potassium-channel-opening activity.
Antioxidant Activity of Guaiazulene and Protection Against Paracetamol Hepatotoxicity in Rats
Authors: Kourounakis Angeliki P , Rekka Eleni A , Kourounakis Panos N
Published: April 2011

The effect of guaiazulene, a lipophilic azulene derivative widely found in nature, on radical-mediated processes is examined. The ability of guaiazulene to inhibit rat hepatic microsomal membrane lipid peroxidation and to scavenge hydroxyl radicals, as well as to interact with 1,1-diphenyl-2-picrylhydrazyl radical (DPPH), was estimated.

It was found that guaiazulene can inhibit lipid peroxidation very significantly, having an IC50 value of 9.8 μm. It can also scavenge hydroxyl radicals and interact with DPPH. The protection afforded by guaiazulene to rats with paracetamol-induced liver injury was also investigated. Paracetamol hepatotoxicity is caused by the reactive metabolite N-acetyl-p-benzoquinone imine (NAPQI), which causes oxidative stress and glutathione (GSH) depletion. Hepatic cytosolic protein, GSH, glutathione transferase and glutathione reductase levels are determined as indices of hepatic injury with or without the administration of guaiazulene. It was found that all parameters affected by paracetamol are restored to normal by guaiazulene treatment, while the administration of guaiazulene alone has no effect on the performed tests compared with the control values.

It was concluded that the significant protection against paracetamol-induced GSH depletion and hepatic damage afforded by guaiazulene is probably connected with its antioxidant activity. A molecular mechanism of action of guaiazulene is suggested.
Fluorimetric Studies of the Formation of Riboflavin-β-Cyclodextrin Inclusion Complex: Determination of the Stability Constant by use of a Non-linear Least-squares Model
Authors: Loukas Yannis L , Vraka Vassiliki , Gregoriadis Gregory
Published: April 2011

The non-linear least-squares model for calculation of the stability constant (Kst) of a drug-cyclodextrin complex has been used in fluorimetry studies.

Complexation of riboflavin with β-cyclodextrin (β-CyD) was monitored fluorimetrically by measuring changes in the fluorescence intensity of the vitamin in the presence of various amounts of β-CyD. Formation of an inclusion complex was confirmed in the solid state by differential scanning calorimetry (DSC) and in aqueous solution by proton nuclear magnetic resonance spectroscopy (1H NMR).

The experimental Kst value (2112 M−1) derived from the fluorimetry studies appeared to fit well to a 1:1 drug-to-cyclodextrin molar ratio according to the non-linear mathematical model. The model is particularly suitable for fluorescent compounds of which fluorescence intensity is influenced by the presence of cyclodextrins.
Ocular Membrane Permeability of Hydrophilic Drugs for Ocular Peptide Delivery
Authors: Sasaki Hitoshi , Ichikawa Masataka , Yamamura Kenzo , Nishida Koyo , Nakamura Junzo
Published: April 2011

The purpose of this study is to investigate the ocular membrane permeability and the permeation mechanism of hydrophilic drugs such as thyrotropin-releasing hormone (TRH), p-nitrophenyl β-cellopentaoside (PNP) and luteinizing hormone-releasing hormone (LHRH).

The penetration of hydrophilic drugs was measured across the isolated corneal and conjunctival membranes of albino rabbits using a two-chamber diffusion glass cell. The corneal permeabilities of hydrophilic drugs were much lower than those of beta blockers reported previously. The corneal penetration of TRH was the highest among the hydrophilic drugs studied. Scraping the corneal epithelium increased the penetration of hydrophilic drugs. Conjunctival membranes showed higher permeability to hydrophilic drugs compared with corneal membranes. The permeability of drugs was also analysed by Fick's equation. The partition parameter and diffusion parameter of TRH, PNP and LHRH in the cornea were lower than those in scraped cornea and conjunctiva. In addition to the data of fluorescein isothiocyanate-dextran reported previously, the permeability coefficient of hydrophilic drugs through the cornea, scraped cornea and conjunctiva correlated with molecular weight of the drugs. The diffusion parameters of hydrophilic drugs decreased with an increase of molecular weight for all ocular membranes. The extent of dependency of partition parameters on the molecular weights of drugs varied according to the ocular membrane. These results indicate that ocular membranes are sufficiently different in permeation character and mechanism to control the extent and pathway for ocular absorption of hydrophilic drugs.
In-situ Ocular Absorption of Ophthalmic β-Blockers through Ocular Membranes in Albino Rabbits
Authors: Sasaki Hitoshi , Ichikawa Masataka , Kawakami Shigeru , Yamamura Kenzo , Mukai Takahiro , Nishida Koyo , Nakamura Junzo
Published: April 2011

Ocular membranes have been characterized by in-situ absorption of the ophthalmic β-blockers carteolol (hydrophilic) and timolol and befunolol (lipophilic) using a cylindrical cell.

After introduction of drug solution into the cell on the cornea, sclera (bulbar conjunctival and scleral layer) or palpebral conjunctiva, the disappearance of the drug from the cell was determined as in-situ absorption. The ophthalmic drugs disappeared from the conjunctival and scleral membranes although disappearance from the cornea was hardly observed. The conjunctival membrane showed the highest permeability.

Lipophilic drugs were more permeable than hydrophilic. In-situ apparent permeability coefficients of the ophthalmic drugs through the conjunctiva and sclera correlated with the lipophilicity of drugs. A high drug concentration in the aqueous humor was observed after corneal application. There is a relationship between concentrations of drugs in the aqueous humor and previously reported in-vitro apparent permeability coefficients of the drugs in the cornea.

This in-situ method using a cylindrical cell is a useful method of investigating the ocular absorption of ophthalmic drugs.
Degradation of Insulin and Calcitonin and Their Protection by Various Protease Inhibitors in Rat Caecal Contents: Implications in Peptide Delivery to the Colon
Authors: Tozaki Hideyuki , Emi Yasuharu , Horisaka Eri , Fujita Takuya , Yamamoto Akira , Muranishi Shozo
Published: April 2011

The objective of this study was to examine the metabolism of insulin and calcitonin, and their protection by various protease inhibitors, in the large intestine.

Fresh caecal contents were prepared from non-fasted rats and the degradation of insulin and calcitonin was studied in a suspension of rat caecal contents, as a model of the content of the large intestine. Both insulin and calcitonin were metabolized in suspensions of rat caecal contents, but the degradation of calcitonin was much faster than that of insulin. The degradation of insulin was fastest at pH 6.8. Protease inhibitors such as camostat and aprotinin inhibited the degradation of insulin and calcitonin in rat caecal contents, which was consistent with the high chymotrypsin activity of these contents.

These findings suggest that care should be taken when administering peptide drugs to the large intestine for colon-specific drug delivery because they can be degraded in rat caecal contents. Protease inhibitors might be useful for increasing the stability of these peptides in the large intestine, thereby improving their large-intestinal absorption to the systemic circulation.
Low-dose Pulse Methotrexate Inhibits Articular Destruction of Adjuvant Arthritis in Rats
Authors: Kawai Shinichi , Nagai Kasumi , Nishida Shinichi , Sakyo Katsufumi , Murai Etsuko , Mizushima Yutaka
Published: April 2011

The purpose of this study was to determine whether low-dose methotrexate pulse therapy, which had recently become important in the treatment of rheumatoid arthritis, was effective for controlling the progression of articular destruction in rats with adjuvant arthritis.

Intraperitoneal methotrexate at a dose of 0.05 or 0.1 mg kg−1 twice weekly inhibited inflammation in rats with adjuvant arthritis, as shown by reduction of the hind-paw volume. Methotrexate also inhibited articular destruction, as shown by X-ray findings.

Although the mechanisms by which low-dose pulse methotrexate acts on rat adjuvant arthritis are still unclear, our results imply that it might effectively slow the progression of articular destruction in rheumatoid arthritis in man. In addition, assessment of articular destruction in this animal model might be useful when evaluating new treatments for rheumatoid arthritis.
In-vitro Permeability of the Human Nail and of a Keratin Membrane from Bovine Hooves: Penetration of Chloramphenicol from Lipophilic Vehicles and a Nail Lacquer
Authors: Mertin Dirk , Lippold Bernhard C
Published: April 2011

Lipophilic vehicles and especially nail lacquers are more appropriate for topical application on the nail than aqueous systems because of their better adhesion. This work has, therefore, studied the penetration through the human nail plate of the model compound chloramphenicol from the lipophilic vehicles medium chain triglycerides and n-octanol and from a lacquer based on quaternary poly(methyl methacrylates) (Eudragit RL). The results were compared with data obtained with a keratin membrane from bovine hooves.

If the swelling of the nail plate or the hoof membrane is not altered by use of lipophilic vehicles, the maximum flux of the drug is independent of its solubility in the vehicle and is the same as that from a saturated aqueous solution. These vehicles are not able to enter the hydrophilic keratin membrane because of their non-polar character and so cannot change the solubility of the penetrating substance in the barrier. If the concentration of the drug in the nail lacquer is sufficiently high, the maximum flux through both barriers equals that from aqueous vehicles or even exceeds it because of the formation of a supersaturated system. Penetration through the nail plate follows first order kinetics after a lag-time of 400 h. The course of penetration through the hoof membrane is initially membrane-controlled and later becomes a matrix-controlled process because of the membrane's greater permeability. Chloramphenicol is dissolved in the lacquer up to a concentration of 31%. The relative release rates from these solution matrices are independent of the drug concentration but they decrease on changing to a suspension matrix.

These results show that drug flux is independent of the character of the vehicle and that penetration of the drug is initially membrane-controlled and changes to being matrix-controlled as the drug content of the lacquer decreases.
The Role of Mammalian Intestinal Bacteria in the Reductive Metabolism of Zonisamide
Authors: Kitamura Shigeyuki , Sugihara Kazumi , Kuwasako Mie , Tatsumi Kiyoshi
Published: April 2011

Zonisamide (1,2-benzisoxazole-3-methanesulphonamide), a new anticonvulsant, is mainly metabolized to 2-sulphamoylacetylphenol by reduction of the benzisoxazole ring. Recent studies have shown that mammalian liver enzymes are responsible for the reduction of zonisamide. Because intestinal bacteria can also mediate the reduction of xenobiotics, this study was designed to evaluate the role of intestinal bacteria in in-vivo reductive metabolism of zonisamide.

Treatment of rats with antibiotics significantly reduced the urinary and faecal excretion of 2-sulphamoylacetylphenol after oral administration of zonisamide. Re-contamination of the antibiotic-treated rats with microflora restored the excretion of the metabolite. The caecal contents of the control rats had significant zonisamide reductase activity, whereas little or no zonisamide reductase activity was observed with the caecal contents of the antibiotic-treated rats. Eight pure strains of intestinal bacteria were tested for zonisamide reductase activity and the highest was observed in Clostridium sporogenes.

We concluded that intestinal bacteria play a major role in the reductive metabolism of zonisamide to 2-sulphamoylacetylphenol in-vivo.
In-vitro Binding of Propiverine Hydrochloride and Some of its Metabolites to Serum Albumin in Man
Authors: Meisel P , Langner Steffi , Siegmund W
Published: April 2011

The distribution and pharmacological action of propiverine, a bladder spasmolytic agent, are affected by the extent of plasma-protein binding. Because attempts to assess the albumin-binding of propiverine have produced conflicting results, the binding parameters of the drug and some of its metabolites to serum albumin in man have been re-evaluated.

In man propiverine is bound to serum albumin at a single site with high affinity (KA1 = 1.45 × 104 L mol−1) and at least two sites with low affinity (KA2 = 2.5 × 102 L mol−1). The metabolites of propiverine, namely M2 (dealkylated propiverine), M5 (the N-oxide of propiverine) and M6 (the N-oxide of M2), are less firmly bound to serum albumin; this is considered to be non-specific binding. Binding experiments with human serum revealed that there are additional binding proteins. At therapeutic plasma levels the extent of binding was calculated to be 90, 15, 60, and 20% for propiverine and the metabolites M2, M5, and M6, respectively.

The strong binding of propiverine to serum proteins controls its availability to the liver. Because the metabolites are not tightly bound to serum proteins, after metabolism of propiverine its metabolites are easily eliminated.
Neuromuscular and Microvascular Changes Associated with Chronic Administration of an Extract of Teucrium stocksianum in Mice
Authors: Tanira M O M , Ali B H , Bashir A K , El-Sabban F F , Homsi M Al
Published: April 2011

This work examines the effect on the weights of vital body organs, on blood biochemical variables, on neuromuscular coordination and on cerebral microcirculation of aqueous extracts of Teucrium stocksianum, given to mice in drinking water at concentrations of 2 and 4% for 56 days.

The treatment caused progressive impairment of neuromuscular coordination, as evidenced by the time spent on the rota-rod. After photochemical challenge, the time for first observable platelet aggregation in arterioles was shorter than for the control group by 22 and 45% in the 2 and 4% T. stocksianum-treated groups, respectively. Platelet aggregation on the venular side was not affected by the treatment nor were microvascular diameters. Treatment with the plant extract produced no statistically significant effect on the plasma biochemical variables that are considered indices of liver and kidney function. Histologically, brains obtained from mice treated with T. stocksianum showed loss of cerebellar Purkinje cells.

Although it is likely that the accelerated platelet aggregation might have contributed to an ischaemic effect which could, at least in part, have caused the cytotoxicological changes, this does not exclude the possibility of a direct cytotoxicological effect of the plant extract. Further pharmacological and toxicological investigations on Teucrium species seem warranted.
Age-related Changes in [3H]Nimodipine and [3H]Rolipram Binding in the Rat Brain
Authors: Araki T , Kato H , Shuto K , Itoyama Y
Published: April 2011

Ageing is associated with changes in neurotransmission which might be correlated with abnormal calcium metabolism. Because there is evidence that nimodipine can enhance the learning abilities of ageing animals and rolipram can enhance the excitability of neurons, providing a functional basis for cognition-enhancing activity, age-related alterations in the binding of voltage-dependent L-type calcium channels and calcium/calmodulin-independent cyclic adenosine monophosphate-selective phosphodiesterase (cyclic-AMP PDE) were studied in 3-week- and 6-, 12-, 18- and 24-month-old Fisher 344 rats by use of receptor autoradiography.

[3H]Nimodipine and [3H]rolipram were used to label the voltage-dependent L-type calcium channels and calcium/calmodulin-independent cyclic-AMP PDE, respectively. [3H]Nimodipine binding showed no obvious change in all brain areas of 12- and 18-month-old rats, as compared with 6-month-old animals. In 24-month-old rats, however, [3H]nimodipine binding increased significantly in the striatum and hippocampal CA3 sector. In contrast, [3H]rolipram binding showed no significant change in most brain areas during ageing, except for a transient change only in the hippocampal CA1 sector of 12-month-old animals. [3H]Nimodipine and [3H]rolipram binding showed a significant increase in some brain areas of 3-week-old rats compared with 6-month-old animals.

The results indicate that in rats voltage-dependent L-type calcium channels are more susceptible to ageing processes than calcium/calmodulin-independent cyclic-AMP PDE. Our data also demonstrate that voltage-dependent L-type calcium channels and calcium/calmodulin-independent cyclic-AMP PDE might play roles in developmental processes. These findings might help further elucidation of the relationship between age-related neurological deficits and behavioural pharmacology including cognitive function.
Estimation of the Chemosensitizing Activity of Modulators of Multi-drug Resistance via Combined Simultaneous Analysis of Sigmoidal Dose-Response Curves
Authors: Ecker Gerhard , Chiba Peter , Schaper Klaus-Jürgen
Published: April 2011

The potency of modulators which re-establish sensitivity of resistant tumour cells to cytotoxic drugs is not usually described by ED50 values, even though such values are needed for comparison of modulator activity.

Various methods are reported for the determination of ED50 values of propafenone-type modulators of multi-drug resistance in cytotoxicity assays. Best results were obtained by using a combined simultaneous analysis of dose-response curve families. This approach enables calculation of statistically highly significant ED50 values without any data reduction directly from the original data points obtained in daunomycin cytotoxicity assays.

The method also enables extrapolation of the ED50 values of compounds with low activity or poor solubility, or both.
The Effects of a Triterpene Fraction Isolated from Crataegus monogyna Jacq. on Different Acute Inflammation Models in Rats and Mice. Leucocyte Migration and Phospholipase A2 Inhibition
Authors: Ahumada Carmen , Sáenz Teresa , García Dolores , De La Puerta Rocio , Fernandez Angeles , Martinez Eugenia
Published: April 2011

The plant Crataegus monogyna has action against cardiac insufficiency, angina and arrhythmia. The antiinflammatory properties of the cycloartenol fraction from this plant have been investigated.

Chromatographic fractionation of the hexane extract of Crataegus monogyna Jacq. (Rosaceae) furnished a triterpene fraction containing cycloartenol as the main component (80.87%). The anti-inflammatory activity of the fraction was tested against hind-paw oedema induced by carrageenan in rats. At the highest oral dose (40 mg kg−1) inhibition was 61.5 and 52.5% at 3 and 5 h respectively. In the mouse carrageenan peritonitis test, the triterpene fraction given orally inhibited peritoneal leucocyte infiltration (41.9, 64.7 and 89.4% at 10, 20 and 40 mg kg−1, respectively). The fraction also showed weak inhibition of phospholipase A2 (PLA2) in-vitro.

These results suggest that the fraction containing cycloartenol as the main component exerts an important anti-inflammatory action in-vivo by reducing the oedema.
Characterization of the Influence of some Cyclodextrins on the Stratum Corneum from the Hairless Mouse
Authors: Bentley M Vitória L B , Vianna Renata F , Wilson Susan , Collett John H
Published: April 2011

Differential scanning calorimetry (DSC), Fourier-transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM) have been used to determine the influence of β-cyclodextrin (β-CyD), hydroxypropyl-β-CyD (HP-β-CyD) and γ-CyD on the structural properties of the stratum corneum from the hairless mouse.

Some modest changes in the stratum corneum lipid transition temperature were induced by HP-β-CyD and blue shifts were observed in the FTIR spectra of the C–H asymmetric and symmetric stretching of the lipids from the stratum corneum. Results from TEM studies indicated that HP-β-CyD caused removal and possible disorganization of the lipid matrix that envelopes the corneocytes of the stratum corneum, whereas no effect was seen after treatment of the samples with β-CyD and γ-CyD.

These results suggest that HP-β-CyD can increase the permeability of the stratum corneum possibly as a result of extraction of lipids, and might thus enhance drug permeation through the skin.
Neuromuscular Blockade: Offset Anomalies. Are they Simply Potency-related Receptor Bonding Effects?
Authors: Midgley John M , Stenlake John B
Published: April 2011

Rapid making and breaking of bonds between quaternary ammonium compounds and cholinergic receptors is typical of ion-pair bonding, which is weak, and ion-pair reactions, which are extremely fast. These properties explain the observed rapid association and dissociation of turbocurarine at receptors.

The time course receptor offset is determined by two factors, buffered diffusion due to repetitive bonding, and a potency-related offset-retarding effect. The strength of the latter is a function of chemical structure, which determines the microscopic molecular rate of drug-receptor association and dissociation. Together, buffered diffusion and the potency-related offset-retarding effect provide a complete rational physico-chemical explanation for the marked, yet variable, differences between onset and offset times of non-depolarizing neuromuscular blocking agents.

The influence of a potency-related offset-retarding effect together with differing structural requirements for neuromuscular blocking potency and plasma carboxyesterase hydrolysis, suggests that a high potency ultrashort duration block is unlikely to be achieved in a non-depolarizing compound metabolized by plasma esterases alone.
Role of the Endothelium in the Relaxation Induced by Propofol and Thiopental in Isolated Arteries from Man
Authors: Moreno Lucrecia , Martínez-Cuesta M Angeles , Muedra Vicente , Beltrán Belén , Esplugues Juan
Published: April 2011

Induction of anaesthesia with intravenous propofol and thiopental is often accompanied by hypotension. This study evaluates whether propofol and thiopental induce relaxation of isolated arteries from man and whether this effect is modulated by the endothelium.

Mesenteric artery rings (with and without endothelium) from 12 patients were placed in organ baths and precontracted with phenylephrine before addition of propofol (10−3 M) or thiopental (10−3 M). Relaxation induced by propofol and thiopental was evaluated for rings with intact endothelium in the presence of the nitric oxide synthase inhibitor NG-nitro-l-arginine methyl ester (l-NAME; 10−4 M) or the cyclooxygenase inhibitor indomethacin (10−5 M). The vasodilator effect of propofol was similar for intact and denuded endothelium rings whereas the relaxation induced by thiopental was significantly attenuated in denuded-rings. In intact endothelium rings, l-NAME and indomethacin caused marked inhibition of the relaxation induced by thiopental, but not that induced by propofol.

These results suggest that propofol induces endothelium-independent relaxation of isolated mesenteric arteries in man, whereas thiopental causes endothelium-dependent relaxation mediated by nitric oxide and prostaglandins.
Analysis of the Role of Nitric Oxide in the Relaxant Effect of the Crude Extract and Fractions from Eugenia uniflora in the Rat Thoracic Aorta
Authors: Wazlawik Elisabeth , da Silva Marco Antônio , Peters Rodrigo Rebelo , Correia João Francisco Gomes , Farias Mareni Rocha , Calixto João Batista , Ribeiro-do-Valle Rosa Maria
Published: April 2011

This study has evaluated the possible role played by the l-arginine-nitric oxide pathway in the vasorelaxant action of the hydroalcoholic extract from Eugenia uniflora, and fractions from the extract, in rings of rat thoracic aorta.

The addition of an increasing cumulative concentration of hydroalcoholic extract from E. uniflora (1–300 μg mL−1) caused a concentration-dependent relaxation response in intact endothelium-thoracic aorta rings pre-contracted with noradrenaline (30–100 nm). The IC50 value, with its respective confidence limit, and the maximum relaxation (Rmax) were 7.02 (4.77–10.00) μg mL−1 and 83.94 ± 3.04%, respectively. The removal of the endothelium completely abolished these responses. The nitric oxide synthase inhibitors Nω-nitro-l-arginine (l-NOARG, 30 μm) and Nω-nitro-l-arginine methyl ester (l-NAME, 30 μm), inhibited the relaxation (Rmax) to −10.43 ± 7.81% and −3.69 ± 2.62%, respectively. In addition, l-arginine (1 mm), but not d-arginine (1 mm), completely reversed inhibition by l-NOARG. Methylene blue (30 μm), a soluble guanylate cyclase inhibitor, reduced the relaxation induced by the extract to 14.60 ± 7.40%.

These data indicate that in the rat thoracic aorta the hydroalcoholic extract, and its fractions, from the leaves of E. uniflora have graded and endothelium-dependent vasorelaxant effects.
A Comparative Pharmacokinetic-Pharmacodynamic Study of the Electrocardiographic Effects of Epinastine and Terfenadine in Rats
Authors: Ohtani Hisakazu , Kotaki Hajime , Sawada Yasufumi , Iga Tatsuji
Published: April 2011

The effects of epinastine hydrochloride and terfenadine on electrocardiographic (ECG) parameters in rats were investigated from a pharmacokinetic and pharmacodynamic perspective.

Epinastine hydrochloride (1 or 3 mg kg−1 h−1) or terfenadine (5, 10 or 15 mg kg−1 h−1) was intravenously infused into rats anaesthetized with urethane and α-chloralose. The changes in the QT interval derived from limb lead II and the chest lead, heart rate and PR interval were analysed. The time-course of the plasma drug-concentration of each drug was also investigated. Terfenadine prolonged the QT interval in an infusion-rate-dependent manner; its EC50 value was 792–1039 ng mL−1. An obvious QT prolongation was, moreover, observed even at a plasma terfenadine concentration of 100–200 ng mL−1, which is clinically quite high, but might be achieved under a definite condition such as a restrained terfenadine metabolism. Terfenadine also induced PR prolongation and bradycardia in an infusion-rate dependent manner. Epinastine slightly increased the heart rate, but did not affect any of the other ECG parameters even at a plasma concentration of 400 ng mL−1, which is more than 10 times the maximum concentration attained after an ordinary dosage regimen in man.

We conclude that epinastine might have an advantage over terfenadine in avoiding adverse electrocardiographic reactions.
Characterization and Trypanocidal Activity of Nifurtimox-containing and Empty Nanoparticles of Polyethylc y anoacrylates
Authors: Gonzalez-Martin Guillermo , Merino Isabel , Rodriguez-Cabezas M Nieves , Torres Marisa , Nuáez Rebeca , Osuna Antonio
Published: April 2011

The aim of this study was to evaluate the utility of nanoparticles of polyalkylcyanoacrylate as a targeted delivery system for nifurtimox against Trypanosoma cruzi, responsible for Chagas’ disease. Ethylcyanoacrylate nanoparticles were prepared by an emulsion polymerization process and formulations containing different concentrations of nifurtimox, polyethylcyanoacrylates and surfactants were investigated and analysed for size and drug content.

The nanoparticles obtained were less than 200 nm in size, as measured by electron microscopy and cytometry. The peak percentage of nifurtimox uptake into the nanoparticles was 33.4% for use of 500 μL polyethylcyanoacrylate, 200 μL surfactant (Tween 20) and 10 mg nifurtimox in 50 mL polymerization medium. The highest release of nifurtimox from the nanoparticles was 65.4% after 6-h incubation at pH 7.4. In-vitro studies using cultures of T. cruzi epimastigotes revealed considerably increased trypanocidal activity compared with a standard solution of nifurtimox. Studies of cell cultures previously infected with metacyclic forms of the parasite showed that only 2-h treatment with solutions of 0.001% of the nanoparticle suspension reduced parasitism by 87–94% both when the nanoparticles were loaded with nifurtimox and when unloaded. Electron-microscopic examination revealed processes of degeneration and lysis, suggesting apoptotic processes, in intracellular amastigotes and free amastigotes treated with the nanoparticles. It was demonstrated that unloaded nanoparticles, by mechanisms not completely elucidated, have trypanocide activity similar to that of a standard solution of nifurtimox. It is concluded that the nanoparticles loaded with nifurtimox constitutes a good carrier of the drug against T. cruzi. The loaded-nanoparticles significantly increase trypanocidal activity.
Formulation-dependent Pharmacokinetics and Pharmacodynamics of Propofol in Rats
Authors: Dutta Sandeep , Ebling William F
Published: April 2011

Propofol, a highly lipophilic anaesthetic, is commercially formulated as a lipid emulsion (diprivan) for intravenous use. This formulation is characterized by rapid onset and offset of effect after rapid intravenous administration and an effect-site equilibration half-life (t 1/2 kE0) of 1.7min in rats. Paradoxically these characteristics are usually associated with relatively water-soluble anaesthetics. To test the influence of the formulation on propofol pharmacokinetics, effect-site equilibration kinetics and pharmacodynamics we performed a pharmacokinetic-pharmacodynamic study of propofol in chronically instrumented rats after administration in a lipid-free formulation. In this report we present the results of this study and compare these results with previous data obtained with rats receiving propofol in the emulsion formulation.

Compared with the emulsion formulation the distribution volumes (Vdc and Vdss) were significantly higher but the t 1/2 kE0 (2.0 min) was similar for the lipid-free formulation. The concentration-effect relationship was biphasic. Propofol effect-site concentrations required to achieve 50% activation, peak activation, 50% inhibition of peak activation effect and maximum inhibition were significantly lower, indicating a higher apparent steady-state potency for the lipid-free formulation compared with the emulsion formulation. The evanescent characteristics of propofol’s effect-time-course disappeared when the anaesthetic was administered in the lipid-free formulation.

These results suggest that the nature of the formulation can profoundly influence the clinical characteristics of intravenously administered drugs by modifying the pharmacokinetics or pharmacodynamics or both.
The Effect of Protein Binding on the Hepatic First Pass of O-Acyl Salicylate Derivatives in the Rat
Authors: Hung Daniel Y , Mellick George D , Whitehead Benjamin D , Roberts Michael S
Published: April 2011

In this work the in-situ perfused rat liver has been used to examine the effect of changing the protein content of the perfusate on the hepatic extraction of O-acyl esters of salicylic acid. The hepatic availability (F) of these solutes was studied at a flow-rate of 30 mL min−1 with perfusate albumin concentrations of 0, 2, and 4% w/v.

The hepatic availability of the esters was shown to decrease with increasing carbon-chain length in the O-acyl group; for all the esters the hepatic availability increased with increasing albumin concentration in the perfusate. The dispersion-model-derived efficiency number (RN) of the esters was shown to increase with increasing lipophilicity and decrease with increasing albumin concentration in the perfusate. The unbound fraction (fu) of the esters decreased with lipophilicity. RN/fu for acetylsalicylic acid remained relatively constant as the albumin concentration was increased. However, RN/fu for n-pentanoyl-and n-hexanoylsalicylic acids increased significantly as albumin concentration increased from 0% to 4%.

Thus, for the more lipophilic solutes (n-pentanoyl- and n-hexanoylsalicylic acids) the presence of albumin apparently facilitates the uptake of unbound solute relative to acetylsalicylic acid.
Inhibition of Human Platelet Aggregation by Diazeniumdiolates: Extent of Inhibition Correlates with Nitric Oxide Load Delivered
Authors: Raulli Robert
Published: April 2011

The profile of nitric oxide (NO) release from the diazeniumdiolate class of NO donors was evaluated using inhibition of platelet aggregation as a model.

At 37°C, the NO complexes (Z)-1-{N-methyl-N-[6-(N-methylammoniohexyl)amino]}-diazen-1-ium-1, 2-diolate (dimethylhexanediamine complex), sodium (Z)-1-(N,N-diethylamino)diazen-1-ium-1,2-diolate (diethylamine complex), (Z)-1-{N-3-aminopropyl-N-[N-(3-aminopropylammonio)butyl]amino}diazen-1-ium-1,2-diolate (spermine complex), and (Z)-1-[N-(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,22-diolate (diethylene-triamine complex) have half-lives of 1, 2 and 39min, and 20 h, respectively. All the diazeniumdiolates caused concentration-dependent inhibition of platelet aggregation; IC50 values (values for which the effect was half the maximum) were 26.0 ± 24.1, 34.9 ± 24.0 and 14.9 ± 6.4 nM for dimethylhexanediamine complex, diethylamine complex and spermine complex, respectively, when pre-incubated with platelets for one half-life. Inhibition by all compounds was time-dependent. Pretreatment of platelets with spermine complex for 5 and 39 min resulted in IC50 values of 1.7 ± 0.85 μM and 19.7 ± 0.12 nM, whereas IC50 values for sodium nitroprusside were 27.3 ± 1.25 nM and 25 nM (average, n = 2), at 5 and 39 min, respectively. Pre-incubation of each diazeniumdiolate at a concentration of 100 nM for 5 min at 37°C, which resulted in the theoretical delivery of NO loads from 96.9% down to 0.3%, resulted in decreasingly efficacious inhibition of platelet aggregation. Linear regression analysis of the theoretical NO load delivered against the actual maximum inhibition (%) showed a strong correlation (r2 = 0.975). All four diazeniumdiolates caused concentration- and time-dependent inhibition of agonist-stimulated elevation of intra-platelet Ca2+ levels; IC50 values were, respectively, 8.7 ± 1.49nM and 11.5 ± 1.36nM for dimethylhexanediamine complex and diethylamine complex at their half-lives, and 176 ± 16.9 nM and > 100 μM, for spermine complex and diethylenetriamine complex at 2 min pre-incubation time. The respective nucleophiles not complexed with NO did not show anti-aggregatory properties or inhibition of agonist-induced elevation of intra-platelet Ca2+ levels. The inhibitory effects of all diazeniumdiolates tested were attenuated by 10 μm haemoglobin.

These studies indicate that these compounds induce controlled, predictable release of NO at biological pH and temperature.
ATP-sensitive Potassium-channel-opening Activity of CL-065, a 3-[(Substituted-carbonyl)amino]-2H-1-benzopyran, in the Rat
Authors: Chen Mei-Jung , Lee Yen-Mei , Sheu Joen-Rong , Hu Cheng-Tao , Yen Mao-Hsiung
Published: April 2011

The pharmacological activity of CL-065 (trans-3-acetamido-2, 2-dimethyl-4-hydroxy-3, 4-dihydro-2H-1-benzopyran-6-carbonitrite) was investigated in anaesthetized spontaneously hypertensive rats (SHR) and isolated thoracic aorta of Sprague-Dawley rats.

The intravenous administration of CL-065 (0.1–2.0 mg kg−1) to anaesthetized SHR induced a dose-dependent reduction of mean arterial pressure (MAP) with maximum effect approximately 5 min after injection and which persisted for over 3 h. CL-065 also induced a reflex tachycardia which seemed to parallel the time course of the hypotensive effect. The hypotensive effect of CL-065 was blocked by pretreatment with glibenclamide (5 mg kg−1, i.v.), a specific ATP-sensitive potassium (KATP) channel blocker. Moreover, CL-065 (0.01–10 μM) resulted in dose-dependent vasodilatory effects on phenylephrine (0.3 μM)-induced vasoconstriction in isolated thoracic aorta. The vasorelaxation elicited by CL-065 was antagonized competitively by pretreatment with glibenclamide (0.1–1.0 μM; pA2 = 6.90 ± 0.09; slope = 1.03 ± 0.18). Similarly, the other two KATP-channel openers cromakalim (1.0 nM–1.0 μM) and nicorandil (0.1–30 μM) also induced vasorelaxation in thoracic aorta. The EC50 of cromakalim, CL-065 and nicorandil (i.e. the doses having half the maximum effect) were approximately 0.083, 0.17, and 4.5 μM, respectively, for phenylephrine (0.3 μM)-induced vasoconstriction in isolated thoracic aorta. Moreover, increased extracellular potassium levels (20–60 mM) resulted in concentration-dependent attenuation of the vasodilator effect of CL-065.

In conclusion, CL-065 induces a depressor effect via activation of KATP channels.
Anti-proliferative Effects of Lichen-derived Inhibitors of 5-Lipoxygenase on Malignant Cell-lines and Mitogen-stimulated Lymphocytes
Authors: Ögmundsdóttir Helga M , Zoëga Gunnar Már , Gissurarson Stefán R , Ingólfsdóttir Kristín
Published: April 2011

Several lichen species have been used traditionally as medicinal plants. It has previously been shown that two low-molecular-weight lichen metabolites, lobaric acid isolated from Stereocaulon alpinum Laur. and protolichesterinic acid isolated from Cetraria islandica L. (Ach.), have in-vitro inhibitory effects on arachidonate 5-lipoxygenase. We have studied the effects of these compounds on cultured cells from man, including three malignant cell-lines (T-47D and ZR-75-1 from breast carcinomas and K-562 from erythro-leukaemia), as well as normal skin fibroblasts and peripheral blood lymphocytes.

Both test substances caused a significant reduction in DNA synthesis, as measured by thymidine uptake, in all three malignant cell-lines; the dose inducing 50% of maximum inhibition (ED50) was between 1.1 and 24.6 μg mL−1 for protolichesterinic acid and between 14.5 and 44.7 μg mL−1 for lobaric acid. The breast-cancer cell-lines were more sensitive than K-562. The proliferative response of mitogen-stimulated lymphocytes was inhibited with a mean ED50 of 8.4 μg mL−1 and 24.5 μg mL−1 for protolichesterinic acid and lobaric acid, respectively. These concentrations are of the same order of magnitude as the IC50 values in the 5-lipoxygenase assay. Significant cell death (assessed by the MTS (3–4, 5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay and trypan blue exclusion) occurred in the three malignant cell-lines at protolichesterinic acid and lobaric acid concentrations above 20 and 30 μg mL−1, respectively. In K-562 morphological changes consistent with apoptosis were detected. Up to 38% cell death was observed at 20 μg mL−1 for protolichesterinic acid and 15 μg mL−1 for lobaric acid in mitogen-stimulated lymphocytes but unstimulated lymphocytes were clearly less sensitive. In contrast, the DNA synthesis, proliferation and survival of normal skin fibroblasts were not affected at doses up to 20 μg mL−1 for protolichesterinic acid and 30 μg mL−1 for lobaric acid.

We conclude that the anti-proliferative and cytotoxic effects observed might be related to the 5-lipoxygenase inhibitory activity of protolichesterinic acid and lobaric acid. These results open up the opportunity for future studies of these lichen metabolites with regard to their anti-tumour and anti-inflammatory properties.
Abstract
Authors: Papakonstantinou-Garoufalia Spyroula S , Tani Ekaterini , Todoulou Ourania , Papadaki-Valiraki Aspasia , Filippatos Evagelos , De Clercq Erik , Kourounakis Panos N
Published: April 2011

We report the synthesis of some mercaptotriazole derivatives in an effort to discover underlying structural requirements for antiviral activity. A preliminary antiviral study was performed and the contribution of the compounds to free radical processes was investigated. Because lipophilicity influences both biological activity and antioxidant potential we calculated lipophilicity and attempted to correlate this with antioxidant activity.

Treatment of the N-(aryl)piperazineacetohydrazides (compounds 1) with 2, 4-dichloro-phenylisothiocyanate gave the N-(aryl)piperazinethiosemicarbazides (compounds 2) in good yield. Cyclization of these compounds after treatment with NaOH solution provided the corresponding 5-(4-aryl-1-piperazinylmethyl)-4-(2, 4-dichlorophenyl)-4H-1, 2, 4-triazole-3-thiols (compounds 3) in good yield. Reaction of compounds 3 with 2, 4-dichloro-or 4-fluorobenzyl chloride in acetone in the presence of potassium carbonate gave the target compounds (compounds 4) in about 70% yield. The antioxidant effect of the compounds on non-enzymatic lipid peroxidation of rat hepatic microsomal membranes was studied. Most of the examined compounds were active at concentration of 0.1 mM and most were found to prevent dimethylsulphoxide oxidation moderately (20–50%) at a concentration tenfold less than that of dimethylsulphoxide. The interaction of the synthesized compounds with 1, 1-diphenyl-2-picrylhydrazyl stable free radical was also studied. Correlation was found between the two expressions of calculated lipophilicity, antioxidant activity and the lipophilicity of the synthesized compounds, and a correlation was derived between antioxidant activity and logP, which expresses the compounds’ hydrogenbonding capacity.