bluuebunny/crossref_metadata_2025 huggingface dataset:
Cold-storage of Rabbit Thoracic Aorta in University of Wisconsin Solution Reduces Endothelium-independent Vasodilation
Authors: Gryf-Lowczowski J V D , Sherlock D , Salisbury J , Benjamin I S , Alexander B
Published: April 2011

Optimum preservation conditions for storage of donor livers and blood vessels are essential for successful transplantation. The blood vessels are used as vascular conduits to facilitate anastomosis of the liver to the recipient's systemic vasculature. Failure of some transplants has been ascribed to thrombosis of these vascular conduits possibly because of alterations in vascular reactivity owing to inadequate storage techniques. To restrict data variability previously associated with studies using a heterogeneous sample of vessels from man, this study investigated changes in vascular reactivity in segments of rabbit thoracic aorta from male, age-matched, New Zealand White rabbits stored at 4°C in either University of Wisconsin solution (UW; Du Pont Pharmaceuticals, UK) or Krebs-Bülbring buffer (KB).

Percent vasodilation to acetylcholine remained significantly greater in UW than in KB at –log (m) concentrations of 70 (UW = 47.05 ± 4.26 compared with KB = 13.20 ± 7.20%; P < 0.001), 6.5 (UW = 66.82 ± 4.83 compared with KB = 26.60 ± 9.48%; P < 0.01), and 60 (UW = 83.68 ± 5.26 compared with KB = 31.20 ± 9.83%; P < 0.001). This was not significantly different to relaxation in unstored arteries and suggested improved endothelial function and structure, confirmed by electron microscopy. Percent vasodilation to sodium nitroprusside was significantly lower in UW than in unstored (D0) arteries at –log (M) concentrations of 7.5 (D0 = 28.27 ± 4.02 compared with UW = 15.21 ± 1.82%; P < 0.01), 7.3 (D0 = 52.58 ± 5.05 compared with UW = 29.23 ± 1.94%; P < 001), 70 (D0 = 69.70 ± 4.85 compared with UW = 49.72 ± 2.49%; P < 005), and 6.4 (D0 = 93.16 ± 2.93 compared with UW = 71.29 ± 5.20%; P < 0.05). Percent vasodilation was also lower in UW- compared with KB-stored arteries at –log (m) sodium nitroprusside concentrations of 7.0 (UW = 49.72 ± 2.49 compared with KB = 64.11 ±5.03%; P < 0.05) and 6.4 (UW = 71.29 ± 5.20 compared with KB = 96.91 ± 5.96; P < 0.05). Electron microscopy confirmed that this was not a result of degradation of smooth muscle structure. The nitric oxide synthase inhibitor l-NG-nitro-l-arginine methyl ester (100 μm) did not significantly modulate sodium nitroprusside-induced vasodilation in unstored arteries, when endothelial function was maximum, or in UW-stored arteries, suggesting that the reduced responses in UW-stored arteries were not because of increased synthesis of nitric oxide. This reduced relaxation to sodium nitroprusside was therefore nitric oxide-independent and not a result of competition between sodium nitroprusside and endothelial ‘nitric oxide donation’ for cGMP.

In summary, cold-storage preservation with UW reduced endothelium-independent vascular relaxation by mechanisms other than competition with NO; this requires further evaluation.
Several Receptor Subtypes Contribute to 5-Hydroxytryptamine-induced Secretion by Rat Ileum In-vitro
Authors: Hardcastle J , Hardcastle P T
Published: April 2011

The receptors contributing to 5-hydroxytryptamine (5-HT)-induced secretion by rat ileum were investigated in-vitro using selective agonists and antagonists.

5-HT induced a dose-dependent increase in the short-circuit current (SCC) generated by both intact and stripped sheets of rat ileum. 1-Phenylbiguanide, a selective 5-HT3 agonist, and 5-methoxytryptamine, an agonist that lacks affinity for 5-HT3 receptors, also increased the SCC. In intact sheets 5-HT was more effective than either 1-phenylbiguanide or 5-methoxytryptamine, whereas in stripped sheets 5-HT and 5-methoxytryptamine were equipotent, with 1-phenylbiguanide having little effect. Tetrodotoxin abolished the response of intact sheets to 1-phenylbiguanide but only reduced the responses to 5-HT and 5-methoxytryptamine by 57% and 54%, respectively. This inhibition was reduced to 25% in stripped sheets. The 5-HT3 antagonist granisetron abolished the response to 1-phenylbiguanide, but did not alter the effects of 5-HT. Ketanserin, a 5-HT2 antagonist, had a small effect on the actions of 5-methoxytryptamine in intact, but not stripped, sheets and no effect on the response to 5-HT in either preparation. Tropisetron, a 5-HT3 and 5-HT4 antagonist, inhibited the response to 5-methoxytryptamine, but had less effect on the response to 5-HT. Desensitization to 1-phenylbiguanide inhibited the response to 5-HT in intact, but not stripped sheets, whereas desensitization to 5-methoxytryptamine abolished the 5-HT response in stripped sheets, but induced only 42% inhibition in intact sheets. Previous exposure to a combination of both 1-phenylbiguanide and 5-methoxytryptamine abolished the 5-HT-induced increase in SCC in both preparations.

The findings suggest that 5-HT-induced ileal secretion involves more than one 5-HT receptor subtype and that both neural and non-neural mechanisms contribute to the response.
Screening of Hepatoprotective Plant Components using a HepG2 Cell Cytotoxicity Assay
Authors: Thabrew M Ira , Hughes Robin D , McFarlane Ian G
Published: April 2011

Identification of the active components of plants with hepatoprotective properties requires screening of large numbers of samples during fractionation and purification. A screening assay has been developed based on protection of human liver-derived HepG2 cells against toxic damage.

Various hepatotoxins were incubated with HepG2 cells in 96-well microtitre plates (30000 cells well−1) for 1 h and viability was determined by metabolism of the tetrazolium dye 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxy phenyl)-2-(4-sulphophenyl)-2H-tetrazolium (MTS). Bromobenzene (10 mm) and 2,6-dimethyl-N-acetyl-p-quinoneimine (2,6-diMeNAPQI, 200 mm) had greater toxic effects than tert-butyl hydroperoxide (1.8 mm) or galactosamine (10 mm), reducing mean viability to 44.6 ± 1.2% (s.e.m.) and 561 ± 21% of control, respectively. Protection against toxic damage by these agents was tested using a crude extract of a known hepatoprotective Sri Lankan plant, Osbeckia aspera, and two pure established hepatoprotective plant compounds, (+)-catechin and silymarin (1 mg mL−1). Viability was significantly improved by Osbeckia (by 37.7 ± 2.4%, P < 0.05, and 36.5 ± 21%, P < 0.05, for bromobenzene and 2,6-diMeNAPQI toxicity, respectively). Comparable values for (+)-catechin were 68.6 ± 2.9% and 63.5 ±11%, and for silymarin 24.9 ± 1.4% and 25.0 ± 1.6%.

This rapid and reproducible assay should prove useful for the isolation and identification of active hepatoprotective compounds in crude plant extracts.
Cisplatin-induced Changes in Adenine Nucleotides in Rat Kidney Slices: Amelioration by Tiopronin and Procaine
Authors: Zhang Jin-Gang , Lindup W Edward
Published: April 2011

The adenine nucleotides (ATP, ADP and AMP) in rat renal cortical slices exposed in-vitro to cisplatin, an anticancer drug, were determined by HPLC.

Cisplatin had no effect on total adenine nucleotides in the slices but caused a time- and concentration-dependent decrease in ATP levels with a concomitant increase in ADP and AMP levels. The decrease in ATP and increases in ADP and AMP concentrations became statistically significant after incubation with cisplatin (2 mm) for 90 min or after cisplatin (1 mm) for 120 min. Both tiopronin, a sulphydryl-containing drug, and procaine, an antioxidant, protected against cisplatin-induced changes in the adenine nucleotides.

The results indicate a cisplatin-induced defect in cellular energetics that occurs at a relatively late stage in the process of toxicity to the slices in this in-vitro model. Cisplatin-induced depletion of ATP in the slices might result from an increase in catabolism of ATP to ADP and AMP. Maintenance of the normal concentration of ATP in the slices might be involved in the protection afforded by tiopronin and procaine against cisplatin-induced nephrotoxicity.
Application of Muscle Microdialysis to Evaluate the Concentrations of the Fluoroquinolones Pazufloxacin and Ofloxacin in the Tissue Interstitial Fluids of Rats
Authors: Araki Harumi , Ogake Naoko , Minami Shinazburo , Watanabe Yasuo , Narita Hirokazu , Tamai Ikumi , Tsuji Akira
Published: April 2011

Muscle microdialysis has been used to determine the unbound concentrations of the fluoroquinolones, pazufloxacin and ofloxacin, in tissue interstitial fluids (Cisf, u) of rats under steady state conditions.

Cisf, u was estimated from the concentration in dialysate and the in-vitro permeability rate constant by the extrapolation method based on the clearance concept. Paper disks were inserted under the abdominal skin of rats, and the drug concentrations in the fluids penetrating into the disks (Cdisk) were measured and compared with Cisf, u. The Cisf, u of pazufloxacin and ofloxacin in muscle were close to their unbound concentrations in the venous plasma; these were 75.3% and 77.1%, respectively, of the total concentrations in plasma at the steady state. The Cdisk of pazufloxacin and ofloxacin were also close to their Cisf, u.

These results indicate that the unbound concentrations of the fluoroquinolones in the tissue interstitial fluids were the same as those in the venous plasma. The disk insertion technique seems to be useful for evaluating drug concentrations in tissue interstitial fluid.
Isoquinoline Derivatives Isolated from the Fruit of Annona muricata as 5-HTergic 5-HT1A Receptor Agonists in Rats: Unexploited Antidepressive (Lead) Products
Authors: Hasrat J A , De Bruyne T , De Backer J-P , Vauquelin G , Vlietinck A J
Published: April 2011

The fruit and the leaves of Annona muricata (Annonaceae) are used in traditional medicine for their tranquillizing and sedative properties. Extracts of the plant have been shown to inhibit binding of [3H]rauwolscine to 5-HTergic 5-HT1A receptors in calf hippocampus, and three alkaloids, annonaine (1), nornuciferine (2) and asimilobine (3), isolated from the fruit have been shown to have IC50 values of 3 μm, 9 μm and 5 μm, respectively, although in ligand-binding studies it was not possible to determine whether interaction of these ligands with the receptor was agonistic or antagonistic. This paper presents the results of functional assays of the alkaloids.

The inhibition of cAMP accumulation was tested in NIH-3T3 cells stably transfected with the 5-HT1A receptor from man. None of the alkaloids showed antagonistic properties towards the 5-HT1A receptors because in the antagonistic tests no influence on the forskolin-stimulated increase of cAMP level was detected. Full agonistic properties were measured for all three compounds; the inhibition constants (Ki) for 1, 2 and 3 were < 10 μm. Inhibition of the binding of the radioligand to the 5-HT1A receptor was observed in every ligand-binding assay performed with the alkaloids; the Ki values for 1, 2 and 3 were in the μm range.

These results imply that the fruit of Annona muricata possesses anti-depressive effects, possibly induced by compounds 1, 2 and 3, and that in the past potent leads for the development of anti-depressive therapeutics have not been used.
Pharmacology of the Gastric Pro-kinetic Drug Ecabapide (DQ-2511)
Authors: Furuhama Kazuhisa , Wood Jackie D
Published: April 2011

The pharmacology of ecabapide (DQ-2511; 3-[2-(3,4-dimethoxyphenyl)ethylcarbamoylmethyl]amino-N-methylbenzamide) is reviewed.

Evidence from basic studies in animal models suggests that the drug acts on peripheral mechanisms of neural control. In the stomach, ecabapide acts to suppress firing in vagal afferent nerves and thereby reduce the flow of sensory information into the dorsal vagal complex.

The enhancement of the efferent discharge provoked by ecabapide was completely blocked by bilateral vagotomy, as suggested by increased firing in vagal efferent fibres, preceded by suppression of activity in the sensory limb of the putative vago-vagal reflex pathway.

The mechanism of action of ecabapide in suppressing discharge in vagal afferent terminals appears to mimic that of nitric oxide by stimulating formation of cGMP and activation of an inhibitory transduction cascade in the sensory fibres. In this respect the mechanism of its pro-kinetic action differs from other promoter agents. In addition to selective actions in the stomach, evidence from electrophysiological studies of enteric neurons in the small intestine suggests that ecabapide might have actions similar to those of other substituted benzamides on synaptic transmission in the intramural nervous system of this specialized region of the digestive tract. These actions include enhanced release of acetylcholine at excitatory synapses and suppression of the release of noradrenaline at inhibitory synapses.
The Effect of Surfactant and Suspending Agent Concentration on the Effective Particle Size of Metered-dose Inhalers
Authors: Fedina L T , Zelkó R , Fedina L I , Szabados Z S , Szántó M , Vakulya G
Published: April 2011

The aim of this study was to examine the influence of the concentrations of surfactant and suspending agent on the quantity of effective particles (size < 10 μm) delivered by metered-dose inhalers.

A 2-factor, 3-level, face-centred central composite design was used to construct a second-order polynomial model which describes the effect of formulation factors (suspending agent, surface-active ingredient) on the therapeutically important characteristic (effective particle size) delivered by metered-dose inhalers. Oleic acid was selected as the surface-active ingredient, and the suspending agent was anhydrous alcohol. A non-linear model demonstrated with good correlation the effect of the amounts of surfactant and suspending agent on the quantity of particles of effective size.

The results obtained enable determination of the correct amount of surface-active ingredient and the optimum quantity of the suspending agent, thus enabling formulation of a therapeutically effective formulation.
Change of the Microstructure of Microcrystalline Cellulose with Grinding and Compression
Authors: Yamamura Shigeo , Terada Katsuhide , Momose Yasunori
Published: April 2011

The microstructure of microcrystalline cellulose was investigated by use of a radial distribution function (RDF) based on the intensity of X-ray scattering data. Changes in the microstructure of the cellulose as a result of grinding and compression were detected by use of the RDF.

The RDF of intact microcrystalline cellulose had peak maxima corresponding to distances of approximately 1.5, 2.6, 5.0, 8.2, 13.3 and 170 Å. The first two corresponded to the intramolecular atomic distances; other peaks were attributable to the intermolecular (inter-fibre) atomic distance. Changes in the RDF as a result of grinding indicated that the regular intermolecular atomic arrangement was gradually lost. Compression resulted in formation of long-range (> 20 Å) ordering of the intermolecular (inter-fibre) atomic arrangement.

These results show that RDF analysis is suitable for monitoring changes in the structure of microcrystalline cellulose which occur as a result of grinding and compression.
Short-period Double-dosing for Simultaneous Evaluation of Intestinal Absorption and Hepatic Disposition in a Single Conscious Rat Using Cephalexin as Test Drug
Authors: Ito Takashi , Yamaoka Kiyoshi , Nakagawa Terumichi
Published: April 2011

A new method has been developed for simultaneous evaluation of local absorption from the intestine into the portal system and local disposition through the liver, and for assessment of the bioavailability of a drug in a single conscious rat. The method is based on the difference between plasma concentrations in portal and systemic blood (PS method).

Because cephalexin is known to be absorbed completely from the intestine and not to be eliminated through the liver, it was used as test drug to confirm the validity of the new method. The portal vein and the femoral artery of a rat were simultaneously cannulated and blood samples were obtained from both sites. Two methods of administration, single-dosing and double-dosing, were investigated and the efficacy of double-dosing (DD) was demonstrated. Rats received an intra-arterial (group A) or oral (group B) dose in single-dosing, whereas rats used for double-dosing received an oral dose 3 h after an intra-arterial dose (group C). After administration of cephalexin, the portal and arterial plasma concentrations were determined by HPLC. Groups A and B were monitored for 4 h and group C for 8 h. The portal-blood flow rate was measured by means of an electromagnetic flow-meter. Global and local moments were calculated by trapezoidal integration with extrapolation to infinite time. On the basis of the PS method, the local absorption ratio (Fa) and the mean local absorption time (t̄a) were estimated to be 0.975 ± 0.104 and 2.19 ± 0.51 h, respectively, in group B. By comparing the averaged moments between groups A and B, the extent of bioavailability (F), the mean absorption time (MAT) and the hepatic recovery ratio (FH) were calculated to be 1.01, 1.92 h and 1.04, respectively. The mean hepatic transit time (t̄H) was negligible. In group C, Fa = 0.936 ± 0.107, t̄H = 1.55 ± 0.32 h, F = 1.08 ± 0.07, MAT = 1.55 ± 0.40 h and FH = 1.17 ± 0.14 h, the mean values being close to those from groups A and B.

In conclusion, the PS method with short-period double-dosing (PS-DD method) can offer an effective means of evaluating the local absorption kinetics of drugs, because F, MAT and FH are obtained from a single conscious rat, and consequently the standard deviations of the quantities can be quickly estimated.
Control of the Amount of Free Molecular Iodine in Iodine Germicides
Authors: Hickey John , Panicucci Rick , Duan Yongjun , Dinehart Kirk , Murphy Joe , Kessler Jack , Gottardi Waldemar
Published: April 2011

Horseradish peroxidase has been used to generate iodine compositions that comprised principally free molecular iodine.

The concentration of free molecular iodine in these enzyme-based compositions ranged from 44 to 63% of the thiosulphate titratable iodine; this is substantially higher than the corresponding value for the povidoneiodine preparation betadine. The biocidal efficacy of these compositions was proportional to the concentration of free molecular iodine. Iodine compositions with relatively low total iodine concentrations but high levels of free molecular iodine (20–175 ppm) killed Staphylococcus aureus and spores of Bacillus subtilis more rapidly than betadine. The effects of normal saline and these enzyme-based iodine compositions on the rate of epidermal regeneration in superficial swine wounds were comparable.

These results suggest that an effective germicide containing a high level of molecular iodine need not be irritating or toxic.
Relationship between Plasma Concentration and Antihypertensive Effect of the Dihydropyridine Calcium Antagonist, Benidipine, in Rats
Authors: Kobayashi Hiroyuki , Kobayashi Satoshi
Published: April 2011

Although benidipine hydrochloride, a hydrophobic and weakly cationic dihydropyridine calcium antagonist, has slow onset but long-lasting anti-hypertensive effect in experimental animals and man, after administration it rapidly disappears from the plasma. Correlation of the plasma concentration with reduction in blood pressure has been investigated in spontaneously hypertensive rats, and concentrations in the mesenteric artery were compared with those in plasma after oral and intravenous administration of benidipine to rats.

After oral administration of benidipine to spontaneously hypertensive rats, the fall in blood pressure showed an anti-clock hysteresis phenomenon. Using concomitant analysis, plasma concentrations and anti-hypertensive activity could both be closely fitted to a one-compartment open model and the effect compartment for the pharmacological activity of benidipine could be described by a Hill equation. Concentrations in the mesenteric artery increased rapidly and then declined more slowly than in plasma. The mean residence time of benidipine in the mesenteric artery corresponded closely to the reciprocal of the rate constant for elimination of benidipine from the effect compartment.

From these results it seems that benidipine is retained longer in the plasma membrane, an effective site, because of its physicochemical properties, and thus shows a more sustained anti-hypertensive effect than would be predicted from its disposition in plasma.
Inhibition of Nifedipine Metabolism in Dogs by Erythromycin: Difference between the Gut Wall and the Liver
Authors: Tsuruta Satoshi , Nakamura Kazumi , Arimori Kazuhiko , Nakano Masahiro
Published: April 2011

The purpose of this study was to evaluate possible interaction of nifedipine with erythromycin or rokitamycin in the intestinal mucosa. Male beagle dogs were orally administered nifedipine (10 mg), with or without oral pre-medication with erythromycin (300 mg), and 300 mg erythromycin or rokitamycin twice a day for 3 days. The experiments were of randomized cross-over design with a two-week wash-out period between dosing regimens.

Erythromycin pre-medication for 3 days resulted in a significant increase in the area under the serum nifedipine concentration-time curve (AUC), whereas the curve for one nifedipine metabolite (M-2) decreased significantly. When the effects of erythromycin on the metabolism of nifedipine were studied using dog liver microsomes it was found that erythromycin significantly inhibited formation of M-2 but not of the metabolite M-1. These results indicate that formation of M-2 from M-1 in the liver might be reduced by erythromycin premedication. To avoid possible metabolism in the gut, the dogs were then administered 8 mg nifedipine into the peritoneal cavity, with or without multiple dose pre-treatment with erythromycin for 3 days. After intraperitoneal administration of nifedipine, the maximum concentration (Cmax) of nifedipine increased significantly.

After pre-administration of erythromycin the relative bioavailability of nifedipine after oral administration was increased compared with injection into the peritoneal cavity. In-vitro study using rat intestinal microsomes and the in-vivo rat intestinal loop technique also showed that pre-administration of erythromycin inhibits nifedipine metabolism in the small intestine.
Comparison of the Effects of Histamine and Nα-Methylhistamine on Neuronal Function in the Guinea-pig Oesophagus and Ileum
Authors: Hemedah Maggie , Mitchelson Frederick
Published: April 2011

The effects of histamine and Nα-methylhistamine, two components of gastric juice, on vagal and transmural stimulation of the guinea-pig isolated oesophagus were compared with their effects on cholinergic and on non-adrenergic-non-cholinergic (NANC) neuronal responses in the isolated ileum, both tissues having been pretreated with mepyramine (1 μm).

Histamine (≤10 μm) and Nα-methylhistamine (≤1 μm) had no significant effect on either vagal or transmural stimulation in the oesophagus. Substance P, which produces a contraction by activation of cholinergic nerves in the oesophagus also was unaffected by histamine. In contrast, the agonists inhibited contractions produced by cholinergic nerve stimulation in the ileum; the inhibition produced by histamine (10 μm) was up to 73 ± 5%, that by Nα-methylhistamine (1 μm), 48 ± 5%. Histamine also inhibited responses to stimulation of NANC neurons by up to 37 ± 14%. The effects of histamine and Nα-methylhistamine in the ileum were inhibited by clobenpropit (01 μm).

These findings suggest that histamine and Nα-methylhistamine have no role in the modulation of neuronal function in the oesophagus, in contrast with their effect in the ileum.
Stability of Artemisinin in Aqueous Environments: Impact on its Cytotoxic Action to Ehrlich Ascites Tumour Cells
Authors: Beekman Aäron C , Woerdenbag Herman J , Van Uden Wim , Pras Niesko , Konings Antonius W T , Wikström Håkan V
Published: April 2011

We have recently shown artemisinin to be cytotoxic against Ehrlich ascites tumour cells. The aim of this study was to investigate the stability of this compound in the aqueous environment of the in-vitro Ehrlich ascites tumour cell system (RPMI 1640 cell culture medium supplemented with 10% foetal bovine serum (RPMI/FBS) with reference to its cytotoxic action.

Literature data show that artemisinin can react with Fe2+ yielding reactive intermediates leaving artemisinin G as a major end-product. The current study showed that only excess addition of Fe2+ to artemisinin in distilled water, phosphate-buffered saline (PBS) and RPMI/FBS and incubation for 24 h led to degradation of artemisinin and yielded artemisinin G. If Fe2+ was not added results from HPLC analysis were indicative of complete recovery of artemisinin from distilled water and RPMI/FBS, with or without cells, at 37°C for at least 24 h. In addition, incubation of artemisinin in RPMI/FBS with or without cells at 37°C for 24 h before cytotoxicity assay did not change its cytotoxic action.

On the basis of these results, we suggest that cytotoxicity to tumour cells was caused by unchanged artemisinin. This is not so for the antimalarial activity of artemisinin and derivatives, for which the presence of a pool of (haem) Fe2+ is a prerequisite resulting in free radicals or electrophilic intermediates or both.
Human Jejunal Effective Permeability and Its Correlation with Preclinical Drug Absorption Models
Authors: LennernÄs Hans
Published: April 2011

This review focuses on intestinal permeability measurements in humans and various aspects of in-vivo transport mechanisms. In addition, comparisons of human data with preclinical models and the blood-brain barrier is discussed.

The regional human jejunal perfusion technique has been validated by several crucial points. One of the most important findings is that there is a good correlation between the measured human effective permeability values and the extent of absorption of drugs in humans determined by pharmacokinetic studies. We have also shown that it is possible to determine the effective permeability (Peff) for carrier-mediated transported compounds, and to classify them according to the proposed Biopharmaceutical Classification System (BCS). Furthermore, it is possible to predict human in-vivo permeability using precuneal permeability models, such as in-situ perfusion of rat jejunum, the Caco-2 model and excized intestinal segments in the Ussing chamber. The permeability of passively transported compounds can be predicted with a particularly high degree of accuracy. However, special care must be taken for drugs with a carrier-mediated transport mechanism, and a scaling factor has to be used. It is also suggested that it is possible to roughly estimate the permeability of the blood-brain barrier using measurements of intestinal permeability, even if the quantitative role of efflux of P-glycoprotein(s) in-vivo still remains to be clarified.

Finally, the data obtained in-vivo in humans emphasize the need for more clinical studies investigating the effect of physiological in-vivo factors and molecular mechanisms influencing the transport of drugs across the intestinal and as well as other membrane barriers. It is also important to study the effect of anti-transport mechanisms, such as efflux by P-glycoprotein(s), and gut wall metabolism, for example CYP 3A4, on the bioavailabaility.
Characterization of the Block Structure and Molecular Weight of Sodium Alginates
Authors: Johnson Fiona A , Craig Duncan Q M , Mercer Amanda D
Published: April 2011

Sodium alginates are widely used within the pharmaceutical sciences, yet the molecular characteristics of these materials are frequently not stated. In this study, a range of characterization techniques is applied to five sodium alginate samples and the data compared, both between techniques and with the information obtained from the manufacturer.

The mannuronic acid to guluronic acid (MG) ratio and the distribution of uronic acid residues of five sodium alginate samples have been measured using circular dichroism and NMR, with circular dichroism yielding MG ratios between 42.1 and 63.6%, depending on the grade of alginate used. The MG ratios obtained from NMR studies were in broad agreement with these values, and the technique also yielded information on the distribution of uronic acid residues within each batch; this was again found to vary considerably (NG > 1 values ranging from 6.9 to 17.5). It was noted that samples with similar MG ratios could have markedly different chain-distribution characteristics. The uronic acid ratio ranges obtained from the manufacturers were found to be in good agreement with those found experimentally. Intrinsic viscosity measurements were used to compare the molecular weights of the samples; values between approximately 12000 and 180000 were obtained for the different batches.

The study has enabled comparison of different methods for characterization of sodium alginate samples, highlighting their relative merits and the possible protocols that might be adopted. A critical discussion is given of the individual and combined use of these techniques and the relevance of such studies to the rational design and quality control of alginate-based pharmaceutical systems.
Oral Delivery and Fate of Poly(lactic acid) Microsphere-encapsulated Interferon in Rats
Authors: Eyles J E , Alpar H O , Conway B R , Keswick M
Published: April 2011

In the light of previous findings which suggest that particulate material can be absorbed and thence systemically disseminated from the gastrointestinal tract, we have investigated the oral uptake and distribution of soluble and microsphere-encapsulated radiolabelled interferon-γ.

For trace-loaded (0.01% w/w interferon) microspheres, a quite different distribution of radioactivity was observed in-vivo 15 and 240 min after oral administration, in comparison with the control group which received equivalent doses of unencapsulated interferon-γ. Thyroid gland activity in control animals killed at these times was significantly higher than that detected in those rodents receiving trace amounts of microencapsulated interferon-γ (P ≤ 0.05). For poly(l-lactide) particles with higher interferon loadings (0.97% w/w interferon-γ) the distinction between the two experimental groups was less significant. During incubation in-vitro, the trace-loaded particles released a significantly lower percentage of interferon-γ in comparison with 0.97% w/w loaded microspheres (P ≤ 1).

Bio-distribution data from rats treated orally with trace amounts of unencapsulated and microencapsulated interferon-γ leads us to the tentative conclusion that microencapsulation of proteins markedly affects oral uptake, and possibly post-absorption pharmacokinetic parameters also.
Effect of the Size of Liposomes on the Transfer and Uptake of Carboxyfluorescein by the Perfused Human Term Placenta
Authors: Bajoria Rekha , Contractor Soli F
Published: April 2011

The effect of the size of liposomes on the uptake and transfer of the low molecular-weight, hydrophilic and polar molecule carboxyfluorescein has been determined across the perfused human term placenta.

Carboxyfluorescein-encapsulated neutral liposomes of three different sizes were prepared from equimolar concentrations of lecithin and cholesterol. Size distribution, encapsulation efficiency and stability of liposomes in blood-based media were determined. The concentration of carboxyfluorescein was measured spectro-photometrically. The transplacental transfer and placental uptake of free carboxyfluorescein (control data) were respectively 1.9 ±0.2 and 5.0 ± 0.7% of initial dose. The placental uptake and foetal concentration of carboxyfluorescein were significantly increased by small liposomes (P < 0.05), and reduced by large (0.82 ± 0.13%; P < 0.05) and multilamellar liposomes (0.32 ± 0.11%). There was a negative correlation between liposome size and transplacental transfer (y = −0.53 + 0.9x; r = 0.96; P < 0.001; n = 24) and placental uptake of carboxyfluorescein (y = −5.9 + 6.5x; r = 0.84; P < 0.001; n = 24).

The study indicates that placental uptake and transfer rate of liposomal carboxyfluorescein were dependant upon the size of liposomes.
Cholinergic Modulation of Electrogenic Ion Transport in Different Regions of the Rat Small Intestine
Authors: Przyborski S A , Levin R J
Published: April 2011

Acetylcholine acting via muscarinic receptors located in the intestinal mucosa controls ion and fluid transport. This study examined the pathway(s) by which cholinergic receptors mediate secretion in rat isolated duodenum, jejunum and ileum using the short-circuit current (Isc) as an index of electrogenic Cl− secretion.

Carbachol and bethanechol induced electrogenic Cl− transport which was insensitive to the neural blocker tetrodotoxin, indicating their direct action on the enterocytes. Functional characterization of electrogenic secretion activated via muscarinic receptors on jejunal and ileal enterocytes was achieved by use of selective muscarinic antagonists in the presence of tetrodotoxin. In both regions the rank order of potency of these compounds (atropine > 4-diphenylacetoxy-N-piperidine methiodide (4-DAMP) > hexahydro-sila-difenidol (HHSiD) > pirenzepine > methoctramine) indicated the M3 receptor subtype. Secretion activated by the muscarinic agonist 4-[[(3-chlorophenyl)amino]carbonyl]-N,N,N-trimethyl-2-butyn-1-ammonium chloride (McN-A-343) was sensitive to tetrodotoxin and pirenzepine but not to the ganglionic blocker, hexamethonium, indicating the M1 receptor subtype on post ganglionic neurons. Regional differences for bethanechol-activated secretion showed an increasing gradient in secretory capacity (Isc max) in a proximal-to-distal direction along the small intestine. Responses to McN-A-343 also showed regional differences but these were unlike those of bethanechol.

These results show that cholinomimetic-induced electrogenic Cl− secretion in rat isolated small intestine appears to be mediated by two dissimilar populations of muscarinic receptor: M3 muscarinic receptors positioned on enterocytes and M1 muscarinic receptors sited on submucosal neurons.
The Ligand-binding Site of Buspirone Analogues at the 5-HT1A Receptor
Authors: Sylte Ingebrigt , Chilmonczyk Zdzislaw , Dahl Svein G , Cybulski Jacek , Edvardsen Øyvind
Published: April 2011

A three-dimensional model of the 5-HT1A receptor in man was constructed by molecular-modelling techniques and used to study the molecular interactions of a series of buspirone analogues with the 5-HT1A receptor by molecular-mechanical-energy minimization and molecular-dynamics simulations.

The receptor has seven trans-membrane α helices (TMHs) organized according to the electron-density-projection map of visual rhodopsin, and includes all loops between TMHs and the N- and C-terminal parts. The best fit between the buspirone analogues and the receptor model was obtained with the quinolinyl part of the ligand molecules interacting with amino acids in TMH6, the imide group interacting with amino acids in TMH2, TMH3 and TMH7, and the carbonyl groups hydrogen-bonded with Ser86 and Ser393. The ligand-binding rank order deduced from the experimentally determined inhibition constant was reproduced by calculation of receptor-binding energies of the buspirone analogues.

The models suggest that steric hindrance and repulsive forces between the receptor and the imide group of the buspirone analogues are the most important determinants of ligand-binding affinity for discriminating between these ligands.
Indole Alkaloids from Sickingia williamsii Reduce the In-vitro Effects of Morphine Withdrawal in the Guinea-pig
Authors: Capasso A , Aquino R , Garofalo L , de Simone F , Sorrentino L
Published: April 2011

The effect of indole alkaloids from Sickingia williamsii Standi. (Rubiaceae) on the effects of morphine withdrawal have been examined in-vitro.

All the indole alkaloids isolated from S. williamsii (10−4, 5 ×10−5 and 10−5 m) significantly and in a concentration-dependent manner reduced the effects of morphine withdrawal on the guinea-pig ileum.

The results suggest that these alkaloids might be potential anti-addictive agents.
Interaction of Local Anaesthetics with Histamine H1 Receptors in Guinea-pig Ileum
Authors: Horio Shuhei , Nagare Toshitaka , Ishida Yukio , Moritoki Hideki
Published: April 2011

The interaction of amine local anaesthetics and related compounds with histamine H1 receptors was investigated in guinea-pig ileal longitudinal muscle.

Quinacrine, chloroquine, tetracaine and procaine inhibited [3H]mepyramine binding to solubilized membrane from ileal muscle with pKi values of 5.27 ± 0.11, 5.66 ± 0.01, 4.28 ± 0.08 and 3.97 ± 0.11, respectively. The pKB values obtained from the initial parallel shift of the dose-response curves for histamine in the presence of these drugs were 549 ± 0.11, 6.14 ± 0.09, 4.86 ± 0.06 and 4.58 ± 0·06, respectively, in reasonable agreement with the pKi values. The combined dose-ratio test with both local anaesthetics and antagonist (mepyramine) present showed that tetracaine and procaine were competitive and chloroquine was partially competitive, but that quinacrine was not competitive at histamine H1 receptors. These local anaesthetics inhibited histamine-induced desensitization in guinea-pig ileum. Receptor occupancy (%) by agonist decreased from 95.2 (without inhibitor) to 73.9, 42.8, 35.9 and 33.9 in the presence of quinacrine, chloroquine, tetracaine or procaine, respectively, under the conditions where each inhibitor drug induced half maximum inhibition of desensitization.

The results suggested that most of these local anaesthetics interacted competitively at histamine H1 receptors and inhibited desensitization through their antagonizing actions, whereas quinacrine interacted allo-sterically and inhibited desensitization through a separate action.
Use of Microdialysis for In-vivo Monitoring of Hydroxyl Free-radical Generation in the Rat
Authors: Obata Toshio
Published: April 2011

Free-radicals are reported to cause the tissue-damage associated with some toxins and diseases, yet there is no suitable method for routine in-vivo monitoring of these species. This paper introduces an in-vivo microdialysis technique in which the hydroxyl radical reacts with salicylate to generate dihydroxybenzoic acids (DHBA) which are measured by HPLC with electrochemical detection.

When pargyline, a monoamine oxidase inhibitor, was infused into rat brain, the levels of DHBA increased markedly. When noradrenaline was administered to animals pre-treated with pargyline, DHBA levels increased markedly compared with the group treated with noradrenaline only. When the heart was subjected to 15-min regional ischaemia by occlusion of the left anterior descending coronary artery, levels of DHBA in heart dialysate were unchanged. Electrical stimulation of the stellate ganglion resulted in marked elevation of levels of DHBA the myocardial dialysate. Infusion of Fe2+ into rat liver resulted in increased formation of DHBA. When the intestine was rendered ischaemic for 10, 20 and 30 min, the highest DHBA level was obtained after 10-min ischaemia and the lowest after 30 min.

These results confirm that free-radical production might make a major contribution at certain stages in the progression of the injury.
Synthesis and Evaluation of Brain-targeted Chemical Delivery Systems for the Neurotrophomodulator 4-Methylcatechol
Authors: Kourounakis Angeliki , Bodor Nicholas , Simpkins James
Published: April 2011

Since various 4-alkylcatechols stimulate nerve growth factor (NGF) biosynthesis both in-vitro and in-vivo, delivery of these agents to the brain may provide beneficial effect for the treatment of neurodegenerative diseases such as Alzheimer's.

Several dihydropyridine-pyridinium salt type redox chemical delivery systems (CDS) of 4-methylcatechol (4-methylcatechol) were prepared as potential brain selective targetry forms for 4-methylcatechol. After preliminary evaluation by in-vitro stability studies in various buffer solutions and biological media, a selected CDS was further investigated in the rat to determine its in-vivo distribution. Selective and sustained delivery of the compound of interest to the rat brain was achieved. Furthermore, the NGF stimulatory activity in the rat brain after peripheral administration of the selected CDS was evaluated by measuring the levels of pre-pro-NGF mRNA in the rat hippocampus and frontal cortex, by dot blot hybridization and analysis.

Results showed the peripheral administration of the CDS to achieve a 1.7-fold increase in NGF mRNA compared to control in the rat hippocampus, and an approximately 1.4-fold increase in the frontal cortex.
Pharmacological Studies of 1-(p-Chlorophenyl)propanol and 2-(1-Hydroxy-3-butenyl)phenol: Two New Non-narcotic Analgesics Designed by Molecular Connectivity
Authors: GarcíA-March F J , García-Domenech R , Gálvez J , Antón-Fos G M , de Julián-Ortiz J V , Giner-Pons R , Recio-Iglesias M C
Published: April 2011

Molecular topology has been applied to the design of new analgesic drugs. Linear discriminant analysis and connectivity functions were used to design two potentially suitable drugs which were synthesized and tested for analgesic properties by the acetic acid-induced abdominal constriction test in mice and the tail-flick test in rats.

In mice, the compound 1-(p-chlorophenyl)propanol showed higher analgesic activity, both intraperitoneally and orally, than acetylsalicylic acid. 2-(1-Hydroxy-3-butenyl)phenol exhibited a lesser protective effect (70% of that shown by acetylsalicylic acid). In rats, acetylsalicylic acid gave the greatest protection against pain when administered intraperitoneally, while 1-(p-chlorophenyl)propanol was the most active orally. The 2-(1-hydroxy-3-butenyl)phenol, both intraperitoneally and orally, snowed the least protective effect.

These results demonstrated the peripheral analgesic properties of the selected compounds, thus confirming the validity of the molecular design method.
A Submicron Lipid Emulsion Coated with Amphipathic Polyethylene Glycol for Parenteral Administration of Paclitaxel (Taxol)
Authors: Lundberg Bo B
Published: April 2011

Paclitaxel is a promising anticancer agent with poor solubility in water and requires a suitable formulation for intravenous administration. Presently paclitaxel is formulated for clinical use in ethanol and Cremophor EL (Diluent 12), a solvent system associated with severe adverse effects. In this study paclitaxel was entrapped in lipid emulsion droplets with triolein as oil core and dipalmitoyl phosphatidylcholine as the principal emulsifier. The emulsion was further stabilized with polysorbate 80 and polyethylene glycol-dipalmitoyl phosphatidy-lethanolamine.

The drug-emulsion droplets (diameter about 40 nm) were physically and chemically stable during several months at 4°C. Lyophilized preparations in 5% glucose were completely restored by distilled water. Studies of the integrity of the drug-emulsion showed a release of the drug from emulsion globules and surface transfer was found to be the major mechanism for cellular uptake. The in-vitro antiproliferative activity of paclitaxel against T-47D cells was retained by the drug-emulsion with an ID50 value of 7 nM compared to 10 and 35 nM for paclitaxel in liposomes and Diluent 12, respectively.

Long-circulating submicron lipid emulsions may prove useful, not only for replacement of the more toxic Cremophor EL vehicle, but also by improving the distribution of the drug to the tumour.
Comparative Assessment of D-Xylose Absorption between Small Intestine and Large Intestine
Authors: Yuasa Hiroaki , Kuno Chiaki , Watanabe Jun
Published: April 2011

The present study aimed to evaluate the absorption of D-xylose, a passively absorbed five-carbon monosaccharide, from the large intestine compared with the small intestine, in order to explore the absorption potential of the large intestine.

D-Xylose absorption was evaluated in the intestinal loop and everted sacs in rats and comparisons were made between small intestine (mid-gut) and large intestine (colon). The absorption of D-xylose was smaller, by an order of magnitude or more, after administration into the loop of large intestine than after administration into that of small intestine, based on appearance in plasma and disappearance from the intestinal loop. D-Xylose absorption was practically insignificant (nominal 4.9%) in 60 min in the large intestine, whereas it was moderate (57.0%) in the small intestine. Consistently, the uptake of D-xylose in everted sacs was about 20 times larger in the small intestine than in the large intestine.

Thus the passive membrane permeability of D-xylose was demonstrated to be negligible in the large intestine, even though the small intestine was fairly permeable. This result helps rationalize kinetic modelling strategies assuming the small intestine as the sole absorption site for gastrointestinal absorption in-vivo. It also suggests that hydrophilic drugs with molecular size similar to or larger than D-xylose may not be good candidates for colonic drug delivery by controlled release.
In-vitro Permeability of the Human Nail and of a Keratin Membrane from Bovine Hooves: Influence of the Partition Coefficient Octanol/Water and the Water Solubility of Drugs on their Permeability and Maximum Flux
Authors: Mertin Dirk , Lippold Bernhard C
Published: April 2011

Penetration of homologous nicotinic acid esters through the human nail and a keratin membrane from bovine hooves was investigated by modified Franz diffusion cells in-vitro to study the transport mechanism.

The partition coefficient octanol/water PCOct/w of the esters was over the range 7 to > 51000. The permeability coefficient P of the nail plate as well as the hoof membrane did not increase with increasing partition coefficient or lipophilicity of the penetrating substance. This indicates that both barriers behave like hydrophilic gel membranes rather than lipophilic partition membranes as in the case of the stratum corneum. Penetration studies with the model compounds paracetamol and phenacetin showed that the maximum flux was first a function of the drug solubility in water or in the swollen keratin matrix. Dissociation hindered the diffusion of benzoic acid and pyridine through the hoof membrane. Since keratin, a protein with an isoelectric point of about 5, is also charged, this reduction can be attributed to an exclusion of the dissociating substance due to the Donnan equilibrium. Nevertheless, the simultaneous enhancement of the water solubility makes a distinct increase of the maximum flux possible.

In order to screen drugs for potential topical application to the nail plate, attention has to be paid mainly to the water solubility of the compound. The bovine hoof membrane may serve as an appropriate model for the nail.
Effect of Tamoxifen on the Pharmacokinetics of Theophylline in Rats
Authors: Poisson Denise , Dupuis Antoine , Breteau Michel , Bouquet Serge , Poterre Marc , Couet William
Published: April 2011

The effect of tamoxifen on the pharmacokinetics of theophylline was investigated in male Sprague–Dawley rats.

The oral administration of tamoxifen at a dose equal to 40 mg kg−1 48 h before the intravenous injection of theophylline 10 mg kg−1, significantly (P < 005) increased the clearance of theophylline by 39%, with no apparent effect on the volume of distribution. As a consequence, the elimination half-life of theophylline was significantly (P < 005) shortened in the tamoxifen-treated rats (3.56 ± 0.39 h vs 5.25 ± 0.48 h) as well as its mean residence time (5.04 ± 0.60 h vs 7.50 ± 0.75 h). Although these data cannot be directly extrapolated to the clinical situation, they provide experimental support to suggest that more attention should be paid to the potential risk of pharmacokinetic interactions in the presence of tamoxifen.