bluuebunny/crossref_metadata_2025 huggingface dataset:
Antagonistic effects of selective α1-adrenoceptor antagonists MDL73005EF and tamsulosin and partial agonists clonidine and tizanidine in rat thoracic aorta and rabbit iliac artery
Authors: Satoh Mitsutoshi , Enomoto Keisuke , Koike Katsuo
Published: July 2003

The antagonistic effects of MDL73005EF and tamsulosin and partial agonists clonidine and tizanidineat rat thoracic aorta and rabbit iliac artery α1-adrenoceptors were investigated in this study.

Selective α1-adrenoceptor antagonists MDL73005EF and tamsulosin dose-dependently shifted the concentration-response curves for noradrenaline to the right. Schild plots of the results obtained from the inhibition by MDL73005EF (pA2 8.30 ± 0.04) and tamsulosin (pA2 10.51 ± 0.06) of noradrenaline yielded a straight line with a slope of unity in rat thoracic aorta. The slopes of Schild plots obtained from the inhibition by MDL73005EF and tamsulosin of noradrenaline were significantly different from unity in rabbit iliac artery. Schild plots of the results obtained from the inhibition by clonidine and tizanidine of noradrenaline yielded a straight line with a slope of unity in rat thoracic aorta (pA2 7.08 ± 0.04 and 7.32 ± 0.04, respectively).

These results suggest that α1D-adrenoceptors play a significant role in the α1-adrenoceptor-agonist-induced contraction of rat thoracic aorta and rabbit iliac artery, and that clonidine and tizanidine interact with the α1D-adrenoceptor subtype as competitive antagonists in rat thoracic aorta.
Enhanced nasal retention of hydrophobically modified polyelectrolytes
Authors: Bromberg L E
Published: July 2003

Hydrophobically modified polyelectrolytes (HMP) are polymers with a high content of ionizable groups bonded to hydrophobic groups. Copolymers of poly(acrylic acid) and Pluronic surfactants constitute a special class of HMP whereby poly(propylene oxide) segments act as hydrophobes. The poly(propylene oxide) segments possess temperature-dependent aqueous solubility and the solutions of the Pluronic-poly(acrylic acid) copolymers (MW > 3000000) undergo a sol-gel transition when kept at body temperature. Due to the presence of the poly(acrylic acid) segments, the Pluronic-poly(acrylic acid) copolymers are bioadhesive. We have examined the hypothesis that the in-situ gelling polymer formulations of Pluronic-poly(acrylic acid) copolymers may have an enhanced retention in the nasal cavity. The effects of putative bioadhesive (Carbomer 934P) and thermogelling (Pluronic F127) polymers on nasal clearance were compared with Pluronic-poly(acrylic acid) copolymers using a rat model.

The enhancement of the residence time of fluorescent labels by the Pluronic-poly(acrylic acid) copolymers was shown to be 5–8-fold that of Carbomer, and 3–6-fold that of Pluronic F127. The results unequivocally demonstrate the superior retention of the HMP that combines bioadhesive and thermogelling capabilities over either a bioadhesive polyelectrolyte or a polymer of a low molecular weight that undergoes a sol-gel transition.
Reduction of structural perturbations in bovine serum albumin by non-aqueous microencapsulation
Authors: Carrasquillo Karen G , Carro Juan Carlos Aponte , Alejandro Adriana , Toro Diana Diaz , Griebenow Kai
Published: July 2003

Protein stability is a factor limiting the use of sustained-release devices in medical applications. The aim of this study was to reduce structural perturbations occurring in the frequently used model protein, bovine serum albumin (BSA), upon microencapsulation in poly(D,L-lactide-co-glycolide) (PLG) microspheres.

Spray freeze-dried BSA was encapsulated into PLG microspheres by a completely nonaqueous oil-in-oil encapsulation procedure. FTIR spectroscopy was used as a non-invasive method to quantify procedure-induced structural perturbations in BSA. Spray-freeze drying of BSA caused significant structural perturbations that were minimized by co-spray freeze-drying BSA with trehalose. BSA-containing microspheres were produced by suspension of the powder by homogenization in methylene chloride containing PLG, followed by formation of coacervate droplets by the addition of silicon oil and hardening using the solvent heptane. Resulting microspheres had dimensions of approximately 100 μm and the encapsulation efficiency for BSA was > 90 %. FTIR data showed that the structure of the BSA-trehalose formulation encapsulated into PLG microspheres was less perturbed than that of BSA obtained from buffer alone.

The results demonstrate that the structure-guided encapsulation approach introduced for non-aqueous casting encapsulation procedures can be extended to the non-aqueous production of pharmaceutically relevant PLG microspheres involving a complex encapsulation procedure.
Biphasic effects of acetaldehyde-biogenic amine condensation products on membrane fluidity
Authors: Tsuchiya Hironori
Published: July 2003

I have studied the effects of four acetaldehyde-biogenic amine condensation products on membrane fluidity of liposomes, consisting of 1-palmitoyl-2-oleoylphosphatidylcholine and cholesterol, by measuring fluorescence polarization using different probes.

The condensation products were 1-methyl-1,2,3,4-tetrahydro-β-carboline (MTBC), 6-hydroxy-1-methyl-1,2,3,4-tetrahydro-β-carboline (6-OH-MTBC), 3-carboxy-1-methyl-1,2,3,4-tetrahydro-β-carboline (3-C-MTBC) and 6,7-dihydroxy-1-methyl-1,2,3,4-tetrahydroisoquinoline (salsolinol). They changed the fluidity of the hydrophobic and hydrophilic regions of liposomal membranes at micromolar levels almost corresponding to their antibacterial and antiplatelet concentrations, but their membrane effects varied by structure, concentration and membrane lipid composition. MTBC and salsolinol showed biphasic effects on the inner layers of membranes to enhance the fluidity at 250–1000 μM and reduce the fluidity at 50–100 μM, whereas both of them fluidized the outer layers of the membranes. 3-C-MTBC concentration-dependently fluidized both layers of membranes. 6-OH-MTBC most weakly enhanced and reduced the fluidity of the outer and inner layers, respectively. The membrane effect of MTBC was the greatest of the four condensation products. MTBC (50–1000 nM) significantly reduced the fluidity by exclusively acting on the membrane core, but was less effective in fluidizing the membrane surface. However, the others were not active at low nanomolar levels.

The membrane effects may be partly responsible for the antibacterial and antiplatelet actions of the acetaldehyde-biogenic amine condensation products, although they do not appear to be simple membrane fluidizers.
Vancomycin resistance reversal in enterococci by flavonoids
Authors: Liu Iain X , Durham David G , Richards R Michael E
Published: July 2003

The development of clinical vancomycin-resistant strains of enterococci (VRE) is a major cause for concern. Here we show that a combination of galangin or 3,7-dihydroxyflavone with vancomycin may be used to sensitize resistant strains of Enterococcus faecalis and Enterococcus faecium to the level of vancomycin-sensitive strains.

Minimum inhibitory concentrations (MICs) and viable counts were determined in Iso-sensitest broth using a microtitre method. MICs of vancomycin against 67% of resistant clinical isolates and a type strain of enterococci were lowered from > 250 μg mL−1 to < 4 μg mL−1 in the presence of galangin (12.5 μg mL−1) or 3,7-dihydroxyflavone (6.25 μg mL−1).

Viable counts for type culture E. faecalis ATCC 51299 showed the flavonoids alone significantly lowered numbers of colony forming units (CFUs). CFUs were maintained at low levels (< 103 CFU mL−1) for 24 h by vancomycin/flavone combinations. This combinational action in reversing vancomycin resistance of enterococci highlights novel drug targets and has importance in the design of new therapeutic regimes against resistant pathogens.
The biopharmaceutical aspects of nasal mucoadhesive drug delivery
Authors: Ugwoke Michael Ikechukwu , Verbeke Norbert , Kinget Renaat
Published: July 2003

Nasal drug administration has frequently been proposed as the most feasible alternative to parenteral injections. This is due to the high permeability of the nasal epithelium, allowing a higher molecular mass cut-off at approximately 1000 Da, and the rapid drug absorption rate with plasma drug profiles sometimes almost identical to those from intravenous injections. Despite the potential of nasal drug delivery, it has a number of limitations. In this review, the anatomy and physiology of the nasal cavity, as well as ciliary beating and mucociliary clearance as they relate to nasal drug absorption, are introduced. The rationale for nasal drug delivery and its limitations, some factors that influence nasal drug absorption, and the experimental models used in nasal drug delivery research are also reviewed. Nasal mucoadhesion as a promising method of nasal absorption enhancement is discussed, and factors that influence mucoadhesion, as well as safety of nasal mucoadhesive drug delivery systems are reviewed in detail.

Nasal drug administration is presently mostly used for local therapies within the nasal cavity. Anti-allergic drugs and nasal decongestants are the most common examples. However, nasal drug administration for systemic effects has been practised since ancient times. Nasally-administered psychotropic drugs by native Americans, the use of tobacco snuffs, and nasal administration of illicit drugs such as cocaine are all well known (Illum & Davis 1992). Nowadays, the nasal cavity is being actively explored for systemic administration of other therapeutic agents, particularly peptides and proteins (Illum 1992; Edman & Bjork 1992), as well as for immunization purposes (Lemoine et al 1998). To better understand the basis for nasal drug absorption and factors that can influence it, a brief review of the anatomy and physiology of the nose is appropriate.
Formulation and release characteristics of poly(lactic-co-glycolic acid) microspheres containing chemically modified protein
Authors: Kim Tae-Kyoung , Burgess Diane J
Published: July 2003

Chemical modification of proteins may influence their formulation into and release from polymeric microspheres. Three chemical modifications of rat serum albumin (RSA) were effected on the amine groups of this protein: conjugation with a polyanion using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide, intermolecular cross-linking using glutaraldehyde, and reductive alkylation using propyl aldehyde. The modified proteins had different physicochemical properties as well as improved encapsulation efficiencies compared with native RSA microspheres.

The microspheres were incubated at 37°C for over one month to investigate the influence of protein modification on the release profiles. Microsphere degradation accelerated from the ninth day of the release studies and this coincided with an increase in the release rates. The degradation rates of poly(lactic-co-glycolic acid) microspheres containing either native or crosslinked RSA were more rapid than those containing either heparin conjugated or propylated RSA. This was in agreement with the release data, since the release of the native and crosslinked RSA were more rapid than those of the other modified proteins. The release profiles of the RSA-heparin conjugates and the propylated RSA were approximately zero rather than first order between the tenth and thirtieth day of study.

Chemical modification of protein may be a useful method to increase encapsulation efficiency and to decrease release rates of proteins that are to be used in microsphere formulations of potent therapeutic proteins.
Gastrointestinal transit of dosage forms in the pig
Authors: Davis S S , Illum L , Hinchcliffe M
Published: July 2003

The gastrointestinal transit of liquid, pellet and tablet formulations was measured under fasted conditions in the domestic pig (n = 4) using the technique of gamma scintigraphy.

The mean times for 50% gastric emptying for liquid and pellet systems were 1.4 and 2.2 h, respectively; tablets emptied between 1.5 and 6.0 h. Total transit times were in the order of 50 h. These data conform well to published values for the transit of liquid and solid food materials in the pig. The times are much shorter than those previously published for the transit of solid dosage forms in the pig.

We conclude that the domestic pig would be a good model to study the gastrointestinal transit of pharmaceutical formulations and the absorption of drug compounds.
An investigation into the thermal behaviour of an amorphous drug using low frequency dielectric spectroscopy and modulated temperature differential scanning calorimetry
Authors: He Renren , Craig Duncan Q M
Published: July 2003

The objective of the study was to investigate the use of low frequency dielectric spectroscopy as a means of characterizing the thermal transitions of an amorphous drug substance, indometacin, with particular emphasis on modelling the response using the Dissado-Hill function.

The low frequency dielectric behaviour of indometacin was measured over a temperature range of 10–160°C and a frequency range of 10−3-106 Hz. Modulated temperature differential scanning calorimetry (MTDSC) studies were also performed on equivalent samples, showing a glass transition, recrystallization and melting. Isothermal low frequency dielectric spectra of the sample at temperatures below recrystallization showed the dynamic dielectric relaxation associated with the amorphous phase, while changes in the real and imaginary permittivities were observed that were associated with recrystallization and subsequent melting. A small discontinuity was observed immediately above the recrystallization process in the MTDSC and dielectric data, suggested to correspond to a solid state transformation. The use of the Dissado-Hill function as a means of modelling the dielectric behaviour has also been described.

The study suggests that low frequency dielectric spectroscopy, used in conjunction with MTDSC and Dissado-Hill modelling, maybe a useful tool for the characterization of amorphous and crystalline drugs.
Effect of FITC-dextran molecular weight on its release from floating cetyl alcohol and HPMC tablets
Authors: Xu Guojie , Groves Michael J
Published: July 2003

The release mechanism of high molecular weight fluorescein isothiocyanate dextrans (FITC-dextrans) from HPMC hydrogel matrices was studied.

An anomaly was noted in the release behaviour of a series of high molecular weight FITC-dextrans from a tablet formulation designed to float in stomach contents. The tablets contained sodium bicarbonate and hydroxypropylmethyl cellulose (HPMC) in a cetyl alcohol matrix. When hydrated in an acid medium, this tablet consisted of a mixed solid with a viscous surface layer containing carbon dioxide bubbles through which the active ingredient (FITC-dextran) was released into the aqueous environment. However, it was observed that, above a critical molecular weight (approx. 65 kDa), the FITC-dextran was only released into the medium by an erosion-type mechanism, whereas, below this value, both diffusion and erosion processes took place. The key constraint appearedto bethe apparent gel pore-size of the hydrated HPMC that was approximately 12 nm in diameter, irrespective of the molecular weight of the HPMC samples evaluated.

It was concluded that FITC-dextran release was controlled by both FITC-dextran molecular weight and the HPMC hydrogel structure.
Microparticulate uptake mechanisms of in-vitro cell culture models of the respiratory epithelium
Authors: Foster Kimberly A , Yazdanian Mehran , Audus Kenneth L
Published: July 2003

The objective of this study was to examine the uptake mechanisms of fluorescent polystyrene microspheres of various diameters and surface chemistry by two human cell lines derived from the respiratory epithelium, A549 and Calu-3.

These results suggest that A549 and Calu-3 cells can internalize microspheres and that size and effective charge played an important role in the uptake process.
Pharmacokinetics and bioavailability of α-, γ- and δ-tocotrienols under different food status
Authors: Yap S P , Yuen K H , Wong J W
Published: July 2003

We have investigated the pharmacokinetics and bioavailability of α-, γ- and δ-tocotrienols under fed and fasted conditions in eight healthy volunteers.

The volunteers were administered a single oral dose of mixed tocotrienols (300 mg) under fed or fasted conditions. The bioavailability of tocotrienols under the two conditions was compared using the parameters peak plasma concentration (Cmax), time to reach peak plasma concentration (Tmax) and total area under the plasma concentration-time curve (AUC0-∞).

A statistically significant difference was observed between the fed and fasted logarithmic transformed values of Cmax (P < 0.01) and AUC0-∞ (P < 0.01) for all three tocotrienols. In addition, the 90% confidence intervals for the ratio of the logarithmic transformed AUC0-∞ values of α-, γ- and δ-tocotrienols under the fed state over those of the fasted state were found to lie between 2.24-3.40, 2.05-4.09 and 1.59-3.81, respectively, while those of the Cmax were between 2.28-4.39, 2.31-5.87 and 1.52-4.05, respectively. However, no statistically significant difference was observed between the fed and fasted Tmax values of the three homologues. The mean apparent elimination half-life (t1/2) of α-, γ- and δ-tocotrienols was estimated to be 4.4, 4.3 and 2.3 h, respectively, being between 4.5- to 8.7-fold shorter than that reported for α-tocopherol. No statistically significant difference was observed between the fed and fasted t1/2 values. The mean apparent volume of distribution (Vd/f) values under the fed state were significantly smaller than those of the fasted state, which could be attributed to increased absorption of the tocotrienols in the fed state.
Secretory transport of p-aminohippuric acid across intestinal epithelial cells in Caco-2 cells and isolated intestinal tissue
Authors: Naruhashi Kazumasa , Tamai Ikumi , Sai Yoshimichi , Suzuki Nagao , Tsuji Akira
Published: July 2003

The intestinal transport of an organic anion, p-aminohippuric acid (PAH), was studied in Caco-2 cell monolayers and rat intestinal tissue mounted in Ussing chambers.

In both experimental methods, PAH exhibited vectorial transport with significantly greater permeability in the secretory direction than the absorptive direction, indicating net secretion. This secretory transport required metabolic energy, but protons or hydroxyl ions were not involved as the driving force. In Caco-2 monolayers, secretory transport of [3H]PAH was decreased, and the intracellular accumulation of PAH was increased with increasing concentration of unlabelled PAH at the basolateral side. Addition of probenecid and genistein at the basolateral side decreased the secretory transport of [3H]PAH; the accumulation was not changed by probenecid, but was increased by genistein. In addition, the initial uptake rate of [3H]PAH from the basolateral side was decreased by both PAH and probenecid, but not by genistein. Therefore, it is suggested that the transport of PAH in Caco-2 cells is regulated by several transporters: a genistein-sensitive transporter on the apical membrane and probenecid-sensitive transporters on both the basolateral and apical membranes. In rat intestinal tissues, the transport rate of PAH showed regional variation (ileum > jejunum > duodenum), suggesting that secretory transporters with high activity exist predominantly in the lower region of the small intestine.

The results suggest that PAH transport in both Caco-2 cells and rat intestinal tissues is regulated by multiple transporters on the apical and basolateral membranes, and these transporters have different characteristics.
Imidazolines inhibit secretory responses of rat colonic mucosa to calcium-dependent but not cyclic AMP-dependent secretagogues
Authors: Anderson Malcolm , Burleigh David
Published: July 2003

The purpose of this study was to investigate whether imidazolines have an anti-secretory action on intestinal epithelial cells. Muscle-stripped preparations of rat colon and monolayers of T84 human colonic epithelial cells were set up in Ussing chambers for measurement of short-circuit current. In rat colon acetylcholine, histamine, vasoactive intestinal polypeptide and forskolin elicited secretory responses which were recorded as increases in short-circuit current. Secretory responses to acetylcholine were inhibited in a concentration-dependent manner by the imidazolines phentolamine, idazoxan and clonidine. The effect of clonidine was not reversed by pre-incubation of mucosal preparations with yohimbine. Secretory responses to vasoactive intestinal polypeptide were unaffected by the three imidazolines. Phentolamine reduced responses of colonic mucosa to histamine but had no effect on responses to forskolin. Responses to vasoactive intestinal polypeptide and forskolin were significantly reduced in the presence of barium. In T84 cell monolayers phentolamine significantly reduced responses to acetylcholine. Three imidazolines, two with alpha-adrenoceptor-antagonist properties and one with alpha-agonist properties, have anti-secretory effects in rat colonic mucosal preparations. The anti-secretory action appears to discriminate between calcium-dependent and cyclic AMP-dependent secretagogues, inhibiting the former but not the latter.
Effect of chronic and acute administration of fluoxetine and its additive effect with morphine on the behavioural response in the formalin test in rats
Authors: Nayebi A R M , Hassanpour M , Rezazadeh H
Published: July 2003

Serotonergic systems are involved in the central regulation of nociceptive sensitivity. Fluoxetine, a selective inhibitor of the reuptake of serotonin (5-hydroxytryptamine, 5-HT), was administered orally (0.16, 0.32, 0.8 mg kg−1 daily for 7 days), intraperitoneally (0.04, 0.08, 0.16 mg kg−1 day−1 for 7 days and a single dose of 0.32 mg kg−1) and intracerebroventricularly(10 μg/rat) to rats and nociceptive sensitivity was evaluated using the formalin test (50 μL of 2.5% formalin injected subcutaneously). The effect of fluoxetine was also studied in the presence of 5,7-dihydroxytryptamine creatinine sulfate (5,7-DHT) and after co-administration with morphine. Oral (0.8 mg kg−1), intraperitoneal (0.16 and 0.32 mg kg−1) and intracerebroventricular (10 μg/rat) fluoxetine induced antinociception in the late phase of the formalin test. Furthermore, intrathecal administration of 5-HT (100 μg/rat) induced an analgesic effect. The analgesic effect of fluoxetine (0.16 and 0.32 mg kg−1, i.p.) and 5-HT (100 μg/rat, i.t.) was abolished by pre-treatment with 5,7-DHT (100 μg/rat, i.t.). In addition, the analgesic effect of 5-HT (100 μg/rat, i.t.) was decreased by pre-treatment with naloxone(2 mg kg−1, i.p.). Morphine (5 mg kg−1, i.p.) induced analgesia that was increased by fluoxetine (0.32 mg kg−1, i.p.). These results suggest that fluoxetine has an antinociceptive effect in tonic inflammatory pain through functional alteration of the serotonergic system and also potentiates the analgesic effect of morphine.
Antioxidative effect of fluvastatin, an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase, on peroxidation of phospholipid liposomes
Authors: Yamamoto Atsuko , Ichihara Kazuo , Hoshi Katsuji
Published: July 2003

The antioxidative effect of fluvastatin sodium (fluvastatin), a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, on lipid peroxidation of phosphatidylcholine (PC) liposomes was investigated in various peroxidizing systems. Fluvastatin markedly inhibited the formation of thiobarbituric acid reactive substances in iron (II)-supported peroxidation of liposomes (IC50 = 1.2 × 10−5 M). The order of magnitude of inhibition of each drug on the peroxidation was: butylated hydroxytoluene > fluvastatin ≥ probucol ≥ pravastatin. Moreover, concentrations of fluvastatin ranging from 1 × 10−6 to 1 × 10−4 M inhibited peroxyl radical-mediated peroxidation of liposomes induced by water-soluble and lipid-soluble radical generators, 2,2-azobis (2-amidinopropane) dihydro-chloride and 2,2-azobis (2,4-dimethylvaleronitrile), respectively. However, pravastatin showed no effect against peroxyl radical-mediated peroxidation. These results indicate that fluvastatin acted non-enzymatically as an effective inhibitor against lipid peroxidation of PC liposomes and that the antioxidative effects of fluvastatin may be due to the scavenging action of fluvastatin on liposomal lipid peroxidation induced by peroxyl radicals generated in the aqueous and lipid phases.
Effects of long-term pretreatment with isoproterenol on inotropic responsiveness to α-adrenoceptor stimulation: study in isolated perfused rat hearts
Authors: Silva Cristina O , Monteiro-Filho Waldo O , Duarte Gloria P , Lahlou Saad
Published: July 2003

The effects of chronic pretreatment with isoproterenol (5 mg kg−1) daily for 10 days on cardiac α-adrenergic responsiveness in Langendorff heart preparations were investigated. Isoproterenol pretreatment caused cardiac hypertrophy (29%) as shown by a significant increase in the ratio of ventricular dry weight to body weight. In preparations from isoproterenol-pretreated rats, both maximum increases in left ventricular systolic pressure and heart rate elicited by isoproterenol (10−12 to 10−4 M) were significantly reduced (the isoproterenol concentration producing 50% of the maximum positive inotropic and chronotropic responses was enhanced almost 32- and 4-fold, respectively), while the positive inotropic response to phenylephrine (10−12 to 10−4 M) was significantly enhanced (the phenylephrine concentration producing 50% of the maximum positive inotropic effect was reduced almost 100-fold), compared with saline-pretreated rats. In preparations from both groups, phenylephrine infusion induced non-significant changes in heart rate and its positive inotropic response was reduced in the presence of propranolol (10−7 M) in the perfusion medium. Even under β-adrenoceptor blockade, the curve for the phenylephrine-induced positive inotropic effect remained shifted upward after isoproterenol pretreatment. Chronic isoproterenol pretreatment induces the expected cardiac β-adrenoceptor desensitization while simultaneously enhancing the positive inotropic responsiveness to phenylephrine in Langendorff heart preparations. These findings support the hypothesis that cardiac α1-adrenoceptor stimulation may contribute to the maintenance of myocardial function under conditions in which β-adrenoceptor function is compromised.
Antioxidants, vitamin C and dithiothreitol, activate membrane-bound guanylate cyclase in PC12 cells
Authors: Chen Zi-Jiang , Che Danian , Chang Chung-Ho
Published: July 2003

Antioxidants and antioxidant enzymes are known to protect against cell death induced by reactive oxygen species. However, apart from directly quenching free radicals, little is known about the effect of antioxidants on hormone-activated second messenger systems. We previously found that antioxidants such as 17-β estradiol and resveratrol activate membrane-bound guanylate cyclase GC-A, the receptor for atrial natriuretic factor (ANF), in PC12 cells. It is possible that other antioxidants may also activate membrane-bound guanylate cyclase GC-A. The aim of this study was to determine if dithiothreitol (DTT), vitamin C, and vitamin E activate membrane-bound guanylate cyclase GC-A in PC12 cells. The results showed that both DTT and vitamin C increased cGMP levels in PC12 cells, whereas vitamin E had no effect. DTT and vitamin C inhibited membrane-bound guanylate cyclase activity stimulated by ANF in PC12 cells. In contrast, DTT and vitamin C had no effect on soluble guanylate cyclase activity stimulated by substance P. Furthermore, NO synthase inhibitors L-NAME and aminoguanidine did not affect DTT- and vitamin C-stimulated guanylate cyclase activity. The results indicate that DTT and vitamin C, but not vitamin E, activate membrane-bound guanylate cyclase GC-A in PC12 cells.
Inhibition of oxotremorine-induced desensitization of guinea-pig ileal longitudinal muscle in Ca2+-free conditions
Authors: Horio Shuhei , Fukui Hiroyuki
Published: July 2003

The aim of this study was to investigate the differences between oxotremorine-induced and acetylcholine (ACh)-induced desensitization, particularly under Ca2+-free conditions, in guinea-pig ileal longitudinal muscle, and to elucidate the different mechanisms of desensitization that might exist between these two muscarinic agonists. Pretreatment of the tissue with 10−7 — 10−5 M oxotremorine (desensitizing treatment) in normal Tyrode solution caused desensitization of the responses to ACh, as did the desensitizing treatment with ACh. However, Ca2+-free conditions significantly reduced oxotremorine-induced desensitization, contrary to the previous findings that Ca2+-free conditions enhanced ACh-induced desensitization. The desensitizing treatment with oxotremorine caused suppression of the responses to high K+ (tonic phase), as did the ACh treatment. Ca2+-free conditions removed this suppression, whereas this condition enhanced ACh-induced suppression of the K+ response. A protein kinase C inhibitor, 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (10−4 M) had no effect on oxotremorine-induced desensitization of the ACh response. The results suggest that a voltage-gated Ca2+ channel was involved in oxotremorine-induced desensitization, as in ACh-induced desensitization, but that the process of inactivation of Ca2+ channels was different between oxotremorine and ACh, and that oxotremorine-induced desensitization was due not only to Ca2+ channel, but also to other unknown factors. Protein kinase C did not participate in oxotremorine-induced desensitization.
Preparation and characterization of biodegradable or enteric-coated microspheres containing the protease inhibitor camostat
Authors: Uchida Takahiro , Yasuda Noriko , Matsuyama Kenji
Published: July 2003

We have produced biodegradable or enteric-coated microspheres containing camostat mesylate, a protease inhibitor, using a water-oil-water emulsion solvent evaporation method. The characteristics of the microspheres were determined. When polylactic acid, a biodegradable polymer, was used as a wall material, the optimized microsphere obtained showed a loading efficiency of almost 95% and had a mean diameter of 30 pim. This microsphere showed a sustained-release profile, with nearly 25% of drug being released at seven days in a dissolution test. When hypromellose acetate succinate (AS-HG type, with a high content of succinyl group) was used as an enteric wall material, optimized microspheres showed a loading efficiency of almost 80%. In this case, pH 3.0 citrate buffer was used as an internal aqueous phase, and citrate buffer containing 0.5 % polyvinylalcohol was used as the external aqueous phase. These microspheres showed a rapid release profile in pH 6.8 buffer, whereas the release was extremely slow in pH 1.2 buffer. Hypromellose acetate succinate microspheres were also prepared containing 10% (w/w) N-benzoyl-dl-arg-4-nitroanilide as a model substrate for trypsin, with or without 5% (w/w) camostat. These microspheres were incubated in pH 6 or 7 buffer containing trypsin at 37°C. When camostat was included in the microspheres, the substrate was protected from attack by trypsin, while in the absence of camostat, the released substrate was immediately attacked by trypsin to produce the degradation product N-benzoyl-dl-arginine.
A sensitive and reliable method for the detection of lipid peroxidation in biological tissues
Authors: Anoopkumar-Dukie Shailendra , Walker Roderick B , Daya Santy
Published: July 2003

A simple, accurate and cost effective method has been designed for the determination of lipid peroxidation in biological tissue samples. The method was a modification and improvement on existing methods available for lipid peroxidation determination. Solid-phase extraction was used to separate the thiobarbituric acid-malondialdehyde complex from thiobarbituric acid-reactive substances and HPLC was performed using a C18 (Waters Spherisorb, 5μm, 250 × 4.6 mm i.d.) column to achieve isolation of the complex. The procedure was validated with respect to linearity of calibration (0.998), precision, sensitivity and limits of quantitation (1 nmol mL−1) and detection (0.5 nmol mL-1). Resorcinol was used as an external standard. The method was tested by inducing free radical generation with a known free radical generator, quinolinic acid, in rat brain homogenate. The results showed that the method presented allowed detection of lipid peroxidation products at concentrations in the nanomolar (nM) range compared with the micromolar (μM) range detected by other methods, thus rendering it suitable for use with biological samples. In addition, the modified method allowed for detection of the purified lipid peroxidation products, thus eliminating the possibility of simultaneous detection of impurities that absorb at the same wavelength.
Synthesis and in-vitro antimicrobial activity of new 1,2,4-triazoles
Authors: Bhat A R , Bhat G Varadaraj , Shenoy G Gautham
Published: July 2003

We have described the synthesis of new 1,2,4-triazoles and have evaluated their antimicrobial profile. Antitubercular activity was determined in triplicate using the Lowenstein-Jensen medium. A loopful of Mycobacterium tuberculosis suspension was inoculated on the surface of each Lowenstein-Jensen media containing the test compounds (100, 10 or 1 μg mL−1). To evaluate in-vitro antibacterial activity, compounds (50, 5 or 0.5 μg) were evaluated against B. subtilis, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Staphylococcus typhi by the disc diffusion method. To evaluate antifungal activity Sabourauds Dextrose agar medium was used. Some of the compounds (5, 0.5 or 0.05 μg mL−1) were screened for activity against Aspergillus niger 88 and Aspergillus niger 90 and others were screened for activity against T. rubrum TR1, T. rubrum R6, T. rubrum R7 and T. mentagrophyte M1, using the cup plate method. Our results show that the triazoles with a pyrazine moiety at position 3 were more active as antitubercular and antifungal agents compared with the triazoles which had a pyrazine moiety at position 4 of the molecule.
Stimulation of insulin release in rats by Die-Huang-Wan, a herbal mixture used in Chinese traditional medicine
Authors: Cheng Juei-Tang , Liu I-Min , Chi Tzong-Cherng , Su Hui-Chen , Chang Chung-Gwo
Published: July 2003

Die-Huang-Wan is a herbal mixture widely used in Chinese traditional medicine to treat diabetic disorders. We have investigated the effect of Die-Huang-Wan on plasma glucose concentration in-vivo. Die-Huang-Wan was administered orally (5.0, 15.0 or 26.0 mg kg−1) to three rat models. Wistar rats were used as the normal animal model, rats with insulin-resistance (induced by the repeated thrice daily injection of human long-acting insulin) were used as the non-insulin-dependent diabetic model, and streptozotocin-induced diabetic rats were used as the insulin-dependent diabetic model. In normal rats, approximately 1 h after oral administration of Die-Huang-Wan the plasma glucose concentration decreased significantly in a dose-dependent manner, from 5 to 26.0 mg kg−1. A similar effect was observed in rats with insulin-resistance. However, this effect was not observed in streptozotocin-induced diabetic rats, even at an oral dose of 26.0 mg kg−1. These results suggested an insulin-dependent action, a view supported by the increase of plasma insulin-like immunoreactivity in normal rats receiving Die-Huang-Wan. The results indicated that Die-Huang-Wan had an ability to stimulate the secretion of insulin and this preparation seemed helpful in improving the diabetic condition, especially hyperglycaemia in type-II diabetes.
Role of nitric oxide in hypodipsia of rats with obstructive cholestasis
Authors: Mani Ali Reza , Nahavandi Arezo , Mani Amir Hossein , Dehpour Ahmad Reza
Published: July 2003

Cholestasis is associated with the overproduction of nitric oxide (NO), and NO acts as an inhibitory mechanism when thirst is stimulated by water deprivation or by angiotensin II. Due to the presence of hypodipsia in the cholestatic condition, we have compared the rate of water intake between bile duct-ligated (cholestatic) and sham-operated rats. We have evaluated the effect of NO synthesis inhibition by NG-nitro-L-arginine (L-NNA, 10 mg kg−1/day) on the rate of water intake in cholestatic rats. The results showed that plasma alkaline phosphatase activity (a marker of liver damage) increased after bile-duct ligation, and that its elevation was partially (but significantly) prevented by treatment with L-arginine. A two-week bile-duct obstruction induced a significant decrease in the rate of water intake compared with sham-operated animals (35.87 ± 1.45 vs 42.37 ± 1.99 mL/day, P < 0.05). This effect was corrected by the daily administration of L-NNA. Surprisingly, L-arginine (200 mg kg−1/day) showed similar activity as L-NNA in cholestatic rats and increased water intake, but not in control animals. Systemic NO synthesis inhibition corrected the decrease in water intake observed in cholestatic rats. This suggests an important role for NO in the pathophysiology of hypodipsia in cholestatic subjects. The effect of chronic L-arginine administration observed in cholestatic rats but not seen in the control rats could be explained theoretically by the amelioration of cholestasis-induced liver damage by chronic L-arginine administration in bile duct-ligated rats.
Pharmacognosy in the 21st century
Authors: Kinghorn A Douglas
Published: July 2003

The term pharmacognosy as a constituent scientific discipline of pharmacy has been in use for nearly 200 years, and it refers to studies on natural product drugs. During the last half of the 20th century, pharmacognosy evolved from being a descriptive botanical subject to one having a more chemical and biological focus. At the beginning of the 21st century, pharmacognosy teaching in academic pharmacy institutions has been given new relevance, as a result of the explosive growth in the use of herbal remedies (phytomedicines) in modern pharmacy practice, particularly in western Europe and North America. In turn, pharmacognosy research areas are continuing to expand, and now include aspects of cell and molecular biology in relation to natural products, ethnobotany and phytotherapy, in additiontothe more traditional analytical method development and phytochemistry. Examples are provided in this review of promising bioactive compounds obtained in two multidisciplinary natural product drug discovery projects, aimed at the elucidation of new plant-derived cancer chemotherapeutic agents and novel cancer chemopreventives, respectively. The systematic study of herbal remedies offers pharmacognosy groups an attractive new area of research, ranging from investigating the biologically active principles of phytomedicines and their mode of action and potential drug interactions, to quality control, and involvement in clinical trials.
Increased vigabatrin entry into the brain by polysorbate 80 and sodium caprate
Authors: Dimitrijevic D , Whitton P S , Domin M , Welham K , Florence A T
Published: July 2003

The effects of a non-ionic surfactant, polysorbate 80, and the sodium salt of the saturated fatty acid, sodium caprate (C10), as potential brain absorption enhancers for vigabatrin were studied. Vigabatrin is an enzyme-activated irreversible inhibitor of γ-aminobutyric acid (GABA) transaminase that increases brain and cerebrospinal GABA concentrations in animals and man. Before intravenous administration, a range of concentrations of the surfactants were tested using erythrocyte lysis or the red blood cell lysis test to establish the non-toxic concentration range. Vigabatrin was dissolved in 0.1% polysorbate 80 and 0.1% sodium caprate and administered intravenously in doses of 4 mL kg−1 to male Wistar rats (230–250 g; n = 3). Rats were killed 2 h after drug and surfactant administration and the brains were immediately removed and homogenized in 0.4m perchloric acid. Selected ion monitoring electrospray mass spectrometry was used to determine the concentration of vigabatrin and GABA directly from the perchloric acid extract of the rat brain. This method was developed to increase the speed and efficiency of the analysis by removing the need for complex extraction and derivatization procedures while retaining the specificity of the mass spectrometer as a detector. The stability of both vigabatrin and GABA in perchloric acid was established by monitoring their pseudo molecular ions in standard solutions at timed intervals over 24 h. Although the detection level for vigabatrin and GABA was at least 50 pg, only GABA was detected in rat brain. Vigabatrin caused a small increase in whole brain GABA. However, GABA levels were higher in the samples with vigabatrin + enhancer than in the samples where vigabatrin alone was administered. One-way analysis of variance indicated a significant effect of the surfactants on GABA levels (F (5,17) = 11.86, P < 0.01) and vigabatrin absorption was presumed. The rectal temperature of the rats is lowered by the presence of vigabatrin in the brain. Vigabatrin alone decreased rectal temperature by 6%. When given with either polysorbate 80 or sodium caprate, the extent of temperature lowering was significantly greater (P < 0.001). There was no significant difference after 2 h between polysorbate 80 + vigabatrin, and sodium caprate + vigabatrin.
In-vitro and in-vivo evaluation of pH-responsive polymeric micelles in a photodynamic cancer therapy model
Authors: Taillefer J , Brasseur N , van Lier J E , Lenaerts V , Garrec D Le , Leroux J-C
Published: July 2003

pH-sensitive polymeric micelles of randomly and terminally alkylated N-isopropylacrylamide copolymers were prepared and characterized. Aluminium chloride phthalocyanine (AlClPc), a second generation sensitizer for the photodynamic therapy of cancer, was incorporated in the micelles by dialysis. Their photodynamic activities were evaluated in-vitro against EMT-6 mouse mammary tumour cells and in-vivo against EMT-6 tumours implanted intradermally on each hind thigh of Balb/c mice. pH-sensitive polymeric micelles were found to exhibit greater cytotoxicity in-vitro than control Cremophor EL formulations. In the presence of chloroquine, a weak base that raises the internal pH of acidic organelles, in-vitro experiments demonstrated the importance of endosomal/lysosomal acidity for the pH-sensitive polymeric micelles to be fully effective. Biodistribution was assessed by fluorescence of tissue extracts after intravenous injection of 2 μmol kg−1 AlClPc. The results revealed accumulation of AlClPc polymeric micelles in the liver, spleen and lungs, with a lower tumour uptake than AlClPc Cremophor EL formulations. However, polymeric micelles exhibited similar activity in-vivo to the control Cremophor EL formulations, demonstrating the higher potency of AlClPc polymeric micelles when localized in tumour tissue. It was concluded that polymeric micelles represent a good alternative to Cremophor EL preparations for the vectorization of hydrophobic drugs.
Encapsulation of bovine serum albumin in poly(lactide-co-glycolide) microspheres by the solid-in-oil-in-water technique
Authors: Castellanos Ingrid J , Carrasquillo Karen G , López Jesiebel De Jésus , Alvarez Mariali , Griebenow Kai
Published: July 2003

Non-aqueous protocols to encapsulate pharmaceutical proteins into biocompatible polymers have gained much attention because they allow for the minimization of procedure-induced protein structural perturbations. The aim of this study was to determine if these advantages could be extended to a semi-aqueous encapsulation procedure, namely the solid-in-oil-in-water (s/o/w) technique. The model protein bovine serum albumin (BSA) was encapsulated into poly(lactide-co-glycolide) (PLG) microspheres by first suspending lyophilized BSA in methylene chloride containing PLG, followed by emulsification in a 1% aqueous solution of polyvinyl alcohol). By variation of critical encapsulation parameters (homogenization intensity, BSA:PLG ratio, emulsifier concentration, ratio of organic to aqueous phase) an encapsulation efficiency of > 90 % was achieved. The microspheres obtained showed an initial burst release of < 20 %, a sustained release over a period of about 19 days, and a cumulative release of at least 90% of the encapsulated BSA. Different release profiles were observed when using different encapsulation protocols. These differences were related to differences in the microsphere erosion observed using scanning electron microscopy. Release of BSA was mainly due to simple diffusion orto both diffusion and microsphere erosion. Fourier-transform infrared studies were conducted to investigate the secondary structure of BSA during the encapsulation. Quantification of the α-helix and β-sheet content as well as of overall structural changes showed that the secondary structure of encapsulated BSA was not more perturbed than in the lyophilized powder used initially. Thus, the encapsulation procedure did not cause detrimental structural perturbations in BSA. In summary, the results demonstrate that the s/o/w technique is an excellent alternative to the water-in-oil-in-water technique, which is still mainly used in the encapsulation of proteins in PLG microspheres.
Pharmacokinetics of diaspirin cross-linked haemoglobin in a rat model of hepatic cirrhosis
Authors: Palaparthy R , Kastrissios H , Gulati A
Published: July 2003

The aim of the study was to evaluate the effect of cirrhosis on the disposition of the haemoglobin-based oxygen carrier, diaspirin cross-linked haemoglobin (DCLHb). Cirrhosis was induced in male Sprague-Dawley rats (200–250 g) by inhalational exposure to carbon tetrachloride (CCl4), over a period of 6 weeks. Pharmacokinetic evaluation was performed after a single intravenous bolus administration of DCLHb (400 mg kg−1). Serum biochemistry, including aspartate transaminase, alkaline phosphatase, bile acids, serum albumin, and serum creatinine, were measured in CCl4-treated (n = 6) and age-matched control (n = 6) rats. After 6 weeks, the jugular vein and carotid artery were cannulated for bolus DCLHb administration (400 mg kg−1) and blood sampling, respectively, in both groups of rats. Cirrhosis produced significant (P < 0.05) elevations in alkaline phosphatase (497.4 ± 84.8 U L−1 vs 241.2 ± 5.1 U L−1), aspartate transaminase (920.5 ± 190.9 U L−1 vs 238.2 ± 118.1 U L−1) and bile acids (333.8 ± 77.3 mg dL−1 vs 43.8 ± 4.2 mg dL−1) compared with the control group. No significant renal dysfunction was observed as a result of CCl4 exposure. Plasma DCLHb concentrations declined approximately log-linearly. Systemic clearance of DCLHb was estimated to be 2.2 ± 0.7 mL h−1 in the treatment group and was slightly, but not significantly, less in the control group (3.6 ± 1.7 mL h−1). There was also a trend toward a longer elimination half-life in the treatment group (4.7 ± 2.2 h) compared with the control group (3.8 ± 0.8 h), although this difference was not statistically significant. Cirrhosis does not significantly alter the disposition of DCLHb perhaps due to increased extra-hepatic metabolism by the reticulo-endothelial system.
Antimicrobial activity of tannin components from Vaccinium vitis-idaea L.
Authors: Ho K Y , Tsai C C , Huang J S , Chen C P , Lin T C , Lin C C
Published: July 2003

Reactive oxygen species have been implicated as important pathological mediators in many clinical disorders, including periodontal disease. As a possible alternative for the treatment of periodontal disease, the antimicrobial activity of six tannins isolated from Vaccinium vitis-idaea L., with confirmed antioxidant activity, were assayed by the agar dilution method against selected periodontal pathogens, Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis and Prevotella intermedia. The results showed that epicatechin-(4β → 8)-epicatechin-(4β → 8, 2β → O → 7)-catechin had strong antimicrobial activity against P. gingivalis and P. intermedia, but not A. actinomycetemcomitans. The other tannins tested did not show antimicrobial activity. We conclude that tannins isolated from V. vitis-idaea L. with antimicrobial activity could potentially be used for the treatment of periodontal disease.