Vancomycin-loaded HPMC microparticles embedded within injectable thermosensitive chitosan hydrogels.

Antibiotic use is an essential method for the treatment of bacterial infections. In certain cases, antibiotics are not effective because of the distribution problems caused by physiological barriers in the body. Such problems are thought to be minimized by development of sustained release systems which involve implantation of antibiotic loaded polymeric systems directly to the site of infection. In this work, a new composite vancomycin hydrochloride release system based on HPMC microparticles and chitosan/glycerophosphate (Ch/Gp) thermosensitive hydrogel was designed for the aim of local treatment of osteomyelitis. Vancomycin-loaded HPMC microparticles (Van-HPMCs) were prepared by spray drying method. The SEM results showed that these particles had a mean diameter of 1.5-6.4 µm with a narrow size distribution and homogeneous particle production. Their drug encapsulation efficiency was 72.6%. The Van-HPMCs were embedded in an injectable Ch/Gp solution to introduce a composite drug release platform (Van/HPMC-Ch/Gp). In vitro release studies indicated that inclusion of the Van-HPMCs into the Ch/Gp hydrogel caused a reduction in both the release rate and total amount of vancomycin release, which suggests that HPMC microparticles entrapped into the Ch/Gp hydrogels showed more suitable sustained release kinetics for local antibiotics delivery.

Synthesis and characterization of Co3O4 ultra-nanosheets and Co3O4 ultra-nanosheet-Ni(OH)2 as non-enzymatic electrochemical sensors for glucose detection.

The present study examines the synthesis of Co3O4 ultra-nanosheets (Co3O4 UNSs) and Co3O4 ultra-nanosheet-Ni(OH)2 (Co3O4 UNS-Ni(OH)2) via solvothermal process and their application as non-enzymatic electrochemical sensors for glucose detection. X-ray diffraction and transmission electron microscopy results confirmed the Co3O4 UNS deposition on Ni(OH)2 surface. The presence of Co3O4 UNSs on Ni (OH) 2 surface improved the sensitivity of glucose detection, from the increase of glucose oxidation peak current at the Co3O4 UNS-Ni(OH)2/glassy carbon electrode (current density: 2000µA·cm(-2)), compared to the Co3O4 UNSs. These results confirmed that Ni(OH)2 on glassy carbon electrode is a sensitive material for glucose detection, moreover the Co3O4 UNSs can increase the interaction and detection of glucose due to their high surface area. The estimated limit of detection (S/N=3) and limit of quantification (S/N=10) of the linear segment (5-40µM) are 1.08µM and 3.60µM respectively. The reproducibility experiments confirmed the feasibility of Co3O4 UNS-Ni(OH)2 for the quantitative detection of certain concentration ranges of glucose.

Effect of the two new calcium channel blockers mebudipine and dibudipine in comparison to amlodipine on vascular flow of isolated kidney of diabetic rat.

Calcium channel blockers are clinically useful vasodilators, used widely in the treatment of hypertension. These agents are reported to preserve or improve renal function in patients with essential hypertensive renal disease or diabetic renal disease. Among the classes of calcium channel blockers, dihydropyridine derivatives are widely used because of their potent vasodilating activity and weak cardiodepressant action. Mebudipine and dibudipine are two new 1,4-dihydropyridine calcium channel blockers that recently have been synthesized. In previous research mebudipine and dibudipine showed considerable relaxant effects on vascular and ileal smooth muscle cells. In this study we investigated the effects of these new drugs on vascular flow of isolated kidney of diabetic rat and compare their potencies to amlodipine. It is concluded that mebudipine and dibudipine (1-10 µM) are at least as potent as amlodipine in inhibiting PE-induced perfusion pressure in isolated kidney of diabetic rats. These new dihydropyridines improve kidney perfusion of diabetic rat in the setting of PE infusion. Similarly, amlodipine.

Agrobacterium tumefaciens-mediated genetic transformation of a recalcitrant grain legume, lentil (Lens culinaris Medik).

A simple and reproducible Agrobacterium-mediated transformation protocol for a recalcitrant legume plant, lentil (Lens culinaris M.) is reported. Application of wounding treatments and efficiencies of three Agrobacterium tumefaciens strains, EHA105, C58C1, and KYRT1 were compared for T-DNA delivery into lentil cotyledonary node tissues. KYRT1 was found to be on average 2.8-fold more efficient than both EHA105 and C58C1 for producing transient beta-glucuronidase (GUS) gene (gus) expression on cotyledonary petioles. Wounding of the explants, use of an optimized transformation protocol with the application of acetosyringone and vacuum infiltration treatments in addition to the application of a gradually intensifying selection regime played significant roles in enhancing transformation frequency. Lentil explants were transformed by inoculation with Agrobacterium tumefaciens strain, KYRT1 harboring a binary vector pTJK136 that carried neomycin phosphotransferase gene (npt-II) and an intron containing gusA gene on its T-DNA region. GUS-positive shoots were micrografted on lentil rootstocks. Transgenic lentil plants were produced with an overall transformation frequency of 2.3%. The presence of the transgene in the lentil genome was confirmed by GUS assay, PCR, RT-PCR and Southern hybridization. The transgenic shoots grafted on rootstocks were successfully transferred to soil and grown to maturity in the greenhouse. GUS activity was detected in vegetative and reproductive organs of T(0), T(1), T(2) and T(3) plants. PCR assays of T(1), T(2) and T(3) progenies confirmed the stable transmission of the transgene to the next generations.

Effects of mebudipine and dibudipine, two new calcium channel blockers on voltage-activated calcium currents of PC12 cells.

Mebudipine and dibudipine are two newly synthesized dihydropyridine (DHP) calcium channel blockers that have been shown to have considerable relaxant effects on vascular and atrial smooth muscle. The in vitro half-lives of mebudipine and dibudipine are reported to be significantly longer than that of nifedipine. In this study, we investigated the effects of mebudipine and dibudipine on voltage-activated Ca2+ channels on differentiated PC12 cells and compared their potencies to amlodipine. Our results point to absence of voltage-activated Ca2+ currents in undifferentiated PC12 cells. It is also concluded that mebudipine and dibudipine, like amlodipine are L-type calcium channel blockers. When tested in a range of 10-100 microM, mebudipine is at least as potent as amlodipine in inhibition of peak Ba2+ currents in differentiated PC12 cells while dibudipine is significantly less potent compared to amlodipine and mebudipine.

Effect of sildenafil (Viagra) on memory retention of a passive avoidance response in rats.

The effects of an intraperitoneal (i.p.) injection of different doses of sildenafil, a cyclic guanosin monophosphate (cGMP) specific phosphodiesterase type 5 (PDE 5) inhibitor, on memory retention of young (2-month-old) and middle aged (12-month-old) male Wistar rats were investigated. Passive avoidance behaviour was studied in a one trial learning, step--through type, passive avoidance task utilizing the natural preference of rats for a dark environment. In each category (young or middle-aged) different groups of rats received vehicle or sildenafil (1, 3, 10, 20 mg*kg(-1), i.p.) immediately after training and one group remained uninjected serwing as control. Retention latencies were measured 48 h later. To asses a possible non-specific proactive effect of sildenafil, the response latencies in a group of rats not receiving foot shock were also tested. The results showed that the post-training i.p. administration of sildenafil did not facilitate retention performance of a passive avoidance response in both young and middle aged rats compared to control or vehicle groups. Also, sildenafil did not affect response latencies in rats not having received the footshock on the training trial, indicating that sildenafil does not show a non-specific proactive affect on retention performance. The comparison of retention time between young and middle aged rats showed that the memory of the latter had been significantly reduced. In conclusion, this study suggests that sildenafil has no effects on memory retention in Wistar rats.

Interaction of papaverine with the enalapril-induced cough in guinea pig.

BACKGROUND: Angiotensin Converting Enzyme Inhibitors (ACEIs) like enalapril are extremely effective in the treatment of hypertension and heart failure. One of the most important side-effects of these drugs which can lead to cessation of therapy is a persistant dry cough, induced because of increased bradykinin levels in the lung. Although antitussive alkaloids like codeine are effective in suppressing this cough, they too present a wide range of side-effects, most notably addiction. OBJECTIVE: In a previous work we were able to show that noscapine, a non-narcotic antitussive agent, was able to decrease enalapril induced cough in guinea pigs. In this work, papaverine, another non-narcotic alkaloid found in opium latex was tested in the guinea pig model for antitussive activity. METHOD: Cough was induced in enalapril pretreated guinea pigs by forcing the animals to inspire capsaicin aerosol in an air-tight chamber. Coughs were recorded in control animals and in those which had received different doses of papaverine. Characteristic changes in chamber air pressure, were detected by a pressure transducer. RESULTS: . At low doses (0.5 and 0.25 mg/kg) papaverine was able to decrease enalapril induced cough. CONCLUSION. This effect was not mediated by the action of the drug on mu receptors and was only observed in animals treated with enalapril.

Metabolism of the dihydropyridine calcium channel blockers mebudipine and dibudipine by isolated rat hepatocytes.

The prototype 1,4-dihydropyridine (1,4-DHP) nifedipine, indicated for the management of hypertension and angina pectoris, has drawbacks of rapid onset of vasodilating action and a short half-life. Several newer analogues have been designed to offset these problems and these include mebudipine and dibudipine. These analogues contain t-butyl substituents that have been selected to alter the fast metabolism without altering pharmacological activity. In this study, the metabolism of mebudipine and dibudipine by isolated rat hepatocytes has been investigated. These compounds were extensively metabolized in 2 h by oxidative pathways, analogous to those known for nifedipine, and by O-glucuronidation after hydroxylation of the t-butyl substituents. The in-vitro half-lives of mebudipine (22 +/- 7.1 min) and dibudipine (40 +/- 9.8 min) were significantly longer than that of nifedipine (5.5 +/- 1.1 min), which was investigated in parallel in this study. These newer 1,4-DHPs address the problem of the short half-life of nifedipine and have potential for further development in view of their comparable potency to nifedipine.

Effects of mebudipine and dibudipine, two new calcium channel blockers, on guinea-pig isolated common bile duct.

The inhibitory effects of calcium channel blockers; nifedipine and two new compounds, mebudipine and dibudipine, on contractions of isolated guinea-pig common bile duct were investigated. All the compounds tested induced a concentration-dependent reduction of the amplitude of contractile response to electrical stimulation and all the compounds displaced concentration-response curve of calcium chloride to the right in a concentration-dependent manner. The pIC50 values for these compounds acting on electrically stimulated common bile duct were calculated as: dibudipine: 8.50 +/- 0.17; mebudipine: 8.27 +/- 0.20; nifedipine: 7.96 +/- 0.07. The compounds also antagonized the contractile response of K+-depolarized guinea-pig common bile duct to cumulative concentration of calcium. However the inhibitory effect of these compounds were not significantly different.

Solid-phase microextraction (SPME) of permethrin residues from cucumber using a silica-bonded phase-coated stainless steel fibre.

Solid-phase microextraction (SPME) is a rapid, economic and solvent-free sample preparation method for the isolation of an analyte from its matrix. The technique uses a few centimetres of some adsorptive materials such as activated charcoal, polydimethylsiloxane or octadecyl silane coated onto fused silica optical fibres or, more recently, stainless steel fibres mounted into a microsyringe. The proposed method allows the extraction of permethrin from cucumber matrix into the coating, avoiding sample handling and saving evaporation of solvents and concentration steps. Adsorbed permethrin was desorbed in the split/splitless injection port of the gas chromatograph. The time required for each run was about 1.5 h, which gave a preconcentration of several orders of magnitude. The method could separate and quantify cis- and trans-isomers of permethrin. The calibration curve showed linearity in the range 1-9 micrograms ml-1, with detection limits of 0.03 and 0.05 microgram ml-1 for the cis- and trans-isomers of permethrin, respectively. The method had a recovery rate of about 70% and a relative standard deviation of less than 13%. Results suggest that this procedure provides a rapid and sensitive alternative method to those currently available.

Histochemical assessment of nitric oxide synthase activity in aortic endothelial cells of streptozotocin-induced diabetic rats.

Impaired endothelium-dependent relaxation of blood vessels is a common feature in diabetes, but the exact underlying mechanisms have not yet been clarified. In present study, endothelium-dependent vasorelaxation of aortic rings were evaluated in vitro in streptozotocin (STZ)-induced diabetic and age-matched control rats. Moreover, nitric oxide synthase (NOS) activity of aortic endothelial cells was assessed in both diabetic and healthy rats using histochemical staining for nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase activity. The results showed a significant decrease of endothelium-dependent relaxation in response to acetylcholine (ACh) in diabetic rings, compared with controls, that was accompanied by a remarkable attenuation of NOS activity in diabetic sections of rat aorta stained for NADPH-diaphorase. Furthermore, a membrane disruption of some endothelial cells was also observed in all diabetic sections. It can be concluded that a decrease in NOS activity together with a disruption of endothelial cell membrane play a major role in endothelial dysfunction observed in diabetes.

The effect of mebudipine and dibudipine, two new Ca2+ channel blockers, in comparison with nifedipine on Ca2+ spikes of F1 neuronal soma membrane in Helix aspersa.

Mebudipine and dibudipine are two new dihydropyridine (DHP) Ca2+ channel blockers that have been synthesized by Mahmoudian et al. (1997). In previous studies, they showed considerable relaxant effect on vascular and ileal smooth muscles. These two compounds also reduced the contraction force of rat left atrium (20, 22). In the present study, we attempted to compare the inhibitory actions of these new DHPs and nifedipine on the high threshold Ca2+ spikes of F1 neuronal soma membrane in the subesophageal ganglia of Helix aspersa, using current-clamp method. At a concentration of 1 microM, two new DHP compounds (mebudipine and dibudipine) were tested for their L-type Ca2+ channel blocker activity. Both compounds reversibly reduced the peak amplitude of action potential and after hyperpolarization potential and markedly decreased the duration of Ca2+ spikes. The most potent of these DHPs was mebudipine. Neither the two new DHPs nor nifedipine changed the resting membrane potential in a statistically significant way.

Interaction of noscapine with the bradykinin mediation of the cough response.

Angiotensin Converting Enzyme Inhibitors (ACEI) like captopril and enalapril, can induce persistant cough in man. Noscapine, an antitussive alkaloid, can be used to suppress ACEI-induced cough. Some workers have suggested a role for bradykinin in precipitation of ACE-induced cough. Work carried out in our laboratory has shown noscapine to be a non-competitive inhibitor of bradykinin in guinea pig ileum. It is therefore possible that noscapine suppresses cough by blocking the effect of bradykinin receptor activation in the airways. Guinea pigs were placed in a cough-chamber connected to an air pump and a pressure transducer. Capsaicin was sprayed into the chamber and cough was recorded as a distinctive change in air pressure inside the cough-chamber. Animals treated with 1 mg/kg captopril and enalapril for 7 days, showed increased cough response. Ten microgram/kg FR190997, a non-peptide agonist of the bradykinin B2 receptor, also increased the cough response. Noscapine at 0.5, 1 and 2 mg/kg was able to reverse the effects of ACEI and FR190997. Naloxone, a specific opioid receptor inhibitor, did not block the antitussive effects of noscapine in enalapril or FR190997 treated guinea pigs. This antitussive effect of noscapine is not mediated via the mu, kappa or delta opioid receptors. It is therefore possible that noscapine exerts its antitussive action by interfering with the bradykinin cough mediation.

Reduction of the prenatal hypoxic-ischemic brain edema with noscapine.

Cytotoxic free radicals and release of several neurotransmitters such as bradykinin contribute to the pathogenesis of hypoxic-ischemic brain damage. We have studied the efficacy of noscapine, an opium alkaloid and a bradykinin antagonist, in reducing post-hypoxic-ischemic damage in developing brain of 7-d-old rat pups. Hypoxic-ischemic injury to the right cerebral hemisphere was produced by legation of the right common carotid artery followed by 3 h of hypoxia with 8% oxygen. Thirty to 45 min before hypoxia the rat pups received noscapine (dose = 0.5-2 mg/kg) or saline. Pups were scarified at 24 h post recovery for the assessment of cerebral damage by histological methods. Our results showed that noscapine was an effective agent in reducing the extent of brain injury after hypoxic-ischemic insult to neonatal rats. Therefore, it is concluded that noscapine may be a useful drug in the managements of patients after stroke.

A quantitative thin layer chromatography method for determination of theophylline in plasma.

A simple assay method for theophylline in plasma using thin layer chromatography (TLC) was developed. The method involves extraction of the drug and internal standard (acetaminophen) by chloroform-isopropanol (75:25) followed by separation on TLC silica plates using a mixture of acetic acid, isopropanol, toluene (1: 12: 6), as the eluting solvent. Both peak height ratios and peak are ratios showed high correlation coefficient (r>0.98, p<0.001). However we used peak heights for the determinations. Within-day and between-day coefficients of variation were less than 4.4% and 7.8% respectively. The assay proved inexpensive, accurate and reproducible with a limit of detection of 100 ng/ml that makes it suitable for bioavailability studies.

High performance liquid chromatography of mebudipine: application to pharmacokinetic study.

PURPOSE: To develop a high performance liquid chromatography system for the determination of a new 1,4-dihydropyridine, mebudipine, in rabbit plasma. METHODS: To 1 ml of rabbit plasma was added internal standard (dibudipine) and 0.5 ml of 1 M NaOH. Mebudipine and internal standard were extracted to 5 ml ethyl acetate, evaporated under slow stream of nitrogen. The residue was reconstituted in 200 microl mobile phase and 20 microl of aliquots were injected into a HPLC system equipped with 4.6 x 250 mm i.d. C18 analytical column. Mobile phase consisted of methanol (70%), water (25%) and acetonitril (5%) and its flow rate was 1 ml/min. RESULTS: There were no interfering peaks from endogenous components in blank plasma chromatograms. Standard curves were linear (r(2)>0.99) over 10 to 500 ng/ml. The extraction efficiency was >90% and the minimum quantifiable concentration was 10 ng/ml (CV<10%). CONCLUSION: A suitable, convenient and simple HPLC assay for pharmacokinetic study of mebudipine in rabbits was developed.

Efffect of noscapine, the antitussive opioid alkaloid, on bradykinin-induced smooth muscle contraction in the isolated ileum of the guinea-pig.

Bradykinin (BK) and related kinins are autocoid peptides that play integral roles in many pathophysiological processes such as cough. In this study, the inhibitory effect of noscapine, the antitussive opioid alkaloid, on BK receptors, was tested in the guinea-pig ileum. Contractions of the isolated ileum of the guinea-pig in response to BK were inhibited by noscapine (10-1,000 nM) in a concentration-dependent manner. Concentration-response curves (CRCs) to BK were slightly shifted to the right with a concomitant decrease in the maximum effect. A pA2 value of 6.68 was calculated for noscapine. The slope of the Schild plot of the antagonism was found to be 0.56. Noscapine had no effect on contractions induced by KCl, acetylcholine, histamine, 5-hydroxy tryptamine or angiotensin II. In conclusion, noscapine has a specific antagonistic effect on BK receptors and the mode of inhibition was found to be non-competitive.

Effect of smoking on single dose pharmacokinetics of phenobarbital.

In order to determine interaction of smoking with single dose pharmacokinetics of phenobarbital, a 60 mg tablet of the drug was given to 12 healthy male subjects in two groups (6 smokers and 6 non-smokers) in a double blind study. An HPLC method using UV detection was developed to assess phenobarbital in plasma of the subjects. Pharmacokinetic parameters were calculated and compared in the two groups. Pharmacokinetic parameters of the two groups were not significantly different in the two groups (p<0.05). The results show no considerable effect of cigarette smoking on phenobarbital pharmacokinetics, which is in agreement with enzyme studies performed previously.

A study on the teratogenic and cytotoxic effects of safflower extract.

In recent years, the use of carthami flos (the flowers of Carthamus tinctorius L.) as a coloring and flavoring agent has increased as a food additive in Iran. In order to evaluate its safety, the teratogenic effects of carthami flos on the central nervous system development in mice was investigated. Furthermore, its cytotoxic effect on the rat nervous cell culture was studied to complete safety evaluations. For teratogenic studies, after natural mating, pregnant mice were divided into test and control groups. The groups were treated with different dosage regimens of aqueous carthami flos extract during 0-8 days of gestation. Embryos were then isolated at the 13th gestation day and evaluated for macroscopic, microscopic and morphometric characteristics. The results showed that in higher doses (1.6 and 2 mg/kg/day) the embryos were absorbed, whereas with lower dose (1.2 mg/kg/day) changes in external, internal and longitudinal diameters, open neuropore, changes in cellular orientation and cellular degeneration were observed. The results obtained from cytotoxic assay also demonstrated a concentration-dependent cytotoxic effect of carthami flos extract. It is concluded that the use of carthami flos as a food additive should be reconsidered.