Viscoelastic evaluation of topical creams containing microcrystalline cellulose/sodium carboxymethyl cellulose as stabilizer

The purpose of this study was to examine the viscoelastic properties of topical creams containing various concentrations of microcrystalline cellulose and sodium carboxymethyl cellulose (Avicel(R) CL-611) as a stabilizer. Avicel CL-611 was used at 4 different levels (1%, 2%, 4%, and 6% dispersion) to prepare topical creams, and hydrocortisone acetate was used as a model drug. The viscoelastic properties such as loss modulus (G"), storage modulus (G'), and loss tangent (tan delta) of these creams were measured using a TA Instruments AR 1000 Rheometer and compared to a commercially available formulation. Continuous flow test to determine the yield stress and thixotropic behavior, and dynamic mechanical tests for determining the linear viscosity time sweep data, were performed. Drug release from the various formulations was studied using an Enhancer TM Cell assembly. Formulations containing 1% and 2% Avicel CL-611 had relative viscosity, yield stress, and thixotropic values that were similar to those of the commercial formulation. The elastic modulus (G') of the 1% and 2% formulation was relatively high and did not cross the loss modulus (G"), indicating that the gels were strong. In the commercial formulation, G' increased after preshearing and broke down after 600 seconds. The strain sweep tests showed that for all formulations containing Avicel CL-611, the G' was above G" with a good distance between them. The gel strength and the predominance of G' can be ranked 6% > 4% > 2%. The strain profiles for the 1% and 2% formulations were similar to those of the commercial formulation. The delta values for the 1% and 2% formulations were similar, and the formulations containing 4% Avicel CL-611 had lower delta values, indicating greater elasticity. Drug release from the commercial preparation was fastest compared to the formulations prepared using Avicel CL-611, a correlation with the viscoelastic properties. It was found that viscoelastic data, especially the strain sweep profiles of products containing Avicel CL-611 1% and 2%, correlated with the commercial formulation. Rheological tests that measure the viscosity, yield stress, thixotropic behavior, other oscillatory parameters such as G' and G" are necessary tools in predicting performance of semisolids.     

Conformation of the hexasaccharide repeating subunit from the Vibrio cholerae O139 capsular polysaccharide

In the past decade, several outbreaks of cholera have been reported to be caused by Vibrio cholerae O139, a strain which differs from the more common O1 strain in that the former is encapsulated. The hexasaccharide repeating subunit has been isolated from the V. cholerae O139 capsular polysaccharide by digestion with a recently discovered polysaccharide lyase derived from a bacteriophage specific for this serogroup. It specifically cleaves at a single position of the 4-linked galacturonic acid producing an unsaturated sugar product in quantities for conformational studies by (1)H and (13)C NMR spectroscopy. We report conformational studies on this oligosaccharide by molecular modeling and NMR spectroscopy including nuclear Overhauser effects and residual dipolar coupling of a sample weakly oriented in liquid crystalline solution. The structure contains a tetrasaccharide epitope homologous to the human Lewis(b) blood group antigen, which adopts a relatively well-defined single conformation. Comparison of these results with those of a previously published study of the intact capsular polysaccharide indicates that the conformations of the epitope in the two cases are identical or at least closely similar. Thus, this epitope, which may be essential for the pathogenicity of this V. cholerae strain, is not a "conformational epitope" requiring a certain critical size for antigenicity as has been reported for several other bacterial capsular antigens.     

Comparative chemical analysis,mutagenicity, and genotoxicity of Petroleum refinery wastewater and its contaminated river using prokaryotic and eukaryotic assays

Concern on the toxicity of final wastewater generated by the petroleum refining industry has increased in recent years due to the potential health threats associated with their release into the waterways. This study determined the mutagenic and genotoxic potential of petroleum refinery wastewater and a receiving river using the Ames fluctuation test on Salmonella typhimurium strains TA100 and TA98, SOS chromotest on Escherichia coli PQ37, and piscine peripheral micronucleus (MN) assay. Analyses of the physicochemical parameters, heavy metal, and organic contents of the samples were also performed. Ames test result showed that the two tested samples were mutagenic with TA100 strain as the more responsive strain for both the refinery wastewater and the river sample in terms of the calculated mutagenic index. A similar result was obtained in the SOS chromotest; however, the E. coli PQ37 system recorded a slightly higher sensitivity for detecting genotoxins than the Salmonella assay in the two samples. MN data showed induction of a concentration-dependent significant (p < 0.05) increase in the frequency of MN by both samples when compared with the negative control. Generally, the refinery wastewater induced the highest mutagenicity and genotoxicity compared to the river sample in the three assays used. Haemoglobin, platelets, red blood cells, mean corpuscular volume, total white blood cells, heterophils, haematocrit, and eosinophils reduced significantly with increased lymphocytes, basophils, mean corpuscular haemoglobin, and mean corpuscular haemoglobin concentration in fishes exposed to both samples. Total petroleum hydrocarbon, benzene, toluene, phenol index, polycyclic aromatic hydrocarbons, cadmium, mercury, nickel, lead, and vanadium contents analysed in the samples were believed to be responsible for the observed genotoxicity and mutagenicity. The findings of this study revealed that petroleum refinery wastewater is a potential mutagenic and genotoxic risk to the environment.

     

Studies on the chemical constitution of cell wall lipo-oligosaccharide from Campylobacter coli Labet 227

The lipo-oligosaccharide (LOS) from Campylobacter coli Labet 227 was extracted by aqueous phenol. After delipidation and gel chromatography, two oligosaccharides were isolated. The higher molecular weight material OS (I) which was estimated to contain six to seven sugar units was found to contain glucose, galactose, 2-acetamido-2-deoxyglucose, 2-acetamido-2-deoxygalactose and heptose. Analysis of the partially methylated alditol acetates by g.c.-m.s. revealed the presence of terminal hexoses, a 1.3-linked hexose, a terminal heptose, a 1,2,3-linked heptose as well as smaller quantities of a 1,3,4-linked heptose. 1H-n.m.r. spectra showed signals corresponding to six anomeric protons. The signals which corresponded to the methyl protons of the acetamido side chain confirmed that the acetamido forms of both amino sugars were present in OS (I). The lower molecular weight material OS (II) which was estimated to contain four sugar units was found to contain glucose, 2-acetamido-2-deoxy-galactose and very small quantities of heptose. It thus appears that OS (I) and OS (II) are the core oligosaccharides elaborated by this micro-organism. The possibility of a heterogeneous core is thus presented. The fatty acids present in the LOS were mainly 3-hydroxytetradecanoic acid, n-hexadecanoic acid and trace amounts of n-tetradecanoic acid and n-octadecanoic acid.     

Fermentation of prebiotics by human colonic microbiota in vitro and short-chain fatty acids production: a critical review

Prebiotics are known for their health benefits to man, including reducing cardiovascular disease and improving gut health. This review takes a critical assessment of the impact of dietary fibres and prebiotics on the gastrointestinal microbiota in vitro. The roles of colonic organisms, slow fermentation of prebiotics, production of high butyric and propionic acids and positive modulation of the host health were taken into cognizance. Also, the short-chain fatty acids (SCFAs) molecular signalling mechanisms associated with their prebiotic substrate structural conformations and the phenotypic responses related to the gut microbes composition were discussed. Furthermore, common dietary fibres such as resistant starch, pectin, hemicelluloses, β-glucan and fructan in context of their prebiotic potentials for human health were also explained. Finally, the in vitro human colonic fermentation depends on prebiotic type and its physicochemical characteristics, which will then affect the rate of fermentation, selectivity of micro-organisms to multiply, and SCFAs concentrations and compositions.     

Parasitism-linked block of host plasma melanization

When parasitized by the Ichneumonid parasitoid Campoletis sonorensis, larvae of the Noctuid moth, Heliothis virescens, are unable to mount an effective immune response against parasitoid eggs. Defensive melanization of plasma and cellular encapsulation of parasite eggs are dramatically inhibited by infection with the symbiotic immunosuppressive C. sonorensis ichnovirus (CsIV). This study demonstrates that the CsIV-mediated inhibition of melanization is associated with reduction in the enzymatic activity and protein titer of key enzymes in the melanization pathway, phenoloxidase, dopachrome isomerase, and DOPA decarboxylase. Inhibition of the synthesis of key melanization enzymes leads to reductions in the melanization substrates l-dihydroxyphenylalanine, N-acetyldopamine, and N-beta-alanyl dopamine from millimolar to nanomolar levels in parasitized larvae. By contrast, concentration of a precursor catecholamine, dopamine, rises fourfold in these larvae. Thus in CsIV-infected larvae, enzymatic deficiencies in the melanization pathway lead to reduced concentrations of specific enzyme substrates, causing failure of melanization in parasitized insects.     

The capsule polysaccharide structure and biogenesis for non-O1 Vibrio cholerae NRT36S: genes are embedded in the LPS region

Background  

In V. cholerae, the biogenesis of capsule polysaccharide is poorly understood. The elucidation of capsule structure and biogenesis is critical to understanding the evolution of surface polysaccharide and the internal relationship between the capsule and LPS in this species. V. cholerae serogroup O31 NRT36S, a human pathogen that produces a heat-stable enterotoxin (NAG-ST), is encapsulated. Here, we report the covalent structure and studies of the biogenesis of the capsule in V. cholerae NRT36S.     

Respiratory metabolism of the soft tick,Ornithodoros turicata (Dugès)

The rate of oxygen consumption was investigated in fed larval, nymphal and adult Ornithodoros turicata ticks and in starved nymphal and adult ticks. Oxygen consumption rate of fed adult ticks increased with increasing temperature. The metabolic rate of adult ticks was affected by starvation whereby starved adult ticks showed a significantly lower oxygen consumption than their fed counterparts. The oxygen consumption rate of fed female ticks was significantly higher than that of fed males but, there was no significant difference between the oxygen consumption rates of starved female versus starved male ticks. Oxygen consumption of fed larvae was significantly greater than those of fed first through third instar nymphs. Fed and starved nymphal ticks as well as fed adult ticks ventilated continuously. In contrast, starved adults ventilated discontinuously. The ability to reduce metabolic rate, plus the capability to ventilate discontinuously allow O. turicata adults to cope with prolonged starvation.     

Feasibility studies in spheronization and scale-up of ibuprofen microparticulates using the rotor disk fluid-bed technology

The aim of this study was to develop spheronized microparticulates as a drug delivery system using the 1-step closed rotor disk fluid-bed technology, and to scale up the batch spheronization process. Ibuprofen was used as the model drug and microcrystalline cellulose/sodium carboxymethyl cellulose hydrocolloid (Avicel(R) RC-581 or CL-611) was present as the diluent/binder. The mixture, in 1:1 ratio, was blended with and without 1% sodium lauryl sulfate (SLS) and spheronized with the rotor disk insert, using either water or hydroxypropylmethyl cellulose (HPMC) as binder. Fluid-bed machines (Vector/Freund Flo-Coater model) FLM-1 (with 9-inch rotor insert for 0.75 kg) and FLM-15 (with a 12-inch and 19-inch rotor inserts for 1 kg and 5, 10 kg, respectively) were used. The critical process parameters included inlet air temperature, rotor disk speed and configuration, air flow, and rate of binder application. The 1 kg batch containing SLS that was made with 12-inch smooth stainless steel or waffle teflon plates rotating at 500 rpm had desirable characteristics. The sphericity values were 0.88 and 0.91, with percent yield of 85.4 and 91.2 and drug content values of 94.47% and 91.44%, respectively. The spheroids showed good flow properties with respective rapid drug release (Q20 = 83.27 and 91.75). No difference was seen in the Avicel RC-581 and CL-611. Based on the 1 kg data, Avicel RC-581 and smooth stainless steel and waffle teflon plates (12 inch and 19 inch), the batch was scaled up to 5 and 10 kg. The scale-up parameters included rotor speed (124 -300 rpm) and spray rate (90-140 g/min). The scale-up batches had similar flow characteristics, release rate, and size distribution. The geometric mean diameter increased as batch size increased, and slightly bigger spheroids were obtained using the waffle teflon plate. Ibuprofen spheres with very good physical characteristics were developed using the rotor disk fluid-bed technology, a 1-step closed process that did not require additional unit processes.     

Reproductive bionomics of the soft tick, Ornithodoros turicata (Acari: Argasidae)

The effects of different temperatures and relative humidities (RHs) were tested on various reproductive parameters of Ornithodoros turicata, an argasid tick that inhabits gopher tortoise burrows in Florida, USA. The pre-oviposition, oviposition and incubation periods of the ticks decreased as temperature increased. These periods were also affected by the RH. The number of eggs oviposited was affected significantly by the combined effect of temperature and RH. Fewer eggs were laid by ticks in the 24°C regimes and the 27°C/95%RH regime compared to those in the other temperature/RH groups. There was an inverse relationship between the number of eggs oviposited and the percentage of hatched larvae that was correlated with the temperature and RH. Ticks reared at 27°C/90%RH and 30°C/90%RH laid more eggs than those reared in the other combinations of temperature and humidity but fewer larvae hatched from these eggs. The reproductive fitness index (RFI) values were highest in females held in the 24°C groups and the 30°C/95%RH group, although significantly more larvae hatched at the lower temperatures. The optimum reproductive conditions for O. turicata under laboratory conditions appear to be 24°C and 90–95%RH. While mating occurred at all temperatures, none of the females laid eggs at 22°C. The ticks may move preferentially to low temperatures when not feeding to remain above the critical equilibrium humidity and/or below the critical metabolic level necessary for prolonged survival. However, most female ticks oviposited after 45 days when moved to 27°C/95%RH. Ornithodoros turicata females may have a limited capability to delay oviposition until an optimal microenvironment for egg deposition can be located in the burrow.