Risdiplam in Type 1 Spinal Muscular Atrophy

BACKGROUND

Type 1 spinal muscular atrophy is a rare, progressive neuromuscular disease that is caused by low levels of functional survival of motor neuron (SMN) protein. Risdiplam is an orally administered, small molecule that modifies SMN2 pre-messenger RNA splicing and increases levels of functional SMN protein.

METHODS

We report the results of part 1 of a two-part, phase 2-3, open-label study of risdiplam in infants 1 to 7 months of age who had type 1 spinal muscular atrophy, which is characterized by the infant not attaining the ability to sit without support. Primary outcomes were safety, pharmacokinetics, pharmacodynamics (including the blood SMN protein concentration), and the selection of the risdiplam dose for part 2 of the study. Exploratory outcomes included the ability to sit without support for at least 5 seconds.

RESULTS

A total of 21 infants were enrolled. Four infants were in a low-dose cohort and were treated with a final dose at month 12 of 0.08 mg of risdiplam per kilogram of body weight per day, and 17 were in a high-dose cohort and were treated with a final dose at month 12 of 0.2 mg per kilogram per day. The baseline median SMN protein concentrations in blood were 1.31 ng per milliliter in the low-dose cohort and 2.54 ng per milliliter in the high-dose cohort; at 12 months, the median values increased to 3.05 ng per milliliter and 5.66 ng per milliliter, respectively, which represented a median of 3.0 times and 1.9 times the baseline values in the low-dose and high-dose cohorts, respectively. Serious adverse events included pneumonia, respiratory tract infection, and acute respiratory failure. At the time of this publication, 4 infants had died of respiratory complications. Seven infants in the high-dose cohort and no infants in the low-dose cohort were able to sit without support for at least 5 seconds. The higher dose of risdiplam (0.2 mg per kilogram per day) was selected for part 2 of the study.

CONCLUSIONS

In infants with type 1 spinal muscular atrophy, treatment with oral risdiplam led to an increased expression of functional SMN protein in the blood. (Funded by F. Hoffmann-La Roche; ClinicalTrials.gov number, NCT02913482.).

Supramolecularly Engineered NIR-II and Upconversion Nanoparticles In Vivo Assembly and Disassembly to Improve Bioimaging

Contrast agents for bioimaging suffer from low accumulation at lesion area and high uptake in the reticuloendothelial system (RES). Assembly of nanoparticles in vivo improves their enrichment at tumors and inflamed areas. However, uncontrollable assembly also occurs at the liver and spleen owing to the uptake of nanoparticles by the RES. This is known to probably cause a higher bioimaging background and more severe health hazards, which may hamper the clinical application. Herein, a new near-infrared (NIR)-controlled supramolecular engineering strategy is developed for in vivo assembly and disassembly between lanthanide upconversion nanoparticles and second near-infrared window (NIR-II, 1000-1700 nm) nanoprobes to realize precision bioimaging of tumors. A supramolecular structure is designed to realize assembly via host-guest interactions of azobenzene and β-cyclodextrin to enhance the retention of NIR-II nanoprobes in the tumor area. Meanwhile NIR-laser-controllable nanoprobes disassembly brings about a reduction in the bioimaging background as well as acceleration of their RES clearance rate. This strategy may also be used in other nano-to-micro-scale contrast agents to improve bioimaging signal-to-noise ratio and reduce long-term cytotoxicity.

Risdiplam distributes and increases SMN protein in both the central nervous system and peripheral organs

Spinal muscular atrophy (SMA) is a rare, inherited neuromuscular disease caused by deletion and/or mutation of the Survival of Motor Neuron 1 (SMN1) gene. A second gene, SMN2, produces low levels of functional SMN protein that are insufficient to fully compensate for the lack of SMN1. Risdiplam (RG7916; RO7034067) is an orally administered, small-molecule SMN2 pre-mRNA splicing modifier that distributes into the central nervous system (CNS) and peripheral tissues. To further explore risdiplam distribution, we assessed in vitro characteristics and in vivo drug levels and effect of risdiplam on SMN protein expression in different tissues in animal models. Total drug levels were similar in plasma, muscle, and brain of mice (n = 90), rats (n = 148), and monkeys (n = 24). As expected mechanistically based on its high passive permeability and not being a human multidrug resistance protein 1 substrate, risdiplam CSF levels reflected free compound concentration in plasma in monkeys. Tissue distribution remained unchanged when monkeys received risdiplam once daily for 39 weeks. A parallel dose-dependent increase in SMN protein levels was seen in CNS and peripheral tissues in two SMA mouse models dosed with risdiplam. These in vitro and in vivo preclinical data strongly suggest that functional SMN protein increases seen in patients' blood following risdiplam treatment should reflect similar increases in functional SMN protein in the CNS, muscle, and other peripheral tissues.

Cellulose nanocrystal-reinforced keratin bioadsorbent for effective removal of dyes from aqueous solution

High-efficiency and recyclable three-dimensional bioadsorbents were prepared by incorporating cellulose nanocrystal (CNC) as reinforcements in keratin sponge matrix to remove dyes from aqueous solution. Adsorption performance of dyes by CNC-reinforced keratin bioadsorbent was improved significantly as a result of adding CNC as filler. Batch adsorption results showed that the adsorption capacities for Reactive Black 5 and Direct Red 80 by the bioadsorbent were 1201 and 1070mgg^-1, respectively. The isotherms and kinetics for adsorption of both dyes on bioadsorbent followed the Langmuir isotherm model and pseudo-second order model, respectively. Desorption and regeneration experiments showed that the removal efficiencies of the bioadsorbent for both dyes could remain above 80% at the fifth recycling cycles. Moreover, the bioadsorbent possessed excellent packed-bed column operation performance. Those results suggested that the adsorbent could be considered as a high-performance and promising candidate for dye wastewater treatment.

Genotoxic and carcinogenic products arising from reductive transformations of the azo dye, Disperse Yellow 7

Selected aromatic azo and benzidine based dyes are priority compounds under the Government of Canada's Chemical Management Plan (CMP) for environmental risk assessments. Organic compounds undergo chemical and biological transformations when they interact with environmental matrices and biotic species; identifying the transformation products is thus a critical component of the risk assessment process. Here, we used zero valent iron (ZVI) to initiate the reduction of the diazo compound dye Disperse Yellow 7 (DY 7). Using state-of-the-art accurate mass Liquid Chromatography-Quadrupole Time of Flight-Mass Spectroscopy (LC-QToF-MS), four transformation products were conclusively identified, while a fifth product was tentatively ascertained. The conclusively established transformation products included p-phenylenediamine (p-PDA, a known genotoxin), 4-aminoazobenzene (4-AAB, a category 2 carcinogen) and 4-aminobiphenyl (4-ABP, a category 1 human carcinogen). 4-ABP is thought to form via a benzidine rearrangement; this is the first report of DY 7 undergoing a benzidine rearrangement. Given the importance of reduction processes in the metabolism of organic contaminants by aquatic species, we used LC-MS/MS to analyze sediment samples that had been generated previously upon exposure of Western clawed frogs (Silurana tropicalis) to DY 7 (at exposure levels where cellular stress was observed in S. tropicalis). We found p-PDA, 4-AAB, and 4-ABP were present in all exposures, but not in any of the sediment controls, demonstrating that upon release of DY 7 to the aquatic environment, sediment dwelling organisms will metabolize DY 7 to generate known (and suspected) human carcinogens, including through a previously unreported in vivo benzidine rearrangement to produce 4-ABP.

Removal of hazardous azopyrazole dye from an aqueous solution using rice straw as a waste adsorbent: Kinetic, equilibrium and thermodynamic studies

In this research, activated carbonmade from rice straw (ACRS) was synthesized simply by a low cost and nontoxic procedure and used for the adsorption of hazardous azopyrazole dye. The effect of different variables in the batch method as a function of solution pH, contact time, concentration of adsorbate, adsorbent dosage and temperature were investigated and optimal experimental conditions were ascertaine. Surface modification of ACRS using scanning electron microscopy (SEM) was obtained. More than 75% removal efficiency was obtained within 75min at adsorbent dose of 0.5g for initial dye concentration of 30-100mgL(-1) at pH 3. The experimental equilibrium data were tested by the isotherm models namely, Langmuir and Freundlich adsorption and the isotherm constants were determined. The kinetic data obtained with different initial concentration and temperature were analyzed using a pseudo-first-order and pseudo-second-order equations. The activation energy of adsorption was also evaluated and found to be +13.25kJmol(-1) indicating that the adsorption is physisorption. The thermodynamics of the adsorption indicated spontaneous and exothermic nature of the process. The results indicate that ACRS could be employed as low-cost material for the removal of acid dyes from aqueous solution.

Dose-dependent bioavailability indicators for curcumin and two of its novel derivatives

Novel water-soluble curcumin derivatives have been developed to overcome low in vivo bioavailability of curcumin. The aim of this work is to assess the potential utility of certain downstream targets as bioavailability indicators of systemic activity of pure curcumin and two novel water-soluble curcumin derivatives (NCD) by constructing dose-dependent response curves and to prove whether this novel curcumin derivatives retained, improved, or abolished biological activity of pure curcumin when applied in vivo. Pure curcumin (CUR), curcumin-carboxy derivative (NCD-1), and curcumin protein conjugate (NCD-2) were administered orally to rats at escalating doses: 37, 74, 148, and 296 μM/kg body weight, respectively. Plasma levels of GST activity, cavernous tissue levels of cGMP, and enzymatic activity of both HO-1 and GST were assessed one and half and 24 hours after oral administration of curcumin formulae. This study showed that there was a progressive elevation of cavernous tissue levels of cGMP and enzymatic activity of both HO-1 and GST in a dose-dependent manner that was maintained for 24 h with CUR, NCD-1, and NCD-2. Plasma GST activity was decreased by the lowest doses on the curve. The three dose-dependent bioavailability indicators as surrogates of curcumin and two of its novel derivatives are valid in the studied range of concentration and extended time. The novel curcumin derivatives still conserve with improvement the biological activity of natural curcumin when applied in vivo.

Equilibrium, kinetic and thermodynamic studies on the biosorption of reactive acid dye on Enteromorpha flexuosa and Gracilaria corticata

PURPOSE

Biosorption is an emerging, eco-friendly and economical method for treating the wastewater effluents. Compared to many other biological materials, algae biomass proved to be the better biosorbent due to the presence of cell wall polymers in them.

METHODS

Algal biomasses namely Enteromorpha flexuosa and Gracilaria corticata were dried, crushed and used as biosorbents. Ponceau S, a diazo dye was used as a model adsorbate for the biosorption studies. The biosorbents were characterized by Scanning Electron Microscopy, FT-IR and zero point charge. Batch studies were performed by varying pH, biosorbent dosage and initial dye concentrations. Adsorption isotherms, kinetic and thermodynamic analyses were carried out. The effect of electrolytes was also studied. Batch desorption studies were also carried out using various reagents.

RESULTS

Isotherm data were tested with Langmuir and Freundlich isotherm models and the results suggested that the Freundlich isotherm fitted the data well. Kinetic studies were performed with varying initial dye concentrations and the data were incorporated with pseudo first-order and pseudo second-order kinetic equations and was found that the studied biosorption processes followed pseudo second-order kinetic equation. Thermodynamic parameters were evaluated at three different temperatures 293 K, 300 K and 313 K. About 95% of the dye could be desorbed from both the biosorbents.

CONCLUSION

Both the algal biomasses had heterogeneous surfaces and followed pseudo second-order chemical kinetics. Thermodynamic parameters proved that the biosorption by both the biomasses were spontaneous, feasible and endothermic processes. Desorption studies proved the worth of the algal biomasses as biosorbents in industrial level.

Preoperative administration of Sudan III and successful treatment of persistent chylous ascites in a neonate

Congenital chylous ascites is a rare entity, and surgical treatment is confined to selected intractable cases. We report 2 cases of refractory congenital chylous ascites successfully treated with preoperative administration of lipophilic dye (Sudan III) followed by abdominal systematic surgical exploration, cauterization, and fibrin glue application.

Bioremediation of dyes in textile effluents by Aspergillus oryzae

In this study Aspergillus oryzae was utilized to remove azo dyes from aqueous solution. Physically induced in its paramorphogenic form to produce standardized mycelial pellets, the non-autoclaved and autoclaved hyphae biomass was applied to biosorb the reactive dyes Procion Red HE7B (PR-HE7B) and Procion Violet H3R (PV-H3R) at different pH values (2.50, 4.50, and 6.50). The best pH for biosorption was 2.50, though the autoclaved demonstrated a higher biosorption capacity than the non-autoclaved pellets. The toxicity level was determined using the Trimmed Spearman-Karber method with Daphnia similis in all bioassays. The calculated toxicity of PV-H3R (LC100 62.50 microg mL(-1)) was higher than to PR-HE7B (LC100 300.00 microg mL(-1)), and its results brought out that the decrease of toxicity levels to zero might be accomplished by adding small quantities of pelletized A. oryzae to the solutions.

Azoreductase in Staphylococcus aureus

Azoreductase(s) catalyze a NAD(P)H-dependent reaction in bacteria to metabolize azo dyes to colorless aromatic amines. Azoreductases from bacteria represent a novel family of enzymes with little similarity to other reductases. This unit will describe the current methods for measuring azoreductase from Staphylococcus aureus, which has been suggested to serve as a model strain to study the azo dye degradation by human skin microflora.

Decolorization and Degradation of Textile Dyes with Biosulfidogenic Hydrogenases

Successful decolorization of azo dyes (Orange II, Amido Black 10, Reactive Black 5, and Reactive Red 120) and industrial textile dye influents and effluents with sulfate-reducing bacteria from within a biosulfidogenic reactor was achieved with decolorizations ranging from 96% to 49% over 144 h. Concomitant with the decrease in absorbance of the dye in the visible region (480-620 nm) was an increase in the absorbance at 280 nm, over 48 h, suggesting an increase in concentration of single aromatic amines. With an extended period of time there was a subsequent decrease in the absorbance at 280 nm indicating that the aromatic amines had been degraded. The anthraquinone dye, Reactive Blue 2, remained unchanged after 144 h of incubation in the biosulfidogenic reactor and was only rapidly decolored at 192 h, implying that certain factors are induced in the reactor to break down this non-azo dye. The fastest decolorization/degradation rates and highest hydrogenase enzyme production were observed with Orange II, while the slowest decolorization/degradation rate and least enzyme production were with Reactive Blue 2, suggesting that these processes are controlled, to a certain degree, by an enzymatic mechanism. With sulfate-reducing bacteria that had been cultured on a lactate medium, there was complete decolorization of both authentic dyes and industrial influents and effluents as monitored by the decrease of absorbance in the visible region (480-620 nm). There was, however, very little breakdown of the single aromatic compounds as the absorbance at 280 nm remained fairly significant. This supports the suggestion that, within the biosulfidogenic reactor, there are factors other than the identified hydrogenases that are responsible for degradation of the aromatic compounds.

Bioaccumulation and ROS generation in liver of freshwater fish, goldfish Carassius auratus under HC Orange No 1 exposure

HC Orange No. 1 (CAS No. 54381-08-7, 2-nitro-4'-hydroxydiphenylamine) is used as a color additive in hair dyes. In this study, laboratory experiment was carried out to determine HC Orange No. 1 bioaccumulation and oxidative stress in the liver of freshwater fish, goldfish Carassius auratus. Fish were exposed to different concentrations (0.05, 0.1, 0.2, 0.5, and 1.0 mg/L) of HC Orange No. 1 for 10 days, with one group assigned as control. The accumulation of HC Orange No. 1 in liver increased with the exposure concentration (R(2) = 0.94). A secondary spin trapping technique was used followed by electron paramagnetic resonance (EPR) analysis to study the reactive oxygen species (ROS) production. On the basis of the hyperfine splitting constants and shape of the EPR spectrum, the ROS generated in fish liver after exposure was identified as hydroxyl radical (*OH). There is a good correlation between the exposure concentrations and *OH generation (R(2) = 0.92). The *OH signal intensity of the EPR spectrum showed a significant increase (P < 0.05) when the HC Orange No. 1 concentration was 1.0 mg/L, compared with that of the control. A good positive relationship (R(2) = 0.95) was found between the *OH formation and accumulation level of HC Orange No. 1 in liver. The changes of the activities of catalase (CAT), superoxide dismutase (SOD), glutathione S-transferase (GST), and contents of reduced glutathione (GSH) were also detected. These observations indicated a possible mechanism of oxidative stress induced by HC Orange No. 1 on fish.

In vitro dermal absorption and metabolism of D&C red no. 17 in human and porcineskin

D&C red no. 17 is approved for use in externally applied drug and cosmetic applications, in amounts consistent with good manufacturing practice. Concerns about the safety of the color additive (1-[4-phenylazophenylazo]-2-napthol (PAN) is the primary color constituent) have been raised due to potential metabolic cleavage of PAN to yield 4-aminoazobenzene. (14)C-PAN was applied in a commercially available suntan vehicle containing D&C red no. 17 to viable porcine and non-viable (cadaver) human skin in flow-through diffusion cells. At the end of 24 h, unabsorbed material was removed from the skin and some cells were allowed to continue for an additional 48 h. In human skin, 0.07% and 0.17% of the applied dose were absorbed into the receptor fluid after 24 and 72 h, respectively. At the end of 24 h, 12.5% of the applied dose remained in the skin, which did not decrease at 72 h. When PAN was applied to viable porcine skin for 24 h, 0.3% of the applied dose was absorbed and 12.7% remained in the skin. Additional studies to simulate short-term exposure were completed with PAN applied to the skin for only 15 min, and absorption was determined for 24 and 72 h. These studies in human cadaver skin found 0.02% and 0.08% of the applied dose in the receptor fluid after 24 and 72 h, respectively. Viable porcine skin studies with the 15-min application resulted in receptor fluid values of 0.1% of the applied dose after 24 h. Lipophilic receptor fluids composed of the non-ionic surfactant Volpo 20 at wt% concentrations of 1%, 3%, or 6% in water did not increase partitioning of PAN from the skin into the receptor fluid. No metabolism of PAN was found in viable porcine skin when examined by HPLC. In conclusion, skin absorption of PAN from a commercially available suntan product was low.

Accumulation of Acid Orange 7, Acid Red 18 and Reactive Black 5 by growing Schizophyllum commune

The effect of Acid Orange 7, Acid Red 18 and Reactive Black 5 on the growth and decolorization properties of Schizophyllum commune was studied with respect to the initial pH varying from 1 to 6 and initial dye concentration (10-100 mg/L). The optimum pH value was found to be 2 for both growth and color removal of these azo dyes. Increasing the concentration of azo dyes inhibited the growth of S. commune. It was observed that S. commune was capable of removing Acid Orange 7, Acid Red 18 and Reactive Black 5 with a maximum specific uptake capacity of 44.23, 127.53 and 180.17 (mg/g) respectively for an initial concentration of 100 mg/L of the dye. Higher decolorization was observed at lower concentrations for all the dyes. Finally it was found that the percentage decolorization was more in the case of Reactive Black 5 dye compared to the other two dyes used in the present investigation.

Adsorption of dyes and phenol from water on resin adsorbents: effect of adsorbate size and pore size distribution

Batch adsorption runs of two commercial reactive dyes (methylene blue and reactive orange X-GN) and phenol from water onto two resin adsorbents (Amberlite XAD-4, a macroreticular adsorbent and ZCH-101, a hyper-cross-linked adsorbent) were carried out in the present study. Effect of adsorbate size and pore structure of the resin adsorbents on adsorption was discussed and Langmuir and Freundlich models were tested for the relevant adsorption isotherms. In the kinetic section concentration-time profiles were obtained to further elucidate the effect of adsorbate size and porous structure on adsorption mechanism. A pseudo-second-order model was proved to give a satisfactory description of the related kinetic results. Two-stage kinetic curve of methylene blue onto ZCH-101 was observed at a specific experimental condition and modeled schematically according to its specific pore size distribution. Furthermore, other kinetic experiments were performed at different ambient temperature to validate the proposed schematic model.

Triazolo-tetrahydrofluorenones as selective estrogen receptor beta agonists

Several tetrahydrofluorenones with a triazole fused across C7-C8 showed high levels of ERbeta-selectivity and were found to be potent ERbeta-agonists. As a class they demonstrate improved oral bioavailability in the rat over a parent class of 7-hydroxy-tetrahydrofluorenones. The most selective agonist displayed 5.7 nM affinity and 333-fold selectivity for ERbeta.

Radiolytic and cellular reduction of a novel hypoxia-activated cobalt(III) prodrug of a chloromethylbenzindoline DNA minor groove alkylator

Metabolic reduction can be used to activate prodrugs in hypoxic regions of tumours, but reduction by ionising radiation is also theoretically attractive. Previously, we showed that a cobalt(III) complex containing 8-hydroxyquinoline (8-HQ) and cyclen ligands releases 8-HQ efficiently on irradiation in hypoxic solutions [Ahn G-O, Ware DC, Denny WA, Wilson WR. Optimization of the auxiliary ligand shell of cobalt(III)(8-hydroxyquinoline) complexes as model hypoxia-selective radiation-activated prodrugs. Radiat Res 2004;162:315-25]. Here we investigate an analogous Co(III) complex containing the potent DNA minor groove alkylator azachloromethylbenzindoline (azaCBI, 1) to determine whether it releases 1 on radiolytic and/or enzymatic reduction under hypoxia. Monitoring by HPLC, the azaCBI ligand in the Co(III)(cyclen)(azaCBI) complex (2) slowly hydrolysed in aqueous solution, in contrast to the free ligand 1 which readily converted to its reactive cyclopropyl form. Irradiation of 2 (30-50 microM) in hypoxic solutions released 1 with yields of 0.57 micromol/J in formate buffer and 0.13 micromol/J in human plasma. Using bioassay methods, cytotoxic activation by irradiation of 2 at 1 microM in hypoxic plasma was readily detectable at clinically relevant doses (> or = 1 Gy), with a estimated yield of 1 of 0.075 micromol/J. Release of 1 from 2 was also observed in hypoxic HT29 cultures without radiation, with subsequent conversion of 1 to its O-glucuronide. Surprisingly, overexpression of human cytochrome P450 reductase in A549 cells did not increase the rate of metabolic reduction of 2, suggesting that other reductases and/or non-enzymatic reductants are responsible. Thus the cobalt(III) complex 2 is a promising prodrug capable of being activated to release a very potent cytotoxin when reduced by either ionising radiation or cells under hypoxic conditions.

Competitive adsorption of dye metanil yellow and RB15 in acid solutions on chemically cross-linked chitosan beads

One kind of adsorbent with a high adsorption capacity for anionic dyes was prepared using ionically and chemically cross-linked chitosan beads. A batch system was applied to study the adsorption behavior of one acid dye (MY, metanil yellow) and one reactive dye (RB15, reactive blue 15) in aqueous solutions by the cross-linked chitosan beads. The adsorption capacities was 3.56 mmol g(-1) (1334 mg g(-1)) for dye MY and 0.56 mmol g(-1) (722 mg g(-1)) for dye RB15 at pH4, 30 degrees C. The Langmuir model agreed very well with the experimental data (R(2)>0.996). The kinetics of adsorption for a single dye and the kinetics of removal of ADMI color value in mixture solutions at different initial dye concentrations were evaluated by the nonlinear first-order and second-order models. The first-order kinetic model fits well with the dynamical adsorption behavior of a single dye for lower initial dye concentrations, while the second-order kinetic model fits well for higher initial dye concentrations. The competitive adsorption favored the dye RB15 in the mixture solution (initial conc. (mM): MY=1.34; RB15=1.36); while it favored the dye MY in the mixture solution (initial conc. (mM): MY=3.00; RB15=1.34) and the adsorption kinetics for dye RB15 has the tendency to shift to a slower first order model.

Safety assessment and risk–benefit analysis of the use of azodicarbonamide in baby food jar closure technology: Putting trace levels of semicarbazide exposure into perspective – A review

The discovery of trace levels of semicarbazide (SEM) in bottled foods (especially baby foods) led to a consideration of the safety of this hydrazine compound by regulatory agencies worldwide. Azodicarbonamide, which is used in the jar-sealing technology known as Press On-Twist Off (or Push-Twist/PT) closures for the formation of a hermetic, plastisol seal, partially degrades with the heat of processing to form trace amounts of SEM. This review has evaluated the potential toxicological risks of resulting exposure to SEM and also the benefit of the PT technology (with azodicarbonamide) in the context of possible microbial contamination. It also considers the potential impact on infant nutrition if parents come to the conclusion that commercial baby foods are unsafe. SEM shows limited genotoxicity in vitro that is largely prevented by the presence of mammalian metabolic enzymes. Negative results were found in vivo in DNA alkaline elution, unscheduled DNA synthesis and micronucleus assays. This pattern is in contrast to the genotoxic hydrazines that also have been shown to cause tumours. Carcinogenicity studies of SEM are of limited quality, show a questionable weak effect in mice at high doses, which are not relevant to human exposure at trace levels, and show no effect in the rat. The IARC has assigned SEM as Group 3, 'Not classifiable as to its carcinogenicity to humans'. Based on estimates of exposure to infants consuming baby foods (with the assumption of SEM levels at the 95th percentile of 20 ng g(-1) in all of the consumed 'ready-to-eat' foods) compared with a no observed adverse effect level (NOAEL) in developmental toxicity studies, the margin of safety is more than 21 000. Since the risk of an adverse effect is negligible, it is clear that any theoretical risk is outweighed by the benefits of continuing use of the PT closure (with azodicarbonamide blowing agent) to ensure both the microbial integrity and availability of commercial baby foods as a valuable source of infant nutrition.

Monoazo and diazo dye decolourisation studies in a methanogenic UASB reactor

Mixed anaerobic bacterial consortia have been show to reduce azo dyes and batch decolourisation tests have also demonstrated that predominantly methanogenic cultures also perform azo bond cleavage. The anaerobic treatment of wool dyeing effluents, which contain acetic acid, could thus be improved with a better knowledge of methanogenic dye degradation. Therefore, the decolourisation of two azo textile dyes, a monoazo dye (Acid Orange 7, AO7) and a diazo dye (Direct Red 254, DR254), was investigated in a methanogenic laboratory-scale Upflow Anaerobic Sludge Blanket (UASB), fed with acetate as primary carbon source. As dye concentration was increased a decrease in total COD removal was observed, but the acetate load removal (90%) remained almost constant. A colour removal level higher than 88% was achieved for both dyes at a HRT of 24h. The identification by HPLC analysis of sulfanilic acid, a dye reduction metabolite, in the treated effluent, confirmed that the decolourisation process was due mainly to azo bond reduction. Although, HPLC chromatograms showed that 1-amino-2-naphthol, the other AO7 cleavage metabolite, was removed, aeration batch assays demonstrated that this could be due to auto-oxidation and not biological mineralization. At a HRT of 8h, a more extensive reductive biotransformation was observed for DR254 (82%) than for AO7 (56%). In order to explain this behaviour, the influence of the dye aggregation process and chemical structure of the dye molecules are discussed in the present work.

Carcinogenicity of azo colorants: influence of solubility and bioavailability

In the past, azo colorants based on benzidine, 3,3'-dichlorobenzidine, 3,3'-dimethylbenzidine (o-tolidine), and 3,3'-dimethoxybenzidine (o-dianisidine) have been synthesized in large amounts and numbers. Studies in exposed workers have demonstrated that the azoreduction of benzidine-based dyes occurs in man. The metabolic conversion of benzidine-, 3,3'-dimethylbenzidine- and 3,3'-dimethoxybenzidine-based dyes to their (carcinogenic) amine precursors in vivo is a general phenomenon that must be considered for each member of this class of chemicals. Several epidemiological studies have demonstrated that the use of the benzidine-based dyes has caused bladder cancer in humans. However, in contrast to water-soluble dyes, the question of biological azoreduction of (practically insoluble) pigments has been a matter of discussion. As a majority of azo pigments are based on 3,3'-dichlorobenzidine, much of the available experimental data are focused on this group. Long-term animal carcinogenicity studies performed with pigments based on 3,3'-dichlorobenzidine did not show a carcinogenic effect. The absence of a genotoxic effect has been supported by mutagenicity studies with the 3,3'-dichlorobenzidine-based Pigment Yellow 12. Studies in which azo pigments based on 3,3'-dichlorobenzidine had been orally administered to rats, hamsters, rabbits and monkeys could generally not detect significant amounts of 3,3'-dichlorobenzidine in the urine. It, therefore, appears well established that the aromatic amine components from azo pigments based on 3,3'-dichlorobenzidine are practically not bioavailable. Hence, it is very unlikely that occupational exposure to insoluble azo pigments would be associated with a substantial risk of (bladder) cancer in man. According to current EU regulations, azo dyes based on benzidine, 3,3'-dimethoxybenzidine and 3,3'-dimethylbenzidine have been classified as carcinogens of category 2 as "substances which should be regarded as if they are carcinogenic to man". This is not the case for 3,3'-dichlorobenzidine-based azo pigments.

Adsorptive stripping voltammetric behaviour of azomethine group in pyrimidine-containing drugs

The stripping voltammetric behaviour of buspirone hydrochloride (BUS) and piribedil (PIR), as models of pyrimidine-containing compounds, was studied using a hanging mercury drop electrode (HMDE). A sensitive adsorptive stripping voltammetric method for determination of such drugs is described. The voltammetric peaks were obtained at -1.23 and -1.22 V for BUS and PIR. respectively, which correspond to the reduction of the azomethine group of pyrimidine ring in Britton-Robinson buffer (pH 7). Factors such as pH of supporting electrolyte, accumulation potential and time and instrumental parameters were optimized. Calibration plots and regression data validation, accuracy, precision, limits of detection, limits of quantification, and other aspects of analytical merit are presented. The applicability of the method was evaluated through determination of BUS and PIR in tablet dosage forms. A preliminary study of the analysis of plasma samples, spiked with the investigated drug, after a simple extraction procedure is described.

Decolorization of azo dyes by Rhodobacter sphaeroides

Rhodobacter sphaeroides AS1.1737 decolorized more than 90% of several azo dyes (200 mg dyes l(-1)) in 24 h. The optimal culture conditions were: anaerobic illumination (1990 1x), peptone as carbon source, temperature 35-40 degrees C and pH 7-8. Intracellular crude enzyme from this strain had azoreductase activity, optimized temperature as 45-50 degrees C, and decolorization kinetics which were consistent with a ping-pong mechanism.

The influence of FeCl3 on the photocatalytic degradation of dissolved azo dyes in aqueous TiO2 suspensions

The study concerned decolouration of solutions of azo, anionic (Acid Orange 7, Reactive Red 45, Acid Yellow 23) and cationic (Basic Blue 41 and Basic Orange 66) dyes during illumination with UV (lambdamax 366 nm) irradiation in the presence of TiO2 and FeCl3. The process of decolouration during illumination of the solutions studied containing FeCl3 underwent significant intensification in the case of anionic dyes and unfavourable inhibition in case of cationic dyes. It was also observed that FeCl3 had a diverse influence on the adsorption of the dyes studied on TiO2. The adsorption of anionic dyes and decolouration of solutions before the illumination was observed only in the presence of FeCl3. In case of cationic dyes the addition of FeCl3 caused elimination of these phenomena. An additional cause of decolouration of anionic dyes solutions before illumination was the precipitation of their poorly soluble compounds from Fe3+. The processes of degradation and mineralization of the dye that accompanied decolouration of Acid Orange 7 solutions were also observed. It was stated that similarly to the case of Acid Orange 7, the decolouration of the studied anionic dyes' solutions can depend on the concentration of FeCl3, the amount of TiO2 and the initial concentration of the dye in its solution.

Attachment of phosphonate-functionalised azo-dyes to oxide surfaces to give enhanced light and wet fastness

Phosphonate-functionalised dyes have been shown to bind strongly to aluminium oxides and to form stable 1:1 complexes with cyclodextrins at the surface.

Bioremediation of textile azo dyes by an aerobic bacterial consortium using a rotating biological contactor

The degradation of an azo dye mixture by an aerobic bacterial consortium was studied in a rotating biological reactor. Laterite pebbles of particle size 850 microm to 1.44 mm were fixed on gramophone records using an epoxy resin on which the developed consortium was immobilized. Rate of degradation, BOD, biomass determination, enzymes involved, and fish bioassay were studied. The RBC has a high efficiency for dye degradation even at high dye concentrations (100 microg/mL) and high flow rate (36 L/h) at alkaline pH and salinity conditions normally encountered in the textile effluents. Bioassays (LD-50) using Thilapia fish in treated effluent showed that the percentage mortality was zero over a period of 96 h, whereas the mortality was 100% in untreated dye water within 26 h. Fish bioassay confirms that the effluent from RBC can be discharged safely to the environment.

Release characteristics of an azo dye from poly(ureaurethane) microcapsules

The time course for the transfer of azo dyes from the microcapsule core of dioctylphthalate to the dispersing medium of methanol through a poly(ureaurethane) (PUU) membrane was measured for various average size microcapsules with a size distribution. The dye release curves are represented by a stretched exponential function C(t)=C(eq)[1-exp [-(t/tau(eff))(alpha)]], where C(t) is the concentration of the dye in methanol, C(eq) that at the equilibrium state, and t the time. The exponent alpha decreased by increasing the variance of the size distribution of microcapsules. The effective time constant tau(eff) was expressed by tau(eff)=c(0)<R(2)>/kappa(alpha), where <R(2)> and kappa(alpha) are the mean square of microcapsule radius and a correction for the size distribution, respectively. The characteristic proportional constant, c(0), was determined as 2.6+/-0.2 min/microm(2). From the value of the constant, the diffusion coefficient of the azo dye in the PUU membrane was evaluated as 2.6 x 10(-12) cm(2)/s.

Novel method to control release of lipophilic drugs with high potency from silicone

Silicone has been utilized as a carrier material for sustained release system of lipophilic drugs. Extensive studies revealed that drug release rate is influenced by factors such as physicochemical properties of the drug and additives.(1-5)) When a lipophilic drug is highly potent at low concentrations, the drug release rate should be strictly controlled so as to avoid side effects. In this study, using vitamin D(3) (VD(3)) as an example of such drugs, we investigated novel method to suppress initial burst and to modify drug release rate from silicone matrix. As a result, it was found that (a). addition of human serum albumin (HSA) suppressed initial burst and enhanced release rate in the later stage, resulting constant release of VD(3), (b). covering a matrix formulation with a membrane of low diffusivity (core-rod formulation) suppressed initial burst and released drug in a constant rate, and (3) using materials for which the drug has high affinity as dissolution solvent (reservoir formulation), the drug release rate was reduced.

Plasma pharmacokinetics of a liver-selective nitric oxide-donating diazeniumdiolate in the male C57BL/6 mouse

1. The single-dose plasma pharmacokinetics of O(2)-vinyl 1-(pyrrolidin-1-yl)diazen-1-ium-1,2-diolate (V-PYRRO/NO) following intravenous (i.v.) and intraperitoneal (i.p.) bolus administration to the male C57BL/6 mouse was studied in an effort to characterize the disposition of the agent and to serve as a basis for the design of in vivo efficacy studies. 2. Plasma V-PYRRO/NO concentrations declined rapidly in a bi-exponential manner after i.v. administration of 5 mg kg(-1) body weight to mouse. The terminal half-life was 9.4 min and the mean residence time was 3.4 min. 3. V-PYRRO/NO was absorbed rapidly following i.p. administration, with peak plasma concentrations being observed 3 min after injection. Levels then declined with a terminal half-life of 11.7 min. The bioavailable fraction from the i.p. compartment was 19%, indicating a high first-pass effect. 4. The results provide additional evidence for a liver-selective metabolism of this nitric oxide-donating prodrug.

Influence of the composition of in-vitro azo-reducing systems on the degradation kinetics of the model compound amaranth

The purpose of this study was to investigate the influence of the composition of in-vitro azo-reducing systems on the degradation kinetics of the model compound amaranth. The degradation kinetics of amaranth were determined under anaerobic conditions both in rat caecal content (ex-vivo) and in a variety of in-vitro degradation media derived from rat caecal content. It was observed that the reducing activity was highly dependent on the preparation method and composition of the degradation medium. In pure rat caecal content, the degradation of amaranth was apparent first order (k = 0.044 +/- 0.002 min(-1)), while dilution of the rat caecal content resulted in an apparent zero-order degradation. Both apparent zero- and first-order degradations were also observed in media made up of diluted rat caecal content to which cofactors such as NADP, D-glucose-6-phosphate, glucose-6-phosphate dehydrogenase and Bz were added. This study demonstrates that in-vitro azo-reducing kinetics are dependent on the composition and mode of preparation of the in-vitro media used. This has to be taken into account when evaluating the degradability of azo-aromatic drug delivery systems in-vitro.

Characterization of the interactions between polymethacrylate-based aqueous polymeric dispersions and aluminum lakes

Instability in film coating formulations can arise from interactions between aluminum lake pigments and aqueous polymeric dispersions. The purpose of this study was to characterize the interactions between three polymethacrylate-based aqueous polymeric dispersions (Eudragit RS 30 D, Eudragit L 30 D-55, and Eudragit NE 30 D) and aluminum lakes. Particle size measurements, pH stability profiles, zeta potential measurements, and microscopy were used to study mixed dispersions of the polymeric latices and the lakes. Interactions leading to dispersion instability were related to the surface charge of the components in the formulation. Interactions between the ionic polymers and the lakes arose from instability of the lakes outside a certain pH range resulting in the release of electrolytes, which led to aggregation of the polymeric particles. Interactions between the nonionic polymer and the lakes were related to the polymer modifying the surface charge of the lakes, resulting in aggregation of the pigment particles.

Novel azo derivatives as prodrugs of 5-aminosalicylic acid and amino derivatives with potent platelet activating factor antagonist activity

This paper describes the synthesis of a series of azo compounds able to deliver 5-aminosalicylic acid (5-ASA) and a potent platelet activating factor (PAF) antagonist in a colon-specific manner for the purpose of treating ulcerative colitis. We found it possible to add an amino group on the aromatic moiety of our reported 1-[(1-acyl-4-piperidyl)methyl]-1H-2-methylimidazo[4,5-c]pyridine derivatives or on British Biotech compounds BB-882 and BB-823 maintaining a high level of activity as PAF antagonist. A selected compound UR-12715 (49c) showed an IC(50) of 8 nM in the in vitro PAF-induced aggregation assay, and an ID(50) of 29 microg/kg in the in vivo PAF-induced hypotension test in normotensive rats. Through attachment of 49c to the 5-ASA via azo functionality we obtained UR-12746 (70). Pharmacokinetics experiments with [14C]-70 allow us to reach the following conclusions, critical in the design of these new prodrugs of 5-ASA. Neither the whole molecule 70 nor the carrier 49c were absorbed after oral administration of [14C]-70 in rat as was demonstrated by the absence of plasma levels of radioactivity and the high recovery of it in feces. Effective cleavage of azo bond (84%) by microflora in the colon is achieved. These facts ensure high topical concentrations of 5-ASA and 49c in the colon. Additionally, 70 exhibited a potent anticolitic effect in the trinitrobenzenesulfonic acid-induced colitis model in the rat. This profile suggests that UR-12746 (70) provides an attractive new approach to the treatment of ulcerative colitis.

Azo-containing urethane analogues for colonic drug delivery: synthesis, characterization and in-vitro evaluation

A urethane-based analogue containing an azo aromatic linkage in the backbone was synthesized for use in colon-specific delivery systems by reacting toluene-2,6-diisocyanate with a mixture of an aromatic azo diol, (bis-4-hydroxyphenyl)-4,4'-diazobiphenyl, poly(ethylene glycol) (Mn = 4000; number-average molecular weight) and 1,2-propanediol (propylene glycol). The resultant compounds (UR-1 and UR-2) were characterized by IR spectroscopy, 1H NMR spectroscopy, DSC studies, X-ray diffraction studies and molecular weight determination by gel permeation chromatography. The compounds exhibited low molecular weight, lacked film-forming properties and crystallinity in the structure. An in-vitro bacterial degradation test to demonstrate the susceptibility of azo bond to bacterial enzymes was performed using media inoculated with lactobacillus culture. The results indicated degradation of films by azoreductase. In-vitro permeation of 5-aminosalicylic acid was studied in control and lactobacilli-treated films. The permeability of the lactobacilli treated films was significantly increased suggesting the potential of these compounds for application in colonic targeting.

Fungal mediated decolorization of media containing procion dyes

An isolated fungus, Aspergillus foetidus was found to effectively decolorize media containing azo reactive dyes, namely Procion dyes, under aerobic conditions. The extent of colour removal was 90% within 48 h of growth of the fungus. The entire colour was found to be strongly bioadsorbed to the rapidly settling spherical fungal biomass pellets. Our investigations reveal that the process of decolorization is concomitant with the exponential growth phase of the fungus and has an obligate requirement for a biodegradable substrate such as glucose. Kinetic analyses of fungal decolorization indicate that the rates of colour uptake decrease to a significant extent with increasing initial concentrations of dye. The fungus was able to grow and decolorize media in the presence of 5 ppm of chromium and 1% sodium chloride. An alternate and cheaper carbon source such as starch supported the growth and decolorization process. These results suggest that the dye uptake process mediated by Aspergillus foetidus has a potential for large-scale treatment of textile mill discharges.

Role of inflammatory mediators in lipid A analogue (ONO-4007)-induced vascular permeability change in mouse skin

1. Endotoxin shock is accompanied by an increase in peripheral vascular permeability. It has been postulated that most biological activities of LPS are derived from lipid A moiety. Here we examined the effect of lipid A analogue ONO-4007 in increasing vascular permeability and the possible mediators in mouse skin by a dye leakage method. 2. Subcutaneous injection of ONO-4007 (1 - 2 mg site(-1)) induced a dose-dependent increase in vascular permeability which was evident after 120 min. 3. ONO-4007-induced dye leakage was significantly attenuated by pretreatments with anti-tumour necrosis factor-alpha (TNF-alpha) and anti-interleukin-1alpha (IL-1alpha) antibodies, but not with indomethacin (5 mg kg(-1)) or diphenhydramine (10 mg kg(-1)). ONO-4007-induced dye leakage was significantly inhibited by a pretreatment with N(G)-nitro-L-arginine methyl ester (L-NAME) (10 mg kg(-1)) but not with aminoguanidine (50 mg kg(-1)). In inducible nitric oxide synthase (iNOS)-deficient mice, ONO-4007 significantly increased the dye leakage, while ONO-4007 dilated rat thoracic aortic rings pre-contracted with phenylephrine, and the L-NAME pretreatment inhibited the dilation. 4. Thus, TNF-alpha, IL-1alpha and constitutive NOSs-derived nitric oxide but not prostaglandins or histamine play a role in ONO-4007-induced increase in vascular permeability. Although ONO-4007 mimics LPS in increasing vascular permeability, mechanisms of permeability change elicited by ONO-4007 were not identical to those of LPS.

Study on the physiology and degradation of dye with immobilized algae

Immobilization of chlorella (pyrenoidosa) with calcium alginate was carried out. Both algal growth and physiological activity increased after immobilization. Algal size and initial density have little influence on cell growth and physiological activity. Algal cell division inside the support was restricted without bubbling air containing 2% CO2. Individual algal cell increased and algal distribution inside the support was not homogeneous, indicating that within the support the resistance of mass transfer of CO2 was the limiting factor for the growth and cell division of immobilized algae. After bubbling 2% CO2, algal growth, the cell division considerably increased and individual cell size restored normally. Study of the degradation of dye (direct brown NM) by immobilized algae was better than that of free algae. Bubbling air containing 2% CO2 in the culture solution was more favorable for increasing decolorization rate. Preliminary study of co-immobilization of algae plus bacterium illustrated that the addition of bacterium increased the anabolic activity of algae, thus increased the decolorization capacity if immobilized algae for dye.

Non-enzymatic reduction of azo dyes by NADH

Nicotinamide adenine dinucleotide (NADH) reduces a variety of azo dyes by four electrons to generate the corresponding aromatic amines. This reduction is pH-dependent and increases with decreasing pH. Reduction of 4-(4'-sulfophenylazo)-phenol and 2-(4'-sulfophenylazo)-phenol, specifically substituted with methyl, methoxy, halo, and nitro groups, was examined to determine the susceptibility of azo dyes to reduction by NADH. Except for the nitro-substituted azo dyes, all other azo dyes were reduced. Possible mechanisms of reduction are proposed. The implications of our findings to microbial degradation and mammalian metabolism of azo dyes are discussed.

Photosensitive liposomes as 'cages' for laser-triggered solute delivery: the effect of bilayer cholesterol on kinetics of solute release

Liposomes containing acyl chains incorporating azobenzene chromophores have been investigated as potential 'caging' agents for fast solute release. On photolysis, trapped marker dye can be released from gel-phase liposomes within milliseconds. Solute release is markedly sensitive to the presence of cholesterol in the bilayer. Phospholipids bearing one saturated acyl chain and an azobenzene-substituted chain are ineffective as sensitisers unless cholesterol is present, while doubly substituted phospholipids sensitise release in its absence. Cholesterol markedly affects the temperature profile of solute release depending on the host phospholipid chain length. Solute release is not seen for lipid hosts with unsaturated acyl chains.

Ovarian follicular growth and maturity and follicular production of progesterone and oestradiol in response to porcine luteinising hormone and porcine follicle stimulating hormone in albino (S*AS) hens in vivo and in vitro

The effects of the SAS gene on follicular growth were studied by feeding Sudan IV and Sudan Black B, on follicular maturity by measuring P4 and E2 output of the 5 largest follicles (F1 to F5) in vitro, and on ovarian response (plasma progesterone, P4, and oestradiol, E2) to administration of porcine follicle-stimulating hormone (pFSH) and porcine luteinising hormone (pLH) in old laying hens. Albino hens had fewer dye rings in the yolks of their eggs than non-albinos (8.32 compared to 8.59) and the yolks from albinos weighed less. The numbers of normal and atretic follicles larger than 3 mm in diameter did not differ between the two genotypes. The P4 outputs from the F1 and F2 follicles were significantly greater for albino hens, but P4 production of other follicles was not different for the two genotypes. The P4 output of the F1 follicle in response to pLH was dose-dependent and greater for albino hens than for non-albinos. Porcine LH did not increase the follicular E2 output in either genotype. Administration of pLH, but not pFSH, increased plasma P4 and E2 concentrations, with no difference between genotypes. These data suggest that the F1 follicles for albino hens are precocious, resulting in a reduced growth period and a smaller weight at ovulation.

Site-specific consultation for a chemical mixture

The Agency for Toxic Substances and Disease Registry (ATSDR) uses the weight of evidence methodology to evaluate interactions of chemical mixtures. In the process, toxicity, toxicokinetics, and toxicodynamics of chemical components of the mixture are carefully examined. Based on the evaluation, predictions are made that can be used in real-life situations at hazardous waste sites. In this paper, health outcomes were evaluated for a mixture of eight compounds that were found at a specific site. These eight chemicals were identified and possibly associated with human exposure. The health assessors could consider similar thought processes when evaluating chemical mixtures at hazardous waste sites.

Interaction of 7-hydroxy-8-(phenylazo)1,3-naphthalenedisulfonate with bovine plasma albumin. Spectroscopic studies

Interaction of Orange G (OG) with bovine plasma albumin (BPA) has been investigated using NMR, UV-visible absorption, CD, and fluorescence techniques. The bound conformation of OG is a compact structure with N9-N10 bond in a non-planar syn conformation. The binding causes a decrease in the 478-nm absorption band of OG. The analysis of the binding isotherm generated from UV-visible absorption measurements gives a dissociation constant of 10 microM and stoichiometry 1:1 for BPA.OG complex. Dissociation constant is invariant in the pH range 5.0-8.0 and is approximately 20 times higher at pH 4.0 than its value at pH 7.0. Near and far UV-CD studies indicate alterations in the helical content and in the tertiary structure of the protein on complexation. The binding induces (-) and (+) CD at 335 nm and 465 nm, respectively. The binding also results into an increase in the steady state fluorescence anisotropy of OG without affecting emission maximum and quantum yield. Fluorescence data indicate that quenching of Trp fluorescence by OG is static in nature and OG selectively binds near Trp-135. Observation of similar rotational correlation time for BPA and BPA.OG complex indicates that the overall globular structure of BPA remains unaltered on binding despite certain internal rearrangement in the protein structure.

Genotoxicity studies on the azo dye Direct Red 2 using the in vivo mouse bone marrow micronucleus test

The clastogenicity of the azo dye Direct Red 2 (DR2) has been investigated using the murine bone marrow micronucleus assay. A potent dose-dependent response was observed following oral gavage of DR2 up to 4 mg/kg, after which significant toxicity to the erythroid compartment was observed. The route of administration had a significant effect on the frequency of micronucleus formation: intraperitoneal injection was approximately two-fold less clastogenic than the equivalent dose delivered orally (p<0.05). The requirement for activation of DR2 by intestinal microflora was indicated by the fact that mice given acid-treated water prior to administration of DR2 showed a significant reduction (40%; p<0.001) in micronucleated polychromatic erythrocyte formation. The implications of these findings for the health and safety of occupationally exposed workers are discussed.

O/W lipid emulsions for parenteral drug delivery. III. Lipophilicity necessary for incorporation in oil particles even after intravenous injection

The potential usefulness of oil-in-water (O/W) lipid emulsions as injectable drug delivery systems was examined. Plasma concentrations of oil particles after intravenous injection of a standard lipid emulsion composed of soybean oil and egg yolk phosphatides were monitored based on the plasma concentrations of phospholipids and triglycerides, and the light scattering intensity of the plasma. Their time profiles were similar to each other, and the oil particle size decreased time-dependently. Pretreatment with dextran sulfate, a known reticuloendothelial system (RES) suppressor, resulted in marked reduction of the plasma clearance of the oil particles and of the time-dependent alteration of oil particle size, suggesting that oil particles were trapped by RES. The lipophilicity of the drug needed for its incorporation in the oil particles even after intravenous injection was found to be clog P > 8, where clog P is the calculated logarithm of the partition coefficient between n-octanol and water. In the case of sudan II (clog P = 5.4), the release from the oil particles was very quick after intravenous injection, resulting in slight alteration in biodistribution when compared with its micellar solution. In contrast, menatetrenone (clog P = 9.5) was selectively delivered to the liver, lungs and spleen, being consistent with the oil particles taken up by RES.

Fluorescent cytochemistry of acid phosphatase and demonstration of fluid-phase endocytosis using an azo dye method

The aim of this work was the development of a fluorescent microscopy technique to visualize acid phosphatase activity in living and pre-fixed cells. We have shown that a coupling azo dye method, using naphthol AS-MX phosphate (NP) as substrate and fast red TR (FR) as a diazonium salt coupling agent, gives rise to a fluorescent azo dye reaction product which permits a highly sensitive demonstration of lysosomal acid phosphatase in both living and pre-fixed monolayer cell cultures. The granular staining is prevented by inhibition of acid phosphatase activity using fluoride and/or orthovanadate in both living and pre-fixed preparations. Lysosomal staining in living cells is also abolished by inhibition of fluid-phase endocytosis using low temperatures or inhibition of oxidative phosphorylation. It was shown that whilst NP entered living cells by passive diffusion, occurrence of FR in lysosomes resulted from fluid-phase endocytosis. Spectroscopic analysis of the emission and absorption features of FR, NP, naphthol AS-MX (N), and the N-FR azo dye reaction product in solution corroborated our microscopic results. The differing uptake mechanisms, and the occurrence of lysosomally localized azo dye, were also in keeping with the predictions of quantitative structure-activity relationship models of this system.

Biodistribution of cyclosporin encapsulated in liposomes modified with bioadhesive polymer

The purpose of this investigation was to study the possibility of renewing the immunosuppressive activity of cyclosporin by formulating the compound in liposomes modified with bioadhesive polymers. The liposomes prepared were evaluated both pharmacokinetically and pharmacodynamically. Tissue distribution and plasma pharmacokinetics of cyclosporin and model dye, sudan black, which is as hydrophobic as cyclosporin, were studied in rats after intravenous infusion (10 mg kg-1). The immunosuppressive efficacy of liposomal cyclosporin preparations was studied in the allogenic rat-heart-transplantation model, where cyclosporin therapy (10 mg kg-1) continued for one week. The entrapment of sudan black in liposomes modified with bioadhesive polymers resulted in higher sudan black delivery to the spleen and the liver than with standard sudan-black-loaded liposomes. Among the modified liposomes, those modified with carbopol 941 showed the most remarkable enhancing effect on the delivery of sudan black to these organs and total plasma clearance of sudan black decreased to 38.6 +/- 7.8 mL h-1 kg-1 (standard liposomes, 58.9 +/- 6.4 mL h-1 kg-1). Delivery of cyclosporin to the spleen and the liver was increased approximately twofold by modifying the liposomes with carbopol 941. In the preliminary study on the allogenic rat-heart-transplantation model, the mean survival days of the graft were 18.8 +/- 2.9 days for the group receiving cyclosporin liposomes modified with carbopol 941, 14.2 +/- 4.4 days for the group receiving standard cyclosporin liposomes and 7.6 +/- 0.5 days for the group receiving cyclosporin solution. The encapsulation of cyclosporin in liposomes modified with bioadhesive polymer enhanced the residence time of cyclosporin in the systemic circulation, resulting in approximately twofold greater delivery of cyclosporin to the spleen and liver. However, in the allogenic rat-heart-transplantation model no significant difference was detected between the immunosuppressive efficacy of cyclosporin encapsulated in bioadhesive polymer-modified liposomes and that encapsulated in standard liposomes.

Low levels of cadmium chloride damage the corneal endothelium

The effect of cadmium chloride on the integrity of the endothelium of isolated bullfrog (Rana catesbeiana) corneas was examined by spectrophotometric analysis of corneal uptake of the vital stain Janus green and by scanning electron microscopy (SEM). The uptake of Janus green by the endothelium was dose related between 1.0 and 100.0 microM CdCl2. The effect of cadmium was significantly attenuated by the calcium channel blocker SKF 96365 and was augmented by the calcium ionophore A23187, indicating that cadmium influx through calcium channels is an important determinant of its cellular effect. The effect of cadmium was not altered by changes in the external calcium concentration, indicating that the mechanism does not involve competitive inhibition by calcium. SEM demonstrated significant structural damage to the corneal endothelium exposed to cadmium chloride, including focal disruption and denuding of the apical endothelial membrane.