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No description available.

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Investigations concerning metallothionein (MT) have covered 4 main areas. Initial studies were carried out to develop an immunocytochemical technique for the detection of MT. An indirect peroxidase technique was used to localise MT within the livers and kidneys of rats injected with CuSO4. An increase in immunocytochemical staining was observed following Cu injection which was consistent with the increase in MT-I concentrations as detected by RIA. To establish whether degradation of MT in vitro is influenced by prior exposure of protein to oxygen free radicals. (Cu,Zn)-MT with Cu:Zn ratio 1:1, purified from pig liver following injection with diethylamine copper oxyquinoline sulphonate (Cujec), was found to be extensively degraded after incubation with a free radical generating system (xanthine/xanthine oxidase) and subsequently with trypsin. However proteins with Cu:Zn ratios of 2:1 or 5:1 were not greatly affected. This indicates that an oxidative step may be involved in the degradation pathway and/or aggregation of MT but the magnitude of the effect is ultimately determined by the ratio of metals present within MT. To establish whether the turnover rate of hepatic CuMT is increased in vivo in animals subjected to oxidant stress. Iron overload was used to initiate oxidant stress in rats prior to injection of Cu using a mixture of Cujec and CuSO4. It could not be concluded, however, if in vivo degradation of CuMT was influenced by the application of iron-induced oxidant stress. Subcellular localisation of MT by fractionation of liver and kidney homogenates using preformed Percoll gradients did, however, demonstrate that MT was not associated with the lysosomal fraction but within the nuclear fraction in correlation with previous studies. To identify specific chelators for selective removal of Cu from CuMT in vitro and to establish the effect of administration of such chelators on the turnover of CuMT in vivo. Ammonium terathiomolybdate [(NH4)2MoS4] was incubated with (Cu,Zn)-MT and Cd, resulting in the complete removal of Cu from protein and replacement with Cd. The effect of this chelating action for Cu was then studied in vivo by administration of (NH4)2MoS4 to rats following injection of Cu using a mixture of Cujec and CuSO4. The turnover and degradation of induced CuMT, however, could not be said to be increased by the addition of the Cu chelator, (NH4)2MoS4, conclusively.

Class of 2007 Abstract / Objectives: The purpose/objective of this study is to determine the effects of heat exposure, on the levels of active ingredient in three selected medications with narrow therapeutic indices: levothyroxine, epinephrine, and timolol. Methods: In order to complete the study, a variety of methods were carried out to simulate the desired and appropriate environmental conditions. The drug selection was based on the medications pharmacokinetic properties. Levothyroxine was considered ideal to include in the study due to the medication's short shelf life and narrow therapeutic window. Epinephrine was selected since it is a life-saving medication, which has been reported to degrade to a significant extent under extreme heat. Timolol was chosen since its liquid formulation can be unstable when exposed to extreme heat. Epi- Pen ®, levothyroxine 150 mcg, and timolol 0.5% were mailed from Phoenix on 7/12/06, via FedEx in order to simulate the mail order prescription delivery process. Alternatively, other samples of the medications were also placed at room temperature and a variety of heat and humidity conditions. The temperature and relative humidity profiles for the mail order drugs were monitored by a temperature and RH device. Three different assessments were made for each drug. Within each assessment, three analyses were conducted on that same sample. For the timolol drops, each 5ml (??)bottle was assayed three times in addition to baseline measurements. Likewise, the levothyroxine tablets and epinephrine injections each were analyzed three times from the same sample, from three different lots. In addition, we also examined the degredation of these three drugs when subjected to constant temperature exposure of 37, 45, 45 with RH, and 55 degrees Celsius in a lab oven. Samples were collected after 1-. 4-, and 7-days of heat exposure in both the mail box and the oven; 7/14/06, 7/17/06, and 7/20/06, respectively. Each medication was analyzed by its respective high-performance liquid chromatography (HPLC) method. The amount of drug taken for each sample was 0.5mL of epinephrine, 10 tablets of levothyroxine, and 0.5mL of timolol were used in the preparation for HPLC analysis. Results: The temperature and RH profile were recorded and graphed. The temperature measured in the mail box ranged from ~75 degreees Fahrenheit to ~140 degrees Fahrenheit. Based on the extrapolation to the baseline, the amount of drug measured on days 1, 4, and 7 were the following: 1) Levothyroxine: 123.66 mcg, 118.61mcg, and 119.3 mcg, respectively; 2) EpiPen: 1121.48 mcg/ml, 1215.52 mcg/ml, and 1167.22 mcg/ml, respectively; 3) timolol: 6766.30 mcg/ml, 6659.52 mcg/ml, and 6508.48 mcg/ml, respectively. Conclusions: The medications studied were exposed to temperatures above the manufacturer’s recommended storage conditions for the majority of the time. Despite being out of opitmal conditions, the results indicated that all three drugs did not have significant degradation.

Atrazine, a member of the s-triazine herbicides, appears on the EC Red List of chemicals that cause environmental concern, with residues occurring frequently in sub-soils and aquifers world-wide. Microbial metabolism is considered to be the major mechanism of complete removal of atrazine from the soil environment. Laboratory-based studies were carried out to investigate the microbial mineralisation of atrazine in soil, and to develop novel methods for potential acceleration of breakdown. In initial investigations, simple microcosm experiments were carried out to identify the importance of different fractions (water-soluble and water-insoluble) of plant residues to the dynamics, and extent of atrazine mineralisation. The amendment of soil with different plant residue fractions initially inhibited (for the water-soluble fraction) or enhanced (for the water-insoluble fraction) dynamics of atrazine mineralisation. However, by the end of the incubation, there was no overall effect on atrazine mineralisation. This suggested that increasing the soil organic matter content may render the herbicide less bioavailable to the degrader population. Investigations carried out to determine which component of the microbial biomass was more important in atrazine mineralisation showed that substantial removal of the fungal and Gram-negative bacterial population inhibited atrazine mineralisation in the soil. Experiments to selectively enrich the soil for fungal or bacterial atrazine degraders isolated a mixed bacterial culture able to accelerate atrazine mineralisation when inoculated into soil. The effect of the presence of the earthworm Lumbricus terrestris on the indigenous atrazine degrading microflora was investigated. Results indicated that atrazine mineralisation could be accelerated, but this was not primarily due to increases in microbial biomass, but possibly due to physio-chemical changes brought about by the earthworm and subsequent alterations in atrazine bioavailability.

No description available.

Poly(L-lactide) (PLLA) is a well-recognised bioresorbable polymer known to degrade after 1.5 to 5 years by hydrolysis. For certain medical device or drug delivery applications, it would be desirable to reduce this degradation time as strategies for tailoring degradation and drug release rates remain limited. This work aimed to examine a consistent series of polymers based on a large block of PLLA and small quantities of hydrophilic poly(ethylene glycol) (PEG) initiator. The polymers had PLLA number average molecular weight (Mn) values ranging between about 60 kDa and 200 kDa and PEG Mns ranging between 550 Da and 5000 Da giving very low PEG wt% values ranging between 0.1 and 1.5 wt%. There are currently no studies which consider high molecular weight PLLA polymers with small quantities of PEG for potential use in structural implants. Furthermore, reports in the literature do not consider the individual effects of PEG addition and PEG and PLLA lengths. The focus of this project was on the impact of processing, hydrolytic degradation and drug release on the morphological aspects of the materials. The materials were thoroughly characterised in their as-synthesised and processed forms. The assynthesised polymers were semi-crystalline and retained the unit cell of PLLA. The glass transition temperature (Tg) was significantly reduced by PEG functionalisation. After injection moulding, nuclear magnetic resonance (NMR) indicated that the PEG component was still present. The Mn of the PEG functionalised samples decreased by approximately two-fold compared with the as-synthesised materials while the PLLA control polymers, processed beyond 200 °C, were more affected as the processing temperature was increased. The degradation properties of the materials were considered. The processed materials were submerged in phosphate buffered saline (PBS) (pH = 7.4) at 37 °C over an 8-month degradation study. During hydrolytic degradation, PEG functionalisation resulted in an increased water uptake. Mass loss began in all polymers when the Mn fell below a threshold of about 20 kDa. In the PEG functionalised samples, the degree of crystallinity increased with time, facilitated by plasticisation from PEG and the increased water content. The molecular degradation rate, k for the PEG-functionalised polymers was dependent on the presence of PEG functionalisation but was little affected by PEG length or PLLA length in the ranges studied. The time taken to reach the critical Mn, and hence the time for mass loss to begin, therefore depended on both the initial Mn and the presence or absence of PEG functionalisation. In the presence of PEG, k, was dramatically enhanced: k for PEG-functionalised polymers fell in the range of 6 x $10^{-4}$ $h^{-1}$ to 1 x $10^{-3}$ $h^{-1}$, as compared with that of the PLLA control of 2.9 x $10^{-5}$ $h^{-1}$. The mechanism of drug release from an analogous series of polymers was investigated. Propranolol. HCl was selected as a model drug for the drug release studies due to its thermal stability and solubility in PBS. Drug loading of propranolol.HCl was achieved by mixing the polymer and drug then injection moulding. A second method of drug incorporation using supercritical CO2 to load propranolol into as-synthesised polymer granules before injection moulding was examined for comparison. The materials processed through injection moulding showed that while drug crystals were present at the surface and in the polymer matrix, a level of drug solubility was also achieved in the PEG-functionalised polymers whereas the PLLA control showed no signs of polymer-drug interaction and only a distribution of drug crystals confined to the surface. The presence of drug crystals on the surface of the PLLA control resulted in the instant dissolution of propranolol.HCl and gave a burst release compared with an initial burst release in the PEG-functionalised polymers followed by a gradual release of the drug. This initial burst release was eliminated from the profile of the samples processed via supercritical CO2. The amorphous dispersion of the drug in the matrix gave a slow, sustained release throughout the duration of the drug release study. The results in this thesis have elucidated the intricate mechanisms of degradation and drug release from PEG-functionalised PLLA polymers. The overall outcome shows new ways of controlling the degradation and drug release rates of already medically established poly(-hydroxy acid) polymers extending their potential for use within temporary structural implants.

Hyaluronic acid (HA) is an unbranched polysaccharide consisting of the repeating disaccharide unit β(1→4)-GlcA-β(1→3)-GlcNAc and is a naturally occurring biopolymer in bacteria and vertebras. HA is predominantly found in the extracellular matrix (ECM) and the in vivo function of HA can vary depending on molecular weight (Mw) for instance high Mw HA is reported to be anti-angiogenic while low Mw HA induces angiogenesis. HA is a popular component for hydrogels such as dermal fillers. HA is commonly used in dermal fillers. However, other materials, such as other polymers, can be used as well. The project goal was to investigate different degradation processes for production of target Mw HA. Alkaline and acidic degradation processes in combination with increased temperatures seemed as the most promising methods. Degradation tests performed both in aqueous solution as well as heterogeneously in ethanol were evaluated. The acidic degradation in aqueous solution was proven to have the largest degradation constant. Both a robustness test as well as a Design of Experiments (DoE) was performed to investigate the influence different factors had on the degradation speed. The investigated factors were HA concentration, HCl concentration and temperature. Temperature and HCl concentrations proved to be the most influencing factors and a model was developed in the DoE software MODDE to describe how the factors influenced the degradation constant. The model was established as a good significant model with a Q2 value of 0.998 and relative standard deviation (RSD) value of 0.022 after a logarithmic transformation was performed as well as a simplification of the model by excluding some of the factor interactions. The acidic degradation method also proved to be a highly robust method which easily could be used to produce target Mw HA.