Due to the depletion of petroleum reserves and environmental concerns, bioethanol has been identified as an alternative fuel to petrol. Bioethanol is a fuel of bio-origin derived from renewable biomass. Starch and sugar containing materials are the primary sources of carbon for bioethanol production. Starch is firstly hydrolysed into simple sugars which are later fermented to bioethanol using Saccharomyces cerevisiae (S. cerevisiae). The fermentation of sugars to bioethanol is however limited by inhibition of S. cerevisiae by the major product of the process, bioethanol. The challenge is thus in keeping the bioethanol concentration at levels which are not harmful to the fermenting organism. Keeping bioethanol concentration low in the broth will provide a suitable environment for yeast to grow and thus increase the overall production. Currently bioethanol producers use high water dilution rates to keep the bioethanol concentrations in the broth low enough so that yeast is not harmed. This excess water has to be removed in the downstream process, which is expensive. The use of excessive amounts of water in the fermentation can be avoided by continual removal of bioethanol from the broth. During this investigation the experimental conditions for the hydrolysis process were determined. A pH of 5.5 was determined as the best pH for Termamyl SC at 95°C with a pH of 5.0 for Spirizyme Fuel at 55°C during the liquefaction and the saccharification step, respectively. During the fermentation process the influence of yeast concentration on bioethanol production was investigated by varying the yeast concentration between 2 g.L-1 and 7 g.L-1. A yeast concentration of 5 g.L-1 produced the highest bioethanol yield of 0.48 g.g-1 after 48 hours of fermentation using S. cerevisiae. Later during the investigation a coupled fermentation/pervaporation system was employed in a batch system for continual removal of bioethanol in the fermentation broth in a process called simultaneous fermentation and separation (SFS). Through the continuous removal of bioethanol from the fermentation broth, the bioethanol concentration in the broth was kept low enough so that it was not harmful to the fermenting organism but the overall fermentation yield was not improved. Pervaporation is a membrane separation process used to separate azeotropic mixtures such as bioethanol and water. It is highly efficient, cost effective and uses less energy than distillation. During the SFS process a bioethanol yield of 0.22 g.g-1 was obtained. The SFS process yield for bioethanol was low compared to 0.45 g.g-1 of the traditional batch fermentation process. The lower overall bioethanol yield obtained in the SFS process could be attributed to only the supernatant being used in the SFS process and not the entire fermentation broth as in the traditional process. The results from this study proved that the SFS process was less efficient compared to the traditional batch fermentation process with respect to the bioethanol yield, but that the fermentation could be carried out without the necessity for additional process water. / Thesis (M.Sc. Engineering Sciences (Chemical and Minerals Engineering))--North-West University, Potchefstroom Campus, 2010.

During rhythmic arm cycling soleus H-reflex amplitudes are reduced by modulation of group Ia presynaptic inhibition (Frigon et al, 2004). This reflex suppression is graded with the frequency of arm cycling (Loadman & Zehr 2007; Hundza & Zehr 2009) and 0.8 Hz is the minimum frequency to significantly reduce the soleus H-reflex (Hundza & Zehr 2009). Despite the data on modulation of the soleus H-reflex amplitude induced by rhythmic arm cycling, comparatively little is known about the modulation of stretch reflexes due to remote limb movement. Therefore, the present study was intended to explore the effect of arm cycling on stretch and H-reflex amplitudes in the soleus muscle. In so doing, additional information on the mechanism of action during rhythmic arm cycling would be revealed. Although both reflexes share the same afferent pathway, we hypothesized that stretch reflex amplitudes would be less suppressed by arm cycling because they are less inhibited by presynaptic inhibition (Morita et al, 1998). Failure to reject this hypothesis would add additional strength to the argument that Ia presynaptic inhibition is the mechanism modulating soleus H-reflex amplitude during rhythmic arm cycling. Participants were seated in a customized chair with feet strapped to footplates. Three motor tasks were performed: static control trials and arm cycling at 1 and 2 Hz. Soleus H-reflexes were evoked using single 1 ms pulses of electrical stimulation delivered to the tibial nerve at the popliteal fossa. A constant M-wave and ~6% MVC activation of soleus was maintained across conditions. Stretch reflexes were evoked using a vibratory shaker (ET-126; Labworks Inc). The shaker was placed over the triceps surae tendon and controlled by a custom written LabView program (single sinusoidal pulse at 100Hz). Results demonstrated that rhythmic arm cycling that was effective for conditioning soleus H-reflexes did not show a suppressive effect on the amplitude of the soleus stretch reflex. We suggest this indicates that stretch reflexes are less sensitive to conditioning by rhythmic arm movement, as compared to H-reflexes, due to the relative insensitivity of Ia presynaptic inhibition. / Graduate

Evidence that individuals distinguish between moral and conventional rules is reviewed. Moral rules prohibit actions that result in victims (e.g., violence, stealing, etc.). Conventional rules prohibit actions that do not result in victims (e.g., not saying please, dressing in opposite sex clothes). Previous theoretical accounts of the development of the moral/conventional distinction are discussed. These theories are contrasted with an approach that is developed here. It is proposed that there is a mechanism, a Violence Inhibition Mechanism (VIM), that is responsible for the previously observed aversive arousal response to the distress of others. It is proposed that this aversive arousal response is a prerequisite for the development of the moral/ conventional distinction, the moral emotions and the inhibition of violent behaviour. Previous accounts have stressed role taking as a prerequisite for the moral/ conventional distinction. However, this was found not to be the case. Autistics, already known to be lacking a 'Theory of Mind' and therefore unable to role take, were found to make the moral/ conventional distinction. It was hypothesized that Antisocial Personality Disorder (APD) might be a consequence of a lack of VIM; the clinical description of APD stresses their lack of the moral emotions and their inability to inhibit their violent actions. In line with this, APD subjects were not found to make a moral/conventional distinction. Two rival explanations of APD were investigated: that APD is due to an inability to role take and; that APD is due to frontal lobe damage. APD subjects were not found to be impaired in either of these respects in comparison to criminal controls. A final investigation focused on the emotion attributions of APD subjects. It was hypothesized, given the contention that VIM is a prerequisite for the development of the moral emotions, that APD subjects might make anomalous attributions in victim situations though their attributions of other situations should prove normal. This study observed that while the attributions of APD subjects and criminal controls did not differ if the emotions attributed were happiness, sadness or embarrassment there was significant difference in victim situations where APD subjects were less likely to attribute guilt and more likely to attribute indifference than criminal controls. This finding was taken as indirect support of the VIM position. Additional tests, and implications of the VIM model are then discussed.

Practicing the retrieval of some information can lead to poorer retrieval of other related information; this phenomenon is called retrieval-induced forgetting. This pattern has been explained as the result of inhibition of the related information during retrieval practice (Anderson, 2003). A core assumption of this inhibition account is that, to be suppressed, the related information must compete with the target information at the time of practice. Four experiments are reported that test this competition assumption. Two experiments showed that retrieval-induced forgetting did not occur without specific retrieval practice of the target items, replicating and extending prior findings. Two further experiments then showed that retrieval-induced forgetting did occur, however, when competition between target information and related information during retrieval practice was eliminated, undermining the competition assumption and hence the inhibition account. A new explanation of retrieval-induced forgetting is introduced that emphasizes context change between study, retrieval practice, and test.

Research Doctorate - Doctor of Philosopy (PhD) / Tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholamine biosynthesis, is regulated acutely by a combination of phosphorylation of three key serine (Ser) residues (Ser19, Ser31 and Ser40), and feedback inhibition by the catecholamines. Phosphorylation of Ser40 directly increases TH activity by relieving feedback inhibition of the enzyme. The phosphorylation of Ser19 or Ser31 can potentiate the phosphorylation of Ser40 in a process known as hierarchical phosphorylation. The 2 major human TH isoforms, hTH1 and hTH2, are differentially regulated by hierarchical phosphorylation in vitro. In this study, the human neuroblastoma SH-SY5Y cell line has been transfected with hTH1 and hTH2, and it has been demonstrated that phosphorylation of Ser31 potentiates the phosphorylation of Ser40 in hTH1. Phosphorylation of the equivalent Ser31 residue in hTH2 was not detectable, and thus this enzyme is not subject to Ser31-mediated hierarchical phosphorylation of Ser40 in situ. This is the first study to demonstrate that hTH1 and hTH2 are differentially regulated in situ. In addition, we have examined the nature of feedback inhibition of TH by the catecholamines. In addition to the high affinity, non-dissociable dopamine binding that is relieved by Ser40 phosphorylation, we have identified a second low affinity, readily dissociable binding site which regulates TH activity both in vitro and in situ regardless of the phosphorylation state of the enzyme. This low affinity binding site responds to changes in cytosolic catecholamine levels in situ in order to regulate TH activity. This work has contributed to our understanding of the complex nature of the regulation of TH activity.

GABAergic interneurons in the basolateral complex (BLC) of the amygdala are a part of the emotional-learning circuitry of the brain and receive excitatory inputs from all sensory modalities via cortex and thalamus. Although the BLC, which is made up of the lateral amygdala (LA), basal amygdala (BA) and accessory basal nucleus, is under the influence of a strong inhibition brought about by local interneurons, little is known about the diversity, characteristics and functioning of these interneurons. In this study, I have characterised the BLC interneuron population using a transgenic mouse model in which enhanced green fluorescent protein has been tagged to the GAD67 promoter. This promoter is specifically expressed in all GABAergic interneurons, enabling us to visualise interneurons under UV light. Whole-cell recordings were made from GAD67 interneurons in the BLA to study their membrane and synaptic properties. On the basis of their firing properties, interneurons in the BLC were classified into six distinct groups. The calcium-binding proteins calbindin, calretinin and parvalbumin were found to be expressed differently in the LA and BA interneurons, with the majority of the interneurons in the LA expressing calretinin, whereas those in the BA mostly expressed parvalbumin. We also found diversity in the expression of postsynaptic glutamate receptors in the BLC. Long-term potentiation induced at the interneurons was specific to the cortical inputs in the LA. LTP was expressed only in interneurons that either lacked NMDA receptors or had NMDA receptors with fast decay kinetics. This form of LTP was mediated by calcium-permeable AMPA receptors and required a postsynaptic calcium rise for its induction This study shows that the interneurons in the BLC are a heterogenous population with respect to the expression of calcium-binding proteins, axonal morphology, synaptic and membrane properties. This heterogeneity in interneuron population may be essential for the specialised roles various types of interneurons play in the functioning of the amygdala and in emotional learning.

The experiments reported in the present thesis examined the behavioural processes of Pavlovian fear extinction and latent inhibition. The first series of experiments studied the reacquisition of extinguished fear responses following different amounts of extinction training. Rapid reacquisition occurred when rats were reconditioned after moderate extinction, showing that the original learning remained intact across this extinction. In contrast, when reconditioning was given after massive extinction, reconditioned responding was first depressed but then spontaneously recovered over time. This suggests that massive extinction produces a relatively permanent loss of the originally learned responding, while additionally imposes on the extinguished CS a transient latent inhibitory process that prevented the immediate but not the delayed expression of reconditioning. The second series of experiments studied the impact of spontaneous recovery of extinguished fear responses on their additional extinction. These experiments demonstrated that a CS that had time to show spontaneous recovery underwent greater response loss across additional extinction than one lacking recovery. They also showed that an excitor extinguished in compound with a CS showing recovery suffered greater response loss than an excitor extinguished in compound with a CS lacking recovery. Further, extinction of a compound composed of two CSs, one showing recovery and a second lacking recovery, produced greater extinction to the CS that showed recovery. These results show that spontaneous recovery of extinguished responses deepens their extinction through an error-correction mechanism regulated by both common and individual error terms. The third series of experiments studied the spontaneous recovery of latently inhibited and extinguished fear responses in within-subject designs. Using a compound test procedure, a CS that had received extensive preexposure or extensive extinction was found to have undergone greater spontaneous recovery relative to a CS just moderately preexposed or moderately extinguished. A CS given a mixed history of preexposure and extinction also underwent greater recovery relative to a CS just preexposed or just extinguished. These results suggest that both latent inhibition and extinction share a transient depressive process, and that the resulting recovery of responding is proportional to the amount of this depression.

The experiments reported in the present thesis examined the behavioural processes of Pavlovian fear extinction and latent inhibition. The first series of experiments studied the reacquisition of extinguished fear responses following different amounts of extinction training. Rapid reacquisition occurred when rats were reconditioned after moderate extinction, showing that the original learning remained intact across this extinction. In contrast, when reconditioning was given after massive extinction, reconditioned responding was first depressed but then spontaneously recovered over time. This suggests that massive extinction produces a relatively permanent loss of the originally learned responding, while additionally imposes on the extinguished CS a transient latent inhibitory process that prevented the immediate but not the delayed expression of reconditioning. The second series of experiments studied the impact of spontaneous recovery of extinguished fear responses on their additional extinction. These experiments demonstrated that a CS that had time to show spontaneous recovery underwent greater response loss across additional extinction than one lacking recovery. They also showed that an excitor extinguished in compound with a CS showing recovery suffered greater response loss than an excitor extinguished in compound with a CS lacking recovery. Further, extinction of a compound composed of two CSs, one showing recovery and a second lacking recovery, produced greater extinction to the CS that showed recovery. These results show that spontaneous recovery of extinguished responses deepens their extinction through an error-correction mechanism regulated by both common and individual error terms. The third series of experiments studied the spontaneous recovery of latently inhibited and extinguished fear responses in within-subject designs. Using a compound test procedure, a CS that had received extensive preexposure or extensive extinction was found to have undergone greater spontaneous recovery relative to a CS just moderately preexposed or moderately extinguished. A CS given a mixed history of preexposure and extinction also underwent greater recovery relative to a CS just preexposed or just extinguished. These results suggest that both latent inhibition and extinction share a transient depressive process, and that the resulting recovery of responding is proportional to the amount of this depression.

The experiments reported in the present thesis examined the behavioural processes of Pavlovian fear extinction and latent inhibition. The first series of experiments studied the reacquisition of extinguished fear responses following different amounts of extinction training. Rapid reacquisition occurred when rats were reconditioned after moderate extinction, showing that the original learning remained intact across this extinction. In contrast, when reconditioning was given after massive extinction, reconditioned responding was first depressed but then spontaneously recovered over time. This suggests that massive extinction produces a relatively permanent loss of the originally learned responding, while additionally imposes on the extinguished CS a transient latent inhibitory process that prevented the immediate but not the delayed expression of reconditioning. The second series of experiments studied the impact of spontaneous recovery of extinguished fear responses on their additional extinction. These experiments demonstrated that a CS that had time to show spontaneous recovery underwent greater response loss across additional extinction than one lacking recovery. They also showed that an excitor extinguished in compound with a CS showing recovery suffered greater response loss than an excitor extinguished in compound with a CS lacking recovery. Further, extinction of a compound composed of two CSs, one showing recovery and a second lacking recovery, produced greater extinction to the CS that showed recovery. These results show that spontaneous recovery of extinguished responses deepens their extinction through an error-correction mechanism regulated by both common and individual error terms. The third series of experiments studied the spontaneous recovery of latently inhibited and extinguished fear responses in within-subject designs. Using a compound test procedure, a CS that had received extensive preexposure or extensive extinction was found to have undergone greater spontaneous recovery relative to a CS just moderately preexposed or moderately extinguished. A CS given a mixed history of preexposure and extinction also underwent greater recovery relative to a CS just preexposed or just extinguished. These results suggest that both latent inhibition and extinction share a transient depressive process, and that the resulting recovery of responding is proportional to the amount of this depression.

This thesis examines the design, synthesis and biological applications of a series of inhibitors which incorporate an azobenzene photoswitch, a peptidyl backbone and a trifluoromethyl ketone warhead. The photoswitch can be isomerised by irradiation with UV or visible light and has been employed to modulate the reactivity of the enzyme. Chapter one gives a brief outline of some of the important areas related to this work. Examples of previously utilised photoswitches as well as some background on serine protease and the uses of fluorine in medicine has been covered. Chapter two outlines the synthesis of the key trifluoromethyl carbinol 2.6 by two different methods. The condensation of a fluorinated aldehyde with a nitroalkane affords an α-nitro trifluoromethyl carbinol which can be reduced to give the desired amine 2.6. Treatment of oxazolones with trifluoroacetic anhydride via a modified Dakin-West reaction gives trifluoromethyl ketones which can be reduced to give trifluoromethyl carbinols. Chapter three investigate the synthesis of substituted stilbenes and phenanthrenes as alternative molecular switches to azobenzenes. Molecular modelling of phenanthrenes suggests they may be suitable mimics of E-azobenzenes. Chapter four outlines the synthesis of a series of mono and disubstituted azobenzenes by direct sulfonation of azobenzene or by condensation of nitroso arenes with aryl amines. The switches incorporate one or two peptidyl residues designed to improve specificity towards the enzyme. Chapter five examines the photoisomerisation of eight potential inhibitors by irradiating with UV or visible light. Irradiation with UV light enriches the sample to give 78-93 % of the Z-isomer. Irradiation with visible light gave photostationary states with 14-21 % Z-isomer. Ambient photostationary states are ca. 22 % Z-isomer. Chapter six looks at the testing of five trifluoromethyl ketones as potential inhibitors ofα-chymotrypsin. The inhibitors vary in substituents, substitution patterns and chain length. The inhibitors were tested at both ambient and Z-enriched photostationary states and were found to exhibit slow binding kinetics. In all cases the Z-enriched inhibitor solution was at least 3-fold more potent than the ambient solution. Chapter seven is an experimental chapter and outlines the synthesis of the compounds prepared in this thesis.