Vivapain : a cysteine peptidase from Trypanosoma vivax.

Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.African animal trypanosomosis is a devastating disease affecting livestock mainly found in sub-Saharan Africa. This disease is known as nagana and is transmitted by the trypanosome parasite from the tsetse fly vector to a mammalian host. There are three African trypanosomes namely Trypanosoma vivax, T. congolense and T. brucei brucei that are the causative agents responsible for this disease in African cattle. This disease is serious since it not only affects livestock but also has a negative impact on the sub-Saharan African economy. There is, therefore, a great demand for better control methods of the disease and suitable diagnostic methods. Current control measures such as the use of trypanocidal drugs, tsetse fly eradication methods and trypanotolerant cattle have become inadequate. The defence mechanism of the trypanosome to continuously change its surface coat by a process of antigenic variation has made it impossible to produce a suitable vaccine. Therefore, chemotherapy is still one of the key approaches for control of this wasting disease. The long existence of the current trypanocidal drugs has allowed the development of drug resistance. The development of new chemotherapeutic drugs is focused on targeting the pathogenic factors such as parasite cysteine peptidases that contribute to the disease. Vivapain is the main cysteine peptidase of T. vivax and shares high sequence identity with congopain, the main cysteine peptidase of T. congolense, which was previously shown to be a pathogenic factor contributing to trypanosomosis. Vivapain, thus, has potential as a target for chemotherapeutic drug design. Hence, the first part of this study involved the recombinant expression and enzymatic characterisation of vivapain for future production of new synthetic inhibitors for the use in new trypanocidal drugs. The catalytic domain of vivapain (Vp) was recombinantly expressed in the Pichia pastoris yeast expression system and enzymatically characterised. The main finding from this study was that Vp was only able to hydrolyse a substrate if the P2 position was occupied by either a hydrophobic Phe or Leu residue. Vp was also found to be active close to physiological pH and was inhibited by the reversible cysteine peptidases, leupeptin, antipain and chymostatin and the irreversible cysteine peptidases L-trans-epoxysuccinyl-leucylamido (4-guanidino) butane (E-64), iodoacetic acid (IAA) and iodoacetamide (IAN). A further important aspect of controlling trypanosomosis is the diagnosis of the disease. Clinical, parasitological, molecular and serological techniques have been applied and used to diagnose trypanosomosis. One of the most promising serological techniques has proven to be the enzyme-linked immunosorbent assay (ELISA), more specifically the antibody and antigen detection ELISAs. The main requirement for this technique is a readily available and reproducible antigen such as that produced by recombinant expression. While there are recombinant antigens that are available to be used to detect T. congolense, T. brucei brucei and even T. evansi infections, there are none available to detect T. vivax infections. In the second part of this study, a mutant inactive full length form of vivapain (FLVp) was expressed in a bacterial expression system for the detection of T. vivax infections. Antibodies against this antigen were produced in both chickens and mice. Both the chicken IgY and mice sera were able to detect the recombinant FLVp in western blots. The mice sera were also able to detect native vivapain in a T. vivax lysate, which is very promising for future use of the FLVp antigen and the corresponding antibodies in diagnosis of T. vivax infections in sera of infected animals

PHASES: Opto-mechanical Solutions to Perform Absolute Spectrophotometry from Space

This work provides an update of the current status of PHASES, which is a project aimed at developing a space-borne telescope to perform absolute flux calibrated spectroscopy of bright stars. PHASES will make it possible to measure micromagnitude photometric variations due to, e.g., exo-planet/moon transits. It is designed to obtain 1% RMS flux calibrated low resolution spectra in the wavelength range 370–960 nm with signal-to-noise ratios \u3e100 for stars with V∼1 minute. The strategy to calibrate the system using A-type stars is outlined. PHASES will make possible a complete characterization of stars, some of them hosting planets. From the comparison of observed spectra with accurate model atmospheres stellar angular diameters will be determined with precisions of ∼0.5%. The light curves of transiting systems will be then used to extract the radius of the planet with similar precision. The demanding scientific requirements to be achieved under extreme observing conditions have shaped the optomechanical design. A computational model and a high-precision interferometric system have been developed to test the performance of the instrument

Calibration and Validation of the Cosmic Ray Neutron Rover for SoilWater Mapping within Two South African Land Classes

Knowledge of soil water at a range of spatial scales would further our understanding of the dynamic variable and its influence on numerous hydrological applications. Cosmic ray neutron technology currently consists of the Cosmic Ray Neutron Sensor (CRNS) and the Cosmic Ray Neutron Rover (CRNR). The CRNR is an innovative tool to map surface soil water across the land surface. This research assessed the calibration and validation of the CRNR at two survey sites (hygrophilous grassland and pine forest) within the Vasi area with an area of 72 and 56 ha, respectively. The assessment of the calibrations showed that consistent calibration values (N0) were obtained for both survey sites. The hygrophilous grassland site had an average N0 value of 133.441 counts per minute (cpm) and an average error of 2.034 cpm. The pine site had an average N0 value of 132.668 cpm and an average error of 0.375 cpm between surveys. The validation of CRNR soil water estimates with interpolated hydro-sense soil water estimates showed that the CRNR can provide spatial estimates of soil water across the landscape. The hydro-sense and CRNR soil water estimates had a R2 of 0.439 at the hygrophilous grassland site and 0.793 at the pine site

The factors driving staff turnover in the hardware retail industry

The following quantitative study investigated staff turnover at Company H, a hardware retailer, where 174 former employees were telephonically interviewed via a questionnaire. The results showed that staff enjoyed various factors at Company H but found their present management better than that of Company H. The staff also viewed written and spoken English and PC skills as very important factors for their training in retail, their career advancement and their decisions to stay in retail. Issues of gender, age and further customer training was also found to be important factors. These findings were discussed in light of the literature review conducted and a detailed model of learning and turnover intentions was proposed. The study was concluded with a list of recommendations for company H and a list of areas for further research.Dissertation (MBA)--University of Pretoria, 2010.Gordon Institute of Business Science (GIBS)unrestricte

Comparison between satellite-based and cosmic ray probe soil moisture estimates : a case study in the Cathedral Peak catchment.

Master of Science in Environmental Hydrology. University of KwaZulu-Natal, Pietermaritzburg 2015.Abstract available in PDF file

Cosmic ray neutrons provide an innovative technique for estimating intermediate scale soil moisture

Soil moisture is an important hydrological parameter, which is essential for a variety of applications, thereby extending to numerous disciplines. Currently, there are three methods of estimating soil moisture: ground-based (in-situ) measurements; remote sensing based methods and land surface models. In recent years, the cosmic ray probe (CRP), which is an in-situ technique, has been implemented in several countries across the globe. The CRP provides area-averaged soil moisture at an intermediate scale and thus bridges the gap between in-situ point measurements and global satellite-based soil moisture estimates. The aim of this study was to test the suitability of the CRP to provide spatial estimates of soil moisture. The CRP was set up and calibrated in Cathedral Peak Catchment VI. An in-situ soil moisture network consisting of time-domain reflectometry and Echo probes was created in Catchment VI, and was used to validate the CRP soil moisture estimates. Once calibrated, the CRP was found to provide spatial estimates of soil moisture, which correlated well with the in-situ soil moisture network data set and yielded an R2 value of 0.845. The use of the CRP for soil moisture monitoring provided reliable, accurate and continuous soil moisture estimates over the catchment area. The wealth of current and potential applications makes the CRP very appealing for scientists and engineers in various fields

Consumers’ understandings of natural implied health claims and the effects of natural implied health claims on food product evaluation and food choice

Nutrition educators and policy makers are interested in how consumers use nutrition information on food packaging labels, to enable policy makers to improve health awareness, and to affect positive dietary change. In New Zealand two types of explicit health claims are allowed (general level health claims e.g. ‘gives you energy’ and nutrient content claims e.g. ‘high in calcium’) (FSANZ 2008a), and these claims are used by food manufacturers to market their food products. While manufacturers argue that health claims inform consumers’ choices, ambiguous terms may create confusion, particularly if consumers interpret these differently. The last two decades have seen the regulation of explicit health claims on manufactured food products internationally and in New Zealand, with health claims being the focus of extensive research. Literature has demonstrated that consumers use explicit health claims made by manufacturers and see these claims as beneficial. However, manufacturers also use implied health claims to market their food products. This study investigates, in the lives of ten adult New Zealanders, the personal meanings attached to implied health claims and the effects of these implied health claims on food product evaluation and choice. The study design consisted of two phases. Phase I comprised ten structured interviews that explored consumers’ understandings of natural implied health claims and the effects of the natural claim on the evaluation of a mock cereal product. Phase II comprised three follow up interviews with existing participants that explored participants’ beliefs on both explicit and implied health claims whilst examining manufactured food products. Participant interviews were transcribed verbatim and analysed using grounded theory analysis in order to develop a conceptual framework and uncover emergent themes that could provide insight on the research question. Descriptive analysis resulted in five descriptive categories that described participants’ understandings of implied health claims and their behaviour when they evaluated a natural implied health claim on a mock cereal product. The descriptive categories were: factors that influence food choice, natural claim interpretation, benefits, evidence and behaviour. The descriptive analysis was followed by a conceptual analysis of phase I and phase II interviews of these ten participants, and resulted in six concepts. These concepts analysed different aspects of participants’ understandings of natural implied health claims, relevant to the research question, and cohered to form the conceptual framework. The six conceptual areas were: conflicting product choice, avoiding interpersonal conflict, information preferences, perceptions of Front of Pack (FoP) information, difficulties with manufacturers’ use of implied claims and managing FoP information. Data analysis through the conceptual framework generated the analytical themes of risk, trust and scepticism. Participants’ comments suggested that their food choices were dictated by an avoidance of ‘bad’ choices. In product evaluation, several participants recounted a ‘negative logic’ of ‘bad’ nutrients they wished to avoid in a healthy food. Artificial ingredients were avoided because they represented a risk that could not be easily measured. Overall, participants’ comments suggested that artificial additives are an unnecessary risk and displayed a preference for more natural options when given a choice. Participants’ expressed concerns hinged on trust they felt in the information. Individuals described foods that they habitually purchased in terms of their trust in the product content and in the food manufacturer. Participants noted that inconsistencies in product content and product claims affected their ability to trust the information, and led some participants to view FoP information sceptically. In general, participants described a preference for FoP claims to aid product evaluation and food choice, but were also aware that the information was a form of marketing. They evaluated claims with caution, and in context of other personally relevant product information. Participants described being faced with a myriad of food choices daily. These ten participants expressed various strategies to make food purchase decisions manageable; within these strategies were a number of contradictions. In the present study, several participants’ descriptions of natural implied health claims suggested a ‘halo effect’ as they inferred positive attributes beyond the scope of the claim, while knowledge of this misleading claim led participants to view FoP claims with scepticism. Regulatory body decisions to not define natural implied health claims adds to consumers’ confusion and scepticism of FoP claims and detracts from the ability of credible claims to convey useful product information to the consume

Deployment and Characterisation of a Telescopic Boom for Sounding Rockets

In any sounding rocket, volume and mass are at a premium. Payload designers strive towards smaller, lighter and cheaper mechanisms which can achieve the same goals. This project aims to reduce the mass and volume for probe deployment booms and their deployment mechanisms. An experiment (Telescobe) to test a low cost novel method of boom deployment using telescopic carbon fibre poles was developed. A custom camera measurement system was also developed to measure boom length and harmonic deflection. This experiment was flown onboard the REXUS 9 sounding rocket [1] in February 2011 from Esrange space centre, Sweden. The experiment functioned as expected in all pre-flight tests. However, an unexpected malfunction in the experiment hatch door was experienced during flight which prevented the boom from being extended through the hatch. Despite this, it was found that the carbon fibre sections, all mechanisms and hardware, survived the flight and functioned as expected as far as possible. It is hoped that with a redesigned hatch, the experiment can be relaunched onboard a future REXUS rocket

A Novel Telescopic Boom Deployment System for Use in Upper Atmosphere Research

Typical measurement probe deployment systems on sounding rockets employ hinged booms which extend the probes away from the rocket. This configuration often has a significant mass and may require a considerable amount of the rocket’s valuable payload volume. In an effort to reduce both mass and volume, the DIT Space Research Group have designed a light weight carbon fibre telescopic boom system, compatible with measurement probes commonly used in upper atmosphere research. Our design has been selected to be tested on a suborbital space flight onboard the REXUS 9 sounding rocket in March 2011. The purpose of this test is to characterise the boom system in-situ and increase its Technology Readiness Level (TRL). The system is capable of deploying a boom with a mock electromagnetic field (E-field) probe to a length of 1.63m ±0.5%. The mock probe will be attached to the distal end of the boom and will house six LEDs, which emit light at a wavelength of 620 nm. A filtered camera measurement system will gather this light allowing the boom deployment length, deflection and amplitudes of any displacement due to vibration to be measured and recorded. An accelerometer mounted in the probe will monitor vibration frequencies. The boom will deploy from the rocket at an altitude of approximately 70Km and will be jettisoned before re-entry. All data obtained during the flight will be stored on a solid state memory device and then recovered for post flight analysis. A downlink to a ground station will provide a live TV feed of boom deployment and jettison. The entire system has a mass budget of less than 4kg and can be contained in a rocket module of 348 mm diameter and 220 mm height

EBNEO commentary: Maternal high-dose DHA supplementation and neurodevelopment in infants born before 29 weeks' gestation

Commentary Published May 2023Deeva Vather, Amy Kei