Dry matter yields and hydrological properties of three perennial grasses of a semi-arid environment in east Africa

Enteropogon macrostachyus (Bush rye), Cenchrus ciliaris L. (African foxtail grass) and Eragrostis superba Peyr (Maasai love grass) are important perennial rangeland grasses in Kenya. They provide an important source of forage for domestic livestock and wild ungulates. These grasses have been used extensively to rehabilitate denuded patches in semi-arid environment of Kenya. This study investigated the dry matter yields and hydrological properties of the three grasses under simulated rainfall at three phenological stages; early growth, elongation and reproduction. Laboratory seed viability tests were also done. Hydrological properties of the three grasses were estimated using a Kamphorst rainfall simulator. Results showed that there was a significant difference (p > 0.05) in dry matter yields and soil hydrological properties at the different grass phenological stages. Generally, all the three grasses improved the soil hydrological properties with an increase in grass stubble height. C. ciliaris gave the best soil hydrological properties followed by E. macrostachyus and E. superba, respectively. E. macrostachyus recorded the highest seed viability percentage. C. ciliaris and E. superba were ranked second and third, respectively. C. ciliaris yielded the highest biomass production at the reproductive stage followed by E. superba and E. macrostachyus, respectively. (Résumé d'auteur

Preparation and Evaluation of Single-Stranded DNA Aptamer-Based Immunological Adjuvant in Broiler Chickens

Mineral oils and metal salts are commonly used as adjuvants to enhance acquired immunity. Recently, monoclonal antibodies (MAbs) and recombinant peptides agonist CD40 receptor have shown remarkable promise for induction of rapid and robust immune responses. Limitations of this approach MAb production costs and multiple administrations due to anti-MAb immune responses. Here we demonstrate the development of a unique and sophisticated DNA aptamer-based alternative for CD40-directed delivery of universal antigens as an alternative in chickens, and potentially other vertebrate species. This receptor, expressed by antigen-presenting cells, acts as a costimulatory molecule for activated T helper lymphocytes. After initially selecting for high affinity aptamers of independent sequence, we utilized a polymerization process where multiple aptamers were simultaneously and sequentially arranged through rolling circle amplification products (RCA-p), potentially capable of binding multiple recognition sites and causing receptor clustering. Selected sequences were demonstrated to effectively activate chicken macrophage HD11 cell line through CD40 receptors, demonstrating proof of concept in vitro. Additionally, using limited proteolysis liquid chromatography electrospray ionization mass spectrometry (LC-ESI-MS), we deduced the actual amino acid sequences targeted by these aptamer products, which are essential for activation. In chapter III, we produced a biotinylated version of an effective CD40-activating RCA-p, and streptavidin-conjugated this RCA-p to a biotinylated peptide of the highly conserved type-A influenza peptide M2e. This conjugate was administered subcutaneously at either (25μg/bird) or (50μg/bird) at age 7 and 21 days. Anti-M2e IgG responses were determined at 14, 21, 28 and 35 days of age by ELISA. The RCA-p-M2e complex, at 50μg/bird, was able to induce robust seroconversion as early as 7 days post-immunization, with high antibody titer consistent through the end of the experiment. The lower dose, however, showed delayed responses and required the second administration. Taken together, these results constitute proof of concept for RCA-p-directed antigen delivery for peptide antigens and a potential tool for rapid generation of new vaccines against animal diseases. In chapter IV we discuss PCR artifacts that develop during traditional DNA aptamers selection and proposed a repetitive thermal correction cycles [(65°C/10min, 20°C/1min)x6] of the PCR. This may improve future selection of aptamers for similar purposes

Students as Consumers? Chinese International Students’ Perspectives and Experiences in UK Universities

With the neoliberal ideology permeating the British higher education (HE) sector, students are repositioned as consumers, which has attracted substantial criticism. However, little empirical evidence proves that students identify themselves as consumers. This study engages Chinese international students from 43 universities in the United Kingdom (UK) with 848 survey responses and 51 interviews to contribute their perspectives and experiences on the controversial proposition. Findings capture some consumerism features among students, but these relate to more marginal parts of the student experience. A range of intrinsic motivations drive students to engage with their studies, such as subject interest and self-development. Despite paying high tuition, most students do not express entitlement to a degree with minimum effort. While some students support consumer rights, they challenge the rationality of consumer identity conflicting with their other social categories. Chinese students are highly aware of marketisation and their role as international students in perceived profit-making intention in UK HE. However, their attitudes towards marketisation executed by different HE stakeholders vary. Students show greater acceptance of the UK government and university managers marketising HE so that more international students can study in the UK and sufficient funding can be devoted to better facilities and teaching. They are very critical of applying the market mechanisms to teaching and learning. They urge their teaching staff to see their demands stemming from their identities as learners rather than consumers. This study sheds light on the rise of student consumerism and the impacts of marketisation on students’ lives and studies. The empirical insights challenge the pervasiveness of the conceptualisation of students as consumers and broaden institutional practitioners’ understanding of students’ educational orientation and identity construction. The results inform policymakers and institutional practitioners to rethink student-consumer positioning and promote more scholarly attention to international student construction in higher education policy