No

No

No

The evaluation of the state of grass species composition was conducted as an attempt to confirm the survey conducted by the United Nations Convention to Combat Desertification (UNCCD), where the Zeerust District was identified as an area with serious degradation problems. Quantitative data was obtained through botanical surveys (April 2001-February 2002) and verified by household surveys (March 2001-April 2002). Study sites included Braklaagte, Dinokana, Doomlaagte, Serake and Supingstad, with benchmark sites in Madikwe Grune Reserve. Between 6-12 survey points per site were selected after consultation with local Agricultural Extension Officers and communities. Survey points included the range of veld condition between bush encroached and severely denuded and eroded areas. The results indicate 12.3 % to 45.1 % loss of vegetal cover. Resistance above 2 000 ohms, base saturation exceeding 100 % and pH values below 5.5 are evidence of soil degradation. The general profile of the fanning household is that of an aging adult community, with however, a relatively good knowledge of fanning practices. 52 % of the respondents depend on the government pension fund as a source of income. 60 % of the respondents use crop fanning products strictly for household purposes. Poor economic return from fanning activities has resulted in overutilization of the herbaceous layer with consequent changes of grass species composition towards retrogression and the establishment of woody species. This environmental degradation is a serious risk to long-term sustainable development. It is therefore, recommended that environmental education programmes and ecological restoration projects be started in degraded areas. The government should set up and enforce land-use policies. Community participation should be encouraged in all land care activities. Land degradation is a real social problem that must be tackled before many people's aspirations of a better life are met. / Thesis (M.Sc. (Biology) North-West University, Mafikeng Campus, 2003

Tumor cells often hijack endoplasmic reticulum (ER) mediated signaling to facilitate tumor progression by adapting to the cellular stress evoked by oncogene overexpression and adverse microenvironment. Despite the prevalence of MYC-driven cancers, how the MYC oncoprotein regulates ER stress response pathways during tumorigenesis remains incompletely understood. Here we show that MYC drives continuous upregulation of ubiquitin fusion degradation 1 (UFD1) during T-cell acute lymphoblastic leukemia (T-ALL) development. As the E2 component of an ER-associated degradation (ERAD) complex, UFD1 facilitates the elimination of misfolded/unfolded proteins from the ER. We found that genetic and pharmacological disruption of UFD1 function exacerbates ER stress and activates the unfolded protein response (UPR). Specifically, UFD1 knockdown in human T-ALL cells impairs ERAD and promotes the proapoptotic UPR through the PERK-CHOP-BCL2 axis. This effect is demonstrated by an upregulation of PERK, phospho-PERK and its downstream effector CHOP, as well as a downregulation of BCL2 and BCLxL. Indeed, CHOP inactivation or BCL2 overexpression is sufficient to rescue tumor-cell apoptosis induced by UFD1 knockdown. Allelic loss of ufd1 in zebrafish similarly induces tumor-cell apoptosis and impairs MYC-driven T-ALL progression without affecting general animal health. These studies establish the UFD1-mediated ER stress response as an important mediator of MYC-driven tumor progression and suggest strategies for targeted therapy in T-ALL, and perhaps other MYC-driven cancers. Although UFD1-specific inhibitors have yet to be developed, inhibitors that target the p97 co-factor in UFD1-mediated ERAD are readily available. Importantly, we show that treatment with CB-5083, a selective and oral bioactive inhibitor of p97, can effectively kill human MYC-overexpressing T-ALL patient cells ex vivo and inhibits tumor progression in zebrafish models of MYC-driven T-ALL. Thus, CB-5083 treatment may represent an effective targeted therapy for T-ALL, especially relapsed/refractory ones with gain-of-function NOTCH1 mutations and thus MYC-overexpression.

Poly(butylene succinate) (PBSu), poly(2-methyl-1,3-propylene succinate) (PMPSu), and their two novel poly(butylene succinate-co-2-methyl-1,3-propylene succinate)s (PBMPSu 95/05 and PBMPSu 90/10) were synthesized by a two-stage esterification reaction. PBMPSu 95/05 and PBMPSu 90/10 were characterized as having 6.5 and 10.8 mol% 2-methyl-1,3-propylene succinate (MPS) units, respectively, by 1H NMR. These copolymers were characterized to be random from the 13C NMR spectra. In this study, the nonisothermal crystallization and thermal degradation behaviors of the polyesters were investigated via different approaches. A differential scanning calorimeter (DSC) and a polarized light microscope (PLM) were employed to investigate the nonisothermal crystallization of these copolyesters and neat PBSu. Morphology and the isothermal growth rates of spherulites under PLM experiments at three cooling rates of 1, 2.5 and 5 ¢XC/min were monitored and obtained by curve-fitting. These continuous rate data were analyzed with the Lauritzen-Hoffman equation. A transition of regime II ¡÷ III was found at 96.2, 83.5, and 77.9 ¢XC for PBSu, PBMPSu 95/05, and PBMPSu 90/10, respectively. DSC exothermic curves at five cooling rates of 1, 2.5, 5, 10 and 20 ¢XC/min show that almost all of the nonisothermal crystallization occurred in regime III. DSC data were analyzed using modified Avrami, Tobin, Ozawa, Mo, Friedman and Vyazovkin equations. All the results of PLM and DSC measurements reveal that incorporation of minor MPS units into PBSu markedly inhibits the crystallization of the resulting polymer. The nonisothermal crystallization behavior of these polyesters was also investigated using a Fourier-transform infrared spectrometer (FTIR) with an attenuated total reflection (ATR). The absorbance peaks of crystals for the £\ form (918, 955, and 1045 cm-1) of PBSu and PBMPSu copolyesters were observed by ATR-FTIR under nonisothermal crystallization. When these semicrystalline polyesters started to be solidified from the melt state, these characteristic absorption bands for PBSu and its copolyesters crystals have been detected. In this study, the thermal degradation mechanisms of PBSu, PMPSu, PBMPSu 95/05, and PBMPSu 90/10 were investigated using a thermogravimetric analyzer combined Fourier-transform infrared spectrometer (TGA-FTIR) and a pyrolysis-gas chromatography¡Vmass spectrometry (Py-GC-MS). The volatile products evolved from the thermal degradation of these two copolyesters were identified to be anhydride, ether, ester, alcohol, alkene, aldehyde, and CO2. FTIR spectra displayed that the main degradation products for these four polymers were anhydrides. Moreover, PBSu-rich PBMPSu copolymers exhibited the same thermal degradation mechanism as that of PBSu at lower thermal degradation temperatures (< 403 ºC) and as that of PMPSu at higher thermal degradation temperatures (> 403 ºC) by the TGA-FTIR analysis. The results of the TGA-FTIR analysis clearly demonstrates that the influence of MPS units on the thermal degradation process is gradually increased as the temperature increases for PBMPSu copolymers. The degradation mechanism of PBMPSu at lower thermal degradation temperatures and PBSu mainly follows the £]-hydrogen bond scission mechanism and the back-biting process from the polymer chains. Moreover, the degradation mechanism of PBMPSu at higher thermal degradation temperatures and PMPSu occurred mainly through the £]-hydrogen bond scission and secondarily through £\-hydrogen bond scission. Finally, the thermal stability and degradation kinetics of these polyesters were investigated using a TGA at heating rates of 1, 3, 5, and 10 ºC/min under dynamic nitrogen. The activation energies of thermal degradation in elective conversions were estimated using the Friedman and Ozawa methods. The results clearly demonstrated that the thermal stabilities of these PBMPSu copolyesters were slightly reduced with the incorporation of minor MPS units into PBSu. Two model-fitting methods of nth-order and autocatalysis nth-order reaction mechanisms were adopted to determine the mass loss function f(£\), the activation energy and the associated degradation parameters. The results revealed that the mechanism of autocatalysis nth-order fitted the experimental data much more closely than did the nth-order mechanism for PBSu, PMPSu and PBMPSu copolymers.

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references (leaves 207-223). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references (leaves 207-223). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references (leaves 207-223). Also available on the Internet.

Thesis (doctoral)--Stockholm School of Economics, 1991. / Includes bibliographical references.