Introduction: L'homéostasie du cholestérol est indispensable à la synthèse de la testostérone dans le tissu interstitiel et la production de gamètes mâles fertiles dans les tubules séminifères. Les facteurs enzymatiques contribuent au maintien de cet équilibre intracellulaire du cholestérol. L'absence d'un ou de plusieurs enzymes telles que la HMG-CoA réductase, la HSL et l'ACAT-1 a été associée à l'infertilité masculine. Toutefois, les facteurs enzymatiques qui contribuent au maintien de l'équilibre intra-tissulaire du cholestérol n'ont pas été étudiés. Cette étude a pour but de tester l'hypothèse que le maintien des taux de cholestérol compatibles avec la spermatogenèse nécessite une coordination de la fonction intracellulaire des enzymes HMG-CoA réductase, ACAT1 et ACAT2 et la HSL. Méthodes: Nous avons analysé l'expression de l’ARNm et de la protéine de ces enzymes dans les fractions enrichies en tubules séminifères (STf) de vison durant le développement postnatal et le cycle reproductif annuel et dans les fractions enrichies en tissu interstitiel (ITf) et de STf durant le développement postnatal chez la souris. Nous avons développé deux nouvelles techniques pour la mesure de l'activité enzymatique de la HMG-CoA réductase et de celle de l'ACAT1 et ACAT2. En outre, l'immunohistochimie a été utilisée pour localiser les enzymes dans le testicule. Enfin, les souris génétiquement déficientes en HSL, en SR-BI et en CD36 ont été utilisées pour élucider la contribution de la HMG-CoA réductase, l'ACAT1 et l'ACAT2 et la HSL à l'homéostasie du cholestérol. Résultats: 1) HMG-CoA réductase: (Vison) La variation du taux d’expression de l’ARNm de la HMG-CoA réductase était corrélée à celle de l'isoforme de 90 kDa de la protéine HMG-CoA réductase durant le développement postnatal et chez l'adulte durant le cycle reproductif saisonnier. L'activité enzymatique de la HMG-CoA réductase augmentait de façon concomitante avec le taux protéinique pour atteindre son niveau le plus élevé à 240 jours (3.6411e-7 mol/min/μg de protéines) au cours du développement et en Février (1.2132e-6 mol/min/μg de protéines) durant le cycle reproductif chez l’adulte. (Souris), Les niveaux d'expression de l'ARNm et l'activité enzymatique de la HMG-CoA réductase étaient maximales à 42 jours. A l'opposé, le taux protéinique diminuait au cours du développement. 2) HSL: (Vison), l'expression de la protéine de 90 kDa de la HSL était élevée à 180- et 240 jours après la naissance, ainsi qu'en Janvier durant le cycle saisonnier chez l'adulte. L'activité enzymatique de la HSL augmentait durant le développement pour atteindre un pic à 270 jours (36,45 nM/min/μg). Chez l'adulte, l'activité enzymatique de la HSL était maximale en Février. (Souris) Le niveau d’expression de l'ARNm de la HSL augmentait significativement à 21-, 28- et 35 jours après la naissance concomitamment avec le taux d'expression protéinique. L'activité enzymatique de la HSL était maximale à 42 jours suivie d'une baisse significative chez l'adulte. 3) ACAT-1 et ACAT-2: Le présent rapport est le premier à identifier l’expression de l'ACAT-1 et de l'ACAT-2 dans les STf de visons et de souris. (Vison) L'activité enzymatique de l'ACAT-2 était maximale à la complétion du développement à 270 jour (1190.00 CPMB/200 μg de protéines) et en janvier (2643 CPMB/200 μg de protéines) chez l'adulte. En revanche, l'activité enzymatique de l'ACAT-1 piquait à 90 jours et en août respectivement durant le développement et chez l'adulte. (Souris) Les niveaux d'expression de l'ARNm et la protéine de l'ACAT-1 diminuait au cours du développement. Le taux de l'ARNm de l'ACAT-2, à l’opposé du taux protéinique, augmentait au cours du développement. L'activité enzymatique de l'ACAT-1 diminuait au cours du développement tandis que celle de l'ACAT-2 augmentait pour atteindre son niveau maximal à 42 jours. 4) Souris HSL-/ -: Le taux d’expression de l'ARNm et l'activité enzymatique de la HMG-CoA réductase diminuaient significativement dans les STf de souris HSL-/- comparés aux souris HSL+/+. Par contre, les taux de l'ARNm et les niveaux des activités enzymatiques de l'ACAT-1 et de l'ACAT-2 étaient significativement plus élevés dans les STf de souris HSL-/- comparés aux souris HSL+/+ 5) Souris SR-BI-/-: L'expression de l'ARNm et l'activité enzymatique de la HMG-CoA réductase et de l'ACAT-1 étaient plus basses dans les STf de souris SR-BI-/- comparées aux souris SR-BI+/+. A l'opposé, le taux d'expression de l'ARNm et l'activité enzymatique de la HSL étaient augmentées chez les souris SR-BI-/- comparées aux souris SR-BI+/+. 6) Souris CD36-/-: L'expression de l'ARNm et l'activité enzymatique de la HMG-CoA réductase et de l'ACAT-2 étaient significativement plus faibles tandis que celles de la HSL et de l'ACAT-1 étaient inchangées dans les STf de souris CD36-/- comparées aux souris CD36+/+. Conclusion: Nos résultats suggèrent que: 1) L'activité enzymatique de la HMG-CoA réductase et de la HSL sont associées à l'activité spermatogénétique et que ces activités ne seraient pas régulées au niveau transcriptionnel. 2) L'ACAT-1 et de l'ACAT-2 sont exprimées dans des cellules différentes au sein des tubules séminifères, suggérant des fonctions distinctes pour ces deux isoformes: l'estérification du cholestérol libre dans les cellules germinales pour l'ACAT-1 et l'efflux du cholestérol en excès dans les cellules de Sertoli au cours de la spermatogenèse pour l'ACAT-2. 3) La suppression génétique de la HSL diminuait la HMG-CoA réductase et augmentait les deux isoformes de l'ACAT, suggérant que ces enzymes jouent un rôle critique dans le métabolisme du cholestérol intratubulaire. 4) La suppression génétique des transporteurs sélectifs de cholestérol SR-BI et CD36 affecte l'expression (ARNm et protéine) et l'activité des enzymes HMG-CoA réductase, HSL, ACAT-1 et ACAT-2, suggérant l'existence d’un effet compensatoire entre facteurs enzymatiques et non-enzymatiques du métabolisme du cholestérol dans les fractions tubulaires. Ensemble, les résultats de notre étude suggèrent que les enzymes impliquées dans la régulation du cholestérol intratubulaire agissent de concert avec les transporteurs sélectifs de cholestérol dans le but de maintenir l'homéostasie du cholestérol intra-tissulaire du testicule. / Introduction: Cholesterol homeostasis is essential for the synthesis of testosterone in interstitial tissue and the production of fertile gametes in the seminiferous tubules of the testis. Intracelluar cholesterol equilibrium in the testis is delicately maintained and regulated by enzymatic factors. The absence of one or more enzymes (HMG-CoA reductase, HSL and ACAT) has been implicated in the development of male infertility. However, the enzymatic factors that contribute to the maintenance of cholesterol equilibrium have not been investigated. This study is to test the hypothesis that the coordinated function of intracellular enzymes, HMG-CoA reductase, HSL and ACAT isoforms, are the basis of a system that helps to maintain cholesterol equilibrium during spermatogenesis. Methods: We characterized mRNA and protein expression levels of these enzymes in mink seminiferous tubules-enriched fraction (STf) during development and the annual reproductive cycle; or in mouse interstitial tissue-enriched fraction (ITf) and STf during postnatal development. Two novel techniques were developed to measure the HMG-CoA reductase, HSL and ACAT activities in mink and mouse STf. Additionally, immunohistochemistry was used to localize the enzymes in the testis. Finally, HSL knockout (KO) infertile male mice and selective cholesterol transporter (SR-BI, CD36) KO mice were used to elucidate the contribution of HMG-CoA reductase, HSL and ACAT isoforms in testicular cholesterol homeostasis when the enzyme or cholesterol transport system was genetically impeded. Results: 1) HMG-CoA reductase: (In mink STf), HMG-CoA reductase mRNA levels were relatively independent of 90kDa protein expression during development and the seasonal cycle. HMG-CoA reductase activity increased independently of its protein expression and reached maximal values by day 240 (3.6411e-7 mol/min/μg protein) during development and peaked in February (1.2132e-6 mol/min/μg protein) during the seasonal cycle. (In mouse STf), HMG-CoA reductase mRNA levels and enzymatic activity peaked by 42 days before decreasing while the protein levels tended to decrease steadily. 2) HSL: (In mink STf), an increase of 90kDa HSL protein expression by day 180- and 240 after birth as well as in January in seasonal cycle, was not related to the enzyme mRNA expression. HSL activity increased progressively through development and peaked by 270 days (36.45 nM/min/μg); another high HSL activity was shown in February. (In mouse STf), three significant elevations in HSL mRNA levels by day 21, 28, and 35 corresponded to a steady elevation of HSL protein expression throughout development. HSL activity peaked by day 42 but decreased remarkably in the adult. 3) ACAT-1 and ACAT-2: This is the first report to establish the presence of both ACAT-1 and ACAT-2 in the mink and mouse testis. (In mink STf), ACAT-2 activity reached its maximal value at 1190.00 CPMB/200μg protein by day 270 and 2643 CPMB/200μg protein in January. In contrast, ACAT-1 activity peaked by day 90 or in August during the seasonal cycle. (In mouse STf), ACAT-1 mRNA and protein levels were both decreased throughout development; ACAT-2 mRNA levels changes in the opposite direction of the protein levels, increasing throughout development. ACAT-1 activity in STf decreased throughout the development; while ACAT-2 activity increased significantly during development and peaked by day 42. 4) HSL-/- mice: KO HSL gene caused a decrease of HMG-CoA redutase mRNA expression and enzymatic activity in STf. However, ACAT-1 and ACAT-2 mRNA levels and enzymatic activities significantly increased in STf. 5) SR-BI-/- mice: The mRNA expression and activity of HMG-CoA reductase as well as ACAT-1 were statistically decreased in STf; whereas HSL mRNA level and activity were increased. 6) CD36-/- mice: The mRNA expression and activity of HMG-CoA reductase as well as ACAT-2 were significantly decreased in STf; while HSL and ACAT-1 mRNA levels and activities remained constant. Conclusion: These results suggest that 1) Activation of HMG-CoA reductase and HSL is associated with spermatogenetic activity, while the enzymatic activities may not only be regulated transcriptionally. 2) ACAT-1 and ACAT-2 are expressed in different cells of the tubules, suggesting distinct functions for these two closely related enzyme isoforms, with ACAT-1 being related to cholesterol esterification in germ cells and with ACAT-2 being associated with the removal of excessive cholesterol by Sertoli cells during spermatogenesis. 3) Genetically blocking HSL reduced the activity of HMG-CoA reductase while increasing activity of ACAT isoforms, suggesting the turn-off the enzyme in the cholesterol ester cycle may be essential for the accumulation of cholesterol esters in the tubules. 4) The dysfunction of intracellular cholesterol transporters affects regulation of the enzymes (HMG-CoA reductase, HSL and ACAT-1 and ACAT-2), which is presumably in response to compensatory extracellular cholesterol uptake. This study suggests that the enzymes implicated in the regulation of intracellular cholesterol may act cooperatively to maintain cholesterol homeostasis in testis.

In the terrestrial biosphere forests have a significant role as a carbon sink. Under recent climate change, it is increasingly important to detect seasonal change or ‘phenology’ that can influence the global carbon cycle. Monitoring canopies using camera systems has offered an inexpensive means to quantify the phenological changes. However, the reliability is not well known. In order to examine the usefulness of cameras to observe forest phenology, we analysed canopy images taken in two deciduous forests in Japan and England and investigate which colour index is best for tracking forest phenology and predict carbon uptake by trees. A camera test using model leaves under controlled conditions has also carried out to examine sensitivity of colour indices for discriminating leaf colours. The main findings of the present study are: 1) Time courses of colour indices derived from images taken in deciduous forests showed typical patterns throughout the growing season. Although cameras are not calibrated instrument, analysis of images allowed detecting the timings of phenological events such as leaf onset and leaf fall; 2) The strength of the green channel (or chromatic coordinate of green) was useful to observe leaf expansion as well as damage by spring late frost. However, the results of the camera test using model leaves suggested that this index was not sufficiently sensitive to detect leaf senescence. Amongst colour indices, Hue was the most robust metric for different cameras, different atmospheric conditions and different distances. The test also revealed Hue was useful to track nitrogen status of leaves; 3) Modelling results using a light use efficiency model for GPP showed a strong relationship between GPP and Hue, which was stronger than the relationships using alternative traditional indices.

Introduction: L'homéostasie du cholestérol est indispensable à la synthèse de la testostérone dans le tissu interstitiel et la production de gamètes mâles fertiles dans les tubules séminifères. Les facteurs enzymatiques contribuent au maintien de cet équilibre intracellulaire du cholestérol. L'absence d'un ou de plusieurs enzymes telles que la HMG-CoA réductase, la HSL et l'ACAT-1 a été associée à l'infertilité masculine. Toutefois, les facteurs enzymatiques qui contribuent au maintien de l'équilibre intra-tissulaire du cholestérol n'ont pas été étudiés. Cette étude a pour but de tester l'hypothèse que le maintien des taux de cholestérol compatibles avec la spermatogenèse nécessite une coordination de la fonction intracellulaire des enzymes HMG-CoA réductase, ACAT1 et ACAT2 et la HSL. Méthodes: Nous avons analysé l'expression de l’ARNm et de la protéine de ces enzymes dans les fractions enrichies en tubules séminifères (STf) de vison durant le développement postnatal et le cycle reproductif annuel et dans les fractions enrichies en tissu interstitiel (ITf) et de STf durant le développement postnatal chez la souris. Nous avons développé deux nouvelles techniques pour la mesure de l'activité enzymatique de la HMG-CoA réductase et de celle de l'ACAT1 et ACAT2. En outre, l'immunohistochimie a été utilisée pour localiser les enzymes dans le testicule. Enfin, les souris génétiquement déficientes en HSL, en SR-BI et en CD36 ont été utilisées pour élucider la contribution de la HMG-CoA réductase, l'ACAT1 et l'ACAT2 et la HSL à l'homéostasie du cholestérol. Résultats: 1) HMG-CoA réductase: (Vison) La variation du taux d’expression de l’ARNm de la HMG-CoA réductase était corrélée à celle de l'isoforme de 90 kDa de la protéine HMG-CoA réductase durant le développement postnatal et chez l'adulte durant le cycle reproductif saisonnier. L'activité enzymatique de la HMG-CoA réductase augmentait de façon concomitante avec le taux protéinique pour atteindre son niveau le plus élevé à 240 jours (3.6411e-7 mol/min/μg de protéines) au cours du développement et en Février (1.2132e-6 mol/min/μg de protéines) durant le cycle reproductif chez l’adulte. (Souris), Les niveaux d'expression de l'ARNm et l'activité enzymatique de la HMG-CoA réductase étaient maximales à 42 jours. A l'opposé, le taux protéinique diminuait au cours du développement. 2) HSL: (Vison), l'expression de la protéine de 90 kDa de la HSL était élevée à 180- et 240 jours après la naissance, ainsi qu'en Janvier durant le cycle saisonnier chez l'adulte. L'activité enzymatique de la HSL augmentait durant le développement pour atteindre un pic à 270 jours (36,45 nM/min/μg). Chez l'adulte, l'activité enzymatique de la HSL était maximale en Février. (Souris) Le niveau d’expression de l'ARNm de la HSL augmentait significativement à 21-, 28- et 35 jours après la naissance concomitamment avec le taux d'expression protéinique. L'activité enzymatique de la HSL était maximale à 42 jours suivie d'une baisse significative chez l'adulte. 3) ACAT-1 et ACAT-2: Le présent rapport est le premier à identifier l’expression de l'ACAT-1 et de l'ACAT-2 dans les STf de visons et de souris. (Vison) L'activité enzymatique de l'ACAT-2 était maximale à la complétion du développement à 270 jour (1190.00 CPMB/200 μg de protéines) et en janvier (2643 CPMB/200 μg de protéines) chez l'adulte. En revanche, l'activité enzymatique de l'ACAT-1 piquait à 90 jours et en août respectivement durant le développement et chez l'adulte. (Souris) Les niveaux d'expression de l'ARNm et la protéine de l'ACAT-1 diminuait au cours du développement. Le taux de l'ARNm de l'ACAT-2, à l’opposé du taux protéinique, augmentait au cours du développement. L'activité enzymatique de l'ACAT-1 diminuait au cours du développement tandis que celle de l'ACAT-2 augmentait pour atteindre son niveau maximal à 42 jours. 4) Souris HSL-/ -: Le taux d’expression de l'ARNm et l'activité enzymatique de la HMG-CoA réductase diminuaient significativement dans les STf de souris HSL-/- comparés aux souris HSL+/+. Par contre, les taux de l'ARNm et les niveaux des activités enzymatiques de l'ACAT-1 et de l'ACAT-2 étaient significativement plus élevés dans les STf de souris HSL-/- comparés aux souris HSL+/+ 5) Souris SR-BI-/-: L'expression de l'ARNm et l'activité enzymatique de la HMG-CoA réductase et de l'ACAT-1 étaient plus basses dans les STf de souris SR-BI-/- comparées aux souris SR-BI+/+. A l'opposé, le taux d'expression de l'ARNm et l'activité enzymatique de la HSL étaient augmentées chez les souris SR-BI-/- comparées aux souris SR-BI+/+. 6) Souris CD36-/-: L'expression de l'ARNm et l'activité enzymatique de la HMG-CoA réductase et de l'ACAT-2 étaient significativement plus faibles tandis que celles de la HSL et de l'ACAT-1 étaient inchangées dans les STf de souris CD36-/- comparées aux souris CD36+/+. Conclusion: Nos résultats suggèrent que: 1) L'activité enzymatique de la HMG-CoA réductase et de la HSL sont associées à l'activité spermatogénétique et que ces activités ne seraient pas régulées au niveau transcriptionnel. 2) L'ACAT-1 et de l'ACAT-2 sont exprimées dans des cellules différentes au sein des tubules séminifères, suggérant des fonctions distinctes pour ces deux isoformes: l'estérification du cholestérol libre dans les cellules germinales pour l'ACAT-1 et l'efflux du cholestérol en excès dans les cellules de Sertoli au cours de la spermatogenèse pour l'ACAT-2. 3) La suppression génétique de la HSL diminuait la HMG-CoA réductase et augmentait les deux isoformes de l'ACAT, suggérant que ces enzymes jouent un rôle critique dans le métabolisme du cholestérol intratubulaire. 4) La suppression génétique des transporteurs sélectifs de cholestérol SR-BI et CD36 affecte l'expression (ARNm et protéine) et l'activité des enzymes HMG-CoA réductase, HSL, ACAT-1 et ACAT-2, suggérant l'existence d’un effet compensatoire entre facteurs enzymatiques et non-enzymatiques du métabolisme du cholestérol dans les fractions tubulaires. Ensemble, les résultats de notre étude suggèrent que les enzymes impliquées dans la régulation du cholestérol intratubulaire agissent de concert avec les transporteurs sélectifs de cholestérol dans le but de maintenir l'homéostasie du cholestérol intra-tissulaire du testicule. / Introduction: Cholesterol homeostasis is essential for the synthesis of testosterone in interstitial tissue and the production of fertile gametes in the seminiferous tubules of the testis. Intracelluar cholesterol equilibrium in the testis is delicately maintained and regulated by enzymatic factors. The absence of one or more enzymes (HMG-CoA reductase, HSL and ACAT) has been implicated in the development of male infertility. However, the enzymatic factors that contribute to the maintenance of cholesterol equilibrium have not been investigated. This study is to test the hypothesis that the coordinated function of intracellular enzymes, HMG-CoA reductase, HSL and ACAT isoforms, are the basis of a system that helps to maintain cholesterol equilibrium during spermatogenesis. Methods: We characterized mRNA and protein expression levels of these enzymes in mink seminiferous tubules-enriched fraction (STf) during development and the annual reproductive cycle; or in mouse interstitial tissue-enriched fraction (ITf) and STf during postnatal development. Two novel techniques were developed to measure the HMG-CoA reductase, HSL and ACAT activities in mink and mouse STf. Additionally, immunohistochemistry was used to localize the enzymes in the testis. Finally, HSL knockout (KO) infertile male mice and selective cholesterol transporter (SR-BI, CD36) KO mice were used to elucidate the contribution of HMG-CoA reductase, HSL and ACAT isoforms in testicular cholesterol homeostasis when the enzyme or cholesterol transport system was genetically impeded. Results: 1) HMG-CoA reductase: (In mink STf), HMG-CoA reductase mRNA levels were relatively independent of 90kDa protein expression during development and the seasonal cycle. HMG-CoA reductase activity increased independently of its protein expression and reached maximal values by day 240 (3.6411e-7 mol/min/μg protein) during development and peaked in February (1.2132e-6 mol/min/μg protein) during the seasonal cycle. (In mouse STf), HMG-CoA reductase mRNA levels and enzymatic activity peaked by 42 days before decreasing while the protein levels tended to decrease steadily. 2) HSL: (In mink STf), an increase of 90kDa HSL protein expression by day 180- and 240 after birth as well as in January in seasonal cycle, was not related to the enzyme mRNA expression. HSL activity increased progressively through development and peaked by 270 days (36.45 nM/min/μg); another high HSL activity was shown in February. (In mouse STf), three significant elevations in HSL mRNA levels by day 21, 28, and 35 corresponded to a steady elevation of HSL protein expression throughout development. HSL activity peaked by day 42 but decreased remarkably in the adult. 3) ACAT-1 and ACAT-2: This is the first report to establish the presence of both ACAT-1 and ACAT-2 in the mink and mouse testis. (In mink STf), ACAT-2 activity reached its maximal value at 1190.00 CPMB/200μg protein by day 270 and 2643 CPMB/200μg protein in January. In contrast, ACAT-1 activity peaked by day 90 or in August during the seasonal cycle. (In mouse STf), ACAT-1 mRNA and protein levels were both decreased throughout development; ACAT-2 mRNA levels changes in the opposite direction of the protein levels, increasing throughout development. ACAT-1 activity in STf decreased throughout the development; while ACAT-2 activity increased significantly during development and peaked by day 42. 4) HSL-/- mice: KO HSL gene caused a decrease of HMG-CoA redutase mRNA expression and enzymatic activity in STf. However, ACAT-1 and ACAT-2 mRNA levels and enzymatic activities significantly increased in STf. 5) SR-BI-/- mice: The mRNA expression and activity of HMG-CoA reductase as well as ACAT-1 were statistically decreased in STf; whereas HSL mRNA level and activity were increased. 6) CD36-/- mice: The mRNA expression and activity of HMG-CoA reductase as well as ACAT-2 were significantly decreased in STf; while HSL and ACAT-1 mRNA levels and activities remained constant. Conclusion: These results suggest that 1) Activation of HMG-CoA reductase and HSL is associated with spermatogenetic activity, while the enzymatic activities may not only be regulated transcriptionally. 2) ACAT-1 and ACAT-2 are expressed in different cells of the tubules, suggesting distinct functions for these two closely related enzyme isoforms, with ACAT-1 being related to cholesterol esterification in germ cells and with ACAT-2 being associated with the removal of excessive cholesterol by Sertoli cells during spermatogenesis. 3) Genetically blocking HSL reduced the activity of HMG-CoA reductase while increasing activity of ACAT isoforms, suggesting the turn-off the enzyme in the cholesterol ester cycle may be essential for the accumulation of cholesterol esters in the tubules. 4) The dysfunction of intracellular cholesterol transporters affects regulation of the enzymes (HMG-CoA reductase, HSL and ACAT-1 and ACAT-2), which is presumably in response to compensatory extracellular cholesterol uptake. This study suggests that the enzymes implicated in the regulation of intracellular cholesterol may act cooperatively to maintain cholesterol homeostasis in testis.

This dissertation studies poverty and the economics of child-headed and grandmother-headed households in Sebokeng. The study takes interest in five main areas, namely, poverty, unemployment, child and grandmother-headed households, the state of poverty and unemployment in Sebokeng as well as the living conditions of child and grandmother-headed households in Sebokeng. The approach in this dissertation was to define and measure poverty and unemployment and to determine the poor population of Sebokeng. This was done by making use of household level indicators. Poverty was measured by employing the following indicators: the Household Subsistence level (HSL) as poverty line, the head count index, the poverty gap and the dependency ratio. A comparison was done between Sebokeng and Bophelong. Sebokeng has a higher level of poverty (85%) than that of Bophelong (67%) while the unemployment rates (27%) is lower than that of Bophelong (31%). Most indicators (level of education, income, expenditure) prove that Bophelong is better off compared to Sebokeng. This dissertation takes further interest in comparing child and grandmother-headed households to “normal” households in Sebokeng. The study found that the main source of income for child-headed households is foster and child support grants (54%) while pension grants serve as the main source of income for both grandmother-headed households and “normal” households (65%).The study therefore proves that child-headed households are worse off financially and otherwise in comparison to grandmother-headed and “normal” households. If more social worker assistance was available to these orphans in the form of assistance with the application for identity documents and birth certificates at the Department of Home Affairs, these orphans would not be as worse-off as was found in this study. The dissertation concludes that the depth of poverty in child-headed households is thus greater than that of grandmother-headed and “normal” households, and it recommends that government should take further steps to reduce the unemployment rate by paying attention to the preferred skills of the population of Poverty and the economics of child and grandmother-headed households in Sebokeng. Sebokeng by offering training to enhance those skills. Food gardening projects should be organised so that the poor can sustain themselves and earn an income in the process. The dissertation also recommends that government should take more interest in improving the lives of these orphans by encouraging them to go to school and in obtaining identity documents. This can be possible through the assistance of social workers as these two elements can open many doors to a better life for these orphans. / Thesis (M.Com. (Economics))--North-West University, Vaal Triangle Campus, 2011

This dissertation studies poverty and the economics of child-headed and grandmother-headed households in Sebokeng. The study takes interest in five main areas, namely, poverty, unemployment, child and grandmother-headed households, the state of poverty and unemployment in Sebokeng as well as the living conditions of child and grandmother-headed households in Sebokeng. The approach in this dissertation was to define and measure poverty and unemployment and to determine the poor population of Sebokeng. This was done by making use of household level indicators. Poverty was measured by employing the following indicators: the Household Subsistence level (HSL) as poverty line, the head count index, the poverty gap and the dependency ratio. A comparison was done between Sebokeng and Bophelong. Sebokeng has a higher level of poverty (85%) than that of Bophelong (67%) while the unemployment rates (27%) is lower than that of Bophelong (31%). Most indicators (level of education, income, expenditure) prove that Bophelong is better off compared to Sebokeng. This dissertation takes further interest in comparing child and grandmother-headed households to “normal” households in Sebokeng. The study found that the main source of income for child-headed households is foster and child support grants (54%) while pension grants serve as the main source of income for both grandmother-headed households and “normal” households (65%).The study therefore proves that child-headed households are worse off financially and otherwise in comparison to grandmother-headed and “normal” households. If more social worker assistance was available to these orphans in the form of assistance with the application for identity documents and birth certificates at the Department of Home Affairs, these orphans would not be as worse-off as was found in this study. The dissertation concludes that the depth of poverty in child-headed households is thus greater than that of grandmother-headed and “normal” households, and it recommends that government should take further steps to reduce the unemployment rate by paying attention to the preferred skills of the population of Poverty and the economics of child and grandmother-headed households in Sebokeng. Sebokeng by offering training to enhance those skills. Food gardening projects should be organised so that the poor can sustain themselves and earn an income in the process. The dissertation also recommends that government should take more interest in improving the lives of these orphans by encouraging them to go to school and in obtaining identity documents. This can be possible through the assistance of social workers as these two elements can open many doors to a better life for these orphans. / Thesis (M.Com. (Economics))--North-West University, Vaal Triangle Campus, 2011

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The individual behaviour of prokaryotic organisms such as bacteria often gives rise to complexity that is commonly associated with multicellular behaviour. The transition from unicellular to multicellular behaviour occurs in response to chemical signals, called autoinducers, which bacteria generate and receive internally within a given population. These autoinducers control the gene expression necessary for the emergence of group-behaviour-phenotype. This phenomenon is called quorum sensing (QS). An example of the quorum sensing control of gene regulation has been the luminescence (lux) operon in Vibrio fischeri. The luxI and ainS quorum signalling systems work in conjunction to regulate luminescence in V. fischeri. LuxI and AinS are acyl-synthases that catalyse the production of the autoinducers C6-HSL and C8-HSL respectively. These autoinducers bind to LuxR, a transcriptional activator of the lux operon, which activates expression of the lux genes causing an increase in luminescence. It was shown that quorum signalling also affects motility and biofilm formation in bacteria. However, the evidence with respect to these phenotypes is conflicting and inconclusive, the reason being the state of quorum is ambiguously defined. It is not properly known whether the observed collective behaviour is purely a result of physical crowding of bacteria, or that both chemical signalling and crowding contribute to this phenomenon. This work attempts to address these issues by studying luminescence, motility, and biofilm, a diverse set of behaviours, yet closely linked to each other in V. fischeri-squid symbiosis. We studied the luminescence response of V. fischeri to both endogenous and externally added signals at per-cell and population level. Experiments with ES114, a wild-type strain of V. fischeri, and ainS mutant showed that (i) luminescence per cell does not mutually correlate with the cell-density, indicating that bacteria do not show greater response to the signal at higher densities; (ii) the activity of the lux signalling circuit shows a strong dependence on the growth stage, (iii) the cells do not show enhanced growth, i.e., they do not derive fitness benefits at higher densities in response to the signal. We anticipated that the culture with a higher cell-density should exhibit greater per-cell-luminescence. However, we found that the luminescence curve of the culture with lower density crosses that of the cultures with higher densities during the exponential phase. Kinetic modelling of the luxI mRNA expression showed that the expression profile qualitatively agrees with the luminescence trend observed in the cultures, supporting the observation that growth-phase plays a major role in regulating the luminescence gene expression. We also studied the effect of autoinducers on motility of V. fischeri. V. fischeri uses flagella to move into the inner crypts of the light organ of the squid. The bacterium secretes autoinducers, encounters secretions of the light organ, and slows down during the final stage of colonization process. Studies have shown that flagellar elaboration is repressed as a consequence of ainS signalling. However, those studies were soft-agar migration assays and carried out with the mutant strain of ainS. We measured real-time planktonic motility of ES114 and the signalling mutant strains of V. fischeri in response to autoinducers added exogenously at different concentrations. We found that the autoinducers do not affect the motility of the strains. We also showed that reduction in motility is purely a consequence of physical crowding of bacteria, and chemical signalling may not be involved in the process. It was shown that reduction in motility leads to biofilm formation. Motile bacteria must lose flagella in order to form biofilm, and signalling controls biofilm formation in many species. Our study on motility showed that reduction in motility occurs because of physical crowding in V. fischeri. Hence, we explored the possibility that physical crowding might lead to formation of biofilm rather than signalling in this species. We quantified exopolysaccharide production by crystal violet assay, which revealed that planktonic cells produce exopolysaccharides, in addition to biofilm cells. The study revealed that V. fischeri cells always produce exopolysaccharides irrespective of their physiological state. We examined the effect of signalling on biofilm in ES114 and the mutant strains using gene-expression analysis. We quantified the expression of various genes involved in biofilm formation and found that both ES114 and the mutants expressed rscS and sypP indicating that exopolysaccharide production is not under the control of autoinducers. Therefore, we hypothesized that biofilm formation in V. fischeri may be a result of physical agglomeration of cells. Our observations indicate that the state of quorum is inadequately defined and there is no direct measure of the underlying process. Multicellular behaviour in V. fischeri is regulated by a complex interplay of cell-density, signalling, and other factors such as the growth phase of the culture, indicating that the state of quorum employs different mechanisms to regulate various phenotypes. Our study reveals that QS is an intricate process, and the accepted mechanisms for QS are incomplete at best.

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Thesis (M.Com. (Economics))--North-West University, Vaal Triangle Campus, 2005.

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