Thesis (MSc (Physiological Sciences))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Bi-directional communication exists between HPA-axis activation and interleukin-6 (IL-6). However, the relative contribution of centrally versus peripherally secreted IL- 6 remains unclear, especially under psychological stress conditions. We hypothesised that the HPA response to mild psychological stress is dependent on IL- 6, both centrally and peripherally. 120 male Wistar rats were divided into four groups, depending on whether they received an anti-IL-6 antibody (Ab) (2μg/ml/kg body weight) or a placebo (sterile saline) injection and whether or not they were subjected to 1 hour of restraint stress for 1, 2 or 3 days. Rats were euthanized 24 hours after stress exposure. Plasma corticosteroid (GC) levels remained significantly increased 24 hours after a single stress exposure (control placebo (CP) versus stress placebo (SP): p < 0.05). The undetectable plasma IL-6 levels evident across all groups may be explained by the short half-life of IL-6. Plasma IL-1β levels decreased when IL-6 was blocked in unstressed animals (CP versus CAb: p < 0.05), suggesting a role for IL-6 in the maintenance of IL-1β levels under tonic physiological conditions. At tissue level, pituitary gland mass increased significantly at time point 2, independently of stress when blocking IL-6 (CAb: p < 0.05). This suggests that when normal homeostasis is threatened, immediate adaption or at least compensation may occur. It was observed that GR, IL-1β, IL-1βR, IL-6, IL-6R and GABAARα1 showed no response to stress alone in the pituitary. It is therefore more likely that resistance to adaptation exists centrally. IL-1β and IL-1βR (p < 0.05) and GABAARα1 (p < 0.005) expression increased in the CAb group in the pituitary, again suggesting a role for IL-6 under control conditions. In terms of the adrenal, blocking IL-6 resulted in decreased glandular mass at time point 1, independent of stress (CAb and SAb: p < 0.005). The up-regulation in GR expression seen in CAb and SAb (p < 0.05) may be the effect of a compensatory mechanism to increase IL-6 dependent bioactivity of GCs. The fact that expression of IL-6, IL-6R, IL-1β and IL- 1βR consistently increased in the Ab groups, and mostly in the zona fasciculata and zona reticularis, suggests that lack of local direct negative cytokine feedback occurred in response to very low plasma IL-6 levels and that this contributes more than GCs in the down-regulation of inflammatory cytokine release. In conclusion, consistent effects of the Ab were apparent in the tissues investigated, even in control conditions, suggesting that IL-6 plays a role in the maintenance of basal homeostasis, including its regulation of the response to psychological stress. We found differential regulation in terms of cytokines and GCs when comparing peripheral versus central effects of stress and Ab, as well as the levels of cytokines in the blood compartment, compared to within tissues. / AFRIKAANSE OPSOMMING: Daar bestaan twee-rigting kommunikasie tussen HPA-as aktivering en interleukin-6 (IL-6), allhoewel die relatiewe bydrae van sentraal versus perifeer afgeskeide IL-6 nog onduidelik is, veral gedurende sielkundige strestoestande. Ons hipotese is dat die HPA reaksie tot sielkundige stres afhanklik van IL-6 is, beide sentraal en in die periferie. 120 manlike Wistar rotte is in vier groepe verdeel, afhangende van of hulle ‘n anti-IL- 6 teenliggaampie (Ab) (2μg/ml/kg liggaamsgewig) of ‘n plasebo (steriele soutoplossing) inspuiting gekry het, en of hulle onderworpe was aan 1 uur van vaskeer-stres vir 1, 2 of 3 dae. Rotte is 24 uur na blootstelling aan stres aan genadedood onderwerp. Bloed kortikosteroïed (GC) vlakke het beduidend toegeneem binne 24 uur na ‘n eenmalige stres blootstelling (kontrole plasebo (CP) versus stres plasebo (SP): p < 0.05). Die onmeetbaar lae vlakke van IL-6 regoor al die groepe, kan verduidelik word na aanleiding van die kort half-leeftyd van IL-6. Bloed IL-1β vlakke het afgeneem in kontrole rotte wanneer IL-6 geblok is (CP versus CAb: p < 0.05). Dit kan beteken dat IL-6 noodsaaklik is vir die onderhoud van IL-1β vlakke gedurende basale toestande. Op weefselvlak het die hipofise massa toegeneem by tydpunt 2 toe IL-6 geblok is, onafhanklik van stres (CAb: p < 0.05). Dit dui aan dat wanneer normale homeostase bedreig word, daar onmiddelike aanpassing of kompensasie plaasvind. Dit is opvallend dat GR, IL-1β, IL-1βR, IL-6, IL-6R en GABAARα1 geen respons in terme van stres alleen in die hipofise getoon het nie. Na aanleiding daarvan is dit meer waarskynlik dat weerstand tot aanpassing sentraal bestaan. IL-1β and IL-1βR (p <0.05) en GABAARα1 (p < 0.005) uitdrukking in die hipofise het toegeneem in die CAb groep, wat weereens ‘n rol vir IL-6 onder kontrole toestande uitwys. In terme van die bynier, het die blok van IL-6 ‘n afname in massa veroorsaak by tydpunt 1, wat weer onafhanklik van stres was (CAb en SAb: p < 0.005). Die opregulering in die CAb en SAb groepe (p < 0.05), kan wees as gevolg van ‘n kompensasie meganisme om IL-6 afhanklike GC aktiwiteit te verhoog. Die feit dat die uitdrukking van IL-6, IL-6R, IL-1β and IL-1βR in die Ab groepe deurlopend verhoog was, en meeste in die zona fasciculata en zona reticularis, stel voor dat daar ‘n tekort aan plaaslike, direkte sitokien negatiewe terugvoering was, as gevolg van die merkwaardige lae bloed IL-6 vlakke en dat dit meer bydra as GCs in die afregulering van inflammatoriese sitokien vrystelling.

Thesis (MScAgric (Animal Sciences))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: The production and especially the export of game meat from Southern African are steadily increasing and with this growth, it is inevitable that more emphasis is being placed on the quality of game meat. Research regarding the effect of different cropping methods on ante-mortem stress, and as a result, on meat quality in wild ungulates, is lacking and thus the purpose of this study was to investigate the effect of some of the commonly used cropping methods on the meat quality of red hartebeest, impala, gemsbok and kudu. Antemortem stress was measured using serum cortisol levels (nmol/L), a subjective stress score allocated to each animal as well as the rate and extent of pH decline in the M. longissimus dorsi. Special emphasis was also placed on the meat quality parameters drip loss, cooking loss, colour and Warner-Bratzler shear force (kg/1.27 cm diameter). The effect of day and night cropping on the meat quality of red hartebeest, gemsbok and kudu was investigated. An exponential decay model, y = a + b-ct, was fitted to the pH data of the gemsbok and red hartebeest, and pHu measurements taken at 24 hours post-mortem. Only pHu readings taken at 48 hours post-mortem were analysed in the kudu. Day-cropped kudu had a lower mean pHu (5.40 ± 0.030) than nightcropped kudu (5.48 ± 0.041). No differences in pHu were found for the red hartebeest although night-cropped gemsbok had a higher mean pHu (5.54 ± 0.013) than day-cropped gemsbok (5.49 ± 0.014). None of the constants of the exponential decay model differed for the red hartebeest although day-cropped gemsbok produced a lower constant than night-cropped gemsbok. Mean stress scores and cortisol levels were found to be higher in day-cropped animals for both the gemsbok and kudu while only cortisol levels were higher in die day-cropped red hartebeest. Stress score and cortisol levels were found to be correlated in all three species (red hartebeest: r = 0.51; gemsbok: r = 0.786; kudu: r = 0.823). No treatment differences in drip loss or cooking loss were found for either the red hartebeest or gemsbok, while day-cropped kudu had a higher mean drip loss % (2.76 ± 0.261%) than night-cropped kudu (1.36 ± 0.361%). Night-cropped gemsbok and kudu produced higher mean shear force values (gemsbok = 4.19 ± 0.138; kudu = 4.06 ± 0.237 kg/1.27 cm diameter) than day-cropped animals (gemsbok = 3.57 ± 0.154; kudu = 3.45 ± 0.171 kg/1.27 cm diameter). Colour differences indicated that day-cropped gemsbok and kudu produced lighter meat than night-cropped animals. The results indicate no difference in the effects of day and night cropping in red hartebeest although day-cropped gemsbok and kudu experienced more ante-mortem stress than their night-cropped counterparts. The effect of conventional hunting during the day and night cropping on impala meat was also investigated. No differences were found in pH45 or pHu (taken at 45 minutes and 24 hours post-mortem respectively) although the exponential decay model, y = a + b-ct, fitted to the pH data revealed differences in all the constants (day: a = 5.424 ± 0.039, b = 1.405 ± 0.034, c = -0.385 ± 0.022; night: a = 5.295 ± 0.033, b = 1.556 ± 0.029, c = -0.184 ± 0.019). No differences were found for drip loss, cooking loss or shear force although day-cropped animals produced higher a* and chroma values. The results indicate that, although conventional hunting caused a faster and more severe post-mortem pH decline, both treatments produced meat of similar quality. / AFRIKAANSE OPSOMMING: Die produksie en veral die uitvoer van wildsvleis vanuit Suidelike Afrika is gedurig aan die toeneem en met hierdie groei is dit onvermydelik dat meer klem op die gehalte van wildsvleis gelê word. Daar is ’n tekort aan navorsing oor die uitwerking van verskillende oesmetodes op ante mortem stres en gevolglik ook vleisgehalte van verskillende wildspesies en dus was die doel van dié studie om die uitwerking van sommige van die gewildste oesmetodes op die vleisgehalte van rooihartebees, gemsbok, koedoe en rooibok te ondersoek. Ante mortem stres is gemeet deur die gebruik van serum-kortisolvlakke (nmol/L), ʼn subjektiewe strestelling wat aan elke dier gegee is asook die tempo en vlak van pH-daling in die M. longissimus dorsi. Spesiale klem is gelê op die vleisgehalteparameters drupverlies, kookverlies, kleur en Warner-Bratzlerskeurwaarde (kg/1.27 cm deursnee). Die uitwerking van dag- en nag-oes op die vleisgehalte van rooihartebees, gemsbok en koedoe is ondersoek. ’n Eksponensiële vervalkurwe, y = a + b-ct, is aan die pH-data van die gemsbokke en rooihartebeeste gepas en pHu-metings is op 24 uur ná dood geneem. Net pHu-lesings op 48 uur ná dood in die koedoe is geanaliseer. Koedoes wat in die dag geoes is, het ’n laer pHu (5.40 ± 0.030) gehad as koedoes wat in die nag geoes is (5.48 ± 0.041). Daar was geen verskille in pHu vir die rooihartebeeste nie, alhoewel die gemsbokke wat in die nag geoes is, ’n hoër pHu (5.54 ± 0.013) gehad het as gemsbokke wat in die dag geoes is (5.49 ± 0.014) . Geeneen van die konstantes van die eksponensiële vervalkurwe het verskil in die geval van rooihartebeeste nie terwyl gemsbokke wat in die dag geoes is ʼn hoër konstante a en ʼn laer konstante c getoon het as gemsbokke wat in die nag geoes is. Gemiddelde strestellings en kortisolvlakke was hoër in die geval van gemsbokke en koedoes wat in die dag geoes is terwyl net die kortisolvlakke hoër was in die rooihartebeeste wat in die dag geoes is. Daar is ook bevind dat die strestelling en kortisolvlakke gekorreleer was in al drie spesies (hartebees: r = 0.51; gemsbok: r = 0.786; koedoe: r = 0.823). Geen verskille in drupverlies of kookverlies is aangetref vir die rooihartebeeste of gemsbokke nie, alhoewel koedoes wat in die dag geoes is ʼn hoër gemiddelde drupverlies % (2.76 ± 0.261%) getoon het in vergelyking met koedoes wat in die nag geoes is (1.36 ± 0.361%). Gemsbokke en koedoes wat in die nag geoes is, het ’n hoër gemiddelde skeurwaarde gehad (gemsbokke = 4.19 ± 0.138; koedoes = 4.06 ± 0.237 kg/1.27 cm deursnee) as diere wat in die dag geoes is (gemsbokke = 3.57 ± 0.154; koedoes = 3.45 ± 0.171 kg/1.27 cm deursnee). Kleurverskille het aangedui dat gemsbokke en koedoes wat in die dag geoes is, ligter gekleurde vleis geproduseer het as diere wat in die nag geoes is. Die resultate dui aan dat daar by rooihartebeeste geen verskil is tussen die uitwerking van dag-oes en nag-oes nie, maar dat die dag-oes van gemsbokke en koedoes meer voordoodse stres veroorsaak het as nag-oes. Die uitwerking van konvensionele jag gedurende die dag- en nag-oes op die vleisgehalte van rooibokke is ook ondersoek. Geen verskille is aangetref in pH45 of pHu (geneem op 45 minute en 24 uur ná dood onderskeidelik) nie, alhoewel die eksponensiële vervalkurwe, y = a + b-ct, wat gepas is aan die pH-data verskille getoon het in al die konstantes (dag: a = 5.424 ± 0.039, b = 1.405 ± 0.034, c = -0.385 ± 0.022; nag: a = 5.295 ± 0.033, b = 1.556 ± 0.029, c = -0.184 ± 0.019). Geen verskille is aangetref ten opsigte van drupverlies, kookverlies of skeurkrag nie. Diere volgens die konvensionele maniere geoes het wel hoër a*-en chroma-waardes getoon. Die resultate dui daarop dat, alhoewel konvensionele jag ʼn vinniger en meer ekstreme pH-daling veroorsaak het, albei behandelinge tot dieselfde vleisgehalte gelei het.

Thesis (PhD (Biomedical Sciences. Medical Physiology))--University of Stellenbosch, 2006. / Early life trauma leads to behavioural abnormalities later in life. These include mood and anxiety disorders such as depression and posttraumatic stress disorder (PTSD). This association may be due in part to the effects of trauma on brain development. Data from basic and clinical experiments suggest that alterations in the hippocampus may be fundamental to the development of these disorders. Here we used an animal model of early life trauma to investigate its effects on the behaviour and neurochemistry of the adult rat. Adolescent rats were subjected to time-dependent sensitization stress consisting of a triple stressor (2 hours restraint, 20 min swim stress and exposure to ether vapour) on post-natal day (PND) 28, a single re-stress on PND 35 (20 min swim stress), and a second re-stress in adulthood (PND 60, 20 min swim stress). The rationale was that the frequency of exposure to situational reminders contributes to the maintenance over time of fear-related behavioural disturbances. The effects of trauma on the hypothalamus-pituitary-adrenal-axis, hippocampal and plasma neurotrophin levels, behaviour and phosphoinositide-3 kinase (PI-3 kinase) signaling proteins were initially investigated. In addition, proteomic technologies such as protein arrays and 2D-SDS PAGE combined with liquid chromatography tandem mass spectrometry (LC-MS/MS) were employed to study trauma-induced effects on the hippocampus. Traumatized animals showed a decrease in glucocorticoid receptors in the dentate gyrus of the hippocampus and an increase in basal corticosterone levels 24 hours after adulthood re-stress. These effects were reversed by pretreatment with the serotonin selective reuptake inhibitor, escitalopram. A decrease in the neurotrophins, BDNF and NT-3 were evident 8 days, but not 24 hours after adulthood re-stress. This decrease was not accompanied by decreases in plasma neurotrophin or PI-3 kinase, protein kinase B (PKB), phosphatase and tensin homologue (PTEN), phospho-forkhead and phospho-AFX protein levels. In addition, traumatized animals showed increased rearing in both the elevated plus maze and open field. Proteomic analysis of trauma-induced changes in the hippocampus show increases in Ca2+ homeostasis / signaling proteins such as S-100B, phospho-JNK and calcineurin. Apoptotic initiator proteins, including caspase 9, -10 and -12 were increased and there was evidence of cytoskeletal protein dysregulation. Furthermore, cell cycle regulators and energy metabolism proteins were decreased. These effects indicate to a cellular state of cell cycle arrest after increased calcium influx to avoid apoptosis. Our data suggest that adolescent trauma with adulthood re-stress may affect numerous systems at different levels. These include neuroendocrine-, protein systems and behaviour, and confirmed that a systems biology approach is needed for a better understanding of the neurobiology of mental disorders.

Thesis (MSc)--University of Stellenbosch, 2007. / ENGLISH ABSTRACT: The tolerance of Enterococcus mundtii ST4SA to stressful gastro-intestinal conditions in humans and animals is vital to its success as a probiotic. The need for new effective probiotics with stronger inhibitory (bacteriocin) activity has arisen due to the increasing number of antibiotic resistant pathogens. Enterococci are used in the fermentation of sausages and olives, cheese making and as probiotics. Their role as opportunistic pathogens in humans makes them a controversial probiotic (Moreno et al., 2005). Enterococci occur naturally in the gastro-intestinal tract which renders them intrinsic acid and bile resistance characteristics. E. mundtii ST4SA produces a 3950 Da broad-spectrum antibacterial peptide active against Gram-positive and Gram-negative bacteria, and viruses. The bacteria include Enterococcus faecalis, Streptococcus spp., Pseudomonas aeruginosa, Klebsiella pneumoniae, Streptococcus pneumoniae and Staphylococcus aureus. E. mundtii ST4SA inactivates the herpes simplex viruses HSV-1 (strain F) and HSV-2 (strain G), a measles virus (strain MV/BRAZIL/001/91, an attenuated strain of MV), and a polio virus (PV3, strain Sabin). This study focuses on the genetic stability of E. mundtii ST4SA genes when exposed to stress factors in the human and animal gastrointestinal tract. Based on results obtained by real-time PCR, the expression of genes encoding bacST4SA, RecA, GroES and 23S rRNA by E. mundtii ST4SA were not affected when the cells were exposed to acid, bile and pancreatic juice. This suggests that these genes of E. mundtii ST4SA will remain stable in the intestine. This could indicate that other genes of E. mundtii ST4SA could remain stable in the host. Further studies on the stability of genes encoding antibiotic resistance and virulence factors should be conducted to determine their stability and expression in the host in stress conditions. Concluded from this study, E. mundtii ST4SA is an excellent probiotic strain. / AFRIKAANSE OPSOMMING: Enterococcus mundtii ST4SA se weerstandsvermoë teen stresvolle gastrointestinale kondisies is essensieel vir die sukses van hierdie organisme as ‘n probiotikum. Die aanvraag vir nuwe, meer effektiewe probiotika met sterker inhibitoriese (bakteriosien) aktiwiteit is as gevolg van die toename in antibiotikum weerstandbiedende patogene. Enterococci word algemeen gebruik as probiotika, sowel as in die fermentasie van worse, olywe en kaas. Hulle rol as oppertunistiese patogene in mense veroorsaak kontroversie as gevolg van hul toenemende gebruik as probiotika. Enterococci is deel van die natuurlike mikroflora in die gastrointestinale weg van mense en diere. Dit verleen aan hierdie spesies ‘n natuurlike weerstandsvermoë teen maagsure, galsoute en pankreatiese afskeidings. E. mundtii ST4SA produseer ‘n 3950 Da wye spektrum anti-bakteriese peptied, aktief teen Gram positiewe en Gram negatiewe bakterieë sowel as virusse. Hierdie bakterieë sluit Enterococcus faecalis, Streptococcus spp., Pseudomonas aeruginosa, Klebsiella pneumoniae, Streptococcus pneumoniae en Staphylococcus aureus in. E. mundtii ST4SA inaktiveer die herpes simpleks virus HSV-1 en HSV-2, ‘n masels virus (MV/BRAZIL/001/91), en ‘n polio virus (PV3, stam Sabin). Hierdie studie fokus op die genetiese stabiliteit van E. mundtii ST4SA gene, wanneer hulle blootgestel word aan stress faktore in die mens en dier gastrointestinale weg. “Intydse” PKR data gebasseer op die uitdrukking van die bacST4SA, RecA, GroES en 23S rRNA gene in stresvolle kondisies dui aan dat E. mundtii ST4SA nie geaffekteer word wanneer die sel blootgestel word aan suur, gal en pankreatiese vloeistowwe nie. Hierdie resultate dui aan dat hierdie gene van E. mundtii ST4SA stabiel sal bly in die intestinale weg van die mens en dier. Dit kan aandui dat ander gene van E. mundtii ST4SA soos die wat kodeer vir virulensie faktore en antibiotikum se weerstandsvermoë stabiel mag bly in die gasheer. Verdere studies wat fokus op die stabiliteit van gene wat kodeer vir antibiotikum weerstandbiedendheid en virulensie faktore moet uitgevoer word om hulle stabiliteit en uitdrukking in die gasheer te bepaal. Bevindings van hierdie studie dui aan dat E. mundtii ST4SA goeie potensiaal het as ‘n probiotikum.

Cowpea (Vigna unguiculata (L.) Walp) is an important protein-rich grain legume of major economic importance. It is widely grown by small-scale farmers in the arid and semi-arid regions of the world where it is cultivated for its leaves, fresh immature pods and dry grains. However, it is also an underutilized grain legume. In sub-Saharan Africa where most of the cowpea is produced, drought stress is one of the major factors limiting its productivity. Despite the inherent capacity to survive drought stress, several cowpea varieties are affected by mid and late season drought. Therefore, varieties with a higher tolerance to drought stress are required to obtain higher and more stable yields. The objectives of this study were: (i) to determine morphological responses of four dual-purpose cowpea landraces to water deficits during vegetative and reproductive stages (ii) to determine physiological responses of four dual-purpose cowpea landraces to water deficits and recovery during the reproductive stage (iii) to determine yield performance of cowpea landraces after recovery from water stress and how this relates to (ii) above. Four cowpea landraces namely; Lebudu, Lehlodi, Sejwaleng and Morathathane collectedfrom Kgohloane and Ga-Mphela villages, Limpopo Province, South Africa were used in the study. Pot experiments were conducted under glasshouse conditions at the Controlled Environment Facility (CEF), University of KwaZulu-Natal. The first pot experiment evaluated the morphological responses of four cowpea landraces to water stress and recovery. The study was conducted as a single factor experiment laid out in randomized complete block design (RCBD). The treatments (four cowpea landraces) were each planted in 40 pots giving a total of 160 experimental units (drained polyethylene pots with a 5 litre capacity). Each plant in each pot was treated as a replicate. Plants were well-watered until the formation of six fully expanded trifoliates, then irrigation was withheld for 28 days to simulate drought stress during the vegetative growth. The imposition of drought stress was terminated by re-watering all plants after 28 days. The cowpea plants were re-watered sufficiently and allowed to grow until the four landraces reached 50% flowering stage. Watering was withheld again at 50% flowering for a two-week period for all the four landraces to simulate drought stress during the reproductive growth. The second experiment was conducted to investigate physiological responses of the four cowpea landraces to water stress during the reproductive stage. The experiment was laid out as a 4 x 2 factorial treatment structure in randomized complete design (CRD) with the following three factors: cowpea landraces – 4 levels (Lebudu, Lehlodi, Sejwaleng and Morathathane), water regimes – 2 levels (stressed and well-watered) treatment combinations each replicated 20 times (20 pots each containing one plant) giving a total of 160 experimental units (drained polyethylene pots with a 5 litre capacity). Data on morphological responses were collected and included: number of green vs. senesced leaves, visual assessment of leaf greenness, stem, branch greenness and survival percentage. Physiological responses to water stress were determined during the reproductive stage and included: leaf water potential, relative water content, stomatal conductance, proline content, chlorophyll content, carotenoid content, chlorophyll a content, phenolics (free and membrane-bound), total antioxidant capacity and chlorophyll fluorescence parameters (Fv/Fm). Genstat 14th edition (VSN International, UK) was used to perform analyses of variance (ANOVA) and differences between means were determined by the Least Significant Differences (LSD) at the 5% probability level. Landraces showed different morphological responses during both vegetative and reproductive growth stages. Lebudu, Lehlodi and Sejwaleng displayed a strong ability to maintain stem greenness longer as compared to Morathathane during vegetative growth. Lebudu delayed leaf senescence more than other landraces; no differences in survival were observed. All landraces survived for 28 days without water and resumed growth after re-watering. During the reproductive stage, Lebudu displayed a strong ability to maintain leaf, branches and stem greenness longer and showed relatively higher tolerance to drought stress compared to other three landraces. Water stress caused a decline in leaf water potential, relative water content, carotenoid content, chlorophyll content, stomatal conductance and increased proline content, phenolics, chlorophyll a content, total antioxidant capacity and while chlorophyll fluorescence parameter, Fv/Fm, was not affected. All landraces maintained higher relative water content above a critical threshold with Sejwaleng maintaining a significantly higher RWC (69%) than Lehlodi, Lebudu and Morathathane. Morathathane developed a more negative leaf water potential at maximum stress than Lebudu, Lehlodi and Sejwaleng. Stomatal closure was observed in all cowpea landraces during water stress, but re-opened after re-watering. Chlorophyll content was considerably reduced in Morathathane as compared to Lebudu, Lehlodi and Sejwaleng. No significant differences were observed between the cowpea landraces with respect to carotenoid content at maximum stress. Chlorophyll a content increased significantly for Morathathane as compared to Lebudu, Lehlodi and Sejwaleng. High accumulation of proline was observed for Lebudu, Lehlodi and Morathathane as compared to Sejwaleng, which showed a very slow accumulation of proline. Lebudu, Lehlodi and Sejwaleng showed an increase in phenolic compounds while a decline was observed for Morathathane. Total antioxidant capacity (TAOC) was high in all cowpea landraces during water stress. Also, all chlorophyll fluorescence parameters showed that cowpea landraces had efficient photo-protection mechanisms during drought stress. After re-watering, relative water content, leaf water potential, stomatal conductance, chlorophyll content, carotenoids, chlorophyll a, proline content and TAOC recovered and reached the same level as that of well-watered plants. All four landraces were re-watered after the imposition of stress and above ground biomass, pod mass and number and seed yield determined. Although there was a reduction in the total above-ground biomass, pod mass and number in all four landraces under water stress compared to the well–watered treatment; this was not statistically significant (P > 0.05). Furthermore, no significant differences (P > 0.05) were observed between the four landraces with respect to seed yield under stressed and well-watered conditions. This study established that cowpea landraces vary with respect to the various morphological and physiological adaptive mechanisms in response to water deficits. Such adaptive mechanisms probably ensure their survival under severe water stress conditions until the next rainfall and therefore allowing them to produce reasonably relatively higher leaf and seed yield. Detailed knowledge of these mechanisms in the landraces could be useful in the genetic enhancement and breeding for drought tolerance in the existing cowpea germplasm. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.

Phenotypic plasticity is the ability of an organism to express different phenotypes in response to biotic or abiotic environmental cues. The ability of an organism to make changes during development to adjust to changes in its environment is a key to survival. Sexually reproducing organisms that have short life cycles and that are easy to raise in the laboratory are more conducive for developmental phenotypic plasticity. Considerable research has already been carried out on the brine shrimp, Artemia franciscana, regarding its morphology due to changing salinities. There is, however, little research considering subsequent generations and how there morphology might be affected by parental experiences. This study has examined: 1) the morphological effects of different rearing regimes of different salinity levels, and 2) the epigenetic transgenerational transfer of these morphological traits in A. franciscana. Measurements included rate of growth (as measured by instar), body size, body length, and other morphological traits. A gradual increase to more hyperosmotic conditions during development produced brine shrimp that were larger in size and also more developmentally advanced. Salinity stress experienced by adults had increased the growth rate in the F1 offspring of A. franciscana. Collectively, these data indicate that Artemia franciscana is a tractable model for investigating phenotypic plasticity. These findings have added to the ever-growing field of developmental phenotypic plasticity while also providing more information on the natural history and adaptive abilities of A. franciscana.

Resource availability follows seasonal cycles in environmental conditions. To align physiology and behavior with prevailing environmental conditions, seasonal animals integrate cues from the environment with their internal state. One of the systems animals use to integrate those cues is the hypothalamus-pituitary-adrenal (HPA) axis and its primary effector, glucocorticoid hormones. The HPA axis has wide-ranging effects on physiology and behavior and, in the context of a glucocorticoid stress response, is known to mediate tradeoffs between immediate survival and future fitness. The HPA axis also plays an important role in facilitating predictable life-history events. Variation in HPA axis activity has been reported in all vertebrates, often coordinating seasonal reproduction and possibly also transitions between life-history stages. My dissertation research used red-sided garter snakes (Thamnophis sirtalis parietalis) to examine the role of the HPA axis in regulating seasonal life-history transitions, especially in females. In Chapter 2, I hypothesized that seasonal plasticity in stress responses is regulated, in part, by changes in the responsiveness of the adrenal glands to adrenocorticotropic hormone (ACTH). I found that glucocorticoid responses to ACTH challenge were smaller in males than in females during the spring, suggesting that reports of reduced stress responsiveness in males may reflect lower adrenal responsiveness to ACTH. The sex difference in mating season duration and consequently also in the timing of migration led me to hypothesize that sex differences in HPA axis activity could explain sex differences in the timing of migration. Furthermore, adrenal responsiveness to ACTH also varied seasonally in males, but not females, suggesting that female stress responses, which have not been studied, may not vary seasonally. In Chapter 3, I investigated potential seasonal variation in female stress responses, which have not previously been examined. In males, baseline glucocorticoids decrease over the course of the mating season resulting in significantly lower baseline levels in males that have begun to migrate. I hypothesized that a change in HPA axis activity occurs during spring and fall migration. Peak stress-induced glucocorticoid concentration occurred at an earlier sampling time in females during the spring compared to the fall. Peak stress-induced glucocorticoid concentrations also occurred at a later sampling time in migrating females than in pre-migratory females during the spring, suggesting that negative feedback regulation of the HPA axis changes as soon as females begin to migrate during the spring. Female red-sided garter snakes are biennial breeders that give birth approximately every other year implying that a female's recent reproductive history can influence whether or not she will reproduce in a given year. Body condition can be used as a proxy for recent reproductive history and can be related to baseline and stress-induced glucocorticoid concentrations. In Chapter 4, I hypothesized that hormonal and behavioral stress responses vary with body condition. Baseline glucocorticoids did not vary with body condition, but females in low body condition showed a significantly larger increase in plasma glucocorticoids in response to capture stress. Body condition, but not capture stress, influenced latency to copulate, suggesting that females are resistant to the behavioral effects of capture stress during the spring mating season. Only females in low body condition increased latency to copulate in response to injection of a physiological (15 µg) dose of exogenous CORT, while all females responded to a pharmacological (60 µg) dose, indicating that behavioral responses to exogenous glucocorticoids vary with female body condition. These data suggest that variation in body condition may be associated with differences in HPA axis sensitivity and/or glucocorticoid receptor (GR) density in the brain. I directly tested if there is a relationship among body condition, reproductive history and HPA axis activity in Chapter 5. I found that glucocorticoid stress responses and mating behavior did not vary with body condition, nor was body condition related to brain GR or reproductive condition (parturient vs post-parturient females). Only unreceptive females showed a significant stress-induced increase in glucocorticoids, suggesting that reduced stress responsiveness is associated with receptivity. Parturient females mated faster (were more proceptive) than post-parturient females. These data suggest that HPA axis activity influences reproductive "decisions" by modulating receptivity, while proceptivity is related primarily to recent reproductive history. Together, these chapters help characterize how HPA axis activity varies with season, sex, reproductive history and migration status. By systematically probing the HPA axis in a single, tractable system, I have gained insight into how changes in the HPA axis support and modulate transitions between life-history stages. These results highlight the HPA axis' important function in mediating the critical trade-offs all animals must navigate to be successful in a changing world.

"April 2001" / Includes bibliographical references (leaves 198-214) / xv, 214, [12] leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Agronomy and Farming Systems, 2005

Bibliography: leaves 158-176. / xxii, 200 leaves : ill. (chiefly col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Yield variation of faba bean in southern Australia is associated with seasonal and site variation in stress levels during podsetting and podfilling. This study examined the development of pods and seed growth in the field; quantified the effects of water stress and temperature on pod and seed development; quantified the importance of stem and podwall dry matter to seed growth and seed yield and examined the importance of genotype to these responses. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Science, 1995

Bibliography: leaves 158-176. Yield variation of faba bean in southern Australia is associated with seasonal and site variation in stress levels during podsetting and podfilling. This study examined the development of pods and seed growth in the field; quantified the effects of water stress and temperature on pod and seed development; quantified the importance of stem and podwall dry matter to seed growth and seed yield and examined the importance of genotype to these responses.