The effects of chlormequat chloride and ethephon on selected small grain cereals in South Africa.

Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.Lodging poses a serious limitation to successful economic production of small grain cereals and can lead to extensive yield and quality losses. Plant growth regulators (PGR's) that reduce plant height and lodging have been employed in management systems in Europe and the United States, however, these compounds have not been evaluated on commercial cultivars of wheat, barley and oats in South Africa. Current recommendations to reduce lodging include limiting N inputs, seeding rates and critical irrigations, all of which may also limit yield potential and grain quality. The objectives of this study were to assess the effects of two common stem-elongation-inhibiting PGR's (chlormequat chloride and ethephon) on the growth, development, and agronomic characteristics of wheat, barley and oats. The aim of the study was to introduce an additional component of intensive cereal management in the form of PGR's, and to allow producers to implement intensive production practices without incurring losses due to lodging. Field trials were conducted with each of the three cereal crops in the 2003 and 2004 seasons at Vaalharts and Bethlehem. The PGR's were applied separately and in combination with each other to lodging-tolerant and -susceptible cultivars (wheat and oats) at different stages of development (tillering, elongation, flag leaf stage). The PGR's were also tested in combination with different levels of N (barley) applied at the haulm elongation stage, the flag leaf stage, or both. The PGR chlormequat produced negligible effects on plant height, lodging, yield, or quality components in all of the tested cultivars . Ethephon and the PGR combination successfully reduced plant height (by 120 to 150mm) and lodging (by 25 to 94%) when applied to the lodging susceptible cultivars of wheat and oats at the flag leaf stage or as a split application to the barley cultivar "Puma" (plant height and lodging reduced by 180 to 230mm and 83 to 92% respectively). Effects on grain yield were variable, ranging from occasional reductions (by 3 t ha(-1) and improvements (by 1 t ha(-1) with the barley, and no effects with the wheat and oats. Wheat quality parameters such as protein content and hectolitre mass were improved by 2 and 4% respectively. However, the nature of the responses was highly dependent on the times of application with later applications producing the greatest positive effects on quality, yield and lodging reductions. Additionally, ethephon and the PGR combination allowed higher levels of N to be employed without increases in lodging of barley. Generally, ethephon and the PGR combination applied at the flag leaf stage of growth are suitable anti-lodging tools for small grain cereal production and should be employed as an insurance measure against lodging in intensive management systems

Cardiac myosin binding protein C, adrenergic stimulation and cardiac contractility

Myosin binding protein C remained a perplexing although integral component of the sarcomeric thick filament until the discovery that genetic defects in its corresponding gene is a frequent cause of hypertrophic cardiomyopathy. Basic science investigation subsequently revealed that it is one of the most potent regulators of cardiac contractility. Phosphorylation of its N-terminus upon adrenergic stimulation, causes increased order in myosin heads as well as increased ATPase activity, Fmax and Ca2+-sensitivity of contraction, while its dephosphorylation upon cholinergic stimulation or during low flow ischaemia leads to changes in the sarcomeric thick filament that diminish interaction between myosin heads and actin. This dynamic flux in phosphorylation upon adrenergic stimulation is not only crucial to normal cardiac function and structure, but also vital for protection against ischaemic injury. Genetically-driven deficiency or inadequacy in cMyBPC leads to severe cardiac dysfunction and structural changes, including cardiac hypertrophy and dilation, and particularly attenuates the adaptive increase in left ventricular contractility that follows on β-adrenergic stimulation or pressure overload, resulting in decreased systolic function, and reduced cardiac output

Myomegalin is a novel A-kinase anchoring protein involved in the phosphorylation of cardiac myosin binding protein C

<p>Abstract</p> <p>Background</p> <p>Cardiac contractility is regulated by dynamic phosphorylation of sarcomeric proteins by kinases such as cAMP-activated protein kinase A (PKA). Efficient phosphorylation requires that PKA be anchored close to its targets by A-kinase anchoring proteins (AKAPs). Cardiac Myosin Binding Protein-C (cMyBPC) and cardiac troponin I (cTNI) are hypertrophic cardiomyopathy (HCM)-causing sarcomeric proteins which regulate contractility in response to PKA phosphorylation.</p> <p>Results</p> <p>During a yeast 2-hybrid (Y2H) library screen using a trisphosphorylation mimic of the C1-C2 region of cMyBPC, we identified isoform 4 of myomegalin (MMGL) as an interactor of this N-terminal cMyBPC region. As MMGL has previously been shown to interact with phosphodiesterase 4D, we speculated that it may be a PKA-anchoring protein (AKAP).</p> <p>To investigate this possibility, we assessed the ability of MMGL isoform 4 to interact with PKA regulatory subunits R1A and R2A using Y2H-based direct protein-protein interaction assays. Additionally, to further elucidate the function of MMGL, we used it as bait to screen a cardiac cDNA library. Other PKA targets, viz. CARP, COMMD4, ENO1, ENO3 and cTNI were identified as putative interactors, with cTNI being the most frequent interactor.</p> <p>We further assessed and confirmed these interactions by fluorescent 3D-co-localization in differentiated H9C2 cells as well as by <it>in vivo </it>co-immunoprecipitation. We also showed that quantitatively more interaction occurs between MMGL and cTNI under β-adrenergic stress. Moreover, siRNA-mediated knockdown of MMGL leads to reduction of cMyBPC levels under conditions of adrenergic stress, indicating that MMGL-assisted phosphorylation is requisite for protection of cMyBPC against proteolytic cleavage.</p> <p>Conclusions</p> <p>This study ascribes a novel function to MMGL isoform 4: it meets all criteria for classification as an AKAP, and we show that is involved in the phosphorylation of cMyBPC as well as cTNI, hence MMGL is an important regulator of cardiac contractility. This has further implications for understanding the patho-aetiology of HCM-causing mutations in the genes encoding cMyBPC and cTNI, and raises the question of whether MMGL might itself be considered a candidate HCM-causing or modifying factor.</p

Growth and yield responses of commercial sugarcane cultivars to mulching in the coastal rainfed region of South Africa

The perceived negative cultivar responses to mulching has limited the adoption of this practice in the South African sugarcane industry. This study was aimed at evaluating cane yield and quality responses and population dynamics of popular cultivars to mulching in the rainfed region of South Africa. A four-replicate field trial was established using a strip-plot design. Cane and tonnes estimated recoverable crystal yields (TERC) yields, and yield components were determined in three summer ratoons and one winter ratoon. In-season soil water and temperature were monitored. Mulching significantly improved cane and TERC of all cultivars across ratoons. The highest improvements in cane and TERC were 85% (N45) and 92% (N39), respectively. The improvements were attributed to the higher soil water content under the mulch blanket. Stalk height, mass and population (winter ratoon) were improved at harvest for most cultivars across ratoons with mulching. Mulching reduced emergence and tillering presumably due to lower soil temperatures under the mulch blanket. The highest mulch-yielding cultivars were N47 and N42, for which yield increased by 15 and 13 t ha−1, respectively. Mulching was beneficial for sugarcane production, regardless of the cultivar and ratooning season, and can be recommended for all current cultivars in the coastal rainfed region.http://www.tandfonline.com/loi/tjps202018-02-27hb2016Plant Production and Soil Scienc

Investigation of the N-terminal interactions of cardiac myosin-binding protein C (cMyBPC) under defined phosphorylation states

PhDThe overall objective of this thesis is to provide additional data to assist clinicians and experimental neurologists alike in the quest for better understanding, more accurately diagnosing and more successfully treating patients suffering from Parkinson’s disease (PD). The general theme of the thesis is the interaction between certain environmental stimuli, including the exposure to adverse events during early central nervous system (CNS) development and the manifestation of elements of neurodegeneration, whether by means of neurochemical changes or expressed as a dysfunctional voluntary motor system. The first chapter provides a general introduction to the research theme of the thesis. This includes, in particular, a discussion on current understanding concerning the etiology and clinical profile of PD, the relative contribution made by genetic factors compared to environmental ones, and current treatment strategies for treating the disease. Mention is also made of the failure of these therapeutic applications for reversing or protecting against the disease, due to the side-effects associated with them. The material covered in chapter 1 provides the basis for the more complete discussion concerning these various aspects, contained in the chapters to follow. The overall aim was also to characterise the effects of commonly used toxin-induced animal models of PD, and the extent of vulnerability that the CNS displays towards them. The destruction of dopaminergic neurons following the administration of 6-OHDA at targeted points along the nigrostriatal tract is used extensively to model PD pathology in rats and is an established animal model of the disease. However, mature or even aged animals are mainly used in these studies, while the effects that the toxin might have on the developing CNS remain unclear. The study reported in chapter 4 aimed to elucidate some of 6-OHDA’s actions on the young adolescent (35 days-old) CNS by comparing the motor and biochemical effects of a unilateral infusion of the toxin into two anatomically distinct basal ganglia loci: The medial forebrain bundle (MFB) and the striatum. Animals were randomly assigned to receive either a direct delivery of 6-OHDA (12μg/4μl) into the MFB or an indirect injection, into the striatum. Although both lesion types were used, the MFB model is considered a more accurate portrayal of end-stage PD, while the striatum-model better reflects the long-term progressive pathology of the disease. The different lesions’ effects on motor function were determined by observing animal’s asymmetrical forelimb use to correct for weigh shifting during the vertical exploration of a cylindrical enclosure. Following the final behavioral assessment, the concentration of dopamine (DA) and DA metabolites remaining in the post-mortem brains were determined using 4 HPLC electrochemistry (HPLC-EC) and the levels compared between the two groups. The HPLC-EC results revealed a compensatory effect for DA production and DA turnover on the lesioned hemisphere side of the toxin-infused animal group. Thus, following 6-OHDA treatment, there appears to be extensive adaptive mechanisms in place within the remaining dopaminergic terminals that may be sufficient for maintaining relatively high extracellular and synaptic concentrations of DA. However, since substantial changes in motor-function were observed, it is suggested that the capacity of the remaining dopaminergic neurons to respond to increased functional demands may be limited. In addition, the behavioral results indicate that the distinct indices relating to different functional deficits depend on the lesioning of anatomically distinct structures along the nigrostrial tract. It has long been known that far fewer women are diagnosed with PD than men are. This seeming protection offered to females against degenerative disease of the CNS may relate to estrogen, although the hormone’s mechanism of action on the dopaminergic system is poorly defined. With an estimated 10-15 million women using oral contraceptives (OCs) in the United States alone, the aim of chapter 2 was to examine the evidence for a possible relationship between PD and the female reproductive hormone estrogen. A review of the current literature available on the topic was performed by consulting Medline, and by performing a search of the case-reports contained within the World Health Organization’s (WHO) International Drug Monitoring database, for possible PD-related symptoms that may arise from estrogen replacement therapy (ERT). The results, whilst conflicting, seem to suggest that estrogen protects women from obtaining the disease, or at least some features of it. Intensive research efforts are called for, with sufficient power to establish the relationship between ERT and the onset and development of parkinsonism. Chapter 3 reports on the results obtained from an experiment that subjected young Sprague-Dawley rats, 35 days of age, to a lower and a higher dose of 6-OHDA delivered to the MFB. Control rats received equivalent saline infusions. At 14 days post-surgery, the rats were evaluated for forelimb akinesia. For the higher dose of 6- OHDA the female rats were less impaired than males in making adjustment steps in response to a weight shift and in the vibrissae-evoked forelimb placing test. In addition, Tyrosine hydroxylase (TH) immunoreactivity was significantly higher for the female rats. Early gender differences in cell survival factors and/or other promoters of neuroplasticity may have contributed to the beneficial outcome seen in the females. For example, nerve growth factor (NGF) was found to be higher in the female rats following administration of the DA neurotoxin. It is unclear whether gonadal steroids are involved, and, if so, whether female hormones are protective or whether male hormones are prodegenerative. Determining the mechanisms for the improved outcome seen in the young female rats may lead to potential treatment strategies against PD. 5 Many studies have shown that early life stress may lead to impaired brain development, and may be a risk factor for developing psychiatric diseases, including clinical depression. However, few studies have investigated the impact that early stress may have on the onset and development of neurodegenerative disorders such as PD. The study reported on in chapter 5 conjointly subjected rat pups to a maternal separation (MS) paradigm that is a well characterised model of adverse early life events, and a unilateral, intrastriatal injection of 6- OHDA. The combined effects of these models on motor deficits and brain protein levels were investigated. Specifically, the animals were assessed for behavioral changes at 28 days postlesion with a battery of tests that are sensitive to the degree of DA loss sustained. The results show that animals that had been subjected to MS display poorer performance in the vibrissae and single-limb akinesia test compared to non-MS control animals (that had also been subjected to the toxin exposure). In addition, there was a significant increase in the loss of TH staining in MS rats compared to non-MS ones. The results from this study therefore suggest that exposure to adverse experiences during the early stages of life may contribute towards making dopaminergic neurons more susceptible to subsequent insults to the CNS occurring during mature stages of life. Therefore, taken together, early exposure to stress may predispose an individual towards the onset and development of neurodegenerative disease, which especially becomes a threat during the later stages of adult life. Moreover, within the framework of these characteristics, the capacity of a widely-used pharmacological agent (statins) was tested for possible future therapeutic application in PD (chapter 7). Although the precise cause of sporadic PD remains an enigma, evidence suggests that it may associate with defective activity of complex I of the mitochondrial electron transport chain. Mitochondrial DNA transmit and express this defect in host cells, resulting in increased oxygen free radical production, depressed antioxidant enzyme activities, and greater susceptibility to apoptotic cell death. Simvastatin is a member of the 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) group of drugs that are widely used for lowering cholesterol levels in patients who display elevated concentrations of low-density lipoprotein cholesterol. The study aimed to investigate the effects that statin-treatment have on motor-function and at the mitochondrial-protein level, using rotenone, a mitochondrial complex I inhibitor, as a rat-model of PD. Adult male Sprague-Dawley rats were treated either with simvastatin (6mg/day for 14 days) or with a placebo. Two different tests to assess motor function were used: The apomorphine-rotation test, and the vibrissae-elicited forelimb placement test. Following the drug administration protocol, the nigrostriatal tract was unilaterally lesioned with either rotenone (3 μg/4 μl) or, for the controls, were sham-operated by infusing the vehicle (DMSO:PEG) only. Five days later the rats were killed and a highly purified concentration of isolated mitochondria was prepared from the substantia nigra (SN) sections. 2- 6 Dimensional electrophoresis (2-DE) with subsequent identification of the spots using electronspray ionization quadruple time-of-flight mass spectrometrical (ESI-Q-TOF MS) was performed and the results BLAST-searched using bio-informatics tools for naming the identified peptides. The motor test results indicate that while unilateral rotenone causes behavioral asymmetries, treatment with simvastatin improved motor function relative to the rotenoneinduced ones. Mass Spectroscopy identified 23 mitochondrial proteins that differ significantly in protein expression (p < 0.05) following simvastatin treatment. The altered proteins were broadly classified according to their cellular function into 6 categories, with the majority involved in energy metabolism. This study effectively illustrated how neuroproteomics, with its sophisticated techniques and non-biased ability to quantify proteins, provides a methodology with which to study the changes in neurons associated with neurodegeneration. As an emerging tool for establishing disease-associated protein profiles, it also generates a greater understanding as to how these proteins interact and undergo post-translational modifications. Furthermore, due to the advances made in bioInformatics, insight is created concerning their functional characteristics. Chapter 4 summarises the most prominent proteomics techniques and discuss major advances made in the fast-growing field of neuroproteomics in PD. Ultimately, it is hoped that the application of this technology will lead towards a presymptomatic diagnosis of PD, and the identification of risk factors and new therapeutic targets at which pharmacological intervention can be aimed. The final chapter (chapter 8) provides a retrospective look at the academic work that had been performed for the purpose of this thesis, recaps on the main findings, and also highlights certain aspects of the project and provides relevant suggestions for future research. Lastly, the appendix provides a detailed overview of the methods followed for the experiments described in this thesis. It provides not only a comprehensive description of the techniques that had been followed, but provides information concerning the care taken with the animals (i.e. post-surgery) in order to control for the potential influence of experimental variables on the results

Integrating Complementary and Alternative Medicines into Pharmacy Practice: Identifying challenges in meeting professional responsibilities and training needs

Magister Pharmaceuticae - MpharmCommunity pharmacies are popular suppliers of complementary and alternative medicines (CAMs) and pharmacists encounter requests from consumers for information on them. The purpose of this study was to assess the extent to which community pharmacists, and final year pharmacy students at the University of the Western Cape, can meet their professional obligations to advise on CAMs