A Dissertation Submitted to the Faculty of SCience University of the Witwatersrand, Johannesburg In fulfilment of the requirements for the Degree of Doctor of Philosophy / Living cells are highly auto-dynamic entities which means that the underlying biochemistry is equally dynamic, a reality which is ignored by most researchers. Theoretical studies indicate that such a state must be due to the existence of oscillatory variations in the levels and activities of key components in the cell. In this study, the dynamic behaviour of four major, interrelated areas of cell biochemistry (phosphorylation, dephosphorylation, the terminal reaction of glycolysis and the amount of soluble protein) were examined and all systems found to oscillate in murine erythroleukaemic cells (MEL) and, where examined, also in the human HL-60 leukaemic cell line. (Abbreviation abstract) / AC 2018

A Dissertation Submitted to the Faculty of Science University of the Witwatersrand, Johannesburg In fulfilment of the requirements for the Degree of Doctor of Philosophy / Living cells are highly auto-dynamic entities which means that the underlying biochemistry is equally dynamic, a reality which is ignored by most researchers. Theoretical studies indicate that such a state must be due to the existence of oscillatory variations in the levels and activities of key components in the cell. In this study, the dynamic behaviour of four major, interrelated areas of cell biochemistry (phosphorylation, dephosphorylation, the terminal reaction of glycolysis and the amount of soluble protein) were examined and all systems found to oscillate in murine erythroleukaemic cells (MEL) and, where examined, also in the human HL-6Q leukaemic cell line. certain processes have been shown to be oscillatory for the first time ( phosphorylation potential, the lactate dehydrogenase active isozyme level and aspects of the regulation thereof). While others have been shown to occur at a higher frequency than previously reported (phosphotyrosine phosphatase activity, the activity and apparent isozyme pattern of lactate dehydrogenase, the amount of extractable protein). All rhythms are shown (for the first time) to be complex and to involve several contributing periodicities, some modulating the period and amplitude of the observed oscillation. The frequencies are very high (periods of 1-20 minutes and probably Less) and the amplitudes are equally high (variations in magnitude of as much as a hundred fold). Phosphorylation processes, currently of particular interest with regard to the nature and control of cell proliferation are thus found to be more highly dynamic than previously believed, a fact which throws some doubt on the current ideas on cell proliferation. The actual lactate dehydrogenase (LDH) active isozyme pattern is shown not to be constant (as generally believed) but to vary at high frequency (possibly due to phosphorylation of the the enzyme) while the kinetics and specificity of the lone isozyme in murine erythroleukaemic cells appear to be varying at equally high frequency due to the action of regulators (perhaps arising elsewhere within the glycolytic pathway). Similar results were obtained with HL-60 leukaemic cells with at least two of the isozymes varying in level, to some extent independently. The hormone, insulin, and the inducer of cell differentiation, HMBA (hexamethylenebisacetamide), have been found to affect the dynamics of the four systems although, because of the complexity of the rhythms the actual effects on the dynamics are not easily defined. Insulin has a marked effect on the mean level of the activity of the LDH isozyme. The fact that all oscillations are seen despite no attempt being made to synchronise the cell population suggests the existence of communication between cells but how this can occur when the rhythms are of such high frequency is intriguing. All the results add further support for the long standing view of my supervisor, that the properties and behaviour of cells reflect the internal dynamics and that differentiation, cancer and intracellular signalling occur through changes in the pattern of temporal organisation of cellular oscillations. / AC2018

A Dissertation Submitted to the Faculty of Science University of the Witwatersrand, Johannesburg In fulfilment of the requirements for the Degree of Doctor of Philosophy Johannesburg 1994 / Living cells are highly auto-dynamic entities which means that the underlying biochemistry is equally dynamic, a reality which is ignored by most researchers. Theoretical studies indicate that such a state must be due to the existence of oscillatory variations in the levels and activities of key components in the cell. In this study, the dynamic behaviour of four major, interrelated areas of cell biochemistry (phosphorylation, dephosphorylation, the terminal reaction of glycolysis and the amount of soluble protein) were examined and all systems found to oscillate in murine erythroleukaemic cells (MEL) and, where examined, also in the human HL-6Q leukaemic cell line. [Abbreviated Abstract. Open document to view full version] / MT2017

No description available.

No description available.

A single field experiment was conducted in 1998 at Marana, AZ to evaluate a scheduled (based upon stage of growth) versus a feedback approach (based upon growth parameters and crop conditions) to nitrogen (N) and mepiquat chloride (PixTM) applications on upland cotton (Gossypium hirsutum L.). The parameters used in evaluating feedback applications for both N and Pix included fruit retention (FR) levels and height to node ratios (HNRs) with respect to established baselines for cotton grown in the desert Southwest. Scheduled and feedback Pix applications were made for a total of 1.5 and 2.5 pint Pix/acre, respectively, with the feedback treatments receiving a late season application at approximately 3100 heat units after planting (HUAP 86/550 F threshold). Scheduled Pix treatments received a single 1.5 pint Pix/acre application prior to peak bloom (approximately 2000 HUAP). Scheduled applications of fertilizer N totaled 205 lbs. N/acre from three applications. Feedback applications of N received a total of 100 lbs. N/acre from two applications. Treatments consisted of all combinations of feedback and scheduled applications of both N and Pix. The highest lint yields occurred in the treatment consisting of Pix feedback and N feedback (treatment two), however, there were no significant differences (P≥0.05) among any of the treatments with respect to yield.

A series of boll measurements were taken at numerous locations in cotton producing areas across Arizona in 1998 in an attempt to continue to develop a yield prediction model with a project that began in 1993. Results from 1995 showed the strongest relationship between final open boll counts and yield compared to a number of other measurements. Based on these results, data collection on boll counts began in 1996 and has continued in 1997 and 1998. Boll counts were taken as the number of harvestable bolls meter-1. All boll count measurements were made within one week of harvest. Number of bolls per unit area were then correlated to lint yield and an estimate for the number of bolls per area needed to produce a bale of lint was calculated. Estimates using all three years data combined indicate that approximately 38 bolls meter-1 are needed to produce one bale of lint per acre.

A single field experiment was conducted at Marana, AZ in 1988 and 1999 to evaluate a scheduled (based upon stage of growth) versus a feedback approach (based upon growth parameters and crop conditions) to nitrogen (N) and mepiquat chloride (PixTM) applications on Upland cotton (Gossypium hirsutum L.). The parameters used in the feedback applications for both N and Pix included fruit retention (FR) levels and height to node ratios (HNRs) with respect to established baselines for irrigated cotton grown in the desert Southwest. Treatments consisted of all combinations of feedback and scheduled applications of both N and Pix. In 1998, the highest lint yields occurred in the treatment consisting of Pix feedback and N feedback (treatment two) management. However, there were no significant differences (P≤0.05) among any of the treatments with respect to yield. In 1999, significant light yield increases (P<0.05) were found in the treatments consisting of Pix feedback and N feedback (treatment two), Pix scheduled and N scheduled (treatment three), and Pix scheduled and N scheduled (treatment five) management approaches.

A series of experiments have been conducted from 1988 to 1999 at various locations across the cotton producing regions of Arizona to evaluate mepiquat chloride (MC) applications in terms of plant growth and yield. These experiments were designed to evaluate MC under three application regimes. These regimes included low rate multiple applications, late season applications, and a feedback vs. scheduled management of MC and nitrogen (N) applications. The objective of this summary (including a total of 31 site-years) is to determine which of these three application regimes offer the greatest opportunity for a positive lint yield response to MC. Stability analysis was conducted by regressing the treatment mean lint yield against the environmental mean for each application regime. Results from the stability analyses revealed that the most viable method of application is a feedback approach for both MC and fertilizer N. The most reliable technique associated with plant assessment in a feedback approach was the height to node ratio (HNR) to indicate vegetative tendencies for determining the appropriate rate and timing of MC applications.

Messenger® was applied ar various growth stages of cotton to ascertain effects upon yield and quality. Plant mapping data indicated that treated cotton aborted lowest developing fruits when temperatures caused stress during experiment, untreated cotton did not. Lack of Messenger® after first bloom resulted in lower lint quality. Untreated cotton had highest yields and value/ acre from the Nov. 9 harvest date, although Messenger® applied at both first bloom and three weeks after first bloom had highest yields and value/acre when harvested on October 15.