published_or_final_version / Biochemistry / Master / Master of Philosophy

Τα επίπεδα φωσφόρου αλλάζουν με την ηλικία. Ο αυξητικός παράγοντας των ινοβλαστών 23 (FGF23) είναι μία φωσφατουρική ορμόνη που παίζει σημαντικό ρόλο στην ομοιόσταση φωσφόρου. Η πρωτεΐνη Klotho είναι ο συμπαράγοντας του FGF23 που μεσολαβεί τη σύνδεση του FGF23 στον υποδοχέα του. Στη βιβλιογραφία για τα υγιή παιδιά υπάρχουν λίγα δεδομένα για τον FGF23 και ακόμη λιγότερα για το Klotho. Σκοπός μελέτης: Nα διερευνήσουμε την ύπαρξη πιθανής συσχέτισης μεταξύ των κυκλοφορούντων επιπέδων FGF23 και Klotho με την ηλικία και το ρυθμό μέγιστης σωληναριακής επαναρρόφησης φωσφόρου (TmP/GFR) και να μελετήσουμε τις παραμέτρους που τυχόν επηρεάζουν τα επίπεδα FGF23 και Klotho. Μέθοδοι: Σε 159 υγιή παιδιά (82 αγόρια) με μέση ± SD ηλικία 8.78 ± 3.47 έτη μετρήθηκε ο FGF23 (τόσο ο iFGF23 όσο και ο cFGF23) και το κυκλοφορούν Klotho (sKlotho) με τεχνικές ELISA. Υπολογίσαμε επίσης τα επίπεδα του TmP/GFR. Αποτελέσματα: Η μέση τιμή ± SD του cFGF23 ήταν 51.14 ± 12.79 RU/ml ενώ η διάμεσος (εύρος) του iFGF23 και του Klotho ήταν 35 (8.8, 120) pg/ml and 1945 (372, 5866) pg/ml αντιστοίχως. Ούτε ο FGF23 αλλά ούτε και το Klotho δε σχετίζονταν με την ηλικία. Τα παιδιά που είχαν μπει στην εφηβεία είχαν υψηλότερα επίπεδα Klotho (p < 0.05). Τα κορίτσια είχαν υψηλότερα επίπεδα cFGF23 (p < 0.05) και Klotho (p < 0.001). Τα επίπεδα του κυκλοφορούντος φωσφόρου και TmP/GFR ήταν θετικώς συσχετιζόμενα με τον cFGF23 (p < 0.01 και p < 0.001), iFGF23 (p < 0.05 και p < 0.001) και Klotho (p < 0.05 και p < 0.01). Το Klotho ήταν θετικώς συσχετιζόμενο με τον IGF-I (p < 0.0001) και 1,25 (OH)2 βιταμίνη D (p < 0.05). Συμπεράσματα: Στην παρούσα μελέτη παρουσιάζουμε δεδομένα για τα επίπεδα cFGF23, iFGF23, και Klotho που μετρήθηκαν ταυτόχρονα σε υγιή παιδιά. Η θετική συσχέτιση μεταξύ κυκλοφορούντος φωσφόρου και TmP/GFR με τον FGF23 και το Klotho υποδηλώνει ότι έχουν έναν αντισταθμιστικό ρόλο στην ομοιόσταση φωσφόρου. Η ισχυρή συσχέτιση μεταξύ Klotho και IGF-I μπορεί να σημαίνει ότι το Klotho έχει κάποιο ρόλο στην κατά μήκος ανάπτυξη κατά την παιδική ηλικία μέσω ρύθμισης της ομοιόστασης του φωσφόρου αλλά περισσότερες μελέτες χρειάζονται για να διευκρινιστεί αυτό περαιτέρω. / Phosphate serum levels in children vary with age. Fibroblast Growth Factor 23 (FGF23) is a phosphaturic hormone that plays an important role in phosphate homeostasis. Klotho is the essential co-player of FGF23 that mediates the binding of FGF23 to its receptor. Data for fibroblast growth factor 23 (FGF23) and particularly for Klotho in healthy children are limited. Objective and hypotheses: We aimed to investigate the relationship between FGF23 and Klotho serum levels with age and TmP/GFR and to evaluate parameters that might affect FGF23 and Klotho. Methods: In 159 healthy children (82 boys) with a mean ± SD age of 8.78 ± 3.47 years we measured FGF23 (intact FGF23/ iFGF23 and C-terminal FGF23/ cFGF23) and soluble Klotho (sKlotho) serum levels by ELISA. We also determined the TmP/GFR. Results: Mean ± SD value for cFGF23 was 51.14 ±12.79 RU/ml whereas median (range) values for iFGF23 and Klotho were 35 (8.8, 120) pg/ml and 1945 (372, 5866) pg/ml respectively. Neither FGF23 nor Klotho were significantly associated with age. Pubertal children had higher Klotho (p < 0.05). Girls had higher levels of cFGF23 (p < 0.05) and Klotho (p < 0.001). Serum phosphate and TmP/GFR were positively associated with cFGF23 (p < 0.01 and p < 0.001), iFGF23 (p < 0.05 and p < 0.001) and sKlotho (p < 0.05 and p < 0.01). Klotho was positively correlated with IGF-I (p < 0.0001) and 1,25 (OH)2 vitamin D (p < 0.05). Conclusions: We provide data on FGF23, and Klotho measured simultaneously in healthy children. The positive association of serum phosphate and TmP/GFR with FGF23 and Klotho suggests that they have a counterregulatory effect on phosphate homeostasis. The strong association of Klotho with IGF-I could indicate a role of Klotho in linear growth through regulation of phosphate homeostasis, but further studies are required.

No description available.

The export of nitrogen (N) and phosphorus (P) from agricultural catchments is a major problem worldwide. The export of these nutrients is largely driven by storm events, and the hydrologic response of catchments varies within and between storm events. Antecedent soil moisture and rainfall rates have both been shown to affect the discharge and nutrient export from agricultural catchments, but their relationship to nutrient export is not fully understood. Currently, there are no studies that examine the leaching of both nitrate and phosphate from soil pools under the combined influence of differences in soil moisture and rainfall rates. The objectives of this study were to examine the combined effect of antecedent soil moisture and rainfall rates on the hydrologic response of soil and the export of nitrate and phosphate from the soil. The approach used intact soil monoliths in two experiments to first characterize the hydrologic response of the soil, and secondly to assess how the hydrologic response of the soil affects the leaching of nitrate and phosphate from soil pools. Differences in antecedent soil moisture and rainfall rates influenced both the amount of discharge and the hydrologic flow paths in the soil. As was expected, antecedent soil moisture governed the depth of discharge, with more discharge (runoff ratios= 0.89 to 0.91) produced by wet soil and the least runoff produced by dry soil (runoff ratios= 0.08 to 0.14) although this was not affected by the rainfall rate. Instead, rainfall rates predominantly affected hydrologic flow paths in the soil, with preferential flow at the beginning of the leaching period under high intensity rainfall (especially in wet soil), and predominantly matrix flow occurring under low intensity rainfall. The rainfall intensity did not appear to affect discharge volume. The mass of both nitrate and phosphate exported was higher under low intensity rainfall, ranging from 11.2 to 60.1mg/mU+00B2 and 77 to 4980μg/mU+00B2, respectively and from 0.9 to 34.4mg/mU+00B2 and 18.4 to 732μg/mU+00B2, respectively under high intensity rainfall. Antecedent soil moisture was significantly positively correlated with the depth of discharge produced, which also had a significant positive relationship with the mass of nitrate and phosphate exported (Spearman’s ρ= 0.75 to 0.81, p= <0.001), with greater masses of both nutrients exported from wet soil than dry soil. Soil moisture had contrasting influences on the nitrate concentrations in leachate, where nitrate concentrations and soil moisture were negatively related under low intensity rainfall and positively related under high intensity rainfall. Concentrations of phosphate in leachate were more variable, with no clear relationship to soil moisture, discharge, rainfall rate or soil phosphate pools. Antecedent soil moisture and the rainfall rate have a combined influence on the concentration of nitrate in leachate and an influence on the mass of both nitrate and phosphate exported. Although different hydrologic flow paths (matrix, preferential) were observed under the variable antecedent conditions and rainfall rates, this did not appear to affect nutrient fluxes from soil. This may be related to available nutrient pools and distributions in the soil in the current study. Understanding of the influence of flow types on the export of soil nutrient pools requires further study in a lab and a comparison of the breakthrough of nitrate and phosphate from soil pools with that of a conservative tracer (chloride). Nutrient and tracer breakthrough could then be compared to the hydraulic conductivity of the soil and the progression of the wetting front to fully understand the flow paths occurring and their effect on nutrient leaching.

The silicon complexes in silicon doped calcium phosphate bioceramics have been studied using $^{29}$Si magic angle spinning nuclear magnetic resonance spectroscopy. The replacement of phosphorus by silicon in these materials requires a charge compensation mechanism which is difficult to study by many experimental techniques due to the small amount of silicon added. Producing these materials using an isotopically enriched source of silicon made the use of NMR spectroscopy feasible. Three different materials have been studied: a multiphase material commercially available under the trade name Skelite$^{\rm TM}$ composed of predominantly a silicon stabilized $\alpha$-tricalcium phosphate ($\alpha$-TCP) phase as well as a silicon doped hydroxyapatite (HA) phase, a single phase Si-HA material and a single phase silicon stabilized $\alpha$-TCP material. Slight changes to the material production method were first introduced to accommodate the switch to an isotopically enriched silicon source. Characterization of the enriched materials was carried out using Rietveld refinement of X-ray powder diffraction spectra and X-ray fluorescence spectroscopy to confirm that these materials were similar to the previously studied, non-enriched, materials in terms of the silicon contents, Ca/(P+Si) molar ratios and lattice parameters. NMR Spectroscopy showed that in all three materials, the silicon formed Q$^1$ structures in which two silicate tetrahedra joined together by sharing an oxygen, creating an oxygen vacancy which compensated the substitution of two silicon for phosphorus. This is the first observation of this charge compensation mechanism in Si-HA and may explain the interesting phase evolution previously found in the system studied in this work in which the Si-HA transforms to silicon stabilized $\alpha$-TCP upon sintering. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2007-12-18 14:45:38.721

Acid phosphatases (APases; E.C. 3.1.3.2) catalyze the hydrolysis of phosphate (Pi) from Pi monoesters and anhydrides within the acidic pH range. Induction of intracellular and secreted purple acid phosphatases (PAPs) is a widespread plant response to nutritional Pi-deficiency. The probable function of intracellular APases is to recycle Pi from expendable intracellular organophosphate pools, whereas secreted APases likely scavenge Pi from the organically bound Pi that is prevalent in most soils. Although the catalytic function and regulation of plant PAPs have been described, their physiological function in plants has not been fully established. Recent biochemical and proteomic studies indicated that AtPAP26 is the predominant intracellular (vacuolar) and a major secreted purple APase isozyme upregulated by Pi-starved (-Pi) Arabidopsis thaliana. The in planta function of AtPAP26 was assessed by molecular, biochemical, and phenotypic characterization of a homozygous Salk T-DNA insertion mutant. Loss of AtPAP26 expression resulted in the elimination of AtPAP26 transcripts and 55-kDa immunoreactive AtPAP26 polypeptides, correlated with a 9- and 5-fold decrease in extractable shoot and root APase activity, respectively, as well as a 40% reduction in secreted APase activity of –Pi seedlings. The results corroborate previous findings implying that AtPAP26 is: (i) the principal contributor to Pi starvation inducible APase activity in Arabidopsis, and (ii) controlled post-transcriptionally mainly at the level of protein accumulation. Total shoot free Pi level was about 40% lower in –Pi atpap26 mutants relative to wild-type controls, but unaffected under Pi-sufficient conditions. Moreover, shoot, root, inflorescence, and silique development of the atpap26 mutant was impaired during Pi deprivation, but unaffected under Pi-replete conditions, or during nitrogen or potassium-limited growth, or oxidative stress. The results suggest that the hydrolysis of Pi from organic-phosphate esters by AtPAP26 makes an important contribution to Pi-recycling and scavenging in –Pi Arabidopsis. / Thesis (Master, Biology) -- Queen's University, 2009-09-01 09:46:39.302

Orthopaedic reconstruction often involves the surgical introduction of structural implants that provide for rigid fixation, skeletal stabilization, and bone integration. The high stresses incurred by these implanted devices have historically limited material choices to metallic and select polymeric formulations. While mechanical requirements are achieved, these non-degradable materials do not participate actively in the remodeling of the skeleton and present the possibility of long-term failure or rejection. This is particularly relevant in cervical fusion, an orthopaedic procedure to treat damaged, degenerative or diseased intervertebral discs. A significant improvement on the available synthetic bone replacement/regeneration options for implants to treat these conditions in the cervical spine may be achieved with the development of primarily mineral biocomposites comprised of a bioactive ceramic matrix reinforced with a biodegradable polymer. Such a biocomposite may be engineered to possess the clinically required mechanical properties of a particular application, while maintaining the ability to be remodeled completely by the body. A biocomposite of Si-doped calcium phosphate (Si-CaP) and poly(ε-caprolactone) (PCL) was developed for application as such a synthetic bone material for potential use as a fusion device in the cervical spine. In this thesis, a method by which high mineral content Si-CaP/PCL biocomposites with interpenetrating matrices of mineral and polymer phases may be prepared will be demonstrated, in addition to the effects of the various preparation parameters on the biocomposite density, porosity and mechanical properties. This new technique by which dense, primarily ceramic Si-CaP/PCL biocomposites were prepared, allowed for the incorporation of mineral contents ranging between 45-97vol%. Polymer infiltration, accomplished solely by passive capillary uptake over several days, was found to be capable of fully infiltrating the microporosity of the sintered calcium phosphate ceramic. After infiltration, these biocomposite materials demonstrated an increase in compressive strength, flexural strength and Young’s modulus with increasing ceramic content and met design targets for use as a cervical fusion prosthesis. The biocomposite was amenable to shaping and drilling and was found to maintain its strength after 30 days immersion in Earle’s Balanced Salt. / Thesis (Ph.D, Mechanical and Materials Engineering) -- Queen's University, 2009-11-24 16:18:16.461

No description available.

Thesis (M.Tech.: Chiropractic) -Dept. of Chiropractic, Technikon Natal, 2002 1 v. (various pagings) / The purpose of this clinical trial was to evaluate the efficacy of Magnesium phosphate, as an adjunct to dry needling, in the treatment of Myofascial Pain Syndrome (MPS), in terms of objective and subjective clinical findings. MPS is a frequently encountered condition. If not treated adequately, this condition can lead to long term, recurrent pain, as well as patient and physician frustration. Many treatment protocols have been examined with contradictory results and research into epidemiological studies and combinations of various treatment protocols are lacking.

Cadmium (Cd) is a potentially toxic trace element. Two growth chamber studies were conducted to understand how: i) mono-ammonium phosphate affects durum wheat, flax or canola Cd uptake due to fertilizer induced changes in soil solution and plant; ii) preceding canola and barley affect the Cd uptake of subsequent durum wheat or flax. Durum wheat and flax shoot Cd concentrations were greater when grown on previous crop canola soil than when grown on previous crop barley soil regardless of what type of crop residue, if any, was added. The increase in Cd uptake for durum wheat and flax when on canola soil was probably due to increased availability of Cd in soil. Conversely, the application of mono-ammonium phosphate – reagent grade and the incorporation of preceding crop residue did not increase the crop Cd uptake of canola, durum wheat or flax and durum wheat or flax, respectively.