Njur-och avflödesfunktionen kan bedömas genom mätning av upptaget och utsöndringen av ett spårämne (99mTc-MAG3) från vardera njure, kombinerat med intravenös injektion av diuretika. Denna metod benämns diuresrenografi. Hydronefros med, respektive utan, avflödeshinder särskiljs genom injektion av diuretika. Bedömning av upptaget och avflödesfunktionen i njurarna återspeglas av ett renogram, som avspeglar upptag och utsöndring av radiofarmakat i njurarna och urinvägarna efter injektion, en så kallat tid-aktivitetskurva. Bildtagningen behöver vid en bristande tömning av njurarna kompletteras med postmiktion (PM) bilder. Vid Klinisk fysiologi och nuklearmedicin på Skånes Universitetssjukhus har kriterierna för när en sen bild ska tas ändrats till den nuvarande gränsen på ≥ 50% kvarstående aktivitet, som ökat antalet kompletteringar. Syftet med studien är att utvärdera kriterierna för PM-bilder före och efter ändringen av kriterierna på kliniken. Dessutom undersöka möjligheten av att höja den nuvarande gränsen på ≥ 50% kvarstående aktivitet, för bildtagning av PM-bilder vid renografi. En retrospektiv studie av 45 patienter, barn och vuxna med en medelålder på 37,3±32,8 år, där samtliga genomgått diuresrenografi med PM-bilder. Studien visade att det inte föreligger något samband mellan kvarstående aktivitet vid 20 min respektive PM, därmed ges ingen möjlighet att höja den nuvarande gränsen. Interbedömarreliabilitet mellan biomedicinska analytiker, enligt tidigare kriterier visade en god styrka i överenstämmelse (κ) = 0,61, som är statistisk signifikant (p < 0,05). / The renal-and effluent function can be assessed by measuring the uptake and secretion of a tracer (99mTc-MAG3) from each kidney, combined with intravenous injection of diuretics, is termed diuresis renography. Hydronephrosis with and without obstruction, is differentiated by diuretic administration. Assessment of the uptake and renal effluent function is displayed by a renogram, which provides the uptake and excretion of a radiopharmaceutical by the kidneys and urinary tract after injection, a so-called time-activity curve. In the case of incomplete renal emptying, the imaging needs to be supplemented with post micturition (PM) images. At the department of Clinical Physiology and Nuclear Medicine at Skånes University Hospital, the criteria for when to take a late image have been changed to the current limit of 50% residual activity, which have increased the number of supplements. The objective of this study is to evaluate the criteria for PM images, before and after changing the criteria at the hospital. In addition, the study will investigate the possibility of raising the current limit of 50% residual activity, for imaging PM-images during renography. This was a retrospective study of 45 patients, children and adults with a mean age of 37,3±32,8 years, all had undergone diuresis renography with PM images. The study showed that there was no relation between the residual activity at 20 min and PM, thus there are no possibility to raise the current limit. Interrater reliability between biomedical scientists, according to previous criteria, indicating as substantial strength of agreement (κ) = 0,61, which is statistically significant (p < 0,05).

Values of the rate constant for the alkaline hydrolysis of methyl acetate in various aqueous-organic solvent mixtures (dimethyl sulfoxide 0<x40.2, dioxane 0 <, x., < 0.2, methyl ethyl ketone 0<x<0.06 and diglyme, i. e. ether-bis (2-methyloxethyl) 0x<0.10) have been determined for the temperatures 15 0 C, 25 0C and 35 0C conductometrically. To interpret these results the approach adapted is to experimentally determine the activity coefficient of the ester (YE ) and the activity of the water (aH20', mechanistically, at least one molecule of water is involved in the rate-determining step) and then to use the Bronsted-Bjerrum equation to determine the residual activity coefficient ratio of the participating ions, y (Yf - for Oil the transition state). Values of YE and aH 20 have been determined by a transpiration method, using gas-chromatographic analysis of the vapours of solutions of methyl acetate in aqueous-organic solvent mixtures of dir. ethyl sulfoxide, dioxane, methyl ethyl ketone and diglyme in the same composition ranges as above, tetrahydrofuran 04x org z<, 0.15, methanol, ethanol and tert-butanol in t1h6e range 04x0.20'at 25oC. These results indicate that on changing org the solvent composition YE varies by a larger factor than is predicted for the ratio YOH-/yýO_ by the Debye-Iluckel approach, and hence is the dominant factor in determining the effects of solvent composition on the rates of the hydrolysis. This is in contradiction to the assumptions of the electrostatic theories of Laidler and Eyring, and of Amis and Jaffe. The gas-chromatographic results also indicate that whilst the concentration of the water varies in each mixture studied, the activity coefficient varies in the opposite way to produce almost constant values of aý, 0* Using the transpiratioii/gas-chromatogralýlic method, the thermodynamic properties of the ternary systems, methyl acetate-water-organic Solvcat, using the organic solvents mentioned above (excepting, diglyme) have been investigated, and the results indicate that the variation of *ýE with solvent composition, for the dilute solutions of ester used, can be estimated from the thermodynamic properties of the binary water-organic solvent mixtures, using the Gibbs-Dahem equation. Single ion activity coefficients in the literature for small negative ions, to represent the OH_ ion, and for large ions, to rep-resent the transition state ion, have been used to explain the experimentally fomd variation of the residual activity coefficient -ratio with solvent composition. Hence, it is concluded that the importance of the parameters involved in the hydrolysis of esters - an ion-molecule reaction - in aqueousorganic solvent mixtures are in the order of Ymolecule > aH 20> YOH_/YM+ -> (dielectric constant), and that the nonelectrostatic effects -- thermodynamic effects - are more important in these studies than the electrostatic effects. From a preliminary investigation of the data in the literature the thermodynamic approach also yields a valid interpretation of the effect of solvent composition on the rates of the acid hydrolysis of esters.

Values of the rate constant for the alkaline hydrolysis of methyl acetate in various aqueous-organic solvent mixtures (dimethyl sulfoxide 0<x40.2, dioxane 0 <, x., < 0.2, methyl ethyl ketone 0<x<0.06 and diglyme, i. e. ether-bis (2-methyloxethyl) 0x<0.10) have been determined for the temperatures 15 0 C, 25 0C and 35 0C conductometrically. To interpret these results the approach adapted is to experimentally determine the activity coefficient of the ester (YE ) and the activity of the water (aH20', mechanistically, at least one molecule of water is involved in the rate-determining step) and then to use the Bronsted-Bjerrum equation to determine the residual activity coefficient ratio of the participating ions, y (Yf - for Oil the transition state). Values of YE and aH 20 have been determined by a transpiration method, using gas-chromatographic analysis of the vapours of solutions of methyl acetate in aqueous-organic solvent mixtures of dir. ethyl sulfoxide, dioxane, methyl ethyl ketone and diglyme in the same composition ranges as above, tetrahydrofuran 04x org z<, 0.15, methanol, ethanol and tert-butanol in t1h6e range 04x0.20'at 25oC. These results indicate that on changing org the solvent composition YE varies by a larger factor than is predicted for the ratio YOH-/yýO_ by the Debye-Iluckel approach, and hence is the dominant factor in determining the effects of solvent composition on the rates of the hydrolysis. This is in contradiction to the assumptions of the electrostatic theories of Laidler and Eyring, and of Amis and Jaffe. The gas-chromatographic results also indicate that whilst the concentration of the water varies in each mixture studied, the activity coefficient varies in the opposite way to produce almost constant values of aý, 0* Using the transpiratioii/gas-chromatogralýlic method, the thermodynamic properties of the ternary systems, methyl acetate-water-organic Solvcat, using the organic solvents mentioned above (excepting, diglyme) have been investigated, and the results indicate that the variation of *ýE with solvent composition, for the dilute solutions of ester used, can be estimated from the thermodynamic properties of the binary water-organic solvent mixtures, using the Gibbs-Dahem equation. Single ion activity coefficients in the literature for small negative ions, to represent the OH_ ion, and for large ions, to rep-resent the transition state ion, have been used to explain the experimentally fomd variation of the residual activity coefficient -ratio with solvent composition. Hence, it is concluded that the importance of the parameters involved in the hydrolysis of esters - an ion-molecule reaction - in aqueousorganic solvent mixtures are in the order of Ymolecule > aH 20> YOH_/YM+ -> (dielectric constant), and that the nonelectrostatic effects -- thermodynamic effects - are more important in these studies than the electrostatic effects. From a preliminary investigation of the data in the literature the thermodynamic approach also yields a valid interpretation of the effect of solvent composition on the rates of the acid hydrolysis of esters. / Ministry of Science and Higher Education of Iran

Made available in DSpace on 2017-07-21T18:53:11Z (GMT). No. of bitstreams: 1 dissertacao parcial.pdf: 389132 bytes, checksum: 1072407aabab8f91b6ea13999acc01d4 (MD5) Previous issue date: 2009-02-06 / Pectinases, a group of enzymes that degrade pectic substances and break glycosidic linkages, are produced by fungi, yeasts and bacteria, but are also in plants in general and fruit in particular.In the juice industry the pectinolytic enzymes are added to increase the efficiency of the process, decrease the viscosity and reduce the time of filtration. The pectin methylesterase, PME, hydrolyzes the methyl ester groups, forming carboxyl groups in pectin chain, releasing methanol end H3O+. Therefore, its knowledge is vital in order to control the effectiveness of the treatment. The purpose of this study was to determine the optimum conditions of the activity of the pectin methylesterase in industry preparations, proposing a potentiometric procedure for determining the PME activity and compare the data with those obtained by traditional potentiometry and Uv-Vis, evaluate the efficacy of this method in determining the residual activity exogenous of PME in mango juice. The activity of PME in the three commercial samples, Pectinex 100L Plus, Panzym Univers and Panzym Clears, was determined by potentiometry, Uv-Vis spectroscopy, with the bromophenol blue indicator, and the action of alcohol oxidase with acetyl acetone. The reaction consisted of 5.00 mg.mL-1 apple pectin, 0.100 mol.L-1 sodium chloride and 50 μL commercial pectinolytic enzyme for a volume of 30 mL. In all experiments the enzyme deesterification showed first-order kinetics, with increased activity at pH 4.0 to 4.5 and 45 ºC, whereas the complete inactivation occurred at 75 ºC for 10 minutes, in the three industrial preparations. The thermal inactivation of the PME of Pectinex 100L Plus and Panzym Clears preparations occurred under the same conditions, when the activity was measured by the procedures of ΔVNaOH / Δttime or of ΔpH/ Δttime. The activity of PME in industrial preparations at 25 °C and pH 4.5, determined by UV-Vis spectroscopy with bromophenol blue indicator, showed good correlation with the activity determined by the procedures by potentiometry. The stability of the indicator in the pectin solution allows its use to determine the PME activity in samples in which the optimum pH is located in acid band. The release of methanol as measured by alcohol oxidase, followed by the reaction with acetyl acetone to determine the formaldehyde, showed good agreement with the results of the enzyme activity measuring procedures used in this research. The inactivation of residual PME in mango juice occurred at 75 ºC for 20 minutes of exposure in the procedure ΔVNaOH / Δttime and 10 minutes of exposure during the procedure ΔpH/ Δttime. The residual activity of PME in 70 °C for 10, 20 and 30 minutes of exposure in the presence of juice was higher than in the control, indicating its protective effect. The procedure of ΔpH/ Δttime shows good correlation with other methods, with the advantage of precise and direct measures of [H+], excusing a series of reagents and high costs materials. / As pectinases, um grupo de enzimas que degradam substâncias pécticas e rompem ligações glicosídicas, são produzidas por fungos filamentosos, leveduras e bactérias, mas encontram-se também em plantas em geral e em frutas, em particular. Na indústria de sucos as enzimas pectinolíticas são adicionadas para aumentar o rendimento do processo, diminuir a viscosidade e reduzir o tempo de filtração. A pectina metilesterase, PME, hidrolisa os grupos metil éster, formando grupos carboxilícos na cadeia da pectina, produzindo metanol e H3O+.Portanto, é fundamental o seu conhecimento, a fim de controlar a eficiência do tratamento. O objetivo deste trabalho foi determinar as condições ótimas da atividade da PME presente em preparações industriais, propor um procedimento potenciométrico para determinação da atividade da enzima e comparar os dados com os obtidos por potenciometria tradicional e Uv- Vis, avaliar a eficiência do método proposto na determinação da atividade residual da PME exógena no suco de manga. A atividade da PME nas três amostras comerciais, Pectinex 100L Plus, Panzym Univers e Panzym Clears, foi determinada por potenciometria, espectroscopia Uv-Vis, com o indicador azul de bromofenol, e pela ação do álcool oxidase com acetil acetona. A reação consistiu de 5,00 mg.mL-1 de pectina de maçã, 0,100 mol.L-1 de cloreto de sódio e 50 μL de enzima pectinolítica comercial para um volume de 30 mL. Em todos os experimentos a desmetoxilação enzimática mostrou uma cinética de primeira ordem, com maior atividade em pH 4,0 a 4,5 e 45 ºC, sendo que a inativação completa ocorreu a 75 ºC por 10 min, nas três preparações industriais. A inativação térmica da PME das preparações Pectinex 100L Plus e da Panzym Clears ocorreu sob mesmas condições, quando a atividade foi medida pelos procedimenos de ΔVNaOH / Δttempo ou de ΔpH/ Δttempo. A atividade da PME nas preparações industriais a 25 ºC e pH 4,5, determinada por espectroscopia Uv-Vis com o indicador azul de bromofenol, apresentou boa correlação com a atividade determinada pelos procedimentos por potenciometria. A estabilidade do indicador em solução com a pectina permite a sua utilização para determinar a atividade da PME em amostras nas quais o pH ótimo localiza-se na faixa ácida. A liberação do metanol medida pela álcool oxidase, seguida da reação com a acetil acetona para determinar o formaldeído, mostrou boa concordância com os resultados dos procedimentos de medida de atividade enzimática utilizados neste trabalho. A inativação da PME residual em suco de manga ocorreu na temperatura de 75 ºC por 20 min de exposição no procedimento ΔVNaOH / Δttempo e durante 10 min de exposição pelo procedimento ΔpH/ Δttempo. A atividade residual da PME a 70 ºC por 10, 20 e 30 min de exposição em presença do suco foi maior do que no controle, indicando o seu efeito protetor. O procedimento da ΔpH/ Δttempo apresenta boa correlação com os demais métodos, com a vantagem de medidas precisas e diretas da [H+], dispensando uma série de reagentes e materiais de custos elevados.

<p>Sialic acid synthase (NeuB) is a key enzyme in bacterial biosynthesis of the sialic acid <em>N</em>-acetylneuraminic acid (NeuNAc). It catalyzes the addition of phosphoenolpyruvate (PEP) to <em>N</em>-acetylmannosamine (ManNAc) in the presence of a divalent cation such as Mn²⁺. We have explored the inhibition of NeuB by an oxacarbenium ion mimic, NeuNAc oxime, and hydroxylamine (NH₂OH). NeuNAc oxime shows slow-binding inhibition with a binding half-life of 2.5 h and an inhibition constant (<em>K</em>_i^*) of 1.6(± 0.7) pM. Even though NeuNAc oxime binds NeuB with high affinity, there remains approximately 10% residual activity even after extended pre-incubation with high inhibitor concentrations. In contrast, in the presence of substrates, when NeuB was actively catalyzing NeuNAc synthesis, complete inhibition by NeuNAc oxime was observed within 6 h. This inhibition profile is similar to NH₂OH; which has previously been shown to elicit complete, time-dependent inhibition. We propose the existence of two NeuB conformations: an asymmetric idle state conformation (NeuB^IS), in which NeuNAc oxime is able to bind to only one monomer of this dimeric enzyme, and a second conformation, running state NeuB (NeuB^RS), which is completely inhibited due to either NeuNAc oxime binding to the second monomer, or the dimer adopting a conformation in which the unbound monomer is inactive. Experiments with [1-¹⁴C]PEP showed that in the presence of large excess of substrate, inhibition occurred faster than with a lower excess. This suggests that a sustained buildup of NeuB^{RS<strong> </strong>}is required for complete inhibition.</p> / Master of Science (MSc)