Kinetik der Lipide und Lipoproteine mit Bestimmung der Recovery-Rate im Non Steady State nach Plasma-, Membranfiltrations- und Dextransulfatadsorptionsapherese bei Hypercholesterinämie - Kinetics of Lipids and Lipoproteins with Determination of Recovery Rates in non-steady state after Plasma-, Membranefiltration and Dextransulfate Adsorption Apheresis for Hypercholesterolemia

1989 ◽  
Vol 34 (10) ◽  
pp. 232-242 ◽  
Author(s):  
W. Schwartzkopff ◽  
H. Gräfenhahn ◽  
A. Nold ◽  
H. v. Baeyer ◽  
A. Bimmermann ◽  
...  
Keyword(s):  
Steady State ◽  
Recovery Rate ◽  
Recovery Rates ◽  
Lipids And Lipoproteins ◽  
Kinetics Of

scholarly journals Determination of the steady-state turnover rates of the metabolically active pools of phosphatidylinositol 4-phosphate and phosphatidylinositol 4,5-bisphosphate in human erythrocytes

1989 ◽  
Vol 259 (3) ◽  
pp. 893-896 ◽  
Author(s):  
C E King ◽  
P T Hawkins ◽  
L R Stephens ◽  
R H Michell
Keyword(s):  
Steady State ◽  
Rate Constants ◽  
Human Erythrocytes ◽  
Turnover Rates ◽  
Metabolic Fluxes ◽  
Metabolic Pool ◽  
Phosphatidylinositol 4 ◽  
Kinetics Of ◽  
Phosphate Groups

When intact human erythrocytes are incubated at metabolic steady state in a chloride-free medium containing [32P]Pi, there is rapid labelling of the gamma-phosphate of ATP, followed by a slower labelling of the monoester phosphate groups of phosphatidylinositol 4-phosphate (PtdIns4P) and phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] [King, Stephens, Hawkins, Guy & Michell (1987) Biochem. J. 244, 209-217]. We have analysed the early kinetics of the labelling of these phosphate groups, in order to determine: (a) the steady-state rates of the interconversions of phosphatidylinositol, PtdIns4P and PtdIns(4,5)P2; and (b) the fractions of the total cellular complement of PtdIns4P and PtdIns(4,5)P2 that participate in this steady-state turnover. The experimental data most closely fit a pattern of PtdIns4P and PtdIns(4,5)P2 turnover in which one-quarter of the total cellular complement of each lipid is in the metabolic pool that participates in rapid metabolic turnover, with rate constants of 0.028 min-1 for the interconversion of PtdIns and PtdIns4P, and of 0.010 min-1 for the PtdIns4P/PtdIns(4,5)P2 cycle. These rate constants represent metabolic fluxes of approx. 2.1 nmol of lipid/h per ml of packed erythrocytes between PtdIns and PtdIns4P and of approx. 5.7 nmol/h per ml of cells between PtdIns4P and PtdIns(4,5)P2.

Measurement of leucine metabolism in man from a primed, continuous infusion of L-[1-3C]leucine

1980 ◽  
Vol 238 (5) ◽  
pp. E473-E479 ◽  
Author(s):  
D. E. Matthews ◽  
K. J. Motil ◽  
D. K. Rohrbaugh ◽  
J. F. Burke ◽  
V. R. Young ◽  
...  
Keyword(s):  
Steady State ◽  
Continuous Infusion ◽  
Co2 Production ◽  
Human Beings ◽  
Priming Dose ◽  
Leucine Metabolism ◽  
Kinetics Of ◽  
13Co2 Enrichment

Leucine metabolism in vivo can be determined from a primed, continuous infusion of L-[1-13C]leucine by measuring, at isotopic steady state, plasm [-13C]leucine enrichment, expired 13CO2 enrichment, and CO2 production rate. With an appropriate priming dose of L-[1-13C]leucine and NaH13CO3, isotopic steady state is reached in less than 2 h, and the infusion is completed in 4 h. The method can determine rates of leucine turnover, oxidation, and incorporation into protein with typical relative uncertainties of 2, 10, and 4%, respectively. The method requires no more than 1 ml of blood and uses stable isotope rather than radioisotope techniques. Thus, the method is applicable to studies of human beings of all ages. L-[1-13C]leucine may be infused with a second amino acid labeled with 15N for simultaneous determination of the kinetics of two amino acids.

scholarly journals Effectiveness of Reversible Contraception in Dog Population Management

2018 ◽  
Vol 44 (1) ◽  
pp. 6
Author(s):  
Oswaldo Santos Baquero ◽  
Ana Pérola Drulla Brandão ◽  
Marcos Amaku ◽  
Fernando Ferreira
Keyword(s):  
Sensitivity Analysis ◽  
Steady State ◽  
Recovery Rate ◽  
Treatment Effectiveness ◽  
Population Management ◽  
Management Tool ◽  
Estimation Of Parameters ◽  
Recovery Rates ◽  
Surgical Sterilization ◽  
Fertility Recovery

Background: Dog fertility depends on human-influenced factors such as sterilization. Uncontrolled fertility can result in unwanted births and overpopulation, which causes problems of public health and animal welfare. Surgical sterilization has been the traditional means of reproduction control but its cost and time can be prohibitive for mass sterilization programs. Non-surgical sterilization alternatives exist, but most of them are reversible and their effectiveness as a population management tool is unknown. To better understand the consequences of reversible contraception, the fertility dynamics was modeled in a hypothetical dog population in a steady-state condition.Materials, Methods & Results: The effect of reversible contraception was simulated using a coupled system of ordinary differential equations. A hypothetical steady-state population of 1000 animals was considered. It was formed by two compartments, one of fertile dogs and the other of infertile dogs. Natality compensated for a fraction of mortality, and the immigration rate compensated for the remaining fraction. The group of immigrant dogs was composed of fertile and infgertile dogs. The dog flow between compartments was given by both the contraception and fertility recovery rate. It was assumed that fertility reversibility in animals of the immigrant group was equal to that of animals already present in the population. Global sensitivities were calculated to assess the uncertainties of fertility dynamics associated with estimation of parameters. In addition, the local sensitivities were calculated to assess the influence of each parameter on fertility dynamics. The treatment effectiveness were expressed in terms of the total number of dogs treated for 20 years by taking a given irreversible contraception rate divided by the total number of dogs treated during the same period, and using the corresponding reversible contraception rate. The global sensitivity analysis consistently indicated a reduction in the number of fertile dogs. The local sensitivity analysis indicated that contraception rate was the most influential parameter, followed by the fertility recovery rate. The fraction of mortality compensated by natality was more influential than the fraction of infertile immigrants. Simulated scenarios indicated that the higher the contraception rate, the greater the difference between the effects of different fertility recovery rates. Variations in the proportion of infertile immigrants minimally changed the number of fertile dogs and the accumulated number of treated dogs. The increase in the fertility recovery rate caused effectiveness to decrease, especially when contraception rates were higher.Discussion: In certain scenarios, reversible contraception can be a viable option for reproduction control. Evaluation of effectiveness of the reversible contraception showed both the importance of duration of the contraceptive effect and the interaction between the contraception and fertility recovery rates. Although the contraception rate is the main determinant of population fertility dynamics, the fertility recovery rate modulates the effect of contraception and determines its viability. Reversible contraception is a viable alternative when loss in effectiveness is compensated by a reduction in costs and ease of application of contraceptive treatments. The lower the contraception rate, the higher the similarity between the effects of reversible and irreversible contraception.

scholarly journals Interpretation of the Kinetics of Consecutive Enzyme-catalysed Reactions: Studies on the Arginase-Ornithine Carbamoyltransferase System

1982 ◽  
Vol 35 (2) ◽  
pp. 137 ◽  
Author(s):  
RD Teasdale ◽  
PD Jeffrey ◽  
PW Kuchel ◽  
LW Nichol
Keyword(s):  
Steady State ◽  
Ornithine Carbamoyltransferase ◽  
Enzyme Substrate ◽  
Steady State Kinetic ◽  
Kinetic Mechanisms ◽  
Heterogeneous Association ◽  
Kinetics Of ◽  
State Kinetic ◽  
Enzymic Assay

A method that permits the use of measurements on the concentration of the intermediate in a coupled enzymic assay in determining the presence or absence of an interaction between the enzymes is presented. The method is shown to be closely analogous to a previously formulated procedure involving the determination of the rate of production of the final product of such a sequence and is shown to be applicable regardless of the complexity of the operative kinetic mechanisms, provided it may be assumed that all enzyme-substrate complexes are in the steady-state. Kinetic results obtained with the arginase--ornithine carbamoyltransferase couple, in which the intermediate ornithine is monitored, are examined in these terms to conclude that no heterogeneous association is operative between the enzymes.

scholarly journals Determination of Michaelis parameters from differentials of progress curves

1983 ◽  
Vol 215 (3) ◽  
pp. 589-595 ◽  
Author(s):  
L C Petersen
Keyword(s):  
Steady State ◽  
Cytochrome C ◽  
Kinetic Analysis ◽  
Cytochrome C Oxidase ◽  
Enzyme Assay ◽  
Serine Proteinases ◽  
Steady State Concentration ◽  
Kinetics Of ◽  
State Concentration

First differentials of progress curves are easily obtainable in many enzyme assay systems. Such curves may be more readily applicable to kinetic analysis than are the usual progress curves. The theory for this approach is developed, and simple graphical procedures for the determination of Michaelis parameters are indicated. By using an electronic differentiator device the application of the method is demonstrated on the kinetics of three different serine proteinases with various synthetic substrates. Whenever the steady-state concentration of an intermediate of the reaction is proportional to the rate, the transition of this intermediate in substrate-depletion experiments may be analysed in similar terms. This is demonstrated with cytochrome c oxidase kinetics. A number of other possible applications are discussed.

scholarly journals Crystallization kinetics of amorphous calcium carbonate in confinement

2019 ◽  
Vol 10 (19) ◽  
pp. 5039-5043 ◽  
Author(s):  
Jack Cavanaugh ◽  
Michael L. Whittaker ◽  
Derk Joester
Keyword(s):  
Steady State ◽  
Calcium Carbonate ◽  
Crystal Nucleation ◽  
Amorphous Calcium Carbonate ◽  
Emulsion Droplets ◽  
Individual Crystal ◽  
Upper Limit ◽  
Kinetics Of

In situ observation of amorphous calcium carbonate (ACC) confined in ∼500 pL emulsion droplets allows determination of the timing of individual crystal nucleation events. Statistical analysis of events in hundreds of droplets establishes an upper limit for the steady-state nucleation rate of 1.2 cm−3 s−1 for the crystallization from ACC.

Sign in / Sign up

Export Citation Format

Share Document