scholarly journals 32P-labelling anomalies in human erythrocytes. Is there more than one pool of cellular Pi?

1989 ◽  
Vol 264 (3) ◽  
pp. 729-736 ◽  
Author(s):  
G J Kemp ◽  
A Bevington ◽  
D Khodja ◽  
A Challa ◽  
R G G Russell
Keyword(s):  
Steady State ◽  
Initial Rate ◽  
Specific Radioactivity ◽  
Organic Phosphate ◽  
Human Erythrocytes ◽  
Autologous Plasma ◽  
Intact Cells ◽  
Organic Phosphates ◽  
A Value ◽  
The Mean

1. Human erythrocytes were incubated in autologous plasma containing [32P]Pi, and sampled by a method which avoids washing the cells. 2. In experiments of up to 3 h duration, the specific radioactivity of cellular Pi stabilized at a value below that of extracellular Pi. This can be explained on the basis of a single cellular Pi pool exchanging with a large unlabelled pool of cellular organic phosphates. 3. However, a rapid initial phase of labelling, occurring within 30 s, was inconsistent with the situation described in point 2. A possible explanation is that about 1/4 of cellular Pi occurs in a separate, fast-labelling pool. 4. When the extracellular Pi concentration was doubled, most of the corresponding increase in the steady-state cellular Pi concentration was accounted for by the apparent fast-labelling Pi pool, which also doubled. 5. The observed initial rate of labelling of cellular organic phosphates [which probably occurs through the reaction catalysed by glyceraldehyde-3-phosphate dehydrogenase (E.C. 1.2.1.12)] was considerably lower than that predicted from the flux through the Embden-Meyerhof pathway. This implies that the enzyme is exposed to Pi whose specific radioactivity is lower than the mean specific radioactivity of cellular Pi, and fails to support earlier suggestions that this enzyme uses extracellular Pi. 6. In 3 h incubations, the rate of organic phosphate labelling was roughly constant throughout, even though the specific radioactivity of cellular Pi had risen slowly to a plateau. Viewed in conjunction with point 5, this again suggests some inhomogeneity in cellular Pi. 7. Cellular Pi and extracellular Pi only reached isotopic steady state after 2 days. At this stage some organic phosphates were probably still incompletely labelled. 8. We conclude that, whatever their physical or technical reasons, such labelling inhomogeneities and slow attainment of isotopic steady state may cause serious misinterpretation of results if ignored during 32P-labelling of intact cells.

scholarly journals Quantitative analysis of proton-linked transport systems. Glutamate transport in Staphylococcus aureus

1979 ◽  
Vol 184 (2) ◽  
pp. 441-449 ◽  
Author(s):  
W J Mitchell ◽  
I R Booth ◽  
W A Hamilton
Keyword(s):  
Staphylococcus Aureus ◽  
Steady State ◽  
Initial Rate ◽  
Glutamate Uptake ◽  
Transport Systems ◽  
Protonmotive Force ◽  
Electrogenic Transport ◽  
Soluble Cell ◽  
A Value ◽  
Ph Range

1. The magnitude of the protonmotive force in respiring Staphylococcus aureus was measured over the range of extracellular pH from 5.6 to 7.8. 2. The membrane potential remains constant at 150 mV, inside-negative, but the pH gradient decreases from 2.1 units, inside-alkaline, at pH 5.6 to zero at pH 7.5 and above. 3. The accumulation of glutamate in the soluble cell pool is pH-independent at a value equivalent to 100 mV. 4. The results of experiments studying co-transport of protons are consistent with a proton/glutamate stoichiometry of 2 and electrogenic transport across the pH range examined. 5. The amount of glutamate uptake is the result of a kinetic steady state between influx and efflux pathways. 6. Evidence is presented for the regulation of this kinetic steady state by the response of the initial rate of uptake to changes in the protonmotive force.

Thermal diffusion in solutions of electrolytes

1960 ◽  
Vol 255 (1282) ◽  
pp. 307-330 ◽  
Keyword(s):  
Steady State ◽  
Initial Rate ◽  
Wheatstone Bridge ◽  
Rate Of Change ◽  
Soret Coefficient ◽  
Free System ◽  
Platinized Platinum ◽  
Solutions Of Electrolytes ◽  
Concentration Changes ◽  
The Mean

A conductimetric method for following the small concentration changes that occur when a temperature gradient is maintained in an aqueous electrolyte is described. The solution is contained in a Perspex cell between silver end-plates which are faced with platinized platinum and kept at temperatures differing by about 10°C. A further connexion to the cell (a ‘centretap’) is made through a small lateral hole equidistant from the ends. The cell is incorporated in an audio-frequency Wheatstone bridge and movement of solute from one half of the cell to the other is followed by measuring the ratio of their resistances. For a convection-free system, the Soret coefficient (σ) may be derived either from the initial rate of change of the ratio or from its value in the steady state. It is found experimentally that there are discrepancies between the two estimates of σ, and also related anomalies in the rate of change of concentration, which can be ascribed to convection. It can be shown that the initial rate observations should be free from convection errors, and the effect of convection on the steady state can be analysed by dimensional methods. The observed discrepancies are correlated with the relevant properties of the solutions in the manner suggested by this analysis. The Soret coefficients of eighteen 1:1 salts in 0⋅01 m aqueous solution and at mean temperature 25⋅0°C have been determined by this method. Some additional measurements have been made at 34⋅7°C and at other concentrations in the range 0⋅002 to 0⋅02m. Three salts of other valency types (potassium, thallous and cadmium sulphates) have also been studied. The molar heats of transport of the salts ( Q *) have been calculated from the Soret coefficients. The results show that Q * (i) is an additive function of contributions characteristic of the constituent ions in dilute (0⋅01 M) solutions of 1:1 electrolytes, (ii) increases markedly on raising the mean temperatures from 25⋅0 to 34⋅7°C, in agreement with the results of Alexander (1954) and Longsworth (1957) (iii) increases appreciably on dilution below 0⋅01 M, indicating that heats of transport are influenced by long-range inter-ionic forces.

scholarly journals Variation in glacier length and ice volume of Rabots Glaciär, Sweden, in response to climate change, 1910–2003

2005 ◽  
Vol 42 ◽  
pp. 180-188 ◽  
Author(s):  
Keith A. Brugger ◽  
Kurt A. Refsnider ◽  
Matthew F. Whitehill
Keyword(s):  
Climate Change ◽  
Steady State ◽  
Sharp Increase ◽  
Initial Rate ◽  
Response Times ◽  
Historical Records ◽  
Climatic Warming ◽  
Ice Volume ◽  
Glacier Length ◽  
The Mean

AbstractHistorical records, photographs, maps and measurements were used to determine changes in the length, geometry and volume of Rabots Glaciär, Sweden, in response to a ∼1°C warming that occurred early in the 20th century. The glacier’s initial rate of retreat from its 1910 maximum was ~2.0 m a–1. After a sharp increase to ∼11.7 m a–1 between 1933 and 1946, the mean retreat rate decreased to ∼5.5 m a-1 between 1946 and 1959. Thereafter the rate of retreat increased to ∼11.0 m a-1 and has remained relatively constant to the present time. Concomitant decreases in ice volume were estimated to be 77.3 × 106m3 between 1910 and 1959, 51.1 × 106m3 between 1959 and 1980, at least 10.4 × 106m3 between 1980 and 1989, and 14.4 × 106m3 between 1989 and 2003. The total volume change over the last 93 years is estimated at ∼153.2 × 106m3 corresponding to 1.6 × 106m3a–1.. The magnitude of the ongoing changes in length and volume suggests that Rabots Glaciär has not yet completed its response to the earlier climatic warming. In contrast, several nearby glaciers, most notably Storglaciären, have completed their adjustments and established new steady-state profiles as a result of having shorter response times.

scholarly journals Steady-state kinetic analysis of aldehyde dehydrogenase from human erythrocytes

1992 ◽  
Vol 287 (1) ◽  
pp. 145-150 ◽  
Author(s):  
G T M Henehan ◽  
K F Tipton
Keyword(s):  
Steady State ◽  
Aldehyde Dehydrogenase ◽  
Initial Rate ◽  
Substrate Inhibition ◽  
Human Erythrocytes ◽  
Steady State Kinetics ◽  
Steady State Kinetic ◽  
Sequential Mechanism ◽  
Kinetics Of

The steady-state kinetics of purified cytoplasmic aldehyde dehydrogenase (EC 1.2.1.3) from human erythrocytes have been studied at 37 degrees C. Previous studies of the enzyme from several mammalian sources, which used a lower assay temperature, have been difficult to interpret because of the substrate activation by acetaldehyde which led to complex kinetic behaviour. At 37 degrees C the initial-rate data do not depart significantly from Michaelis-Menten kinetics. Studies of the variation of initial rates as a function of the concentrations of both substrates and studies of the inhibition by NADH were consistent with a sequential mechanism being followed. High-substrate inhibition by acetaldehyde was competitive with respect to NAD+. The enzyme was not inhibited by the product acetate and thus the results of these studies, although consistent with an ordered mechanism in which NAD+ was the first substrate to bind, were inconclusive. That such a mechanism was followed was confirmed by determination of the initial-rate behaviour in the presence of acetaldehyde and glycolaldehyde as alternative substrates. When the reciprocal of the initial rate of NADH formation was plotted against the acetaldehyde concentration at a series of fixed ratios between that substrate and glycolaldehyde, a linear ‘mixed inhibition’ pattern was obtained, confirming the mechanism to be ordered with NAD+ being the leading substrate and with kinetically significant ternary complex-formation.

THE EFFECT OF ALTERATION OF THYROXINE BINDING CAPACITY ON THE DIALYZABLE AND ABSOLUTE FRACTIONS OF TRIIODOTHYRONINE IN CIRCULATION

1973 ◽  
Vol 72 (2) ◽  
pp. 265-271 ◽  
Author(s):  
J. H. Dussault ◽  
D. A. Fisher ◽  
J. T. Nicoloff ◽  
V. V. Row ◽  
R. Volpe
Keyword(s):  
Correlation Coefficient ◽  
Inverse Relationship ◽  
Binding Capacity ◽  
Hormone Concentration ◽  
Thyroxine Binding Globulin ◽  
Serum Thyroxine ◽  
A Value ◽  
The Mean ◽  
Male Subjects ◽  
Female Subjects

ABSTRACT In order to determine the effect of alterations in binding capacity of thyroxine binding globulin (TBG) on triiodothyronine (T3) metabolism, studies were conducted in 10 patients with idiopathically low (7 subjects) or elevated (3 subjects) TBG levels and 10 subjects given norethandrolone (7 male subjects) or oestrogen (3 female subjects). Measurements of serum thyroxine (T4) concentration, maximal T4 binding capacity, serum T3 concentration and per cent dialyzable T3 were conducted. Serum T3 was measured both by chemical and radioimmunoassay methods. In patients with idiopathically low TBG, the mean serum T4 concentration was low (2.4 μg/100 ml), the mean serum T3 level low (55 ng/100 ml), the mean per cent dialyzable T3 increased (0.52%), and the calculated free T3 concentration normal (186 pg/100 ml). In patients with idiopathically high TBG levels the mean T4 concentration was high (10.3 μg/100 ml), the mean T3 level slightly elevated (127 ng/100 ml), the% dialyzable T3 low (0.10%) and the calculated free T3 concentration low normal (123 pg/100 ml). The correlation coefficient between the per cent dialyzable T3 and maximal TBG binding capacity in the 20 subjects was 0.68, a value significant at the P < 0.01 level. Thus, alterations in binding capacity of TBG seem to influence T3 and T4 metabolism similarly; the inverse relationship between the % of dialyzable hormone and total hormone concentration tends to keep the absolue levels of free hormones stable.

PENGARUH PENDIDIKAN KESEHATAN REPRODUKSI PADA PEER GROUP (TEMAN SEBAYA) TERHADAP PENGETAHUAN DAN PERSEPSI REMAJA TENTANG PENDEWASAAN USIA PERKAWINAN DI SMA NEGERI 1 KECAMATAN NAMORAMBE KAB. DELI SERDANG 2018

2020 ◽  
Vol 1 (2) ◽  
pp. 56-66
Author(s):  
Irma Linda
Keyword(s):  
Standard Deviation ◽  
Health Education ◽  
Reproductive Health ◽  
Peer Group ◽  
Peer Groups ◽  
A Value ◽  
Significant Difference ◽  
Reproductive Health Education ◽  
The Mean ◽  
Adolescent Perceptions

Background: Early marriages are at high risk of marital failure, poor family quality, young pregnancies at risk of maternal death, and the risk of being mentally ill to foster marriage and be responsible parents. Objective: To determine the effect of reproductive health education on peer groups (peers) on the knowledge and perceptions of adolescents about marriage age maturity. Method: This research uses the Quasi experimental method with One group pre and post test design, conducted from May to September 2018. The statistical analysis used in this study is a paired T test with a confidence level of 95% (α = 0, 05). Results: There is an average difference in the mean value of adolescent knowledge between the first and second measurements is 0.50 with a standard deviation of 1.922. The mean difference in mean scores of adolescent perceptions between the first and second measurements was 4.42 with a standard deviation of 9.611. Conclusion: There is a significant difference between adolescent knowledge on the pretest and posttest measurements with a value of P = 0.002, and there is a significant difference between adolescent perceptions on the pretest and posttest measurements with a value of p = 0.001. Increasing the number of facilities and facilities related to reproductive health education by peer groups (peers) in adolescents is carried out on an ongoing basis at school, in collaboration with local health workers as prevention of risky pregnancy.

Acidification of rat liver lysosomes: quantitation and comparison with endosomes

1993 ◽  
Vol 265 (4) ◽  
pp. C901-C917 ◽  
Author(s):  
R. W. Van Dyke
Keyword(s):  
Steady State ◽  
Membrane Potential ◽  
Rat Liver ◽  
Proton Pumps ◽  
Intact Cells ◽  
Early Endosomes ◽  
Medium Permeability ◽  
Electrogenic Proton Pump ◽  
Secondary Lysosomes ◽  
Permeability Studies

Both lysosomes and endosomes are acidified by an electrogenic proton pump, although studies in intact cells indicate that the steady-state internal pH (pHi) of lysosomes is more acid than that of endosomes. We undertook the present study to examine in detail the acidification mechanism of purified rat liver secondary lysosomes and to compare it with that of a population of early endosomes. Both endosomes and lysosomes exhibited ATP-dependent acidification, but proton influx rates were 2.4- to 2.7-fold greater for endosomes than for lysosomes because of differences in both buffering capacity and acidification rates, suggesting that endosomes exhibited greater numbers or rates of proton pumps. Lysosomes, however, exhibited a more acidic steady-state pHi due in part to a slower proton leak rate. Changes in medium Cl- increased acidification rates of endosomes more than lysosomes, and the lysosome ATP-dependent interior-positive membrane potential was only partially eliminated by high-Cl- medium. Permeability studies suggested that lysosomes were less permeable to Na+, Li+, and Cl- and more permeable to K+ and PO4(2-) than endosomes. Na-K-adenosine-triphosphatase did not appear to regulate acidification of either vesicle type. Endosome and lysosome acidification displayed similar inhibition profiles to N-ethylmaleimide, dicyclohexyl-carbodiimide, and vanadate, although lysosomes were somewhat more sensitive [concentration producing 50% maximal inhibition (IC50) 1 nM] to bafilomycin A1 than endosomes (IC50 7.6 nM). Oligomycin (1.5-3 microM) stimulated lysosome acidification due to shunting of membrane potential. Overall, acidification of endosomes and lysosomes was qualitatively similar but quantitatively somewhat different, possibly related to differences in the density or rate of proton pumps as well as vesicle permeability to protons, anions, and other cations.

The evolution of star formation in QSOs according to WISE

2020 ◽  
Vol 15 (S359) ◽  
pp. 33-34
Author(s):  
K. A. Cutiva-Alvarez ◽  
R. Coziol ◽  
J. P. Torres-Papaqui ◽  
H. Andernach ◽  
A. C. Robleto-Orús
Keyword(s):  
Star Formation ◽  
Gradual Increase ◽  
A Value ◽  
Star Formation Activity ◽  
The Mean ◽  
Lower Redshift

AbstractUsing WISE data, we calibrated the W2-W3 colors in terms of star formation rates (SFRs) and applied this calibration to a sample of 1285 QSOs with the highest flux quality, covering a range in redshift from z ˜ 0.3 to z ˜ 3.8. According to our calibration, the SFR increases continuously, reaching a value at z ˜ 3.8 about 3 times higher on average than at lower redshift. This increase in SFR is accompanied by an increase of the BH mass by a factor 100 and a gradual increase of the mean Eddington ratio from 0.1 to 0.3 up to z ˜ 1.5 – 2.0, above which the ratio stays constant, despite a significant increase in BH mass. Therefore, QSOs at high redshifts have both more active BHs and higher levels of star formation activity.

SET-VALUED PERFORMANCE APPROXIMATIONS FOR THE QUEUE GIVEN PARTIAL INFORMATION

2020 ◽  
pp. 1-23
Author(s):  
Yan Chen ◽  
Ward Whitt
Keyword(s):  
Steady State ◽  
Decay Rate ◽  
Waiting Time ◽  
Partial Information ◽  
Upper And Lower Bounds ◽  
Interarrival Time ◽  
Limited Information ◽  
Wide Range ◽  
The Mean ◽  
Third Moment

In order to understand queueing performance given only partial information about the model, we propose determining intervals of likely values of performance measures given that limited information. We illustrate this approach for the mean steady-state waiting time in the $GI/GI/K$ queue. We start by specifying the first two moments of the interarrival-time and service-time distributions, and then consider additional information about these underlying distributions, in particular, a third moment and a Laplace transform value. As a theoretical basis, we apply extremal models yielding tight upper and lower bounds on the asymptotic decay rate of the steady-state waiting-time tail probability. We illustrate by constructing the theoretically justified intervals of values for the decay rate and the associated heuristically determined interval of values for the mean waiting times. Without extra information, the extremal models involve two-point distributions, which yield a wide range for the mean. Adding constraints on the third moment and a transform value produces three-point extremal distributions, which significantly reduce the range, producing practical levels of accuracy.

scholarly journals The fate of Si and Fe while nuclear glass alters with steel and clay

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
C. Carriere ◽  
P. Dillmann ◽  
S. Gin ◽  
D. Neff ◽  
L. Gentaz ◽  
...  
Keyword(s):  
Dissolution Rate ◽  
Protective Layer ◽  
Glass Dissolution ◽  
A Value ◽  
Waste Forms ◽  
Controlling Mechanism ◽  
Geological Repository ◽  
The Mean ◽  
High Level ◽  
Initial Dissolution Rate

AbstractThe French concept developed to dispose high-level radioactive waste in geological repository relies on glassy waste forms, isolated from the claystone host rock by steel containers. Understanding interactions between glass and surrounding materials is key for assessing the performance of a such system. Here, isotopically tagged SON68 glass, steel and claystone were studied through an integrated mockup conducted at 50 °C for 2.5 years. Post-mortem analyses were performed from nanometric to millimetric scales using TEM, STXM, ToF-SIMS and SEM techniques. The glass alteration layer consisted of a crystallized Fe-rich smectite mineral, close to nontronite, supporting a dissolution/reprecipitation controlling mechanism for glass alteration. The mean glass dissolution rate ranged between 1.6 × 10−2 g m−2 d−1 to 3.0 × 10−2 g m−2 d−1, a value only 3–5 times lower than the initial dissolution rate. Thermodynamic calculations highlighted a competition between nontronite and protective gel, explaining why in the present conditions the formation of a protective layer is prevented.

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