scholarly journals Intra-axonal transport and turnover of neurophysins in the rat. A proposal for a possible origin of the minor neurophysin component

1973 ◽  
Vol 136 (4) ◽  
pp. 1047-1052 ◽  
Author(s):  
Graham D. Burford ◽  
Brian T. Pickering
Keyword(s):  
Axonal Transport ◽  
Rate Constant ◽  
Half Life ◽  
Minor Component ◽  
The Other ◽  
Metabolic Product ◽  
Exponential Rate ◽  
Neural Lobe ◽  
Intracisternal Injection ◽  
Kinetics Of

1. Radioactivity associated with the three neurophysins in the neural lobe of the rat was determined at intervals up to 5 weeks after an intracisternal injection of [35S]cysteine. 2. The radioactivity associated with the two major neurophysins (one supposedly associated with vasopressin and the other with oxytocin) increased linearly for 12h after the injection and the ratio of the rates of increase in the two proteins was very similar to the ratio of vasopressin to oxytocin in the gland. 3. From 12h onwards the radioactivity associated with each major neurophysin declined exponentially but the half-life of the supposed oxytocin–neurophysin (13.3 days) was shorter than that for the supposed vasopressin–neurophysin (19.8 days). 4. The kinetics of labelling of the minor neurophysin was quite different from that of the two major ones. It became slowly labelled during 3–5 days after injection and the radioactivity hardly decreased during the following 4 weeks. 5. The data could support the hypothesis that the minor neurophysin is a metabolic product of oxytocin–neurophysin. The exponential rate of disappearance of radioactivity from oxytocin–neurophysin and the minor component taken together has a rate constant similar to that for vasopressin–neurophysin (e.g. half-life=18.9 days).

Reactions of hydrogen atoms with hexafluoroacetone

1978 ◽  
Vol 56 (20) ◽  
pp. 2638-2645 ◽  
Author(s):  
D. W. Grattan ◽  
K. O. Kutschke
Keyword(s):  
Rate Constant ◽  
Cross Sections ◽  
The Other ◽  
Hydrogen Atoms ◽  
Kinetics Of

Attempts were made to study the kinetics of the reaction of atomic H with (CF3)2CO vapour (HFA). Atomic H was generated from H2 by mercury photosensitization in the presence of C2H4 and HFA but the system was complicated by the loss of C2H5 radicals by addition to HFA and the kinetic results were intractable. When atomic H was generated from C3H8, the kinetics again were obscured by some unidentified reaction(s) which became more important at higher [HFA]/[C3H8]. An estimate of the rate constant for the addition of H to HFA obtained at low [HFA]/[C3H8] yielded k9 = 8.5 × 105 l mol−1 s−1. Trifluoroacetaldehyde was identified with some reliability but many of the other heavier products formed in the H2 + HFA reaction could not be identified. Quenching cross-sections were determined for C2H4, C3H8, C4H10, and HFA relative to that for N2O.

scholarly journals Genetic variations in kinetic constants that describe beta-glucuronidase mRNA induction in androgen-treated mice.

1987 ◽  
Vol 7 (3) ◽  
pp. 1085-1090 ◽  
Author(s):  
G Watson ◽  
K Paigen
Keyword(s):  
Rate Constant ◽  
Transcriptional Activation ◽  
Half Life ◽  
Order Rate Constant ◽  
Gene Copy ◽  
Initial Slope ◽  
Half Time ◽  
Mrna Induction ◽  
Lag Period ◽  
Kinetics Of

The kinetics of beta-glucuronidase mRNA induction by androgen in mouse kidney were determined for A, B, and CS haplotypes of the beta-glucuronidase gene. After a lag period, the kinetics of mRNA (R) induction are approximated by the turnover equation dR/dt = k1 - k2R. The A haplotype differs from the B primarily in the duration of the lag period and in k1, the rate constant determining the initial slope of the induction curve. The CS haplotype differs from B primarily in k2, the first-order rate constant that determines the half-time for induction. None of the haplotypes differs significantly in the half-life of beta-glucuronidase mRNA as measured by deinduction. Thus, there was no correlation between the half-time or extent of induction and the half-life of the RNA. Comparing half-times for induction with the half-life of the mRNA suggests that message stabilization can at most account for only part of the induction. We conclude that transcriptional activation of the beta-glucuronidase gene must be an important component of induction. Estimating absolute numbers of mRNA molecules and absolute rates of gene transcription, it appears that before induction there is approximately one molecule of beta-glucuronidase mRNA per cell and that each gene copy is transcribed once every 35 to 40 h. Depending on the haplotype examined, after induction, mRNA goes up to 80 to 400 molecules per induced cell. In the A haplotype, which has the highest induction, this corresponds to one transcript from each gene every 6 min if there is no induced stabilization of beta-glucuronidase mRNA, and one every 30 min if there is. Thus, it seems unlikely that more than one transcript is ever being synthesized at the same time from the beta-glucuronidase gene.

scholarly journals The synthesis of inhibitors for processing proteinases and their action on the Kex2 proteinase of yeast

1993 ◽  
Vol 293 (1) ◽  
pp. 75-81 ◽  
Author(s):  
H Angliker ◽  
P Wikstrom ◽  
E Shaw ◽  
C Brenner ◽  
R S Fuller
Keyword(s):  
Rate Constant ◽  
Potent Inhibitor ◽  
Protein Processing ◽  
The Other ◽  
Peptide Sequence ◽  
Cleavage Sites ◽  
Precursor Processing ◽  
Inactivation Rate Constant ◽  
Potential Inhibitors ◽  
Kinetics Of

Peptidyl chloromethane and sulphonium salts containing multiple Arg and Lys residues were synthesized as potential inhibitors of prohormone and pro-protein processing proteinases. The potencies of these compounds were assayed by measuring the kinetics of inactivation of the yeast Kex2 proteinase, the prototype of a growing family of eukaryotic precursor processing proteinases. The most potent inhibitor, Pro-Nvl-Tyr-Lys-Arg-chloromethane, was based on cleavage sites in the natural Kex2 substrate pro-alpha-factor. This inhibitor exhibited a Ki of 3.7 nM and a second-order inactivation rate constant (k2/Ki) of 1.3 x 10(7) M-1.s-1 comparable with the value of kcat./Km obtained with Kex2 for the corresponding peptidyl methylcoumarinylamide substrate. The enzyme exhibited sensitivity to the other peptidyl chloromethanes over a range of concentrations, depending on peptide sequence and alpha-amino decanoylation, but was completely resistant to peptidyl sulphonium salts. Kinetics of inactivation by these new inhibitors of a set of ‘control’ proteinases, including members of both the trypsin and subtilisin families, underscored the apparent specificity of the compounds most active against Kex2 proteinase.

The Kinetics of Polymerization Reactions

1945 ◽  
Vol 18 (2) ◽  
pp. 223-235 ◽  
Author(s):  
G. Gee ◽  
H. W. Melville
Keyword(s):  
Half Life ◽  
Molecular Size ◽  
The Other ◽  
Chain Growth ◽  
Extreme Conditions ◽  
Kinetics Of Polymerization ◽  
Molecular Sizes ◽  
Mathematical Difficulties ◽  
The One ◽  
Kinetics Of

Abstract A general treatment of the kinetics of polymerization reactions is given to cover the two extreme conditions in which the lifetime of chain growth is (1) small, and (2) large compared with the half life of the monomer. Case (1) is considered on the basis of the assumption that the velocity coefficients do not depend on molecular size. Case (2) is considered for propagation coefficients which are on the one hand independent, and on the other hand dependent on molecular size. In addition, the distribution of molecular sizes is computed in those cases where the mathematical difficulties are not insurmountable. The application of these results to the analysis of polymerization reactions is discussed. The work described in this paper was completed when war broke out, and was to have been published as part of a book on polymerization processes. In view of the interest and development in these matters, it was felt desirable to give this account of these ideas now.

Genetic variations in kinetic constants that describe beta-glucuronidase mRNA induction in androgen-treated mice

1987 ◽  
Vol 7 (3) ◽  
pp. 1085-1090 ◽  
Author(s):  
G Watson ◽  
K Paigen
Keyword(s):  
Rate Constant ◽  
Transcriptional Activation ◽  
Half Life ◽  
Order Rate Constant ◽  
Gene Copy ◽  
Initial Slope ◽  
Half Time ◽  
Mrna Induction ◽  
Lag Period ◽  
Kinetics Of

The kinetics of beta-glucuronidase mRNA induction by androgen in mouse kidney were determined for A, B, and CS haplotypes of the beta-glucuronidase gene. After a lag period, the kinetics of mRNA (R) induction are approximated by the turnover equation dR/dt = k1 - k2R. The A haplotype differs from the B primarily in the duration of the lag period and in k1, the rate constant determining the initial slope of the induction curve. The CS haplotype differs from B primarily in k2, the first-order rate constant that determines the half-time for induction. None of the haplotypes differs significantly in the half-life of beta-glucuronidase mRNA as measured by deinduction. Thus, there was no correlation between the half-time or extent of induction and the half-life of the RNA. Comparing half-times for induction with the half-life of the mRNA suggests that message stabilization can at most account for only part of the induction. We conclude that transcriptional activation of the beta-glucuronidase gene must be an important component of induction. Estimating absolute numbers of mRNA molecules and absolute rates of gene transcription, it appears that before induction there is approximately one molecule of beta-glucuronidase mRNA per cell and that each gene copy is transcribed once every 35 to 40 h. Depending on the haplotype examined, after induction, mRNA goes up to 80 to 400 molecules per induced cell. In the A haplotype, which has the highest induction, this corresponds to one transcript from each gene every 6 min if there is no induced stabilization of beta-glucuronidase mRNA, and one every 30 min if there is. Thus, it seems unlikely that more than one transcript is ever being synthesized at the same time from the beta-glucuronidase gene.

scholarly journals HPLC INVESTIGATION OF THE DEGRADATION OF SOME ARTIFICIAL AZO FOOD COLORANTS IN THE PRESENCE OF ASCORBIC ACID

2017 ◽  
Vol 29 (1-2) ◽  
Author(s):  
Vesna Kostić ◽  
Trajče Stafilov ◽  
Kiro Stojanoski
Keyword(s):  
Ascorbic Acid ◽  
Rate Constant ◽  
Rate Constants ◽  
Half Life ◽  
The Other ◽  
Brilliant Blue ◽  
Food Colorants ◽  
Brilliant Blue Fcf ◽  
Patent Blue ◽  
Patent Blue V

A b s t r a c t: The influence of the concentration of ascorbic acid on some azo food colorant (Brilliant Black BN, Brilliant Blue FCF, Chinoline Yellow, Indigotine, Patent Blue V and Tartazine) degradation in the solution has been studied. Rate constant (k), time of colorant half-life (t1/2), as well as the type of the kinetic reaction have been determined. The colorants and the ascorbic acid have been determined by high performance liquid chromatography (HPLC) with diode array detector (DAD) and UV-VIS spectrometry. It was found that the higher concentration of ascorbic acid leads to the higher rate constant and lower colorants half-life. The values of the rate constants are 2.50–4.25 times higher when the colorant degradation was run in the presence of 500 mg L–1 of ascorbic acid than in the case of the presence of 100 mg L–1 ascorbic acid for Brilliant Blue FCF, Chinoline Yellow, Patent Blue V and Tartazine. From the other side, the degradation of Brilliant Black BN and Indigotine is very fast with a total degradation for 6–9 days. Therefore, the rate constants for those two food colorants are much higher than for the other investigated colorants. According to the linearity of the kinetics curves (ln(c/co) v.s. time) it appeared to be first order kinetics for the interval up to 4 days.

Kinetics of Various 99mTc-Sn-Pyrophosphate Compounds in the Rat

1977 ◽  
Vol 16 (04) ◽  
pp. 157-162 ◽  
Author(s):  
C. Schümichen ◽  
B. Mackenbrock ◽  
G. Hoffmann
Keyword(s):  
Normal Saline ◽  
Half Life ◽  
Compound A ◽  
Short Half Life ◽  
Low Concentrations ◽  
The Stability ◽  
Kinetics Of ◽  
In Vitro Stability

SummaryThe bone-seeking 99mTc-Sn-pyrophosphate compound (compound A) was diluted both in vitro and in vivo and proved to be unstable both in vitro and in vivo. However, stability was much better in vivo than in vitro and thus the in vitro stability of compound A after dilution in various mediums could be followed up by a consecutive evaluation of the in vivo distribution in the rat. After dilution in neutral normal saline compound A is metastable and after a short half-life it is transformed into the other 99mTc-Sn-pyrophosphate compound A is metastable and after a short half-life in bone but in the kidneys. After dilution in normal saline of low pH and in buffering solutions the stability of compound A is increased. In human plasma compound A is relatively stable but not in plasma water. When compound B is formed in a buffering solution, uptake in the kidneys and excretion in urine is lowered and blood concentration increased.It is assumed that the association of protons to compound A will increase its stability at low concentrations while that to compound B will lead to a strong protein bond in plasma. It is concluded that compound A will not be stable in vivo because of a lack of stability in the extravascular space, and that the protein bond in plasma will be a measure of its in vivo stability.

Turnover and Distribution of 131Iodine-Labelled Human Fibrinogen

1964 ◽  
Vol 11 (02) ◽  
pp. 404-422 ◽  
Author(s):  
Annemarie Amris ◽  
C. J Amris
Keyword(s):  
Body Weight ◽  
Cancer Patient ◽  
Distribution Ratio ◽  
Half Life ◽  
Fibrinolytic Activity ◽  
The Other ◽  
Turnover Rates ◽  
Human Fibrinogen ◽  
Coagulation Defects ◽  
Fractional Turnover

Summary14 patients (5 diabetics with arteriosclerotic complications, 4 patients with thrombo-embolic disease, 4 with cirrhosis, coagulation defects and increased fibrinolytic activity, and 1 cancer patient) and 3 control patients were subjected to turnover studies with 13iodine labelled human fibrinogen.Half-life times in the control patients were found to be 4 days, the fractional turnover rates 19–23 per cent, of intravascular fibrinogen per day, and the absolute turnover 0.02 to 0.06 gm per day per kg. body weight. The other patient’s half-life times and turnover rates varied considerably from 0.9–5.5 days, 13–160 per cent, per day of intravascular fibrinogen and 0.02–0.4 gm per day per kg. body weight respectively.As fibrinogen unlike other proteins subjected to turnover studies, is converted to fibrin, it is not possible to measure the true intra-extravascular distribution ratio of fibrinogen. But intravascular fibrinogen could be approximated to constitute 68–99 per cent, of the total fibrinogen. There is justification in believing that fibrinogen is degradated through a continuous coagulation in equilibrium with fibrinolysis, and that the organism contains a greater mass of fibrin, the “fibrin pool”. Considerations of the turnover mechanism can however only be hypothetical.

The role of a metabolic intermediate in the biodegradation of inhibitory substrates

1997 ◽  
Vol 36 (10) ◽  
pp. 27-36 ◽  
Author(s):  
P. Mungkarndee ◽  
S. M. Rao Bhamidimarri ◽  
A. J. Mawson ◽  
R. Chong
Keyword(s):  
The Other ◽  
Metabolic Product ◽  
Dichlorophenoxyacetic Acid ◽  
Mutual Inhibition ◽  
Metabolic Intermediate ◽  
Batch Cultures ◽  
Ortho Cresol ◽  
2,4 Dichlorophenoxyacetic Acid

Biodegradation of the mixed inhibitory substrates, 2,4-dichlorophenoxyacetic acid (2,4-D) and para-chloro-ortho-cresol (PCOC) was studied in aerobic batch cultures. Each substrate added beyond certain concentrations inhibited the degradation of the other. This mutual inhibition was found to be enhanced by 2,4-dichlorophenol (2,4-DCP) which is an intermediate metabolic product of 2,4-D. When 2,4-DCP accumulated to approximatelY 40 mg/l degradation of all compounds in the mixed 2,4-D and PCOC substrate system was completely inhibited. The degradation of 2,4-D and PCOC individually was also found to be inhibited by elevated concentrations of 2,4-DCP added externally, while PCOC inhibited the utilization of the intermediate.

Study of nickel-molybdenum catalysts for methanation of carbon monoxide

1980 ◽  
Vol 45 (3) ◽  
pp. 783-790 ◽  
Author(s):  
Petr Taras ◽  
Milan Pospíšil
Keyword(s):  
Carbon Monoxide ◽  
Catalytic Activity ◽  
Mixed Oxides ◽  
Minor Component ◽  
Fast Neutrons ◽  
Scanning Calorimetry ◽  
Low Concentrations ◽  
Γ Rays ◽  
Molybdenum Catalysts ◽  
Kinetics Of

Catalytic activity of nickel-molybdenum catalysts for methanation of carbon monoxide and hydrogen was studied by means of differential scanning calorimetry. The activity of NiMoOx systems exceeds that of carrier-free nickel if x < 2, and is conditioned by the oxidation degree of molybdenum, changing in dependence on the composition in the region Mo-MoO2. The activity of the catalysts is adversely affected by irradiation by fast neutrons, dose 28.1 Gy, or by γ rays using doses in the region 0.8-52 kGy. The system is most susceptible to irradiation in the region of low concentrations of the minor component (about 1 mol.%). The dependence of changes in catalytic activity of γ-irradiated samples on the dose exhibits a maximum in the range of 2-5 kGy. The changes in catalytic activity are stimulated by the change of reactivity of the starting mixed oxides, leading to different kinetics of their reduction and modification of their adsorption properties. The irradiation of the catalysts results in lowered concentration of the active centres for the methanation reaction.

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