The in vivo regeneration of goldfish rhodopsin and porphyropsin

1986 ◽  
Vol 122 (1) ◽  
pp. 269-275
Author(s):  
A. T. Tsin ◽  
J. M. Flores
Keyword(s):  
Body Weight ◽  
Rate Constant ◽  
Half Life ◽  
Visual Pigment ◽  
Initial Period ◽  
Direct Result ◽  
Order Kinetic ◽  
Kinetic Rate Constant ◽  
First Order

Goldfish with retinas rich in either rhodopsin or porphyropsin were illuminated with bright light and then placed in the dark room to allow visual pigment regeneration. The kinetics of this in vivo pigment regeneration were followed by sampling these animals at regular time intervals. The first-order kinetic rate constant for the initial period of porphyropsin regeneration at 20 degrees C was 8.3 X 10(−3) nmol kg-1 body weight min-1 and the half-life of this reaction was 83 min. At 30 degrees C, the rate constant was increased to 1.4 X 10(−2) nmol kg-1 body weight min-1, yielding a reduced half-life of 49 min. This suggests that the Q10 of porphyropsin regeneration is about 1.7. In goldfish retinas enriched with rhodopsin (62% rhodopsin and 38% porphyropsin), the initial phase of visual pigment regeneration (at 30 degrees C) proceeded at a slower rate (first-order rate constant: 6.5 X 10(−3) nmol kg-1 body weight min-1; half-life of reaction = 106 min) than the rate of porphyropsin regeneration. This suggests that the high proportion of rhodopsin in the retina of goldfish held at 30 degrees C is not a direct result of a faster rate of regeneration of rhodopsin than of porphyropsin.

Biodegradation of Bisphenol-A in aerobic membrane bioreactor sludge

2013 ◽  
Vol 68 (9) ◽  
pp. 1926-1931 ◽  
Author(s):  
Brahima Seyhi ◽  
Patrick Drogui ◽  
Gerardo Buelna ◽  
Jean François Blais
Keyword(s):  
Bisphenol A ◽  
Chemical Oxygen Demand ◽  
Rate Constant ◽  
Membrane Bioreactor ◽  
Oxygen Demand ◽  
Degradation Process ◽  
Order Kinetic ◽  
Kinetic Rate Constant ◽  
Kinetic Rate ◽  
First Order

Bisphenol-A (BPA) biodegradation was studied in a membrane bioreactor under aerobic conditions. The effects of the initial BPA concentration and initial chemical oxygen demand (COD) concentration on BPA biodegradation were investigated. The degradation process followed a first-order kinetic (more than 98% of BPA was removed) with a kinetic rate constant of 1.134 h−1 using an initial BPA concentration of 1.0 mg L−1. The kinetic rate constant decreased to 0.611 h−1 when the initial BPA concentration increased to 5.0 mg L−1. The initial COD concentration (400 and 2,000 mg L−1) did not affect the biodegradation kinetic of BPA.

Observation of a radical intermediate in the one electron oxidation of 5-methyl-1-thia-5-azacyclooctane by •Br2−

1984 ◽  
Vol 62 (9) ◽  
pp. 1874-1876 ◽  
Author(s):  
Warren Kenneth Musker ◽  
Parminder S. Surdhar ◽  
Rizwan Ahmad ◽  
David A. Armstrong
Keyword(s):  
Aqueous Solution ◽  
Rate Constant ◽  
Half Life ◽  
Cation Radical ◽  
Order Rate Constant ◽  
Type Structure ◽  
Radical Intermediate ◽  
Text Type ◽  
First Order ◽  
The One

The one electron oxidant •Br2− reacts with 5-methyl-1-thia-5-azacyclooctane (4) in aqueous solution at high pH with an overall rate constant of ~2 × 108 M s−1. The radical intermediate produced has a broad maximum at 500 nm with ε = 2400 M−1 cm−1 and at pH 10 decays with a first order rate constant of 2.3 ± 0.3 × 104 s−1, first half-life of 30 ± 5 μs. Its characteristics do not correspond to those of the [Formula: see text] species reported by Asmus and co-workers. The species appears to be the same as the cation radical reported earlier in the one electron oxidation of 4 in acetonitrile. This species is considered to have an [Formula: see text] type structure, which provides transannular stabilization.

Pharmacokinetics of Intermittent Intraperitoneal Cefazolin in Continuous Ambulatory Peritoneal Dialysis Patients

1999 ◽  
Vol 19 (1) ◽  
pp. 65-70 ◽  
Author(s):  
Harold J. Manley ◽  
George R. Bailie ◽  
Rupesh D. Asher ◽  
George Eisele ◽  
Reginald F. Frye
Keyword(s):  
Body Weight ◽  
Peritoneal Dialysis ◽  
Continuous Ambulatory Peritoneal Dialysis ◽  
Rate Constant ◽  
Half Life ◽  
Elimination Rate ◽  
Pharmacokinetic Parameters ◽  
Number Of Patients ◽  
The Mean ◽  
Concentration Levels

Objective To investigate the pharmacokinetic parameters of intermittent intraperitoneal (IP) cefazolin, and recommend a cefazolin dosing regimen in continuous ambulatory peritoneal dialysis (CAPD) patients. Design Prospective nonrandomized open study. Setting CAPD outpatient clinic in Albany, New York. Patients Seven volunteer CAPD patients without peritonitis. Three of the patients were nonanuric while 4 were anuric. Interventions Cefazolin (15 mg/kg total body weight) was given to each patient during the first peritoneal exchange. Blood and dialysate samples were collected at times 0, 0.5, 1, 2, 3, 6 (end of the first antibiotic-containing dwell), 24, and 48 hours after the administration of IP cefazolin. Urine samples were collected in nonanuric patients over the study period. Results The mean ± SD amount of cefazolin dose absorbed from the dialysate after the 6-hour dwell was 69.7% ± 8.0% of the administered dose. The cefazolin absorption rate constant from dialysate to serum was 0.21 ± 0.1 /hr (absorption half-life 3.5 ± 0.8 hr). The mean serum concentrations reached at 24 and 48 hours were 52.4 ± 3.7 mg/L and 30.3 ± 5.9 mg/L, respectively. The mean dialysate cefazolin concentrations reached at 24 and 48 hours were 15.1 ± 3.4 mg/L and 7.9 ± 1.4 mg/L, respectively. The cefazolin serum elimination rate constant was 0.02 ± 0.01 /hr (elimination half-life 31.5 ± 8.8 hr). The total cefazolin body clearance was 3.4 ± 0.6 mL/min. In the 3 nonanuric patients the mean renal clearance of cefazolin was 0.6 ± 0.4 mL/min. The peritoneal clearance of cefazolin was 1.0 ± 0.3 mL/min. The systemic volume of distribution of cefazolin was 0.2 ± 0.05 L/kg. No statistical difference was detected in pharmacokinetic parameters between anuric and nonanuric patients, although this may be due to the small number of patients in each group. Conclusion A single daily dose of cefazolin dosed at 15 mg/kg actual body weight in CAPD patients is effective in achieving serum concentration levels greater than the minimum inhibitory concentration for sensitive organisms over 48 hours, and dialysate concentration levels over 24 hours. Caution is warranted in extrapolation of dosing recommendations to patients who maintain a significant degree of residual renal function.

THE DECOMPOSITION OF SILYL PEROXIDES

1964 ◽  
Vol 42 (5) ◽  
pp. 985-989 ◽  
Author(s):  
Richard R. Hiatt
Keyword(s):  
Thermal Decomposition ◽  
Rate Constant ◽  
Half Life ◽  
Order Rate Constant ◽  
Butyl Alcohol ◽  
Base Catalysis ◽  
First Order ◽  
Tert Butyl ◽  
Tert Butyl Alcohol ◽  
Acid And Base

The thermal decomposition of tert-butyl trimethylsilyl peroxide has been investigated and found to be sensitive to acid and base catalysis and to the nature of the solvent. In heptane and iso-octane the first-order rate constant could be expressed as 1.09 × 1015e−41200/RT and in 1-octene as 3.90 × 1015e−41200/RT (sec−1). The half life at 203 °C was about 1 hour. The reaction was faster in aromatic solvents; in chlorobenzene it was complicated by formation of HCl from the solvent.Products of the reaction were acetone, tert-butyl alcohol and hexamethyldisiloxane.

scholarly journals Activity and Diffusion of Tigecycline (GAR-936) in Experimental Enterococcal Endocarditis

2003 ◽  
Vol 47 (1) ◽  
pp. 216-222 ◽  
Author(s):  
Agnès Lefort ◽  
Matthieu Lafaurie ◽  
Laurent Massias ◽  
Yolande Petegnief ◽  
Azzam Saleh-Mghir ◽  
...  
Keyword(s):  
Body Weight ◽  
Half Life ◽  
Type Strain ◽  
Postantibiotic Effect ◽  
Bacteriostatic Effect ◽  
Elimination Half ◽  
Resistant Mutants ◽  
And Diffusion

ABSTRACT The activity of tigecycline (GAR-936), a novel glycylcycline, was investigated in vitro and in experimental endocarditis due to the susceptible Enterococcus faecalis JH2-2 strain, its VanA type transconjugant BM4316, and a clinical VanA type strain, E. faecium HB217 resistant to tetracycline. MICs of GAR-936 were 0.06 μg/ml for the three strains. In vitro pharmacodynamic studies demonstrated a bacteriostatic effect of GAR-936 that was not enhanced by increasing concentrations to more than 1 μg/ml and a postantibiotic effect ranging from 1 to 4.5 h for concentrations of 1- to 20-fold the MIC. Intravenous injection of [14C]GAR-936 to five rabbits with enterococcal endocarditis sacrificed 30 min, 4 h, or 12 h after the end of the infusion evidenced a lower clearance of GAR-936 from aortic vegetations than from serum and a homogeneous diffusion of GAR-936 into the vegetations. In rabbits with endocarditis, GAR-936 (14 mg/kg of body weight twice a day [b.i.d.]) given intravenously for 5 days was bacteriostatic against both strains of E. faecalis. Against E. faecium HB217, bacterial counts in vegetations significantly decreased during therapy (P < 0.01), and the effect was similar with GAR-936 at 14 mg/kg b.i.d., 14 mg/kg once a day (o.d.), and 7 mg/kg o.d., which provided concentrations in serum constantly above the MIC. Mean serum elimination half-life ranged from 3.3 to 3.6 h. No GAR-936-resistant mutants were selected in vivo with any regimen. We concluded that the combination of prolonged half-life, significant postantibiotic effect, and good and homogeneous diffusion into the vegetations may account for the in vivo activity of GAR-936 against enterococci susceptible or resistant to glycopeptides and tetracyclines, even when using a o.d. regimen in rabbits.

Characterization of Dioctyl terephthalate biodegradation by food waste composting

2019 ◽  
Vol 33 (14n15) ◽  
pp. 1940048 ◽  
Author(s):  
Sung Tse Lee ◽  
Huu Tuan Tran ◽  
Chitsan Lin ◽  
Hong Giang Hoang ◽  
Thi Dieu Hien Vo ◽  
...  
Keyword(s):  
Removal Efficiency ◽  
Food Waste ◽  
Half Life ◽  
Order Kinetic ◽  
Aerobic Composting ◽  
First Order ◽  
Competitive Process ◽  
Plastic Products

Dioctyl terephthalate (DOTP), a plasticizer is used as an additive in many plastic products. Disposal of DOTP into environment has been of concern because it is hardly biodegradable in nature. Therefore, the aim of this study is to investigate the biodegradation of DOTP by aerobic composting processes without bioaugmentation. The initial DOTP concentration in the compost mixture was 11,882 mg/kg, after 35-day incubation, the removal efficiency of the compost reactor was 98%. The degradation was found to follow the first-order kinetic with the half-life of 5.2 days. Food waste composting was demonstrated as a technically robust and economically competitive process for the degradation of DOTP, and that of other similar plasticizers are expected.

scholarly journals Modification of Immobilized Titanium Dioxide Nanostructures by Argon Plasma for Photocatalytic Removal of Organic Dyes

Molecules ◽  
2019 ◽  
Vol 24 (3) ◽  
pp. 383 ◽  
Author(s):  
Hamid Khaledian ◽  
Pezhman Zolfaghari ◽  
Vahide Elhami ◽  
Mostafa Aghbolaghy ◽  
Sirous Khorram ◽  
...  
Keyword(s):  
Plasma Treatment ◽  
Malachite Green ◽  
Rate Constant ◽  
Exposure Time ◽  
Cold Plasma ◽  
Organic Dyes ◽  
Superior Performance ◽  
Synthetic Dyes ◽  
Order Kinetic ◽  
Kinetic Rate Constant

The aim of this study was to modify surface properties of immobilized rutile TiO2 using Argon cold plasma treatment and to evaluate the performance of the catalyst in photocatalytic elimination of synthetic dyes in UV/TiO2/H2O2 process. The surface-modified TiO2 was characterized by XRD, EDX, SEM, UV-DRS and XPS analyses. Response surface methodology was adopted to achieve high catalyst efficiency by evaluating the effect of two main independent cold plasma treatment parameters (exposure time and pressure) on surface modification of the catalyst. The increase of the plasma operation pressure led to higher decolorization percentage, while the increase of plasma exposure time decreased the decolorization efficiency. RSM methodology predicted optimum plasma treatment conditions to be 0.78 Torr and 21 min of exposure time, which resulted in decolorization of 10 mg/L solution of the malachite green solution by 94.94% in 30 min. The plasma treatment decreased the oxygen to titanium ratio and caused oxygen vacancy on the surface of the catalyst, resulting in the superior performance of the plasma-treated catalyst. Pseudo first-order kinetic rate constant for the plasma-treated catalyst was 4.28 and 2.03 times higher than the rate constant for the non-treated photocatalyst in decolorization of aqueous solutions of malachite green and crystal violet, respectively.

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