scholarly journals REGENERATION OF VISUAL PURPLE IN SOLUTION

1939 ◽  
Vol 23 (1) ◽  
pp. 21-39 ◽  
Author(s):  
Aurin M. Chase ◽  
Emil L. Smith
Keyword(s):  
Order Process ◽  
First Order ◽  
Color Changes ◽  
Violet Light ◽  
Frog Retina ◽  
Significant Difference ◽  
Kinetics Of ◽  
Photosensitive Substance ◽  
Subsequent Regeneration

1. Measurements of visual purple regeneration in solution have been made by a procedure which minimized distortion of the results by other color changes so that density changes caused by the regenerating substance alone are obtained. 2. Bleaching a visual purple solution with blue and violet light causes a greater subsequent regeneration than does an equivalent bleaching with light which lacks blue and violet. This is due to a photosensitive substance which has a gradually increasing effective absorption toward the shorter wavelengths. It is uncertain whether this substance is a product of visual purple bleaching or is present in the solution before illumination. 3. The regeneration of visual purple measured at 560 mµ is maximal at about pH 6.7 and decreases markedly at more acid and more alkaline pH's. 4. The absorption spectrum of the regenerating material shows only a concentration change during the course of regeneration, but has a higher absorption at the shorter wavelengths than has visual purple before illumination. 5. Visual purple extractions made at various temperatures show no significant difference in per cent of regeneration. 6. The kinetics of regeneration is usually that of a first order process. Successive regenerations in the same solution have the same velocity constant but form smaller total amounts of regenerated substance. 7. In vivo, the frog retina shows no additional oxygen consumption while visual purple is regenerating.

scholarly journals Comparative Study of Chemical Stability of Two H1Antihistaminic Drugs, Terfenadine and ItsIn VivoMetabolite Fexofenadine, Using LC-UV Methods

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Anna Gumieniczek ◽  
Anna Berecka-Rycerz ◽  
Rafał Pietraś ◽  
Izabela Kozak ◽  
Karolina Lejwoda ◽  
...  
Keyword(s):  
Comparative Study ◽  
Chemical Stability ◽  
First Order ◽  
First Order Kinetics ◽  
Kinetics Of Degradation ◽  
Effects Of Temperature ◽  
High Doses ◽  
Antihistaminic Drugs ◽  
Kinetics Of

A comparative study of chemical stability of terfenadine (TER) and itsin vivometabolite fexofenadine (FEX) was performed. Both TER and FEX were subjected to high temperature at different pH and UV/VIS light at different pH and then quantitatively analyzed using new validated LC-UV methods. These methods were used to monitor the degradation processes and to determine the kinetics of degradation for both the compounds. As far as the effects of temperature and pH were concerned, FEX occurred more sensitive to degradation than TER. As far as the effects of UV/VIS light and pH were concerned, the both drugs were similarly sensitive to high doses of light. Using all stress conditions, the processes of degradation of TER and FEX followed the first-order kinetics. The results obtained for these two antihistaminic drugs could be helpful in developing their new derivatives with higher activity and stability at the same time.

Spectrochemical Behavior of Carcinogenic Polycyclic Aromatic Hydrocarbons in Biological Systems. Part II: A Theoretical Rate Model for BaP Metabolism in Living Cells

1996 ◽  
Vol 50 (11) ◽  
pp. 1352-1359 ◽  
Author(s):  
Ping Chiang ◽  
Kuang-Pang Li ◽  
Tong-Ming Hseu
Keyword(s):  
Rate Constant ◽  
Living Cells ◽  
Rate Model ◽  
Number Density ◽  
Order Process ◽  
Irreversible Reaction ◽  
First Order ◽  
Metabolism Rate ◽  
Polycyclic Aromatic ◽  
Kinetics Of

An idealized model for the kinetics of benzo[ a]pyrene (BaP) metabolism is established. As observed from experimental results, the BaP transfer from microcrystals to the cell membrane is definitely a first-order process. The rate constant of this process is signified as k1. We describe the surface–midplane exchange as reversible and use rate constants k2 and k3 to describe the inward and outward diffusions, respectively. The metabolism is identified as an irreversible reaction with a rate constant k4. If k2 and k3 are assumed to be fast and not rate determining, the effect of the metabolism rate, k4, on the number density of BaP in the midplane of the microsomal membrane, m3, can be estimated. If the metabolism rate is faster than or comparable to the distribution rates, k2 and k3, the BaP concentration in the membrane midplane, m3, will quickly be dissipated. But if k4 is extremely small, m3 will reach a plateau. Under conditions when k2 and k3 also play significant roles in determining the overall rate, more complicated patterns of m3 are expected.

scholarly journals Fetal DNA Clearance from Maternal Plasma Is Impaired in Preeclampsia

2002 ◽  
Vol 48 (12) ◽  
pp. 2141-2146 ◽  
Author(s):  
Tai-Wah Lau ◽  
Tse N Leung ◽  
Lisa YS Chan ◽  
Tze K Lau ◽  
KC Allen Chan ◽  
...  
Keyword(s):  
Maternal Plasma ◽  
Circulating Dna ◽  
First Order ◽  
Real Time Quantitative Pcr ◽  
Fetal Dna ◽  
Significant Difference ◽  
Apparent Clearance ◽  
And Control ◽  
Kinetics Of ◽  
Clearance Model

Abstract Background: Increased fetal DNA in maternal plasma/serum has been reported in pregnancies complicated by preeclampsia. We hypothesized that impaired clearance of fetal DNA might contribute, at least in part, to the above-mentioned phenomenon. Methods: We studied 7 preeclamptic and 10 control pregnant women. All had male fetuses. Serial blood samples were obtained from before delivery to 6 h postpartum. Male fetal DNA in maternal plasma was measured by real-time quantitative PCR for the SRY gene on the Y chromosome. Results: The median fetal DNA concentrations before delivery were significantly higher in the preeclamptic women than in the controls (521 vs 227 genome-equivalents/mL for preeclamptic and control women, respectively; Mann–Whitney rank-sum test, P = 0.017). The median fetal DNA concentrations at 6 h after delivery were also significantly different between the two groups (208 vs 0 genome-equivalents/mL for preeclamptic and control women, respectively; Mann–Whitney rank-sum test, P = 0.002). A first-order clearance model was found to best describe the kinetics of maternal plasma fetal DNA clearance. Moreover, we observed a significant difference in the median apparent clearance half-lives of fetal DNA between the preeclamptic women (114 min) and controls (28 min; Mann–Whitney rank-sum test, P = 0.007). Conclusions: This study represents the first documentation of impaired fetal DNA clearance from maternal plasma in preeclampsia. Such an abnormality in circulating DNA clearance may also be present in other medical conditions associated with quantitative aberrations in circulating DNA concentrations.

3D culture model and computer-assisted videomicroscopy to analyze migratory behavior of noninvasive and invasive bronchial epithelial cells

2005 ◽  
Vol 289 (6) ◽  
pp. C1547-C1552 ◽  
Author(s):  
Salma Hazgui ◽  
Noël Bonnet ◽  
Jérôme Cutrona ◽  
Béatrice Nawrocki-Raby ◽  
Myriam Polette ◽  
...  
Keyword(s):  
Cell Migration ◽  
Cell Line ◽  
3D Model ◽  
Migratory Behavior ◽  
Computer Assisted ◽  
Data Set ◽  
Significant Difference ◽  
Kinetics Of ◽  
Invasive Cell

To date, most of the studies in the field of cell migration have been applied to two-dimensional (2D) models. To mimic the three-dimensional (3D) conditions similar to those observed in vivo during tumor invasion, we developed a 3D model of cell migration in which cells were embedded in a collagen I matrix placed in a double-compartment chamber. Using time-lapse videomicroscopy and interactive cell tracking in a four-dimensional data set, we determined the cell trajectories and their migration kinetics. We compared the 2D and 3D migratory behavior of a noninvasive cell line (16HBE) with the migratory behavior of an invasive cell line (BZR). Our results show that the 3D migration kinetics of the noninvasive cell line were lower than the migration kinetics of the invasive cell line. In contrast, in 2D models, no significant difference was observed between the two cell lines. To validate our 3D model, we further investigated the effect of epidermal growth factor (EGF), a promoter of tumor cell motility and invasion on the noninvasive cell line (16HBE). EGF increased significantly the migration kinetics of the noninvasive cell line. Our results show that the 3D model of cell migration allowed us to differentiate the migratory behavior of invasive and noninvasive cells and that such a model can help in the development of molecular targeted therapy as it approaches the in vivo conditions.

scholarly journals The combination of carbon monoxide–haem with apoperoxidase

1969 ◽  
Vol 114 (4) ◽  
pp. 719-724 ◽  
Author(s):  
Charles Phelps ◽  
Eraldo Antonini
Keyword(s):  
Activation Energy ◽  
Carbon Monoxide ◽  
Rate Constant ◽  
Binding Sites ◽  
Order Process ◽  
First Order ◽  
Effects Of Ph ◽  
Kinetics Of

1. Static titrations reveal an exact stoicheiometry between various haem derivatives and apoperoxidase prepared from one isoenzyme of the horseradish enzyme. 2. Carbon monoxide–protohaem reacts rapidly with apoperoxidase and the kinetics can be accounted for by a mechanism already applied to the reaction of carbon monoxide–haem derivatives with apomyoglobin and apohaemoglobin. 3. According to this mechanism a complex is formed first whose combination and dissociation velocity constants are 5×108m−1sec.−1 and 103sec.−1 at pH9·1 and 20°. The complex is converted into carbon monoxide–haemoprotein in a first-order process with a rate constant of 235sec.−1 for peroxidase and 364sec.−1 for myoglobin at pH9·1 and 20°. 4. The effects of pH and temperature were examined. The activation energy for the process of complex-isomerization is about 13kcal./mole. 5. The similarity in the kinetics of the reactions of carbon monoxide–haem with apoperoxidase and with apomyoglobin suggests structural similarities at the haem-binding sites of the two proteins.

Reaction Kinetics of Thrombin Activity in Decalcified Plasma and Blood

1969 ◽  
Vol 21 (03) ◽  
pp. 580-593
Author(s):  
L. A Pálos ◽  
G Sas ◽  
A Csurgay
Keyword(s):  
Reaction Kinetics ◽  
Mathematical Expression ◽  
Second Phase ◽  
Thrombin Time ◽  
First Order ◽  
Functional Relationships ◽  
First Order Kinetics ◽  
Set Up ◽  
Kinetics Of

SummaryThe reaction kinetics of the second phase of blood clotting (conversion of fibrinogen to fibrin) has been studied in euglobulin and thrombin-antithrombin systems. It was intended to set up relationships that would make mathematical expression of the processes possible and which would, moreover, help in detecting dynamic and functional relationships characteristic of the mechanism involved in coagulation.The experiments have yielded the following results:1. In the euglobulin solution containing no antithrombin the fibrinogen-thrombin reaction can be characterized with a constant deviation from the first order kinetics.2. The process of thrombin inactivation is a reaction of first order in the initial phase.3. The two basic processes (clotting by thrombin in euglobulin solution, inactivation of thrombin in defibrinated plasma) make it possible to predetermine the thrombin time of citrated plasma. Theoretical and actual clotting times were in good agreement.4. The thrombin time of plasma can be computed even if thrombin is not introduced to the system at one stride but gradually, a manner of administration which is a better imitation of what happening in vivo. 5. In connection with the computation of the “thrombin time” of citrated blood, we determined experimentally (and expressed by means of a function) the modification produced by the corpuscular elements of the blood in the reaction between fibrinogen and thrombin under atraumatic conditions.

Kinetics of glucose transport and sequestration in lactating bovine mammary glands measured in vivo with a paired indicator/nutrient dilution technique

2005 ◽  
Vol 99 (3) ◽  
pp. 799-806 ◽  
Author(s):  
Fulong Qiao ◽  
Donald R. Trout ◽  
Changting Xiao ◽  
John P. Cant
Keyword(s):  
Glucose Transport ◽  
Goodness Of Fit ◽  
Mammary Glands ◽  
Integration Model ◽  
Intracellular Space ◽  
First Order ◽  
Extracellular Glucose ◽  
Kinetics Of ◽  
Dilution Curves

To quantify kinetics of mammary glucose utilization in vivo, 24 paired glucose and extracellular indicator ( p-aminohippuric acid) dilution curves across intact bovine mammary glands were obtained after bolus injections into the external iliac artery. Dilution curves were analyzed using a compartmental capillary, convolution integration model. Four candidate submodels of glucose transport and metabolism in capillary supply zones were fit to the glucose dilution curves and evaluated. Model I, with one extracellular compartment for glucose and first-order unidirectional uptake, failed, indicating that efflux of glucose from the intracellular space could not be ignored. Model II, with first-order exchanges between extracellular and intracellular compartments and sequestration from the latter, was overdefined because unidirectional clearance of glucose was at least five times the blood flow rate and 20 times the net clearance rate. Model III, combining extracellular and intracellular space into one compartment, was superior in its goodness-of-fit to curves and identifiability of parameters. Michaelis-Menten parameters of sequestration were not identifiable. Parameters of the optimal compartmental capillary, convolution integration model were applicable to both the dynamics of injected glucose dilution and the steady-state background arteriovenous difference of glucose. Glucose sequestration followed first-order kinetics between 0 and 7 mM extracellular glucose with an average rate constant of 0.006 s−1 or a clearance of 44 ml/s. The ratio of intracellular to extracellular glucose distribution space was 0.34, which is considerably lower than the expected intracellular volume and suggests an intracellular occlusion compartment with which extracellular glucose rapidly exchanges.

scholarly journals Hepatic uptake and metabolism of galactose can be quantified in vivo by 2-[18F]fluoro-2-deoxygalactose positron emission tomography

2008 ◽  
Vol 295 (1) ◽  
pp. G27-G36 ◽  
Author(s):  
Michael Sørensen ◽  
Ole Lajord Munk ◽  
Frank Viborg Mortensen ◽  
Aage Kristian Olsen ◽  
Dirk Bender ◽  
...  
Keyword(s):  
Removal Rate ◽  
Hepatic Uptake ◽  
Metabolic Clearance ◽  
Blood Concentrations ◽  
First Order ◽  
First Order Kinetics ◽  
Significant Difference ◽  
Saturation Kinetics ◽  
Uptake And Metabolism

Metabolism of galactose is a specialized liver function. The purpose of this PET study was to use the galactose analog 2-[18F]fluoro-2-deoxygalactose (FDGal) to investigate hepatic uptake and metabolism of galactose in vivo. FDGal kinetics was studied in 10 anesthetized pigs at blood concentrations of nonradioactive galactose yielding approximately first-order kinetics (tracer only; n = 4), intermediate kinetics (0.5–0.6 mmol galactose/l blood; n = 2), and near-saturation kinetics (>3 mmol galactose/l blood; n = 4). All animals underwent liver C15O PET (blood volume) and FDGal PET (galactose kinetics) with arterial and portal venous blood sampling. Flow rates in the hepatic artery and the portal vein were measured by ultrasound transit-time flowmeters. The hepatic uptake and net metabolic clearance of FDGal were quantified by nonlinear and linear regression analyses. The initial extraction fraction of FDGal from blood-to-hepatocyte was unity in all pigs. Hepatic net metabolic clearance of FDGal, KFDGal, was 332–481 ml blood·min−1·l−1 tissue in experiments with approximately first-order kinetics and 15.2–21.8 ml blood·min−1·l−1 tissue in experiments with near-saturation kinetics. Maximal hepatic removal rates of galactose were on average 600 μmol·min−1·l−1 tissue (range 412–702), which was in agreement with other studies. There was no significant difference between KFDGal calculated with use of the dual tracer input (KdualFDGal) or the single arterial input (KarterialFDGal). In conclusion, hepatic galactose kinetics can be quantified with the galactose analog FDGal. At near-saturated kinetics, the maximal hepatic removal rate of galactose can be calculated from the net metabolic clearance of FDGal and the blood concentration of galactose.

Kinetics of Chain Scission of Natural Rubber

1989 ◽  
Vol 62 (5) ◽  
pp. 779-787
Author(s):  
M. S. Sambhi
Keyword(s):  
Oxidative Degradation ◽  
Oxidation Mechanism ◽  
Chain Scission ◽  
Bimolecular Reaction ◽  
Zero Order ◽  
Order Kinetic ◽  
Peroxy Radicals ◽  
Order Process ◽  
First Order ◽  
Kinetics Of

Abstract The first-order and zero-order kinetic models of chain scission, based on random chain scission processes, are critically examined. It is likely that for many practical situations, the first-order chain scission kinetics can be represented by pseudozero-order kinetic types of equations. The kinetic results indicate that chain scission of NR occurs either by a pseudofirst-order or a pseudozero-order process. The pseudozero-order chain scission kinetics of NR are in consonance with the result that chain scission involves the bimolecular reaction of peroxy radicals in the termination step of the oxidation mechanism. However, this does not preclude unambiguously other chain scission reactions. The chain scission activation energy of NR is determined with the use of expressions derived for the oxidative degradation of NR as measured in terms of Wallace plasticities.

scholarly journals The kinetics of γ-H2AX during radiotherapy of head and neck cancer potentially allow for prediction of severe mucositis

2020 ◽  
Vol 54 (1) ◽  
pp. 96-102
Author(s):  
Joanna Kazmierska ◽  
Wojciech Barczak ◽  
Tomasz Winiecki ◽  
Łukasz Łuczewski ◽  
Magdalena Marciniak ◽  
...  
Keyword(s):  
Head And Neck Cancer ◽  
Head And Neck ◽  
Neck Cancer ◽  
Peripheral Blood Lymphocytes ◽  
Significant Difference ◽  
Radiation Induced ◽  
The Difference ◽  
Kinetics Of ◽  
Severe Mucositis

AbstractBackgroundThe aim of the study was to evaluate the changes in γ-H2AX expression in peripheral blood lymphocytes (PBL) according to severity of radiation-induced mucositis.Patients and methodFifty patients with head and neck cancer treated with radiotherapy (RT) or chemoradiation were included in the study. Blood samples were collected before treatment to measure baseline γ-H2AX levels. Second sample was taken 45 minutes after the first RT fraction and then once a week, 45 min after irradiation. In patients treated with chemoradiation the blood sample was taken the day after chemotherapy. Mucositis was evaluated once a week and reported according to CTCAE v4 and RTOG/EORTC scales. PBL were analyzed with flow cytometry and level of H2AX phosphorylation at every time point was evaluated.ResultsIn 35 patients mild to moderate (grade 1–2) mucositis was observed and 15 patients developed severe (grade 3) mucositis. No cases of grade 4 mucositis were observed. The difference in baseline levels of γ-H2AX between groups with mild and severe mucositis was statistically insignificant (p = 0.25). The statistically significant difference in γ-H2AX level was observed in week 7 of treatment (p = 0.01). No significant differences in γ-H2AX level were found neither between group treated with concomitant chemoradiation or RT alone neither between groups with and without common comorbidities. In the analysis of the kinetics of γ-H2AX during treatment, a statistically significant difference (p = 0.0088) between groups with mild and severe mucositis was observed. After fourth week of treatment levels of γ-H2AX decreased significantly in the group with severe mucositis and increased in patients with mild side effects. The observed difference was not caused by the decrease in peripheral lymphocyte count, which was similar in both groups.ConclusionsPresented results indicate that severity of radiation-induced mucositis does not correlate directly with γ-H2AX levels measured in vivo in PBL. Prediction of mucositis grade based on γ-H2AX level is not yet possible, either before treatment or early during treatment, but preliminary results, indicating significant differences in γ-H2AX kinetics between groups, encourage further studies.

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