scholarly journals KCl Transport Across an Insect Epithelium: Characterization of K-Stimulated Cl Absorption and Active K Transport

1984 ◽  
Vol 111 (1) ◽  
pp. 201-223
Author(s):  
J. W. HANRAHAN ◽  
J. E. PHILLIPS
Keyword(s):  
Fold Increase ◽  
Open Circuit ◽  
Cl Transport ◽  
Kcl Transport ◽  
Low Levels ◽  
Mucosal Side ◽  
Kinetics Of ◽  
K Transport ◽  
Stimulation Of

The kinetics of 36C1 fluxes across cAMP-stimulated, short-circuited locust rectum were studied. Raising external K+ from 0 to 100 mM increased both Kt and Vmax for net Cl transport (JnetCl) by four- to six-fold. Hill plots of JnetCl indicated non-cooperative Cl interactions. The sequence for cation stimulation of JnetCl was K > Rb > Cs > Na > NH4. Low levels of K were stimulatory only when added to the mucosal side. Cyclic AMP (cAMP) caused a small active absorption of K, although this was minor compared to the four-fold increase in transepithelial K diffusion (PK). Neither cAMP stimulation of JnetK nor of PK was sensitive to Cl removal, suggesting that K-stimulated Cl absorption and K transport are not mediated by the same co-transport mechanism. Potassium is the counter-ion for electrogenic Cl transport because JnetK was less than 10% of the JnetK during cAMP exposure under Isc conditions, but JnetK equalled JnetCl at open-circuit.

Secretion of H+ and K+ by bullfrog gastric mucosa: characterization of K+ transport pathway

1980 ◽  
Vol 239 (6) ◽  
pp. G485-G492
Author(s):  
P. C. Sen ◽  
L. L. Tague ◽  
T. K. Ray
Keyword(s):  
Gastric Mucosa ◽  
Nutrient Solution ◽  
Rana Catesbeiana ◽  
Transport Pathway ◽  
Mucosal Side ◽  
Apical Membranes ◽  
K Transport ◽  
Co2 Addition

The transport of K+ and H+ (both expressed as mueq/h) by in vitro chambered bullfrog (Rana catesbeiana) gastric mucosa have been studied under a variety of conditions such as anoxia, addition of p-chloromercuribenzene sulfonic acid (PCMBS) into the secretory solution, inclusion of ouabain in the nutrient solution, addition of thiocyanate (SCN-) into the mucosal solution, and replacement of nutrient chloride (Cl-) with sulfate (SO4(2-)), or gluconate (Gl). Anoxia reversibly reduced the H+ transport close to zero within 15 min and gradually reduces the K+ transport throughout the 2-h period of anoxia. The presence of 2.5 X 10(-4) M mucosal PCMBS in the histamine-stimulated mucosa increases the K+ transport, which is promptly reduced by changing the gas phase to 95% N2-5% CO2. Addition of ouabain to the nutrient solution of the histamine-stimulated mucosa with PCMBS on the mucosal side significantly (P < 0.05) reduces the K+ transport within 60 min. Addition of SCN- to the mucosal solution of a histamine-stimulated mucosa with regular nutrient or O, K+ nutrient and 10, K+ mucosal solution reduces the H+ transport to near zero within 60 min. This SCN- inhibition can be reversed by elevating secretory K+. Substitution of nutrient Cl- with SO4(2-) or Gl in the histamine-stimulated mucosa reversibly inhibits H+ transport and reduces K+ transport to a low level (0.7 +/- 0.05). Our data suggest that the K+ transport across the apical membranes of gastric cells is to a large extent a passive carrier-mediated process, and the transport of both K+ and Cl- are coupled at the apical membrane.

Kinetics of Platelet Adhesion to Artificial Surfaces in Vitro

1975 ◽  
Author(s):  
J. L. Brash ◽  
I. A. Feuerstein
Keyword(s):  
Fold Increase ◽  
Red Cells ◽  
Sulfonated Polystyrene ◽  
Segmented Polyurethane ◽  
Coated Glass ◽  
Platelet Concentration ◽  
Low Levels ◽  
Kinetics Of ◽  
Adhesion Of Platelets

Adhesion of platelets to glass, collagen-coated glass, albumin-coated glass, polystyrene, sulfonated polystyrene and a segmented polyurethane, has been studied in vitro. The apparatus is of the Couette flow type and allows close control of fluid shear and diffusional factors. Suspensions of washed pig platelets constitute the basic platelet medium. This can be modified by adding back red cells and specific plasma proteins in varying concentration and the platelet concentration can be varied without compromising viability. Adhesion is measured by radiolabelling methods.In the absence of red cells, low levels of adhesion were seen on all surfaces with saturation occurring at 4 to 6 platelets/1000 μ2 in 2 to 4 minutes. In the presence of red cells adhesion was much greater. Collagen was the most reactive surface and adhesion data was consistent with a platelet diffusivity 10 to 100 times that predicted by Brownian motion. The diffusivity was dependent on shear rate and hematocrit. All other surfaces showed a 2-fold increase in adhesion compared to the values without red cells. However adhesion was independent of hematocrit above 10% and reached a constant value of about 12 (less for albumin monolayer) in 2 to 10 minutes.

Basis for apparent saturation kinetics of Na+ influx in freshwater hyperregulators

1988 ◽  
Vol 254 (6) ◽  
pp. R984-R988
Author(s):  
L. B. Kirschner
Keyword(s):  
Transport System ◽  
Open Circuit ◽  
Na Transport ◽  
Proton Efflux ◽  
Electrical Neutrality ◽  
Saturation Kinetics ◽  
Kinetics Of ◽  
Stimulation Of ◽  
Cl Permeability

Uptake of Na+ by intact frogs has been reported to show saturation kinetics at low external concentrations (less than 2 mM); yet other evidence shows that the transport system is far from saturated in this concentration range. The saturation behavior was reproduced here in isolated frog skins that were then used as appropriate models for investigating the paradox. When the skin was bathed by 2 mM Na+ outside and open circuited, influx (JNain) was near maximum. If, under these conditions, the skin was short circuited, JNain increased threefold. Alternatively, if Cl- permeability was increased in the open-circuited skin, JNain doubled. Both perturbations uncouple JNain from the efflux of a cation (nominally H+), which normally maintains electrical neutrality under open-circuit conditions. This suggests that the apparent saturation of JNain is caused by limiting efflux of the counterion. In confirmation of this prediction, stimulation of proton efflux markedly increased JNain. Thus the apparent Michaelis-Menten kinetics observed in frogs, and probably in other freshwater animals as well, do not represent saturation of an element in Na+ transport, either the amiloride-sensitive apical channel or the basolateral Na+-K+-ATPase.

Effects of biguanides on short-circuit current in frog skin

1984 ◽  
Vol 247 (2) ◽  
pp. F277-F281
Author(s):  
T. Saito ◽  
S. Yoshida
Keyword(s):  
Sodium Transport ◽  
Frog Skin ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Open Circuit ◽  
Apical Surface ◽  
Sodium Permeability ◽  
Total Conductance ◽  
Mucosal Side ◽  
Stimulation Of

The addition of phenformin to the solution bathing the mucosal side of frog skin resulted in a sustained stimulation of short-circuit current accompanied by an increase in open-circuit potential and total conductance of the membrane. The flux of 22Na from the mucosal to the serosal side of the skin was increased by phenformin, whereas no significant effect on the flux from the serosal to the mucosal side was observed. The increases in the short-circuit current and total conductance with phenformin were completely abolished by the addition of 5 X 10(-5) M amiloride, which blocks sodium permeability at the apical surface of the membrane. Thus, the stimulation of active sodium transport in frog skin by phenformin would be due to the increase in the amiloride-sensitive sodium permeability of the membrane. Phenformin may prove to be a useful tool for the study of sodium transport in amphibian epithelia.

Characterization of non-cytosolic hexokinase activity in white skeletal muscle from goldfish (Carassius auratus L.) and the effect of cold acclimation

2010 ◽  
Vol 30 (6) ◽  
pp. 413-423 ◽  
Author(s):  
Reinaldo Sousa dos Santos ◽  
Luan Pereira Diniz ◽  
Antonio Galina ◽  
Wagner Seixas da-Silva
Keyword(s):  
Skeletal Muscle ◽  
Cold Acclimation ◽  
Carassius Auratus ◽  
White Muscle ◽  
Fold Increase ◽  
Mitochondrial Fraction ◽  
Goldfish Carassius Auratus ◽  
Phosphate Donor ◽  
Kinetics Of

HK (hexokinase) is an enzyme involved in the first step in the glucose metabolism pathway, converting glucose into G6P (glucose 6-phosphate). Owing to the importance of skeletal muscle for fish swimming and acclimation processes, we used goldfish (Carassius auratus L.) white muscle in order to investigate subcellular distribution and kinetics of HK. In this study, we report that HK activity is predominantly localized in the mitochondrial fraction [NC-HK (non-cytosolic HK)] in goldfish white muscle. Studies of the kinetic parameters revealed that the Km (Michaelis–Menten constant) for glucose was 0.41±0.03 mM and that for mannose was 3-fold lower, whereas the affinity for fructose was too low to be measured. The Km for ATP was 0.88±0.05 mM, whereas no activity was observed when either GTP or ITP was used as a phosphate donor. A moderate inhibition (20–40%) was found for ADP and AMP. Similar to mammalian HK, G6P and glucose analogues were able to promote an inhibition of between 85 and 100% of activity. Here, we found that acclimation of goldfish at 5°C promoted a 2.5-fold increase in NC-HK compared with its counterpart acclimated at 25°C. However, cytosolic HK activity was not altered after thermal acclimation. In summary, our results suggest that the goldfish has a constitutive NC-HK that shows some similarities to mammalian HK-II and, curiously, may play a role in the broad metabolic changes required during the cold acclimation process.

scholarly journals Efecto del tipo de acero y su acabado superficial sobre la cinética de fosfatizado con manganeso

2020 ◽  
pp. 1-17
Author(s):  
Josúe Gómez-Macías ◽  
Ricardo Conejo-Flores ◽  
Juan Manuel García-Gonzále ◽  
Juan Carlos Fuentes-Aceituno
Keyword(s):  
Steel Surface ◽  
Open Circuit Potential ◽  
Open Circuit ◽  
Phosphate Coating ◽  
Energy Dispersion Spectroscopy ◽  
X Ray ◽  
Manganese Phosphate ◽  
Kinetics Of ◽  
Scanning Electron

The objective of this work is to study the process of phosphatizing with manganese by immersion. In the literature there is not enough information on the phosphate process with manganese phosphate, hence the main contribution of the present. The methodology involves an electrochemical study, using open circuit potential techniques in order to follow the kinetics of the process. In the same way, the characterization of the coating formed on the surface of each steel used was carried out using scanning electron microscopy and X-ray energy dispersion spectroscopy. Through this technique, the time was found in which the internal layer of the coating developed on the phosphatized substrates, both on the rough and the rough sides of the steel samples. The results obtained show that the formation of the manganese phosphate coating on the steels depends both on the grain size of the steels at the beginning of the process, as well as on the surface finish to which the steel surface is subjected, resulting in an increase in the size of the crystals, and affecting the rate of disintegration and growth of the same.

Irradiation behavior of pyrolytic silicon carbide

1983 ◽  
Vol 41 ◽  
pp. 72-73
Author(s):  
R. J. Lauf
Keyword(s):  
Silicon Carbide ◽  
Fission Products ◽  
Thermodynamics And Kinetics ◽  
Neutron Fluences ◽  
Fuel Particles ◽  
Sic Coatings ◽  
Irradiation Behavior ◽  
Kinetics Of ◽  
Htgr Fuel

Fuel particles for the High-Temperature Gas-Cooled Reactor (HTGR) contain a layer of pyrolytic silicon carbide to act as a miniature pressure vessel and primary fission product barrier. Optimization of the SiC with respect to fuel performance involves four areas of study: (a) characterization of as-deposited SiC coatings; (b) thermodynamics and kinetics of chemical reactions between SiC and fission products; (c) irradiation behavior of SiC in the absence of fission products; and (d) combined effects of irradiation and fission products. This paper reports the behavior of SiC deposited on inert microspheres and irradiated to fast neutron fluences typical of HTGR fuel at end-of-life.

Characterization of early and late cerebral evoke responses (CEP) to stimulation of afferent esophageal pathways in humans

2001 ◽  
Vol 120 (5) ◽  
pp. A630-A630
Author(s):  
C DIENEFELD ◽  
R BECKER ◽  
M KAMATH ◽  
G TOUGAS ◽  
M HAUPTS ◽  
...  
Keyword(s):  
Stimulation Of

Kinetics of Light-Induced Effects in Mixed-Phase Hydrogenated Silicon Solar Cells

2003 ◽  
Vol 762 ◽  
Author(s):  
Guozhen Yuea ◽  
Baojie Yan ◽  
Jeffrey Yang ◽  
Kenneth Lord ◽  
Subhendu Guha
Keyword(s):  
Solar Cells ◽  
Fill Factor ◽  
Equivalent Circuit Model ◽  
Open Circuit ◽  
Mixed Phase ◽  
Silicon Solar Cells ◽  
Initial Increase ◽  
Soaking Time ◽  
Hydrogenated Silicon ◽  
Kinetics Of

AbstractWe have observed a significant light-induced increase in the open-circuit voltage (Voc) of mixed-phase hydrogenated silicon solar cells. In this study, we investigate the kinetics of the light-induced effects. The results show that the cells with different initial Voc have different kinetic behavior. For the cells with a low initial Voc (less than 0.8 V), the increase in Voc is slow and does not saturate for light-soaking time of up to 16 hours. For the cells with medium initial Voc (0.8 ∼ 0.95 V), the Voc increases rapidly and then saturates. Cells with high initial Voc (0.95 ∼ 0.98 V) show an initial increase in Voc, followed bya Voc decrease. All light-soaked cells exhibit a degradation in fill factor. The temperature dependence of the kinetics shows that light soaking at high temperatures causes Voc increase to saturate faster than at low temperatures. The observed results can be explained by our recently proposed two-diode equivalent-circuit model for mixed-phase solar cells.

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