scholarly journals Carrier-mediated Potassium Efflux Across the Cell Membrane of Red Beet

1969 ◽  
Vol 44 (4) ◽  
pp. 485-490 ◽  
Author(s):  
Ronald J. Poole
Keyword(s):  
Cell Membrane ◽  
Potassium Efflux ◽  
Red Beet

Potassium exchange and mechanical performance in anoxic mammalian myocardium

1977 ◽  
Vol 232 (1) ◽  
pp. H85-H94 ◽  
Author(s):  
E. E. Rau ◽  
K. I. Shine ◽  
G. A. Langer
Keyword(s):  
Cell Membrane ◽  
Mechanical Performance ◽  
Tyrode Solution ◽  
Potassium Efflux ◽  
Metabolic Substrate ◽  
Potassium Loss ◽  
Probe Analysis ◽  
Mammalian Myocardium ◽  
Rate Limiting ◽  
Potassium Exchange

Mechanical performance and 42K exchange were studied during anoxia in isoalted, arterially perfused, interventricular rabbit septa at 42 beats/min and 28 degree C. The septa were perfused at 1.8 ml/min per g with a modified Tyrode solution having dextrose as the metabolic substrate. Developed tension declined to 16% of preanoxic control values during 60 min of anoxia, and returned to 65% of control during a 60–70 min recovery. Anoxia induced net potassium losses of 31+/-2, 53+/-2, and 90+/-14 mmol K+/kg dry tissue (means+/-SE) during 20, 40, and 60 min of anoxic stresses, determined by tissue probe analysis after asymptotic labeling. Potassium losses attributed to increased efflux of the ion from the cells during 20, 40, and 60 min of anoxia were determined from effluent analyses to be 32+/-4, 60+/-6, and 98+/-11 mmol K+/kg dry wt. Potassium loss began within seconds of the onset of anoxia and reoxygenation immedaitely reversed the potassium loss. These data indicate that 1) function of the membrane Na-K pump is maintained through 60 min of anoxia with the entire net potassium loss attributable to increased efflux from the cells, 2) anoxia decreases the rate of exchange of potassium after recovery, and 3) the cell membrane appears to be the rate-limiting site of potassium efflux during anoxia.

scholarly journals Effect of eugenol on growth and listeriolysin o production by Listeria monocytogenes

2006 ◽  
Vol 49 (3) ◽  
pp. 405-409 ◽  
Author(s):  
Cristina Tostes Filgueiras ◽  
Maria Cristina Dantas Vanetti
Keyword(s):  
Listeria Monocytogenes ◽  
Essential Oil ◽  
Cell Membrane ◽  
Inhibitory Effect ◽  
Listeriolysin O ◽  
Potassium Efflux ◽  
Naturally Occurring ◽  
Oil Fraction ◽  
Phosphate Buffered Saline ◽  
External K

The inhibitory effect of eugenol, a naturally occurring compound mainly present in the essential oil fraction of cloves, was studied on the growth and listeriolysin O (LLO) production by Listeria monocytogenes. Potassium efflux from cells promoted by eugenol was also determined after 24 h incubation in phosphate buffered saline. Eugenol promoted a delay on the growth of L. monocytogenes at concentrations of 100, 300 and 500 µg mL-1and above 800 µg mL-1 the effect was bactericidal. Production of LLO by L. monocytogenes in the presence of eugenol was reduced 80-100%. An accumulation of external K+ was observed above 300 µg mL-1 of eugenol which indicated that the cell membrane was affected. The results showed the effectiveness of eugenol in controlling growth and LLO production of L. monocytogenes cells.

scholarly journals The Effect of Saturated Fatty Acids on Methanogenesis and Cell Viability ofMethanobrevibacter ruminantium

Archaea ◽  
2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Xuan Zhou ◽  
Leo Meile ◽  
Michael Kreuzer ◽  
Johanna O. Zeitz
Keyword(s):  
Fatty Acids ◽  
Cell Membrane ◽  
Cell Viability ◽  
Membrane Permeability ◽  
Production Rate ◽  
Methane Production ◽  
Saturated Fatty Acids ◽  
Cell Membrane Permeability ◽  
Potassium Efflux ◽  
Methane Production Rate

Saturated fatty acids (SFAs) are known to suppress ruminal methanogenesis, but the underlying mechanisms are not well known. In the present study, inhibition of methane formation, cell membrane permeability (potassium efflux), and survival rate (LIVE/DEAD staining) of pure ruminalMethanobrevibacter ruminantium(DSM 1093) cell suspensions were tested for a number of SFAs. Methane production rate was not influenced by low concentrations of lauric (C12; 1 μg/mL), myristic (C14; 1 and 5 μg/mL), or palmitic (C16; 3 and 5 μg/mL) acids, while higher concentrations were inhibitory. C12and C14were most inhibitory. Stearic acid (C18), tested at 10–80 μg/mL and ineffective at 37°C, decreased methane production rate by half or more at 50°C and ≥50 μg/mL. Potassium efflux was triggered by SFAs (C12= C14> C16> C18= control), corroborating data on methane inhibition. Moreover, the exposure to C12and C14decreased cell viability to close to zero, while 40% of control cells remained alive after 24 h. Generally, tested SFAs inhibited methanogenesis, increased cell membrane permeability, and decreased survival ofM. ruminantiumin a dose- and time-dependent way. These results give new insights into how the methane suppressing effect of SFAs could be mediated in methanogens.

Effect of angiotensin II, ATP, and ionophore A23187 on potassium efflux in adrenal glomerulosa cells

1986 ◽  
Vol 250 (2) ◽  
pp. E125-E130
Author(s):  
M. V. Lobo ◽  
E. T. Marusic
Keyword(s):  
Angiotensin Ii ◽  
Cell Membrane ◽  
Ionophore A23187 ◽  
Potassium Efflux ◽  
K Channels ◽  
Glomerulosa Cells ◽  
Hormonal Stimulus ◽  
K Permeability ◽  
K Release ◽  
External K

Angiotensin II stimulus on perifused bovine adrenal glomerulosa cells elicited an increase in 86Rb efflux from cells previously equilibrated with the radioisotope. When 45Ca fluxes were measured under similar conditions, it was observed that Ca and Rb effluxes occurred within the first 30 s of the addition of the hormone and were independent of the presence of external Ca. The 86Rb efflux due to angiotensin II was inhibited by quinine and apamin. The hypothesis that the angiotensin II response is a consequence of an increase in the K permeability of the glomerulosa cell membrane triggered by an increase in cytosolic Ca is supported by the finding that the divalent cation ionophore A23187 also initiated 86Rb or K loss (as measured by an external K electrode). This increased K conductance was also seen with 10(-4) M ATP. Quinine and apamin greatly reduced the effect of ATP or A23187 on 86Rb or K release in adrenal glomerulosa cells. The results suggest that Ca-dependent K channels or carriers are present in the membranes of bovine adrenal glomerulosa cells and are sensitive to hormonal stimulus.

The mode of action of helminthosporal. II. Effect on the permeability of plant cell membranes

1972 ◽  
Vol 50 (6) ◽  
pp. 1415-1420 ◽  
Author(s):  
G. A. White ◽  
E. Taniguchi
Keyword(s):  
Cell Membrane ◽  
Plant Cell ◽  
Mode Of Action ◽  
Cell Membranes ◽  
Root Tissue ◽  
Tissue Cell ◽  
Beet Root ◽  
Respiratory Inhibition ◽  
Red Beet ◽  
Plant Cell Membranes

The phytotoxin, helminthosporal (H-al), can damage the permeability of plant cell membranes and it is suggested that this may be an important factor in the susceptibility or predisposition of cereal tissues to attack by Bipolaris sorokiniana, the fungus which produces the toxin. Helminthosporal was tested for its effect on the apparent free space (AFS) of barley roots and the efflux of betacyanin from red beet root tissue. Cell membrane disruption was indicated by an increase in the AFS of H-al-treated barley roots. The effect of H-al on the AFS of barley roots did not appear to be correlated with respiratory inhibition by the toxin since cyanide, azide, and 2,4-dinitrophenol failed to increase the AFS. Oxygen uptake by red beet root tissue was strongly inhibited by H-al at concentrations of 1.0 mM and 2.0 mM, and was accompanied by an immediate and large efflux of betacyanin. No correlation was found, however, between the extent of respiratory inhibition and the amount of pigment released. Helminthosporal reacts directly with both the plasmalemma and the tonoplast membranes of the beet root cell, exclusive of effects on respiration, since the loss of betacyanin was equally rapid under aerobic or anaerobic conditions. The integrity of the beet cell tonoplast membrane appeared to be unrelated to respiration and energy supply. Calcium ions, which act to stabilize membranes, partially alleviated the loss of pigment from red beet tissue exposed to n-propanol and H-al. Permeability change in the plant cell membrane may be as important in the mode of action of H-al as are the effects of the toxin on respiration and oxidative phosphorylation.

Sarcolemmal permeability changes during early myocardial anoxia

1978 ◽  
Vol 36 (2) ◽  
pp. 642-643
Author(s):  
M. Ashraf ◽  
L. Landa ◽  
L. Nimmo ◽  
C. M. Bloor
Keyword(s):  
Cell Membrane ◽  
Membrane Permeability ◽  
Coronary Artery Occlusion ◽  
Artery Occlusion ◽  
Cell Membrane Permeability ◽  
Enzyme Release ◽  
Sprague Dawley ◽  
Sprague Dawley Rats ◽  
Sarcolemmal Permeability ◽  
Membrane Changes

Following coronary artery occlusion, the myocardial cells lose intracellular enzymes that appear in the serum 3 hrs later. By this time the cells in the ischemic zone have already undergone irreversible changes, and the cell membrane permeability is variably altered in the ischemic cells. At certain stages or intervals the cell membrane changes, allowing release of cytoplasmic enzymes. To correlate the changes in cell membrane permeability with the enzyme release, we used colloidal lanthanum (La+++) as a histological permeability marker in the isolated perfused hearts. The hearts removed from sprague-Dawley rats were perfused with standard Krebs-Henseleit medium gassed with 95% O2 + 5% CO2. The hypoxic medium contained mannitol instead of dextrose and was bubbled with 95% N2 + 5% CO2. The final osmolarity of the medium was 295 M osmol, pH 7. 4.

Flagellar Attachment in Selected Trypanosomes

1973 ◽  
Vol 31 ◽  
pp. 496-497
Author(s):  
J. J. Paulin
Keyword(s):  
Cell Membrane ◽  
Lateral Surface ◽  
The Body ◽  
Flagellar Pocket ◽  
Integral Component ◽  
Free Flagellum ◽  
Flagellar Axoneme

Movement in epimastigote and trypomastigote stages of trypanosomes is accomplished by planar sinusoidal beating of the anteriorly directed flagellum and associated undulating membrane. The flagellum emerges from a bottle-shaped depression, the flagellar pocket, opening on the lateral surface of the cell. The limiting cell membrane envelopes not only the body of the trypanosome but is continuous with and insheathes the flagellar axoneme forming the undulating membrane. In some species a paraxial rod parallels the axoneme from its point of emergence at the flagellar pocket and is an integral component of the undulating membrane. A portion of the flagellum may extend beyond the anterior apex of the cell as a free flagellum; the length is variable in different species of trypanosomes.

Trophoblast Cell Membrane Interactions at Implantation

1970 ◽  
Vol 28 ◽  
pp. 310-311
Author(s):  
A. C. Enders
Keyword(s):  
Epithelial Cells ◽  
Cell Membrane ◽  
Membrane Fusion ◽  
Trophoblast Cell ◽  
Membrane Interactions ◽  
Uterine Epithelial Cells ◽  
Functional Complex ◽  
Cytotrophoblast Cells ◽  
Complex Relationships ◽  
Syncytial Trophoblast

The alteration in membrane relationships seen at implantation include 1) interaction between cytotrophoblast cells to form syncytial trophoblast and addition to the syncytium by subsequent fusion of cytotrophoblast cells, 2) formation of a wide variety of functional complex relationships by trophoblast with uterine epithelial cells in the process of invasion of the endometrium, and 3) in the case of the rabbit, fusion of some uterine epithelial cells with the trophoblast.Formation of syncytium is apparently a membrane fusion phenomenon in which rapid confluence of cytoplasm often results in isolation of residual membrane within masses of syncytial trophoblast. Often the last areas of membrane to disappear are those including a desmosome where the cell membranes are apparently held apart from fusion.

Some Conditions Necessary for Pinocytosis

1968 ◽  
Vol 26 ◽  
pp. 142-143
Author(s):  
M. W. Brightman
Keyword(s):  
Smooth Muscle ◽  
Cell Membrane ◽  
Toxic Effects ◽  
Cytological Evidence ◽  
Cell Processes

The cytological evidence for pinocytosis is the focal infolding of the cell membrane to form surface pits that eventually pinch off and move into the cytoplasm. This activity, which can be inhibited by oxidative and glycolytic poisons, is performed only by cell processes that are at least 300A wide. However, the interpretation of such toxic effects becomes equivocal if the membrane invaginations do not normally lead to the formation of migratory vesicles, as in some endothelia and in smooth muscle. The present study is an attempt to set forth some conditions under which pinocytosis, as distinct from the mere inclusion of material in surface invaginations, can take place.

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