scholarly journals Changes in the ordering of lipids in the membrane of Dunaliella in response to osmotic-pressure changes. An e.s.r. study

1983 ◽  
Vol 213 (1) ◽  
pp. 131-136 ◽  
Author(s):  
C C Curtain ◽  
F D Looney ◽  
D L Regan ◽  
N M Ivancic
Keyword(s):  
Osmotic Pressure ◽  
Solute Concentration ◽  
Short Term ◽  
Size And Shape ◽  
Head Groups ◽  
Nacl Concentration ◽  
Original Size ◽  
Sudden Decrease ◽  
Pressure Changes ◽  
In Cells

Changes in the ordering and motion of lipids in response to changes in the external solute concentration have been studied by using the 5-nitroxide stearate (5NS) and 16-nitroxide stearate (16NS) spin probes in the plasma membrane of the halotolerant unicellular alga Dunaliella salina. Increases in ordering of the 5NS probe and decreases in motion of the 16NS probe were observed in cells equilibrated over 18 h at increasing NaCl concentrations. These changes probably resulted from the influence of the high NaCl concentration on the charged phospholipid head groups of the membrane. A short-term (less than 100 min) decrease in the order parameter, S, of the 5NS probe was observed for cells swollen by exposure to a sudden decrease of NaCl concentration from 5.0 to 2.5 M. After 100 min the value of S for 5NS was close to the value obtained in cells that had been equilibrated in 2.5 M-NaCl for 18 h. Since the cells had regained their original size and shape by 100 min it was assumed that the short-term decrease in S was associated with the swelling. A similar result was obtained when the cells were suddenly changed from 3.0 M- to 1.5 M-sorbitol. Conversely, an increase in S was observed for cells shrunk when the external solute concentration was doubled from 1.5 M- to 3.0 M-NaCl. As the cells regained their original size and shape the value of S decreased to the value observed in cells that had been equilibrated in 3.0 M-NaCl for 18 h. It is suggested that the changes in S are related to the movement of lipid into or out of a reservoir of membrane material as the membrane shrinks or expands. This movement of lipid maintains the tension of the membrane below the value at which it is disrupted. Such changes in lipid ordering could provide a mechanism whereby information about external osmotic-pressure changes is transmitted across the cell wall.

Effect of medium of lowered NaCl concentration on virus release and protein synthesis in cells infected with reticuloendotheliosis virus.

1976 ◽  
Vol 17 (2) ◽  
pp. 446-452 ◽  
Author(s):  
J M Bishop ◽  
R L Maldonado ◽  
R F Garry ◽  
P T Allen ◽  
H R Bose ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Virus Release ◽  
Reticuloendotheliosis Virus ◽  
Nacl Concentration ◽  
In Cells

scholarly journals Direct Measurement of Stress at the Base of a Glacier

1979 ◽  
Vol 22 (86) ◽  
pp. 3-24 ◽  
Author(s):  
G. S. Boulton ◽  
E. M. Morris ◽  
A. A. Armstrong ◽  
A. Thomas
Keyword(s):  
Shear Stress ◽  
Volume Concentration ◽  
Normal Pressure ◽  
Spatial Average ◽  
Short Term ◽  
Overburden Pressure ◽  
Basal Ice ◽  
Debris Particles ◽  
Or Groups ◽  
Pressure Changes

AbstractContact stress transducers were placed in subglacial bedrock and used to monitor continuously shear stress and normal pressure changes at the contact with the overriding glacier sole 100 m beneath the surface of the Glacier d’Argentière during periods in summer 1973 and spring 1975. The measured fluctuations in normal pressure and shear stress do not appear to be related to changes in sliding velocity. Analysis of the data reveals short-term fluctuations in normal pressure and shear stress which appear to be related to the passage of individual large debris particles or groups of particles over the transducer. The shear stress appears to be a function of the volume concentration of debris in the ice. The volume concentration at any point appears to be partially dependent on a “streaming” process by which basal debris-rich ice tends to flow around the lateral flanks of hummocks on the glacier bed. Where sub-glacial cavities occur, this streaming effect appears to be dependent on the extent of cavitation and thus on ice overburden pressure and velocity. It is suggested that this process can account for an apparent lag between changes in normal pressure and shear stress.The maximum ratio between shear and normal stress averaged over a period of 10 min was 0.44. This is equivalent to a spatial average over 0.3 cm. Debris concentrations in basal ice of up to 43% by volume occurred. It is suggested that concentrations of this order are common at the base of temperate glaciers and thus that a significant part of the drag at the base of a glacier may be contributed by frictional interactions between the basal-debris load and the bed.

Colloid osmotic pressure changes of dog's blood exposed to different mixtures of CO2 and air

1978 ◽  
Vol 44 (2) ◽  
pp. 254-257 ◽  
Author(s):  
Y. Kakiuchi ◽  
A. B. DuBois ◽  
D. Gorenberg
Keyword(s):  
Red Blood Cells ◽  
Osmotic Pressure ◽  
Cell Volume ◽  
Blood Cells ◽  
Freezing Point ◽  
Colloid Osmotic Pressure ◽  
Red Cell ◽  
Freezing Point Depression ◽  
Pressure Changes ◽  
Different Levels

Hansen's membrane manometer method for measuring plasma colloid osmotic pressure was used to obtain the osmolality changes of dogs breathing different levels of CO2. Osmotic pressure was converted to osmolality by calibration of the manometer with saline and plasma, using freezing point depression osmometry. The addition of 10 vol% of CO2 to tonometered blood caused about a 2.0 mosmol/kg H2O increase of osmolality, or 1.2% increase of red blood cell volume. The swelling of the red blood cells was probably due to osmosis caused by Cl- exchanged for the HCO3- which was produced rapidly by carbonic anhydrase present in the red blood cells. The change in colloid osmotic pressure accompanying a change in co2 tension was measured on blood obtained from dogs breathing different CO2 mixtures. It was approximately 0.14 mosmol/kg H2O per Torr Pco2. The corresponding change in red cell volume could not be calculated from this because water can exchange between the plasma and tissues.

scholarly journals Short‐term blood pressure changes have a more strong impact on stroke and its subtypes than long‐term blood pressure changes

2019 ◽  
Vol 42 (10) ◽  
pp. 925-933
Author(s):  
Rongrong Guo ◽  
Yanxia Xie ◽  
Jia Zheng ◽  
Yali Wang ◽  
Yue Dai ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Strong Impact ◽  
Short Term ◽  
Pressure Changes

The Sensitivity of the Pedal Ganglion of the Slug to Osmotic Pressure Changes

1956 ◽  
Vol 33 (3) ◽  
pp. 493-501
Author(s):  
G. A. KERKUT ◽  
B. J. R. TAYLOR
Keyword(s):  
Osmotic Pressure ◽  
Ionic Concentration ◽  
The Body ◽  
Bathing Solution ◽  
Pedal Ganglion ◽  
Bathing Medium ◽  
Rates Of Change ◽  
Fluid Concentration ◽  
Locke Solution ◽  
Pressure Changes

1. The effects of different dilutions of Locke solution on the electrical activity of the isolated pedal ganglion of the slug can be reproduced by adding different concentrations of glucose of mannitol to a given concentration of Locke. 2. This indicates that certain cells in the pedal ganglion are sensitive to the osmotic pressure of the solution and not its ionic concentration. 3. The preparation is sensitive to slow changes in the concentration of the bathing medium. The cells increased their activity when the bathing solution was slowly changed from 0.7 Locke to 0.6 Locke, the change taking 43 min. This corresponds approximately to a change of 1% of the body fluid concentration over 4 min. Such rates of change are found in the normal intact animal. 4. The sensitivity of the preparation compares well with that of the mammalian osmoreceptors.

Failure of tubule fluid osmolarity to affect feedback regulation of glomerular filtration

1980 ◽  
Vol 239 (5) ◽  
pp. F427-F432 ◽  
Author(s):  
J. P. Briggs ◽  
J. Schnermann ◽  
F. S. Wright
Keyword(s):  
Flow Rate ◽  
Feedback Regulation ◽  
Solute Concentration ◽  
Tubuloglomerular Feedback ◽  
Sprague Dawley ◽  
Perfusion Flow ◽  
Sprague Dawley Rats ◽  
Nacl Concentration ◽  
Osmotic Agents ◽  
Feedback Responses

Experiments were performed in Sprague-Dawley rats in order to distinguish between sodium chloride and total solute concentration as possible luminal signals capable of eliciting tubuloglomerular feedback responses. Early proximal flow rate (VEP), an index of nephron filtration rate, was measured without perfusion of the loop of Henle and during retrograde perfusion with solutions containing 20, 35, 60 to 100 mM NaCl and varying amounts of either urea or mannitol to achieve total solute concentrations of 130, 280, or 400 mosM. Perfusion flow rate was kept constant at 20 nl/min. Perfusion with a solution containing 20 mM NaCl and made hypo-, iso-, or hypertonic with urea or mannitol caused little or no change in VEP. Perfusion with a 35 mM NaCl solution made hypo-, iso-, or hypertonic with mannitol resulted in a fall of VEP of 6-7 nl/min. When NaCl concentration was 60 mM, VEP fell by 10-14 nl/min with solutions made hypo-, iso-, or hypertonic with urea or mannitol. With 100 mM NaCl solutions made hypo-, iso-, or hypertonic with mannitol, VEP fell approximately 12 nl/min. These results indicate that feedback responses are determined by the NaCl concentration of the perfusate and that this NaCl dependency is not modified by varying perfusate osmolarity between 130 and 400 mosM with urea or mannitol as osmotic agents.

Peripartum Colloid Osmotic Pressure Changes

1985 ◽  
Vol 5 (3) ◽  
pp. 96
Author(s):  
B. Gonik ◽  
D. Cotton ◽  
T. Spillman ◽  
E. Abouleish ◽  
F. Zavisca ◽  
...  
Keyword(s):  
Osmotic Pressure ◽  
Colloid Osmotic Pressure ◽  
Pressure Changes
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