Osmotic Cells Research Articles

Studies on gliding motility in Myxococcus xanthus.

1. Gliding motility ofMyxococcus xanthus FBt is reversibly inhibited by treatment with proteolytic enzymes and with 10-3 M ethylenediaminetetraacetic acid and by osmotic shock. Chloramphenicol inhibits regeneration of the ability to glide. Shearing and ultrasound treatments do not affect movement. 2. At least 18 periplasmic proteins are released by osmotic shock, as determined by SDS-polyacrylamide gel electrophoresis. These proteins are indistinguishable from those of the non-motile strain NM. Pronase treatment of FBt degrades most of the higher molecular weight periplasmic proteins. 3. Antisera prepared against periplasmic antigens of FBt and NM do not demonstrate strain-specific antigenic differences by immunodiffusion. NM does not agglutinate as well as FBt with either antiserum. Osmotic shocked FBt cells do not agglutinate. Both strains FBt and NM demonstrate a predominance of pole-to-pole agglutination. 4. These antisera inhibit gliding motility. Serum against FBt periplasmic antigens, adsorbed with FBt, does not inhibit gliding; adsorption with NM or osmotically shocked FBt only partially inhibits gliding. 5. Surface property differences among strains FBt, NM and SM (semi-motile) are indicated.

Cell volume as a factor influencing electrical and mechanical activity of vascular smooth muscle.

ABSTRACTThe effects of variations in the extracellular osmolarity on the electrical and mechanical activity of the isolated rat portal vein were studied. Addition of sucrose or xylose (20–100 mmoles/l) to the “normal” solution caused inhibition of contractile activity which could be ascribed to changes in the electrical discharge pattern. Increasing osmolarity with urea produced transient inhibition, return to control activity, and, on return to normal solution, a transient excitation. Reducing osmolarity by 30–60 mOsm/l by decreasing the [Na+] and [Cl] of the medium caused sustained excitation with continuous spike discharge and tetanic contraction. Comparable decreases in the ionic concentrations but with osmotic substitution by sucrose or xylose had little influence on muscle activity. Substituting Na+ and Cl with urea on an equiosmolar basis caused excitation resembling that in hypoosmotic solution. If the smooth muscle cells are looked upon as osmotic cells with membranes that are freely permeable to H2O and urea but less permeable to sugar and ions, the results indicate a consistent correlation between cell volume and state of activity; shrinkage associated with inhibition, swelling with excitation. Changes in the transuiembrane concentration gradients for K+, Na+ and Cl‐, caused by the cellular volume changes, are not sufficient to explain the electrical responses. Changes in ionic membrane permeability are assumed to occur.

Cell Volume as a Factor Influencing Electrical and Mechanical Activity of Vascular Smooth Muscle

The effects of variations in the extracellular osmolarity on the electrical and mechanical activity of the isolated rat portal vein were studied. Addition of sucrose or xylose (20–100 mmoles/l) to the “normal” solution caused inhibition of contractile activity which could be ascribed to changes in the electrical discharge pattern. Increasing osmolarity with urea produced transient inhibition, return to control activity, and, on return to normal solution, a transient excitation. Reducing osmolarity by 30–60 mOsm/l by decreasing the [Na+] and [Cl] of the medium caused sustained excitation with continuous spike discharge and tetanic contraction. Comparable decreases in the ionic concentrations but with osmotic substitution by sucrose or xylose had little influence on muscle activity. Substituting Na+ and Cl with urea on an equiosmolar basis caused excitation resembling that in hypoosmotic solution. If the smooth muscle cells are looked upon as osmotic cells with membranes that are freely permeable to H2O and urea but less permeable to sugar and ions, the results indicate a consistent correlation between cell volume and state of activity; shrinkage associated with inhibition, swelling with excitation. Changes in the transuiembrane concentration gradients for K+, Na+ and Cl-, caused by the cellular volume changes, are not sufficient to explain the electrical responses. Changes in ionic membrane permeability are assumed to occur.

Swollen starch grains and osmotic cells

Es wird gezeigt, dass die Wande gequollener Starkekorner nicht semipermeabel sind und dass demzufolge die Blasen nicht mit osmotischen Zellen verglichen werden konnen. Quellung und Schrumpfung der Blasen unter dem Einfluss verschiedener Substanzen sind die Folge kolloid-chemischer Strukturanderungen in der Blasenwand selber.

Carlsbad Meeting of the German Association of Naturalists and Physicians

THE seventy-fourth annual meeting of the Association of German Naturalists and Physicians was held on September 21–28 at Carlsbad, after an interval of not less than forty years. At the meeting, very naturally, the hot springs for which the place is famous suggested a suitable subject for discussion. Geologists and chemists alike concentrated their attention upon them. Prof, van't Hoff, who may be regarded as the veritable creator of modern theoretical and physical chemistry, was there to elucidate the subject. Prof. Meyerhofer applied the latest teaching of that particular science to the springs, exciting a keen interest by his masterly method of dealing with the subject, more particularly when entering into the newest discoveries with regard to the theory of osmotic pressure and of ions which van't Hoff and Arrhenius have effectively established. The entire organism in biology may be shown to be a collection of osmotic cells, enclosing saline solutions, and the movement of liquids in them is to a high degree, if not entirely, determined by the laws of osmotic pressure.