scholarly journals INFLUENCE OF EXTERNAL POTASSIUM ON THE SYNTHESIS AND DEPOSITION OF MATRIX COMPONENTS BY CHONDROCYTES IN VITRO

1974 ◽  
Vol 63 (3) ◽  
pp. 843-854 ◽  
Author(s):  
Jon C. Daniel ◽  
Robert A. Kosher ◽  
James E. Hamos ◽  
James W. Lash
Keyword(s):  
Culture Medium ◽  
Hyaline Cartilage ◽  
Cell Layer ◽  
Potassium Concentration ◽  
Cartilage Matrix ◽  
High Potassium ◽  
External Potassium ◽  
Matrix Components ◽  
High Potassium Concentration

The effect of a high external potassium concentration on the synthesis and deposition of matrix components by chondrocytes in cell culture was determined. There is a twofold increase in the amount of chondroitin 4- and 6-sulfate accumulated by chondrocytes grown in medium containing a high potassium concentration. There is also a comparable increase in the production of other sulfated glycosaminoglycans (GAG) including heparan sulfate and uncharacterized glycoprotein components. The twofold greater accumulation of GAG in the high potassium medium is primarily the result of a decrease in their rate of degradation. In spite of this increased accumulation of GAG, the cells in high potassium fail to elaborate appreciable quantities of visible matrix, although they do retain the typical chondrocytic polygonal morphology. Although most of the products are secreted into the culture medium in the high potassium environment, the cell layer retains the same amount of glycosaminoglycan as the control cultures. The inability of chondrocytes grown in high potassium to elaborate the typical hyaline cartilage matrix is not a consequence of an impairment in collagen synthesis, since there is no difference in the total amount of collagen synthesized by high potassium or control cultures. There is, however, a slight increase in the proportion of collagen that is secreted into the medium by chondrocytes in high potassium. Synthesis of the predominant cartilage matrix molecules is not sufficient in itself to ensure that these molecules will be assembled into a hyaline matrix.

IN VITRO STUDIES OF THE RELEASE MECHANISM FOR VASOPRESSIN IN RATS.

1967 ◽  
Vol 56 (1) ◽  
pp. 139-145 ◽  
Author(s):  
P. Bie ◽  
N. A. Thorn
Keyword(s):  
Supraoptic Nucleus ◽  
Potassium Concentration ◽  
Nerve Endings ◽  
Release Mechanism ◽  
High Potassium ◽  
Paraventricular Nuclei ◽  
Pressor Activity ◽  
High Potassium Concentration ◽  
Vasopressor Activity

ABSTRACT Isolated pieces of rat hypothalamus containing the supraoptic and paraventricular nuclei, respectively, did not release vasopressin when incubated in a medium with a high potassium concentration, or in media containing acetylcholine, noradrenaline or sodium chloride in a hypertonic concentration. The average vasopressor activity that could be extracted from the supraoptic region was equivalent to 8 milli-units of vasopressin per 100 g rat, whereas extract of the paraventricular region contained little pressor activity. The results seem to be in accordance with the hypothesis that the first precursor(s) of vasopressin is synthesized predominantly in the supraoptic nucleus and that the neurosecretory granules go through a »maturation« process during their passage from the hypothalamus to nerve endings in the neurohypophysis. Not until they reach the nerve endings do they contribute to the formation of the pool from which the hormone may be easily mobilized.

THE RELEASE IN VITRO OF VASOPRESSIN UNACCOMPANIED BY THE AXOPLASMIC ENZYMES: LACTIC ACID DEHYDROGENASE AND ADENYLATE KINASE

1973 ◽  
Vol 72 (3) ◽  
pp. 417-424 ◽  
Author(s):  
B. A. Edwards ◽  
M. E. Edwards ◽  
N. A. Thorn
Keyword(s):  
Lactic Acid ◽  
Adenylate Kinase ◽  
Potassium Concentration ◽  
Supernatant Fraction ◽  
High Potassium ◽  
Lactic Acid Dehydrogenase ◽  
Acid Dehydrogenase ◽  
High Potassium Concentration ◽  
Vasopressor Activity

ABSTRACT Lactic acid dehydrogenase (LDH) and adenylate kinase were shown by differential centrifugation to be mainly associated with the supernatant fraction of ox neurohypophyses. In vitro release of vasopressor activity, LDH and adenylate kinase from groups of rat neural hemilobes or slices of ox neurohypophyses was studied at rest and after stimulation with a high potassium concentration or after electrical stimulation. Although release of vasopressor activity increased considerably on stimulation, no significant change in the release of LDH or adenylate kinase could be detected. The findings are discussed in relation to the different hypotheses for the mechanism of release of vasopressin.

High potassium concentration accelerate pig sperm ability to penetrate oocytes in vitro

1994 ◽  
Vol 41 (1) ◽  
pp. 308
Author(s):  
K. Suzuki ◽  
T. Mori ◽  
M. Yamaguchi ◽  
H. Shimizu
Keyword(s):  
Potassium Concentration ◽  
High Potassium ◽  
High Potassium Concentration

Relation of Intracellular K+ and Steroidogenesis in Isolated Adrenal Zona Glomerulosa and Fasciculata Cells

1975 ◽  
Vol 49 (1) ◽  
pp. 13-26
Author(s):  
F. A. Mendelsohn ◽  
C. Mackie
Keyword(s):  
Potassium Concentration ◽  
Zona Glomerulosa ◽  
Zona Fasciculata ◽  
High Potassium ◽  
External Potassium ◽  
Glomerulosa Cells ◽  
Unit Gravity Sedimentation ◽  
Zona Glomerulosa Cells ◽  
Stimulation Of

1. Intracellular K+ content, water spaces and corticosterone output were measured in isolated zona glomerulosa and zona fasciculata-reticularis cell suspensions of rat adrenal cortex, after incubations in vitro under conditions designed to alter steroidogenesis. 2. Intracellular K+ of unpurified zona glomerulosa cells was not altered after stimulation of corticosterone output with serotonin. Similarly, with zona glomerulosa cells purified by unit gravity sedimentation, no change in intracellular K+ was detected after stimulation of steroidogenesis with serotonin or angiotensin II. 3. In high-potassium medium (final concentration 84 mmol/l), parallel increases in intracellular K+ and corticosterone output were observed with both unpurified and purified zona glomerulosa cells. However, a similar increase in intracellular K+ also occurred in high-potassium medium with zona fasciculata cells, whose steroid output is unresponsive to external potassium concentration ([K+]). 4. Ouabain at 10−5 mol/l depressed the intracellular [K+] of glomerulosa cells but did not alter basal or stimulated corticosterone output. Similar results were obtained with fasciculata cells. 5. Ouabain at 5×10−4 mol/l further depressed intracellular [K+] of glomerulosa cells and inhibited basal and stimulated corticosterone output. However, this concentration of ouabain also inhibited steroidogenesis in fasciculata cells. 6. These results demonstrate a variety of situations where changes in intracellular [K+] are dissociated from those in corticosterone output and indicate that intracellular [K+] cannot be the sole mechanism regulating steroidogenesis under these conditions.

Movement of Aldolase From Excised Rat Diaphragm

1956 ◽  
Vol 185 (1) ◽  
pp. 1-11 ◽  
Author(s):  
Kenneth L. Zierler
Keyword(s):  
Aqueous Solution ◽  
Cell Membrane ◽  
Potassium Concentration ◽  
Fiber Surface ◽  
Rat Diaphragm ◽  
High Potassium ◽  
Flow Through ◽  
High Potassium Concentration

A protein, aldolase, flows from excised rat diaphragm incubated in a variety of media. The rate of outflow of aldolase is increased by anoxia and by a high potassium concentration in the medium, and it is decreased by a reduction in temperature and by addition of glucose. When diaphragm is transferred to fresh media and reincubated the rate of outflow of aldolase is also accelerated. From measurements of rates of outflow of aldolase, estimates have been made of the area of the membrane required for aldolase to flow through the cell membrane as though it were flowing simply through an aqueous solution. This area is about 10–7–10–8 of the estimated total fiber surface. The estimated area for diffusion of aldolase is modified 16-fold by factors which alter the metabolism of diaphragm.

Effect of Extracellular Potassium on the Transport of Sodium and Potassium in Rat Thymocytes

1981 ◽  
Vol 61 (3) ◽  
pp. 307-312 ◽  
Author(s):  
R. B. Jones ◽  
J. Patrick ◽  
P. J. Hilton
Keyword(s):  
Potassium Concentration ◽  
Extracellular Potassium ◽  
Sodium Influx ◽  
Potassium Efflux ◽  
Sodium Efflux ◽  
Extracellular Potassium Concentration ◽  
External Potassium ◽  
Potassium Influx ◽  
Sodium And Potassium

1. The effect of extracellular potassium on the transport of sodium and potassium in rat thymocytes has been studied in vitro. 2. A significant increase in the rate constant for total and ouabain-sensitive sodium efflux was demonstrated at an extracellular potassium concentration of 1 mmol/l as compared with that at either 0 or 2 mmol/l. 3. At potassium concentrations below 3 mmol/l ouabain-sensitive sodium influx was observed suggesting sodium-sodium exchange catalysed by the sodium pump. 4. Both total and ouabain-insensitive potassium efflux rose with external potassium. A small ouabain-sensitive potassium efflux was observed at all levels of external potassium studied. 5. Total and ouabain-insensitive potassium influx increased with external potassium, but did not appear to saturate. Ouabain-sensitive potassium influx reached a maximum at an external potassium concentration of 2 mmol/l then decreased with increasing external potassium.

Protection of atrial function in hypoxia by high potassium concentration

1994 ◽  
Vol 25 (3) ◽  
pp. 401-407 ◽  
Author(s):  
Guglielmina Froldi ◽  
Luisa Pandolfo ◽  
Alessandro Chinellato ◽  
Eugenio Ragazzi ◽  
Laura Caparrotta ◽  
...  
Keyword(s):  
Potassium Concentration ◽  
Atrial Function ◽  
High Potassium ◽  
High Potassium Concentration
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