scholarly journals The Influence of High Potassium Depolarization and Acetylcholine on Calcium Exchange in the Rat Uterus

1966 ◽  
Vol 49 (6) ◽  
pp. 1299-1317 ◽  
Author(s):  
CASEY van BREEMEN ◽  
E. E. DANIEL
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Membrane ◽  
Cell Membranes ◽  
Cytoplasmic Calcium ◽  
Calcium Efflux ◽  
Rat Uterus ◽  
Potassium Depolarization ◽  
High Potassium ◽  
Calcium Exchange

Net and radioactive calcium movements were studied in the rat uterus during stimulation with acetylcholine and high potassium solutions. High potassium did not affect the efflux of intracellular Ca45, but was able to release Ca45 from a small parallel Ca fraction which was believed to be located in the cell membranes. High potassium did markedly slow the influx of Ca45 and caused a net calcium efflux. Acetylcholine had no effect on calcium movements in polarized myometrium, but it increased the Ca45 influx in depolarized uteri. Ca45 taken up during contraction exchanged more slowly during subsequent efflux than Ca45 taken up at rest. The results were interpreted as supporting the hypothesis that myometrial contraction is induced by a release of calcium from the inside of the cell membrane and the endoplasmic reticulum, and relaxation follows the removal of ionic cytoplasmic calcium by these same structures.

Effects of acidosis on mechanical function and Ca2+ exchange in rabbit myocardium

1979 ◽  
Vol 236 (4) ◽  
pp. H525-H533 ◽  
Author(s):  
P. A. Poole-Wilson ◽  
G. A. Langer
Keyword(s):  
Cell Membrane ◽  
Myocardial Function ◽  
Interventricular Septum ◽  
Mechanical Function ◽  
Calcium Efflux ◽  
Stimulation Rate ◽  
Extracellular Acidosis ◽  
Rapid Fall ◽  
Rabbit Myocardium ◽  
Calcium Exchange

The effects of acidosis on myocardial function and calcium exchange have been studied in the isolated but arterially perfused interventricular septum of the rabbit. Temperature was 28 degrees C and stimulation rate 48 beats/min. Acidosis was induced either by increase of the perfusate PCO2 (pH reduced from 7.35 to 6.68) or by decrease of the bicarbonate-chloride ratio (pH 7.35 to 6.72). The effect on calcium efflux was assessed by introduction of acidosis at different times during the washout of 45Ca2+ from the muscle. The uptake of 47Ca2+ was recorded directly with a NaI crystal and counter. An increase of perfusate PCO2 caused a rapid fall in developed tension. The efflux of slowly exchanging 45Ca2+ and the uptake of 47Ca2+ were inhibited. There was no rapid displacement of calcium from the muscle. Decrease of the bicarbonate-chloride ratio caused a slower fall of developed tension and neither the efflux nor uptake of calcium were altered. These results suggest that developed tension and calcium exchange in the myocardium are more responsive to acidosis within the cell or cell membrane than to extracellular acidosis.

Ultrastructure of the Pharynx and Some Parenchyma Cells of Zeuxapta-Seriolae and Paramicrocotyloides-Reticularis (Monogenea, Polyopisthocotylea, Microcotylidae)

1986 ◽  
Vol 34 (4) ◽  
pp. 473 ◽  
Author(s):  
K Rohde
Keyword(s):  
Endoplasmic Reticulum ◽  
Connective Tissue ◽  
Cell Membrane ◽  
Basal Lamina ◽  
Cell Membranes ◽  
Granular Endoplasmic Reticulum ◽  
Loose Connective Tissue ◽  
Parenchyma Cells ◽  
Glandular Cells ◽  
Tissue Cells

The ultrastructure of the pharynx of Zeuxapta seriolae and Paramicrocotyloides reticularis (Monogenea : Microcotylidae) is described. The pharynx of both species is surrounded by a thick sheath resembling a basal lamina. It contains layers of longitudinal, circular and radial muscles, glandular cells, smaller cells interpreted as connective tissue cells, axons, and loose connective tissue. The cell bodies of the glandular cells are subdivided by deep invaginations of cell membranes; the cytoplasm is rich in granular endoplasmic reticulum and golgi complexes. The pharyngeal lumen is branched and lined with a layer of cytoplasm which contains numerous surface lamellae, branched 'supportive' lamellae, and vesicles. A body consisting of stacks of tubules, and associated with axons, is interpreted as a proprioceptor. Bacteria were found in the cytoplasm of some parts of the pharynx of Z. seriolae, particularly near the lumen. In Z. seriolae, three types of parenchyma cells near the pharynx were examined. All have deep invaginations of the cell membrane which, at least in some cells, are anchored near the nucleus by means of desmosomes, and which contain processes of adjacent cells.

scholarly journals A DISTINCTIVE CELL CONTACT IN THE RAT ADRENAL CORTEX

1972 ◽  
Vol 53 (1) ◽  
pp. 148-163 ◽  
Author(s):  
Daniel S. Friend ◽  
Norton B. Gilula
Keyword(s):  
Cell Membrane ◽  
Adrenal Cortex ◽  
Cell Membranes ◽  
Freeze Fracture ◽  
Typical Feature ◽  
Cell Contact ◽  
Cortical Cells ◽  
Cell Dispersion ◽  
Extensive Cell ◽  
Distinctive Cell

Extensive cell contacts which resemble septate junctions occur between cells in the three major zones of the rat adrenal cortex. Characteristically, they extend between small intercellular canaliculi and the periendothelial space, frequently interrupted by gap junctions and rarely by desmosomes. Zonulae occludentes have not been identified in the adrenal cortex. Along this distinctive cell contact, the cell membranes of apposing cells are separated by 210–300 a bisected by irregularly spaced 100–150-A extracellular particles which are often circular in profile. In lanthanum preparations, these particles appear to form a continuous chain throughout the intercellular space and are visualized as an alveolate structure in sections parallel to the plane of the cell membrane. The cell membrane in the area of septate-like contact does not differ from nonjunctional areas of the cell membrane in freeze-fracture replicas. The cell contact retains its integrity after cell dispersion and after the separation of cell membranes from disrupted cells. The intercellular particles also persist after brief extraction in lipid solvents. Besides adherence, possible functions of this adrenal contact include maintenance of the width of the extracellular space, the provision of channels between intercellular canaliculi and the bloodstream, and utilization as cation depots. Similar structures are also present between adrenal cortical cells of several other species and between interstitial cells of the testis. This type of cell contact may, in fact, be a typical feature of steroid-hormone-secreting tissues in vertebrates.

Nitrendipine blocks high potassium contractures but not twitches in rat skeletal muscle

1988 ◽  
Vol 66 (9) ◽  
pp. 1210-1213 ◽  
Author(s):  
G. B. Frank ◽  
L. Konya ◽  
T. Subrahmanyam Sudha
Keyword(s):  
Skeletal Muscle ◽  
Calcium Ions ◽  
Calcium Uptake ◽  
Channel Blocker ◽  
Mechanical Response ◽  
Extracellular Calcium ◽  
The Other ◽  
Rat Skeletal Muscle ◽  
Potassium Depolarization ◽  
High Potassium

The effects of the organic calcium channel blocker nitrendipine was tested on electrically evoked twitches and on potassium depolarization-induced contractures of rat lumbricalis muscles. Nitrendipine (10−7 to 5 × 10−5 M) blocked only the potassium contractures. It was concluded that blocking calcium uptake through the slow voltage-senstitive calcium channels during potassium depolarization blocks the mechanical response of the muscle. Thus extracellular calcium ions are required for the excitation–contraction (E–C) coupling during depolarization contractures. On the other hand, electrically evoked twitches were not affected by nitrendipine; therefore, extracellular calcium ions entering via the slow voltage-sensitive channels are not required for E–C coupling during the twitch.

Structure of the chloroplast and its DNA in chloromonadophycean algae

1981 ◽  
Vol 49 (1) ◽  
pp. 401-409
Author(s):  
A.W. Coleman ◽  
P. Heywood
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Membrane ◽  
Nuclear Envelope ◽  
Chloroplast Dna ◽  
Single Layer ◽  
Longitudinal Axis ◽  
Chloroplast Envelope ◽  
Large Numbers ◽  
Gonyostomum Semen ◽  
Chloroplast Stroma

The arrangement and ultrastructure of chloroplasts is described for the Chloromonadophycean algae gonyostomum semen Diesing and Vacuolaria virescens Cienkowsky. The chloroplasts are present in large numbers and are discoid structures approximately 3–4 micrometer in length by 2–3 micrometer in width. In Gonyostomum semen the chloroplasts form a single layer immediately interior to the cell membrane; frequently their longitudinal axis parallels the longitudinal axis of the cell. The chloroplasts in Vacuolaria virescens are more than I layer deep and do not appear to be preferentially oriented. In both organisms, chloroplast bands usually consist of 3 apposed thylakoids, although fusion and interconnections between adjacent bands frequently occur. External to the girdle band (the outermost thylakoids) is the chloroplast envelope. This is bounded by endoplasmic reticulum but there is no immediately apparent continuity between this endoplasmic reticulum and the nuclear envelope. Electron-dense spheres in the chloroplast stroma are thought to be lipid food reserve. Ring-shaped electron-translucent regions in the chloroplast contain chloroplast DNA. The DNA is distributed along this ring in an uneven fashion and, when stained, resembles a string of beads. Each plastid has I ring, and the ring is unbroken in the intact plastid.

scholarly journals Pathogenesis of shigella diarrhea. VII. Evidence for a cell membrane toxin receptor involving β1 {arrow} 4-linked N-acetyl-D-glucosamine oligomers

1977 ◽  
Vol 146 (2) ◽  
pp. 535-546 ◽  
Author(s):  
GT Keusch ◽  
M Jacewicz
Keyword(s):  
Cell Membrane ◽  
Cholera Toxin ◽  
Liver Cell ◽  
Hela Cells ◽  
Mammalian Cells ◽  
Cell Membranes ◽  
Proteolytic Enzymes ◽  
Cell Monolayer ◽  
Toxin Receptor ◽  
Toxin Uptake

The binding of ShigeUa dysenteriae 1 cytotoxin to HeLa cells in culture and to isolated rat liver cell membranes was studied by means of an indirect consumption assay of toxicity from the medium, or by determination of cytotoxicity to the HeLa cell monolayer. Both liver cell membranes and HeLa cells removed toxicity from the medium during incubation, in contrast to WI-38 and Y-1 mouse adrenal tumor cells, both of which neither bound nor were affected by the toxin. Uptake of toxin was directly related to concentration of membranes added, time,and temperature, and indirectly related to the ionic strength of the buffer used. The chemical nature of the membrane receptor was characterized by using three principal approaches: (a) enzymatic sensitivity; (b) competitive inhibition and (c) receptor blockade studies. The receptor was destroyed by proteolytic enzymes, phospholipases (which markedly altered the gross appearance of the membrane preparation) and by lysozyme, but not by a variety of other enzymes. Of 28 carbohydrate and glycoprotein haptens studied, including cholera toxin and ganglioside, only the chitin oligosaccharide lysozyme substrates, per N-acetylated chitotriose, chitotetraose, and chitopentaose were effective competitive inhibitors. Greatest inhibition was found with the trimer, N, N', N" triacetyl chitotriose. Of three lectins studied as possible receptor blockers, including phytohemagglutinin, concanavalin A, and wheat germ agglutinin, only the latter, which is known to possess specific binding affinity for N, N', N" triacetyl chitotriose, was able to block toxin uptake. Evidence from all three approaches indicate, therefore, existence of a glycoprotein toxin receptor on mammalian cells, with involvement of oligomeric β1{arrow}4-1inked N-acetyl glucosamine in the receptor. This receptor is clearly distinct from the G(M1) ganglioside thought to be involved in the binding of cholera toxin to the cell membrane of a variety of cell types susceptible to its action.

Ammonia movement and distribution after exercise across white muscle cell membranes in rainbow trout

1996 ◽  
Vol 271 (3) ◽  
pp. R738-R750 ◽  
Author(s):  
Y. Wang ◽  
G. J. Heigenhauser ◽  
C. M. Wood
Keyword(s):  
Membrane Potential ◽  
Cell Membrane ◽  
Intracellular Ph ◽  
Muscle Cell ◽  
Cell Membranes ◽  
White Muscle ◽  
Extracellular Ph ◽  
Posterior Portion ◽  
Arterial Inflow ◽  
Muscle Cell Membrane

Manipulations of pH and electrical gradients in a perfused preparation were used to analyze the factors controlling ammonia distribution and flux in trout white muscle after exercise. Trout were exercised to exhaustion, and then an isolated-perfused white muscle preparation with discrete arterial inflow and venous outflow was made from the posterior portion of the tail. The tail-trunks were perfused with low (7.4)-, medium (7.9)-, and high (8.4)-pH saline, achieved by varying HCO3- concentration ([HCO3-]) at constant Pco2. Intracellular and extracellular pH, ammonia, CO2, K+, Na+, and Cl- were measured. Muscle intracellular pH was not affected by changes in extracellular pH. Increasing extracellular pH caused a decrease in the transmembrane NH3 partial pressure (PNH3) gradient and a decrease in ammonia efflux. When extracellular K+ concentration was increased from 3.5 to 15 mM in the medium-pH group, a depolarization of the muscle cell membrane potential from -92 to -60 mV and a 0.1-unit depression in intracellular pH occurred. Ammonia efflux increased despite a marked reduction in the PNH3 gradient. Amiloride (10(-4) M) had no effect, indicating that Na+/H(+)-NH4+ exchange does not participate in ammonia transport in this system. A comparison of observed intracellular-to-extracellular ammonia distribution ratios with those modeled according to either pH or Nernst potential distributions supports a model in which ammonia distribution across white muscle cell membranes is affected by both pH and electrical gradients, indicating that the membranes are permeable to both NH3 and NH4+. Membrane potential, acting to retain high levels of NH4+ in the intracellular compartment, appears to have the dominant influence during the postexercise period. However, at rest, the pH gradient may be more important, resulting in much lower intracellular ammonia levels and distribution ratios. We speculate that the muscle cell membrane NH3-to-NH4+ permeability ratio in trout may change between the rest and postexercise condition.

scholarly journals Model of skeletal muscle cramp and its reversal

2020 ◽  
Author(s):  
Kazuyo Tasaki ◽  
Penelope J. Noble ◽  
Alan Garny ◽  
Paul R. Shorten ◽  
Nima Afshar ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Regulatory Networks ◽  
Calcium Influx ◽  
Muscle Cramp ◽  
Extracellular Potassium ◽  
Extended Model ◽  
Calcium Efflux ◽  
Sodium Calcium ◽  
Calcium Exchange ◽  
Increased Blood Flow

In an accompanying paper [2], we developed the Shorten [3] model of skeletal muscle by incorporating equations such as surface calcium fluxes. In further research in this paper, we succeeded in reproducing muscle cramp, as well as its prevention and reversal, by investigating muscle contraction and cramp, in which calcium regulatory networks are involved, using the extended model in comparison with the original model. Incorporation of data from a traditional medicine from root extracts of paeony and licorice and one of its pure chemicals was modeled. The sensitivity analysis of the extended model shows the robustness of the calcium regulatory networks. Muscle cramp, in the extended model, requires calcium influx via the L-type calcium channel and it will not occur without calcium influx. Reduced calcium influx can delay or prevent cramp. Increased interstitial potassium is implicated in developing and maintaining cramp. Mechanism of reversal of cramp requires wash-out of extracellular potassium via increased blood flow, followed by calcium efflux via sodium-calcium exchange. This paper shows the first successful quantitative electrophysiological and mechanical model of cramp and of its reversal.

scholarly journals Model of skeletal muscle cramp and its reversal

2020 ◽  
Author(s):  
Kazuyo Tasaki ◽  
Denis Noble ◽  
Penelope J. Noble ◽  
Paul R. Shorten ◽  
Alan Garny ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Regulatory Networks ◽  
Calcium Influx ◽  
Muscle Cramp ◽  
Extracellular Potassium ◽  
Extended Model ◽  
Calcium Efflux ◽  
Sodium Calcium ◽  
Calcium Exchange ◽  
Increased Blood Flow

In an accompanying paper [2], we developed the Shorten [3] model of skeletal muscle by incorporating equations such as surface calcium fluxes. In further research in this paper, we succeeded in reproducing muscle cramp, as well as its prevention and reversal, by investigating muscle contraction and cramp, in which calcium regulatory networks are involved, using the extended model in comparison with the original model. Incorporation of data from a traditional medicine from root extracts of paeony and licorice and one of its pure chemicals was modeled. The sensitivity analysis of the extended model shows the robustness of the calcium regulatory networks. Muscle cramp, in the extended model, requires calcium influx via the L-type calcium channel and it will not occur without calcium influx. Reduced calcium influx can delay or prevent cramp. Increased interstitial potassium is implicated in developing and maintaining cramp. Mechanism of reversal of cramp requires wash-out of extracellular potassium via increased blood flow, followed by calcium efflux via sodium-calcium exchange. This paper shows the first successful quantitative electrophysiological and mechanical model of cramp and of its reversal.

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