On the Ability of Isolated Frog Skin to Manufacture Ringer's Fluid

Fresh, empty, isolated sacs of leg skin from R. pipiens manufacture a salt solution reasonably balanced with respect to ions and approximating a somewhat dilute Ringer's fluid. Concentrations of ions bear little relationship to concentrations in the external medium even down to 12 mM. An effective regulatory mechanism is indicated whereby the amount of salt transported is adjusted to the amount of water or vice versa, the rate of movement of either salt or water being largely independent of osmotic or ionic gradients (outer fluid to manufactured inner fluid). Concentrations of the inner fluids appear to be regulated to conform to a fairly constant concentration within the skin. Some evidence is presented that a major factor in regulating concentration of the inner fluid is triggered by an initial dilution of the inner fluid, followed by stimulation of salt uptake.

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The endosomal transcriptional regulator RNF11 integrates degradation and transport of EGFR

The Journal of Cell Biology ◽

10.1083/jcb.201601090 ◽

2016 ◽

Vol 215 (4) ◽

pp. 543-558 ◽

Cited By ~ 25

Author(s):

Sandra Scharaw ◽

Murat Iskar ◽

Alessandro Ori ◽

Gaelle Boncompain ◽

Vibor Laketa ◽

...

Keyword(s):

Endoplasmic Reticulum ◽

Plasma Membrane ◽

Egf Receptor ◽

Regulatory Mechanism ◽

Transcriptional Regulator ◽

Transport Efficiency ◽

Early Endosomes ◽

Epidermal Growth ◽

Partial Degradation ◽

Stimulation Of

Stimulation of cells with epidermal growth factor (EGF) induces internalization and partial degradation of the EGF receptor (EGFR) by the endo-lysosomal pathway. For continuous cell functioning, EGFR plasma membrane levels are maintained by transporting newly synthesized EGFRs to the cell surface. The regulation of this process is largely unknown. In this study, we find that EGF stimulation specifically increases the transport efficiency of newly synthesized EGFRs from the endoplasmic reticulum to the plasma membrane. This coincides with an up-regulation of the inner coat protein complex II (COPII) components SEC23B, SEC24B, and SEC24D, which we show to be specifically required for EGFR transport. Up-regulation of these COPII components requires the transcriptional regulator RNF11, which localizes to early endosomes and appears additionally in the cell nucleus upon continuous EGF stimulation. Collectively, our work identifies a new regulatory mechanism that integrates the degradation and transport of EGFR in order to maintain its physiological levels at the plasma membrane.

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Stimulation of HCO3− excretion in frog skin by urinary and adrenal cortical extracts

Comparative Biochemistry and Physiology Part A Physiology ◽

10.1016/0300-9629(89)90491-x ◽

1989 ◽

Vol 93 (4) ◽

pp. 717-720

Author(s):

John C. Vanatta

Keyword(s):

Frog Skin ◽

Stimulation Of

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Transient changes in intracellular calcium associated with a prolonged increase in excitability in neurons of Aplysia californica

Journal of Neurophysiology ◽

10.1152/jn.1994.71.3.1254 ◽

1994 ◽

Vol 71 (3) ◽

pp. 1254-1257 ◽

Cited By ~ 22

Author(s):

T. E. Fisher ◽

S. Levy ◽

L. K. Kaczmarek

Keyword(s):

Intracellular Calcium ◽

Action Potentials ◽

Calcium Release ◽

External Medium ◽

Aplysia Californica ◽

Spontaneous Firing ◽

Barium Ions ◽

Transient Elevation ◽

Bag Cell Neurons ◽

Stimulation Of

1. Transient stimulation of an afferent input to the bag cell neurons of Aplysia californica triggers a 30-min period of spontaneous firing termed the afterdischarge. Measurement of free calcium ion concentrations using calcium-sensitive electrodes revealed a biphasic pattern of elevation of intracellular calcium levels during the afterdischarge. Basal calcium levels at the soma were found to rise rapidly during afferent stimulation and then to decline before the onset of spontaneous firing. This early peak in intracellular calcium was followed by a slower, transient elevation of calcium levels during the period of rapid firing that occurs in the first few minutes of afterdischarge. Stimulation of clusters of bag cell neurons in a calcium-free external medium failed to trigger afterdischarge and produced no changes in basal intracellular calcium levels. 2. When calcium ions in the external medium were replaced by barium ions, stimulation of clusters of bag cell neurons triggered afterdischarges that were characterized by long-duration action potentials. Intracellular calcium levels during these afterdischarges rose slowly over the first few minutes of spontaneous firing. Because calcium-sensitive microelectrodes do not respond to barium ions, these data suggest that stimulation of afterdischarge triggers calcium release from an intracellular compartment. 3. During afterdischarges in barium-containing external media, each broadened action potential produced a discrete transient elevation of intracellular calcium levels. A similar effect was observed in isolated bag cell neurons in primary culture when action potentials were stimulated by depolarizing current pulses in a barium-containing medium. These data suggest that, under these conditions, individual action potentials trigger the release of intracellular calcium from some intracellular pool.

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Potassium movement across serosal and mucosal surfaces of frog gastric mucosa

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1965.208.3.528 ◽

1965 ◽

Vol 208 (3) ◽

pp. 528-530 ◽

Cited By ~ 3

Author(s):

Horace W. Davenport ◽

Peter H. Abbrecht

Keyword(s):

Gastric Mucosa ◽

Large Volume ◽

Salt Solution ◽

Serosal Surface ◽

Mucosal Surfaces ◽

Specific Activities ◽

Mucosal Side ◽

Total Potassium ◽

Rate Of Movement

Frog gastric mucosa was formed into a sac, filled with 1 ml salt solution and incubated in a large volume of identical salt solution containing 3 mm potassium and K42. Total potassium and specific activities of tissue and fluid were measured at 5, 10, 20, 40, 80, and 160 min after start of incubation. The measurements were repeated on mucosas formed into sacs with the mucosal side out. Both types of sacs were also incubated in solutions containing 0.1 mm histamine. Results confirm observations of others that there is net movement of potassium from fluid bathing the serosal surface into the tissue and mucosal fluid and that histamine stimulates potassium movement from tissue into mucosal fluid. The data were used to calculate the ratio of the rate of movement of potassium across the serosal and mucosal surfaces, Rs/Rm. The numerical value of 4.72 was obtained without histamine and 7.16 with histamine.

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Progressive potentiation of peptide release during a neuronal discharge

Journal of Neurophysiology ◽

10.1152/jn.1990.63.4.738 ◽

1990 ◽

Vol 63 (4) ◽

pp. 738-744 ◽

Cited By ~ 26

Author(s):

K. J. Loechner ◽

E. M. Azhderian ◽

R. Dreyer ◽

L. K. Kaczmarek

Keyword(s):

Time Course ◽

External Medium ◽

Egg Laying ◽

Maximal Rate ◽

Peptide Release ◽

Acidic Peptide ◽

Neuroactive Peptides ◽

Connective Tissue Sheath ◽

Bag Cell Neurons ◽

Stimulation Of

1. In response to electrical stimulation, the bag cell neurons of Aplysia generate an afterdischarge that lasts 20-40 min. During this afterdischarge several neuroactive peptides are released. We have now studied the time course of release of two of these peptides, egg-laying hormone (ELH) and acidic peptide (AP). For the collection of released peptides, the artery to the bag cell clusters was perfused. The medium surrounding the clusters (artificial seawater, ASW) was completely exchanged at 5-min intervals before, during, and after stimulation of an afterdischarge. Peptides released into the external medium were analyzed with the use of high-pressure liquid chromatography. 2. Before stimulation, no detectable ELH and AP were found in the external medium. After the onset of an afterdischarge, the amount of ELH and AP released increased progressively until 15-20 min of firing. Toward the conclusion of an afterdischarge, the release of ELH and AP returned to control levels. 3. In contrast to the pattern of release of the peptides, the firing rate of the bag cell neurons is maximal within the first minute of afterdischarge and thereafter declines. 4. Release of the peptides from axonal varicosities occurs within the vascularized connective-tissue sheath that covers the clusters of bag cell neurons. Experiments were therefore carried out to establish whether the observed time course of release is affected by diffusion of the peptides through the vasculature into the external medium and, in particular, to determine whether the maximal rate of release at 15-20 min into the afterdischarge could be accounted for by a delay in transport of peptides from the neurites.(ABSTRACT TRUNCATED AT 250 WORDS)

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