scholarly journals External pH modulation during the growth of Vibrio tapetis , the aetiological agent of brown ring disease

2020 ◽  
Vol 129 (1) ◽  
pp. 3-16 ◽  
Author(s):  
A. Rahmani ◽  
C. Mathien ◽  
A. Bidault ◽  
N. Le Goïc ◽  
C. Paillard ◽  
...  
Keyword(s):  
Aetiological Agent ◽  
External Ph ◽  
Brown Ring Disease

scholarly journals The molecular identity of the characean OH− transporter: a candidate related to the SLC4 family of animal pH regulators

PROTOPLASMA ◽  
2021 ◽  
Author(s):  
Bianca N. Quade ◽  
Mark D. Parker ◽  
Marion C. Hoepflinger ◽  
Shaunna Phipps ◽  
Mary A. Bisson ◽  
...  
Keyword(s):  
Inorganic Carbon ◽  
Membrane Conductance ◽  
Resting Potential ◽  
Large Scatter ◽  
Intrinsic Variability ◽  
Molecular Identity ◽  
Ph Banding ◽  
Chara Australis ◽  
Ph Increase ◽  
External Ph

AbstractCharaceae are closely related to the ancient algal ancestors of all land plants. The long characean cells display a pH banding pattern to facilitate inorganic carbon import in the acid zones for photosynthetic efficiency. The excess OH−, generated in the cytoplasm after CO2 is taken into the chloroplasts, is disposed of in the alkaline band. To identify the transporter responsible, we searched the Chara australis transcriptome for homologues of mouse Slc4a11, which functions as OH−/H+ transporter. We found a single Slc4-like sequence CL5060.2 (named CaSLOT). When CaSLOT was expressed in Xenopus oocytes, an increase in membrane conductance and hyperpolarization of resting potential difference (PD) was observed with external pH increase to 9.5. These features recall the behavior of Slc4a11 in oocytes and are consistent with the action of a pH-dependent OH−/H+ conductance. The large scatter in the data might reflect intrinsic variability of CaSLOT transporter activation, inefficient expression in the oocyte due to evolutionary distance between ancient algae and frogs, or absence of putative activating factor present in Chara cytoplasm. CaSLOT homologues were found in chlorophyte and charophyte algae, but surprisingly not in related charophytes Zygnematophyceae or Coleochaetophyceae.

Ammonia excretion by the skin of zebrafish (Danio rerio) larvae

2008 ◽  
Vol 295 (6) ◽  
pp. C1625-C1632 ◽  
Author(s):  
Tin-Han Shih ◽  
Jiun-Lin Horng ◽  
Pung-Pung Hwang ◽  
Li-Yih Lin
Keyword(s):  
Direct Evidence ◽  
Ammonia Excretion ◽  
Bafilomycin A1 ◽  
Selective Electrode ◽  
Zebrafish Larvae ◽  
Trapping Mechanism ◽  
Morpholino Oligonucleotides ◽  
Electrode Technique ◽  
External Ph ◽  
Freshwater Teleosts

The mechanism of ammonia excretion in freshwater teleosts is not well understood. In this study, scanning ion-selective electrode technique was applied to measure H+ and NH4+ fluxes in specific cells on the skin of zebrafish larvae. NH4+ extrusion was relatively high in H+ pump-rich cells, which were identified as the H+-secreting ionocyte in zebrafish. Minor NH4+ extrusion was also detected in keratinocytes and other types of ionocytes in larval skin. NH4+ extrusion from the skin was tightly linked to acid secretion. Increases in the external pH and buffer concentration (5 mM MOPS) diminished H+ and NH4+ gradients at the larval surface. Moreover, coupled decreases in NH4+ and H+ extrusion were found in larvae treated with an H+-pump inhibitor (bafilomycin A1) or H+-pump gene ( atp6v1a) knockdown. Knockdown of Rhcg1 with morpholino-oligonucleotides also decreased NH4+ excretion. This study demonstrates ammonia excretion in epithelial cells of larval skin through an acid-trapping mechanism, and it provides direct evidence for the involvement of the H+ pump and an Rh glycoprotein (Rhcg1) in ammonia excretion.

scholarly journals THE KINETICS OF PENETRATION

1937 ◽  
Vol 20 (5) ◽  
pp. 737-766 ◽  
Author(s):  
A. G. Jacques
Keyword(s):  
Sea Water ◽  
Surface Layers ◽  
Marked Contrast ◽  
External Concentration ◽  
Protoplasmic Surface ◽  
Kinetics Of ◽  
External Ph

When 0.1 M NaI is added to the sea water surrounding Valonia iodide appears in the sap, presumably entering as NaI, KI, and HI. As the rate of entrance is not affected by changes in the external pH we conclude that the rate of entrance of HI is negligible in comparison with that of NaI, whose concentration is about 107 times that of HI (the entrance of KI may be neglected for reasons stated). This is in marked contrast with the behavior of sulfide which enters chiefly as H2S. It would seem that permeability to H2S is enormously greater than to Na2S. Similar considerations apply to CO2. In this respect the situation differs greatly from that found with iodide. NaI enters because its activity is greater outside than inside so that no energy need be supplied by the cell. The rate of entrance (i.e. the amount of iodide entering the sap in a given time) is proportional to the external concentration of iodide, or to the external product [N+]o [I-lo, after a certain external concentration of iodide has been reached. At lower concentrations the rate is relatively rapid. The reasons for this are discussed. The rate of passage of NaI through protoplasm is about a million times slower than through water. As the protoplasm is mostly water we may suppose that the delay is due chiefly to the non-aqueous protoplasmic surface layers. It would seem that these must be more than one molecule thick to bring this about. There is no great difference between the rate of entrance in the dark and in the light.

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