No abstract available.
Animal ; Isomerism ; Saliva/secretion* ; Sodium-Hydrogen Antiporter/secretion ; Sodium-Hydrogen Antiporter/physiology* ; Sodium-Hydrogen Antiporter/chemistry*

No abstract available.
Animal ; Isomerism ; Saliva/secretion* ; Sodium-Hydrogen Antiporter/secretion ; Sodium-Hydrogen Antiporter/physiology* ; Sodium-Hydrogen Antiporter/chemistry*

A new method of axon recording through axon bleb has boosted the studies on the functional role of central nervous system (CNS) axons. Using this method, we have revealed the mechanisms underlying the initiation and propagation of the digital-mode signal, all-or-none action potentials (APs), in neocortical pyramidal neurons. Accumulation of the low-threshold Na(+) channel subtype Na(v)1.6 at the distal end of the axon initial segment (AIS) determines the lowest threshold for AP initiation, whereas accumulation of the high-threshold subtype Na(v)1.2 at the proximal region of the AIS promotes AP backpropagation to the soma and dendrites. Through dual recording from the soma and the axon, we have showed that subthreshold membrane potential (V(m)) fluctuations in the soma propagate along the axon to a long distance and probably reach the axon terminals. Paired recording from cortical neurons has revealed that these V(m) changes in the soma modulate AP-triggered synaptic transmission. This new V(m)-dependent mode of synaptic transmission is called analog communication. Unique properties of axonal K(+) channels (K(v)1 channels) may contribute to shaping the AP waveform, particularly its duration, and thus controlling synaptic strength at different levels of presynaptic V(m). The level of background Ca(2+) may also participate in mediating the analog signaling. Together, these findings enrich our knowledge on the principles of neuronal signaling in the CNS and help understand how the brain works.
Action Potentials ; physiology ; Animals ; Axons ; physiology ; Central Nervous System ; cytology ; physiology ; Humans ; Membrane Potentials ; physiology ; NAV1.2 Voltage-Gated Sodium Channel ; physiology ; NAV1.6 Voltage-Gated Sodium Channel ; physiology ; Neocortex ; cytology ; physiology ; Patch-Clamp Techniques ; Pyramidal Cells ; physiology ; Sodium Channels ; physiology

Sodium calcium exchanger (NCX), which is widely expressed in the plasma membrane, mitochondrial membrane and secretory vesicles in diverse kinds of cells, belongs to a type of cation translocators. NCX works in two modes, the forward mode and reverse mode, to regulate the intracellular Ca(2+) concentration bi-directionally. In the forward mode, NCX carries Ca(2+) out of the cell against its electrochemical gradients coupled to the influx of Na(+) down its electrochemical gradients; alternatively, Ca(2+) enters through the reverse mode of NCX, and Na(+) is carried out of the cell. Exactly through the two-way modes, NCX can regulate intracellular Ca(2+) concentration fleetly and accurately, and plays a critical role in a series of physiological processes including intracellular signal transduction, growth and development of cells, excitation and its coupled functions of excitable cells. NCX are acknowledged to be involved in myofiber contraction, neurotransmission, migration and differentiation of neurogliocyte, activation of immune cells, secretion of cytokines and hormones etc. Moreover, abnormal activation of the reverse mode of NCX plays a vital role in many pathological processes including cell apoptosis, ischemia-reperfusion injury, insulin secretion, tumor etc. Here we reviewed the research status about the NCX's participation in some physiological and pathophysiological processes, so as to provide comprehensive understanding about its functions.
Animals ; Apoptosis ; Calcium ; physiology ; Humans ; Ion Transport ; Reperfusion Injury ; physiopathology ; Signal Transduction ; Sodium ; physiology ; Sodium-Calcium Exchanger ; physiology

Aquaporin belongs to a highly conserved group of membrane proteins called major intrinsic proteins (MIPs) that facilitate water transport across biological membranes. Aquaporins are membrane water channels that play critical roles in controlling the water content of cells and tissues. We focused on GhPIP1;2 which belongs to the PIP subfamily and GhgammaTIP1 which belongs to the gammaTIP group of the TIP subfamily. Northern blot analysis with gene-specific probes and real-time PCR demonstrated that GhPIP1;2 and GhgammaTIP1 are predominantly expressed during cotton fiber elongation, with the highest expression levels at 5 days post anthesis. The high and preferential expression of GhPIP1;2 and GhgammaTIP1 suggests that they may play important roles in supporting the rapid influx of water into vacuoles during cotton fiber cell expansion. Also, the effects of Ca2+ on aquaporins in salinity-stressed plants were studied. Researchers treated the protoplasts and plasma membrane with NaCl or CaCl2, alone or in combination. Under saline conditions, osmotic water permeability (Pf) values decreased in protoplasts and plasma membrane vesicles, and the same reduction was observed in the PIP1 aquaporin abundance, indicating inhibitory effects of NaCl on aquaporin functionality and protein abundance. Two different actions of Ca2+ were observed. Increase in free cytosolic calcium concentrations associated with stress perception may lead to aquaporin closure, however, the extra-calcium would lead to an upregulation of aquaporins. Meanwhile, experiments have demonstrated HvPIP2;1, one of barley aquaporins, has a higher water and CO2 transport activity. The goal of our plant aquaporin research is to determine the key aquaporin species responsible for water and CO2 transport, and to improve plant water relations, stress tolerance, CO2 uptake or assimilation, and plant productivity.
Aquaporins ; physiology ; Cell Enlargement ; Cotton Fiber ; Gossypium ; metabolism ; physiology ; Photosynthesis ; physiology ; Plant Proteins ; physiology ; Sodium Chloride ; pharmacology ; Stress, Physiological ; physiology

OBJECTIVETo review the recent developments in the mechanisms of epithelium sodium channels (ENaCs) induced bone formation and regulation.

DATA SOURCESStudies written in English or Chinese were searched using Medline, PubMed and the index of Chinese-language literature with time restriction from 2005 to 2014. Keywords included ENaC, bone, bone formation, osteonecrosis, estrogen, and osteoporosis. Data from published articles about the structure of ENaC, mechanism of ENaC in bone formation in recent domestic and foreign literature were selected.

STUDY SELECTIONAbstract and full text of all studies were required to obtain. Studies those were not accessible and those did not focus on the keywords were excluded.

RESULTSENaCs are tripolymer ion channels which are assembled from homologous α, β, and γ subunits. Crystal structure of ENaCs suggests that ENaC has a central ion-channel located in the central symmetry axis of the three subunits. ENaCs are protease sensitive channels whose iron-channel activity is regulated by the proteolytic reaction. Channel opening probability of ENaCs is regulated by proteinases, mechanical force, and shear stress. Several molecules are involved in regulation of ENaCs in bone formation, including nitride oxide synthases, voltage-sensitive calcium channels, and cyclooxygenase-2.

CONCLUSIONThe pathway of ENaC involved in shear stress has an effect on stimulating osteoblasts even bone formation by estrogen interference.

Calcium Channels ; physiology ; Epithelial Sodium Channels ; chemistry ; physiology ; Estrogens ; pharmacology ; Humans ; Osteogenesis ; physiology

Na+/H+ antiporter plays an important role in mechanisms of the plant salt tolerance, it extrudes Na+ from cell energized by the proton gradient generated by the plasm membrane H(+)-ATPase and/or compartmentalizes Na+ in vacuole energized by the proton gradient generated by the vacuolar membrane H(+)-ATPase and H(+)-PPiase. This review mainly discusses the latest progress in the study of Na+/H+ antiporter in plant and yeast at molecular level.
Phylogeny ; Plants ; metabolism ; Salts ; metabolism ; Sodium ; metabolism ; Sodium-Hydrogen Exchangers ; classification ; metabolism ; Vacuoles ; physiology

The present study evaluated the effects of glyphosate on Pisum sativum germination as well as its effect on the physiology and biochemistry of germinated seedlings. Different physico-chemical biomarkers, viz., chlorophyll, root and shoot length, total protein and soluble sugar, along with sodium and potassium concentration, were investigated in germinated seedlings at different glyphosate concentrations. This study reports the influence of different concentrations of glyphosate on pea seeds and seedlings. Physicochemical biomarkers were significantly changed by glyphosate exposure after 15 days. The germination of seedlings under control conditions (0 mg/L) was 100% after 3 days of treatment but at 3 and 4 mg/L glyphosate, germination was reduced to 55 and 40%, respectively. Physiological parameters like root and shoot length decreased monotonically with increasing glyphosate concentration, at 14 days of observation. Average root and shoot length (n=30 in three replicates) were reduced to 14.7 and 17.6%, respectively, at 4 mg/L glyphosate. Leaf chlorophyll content also decreased, with a similar trend to root and shoot length, but the protein content initially decreased and then increased with an increase in glyphosate concentration to 3 mg/L. The study suggests that glyphosate reduces the soluble sugar content significantly, by 21.6% (v/v). But internal sodium and potassium tissue concentrations were significantly altered by glyphosate exposure with increasing concentrations of glyphosate. Biochemical and physiological analysis also supports the inhibitory effect of glyphosate on seed germination and biochemical effects on seedlings.
Biochemistry ; Biomarkers ; Chlorophyll ; Germination ; Peas ; Physiology ; Potassium ; Seedlings ; Sodium

Animals ; Autonomic Nervous System ; physiology ; Cardiovascular Physiological Phenomena ; Cytokines ; physiology ; Humans ; Potassium Channels ; physiology ; Sodium-Hydrogen Exchangers ; physiology

K(+) channels form a large family of membrane proteins that are expressed in a polarized fashion in any epithelial cell. Based on the transmembrane gradient for K(+) that is maintained by the Na(+)-K(+)-ATPase, these channels serve two principal functions for transepithelial transport: generation of membrane voltage and recycling of K(+). In this brief review, we will outline the importance of this ancient principle by examples of epithelial transport in the renal proximal tubule and gastric parietal cells. In both tissues, K(+) channel activity is rate-limiting for transport processes across the epithelial cells and essential for cell volume regulation. Recent experimental data using pharmacological tools and genetically modified animals have confirmed the original physiological concepts and specified the knowledge down to the molecular level. The development of highly active and tissue selective small molecule therapeutics has been impeded by two typical features of K(+) channels: their molecular architecture challenges the design of molecules with high affinity binding and they are expressed in a variety of tissues at the same time. Nevertheless, new insights into pathophysiology, e.g. that K(+) channel inhibition can block gastric acid secretion, render the clinical use of K(+) channel drugs in gastric disease and as kidney transport inhibitors highly attractive.
Animals ; Biological Transport ; Epithelial Cells ; physiology ; Kidney ; physiology ; Potassium ; Potassium Channels ; physiology ; Sodium-Potassium-Exchanging ATPase ; physiology