scholarly journals Electrophysiology of K+ Transport by Midgut Epithelium of Lepidopteran Insect Larvae: The Transbasal Electrochemical Gradient

1988 ◽  
Vol 135 (1) ◽  
pp. 25-38 ◽  
Author(s):  
DAVID F. MOFFETT ◽  
ALAN R. KOCH
Keyword(s):  
Lucifer Yellow ◽  
Electrical Coupling ◽  
Basal Membrane ◽  
Cell Types ◽  
Transepithelial Transport ◽  
Electrochemical Gradient ◽  
Insect Larvae ◽  
Lepidopteran Insect ◽  
Columnar Cells ◽  
K Transport

Basal membrane potential (Vb) and intracellular K+ activity [(K+)i] were recorded, using microelectrodes, in isolated, superfused, short-circuited midgut of fifth instar larvae of Manduca sexta. The electrochemical gradient across the basal membrane was favourable for K+ entry as long as [K+]b was 32mequivl−1 or greater. In 20 mequiv 1−1 K+ Vb rose so that in some cells the basal electrochemical gradient was unfavourable for K+ entry. In 10 mequivl−1 K+, the basal electrochemical gradient of all cells was unfavourable for K+ entry. This result suggests that an active K+ pump may augment passive basal K+ entry. Addition of 2mmoll−1 Ba2+ to midgut resulted in substantial hyperpolarization of Vb accompanied by relatively small changes in (K+)i; the net effect was to move (K+); farther away from electrochemical equilibrium with external K+. Identification of recorded cells by ionophoretic injection of Lucifer Yellow showed that both major cell types of the epithelium (goblet and columnar cells) had similar control values of Vb and (K+)i; and responded similarly to Ba2+, suggesting the presence of effective chemical or electrical coupling between the transporting goblet cells and the non-transporting columnar cells. Hypoxia reduced transepithelial K+ transport, both in the absence and in the presence of Ba2+. In the absence of Ba2+, (K+)i; was within a few millivolts of equilibrium and the effect of hypoxia was small. In the presence of Ba2+, when (K+)i; was far from equilibrium with extracellular K+, hypoxia markedly depolarized the basal membrane. The results are compatible with the suggestion that Ba2+ partially blocks basal K+ entry, but does not directly affect the apical pump. Hypoxia inhibits the apical pump. Since the active transepithelial transport of K+ was reduced after Ba2+ treatment even though (K+)i; was unchanged, it appears that the activity of the apical pump is primarily controlled by the voltage step across the apical membrane.

scholarly journals Physiological and morphological evidence for coupling in mouse salivary gland acinar cells.

1978 ◽  
Vol 79 (1) ◽  
pp. 20-26 ◽  
Author(s):  
S B Kater ◽  
N J Galvin
Keyword(s):  
Salivary Gland ◽  
Lucifer Yellow ◽  
Electrical Coupling ◽  
Freeze Fracture ◽  
Acinar Cells ◽  
Cell Types ◽  
Morphological Evidence ◽  
Secretory Cells ◽  
Intercellular Exchange ◽  
Dc Current

Three experimental techniques were employed to examine coupling between acinar cells of the mouse salivary gland. Passage of DC current pulses via intracellular microelectrodes between neighboring cells showed that small ions could be directly passed from one cell to another. Intracellular iontophoresis of the dye Lucifer Yellow CH into a single cell indicated that small molecules could spread by means of intercellular cytoplasmic bridges througout an acinus and, occasionally, into cells of adjacent acini. Freeze-fracture replicas of acinar cell membranes indicated the presence of gap junctions which were correlated with both electrical and dye coupling experiments. Suggestions are made for the function of direct intercellular exchange in salivary secretory cells. The role of electrical coupling in coordination of the activity of different secretory cell types is discussed as one possible function.

Electrophysiology of K+ Transport by Midgut Epithelium of Lepidopteran Insect Larvae: II. The Transapical Electrochemical Gradients

1988 ◽  
Vol 135 (1) ◽  
pp. 39-49
Author(s):  
DAVID F. MOFFETT ◽  
ALAN R. KOCH
Keyword(s):  
Electrical Potential ◽  
Potential Gradient ◽  
Goblet Cells ◽  
Mean Value ◽  
Bathing Solution ◽  
Voltage Sensitivity ◽  
Apical Surface ◽  
Insect Larvae ◽  
Lepidopteran Insect ◽  
K Transport

The apical surface of the midgut of Manduca sexta larvae is composed of the apical membranes of columnar cells, in the form of microvilli, and the apical goblet of goblet cells. Considerable evidence has suggested that the apical electrogenic pump that is responsible for transepithelial K+ transport is located on the apical membrane of goblet cells. In the present study the transapical potentials and K+ chemical activity [(K+)] gradients of columnar and goblet cells of posterior midgut were examined in the short-circuited gut. In some experiments the recording site was localized by ionophoresis of NiCl2 followed immediately by fixation in rubeanic acid. The (K+) of goblet cavities was substantially higher than that of the free solution on the gut luminal side (mean value of 94mmoll−1 in standard bathing solution). The goblet cavity was electrically positive to the gut lumen (mean value of 40 mV in standard bathing solution). When the rate of pumping of K+ into the goblet cavity was decreased by hypoxia or decreased bathing solution [K+], the electrical potential gradient between cytoplasm and goblet cavity decreased while intracellular (K+) and goblet cavity (K+) were relatively stable. These studies provide evidence that a negatively charged goblet matrix is present in goblet cavities. Furthermore, they suggest that it is the voltage-sensitivity of the apical pump to the electrical component of the transapical electrochemical gradient, and not a concentrationdependence of the pump, that exercises the major role in determining the relationship between extracellular (K+) and net K+ transport by the isolated gut.

Active Potassium Ion Transport Across the Caterpillar Midgut: II. Intracellular Microelectrode Studies

1984 ◽  
Vol 108 (1) ◽  
pp. 293-304
Author(s):  
M. V. THOMAS ◽  
T. E. MAY
Keyword(s):  
Ion Transport ◽  
Lucifer Yellow ◽  
Single Cells ◽  
Basal Membrane ◽  
Cell Types ◽  
Bimodal Distribution ◽  
Membrane Potentials ◽  
Potassium Ion ◽  
Tissue Resistance ◽  
Potassium Ion Transport

Intracellular microelectrodes were used to record from individual cells in midguts isolated from Spodoptera littoralis caterpillars. Recorded potentials, referenced to the basal (haemolymph) surface, showed a bimodal distribution, with maxima in the ranges 0 to −10 and −30 to −40 mV. In experiments where the fluorescent dye Lucifer Yellow CH was ionophoresed from the recording microelectrode, fluorescence was associated with single cells only for membrane potentials more negative than −25 mV. Examination of tissue sections showed these cells to be of both columnar and goblet types, in an approximate 2:1 ratio. This conclusion conflicts with that of a previous study on other caterpillar species, in which it was concluded that the goblet cells had basal membrane potentials of only a few mV. Attempts to discriminate between the two cell types by resistance measurements were unsuccessful. The resistance values obtained were substantially higher than those in the previous study, although they are consistent with those predicted from the overall tissue resistance. The major electrical effect of potassium ion transport inhibition by 1 m-KCN was on the apical membrane, supporting the view that the potassium pump is located there. The major initial effect of potassium ion removal was on the basal membrane, which is as expected if this membrane is permeable primarily to potassium. Our inability to discriminate between goblet and columnar cells by any electrical criterion suggests that both cell types may be able to transport potassium.

scholarly journals Characteristics of bipolar-bipolar coupling in the carp retina.

1988 ◽  
Vol 91 (2) ◽  
pp. 275-287 ◽  
Author(s):  
T Saito ◽  
T Kujiraoka
Keyword(s):  
Receptive Field ◽  
Bipolar Cell ◽  
Lucifer Yellow ◽  
Electrical Coupling ◽  
Coupling Efficiency ◽  
Receptive Fields ◽  
Spatial Summation ◽  
Cell Types ◽  
Bipolar Cells ◽  
Cell Pair

ON and OFF bipolar cells were identified in the light-adapted carp retina by means of intracellular recording and Lucifer yellow dye injection. The receptive field centers, determined by measuring the response amplitudes obtained by centered spots of different diameters, were 0.3-1.0 mm for ON bipolar cells and 0.3-0.4 mm for OFF bipolar cells. These central receptive field values were much larger than the dendritic field diameters measured by histological methods. Simultaneous intracellular recordings were made from pairs of neighboring bipolar cells. Current of either polarity injected into one member of a bipolar cell pair elicited a sign-conserving, sustained potential change in the other bipolar cell. The coupling efficiency was nearly identical for both depolarizing and hyperpolarizing currents. The maximum separation of coupled bipolar cells was approximately 130 microns. This electrical coupling was reciprocal and summative, and it was observed in cell types of similar function and morphology. Dye coupling was observed in 4 out of 34 stained cells. These results strongly suggest that there is a spatial summation of signals at the level of bipolar cells, which makes their central receptive fields much larger than their dendritic fields.

Electrically coupled pacemaker neurons respond differently to same physiological inputs and neurotransmitters

1984 ◽  
Vol 51 (6) ◽  
pp. 1362-1374 ◽  
Author(s):  
E. Marder ◽  
J. S. Eisen
Keyword(s):  
Motor Neurons ◽  
Slow Wave ◽  
Lucifer Yellow ◽  
Electrical Coupling ◽  
Excitatory Postsynaptic Potential ◽  
Panulirus Interruptus ◽  
Bursting Neuron ◽  
Postsynaptic Potential ◽  
Pyloric Dilator ◽  
Muscarinic Cholinergic

The two pyloric dilator (PD) motor neurons and the single anterior burster (AB) interneuron are electrically coupled and together comprise the pacemaker for the pyloric central pattern generator of the stomatogastric ganglion of the lobster, Panulirus interruptus. Previous work (31) has shown that the AB neuron is an endogenously bursting neuron, while the PD neuron is a conditional burster. In this paper the effects of physiological inputs and neurotransmitters on isolated PD neurons and AB neurons were studied using the lucifer yellow photoinactivation technique (33). Stimulation of the inferior ventricular nerve (IVN) fibers at high frequencies elicits a triphasic response in AB and PD neurons: a rapid excitatory postsynaptic potential (EPSP) followed by a slow inhibitory postsynaptic potential (IPSP), followed by an enhancement of the pacemaker slow-wave depolarizations. Photoinactivation experiments indicate that the enhancement of the slow wave is due primarily to actions of the IVN fibers on the PD neurons but not on the AB neuron. Bath-applied dopamine dramatically alters the motor output of the pyloric system. Photoinactivation experiments show that 10(-4) M dopamine increases the amplitude and frequency of the slow-wave depolarizations recorded in the AB neurons but hyperpolarizes and inhibits the PD neurons. Bath-applied serotonin increases the frequency and amplitude of the slow-wave depolarizations in the AB neuron but has no effect on PD neurons. Pilocarpine, a muscarinic cholinergic agonist, stimulates slow-wave depolarization production in both PD neurons and the AB neuron, but the waveform and frequency of the slow waves elicited are quite different. These results show that although the electrically coupled PD and AB neurons always depolarize synchronously and act together as the pacemaker for the pyloric system, they respond differently to a neuronal input and to several putative neuromodulators. Thus, despite electrical coupling sufficient to ensure synchronous activity, the PD and AB neurons can be modulated independently.

scholarly journals Purinergic responses of chondrogenic stem cells to dynamic loading

2013 ◽  
Vol 78 (12) ◽  
pp. 1865-1874 ◽  
Author(s):  
Ivana Gadjanski ◽  
Gordana Vunjak-Novakovic
Keyword(s):  
Stem Cells ◽  
Dynamic Loading ◽  
Lucifer Yellow ◽  
Atp Release ◽  
Human Mesenchymal Stem Cells ◽  
Cell Types ◽  
Flufenamic Acid ◽  
Release Assay ◽  
Extracellular Environment ◽  
Connexin Hemichannels

In habitually loaded tissues, dynamic loading can trigger ATP (adenosine 5?- triphosphate) release to extracellular environment, and result in calcium signaling via ATP binding to purine P2 receptors1. In the current study we have compared purinergic responses (ATP release) of two types of cells: bovine chondrocytes (bCHs) and human mesenchymal stem cells (hMSC) that were encapsulated in agarose and subjected to dynamic loading. Both cell types were cultured under chondrogenic conditions, and their responses to loading were evaluated by ATP release assay in combination with connexin (Cx)-sensitive fluorescent dye (Lucifer Yellow - LY) and a Cx-hemichannel blocker (Flufenamic acid - FFA). In response to dynamic loading, chondrogenic hMSCs released significantly higher amounts of ATP (5-fold) in comparison to the bCHs early in culture (day 2). Triggering of LY uptake in the bCHs and hMSCs by dynamic loading implies opening of the Cx-hemichannels. However, the number of LY-positive cells in hMSC-constructs was 2.5-fold lower compared to the loaded bCH-constructs, suggesting utilization of additional mechanisms of ATP release. Cx-reactive sites were detected in both bCHs and hMSCs-constructs. FFA application led to reduced ATP release both in bCHs and hMSCs, which confirms the involvement of connexin hemichannels, with more prominent effects in bCHs than in hMSCs, further implying the existence of additional mechanism of ATP release in chondrogenic hMSCs. Taken together, these results indicate stronger purinergic response to dynamic loading of chondrogenic hMSCs than primary chondrocytes, by activation of connexin hemichannels and additional mechanisms of ATP release.

scholarly journals A transcriptomic atlas of the mouse cerebellum reveals regional specializations and novel cell types

2020 ◽  
Author(s):  
Velina Kozareva ◽  
Caroline Martin ◽  
Tomas Osorno ◽  
Stephanie Rudolph ◽  
Chong Guo ◽  
...  
Keyword(s):  
Transcriptional Profiling ◽  
Molecular Layer ◽  
Electrical Coupling ◽  
Cell Types ◽  
Brain Cell ◽  
Brush Cells ◽  
Electrophysiological Properties ◽  
Regional Specialization ◽  
Mouse Cerebellum ◽  
Electrophysiological Recordings

The cerebellum is a well-studied brain structure with diverse roles in motor learning, coordination, cognition, and autonomic regulation. Nonetheless, a complete inventory of cerebellar cell types is presently lacking. We used high-throughput transcriptional profiling to molecularly define cell types across individual lobules of the adult mouse cerebellum. Purkinje and granule neurons showed considerable regional specialization, with the greatest diversity occurring in the posterior lobules. For multiple types of cerebellar interneurons, the molecular variation within each type was more continuous, rather than discrete. For the unipolar brush cells (UBCs)—an interneuron population previously subdivided into two discrete populations—the continuous variation in gene expression was associated with a graded continuum of electrophysiological properties. Most surprisingly, we found that molecular layer interneurons (MLIs) were composed of two molecularly and functionally distinct types. Both show a continuum of morphological variation through the thickness of the molecular layer, but electrophysiological recordings revealed marked differences between the two types in spontaneous firing, excitability, and electrical coupling. Together, these findings provide the first comprehensive cellular atlas of the cerebellar cortex, and outline a methodological and conceptual framework for the integration of molecular, morphological, and physiological ontologies for defining brain cell types.

scholarly journals KCNQ5/Kv7.5 potassium channel expression and subcellular localization in primate retinal pigment epithelium and neural retina

2011 ◽  
Vol 301 (5) ◽  
pp. C1017-C1026 ◽  
Author(s):  
Xiaoming Zhang ◽  
Dongli Yang ◽  
Bret A. Hughes
Keyword(s):  
Visual Information ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Basal Membrane ◽  
Cell Types ◽  
Neural Retina ◽  
Pcr Analysis ◽  
Rod Photoreceptor ◽  
Rpe Cells ◽  
Channel Expression

Previous studies identified in retinal pigment epithelial (RPE) cells an M-type K+ current, which in many other cell types is mediated by channels encoded by KCNQ genes. The aim of this study was to assess the expression of KCNQ genes in the monkey RPE and neural retina. Application of the specific KCNQ channel blocker XE991 eliminated the M-type current in freshly isolated monkey RPE cells, indicating that KCNQ subunits contribute to the underlying channels. RT-PCR analysis revealed the expression of KCNQ1, KCNQ4, and KCNQ5 transcripts in the RPE and all five KCNQ transcripts in the neural retina. At the protein level, KCNQ5 was detected in the RPE, whereas both KCNQ4 and KCNQ5 were found in neural retina. In situ hybridization in frozen monkey retinal sections revealed KCNQ5 gene expression in the ganglion cell layer and the inner and outer nuclear layers of the neural retina, but results in the RPE were inconclusive due to the presence of melanin. Immunohistochemistry revealed KCNQ5 in the inner and outer plexiform layers, in cone and rod photoreceptor inner segments, and near the basal membrane of the RPE. The data suggest that KCNQ5 channels contribute to the RPE basal membrane K+ conductance and, thus, likely play an important role in active K+ absorption. The distribution of KCNQ5 in neural retina suggests that these channels may function in the shaping of the photoresponses of cone and rod photoreceptors and the processing of visual information by retinal neurons.

scholarly journals Altered conductance and permeability of Cx40 mutations associated with atrial fibrillation

2015 ◽  
Vol 146 (5) ◽  
pp. 387-398 ◽  
Author(s):  
Ana Santa Cruz ◽  
Gülistan Meşe ◽  
Laima Valiuniene ◽  
Peter R. Brink ◽  
Thomas W. White ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Gap Junctions ◽  
Lucifer Yellow ◽  
Electrical Coupling ◽  
Primary Component ◽  
Base Substitution ◽  
Cardiac Tissues ◽  
Gap Junction Channel ◽  
Channel Selectivity ◽  
Mutant Forms

Gap junctions ensure the rapid propagation of the action potential throughout the myocardium. Three mutant forms of connexin40 (Cx40; A96S, M163V, and G38D), the primary component of the atrial gap junction channel, are associated with atrial fibrillation and retain the ability to form functional channels. We determined the biophysical properties of these mutant gap junctions in transiently transfected HeLa and N2A cells. All three mutants showed macroscopic junctional conductances over the range of 0.5 to 40 nS, and voltage dependences comparable to those of wild-type (WT) Cx40. However, the unitary conductance of G38D channels was ∼1.6-fold higher than that of WT Cx40 channels (∼220 vs. ∼135 pS), whereas the unitary conductances of the A96S and M163V mutants were similar to that of WT Cx40. Furthermore, the M163V and G38D channels exhibited approximately two- and approximately fivefold higher permeability to the anionic dye Lucifer yellow (LY) relative to K+ (LY/K+) compared with that of WT Cx40, whereas A96S LY transfer was similar to that of WT (G38D > M163V > A96S ≈ Cx40WT). In contrast, G38D channels were almost impermeable to cationic ethidium bromide (EtBr), suggesting that G38D alters channel selectivity. Conversely, A96S and M163V channels showed enhanced EtBr permeability relative to WT Cx40, with the following permeability order: M163V > A96S > Cx40WT > G38D. Altered conductive and permeability properties of mutant channels suggest an essential role for Cx40-mediated biochemical and electrical coupling in cardiac tissues. The altered properties of the three single-base substitution mutants may play a role in mechanisms of reentry arrhythmias.

scholarly journals Octopamine: a new feeding modulator in Lymnaea

1998 ◽  
Vol 353 (1375) ◽  
pp. 1631-1643 ◽  
Author(s):  
Á Vehovszky ◽  
C. J. H. Elliott ◽  
E. E. Voronezhskaya ◽  
L. Hiripi ◽  
K. Elekes
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Lymnaea Stagnalis ◽  
Lucifer Yellow ◽  
Electrical Coupling ◽  
Pond Snail ◽  
Double Labelling ◽  
Feeding System ◽  
Morphological Criteria ◽  
Stimulation Of

The role of octopamine (OA) in the feeding system of the pond snail, Lymnaea stagnalis , was studied by applying behavioural tests on intact animals, and a combination of electrophysiological analysis and morphological labelling in the isolated central nervous system. OA antagonists phentolamine, demethylchlordimeform (DCDM) and 2–chloro–4–methyl–2–(phenylimino)–imidazolidine (NC–7) were injected into intact snails and the sucrose–induced feeding response of animals was monitored. Snails that received 25–50 mg kg -1 phentolamine did not start feeding in sucrose, and the same dose of NC–7 reduced the number of feeding animals by 80–90% 1–3 hours after injection. DCDM treatment reduced feeding by 20–60%. In addition, both phentolamine and NC–7 significantly decreased the feeding rate of those animals that still accepted food after 1–6 hours of injection. In the central nervous system a pair of buccal neurons was identified by electrophysiological and morphological criteria. After double labelling (intracellular staining with Lucifer yellow followed by OA–immunocytochemistry) these neurons were shown to be OA immunoreactive, and electrophysiological experiments confirmed that they are members of the buccal feeding system. Therefore the newly identified buccal neurons were called OC neurons (putative OA containing neurons or OAergic cells). Synchronous intracellular recordings demonstrated that the OC neurons share a common rhythm with feeding neurons either appearing spontaneously or evoked by intracellularly stimulated feeding interneurons. OC neurons also have synaptic connections with identified members of the feeding network: electrical coupling was demonstrated between OC neurons and members of the B4 cluster motoneurons, furthermore, chemically transmitted synaptic responses were recorded both on feeding motoneurons (B1, B2 cells) and the SO modulatory interneuron after the stimulation of OC neurons. However, elementary synaptic potentials could not be recorded on the follower cells of OC neurons. Prolonged (20 to 30 s) intracellular stimulation of OC cells activated the buccal feeding neurons leading to rhythmic activity pattern (fictive feeding) in a way similar to OA applied by perfusion onto isolated central nervous system (CNS) preparations. Our results suggest that OA acts as a modulatory substance in the feeding system of Lymnaea stagnalis and the newly identified pair of OC neurons belongs to the buccal feeding network.

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