Ion Transport Across the Midgut of the Tobacco Hornworm (Manduca Sexta)

1990 ◽  
Vol 150 (1) ◽  
pp. 425-442 ◽  
Author(s):  
M. E. CHAMBERLIN
Keyword(s):  
Ion Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Tobacco Hornworm ◽  
Open Circuit ◽  
Middle Section ◽  
Anterior Section ◽  
K Secretion ◽  
K Transport ◽  
Subsequent Addition

1. The transport of K+, Na+ and Cl− across the three morphologically distinct regions of the tobacco hornworm midgut was measured under open-circuit and short-circuit conditions. Using a saline which contained physiological levels of haemolymph ions, amino acids and sugars, it was shown that all three sections actively secrete K+ and Cl− and absorb Na+. 2. The anterior section maintained the highest short-circuit current (Isc), transepithelial potential difference (PD) and net K+ secretion. The middle section had the lowest Isc, PD and K+ secretion, but absorbed Na+ at the greatest rate. The posterior section had the greatest rate of Cl− secretion. 3. Omission of K+ depressed the Isc. Subsequent addition of K+ stimulated the Isc to control levels in the middle and posterior sections, but not in the anterior section. Omission of Cl− or Na+ also inhibited the Isc. Reintroduction of Cl− had no stimulatory effect and, although reintroduction of Na+ stimulated the Isc, control levels were not attained. 4. Unlike the results reported in previous studies, the net K+ transport exceeded the Isc in all three midgut sections. The deficit in Isc was not made up by the transport of Na+ and Cl−. The results are discussed with respect to proposed models of ion transport across this epithelium.

A primary cation transport by a V-type ATPase of low specificity

1996 ◽  
Vol 199 (6) ◽  
pp. 1327-1334 ◽  
Author(s):  
J Küppers ◽  
I Bunse
Keyword(s):  
Ion Transport ◽  
Proton Transport ◽  
Short Circuit ◽  
Membrane Conductance ◽  
Short Circuit Current ◽  
Potential Difference ◽  
Lepidopteran Larvae ◽  
The Family ◽  
K Transport

The enzyme involved in outward K+ transport in insect epithelia belongs to the family of V-ATPases. Evidence has been reported relating the generation of the K+ gradient to a primary electrogenic proton transport via a distinct electrophoretic nH+/K+ antiport. The subject of this paper is the transport of K+ at a thread hair sensillum of the cockroach in situ. We recorded changes in the voltage and resistance of the ion-transporting membrane and of shifts in pH caused by inhibition of energy metabolism and by putative inhibitors of a proton/cation exchanger. The results are supplemented by previous determinations of the K+ activities in the same preparation. 1. In cockroach hair sensilla, the ion transport generates a membrane voltage of 105 mV. We found that the transport rendered the positive output compartment alkaline with respect to the cytoplasm by 1.0 pH unit compared with the pH at equilibrium distribution, and we infer that proton transport cannot be the process that energizes the generation of the K+ gradient. 2. The ion transport created an electrochemical potential difference for protons, DeltaetaH, of approximately 4.5 kJ mol-1, while the potential difference for K+, DeltaetaK, amounted to approximately 11 kJ mol-1. Both potential differences are directed to the cytosol. It follows from DeltaetaK/DeltaetaH that an antiport would have to be electrophoretic to drive K+ by DeltaetaH and it should, therefore, contribute to the membrane conductance. Amiloride and harmaline did not significantly change the pH in the adjacent spaces and did not affect the voltage or the resistance of the transporting membrane. Previous determinations of the impedance have shown that the ATP-independent conductance of this membrane is small, supporting the conclusion that it lacks an electrophoretic antiport. From these results, we deduce that K+ transport in cockroach sensilla is not secondary to a proton transport and an electrochemical proton gradient. The phenomena observed match the performance of a primary, electrogenic, cation-translocating ATPase of the type deduced from analyses of the short-circuit current at the midgut epithelium of lepidopteran larvae. The validity of the H+ transport/antiport hypothesis is discussed.

Ion transport characteristics of the murine trachea and caecum

1992 ◽  
Vol 82 (6) ◽  
pp. 667-672 ◽  
Author(s):  
S. N. Smith ◽  
E. W. F. W. Alton ◽  
D. M. Geddes
Keyword(s):  
Cystic Fibrosis ◽  
Ion Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Chloride Secretion ◽  
Open Circuit ◽  
Potential Difference ◽  
Cystic Fibrosis Gene ◽  
Tissue Type ◽  
Ussing Chambers

1. The basic defect in cystic fibrosis relates to abnormalities of ion transport in affected tissues, such as the respiratory and gastrointestinal tracts. The identification of the cystic fibrosis gene has enabled studies on the production of a cystic fibrosis transgenic mouse to be undertaken. Knowledge of normal ion transport will be necessary for the validation of any such animal model. We have therefore characterized selected responses of the murine trachea and caecum mounted in ‘mini’ Ussing chambers under open-circuit conditions. 2. Basal values for the trachea were: potential difference, 1.1 mV (sem 0.2; n=18); equivalent short-circuit current, 20.4 μA/cm2 (3.6); conductance, 18.2 mS/cm2 (1.7). Corresponding values for the caecum were: potential difference, 0.7 mV (0.1; n=18); equivalent short-circuit current, 11.0 μA/cm2 (1.6); conductance, 14.5 mS/cm2 (1.4). 3. Amiloride (10 μmol/l) produced a significant (P < 0.001) fall in potential difference of 43.0% (5.7) in the trachea, but had no significant effect in the caecum. 4. Subsequently, one of three protocols was used to assess the capacity of either tissue for chloride secretion. Addition of a combination of forskolin (1 μmol/l) and zardaverine (10 μmol/l) produced rises in the potential difference of 873% (509) in the trachea and 399% (202) in the caecum. Both A23187 (10 μmol/l) and phorbol dibutyrate (10 nmol/l) increased tracheal potential difference by 350% (182) and 147% (47), respectively. Neither had a significant effect in the caecum. 5. Subsequent addition of bumetanide caused a fall in the stimulated potential difference of between 39.8% and 71.7%, depending on secretagogue and tissue type. 6. When a homozygous transgenic cystic fibrosis mouse becomes available, these responses should allow such an animal to be distinguished from normal or heterozygous mice.

Changes in midgut active ion transport and metabolism during larval-larval molting in the tobacco hornworm (Manduca sexta)

1997 ◽  
Vol 200 (3) ◽  
pp. 643-648 ◽  
Author(s):  
M Chamberlin ◽  
C Gibellato ◽  
R Noecker ◽  
E Dankoski
Keyword(s):  
Ion Transport ◽  
Manduca Sexta ◽  
Aerobic Capacity ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Tobacco Hornworm ◽  
Maximal Aerobic Capacity ◽  
Posterior Midgut ◽  
Molting Process ◽  
Active Ion Transport

Ion transport and metabolism in the posterior midgut before, during and after the molt to the fifth instar of the tobacco hornworm Manduca sexta were investigated. In situ measurements reveal that the transepithelial potential difference of the posterior midgut falls during the molting process. This finding was confirmed by in vitro experiments in which it was demonstrated that both the transepithelial potential and the short-circuit current are lower in molting fourth instars compared with feeding fourth instars. The short-circuit current increases after ecdysis, with a maximal rate being achieved approximately 4 h after the molt. Resumption of feeding after the molt is not necessary to initiate this increase in active ion transport. The metabolic organization of the tissue also changes during the molting process. The maximal activities of glycolytic enzymes and 3-hydroxyacyl-CoA dehydrogenase, an enzyme of lipid ss-oxidation, decrease during the molting process and increase after ecdysis. Although citrate synthase activity, an index of maximal aerobic capacity, decreases during the molt and increases again after ecdysis, tissue respiration is the same in feeding fourth instars and molting larvae. This result indicates that a greater percentage of maximal aerobic capacity is used during molting and that energy may be diverted to cell proliferation and differentiation and away from the support of active ion transport at this time.

Bioelectric properties and ion transport across excised canine fetal and neonatal airways

1988 ◽  
Vol 65 (6) ◽  
pp. 2367-2375 ◽  
Author(s):  
C. U. Cotton ◽  
R. C. Boucher ◽  
J. T. Gatzy
Keyword(s):  
Ion Transport ◽  
Short Circuit ◽  
Fetal Lung ◽  
Short Circuit Current ◽  
Open Circuit ◽  
Airway Epithelial ◽  
Cl Secretion ◽  
Fetal Plasma ◽  
Large Airways ◽  
Lung Liquid

Knowledge of liquid secretion by fetal lung stems from studies of sheep. We extended these studies to dogs and examined the persistence of the fetal pattern of airway epithelial permeability and ion transport in the neonatal animal. Plasma and lung liquid from fetal dogs were analyzed for Na+, K+, Cl-, and HCO3-. Only the Cl- concentration of fetal lung liquid (129 meq/l) was significantly different from that of fetal plasma (111 meq/l). Segments of trachea from fetal and neonatal (less than 1, 7-10, and 21-46 days after birth) dogs were excised and mounted in flux chambers. The transepithelial potential difference (PD) of all tissues was oriented lumen negative (9.8-14.8 mV). Under short-circuit conditions, unidirectional Na+ flows were symmetrical. Cl- was secreted, and the secretion was equivalent to short-circuit current (Isc). Cl- secretion persisted under open-circuit conditions. Lobar bronchi from 21- to 46-day neonates absorbed Na+ (1.9 mueq.cm-2.h-1), but unidirectional flows of Cl- were symmetrical. Amiloride (10(-4) M) reduced Isc of neonatal bronchi by 47% but did not affect fetal bronchi. Isoproterenol increased Isc of both fetal (33%) and neonatal (40%) bronchi. These responses suggest that fetal bronchi do not absorb Na+ but can be stimulated to secrete Cl-. We conclude that Cl- secretion by epithelium of large airways may contribute to fetal lung liquid production, but it is unlikely that the tracheal epithelium is involved in fluid absorption at birth. Whereas fetal bronchi appear to secrete Cl-, neonatal bronchi absorb Na+.(ABSTRACT TRUNCATED AT 250 WORDS)

Active K transport across rabbit distal colon: relation to Na absorption and Cl secretion

1986 ◽  
Vol 251 (2) ◽  
pp. C252-C267 ◽  
Author(s):  
D. R. Halm ◽  
R. A. Frizzell
Keyword(s):  
Apical Membrane ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Secretory Process ◽  
Cl Secretion ◽  
K Secretion ◽  
Transport Inhibitors ◽  
Unidirectional Fluxes ◽  
K Transport

We measured isotopic unidirectional fluxes of K to elucidate the mechanisms of active K transport across the distal colon of the rabbit. Separate pathways for active K absorption and active K secretion were detected using various transport inhibitors and stimulators. The rate and direction of net K transport depend on the activities of these two pathways. K absorption was reduced by orthovanadate (both solutions) or serosal Ba, consistent with ATPase-dependent uptake of K across the apical membrane and exit via a Ba-sensitive basolateral K conductance. K secretion was inhibited by serosal ouabain or mucosal Ba, indicating that K secretion involves basolateral uptake via the Na-K pump and apical exit via a Ba-sensitive K conductance. Active K secretion appears to be electrogenic, since inhibition by ouabain produced equivalent changes in the net K flux and short-circuit current. Addition of bumetanide to the serosal solution or the removal of either Na or Cl from the serosal solution inhibited K secretion; mucosal solution amiloride was without effect. These results indicate that this K secretory process is independent of electrogenic Na absorption but is mechanistically similar to Cl secretory processes. Both epinephrine and prostaglandin E2 (PGE2) stimulate K secretion, but only PGE2 also stimulates Cl secretion. The response to these secretogogues suggests that the mechanisms underlying K and Cl secretion are closely linked but can be regulated independently.

K+ transport by rat colon: adaptation to a low potassium diet

1986 ◽  
Vol 250 (3) ◽  
pp. F483-F487
Author(s):  
R. L. Tannen ◽  
R. Marino ◽  
D. C. Dawson
Keyword(s):  
Rat Kidney ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Rat Colon ◽  
High K ◽  
Isotope Technique ◽  
K Secretion ◽  
Low K ◽  
K Transport

Recent studies with the isolated perfused rat kidney have demonstrated the existence of an intrinsic renal adaptation to conserve K+ in response to ingestion of a low K+ diet for 3 days. To determine whether the colon alters its K+ transport properties in a similar fashion, we measured transmural 86Rb fluxes across sheets of distal colonic epithelium under short-circuit conditions. Preliminary studies using a double-isotope technique demonstrated that 86Rb and 42K fluxes were similar; therefore 86Rb flux was considered equivalent to K+ flux. The distal half of the colon from each rat was divided into two segments, referred to as early and late distal colon. Experiments were carried out using rats fed a K+ -free, control (0.15 mmol/g), and high K+ (1.13 mmol/g) powdered diet of otherwise identical electrolyte content. Net K+ secretion (Jnet) by the early distal colon was reduced from 0.45 in the controls to -0.02 mueq X cm-2 X h-1 by a low K+ diet as a result of a decrease in serosal-to-mucosal flux (Jsm), with no change in mucosal-to-serosal flux (Jms). Conductance (GT) and short-circuit current (Isc) were unchanged. Jnet by the late distal colon averaged 0.17 in the controls and 0.01 mueq X cm-2 X h-1 with a low K+ diet, but this difference was not significant statistically. In comparison with the controls, a high K+ diet had no effect on Jnet by the early distal colon (0.48 mueq X cm-2 X h-1) but increased Jnet by the late distal colon substantially (0.77 mueq X cm-2 X h-1).(ABSTRACT TRUNCATED AT 250 WORDS)

Lidocaine and Barium Distinguish Separate Routes of Transbasal K+ Uptake in the Posterior Midgut of the Tobacco Hornworm (Manduca Sexta)

1991 ◽  
Vol 157 (1) ◽  
pp. 243-256 ◽  
Author(s):  
DAVID F. MOFFETT ◽  
ALAN KOCH
Keyword(s):  
Intracellular Transport ◽  
Channel Blocker ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Basal Membrane ◽  
Tobacco Hornworm ◽  
K Channel ◽  
K Uptake ◽  
Posterior Midgut ◽  
K Transport

The isolated posterior midgut of the tobacco hornworm maintains a vigorous transepithelial K+ transport from the hemolymphal side to the lumen side at a rate accurately measured by its short-circuit current. Previous studies using the K+ channel blocker Ba2+ suggested that partial inhibition of the short-circuit current by hemolymphal Ba2+ was due to blockage of one of at least two parallel transbasal entry routes for K+ into the intracellular transport pool. The present studies show that the local anesthetic lidocaine, at a concentration of 5 mmoll−1 on the hemolymphal side, partly inhibits net transepithelial K+ transport. The inhibition is accompanied by hyperpolarization of the basal membrane and an increase in transbasal resistance, suggestive of a block of transbasal K+ conductance. The effects of lidocaine and Ba2+ are additive, suggesting that the inhibitors distinguish separate, parallel K+ uptake processes.

scholarly journals CdTe-Based Thin Film Solar Cells: Past, Present and Future

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1684
Author(s):  
Alessandro Romeo ◽  
Elisa Artegiani
Keyword(s):  
Thin Film ◽  
Solar Cells ◽  
Solar Cell ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Short Circuit Current Density ◽  
Open Circuit ◽  
Early Years ◽  
Solar Cell Efficiency ◽  
Cell Efficiency

CdTe is a very robust and chemically stable material and for this reason its related solar cell thin film photovoltaic technology is now the only thin film technology in the first 10 top producers in the world. CdTe has an optimum band gap for the Schockley-Queisser limit and could deliver very high efficiencies as single junction device of more than 32%, with an open circuit voltage of 1 V and a short circuit current density exceeding 30 mA/cm2. CdTe solar cells were introduced at the beginning of the 70s and they have been studied and implemented particularly in the last 30 years. The strong improvement in efficiency in the last 5 years was obtained by a new redesign of the CdTe solar cell device reaching a single solar cell efficiency of 22.1% and a module efficiency of 19%. In this paper we describe the fabrication process following the history of the solar cell as it was developed in the early years up to the latest development and changes. Moreover the paper also presents future possible alternative absorbers and discusses the only apparently controversial environmental impacts of this fantastic technology.

scholarly journals GaInP/GaAs/poly-Si Multi-Junction Solar Cells by in Metal Balls Bonding

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 726
Author(s):  
Ray-Hua Horng ◽  
Yu-Cheng Kao ◽  
Apoorva Sood ◽  
Po-Liang Liu ◽  
Wei-Cheng Wang ◽  
...  
Keyword(s):  
Solar Cells ◽  
Solar Cell ◽  
Low Temperature ◽  
Triple Junction ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Open Circuit ◽  
Metal Line ◽  
Solar Simulator ◽  
Junction Solar Cell

In this study, a mechanical stacking technique has been used to bond together the GaInP/GaAs and poly-silicon (Si) solar wafers. A GaInP/GaAs/poly-Si triple-junction solar cell has mechanically stacked using a low-temperature bonding process which involves micro metal In balls on a metal line using a high-optical-transmission spin-coated glue material. Current–voltage measurements of the GaInP/GaAs/poly-Si triple-junction solar cells have carried out at room temperature both in the dark and under 1 sun with 100 mW/cm2 power density using a solar simulator. The GaInP/GaAs/poly-Si triple-junction solar cell has reached an efficiency of 24.5% with an open-circuit voltage of 2.68 V, a short-circuit current density of 12.39 mA/cm2, and a fill-factor of 73.8%. This study demonstrates a great potential for the low-temperature micro-metal-ball mechanical stacking technique to achieve high conversion efficiency for solar cells with three or more junctions.

scholarly journals Photocurrent density and electrical properties of Bi0.5Na0.5TiO3-BaNi0.5Nb0.5O3 ceramics

2021 ◽  
Author(s):  
Mingqiang Zhong ◽  
Qin Feng ◽  
Changlai Yuan ◽  
Xiao Liu ◽  
Baohua Zhu ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Photovoltaic Effect ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Photocurrent Density ◽  
Open Circuit ◽  
Light Conditions ◽  
X Ray Diffraction ◽  
Solid State Method ◽  
X Ray

AbstractIn this work, the (1−x)Bi0.5Na0.5TiO3-xBaNi0.5Nb0.5O3 (BNT-BNN; 0.00 ⩽ x ⩽ 0.20) ceramics were prepared via a high-temperature solid-state method. The crystalline structures, photovoltaic effect, and electrical properties of the ceramics were investigated. According to X-ray diffraction, the system shows a single perovskite structure. The samples show the normal ferroelectric loops. With the increase of BNN content, the remnant polarization (Pr) and coercive field (Ec) decrease gradually. The optical band gap of the samples narrows from 3.10 to 2.27 eV. The conductive species of grains and grain boundaries in the ceramics are ascribed to the double ionized oxygen vacancies. The open-circuit voltage (Voc) of ∼15.7 V and short-circuit current (Jsc) of ∼1450 nA/cm2 are obtained in the 0.95BNT-0.05BNN ceramic under 1 sun illumination (AM1.5G, 100 mW/cm2). A larger Voc of 23 V and a higher Jsc of 5500 nA/cm2 are achieved at the poling field of 60 kV/cm under the same light conditions. The study shows this system has great application prospects in the photovoltaic field.

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