scholarly journals The potential and short-circuit current across isolated rumen epithelium of the sheep

1966 ◽  
Vol 187 (3) ◽  
pp. 631-644 ◽  
Author(s):  
H. G. Ferreira ◽  
F. A. Harrison ◽  
R. D. Keynes
Animals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 2198
Author(s):  
Reiko Rackwitz ◽  
Franziska Dengler ◽  
Gotthold Gäbel

We hypothesized that, due to the high pH of this compartment, the reticulum epithelium displays particular features in the transport of short-chain fatty acids (SCFA). Ovine reticulum epithelium was incubated in Ussing chambers using a bicarbonate-free buffer solution containing butyrate (20 mmol L−1). p-hydroxymercuribenzoic acid (pHMB), 5-(N-Ethyl-N-isopropyl)amiloride (EIPA), or ouabain were added to the buffer solution as inhibitors of monocarboxylate transporters, sodium-proton-exchangers, or the Na+/K+-ATPase, respectively. The short-circuit current (Isc) and transepithelial conductance (Gt) were monitored continuously while the flux rates of 14C-labelled butyrate were measured in the mucosal-to-serosal (Jmsbut) or serosal-to-mucosal direction (Jsmbut). Under control conditions, the mean values of Isc and Gt amounted to 2.54 ± 0.46 µEq cm−2 h−1 and 6.02 ± 3.3 mS cm−2, respectively. Jmsbut was 2.1 ± 1.01 µmol cm−2 h−1 on average and about twice as high as Jsmbut. Incubation with ouabain reduced Jmsbut, while Jsmbut was not affected. The serosal addition of EIPA did not affect Jmsbut but reduced Jsmbut by about 10%. The addition of pHMB to the mucosal or serosal solution reduced Jmsbut but had no effect on Jsmbut. Mucosally applied pHMB provoked a transient increase in the Isc. The serosal pHMB sharply reduced Isc. Our results demonstrate that butyrate can be effectively transported across the reticulum epithelium. The mechanisms involved in this absorption differ from those known from the rumen epithelium.


The interior of the rumen in cattle and sheep is normally maintained at a potential of about — 40 mV relative to the blood. This potential depends primarily on the occurrence of an active transport of sodium from rumen to blood, since the potential, short-circuit current and the net sodium flux are simultaneously abolished by anoxia, ouabain and removal of sodium from the bathing solutions. There is an appreciable net flux of potassium from blood to rumen. There is also a substantial active transport of chloride in the same direction as sodium and it can be reduced by treatment with acetazolamide without affecting the potential or the sodium system. Nevertheless, sodium transport is reduced by the removal of chloride ions. Omasum epithelium is similar to rumen epithelium. However, the chloride pump appears to work in both directions in this tissue. Short-circuited omasum epithelium can also transport magnesium from omasum to blood.


2006 ◽  
Vol 291 (2) ◽  
pp. G246-G252 ◽  
Author(s):  
S. Leonhard-Marek ◽  
G. Breves ◽  
R. Busche

Active Na+ absorption across rumen epithelium comprises Na+/H+ exchange and a nonselective cation conductance (NSCC). Luminal chloride is able to stimulate Na+ absorption, which has been attributed to an interaction between Cl−/HCO3− and Na+/H+ exchangers. However, isolated rumen epithelial cells also express a Cl− conductance. We investigated whether Cl− has an additional effect on electrogenic Na+ absorption via NSCC. NSCC was estimated from short-circuit current ( Isc) across epithelia of goat and sheep rumen in Ussing chambers. Epithelial surface pH (pHs) was measured with 5- N-hexadecanoyl-aminofluorescence. Membrane potentials were measured with microelelectrodes. Luminal, but not serosal, Cl− stimulated the Ca2+ and Mg2+ sensitive Isc. This effect was independent of the replacing anion (gluconate or acetate) and of the presence of bicarbonate. The mean pHs of rumen epithelium amounted to 7.47 ± 0.03 in a low-Cl− solution. It was increased by 0.21 pH units when luminal Cl− was increased from 10 to 68 mM. Increasing mucosal pH from 7.5 to 8.0 also increased the Ca2+ and Mg2+ sensitive Isc and transepithelial conductance and reduced the fractional resistance of the apical membrane. Luminal Cl− depolarized the apical membrane of rumen epithelium. 5-Nitro-2-(3-phenylpropylamino)-benzoate reduced the divalent cation sensitive Isc, but only in low-Cl− solutions. The results show that luminal Cl− can increase the microclimate pH via apical Cl−/HCO3− or Cl−/OH− exchangers. Electrogenic Na+ absorption via NSCC increases with pH, explaining part of the Cl− effects on Na+ absorption. The data further show that the Cl− conductance of rumen epithelium must be located at the basolateral membrane.


1964 ◽  
Vol 206 (5) ◽  
pp. 1099-1105 ◽  
Author(s):  
Charles E. Stevens

Transepithelial electrical potential, short-circuit current, and resistance measurements were made under different conditions of tissue collection and maintenance. The collection procedure greatly affected tissue resistance and, since the magnitude of the current was relatively independent of the procedure, potential was affected to about the same degree. The highest and least variable resistances were recorded when the tissue was removed from the anesthetized cow and the epithelium carefully dissected free. Short-circuit current and net ion flux decreased with time but the decrease was relatively linear and sufficiently slow to allow their comparison. Rumen epithelium of both species demonstrated active transport of Na and Cl in the direction of lumen to blood. Calculation of partial Na conductances indicated that part of the sodium was transported by exchange diffusion or a sodium chloride transport system.


2021 ◽  
Author(s):  
Shengtao Gao ◽  
Alateng Zhula ◽  
Wenhui Liu ◽  
Zhongyan Lu ◽  
Zanming Shen ◽  
...  

Abstract Background: Disruption of the ruminal epithelium barrier occurs during subacute ruminal acidosis due to low pH, hyper-osmolality, and increased concentrations of lipopolysaccharide and histamine in ruminal fluid. However, the individual roles of lipopolysaccharide and histamine in the process of ruminal epithelium barriers disruption are not clear. The objective of the present investigation was to evaluate the direct effect of lipopolysaccharide and histamine on barrier function of the ruminal epithelium. Results: Compared with control (CON), lipopolysaccharide (HIS) increased the short-circuit current (Isc) (88.2%, P = 0.0022), transepithelial conductance (Gt) (29.7%, P = 0.0564) and the permeability of fluorescein 5(6)-isothiocyanate (FITC) (1.04-fold, P = 0.0047) of ruminal epithelium. The apparent permeability of LPS was 1.81-fold higher than HIS (P = 0.0005). The mRNA abundance of OCLN in ruminal epithelium was decreased by HIS (1.1-fold, P = 0.0473). Conclusions: The results of the present study suggested that histamine plays a direct role in the disruption of ruminal epithelium barrier function while lipopolysaccharide without acidic pH has no significant effect on the permeability of rumen tissues.


2013 ◽  
Vol 133 (1) ◽  
pp. 37-44
Author(s):  
Suresh Chand Verma ◽  
Yoshiki Nakachi ◽  
Yoshihiko Wazawa ◽  
Yoko Kosaka ◽  
Takenori Kobayashi ◽  
...  

2017 ◽  
pp. 34-41
Author(s):  
Andrei V. MAIOROV ◽  
◽  
Kirill A. OSINTSEV ◽  
Andrei V. SHUNTOV ◽  
◽  
...  

2020 ◽  
Vol 16 (4) ◽  
pp. 556-567
Author(s):  
Asma Khalil ◽  
Zubair Ahmad ◽  
Farid Touati ◽  
Mohamed Masmoudi

Background: The photo-absorption and light trapping through the different layers of the organic solar cell structures are a growing concern now-a-days as it affects dramatically the overall efficiency of the cells. In fact, selecting the right material combination is a key factor in increasing the efficiency in the layers. In addition to good absorption properties, insertion of nanostructures has been proved in recent researches to affect significantly the light trapping inside the organic solar cell. All these factors are determined to expand the absorption spectrum and tailor it to a wider spectrum. Objective: The purpose of this investigation is to explore the consequence of the incorporation of the Ag nanostructures, with different sizes and structures, on the photo absorption of the organic BHJ thin films. Methods: Through a three-dimensional Maxwell solver software, Lumerical FDTD, a simulation and comparison of the optical absorption of the three famous organic materials blends poly(3- hexylthiophene): phenyl C71 butyric acid methyl ester (P3HT:PCBM), poly[N-9″-heptadecanyl-2,7- carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)]: phenyl C71 butyric acid methyl ester (PCDTBT:PCBM) and poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b′]dithiophene)-alt- 4,7-(2,1,3-benzothiadiazole)]: phenyl C71 butyric acid methyl ester (PCDPDTBT:PCBM) has been conducted. Furthermore, FDTD simulation study of the incorporation of nanoparticles structures with different sizes, in different locations and concentrations through a bulk heterojunction organic solar cell structure has also been performed. Results: It has been demonstrated that embedding nanostructures in different locations of the cell, specifically in the active layer and the hole transporting layer had a considerable effect of widening the absorption spectrum and increasing the short circuit current. The effect of incorporation the nanostructures in the active layer has been proved to be greater than in the HTL. Furthermore, the comparison results showed that, PCDTBT:PCBM is no more advantageous over P3HT:PCBM and PCPDTBT:PCBM, and P3HT:PCBM took the lead and showed better performance in terms of absorption spectrum and short circuit current value. Conclusion: This work revealed the significant effect of size, location and concentration of the Ag nanostructures while incorporated in the organic solar cell. In fact, embedding nanostructures in the solar cell widen the absorption spectrum and increases the short circuit current, this result has been proven to be significant only when the nanostructures are inserted in the active layer following specific dimensions and structures.


2020 ◽  
Vol 89 (3) ◽  
pp. 30201 ◽  
Author(s):  
Xi Guan ◽  
Shiyu Wang ◽  
Wenxing Liu ◽  
Dashan Qin ◽  
Dayan Ban

Organic solar cells based on planar copper phthalocyanine (CuPc)/C60 heterojunction have been characterized, in which a 2 nm-thick layer of bathocuproine (BCP) is inserted into the CuPc layer. The thin layer of BCP allows hole current to tunnel it through but blocks the exciton diffusion, thereby altering the steady-state exciton profile in the CuPc zone (zone 1) sandwiched between BCP and C60. The short-circuit current density (JSC) of device is limited by the hole-exciton scattering effect at the BCP/CuPc (zone 1) interface. Based on the variation of JSC with the width of zone 1, the exciton diffusion length of CuPc is deduced to be 12.5–15 nm. The current research provides an easy and helpful method to determine the exciton diffusion lengths of organic electron donors.


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