Transport of monovalent cations by the isolated small intestine of the rat

1960 ◽  
Vol 199 (5) ◽  
pp. 898-906 ◽  
Author(s):  
T. W. Clarkson ◽  
A. Rothstein

Everted segments of the small intestine of the rat, taken from both jejunal and ileal regions, were able to transport sodium against an electrochemical gradient by a highly specific mechanism. Other monovalent cations (cesium, potassium, lithium and triethylammonium) moved across the tissue much more slowly than sodium and always in the direction of the electrochemical gradient. Water movement appeared to be passive following the osmotic forces set up by active solute transfer. Both the electrical potential difference across the tissue and the net water transfer fell rapidly when the sodium concentrations in the media were reduced below 120 mm/l. Glucose transport was also responsive to the cation composition of the media; low concentrations of sodium were inhibitory, lithium at 25 mm/l. produced a stimulatory effect, and potassium at 25 mm/l. was inhibitory.

1975 ◽  
Vol 67 (1) ◽  
pp. 119-125
Author(s):  
P. J. BENTLEY

SUMMARY The electrical potential difference and short-circuit current (scc, reflecting active transmural sodium transport) across the toad urinary bladder in vitro was unaffected by the presence of hypo-osmotic solutions bathing the mucosal (urinary) surface, providing that the transmural flow of water was small. Vasopressin increased the scc across the toad bladder (the natriferic response), but this stimulation was considerably reduced in the presence of a hypo-osmotic solution on the mucosal side, conditions under which water transfer across the membrane was also increased. This inhibition of the natriferic response did not depend on the direction of the water movement, for if the osmotic gradient was the opposite way to that which normally occurs, the response to vasopressin was still reduced. The natriferic response to cyclic AMP was also inhibited in the presence of an osmotic gradient. Aldosterone increased the scc and Na+ transport across the toad bladder but this response was not changed when an osmotic gradient was present. The physiological implications of these observations and the possible mechanisms involved are discussed.


1957 ◽  
Vol 41 (1) ◽  
pp. 143-168 ◽  
Author(s):  
Peter F. Curran ◽  
A. K. Solomon

Studies have been carried out on the movement of salt and water across the small intestine of the rat. Segments of the ileum of anesthetized rats have been perfused in vivo with unbuffered NaCl solutions or isotonic solutions of NaCl and mannitol. Kinetic analysis of movements of Na24 and Cl36 has permitted determination of the efflux and influx of Na and Cl. Net water absorption has been measured using hemoglobin as a reference substance. Water was found to move freely in response to gradients of osmotic pressure. Net water flux from isotonic solutions with varying NaCl concentration was directly dependent on net solute flux. The amount of water absorbed was equivalent to the amount required to maintain the absorbed solute at isotonic concentration. These results have been interpreted as indicating that water movement is a passive process depending on gradients of water activity and on the rate of absorption of solute. The effluxes of Na and Cl are linear functions of concentration in the lumen, but both ions are actively transported by the ileum according to the criterion of Ussing (Acta Physiol. Scand., 1949, 19, 43). The electrical potential difference between the lumen and plasma has been interpreted as a diffusion potential slightly modified by the excess of active Cl flux over active Na flux. The physical properties of the epithelial membrane indicate that it is equivalent to a membrane having negatively charged uniform right circular pores of 36 Å radius occupying 0.001 per cent of the surface area.


1963 ◽  
Vol 205 (3) ◽  
pp. 427-438 ◽  
Author(s):  
Henry O. Wheeler

Gall bladders of rabbits were studied in vitro in an apparatus which permitted measurement of electrical potential difference, net flux of water, and changes in electrolyte concentrations in mucosal and serosal fluid. Net water flux (mucosa to serosa) was directly proportional to net solute transport (measured as sodium flux) and the transported solution was slightly hypertonic. When mannitol was added to the mucosal fluid, water movement occurred against osmotic gradients often exceeding 80 mosmol/kg. Electrical potential differences were small, but the lumen was invariably positive. Flux ratio determinations indicated active transport of both chloride and sodium but not potassium. When isethionate was substituted for chloride, active bicarbonate absorption was also evident. Anion and cation transport were not independent and no transport occurred when choline was substituted for sodium. The evidence suggests coupled active transport of sodium and the major anions. Water movement is dependent upon active solute transport by means of an undetermined coupling mechanism.


1971 ◽  
Vol 49 (3) ◽  
pp. 377-386 ◽  
Author(s):  
H. M. NOBLE ◽  
A. J. MATTY

SUMMARY Using a new technique for determining transmucosal electrical potential difference (p.d.) and short-circuit current (Isc.) in the rat small intestine in vivo it would appear that aldosterone had no direct effect on these parameters of intestinal activity. However, adrenalectomy decreased the Isc. while after adrenalectomy aldosterone and cortisol (hydrocortisone) restored the lowered independent and probably also the lowered dependent (hexose) Isc.


1988 ◽  
Vol 255 (4) ◽  
pp. R583-R590
Author(s):  
W. M. Moran ◽  
L. T. Garretson

We have reexamined the notion that sugars stimulate ion absorption differently in invertebrate and vertebrate intestine. In the seahare intestine, mucosal sugar presumably increases the rate of transcellular Na+ and Cl- absorption, whereas only transcellular Na+ absorption is increased in the vertebrate small intestine. Our data indicate that the seahare intestine responds to mucosal D-galactose like the vertebrate small intestine: namely, the apical membrane electrical potential difference depolarizes, the ratio of the mucosal to serosal membrane resistances decreases, and the short-circuit current (Isc) increases. Because mucosal substitution of tetramethylammonium for Na+ abolished the increased Isc, this stimulation resulted from an increase in rheogenic Na+ absorption. Unidirectional transepithelial Cl- fluxes indicate that mucosal D-galactose had no effect on the net Cl- flux under short-circuit conditions. Further, ion substitution experiments indicate that the apical membrane is K+ conductive rather than Cl- conductive as previously reported. These electrophysiological as well as parallel histological findings indicate that studies previously reported on the seahare intestine were in fact conducted on the esophagus.


2016 ◽  
Vol 2 (2) ◽  
pp. 129
Author(s):  
Urtak Hamiti

Barbaric, savage, horrific-these were terms to define the decision of the Islamic State of Iraq and Syria (ISIS) to murder its captured Jordanian pilot by burning him alive inspired a thesaurus of horror and revulsion. The men who did it, the perpetrators were described by the media as mad men, thugs, monsters. To most of the people, the act itself seemed inexplicable and without sense. However, behind the choreographed and videotaped violence lies a calculated horrible cold logic. Although, ISIS is often portrait as a mighty force on the ground in Syria and Iraq, facts state that they control mainly communications between various provinces in both countries, and, as most guerrilla armies, are militarily weak by conventional measure. ISIS has little or almost none defense against the bombing campaign that is facing now, while US has formed a coalition that is confronting them on the ground as well, after President Barack Obama published the “New Security Doctrine” which includes degrading and finally destroying ISIS. ISIS, however, have proven to be very organized in promoting dramatic acts of violence against their enemies and promoting them two achieve two goals: use terror tactics as a psychological weapon against all those facing them and all those that are to face them in combat. Secondly, through usage of social network platforms to promote killings and executions, the aim of ISIS is to encourage recruits from out of Syria and Iraq, and elsewhere, to join them in their cause. Online operations of ISIS fall under a production group called the Al Hayat Media Center. The Center was created to seduce Westerners into joining the ranks of ISIS and also to distribute propaganda through social and media platforms. It is difficult to assess the success of this operation, but solid sources provided by US military and intelligence estimate that at least 300 Americans are fighting in the ranks of ISIS (at least two Americans have been killed fighting for ISIS in Iraq/Syria region) while the number of Europeans is in thousands. The US Response to this psychological kind of warfare came when President Barack Obama established the Center for Strategic Counterterrorism Communications (CSCC) aiming to combat terrorist propaganda. The main strategy of CSCC is not directly to confront ISIS operatives, but rather than that to deal with the people they are trying to recruit. Now, with almost entire international public opinion on their side, it is time for US to more actively respond to ISIS especially in the manner of psychological warfare since it is obvious that operations of “winning hearts and minds” of people in Iraq and Syria are not enough compared to ruthless tactics of ISIS which “winning hearts and minds” by brute force, terror, and vivid violent images. The online propaganda war is a new component to conflicts of 21st century that allows enemies to reach one another’s home fronts directly. ISIS might seem not so strong on the ground but it has captured one fundamental flaw of the media of 21st century-the one that bad news is always good news and that televised violence will always have an audience. ISIS has proclaimed that its goal is to create a caliphate of 21st century but its psychological warfare and propaganda is inspiring individuals throughout the West to commit horrible terrorist crimes. Could this be another mind game set up by ISIS, it remains to be seen. However one thing is for certain, US and its allies must tackle ISIS not only by planes and other military means, but also by a strategy that would eliminate its influence in spreading their propaganda.


1976 ◽  
Vol 26 (1) ◽  
pp. 79-92 ◽  
Author(s):  
Yutaka IGARASHI ◽  
Yoshitaka SAITO ◽  
Masayoshi HIMUKAI ◽  
Takeshi HOSHI

1984 ◽  
Vol 62 (6) ◽  
pp. 1245-1249 ◽  
Author(s):  
L. S. Kott ◽  
K. J. Kasha

Somatic embryogenesis was induced in callus previously initiated from immature embryos of barley. These cultures ranged in age from 6 weeks to 30 months. Embryoids were readily initiated from homogenized suspension-grown aggregates when plated on modified B5 media with 2,4-dichlorophenoxyacetic acid. Low concentrations (0.1 and 0.05 mg∙L−1) of abscisic acid promoted further maturation of embryoids, while gibberellic acid (1 mg∙L−1) and kinetin (0.1 mg∙L−1) were used in the media to encourage embryoid germination. The development of somatic embryoids from initiation through maturation and germination is described.


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