Activation of electroneutral K flux in Amphiuma red blood cells by N-ethylmaleimide. Distinction between K/H exchange and KCl cotransport.

Exposure of Amphiuma red blood cells to millimolar concentrations of N-ethylmaleimide (NEM) resulted in net K loss. In order to determine whether net K loss was conductive or was by electroneutral K/H exchange or KCl cotransport, studies were performed evaluating K flux in terms of the thermodynamic forces to which K flux by the above pathways should couple. The direction and magnitude of the NEM-induced net K flux did not correspond with the direction and magnitude of the forces relevant to K conductance or electroneutral KCl cotransport. Both the magnitude and direction of the NEM-activated K flux responded to the driving force for K/H exchange. We therefore conclude that NEM-induced K loss, like that by osmotically swollen Amphiuma red blood cells, is by an electroneutral K/H exchanger. In addition to the above studies, we evaluated the kinetic behavior of the volume- and NEM-induced K/H exchange flux pathways in media where Cl was replaced by SCN, NO3, para-aminohippurate (PAH), or gluconate. The anion replacement studies did not permit a distinction between K/H exchange and KCl cotransport, since, depending upon the anion used as a Cl replacement, partial inhibition or stimulation of volume-activated K/H exchange fluxes was observed. In contrast, all anions used were stimulatory to the NEM-induced K loss. Since, on the basis of force-flow analysis, both volume-and NEM-induced K loss are K/H exchange, it was necessary to reevaluate assumptions (i.e., anions serve as substrates and therefore probe the translocation step) associated with the use of anion replacement as a means of flux route identification. When viewed together with the force-flow studies, the Cl replacement studies suggest that anion effects upon K/H exchange are indirect. The different anions appear to alter mechanisms that couple NEM exposure and cell swelling to the activation of K/H exchange, as opposed to exerting direct effects upon K and H translocation

The storm-time ring current: a statistical analysis at two widely separated low-latitude stations

We conducted a statistical analysis of the geomagnetic field variations during the storm main phase at two low-latitude stations, separated by several hours in magnetic local time, in order to investigate the asymmetry and longitudinal extent of the storm-time ring current. The results show evidence for an asymmetric current which typically extends from evening to noon and, during moderate solar wind electric field conditions, up to the early morning, confirming the important role of the magnetospheric convection in the ring current energization. We also analyzed a possible relationship between the local current intensity during the storm main phase and the substorm activity observed at different time delays τ with respect to the storm onset. The results show a significant anticorrelation for τ =-1h, indicating that if the substorm activity is high just before the storm, a weaker ring current develops

Effect of pasture in oak and chestnut groves on chemical and sensorial traits of cured lard of Cinta Senese pigs

The objective of this study was to evaluate the effect of pasture in oak and chestnut groves on the chemical and sensorial traits of cured lard. Thirty Cinta Senese barrows (124kg of l.w. on average) were allotted to three groups: one group (CONC) was reared outdoors in a confined area and fed commercial feedstuff. The other two groups were raised under free-range conditions on acorns (AC) or chestnuts (CH). At slaughtering (148kg of LW) the backfat was seasoned for 60 days to obtained cured lard. Results demonstrated that the lard of CH and AC respect to CONC group was the richest in MUFA (46.9 and 47.76 vs 44.78% respectively) because of the higher content of oleic acid (44.2 and 44.91 vs 42.05%, P<0.05, respectively). CH showed a higher percentage of PUFA-n3 than AC and CONC (1.18 vs 1.06 and 1.03%, P<0.05, respectively), a lower content of α-tocopherol (9.77 vs 14.46 and 13.31μ/g, P<0.05 respectively) and a higher content of γ-tocopherol (13.73 vs 6.02 and 4.32μ/g, P<0.05, respectively). As regards sensorial traits, the lard of CH and AC groups exhibited a lower value of pinkness than CONC (29.3 and 32.4 vs 49.2, P<0.05, respectively) and higher scores of yellowness (31.4 and 28.6 vs 18.6, P<0.05, respectively) and oiliness (37.0 and 33.7 vs 24.0, P<0.05, respectively). The pasture in the acorn and chestnut groves affected the chemical traits of lard, prevalently the composition of fatty acids . The consumption of acorns or chestnuts led to a higher content of oleic acid with respect to concentrate, affecting some sensorial traits of lard

Potassium Channel and NKCC Cotransporter Involvement in Ocular Refractive Control Mechanisms

Myopia affects well over 30% of adult humans globally. However, the underlying physiological mechanism is little understood. This study tested the hypothesis that ocular growth and refractive compensation to optical defocus can be controlled by manipulation of potassium and chloride ion-driven transretinal fluid movements to the choroid. Chicks were raised with +/−10D or zero power optical defocus rendering the focal plane of the eye in front of, behind, or at the level of the retinal photoreceptors respectively. Intravitreal injections of barium chloride, a non-specific inhibitor of potassium channels in the retina and RPE or bumetanide, a selective inhibitor of the sodium-potassium-chloride cotransporter were made, targeting fluid control mechanisms. Comparison of refractive compensation to 5mM Ba2+ and 10−5 M bumetanide compared with control saline injected eyes shows significant change for both positive and negative lens defocus for Ba2+ but significant change only for negative lens defocus with bumetanide ; ; ; ; ; ). Vitreous chamber depths showed a main effect for drug conditions with less depth change in response to defocus shown for Ba2+ relative to Saline, while bumetanide injected eyes showed a trend to increased depth without a significant interaction with applied defocus. The results indicate that both K channels and the NKCC cotransporter play a role in refractive compensation with NKCC blockade showing far more specificity for negative, compared with positive, lens defocus. Probable sites of action relevant to refractive control include the apical retinal pigment epithelium membrane and the photoreceptor/ON bipolar synapse. The similarities between the biometric effects of NKCC inhibition and biometric reports of the blockade of the retinal ON response, suggest a possible common mechanism. The selective inhibition of refractive compensation to negative lens in chick by loop diuretics such as bumetanide suggests that these drugs may be effective in the therapeutic management of human myopia

Sviluppo concettuale, implementazione e realizzazione prototipale di macchina per misure millesimali

Sviluppo concettuale di un nuovo prodotto, implementazione e realizzazione prototipale di una macchina metrologica per misure millesimali e controllo qualità

The effect of a weak magnetic field on ionic flux (K-42) across the body wall of the marine polychaete, Myxicola infundibulum

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Activation of electroneutral K flux in Amphiuma red blood cells by N-ethylmaleimide. Distinction between K/H exchange and KCl cotransport.

Exposure of Amphiuma red blood cells to millimolar concentrations of N-ethylmaleimide (NEM) resulted in net K loss. In order to determine whether net K loss was conductive or was by electroneutral K/H exchange or KCl cotransport, studies were performed evaluating K flux in terms of the thermodynamic forces to which K flux by the above pathways should couple. The direction and magnitude of the NEM-induced net K flux did not correspond with the direction and magnitude of the forces relevant to K conductance or electroneutral KCl cotransport. Both the magnitude and direction of the NEM-activated K flux responded to the driving force for K/H exchange. We therefore conclude that NEM-induced K loss, like that by osmotically swollen Amphiuma red blood cells, is by an electroneutral K/H exchanger. In addition to the above studies, we evaluated the kinetic behavior of the volume- and NEM-induced K/H exchange flux pathways in media where Cl was replaced by SCN, NO3, para-aminohippurate (PAH), or gluconate. The anion replacement studies did not permit a distinction between K/H exchange and KCl cotransport, since, depending upon the anion used as a Cl replacement, partial inhibition or stimulation of volume-activated K/H exchange fluxes was observed. In contrast, all anions used were stimulatory to the NEM-induced K loss. Since, on the basis of force-flow analysis, both volume-and NEM-induced K loss are K/H exchange, it was necessary to reevaluate assumptions (i.e., anions serve as substrates and therefore probe the translocation step) associated with the use of anion replacement as a means of flux route identification. When viewed together with the force-flow studies, the Cl replacement studies suggest that anion effects upon K/H exchange are indirect. The different anions appear to alter mechanisms that couple NEM exposure and cell swelling to the activation of K/H exchange, as opposed to exerting direct effects upon K and H translocation