Calcium is transported across the surface membrane of both nerve and muscle by a Na+-dependent mechanism, usually termed the Na:Ca exchange. It is well established from experiments on rod outer segments that one net positive charge enters the cell for every Ca2+ ion extruded by the exchange, which is generally interpreted to imply an exchange stoichiometry of 3 Na+:1 Ca2+. We have measured the currents associated with the operation of the exchange in both forward and reversed modes in isolated rod outer segments and we find that the reversed mode, in which Ca2+ enters the cell in exchange for Na+, depends strongly on the presence of external K+. The ability of changes in external K+ concentration ([K+]o) to perturb the equilibrium level of [Ca2+]i indicates that K+ is co-transported with calcium. From an examination of the relative changes of [Ca2+]o, [Na+]o, [K+]o and membrane potential required to maintain the exchange at equilibrium, we conclude that the exchange stoichiometry is 4 Na+:1 Ca2+, 1 K+ and we propose that the exchange should be renamed the Na:Ca, K exchange. Harnessing the outward K+ gradient should allow the exchange to maintain a Ca2+ efflux down to levels of internal [Ca2+] that are considerably lower than would be possible with a 3 Na+:1 Ca2+ exchange.

SUMMARY1. The concentration of triglyceride in the plasma rises linearly for 3 hr after the intravenous injection ofthe non-ionic detergent, Triton WR 1339, in the rat.2. Minimum rates of triglyceride entry into the plasma have been calculated from measurements of the plasma triglyceride concentration at 1*5 hr after Triton injection. These are 30 and 52 ,tmoles/hr.200 g body weight respectively for male and female animals on a stock laboratory diet and 25 and 33 ,umoles/hr . 200 g body weight respectively for male and female animals starved for 48 hr. The values may have to be increased by 10 or 20 % to take account of a small leak of triglyceride from the plasma in animals injected with Triton and of an effect of ether anaesthesia on the rate of entry of triglyceride into the plasma.3. Substitution of the stock laboratory diet by diets that are lower in fat content does not alter significantly the rate of triglyceride accumulation in the plasma after Triton injection.4. There is no change in the triglyceride content of the livers of male and female rats at 24 hr after Triton injection. At 6 hr after Triton, the liver triglyceride content of female rats which have been fed their normal diet is increased.

Low-energy photoelectron imaging spectroscopy of nitromethane anions: Electron affinity, vibrational features, anisotropies, and the dipole-bound state J. Chem. Phys. 130, 074307 (2009); 10.1063/1.3076892Effect of excess electron and one water molecule on relative stability of the canonical and zwitterionic tautomers of glycine Nitrobenzene anions (NB Ϫ ) in both valence and dipole bound states are examined using laser ͑photodetachment͒ photoelectron and Rydberg electron transfer ͑RET͒ spectroscopies. Photoelectron spectroscopy of the valence NB Ϫ anion yields a valence ͑adiabatic͒ electron affinity of 1.00Ϯ0.01 eV. The reaction rates for charge transfer between atoms of cesium and xenon in high Rydberg states ͓Cs(ns,nd) and Xe(n f )͔ and NB exhibit a prominent peak in their n-dependencies consistent with the formation of a dipole bound anion having an electron affinity of 28 meV. Para-dinitrobenzene ͑pDNB͒ has a zero dipole moment and a large quadrupole moment. RET studies with pDNB show a complex n-dependence. The rate of formation of pDNB Ϫ ions exhibits a broad peak at low n-values and a second very broad feature extending to large n-values. The peak at low n is tentatively attributed to charge exchange into a quadrupole bound state (EA qb ϭ25 meV). The absence of field-detachment for these ions suggests that if these are in a quadrupole bound state they are strongly coupled to the valence state. Meta-dinitrobenzene ͑mDNB͒ has a large dipole moment and a small quadrupole moment. The observation of a weak but narrow peak at a low n-value in the RET measurement is consistent with electron attachment into a primarily dipole bound state (EA db ϭ68 meV) which is also strongly coupled to the valence state.

Study of Nb2O y (y = 2-5) anion and neutral clusters using anion photoelectron spectroscopy and density functional theory calculations

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