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This study documents for the first time the presence of testate amoebae on glaciers. Three shallow firn cores of 10 m depth were obtained from the Mocho-Choshuenco and Osorno volcanoes, Southern Andes, Chile, in October and November, 2005. Euglyphid testate amoebae were detected in 28 samples that correspond to the spring-summer layers of the firn cores. Inspection of 454 collected individuals reveals the presence of four different taxa. Three of these taxa, Trinema lineare, Trinema enchelys and Puytoracia bergeri have previously been reported in ice-free environments. The fourth taxon corresponds to a new species Puytoracia jenswendti nov. sp. The observation of food content and reproductive activities in a significant fraction of specimens evidence that testate amoebae are competent to inhabit glaciers. The testate amoebae found in the firn cores display clear seasonal variations in abundance indicating that these records can provide a new and novel proxy as paleoindicator for firn/ice core dating and for estimation of past glacier mass balance.

The solvent effect on the position of the carbonyl vibrational stretching ofacetylferrocene in aprotic media was studied in this work. The solvent-induced shifts in thisorganometallic compound were interpreted in terms of the alternative reaction field model(SCRF-MO) proposed by Kolling. In contrast to the established trends for carbonyl groupsin organic systems, the results suggest that the continuum models for the reaction field arenot adequate and that the influence of dipolarity-polarizability described by aninhomogeneous coupling function θ (ε ) L(n 2 ) that assumes optical dielectric saturation isresponsible for the carbonyl band shift and, there is empirical evidence that the effect offield-induced intermolecular interaction on band shift, interpreted in terms of the van derWaals forces from the solvent, have a important contribution to this phenomena.

Odorant responses of isolated olfactory neurons from the toad Caudiverbera caudiverbera were monitored by using patch-clamp techniques. Depending on the stimulus, the same neuron responded with an increase or a decrease in action potential firing. Odorants that activate the cAMP cascade in olfactory cilia increased electrical activity, caused membrane depolarization, and triggered inward currents. In contrast, odorants that do not activate the cAMP cascade inhibited electrical activity, produced membrane hyperpolarization, and activated outward currents in a dose-dependent fashion. Such currents were carried by K+ and blocked by tetraethylammonium. Similar currents were recorded from Xenopus laevis. Our results suggest that this K+ current is responsible for odorant-induced inhibition of action potential firing in olfactory neurons.

Porins, polypeptides of ≈ 35 kDa, are present as integral membrane proteins in the outer membranes of a variety of Gram-negative bacteria. As reported previously for a purified porin from Escherichia coli, voltage gating of conductance was found to be induced in a lipid bilayer by the solubilized purified porin, protein I, from Neisseria gonorrhoeae. The unitary response to an applied potential showed a cascade of current from an initial level through at least three levels, more or less equal, to a persisting lower level. The initial level of current corresponded to 1.0-1.3 nS for 0.2 M NaCl on either side of the bilayer. Briefly reducing the potential to zero restored the current to its initial level. Interpretation of the unitary response is suggested by electron microscopic data obtained on negatively stained outer membranes of E. coli indicating the presence of ``pores'' appearing in triplets. Moreover, low-resolution x-ray and neutron diffraction studies on crystals obtained with an E. coli porin show that three polypeptides associate to form a unit. Combining such structural data with the present electrical data lends support for the hypothesis that the unitary response results from three pores acting as a unit in response to an applied potential. Evidence obtained with the patch-clamp technique is mounting for a similar mechanism of many channels operating as a unit in a variety of cell membranes. The porin channel holds promise as a concrete model for the analysis of voltage gating of ionic conductance.

Single-channel recording from longitudinal ventrolateral Drosophila larval muscle reveals the presence of a potassium-selective channel that is directly and reversibly activated by cAMP in a dose-dependent fashion. Activation is specific and it cannot be mimicked by a series of agents that include AMP, cGMP, ATP, inositol trisphosphate, and Ca2+. Channel current records obtained from larval muscle in different dunce mutants possessing abnormally high levels of cAMP show that, in the mutants, the channel displays an increased probability of opening.

The effects of K+-channel blockers on synaptic transmission in dunce (dne ), a Drosophila learning and memory mutant, were investigated. Larvae dne mutants lack facilitation and post-tetanic potentiation (PTP) at their motor end-plates; dne mutants are also deficient in a form of phosphodiesterase, and exhibit abnormally high levels of cyclic adenosine 3', 5' -monophosphate (cAMP). A two-microelectrode voltage-clamp was used to record end-plate currents and spontaneous end-plate currents from longitudinal ventrolateral third-instar larval muscle. The K+-channel blockers 3, 4-diaminopyridine (3, 4-DAP) and tetraethylammonium (TEA), at micromolar concentrations, caused a reversible decrease in end-plate current amplitudes both in wild-type and mutant end-plates. In the presence of blockers, a period of high-frequency stimulation (tetanus) of the nerve gave way to a transient increase in the end-plate currents of dnc mutants resembling facilitation and PTP in normal end-plates; 3, 4-DAP and TEA also restored facilitation and PTP in normal end-plates after incubation with a non-hydrolysable analogue of cAMP (8Br-cAMP). It is suggested that a specific K+ conductance might be relevant to the lack of synaptic plasticity at the dnc neuromuscular synapses.

Single-channel records were obtained after fusion of ciliary membranes from the olfactory epithelium of Rana catesbeiana to planar lipid bilayers, and odorantactivated cation-selective channels were identified. In addition, a 190-pS potassium-selective channel and a 40-pS cation-selective channel were found in a 0.2 M salt-containing buffer. Odorant-sensitive channels were directly and reversibly activated by nanomolar concentrations of the bell pepper odorant 3-isobutyl-2-methoxypyrazine and the citrus odorant 3,7,-dimethyl-2,6-octadienenitrile. These channels display burst kinetics, multiple conductance levels between 35 and 420 pS, and open times in the millisecond range. With increasing concentrations of odorant, the probability of populating the higher conductance levels increases. These results show that direct activation of channels by odorants may mediate excitation of the olfactory receptor cell.

The ratio of the rate of transepithelial sodium transport, JNa, across the isolated toad urinary bladder to the simultaneously measured rate of transport-dependent metabolism, JCO2 sb, has been measured as a function of the transepithelial electrical voltage, Δ ψ . The ratio remains constant with a mean value of 18 to 20 over the range of imposed voltages of 0 to +70 mV. With increasing hyperpolarization of the bladder, JNadecreases and the calculated electromotive force or apparent ``ENa'' of the sodium pump increases. From thermodynamic and kinetic arguments it is shown that the apparent ``ENa'' approaches the maximal electrochemical potential gradient, ENa, against which sodium can be transported by this tissue only when JNa≈ 0. At this unique condition${\\ssf F}$ENa(in which${\\ssf F}$is the Faraday constant) is the maximal free energy of the chemical reaction driving sodium transport and thus equal to the maximal extramitochondrial phosphorylation potential and the maximal free energy of the mitochondrial respiratory chain within the transporting cells.

Single-channel recording from longitudinal ventrolateral Drosophila larval muscle reveals the presence of a potassium-selective channel that is directly and reversibly activated by cAMP in a dose-dependent fashion. Activation is specific and it cannot be mimicked by a series of agents that include AMP, cGMP, ATP, inositol trisphosphate, and Ca super(2+). Channel current records obtained from larval muscle in different dunce mutants possessing abnormally high levels of cAMP show that, in the mutants, the channel displays an increased probability of opening.