Control of passive permeability of chinese hamster ovary cells by external and intracellular ATP

External ATP causes passive permeability change in several transformed cells, but not in untransformed cells. We studied the effect of external ATP on the passive permeability of CHO-K1 cells, a transformed clone of Chinese hamster ovary cells. Treatment of the cells with external ATP alone did not produce a permeability change, and this was observed only when a mitochondrial inhibitor, such as rotenone or oligomycin, was present together with ATP. These inhibitors reduced the concentration of intracellular ATP and a permeability change by external ATP was observed when intracellular ATP was decreased more than 70%. This requirement for permeability change of CHO-K1 cells was quite unique, since passive permeability change of other transformed cells so far tested was induced by ATP alone. Treatment of CHO-K1 cells with cyclic AMP analogues increased their sensitivity to external ATP about 2-fold. The roles of external and intracellular ATP in controlling passive permeability are discussed.     

Modulation of passive permeability by external ATP and cytoskeleton-attacking agents in cultured mammalian cells

External ATP causes a passive permeability change in several transformed cells, but not in untransformed cells. We previously demonstrated that in CHO-K1 cells, a transformed clone of Chinese hamster ovary cells, the external ATP-dependent permeability change was induced when the intracellular ATP concentration was reduced by a mitochondrial inhibitor (Kitagawa, T. and Akamatsu, Y. (1981) Biochim. Biophys. Acta 649, 76–82). A permeability change with similar characteristics was also observed when the CHO cells were treated with external ATP and a cytoskeleton-attacking agent such as vinblastine or cytochalasin B. Just like mitochondrial inhibitors, vinblastine could increase the sensitivity of transformed 3T3 cells to external ATP but showed no effect on passive permeability of normal 3T3 cells. However, in contrast with the effect of the mitochondrial inhibitors, the cytoskeleton drugs caused the permeability change with little reduction of intracellular ATP concentration, suggesting different actions of these two kinds of drug on the permeability change. The present results suggest an important role of cytoskeletal structures in controlling the external ATP-dependent permeability change in transformed cells. Possible effects of intracellular ATP on cytoskeletal structures are also discussed.     

Relative Ion Permeabilities in the Crayfish Giant Axon Determined from Rapid External Ion Changes

The changes in membrane potential of isolated, single crayfish giant axons following rapid shifts in external ion concentrations have been studied. At normal resting potential the immediate change in membrane potential after a variation in external potassium concentration is quite marked compared to the effect of an equivalent chloride change. If the membrane is depolarized by a maintained potassium elevation, the immediate potential change due to a chloride variation becomes comparable to that of an equivalent potassium change. There is no appreciable effect on membrane potential when external sodium is varied, at normal or at a depolarized membrane potential. Starting from the constant field equation, expressions for the permeability ratios P _Cl/P _K, P _Na/P _K, and for intracellular potassium and chloride concentrations are derived. At normal resting membrane potential, P _Cl/P _K is 0.13 but at a membrane potential of -53 mv (external potassium level increased about five times) it is 0.85. The intracellular concentrations of potassium and chloride are estimated to be 233 and 34 mM, respectively, and it is pointed out that this is not compatible with ions distributed in a Nernst equilibrium across the membrane. It is also stressed that the information given by a plot of membrane potential vs. the logarithm of external potassium concentrations is very limited and rests upon several important assumptions.     

Phosphate Uptake and Root Electrical Potential

It is shown that the potential difference between the rootsof five plant species and their external solution is relatedto the ionic strength of the solution in a logarithmic fashionas predicted by diffuse double-layer theory. The slope of thestraight-line relationship indicates a change of 48 mV for atenfold change in the ionic strength of the solution. At lowphosphate concentrations the rate of uptake is linearly relatedto the square root of the ionic strength of the solution. Thisis in agreement with the effect of ionic strength on surfacepotential and in turn with the effect of potential on surfaceconcentration of adsorbed ions.     

The Effect of Inorganic Salts on the Senescence of Dianthus caryophyllus Flowers

Certain inorganic salts like KNO₃, KCl, K₂SO₄, Ca(NO₃)₂ and NH₄NO₃ extend longevity of cut carnation flowers. The effect of KNO₃ was studied in some detail. There is an osmotic adjustment in response to KNO₃ treatment. The osmotic concentration change occurred in the external as well as in the internal compartments. The osmotic concentration change in the external compartment is well correlated with extension of longevity. The effect of KNO₃ on the sensitivity to ethylene, and its significance in delaying senescence is discussed.     

Medullary inspiratory activity: influence of intercostal tendon organs and muscle spindle endings

Studies were conducted to determine the effects of intercostal muscle spindle endings (MSEs) and tendon organs (TOs) on medullary inspiratory activity in decerebrate and allobarbital-anesthetized cats. Impeded muscle contractions, elicited by electrical stimulation of the peripheral cut end of the T6 ventral root, were used to stimulate external and internal intercostal TOs without MSEs. Impeded contractions of either the external or internal intercostal muscles reduced phrenic and medullary inspiratory neuronal activities. Vibration was used to selectively stimulate external or internal intercostal MSEs (90 and 40 micron amplitude, respectively). Selective stimulation of either external or internal intercostal MSEs did not change phrenic or medullary inspiratory neuronal activities. It is concluded that both external and internal intercostal TOs have a generalized inhibitory effect on medullary inspiratory activity and intercostal MSEs have no effect on medullary inspiratory activity.     

美皮康在骨科外固定架患者护理中的应用

目的:探讨美皮康应用于外固定架针孔换药方式的临床效果。方法:将骨科50例四肢骨折行外固定架固定的患者随机分成实验组24例和对照组26例。实验组以美皮康有边型敷料换药,对照组以临床常用的络合碘纱布条进行换药,比较两组每天更换敷料频次,外固定针孔及周围皮肤红肿、渗出情况,护士更换污染床单被套频次及护士满意度。结果:实验组每天更换敷料频次少于对照组(P<0.05),外固定针孔及周围皮肤红肿、渗出等情况,实验组均优于对照组(P<0.05),实验组中护士更换污染床单被套频次明显少于对照组(P<0.05),护士满意度高于对照组(P<0.05)。结论:美皮康对保护骨科外固定针孔的治疗效果优于传统络合碘纱布条换药,对预防外固定针道感染有效,同时减轻护士维持床单位整洁、减少床单被套的更换频次,提高护士的满意度。     

Bacteriorhodopsin Is a Powerful Light-Driven Proton Pump

The activity of bacteriorhodopsin was investigated with Halobacterium halobium cell envelopes, which lack cytoplasmic constituents. It was found that the physiological concentration of magnesium ion greatly enhanced the light-induced pH change; under optimal conditions, the pH change of the external medium was as large as 3.5 pH units, even though the volume fraction of the envelope vesicles was as low as 0.01. This pH change is about three times larger than the largest change reported thus far. This same effect was observed with transition metal ions, but not with other alkaline divalent cations. That is, divalent cations that formed hydroxides below pH 10 were effective in enhancing the light-induced pH change. This result suggests that some divalent cations acted as buffers against a large increase in the internal pH, and that the internal pH was an important factor in determining the activity of bacteriorhodopsin. It was also shown that a high level of the proton-pump activity was maintained in a wide range of external pHs, at least between 4.5 and 9.4.     

A change in the internal affinity of LK goat red-cell sodium pumps induced by high pH

The K inhibition of ouabain-sensitive ATPase activity of LK goat red cell membranes is greatly reduced at high pH. This effect is reversible, and specific, since the apparent affinities for ATP, ouabain or external K do not alter. Anti-L-treated membranes show a similar alkali-induced affinity change, but have a lower pH optimum.     

A change in the internal affinity of LK goat red-cell sodium pumps induced by high pH.

The K inhibition of ouabain-sensitive ATPase activity of LK goat red cell membranes is greatly reduced at high pH. This effect is reversible, and specific, since the apparent affinities for ATP, ouabain or external K do not alter. Anti-L-treated membranes show a similar alkali-induced affinity change, but have a lower pH optimum.     

Remarks on origins of biomolecular asymmetry

A simple criterion for mirror symmetry breaking in a non-linear chemical system is presented. The selection effect of external asymmetric agents in the process of generation and amplification of biomolecular asymmetry is studied. It is pointed out that this effect will play an important role at bifurcation point, but when the asymmetry of a system has been amplified to a certain extent, a weak asymmetric agent will no longer be able to change the chirality of the system.     

Studies on the mechanisms underlying horizontal-bipolar interaction in the carp retina.

Responses of on-center bipolar cells and horizontal cells were recorded simultaneously in the carp retina, and the effect of polarization of horizontal cells on the bipolar cells was studied. Hyperpolarization by extrinsic current of horizontal cells elicited in the bipolar cells a hyperpolarizing response which, unlike the electrical coupling betweeen adjacent horizontal cells, was accompanied by a change in membrane conductance. The bipolar cell responses elicited by polarization of external horizontal cells showed a negative reversal potential, while those elicited by polarization of intermediate horizontal cells showed a positive reversal potential. It was suggested that the external horizontal cells modify the cone-bipolar transmission which involves the conductance change of subsynaptic potassium and/or chloride channels, while the intermediate horizontal cells modify the rod-bipolar transmission which involves the conductance change of sodium channels.     

Effects of external ions on membrane potentials of a lobster giant axon

The effects of varying external concentrations of normally occurring cations on membrane potentials in the lobster giant axon have been studied and compared with data presently available from the squid giant axon. A decrease in the external concentration of sodium ions causes a reversible reduction in the amplitude of the action potential and its rate of rise. No effect on the resting potential was detected. The changes are of the same order of magnitude, but greater than would be predicted for an ideal sodium electrode. Increase in external potassium causes a decrease in resting potential, and a decrease in potassium causes an increase in potential. The data so obtained are similar to those which have been reported for the squid giant axon, and cannot be exactly fitted to the Goldman constant field equation. Lowering external calcium below 25 mM causes a reduction in resting and action potentials, and the occasional occurrence of repetitive activity. The decrease in action potential is not solely attributable to a decrease in resting potential. Increase of external calcium from 25 to 50 mM causes no change in transmembrane potentials. Variations of external magnesium concentration between zero and 50 mM had no measurable effect on membrane potentials. These studies on membrane potentials do not indicate a clear choice between the use of sea water and Cole's perfusion solution as the better external medium for studies on lobster nerve.     

Length-tension relationship of abdominal expiratory muscles: effect of emphysema

The present study examined the active and passive length-tension relationship of the abdominal expiratory muscles in vitro during electrically stimulated contractions. Studies were performed on isolated strips of transverse abdominis and external oblique muscle from nine adult hamsters with normal lung function. The effect of chronic hyperinflation on the two muscles was assessed in eight hamsters with elastase-induced emphysema. In normal animals the maximal active tension per cross-sectional area (Po) was equal in the two muscles. The absolute muscle fiber length at which Po occurred (Lo) was less for the external oblique than the transverse abdominis and the length-tension curve operated at shorter fiber lengths. However, the change in tension produced by an increase or decrease in muscle length expressed in relative terms (i.e., as %Lo) was greater for the transverse abdominis than the external oblique. Mean total lung capacity of emphysematous animals was 198% of control. Po of the transverse abdominis and external oblique were the same in emphysematous and control animals. However, Lo and the length-tension curve of the transverse abdominis occurred at shorter fiber lengths in emphysematous animals because of a reduction in the number of sarcomeres in series along the fiber. The length-tension curve and the number of sarcomeres in the external oblique was the same in emphysematous and control animals. These results in normal animals indicate that the magnitude of the change in active and passive tension produced by a change in muscle length differs in the transverse abdominis and external oblique. Moreover, chronic hyperinflation of the thorax produced by elastase injection alters the length-tension relationships of some but not all the expiratory muscles.     

Potassium ion accumulation slows the closing rate of potassium channels in squid axons.

Potassium ion accumulation in the periaxonal space between squid axonal membrane and the Schwann cell surrounding the axon slows the rate of potassium channel closing to a degree that is consistent with the effect on channel closing of an equivalent change in the bulk external potassium concentration. The alteration of channel gating is independent of membrane potential, V, for V less than or equal to -60 mV, which suggests that the effect is mediated at a site on the outer surface of the membrane, rather than a site within the channel.     

Effect of mass transfer in a recirculation batch reactor system for immobilized penicillin amidase

The effect of external mass transfer resistance on the overall reaction rate of the immobilized whole cell penicillin amidase of E. coli in a recirculation batch reactor was investigated. The internal diffusional resistance was found negligible as indicated by the value of effectiveness factor, 0.95. The local environmental change in a column due to the pH drop was successfully overcome by employing buffer solution. The reaction rate was measured by pH-stat method and was found to follow the simple Michaelis-Menten law at the initial stage of the reaction. The values of the net reaction rate experimentally determined were used to calculate the substrate concentration at the external surface of the catalyst pellet and then to calculate the mass transfer coefficient, k(L), at various flow rates and substrate concentrations. The correlation proposed by Chilton and Colburn represented adequately the experimental data. The linear change of log j(D) at low log N(Re) with negative slope was ascribed to the fact that the external mass transfer approached the state of pure diffusion in the limit of zero superficial velocity.     

The effect of composition and ionic strength of external solution on the aspartate-ammonia lyase and fumarate hydratase activity in Escherichia coli cells

It was found that the nonspecific effect of ionic strength of the external solution on the enzymatic activity of E. coli cells consists in rapid changes in the permeability of cell membranes interacting with the substrate. This effect depends on the initial substrate concentration, i.e., ionic strength of the external solution, and is maintained for some time as the substrate concentration decreases. Chloramphenicol, a protein synthesis inhibitor, and sodium azide, a respiration inhibitor (300 micrograms/ml and 200 microM, respectively) do not change the enzymatic activity of E. coli cells during the synthesis of L-aspartic and L-malic acids from fumaric acid. The kinetic equations of L-aspartate and L-malate synthesis are described by equations of zero and intermediate (between zero and first) order, respectively.     

Cation exchanges of yeast in the absence of magnesium.

Environmental Mg2+ was found to influence the K+/Na+ exchange rate of metabolizing yeast. Addition of EDTA increased the exchange rate and Mg2+ reversed the effect of EDTA. Yeast starved in the absence of Mg2+ exchanged cellular K+ or Na+ for external H+ when maintained at acidic pH. The exchange rate depended on cellular pH and showed the same kinetics for both K+ and Na+. At acidic pH, the presence of external cations neither inhibited H+ absorption nor changed the cation/H+ 1 : 1 stoichiometry. At neutral pH, external cations inhibited H+ influx but did not change the cation efflux. The K+/Na+ exchange is discussed as electrically coupled and the K+/H+ and Na+/H+ exchanges as electroneutral antiports.     

Effect of microwave radiation on a dusty plasma

The effect of microwave radiation on a complex plasma produced by an external ionizer is studied using numerical simulations. It is shown that, as the radiation intensity increases, the scattering of the incident radiation by charged metal grains is enhanced and radiation at the second harmonic of the incident radiation appears in the scattered spectrum. This effect is associated with the grain charge oscillations caused by the nonlinear action of the microwave field. It is found that, under the action of strong microwave radiation, the grain charge can increase by one order of magnitude. It is shown that, when the microwave intensity is high enough, the distribution of the electric field near a dust grain is shown to change so radically that the field component normal to the grain surface can even change its sign.