Transfection of mu MDR 1 inhibits Na(+)-independent Cl-/-HCO3 exchange in Chinese hamster ovary cells

We have used single-cell photometry to measure intracellular pH (pHi) for several MDR cell lines constructed by stably transfecting LR73 chinese hamster ovary fibroblasts with mutant and wild type murine MDR 1 genes. In addition, plasma membrane electrical potential (delta psi) has been measured for the same cells by the K+/valinomycin null point titration method using the ratiometric styryl probe di-4-ANEPPS. Both the untransfected, parental cell line and a cell line expressing substantial mutant MDR 1 protein (K432R/K1074R) that is unable to confer the MDR phenotype are found to have delta psi > or = -40 (+/- 5) mV and pHi < or = 7.16 (+/- 0.03) units. In contrast, MDR cell lines constructed by transfecting wild type mu MDR 1 cDNA are found to exhibit delta psi from 15 to 19 mV lower and pHi from 0.13 to 0.34 units higher. A cell line that overexpresses crippled MDR protein (S941F) that is not resistant to colchicine or doxorubicin, but which is resistant to vinblastine [Gros, P., Dhir, R., Croop, J., & Talbot, F. (1991) Proc. Natl. Acad. Sci. U.S.A. 88, 7289-7293], exhibits elevated pHi and slightly elevated delta psi, relative to LR73. Northern and western blot analyses confirm the substantial overexpression of the mu MDR genes and proteins in these lines, as well as the mild overexpression of endogenous hamster p-GP mRNA in some lines. In general agreement with previous studies that examined myeloma cells overexpressing hu MDR 1 protein [Roepe, P.D., Wei, L.-Y., Cruz, J., & Carlson, D. (1993) Biochemistry 32, 11042-11056] we find that overexpression of wild type mu MDR 1 protein inhibits Cl(-)- and -HCO3-dependent pHi homeostasis. Via single-cell photometry studies we now conclude that this is due to inhibition of Na(+)-independent Cl-/-HCO3 exchange (strict anion exchange or AE). As concluded previously for other MDR cells, decreased AE activity is not due to decreased expression of the exchanger; in fact, again similar to previous work [Roepe et al. (1993) Biochemistry 32, 11042-11056], we find increased levels of AE mRNA in some MDR cell lines. Models that may explain these data that are also consistent with the known physiology of cells that endogenously express MDR protein are suggested. These data are consistent with a model for MDR protein function wherein overexpression of the protein decreases delta psi and/or elevates pHi via Cl(-)- and -HCO3-dependent mechanisms.

Lower electrical membrane potential and altered pHi homeostasis in multidrug-resistant (MDR) cells: further characterization of a series of MDR cell lines expressing different levels of P-glycoprotein

Recently [Roepe, P.D. (1992) Biochemistry 31, 12555-12564], increased steady-state levels of chemotherapeutic drug efflux from multidrug-resistant (MDR) myeloma cells were correlated with intracellular alkalinization. To better understand elevated pHi in MDR cells, Na(+)- and Cl-dependent recovery of pHi upon intracellular acid or alkaline shock has been examined for this same series of MDR cell lines. In agreement with another recent report [Boscoboinik, D., Gupta, R.S., & Epand, R.M. (1990) Br. J. Cancer 61, 568-572], we find that the rate of Na(+)-induced alkalinization after an intracellular acid shock is increased in the MDR cells, relative to the drug-sensitive parent. Interestingly, we also now find that mRNA encoding the human Na+/H+ exchanger (NHE) is overexpressed in these MDR cells, but the level of overexpression does not correlate with the relative drug resistance or steady-state pHi. It is also found that the efficiency of Cl(-)dependent reacidification of pHi, after an intracellular alkaline shock is reduced in the MDR cells. This effect appears to correlate with the relative expression of MDR protein, but not the relative expression of Cl-/HCO3- exchanger (AE), which we now find is also altered in the series of cells. Since elevated pHi will increase delta pH across the plasma membrane, we have also measured the electrical potential for these cells using three different methods. Most interestingly, the magnitude of the plasma membrane electrical potential (delta psi) decreases concomitant with increased expression of the MDR protein. Energy provided by increased delta pH compensates for the lowered delta psi, such that the total electrochemical membrane potential (delta mu H+) remains similar among the cells in this series (delta mu H+ = delta psi - Z delta pH). These data, along with other recent experiments that associated an increased Cl- conductance with the expression of MDR protein [Valverde, M., Diaz, M., Sepúlveda, F.V., Gill, D.R., Hyde, S.C., & Higgins, C.F. (1992) Nature 355, 830-833], are consistent with a model for MDR protein-mediated multidrug resistance that does not entail direct active transport of lipophilic drugs by the MDR protein.

Factors affecting zero background frequency of sister-chromatid exchange in mosquito cells

A background level of sister-chromatid exchange (SCE) is found in mammalian cells. However, in the somatic cells of Drosophila melanogaster, there was no spontaneous SCE if a minimum concentration of bromodeoxyuridine (BrdU) was used. In this communication we report that in a mosquito (Aedes albopictus) cell line (C6/36), some cells also have no background SCE (0-SCE). Subclones of high (44%) or low (12%) frequency of 0-SCE cells were obtained, but none of them contained 100% 0-SCE cells. Increasing frequency of SCE/cell concomitant with decreasing frequency of 0-SCE cells was observed by raising the BrdU concentration in the culture medium during the first cell cycle, culturing cells at lower density and depleting reduced glutathione (GSH) with buthionine sulfoximine. Since these mosquito cells contain much higher level of GSH than Chinese hamster ovary (CHO) cells, and feeding cells with BrdU increased GSH in mosquito cells but decreased GSH in CHO cells, we speculate that GSH may play a role in the low or non-existent background SCE and in the high resistance to many DNA damaging agents of mosquito cells.

Electronic diagnoser of arterial pulse

An electronic diagnoser of the arterial pulse has been designed to give three outputs: pulse amplitude, instantaneous pulse rate (IPR) and spectral energy ratios (SER) at 5 and 10 Hz. The information thus provided will be useful for diagnosing many kinds of disease in the human body.

Area utilization efficiency of a sloping heliostat system for solar concentration

Area utilization efficiency (AUE) is formulated for a sloping heliostat system facing any direction. The effects of slope shading, incidence factor, sun shading, and tower blocking by the mirrors are all taken into account. Our results show that annually averaged AUEs calculated for heliostat systems (1) increase with tower height at low slope angles but less rapidly at high slopes, (2) increase monotonically with slope angle and saturate at large slopes for systems facing due south, (3) reach a maximum at a certain slope for systems facing other directions than due south, and (4) drop sharply at slopes greater than a certain value for systems facing due east or west due to slope shading effect. The results are useful for solar energy collection on nonflat terrains.

General formula for the incidence factor of a solar heliostat receiver system

A general formula is derived for the effective incidence factor of an array of heliostat mirrors for solar power collection. The formula can be greatly simplified for arrays of high symmetry and offers quick computation of the performance of the array. It shows clearly how the mirror distribution and locations affect the overall performance and thus provide a useful guidance for the design of a solar heliostat receiver system.

Scientific advance in acupuncture

In this paper we present scientific advance in acupuncture based on electrical, neurophysiological, biochemical and therapeutic studies made inside and outside China since the early fifties. New modalities other than traditional needling techniques notably developed in Japan, France and Germany are described. For future prospects, efforts by making use of systems approach, field-body interaction, self-defense self-strategy and circadian rhythm are likely to produce great fruition in medicine. Possibilities of making advances in "three P's" medicine (preventive medicine, precision medicine and people medicine) by acupuncture are discussed.

Theoretical foundation of Chinese medicine: a modern interpretation

The theoretical foundation of Chinese medicine as laid down in Hwang Ti Nei Ching is presented and interpreted here in modern language and conception. Our attempt is to bring Chinese medicine in harmony with Western science. Three Yin-Yang laws are formulated based on I Ching and Nei Ching and are justified from physics, mathematics and biology. The Wu-Hsing dynamic model is explained on the basis of dynamic interactions rather than static elements. The Ching-Lo doctrine is stressed upon its apparent correlations with the autonomic nervous system. Finally, the Chi is taken to play a role in life as the fields (gravitational, magnetic, nuclear, etc.) do in the physical world.

Electronic conduction in lipid films with metal contacts

The electrical characteristics of lipid films with Au and Hg contacts were investigated. Our results indicate that the conduction is mainly electronic and is electrode limited. With gold biased negatively, the current-voltage characteristics of thin and thick films follow the equations: I = 4.367 exp [9.58(eV + 0.21)(1/2)]. [1 - exp (-eV/kT)]pA, and I = 3.424 exp [8.59(eV + 0.082)(1/2)][1 - exp (-eV/kT)]pA, respectively. For thick films, the conductivity is insensitive to thickness. By temperature and photoresponse measurements the interface barrier height is found to be 1.09 eV. In view of the possible structural disorders in the films, a model is proposed to explain our findings based on the theory of noncrystalline materials. According to this model, the band gap for the film is 2.016 eV and the density of localized states is near the Fermi level, 1.31 x 10(18) cm(-3) eV(-1). The results may be helpful in providing some insight into the speculated electronic conduction in biological membranes.

Dipole theory of heat production and absorption in nerve axon

EXACT FORMULAS ARE DERIVED FOR THE ENERGY CHANGE OF A DIPOLE SYSTEM WITH TWO ENERGY STATES (OR BANDS) IN A CHANGING FIELD IN TWO CASES: (a) no dipole flip-flop and (b) dipole flip-flop caused by stimulation. Based on these formulas, the positive and negative heats are calculated. The results are in good agreement with experiment in case b but are 60-180% larger in case a. Furthermore, the theory shows that the negative heat cannot be less than the positive heat in case a but can be either way in case b, the latter result being found prevalent in experiment. It is concluded that nerve excitation is most likely to involve dipole flip-flop at the membrane surface. The theory is consistent in the interpretations and correlations of the electrical, optical, and thermal effects observed in nerve axon.

Conduction mechanisms in Lillie's iron-wire model of nerve

Based on theory and experiment, we found that the conduction through the oxide film in Lillie's iron-wire model is dominated by Schottky emission at low fields (below 10(6) v/cm), by electron tunneling from trap to trap at intermediate fields and by direct tunneling (Fowler-Nordheim type) at higher fields (above 3 x 10(6) v/cm). The trap-to-trap tunneling is considered to give rise to the negative resistance and the fixed position of the current maximum as observed. Some of the nervelike properties of the Lillie's model are interpreted on this tunneling mechanism.

Role of surface dipoles on axon membrane

A physical model of nerve excitation and conduction is proposed based on the discovery of three new axon membrane properties: the negative fixed surface charge, the birefringence change, and the infrared emission.

Electric dipole theory of chemical synaptic transmission

In this paper we propose that chemicals such as acetylcholine are electric dipoles which when oriented and arranged in a large array could produce an electric field strong enough to drive positive ions over the junction barrier of the post-synaptic membrane and thus initiate excitation or produce depolarization. This theory is able to explain a great number of facts such as cleft size, synaptic delay, nonregeneration, subthreshold integration, facilitation with repetition, and the calcium and magnesium effects. It also shows why and how acetylcholine could act as excitatory or inhibitory transmitters under different circumstances. Our conclusion is that the nature of synaptic transmission is essentially electrical, be it mediated by electrical or chemical transmitters.