Showing papers by "Max Planck Society published in 1986"
TL;DR: It was found that the gene 5 promoter is active in a tissue-specific fashion whereas this is not the case for the NOS promoter, providing the first documented instance of a gene derived from a procaryotic host the expression of which is apparently regulated by plant growth factors.
Abstract: A “plant gene vector cassette” to be used in combination with various Escherichia coli gene-cloning vectors was constructed. This cassette contains a replication and mobilization unit which allows it to be maintained and to be transferred back and forth between E. coli and Agrobacterium tumefaciens hosts provided these hosts contain plasmid RK2 replication and mobilization helper functions. The cassette also harbors a transferable DNA unit with plant selectable marker genes and cloning sites which can be combined with different bacterial replicons, thus facilitating the reisolation of transferred DNA from transformed plants in E. coli. The vector cassette contains two different promoters derived from the T-DNA-encoded genes 5 and nopaline synthase (NOS). By comparing the levels of expression of the marker enzymes linked to each of these promoter sequences, it was found that the gene 5 promoter is active in a tissue-specific fashion whereas this is not the case for the NOS promoter. This observation provides the first documented instance of a gene derived from a procaryotic host the expression of which is apparently regulated by plant growth factors.
2,064 citations
01 Jan 1986
2,053 citations
Journal Article•
1,882 citations
TL;DR: In this paper, the authors proposed a new constraint on mantle composition: the differentiated part of the mantle, chemically depleted after separation of the major portion of the continental crust, was subsequently internally rehomogenized.
1,475 citations
TL;DR: A new method for rapid NMR imaging dubbed FLASH ( fast low-a ngle sh ot) imaging is described which allows measuring times of the order of 1 s (64 × 128 pixel resolution) or 6 s (256 × 256 pixels), resulting in about a 100-fold reduction in measuring time without sacrificing spatial resolution.
1,227 citations
TL;DR: In this paper, the nearly monochromatic gravitational waves emitted by the decaying orbit of an ultra-compact, two-neutron-star binary system just before the stars coalesce are used to determine the absolute distance to the binary, independently of any assumptions about the masses of the stars.
Abstract: I report here how gravitational wave observations can be used to determine the Hubble constant, H0. The nearly monochromatic gravitational waves emitted by the decaying orbit of an ultra–compact, two–neutron–star binary system just before the stars coalesce are very likely to be detected by the kilometre–sized interferometric gravitational wave antennas now being designed1–4. The signal is easily identified and contains enough information to determine the absolute distance to the binary, independently of any assumptions about the masses of the stars. Ten events out to 100 Mpc may suffice to measure the Hubble constant to 3% accuracy.
1,137 citations
1,133 citations
TL;DR: Plasmid RP4 primase was overproduced by utilizing autoregulated high-level expression vector systems in Escherichia coli and in four other Gram-negative bacterial species.
1,058 citations
TL;DR: The model is an application and illustration of the Correlation Theory of brain function and represents the peripheral evidence represented by amplitude modulations globally present in all components of a sound spectrum.
Abstract: Sensory segmentation is an outstanding unsolved problem of theoretical, practical and technical importance. The basic idea of a solution is described in the form of a model. The response of “neurons” within the sensory field is temporally unstable. Segmentation is expressed by synchronization within segments and desynchronization between segments. Correlations are generated by an autonomous pattern formation process. Neuronal coupling is the result both of peripheral evidence (similarity of local quality) and of central evidence (common membership in a stored pattern). The model is consistent with known anatomy and physiology. However, a new physiological function, synaptic modulation, has to be postulated. The present paper restricts explicit treatment to the peripheral evidence represented by amplitude modulations globally present in all components of a sound spectrum. Generalization to arbitrary sensory qualities will be the subject of a later paper. The model is an application and illustration of the Correlation Theory of brain function.
983 citations
TL;DR: The conductance and gating properties of the two classes of channels suggest that replacement of the γ-subunit by the ε- subunit is responsible for the functional alteration of the receptor during muscle development.
Abstract: Distinct classes of acetylcholine receptor channels are formed when Xenopus oocytes are injected with combinations of the bovine α-, β-, γ- and δ- or the α-, β-, γ- and e-subunit-specific messenger RNAs. The conductance and gating properties of the two classes of channels, in conjunction with the developmental changes in the muscular contents of the mRNAs, suggest that replacement of the γ-subunit by the e-subunit is responsible for the functional alteration of the receptor during muscle development.
944 citations
TL;DR: The results suggest that intracortical 6-OHDA disrupts plasticity by interfering with both cholinergic and noradrenergic transmission and raise the possibility that ACh and NA facilitate synaptic modifications in the striate cortex by a common molecular mechanism.
Abstract: During a critical period of postnatal development, the temporary closure of one eye in kittens will permanently shift the ocular dominance (OD) of neurones in the striate cortex to the eye that remains open1. The OD plasticity can be substantially reduced if the cortex is infused continuously with the catecholamine neurotoxin 6-hydroxydopamine (6-OHDA) during the period of monocular deprivation2–5, an effect that has been attributed to selective depletion of cortical noradrenaline6. However, several other methods causing noradrenaline (NA) depletion leave the plasticity intact7–10. Here we present a possible explanation for the conflicting results. Combined destruction of the cortical noradrenergic and cholinergic innervations reduces the physiological response to monocular deprivation although lesions of either system alone are ineffective. We also find that 6-OHDA can interfere directly with the action of acetylcholine (ACh) on cortical neurones. Taken together, our results suggest that intracortical 6-OHDA disrupts plasticity by interfering with both cholinergic and noradrenergic transmission and raise the possibility that ACh and NA facilitate synaptic modifications in the striate cortex by a common molecular mechanism.
TL;DR: In male subjects, the opiate-active (-)-isomer, but not the (+)- isomer, elicited dose-dependent dysphoric and psychotomimetic effects that were antagonized by naloxone, implying the existence of opposed opioid systems affecting emotional and perceptual experiences.
Abstract: The kappa opioid agonists are analgesics that seem to be free of undesired morphine-like effects. Their dysphoric actions observed with the kappa agonist cyclazocine are thought to be mediated by an action at sigma-phencyclidine receptors. The benzomorphan kappa agonist MR 2033 is inactive at sigma-phencyclidine receptors. In male subjects, the opiate-active (-)-isomer, but not the (+)-isomer, elicited dose-dependent dysphoric and psychotomimetic effects that were antagonized by naloxone. Thus, kappa opiate receptors seem to mediate psychotomimetic effects. In view of the euphorigenic properties of mu agonists, our results imply the existence of opposed opioid systems affecting emotional and perceptual experiences.
TL;DR: In this paper, the wave function for a π-electron is presented in the LCAO form, where π denotes a p π -vorbital located on the j-th atom of a conjugated molecule, and the summation goes over all n atoms which participate in the conjugation.
Abstract: In the present chapter, as well as throughout the entire book, we assume that the reader knows the basic facts about the Huckel molecular orbital (HMO) theory [35, 51, 62]. Hence HMO theory is an approximate quantum-mechanical approach to the description of the π-electrons in unsaturated conjugated molecules. The wave function for a π-electron is presented in the LCAO form
$$ {\psi_i} = \sum\limits_{{j = 1}}^n {{c_{{ij}}}} \left| {{p_j} >} \right. $$
(1)
where {p j > symbolizes a p π -vorbital located on the j-th atom of the conjugated molecule, and the summation goes over all n atoms which participate in the conjugation.
TL;DR: Using autoaggressive rat T lymphocyte lines specific for defined protein components of peripheral or central myelin to study lymphocyte migration and antigen recognition within the nervous system suggests that the nervoussystem is constantly patrolled by low numbers of activated T cells.
TL;DR: In this paper, a general picture of magnetic reconnection in the framework of 2D incompressible resistive magnetohydrodynamic theory is presented, and a theory of the solution in the external and in the diffusion region is developed and analytical expressions in agreement with the simulation results are obtained by means of a variational principle.
Abstract: A general picture of magnetic reconnection in the framework of 2‐D incompressible resistive magnetohydrodynamic theory is presented. Numerical studies of (quasi‐) steady‐state driven reconnection reveal current sheet formation for Mach numbers M=u/vA exceeding the Sweet–Parker reconnection rate MSP=(η/LvA)1/2. Since the thickness δ of the current sheet is found to be invariant to a change of the resistivity η, its length Δ increases rapidly with decreasing η or increasing M, which can be written in the form Δ∼(M/MSP)4, so that Δ reaches the global system size L within a short range of the parameter M/MSP. The results are rather insensitive to the particular choice of boundary conditions. Because of the presence of a current sheet, the overall reconnection process is quite slow. This picture essentially agrees with Syrovatsky’s [Sov. Phys. JETP 33, 933 (1971)] theory and disproves Petschek’s [AAS/NASA Symposium on the Physics of Solar Flares, (NASA, Washington, DC, 1964) p. 425] mechanism of fast magnetic reconnection. A theory of the solution in the external and in the diffusion region is developed and analytical expressions in agreement with the simulation results are obtained by means of a variational principle. For sufficiently long current sheets the tearing mode becomes unstable in spite of the stabilizing effect of the inhomogeneous flow. The tearing mode contributes to the overall reconnection process, but a general assessment of this effect in the asymptotic regime of almost vanishing η is difficult.
TL;DR: The normal dipole source potentials in the intact hemisphere fully explained scalp distributions in these patients, and presence of late dipole sources potentials, which were delayed by 20-30 msec, probably reflected cortical activation via commissural fibres.
TL;DR: The general nature of this methodology has been further shown to be applicable to other restriction enzymes such as Hind II, Pst I and Fsp I and the mutational frequency obtained using these enzymes is between 40-80% mainly because of less efficient nicking and gapping.
Abstract: M13 RF IV DNA where phosphorothioate groups are incorporated at restriction endonuclease Nci I recognition sites in the (-)strand is efficiently nicked by the action of this enzyme. Incubation of such nicked DNA with exonuclease III produces gapped DNA. The gap can be filled by reaction with deoxynucleoside triphosphates and DNA polymerase I. When this sequence of reactions is performed with DNA containing a mismatch oligonucleotide primer in the (-)-strand mutational frequencies of 70-90% can be obtained upon transformation. The general nature of this methodology has been further shown to be applicable to other restriction enzymes such as Hind II, Pst I and Fsp I. The mutational frequency obtained using these enzymes is between 40-80% mainly because of less efficient nicking and gapping. Studies on inhibition of Nci I cleavage show that in addition to a phosphorothioate group at the position of cleavage an additional group in the 5'-neighbouring position is necessary for complete inhibition.
TL;DR: It is shown here that nearly all possible simple motifs occur 5–10 times more frequently than equivalent random motifs, and a new computer algorithm reveals the widespread occurrence of significantly high levels of a new type of ‘cryptic simplicity’ in both coding and noncoding DNA.
Abstract: DNA regions which are composed of a single or relatively few short sequence motifs usually in tandem (‘pure simple sequences’) have been reported in the genomes of diverse species (for reviews see refs 1–4), and have been implicated in a range of functions including gene regulation (for reviews see refs 5–7), signals for gene conversion and recombination8–10, and the replication of telomeres11They are thought to accumulate by DNA slippage12–16 and mispairing during replication and recombination or extension of single-strand ends2,4,10,11. In order to systematize the range of DNA simplicity and the genetic nature of the regions that are simple, we have undertaken an extensive computer search of the DNA sequence library of the European Molecular Biology Laboratory (EMBL)17. We show here that nearly all possible simple motifs occur 5–10 times more frequently than equivalent random motifs. Furthermore, a new computer algorithm reveals the widespread occurrence of significantly high levels of a new type of ‘cryptic simplicity’ in both coding and noncoding DNA. Cryptically simple regions are biased in nucleotide composition and consist of scrambled arrangements of repetitive motifs which differ within and between species. The universal existence of DNA simplicity from monotonous arrays of single motifs to variable permutations of relatively short-lived motifs suggests that ubiquitous slippage-like mechanisms are a major source of genetic variation in all regions of the genome, not predictable by the classical mutation process.
TL;DR: This paper explores possible relations obtaining between unconscious meta-processes and those available to conscious access and verbal statement, and speculations with respect to the plausibility of considering modularity as a product of some aspects of development, rather than restricting modularity solely to innate givens.
TL;DR: In this paper, a Green's function method is used to obtain an integral equation over a toroidal domain φ = Σφ mn sin( mθ − nζ ).
TL;DR: In this article, a chemical mechanism for the formation of the ozone hole is proposed, which involves removal of gaseous odd nitrogen by ion-and/or aerosol-catalysed conversion of N2O5 and ClONO2 to HNO3 vapour.
Abstract: Large depletions in stratospheric ozone were first reported by Farman et al [1] at Halley Bay (76 °S), and confirmed by satellite observations [2] Chubachi [3] gives a detailed account of ozone decreases and temperatures in the lower stratosphere during the spring of 1982 at 69 °S There is now evidence [2] for annual declines in total ozone by ~6 and 3 % in regions of total ozone minima and maxima, respectively, from September to mid-October since the late 1970s We propose here a chemical mechanism for the formation of the ozone hole It involves removal of gaseous odd nitrogen by ion- and/or aerosol-catalysed conversion of N2O5 and ClONO2 to HNO3 vapour, followed by heteromolecular HNO3–H2O condensation, leading to HNO3–H2O aerosols At an altitude of 17 km, these processes start at temperatures below 205 ± 5 K, well above the condensation temperature of pure water vapour We propose that the absence of gaseous odd nitrogen and catalytic methane oxidation reactions driven by sunlight in early spring lead to large OH concentrations which rapidly convert HCl to ClOX Catalytic reactions of ClOX and BrOX cause drastic ozone destructions and can account for the springtime ‘ozone hole’ first observed by Farman et al [1] By our model the depletion would be mainly due to emissions of industrial organic chlorine compounds Arctic regions may also become affected The depletion lasts while HNO3, but not HCl, is incorporated in the particles in the temperature range 205 ± 5 to 192 K
TL;DR: In this paper, the authors tested the hypothesis that a clear-water period, regularly observed in many meso- and eutrophic lakes, is caused by grazing herbivorous zooplankton.
Abstract: We tested the hypothesis that a clear-water period, regularly observed in many meso- and eutrophic lakes, is caused by grazing herbivorous zooplankton. Such a clear-water phase occurs during mid-May in the moderately eutrophic Schiihsee and involves a rapid increase in Secchi transparency, and a drop in chlorophyll and particulate organic carbon in size fractions ~35 Nm. Maxima of zooplankton biomass and community grazing rates (170% of volume cleared per day) coincided with the greatest transparency. The algal decline was not related to nutrient depletion or climatic events. Before the clear-water phase small phytoplankton contributed up to 88% of the primary production, but the contribution of large particles was more important after the zooplankton maximum. The effects of herbivory by zooplankton were examined in a series of time-overlapping enclosure experiments. Concentrations of small ( 35 pm) algae. A distinct period of clear water is typical of the spring algal succession in many mesotrophic and eutrophic lakes of temperate zones (Sommer et al. 1986). An early peak of small, rapidly growing algae (flagellates, small diatoms), which often represents the highest biomass concentration of the annual cycle, is followed by a short period of very clear water and high Secchi transparency. A summer community dominated by large algae and blue-greens develops after the clearwater phase. The period of high Secchi transparency sometimes lasts only 2 weeks or less. The increase in water clarity can be spectacular. In Lake Constance for example transparency may increase from 1 to 10 m in a few days (Lampert
TL;DR: In this article, the authors derived the tight-binding (TB) orbitals by exact transformation of the conventional set of linear muffin-tin orbitals (LMTO's) for crystalline silicon.
Abstract: Plots of the tight-binding (TB) orbitals recently derived by exact transformation of the conventional set of linear muffin-tin orbitals (LMTO's) are presented for crystalline silicon. The TB-LMTO's are found to be extremely compact. As a simple application we show how non-spherically-averaged charge densities may be obtained from standard LMTO calculations. For silicon this charge density is found to be in excellent agreement with the one obtained from a linear augmented plane-wave full-potential calculation. This is true even when the LMTO calculation employs the atomic-sphere approximation for the one-electron potential. A self-contained account of the TB-MTO formalism is presented and a simple way of including the quadratic energy dependence of the MTO's is derived.
TL;DR: It is concluded that the hypo- and hyperglycaemic properties of tolbutamide and diazoxide reflect their ability to induce the closure or opening, respectively, of ATP-regulated K+ channels.
Abstract: The influence of the antidiabetic sulphonylurea tolbutamide on K+ channels of mouse pancreatic beta-cells was investigated using different configurations of the patch clamp technique. The dominant channel in resting cells is a K+ channel with a single-channel conductance of 60 pS that is inhibited by intracellular ATP or, in intact cells, by stimulation with glucose. In isolated patches of beta-cells membrane, this channel was blocked by tolbutamide (0.1 mM) when applied to either the intracellular or extracellular side of the membrane. The dose-dependence of the tolbutamide-induced block was obtained from whole-cell experiments and revealed that 50% inhibition was attained at approximately 7 microM. In cell-attached patches low concentrations of glucose augmented the action of tolbutamide. Thus, the simultaneous presence of 5 mM glucose and 0.1 mM tolbutamide abolished channel activity and induced action potentials. These were not produced when either of these substances was added alone at these concentrations. The inhibitory action of tolbutamide or glucose on the K+ channel was counteracted by the hyperglycaemic sulphonamide diazoxide (0.4 mM). Tolbutamide (1 mM) did not affect Ca2+-dependent K+ channels. It is concluded that the hypo- and hyperglycaemic properties of tolbutamide and diazoxide reflect their ability to induce the closure or opening, respectively, of ATP-regulated K+ channels.
TL;DR: In this paper, the authors showed that a two-dimensional electron gas is necessary for the observation of the Quantized Hall Effect, and the realization and properties of such a gas is discussed in section 2.
Abstract: tory since one may come to the conclusion that such a complicated system like a semiconuctor is not useful for very fundamental discoveries. Indeed, most of the experimental data in solid state physics are analyzed on the basis of simplified theories, and very often the properties of a semiconductor device is described by empirical formulas since the microscopic details are too complicated. Up to 1980 nobody expected that there exists an effect like the Quantized Hall Effect, which depends exclusively on fundamental constants and is not affected by irregularitie s in the semiconductor like impurities or interface effects. The discovery of the Quantized Hall Effect (QHE) was the result of systematic measurements on silicon field effect transistors-the most important device in microelectron ics. Such devices are not only important for applications but also for basic research. The pioneering work by Fowler, Fang, Howard and Stiles [l] has shown that new quantum phenomena become visible if the electrons of a conductor are confined within a typical length of 10 nm. Their discoveries opened the field of two-dimension al electron systems which since 1975 is the subject of a conference series [2]. It has been demonstrated that this field is important for the description of nearly all optical and electrical properties of microelectron ic devices. A two-dimensiona l electron gas is absolutely necessary for the observation of the Quantized Hall Effect, and the realization and properties of such a system will be discussed in section 2. In addition to the quantum phenomena connected with the confinement of electrons within a two-dimensional layer, another quantization - the Landau quantization of the electron motion in a strong magnetic field - is essential for the interpretation of the Quantized Hall Effect (section 3). Some experimental results will be summarized in section 4 and the application of the QHE in metrology is the subject of section 5.
TL;DR: The partially deleted gene for the common biosynthetic precursor of gonadotropin-releasing hormone and GnRH-associated peptide is transcriptionally active as revealed by in situ hybridization histochemistry of hpg hypothalamic tissue sections, but immunocytochemical analysis failed to show the presence of antigen corresponding to any part of the precursor protein.
Abstract: Hereditary hypogonadism in the hypogonadal (hpg) mouse is caused by a deletional mutation of at least 33.5 kilobases encompassing the distal half of the gene for the common biosynthetic precursor of gonadotropin-releasing hormone (GnRH) and GnRH-associated peptide (GAP). The partially deleted gene is transcriptionally active as revealed by in situ hybridization histochemistry of hpg hypothalamic tissue sections, but immunocytochemical analysis failed to show the presence of antigen corresponding to any part of the precursor protein.
TL;DR: This study demonstrates that blastocyst-derived embryonic stem cells (ES cells) can be used as a vehicle for transgenesis, and the introduced neomycin phosphotransferase (neo) gene is stably transmitted through several generations with no apparent loss in G418 resistance.
Abstract: This study demonstrates that blastocyst-derived embryonic stem cells (ES cells) can be used as a vehicle for transgenesis. The method is nearly as efficient as other methods, and the introduced neomycin phosphotransferase (neo) gene is stably transmitted through several generations with no apparent loss in G418 resistance. An important factor contributing to the efficiency of this process is the rigorous selection, before blastocyst injection, of genetically transformed cells for in vitro developmental pluripotency. One of the advantages of the ES cell route to transgenesis is that it provides investigators with the opportunity to screen for the desired genetic alterations before reintroducing the ES cells into the animal.
TL;DR: An X‐ray structure analysis of the photosynthetic reaction centre from the purple bacterium Rhodopseudomonas viridis provides structural details of the pigment‐binding sites that may help to understand why only one branch of pigments is active in the light‐driven electron transfer.
Abstract: An X-ray structure analysis of the photosynthetic reaction centre from the purple bacterium Rhodopseudomonas viridis provides structural details of the pigment-binding sites. The photosynthetic pigments are found in rather hydrophobic environments provided by the subunits L and M. In addition to apolar interactions, the bacteriochlorophylls of the primary electron donor (`special pair') and the bacteriopheophytins, but not the accessory bacteriochlorophylls, form hydrogen bonds with amino acid side chains of these protein subunits. The two branches of pigments which originate at the primary electron donor, and which mark possible electron pathways across the photosynthetic membrane, are in different environments and show different hydrogen bonding with the protein: this may help to understand why only one branch of pigments is active in the light-driven electron transfer. The primary electron acceptor, a menaquinone (QA), is in a pocket formed by the M subunit and interacts with it by hydrophobic contacts and hydrogen bonds. Competitive inhibitors of the secondary quinone QB (o-phenanthroline, the herbicide terbutryn) are bound into a pocket provided by the L subunit. Apart from numerous van der Waals interactions they also form hydrogen bonds to the protein.
TL;DR: The authors used homogenized near-surface temperature data over the land and oceans of both hemispheres during the past 130 years to produce the first comprehensive estimates of global mean temperature, showing little trend in the nineteenth century, marked warming to 1940, relatively steady conditions to the mid-1970s and subsequent rapid warming.
Abstract: Recent homogenized near-surface temperature data over the land and oceans of both hemispheres during the past 130 years are combined to produce the first comprehensive estimates of global mean temperature. The results show little trend in the nineteenth century, marked warming to 1940, relatively steady conditions to the mid-1970s and a subsequent rapid warming. The warmest 3 years have all occurred in the 1980s.
TL;DR: The conductances of rat muscle AChR and sodium channels implanted into the oocyte membrane were similar to those of channels in their native muscle membrane, suggesting that important functional properties of these channels are determined by their primary amino acid sequence.
Abstract: Functional acetylcholine receptor (AChR) and sodium channels were expressed in the membrane of Xenopus laevis oocytes following injection with poly(A)+-mRNA extracted from denervated rat leg muscle. Whole-cell currents, activated by acetylcholine or by depolarizing voltage steps had properties comparable to those observed in rat muscle. Oocytes injected with specific mRNA, transcribed from cDNA templates and coding for the AChR of Torpedo electric organ, expressed functional AChR channels at a much higher density. Single-channel currents were recorded from the oocyte plasma membrane following removal of the follicle cell layer and the vitelline membrane from the oocyte. The follicle cell layer was removed enzymatically with collagenase. The vitelline membrane was removed either mechanically after briefly exposing the oocyte to a hypertonic solution, or by enzyme treatment with pronase. Stretch activated (s.a.) currents were observed in most recordings from cell-attached patches obtained with standard patch pipettes. S.a.-currents were evoked by negative or positive pressure (greater than or equal to 5 mbar) applied to the inside of the pipette, and were observed in both normal and mRNA injected oocytes indicating that they are endogenous to the oocyte membrane. The s.a.-channels are cation selective and their conductance is 28 pS in normal frog Ringer's solution (20 +/- 1 degree C). Their gating is voltage dependent, and their open probability increases toward more positive membrane potentials. The density of s.a.-channels is estimated to be 0.5-2 channels per micron 2 of oocyte plasma membrane. In cell-attached patches s.a.-currents are observed much less frequently when current measurement is restricted to smaller patches of 3-5 micron 2 area using thick-walled pipettes with narrow tips. In outside-out patches s.a.-currents occur much less frequently than in cell-attached or inside-out patches. AChR-channel and sodium channel currents were observed only in a minority of patches from oocytes injected with poly(A)+-mRNA from rat muscle. AChR-channel currents were seen in all patches of oocytes injected with specific mRNA coding for Torpedo AChR. In normal frog Ringer's solution (20 +/- 2 degrees C) the conductance of implanted rat muscle AChR-channels was 38 pS and that of sodium channels 20 pS. The conductance of implanted Torpedo AChR channels was 40 pS. The conductance of implanted channels was similar in cell-attached and in cell-free patches.(ABSTRACT TRUNCATED AT 400 WORDS)