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Biomedical subjects

H Tedeschi

Publications and source records attributed to H Tedeschi.

At least 55 records · Page 3Linked to original sources
PubMed1984

Permeability properties of mammalian cell nuclei in living cells and in vitro.

The present study evaluates the role of the nuclear envelope in mammalian cells by applying two different approaches using either intact cells of mouse liver or isolated nuclei. In one approach the nuclei were studied with microelectrodes. The transmembrane voltage drop produced by passing current through an impaling microelectrode was measured with a second impaling microelectrode. In the second approach, the permeability of the nuclear envelope was studied by injection of a series of fluorescent probes. Lucifer Yellow CH and a variety of exogenous proteins labelled by conjugation with Lucifer Yellow VS were delivered into either the cytoplasm or the nucleus in situ. The fluorescence of the probe was followed either with a video camera or photographically. The results agree with the idea that the mammalian nuclear envelope is permeable to rather large molecules. Molecules with estimated radii below 2.4 nm seem to exchange rapidly, whereas molecules with estimated radii of 2.8 nm or above are excluded. The low electrical resistance of the envelope yields an estimate of pore radius, in the range of 3.4-6.5 nm.

Animals↗
PubMed1983

Kinetics of Lucifer yellow CH efflux in giant mitochondria.

The fluorescent dye Lucifer yellow CH was microinjected electrophoretically into giant mitochondria isolated from mice maintained on a diet containing cuprizone. The dye was retained by the mitochondria, indicating that it was contained in a space bounded by a selectively permeable membrane. The labelling was reversible by reversing the polarity of the current. A study of the disappearance of the fluorescence indicates that the permeability of the mitochondrial membrane to the dye (probably the lithium and/or the potassium salts) ranges from 10(-7) to 10(-8) cm/s.

Animals↗
PubMed1982

Adenosine triphosphate synthesis coupled to K+ influx in mitochondria.

The influx of K+ into swollen mitochondria in the presence of valinomycin results in the synthesis of adenosine triphosphate in which approximately one H+ disappears per adenosine triphosphate synthesized. The synthesis is blocked by atractyloside but is insensitive to oligomycin and relatively insensitive to uncouplers.

Adenosine Triphosphate↗
PubMed1981

The transport of cations in mitochondria.

The present paper has reviewed several factors related to ion transport and examined the properties of cation transport in mitochondria. The analysis suggests that: (1) The concept that a metabolically dependent electrical potential across the mitochondrial membrane plays a role in determining ion fluxes and steady-state concentrations is not justified and the data indicate that such exchanges are generally electroneutral. (2) Generally, the influx and efflux of an ion proceed by the same mechanism with at least one exception. (3) There are indications that some of the steps in transport are common to several cations. (4) The idea that carrier or ionophoric molecules are involved in cation transport has been examined in some detail together with the possible involvement of some known mitochondrial components. In particular, a model has been introduced in which local charge imbalances produced by H+ fluxes serve as the driving force of transport. The molecules of the complex are arranged in series in a tripartite arrangement including a filter or gate, a nonselective channel and an H+-transferring portion linked to either electron transport or the ATPase. Parts of this model have been introduced by other investigators. Models in which different portions of channels have differing functions have been proposed previously for other transport systems.

Animals↗
PubMed1980

Electrophoretic injection of a fluorescent dye into giant mitochondria and mitoplasts.

Studies of the electrical properties of giant mitochondria and mitoplasts with microelectrodes have indicated that there are no significant metabolically dependent membrane potentials. The internal location of the microelectrode has been confirmed by electrophoretically microinjecting the water-soluble dye Lucifer yellow CH into giant mitochondria or mitoplasts.

Animals↗
PubMed1978

Metabolic effects of some electrofluorimetric dyes.

The effect of five electrofluorimetric dyes on mitochondrial metabolism was examined to determine their suitability for mitochondrial studies and other biological uses. The dyes merocyanine 540, 8-anilino-1-naphthalene sulfonic acid and bis(1,3-dibutyl barbituric acid-(5))-pentamethane oxonol were found to be inhibitors of the respiratory chain. However, the first two exerted their effect only at high concentrations. 3.3'-Dihexyl-2,2'-oxacarbocyanine was found to act as an uncoupler. 3,3'-Dipropyl-thiocarbocyanine inhibited beta-hydroxybutyrate respiration while dissociating succinate supported respiration from the phosphorylation of ADP. Merocyanine 540 and 8-anilino-1-naphthalene sulfonic acid may be the best suited for studies of membrane potentials in mitochondria since their effect on metabolism is negligible

Animals↗
PubMed1978

Use of dyes to estimate the electrical potential of the mitochondrial membrane.

A number of cationic or anionic fluorescent dyes were investigated as possible monitors of the membrane potential of rat liver mitochondria, and giant mitochondria isolated from the liver of mice maintained on a diet containing cuprizone. The fluorescence of four dyes (8-anilino-1-naphthalenesulfonic acid, merocyanine 540, 3,3'-dipropyl-thiocarbocyanine, and bis[1,3-dibutylbarbituric acid-(5)]-pentamethine oxonol) was found to respond appropriately to changes in an apparent K+ diffusion potential. Generally, valinomycin-induced K+ diffusion potentials as calculated using the Nernst equation were used to calibrate the dependence of the fluorescence on the membrane potential. The appropriateness of this approach was verified for two dyes using microelectrodes in giant mitochondria. The apparent membrane potential change induced by the addition of succinate was variable but was very low and generally less than 60 mV in magnitude. The results are consistent with the notion that a large membrane potential is not established upon the initiation of metabolism and that the membrane potential does not play a significant role in the observed ADP phosphorylation.

Animals↗
PubMed1978

Membrane potentials and resistances of giant mitochondria. Metabolic dependence and the effects of valinomycin.

The membrane potentials and resistances of giant mitochondria from mice fed cuprizone have been studied. They were found to correspond approx. 10-20 mV, positive inside, and 2 M omega, respectively. These properties were found to be independent of the metabolic state. The microelectrodes were in the inner mitochondrial space since (a) the potentials in the presence of valinomycin depended on the K+ concentration of the medium and magnitude of the K+ diffusion potentials was consistent with the presence of a high internal concentration of K+, (b) almost identical results were obtained with mitochondria from which the external membrane had been removed and the cristae were evaginated, and (c) punch-through experiments, in which the microelectrodes were advanced until they emerged through the other side of the mitochondria, showed an identical membrane potential both in the presence and in the absence of valinomycin. The potentials were stable under a variety of conditions and showed no sign of decay of membrane leakiness. Detailed evidence that the impaled mitochondria are metabolically viable will be presented in a separate publication.

Animals↗
PubMed1978

Assays of the metabolic viability of single giant mitochondria. Experiments with intact and impaled mitochondria.

Single giant mitochondria isolated from mice fed cuprizone were assayed for their metabolic viability. Two tests were devised. One test optically detected the accumulation of calcium phosphate within the mitochondria under massive loading conditions (including the presence of succinate and ATP). The accumulation corresponds to a test of energy coupling from either electron transport or the hydrolysis of ATP since it is blocked by either antimycin A or oligomycin. The other assay tested for the production of ATP from ADP and Pi, using myofibrils. Myofibrils prepared from glycerinated rabbit psoas muscle contract only in the presence of ATP and not in the presence of ADP. Myofibrillar contraction is unaffected by the presence of antimycin A or oligomycin. However, myofibrils in the presence of mitochondria that are phosphorylating ADP to ATP do contract. This contraction is blocked by antimycin A and/or oligomycin. Hence, the ATP which causes myofibrillar contraction is produced by oxidative phosphorylation. At low mitochondrial concentration, only the myofibrils in close proximity with mitochondria contract in the presence of ADP. Therefore the assay can be used to test the viability of individual mitochondria. Individual giant mitochondria were found to be viable, using both of these assays. Comparable results were obtained in mitochondria impaled with microelectrodes. The potentials and resistances were unaffected by concomitant calcium phosphate accumulation or oxidative phosphorylation.

Adenosine Diphosphate↗
PubMed1977

Membrane potential of mitochondrial measured with microelectrodes.

The membrane potentials of giant mitochondria from cuprizone-fed mice were found to be independent of metabolic state. Experiments are described in which the presence of the microelectrodes in the inner mitochondrial space, and the metabolic viability of the impaled mitochonidra, are validated.

Animals↗
PubMed1976

Osmotic behavior and permeability of osmotically lysed mitochondria.

Experiments were carried out with water-treated isolated rat liver mitochondria (mitochondria ghosts) previously studied by Caplan and Greenawalt (Caplan, A.I., and J.W. Greenawalt. 1966. J. Cell Biol. 31:455-472) and Vasington and Greenawalt (Vasington, F., and J. Greenawalt. 1968. J. Cell Biol. 39:661-675). The ghosts have permeability properties and osmotic behavior comparable to those of isolated mitochondria. Although they have lost most of their internal contents, they must have resealed. Four properties were found which have not been previously described in systems derived from biological membranes: (a) an osmotic behavior in the virtual absence of internal components. (b) a self-arranging property in the formation of invaginations corresponding in morphology to the cristae. The results suggest that the assembly of the molecular components of the inner membrane is sufficient to specify the morphology. Hence the surface area to volume ratio of the vesicles may specify the presence or absence of cristae-like folds. (c) an increase in the permeability of the membranes to sucrose in the presence of iso-osmotic concentrations of sucrose. (d) an independence of the light transmitted by suspensions of the vesicles from the refractive index of the external medium. This observations run counter to the general previous experience with either mitochondria or liposomes.

Animals↗
PubMed1975

Donnan potential of rabbit skeletal muscle myofibrils I: electrofluorochromometric detection of potential.

The fluorescence of the dye CC-6 [(3-hexyl-2-(3-hexyl-2-benzoxazolinylidene)-1-propenyl)-benzoxazolium iodide] has been shown to indicate Donnan potentials in rabbit skeletal muscle myofibrils. These results are in agreement with previously published work in which the potentials were measured with microelectrodes on glycerol-extraced muscle fibers. The magnitude of the Donnan potential of the myofibrils has been shown to be dependent on the state (rigor or relaxed) of the system.

Adenosine Triphosphate↗