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J P Caille

Publications and source records attributed to J P Caille.

11 recordsLinked to original sources
PubMed1981

An electrogenic component of resting potential in rabbit ventricular muscle?

The resting potential and the intracellular Na and K concentrations (Nai, Ki) were determined at several extracellular K concentrations (Ko) between 0.5 and 18 mM and after inhibition of the sodium pump with 0.5 microM ouabain. Exposure to low Ko (0.5 mM) produced a transient hyperpolarization (from -80 to -100 mV) followed by a depolarization that led to a stable potential of -60 mV within 25 min. Similar potential levels were observed in the presence of ouabain regardless of the Ko/Ki ratio. Intracellular sodium increased at Ko < 5 mM, whereas Ki rose at Ko less than or equal to 1.0 mM. Because of the large decrease of Ki at Ko = 0.5 mM, Ko/Ki was the same at 0.5 and 1 mM. However, the resting potentials at the steady state differed by 50 mV at these concentrations. A PNa/PK of 0.032 for the control conditions was obtained with the Mullins-Noda equation using 2.5 as the Na-K coupling ratio. This PNa/PK value yielded a Goldman potential of -69 mV; so we estimated that electrogenic sodium extrusion contributed -10 mV to the resting potential. The size of the electrogenic potential increased as Ko was lowered from 5 to 1 mM. This finding suggests that the control of the Na-K coupling ratio may be independent of the mechanism that controls the pumping rate.

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PubMed1981

Intracellular chloride activity in rabbit papillary muscle: effect of ouabain.

Intracellular chloride activity (aiCl) and membrane potential (Vm) were measured in rabbit papillary muscle under in vitro conditions. The cellular chloride concentration (Cli) was estimated from measurements of total water content, extracellular space, and total chloride concentration. The effects of therapeutic (10(-8) M) and toxic (10(-6) M) concentrations of ouabain on these parameters were tested. The chloride-sensitive microelectrodes were of the liquid-ion exchanger type. Selectivity for HCO-3 was taken into account in the calculation of aiCl. In 11 control experiments made with two different protocols aiCl was determined in subendocardial and in deeper cells. The mean membrane potentials were -78.7 and -78.0 mV and the mean cytoplasmic chloride activities were 17.5 and 17.7 mM, respectively. The chloride equilibrium potentials were -43.5 and -43.2 mV. These results indicated that chloride is not passively distributed in rabbit papillary muscle. Ouabain (10(-8) M) did not change Vm or aiCl. At a toxic concentration of ouabain, Vm fell to -68.0 mV in superficial cells and to -67.8 mV in deeper cells, but aiCl remained unchanged . These results suggested that under in vitro conditions intracellular chloride is distributed within more than one cellular compartment.

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PubMed1978

Laser Raman investigation of intact single muscle fibers. On the state of water in muscle tissue.

Laser Raman spectroscopy has been used to investigate the state of water in intact single muscle fibers of the giant barnacle (Balanus nubilus). The spectra in the region of the O-H (or O-2H) stretching modes of water in unfrozen fibers show that there is no appreciable difference between the shape and relative intensity of the Raman bands due to the water molecules located inside a muscle fiber and those of the corresponding bands in the spectrum of pure water. The presence of significant amounts of "structured" intracellular water, greater than approx. 5% of the total water content, in these fibers is thus excluded. The Raman spectra of frozen fibers have also been recorded in order to evaluate the amount of intracellular water which remains unfrozen at temperatures below the normal freezing point of water. We have been able to reproduce these spectra by assuming that the spectrum of a frozen fiber is the sum of the individual spectra of water and ice. To calculate the amount of unfrozen water from these curve fittings, it was also necessary to determine the intensities of the water and ice Raman bands relative to one another. We have found the I(ice)/I(water) ratio is 1.07 +/- 0.01 for H2O and 1.05 +/- 0.03 for 2H2O With these figures, we have calculated that for a fiber with a normal water content of 80%, 20% of the water molecules remain in the supercooled state of -5 degrees C, which corresponds to 1 g of water per g of fiber dry weight. This amount of bound water was also found to be independent of the water content of the fibers.

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PubMed1978

Laser Raman investigations of intact single muscle fibers. Protein conformations.

Raman spectra, in the frequency region of the protein vibrations, of intact single muscle fibers of the giant barnacle are presented. Strong bands at 1521 and 1156 cm-1 in the spectra are attributed to resonance-enhanced Raman bands of membrane-bound beta-carotene. Many bands of the myofibrillar proteins are also observed, and at least three spectral features confirm that these proteins adopt a predominantly alpha-helical structure: (1) the amide I band at 1648 cm-1, (2) the weak scattering in the amide III region, and (3) a strong skeletal C-C stretching band at 939 cm-1. Deuterated fibers have also been examined in order to find the exact shape of the amide III band. The presence in the fibers of paramyosin, which is only found in catch muscles, is also apparent from the spectra.

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