Ethanol-induced changes in the intralobular oxygen gradient of perfused rat liver

A new tissue fluorometric method was developed to estimate the intralobular oxygen gradient in hemoglobin-free perfused rat liver. The method employs a two-branch micro-light guide with a tip diameter of 170 mu. With this light guide, it was possible to measure pyridine nucleotide fluorescence (366 nm leads to 450 nm) from periportal and pericentral regions of the liver lobule. By measuring inflow PO2 values at which pyridine nucleotide fluorescence increased in the pericentral regions of the liver lobule, the mean intralobular oxygen gradient was estimated. The measured gradient was approximately 180 torr in livers from sucrose-treated control rats. Chronic treatment with ethanol increased both the mean intralobular oxygen gradient and the rate of hepatic oxygen uptake by 30%. The antithyroid drug, 6-propyl-2-thiouracil, completely reversed the effects of ethanol on both the intralobular oxygen gradient and the rate of oxygen uptake. These data present direct physical evidence that the increased tissue respiration induced by chronic ethanol treatment indeed accentuates the intralobular oxygen gradient and thus support the hypothesis that selective depletion of oxygen in the pericentral region of the liver lobule may underlie ethanol-induced cellular injury confined to this site.

Micro-light guides: a new method for measuring tissue fluorescence and reflectance

Three-way light guides containing one or more strands of 25-micron or 80-micron diameter optical fibers in each channel have been constructed and used to measure the NADH fluorescence and UV reflectance from mitochondrial suspensions, the perfused, hemoglobin-free rat liver, and the perfused beating interventricular septum of the rabbit. The optical changes measured with these so-called micro-light guides, which have channels containing one or several strands of optical fibers less than 100 micron, are comparable in magnitude with those measured using much larger conventional light guides. The effect of light scattering on the fluorescence channel has been determined and an empirical equation for correcting the fluorescence channel for light scattering has been obtained for mitochondrial suspensions. A mathematical equation characterizing the optical behavior of a two-way micro-light guide has been derived and has been shown to account satisfactorily for reflectance and fluorescence measurements of a mat surface in air.

Action of norepinephrine on microcirculation and PO2 distribution in the isolated perfused rat liver

The addition of a potent vasoconstrictor, such as norepinephrine, induces an influx of sodium and an efflux of calcium and potassium in the parenchymal cells of the perfused liver. This reaction can be reversed by the addition of dihydroergotoxine mesylate (active substance of Hydergine). The example shows clearly that very distinct biological signals are generated under such conditions at the membrane level of the hepatocytes and presumably of other cells of liver tissue. At present, our investigations cannot clearly answer the question of whether or not swelling the shrinkage of parenchymal cells and of endothelial cells can serve as an additional mechanism for regulating microcirculation.

Disturbances of extracellular pK, pNa and pH during no-flow anoxia

The initial period of no-flow anoxia can be divided in at least two parts. During the first period lasting approximately 1 min., the O2 available in tissue gives rise to CO2 which increases hydrogen ion activity and may lead to Na+ influx2 (presumably due to increased membrane permeability to Na+). In the second period, starting after the first minute, the increase in lactate content leads to further decrease in pH and is accompanied by extensive sodium influx and a distinct potassium efflux. However, it is striking that the isolated perfused rat liver is able to tolerate 1 hour of norm-flow anoxia without severe cellular damage, whereas two minutes of no-flow anoxia lead to a decrease in cellular ATP content by 28%.

Two-dimensional analysis of the redox state of the rat cerebral cortex in vivo by NADH fluorescence photography

A photographic method for measuring two-dimensional changes in NADH fluorescence and hemoglobin distributions in the rat cerebral cortex in vivo has been developed. Intracellular NADH was excited by UV light peaking at 360 nm and the emission was observed through a window with the maximum transmission at 450 nm. The fluorescence photographs (360 leads to 450 nm) required 20-25 sec exposures at the aperture opening of f/5.6 and the reflectance photographs (360 leads to 360 nm) 10 sec exposures at f/32. The digitization of photographic images was achieved either by a PDP-8-controlled microdensitometer coupled to an A/D converter or by a combination of a manually operated microdensitometer and a computer-controlled digitizer. In the latter case, a photographic negative was scanned with a Joyce-Loebl microdensitometer in parallel lines 170 mum apart, and the densitometric tracings were digitized with a PDP-8-controlled TV digitizer. The digital data were processed by DEC PDP-10 computer and the results were displayed in 3-dimensional surfaces. Nitrogen anoxia caused increases in fluorescence at 450 nm ranging from 10 to 75% fo the normoxic fluorescence intensities (after correcting for the logarithmic characteristics of the photographic films) and decreases in reflectance intensities in the range of 10-30%. The spatial resolution of the present technique is limited to approximately 30 mum X 30 mum on the cortical surface and the time resolution to 10-25 sec. The optical properties of the cerebral cortex in vivo appear to be controlled primarily by blood vessel patterns and hemodynamic factors and secondarily by the redox state of the tissue. Evidence for a heterogeneous redox response of the cerebral cortex toward N2 anoxia was obtained.

Transductional and structural principles of the mitochondrial transducing unit

The electromechanochemical model has been reformulated to take account of the close connection between energy coupling and catalysis. In catalysis the protein is programmed to utilize thermal energy to produce local strains in the catalytic cavity and to generate conformational states that favor substrate --> product conversion. Energy coupling involves transfer of vibrational energy through the protein. Underlying these two energy transductional maneuvers is the concept of a pulsating protein capable of redistributing electromechanochemical potential energy in a programmed fashion. The mitochondrial supermolecule has been defined, and it has been shown how the supermolecule concept rationalizes the coupling options, the stoichiometry of the coupling complexes, and the multistep character of electron transfer.

Electromechanochemical model of mitochondrial structure and function

A NEW MODEL OF MITOCHONDRIAL STRUCTURE AND FUNCTION IS PROPOSED ON THE BASIS OF FOUR FUNDAMENTAL ASSUMPTIONS: (a) electrons and protons are separated in the electron transfer complexes; (b) the ATPase undergoes conformational state-transitions induced by an electric field; (c) energy is transferred by an electric field effect; and (d) a conformationally strained protein system can be relaxed via a bond-forming chemical reaction. The model can explain all of the mitochondrial coupled processes and, in addition, it provides a reasonable rationalization of the correlation between mitochondrial structure and function.