Lymphocyte glutathione status in relation to their Con A proliferative response.

We studied the intracellular total, oxidized and reduced glutathione levels in thymus and spleen rat lymphocytes cultured with or without Con A and 2-mercaptoethanol (2-ME). After 48 h culture, the total glutathione level decreased and the oxidized glutathione level increased in the two types of unstimulated and stimulated cells. In the presence of 2-ME, the tritiated thymidine incorporation increased in splenocytes but not in thymocytes; on the other hand, the two types of stimulated cells increased their total and oxidized glutathione content. The enhancement of the GSSG/GSH + GSSG ratio, irrespective of culture conditions, indicates a severely disturbed redox state of the cells. 2-ME acts on the glutathione synthesis of stimulated lymphocytes but is unable to maintain a normal redox state of these cells.

Efficacy of continuous zidovudine infusion at early stages of retroviral infection in mice.

We studied the pharmacokinetics of zidovudine (ZDV) in mice after twice-daily s.c. bolus injections and during continuous infusion with s.c. ALZET mini-osmotic pumps. We also compared the antiretroviral efficacy of these two modes of administration against Friend leukemia virus (FLV) infection. Mice were infected by retro-orbital inoculation of about 50 focus-forming units (ffu) of FLV, and treatment was started 1 or 4 h later with ZDV at 40 mg/kg/day for 5 days. Efficacy was evaluated in terms of spleen weight and/or virus titer (spleen focus assay) on day 21 in comparison with untreated infected mice. In a separate experiment, survival time after infection was also monitored over a 140-day period. Plasma concentrations of ZDV were determined by means of high-performance liquid chromatography. Following bolus administration, the peak plasma ZDV concentration (30.5 mg/ml) was reached within 10 min, and elimination was rapid (mean half-life, 0.7 h). During the continuous infusion, the mean concentration was constant at about 1.2 mg/ml. After 5 days of treatment, continuous ZDV infusion consistently inhibited virus-induced splenomegaly by more than 97%; bolus injections were less effective with inhibition ranging from 13 to 98%. These results suggest that moderate constant levels of ZDV have greater antiretroviral efficacy than intermittent high concentrations.

Glutathione status of rat thymocytes and splenocytes during the early events of their ConA proliferative responses.

Glutathione plays an important role in the lymphocyte mitogenic response. We have demonstrated that 2-ME increases the ConA proliferative response of rat splenocytes and in parallel, causes an enhancement of glutathione synthesis in these cells. On the other hand, 2-ME had the same action on the glutathione level of thymocytes during the late phase of their mitogenic response, but it had no effect on the [3H]thymidine uptake of these cells. To clarify this discrepancy and the role of glutathione during the mitogenic response, we studied the glutathione status of thymus cells during the early phase of the ConA-induced proliferative response in the presence or the absence of 2-ME in parallel with that of whole spleen cells and the T cell fraction of splenocytes. During the early events of the mitogenic response, i.e., during the 24th h, we observed a normal 2 GSSG/GSH + 2 GSSG ratio in cultured cells, indicating a normal redox state, and that ConA involved an increased glutathione level in thymocytes but not in whole splenocytes and in splenic T cells. 2-ME had no effect on the glutathione level of stimulated thymocytes during the early phase of the mitogenic response. This phenomenon could be related to an absence of its effect on [3H]thymidine uptake. On the other hand, 2-ME induced an enhancement of the glutathione level and [3H]thymidine uptake in the two types of stimulated splenocytes. This study suggest that thymocytes do not have the same mechanism of glutathione synthesis induction as that which occurs in splenocytes during the ConA proliferative response. This mechanism could be related to the maturation state of the T cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Nebulized cyclosporine in the rat: assessment of regional lung and extrapulmonary deposition.

BACKGROUND: Nebulized cyclosporine (CsA) has been shown to limit lung allograft rejection as well as intramuscular (IM) CsA, with limited blood diffusion. The present study determined the pharmacokinetic parameters of nebulized CsA, by the assessment of regional lung deposition and extrapulmonary diffusion of CsA. METHODS: CsA was given either by IM injection (10 mg/kg) or by aerosol (at 10 and 25 mg/kg doses); 70 rats were killed at 25 and 50 min, and at 2, 4, 6, 8, 12, 24, or 48 hr after CsA administration. CsA levels were measured in the whole lung, in central and peripheral parts of the lung, in whole blood, kidney, and heart. The areas under the concentration time curves (AUCs) were determined. RESULTS: In blood, kidney, and heart, CsA levels were significantly higher for IM than for aerosol administrations at 10 and 25 mg/kg doses. In the whole lung, the AUC was greater for the aerosol route at 25 mg/kg doses (588 ng x hr/mg) than for the low-dose (200 ng x hr/mg) or IM administration (200 ng x hr/mg). The central to peripheral index of CsA (ratio of AUC central/peripheral part of the lung) was not significantly different for both aerosol administrations (0.63 and 0.69, respectively) and for the IM route (0.81). CONCLUSIONS: Nebulized CsA allows better pulmonary concentration than IM administration, with equivalent central and peripheral deposition whatever the mode of administration, and results in lower levels in blood, kidney, and heart.

Evidence of mitochondrial impairment during cardiac allograft rejection.

NADH laser fluorimetry and mitochondrial oxigraphy were used to study myocardial oxidative energy metabolism during cardiac allograft rejection. Heterotopic cardiac transplantation was performed on Lewis rats; allografts (with Fischer rat donors) were compared with isografts (with Lewis rat donors). In vivo and in vitro assays were performed six days after transplantation. Myocardial NADH fluorescence was recorded in vivo from grafted hearts, at baseline; during brief, complete ischemia; and during reperfusion. Oxygen consumption of mitochondria isolated from both native and grafted hearts was determined. Neither baseline levels nor maximum ischemic levels of NADH fluorescence (F0 = k[NADH]) were found to be significantly different between allografts (0.45 +/- 0.05 to 0.87 +/- 0.10) and isografts (0.45 +/- 0.04 to 1.11 +/- 0.05). During recovery, the rate of fluorescence decrease was significantly lower in allografts than in isografts (0.024 +/- 0.001 vs. 0.038 +/- 0.002 delta F0.s-1, P less than 10(-3], indicating a lower rate of NADH reoxidation. In the presence of malate and glutamate substrates, mitochondrial O2 consumption was significantly lower in allografts than in isografts (30 +/- 9 vs. 100 +/- 15 nanoatoms O2. min-1.mg prot-1, P less than 10(-2]. These results indicate that mitochondrial oxidative metabolism was impaired during the rejection process. Such energy production disturbances may contribute to the dysfunction of rejecting hearts.

In vitro O2-induced depression of T and B lymphocyte activation is reversed by diethyldithiocarbamate (DDC) treatment.

In this study, we tried to establish a relationship between the immunopotentiating effects and the antioxidant activity of the immunostimulating compound, diethyldithiocarbamate (DDC). We studied the effects of DDC treatment on enriched T and B murine spleen lymphocytes in an in vivo-ex vivo model of O2-induced immune depression. Female C57B1/6 mice were injected subcutaneously with a single dose of DDC (125 mg.kg-1). Eight days after DDC injection, we evaluated, in vitro, the concanavalin A response of the T cell fraction and the LPS response of the B cell fraction, under standard (air--5% CO2) and hyperoxic (60% O2--5% CO2) culture conditions. The results show that after a lag period, DDC is able to enhance the mitogenic response of T and B murine lymphocytes under standard culture conditions to restore the ConA response and to partially restore the LPS response under hyperoxic conditions. The results of this study suggest that the immunostimulatory effects of DDC could be related to the antioxidant activity of this compound on the lymphoid cellular metabolism. This activity apparently affects both T and B lymphocytes.

High concentrations of oxygen modulate in vitro Con A responses of rat lymphoid cells. Effect of 2-mercaptoethanol.

The effects of different normobaric oxygen concentrations (40, 60 and 95%) on the survival and the proliferative response to Con A of rat lymphoid cells were studied. Spleen, thymus and peripheral blood mononuclear cells were tested. We found that oxygen concentrations modulated the proliferative response independently of cell survival. The addition of 2-mercaptoethanol (2-ME) partially prevented the toxic effects of hyperoxia but the population of thymocytes which responded to Con A stimulation appeared to be less sensitive to the protective action of 2-ME. The relationship between oxygen concentrations and the lymphoid proliferative response could be used as a model of oxidant immunodepression for evaluating pharmacological effects of antioxidant compounds.

Factors influencing zidovudine efficacy when administered at early stages of Friend virus infection in mice.

Strategies for zidovudine (AZT) administration in retrovirus infection may greatly influence treatment efficacy, especially in the case of early intervention. Antiretroviral activity of AZT in mice infected with Friend leukemia virus (FLV) has been investigated using various experimental protocols. Mice were inoculated with FLV and treated with AZT either 1 or 4 h after inoculation. A dose/effect relationship of AZT therapy was established for two different loads of virus inoculum. The effects of treatment duration (5 or 14 days) and route of administration (b.i.d. subcutaneous injection or administration in drinking water) were also evaluated. In all cases AZT therapy suppressed or reduced virus-induced splenomegaly and increased survival time. AZT therapy was more effective when started 1 h rather than 4 h after virus inoculation. A mutual influence between the dosage of the antiviral drug and the virus inoculum size was observed. A 5-day therapy was inadequate to suppress infection. AZT therapy led to similar results whether administered subcutaneously or in drinking water. The present results suggest that AZT efficacy declines when the inoculum size is increased, when the initiation of treatment is delayed and when treatment duration is shortened.

Nebulized cyclosporine for prevention of acute pulmonary allograft rejection in the rat: pharmacokinetic and histologic study.

BACKGROUND: With regard to limiting the systemic effects of cyclosporine A and obtaining better control of acute pulmonary allograft rejection, local immunosuppressive therapy with aerosolized cyclosporine A seems of interest. Given the in situ immunologic mechanisms of acute rejection, as well as the anatomic structure of the lung, this therapy is feasible as previously described by others. The aim of our study is to determine the pharmacokinetic parameters of nebulized cyclosporine A and the best modalities of administration. METHODS: In a pharmacokinetic study, the cyclosporine A was given either by intramuscular injection (10 mg/kg) or by aerosol at 10 and 25 mg/kg doses; 70 rats were killed at 25 and 50 minutes and 2, 4, 6, 8, 12, 24, or 48 hours after cyclosporine A administration. Cyclosporine A levels were measured in whole blood and in the lung. The areas under the concentration time curves were determined. Twenty-four lung transplantations were then performed. The rats were killed on postoperative day 9. Acute rejection was scored on a scale of 0 to 4, and cyclosporine A trough levels were measured in the lung and in the blood. RESULTS: With a jet nebulizer, the mass median aerodynamic diameter was 2.5 microns, with a standard geometric deviation of 2.3. In blood, the area under the concentration curve was greater for intramuscular (80.6 ng.hr/ml) than for aerosol administrations at 10 (15.1 ng.hr/ml) and 25 mg/kg (41.0 ng.hr/ml) doses. In the lungs, the area under the concentration curve was greater for the aerosol route at 25 mg/kg doses (588 ng.hr/mg) than for the low-dose (200 ng.hr/mg) or intramuscular administration (200 ng.hr/mg). The lung targeting index of cyclosporine A (ratio area under the concentration curve-lungs/area under the concentration curve-blood) was greater for both aerosol administrations than for the intramuscular route. In the study of the prevention of acute rejection, rats without immunosuppression (n = 6), rats receiving daily doses of cyclosporine A intramuscularly (10 mg/kg), and rats with aerosolized cyclosporine A daily (10 and 25 mg/kg/day) showed mean grades of acute rejection of, respectively, 4, 2.03 +/- 0.27, 2.33 +/- 0.52, and 2.17 +/- 0.46. The deposition of nebulized cyclosporine A was lower in transplanted than in native lung. CONCLUSIONS: Nebulized cyclosporine A allows better pulmonary concentration than intramuscular administration, and results in lower systemic levels. Prevention of acute rejection is as good with aerosolized cyclosporine A as with intramuscular cyclosporine A. This first pharmacokinetic study of nebulized cyclosporine A could lead to clinical applications.

In situ NADH laser fluorimetry of rat fast- and slow-twitch muscles during tetanus.

To investigate the variations of oxidation-reduction status of fast- and slow-twitch muscles during intense contractions, we performed in situ NADH laser fluorimetry during 25-s tetanus in extensor digitorum longus (EDL) and in soleus (SOL) muscles of eight Sprague-Dawley rats anesthetized with pentobarbital sodium. At base line the compensated NADH fluorescence (F0) was not significantly different between EDL and SOL. In EDL, tetanic stimulation induced an increase of F0, which rapidly reached a plateau that was 124% over the base-line value and stable until the end of the stimulation. In SOL, after an initial shouldering there was a continuous increase of F0 until the end of tetanus, reaching 275% of the base-line value. After the stimulation the initial rate of recovery was significantly faster in SOL than in EDL. We conclude that during and after intense contraction the variation of NADH content vs. time can be evaluated by in situ NADH laser fluorimetry in different muscle types. This nondestructive method can be helpful to differentiate in situ the various physiological or pathological oxidative capabilities of skeletal muscles.

Infinite dilution conductimetry of plasma and urine: correlation with osmolality.

The infinite dilution conductivity (IDC) of plasma and urine allows a measurement of the electrolyte content in small samples (5 to 15 microliter). The method was compared to the corrected osmolality (II'p) measured by the freezing-point depression. A linear correlation existed between II'p and the IDC: for plasma: II'p = 13.10 sigma o,p + 37.00 (n = 46 and r = 0.9949) for urine: II'u = 12.75 sigma o,u + 16.56 (n = 85 and r = 0.9504). The measurement of the IDC does not depend on protein concentration and can be used instead of the osmometer methods to determine the total plasma and urine electrolyte content.

Ceftriaxone diffusion into cardiac fibrin vegetation. Qualitative and quantitative evaluation by autoradiography.

Heterogeneous diffusion of some antibiotics into fibrin rich infectious processes is one explanation of the difficulty to cure infections such as endocarditis. Ceftriaxone is a beta lactam antibiotic, potentially useful due to a broad spectrum of activity and its long elimination half-life. We investigated by means of autoradiography the diffusion of labelled ceftriaxone into large infected cardiac vegetations obtained in a rabbit model of endocarditis. Ten d after infection 250 microCi 14C ceftriaxone was injected over 30 min. Thirty min after the end of infusion (T30) vegetation/blood radioactivity ratio was 0.58 +/- 0.4 (n = 3). At T200, radioactivity decreased approximatively 3-fold, in blood and in vegetations simultaneously. Autoradiography showed that at T30, ceftriaxone was 20-30 times more concentrated at the periphery of vegetation than in the core. Autoradiography obtained at T200 showed a progressive diffusion toward the core. The diffusion gradient may explain the fact that high local concentrations are necessary to sterilize vegetations. The pattern of diffusion of antibiotics in fibrin is an important pharmacokinetic parameter for predicting in vivo activity.

Evaluation of a rabbit model for osteomyelitis by high field, high resolution imaging using the chemical-shift-specific-slice-selection technique.

The rabbit model of osteomyelitis introduced by C.W. Norden, based on injection of an infecting solution (Staphylococcus aureus, sodium morrhuate) into the tibia, was studied at 4.7 Tesla with a time-efficient chemical shift selective imaging technique, Chemical Shift Specific Slice Selection (C4S). The evolution of the disease over several weeks was followed on water-selective, fat-selective, and sum images obtained simultaneously with this imaging sequence. Experiments were performed either on different groups of rabbits at different times after infection with subsequent sacrifice of the animal and microbiological analysis of the infected tibia or on the same group of animals imaged several times after infection. Associated analysis of the water and fat selective images revealed marrow modifications very early (Day 5 after inoculation) demonstrating the high sensitivity of the employed imaging technique. Later on, bone modifications were best identified on the sum images. Additional experiments performed on animals injected with a noninfecting solution containing only sodium morrhuate showed however that the sclerosing agent alone can yield images similar to those produced by infection at early stages after inoculation. Therefore, the Norden model would not be suitable for monitoring quantitatively outcome of therapy by magnetic resonance imaging. It is however well adapted for the evaluation and optimization of MRI techniques or protocols intended to detect early changes of bone marrow produced by septic or aseptic infarct.

Otogenic meningoencephalitis induced by Streptococcus pneumoniae in gerbils.

OBJECTIVE: Study and development of a gerbil model of pneumococcal meningoencephalitis secondary to acute middle ear (ME) otitis. Preliminary data raised the hypothesis of a direct bacterial dissemination from the ME focus to the central nervous system. This infection pattern was examined. DESIGN: Animals were inoculated bilaterally by transbulla challenge with a serotype 3 strain of Streptococcus pneumoniae at various inoculum sizes. The incidence and course of meningeal complications were studied in relation to the course of ME otitis. RESULTS: After inoculation of 40 bacteria per ear, lethal meningeal complications occurred in 14 (29%) of 48 cases. A 76% rate (25 of 33 animals) of early meningeal involvement was observed after inoculation of 10(4) bacteria per ear. Actual involvement of brain was confirmed histologically for both infection schemes. Bacterial counts 20 to 22 hours after infection with the higher inoculum showed various phases of the extension of the ME infection to brain tissue, cerebrospinal fluid, and bloodstream. Bacterial counts in ME and brain tissue were strongly correlated (P < .001). Nine of the 25 animals with infection of the central nervous system had positive brain tissue cultures without bacteremia. CONCLUSION: Gradations in inflammatory aspects of the meninges and cerebral parenchyma, together with bacteriologic findings, indicate a primary invasion of meningeal spaces that can result in lethal encephalitis and septicemia. This model might be useful for preclinical therapeutic assays on pneumococcal meningeal complications, including infections due to strains with abnormal susceptibility to antibiotics.

Lack of correlation between hydrogen peroxide production and nitric oxide production by cultured rabbit articular chondrocytes treated with fluoroquinolone antimicrobial agents.

The arthrotoxicity of fluoroquinolone antibacterial agents so far remains unexplained. Recent experimental data have indicated an early stimulation of the oxidative metabolism within articular chondrocytes. An in vitro model was designed to analyse the production of oxygen-derived reactive species and glutathione by immature rabbit articular chondrocytes, and the influence of different fluoroquinolones on this model was examined. Primary cultures of chondrocytes were exposed to pefloxacin, ofloxacin or ciprofloxacin at 10 mug/ml, for 24 or 48 hr. Flow cytometric analysis used the vital tracer 2',7'-dichlorofluorescein diacetate (DCFH-DA) and evaluated the production of H(2)O(2) and NO by chondrocytes. Separately, NO production and intracellular glutathione levels were evaluated, with the Greiss colorimetric technique and the Tietze method, respectively. With each fluoroquinolone tested, intracellular levels of the fluorescent compound dichlorofluorescein (oxidized form of DCFH-DA) were significantly higher in treated chondrocytes than in control cells. No significant modification of NO or of glutathione cellular levels was noted. Fluoroquinolones stimulate H(2)O(2) production in immature articular chondrocytes, but have no apparent effect on either NO or glutathione production, at least in the early stages of the chondrotoxicity.

Delayed lymphoid lung infiltration induced by cyclophosphamide in rats.

The pulmonary toxicity of antineoplastic drugs may be either direct or mediated by hypersensitivity. The aim of this study was to determine whether the mechanism by which cyclophosphamide (CY) damages the lung is direct and immediate or is the result of delayed immune toxicity. Pulmonary and immune changes following intraperitoneal injection of either CY (50 mg/kg) or NaCl (0.9%) in rats were assessed repeatedly over a period of 31 days by semi-quantitative histological studies, by measuring the pulmonary water/body weight ratio, dry lung weight/body weight ratio, heart weight and by assessing the transfer of [125I]-albumin in lung tissue. Lung damage was delayed and greatest at 11 (D11) and 14 (D14) days after CY injection. The pulmonary lesions were: (i) an infiltration of lymphocytes, plasma cells and histiocytes surrounding blood vessels and small airways, (ii) an alveolitis composed of macrophages, lymphocytes, a few neutrophils and a lymphoid infiltration of alveolar septa. Pulmonary water/body weight and dry lung weight/body weight ratios also increased and peaked at D11-D14 in CY-treated rats. No significant increase in [125I]-albumin in lung tissue or in heart weight was observed. It can be concluded that the mechanism by which CY induces a lymphoid lung infiltration is not direct and immediate but is the result of a delayed immune toxicity.

[Study of myocardial metabolism of NADH by laser fluorimetry during cardiac catheterization]. / Exploration du métabolisme myocardique par fluorimétrie laser du NADH au cours du cathétérisme cardiaque.

Laser fluorimetry of reduced nicotinamide-adenine-dinucleotide (NADH) p6 a new technique used for in situ and real-time study of myocardial metabolism. We have evaluated its applicability to clinical situations in 5 patients undergoing haemodynamic exploration. An optic fibre was inserted in a catheter the end of which was positioned in the postero-diaphragmatic part of the left ventricle. The optic fibre was connected to a Cilas-Alcatel fluorimeter. Variations in fluorescence were studied during variations in left ventricular end-diastolic pressure (LVEDP) and during coronary arteriography. An increase in LVEDP resulted in a slight increase in NADH, but when the LVEDP was reduced by a nitroglycerin infusion, NADH fell significantly below baseline values in patients with coronary disease. This effect was most probably due to redistribution of the coronary blood flow from healthy territories to ischaemic territories. In patients without significant coronary stenosis, NADH was not modified by an injection of 10 ml of contrast medium into the right coronary artery. In contrast, in patients with severe stenosis NADH fluorescence significantly increased during the injection, reflecting the ischaemia or myocardial anoxia induced by the contrast medium. NADH laser fluorimetry therefore seems to be promising as a means of exploring myocardial metabolism during cardiac catheterization.

[Effects of chloroquine on the replication of a murine retrovirus]. / Effets de la chloroquine sur la réplication d'un rétrovirus murin.

The wide use of chloroquine (Cq) for prophylaxis and chemotherapy of malaria in Africa, and the increased spread of AIDS in areas of this continent where malaria is endemic, raised the question of a possible interaction between chloroquine intake and HIV infection. Indeed, hydroxychloroquine and chloroquine itself have been shown to inhibit HIV-1 replication in vitro, hydroxychloroquine being proposed as a potential useful adjunctive therapy in the treatment of HIV-1 infection. On the other hand, chloroquine has been reported to enhance the replication of Semliki forest and encephalomyocarditis viruses in a mouse model. In an attempt to elucidate Cq effect on retroviral replication, we have studied the effect of various concentrations of chloroquine in vitro (0.1 nmol/l to 25 mumol/l) on Friend retrovirus (FV)-infected fibroblasts of mice and in vivo (2 to 30 mg/kg) on FV-infected mice. No reduction in the number of virus foci was found in chloroquine-treated fibroblasts cultures. In chloroquine treated-infected mice, no differences were observed in the spleen weights, except an increase at 10 mg/kg. A decrease in splenocyte virus titer was only observed at 10 and 30 mg/kg. No differences in the median survival time was observed up to 30 mg/kg. The authors concluded that chloroquine seemed to have variable effects on viral replication in vivo depending on the dosage, but has no influence on the course of FV-induced disease.

[Relations between acid-base equilibrium and body temperature. Physiological concepts and practical applications]. / Relations entre équilibre acido-basique et température corporelle. Concepts physiologiques et applications pratiques.

In 1975 H. Rahn put forward a new concept of hydrogen ions regulation which explains acid-base regulation in relation to body temperature and applies to all animal species. At the root of this concept is the finding that maintenance of intracellular neutrality is governed by water dissociation and regulated by imidazole-rich protein buffers. The pH of the extracellular fluid, which receives acid by-products of cell activity, is kept higher than that of the intracellular fluid (relative alkalinity). The difference between extracellular pH and neutrality is constant for each species and ranges from 0.6 to 0.8 pH units. It is unaffected by changes in temperature, and the total CO2 content of extracellular fluid remains constant. The authors were able to confirm the value of this new concept in man by experimental studies of in vitro and in vivo blood of patients undergoing aorto-coronary bypass under controlled hypothermia. They draw the following practical conclusions: (1) in subjects under moderate or deep hypothermia for surgical purposes, the acid-base status can be controlled and the extracellular pH adjusted by ensuring intracellular neutrality; this is done by keeping PCO 2 at such a level that the arterial blood pH measured at 37 degrees C remains around 7.40; (2) the problem of correcting acid-base values (pH-PCO 2) according to body temperature is solved simply by using pH and PCO 2 values measured at 37 degrees C and interpreting them, as usual, in terms of metabolic or respiratory acidosis or alkalosis.

[In situ evaluation of tissue metabolism by laser fluorimetry]. / Evaluation in situ du métabolisme tissulaire par fluorimétrie laser.

Laser fluorimetry is a new technique which provides continuous information on tissue metabolism in situ and without destruction. For the moment, it is mainly applied to the study of changes in redox gradients in various organs, including the heart, brain, liver, kidney and skeletal muscle, in cases with imbalance between oxygen supply and oxygen consumption. Other metabolisms, such as that of the crystalline lens with incipient cataract, can also be investigated by this technique.