Mechanisms of creatine kinase release from isolated rat skeletal muscles damaged by propylene glycol and ethanol

Analgesic effect of the mint terpenoid L-carvone in sheep

OBJECTIVE

To determine whether L-carvone increases the voltage threshold response to a noxious electrical stimulus in sheep.

STUDY DESIGN

Prospective, blinded, randomized, crossover experimental study.

ANIMALS

A group of six healthy adult sheep.

METHODS

Sheep were instrumented with cranial dorsothoracic subcutaneous copper electrodes. A stimulator delivered a 10 ms square-wave stimulus at 50 pps starting at 0.1 V with a 0.2 V second-1 ramp. The stimulus stopped once two observers who were blinded to treatment noted a behavioral pain response or when a 15 V cut-off was reached. Next, 0.15 mL kg-1 of either a 50% L-carvone solution or a saline-vehicle control was administered intramuscularly, and electrical threshold responses were measured every 5-15 minutes over a 6 hour period using methods identical to the baseline. One week following the first treatment (L-carvone or control), sheep were studied using identical methods with the second treatment (control or L-carvone). Drug and time effects were evaluated using a two-way repeated measures analysis of variance, and pairwise comparisons were evaluated with Holm-Sidák tests with values of p < 0.05 considered significant.

RESULTS

L-carvone significantly increased voltage threshold responses for most time points up to 75 minutes compared with baseline and with saline control. The last time point with a significantly different response between L-carvone and saline treatments was 5 hours after drug administration. The saline-vehicle control decreased voltage threshold responses at several time points after 3 hours.

CONCLUSIONS AND CLINICAL RELEVANCE

Intramuscular L-carvone is analgesic in sheep, although the ethanol-propylene glycol vehicle may cause mild hyperalgesia. This study demonstrates that a food-derived compound can be used to relieve pain in a food-producing animal.

Oxidative damage in metal fragment-embedded Sprague-Dawley rat gastrocnemius muscle

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War often results in shrapnel injuries with metals whose toxicity might be unknown.

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A rodent model was used to study-eight military-relevant metals implanted in muscle.

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Creatine kinase activity, protein oxidation and antioxidant capacity were assessed.

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Data obtained were metal-dependent and not all metals showed identical results.

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Results suggest that subtle damage occurs in muscle surrounding metal shrapnel.

Injuries suffered in armed conflicts often result in wounds with embedded metal fragments. Standard surgical guidance has been to leave fragments in place except under certain circumstances; meaning that individuals may carry these retained fragments for their lifetime. Because of advancements in weapon design and the use of improvised explosive devices, the list of metals that could be found in a wound is extensive. In most cases the toxicological properties of these metals when embedded in the body are not known. To assess the potential damage embedded metals may cause to surrounding tissue, we utilized a rodent model to investigate the effect of a variety of military-relevant metals on markers of oxidative damage. The metals tested included tungsten, nickel, cobalt, iron, copper, aluminum, lead, and depleted uranium. Herein we report our findings on creatine kinase activity, lipid and protein oxidation, total antioxidant capacity, and glutathione levels in gastrocnemius homogenates from Sprague-Dawley rats surgically implanted with metal pellets for periods up to 12 months. Not all embedded metals affected the measured markers equally. However, metal-associated effects were seen at various times for muscle and serum creatinine levels, protein oxidation, total antioxidant capacity, and glutathione levels. No metal-induced effects on lipid peroxidation were observed. Taken together, these data suggest that subtle oxidative damage may be occurring in the muscle surrounding an embedded metal and indicates the need for medical surveillance of those individuals wounded by metal shrapnel.

Impact of intramuscular administration of lipid-soluble and water-soluble vehicles into regenerating muscle at the distinct phases of skeletal muscle regeneration

Interpretation on the effectiveness of potential substances to enhance skeletal muscle regeneration is difficult if an inappropriate vehicle is administered, since vehicle administration can directly enhance or suppress regenerative capacity. In the current study, intramuscular administration of lipid-soluble and water-soluble vehicles into regenerating muscle at the distinct phases of skeletal muscle regeneration (regenerative vs. remodeling) were investigated. Tested vehicles included lipid-soluble [olive oil, (0.1, 1, 5, and 40%) dimethyl sulfoxide (DMSO), and 40% propylene glycol (PG)] and water-soluble [0.9% NaCl, PBS, 0.1% ethanol, and distilled water]. Skeletal muscle regeneration was induced by 1.2% BaCl2 injection to the tibialis anterior muscle of 10-week-old C57BL/6 male mice. Histological features, skeletal muscle stem cell activity, regenerating muscle fiber formation, angiogenesis, extracellular matrix remodeling, and macrophage infiltration were examined. The results revealed repeated administration of 40% DMSO and 40% PG causes significant recurrent muscle injury, which is pronounced during the remodeling phase compared to the regenerative phase. These findings were supported by (1) massive infiltration of F4/80+ macrophages; (2) significant increase of skeletal muscle stem cell re-activation and nascent regenerating muscle fiber formation; (3) excess fibrous formation; and (4) decreased regenerating muscle fiber cross-sectional area. These deleterious effects were comparable to 2% trypsin (degenerative substance) administration and less pronounced with a single administration. Nevertheless, recurrent muscle injury was still presented with 5% DMSO administration but it can be alleviated when 0.1% DMSO was administered during the remodeling phase. In contrast, none of the tested vehicles enhanced regenerative capacity compared with IGF-1 administration. Altogether, intramuscular administration of vehicle containing high concentration of DMSO or PG could impair skeletal muscle regenerative capacity and potentially affect validation of the investigational substance.

Oral delivery of 1,3-dicyclohexylurea nanosuspension enhances exposure and lowers blood pressure in hypertensive rats

Cytochrome P450-derived epoxyeicosatrienoic acids (EET) are biologically active metabolites of arachidonic acid that have potent effects on renal vascular reactivity and tubular ion transport and have been implicated in the control of blood pressure. EETs are hydrolyzed to their less active diols, dihydroxyeicosatrienoic acids (DHET), by the enzyme soluble epoxide hydrolase (sEH). 1,3-dicyclohexylurea (DCU), a potent sEH inhibitor, lowers systemic blood pressure in spontaneously hypertensive rats when dosed intraperitoneally. However, DCU has poor aqueous solubility, posing a challenge for in vivo oral delivery. To overcome this limitation, we formulated DCU in a nanosuspension using wet milling. Milling reduced particle size, increasing the total surface area by approximately 40-fold. In rats chronically infused with angiotensin II, the DCU nanosuspension administered orally twice daily for 4 days produced plasma exposures an order of magnitude greater than unmilled DCU and lowered blood pressure by nearly 30 mmHg. Consistent with the mechanism of sEH inhibition, DCU increased plasma 14,15-EET and decreased plasma 14,15-DHET levels. These data confirm the antihypertensive effect of sEH inhibition and demonstrate that greatly enhanced exposure of a low-solubility compound is achievable by oral delivery using a nanoparticle drug delivery system.

Myotoxicity studies of O/W-in situ forming microparticle systems

The objective of this study was to investigate the myotoxicity potential of the solvents used in the preparation of polymer solutions and O/W-in situ forming microparticle (ISM) systems. The acute myotoxicity studies of the tested solvents, emulsions of the solvents, polymer solutions as well as the O/W-ISM formulations with varying phase ratios were investigated using the in vitro isolated rodent skeletal muscle model by measuring the cumulative creatine kinase (CK) efflux. Phenytoin and isotonic sodium chloride solution served as positive and negative controls, respectively. Results from the in vitro myotoxicity studies suggested that the investigated five partially water miscible solvents caused muscle damage in the following rank order: benzyl alcohol>triethyl citrate>triacetin>propylene carbonate>ethyl acetate. Myotoxicity of ethyl acetate was found to be comparable to that of the isotonic sodium chloride solution. Emulsions of the undiluted solvents and an aqueous 0.5% Pluronic F 68 solution (ratio 1:4) could dramatically reduce the myotoxicities to 24-65%. The myotoxicity of O/W-ISM was less than those of the polymer solutions and the undiluted solvents. The cumulative CK level from the muscle treated with the O/W-ISM with phase ratio 1:4 was comparable to those from the negative controls. Area under the CK plasma curve from Sprague-Dawley rats was used to evaluate the in vivo myotoxicity following an intramuscular injection of the formulations. The in vivo myotoxicity data was well correlated with the in vitro myotoxicity data and confirmed the good muscle compatibility of the O/W-ISM formulations.

Longitudinal Analysis of Gene Expression in Porcine Skeletal Muscle After Post-Injection Local Injury

PURPOSE

The purpose of this study is to describe the time course of gene expression in a skeletal muscle local injury induced by an intramuscular (IM) injection, and to compare the dynamics of gene expression with pathological events.

MATERIALS AND METHODS

Ten piglets received 4 IM injections of propylene glycol in the longissimus dorsi muscles 6 h, 2, 7, and 21 days before euthanasia, where control and injected muscle sites were sampled for RNA isolation and microscopic examination. The hybridization of nylon cDNA microarrays was carried out with radioactive probes obtained from the muscle RNA.

RESULTS

153 genes were found under- or over-expressed at least once among the investigated time-conditions. The eight most discriminant genes were also identified: Two genes (GTP-binding protein RAD and Ankyrin repeat domain protein) were over-expressed at 6 h and six genes between 2 and 21 days (Osteonectin, Fibronectin, Matrix metalloproteinase-2, Collagen alpha 1(I) chain, Collagen alpha 2(I) chain, and Thymosin beta-4). Necrosis, inflammation and regeneration were observed through both the dynamics of gene expression profiles and through the microscopic examinations.

CONCLUSION

Our data demonstrate that several pathways are involved in post-injection muscle injury, and that necrosis, inflammation and regeneration are not sequential but occur in parallel.

Acute Changes in Muscle Blood Flow and Concomitant Muscle Damage after an Intramuscular Administration

PURPOSE

The intramuscular route (IM) is widely used but commonly induces injection site muscle damage. This study investigates the hemodynamic changes in an acute lesion induced by the IM administration of propylene glycol (PG) in rabbits.

METHODS

Control groups received 1, 2, or 3 ml of PG (IM). Others were pretreated with pancuronium, dantrolene, indomethacin, or SR140333 and then received 2 ml of PG. The muscle blood flow (MBF) was assessed using fluorescent microspheres before and at 15, 45, 60, 90 min, 3 and 6 h after IM administration. Different areas within the muscle damage were quantified.

RESULTS

Muscle contractions as well as a transient but major MBF increase were observed at the injection site. All treatments reduced hyperemia by up to 81% (dantrolene, 15 min) at 15, 45, and 90 min (p < 0.05). MBF had returned to basal values in all groups at 6 h. The central necrotic area was not modified, but peripheral damage (8.0 +/- 1.3 g) was reduced by dantrolene, indomethacin, and SR140333 (p < 0.05), but not by pancuronium.

CONCLUSIONS

Muscle contraction and hyperemia are not responsible for muscle damage at the injection site, which is the multifactorial phenomenon, involving intracellular calcium and inflammation.

Sustained release veterinary parenteral products

Controlled release parenteral dosage forms have application in veterinary medicine. Systems that minimize the need for repeated injections while achieving therapeutic effects for extended periods offer benefits that make commercial development of these products desirable. While some products have already found commercial success, others will result from application of new controlled release technologies. This review highlights the formulation and technology challenges in developing some of these controlled release technologies into products. Further, examples of application of controlled release technologies in the veterinary field are discussed.

Overexpression of apolipoprotein J in human fibroblasts protects against cytotoxicity and premature senescence induced by ethanol and tert-butylhydroperoxide

Human diploid fibroblasts (HDFs) exposed to subcytotoxic stresses under H2O2, tert-butylhydroperoxide (t-BHP), and ethanol (EtOH) undergo stress-induced premature senescence (SIPS) characterized by many biomarkers of HDFs replicative senescence. Among these biomarkers are a growth arrest, an increase in the senescence-associated beta-galactosidase activity, a senescent morphology, an overexpression of p21waf-1 and the subsequent inability to phosphorylate pRb, the presence of the common 4977-bp mitochondrial deletion, and an increase in the steady-state level of several senescence-associated genes such as apolipoprotein J (apo J). Apo J has been described as a survival gene against cytotoxic stress. In order to study whether apo J would be protective against cytotoxicity SIPS and replicative senescence in human fibroblasts, a full-length complementary deoxyribonucleic acid of apo J was transfected into WI-38 HDFs and SV40-transformed WI-38 HDFs. The overexpression of apo J resulted in an increased cell survival after t-BHP and EtOH stresses at cytotoxic concentrations. In addition, when WI-38 HDFs were exposed to 5 subcytotoxic stresses with EtOH or t-BHP, in conditions that were previously shown to induce SIPS, a lower induction of 2 biomarkers of SIPS was observed in HDFs overexpressing apo J. No effect of apo J overexpression was observed on the proliferative life span of HDFs, even if apo J overexpression triggered osteonectin (SPARC) overexpression, which was shown to decrease the mitogenic potential of platelet-derived growth factor but not of other common growth-inducing conditions. Apo J senescence-related overexpression is proposed to have antiapoptotic rather than antiproliferative effects.

Comparison of the effects of potential parenteral vehicles for poorly water soluble anticancer drugs (organic cosolvents and cyclodextrin solutions) on cultured endothelial cells (HUV-EC)

The effect of dilution of parenteral vehicles (organic cosolvent and 0.1 M cyclodextrin solutions) on cultured endothelial cells (HUV-EC) were compared in vitro. Cell morphology was observed by phase contrast light microscopy and cell viability by measuring 3-[4, 5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) reduction or intracellular lactate dehydrogenase (LDH) activity and total protein. Disruption of the HUV-EC monolayer was observed at dilutions of 1 in 20 for the melphalan and PEP cosolvents, 1 in 100 for an investigational drug cosolvent, and 1 in 10 for 0.1 M dimethyl-beta-cyclodextrin. In comparison, 0.1 M SBE7M- and HP-beta-cyclodextrin caused only minor disruption at a 1 in 5 dilution. MTT reduction, intracellular LDH, and total protein were decreased following exposure to 1 in 10 dilution of the melphalan cosolvent. For other test solutions, intracellular LDH activity and total protein were measured, and reductions were observed following exposure to 1 in 10, 20, and 50 dilutions of the investigational drug cosolvent and 1 in 5 dilution of DM-beta-cyclodextrin (0.1 M). At a dilution of 1 in 10, no delayed toxicity was observed for cosolvents or cyclodextrin solutions. Hence, 0.1 M SBE7M- or HP-beta-cyclodextrin formulations may be less damaging to the venous endothelium at the site of injection than organic cosolvent formulations.

In vitro myotoxicity of selected cationic macromolecules used in non-viral gene delivery

PURPOSE

Cationic lipid/DNA complexes have been proposed as a method of in vivo gene delivery via intravenous or intramuscular injection. A concern with using these polycationic molecules is whether they are associated with tissue toxicity at the injection site. Therefore, the objective of these studies was to investigate the myotoxic potential of selected non-viral gene delivery macromolecules (e.g., cationic lipids and polymers) with and without plasmid DNA (pDNA) in vitro.

METHODS

Myotoxicity was assessed by the cumulative release of creatine kinase (CK) over 90 minutes from the isolated rodent extensor digitorum longus muscle into a carbogenated balanced salt solution (BBS, pH 7.4, 37 degrees C) following a 15 microL injection of the test formulation. Phenytoin (Dilantin) and normal saline served as positive and negative controls, respectively.

RESULTS

The myotoxicity of plasmid DNA (pDNA, approximately 5000bp, 1 mg/ml) was not statistically different from normal saline. However, the myotoxicity of Dilantin was 16-times higher than either normal saline or pDNA (p < 0.05). Cationic liposomes were found to be less myotoxic than polylysine and PAMAM dendrimers. Polylysine's myotoxicity was found to be dependent upon concentration and molecular weight. The myotoxicity of formulations of cationic liposomes(s), lower molecular weight polylysine (25,000) and higher concentration of PAMAM dendrimers with pDNA were found to be statistically less significant than those formulations without pDNA.

CONCLUSIONS

The cationic liposomes were less myotoxic compared to the dendrimers and polylysine. Myotoxicity was dependent upon the type of cationic lipid macromolecule, concentration, molecular weight and the presence of pDNA. A possible explanation for this reduced tissue damage in cationic lipids complexed with pDNA is that the formation of complex reduces the overall positive charge of the injectable system resulting in less damage.

Predicting injection site muscle damage. I: Evaluation of immediate release parenteral formulations in animal models

PURPOSE

The current animal model generally accepted by the pharmaceutical industry and the FDA for assessment of muscle damage following intramuscular injection (IM) is the rabbit lesion volume model (RbLV). However, this model is resource intensive. The goal of this study was to find a resource sparing alternative to the rabbit lesion model for assessing injection site toleration in IM formulation screening.

METHODS

Short term animal model alternatives to RbLV for evaluating IM formulations were examined. In addition to RbLV, myeloperoxidase (MPO), p-nitrophenyl N-acetyl-beta-glucosaminide (NA beta G) and/or plasma creatine phosphokinase (CK) activities were determined in rabbits (Rb) and rats (Rt) after injection of formulations (digoxin, azithromycin and danofloxacin). The edema from these formulations 24 hr after subcutaneous injection into the rat footpad (RFE) was also determined.

RESULTS

MPO and NA beta G were not considered very useful as biochemical predictors of muscle damage for these formulations. Histology generally correlated with RbLV values. Compared to saline, RbLV was marked for all formulations within 1-3 days of injection. After day 3, lesions quickly resolved, and no significant differences were found. For these formulations, all CK animal models and RFE were generally predictive of RbLV. A formulation with RtCK > 1000 U/L or RbCK > 3000 U/L, was predicted to be poorly, tolerated.

CONCLUSIONS

Due to ease, number of animals, time and intrinsic mechanism, we concluded that for most formulations, 2 and 4 hr RtCK data alone should be reasonably predictive of muscle damage.

Predicting injection site muscle damage. II: Evaluation of extended release parenteral formulations in animal models

PURPOSE

The goal of this study was to find a resource sparing alternative to the rabbit lesion model (RbLV) for assessing injection site toleration in extended release (ER) intramuscular (IM) formulation screening.

METHODS

ER formulations (danofloxacin oily and aqueous suspensions) were evaluated in RbLV, rat and rabbit plasma creatine phosphokinase (CK), and rat foot edema (RFE) models as described in the companion article.

RESULTS

None of the short term models could consistently predict acute and chronic effects of the. For example, RFE predicted little muscle damage from aqueous vehicle (0.03 +/- 0.03 g) and 60 mg/ml (0.08 +/- 0.03 g) formulation; while RbLVdays1-3 was marked and greater (p < 0.05) for 60 mg/ml (6.0 +/- 3.1) than vehicle (2.2 +/- 2.9) formulations. Furthermore, RbLVdays 1-3) for vehicle (6.5 +/- 7.5) and 60 mg/ml (4.9 +/- 4.6) danofloxacin oily formulations were worse (p < 0.05) than oil alone (1.4 +/- 2.2); an observation not predicted by CK models, since they apparently reflected only the acute muscle damage of formulation components immediately available to surrounding tissue at the time of injection.

CONCLUSIONS

The CK models may be useful to screen those ER formulations with unacceptable acute damage due to immediately available components. However, to evaluate potential delayed effects from ER formulations, the long-term model RbLV was still recommended.

Hydrotropic solubilization--mechanistic studies

PURPOSE

This study examines the mechanism of hydrotropic solubilization using the riboflavin-nicotinamide system. The most commonly proposed mechanism for hydrotropic solubilization is complexation, and therefore, is investigated. Additionally, since nicotinamide and several other hydrotropic agents self-associate in aqueous solution, the possibility that self-association of the hydrotropic agent is important mechanistically is examined by studying the effect of temperature on hydrotropic ability. Researchers have shown that the degree of self association decreases with increasing temperature. Therefore, if temperature affects the solubilizing capacity of nicotinamide, self-association must be mechanistically significant.

METHODS

The complexation hypothesis is tested by looking at nicotinamide's ability to quench riboflavin fluorescence and by examining changes in the UV/Vis spectrum of riboflavin upon addition of nicotinamide. The solubility of riboflavin in nicotinamide solutions as a function of temperature is determined to assess the impact of self-association on hydrotropicity.

RESULTS

Nicotinamide does not alter the intrinsic fluorescence of riboflavin nor are changes indicative of complexation observed in the UV/Vis spectrum Temperature does have an effect on the hydrotropic ability of nicotinamide. Specifically, as temperature increases, the solubilizing capacity of nicotinamide decreases.

CONCLUSIONS

Because nicotinamide is unable to quench riboflavin fluorescence, and does not produce significant spectral changes, complexation of hicotinamide and riboflavin does not occur. However, since increasing temperature causes a decrease in the hydrotropic ability of nicotinamide and in its degree of self-association, it is proposed here that the self-association of nicotinamide impacts the hydrotropic mechanism.

Creatine kinase release from isolated EDL muscles in chronic ethanol-treated rats

Chronic ethanol abuse has been shown to cause damage to skeletal muscle in animals and patients as reflected by elevated serum levels of cytosolic enzymes and histological examination. The present study investigated the hypothesis that elevated serum creatine kinase levels in ethanol-treated animals vs. sucrose control animals may result from increased enzyme release or efflux from muscle. Creatine kinase release was measured from extensor digitorum longus (EDL) muscles isolated from rats chronically treated for 28 weeks with ethanol and from sucrose fed controls. The in vitro cumulative release of creatine kinase over a 2-h period was significantly higher in the ethanol-treated animals. Consistent with an increased release of enzyme into the bath, creatine kinase levels in muscle homogenates at the end of the incubation period were lower in the ethanol-treated animals. Creatine kinase levels in serum obtained from trunk blood samples were statistically higher in the ethanol-treated animals compared to sucrose controls. These findings demonstrate increased enzyme release from fast-twitch skeletal muscle in chronic ethanol-treated rats.

Effect of alcohol and electrical stimulation on leakage of creatine kinase from isolated fast and slow muscles of rat

Binge drinking of alcohol may lead to acute alcoholic myopathy with rhabdomyolysis, which is characterized by skeletal muscle damage, elevated serum creatine kinase (CK), and myoglobinuria. This study was undertaken to test whether alcohol acts directly on the skeletal muscles to enhance the leakage of CK, and to assess the influence of fiber-type composition and repetitive contractions of the muscle on the effect of alcohol. After 4 hr of incubation in normal physiological solution at 37 degrees C, mean leakage of CK was 0.7 units/mg from isolated rat extensor digitorum longus (EDL), which has more fast-twitch glycolytic muscle fibers, and 1.2 units/mg from the soleus, which has more slow-twitch oxidative muscle fibers. Ethanol at 0.1, 0.2, and 0.5% concentrations caused significantly greater increase in leakage of CK from soleus than from EDL. In normal physiological solution, electrical stimulation at 1 Hz for 4 hr increased the leakage of CK by about the same degree in both EDL and soleus. In the presence of 0.1 and 0.2% ethanol, electrical stimulation markedly potentiated the alcohol-induced leakage of CK from both soleus and EDL. These results indicate that alcohol increases the leakage of CK by acting directly on skeletal muscle fibers, especially of the slow-twitch oxidative type, and that repeated muscle contractions potentiate the alcohol effect. These studies suggest that exercise may increase the chances of rhabdomyolysis in the alcoholics.

Effects of modulations of the energetic metabolism on the mortality of cultured cells

Since cells are open systems which exchange material with their surroundings, they can be considered as open systems far from equilibrium and in this way, they follow the principles of thermodynamics of open systems. This approach stresses the fact that cells optimize their use of energy according to their functions. However, with time and/or under environmental challenges, cells can reorganize themselves at other lower levels of energy production and utilization (Toussaint et al. (1991) Mech. Ageing Dev. 61, 45-64). Considered as optimized systems, cells can adapt their behaviours according to the balance between, on one side, their energetic potential and the level of their defence systems, and on the other side, the intensity of the stress. Mainly three types of behaviour can be theoretically predicted. If the stresses are very low, the damages generated are instantaneously repaired and the cellular system remains at its steady state of energy production and utilization. If the stresses are of an intermediary intensity, it is predicted that the cell can leave its steady state of energy production and utilization and find a new one characterized by a lower level of entropy production and a higher level of errors. Third, if the stresses are of a very high intensity which can be cytotoxic, the level of the energetic potential of the cell is directly related to cell survival. We tested the latter prediction in the present work in two ways. First, the level of energy production was lowered by partially uncoupling the mitochondria. Then the effect of stresses under tert-butylhydroperoxide or ethanol was investigated in order to look for a synergistic effect on cell death with the mitochondria uncoupling. Secondly, the effect of a modification of the energetic sources during the stress was tested. Besides a protective effect found with specific defence systems, the presence of energetic metabolites such as D-glucose, pyruvate/malate, glutamate/malate, was tested and found to be protective. The effect of a stimulator of the energetic metabolism, naftidrofuryl oxalate, was also investigated and found protective. The experimental data provide good evidence that energetic factors can modulate the resistance of cells to various stresses.

Antipneumocystis activity of water-soluble lipopeptide L-693,989 in rats

Water-soluble lipopeptide L-693,989 was evaluated for its antipneumocystis activity in rats. Rats from colonies with latent Pneumocystis carinii infections were immunosuppressed with dexamethasone for 6 weeks to facilitate the development of acute P. carinii pneumonia (PCP). After 6 weeks, the rats were maintained on dexamethasone and were treated twice daily for 4 days with various concentrations of L-693,989. At a dose of 0.15 mg/kg of body weight, the compound effectively eliminated 90% of the cysts in 4 days. Trophozoite forms of P. carinii were still present in these animals, as determined by using a P. carinii-specific DNA probe. A 3-week therapy study showed that the trophozoite load did not expand during treatment and that the trophozoites already present at the initiation of therapy appeared to persist. This may be a consequence of the stage specificity of the compound for cyst development and the severe immunosuppressive effects of dexamethasone on rats. When evaluated as a daily parenteral prophylactic agent, L-693,989 was effective in preventing the development of both P. carinii cysts and trophozoites, demonstrating its potential for use in prophylaxis and implying that the cyst stage of P. carinii is an obligatory step in trophozoite multiplication. The foamy exudate commonly associated with P. carinii infections was absent in the lungs of rats on prophylaxis. The compound was also evaluated via oral administration and was found to have a 90% effective dose of 32 mg/kg for therapy of acute infections and 5 mg/kg for daily prophylaxis.

Aging as a multi-step process characterized by a lowering of entropy production leading the cell to a sequence of defined stages. II. Testing some predictions on aging human fibroblasts in culture

The concepts of irreversible thermodynamics have been used in order to develop a theory of aging considered as a multi-step process leading the cell through a sequence of defined stages characterized by a lower level of entropy production and finally to a critical level of errors involving cell death (Toussaint et al., 1991). One of the predictions of this model is that external stresses which can be considered as fluctuations would accelerate the evolution of the cell from one state to the other according to the intensity of the stress. Seven morphotypes have been observed in the serially cultivated human fibroblasts, cells passing progressively from one morphotype to the other. In this paper, we experimentally tested the effect of two different molecules, tert-butylhydroperoxide and ethanol, in order to determine their influence on the shift from one morphotype to the other. When applied for a single period of time on cultivated cells, both molecules effectively showed a modification in the pattern of the different morphotypes which was dependent on the stress intensity: a decreased proportion of the early morphotypes and an increased proportion of the late and post-mitotic morphotypes were observed within three days after the stresses. Similar results were obtained when successive stresses were performed at every subculture. The results also indicated that all stages are not equally stable with morphotypes III and IV being the most stable. The positive effect on the increased shift of these cells from one morphotype to the other by two different stresses firms one of the prediction of the thermodynamic model which states that cellular aging can be considered as a multi-step process which can be speeded up by various external modifications.