Implantation of the Auditory Nerve via the Middle Ear Cavity in Rats with Partial Hearing Preservation.

The aim of this study was to evaluate the residual hearing function and cochlear morphology after auditory nerve implantation via middle ear spaces in rats. A titanium rod (1.5 mm long and 0.3 mm thick) coated with Parylene was inserted in the cochlear apex in the direction of the modiolus in 9 Wistar rats. Auditory brainstem-evoked responses to tone bursts at 2, 8, 12 and 32 kHz were recorded before surgery and on postoperative days 0, 2, 15 and 30. Eight cochleas were examined microscopically. The rod was inside the modiolus in 4, and partly or totally outside the modiolus in 4 animals. Residual hearing was present in all cases. The average threshold shift in cochleas with modiolar implant was 39 ± 11.2, 54 ± 9.7, 48 ± 20.3 and 43 ± 21.3 dB SPL on postoperative days 0, 2, 15 and 30, respectively. The transmodiolar approach allows a minimally invasive cochlear implantation and a partial hearing preservation.

Early adaptive response of the retina to a pro-diabetogenic diet: Impairment of cone response and gene expression changes in high-fructose fed rats.

The lack of plasticity of neurons to respond to dietary changes, such as high fat and high fructose diets, by modulating gene and protein expression has been associated with functional and behavioral impairments that can have detrimental consequences. The inhibition of high fat-induced rewiring of hypothalamic neurons induced obesity. Feeding rodents with high fructose is a recognized and widely used model to trigger obesity and metabolic syndrome. However the adaptive response of the retina to short term feeding with high fructose is poorly documented. We therefore aimed to characterize both the functional and gene expression changes in the neurosensory retina of Brown Norway rats fed during 3 and 8 days with a 60%-rich fructose diet (n = 16 per diet and per time point). Glucose, insulin, leptin, triacylglycerols, total cholesterol, HDL-cholesterol, LDL-cholesterol and fructosamine were quantified in plasma (n = 8 in each group). Functionality of the inner retina was studied using scotopic single flash electroretinography (n = 8 in each group) and the individual response of rod and cone photoreceptors was determined using 8.02 Hz Flicker electroretinography (n = 8 in each group). Analysis of gene expression in the neurosensory retina was performed by Affymetrix genechips, and confirmed by RT-qPCR (n = 6 in each group). Elevated glycemia (+13%), insulinemia (+83%), and leptinemia (+172%) was observed after 8 days of fructose feeding. The cone photoreceptor response was altered at day 8 in high fructose fed rats (Δ = 0.5 log unit of light stimulus intensity). Affymetrix analysis of gene expression highlighted significant modulation of the pathways of eIF2 signaling and endoplasmic reticulum stress, regulation of eIF4 and p70S6K signaling, as well as mTOR signaling and mitochondrial dysfunction. RT-qPCR analysis confirmed the down regulation of Crystallins, Npy, Nid1 and Optc genes after 3 days of fructose feeding, and up regulation of End2. Meanwhile, a trend towards an increased expression of αA- and αB-crystallin proteins was observed at day 8. Our results are consistent with early alterations of the functioning and gene expression in the retina in a pro diabetogenic environment.

Metabolic syndrome triggered by high-fructose diet favors choroidal neovascularization and impairs retinal light sensitivity in the rat.

Diabetic retinopathy and age-related macular degeneration are the leading causes of blindness in Western populations. Although it is a matter of controversy, large-scale population-based studies have reported increased prevalence of age-related macular degeneration in patients with diabetes or diabetic retinopathy. We hypothesized that metabolic syndrome, one of the major risk factors for type 2 diabetes, would represent a favorable environment for the development of choroidal neovascularization, the main complication of age-related macular degeneration. The fructose-fed rat was used as a model for metabolic syndrome in which choroidal neovascularization was induced by laser photocoagulation. Male Brown Norway rats were fed for 1, 3, and 6 months with a standard equilibrated chow diet or a 60%-rich fructose diet (n = 24 per time point). The animals expectedly developed significant body adiposity (+17%), liver steatosis at 3 and 6 months, hyperleptinemia at 1 and 3 months (two-fold increase) and hyperinsulinemia at 3 and 6 months (up to two-fold increase), but remained normoglycemic and normolipemic. The fructose-fed animals exhibited partial loss of rod sensitivity to light stimulus and reduced amplitude of oscillatory potentials at 6 months. Fructose-fed rats developed significantly more choroidal neovascularization at 14 and 21 days post-laser photocoagulation after 1 and 3 months of diet compared to animals fed the control diet. These results were consistent with infiltration/activation of phagocytic cells and up-regulation of pro-angiogenic gene expression such as Vegf and Leptin in the retina. Our data therefore suggested that metabolic syndrome would exacerbate the development of choroidal neovascularization in our experimental model.

A multi-generational study on low-dose BPA exposure in Wistar rats: effects on maternal behavior, flavor intake and development.

Bisphenol A (BPA) is a common endocrine disruptor found as an environmental and food contaminant. It exerts both developmental and behavioral effects, mainly when exposure occurs in early life. The aim of this study was to determine the multi-generational effects of chronic, human-relevant low-dose exposure to BPA on development, maternal behavior and flavor preference in Wistar rats. BPA was orally administered at a daily dose of 5 µg/kg body weight to F0 pregnant dams from the first day of gestation (GD 1) until the last day of lactation (LD 21), and then to F1 offspring from weaning (PND 21) to adulthood (PND 100). F2 offspring were not exposed. Development and clinical signs of toxicity were assessed daily. Maternal behavior was evaluated by observing nursing and pup-caring actions, as well as "non-maternal" behaviors in F0 and F1 dams from parturition until LD 8. The flavor preferences of F1 and F2 offspring were evaluated based on the intake of sweet, salt and fat solutions using the two-bottle choice test on PND 21-34 and PND 86-99. BPA exposure: 1) decreased maternal behavior in F1 dams, 2) caused developmental defects in both F1 and F2 offspring, with a noticeable decrease in anogenital distance in male rats, and 3) did not affect flavored solution intake in F1, but induced changes in sweet preference in F2 juveniles and in salt and fat solution intakes in F2 adults, and 4) induced a body weight increase in the F2 generation only, whereas food intake and water consumption did not change. Taken as a whole, our findings showed that both gestational (F0) and lifelong (F1) exposures to a human-relevant dose of BPA could induce multi-generational effects on both development and behavior. These results suggest possible selective neuroendocrine defects and/or epigenetic changes caused by BPA exposure.

Oral homeostasis disruption by medical plasticizer component bisphenol A in adult male rats.

OBJECTIVES/HYPOTHESIS: Bisphenol A (BPA) is a synthetic estrogen-like chemical mimetic widely used in the manufacture of polycarbonate plastics and epoxy resins found in numerous consumer products including food packaging, medical devices, and dental sealants. Because it is recovered in fluids and it can reach high levels in saliva, this study aimed to evaluate its safety on oral homeostasis by examining its effects on salivary glands, mouth epithelium, water consumption, and salt preference, each parameter being estrogen sensitive. STUDY DESIGN: Randomized controlled trial involving rats. METHODS: A dose-response study was conducted in adult Wistar rats randomized into five groups (n = 12). BPA was administered over 6 weeks via drinking water to obtain daily dose exposures of 0 µg/kg, 5 µg/kg, 50 µg/kg, 5 mg/kg, and 12.5 mg/kg of body weight. To evaluate salt preference, 1% NaCl solution and pure water intakes were measured for 3 days by offering two-bottle choices. The rats were then killed; oral biopsies were done and submandibular glands were removed for histologic and morphometric analysis. RESULTS: According to the dose-response curve, BPA decreased total drinking but increased salt preference, which was inversely proportional to water consumption (Kruskal-Wallis, P < .01). It also causes oral dryness and histologic changes in the acinar structures of the submandibular glands at the lowest doses (Kruskal-Wallis, P < .01). CONCLUSIONS: This study shows that oral exposure to BPA in the rat disrupts thirst and buccal homeostasis and raises questions about the salivary gland secretions.

Steady-state levels of retinal 24S-hydroxycholesterol are maintained by glial cells intervention after elevation of intraocular pressure in the rat.

PURPOSE: Our previous studies suggested that CYP46A1 and 24S-hydroxycholesterol (24SOH) may be associated with glaucoma. Loss of CYP46A1-expressing retinal ganglion cells is involved in the activation of glia, and therefore possibly in the disbalance of cholesterol. In this context, the purpose of our present work was to emphasize the glial and longitudinal CYP46A1 expression after an interventional glaucoma-related stress triggered by elevated intraocular pressure (IOP). METHODS: Sprague-Dawley rats were submitted to laser photocoagulation of the trabecular meshwork, limbus and episcleral veins in one eye to induce elevated IOP. Rats were euthanized at days 3, 14, 30 and 60 (n = 10 per time-point), and 24SOH was measured in plasma and retina by gas chromatography-mass spectrometry. CYP46A1 was quantified by Western blotting. Glial activation was assessed by glial fibrillary acidic protein immunoreactivity in Western blots and retinal cryosections. RESULTS: Sustained high IOP was observed in experimental eyes from day 1 to day 21. Plasma MCP-1 and ICAM-1, quantified using multiplex assay kits, were increased at day 3. Glial activation was observed bilaterally at all time-points, at lower levels in contralateral eyes than in experimental eyes. In experimental retinas, CYP46A1 expression showed a transient increase at day 3 and then returned to baseline. Plasma and retinal 24SOH peaked at day 14 and 30, respectively. CONCLUSIONS: These data show that CYP46A1 expression was induced early in response to retinal stress but remained constant at late time-points, reinforcing the constitutive role of CYP46A1 in maintaining cholesterol balance in neuronal tissues.

Dietary polyunsaturated fatty acids reduce retinal stress induced by an elevation of intraocular pressure in rats.

N-6 and n-3 polyunsaturated fatty acids (PUFAs) have been shown to prevent tissue release of inflammatory molecules. We have shown that a combination of n-6 and n-3 PUFAs is more efficient than single supplementations on the long-term consequences of intraocular pressure elevation. We hypothesized that such an association is also more effective during early retinal stress by modifying retinal proinflammatory prostaglandin and cytokine productions. Rats were supplemented for 3 months with n-6 PUFAs, n-3 PUFAs, or both n-6 and n-3 PUFAs. After 3 months, a surgical elevation of intraocular pressure was induced. Retinal morphometry and glial cell activation were evaluated 24 hours after laser treatment. The retinal levels of prostaglandin E(1) (PGE(1)) and prostaglandin E(2) (PGE(2)) and the messenger RNA levels of interleukin-1ß, interleukin-6, and tumor necrosis factor-α were measured. Retinal glial cell activation after laser treatment was partly prevented by dietary n-6, n-3, and n-6 and n-3 PUFAs. Retinal PGE(1) was unaffected by the laser treatment or by the diet. Dietary n-6 and/or n-3 PUFAs prevented the increase in PGE(2) levels observed in laser-treated retinas without affecting the induction of interleukin-1ß, interleukin-6, and tumor necrosis factor-α messenger RNAs. This study shows that not only a combination of n-6 and n-3 PUFAs but also single supplementations can preserve the retina from early glial cell activation and PGE(2) release. The protective effect is not mediated by changes in cytokine expression but may be related to modifications in retinal prostaglandin metabolism.

No consequences of dietary n-3 polyunsaturated fatty acid deficiency on the severity of scopolamine-induced dry eye.

PURPOSE: Epidemiological studies suggest that dietary n-3 polyunsaturated fatty acids (PUFAs) may protect against dry eye. This study aimed to evaluate whether a dietary deficiency in n-3 PUFAs may increase the severity of the pathology in a scopolamine-induced model of dry eye in the rat. METHODS: Lewis rats of three consecutive generations were bred under a balanced diet or a diet deprived of n-3 PUFAs. Dry eye was experimentally induced by continuous scopolamine delivery in female animals from the third generation of both groups. After 10 days of treatment, the clinical signs of ocular dryness were evaluated in vivo using fluorescein staining. MHC II and the rat mucin rMuc5AC were immunostained on ocular sphere cryosections. The transcript levels of the pro-inflammatory cytokines interleukin (IL)-1ß, IL-6, tumor necrosis factor (TNF)-α and interferon (IFN)-γ were quantified in the exorbital lacrimal glands (LG) and in the conjunctiva using reverse transcription followed by polymerase chain reaction. Lipids were extracted from the exorbital LG for fatty acid analysis of the phospholipids using gas chromatography. RESULTS: When compared to control animals, the scopolamine treatment induced an increase in the cornea fluorescein staining score (from 0.5 ± 0.0 to 2.5 ± 1.0 arbitrary units (AU) for the balanced diet and from 1.2 ± 0.8 to 2.6 ± 0.5 AU for the n-3 PUFA-deficient diet); a decrease in rMuc5AC immunostaining in the conjunctival epithelium (-34% for the balanced diet and -23% for the n-3 PUFA-deficient diet); an increase in the LG transcript levels of TNF-α for the balanced diet and of TNF-α and IFN-γ for the deficient diet; an increase in the conjunctival transcript levels of IL-1ß and IL-6 for the deficient diet; an increase in arachidonic acid (AA) and in the ∆5-desaturase index (ratio of AA to dihomo-gamma-linolenic acid) in the exorbital LG for both diets. When compared to the balanced diet, the n-3 PUFA-deficient diet induced an increase in the LG transcript levels of IL-6 for the control animals and of TNF-α for the control and dry eye animals as well as an increase in the conjunctival transcript levels of IL-6 for the dry eye animals. There was no significant diet difference in fluorescein staining, rMuc5AC, and MHC II immunostaining scores. CONCLUSIONS: Our data suggest that an n-3 PUFA deficiency does not increase the severity of dry eye in a rat model of dry eye.

Peripheral olfactory sensitivity in rodents after treatment with docetaxel.

OBJECTIVES/HYPOTHESIS: Clinical studies have documented that cytotoxic chemotherapy is often associated with body weight loss and decreased enjoyment of food. Besides taste, olfaction plays a role in food intake. We assessed whether systemic chemotherapeutic cancer treatment compromises olfactory function in rats and mice treated with docetaxel (Taxotere; Sanofi-Aventis, Paris, France). STUDY DESIGN: Randomized, controlled trials on mice and rats. METHODS: Male mice received a single and male rats either a single, two, or three docetaxel administrations. Olfactory function was tested by means of electroolfactograms (EOGs) from the chemosensory epithelium of the nasal septum and the endoturbinates. We evaluated and compared the magnitude of EOG responses evoked by different odorants recorded at different time points after treatment. RESULTS: In both animal species, docetaxel administration reduced body weight gain, thus evidencing the general toxic effect of the drug. In both animal species, the olfactory mucosa remained responsive to stimulation of odorants during the whole course of experiment, but treatment revealed regional differences of docetaxel susceptibility and induced marked transitory electrophysiological changes. In mice and rats a significant transitory decrease in EOG response magnitude occurred after a single administration. Unexpectedly, in rats we also observed an increase of the olfactory response following the second administration of the drug. CONCLUSIONS: Docetaxel exerts a neurotoxic effect on olfactory epithelia of rodents at doses similar to human doses, thus inducing transitory functional alterations. Although moderate, they are consistent with the hypothesis of a dysfunction of olfactory function. Further experiments are needed to elucidate the origin of the electrophysiological effects and their impact on the olfactory perception.

Differential effect of maternal diet supplementation with alpha-Linolenic adcid or n-3 long-chain polyunsaturated fatty acids on glial cell phosphatidylethanolamine and phosphatidylserine fatty acid profile in neonate rat brains.

BACKGROUND: Dietary long-chain polyunsaturated fatty acids (LC-PUFA) are of crucial importance for the development of neural tissues. The aim of this study was to evaluate the impact of a dietary supplementation in n-3 fatty acids in female rats during gestation and lactation on fatty acid pattern in brain glial cells phosphatidylethanolamine (PE) and phosphatidylserine (PS) in the neonates. METHODS: Sprague-Dawley rats were fed during the whole gestation and lactation period with a diet containing either docosahexaenoic acid (DHA, 0.55%) and eicosapentaenoic acid (EPA, 0.75% of total fatty acids) or alpha-linolenic acid (ALA, 2.90%). At two weeks of age, gastric content and brain glial cell PE and PS of rat neonates were analyzed for their fatty acid and dimethylacetal (DMA) profile. Data were analyzed by bivariate and multivariate statistics. RESULTS: In the neonates from the group fed with n-3 LC-PUFA, the DHA level in gastric content (+65%, P < 0.0001) and brain glial cell PE (+18%, P = 0.0001) and PS (+15%, P = 0.0009) were significantly increased compared to the ALA group. The filtered correlation analysis (P < 0.05) underlined that levels of dihomo-gamma-linolenic acid (DGLA), DHA and n-3 docosapentaenoic acid (DPA) were negatively correlated with arachidonic acid (ARA) and n-6 DPA in PE of brain glial cells. No significant correlation between n-3 and n-6 LC-PUFA were found in the PS dataset. DMA level in PE was negatively correlated with n-6 DPA. DMA were found to occur in brain glial cell PS fraction; in this class DMA level was correlated negatively with DHA and positively with ARA. CONCLUSION: The present study confirms that early supplementation of maternal diet with n-3 fatty acids supplied as LC-PUFA is more efficient in increasing n-3 in brain glial cell PE and PS in the neonate than ALA. Negative correlation between n-6 DPA, a conventional marker of DHA deficiency, and DMA in PE suggests n-6 DPA that potentially be considered as a marker of tissue ethanolamine plasmalogen status. The combination of multivariate and bivariate statistics allowed to underline that the accretion pattern of n-3 LC-PUFA in PE and PS differ.

Efficacy of a 2-month dietary supplementation with polyunsaturated fatty acids in dry eye induced by scopolamine in a rat model.

BACKGROUND: This study was conducted to evaluate the efficacy of dietary n-6 and n-3 polyunsaturated fatty acids (PUFAs) in dry eye in a rat model. METHODS: Female Lewis rats were fed with diets containing (1) gamma-linolenic acid (GLA), (2) eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA), or (3) GLA + EPA + DHA, for 2 months before the induction of dry eye using a continuous delivery of scopolamine and during scopolamine treatment. Two, 10 and 28 days after dry-eye induction, clinical signs of corneal dryness were evaluated in vivo using fluorescein staining. MHC II expression and mucin rMuc5AC production in the conjunctival epithelium were evaluated by immunostaining. Lipids and prostaglandins (PGs) E(1) and E(2) were analysed from the exorbital lacrimal gland (LG). RESULTS: Dietary PUFAs minimised the occurrence of corneal keratitis 28 days after induction of dry eye. The decrease in mucin production observed on the conjunctival epithelium was partially prevented by EPA + DHA supplementation after 2 days of scopolamine treatment, as well as by GLA and GLA + EPA + DHA diets after 10 days of treatment. The overexpression of MHC II in the conjunctival epithelium caused by dry eye induction was significantly reduced only with the GLA + EPA + DHA diet after 28 days of treatment. Dietary PUFAs were incorporated into phospholipids of the exorbital LG. Induction of dry eye was associated with a significant increase in PGE(1) and PGE(2) levels in the exorbital LG, which was inhibited by dietary EPA + DHA at 10 days (for PGE(2)) and 28 days (for PGE(1)). CONCLUSIONS: Dietary GLA, EPA and DHA significantly interfered with lipid homeostasis in the exorbital LG and partially prevented the course of dry eye. In particular, our results demonstrate the efficacy of the combination of n-6 and n-3 PUFAs.

A dietary combination of omega-3 and omega-6 polyunsaturated fatty acids is more efficient than single supplementations in the prevention of retinal damage induced by elevation of intraocular pressure in rats.

BACKGROUND: To evaluate the effect of a dietary combination of omega-3 and omega-6 polyunsaturated fatty acids (PUFAs) compared to single PUFA supplementations on the outcome of a substantial elevation of intraocular pressure (IOP) in rats. METHODS: Sprague Dawley rats were fed for 6 months with either a control diet, a diet enriched with omega-3 PUFAs (eicosapentaenoic acid, EPA, and docosahexaenoic acid, DHA), a diet enriched with omega-6 PUFAs (gamma-linolenic acid, GLA) or a diet enriched with both omega-3 and omega-6 PUFAs (EPA + DHA and GLA). After 3 months of feeding, elevation of IOP was induced by photocoagulation of the episcleral veins, limbus and trabecular meshwork using a 532-nm laser. IOP and scotopic electroretinograms (ERGs) were monitored after the induction of IOP elevation until the end of the nutritional supplementation. Retinal morphometry and GFAP immunohistochemistry were performed 3 months after laser photocoagulation. Retinal ganglion cells (RGCs) were quantified using retrograde labelling. RESULTS: A significant rise in IOP was observed in the laser-treated eyes. PUFA supplementation did not influence the time course of IOP in the laser-treated eyes. Three months after laser photocoagulation, the activation of glial cells observed in the laser-treated eyes was significantly lower in animals fed with the EPA + DHA + GLA diet when compared to those fed the control diet, while single supplementations with either EPA + DHA or GLA were not effective. The same protective effect of the EPA + DHA + GLA combination was observed on retinal structures in the laser-treated eyes. However, PUFA supplementation did not influence either ERG b-wave amplitude or the RGC loss in the laser-treated eyes. CONCLUSIONS: This study demonstrates that a 6-month supplementation with a combination of omega-3 and omega-6 PUFAs is more effective than single supplementations, since the EPA + DHA + GLA dietary combination prevented retinal cell structure and decreased glial cell activation induced by the elevation of IOP in rats.

Dietary n-3 and n-6 PUFA enhance DHA incorporation in retinal phospholipids without affecting PGE(1) and PGE (2) levels.

The purpose of this study was to determine whether dietary n-3 and n-6 PUFA may affect retinal PUFA composition and PGE(1) and PGE(2) production. Male Wistar rats were fed for 3 months with diets containing: (1) 10% eicosapentaenoic acid (EPA) and 7% docosahexaenoic acid (DHA), or (2) 10% gamma-linolenic acid (GLA), or (3) 10% EPA, 7% DHA and 10% GLA, or (4) a balanced diet deprived of EPA, DHA, and GLA. The fatty acid composition of retinal phospholipids was determined by gas chromatography. Prostaglandin production was measured by enzyme immunoassay. When compared to rats fed the control diet, the retinal levels of DHA were increased in rats fed both diets enriched with n-3 PUFA (EPA + DHA and EPA + DHA + GLA diets) and decreased in those supplemented with n-6 PUFA only (GLA diet). The diet enriched with both n-6 and n-3 PUFA resulted in the greatest increase in retinal DHA. The levels of PGE(1) and PGE(2) were significantly increased in retinal homogenates of rats fed with the GLA-rich diet when compared with those of animals fed the control diet. These higher PGE(1) and PGE(2) levels were not observed in animals fed with EPA + DHA + GLA. In summary, GLA added to EPA + DHA resulted in the highest retinal DHA content but without increasing retinal PGE(2) as seen in animals supplemented with GLA only.

Time course of ocular surface and lacrimal gland changes in a new scopolamine-induced dry eye model.

BACKGROUND: The aim of this study was to set up an animal model of dry eye showing disturbance in several components of the lacrimal functional unit, and to describe the time course of the appearance of clinical signs and inflammatory markers. METHODS: Dry eye was induced in 6-week-old female Lewis rats by a systemic and continuous delivery of scopolamine via osmotic pumps implanted subcutaneously. We first determined the appropriate dose of scopolamine (6, 12.5, or 25 mg/day) for 28 days. In a second set of experiments, we determined markers after 1, 2, 3, 7, 10, 17, or 28 days of a 12.5-mg/day dose. Clinical signs of corneal dryness were evaluated in vivo using fluorescein staining. MHC II expression and mucin Muc5AC production were detected on the conjunctival epithelium using immunostaining. The level of IL-1beta, IL-6, TNF-alpha, and IFN-gamma mRNA was evaluated by real-time polymerase chain reaction in conjunctiva and exorbital lacrimal gland (LG). Lipids were extracted from the exorbital LG for fatty acid analysis. RESULTS: Daily scopolamine doses of 12.5 mg and 25 mg applied for a 28-day period induced keratitis, a decrease in Muc5AC immunostaining density in the conjunctival epithelium, and modifications in the fatty acid composition of the exorbital LG. Animals treated with a 12.5-mg/day dose of scopolamine exhibited an increase in corneal fluorescein staining after 2, 10, and 28 days. All animals exhibited unilateral or bilateral keratitis after 17 days. In the conjunctival epithelium, a significant decrease in Muc5AC immunostaining density was observed at early and late time points, and MHC II expression tended to be increased after 1, 7, 10, and 28 days, without reaching statistical significance. The levels of TNF-alpha, IL-1beta and IL-6 mRNA were increased with scopolamine treatment in both conjunctiva and exorbital LG. Arachidonic acid and the Delta5 desaturase index were significantly increased in the exorbital LG of dry eye animals at each time point. CONCLUSIONS: This systemic and continuous scopolamine-induced model of dry eye in the rat may represent a helpful tool to investigate moderate dry eye, and makes a contribution in the field of dry eye study.

In vivo oxidation of carboxyl-labelled cyclic fatty acids formed from linoleic and linolenic acids in the rat.

Cyclic fatty acid monomers (CFAM), which occur from the intramolecular cyclisation of linoleic and linolenic acids, are subsequently present in some edible oils and are suspected to induce metabolic disorders. One may suggest that the presence of a ring would alter the ability of the organism to oxidise these molecules. In order to test this hypothesis, we assessed the oxidative metabolism of CFAM in rats. For this purpose, rats were force-fed from 1.5 to 2.6 MBq of [1-(14)C]-linoleic acid, [1-(14)C]-linolenic acid, [1-(14)C]-CFAM-18:2 or [1-(14)C]-CFAM-18:3, and 14CO2 production was monitored for 24 h. The animals were then sacrificed and the radioactivity was determined in different tissues. No significant differences in 14CO2 production were found 24 h after the administration of CFAM and their respective precursors. Our data clearly demonstrate that, at least for the first beta-oxidation cycle, CFAM are oxidised in a similar way as both essential fatty acids.

Peroxisome proliferator-activated receptor alpha is not the exclusive mediator of the effects of dietary cyclic FA in mice.

Cyclic FA monomers (CFAM) formed during heating of alpha-linolenic acid have been reported to interfere in hepatic metabolism in a putatively peroxisome proliferator-activated receptor alpha (PPARalpha)-dependent manner. In the present work, CFAM (0.5% of the diet) were administered for 3 wk to wild-type and PPARalpha-null mice of both genders to elucidate the role of PPARalpha in mediating the effects of CFAM on the activity of acyl-CoA oxidase (ACO) and omega-laurate hydroxylase (CYP4A), the regulation of which is known to be dependent on the PPARalpha. Dietary CFAM enhanced CYP4A activity threefold in male and female wild-type mice. This effect was abolished in PPARalpha-null mice. A twofold induction of ACO activity was found in wild-type female mice fed CFAM; however, no effect was seen in males. In wild-type animals, (omega-1)-laurate hydroxylase (CYP2E1) activity, the expression of which has not been shown to be PPARalpha dependent, was not affected by the CFAM diet. In contrast, stearoyl-CoA desaturase activity was reduced in wild-type mice. CFAM feeding reduced the activities of ACO, CYP2E1, and stearoyl-CoA desaturase and caused accumulation of lipids in the livers of female PPARalpha-null mice. These data show that CFAM apparently activate gene expression via the PPARalpha and have profound effects on lipid homeostasis, exacerbating the disturbances preexisting in mice lacking functional PPARalpha. Although the data emphasize the importance of PPARalpha in the metabolism of the CFAM, these results show that PPARalpha is not the exclusive mediator of the effects of CFAM in lipid metabolism in mice.

Modification of the dopaminergic neurotransmitters in striatum, frontal cortex and hippocampus of rats fed for 21 months with trans isomers of alpha-linolenic acid.

Deficiency in n-3 fatty acids is known to disturb the release of dopaminergic neurotransmitters in rat brain. Since isomerization reduces the bioavailability of dietary fatty acids, the effect of the conversion of alpha-linolenic acid into trans alpha-linolenic acid on the dopaminergic neurotransmission was studied. Rats were fed for 21 months with a control diet, a diet unbalanced in cis alpha-linolenic acid and containing trans alpha-linolenic acid or the same diet in which the imbalance was corrected by increasing the levels of cis alpha-linolenic acid. After 6 and 21 months of diet, the fatty acid composition and the amounts of endogenous dopaminergic neurotransmitters was assessed in the striatum, the frontal cortex and the hippocampus. The isomerization of a part of dietary alpha-linolenic acid induced some modifications of the levels of endogenous dopaminergic neurotransmitters in all brain areas but was related to a very low incorporation of trans polyunsaturated fatty acids. Increasing the dietary levels of cis alpha-linolenic acid succeeded in correcting the endogenous neurotransmitter concentrations only in the frontal cortex but not in the striatum and the hippocampus. Thus, the levels of dopamine were lowered by 95% in the hippocampus. These results suggest that in addition to the imbalance generated by their presence, trans fatty acids may directly act on the concentration of dopaminergic neurotransmitters.