Developmental changes in the optic nerve related to ethanol consumption in pregnant rats: analysis of the ethanol-exposed optic nerve

Stereological examination of effects of ethanol on optic nerve in experimental alcohol model

The objective of the present study was to perform histological and stereological examination of alcohol-induced changes in the optic nerve, considered an extension of white matter of the brain, in rats. This study included 20 male Wistar albino rats aged 60 days and weighing 190-220 g. The rats were divided into three groups: ethanol ( n = 7), maltodextrin ( n = 7), and control ( n = 6) groups. The ethanol group was administered ethanol at a dose of 6.4% (v/v) instead of water for 18 days; the maltodextrin group received maltodextrin for the same time period, and the control group was the sham group. At the end of the experiment, a 0.5-mm long section of the optic nerve starting from the optic chiasma was dissected and examined with routine microscopic histological examination methods. The modified Cavalieri method was used for stereological measurement. Total tissue area ratios were calculated with a point grid provided by the Shtereom 1.5 software package. The statistical comparison of the groups revealed that the ethanol group had a significant reduction in the number of axons and sheath area of the optic nerve compared to the control and maltodextrin groups ( p < 0.017, p < 0.022, respectively). These results indicate the toxic effects of ethanol on the optic nerve.

Optic Nerve Hypoplasia in Fetal Alcohol Syndrome: An Update

Optic nerve hypoplasia was detected in up to one half of a group of Swedish children born to alcoholic mothers. Using an experimental model of pre- and postnatal alcohol exposure in rats fed a liquid diet, reduced optic nerve size from gestational day 21 (294 ± 26×102 μm2 vs 502 ± 16×102 μm2; n=6; p≤0.001) to later in development was observed as a result of the daily mean blood alcohol levels achieved in dams and their offspring. Altered glial cells and degenerating and atrophic optic axons, myelin sheaths and ganglion cells were frequent in the alcohol-exposed optic nerves.

Smaller optic nerve (1,918 ± 61×102 μm2 vs 2.195 ± 40×102 μm2; n=4; p≤0.001), reduced gaglion cell and axonal densities, and ultrastructural damage to the macroglial cells and myelin sheaths were also detected in the treated group. All these changes remained in the retina and optic nerve of the oldest rats, as a consequence of the long-lasting effects of prenatal alcohol exposure. In summary, alcohol as a major teratogenic agent may induce dysmorphogenesis and irremediable damage to the retina and optic nerve, which frequently manifests itself as hypoplastic optic nerve.

FASD: folic acid and formic acid — an unholy alliance in the alcohol abusing mother

Alcohol consumption during pregnancy remains a significant cause of preventable birth defects and developmental disabilities; however, the mechanism of toxicity remains unclear. Methanol is present as a congener in many alcoholic beverages and is formed endogenously. Because ethanol is preferentially metabolized over methanol, it has been found in the sera and cerebro-spinal fluid of alcoholics. Toxicity resulting from methanol has been attributed to formic acid. Formic acid is present in significantly higher quantities in the biofluids of alcoholics. These higher levels can be cytotoxic and cause neuronal cell death. However, the adverse effects can be mitigated by adequate levels of hepatic folic acid, because formic acid elimination depends on folic acid. During pregnancy, folate concentrations are at least 2-fold higher in cord blood then in maternal blood, owing to increased folate requirements. The reverse has been demonstrated in pregnancies with alcohol abuse, suggesting downregulation of folate transporters and low fetal folate levels. Moreover, formic acid can cross the placenta and its adverse effects can be mitigated by folic acid. Thus, the combination of low fetal folate levels and presence of formic acid form a potent cytotoxic combination that may play a significant role in the etiology of fetal alcohol spectrum disorder.

Differences in neural crest sensitivity to ethanol account for the infrequency of anterior segment defects in the eye compared with craniofacial anomalies in a zebrafish model of fetal alcohol syndrome

BACKGROUND

Ethanol (ETOH) exposure during pregnancy is associated with craniofacial and neurologic abnormalities, but infrequently disrupts the anterior segment of the eye. In these studies, we used zebrafish to investigate differences in the teratogenic effect of ETOH on craniofacial, periocular, and ocular neural crest.

METHODS

Zebrafish eye and neural crest development was analyzed by means of live imaging, TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) assay, immunostaining, detection of reactive oxygen species, and in situ hybridization.

RESULTS

Our studies demonstrated that foxd3-positive neural crest cells in the periocular mesenchyme and developing eye were less sensitive to ETOH than sox10-positive craniofacial neural crest cells that form the pharyngeal arches and jaw. ETOH increased apoptosis in the retina, but did not affect survival of periocular and ocular neural crest cells. ETOH also did not increase reactive oxygen species within the eye. In contrast, ETOH increased ventral neural crest apoptosis and reactive oxygen species production in the facial mesenchyme. In the eye and craniofacial region, sod2 showed high levels of expression in the anterior segment and in the setting of Sod2 knockdown, low levels of ETOH decreased migration of foxd3-positive neural crest cells into the developing eye. However, ETOH had minimal effect on the periocular and ocular expression of transcription factors (pitx2 and foxc1) that regulate anterior segment development.

CONCLUSION

Neural crest cells contributing to the anterior segment of the eye exhibit increased ability to withstand ETOH-induced oxidative stress and apoptosis. These studies explain the rarity of anterior segment dysgenesis despite the frequent craniofacial abnormalities in fetal alcohol syndrome. Birth Defects Research 109:1212-1227, 2017. © 2017 Wiley Periodicals, Inc.

Use of novel inhalation kinetic studies to refine physiologically-based pharmacokinetic models for ethanol in non-pregnant and pregnant rats

Ethanol (EtOH) exposure induces a variety of concentration-dependent neurological and developmental effects in the rat. Physiologically-based pharmacokinetic (PBPK) models have been used to predict the inhalation exposure concentrations necessary to produce blood EtOH concentrations (BEC) in the range associated with these effects. Previous laboratory reports often lacked sufficient detail to adequately simulate reported exposure scenarios associated with BECs in this range, or lacked data on the time-course of EtOH in target tissues (e.g. brain, liver, eye, fetus). To address these data gaps, inhalation studies were performed at 5000, 10 000, and 21 000 ppm (6 h/d) in non-pregnant female Long-Evans (LE) rats and at 21 000 ppm (6.33 h/d) for 12 d of gestation in pregnant LE rats to evaluate our previously published PBPK models at toxicologically-relevant blood and tissue concentrations. Additionally, nose-only and whole-body plethysmography studies were conducted to refine model descriptions of respiration and uptake within the respiratory tract. The resulting time-course and plethysmography data from these in vivo studies were compared to simulations from our previously published models, after which the models were recalibrated to improve descriptions of tissue dosimetry by accounting for dose-dependencies in pharmacokinetic behavior. Simulations using the recalibrated models reproduced these data from non-pregnant, pregnant, and fetal rats to within a factor of 2 or better across datasets, resulting in a suite of model structures suitable for simulation of a broad range of EtOH exposure scenarios.

Primary visual response (M100) delays in adolescents with FASD as measured with MEG

Fetal alcohol spectrum disorders (FASD) are debilitating, with effects of prenatal alcohol exposure persisting into adolescence and adulthood. Complete characterization of FASD is crucial for the development of diagnostic tools and intervention techniques to decrease the high cost to individual families and society of this disorder. In this experiment, we investigated visual system deficits in adolescents (12-21 years) diagnosed with an FASD by measuring the latency of patients' primary visual M100 responses using MEG. We hypothesized that patients with FASD would demonstrate delayed primary visual responses compared to controls. M100 latencies were assessed both for FASD patients and age-matched healthy controls for stimuli presented at the fovea (central stimulus) and at the periphery (peripheral stimuli; left or right of the central stimulus) in a saccade task requiring participants to direct their attention and gaze to these stimuli. Source modeling was performed on visual responses to the central and peripheral stimuli and the latency of the first prominent peak (M100) in the occipital source timecourse was identified. The peak latency of the M100 responses were delayed in FASD patients for both stimulus types (central and peripheral), but the difference in latency of primary visual responses to central vs. peripheral stimuli was significant only in FASD patients, indicating that, while FASD patients' visual systems are impaired in general, this impairment is more pronounced in the periphery. These results suggest that basic sensory deficits in this population may contribute to sensorimotor integration deficits described previously in this disorder.

Ethanol alters gene expression and cell organization during optic vesicle evagination

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Ethanol alters eye morphogenesis at early stages of embryogenesis.

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The expression patterns of some genes important for eye morphogenesis are perturbed.

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Ethanol is related to alterations in cell morphology.

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Ethanol interferes with the optic vesicles evagination.

Ethanol has been described as a teratogen in vertebrate development. During early stages of brain formation, ethanol affects the evagination of the optic vesicles, resulting in synophthalmia or cyclopia, phenotypes where the optic vesicles partially or totally fuse. The mechanisms by which ethanol affects the morphogenesis of the optic vesicles are however largely unknown. In this study we make use of in situ hybridization, electron microscopy and immunohistochemistry to show that ethanol has profound effects on cell organization and gene expression during the evagination of the optic vesicles. Exposure to ethanol during early eye development alters the expression patterns of some genes known to be important for eye morphogenesis, such as rx3/1 and six3a. Furthermore, exposure to ethanol interferes with the acquisition of neuroepithelial features by the eye field cells, which is clear at ultrastructual level. Indeed, ethanol disrupts the acquisition of fusiform cellular shapes within the eye field. In addition, tight junctions do not form and retinal progenitors do not properly polarize, as suggested by the mis-localization and down-regulation of zo1. We also show that the ethanol-induced cyclopic phenotype is significantly different to that observed in cyclopic mutants, suggesting a complex effect of ethanol on a variety of targets.

Our results show that ethanol not only disrupts the expression pattern of genes involved in retinal morphogenesis, such as rx3 and rx1, but also disrupts the changes in cell polarity that normally occur during eye field splitting. Thus, ethylic teratology seems to be related not only to modifications in gene expression and cell death but also to alterations in cell morphology.

Effects of early postnatal alcohol exposure on the developing retinogeniculate projections in C57BL/6 mice

Previous studies on the adverse effects of perinatal exposure to ethanol (EtOH) on the developing visual system mainly focused on retinal and optic nerve morphology. The aim of the present study was to investigate whether earlier reported retinal and optic nerve changes are accompanied by anomalies in eye-specific fiber segregation in the dorsal lateral geniculate nucleus (dLGN). C57BL/6 mice pups were exposed to ethanol by intragastric intubation at either 3 or 4 g/kg from postnatal days (PD) 3-10, the third trimester equivalent to human gestation. Control (C) and intubation control (IC) groups not exposed to ethanol were included. On PD9, retinogeniculate projections were labeled by intraocular microinjections of cholera toxin-β (CTB) either conjugated to Alexa 488 (green) or 594 (red) administrated to the left and right eye, respectively. Pups were sacrificed 24 h after the last CTB injection. The results showed that ethanol exposure decreased the total number of dLGN neurons and significantly reduced the total dLGN projection as well as the contralateral and ipsilateral projection areas.

Effects of early postnatal exposure to ethanol on retinal ganglion cell morphology and numbers of neurons in the dorsolateral geniculate in mice

BACKGROUND

The adverse effects of fetal and early postnatal ethanol intoxication on peripheral organs and the central nervous system are well documented. Ocular defects have also been reported in about 90% of children with fetal alcohol syndrome, including microphthalmia, loss of neurons in the retinal ganglion cell (RGC) layer, optic nerve hypoplasia, and dysmyelination. However, little is known about perinatal ethanol effects on retinal cell morphology. Examination of the potential toxic effects of alcohol on the neuron architecture is important because the changes in dendritic geometry and synapse distribution directly affect the organization and functions of neural circuits. Thus, in the present study, estimations of the numbers of neurons in the ganglion cell layer and dorsolateral geniculate nucleus (dLGN), and a detailed analysis of RGC morphology were carried out in transgenic mice exposed to ethanol during the early postnatal period.

METHODS

The study was carried out in male and female transgenic mice expressing yellow fluorescent protein (YFP) controlled by a Thy-1 (thymus cell antigen 1) regulator on a C57 background. Ethanol (3 g/kg/d) was administered to mouse pups by intragastric intubation throughout postnatal days (PDs) 3 to 20. Intubation control (IC) and untreated control (C) groups were included. Blood alcohol concentration was measured in separate groups of pups on PDs 3, 10, and 20 at 4 different time points, 1, 1.5, 2, and 3 hours after the second intubation. Numbers of neurons in the ganglion cell layer and in the dLGN were quantified on PD20 using unbiased stereological procedures. RGC morphology was imaged by confocal microscopy and analyzed using Neurolucida software.

RESULTS

Binge-like ethanol exposure in mice during the early postnatal period from PDs 3 to 20 altered RGC morphology and resulted in a significant decrease in the numbers of neurons in the ganglion cell layer and in the dLGN. In the alcohol exposure group, out of 13 morphological parameters examined in RGCs, soma area was significantly reduced and dendritic tortuosity significantly increased. After neonatal exposure to ethanol, a decrease in total dendritic field area and an increase in the mean branch angle were also observed. Interestingly, RGC dendrite elongation and a decrease in the spine density were observed in the IC group, as compared to both ethanol-exposed and pure control subjects. There were no significant effects of alcohol exposure on total retinal area.

CONCLUSIONS

Early postnatal ethanol exposure affects development of the visual system, reducing the numbers of neurons in the ganglion cell layer and in the dLGN, and altering RGCs' morphology.

Thyroid hormone deficiency disrupts rat eye neurodevelopment

Clinical and experimental studies have highlighted the role played by thyroid hormones (TH) in neural and neuro-sensorial development. However, knowledge on TH mechanisms on the developing visual system is still incomplete. To uncover TH actions on the eyes and vision we carried out a microscopical study on the role of TH in the developing retina and optic nerve, in a rat model of controlled TH deficiency (THD). Morphometric and stereological analyses of the retina and optic nerve showed a reduction in the volume of the eye (p<0.001) and optic nerve cross-sectional area (p<0.001), and thinning of the retinal layers (p<0.001). Glial development and myelination was significantly delayed in the THD optic nerves (p<0.001), as compared to controls. The data indicate that TH play an essential role in neuro-retinogenesis. Substitutive TH therapy in critical periods, should be considered in hypothyroidism-related eye disorders as well as neurodegenerative retinal processes.

Correlation of axon size and myelin occupancy in rats prenatally exposed to methamphetamine

The abuse of methamphetamine (MA) and other psychostimulants is a social and medical problem. In particular, the use of these drugs by pregnant women results in an increased number of children exposed prenatally to psychostimulants. Our previous work has demonstrated that prenatal exposure to MA affects the normal development of the rat visual system due to alterations of biochemical mechanisms and oxidative stress. It was also demonstrated that prenatal exposure to MA affects the dopaminergic system of the rat retina and optic nerve (ON) myelination. The present work was conducted to evaluate the effects of prenatal exposure to MA on the development of the ON in terms of axon growth and the myelin sheath. Pregnant female rats were given 5 mg/kg/day MA, subcutaneously (s.c.), in 0.9% saline from gestational day (GD) 8 to 22. The pair-fed control group was injected s.c. with an isovolumetric dose of 0.9% saline. Qualitative analysis was performed using representative electron ultramicrographs. Quantitative analysis was performed at an electron microscopic level on ON cross sections; parameters measured included myelinated/unmyelinated ratio, outer axon mean area, inner axon mean area, myelin mean area, myelin occupancy and distribution of axons by size. The ON of prenatally MA-exposed rats presented a higher rate of deformed axons and slighter lamellar separation. At PND 21, the average outer axon area of MA-treated males was significantly reduced. The average inner axon area only showed a significant difference between MA and control males for axons with an area of less than 0.3 microm(2). The average myelin area of MA-treated males was significantly reduced, and in MA-treated females was only significantly reduced in axons with an area of less than 0.3 microm(2). The percentage of myelin occupancy was significantly affected in MA-treated males, and in MA-treated females in the group of axons with an area of more than 0.3 microm(2). At PND 14 no significant differences were found between MA and control groups. The spectrum of ON myelinated axon size of MA-treated animals was shifted to the left at PND 14 and PND 21 for both genders. These results are in agreement with previous animal studies of prenatal and perinatal exposure to drugs of abuse. Taken together, these data indicate that the ON is vulnerable to early exposure to MA which causes developmental changes and may interfere with the functioning of the visual system.

Glial fibrillary acidic protein (GFAP) and CD34 expression in the human optic nerve and brain in methanol toxicity

INTRODUCTION

The toxicity of methanol is as a result of its metabolites, formaldehyde and formic acid. Formic acid induces severe metabolic acidosis causing death, and is the primary agent responsible for ocular toxicity. Glial fibrillary acidic protein (GFAP) immunostaining is the most commonly used method for examining astrocyte proliferation and hypertrophy after various central nervous system injuries. The antigen CD34 is expressed widely on vascular endothelium, including that of the central nervous system and high endothelial venules.

METHODS

In this study, GFAP and CD34 were immunohistochemically localised in the post-mortem optic nerve head, and brain tissue (basal ganglia putamen) samples were collected from methanol-exposed and non-methanol-exposed (control) subjects.

RESULTS

There was a positive correlation between the GFAP and CD34 intensity of staining scores in the methanol-exposed group (P=0.711, P=0.010). Furthermore, there was also a positive correlation between the brain putamen and optic nerve head GFAP extent of staining in the methanol-exposed group (P=0.720, P=0.008). A statistically significant difference was found between the methanol-exposed group and the control group optic nerve CD34 intensity scores (P=0.014), but no significant difference was found between optic nerve CD34 and GFAP extent scores (P=0.05).

CONCLUSION

The study revealed that methanol affects brain putamen and the optic nerve selectively. We detected a positive significant correlation between brain and optic nerve GFAP expression. CD34 expression was markedly decreased by the toxic effects of methanol.

Optic nerve alterations in P27(Kip1) knockout mice

PURPOSE

To study the morphologic characteristics of the optic nerve (ON) by using an experimental model of knockout mice for the expression of the P27(Kip1) gene, mainly involved in cell cycle arrest, apoptosis control, and retinoblastoma protein phosphorylation.

METHODS

Eyeballs with the retrobulbar ON attached were obtained from 26-week-old mice. By using morphologic and morphometric techniques, light and electron transmission microscopy, the ON characteristics were determined in two groups of mice: 1) wild type mice as the control group (n=15), 2) homozygous knockout mice (-/-) for the P27(Kip1) gene as the knockout group (n=15). Glial fibrillary acidic protein (GFAP) and myelin basic protein (MBP) were studied using Western blot and immunoblotting approaches.

RESULTS

The ON cross-sectional area was significantly larger in the P27(Kip1) knockout mice group than in the control group (p<0.001). The axon sizes in knockout animals were much larger than in wild-type mice (p<0.001). Higher number of axons forming the ON, intra-axonal degeneration, myelin sheath, and axoplasm density alterations were found in P27(Kip1) knockout mice when compared with control group (p<0.001). Analysis of lysates of optic nerves by Western blot showed less expression of myelin basic protein and GFAP in P27(Kip1) knockout mice as compared to wild type mice (p<0.005, p<0.01, respectively).

CONCLUSIONS

The morphologic and morphometric results suggest that homozygous P27(Kip1) knock-out mice had hypertrophic, hyperplastic, and dystrophic ON.

Effects of ethanol on photoreceptors and visual function in developing zebrafish

PURPOSE

Children born to mothers who have consumed alcohol during pregnancy have an array of retinal abnormalities and visual dysfunctions. In the past, rodent systems have been used to study the teratogenic effects of ethanol on vertebrate embryonic development. The exact developmental windows in which ethanol causes specific developmental defects have been difficult to determine because rodents and other mammals develop in utero. In this study, we characterized how ethanol affects the function and development of the visual system in an ex utero embryonic system, the zebrafish.

METHODS

Zebrafish embryos were raised in fish water containing various concentrations of ethanol from 2 to 5 days after fertilization. The effects of ethanol on retinal morphology were assessed by histologic and immunohistochemical analyses and those on retinal function were analyzed by optokinetic response (OKR) and electroretinography (ERG).

RESULTS

Zebrafish embryos exposed to moderate and high levels of ethanol during early embryonic development had morphological abnormalities of the eye characterized by hypoplasia of the optic nerve and inhibition of photoreceptor outer segment growth. Ethanol treatment also caused an increased visual threshold as measured by the OKR. Analysis with the ERG indicated that there was a severe reduction of both the a- and b-waves, suggesting that ethanol affects the function of the photoreceptors. Indeed, low levels of ethanol that did not cause obvious morphologic changes in either the body or retina did affect both the OKR visual threshold and the a- and b-wave amplitudes.

CONCLUSIONS

Ethanol affects photoreceptor function at low concentrations that do not disturb retinal morphology. Higher levels of ethanol inhibit photoreceptor development and cause hypoplasia of the optic nerve.

The effect of in ovo ethanol exposure on retina and optic nerve in a chick embryo model system

Ocular anomalies seen in children with fetal alcohol syndrome (FAS) suggest that ocular structures are sensitive to alcohol exposure during their development. This study was designed to investigate the effect of in ovo ethanol (EtOH) exposure on retinal development and myelinization of optic nerve fibers at an ultra structural level in a chick embryo model system. Prior to incubation, fertilized chicken eggs were injected once with 100 microl of either 0.9% NaCl (vehicle control), or EtOH solutions at different doses (10, 30, or 50%, v:v in 0.9% NaCl) into their air sacs and incubated at 37.5 degrees C and saturation humidity. On day 20 embryos were analyzed in terms of their viability and growth and the optic cups including the optic nerves were dissected out. Specimens were processed for electron microscopy (EM). Results showed that, EtOH significantly decreased the viability of chick embryos (P < 0.045), and caused significant prenatal growth retardation (P < 0.004) in a dose-dependant manner. Light microscopy of semi thin sections revealed that prenatal exposure to EtOH resulted in both retinal degeneration and optic nerve hypoplasia (P < 0.001) in a dose-dependant manner. EM revealed that a dose-dependant decrease in the number of myelinated nerve fibers was profound in groups exposed to EtOH (P < 0.001). Furthermore, the myelin coats observed were thinner than those seen in control embryos. In groups exposed to EtOH myelin sheets were unorganized and contained vacuolar structures in between them. The tissue in between the cells and optic nerve fibers, on the other hand, lost its intact appearance with vacuolar and vesicular structures in between them. In addition, the optic nerve fibers contained granular accumulations in EtOH exposed groups. A dose dependent degeneration was also observed in retinas of EtOH exposed groups. The effect of EtOH was profound in pigment epithelium (PE), inner plexiform layer (IPL), and ganglion cell layer (GC). Mitochondrial deficiencies, and alterations in melanin granule number and distribution dominated the defects seen in PE. On the other hand, EM findings of all the affected layers were suggestive of induced cell death in EtOH exposed groups. Thus, this study suggests retinal development with the emphasis on melanin pigmentation in PE and optic nerve myelinization as potential targets of prenatal EtOH exposure and discusses potential mechanisms of EtOH action on these tissues.

Myelination changes in the rat optic nerve after prenatal exposure to methamphetamine

The use of psychostimulants during adolescence and early adult life has increased in recent years. It is known that these substances affect the sensory systems, and the optic nerve has been shown to be a target tissue. This work was conducted to evaluate the effects of prenatal exposure to methamphetamine (MA) on the developmental pattern of the rat optic nerve. Pregnant female rats were given 5 mg/kg body weight/day MA, s.c., in 0.9% saline from gestational days 8 to 22. The control group was injected with an isovolumetric dose of 0.9% saline. Animal model parameters, such as gestational body weight evolution, food intake and pups parameters were registered. The offspring were sacrificed at postnatal days (PND) 7, 14 and 21. Morphometric analyses were performed at light and electron microscopic levels on optic nerve cross sections; parameters measured included optic nerve diameter and area, axonal density, total number of axons and myelin thickness. Myelin basic protein (MBP) was measured by western blotting in optic nerve samples at PND14 and PND21. The animal model parameters, such as maternal and pup weight, showed no significant differences between MA and control groups. Optic nerve diameter was smaller at PND7 in the male MA group and in both male and female MA groups at PND21. The mean cross-sectional area was smaller at PND14 in the male MA group and in both male and female groups at PND21. The total number of myelinated axons did not vary between groups at any of the studied ages. The myelin thickness of the axons in MA-treated females was thinner when compared with the respective control group at PND21. No other differences were found concerning myelin thickness. There was a reduction of MBP protein expression in MA-injected females at PND14 and PND21. The combined results suggest that prenatal exposure to MA affects the myelination process.

Prenatal alcohol exposure and early postnatal changes in the developing nerve-muscle system

BACKGROUND

Extensive research on prenatal alcohol exposure has proven the potent teratogenicity of this substance of abuse. Children born to alcoholic mothers are often diagnosed with fetal alcohol syndrome (FAS). Those afflicted with FAS often have muscle weakness, muscle wasting, and atrophy. This study assessed the effects of prenatal alcohol exposure on the developing rat neuromuscular system.

METHODS

Pregnant Sprague-Dawley rats were injected intraperitoneally with 1.0 ml of 20% ethyl alcohol/100 gm body weight. Unexposed rats served as controls. The offspring were killed 2, 3, 4, and 5 weeks after birth, and their body weights were recorded. The tibialis anterior (TA) and extensor digitorum longus (EDL) muscles were recovered and weighed. The TA muscles were histochemically stained by silver cholinesterase in order to study the pattern of innervation. The EDL muscles were processed and stained by hematoxylin-eosin. The number and size of the EDL muscle fibers was quantified. The sciatic nerve was also removed and stained by Swank and Davenport's method to demonstrate the myelin pattern.

RESULTS

Assessment at the neuromuscular junction showed a higher proportion of endplates polyneuronally innervated in the alcohol-exposed rats. The muscle weights, as well as the number and size of the muscle fibers, were significantly reduced in these animals. A light-microscopy examination of the nerve sections revealed alterations in the connectivity of myelin.

CONCLUSIONS

The finding that a higher proportion of endplates were polyneuronally innervated in the alcohol-exposed rats indicates that the maturation process of the neuromuscular system was delayed, thus confirming the deleterious effects of alcohol on growth and maturation of the nerve-muscle system.

Methamphetamine and lipid peroxidation in the rat retina

BACKGROUND

The use of psychoactive drugs during adolescence and early adult life has increased in the last few decades. It is known that developmental exposure to psychostimulants affects the sensory systems, and the retina has been shown to be a target tissue. This work was conducted to evaluate the pattern of lipid peroxidation in the rat retina following prenatal exposure to methamphetamine (MA).

METHODS

Pregnant female Wistar rats were given MA (5 mg/kg of body weight/day; SC, in 0.9% saline) from GD 8 to 22. Offspring were sacrificed at postnatal days (PNDs) 7, 14, and 21. The retinas were homogenized, and both the total antioxidant and superoxide dismutase (SOD) activities were measured by enzymatic-colorimetric methods. The lipid peroxidation byproducts (malondialdehyde [MDA] and MDA-like metabolites) were measured by the thiobarbituric acid test.

RESULTS

Total antioxidant levels were lower in the MA group at PND 21 in both males and females. The activity of SOD was higher in PND 7 females from the MA group. MDA levels were higher in the MA group at PND 21 in both genders.

CONCLUSIONS

These findings suggest that prenatal-induced MA toxicity in the retina may be related to lipid peroxidation processes and oxidative stress.

Visual impairment and ocular abnormalities in children with fetal alcohol syndrome

Children with fetal alcohol syndrome (FAS) may have impaired vision and various ocular abnormalities. All parts of the eye may be affected and anomalies such as microphthalmus, microcornea, Peters' anomaly, cataract, persistent hyperplastic primary hyaloid vitreous body, coloboma of the iris and choroid, retinal dysplasia and, most commonly, optic nerve hypoplasia and tortuosity of the retinal vessels, have been reported. The periocular facial features consist of short palpebral fissures (included in the criteria for diagnosis of FAS), telecanthus, epicanthus and blepharoptosis. Visual function may be reduced to a moderate or severe degree. Refractive errors and strabismus are common. Considering the high frequency of ocular pathology in FAS, an ophthalmological examination is helpful in making the diagnosis. The early detection of impaired vision and ocular abnormalities in affected children is important in the management of the disorder. In this article, the ophthalmological signs and symptoms in children with FAS are presented.

Oligodendroglia in developmental neurotoxicity

The developing nervous system has been long recognized as a primary target for a variety of toxicants. To date, most efforts to understand the impact of neurotoxic agents on the brain have focused primarily on neurons and to a lesser degree astroglia as cellular targets. The role of oligodendroglia, the myelin-forming cells in the central nervous system (CNS), in developmental neurotoxicity has been emphasized only in recent years. Oligodendrocytes originate from migratory, mitotic progenitors that mature progressively into postmitotic myelinating cells. During differentiation, oligodendroglial lineage cells pass through a series of distinct phenotypic stages that are characterized by different proliferative capacities and migratory abilities, as well as dramatic changes in morphology with sequential expression of unique developmental markers. In recent years, it has become appreciated that oligodendrocyte lineage cells have important functions other than those related to myelin formation and maintenance, including participation in neuronal survival and development, as well as neurotransmission and synaptic function. Substantial knowledge has accumulated on the control of oligodendroglial survival, migration, proliferation, and differentiation, as well as the cellular and molecular events involved in oligodendroglial development and myelin formation. Recently, studies have been initiated to address the role of oligodendrocyte lineage cells in neurotoxic processes. This article examines recent progress in oligodendroglial biology, focuses attention on the characteristic features of the oligodendrocyte developmental lineage as a model system for neurotoxicological studies, and explores the role of oligodendrocyte lineage cells in developmental neurotoxicity. The potential role of oligodendroglia in environmental lead neurotoxicity is presented to exemplify this thesis.

A selective loss of small-diameter myelinated optic nerve axons in rats prenatally exposed to ethanol

Pregnant rats were fed an ethanol-containing liquid diet between gestational days 10 and 21. The optic nerves of their litters at 49 days of age were examined using quantitative stereological procedures. Cross-sectional areas of the optic nerve in ethanol-exposed rats were significantly smaller than those in controls. This was reflected in the reduced number of myelinated fibers, but not of non-myelinated fibers. The size distribution histogram indicated a decreased number of small axonal-diameter myelinated fibers in ethanol-exposed rats. The results suggested optic nerve hypoplasia in ethanol-exposed rats characterized by a selective loss of small-diameter myelinated fibers.

Optic nerve hypoplasia and small eyes in presumed amblyopia

PURPOSE

To assess the anatomy of eyes presumed to be amblyopic and their fellow eyes.

PARTICIPANTS

Two hundred seventy-five patients diagnosed with amblyopia and 88 healthy or glaucomatous subjects.

METHODS

All subjects underwent complete examinations, including cycloplegic refraction, slit lamp examination, ophthalmoscopy, and retinal imaging. Axial lengths were determined on 263 amblyopic and 88 healthy and glaucomatous subjects by ultrasonic biometry.

MAIN OUTCOME MEASURES

Optic disc areas were determined by magnification correction of disc images performed with formulas. Dysversion of the optic disc was determined by simultaneous viewing of disc photographs, digitized images of both eyes, or both.

RESULTS

The mean disc area of eyes presumed to be amblyopic was 1.72 mm(2) +/- 0. 73 SD and 1.95 mm(2) +/- 0.69 SD for nonamblyopic eyes (P =.0017). The mean disc area for 176 optic discs of glaucomatous and healthy eyes was 2.61 mm(2) +/- 0.95 SD. The mean axial length for eyes in the general population is 23.65 mm +/- 1.35 SD. The healthy and glaucomatous group in this study had a mean axial length of 23.89 mm +/- 1.29 SD. The eyes with poorer vision that were assumed to be amblyopic averaged 22.42 mm +/- 2.01 SD in length, whereas their nonamblyopic fellow eyes averaged 22.83 mm +/- 1.89 SD (P =.022). The differences between eyes in the healthy population and eyes that are presumably amblyopic, as well as the healthy and fellow eyes, are highly significant (P <.0001)(7.0 x 10(-16)).

CONCLUSION

Vision impairment in presumed amblyopia is associated with optic nerve hypoplasia with relative microphthalmos, which is more notable in those eyes with poorer vision.

Exposure of rats to a high but not low dose of ethanol during early postnatal life increases the rate of loss of optic nerve axons and decreases the rate of myelination

Visual system abnormalities are commonly encountered in the fetal alcohol syndrome although the level of exposure at which they become manifest is uncertain. In this study we have examined the effects of either low (ETLD) or high dose (ETHD) ethanol, given between postnatal days 4-9, on the axons of the rat optic nerve. Rats were exposed to ethanol vapour in a special chamber for a period of 3 h per day during the treatment period. The blood alcohol concentration in the ETLD animals averaged approximately 171 mg/dl and in the ETHD animals approximately 430 mg/dl at the end of the treatment on any given day. Groups of 10 and 30-d-old mother-reared control (MRC), separation control (SC), ETLD and ETHD rats were anaesthetised with an intraperitoneal injection of ketamine and xylazine, and killed by intracardiac perfusion with phosphate-buffered glutaraldehyde. In the 10-d-old rat optic nerves there was a total of approximately 145,000-165,000 axons in MRC, SC and ETLD animals. About 4% of these fibres were myelinated. The differences between these groups were not statistically significant. However, the 10-d-old ETHD animals had only about 75,000 optic nerve axons (P < 0.05) of which about 2.8 % were myelinated. By 30 d of age there was a total of between 75,000-90,000 optic nerve axons, irrespective of the group examined. The proportion of axons which were myelinated at this age was still significantly lower (P < 0.001) in the ETHD animals (approximately 77 %) than in the other groups (about 98 %). It is concluded that the normal stages of development and maturation of the rat optic nerve axons, as assessed in this study, can be severely compromised by exposure to a relatively high (but not low) dose of ethanol between postnatal d 4 and 9.

Effect of alcohol on energy storage of primary astrocytes and C6-glioma cells in vitro

The present experiments were conducted to investigate the direct effects of ethanol on the energy metabolism of astrocytes and C6-glioma cells. Primary astrocytes were prepared from cerebral cortices of neonatal rats, and C6-glioma cells were purchased from American Type Culture Collection (ATCC). These cells were exposed to different concentrations of alcohol (100 mM, 200 mM, and 300 mM) for 15 minutes and 24 hours. The amount of ATP and PCr was measured by the method of Lowry and Passonneau (1972). Following 15 minutes treatment with different doses of ethanol the amount of ATP and PCr increased, in both cell types. Only the increase of ATP concentration with varying doses of ethanol (100 mM, 200 mM, and 300 mM) was statistically significant. Following 24 hours treatment of astrocytes with different doses of ethanol the concentration of ATP and PCr decreased. The decrease in concentration of ATP was significant with all three doses of ethanol, but the decrease of PCr concentration was only statistically significant with 300 mM ethanol. Following 24 hours treatment of C6-glioma cells to varying doses of ethanol, the concentration of PCr and ATP decreased. The decrease of PCr was statistically significant with all three doses of ethanol and the decrease of ATP concentration was only significant with 300 mM ethanol.

Dysversion of the optic disc and axial length measurements in a presumed amblyopic population

PURPOSE

Our purpose was to evaluate anatomic variations of eyes presumed to be amblyopic.

METHOD

Computer imaging and photography of the optic discs of 205 amblyopic subjects were performed and the axial lengths of 183 of the subjects were measured. The paired optic nerve images were evaluated for symmetry of disc contours and orientation of central blood vessels to detect optic nerve head dysversion. Dysversion of the optic nerve head, which is also referred to as segmental hypoplasia, is a congenital disorder characterized by the central retinal vessels emerging temporal to the vertical midline of the disc and being directed nasally or the nerve head tilting in a vertical direction resulting in a downward or oblique tilting of the discs with the blood vessels emerging at the superior or inferior disc rim.

RESULTS

Ninety-three subjects had optic nerve dysversion. There was a greater degree of anisometropia (P< or =.004) in subjects with dysversion (anisometropia factor of 2.51+/-2.15) than in the subjects with symmetric discs (anisometropia factor of 1.76+/-1.63). Axial lengths of the amblyopic eyes were significantly smaller (P<.0001) than those of the nonamblyopic eyes. There was no statistical difference (P< or =.879) in length between amblyopic eyes with dysversion and those with symmetric discs.

CONCLUSION

Optic disc dysversion was identified in 45.4% of patients who were previously assumed to be amblyopic. There are anatomic malformations in the eyes of a significant proportion of the presumed amblyopic population. This suggests that, in these individuals, congenital peripheral factors rather than impaired cortical development may be responsible for decreased unilateral acuity.

Fetal alcohol syndrome: a Japanese perspective

To estimate and prevent the effects of prenatal alcohol on the central nervous system (CNS), brain dysfunction in fetal alcohol syndrome (FAS) and fetal alcohol effects (FAE) was compared by both epidemiological and experimental studies. The FAS infants exhibited a more severe degree of CNS involvement than the FAE infants. The CNS involvement features were developmental delay and intellectual impairment in both FAS and FAE. The increased risk of low birth weight and CNS involvement were much more significant in women who were heavy drinkers or alcoholics and smoked. The beneficial effect of supplementary zinc on the fetal cerebrum of FAS or FAE rats was limited, never reaching the unexposed control level. One of the most vulnerable structures in the rat fetus exposed to ethanol in utero was the synaptic formation in the hippocampus. The consistent dysmorphogenesis of synapses during early brain development may be associated with the functional impairment of the CNS in FAS and FAE.

Alcohol, astroglia, and brain development

Glial cells constitute one of the most common cell types in the brain. They play critical roles in central nervous system (CNS) development. Recent evidence demonstrates that glial cells are profoundly affected by prenatal alcohol exposure, suggesting that alterations in these cells may participate in CNS abnormalities associated with ethanol-induced teratogenesis. In vivo studies show that prenatal exposure to alcohol hampers myelinogenesis and is associated with neuroglial heterotopias and abnormal astrogliogenesis. Studies using primary cultures of rat cortical astrocytes show that ethanol affects DNA, RNA, and protein synthesis, decreases the number of mitotic cells, alters the content and distribution of several cytoskeletal proteins including the astroglial marker, glial fibrillary acidic protein (GFAP), and the levels of plasma-membrane glycoproteins, reduces the capacity of astrocytes to secrete growth factors, and induces oxidative stress. Furthermore, ethanol exposure during early embryogenesis alters the normal development of radial glia cells (the main astrocytic precursors), delays the onset of GFAP expression, and decreases mRNA GFAP levels in fetal and postnatal brains and in radial glia and astrocytes in primary culture. Recent evidence suggests that ethanol interferes with the transcription process of GFAP, thus leading to a reduction in GFAP-gene expression during astrogliogenesis. However, brief exposure of rats to high levels of ethanol during the neonatal period (the period of astrocyte differentiation) causes a transient gliosis, with an increase in GFAP and its mRNA levels. These findings indicate that astroglial cells are an important target of ethanol toxicity during central nervous system (CNS) development.

Eye size in healthy Swedish children and in children with fetal alcohol syndrome

PURPOSE

This study set out to collect reference data for normal ocular growth and to study the teratological effects of alcohol on eye development.

METHODS

Eye size was studied in 92 healthy Swedish children (age 1 month to 16 years) as reference and in 13 children (age 1.4 months to 17 years) with fetal alcohol syndrome (FAS) using ultrasonographic axial length measurements. Another three children with FAS were evaluated by clinical examination only.

RESULTS

The control group demonstrated a marked increase in total axial length during the first 2 years of life. Girls with FAS had a shorter total axial length (p = 0.045) than their controls. Both boys and girls with FAS demonstrated a relatively smaller vitreous body than the controls, p = 0.015 and 0.068, respectively. Three children with FAS had severe structural anomalies.

CONCLUSION

The observations support previous studies indicating that alcohol has an adverse effect on growth and configuration of the eye.

Morphometric analysis of the postnatal mouse optic nerve following prenatal exposure to alcohol

Pregnant female mice were divided on day 12 post coitum into a control and an experimental group. The experimental group was given a single intraperitoneal dose of 0.015 ml/g body weight of 25% solution of alcohol in distilled water while the control group was exposed to a similar weight related dose of normal saline. The optic nerves were isolated from the offspring of both control and experimental groups at wk 2, 3 and 5 (i.e. during the juvenile period of postnatal development) and analysed by light and electron microscopy. Although in both groups the optic nerve grew in size rapidly during the period studied, the rate of growth in the experimental groups lagged behind that of the controls. The difference was initially significant but tailed off, so that by wk 5 it was no longer significant. The time of initial onset and progression of myelinogenesis in the optic nerve of alcohol exposed mice also lagged behind that of controls. In both groups the size distribution of the myelinated nerve fibres in the optic nerve was unimodal with a positive skewing for all ages. The spectrum of size distribution of the nerve fibres was, however, broader in controls than in the corresponding experimental groups. With increasing age the proportion of small and medium size fibres was greater in the experimental group than in the controls, while for the large diameter fibres the reverse was observed. It is suggested that this study may shed light on the teratogenic effect of 'binge' drinking during pregnancy and that it is the critical period when exposure occurs that is more important than the duration of administration.

Hearing, speech, language, and vestibular disorders in the fetal alcohol syndrome: a literature review

Fetal alcohol syndrome (FAS) is characterized in part by mental impairment, as well as craniofacial and ocular anomalies. These conditions are traditionally associated with childhood hearing disorders, because they all have a common embryonic origin in malformations of the first and second branchial arches, and have similar critical periods of vulnerability to toxic insult. A review of human and animal research indicates that there are four types of hearing disorders associated with FAS. These are: (1) a developmental delay in auditory maturation, (2) sensorineural hearing loss, (3) intermittent conductive hearing loss due to recurrent serous otitis media, and (4) central hearing loss. The auditory and vestibular systems share the same peripheral apparatuses (the inner ear and eighth cranial nerve) and are embryologically and structurally similar. Consequently, vestibular disorders in FAS children might be expected. The evidence for vestibular dysfunction in FAS is ambiguous, however. Like other syndromes associated with craniofacial anomalies, hearing disorders, and mental impairment, FAS is also characterized by a high prevalence of speech and language pathology. Hearing disorders are a form of sensory deprivation. If present during early childhood, they can result in permanent hearing, language, and mental impairment. Early identification and intervention to treat hearing, language, and speech disorders could therefore result in improved outcome for the FAS child. Specific recommendations are made for intervention and future research.

Fundus morphology assessed by digital image analysis in children with fetal alcohol syndrome

BACKGROUND

Fetal alcohol syndrome (FAS) is associated with anomalies of the eye ground. The aim of this study was to evaluate the development of fundus morphology in children with FAS from early childhood to adolescence.

METHODS

Funds photographs were evaluated by digital image analysis in 16 children with FAS. Age at the baseline study was between 0.25 and 14 years, and the median follow-up period was 7 years (range: 0.5 to 12). Sixteen sex- and age-matched healthy children were used as controls.

RESULTS

Children with FAS had a smaller optic disc area, lower frequency of excavations, greater tortuosity of retinal vessels, and a smaller number of vascular branching points compared with the controls. There were no significant differences in the funds abnormalities between the first and last examinations.

CONCLUSION

No interval change of retinal funds morphology was found at follow up, suggesting that the ocular abnormalities associated with FAS remain unchanged during childhood.

Ethanol in utero induces epithelial cell damage and altered kinetics in the developing rat intestine

The effect of prenatal ethanol exposure on the intestinal maturation of rat fetuses was investigated to understand the nutritional alterations found in the offspring of alcoholic mothers. Female Wistar rats were maintained on solid diet and 25% ethanol solution as drinking fluid during pregnancy, and non-alcoholic isocaloric pregnant mothers were used as controls. At birth, intestines from unsuckled pups were removed for study. The weight and length of the intestine decreased significantly when ethanol was present in utero. Ultrastructural evaluation of the epithelium revealed loss of contact between neighboring enterocytes and abnormal dilation of the cisternae of the Golgi apparatus in ethanol-exposed pups. Further, increased lysosome-like vesiculation and enhanced lysosomal beta-galactosidase activity was observed in these neonates. The total number of absorptive enterocytes in the epithelium was reduced by 30% in ethanol-exposed neonates as compared to controls, due to altered cell growth and death during fetal life. Ethanol in utero stimulated epithelial cell migration which compensated cell loss, as demonstrated by 5'-Bromodeoxyuridine labeling. These findings could have important implications for the assimilation of nutrients and failure to thrive in infants with fetal alcohol syndrome.

Changes in the enterocyte cytoskeleton in newborn rats exposed to ethanol in utero

BACKGROUND

Cytoskeletal changes after longterm exposure to ethanol have been described in a number of cell types in adult rat and humans. These changes can play a key part in the impairment of nutrient assimilation and postnatal growth retardation after prenatal damage of the intestinal epithelium produced by ethanol intake.

AIMS

To determine, in the newborn rat, which cytoskeletal proteins are affected by longterm ethanol exposure in utero and to what extent.

ANIMALS

The offspring of two experimental groups of female Wistar rats: ethanol treated group receiving up to 25% (w/v) of ethanol in the drinking fluid and control group receiving water as drinking fluid.

METHODS

Single and double electron microscopy immunolocalisation and label density estimation of cytoskeletal proteins on sections of proximal small intestine incubated with monoclonal antibodies against actin, alpha-tubulin, cytokeratin (polypeptides 1, 5, 6, 7, 8, 10, 11, and 18), and with a polyclonal antibody anti-beta 1,4-galactosyl transferase as trans golgi (TG) or trans golgi network (TGN) marker, or both. SDS-PAGE technique was also performed on cytoskeletal enriched fractions from small intestine. Western blotting analysis was carried out by incubation with the same antibodies used for immunolocalisation.

RESULTS

Intestinal epithelium of newborn rats from the ethanol treated group showed an overexpression of cytoskeletal polypeptides ranging from 39 to 54 kDa, affecting actin and some cytokeratins, but not tubulin. Furthermore, a cytokeratin related polypeptide of 28-29 kDa was identified together with an increase in free ubiquitin in the same group. It was noteworthy that actin and cytokeratin were abnormally located in the TG or the TGN, or both.

CONCLUSIONS

Longterm exposure to ethanol in utero causes severe dysfunction in the cytoskeleton of the developing intestinal epithelium. Actin and cytokeratins, which are involved in cytoskeleton anchoring to plasma membrane and cell adhesion, are particularly affected, showing overexpression, impaired proteolysis, and mislocalisation.

Combined pre- and postnatal ethanol exposure alters the development of Bergmann glia in rat cerebellum

The development and maturation of Bergmann glial cells in the rat cerebellum was evaluated on postnatal day 15 by glial fibrillary acidic protein (GFAP) immunocytochemistry, following combined gestational and 10-day postnatal ethanol exposure (a full three trimester human equivalency). GFAP-positive Bergmann glial fibers of lobules I, III, VIb, VII and X of the cerebellar vermis were examined and counted in the molecular layer (ML), the external granular layer (EGL) and the external limiting membrane (ELM). Ethanol exposure reduced: (1) the number of GFAP-positive fibers (per unit length of folia surface) at all three levels; (2) the percentage of mature fibers; and (3) the cross-sectional area in all lobules examined. When data from the five lobules were pooled, there were 7% fewer GFAP-positive fibers in the ML, 15% fewer in the EGL and 20% fewer in the ELM; the percentage of mature fibers was reduced by 16%; and the cross-sectional areas of lobules were reduced by 16%. The altered development of Bergmann glia could be one of the factors causing delayed migration of granular neurons and reductions in the number of granule cells reported in other studies following developmental ethanol exposures and could help to explain some of the motor dysfunctions reported in FAS victims.

Optic nerve hypoplasia: comparative effects in children and rats exposed to alcohol during pregnancy

Children with the fetal alcohol syndrome often have ocular anomalies. These include abnormalities of the eyes and adnexa (strabismus, blepharoptosis, epicanthus), as well as intraocular defects (cataract, glaucoma, persistent hyperplastic primary vitreous, retinal and optic nerve anomalies). Based on the clinical results in an ophthalmological study of a group of Swedish children with the fetal alcohol syndrome, in which optic nerve hypoplasia was found in up to one-half of the group, an experimental study was designed in rats pre- and perinatally exposed to alcohol by means of a liquid diet. The optic nerve was seriously affected. Macroglial cells and optic axons were ultrastructurally damaged. The diameter of the optic nerve cross section, glial cell nuclear area, axonal diameter, and the total number of optic axons showed significantly lower values in the alcohol-exposed group than in the controls. In addition, the retina from the alcohol-exposed animals displayed significantly lower values of the retinal thickness and ganglion cell nuclear volume, as compared to the controls. Thus, rats exposed to alcohol in utero developed hypoplasia of the optic nerve similar to the findings in children born to alcoholic mothers. This strongly supports the hypothesis that prenatal alcohol exposure may adversely affect the development of the optic nerve.