Dose-dependent Degeneration Research Articles

Neomycin-induced deafness in neonatal mice

BackgroundHearing impairment is a rising public health issue, and current therapeutics fail to restore normal auditory sensation. Animal models are essential to a better understanding of the pathophysiology of deafness and developing therapeutics to restore hearing. New MethodsWild-type CBA/CaJ neonatal mice P2–5 were used in this study. Neomycin suspension (500 nl of 50 or 100 mg/ml) was micro-injected into the endolymphatic space. Cochlear morphology was examined 3 and 7 days after injection; hair cell (HC) loss, supporting cell morphology, and neurite denervation pattern were assessed with whole-mounts. At 2 and 4 weeks post-injection, the spiral ganglion neuron (SGN) density was analyzed with cryostat sections. Audiometric responses were measured with auditory brain response (ABR) at 4 weeks. ResultsRapid and complete degeneration of the inner and outer HCs occurred as early as 3 days post-injection. Subsequently, time- and dose-dependent degeneration patterns were observed along the axis of the cochlear membranous labyrinth forming a flat epithelium. Likewise, the SGN histology demonstrated significant cell density reduction at 2 and 4 weeks. The ABR threshold measurements confirmed profound deafness at 4 weeks. Comparison with existing methodsCompared to previously described local and systemic aminoglycoside injections, this method provides a reliable, robust, and rapid deafening model with a single infusion of neomycin in neonatal mice. This model also allows for investigating the effects of inner ear damage during auditory maturation. ConclusionsA single injection of neomycin into the endolymphatic space induces robust HC loss and denervation in neonatal mice.

Dose-Dependent Blood-Feeding Activity and Ovarian Alterations to PM2.5 in Aedes aegypti.

Simple SummaryAedes aegypti (Ae. aegypti) is a mosquito that transmits arboviruses and responds to various biological and environmental stressors, including temperature, rainfall, and humidity. However, there is a lack of knowledge about fine particulate matter (PM2.5) effects on arbovirus vectors. We hypothesized that fine particulate matter (PM2.5) may affect Ae. aegypti blood-feeding rate and organs. We set up an environmental chamber that could adjust the concentration of PM2.5 and observed their blood-feeding activity. We observed a dose–response relationship between PM2.5 level and blood-feeding rate in adult female Ae. aegypti mosquitoes. In addition, histopathological study showed some changes in the ovaries. Vacuolated or vacuolar degeneration characterized by a formation of non-lipid small droplets in the cytoplasm was observed. This demonstrated the degenerative stage of the cells before developing hydropic degeneration or another advanced stage of cellular damage. The present study explored the effects of PM2.5 exposure on the blood-feeding rate and organ integrity in the major arboviral vector Ae. Aegypti, providing information on the potential but indirect operational impact of PM2.5 exposure on the survival and transmission capabilities of this major vector. Our findings may contribute towards the conceptualization and implementation of mosquito control measures with due consideration of the effects of ambient PM2.5 on their populations.High levels of fine particulate matter (PM2.5) air pollution are a concern for human health. Several studies have examined the effects of air pollution on human and animal health. However, there is a lack of knowledge about its effects on arbovirus vectors. Thus, we investigated whether PM2.5 concentration alters the blood-feeding activity of Ae. aegypti mosquitoes. We investigated the effect on the females’ propensity to blood feed at eight concentrations of PM2.5 ranging from 100 to 1000 μg/m3. Correlation analysis showed blood-feeding activity had a significant strong negative correlation with concentration of PM2.5 (rp = −0.85; p ≤ 0.00001). Exploratory linear and non-linear models showed an exponential decay relationship was the best fitting model (corrected Akaike’s information criterion, 193.0; Akaike’s weight, 0.766; adjusted R2, 0.780). Ultrastructural study demonstrated PM2.5 did not obstruct the respiratory system, but some fine particles were present on the antenna and abdominal body parts. Ovaries showed a dose–response relationship between PM2.5 level and vacuolated degeneration. In conclusion, the blood-feeding behavior of Ae. aegypti females may have an exponential decay relationship with PM2.5 level, and their ovaries may demonstrate dose-dependent degeneration. These findings may be important in understanding the vector’s biology and disease transmission in settings with high PM2.5 levels. These results are important to understand blood-feeding and feeding pattern of mosquitoes during PM2.5 pollution, which is important for disease transmission and vector control.

TRPV4 disrupts mitochondrial transport and causes axonal degeneration via a CaMKII-dependent elevation of intracellular Ca2+

The cation channel transient receptor potential vanilloid 4 (TRPV4) is one of the few identified ion channels that can directly cause inherited neurodegeneration syndromes, but the molecular mechanisms are unknown. Here, we show that in vivo expression of a neuropathy-causing TRPV4 mutant (TRPV4R269C) causes dose-dependent neuronal dysfunction and axonal degeneration, which are rescued by genetic or pharmacological blockade of TRPV4 channel activity. TRPV4R269C triggers increased intracellular Ca2+ through a Ca2+/calmodulin-dependent protein kinase II (CaMKII)-mediated mechanism, and CaMKII inhibition prevents both increased intracellular Ca2+ and neurotoxicity in Drosophila and cultured primary mouse neurons. Importantly, TRPV4 activity impairs axonal mitochondrial transport, and TRPV4-mediated neurotoxicity is modulated by the Ca2+-binding mitochondrial GTPase Miro. Our data highlight an integral role for CaMKII in neuronal TRPV4-associated Ca2+ responses, the importance of tightly regulated Ca2+ dynamics for mitochondrial axonal transport, and the therapeutic promise of TRPV4 antagonists for patients with TRPV4-related neurodegenerative diseases.

Arsenic induces transgenerational behavior disorders in Caenorhabditis elegans and its underlying mechanisms

The present study aimed to identify the effects of arsenic on behaviors in Caenorhabditis elegans (C. elegans) and the transgenerational effects. The synchronized C. elegans (P generation) were exposed to 0, 0.2, 1.0, and 5.0 mM NaAsO2 and the subsequent generations (F1 and F2) were maintained on fresh nematode growth medium (NGM). The behaviors and growth were recorded at 0, 12, 24, 36, 48, 60, and 72 h post synchronization. The results demonstrated that arsenic affected various indicators regarding the behavior (head thrash, body bend, movement speed, wavelength, amplitude and so on) and in general the effects started to accumulate from 24 h and lasted throughout the exposure. The behavior impairments were transgenerational with varying patterns, amongst the head thrash and body bend responded most sensitively though the responses gradually declined across generations. Arsenic exposure inhibited the growth (body length, body width, and body area) in P C. elegans from 24 h to 60 h, however there was no difference between treatments groups and the control at 72 h. Arsenic led to a dose-dependent degeneration of dopaminergic neurons in C. elegans, and inhibition of BAS-1 and CAT-2 expressions. The expressions of GCS-1, GSS-1, and SKN-1 were induced by arsenic exposure. Overall, chronic arsenic exposure impaired the behaviors and there were transgenerational effects. The head thrash and body bend responded most sensitively. Arsenic induced behavioral disorders might be attributed to degeneration of dopaminergic neurons which was associated with oxidative stress.

Rabbit Model of Intra-Arterial Chemotherapy Toxicity Demonstrates Retinopathy and Vasculopathy Related to Drug and Dose, Not Procedure or Approach.

PurposeTo use our intra-arterial chemotherapy (IAC) rabbit model to assess the impact of IAC procedure, drug, dose, and choice of technique on ocular structure and function, to study the nature and etiology of IAC toxicity, and to compare to observations in patients.MethodsRabbits received IAC melphalan (0.4-0.8 mg/kg), carboplatin (25–50 mg), or saline, either by direct ophthalmic artery cannulation, or with a technique emulating nonocclusion. Ocular structure/function were assessed with examination, electroretinography (ERG), fundus photography, fluorescein angiography, optical coherence tomography (OCT), and OCT angiography, prior to and 5 to 6 weeks after IAC. Blood counts were obtained weekly. We reviewed our last 50 IAC treatments in patients for evidence of ocular or systemic complications.ResultsNo toxicity was seen in the saline control group. With standard (0.4 mg/kg) melphalan, no vascular/microvascular abnormalities were seen with either technique. However, severe microvascular pruning and arteriolar occlusions were seen occasionally at 0.8 mg/kg doses. ERG reductions were dose-dependent. Histology showed melphalan dose-dependent degeneration in all retinal layers, restricted geographically to areas of greatest vascular density. Carboplatin caused massive edema of ocular/periocular structures. IAC patients experienced occasional periocular swelling/rash, and only rarely experienced retinopathy or vascular events/hemorrhage in eyes treated multiple times with triple (melphalan/carboplatin/topotecan) therapy. Transient neutropenia occurred after 46% of IAC procedures, generally after triple therapy.ConclusionsIAC toxicity appears to be related to the specific drug being used and is dose-dependent, rather than related to the IAC procedure itself or the specific technique selected. These rabbit findings are corroborated by our clinical findings in patients.

Ablation of the riboflavin-binding protein retbindin reduces flavin levels and leads to progressive and dose-dependent degeneration of rods and cones

The interface between the neural retina and the retinal pigment epithelium (RPE) is critical for several processes, including visual pigment regeneration and retinal attachment to the RPE. One of its most important functions is the exchange of metabolites between the photoreceptors and RPE because photoreceptor cells have very high energy demands, largely satisfied by oxidative metabolism. The riboflavin (RF) cofactors, flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN), are two key cofactors involved in oxidative metabolism. We have previously shown that retbindin is a photoreceptor-specific RF-binding protein exclusively expressed in the rods and present in the interphotoreceptor matrix at the interface between the RPE and photoreceptor outer segments. Here, we show that retbindin ablation in mice causes a retinal phenotype characterized by time- and dose-dependent declines in rod and cone photoreceptor functions as early as 120 days of age. Whereas minor retinal ultrastructural defects were observed at all ages examined, a significant decline occurred in photoreceptor nuclei at 240 days of age (∼36.8% rods and ∼19.9% cones). Interestingly, significant reductions in FAD and FMN levels were observed before the onset of degeneration (∼46.1% FAD and ∼45% FMN). These findings suggest that the reduced levels of these flavins result in the disruption of intracellular mechanisms, leading to photoreceptor cell death. Altogether, our results suggest that retbindin is a key player in the acquisition and retention of flavins in the neural retina, warranting future investigation into retbindin's role in photoreceptor cell death in models of retinal degenerative disorders.

The effect of chronic kisspeptin administration on seminal fructose levels in male mice

The discovery that kisspeptin was critical for normal fertility in all mammalian species including humans, ushered in a new chapter in our understanding of the control of GnRH secretion. Kisspeptin, the product of the KISS1 gene, plays an essential role in the regulation of spermatogenesis acting primarily at the hypothalamic level of the gonadotropic axis. Among the many identified substances in human semen, fructose is becoming increasingly significant. Fructose is synthesized and secreted by the seminal vesicles. Its synthesis is regulated by androgens and it is correlated directly with the levels of testosterone. Dose dependent degeneration of seminal vesicle has been described following intraperitoneal kisspeptin treatment; however, effects of kisspeptin administration on the levels of seminal fructose remain elusive till date. The present study, therefore, addresses the effects of 12-day administration of kisspeptin on seminal fructose levels in male mice. Kisspeptin-10 was administered intraperitoneally at different dosage concentrations (1 μg, 1 ng, and 10 ρg) to adult male mice, twice daily for 12 days. Seminal fructose levels were studied photometrically after 12 days of treatment. At the end of the treatment, seminal fructose levels decreased significantly after all tested doses. Chronic intermittent kisspeptin-10 administration negatively regulates seminal fructose levels in adult male mice.

Toxicological studies of zinc oxide nanomaterials in rats

In this study, we have evaluated the ability of zinc oxide (ZnO) nanoparticles to induce pulmonary and extrapulmonary toxicities was examined in rats following intratracheal (IT) instillation. Lungs of rats were instilled IT with either phosphate-buffered saline (PBS) + 1% Tween 80, ZnO nanoparticles, carbonyl iron or quartz particles at a dose of 1 or 5 mg kg−1 body weight. Following exposure, bronchoalveolar lavage (BAL) fluid, blood samples and organs including lung, liver, kidneys, heart, pancreas, and brain were collected at 24 h, 1 week, or 1 month of post instillation of nanoparticles and different parameters estimated to assess toxicity. BAL fluid was analyzed for lactate dehydrogenase (LDH) and alkaline phosphatase (ALP) to assess pulmonary toxicity. Exposures to ZnO or quartz particles produced transient dose-dependant increase in BAL fluid LDH and ALP activities at all post exposure periods. Blood samples were analyzed for the tissue damage biomarkers to assess extrapulmonary toxicity. Histopathological examination of lung, liver and kidneys revealed dose-dependent degeneration and necrosis which worsened at 1 week post-instillation periods but recovered at 1 month post instillation. Histopathological examination of rat pancreas, heart, and brain exposed to quartz or ZnO particles showed no marked changes. Data suggest the instillation of ZnO nanoparticles produced a greater pulmonary toxicity in rats comparable with quartz; and extrapulmonary toxicities of these ZnO nanoparticles might be due to translocation into liver and kidney.

Changes in some biochemical parameters of kidney functions of Plasmodium berghei infected rats administered with some doses of artemether

+) and potassium (K + ) of Plasmodium berghei infected rats during a week of intramuscular administration of artemether (12.5 to 50.0 mg/kg/day) and one week thereafter. Their concentrations and that of creatinine and urea in the plasma were also determined at the end of the study. The observed changes were related to the effects of artemether on the kidneys of the rats. The urine levels of the two electrolytes decreased significantly during treatment (P<0.05). One week post-treatment with 12.5 mg/kg of artemether, the urine concentrations of the electrolytes increased to values that were not significantly different from that of day 0. At 25 and 50 mg/kg, their urine concentrations still remained significantly lower than day 0 values (P<0.05). Plasma concentrations of the electrolytes one week post-treatment increased, but they were only significant at 25 mg/kg for K + . A significant increase in the plasma level of creatinine was observed at all the doses of the drug at one week post-treatment. A dose-dependent degeneration of the renal tissue of all the experimental rats was also observed. We concluded that high doses of artemether caused progressive degeneration of the renal tissue of P. berghei infected rats.

Histological Alteration of the Cerebellum of Adult Male Wistar Rat Treated with the Grapefruit Extract (Citrus paradisi)

Background: There are several beneficial effects of grapefruit (Citrus paradisi) in scientific literature, coupled with nutritional uses as an excellent source of many nutrients and photochemicals; able to contribute to a healthy diet. Studies have shown that grapefruit helps lowered cholesterol and there is evidence that the seeds have high level of antioxidant properties. Histological study of the effects of oral administration of extract of grape fruit juice on the cerebellum of adult male Wistar rats was therefore studied. Methods: The rats (n=20), weighing between 160 g-225 g were divided into four group (A, B, C and D), with each group consisting five rats. Groups A, B and C were the experimental groups and group D was the control group. The rats in the experimental groups received different doses of grape fruit juice extract orally, using a cannula for fourteen days. Group A received 0.6 ml/gBW/day of grapefruit juice, Group B received 0.8 ml/gBW/day of grapefruit juice and group C received 1.0 ml/gBW/day of grapefruit juice. Group D (control group) received equal volume of distilled water without the extract grapefruit juice added. The rats were sacrificed on day fifteen of the experiment. Cerebellum was carefully dissected out and quickly fixed in 10% formal saline for routine histological studies using H/E stain. Results: The histological findings indicated that the treated sections of the cerebellum showed a dose dependent cellular degeneration of the granular layer and atrophic changes in the Purkinje cells of the Purkinje layer. Conclusions: This research work indicates that grapefruit juice consumption at higher dose may probably has adverse effects on the Purkinje and granule cells of the cerebellum.

Caspase-3-independent photoreceptor degeneration by N-methyl-N-nitrosourea (MNU) induces morphological and functional changes in the mouse retina

Retinal degeneration is followed by significant changes in the structure and function of photoreceptors in humans and several genetic animal models. However, it is not clear whether similar changes occur when the degeneration is induced pharmacologically. Therefore, our aim was to investigate the influence of retinotoxic N-methyl-N-nitrosourea (MNU) on the function, morphology and underlying molecular pathways of programmed cell death. C57/BL6 mice were injected with different doses of MNU, and function was determined by analysing optokinetic reflex measurements and cued water maze results at several time points post-injection. Morphometric measurements were also taken from H&E-stained paraffin eye sections. TUNEL-positive cells and caspase-3 and -6 were detected by immunohistochemistry. To assess the molecular changes leading to cell death, qRT-PCR from neurosensory retina mRNA was performed. The application of MNU led to an instant decrease in function and a delayed decrease in the thickness of the retinal outer nuclear layer. These responses were observed in the absence of any structural changes in the retinal pigment epithelium. The degeneration of the photoreceptor cell layer was highest with 60mg/kg MNU. The assessment of TUNEL-positive cells visualised cell death after treatment, but no detectable caspase-3 activity was observed concomitant with these changes. qRT-PCR revealed the possible involvement of the inflammatory mediator caspase-1 and endoplasmic reticulum stress-mediated apoptosis by caspase-12. MNU leads to the dose-dependent degeneration of photoreceptor cells in mice by caspase-3-independent pathways and is, therefore, a suitable model to study retinal degeneration in an animal model.

Kainic acid-induced neurodegeneration and activation of inflammatory processes in organotypic hippocampal slice cultures: Treatment with cyclooxygenase-2 inhibitor does not prevent neuronal death

In the postnatal rodent hippocampus status epilepticus (SE) leads to age- and region-specific excitotoxic neuronal damage, the precise mechanisms of which are still incompletely known. Recent studies suggest that the activation of inflammatory responses together with glial cell reactivity highly contribute to excitotoxic neuronal damage. However, pharmacological tools to attenuate their activation in the postnatal brain are still poorly elucidated. In this study, we investigated the role of inflammatory mediators in kainic acid (KA)-induced neuronal damage in organotypic hippocampal slice cultures (OHCs). A specific cyclooxygenase-2 (COX-2) inhibitor N-[2-(cyclohexyloxy)-4-nitrophenyl]-methanesulfonamide (NS-398) was used to study whether or not it could ameliorate neuronal death. Our results show that KA treatment (24 h) resulted in a dose-dependent degeneration of CA3a/b pyramidal neurons. Furthermore, COX-2 immunoreactivity was pronouncedly enhanced particularly in CA3c pyramidal neurons, microglial and astrocyte morphology changed from a resting to active appearance, the expression of the microglial specific protein, Iba1, increased, and prostaglandin E 2 (PGE 2) production increased. These indicated the activation of inflammatory processes. However, the expression of neither proinflammatory cytokines, i.e. tumour necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β), nor the anti-inflammatory cytokine IL-10 mRNA was significantly altered by KA treatment as studied by real-time PCR. Despite activation of an array of inflammatory processes, neuronal damage could not be rescued either with the combined pre- and co-treatment with a specific COX-2 inhibitor, NS-398. Our results suggest that KA induces activation of a repertoire of inflammatory processes in immature OHCs, and that the timing of anti-inflammatory treatment to achieve neuroprotection is a challenge due to developmental properties and the complexity of inflammatory processes activated by noxious stimuli. This article is part of a Special Issue entitled ‘Trends in Neuropharmacology: In Memory of Erminio Costa’.

TDP-43 transgenic mice develop spastic paralysis and neuronal inclusions characteristic of ALS and frontotemporal lobar degeneration

Neuronal cytoplasmic and intranuclear aggregates of RNA-binding protein TDP-43 are a hallmark feature of neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). ALS and FTLD show a considerable clinical and pathological overlap and occur as both familial and sporadic forms. Though missense mutations in TDP-43 cause rare forms of familial ALS, it is not yet known whether this is due to loss of TDP-43 function or gain of aberrant function. Moreover, the role of wild-type (WT) TDP-43, associated with the majority of familial and sporadic ALS/FTLD patients, is also currently unknown. Generating homozygous and hemizygous WT human TDP-43 transgenic mouse lines, we show here a dose-dependent degeneration of cortical and spinal motor neurons and development of spastic quadriplegia reminiscent of ALS. A dose-dependent degeneration of nonmotor cortical and subcortical neurons characteristic of FTLD was also observed. Neurons in the affected spinal cord and brain regions showed accumulation of TDP-43 nuclear and cytoplasmic aggregates that were both ubiquitinated and phosphorylated as observed in ALS/FTLD patients. Moreover, the characteristic approximately 25-kDa C-terminal fragments (CTFs) were also recovered from nuclear fractions and correlated with disease development and progression in WT TDP-43 mice. These findings suggest that approximately 25-kDa TDP-43 CTFs are noxious to neurons by a gain of aberrant nuclear function.

Striatal Alterations of Secretogranin-1, Somatostatin, Prodynorphin, and Cholecystokinin Peptides in an Experimental Mouse Model of Parkinson Disease

The principal causative pathology of Parkinson disease is the progressive degeneration of dopaminergic neurons in the substantia nigra pars compacta projecting to the striatum in the brain. The information regarding the expression of neuropeptides in parkinsonism is very limited. Here we have elucidated striatal neuropeptide mechanisms in experimental parkinsonism using the unilateral 6-hydroxydopamine model to degenerate dopamine neurons. A thoroughly controlled sample preparation technique together with a peptidomics approach and targeted neuropeptide sequence collections enabled sensitive detection, identification, and relative quantitation of a great number of endogenous neuropeptides. Previously not recognized alterations in neuropeptide levels were identified in the unilateral lesioned mice with or without subchronic 3,4-dihydroxy-L-phenylalanine administration, the conventional treatment of Parkinson disease. Several of these peptides originated from the same precursor such as secretogranin-1, somatostatin, prodynorphin, and cholecystokinin. Disease-related biotransformation of precursors into individual peptides was observed in the experimental model of Parkinson disease. Several previously unreported potentially biologically active peptides were also identified from the striatal samples. This study provides further evidence that neuropeptides take part in mediating the central nervous system failure associated with Parkinson disease.

P53 Mediates Nontranscriptional Cell Death in Dopaminergic Cells in Response to Proteasome Inhibition

Proteasome dysfunction has been demonstrated in Parkinson disease (PD), and proteasome inhibitors have been shown to induce degeneration of dopaminergic neurons in vitro and in vivo. The mechanism whereby proteasome dysfunction leads to dopaminergic cell death, however, is unknown. In this study, we show that proteasome inhibition in both PC12 cells and dopaminergic neurons derived from embryonic stem cells is associated with mitochondrial membrane permeabilization, activation of caspase-3, and nuclear changes consistent with apoptosis. Prior to the emergence of apoptotic features, we found that proteasome inhibition induced increased levels of phosphorylated p53. Inhibition of p53 by pifithrin-alpha or by RNA interference prevented mitochondrial membrane permeabilization and cytotoxicity. There was no increase in p53 mRNA in proteasome-inhibited cells, suggesting that p53 was increased in a transcription-independent manner. Further, there was no increase in Puma or Bax mRNA and p53 co-immunoprecipitated with Bcl-xL and Mdm2. These findings suggest that p53 mediates cell death by way of a direct mitochondrial effect in this model. We also observed increased levels of phosphorylated p53 in dopamine neurons of the substantia nigra pars compacta of mice following systemic administration of a proteasome inhibitor. These changes preceded degeneration of dopaminergic neurons. Increased phosphorylated p53 was also demonstrated in the substantia nigra pars compacta of post-mortem PD brains. These results suggest that abnormalities in p53 signaling play a role in dopaminergic cell death induced by proteasome inhibition and may be relevant to neurodegeneration in PD.

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 μl 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 °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.

Parkinson??s disease-like syndrome in rats induced by 2,9-dimethyl-??-carbolinium ion, a ??-carboline occurring in the human brain

Regarding the pathogenesis of Parkinson's disease, a neurotoxin hypothesis was proposed following the discovery that 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) produces a Parkinson-like syndrome in humans and primates. Since then, researchers have searched for endogenous and exogenous compounds that are structurally similar to this neurotoxin. Such compounds include beta-carbolines, formed from tryptophan and its derivatives. beta-carbolines are present naturally in the human brain and cerebrospinal fluid. The present study examined the effect of bilateral, intranigral administration of 2,9-dimethyl-beta-carbolinium ion on muscle tone, electromyographic activity, dopamine metabolism in the striatum, and the number of tyrosine hydroxylase-immunoreactive neurons and volume of the substantia nigra in rats. We found that the beta-carbolinium ion (15 or 40 nmol per side) caused a significant decrease in the striatal levels of dopamine and its metabolites, which was accompanied by an enhancement of muscle tone and electromyographic activity. Stereological counting revealed that the beta-carbolinium caused a significant decrease in the total number of tyrosine hydroxylase-immunoreactive neurons and shrinkage of the substantia nigra. The findings suggest that the methylated beta-carbolinium ion produces a dose-dependent degeneration of nigrostriatal neurons, leading to deficits in dopaminergic neurotransmission and an increase of muscle resistance and electromyographic activity, a syndrome equivalent to muscle rigidity in Parkinson's disease.

Acute vigabatrin retinotoxicity in albino rats depends on light but not GABA.

Vigabatrin (VGB) is an irreversible inhibitor of gamma-aminobutyric acid (GABA) transaminase. Its use as an antiepileptic drug (AED) has been limited because it causes retinal dysfunction, leading to visual field defects (VFDs). We performed this study to identify factors contributing to acute VGB retinotoxicity. In ex vivo experiments, Sprague-Dawley rat retinas were isolated and incubated with VGB or GABA in the presence or absence of light. In in vivo experiments, Sprague-Dawley rats were given intraperitoneal injections of VGB and then exposed to light or kept in the dark. The retinas were analyzed histologically by using both light and electron microscopy. Incubating retinas with 50-500 microM VGB under 20,000 Lux white light for < or = 20 h caused a characteristic time- and dose-dependent degeneration limited to the outer retina. Incubating retinas with 500 microM VGB in darkness for 20 h caused no damage. Five hundred micromolar GABA and 50 microM tiagabine were not toxic in the presence or absence of light. Sprague-Dawley rats exposed to an intense white light for 20 h after a 1,000-mg/kg intraperitoneal injection of VGB showed damage in the outer retina, whereas those kept in the dark did not. Direct exposure of the retina to VGB causes acute retinotoxicity that depends on light exposure rather than GABA accumulation.

Glomerular calcification induced by bolus injection with dibasic sodium phosphate solution in Sprague-Dawley rats.

To elucidate the nephrotoxicity of phosphate, dibasic sodium phosphate solution was given to Sprague-Dawley rats by daily bolus intravenous administration at concentrations of 0, 1, 25, 250, or 360 mM (0, 1, 28, 284, or 408 mg/kg Na2HPO4) for 14 days, and the kidneys were pathologically examined. There were no remarkable changes in blood chemistry values; however, urinalysis revealed mild to moderate proteinuria in the 250 and 360 mM groups. The kidneys from the 360 mM group were macroscopically pale. Histopathology revealed panglomerular deposition of basophilic dense granules, which were positive for von Kossa's staining, accompanied by dose-dependent degeneration of the glomerular epithelium and parietal epithelium in the 250 and 360 mM groups. Electron microscopic examination showed fusion of podocytes and increased microvilli, with large amounts of debris in the Bowman's space. Low-density lamellar structures were present not only in the glomerular epithelium, basement membrane, mesangial matrix and parietal epithelium but also within the Bowman's space depending on the severity of the glomerular lesion. Phosphorus and calcium were detected by X-ray microanalysis as fine particles admixed with lamellar structures. These results suggest that high-dose phosphate used in this study transiently overloads the glomerular epithelium during filtration through glomerular capillaries and produces insoluble calcium salt and glomerular lesions, resulting in proteinuria.

Proteasome inhibition causes nigral degeneration with inclusion bodies in rats

Structural and functional defects in 26/20S proteasomes occur in the substantia nigra pars compacta and may underlie protein accumulation, Lewy body formation and dopaminergic neuronal death in Parkinson's disease. We therefore determined the pathogenicity of proteasomal impairment following stereotaxic unilateral infusion of lactacystin, a selective proteasome inhibitor, into the substantia nigra pars compacta of rats. These animals became progressively bradykinetic, adopted a stooped posture and displayed contralateral head tilting. Administration of apomorphine to lactacystin-treated rats reversed behavioral abnormalities and induced contralateral rotations. Lactacystin caused dose-dependent degeneration of dopaminergic cell bodies and processes with the cytoplasmic accumulation and aggregation of alpha-synuclein to form inclusion bodies. These findings support the notion that failure of the ubiquitin-proteasome system to degrade and clear unwanted proteins is an important etiopathogenic factor in Parkinson's disease.