Cancer therapy and risk of congenital malformations in children fathered by men treated for testicular germ-cell cancer: A nationwide register study

BACKGROUND

Because of the potential mutagenic effects of chemo- and radiotherapy, there is concern regarding increased risk of congenital malformations (CMs) among children of fathers with cancer. Previous register studies indicate increased CM risk among children conceived after paternal cancer but lack data on oncological treatment. Increased CM risk was recently reported in children born before paternal cancer. This study aims to investigate whether anti-neoplastic treatment for testicular germ-cell cancer (TGCC) implies additional CM risk.

METHODS AND FINDINGS

In this nationwide register study, all singletons born in Sweden 1994-2014 (n = 2,027,997) were included. Paternal TGCC diagnoses (n = 2,380), anti-neoplastic treatment, and offspring CMs were gathered from the Swedish Norwegian Testicular Cancer Group (SWENOTECA) and the Swedish Medical Birth Register. Children were grouped based on +/- paternal TGCC; treatment regimen: surveillance (n = 1,340), chemotherapy (n = 2,533), or radiotherapy (n = 360); and according to time of conception: pre- (n = 2,770) or post-treatment (n = 1,437). Odds ratios (ORs) for CMs were calculated using logistic regression with adjustment for parental ages, maternal body mass index (BMI), and maternal smoking. Children conceived before a specific treatment acted as reference for children conceived after the same treatment. Among children fathered by men with TGCC (n = 4,207), 184 had a CM. The risk of malformations was higher among children of fathers with TGCC compared with children fathered by men without TGCC (OR 1.28, 95% confidence interval [CI] 1.19-1.38, p = 0.001, 4.4% versus 3.5%). However, no additional risk increase was associated with oncological treatment when comparing post-treatment-to pretreatment-conceived children (chemotherapy, OR = 0.82, 95% CI 0.54-1.25, p = 0.37, 4.1% versus 4.6%; radiotherapy, OR = 1.01, 95% CI 0.25-4.12, p = 0.98, 3.2% versus 3.0%). Study limitations include lack of data on use of cryopreserved or donor sperm and on seminoma patients for the period 1995-2000-both tending to decrease the difference between the groups with TGCC and without TGCC. Furthermore, the power of analyses on chemotherapy intensity and radiotherapy was limited.

CONCLUSIONS

No additional increased risk of CMs was observed in children of men with TGCC treated with radio- or chemotherapy. However, paternal TGCC per se was associated with modestly increased risk for offspring malformations. Clinically, this information can reassure concerned patients.

MRI-guided intracerebral convection-enhanced injection of gliotoxins to induce focal demyelination in swine

Demyelinating disorders such as multiple sclerosis (MS) or transverse myelitis are devastating neurological conditions with no effective cure. Prevention of myelin loss or restoration of myelin are key for successful therapy. To investigate the disease and develop cures animal models with good clinical relevance are essential. The goal of the current study was to establish a model of focal demyelination in the brain of domestic pig using MRI-guided gliotoxin delivery. The rationale for developing a new myelin disease model in the domestic pig was based on the fact that the brain in pigs is anatomically and histologically much more similar to that of humans compared to the rodent brain. For MRI-assisted gliotoxin injection, eight 30 kg pigs were subjected to treatment with lysolecithin (20, 30 mg/ml); or with ethidium bromide (0.0125, 0.05, 0.2 mg/ml). Animals were placed in an MRI scanner for intraparenchymal targeting of gliotoxin into the corona radiata (250 μl over 1h), with real-time monitoring of toxin distribution on T1 scans and monitoring of lesion evolution over seven days using both T1 and T2 scans. After the last MRI, animals were transcardially perfused and brains were processed for histological and immunofluorescent analysis. Gadolinium-enhanced T1 MRI during injection demonstrated biodistribution of the contrast (as a surrogate marker for toxin distribution) and its diffusion through the brain parenchyma. Lesion induction was confirmed on T2-weighted MRI and histopathology, thus enabling the establishment of optimal doses of gliotoxins. To conclude, MRI-guided focal demyelination in swine is accurate and provides real-time confirmation of gliotoxin, thus facilitating placement of focal lesions with high precision. This new model of focal demyelination can be used for further investigation and development of novel therapeutic approaches.

Teratogenic effect of Carbamazepine use during pregnancy in the mice

Carbamazepine use is the first choice of antiepileptic drugs among epileptic pregnant females. There are many inconclusive studies regard the safety of carbamazepine use during pregnancy. This study aims to investigate the morphological and histopathological teratogenic effects of carbamazepine use during pregnancy. The healthy pregnant females mice divided into equal five groups (each n=20). The first (control) group received distilled water/day. Second, third, fourth and fifth group received 8.75, 22.75, 52.5, 65 mg of carbamazepine/day respectively. Carbamazepine and water were given by gastric gavage throughout gestational period. Fetuses were delivered on the 18th day of gestation by hysterectomy. Fetal measurements and appearance were assessed with investigation the histopathological changes of brain and spinal cord. There was a significant decrease of weight, different organs weight, length, upper and lower limb length of mice in the first day of delivery in fifth group. There was a significant increase of weight, different organs weight, length, upper and lower limb length in the third group. Many congenital anomalies such as spina bifida, meromelia, microphalmia, oligodactyly, anencephaly, neurodegeneration of brain and spinal cord were noticedin fifth group. Teratogenic effect of carbamazepine represented as growth retardation and neurodevelopmental toxicity depending on its overdose degree.

Comment: valproate dose effects differ across congenital malformations

Fetal valproate exposure has been associated with the highest risk of congenital malformations among antiepileptic drugs.(1) Valproate's effect is dose-dependent(1) and has been associated with multiple specific malformations.(2,3) Vadja et al.(4) examined data from the Australian Pregnancy Registry (1999-2012 data), which included 1,705 pregnancies with 436 valproate exposures.(4) They found that the use and dosages of valproate have fallen over the last 5 years. The rates of spina bifida and hypospadius in those exposed dropped with reducing dosages of valproate, but the rates of other malformations did not. Mean dosages for malformations were higher for spina bifida (2,000 mg/d) and hypospadius (2,417 mg/d) than all other malformations (1,083 mg/d).

Non-occupational exposure to paint fumes during pregnancy and risk of congenital anomalies: a cohort study

BACKGROUND

Occupational exposure to organic solvents during the 1st trimester of pregnancy has been associated with congenital anomalies. Organic solvents are also used in the home environments in paint products, but no study has investigated the effect of such exposure in a general population.

METHODS

We studied associations between residential exposure to paint fumes during the 1st trimester of pregnancy and predefined subgroups of congenital anomalies, using data from the Danish National Birth Cohort (DNBC). During 2001 and 2003, a total of 20,103 pregnant women, enrolled in the DNBC, were interviewed in the 30th week of gestation about the use of paint in their residence during pregnancy. By the end of first trimester, information about smoking habits, alcohol consumption and occupation were collected. Information on congenital anomalies was obtained from national registers. Associations were examined by estimating odds ratios (OR) using logistic regression.

RESULTS

In total 1404 women (7%) had been exposed to paint fumes during the 1st trimester of pregnancy and 1086 children were diagnosed with congenital anomalies; 73 children with congenital anomalies had been exposed to paint fumes in utero. Exposure to paint fumes seemed positively associated with congenital anomalies of the nervous system (OR 2.19, 95% confidence interval (CI) 0.76 to 6.32), ear, face and neck (OR 2.15, 95% CI 0.84 to 5.55) and the renal system (OR 2.16, 95% CI 1.02 to 4.58) after adjustment for maternal age, smoking, alcohol consumption and occupational solvent exposure. Congenital anomalies in the remaining subgroups were not associated with the exposure.

CONCLUSIONS

Our results suggest that in the general population, exposure to paint fumes during the 1st trimester of pregnancy may increase the risk of some types of congenital anomalies, but the findings need to be confirmed.

Neuropathology of the area postrema in sudden intrauterine and infant death syndromes related to tobacco smoke exposure

The area postrema is a densely vascularized small protuberance at the inferoposterior limit of the fourth ventricle, outside of the blood-brain barrier. This structure, besides to induce emetic reflex in the presence of noxious chemical stimulation, has a multifunctional integrative capacity to send major and minor efferents to a variety of brain centers particularly involved in autonomic control of the cardiovascular and respiratory activities. In this study we aimed to focus on the area postrema, which is so far little studied in humans, in a large sample of subjects aged from 25 gestational weeks to 10 postnatal months, who died of unknown (sudden unexplained perinatal and infant deaths) and known causes (controls). Besides we investigated a possible link between alterations of this structure, sudden unexplained fetal and infant deaths and maternal smoking. By the application of morphological and immunohistochemical methods, we observed a significantly high incidence of alterations of the area postrema in fetal and infant victims of sudden death as compared with age-matched controls. These pathological findings, including hypoplasia, lack of vascularization, cystic formations and reactive gliosis, were related to maternal smoking. We hypothesize that components from maternal cigarette smoke, particularly in pregnancy, could affect neurons of the area postrema connected with specific nervous centers involved in the control of vital functions. In conclusion, we suggest that the area postrema should be in depth examined particularly in victims of sudden fetal or infant death with smoker mothers.

Disruption of Sema3A expression causes abnormal neural projection in heavy oil exposed Japanese flounder larvae

It has been well known that oil spills cause serious problems in the aquatic organisms. In particular, some species of teleosts, which develop on the sea surface thought to be affected by heavy oil (HO). During the embryogenesis, the nervous system is constructed. Therefore, it is important to study the toxicological effects of HO on the developing neurons. We exposed HO to eggs of Japanese flounder (Paralichthys olivaceus) and investigated the neural disorder. In larvae exposed by HO at the concentration of 8.75 mg/L, the facial and lateral line nerves partially entered into the incorrect region and the bundle was defasciculated. Furthermore, in the HO-exposed larvae, Sema3A, a kind of axon guidance molecule, was broadly expressed in second pharyngeal arch, a target region of facial nerve. Taken together, we suggested the possibility that the abnormal expression of Sema3A affected by HO exposure causes disruption of facial nerve scaffolding.

Oxidative stress in developmental origins of disease: teratogenesis, neurodevelopmental deficits, and cancer

In the developing embryo and fetus, endogenous or xenobiotic-enhanced formation of reactive oxygen species (ROS) like hydroxyl radicals may adversely alter development by oxidatively damaging cellular lipids, proteins and DNA, and/or by altering signal transduction. The postnatal consequences may include an array of birth defects (teratogenesis), postnatal functional deficits, and diseases. In animal models, the adverse developmental consequences of in utero exposure to agents like thalidomide, methamphetamine, phenytoin, benzo[a]pyrene, and ionizing radiation can be modulated by altering pathways that control the embryonic ROS balance, including enzymes that bioactivate endogenous substrates and xenobiotics to free radical intermediates, antioxidative enzymes that detoxify ROS, and enzymes that repair oxidative DNA damage. ROS-mediated signaling via Ras, nuclear factor kappa B and related transducers also may contribute to altered development. Embryopathies can be reduced by free radical spin trapping agents and antioxidants, and enhanced by glutathione depletion. Further modulatory approaches to evaluate such mechanisms in vivo and/or in embryo culture have included the use of knockout mice, transgenic knock-ins and mutant deficient mice with altered enzyme activities, as well as antisense oligonucleotides, protein therapy with antioxidative enzymes, dietary depletion of essential cofactors and chemical enzyme inhibitors. In a few cases, measures anticipated to be protective have conversely enhanced the risk of adverse developmental outcomes, indicating the complexity of development and need for caution in testing therapeutic strategies in humans. A better understanding of the developmental effects of ROS may provide insights for risk assessment and the reduction of adverse postnatal consequences.

Effects of heavy oil in the developing spotted halibut, Verasper variegatus

It is well known that heavy oil (HO) on the sea surface causes serious problems in the aquatic environment. In particular, some species of teleosts which develop on the sea surface are thought to be affected by the HO which flows out from tankers or coastal industry. However, the toxicological effects of HO are not fully understood. We performed exposure experiments using the Pleuronectiformean fish, spotted halibut (Verasper variegatus), which is an important fishery resource in Japan. In course of the development, HO-exposed embryos showed remarkable delay in developmental processes including somite formation. We further observed abnormal development of the head morphology. Notably, treated embryos had relatively small eyes and craniofacial structures. These findings strongly suggest that HO seriously affects the cell proliferation and differentiation of the embryo. In addition, HO-exposed embryos showed abnormal neuronal development. We also performed the exposure in the larval stage. Treatment of post-hatching larvae with HO resulted in significantly greater mortality compared with controls. Through these observations, we finally conclude that HO is strongly toxic to halibut in their early life stages.

Misoprostol and pregnancy: risk of malformations

(1) Misoprostol, a synthetic prostaglandin E1 analogue, is used to treat gastric and duodenal ulcers, and, in combination with mifepristone, for medical abortion. (2) The French and American summaries of product characteristics, based on data submitted to the relevant regulatory agencies, mention no teratogenicity in animals. However, some studies showed malformations in rats and rabbits. (3) Severe malformations have been reported in countries where misoprostol is frequently used for abortion without medical supervision despite its poor efficacy when used alone. The malformations included cranial nerve defects (especially pairs 6 and 7, characteristic of the Möbius syndrome) and various limb abnormalities. (4) Malformations, including one case of Möbius syndrome, have been reported in France after medically supervised use of misoprostol. (5) In practice, when a patient wishes to continue a pregnancy after a failed attempt at drug-induced abortion, she needs to be informed of the risk to her unborn child. Cranial nerve defects are rarely detectable by sonography, however thorough. In addition, misoprostol has a negative risk-benefit balance in the prevention or treatment of gastro-duodenal ulcers in young women.

Autism: transient in utero hypothyroxinemia related to maternal flavonoid ingestion during pregnancy and to other environmental antithyroid agents

The incidence and prevalence of autism have increased during the past two decades. Despite comprehensive genetic studies the cause of autism remains unknown. This review emphasizes the potential importance of environmental factors in its causation. Alterations of cortical neuronal migration and cerebellar Purkinje cells have been observed in autism. Neuronal migration, via reelin regulation, requires triiodothyronine (T3) produced by deiodination of thyroxine (T4) by fetal brain deiodinases. Experimental animal models have shown that transient intrauterine deficits of thyroid hormones (as brief as 3 days) result in permanent alterations of cerebral cortical architecture reminiscent of those observed in brains of patients with autism. I postulate that early maternal hypothyroxinemia resulting in low T3 in the fetal brain during the period of neuronal cell migration (weeks 8-12 of pregnancy) may produce morphological brain changes leading to autism. Insufficient dietary iodine intake and a number of environmental antithyroid and goitrogenic agents can affect maternal thyroid function during pregnancy. The most common causes could include inhibition of deiodinases D2 or D3 from maternal ingestion of dietary flavonoids or from antithyroid environmental contaminants. Some plant isoflavonoids have profound effects on thyroid hormones and on the hypothalamus-pituitary axis. Genistein and daidzein from soy (Glycine max) inhibit thyroperoxidase that catalyzes iodination and thyroid hormone biosynthesis. Other plants with hypothyroid effects include pearl millet (Pennisetum glaucum) and fonio millet (Digitaria exilis); thiocyanate is found in Brassicae plants including cabbage, cauliflower, kale, rutabaga, and kohlrabi, as well as in tropical plants such as cassava, lima beans, linseed, bamboo shoots, and sweet potatoes. Tobacco smoke is also a source of thiocyanate. Environmental contaminants interfere with thyroid function including 60% of all herbicides, in particular 2,4-dichlorophenoxyacetic acid (2,4-D), acetochlor, aminotriazole, amitrole, bromoxynil, pendamethalin, mancozeb, and thioureas. Other antithyroid agents include polychlorinated biphenyls (PCBs), perchlorates, mercury, and coal derivatives such as resorcinol, phthalates, and anthracenes. A leading ecological study in Texas has correlated higher rates of autism in school districts affected by large environmental releases of mercury from industrial sources. Mercury is a well known antithyroid substance causing inhibition of deiodinases and thyroid peroxidase. The current surge of autism could be related to transient maternal hypothyroxinemia resulting from dietary and/or environmental exposure to antithyroid agents. Additional multidisciplinary epidemiological studies will be required to confirm this environmental hypothesis of autism.

The size and distribution of midbrain dopaminergic populations are permanently altered by perinatal glucocorticoid exposure in a sex- region- and time-specific manner

Central dopaminergic (DA) systems appear to be particularly vulnerable to disruption by exposure to stressors in early life, but the underlying mechanisms are poorly understood. As endogenous glucocorticoids (GCs) are implicated in other aspects of neurobiological programming, this study aimed to characterize the effects of perinatal GC exposure on the cytoarchitecture of DA populations in the substantia nigra pars compacta (SNc) and the ventral tegmental area (VTA). Dexamethasone was administered non-invasively to rat pups via the mothers' drinking water during embryonic days 16-19 or postnatal days 1-7, with a total oral intake circa 0.075 or 0.15 mg/kg/day, respectively; controls received normal drinking water. Analysis of tyrosine hydroxylase-immunoreactive cell counts and regional volumes in adult offspring identified notable sex differences in the shape and volume of the SNc and VTA, as well as the topographical organization and size of the DA populations. Perinatal GC treatments increased the DA population size and altered the shape of the SNc and VTA as well as the organization of the DA neurons by expanding and/or shifting them in a caudal direction. This response was sexually dimorphic and included a feminization or demasculinization of the three-dimensional cytoarchitecture in males, and subtle differences that were dependent on the window of exposure. These findings demonstrate that inappropriate perinatal exposure to GCs have enduring effects on the organization of midbrain DA systems that are critically important for normal brain function throughout life.

Prenatal exposure to bisphenol A affects adult murine neocortical structure

Prenatal exposure to low-doses of bisphenol A (BPA) has been shown to affect murine neocortical development by accelerating neuronal differentiation/migration through disrupting thyroid hormone function. We therefore studied whether prenatal exposure to low-doses of BPA affected organization of adult neocortical structures. Pregnant mice were injected with 20 microg/kg of BPA daily from embryonic day 0.5 (E0.5) and bromodeoxyuridine (BrdU) was injected at E12.5, E14.5 and at E16.5, and the fetal brains were analyzed after birth. The BrdU-positive cells labeled at E14.5 were significantly increased in the Vth and VIth cortical layers of BPA-treated mice at postnatal 3 weeks (P3W), whereas they were confined to the IVth layer of control mice, though such differences disappeared at P12W. The thalamocortical projections demonstrated by DiI-labeling were abnormal at P3W and P12W in BPA-treated mice. These results indicate that BPA might affect not only neocortical development but also thalamocortical connections.

Early cerebrovascular and parenchymal events following prenatal exposure to the putative neurotoxin methylazoxymethanol

One of the most common causes of neurological disabilities are malformations of cortical development (MCD). A useful animal model of MCD consists of prenatal exposure to methylazoxymethanol (MAM), resulting in a postnatal phenotype characterized by cytological aberrations reminiscent of human MCD. Although postnatal effects of MAM are likely a consequence of prenatal events, little is known on how the developing brain reacts to MAM. General assumption is the effects of prenatally administered MAM are short lived (24 h) and neuroblast-specific. MAM persisted for several days after exposure in utero in both maternal serum and fetal brain, but at levels lower than predicted by a neurotoxic action. MAM levels and time course were consistent with a different mechanism of indirect neuronal toxicity. The most prominent acute effects of MAM were cortical swelling associated with mild cortical disorganization and neurodegeneration occurring in absence of massive neuronal cell death. Delayed or aborted vasculogenesis was demonstrated by MAM's ability to hinder vessel formation. In vitro, MAM reduced synthesis and release of VEGF by endothelial cells. Decreased expression of VEGF, AQP1, and lectin-B was consistent with a vascular target in prenatal brain. The effects of MAM on cerebral blood vessels persisted postnatally, as indicated by capillary hypodensity in heterotopic areas of adult rat brain. In conclusion, these results show that MAM does not act only as a neurotoxin per se, but may additionally cause a short-lived toxic effect secondary to cerebrovascular dysfunction, possibly due to a direct anti-angiogenic effect of MAM itself.

Evaluation of the effects of the marine toxin okadaic acid by using FETAX assay

The Frog Embryo Teratogenesis Assay Xenopus (FETAX), is a screening assay using embryos at gastrula stage of the anuran Xenopus laevis to identify substances that may pose a developmental hazard in humans. The FETAX assay evaluates three parameters, i.e. mortality, delayed growth and embryo malformation. In the present investigation, the FETAX protocol was applied to the marine toxin okadaic acid (OA) and the experiments show that OA affects the above parameters in a dose-correlated manner. The morpho-functional modifications induced in embryo organs by OA were also studied. The nervous system, tail skeletal musculature, intestine and kidney appeared particularly damaged, with the former being the most sensitive. On the whole, various advantages emerge from using the FETAX assay: different parameters can be tested simultaneously, the indication of the presence of a potentially dangerous substance is rapid and the assay is a valid alternative to mammalian systems.

Effect of prenatal exposure to an anti-inflammatory drug on neuron number in cornu ammonis and dentate gyrus of the rat hippocampus: A stereological study

Prenatal exposed to an anti-inflammatory drug is a major problem for the developing central nervous system. It is not well known the effect of prenatal exposed to a non-steroidal anti-inflammatory drug on the hippocampus. Total neuron number in one side of the cornu ammonis (CA) and gyrus dentatus (GD) of the hippocampal formation in control and drug-treated (diclofenac sodium, DS) groups of male rats was estimated using the optical fractionator technique. Each main group has also two subgroups that are 4 weeks old (4W-old) and 20 weeks old (20W-old). In CA, no significant difference between 4W-old DS-treated and their control was found, but a significant difference was observed between 20W-old DS-treated and their controls. A decreasing of neuron number was 12% for 20W-old DS-treated group. In GD, a decreasing of the granule cell number in 4W-old of DS-treated group was seen but an increasing of granule cell number was found in the 20W-old drug-treated rats in comparison to its control group, 7% and 9%, respectively. Although an increasing of neuron number in CA at the control group was seen with age, from 4th week to 20th week (10%), age-dependent substantial granule cell decline (17%) was observed in GD. No age effect on the total cell numbers of CA and GD of the drug-treated groups was seen in comparison to 4W-old week and 20W-old. A pronounced neuron loss observed in the drug-treated group may be attributed to the neurotoxicity of diclofenac sodium (DS) on the developing hippocampal formation. Age-dependent neuron increase in the CA of 20W-old and neuron decline in GD of 20W-old control groups may be a result of a dual effect of saline injection during the fetal life, since these animals were exposed to a stress of 15-day-period of saline injection, prenatal stress. The reason of no age effect on CA and GD cell number in the drug-treated groups may be attributed to the depletion of the progenitor cells due to neurotoxicity of DS in the fetal life of these animals.

Herbal medicines used during the first trimester and major congenital malformations: an analysis of data from a pregnancy cohort study

BACKGROUND

Major congenital malformations place a considerable burden on the affected child, the family and society. Any kind of medicine used during pregnancy might have a harmful impact; therefore, such practice has raised concerns. The objective of the current study was to explore the relationship between the use of herbal medicines by pregnant women during the first trimester of pregnancy and the risk of major congenital malformation in their live born infants.

METHODS

This was a cross-sectional analysis of data from a prospective pregnancy cohort, which was established between 1984 and 1987. To assemble the cohort, pregnant women of >or=26 weeks of gestation who came to the Taipei Municipal Maternal and Child Hospital in Taiwan for prenatal care were enrolled in the study and interviewed using a structured questionnaire. Detailed information, including herbal medicine use during different periods of pregnancy, was obtained during the interview. Past medical history, current obstetric data and details on conventional medicines used during pregnancy were abstracted from medical records. Data on birth weight, gestational duration and characteristics of live born infants were gathered from the Taiwan national birth register. Congenital malformation information was obtained from multiple sources: the newborn examination record (1984-7); the national death register (1984-2003); and Taiwan National Health Insurance data (1996-2000). Multiple logistic regression was used to estimate the odds ratio [OR] of major congenital malformation by herbal medicines used during the first trimester.

RESULTS

A total of 14,551 live births were analysed. After adjustment for confounding factors, taking huanglian during the first trimester of pregnancy was found to be associated with increased risk of congenital malformations of the nervous system (adjusted OR 8.62, 95% CI 2.54, 29.24). An-Tai-Yin was associated with an increased risk of congenital malformations of the musculoskeletal and connective tissues (adjusted OR 1.61, 95% CI 1.10, 2.36) and the eye (adjusted OR 7.30, 95% CI 1.47, 36.18).

CONCLUSION

We found evidence for a possible link between the use of specific herbal medicines during the first trimester of pregnancy and increased risks of specific groups of congenital malformations. We could not investigate whether the adverse effects were related to direct toxicity from the herbal medicines, or were from misuse, contamination or uncontrolled confounding. Nonetheless, we would advise caution regarding use of herbal medicines during pregnancy, and we suggest that further investigation of these findings is warranted.

Microanatomy in 21 day rat brains exposed prenatally to cocaine

We examined cell minicolumns, apical dendrite bundles, and inhibitory interneurons, in prefrontal and somatosensory cortex of 21-day-old rat brains exposed to cocaine during fetal development. Cell columns and apical dendrite bundles were found to be narrower, or closer together, in all three areas following in utero cocaine exposure. The inter-rater reliability among different observers was R(2)=0.89. The number of cells stained for glutamic acid decarboxylase (GAD) was not significantly different in the prenatal cocaine exposed group compared to saline controls. The present data suggests that recreational doses of cocaine administered intravenously in early pregnancy, have the capacity to modify the maturation of the ontogenetic cell column.

Focal cortical dysplasia: pathophysiological approach

OVERVIEW

Clinical and experimental studies on focal cortical dysplasia (FCD) were carried out.

MATERIALS AND METHODS

For the experimental study, an experimental FCD model of rats was developed. Twenty Wistar rats at 0-2 days after birth were used for the study. Kainic acid (KA) solution was injected stereotaxically into medial and lateral sites of the sensori-motor cortex. Bipolar electrodes were inserted in five rats. Their behavior and electroencephalogram (EEG) were recorded using a digital-video-EEG monitoring system. After observation periods of 1, 2, and 6 months, rats were perfused for pathological study. FCD was observed adjacent to the site of KA injection in all rats more than 1 month after the injection.

RESULTS AND DISCUSSIONS

EEG recording demonstrated focal spike discharges in and around the site of injection. However, clinical seizure was not observed. Pathological studies showed decrease in GABA-A receptors and increase in GABA-B receptors not only in the lesion but also in perilesional areas. Fifteen surgical cases of FCD with intractable epilepsy were subjected to the clinical study. Neuro-imaging studies including high-resolution magnetic resonance imaging and single-photon emission computed tomography were performed. Conventional EEG studies demonstrated focal EEG abnormalities with epileptic phenomena. At surgery, intraoperative electrocorticography (ECoG) was performed to localize epileptic foci under neuroleptoanalgesia. Thirteen patients showed epileptiform discharges on preresection ECoG. All foci in non-eloquent areas were resected. Pathological studies including immunohistochemical staining were performed, and the characteristics of the FCD in relation to EEG findings were analyzed. Patients in whom total lesionectomy with complete focus resection was performed had favorable postoperative courses. Nine patients (64.3%) have been seizure-free with reduced medication, and significant improvement was achieved in two patients (14.3%). Electrophysiological examination revealed epileptogenecity not only in the lesions but also in perilesional areas. The immunohistochemical studies showed a decrease in GABA-A receptors and an increase in GABA-B receptors in both the lesions and perilesional areas, but N-methyl-D: -aspartate receptors were almost negative in both areas. Glutamate R1 was decreased in both areas, but glutamate R2 was increased in both areas. These findings support the results of a electrophysiological study.

CONCLUSIONS

In conclusion, not only the epileptic property of experimental focal cortical dysplasia but also perilesional epileptogenesis was demonstrated. These findings supported the results of surgery for patients with focal cortical dysplasia. In cases of FCD, total removal of the lesion and resection of the perilesional epileptic focus are needed for a good outcome.

Major congenital malformations after first-trimester exposure to ACE inhibitors

BACKGROUND

Use of angiotensin-converting-enzyme (ACE) inhibitors during the second and third trimesters of pregnancy is contraindicated because of their association with an increased risk of fetopathy. In contrast, first-trimester use of ACE inhibitors has not been linked to adverse fetal outcomes. We conducted a study to assess the association between exposure to ACE inhibitors during the first trimester of pregnancy only and the risk of congenital malformations.

METHODS

We studied a cohort of 29,507 infants enrolled in Tennessee Medicaid and born between 1985 and 2000 for whom there was no evidence of maternal diabetes. We identified 209 infants with exposure to ACE inhibitors in the first trimester alone, 202 infants with exposure to other antihypertensive medications in the first trimester alone, and 29,096 infants with no exposure to antihypertensive drugs at any time during gestation. Major congenital malformations were identified from linked vital records and hospitalization claims during the first year of life and confirmed by review of medical records.

RESULTS

Infants with only first-trimester exposure to ACE inhibitors had an increased risk of major congenital malformations (risk ratio, 2.71; 95 percent confidence interval, 1.72 to 4.27) as compared with infants who had no exposure to antihypertensive medications. In contrast, fetal exposure to other antihypertensive medications during only the first trimester did not confer an increased risk (risk ratio, 0.66; 95 percent confidence interval, 0.25 to 1.75). Infants exposed to ACE inhibitors were at increased risk for malformations of the cardiovascular system (risk ratio, 3.72; 95 percent confidence interval, 1.89 to 7.30) and the central nervous system (risk ratio, 4.39; 95 percent confidence interval, 1.37 to 14.02).

CONCLUSIONS

Exposure to ACE inhibitors during the first trimester cannot be considered safe and should be avoided.

Embryonic and early postnatal abnormalities contributing to the development of hippocampal malformations in a rodent model of dysplasia

While there are many recent examples of single gene deletions that lead to defects in cortical development, most human cases of cortical disorganization can be attributed to a combination of environmental and genetic factors. Elucidating the cellular or developmental basis of teratogenic exposures in experimental animals is an important approach to understanding how environmental insults at particular developmental junctures can lead to complex brain malformations. Rats with prenatal exposure to methylazoxymethanol (MAM) reproduce many anatomical features seen in epilepsy patients. Previous studies have shown that heterotopic clusters of neocortically derived neurons exhibit hyperexcitable firing activity and may be a source of heightened seizure susceptibility; however, the events that lead to the formation of these abnormal cell clusters is unclear. Here we used a panel of molecular markers and birthdating studies to show that in MAM-exposed rats the abnormal cell clusters (heterotopia) first appear postnatally in the hippocampus (P1-2) and that their appearance is preceded by a distinct sequence of perturbations in neocortical development: 1) disruption of the radial glial scaffolding with premature astroglial differentiation, and 2) thickening of the marginal zone with redistribution of Cajal-Retzius neurons to deeper layers. These initial events are followed by disruption of the cortical plate and appearance of subventricular zone nodules. Finally, we observed the erosion of neocortical subventricular zone nodules into the hippocampus around parturition followed by migration of nodules to hippocampus. We conclude that prenatal MAM exposure disrupts critical developmental processes and prenatal neocortical structures, ultimately resulting in neocortical disorganization and hippocampal malformations.

Neuronal apoptosis and gray matter heterotopia in microcephaly produced by cytosine arabinoside in mice

Primary microcephaly can be accompanied by numerous migration anomalies. This experiment was undertaken to examine the pathogenesis of gray matter heterotopia and microcephaly that is produced after administering cytosine arabinoside (Ara-C) to mice. Pregnant mice were intraperitoneally injected with Ara-C at 30 mg/kg body weight on days 13.5 and 14.5 of gestation, and then their offspring were examined. On embryonic day 15.5, in the ventricular zone of the cingulate cortex, the neuroepithelial cells lacked BrdU immunoreactivity. Nestin-immunoreactive radial glial fibers and calretinin-positive subplate fibers were disrupted. TUNEL reaction was remarkable throughout the cerebral hemisphere. Subcortical heterotopia in the cingulate cortex and subependymal nodular heterotopia in the dorsolateral part of the lateral ventricles became detectable by the first day after birth. Thirty-two days after birth, microcephaly was apparent; subcortical heterotopia was observed to have increased in size while it was still located in the frontal and cingulate cortices. This experiment demonstrated that Ara-C induces neuronal apoptosis throughout the cerebral hemisphere. The immunohistochemical characteristics in the gray matter heterotopia suggest that both the subcortical and the subependymal heterotopias were formed by neurons originally committed to the neocortex. We conclude that the gray matter heterotopia that accompanies the microcephaly was produced by a disturbance of radial, tangential, and interkinetic neuronal migrations due to the toxicity of Ara-C in the immature developing brain.

High susceptibility of neural stem cells to methylmercury toxicity: effects on cell survival and neuronal differentiation

Neural stem cells (NSCs) play an essential role in both the developing embryonic nervous system through to adulthood where the capacity for self-renewal may be important for normal function of the CNS, such as in learning, memory and response to injury. There has been much excitement about the possibility of transplantation of NSCs to replace damaged or lost neurones, or by recruitment of endogenous precursors. However, before the full potential of NSCs can be realized, it is essential to understand the physiological pathways that control their proliferation and differentiation, as well as the influence of extrinsic factors on these processes. In the present study we used the NSC line C17.2 and primary embryonic cortical NSCs (cNSCs) to investigate the effects of the environmental contaminant methylmercury (MeHg) on survival and differentiation of NSCs. The results show that NSCs, in particular cNSCs, are highly sensitive to MeHg. MeHg induced apoptosis in both models via Bax activation, cytochrome c translocation, and caspase and calpain activation. Remarkably, exposure to MeHg at concentrations comparable to the current developmental exposure (via cord blood) of the general population in many countries inhibited spontaneous neuronal differentiation of NSCs. Our studies also identified the intracellular pathway leading to MeHg-induced apoptosis, and indicate that NSCs are more sensitive than differentiated neurones or glia to MeHg-induced cytotoxicity. The observed effects of MeHg on NSC differentiation offer new perspectives for evaluating the biological significance of MeHg exposure at low levels.

Neonatal genistein or bisphenol-A exposure alters sexual differentiation of the AVPV

There is growing concern that naturally occurring and chemically manufactured endocrine-active compounds (EACs) may disrupt hormone-dependent events during central nervous system development. We examined whether postnatal exposure to the phytoestrogen genistein (GEN) or the plastics component bisphenol-A (BIS) affected sexual differentiation of the anteroventral periventricular nucleus of the hypothalamus (AVPV) in rats. The AVPV is sexually differentiated in rodents. The female AVPV is larger than the male AVPV and contains a higher number of cells expressing tyrosine hydroxylase (TH). Sexual differentiation of the AVPV results from exposure of the male nervous system to estrogen aromatized from testicular testosterone secreted in the first few days after birth. Thus, we hypothesized that exposure to EACs during this critical period could alter the sexually dimorphic expression of TH and the overall expression of estrogen receptor alpha (ERalpha) in the AVPV. Animals were given 4 subcutaneous injections of sesame oil (control), 50 microg 17beta-estradiol (E2), 250 microg GEN, or 250 microg BIS at 12-h intervals over postnatal days (PND) 1 and 2 and sacrificed on PND 19. E2 treatment masculinized TH immunoreactivity (TH-ir) in the female AVPV while exposure to GEN or BIS demasculinized TH-ir in the male AVPV. In addition, we identified a population of neurons co-expressing TH and ERalpha located primarily in the medial region of the AVPV. Normally, females have nearly three times as many double-labeled cells as males, but their numbers were defeminized by E2, GEN or BIS treatment. These results suggest that acute exposure to EACs during a critical developmental period alters AVPV development.

Molecular mechanisms of hydroxyurea(HU)-induced apoptosis in the mouse fetal brain

Hydroxyurea (HU), a potent mammalian teratogen, affects proliferating embryonic cells and inhibits DNA synthesis. The teratogenic potential of HU has been well known in experimental animals for several decades. In this study, we investigated molecular mechanisms of HU-induced apoptosis in the telencephalon of the fetal brain by exposing pregnant mice to HU on day 13 of gestation. The number of TUNEL-positive cells began to increase at 3 h, peaked at 12 h, and rapidly decreased at 24 h. Although changes of p53 mRNA expression were not observed by RT-PCR, a p53-positive reaction was detected immunohistochemically in the nuclei of neuroepithelial cells from 1 h to 6 h, and p53-protein expression was simultaneously identified by Western blot analysis. The expression of p53-target genes was detected at both the mRNA and protein. The mRNA levels of apotosis-related genes (fas, fasL, and bax) and cell cycle-related genes (mdm2 and p21) were significantly elevated, and the degree to and sequence in which these target genes expressed was similar to those for fas, fasL, mdm2 and p21. Flow-cytometric and Western blot analyses of cell cycle-related proteins suggested that neuroepithelial cells are arrested at the S checkpoint from 3 to 6 h and at the G2/M checkpoint at 12 h, respectively. HU-induced apoptosis is considered to be mediated by p53 in the fetal brain.

The neurotoxic effects of prenatal cardiac glycoside exposure: a hypothesis

Cardiac glycosides (CGs) are beneficial in treating cardiac conditions; depending on time and dosage, they can also be toxic as they regularly cross the blood brain barrier and the placenta and may affect the unborn baby. This paper therefore focuses on the effects of CGs administered to the mother on normal cellular physiology of the foetus with specific reference to neural tissue. CGs act by binding to the Na+/K+-ATPase and decrease or inhibit Na+-K+ pump activity. In the foetus, CGs may disrupt ion homeostasis. An over-dosage of CGs or when it is taken during pregnancy, can also affect the neuro-energy levels of brain tissue in particular. We conclude and hypothesize that CGs in this case will not only cause severe alterations in neuronal function due to disruption of membrane activity, but also in glutamate clearance, affecting neurotransmission in general. Furthermore, elevated cytosolic Ca2+ will lead to permeabilization of the mitochondrial membranes, resulting ultimately in mitochondrial dysfunction. This will result in neurotoxicity--ensuing in neural cell damage or death, and we propose the mechanism to be due to neuro-necrapoptosis.

Adverse effects of prenatal tobacco smoke exposure on biological parameters of the developing brainstem

We aimed to study the consequences of chronic exposure to tobacco smoke in utero on the morphological and functional maturation of the brainstem by comparing stillbirths of smoker mothers versus nonsmoker mothers. A total of 42 stillbirths, aged 25-40 gestational weeks, underwent autopsy according to our guidelines (). The brainstem was studied on serial sections and by immunohistochemistry to assay the expression of the EN2 gene, somatostatin (SS) and the tyrosine hydroxylase enzyme (TH). We observed a significant correlation between maternal smoking and sudden intrauterine unexplained death (SIUD), hypoplasia of the ArcN, no immunostaining of the EN2 in the arcuate nucleus (ArcN), and of TH in the locus coeruleus (LC) (P < 0.05). An increased incidence of maternal smoking was also observed in fetuses with SS negativity in the hypoglossus nucleus (HypoglN). Exposure in utero to maternal smoking may strongly interfere with brain biological parameters, giving rise not only to structural developmental abnormalities of the arcuate nucleus, but also to a decrease of noradrenergic activity in the LC, of EN2 gene expression in the ArcN and of SS in the HypoglN.

Study on the common teratogenic pathway elicited by the fungicides triazole-derivatives

Triazole-derivatives alter the pharyngeal apparatus morphogenesis of rodent embryos cultured in vitro. The hindbrain segmentation and the rhombencephalic neural crest cell (NCCs) migration are altered by Fluconazole exposure in vitro. The aim of the present work is to identify if a common pathogenic pathway is detectable also for other molecules of this class of compounds. 9.5 days post coitum (d.p.c.) old rat embryos were exposed in vitro to the teratogenic concentrations of Flusilazole, Triadimefon and Triadimenol and cultured for 24, 48 or 60 h. The expression and localisation of Hox-b1 and Krox-20 proteins (used as markers for hindbrain segmentation) were evaluated after 24 h of culture. The localisation and distribution of NCC was evaluated after 24, 30 and 48 h of culture. The morphology of the embryos was analysed after 48 h, while the branchial nerve structures were evaluated after 60 h of culture. Hindbrain segmentation and NCC migration alteration as well as pharyngeal arch and cranial nerve abnormalities were detected after exposure of the tested molecules. A common severe teratogenic intrinsic property for the tested molecules of this chemical class has been found, acting through alteration of the normal hindbrain developmental pattern.

Effects of maternal oral morphine consumption on neural tube development in Wistar rats

Opiate abuse during pregnancy may result in abnormal nervous system function. In order to evaluate the effects of morphine on the development of the nervous system, the present study focused on the effects of maternal morphine consumption on neural tube development in Wistar rats. Female Wistar rats (250-300 g) were crossed with male rats and coupling time was recorded (embryonic day 0-E0). Experimental groups received 0.1, 0.05, and 0.01 mg/ml of morphine in drinking water daily (14 ml water for each rat). Control group received tap water. On embryonic day 9.5 (E9.5), the animals were anesthetized and the embryos were surgically removed. The embryos were fixed in 10% formalin for 1 week. After this time, weights and lengths (antero-posterior axis--A-P) of the embryos were determined and then tissues were processed, sectioned, and stained in hematoxylin and eosin (H&E). The sections were investigated for neural tube development by light microscope and MOTIC software. The decrease in "A-P" length and embryonic weight for the group that received 0.01 mg/ml morphine was significant. It seems that daily consumption of morphine sulfate could delay neural tube development. In addition, administration of 0.01 mg/ml of morphine led to damage to the regulated neuro-ectoderm layer and its thickness. This study showed that oral morphine consumption leads to neural tube defects, as indicated in the morphometric change and also reduction in weight and length of the embryos. These defects might affect the behavior of the animals.

Fetal origin of adverse pregnancy outcome: the water disinfectant by-product chloroacetonitrile induces oxidative stress and apoptosis in mouse fetal brain

Epidemiological studies indicate a relationship between water disinfectant by-products (DBP) and adverse pregnancy outcomes (APO) including neural tube defects. These studies suggest that fetal brain may be vulnerable to DBP during early stages of development. Therefore, we examined several molecular markers commonly known to indicate chemical-induced neurotoxicity during fetal brain development following prenatal exposure to the DBP; chloroacetonitrile (CAN). Pregnant mice, at gestation day 6 (GD6), were treated with a daily oral dose of CAN (25 mg/kg). At GD12, two groups of animals were treated with an i.v. tracer dose of [2-14C]-CAN. These animals were sacrificed at 1 and 24 h after treatment and processed for quantitative in situ micro-whole-body autoradiography. The remaining groups of animals continued to receive CAN. At GD18, control and treated animals were weighed, anesthetized, and fetuses were obtained and their brains were removed for biochemical and immunohistochemical analyses. Whole-body autoradiography studies indicate a significant uptake and retention of [2-14C]-CAN/metabolites (M) in fetal brain (cerebral cortex, hippocampus, cerebellum) at 1 and 24 h. There was a 20% reduction in body weight and a 22% reduction in brain weight of fetuses exposed to CAN compared to controls. A significant increase in oxidative stress markers was observed in various fetal brain regions in animals exposed to CAN compared to controls. This was indicated by a 3- to 4-fold decrease in the ratio of the reduced to oxidized form of glutathione (GSH/GSSG), increased lipid peroxidation (1.3-fold), and increased 8-hydroxy-2-deoxyguanosine levels (1.4-fold). Cupric silver staining indicated a significant increase in the number of degenerating neurons in cortical regions in exposed animals. In animals exposed to CAN there was increase in nuclear DNA fragmentation (TUNEL staining) detected in the cerebral cortex and cerebellum (2-fold increase in apoptotic indices). Caspase-3 activity in cerebral cortex and cerebellum of treated animals were also increased (1.7- and 1.5-fold, respectively). In conclusion, this study indicates that CAN/M crossed the placenta and accumulated in fetal brain tissues where it caused oxidative stress and neuronal apoptosis. These events could predispose the fetus to altered brain development leading to APO as well as behavioral and learning and memory deficits.

Signaling pathways involved with serotonin1A agonist-mediated neuroprotection against ethanol-induced apoptosis of fetal rhombencephalic neurons

Previously, this laboratory demonstrated that developing serotonin (5-HT) neurons and other fetal rhombencephalic neurons are reduced by in vivo and in vitro exposure to ethanol, effects that are related to ethanol's augmentation of apoptosis. We also found that 5-HT1A agonists diminished the ethanol-associated reduction of 5-HT neurons and other fetal rhombencephalic neurons by attenuating the pro-apoptotic effects of ethanol. Presently, we investigated the hypothesis that the protective/anti-apoptotic effects of a 5-HT1A agonist on fetal rhombencephalic neurons are mediated by activation of the phosphatidylinositol 3' kinase (PI-3K) and/or the mitogen-activated protein kinase kinase (MAPKK) pathway. Apoptotic and non-apoptotic fetal rhombencephalic neurons were quantitated in primary cultures that were treated with 50 mM ethanol and with 100 nM of a 5-HT1A agonist such as 8-OH-DPAT [8-hydroxy 2-(di-n-propylamino)tetralin], ipsapirone, or buspirone. Analysis of neurons stained with Hoechst 33342 demonstrated the anti-apoptotic effects of 5-HT1A agonists and implicated the involvement of the PI-3K pathway and possibly the MAPKK pathway with the protective effects of these drugs. The protective effects were blocked by a 5-HT1A antagonist (WAY 100635), an inhibitor of PI-3K (LY294002), and an inhibitor of MAPKK (PD98059). Western blot analyses showed that ethanol treatment reduces basal pAkt levels. These analyses also provide support for the involvement of the PI-3K pathway; ipsapirone stimulated the phosphorylation of Akt in control and ethanol-treated neurons, and these effects were antagonized by LY294002.

The neurodevelopmental consequences of prenatal alcohol exposure

During pregnancy, ingestion of alcohol, a known teratogen, can cause harm to the fetus. Prenatal alcohol exposure is one of the leading causes of birth defects, developmental disorders, and mental retardation in children. The fetal central nervous system is particularly vulnerable to alcohol; this vulnerability contributes to many of the long-term disabilities and disorders seen in individuals with prenatal alcohol exposure. Diagnoses associated with prenatal alcohol exposure include fetal alcohol syndrome (FAS), partial fetal alcohol syndrome, fetal alcohol effects, alcohol-related neurodevelopmental disorder, and alcohol-related birth defects. Once diagnosed, early intervention improves the long-term outcome of affected children. Without documentation of maternal alcohol use, a diagnosis, and consequently treatment, is often difficult to attain. It is imperative that nurses, physicians, and other healthcare providers become comfortable with obtaining a history of, and providing anticipatory guidance and counseling about, alcohol use.

Disruption of cortical development as a consequence of repetitive pilocarpine-induced status epilepticus in rats

PURPOSE

The aim of the present study was to observe possible cortical abnormalities after repetitive pilocarpine-induced status epilepticus (SE) in rats during development.

METHODS

Wistar rats received intraperitoneal injection of pilocarpine hydrochloride 2% (380 mg/kg) at P7, P8, and P9. All experimental rats displayed SE after pilocarpine injections. Rats were killed at P10 and P35, and immunocytochemistry procedures were performed on 50-microm vibratome sections, by using antibodies against nonphosphorylated neurofilament (SMI-311), parvalbumin (PV), calbindin (CB), calretinin (CR), and glutamate decarboxylase (GAD-65). Selected sections were used for the TUNEL method and double-labeling experiments, with different mixtures of the same markers.

RESULTS

The major findings of the present work were (a) altered intracortical circuitry development; (b) anticipation of PV immunoreactivity in neocortical interneurons; (c) increased GAD-65 immunoreactivity; and (d) reduced neocortical apoptotic process.

CONCLUSIONS

From these results, we suggest that previously healthy brain, without genetic abnormalities, might develop an "acquired" disruption of cortical development whose evolution reproduces some characteristics of the childhood epilepsies associated with cognitive impairment.

A volumetric screening procedure for the Göttingen minipig brain

A screening procedure was developed to provide quantitative estimates of structural parameters, regional volumes and neuron number, in a neurotoxicologic study of the Göttingen minipig brain. The study material consisted of normal controls and brains collected from young minipigs which had been exposed in utero to the mitotic inhibitor methylazoxymethanol acetate (MAM). Based on stereological principles and systematic sampling techniques, volumetric data from pre-selected regions of the pig brain was obtained using Cavalieri's principles and point-counting. Secondarily, estimates of total hemispheric neocortical cell numbers were obtained from pre-selected groups to test the potential effect of MAM on neuron number. No significant differences were observed in volume of the pre-selected regions of MAM intoxicated pigs nor in estimates of total neocortical neuron number.

Early serotonergic projections to Cajal-Retzius cells: relevance for cortical development

Although the serotonergic system plays an important role in various neurological disorders, the role of early serotonergic projections to the developing cerebral cortex is not well understood. Because serotonergic fibers enter the marginal zone (MZ) before birth, it has been suggested that they may influence cortical development through synaptic contacts with Cajal-Retzius (CR) cells. We used immunohistochemistry combined with confocal and electron microscopy to show that the earliest serotonergic projections to the MZ form synaptic contacts with the somata and proximal dendrites of CR cells as early as embryonic day 17. To elucidate the functional significance of these early serotonergic contacts with CR cells, we perturbed their normal development by injecting pregnant mice with 5-methoxytryptamine. Lower reelin levels were detected in the brains of newborn pups from the exposed animals. Because reelin plays an important role in the cortical laminar and columnar organization during development, we killed some pups from the same litters on postnatal day 7 and analyzed their presubicular cortex. We found that the supragranular layers of the presubicular cortex (which normally display a visible columnar deployment of neurons) were altered in the treated animals. Our results suggest a mechanism of how serotonergic abnormalities during cortical development may disturb the normal cortical organization; and, therefore, may be relevant for understanding neurological disorders in which abnormalities of the serotonergic system are accompanied by cortical pathology (such as autism).

Developmental expression of the cell cycle and apoptosis controlling gene, Lot1, in the rat cerebellum and in cultures of cerebellar granule cells

The Lot1 gene encodes a zinc finger protein that, in vitro, concurrently regulates apoptosis and cell cycle arrest and belongs to a recently identified family of proteins with oncogenic and tumor-supressor functions. The present study, based on the development of the first antibody reportedly produced against rat Lot1, examines protein expression during normal development of the rat cerebellum and following methylazoxymethanol (MAM) administration, which results in hypoplasia of the cerebellar granule cell population. Using light microscopic immunocytochemistry, specific immunostaining for the Lot1 protein was observed at postnatal days 2 to 7 in the superficial external granule layer composed primarily of proliferating neuronal precursor cells. Purkinje cells showed distinct nuclear labeling at P7. In the adult cerebellum, the overall low Lot1 level was essentially associated with Purkinje cells. Experimentally altered developmental conditions, such as those obtained through MAM-induced microencephaly, did not drastically affect the pattern of Lot1 expression. In particular, Purkinje cells continued to show normal levels of immunoreactivity notwithstanding the altered cerebellar architecture. Primary cultures of cerebellar granule cells showed a temporal pattern of Lot1 expression resembling that of in vivo development, with mRNA and protein levels progressively decreasing with differentiation. When cerebellar granule cells were exposed to different neurotoxic challenges, Lot1 appeared not affected by purely apoptotic cell death, while transitorily induced by mixed necrotic-apoptotic cell death.

An examination of calcium current function on heterotopic neurons in hippocampal slices from rats exposed to methylazoxymethanol

PURPOSE

To study voltage-dependent calcium currents (VDCCs) on hippocampal heterotopic neurons by using whole-cell patch-clamp techniques in brain slices prepared from methylaxozymethanol (MAM)-exposed rats.

METHODS

Whole-cell voltage-clamp recordings were obtained from visually identified neurons in acute brain slices by using an infrared differential interference contrast (IR-DIC) video microscopy system. Heterotopic neurons were compared with normotopic pyramidal cells in hippocampal slices from MAM-exposed rats or CA1 pyramidal neurons in slices from controls.

RESULTS

Heterotopic neurons expressed a prominent VDCC, which exhibited a peak current maximum around -30 mV (holding potential, -60 mV) and an inactivation time constant of 48.2 +/- 2.4 ms (n = 91). VDCC peak current and inactivation time constants were similar for normotopic (n = 92) and CA1 pyramidal cells (n = 40). Pharmacologic analysis of VDCC, on heterotopic, normotopic, and CA1 pyramidal cells, revealed an approximately 70% blockade of peak Ca2+ current with nifedipine and amiloride (L- and T-type channel blockers, respectively). Inhibition of VDCC, for all three cell types, also was similar when more specific Ca2+ channel antagonists were used [e.g., omega-conotoxin GVIA (N-type), omega-agatoxin KT (P/Q-type), and sFTX-3.3 (P-type)]. VDCC modulation by norepinephrine (NE) or adrenergic receptor-specific agonists [clonidine (alpha2), isoproterenol (beta), and phenylephrine (alpha1)] was similar for heterotopic and CA1 pyramidal cells.

CONCLUSIONS

Heterotopic neurons do not appear to exhibit Ca2+ channel abnormalities that could contribute to the reported hyperexcitability associated with MAM-exposed rats.

Behavioral Teratology of Mercury and Its Compounds

Mercury and its compounds have a wide spectrum of toxicities depending upon the chemical forms and modes of exposure. Among the various chemical forms, mercury vapor and methylmercury are well known and established as neurotoxic agents. Since the disasters in Minamata and Iraq, in which fetuses were more susceptible than adults to methylmercury exposure, much attention has been focused on prenatal exposure to mercury and its consequence. Recently postnatal effects of in utero exposure to methylmercury through fish (and marine mammals) consumption by mothers have been concerned and several epidemiological studies have been conducted. Therefore, one of the most seriously concerned issues is the postnatal effects of in utero exposure to methylmercury. Because of these observations in humans, animal experiments have been conducted employing prenatal exposure to low levels of mercury. This paper reviews the animal (rodents) experiments concerning "behavioral teratology" of mercury for better understanding of effects of prenatal exposure to mercury and its compounds in addition to commentary on history and framework of behavioral teratology.

Second trimester prenatal alcohol exposure alters development of rat corpus callosum

Prenatal alcohol exposure produces many developmental defects of the central nervous system (CNS), such as in the corpus callosum (CC). This study was designed to observe the effect of prenatal alcohol exposure during the second trimester equivalent on the development of dendritic arbors of CC projection neurons (CCpn) in rat visual cortex. In addition, the effect of second trimester equivalent prenatal alcohol exposure on brain weight was determined. Pregnant dams received 1.2-6.0 g/kg ethanol (EtOH) during gestational day (G) 11-20. Controls consisted of normal and nutritionally matched pairfed (PF) dams. Pups were sacrificed on the day of birth, G26, G29 and G33. DiI crystals were placed in the midsagittal CC bundle to retrogradely label CCpn. Images of visual cortex were obtained from tissue slices using a confocal laser scanning microscope. The number and length of apical and basilar dendrite branches were determined. The results show that prenatal alcohol exposure restricted to the second trimester equivalent alters the development of the CCpn dendritic arbor and the brain weight in a blood alcohol concentration (BAC)-dependent manner. The alteration in the EtOH CCpn is manifested as an increase in the number and length of CCpn apical and basilar dendrite branches, while brain weight is reduced compared with Controls.

Influence of the embryonic preplate on the organization of the cerebral cortex: a targeted ablation model

Transgenic mice were generated to permit the targeted ablation of cortical preplate cells at the time they are born. In these mice, the 1.3 kb golli promoter of the myelin basic protein gene was used to drive the herpes simplex virus thymidine kinase (TK) transgene in cortical preplate cells. Heterozygous transgenic pairs were bred, and pregnant dams were treated with ganciclovir at embryonic days 11-12 to ablate preplate cells at the time the preplate was forming. This paradigm exposed control (TK-) and experimental (TK+) littermates to exactly the same conditions. Embryological ablation of preplate cells led to an early disruption of the radial glial framework and subplate structure in the developing cortex and dramatically altered the cellular lamination and connectivity of the cortical plate. The disturbed radial glial network contributed to an impaired radial migration of neurons into the cortical plate from the ventricular zone. The cortical plate became dyslaminated, and there was a substantial reduction in short- and long-range cortical projections within the cortex and to subcortical regions. Cell death within the cortical plate and the proliferative zones was substantially increased in the ablated animals. After birth, a cortical lesion developed, which became exacerbated with the secondary onset of hydrocephaly in the second postnatal week. The results underscore the critical importance of the preplate in cortex formation, mediated through its guidance of the formation of radial glial scaffolding, subsequent neuronal migration into the incipient cortical plate, and the final arrangement of its vertical organization and cellular connectivity.

Heterotopic neurons with altered inhibitory synaptic function in an animal model of malformation-associated epilepsy

Children with brain malformations often exhibit an intractable form of epilepsy. Although alterations in cellular physiology and abnormal histology associated with brain malformations has been studied extensively, synaptic function in malformed brain regions remains poorly understood. We used an animal model, rats exposed to methylazoxymethanol (MAM) in utero, featuring loss of lamination and distinct nodular heterotopia to examine inhibitory synaptic function in the malformed brain. Previous in vitro and in vivo studies demonstrated an enhanced susceptibility to seizure activity and neuronal hyperexcitability in these animals. Here we demonstrate that inhibitory synaptic function is enhanced in rats exposed to MAM in utero. Using in vitro hippocampal slices and whole-cell voltage-clamp recordings from visualized neurons, we observed a dramatic prolongation of GABAergic IPSCs onto heterotopic neurons. Spontaneous IPSC decay time constants were increased by 195% and evoked IPSC decay time constants by 220% compared with age-matched control CA1 pyramidal cells; no change in IPSC amplitude or rise time was observed. GABA transport inhibitors (tiagabine and NO-711) prolonged evoked IPSC decay kinetics of control CA1 pyramidal cells (or normotopic cells) but had no effect on heterotopic neurons. Immunohistochemical staining for GABA transporters (GAT-1 and GAT-3) revealed a low level of expression in heterotopic cell regions, suggesting a reduced ability for GABA reuptake at these synapses. Together, our data demonstrate that GABA-mediated synaptic function at heterotopic synapses is altered and suggests that inhibitory systems are enhanced in the malformed brain.

Oxidative stress induced by phenylketonuria in the rat: Prevention by melatonin, vitamin E, and vitamin C

Phenylketonuria (PKU) is an autosomal recessive disorder caused by a deficiency of the phenylalanine hydroxylation system and is characterized by a block in the conversion of phenylalanine (PHE) to tyrosine. We examined the effects of maternal hyperphenylalaninemia on the morphological and biochemical development of pup rat brain and cerebellum. In our model of PKU we evaluated a number of markers of oxidative stress such as Ehrlich adducts formation, lipid peroxidation, as well as the levels of reduced and oxidized glutathione, and the activities of the enzymes glutathione peroxidase and glutathione reductase. We also studied the expression of heme-oxigenase-1 and mitogen-activated protein kinase 1/2 (MAPK 1/2) as additional markers of oxidative stress. We demonstrate that PKU strongly increased most of the oxidative stress markers studied and induced significant morphological damage. We also showed that daily administration of melatonin (20 mg/kg BW), vitamin E (30 mg/kg BW), and vitamin C (30 mg/kg BW) until delivery prevented the oxidative biomolecular damage in the rat brain and cerebellum. Although no significant differences were observed among the antioxidants studied, it should be noted that the doses of melatonin were less than those for vitamins E and C. We conclude that PKU induces a clear state of oxidative stress that is somehow involved in the brain and body damage occurring in this inborn error. Moreover, melatonin and other antioxidants are capable of preventing completely the damage induced by PKU.

A role for protein kinase C and its substrates in the action of valproic acid in the brain: implications for neural plasticity

Valproic acid (VPA) is a broad-spectrum anticonvulsant with well-documented teratogenic effects, but whose mechanism of action is largely unknown. In the present study we have examined the effects of VPA on the expression of two prominent substrates for protein kinase C (PKC) in the brain, MARCKS and GAP-43, which have been implicated in actin-membrane plasticity and neurite outgrowth during neuronal differentiation, respectively, and are essential to normal brain development. Immortalized hippocampal HN33 cells exposed to VPA exhibited reduced MARCKS protein expression and demonstrated increased GAP-43 protein expression, with concomitant alterations in cellular morphology, including an increase in the number and length of neurites and accompanied by a reduction in cell growth rate. The effects of VPA were observed at clinically relevant concentrations following chronic (>1 day) VPA exposure. We also present evidence for a VPA-induced alteration in PKC activity, as well as temporal changes in individual PKC isozyme expression. Inhibition of PKC with the PKC-selective inhibitor, LY333531, prevented the VPA-induced down-regulation of membrane-associated MARCKS, but had no effect on the cytosolic MARCKS reduction or the GAP-43 up-regulation. Inhibition of PKC by LY333531 enhanced the differentiating effects of VPA; additionally, LY333531 alone induced greater neurite outgrowth in this cell line. Collectively, these data indicate that VPA induces neuronal differentiation, associated with a reduction in MARCKS expression and an increase in GAP-43 expression, consistent with the hypothesis that a reduction in MARCKS at the membrane may be permissive for cytoskeletal plasticity during neurite outgrowth.

Episodic exposure to ethanol during development differentially affects brainstem nuclei in the macaque

Neuronal vulnerability to ethanol may be non-specific, i.e., vulnerability may be conferred by the developmental state of the population or by the site of derivation. To address these issues, the effect of developmental exposure to ethanol on three brainstem nuclei; the trigeminal motor (MoV), facial motor (MoVII) and medial superior olivary (MSO) nuclei was determined. MoVII and MSO are generated at the same time and from the same rhombomere, r4. MoV is generated earlier from r2. Macaca nemestrina were exposed to ethanol or a control solution one day per week for six or 24 weeks of gestation. Brainstems of the mature offspring were sectioned and stained. The number of neurons and volume of each nucleus were determined stereologically. Neuron number was lower in MoV and MSO following exposure to ethanol whereas MoVII appeared unaffected. No significant effects of ethanol exposure were seen on the volume and weight of the brainstem, or the volume of the individual nuclei. These findings show that ethanol differentially affects brainstem nuclei in a targeted, rather than non-specific, manner. Furthermore, they show that serious ethanol-induced neurological deficits can be present without gross morphological changes.

Photo-mediated gene activation using caged RNA/DNA in zebrafish embryos

We report a new and simple technique for photo-mediated temporal and spatial control of gene activation in zebrafish embryos as an alternative to the gene 'knockdown' approach using antisense, morpholino-modified oligonucleotides (morpholinos). The synthetic compound 6-bromo-4-diazomethyl-7-hydroxycoumarin (Bhc-diazo) forms a covalent bond with the phosphate moiety of the sugar-phosphate backbone of RNA, a process known as caging. The 6-bromo-7-hydroxycoumarin-4-ylmethyl (Bhc) group binds to approximately 30 sites on the phosphate moieties per 1 kb of RNA sequence. Bhc-caged mRNA undergoes photolysis (uncaging) when exposed to long-wave ultraviolet light (350 to 365 nm). We show that Bhc-caged green fluorescent protein (Gfp) mRNA has severely reduced translational activity in vitro, whereas illumination of Bhc-caged mRNA with ultraviolet light leads to partial recovery of translational activity. Bhc-caged mRNA is highly stable in zebrafish embryos. In embryos injected with Bhc-caged Gfp mRNA at the one-cell stage, GFP protein expression and fluorescence is specifically induced by ultraviolet light. We also show that, consistent with results obtained using other methods, uncaging eng2a (which encodes the transcription factor Engrailed2a) in the head region during early development causes a severe reduction in the size of the eye and enhanced development of the midbrain and the midbrain-hindbrain boundary at the expense of the forebrain.