Tyrosine Hydoxylase Research Articles

Tempol and silymarin rescue from zinc-induced degeneration of dopaminergic neurons through modulation of oxidative stress and inflammation.

Oxidative stress and inflammation are the key players in the toxic manifestation of sporadic Parkinson's disease and zinc (Zn)-induced dopaminergic neurodegeneration. A synthetic superoxide dismutase (SOD) mimetic, tempol, and a naturally occurring antioxidant, silymarin protect against oxidative stress-mediated damage. The study intended to explore the effects of tempol and silymarin against Zn-induced dopaminergic neurodegeneration. Exposure to Zn produced neurobehavioral deficits and striatal dopamine depletion. Zn reduced glutathione content and glutathione-S-transferase activity and increased lipid peroxidation, superoxide dismutase activity, and level of pro-inflammatory mediators [nuclear factor-kappa B (NF-κB), tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), and interleukin-6 (IL-6)]. Zn also attenuated the expression of tyrosine hydoxylase (TH), vesicular monoamine transporter 2 (VMAT-2), mitochondrial B-cell lymphoma-2 (Bcl-2), and procaspase-3 and 9 proteins and number of TH-positive neurons. Conversely, Zn elevated the expression of dopamine transporter (DAT) and mitochondrial Bcl-2-associated X (Bax) protein along with mitochondrial cytochrome c release. Administration of tempol significantly alleviated Zn-induced motor impairments, dopamine depletion, reduction in TH expression, and loss of TH-positive neurons similar to silymarin. Silymarin mitigated Zn-induced oxidative stress and inflammation and restored the expression of dopamine transporters and levels of pro-apoptotic proteins akin to tempol. The results demonstrate that both tempol and silymarin protect against Zn-induced dopaminergic neuronal loss through the suppression of oxidative stress and inflammation.

Catecholaminergic axons in the neocortex of adult mice regrow following brain injury

Serotonin axons in the adult rodent brain can regrow and recover their function following several forms of injury including controlled cortical impact (CCI), a neocortical stab wound, or systemic amphetamine toxicity. To assess whether this capacity for regrowth is unique to serotonergic fibers, we used CCI and stab injury models to assess whether fibers from other neuromodulatory systems can also regrow following injury. Using tyrosine-hydoxylase (TH) immunohistochemistry we measured the density of catecholaminergic axons before and at various time points after injury. One week after CCI injury we observed a pronounced loss, across cortical layers, of TH+ axons posterior to the site of injury. One month after CCI injury the same was true of TH+ axons both anterior and posterior to the site of injury. This loss was followed by significant recovery of TH+ fiber density across cortical layers, both anterior and posterior to the site of injury, measured three months after injury. TH+ axon loss and recovery over weeks to months was also observed throughout cortical layers using the stab injury model. Double label immunohistochemistry revealed that nearly all TH+ axons in neocortical layer 1/2 are also dopamine-beta-hyroxylase+ (DBH+; presumed norepinephrine), while TH+ axons in layer 5 are a mixture of DBH+ and dopamine transporter+ types. This suggests that noradrenergic axons can regrow following CCI or stab injury in the adult mouse neocortex and leaves open the question of whether dopaminergic axons can do the same.

Characterizations of a synthetic pituitary adenylate cyclase-activating polypeptide analog displaying potent neuroprotective activity and reduced in vivo cardiovascular side effects in a Parkinson's disease model

Parkinson's disease (PD) is characterized by a steady loss of dopamine neurons through apoptotic, inflammatory and oxidative stress processes. In that line of view, the pituitary adenylate cyclase-activating polypeptide (PACAP), with its ability to cross the blood–brain barrier and its anti-apoptotic, anti-inflammatory and anti-oxidative properties, has proven to offer potent neuroprotection in various PD models. Nonetheless, its peripheral actions, paired with low metabolic stability, hampered its clinical use. We have developed Ac-[Phe(pI)6, Nle17]PACAP(1-27) as an improved PACAP-derived neuroprotective compound. In vitro, this analog stimulated cAMP production, maintained mitochondrial potential and protected SH-SY5Y neuroblastoma cells from 1-methyl-4-phenylpyridinium (MPP+) toxicity, as potently as PACAP. Furthermore, contrasting with PACAP, it is stable in human plasma and against dipeptidyl peptidase IV activity. When injected intravenously to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mice, PACAP and Ac-[Phe(pI)6, Nle17]PACAP(1-27) restored tyrosine hydoxylase expression into the substantia nigra and modulated the inflammatory response. Albeit falls of mean arterial pressure (MAP) were observed with both PACAP- and Ac-[Phe(pI)6, Nle17]PACAP(1-27)-treated mice, the intensity of the decrease as well as its duration were significantly less marked after iv injections of the analog than after those of the native polypeptide. Moreover, no significant changes in heart rate were measured with the animals for both compounds. Thus, Ac-[Phe(pI)6, Nle17]PACAP(1-27) appears as a promising lead molecule for the development of PACAP-derived drugs potentially useful for the treatment of PD or other neurodegenerative diseases.

The proinflammatory cytokine high‐mobility group box‐1 mediates retinal neuropathy induced by diabetes

AbstractPurpose To test the hypothesis that increased expression of proinflammatory cytokine high‐mobility group box‐1 (HMGB1) in epiretinal membranes and vitreous fluid from patients with proliferative diabetic retinopathy and in retinas of diabetic rats plays a pathogenetic role in mediating diabetes‐induced retinal neuropathy.Methods Retinas of 1‐month diabetic rats and HMGB1 intravitreally injected normal rats were studied using Western blot analysis, RT‐PCR and glutamate assay. In addition, we studied the effect of the HMGB1 inhibitor glycyrrhizin on diabetes‐induced biochemical changes in the retina.Results Diabetes and intravitreal injection of HMGB1 in normal rats induced significant upregulation of HMGB1 protein and mRNA, activated extracellular signal‐regulated kinase 1 and 2 (ERK1/2) cleaved caspase‐3 and glutamate and significant downregulation of synaptophysin, tyrosine hydroxylase, glutamine synthetase and glyoxalase 1. Constant glycyrrhizin intake from the onset of diabetes did not affect the metabolic status of the diabetic rats, but it significantly attenuated diabetes‐induced upregulation of HMGB1 protein and mRNA, activated ERK1/2 , cleaved caspase‐3 and glutamate. In the glycyrrhizin‐fed diabetic rats, the decrease in synaptophysin, tyrosine hydoxylase and glyoxalase 1 caused by diabetes was significantly attenuated.Conclusion These findings suggest that early retinal neuropathy of diabetes involves upregulated expression of HMGB1 and can be ameliorated by inhibition of HMGB1.

Abstract 085: Anti-Inflammatory Treatment Reverses The Age-Related Increase In Catecholamine Biosynthetic Enzyme Tyrosine Hydroxylase And NYP In The Adrenal Medulla

Aging is associated with both elevated blood pressure and decreased baroreceptor sensitivity. These have been attributed to increased sympathetic nerve activity with age. One marker of sympathoactivation is protein levels of tyrosine hydoxylase (TH) in the adrenal medulla (AM), and TH levels markedly increase with age. There is also an increase in inflammation with age. To test the hypothesis that increased inflammation with age contributes to the elevated TH levels in the AM, we examined treatment with the anti-inflammatory agents, indomethacin (10 mg/kg, BID) or rosiglitazone (1 mg/kg, BID) on TH synthesis in F344 rats of three ages, 5, 12, 18 months. In addition, NPY, a peptide that is synthesized and co-released with catecholamines in the AM, as well as angiotensin II receptor subtypes, AT1 and AT2 protein levels were assessed in the AM following the anti-inflammatory treatments. Indomethacin and rosiglitazone were administered orally as part of a frozen strawberry treat for 16 days. Although there were no changes in TH or NPY levels between the 5 mo and 12 mo old control animals, TH and NPY were elevated by 27% and 45% (P<0.05), respectively in the 18 compared with 5 mo rats. These age-related increases were completely reversed by treatment with indomethacin or rosiglitazone (P<0.05). There was no effect of either treatment on AT1 or AT2 receptor protein, although AT1 receptor protein levels diminished slightly with age. These data indicate that anti-inflammatory treatment reverses the elevated TH and NPY in AM with age. Increased inflammation with age indirectly through elevated catecholamine synthesis may be contributing to the increased prevalence of hypertension with age.

Human Induced Pluripotent Stem Cells Improve Stroke Outcome and Reduce Secondary Degeneration in the Recipient Brain

Human induced pluripotent stem cells (hiPSCs) are a most appealing source for cell replacement therapy in acute brain lesions. We evaluated the potential of hiPSC therapy in stroke by transplanting hiPSC-derived neural progenitor cells (NPCs) into the postischemic striatum. Grafts received host tyrosine hydroxylase-positive afferents and contained developing interneurons and homotopic GABAergic medium spiny neurons that, with time, sent axons to the host substantia nigra. Grafting reversed stroke-induced somatosensory and motor deficits. Grafting also protected the host substantia nigra from the atrophy that follows disruption of reciprocal striatonigral connections. Graft innervation by tyrosine hydoxylase fibers, substantia nigra protection, and somatosensory functional recovery were early events, temporally dissociated from the slow maturation of GABAergic neurons in the grafts and innervation of substantia nigra. This suggests that grafted hiPSC-NPCs initially exert trophic effects on host brain structures, which precede integration and potential pathway reconstruction. We believe that transplantation of NPCs derived from hiPSCs can provide useful interventions to limit the functional consequences of stroke through both neuroprotective effects and reconstruction of impaired pathways.

Aggressive behavior during social interaction in mice is controlled by the modulation of tyrosine hydroxylase expression in the prefrontal cortex

The Balb/c strain and the C57BL/6 strain show constitutive differences for tyrosine hydroxylase expression, and noradrenaline (NA) prefrontal transmission. Male mice of these strains also show striking differences in social interaction behaviors, with an increased aggressiveness for the Balb/c strain. To test a potential link between these neurobiological and behavioral parameters, we evaluated the behavioral effects of chronic treatment of mice with BC19, a noreburnamine compound previously known as RU24722, found to modify cell organisation, tyrosine hydoxylase (TH) expression, and its activity into the locus coeruleus (LC). We compared the pharmacological effects between the two strains in social behaviors. Our results show that the emergence of additional TH–expressing (TH+) neurons in the rostral part of the LC of Balb/c mice was associated with an increase in the density of TH+ and noradrenergic (NA+) fibers in the molecular layer in the cingular (Cg1) and prelimbic (PrL) parts of the prefrontal cortex (PFC). BC19 treatment resulted in the near-equalization of the LC number of TH+ neurons and of the density of TH+ and NA+ fibers between both strains. The aggressiveness in Balb/c mice was considerably diminished by BC19 treatment, while the originally non aggressive behavior of C57Bl/6 mice was much less affected by BC19 treatment, despite a moderate increase in some offensive behaviors. In additional control experiments, we checked the effect of BC19 on a separate test for anxiety and assessed the effect of noradrenergic N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine hydrochloride (DSP-4) mediated lesions in C57BL/6 mice on social behaviors. In the present study we show that the BC19 effect in Balb/c mice was independent of anxiety as measured in the light/dark test and that DSP-4 lesions in C57BL/6 mice produced a robust increase in aggressive social interaction. Altogether, these results show that the noradrenergic system, and particularly its projections to the PFC, strongly modulates aggressive behaviors.

Male-like sexual behavior of female mouse lacking fucose mutarotase

BackgroundMutarotases are recently characterized family of enzymes that are involved in the anomeric conversions of monosaccharides. The mammalian fucose mutarotase (FucM) was reported in cultured cells to facilitate fucose utilization and incorporation into protein by glycosylation. However, the role of this enzyme in animal has not been elucidated.ResultsWe generated a mutant mouse specifically lacking the fucose mutarotase (FucM) gene. The FucM knockout mice displayed an abnormal sexual receptivity with a drastic reduction in lordosis score, although the animals were fertile due to a rare and forced intromission by a typical male. We examined the anteroventral periventricular nucleus (AVPv) of the preoptic region in brain and found that the mutant females showed a reduction in tyrosine hydoxylase positive neurons compared to that of a normal female. Furthermore, the mutant females exhibited a masculine behavior, such as mounting to a normal female partner as well as showing a preference to female urine. We found a reduction of fucosylated serum alpha-fetoprotein (AFP) in a mutant embryo relative to that of a wild-type embryo.ConclusionsThe observation that FucM-/- female mouse exhibits a phenotypic similarity to a wild-type male in terms of its sexual behavior appears to be due to the neurodevelopmental changes in preoptic area of mutant brain resembling a wild-type male. Since the previous studies indicate that AFP plays a role in titrating estradiol that are required to consolidate sexual preference of female mice, we speculate that the reduced level of AFP in FucM-/- mouse, presumably resulting from the reduced fucosylation, is responsible for the male-like sexual behavior observed in the FucM knock-out mouse.

Abstract 5014: Identification and analysis of critical domains within the neuroblastoma tumor suppressor gene CASZ1

Abstract Neuroblastoma (NB) is an enigmatic pediatric cancer for which highly successful therapies have been developed for tumors displaying favorable characteristics, while poor prognoses persist for unfavorable tumors. Chromosome 1p36 is frequently lost in the tumors of many patients with unfavorable prognoses and harbors the locus of the zinc finger (ZF) transcription factor CASZ1. Low CASZ1 expression is significantly associated with lower overall patient survival in NB. Functionally, CASZ1 suppresses NB tumor cell growth and regulates a number of key genes important in neural development (e.g. TrkA, p75 and tyrosine hydoxylase [TH]). It has been shown that high expression of TrkA and p75 are both independently associated with good prognoses in NB patients. Despite the important role of CASZ1 in neural development and NB tumor suppression, the key domains that mediate the activation role of CASZ1 have never been elucidated. In order to address this question, we performed a detailed analysis of CASZ1 protein isoform A (CASZ1a), which contains five ZF's. Abrogation of CASZ1a function was determined by loss of the ability to induce endogenous TrkA, p75 and TH mRNA transcription as well as by loss of the ability to activate a TH promoter-luciferase reporter construct. Using site-directed mutagenesis, we individually mutated each of the five ZF's and discovered that loss of any one of ZF1-4 resulted in a 72-98% loss of function compared to wild-type CASZ1a (p < 0.001), without altering protein stability or nuclear localization. Also, deletion of the C-terminal sequence AA728-1166 (a 38% truncation of the protein) did not appreciably alter function. However, a series of N-terminal truncations revealed a novel nuclear localization signal (NLS) at AA23-29, and it was found that CASZ1a depends on this NLS to localize to the nucleus. In addition, a critical activation domain was mapped to AA31-185 of the N-terminus, which also coincides with a newly identified CASZ1a homodimerization domain. Loss of this activation domain resulted in a complete loss of CASZ1a-mediated induction of the target genes TrkA, p75 and TH (p < 0.001), without affecting protein stability or nuclear localization. Therefore, the discovery and analysis of critical domains in this study has linked CASZ1a loss of function to the loss of induction of the positive NB prognostic factors p75 and TrkA. This demonstrates how the loss of CASZ1a may contribute to the pathogenesis and abysmal survivability of high stage neuroblastoma. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5014.

No Evidence for Association between Tyrosine Hydroxylase Gene Val81Met Polymorphism and Susceptibility to Tardive Dyskinesia in Schizophrenia

ObjectiveTyrosine hydroxylase (TH) is the rate-limiting enzyme in dopamine biosynthesis. Because the TH Val81Met polymorphism is located in the amino-terminal regulatory domain of the tetrameric enzyme, it is a candidate marker for susceptibility to dopamine-related traits. We investigated the hypothesis that TH Val81Met polymorphism can influence susceptibility to tardive dyskinesia (TD) in schizophrenia.MethodsTH Val81Met polymorphism was analyzed by PCR-based methods in 83 schizophrenic patients with TD and 126 schizophrenic patients without TD, matched for antipsychotic drug exposure and other relevant variables.ResultsThere was no significant association of the genotype and allele frequencies determined by the TH Val81Met polymorphism between TD and non-TD patients. In addition, there was no significant difference in terms of total Abnormal Involuntary Movement Scale scores among the three genotype groups.ConclusionWithin the limitations imposed by the size of the clinical sample, these findings suggest that the Val81Met polymorphism of the TH gene does not contribute significantly to the risk for TD.

Nigral burden of α‐synuclein correlates with striatal dopamine deficit

Aggregated alpha-synuclein is the hallmark of Parkinson's disease (PD), diffuse Lewy body disease (DLBD), and multiple system atrophy (MSA). Physiologically, alpha-synuclein ensures normal functions of dopamine transporter (DAT) and tyrosine hydoxylase. In alpha-synucleinopathies, it accumulates in neuronal cytoplasm and neurites through several stages. It is unclear whether the accumulation of pathological alpha-synuclein in the substantia nigra in PD correlates with the dopaminergic deficit in the striatal target. We evaluated the impact of the nigral burden of pathological alpha-synuclein immunoreactivity in 27 alpha-synucleinopathy brains by morphometric immunohistochemistry. DAT immunoreactivity in the striatum inversely correlates with the total alpha-synuclein burden in the substantia nigra but not with cytoplasmic inclusion counts only. This result has implications for imaging, clinicopathological correlative studies, and staging of the disease process.

Genetic polymorphisms in dopamine-related genes and smoking cessation in women: a prospective cohort study

BackgroundGenes involved in dopaminergic neurotransmission have been suggested as candidates for involvement in smoking behavior. We hypothesized that alleles associated with reduced dopaminergic neurotransmission would be more common in continuing smokers than among women who quit smoking.MethodsThe study included 593 women aged 26–65 years who participated in a twelve month smoking cessation trial conducted in 1993–1994. Participants were contacted three years after the trial to obtain updated smoking history and biological specimens. Seven polymorphisms were assessed in genes involved in dopamine synthesis (tyrosine hydoxylase [TH]), receptor activation (dopamine receptors [DRD2, DRD3, DRD4]), reuptake (dopamine transporter [SLC6A3]), and metabolism (catechol-o-methyltransferase [COMT]). Smoking cessation was assessed as "short-term" quitting (abstinence for the seven days before the conclusion of the trial) and "long-term" quitting (abstinence for the six months before a subsequent interview conducted several years later).ResultsWe observed no association of any polymorphism with either short- or long-term quitting. Although some relative risk estimates were consistent with weak associations, either the direction of effect was opposite of that hypothesized, or results of the short- and long-term cessation endpoints differed. However, effect modification on smoking cessation was observed between DRD2 Taq1A and SLC6A3 VNTR polymorphisms, DRD3 Ser/Gly and d,1-fenfluramine, and DRD4 VNTR and d,1-fenfluramine.ConclusionAlthough these results fail to support prior findings of independent associations of these polymorphisms with smoking status, our exploratory findings suggestive of gene-gene and gene-treatment interactions warrants further investigation.

Prostaglandin E2 Regulates the Nuclear Receptor NR4A2 in Colorectal Cancer

Many lines of research implicate cyclooxygenase 2-derived prostaglandins in tumor growth and metastasis. More specifically, we have shown that prostaglandin E2 (PGE2) promotes cell proliferation and invasion through transactivation of the epidermal growth factor receptor, initiates immune evasion through induction of decay accelerating factor, and transactivates peroxisome proliferator-activated receptor delta, leading to increased polyp size and multiplicity. We continue to identify novel PGE2 target genes in colorectal carcinoma cells and report here that an immediate early gene, nuclear factor NR4A2 (Nurr1), is induced by PGE2 that in turn regulates cell death. Originally described as a critical dopaminergic neuron growth factor receptor, NR4A2 expression is rapidly but transiently induced by PGE2 in a cAMP/protein kinase A-dependent manner. NR4A2 binds to the cognate NBRE response element and enhances transcription of a reporter construct in colorectal carcinoma cells. Furthermore, NR4A2 expression is elevated in Apc-/+ mouse adenomas and its levels were further increased following PGE2 treatment. Human colorectal cancers relative to matched normal mucosa showed increased NR4A2 expression. Although not previously described in epithelial tissues, NR4A2 protein localizes to proliferating crypts of Apc-/+ mouse intestine. Finally, functional studies reveal that PGE2-mediated protection from apoptosis is completely inhibited by a dominant-negative NR4A2 construct. Building on previous reports from our group on the peroxisome proliferator-activated receptor family of nuclear receptors, these most recent data suggest that NR4A2, a member of another family of nuclear receptors can stimulate progression of colorectal cancer downstream from cyclooxygenase 2-derived PGE2.

Differential Expression and Distribution of α-, β-, and γ-Synuclein in the Developing Human Substantia Nigra

Although the functions of α-, β-, and γ-synuclein (αS, βS, γS, respectively) are unknown, these synaptic proteins are implicated in the pathogenesis of Parkinson's disease (PD) and related disorders. For example, αS forms Lewy bodies (LBs) in substantia nigra (SN) neurons of PD. However, since it is not known how these hallmark PD lesions contribute to the degeneration of SN neurons or what the normal function of αS is in SN neurons, we studied the developing human SN from 11 weeks gestational age (GA) to 16 years of age using immunohistochemistry and antibodies to αS, βS, γS, other synaptic proteins, and tyrosine hydoxylase (TH). SN neurons expressed TH at 11 weeks GA and αS, βS, and γS appeared initially at 15, 17, and 18 weeks GA, respectively. These synucleins first appeared in perikarya of SN neurons after synaptophysin, but about the same time as synaptotagmin and synaptobrevin. Redistribution of αS from perikarya to processes of SN neurons occurred by 18 weeks GA in parallel with synaptophysin, while βS and synaptotagmin were redistributed similarly between 20 and 28 weeks GA and this also occurred with γS and synaptobrevin between 33 weeks GA and 9 months postnatal. These data suggest that αS, βS, and γS may play a functional role in the development and maturation of SN neurons, but it remains to be determined how sequestration of αS as LBs in PD contributes to the degeneration of SN neurons.

The metabolic rate and vulnerability of dopaminergic neurons, and adenosine dynamics in the cerebral cortex, nucleus accumbens, caudate nucleus, and putamen of the common marmoset.

The pathophysiology of the striatum and cerebral cortex were studied from the pharmacological aspect. Investigation of the dopamine content in the cerebral cortex revealed that the premotor and motor area showed the highest level (61+/-6.2 ng/g). Intravenous injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) at a dose of 10 mg/kg reduced the dopamine content in the caudate nucleus and putamen to 2-3% of the control level in common marmosets, while it fell to 60% in the nucleus accumbens. There was no alteration of the dopamine content in the cerebral cortex. Immunohistochemical staining for tyrosine hydroxylase in the midbrains of MPTP-treated marmosets showed almost complete disappearance of dopaminergic cells from the substantia nigra and good preservation of cells in the ventrotegmental area. Dopaminergic cells projecting to the caudate/putamen, nucleus accumbens, and cerebral cortex showed marked, moderate, and no vulnerability to MPTP, respectively. After systemic administration of MPTP, dopaminergic neurons projecting to the caudate nucleus and putamen were damaged equally. However, the compensatory increase of dopamine turnover was more prominent in the putamen than in the caudate nucleus. Thus, nigroputaminal dopaminergic neurons may have a higher level of activity than neurons in the caudate. The neural connections and functions of the caudate nucleus and putamen have already been differentiated anatomically or physiologically. This compensatory increase of the dopamine turnover rate is another aspect of functional differences between the caudate nucleus and putamen. Investigation of the dopamine content in the head, body, and tail of the caudate nucleus showed no differences in the concentration of dopamine. However, a study of the metabolic rate of dopamine using alpha-methyl-p-tyrosine, a tyrosine hydoxylase inhibitor, showed higher metabolism of dopamine in the head of the caudate nucleus in common marmosets. Thus, dopaminergic neurons projecting to the caudate nucleus may show topographical differences in their firing rates. A microdialysis study indicated an increase in the metabolism of adenosine in the striatum of MPTP-treated animals. Cholinergic neurons are interneurons and are one of the main sources of adenosine in the striatum. Dopaminergic input from the substantia nigra acting on cholinergic neurons was decreased following MPTP treatment. The increase of adenosine metabolism suggested that cholinergic neurons in the striatum receive inhibitory inputs from nigrostriatal dopaminergic neurons.

Genetic associations with clinical characteristics in bipolar affective disorder and recurrent unipolar depressive disorder

Genetic factors may be associated with disease subtype as well as susceptibility. We have therefore typed polymorphisms at the serotonin transporter, dopamine receptor, tryptophan hydroxylase, tyrosine hydoxylase, and monoamine oxidase A (MAOA) loci in 139 unipolar and 131 bipolar patients and investigated associations with gender, number of episodes, age of onset, history of psychotic symptoms, history of suicidal behavior, and history of substance abuse. In bipolar subjects, the promoter variable number tandem repeat (VNTR) allele 132 of MAOA was associated with history of suicide attempts, P = 0.029, particularly in females, P = 0.006. The Fnu4HI allele 1 of MAOA was also associated with history of suicide attempts in females, P = 0.0162. The serotonin transporter promoter allele 2 was associated with increasing number of manic episodes, P = 0.02, and history of psychotic symptoms, P = 0.0243. One significant association was found in the unipolar group: dopamine D2 receptor promoter allele 2 with history of psychotic symptoms, P = 0. 0165. We have tested multiple loci for a variety of different clinical variables and performed 228 tests of significance in total. It is possible that these preliminary findings are type 1 errors, because one would expect 11 of the 228 tests to reach a nominal significance level of P < 0.05 by chance alone if all the tests were independent. The associations with the MAOA and serotonin transporter loci are consistent with previous data suggesting associations with susceptibility to bipolar affective disorder. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:36-42, 2000

Glial cell line-derived neurotrophic factor protects midbrain dopamine neurons from the lethal action of the weaver gene: a quantitative immunocytochemical study

Glial cell line-derived neurotrophic factor (GDNF) has been shown to protect and repair midbrain dopamine neurons in vivo using animal models created with neurotoxins. The weaver mouse ( wv/wv) has natural and spontaneous midbrain dopaminergic cell death which gives a unique opportunity to examine the effects of GDNF. The present study was designed to investigate a possible neuroprotective role by GDNF for midbrain dopamine neurons in the wv/wv. Weaver pups were given 1 μl injections on postnatal day 1. The wv/wv placebo group received a single unilateral injection into the right lateral ventricle of phosphate buffered saline (PBS) while the GDNF treated wv/wv mice received either 1.0 μg/μl or 10.0 μg/μl GDNF in PBS. All mice were sacrificed on postnatal day 20 and their brains were processed for tyrosine hydoxylase (TH) immunocytochemistry. When compared to the placebo group, the 1 μg GDNF group showed significantly less cell death on the injection side, but the contralateral side showed no significant sparing of TH neurons. The combined counts from both sides show significantly more TH staining neurons in the 1 μg GDNF group compared to placebo. When compared to placebo-injected controls, the 10 μg GDNF treated group showed significantly more TH staining neurons on the injected side, contralateral side, and combined. The results demonstrate that GDNF does protect weaver dopaminergic midbrain neurons from the lethal action of the weaver gene and the effect is positively correlated to dosage.

Diagnosis and Classification of the Small Round-Cell Tumors of Childhood

The small-round-cell tumors of childhood include neuroblastoma, the Ewing family of tumors, rhabdomyosarcoma, lymphoma, and desmoplastic small-round-cell tumor. Although classical histological features are generally highly suggestive of tumor type, on occasion these tumors may be indistinguishable by light microscopy, making a definitive diagnosis difficult. Accurate diagnosis of pediatric small-round-cell tumors has become increasingly crucial, as disparate approaches to therapy are used for distinct tumor types. In addition, because for many pediatric cancers, therapy is also tailored according to patient risk, it has become important to further classify tumors biologically, using cytogenetic or molecular studies to identify chromosome translocations, gene amplification, gene expression patterns, and/or mutations. In this issue of The American Journal of Pathology, Gilbert and colleagues used a reverse transcriptase polymerase chain reaction (RT-PCR) assay to analyze the expression of two genes involved in the catecholamine biosynthetic pathway, tyrosine hydoxylase and dopa decarboxylase, in 84 pediatric malignancies. 1 Their studies demonstrate that the expression of these two genes is highly specific for neuroblastoma. Of the 29 non-neuroblastoma tumor samples examined, only pheochromocytomas expressed clearly detectable levels of the genes. These results suggest that analysis of tyrosine hydoxylase and dopa decarboxylase expression may help distinguish neuroblastoma from other small-round-cell childhood tumors. Despite recent advances in immunohistochemistry and molecular pathology, some cases of small-round-cell tumors of childhood remain diagnostically problematic. Thus, additional diagnostic tools, such as the ones described by Gilbert and co-workers, are needed to ensure that every child with a small-round-cell tumor is diagnosed correctly. The value and limitations of current immunohistochemical, cytogenetic, and molecular studies as diagnostic aids for the small-round-cell tumors of childhood are highlighted below.

Occurrence of axons with certain immunohistochemical markers in teleost gingiva and teeth

The occurrence of axons with certain neurochemical markers in gingiva and teeth in the lower jaw of the cichlid Tilapia mariae was examined by immunohistochemistry. It was found that gingival and pulpal axons can be labelled with antibodies against calcitonin gene-related peptide, substance P, tyrosine hydoxylase, neuropeptide Y, choline acetyl transferase and vasoactive intestinal polypeptide. It is concluded that both gingival and dental domains in T. mariae contain axons with sensory and autonomic chemical phenotypes, the occurrence and distribution of which are generally similar to the mammalian counterpart.

GM1 ganglioside partially rescues cultured dopaminergic neurons from MPP +-induced damage: dependence on initial damage and time of treatment

GM1 ganglioside is believed to be important in promoting the recovery of neurons from injury. The present study assesses the ability of GM1 to repair or prevent the damage of dopamine neurons caused by the neurotoxin 1-methyl-4-phenylpyridinium (MPP +). Treatment of mesencephalic cell cultures with 2.5 μM MPP + resulted in the loss of 30% of tyrosine hydoxylase (TH) immunoreactive neurons. In contrast, cultures administered 100 μM GM1 ganglioside for 3 days after toxin treatment contained nearly control numbers of TH + neurons (97%). This reparative effect of GM1 was reflected in parallel increases in TH enzyme activity, dopamine and dopac levels. Cultures sustaining greater insult from higher doses of MPP + (5.0–10.0 μM) did not benefit from ganglioside treatment, suggesting that rescue by GM1 depended on the degree of initial damage to cells. Moreover, the timing of ganglioside treatment was critical; pretreatment with GM1 alone did not prevent or attenuate the damage caused by subsequent incubation in 2.5 μM MPP +.