Fragile X Mental Retardation Protein expression in the retina is regulated by light.

Fragile X Mental Retardation Protein (FMRP) is a RNA-binding protein that modulates protein synthesis at the synapse and its function is regulated by glutamate. The retina is the first structure that participates in vision, and uses glutamate to transduce electromagnetic signals from light to electrochemical signals to neurons. FMRP has been previously detected in the retina, but its localization has not been studied yet. In this work, our objectives were to describe the localization of FMRP in the retina, to determine whether different exposure to dark or light stimulus alters FMRP expression in the retina, and to compare the pattern in two different species, the mouse and chick. We found that both FMRP mRNA and protein are expressed in the retina. By immunohistochemistry analysis we found that both mouse and chick present similar FMRP expression localized mainly in both plexiform layers and the inner retina. It was also observed that FMRP is down-regulated by 24 h dark adaptation compared to its expression in the retina of animals that were exposed to light for 1 h after 24 h in the dark. We conclude that FMRP is likely to participate in retinal physiology, since its expression changes with light exposure. In addition, the expression pattern and regulation by light of FMRP seems well conserved since it was similar in both mouse and chick.

Review: neuropathology of acute phase encephalitis lethargica: a review of cases from the epidemic period.

INTRODUCTION: Encephalitis lethargica (EL), an epidemic disease of the early 20th century, has continued to be diagnosed sporadically since that time, including a report of 20 new cases in 2004. Many of the recent case reports state that the primary neuropathology of acute EL consists of inflammatory changes and lesions within the midbrain, basal ganglia and substantia nigra. However, the neuropathology of acute EL cases from the epidemic period was actually much more widespread. METHODS: In order to characterize the neuropathology of acute phase EL, we developed a database of EL pathology based on 112 cases from the years 1915 to 1940, of which most died within 2 weeks of EL onset. RESULTS: Our analysis revealed that cortical damage was prevalent in 75% of the 112 cases; damage to the meninges and brainstem occurred in approximately half of the cases; and the substantia nigra was damaged in only 13% of these acute cases. We also found that after 1921, damage to cranial nerve nuclei was not reported. An analysis of the neuropathology and clinical symptoms revealed little correlation. CONCLUSIONS: Based on these findings, putative modern cases of acute EL with MRI/CT indicated lesions confined solely to the midbrain, brainstem, and/or basal ganglia should not be considered, consistent with that reported during epidemic period.

Dopaminergic neurotoxicity of 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine in mice.

1-Methyl-4-phenyl-1,2,5,6- tetrahydropyri dine ( MPTP ) is known to cause an irreversible destruction of the dopaminergic nigrostriatal pathway and symptoms of parkinsonism in humans and in monkeys. However, MPTP has been reported to act only minimally or not at all in several other animal species. When MPTP (30 milligrams per kilogram of body weight) was administered parenterally to mice, a decrease in concentrations of neostriatal dopamine and its metabolites, a decrease in the capacity of neostriatal synaptosomal preparations to accumulate [3H]dopamine, and a disappearance of nerve cells in the zona compacta of the substantia nigra were observed. In contrast, MPTP administration had no effect on neostriatal concentrations of serotonin and its metabolites. MPTP administration thus results in biochemical and histological changes in mice similar to those reported in humans and monkeys and similar to those seen in Parkinson's disease in humans. The mouse should prove to be a useful small animal with which to study the mode of action of MPTP .

Mapping of a gene for Parkinson's disease to chromosome 4q21-q23.

Parkinson's disease (PD) is the second most common neurodegenerative disorder after Alzheimer's disease, affecting approximately 1 percent of the population over age 50. Recent studies have confirmed significant familial aggregation of PD and a large number of large multicase families have been documented. Genetic markers on chromosome 4q21-q23 were found to be linked to the PD phenotype in a large kindred with autosomal dominant PD, with a Zmax = 6.00 for marker D4S2380. This finding will facilitate identification of the gene and research on the pathogenesis of PD.

Mutation in the alpha-synuclein gene identified in families with Parkinson's disease.

Parkinson's disease (PD) is a common neurodegenerative disorder with a lifetime incidence of approximately 2 percent. A pattern of familial aggregation has been documented for the disorder, and it was recently reported that a PD susceptibility gene in a large Italian kindred is located on the long arm of human chromosome 4. A mutation was identified in the alpha-synuclein gene, which codes for a presynaptic protein thought to be involved in neuronal plasticity, in the Italian kindred and in three unrelated families of Greek origin with autosomal dominant inheritance for the PD phenotype. This finding of a specific molecular alteration associated with PD will facilitate the detailed understanding of the pathophysiology of the disorder.

The functional diversity of the neuronal nicotinic acetylcholine receptors is increased by a novel subunit: beta 4.

A new nicotinic acetylcholine receptor (nAChR) subunit, beta 4, was identified by screening a rat genomic library. In situ hybridization histochemistry revealed expression of the beta 4 gene in the medial habenula of adult rat brains. The primary structure of this subunit was deduced from a cDNA clone isolated from a PC12 cDNA library. Functional nAChRs were detected in Xenopus oocytes injected in pairwise combinations with in vitro synthesized RNAs encoding beta 4 and either the alpha 2, alpha 3, or alpha 4 subunit. Unlike the alpha 3 beta 2 receptor, the alpha 3 beta 4 receptor is not blocked by bungarotoxin 3.1, indicating that the beta subunit can affect the sensitivity of neuronal nAChRs to this toxin. These results extend the functional diversity of nicotinic receptors in the nervous system.

Increased seizure susceptibility in mice lacking metabotropic glutamate receptor 7.

To study the role of mGlu7 receptors (mGluR7), we used homologous recombination to generate mice lacking this metabotropic receptor subtype (mGluR7(-/-)). After the serendipitous discovery of a sensory stimulus-evoked epileptic phenotype, we tested two convulsant drugs, pentylenetetrazole (PTZ) and bicuculline. In animals aged 12 weeks and older, subthreshold doses of these drugs induced seizures in mGluR7(-/-), but not in mGluR7(+/-), mice. PTZ-induced seizures were inhibited by three standard anticonvulsant drugs, but not by the group III selective mGluR agonist (R,S)-4-phosphonophenylglycine (PPG). Consistent with the lack of signs of epileptic activity in the absence of specific stimuli, mGluR7(-/-) mice showed no major changes in synaptic properties in two slice preparations. However, slightly increased excitability was evident in hippocampal slices. In addition, there was slower recovery from frequency facilitation in cortical slices, suggesting a role for mGluR7 as a frequency-dependent regulator in presynaptic terminals. Our findings suggest that mGluR7 receptors have a unique role in regulating neuronal excitability and that these receptors may be a novel target for the development of anticonvulsant drugs.

Pharmacological and functional diversity of neuronal nicotinic acetylcholine receptors.

Recent molecular cloning studies have identified several genes encoding alpha and beta subunits of the nicotinic acetylcholine receptor. These genes have distinct, although overlapping, patterns of expression in the brain and peripheral ganglia. Multiple nicotinic receptors with distinct pharmacological and functional properties can be made in oocytes by pairwise combination of different alpha-type subunits with different beta-type subunits. Both alpha and beta subunits contribute to the pharmacological and functional diversity. Evan Deneris and colleagues explain how oocyte expression studies, in concert with immunological and electrophysiological analysis in vivo, are beginning to reveal the subunit compositions of different neuronal nicotinic receptor subtypes.

Simplified production of a recombinant human angiostatin derivative that suppresses intracerebral glial tumor growth.

Angiostatin is an endogenous inhibitor of tumor neovascularization that inhibits the proliferation of endothelial cells. Production of sufficient quantities of biologically active angiostatin by the enzymatic cleavage of plasminogen has proven difficult in that it has delayed clinical testing. We have cloned, expressed, and purified a recombinant human angiostatin derivative (K1-3) using a mammalian expression system. Through the addition of a secretory signal and polyhistidine sequence tag, K1-3 can be purified from post-culture medium by simple column chromatography. Purified K1-3 protein is apparently folded in an active conformation, as evidenced by its ability to bind to lysine-Sepharose. In vitro, recombinant K1-3 significantly suppressed endothelial cell proliferation in a dose-dependent manner with an IC50 of 50 nM. Using an animal model of intracranial brain tumors in immune-competent rats, systemic administration of purified recombinant K1-3 resulted in up to 85% suppression of tumor growth (P = 0.011). Growth suppression was accompanied by a 32% decrease (P = 0.01) in tumor neovascularization. This study demonstrates a simple method to produce a biologically active recombinant angiostatin derivative. The ability to suppress intracerebral tumor growth after systemic administration suggests that K1-3 is likely to have therapeutic value in the treatment of malignant glial tumors.

Hereditary Lewy-body parkinsonism and evidence for a genetic etiology of Parkinson's disease.

The first systematic genetic study of Parkinson's disease (PD) was carried out by Mjönes in 1949. His results indicated autosomal dominant transmission with 60% penetrance. These conclusions, however, were long discounted because oligosymptomatic and atypical relatives were counted as secondary cases without clear justification. Subsequent surveys of patient and twin studies failed to confirm evidence of familial concentration and the hypothesis of a genetic etiology was over-shadowed by interest in possible environmental neurotoxins. A growing accumulation of pedigrees of histologically confirmed Lewy-body PD over the past several years has refocused attention on genetic factors. Fluorodopa positron emission tomography (PET) studies in oligosymptomatic co-twins of probands and recent clinicopathologic studies of atypical cases have provided retrospective support for Mjönes' methodology. A survey of a personal series of PD patients showed that the majority of those for whom pedigree information was available were familial. This along with another recently reported series confirm Mjönes' data showing similar segregation ratios for siblings and parents, a low ratio of maternal:paternal transmission and a marked asymmetry in the distribution of ancestral secondary cases. These findings favor monogenic autosomal dominant inheritance and show reason to argue against a multifactorial etiology or heteroplasmy. The clinical evidence justifies searching for gene loci linked to PD. Available methods are briefly outlined. Preliminary investigations have examined possible allelic associations, e.g., with alleles of MAO-A and debrisoquine hydroxylase and linkage to the tyrosine hydroxylase gene on chromosome 11p15.5 has been excluded in one study of juvenile familial parkinsonism. Linkage mapping studies are presently underway.

A plasmid expression vector that permits stabilization of both mRNAs and proteins encoded by the cloned genes.

Two new expression vectors have been constructed to take advantage of several useful properties of bacteriophage T4-infected Escherichia coli. These plasmids, pRDB8 and pRDB9, contain the promoter region and start codon of T4 gene 32, a contiguous multiple cloning site (MCS), and translation and transcription termination signals. DNA fragments inserted into the MCS are transcribed and translated at a high level in both uninfected and phage T4-infected cells. Furthermore, the extreme stability of the hybrid mRNA after infection permits the specific biosynthetic labeling of the protein encoded by the cloned gene. In addition, the cloned gene product is stabilized, since the host-mediated degradation of foreign proteins is inhibited by phage infection. The properties of this expression system were demonstrated with the constant region of a rabbit immunoglobulin lambda light chain (C lambda) gene. Although proteolytic degradation of the C lambda fusion protein was rapid in uninfected cells, degradation was blocked in phage-infected cells and the protein accumulated in greater amounts.

A survey of tardive dyskinesia in psychiatric outpatients.

The authors found a high prevalence--43.4% of tardive dyskinesia in a sample of psychiatric outpatients, a population previously thought to be at nominal risk for development of this syndrome. There was no significant relationship between the presence of dyskinesia and age, sex, years of neuroleptic use, or various organic factors. The effects of dentures and of drug combinations are discussed, and it is noted that structured scales of dyskinesia and videotope recordings are important tools in diagnosing and following the course of dyskinesia.

Inhibition of 15-lipoxygenase leads to delayed organelle degradation in the reticulocyte.

Mammalian cells are characterized by an endomembrane system. Nevertheless, some cells lose these membranes during their terminal differentiation, e.g. red blood cells and lens fiber cells of the eye. 15-Lipoxygenase is believed to be critical for this membrane degradation. Here we use cultivated rabbit reticulocytes in the presence or absence of a lipoxygenase inhibitor to provide further evidence for the importance of 15-lipoxygenase for the in vivo degradation of mitochondria. We find that inhibitor treatment retarded mitochondrial degradation, as shown by persistence of marker proteins and by direct visualization of mitochondria by electron microscopy.

Localization of mGluR6 to dendrites of ON bipolar cells in primate retina.

We prepared antibodies selective for the C-terminus of the human mGluR6 receptor and used confocal and electron microscopy to study the patterns of immunostaining in retina of monkey, cat, and rabbit. In all three species punctate stain was restricted to the outer plexiform layer. In monkey, stain was always observed in the central element of the postsynaptic "triad" of rod and cone terminals. In monkey peripheral retina, stain was seen only in central elements, but in the fovea, stain was also observed in some dendrites contacting the base of the cone terminal. S-cone terminals, identified by staining for S opsin, showed staining of postsynaptic dendrites. These were identified as dendrites of the ON S-cone bipolar cell by immunostaining for the marker cholecystokinin precursor. The staining pattern suggests that all types of ON bipolar cells, despite their marked differences in function, express a single isoform of mGluR6. Ultrastructurally, mGluR6 was located not on the tip of the central element, near the site of vesicle release, but on its base at the mouth of the invagination, 400-800 nm from the release site. Thus, the mGluR6 receptors of ON bipolar cells lie at about the same distance from sites of vesicle release as the iGluR receptors of OFF bipolar cells at the basal contacts.

Cloning and immunocytochemical localization of a cyclic nucleotide-gated channel alpha-subunit to all cone photoreceptors in the mouse retina.

Cyclic nucleotide-gated channels (CNGC) are ligand-gated ion channels that open and close in response to changes in the intracellular concentration of the second messengers, 3;,5;-cyclic adenosine monophosphate and 3;,5;-cyclic guanosine monophosphate. Most notably, they transduce the chemical signal produced by the absorption of light in photoreceptors into a membrane potential change, which is then transmitted to the ascending visual pathway. CNGCs have also been implicated in the signal transduction of other neurons downstream of the photoreceptors, in particular the ON-bipolar cells, as well as in other areas of the central nervous system. We therefore undertook a search for additional cyclic nucleotide-gated channels expressed in the retina. Following a degenerate reverse transcription polymerase chain reaction approach to amplify low-copy number messages, a cDNA encoding a new splice variant of CNGC alpha-subunit was isolated from mouse retina and classified as mCNG3. An antiserum raised against the carboxy-terminal sequence identified the retinal cell type expressing mCNG3 as cone photoreceptors. Preembedding immunoelectron microscopy demonstrated its membrane localization in the outer segments, consistent with its role in phototransduction. Double-labeling experiments with cone-specific markers indicated that all cone photoreceptors in the murid retina use the same or a highly conserved cyclic nucleotide-gated channel. Therefore, defects in this channel would be predicted to severely impair photopic vision.

Smoking and Parkinson's disease. Search for a dose-response relationship.

We tested the hypothesis that the inverse association of smoking and Parkinson's disease (PD) results from a direct pharmacologic benefit of smoking on PD. We mailed questionnaires to the 32,000 members of the United Parkinson Foundation and searched for evidence of a dose-response effect between increasing intensity of smoking and decreasing intensity of PD. Of the 6006 respondents, 3693 met our diagnostic criteria. Despite confining the analysis to subgroups where confounding effects would be minimized, we found no significant correlation between any measure of smoking and any measure of PD severity and conclude that smoking is probably not of benefit in preventing, delaying, or ameliorating PD.

Hereditary dystonia-parkinsonism syndrome of juvenile onset.

We studied a family with an extrapyramidal disorder characterized by childhood onset of lower-limb and axial dystonia, followed by parkinsonism. Dramatic response to levodopa therapy and minimal progression in adult life was seen. The family included five generations of affected members of both sexes in an autosomal dominant pattern.

"Apraxia" of eyelid opening: an involuntary levator inhibition.

Apraxia of lid opening was described by Goldstein and Cogan as "a non paralytic motor abnormality characterized by the patient's difficulty in initiating the act of lid elevation." We studied six such patients with this finding accompanied by vigorous frontalis contraction and no evidence of ongoing orbicularis oculi contraction, dysfunction of the oculomotor nerve, or loss of ocular sympathetic innervation. Four patients had Parkinson's disease or atypical parkinsonism, one had progressive supranuclear palsy, and one had Shy-Drager syndrome. At onset of ocular symptoms, mean age was 64 years, and the mean duration of extrapyramidal symptoms was 9.7 years. By definition, the motor system must be intact in any apraxia. Therefore, this disorder of lid opening in patients with extrapyramidal motor dysfunction is not an apraxia, but rather involuntary levator palpebrae inhibition of supranuclear origin.

A physiologic and pharmacologic study in anticholinergic-responsive essential myoclonus.

We report the physiologic and pharmacologic analysis in two women, aged 18 and 17 years, with essential myoclonus. Both responded to benztropine mesylate and had been functioning normally. The physiologic analysis suggested ballistic movement overflow and audiogenic stimulus-sensitive myoclonus. The pharmacologic study showed a direct and mutual antagonism of physostigmine and anticholinergic agent on myoclonus, implying cholinergic hyperactivity in the pathophysiology of myoclonus.

Behavioral correlations of dopamine receptor activation.

According to the classification scheme of Kebabian and Calne, there are two types of dopamine (DA) receptors: D1 (activation of which causes increased cyclic AMP formation) and D2 (activation of which causes no increment in cyclic AMP). It is not clear what role the different receptors play in mediating motor behavior. Using drugs that act selectively at only one receptor site, we studied the effects of D1 and D2 receptor activation in two different models of parkinsonism--the rotating rat and the reserpinized mouse. Neither the D1 agonist nor the D2 agonist, given alone, could overcome reserpine akinesia, but together they restored locomotor activity. In rats with unilateral nigrostriatal lesions, both drugs induced a rotational response, each with a distinct temporal pattern. Pretreatment with alpha-methyl-paratyrosine (an inhibitor of DA synthesis) led to decrements in the rotational response induced by D2 agonists, but not that induced by D1 agonists. The mechanism by which these DA agonists induce motor activity is different; activation of both types of DA receptors seems to be necessary for normal motor behavior.