Regulation of skeletal muscle stem cell behavior by Pax3 and Pax7.

Pax genes have important roles in the regulation of stem cell behavior, leading to tissue differentiation. In the case of skeletal muscle, Pax3 and Pax7 perform this function both during development and on regeneration in the adult. The myogenic determination gene Myf5 is directly activated by Pax3, leading to the formation of skeletal muscle. Fgfr4 is also a direct Pax3 target and Sprouty1, which encodes an intracellular inhibitor of fibroblast growth factor (FGF) signaling, is under Pax3 control. Orchestration of FGF signaling, through Fgfr4/Sprouty1, modulates the entry of cells into the myogenic program, thus controling the balance between stem cell self-renewal and tissue differentiation. This and other aspects of Pax3/7 function in regulating the behavior of skeletal muscle stem cells are discussed.

[Multifocal ERG using ERG-jet and Gold Foil electrodes in normal subjects: comparison and reproducibility]. / ERG multifocal avec électrodes ERG-jet et Gold Foil chez le sujet normal: comparaison et reproductibilité.

PURPOSE: To compare multifocal electroretinogram (mfERG) amplitudes with the Gold Foil electrode and ERG-jet electrode. To study mfERG amplitude changes between two successive records (intraindividual reproducibility). METHODS: The right eye of 27 normal subjects was examined. Two mfERG recordings using the 61-hexagon strategy (Vision Monitor, Métrovision, France) were made with both ERG-jet and Gold Foil electrodes. N1 and P1 wave amplitudes were analyzed in the central response and in four concentric rings. Bland and Altman analysis was used for the reproducibility study. RESULTS: MfERG amplitudes were significantly lower with the Gold Foil electrode, which averaged 72+/-10% of ERG-jet amplitudes. For N1 and P1 waves, the percentage change for the intraindividual reproducibility study was 9.1% and 6.7%, respectively, with the ERG-jet electrode and 18.2% and 13.5%, respectively, with the Gold Foil electrode. CONCLUSION: MfERG amplitudes were larger and more reproducible with an ERG-jet electrode than with a Gold Foil electrode. The limits of agreement of each ring can be used in clinical practice to determine whether the variation between two mfERG recordings over time is normal, which could reflect a retinal disorder.

[Improved visualization of fundus with green-light ophthalmoscopy]. / Intérêt de l'examen biomicroscopique du fond d'oeil en lumière verte.

Monochromatic light accentuates details of different retinal layers because of its variable absorption and reflectance by structures both within and above these layers. Red-free light is little used, although it is an elementary method. Green-light ophthalmoscopy, with its short wavelength, enhances some fundus and vitreous structures and may make the examination of pathologic conditions (premacular pathology, vascular abnormalities, etc.) easier. Furthermore, it is often more comfortable for the patient.

[Infectious crystalline keratopathy: a case report]. / Kératopathie cristalline infectieuse: à propos d'une observation.

We report a case of perforated infectious crystalline keratopathy in a 88-year-old woman. Corneal surgery like keratoplasty and topical corticosteroids are the main causative factors present in the rare reported cases. Clinically, the anterior layers of cornea exhibit slowly progressive stellate infiltrates. "Viridans streptococci" are the most common micro-organisms involved but their culture for identification is difficult. As compared to cultures, histologic examination is more sensitive for diagnosis, by showing clusters of bacteria in the corneal stroma with no inflammatory response.

Modular long-range regulation of Myf5 reveals unexpected heterogeneity between skeletal muscles in the mouse embryo.

The myogenic factor Myf5 plays a key role in muscle cell determination, in response to signalling cascades that lead to the specification of muscle progenitor cells. We have adopted a YAC transgenic approach to identify regulatory sequences that direct the complex spatiotemporal expression of this gene during myogenesis in the mouse embryo. Important regulatory regions with distinct properties are distributed over 96 kb upstream of the Myf5 gene. The proximal 23 kb region directs early expression in the branchial arches, epaxial dermomyotome and in a central part of the myotome, the epaxial intercalated domain. Robust expression at most sites in the embryo where skeletal muscle forms depends on an enhancer-like sequence located between -58 and -48 kb from the Myf5 gene. This element is active in the epaxial and hypaxial myotome, in limb muscles, in the hypoglossal chord and also at the sites of Myf5 transcription in prosomeres p1 and p4 of the brain. However later expression of Myf5 depends on a more distal region between -96 and -63 kb, which does not behave as an enhancer. This element is necessary for expression in head muscles but strikingly only plays a role in a subset of trunk muscles, notably the hypaxially derived ventral body muscles and also those of the diaphragm and tongue. Transgene expression in limb muscle masses is not affected by removal of the -96/-63 region. Epaxially derived muscles and some hypaxial muscles, such as the intercostals and those of the limb girdles, are also unaffected. This region therefore reveals unexpected heterogeneity between muscle masses, which may be related to different facets of myogenesis at these sites. Such regulatory heterogeneity may underlie the observed restriction of myopathies to particular muscle subgroups.

[Macular functions in professional divers]. / Fonction maculaire chez le plongeur professionnel.

PURPOSE: Air diving is frequently practiced by professionals or sportsmen. Controversial data exist in the literature on the existence of retinal abnormalities in divers. PATIENTS AND METHODS: 18 divers (aged: 27-58y) who dived around 2000 times in their life were studied: half of them dived only with air while the others used an O2-enriched gas mixture (40 to 60%). None of them had presented a bend (decompression sickness). Visual acuity and ocular fundus examination have been explored. A quantification of color vision and central visual field, so as a fluorescein angiography have been performed. RESULTS: No alteration of visual acuity was noted; abnormalities in the color vision and the visual field are reported; however the angiographic lesions described in the literature have not been observed. DISCUSSION: The alterations of color vision were quite severe but not very frequent. No correlation was found with any characteristics or type of diving. CONCLUSION: These observations are comforting for sportive divers who do not dive very often nor very deep but an individual predisposition is suspected.

Myf5 is a novel early axonal marker in the mouse brain and is subjected to post-transcriptional regulation in neurons.

Myf5 is a key basic Helix-Loop-Helix transcription factor capable of converting many non-muscle cells into muscle. Together with MyoD it is essential for initiating the skeletal muscle programme in the embryo. We previously identified unexpected restricted domains of Myf5 transcription in the embryonic mouse brain, first revealed by Myf5-nlacZ(+/)(-) embryos (Tajbakhsh, S. and Buckingham, M. (1995) Development 121, 4077-4083). We have now further characterized these Myf5 expressing neurons. Retrograde labeling with diI, and the use of a transgenic mouse line expressing lacZ under the control of Myf5 regulatory sequences, show that Myf5 transcription provides a novel axonal marker of the medial longitudinal fasciculus (mlf) and the mammillotegmental tract (mtt), the earliest longitudinal tracts to be established in the embryonic mouse brain. Tracts projecting caudally from the developing olfactory system are also labelled. nlacZ and lacZ expression persist in the adult brain, in a few ventral domains such as the mammillary bodies of the hypothalamus and the interpeduncular nucleus, potentially derived from the embryonic structures where the Myf5 gene is transcribed. To investigate the role of Myf5 in the brain, we monitored Myf5 protein accumulation by immunofluorescence and immunoblotting in neurons transcribing the gene. Although Myf5 was detected in muscle myotomal cells, it was absent in neurons. This would account for the lack of myogenic conversion in brain structures and the absence of a neural phenotype in homozygous null mutants. RT-PCR experiments show that the splicing of Myf5 primary transcripts occurs correctly in neurons, suggesting that the lack of Myf5 protein accumulation is due to regulation at the level of mRNA translation or protein stability. In the embryonic neuroepithelium, Myf5 is transcribed in differentiated neurons after the expression of neural basic Helix-Loop-Helix transcription factors. The signalling molecules Wnt1 and Sonic hedgehog, implicated in the activation of Myf5 in myogenic progenitor cells in the somite, are also produced in the viscinity of the Myf5 expression domain in the mesencephalon. We show that cells expressing Wnt1 can activate neuronal Myf5-nlacZ gene expression in dissected head explants isolated from E9.5 embryos. Furthermore, the gene encoding the basic Helix-Loop-Helix transcription factor mSim1 is expressed in adjacent cells in both the somite and the brain, suggesting that signalling molecules necessary for the activation of mSim1 as well as Myf5 are present at these different sites in the embryo. This phenomenon may be widespread and it remains to be seen how many other potentially potent regulatory genes, in addition to Myf5, when activated do not accumulate protein at inappropriate sites in the embryo.

Comparison of the efficacy and safety of two eye gels in the treatment of dry eyes: Lacrinorm and Viscotears.

PURPOSE: To compare the efficacy and safety of two carbomer 940 eye gels in the treatment of dry eyes: Lacrinorm (also called GelTears), a recently introduced eye gel, and Viscotears (also called Vidisic or Lacrigel), used as a reference gel. The main difference between the two gels is in the preservative, respectively benzalkonium chloride and cetrimide. METHODS: A double-masked, randomised, parallel-group study was conducted in 16 centres in four European countries. A total of 179 patients suffering from aqueous-deficient dry eye were enrolled, of whom 92 were randomised to treatment with Lacrinorm and 87 to the reference gel. Gel was instilled four times a day for a period of 30 days. RESULTS: After 30 days of treatment, subjective symptoms (the combined scores of foreign body sensation, ocular dryness, burning or pain, and photophobia) had improved by 50% in the Lacrinorm group and by 45% in the reference gel group, and objective test results (break-up time, fluorescein test, Schirmer test, Lissamine Green test) by 35-36% in the Lacrinorm group and 25-45% in the reference group. The improvements were significant in both treatment groups (p < 0.001), with no significant differences between the treatment groups. Subjective local tolerability upon instillation on day 30 was rated 'good' or 'very good' by 91% of patients in both treatment groups. Adverse events were reported for 21 patients in the Lacrinorm group and 17 in the reference group, the most frequent being discomfort, blurred vision, hyperaemia, burning and itching. The frequency and descriptions of adverse events did not differ significantly between the two treatment groups. No serious adverse events were reported. CONCLUSIONS: Over the period of study, Lacrinorm eye gel was as effective and safe as Viscotears/Lacrigel in the treatment of dry eye.

Functional analysis of the mouse myelin/oligodendrocyte glycoprotein gene promoter in the oligodendroglial CG4 cell line.

Myelin/oligodendrocyte glycoprotein (MOG) is a late phylogenetic acquisition among vertebrates that is found only in mammals. MOG is a minor component of myelin protein, representing approximately 0.01-0.05% of the total. Regulatory elements in the MOG gene were identified by transfecting the oligodendroglial CG4 cell line with chimeric MOG-luciferase genes. Only a few hundred base pairs upstream of the coding sequence were necessary for high-level activity of the mouse MOG promoter. More distal recognition sites may exist, because silencing activity, indicative of negative regulatory elements, was detected upstream of base pair 657. Transcriptional activity of chimeric MOG- and myelin basic protein-luciferase genes was greater in CG4 cells than in 3T3 fibroblasts or C6 glioblastoma, demonstrating their superiority for functional analysis of myelin gene regulatory elements.

Physical mapping of the human and mouse MOG gene at the distal end of the MHC class Ib region.

Myelin/oligodendrocyte glycoprotein (MOG) is expressed specifically in the central nervous system (CNS) by myelinating glial cells, the oligodendrocytes. The external location of MOG on myelin sheaths and its late expression during myelinogenesis argue for a role of MOG in the completion of myelin and maintenance of its integrity. MOG is a target autoantigen in demyelinating diseases, such as experimental autoimmune encephalomyelitis (EAE) in animals and multiple sclerosis (MS) in humans. We previously located the gene encoding MOG to the major histocompatibility complex (MHC), both in human, by cytogenetics, and in mouse, by analysis of recombinants. To refine the position, we have now selected yeast artificial chromosome clones (YAC) which contain the MOG gene. Physical mapping of the human MOG and the mouse Mog genes by characterization of these YAC clones indicated that the gene is located at the distal end of the major histocompatibility complex (MHC) class Ib region in both species. The human MOG gene lies 60 kilobases (kb) telomeric to HLA-F in a head-to-head orientation; the mouse Mog gene lies 25 (kb) telomeric to H2-M5 in a tail-to-head orientation. These orthologous genes provide markers for comparative analysis of the evolution of the MHC in the two species. The physical mapping of MOG should facilitate analysis of its role in hereditary neurological diseases, and the YAC clones identified here will permit the identification of new genes in the region.

Structure and polymorphism of the mouse myelin/oligodendrocyte glycoprotein gene.

We have isolated and characterized genomic clones containing the mouse myelin/oligodendrocyte glycoprotein (MOG) gene. It spans a region of 12.5 kb and consists of eight exons. Its exon-intron structure differs from that of classical MHC-class I genes, with which it is linked in the mouse genome. Nucleotide sequencing of the 5' flanking region reveals that it contains several putative protein-binding sites, some of them in common with other myelin gene promoters. One intragenic polymorphism has been identified: it consists of a GA repeat, defining at least three alleles in mouse inbred strains, and is easily detectable using the polymerase chain reaction method.

Chicken neuronal acetylcholine receptor alpha 2-subunit gene exhibits neuron-specific expression in the brain and spinal cord of transgenic mice.

Transgenic mice carrying the complete structural gene of the alpha 2 subunit of the chicken neuronal nicotinic acetylcholine receptor (nAChR) and 7 kilobase pairs (kbp) of 5' upstream and 3 kbp of 3' downstream sequences have been generated. The transgene was stably integrated in transgenic lines and transmitted to their progeny. Avian transgene expression was predominant in the central nervous system as detected by specific alpha 2-subunit cDNA amplification. Moreover, in at least two independent mouse lines, its expression appeared to be neuron-specific and reproducibly restricted to subregions in the brain and spinal cord, as revealed by in situ hybridization histochemistry. Most cranial motor nuclei were positive, and several of the alpha 2-subunit transgene-expressing structures corresponded to cholinergic areas in rodents. This study reveals that regulatory mechanisms giving rise to neuronal-specific gene expression have been conserved at least in part between birds and mammals.

Differential expression of the neuronal acetylcholine receptor alpha 2 subunit gene during chick brain development.

In situ hybridization histochemistry reveals localized expression of the nicotinic acetylcholine receptor (nAChR) alpha 2 subunit mRNA restricted to the lateral spiriform nucleus (SpL) of the chick diencephalon. The alpha 2 nAChR transcripts are not detected in immature SpL neurons at 4.5-5 days of embryonic development. They begin to accumulate in the SpL at embryonic day 11 and increase until the newborn stage. Specific alpha 2 cDNA amplification by the polymerase chain reaction shows that during this period, the absolute content of alpha 2 mRNA increases about 20-fold. The expression of the alpha 2 nAChR gene is thus developmentally regulated and appears concomitant with the entry of cholinergic fibers into the SpL, as demonstrated by choline acetyltransferase immunohistochemistry.

[Cornea and anterior chamber implant with flexible closed haptics]. / Cornée et implant de chambre antérieure à anses flexibles fermées.

Authors report the result of 148 cases of flexible (with closed haptics) anterior chamber lens implantation. Analysis of per and post-operative corneal complications, Study shows increase in time of such complications, in relation to secondary displacement and alteration of lens shape.

["Bell clappers" with "ophthalmologic alarm". Apropos of 2 cases of colloid cysts of the 3d ventricle]. / "Battants de cloche" à "alarme ophtalmologique". A propos de deux cas de kyste colloïde du 3e ventricule.

We report two cases of third ventricle colloid cyst in atypical adult's neurological descriptions, tracked down by ophthalmologist, proved by computed tomography and magnetic resonance imaging. We describe physio-pathological mechanism and dwell on different ophthalmological events of exceptional occurrence with those benign tumours and on ophthalmological investigation's importance in case of persisting and unexplained headache. We conclude with spontaneous clinical course, and neurological surgery's efficacy on hydrocephalus.

Functional activity of the two promoters of the myosin alkali light chain gene in primary muscle cell cultures: comparison with other muscle gene promoters and other culture systems.

Proximal upstream flanking sequences of the mouse myosin alkali light chain gene encoding MLC1F and MLC3F, the mouse alpha-cardiac actin gene and the chicken gene for the alpha-subunit of the acetylcholine receptor were linked to the bacterial chloramphenicol acetyl transferase (CAT) gene and transfected into primary cultures derived from mouse skeletal muscle or into myogenic cell lines. We demonstrate that the mouse MLC1F/MLC3F gene has two functional promoters. In primary muscle cultures, a 1200 bp sequence flanking exon 1 (MLC1F) and a 438 bp sequence flanking exon 2 (MLC3F) direct CAT activity in myotubes, but not in myoblasts or in non myogenic 3T6 and CV1 cells. Developmentally regulated expression is also seen with the alpha-cardiac actin (320 bp) and acetylcholine receptor alpha-subunit (850 bp) upstream sequences in the primary culture system. Transfection experiments with myogenic cell lines show different results with a given promoter construct, reflecting possible differences in the levels of regulatory factors between lines. Different muscle gene promoters behave differently in a given cell line, suggesting different regulatory factor requirements between these promoters.

A 5'-flanking region of the chicken acetylcholine receptor alpha-subunit gene confers tissue specificity and developmental control of expression in transfected cells.

The 5' end and promoter region of the alpha-subunit gene of chicken muscle acetylcholine receptor was mapped and sequenced. It includes a TATA and a CAAT box and a potential Sp1-binding site. When inserted in front of the chloramphenicol acetyltransferase gene, this promoter (including 850 base pairs of upstream sequence) directed high transient chloramphenicol acetyltransferase expression in transfected mouse C2.7 myotubes but not in C2.7 myoblasts or nonmyogenic 3T6 cells.

[Dural fistula between the middle meningeal artery and cavernous sinus discovered in ophthalmology]. / Fistule durale entre artère méningée moyenne et sinus caverneux, de découverte ophtalmologique.

The authors report case of a dural arterio-venous fistula fed exclusively by the external carotid artery.