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Cilia are ubiquitous and highly conserved extensions that endow the cell with motility and sensory functions. They were present in the first eukaryotes and conserved throughout evolution (Carvalho-Santos et al., 2011). Paramecium has around 4,000 motile cilia on its surface arranged in longitudinal rows, beating in waves to ensure movement and feeding. As with cilia in other model organisms, direction and speed of Paramecium ciliary beating is under bioelectric control of ciliary ion channels. In multiciliated cells of metazoans as well as paramecia, the cilia become physically entrained to beat in metachronal waves. This ciliated organism, Paramecium, is an attractive model for multidisciplinary approaches to dissect the location, structure and function of ciliary ion channels and other proteins involved in ciliary beating. Swimming behavior also can be a read-out of the role of cilia in sensory signal transduction. A cilium emanates from a BB, structurally equivalent to the centriole anchored at the cell surface, and elongates an axoneme composed of microtubule doublets enclosed in a ciliary membrane contiguous with the plasma membrane. The connection between the BB and the axoneme constitutes the transition zone, which serves as a diffusion barrier between the intracellular space and the cilium, defining the ciliary compartment. Human pathologies affecting cilia structure or function, are called ciliopathies, which are caused by gene mutations. For that reason, the molecular mechanisms and structural aspects of cilia assembly and function are actively studied using a variety of model systems, ranging from unicellular organisms to metazoa. In this review, we will highlight the use of Paramecium as a model to decipher ciliary beating mechanisms as well as high resolution insights into BB structure and anchoring. We will show that study of cilia in Paramecium promotes our understanding of cilia formation and function. In addition, we demonstrate that Paramecium could be a useful tool to validate candidate genes for ciliopathies.

Schizophrenia spectrum disorders are associated with incapacitating social impairments, mostly due to Theory of Mind (ToM) deficits. Theory of mind difficulties often precede the beginning of schizophrenia spectrum disorders and contribute highly to the social withdrawal of patients. They also predict bad outcome for individuals suffering from this condition. The use of samples of individuals presenting subclinical forms of schizophrenia spectrum disorders constitute an opportunity to study theory of mind capacities. Notably, the study of theory of mind deficits in schizotypy allows a better understanding of predictive markers of schizophrenia spectrum disorders. They also contribute to the identification of primary processes involved in social difficulties associated with these disorders.We searched PubMed, Science Direct and Google Scholar databases for peer-reviewed articles studying the association between theory of mind performance and schizotypal traits up to the 1 April 2020. The following syntax was used: schizotypy AND ("theory of mind" OR "social cognition" OR "irony" OR "false belief" OR "social inference" OR "hinting task"). We also checked the references from these articles for additional papers. Only English and French written articles were considered.Twenty-three articles were included in the review. The majority of these studies (n=20) used behavioral measures of theory of mind (i.e. percentages of correct responses on a theory of mind task). Only a few (n=3) recent studies used brain imaging to study theory of mind in psychometric schizotypy. In those 23 studies, 18 report theory of mind difficulties in individuals with high schizotypal traits. Ten out of these 19 studies report an association between positive schizotypy and theory of mind deficits/hypomentalizing. The positive dimension was the most associated with theory of mind difficulties. The negative dimension was associated with theory of mind deficits in six studies out of 19 (33 %). The association between disorganization and theory of mind deficits was weak, mostly because of a lack of studies measuring this dimension (only one study out of 13 measured this particular trait). The association between hypermentalizing and schizotypy was poorly characterized, due to high heterogeneity in how this feature was conceptualized and measured. In summary, some authors consider good performance on a theory of mind task as a sign of hypermentalizing, while other authors consider that this feature relates to the production of erroneous interpretations of mental states. We advocate in favor of the second definition, and more studies using this framework should be conducted. Interestingly, the three studies using fMRI showed no significant behavioral differences between high and low schizotypal groups on theory of mind performance, while the patterns of brain activation differed. This shows that in individuals with schizotypy, theory of mind anomalies are not always captured just by behavioral performance. Brain imagery should be included in more studies to better understand theory of mind in schizotypy. In general, high heterogeneity in ways of assessing schizotypy, and in the tasks used to evaluate theory of mind, were found. Notably, some tasks require shallower theory of mind processing than others. It is a priority to design theory of mind tasks that allow for manipulating the difficulty of the items within one task, as well as the level of help that can be given, in order to allow for a better assessment of the impact of theory of mind difficulties and the ways to compensate for them.The studies included in this review confirm the association between psychometric schizotypy and theory of mind. But the high heterogeneity in methods used in these studies, and notably the diversity in ways of assessing schizotypal traits and theory of mind, hinder a precise description of such an association. Additional studies are required. In particular, fMRI studies using tasks allowing for a precise description of altered and preserved theory of mind processes could be of great use in characterizing theory of mind difficulties associated with schizotypy.

To review prognostic parameters reported recently in the evaluation of abdominal wall defects in the first trimester.Evaluation of abdominal wall defects in the first trimester is based principally on associated structural or chromosomal anomalies. In the case of gastroschisis, which is rarely associated with other anomalies, evaluation of prenatal or postnatal outcome is based mainly on the course of pregnancy. In the case of isolated omphalocele in the first trimester, recent studies have evaluated parameters that could help predict prenatal or postnatal outcome.We review recent studies using new parameters to diagnose abdominal wall defects in the first trimester and to provide early prenatal counselling to parents regarding prenatal and postnatal prognosis.

The arbitration case concerning the delimitation of the maritime boundary between Bangladesh and India provides an original contribution to international law. The delimitation made by the Arbitral Tribunal is a classic application of the method of equidistance and relevant circumstances. However, the Tribunal analyses finely the value to be attributed to ancient maps and confronts itself to the thorny issue of the effect to be attributed to climate change when drawing a border. It contributes greatly to the future of the law of delimitation anchoring strongly the delimitation exercise in a well-defined time frame : the moment of the judgment. This case is also the second maritime delimitation case dealing with the delimitation of the outer continental shelf. By using the principles established by the International Tribunal for the Law of the Sea in the Bangladesh/ Myanmar case and by affirming its jurisdiction vis-à-vis the extended continental shelf, the jurisprudence of this Arbitral Tribunal strengthens the implementation of the legal regime continental shelf and advocates a harmonious joint work of the Commission on the Limits of the Continental Shelf and of International Courts and Tribunals., L’affaire d’arbitrage relatif à la délimitation de la frontière maritime entre le Bangladesh et l’Inde offre une contribution originale au droit international. La délimitation réalisée par le Tribunal arbitral suit une application classique de la méthode de l’équidistance et des circonstances pertinentes. Le Tribunal analyse cependant très finement la valeur à attribuer aux cartes anciennes et se confronte à la question épineuse de l’effet à attribuer au changement climatique lors du tracé d’une frontière. Il contribue ainsi grandement à l’avenir du droit de la délimitation en ancrant très fortement l’exercice de délimitation dans un espace-temps bien défini : le moment présent du jugement. Cette affaire est par ailleurs la deuxième affaire de délimitation maritime traitant de la délimitation du plateau continental étendu. En reprenant les principes dégagés par le Tribunal international du droit de la mer en l’affaire Bangladesh/ Myanmar et en affirmant sa compétence vis-à-vis du plateau continental étendu, la jurisprudence de ce Tribunal arbitral renforce la mise en oeuvre du régime juridique du plateau continental et prône une articulation harmonieuse du travail de la Commission des Limites du Plateau Continental et des cours et tribunaux internationaux., Tassin Virginie J. M. La contribution au droit international de l’affaire de délimitation maritime Bangladesh/Inde dans la baie du Bengale. In: Annuaire français de droit international, volume 60, 2014. pp. 109-132.

Journal de Gynecologie Obstetrique et Biologie de la Reproduction - Vol. 41 - N° 7 - p. 684-688

Journal de Gynecologie Obstetrique et Biologie de la Reproduction - Vol. 41 - N° 7 - p. 679-683

Los traumatismos faciales de la poblacion pediatrica requieren un tratamiento adecuado. Debido a las peculiaridades fisiologicas y anatomicas propias de esta poblacion, este tratamiento puede diferir del aplicado en los adultos. La exploracion fisica sera suave y hay que evitar cualquier dolor inutil. Las exploraciones radiologicas que pueden realizarse en los adultos no siempre son factibles en los ninos, lo que puede aumentar la frecuencia de exploraciones mediante tomografia computarizada (TC), a pesar de la sensibilidad pediatrica a los rayos X. La exploracion fisica adecuada permite orientar mejor las pruebas de imagen en funcion de los signos clinicos. El tratamiento variara tanto en lo referente a sus modalidades tecnicas (adaptacion de las osteosintesis, prioridad de los tratamientos funcionales) como a la menor duracion de la inmovilizacion. En los traumatismos de los tejidos blandos, se establece una diferencia entre las heridas simples y aquellas con riesgo de lesion de los organos nobles. Los traumatismos dentales requieren una descripcion perfecta, debido a su repercusion futura social y economica. En este articulo se describen las distintas fracturas, enumeradas por orden de frecuencia: fracturas de los huesos propios nasales, fracturas alveolodentales, fracturas mandibulares, fracturas del hueso cigomatico, fracturas del piso orbitario, etcetera. Se describen desde los puntos de vista etiopatogenico, clinico y de las pruebas complementarias. En cada caso, se indica el tratamiento. La iconografia permite apreciar el aspecto radiografico de las distintas fracturas.

Radiologic embolization of the uterine arteries is increasingly used to treat severe postpartum hemorrhage, as an alternative to surgical procedures. Guidelines have been published in order to standardize the indications as well as the technique. An important objective was to limit severe complications such as uterine necrosis. We report a case of a uterine necrosis after arterial embolization for severe postpartum hemorrhage due to uterine atony on a uterus with fibroids. This complication occurred despite the use of the recommended technique.

Fetal hydrops and myocarditis were diagnosed in a woman at 32 weeks of gestation (WG). Transplacental enterovirus infection was suspected because all other causes of myocarditis and hydrops were excluded, it was during an endemic period, and there was a setting of maternal infection (fever a few days before). We opted for in utero treatment because of the risk of resuscitating a neonate with myocarditis and hydrops. We administered dexamethasone 12mg twice for pulmonary maturation and presumed it would partially improve the myocarditis. Fetal arrhythmia was noted at 35 WG and we decided to deliver the infant as postnatal treatment of the heart disorder would be more effective. RT-PCR (ARGENE(®)) showed that the neonate's throat and anal tissues and cord blood sampled on the day of birth contained enterovirus ribonucleic acid and coxsackievirus B5, as did the mother's anal sample. Laboratory tests, heart MRI and probably brain MRI indicated neonatal enterovirus infection. Findings were normal at two-year follow-up.

Enterovirus (EV) maternal infection during pregnancy and its relation to fetal developmental pathology are seldomly described. When reported, the main manifestations of EV congenital infections are myocarditis or intra-uterine fetal demise (IUFD). No information on intrauterine Echovirus 11 infection or the effect of transplacental Echovirus 11 infection on development of the fetus has been described in literature up to date (excluding late-pregnancy infections). We report here a case of an extreme form of pulmonary hypoplasia in a neonate, characterized by total failure of development of terminal respiratory units. This pregnancy was marked by spontaneous demise of a co-twin at 14 weeks of gestation (WG), as well as by positive PCR for EV (Echovirus 11 serotype) in the amniotic fluid, performed for moderate pericardial effusion at 22 WG. No signs of cardiac disease were further observed, but at 32 WG a bilateral abnormal lung development was noticed After spontaneous delivery at 38 WG, the child could not be resuscitated, and died at one hour after birth. Pulmonary hypoplasia is usually described following decrease intrapulmonary pressure due to oligohydramnios or compression due to intrathoracic mass of variable cause. However, rare cases of primary pulmonary hypoplasia are also described and usually of unknown etiology. The coexistence in our case of a congenital EV infection and a severe primary pulmonary hypoplasia with congenital acinar aplasia, challenges our understanding of the pathogenesis of this severe pulmonary growth arrest.

A need for capacity augmentation for the Vivekananda Bridge across River Hooghly connecting the twin city of Kolkata and Howrah, in the vicinity of Dakshineshwar, near Kolkata, was felt and the initiative started with a techno-economic feasibility study. The initiative further developed into the largest BOT project in the bridge sector in India which promoted by an international consortium. In this process, the designs were carried out accommodating various concerns, both technical, like river regime and constructability and non-technical, like environmental issues, land acquisition and resource mobilization. It was taken on concession for a period of thirty years, including three years for construction. The facility was thrown open to public on July 4th 2007, within the time frame and cost.. The paper describes the process of conceptualization all through to implementation, realization and operation and maintenance.

The continuous technological innovations which took place after the 1958 Geneva Conventions has led to an important development of exploration and exploitation activities on the seabed through an increased number of platforms at sea. The 1982 United Nations Convention on the Law of the Sea does not give a definition of a platform. Likewise, the other conventions which contain provisions applicable to platforms do not provide a definition of this them. It is possible, nevertheless, to define the legal régime applicable to platforms, taking into account the legal status of the different areas where they are located (continental shelf and exclusive economic zone, high seas and international seabed area) as well as of the seabed and the superjacent waters. As a result, the régime of platforms may be characterized as a complex system where the rights of the coastal States need to coexist with the rights of other States to use the areas concerned. Certain questions require a more detailed examination in light of the practical issues which have arisen in international practice. This concerns the navigation of platforms, their installation in disputed maritime areas, the safety of platforms and the protection of the marine environment (prevention and reparation) vis-à-vis damage which may occur from their activities, as well as the removal of disused platforms., Le progrès continu des techniques depuis les Conventions de Genève de 1958 a favorisé l’expansion considérable de l’exploration et de l’exploitation du fond des mers à partir de plates-formes installées en surface, qui se sont multipliées et diversifiées. La Convention des Nations Unies de 1982 ne comporte pas de définition précise, et les conventions particulières qui leur consacrent certaines de leurs dispositions ne s’accordent pas sur une définition uniforme. Il est cependant possible de systématiser le régime qui leur est applicable, en tenant compte de la diversité juridique des espaces dans lesquels elles sont implantées (plateau continental et zone économique exclusive, haute mer et Zone internationale des fonds marins) et du statut respectif des fonds marins et des eaux surjacentes. Il en résulte un régime complexe, dans lequel les droits de l’État côtier coexistent avec le droit qu’ont les États d’utiliser les espaces concernés. Certaines matières spécifiques font l’objet d’un examen plus détaillé, en raison des problèmes concrets que suscitent l’installation et l’utilisation des plates-formes en mer. Il s’agit des questions relatives à la navigation des plates-formes, à leur installation dans des zones où le titre territorial est contesté, à la sécurité des plates-formes et à la protection du milieu marin (prévention et réparation des dommages) contre la pollution qui peut résulter de leurs activités, ainsi qu’à l’enlèvement des plates-formes désaffectées., Gautier Philippe, Tassin Virginie J. M. Les plates-formes en mer et le droit international. In: Annuaire français de droit international, volume 59, 2013. pp. 185-220.

Background NMR spectroscopy–based metabolomics is a system approach used to investigate the metabolic profile of biological fluids with multivariate data analysis tools. The aim of this study was to examine the kidney graft recovery process noninvasively through the examinations of urine samples using 1 H NMR spectroscopy combined with chemometric tools. Methods Urine samples were treated as the source of metabolites reflecting the pathological and clinical conditions of patients with transplanted kidneys. We observed 15 subjects (9 males and 6 females) during the graft recovery process and initial days thereafter. The patients provided at least 9 samples each, applying advanced statistical methods of analysis: Principal Component Analysis (PCA) and Partial Least Square Discriminant Analysis PLS-DA). Results The PCA model (for all subjects exp. var. PC1 13.96% and PC2 9.88%) allowed us to clearly designate 3 stages of recovery: initially the kidney is not working; in the second stage, it regains functions, and the third stage includes follow-up during hospitalization. PCA analysis of a single patient follows graft recovery based on biochemical (metabolites) information, assigning the appropriate recuperation stage. Conclusions NMR spectroscopy together with chemometric analysis allow monitoring of kidney graft recovery to identify patients who are not progressing within the normal range.

Amniocentesis is the most common invasive procedure for prenatal diagnosis. It is essential to master this sampling technique prior to performing more complex ultrasound-guided interventions (cordocentesis, drain insertion). Training is a challenge because of the risks associated with the procedure, as well as the impact on the patient's anxiety. An amniocentesis simulator allows for safe training and repeats interventions, thus accelerating the learning curve, and also allows for periodic evaluation of proficiency. We present here a new, simple, and cost-effective amniotrainer model that reproduces real life conditions, using chicken breast and condoms filled with water.

Chorionic villus sampling (CVS) in the first trimester of pregnancy has become a major tool in prenatal diagnosis. To increase the safety of CVS during training period, we have built a "BT-Trainer".A medical device has been developed which simulates the in vivo procedure with the various layers to cross. The stratum of the layer and the accessibility of the placenta can modulate the level difficulty.Traditional strategies for clinical teaching are often insufficient and trainees may fail to achieve competence in even basic procedural skills. We present herein an easy and reproducible model of "BT-Trainer" which allows a safe and repeatable training. Efficacy of this model is currently under evaluation in a teaching program. This trainer could help gynaecologists in order to learn gradually and safely the technique and to enhance their skills and coordination.

Radiologic embolization of the uterine arteries is increasingly used to treat severe postpartum hemorrhage, as an alternative to surgical procedures. Guidelines have been published in order to standardize the indications as well as the technique. An important objective was to limit severe complications such as uterine necrosis. We report a case of a uterine necrosis after arterial embolization for severe postpartum hemorrhage due to uterine atony on a uterus with fibroids. This complication occurred despite the use of the recommended technique.

In a fundamental test of quantum mechanics, we have observed 228~000 quantum jumps of a single trapped and laser cooled $^{88}$Sr$^+$ ion. This represents a statistical increase of two orders of magnitude over previous similar analyses of quantum jumps. Compared to other searches for non-randomness in quantum mechanical processes, using quantum jumps simplifies the interpretation of data by eliminated multi-particle effects and providing near-unit detection efficiency of transitions. We measure the fractional reduction in the entropy of information to be $< 6.5~10^{-4}$ when the value of any interval between quantum jumps is known. We also find that the number of runs of successively increasing or decreasing interval times agrees with the theoretically expected values. Furthermore, we analyze 238~000 quantum jumps from two simultaneously confined ions and find that the number of apparently coincidental transitions is as expected. Finally, we observe 8400 spontaneous decays of two simultaneously trapped ions and find that the number of apparently coincidental decays from the metastable state agrees with the expected value. We find no evidence for short- or long-term correlations in the intervals of the quantum jumps or in the decay of the quantum states, in agreement with quantum theory., 4 pages, 5 figures. To appear in PRA. New version replaces much of the previous analysis with a more simple measurement of the reduction of entropy of information. Also includes smaller changes to text and figures to improve clarity

Genetic studies in the budding yeast have led to the molecular characterization of gamma-tubulin associated proteins and to the identification of orthologues in animal cells. While the gamma-tubulin complex is more complex in animal cells than in budding yeast, its function is probably maintained throughout evolution. In this review we discuss some of the possible regulations of the nucleation activity in the light of the centrosome structure. A potential cross-talk between microtubule nucleation and centrosome duplication is suggested by some, still scarce, data.

The Saccharomyces cerevisiae mating pheromone precursor, prepro-alpha-factor, can be translocated across yeast endoplasmic reticulum membranes post-translationally in an in vitro system. This characteristic makes prepro-alpha-factor potentially useful as a probe in the biochemical dissection of the mechanism of this basic cellular process. Efforts have been limited by the inability to isolate sufficient quantities of such secretory protein precursors in a translocation-competent form. We report here the one-step purification of chemical amounts of translocation-competent prepro-alpha-factor using nickel ion affinity chromatography on nitrilotriacetate resin. An oligonucleotide encoding 6 histidine residues was inserted into a genomic clone encoding prepro-alpha-factor 5' of the naturally occurring translational stop codon by site-directed mutagenesis. The construct was expressed at high levels in a SecY- strain of Escherichia coli. The produced preprotein was solubilized in 6 M guanidine hydrochloride and bound to nitrilotriacetate resin. Prepro-alpha-factor was recovered at a purity in excess of 95% by elution with 0.25 M imidazole, 8 M urea, which competitively displaced the histidine affinity tag from the nickel column. The chemical amounts of prepro-alpha-factor obtained in this way were determined to be competent for translocation across yeast microsomal membranes and for subsequent modifications such as signal sequence cleavage and N-linked glycosylation.

Myotubes prepared from mice with muscular dysgenesis (mdg) were used to further elucidate the putative role of inositol triphosphate (InsP3) in excitation-contraction (E-C) coupling of skeletal muscle. The mdg mutation is characterized by an uncoupling of the E-C coupling. InsP3 production in normal and mdg/mdg myotube cultures and its relation to the levels of cytosolic free calcium were analyzed. Basal and ATP-stimulated levels of InsP3 were equal in normal and mdg/mdg myotube cultures. In contrast, the transient increases of cytosolic free calcium in mdg/mdg myotubes in culture were generally much lower than those in normal ones. This suggests that the defect in dysgenic myotubes does not rest on the InsP3 formation but on the InsP3-triggered transduction of excitation and/or the induction of calcium release from internal stores.

The electrochemical reduction of dinitronaphthalene to produce diaminonaphthalene has been optimized. The synthesis of diaminonaphthalene by the electrolysis of a suspension of dinitronaphthalene in sulphuric acid with a titanium salt gives a yield and purity similar to the synthesis by catalytic hydrogenation. Technical and economical comparisons of the two processes show that for large capacities (several hundred tons per year), reduction by catalytic hydrogenation is more feasible. However, for smaller quantities (several tons per year) the flexibility of exploitation by electrolysis has economic advantages.

The muscular dysgenesis recessive autosomal mutation is characterized by a total lack of muscular contraction and a myofibrillar non-organization. Many abnormalities involved in the excitation-contraction coupling are found in mdg/mdg myotubes: 1) the internal structural organization of the membrane coupling between the sarcoplasmic reticulum (SR) and the transverse (T)-tubule forming the triadic association is defective: the triad number is decreased in the muscle and there are a lack of periodic densities between the SR and T-tubule apposed membranes. 2) the voltage-dependent Ca2+ channel contents, identified by binding with the specific blocker PN 200-110, are decreased. The two fast (30 ms) and slow (100 ms) Ca2+ currents present in normal myotubes are absent in mdg/mdg myotubes in vitro. 3) the Ca2+-dependent K+ conductance triggering an action potential followed by a long lasting after hyperpolarization (ahp) is absent in mdg/mdg myotubes. This indicates a lack of the free intracellular Ca2+ increased by the action potential. These results suggest that: 1) the lack of differentiated triadic junctions is directly correlated with very low amounts of voltage-dependent Ca2+ channels; 2) the low amount of Ca2+ channels results directly in decreased Ca2+ currents; 3) the decreased Ca2+ currents are the consequence of the low intracellular Ca2+ concentration which is not sufficient to trigger a contraction. However, the addition of normal motoneurones to mdg/mdg myotubes in culture induces, few days later, an increase in Ca2+ currents.

Microtubule organization and nucleation were studied during in vitro human myogenesis by immunocytology that used monoclonal and polyclonal antitubulin antibodies and a rabbit nonimmune serum that reacts with human centrosomes. In myoblasts, we observed a classical microtubule network centered on juxtanuclear centrosomes. Myotubes possessed numerous microtubules organized in parallel without any apparent nucleation centers. Centrosomes in these cells were not associated one to each nucleus but were often clustered in the vicinity of nuclei groups. They were significantly smaller than those of the mononucleated cells. The periphery of each nucleus in myotubes was labeled with the serum that labels centrosomes suggesting a profound reorganization of microtubule-nucleating material. Regrowth experiments after Nocodazole treatment established that microtubules were growing from the periphery of the nuclei. The redistribution of nucleating material was shown to take place early after myoblast fusion. Such a phenomenon appears to be specific to myogenic differentiation in that artificially induced polykaryons behaved differently: the centrosomes aggregated to form only one or a few giant nucleating centers and the nuclei did not participate directly in the nucleation of microtubules. The significance of these results is discussed in relation to the possible role of the centrosome in establishing cell polarity.

Cytoskeletal intermediate filaments were studied in muscular dysgenesis ( mdg ) and tetrodotoxin-treated inactive mouse embryo muscle cultures during myofibrillogenesis. Both muscular dysgenesis and tetrodotoxin-treated muscles are characterized in vitro by a total lack of contractile activity and an abnormal development of myofibrils. We studied the organization of the microtubule and intermediate filament networks with immunofluorescence, using anti-tubulin, anti-vimentin, and anti-desmin antibodies during normal and mdg mdg myogenesis in vitro . Mdg mdg myotubes present a heterogeneous microtubule network with scattered areas of decreased microtubule density. At the myoblast stage, cells expressed both vimentin and desmin. After fusion only desmin expression is revealed. In mutant myotubes the desmin network remains in a diffuse position and does not reorganize itself transversely, as it does during normal myogenesis. The absence of a mature organization of the desmin network in mdg mdg myotubes is accompanied by a lack of organization of myofibrils. The role of muscle activity in the organization of myofibrils and desmin filaments was tested in two ways: (i) mdg mdg myotubes were rendered active by coculturing with normal spinal cord cells, and (ii) normal myotubes were treated with tetrodotoxin (TTX) to suppress contractions. Mdg mdg innervated myotubes showed cross-striated myofibrils, whereas desmin filaments remained diffuse. TTX-treated myotubes possessed disorganized myofibrils and a very unusual pattern of distribution of desmin: intensively stained desmin aggregates were superimposed upon the diffuse network. We conclude, on the basis of these results, that myofibrillar organization does not directly involve intermediate filaments but does need contractile activity.