Extended amplification in vitro and replicative senescence: key factors implicated in the success of human myoblast transplantation.

The limited success of human myoblast transplantation has been related to immune rejection, poor survival, and limited spread of injected myoblasts after transplantation. An important issue that has received little attention, but is nevertheless of fundamental importance in myoblast transplantation protocols, is the proliferative capacity of human satellite cells. Previous studies from our laboratory have demonstrated that the maximum number of divisions that a population of satellite cells can make decreases with age during the first two decades of life then stabilizes in adulthood.

Inhibition of poliovirus RNA synthesis as a molecular mechanism contributing to viral persistence in the mouse central nervous system.

Many survivors of poliomyelitis, several decades after the acute phase of the disease, develop a set of new muscle symptoms called post-polio syndrome. The persistence of poliovirus (PV) in the central nervous system (CNS) may be involved in the aetiology of this syndrome. By using a mouse model, we have shown that PV persists in the CNS of paralysed mice for over a year after the acute disease.

Alpha-motoneurons of the injured cervical spinal cord of the adult rat can reinnervate the biceps brachii muscle by regenerating axons through peripheral nerve bridges: combined ultrastructural and retrograde axonal tracing study.

Following our previous studies related to brachial plexus injury and repair, the present experimentation was designed to examine the ultrastructural features of those motoneurons of the locally injured cervical spinal cord of adult rats that were seen to regenerate into peripheral nerve (PN) bridges and to reinnervate nearby skeletal muscles. Here, the peripheral connection of the PN bridge was made with the biceps brachii (BB) muscle. Three months postsurgery, the spinal motoneurons labelled by retrograde axonal transport of horseradish peroxidase (HRP), after its injection into the BB, were selected on thick sections, using light microscopy, for the presence of dark amorphous granules of the HRP reaction product.

Regenerative capacity of human satellite cells: the mitotic clock in cell transplantation.

In this communication, we will review the problems caused by cell-mediated gene therapy, taking skeletal muscle as a physiological model. In particular we have utilised vectors transferring telomerase under the control of retroviral promoters into human satellite cells. The set of results presented here has several implications regarding gene therapy trials.

Age-related appearance of tubular aggregates in the skeletal muscle of almost all male inbred mice.

Tubular aggregates (TAs) which have been recently observed in a few mouse myopathies are identical to those described in human diseases. In this study we show that TAs are also found in the skeletal muscle of almost all normal inbred mice strains. In these inbred strains of mice the presence of TAs is shown to be related to both age and sex.

Reciprocal connections between the red nucleus and the trigeminal nuclei: a retrograde and anterograde tracing study.

An anterograde biocytin and a retrograde WGA-colloidal gold study in the rat can provide information about reciprocal communication pathways between the red nucleus and the trigeminal sensory complex. No terminals were found within the trigeminal motor nucleus, in contrast with the facial motor nucleus. A dense terminal field was observed in the parvicellular reticular formation ventrally to the trigeminal motor nucleus.

Poliovirus induces apoptosis in the mouse central nervous system.

Poliovirus (PV) is the etiological agent of human paralytic poliomyelitis. Paralysis results from the destruction of motoneurons, a consequence of PV replication. However, the PV-induced process leading to the death of motoneurons is not well known.

Expression and genetic interaction of transcription factors GATA-2 and GATA-3 during development of the mouse central nervous system.

Here we examine the expression of transcription factors GATA-2 and GATA-3 during early stages of embryonic development in the central nervous system (CNS) of the mouse. GATA-2 is expressed as early as 9 dpc in the hindbrain, in ventral rhombomere 4, and transiently in ventral rhombomere 2 (r2). From 9.

Indications for GABA-immunoreactive axo-axonic contacts on the intraspinal arborization of a Ib fiber in cat: a confocal microscope study.

Confocal microscopy was used to detect GABA-immunoreactive axo-axonic appositions, indicating possible synaptic contacts, on Ib fiber terminals in the lumbosacral spinal cord. A Ib fiber from posterior biceps-semitendinosus muscles was labeled by intra-axonal ejection of tetramethylrhodamine dextran (red), and serial sections of S1-L7 spinal cord segments were processed for GABA immunocytochemistry revealed by fluorescein isothiocynate (green). Appositions between GABA-immunoreactive structures and the labeled fiber appeared as yellow spots because of the presence of both fluorochromes in small volumes (0.

Persistent poliovirus infection in mouse motoneurons.

Poliovirus (PV) is the causal agent of paralytic poliomyelitis. Many survivors of the acute disease, after decades of clinical stability, develop new muscular symptoms called postpolio syndrome. It has been hypothesized that the persistence of PV in the spinal cord is involved in the etiology of this syndrome.

Postnatal development of alpha- and gamma-peroneal motoneurons in kittens: an ultrastructural study.

Motoneurons innervating the peroneus brevis muscle of 1 week- and 3 week-old kittens were retrogradely labelled by HRP and examined by electron microscopy. At 1 week the distribution of mean cell body diameters was unimodal. Consequently alpha- and gamma-motoneurons could not be identified by their size.

Gaba-like immunoreactive terminals on lumbar motoneurons of the adult cat. A quantitative ultrastructural study.

The aim of this ultrastructural study was to analyse quantitatively the distribution of gamma-aminobutyric acid (GABA)-like immunoreactivity in axon terminals apposed to somatic and proximal dendritic membranes of cat motoneurons in lumbar column 2. Preembedding immunocytochemistry was used to count the GABAergic terminals contacting profiles of eighteen alpha-and six gamma-motoneurons. Of the 1293 terminals counted on the somatic and proximal dendritic compartments of alpha-motoneurons, 197 were GABAergic.

Distribution of glycinergic terminals on lumbar motoneurons of the adult cat: an ultrastructural study.

The distribution of glycine-like immunoreactivity on cat lumbar motoneurons was examined in electron microscopy, using pre-embedding immunocytochemistry. In the dorsolateral portion of the ventral horn, numerous labeled axon terminals were presynaptic to somatic and dendritic profiles of alpha-motoneurons. Most of the glycinergic boutons contained pleomorphic vesicles and showed symmetrical contacts.

Alpha and gamma motoneurons in the peroneal nuclei of the cat spinal cord: an ultrastructural study.

The aim of the present study was to investigate whether ultrastructural features can be used as a guide to identify alpha- and gamma-motoneurons among the intermediate-size neurons of the peroneal motor nuclei. The peroneus brevis and peroneus tertius muscles of adult cats were injected with horseradish peroxidase, and motoneurons labeled by retrograde axonal transport were examined by electron microscopy. In both nuclei, the distributions of cell-body diameters, measured in the light microscope, were bimodal covering the range of 28-84 microns, with a trough around 50 microns.

Postnatal development of peroneal motoneurons in the kitten.

In 1- to 72-day-old kittens, motoneurons of the 3 peroneal muscle nuclei were labeled by retrograde axonal transport of horseradish peroxidase from individual muscles. At birth, the locations of peroneal nuclei were similar to those of the adult cat. Counts of motoneurons at different ages indicated that postnatal cell death does not occur in peroneal motor nuclei.

Motor nuclei of peroneal muscles in the cat spinal cord.

The cat peroneal muscles have been used in numerous investigations dealing with the physiological properties of motor units, muscle spindles, and Golgi tendon organs. This report presents a study of the organization of peroneal motor pools in the cat spinal cord by means of retrograde axonal transport of horseradish peroxidase from individual muscles to the corresponding motoneurons. The motor nuclei of peroneus longus (PL), peroneus brevis (PB), and peroneus tertius (PT) muscles formed thin columns in the lateral part of the ventral horn in spinal segments L6-S1.

Afferent fibres in cat ventral roots: electrophysiological and histological evidence.

Electrophysiological experiments using averaging techniques, as well as anatomical experiments using horseradish peroxidase staining, have provided further evidence of afferent axons in lumbosacral ventral roots of cats. Recording from dorsal root filaments in L7, S1 or S2, following stimulation of the companion ventral root close to the dura, often shows action potentials of slow conduction velocity belonging to the A delta or C group. Stimulation applied to the proximal part of the ventral root failed to evoke such responses.

Histochemical identification of two fibre types in the retractor bulbi muscle of the cat.

In adult cats, the fibre population of the retractor bulbi muscle (RB) was analysed, using the histochemical reactions of ATPases. The muscle was found to contain type-2 fibres only, of which 70% were 2a and 30% 2b. Such ATPase profiles, corresponding to fast-twitch fibers, are in agreement with the mechanical properties of the muscle.

Resistance to glycogen depletion of motor units in the cat rectus lateralis muscle.

In nembutal anesthetized adult cats, intracellular stimulation of single abducens motoneurones was used to elicit glycogen depletion of their muscle units. Stimulation by short trains (13 pulses at 40 Hz) delivered once a second, was applied for 20 to 110 min. The activation of the motor unit was monitored by intracellular recording of motoneurone action potentials and by EMG.

Tight junctions in the ependyma of the spinal cord of the urodele Pleurodeles waltlii.

The ependymal junction pattern in the spinal cord of postmetamorphic ribbed newts has been studied, using transmission electron microscopy of ultrathin sections of normal animals and of animals perfused through the IVth ventricle with lanthanum. Contrary to what has been observed in mammalian CNS, the ependyma of the urodelan spinal cord is furnished with tight junctions that seal the luminal border of the terminal bars. These occludens junctions are made up of two to seven punctate fusions of the plasma membranes.