Cadherins in the central nervous system

The central nervous system (CNS) is divided into diverse embryological and functional compartments. The early embryonic CNS consists of a series of transverse subdivisions (neuromeres) and longitudinal domains. These embryonic subdivisions represent histogenetic fields in which neurons are born and aggregate in distinct cell groups (brain nuclei and layers). Different subsets of these aggregates become selectively connected by nerve fiber tracts and, finally, by synapses, thus forming the neural circuits of the functional systems in the CNS. Recent work has shown that 30 or more members of the cadherin family of morphoregulatory molecules are differentially expressed in the developing and mature brain at almost all stages of development. In a regionally specific fashion, most cadherins studied to date are expressed by the embryonic subdivisions of the early embryonic brain, by developing brain nuclei, cortical layers and regions, and by fiber tracts, neural circuits and synapses. Each cadherin shows a unique expression pattern that is distinct from that of other cadherins. Experimental evidence suggests that cadherins contribute to CNS regionalization, morphogenesis and fiber tract formation, possibly by conferring preferentially homotypic adhesiveness (or other types of interactions) between the diverse structural elements of the CNS. Cadherin-mediated adhesive specificity may thus provide a molecular code for early embryonic CNS regionalization as well as for the development and maintenance of functional structures in the CNS, from embryonic subdivisions to brain nuclei, cortical layers and neural circuits, down to the level of individual synapses.     

Effect of maximal arm exercise on skin blood flux in the paralyzed lower limbs in persons with spinal cord injury

 The purpose of the present study was to examine the effect of maximal arm exercise on the skin blood circulation of the paralyzed lower limbs in persons with spinal cord injury (PSCI). Eight male PSCI with complete lesions located between T3 and L1 performed graded maximal arm-cranking exercise (MACE) to exhaustion. The skin blood flux at the thigh (SBFT) and that at the calf (SBFC) were monitored using laser-Doppler flowmeter at rest and for 15 s immediately after the MACE. The subject's mean peak oxygen uptake and peak heart rate was 1.41 ± 0.22 l · min^–1 and 171.6 ± 19.2 beats · min^–1, respectively. No PSCI showed any increase in either SBFT or SBFC after the MACE, when compared with the values at rest. These results suggest that the blood circulation of the skin in the paralyzed lower limbs in PSCI is unaffected by the MACE. Accepted: 12 September 1996     

Anaplastic Ependymoma of the Spinal Cord in Childhood A Case Report

We report a 6-year-old girl with anaplastic ependymoma probably originating in the region of the conus medullaris and probably spreading retrogradely to the region of the interventricular foramen (Monro) through the cere-brospinal fluid (CSF). Since ependymoma of the spinal cord rarely occurs in children, and retrograde spreading is extremely rare, the histological features and mechanism of metastasis of the tumor are discussed.     

DGGE-based whole-gene mutation scanning of the dystrophin gene in Duchenne and Becker muscular dystrophy patients

Duchenne and Becker muscular dystrophy (DMD and BMD) are caused by mutations in the dystrophin gene. Large rearrangements in the gene are found in about two-thirds of DMD patients, with approximately 60% carrying deletions and 5-10% carrying duplications. Most of the remaining 30-35% of patients are expected to have small nucleotide substitutions, insertions, or deletions. To detect these subtle changes within the coding and splice site determining sequences of the dystrophin gene, we established a semiautomated denaturing gradient gel electrophoresis (DGGE) mutation scanning system. The DGGE scan covers the dystrophin gene with 95 amplicons, PCRed either individually or in a multiplex setup. PCR and pooling were performed semiautomatically, using a pipetting robot and 384-well plates, enabling concurrent amplification of DNA of four patients in one run. Amplification of individual fragments was performed using one PCR program. The products were pooled just before gel loading; DGGE requires only a single gel condition. Validation was performed using DNA samples harboring 39 known DMD variants, all of which could be readily detected. DGGE mutation scanning was applied to analyze 135 DMD/BMD patients and potential DMD carriers without large deletions or duplications. In DNA from 25 out of 44 DMD patients (57%) and from 5 out of 39 BMD patients (13%), we identified clear pathogenic changes. All mutations were different, with the exception of one DMD mutation, which occurred twice. In DNA from 10 out of 44 potential DMD carriers, including four obligate carriers, we detected causative changes, including one pathogenic change in every obligate carrier. In addition to these pathogenic changes, we detected 15 unique unclassified variants, i.e., changes for which a pathogenic nature is uncertain.     

Autosomal dominant late adult spinal muscular atrophy,type finkel

We describe clinical and genetic data from the study of two families with 80 members affected with the autosomal dominant, slowly progressive spinal muscular atrophy of late onset (average 48.8 years), first described by Finkel in 1962. Electromyography and muscle biopsy of a number of patients confirmed the neurogenic nature of the condition. Unusual findings in this disorder were cramps, spontaneous fits of suffocation, and symptomatic myotonia. Other manifestations are slow loss of muscle strength and progressive proximal atrophy, which starts in the lower limbs and progresses to the upper limbs; hypoactive or absent tendinous reflexes; and generalized fasciculations. Sensory and cranial nerve function is unimpaired. Probabilities for genetic counseling are evaluated by means of a method adequate to the late-onset nature of the condition.     

Serum CK-MB activity in progressive muscular dystrophy: Is it of nosologic value?

Serum creatine-kinase (CK) isoenzyme MB was measured in 53 patients affected by different types of myopathies (20 with Duchenne muscular dystrophy (DMD), eight with the Becker form (BMD), ten with the limb-girdle form (LGMD), six with the facioscapulohumeral form (FSH), and nine affected by polymyositis and in 21 normal control subjects). The aim of this study was to compare each group with the control individuals and to assess the nosologic value of CK-MB activity among some clinically similar dystrophies, which may have an important application for genetic counseling. A statistically significant increased CK-MB activity was found only in the Duchenne and Becker patients when compared with control persons (p < 0.05). When the different groups of patients were compared among themselves, no significant difference was found between DMD and BMD or LGMD and polymyositis. However, a significant difference was found between BMD and LGMD. Based on these data, it is possible, through discriminant analysis, to estimate the relative biochemical probability of an isolated male patient belonging to either group.     

Extracellular ionic and volume changes: The role in glia—Neuron interaction

Activity-related changes in extracellular K⁺ concentration ([K⁺]_e), pH (pH_e) and extracellular volume were studied by means ofion-selective microelectrodes in the adult rat spinal cord in vivo and in neonatal rat spinal cords isolated from pups 3–14 days of age (P3–P14). Concomitantly with the ionic changes, the extracellular space (ECS) volume fraction (α), ECS tortuosity (λ) and non-specific uptake (k′), three parameters affecting the diffusion of substances in nervous tissue, were studied in the rat spinal cord gray matter. In adult rats, repetitive electrical nerve stimulation (10–100 Hz) elicited increases in [K⁺]_e of about 2.0–3.5 mm, followed by a post-stimulation K⁺-undershoot and triphasic alkaline-acid-alkaline changes in pH_e with a dominating acid shift. The ECS volume in the adult rat occupies about 20% of the tissue, α = 0.20 ± 0.003, λ = 1.62 ± 0.02 and k′ = 4.6 ± 0.4 × 10⁻³s⁻¹ (n = 39). In contrast, in pups at P3–P6, the [K⁺]_e increased by as much as 6.5 mm at a stimulation frequency of 10 Hz, i.e. K⁺ ceiling level was elevated, and there was a dominating alkaline shift. An increase in [K⁺]_e as large as 1.3–2.5 mm accompanied by an alkaline shift was evoked by a single electrical stimulus. The K⁺ ceiling level and alkaline shifts decreased with age, while an acid shift, which was preceded by a small initial alkaline shift, appeared in the second postnatal week. In pups at P1–P2, the spinal cord was X-irradiated to block gliogenesis. The typical decrease in [K⁺]_e ceiling level and the development of the acid shift in pH_e at P10–P14 were blocked by X-irradiation. Concomitantly, continuous development of glial fibrillary acidic protein positive reaction was disrupted and densely stained astrocytes in gray matter at P10–P14 revealed astrogliosis.The alkaline, but not the acid, shift was blocked by Mg²⁺ and picrotoxin (10⁻⁶m). Acetazolamide enhanced the alkaline but blocked the acid shift. Furthermore, the acid shift was blocked, and the alkaline shift enhanced, by Ba²⁺, amiloride and SITS. Application of glutamate or gamma-aminobutyric acid evoked an alkaline shift in the pH_e baseline at P3–P14 as well as after X-irradiation. The results suggest that the activity-related acid shifts in pH_e are related to membrane transport processes in mature glia, while the alkaline shifts have a postsynaptic origin and are due to activation of ligand-gated ion channels.At P4–P6, the ECS volume was almost double that in adult rats, α = 0.37 ± 0.01 (n = 17), the ECS tortuosity was significantly higher, λ = 1.78 ± 0.02, while the non-specific uptake was not significantly different, k′ = 3.61 ± 0.56 × 10⁻³ s⁻¹. The α gradually decreased to about 24% at P12. In adult rats, electrical or adequate stimulation evoked a shrinkage of the extracellular space by 20–50%, while no significant changes in ECS volume were found in P3–P6. We conclude that the [K⁺]_e ceiling level, character of the pH_e transients, the size of the ECS volume and the activity-related ECS shrinkage are closely related to gliogenesis.     

Fourteen novel OPA1 mutations in autosomal dominant optic atrophy including two de novo mutations in sporadic optic atrophy

The OPA1 gene, encoding a dynamin-related GTPase that plays a role in mitochondrial biogenesis, is implicated in most cases of autosomal dominant optic atrophy (ADOA). Sixty-nine pathogenic OPA1 mutations have been reported so far. Most of these are truncating mutations located in the GTPase domain coding region (exons 8-16) and at the 3'-end (exons 27-28). We screened 44 patients with typical ADOA using PCR-sequencing. We also tested 20 sporadic cases of bilateral optic atrophy compatible with ADOA. Of the 18 OPA1 mutations found, 14 have never been previously reported. The novel mutations include one nonsense mutation, 3 missense mutations, 6 deletions, one insertion and 3 exon-skipping mutations. Two of these are de novo mutations, which were found in 2 patients with sporadic optic atrophy. The recurrent c.2708_2711delTTAG mutation was found in 2 patients with a severe congenital presentation of the disease. These results suggest that screening for OPA1 gene mutations may be useful for patients with optic atrophy who have no affected relatives, or when the presentation of the disease is atypical as in the case of early onset optic atrophy.     

Forelimb reflexes modulated by tonic neck positions in cats

The modulation of monosynaptic forelimb reflexes by tonic neck positions was investigated in cats with the head fixed.Lateral flexion of the body in a horizontal plane markedly facilitates reflexes of the deep radial nerve (DR) in the ipsilateral forelimb, while the antagonistic ulnar nerve (ULN) reflexes are strongly inhibited. Opposite effects are seen after contralateral body movement.Dorsiflexion of the body clearly increases DR-reflexes and exerts a reciprocal although more pronounced inhibition on ULN reflexes. Opposite effects appear after ventriflexion.The reflex modulation starts with head-body displacements of approximately 5° and increases with increasing angles. Furthermore reflex modulation does not depend on the intact cerebrum and cerebellum. The comparison of forelimb and hindlimb reflexes shows a decrease of the neck influences along the spinal cord.Supported by Sonderforschungsbereich Hirnforschung und Sinnes-physiology (SFB 70) der Deutschen Forschungsgemeinschaft (DFG).Essential parts of this paper will be submitted by A. F. as a thesis to the Faculty of Medicine, Freiburg/Breisgau, Germany.     

No disturbance of myelination in the central nervous system by selective3Hβ-irradiation

Summary The effect of a selective irradiation of myelin by³H -particles was studied by light and electron microscopic methods in guinea pig spinal cord. The animals were injected with [³H]leucine shortly after birth when the rate of myelin biosynthesis is high and sacrificed 130 days later. In spinal cord the radioactivity was mainly preserved in myelin because the half life of myelin proteins is much higher than that of most other CNS protein. As a consequence the irradiation dose in the white matter was much higher than in the gray matter. In myelin internally irradiated by³H -particles within 130 days at a dose of 10 Gy no alterations could be detected either by morphological or by morphometric methods.Supported by the Deutsche Forschungsgemeinschaft