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At least 1,117 records · Page 62Linked to original sources
PubMed2000

Axotomized and intact muscle afferents but no skin afferents develop ongoing discharges of dorsal root ganglion origin after peripheral nerve lesion.

After peripheral nerve lesions, some axotomized afferent neurons develop ongoing discharges that originate in the dorsal root ganglion (DRG). We investigated in vivo which functional types of afferent neurons contributed to this ectopic activity. Six to twelve days after the gastrocnemius soleus (GS) nerve supplying skeletal muscle and the sural (SU) nerve supplying skin had been transected (experimental group E1), 20.4% of afferent neurons with myelinated axons projecting into the GS nerve produced ongoing discharges of irregular or bursting pattern. In contrast, all SU neurons were silent. Additional transection of peroneal and tibial nerves (group E2) induced ongoing activity in a similar percentage of GS neurons (22.1%), but their mean discharge frequency was higher (6.0 vs 2.7 Hz), and more of them exhibited bursting discharges (63 vs 17%). When the GS nerve had been left intact while tibial, peroneal, and SU nerve had been transected (group E3), 18.8% of unlesioned GS neurons developed ongoing discharges at a mean frequency of 6.1 Hz; most of them exhibited a bursting pattern. Without a preceding nerve lesion, almost no GS neuron (1.1%) fired spontaneously. Most afferent neurons with ongoing activity had an axonal conduction velocity of 5-30 m/sec indicating that some of these neurons may have had nociceptive function. These findings provide the first evidence that after peripheral nerve injury both axotomized as well as intact afferent neurons supplying skeletal muscle but not skin afferents generate ongoing activity within the DRG, probably because of a yet unknown signal in the DRG triggered by axotomy.

Animals↗
PubMed1993

Developmental regulation of carbonic anhydrase expression in mouse dorsal root ganglia.

The development of proprioceptive neurons in mammalian dorsal root ganglia (DRG) remains poorly documented since few specific markers for these neurons are known. Recent studies suggest that carbonic anhydrase (CA) is a specific marker of this functionally defined neuronal population. The present study was designed to investigate the development of CA staining in sensory neurons. We investigated CA reactivity in mouse lumbar DRGs from embryonic day 13 (E13) to postnatal day 100 (P100) using a modified cytoenzymatic Hansson method. Neuronal CA reactivity was first detected during the perinatal stage (1-3% of DRG neurons) and increased progressively from P0 to P60 when it reached a plateau (about 30-33% of DRG neurons). Statistical morphometric analysis was used to define whether CA staining identifies the same population(s) during development. The results demonstrated that, whatever the stage of development, reactive neuronal cells are included in the well-defined large type A population. The possibility that neuronal CA expression is a reliable marker of the 'functional activity' of the proprioceptive neurons in mammals is discussed. The late development expression of the enzyme (after target innervation) raises the possibility of a regulation of the CA phenotype by neuron-target interactions.

Animals↗
PubMed1979

Development of mouse dorsal root ganglia: an autoradiographic and quantitative study.

Pulse labelling with tritiated thymidine was used to determine the cell birthdays of dorsal root ganglion (DRG) neurons in foetal mice. The peak number of cell birthdays occurred at 11.5 days foetal age in cervical DRGs, and at 12.5 days in lumbar DRGs. The satellite cells were becoming heavily labelled by day 13.5 in lumbar and some hours earlier in cervical regions. A very sharp peak of satellite cell labelling was seen at 13 days in the lumbar region. Evidence for the existence of more than one neuronal cell type is presented. The earliest cells to stop dividing were part of a widely spread distribution which included all the large neurons. The birthdays of the population of small neurons began later and continued for at least 48 h after division of the large cells had ceased.

Animals↗
PubMed1987

Conduction properties of single nerve fibers in developing rat spinal nerve roots.

We have examined conduction properties and distribution of membrane currents in ventral spinal root axons of rats 12-47 days of age. Internodal length of the largest myelinated fibers increases at a steady 17-19 micron/day during this period as internodal conduction time decreases. Despite the rapid remodelling of fiber dimensions during the first few weeks of postnatal life, potassium channels are continually excluded from participation in action potential generation at the axon membrane of most nodes of Ranvier.

4-Aminopyridine↗
PubMed1996

Effects of gravitropic stress on the development of the primary root of lentil seedlings grown in space.

Root growth and cell differentiation were analysed in lentil seedlings grown (1) in microgravity (F microg), (2) on the 1 x g centrifuge (F1 x g), (3) in microgravity and placed on the 1 x g centrifuge for 4 h [F(microg + 1 x g)], (4) on the 1 x g centrifuge and placed in microgravity for 4 h [F(1 x g + microg)]. In microgravity, there were strong oscillations of the root tip, even when the seedlings were grown first on the 1 x g centrifuge [F(1 x g + microg)]. In the [F(microg + 1 x g)] sample, the roots grown in microgravity were oblique with respect to the 1 x g acceleration when the seedlings were placed on the centrifuge. They were therefore gravistimulated. However, root length was similar in the 4 samples after 29 h of growth and growth rate of the root was the same between 25 h and 29 h although it appeared to be slightly greater in the [F(microg + 1 x g)] sample. Cell elongation was analysed as a function of the distance from the root cap junction. Cell length was similar in the seedlings grown in microgravity or on the 1 x g centrifuge. The transfer from the 1 x g centrifuge to microgravity [F(1 x g + microg)] did not modify cell elongation in the roots. Cell length in the roots which were grown in microgravity and gravistimulated [F(microg + 1 x g)] was different from that observed in microgravity but this was only due to gravistimulation. Thus, gravity does not have an effect on cell elongation when the roots are strictly oriented in the vertical position but it does as soon as the root tip deviates from this orientation.

Centrifugation↗
PubMed2006

"Chromoplast" development in arbuscular mycorrhizal roots.

The accumulation of apocarotenoids in arbuscular mycorrhizal (AM) roots suggests a dramatic reorganization of the plastids responsible for the biosynthesis of these compounds. This review describes the cytological and biochemical characterization of this phenomenon. The results presented suggest that plastids are key organelles for the establishment of the symbiotic interface of the AM symbiosis. In addition, a complex interplay of various plant cell components during the different functional phases of this interface is suggested. Arbuscule degradation appears to be of particular interest, as it correlates with the formation of the most extensive plastid structures and with apocarotenoid accumulation.

Mycorrhizae↗
PubMedDate not supplied

[Synovial cytokines facilitate the development of spontaneous nerve root activity following compression].

The nerve roots of Wistar rats were studied electrophysiologically following exposure to synovial cytokines. A total of 12 rats was examined. In the experimental series a preparation of synovial cytokines (50 microliters, 250 micrograms protein) was injected into the S1 nerve root of 6 Wistar rats. Six animals served as controls and were injected with a similar solution lacking cytokines. Forty-eight hours after this procedure the S1 nerve root was compressed by a force of 0.2 N for 1 hour. EMG recordings at mid-gastrocnemius levels were performed during, and 3 hours after, compression. The neurophysiological testing performed 3 hours after compression showed a significantly higher level of compression-induced muscle activity in the cytokine group compared to the control.

Animals↗
PubMed2003

Development of the primary root and mobilisation of reserves in etiolated seedlings of Brassica napus grown on a slowly rotating clinostat.

The effect of the slow rotating clinostat (1 rpm) on the growth of the primary root was studied on Brassica napus seedlings. After 5 d in darkness, the primary root was longer and thinner in seedlings grown on the clinostat than in seedlings grown in the vertical position. However, the breakdown of lipid reserves, sucrose level and transport of 14C-labeled sucrose from the cotyledons to the primary root, were not altered by growth on the clinostat. Moreover, the activity of isocitrate lyase, one of the two enzymes necessary for the conversion of lipids into glucids also was also not modified in the cotyledons of clinorotated seedlings. Thus, there was clear evidence that clinorotation had a direct effect on the growth of the primary root that was independent of the mobilisation of lipid reserves in the cotyledons. As a sink, the primary root had the same strength on the clinostat as in the vertical position, but the reserves were used in a different way. The increase in root elongation on the clinostat could be due to the slight, but continuous, omnilateral gravitropic stimulation due to the rotation of the seedlings about a horizontal axis.

Brassica↗
PubMed1969

Ethylene and carbon dioxide in the growth and development of cultured radish roots.

Ethylene is produced by cultured radish roots in amounts large enough to be physiologically important. When roots were grown in controlled atmospheres, applied ethylene was generally inhibitory to elongation, lateral root initiation, and cambial activity. 1% CO(2) similarly affected roots not given ethylene. In contrast, elongation and lateral root production of ethylene-treated roots were stimulated by 1% CO(2). The results suggest that the often-observed stimulation of root growth by CO(2) is due to an interaction with endogenous ethylene.

Journal Article↗
PubMed1995

Role of two mineral-associated adhesion molecules, osteopontin and bone sialoprotein, during cementogenesis.

Adhesion molecules and their cell membrane receptors are known to play important regulatory roles in cell differentiation. Consequently, the following experiments were conducted to determine the role of two adhesion molecules, bone sialoprotein (BSP) and osteopontin (OPN) in tooth root formation. Developing murine molar tooth germs at sequential stages of development (developmental days 21-42) were analyzed using immunohistochemical and in situ hybridization techniques. While BSP was localized to alveolar bone and odontoblasts early in development, BSP was distinctly localized to the cemental root surface at latter periods coincident with the initiation of root formation and cementogenesis. Conversely, OPN was distributed in a nonspecific fashion throughout the PDL and the eruption pathway of the forming tooth. In situ hybridization confirmed that cells lining the root surface express BSP. The fact that BSP is specifically localized to the cemental surface suggests that this protein is involved in cementoblast differentiation and/or early mineralization of the cementum matrix. Localization of OPN to non-mineralized tissues further suggests that OPN functions as an inhibitor of mineralization during periodontal ligament formation. These findings collectively suggest that BSP and OPN are intimately involved in the sequence of cellular and molecular events accompanying cementogenesis.

Alveolar Process↗