Myelin Sheath Of Axons Research Articles

Effects of high fat diet induced obesity on peripheral nerve regeneration and levels of GAP 43 and TGF-β in rats

The increasing frequency of obesity is important because of its accompanying related health problems. The effects of obesity on peripheral nerves have not been elucidated. We investigated the effects of obesity on sciatic nerve regeneration using electrophysiology, stereology, immunohistochemistry, histopathology and functional tests. We used control, obese, control injured and obese injured groups of rats. Electrophysiological results showed that nerve conduction velocity and EMG were same in the experimental groups, but the amplitude of the compound action potential of the control group was significantly higher than that of the obese group. Examination of the nerves showed that the control and obese groups had both larger axon diameters and thicker myelin sheaths. The number of myelinated axons was decreased in both of the injured groups. Axon diameters and myelin sheath thicknesses of the control injured group were significantly greater those of the obese injured group. There were no significant differences in functional tests among the groups. Although growth associated protein 43 immunostaining in the control injured group was significantly greater than that of the obese injured group, no significant difference was observed between the control and obese groups. There was no significant difference in immunohistochemical staining for transforming growth factor beta 3 between the control injured and obese injured groups. Our results suggest that obesity may affect peripheral nerve regeneration negatively after crush injury.

Mitoxantrone – an anthraquinone antibiotic with antitumor activity applied for the treatment of multiple sclerosis

Mitoxantrone is an antineoplastic agent approved for clinical use in the secondary progressive phase of multiple sclerosis (MS). Several scientific reports indicate that mitoxantrone acts through the induction of short-term cell lysis at high concentrations and long-term induction of programmed cell death at lower concentrations of antigen-presenting cells. In this paper, we present the potential cytotoxic effects of mitoxantrone on the cells of the immune system, whose activity is associated with their degenerative effects on axonal myelin sheaths. The article also evaluates the results from the hospital treatment of patients diagnosed with MS. The presented data indicate that, apart from the cytostatic properties, mitoxantrone also exhibits side effects of its clinical application. This drug has high cardiotoxicity, and is associated with decreased left ventricular ejection fraction and increased risk of congestive heart failure. Therefore researchers are currently looking for new substances that can reduce the toxic effects of mitoxantrone in healthy tissues, resulting in the generation of reactive oxygen species during its metabolism.

Reconditioning effect of oligodendrocyte-like cell transplantation in acute spinal cord injury in rats

To observe the reconditioning effect of oligodendrocyte-like cell transplantation in acute spinal cord injury in rats, bone marrow mesenchymal stem cells were differentiated into oligodendrocyte-like cells induced by cytokines including insulin-like growth factor-1(IGF-1). Rats with acute spinal cord injury were treated with the oligodendrocyte-like cells for 8 weeks by local injection. The therapeutic effect was compared with oligodendrocytes transplantation and saline. Regeneration of axon myelin sheath and functional recovery of hind limbs were significantly improved after transplantation with oligodendrocyte-like cells than that with saline. But there was no significant difference between rats treated with oligodendrocyte-like cells and oligodendrocytes. Bone marrow mesenchymal stem cells differentiating into oligodendrocyte-like cells can be induced by cytokines including IGF-1, with similar specific surface markers of oligodendrocytes. These cells can survive in injury sites of the spinal cord for a long duration after transplantation to improve recovery of neural function and reduce cavity area at injury site after acute spinal injury in rats. The possible mechanism may be regeneration of axon myelin sheath, which is helpful for reconstruction of neural reflex function. Key words: Oligodendrocyte-like cells, differentiation, spinal cord injury, transplantation.

Derivation of Pre-oligodendrocytes from Human Endometrial Stromal Cells by Using Overexpression of MicroRNA 338

MicroRNAs have a critical role in oligodendrocyte development including cell proliferation, differentiation, and myelin formation. MicroRNA 338 (miR-338) is necessary to promote oligodendrocyte differentiation by repressing negative regulators of oligodendrocyte differentiation. Oligodendrocytes (OLs) are responsible for myelin sheath synthesis around nerve fibers in the central nervous system (CNS) that form the myelin sheath of axons. Human endometrial-derived stromal cells (hEnSCs) are a new source of mesenchymal-like stem cells for cell replacement therapy. The hEnSCs, after treating with fibroblast growth factor 2/epidermal growth factor (20 ng/mL) and platelet-derived growth factor (PDGF)-AA (10 ng/mL) for 12 days, were divided in two groups: in the first group, the cells were treated by triiodothyronine (T3), and in the second group, the cells were infected by miR-338-green fluorescent protein-expressing lentiviruses. Six days after infection, the cells were collected and analyzed for the expression of stage-specific markers Nestin, microtubule-associated protein 2, neurofilament-L, oligodendrocyte lineage transcription factor, SRY-box containing gene 10, PDGF receptor alpha, 2',3'-cyclic nucleotide 3' phosphodiesterase, A2B5, O4, and myelin basic protein by immunocytochemistry and quantitative reverse transcription PCR. Result showed that in the infected cells, the expression of pre-oligodendrocyte markers was higher than that of T3-treated cells. The EnSCs can differentiate to oligodendrocyte cells by the overexpression of miR-338, and these cells can be used as a unique source for cell therapy of neurodegenerative disease.

Effect of platelet rich plasma and platelet rich fibrin on sciatic nerve regeneration in a rat model

The aim of this study was to evaluate the effect of Platelet Rich Plasma (PRP) and Platelet Rich Fibrin (PRF) on peripheral nerve repair. Thirty-two Wistar rats were randomly divided into four equal treatments groups: autologous nerve grafts (ANG), silicon tube plus saline solution (SS), silicon tube plus PRP, and silicon tube plus PRF. In ANG group, 10 mm segment from sciatic nerve was excised and reimplanted between the nerve stumps. In the SS, PRP, and PRF groups, 5 mm segment from sciatic nerve was excised and bridged with a 12 mm silicone conduit to create a 10 mm nerve gap. The conduit was filled in accordance with the different treatments. Walking track analysis was performed periodically and on the 90th post-operative day histomorphometric analysis was performed. The ANG, PRF, and PRP groups presented a significant functional improvement in relation to the SS group (P = 0.001) on 90 days after surgery. Histomorphometric analysis demonstrated that the ANG group achieved a larger nerve fiber diameter in proximal stump while comparing with the SS group (P =0.037) and showed larger fiber diameter in median stump in comparison to the PRP group (P = 0.002) and PRF group (P = 0.001). Axonal diameter and myelin sheath thickness showed no statistical significant difference between the groups in the three stumps (P ≥ 0.05). This study suggests that PRP and PRF have positive effects on the functional nerve recovery; however, these groups don't achieve a significant improvement on the histomorphometric analysis.

Transplantation of Nogo-66 receptor gene-silenced cells in a poly(D,L-lactic-co-glycolic acid) scaffold for the treatment of spinal cord injury.

Inhibition of neurite growth, which is in large part mediated by the Nogo-66 receptor, affects neural regeneration following bone marrow mesenchymal stem cell transplantation. The tissue engineering scaffold poly(D,L-lactide-co-glycolic acid) has good histocompatibility and can promote the growth of regenerating nerve fibers. The present study used small interfering RNA to silence Nogo-66 receptor gene expression in bone marrow mesenchymal stem cells and Schwann cells, which were subsequently transplanted with poly(D,L-lactide-co-glycolic acid) into the spinal cord lesion regions in rats. Simultaneously, rats treated with scaffold only were taken as the control group. Hematoxylin-eosin staining and immunohistochemistry revealed that at 4 weeks after transplantation, rats had good motor function of the hind limb after treatment with Nogo-66 receptor gene-silenced cells plus the poly(D,L-lactide-co-glycolic acid) scaffold compared with rats treated with scaffold only, and the number of bone marrow mesenchymal stem cells and neuron-like cells was also increased. At 8 weeks after transplantation, horseradish peroxidase tracing and transmission electron microscopy showed a large number of unmyelinated and myelinated nerve fibers, as well as intact regenerating axonal myelin sheath following spinal cord hemisection injury. These experimental findings indicate that transplantation of Nogo-66 receptor gene-silenced bone marrow mesenchymal stem cells and Schwann cells plus a poly(D,L-lactide-co-glycolic acid) scaffold can significantly enhance axonal regeneration of spinal cord neurons and improve motor function of the extremities in rats following spinal cord injury.

Elevated serum measures of lipid peroxidation and abnormal prefrontal white matter in euthymic bipolar adults: toward peripheral biomarkers of bipolar disorder.

Diffusion tensor imaging (DTI) studies consistently reported abnormalities in fractional anisotropy (FA) and radial diffusivity (RD), measures of the integrity of white matter (WM), in bipolar disorder (BD), that may reflect underlying pathophysiologic processes. There is, however, a pressing need to identify peripheral measures that are related to these WM measures, to help identify easily-obtainable peripheral biomarkers of BD. Given the high lipid content of axonal membranes and myelin sheaths, and that elevated serum levels of lipid peroxidation are reported in BD, these serum measures may be promising peripheral biomarkers of underlying WM abnormalities in BD. We used DTI and probabilistic tractography to compare FA and RD in ten prefrontal-centered WM tracts, 8 of which are consistently shown to have abnormal FA (and/or RD) in BD, and also examined serum lipid peroxidation (lipid hydroperoxides, LPH and 4-hydroxy-2-nonenal, 4-HNE), in 24 currently euthymic BD adults (BDE)and 19 age- and gender- matched healthy adults (CONT). There was a significant effect of group upon FA in these a priori WM tracts (BDE<CONT:F[1,41]=6.8;p=0.013) and RD (BDE>CONT:F[1,41]=10.3;p=0.003), and a significant between-group difference in LPH (BDE>CONT:t[40]=2.4;p=0.022), but not 4-HNE. Multivariate multiple regression analyses revealed that LPH variance explained, respectively, 59% and 51% of the variance of FA and RD across all study participants. This is the first study to examine relationships between measures of WM integrity and peripheral measures of lipid peroxidation. Our findings suggest that serum LPH may be useful in the development of a clinically-relevant, yet easily obtainable and inexpensive, peripheral biomarkers of BD.

Programming of human endometrial-derived stromal cells (EnSCs) into pre-oligodendrocyte cells by overexpression of miR-219

Oligodendrocytes are myelinating cells in the central nervous system that form the myelin sheath of axons to support rapid nerve conduction. MicroRNAs have critical roles in oligodendrocyte development. Several studies have shown that miR-219 is necessary to promote oligodendrocyte differentiation through repressing negative regulators of oligodendrocyte development. Human endometrial-derived stromal cells (EnSCs) are abundant and available adult stem cells with low immunological incompatibility, which could be considered for cell replacement therapy in future. After induction of EnSCs by FGF2, EGF and PDGF-AA, they were infected by miR-219-GFP-expressing lentiviruses. The cells were analyzed for expression of stage-specific oligodendrocyte cells markers. Quantitative RT-PCR and immunocytochemistry analyses showed that stage-specific markers Nestin, Olig2, Sox10, PDGFRa, CNP, A2B5, O4, and MBP are expressed in their specific stages through differentiation protocol. Results showed that expression of pre-oligodendrocyte markers in miR-219-GFP-expressing cells were higher than triiodothyronine (T3) treated cells. In conclusion, the EnSCs could be programmed into pre-oligodendrocyte cells by overexpression of miR-219, and may convince to consider these cells as safe source for cell replacement therapy of neurodegenerative diseases.

Differentiation of Human Endometrial Stromal Cells into Oligodendrocyte Progenitor Cells (OPCs)

Oligodendrocytes are myelinating cells in the central nervous system that form the myelin sheath of axons to support rapid nerve conduction. Human endometrial stromal cells (EnSCs) are the abundant and easy available source for cell replacement therapy. In the present study, the EnSCs were coaxed to oligodendrocyte progenitor programming by induction of neuronal condition media, including bFGF, epidermal growth factor, and platelet-derived growth factor (PDGF)-AA signaling molecules as well as triiodothyronine. Differentiated cells were analyzed for expression of oligodendrocytic markers by quantitative reverse transcription PCR and immunocytochemistry. The results showed the expression of oligodendrocyte lineage markers such as nestin, PDGF receptor alpha (PDGFRα), Sox10, and Olig2 in the level of mRNAs. The expression of nestin and PDGFRα increased after 8days posttreatment. Interestingly, the expression of nestin and PDGFRα genes at the levels of mRNA and proteins decreased 24days after induction. The expression of A2B5, O4, and Olig2 proteins in EnSCs was confirmed using immunocytochemistry. The results confirmed that EnSCs could response to the signaling molecules which routinely applied for oligodendrocyte differentiation. Here for the first time, we demonstrated that EnSCs could be programmed into oligodendrocyte progenitor cells and may convince to consider these cells as suitable source for cell therapy of neurodegenerative diseases.

Positive effect of Mesenchymal Stem Cells therapeutic administration on chronic Experimental Autoimmune Encephalomyelitis

Multiple Sclerosis (MS) is a crippling chronic disease of the Central Nervous System caused by the presence of self-antibodies which progressively damage axonal myelin sheath, leading to axonal transmission impairment and to the development of neurological symptoms. MS is characterized by a Relapsing-Remitting course, and current therapies rely only on the use of immunosuppressive drugs, which are however unable to reverse disease progression. Encouraging results have been obtained in preclinical studies with the administration of Mesenchymal Stem Cells (MSCs) before disease onset (Zappia et al., 2005). Here, we investigate the therapeutic potential of MSC administration after disease onset into an animal model of MS, represented by Dark Agouti rats affected by chronic Relapsing-Remitting Experimental Autoimmune Encephalomyelitis (EAE) (Cavaletti et al., 2004). 106 MSC were intravenously injected in EAE rats after disease onset. Clinical score was assessed daily, and after 45 days rats were sacrificed and histological analysis of spinal cords performed to evaluate the demyelinating lesions. After the first peak of disease, no further relapses were observed in EAE rats treated with MSCs, differently from what observed in EAE group. Histological analysis demonstrated the presence of demyelinated plaques in spinal cords of EAE rats, (Luxol fast Blue staining and anti-MBP immunohystochemistry). On the contrary the therapeutic schedule with MSCs significantly reduces the number and the extension of demyelinated areas in the spinal cords, confirming clinical score evaluations. These results demonstrated that MSCs ameliorate the clinical course of EAE and hamper the disease relapsing by reducing the areas of demyelinated lesions. Granted by MIUR – FIRB Futuro in Ricerca 2008 Prot. N° RBFR08VSVI_001.

Hypermyelination and overexpression of neuregulin-1 in thoracic sympathetic nerves in patients with primary palmar hyperhidrosis

Primary palmar hyperhidrosis (PPH) is a condition characterized by high levels of palmar perspiration in excess of physiological need. The etiopathogenesis of PPH is thought to be related to hyperactivity of the sympathetic system, but the exact mechanism is still obscure. The aim of this study was to observe the ultrastructure of the thoracic sympathetic nerves and measure the expression of neuregulin-1 (Nrg-1) in thoracic sympathetic nerve tissue in patients with PPH relative to control subjects. Samples of T3 sympathetic ganglia were obtained from 58 subjects: 30 PPH patients who underwent endoscopic thoracic sympathectomy and 28 control subjects who underwent pleurectomy for chronic empyema. The ultrastructure of the myelin sheath of the sympathetic axons was observed using electron microscopy, and the thickness of the myelin sheath was compared between the two groups. Expression of Nrg-1 mRNA in thoracic sympathetic nerve tissue was evaluated using reverse transcription–polymerase chain reaction analysis. Subjects in the hyperhidrosis group had a significantly greater average myelin thickness and a significantly lower g-ratio relative to the control group. The hyperhidrosis group had significantly higher relative expression of Nrg-1 mRNA in thoracic sympathetic nerve tissue. Hypermyelination of the thoracic sympathetic axons is probably one pathogenetic mechanism underlying PPH. Nrg-1 is likely to be an important cause of hypermyelination in thoracic sympathetic axons in patients with PPH.

CD137 ligand activated microglia induces oligodendrocyte apoptosis via reactive oxygen species

CD137 (4-1BB, TNFRSF9), a member of the tumor necrosis factor (TNF) receptor family, is a potent T cell co-stimulatory molecule. CD137 ligand (CD137L) is expressed by antigen presenting cells (APC) as a transmembrane protein and transmits activating signals into APC. In this study we investigated the effects of CD137L signaling in microglia, the resident APC in the central nervous system. In vitro, the murine microglia cell lines BV-2 and N9, as well as primary murine microglia responded with activation as evidenced by adherence and secretion of proinflammatory cytokines, MMP-9, and soluble intercellular adhesion molecule (ICAM). CD137L signaling is also important for microglia activation in vivo, since CD137L-deficient mice exhibited profoundly less microglia activation during experimental autoimmune encephalomyelitis (EAE) which is a well-established murine model for neuroinflammation and human multiple sclerosis (MS). Also CD137 is expressed in the CNS of mice during EAE. Activated microglia has been reported to mediate the destruction of axonal myelin sheaths and cause the death of oligodendrocytes, the main pathogenic mechanisms in EAE and MS. Corresponding to the lower microglia activation there were also fewer apoptotic oligodendrocytes in the CNS of CD137L-deficient mice. In vitro co-culture confirmed that CD137L-activated microglia induces apoptosis in oligodendrocytes, and identified reactive oxygen species as the mechanism of apoptosis induction. These data demonstrate activating effects of CD137L signaling to microglia, and show for the first time that the CD137 receptor/ligand system may be a mediator of neuroinflammatory and neurodegenerative disease, by activating microglia which in turn kill oligodendrocytes.

Mixing Properties of Sphingomyelin Ceramide Bilayers: A Simulation Study

Ceramide is the simplest molecule in the class of glycosphingolipids composed of a sphingosine backbone and acyl moiety. It plays significant roles in cell signaling; apoptosis; binding of hormones, toxins, and viruses; and many other biologically important functions. Sphingomyelin, ceramide with a phosphotidylcholine headgroup, is another biologically vital lipid present in the myelin sheath of nerve cell axons. Regions with high concentrations of ceramide can be formed in biological membranes composed of sphingomyelin by enzymatic catalysis with sphingomyelinase. To better understand the biophysical and thermodynamic properties of these molecules and their mixtures, we have preformed NPT molecular dynamics simulations of hydrated 16:0 sphingomyelin bilayers with increasing concentrations of 16:0 ceramide at 323, 332, 340, and 358 K. From analyses of electron densities, hydrogen bonding, NMR order parameters, partial molecular volume, and partial molecular area, we have identified possible structural changes corresponding to liquid ordered and liquid disordered phases. These structural changes are the results of changes in intra- and intermolecular hydrogen bonds between SM and Cer molecules. Our results correspond to DSC experiments for sphingomyelin bilayer concentrations up to 50% Cer. Above 50% concentration, we observe conformational changes in the SM headgroup similar to that of the umbrella model for lipid cholesterol mixtures.

The Splay Leg Syndrome in Piglets: A Review

Problem statement: The splay leg syndrome is the major congenital cause of lameness in suckling piglets. It is characterized by a temporarily impaired functionality of the hind leg muscles immediately after birth, resulting in an ability to stand and walk. Etiology and pathogenesis is complex and remain still poorly understood. Approach: The aim of the present study is to perform the update information about the etiology, clinical signs and control strategies of the syndrome. Results: A sex-affected inheritance of the splay leg syndrome is assumed since higher frequencies have been observed in male piglets. Several biochemical and histomorphological investigations indicate an immaturity of the skeletal muscle in the affected piglets at birth. Splay leg is caused by a reduction of the axonal diameter and myelin sheath thickness of the fiber that innervate the hindlimb adductors. The existence of one or more major genes for congenital splay leg seems possible. Among the fragments strongly displayed in the splay leg muscle, are identified the porcine CDKN3 gene. Various management and genetic factors have been connected with the etiology, such as the farrowing induction, low birth weight, short gestation lengths, slippery floors and breeds (e.g., Large White and Landrace). Moreover, nutrition can play a role to pathogenesis, as choline or methionine deficiency in sow diets and the fusarium toxicity. Furthermore, Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) are also involved in etiological factors. Piglets suffering from splay leg should be kept in a warm place and be helped to take colostrums or artificial milk for 2-3 days. Conclusion: Management practices should be applied in order to be avoided the occurrence of splay leg syndrome, such as non-slip floors, use of anti-mycotoxins products in feed, avoiding the farrowing induction before day 113. Finally, a herd health management programme should be applied in order to prevent and control PRRSV infection.

Ultrastructural study on the facial nerve of rabbit after (125)I seed implantation

To investigate the ultrastructural variation of the facial nerve of rabbit with different dosage of (125)I seed brachytherapy. Fifty-four big ear rabbits were divided into 3 groups randomly and given 40 Gy, 80 Gy, 120 Gy respectively. Radioactive seeds were implanted in one side of parotid gland, the other side was implanted with vacant shell as a control group. The facial nerves were obtained 2, 4, 6 months respectively after operation and the histological ultrastructural changes observed by electromicroscope. In the control group, epineurium was continuous, there was slight pitting edema under the epineurium, and axonal myelin was loose. In the test groups, there was slight pitting edema under the epineurium, and axonal myelin sheath was loose at 4th month. Macrophage and regenerated fibers were found in the 80 Gy group and myelin sheath lamellar separation, regeneration of nerve in the 120 Gy dosage. The myelin sheath lamellar was separated and axonal myelin loose in the test group at 6th month. Myelin sheath amellar separation and edema under the epineurium were found in the group of 80 Gy and 120 Gy. The ultrastructure of the facial nerve is damaged by the dosage of 40 Gy, 80 Gy brachytherapy with (125)I seeds. The higher dosage the nerve receives, the more serious the damage will be. Both of the epineurium and axonal myelin sheath are integral and continuous 6 months after operation with dosage of 120 Gy.

Chronic Swelling and Abnormal Myelination during Secondary Degeneration after Partial Injury to a Central Nervous System Tract

Secondary degeneration is a serious consequence of traumatic injury to the central nervous system (CNS) and involves the progressive loss of neurons and function. However, while disruption to myelin has been observed in spared axons, the ultrastructural abnormalities that occur in myelin and axons spatially separated from the primary injury and susceptible exclusively to secondary degeneration are unknown. We used a model of secondary degeneration in which the dorsal aspect of rat optic nerve (ON) was transected leaving the central/ventral ON undamaged, but vulnerable to secondary degeneration. Transmission electron microscopy of the central/ventral ON at 1 and 3 months was used to quantify secondary changes in axon diameter, myelin sheath thickness and morphology, compared to normal animals. Three months after partial ON transection, cross-sectional nerve area at the injury site was increased (p ≤ 0.05), and changes in axons and myelin sheaths were detected in the central/ventral ON. Although myelin sheath thickness remained normal at both time points, average axon diameter significantly increased at 3 months. The density of the total axon population was decreased by 1 month, reflecting loss of retinal ganglion cells as previously published, with a decrease in the density of normally-myelinated axons, but an increase in unmyelinated axon density (p ≤ 0.05). Myelin basic protein immunoreactivity and fluoromyelin staining were also significantly reduced. Within four subpopulations of abnormally-myelinated axons, there was: no change in lightly-myelinated axons; an increase in axons with excessive myelination (at 1 month); and an increase in the density of axons with partial and fully-decompacted myelin (at 3 months, p ≤ 0.05). Chronic axon swelling and myelin sheath compaction defects are features of secondary degeneration, and may contribute to the reported loss of ON function following partial transection.

The role of chronic cerebrospinal insufficiency in multiple sclerosis

Multiple sclerosis is a non-hereditary neurodegenerative disease caused by an autoimmune process that results in demyelination of axons in the central nervous system thus leading to a broad spectrum of neurological symptoms. The etiology of multiple sclerosis is multifactorial and a single cause explaining all aspects of the disease has not yet been identified. Authors have agreed that this disorder is most likely due to a combination of factors, which includes a genetic predisposition, combined with environmental elements and possibly an infectious component. The cascade is initiated by the blood-brain barrier breakdown. This allows T-cell infiltration into the central nervous system, which triggers an inflammatory process that causes axonal myelin sheath damage resulting in poor neuronal action potential propagation. Oligodendrocytes attempt to remyelinate, although insufficient to compensate for demyelination in the long term. The end result is permanent neuronal scarring and damage and loss of parenchyma. According to the National Multiple Sclerosis Society, multiple sclerosis patients may present three distinct clinical courses: relapsing remitting, primary progressive, and secondary progressive. In the last five years, additional propositions have been made to unveil the causes of multiple sclerosis. Zamboni has raised the possibility that multiple sclerosis and chronic venous disease may share some key features, particularly, increased iron deposition in the brain. This has been first described by Adams et al.: “In active multiple

Visualization of cytoplasmic diffusion within living myelin sheaths of CNS white matter axons using microinjection of the fluorescent dye Lucifer Yellow

The compactness of myelin allows for efficient insulation defining rapid propagation of action potentials, but also raises questions about how cytoplasmic access to its membranes is achieved, which is critical for physiological activity. Understanding the organization of cytoplasmic (‘water’) spaces of myelin is also important for diffusion MRI studies of CNS white matter. Using longitudinal slices of mature rat spinal cord, we monitored the diffusion of the water-soluble fluorescent dye Lucifer Yellow injected into individual oligodendrocytes or internodal myelin. We show that living myelin sheaths on CNS axons are fenestrated by a network of diffusionally interconnected cytoplasmic ‘pockets’ (1.9 ± 0.2 pockets per 10 μm sheath length, n = 58) that included Schmidt–Lanterman clefts (SLCs) and numerous smaller compartments. 3-D reconstructions of these cytoplasmic networks show that the outer cytoplasmic layer of CNS myelin is cylindrically ‘encuffing’, which differs from EM studies using fixed tissue. SLCs were found in different ‘open states’ and remained stable within a 1–2 hour observation period. Unlike the peripheral nervous system, where similarly small (< 500 Da) molecules diffuse along the whole myelin segment within a few minutes, in mature CNS this takes more than one hour. The slower cytoplasmic diffusion in CNS myelin possibly contributes to its known vulnerability to injury and limited capacity for repair. Our findings point to an elaborate cytoplasmic access to compact CNS myelin. These results could be of relevance to MRI studies of CNS white matter and to CNS repair/regeneration strategies.

Enhanced adenoviral gene delivery to motor and dorsal root ganglion neurons following injection into demyelinated peripheral nerves

Injection of viral vectors into peripheral nerves may transfer specific genes into their dorsal root ganglion (DRG) neurons and motoneurons. However, myelin sheaths of peripheral axons block the entry of viral particles into nerves. We studied whether mild, transient peripheral nerve demyelination prior to intraneural viral vector injection would enhance gene transfer to target DRG neurons and motoneurons. The right sciatic nerve of C57BL/6 mice was focally demyelinated with 1% lysolecithin, and the left sciatic nerve was similarly injected with saline (control). Five days after demyelination, 0.5 microl of Ad5-GFP was injected into both sciatic nerves at the site of previous injection. The effectiveness of gene transfer was evaluated by counting GFP(+) neurons in the DRGs and ventral horns. After peripheral nerve demyelination, there was a fivefold increase in the number of infected DRG neurons and almost a 15-fold increase in the number of infected motoneurons compared with the control, nondemyelinated side. Focal demyelination reduced the myelin sheath barrier, allowing greater virus-axon contact. Increased CXADR expression on the demyelinated axons facilitated axoplasmic viral entry. No animals sustained any prolonged neurological deficits. Increased gene delivery into DRG neurons and motoneurons may provide effective treatment for amyotrophic lateral sclerosis, pain, and spinal cord injury.

The fatty acid compositions of erythrocyte and plasma polar lipids in children with autism, developmental delay or typically developing controls and the effect of fish oil intake

The erythrocyte and plasma fatty acid compositions of children with autism were compared in a case-control study with typically developing (TD) children and with children showing developmental delay (DD). Forty-five autism subjects were age-matched with TD controls and thirty-eight with DD controls. Fatty acid data were compared using paired t tests. In addition, blood fatty acids from treatment-naive autism subjects were compared with autism subjects who had consumed fish oil supplements by two-sample t tests. Relatively few differences were seen between erythrocyte fatty acids in autism and TD subjects although the former had an increased arachidonic acid (ARA):EPA ratio. This ratio was also increased in plasma samples from the same children. No changes in n-3 fatty acids or ARA:EPA ratio were seen when comparing autism with DD subjects but some SFA and MUFA were decreased in the DD subjects, most notably 24 : 0 and 24 : 1, which are essential components of axonal myelin sheaths. However, if multiple comparisons are taken into account, and a stricter level of significance applied, most of these values would not be significant. Autism subjects consuming fish oil showed reduced erythrocyte ARA, 22 : 4n-6, 22 : 5n-6 and total n-6 fatty acids and increased EPA, 22 : 5n-3, 22 : 6n-3 and total n-3 fatty acids along with reduced n-6:n-3 and ARA:EPA ratios. Collectively, the autism subjects did not have an underlying phospholipid disorder, based on erythrocyte fatty acid compositions, although the increased ARA:EPA ratio observed suggested that an imbalance of essential highly unsaturated fatty acids may be present in a cohort of autism subjects.