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PubMed1988

Remyelination in the central nervous system and the peripheral nervous system.

Remyelination in the PNS is efficient, quick, and consistently found in all demyelinating diseases. Schwann cell proliferation in response to demyelination is rapid and prolific, and the numbers of Schwann cells generated are in excess of those required for adequate remyelination. This cell poses no limit to regenerative potential, and it can divide and remyelinate following numerous repetitive episodes. The Schwann cell generally has easy access to the denuded axons. The limiting factor to remyelination is the persistence of the demyelinating agent, be it directed at the myelin or secondarily through axonal disease. CNS remyelination differs in some respects. Although it has now become clear that it may occur in a variety of clinical and experimental situations, it is slower and often less complete than in the PNS. The limiting factors here include the nature of the demyelinating process, the regenerative potential of the oligodendrocyte, and the accessibility of the latter to the demyelinated axon. It is apparent that the oligodendrocyte is capable of some proliferation, but the time frame in which this can occur is more constrained than for the Schwann cell. Nevertheless the demonstration that the process occurs leads to increasing hope that clinically useful remyelination may be encouraged in the future either by more carefully controlling the extent of demyelination or by finding ways of stimulating oligodendrocyte proliferation and access to the axon.

Animals↗
PubMed1994

Cross talk between the immune system and the nervous system in response to injury: implications for regeneration.

The central nervous system has long been regarded as an immunologically privileged site. Accumulating evidence suggests, however, that the privilege is not total, and that certain immune functions involving immune components and resident glial cells can operate in the central nervous system. The nervous and immune systems interact during normal development, but in the mature brain their interaction is restricted mainly to cases of pathogenic infections and traumatic lesions. The focus of this review is on bidirectional interactions between immune and neuroglial components in response to nerve injury. The macrophage is the most ubiquitous of the immune-derived cell types associated with injury. Its role, as in any other organ, is tissue remodeling and promotion of healing. Macrophage activities include removal of dead tissue and debris by phagocytosis, lipid recycling, and secretion of a wide spectrum of cytokines possessing trophic, mitogenic, and chemotactic properties. These activities affect the behavior of resident cells in the vicinity of the wound. We discuss the possible association of these cytokines with the ability of injured nerves to regenerate. Finally, we consider the apparently conflicting effects of posttraumatic inflammation on the recovery of function.

Animals↗
PubMed1987

Progressive systemic sclerosis and nervous system involvement. A review of 14 cases.

Nervous system involvement in progressive systemic sclerosis (PSS) has been considered rare compared to other collagen diseases. We present 14 additional cases of PSS with neurological manifestations. Primary involvement of the peripheral nerves could be detected in 4 of 14 patients and is documented by electromyo- and electroneurographical examinations. Central nervous system (CNS) manifestations directly related to PSS are a rarity, which may reflect the lack of collagen in the brain, histological differences between cerebral and other arteries and the immunological particularity of the brain. There may have been a direct relationship between CNS involvement and PSS in only one patient presenting with an overlap-syndrome.

Aged↗
PubMed2005

Rejuvenation of antioxidant system in central nervous system of aged rats by grape seed extract.

Oxidative stress is considered as a major risk factor that contributes to age-related increase in lipid peroxidation and declined antioxidants in the central nervous system during aging. Grape seed extract, one of the bioflavonoid, is widely used for its medicinal properties. In the present study, we evaluated the role of grape seed extract on lipid peroxidation and antioxidant status in discrete regions of the central nervous system of young and aged rats. Male albino rats of Wistar strain were divided into four groups: Group I-control young rats, Group II-young rats treated with grape seed extract (100 mg/kg body weight) for 30 days, Group III-aged control rats and Group IV-aged rats supplemented with grape seed extract (100 mg/kg body weight) for 30 days. Age-associated increase in lipid peroxidation was observed in the spinal cord, cerebral cortex, striatum and the hippocampus regions of aged rats (Group III). Activities of antioxidant enzymes like superoxide dismutase, catalase, glutathione peroxidase and levels of non-enzymic antioxidants like reduced glutathione, Vitamin C and Vitamin E were found to be significantly decreased in all the brain regions studied in aged rats when compared to young rats. However, normalized lipid peroxidation and antioxidant defenses were reported in the grape seed extract-supplemented aged rats. These findings demonstrated that grape seed extract enhanced the antioxidant status and decreased the incidence of free radical-induced lipid peroxidation in the central nervous system of aged rats.

Aging↗
PubMed1988

[A model for exploring afferent signals from the immune system to the nervous system].

Mechanisms of information transmission from the immune system to the nervous system have been studied. The results of the studies support the assumption that these signals can be transmitted by oligopeptides (the products of limited proteolysis) which are the fragments found in the active sites of many regulatory peptides of the nervous and immune systems. The testing of a synthesized tripeptide (Ser-Lys-Asp) has shown that it inhibits the antibody-forming cells in intact mice only in response to the administration of large antigen doses and exerts a protective effect against viral infection. When added to the culture of the incubated leukocytes from the peripheral blood of the oncological patients, the tripeptide lowers an increased or normal functional activity of natural killers. In rabbits, tripeptide administration brings about a complex long-lasting reorganization of bioelectrical activity in subcortical structures of the brain.

Animals↗
PubMed2003

Mouse models of human cancer consortium symposium on nervous system tumors.

Nervous system tumors represent unique neoplasms that arise within the central and peripheral nervous system. Recent progress in generating genetically engineered mouse models of these tumors has advanced our understanding of the critical molecular and cellular events important for the development of these tumors. Recently, the National Cancer Institute-sponsored Mouse Models of Human Cancer Consortium convened a meeting on Nervous System Tumors to review recent advances and suggest directions for future research. Refined and novel approaches to modeling central nervous system tumors, including gliomas, meningiomas, medulloblastomas, and oligodendrogliomas, as well as peripheral nervous system tumors such as neurofibromas, schwannomas, and malignant peripheral nerve sheath tumors, were presented. In this review, we discuss the current status of mouse modeling of human nervous system cancers with a specific focus on unresolved scientific questions pertaining to the molecular genetics and cellular biology of these tumors.

Animals↗
PubMed2004

[The MMP/TIMP system in the nervous system].

The matrix metalloproteinases (MMP) belong to a growing family of secreted or membrane-bound (MT-MMP) enzymes that cleave protein components of the extracellular matrix and bioactive factors involved in intercellular signaling. MMP activity is counterbalanced by their four physiological inhibitors, the tissue inhibitors of MMP (TIMPs). Together, MMP and TIMP control cell-cell and cell-matrix interactions associated with physiological processes. However, the breakdown of the protease-inhibitor balance may lead to the loss of tissue homeostasis and the development of degenerative and tumorigenic processes in various tissues. The emerging idea is that the MMP/TIMP system also plays a major role in the pathology and physiology of the nervous system and that mastering MMP activity will set the basis for new and more efficient therapeutic strategies against nervous system disorders.

Blood-Brain Barrier↗
PubMed1987

L3T4 and the immunoglobulin gene superfamily: new relationships between the immune system and the nervous system.

L3T4 is a mouse cell surface protein expressed on most thymocytes and on the subset of mature T cells that recognizes class II MHC molecules. Its primary function on T cells is most likely that of increasing the avidity of the interaction between T cells and antigen-presenting or target cells. It may accomplish this by binding to a nonpolymorphic region on class II MHC molecules. The cDNA and gene encoding L3T4 have been isolated and sequenced. Analysis of the amino acid sequence predicted by the nucleotide sequence indicates that L3T4 is a member of the Ig gene superfamily. It is most closely related to Ig and Tcr V regions. Although the amino-terminal domain of L3T4 is the portion of the molecule that is most similar to V-regions, L3T4 is one of the polydomain members of the Ig gene superfamily. Studies of the expression of L3T4 mRNA in various tissues led to the surprising finding that this gene is transcribed not only in T lymphoid cells, but also in brain. The predominant form of L3T4 mRNA expressed in brain is foreshortened as compared to that in T lineage cells, and it is most likely the product of a distinct transcriptional start site. If translated, the protein encoded by this brain transcript would be 217 amino acids in length and would lack the signal peptide and the amino-terminal 214 amino acids of the mature protein. It is not known whether a stable protein product is synthesized from this mRNA or what its function might be. However, these findings place L3T4 in an intriguing class of Ig gene superfamily members characterized by coexpression in the immune system and the nervous system.

Animals↗
PubMed1986

Extensive intraneuronal spread of horseradish peroxidase from a focus of vasogenic edema into remote areas of central nervous system. Observations on mouse central nervous system subjected to cortical cold injury.

A study was made of the uptake of horseradish peroxidase (HRP) into neurons from a cryogenic cortical lesion in the mouse brain associated with vasogenic edema, following intravenous administration of the tracer. Particular emphasis was placed on the axonal spread of HRP from the primary lesion to other areas of the central nervous system. The distribution of HRP was studied by light microscopy, using highly sensitive histochemical methods, 3-144 h after the onset of the injury. Extravasated HRP was taken up into nerve cell bodies in and around the primary lesion, forming different patterns of labelling: (1) granular, (2) diffuse, and (3) a combination of granular and diffuse staining. Granularity is considered to be the result of HRP accumulation in lysosomes occurring in undamaged or slightly damaged nerve cells, whereas the diffuse, non-granular pattern presumably occurs in severely damaged neurons. Nerve cell bodies containing HRP reaction product were also found in the contralateral cortex, ipsilateral thalamus, substantia nigra, amygdala and ventral tegmental area, presumably a consequence of retrograde axonal transport of the tracer from the primary injury. HRP-containing axons were present in the corpus callosum and in the pyramidal tract of the injured hemisphere all the way down to the cervical spinal cord. Labelling of axonal terminals and preterminal axons in the ipsilateral thalamus, entopeduncular nucleus, subthalamic nucleus, substantia nigra and pons indicated anterograde transport of HRP to these regions. Thus very extensive intraneuronal spread of a macromolecular edema component takes place from a primary focal brain lesion to areas located far away from but neuroanatomically connected to this injured region. The brain thus seems to be affected by focal vasogenic edema in many more ways than are recognized at present.

Animals↗
PubMed1991

Immunoregulators in the nervous system.

The nervous system, through the production of neuroregulators (neurotransmitters, neuromodulators and neuropeptides) can regulate specific immune system functions, while the immune system, through the production of immunoregulators (immunomodulators and immunopeptides) can regulate specific nervous system functions. This indicates a reciprocal communication between the nervous and immune systems. The presence of immunoregulators in the brain and cerebrospinal fluid is the result of local synthesis--by intrinsic and blood-derived macrophages, activated T-lymphocytes that cross the blood-brain barrier, endothelial cells of the cerebrovasculature, microglia, astrocytes, and neuronal components--and/or uptake from the peripheral blood through the blood-brain barrier (in specific cases) and circumventricular organs. Acute and chronic pathological processes (infection, inflammation, immunological reactions, malignancy, necrosis) stimulate the synthesis and release of immunoregulators in various cell systems. These immunoregulators have pivotal roles in the coordination of the host defense mechanisms and repair, and induce a series of immunological, endocrinological, metabolical and neurological responses. This review summarizes studies concerning immunoregulators--such as interleukins, tumor necrosis factor, interferons, transforming growth factors, thymic peptides, tuftsin, platelet activating factor, neuro-immunoregulators--in the nervous system. It also describes the monitoring of immunoregulators by the central nervous system (CNS) as part of the regulatory factors that induce neurological manifestations (e.g., fever, somnolence, appetite suppression, neuroendocrine alterations) frequently accompanying acute and chronic pathological processes.

Adjuvants, Immunologic↗
PubMed1986

Dissociation of the responses of the renin-angiotensin system and sympathetic nervous system to a vasodilator stimulus in congestive heart failure.

The ability of neurohumoral reflex control mechanisms to respond to a vasodilator mediated alteration in hemodynamic status was studied. A sodium nitroprusside infusion was administered to 5 normal subjects and 47 patients with severe congestive heart failure resulting in significant decreases in mean arterial pressure and in systemic vascular resistance. As expected in normals the vasodilator stimulus caused a reflex activation in both the renin-angiotensin system and sympathetic nervous system as measured by increased plasma renin activity and plasma norepinephrine, respectively. In the patients with heart failure, plasma renin activity rose similarly in response to nitroprusside (+63% in heart failure, 100% in normals, P = NS) while plasma norepinephrine remained essentially unchanged (+11% in heart failure, 98% in normals, P less than 0.01). These data demonstrate that the neurohumoral dysfunction seen in patients with heart failure is not uniform. In patients with severe congestive heart failure the renin-angiotensin system apparently is activated by mechanisms other than sympathetic nervous stimulation. This intact reflex humoral response may still function in opposition to the beneficial hemodynamic effects produced by direct vasodilators such as nitroprusside.

Adult↗
PubMed2003

APOE genotype and an ApoE-mimetic peptide modify the systemic and central nervous system inflammatory response.

Human apolipoprotein E is the major apolipoprotein expressed in the brain and exists as three isoforms, designated E2, E3, and E4. Although evidence suggests that apolipoprotein E plays an important role in modifying systemic and brain inflammatory responses, there is little data investigating apoE isoform-specific effects in vivo. In this study, we compared the inflammatory responses of targeted-replacement mice expressing the human APOE3 and APOE4 genes after intravenous administration of lipopolysaccharide. Animals expressing the E4 allele had significantly greater systemic and brain elevations of the pro-inflammatory cytokines TNFalpha and IL-6 as compared with their APOE3 counterparts, suggesting an isoform-specific effect of the immunomodulatory properties of apoE. Furthermore, intravenous administration of a small apoE-mimetic peptide derived from the receptor-binding region of the apoE holoprotein (apoE-(133-149)) similarly suppressed both systemic and brain inflammatory responses in mice after lipopolysaccharide administration. These results suggest that apoE plays an isoform-specific role in mediating the systemic and brain inflammatory responses. Moreover, because exogenous administration of this apoE mimetic peptide is effective at suppressing both systemic and brain inflammation, it may represent a novel therapeutic strategy for diseases characterized by systemic or central nervous system inflammation, such as septic shock, multiple sclerosis, and traumatic brain injury.

Amino Acid Sequence↗
PubMed1995

Remodeling of the insect nervous system.

Our nervous systems and behavior are shaped by hormonally driven developmental changes that continue beyond the embryonic period. Key insights into this process have emerged from studies of the insect nervous system. During insect metamorphosis, the nervous system is remodeled through postembryonic neurogenesis, programmed cell death and the modification of persistent neurons. These changes are regulated to a large degree by gene cascades that are triggered by steroid hormones, the ecdysteroids. Current studies are attempting to reveal the molecular mechanisms involved in regulating these dramatic examples of developmental plasticity.

Animals↗