Comparative fine structural distribution of endopeptidase 24.15 (EC3.4.24.15) and 24.16 (EC3.4.24.16) in rat brain

Glial-cell-line--derived neurotrophic factor (GDNF) has been identified as a potent survival and differentiation factor for several neuronal populations in the central nervous system (CNS), but to date, distinct effects of GDNF on motor axon growth and regeneration in the adult have not been demonstrated. In the present study, ex vivo gene delivery was used to directly examine whether GDNF can influence axonal growth, expression of neuronal regeneration-related genes, and sustain the motor neuronal phenotype after adult CNS injury. Adult Fischer 344 rats underwent unilateral transections of the hypoglossal nerve, followed by intramedullary grafts of fibroblasts genetically modified to secrete GDNF. Control animals received lesions and grafts of cells expressing a reporter gene. Two weeks later, GDNF gene delivery (1) robustly promoted the growth of lesioned hypoglossal motor axons, (2) altered the expression and intracellular trafficking of the growth-related protein calcitonin gene-related peptide (CGRP), and (3) significantly sustained the cholinergic phenotype in 84 +/- 6% of hypoglossal neurons compared with 39 +/- 6% in control animals (P < 0.001). This is the first neurotrophic factor identified to increase the in vivo expression of the trophic peptide CGRP and the first report that GDNF promotes motor axonal growth in vivo in the adult CNS. Taken together with previous in vitro studies, these findings serve as the foundation for a model wherein GDNF and CGRP interact in a paracrine manner to regulate neuromuscular development and regeneration.     

Regulators of the neuropeptide-degrading enzyme, EC 3.4.24.15 (thimet oligopeptidase), in cerebrospinal fluid

Endopeptidase EC 3.4.24.15 (EP 24.15; thimet oligopeptidase) is a soluble metalloendopeptidase implicated in the metabolism of a number of neuropeptides, including neurotensin, gonadotropin-releasing hormone, and opioid peptides. We have shown previously that thiol reducing agents, such as dithiothreitol, activate EP 24.15 by mediating the conversion of inactive multimeric forms to active monomers and that this conversion involves the disruption of intermolecular disulfide bonds involving cysteine residues 246, 248, and 253. We have identified two components of cerebrospinal fluid that activate recombinant EP 24.15, but have no effect on a thiol-independent cysteine mutant form of the enzyme. The low molecular weight (<10 kDa) component co-elutes with glutathione by reversed-phase HPLC, whereas the high molecular weight component (>50 kDa) is sensitive to digestion with trypsin, suggesting it is proteinaceous in nature. These results suggest that EP 24.15 activity in the brain may be modulated by factors released into cerebrospinal fluid.     

Activities of amidophosphoribosyltransferase (EC2.4.2.14) and the purine phosphoribosyltransferases (EC2.4.2.7 and 2.4.2.8), and the phosphoribosylpyrophosphate content of rat central nervous system at different stages of development--their possible relationship to the neurological dysfunction in the Lesch-Nyhan syndrome

(1) This communication reports the amidophosphoribosyltransferase (PRPP-At; EC2.4.2.14), hypoxanthine phosphoribosyltransferase (HPRT; EC2.4.2.7) and adenine phosphoribosyltransferase (APRT; EC2.4.2.8) activities and the phosphoribosylpyrophosphate (PRPP) content of rat brain at different stages of development. The results are not age-related in the foetal and neonatal animals and the data for whole brain homogenates are similar to the average results for the individual regions of the brain at the same stage of development. (2) The enzyme activities and PRPP content are similar in the different regions of the rat central nervous system. PRPP-At has the lowest activity of the 3 enzymes studied and this decreases gradually from birth until 8 weeks. HPRT is the most active of the three enzymes, its activity increases markedly between birth and the end of the third week of life. The time course of these changes shows only minor differences between the regions of the brain studied. The ratio of HPRT activity to PRPP-At activity increases from age 1 week in all parts of the rat brain. (3) The APRT activities in rat brain are intermediate between those of PRPP-At and HPRT and essentially steady except for a decrease in the cerebellum during the first 3 weeks of life. (4) The PRPP concentrations in rat brain decrease between birth and the end of the 3rd week of life. (5) The systemic tissues examined have PRPP-At, HPRT and APRT activities. The relationship between the activities of the different enzymes appears to be characteristic of the tissue concerned. (6) Correlating the observed time course of the changes in the ratio of hypoxanthine phosphoribosyltransferase activity to amidophosphoribosyltransferase activity in the rat with other workers' data on changes in the rate of DNA accretion in human brain during development indicates that the main increase in this ratio is after the major bursts of neuroblast and neuroglia proliferation. We suggest that the neurological dysfunction in the Lesch-Nyhan syndrome is due to lack of a purine derivative with a physiological or neuropharmacological function, rather than to an effect of the biochemical lesion on brain morphogenesis.     

Presence of immune complexes in ischemic stroke]

There is increasing evidence that inflammatory responses play an important role in the pathogenesis of atherosclerosis and cerebral infarct. The aim of this study was to determine the amount of immunocomplexes (i.c.) in patients with stroke in the early period of the disease. Studies were performed on 35 subjects. The concentration of immunocomplexes was determined with the precipitation method (3.5% polyethylenoglikol was used). Increased concentration of i.c. was found in patients with cerebral infarct (after 12 hours and 7 days). It suggests, that i.c. could be one of the markers for systemic inflammation and be important in the patogenesis of atherosclerosis and stroke.     

Central nervous system perivascular cells are immunoregulatory cells that connect the CNS with the peripheral immune system

Perivascular cells are a heterogeneous population found in the central nervous system (CNS) and the peripheral nervous system (PNS). Several terms are used for these cells, including perivascular cells, perivascular macrophages, perivascular microglia, fluorescent granular perithelial cells (FGP), or Mato cells. Different terminology used may reflect subpopulations of perivascular cells within different anatomic regions and experimental paradigms, neuropathological conditions, and species studied. Different terminology also points to the lack of clear consensus of what cells are perivascular cells in different disease states and models, especially with breakdown of the blood-brain barrier (BBB). Despite this, there is consensus that perivascular cells, although a minor component of the CNS, are important immunoregulatory cells. Perivascular cells are bone marrow derived, continuously turn over in the CNS, and are found adjacent to CNS vessels. Thus, they are potential sensors of CNS and peripheral immune system perturbations; are activated in models of CNS inflammation, autoimmune disease, neuronal injury and death; and are implicated as phagocytic and pinocytotic cells in models of stroke and hypertension. Recent evidence from our laboratory implicate perivascular cells as primary targets of human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) infection in the CNS of humans and macaques. This article reviews current knowledge of perivascular cells, including anatomic location and nomenclature and putative immunoregulatory roles, and discusses new data on the infection of these cells by SIV, their accumulation after SIV infection, and a possible role of the immune system in SIV encephalitis.     

Distribution of a putative endogenous modulator of the GABAergic system in human brain

Diazepam binding inhibitor (DBI) is a novel neuropeptide purified from rat, cow, and human brain that allosterically modulates GABAergic transmission by binding to benzodiazepine (BDZ)-recognition sites. Using a specific radioimmunoassay for human DBI, we investigated the distribution of this peptide in different brain areas. We characterized with high-pressure liquid chromatography the DBI immunoreactivity in brain tissue obtained by biopsy and autopsy; we detected one molecular species of DBI in both instances. The regional distribution of DBI in the human brain is similar to that observed in rat brain: high concentrations in cortical and limbic areas, cerebellum, and brainstem, and low concentrations in the basal ganglia. These data suggest a modulatory role for DBI in human brain.     

Effects of benzodiazepines on the immune system.

Benzodiazepines (BDZ) are psychotropic drugs largely used in patients with affective disorders. As far as their effects on the immune system are concerned, a few studies have been carried out until now. Diazepam is inhibitory in vitro for the phagocytic functions and the antibody synthesis, being its action mediated via specific receptors on immunocompetent cells. On the contrary, alprazolam results to be enhancing for the antibacterial activity exerted by normal human peripheral blood T lymphocytes in vitro. Taken together, these data point out the different role which BDZ play on the immune response.     

Cellular and humoral immune system in schizophrenia: a conceptual re-evaluation.

Immune alterations in schizophrenia have been described for decades. However, modern immunological methods and new insights into the highly developed and functionally differentiated immune system allow an integrative view of both the older and also more recent findings of immunological abnormalities in schizophrenia. The conceptual advances in immunology require the re-evaluation of elder immunological findings in schizophrenia. In this overview, recent advances in immunological research regarding the differentiation between T-Helper-1 and T-Helper-2 cells and between the so-called specific and unspecific arms of the immune system are discussed. The unspecific "innate" immune system shows signs of an over-activation in unmedicated schizophrenic patients, as increased monocytes and gamma delta-cells point to. Increased levels of Interleukin-6 (IL-6) and the activation of the IL-6 system in schizophrenia might be the result of the activation of monocytes/macrophages, too. In contrast, several parameters of the specific cellular immune system are blunted, e.g. the decreased T-helper-1 (TH-1) related immune parameters in schizophrenic patients, both in vitro and in vivo. It seems that a TH-1-TH-2 imbalance with a shift to the TH-2 system is associated with schizophrenia. During therapy with antipsychotics, the specific TH-1 related immune answer becomes activated, but the B-cell system and the antibody production become activated too.     

Neuroendocrinological effects of L-threo-3, 4-dihydroxyphenylserine (DOPS), a putative norepinephrine precursor, on healthy volunteers

The effect of L-threo-3, 4-dihydroxyphenylserine (DOPS) on plasma cortisol, prolactin, thyrotropin-stimulating hormone (TSH) and growth hormone concentrations was studied in nine healthy male volunteers. The drug was administered orally (300 mg or 600 mg DOPS) using a multiple crossover placebo-controlled study design. Plasma hormone concentrations were measured at 30 minute intervals for 3 hours after dosing. Plasma DOPS peak concentrations were observed between 2 and 3 hours after dosing. DOPS, however, had no effect on plasma hormone concentrations and this may be attributed to the known low brain permeability of DOPS in healthy subjects.     

Presence and coexistence of putative neurotransmitters in carotid sinus baro- and chemoreceptor afferent neurons

The presence and coexistence of tyrosine hydroxylase (TH), vasoactive intestinal polypeptide (VIP), calcitonin gene-related peptide (CGRP), substance P (SP) and galanin (GAL) were studied in the petrosal and jugular neurons innervating the carotid body and carotid sinus of the rat. The retrograde labeling of the carotid sinus nerve with Fluoro-gold (FG) demonstrated that most (94.5%) FG-labeled ganglionic neurons were observed in the petrosal ganglion. Fewer (5.2%) FG-labeled neurons were seen in the jugular ganglion and very few (0.3%) were observed in the nodose ganglion. Immunohistochemistry revealed that subpopulations of TH-, VIP-, CGRP-, SP- and GAL-immunoreactive (-ir) neurons in the petrosal ganglion projected to the carotid sinus nerve. Approximately 4% of FG-labeled neurons contained TH-ir and were predominantly found in the caudal portion of the petrosal ganglion. Nearly 90% of total TH-ir neurons in the petrosal ganglion were labeled with FG. Less than 1% of FG-labeled neurons were immunoreactive for VIP in this ganglion. In the petrosal ganglion, 25% of FG-labeled neurons contained CGRP-ir, and 16.7% of FG-labeled neurons contained SP-ir. 30% of CGRP-ir or SP-ir neurons in the petrosal ganglion were labeled with FG. In the jugular ganglion, no TH- or VIP-ir neurons projected to the carotid sinus nerve and only small populations of CGRP- or SP-ir neurons projected to the carotid sinus nerve. Many FG-labeled and GAL-ir neurons were observed in the petrosal and jugular ganglia. The double-immunofluorescence method revealed the coexistence of CGRP- and SP-ir in carotid sinus nerve-projecting neurons in the petrosal and jugular ganglia. Likewise, GAL-ir coexisted with CGRP- and SP-ir in these ganglionic neurons. There was no coexistence of TH-ir and VIP-ir in carotid sinus nerve projections. The present study demonstrates the presence of multiple putative transmitters in baro- and chemoreceptor afferent neurons of the carotid sinus nerve. These neurochemicals are likely to contribute to transmission of signals from the carotid body and carotid sinus to neurons of the brainstem.     

Presence of lymphocyte membrane surface markers on "small cells" in a pineal germinoma.

A 16-year-old boy was operated on via an occipital transtentorial craniotomy for a pineal tumor. Routine histological examination of the tissue revealed it to be a germinoma, as characterized by the presence of two cell populations: large cells and small, lymphoid-appearing cells. The cells were evaluated in a single-cell suspension for the presence of lymphocyte membrane surface markers; small cells exclusively were found to have such markers. A T-lymphocyte membrane marker was present in 51% of the small cells, whereas 15 to 18% of the small cells had a B-lymphocyte membrane marker.     

Regulatory mechanisms of the immune system in multiple sclerosis. T regulatory cells: turned on to turn off

Journal of Neurology - The immune system is homeostatically regulated to maintain a balance between triggering of inflammatory responses and protecting against self-directed autoimmunity. In...