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Common ethical issues in regenerative medicine.

One of the common ethical issues in regenerative medicine is progress in 'componentation' (= being treated as parts) of the human body, and the enhancement of the view of such "human body parts." 'Componentation' of the human body represents a preliminary step toward commodification of the human body. The process of commodification of the human body follows the steps of 'materialization' (= being treated as a material object) [first step] -- 'componentation' [second step] -- 'resourcialization' (= being treated as resources) [third step] -- commodification [fourth step]. Transplantation medicine and artificial organ developments have dramatically exposed the potential of organs and tissues as parts, and regenerative medicine has a role in advancing 'componentation' of the human body and further enhancing the view of human body parts. The 'componentation' of the human body, regardless of the degree of regenerative medicine's contribution to it, is considered as a challenge to the traditional view of human bodies and the abstract value of "Human Dignity" in the same way or alongside the 'resourcialization' and commodification. However, in the future, a new perspective of human bodies that means "a perspective whereby human bodies, organs, tissues, and even the bodies themselves are perceived as disposable tools like disposable cameras, syringes, or contact lens" and therefore a new ethical view, suitable for a new reality, may emerge.

Biomedical Research↗

[The use of the hypoglycemic preparation gliquidone in patients with digestive organ diseases combined with diabetes mellitus].

A peroral sugar-reducing preparation gliquidone (glurenorm) was tried in treatment of 66 patients with digestive diseases (peptic ulcer, chronic pancreatitis, cirrhosis of the liver), presenting with diabetes mellitus. The results of the studies made showed glurenorm to be a highly effective preparation in term of both its sugar-reducing effect and its capability to improve energy processes in gastric and duodenal mucosa, pancreacytes, hepatocytes, besides which, it appear to dispel metabolic disturbances and stimulate reparative processes in body organs, improves protein-synthetic processes in the liver, pancreas, mucosa of the gastroduodenal region.

Diabetes Mellitus, Type 2↗

Nuclear domains enriched in RNA 3'-processing factors associate with coiled bodies and histone genes in a cell cycle-dependent manner.

Nuclear domains, called cleavage bodies, are enriched in the RNA 3'-processing factors CstF 64 kDa and and CPSF 100 kDa. Cleavage bodies have been found either overlapping with or adjacent to coiled bodies. To determine whether the spatial relationship between cleavage bodies and coiled bodies was influenced by the cell cycle, we performed cell synchronization studies. We found that in G1 phase cleavage bodies and coiled bodies were predominantly coincident, whereas in S phase they were mostly adjacent to each other. In G2 cleavage bodies were often less defined or absent, suggesting that they disassemble at this point in the cell cycle. A small number of genetic loci have been reported to be juxtaposed to coiled bodies, including the genes for U1 and U2 small nuclear RNA as well as the two major histone gene clusters. Here we show that cleavage bodies do not overlap with small nuclear RNA genes but do colocalize with the histone genes next to coiled bodies. These findings demonstrate that the association of cleavage bodies and coiled bodies is both dynamic and tightly regulated and suggest that the interaction between these nuclear neighbors is related to the cell cycle-dependent expression of histone genes.

Cell Cycle↗

Calbindin D-28k distribution in odontoblasts underneath tertiary dentine in human carious teeth.

OBJECTIVE: The aim of this study was to examine the calbindin D-28k immunoreactivity in carious teeth to know whether this protein may have a function in tertiary dentine formation. METHODS: Human extracted teeth with or without carious lesions were immersion-fixed with Zamboni fixative, demineralized in 4.13% EDTA solution (pH 7.4), frozen-sectioned, and processed for calbindin immunoreactivity and hematoxylin-eosin stain. The intensity of the immunostaining was evaluated by quantitative densitometry. RESULTS: In intact teeth, numerous odontoblasts were aligned underneath the secondary dentine and their cell bodies showed the immunoreactivity. In carious teeth, tertiary dentine had poor- or rich tubular patterns under the carious lesion. Underneath the tubule-poor tertiary dentine, distinct odontoblasts could not be seen at the central site. However, some cells with a flat appearance were located at this site and were immunonegative for calbindin D-28k. On the other hand, columnar odontoblasts were seen at the peripheral site, and their cell bodies and processes showed strong immunoreactivity. Underneath the tubule-rich tertiary dentine, columnar odontoblasts were abundantly distributed, and the strong immunoreactivity was observed in their cell bodies and processes. The immunoreactivity in odontoblasts underneath the tertiary dentine with poor or rich tubular pattern was more intense than that for the secondary dentine in intact teeth (P<0.05). On the other hand, the intensity of the immunoreactivity in odontoblasts was similar underneath the secondary dentine in intact and carious teeth. CONCLUSIONS: The present study demonstrated that calbidin D-28k was actively synthesised by odontoblasts under the carious lesion. These findings may suggest that this protein plays an important role in the tertiary dentine formation.

Adult↗

Division and migration of satellite glia in the embryonic rat superior cervical ganglion.

While distinct precursors committed to a neuronal or glial cell fate are generated from neural crest cells early in peripheral gangliogenesis, little is known about the subsequent generation and maturation of young satellite glia from restricted glial precursor cells. To examine the division and migration of glial precursor cells and their satellite cell progeny, morphological, immunocytochemical and culture techniques were applied to the developing rat superior cervical ganglion. At embryonic day (E)18.5, numerous clusters of nonneuronal cells appeared transiently in the ganglion. Individual cells with a similar morphology were present in E16.5 ganglia, and are likely to represent the precursor cells which generate these clusters. The clustered cells were distinguishable from neighbouring neurons as well as from endothelial cells and fibroblasts. Morphologically similar cells were present in nerve bundles at E18.5 and surrounding principal neurons and nerve bundles in the adult ganglion. Double-label studies of the E18.5 ganglion with tyrosine hydroxylase to identify noradrenergic neurons and propidium iodide counterstaining to visualize all cell nuclei revealed that the cells in clusters stained with propidium iodide but lacked tyrosine hydroxylase immunoreactivity. To determine if cell clusters arose from division, bromodeoxy-uridine, a thymidine analogue, was administered to pregnant mothers between E16.5-E18.5, and ganglionic cells examined at E18.5 both in vivo and in vitro. Numerous non-neuronal cells divided during this period in situ and composed portions of clusters. When dissociated, superior cervical ganglion satellite glia reacted with an NGF-receptor antibody (MAb 217c) and possessed a flattened shape, in contrast to bipolar Schwann cells. Over half of the 217c-immunoreactive glia at E18.5 had incorporated bromodeoxyuridine during E16.5-18.5 in vivo. At birth, non-neuronal cells were no longer grouped in clusters, but were associated with neuronal cell bodies and processes. These findings suggest that, between E16.5-E18.5, glial precursors divide rapidly to form clusters, and that, after the peak of neurogenesis, daughter cells migrate within the ganglion to associate with nerve cell bodies and processes where proliferation continues at a slower rate. Distinct cellular and molecular interactions are likely to trigger the initial rapid division of glial precursors, initiate their migration and association with neuron cell bodies, and control their subsequent slower division.

Animals↗

Expression of vimentin intermediate filament in human odontoblast.

BACKGROUND: Vimentin (57 Kda) is a cytoskeletal protein. Odontoblasts contain vimentin and it seems that this protein may function to keep the organelles and the nucleus in a definite place. However little is known about vimentin in the cytoskeleton of odontoblast processes. The purpose of the present study was, therefore to immunolocalize vimentin intermediate filament in odontoblast body and process in order to clarify the distribution of this cytoskeletal element. METHODS: 12 extracted intact premolars, from children, were used in the present study. Each specimen was decalcified in EDTA. Each tissue portion was embedded in paraffin. On sections a monoclonal anti-vimentin antibody was applied. The immunoreaction was visualized by ABC technique. RESULTS: Vimentin was expressed in the cell body and cell process of odontoblasts, however with a different immunolabeling pattern related to the topographical area of observations. In odontoblast cell bodies vimentin showed a perinuclear and cytoplasmatic staining. In the very initial portion of odontoblast process immunoreaction products for vimentin were observed in the core of the process. In the middle zone of dentin vimentin immunoreactions products also showed a granular and cross-bridge arrangements, and also, vimentin was also detected under the plasma membrane, at the periphery of the odontoblast process. Nearby the dentino-enamel junction vimentin immunolabeling was appreciated, mainly under the plasma membrane. CONCLUSIONS: On the basis of vimentin distribution in the odontoblast process it seems plausible to assume that this IF vimentin is important in forming a flexible scaffold essential for structuring cytoplasm.

Child↗

S100 protein-immunoreactive trigeminal neurons innervating the rat molar tooth pulp.

S100-immunoreactivity (ir) was examined in tooth pulp primary neurons of the rat. An immunofluorescence method demonstrated that the molar tooth pulp contained S100-immunoreactive (ir) nerve fibers. In the root pulp, pulp horn and roof of the pulp chamber, S100-ir smooth and varicose fibers ramified and formed subodontoblastic nerve plexuses. All the fibers became varicose at the base of the odontoblastic layer and extended to the odontoblastic layer. Some varicose endings could be traced into the dentin. The trigeminal neurons retrogradely labeled with fluorogold (FG) from the first and second maxillary molar tooth pulps exhibited S100- and parvalbumin-ir. Approximately 60% and 24% of the labeled cells were ir for S100 and parvalbumin, respectively. Virtually all parvalbumin-ir FG-labeled cells showed S100-ir, while 40% of S100-ir ones coexpressed parvalbumin-ir. An immunoelectron microscopic method revealed that all myelinated axons and half of the unmyelinated axons in the root pulp contained S100-ir. In the odontoblastic layer, predentin and dentin, S100-ir neurites lost the Schwann cell ensheathment and made close contact with cell bodies and processes of odontoblasts. The odontoblastic layer also contained parvalbumin-ir neurites. These neurites were devoid of the Schwann cell ensheathment and in close apposition to cell bodies and processes of odontoblasts. S100-ir pulpal axons seemed to be insensitive to repeated neonatal capsaicin treatment. This study suggests that S100-ir tooth pulp primary neurons are mostly myelinated and that S100-ir unmyelinated axons in the root pulp are preterminal segments of myelinated stem axons.

Animals↗

Thyroxine-dependent modulations of the expression of the neural cell adhesion molecule N-CAM during Xenopus laevis metamorphosis.

During amphibian metamorphosis, a complete remodeling of the phenotype takes place under complex hormonal control whose final effectors are thyroid hormones. This process implies the activation of coordinated programs of cell death, proliferation, migration, adhesion and differentiation. Inasmuch as the neural cell adhesion molecule N-CAM is thought to play a central role in the control of morphogenetic processes, we have studied by immunohistofluorescence and immunoblots the patterns of expression of N-CAM at different stages of Xenopus laevis metamorphosis. A scan was made of all major organs and appendages. Before the metamorphic climax, all neuronal cell bodies and processes express high levels of N-CAM. During the metamorphic climax, N-CAM expression decreases sharply on the cell bodies and processes of the peripheral nervous system (PNS) but remains high in the central nervous system (CNS). Towards the end of metamorphosis, the PNS and spinal nerves are virtually negative for N-CAM while the CNS is still positive. The optic and olfactory nerves, although myelinated, are still strongly positive for N-CAM. The lens and olfactory epithelia express N-CAM throughout metamorphosis. In the brain. N-CAM is present at all times as three polypeptides of 180, 140, and 120 X 10(3) Mr; before metamorphosis some of the N-CAM is in its polysialylated form. During metamorphosis and the subsequent growth of the animal, the amount of N-CAM decreases gradually. In all polypeptides, the polysialylated form is the first to disappear. Cardiac muscle expresses high level of N-CAM from its first formation throughout metamorphosis; in contrast, the level of N-CAM in skeletal muscle is high in newly formed muscles, but decreases rapidly after myoblast fusion. The liver of adult Xenopus contains large amounts of a 160 X 10(3) polypeptide that is recognized by polyclonal and monoclonal antibodies against N-CAM. cDNA probes of Xenopus brain N-CAM recognize major transcripts of 9.2, 3.8 and 3.3 kb in Xenopus liver mRNA; these bands are different in size from those recognized in brain mRNA (9.5, 4.2 and 2.2 kb). Premetamorphic liver does not express the 160 X 10(3) form of N-CAM, which can be first detected at stage 59 and persists then through all the life of the animal. Expression of N-CAM in the liver can be induced in premetamorphic animals (stage 51-52) by a 48 h treatment with thyroxine. All hepatocytes are responsive.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

Serotonin and gastrin/cholecystokinin-like immunoreactive neurons in the larval retrocerebral complex of the blowfly Calliphora erythrocephala.

The presence and distribution of neurons immunoreactive against antibodies to serotonin (5-HT) and gastrin/cholecystokinin (gastrin/CCK) has been studied in the larval retrocerebral complex of the blowfly Calliphora erythrocephala, a composite structure which consists of the corpus cardiacum, the corpus allatum, the thoracic gland and a portion of the cephalic aorta. Immunoreactive material was found in all these elements except in the corpus allatum. Six to eight cell bodies in the corpus cardiacum and four to eight cell bodies in the thoracic gland were 5-HT immunoreactive (5-HTi). These 5-HTi cell bodies send processes to the neuropil of the corpus cardiacum and to neurohemal sites in the cephalic aorta, corpus cardiacum and ventral part of the thoracic gland. Six to eight cell bodies in the corpus cardiacum and four to six cell bodies in the thoracic gland reacted with antibodies against gastrin/CCK. These cell bodies send processes to the neuropil of the corpus cardiacum and to neurohemal sites in the corpus cardiacum and the cephalic aorta in a pattern resembling that of the 5-HTi fibers. Additional gastrin/CCK-like immunoreactive fibers were shown to come from the central nervous system via the two nervi corporis cardiaci. An electron-microscopical analysis was performed to analyze further the morphological features revealed by the light-microscopic immunocytochemical technique. This confirmed the existence of neurosecretory-like terminals among the gland cells of the thoracic glands and the existence of neurohemal sites in several regions of the larval retrocerebral complex. Some functional aspects of the retrocerebral complex are discussed on the basis of the presented data.

Animals↗

Glutamic acid decarboxylase immunoreactive large neuron types in the granular layer of the human cerebellar cortex.

'Non-traditional' large neurons of the granular layer of the cerebellar cortex include all its large neuronal types, except the Golgi neuron, which is instead one of the five 'classic' types of corticocerebellar neurons. The morphological, chemical and functional characteristics of the 'non-traditional' large neurons have not been entirely ascertained. The aim of this study was to ascertain whether morphological evidence can be provided of GABA synthesis within the 'non-traditional' large neurons of the human cerebellar cortex by means of immunocytochemistry for glutamic acid decarboxylase (GAD). Fragments of postmortem cerebellar cortex of various lobules from the hemispheres and vermis were studied. Immunoreactions revealed large neurons distributed throughout the granular layer in all lobules examined. They were discriminated by analyzing the morphological features of their bodies and processes and were identified as Golgi neurons and as some 'non-traditional' types, such as the candelabrum, Lugaro and synarmotic neurons. In addition, immunoreactive large neurons, with their bodies and processes closely adjacent to microvessels, were observed throughout the layer: these perivascular neurons could represent a new type of 'non-traditional' neuron of the cerebellar cortex. This study supplies the first indication that in the human cerebellar cortex some types of 'non-traditional' large neurons are GAD-immunoreactive, in addition to those neurons already known to be GABAergic (i.e., stellate, basket, Purkinje and Golgi neurons). These morphological data further point out possible functional roles for GABA as a neurotransmitter/neuromodulator in intrinsic, associative and projective circuits of the cerebellar cortex.

Adult↗

Nucleotide sequence of vitellogenin mRNA in the bean bug, Riptortus clavatus: analysis of processing in the fat body and ovary.

The bean bug, Riptortus clavatus, has immunologically distinct yolk proteins, vitellin (Vn)-1 and-2 and their precursors, vitellogenin (Vg)-1 and-2. We have cloned the full nucleotide sequence of Vg-1 cDNA. The deduced amino acid sequence has some similarities to other insect Vgs. It contains two polyserine regions, which are characteristic of other Vgs. Vg-1 mRNA appeared after treatment with the juvenile hormone analogue, methoprene, implying transcriptional regulation. We found four enzymatic cleavage sites in the Vg molecule. Two of them match the consensus for dibasic processing endoprotease, which is also conserved in processing sites for other insect Vgs. We showed that the processing at each site was incomplete, and this resulted in production of more than the five polypeptides which would be expected from four processing sites in the molecule. The physiological significance of multiple polypeptides in insect Vgs is still unclear.

Amino Acid Sequence↗

Compartmental distribution of cytochrome oxidase in the striatum of the rat.

Endogenous cytochrome oxidase activity was investigated in the adult rat striatum at the light microscope level to see if it was distributed in accordance with the established striatal patch/matrix compartmentalisation. Striatal sections stained to visualise cytochrome oxidase activity were compared with serial sections stained to visualise tyrosine hydroxylase and calbindinD28k-like immunoreactivity, established markers of the matrix compartment. The distribution of endogenous cytochrome oxidase activity was found to coincide with the immunocytochemical staining pattern seen for tyrosine hydroxylase and calbindinD28k whereby areas of intense tyrosine hydroxylase and calbindinD28k-like immunoreactivity (termed the matrix) corresponded to areas of intense cytochrome oxidase activity. Conversely, areas of less intense tyrosine hydroxylase and calbindinD28k-like immunoreactivity (termed patches) corresponded to areas of low cytochrome oxidase activity. In addition, the distribution of two other oxidative enzymes involved in the regulation of mitochondrial respiration, succinic dehydrogenase and NADH-diaphorase, was examined in the striatum and substantia nigra by using histochemical techniques. Both NADH-diaphorase and succinic dehydrogenase histochemistry showed an uneven pattern of neuropil staining in the striatum. In the substantia nigra a few intensely stained cell bodies were seen in the dorsal-lateral tip of the pars reticulata with both histochemical techniques. By using an anti-cytochrome oxidase antibody an abundance of immunoreactive cell bodies and processes were seen in the substantia nigra, particularly in the dorso-medial rim and dorsal tip of the pars reticulata. The substantia nigra pars lateralis contained many intensely stained cytochrome oxidase-like immunoreactive cell bodies and processes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Catecholaminergic innervation of GRF-containing neurons in the rat hypothalamus revealed by electron-microscopic cytochemistry.

The catecholaminergic innervation of neurons containing growth hormone-releasing factor (GRF) was examined by use of a method which combined either 5-hydroxydopamine (5-OHDA) uptake or autoradiography after intraventricular injection of 3H-noradrenaline with immunocytochemistry for GRF in the same tissue sections at the electron-microscopic level. In the ventrolateral part of the arcuate nucleus of the rat hypothalamus a large number of immunonegative axon terminals were found to make synaptic contact with GRF-like immunoreactive (GRF-LI) cell bodies and processes. 3H-noradrenaline autoradiography or 5-OHDA-labeling combined with GRF immunocytochemistry revealed that axon terminals labeled with 3H-noradrenaline or 5-OHDA make synaptic contact with the GRF-LI nerve cell bodies and processes. These findings indicate that catecholamine-containing neurons innervate GRF neurons to regulate GRF secretion via synapses in the rat arcuate nucleus.

Animals↗

Differential localization of Ca2+ channel alpha1 subunits in the enteric nervous system: presence of alpha1B channel-like immunoreactivity in intrinsic primary afferent neurons.

Immunocytochemistry was employed to locate calcium (Ca2+) channel proteins in the enteric nervous system (ENS) of the rat and guinea pig. Anti-peptide antibodies that specifically recognize the alpha1 subunits of class A (P/Q-type), B (N-type), C and D (L-type) Ca2+ channels were utilized. Alpha1B channel-like immunoreactivity was abundant in both enteric plexuses, the mucosa, and circular and longitudinal muscle layers. Immunoreactivity was predominantly found in cholinergic varicosities, supporting a role for Ca2+ channels, which contain the alpha1B subunit, in acetylcholine release. Immunoreactivity was also associated with the cell soma of calbindin-immunoreactive submucosal and myenteric neurons, cells that have been proposed to be intrinsic primary afferent neurons. Alpha1C channel-like immunoreactivity was distributed diffusely in the cell membrane of a large subset of neuronal cell bodies and processes, whereas alpha1D was found mainly in the cell soma and proximal dendrites ofvasoactive intestinal polypeptide-immunoreactive neurons in the guinea pig gut. Alpha1A channel-like immunoreactivity was found in a small subset of cell bodies and processes in the rat ENS. The differential localization of the alpha1 subunits of Ca2+ channels in the ENS implies that they serve distinct roles in neuronal excitation and signaling within the bowel. The presence of alpha1B channel-like immunoreactivity in putative intrinsic primary afferent neurons suggested that class B Ca2+ channels play a role in enteric sensory neurotransmission; therefore, we determined the effects of the N-type Ca2+ channel blocker, omega-conotoxin GVIA (omega-CTx GVIA), on the reflex-evoked activity of enteric neurons. Demonstrating the phosphorylation of cyclic AMP (cAMP)-responsive element-binding protein (pCREB) identified neurons that became active in response to distension. Distension elicited hexamethonium-resistant pCREB immunoreactivity in calbindin-immunoreactive neurons in each plexus; however, in preparations stimulated in the presence of omega-CTx GVIA, pCREB immunoreactivity was found only in calbindin-immunoreactive neurons in the submucosal plexus and not in myenteric ganglia. These data confirm that intrinsic primary afferent neurons are located in the submucosal plexus and that N-type Ca2+ channels play a role in sensory neurotransmission.

Animals↗

Expression of metabotropic glutamate receptor 8 in autonomic cell groups of the medulla oblongata of the rat.

Metabotropic glutamate receptors (mGluRs) in the medulla oblongata have been suggested to have a functional role in the regulation of cardiovascular baroreflexes. The present study examines the localization of mGluR8 autonomic nuclei of the medulla of the rat. mGluR8 immunoreactivity was observed in the cell bodies and/or processes of the dorsolateral, interstitial, medial, intermediate, ventral, ventrolateral, subpostremal, commissural, parvicellular and gelatinosus subnuclei of the nucleus tractus solitarius (NTS). The intensity of mGluR8 staining was highest in the commissural and interstitial subnuclei at the level of the area postrema. Commissural NTS is involved in regulation of baro-, and chemo-reflexes whereas the interstitial nucleus mediates respiratory reflexes. In the area postrema, diffuse staining was observed in the cell bodies, dendrites and fibers of the dorsal and central regions. In vagal outflow nuclei, mGluR8 immunoreactivity was observed in: (1). the cell bodies and processes of the dorsal motor nucleus of the vagus (DMN) throughout the rostro-caudal extent; and (2). the cell bodies and fibers throughout the rostro-caudal extent of the dorsal and ventral division the nucleus ambiguus (NA). Staining in the ventrolateral medulla was restricted to regions ventral to the nucleus ambiguus and dorsal to the lateral reticulate nucleus. The present study is the first to provide a detailed mapping of mGluR8 within the autonomic nuclei of the medulla and suggests that this subtype may be involved in shaping synaptic transmission in these central nuclei.

Animals↗

Processing of pain- and body-related verbal material in chronic pain patients: central and peripheral correlates.

The processing of pain-related, body-related and neutral words was assessed in chronic pain patients and matched healthy controls. During and after word presentation at perception threshold, electromyographic activity (EMG), heart rate, skin conductance level and electroencephalographic (EEG) data from 11 electrode sites were recorded. Startle responses were measured to suprathreshold word stimuli. Although the patients did not recognize more pain-related words, they produced an enhanced left-hemispheric N100 and N200 to pain-related as compared to neutral words. In addition, the patients did not show a distinct P300 but a continuous positive shift to all words extending into the 800-ms range. Skin conductance levels to the pain-related words were also enhanced in patients only. These data partially support the notion of pain-related implicit memory structures in the brain of chronic pain patients that may selectively draw attention to pain-related stimuli and may thus enhance pain perception.

Adult↗

[The effect of enalapril maleate on the lipid peroxidation processes and on the body's antioxidant system in patients with hypertension].

Overall, forty-five patients with essential hypertension (EH) were examined. EH patients revealed dysbalance between lipid peroxidation and the antioxidant system. These disorders were found to correlate, to a certain extent, with severity of the malady, and to affect the character of the course of the process. Enalapril in a dose of 2.5 to 20 mg for 15 days, along with its hypotensive effect, has an antioxidant action on the metabolic processes at the expense of increase in the activity of enzymes of the antioxidant defense, such as catalase and peroxidase, which fact leads to augmentation of the antiperoxidative potential and prevention of further EH progression.

Adult↗

Selective uptake of neuroactive amino acids by both oligodendrocytes and astrocytes in primary dissociated culture: a possible role for oligodendrocytes in neurotransmitter metabolism.

CNS glia may be involved in the modulation of neuronal excitability through their capacity to accumulate and metabolize neuroactive amino acids. To investigate the possible role of oligodendrocytes in amino acid neurotransmitter metabolism, we have used light microscopic autoradiography, following the uptake of 3H-labelled amino acids by dissociated cultures of neonatal mouse brain, characterized immunocytochemically using cell-type specific markers. Oligodendrocytes, recognized by their characteristic galactocerebroside membrane staining, rapidly accumulated [3H] gamma-aminobutyric acid (GABA), becoming intensely labelled over cell body and processes after short incubations. In contrast, oligodendrocytes became only lightly labelled with [3H]L-glutamate and aspartate, which preferentially labelled astrocytes. [3H]D-aspartate, a non-metabolized analogue of L-glutamate, was avidly accumulated by oligodendrocytes, labelling cell bodies and processes after short incubations, to a similar extent as GABA. Thus, oligodendrocytes possess a transport mechanism for these excitatory amino acids, but rapidly metabolize them and release the metabolites. Not only the GC-positive cells but also the GC-negative undifferentiated oligodendrocyte precursors accumulated both GABA and D-aspartate, suggesting that this may be a function expressed early in the differentiation of oligodendrocytes. Net uptake of [3H] beta-alanine and [3H]glycine by oligodendrocytes was not observed under any conditions tested. A small number of oligodendrocytes were labelled with [3H]taurine after longer incubations. The uptake of certain neuroactive amino acids is thus a property shared by astrocytes and oligodendrocytes, the latter acting in a protective fashion around neuronal perikarya and axons.

Alanine↗