Biomedical subjects

M Barbu

Publications and source records attributed to M Barbu.

9 recordsLinked to original sources

PubMed1992

Phenotypic plasticity of avian embryonic sympathetic neurons grown in a chemically defined medium: direct evidence for noradrenergic and cholinergic properties in the same neurons.

Avian embryonic sympathetic ganglia possess both catecholaminergic and cholinergic features and can synthesize noradrenaline (NAd) and acetylcholine (ACh) simultaneously. In the present study we sought to determine (1) whether or not this coproduction of NAd and ACh corresponds to the existence of two non-overlapping populations, and (2) to what extent the levels of synthesis are influenced by non-neuronal ganglion cells. We have focused on the correlation between the immunocytochemically demonstrable presence of the noradrenergic and cholinergic enzymes tyrosine hydroxylase (TH) and choline acetyltransferase (ChAT), respectively, and the synthesis of the corresponding neurotransmitters in embryonic quail sympathetic neuronal and non-neuronal cells purified by fluorescence-activated cell sorting. We show that (1) freshly sorted neurons synthesize both NAd and ACh, whereas non-neuronal cells produce neither; (2) the overwhelming majority of the sympathetic neurons display TH immunoreactivity; (3) about half of the TH-positive neurons are recognized by an anti-ChAT antibody in an artificial medium that selectively enhances synthesis and/or accumulation of ACh; (4) the non-neuronal cells are important for survival of the neurons and potentiate their synthesis of ACh in this medium, and (5) finally, we present evidence that expression of TH in noradrenergic neurons and in small intensely fluorescent cells of sympathetic ganglia is differentially regulated.

Animals↗

PubMed1990

Molecular cloning of cDNAs that encode the chicken P0 protein: evidence for early expression in avians.

As the major transbilayer glycoprotein of peripheral myelin, P0 is believed to play a prominent role in the formation of this structure by Schwann cells. The amino acid sequence of the chicken P0 molecule, deduced from the nucleotide sequence of cDNA clones, is reported here. Comparison with the mammalian molecule reveals an extensive overall homology, thus underlining the importance both of the cytoplasmic and of the extracellular domains of this protein in the establishment and preservation of peripheral myelin structure. Unexpectedly, an avian P0 cDNA probe was found to hybridise with several mRNA species, present exclusively in peripheral nerve and in proportions that varied according to the developmental stage. The expression of these transcripts was detected significantly earlier than that of P0 mRNA in mammals.

Amino Acid Sequence↗

PubMed1990

Expression of GlN1-immunoreactive glycoproteins during development and regeneration in avian peripheral nerve.

Reactivity of the monoclonal antibody GlN1 was examined by immunocytochemistry and immunoblotting in quail and chick developing and regenerating wing nerves; its distribution is compared to that of HNK-1 which detects a carbohydrate epitope widely distributed in the nervous system. Reactivity was detected by immunofluorescence in cryostat sections, by a postembedding electron-microscopic immunogold technique and in immunoblots of nerve homogenates. From E11-E16, reactivity was detected in several large (120-260 kD) glycoprotein bands; and thereafter, principally, in 3 myelin-related glycoproteins (100, 26.5, and 21.5/ 19.5 kD). The HNK-1 carbohydrate epitope was detected in all these and in other bands permitting identification of the 100-kD moiety as the myelin-associated glycoprotein and the 26.5-kD protein as the P0 protein; the myelin-related 21.5/19.5-kD doublet appears as distinct, probable adhesion molecule(s). During development and regeneration, GlN1 reactivity detected by immunogold labeling of sections appeared first over the extracellular matrix, and later over thicker myelin sheaths. After transection, immunoreactivity in immunoblots was lost in distal stumps but reappeared with time; first in the larger (greater than 120 kD) moieties and then in the myelin-related bands, the same sequence observed in development. Electron-microscopic detection of both GlN1 and HNK-1 carbohydrate epitopes by immunogold labeling of resin-embedded sections is localized most consistently in the thicker (greater than 0.3 microns) myelin sheaths of nerves from chicks at or after hatching. Immunoblots of mature fowl nerve tissues homogenized at various stages of preparation for electron microscopy (after fixation or after fixation and dehydration) show sustained immunoreactivity in the 21.5/19.5-kD bands, reduction or complete suppression in others, and evidence of immunoreactivity in high molecular weight, presumably cross-linked, constituents that remain in the stacking gel portion of the blots.

Animals↗

PubMed1987

Phylogenetically conserved antigen on nerve cells and lymphocytes resembles myelin-associated glycoprotein.

The HNK-1 (Leu 7) and NC-1 monoclonal antibodies, raised against a human T-cell line and against nerve cells of quail embryos, respectively, have been shown to bind to a shared epitope present on the surface of human large granular lymphocytes and on nerve cells in species ranging from amphibians to humans. We demonstrate that a related antigen is also expressed on the lymphocyte surface in the avian central lymphoid organs, thymus and bursa, and in the spleen during embryonic and adult life. The expression of the HNK-1/NC-1-reactive determinant differs remarkably in the bursal and thymic compartments, antigen expression being stabilized at a high level early in development of the bursa, whereas its expression fluctuates in the thymus. The material immunoprecipitated from bursal and thymic lymphocytes by the HNK-1/NC-1 antibodies exhibits the same relative molecular mass as myelin-associated glycoprotein, which is one of the molecules recognized by these antibodies in the nervous system. Together with the observation that an antiserum reactive with the protein part of chicken myelin-associated glycoprotein detects similar material in membrane extracts of HNK-1/NC-1-positive thymocytes, this suggests that a molecule sharing structural analogies with this nerve cell component is expressed on cells of the immune system.

Animals↗

PubMed1986

Heterogeneity in migrating neural crest cells revealed by a monoclonal antibody.

A monoclonal antibody, GlN1, obtained by immunization with extracts of the 14 d embryonic quail nodose ganglion, is described. GlN1 recognizes an antigenic determinant present in virtually all the satellite cells of the peripheral ganglia, all Schwann cells of the peripheral nerves, and in subpopulations of sensory and autonomic neurons of embryonic and adult quails and chickens. The molecular weight of the antigen(s) revealed by GlN1 in embryonic day 12 quail dorsal root ganglion (DRG) cultures is around 80 kDa. In the neural crest, GlN1 determinant is found as soon as the crest cells leave the neural primordium. Only a proportion (25%) of the migrating neural crest cells carry the antigen. This demonstrates that the neural crest is composed of a heterogeneous population of cells from its early migratory stages. Being selectively distributed on neural crest cells and its derivatives, the GlN1 determinant may be considered as a "differentiation antigen" that will be useful in further studies on cell-line segregation during the ontogeny of the PNS.

Animals↗

PubMed1984

Technetium 99m autoradiography of labelled white cells.

The cellular uptake of technetium 99m was determined on white blood cells (WBC) by autoradiography, after 'cold' tin pyrophosphate prelabelling followed by pertechnetate labelling. The autoradiographic method gave visible tracks of 99mTc internal conversion and Auger electrons. 75 +/- 5% of the treated WBC were labelled but none of the control WBC. The number and length of tracks per cell varied greatly. This was perhaps due to imaging conditions as well as to variations in cell uptake.

Autoradiography↗

PubMed1984

99m Technetium labelled heparin: potential value as a tracer of heparin activity in pharmacokinetic and biodistribution studies.

Pharmacokinetics and biodistribution of 99m Technetium (99mTc) labelled heparin were studies to assess its value as a tracer of heparin kinetics in comparison with unlabelled heparin. In vitro, the stability and labelling efficiency (98%) of the labelled drug were excellent and elution was minimal. In vivo, after I.V. infusion of the drug, there was no difference in the same animal between anticoagulant activity measurements and radioactive countings, both displaying a plasmatic biexponential pattern (T1 = 2.9 minutes, T2 = 76 minutes). Biodistribution studies showed primarily liver, spleen and kidney accumulation, with no thyroid uptake. The advantages of this technetium labelling may therefore be used for the heparin drug in various experimental and pathological situations even in humans.

Animals↗

PubMed1983

Five leucocyte labelling techniques: a comparative in-vitro study.

During the past years, several authors have used labelled leucocytes to detect inflammatory foci. However, before routine use in man. It is necessary to control the viability of labelled cells. Five leucocyte labelling techniques (111In-oxine, 111In-oxine without extraction, 99mTc oxine, pyrophosphate 99mTc, 51Cr) were compared using the same separation methods, conservation medium, viability assays and migration studies. Electron microscopic studies allowed the assessment of cellular damage induced by the labelling techniques as well as the calculation of the percentage of cells disrupted during preparation. Results obtained in vitro using 111In-oxine were not satisfactory and in fact appeared contradictory to those published by the authors using this technique in vivo. Even the best method, pyrophosphate 99mTc labelling, was not completely atoxic, but the functional behaviour of the leucocytes did not seem affected. While in vitro studies offer much information concerning labelled cells, they cannot predict the in vivo behaviour of these cells.

Chemotaxis, Leukocyte↗

PubMedDate not supplied

[Jaundice with indirect bilirubinemia via the mother's milk].

Among the clinical entities included in the differential diagnosis of the prolonged jaundice at the end of neonatal period and in the small infant is the jaundice due to mother's milk, whose incidence is of 0.5-2% in the naturally fed infants. The authors present two cases in which the diagnosis was reached by exclusion and confirmed by the therapeutically positive test. Physiopathologic considerations are made on the basis of the literature data, and the nosologic background of the affection is presented. This clinical entity, considered to have an excellent prognosis, presented a special evolution in one of the cases.

Diagnosis, Differential↗