Biomedical subjects

D Dahl

Publications and source records attributed to D Dahl.

At least 37 records · Page 2Linked to original sources

PubMed1994

Distribution of cytoskeletal proteins (neurofilaments, peripherin and MAP-tau) in the cochlea of the human fetus.

We report here an immunohistochemical study of the distribution of intermediate filaments (neurofilament, peripherin) and a microtubule-associated protein, tau, in the human fetal cochlea at 27 weeks of gestation. Neurofilament immunoreactivity (160 and 200 KDa) was localized in afferent and efferent fibers of the cochlear innervation and restricted to a few small spiral ganglion neurons. Peripherin immunoreactivity was specifically distributed in some small ganglion neurons and in their central and peripheral extensions, particularly in fibers reaching the lower part of the outer hair cells. Double immuno-labelling studies with these neurofilaments and peripherin antibodies show that only small neuron cell bodies were stained. Morpholometrical data indicate that immunostained neurons could be related to the Type II neuron population in the spiral ganglion. Tau protein was localized in intraganglionic spiral bundle fibers and in fibers that reach the lower part of hair cells. These observations suggest that neurofilament and peripherin antibodies stain a particular population of human spiral ganglion neurons with Type II characteristics. Moreover, the specificity of peripherin labelling in Type II cells and their processes suggest that peripherin could be used as a probe for the developmental study of this system in the human cochlea. On the other hand, tau antibody appeared as a marker for efferent fibers during development and could give information on the ontogenesis of efferent innervation.

Cochlea↗

PubMed1993

Hyaluronic acid and hyaluronic acid-binding proteins in brain extracellular matrix.

Hyaluronic acid (HA) plays the main structural role in the formation of brain extracellular matrix (ECM). The extracellular space appears empty by electron microscopy because HA is readily dissolved during the preparation of tissues for ultrastructural studies. The HA-binding proteins so far identified in brain ECM are versican, aggrecan and the glial HA-binding protein. Versican is a large fibroblast proteoglycan preferentially expressed in embryonic cartilage at the time of mesenchymal condensation. Glial HA-binding protein (GHAP) is probably a proteolytic product of versican corresponding to its HA-binding amino-terminal domain. It is mainly a white-matter protein, suggesting that the proteinase responsible for its cleavage from versican is normally activated in this location. Versican is found in both white matter and gray matter, where it forms pericellular coats around large neurons. Aggrecan, the aggregating proteoglycan of mature cartilage, co-localizes with versican in this location. In white matter, the localization of GHAP and versican is identical to that of the glial fibrillary acid protein, suggesting that both proteins are produced by astrocytes. An important difference between GHAP and versican is that GHAP but not versican is released from the tissues by hyaluronidase digestion, which suggests that versican is anchored to the cell membranes lining the extracellular space. GHAP was localized at the ultrastructural level in the granule cell layer of rat cerebellum, the only region of gray matter that is positive for GHAP in this species. Rats were perfused with aqueous fixatives containing cetylpyridinium chloride or tannic acid to prevent the solubilization of HA. GHAP is found throughout the extracellular space, the synaptic clefts being a notable exception. GHAP appears late in development, and the same is true for versican, the characteristic perineuronal coats first becoming apparent in the third postnatal week. It is suggested that a marked change occurs in the structure of brain ECM when HA-binding proteins first appear, and that the change is similar to that observed in prechondrogenic mesenchyme, i.e., reduction of the extracellular space and cell aggregation.

Animals↗

PubMed1993

Modulation of paired-pulse activation in the hippocampal dentate gyrus by cholecystokinin, baclofen and bicuculline.

Paired-pulse stimulation was used to evaluate the effects of the sulfated octapeptide of cholecystokinin (CCK8-S), the gamma-aminobutyric acidB (GABAB) agonist (-) baclofen, and the GABAA antagonist (-) bicuculline on hippocampal dentate gyrus (DG) granule cell excitability. Evoked action potentials (EAPs) and excitatory postsynaptic potentials (EPSPs) were recorded in response to orthodromic stimulation of the medial (MPP) or lateral (LPP) perforant pathway. Paired-pulse indices were determined using interpulse intervals (IPIs) across the range of 5-1000 ms. As reported by others, three phases of paired-pulse effects were revealed under control (drug-free ACSF) conditions: early paired-pulse inhibition (PPI), intermediate paired-pulse facilitation (PPF) and late PPI. With EAPs, CCK8-S enhanced only the intermediate PPF on both pathways, with no effect on the early or late PPIs. The effects of (-) baclofen were similar to CCK8-S. (-) Bicuculline attenuated the early and late PPI as well as the PPF. No differences were measured on the MPP- or LPP-evoked EPSPs in any of the drug conditions. These results indicate a similarity of CCK8-S- with GABAB-mediated modulation on neuronal activation in the DG. CCK8-S disinhibition of DG granule cells may play a role in the induction of long-lasting synaptic modifications.

Action Potentials↗

PubMed1993

An original organotypic culture method to study the organ of Corti of the newborn rat in vitro.

The inner ear growth is related to several factors which are not yet well known. In order to study the effect of growth factors on the development of the auditory receptor cells, we have chosen first to establish an in vitro model of the inner ear. Newborn rats were selected as the source of tissue because the inner ear is immature enough at this stage of development for studying some relations between receptors and their innervation. Until recently, the Maximov slide assembly technique was the only organ culture system available and silver neurofibrillary methods were used to stain the nervous structures. These are difficult and time-consuming techniques. With the use of a collagen gel drop floating in the culture medium, we have developed a simple and reliable method. Furthermore, an immunohistochemical fiber-staining technique with anti-neurofilament and histochemical staining technique with phalloidin allows us to check in a few days the organotypy at the spiral ganglion and hair cell levels. This floating drop method gave us some preliminary information about the spiral neuron cells which survived.

Animals↗

PubMed1993

Extracellular matrix in regenerating rat sciatic nerve: a comparative study on the localization of laminin, hyaluronic acid, and chondroitin sulfate proteoglycans, including versican.

Using a glial hyaluronate-binding protein as a probe, monoclonal antibodies against versican and ABC digested chondroitin sulfate proteoglycans, and polyclonal antibodies against laminin, we localized these extracellular matrix (ECM) components in the endoneurium of the adult rat sciatic nerve. During Wallerian degeneration caused by nerve crushing, the staining pattern of these ECM elements changed dramatically. In the first stages and up to 5 days after injury, the tubular endoneurial structures remained the same as in control nerves. Ten days after crush, the bands of Büngner formed by proliferating Schwann cells in the distal stump of crushed nerves stained diffusely for hyaluronate, laminin, and chondroitin sulfate. Regenerating axons were demonstrated in this location by double-labeling experiments with neurofilament antibodies. Conversely, staining with antibodies against versican, a hyaluronate binding proteoglycan, was reduced and the bands of Büngner were not stained. After 30 days the endoneurial tubes made their reappearance and, as in normal nerve, they stained for hyaluronate, laminin, versican, and chondroitin sulfate. It is concluded that proliferating Schwann cells in peripheral nerve undergoing Wallerian degeneration are capable of producing several endoneurial ECM constituents, versican being a notable exception.

Animals↗

PubMed1992

The astrocyte--extracellular matrix complex in CNS myelinated tracts: a comparative study on the distribution of hyaluronate in rat, goldfish and lamprey.

The localization of hyaluronate was studied in the CNS of rat, goldfish and lamprey. Cryostat sections were incubated with glial hyaluronate-binding protein of human origin and stained by indirect immunofluorescence with glial hyaluronate binding protein antibodies not reaching with rat and fish. As previously reported for glial hyaluronate-binding protein and glial fibrillary acidic protein, hyaluronate and glial fibrillary acidic protein had a similar distribution in rat spinal cord and optic nerve, both substances forming ring-like structures around individual myelinated axons. A similar periaxonal distribution was observed in goldfish spinal cord and medulla, except that the rings were much wider, to accommodate the large goldfish axons. The glial fibrillary acidic protein-positive neuroglial tissue forming distinctive structures in goldfish vagal lobes also stained for hyaluronate. In both rat and goldfish spinal cord, motoneurons were surrounded by a hyaluronate coat. Goldfish optic nerve and lamprey spinal cord were hyaluronate-negative and, as previously reported, they stained for keratin but not for glial fibrillary acidic protein. The findings suggest that hyaluronate in CNS fibre tracts in a product of glial fibrillary acidic protein-positive neuroglia. They also suggest that the appearance of glial fibrillary acidic protein-positive neuroglia and the formation of a hyaluronate-bound extracellular matrix are related phenomena in phylogeny.

Animals↗

PubMed1992

Effect of the substrate on neurofilament phosphorylation in mixed cultures of rat embryo spinal cord and dorsal root ganglia.

The effect of the substrate on neurofilament phosphorylation was studied in primary cultures of spinal cord and dorsal root ganglia dissociated from 15-day-old rat embryos. On polylysine and Primaria substrates, spinal cord neurons formed aggregates connected by bundles of neurites. (Primaria dishes have a modified plastic surface with a net positive charge). On both polylysine and Primaria substrates, spinal cord neurons were stained with neurofilament monoclonal antibodies reacting with phosphorylated epitopes appearing early in rat embryo development, i.e. soon after neurofilament expression. Conversely, immunoreactivity with antibodies recognizing late phosphorylation events was only observed on Primaria substrates. As reported by many investigators, fibronectin and laminin were excellent substrates for dorsal root ganglia neurons in culture. However, on both laminin and fibronectin substrates immunoreactivity with antibodies recognizing late phosphorylation events, was only observed on Primaria substrates. As reported by many investigators, fibronectin and laminin were excellent substrates for dorsal root ganglia neurons in culture. However, on both laminin and fibronectin substrates immunoreactivity with antibodies recognizing late phosphorylation events, only occurred after several days in culture, at a time when non-neuronal cells (mainly astrocytes) had formed a confluent monolayer.

Animals↗

PubMed1992

Brain filament proteins in primary cultures derived from chick embryos early in development.

Brain filament expression and neurofilament post-translational modifications (phosphorylations) were studied in primary cultures derived from whole 3-4 day chick embryos. After 2-3 days in culture, neurofilament-positive cells formed neuronal aggregates connected by bundles of neurites in a distinctive pattern similar to that observed in cultures derived from embryonal rat brain and neonatal rat cerebellum. Aggregates and neuritic bundles were stained with several monoclonal antibodies reacting with phosphorylated neurofilament epitopes. With two monoclonal antibodies reacting with phosphorylated forms of the high molecular weight neurofilament subunit, staining was only observed after 8 and 10 days in vitro. There was a major difference between rat and chicken with respect to astrocyte differentiation in culture. In chicken, the flat cells surrounding the neuronal aggregates remained constantly GFAP-negative throughout the whole experimental period (10 days). GFAP-positive cells were first observed within the neuronal aggregates on day 8 in vitro.

Animals↗

PubMed1991

Neurofilament phosphorylation in the axonless horizontal cells of rat retina.

Axonless horizontal cells in the outer plexiform layer of rat retina were studied with 19 monoclonal antibodies reacting with phosphorylated and non-phosphorylated epitopes of the two high molecular weight neurofilament proteins (NF 150K and NF 200K). With 6 antibodies, immunoreactivity was confined to the nerve fiber layer on the inner surface of the retina. Horizontal cells were not stained. Four antibodies in this group were axon-specific, while the remaining two stained motor and sensory neuron perikarya in rat spinal cord and dorsal root ganglia, respectively. Of the 13 antibodies which stained horizontal cells, 11 reacted with phosphorylated epitopes and failed to decorate motor neuron perikarya in the spinal cord, while in dorsal root ganglia, they stained a subpopulation of sensory neurons.

Animals↗

PubMed1991

Heterogeneous visceral nerve changes in acrylamide intoxication.

A variety of visceral nerves were studied by intermediate filament immunocytochemistry in rats intoxicated with acrylamide. In such animals, oesophageal and diaphragmatic motor end-plates were invaded and deformed by neurofilament protein-like material, while afferent fibres of diaphragmatic neuromuscular spindles and myelinated sensory fibres of the iris showed striking terminal accumulation of similar material. Conversely, the rich population of thin afferent fibres of the iris showed no obvious abnormality, while pre-terminal changes were seen along the extrinsic nerve fibres supplying the cornea and myenteric ganglia. Multiple lesions were demonstrated in gut nerves of acrylamide-treated rats, while scattered "enteric glial cells" showed abnormally coarse morphology and a striking increase in glial fibrillary acidic protein immunoreactivity. A distinct, delicately varicose appearance was revealed by neurofilament protein-immunostaining in bladder nerve fibres of normal rats, which was changed to one of coarse dilations by acrylamide. In conclusion, apparently selective changes were found along different types of axons, indicating marked heterogeneity in cytoskeletal organisation among visceral nerves. Taken together with the proposed inhibition by acrylamide of neurofilament proteins degradation, the above findings may suggest a non-uniform distribution of neurofilament degradation sites along distal regions of different axons.

Acrylamide↗

PubMed1991

Acrylamide-induced visceral neuropathy: evidence for the involvement of capsaicin-sensitive nerves of the rat urinary bladder.

The mechanisms underlying the severe urinary retention induced by acrylamide intoxication were studied in detail in the rat. Subcutaneous treatment with acrylamide monomer (50 mg/kg daily for 10 days) almost completely impaired the micturition reflex, resulting in urinary retention. In fact, the ability to eliminate an oral water load was virtually abolished, while bladder filling with saline (transvesical cystometrogram) failed to activate reflex micturition. Instead, a picture of overflow incontinence resulted in urethane-anaesthetized rats, which was not reversed by intravenous administration of 4-aminopyridine. The nerve-mediated contractile response to field stimulation (0.1-20 Hz, 0.5 ms, 60 V) of the isolated bladder was unaffected, thus suggesting the integrity of bladder efferent innervation, and no evidence was found from in vitro experiments that the myogenic contractility of the bladder was depressed by acrylamide treatment. Conversely, the sensory nerve-mediated response to capsaicin was abolished and sensory nerve fibres of the bladder were selectively depleted of their content of substance P- and calcitonin gene-related peptide immunoreactivity following acrylamide treatment. In fact, concentrations of the same neuropeptides in other organs, including the adjoining ureters, were unaffected. As to the urethral segment, including the striated sphincter, the D-tubocurarine (0.2 mM)-sensitive urethral response to electrical stimulation (0.1 Hz, 0.1 ms, 20 V) was significantly reduced in acrylamide-treated animals. At the same level, neurofilament protein immunostaining revealed striking accumulations of neurofilament protein-like material in motor end-plates, thus indicating that neuromuscular junctions of the urethral striated sphincter were severely affected. Thus, the afferent arm of the micturition reflex was shown to be severely deranged by acrylamide intoxication, especially in its capsaicin-sensitive component. Since twitch-like contractions of the urethral striated sphincter are probably involved in promoting bladder voiding, a decreased efficiency of this mechanism could participate in the picture of urinary retention induced by acrylamide.

Acrylamide↗

PubMed1991

Astrocytes colonize dorsal root ganglia transplanted into rat brain.

Fragments of dorsal root ganglia (DRG) were grafted into rat brain and examined one month later. The autografts were similar to their normal counterparts when stained with toluidine blue or by indirect immunofluorescence with laminin and neurofilament antibodies. However, a major difference was observed with antibodies to the glial fibrillary acidic protein (GFAP). Normal DRG were GFAP-negative while the autografts were intensely and diffusely stained. The GFAP antibodies used in this study did not decorate Schwann cells or satellite cells in peripheral nerve and DRG, and thus appeared to recognize the "central" form of GFAP (17). Thus reactive astrocytes appear to be capable of migration into grafted nervous tissues without producing apparent neuronal damage.

Animals↗

PubMed1990

Beta-adrenergic agonist-induced long-lasting synaptic modifications in hippocampal dentate gyrus require activation of NMDA receptors, but not electrical activation of afferents.

Isoproterenol induced long-lasting potentiation (LLP) of the medial perforant path-evoked excitatory post-synaptic potential (EPSP) and long-lasting depression (LLD) of the lateral perforant path-evoked EPSP in the absence of perforant path activation. The NMDA receptor antagonist D-(-)-2-amino-5-phosphonovaleric acid [D(-)APV] blocked the induction of LLP and LLD. After wash, a subsequent exposure to isoproterenol induced only LLP of medial perforant path EPSPs; LLD of lateral perforant path-evoked EPSPs did not occur. Our results are consistent with the hypothesis that beta-adrenergic agonist-induced synaptic modifications in the dentate gyrus arise from pre- and postsynaptic events.

2-Amino-5-phosphonovalerate↗

PubMed1990

Neuronal intermediate filaments in rat dorsal root ganglia: differential distribution of peripherin and neurofilament protein immunoreactivity and effect of capsaicin.

Two major neuronal populations were revealed in rat dorsal root ganglia, immunoreactive for either peripherin, or neurofilament triplet proteins (adult L2 ganglia: 66.2% and 25.6%, mainly small and large diameter cells, respectively), together with a minor, double-immunostained population (L2: 8.1%, mainly intermediate-size neurons). After capsaicin treatment, a striking expansion in the latter population was seen (L2: 22.0%) together with a significant increase in size, restricted to the same population and the (remaining) peripherin-only immunoreactive neurons. Calcitonin gene-related peptide (CGRP) immunoreactivity was revealed in neurons of all 3 groups, in both normal and capsaicin-treated rats.

Animals↗

PubMed1990

Glial hyaluronate-binding protein (GHAP) in optic nerve and retina.

The distribution of glial fibrillary acidic protein (GFAP) and of glial hyaluronate-binding protein (GHAP) was studied by indirect immunofluorescence with monoclonal and polyclonal antibodies in dog, rat and rabbit optic nerve. In dog and rabbit, myelination extends into the optic nerve head inside the eye, while in the rat myelination of the optic nerve ceases abruptly at its entry into the eye. Outside the eye the distribution of the two proteins was similar. Both antigens formed a delicate mesh surrounding myelinated optic nerve axons. In all 3 species GFAP immunoreactivity continued uninterrupted into the optic nerve head inside the eye. Conversely, in both dog and rat, GHAP immunoreactivity ceased abruptly in the region of the lamina cribrosa, a sieve-like structure continuous with the sclera through which bundles of optic nerve axons pass. No staining was observed in the myelinated optic nerve head of the dog nor in the non-myelinated optic nerve head of the rat. In the rabbit lacking a lamina cribrosa, GHAP immunoreactivity did not cease abruptly at the optic nerve entry into the eye, but the staining intensity was reduced in the optic nerve head.

Animals↗

PubMed1990

Dibutyryl cyclic AMP-induced changes in neuron-astroglia interactions and fibronectin immunocytochemistry in dissociated rat cerebellar cultures.

In mixed primary embryonic CNS cultures flat astroglia grow exclusively underneath the initially formed neuronal network. This invasive under-growth results in neuronal detachment and degeneration. The present study sought to find out whether or not morphological differentiation of astroglia, from flat to process-bearing cells, could alter astroglial-neuronal growth relationships in rat cerebellar cultures. Morphological differentiation of astroglia was induced by treatment with dibutyryl cyclic AMP. The results demonstrate that in contrast to flat astroglia, large stellate astroglia can grow over the neurite bundles, and that in these dibutyryl cyclic AMP-treated cultures neurons can persist. Immunocytochemical studies show that the extracellular matrix protein fibronectin is present in these cultures and appears to be associated with flat astroglia rather than with stellate astroglia. The study indicates that in the presence of dibutyryl cyclic AMP transformed stellate astroglia interact differently with neurons and with the growth substratum as compared with flat astroglia.

Animals↗

PubMed1990

Permissive and non-permissive reactive astrocytes: immunofluorescence study with antibodies to the glial hyaluronate-binding protein.

Two distinct types of reactive astrocytes were studied in rat CNS. Reactive astrocytes secondary to penetrating trauma (anisomorphic gliosis) were induced by stab wounds to the brain. Reactive astrocytes secondary to Wallerian degeneration (isomorphic gliosis) were induced in spinal cord dorsal columns by dorsal rhizotomy proximal to dorsal root ganglia. Anisomorphic glial scars did not stain with antibodies to the glial hyaluronate-binding protein (GHAP), a structural glycoprotein of white matter extracellular matrix. Conversely, isomorphic glial scars were still GHAP-positive 3 months after dorsal root transection. Only after 5 months did GHAP immunoreactivity start to disappear from the isomorphic glial scar. Extensive dorsal rhizotomy was performed at the lumbar level to produce Wallerian degeneration of spinal cord dorsal columns. One month later, the rats were reoperated and two thoracic dorsal roots were implanted in the degenerated dorsal columns. The rats were examined 1 month after grafting. As expected, there was a dense anisomorphic glial scar at the site of surgery, while the dorsal columns above the graft showed isomorphic gliosis. Extensive axonal growth was observed in the dense glial scar surrounding the graft. Conversely, no axonal growth was observed in the degenerated dorsal columns undergoing isomorphic gliosis above the implant. The findings suggested that GHAP-negative astrocytes responding to traumatic injury are permissive for axonal growth and that GHAP-positive astrocytes responding to Wallerian degeneration are not permissive.

Animals↗

PubMed1990

Thy-1 is a neuronal and glial surface antigen which interacts with matrix proteins and plasminogen activator.

Thy-1 antigen is expressed at high levels in the thymus and in adult brain of rodents however its function remains undetermined. We report that immobilised Thy-1 binds laminin, fibronectin and the less active precursor form of the tissue type plasminogen activator (t-PA) yet it does not bind urokinase. The incorporation of serine protease inhibitors within the experimental procedures suggested that Thy-1 bound to the lysine-containing, protein-binding domain of t-PA thus leaving the active site available to interact with other proteins. By using an immunocytochemical approach designed to maximally preserve Thy-1 antigenicity, we were able to demonstrate that in the adult rat peripheral nervous system (PNS) Thy-1 was seen to co-localise with laminin on the Schwann cell membranes and accumulated at the nodes of Ranvier within sciatic nerve. The only neuronal structures to express Thy-1 within the PNS were the unmyelinated nerve fibres. In the adult rat central nervous system (CNS), the most distinct and novel association of Thy-1 was its presence along the myelin forming glial cells and their fibres.

Animals↗