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Biomedical subjects

T Ebendal

Publications and source records attributed to T Ebendal.

At least 145 records · Page 8Linked to original sources
PubMed1986

Nerve growth factor in medium conditioned by embryonic chicken heart cells.

The present report demonstrates that embryonic chicken heart cells in culture release different nerve growth promoting factors to their culture medium, one which is biologically and immunologically similar to mouse gland beta NGF. Serum-free heart cell conditioned medium thus promoted neurite outgrowth from sympathetic and ciliary ganglia and supported survival of dissociated ciliary neurons. The addition of affinity purified antibodies against mouse beta NGF does substantially but not completely inhibit the fibre outgrowth from sympathetic ganglia, but does not to any extent diminish the effects on the parasympathetic neurons. The chicken NGF recovered from polyacrylamide gels after electrophoresis greatly enhanced sympathetic fibre outgrowth, an activity completely suppressive by anti-beta NGF antibodies. We conclude that a chicken NGF is being produced by the embryonic heart cells in culture, and that this factor may be produced also in the embryo to fulfill a role in heart innervation.

Animals↗
PubMed1986

Development and regional expression of beta nerve growth factor messenger RNA and protein in the rat central nervous system.

The presence of nerve growth factor (NGF) mRNA and protein in the rat central nervous system is documented. Blot-hybridization analysis showed an abundance of NGF mRNA in the hippocampus, cerebral cortex, and olfactory bulb. Enzyme immunoassay confirmed significant levels of a NGF-like protein in the hippocampus and cerebral cortex. Bioassay of a NGF-like immunoaffinity-purified protein from these regions was physiologically indistinguishable from NGF. Immunohistochemistry revealed a widespread distribution of NGF-like reactivity in the adult brain, preferentially in fiber tracts. NGF mRNA accumulation began at birth, with adult levels reached 3 weeks postnatally. Enzyme immunoassay detected the presence of a NGF-like protein in the embryonic rat brain. Postnatally, the level of NGF-like protein reached a maximum at 3 weeks. Additionally, a distinct fetal form of NGF may exist.

Animals↗
PubMed1985

Nerve fiber production by intraocular adrenal medullary grafts: stimulation by nerve growth factor or sympathetic denervation of the host iris.

This study evaluates the production of adrenergic nerve fibers by adrenal medullary tissue of the adult rat grafted to the anterior chamber of the eye of adult recipients. The chromaffin grafts attach to and become vascularized by the host iris. They decrease in size intraocularly during the first 3 weeks. This decrease is somewhat counteracted by sympathetic denervation of the host iris, and better counteracted by sympathetic denervation and addition of nerve growth factor (NGF, given at grafting and 1 and 2 weeks after grafting). Outgrowth of adrenergic nerve fibers from the grafts into the host iris was studied in wholemount preparations by use of the Falck-Hillarp technique 3 weeks after grafting. The innervated area of the host iris was approximately doubled in the chronically sympathectomized group and doubled again in the chronically sympathectomized NGF-supplemented group. Chronic sympathetic denervation had no effect on density of outgrowing nerves, whereas addition of NGF more than doubled nerve density. Since sympathetic denervation causes a slight elevation of NGF activity in the iris, the present experiments are taken as evidence that the level of NGF in the iris regulates formation of nerve fibers by adrenal medullary tissue grafts from adult rats.

Adrenal Medulla↗
PubMed1985

Chronic implants of chromaffin tissue into the dopamine-denervated striatum. Effects of NGF on graft survival, fiber growth and rotational behavior.

Adult rat chromaffin tissue was transplanted into striatum of adult rat recipients whose nigrostriatal dopamine pathway had been lesioned on the grafted side by 6-hydroxydopamine. Long-term survival of the intrastriatal chromaffin grafts and the effects of treatment with nerve growth factor (NGF) was studied histochemically using Falck-Hillarp fluorescence histochemistry and functionally using rotational behavior induced by apomorphine. Small, cortex-free adrenal chromaffin tissue grafts survived permanently in striatum. The number of surviving cells was significantly increased by NGF. NGF treatment also caused transformation of many cells towards a more neuronal phenotype and greatly enhanced the adrenergic nerve fiber outgrowth into host brain tissue. NGF was either injected stereotaxically into the site of transplantation or infused continuously using implantable osmotic minipumps and a stereotaxically placed chronic indwelling dialysis fiber through striatum. The latter arrangement permitted continuous infusion of NGF for 14-28 days and caused a vigorous adrenergic nerve growth response by the grafts directed towards the source of NGF in the brain. There was a clearcut correlation between morphological signs of taking and rotational behavior. Grafts, and in particular grafts treated with NGF, were able to significantly and permanently counteract the rotational behavior induced by apomorphine. There seemed to be a dose relationship between NGF treatments and amount of reduction of asymmetric behavior. NGF treatment probably decreased the relative importance of diffuse release of catecholamines from chromaffin cells in the graft and increased the importance of adrenergic innervation of host striatum by cells in the graft. Immunofluorescence using antibodies against glial fibrillary acidic protein did not reveal any marked gliosis around the grafts nor were there any marked gliotic reactions around chronic indwelling dialysis fibers. We conclude that implantation of chromaffin tissue into striatum in conjunction with NGF treatments is an effective means of counteracting some of the symptoms of experimentally induced unilateral parkinsonism in rats.

Adrenal Medulla↗
PubMed1985

Parasympathetic neurotrophic activity in the rat iris: determination after different denervations.

The iris of the adult rat contains one or several neurotrophic factors that enhance the survival of dissociated parasympathetic neurons (from the embryonic chick ciliary ganglion) in culture. To assay survival activity, iris homogenates were serially diluted with culture medium and the percentage of neurons surviving for 2 days in a collagen matrix in culture determined. The extract induced survival curves that were similar for denervated and normal irides. Similarly no differences in fibre outgrowth from cultured whole ciliary ganglia were found. The results suggest that the apparent level of parasympathetic growth factor(s) is not under strict control of the innervation of the iris.

Animals↗
PubMed1984

Nerve growth factor in three neurologically deficient mouse mutants.

The activity of nerve growth factor (NGF) in the salivary glands and in the sciatic nerve was compared between normal mice and mice affected by either of three neurological mutations by the use of a biological assay. No evidence was obtained for defects in amount or activity of NGF associated with the sprawling or splotch mutations. A reduction in the NGF content was found in salivary glands and sciatic nerve in homozygous dystonia musculorum mice. It is pointed out that the low amounts of NGF in dtJ/dtJ mice is likely to be a consequence of the general disturbances in development seen in this mutant rather than the specific cause for the neurological disorder.

Animals↗
PubMed1984

Intraocular grafting of cultured brain tissue: growth, vascularization and neuron survival in locus coeruleus and cortex cerebri.

Locus coeruleus and cortex cerebri from embryonic (ED 17) and newborn rats were kept 4 days in tissue culture under conditions maintaining organotypic features and then transplanted to the anterior chamber of the eye of adult rats. Vascularization from the host iris was delayed in pre-cultured grafts as compared to directly grafted material. In spite of this, several morphological parameters developed normally. Thus, pre-cultured grafts grew considerably in oculo. Falck-Hillarp histochemistry showed that grafts of cortex cerebri received an adrenergic innervation from the host iris and that locus coeruleus grafts contained central adrenergic neurons capable of innervating a sympathetically denervated host iris. The successful combination of tissue culture and intraocular transplantation should permit the selective advantages of both techniques to be applied to the same tissue pieces, generating new information unobtainable by either method alone.

Animals↗
PubMed1984

Production of nerve growth-stimulating factor(s) from chick embryo heart cells. Use of Cytodex 3 microcarriers and serum-free media.

Medium conditioned by embryonic chick heart cells is known to support extensive neurite outgrowth from autonomic and sensory neurons. In the present report we describe the use of microcarrier cell culture with serum-free media to scale up the production of the nerve growth-stimulating factors. A growth medium composed of DME /F10 supplemented with insulin, transferrin, human serum albumin and fibronectin in combination with a low molecular weight (MW) fraction of fetal calf serum (FCS) or a mixture of FGF, dexamethasone, calmodulin and thrombin supported the heart cell proliferation at a rate similar to that of medium with 10% FCS. Furthermore, the level of successively accumulated nerve growth activity measured in a bioassay with sympathetic ganglia proved to be nearly equivalent to what was obtained when cells were grown in medium containing serum. The results confirm the potential of microcarrier cell culture in serum-free media for the production and subsequent recovery of a specific cell product.

Animals↗
PubMed1983

The level of nerve growth factor (NGF) as a function of innervation. A correlation radio-immunoassay and bioassay study of the rat iris.

A two-site radio-immunoassay for beta NGF demonstrated 5-10 pg of NGF in the normal, adult rat iris. Ciliarectomy or sympathectomy did not significantly alter the amount of NGF after 10 days. However, denervation including all sensory axons (stereotactic lesion distal to the trigeminal ganglion) increased the level to about 100 pg of NGF. Total denervation resulting from homologous transplantation of the iris gave a similar increase after only 2 days. Fibre outgrowth responses evoked by corresponding iris explants in an NGF bioassay supported the results and suggested in addition that sympathetic denervation may cause a moderate transient increase in NGF after 3 days. It seems that sensory nerves in particular influence the level of NGF in a terminal field, either by a high capacity for uptake and removal of NGF or by exerting a negative feed-back on the production or processing of this growth factor.

Animals↗
PubMed1983

Organotypic cultures of neural retina: neurite outgrowth stimulated by brain extracts.

A bioassay for the growth of retinal neurites was designed. Circular plugs 0.5-1.5 mm in diameter were excised from the chick neural retina at embryonic day 6 and cultured as organotypic explants on a collagen gel. After addition of medium or various tissue extracts cultures were incubated and the length of extending neurites measured. In control medium with 10% serum, neurites were sparse and reached less than 0.2 mm after 4 days. Extract of the optic lobe from 18-day-old chick embryos distinctly increased the density and length of neurites in a dose-dependent manner reaching 1.2 mm after 4 days. A unit of outgrowth activity corresponding to half the maximum length of fibers was defined. The activity of the optic lobe extracts was retained in fractions with nominal molecular weights over 100,000 daltons upon pressure dialysis. Extract from the forebrain hemispheres had nearly the same effect on retinal neurite growth. Mouse submandibular gland NGF failed to evoke retinal fiber growth. Our data imply that macromolecules of the developing brain can support the growth of optic axons.

Animals↗
PubMed1983

Localization of nerve growth factor-like immunoreactivity in rat nervous tissue.

The use of immunofluorescence with affinity-purified antibodies enabled cytological localization of nerve growth factor-like material in the rat. Immunoreactivity was observed along various nerve tracts of the foetal rat brain and spinal cord at day 15 of gestation. Longitudinal pathways in ventral and dorsal spinal cord, ventral lower brain stem, posterior commissure, retroflex fascicle and in the olfactory bulb were all positive. A weaker and more widely spread immunostaining was visible in many areas in the central nervous system. Cranial nerves were strongly immunoreactive. Neuronal perikarya in the retina and the olfactory mucosa as well as filae olfactoriae and the olfactory nerve all the way to the olfactory bulb were also positive. In sensory ganglia and peripheral nerves most immunoreactivity was confined to supporting tissues, probably including Schwann cells. In irides, the pattern of immunoreactivity was similar to that of the sensory and autonomic innervation. More intensively fluorescent material was found in regrowing nerve fibres in iris transplants. Our histochemical results suggest that nerve growth factor and/or a related protein is present in large amounts along nerve pathways in supportive tissues of the peripheral nervous system as well as in the central nervous system during early development.

Animals↗
PubMed1983

The use of Cytodex 3 microcarriers and reduced-serum media for the production of nerve growth promoters from chicken heart cells.

Microcarrier cell culture provides an efficient method for the production of cell products. Cytodex 3 microcarriers were used for the production of an active nerve growth-promoting substance from chicken heart fibroblasts (1 degree -4 degrees cultures). Such cells release into culture medium a factor which stimulates the growth of nerve fibres from explanted ciliary, sympathetic and spinal neurons. Furthermore, culture in low-serum or serum-free media reduces the presence of contaminating proteins and facilitates the production and biochemical analysis of this factor. A mixture of DME/F 10 was supplemented with either 10% (v/v) foetal calf serum (FCS), 0.5% FCS, a low molecular weight fraction of FCS, (MW less than 10,000; prepared by dialysis) or different hormones and growth factors. Cells cultured in medium supplemented with insulin (I, 1 microgram/ml), transferrin (T, 25 micrograms/ml), human serum albumin (HSA, 2 mg/ml) and fibronectin (F, 10 micrograms/ml) (ITAF) in combination with 0.5% FCS or a low molecular weight fraction of FCS progressed through the cell cycle with normal kinetics and maximum DNA synthesis was after 20 h. The results were similar to those obtained with a supplement of 10% FCS alone. Media supplemented with insulin, transferrin, fibronectin and HSA in combination with dexamethasone (200 ng/ml) or epidermal growth factor (10 ng/ml) did not promote cell proliferation to the same extent. The fibroblasts proliferated on Cytodex 3 at a rate similar to cells grown on cell culture plastic and produced sufficient amounts of nerve growth-promoting substance for biological analysis. Production of this factor was generally associated with cell proliferation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Nerve growth-promoting activity in the chick embryo: quantitative aspects.

Nerve growth-promoting activity in organ extracts from the chick embryo was titrated using ganglia explanted to a collagen gel. Fibre outgrowth responses evoked in ciliary, sympathetic and spinal ganglia were well correlated. At embryonic day 8, 66% of the activity was localized in the yolk sac, 19% to the chorioallantois and the remaining 15% was widespread in the embryo. At day 18, total activity had increased 27-fold, the carcass now accounting for 90%. In parallel, the embryo extracts also promoted survival and neurite extension in dissociated ganglionic neurons seeded at low density in the gel. It is suggested that the observed effects are due to one active substance widely distributed in the embryo and increasing in amount during development. The substance has a molecular weight of over 10,000 and is distinct from nerve growth factor (NGF). A function of it may be to regulate axonal growth and survival of autonomic and sensory neurons.

Animals↗
PubMed1982

Nerve growth activities in rat peripheral nerve.

Nerve growth activities in rat sciatic nerves were assayed by recording the neuritic outgrowth from chick embryonic ganglia cultured in collagen gels beside nerve fragments for two days. Living nerve explants released activity that resembled nerve growth factor (NGF) in its effect on sympathetic ganglia and that was almost totally blocked by an antiserum to 2.5 S mouse NGF. Frozen and thawed specimens from normal nerves elicited responses from sympathetic ganglia that were only partially suppressed by anti-NGF and also induced neuritic outgrowth from ciliary ganglia. Thus, from observations on normal nerves, at least two agents promoting axonal extension in vitro were deduced to exist; one substance similar to NGF plus another, non-NGF factor. The level of NGF-like activity was low in killed segments of normal nerves but higher in autologous nerve grafts and degenerating nerves two days after grafting or cutting. However, one or two weeks after nerve transection, distal nerve segments contained little nerve growth activity of either kind. Furthermore, when endoneurial fragments from chronically denervated stumps were cultured, they appeared to have lost some of their capacity to produce NGF-like activity in vitro although the production of activity had, if anything, increased in the perineurial region. In summary, rat peripheral nervous tissue releases two or more soluble substances that stimulate neuritic outgrowth. The level of one or both activities in the endoneurium can be altered by manipulation of nerves in vivo.

Animals↗
PubMed1982

Nerve growth factors in chick tissues.

Bioassays of factors promoting nerve growth in embryonic ganglia are described. Chick embryo extract evokes fiber outgrowth in both sympathetic and ciliary ganglia explanted into a collagen gel. The response is not suppressed by antibodies directed against mouse nerve growth factor (NGF). Chick embryo extract also supported survival of neurons in both intact and dissociated ganglia. In addition to these non-NGF activities, preliminary evidence is presented for the release of a NGF-like factor from cultured iris of the adult chick.

Animals↗
PubMed1981

Factors regulating growth of catecholamine-containing nerves, as revealed by transplantation and explantation studies.

Intraocular grafting of various types of neuron and target tissue shows that peripheral and central noradrenergic neurons may substitute morphologically and functionally for each other in certain, but not all, target tissues. The morphology of growing adrenergic nerve terminals, their patterning, and the number of fibres are completely determined by the target tissues. Thus, the sympathetic adrenergic neuron of an adult organism is a highly plastic unit which may, for instance, double or even triple its terminal field in response to new demands from the environment. Several differences exist between central and peripheral adrenergic nerves: locus coeruleus will not innervate heart grafts; sympathetic fibres will not innervate the spinal cord; and central adrenergic neurons are not sensitive to nerve growth factor (NGF). Chromaffin cells can be made to innervate peripheral and central targets. No NGF is detected in normal adult iris. The iris responds to grafting, explantation, and to sensory or sympathetic denervation with rapid production of NGF as shown by bioassays on chick embryonic ganglia. This iris also contains a potent stimulatory factor for the ciliary ganglion. Trauma to the iris or to the anterior eye chamber may cause it to become hyperinnervated. Heavy metals have characteristic and different effects on the sympathetic nerves of the iris: lead and manganese causes hyperinnervation; cadmium does not change the number of nerves; while mercury causes severe terminal degeneration followed by regeneration.

Animals↗
PubMed1981

Control of neurite extension by embryonic heart explants.

The dynamics of neurite outgrowth elicited by embryonic chick heart explants in sympathetic, spinal, ciliary and Remak's ganglia were investigated in collagen gel cocultures. Neurites emerged preferentially on the side facing the heart explants even after only 6 h and continued to increase in density and length for the next 2 days. Removal of the heart explants after only initial stimulation resulted in less-dense neurite outgrowth. Washing of such cultures led to retraction or degeneration of neurites, effects which could be countered by again adding heart explants. Addition of a second set of heart explants on the back of ganglia initiated a second wave of neuritic outgrowth locally. Ganglia extracted from gels separate from their fibre halos and transferred to a second gel did not regenerate neurites unless again stimulated by heart explants. Neurites from additional, distally positioned ganglia failed to advance into parts of the gel shadowed from the heart explants by proximal ganglia. The asymmetry of neurite outgrowths may be explained by local chemokinetic stimulation of extension, possibly in combination with chemotactic orientation of fibre tips up concentration gradients. The results show that the extension of several categories of ganglionic neurites was reversible, being controlled by the concentration of a soluble neuronotrophic factor released from a developing end organ.

Animals↗