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T Ebendal

Publications and source records attributed to T Ebendal.

At least 19 recordsLinked to original sources
PubMed1992

Widespread increase of nerve growth factor protein in the rat forebrain after kindling-induced seizures.

Nerve growth factor (NGF) protein levels were determined in various forebrain regions using a two-site immunoassay following kindling-induced seizures. In the dentate gyrus the NGF content was significantly elevated 7 days after the last seizure (to 152% of control). In the piriform and parietal cortices, maximal increases were seen at 12 h (to 261% of control) and at 24 h (to 169% of control), respectively, and the NGF content was then normalized at 7 days. The increased production of NGF might be a protective response or could be involved in plastic changes underlying kindling epileptogenesis.

Animals↗
PubMed1992

Hippocampal nerve growth factor levels are related to spatial learning ability in aged rats.

Brain nerve growth factor (NGF) was determined in two groups of aged rats: 'good' and 'poor' performers. The animals were selected out of a population of 40 aged rats (26-28 months old) trained in a spatial learning task. Animals performing well in the test had significantly higher NGF in the hippocampus when compared to 'poor' performers. No differences in the levels of NGF were found in the cortex, septum and cerebellum. The results implicate hippocampal NGF in cognitive functioning of aged rats, and suggests that the forebrain cholinergic neuronal atrophy which has been observed in cognitively impaired aged rats may be due to reduced availability of target-derived NGF.

Aging↗
PubMed1992

Disruption of the low affinity receptor-binding site in NGF allows neuronal survival and differentiation by binding to the trk gene product.

Nerve growth factor (NGF), like many other growth factors and hormones, binds to two different receptor molecules on responsive cells. The product of the proto-oncogene trk, p140trk, is a tyrosine kinase receptor that has been identified as a signal-transducing receptor for NGF, while the role of the low affinity NGF receptor, p75NGFR, in signal transduction is less clear. The crystal structure of NGF has recently been determined, although structures involved in receptor binding and biological activity are unknown. Here we show that Lys-32, Lys-34, and Lys-95 form a positively charged interface involved in binding to p75NGFR. Simultaneous modification of Lys-32 with either of the two other lysines resulted in loss of binding to p75NGFR. Despite the lack of binding to p75NGFR, these mutants retained binding to p140trk and biological activity, demonstrating a functional dissociation between the two NGF receptors.

Amino Acid Sequence↗
PubMed1992

Two-site enzyme immunoassay for beta NGF applied to human patient sera.

Nerve growth factor (NGF) supports sympathetic and sensory neurons in the peripheral nervous system and serves functions in the development and maintenance of cholinergic neurons in the basal forebrain. NGF distribution can be studied with the use of a sensitive two-site enzyme immunoassay (EIA). The monoclonal antibody 27/21 to mouse NGF was recently shown to effectively block the activity of both recombinant human NGF and native mouse NGF, and a two-site EIA using monoclonal antibody 27/21 was optimized. We have now applied this assay to examine NGF levels in normal human serum and serum from Parkinson, Alzheimer, and Huntington patients. To further test the specificity of conjugate binding, dilutions of the human sera were preincubated with an excess of monoclonal NGF antibody 27/21 in solution. With this strategy it was possible to completely block the signal obtained using the two-site EIA. Furthermore, we show that recombinant BDNF and NT-3 do not cross-react with monoclonal antibody 27/21 under our conditions. We found low levels of specific NGF immunoreactivity in normal human sera (0.4 +/- 0.1 ng/ml). Significantly lower levels of NGF were found in sera from patients with Parkinson's and Huntington's disease whereas sera from Alzheimer patients showed only slight reductions in the NGF level. Two patients who had received intracerebral NGF infusions (one with Parkinson's and other with Alzheimer's disease) showed significantly elevated serum levels of NGF during the period of infusion. Due to an inhibitory activity in human serum, it was impossible to demonstrate the low levels of NGF activity in the human serum samples using explanted embryonic sympathetic ganglia, even after concentration by pressure dialysis. Thus, the serum levels are below the limit to evoke a response in NGF-sensitive neurons and thus to expect any physiological effect. Nevertheless, the levels measured may be used as indicators in clinical conditions such as Parkinson's and Huntington's disease.

Aged↗
PubMed1992

Function and evolution in the NGF family and its receptors.

The gene family of neurotrophins includes nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), and neurotrophin-4 (NT-4). Recently, neurotrophin-5 (NT-5), a possible mammalian homologue to NT-4 described in the frog Xenopus, has been cloned in man and rat. The neurotrophins stimulate survival and differentiation of a range of target neurons by binding to cell surface receptors. The structure of NGF has recently been clarified from crystallographic data. The similarities between the different neurotrophins are substantial with the variable regions, giving specificity to each of the family members, being localized to some exposed loop regions. Low-affinity binding (Kd of 10(-9) M) of all tested neurotrophins is mediated via a 75 K glycoprotein (LNGFR) that has been cloned and characterized. A 140 K tyrosine protein kinase encoded by the proto-oncogene trk has been found to bind NGF with high affinity (Kd of 10(-11) M) and to evoke the cellular neurotrophic responses. In addition, a protein encoded by the trk-related gene trkB has been shown to bind BDNF. Recently, a third member of the trk family, trkC, has been cloned and demonstrated to function as a high-affinity receptor for NT-3. The expression of trk and LNGFR mRNA are co-localized in the rat brain to the medial septal nucleus and the nucleus of Broca's diagonal band containing the NGF-responsive magnocellular cholinergic neurons projecting to hippocampus and cerebral cortex. In sharp contrast, the pattern of expression of trkB is widely spread in many areas of the cortex as well as lateral septum. The trkB protein might serve general functions in large areas of the cortex. Site-directed mutagenesis and expression of recombinant chimaeric neurotrophin proteins have made it possible to localize a likely region for the interaction between NGF and the LNGFR. This region could be altered, resulting in the total loss of LNGFR binding by the mutant NGF protein without affecting the binding to the trk receptor which was sufficient for the full biological activity. Cladistic analysis of likely phylogenies within the neurotrophins shows BDNF and NT-4 to be most closely related whereas NGF may be the sister group to NT-3, BDNF, and NT-4. Neurotrophins offer obvious clinical possibilities for treatment of neurodegenerative diseases.

Amino Acid Sequence↗
PubMed1992

Nerve growth factor affects 11C-nicotine binding, blood flow, EEG, and verbal episodic memory in an Alzheimer patient (case report).

Based on animal research suggesting that nerve growth factor (NGF) can stimulate central cholinergic neurons, the known losses of cholinergic innervation of the cortices in Alzheimer's disease (AD), and our experience of infusing NGF to support adrenal grafts in parkinsonian patients, we have initiated clinical trials of NGF infusions into the brain of patients with AD. Here we report a follow-up of our first case, a 69-year-old woman, with symptoms of dementia since 8 years. Intraventricular infusion of 6.6 mg NGF during three months resulted in a marked transient increase in uptake and binding of 11C-nicotine in frontal and temporal cortex and a persistent increase in cortical blood flow as measured by PET as well as progressive decreases of slow wave EEG activity. After one month of NGF, tests of verbal episodic memory were improved whereas other cognitive tests were not. No adverse effects could be ascribed to the NGF infusion. Taken together, the results of this case study indicate that NGF may counteract cholinergic deficits in AD, and suggest that further clinical trials of NGF infusion in AD are warranted.

Aged↗
PubMed1992

Neuritogenesis on collagen substrates. Involvement of integrin-like matrix receptors in retinal fibre outgrowth on collagen.

Extracellular matrix molecules such as laminin, fibronectin and collagen promote neurite outgrowth in vitro. We have investigated the capacity of hydrated gels of collagen types I-III and monomeric collagen types I-VI on plastic surfaces to support neuritogenesis. The attachment and survival of explants from the day 6 chick embryo were studied and neurite outgrowth measured as mean elongation rate and maximal neurite length. Collagen types I and III, both as three-dimensional gels or as native monomers supported neuritogenesis equal to or better than laminin. Collagen type V also supported neurite out-growth although less effectively. Collagen types II, IV and VI, as well as denatured collagens of all types tested, did not support outgrowth. The monoclonal anti-beta 1 integrin antibody (CSAT), as well as rabbit polyclonal antibodies directed to the integrin beta 1-chain, effectively inhibited neurite outgrowth on permissive collagenous substrata, indicating that collagen-binding integrins were involved in the neuritogenesis. These beta 1-integrins were independent of Arg-Gly-Asp (RGD) since neurite formation proceeded in the presence of synthetic RGD-containing peptides. Fluorescence immunohistochemistry revealed the presence of the integrin beta 1-chain on the outgrowing neurites. The results suggest a possible function of collagen and collagen-binding integrins in the development of the visual system.

Animals↗
PubMed1992

Effects of low-dose X-irradiation on mouse-brain aggregation cultures.

Biochemical and morphological differentiation in reaggregating mouse-brain cell cultures after low-dose radiation (0.5 Gy) in vitro was studied. Cells were irradiated on culture day 2, corresponding to embryonic day 15-16, and different glial and neuronal markers were followed through development to postnatal day 40. The shape and size of irradiated aggregates were more irregular and smaller compared with controls. Total amounts of DNA and protein were significantly lower in irradiated aggregates than in controls between days 8 and 20. After 30 days in culture activities of the glial markers glutamine synthetase (GS) and 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP) were lower in X-irradiated aggregates than in controls. However, after 40 days the CNP activity in irradiated aggregates increased to levels above those of the controls. Irradiated and control aggregates did not differ significantly in neuronal marker enzyme activities, i.e. choline acetyltransferase (ChAT), acetylcholine esterase (AChE) and glutamic acid decarboxylase (GAD) measured on a per mg protein basis. On days 20 and 30 the amount of nerve growth factor (NGF) was two-fold higher in irradiated aggregates compared with non-irradiated ones, suggesting that, after irradiation, surviving cells in culture were induced to produce more NGF. After 40 days the amount of NGF in irradiated aggregates had decreased to the level found in the control aggregates.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1992

No re-expression of high-affinity nerve growth factor binding sites in spinal motor neurons in amyotrophic lateral sclerosis.

Autoradiographic studies of high-affinity nerve growth factor binding sites in the cervical human spinal cord revealed a high density of binding sites in the dorsal horn and in the tract of Lissauer, which is in agreement with investigations in nonprimates. Very low or no binding was found in the motor neuron areas of controls as well as in amyotrophic lateral sclerosis cases, which indicates that the degeneration of motor neurons in this disease is not accompanied by re-expression of high-affinity nerve growth factor receptors.

Aged↗
PubMed1991

Methylmercury induced alterations in the nerve growth factor level in the developing brain.

Pre- and early postnatal stages in the development of the central nervous system (CNS) are very sensitive to the toxic effects of methylmercury. The influence of methylmercury on the level of nerve growth factor (NGF) during the development of CNS was studied. Sprague-Dawley rats were exposed indirectly throughout the fetal and suckling periods until weaning on postnatal day 25 (P 25) via their dams given methylmercury in the diet (3.9 mg/kg diet). In addition, after weaning offsprings were exposed directly to methylmercury via the diet until postnatal day 50 (P 50). The level of NGF was analyzed in cortical areas and in the septum with a sensitive enzyme immunoassay. The pups exposed to MeHg exhibited a 50% elevation in the level of NGF in the hippocampus on P 25 and P 50 compared to control animals. Concomitantly, the level of NGF decreased by 30% in the septum on P 25 and P 50, suggesting that the retrograde transport of NGF from hippocampus to septum could be affected by the exposure of methylmercury. The exact mechanism by which the low level of mercury is affecting the NGF concentration in the developing brain is yet unknown. The increase of NGF in the hippocampus and the decrease of NGF measured in the septum could reflect altered conditions for neurotrophic support in these areas of the brain as a result of the exposure to heavy metal. Thus, this finding might indicate a connection between exposure of heavy metals and neurodegeneration, such as that found in the basal forebrain in Alzheimer's disease.

Animals↗
PubMed1991

Intraputaminal infusion of nerve growth factor to support adrenal medullary autografts in Parkinson's disease. One-year follow-up of first clinical trial.

Experimental studies in rodents show that beta-nerve growth factor can increase the survival, neurite outgrowth, and functional effect of grafts of adrenal chromaffin cells to the basal ganglia. We, therefore, have begun to investigate whether treatment with nerve growth factor might also increase the functional effect of autografts of adrenal medullary tissue in patients with Parkinson's disease. Previous studies have shown that stereotactic implantation of adrenal tissue pieces produces a transient functional improvement that lasts for a few months. This report describes a trial of grafting of adrenal chromaffin tissue into the putamen, supported by infusion of nerve growth factor. The patient is a 63-year-old woman with a 19-year history of Parkinson's disease, now complicated by on-off phenomena and drug-induced hyperkinesia, despite optimized medical management. The left adrenal gland was removed, and the medulla was dissected into 1- to 2-mm3 pieces in a solution containing nerve growth factor purified from mouse submandibular gland. Pieces were implanted in six tracts 3 to 4 mm from a previously placed cannula in the left putamen. Through the cannula, nerve growth factor was infused for 23 days for a total dose of 3.3 mg. Clinical assessment consisted of global ratings for rigidity and/or hypokinesia and for drug-induced hyperkinesia. Measures of gait and fine-motor control were also made. The motor readiness potential and auditory evoked potentials were recorded.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Medulla↗
PubMed1991

Chimeric molecules with multiple neurotrophic activities reveal structural elements determining the specificities of NGF and BDNF.

Nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) are two members of a family of neurotrophic factors which show both overlapping and distinct neurotrophic activities. Using site-directed mutagenesis, chimeric molecules were constructed where different combinations of sequences from BDNF replaced the corresponding sequences in NGF. The resulting molecules were transiently expressed in COS cells and conditioned media containing the chimeric proteins were assayed for biological activity in explanted chick sympathetic, spinal and nodose ganglia. Our results show that the biological specificities of the two proteins are obtained by specific combinations of a set of sequences that differ between the two molecules. Some of these combinations allowed us to engineer molecules which display multiple neurotrophic activities recruited from both the NGF and BDNF proteins.

Amino Acid Sequence↗
PubMed1991

Messenger RNAs for trk and the low-affinity NGF receptor in rat basal forebrain.

Nerve growth factor (NGF) acts by binding to specific sets of neurons. Low-affinity binding (Kd of 10(-9) M) is mediated via a 75 kDa glycoprotein (LNGFR). Recently, a 140 kDa tyrosine protein kinase encoded by the proto-oncogene trk has been found to bind NGF with high affinity (Kd of 10(-11) M) and to evoke neurotrophic responses. In addition, the related trkB protein and the LNGFR have been shown to bind brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) with an affinity of Kd 10(-9) M. We demonstrate the distribution of mRNA encoding the neurotrophin-binding proteins in the forebrain of the 21-day-old Sprague-Dawley rat by in-situ hybridization. Expression of trk and LNGFR mRNA showed co-localization and was restricted to the medial septal nucleus and the nucleus of Broca's diagonal band, suggesting a receptor function in these cells for both proteins encoded. In contrast, expression of trkB was widely spread in many areas. Thus trkB protein might serve general functions in the forebrain.

Aging↗
PubMed1991

Biological and immunological properties of recombinant human, rat, and chicken nerve growth factors: a comparative study.

Biological and immunological properties of recombinant human, rat, and chicken nerve growth factors (NGFs) were studied and compared. Recombinant NGF proteins were produced in a transient expression system using COS cells and levels of secreted NGF protein were assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of conditioned media from in vivo [35S]cysteine-labeled cell cultures. Antigenic differences among the three NGFs were studied by immunoblotting and immunoprecipitation of secreted cell products using a rabbit polyclonal antiserum against purified mouse NGF, and by a two-site enzyme immunoassay (EIA) with a monoclonal antibody against mouse NGF. Although all three NGFs were recognized equally well in the immunoblotting, only one-third of the chicken NGF protein could be detected by immunoprecipitation or by the EIA as compared to the rat and human NGFs. Thus, changes in the three-dimensional structure of the NGF molecule are most likely responsible for the antigenic differences between avian and mammalian NGFs. The three NGF proteins were also compared in their ability to displace 125I-mouse NGF from low-affinity NGF receptors on rat pheochromocytoma PC12 cells. Similar displacement curves and values were obtained for each NGF protein, indicating that structural differences among these molecules do not affect low-affinity binding to NGF receptors. Biological activities were studied by the ability of the conditioned media to promote neurite outgrowth from explants of E9 chick sympathetic ganglia and from PC12 cells. Although the rat system showed a slight preference for the homologous molecule, the morphological changes, dose-response curves, and maximal stimulation values obtained with the different NGFs were practically indistinguishable in the chicken bioassay.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Gland Neoplasms↗
PubMed1991

Thyrocyte migration and histiotypic follicle regeneration are promoted by epidermal growth factor in primary culture of thyroid follicles in collagen gel.

The effect of epidermal growth factor (EGF) on the morphology of porcine thyroid follicles cultured in collagen gel was studied by light and electron microscopy. Treatment with EGF (10 ng/ml) for 1-4 days induced a progressive migration of thyrocytes radiating from the mother follicles into the collagen lattice. Migrating cells were often connected with junctional complexes, thus forming small follicles containing microlumina, in which the limiting portion of the plasma membrane expressed microvilli. Autoradiography of [3H]thymidine incorporation in EGF-treated cultures showed that more than 80% of nuclei in mother follicles and migrating cells were labeled after 4 days. TSH (2 mU/ml) given simultaneously with EGF did not influence the effect of EGF on multiplication, migration, and formation of microfollicles. TSH given for 12 h after 4 days of exposure to EGF was able to induce luminal dilation of mother follicles, but caused no change in the appearance of microlumina. It is concluded that thyrocytes in collagen gel retain epithelial characteristics during prolonged stimulation with EGF, in spite of a migrating response. The whole sequence of events, starting with the intact follicle, i.e. multiplication, migration of thyrocytes, and formation of new follicles, could, thus, be visualized to occur in response to a single mitogen, EGF. EGF might be involved in the generation of new follicles in the intact gland.

Animals↗
PubMed1990

Environmental influence on behaviour and nerve growth factor in the brain.

The influence of the environment on the endogenous levels of nerve growth factor (NGF) in the cortex, hippocampus and septum was examined in adult (82 days old) and juvenile (51 days old) rats. Animals were reared/housed for 30 days in an enriched, standard or isolated environment prior to analysis. In addition, another group of rats were given behavioural tests (4 days) after differential rearing/housing before measurements of NGF. We found complex variations in the level of NGF both in juvenile and adult hippocampus after differential environmental rearing/housing. Rearing/housing in an enriched environment improved performance in the Morris maze and decreased spontaneous motor activity. Exposure to behavioural tests caused alterations in adult hippocampus and septum NGF levels. The results show that testing in a novel environment causes small but significant changes in the hippocampal and septal NGF levels depending upon the environmental history of the animal. In view of the purported involvement of the septohippocampal pathway and NGF in the pathophysiology of Alzheimer's disease, our finding suggests that lack of adequate environmental stimulation might be of importance in age-related behavioural and neurochemical deficits.

Analysis of Variance↗
PubMed1990

[Nerve growth factor as a therapeutic agent: transplantation of brain tissue as a possible treatment of neurodegenerative disorders].

An account of experiments focused on the treatment of neurodegenerative disease by means of cell grafts, in which genetically modified cells that release abundant nerve growth factor are described, and their transplantation to the rat brain reported. The cells can survive in the rat brain and exert potent effects on cholinergic neurons both in the host cortex, basal forebrain and striatum, and in tissue grafts.

Animals↗