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Biomedical subjects

L Olson

Publications and source records attributed to L Olson.

At least 199 records · Page 11Linked to original sources
PubMed1993

Glial cell line-derived neurotrophic factor is expressed in the developing but not adult striatum and stimulates developing dopamine neurons in vivo.

The potential role of glial cell line-derived neurotrophic factor (GDNF) as a trophic molecule for midbrain dopamine neurons was examined using two different approaches: in situ hybridization and intraocular transplantation. The presence of mRNA for GDNF was noted in striatal and ventral limbic dopaminergic target areas in the developing (E20-P7) rat, but not the adult rat. Signals were also found in nondopaminergic areas during maturation, such as the cerebellar anlage, spinal cord, and thalamus. Lesions of the nigrostriatal pathway in neonatal or adult rats, using 6-hydroxydopamine injected into the medial forebrain bundle, did not elicit upregulation of mRNA for GDNF. Grafts of fetal ventral mesencephalon in the anterior eye chamber were exposed to repeated injections of GDNF, which elicited a marked and dose-dependent increase in transplant volume. A low (0.1 microgram/eye) and high (1 microgram/eye) dose of GDNF both led to a somewhat larger mean area of dopamine fiber outgrowth into host irides. In the transplants, cell counts of tyrosine hydroxylase (TH)-immunoreactive neurons revealed a doubling of cell numbers in the low-dose group and about four times as many cells in the high-GDNF-dose group compared to controls. Moreover, the density of TH-immunoreactive nerve fibers was markedly and significantly higher in transplants treated with the high GDNF dose. Since the volumes of these transplants were also larger, the total amount of both TH-positive cells and TH-positive nerve fibers was many-fold greater in the high-GDNF group than that in the controls. Taken together, these data support the concept that GDNF functions as a dopaminotrophic factor in vivo.

Aging↗
PubMed1993

Reparative strategies in the brain: treatment strategies based on trophic factors and cell transfer techniques.

Three reparative strategies based on transfer of genes, molecules, or cells to the central nervous system are reviewed. When neurons are already lost, they can sometimes be replaced by transfer to the target area of neurons or other cells compensating for the lost functions. This technique is undergoing clinical trials in Parkinson's disease. Before neurons have died, it may be possible to prevent "stressed" neurons from dying, and stimulate nerve terminal ramifications from remaining neurons using treatment with neurotrophic factors. Such approaches, with an emphasis on the NGF family of neurotrophins and their receptors, are reviewed. Finally, advances of molecular biology techniques suggest that it should be possible to transfer genes directly into non-dividing cells of the central nervous system. The three different approaches all aim at long-lasting counteractive and reparative measures in the central nervous system. It is predicted that they have general applicability, and may become important not only in neurodegenerative diseases, but also in other common afflictions of the nervous system such as ischaemia, stroke and injury.

Adrenal Medulla↗
PubMed1993

Nerve growth factor-induced excitation of selected neurons in the brain which is blocked by a low-affinity receptor antibody.

We have investigated the electrophysiological effects of nerve growth factor (NGF) on single-neuron activity in central nervous system (CNS) grafts of septum, spinal cord, and hippocampus in oculo. NGF was found to have slow-onset, long-lasting excitatory effects on the spontaneous firing of neurons in septal grafts, while no such effects were found in neurons of either hippocampal or spinal cord grafts. Pretreatment with an antibody against the p75 low-affinity NGF receptor blocked the NGF-induced excitations. A second NGF application caused much stronger excitatory responses in sensitive neurons. Our data suggest that forebrain cholinergic neurons may be selectively sensitive to NGF also at the neurophysiological level, responding by excitations, and that NGF upregulates these responses within less than an hour.

Action Potentials↗
PubMed1993

A one-step immunohistochemical method for detection of blood-brain barrier disturbances for immunoglobulins in lesioned rat brain with special reference to false-positive labelling in immunohistochemistry.

Disturbances of the blood-brain barrier (BBB) following brain lesions lead to extravasation of serum proteins that can be detected by immunohistochemical methods in tissue sections. Here, extravasated immunoglobulins were visualized by a 1-step technique using rabbit anti-rat immunoglobulins conjugated to horseradish peroxidase (HRP). This method is associated with a lower background staining than the conventional 3-step peroxidase-antiperoxidase (PAP) technique using rabbit antibodies against rat whole-serum proteins or immunoglobulins (IgG). Further tests using a direct conjugate of rabbit anti-rat immunoglobulins to fluorescein isothiocyanate (FITC) showed usefulness of the approach for fluorescence microscopy. Additional experiments showed that antibodies directed against mouse immunoglobulins as used for detection of mouse monoclonal antibodies can cross-react with extravasated rat immunoglobulins. Therefore, immunohistochemical studies on lesioned rat brain should routinely include a visualization of areas containing extravasated serum proteins including immunoglobulins.

Animals↗
PubMed1993

Fast and widespread increase of basic fibroblast growth factor messenger RNA and protein in the forebrain after kainate-induced seizures.

Basic fibroblast growth factor promotes the survival and outgrowth of neurons and protects neurons from glutamate mediated excitotoxicity. The present study investigates the effects of kainate-induced epileptic seizures on the cellular expression of basic fibroblast growth factor messenger RNA and protein. Seizures were induced by injection of 12 mg/kg kainic acid. Rats were killed 3 h, 6 h, and 24 h after injection of the drug and analysed by radioactive and non-radioactive in situ hybridization as well as immunohistochemistry for glial fibrillary acidic protein and basic fibroblast growth factor. Radioactive in situ hybridization revealed a fast (6 h), strong (300-400% of control) and widespread increase of basic fibroblast growth factor messenger RNA after kainate-induced seizures. Non-radioactive in situ hybridization using digoxigenin-labeled riboprobes combined with glial fibrillary acidic protein immunohistochemistry showed that basic fibroblast growth factor messenger RNA was markedly increased in astroglial cells throughout the brain. Immunohistochemistry for basic fibroblast growth factor revealed labeling of nuclei in astrocytes in many forebrain areas and in neurons in area CA2 and fasciola cinereum. Kainate markedly increased basic fibroblast growth factor-like immunoreactivity in nuclei of astrocytes in several forebrain areas. This effect peaked 24 h after injection. It is concluded that basic fibroblast growth factor may play a neuroprotective role in kainate mediated excitotoxicity as seen from a massive and widespread astroglial increase in basic fibroblast growth factor messenger RNA and -like immunoreactivity. These effects may, to a large degree, be mediated through the excessive release of endogenous glutamate, induced by the epileptic seizures, leading to activation of glutamate receptors on astroglial cells through volume transmission, i.e. via diffusion of electrochemical signals in the extracellular fluid pathways.

Animals↗
PubMed1993

Differential effects of platelet-derived growth factor isoforms on dopamine neurons in vivo: -BB supports cell survival, -AA enhances fiber formation.

Trophic effects of platelet-derived growth factor -AA and -BB on developing (embryonic day 14) ventral mesencephalon were studied using the in vivo model of intraocular transplantation to sympathetically denervated host eyes. This model enabled studies of survival and growth of grafted brain tissue, dopaminergic fiber outgrowth from the grafts onto the host iris as well as morphological effects of platelet-derived growth factor on grafted tissue using markers for tyrosine hydroxylase and glial fibrillary acid protein. Growth of grafts was followed by repeated observations directly through the cornea of the host using a stereomicroscope. This revealed that there was no apparent effect on volume increase of mesencephalic grafts after treatments with either platelet-derived growth factor-AA (100 ng/ml buffer), platelet-derived growth factor-BB (100 ng/ml buffer) or vehicle solution (high salt buffer) alone. Growth factor treatments were administered immediately prior to grafting by incubating the grafts in the appropriate factor as well as on days 5, 10 and 15 postgrafting by administration of 5-microliters intraocular injections of similar solutions as used for incubation. Platelet-derived growth factor-AA significantly enhanced dopaminergic fiber outgrowth from mesencephalic grafts when compared to both platelet-derived growth factor-BB and controls, without an accompanying rise in the number of tyrosine hydroxylase-positive neurons. In contrast, a significantly greater number of tyrosine hydroxylase-positive neurons was seen in grafts treated with platelet-derived growth factor-BB but without an accompanying increase in outgrowth of dopamine-containing fibers.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

In vivo electrochemical measurements and electrophysiological studies of rat striatum following neonatal 6-hydroxydopamine treatment.

The effects of neonatal treatment (one day after birth) with the neurotoxin, 6-hydroxydopamine (75 micrograms/10 microliters intracisternal), were studied in the striatum of normal adult and treated Sprague-Dawley rats. Measurements of monoamine levels in the dorsal striatum and nucleus accumbens, by high-performance liquid chromatography coupled with electrochemical detection, showed that neonatal 6-hydroxydopamine treatment produced a permanent and massive destruction of striatal dopamine. The effects were more pronounced in the dorsal striatum than in the nucleus accumbens. In addition, serotonin levels were elevated in the rat striatum as a consequence of the neonatal treatment. Rapid chronoamperometric recordings of K(+)-evoked monoamine overflow using Nafion-coated recording electrodes were investigated in both the dorsal and ventral striatum of control and neonatally lesioned rats. The potassium-evoked responses recorded from the dorsal striatum of the 6-hydroxydopamine-treated rats were significantly reduced in amplitude as compared to controls. In addition, the reduction/oxidation current ratios of the responses were more serotonin-like, in contrast to the dopamine-like current ratios measured in the striatum of untreated animals. In ventral striatum, the amplitudes of the K(+)-evoked responses were not significantly reduced versus control. However, the K(+)-evoked signals were more serotonin-like in their electrochemical characteristics as compared to controls. In addition to the release studies, extracellular single-unit electrophysiological recordings were performed in normal and neonatally 6-hydroxydopamine-treated rats. The spontaneous discharge rate of striatal neurons in the neonatally 6-hydroxydopamine-treated rats was similar to that of control rats. This is in contrast to dopamine lesions in adult animals, where a marked elevation of the discharge rate is observed. Local applications of dopamine and serotonin into the striatum of neonatally 6-hydroxydopamine-treated rats elicited excitations of striatal cells rather than the normal inhibitory effects seen in control animals. Taken together, these data suggest that loss of striatal dopamine terminals at birth leads to both pre- and postsynaptic alterations in monoamine pathways.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1993

Regulation of brain-derived neurotrophic factor messenger RNA and protein at the cellular level in pentylenetetrazol-induced epileptic seizures.

We have examined the effects of pentylenetetrazol-induced epileptic seizures on brain-derived neurotrophic factor messenger RNA and protein and on the messenger RNA of its receptor in the rat. Pentylenetrazol, which acts at the picrotoxin recognition site of the GABAA receptor, was injected intraperitoneally and induced seizures by decreasing the inhibitory GABAergic activity. The effects of a single acute convulsive dose (50 mg/kg) of pentylenetetrazol were analysed at different time points by in situ hybridization or immunohistochemistry. Kindling was induced by daily subconvulsive injections (30 mg/kg) of pentylenetetrazol. At different time points during the kindling process, the messenger RNAs of brain-derived neurotrophic factor and trkB and the protein levels of brain-derived neurotrophic factor were analysed. We showed that brain-derived neurotrophic factor messenger RNA dramatically increased in neurons of the granule cell layer, piriform cortex and amygdala 3 h but not 6 h after an acute high dose of pentylenetetrazol, while brain-derived neurotrophic factor-like immunoreactivity was decreased in the granule cell layer and neurons of the hilus. The trkB messenger RNA was similarly increased 3 h and 6 h after the injection and returned to control levels after 24 h. The first change during the kindling development was seen after the first severe seizure: brain-derived neurotrophic factor messenger RNA was markedly increased in the piriform cortex and amygdala but not in the hippocampus. In fully kindled rats, which had several severe seizures, brain-derived neurotrophic factor messenger RNA and trkB messenger RNA were unaffected 3 h and 24 h after the last pentylenetetrazol injection. However, brain-derived neurotrophic factor-like immunoreactivity was markedly increased in the hippocampal formation 3 h, 24 h and three days after the last pentylenetetrazol injection, and still increased after 10 days. These results suggest that brain-derived neurotrophic factor may be involved in protection mechanisms after damage during seizures and in sprouting responses. The piriform cortex/amygdala seems to be an area of origin for the kindling development.

Amino Acid Sequence↗
PubMed1993

Development of monoamine systems after neonatal anoxia in rats.

Neurochemical and morphological effects of neonatal anoxia on monoamine systems were studied after 100% N2 exposure for 25 min at 30 h postnatally (postnatal day 2-P2). At 20 min after anoxia, reductions of tissue levels of cerebellar noradrenaline (NA) and striatal dopamine (DA) and metabolites were seen, while 5-hydroxyindoleacetic acid (5-HIAA) was increased in cortex and cerebellum. At P7, NA increased in cerebellum, while serotonin (5-HT) and 5-HIAA decreased in cortex and cerebellum. At P21, increased hippocampal NA and striatal homovanillic acid (HVA) were found, while striatal 5-HT decreased and 5-HIAA increased in striatum and hippocampus. At P60, striatal 3,4-dihydroxyphenylacetic acid (DOPAC) and 5-HIAA levels were found to be enhanced. No effects were seen on 5-HT, tyrosine hydroxylase, or DARPP-32 immunostaining in cortex, hippocampus, and striatum. Thus, the neonatal anoxia induced both acute and persistent neurochemical abnormalities in monoamine systems that were not accompanied by morphological changes detectable with the methods used. The monoamine alterations found could be critically connected to the behavioral disturbances observed in rats after neonatal anoxia. The findings may also be of relevance to dysfunctions seen in humans after perinatal oxygen deficiency, e.g., the attention deficit hyperactivity disorder syndrome.

Animals↗
PubMed1993

Nerve growth factor increases the size of intracortical cholinergic transplants.

The effects of continuous intracortical mouse Nerve Growth Factor on fetal rat basal forebrain transplants in denervated adult rat neocortex were investigated. Enzyme-linked immunoassay (ELISA) was used to measure the time course of endogenous NGF protein production in neocortex, hippocampus, and basal forebrain in a cohort of animals receiving unilateral ibotenic acid (IBO) lesions of the nucleus basalis magnocellularis (nBM). A second cohort of IBO-nBM lesioned animals received transplants of fetal basal forebrain followed by two to four weeks of continuous NGF or cytochrome-C infusion into the ipsilateral frontoparietal neocortex. To study the effects of abnormally high NGF doses on transplanted and host tissue, the cumulative dose of intracortical NGF was on the order of micrograms, compared with maximum picogram levels of neocortical NGF produced following IBO-nBM lesions. A four-fold increase in transplant size, and greater cell and fiber densities were observed in NGF-treated compared with NGF-untreated transplants. No adverse histological effects of long-term, high-dose NGF treatment were observed on transplanted basal forebrain or host neocortical tissue. These data indicate that cholinergic-rich mammalian brain tissue and intrinsic host tissue can be stimulated by high doses exogenous NGF without obvious deleterious effects.

Acetylcholinesterase↗
PubMed1993

Brain-derived neurotrophic factor (BDNF) peptide antibodies: characterization using a Vaccinia virus expression system.

We describe and characterize a series of polyclonal antibodies, generated against amino acid sequences unique to various regions within pro- and mature brain-derived neurotrophic factor (BDNF), a member of the highly conserved nerve growth factor (NGF) family of neurotrophins. Synthetic peptides were coupled to carrier proteins in the presence of glutaraldehyde to restrict the host animals' immune response to epitopes that are compatible with aldehyde fixation. Initial screenings of the reactivity of the antisera were made on brain sections processed for immunohistochemistry after peptide injections into brain parenchyma. As a means of further characterizing these peptide antisera, we have evaluated the reactivity and specificity of the peptide antibodies in BHK cells expressing recombinant pro- and mature BDNF protein from a T7 RNA polymerase-driven Vaccinia virus system. Several of the antibodies strongly stained components of cells transfected with the BDNF gene but did not label wild-type cells nor cells containing only the expression vector. It has also been possible to detect differential compartmentalization of the BDNF protein at various stages of processing in the BHK cells, as well as in situ in cryostat sections of brain tissue, with antisera to the pro- and mature protein. We conclude that several of our antisera recognize not only the specific peptide immunogens but also what appears to be the corresponding protein native to neurons.

Amino Acid Sequence↗
PubMed1993

Detection of nerve growth factor mRNA in rodent salivary glands with digoxigenin- and 33P-labeled oligonucleotides: effects of castration and sympathectomy.

Nerve growth factor (NGF) is a protein highly expressed in the male mouse submandibular gland. We have applied a non-radioactive in situ hybridization method using digoxigenin-labeled NGF oligonucleotides, and have found the highest amounts of NGF mRNA in the secretory striated ducts of the male mouse submandibular gland. Scattered strongly positive cells were found in male mouse sublingual glands. Weakly labeled cells were seen in female mouse and in male rat submandibular gland striated duct cells. Using 33P as an alternative to 32P and 35S, we demonstrated a 1.3 KB NGF mRNA in salivary glands of male mice by Northern blot hybridization. Using 33P we detected NGF mRNA in male mouse submandibular glands by in situ hybridization but with a signal that, compared with the non-radioactive method, had a very low resolution. Castration of male mice almost abolished both the 1.3 KB NGF mRNA seen with Northern blots and the NGF mRNA labeling in submandibular glands 4 weeks after the operation, whereas levels were increased 6 hr and 2 days after sympathectomy. We conclude that hybridization with digoxigenin-labeled NGF oligonucleotides is a good tool to study the expression and regulation of NGF mRNA in male mouse submandibular glands.

Animals↗