Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.14.16.2 (tyrosine hydroxylase)
 14,760 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Neural transplantation in experimental Parkinsonism has so far focused on the ectopic placement of fetal ventral mesencephalic (VM) neurons into the dopamine-denervated caudate-putamen. VM grafts are effective in restoring dopamine neurotransmission in the grafted caudate-putamen and in partial amelioration of behavioral deficits. Recent pharmacological and physiological data have provided strong evidence that dopamine released from dendrites of the substantia nigra pars compacta (SNc) neurons within the pars reticulata (SNr) plays an important role in the regulation of the basal ganglia output pathways. Using a novel microtransplantation approach, multiple small cell suspension grafts (250 nl) derived from the VM of E14 rat embryos were implanted into the SNr of unilaterally 6-hydroxydopamine-lesioned rats. Behavioral changes in drug-induced rotation asymmetry were monitored for up to 14 weeks postgrafting, followed by a quantitative assessment and correlation of tyrosine hydroxylase (TH)-positive cell survival. The reduction in rotational asymmetry caused by the intranigral VM grafts was 64% for SKF 38393 (D1 agonist), 54% for apomorphine (mixed D1 and D2 agonist), and 67% for quinpirole (D2 agonist) when compared to a control spinal cord graft group. By contrast, amphetamine-induced rotation was completely unaffected. The correlation between number of TH-positive cells and behavioral compensation was highest for the D1 agonist (R = -0.729), though clear-cut also for the mixed D1/D2 agonist apomorphine (R = -0.664) and the D2 agonist quinpirole (R = -0.642). Favorable morphological features of the VM micrografts included extensive migration of the dopaminergic neurons into the host SNr and the formation of dense patches of dendrite-like TH-positive terminal networks within the SNr. The results demonstrate a novel pattern of behavioral recovery induced by intranigral VM transplants in the rat Parkinson model. This may have important implications for the understanding of how the nigrostriatal dopamine system influences motor control in the basal ganglia as well as for the development of optimal transplantation strategies in Parkinson's disease.
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PMID:Intranigral fetal dopamine grafts induce behavioral compensation in the rat Parkinson model. 791 16

We have established a primary neuronal culture of the embryonic day 14 rat, ventral mesencephalic region, centered on the A8, A9, and A10 dopaminergic nuclei (approximately 1.0 mm3 of tissue). At 16 hr after plating on a substrate of poly-D-lysine, in a serum-free or serum-supplemented growth medium, using a microisland culturing method, 95% of the cells stained positive for neuron-specific enolase, 20% for tyrosine hydroxylase, and < 5% for vimentin. When the growth medium was supplemented with 10% fetal calf serum, the percentage of tyrosine hydroxylase-positive neurons increased significantly (p < 0.05) at the 7th and 10th days in culture, compared with the percentage present at 16 hr after plating. When cultured in a serum-free growth medium, the percentage of tyrosine hydroxylase-positive neurons decreased to < 5% and to 0% by the 5th and 7th days, respectively, while the percentage of GABA-IR neurons increased. The addition of serum to the serum-free culture rescued dopaminergic neurons from death induced by serum deprivation. The effect of serum was dependent both on the time of addition after plating, and on the percentage added. When the cells were plated in a serum-free medium, on a confluent, type 1 astrocyte monolayer, prepared from the ventral mesencephalon of the embryonic day 16 rat, the survival of dopaminergic neurons increased significantly (p < 0.01) at DIV5, versus survival after plating on poly-D-lysine. Conditioned medium prepared from the same mesencephalic type 1 astrocyte monolayer also rescued dopaminergic neurons from death. The rescue mediated by the astrocyte monolayer or the conditioned medium was not inhibited by the mitotic inhibitor cytosine arabino furanoside (1.0 microM). Type 1 astrocyte monolayers and conditioned media prepared from the striatum and cerebral cortex of the embryonic day 16 rat had weaker trophic effects than those mediated by mesencephalic glia. We conclude that serum deprivation causes the selective death of dopaminergic neurons in a primary culture of the rat E14 ventral mesencephalon. Type 1 astrocytes or the conditioned medium from type 1 astrocytes can rescue dopaminergic neurons from death induced by serum deprivation.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Mesencephalic type 1 astrocytes rescue dopaminergic neurons from death induced by serum deprivation. 791 55

Mature sympathetic neurons contain one or more neuropeptides in addition to a classical neurotransmitter. We compared the development of two peptides, neuropeptide Y (NPY) and vasoactive intestinal peptide (VIP), in rat superior cervical (SCG) and stellate ganglia. NPY immunoreactivity (-IR) was first detected at embryonic day (E) 12.5. It was of similar immunofluorescence intensity in almost all tyrosine hydroxylase (TH)-IR cells. In contrast, VIP-IR, of variable fluorescence intensity, appeared at E14.5 in a subset of TH-IR cells in the stellate ganglion but not in SCG. Both peptides were present in bromodeoxyuridine-labeled neuronal precursors as well as neurons. The intensity of NPY immunofluorescence increased until E16.5. Subsequently, while it continued to increase in some neurons, the intensity decreased in others so that at birth approximately 55% of SCG and stellate neurons were NPY-IR. Developmental changes in NPY concentration, determined by radioimmunoassay, were similar in both ganglia, increasing between E14.5 and E16.5 and then decreasing 60% between E16.5 and birth. VIP expression differed from that of NPY. The proportion of VIP-IR cells began to decrease the day after VIP-IR was first detected. Although VIP-IR was present in one-third of E14.5 TH-IR stellate cells, at birth only 2% were VIP-IR. VIP-IR, measured by radioimmunoassay, was uniformly severalfold more concentrated in the stellate than SCG, and its concentration decreased throughout embryonic development, 40% between E14.5 and E16.5 and 95% by birth. In situ hybridization revealed detectable mRNA for both NPY and VIP at E14.5 in stellate ganglion and mRNA for NPY, but not VIP, in SCG. Initially, ganglionic neuropeptide mRNA appeared uniformly distributed but became heterogeneous. Our data indicate that features of the diverse peptidergic phenotypes expressed by sympathetic neurons are present when peptides are first detected while others arise subsequently. The final acquisition of peptidergic phenotypic diversity is complex, entailing both early induction in many cells and subsequent restriction to specific subpopulations.
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PMID:The appearance of NPY and VIP in sympathetic neuroblasts and subsequent alterations in their expression. 802 92

There is a delay from the time when amacrine cells are generated to the time when the dopaminergic phenotype is first expressed, in the chick retina. In order to determine the birthdate of amacrine cells expressing the tyrosine hydroxylase (TH) phenotype, we combined autoradiography of [3H]thymidine incorporated into dividing cells with the immunocytochemical method for TH in mature retinas. We also investigated the morphogenesis and the topographical distribution of dopaminergic amacrine cells using radial and horizontal sections of the chick retina. Although TH immunoreactivity was first detected at E12, the morphological pattern of TH-immunoreactive (TH-IR) amacrine cells started to be defined at E16, with an increasing arborization complexity until hatching. The topographical distribution of dopaminergic cells revealed that TH-IR neurons were predominantly concentrated in the dorsal retina of E13 and E14 embryos. At E18 and PH2 the distribution of dopaminergic cells was uniform throughout the retina. Autoradiography of [3H]thymidine incorporated association with TH immunocytochemistry showed that dopaminergic amacrine cells are generated during a discrete period (E3 through E7) of amacrinogenesis that occurs from E3 to E9. Therefore, a delay of days between histogenesis of dopaminergic amacrine cells and their differentiation is observed.
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PMID:Histogenesis and topographical distribution of tyrosine hydroxylase immunoreactive amacrine cells in the developing chick retina. 809 72

Axonal growth from cortically placed fetal neural transplants to subcortical targets in adult hosts has been difficult to demonstrate and is assumed to be minimal; however, experiments using xenogeneic neural grafts of either human or porcine fetal tissues into the adult rat striatum, mesencephalon, and spinal cord have demonstrated the capability for long-distance axonal growth. This study reports similar results for porcine cortical xenografts placed in the adult rat cerebral cortex and compares these findings with results from cortical allografts. Adult rats that previously received unilateral cortical lesions by an oblique intracortical stereotaxic injection of quinolinic acid, were implanted with suspensions of either E14 rat or E38 xenogeneic porcine fetal cortical cells. Xenografted rats were immunosuppressed by cyclosporin A. The corpus callosum was intact in all cases and grafts were confined to the overlying cortex. After a 31-34 wk posttransplant survival period, acetylcholinesterase (AChE) staining and tyrosine hydroxylase (TH) immunocytochemistry revealed that both allo- and xenografts received host afferents. Retrograde tracer injections into the ipsilateral striatum and cerebral peduncle in allografted animals failed to show any axonal growth to either subcortical target. Using a porcine-specific axonal marker in xenografted animals, we found graft axons in white matter tracts (corpus callosum, internal capsule, cingulum bundle, and medial forebrain bundle) and within the caudate-putamen and both the ipsilateral and contralateral cerebral cortex. Graft axons were not found in the thalamus, midbrain, or spinal cord. In addition, using an antibody to porcine glial fibers, we observed more extensive graft glial fiber growth into the same host fiber tracts, as far caudally as the cerebral peduncle, but not into gray matter targets outside the cortex. These results demonstrate that porcine cortical xenograft axons and glia can extend from lesioned cerebral cortex to cortical and subcortical targets in the adult rat brain. These findings are relevant for prospects of repairing cortical damage and obtaining functional recovery.
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PMID:Extensive axonal and glial fiber growth from fetal porcine cortical xenografts in the adult rat cortex. 852 Aug 35

In order to evaluate the neurotrophic potential that interleukins may have for nigrostriatal dopaminergic neurons, we have applied the interleukins 1 alpha, 1 beta, and 2 through 12 to cultures of E14 rat midbrain floor cells enriched for dopaminergic neurons. IL-6 and -7 were the only interleukins that modestly (130%, as compared to controls, 100%) promoted survival of dopaminergic neurons visualized by their immunoreactivity for tyrosine hydroxylase over an 8-day culture period. The effect was not mediated by astroglial cells. We conclude that most interleukins per se may not act as neurotrophic factors for dopaminergic neurons, although several of them occur in the embryonic and adult CNS.
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PMID:Screening of interleukins for survival-promoting effects on cultured mesencephalic dopaminergic neurons from embryonic rat brain. 857 89

Cryopreservation may allow long-term storage of fetal ventral mesencephalon (VM) for transplantation in patients suffering from Parkinson's disease (PD). We investigated whether the polymer methylcellulose protects fetal rat VM during cryopreservation in liquid nitrogen and improves survival and function of this tissue as intrastriatal suspension grafts in the 6-hydroxydopamine (6-OHDA) rat model. VM tissue fragments (E14-E15) were either immediately dissociated and grafted as a cell suspension (FRESH) or cryopreserved under controlled conditions for 7 days in a conventional cryoprotective medium (CRYO) or a medium containing 0.1% methylcellulose (mCRYO) and then dissociated and grafted. Rats from the cryo-groups showed only limited behavioral compensation in contrast to complete compensation observed in rats from the FRESH group. Cryopreservation of fetal rat VM decreased the viability of cell suspensions in vitro to about 70%, survival of grafted tyrosine hydroxylase-immunoreactive (TH-IR) neurons to 11% and 20%, and transplant volume to 8% and 17% (mCRYO and CRYO, respectively, compared to FRESH). The addition of 0.1% methylcellulose to tissue fragments during freezing did neither improve in vitro viability nor survival of TH-IR neurons nor behavioral compensation when compared to the control CRYO group. These results suggest that methylcellulose failed to improve survival of cryopreserved dopaminergic ventral mesencephalic neurons.
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PMID:Methylcellulose during cryopreservation of ventral mesencephalic tissue fragments fails to improve survival and function of cell suspension grafts. 869 78

Our previous work has shown that the functional efficacy of nigral tissue transplants into dopamine (DA)-depleted rats is increased when embryonic striatal tissue is included (Costantini et al.: Exp Neurol 127:219-231, 1994). To examine further the influence of striatal patch neurons in this regard, we employed co-cultures of dissociated nigral and striatal cells taken from embryos at different ages. Striatal patch neurons were labeled by in vivo bromodeoxyuridine (BrdU) on embryonic day (E)13 and E14. The percentage of striatal cells that were BrdU labeled was greater in E14 striatal cultures (51.0%) compared with E16 (33.9%) and E20 (3.5%) striatal cultures at 1 day in vitro (DIV). The proportion of surviving BrdU-labeled cells in striatal cultures decreased over time. The inclusion of E14 nigral cells attenuated this decline. Similarly, the number of dopaminergic [tyrosine hydroxylase (TH)-immunoreactive] neurons in pure nigral cultures decreased with time in vitro (8.2% at 1 DIV to 3.5% at 12-15 DIV). The inclusion of E14 striatal tissue increased the number of TH-immunoreactive neurons at all time points, whereas E16 and E20 striatal tissue was somewhat less effective. Thus, the survival of nigral DA neurons and striatal patch neurons in culture appears to be enhanced in the presence of the other. These reciprocal influences on neuronal survival may be relevant to the in vivo development of the nigrostriatal system as well as the enhanced function of cells in co-transplants.
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PMID:Reciprocal influences of nigral cells and striatal patch neurons in dissociated co-cultures. 879 45

Our previous studies have shown that primary mesencephalic glia secrete factors that promote dopaminergic cell survival and differentiation in vitro. To obtain enough starting material to identify the neurotrophic activity, embryonic day (E)14.5 rat mesencephalic glia were stimulated with acidic fibroblast growth factor to increase number of cells. These cells were replated in the absence of neurons and immortalized by transfection with the SV 40 large T-antigen. Clonal cell lines were established and characterized for immunoreactivity (IR) to various glial and non-glial markers. Media conditioned by these cell lines were tested for survival-promoting effects on dopaminergic neurons in serum-free cultures of the dissociated E14.5 rat mesencephalon. All cell lines expressed IR for the astrocytic marker, GFAP, the oligodendroglial marker, CNP, and for A2B5, a marker for O-2A progenitor cells, but were negative for the neuronal marker, microtubule associated protein-2, and the fibroblast marker, fibronectin. Moreover, treatment of serum-free cultures of the dissociated E14.5 mesencephalon with glial cell line-CM conditioned medium (CM) delayed dopaminergic cell death in a dose-dependent manner, resulting in a maximal twofold to sixfold increase in the number of surviving tyrosine hydroxylase-IR neurons at various days in vitro. This increase in dopaminergic cell survival was not mimicked by GDNF, BDNF or NT-3 within the initial 3 days of cultivation. Moreover, initial biochemical characterization demonstrated that the neurotrophic activity is restricted to the high MW fraction of >50 kD of glial cell line-CM. Since the apparent MW of this factor exceeds the size of most known growth factors, it may represent a novel dopaminergic neurotrophic factor.
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PMID:Evidence for a novel neurotrophic factor for dopaminergic neurons secreted from mesencephalic glial cell lines. 883 92

The search for specific neurotrophic factors that will eventually be used to reduce or arrest the rate of degeneration of dopaminergic neurons in Parkinson's disease is being pursued by first testing the ability of putative compounds to increase the survival of dopaminergic neurons in primary cultures of the fetal, ventral mesencephalon. This research has intensified in recent years. The experimental procedures used by different laboratories in these studies differ widely, and meaningful comparisons of the results obtained are accordingly difficult to make. Some important experimental variables include the age of the fetal tissue used; the dissection technique used to isolate the ventral mesencephalon; the percentage of dopaminergic neurons present in the culture initially; handling of the tissue during dissection; the technique used to disperse the cells; the use of serum; the technique of plating the cells; the attachment factors used; detachment and loss of cells during the staining procedure; the age of the cultures at the time of analysis; the uneven distribution of cells at the time of analysis and the use of imaging techniques in the analysis. We show that when the E14 rat embryo is used, it is possible to consistently obtain a culture with 20% of tyrosine hydroxylase-positive neurons. Neither the plating density in the range of 7.8 x 10(3) to 1.25 x 10(5) cells/cm2, nor the percentage of serum in the growth medium affected the percentage of cells that expressed TH initially, at 4 or 12 h after plating. When the cells were plated as 25 microliters droplets, called microislands (area approximately 12.5 mm2), and allowed to attach before additional growth medium was added, cell density remained uniform at the center of the microisland for the duration of the culture. Restriction of the analysis of cell survival to the center of the microisland therefore helped to decrease the variability in counting that could occur when cells are dispersed over a larger area. In contrast, in an 8-well chamber slide or 35 mm petri dish, in which the whole area is plated, cell density was consistently higher at the edge (edge effect), versus the centre, by a factor of about three. The use of microisland cultures also has the additional benefit of increasing by a factor of about five the number of individual cultures that can be set up per liter, and a proportionate reduction in the number of animals used per experiment. When the percentage of serum in the growth medium was 0% always, or 10% for the first 12 h, and 0% thereafter, or 10% always, the number of TH-pos neurons per field (using a x 20 objective, column factor 1.25; area 320 microns2) after 5 days in culture (DIV5) was < 1,3-8 and 14-22, respectively. Under the same experimental conditions, the number of neurons (MAP2-positive) per field was 5-8, 18-30 and 45-65 (N = 10 in all cases), respectively. Serum deprivation therefore has a highly deleterious effect on neuronal survival in culture. We suggest that cultures that were exposed to serum at any stage of the experiment, should not be referred to as "serum-free', since even a brief exposure to serum exerts a protective effect on neurons, and especially on dopaminergic neurons. Instead, the percentage and kind of serum used, the exact usage, and the duration of exposure of the cells to serum should be stated. Finally, it is suggested that where possible, an imaging system with manual count and journaling capabilities be used in the analysis. The methods described are illustrated by dose-response curves of the neurotrophic effects of BDNF, NGF-beta and IL-6 versus percentage survival on dopaminergic neurons, when grown in serum-free medium throughout.
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PMID:Standardized methods to bioassay neurotrophic factors for dopaminergic neurons. 884 22


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