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

Tissues from products of conception were examined to determine the feasibility of obtaining viable neural tissue after suction abortion at 9-12 weeks of gestation. The ventral mesencephalon, a prototype region whose maturation can be monitored and which is a potential tissue for transplantation, was identified in 32 of 120 cases. The tissue was then screened for the presence of infectious agents, while being held at -196 degrees C in cryopreservative solutions. Three of 32 specimens were found to be contaminated by normal vaginal bacteria; all other viral, fungal, and mycoplasma testing was negative. Thawed brain fragments retained high viability after storage in liquid nitrogen and when grown in vitro exhibited neuronal morphology, tyrosine hydroxylase immunoreactivity, and dopamine production. We have demonstrated that human fetal brain tissue can be cryopreserved in a manner which not only retains viability but allows normal phenotypic differentiation after thawing.
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PMID:Cryopreservation of human brain tissue. 196 97

Sex steroids have been shown to influence the secretion of GH. There appears to be no good evidence of the effect of estradiol on the anterior pituitary, while the central site of estradiol action on the regulation of GH secretion is not known. The present investigation was carried out to determine whether some of the GH-releasing factor (GRF) neurons and somatostatin (SRIF) neurons in the hypothalamus and GH cells in the pituitary contain estradiol receptors. Colocalization of [3H]estradiol and antibodies to GRF or SRIF in brain and antibodies to GH in pituitary was studied to show interrelationships between estrogen target cells and peptidergic cells. Eight female Sprague-Dawley rats were ovariectomized, each rat was treated with colchicine, and 24-48 h later the animals were given an iv injection of [2,4,6,7,16,17-3H]estradiol (SA, 166 Ci/mM) at a dose of 0.5 micrograms/100 g BW. One hour after the injection, the rats were perfused with 4% paraformaldehyde in 0.1 M phosphate buffer (pH 7.4). The hypothalami from the perfused rats and the pituitaries from unperfused rats were frozen in isopentane precooled in liquid nitrogen (-190 C) and processed for autoradiography. The brain autoradiograms were immunostained for GRF, SRIF, and tyrosine hydroxylase [TH; an enzyme for the synthesis of dopamine (DA)], and the pituitary autoradiograms were immunostained for GH by the avidin-biotin peroxidase method. The majority of GRF-containing neurons were found in the arcuate nucleus, with some scattered cells in the lateral region of the ventromedial nucleus and the basal lateral hypothalamus. In the central portion of the arcuate nucleus, 20-30% of GRF-containing neurons showed nuclear concentration of [3H]estradiol. In the anterior portion of the hypothalamus, 10-15% of immunoreactive GRF-containing neurons were labeled with [3H]estradiol. In the lateral basal hypothalamus and the lateral region to the ventromedial nucleus, a few GRF neurons showed nuclear concentration of radioactivity. In contrast, a few SRIF cells in hypothalamic periventricular nucleus showed nuclear labeling with [3H]estradiol. Dual immunostaining with GRF and TH antibodies revealed that the estradiol-labeled GRF neurons did not contain TH immunoreactivity. In addition, 80-90% of GH cells in the anterior pituitary showed nuclear concentration of [3H]estradiol. The present studies demonstrate for the first time that certain populations of GRF neurons are targets for estradiol and indicate that estradiol acts directly on certain hypothalamic GRF neurons. The results suggest that estradiol may have a role in the regulation of GH secretion by modulating GRF release and acting directly on the somatotrophs.
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PMID:Evidence for direct action of estradiol on growth hormone-releasing factor (GRF) in rat hypothalamus: localization of [3H]estradiol in GRF neurons. 197 21

Dopamine neurons from the ventral midbrain and olfactory bulb of fetal and postnatal African green monkeys were frozen, stored in liquid nitrogen for intervals of 4-28 days, thawed, and tested for viability and growth following intracerebral transplantation into 3 adult monkeys. Well developed tyrosine hydroxylase positive neurons from all donors were seen in intracerebral transplants at 7-50 days after grafting. Freeze-stored neurons also were tested at various intervals by Trypan blue dye exclusion and development in tissue culture. More than 99% of the cryopreserved cells from both pre- and postnatal donors were viable by dye exclusion, and fetal tissue developed neuronal morphology in culture. This evidence further supports the fact that primate neurons survive intracerebral transplantation, even after cryopreservation and storage. The ability to store, transport and verify the transmitter phenotype of neurons offered by this approach is pertinent to possible therapeutic applications.
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PMID:Intracerebral grafting and culture of cryopreserved primate dopamine neurons. 343 33

Under conditions of cyclic AMP-dependent protein phosphorylation, tyrosine hydroxylase (EC 1.14.16.2; TH) is activated. Kinetic analysis reveals that, upon activation the affinity of the enzyme cofactor tetrahydrobiopterin, Vmax, as well as the Ki of its putative feedback inhibitor dopamine, are increased. Catecholic inhibitors of rat striatal TH have been assessed for the structural requirements that impart differential sensitivity to activated and control enzyme. By varying cofactor and inhibitor concentrations, Ki's were generated from Dixon plots. Structural analogs of dopamine in which the amino group was fixed in a cis conformation, i.e., 6,7-dihydroxytetrahydroisoquinolines, exhibit the same Ki for activated and nonactivated TH. However, 2-amino-6,7-dihydroxytetralin (ADTN), in which the nitrogen is extended in a fixed trans conformation of the beta-rotamer, exhibited a fourfold increase in Ki upon assaying tyrosine hydroxylase under phosphorylation conditions. By systematically increasing the hydrophobicity of the substituent at C-1 of 1-carboxy-6,7-dihydroxytetrahydroisoquinolines the inhibitory potency was enhanced, suggesting the presence of a hydrophobic region near the catecholic binding site. If the hydrophobic group was rigid as in the catechol estrogens, 2-hydroxy-estradiol and 2-hydroxyestrone, the Ki was relatively low (2 X 10(-5) M) despite the absence of an amino group. Upon activation the Ki increased fourfold. These studies provide insight into the topography of the catecholic binding site on TH and to attendant changes occurring upon activation. The results suggest that the catechol binding site includes both amino group-interacting and hydrophobic regions which are influenced by enzyme activation.
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PMID:Differential inhibition of activated tyrosine hydroxylase. 614 65

Although intracerebral grafting has become a new strategy for the treatment of Parkinson's disease, many problems related to the grafts remain. We focused on primary skin fibroblasts as grafts. Rat primary skin fibroblasts were transfected with a retrovirus vector containing the cDNA of human tyrosine hydroxylase (TH) (pLTHSNL) or cytomegalovirus promoter (pCTHSNL) as a foreign promoter, and catecholamine production and release by these genetically modified fibroblasts, were analyzed in vitro immunocytochemically and by high-performance liquid chromatography with electrochemical detection (HPLC-ECD). The cells were supplemented with biopterin (BH4; (6R)-L-erythro-tetrahydrobiopterin), a cofactor required for TH activity, and they produced and released L-DOPA into the culture medium. When exposed to the combination of a foreign promoter and BH4, L-DOPA production increased in a time-dependent manner, and was unaffected by the number of cell-passages or the duration of liquid-nitrogen freezing. This suggests that the foreign gene (THcDNA)-containing retrovirus vector had integrated into the chromosomal DNA of the target cells (fibroblasts). Primary fibroblasts can be easily obtained and cultured. Thus, genetically modified primary skin fibroblasts transfected with THcDNA using this retrovirus vector system appear to be a promising graft for transplantation and gene therapy of Parkinson's disease in the future.
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PMID:[L-DOPA-producing primary fibroblasts genetically modified with a retrovirus vector system]. 754 38

In vivo and in vitro activity of tyrosine hydroxylase (TH) was estimated in the catecholaminergic A2 cell group of the nucleus tractus solitarius (NTS) in rats exposed to normobaric hypoxia (10% O2 in nitrogen) for 2 h, 3, 7, 14 or 21 days. The A2 cell group was subdivided into two subgroups. In the caudal A2 subgroup located caudal to the calamus scriptorius, long-term but not acute hypoxia elicited an increase of in vivo tyrosine hydroxylation rate after 7 days of exposure (+60% above normoxic controls). The increase of in vivo TH activity was maintained at the same level at the end of hypoxic exposure. In vitro TH activity was increased transiently after 7 days of hypoxia (+92% above normoxic (controls). In thr rostral A2 subgroup, hypoxia elicited a significant increase of in vivo tyrosine hydroxylation at 7 days (+38%) but did not alter in vitro TH activity throughout the whole exposure. Hypoxia produced no detectable change in TH activity in other noradrenergic cell groups of the brain stem (locus coeruleus, A5) except for a transient inhibition of in vivo TH activity in A5 after 2 h. Immunocytochemical analyses confirmed that the catecholaminergic neurons in the caudal A2 area are not only of a noradrenergic nature. The neurons were located in the commissural subnucleus of the NTS. On the other hand, the rostral A2 area contains noradrenergic neurons intermingled with a small number of adrenergic cell bodies.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Delayed increase of tyrosine hydroxylation in the rat A2 medullary neurons upon long-term hypoxia. 779 97

Certain novel 1-phenyl-3-amino-1,2,3,4-tetrahydronaphthalenes (1-phenyl-3-aminotetralins, PATs) produced stimulation (ca. 30% above basal levels) of tyrosine hydroxylase (TH) activity at 0.1 microM concentrations in rodent brain tissue. This effect on TH was blocked by the putative sigma-receptor antagonist BMY-14802, suggesting involvement of a novel neuromodulatory sigma-like receptor. Within the new phenylaminotetralin series, a correlation was found between the ability to stimulate TH and the potency to compete for binding sites labeled by (+/-)-[3H]1-phenyl-3-(N,N-dimethylamino)-6-chloro-7-hydroxy-1,2,3,4- tetrahydronaphthalene ([3H](+/-)-4). trans-Catechol analogs had low affinity for [3H]4 sites, and although they inhibited TH activity, this effect was not blocked by known sigma or dopamine antagonists. Analogs with dihydroxy substituents (catechols), as well as nitrogen substituents larger than methyl, had little affinity for [3H]4 binding sites and did not significantly affect TH activity. The pharmacology of the [3H]4 binding site is unique from that of any known sigma or dopamine receptor, thus the effects appear to be mediated by a previously uncharacterized binding site/receptor. The site has stereoselectivity for the (1R,3S)-(-)-isomer of 1-phenyl-3-(N,N-dimethylamino)-1,2,3,4-tetrahydronaphthalene; this isomer is also more active at stimulating TH. Thus, certain 1-phenyl-3-amino-1,2,3,4-tetrahydronaphthalenes appear to be selective probes of a novel receptor type that mediates sigma-like neuromodulatory activity and may have pharmacotherapeutic utility in conditions in which modulation of dopamine function is important.
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PMID:Synthesis and pharmacological evaluation of 1-phenyl-3-amino-1,2,3,4-tetrahydronaphthalenes as ligands for a novel receptor with sigma-like neuromodulatory activity. 810 51

In previous studies, we have reported the long-term effects of several metabolites of 3,4-methylenedioxymethamphetamine (MDMA) on tryptophan hydroxylase (TPH) activity. In this study, the short-term effects of three metabolites of MDMA. 2,4,5-trihydroxyamphetamine (THA), 2,4,5-trihydroxymethamphetamine (THM) and 3,4-dihydroxymethamphetamine, and the in vitro effect of THA on TPH activity are reported. After short-term treatment, hippocampal TPH activity was decreased to 8 and 54% of control in response to THA and THM, respectively, but was unaltered after 3,4-dihydroxymethamphetamine. Incubating TPH from THM-treated rats with dithiothreitol under nitrogen failed to reverse the decrease in enzyme activity induced by THM treatment. THA also decreased tyrosine hydroxylase activity to 75% of control, whereas the enzyme activity remained unaltered by THM. The structural analog of THA, 6-hydroxydopamine, failed to reproduce the effect of THA on TPH activity; however, 5,6-dihydroxytryptamine decreased hippocampal TPH activity to 18% of control. In the in vitro study, the hippocampus and the striatum were incubated in varying concentrations of THA. After a 1-h incubation at 37 degrees C, hippocampal TPH activity was decreased to 83, 71, 68, 47 and 3% of control after exposure to 0.001, 0.01, 0.1, 0.5 or 5.0 mM THA, respectively; striatal TPH activity was reduced to 98, 95, 70, 54 and 17% of control, respectively. Incubating the enzyme under reducing conditions failed to restore the enzyme activity to control levels.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Short-term effects of 2,4,5-trihydroxyamphetamine, 2,4,5-trihydroxymethamphetamine and 3,4-dihydroxymethamphetamine on central tryptophan hydroxylase activity. 849 26

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

Tissue storage prior to intracerebral transplantation would represent a major advantage when conducting clinical transplantation trials in that the procurement of the embryonic donor tissue and the timing of neurosurgery could be planned more efficiently. In the present study, the effects of storing rat embryonic striatal tissue at either +4 degrees C or below freezing temperature prior to grafting to the adult striatum, were assessed with regard to transplant survival, morphology and integration. Eleven days following a unilateral injection of ibotenic acid into the head of the caudate-putamen, a control group of rats received grafts of striatal primordium prepared immediately after dissection from rat embryos (embryonic day 16). A second group of rat embryonic striatal tissue was stored at 4 degrees C (hibernation) for 5 days and then transplanted. A third group of the striatal donor tissue was cryopreserved in liquid nitrogen for 5 days before implantation surgery. Six to seven weeks following transplantation surgery, the grafts were analysed in brain sections processed for acetylcholinesterase histochemistry, DARPP-32 (dopamine and cyclic AMP regulated phosphoprotein with a molecular weight of 32 kDa) and tyrosine hydroxylase (TH) immunocytochemistry. The mean total graft volume and the relative size of the AChE-positive regions were not significantly different between the three groups. Striatal-specific graft regions, positively stained for AChE and DARPP-32, generally exhibited TH immunoreactivity, suggesting that they had received dopaminergic afferents from the host brain. We conclude that embryonic rat striatal tissue can be cryopreserved or hibernated over 5 days without significant impairment in the yield of striatal neurons following intrastriatal implantation and without markedly affecting transplant morphology.
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PMID:Effects of hibernation or cryopreservation on the survival and integration of striatal grafts placed in the ibotenate-lesioned rat caudate-putamen. 871 78


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