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PubMed1996

Co-expression of tyrosine hydroxylase and glutamic acid decarboxylase in dopamine differentiation factor-treated striatal neurons in culture.

We have previously shown that dopamine differentiation factors (DDF) can stimulate the novel expression of tyrosine hydroxylase (TH) in the phenotypically plastic neurons of the embryonic mouse striatum (Du et al., J. Neurosci., 14 (1994) 7688-7694; Du and Iacovitti, J. Neurosci., 15 (1995) 5420-5427). The present study sought to determine whether TH induction required down-regulation of an existing GABAergic trait in striatal neurons or whether enzymes of both neurotransmitter systems were simultaneously expressed. Immunocytochemical analysis revealed that, following treatment with DDFs, TH and the GABA synthesizing enzyme glutamic acid decarboxylase (GAD) were co-expressed in the same neurons. Moreover, GAD enzyme activity was not affected by the dramatic increase in TH. Thus, the induction of a novel neurotransmitter phenotype in brain neurons does not appear to occur at the expense of the existing phenotype.

Animals↗
PubMed1984

Inhibition of aminoacid decarboxylases by non-steroidal antiinflammatory drugs.

Several non-steroidal antiinflammatory drugs (NSAID) were shown to inhibit to various extents the decarboxylases of ornithine, lysine, histidine, arginine, and tyrosine. The most sensitive enzyme was ornithine decarboxylase, for which piroxicam, benoxaprofen and aminophenazone showed an IC50 of 0.007 mM; ibuprofen competitively inhibits the lysine decarboxylase. The most effective NSAID's in inhibiting histidine decarboxylase were mefenamic acid, ibuprofen and flufenamic acid. Arginine and tyrosine decarboxylase were inhibited by NSAID's only at high concentrations. None of the decarboxylase inhibitions were reversed by pyridoxal phosphate. Subplantar injection of the 5 amines formed by these aminoacid decarboxylases elicited a paw oedema in rat which was not antagonized by the various NSAID's. Some of the NSAID's stimulated all the decarboxylases and did not antagonize the carrageenin-induced paw oedema. With one exception, all the NSAID's tested in vivo inhibited the elimination of 14CO2 from labeled ornithine and lysine. The inhibition of certain aminoacid decarboxylases, particularly ornithine and lysine decarboxylase, appears to be a noteworthy mechanism of action for certain NSAID's.

Animals↗
PubMed1987

Effect of decarboxylase inhibitors on brain p-tyrosine levels.

A number of inhibitors of L-aromatic amino acid decarboxylase (AAD) and monoamine oxidase (MAO) were tested to determine whether they also inhibited tyrosine aminotransferase (TAT). The AAD inhibitors carbidopa, NSD-1015, NSD-1034 and Ro4-5127 inhibited liver TAT. Carbidopa inhibited brain AAD and liver TAT equally well. In contrast, other AAD inhibitors (Ro4-4602 and alpha-monofluoromethyldopa) did not inhibit TAT. Phenelzine, an MAO inhibitor, inhibited liver TAT, but other MAO inhibitors (tranylcypromine and isocarboxazid) did not. Systemic administration of those drugs that were found to be inhibitors of TAT in vitro caused significant increases in rat brain p-tyrosine levels.

Animals↗
PubMed2003

Detection of autoantibodies to protein tyrosine phosphatase-like protein IA-2 with a novel time-resolved fluorimetric assay.

BACKGROUND: Circulating autoantibodies to pancreatic glutamic acid decarboxylase (GAD65; the 65-kDa isoform of glutamic acid decarboxylase), protein tyrosine phosphatase-like protein IA-2, and insulin can be used as predictive markers of type 1 diabetes. We developed a novel assay for the detection of IA-2 autoantibodies (IA-2As) in serum based on time-resolved fluorimetry, hypothesizing that this kind of assay could provide several advantages over methods described to date, including radiobinding assays (RBAs) and ELISAs. METHODS: The intracellular part of IA-2 (IA-2ic) was biotinylated and bound to streptavidin-coated 96-well plates by simultaneous incubation with serum samples and glutathione S-transferase (GST)-IA-2ic fusion protein. GST-IA-2ic captured by autoantibodies in the serum was detected with europium-labeled anti-GST antibody, and the signal was measured in a time-resolved fluorimeter. A serum sample panel from 100 patients with newly diagnosed type 1 diabetes and 100 unaffected controls was analyzed with the new assay and a conventional RBA. RESULTS: Among the 100 serum samples from patients with type 1 diabetes, the time-resolved fluorimetric assay identified 74 IA-2A-containing sera, whereas the RBA detected 80 IA-2A-positive samples. Five of the six samples positive in the RBA but not detected by the time-resolved fluorimetric assay were only weakly positive in the RBA. The performance time of the time-resolved fluorimetric assay was 2.5 h compared with 10-12 h required by the RBA. CONCLUSIONS: The time-resolved fluorimetric assay provides a simple, nonradioactive analysis method for the detection of IA-2As with a specificity and a sensitivity comparable to the RBA method. This assay allows substantial reduction in performance time compared with the conventional RBA.

Adolescent↗
PubMed2003

Increased levels of tyrosine hydroxylase and glutamic acid decarboxylase in locus coeruleus neurons after rapid eye movement sleep deprivation in rats.

Norepinephrine, acetylcholine and GABA levels alter during rapid eye movement (REM) sleep and its deprivation. Increased synthesis of those neurotransmitters is necessary for their sustained release. Hence, in this study, the concentrations of tyrosine hydroxylase (TH), choline acetyl transferase (ChAT) and glutamic acid decarboxylase (GAD), the enzymes responsible for their synthesis, were immunohistochemically estimated within the neurons in locus coeruleus, laterodorsal tegmentum and pedunculopontine tegmentum and medial preoptic area in REM sleep deprived and control rats. It was observed that as compared to controls, deprivation increased TH and GAD significantly in the locus coeruleus only, while in other areas, they remained unchanged. The findings help explaining the mechanism of increase in neurotransmitter levels in the brain after REM sleep deprivation and their significance has been discussed.

Animals↗
PubMed1999

Cholinergic neurons of the nucleus basalis of Meynert receive cholinergic, catecholaminergic and GABAergic synapses: an electron microscopic investigation in the monkey.

An electron microscopic analysis of the nucleus basalis in the macaque monkey was carried out following the immunohistochemical labeling of choline acetyltransferase, either by itself or in conjunction with glutamate decarboxylase or tyrosine hydroxylase. Cholinergic axon varicosities were frequently encountered, and formed large, usually asymmetric, synapses on both choline acetyltransferase-immunopositive and -immunonegative dendrites of nucleus basalis neurons. Catecholaminergic (tyrosine hydroxylase-immunoreactive) axon varicosities formed synapses which in most cases were classified as asymmetric, and glutamate decarboxylase-immunoreactive (GABAergic) axons formed clearly symmetric synapses, each on to choline acetyltransferase-immunopositive or -immunonegative dendrites. These findings indicate that cholinergic cells in the nucleus basalis of the monkey, also known as Ch4 neurons, receive numerous synaptic inputs from cholinergic, catecholaminergic and GABAergic axons.

Animals↗
PubMed1986

A simplified method for determination of pyridoxal phosphate in biological samples.

A new method for the determination of pyridoxal phosphate in plasma and in cerebrospinal fluid is described. It is based on the generally accepted apotyrosine decarboxylase method, but, in stead of following the decarboxylation rate using 14C- och 3H-labelled tyrosine, a high performance liquid chromatography (HPLC) method for separation of tyrosine and tyramine is used. This procedure is recommended as it is less time consuming and avoids utilizing radioactive material.

Carbon Radioisotopes↗
PubMed1986

The use of gold-substituted silver-intensified diaminobenzidine (DAB) and non-intensified DAB for simultaneous electron microscopic immunoperoxidase labeling of tyrosine hydroxylase and glutamic acid decarboxylase immunoreactivity in the rat medial preoptic area.

An improved gold-substituted silver intensification procedure for the peroxidase-diaminobenzidine (DAB) reaction product was developed. The method was applied in the rat medial preoptic area to label tyrosine hydroxylase (TH)-immunoreactive profiles. Following the gold toning, the same sections were immunostained for glutamic acid decarboxylase (GAD) immunoreactivity with non-intensified peroxidase-DAB. Single DAB-labeled GAD axons were found in symmetric synaptic connection with unlabeled dendrites as well as with gold-toned immunoperoxidase-containing TH neurons.

3,3'-Diaminobenzidine↗
PubMed2003

Effects of acute, repeated and chronic variable stress on in vivo tyrosine hydroxylase activity and on alpha(2)-adrenoceptor sensitivity in the rat brain.

We assessed the effects of a single tail pinch and two chronic stress regimes, repeated and variable, on in vivo tyrosine hydroxylase activity and on alpha2-adrenoceptor sensitivity in two brain regions. After administering a 3,4-dihydroxyphenylalanine (DOPA) decarboxylase inhibitor, tyrosine hydroxylase activity, measured as the accumulation of DOPA, and noradrenaline (NA) content were determined by using high-performance liquid chromatography. A single tail pinch for 5 min induced an enhancement of DOPA content in hippocampus (28%) and hypothalamus (67%) which was still present 24 h later. This increase could account for the lack of changes in NA content in both regions after the application of this stressor. However, tyrosine hydroxylase activity was unmodified 24 h after exposure to both repeated (5 min of tail pinch, twice daily, for 14 days) and chronic variable stress (one of 5 different stressors, once daily, for 14 days) although there was an enhancement of NA levels in hippocampus (45 and 54%, respectively) and hypothalamus (24.5 and 36%, respectively). The sensitivity of the alpha2-adrenoceptors which regulate [3H]-NA release in hippocampal and hypothalamic synaptosomes was not modified by the acute or chronic stress protocols assayed. The results show that both paradigms of chronic stress had similar effects on the noradrenergic indices evaluated.

Acute Disease↗
PubMed1999

Tryosine kinase and ornithine decarboxylase activation in children with Helicobactor pylori gastritis.

H. pylori infection has been considered a risk factor for the development of gastric malignancy. Ornithine decarboxylase and tyrosine kinases activities are increased in patients with colon or esophageal cancer. In this study we compared the ODC and tyrosine kinases activities in the gastric mucosa of children with H. pylori infection and normal mucosa. Gastric biopsies were prospectively collected from children during routine upper endoscopic procedure. H. pylori infection was determined histologically. Biopsies were analyzed for ODC activity, total tyrosine kinases activities, and for the activity of protooncogene tyrosine kinase pp60(c-src). The mean ODC activity (pmol 14CO2/mg. protein/hr) and total tyrosine kinases activity (pmol 32P/mg. protein) were 186 and 5877 for H. pylori infected mucosa; and 229 and 4300, for normal mucosa, respectively (p> 0.05). Tyrosine kinase pp60(c-src) protein levels were similar between H. pylori infected mucosa and normal mucosa (3.12 and 2.15 pmol 32P/mg. protein, respectively; p>0.05). There was no correlation between gastric inflammation and the level of ODC or tyrosine kinase activities. ODC and tyrosine kinase activities in the gastric mucosa are similar in children with H. pylori infection compared to normal mucosa. The data suggest that these enzymes cannot be used as markers for future cancer development in children.

Adolescent↗
PubMed1980

Inhibition of protein degradation in regenerating rat liver by ethanol treatment.

The effect of ethanol on the activity of ornithine decarboxylase (ODC), tyrosine aminotransferase (TAT), alanine aminotransferase (ALAT) and lactate dehydrogenase (LD), as well as on protein concentration, was studied in regenerating rat liver after partial hepatectomy. It was found that administration of an ethanol-containing liquid diet for 5 days after partial hepatectomy caused a significant accumulation of proteins in the liver. The activities of ODC and TAT were stimulated by ethanol treatment in the beginning of the regeneration. In control livers, partial hepatectomy decreased the activity of ALAT, but ethanol prevented this decrease. No differences in the activity of LD was found between ethanol and control groups after partial hepatectomy. When the half-lives of ODC and TAT were measured 24 hr after partial hepatectomy by using cycloheximide, it appeared that ethanol caused a significant stabilization of both enzymes. It is concluded that ethanol caused inhibition of degradation of ODC and TAT and it is suggested that this could be a general phenomenon, and could markedly contribute to the pathological accumulation of proteins in the liver after chronic ethanol consumption.

Alanine Transaminase↗
PubMed1991

Differential effect of functional olfactory bulb deafferentation on tyrosine hydroxylase and glutamic acid decarboxylase messenger RNA levels in rodent juxtaglomerular neurons.

Expression of the dopaminergic phenotype in olfactory bulb (OB) juxtaglomerular neurons (constituting a population of periglomerular and external tufted cells) is dependent upon functional innervation by peripheral olfactory receptors. Loss of functional input in rodents, by either peripheral deafferentation or deprivation of odorant access, results in a profound decrease in the expression of juxtaglomerular tyrosine hydroxylase (TH). We have examined the effects of such treatments on the expression of the neurotransmitter biosynthetic enzyme glutamic acid decarboxylase (GAD), which is colocalized with TH in the majority of TH-containing juxtaglomerular neurons. Following either chemically induced OB deafferentation in adult mice or unilateral odor deprivation in neonatal rats, steady-state OB GAD messenger RNA levels remained essentially unchanged as assessed by Northern blot analysis 20-40 days after treatment. These results were confirmed by in situ hybridization analysis, which demonstrated a profound loss of juxtaglomerular TH messenger RNA but no accompanying decrease in regionally colocalized GAD message. Since GAD is found in nearly all dopaminergic OB cells, the preservation of juxtaglomerular GAD message implies that olfactory receptor neurons exert a differential transneuronal regulation of TH and GAD gene transcription.

Animals↗