Identification of a highly polymorphic length variant in the 3'UTR of NRAMP1.
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Base Sequence↗
Biomedical subjects
N T Buu
Publications and source records attributed to N T Buu.
Identification of polymorphisms and sequence variants in the human homologue of the mouse natural resistance-associated macrophage protein gene.
The most common mycobacterial disease in humans is tuberculosis, and there is evidence for genetic factors in susceptibility to tuberculosis. In the mouse, the Bcg gene controls macrophage priming for activation and is a major gene for susceptibility to infection with mycobacteria. A candidate gene for Bcg was identified by positional cloning and was designated "natural resistance-associated macrophage protein gene" (Nramp1), and the human homologue (NRAMP1) has recently been cloned. Here we report on (1) the physical mapping of NRAMP1 close to VIL in chromosome region 2q35 by PCR analysis of somatic cell hybrids and YAC cloning and (2) the identification of nine sequence variants in NRAMP1. Of the four variants in the coding region, there were two missense mutations and two silent substitutions. The missense mutations were a conservative alanine-to-valine substitution at codon 318 in exon 9 and an aspartic acid-to-asparagine substitution at codon 543 in the predicted cytoplasmic tail of the NRAMP1 protein. A microsatellite was located in the immediate 5' region of the gene, three variants were in introns, and one variant was located in the 3' UTR. The allele frequencies of each of the nine variants were determined in DNA samples of 60 Caucasians and 20 Asians. In addition, we have physically linked two highly polymorphic microsatellite markers, D2S104 and D2S173, to NRAMP1 on a 1.5-Mb YAC contig. These molecular markers will be useful to assess the role of NRAMP1 is susceptibility to tuberculosis and other macrophage-mediated diseases.
Alleles↗
Norepinephrine in neonatal rat ventricular myocytes: association with the cell nucleus and binding to nuclear alpha 1- and beta-adrenergic receptors.
Chronic exposure of neonatal rat ventricular myocytes to norepinephrine (NE) has been demonstrated to induce fetal cardiac gene expression and hypertrophy. The precise signaling mechanism of NE induction, as well as the long delay for the onset of NE effect, are not well understood. To examine the possibility that the hormone may be transported into the cell and exerts its effect through an intracellular site, ventricular myocytes from neonatal rats were incubated with [3H]-labeled NE and the cytosolic and nuclear fractions of the cell were measured for radioactivity. The presence of intracellular adrenergic binding sites was also explored. Following incubation of neonatal rat ventricular myocytes with [3H]NE for different time intervals (from 30 min to 22 h), the highest proportion (more than 80%) of NE taken up by the cell was recovered in the nuclear fraction. The nuclear accumulation was slow and time-dependent, being non-detectable in the first 60 min. Furthermore, isolated nuclei from the ventricular myocytes contain binding sites for [3H]prazosin and dihydroalprenolol, suggesting the presence of alpha 1 and beta 1 adrenergic receptors. The apparent KD and Bmax were 0.6 nM and 0.6 fmol/mg protein for alpha 1-adrenergic receptors, while beta-adrenergic nuclear receptors exhibited an apparent KD of 12 nM and a Bmax of 61 fmol/mg protein. Thus, neonatal rat ventricular myocytes exposed to NE accumulate the hormone in the cell nucleus where it can bind to high affinity alpha 1- and beta-adrenergic receptors.
Animals↗
Uptake of 1-methyl-4-phenylpyridinium and dopamine in the mouse brain cell nuclei.
The neurotoxin N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) causes, via its metabolite 1-methyl-4-phenylpyridinium (MPP+), parkinsonism in humans, monkeys, and mice but not in rats. When incubated with mouse brain homogenates, [3H]-MPP+ is recovered in relatively large concentrations in the brain cell nucleus. Although isolated cell nuclei from rat and mouse brain contain uptake systems for dopamine (DA), only brain cell nuclei from mice avidly take up [3H]MPP+. This nuclear uptake is ATP dependent and can be blocked by ouabain and N-ethylmaleimide. It is not, however, affected by neuronal and vesicular blockers such as benztropine, mazindol, and reserpine. Selective uptake of MPP+ into brain cell nuclei may provide a new avenue for future investigation into the complex modes of action of the neurotoxin MPTP.
1-Methyl-4-phenylpyridinium↗
Dopaminergic abnormalities in borderline essential hypertensive patients.
To explore whether an altered metabolic pathway of dihydroxyphenylalanine (DOPA) may be related to some previously observed dopamine abnormalities in borderline hypertension, we measured basal and DOPA-induced (500 mg orally) changes in blood pressure and pulse rate as well as in three hourly plasma and urine samples. We found that borderline hypertensive patients compared with controls 1) showed a higher baseline urinary excretion of methoxytyramine, a marker of exocytotic dopamine release, with a greater DOPA-induced decrease of systolic blood pressure without reflex tachycardia; 2) had in response to DOPA a blunted plasma DOPA and free dopamine increase but an accentuated plasma dopamine sulfate and urinary DOPAC excretion; and 3) eliminated comparable quantities of dopamine in urine despite a lower rise in the glomerular DOPA load. Furthermore, although DOPA elicited natriuresis in both groups, its effect was greater in borderline hypertensive patients, who lacked the urinary sodium correlation with urinary dopamine excretion seen in control subjects. These data are compatible with increased basal exocytotic dopamine release and accelerated neuronal and renal (extraneuronal) dopamine generation from administered DOPA in borderline hypertension. The DOPA-induced hypernatriuresis exceeding augmented dopamine in borderline hypertensive patients, contrasting with the urinary sodium and dopamine correlation in control subjects, suggests that DOPA induced an additional natriuresis in borderline hypertensive patients by a decrease in renal sympathetic tone because of its central inhibition of sympathetic outflow, which also may account for the absence of reflex tachycardia.
Adult↗
Atrial natriuretic factor is a new neuromodulatory peptide.
In this commentary, we will briefly discuss the potential regulatory role of atrial natriuretic factor in peripheral autonomic nervous system function. The focus will be on atrial natriuretic factor's involvement in cardiovascular homeostasis through its peripheral effect on sympathetic nervous activity, which may complement its humoral role. [Kuchel et al. (1987) Life Sci. 40, 1545-1551; Lang et al. (1985) Nature 314, 264-266]. We will attempt to support the hypothesis of its neuromodulatory action on efferent autonomic outflow. Specifically, the role of atrial natriuretic factor in the regulation of the synthesis and release of neurotransmitters and in synaptic transmission at the level of the sympathetic ganglia will be outlined. Its potential usefulness in neurobiological studies will also be indicated.
Animals↗
Atrial natriuretic factor constitutes an intrinsic functional unit within superior cervical ganglia of the rat.
The molecular forms of atrial natriuretic factor were studied in the sympathetic ganglia of the rat. The peptide atrial natriuretic factor was also tested for its ability to induce intracellular changes in ganglionic elements. Chromatographic evaluation of extracted ganglionic atrial natriuretic factor revealed the presence of proatrial natriuretic factor together with lower molecular weight peptides. Atrial natriuretic factor induced a maximal six-fold increase of cGMP accumulation within ganglia in vitro, most probably in principal ganglionic cells. Its effect on cGMP was not mediated by acetylcholine or any other neurotransmitter because it persisted after muscarinic receptor blockade and in a calcium-free medium and was not affected by ganglia decentralization. Thus, atrial natriuretic factor appears to be produced by a structural neural component of ganglia (in preganglionic cholinergic neurons or small intensely fluorescent cells?) and has receptors at sites different from its source. It is suggested that atrial natriuretic factor may be locally involved in the process of neurotransmission and may be yet another peptide neurotransmitter and/or neuromodulator.
Animals↗
Vesicular and ganglionic norepinephrine in the rat: progressive increase with age.
This study analyzed dopamine (DA) and norepinephrine (NE) in the synaptic vesicles and cytoplasm of brains of rats of 2 months and 14 months. The data revealed a clear NE increase in the synaptic vesicles of the 14-month-old rats, contrasting with NE in the cytoplasmic fraction of the rat brain, which remained unchanged with age. Synaptic vesicles from different regions of rat brain, including those from the striatum, consistently exhibited higher NE than DA concentrations, suggesting that they are predominantly noradrenergic. In the brain, DA concentrations in vesicular and cytoplasmic fractions did not vary with age, whereas in the superior cervical ganglia DA and NE concentrations increased in the older rats. L-3,4-Dihydroxyphenylalanine administration significantly increased DA without affecting NE in the ganglia of rats of all ages. In the brain, such a treatment significantly raised DA only in the synaptic vesicles of the older rats, suggesting an increased facilitation of DA transport into the synaptic vesicles with age, which may account for the higher vesicular NE in the older rats.
3,4-Dihydroxyphenylacetic Acid↗
ANF disappearance and tissue distribution in rats.
The disappearance of [125I]atrial natriuretic factor (ANF; Ser99-Tyr126) from the circulation and its tissue distribution with or without nonlabeled ANF pretreatment were investigated in normotensive Sprague-Dawley rats. Preadministration of the cold peptide increased plasma radioactivity levels for over 8 min following labeled ANF injection but did not change the half-life of circulating labeled ANF. The metabolic clearance rate (MCR) and volume of distribution in the first, second, and steady state phase were significantly decreased after cold ANF pretreatment. Circulating iodo-labeled ANF was taken up by several organs, even by tissues such as fat or bone, but its urinary excretion was very low. The highest uptake was found in the liver (16 +/- 1% of the injected dose), lung (14 +/- 1%), and kidney (12 +/- 1%), diminishing by 21, 89, and 59%, respectively, after cold ANF preinjection. The brain radioactivity was negligible implying an inability of [125I]ANF to cross the blood-brain barrier. Our data underscore the importance of the uptake-mediated, cold ANF preadministration suppressible clearance of ANF from the circulation, probably one of its basic elimination mechanisms. The liver, lung, and kidney are probably the most important participants in the MCR of ANF.
Animals↗
Origin of dopamine in the rat adrenal cortex.
The hypothesis that dopamine (DA) is involved in the control of aldosterone secretion is given some support by the finding of DA in the adrenal cortex of several species, but the source of this DA is not known. This study showed that the administration of L-dopa to intact rats or medullectomized rats caused a significant DA increase in the adrenal cortex. The DA increase in the cortex was more pronounced than in the medulla, coincident with higher L-dopa uptake by the cortical tissue. Tyrosine administration raised DA levels only in the medulla. Sympathectomy of the rat by 6-hydroxydopamine treatment did not affect DA basal levels in the cortex or the DA increase in this tissue after L-dopa injection. 3,4-Dihydroxyphenylacetic acid (DOPAC) is detectable in the adrenal cortex but not in the adrenal medulla, and DOPAC levels increased significantly after L-dopa, which indicates monoamine oxidase (MAO) activity within the adrenal cortex. Because 6-hydroxydopamine pretreatment did not alter DOPAC levels, cortical MAO may be located outside catecholaminergic neurons. The results established circulating L-dopa as a precursor for DA in the adrenal cortex of the rat. They also showed that tyrosine hydroxylase activity is absent from the adrenal cortex of this species.
3,4-Dihydroxyphenylacetic Acid↗
Effect of prolonged high salt diet on atrial natriuretic factor in rats.
Normotensive Sprague-Dawley rats were given 8% NaCl for 5 weeks. This salt load did not affect their blood pressure nor hematocrit, and plasma atrial natriuretic factor (ANF) showed no change at 3 weeks but decreased after 5 weeks of the experimental period when compared with control rats. The responsiveness of particulate guanylate cyclase and formation of cGMP in ANF target organs suggested an augmented baseline activity of the cGMP system but its relative hyporesponsiveness to exogenous ANF following prolonged salt loading. Decreased plasma ANF levels cannot be explained by its altered production since atrial levels of the peptide were comparable in rats with or without salt loading. Atrial ANF mRNA was unaffected by the salt regimen. This study demonstrates that plasma ANF does not increase during long-term NaCl loading and even decreases after 5 weeks of 8% NaCl. The changes in plasma ANF are associated with changes in the functional state of ANF receptors coupled to particulate guanylate cyclase, but in the opposite direction than expected from lowered plasma ANF. Thus, ANF may not play a significant role in the regulation of sodium excretion in response to prolonged high salt consumption or, if it does, it is not reflected by expected changes in its plasma levels.
Adrenal Cortex↗
Alternative catecholamine pathways after tyrosine hydroxylase inhibition in malignant pheochromocytoma.
A suppression of norepinephrine, epinephrine, and its metabolites in malignant pheochromocytoma by metyrosine was associated with an increase in tyrosine, plasma DOPA, and sulfate esters of DOPA and dopamine, followed, with continuing metyrosine administration, by a further rise of both DOPA sulfate and dopamine sulfate. Urinary dopamine progressively increased in the course of metyrosine treatment, and this, along with the increase of the dopamine metabolite, dihydroxyphenylethanol, and plasma dopamine sulfate, occurred in the absence of any change in plasma dopamine. The octopamine metabolite para-hydroxyphenylglycol, which was initially elevated at least 10-fold, also increased after metyrosine treatment. The unexpected increase of DOPA (progressively more converted toward DOPA sulfate) in the presence of tyrosine hydroxylase inhibition and increase in tyrosine may result from channeling the excess tyrosine toward DOPA and melanin through tyrosinase. Increases in plasma dopamine sulfate and urinary dopamine suggest that dopamine sulfate may be generated via DOPA sulfate and urinary dopamine may originate from circulating DOPA. Tyrosine hydroxylase inhibition may thus result in DOPA generation in non-catecholamine-producing tissues by an alternative pathway. The resulting progressive increase in DOPA and its sulfate may lead to increased urinary dopamine. DOPA sulfate may be an alternative source of dopamine sulfate.
Adrenal Gland Neoplasms↗
Vesicular accumulation of dopamine following L-DOPA administration.
In this study, the accumulations of dopamine (DA) and norepinephrine (NE) were measured in the brain tissues and in the synaptic vesicle fractions prepared from whole brain of control rats and rats injected with L-DOPA. In the normal rat brain, a 3-fold increase in DA following L-DOPA administration was followed by a small, but not significant increase in vesicular DA, indicating a restricted vesicular uptake of exogenous DA. At the same time, NE in the vesicular fraction and in the whole brain tissue did not change, suggesting a possible link between DA vesicular uptake of DA and brain NE. However, in rats pretreated with alpha-methyl-p-tyrosine, which significantly (P less than 0.05) reduced DA and NE levels in brain tissues and in the synaptic vesicles, L-DOPA administration led to a significant increase in vesicular DA (P less than 0.05), suggesting that catecholamine depletion may result in greater vesicular uptake of cytoplasmic DA. The increase in vesicular DA was accompanied by increases in tissue and vesicular NE, underscoring again the existence of a link between vesicular uptake of DA and brain NE following L-DOPA administration. The results also demonstrated a large increase in 3,4-dihydroxyphenylacetic acid (DOPAC) following L-DOPA, in the brain tissues but not in the synaptic vesicle, indicating that monoamine oxidase activity is confined to the cytoplasm.
Animals↗
Modification of vesicular dopamine and norepinephrine by monoamine oxidase inhibitors.
The possible effects of inhibitors of the two forms of monoamine oxidase (types A and B) on dopamine (DA) and norepinephrine (NE) accumulation and metabolism in the cytoplasmic and microsomal (vesicular) fractions of the rat brain have been examined. It was found that, while L-DOPA treatment raised only cytoplasmic DA without affecting vesicular DA and NE, clorgyline and pargyline treatments caused significant increases in DA and NE concentrations in both cytoplasmic and vesicular fractions. The DA increase in the synaptic vesicles (200-600%) was much more pronounced than that (150%) in the cytoplasm. In contrast, deprenyl treatment increased vesicular DA only slightly without any effect on either vesicular or cytoplasmic NE. L-DOPA administration to rats pretreated with clorgyline and pargyline, but not with deprenyl, further increased cytoplasmic and vesicular DA and NE concentrations. However, excessive increases in vesicular DA lowered vesicular NE. Reserpine drastically reduced vesicular and cytoplasmic DA and NE, and L-DOPA administration to the reserpine-treated rats caused a DA increase only in the cytoplasmic fraction without affecting vesicular DA or NE. The effect of reserpine was abolished by pargyline treatment, which suggests that pargyline may interact with the reserpine-sensitive vesicular uptake. There was a significant correlation between vesicular DA and NE increase.
3,4-Dihydroxyphenylacetic Acid↗
Consequences of monoamine oxidase inhibition: increased vesicular accumulation of dopamine and norepinephrine and increased metabolism by catechol-O-methyltransferase and phenolsulfotransferase.
1. Male Sprague-Dawley rats were injected with saline, L-Dopa or pargyline. 2. Synaptic vesicles were prepared from whole brain homogenates. Catecholamines and their metabolites in brain tissues and in synaptic vesicles were measured by high performance liquid chromatography with electrochemical detection. 3. L-Dopa administration raised brain dopamine markedly but did not significantly change dopamine and norepinephrine in the vesicular fraction. 4. The dopamine increase following L-Dopa was not accompanied by any change in normetanephrine, 3-methoxytyramine or dopamine sulfate. 5. In comparison to the control rats and rats injected with L-Dopa, pargyline-treated rats exhibited significantly higher vesicular norepinephrine and dopamine. 6. The dopamine and norepinephrine increases following pargyline treatment were accompanied by significant increases in 3-methoxytyramine, normetanephrine and dopamine sulfate. 7. The increases in vesicular dopamine and norepinephrine may be the origin of their increased metabolism by extraneuronal enzymes, catechol-O-methyltransferase and phenolsulfotransferase.
Animals↗
A defective beta-hydroxylation of dopamine may precede the full development of hypertension in spontaneously hypertensive rats.
A possible mechanism of the previously observed increased adrenal dopamine release and tissue content in spontaneously hypertensive rats (SHR) was explored. The following changes in dopamine beta-hydroxylase activity and catecholamines were noted. At age four weeks (normotensive) or 12 weeks (hypertensive), SHR had lower dopamine beta-hydroxylase activity in the adrenals, heart ventricle and spleen than Wistar Kyoto rats. Tissue dopamine beta-hydroxylase activity in Wistar Kyoto rats was increased with age in the atria but decreased in the ventricles and did not change in the spleen. SHR also had reduced right heart atrial dopamine beta-hydroxylase activity in the hypertensive stage and an overall increase in atrial dopamine content even in the prehypertensive state compared to Wistar Kyoto rats. The increase in noradrenaline content seen with age in the right atrium and spleen in Wistar Kyoto rats was not found in SHR, possibly because of concomitantly decreased dopamine beta-hydroxylase activity. An augmented dopamine:noradrenaline ratio in the spleen of hypertensive SHR may also have been related to an abnormality of the synthesis of noradrenaline from dopamine not necessarily reflected by tissue dopamine beta-hydroxylase determination. A defect of beta-hydroxylation, partly attributable to deficient dopamine beta-hydroxylase activity, may thus precede hypertension and contribute to the hyperdopaminergic state found in SHR.
Adrenal Glands↗
Atrial natriuretic factor in sympathetic ganglia of the rat: dependence on cholinergic innervation.
Atrial natriuretic factor is detectable in the peripheral autonomic ganglia of the rat by radioimmunoassay and immunohistochemistry. In the present study, surgical and neurochemical methods were used to evaluate the source of this peptide in sympathetic ganglia. Decentralization of the ganglia and/or central administration of colchicine diminished the atrial natriuretic factor content in para- and prevertebral ganglia. Axotomy did not affect levels of ganglionic atrial natriuretic factor. A messenger ribonucleic acid species hybridizing with rat atrial natriuretic factor complementary deoxyribonucleic acid was not found within the total ribonucleic acid extracted from superior cervical ganglia. These results indicate a direct dependence of ganglionic atrial natriuretic factor on cholinergic innervation.
Acetylcholine↗
Ganglionic immunoreactive atrial natriuretic factor in rat experimental hypertension.
Because previous data have suggested a dependence of ganglionic atrial natriuretic factor (ANF) content on preganglionic cholinergic input, we investigated the possibility that the increased neural activity observed in spontaneously hypertensive rats (SHR) may be reflected by ganglionic immunoreactive ANF levels. Four-week-old normotensive SHR had celiac ganglionic immunoreactive ANF values comparable to those of Wistar-Kyoto rats (WKY). When they became hypertensive, however, at 12 weeks of age, the SHR manifested higher immunoreactive ANF levels in celiac ganglia than the WKY group (25.3 +/- 2.6 vs 14.5 +/- 1.7 pg/ganglion; p less than 0.01), but there were no differences in levels in the superior cervical and nodose ganglia. The values in celiac ganglia were quadrupled on the average in hypertensive Dahl salt-sensitive rats under the influence of an 8% salt intake for 5 weeks, but no difference was noted in any of these ganglia between this group and their salt-resistant partners. The celiac and superior cervical ganglionic immunoreactive ANF content in normotensive Sprague-Dawley rats was higher with high salt than with normal salt intake. Hypertensive rats treated with deoxycorticosterone acetate (DOCA)-salt and sham-treated controls showed immunoreactive ANF concentrations in celiac ganglia similar to those detected in Dahl rats but, again, no differences were found between groups. Thus, hypertensive SHR, compared to WKY, have higher celiac ganglionic immunoreactive ANF levels, unlike Dahl salt-sensitive and DOCA-salt animals relative to their respective controls. This increase is unique to SHR (although all three models have elevated plasma immunoreactive ANF when they are hypertensive) and to the celiac ganglia.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗