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A Ferron

Publications and source records attributed to A Ferron.

At least 19 recordsLinked to original sources
PubMed2000

Molecular strategies to define HLA haplotype loss in microdissected tumor cells.

Loss of heterozygosity (LOH) of chromosome 6p21 is an important mechanism that generates HLA haplotype loss in various human tumors. This mechanism produces non-reversible HLA-deficient tumor cells that can escape T cell immune responses in peptide-vaccinated cancer patients. However, the exact frequency of this mechanism is still unknown, because contaminating stroma in solid tumor tissues masks the tumor DNA obtained from solid samples. A microdissection technique was applied to 4-8 microm sections of cryopreserved tumor tissues from a group of colorectal and laryngeal carcinomas. Fifteen patients were analyzed for the presence of LOH associated with the beta(2)-microglobulin gene in chromosome 15, and five patients for LOH associated with HLA genes in chromosome 6. In two cases, autologous metastasis tissue samples were also available. The patients were selected for showing an altered HLA class I tumor phenotype as determined by immunohistological techniques. DNA was obtained from this microdissected material and amplified in order to detect the presence or absence of nine previously selected microsatellite markers. HLA sequence based typing (SBT) was also applied to these microdissected DNA samples to define the HLA genotype. Microdissection greatly improved the definition of LOH, with nearly 100% signal reduction in one of the alleles. In addition, this procedure allowed us to detect beta(2)-microglobulin LOH in tumors that expressed some HLA molecules. Our data indicate that this procedure can be successfully applied to microdissected samples from solid tumors, thus enhancing the power and sensitivity of LOH detection.

Colorectal Neoplasms↗
PubMed1998

High frequency of altered HLA class I phenotypes in invasive colorectal carcinomas.

We analyzed the expression of HLA class I antigens in 78 tumor tissue samples obtained from patients diagnosed as having colorectal carcinomas. A broad panel of mAbs defining HLA monomorphic, locus-specific and allele-specific determinants was used. In addition, an antibody defining HLA-C locus-specific determinant (L31) was also tested. Previous reports on these tumors indicated HLA class I losses of 30 to 40%. At least 73% of the patients in the present study had a detectable HLA class I alteration. These altered HLA phenotypes were classified as total HLA loss (18%) (phenotype I); HLA-A locus-specific loss (9%) (phenotype IIIa); HLA-B locus-specific loss (8%) (phenotype IIIb); HLA-A and B locus losses (2%) and HLA allelic losses (36%) (phenotype IV). We found no HLA-C locus losses. Autologous peripheral blood lymphocyte HLA class I typing was always necessary to define phenotype IV. We also studied the CD3 zeta chain in tumor tissues to correlate possible changes in the CD3 signal transduction pathway with HLA alterations. The CD3 ratio was frequently altered, but this alteration could not be correlated with tumor HLA phenotypes. The high frequency of HLA class I losses in colorectal carcinomas suggests that this finding is a widespread phenomenon and may be required to escape T-cell recognition. It remains to be determined whether HLA expression is "normal" in the rest of the 27% of our patients.

Alleles↗
PubMed1994

Hypersensitivity to serotonin and its agonists in serotonin-hyperinnervated neostriatum after neonatal dopamine denervation.

Neonatal destruction of the nigrostriatal dopamine projection by intraventricular 6-hydroxydopamine leads to a serotonin (5-hydroxytryptamine, 5-HT) hyperinnervation of the adult neostriatum accompanied by increased radioligand binding to 5-HT1B, 5-HT1nonAB and 5-HT2 receptors. The consequences of such 5-HT receptor changes on neuronal responsiveness to 5-HT and corresponding receptor agonists were assessed with a quantitative iontophoretic approach. For comparative purposes, similar data were also obtained from rats 6-hydroxydopamine lesioned as adults, showing severe neostriatal dopamine denervation but no 5-HT hyperinnervation. In controls, 5-HT and its receptor agonists, m-chlorophenylpiperazine (mCPP; 5-HT1B/2C agonist) and dimethoxy-iodophenyl-aminopropane (DOI; 5-HT2A/2C agonist), depressed the firing rate of a majority of the unit tested. Three months after neonatal 6-hydroxydopamine lesion (5-HT-hyperinnervated tissue), inhibitory responses to all three agents were significantly increased and comparable results were obtained for 5-HT and DOI in the rostral versus caudal neostriatum. After 6-hydroxydopamine lesion in adults, neither responsiveness to 5-HT, mCPP or DOI nor the density of 5-HT1B or 5-HT2A binding were significantly different from control. Thus, the up-regulation of 5-HT1B, 5-HT2A and possibly 5-HT2C receptors accompanying the 5-HT hyperinnervation after neonatal but not after adult dopamine denervation was associated with increased responsiveness (IT50) of neostriatal neurons to iontophoresed 5-HT and its receptor agonists. Under these conditions, neostriatal 5-HT transmission might be enhanced in spite of a basal release seemingly comparable to normal (Jackson and Abercrombie, 1992, J. Neurochem. 58, 890).(ABSTRACT TRUNCATED AT 250 WORDS)

Amphetamines↗
PubMed1993

Changes of D1 and D2 receptors in adult rat neostriatum after neonatal dopamine denervation: quantitative data from ligand binding, in situ hybridization and iontophoresis.

The specific binding of [3H]SCH23390 to D1 and of [3H]raclopride to D2 dopamine receptors was measured by autoradiography in the rostral and caudal halves of neostriatum and in the substantia nigra of adult rats subjected to near total destruction of nigrostriatal dopamine neurons by intraventricular 6-hydroxydopamine soon after birth. Three months after this lesion, [3H]SCH23390 binding (D1 receptors) was slightly but significantly decreased in the rostral neostriatum (22%), but unchanged in its caudal half and in the substantia nigra. In contrast, [3H]raclopride binding (D2 receptors) was considerably increased throughout the neostriatum (10-40%), while markedly decreased in the substantia nigra (80%). In the rostral neostriatum, there were no parallel changes in D2 receptor messenger RNA levels, as measured by in situ hybridization on adjacent sections. Caudally, however, slight but significant increases in D2 messenger RNA could be observed (10-20%). As assessed by quantitative iontophoresis, there was a marked enhancement (63%) of the inhibitory responsiveness of spontaneously firing units in the rostral neostriatum to dopamine and the D1 agonist, SKF38393, in neonatally lesioned compared to control rats. On the other hand, responsiveness to PPHT, a potent D2 agonist, appeared to be unchanged. Such opposite changes in the number of D1 and D2 binding sites, dissociated from the expression of D2 receptor messenger RNA and from the sensitivity to dopamine and D1 and D2 agonists, suggested independent adaptations of these various parameters following the neonatal dopamine denervation of neostriatum. They also provided further evidence for mechanisms other than the dopamine innervation in the control of the expression of neostriatal D2 receptor messenger RNA during ontogenesis, and emphasized that the effects of dopamine and its D1 and D2 agonists in neostriatum do not depend strictly on the number of D1 and D2 primary ligand recognition sites.

Animals↗
PubMed1992

Opposite effects of neurotensin on dopamine inhibition in different regions of the rat brain: an iontophoretic study.

Anatomical, biochemical and behavioral data suggest functional interactions between dopamine and neurotensin in regions of the brain receiving a co-existent and/or distinct innervation by these two transmitters. We therefore measured and compared the effects of iontophoretically applied dopamine and neurotensin in the prefrontal and anterior cingulate cortex (co-existent innervation) vs the nucleus accumbens and neostriatum (distinct innervation) of urethane-anesthetized rats. In every region, the firing rate of most spontaneously active neurons was depressed by dopamine. Neurotensin had no effect on the same cells, except for a few nucleus accumbens units which were inhibited by the peptide. When dopamine and neurotensin were concomitantly applied, the magnitude of maximal inhibitions induced by dopamine was modified in the majority of neurons tested. A significant decrease in dopamine inhibition was observed in 100% of anterior cingulate, 74% of prefrontal cortex and 48% of accumbens units. On the contrary, in neostriatum, dopamine inhibition was significantly increased in 60% of the units tested. In every region, the remaining neurons showed less than 30% changes in dopamine responsiveness, and were therefore considered unaffected by neurotensin. In the anterior cingulate cortex, inhibitions, respectively, induced by the dopamine D1 agonist, SKF 38393, and the D2 agonist, LY 171555, were also decreased by simultaneous application of neurotensin. Together with currently available data on the cellular localization of neurotensin receptors in rat brain, these results suggest that the modulation of dopamine inhibition by neurotensin may have opposite effects depending on whether the neurotensin receptors are located postsynaptically on target neurons (antagonistic effects) or presynaptically on dopamine terminals (potentiating effects).

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1991

Dopamine modulates the inhibition induced by GABA in rat cerebral cortex: an iontophoretic study.

Effects of iontophoresed gamma-aminobutyric acid (GABA) and two GABA agonists, 4,5,6,7-tetrahydroisooxazolo-[5,4-c]pyridine-3-ol (THIP) and baclofen were quantitatively compared in the anterior cingulate, frontal, and parietal cortex of urethane-anesthetized intact rats after catecholamine (CA) depletion with alpha-methyl-p-tyrosine (alpha-MPT) or selective dopamine (DA) denervation with 6-hydroxydopamine (6-OHDA). As assessed with to the IT50 index, the postsynaptic sensitivity to GABA was significantly higher in anterior cingulate than in frontal and parietal cortex. The responsiveness to GABA was also greater in frontal than in parietal cortex. Sensitivity to GABA was significantly reduced in both anterior cingulate and frontal cortex after CA depletion, and similarly, after DA denervation with 6-OHDA. The difference in the sensitivity to GABA between the three cortical regions in intact rats as well as after CA depletion did not seem to be correlated with either GABAA or GABAB receptors since the responsiveness to both GABA agonists in every region examined was comparable in intact rats, and remained unchanged after alpha-MPT treatment. This finding raises the possibility that some GABA receptors in the cerebral cortex may be pharmacologically distinct from the two main subtypes of GABA receptors, GABAA and GABAB. When GABA was administered by iontophoresis in the anterior cingulate cortex during continuous applications of subthreshold currents of DA, the inhibition induced by GABA was either increased or decreased. As DA innervation density is nearly two-fold greater in anterior cingulate than in frontal cortex, and 30-fold greater in anterior cingulate than in parietal cortex, these results suggest that responsiveness to GABA may be correlated with the regional density of DA innervation and that elevated levels of DA may enhance the sensitivity to GABA.

Animals↗
PubMed1991

Comparative analysis of the effects of iontophoretically applied dopamine in different regions of the rat brain, with special reference to the cingulate cortex.

A systematic comparison of the effects of iontophoresed dopamine (DA) was carried out in the neostriatum (NS), nucleus accumbens (Acb) and anterior cingulate (ACg), prefrontal (PF) and parietal (Par) cortex of urethane-anesthetized rats, before and after treatment with the specific DA uptake blockers GBR 12909 and Bupropion. Similar experiments were also conducted after DA denervation with 6-hydroxydopamine and after DA depletion with alpha-methyl-p-tyrosine. The average rate of spontaneous neuronal firing was comparable in all regions, except in the NS after DA depletion. A majority of the units were inhibited by DA in every region and condition tested. As assessed with the IT50 index, the responsiveness to DA was not markedly different between regions, indicating that the postsynaptic sensitivity to this amine is independent of the density of DA receptors and of DA innervation. In contrast, the average duration of DA inhibitions (RT90) was considerably longer (5-fold) in the intact ACg than in the PF, Par, NS, or Acb. Moreover, treatment with both DA uptake blockers reduced the duration of DA inhibitions in ACg (4- to 9-fold); while lengthening it in PF, NS and Acb; and having no apparent effect in Par. DA depletion and DA denervation also reduced the duration of the DA inhibitions in ACg without effect in Par. Taken together, these results provide further evidence for the existence of a presynaptic, positive-feedback mechanism in ACg, triggered by DA, and favouring the further release of this transmitter upon its reuptake in DA nerve terminals.

Animals↗
PubMed1989

Possible existence of a presynaptic positive feedback mechanism enhancing dopamine transmission in the anterior cingulate cortex of the rat.

A series of microiontophoretic and VTA stimulation experiments, conducted in intact, GBR-12909-treated, alpha-methylparatyrosine-depleted or 6-hydroxydopamine-denervated rats, provide suggestive evidence for the existence of a presynaptic, positive feedback mechanism triggered by dopamine reuptake and favoring the release of this transmitter in the anterior cingulate cortex.

Animals↗
PubMed1989

Acute and chronic effects of methylphenidate on cortical adrenoceptors in the rat.

The effects of acute and chronic treatments with methylphenidate were examined on cortical adrenoceptors. A single dose of methylphenidate increased the affinity of [3H]prazosin and [3H]idazoxan binding sites. Acute and chronic methylphenidate treatments caused a down-regulation of alpha 1-adrenoceptors. There were no changes in cortical beta-adrenoceptors measured with [3H]dihydroalprenolol nor in endogenous monoamine levels. The alterations in alpha-adrenoceptors can be attributed to an indirect action of methylphenidate possibly through an accrued release of noradrenaline or tyramine.

Animals↗
PubMed1988

Electrophysiological effects of methylphenidate on the coeruleo-cortical noradrenergic system in the rat.

The effect of methylphenidate on noradrenergic neurotransmission was investigated in urethane-anesthetized rats. The spontaneous activity of locus coeruleus noradrenergic neurons was the same in rats treated for 7 days with methylphenidate as in the controls. In control rats, i.v. methylphenidate induced a reduction of locus coeruleus neuronal firing whereas in rats treated for 7 days with methylphenidate, the same dose of methylphenidate failed to induce any change in locus coeruleus activity. At this time, clonidine induced a lesser reduction of locus coeruleus neuronal firing than in the controls, indicating that their autoreceptors had become desensitized. Following electrical stimulation of the locus coeruleus, most of the spontaneously firing cortical neurons were inhibited but the percentage of such neurons was reduced and the neurons showed a decreased responsiveness after methylphenidate treatment. The responsiveness of cortical neurons to microiontophoretic applications of NA as assessed by the I.T50 method was reduced after 7 days of treatment with methylphenidate. These findings suggest that the efficacy of cortical NA neurotransmission is markedly reduced following methylphenidate treatment.

Animals↗
PubMed1988

Modified coeruleo-cortical noradrenergic neurotransmission after serotonin depletion by PCPA: electrophysiological studies in the rat.

To detect eventual modifications in the efficacy of the noradrenergic (NA) coeruleo-cortical system after serotonin (5-HT) depletion by parachlorophenylalanine (PCPA), three electrophysiological parameters were investigated in urethane-anesthetized rats which were treated for 2 days with daily injections of this inhibitor of 5-HT synthesis. 1) The spontaneous activity of locus coeruleus (LC) noradrenergic neurons showed a significant increase in PCPA-treated compared to control rats (4.3 vs. 2.6 Hz). 2) The sensitivity of NA autoreceptors was measured in the LC by the effect of intravenous administrations of clonidine or microiontophoretic applications of NA on spontaneous neuronal firing. In treated rats, clonidine and NA induced a lesser reduction of LC neuron firing than in the controls (27 vs. 75% decreases and 1,367 vs. 280 nC, respectively). 3) The responsiveness of cortical neurons to electrical stimulation of the LC was assessed by peristimulus time histograms in the dorsal fronto-parietal cortex. Following stimulation at 2 or 4 Hz, a majority of spontaneously firing cortical units was inhibited by electrical stimulation of the LC, but the percentage of such units was reduced and showed a decreased responsiveness after PCPA treatment. These findings suggest that following 5-HT depletion by PCPA, cortical NA neurotransmission is markedly reduced in its efficacy in spite of some increase in the spontaneous activity of coeruleo-cortical NA neurons.

Animals↗
PubMed1986

Effects of p-chlorophenylalanine on cortical monoamines and on the activity of noradrenergic neurons.

The catecholamines noradrenaline, dopamine, adrenaline, the indoleamine 5-hydroxy-tryptamine (5-HT; serotonin), and some of their major metabolites were assayed, using high performance liquid chromatography (HPLC), in the neocortex of normal rats as well as in animals in which 5-HT synthesis had been inhibited with p-chlorophenylalanine. Besides important depletions in serotonin and in 5-hydroxyindole-3-acetic acid, noradrenaline levels were significantly reduced, but the content in 3-methoxy-4-hydroxyphenylglycol was increased, indicating an augmented utilization of this amine. The levels of dopamine and 3-methoxytyramine were also reduced, although homovanillic acid and 3,4-dihydroxyphenylacetic acid levels remained constant. The spontaneous unitary activity of identified noradrenergic neurons in the Locus coeruleus was increased, indicating an hyperactivity of this system. These results can be interpreted in relation to functional interactions between the catecholamines and serotonin; i.e.: a decrease in endogenous serotonin results in the loss of a negative feedback control of noradrenaline release.

Adrenergic Fibers↗
PubMed1986

Variation in the ability of neuroleptics to block the inhibitory influence of dopaminergic neurons on the activity of cells in the rat prefrontal cortex.

The stimulation of the ventro-medial mesencephalic tegmentum (VMT) induces an inhibition of the spontaneous activity of prefrontal cortical cells and blocks the excitatory responses evoked by the stimulation of the medio-dorsal nucleus of the thalamus (MD). This effect is mediated by the activation of the mesocortical dopaminergic (DA) system. In the present study, the influence of the systemic administration of several neuroleptics on the inhibition of prefrontal cortical cells induced by VMT stimulation has been analyzed in ketamine anaesthetised rats. The acute IP administration of fluphenazine (2 mg/kg), spiroperidol (2 mg/kg) or (+/-)sulpiride (100 mg/kg) reversed the inhibitory responses. Moreover, the number of cortical cells inhibited by VMT stimulation was considerably decreased after these treatments. Surprisingly, neither haloperidol at any dose used (0.1 to 0.5 mg/kg IV or 0.5 to 5 mg/kg IP) nor levomepromazine (25 mg/kg IP) nor the long acting neuroleptic, pipotiazine palmitic ester (32 mg/kg SC) blocked the inhibitory effect of VMT stimulation and in fact they lengthened the duration of the inhibition. Finally, the inhibition of MD evoked spikes in prefrontal cortical cells produced by VMT stimulation was no longer observed after sulpiride but persisted after haloperidol administration. Our findings confirm that the mesocortico-prefrontal DA neurons exert an inhibitory influence on target cells but they reveal differences in the efficacy of neuroleptics in blocking this effect.

Animals↗
PubMed1985

Vasoactive intestinal polypeptide acts synergistically with norepinephrine to depress spontaneous discharge rate in cerebral cortical neurons.

Cortical neurons are densely innervated by noradrenergic fibers and by intrinsic cortical interneurons containing vasoactive intestinal polypeptide (VIP). Biochemically, VIP and norepinephrine (NE) synergistically interact to stimulate the synthesis of cyclic AMP in cortical slices. Therefore, we sought physiological indices of this peptide-monoamine interaction by applying VIP and NE to single cortical neurons of the rat while recording their spontaneous discharge. VIP applied alone inhibited discharge of 24% and accelerated discharge in 20% of cortical neurons. NE alone had a predominantly depressant effect on the same neurons. However, when VIP was retested during the continuous application of subthreshold currents of NE, VIP exerted predominantly depressant effects. These synergistic inhibitions resulted even in cells previously showing excitations to VIP alone. If VIP alone was depressant, subthreshold NE further enhanced the VIP depression. Subthreshold amounts of phenylephrine, an alpha-adrenoceptor agonist, also produced comparable interactions, suggesting involvement of an alpha receptor, as in the biochemical studies. These results support a peptide-monoamine interaction in cortex that could have important ramifications for neuronal integration.

Action Potentials↗
PubMed1984

Evidence for a dopaminergic innervation of the cat lateral habenula: its role in controlling serotonin transmission in the basal ganglia.

The presence of a dopaminergic innervation of the cat lateral habenula and its possible role in modulating serotonin transmission within the basal ganglia were investigated using both in vitro and in vivo approaches. A high density of [3H]spiroperidol binding sites with similar affinities for domperidone and apomorphine as those present in the cat striatum were found in the habenula. By means of the push-pull cannula technique, a substantial release of [3H]dopamine continuously formed from [3H]tyrosine was detected in the lateral habenula of halothane-anesthetized cats since the amount of [3H]catecholamines was enhanced in the presence of benztropine, an inhibitor of dopamine uptake into dopaminergic nerve terminals. Furthermore, in anesthetized animals with a push-pull cannula implanted in each caudate nucleus and substantia nigra habenular applications of dopamine (10(-7) M) reduced nigral but not striatal release of [3H]serotonin continuously formed from [3H]tryptophan. This change was prevented either by the delivery of domperidone to the lateral habenula or by the blockade of GABAergic transmission (picrotoxin 10(-5) M) in the dorsal raphe. These data support the involvement of habenulo-raphe pathways in the regulation of serotonin transmission in the cat basal ganglia and indicate that dopaminergic inputs to the lateral habenula participate in such a control.

Animals↗