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Biomedical subjects

P Barone

Publications and source records attributed to P Barone.

At least 109 records · Page 6Linked to original sources
PubMed1987

Improved procedure for neuromagnetic localisation.

We describe an improved algorithm for localising equivalent sources of biomagnetic fields in the human brain. The algorithm is an improvement over the sphere model in that it considers two distinct surfaces: an ellipsoid, to model the region of the skull on which the sensors are placed, and a sphere as the medium in which the current dipole model is considered. This allows us to easily correct the formula of the magnetic field in order to take better account of the true position of the sensor with respect to the subject's head.

Algorithms↗
PubMed1987

Is the dexamethasone suppression test predictive of response to specific antidepressant treatment in major depression?

The authors attempt to correlate the response to dexamethasone suppression test (DST) with a clinical response to antidepressant drugs in 68 patients with major depression. Antidepressants that influence noradrenergic or serotonergic transmission with relative different potencies were selected and used in standard doses for 6 weeks. The response was evaluated weekly by raters blind to DST results and to antidepressant medications prescribed. The retrospective analysis failed to correlate DST response with outcome of treatment. Therefore the present results suggest that this laboratory test does not help to identify subgroups of depressed patients responding preferentially to various antidepressant drugs.

Adult↗
PubMed1987

Dopaminergic mechanisms in hemiparkinsonian monkeys.

The motor effects of direct agonists which act selectively on certain dopamine receptors were studied in monkeys rendered hemiparkinsonian by unilateral intracarotid injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). The D-2 dopamine agonist, LY 171555, but not the D-1 agonist, SKF 38393, reduced parkinsonian signs and induced rotation away from the side of the nigral lesion. When administered together, SKF 38393 diminished the LY 171555-induced turning in a dose-dependent manner. A selective D-1 antagonist, SCH 23390, induced mild and brief rotation when administered alone. These results suggest that D-2 receptor stimulation is necessary to ameliorate parkinsonism, but that pharmacologic manipulation of both D-1 and D-2 receptors may be required for an optimal therapeutic response.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1987

Nonlinear methods in spectral analysis of NMR signals from living systems.

Two autoregressive procedures, namely Burg's maximum entropy method and Prony's method, have been applied to the processing of 31P NMR signals (free induction decays) of human cells. A comparison of the main advantages obtained by using these methods in the field of the NMR spectral analysis of signals from living samples is here illustrated. Improvements in sensitivity and resolution are obtained with respect to Fourier transform method by using only very few data points.

Adenine Nucleotides↗
PubMed1986

Quantitative autoradiographic localization of D-1 dopamine receptors in the rat brain: use of the iodinated ligand [125I]SCH 23982.

In vitro autoradiography was used to visualize [125I]SCH 23982 binding sites in rat brain. Labeling was concentrated in the caudate-putamen, accumbens nucleus, olfactory tubercle, substantia nigra pars reticulata and the entopeduncular nucleus. [125I]SCH 23982 labels predominantly D-1 receptors but also labels 5-HT2 receptors in certain areas of the brain. These findings may relate to the distribution of dopamine's cerebral loci of action on D-1 receptors.

Animals↗
PubMed1986

Dopaminergic mechanisms and motor function: characterization of D-1 and D-2 dopamine receptor interactions.

The effect of selective D-1 and D-2 dopamine receptor agonists (SKF 38393 and LY 171555, respectively) on motor function was studied in rats with unilateral, quinolinic acid-induced striatal lesions. Dose-dependent turning ipsilateral to the side of the lesion was elicited by LY 171555, but not by SKF 38393. When the drugs were given together, however, SKF 38393 was able to increase the total number (but not the duration) of turning induced by LY 171555 in a dose-dependent fashion. Furthermore, either alpha-methyl-paratyrosine pretreatment, a DA-depleting agent, or SCH 23390, a D-1 antagonist, inhibited the LY 171555-induced rotation, which would be restored by SKF 38393. These observations suggest that both the D-1 and D-2 dopamine receptor systems participate in the regulation of rotational behaviors in striatally lesioned rats with normosensitive DA receptors.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1986

Carbamazepine lowering effect on CSF somatostatin-like immunoreactivity in temporal lobe epileptics.

The effect of carbamazepine treatment on CSF-somatostatin-like immunoreactivity (SLI) in patients suffering from temporal lobe epilepsy was investigated. A baseline lumbar puncture was performed on 12 patients and 10 normal volunteers. A second tap was repeated only in patients when they were on peak of carbamazepine concentration for 10 days. Levels of CSF-SLI were measured by RIA. No significant differences were found in CSF-SLI basal concentrations between epileptics and controls, whereas a significant decrease (p less than .0002 Duncan's multiple range test) of CSF peptide levels occurred in 9 of 12 patients under medication. Although the neural mechanism through which carbamazepine lowers CSF-SLI is still unknown, the results of the present study suggest that the reported effect might be part of the apparatus by which carbamazepine exerts its anticonvulsant action.

Adolescent↗
PubMed1986

Huntington's disease: effect of cysteamine, a somatostatin-depleting agent.

Somatostatin levels in the basal ganglia are elevated in Huntington's disease. A controlled therapeutic trial of the somatostatin-depleting agent, cysteamine, was therefore conducted in five patients, including one with the rigid-akinetic form. Maximum tolerated dosage for 2 weeks produced no consistent change in extrapyramidal or dementia scores. Somatostatin concentrations were not significantly altered in plasma or CSF. Growth hormone levels, on the other hand, more than doubled, suggesting a functionally significant decrease in central somatostatin levels.

Adult↗
PubMed1986

Effect of a radiographic contrast agent on renal function in the rat. Comparison with equiosmolar mannitol.

The renal effects of the radiographic contrast agent meglumine iothalamate (Conray; C) were evaluated in rats. C produced a 42% fall in glomerular filtration rate (p less than 0.05) and a 44% fall in effective renal plasma flow (p less than 0.05). The effects of C were blunted by both acute and chronic volume expansion. Equiosmolar mannitol produced similar hemodynamic responses as C. The fractional excretions of sodium and potassium were similar in rats given C or mannitol. The renal effects of C appear to be due to its hypertonicity. These effects may be modified by volume expansion.

Animals↗
PubMed1985

CCK26-33 degrading activity in brain and nonneural tissue: a metalloendopeptidase.

Cholecystokinin octapeptide (CCK26-33) is metabolized by neural membranes with an initial cleavage to CCK29-33 and subsequent breakdown to CCK31-33 and CCK32-33; this pattern of proteolysis occurs on incubation with either P2 or purified lysed synaptosomal membranes. To determine whether the pattern of CCK26-33 proteolysis is unique to the brain and whether regional brain differences in its pathway or rate exist, we analyzed the proteolysis of CCK by synaptic membranes of various brain areas and cellular membranes of peripheral tissue. The pattern of degradation in brain did not differ among the regions studied. The overall proteolysis rate, as measured by the formation of tryptophan, was higher in the striatum than in the cortex, although CCK29-33 was formed at the same rate in both areas. In nonneural tissue, the rate of degradation was highest in liver membranes and lowest in pancreatic acinar cell preparations. Thus, it appears that degradative peptidases are not necessarily colocalized with CCK receptors. The pattern of product formation is the same in peripheral compared with CNS membranes; thus, the degradative pathway does not appear to be unique to brain tissue. The enzyme present in synaptic membranes that is responsible for CCK29-33 formation requires a metal ion and sulfydryl groups for the catalysis and thus is a metalloendopeptidase. Furthermore, its activity is inhibited by Ac-Gly-Phe-Nle-al, a peptide aldehyde whose sequence bears some homology to the amino acid sequence in the region of CCK26-33 that is cleaved by this enzyme.

Animals↗
PubMed1984

Cholecystokinin-octapeptide fragments: binding to brain cholecystokinin receptors.

Structural determinants of cholecystokinin octapeptide (CCK-8) binding to central nervous system receptors have been studied to assess the relative importance of the amino and the carboxyl end of the active peptide sequence, CCK-(26-33). The relative ability to inhibit equilibrium binding of [125I]CCK-33 to guinea pig cortical membranes was determined for a series of amino and carboxyl terminal fragments of CCK-8. While N-acetyl CCK-(26-29), N-acetyl CCK-(26-30) amide and N-acetyl CCK-(26-31) amide were inactive, the N-acetyl CCK-(26-32) amide fragment displayed binding to central receptors. Of the carboxyl terminal peptide fragments, both CCK-(29-33) and CCK-(30-33) bound less potently than CCK-8; CCK-(31-33) interacted more weakly than the tetra- and pentapeptide, but with a higher affinity to brain receptors than to peripheral receptors. The heptapeptide, CCK-(26-32) amide, and the tripeptide, CCK-(31-33), are known to antagonize CCK action at peripheral receptors. The heptapeptide bound to central receptors 25 times more potently than a known peripheral antagonist, dibutyryl cyclic GMP. Thus these peptides may act centrally to oppose CCK-8 mediated functions.

Amino Acid Sequence↗
PubMed1984

Blood pressure control in pregnant rabbits: norepinephrine and prostaglandin interactions.

The relationship between norepinephrine (NE) and prostaglandins in the regulation of systemic blood pressure during pregnancy was examined in conscious rabbits. The arterial prostaglandin E2 (PGE2) concentration was higher in pregnant than in nonpregnant rabbits. Resting blood pressure was slightly lower in the gravid animals. The pressor response to incremental doses of intravenous NE was blunted in the pregnant rabbits. Meclofenamate, a cyclooxygenase inhibitor, failed to alter the resting blood pressure in either group of animals, although it reduced PGE2 levels more than 60% in the pregnant rabbits. The pressor response to NE was significantly increased only in the pregnant rabbits when the NE infusion was repeated following meclofenamate. Pregnant rabbits could also be differentiated from nonpregnant by their higher peripheral blood levels of NE and their uniform hypotensive response to alpha-adrenergic blockade. These observations define an altered responsiveness to both endogenous and exogenous NE in pregnant rabbits that appears to be related to an increase in vasodilator prostaglandins.

Animals↗
PubMed1983

Inhibition of septal hyperreactivity by testosterone and its reversion by an estrogen antagonist in weanling female rats.

Neonatal administration of testosterone inhibits emotional hyperreactivity to capture and tactile stimulation in female rats following septal lesions at 25 days of age. Testosterone, an aromatizable androgen, after metabolization to estrogen interacts with estrogen receptors in neonatal rat brain. In order to investigate whether the testosterone inhibited septal hyperreactivity via estrogen receptors rats were tested after pretreatment with the estrogen receptor antagonist tamoxifen. Weanling female rats pretreated with tamoxifen showed emotional hyperreactivity, while androgenized females showed no change. In addition, estradiol benzoate, neonatally administered, was able to inhibit emotional reactivity displayed after septal lesions. These results suggest that the action of testosterone on septal hyperreactivity might be mediated by estrogen receptors.

Animals↗
PubMed1983

Auditory processing and language impairment in children: stimulus considerations for intervention.

Two experiments were undertaken to examine the performance of language-impaired children on auditory identification and sequencing tasks which employed different stimuli. The purpose of Experiment I was to determine if introduction of linguistic stimuli (words) into tasks using nonlinguistic stimuli (complex tones) would change subjects' performance. Experiment II was designed to measure differences in response when words and tones were presented separately. Responses to utterances of increasing length (up to four words) were also measured. Results indicated that some children performed significantly better when words were used as stimuli. No child responded better when tones were used as stimuli and there were no significant differences between utterances of different length. Based on these results and on the related literature, considerations for choice of stimuli for intervention with language-impaired children are discussed.

Auditory Perception↗
PubMed1983

Timed-release dihydroergotamine in the prophylaxis of mixed headache. A study versus amitriptyline.

A pharmacological trial has been carried out on 41 out-patients suffering from mixed headache. The prophylactic effect of a timed-release dihydroergotamine formulation was tested versus amitriptyline. Patients reported daily, on appropriate cards, the hours of headache and the degree of pain during the month before therapy and on the following two months of treatment. Whereas amitriptyline was found to be more effective than dihydroergotamine in reducing headache intensity, timed-release dihydroergotamine was found significantly more effective than amitriptyline in reducing attacks of "migraine" type.

Adolescent↗