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Biomedical subjects

L Pieri

Publications and source records attributed to L Pieri.

At least 19 recordsLinked to original sources
PubMed1991

[The continent perineal colostomy after abdominoperineal resection of the rectum. A digital defecographic study].

For 10 years, in the Surgery Dept. of the University of Pisa, perineal colostomies have been performed on patients who had undergone abdominoperineal rectal amputation. The gracilis muscles of the thighs, transposed to the perineum, are used for building a continent muscular apparatus. Seventeen of 40 patients operated with this procedure have been submitted to defecographic studies, by means of digital fluoroscopic image acquisition. This modality allowed the visualization of anastomotic colon morphology as well as of the functionality of the transposed gracilis muscles during the various phases of defecography. The muscle surrounding the colostomy acts as a sphincter and relaxes only during evacuation; the one positioned as a sling acts as the normal puborectalis muscle. In two patients a perineocele was documented, causing problems in the evacuation phase, which were solved after surgical intervention.

Colostomy↗
PubMed1990

Physical dependence induced in DBA/2J mice by benzodiazepine receptor full agonists, but not by the partial agonist Ro 16-6028.

Continuous administration of triazolam, alprazolam or diazepam for a 7-day period by means of minipumps or chronic (17 days) p.o. treatment with alprazolam induced clear physical dependence in DBA/2J mice as assessed by precipitation of a withdrawal syndrome with an i.v. injection of the benzodiazepine receptor partial inverse agonist Ro 15-3505. In contrast, no precipitated withdrawal signs were observed following chronic exposure to high doses of the benzodiazepine receptor partial agonist Ro 16-6028. The use of minipumps and precipitation with a benzodiazepine receptor antagonist permits a simple and rapid evaluation of the physical dependence liability of potent compounds acting at the benzodiazepine receptor. Furthermore, these results support the hypothesis that benzodiazepine receptor partial agonists are less likely to induce physical dependence than full agonists.

Administration, Oral↗
PubMed1990

In vitro and in vivo evaluation of iodine-123-Ro 16-0154: a new imaging agent for SPECT investigations of benzodiazepine receptors.

The flumazenil analogue, Ro 16-0154, a benzodiazepine partial inverse agonist, has been labeled by halogen exchange to enable SPECT investigations of central benzodiazepine receptors in the human brain. The purified 123I-Ro 16-0154 was found to be stable in rat brain preparations and to be metabolized in rat liver preparations. Its pharmacologic properties were comparable to those of flumazenil. The biodistribution in rats (1 hr postinjection) resulted in a high brain-to-blood ratio of 16. Clinical studies revealed images of the benzodiazepine receptor density in the brain. Since the receptor labeling was markedly reduced by injection of flumazenil, it was considered to be specific. Storage defects due to pathologic cerebral blood flow and changed receptor density were detected; this shows the potential usefulness of the substance for diagnostic purposes, e.g., the differential diagnosis of various forms of epilepsy.

Animals↗
PubMed1989

Convulsions induced by centrally administered NMDA in mice: effects of NMDA antagonists, benzodiazepines, minor tranquilizers and anticonvulsants.

1. Convulsions were induced reproducibly by intracerebroventricular injection of N-methyl-D-aspartic acid (NMDA) to conscious mice. 2. Competitive (carboxypiperazine-propylphosphonic acid, CPP; 2-amino-7-phosphonoheptanoic acid, AP7) and non-competitive (MK801; phencyclidine, PCP; thienylcyclohexylpiperidine, TCP; dextrorphan; dextromethorphan) NMDA antagonists prevented NMDA-induced convulsions. 3. Benzodiazepine receptor agonists and partial agonists (triazolam, diazepam, clonazepam, Ro 16-6028), classical anticonvulsants (diphenylhydantoin, phenobarbitone, sodium valproate) and meprobamate were also found to prevent NMDA-induced convulsions. 4. Flumazenil (a benzodiazepine receptor antagonist) and the GABA agonists THIP and muscimol (up to subtoxic doses) were without effect. 5. Flumazenil reversed the anticonvulsant action of diazepam, but not that of MK801. 6. Results obtained in this model differ somewhat from those described in a seizure model with systemic administration of NMDA. An explanation for this discrepancy is offered. 7. This model is a simple test for assessing the in vivo activity of NMDA antagonists and also expands the battery of chemically-induced seizure models for characterizing anticonvulsants not acting at NMDA receptors.

Animals↗
PubMed1989

[Digital videoradiography applied to the study of stress urinary incontinence in women].

A digital videofluoroscopic unit was employed to evaluate 42 female patients with urinary stress incontinence, cystocele or endometrial neoplasms, using either voiding cystourethrography or colpo-cysto-urethrorectography (CCURG), with or without urethral metallic bead chain. The digital subtraction technique allowed the direct visualization (on a single frame) of the lowering of both bladder base and other pelvic structures, and of the modification of urethral angles during Valsalva and micturition. The demonstration of contrasted urethra during micturition and Valsalva in incontinent patients allowed CCURG to be performed without urethral chain, with encouraging diagnostic accuracy. The advantages of digital CCURG are emphasized.

Algorithms↗
PubMed1988

Ro 15-4513: partial inverse agonism at the BZR and interaction with ethanol.

The imidazobenzodiazepinone derivative Ro 15-4513 has the activity profile of a partial inverse (low efficacy) agonist at the benzodiazepine receptor (BZR). It reverses central nervous depressant effects of diazepam, and, in part, of phenobarbitone and ethanol in mice, rats and cats in behavioural, electrophysiological, and neurochemical paradigms. The interaction of Ro 15-4513 with barbiturates and ethanol is due to its inverse agonistic (negative allosteric modulatory) property at the BZR, as it was reversed by the selective BZR blocker flumazenil (Ro 15-1788). In the present experiment situations, other BZR partial inverse agonists in subconvulsant or overt convulsant doses were less effective against ethanol effects than Ro 15-4513. Possible mechanisms for this differential activity of BZR inverse agonists are discussed.

Animals↗
PubMed1988

Effects of an intrathecally administered benzodiazepine receptor agonist, antagonist and inverse agonist on morphine-induced inhibition of a spinal nociceptive reflex.

1. The effects of an intrathecally administered benzodiazepine receptor (BZR) agonist (midazolam, up to 50 micrograms), antagonist (flumazenil, Ro 15-1788, 5 micrograms) and inverse agonist (Ro 19-4603, 15 micrograms) on nociception and on morphine-induced antinociception were studied in rats. 2. By themselves, none of these compounds significantly altered pain threshold. 3. The BZR agonist midazolam enhanced the morphine-induced antinociceptive effect whereas the antagonist flumazenil did not alter it. In contrast, the BZR inverse agonist Ro 19-4603 decreased the morphine-induced antinociceptive effect. 4. Naloxone (1 mg kg-1 i.p.) completely reversed all these effects. 5. These results demonstrate that BZR agonists and inverse agonists are able to affect, by allosteric up- or down-modulation of gamma-aminobutyric acidA (GABAA)-receptors, the transmission of nociceptive information at the spinal cord level, when this transmission is depressed by mu-opioid receptor activation.

Animals↗
PubMed1988

[Digital radiology in the study of the lacrimal ducts].

The authors emphasize the usefulness of digital dacryocystography (DCG), as compared with various current techniques. Utilizing a radiographic unit equipped with a video-fluoroscopic system and interfaced to a digital video-processor, several digitalized images are acquired before, during and after the injection of contrast medium. Final images are obtained by subtraction of suitable pairs of source frames. Twenty-six patients affected by epiphora have been examined so far. In 21 cases digital subtraction DCG allowed an accurate visualization of the lacrimal system; in the other five patients the amount of information was acceptable. This methodology allows the assessment of both the normal anatomy of the lacrimal passages and their pathological patterns, such as obstructions, stenoses, fistulas, chronic dacryocystitis, lacrimal stones. The examination is easy and quick to perform, with no discomfort for the patient. Digital subtraction DCG proves thus to be a very valuable technique thanks to its possible electronic elaboration--i.e. the subtraction and the magnification of images--to its better contrast resolution, and to the possibility it yields of dynamic studies under radioscopic control.

Humans↗
PubMed1986

L-cycloserine: behavioural and biochemical effects after single and repeated administration to mice, rats and cats.

L-Cycloserine dose-dependently inhibited the activity of gamma-aminobutyric acid (GABA)-transaminase (GABA-T) and elevated the level of GABA in whole mouse brain with a peak effect 3-4 hr after a single intraperitoneal injection. At a dose (30 mg/kg) which elevated the level of GABA almost 4-fold, L-cycloserine moderately increased the content of alanine and slightly reduced that of aspartate, glutamate and glycine in the brain. L-Cycloserine (10-30 mg/kg, p.o. or i.p.) prevented tonic seizures induced by 3-mercaptopropionic acid (3-MPA) and audiogenic seizures in DBA/2 mice, without affecting those evoked by pentylenetetrazol, bicuculline and electroshock. Similarly small doses of L-cycloserine reduced the level of cGMP in the cerebellum of rats, prevented its elevation by 3-MPA and attenuated the hypothalamically-elicited rage reaction in cats. Larger doses of L-cycloserine (greater than 30-100 mg/kg) impaired the performance of mice in the rotarod, chimney and horizontal wire tests, and reduced spontaneous locomotor activity of rats. Upon repeated administration the inhibitory effect of L-cycloserine on the activity of GABA-T and on seizures elicited by 3-MPA in mice increased. In contrast, the depressant action of L-cycloserine on motor performance and locomotion declined in subchronically-treated mice and rats. The levels of amino acids in brain after repeated administration did not differ markedly from those in acutely-treated mice. It is suggested that small doses of L-cycloserine, probably by increasing GABAergic inhibition, reduce hyperexcitability in the brain in acute- and subchronically-treated animals. Larger doses of L-cycloserine, possibly by inducing multiple neurochemical changes, evoke central depressant effects which diminish during subchronic treatment.

4-Aminobutyrate Transaminase↗
PubMed1985

Isoniazid-induced convulsions in rats: effects of Ro 15-1788 and beta-CCE.

Dose-response curves for the convulsant effect of isoniazid were determined in male rats. The specific benzodiazepine antagonist Ro 15-1788, at doses from 20 to 100 mg/kg i.v. or at 300 mg/kg p.o., failed to produce any relevant shift of the isoniazid dose-response curves to the left (proconvulsant) or to the right (anticonvulsant). In contrast, the benzodiazepine receptor ligand ethyl-beta-carboline-3-carboxylate (beta-CCE) 10 mg/kg i.v. produced a clear-cut shift to the left of the isoniazid dose-response curve. Ro 15-1788 was inactive up to high p.o. or i.v. doses, versus convulsions induced by a low supraliminal dose of isoniazid, whereas beta-CCE had a significant proconvulsant effect beginning at 5 mg/kg i.v. This effect of beta-CCE was dose dependently antagonized by Ro 15-1788. In conclusion, in the present experimental conditions Ro 15-1788 showed no inverse agonistic properties at benzodiazepine receptors, in contrast to beta-CCE.

Animals↗
PubMed1976

The effect of diphenylhydantoin, diazepam and clonazepam on the activity of Purkinje cells in the rat cerebellum.

Spike discharges of single cerebellar Purkinje cells were recorded continuously with extracellular microelectrodes in unanesthetized curarized rats. The intravenous injection of diphenylhydantoin in doses between 10 and 100 mg kg-1 did not substantially alter the activity of Purkinje cells within 2--3 h. The two benzodiazepines, diazepam and clonazepam, already in low i.v. doses (0.03--0.1 mg kg-1) consistently and reversibly depressed the firing rate. Our results do not support the previously advanced hypothesis that these drugs reduce epileptiform activities by increasing the output from the cerebellar cortex. They rather point to the possibility that a reduced firing rate of cerebellar Purkinje cells mediates at least in part ataxia and muscular hypotonia observed after the drugs.

Action Potentials↗