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Biomedical subjects

A Pisani

Publications and source records attributed to A Pisani.

At least 127 records · Page 7Linked to original sources
PubMed1994

Post-receptor mechanisms underlying striatal long-term depression.

Extracellular and intracellular recordings were obtained from striatal neurons in a brain slice preparation in order to characterize the post-receptor mechanisms underlying striatal posttetanic long-term depression (LTD). Striatal LTD was blocked in neurons intracellularly recorded either with 1,2-bis (o-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid (BAPTA) or with EGTA, calcium (Ca2+) chelators. Intracellular injection of QX-314, a lidocaine derivative that has been shown to block voltage-dependent sodium channels, abolished action potential discharge and blocked striatal LTD. However, under this condition, striatal LTD was restored when, immediately before the delivery of the tetanus, the cell was depolarized at a membrane potential ranging between -30 mV and -20 mV by injecting continuous positive current. Nifedipine (10 microM), a blocker of voltage-dependent L-type Ca2+ channels, blocked striatal LTD. Nifedipine by itself altered neither cortically evoked EPSPs nor input resistance and firing properties of most of the recorded cells. Striatal LTD was also reduced or blocked by incubation of the slices in the presence of the following inhibitors of Ca(2+)-dependent protein kinases: staurosporine (10-50 nM), 1-(5-isoquinolinesulfonyl)-2- methylpiperazine (H-7; 10-50 microM), and calphostin C (1 microM). Our findings suggest that generation of striatal LTD requires a Ca2+ influx through voltage-dependent nifedipine-sensitive Ca2+ channels and a sufficient intracellular free Ca2+ concentration. Furthermore, this form of synaptic plasticity seems to involve the activation of Ca(2+)-dependent protein kinases. Different drugs, acting at receptor and/or post-receptor level, may affect this form of synaptic plasticity and might alter the formation of motor memory.

Action Potentials↗
PubMed1993

Heterogeneity of metabotropic glutamate receptors in the striatum: electrophysiological evidence.

In order to investigate the functional role of metabotropic glutamate receptors (mGluRs) in the striatum we performed extracellular and intracellular recordings from a corticostriatal brain slice preparation. The effects of L-2-amino-3-phosphopropionic acid (L-AP3), an antagonist of mGluRs, were studied both on long-term synaptic depression (LTD) and on presynaptic inhibition of excitatory postsynaptic potentials (EPSPs) induced by different agonists of mGluRs. L-AP3 produced a dose-dependent (3-30 microM) reduction of the LTD evoked in the striatum by the tetanic stimulation of the corticostriatal pathway. In contrast to this action, L-AP3 (10-100 microM) did not significantly affect the presynaptic inhibitory effect of 1-amino-cyclopentyl-trans-dicarboxylic acid (t-ACPD), an agonist of mGluRs, on corticostriatal transmission. Higher concentrations of L-AP3 (0.3-1 mM) reduced by themselves the EPSP amplitude. The inhibitory effect of t-ACPD on the cortically evoked EPSPs was mimicked either by the active stereoisomer 1S,3R-ACPD or by amino-4-phosphonobutyric acid (L-AP4), a glutamate autoreceptor agonist. In some neurons, these inhibitory actions were coupled with membrane depolarizations. The depression of synaptic transmission caused by t-ACPD, 1S,3R-ACPD and L-AP4 was not altered following the induction of LTD. Chronic lithium treatment of the animals (60-120 mg/kg i.p. for 10 days) blocked striatal LTD but not presynaptic inhibition mediated by mGluR agonists. The present findings show that the mechanisms underlying LTD and the presynaptic inhibition induced by different agonists of mGluRs exhibit functional and pharmacological differences. These data suggest heterogeneity of mGluRs in the striatum.

Alanine↗
PubMed1993

Peripherin, a neuronal intermediate protein, is stably expressed by neuroendocrine carcinomas of the skin, their xenograft on nude mice, and the corresponding primary cultures.

The histogenesis of neuroendocrine carcinomas of the skin is still controversial. To determine the degree of neural differentiation of these neoplasias, we studied the expression of intermediate filament proteins in tumoral tissues. Expressions of peripherin, the neurofilament protein NF-L, vimentin, and cytokeratin 8 were analyzed by immunohistochemical methods on 12 human primary tumors and 3 tumor xenografts on nude mice. Peripherin was detected in 10 primary tumors by immunofluorescence. The protein and the corresponding messenger RNA were identified by two-dimensional gel electrophoresis and Northern analysis in extracts of an immunofluorescence-negative tumor. Peripherin, NF-L, and cytokeratin 8 were detected in tumoral cells, whereas vimentin was found exclusively in the stroma. The histological and ultrastructural properties of the original cells of neuroendocrine carcinomas of the skin, as well as coexpression of peripherin, cytokeratin 8, and neurofilament polypeptides, were preserved in tumor xenografts and their primary cultures in vitro. These results bring new elements to the knowledge of the biology of neuroendocrine carcinomas of the skin and indicate that peripherin constitutes a marker for tumor identification.

Animals↗
PubMed1993

Lithium treatment blocks long-term synaptic depression in the striatum.

We have studied the effect of acute and chronic lithium treatment on the activity of striatal neurons recorded from corticostriatal slices. Under control conditions, tetanic stimulation of glutamatergic corticostriatal terminals caused long-term depression (LTD) of excitatory synaptic potentials. Acute lithium treatment did not affect the peak of the induction phase, but it reduced the following phases of LTD. LTD was completely blocked in slices obtained from rats chronically injected with LiCl. Lithium treatment failed to affect the intrinsic membrane properties of striatal neurons and the presynaptic inhibitory effects of carbachol and t-ACPD. We suggest that the lithium-induced blockade of LTD may contribute to the therapeutic action of lithium salts in mania and depression.

Animals↗
PubMed1993

Production of basement membrane components by a reconstructed epidermis cultured in the absence of serum and dermal factors.

A fully differentiated epithelium displaying features of human epidermis was obtained in vitro by culturing second-passage normal human keratinocytes for 14 days in defined medium and on an inert polycarbonate filter substratum at the air-liquid interface. Vertical sections stained for histology and indirect immunofluorescence studies showed that the 'basal' cells synthesize and secrete all major markers of hemidesmosomes and the lamina lucida. Components of the lamina densa are also expressed. Collagen VII is synthesized, but not secreted. Ultrastructural studies showed the presence of hemidesmosomes with major dense plaques and anchoring filaments, and a basement membrane-like structure was clearly identified. These results show that epidermal cells are able to produce hemidesmosomes and to secrete the major components of the dermo-epidermal junction in the absence of serum and dermal factors, suggesting that basement membrane synthesis and hemidesmosome assembly are not dependent on the presence of dermis.

Basement Membrane↗
PubMed1993

[Obstruction of the Le Veen shunt: a new surgical solution].

The authors propose an alternative which has been proved valid in four cases of peritoneovenous shunt with an occluded Le Veen valve for venous thrombosis implanted in cirrhotic patients with refractory ascites. After having explored the various possibilities using the vessels adjacent to the superior cava branch, the authors resolved the problem of reimplanting the valve by using an access route through the saphenous vein and inferior vena cava. Using this technique it was possible to reactivate the shunt with a marked improvement in the recurrent ascitic state and above all shunt functionality, and consequently in the clinical conditions and quality of life of these patients.

Equipment Failure↗
PubMed1992

Lethal junctional epidermolysis bullosa with normal expression of BM 600 and antro-pyloric atresia: a new variant of junctional epidermolysis bullosa?

A newborn girl is described with a lethal junctional epidermolysis bullosa (Herlitz form) (JEB) associated with a congenital localized absence of skin, and a pyloric atresia (PA). The post-mortem examination of the digestive tract showed a widespread cleavage between the epithelium and the chorion. Immunohistological and electron microscopical examination showed a cleavage occurring through the lamina lucida of the digestive basement membrane, as for the skin blisters. Despite the lethal character of this form of JEB, the BM 600 glycoprotein was normally recognized at the dermo-epidermal junction by the monoclonal antibody GB3. This rare association of lethal JEB-PA-localized absence of skin, with a quite unusual GB3 positive immunophenotype could correspond to a new variant of JEB.

Antibodies, Monoclonal↗
PubMed1992

Blood-brain barrier dysfunctions following systemic injection of kainic acid in the rat.

Changes in blood-brain barrier (BBB) permeability and cerebral metabolic activity following intravenous injection of kainic acid (KA; 6, 12 mg/Kg) in rats were assessed by calculating respectively a blood-to-brain transfer constant (Ki) for [14C]alpha-aminoisobutyric acid and local cerebral glucose utilization (LCGU) values, at different times (1 h, or acute seizures phase, and 48 h, or chronic pathology phase) after the induction of seizures. A significant increase in the local permeability of the BBB was observed 1 h after the injection of KA 6 mg/Kg (eliciting no significant changes in cerebral metabolic activity, except within the frontal cortex and the hippocampus) and 12 mg/Kg (which induced a marked and widespread enhancement of LCGU). On the contrary, during the pathology phase, persistent regional increases in Ki values were evidenced in rats treated with the lowest dose of the convulsant, but not in rats injected with KA 12 mg/Kg (a dose able to cause extensive neuronal damage). Thus one can speculate that: 1) KA-induced regional changes in the permeability of the BBB are not correlated with changes in neuronal activity; 2) opening of the BBB is not reliably associated with neuronal injury.

Aminoisobutyric Acids↗
PubMed1992

Increased expression of tenascin in the dermis in scleroderma.

The expression of tenascin, a recently discovered extracellular matrix protein, was studied by immunohistochemical techniques in scleroderma skin and compared with its distribution in normal skin. In progressive systemic sclerosis, a marked increase in tenascin content was observed in the superficial reticular dermis. In localized scleroderma, the deposition of tenascin was increased both in the superficial and deep dermis of involved skin, whereas in clinically uninvolved skin the distribution of tenascin was the same as in normal control skin, i.e. the papillary dermis and peri-appendiceal zone. The distribution of tenascin did not strictly parallel that of fibronectin. These findings and the current knowledge of tenascin biology suggest that the overproduction of tenascin in scleroderma dermis could be secondary to stimulation of fibroblasts by immune cell-derived cytokines, or could be due to abnormal fibroblasts, or a subpopulation of fibroblasts, producing high levels of this extracellular matrix protein.

Adult↗
PubMed1992

The 6/2 (AA3) polyclonal antibody identifying a 37 kD keratinocyte protein reacts also with BM-600/nicein, the basement membrane component bound by the monoclonal antibody GB3.

An unexpected finding concerning our previously reported polyclonal antibody raised against an extract from human amnion (pAb 6/2, also termed AA3), and which recognizes an epidermal keratinocyte protein, is presented in this study. Using the immunoblot technique, pAb 6/2 binds to a 37 kD intracellular protein antigen. We have subsequently found that, by radioimmunoprecipitation performed after metabolic labelling with 35S-methionine of cultured keratinocytes, pAb 6/2 recognizes the 600 kD epidermal basement membrane component (termed BM-600/nicein) which was reported to be bound by the monoclonal antibody mAb GB3. Specifically, pAb 6/2 reacts with immunoaffinity chromatography-isolated BM-600/nicein blotted onto nitrocellulose. The data suggest the existence of two immunological reactivities borne by pAb 6/2, each of them being directed against, respectively, the 37 kD (seen in immunoblots) and the 600 kD protein (seen in immunoprecipitations). The data further suggest possible independent expression of these two proteins in cell culture. In comparison with the staining pattern of normal skin, immunofluorescence was previously noted to be impaired (pAb 6/2) or absent (mAb GB3) in lethal junctional epidermolysis bullosa. Thus, we conclude that mAb GB3, rather than pAb 6/2, is a more appropriate probe for the comprehensive biochemical study of this genodermatosis.

Antibodies↗
PubMed1992

Kalinin is abnormally expressed in epithelial basement membranes of Herlitz's junctional epidermolysis bullosa patients.

Kalinin is an extracellular adhesion molecule specific to epithelial basement membranes (BM) identified as a component of anchoring filaments of hemidesmosomes. This heterotrimeric protein is synthesized by cultured normal human keratinocytes and is involved in cell attachment. In indirect immunofluorescence studies, the epidermal BM of patients with junctional epidermolysis bullosa (JEB) of Herlitz's type were found not to be reactive with the anti-kalinin monoclonal antibodies ka146 and K140 and displayed a decreased immunoreactivity to two anti-kalinin antibodies cross-reacting with K-laminin, an anchoring filament component recently described. The intrinsic defect of JEB keratinocytes in the synthesis of kalinin was further documented by indirect immunofluorescence on in vitro cultures of these cells. In non-Herlitz JEB patients, staining of BM was constantly detected. Impairment of expression of kalinin correlated with the lack of reactivity to the monoclonal antibody GB3, which detects the BM component nicein/BM600. These results clearly demonstrate a defect of kalinin expression in epithelial basement membranes of Herlitz JEB patients and suggest that kalinin may play a role in the pathogenesis of the disease. Further studies are in progress to define possible relationships between kalinin and nicein.

Basement Membrane↗
PubMed1992

Long-term synaptic depression in the striatum: physiological and pharmacological characterization.

The effect of tetanic activation of corticostriatal glutamatergic fibers was studied in striatal slices by utilizing extracellular and intracellular recording techniques. Tetanic stimulation produced a long-term synaptic depression (LTD) (> 2 h) of both extracellularly recorded field potentials and intracellularly recorded EPSPs. LTD was not coupled with changes of intrinsic membrane properties of the recorded neurons. In some neurons, repetitive cortical activation produced a short-term posttetanic potentiation (1-3 min). Subthreshold tetanic stimulation, which under control condition did not cause LTD, induced LTD when associated with membrane depolarization. Moreover, LTD was not expressed in cells in which the conditioning tetanus was coupled with hyperpolarization of the membrane. Bath application of aminophosphonovalerate (30-50 microM), an antagonist of NMDA receptors, did not affect the amplitude of the synaptic potentials and the expression of LTD. Striatal LTD was significantly reduced by the pretreatment of the slices with 30 microM 2-amino-3-phosphonopropionic acid, an antagonist of glutamate metabotropic receptors. LTD was not blocked by bicuculline (30 microM), a GABA(A) receptor antagonist. Scopolamine (3 microM), an antagonist of muscarinic receptors, induced a slight, but significant, increase of the amplitude of LTD. Both SCH 23390 (3 microM), an antagonist of D1 dopamine (DA) receptors, and I-sulpiride (1 microM), an antagonist of D2 DA receptors, blocked LTD. LTD was also absent in slices obtained from rats in which the nigrostriatal DA system was lesioned by unilateral nigral injection of 6-hydroxydopamine. In DA-depleted slices, LTD could be restored by applying exogenous DA (30 microM) before the conditioning tetanus. In DA-depleted slices, LTD could also be restored by coadministration of SKF 38393 (3-10 microM), a D1 receptor agonist, and of LY 171555 (1-3 microM), a D2 receptor agonist. Application of a single class of DA receptor agonists failed to restore LTD. These data show that striatal LTD requires three main physiological and pharmacological conditions: (1) membrane depolarization and action potential discharge of the postsynaptic cell during the conditioning tetanus, (2) activation of glutamate metabotropic receptors, and (3) coactivation of D1 and D2 DA receptors. Striatal LTD may alter the output signals from the striatum to the other structures of the basal ganglia. This form of synaptic plasticity can influence the striatal control of motor activity.

2-Amino-5-phosphonovalerate↗
PubMed1991

Anatomical mapping of Merkel cells in normal human adult epidermis.

The distribution of Merkel cells (MCs) in normal human skin and mucosa was studied using the mouse monoclonal antibody Troma-1, reacting specifically with component 8 of the Moll cytokeratin catalogue. The specificity of this antibody for MCs in human skin was assessed by double indirect immunofluorescence (IIF) and immunoelectron microscopy. Two-hundred and thirty 6-mm punch biopsies were obtained from 44 different sites from six human cadavers within 48 h post-mortem. IIF was performed with Troma-1 on EDTA-split epithelial sheets and the MCs were counted and the mean values per mm2 calculated for each site. Regions with greater than 50 MC/mm2 were the lips, hard palate, palms, finger pads, proximal nail fold, and dorsum of the feet. Three different patterns were observed in the epidermis or mucosa: MCs grouped in clumps, linear and arciform arrangements, and scattered MCs. In the hair follicles grouped MCs were observed in the bulb and scattered MCs were seen in the outer root sheath.

Adult↗
PubMed1991

Monoclonal antibody GB3 defines a widespread defect of several basement membranes and a keratinocyte dysfunction in patients with lethal junctional epidermolysis bullosa.

An antigen expressed at the dermal-epidermal junction as well as in some other human basement membranes (BM) has been detected by the use of a monoclonal antibody termed GB3. This antigen, synthesized by cultured normal human keratinocytes, has been identified as a 600-kilodalton glycoprotein different from other known components of BM. Using indirect immunofluorescence, GB3 was found to be not reactive with the epidermal BM in patients with lethal junctional epidermolysis bullosa. The present study demonstrates (by indirect immunofluorescence) that GB3 defines a widespread defect of several BM in these patients. Furthermore, it gives evidences for an intrinsic biologic defect of lethal junctional epidermolysis bullosa epidermal keratinocytes using in vitro culture of these cells. Whether the lack of GB3 reactivity is the consequence of a true absence of the antigen or an alteration of its molecular structure is not yet known. Nevertheless, GB3 is a useful probe for both rapid and prenatal diagnosis of lethal junctional epidermolysis bullosa, which will give new insights into the molecular comprehension of this disorder.

Antibodies, Monoclonal↗
PubMed1990

Flecainide excretion in human breast milk.

Healthy human volunteers who intended not to breast feed were placed on a regimen of 100 mg oral flecainide every 12 hours for 5 1/2 days beginning 1 day after parturition. Milk and blood samples were collected during the dosing period and for 2 days after the last dose. Concentrations of flecainide in milk and plasma were assayed by HPLC. Apparent steady-state levels of flecainide in both milk and plasma were achieved in most cases by day 4 of the study. Highest daily average concentration of flecainide in milk ranged from 270 to 1529 ng/ml for the 11 subjects. Mean +/- SD milk to plasma flecainide ratios were 3.7 +/- 3.5, 3.2 +/- 2.3, 3.5 +/- 2.1, and 2.6 +/- 0.7 on study days 2, 3, 4, and 5, respectively. After the last dose of flecainide, peak milk levels of the drug occurred at 3 to 6 hours and then declined monoexponentially. The half-life for elimination of flecainide from milk was 14.7 +/- 3.5 hours and is very similar to the plasma elimination half-life of flecainide in healthy human subjects. The mean milk to plasma ratios for flecainide after the last dose were 2.3 +/- 1.0 and 2.9 +/- 1.1 at 24 and 48 hours after the dose, respectively. Based on the pharmacokinetics of flecainide in infants, the expected average steady-state plasma concentration of flecainide in a newborn infant consuming all of the milk production of its mother (approximately 700 ml/day) would not be expected to exceed about 62 ng/ml.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗