Biomedical subjects

F Conti

Publications and source records attributed to F Conti.

At least 109 records · Page 6Linked to original sources

PubMed1996

GAT-3, a high-affinity GABA plasma membrane transporter, is localized to astrocytic processes, and it is not confined to the vicinity of GABAergic synapses in the cerebral cortex.

The termination of GABA synaptic action by high-affinity, Na(+)-dependent, neuronal, and glial plasma membrane transporters plays an important role in regulating neuronal activity in physiological and pathological conditions. We have investigated the cellular localization and distribution in the cerebral cortex of adult rats of one GABA transporter (GAT), GAT-3, by immunocytochemistry with affinity-purified polyclonal antibodies directed to its predicted C terminus that react monospecifically with a protein of approximately 70 kDa. Light microscopic studies revealed specific GAT-3 immunoreactivity (ir) in small punctate structures, and it was never observed in fibers or cell bodies. No changes in immunostaining were observed in sections incubated with GAT-3 antibodies preadsorbed with the related rat GAT-1 or mouse GAT-2/ BGT-1 C-terminal peptides, whereas in sections incubated with GAT-3 antibodies preadsorbed with rat GAT-3 C-terminal peptide, ir was not present. The highest number of GAT-3-positive puncta was in layer IV and in a narrow band corresponding to layer Vb, followed by layers II and III. Many GAT-3-positive puncta were in close association with pyramidal and nonpyramidal neuron cell bodies. Ultrastructural studies showed that GAT-3 ir was localized exclusively to astrocytic processes, which were found in the neuropil and adjacent to axon terminals having either symmetric or asymmetric specializations. In sections processed by both preembedding labeling for GAT-3 and postembedding immunogold labeling for GABA, only some of the GAT-3-positive astrocytic processes were found close to GABAergic profiles. These findings on the localization of GAT-3 in the cerebral cortex indicate that this transporter mediates GABA uptake into glial cells, and suggest that glial GABA uptake may function to limit the spread of GABA from the synapse, as well as to regulate overall GABA levels in the neuropil.

Animals↗

PubMed1996

Comparison between aortic and sinusoidal liver endothelial cells as targets of hyperacute xenogeneic rejection in the pig to human combination.

Endothelial cells of aortic origin are usually used in vitro as targets of hyperacute xenogeneic rejection, although endothelial cells from organs may have different properties. The sensitivities of aortic and liver endothelial cells to hyperacute xenogeneic rejection were compared in the pig to human combination. Sinusoidal liver endothelial cells were isolated and purified by collagenase perfusion of pig livers, sedimentation on a percoll gradient and selective adherence. Purity and viability of isolated liver endothelial cells after adherence were 85+/-6% and >95%, respectively. Endothelial cells from pig aortae (purity and viability >95%) were isolated by scraping. Immunoblotting analysis of xenoantigens on liver and aortic endothelial cell membranes preparations showed identical patterns. The strongest bands revealed by human IgM were located between 110 and 135 kD, while human IgG detected two major bands at 115 and 75kD. The membrane expression of xenoantigens recognized by human sera, analyzed by flow cytometry, was significantly lower on liver than on aortic endothelial cells (IgM: P=0.0006; IgG: P=0.0009). However, the complement-dependent cytotoxic activity of human sera was the same whether liver (54.5+/-1.4%) or aortic endothelial cells (50.0+/-4.2%) were used as targets. Taken together, those results allow the use of aortic instead of sinusoidal liver endothelial cells in the characterization of pig antigens recognized by human natural antibodies.

Acute Disease↗

PubMed1996

Changes in glutamate immunoreactivity in the somatic sensory cortex of adult monkeys induced by nerve cuts.

Antibodies to glutamate (Glu) were used to study the effects of reduced afferent input on excitatory neurons in the somatic sensory cortex of adult monkeys. In each monkey, immunocytochemical staining was compared to thionin and cytochrome oxidase (CO) staining in adjacent sections. In the cervical spinal cord, dorsal column nuclei, ventroposterior thalamus, and primary somatic sensory cortex (SI), Glu immunoreactivity (Glu-ir) was analogous to that described in normal animals; regions with reduced or absent Glu-ir were never observed and no appreciable differences were noted between the experimental and normal side. There were also no differences in CO or thionin-stained sections from the affected hemisphere. In the insuloparietal operculum, sections in the hemisphere contralateral to the nerve cut showed that most cortical fields had a normal pattern of Glu-ir (pattern a), some exhibited a reduction of Glu-ir (pattern b), and that in the central portion of the upper bank of the central sulcus, which corresponds to the general location of the hand representation of the second somatic sensory cortex (SII), Glu-ir had virtually disappeared (pattern c). Adjacent sections processed for CO or stained with thionin showed that in the regions corresponding to those characterized by pattern c, CO was slightly decreased and that glial cells had increased in number. In the regions of SII characterized by pattern c, small intensely stained glial cells displayed Glu-ir. These findings indicate that Glu-ir is regulated by afferent activity and suggest that changes in Glu levels in neurons as well as in glial cells may trigger the biochemical processes underlying the functional and structural changes occurring during a slow phase of reorganizational plasticity in the cerebral cortex of adult monkeys.

Afferent Pathways↗

PubMed1996

Expression of NR1 and NR2A/B subunits of the NMDA receptor in cortical astrocytes.

Ionotropic glutamate (Glu) receptors of the N-methyl-D-aspartate type (NMDA) play a fundamental role in many cortical functions. Native NMDA receptors are composed of a heteromeric assembly of different subunits belonging to two classes: NMDAR1 (NR1) and NMDAR2 (NR2). To date, NMDA receptors are believed to be expressed only in neurons, although electrophysiological and in situ hybridization studies have suggested that this class of Glu receptors might be also expressed by some astrocytes. In this study, we have investigated in the cerebral cortex of adult rats the presence of astrocytes expressing NR1 and NR2A/B subunits by immunocytochemistry with specific antibodies, and we show that some distal astrocytic processes, but only rarely astrocytic cell bodies, contain immunoreaction product indicative of NR1 and NR2A/B expression. These findings suggest that at least part of the role NMDA has in cortical functions might depend on the activation of astrocytic NMDA receptors; the subcellular localization of NR1 and NR2A/B subunits in distal processes suggests that NMDA receptors contribute to monitoring Glu levels in the extracellular space.

Animals↗

PubMed1996

Accumulation of long-lasting inactivation in rat brain K(+)-channels.

We studied the phenomenon of cumulative inactivation in the voltage-dependent K+ channels of the Shaker-related subfamily Kv1 cloned from rat brain and expressed in Xenopus oocytes. In Kv1.4, repetitive stimulations at intervals shorter than 20 s produce cumulative inactivation even for brief stimuli that elicit K+ currents which do not show any significant decline during the depolarising pulse. These effects are absent or greatly reduced in the clones Kv1.1, Kv1.3, Kv1.5 and Kv1.6, and in the deletion mutant Kv1.4-delta-110, characterised by lack of "fast" (N-type) inactivation. We find that the inactivation caused by a single pulse increases after the pulse while the channels deactivate, and subsides with two time constants, indicating the existence of (at least) two inactivated states: IS, with a slow recovery kinetics and IF, with faster kinetics. In the simplest kinetic scheme accounting for our observations, IF is coupled sequentially to the open state O, while IS can be reached at a fast rate both from IF and from a pre-open, activated state, A, that is in fast equilibrium with O. The accumulation of long-lasting inactivation during the repolarisation is favoured by the prolongation of the lifetime of activated states due to the presence of IF. This explains the smaller accumulation effect observed in channels lacking fast inactivation. The physiological implications of these findings suggest how different channels of the Kv1 subfamily can affect differently the firing behaviour of neurones.

Animals↗

PubMed1996

Role and operative risk of bilateral adrenalectomy in hypercortisolism.

Transsphenoidal pituitary surgery has radically modified the management of pituitary-dependent hypercortisolism (Cushing's disease). Bilateral adrenalectomy may, however, represent the ultimate treatment in some cases of hypercortisolism. In the present study we report our experience of bilateral adrenalectomy in 82 patients operated on during the last 15 years. The causes of hypercortisolism were Cushing's disease (n = 78), ectopic ACTH syndrome (n = 3), and primary adrenocortical nodular dysplasia (Carney-Meador syndrome) (n = 1). Before operation 37% of the patients had severe symptoms of hypercortisolism. A bilateral posterior approach was undertaken in 58 patients, whereas 18 patients had an anterior transabdominal approach and 6 patients a laparoscopic approach. There were two operative deaths (2.4%). Postoperative complications occurred mostly in cases of advanced disease and were observed in 14 patients (17%), among whom 4 had severe complications. At long-term follow-up, one recurrence of hypercortisolism and 12 Nelson syndromes (15%) were observed. In conclusion, bilateral adrenalectomy carries an acceptable operative risk, and we recommend bilateral adrenalectomy rather than long-term suppressive therapy in patients requiring prompt and definitive control of their hypercortisolism or after pituitary surgery failure.

ACTH Syndrome, Ectopic↗

PubMed1996

Use dependence of tetrodotoxin block of sodium channels: a revival of the trapped-ion mechanism.

The use-dependent block of sodium channels by tetrodotoxin (TTX) has been studied in cRNA-injected Xenopus oocytes expressing the alpha-subunit of rat brain IIA channels. The kinetics of stimulus-induced extra block are consistent with an underlying relaxation process involving only three states. Cumulative extra block induced by repetitive stimulations increases with hyperpolarization, with TTX concentration, and with extracellular Ca2+ concentration. We have developed a theoretical model based on the suggestion by Salgado et al. that TTX blocks the extracellular mouth of the ion pore less tightly when the latter has its external side occupied by a cation, and that channel opening favors a tighter binding by allowing the escape of the trapped ion. The model provides an excellent fit of the data, which are consistent with Ca2+ being more efficient than Na+ in weakening TTX binding and with bound Ca2+ stabilizing the closed state of the channel, as suggested by Armstrong and Cota. Reports arguing against the trapped-ion mechanism are critically discussed.

Animals↗

PubMed1996

[Esophagectomy without thoracotomy: indications and our experience].

In this paper the Authors report their experience of Orringer operation in 12 patients with oesophageal cancer observed from 1978 to 1992, and stress the possibility to extend the indications to Akijama oesophagectomy without thoracotomy for the treatment of malignant tumors of the entire oesophagus.

Aged↗

PubMed1996

Eosinophil cationic protein serum levels and allergy in chronic fatigue syndrome.

Chronic fatigue syndrome (CFS) is a syndrome of uncertain etiopathogenesis characterized by disabling fatigue associated with a variable number of somatic and/or neuropsychologic symptoms. In patients with CFS, several immunologic abnormalities can be detected, including a higher prevalance of allergy. The aim of this study was to determine whether CFS patients, well studied for their allergy profile, show signs of eosinophil activation, as detectable by the measurement in serum of eosinophil cationic protein (ECP) levels. In 35 consecutive CFS outpatients (diagnosis based on the Centers for Disease Control case definition), ECP was measured in serum by a competitive enzyme immunoassay (ECP-FEIA kit, Kabi Pharmacia Diagnostics, Uppsala, Sweden). Fourteen disease-free subjects with no history of CFS or allergy were selected as controls. ECP serum levels were significantly higher in CFS patients than in controls (18.0 +/- 11.3 micrograms/l vs 7.3 +/- 2.1 micrograms/l; P < 0.01). In the CFS population, the prevalence of RAST positivity to one or more allergens was 77%, while no control showed positive RAST. Twelve of the 14 CFS patients with increased ECP serum levels were RAST-positive. However, CFS RAST-positive patients had no significantly higher ECP serum levels than CFS RAST-negative patients (19.3 +/- 12.4 micrograms/l vs 13.6 +/- 3.7 micrograms/l; P = 0.4). This is the first report of increased serum levels of ECP in CFS. On the basis of the available data, it is discussed whether eosinophil activation has a pathogenetic role in CFS or is linked to the frequently associated allergic condition, or, finally, whether a common immunologic background may exist for both atopy and CFS.

Adult↗

PubMed1996

[Sclerosing adenocarcinomas of the hepatic hilum].

The authors report their series of 7 adenocarcinomas of the hepatic hilum. Five patients with a stage IV tumor underwent palliative surgery while the remaining 2 patients underwent radical surgery. One patient died and 3 reported postoperative complications. Overall survival was 2 years and 6 months: these results can be considered satisfactory taking into account the advanced stage and the bad prognosis of this type of tumor. The aim of a better quality of life may represent a reasonable indication to surgery.

Adenocarcinoma↗

PubMed1996

Management of thoracic duct complex lesions (chylothorax): experience in 16 patients.

From our experience in 16 patients with persistent chylothorax from fistulas of the thoracic duct or its tributaries, we conclude that no standard treatment is uniformly successful and multimodality therapy should be considered. In selected patients, an anastomosis between ectatic lymphatics or hyperplastic lymph nodes and an adjacent vein may be attempted. Chylothorax from "leakage" of the thoracic duct or its tributaries is rare. Rupture of the thoracic duct superior to the sixth thoracic vertebrae generally results in a left-sided chylothorax; below that level, injury usually results in a right-sided chylothorax. The etiology is heterogeneous and includes blunt trauma, penetrating wounds (1), iatrogenic operative injury and lymphatic obstructions due to congenital abnormalities, inflammatory processes or neoplasms. Based on our experience in 16 patients with persistent chylothorax from thoracic duct complex lesions, we review the available treatment options.

Adolescent↗

PubMed1996

Amino acids as the source of considerable excitation in cerebral cortex.

A number of different factors contributed to the rationale for providing a critical review of the field of excitatory amino acids in the cerebral cortex at this time. In addition to the recent growing realisation by clinicians that the excitatory amino acids are linked critically to a number of neurological conditions, including neurodegenerative syndromes such as Alzheimer's disease, cortical damage due to stroke and cerebral ischemia, epilepsy, amyotropic lateral sclerosis, and schizophrenia, the recent cloning and membrane reconstitution of specific receptors known as AMPA, NMDA, kainate, and metabotropic receptors and their known subunits have prompted a surge of renewed interest in this important family of synaptic transmitter molecules. Moreover, recent advances in our understanding of the molecular events involved in growth promotion in the early stages of the development of the cortex have shown that both NMDA and non-NMDA receptor subtypes perform important roles in certain aspects of target selection and neurite outgrowth, in cone stimulation and guidance, and in spine formation and morphological alterations. A recent explosive growth in interest in the possible roles of nitric oxide and related short-lived radicals in plasticity, disease, and synaptic transmission also is related closely with the actions of excitatory amino acids. All these relatively new advances have transpired in parallel with ongoing work that has extended our appreciation for the roles of excitatory amino acids in the areas of synaptic plasticity (long-term potentiation, long-term depression, receptive field reorganisation following drug-induced or peripheral sensory disturbances, such as denervation or amputation), in processes of normal transmission at functionally and electrophysiologically identified neurones of the cerebral cortex, and in distinct proposed roles for cortical glia. A greater appreciation of the diverse types and properties of the burgeoning family of receptors for the metabotropic receptor also contributed to our desire to feature that aspect of the field in the context of glia and neurones of the cerebral cortex. That part of the field of neuroscience concerned with the functions of excitatory amino acids has grown so large over the past 10 years or so, that a review paper focusing on the contributions to a specialized meeting devoted solely to cerebral cortex could easily be supported by material comprising a sufficient body of communications from top-quality research laboratories. The present account endeavours to summarize and discuss the biochemical characteristics, physiological roles, pharmacological properties, clinical relevance, developmental involvements, and anatomical-morphological aspects pertaining to the excitatory amino acid transmitters in cerebral cortex.

Animals↗

PubMed1995

Enhanced risk of steroid-resistant acute rejection following pretransplant steroid therapy in liver graft recipients.

Most episodes of acute rejection will resolve after steroid therapy without detrimental consequences on the liver allograft. However, steroid-resistant acute rejection may induce irreversible lesions of the graft and is associated with an increased risk of chronic rejection. The aim of this study was to determine whether there were predictive factors for steroid-resistant acute rejection after liver transplantation. A total of 108 adult liver recipients with a follow-up of at least 2 years have been analyzed; sixty-two (57%) patients had at least one episode of acute rejection. The rates of steroid resistance were 35%, 52% and 83% after a first (n = 62), second (n = 25), or third (n = 7) episode of acute rejection, respectively. Steroid resistance of acute rejection was significantly associated with a past history of pretransplant steroid therapy (P = 0.004). High levels of ALT (P = 0.03) and serum bilirubin (P = 0.002) were also predictive of steroid-resistant acute rejection. Eight (7%) patients eventually developed chronic rejection. Predictive factors for chronic rejection included steroid-resistant acute rejection (P = 0.01), recurrent acute rejection (P = 0.03), and CMV infection (P = 0.01). In conclusion, this study suggests that pretransplant steroid administration or high levels of ALT and bilirubin in rejecting patients are risk factors for steroid resistance and should lead to aggressive antirejection therapy without delay.

Adolescent↗

PubMed1995

Properties of the Kv1.1 rat brain potassium channels expressed in mammalian cells: temperature effects.

We studied the temperature dependence of the currents mediated by potassium channels Kv1.1 cloned from rat brain expressed by permanent transfection in the human embryonic kidney cell line 292er. Voltage-gated outward currents, with a reversal potential near to the Nernst potential for potassium, were elicited by depolarising pulses. The currents activate fast and do not show inactivation during 50-ms test pulses. Increasing temperature decreased the amplitude of the currents, slowed the kinetics of activation and deactivation and shifted the activation curve to more negative potentials. We conclude that in Kv1.1 channels the closed states are associated with more ordered structure of the channel protein than the open state. The voltage-dependence and the kinetic properties are similar to those expressed in frog oocytes injected with cRNA coding the same Kv1.1.

Animals↗

PubMed1995

Saddle nose.

Explore the source record for details and available documents.

Aged↗

PubMed1995

Inward rectifier potassium channels in plants differ from their animal counterparts in response to voltage and channel modulators.

We have investigated the electrophysiological basis of potassium inward rectification of the KAT1 gene product from Arabidopsis thaliana expressed in Xenopus oocytes and of functionally related K+ channels in the plasma membrane of guard and root cells from Vicia faba and Zea mays. The whole-cell currents passed by these channels activate, following steps to membrane potentials more negative than -100 mV, with half activation times of tens of milliseconds. This voltage dependence was unaffected by the removal of cytoplasmic magnesium. Consequently, unlike inward rectifier channels of animals, inward rectification of plant potassium channels is an intrinsic property of the channel protein itself. We also found that the activation kinetics of KAT1 were modulated by external pH. Decreasing the pH in the range 8.5 to 4.5 hastened activation and shifted the steady state activation curve by 19 mV per pH unit. This indicates that the activity of these K+ channels and the activity of the plasma membrane H(+)-ATPase may not only be coordinated by membrane potential but also by pH. The instantaneous current-voltage relationship, on the other hand, did not depend on pH, indicating that H+ do not block the channel. In addition to sensitivity towards protons, the channels showed a high affinity voltage dependent block in the presence of cesium, but were less sensitive to barium. Recordings from membrane patches of KAT1 injected oocytes in symmetric, Mg(2+)-free, 100 mM-K+, solutions allowed measurements of the current-voltage relation of single open KAT1 channels with a unitary conductance of 5 pS. We conclude that the inward rectification of the currents mediated by the KAT1 gene product, or the related endogenous channels of plant cells, results from voltage-modulated structural changes within the channel proteins. The voltage-sensing or the gating-structures appear to interact with a titratable acidic residue exposed to the extracellular medium.

Animals↗

PubMed1995

Evidence for the detrimental role of proteolysis during liver preservation in humans.

BACKGROUND/AIMS: Proteolysis may persist in the liver allograft during cold storage. The aim of this study was to determine the significance of proteolysis within liver allografts stored at 4 degrees C in University of Wisconsin preservation fluid. METHODS: Thirty recipients of 32 liver allografts were studied prospectively. Amino acid content of the preservation fluid was analyzed at the end of cold storage and was correlated to graft and patient outcome after transplantation. RESULTS: Analysis of the preservation fluid showed the presence of free amino acids, the profile of which was different from that of stored liver parenchyma. Concentrations of amino acids (alanine, cysteine, leucine, isoleucine, methionine, lysine, ornithine, and threonine) and transaminases (alanine aminotransferase and aspartate aminotransferase) in the preservation fluid correlated with the duration of cold ischemia. Indexes of graft dysfunction (serum alanine aminotransferase and aspartate aminotransferase peaks and prothrombin rate) correlated with concentrations of cysteine, alanine, isoleucine, leucine, methionine, lysine, ornithine, and threonine, whereas enzyme concentrations in the fluid were not predictive of graft dysfunction. CONCLUSIONS: These data suggest that liver proteolysis occurs during cold storage and may have a detrimental effect on the outcome after transplantation. The measurement of the amino acids in the preservation fluid at the end of the cold storage period could help to identify the most severely damaged organs.

Adenosine↗

PubMed1995

Intrapatient comparison of single-agent epirubicin with or without lonidamine in metastatic breast cancer.

The aim of this study was to determine if lonidamine (LND) supplementation to single-agent epirubicin (EPI) could reverse anthracycline resistance in patients with metastatic breast cancer. 45 patients with metastatic breast cancer were treated with EPI 120 mg/m2 by intravenous (i.v.) bolus every 3 weeks. Patients who progressed were given the same chemotherapy regimen on day 4 in combination with oral LND, 150 mg on day 1, 300 mg on day 2 and 450 mg on days 3-5. Among the 40 evaluable patients, 6 complete responses (CR) and 14 partial responses (PR) were achieved with EPI treatment alone for an overall response rate of 50%. The median duration of response was 6.5 months. Among the 25 patients treated with EPI+LND, 5 PR (21% of 24 evaluable patients) were observed with a median duration of response of 7 months. The median survival in patients receiving both treatments was 20 months. The survival for all patients was 18 months. The survival of patients receiving LND was not significantly longer than for the other patients. Myelotoxicity was the most common side-effect followed by alopecia, nausea and vomiting, and stomatitis. LND-related toxic effects were mild-to-moderate epigastralgia and myalgia. Anthracycline-related toxicity was the same in the two treatment groups. This study indicates that LND may circumvent clinical resistance to EPI without altering the pattern or severity of the toxicity of this anthracycline. Continued investigation of the clinical modulation of EPI resistance by LND in breast cancer is warranted, hopefully in patients with known multidrug resistance status.

Adult↗