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Biomedical subjects

M Conti

Publications and source records attributed to M Conti.

At least 73 records · Page 4Linked to original sources
PubMed2000

[Gallbladder carcinoma and laparoscopic cholecystectomy. An emergent problem].

BACKGROUND: Gallbladder cancer (GC) is reported in 1.5-3% of cholecystectomies. Since the introduction of laparoscopic surgery, cholecystectomies have increased and occult GC may therefore be more frequent. METHODS: Here we conduct a retrospective study on a series of 1200 LC performed between January 1991 and December 1998 at our Institution, to determine whether there was an increase in GC. We also evaluated the risk factors for this outcome and the possibilities of treatment, in case of unsuspected GC discovered after LC at histological examination. Seven cases of GC undiagnosed before surgery (0.6% of the study population) were submitted to LC (against 0.3% GC discovered after open surgery). The clinical course depended on the histopathologic stage of the cancer. RESULTS: After a median follow-up of 18 months (range 12-48), 2 pT1 patients were alive and well, 2 pT2 patients were alive and disease free (in 1 case after a surgical removal of a trocar site metastasis appeared 6 months after LC). The other 3 patients died, 2 (1 pT2 and 1 pT3) after an additional resection of the liver bed with lymph node dissection, due to peritoneal dissemination of the disease. In 2 cases we found a gallbladder polyp pre and intraoperatively, which proved to be a carcinoma. CONCLUSIONS: Undiagnosed GC is on the increase with the introduction of LC. Polypoid lesions of the gallbladder, age > 70 years: a long history of stones and a thickened gallbladder wall all represent significant risk factors. If one or more is present, examination of the gallbladder and a frozen section are recommended.

Adenocarcinoma↗
PubMed1999

Activation of the mitogen-activated protein kinase ERK1 during meiotic progression of mouse pachytene spermatocytes.

Okadaic acid (OA) causes meiotic progression and chromosome condensation in cultured pachytene spermatocytes and an increase in maturation promoting factor (cyclin B1/cdc2 kinase) activity, as evaluated by H1 phosphorylative activity in anti-cyclin B1 immunoprecipitates. OA also induces a strong increase of phosphorylative activity toward the mitogen-activated protein kinase substrate myelin basic protein (MBP). Immunoprecipitation experiments with anti-extracellular signal-regulated kinase 1 (ERK1) or anti-ERK2 antibodies followed by MBP kinase assays, and direct in-gel kinase assays for MBP, show that p44/ERK1 but not p42/ERK2 is stimulated in OA-treated spermatocytes. OA treatment stimulates phosphorylation of ERK1, but not of ERK2, on a tyrosine residue involved in activation of the enzyme. ERK1 immunoprecipitated from extracts of OA-stimulated spermatocytes induces a stimulation of H1 kinase activity in extracts from control pachytene spermatocytes, whereas immunoprecipitated ERK2 is uneffective. We also show that natural G(2)/M transition in spermatocytes is associated to intracellular redistribution of ERKs, and their association with microtubules of the metaphase spindle. Preincubation of cultured pachytene spermatocytes with PD98059 (a selective inhibitor of ERK-activating kinases MEK1/2) completely blocks the ability of OA to induce chromosome condensation and progression to meiotic metaphases. These results suggest that ERK1 is specifically activated during G(2)/M transition in mouse spermatocytes, that it contributes to the mechanisms of maturation promoting factor activation, and that it is essential for chromosome condensation associated with progression to meiotic metaphases.

Animals↗
PubMed1999

Impaired growth and fertility of cAMP-specific phosphodiesterase PDE4D-deficient mice.

In eukaryotic cells, the inactivation of the cyclic nucleotide signal depends on a complex array of cyclic nucleotide phosphodiesterases (PDEs). Although it has been established that multiple PDE isoenzymes with distinct catalytic properties and regulations coexist in the same cell, the physiological significance of this remarkable complexity is poorly understood. To examine the role of a PDE in cAMP signaling in vivo, we have inactivated the type 4 cAMP-specific PDE (PDE4D) gene, a mammalian homologue of the Drosophila dunce. This isoenzyme is involved in feedback regulation of cAMP levels. Mice deficient in PDE4D exhibit delayed growth as well as reduced viability and female fertility. The decrease in fertility of the null female is caused by impaired ovulation and diminished sensitivity of the granulosa cells to gonadotropins. These pleiotropic phenotypes demonstrate that PDE4D plays a critical role in cAMP signaling and that the activity of this isoenzyme is required for the regulation of growth and fertility.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1999

Activation of the cAMP-specific phosphodiesterase PDE4D3 by phosphorylation. Identification and function of an inhibitory domain.

Splicing variants of type 4 phosphodiesterases (PDE4) are regulated by phosphorylation. In these proteins, a conserved region is located between the amino-terminal domain, which is the target for phosphorylation, and the catalytic domain. Previous studies have indicated that nested deletions encompassing this region cause an increase in catalytic activity, suggesting this domain exerts an inhibitory constraint on catalysis. Here, we have further investigated the presence and function of this domain. A time-dependent increase in hydrolytic activity was observed when PDE4D3 from FRTL-5 cells was incubated with the endoproteinase Lys-C. The activation was abolished by protease inhibitors and was absent when a phosphorylated enzyme was used. Western blot analysis with PDE4D-specific antibodies indicated the Lys-C treatment separates the catalytic domain of PDE4D3 from the inhibitory domain. Incubation with antibodies recognizing an epitope within this domain caused a 3- to 4-fold increase in activity of native or recombinant PDE4D3. Again, PDE activation by these antibodies had properties similar to, and not additive with, the activation by protein kinase A phosphorylation. An interaction between the inhibitory domain and both regulatory and catalytic domains of PDE4D3 was detected by the yeast two-hybrid system. Mutations of Ser54 to Ala in the regulatory domain decreased or abolished this interaction, whereas mutations of Ser54 to the negatively charged Asp strengthened it. These data strongly support the hypothesis that an inhibitory domain is present in PDE4D and that phosphorylation of the regulatory domain causes activation of the enzyme by modulating the interaction between inhibitory and catalytic domains.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1999

Interleukin-1beta immunoreactivity and microglia are enhanced in the rat hippocampus by focal kainate application: functional evidence for enhancement of electrographic seizures.

Using immunocytochemistry and ELISA, we investigated the production of interleukin (IL)-1beta in the rat hippocampus after focal application of kainic acid inducing electroencephalographic (EEG) seizures and CA3 neuronal cell loss. Next, we studied whether EEG seizures per se induced IL-1beta and microglia changes in the hippocampus using bicuculline as a nonexcitotoxic convulsant agent. Finally, to address the functional role of this cytokine, we measured the effect of human recombinant (hr)IL-1beta on seizure activity as one marker of the response to kainate. Three and 24 hr after unilateral intrahippocampal application of 0.19 nmol of kainate, IL-1beta immunoreactivity was enhanced in glia in the injected and the contralateral hippocampi. At 24 hr, IL-1beta concentration increased by 16-fold (p < 0.01) in the injected hippocampus. Reactive microglia was enhanced with a pattern similar to IL-1beta immunoreactivity. Intrahippocampal application of 0.77 nmol of bicuculline methiodide, which induces EEG seizures but not cell loss, enhanced IL-1beta immunoreactivity and microglia, although to a less extent and for a shorter time compared with kainate. One nanogram of (hr)IL-1beta intrahippocampally injected 10 min before kainate enhanced by 226% the time spent in seizures (p < 0.01). This effect was blocked by coinjection of 1 microgram (hr)IL-1beta receptor antagonist or 0.1 ng of 3-((+)-2-carboxypiperazin-4-yl)-propyl-1-phosphonate, selective antagonists of IL-1beta and NMDA receptors, respectively. Thus, convulsant and/or excitotoxic stimuli increase the production of IL-1beta in microglia-like cells in the hippocampus. In addition, exogenous application of IL-1beta prolongs kainate-induced hippocampal EEG seizures by enhancing glutamatergic neurotransmission.

Animals↗
PubMed1999

Chronic antidepressant administration increases the expression of cAMP-specific phosphodiesterase 4A and 4B isoforms.

The influence of chronic antidepressant administration on expression of the three major phosphodiesterase (PDE) 4 subtypes found in brain (PDE4A, PDE4B, and PDE4D) was examined. The treatments tested included representatives of four major classes of antidepressants: selective reuptake inhibitors of serotonin (sertraline and fluoxetine) or norepinephrine (desipramine), a monoamine oxidase inhibitor (tranylcypromine), and electroconvulsive seizure. Expression of PDE4A and PDE4B, but not PDE4D, mRNA and immunoreactivity were significantly increased in rat frontal cortex by chronic administration of each of the four classes of antidepressants. We also found that antidepressant administration significantly increased the expression of PDE4B mRNA in the nucleus accumbens, a brain region thought to mediate pleasure and reward that could also contribute to the anhedonia often observed in depressed patients. In contrast, expression of PDE4A and PDE4B were not influenced by short-term treatment (1 or 7 d) and were not influenced by chronic administration of nonantidepressant psychotropic drugs (cocaine or haloperidol), demonstrating the time dependence and pharmacological specificity of these effects. Upregulation of PDE4A and PDE4B may represent a compensatory response to antidepressant treatment and activation of the cAMP system. The possibility that targeted inhibition of these PDE4 subtypes may produce an antidepressant effect is discussed.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1999

Do acute lesions of Wernicke's encephalopathy show contrast enhancement? Report of three cases and review of the literature.

Contrast medium was given intravenously to three nonalcoholic patients who underwent MRI or CT in the acute stage of Wernicke's encephalopathy. Lesions enhancement was not seen in one patient examined within 4 days of clinical onset, was mild in a another 3 days after clinical deterioration and marked in a patient examined 12 days after admission. Contrast enhancement of lesions was present in half of 12 cases of acute disease reported previously. There was a substantial overlap in the time interval between clinical onset and contrast-enhanced CT or MRI in the groups of enhancing and nonenhancing lesions. Since contrast enhancement may be absent in acute WE, proton-density and T2-weighted images are more useful for diagnosis of this reversible but potentially fatal condition.

Acute Disease↗
PubMed1999

The molecular biology of cyclic nucleotide phosphodiesterases.

Recent progress in the field of cyclic nucleotides has shown that a large array of closely related proteins is involved in each step of the signal transduction cascade. Nine families of adenylyl cyclases catalyze the synthesis of the second messenger cAMP, and protein kinases A, the intracellular effectors of cAMP, are composed of four regulatory and three catalytic subunits. A comparable heterogeneity has been discovered for the enzymes involved in the inactivation of cyclic nucleotide signaling. In mammals, 19 different genes encode the cyclic nucleotide phosphodiesterases (PDEs), the enzymes that hydrolyze and inactivate cAMP and cGMP. This is only an initial level of complexity, because each PDE gene contains several distinct transcriptional units that give rise to proteins with subtle structural differences, bringing the number of the PDE proteins close to 50. The molecular biology of PDEs in Drosophila and Dictyostelium has shed some light on the role of PDE diversity in signaling and development. However, much needs to be done to understand the exact function of these enzymes, particularly during mammalian development and cell differentiation. With the identification and mapping of regulatory and targeting domains of the PDEs, modularity of the PDE structure is becoming an established tenet in the PDE field. The use of different transcriptional units and exon splicing of a single PDE gene generates proteins with different regulatory domains joined to a common catalytic domain, therefore expanding the array of isoforms with subtle differences in properties and sensitivities to different signals. The physiological context in which these different isoforms function is still largely unknown and undoubtedly will be a major area of expansion in the years to come.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1999

Brain-derived neurotrophic factor immunoreactivity in the limbic system of rats after acute seizures and during spontaneous convulsions: temporal evolution of changes as compared to neuropeptide Y.

Seizures increase the synthesis of brain-derived neurotrophic factor in forebrain areas, suggesting this neurotrophin has biological actions in epileptic tissue. The understanding of these actions requires information on the sites and extent of brain-derived neurotrophic factor production in areas involved in seizures onset and their spread. In this study, we investigated by immunocytochemistry the changes in brain-derived neurotrophic factor in the hippocampus, entorhinal and perirhinal cortices of rats at increasing times after acute seizures eventually leading to spontaneous convulsions. We also tested the hypothesis that seizure-induced changes in brain-derived neurotrophic factor induce later modifications in neuropeptide Y expression by comparing, in each instance, their immunoreactive patterns. As early as 100 min after seizure induction, brain-derived neurotrophic factor immunoreactivity increased in CA1 pyramidal and granule neurons and in cells of layers II-III of the entorhinal cortex. At later times, immunoreactivity progressively decreased in somata while increasing in fibres in the hippocampus, the subicular complex and in specific layers of the entorhinal and perirhinal cortices. Changes in neuropeptide Y immunoreactivity were superimposed upon and closely followed those of brain-derived neurotrophic factor. One week after seizure induction, brain-derived neurotrophic factor and neuropeptide Y immunoreactivities were similar to controls in 50% of rats. In rats experiencing spontaneous convulsions, brain-derived neurotrophic factor and neuropeptide Y immunoreactivity was strongly enhanced in fibres in the hippocampus/parahippocampal gyrus and in the temporal cortex. In the dentate gyrus, changes in immunoreactivity depended on sprouting of mossy fibres as assessed by growth-associated protein-43-immunoreactivity. These modifications were inhibited by repeated anticonvulsant treatment with phenobarbital. The dynamic and temporally-linked alterations in brain-derived neurotrophic factor and neuropeptide Y in brain regions critically involved in epileptogenesis suggest a functional link between these two substances in the regulation of network excitability.

Acute Disease↗
PubMed1999

Artificial neural networks as approximators of stochastic processes.

Artificial Neural Networks (ANNs) must be able to learn by experience from environment. This property can be considered as being closely related to the approximating capabilities of the networks. Unfortunately at present only the ability of ANNs in approximating deterministic input-output mappings has been exploited. In this article it has been shown that some classes of neural networks, named Stochastic Neural Networks, which are capable of using approximating stochastic processes are defined. As stochastic processes may also be viewed as random functions, they include deterministic (non-random) functions as a particular case. Thus the class of Stochastic Neural Networks can be considered as a generalisation of the usually defined neural networks. From an application point of view such a class of networks is more adherent to real world in which neural networks must work in an environment which is essentially stochastic. The theory presented in the article has been carried out starting from the so-called "canonical representation" for non-stationary stochastic processes. Finally, an application example showing in detail the validity of the proposed approach has been reported.

Journal Article↗
PubMed1999

Involvement of type 4 cAMP-phosphodiesterase in the myogenic differentiation of L6 cells.

Myogenic cell differentiation is induced by Arg(8)-vasopressin, whereas high cAMP levels and protein kinase A (PKA) activity inhibit myogenesis. We investigated the role of type 4 phosphodiesterase (PDE4) during L6-C5 myoblast differentiation. Selective PDE4 inhibition resulted in suppression of differentiation induced by vasopressin. PDE4 inhibition prevented vasopressin-induced nuclear translocation of the muscle-specific transcription factor myogenin without affecting its overall expression level. The effects of PDE4 inhibition could be attributed to an increase of cAMP levels and PKA activity. RNase protection, reverse transcriptase PCR, immunoprecipitation, Western blot, and enzyme activity assays demonstrated that the PDE4D3 isoform is the major PDE4 expressed in L6-C5 myoblasts and myotubes, accounting for 75% of total cAMP-hydrolyzing activity. Vasopressin cell stimulation caused a biphasic increase of PDE4 activity, which peaked at 2 and 15 min and remained elevated for 48 h. In the continuous presence of vasopressin, cAMP levels and PKA activity were lowered. PDE4D3 overexpression increased spontaneous and vasopressin-dependent differentiation of L6-C5 cells. These results show that PDE4D3 plays a key role in the control of cAMP levels and differentiation of L6-C5 cells. Through the modulation of PDE4 activity, vasopressin inhibits the cAMP signal transduction pathway, which regulates myogenesis possibly by controlling the subcellular localization of myogenin.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1999

Phase and solute fields across the solid-liquid interface of a binary alloy.

Solidification of binary alloys is characterized by a sharp structural transition across the solid-liquid interface. It is a typical situation which suggests a nonlocal dependence of the appropriate thermodynamic potential on its associate fields. Phase-field models with a gradient contribution for the order parameter have proved to account for nonequilibrium effects, as solute trapping and kinetic undercooling of the solid-liquid interface. The inclusion of a gradient term for the concentration field has also been theoretically investigated, but in this case the correspondence between predicted phenomena and experimental results is still rather unexplored. In the present study we analyze numerical solutions of a phase-field model in both steady and transient conditions. We focus on effects which are critically dependent on the composition field across the solid-liquid interface; the extent of the concentration gradient correction is related to measurable quantities to suggest methods for a comparison between the model predictions and experimental data.

Journal Article↗
PubMed1999

Type 4 cyclic adenosine monophosphate-specific phosphodiesterases are expressed in discrete subcellular compartments during rat spermiogenesis.

The type 4 cAMP-specific phosphodiesterases (PDE4) are a family of closely related enzymes with similar catalytic domains and divergent amino- and carboxyl-terminus domains. Multiple PDE proteins with heterogeneous amino termini are derived from each gene. To understand the significance of this heterogeneity, the expression and localization of variants derived from PDE4A and PDE4D genes was investigated during spermatogenesis in the rat. RNase protection analysis with mRNA for testes at different ages of development showed that two transcripts (PDE4D1 and PDE4D2) are expressed at day 10 and 15 of age and become undetectable thereafter. An additional PDE4D transcript appears at day 30 and increased during testid maturation. This latter transcript codes for a long variant of the PDE4D gene and is expressed in germ cells as demonstrated by RNase protection with RNA from isolated pachytene spermatocytes and round spermatids. The presence of a corresponding PDE4D protein with a molecular mass of 98 kDa was established by immunoprecipitation and Western blot analysis with antibodies specific for PDE4D and by immunoaffinity chromatography purification of the 98 kDa variant from isolated germ cells. PDE4A transcripts were also expressed in pachytene spermatocytes and round spermatids. Two polypeptides encoded by these PDE4A transcripts were expressed in pachytene spermatocytes, reached a maximum in round spermatids, and declined thereafter. Immunofluorescence analysis demonstrated a localization of the PDE4D protein in the manchette and in a periacrosomal region of the developing spermatid, a localization confirmed by immunogold electron microscopy. Conversely, the PDE4A was mostly soluble in the cytoplasm of round spermatids. These data demonstrate that PDE4D and PDE4A variants are expressed at different stages and localized in distinct subcellular structures of developing spermatids. Different properties of the mRNAs derived from the two genes and localization signals are responsible for the temporal and spatial expression of the different PDE4 isoenzymes.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1999

Mediation of the hepatic effects of growth hormone by its lipolytic activity.

The aim of the study was to investigate the acute effect of GH per se, independent from its lipolytic activity, on glucose and lipid oxidation and glucose turnover in seven healthy subjects. Five tests lasting 360 min were performed. Each test consisted of a 4-h equilibration period followed by a euglycemic hyperinsulinemic (25 mU/kg x h) clamp lasting 2 h. In test 1 (control experiment) saline was infused, leaving GH and FFA at basal levels. In tests 2, 3, and 4, GH was infused (80 ng/kg x min) to increase GH levels. Whereas in test 2 FFA levels were free to increase due to GH lipolytic activity, in test 3 FFA elevation was prevented by using an antilipolytic compound (Acipimox) that allowed evaluation of the effect of GH at low FFA levels. In test 4 (GH+Acipimox+heparin) GH infusion was associated with the administration of Acipimox and heparin to maintain FFA at the basal level to evaluate the effect of GH per se independent from GH lipolytic activity. In test 5 Acipimox and a variable heparin infusion were given to evaluate possible effects of Acipimox other than the inhibition of lipolysis. During the euglycemic hyperinsulinemic clamp in the presence of high GH and FFA levels (test 2), glucose oxidation was significantly lower and lipid oxidation was significantly higher than in tests 1, 3, 4, and 5. During the same period, hepatic glucose production was completely suppressed in the control study (test 1; 94%) and in test 5 (99.6%), whereas it was significantly less inhibited (65%, 74%, and 73%) when GH was administered in tests 2, 3, and 4. In conclusion, these results suggest that GH directly mediates the reduction of insulin's effect on the liver. In addition, the effect of GH on glucose and lipid oxidation is not direct, but is mediated by its lipolytic activity.

Adult↗
PubMed1999

[Latex allergy. An not rare intraoperative event].

Latex allergy has become a real problem among both surgical staff (paramedics and physicians) and patients especially pediatric patients with urogenital malformations and spina bifida. Latex allergy is produced from both natural molecules which compose the substance produced from Hevea brasiliensis (rubber tree) and industrial additives contents in latex devices. Diagnosis of latex allergy may be carried out through a preoperative Prik-test. A characteristic of latex allergy reaction is the starting of symptoms (more than 15 minutes after allergen contact). Pathophysiology of latex allergy is the same of all allergic reactions; it is an antigen-antibody reaction and type I or II reaction may occur. There are a lot of devices that surgeons and anesthesists use in the operative theatre and that should not be used in presence of a patient with latex allergy. Guaranteed latex-free devices should always be present in store.

Humans↗
PubMed1999

In situ detection of lipid peroxidation by-products as markers of renal ischemia injuries in rat kidneys.

PURPOSE: Lipid peroxidation is an autocatalytic mechanism leading to oxidative destruction of cellular membranes. In renal transplantation, this mechanism is triggered by ischemia/reperfusion and may be of relevance in graft failure. MATERIALS AND METHODS: Using specific antibodies directed against malondialdehyde (MDA) and 4-hydroxynonenal (HNE) adducts, major aldehydic metabolites of lipid peroxidation, we investigated, in situ, by means of an immunohistochemical procedure, the occurrence of lipid peroxidation during different warm ischemic periods of 0, 15, 30, 45 and 60 minutes in rat kidneys prior to reperfusion. The same experiments included followup of the rats after nephrectomy and reperfusion for 10 days. RESULTS: We observed superficial and deep cortex immunostaining with both antibodies against MDA and HNE after 30 minutes of warm ischemia. This immunostaining was observed in the absence of any histological lesions, as assessed by routine staining. After 45 and 60 minutes of warm ischemia, lipid peroxidation byproducts were detected both in the cortex and in the medulla, which is associated with 33% and 66% of rat deaths respectively. CONCLUSIONS: This study confirms the involvement of the lipid peroxidation process in kidney damage during anoxia before reperfusion, and its extension to the whole organ. Lipid peroxidation byproducts were detectable in warm ischemic kidney, and the presence of medulla immunostaining was associated with the animals' death. Lipid peroxidation immunostaining might thus be useful as a sensitive tool to detect ischemic damage after warm ischemia prior to reperfusion, as well as in the decision to carry out kidney transplantation in humans.

Aldehydes↗
PubMed1999

Plasmodesmata and plant viruses. A centenary story.

The passage of plant viruses from a cell to adjacent ones remained for a long time an unexplained event. Only during the thirties did Samuel and other plant virologists put forward the hypothesis that the passage occurred through plasmodesmata, i.e. those protoplasmic connections between plant cells described since the late 19th century. A direct relation between viruses and plasmodesmata was first demonstrated by electron microscopy during the late 1960s by Esau and co-workers, and then widely confirmed. The mechanism of the passage was investigated in depth starting from the 1970s, and research received a remarkable impulse after that a well-defined model of plasmodesmata had been obtained thank, in particular, to work of the Robards' and Gunning's groups. In this context, the discovery of the polycystronic functionality of the viral genomes was fundamental. A protein coded by tobacco mosaic virus, discovered in 1982 independently by the Soviet group of Atabekov and the American group of Zaitlin, was demonstrated to be indispensable for the transport of virus infection from cell to cell through plasmodesmata. Elegant investigations on this 'movement protein' demonstrated that it actually increases the permeability of plasmodesmata. The relation between viruses and plasmodesmata is one of the most interesting and investigated theme of research, which is receiving much attention from plant virologists, physiologists and molecular biologists. The current status of knowledge still presents unsolved questions, and the story is far from over.

History, 20th Century↗