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Biomedical subjects

M Conti

Publications and source records attributed to M Conti.

At least 37 records · Page 2Linked to original sources
PubMed2001

Randomized controlled trial of a synthetic sealant for preventing alveolar air leaks after lobectomy.

BACKGROUND: The intraoperative application of synthetic surgical lung sealant (SLS) to surfaces leaking air or at risk of air leaks has been advocated to reduce alveolar air leaks (AAL) after lobectomy. METHODS: This study was designed to investigate the effectiveness of SLS in reducing AAL in patients considered intraoperatively to have moderate to severe AAL, after all conventional measures to reduce such leaks had been used. Over 17 months, 124 patients undergoing standard lobectomy were randomized to standard closure of parenchymal surgical sites, with or without SLS. RESULTS: In treated patients, the mean numbers of intraoperative AAL after application of SLS were significantly smaller than in untreated patients (38.5 mL versus 59.9 mL, p = 0.0401). Postoperatively, the mean time to last observable AAL was shorter in the treated group (33.7 hours versus 63.2 hours, p = 0.0134) and the mean percentage of patients free of AAL at days 3 and 4 was smaller (87% versus 58.5%, p = 0.002). However, the occurrence of incomplete lung expansion after drain removal, and the length of the postoperative hospital stay due to prolonged AAL, were not different. In the treatment group, 4 patients developed localized empyema and incomplete lung expansion without bronchopleural fistula 7, 12, 15, and 20 days, respectively, after operation. In these 4 patients, inserted chest tubes drained infected sealant. CONCLUSIONS: Surgical lung sealant may be a useful adjunct to conventional techniques for reducing moderate and severe AAL after lobectomy, but its use seems to increase the risk of postoperative empyema.

Acrylates↗
PubMed2001

High glucose and hyperinsulinemia stimulate connective tissue growth factor expression: a potential mechanism involved in progression to fibrosis in nonalcoholic steatohepatitis.

Nonalcoholic steatohepatitis (NASH) may progress to liver fibrosis and cirrhosis. Mechanisms directly involved in the development of fibrosis have been poorly investigated. Because connective tissue growth factor (CTGF) is an intermediate key molecule involved in the pathogenesis of fibrosing chronic liver diseases and is potentially induced by hyperglycemia, the aims of this study were to (1) study the expression of CTGF in vivo both in human liver biopsy specimens of patients with NASH and in an experimental model of obesity and type II diabetes (Zucker rats); and (2) analyze the effects of hyperglycemia and insulin in vitro on hepatic stellate cells. In vivo, CTGF overexpression was observed in the liver tissue of all of the 16 patients with NASH. CTGF immunostaining was mild in 7 cases (44%) and moderate or strong in 9 cases (56%). Staining was mainly detected in the liver extracellular matrix in parallel with the amount of liver fibrosis. Liver from fa/fa rats also showed CTGF overexpression by comparison with Fa/fa rats both at the messenger RNA (mRNA) level (3-fold increase) and protein level. In vitro, both CTGF mRNA and protein were significantly increased when hepatic stellate cells were incubated with either glucose or insulin. A slight increase in type I procollagen mRNA level was also observed in hepatic stellate cells incubated with glucose. In conclusion, this study suggests that hyperglycemia and insulin are key-factors in the progression of fibrosis in patients with NASH through the up-regulation of CTGF.

Adult↗
PubMed2001

Increased absorption rate of diclofenac from fast acting formulations containing its potassium salt.

Diclofenac (CAS 15307-86-5) is a non-steroidal anti-inflammatory drug largely used, mainly to relief pain of various origin. Diclofenac is present on the market as free acid, as sodium salt (CAS 15307-79-6) and as potassium salt (CAS 15307-81-0). The last salification form has shown a prompter absorption rate and a faster onset of analgesic activity than the acid form and sodium salt. This paper extensively reviews three trials carried out on healthy volunteers, where potassium salt of diclofenac present in three fast-acting formulations, namely sachets (Trial 1), tablets (Trial 2) and oral drops (Trial 3), were compared to reference tablet formulations from the market. A very fast absorption rate was encountered with the three test formulations, with the peak reached in one case 5 min and in most cases within 10-15 min after dosing. The quick absorption rate of test formulations was attributed to the special combination of the salt of diclofenac with a dynamic buffering agent, namely bicarbonate, present in the test formulations and covered by an international patent. The prompt absorption of diclofenac from the new fast-acting formulations was accompanied by the presence of only one peak, whereas the reference formulations produced in most cases two peaks, as widely described in literature. This finding suggested the hypothesis that the absorption of test formulations should occur in a shorter tract of the gut. The faster absorption of diclofenac from the three fast-acting formulations is expected to produce a faster onset of analgesic action, which highlights these new formulations as particularly indicated to relief pain of any origin.

Adult↗
PubMed2001

Self-expandable metal stents in the treatment of antro-pyloric and/or duodenal strictures.

PURPOSE: To assess the usefulness of self-expandable metal stents in the recanalization of antro-pyloric and/or duodenal strictures. MATERIAL AND METHODS: We report our experience of 15 patients with inoperable antro-pyloric and/or duodenal strictures treated by implantation of 21 self-expandable metal stents (18 uncovered and 3 covered) inserted perorally under fluoroscopic guidance. The patients were 11 men and 4 women, mean age 65.3 years. Fourteen of 15 patients were affected by a malignant stricture of the antro-pyloric region and/or duodenum either primary or secondary in 10 and 4 cases, respectively. Only in 1 case there was a benign stricture from postoperative scarring. Stricture length and diameter varied from 3 to 9 cm (mean 5.4 cm) and from 0 to 4 mm (mean 1.27 mm), respectively. RESULTS: Twenty-one stents were placed in 15 patients: Technical success was achieved in all cases while clinical improvement was obtained in 14 cases. No short-term complications were observed. A mean 4.3-month follow-up was obtained. Two patients had emesis secondary to peritoneal dissemination of the tumor after 1 and 2 months, respectively. Two other patients showed tumor overgrowth of the oral edge of the prosthesis after 3 and 2 months, respectively, and required another coaxial stent to bridge the new stenosis. The patient treated for a benign stricture had jaundice after 3 months and percutaneous internal-external biliary drainage was necessary. CONCLUSION: Self-expandable metal stents are a safe and effective treatment of antro-pyloric and duodenal strictures; therefore, they should be considered an alternative to palliative resection in cases of advanced stage disease or poor general physical condition.

Adult↗
PubMed2001

Surgically induced cryptorchidism-related degenerative changes in spermatogonia are associated with loss of cyclic adenosine monophosphate-dependent phosphodiesterases type 4 in abdominal testes of rats.

The present study was undertaken to investigate the role of phosphodiesterase type 4 (PDE4) enzymes in cryptorchidism-induced apoptosis of the germ cells. Regulation of expression of PDE4 enzymes was studied in the abdominal and scrotal testes of surgically induced cryptorchid rats for 10, 20, and 30 days. In some cases orchidopexy was performed after 30 days of cryptorchidism, and rats were allowed to recover for an additional 50 days. Upon histological examination, marked degenerative changes in the epithelial lining of the seminiferous tubules within abdominal testes were observed compared with contralateral control or age-matched sham-operated rats. These changes included degeneration of some spermatogonia, apoptosis of the secondary spermatocytes, incomplete spermatogenesis, and lack of spermatozoa in the lumen. In contrast, contralateral scrotal testes exhibited normal histology. Significant improvement in the regeneration of spermatogonia was observed in rats after 50 days of recovery following orchidopexy. Immunocytochemical examination suggested the presence of PDE4A in germ cells while PDE4B was predominantly expressed on somatic cells. Western blotting using PDE4 subtype-selective antibodies showed the presence of two PDE4A variants (a 109-kDa PDE4A8 and a previously uncharacterized 88-kDa PDE4A variant) and two PDE4B (78-kDa PDE4B2 and 66-kDa PDE4B variant) bands. In unilaterally cryptorchid animals, the abdominal testis showed a time-dependent decrease in both PDE4A8 and 88-kDa PDE4A variants. In contrast, the expression of 66-kDa PDE4B was markedly increased in a time-dependent fashion in abdominal testes of cryptorchid rats. Animals surgically corrected for cryptorchidism and allowed to recover for 50 days exhibited normal expression of both PDE4A and PDE4B variants compared with aged-matched, sham-operated controls. In conclusion, this study suggests that down-regulation of PDE4A variants in cryptorchid testes may play an important role in the degeneration of spermatogonia and increased apoptotic activity in the germ cells.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2001

Cloning and characterization of the cyclic guanosine monophosphate-inhibited phosphodiesterase PDE3A expressed in mouse oocyte.

In the preovulatory follicle, oocyte meiotic resumption occurs soon after the LH surge and is associated with a decrease in cAMP. Inhibition of cAMP degradation blocks germinal vesicle breakdown as well as activation of meiotic promoting factor, both hallmarks of reentry into the cell cycle. In situ and pharmacological analysis of rodent ovaries suggested the presence of a phosphodiesterase 3 (PDE3) in the germ cell but not the somatic cell compartment. Here we have investigated the structure and properties of the PDE form expressed in mouse oocytes. Polymerase chain reactions using a mouse oocyte cDNA library as a template, and primers based on the conserved sequence of rat and human PDE3As, yielded partial fragments corresponding to mouse PDE3A. Further screening of the mouse oocyte cDNA library and subsequent ligation of individual cDNA clones yielded PDE3A cDNA containing the entire coding region of mouse PDE3A. To determine the kinetic properties of this PDE, the cDNAs encoding the full-length PDE3A and NH(2)-truncation forms Delta 1 (Delta346aa) and Delta 2 (Delta608aa) were expressed in mouse Leydig tumor cells. Whereas the full-length recombinant protein was always found in the particulate fraction, the Delta 1 and Delta 2 truncated PDE3As were recovered mostly in the soluble fraction. The Michaelis constant values for hydrolysis of cAMP of PDE3A Delta 1 and PDE3A Delta 2 were similar to those of intact full-length PDE3A or oocyte PDE (0.2-0.5 microM). More importantly, there was good correlation between the rank of potency of selective and nonselective compounds in inhibiting recombinant PDE3A or PDE activity derived from cumulus-oocyte complexes and in blocking resumption of meiosis. These data provide evidence that the PDE expressed in the oocyte is a soluble form of PDE3A and that activity of this enzyme is involved in the control of resumption of meiosis.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2001

Role of phosphodiesterase type 3A in rat oocyte maturation.

It is generally accepted that cyclic nucleotides are key signaling molecules in the control of oocyte meiotic resumption. Given the role of phosphodiesterases (PDEs) in cyclic nucleotide degradation, this study was undertaken to investigate the properties and regulation of PDEs expressed in rat oocytes. Cilostamide-sensitive PDE3 was the major activity detected in denuded oocytes, whereas no PDE3 activity could be detected in cumulus cells. Moreover, comparable levels of PDE3 activity were measured in cumulus-oocyte complexes (COCs) and in denuded oocytes. The oocyte PDE was recovered in the soluble fraction of the homogenate and immunoprecipitated with a specific PDE3A antibody. A significant and transient increase (P < 0.05) in PDE3 activity was measured in the oocytes after 30 min of culture (70 min after isolation) compared with immediately after collection (10 min after isolation). Conversely, no changes in activity were observed when denuded oocytes or cumulus cells were incubated for up to 130 min. Evaluation of oocyte maturation indicated that only 10% of oocytes had resumed meiosis at the peak of the PDE3 activity. A significant increase (P < 0.05) in PDE3 activity was measured in COCs when follicle-enclosed oocytes were cultured in the presence of hCG. Again, this increase preceded oocyte maturation. In conclusion, these data demonstrate that PDE3A is the major PDE form expressed in mammalian oocytes. PDE3A activity increases prior to resumption of meiosis in both spontaneous and gonadotropin-stimulated maturation. These findings strongly support the hypothesis that an increase in oocyte PDE3A activity is one of the intraoocyte mechanisms controlling resumption of meiosis in rat oocytes, at least in vitro.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2001

Relevant cAMP-specific phosphodiesterase isoforms in human pituitary: effect of Gs(alpha) mutations.

Both cAMP production by adenylyl cyclase and cAMP degradation by phosphodiesterases account for intracellular cAMP levels. We previously demonstrated an increased phosphodiesterase activity in GH-secreting adenomas bearing the gsp oncogene. Here we characterize both the activity and the expression of cAMP-specific phosphodiesterase genes in the human pituitary and in gsp+ and gsp- GH-secreting adenomas and analyze the impact of this intracellular feedback mechanism on the levels of cAMP-responsive element-binding protein phosphorylation. Normal pituitary and gsp- GH-secreting adenomas showed similar phosphodiesterase activities, and 7-fold higher levels were observed in gsp+ tumors. In these tumors the increased activity was mainly owing to isobutyl-methyl-xanthine-sensitive phosphodiesterase 4 and to isobutyl-methyl-xanthine-insensitive isoforms. By semiquantitative RT-PCR, all phosphodiesterase 4 transcripts were expressed in the normal and tumoral pituitary. However, the levels of phosphodiesterase 4C and 4D messenger RNAs were significantly higher in gsp+ than in gsp- GH-secreting adenomas and normal pituitary. Expression of the thyroid-specific isobutyl-methyl-xanthine-insensitive phosphodiesterase 8B was absent in the normal pituitary but detectable in almost all GH-secreting adenomas and higher in gsp+ (P < 0.02). Therefore, this study provides a characterization of phosphodiesterase expression in human pituitary and demonstrates a dramatic induction of the cAMP-specific phosphodiesterases 4C and phosphodiesterases 4D and phosphodiesterases 8B in gsp+ GH-secreting adenomas. Similar levels of cAMP-responsive element-binding protein phosphorylation were observed in gsp- and gsp+ GH-secreting adenomas; however, phosphodiesterase blockade caused an increase in cAMP-responsive element-binding protein phosphorylation that was significantly higher in gsp+ than in gsp- adenomas. Because cAMP-responsive element-binding protein represents the principal end point of the cAMP pathway, these results suggest that the enhanced phosphodiesterase activity may have a significant impact on the phenotypic expression of gsp mutations.

1-Methyl-3-isobutylxanthine↗
PubMed2001

A history of plant virology. Cross protection.

Cross protection is a type of induced resistance developing in plants against viruses. Its basis is that prior infection with one virus affords protection against closely related ones. Its history started about seventy years ago, when the Dutchman Thung and the Englishman Salaman described the phenomenon independently. During the 1930s, several virologists confirmed the discovery, which was considered the first possibility to protect plants against virus infection. Growing interest also led plant virologists to formulate the first hypotheses on its mechanism, with the onset of a still unsolved debate. The hypotheses, that have been succeeded until the 1970s, included (i) antibody formation, (ii) exhaustion of essential metabolites, (iii) limited sites for virus multiplication, and (iv) specific adsorption by new cell compounds. These hypotheses were re-proposed and discussed on several occasions without arriving at a final conclusion. The statement of molecular genetics of viruses produced new interesting "theories", fundamentally based on the interference between virus strains. A model developed by the Americans Palukaitis and Zaitlin in 1984 indicates that excess of progeny positive-sense RNA of the protecting strain would sequester the minus-strand RNA of the challenging strain. Other models involve a function of the coat protein, or gene recombination. However, no model that could unify all the various facets of cross protection has hitherto been proposed. All that has not stopped the phenomenon having practical application. From the first attempts against a severe disease of cocoa in West Africa realized by Posnette in the 1940s, a number of crops (such as tomato, tobacco, citrus, cucurbits, grapevine, soybean, papaya, and so on) have been submitted to this practice. During the 1980s, cross protection came to a standstill because of the development of new resistant or tolerant cultivars. Its story is by no means ended, and much work is needed to understand its limits and possibilities.

Botany↗
PubMed2001

A history of plant virology. Mendelian genetics and resistance of plants to viruses.

Virology was borne at the end of the nineteenth century, some years before the re-discovery of the so-called "Mendel's Laws". The rapid development of genetics was helpful to horticulturists and plant pathologists to produce hybrids of important cropping species resistant to several virus diseases. The concepts of Mendelian genetics were applied to plant virology by Francis Oliver Holmes, an American scientist who must be considered a pioneer in several fields of modern plant virology. During the Thirties, Holmes studied in particular the hypersensitive response of solanaceous plants to TMV and discovered the N dominant gene of tobacco hypersensitive to this virus. After the Second World War, the theoretic and practical support given by geneticists assisted plant virologists in better understanding the mechanism of inheritance of the character "resistance". The major problems posed by breeding for plant resistance were detected and critically discussed in several reviews published between the Fifties and the Sixties. These results, together with the discovery of the genetic functions of RNA virus raised interest on the possible relations between viral and plant genes. This fundamental subject saw the entry into the virological scene of molecular genetics, and in 1970 the Russian virologist Joseph Atabekov introduced host specificity to viruses as a central point of plant virology. From the mid 1980s, this point attracted the interest of several virologists, and many results led to several theoretic models of genetic interactions between plant and virus products. In the last fifteen years, the introduction of transgenic plants has given a remarkable contribution to the question of host specificity, which, however, still awaits a general explanation.

Botany↗
PubMed2000

Myomegalin is a novel protein of the golgi/centrosome that interacts with a cyclic nucleotide phosphodiesterase.

Subcellular targeting of the components of the cAMP-dependent pathway is thought to be essential for intracellular signaling. Here we have identified a novel protein, named myomegalin, that interacts with the cyclic nucleotide phosphodiesterase PDE4D, thereby targeting it to particulate structures. Myomegalin is a large 2,324-amino acid protein mostly composed of alpha-helical and coiled-coil structures, with domains shared with microtubule-associated proteins, and a leucine zipper identical to that found in the Drosophila centrosomin. Transcripts of 7.5-8 kilobases were present in most tissues, whereas a short mRNA of 2.4 kilobases was detected only in rat testis. A third splicing variant was expressed predominantly in rat heart. Antibodies against the deduced sequence recognized particulate myomegalin proteins of 62 kDa in testis and 230-250 kDa in heart and skeletal muscle. Immunocytochemistry and transfection studies demonstrate colocalization of PDE4D and myomegalin in the Golgi/centrosomal area of cultured cells, and in sarcomeric structures of skeletal muscle. Myomegalin expressed in COS-7 cells coimmunoprecipitated with PDE4D3 and sequestered it to particulate structures. These findings indicate that myomegalin is a novel protein that functions as an anchor to localize components of the cAMP-dependent pathway to the Golgi/centrosomal region of the cell.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2000

The cAMP-specific phosphodiesterase PDE4D3 is regulated by phosphatidic acid binding. Consequences for cAMP signaling pathway and characterization of a phosphatidic acid binding site.

Hormones and growth factors induce in many cell types the production of phosphatidic acid (PA), which has been proposed to play a role as a second messenger. We have previously shown in an acellular system that PA selectively stimulates certain isoforms of type 4 cAMP-phosphodiesterases (PDE4). Here we studied the effect of endogenous PA on PDE activity of transiently transfected MA10 cells overexpressing the PA-sensitive isoform PDE4D3. Cell treatment with inhibitors of PA degradation, including propranolol, induced an accumulation of endogenous PA accompanied by a stimulation of PDE activity and a significant decrease in both cAMP levels and protein kinase A activity. Furthermore, in FRTL5 cells, which natively express PDE4D3, pretreatment with compounds inducing PA accumulation prevented both cAMP increase and cAMP-responsive element-binding protein phosphorylation triggered by thyroid-stimulating hormone. To determine the mechanism of PDE stimulation by PA, endogenous phospholipids were labeled by preincubating MA10 cells overexpressing PDE4D3 with [(32)P]orthophosphate. Immuno- precipitation experiments showed that PA was specifically bound to PDE4D3, supporting the hypothesis that PDE4D3 activation occurs through direct binding of PA to the protein. PA binding site on PDE4D3 was characterized by engineering deletions of selected regions in the N-terminal regulatory domain of the enzyme. Deletion of amino acid residues 31-59 suppressed both PA-activating effect and PA binding, suggesting that this region rich in basic and hydrophobic residues contains the PA binding site. These observations strongly suggest that endogenous PA can modulate cAMP levels in intact cells, through a direct activation of PDE4D3.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2000

Powerful anticonvulsant action of IL-1 receptor antagonist on intracerebral injection and astrocytic overexpression in mice.

IL-1beta and its endogenous receptor antagonist (IL-1Ra) are rapidly induced by seizures in the rodent hippocampus. Exogenously applied IL-1beta prolongs seizures in an IL-1R type I-mediated manner. This effect depends on N-methyl-d-aspartate receptor activation. We report here that intrahippocampal application of recombinant IL-1Ra or its selective endogenous overexpression in astrocytes under the control of glial acidic fibrillary protein promoter potently inhibits motor and electroencephalographic seizures induced by bicuculline methiodide in mice. Accordingly, transgenic mice show a reduced seizure-related c-fos mRNA expression in various forebrain areas compared with their wild-type littermates. Recombinant IL-1Ra was ineffective in mice deficient in IL-1R type I, having per se a delayed onset to generalized convulsions. These results demonstrate that IL-1Ra mediates potent anticonvulsant effects acting on IL-1R type I and suggest that the balance between brain IL-1beta and IL-1Ra represents a crucial mechanism to control seizure generalization.

Animals↗
PubMed2000

Absence of muscarinic cholinergic airway responses in mice deficient in the cyclic nucleotide phosphodiesterase PDE4D.

Muscarinic cholinergic signaling plays an essential role in the control of the normal airway functions and in the development of pulmonary pathologies including asthma. In this paper we demonstrate that the airways of mice deficient in a cAMP-specific phosphodiesterase (PDE4D) are no longer responsive to cholinergic stimulation. Airway hyperreactivity that follows exposure to antigen was also abolished in PDE4D(-/-) mice, despite an apparently normal lung inflammatory infiltration. The loss of cholinergic responsiveness was specific to the airway, not observed in the heart, and was associated with a loss of signaling through muscarinic receptors with an inability to decrease cAMP accumulation. These findings demonstrate that the PDE4D gene plays an essential role in cAMP homeostasis and cholinergic stimulation of the airway, and in the development of hyperreactivity. In view of the therapeutic potentials of PDE4 inhibitors, our findings provide the rationale for novel strategies that target a single PDE isoenzyme.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2000

Short term feedback regulation of cAMP in FRTL-5 thyroid cells. Role of PDE4D3 phosphodiesterase activation.

Together with a transient accumulation of intracellular cAMP, thyrotropin (TSH) stimulation of the FRTL-5 thyroid cell induces phosphorylation and activation of a cAMP-specific phosphodiesterase (PDE4D3). Here we have investigated the impact of PDE4D3 activation on hormone responsiveness. Stimulation of FRTL-5 cells with TSH caused an increase in PDE activity within 3 min, with a maximal stimulation reached after 5 min. Preincubation with the protein kinase A (PKA) inhibitor H89 or (R(p))-cAMPS, but not with the inactive isomer H85, blocked this activation. Preincubation with PKA inhibitors also blocked the shift in mobility of the PDE4D3 protein. Under these conditions, H89, but not H85, potentiated the cAMP accumulation induced by TSH. Incubation of FRTL-5 cells with the PKA activator 8-(4-chlorophenylthio)adenosine-cAMP caused an increase in PDE activity and a decrease in the endogenous cAMP, confirming the presence of a PKA-PDE feedback loop. MA-10 Leydig tumor cells stably transfected with either a wild type PDE4D3 or a PDE4D3 with mutations in the PKA phosphorylation sites showed an increase in PDE activity when compared with control cells. Human choriogonadotropin or Bt(2)cAMP treatment induced a stimulation of PDE activity in cells transfected with wild type PDE4D3, whereas the activation was absent in mutant- and control-transfected cells. The increase in cAMP accumulation elicited by human choriogonadotropin was reduced in cells transfected with the wild type PDE4D3, but not in cells transfected with the mutant PDE. Rolipram, a specific inhibitor of PDE4, restored the cAMP accumulation in the PDE4D3-transfected cells. These data provide evidence that a rapid activation of PDE4D3 is one of the mechanisms determining the intensity of the cAMP signal.

3',5'-Cyclic-AMP Phosphodiesterases↗