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M Prat

Publications and source records attributed to M Prat.

At least 19 recordsLinked to original sources
PubMed2006

Caspase-independent death of meiotic and postmeiotic cells overexpressing p53: calpain involvement.

In a model of male sterility (MTp53) owing to enforced p53 expression in spermatocytes II and spermatids of transgenic mice, we focused on the role of caspases. Most of them are expressed in all differentiation stages, but only the transcriptional levels of caspase-2 and caspase-3 are modified in MTp53 germ cells. In normal testis, cleaved caspase-3 and caspase-9 are detected during the elongation of spermatids. Despite this constitutive presence of caspases during terminal differentiation, calpains are the main effectors of germ cell loss in MTp53 testes: calpain 1 RNA levels are increased, caspase-3-like activity is markedly decreased while calpain activity is higher and the calpain inhibitor E64d ((2S, 3S)-trans-epoxysuccinyl-L-leucylamido-3-methylbutane ethyl ester) reduces TUNEL labeling in MTp53 testis, whereas pancaspase inhibitor zVADfmk (N-benzyloxycarbonyl-Val-Ala-Asp(OMe)-fluoromethylketone) has no effect. Our work suggests that despite the presence, and potent involvement, of caspases in male haploid cell maturation, calpains are the executioners of the death of terminally differentiating germ cells.

Amino Acid Sequence↗
PubMed2006

Geodesic network method for flows between two rough surfaces in contact.

A discrete network method based on previous asymptotic analysis for computing fluid flows between confined rough surfaces is proposed. This random heterogeneous geodesic network method could be either applied to surfaces described by a continuous random field or finely discretized on a regular grid. This method tackles the difficult problem of fluid transport between rough surfaces in close contact. We describe the principle of the method as well as detail its numerical implementation and performances. Macroscopic conductances are computed and analyzed far from the geometrical percolation threshold. Numerical results are successfully compared with the effective medium approximation, the application of which is also studied analytically.

Journal Article↗
PubMed2006

An outbreak of airborne tularaemia in France, August 2004.

Fifteen tularaemia cases were identified after a holiday spent at a converted mill in the Vendee region in France, between 9 and 12 August 2004. The mill was visited, and descriptive, retrospective cohort and environmental investigations were conducted. The 39 people who had stayed at the mill between 24 July and 11 August were asked about symptoms, exposure to food and animals, and leisure activities. A case was defined as a person with evidence of fever and a positive serology (seroconversion or significant rise in antibody titre, or a single titre) = 40. Culture for Francisella tularensis and polymerase chain reaction (PCR) diagnosis was carried out for drinking water, firewood, and domestic animals at the mill. Fifteen cases of tularaemia (38%) were confirmed. Twelve of the cases (80%) had the pulmonary form. None of the patients was admitted to hospital. There was a strong association between infection and participation in a dinner at the mill on 4 August (p < 10(-8)). One of the three dogs present in the dining room was serologically positive for F. tularensis. Results of analysis of environmental samples were negative. These investigations confirmed the occurrence of a cluster of 15 tularaemia cases, in patients who were infected on the evening of 4 August, in a mill in VendAe, an endemic area for tularaemia. The investigations highlight the existence of nonspecific and benign pulmonary forms of the illness in France. The pulmonary form of infection in the human cases and the positive serology of the dog suggest contamination by inhalation of contaminated particles from the dogos fur disseminated by the dog shaking itself.

Adolescent↗
PubMed2005

A comparison of raloxifene and calcium plus vitamin D on vaginal atrophy after discontinuation of long-standing postmenopausal hormone therapy in osteoporotic women. A randomized, masked-evaluator, one-year, prospective study.

OBJECTIVES: We assessed the effects of the discontinuation of long-standing transdermal estrogen replacement therapy (>4 years) and substitution of this treatment by calcium or raloxifene on the vaginal epithelium and climateric symptoms in a study population of osteoporotic women. METHODS: A total of 136 women (mean age 55.5 years) were randomized to calcium (500 mg elemental calcium, 400 IU Vitamin D3) (n=40), raloxifene (60 mg/day) (n=48), or estrogen patches (3.9 mg estradiol) and progesterone (100 mg/day) (n=48). Treatment was given for 1 year. The vaginal maturation value (VMV), serum estradiol levels, and climateric symptoms using a 12-item modification of the SF-36 quality of life questionnaire were evaluated at baseline and at 6 and 12 months. RESULTS: At 6 months, mean VMV decreased significantly (P<0.001) in the calcium (-51.8%) and raloxifene (-18.6%) groups compared with baseline and the estrogen/progesterone group. At 12 months, significant decreases of mean VMV in the calcium (-38.7%) and raloxifene groups (-32%) (P<0.001) were also observed. Serum estradiol levels and changes of VMV correlated significantly at 6 months (rho=0.361, P<0.01) and at 12 months (rho=0.269, P<0.035). A significantly higher number of patients complained of hot flushes and palpitations in the calcium and raloxifene groups than in the estrogen/progesterone group. Raloxifene-treated women reported a significantly higher number of adverse events at 6 months compared to the other treatment groups. CONCLUSIONS: Withdrawal and change of long-standing transdermal hormone replacement therapy by treatment with calcium or raloxifene resulted in worsening of vaginal atrophy assessed by the VMV, although it was not clinically perceived by the patients. However, increases in dyspareunia and urinary leaks were reported. Menopausal complaints related to vasomotor symptoms worsened in the calcium- and raloxifene-treated groups and persisted throughout the study period.

Administration, Cutaneous↗
PubMed2005

Quasi-static liquid-air drainage in narrow channels with variations in the gap.

This paper studies the shape of an air bubble quasi-statically flowing in the longitudinal direction of narrow channels. Two bottom topographies are treated, i.e., linear and quadratic variations of the gap along the transverse direction. This work analyses the main characteristics of the gas-liquid interface with respect to the wedge aspect ratio. From the convergence of asymptotic, numerical and experimental analyses, we found simple dependences for the finger width and total curvature as a function of channel aspect ratio. These results provide simple and general expressions for the pressure drop needed to overcome capillary forces and push the air finger inside the channel.

Journal Article↗
PubMed2002

Drying processes in the presence of temperature gradients--pore-scale modelling.

The influence of temperature gradients on the drying of water-saturated porous networks has been studied. We have focussed on the influence of the temperature on the drying process via the equilibrium vapor density rhoe, because this is the most sensitive parameter with respect to variations of the temperature T. We have used a 2D model which accounts for both capillary and buoyancy forces. Invasion events by air or water are handled by standard rules of invasion percolation in a gradient (IPG). Vapor fluxes are calculated by solving a discretized version of the Laplace equation. In the model the temperature T varies linearly from the open side T0 to the closed side TL. The temperature gradients strongly influence the cluster evolution during the process, because they facilitate vapor transport through wet regions. When T0 TL, the front movement is enhanced and the air ingress in the wet region behind the front is inhibited. The behavior of 3D systems differs from that of 2D systems, because the point where air percolates the system and the point where the water network breaks up in isolated clusters do not coincide. Before the latter fragmentation point the temperature will mainly influence the drying rates. After this point also the water distribution becomes sensitive to the temperature profile.

Journal Article↗
PubMed2001

[Prevalence of hypovitaminosis D in elderly institutionalized residents: influence of a substitutive treatment].

BACKGROUND: Osteoporosis in the elderly is a common and severe disease, vitamin D deficiency being an important causative factor. Hypovitaminosis D is frequent in old people, particularly those living in nursing homes. SUBJECTS AND METHOD: We performed a cross-sectional study of 100 randomly recruited elderly institutionalized subjects. The prevalence of hypovitaminosis D and its possible repercussion on the phosphocalcium metabolism were assessed. The degree of sun exposure and the existence of co-morbidity were also recorded. Individuals with hypovitaminosis D were included in a longitudinal study (6 months' duration) aimed at assess the efficacy of treatment with calcium and two different therapeutic regimens with calcidiol (16,000 IU/week or 16,000 IU every 3 weeks). RESULTS: 87% of individuals had hypovitaminosis D; 21.8% of them had secondary hyperparathyroidism. The study population had a low degree of sun exposure and a high level of co-morbidity. The two doses of calcidiol led to a normalization of 25-OHD3 levels, increased calciuria and compensated secondary hyperparathyroidism, yet higher 25-OHD3 levels were achieved with the weekly therapeutic scheme. CONCLUSIONS: Hypovitaminosis D prevalence appears to be very high In the elderly institutionalized population. Calcium and calcidiol supplementation normalized 25-OHD3, improved calcium absorption and compensated secondary hyperparathyroidism. Calcium and vitamin D supplementation should be employed routinely in the elderly institutionalized population.

Aged↗
PubMed2001

Sliding lubricated anisotropic rough surfaces.

The object of this paper is to study the effects of lubricant film flow, pressurized and sheared between two parallel rough surfaces in sliding motion. The influence of microscopic surface roughness on lubricant film flow macroscopic behavior is described through five nondimensional parameters called flow factors. These macroscopic transport parameters are related to the local geometry of apertures and surfaces. Short- and long-range-correlated surface roughnesses display very different macroscopic behaviors when surfaces are close to contact. These behaviors are related to underlying surface roughness parameters such as the correlation length and the self-affine Hurst exponent. The problem is numerically studied, and results are compared to some analytical asymptotic results.

Journal Article↗
PubMed2001

Met protein and hepatocyte growth factor (HGF) in papillary carcinoma of the thyroid: evidence for a pathogenetic role in tumourigenesis.

In the last 10 years, evidence has accumulated that overexpression of Met protein is a distinguishing feature of almost every case of well-differentiated papillary carcinoma. Increased expression of the protein is probably due to enhanced transcription of the MET gene and/or to post-transcriptional mechanisms. So far, alterations of the MET gene have not been recognized, but evidence has been provided that activated RAS and RET can cause accumulation of MET RNA. Thus, the possibility exists that dysregulation of MET is the final result of different molecular pathways capable of inducing thyroid cell transformation; RET rearrangements might account for some of the cases, but the demonstration that the majority of papillary carcinomas do not have recognized alterations of the RET gene strongly suggests that MET gene dysregulation can also be achieved through other molecular pathways. Dysregulation of MET causes marked accumulation of Met protein in tumour cells that is promptly detected by immunohistochemistry. Thus, overexpression of Met protein might represent an immunohistochemical marker of papillary carcinoma, potentially helpful in problematic cases, but caution is required; moderate expression of Met protein is observed in non-neoplastic thyroid diseases, such as Graves' and Hashimoto's thyroiditis, and reagents active on paraffin sections may have a low affinity and/or low specificity for Met protein, leading to artifactual staining. Met protein-positive papillary carcinoma cells may produce hepatocyte growth factor (HGF) and may activate HGF through the urokinase-type plasminogen activator (uPA) bound to urokinase-type plasminogen activator receptor (uPA-R). Thus, papillary carcinoma cells possess the molecular machinery necessary for a productive HGF/Met interaction. In vitro studies have demonstrated that HGF enhances the motility and invasiveness of tumour cells and induces the synthesis and release of chemokines active in the recruitment of dendritic cells. These observations provide a rational basis for the understanding of two distinguishing features of papillary carcinoma. First, the tumour is often characterized by early metastatic spread to regional lymph nodes and by multifocal involvement of the gland, which suggests highly invasive behaviour. Second, a prominent peritumoural inflammatory reaction is often observed, which suggests cross-talk between tumour cells and the immune system.

Biomarkers, Tumor↗
PubMed2000

Expression of functional tyrosine kinases on immortalized Kaposi's sarcoma cells.

Kaposi's sarcoma (KS) is the most frequent malignant lesion in patients with AIDS and is characterized by spindle cell proliferation, inflammatory cell infiltration, angiogenesis, edema, and invasiveness. KS origin is still debated. The complex aspect of this disease is probably supported by multiple concomitant pathogenetic factors, among which growth factors and their cognate tyrosine kinase receptors are deeply involved. Here we have investigated the expression status and functional integrity of KDR and Met receptors, as well as of their ligands, in an immortalized KS cell line (KS-IMM). The MET and KDR genes encode the tyrosine kinase receptors for Hepatocyte Growth Factor (HGF) and Vascular Endothelial Growth Factor (VEGF) respectively. Both factors are pleiotropic cytokines controlling growth, survival, motility, invasive migration and differentiation of endothelial cells. We have found that KS-IMM cells, which retain most of the features of the parental tumor and can induce KS-like sarcomas when injected subcutaneously in nude mice, express the Met receptor, but not its ligand. The receptor, which is basally inactive, is functional, being tyrosine phosphorylated in response to ligand stimulation and mediating the expected HGF-dependent biological responses of motility, invasion and proliferation. Moreover, we report that KS-IMM cells coexpress VEGF and KDR and that KDR is constitutively tyrosine phosphorylated, possibly as a consequence of the establishment of an autocrine loop. The receptor, however, maintains responsiveness to exogenously added ligand, by increasing the level of tyrosine phosphorylation and by responding in biological assays of motility, invasion and proliferation. Finally, we have found that the two growth factors synergize in a motility assay. These data show that HGF and VEGF are growth factors active on KS-IMM cells.

Animals↗
PubMed2000

Phenotypic alterations in Kaposi's sarcoma cells by antisense reduction of perlecan.

Metastasis is a sequence of events including proliferation, migration, adhesion, invasion and subsequent metastatic growth of tumour cells in distant organs. We previously showed that highly metastatic variants of murine melanoma cells express higher levels of the basement membrane proteoglycan perlecan than low or non metastatic variants and expression of an antisense perlecan can reduce metastatic potential. In contrast, antisense expression of perlecan in fibrosarcoma cells was reported to enhance tumorigenesis. To better understand the role of perlecan in angiogenesis we have transfected KS-IMM, an immortalized cell line derived from a human Kaposi s sarcoma, with an antisense perlecan construct and investigated the positive/negative role of perlecan in KS. KS-IMM cells were transfected with either empty vector (neo) or the antisense perlecan construct and clones were isolated. Immuno-blot analysis showed a reduction of perlecan levels in two (AP3 and AP4) isolated clones, in Northern blot analysis endogenous perlecan was undetectable in the AP3 and AP4 clones, while it was present in the neo control clones. AP clones had a reduced migration to HGF in Boyden chambers as compared to neo clones. Proliferation in low serum or serum-free conditions was strongly reduced in the AP clones as compared to the neo control cells. The neotransfected cells showed rapid proliferation in low serum supplemented with HGF and VEGF, while antisense transfected clones showed little response. Finally, AP-trasfected KS-IMM cells had significantly reduced migration to VEGF and HGF with respect to controls. In contrast, when the AP transfected cells were injected in nude mice they paradoxically showed enhanced tumor growth as compared to controls. Our preliminary data indicate that perlecan reduction plays a crucial role on Kaposi s sarcoma cell migration and proliferation in vitro. However, in vivo KS-IMM depleted of perlecan had a growth advantage. A possible hypothesis is that perlecan is necessary for growth of KS-IMM cells in vitro, however its down-regulation might promote angiogenesis through increased angiogenic growth factor diffusion, resulting in enhanced tumor growth in vivo.

Animals↗
PubMed2000

Papillary carcinoma of the thyroid: hepatocyte growth factor (HGF) stimulates tumor cells to release chemokines active in recruiting dendritic cells.

Tissue distribution of dendritic cells was investigated in eight cases of papillary carcinoma of the thyroid using immunohistochemistry. Most dendritic cells had an immature phenotype (CD1a++, CD11c+, CD40+, CD86-, HLA-DR-) and were located at the invasion edge of the tumor. This pattern of distribution was profoundly different from that of CD68+ macrophages, which were evenly distributed throughout the tumor. The ability of tumor cells to release chemotactic factors active on dendritic cells was investigated in primary cultures of the same cases of papillary carcinoma, and was compared to that of the corresponding normal thyroid cells obtained from the tumor-free contralateral lobe. Chemotactic activity of culture supernatants was tested against dendritic cells in a chemotaxis chamber. It was found that papillary carcinoma cells were active in releasing chemotactic activity, that hepatocyte growth factor (HGF; 100 ng/ml) or interleukin (IL)-1beta (10(3) U/ml) induced a fourfold increase in the amount of chemotactic activity released, and that normal thyroid cells obtained from the same patients were as effective as tumor cells. Characterization of chemokines at RNA level revealed that unstimulated cells contain large amounts of IL-8 and monocyte chemotactic protein (MCP)-1 RNAs, and that stimulation with HGF or IL-1beta induced RNAs for regulated upon activation normal T expressed and secreted (RANTES), macrophage inflammatory protein (MIP)-3alpha, interferon-gamma-inducible protein 10 (IP-10), and, to a lesser extent, MIP-1alpha and MIP-1beta. The possibility that HGF/Met interaction has a biological role in vivo was investigated in serial sections of six tumors immunostained for CD1a+, Met protein, and HGF. It was found that all six tumors were intensely and diffusely positive for Met protein, that HGF staining was present in tumor cells of the advancing edge, and that HGF+/Met+ tumor cell nests were infiltrated by CD1a+ dendritic cells. The foregoing observations are consistent with the possibility that HGF stimulation of Met+ tumor cells is one of the molecular mechanisms involved in the recruitment of dendritic cells.

Adolescent↗
PubMed2000

Molecular characterization of HHV-8 positive primary effusion lymphoma reveals pathogenetic and histogenetic features of the disease.

BACKGROUND: Primary effusion lymphoma (PEL) associates with HHV-8 infection, preferentially develops in immunodeficient patients and grows in the serous body cavities. PEL derives from post-germinal center, pre-terminally differentiated B-cells. The pathogenesis of PEL is unclear and the sole identified genetic lesions are human herpesvirus type-8 (HHV-8) infection in all cases and EBV infection in 70% of cases. Epstein-Barr virus (EBV) infection in PEL displays a latency I phenotype. OBJECTIVES: To clarify the pathogenesis and histogenesis of PEL by investigating (1) the lymphoma karyotype; (2) the expression status of the Met tyrosine kinase receptor and of its ligand hepatocyte growth factor (HGF); (3) the molecular profile of EBV, with particular focus on mutations of EBNA-1 genes, which are thought to affect viral tumorigenicity in EBV-infected neoplasms displaying the latency I phenotype. STUDY DESIGN: Twenty-four PEL (nine cell lines and 15 primary specimens) formed the basis of the study. Karyotypes were investigated by conventional cytogenetics and fluorescent in situ hybridization (FISH) in selected cases. The expression status of Met and HGF was defined by multiple techniques, including RT-PCR, FACS analysis, immunocytochemistry, Western blot studies and ELISA. The molecular profile of EBNA-1 genes of EBV were investigated by DNA direct sequencing. RESULTS: Trisomy 7, trisomy 12 and breaks at 1q21-q25 are recurrently associated with PEL. PEL consistently co-express Met and HGF both at the mRNA and protein level. Among aggressive B-cell lymphomas, Met/HGF co-expression appears to be relatively specific for PEL. The EBNA-1 gene of EBV displays a high degree of genetic heterogeneity in PEL, with no preferential association with one specific variant. CONCLUSIONS: PEL associates with recurrent chromosomal alterations, suggesting that viral infection is not sufficient for tumor development and that lesions of cellular genes may be required. The expression of Met/HGF by PEL cells may bear implications for the lymphoma proliferation and growth pattern, since Met/HGF interactions influence cell mitogenesis and motogenesis. EBV infection in PEL displays a latency I phenotype and fails to associate with specific EBNA-1 variants, suggesting that the role of EBV in PEL is not mediated by the major transforming pathways currently known in EBV positive lymphomas.

Epstein-Barr Virus Nuclear Antigens↗
PubMed2000

The tyrosine kinase receptor met and its ligand HGF are co-expressed and functionally active in HHV-8 positive primary effusion lymphoma.

Primary effusion lymphoma (PEL) harbors consistent infection by human herpesvirus-8, preferentially develops in immunodeficient patients and selectively localizes to the serous body cavities. Histogenetic analysis has suggested that PEL originates from post-germinal center, pre-terminally differentiated B cells sharing phenotypic features with plasma cells. Here we have investigated the expression status and functional integrity of the Met tyrosine kinase receptor and of its ligand hepatocyte growth factor (HGF). Thirteen PEL (nine cell lines and four primary specimens) were analyzed for Met and HGF expression and function by multiple assays. For comparison, a panel of 34 high grade B cell non-Hodgkin lymphomas (NHL) other than PEL was also investigated. Co-expression of Met and HGF was found in all PEL analyzed, whereas it was restricted to 1/34 B cell NHL other than PEL (P < 0.001; chi2 test). The Met protein expressed by PEL displays biochemical characteristics typical of Met expressed by other cell types and is capable of tyrosine autophosphorylation. By using a combination of immunological and biological assays, production and secretion of a functional HGF species was identified in all PEL cell lines analyzed. HGF stimulation of PEL cells rapidly induces Met tyrosine phosphorylation, demonstrating the functional integrity of the Met/HGF loop. Because of the well known mitogenic and motogenic properties of Met/HGF interactions, these data may bear implications for PEL growth and dissemination. Among B cell neoplasms, Met/HGF co-expression selectively clusters with PEL and, as demonstrated by previous studies, with multiple myeloma plasma cells, thus reinforcing the notion that PEL displays biologic similarities with tumors derived from late stages of B cell differentiation.

Gene Expression Regulation, Neoplastic↗
PubMed1999

Hepatocyte growth factor (HGF) stimulates tumour invasiveness in papillary carcinoma of the thyroid.

The present study has investigated the functional role of the Met receptor in primary cultures of 20 papillary carcinomas and of normal thyroid cells obtained from the same patients. Normal and tumour cells grew as adherent cells, formed a confluent monolayer after 10-20 days, had epithelial morphology, and were immunoreactive for cytokeratin, vimentin, and thyroglobulin. The potential effect of hepatocyte growth factor (HGF) on cell invasiveness was investigated in Boyden chambers, using a nucleopore filter coated with Matrigel as the barrier and HGF as the chemoattractant. Tumour cells of five out of seven cases of papillary carcinoma were more responsive to HGF than the corresponding normal cells in terms of the number of migrated cells per mm(2). Involvement of the Met receptor in the HGF-induced migratory response was suggested by the observation that the agonistic anti-Met monoclonal antibody (MAb) DO-24 was equally effective. HGF did not affect the proliferative activity of thyroid cells. Under the same experimental conditions, 10 per cent fetal bovine serum (FBS) induced a two-fold increase in [(3)H]thymidine incorporation into normal cells and tumour cells. These findings are consistent with the possibility that HGF plays a crucial role in determining the invasiveness of tumour cells in papillary carcinoma of the thyroid.

Antibodies, Monoclonal↗
PubMed1999

Drying of capillary porous media with a stabilized front in two dimensions.

We study a two-dimensional model of drying of capillary porous media when gravity or viscous forces lead to the formation of a stabilized front. When gravity forces stabilize the front, the mean front width, defined as the mean perpendicular distance between the front's most advanced and least advanced points, is found theoretically to scale with the Bond number B as B(-1+(1+beta)/(1+nu)), where beta is the percolation probability exponent and nu is the correlation length exponent. This scaling is confirmed numerically and is consistent with the experimental results of Shaw [Phys. Rev. Lett. 59, 1671 (1987)]. The global mass transfer coefficient of the front is studied numerically. To this end, we study the position z(c)-delta of the equivalent smooth line leading to the same evaporation flux as the front. In the transient case, z(c)-delta is found to scale with the Bond number B as B-0.63. In the stationary case, i.e., when the front reaches a stationary position within the medium, it is found that z(c)-delta approximately sigma where sigma is the standard deviation of the positions of the points forming the front around its mean position z(c). These results are exploited to study the evaporation flux when viscous effects stabilize the front. In particular, we discuss the possibility of nontrivial behaviors, i.e., drying rates not scaling as 1/square root of t for drying under constant external conditions.

Journal Article↗