Search PubMed⌕ Search

Biomedical subjects

S Navarro

Publications and source records attributed to S Navarro.

At least 91 records · Page 5Linked to original sources
PubMed1997

Molecular alterations of the RB1, TP53, and MDM2 genes in primary and xenografted human osteosarcomas.

We report the status of the RB1, TP53, and MDM2 genes in human osteosarcomas and cell lines established from surgical specimens and transplanted into athymic naked mice. By using reverse transcriptase-polymerase chain reaction (RT-PCR) as a prescreening technique and posterior sequencing, we observe new mutations in the RB1 gene, notably a duplication in tandem of exons 3 through 6. TP53 mutations appear in codons most frequently mutated in osteosarcomas. We have not seen MDM2 gene amplification in any reported case. These molecular alterations appear in different osteosarcomas not simultaneously present in the same tumor sample. A link has been described between these three genes in the pathways that control the cell cycle and the tumoral progression, but their functions are probably independent in the development of osteosarcomas. TP53 mutations appear in adult patients, whereas RB1 alterations occur mostly in younger patients.

Adolescent↗
PubMed1997

Ultrasonographic study of pancreatic cysts in autosomal dominant polycystic kidney disease.

Pancreatic cysts are an uncommon extrarenal clinical feature of autosomal dominant polycystic kidney disease (ADPKD). The prevalence of pancreatic cysts, sonographically assessed in ADPKD and in the different typs of ADPKD (PKD1 and PKD2) has not been reported. We have studied 173 ADPKD patients and 160 non-affected family members and found a prevalence of pancreatic cysts, of 9% in ADPKD patients over 30 years of age. The presence of pancreatic cysts was related to the increasing age, to the female sex and to the type of ADPKD, found exclusively in PKD1 patients. No complications related to pancreatic cysts were recorded. Pancreatic cysts are an unusual feature of ADPKD and do not appear to contribute to morbidity or mortality.

Adolescent↗
PubMed1997

Acute pancreatitis after long-term 5-aminosalicylic acid therapy.

Acute pancreatitis is a known, although rare, complication of mesalamine treatment. This complication typically appears within the first days or weeks after initiation of therapy. We describe two cases of acute pancreatitis that occurred after long term mesalamine therapy for ulcerative colitis. A rechallenge, performed in both patients, confirmed the diagnosis of mesalamine-induced pancreatitis. These case reports provide evidence that 5-aminosalicylic acid may induce acute pancreatitis after long term treatment.

Acute Disease↗
PubMed1996

Identification of distal silencing elements in the murine interferon-A11 gene promoter.

The murine interferon-A11 (Mu IFN-A11) gene is a member of the IFN-A multigenic family. In mouse L929 cells, the weak response of the gene's promoter to viral induction is due to a combination of both a point mutation in the virus responsive element (VRE) and the presence of negatively regulating sequences surrounding the VRE. In the distal part of the promoter, the negatively acting E1E2 sequence was delimited. This sequence displays an inhibitory effect in either orientation or position on the inducibility of a virus-responsive heterologous promoter. It selectively represses VRE-dependent transcription but is not able to reduce the transcriptional activity of a VRE-lacking promoter. In a transient transfection assay, an E1E2-containing DNA competitor was able to derepress the native Mu IFN-A11 promoter. Specific nuclear factors bind to this sequence; thus the binding of trans-regulators participates in the repression of the Mu IFN-A11 gene. The E1E2 sequence contains an IFN regulatory factor (IRF)-binding site. Recombinant IRF2 binds this sequence and anti-IRF2 antibodies supershift a major complex formed with nuclear extracts. The protein composing the complex is 50 kDa in size, indicating the presence of IRF2 or antigenically related proteins in the complex. The Mu IFN-A11 gene is the first example within the murine IFN-A family, in which a distal promoter element has been identified that can negatively modulate the transcriptional response to viral induction.

Animals↗
PubMed1996

Aprotinin inhibits unspecific degradation of collagen in rat and human pancreas.

CONCLUSION: Addition of aprotinin in human and rat pancreatic extracts inactivates nonspecific proteases that completely degrade collagen. BACKGROUND: We sought to clarify the relative roles of collagenase and nonspecific proteases in the breakdown of collagen by the pancreas. METHODS: The degradation of [3H] collagen fibrils by pancreatic extracts to small fragments of low molecular weight was determined by SDS-electrophoresis and autoradiography. Aprotinin (0.14 mg/mL) was added to inhibit nonspecific protease activity. RESULTS: Rat and human pancreas extracts contained a high collagenolytic activity that was demonstrated to be the result of the combined action of collagenase and other pancreatic proteases. Seventy percent of the total collagenolytic activity in rat pancreas extracts was inhibited by aprotinin. The same aprotinin concentration had no effect on two commercially available collagenases. The electrophoretic pattern obtained from [3H] collagen treated with rat and human pancreatic extracts containing aprotinin confirmed the presence of a true specific collagenase in the pancreas.

Animals↗
PubMed1996

Serum amino-terminal propeptide of type III procollagen levels in chronic pancreatitis.

The severity of pancreatic fibrosis, a characteristic feature of patients with chronic pancreatitis (CP), can be assessed only by direct histologic analysis of pancreatic tissue. Since serum levels of the amino-terminal type III procollagen propeptide (PIIIP) can reflect the degree of fibrogenic activity in several diseases associated with fibrosis, the current study was aimed at investigating whether PIIIP are increased in chronic pancreatitis, the relationship between PIIIP and pancreatic fibrogenic activity, and the influence of pancreatectomy, pancreatic exocrine function, and duration of disease on PIIIP levels. Serum PIIIP was measured in 18 patients with CP (15 without liver disease and three with cholestasis) and in 21 healthy controls. The effect of pancreatectomy on PIIIP was evaluated in seven patients, in whom PIIIP was measured immediately before and 2 months after surgery. Prolylhydroxylase (PHase) activity as an index of pancreatic fibrogenesis was evaluated in pancreatic tissue from 11 patients who had undergone subtotal pancreatectomy and from 11 organ donors. The bentiromide (BT)-PABA test as an index of exocrine pancreatic function was measured in all patients. PIIIP was significantly higher in patients who had or had not undergone pancreatectomy (17.3 +/- 4.0 and 25 +/- 11.4 ng/ml, respectively) than in controls (12.3 +/- 3.1 ng/ml) (p < 0.001). PIIIP decreased significantly after pancreatectomy (before, 32.0 +/- 9.3 ng/ml; after, 18.4 +/- 4.8 ng/ml; p = 0.005). PHase was significantly higher in patients (773 +/- 250 cpm/mg protein) than in controls (405 +/- 121 cpm/mg protein) (p < 0.001). PIIIP was correlated with pancreatic PHase (r = 0.7, p = 0.001) but not with BT-PABA or with the duration of the disease. In conclusion, serum PIIIP levels are increased in patients with CP and reflect the severity of pancreatic fibrogenic activity. No relationship between the serum PIIIP levels and the pancreatic exocrine function and duration of disease was found.

Adult↗
PubMed1996

Effects of prolonged ethanol intake and malnutrition on rat pancreas.

Nutritional factors, especially the protein and fat content of the diet, may change pancreatic morphology after ethanol induced injury. This study was performed to delineate the combined effects of a low fat diet and longterm ethanol ingestion on the rat pancreas. Male Sprague-Dawley rats were maintained with five different diets for 12 weeks and the pancreas removed on the day they were killed. Rats fed a very low fat diet without ethanol (5% of total calories as lipid) developed malnutrition, pancreatic steatosis, and reduction in zymogen granules content. Animals fed a 35% lipid diet with ethanol also developed pancreatic steatosis but changes in zymogen granules content were not detected. Both malnutrition and longterm ethanol consumption increased pancreatic cholesterol ester content, and their effects were additive. Pancreatic steatosis was accompanied with hypercholesterolaemia. Amylase, lipase, and cholesterol esterase content were reduced in malnourished rats; but longterm ethanol ingestion, regardless of the nutritional state, increased lipase content and decreased amylase. It is suggested that high serum cholesterol concentrations and increased pancreatic lipase activity could cause accumulation of cholesterol esters in acinar cells. Fat accumulation in the pancreas has been reported as the earliest histopathological feature in alcoholic patients and may be responsible for cytotoxic effects on the acinar cells at the level of the cell membrane. Although it is difficult to extrapolate results in this animal study to the human situation, the results presented in this work might explain the higher incidence of pancreatitis is malnourished populations as well as in alcoholic subjects that is reported in dietary surveys.

Animals↗
PubMed1996

Immunohistochemical detection of the type I interferon receptor in human fetal, adult, and neoplastic tissues.

We have used the monoclonal antibody IFNaR3 that recognizes the alpha subunit of the type I interferon (IFN) receptor to study the expression of this receptor in a large series of normal human adult and fetal tissues, as well as in a large number of tumors of diverse origin. Among fetal tissues (8-20 weeks) the type I IFN receptor was expressed in liver, striated muscle, epidermis, renal tubules, choroid plexus of the CNS, and epithelia of different origins (bronchial, gastrointestinal, and pancreatic). Adult tissues showed a similar pattern that includes epithelia from salivary ducts, genital tract, bladder, breast, as well as germinal centers of lymph nodes, tonsils, and spleen. The study of a large series of tumors revealed that the type I IFN receptor is expressed in most, but not all, melanomas, bladder, kidney, small bowel, lung, and breast adenocarcinomas. The majority of lymphomas, sarcomas, and endocrine tumors proved negative. These results support the concept that the type I IFN receptor is rather ubiquitously expressed in normal and malignant epithelial tissues. More interestingly, the expression of the type I IFN receptor was not detected in all tumors, raising the question of whether some cases may fail IFN alpha therapy due to the lack of receptor expression. This report demonstrates that the IFNaR3 monoclonal antibody can be used for receptor detection in paraffin-embedded sections and it could represent a useful tool in the search for correlations between IFN alpha response and receptor expression in different diseases.

Adult↗
PubMed1995

The treatment of advanced neuroblastoma. Results of the Spanish Neuroblastoma Study Group (SNSG) studies.

The Spanish Neuroblastoma Study Group has conducted a study on advanced neuroblastoma (N-I-87), which included 33 stage III and 60 stage IV neuroblastoma children more than 1 year of age, enrolled between October 1987 and April 1992. They were staged according to Evans and treated with induction chemotherapy (IC) consisting of 3 courses of cyclophosphamide-doxorubicin alternating with 3 of high-dose cisplatin-teniposide. Evaluation after IC and surgery demonstrated an overall response rate of 88% for stage III and 69% for stage IV. In the latter, complete responses and good partial responses were 33 and 14%, respectively. After surgery, children received maintenance chemotherapy (all stage III except 2 and 30 stage IV) or autologous bone marrow transplantation (ABMT) (11 stage IV), the distribution was not randomised. Probability of survival at 5 years was 0.60 +/- 0.12 for stage III and 0.24 +/- 0.07 for stage IV. A significant difference in survival at 5 years was found between "good responders" and "non-responders" to initial chemotherapy.

Adolescent↗
PubMed1995

Mesenteric panniculitis presenting as fever of unknown origin.

A 40-yr-old man was admitted for fever of unknown origin. Mesenteric panniculitis was suspected as a result of ultrasonography, computed tomography, and nuclear magnetic resonance findings, and that diagnosis was confirmed by laparoscopy with retroperitoneal mass biopsy. Mesenteric panniculitis is a rare disease characterized by an inflammatory process of the mesenteric adipose tissue. Abdominal pain, weight loss, and abdominal mass are the most frequent symptoms. High fever and leukocytosis are uncommon. To the best of our knowledge, only two reports of mesenteric panniculitis presenting as fever of unknown origin have been described previously, with no cases published in the English literature. In the case reported, steroid therapy was started with initial improvement. Despite the temporary addition of azathioprine and the maintenance of the prednisone treatment, no further improvement has been achieved. Two years and 5 months after admission, the patient presents intermittent episodes of fever and muscle pain.

Adult↗
PubMed1994

Aggregated IgE mimic interleukin-3-induced histamine synthesis by murine hematopoietic progenitors.

Similar to interleukin-3 (IL-3), IgE acts on murine bone marrow cells by inducing histamine production. This effect does not result from degranulation of histamine-containing cells, but from histamine synthesis, as assessed by the following findings. (1) The histamine content of freshly isolated bone marrow cells is too low to account for the increase in extracellular histamine levels. (2) Neither IL-3 nor IgE induced histamine production in the presence of the specific inhibitor of histidine decarboxylase (HDC), the histamine-forming enzyme. (3) Both the enzymatic activity and the mRNA expression of HDC were enhanced in response to IL-3 or IgE. Artificial aggregation or formation of IgE immune complexes augmented ther effect on histamine synthesis, indicating that the aggregated form is responsible for this biologic activity. Yet, it is apparently not mediated by Fc epsilon RI because their cross-linkage by dinitrophenyl bovine serum albumin after presensitization with IgE did not induce histamine production by hematopoietic progenitors. Among other aggregated isotypes tested, only IgG2a and, to a lesser extent, IgG1 had a consistent but lower effect, whereas IgM and IgA were completely inactive. The target cells of IL-3 and IgE in terms of histamine synthesis do not belong to mature bone marrow populations, especially mast cells. They copurify with hematopoietic progenitors in the low-density layers of a discontinuous Ficoll gradient where they represent around 5% of the cells, as determined by in situ hybridization. This percentage remained the same, regardless of whether the cells were stimulated by IgE or IL-3 alone or by a combination of both, suggesting a common responder cell. In accordance with this notion, histamine-producing cells could not be distinguished from each other on the basis of density, size and internal structure, or rhodamine (Rh) retention. Finally, the effect of IgE is not caused by the induction of IL-3 because anti-IL-3 antibodies did not abrogate the effect of IgE.

Animals↗
PubMed1994

Patterns of differentiation in extraosseous Ewing's sarcoma cells. An in vitro study.

BACKGROUND: In vitro, tissue culture-associated differentiation assays have facilitated the identification of multiple tumor-cell types. METHODS: We have investigated the capability of differentiation of three extraosseous Ewing's sarcoma cell lines toward a neural and muscular direction by in vitro stimulation with dibutyryl cyclic adenosine-monophosphate (db cAMP) and 5-azacytidine, respectively. RESULTS: Elongation of cytoplasmic processes and increase of neural markers chromogranin, S-100 protein, and glial fibrillary acidic protein were observed after db cAMP treatment of these lines and neurosecretory granules as well as myelin figures were demonstrated ultrastructurally. These results support the existence of several pathways of neural differentiation in vitro--neuroblastic, Schwannian, and central glial--in stages of maturation more advanced than those previously reported in Ewing's sarcoma of bone. The cell lines showed no definitive myoblastic differentiation after 5-azacytidine treatment. CONCLUSIONS: These data suggest that these three extraosseous Ewing's sarcoma cell lines configurate a heterogeneous group of tumors with respect to capability of differentiation into the neural lineage, arrested at more advanced stages of neural crest development than Ewing's sarcoma of bone and without capability of myoblastic differentiation with 5-azacytidine.

Abdominal Neoplasms↗
PubMed1994

Developmental control of IFN-alpha expression in murine embryos.

The expression of IFN-alpha transcripts was investigated in murine embryos, fetuses, and fetal annexes in mid and late pregnancy. We have shown by Northern blot analysis, reverse transcription-polymerase chain reaction, and in situ hybridization the presence of IFN-alpha transcripts in mouse placenta, fetus, and newborn. From the 14th day of gestation until birth, a typical IFN-alpha transcript (1.2 kb) is found in the fetus. A transcript of larger size (2.2 kb) appears near birth and is present in the newborn mouse. Fetal annexes between the 10th and 21st days of gestation also express IFN-alpha. From the 10th day until birth, the 1.2-kb IFN-alpha mRNA species is present, as well as unusually large transcripts: 4 and 7 kb. To localize IFN-alpha transcripts, in situ hybridization was performed, using 35S-IFN-alpha antisense RNA probe in comparison with the sense RNA probe. The tissue pattern of IFN-alpha transcription in fetuses shows a clear labeling of many epithelia, such as skin, ependyme, and intestine glandular epithelium. A possible relation with cellular differentiation is discussed.

Animals↗
PubMed1994

HYDRO: a computer program for the prediction of hydrodynamic properties of macromolecules.

HYDRO is a program for the calculation of sedimentation and diffusion coefficients, rotational relaxation times, and intrinsic viscosities of rigid macromolecules of arbitrary shape that are represented by bead models. Actually, HYDRO contains various FORTRAN callable subroutines that can be linked to the user's own programs to account for variability of shape or flexibility. Some hints are given for the use of HYDRO in various situations.

Computer Simulation↗
PubMed1994

Hydrodynamic properties of a double-helical model for DNA.

The translational and rotational diffusion coefficients of very short DNA fragments have been calculated using a double-helical bead model in which each nucleotide is represented by one bead. The radius of the helix is regarded as an adjustable parameter. The translational coefficient and the perpendicular rotation coefficient agree very well with experimental values for oligonuclotides with 8, 12, and 20 base pairs, for a single value of the helical radius of about 10 A. We have also calculated a nuclear magnetic resonance relaxation time in which the coefficient for rotation about the main axis is involved. As found previously with cylindrical models, the results deviate from experimental values, indicating that the internal motion of the bases has a remarkable amplitude. An attempt to quantify the extent of internal motions is presented.

Biophysical Phenomena↗
PubMed1994

Immunohistochemical detection of P-glycoprotein in Ewing's sarcoma and peripheral primitive neuroectodermal tumors before and after chemotherapy.

The authors evaluated P-glycoprotein expression in a total of 35 cases of Ewing's sarcoma and peripheral primitive neuroectodermal tumors (PNET). Fifteen cases had matched tumors before and after treatment. The 20 unmatched tumors included 14 pretreatment PNETs and Ewing's sarcomas and 6 posttreatment Ewing's sarcomas. Two antibodies, C219 and JSB-1, were used. Immunoreactivity was almost exclusively membranous. Variability in the number of positive cells and in staining intensity was noted within individual tumors. Among the 15 matched tumors, 7 were positive for P-glycoprotein before treatment; 6 of these remained positive after treatment. Four of the 8 that were negative for P-glycoprotein before treatment became positive after treatment. Of the unmatched tumors, 9 of 14 pretreatment and 3 of 6 posttreatment tumors were positive. When relapse-free survival time, based on the presence or absence of P-glycoprotein positivity in pretreatment tumor samples, was evaluated in this group, no significant difference was found (P2 = .92); however, the numbers are too small to draw definitive conclusions. The high incidence of positive primary tumors suggests that P-glycoprotein expression is probably intrinsic in Ewing's sarcoma and PNET and not necessarily induced by therapy.

ATP Binding Cassette Transporter, Subfamily B, Mem↗