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J M Silva

Publications and source records attributed to J M Silva.

At least 19 recordsLinked to original sources
PubMed2006

Magnetic field exposure and long-term survival among children with leukaemia.

We examined the association between magnetic field (MF) exposure and survival among children with acute lymphoblastic leukaemia (ALL) treated at 51 Pediatric Oncology Group centres between 1996 and 2001. Of 1672 potentially eligible children under treatment, 482 (29%) participated and personal 24-h MF measurements were obtained from 412 participants. A total of 386 children with ALL and 361 with B-precursor ALL were included in the analysis of event-free survival (time from diagnosis to first treatment failure, relapse, secondary malignancy, or death) and overall survival. After adjustment for risk group and socioeconomic status, the event-free survival hazard ratio (HR) for children with measurements >/=0.3 muT was 1.9 (95% confidence interval (CI) 0.8, 4.9), compared to <0.1 muT. For survival, elevated HRs were found for children exposed to >/=0.3 muT (multivariate HR=4.5, 95% CI 1.5-13.8) but based on only four deaths among 19 children. While risk was increased among children with exposures above 0.3 muT, the small numbers limited inferences for this finding.

Adolescent↗
PubMed2006

Control of oestradiol secretion and of cytochrome P450 aromatase messenger ribonucleic acid accumulation by FSH involves different intracellular pathways in oestrogenic bovine granulosa cells in vitro.

The objective of this study was to determine the major intracellular signalling pathways used by FSH and insulin to stimulate cytochrome P450 aromatase (Cyp19) mRNA and oestradiol accumulation in oestrogenic bovine granulosa cells in vitro. Bovine granulosa cells from small follicles (2-4 mm diameter) were cultured for 6 days under non-luteinizing conditions in the presence of insulin at 100 ng/ml, or insulin (10 ng/ml) and FSH (1 ng/ml). On day 4 of culture, specific inhibitors of phosphatidylinositol 3-kinase (PI3K; LY-294002), protein kinase C (PKC; GF-109203X), protein kinase A (PKA; H-89) or mitogen-activated protein (MAP) kinase activation (PD-98059) were added. The addition of PI3K and PKC inhibitors, but not of PKA inhibitor, significantly decreased insulin-stimulated Cyp19 mRNA levels and oestradiol accumulation (P < 0.001). The PKA inhibitor significantly decreased FSH-stimulated Cyp19 mRNA abundance and oestradiol secretion, whereas PI3K and PKC inhibitors decreased oestradiol secretion without affecting Cyp19 mRNA accumulation. Inhibition of MAP kinase pathway significantly increased Cyp19 mRNA abundance in insulin- and FSH-stimulated cells. P450scc mRNA levels and progesterone secretion were not affected by any inhibitor in either experiment. Although FSH stimulates Cyp19 expression predominantly through PKA, oestradiol secretion is altered by PI3K and PKC pathways independently of Cyp19 mRNA levels. In addition, we suggest that Cyp19 is under tonic inhibition mediated through a MAP kinase pathway.

Animals↗
PubMed2004

Activated carbon and tungsten oxide supported on activated carbon catalysts for toluene catalytic combustion.

We have used activated carbon (AC) prepared from almond shells as a support for tungsten oxide to develop a series of WOx/AC catalysts for the catalytic combustion of toluene. We conducted the reaction between 300 and 350 degrees C, using a flow of 500 ppm of toluene in air and space velocity (GHSV) in the range 4000-7000 h(-1). Results show that AC used as a support is an appropriate material for removing toluene from dilute streams. By decreasing the GHSV and increasing the reaction temperature AC becomes a specific catalyst for the total toluene oxidation (SCO2 = 100%), but in less favorable conditions CO appears as reaction product and toluene-derivative compounds are retained inside the pores. WOx/AC catalysts are more selective to CO2 than AC due to the strong acidity of this oxide; this behavior improves with increased metal loading and reaction temperature and contact time. The catalytic performance depends on the nonstoichiometric tungsten oxide obtained during the pretreatment. In comparison with other supports the WOx/AC catalysts present, at low reaction temperatures, higher activity and selectivity than WO, supported on SiO2, TiO2, Al2O3, or Y zeolite. This is due to the hydrophobic character of the AC surface which prevents the adsorption of water produced from toluene combustion thus avoiding the deactivation of the active centers. However, the use of WOx/AC system is always restricted by its gasification temperature (around 400 degrees C), which limits the ability to increase the conversion values by increasing reaction temperatures.

Air Pollution↗
PubMed2004

Expression of 17beta- and 3beta-hydroxysteroid dehydrogenases and steroidogenic acute regulatory protein in non-luteinizing bovine granulosa cells in vitro.

Granulosa cells of small follicles differentiate in vitro in serum-free medium, resulting in increased estradiol secretion and abundance of mRNA encoding cytochrome P450aromatase (P450arom). We tested the hypothesis that differentiation in vitro also involves increased expression of 3beta- and 17beta-hydroxysteroid dehydrogenases (HSD) in the absence of steroidogenic acute regulatory protein (StAR) expression, as has been observed in vivo. Granulosa cells from small (<6 mm diameter) follicles were cultured for up to 6 days, and mRNA levels quantified by Northern hybridization or RT-PCR. Estradiol and progesterone concentrations in medium increased with time in culture, as did mRNA encoding P450arom, 3beta- and 17beta-HSD but not P450scc. Both P450arom and 17beta-HSD were significantly correlated with estradiol accumulation in culture medium. Progesterone secretion was correlated with 3beta-HSD but not P450scc mRNA levels. StAR mRNA was detectable by RT-PCR, did not change with duration of culture and was not correlated with progesterone secretion. FSH significantly stimulated P450arom and 17beta-HSD mRNA levels. Cell origin (from the antral or the basal layer of the membrana granulosa) did not affect steroidogenesis. We conclude that under the present cell culture system granulosa cells do not luteinize, and show expression of key steroidogenic enzymes in patterns similar to those occurring in differentiating follicles in vivo. Further, the data suggest that 17beta-HSD may be as important as P450arom in regulating estradiol secretion, and that 3beta-HSD is more important than P450scc as a regulator of progesterone secretion in non-luteinizing granulosa cells.

17-Hydroxysteroid Dehydrogenases↗
PubMed2003

Eicosapentaenoic acid restores tamoxifen sensitivity in breast cancer cells with high Akt activity.

BACKGROUND: Tamoxifen resistance is the underlying cause of treatment failure in a significant number of patients with breast cancer. Activation of Akt, a downstream mediator in the phosphatidylinositol 3-kinase (PI3K) signaling pathway has been implicated as one of the mechanisms involved in tamoxifen resistance. Breast cancers with heightened Akt activity are frequently associated with an aggressive disease and resistance to chemo- and hormone-therapy-induced apoptosis. Inhibition of PI3K restores apoptotic response to tamoxifen in hyperactive Akt cells. Therefore, agents that demonstrate Akt inhibitory properties are attractive therapeutic agents for the treatment of hormone-resistant breast cancer. n-3 fatty acids have proven to be potent and efficacious broad-spectrum protein kinase inhibitors. MATERIALS AND METHODS: In this study we demonstrate that the n-3 fatty acid, eicosapentaenoic acid (EPA), inhibits the kinase activity of Akt. Co-treatment with EPA renders breast cancer cells that overexpress a constitutively active Akt more responsive to the growth inhibitory effects of tamoxifen by approximately 35%. CONCLUSIONS: These findings suggest that EPA may be useful for the treatment of tamoxifen-resistant breast cancer cells with high levels of activated Akt and provide the rationale to test this hypothesis in the clinic.

Breast Neoplasms↗
PubMed2003

Prognostic significance of the allelic loss of the BRCA1 gene in colorectal cancer.

BACKGROUND: Survival at the intermediate stage of colorectal cancer (CRC) is less predictable than in the early and advanced stages. Several genetic markers possibly involved in growth and progression of CRC can be used for prognosis. AIMS: This study investigated the proportion of allelic loss (loss of heterozygosity (LOH)) at the BRCA1 locus in sporadic CRC and its value in patient prognosis. PATIENTS AND METHODS: A total of 314 patients were investigated for LOH at the BRCA1 locus using polymerase chain reaction by means of three intragenic polymorphic microsatellite markers. Allelic losses were compared with clinicopathological characteristics of patients, recurrence rate, disease free survival (DFS), and overall survival. RESULTS: Twenty six patients were excluded because of microsatellite instability. Of the remaining 288 cases, 244 (84.7%) were informative, with 97 (39.8%) patients bearing BRCA1 LOH. Recurrence rate was higher in patients with LOH (p=0.0003), and DFS was 73.3% (SEM 5.7) at five years in patients without LOH, and 49.2% (7.1) in cases with positive allelic loss (p=0.0004). Retention of alleles at the BRCA1 locus was associated with a favourable DFS in stages I and II (p<0.05). The presence of LOH was also significantly associated with short overall survival (p=0.02). Multivariate analysis in the complete series showed that stage (p=0.006) and lymph node metastases (> or =4 nodes, p=0.0001; 1-3 nodes, p=0.038) were independent prognostic factors. However, multivariate study by stages revealed that BRCA1 LOH was an independent prognostic factor in stages I and II (p=0.001). CONCLUSIONS: BRCA1 LOH is a molecular alteration present in CRC, with unfavourable repercussions for overall survival, that could be considered as an outstanding independent prognostic factor in stages I and II.

Aged↗
PubMed2003

Ki-67 immunolabeling in pre-malignant lesions and carcinoma of the prostate. Histological correlation and prognostic evaluation.

The antigen Ki-67, which is associated with cell proliferation, has been demonstrated to be useful in predicting the development of human tumors. The objective of this study was to evaluate the prognostic utility of this biomarker in pre-malignant and malignant lesions of the prostate. A total of 162 prostate biopsies taken from patients diagnosed for benign prostatic hyperplasia (BPH, n=49), low grade prostatic intraepithelial neoplasia (LGPIN, n=53), high grade prostatic intraepithelial neoplasia (HGPIN, n=25) and carcinoma (CAR, n=35), were studied. Immunohistochemistry for Ki-67 was carried out on all the samples and the number of labeled cells was semi-quantitatively evaluated (weak, moderate or intense). In the non-invasive lesions, the presence of Ki-67-positive cells in the luminal layer of the epithelium was evaluated qualitatively as positive or negative. The correlation between the immunolabeling for Ki-67 and the histological diagnosis showed highly significant differences between BPH and CAR, LGPIN and CAR and HGPIN and CAR, with no significant differences being found among the other groups. Analysis of the immunolabeling in luminal cells of non-invasive lesions showed an increase in accordance with the increase in the degree of histological lesion, the greatest percentage being obtained in the HGPIN lesions (88.0%), with significant differences among all the groups. Bearing in mind that Ki-67 is a prognostic biomarker for cell proliferation, our results demonstrating the immunolabeling of Ki-67 in the luminal compartment of non-invasive lesions having the potential to evolve to malignancy, may have prognostic implications.

Biomarkers, Tumor↗
PubMed2002

Detection of epithelial tumour RNA in the plasma of colon cancer patients is associated with advanced stages and circulating tumour cells.

BACKGROUND: Although circulating tumour DNA has been detected in patients with different types of cancer, little is known of free RNA in cancer patients. AIMS: We investigated the presence of RNA from epithelial tumours in plasma from patients with colorectal carcinomas, and its correlation with tumour characteristics and circulating tumour cells. METHODS: beta-actin mRNA was analysed to assess the viability of plasma RNA in samples from 53 patients with colonic cancer and 25 controls. Subsequently, nested primers were used to detect the presence of cytokeratin 19 (CK19) and carcinoembryonic antigen (CEA) RNA in the same samples. Nine clinicopathological parameters were studied to correlate the molecular and clinical parameters. Additionally, we investigated for micrometastases in blood in 18 of these patients and in 10 of the controls samples. RESULTS: All samples had detectable quantities of beta-actin RNA. In the controls, one case (4%) was positive for CEA and five (20%) for CK19 RNA; of the 53 patients, 17 cases (32%) were positive for CEA and 39 (73.6%) for CK19 RNA. This was statistically significant (p=0.000001). Advanced stages (p=0.03) and soluble CEA status (p=0.03) were associated with the presence of CEA, CK19, or both RNAs in plasma. Lymph node metastases (p=0.06) and vascular invasion (p=0.07) were almost significant. On the basis of these results, we examined the possible presence of micrometastases in blood in several of these patients. The presence of plasma tumour RNA was found to be associated with circulating tumour cells in blood (p=0.04). CONCLUSIONS: Epithelial tumour RNA is detectable in plasma from colon cancer patients. This molecular event is associated with advanced stages and circulating tumour cells. Our results could offer new approaches in the diagnosis and monitoring of colon cancer.

Actins↗
PubMed2002

Insulin and IGF-I are necessary for FSH-induced cytochrome P450 aromatase but not cytochrome P450 side-chain cleavage gene expression in oestrogenic bovine granulosa cells in vitro.

The earliest biochemical indicators of ovarian follicle deviation in cattle include lower oestradiol and free IGF concentrations in subordinate compared with dominant follicles. We determined if decreases in FSH, IGF-I or insulin cause decreased P450 aromatase (P450arom) or P450 cholesterol side-chain cleavage (P450scc) mRNA expression in oestrogenic bovine granulosa cells in vitro. In the first experiment, cells obtained from small follicles (2-5 mm diameter) were cultured in serum-free medium supplemented with physiological concentrations of FSH, IGF-I and insulin for 4 days. A decrease in specific hormone concentration was produced by replacing 70% of spent medium with medium devoid of FSH, insulin, or insulin and IGF-I on day 4 and again on day 5 of culture. Cultures were terminated on day 7. A reduction in FSH concentrations during the last 3 days of culture decreased P450arom and P450scc mRNA levels. A reduction in insulin reduced P450arom but not P450scc mRNA levels, and a reduction of both insulin and IGF-I concentrations further decreased P450arom mRNA levels and decreased P450scc mRNA levels. In a second experiment, cells obtained from small follicles (2-5 mm diameter) were cultured with insulin (100 ng/ml) without FSH for 4 days, and then insulin was withdrawn from the culture and FSH added for a further 3 days. The withdrawal of insulin decreased (P<0.02) oestradiol accumulation and reduced P450arom mRNA to below detectable levels, but did not affect P450scc mRNA levels. The addition of FSH transiently increased oestradiol secretion and P450arom mRNA levels, but P450arom mRNA levels were undetectable at the end of the culture period. The addition of FSH significantly enhanced P450scc mRNA levels and progesterone accumulation. These data demonstrated that a reduction of insulin-like activity reduced aromatase gene expression in bovine follicles without necessarily affecting progesterone synthetic capability, and thus may initiate follicle regression in cattle at the time of follicle divergence.

Animals↗
PubMed2001

Analysis of genetic and epigenetic processes that influence p14ARF expression in breast cancer.

The INK4a/ARF locus encodes two unrelated cell cycle-regulatory proteins that both function in tumor suppression, p16INK4a and p14ARF. In human tumors including breast cancer, alterations affecting selectively p14ARF have been poorly analysed. We have performed a comprehensive analysis of the inactivation mechanisms (mutation, homozygous and hemizygous deletion, and promoter hypermethylation) in a large series of 100 primary breast carcinomas. RT-PCR showed expression variable of the p14ARF transcript, with 17% demonstrating overexpression and 26% demonstrating decreased expression. No detectable alterations were observed in the majority of cases with overexpressed p14ARF mRNA, but 77% of tumors with decreased expression presented at least one of these genetic/epigenetic alterations. Nevertheless, a statistically significant correlation was observed between decreased p14ARF expression and several poor prognostic parameters.

Breast Neoplasms↗
PubMed2001

Alternative magnetic field exposure metrics: relationship to TWA, appliance use, and demographic characteristics of children in a leukemia survival study.

The ongoing Childhood Leukemia Survival Study is examining the possible association between magnetic field exposure and survival of children with newly diagnosed acute lymphocytic leukemia (ALL). We report the results of the first year 24 h personal magnetic field monitoring for 356 US and Canadian children by time weighted average TWA and alternative exposure metrics. The mean TWA of 0.12 microT was similar to earlier personal exposure studies involving children. A high correlation was found between 24 h TWA and alternative metrics: 12 h day TWA, 12 night TWA, geometric mean, 95th percentile value, percentage time over 0.2 and 0.3 microT, and an estimate of field stability (Constant Field Metric). Two measures of field intermittency, rate of change metric (RCM) and standardized rate of change metric (RCMS), were not highly correlated with TWA. The strongest predictor of TWA was location of residence, with highest TWAs associated with urban areas. Residence in an apartment, lower paternal educational level, and residential mobility were also associated with higher TWAs. There were no significant differences in the appliance use patterns of children with higher TWA values. Children with the highest field intermittency (high RCM) were more likely to sit within 3 feet of a video game attached to the TV. Our results suggest that 24 h TWA is a representative metric for certain patterns of exposure, but is not highly correlated with two metrics that estimate field intermittency.

Adolescent↗
PubMed2001

Different expression of P14ARF defines two groups of breast carcinomas in terms of TP73 expression and TP53 mutational status.

In 95 breast carcinomas, we investigated P14ARF and TP73 mRNA expression and their relationship to TP53 mutations, determined by an immunohistochemical method, studying several clinicopathologic features of the tumors. P14ARF and TP73 mRNA levels were determined by semiquantitative reverse transcription polymerase chain reaction (RT-PCR), using beta-actin as a control. P14ARF was overexpressed in 19% of the cases and underexpressed in 24%. TP73 was overexpressed in 22% of the tumors, and normal levels were found in the remaining 78%. The analysis of TP53 showed positive immunostaining in 38% of cases. The association of P14ARF and TP73 overexpression was statistically significant, as was the association between positive TP53 staining and TP73 overexpression. P14ARF was related to TP53 only in those cases in which there was low expression of P14ARF. Concomitant overexpression of P14ARF and TP73 was statistically related to positive TP53 immunostaining. The analysis of concomitant P14ARF and TP73 overexpression and clinicopathologic parameters of the tumors showed a statistically significant difference with respect to peritumoral vessel invasion (P = 0.01), lymph node metastasis (P = 0.03), negative ERBB2 expression (P = 0.005), and more advanced pathologic stages (P = 0.03). These results suggest that overexpression of P14ARF and TP73 could be implicated in breast carcinoma tumorigenesis and, ultimately, in the phenotypic features of these lesions.

Adenocarcinoma↗
PubMed2001

Multicystic dysplastic kidney detected by fetal sonography: conservative management and follow-up.

The most common cystic lesion recognized antenatally is multicystic dysplastic kidney (MCDK). Recently, conservative management without nephrectomy has been advocated. The purpose of this study was to report our experience in the conservative management of unilateral MCDK. Between 1989 and 1997, 20 children with MCDK detected by prenatal ultrasonography (US) were prospectively followed. At birth, US confirmed the prenatal findings in all cases. All patients were submitted to radioisotope scans and a micturating cystogram. Follow-up US examinations were performed annually. Mean age at diagnosis during the prenatal period was 31 weeks of gestation (range 24-38). Median follow-up time was 33 months (range 7-91). Follow-up US was performed in 19 children; 13 (68%) showed partial involution, 4 (21%) complete involution, and 2 (11%) an increase in unit size. The mean age at complete or partial involution of the lesion was 18 months. No children developed hypertension or tumors, and all maintained normal growth. In conclusion, the natural history of MCDK is usually benign, and serial US examinations show that affected kidneys frequently show involution with time.

Female↗
PubMed2001

Wild type p73 overexpression and high-grade malignancy in breast cancer.

The overexpression of wild type p73 is the most frequent alteration of p73 in malignancies. We investigated, in 70 breast carcinomas, p73 mRNA expression and its relationship to p53 mutations, determined by an immunohistochemical method, and loss heterozygosity (LOH) status of the 1p36 region, together with its possible implication in the pathogenesis of breast carcinomas. LOH, amplifying DNA by PCR using 5 markers, of 1p36 region (one intragenic to p73 gene) was found in 17% of cases but no significant correlation was observed with p73 overexpression. p53 positive immunostaining was present in 33% of breast carcinomas, and these exhibited a statistically significant relation with p73 overexpressed tumors. Overexpression of p73 mRNA was observed in 19 tumors (27%). The analysis of cases with p73 overexpression and cases with normal mRNA expression, in terms of age and pathologic characteristics of the tumors showed a significant association of p73 overexpression and tumors with lymph node metastases, vascular invasion and higher pathologic stage. These results suggest that p73 overexpression is a molecular alteration that could be implicated in the tumorigenesis of breast carcinomas and, eventually, in a poor clinical behavior.

Adult↗
PubMed2001

Application of rat hepatocyte culture to predict in vivo metabolic auto-induction: studies with DFP, a cyclooxygenase-2 inhibitor.

The drug candidate DFP [5,5-dimethyl-3-(2-isopropoxy)-4-(4-methanesulfonylphenyl)-2(5H)-furanone] is a selective cyclooxygenase-2 inhibitor under evaluation for analgesic and anti-inflammatory therapy. The in vitro metabolic pathways (rat microsomes) involve hydroxylation of the isopropyl side chain at either of two positions, the methyl or the methine, thus producing a hydroxylated metabolite (DFHP) or a dealkylated metabolite (DFH). DFH formation was the major pathway. Using hepatic microsomes from rats treated with agents that induce specific CYP isozymes, it was shown that the dexamethasone-inducible rat CYP3A isozyme(s) play a major role in DFH formation. The roles of CYP3A1 and -3A2 were confirmed with genetically engineered rat CYP enzymes. The potential for induction of rat CYP3A by DFP was evaluated by incubating DFP in rat hepatocyte cultures and measuring the CYP3A levels. Both CYP3A immunoreactive protein and enzyme activity were induced in a dose-dependent manner. The induction was confirmed in vivo by dosing rats with DFP at 100 mg/kg for 4 days. Microsomes prepared from the excised livers showed that DFP gave approximately 55% of the induction observed with dexamethasone, as determined by Western blot. In vitro metabolic auto-induction of DFP was assessed by measuring the metabolism of DFP in hepatocytes treated with DFP. DFH formation was significantly enhanced in the DFP-treated cells. In vivo, treating rats with DFP at doses of 10 to 100 mg/(kg.day) for 13 weeks indicated that DFP induced its own metabolism. The C(max) and plasma drug area under the curve values during the thirteenth week were significantly lower than that on the first day, and the effect was dose-dependent.

Alkylation↗
PubMed2001

Investigation of the in vitro metabolism profile of a phosphodiesterase-IV inhibitor, CDP-840: leading to structural optimization.

CDP-840 is a selective and potent phosphodiesterase type IV inhibitor, whose in vitro metabolism profile was first investigated using liver microsomes from different species. At least 10 phase I oxidative metabolites (M1-M10) were detected in the microsomal incubations and characterized by capillary high-performance liquid chromatography continuous-flow liquid secondary ion mass spectrometry (CF-LSIMS). Significant differences in the microsomal metabolism of CDP-840 were found between rat and other species. The major route of metabolism in rat involved para-hydroxylation on the R4 phenyl. This pathway was not observed in human and several other species. The in vitro metabolism profile of CDP-840 was further examined using freshly isolated hepatocytes from rat, rabbit, and human. The hepatocyte incubations indicated more extensive metabolism relative to that in microsomes. In addition to the phase I oxidative metabolites observed in microsomal incubations, several phase II conjugates were identified and characterized by CF-LSIMS. Interspecies differences in phase II metabolism were also found in these hepatocyte incubations. The major metabolite in human hepatocytes was identified as the pyridinium glucuronide, which was not detected in rat hepatocytes. Simple structural modification on R4, such as p-Cl substitution, greatly reduced the species differences in microsomal metabolism. Furthermore, modifications on R3, such as the N-oxide, eliminated the N-glucuronide formation in human. These results not only helped in determining the suitability of animal species used in the preclinical safety studies but also provided valuable directions for the synthetic efforts in finding backup compounds that are more metabolically stable.

3',5'-Cyclic-AMP Phosphodiesterases↗