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Biomedical subjects

Luiz De Marco

Publications and source records attributed to Luiz De Marco.

10 recordsLinked to original sources
PubMed2006

Neuroprotective effect on brain injury by neurotoxins from the spider Phoneutria nigriventer.

The role of calcium channels blockers in ischemic condition has been well documented. The PhTx3 neurotoxic fraction of the spider Phoneutria nigriventer venom is a broad-spectrum calcium channel blocker that inhibits glutamate release, calcium uptake and also glutamate uptake in synaptosomes. In the present study we describe the effect of PhTx3 (1.0 microg/mL), omega-conotoxin GVIA (1.0 micromol/L) and omega-conotoxin MVIIC (100 nmol/L) on neuroprotection of hippocampal slices and SN56 cells subjected to ischemia by oxygen deprivation and low glucose insult (ODLG). After the insult, cell viability in the slices and SN56 cells was assessed by confocal microscopy and epifluorescence, using live/dead kit containing calcein-AM and ethidium homodimer. Confocal images of CA1 region of the rat hippocampal slices subjected to ischemia insult and treated with omega-conotoxin GVIA, omega-conotoxin MVIIC and PhTx3 showed a percentage of dead cells of 68%, 54% and 18%, respectively. The SN56 cells subjected to ischemia were almost completely protected from damage by PhTx3 while with omega-conotoxin GVIA or omega-conotoxin MVIIC the cell protection was only partial. Thus, PhTx3 provided robust ischemic neuroprotection showing potential as a novel class of agents that targets multiple components and exerts neuroprotection in in vitro model of brain ischemia.

Animals↗
PubMed2006

Characterization of the tumor suppressor gene WWOX in primary human oral squamous cell carcinomas.

Oral squamous cell carcinoma (OSCC) is the most common malignant neoplasm of the oral cavity, representing 90% of all oral carcinomas and accounting for 3-5% of all malignancies. The WWOX gene (WW-domain containing oxidoreductase) is a candidate tumor suppressor gene located at 16q23.3-24.1, spanning the second most common fragile site, FRA16D. In this report, the role of the WWOX gene was investigated in 20 tumors and 10 normal oral mucosas, and we demonstrated an altered WWOX gene in 50% (10/20) of OSCCs. Using nested RT-PCR, mRNA transcription was altered in 35% of the tumors, with the complete absence of transcripts in 2 samples as well as absence of exons 6-8 (2 tumors), exon 7 (1 tumor), exon 7 and exon 6-8 (1 tumor) and partial loss of exons 8 and 9 (1 tumor). To determine if the aberrant transcripts were translated, Western blots were performed in all samples; however, only the normal protein was detected. By immunohistochemistry, a reduction in Wwox protein expression was observed, affecting 40% of the tumors when compared with normal mucosa. In addition, a novel somatic mutation (S329F) was found. The presence of alterations in mRNA transcription correlated with the reduced expression of Wwox protein in the tumors. These results show that the WWOX gene is frequently altered in OSCC and may contribute to the carcinogenesis processes in oral cancer.

Base Sequence↗
PubMed2006

HRPT2 gene alterations in ossifying fibroma of the jaws.

Ossifying fibroma (OF) is a benign neoplasm related to bone characterized by a progressive enlargement of the affected jaw. Recently, the candidate tumor suppressor gene HRPT2 was identified and alterations in this gene were related with the Hyperparathyroidism-jaw tumor syndrome that is characterized by parathyroid adenoma or carcinoma, fibro-osseous lesions (mainly OF) of the jaws, and renal lesions. The purpose of the present study was to evaluate the HRPT2 gene in OF. Tumour and blood samples were obtained from 3 patients with OF and one with juvenile ossifying fibroma (JOF). The results demonstrated three novel mutations in two out of three genotyped OF's. Interestingly, one of these patients showed a germ-line mutation after blood analysis. RT-PCR amplification was performed to analyze HRPT2 mRNA expression and only wild-type HRPT2 transcript was found in all tumours. Investigation of the parafibromin protein by immunohistochemistry showed a similar pattern of immunolocalization with strong nuclear and cytoplasmic staining in all cases. In conclusion, the present study shows for the first time mutations of HRPT2 gene in OF and suggests that OF may arise due to haploinsufficiency of the HRPT2 gene.

Adolescent↗
PubMed2005

Association between GSTT-1 gene deletion and the susceptibility to oral squamous cell carcinoma in cigarette-smoking subjects.

Oral squamous cell carcinoma (OSCC) is related to tobacco use and alcohol consumption and the individual susceptibility for development of this tumor has been associated with xenobiotic-metabolizing enzymes polymorphisms. Glutathione S-transferase Theta-1 (GSTT1) is a phase II metabolic enzyme that catalyzes detoxification reactions of carcinogenic compounds. A genetic polymorphism of the GSTT1 gene is characterized by a complete gene deletion and consequent absence of the enzyme. The null genotype (gene deleted) of GSTT1 has a decreased capacity in detoxifying carcinogens present in tobacco smoke, leading the formation of DNA-adducts and DNA damage. The purpose of the present study was to evaluate the association between GSTT1 polymorphism and risk for OSCC development in a Brazilian population. We investigated the GSTT1 polymorphism in 87 patients with OSCC and 81 age-sex matched controls. The genotypes were studied by PCR-based methods. Individuals homozygous for the wild type GSTT1 (+/+) and heterozygous (+/0) were grouped together. The prevalence of GSTT1 deficiency (null) was significantly higher in the group with OSSC patients with oral cancer of the floor of the mouth. The results suggest that GSTT1 polymorphism increases the risk for OSCC development.

Adult↗
PubMed2005

Molecular and immunohistochemical investigation of protein kinase a regulatory subunit type 1A (PRKAR1A) in odontogenic myxomas.

Odontogenic myxomas are rare benign neoplasms affecting the jaw. Myxomas of bones and other sites occur as part of Carney complex (CNC), a multiple neoplasia syndrome caused by mutations in the PRKAR1A gene, which codes for the regulatory subunit of protein kinase A (PKA). In the present study, 17 odontogenic myxomas from patients without CNC were screened for PRKAR1A mutations and PRKAR1A protein expression by immunohistochemistry (IHC). Mutations of the coding region of the PRKAR1A gene were identified in 2 tumors; both these lesions showed no or significantly decreased immunostaining of PRKAR1A in the tumor compared to that in the surrounding normal tissue. One mutation (c.725C>A) led to a nonconservative amino acid substitution in a highly conserved area of the gene (A213D); the other was a single base-pair deletion that led to a frameshift (del774C) and a stop codon 11 amino acids downstream of the mutation site; both tumors were heterozygous for the respective mutations. Of the remaining tumors, 7 of the 15 without mutations showed almost no PRKAR1A in the tumor cells, whereas IHC showed that the protein was abundant in nontumorous cells. We concluded that PRKAR1A may be involved by its down-regulation in the pathogenesis of odontogenic myxomas caused by mutations and/or other genetic mechanisms. Of the sporadic, nonfamilial tumors associated with PRKAR1A mutations, the odontogenic type was the first myxomatous lesion found to harbor somatic PRKAR1A sequence changes.

Cyclic AMP-Dependent Protein Kinase RIalpha Subuni↗
PubMed2005

Beta-catenin mutations in craniopharyngiomas and pituitary adenomas.

Craniopharyngiomas and pituitary adenomas are both tumors of the hypothalamic and pituitary region, respectively that are frequently associated with endocrine defects either because of direct involvement of hormone producing cells (most pituitary tumors) or because of secondary defects due to disturbance of hypothalamic function (some pituitary tumors and craniopharyngiomas). Some studies suggest that mutant beta-catenin gene cells in craniopharyngiomas and pituitary adenomas contribute to their tumorigenesis. DNA was extracted from 73 cranial tumors and subjected to polymerase chain reaction (PCR) with previously described primers encompassing glycogen synthase kinase-3beta phosphorylation sites of the beta-catenin gene. Sequenced PCR products for possible beta-catenin gene mutations showed a total of 7/43 alterations in adamantinomatous craniopharyngioma-derived DNA samples. Two previously described beta-catenin mutations in codon 33 TCT(Ser) > TGT(Cys) and codon 37 TCT(Ser) > TTT(Phe), whereas three novel mutations in codon 41 ACC(Thr) > ATC(Ile), codon 33 TCT(Ser) > TAT(Tyr) and codon 32 GAC(Asp) > AAC(Asn) were observed. None of the 22 pituitary adenomas and the eight papillary craniopharyngiomas analyzed presented any sequence alterations. These findings demonstrate an association between beta-catenin gene alterations and craniopharyngiomas of the adamantinomatous type. Since this gene product is involved with development, these results suggest that beta-catenin mutations may contribute to the initiation and subsequent growth of congenital craniopharyngiomas.

Adenoma↗
PubMed2004

GSTM1 polymorphism and oral squamous cell carcinoma.

We investigated the frequency of the GSTM1 genotypes in 70 Brazilian patients with oral squamous cell carcinoma (OSCC) and 82 age-sex matched controls. The GSTM1 genotypes were studied by PCR-based methods. The frequency of male patients with OSCC and null for the GSTM1 (70.5%) was statistically different from the male patients from the control group (48.5%) (Odds Ratio, OR=2.53, 95% CI=1.22-5.24, P<0.05). The frequency of the GSTM1 null genotype (0/0) in the group with OSCC (65.7%) was statistically different from the controls (48.7%) (OR=2.01, 95% CI=1.04-3.88, P<0.05). The prevalence of GSTM1 deficiency (null) was significantly higher for patients with oral cancer of the floor of the mouth (OR=3.67, 95% CI=1.11-12.11, P<0.05). In conclusion, the GSTM1 null genotype may increase the risk for OSCC development.

Adult↗
PubMed2003

A signal peptide mutation of the arginine vasopressin gene in monozygotic twins.

Familial neurohypophysial diabetes insipidus (FNDI) is a rare autosomal dominant syndrome stemming from the absence of arginine vasopressin (AVP). More than thirty-five different germline mutations in the arginine vasopressin-neurophysin II gene have been reported. These mutations are either in the signal peptide or scattered throughout the neurophysin II domain. A missense mutation altering alanine at position -1 to either valine or threonine in the signal peptide domain has previously been found in ten unrelated families. In the present report, Brazilian female monozygotic twins with clinically typical central DI in whom biochemical and molecular characterization were carried out are described. Direct mutational analysis by sequencing of the vasopressin gene in germline DNA revealed a heterozygous missense mutation (G-->A) at nucleotide 279, predicting the substitution of alanine by threonine at position -1 of the signal peptide moiety. In summary, we present an extremely rare case of familial central diabetes insipidus in monozygotic Brazilian twins with a seemingly common missense mutation in the AVP gene.

Adult↗
PubMedDate not supplied

TP53 codon 72 polymorphism in oral squamous cell carcinoma.

BACKGROUND: Oral squamous cell carcinoma (OSCC) is a multifactorial neoplasm related to tobacco smoke, alcohol consumption and molecular genetic changes such as p53 mutations. The human tumor suppressor gene TP53 contains single nucleotide polymorphism that encodes either arginin (Arg) or proline (Pro) at amino acid codon 72 of the p53 protein. The relationship between human cancer susceptibility and p53 polymorphism at codon 72 is controversial. The aim of this study was to investigate the association between this polymorphism and OSCC development in a Brazilian population. MATERIALS AND METHODS: Eighty-two patients with OSCC and 82 age-sex-matched controls were included in the study. DNA was extracted from all subjects' normal oral mucosa and the polymerase chain reaction amplification (PCR) was performed for detection of the TP53 genotypes. PCR products were analyzed in a 6.5% polycrylamide gel and silver-stained. Statistical analyses were performed with the chi 2 test and Fisher's exact test. RESULTS: The frequencies of the genotypes Arg/Arg, Arg/Pro and Pro/Pro, were 37.8%, 54.8% and 7.4%, respectively, for OSCC cases and 40.2%, 54.8% and 4.9% for controls. No significant differences in the distribution of TP53 genotypes were seen between the groups (p = 0.794). CONCLUSION: The present study does not support the hypothesis that this TP53 polymorphism is associated with oral cancer susceptibility.

Alleles↗