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Biomedical subjects

M Silva

Publications and source records attributed to M Silva.

At least 163 records · Page 9Linked to original sources
PubMed1988

Addition of growth hormone secretion signal to basic fibroblast growth factor results in cell transformation and secretion of aberrant forms of the protein.

Basic fibroblast growth factor (bFGF) is a potent mitogen for a wide variety of cell types. Unlike most growth factors, the primary translation product for bFGF appears to lack a secretory signal peptide. To explore the normal mode of bFGF release, as well as to investigate the growth factor's oncogenic potential, expression vectors were created for a bFGF cDNA and for a chimeric molecule in which the bFGF coding sequence was linked to the human growth hormone signal peptide sequence. Transfection of NIH3T3 cells with the bFGF cDNA vectors caused the synthesis of high levels of biologically active, cell-associated bFGF, but no evidence of transformation was detected. In contrast, the chimeric bFGF-signal peptide expression vector induced foci of transformation at a very high frequency. The transformed cells grew in soft agar and were tumorigenic in nude mice. The majority of the immunoreactive bFGF species made by the transformed cells was found in the conditioned medium and appeared to be posttranslationally modified, indicating that the chimeric bFGF-signal peptide molecule was processed through the secretory pathway. The secreted bFGF exhibited little mitogenic activity, suggesting that interaction of bFGF with its receptor likely occurs while the fusion protein is being processed along the secretory pathway.

Animals↗
PubMed1987

Inhibition of epoxide hydrolases and glutathione S-transferases by 2-, 3-, and 4-substituted derivatives of 4'-phenylchalcone and its oxide.

4'-Phenylchalcones, chalcone oxides, and related compounds were synthesized and tested as inhibitors of cytosolic epoxide hydrolase, microsomal epoxide hydrolase, and glutathione S-transferases from mouse and rat liver. Several compounds were more potent inhibitors of the cytosolic epoxide hydrolase than the parent 4'-phenylchalcone oxide while large substituents in the 4- and especially the 2-position caused a reduction in inhibition. The chalcone oxides showed selectivity as inhibitors of the cytosolic epoxide hydrolase acting on trans-stilbene oxide, while chalcones were inhibitors of cytosolic glutathione S-transferase acting on cis-stilbene oxide. Data are consistent with the hypothesis that much of the inhibition of the glutathione S-transferase is caused by the glutathione conjugate of the chalcone.

Animals↗
PubMed1987

Antimicrobial substance from a human Lactobacillus strain.

Lactobacillus sp. strain GG, which was isolated from the feces of a normal person, produced a substance with potent inhibitory activity against a wide range of bacterial species. It inhibited anaerobic bacteria (Clostridium spp., Bacteroides spp., Bifidobacterium spp.), members of the family Enterobacteriaceae, Pseudomonas spp. Staphylococcus spp., and Streptococcus spp., as demonstrated by a microbiological assay; however, it did not inhibit other lactobacilli. The inhibitory activity occurred between pH 3 and 5 and was heat stable. Bactericidal activity against Escherichia coli was demonstrated at a dilution of 1:128. The inhibitory substance was distinct from lactic and acetic acids. It had a low molecular weight (less than 1,000) and was soluble in acetone-water (10:1). Because of these characteristics, the inhibitory material could not be considered a bacteriocin; it most closely resembled a microcin, which has been associated previously with members of the family Enterobacteriaceae.

Acetates↗
PubMed1986

Paratesticular rhabdomyosarcoma in children.

The clinicopathological features of 10 children with paratesticular rhabdomyosarcoma treated between 1965 and 1984 are reviewed. Of the patients 9 had embryonal rhabdomyosarcoma and 1 was pleomorphic. Median age was 4 years (range 2 to 11 years). Staging was based on clinical findings, chest x-ray, lymphoangiography, computerized tomography and histological studies. The disease was stage I in 5 patients, stage II in 2 and stage IV in 3. Treatment included radical orchiectomy in all patients, chemotherapy in 8 and lumboaortic radiotherapy in 5. No retroperitoneal node lymphadenectomy was performed. Of the 10 children 7 are free of disease after 2 to 19 years (median 7 years) of followup, including all of those with stages I and II disease.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1986

3-D reconstruction of endometrial carcinoma in situ.

Reconstructions in 3-D of 4 of 18 endometrial carcinoma in situ specimens demonstrated a simple branching tubular pattern, distinctively different from atypical adenomatous hyperplasia and invasive endometrial adenocarcinoma. A clonal origin of carcinoma in situ was suggested.

Carcinoma in Situ↗
PubMed1986

Allergy to oil of turpentine in Portugal.

Oil of turpentine is still a common allergen in Portugal although it does not contain delta 3-carene, as ascertained by gas chromatography. Patch tests with 6 terpenes on 22 patients revealed that 17 were allergic to alpha-pinene and 15 to dipentene; 12 were allergic to both. 4 patients were sensitive to delta 3-carene, 3 to alpha-terpineol and 2 to beta-pinene. These results explain the incidence of allergy to oil of turpentine in Portugal.

Dermatitis, Contact↗
PubMed1985

Use of quinones in brain-tumor therapy: preliminary results of preclinical laboratory investigations.

Failure of current chemotherapeutic agents to effectively treat human brain tumors has prompted the search for alternative regimens based on the inherent metabolic pathways of target cells. One way to accomplish this goal would be to design drugs in an inactive form, which upon entry into the cell would be transformed to a toxic metabolite by a naturally occurring pathway. One such pathway may be the reductive activation of naphthoquinones with one or two side chains capable of alkylation, such as 2,3-dibromomethyl-1,4-naphthoquinone (DBNQ). This reductive activation can be catalyzed by the flavoprotein DT-diaphorase [NAD(P)H:quinone oxidoreductase]. We have found that both rat 9L and some human brain-tumor cell lines contain very high levels of this enzyme and that halogenated dimethyl naphthoquinones, such as DBNQ, are highly toxic to these cells in vitro. Moreover, we have found that the cytotoxic effects of DBNQ on human tumor and murine bone marrow stem cells can be prevented or lessened by pretreatment of the cells with dicoumarol, a potent inhibitor of DT-diaphorase. Since dicoumarol does not cross the blood-brain barrier, the potential exists for human brain tumors to be destroyed with halogenated dimethylquinones and for peripheral host toxicity to be prevented by coadministration of dicoumarol.

Animals↗
PubMed1984

Genetic control of a structural polymer of the Neurospora crassa cell wall.

The heteropolysaccharide present in fraction 1 of the Neurospora crassa cell wall has been characterized in wild-type and morphological mutant strains of this fungus. Single and double mutations have been studied to determine possible genetic interactions controlling the chemical composition of such heteropolysaccharides . Single mutations studied were peak-2, scumbo ( FGSC 49), ragged ( FGSC 296), and crisp -1 ( FGSC 488). Double mutations studied were peak-2, scumbo ( FGSC 419), and ragged crisp -1. In all these strains, the main constituents of the heteropolysaccharide were glucose, mannose and galactose. Glycosidic linkages binding these neutral sugars have been identified by gas-liquid chromatography. A chemical structure of fraction I heteropolysaccharide is proposed. The results obtained with double mutants suggest the existence of genetic interactions, such as complementation or additive effects of lesions of different genes, to control the chemical composition and structure of the cell wall and the morphology of N. crassa mycelium.

Acetylation↗