Biomedical subjects

L Ventura

Publications and source records attributed to L Ventura.

16 recordsLinked to original sources

PubMed1992

Isolation of an Aspergillus terreus mutant impaired in arginine biosynthesis and its complementation with the argB gene from Aspergillus nidulans.

Using filtration enrichment techniques, an Aspergillus terreus arginine auxotrophic strain which contains a mutation that abolishes ornithine transcarbamylase (OTCase) activity has been isolated. This mutant has been genetically transformed with the cloned Aspergillus nidulans OTCase gene. Prototrophic transformants arose at a frequency of about 50 transformants per microgram of plasmid DNA. Southern blot analysis of DNA from the transformants showed that the transforming DNA was ectopically integrated at different locations in the A. terreus genome, often in multiple tandem copies. The transformants were phenotypically stable for several mitotic divisions and retained their capacity to produce extracellular enzymes.

Arginine↗

PubMed1992

Skin cytogenetic assay for the detection of clastogens-carcinogens topically administered to mice.

A method for assessing the effect of clastogens on mouse skin epidermal cells was devised and applied. Toxic and mutagenic responses in epidermal cells were tested using two known mutagens and carcinogens, urethane (URE) and 7,12-dimethylbenz[a]anthracene (DMBA). Cell generation time, sister-chromatid exchanges (SCE) and chromosomal aberrations (CA) after topical and intraperitoneal (i.p.) treatment were measured in epidermal and bone marrow cells. After topical administration both tissues responded similarly, whereas after i.p. treatment skin cells were less responsive than bone marrow cells. However, the results indicate the validity of this new cytogenetic approach for the assessment of the genotoxicity of compounds applied directly to skin.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed1992

[Specific induction by phorbol ester of the gene transcription and of the activity of ornithine decarboxylase in two control and transformed epithelial cell lines. Modulator effect of anti-inflammatory agents].

The mechanism of ornithine decarboxylase (ODC) induction by phorbol ester (TPA) has been studied in two permanent epithelial cell lines, a control (Ctr) and a Benzo (a) pyrene transformed line (BaP-tr); the degree of ODC gene expression (ODC-mRNA) was evaluated in comparison to the ODC activity. A small dose of TPA (4 x 10(-8) M) highly induced ODC activity in these cells. The induction levels differed however, corresponding respectively to 4:1 (induced: basal ODC) in Ctr cells and to 2:1 in BaP-tr cells. This difference reflected the variation of ODC gene expression; the ODC-mRNA induction was 6:1 in Ctr cells and 3:1 in BaP-tr cells. Repetitive TPA treatment decreased the ODC induction in these cells, as compared to that resulting from a single TPA treatment. Studies of ODC modulation were performed in presence of anti-inflammatory agents. In the two cell lines, Indomethacin (anti-cyclooxygenase) did not change the level of ODC induction by TPA. Nordihydroguaiaretic acid (NDGA, anti-lipoxygenase) inhibited this induced ODC. These results differed from that obtained in vivo in mouse skin. Dexamethasone (DXME, anti-phospholipase A2) showed different action according to treatment time. Used together with TPA (t0), DXME inhibited ODC induction by the carcinogen; with three hours delay after TPA (t3), DXME treatment stimulated ODC in the cells. This divergent action may be reproduced by Actinomycin D, while Cycloheximide only exhibited constant inhibition. Studies now in progress suggested that the inhibition of TPA induced ODC by DXME may reflect ODC gene repression, as for the stimulating effect it could be related to ODC post-transcriptional modulation, owing to the decrease of proteolytic action.

Animals↗

PubMed1991

Transformation of Aspergillus terreus with the hygromycin B resistance marker from Escherichia coli.

Aspergillus terreus was transformed to hygromycin B resistance using a bacterial resistance gene under the control of Aspergillus nidulans regulatory sequences. Southern hybridization of transformants indicated that in most of the cases the vector DNA was integrated into the recipient chromosome in the form of tandem arrays. Transformants were mitotically stable in both selective and non-selective medium and retained their capacity to produce xylanase or glucoamylase activities.

Aspergillus↗

PubMed1990

Study of various transforming effects of the anabolic agents trenbolone and testosterone on Syrian hamster embryo cells.

Trenbolone, a synthetic androgen together with testosterone, a natural androgen, were studied comparatively for their transforming effects on Syrian hamster embryo (SHE) cells. The data indicated that both androgens exhibited weak positive complete transforming activities without a dose response relationship. Trenbolone is more toxic than testosterone when the concentrations tested are higher than 10 micrograms/ml, but is less able to transform SHE cells. Medium H21 offers a higher transformation frequency than medium H16. Their transforming effect can be amplified by TPA. However, both products can also reduce the transforming effect of benzo[a]pyrene (B[a]P) either in sequential treatment or when mixed together. The transforming effects of the two androgens including TPA effects can be inhibited completely by dexamethasone, which suggests that such transformation in SHE cells is an epigenetic effect. In conclusion, trenbolone and testosterone themselves exhibit a weak transforming effect on SHE cells, predominantly as promoting potential, especially when associated with 12-O-tetradecanoyl-phorbol-13-acetate, which is related to hormonal action. They also exhibit weak anti-transforming effects when associated with B[a]P.

Animals↗

PubMed1989

Micronuclei and nuclear anomalies induced in the gastro-intestinal epithelium of rats treated with formaldehyde.

The induction of micronuclei and nuclear anomalies in cells of the gastro-intestinal epithelium of rats treated per os with formaldehyde (200 mg/kg) was assessed in comparison with N-methyl-N'-nitro-N-nitrosoguanidine as a positive standard. Formaldehyde and N-methyl-N'-nitro-N-nitrosoguanidine both increased micronuclei and nuclear anomalies in almost all tissues analysed (stomach, duodenum, ileum and colon) though with different patterns and to different extents, reflecting different potency and specificity of target. In the case of formaldehyde these effects were observed in conjunction with signs of severe local irritation. This assay can be employed to detect the genotoxic potential of chemicals in vivo directly on target cells in the proximity of the administration site, thus reducing the likelihood of false-negative results.

Animals↗

PubMed1988

[Incontinentia pigmenti in 2 newborn infants].

Incontinentia pigmenti (IP) is a genodermatosis, which is of X-linked dominant transmission, uncommonly diagnosed in newborn babies. The skin lesions usually develop in 4 stages: inflammatory, hypertrophic, pigmentary and regressive. The authors report 2 cases of IP in female newborn babies who were previously treated for pyodermatitis.

Female↗

PubMed1986

Cell kinetics of gliomas by serial stereotactic biopsy.

The potential proliferative activity of glial tumors has been investigate by serial stereotactic biopsies and by "in vitro" 3H-thymidine incorporation procedure (labeling index, LI). The methodology of this combined approach and the preliminary results in 33 patients are reported. Cell kinetic data have been matched with the histological classification (W.H.O.).

Adolescent↗

PubMed1986

Breast cancer: implications of tumor cell kinetics on clinical outcome.

The relevance of tumor proliferative activity as an indicator of biologic aggressiveness was analyzed on a series of 506 patients with primary breast cancer. In 258 patients with operable tumors without nodal and distant metastases, none of whom was subjected to postoperative irradiation or systemic adjuvant therapy, proliferative activity was significantly correlated with prognosis; 6-year relapse-free survival (RFS) and overall survival (OS) were higher for patients with slowly proliferating tumors for patient with fast-proliferating tumors (RFS: 80.5% vs 59.6%, p = 0.00004; OS: 90.8% vs 74.4%, p = 0.002). On a series of 196 patients with node-positive operable tumors, subjected to 6 or 12 cycles of cyclophosphamide, methotrexate and 5-fluorouracil, a trend in favor of longer 6-year RFS was observed for patients with slowly proliferating tumors than for patients with fast-proliferating tumors (62.5% vs 48.3%, p = 0.08), whereas proliferative activity did not influence OS. In 52 patients with locally advanced disease treated with a multimodality approach, including chemotherapy (adriamycin and vincristine), surgery or radiotherapy, tumor proliferative activity was a strong indicator of biologic aggressivity, since women with slowly proliferating cancers had a higher 4-year probability of OS than women with fast-proliferating tumors (68.1% vs 36.7%, p = 0.02).

Actuarial Analysis↗

PubMed1976

Use of an iridium electrode for direct measurements of pI of proteins after isoelectric focusing in polyacrylamide gel.

The use of an iridium microelectrode 0.5 mm in diameter is proposed for measuring the pH gradient in polyacrylamide gels after isoelectric focusing. The electrode exhibits a perfectly linear potential/pH relationship; thus it can be used directly in conjunction with a pH meter using the pH scale for readings. pH equilibrium values are rapidly reached (10-15 s) and pI determinations are obtainable with good accuracy (better than 0.1 pH).

Calorimetry↗

PubMed1970