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Biomedical subjects

G Barrera

Publications and source records attributed to G Barrera.

69 records · Page 4Linked to original sources
PubMed1980

Lysis of rat liver lysosomes through incubation with 1-leucyl-glycine, substrate for a lysosomal dipeptidase.

1-Leu-Gly is a substrate for a lysosomal dipeptidase. The incubation of subcellular fractions in the presence of the dipeptide causes a rapid lysis of the particles, as revealed by the increase of both free and soluble activities of acid phosphatase. This effect is due to the hydrolysis of the dipeptide within the particles, as documented by the concomitant aminoacid production. The enhancing effect of EDTA on this phenomenon is reported.

Acid Phosphatase↗
PubMed1980

Effect of fasting and glucagon on the residual latent activity of acid phosphatase in rat liver.

Data are presented on the variation of the residual latent activity of acid phosphatase after hypo-osmotic shock in relation to differences in the functional state of the vacuolar apparatus, as obtained after 24 hours of fasting or treatment with glucagon. It is moreover reported the effect of cycloheximide, which appears able to interfere not only with the glucagon-induced autophagy, but in all likelihood also with the basal autophagic processes.

Acid Phosphatase↗
PubMed1978

The coronal incision in rhytidectomy--the brow lift.

Rhytidectomy is not a routine procedure applicalbe to all patients. Variations of technique must be chosen for each individual case. Integral correction of the face is important and brow-lifting must often be done. Our criteria for selecting the coronal incision for the brow-lift are discussed and the surgical techniques are described in detail. Results are analyzed and a simple method for evaluation is presented.

Dermatologic Surgical Procedures↗
PubMedDate not supplied

Effects of 4-hydroxynonenal on adenylate cyclase and 5'-nucleotidase activities in rat liver plasma membranes.

Adenylate cyclase and 5'-nucleotidase activities in rat liver plasma membranes were assayed in vitro in the presence of 4-hydroxy-2,3-trans-nonenal (HNE), a major end-product of microsomal lipid peroxidation. Both basal and glucagon-stimulated adenylate cyclase were inhibited in a dose-dependent manner, even at micromolar HNE concentrations, whereas fluoride-stimulated activity increased. A biphasic, dose- and time-dependent effect was noted when the basal activity was monitored at increasing doses. 5'-Nucleotidase activity was also decreased by HNE, but only at millimolar concentrations. These findings are related to the view that aldehydes, especially HNE, may act as diffusible cytotoxic compounds when lipid peroxidative derangement of membrane lipids is provoked by toxic conditions.

5'-Nucleotidase↗
PubMedDate not supplied

Effect of 4-hydroxynonenal, a product of lipid peroxidation, on natural cell mediated cytotoxicity.

Lipid peroxidation of cell membrane yields a variety of final products whose a quantitatively important component is 4-hydroxynonenal (HNE). Previous studies performed in our laboratory suggest that HNE may play a physiological role in the control of cellular proliferation and/or differentiation. This appears to be further supported by our recent findings showing that pre-treatment of K562 cells with a physiological concentration of HNE leads to a marked reduction of susceptibility of NK cells. The observed regulatory effects of HNE on tumor cell growth and susceptibility to natural immune resistance, led us to try to better understand the immunotoxicological properties of this aldehyde. The present study analyses the effects of HNE on NK-mediated cytotoxicity. Treatment of MNC as effector cells with concentrations of HNE ranging from 0.001 to 1 microM for 1 h, did not produce noticeable effects on NK activity. Therefore, this aldehyde at physiological concentrations is able to differentiate tumor cells and to down-regulate target susceptibility to NK effectors from one side. On the other side, it is not able to modify the efficiency of the NK function. Moreover, HNE concentrations higher than 1 microM showed significant and concentration-dependent inhibition of NK activity. However, this effect is reversible and can be antagonized, at least in part, by treatment of effector cells with HNE in combination with beta-interferon.

Aldehydes↗
PubMedDate not supplied

Effect of 4-hydroxynonenal, a product of lipid peroxidation, on NK susceptibility of human K562 target cells.

4-Hydroxynonenal (HNE) is one of the major breakdown products generated by lipid peroxidation of cellular membranes. The level of lipid peroxidation and the concentration of its products are inversely related to the rate of cell proliferation and directly related to the level of cell differentiation. It has been reported that HNE inhibits DNA synthesis, ornithine decarboxylase (ODC) activity and c-myc expression in different leukemic cells lines. It has also been demonstrated that HNE inhibits proliferation and induces differentiation in HL60 cell line. In the present study the effects of HNE, at concentrations close to those found in the normal tissues, on the NK susceptibility of human K562 target cells were analyzed. Repeated treatments at 45 minutes intervals with 1 microM HNE were performed to maintain the cells in the presence of the aldehyde for 12 hours. The effect of HNE was compared with that obtained in Haemin-treated cells. HNE causes a strong inhibition of cells growth (53% vs. 34% with Haemin) without affecting cell viability. We further investigated the NK susceptibility of K562 cell line upon in vitro treatment with HNE. Cytotoxic activity of mononuclear cells (MNC) from peripheral blood of healthy donors was determined by 4 hours Cr51-release assay. The results obtained, expressed in terms of percentage of specific lysis at different E:T ratios and in terms of KC (10(6)) at the E:T ratio of 50:1, show that HNE treatment of K562 cells leads to a marked reduction of susceptibility to NK cells; this decrease is very close to that found in the K562 cells treated with Haemin used as inducer. Similar results were obtained using MNC pre-treated with beta-interferon (IFN) as effector cells. MNC show a reduced capacity to lyse HNE-treated cells also under the enhancing cytolytic effect of IFN. These results are in line with data obtained with several common inducers of differentiation such as DMSO, retinoic acid or others.

Aldehydes↗