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Biomedical subjects

A Cano

Publications and source records attributed to A Cano.

At least 199 records · Page 11Linked to original sources
PubMed1979

Purification and properties of a histone acetyltransferase from Artemia salina, highly efficient with H1 histone.

An histone acetyltransferase has been purified from nuclei of 40-h-old Artemia salina larvae. The enzyme is very unstable at 0 degrees C, requires free -SH groups for activity and is rapidly inactivated at 40 degrees C. The optimal pH for activity is 8.5 and the activity is half inhibited by millimolar concentrations of Mn2+, Ca2+ or Mg2+ or decimolar concentrations of Na+ and K+. The molecular weight of the enzyme, determined by gel filtration chromatography, changed with the ionic strength of the medium (280,000 in 10 mM Tris . HCl, 170,000 in 0.2 M KCl). The very-lysine-rich histone H1 is a better substrate acceptor than the arginine-rich histones H3 or H4. Under proper conditions, the enzyme can modify all the internal lysyl residues in histones H1 and H4. The acetylation of H1 is inhibited when all the other histone fractions are present in the assay mixture.

Acetyltransferases↗
PubMedDate not supplied

Estimation of free radical-quenching activity of leaf pigment extracts.

The chromogen 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulphonic acid) radical (ABTS.+) can be directly generated by the enzymatic system formed by hydrogen peroxide and horseradish peroxidase in ethanolic media. The reaction is time- and concentration-dependent, and the ABTS.+ generated shows excellent stability. The method is an adaptation of the decolouration method previously reported (Cano et al. 1998. Phytochem Anal 9:196-202), which was used for estimating anti-oxidant activity in aqueous media. When the assay described here was used to quantify the anti-oxidant activity of two anti-oxidants, Trolox (an analogue of vitamin E) and beta-carotene, the latter had 2.5 times better anti-oxidant capacity than Trolox at the same concentration. The free radical quenching activity (anti-oxidant activity) of leaf pigment extracts was measured and related to the the carotenoid contents in leaf extracts of barley, oat and citrus. The possibilities of using this experimental approach to evaluate the status of photoprotective pigments are discussed.

Avena↗
PubMedDate not supplied

Oestrogen and progesterone receptors in human term placenta. Measurement by binding assays and immunological methods.

Oestrogen and progesterone receptors have been implicated in human placental steroidogenesis, but studies developed to measure their concentration in this tissue at term yielded discrepant results. Potential inaccuracy of the binding assays, the technique used in previous studies, might influence the discrepancy. In the present study, oestrogen and progesterone receptors were investigated by two different approaches: binding assays with radiolabelled ligand and immunoassays with monoclonal antibodies against receptors. Binding assays included techniques to quantify free and occupied sites in both the cytosolic and nuclear fraction. Conditions intended to block or decrease potential causes of inaccuracy, such as proteolysis or thermal denaturation of the sites, were included in the assays. Cytosolic specific binding was measured by two different techniques, dextran-coated charcoal and hydroxylapatite, whereas nuclear sites were studied on salt-extracts and by exchange. Negative or moderately positive results were obtained for either oestrogen or progesterone receptors, but high levels of non-specific binding made the technique unreliable. Immunoassays included the use of two techniques, histochemistry and enzyme-linked-immunosorbent-assay (ELISA). Both frozen and paraffin (Bouin solution or buffered formalin as fixatives) sections were stained with monoclonal antibodies against the oestrogen receptor. Results were always negative in all cases. Levels of oestrogen and progesterone receptors were measured in either cytosol or nuclear extracts by ELISA. This technique was highly sensitive and reproducible. Results were negative for both the cytosolic and nuclear fractions of oestrogen receptors. For progesterone receptors, low positivity was obtained in either crude (3.2 +/- 0.4 fmol/mg protein, mean +/- s.e.) or ammonium sulphate precipitated cytosols (12.6 +/- 3.5 fmol/mg protein, mean +/- s.e.), whereas the values for nuclear extracts were 62.0 +/- 9.0 fmol/mg DNA (mean +/- s.e.). We conclude that: (1) oestrogen receptors could not be detected in human term placenta by the methods used in this study, and (2) low levels of progesterone receptors were detected in both cytosolic and nuclear extracts.

Antibodies, Monoclonal↗
PubMedDate not supplied

Demonstration of P29, an oestrogen receptor-associated tumor marker, in human term placenta.

A Mr29,000 serine phosphoprotein (P29) related to oestradiol receptor was studied in human term placenta with the use of a specific monoclonal antibody (D5). D5 was used with two different methods, immunohistochemistry and immunoradiometry. For immunohistochemistry, an indirect immunoperoxidase method was chosen to detect P29 in methacarn-fixed, wax-embedded sections. P29 was mostly confined to the syncytiotrophoblast surrounding placental villi, staining being positive in both cytoplasm and nuclei. The stroma of villi was negative. Content of P29 was uniformly high in crude placental cytosol, as measured by immunoradiometry assays. Specificity of D5 against P29 in placenta was tested by an immunoblotting technique. This showed a single band corresponding to a molecular weight of 29 kDa. The biological meaning of the finding is unknown at present.

Antibodies, Monoclonal↗
PubMedDate not supplied

Adenovirus lacking the 19-kDa and 55-kDa E1B genes exerts a marked cytotoxic effect in human malignant cells.

UNLABELLED: The adenovirus (Ad) E1A gene exerts an antitumor effect and can induce sensitivity to treatment with DNA-damaging agents. In contrast, the Ad 19-kDa E1B protein inhibits E1A-mediated apoptosis and the 55-kDa E1B inactivates the p53 protein. In this paper, we study the in vitro and in vivo effects of a 19-kDa and 55-kDa E1B-defective Ad in several malignant human tumor cell lines. MATERIALS AND METHODS: Nontumorigenic human fibroblasts (CCD-45SK and Hs67), peripheral blood lymphocytes, and several human tumor cell lines derived from cervix, colon, and breast carcinomas, epidermoid carcinoma, and osteosarcoma (HeLa, HT29, MCF7, Saos-2, and A431 cell lines) were studied. Wild-type (wt) Ad type 5 and H5 dL118 Ad, a mutant with the deleted E1B region, were employed. The cells were infected at 20 plaque-forming units, and cell viability was evaluated by the crystal violet method. In the in vivo experiments, 2 x 10(6) cells from the carcinoma cell lines HeLa, A431 and HT29 were injected into nude mice. The tumorigenicity of previously infected cells and after an intratumoral injection of Ad was analyzed. The mice received whole-body gamma-irradiation. RESULTS: The H5 dL118 mutant produced a marked cytopathic effect in all of the malignant cells, surpassing that of the wt Ad; viability at 72 hours ranged from 11% to 20% for H5 dL118 Ad and from 70% to 93% for the wt Ad with respect to uninfected controls. In the in vivo experiments, a total inhibition of tumorigenicity was detected when cells were infected prior to injection and a partial and transitory decrease in tumorigenicity was detected when the mutant H5 dL118 was injected intratumorally. gamma-irradiation enhanced the in vivo antitumor effects. CONCLUSIONS: These results indicate that infection with completely E1B-deficient Ads induced a marked cytopathic effect on malignant cells that was higher than that seen for wt Ads; in addition, infection with such Ads exerts a tumor suppressor effect in vivo.

Adenoviridae↗
PubMedDate not supplied

Dietary antioxidant supplementation did not affect declining sperm function with age in the mouse but did increase head abnormalities and reduced sperm production.

The present study aims to ascertain whether dietary administration of a mixture of vitamins C and E may prevent the negative effects of paternal age on male fertility variables in the mouse. Experimental males were fed a standard diet supplemented with either a low or high dose of vitamins C and E. Oocytes enclosed in cumulus masses were inseminated using a 2 x 2 factorial design established according to whether males were young (3-4 months of age) or aged (22-24 months of age) and whether they were fed a control or antioxidant diet. Aged males showed a significant decrease in number of spermatozoa/mg epididymis when compared to young males. Dietary supplementation with low doses of vitamins C and E did not have any effect on sperm quality, fertilization and conceptus development in vitro. However, high doses of dietary vitamins C and E decreased the number of spermatozoa/mg epididymis, and increased the percentage of spermatozoa with misshapen heads distended in the distal part. These findings suggest that dietary supplementation with pharmacological doses of vitamins C and E may disturb spermatogenesis. The mechanism involved may be associated with either the antioxidant properties of vitamins C and E or their inhibitory action on steroidogenesis by Leydig and/or Sertoli cells.

Aging↗
PubMedDate not supplied

Effects of maternal ageing and dietary antioxidant supplementation on ovulation, fertilisation and embryo development in vitro in the mouse.

The present study aims to ascertain whether dietary supplementation with a mixture of vitamins C and E may prevent the maternal-age-associated decrease in both the number of ovulated oocytes after exogenous ovarian stimulation and embryo development in vitro in the mouse. Experimental females were fed a standard diet supplemented with i) high doses of vitamins C and E from the first day of weaning until 12 or 40 weeks of age; or ii) moderate doses of vitamins C and E from the first day of weaning until 12 weeks of age or from 22 to 33 weeks of age. The age-related reduction in ovulation rate was partially prevented by supplementing diet with high doses of vitamins C and E from the first day of weaning. Shorter periods of treatment and lower doses of vitamins C and E were also efficient in preventing the maternal-age-associated reduction in ovulation rate after exogenous ovarian stimulation. No effect of maternal diet on fertilisation and embryo development was observed until the blastocyst stage. Although any extrapolation to human fertility should be made with caution, these findings may have direct implications for preventing or delaying maternal-age-associated infertility in humans.

Aging↗