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T Sánchez

Publications and source records attributed to T Sánchez.

At least 19 recordsLinked to original sources
PubMed2003

Ehp53, an Entamoeba histolytica protein, ancestor of the mammalian tumour suppressor p53.

This paper reports the identification of Ehp53, a p53-like Entamoeba histolytica protein, which binds to the human p53 DNA consensus sequence (oli-p53). Monoclonal antibodies against p53 (Ab-1 and Ab-2) recognized a single 53 kDa spot in two-dimensional gels and inhibited the formation of complexes produced by E. histolytica nuclear extracts and oli-p53. Additionally, E. histolytica gene promoter sequences with high homology to oli-p53 formed complexes with nuclear proteins that were abolished by oli-p53. Ehp53 protein levels increased in UV-irradiated trophozoites. This protein was also detected in Entamoeba moshkovskii and Entamoeba invadens. By confocal microscopy, Ehp53 was located in the nuclei, EhkO organelles and cytoplasm. The Ehp53-encoding gene was cloned and its predicted amino acid sequence showed 30-54 % and 50-57 % homology with important domains of the human and the Drosophila melanogaster p53 proteins, respectively. This homology included the tetramerization domain, the nuclear export signal and a nuclear localization signal. Ehp53 also contains seven of the eight DNA-binding residues and two of the four Zn(2+)-binding sites described for p53. A recombinant Ehp53 was recognized by Ab-2. Ehp53 is believed to be the first p53-like protein found in protozoa and may be the evolutionary ancestor of the mammalian p53.

Amino Acid Sequence↗
PubMed2002

Beamforming with a reduced sampling rate.

The beamforming process requires a high delay resolution to avoid the deteriorating effects of the delay quantization lobes on the image dynamic range and signal to noise ratio. Wideband transducers require delay resolutions in the order of 1/16 the signal period. If oversampling is used to achieve this timing resolution, a huge data volume has to be acquired and processed in real time. This is usually avoided by sampling just above the Nyquist rate and interpolating to achieve the required delay resolution. However this increases the hardware complexity. Baseband sampling has been alternatively proposed with sampling rates as low as the transducer frequency or even lower. This approach uses two A/D converters and processing chains for every channel, thus doubling the hardware requirements. Quadrature sampling can be used instead with a single A/D converter, but the sampling rate must be a multiple of four times the transducer frequency, decreasing the application flexibility. Furthermore, it produces relatively high errors in the detected envelope if wideband transducers are used. This work presents a new approach, the selective sampling technique (SST), which keeps the lowest sampling rate required by the imaging process or the signal bandwidth (whatever is larger) and, at the same time, provides a high delay resolution to keep the highest image dynamic range. The SST is based on a second order sampling process which, differently from the mentioned approaches, does not pose any constraints in the time interval between samples and produce lower errors in the detected envelope. The hardware requirements are low (a single A/D converter and processing chain for every transducer element), working at the lowest data rate compatible with the Nyquist criterion, thus reducing the data bandwidth. Furthermore, the sampling points can be also freely chosen, so that the SST simplify the usually required scan conversion process to a simple linear interpolation easily carried out by software in real-time.

Journal Article↗
PubMed2001

Role of phospholipases A(2) in growth-dependent changes in prostaglandin release from 3T6 fibroblasts.

Previously, we reported a growth-dependent change in prostaglandin production as a consequence of a marked growth-dependent alteration in arachidonic acid (AA) mobilization from phospholipids. Our present results show that fetal calf serum (FCS) and 4 beta-phorbol-12-myristate acetate (PMA) caused an enhancement of phospholipase A(2) (PLA(2)) activity in the membrane fraction of non-confluent cells allowing PLA(2) access to its substrate and the release of AA. Western blot analysis has shown that FCS and PMA increased secreted PLA(2) (sPLA(2)) expression in non-confluent 3T6 fibroblast cultures. Moreover, FCS and PMA induced dithiothreitol-sensitive and bromoenol lactone-sensitive PLA(2) activities in cytosol and membrane fraction. However, these stimuli did not modify significantly the PLA(2) activity in both fractions when 3T6 fibroblasts reached a high cell density. This could be associated with the impairment of AA mobilization in these cell culture conditions. On the other hand, we observed that FCS and PMA induced the same prostaglandin H synthase-2 induction in non-confluent and confluent culture conditions. Moreover, the prostaglandin E(2) levels reached in cell culture supernatants were independent of the degree of confluence when AA was added exogenously. These results suggest that the changes of intracellular distribution of PLA(2) activity of sPLA(2) and iPLA(2) stimulated by exogenous stimuli may be controlled by cell density conditions which constitute an important mechanism in the regulation of prostaglandin release.

Animals↗
PubMed2001

Olive oil decreases both oxidative stress and the production of arachidonic acid metabolites by the prostaglandin G/H synthase pathway in rat macrophages.

Fish oil has a preventive role in cardiovascular and inflammatory diseases, but little is known about the effect of olive oil, which is widely consumed in Mediterranean regions. We examined the influence of dietary olive oil, corn oil and fish oil-rich diets on the production of superoxide anion (O2-) and nitric oxide (.NO) by resident macrophages stimulated by phorbol 12-myristate 13-acetate (PMA) and their effect on arachidonic acid release, prostaglandin G/H synthase-2 (PGHS-2) expression and the subsequent prostaglandin E(2) production. Resident peritoneal macrophages stimulated by PMA from rats fed with olive oil or corn oil had the same level of O2- production, but these levels were increased by the fish oil diet. Olive oil and the fish oil diets increased .NO and decreased arachidonic acid mobilization and the production of prostaglandin E(2). PGHS-2 expression, however, was not affected by diet. We conclude that although olive oil and fish oil reduce arachidonic acid mobilization and subsequent metabolism through the PGHS-2 pathway in PMA-stimulated macrophages, only olive oil offers an additional beneficial effect by increasing .NO/O2- production.

Animals↗
PubMed1999

Role of leukocyte influx in tissue prostaglandin H synthase-2 overexpression induced by phorbol ester and arachidonic acid in skin.

The accumulation of neutrophils and mononuclear cells is a characteristic feature of 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced ear edema. This cell influx was accompanied by the enhancement of eicosanoid tissue levels and prostaglandin H synthase-2 (PGHS-2) overexpression. Sialidase treatment, which affects the structure of selectins and inhibits leukocyte influx, significantly reduced eicosanoid and PGHS-2 levels and edema. In contrast, skin PGHS-2 overexpression induced by arachidonic acid (AA) application was not affected by sialidase treatment. These results suggest that PGHS-2 overexpression induced by TPA could be induced by AA and/or AA metabolite release by leukocyte infiltrated during the inflammatory process.

Acute Disease↗
PubMed1999

Ketoprofen S(+) enantiomer inhibits prostaglandin production and cell growth in 3T6 fibroblast cultures.

The ketoprofen S(+) enantiomer inhibits with great stereoselectivity both prostaglandin H synthase isoenzymes. Thus, the biological effects of ketoprofen on inflammation are due almost entirely to the S(+) isomer. Here, we report that the S(+) enantiomer, at doses that inhibit prostaglandin synthesis, is effective in reducing DNA synthesis and 3T6 fibroblast growth. Our data suggest that prostaglandins are involved in the control of 3T6 fibroblast growth and that the effect of the ketoprofen S(+) enantiomer on 3T6 proliferation is correlated with its effects on prostaglandin H synthase and prostaglandin production.

Animals↗
PubMed1999

Role of prostaglandin H synthase isoforms in murine ear edema induced by phorbol ester application on skin.

Topical application of TPA to a murine ear induced an edema that was accompanied by eicosanoid biosynthesis and an early enhancement of prostaglandin H synthase 2 (PGHS-2) expression. PGHS-2 induction may be correlated with the time-course of TPA-induced edema formation. Treatment with drugs that inhibit AA mobilization such as dexamethasone or manoalide or inhibitors of leukotriene formation such as zileuton or baicalein, reduced TPA-induced edema development and PGHS-2 levels. On the other hand, arachidonic acid (AA) application on the murine ear induced rapid expression of PGHS-2. This effect was not reproduced by other fatty acids such as oleic, linoleic, eicosatetraynoic or eicosapentaenoic acids. PGHS-2 expression induced by AA application was independent of PGHS and lipoxygenase metabolite synthesis. However, topical application of PGE2 on skin induced PGHS-2 overexpression. This study suggests that AA release and/or subsequent metabolism by PGHS may be involved in the induction of PGHS-2 expression in murine TPA- and AA-induced ear oedema.

Animals↗
PubMed1998

Concentrations of gonadotropins, estradiol and progesterone in sows selected on an index of ovulation rate and embryo survival.

The objective of this study was to determine concentrations of follicle stimulating hormone (FSH), luteinizing hormone (LH), progesterone (P4) and 17beta-estradiol (E2) in sows from a line selected on an index which emphasized ovulation rate (Select) and from a control line. A further classification of the sows in each line was made according to the estimated number of ovulations during an estrous cycle. Sows in the Select line were ranked into a high (HI) or low group (LI) when their estimated number of ovulations were 25 or more and 14 to 15, respectively. Sows of the control line were classified into groups as high (HC) or low (LC) when the estimated values for ovulation rate were 14-15 and 8-9 ovulations, respectively. Blood samples were collected every 12 h during a complete estrous cycle and samples were analyzed for concentrations of FSH and LH. Samples collected every 24 h were assayed for P4 and E2. Mean concentrations of FSH, LH, P4 and E2 did not differ (P > 0.10) between lines or between HI and LI or HC and LC groups. Selection of pigs for ovulation rate and embryonal survival did not affect concentrations of FSH, LH, P4 and E2 in sows during the estrous cycle.

Animals↗
PubMed1998

The pyruvate:ferredoxin oxidoreductase enzyme is located in the plasma membrane and in a cytoplasmic structure in Entamoeba.

This work investigated the cellular location of the pyruvate:ferredoxin oxidoreductase (PFO) enzyme in Entamoeba. A 1.9 kb fragment located at the 3' end of the Ehpfo gene was cloned in the pRSETB vector and expressed. The recombinant peptide was purified and inoculated in rabbits. By Western blot assays the antibodies detected a single 130 kDa band in all E. histolytica strains tested and in E. moshkovskii. By immunofluorescence, the antibodies showed the presence of PFO in the plasma membrane and in a cytoplasmic structure that appeared as a ring or as a compact small body in E. histolytica strains. In E. invadens and E. moshkovskii (strains FIC and Laredo) PFO was located in the plasma membrane showing different fluorescence patterns. Immunofluorescence on E. histolytica synchronized cultures showed that the cytoplasmic structure appeared in 85, 60, 20 and 10% of the trophozoites in mitosis, G1, S and G2 phases, respectively. By in situ hybridization the Ehpfo gene was found in the nuclei and the trophozoites of the clone A, strain HM1:IMSS, differed in the Ehpfo gene content.

Animals↗
PubMed1997

A novel cytoplasmic structure containing DNA networks in Entamoeba histolytica trophozoites.

We report here the presence of cytoplasmic DNA arranged in networks in the trophozoites of the human parasite Entamoeba histolytica. Cytoplasmic DNA was detected in live trophozoites in a structure that we called EhkO, using the fluorescent dye acridine orange, and by in situ hybridization to trophozoites with a rDNA probe. The EhkO was found in the axenically grown clones A, L6 (strain HMI:IMSS) and MAVax (strain MAV) and in the polyxenically grown clone MAVpx (strain MAV). Bacteria present in MAVpx did not cross hybridize with the DNA probe neither in in situ hybridization or in Southern blot experiments. Autoradiography of metabolically [3H]thymidine-labeled trophozoites showed the presence of EhkO, and an EhkO-enriched fraction, purified from a nuclei-free extract and examined by light microscopy, exhibited [3H]thymidine incorporation into this structure. DNA was purified from the EhkO and enriched nuclear fractions and analyzed by transmission electron microscopy. The EhkO fraction contained DNA networks resembling those of trypanosome kDNA, whereas nuclear DNA was present mainly as linear molecules and some circles. Our findings imply that E. histolytica may be taxonomically more closely related to the Trypanosomatidae than previously suspected.

Animals↗
PubMed1997

Cytoplasmic DNA in Entamoeba histolytica: its biological significance.

We report a study on the DNA organization in Entamoeba histolytica using a ribosomal DNA probe. The rDNA genes were found forming mers which were separated in a typical ladder pattern by pulse field electrophoresis. DNA rosette structures were visualized through electron microscopy in DNA eluted from bands recognized by the ribosomal probe. The in situ hybridization experiments using a DNA probe suggested that the rDNA genes are portioned between the nucleus and a cytoplasmic structure. These findings provide new data on DNA organization in E. histolytica and open the question concerning the presence of a novel organelle in this eukaryotic parasite.

Animals↗
PubMed1996

Entamoeba histolytica: gene linkage groups and relevant features of its karyotype.

We identified some gene linkage groups in Entamoeba histolytica using a 4-M urea improved transversal alternating field electrophoresis (TAFE) method. Complex rosette-structured DNA molecules were found trapped along the gel lanes, explaining the fuzziness of the patterns. Using several episomal probes, including 16 S, 5.8 S, and 25 S ribosomal (r)Dna genes, an autonomous replication sequence (ARS), and EhVR1, we identified a complete ribosomal episome linkage group (CELG) at the 1.2-Mb position. Three other incomplete groups were found: IELG-1, formed by EhVR1, 16 S, 5.8 S, and 25 S genes; IELG-2 formed by EhVR1, 16 S and 25 S; and IELG-3 formed only by 5.8 S. Ehadh3, Ehpfo, and Ehredox genes migrated at the 1.8-Mb position, forming the non-ribosomal linkage group, NRLG-1.8, while the Ehenl-1 gene migrated at 1.6 Mb forming the NRLG-1.6 group. Ehhk was located at 1.2, 0.8, and 0.17 Mb in three different groups: NRLG-1.2, IELG-3-0.8, and NRLG-0.17. Putative lineal chromosomes were also identified using an heterologous telomeric probe. By in situ hybridization experiments, the rDNA and Ehhk genes were located in both nucleus and cytoplasm, while the Ehpfo and Ehredox genes were found mainly in the nucleus. We propose a model hypothezising that the 16 S and 25 S genes are in a linear molecule, duplicated in two inverted repeats, which may be looped out of the linear DNA to form an episome probably lacking or not the 5.8 S sequence, which could be added later by recombination.

Animals↗
PubMed1996

Comparison of circulating concentrations of reproductive hormones in boars of lines selected for size of testes or number of ovulations and embryonal survival to concentrations in respective control lines.

The objectives of this study were to determine whether circulating concentrations of genadotropins and gonadal hormones of boars were altered as a result of selection of pigs for size of testes or for embryonal survival and(or) number of ovulations. Included in Exp. 1 and 2 were boars with the greatest estimated paired weight of testes (TS) and boars from a control (C) line. Concentrations of FSH were similar (P > .10) in boars from the TS and C lines. In Exp. 3, 4, and 5, circulating concentrations of FSH and 17 beta-estradiol (E2) were evaluated in neonates, during pubertal development, and in mature boars of lines selected for an index of number of ovulations and embryonal survival (I), and data were compared to those for boars from a respective C line. Concentrations of E2 were not different in boars from the I line and those from the C line during the early neonatal period but were greater (P < .05) in boars of the C line than in those from the I line during pubertal development. Concentrations of FSH were greater (P < .05) in mature boars from the I line than in those from the C line. In summary, selection for size of testes did not influence circulating concentrations of FSH in mature boars. The secretory pattern of E2 in boars before puberty changed as a result of selection for embryonal survival and number of ovulations in females of the I line, and the different patterns of circulating E2 early in life may result in enhanced circulating concentrations of FSH in adult boars of the I line compared with boars of the C line.

Animals↗
PubMed1994

Thermal resistance characteristics of PA 3679 in the temperature range of 110-121 degrees C as affected by pH, type of acidulant and substrate.

The influence of mushroom extract, acidification and type of acidulant (citric acid or glucono-delta-lactone) on the thermal resistance of PA 3679 spores has been studied. The pH values were 7 (phosphate buffer), 6.7 (non acidified mushroom extract), 6.22, 5.34 and 4.65 (acidified mushroom extract). Spores were less heat resistant in the non-acidified mushroom extract than in phosphate buffer. However, acidification of the extract had an effect on D values which was dependent on the specific pH. At pH 6.22, D values were higher than those in non-acidified extract, for both type of acidulants, but the difference between D values in both substrates was affected by temperature, the higher the temperature, the less the difference. Acidification at other pH levels did not significantly affect D values obtained, neither did the type of acidulant. The z value ranged from 9.79 to 12.09 degrees C for citric acid and from 8.18 to 10.18 degrees C for glucono-delta-lactone. When pH was decreased the z value increased for both acidulants.

Basidiomycota↗
PubMed1992

[The reactive hemophagocytic syndrome associated with immunoblastic B-cell lymphoma].

The reactive hemophagocytic syndrome is a rare clinical-pathological entity which usually has a benign evolution and which is characterized by the systemic proliferation of mature histiocytes, with a great phagocytosis ability and which occurs in a secondary form in some infections and neoplasias and after the administration of certain drugs. We present a case of reactive hemophagocytic syndrome in a patient presenting a non-Hodgkin lymphoma, of crest malignancy, B immunoblastic and kappa monoclonal, with fatal evolution and in which the diagnosis was obtained after necropsy.

Aged↗