Scielo RSS <![CDATA[Biological Research]]> vol. 35 num. 1 lang. en <![CDATA[SciELO Logo]]> <![CDATA[FONDECYT Decreases Research Projects in Biological Sciences]]> <![CDATA[Capital Humano en Ciencias]]> <![CDATA[On living beings and metaphysical options]]> <![CDATA[Glucose transporters: expression, regulation and cancer]]> Mammalian cells depend on glucose as a major substrate for energy production. Glucose is transported into the cell via facilitative glucose transporters (GLUT) present in all cell types. Many GLUT isoforms have been described and their expression is cell-specific and subject to hormonal and environmental control. The kinetic properties and substrate specificities of the different isoforms are specifically suited to the energy requirements of the particular cell types. Due to the ubiquitousness of these transporters, their differential expression is involved in various disease states such as diabetes, ischemia and cancer. The majority of cancers and isolated cancer cell lines over-express the GLUT family members which are present in the respective tissue of origin under non-cancerous conditions. Moreover, due to the requirement of energy to feed uncontrolled proliferation, cancer cells often express GLUTs which under normal conditions would not be present in these tissues. This over-expression is predominantly associated with the likelihood of metastasis and hence poor patient prognosis. This article presents a review of the current literature on the regulation and expression of GLUT family members and has compiled clinical and research data on GLUT expression in human cancers and in isolated human cancer cell lines. <![CDATA[Hemoglobin affinity in Andean rodents]]> Blood hemoglobin oxygen affinity (P50) was measured in three Andean species and in the laboratory rat (control), all raised near sea level. Chinchilla lanigera (Molina, 1792) has an altitudinal habitat range from low Andean slopes up to 3000 m., while Chinchilla brevicaudata (Waterhouse, 1848) has an altitudinal range from 3000 to 5000 m. The laboratory type guinea pig, wild type guinea pig (Cavia porcellus), (Waterhouse, 1748), and laboratory rat (Rattus norvegicus) were also raised at sea level. The Andean species had high hemoglobin oxygen affinities (low P50) compared with the rat. Chinchilla brevicaudata had a higher affinity than Chinchilla lanigera. The wild type guinea pig had a higher affinity than the laboratory type. As has been shown in other species, this is another example of an inverse correlation between the altitude level and the P50 values. This is the first hemoglobin oxygen affinity study in Chinchilla brevicaudata. <![CDATA[Vincristine induces somatic segregation, via mitotic crossing-over, in diploid cells of <I>Aspergillus nidulans </I>]]> Vincristine is an alkaloid widely used as an antineoplastic agent. In eukaryotic cells the drug causes blockage in the G2 phase of the cell cycle and an increase in the frequency of sister chromatid exchanges. Due to the fact that germinating Aspergillus nidulans cells spend most of their cycle in G2 phase, they provide an excellent system for the study of mitotic crossing-over. Taking into account that mitotic crossing-over occurs during G2 period, the evaluation of recombinagenic and aneugenic potential of vincristine is provided with regard to two diploid strains of A. nidulans: a wild strain (uvsH+//uvsH+) and a defective one in DNA repair (uvsH//uvsH). Drug toxicity and its effect on the asexual cycle of A. nidulans has been evaluated as well. Treatment of both strains with vincristine did not change colony growth in the culture, however cytological analyses showed aberrant conidiophores. Recombinagenic potential of vincristine was evaluated by induction of gene homozygosis originally present in heterozygosity diploid strains (Homozygotization Index). Results show that vincristine induces mitotic crossing-over and higher frequency of aneuploid mitotic segregants. The results also show the recombinagenic and aneuploidogenic potential of vincristine and suggest its participation in the induction of secondary malignancies <![CDATA[Cytotoxicity and trypanocidal activity of nifurtimox encapsulated in ethylcyanoacrylate nanoparticles]]> The aim of the present study was to study the trypanocidal activity of nanoparticles loaded with nifurtimox in comparison with the free drug against Trypanosoma cruzi, responsible for Chagas' disease. Ethylcyanoacrylate nanoparticles acted as the delivery system into cells. As the obligate replicative intracellular form is amastigote, in vitro studies were performed on this form of parasite as well as on cell culture derived trypomastigotes. The fluorescence method used here was very useful as it allowed for the simultaneous study of trypanocide activity and cytotoxicity by determining living or dead parasites within living or dead host cells. According to these results, the greatest trypanocide activity on cell culture-derived trypomastigotes was recorded for nifurtimox-loaded nanoparticles with a 50% inhibitory concentration (IC50) twenty times less than that of the free drug. The cytotoxycity of unloaded nanoparticles at low concentrations was similar to that obtained by free drug when evaluated on Vero cells. Furthermore, nifurtimox-loaded nanoparticles showed increased trypanocide activity on intracellular amastigotes with an IC50 thirteen times less than that of nifurtimox. We also observed that the unloaded nanoparticles possess the previously-described trypanocide activity, similar to the standard solution of nifurtimox, although the mechanism for this has not yet been elucidated. In conclusion, it was possible to establish in vitro conditions using nifurtimox encapsulated nanoparticles in order to decrease the doses of the drug and thus to obtain high trypanocidal activity on both free trypomastigotes and intracellular amastigotes with low cytotoxicity for the host cell. <![CDATA[Early and late molecular and morphologic changes that occur during the in vitro transformation of <I>Trypanosoma cruzi</I> metacyclic trypomastigotes to amastigotes]]> The amastigogenesis primary of T. cruzi occurs naturally when metacyclic trypomastigotes transform into amastigotes within the cells of the mammalian host. The in vitro study of the macromolecular changes that occur over several days during the transformation process should provide significant indications of how the parasite adapts to the mammalian host environment. We show here that metacyclic trypomastigotes pre-incubated at 37&deg; C in a protein-rich medium reach a high degree of transformation to amastigotes when re-incubated in the fresh medium. Giemsa-stained smears show that during the pre-incubation phase, the metacyclic trypomastigotes undergo lengthening at the posterior end and a thinning out of the entire body. SDS-PAGE analysis of polypeptides and glycopeptides or Western blot with stage-specific antisera analyses indicate that the in vitro primary amastigogenesis is associated with abrupt changes in protein, glycoprotein, and stage-specific antigens that occur simultaneously during the first 24 hours of pre-incubation. Since the differentiating system consists of a rich media at 37&deg; C, temperature and medium constitution must trigger a macromolecular differentiation to amastigotes that precedes the morphological transformation by several days. This transformation is associated with the rearrangement of stage-specific antigens and takes place when the culture medium is changed. <![CDATA[Peroxidase and phenylalanine ammonia-lyase activities, phenolic acid contents, and allelochemicals-inhibited root growth of soybean]]> The influence of the allelochemicals ferulic (FA) and vanillic (VA) acids on peroxidase (POD, EC and phenylalanine ammonia-lyase (PAL, EC activities and their relationships with phenolic acid (PhAs) contents and root growth of soybean (Glycine max (L.) Merr.) were examined. Three-day-old seedlings were cultivated in nutrient solution containing FA or VA (0.1 to 1 mM) for 48 h. Both compounds (at 0.5 and 1 mM) decreased root length (RL), fresh weight (FW) and dry weight (DW) and increased PhAs contents. At 0.5 and 1 mM, FA increased soluble POD activity (18% and 47%, respectively) and cell wall (CW)-bound POD activity (61% and 34%), while VA increased soluble POD activity (33% and 17%) but did not affect CW-bound POD activity. At 1 mM, FA increased (82%) while VA reduced (32%) PAL activities. The results are discussed on the basis of the role of these compounds on phenylpropanoid metabolism and root growth and suggest that the effects caused on POD and PAL activities are some of the many mechanisms by which allelochemicals influence plant growth <![CDATA[Cloning and comparison of ten gene sequences of a Chilean<I> H. pylori </I>strain with other <I>H. pylori</I> strains revealed higher variability for VacA and CagA virulence factors]]> We have cloned and sequenced ten Helicobacter pylori genes from a Chilean strain (CH-CTX1) including: a cytotoxin VacA fragment, a CagA fragment (A17), a species-specific protein (TsaA), urease subunits (UreA, UreB), a flagellin subunit (FlaB), heat shock proteins (HspA and HspB), adhesin (HpaA) and a lipoprotein (Lpp20). We compared their deduced amino acid sequences with the corresponding sequences from three unrelated H. pylori strains, including fully sequenced strains 26695(UK) and J99(USA), and found that eight of them (UreA, UreB, FlaB, HspA, HspB, Lpp20, TsaA and HpaA) presented more than 97.3% identity. In contrast, VacA partial sequence showed lower identity values (93.2 - 94.9%). Moreover, we found major differences in the A17 region respect to the number and arrangement of the internal repeated elements when sequences from different strains were aligned. The A17 regions from strains CH-CTX1 and 26695 are very similar (91.8% identity) but lacked 6 repeated elements when compared to the Australian strains ATCC 43526 and NCTC 11637. The CCUG 17874 A17 region showed the largest deletion involving 9 repeats. A17 size differences between strains CCUG 17874 and CH-CTX1 were verified by PCR and polypeptide size. Such differences may explain variations in virulence among H. pylori strains as well as diversity in serum immunoreactivity. <![CDATA[Analysis of 5382insC (BRCA1) and 6174delT (BRCA2) mutations in 382 healthy Chilean women with a family history of breast cancer]]> Breast cancer is the most common malignancy among women. Chilean studies reveal that this cancer presents the third highest mortality rate. A family history of breast cancer is one of the major risk factors for the development of this disease. BRCA1 and BRCA2 are the two main hereditary breast cancer susceptibility genes, and mutations in these genes are related to inherited breast cancer. In specific populations only some mutations have been found to be associated with susceptibility. The purpose of this study was to establish the frequency of 5382insC (BRCA1) and 6174delT (BRCA2) germline mutations in 382 healthy Chilean women with at least two relatives affected with breast cancer and in probands and their relatives from 8 high risk families for breast cancer, using mismatch PCR assay. The results obtained showed that 5382insC and 6174delT mutations were not found in either of the groups studied. The ethnic origin of the contemporary Chilean population and the data reported in the literature suggest that these mutations may be absent or have a very low frequency in this population.. This genetic study is part of a breast cancer screening program that also includes annual mammography and clinical breast examination over a five-year period. Strategies to reduce morbidity and mortality associated with breast cancer lie in early detection in women with genetic risk. <![CDATA[A Scientometric view of some Biological disciplines in Chile]]> During the last decade the articles published by Chilean Research Centers grew 1,73 which compares to the 2.34 fold increase of mainstream research articles registered as a whole in Latin America. However, the relative impact of the Chilean publications surpassed that of Latin America. In Biological Sciences, traditionally the strongest research area within Chile, Latin America also shows a steeper slope of growth. Qualitatively, biological disciplines in Chile are comparable to those published in Latin America although in Chile there are specialties as Physiology that surpass the average world's impact. The scientometric data is consistent with the fall in individual grants that the Chilean Research Fund (FONDECYT) has been allocating during the last decade.