Browsing by Author "Palma, Veronica"

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    Adaptive Physiological and Morphological Adjustments Mediated by Intestinal Stem Cells Response to Food Availability in Mice
    (2019) Pena-Villalobos, Isaac; Casanova-Maldonado, Ignacio; Lois, Pablo; Sabat, Pablo; Palma, Veronica
    Several studies have evaluated plastic changes in the morphology of the digestive tract in rodents subjected to caloric restriction or restricted availability. Nevertheless, studies that link these morphological responses to physiological consequences are scarce. In order to investigate short-term plastic responses in the intestine, we acclimated adult Mus musculus (BALB/c) males for 20 days to four distinctive treatments: two caloric regimens (ad libitum and 60% of calorie ingestion) and two levels of periodicity of the regimens (continuous and stochastic treatment). At the end of the treatment we analyzed the cell proliferation and cell death dynamics of small intestinal crypts in these animals. In addition, we measured organ masses and lengths, hydrolytic digestive enzyme activities, and energy output from feces. Finally, in order to explore the metabolic changes generated by these dietary conditions we assessed the catabolic activity (i.e., enzymes) of the liver. Our results show that individuals acclimated to a continuous and 60% regimen presented longer intestines in comparison to the other treatments. Indeed, their intestines grew with a rate of 0.22 cm/day, generating a significant caloric reduction in the content of their feces. Besides, both mass and intestinal lengths were predicted strongly by the stabilization coefficient of BrdU+ proliferating cells per crypt, the latter correlating positively with the activity of n-aminopeptidases. Interestingly, by using pharmacological inhibition of the kinase mammalian target of rapamycin complex 1 (mTORC1) by Rapamycin, we were able to recapitulate similar changes in the proliferation dynamics of intestinal stem cells. Based on our results, we propose that the impact of caloric restriction on macroscopic variation in morphology and functional changes in digestive n-aminopeptidases occurs through synchronization in the proliferation rate of stem and/or progenitor cells located in the small intestinal crypts and requires mTORC1 as a key mediator. Hence, we suggest that an excessive stem and progenitor activity could result in increased crypts branching and might therefore underlie the reported intestinal tissue expansion in response to short-term caloric restriction. Summarizing, we demonstrate for the first time that short-term caloric restriction induces changes in the level of cell proliferation
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    Blends based on amino acid functionalized poly (ethylene-alt-maleic anhydride) polyelectrolytes and PEO for nanofiber elaboration: Biocompatible and angiogenic polyelectrolytes
    (2022) Leal, Matias; Leiva, Angel; Villalobos, Valeria; Palma, Veronica; Carrillo, Daniela; Edwards, Natalie; Maine, Arianne; Cauich-Rodriguez, Juan, V; Tamayo, Laura; Neira-Carrillo, Andronico; Urzua, Marcela
    A wide variety of polymers have been electrospun to obtain nanofibers. However, obtaining nanofibers from polyelectrolytes is less frequent due to the charges of these polymers, which hinder the electrospinning process. Poly (ethylene-alt-maleic anhydride) (PEMA) was modified with a series of amino acids (Aa). The functionalization of PEMA with Aa (PEMA-Aa) was demonstrated by FT-IR, H-1 NMR, and C-13 NMR. Blends of PEMA-Aa and poly (ethylene oxide), PEO, with different ratios were prepared. Nanofibers were obtained by electrospinning using blends of 10-20% w/v of PEMA-Aa and 10% w/v of PEO. The conductivity of blends decreased, and the surface tension increased as the quantity of PEO in the blends was increased. TGA showed intermediate thermal properties compared with the blend components. Nanofibers were obtained for all PEMA-Aa/PEO blends, with diameters between 170 and 350 nm. Continuous fibers without morphological defects were obtained at concentrations of 20% w/v and 10% w/v of PEMA-Aa and PEO. Wharton's Jelly Mesenchymal Stem Cells viability, chicken embryo chorioallantoic membrane (CAM) assay and embryo viability measurements were realized for PEMA-Aa. Cytotoxicity test showed both composition and concentration-dependent behavior for PEMA-Aa, with higher WJ-MSC viability at 0.1 mg/mL at 24 h. CAM assay showed the formation of a high number of blood vessels and chicken embryo viability was close to 100% in the presence of polyelectrolytes. This, study demonstrates that electrospun nanofibers obtained from PEMA-Aa/PEO modified polyelectrolyte blends can be considered as a promising material for biomedical applications.
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    Costs of exploratory behavior: the energy trade-off hypothesis and the allocation model tested under caloric restriction
    (2020) Pena-Villalobos, Isaac; Casanova-Maldonado, Ignacio; Lois, Pablo; Palma, Veronica; Sabat, Pablo
    In order to maintain the energy balance, animals often exhibit several physiological adjustments when subjected to a decrease in resource availability. Specifically, some rodents show increases in behavioral activity in response to food restriction; a response regarded as a paradox because it would imply an investment in locomotor activity, despite the lack of trophic resources. Here, we aim to explore the possible existence of trade-offs between metabolic variables and behavioral responses when rodents are faced to stochastic deprivation of food and caloric restriction. Adult BALB/c mice were acclimatized for four weeks to four food treatments: two caloric regimens (ad libitum and 60% restriction) and two periodicities (continuous and stochastic). In these mice, we analyzed: exploratory behavior and homecage behavior, basal metabolic rate, citrate synthase and cytochrome oxidase c enzyme activity (in liver and skeletal muscle), body temperature and non-shivering thermogenesis. Our results support the model of allocation, which indicates commitments between metabolic rates and exploratory behavior, in a caloric restricted environment. Specifically, we identify the role of thermogenesis as a pivotal budget item, modulating the reallocation of energy between behavior and basal metabolic rate. We conclude that brown adipose tissue and liver play a key role in the development of paradoxical responses when facing decreased dietary availability.
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    Energetic Effects of Pre-hatch Albumen Removal on Embryonic Development and Early Ontogeny in Gallus gallus
    (2017) Pena-Villalobos, Isaac; Piriz, Gabriela; Palma, Veronica; Sabat, Pablo
    Studies on the yolk and albumen content in bird eggs, and the effects of variations in their relative loads in the phenotype of the birds, have revealed multiple consequences at different levels of biological organization, from biochemical traits to behavior. However, little is known about the effect of albumen variation on energetics performance during development and early ontogeny, despite the fact that variation in energy expenditure may have consequences in terms of fitness for both feral and domestic species. In this work, we evaluated experimentally whether variations in the content of albumen of Gallus gallus eggs could generate differences in metabolic rates during embryonic development. Additionally, we assessed changes in the activity of mitochondrial enzymes (cytochrome c oxidase and citrate synthase) in skeletal muscles and liver. Finally, we evaluated the success of hatching of these embryos and their metabolic rates (MR) post-hatching. The results revealed a significant reduction in MR in the last fifth of embryonic life, and reduced catabolic activities in the skeletal muscle of chicks hatched from albumen-removed eggs. However, the same group demonstrated an increase in catabolic activity in the liver, suggesting the existence of changes in energy allocation between tissues. Besides, we found a decrease in hatching success in the albumen-removed group, suggesting a negative effect of the lower albumen content on eggs, possibly due to lower catabolic activities in skeletal muscle. We also found a compensatory phenomenon in the first week after hatching, i.e., birds from albumen-removed eggs did not show a decrease in MR either at thermoneutral temperatures or at 10 degrees C, compared to the control group. Collectively, our data suggest that a reduction in albumen may generate a trade-off between tissue metabolic activities, and may explain the differences in metabolic rates and hatching success, supporting the immediate adaptive response (IAR) hypothesis.