http://hdl.handle.net/10366/3970 2026-04-23T08:25:19Z http://hdl.handle.net/10366/169871 [ENG]This chapter examines the complex biological role of milk carbohydrates, particularly human milk oligosaccharides (HMOs), as a primary defense mechanism against neonatal infections. While lactose serves as a major energy source, the focus here is on the diverse array of glycoconjugates—including free oligosaccharides, glycoproteins, and glycolipids—that function as potent anti-adhesive agents.Molecular Mimicry and Anti-Adhesion MechanismThe fundamental premise is the inhibition of bacterial adherence to host tissues, which is the requisite first step for most infectious diseases. Many pathogenic microorganisms, such as various strains of Escherichia coli (ETEC, EPEC, EHEC), Campylobacter jejuni, and Vibrio cholerae, utilize surface lectins or adhesins to recognize and bind to specific carbohydrate sequences on the surface of the infant's intestinal epithelium.Milk carbohydrates act as "soluble decoy receptors." Because their chemical structures mimic the carbohydrate moieties found on the host’s cell membranes, they compete with the host receptors for bacterial binding sites. Once the pathogens or their toxins bind to these soluble milk glycans instead of the intestinal wall, they are neutralized and eventually flushed out of the gastrointestinal tract, preventing colonization and subsequent infection.Compositional Complexity and Genetic VariabilityHuman milk is uniquely rich in complex oligosaccharides (12–14 g/L) compared to bovine milk, which contains significantly lower concentrations and simpler structures. The structural diversity of HMOs is largely determined by the mother's genetic profile, specifically the Secretor (Se) and Lewis (Le) blood group systems. These genes encode specific fucosyltransferases that determine the presence of terminal epitopes like $\alpha$1-2 linked fucose. For instance, "Secretor" mothers produce milk rich in 2'-fucosyllactose, which is highly effective against specific enteric pathogens.Analytical MethodologiesThe chapter also details the rigorous technical processes required to study these molecules. Due to their low concentration and structural microheterogeneity, isolation involves sophisticated techniques such as ultrafiltration and gel filtration chromatography. Characterization is achieved through High-Performance Liquid Chromatography (HPLC), High-Performance Anion-Exchange Chromatography (HPAEC), and Mass Spectrometry (notably MALDI-TOF), which allow for the identification of specific glycan sequences and linkage patterns.ConclusionThe protective effect of milk carbohydrates provides a crucial advantage for breastfed infants, significantly reducing the morbidity associated with diarrheal diseases. The chapter concludes that while modern infant formulas attempt to replicate this protection, the immense structural complexity and biological specificity of human milk carbohydrates remain a major challenge for food engineering and clinical nutrition. 2005-05-27T00:00:00Z http://hdl.handle.net/10366/157183 [EN]The versatility of nitric oxide (NO) as a free radical that mediates numerous biological functions within early plant development is widely accepted. NO action in seed germination and root developmental processes involves a complex signaling pathway that includes the cellular redox levels, the posttranslational modification of specific proteins by S-nitrosylation, and the interaction with other plant growth regulators (i.e., phytohormones) using similar molecular com ponents. Recent evidence indicates that changing levels of this reactive nitrogen species (NO) may also fine-tune the molecular mechanisms by which NO leads to changes in seed germination and root growth. This chapter briefly introduces the key processes for the NO transmission during seed germination and root development and focuses on the sensing mechanisms underlying the effects of NO and its interaction with other plant hormones linking these changes. 2016-03-01T00:00:00Z http://hdl.handle.net/10366/157181 [EN]Post-embryonic cell proliferation allows for the development of an extensive root system. Recent genetic analysis in Arabidopsis thaliana has revealed several mechanisms involved in cell proliferation control during root development, including hormone signaling and regulatory loops. Furthermore, cell division responds to changes in redox status induced by environmental stresses, and we explore putative connections to the pathways that regulate cell proliferation. 2012-01-01T00:00:00Z http://hdl.handle.net/10366/157172 [EN]Auxin transport is a central process in plant growth and development and as a result is highly regulated. The amount and direction of auxin transport is defined by a set of auxin influx and efflux carriers with precise localization that lead to long distance polar auxin transport. These auxin transport proteins are regulated by transcriptional and posttranslational mechanisms and through protein-targeting machinery that directs them to the appropriate plasma membrane location. A variety of signals initiate regulatory changes in the abundance, activity, or localization of these proteins, with plant hormones, light, and other environmental signaling implicated in this process. Recent evidence indicates that changing levels of reactive oxygen species (ROS) and reactive nitrogen species (RNS) may also fine-tune the activity or synthesis of these proteins. This insight has been obtained by using mutants or treatments that alter the levels of ROS or RNS and demonstration of changing auxin transport and abundance of transport proteins. The molecular mechanisms by which ROS and RNS lead to changes in auxin transport are not yet clear but likely include changes in protein synthesis and abundance. This chapter briefly introduces the key proteins and antioxidant molecules that control the levels of ROS and RNS and focuses on the evidence linking these changes to altered auxin transport. 2013-01-01T00:00:00Z http://hdl.handle.net/10366/157144 [EN]Trichoderma species are filamentous fungi with high economic importance since they participate as biocontrol or biological pesticide agents, inhibiting the growth of phytopathogenic fungi that could destroy a large variety of crops. The biocontrol ability of Trichoderma seems to be due to multiple factors, as they have the ability to produce a variety of extracellular lytic enzymes and the production of many secondary metabolites. Three kinds of compounds are mainly produced by different species of Trichoderma: peptaibols, polyketides and terpenes, some of them with antifungal activity. There exist many reports about their chemical structure and, in some cases, the complete biosynthetic pathway has been elucidated thanks to the isolation and detection of many intermediate compounds. However, nothing or little information exists about the genes involved in their biosynthesis, mainly because each individual strain of Trichoderma has the ability to produce simultaneously large quantities of these kinds of compounds, which make difficult to relate one gene with one intermediate or final product. 2005-01-01T00:00:00Z http://hdl.handle.net/10366/119454 Una introducción al metabolismo de biomoléculas, con una introducción sobre ciclos geoquímicos. Trata también de metabolismo de xenobióticos, iones inorgánicos, metabolismo basal y aspectos metabólicos de la dieta 2013-02-05T00:00:00Z http://hdl.handle.net/10366/119453 Un compendio de Enzimología apto para cursos de Bioquímica General, especialmente en Ciencias de la Salud. 2013-02-05T00:00:00Z