Reactivo de Lugol: Historia de su descubrimiento y aplicaciones didácticas

Our paper is a brief historical study of aqueous solutions of potassium iodide and iodine. It also analyzes why, in Biology and Medicine, these solutions are known as Lugol reactive. Moreover, we study their use for educational purposes to deepen in various topics such as redox reactions and the relationship between solubility and bond types.

Extracellular HIV-1 virus protein R causes a large inward current and cell death in cultured hippocampal neurons: Implications for AIDS pathology

The small HIV-1 accessory protein Vpr (virus protein R) is a multifunctional protein that is present in the serum and cerebrospinal fluid of AIDS patients. We previously showed that Vpr can form cation-selective ion channels across planar lipid bilayers, introducing the possibility that, if incorporated into the membranes of living cells, Vpr might form ion channels and consequently perturb the maintained ionic gradient. In this study, we demonstrate, by a variety of approaches, that Vpr added extracellularly to intact cells does indeed form ion channels. We use confocal laser scanning microscopy to examine the subcellular localization of fluorescently labeled Vpr. Plasmalemma depolarization and damage are examined using the anionic potential-sensitive dye bis(1,3-dibutylbarbituric acid) trimethine oxonol and propidium iodide (PI), respectively, and the effect of Vpr on whole-cell current is demonstrated directly by using the patch-clamp technique. We show that recombinant purified extracellular Vpr associates with the plasmalemma of hippocampal neurons to cause a large inward cation current and depolarization of the plasmalemma, eventually resulting in cell death. Thus, we demonstrate a physiological action of extracellular Vpr and present its mechanistic basis. These findings may have important implications for neuropathologies in AIDS patients who possess significant amounts of Vpr in the cerebrospinal fluid.

Heteromultimeric CLC chloride channels with novel properties

The skeletal muscle chloride channel CLC-1 and the ubiquitous volume-activated chloride channel CLC-2 belong to a large gene family whose members often show overlapping expression patterns. CLC-1 and CLC-2 are coexpressed in skeletal and smooth muscle and in the heart. By coexpressing CLC-1 and CLC-2 in Xenopus oocytes, we now show the formation of novel CLC-1/CLC-2 heterooligomers that yield time-independent linear chloride currents with a chloride → bromide → iodide selectivity sequence. Formation of heterooligomeric CLC channels increases the number and possible functions of chloride channels.

Cotransport of water by the Na+/glucose cotransporter

Water is transported across epithelial membranes in the absence of any hydrostatic or osmotic gradients. A prime example is the small intestine, where 10 liters of water are absorbed each day. Although water absorption is secondary to active solute transport, the coupling mechanism between solute and water flow is not understood. We have tested the hypothesis that water transport is directly linked to solute transport by cotransport proteins such as the brush border Na+/glucose cotransporter. The Na+/glucose cotransporter was expressed in Xenopus oocytes, and the changes in cell volume were measured under sugar-transporting and nontransporting conditions. We demonstrate that 260 water molecules are directly coupled to each sugar molecule transported and estimate that in the human intestine this accounts for 5 liters of water absorption per day. Other animal and plant cotransporters such as the Na+/Cl−/γ-aminobutyric acid, Na+/iodide and H+/amino acid transporters are also able to transport water and this suggests that cotransporters play an important role in water homeostasis.

Hypothyroidism in transgenic mice expressing IFN-γ in the thyroid

IFN-γ has been implicated with contradictory results in the pathogenetic process of autoimmune (Hashimoto's) thyroiditis, the most common cause of hypothyroidism in adults. To test whether the local production of IFN-γ can lead to thyroid dysfunction, we have generated transgenic mice that express constitutively IFN-γ in the thyroid follicular cells. This expression resulted in severe hypothyroidism, with growth retardation and disruption of the thyroid architecture. The hypothyroidism derived from a profound inhibition of the expression of the sodium iodide symporter gene. Taken together, these results indicate a direct role of IFN-γ in the thyroid dysfunction that occurs in autoimmune thyroiditis.

Pax8 has a key role in thyroid cell differentiation

Transformation of rat thyroid cells with polyoma virus middle T antigen results in loss of the thyroid-differentiated phenotype, measured as the expression of the thyroglobulin (Tg), thyroperoxidase (TPO), and sodium/iodide symporter (NIS) genes. Among the transcription factors involved in the regulation of these genes, TTF-1 and TTF-2 were still detected at nearly wild-type levels, while a specific loss of the paired domain transcription factor Pax8 was observed. In this study, we used the PCPy cell line as a model system to study the role of Pax8 in thyroid differentiation. We demonstrate that the reintroduction of Pax8 in PCPy cells is sufficient to activate expression of the endogenous genes encoding thyroglobulin, thyroperoxidase, and sodium/iodide symporter. Thus, this cell system provides direct evidence for the ability of Pax8 to activate transcription of thyroid-specific genes at their chromosomal locus and strongly suggests a fundamental role of this transcription factor in the maintenance of functional differentiation in thyroid cells. Moreover, we show that Pax8 and TTF-1 cooperate in the activation of the thyroglobulin promoter and that additional thyroid-specific mechanism(s) are involved in such a cooperation. To identify the Pax8 domain able to mediate the specific activation of the thyroglobulin promoter, we transfected in PCPy cells three different Pax8 isoforms. The results of such experiments indicate that for the transcriptional activation of thyroid-specific genes, Pax8 uses an as yet unidentified functional domain.