The Endomembrane System of Giardia intestinalis

Giardia intestinalis is a protozoan that colonizes the small intestine of virtually all mammals, adhering to the mucosal epithelial cells. It is a cosmopolitan parasite and agent of giardiasis, which can lead to human diarrheal diseases. The Giardia life cycle presents two forms—the trophozoite and the cyst—which are responsible for infection and transmission, respectively. This cell has been considered an excellent model for evolutionary studies, even though there are controversial hypotheses as to whether this parasite is an early eukaryote or not. G. intestinalis has a unique and very basic endomembrane system. The trophozoite gathers a very small pack of membrane-bounded structures: nuclei, endoplasmic reticulum (ER), peripheral vesicles (PV) and mitosomes. These organelles are involved in many functions from regulatory aspects in gene expression as well as membrane traffic events. Two functional nuclei are observed in the parasite; they are always located symmetrically in the anterior region of the trophozoite. The ER and PV commonly share and accumulate functions in the secretory pathway, they are responsible for endocytosis and digestion processes. The mitosome is a mitochondria-related organelle that does not produce ATP and lacks several mitochondrial characteristics. During the parasite differentiation into cyst, different types of vesicles appear into the cell body: the encystation specific vesicles (ESVs) and the encystation carbohydrate-positive vesicles (ECVs). These vesicles work together to form the parasite’s cyst wall in order to ensure that the cell reaches the cyst stage. Interestingly, Giardia does not present a morphologically recognized Golgi apparatus. It has been claimed that during the encystation process, the ESVs could represent a Golgi-like structure, because this organelle presents some characteristics of that high eukaryotic Golgi apparatus. In this book chapter, we highlight the G. intestinalis endomembrane system, emphasizing their morphology, proteins involved in its organization as well as their functional role

Evaluation of the Glomerular Filtration Barrier by Electron Microscopy

The plasma filtration and formation of the urine is a very complex process necessary for the elimination of metabolites, toxins, and excessive water and electrolytes from the body. The initial process of urine formations is done by the glomerular filtration barrier inside the glomeruli. This specialized barrier consists of three layers, fenestrated endothelium, basement membrane, and podocytes, which ensure that water and small molecules pass through while cells and large molecules are retained. The glomerular filtration barrier is found with abnormal morphology in several diseases and is associated with renal malfunction; thus, it is interesting to study these structures in different experimental and clinical conditions. The normal glomerular barrier and its alterations in some conditions (hypertension, diabetes, and fetal programming) are discussed in this chapter. Furthermore, some methods for studying the glomerular filtration barrier by electron microscopy, both by qualitative and quantitative methods, are present

The Cytoskeleton of Giardia intestinalis

Giardia intestinalis is a pathogenic protozoan, which is the causative agent of giardiasis. The Giardia trophozoite presents a cytoskeleton formed by specialized microtubular structures such as the ventral disk, four pairs of flagella, the median body, and the funis that are involved in cell division and differentiation. Because trophozoite motility and adhesion to the host intestinal cells are important processes mediated by the parasite cytoskeleton, the fine regulation of these elements may be directly related to the mechanisms that underlie infection. The organization of Giardia cytoskeleton at the ultrastructural level has been analyzed by different classical microscopy methods, including negative stain and chemical fixation for scanning and transmission electron microscopy. In this chapter, we provide an overview of the G. intestinalis cytoskeleton, emphasizing its structural organization and proteins involved in the maintenance of the structures as well as their functional role. These structures have been recently analyzed in some detail using techniques such as electron microscopy tomography, cryoelectron microscopy, ultra-high resolution scanning electron microscopy (UHRSEM), and helium ion microscopy (HIM). In addition, genome survey and phylogenetic analysis as well as proteomic analysis have revealed the presence of several new and not yet well-characterized proteins

The protist Trichomonas vaginalis harbors multiple lineages of transcriptionally active Mutator-like elements

<p>Abstract</p> <p>Background</p> <p>For three decades the <it>Mutator </it>system was thought to be exclusive of plants, until the first homolog representatives were characterized in fungi and in early-diverging amoebas earlier in this decade.</p> <p>Results</p> <p>Here, we describe and characterize four families of <it>Mutator</it>-like elements in a new eukaryotic group, the Parabasalids. These <b><it>T</it></b><it>richomonas </it><b><it>v</it></b><it>aginalis </it><it><b>Mu</b>tator- <b>l</b>ike </it><it><b>e</b>lements</it>, or <it>TvMULEs</it>, are active in <it>T. vaginalis </it>and patchily distributed among 12 trichomonad species and isolates. Despite their relatively distinctive amino acid composition, the inclusion of the repeats <it>TvMULE1</it>, <it>TvMULE2</it>, <it>TvMULE3 </it>and <it>TvMULE4 </it>into the <it>Mutator </it>superfamily is justified by sequence, structural and phylogenetic analyses. In addition, we identified three new <it>TvMULE</it>-related sequences in the genome sequence of <it>Candida albicans</it>. While <it>TvMULE1 </it>is a member of the <it>MuDR </it>clade, predominantly from plants, the other three <it>TvMULEs</it>, together with the <it>C. albicans </it>elements, represent a new and quite distinct <it>Mutator </it>lineage, which we named <it>TvCaMULEs</it>. The finding of <it>TvMULE1 </it>sequence inserted into other putative repeat suggests the occurrence a novel TE family not yet described.</p> <p>Conclusion</p> <p>These findings expand the taxonomic distribution and the range of functional motif of <it>MULEs </it>among eukaryotes. The characterization of the dynamics of <it>TvMULEs </it>and other transposons in this organism is of particular interest because it is atypical for an asexual species to have such an extreme level of TE activity; this genetic landscape makes an interesting case study for causes and consequences of such activity. Finally, the extreme repetitiveness of the <it>T. vaginalis </it>genome and the remarkable degree of sequence identity within its repeat families highlights this species as an ideal system to characterize new transposable elements.</p

2D and 3D-Organized Cardiac Cells Shows Differences in Cellular Morphology, Adhesion Junctions, Presence of Myofibrils and Protein Expression

Cardiac cells are organized in vivo in a complex tridimensional structural organization that is crucial for heart function. While in vitro studies can reveal details about cardiac cell biology, usually cells are grown on simplified two-dimensional (2D) environments. To address these differences, we established a cardiac cell culture composed of both 2D and three-dimensional (3D)-organized cells. Our results shows significant differences between the two culture contexts in relation to the overall morphology of the cells, contraction ability, proliferation rate, presence of intercellular adhesion structures, organization of myofibrils, mitochondria morphology, endoplasmic reticulum contents, cytoskeletal filaments and extracellular matrix distribution, and expression of markers of cardiac differentiation. Cardiac cells grown in 2D-context displayed a flattened and well spread shape, were mostly isolated and their cytoplasm was filled with a large network of microfilaments and microtubules. In contrast, 3D-cells were smaller in size, were always in close contact with each other with several cellular junctions, and displayed a less conspicuous cytoskeletal network. 3D-cells had more mitochondria and myofibrils and these cells contract spontaneously more often than 2D-cells. On the other hand, endoplasmic reticulum membranes were present in higher amounts in 2D-cells when compared to 3D-cells. The expression of desmin, cadherin and alpha-actinin was higher in 3D-aggregates compared to 2D-spread cells. These findings indicate that the tridimensional environment in which the cardiac cells are grown influence several aspects of cardiac differentiation, including cell adhesion, cell shape, myofibril assembly, mitochondria contents and protein expression. We suggest that the use of this cardiac culture model, with 2D and 3D-context cells, could be useful for studies on the effects of different drugs, or growth factors, giving valuable information on the biological response of cells grown in different spatial organizations

Fusion of the Endoplasmic Reticulum and Mitochondrial Outer Membrane in Rats Brown Adipose Tissue: Activation of Thermogenesis by Ca2+

Brown adipose tissue (BAT) mitochondria thermogenesis is regulated by uncoupling protein 1 (UCP 1), GDP and fatty acids. In this report, we observed fusion of the endoplasmic reticulum (ER) membrane with the mitochondrial outer membrane of rats BAT. Ca2+-ATPase (SERCA 1) was identified by immunoelectron microscopy in both ER and mitochondria. This finding led us to test the Ca2+ effect in BAT mitochondria thermogenesis. We found that Ca2+ increased the rate of respiration and heat production measured with a microcalorimeter both in coupled and uncoupled mitochondria, but had no effect on the rate of ATP synthesis. The Ca2+ concentration needed for half-maximal activation varied between 0.08 and 0.11 µM. The activation of respiration was less pronounced than that of heat production. Heat production and ATP synthesis were inhibited by rotenone and KCN

DESENVOLVIMENTO DE MATERIAL MULTIMÁDIA NO ENSINO DE BIOLOGIA

oai:ojs.eademfoco.cecierj.edu.br:article/5Apresentamos uma metodologia de produção de aulas multimídia para estudantes do curso de Licenciatura em Ciências Biológicas, na modalidade semipresencial. Nosso método tem como base um conteúdo disponibilizado sob a forma de animações interativas. Através de uma navegação linear, o aluno possui pleno controle do andamento da aula, tendo como estímulos a riqueza visual e a interatividade, permitindo caminhar no seu próprio tempo até a completa compreensão do conteúdo. Este conteúdo se apresenta em uma linguagem coloquial simulando a presença de um professor competente e simpático, além de descomplicado. Toda a estrutura da aula é fundamentada no construtivismo e no cognitivismo e cada um dos aspectos envolvidos na produção do material multimídia, como cores, tipografia, animações, analogias e bom humor são utilizados como estratégias motivadoras e facilitadoras do processo de aprendizado. Uma equipe especializada na produção gráfica, acompanhada de pós-graduados em biociências, revisores de português e de conteúdo produz cada aula, discutindo aspectos relevantes do ensino-aprendizagem. O resultado é um material multimídia rico, disponibilizado em CD e/ou online, que permite que o aluno aprenda sozinho