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Paracellular absorption is relatively low in the herbivorous Egyptian spiny-tailed lizard, Uromastyx aegyptia.
PUBLISHED: 01-01-2013
Absorption of small water-soluble nutrients in vertebrate intestines occurs both by specific, mediated transport and by non-specific, passive, paracellular transport. Although it is apparent that paracellular absorption represents a significant route for nutrient absorption in many birds and mammals, especially small, flying species, its importance in ectothermic vertebrates has not previously been explored. Therefore, we measured fractional absorption (ƒ) and absorption rate of three paracellular probes (arabinose, L-rhamnose, cellobiose) and of 3-O-methyl D-glucose (absorbed by both mediated and paracellular pathways) by the large herbivorous lizard, Uromastyx aegyptia, to explore the relative importance of paracellular and mediated transport in an ectothermic, terrestrial vertebrate. Fractional absorption of 3-O-methyl D-glucose was high (ƒ?=?0.73±0.04) and similar to other vertebrates; ƒ of the paracellular probes was relatively low (arabinose ƒ?=?0.31±0.03, L-rhamnose ƒ?=?0.19±0.02, and cellobiose ƒ?=?0.14±0.02), and decreased with molecular mass, a pattern consistent with other vertebrates. Paracellular absorption accounted for approximately 24% of total 3-O-methyl D-glucose uptake, indicating low reliance on this pathway for these herbivorous lizards, a pattern similar to that found in other terrestrial vertebrates, and different from small flying endotherms (both birds and bats).
Published: 08-14-2014
19 Related JoVE Articles!
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Sensing of Barrier Tissue Disruption with an Organic Electrochemical Transistor
Institutions: Ecole Nationale Superieure des Mines, Johns Hopkins University.
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Microgavage of Zebrafish Larvae
Authors: Jordan L. Cocchiaro, John F. Rawls.
Institutions: University of North Carolina at Chapel Hill .
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Authors: Rasa Ghaffarian, Silvia Muro.
Institutions: University of Maryland, University of Maryland.
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Analysis of Nephron Composition and Function in the Adult Zebrafish Kidney
Institutions: University of Notre Dame.
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Exfoliation of Egyptian Blue and Han Blue, Two Alkali Earth Copper Silicate-based Pigments
Authors: Darrah Johnson-McDaniel, Tina T. Salguero.
Institutions: The University of Georgia.
In a visualized example of the ancient past connecting with modern times, we describe the preparation and exfoliation of CaCuSi4O10 and BaCuSi4O10, the colored components of the historic Egyptian blue and Han blue pigments. The bulk forms of these materials are synthesized by both melt flux and solid-state routes, which provide some control over the crystallite size of the product. The melt flux process is time intensive, but it produces relatively large crystals at lower reaction temperatures. In comparison, the solid-state method is quicker yet requires higher reaction temperatures and yields smaller crystallites. Upon stirring in hot water, CaCuSi4O10 spontaneously exfoliates into monolayer nanosheets, which are characterized by TEM and PXRD. BaCuSi4O10 on the other hand requires ultrasonication in organic solvents to achieve exfoliation. Near infrared imaging illustrates that both the bulk and nanosheet forms of CaCuSi4O10 and BaCuSi4O10 are strong near infrared emitters. Aqueous CaCuSi4O10 and BaCuSi4O10 nanosheet dispersions are useful because they provide a new way to handle, characterize, and process these materials in colloidal form.
Chemistry, Issue 86, Nanosheets, Egyptian Blue, Han Blue, Pigment, Near Infrared, Luminescence, Exfoliation, Delamination, Two-Dimensional, Ink, Colloidal Dispersion
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Authors: Jennifer C. Arnold, Michael F. Salvatore.
Institutions: Louisiana State University Health Sciences Center.
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Institutions: University College London.
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Isolation of Primary Murine Brain Microvascular Endothelial Cells
Authors: Tobias Ruck, Stefan Bittner, Lisa Epping, Alexander M. Herrmann, Sven G. Meuth.
Institutions: University of Münster, Interdisciplinary Center for Clinical Research (IZKF) Münster, University of Münster.
The blood-brain-barrier is ultrastructurally assembled by a monolayer of brain microvascular endothelial cells (BMEC) interconnected by a junctional complex of tight and adherens junctions. Together with other cell-types such as astrocytes or pericytes, they form the neurovascular unit (NVU), which specifically regulates the interchange of fluids, molecules and cells between the peripheral blood and the CNS. Through this complex and dynamic system BMECs are involved in various processes maintaining the homeostasis of the CNS. A dysfunction of the BBB is observed as an essential step in the pathogenesis of many severe CNS diseases. However, specific and targeted therapies are very limited, as the underlying mechanisms are still far from being understood. Animal and in vitro models have been extensively used to gain in-depth understanding of complex physiological and pathophysiological processes. By reduction and simplification it is possible to focus the investigation on the subject of interest and to exclude a variety of confounding factors. However, comparability and transferability are also reduced in model systems, which have to be taken into account for evaluation. The most common animal models are based on mice, among other reasons, mainly due to the constantly increasing possibilities of methodology. In vitro studies of isolated murine BMECs might enable an in-depth analysis of their properties and of the blood-brain-barrier under physiological and pathophysiological conditions. Further insights into the complex mechanisms at the BBB potentially provide the basis for new therapeutic strategies. This protocol describes a method to isolate primary murine microvascular endothelial cells by a sequence of physical and chemical purification steps. Special considerations for purity and cultivation of MBMECs as well as quality control, potential applications and limitations are discussed.
Neuroscience, Issue 93, Blood brain barrier, central nervous system, endothelial cells, immune cell trafficking, neuroinflammation, neurodegeneration, neurovascular unit
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Authors: Darius J. R. Lane, Alfons Lawen.
Institutions: University of Sydney, Monash University.
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Construction and Characterization of External Cavity Diode Lasers for Atomic Physics
Institutions: The Australian National University.
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Helminth Collection and Identification from Wildlife
Authors: Maria S Sepulveda, John M Kinsella.
Institutions: Purdue University, Helm West Laboratory.
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Simulation, Fabrication and Characterization of THz Metamaterial Absorbers
Institutions: University of Glasgow.
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Institutions: University of Calgary .
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An Assay for Permeability of the Zebrafish Embryonic Neuroepithelium
Authors: Jessica T. Chang, Hazel Sive.
Institutions: Massachusetts Institute of Technology, Whitehead Institute of Biomedical Research.
The brain ventricular system is conserved among vertebrates and is composed of a series of interconnected cavities called brain ventricles, which form during the earliest stages of brain development and are maintained throughout the animal's life. The brain ventricular system is found in vertebrates, and the ventricles develop after neural tube formation, when the central lumen fills with cerebrospinal fluid (CSF) 1,2. CSF is a protein rich fluid that is essential for normal brain development and function3-6. In zebrafish, brain ventricle inflation begins at approximately 18 hr post fertilization (hpf), after the neural tube is closed. Multiple processes are associated with brain ventricle formation, including formation of a neuroepithelium, tight junction formation that regulates permeability and CSF production. We showed that the Na,K-ATPase is required for brain ventricle inflation, impacting all these processes 7,8, while claudin 5a is necessary for tight junction formation 9. Additionally, we showed that "relaxation" of the embryonic neuroepithelium, via inhibition of myosin, is associated with brain ventricle inflation. To investigate the regulation of permeability during zebrafish brain ventricle inflation, we developed a ventricular dye retention assay. This method uses brain ventricle injection in a living zebrafish embryo, a technique previously developed in our lab10, to fluorescently label the cerebrospinal fluid. Embryos are then imaged over time as the fluorescent dye moves through the brain ventricles and neuroepithelium. The distance the dye front moves away from the basal (non-luminal) side of the neuroepithelium over time is quantified and is a measure of neuroepithelial permeability (Figure 1). We observe that dyes 70 kDa and smaller will move through the neuroepithelium and can be detected outside the embryonic zebrafish brain at 24 hpf (Figure 2). This dye retention assay can be used to analyze neuroepithelial permeability in a variety of different genetic backgrounds, at different times during development, and after environmental perturbations. It may also be useful in examining pathological accumulation of CSF. Overall, this technique allows investigators to analyze the role and regulation of permeability during development and disease.
Neuroscience, Issue 68, Zebrafish, neuroepithelium, brain ventricle, permeability
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Born Normalization for Fluorescence Optical Projection Tomography for Whole Heart Imaging
Authors: Claudio Vinegoni, Daniel Razansky, Jose-Luiz Figueiredo, Lyuba Fexon, Misha Pivovarov, Matthias Nahrendorf, Vasilis Ntziachristos, Ralph Weissleder.
Institutions: Harvard Medical School, MGH - Massachusetts General Hospital, Technical University of Munich and Helmholtz Center Munich.
Optical projection tomography is a three-dimensional imaging technique that has been recently introduced as an imaging tool primarily in developmental biology and gene expression studies. The technique renders biological sample optically transparent by first dehydrating them and then placing in a mixture of benzyl alcohol and benzyl benzoate in a 2:1 ratio (BABB or Murray s Clear solution). The technique renders biological samples optically transparent by first dehydrating them in graded ethanol solutions then placing them in a mixture of benzyl alcohol and benzyl benzoate in a 2:1 ratio (BABB or Murray s Clear solution) to clear. After the clearing process the scattering contribution in the sample can be greatly reduced and made almost negligible while the absorption contribution cannot be eliminated completely. When trying to reconstruct the fluorescence distribution within the sample under investigation, this contribution affects the reconstructions and leads, inevitably, to image artifacts and quantification errors.. While absorption could be reduced further with a permanence of weeks or months in the clearing media, this will lead to progressive loss of fluorescence and to an unrealistically long sample processing time. This is true when reconstructing both exogenous contrast agents (molecular contrast agents) as well as endogenous contrast (e.g. reconstructions of genetically expressed fluorescent proteins).
Bioengineering, Issue 28, optical imaging, fluorescence imaging, optical projection tomography, born normalization, molecular imaging, heart imaging
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