scholarly journals In Vivo Nitrogenase Regulation by Ammonium and Methylamine and the Effect of MSX on Ammonium Transport in Anabaena flos-aquae

1984 ◽  
Vol 74 (3) ◽  
pp. 701-704 ◽  
Author(s):  
David H. Turpin ◽  
Scott A. Edie ◽  
David T. Canvin
Keyword(s):  
Ammonium Transport ◽  
Nitrogenase Regulation

scholarly journals Nitrogen isotope signature evidences ammonium deprotonation as a common transport mechanism for the AMT-Mep-Rh protein superfamily

2018 ◽  
Vol 4 (9) ◽  
pp. eaar3599 ◽  
Author(s):  
Idoia Ariz ◽  
Mélanie Boeckstaens ◽  
Catarina Gouveia ◽  
Ana Paula Martins ◽  
Emanuel Sanz-Luque ◽  
...  
Keyword(s):  
Isotope Fractionation ◽  
Physical Property ◽  
Nitrogen Isotope ◽  
Ph Control ◽  
Isotopic Signature ◽  
Ammonium Transport ◽  
Ammonium Toxicity ◽  
Cytotoxic Compound ◽  
Wide Range

Ammonium is an important nitrogen (N) source for living organisms, a key metabolite for pH control, and a potent cytotoxic compound. Ammonium is transported by the widespread AMT-Mep-Rh membrane proteins, and despite their significance in physiological processes, the nature of substrate translocation (NH3/NH4+) by the distinct members of this family is still a matter of controversy. Using Saccharomyces cerevisiae cells expressing representative AMT-Mep-Rh ammonium carriers and taking advantage of the natural chemical-physical property of the N isotopic signature linked to NH4+/NH3 conversion, this study shows that only cells expressing AMT-Mep-Rh proteins were depleted in 15N relative to 14N when compared to the external ammonium source. We observed 15N depletion over a wide range of external pH, indicating its independence of NH3 formation in solution. On the basis of inhibitor studies, ammonium transport by nonspecific cation channels did not show isotope fractionation but competition with K+. We propose that kinetic N isotope fractionation is a common feature of AMT-Mep-Rh–type proteins, which favor 14N over 15N, owing to the dissociation of NH4+ into NH3 + H+ in the protein, leading to 15N depletion in the cell and allowing NH3 passage or NH3/H+ cotransport. This deprotonation mechanism explains these proteins’ essential functions in environments under a low NH4+/K+ ratio, allowing organisms to specifically scavenge NH4+. We show that 15N isotope fractionation may be used in vivo not only to determine the molecular species being transported by ammonium transport proteins, but also to track ammonium toxicity and associated amino acids excretion.

Effects of chronic Cl depletion alkalosis on proximal tubule transport and renal production of ammonium

1995 ◽  
Vol 269 (4) ◽  
pp. F508-F514 ◽  
Author(s):  
T. D. DuBose ◽  
D. W. Good
Keyword(s):  
Metabolic Alkalosis ◽  
Filtration Rate ◽  
Ammonium Transport ◽  
Ammonium Excretion ◽  
Elevated Plasma ◽  
Urine Ph ◽  
Chloride Depletion ◽  
Ammonium Production

The role of renal ammonium excretion in the maintenance of chronic metabolic alkalosis is poorly defined, particularly under conditions in which the alkalosis is associated with secondary potassium depletion. Therefore, free-flow micropuncture experiments were performed to examine the effects of chronic chloride depletion metabolic alkalosis (CDAlk) on renal ammonium production, urinary ammonium excretion, and proximal convoluted tubule (PCT) ammonium transport in the rat in vivo. CDAlk was generated by peritoneal dialysis against NaHCO3 and maintained for 6–7 days by dietary Cl- restriction. Pair-fed controls were dialyzed against NaCl. Rats with CDAlk had elevated plasma HCO3- concentration, hypokalemia, and hypochloremia. HCO3- excretion was negligible in both control and CDAlk rats. Glomerular filtration rate and urine pH did not differ. CDAlk reduced urinary ammonium excretion by 35% but had no significant effect on whole kidney ammonium production. Net secretion of ammonium by the PCT was decreased by 70% and absolute delivery of ammonium out of the PCT was decreased by 55% in the CDAlk rats. The decrease in PCT ammonium secretion was the combined result of a decrease in net ammonium secretion along the early PCT and an increase in net ammonium absorption along the late PCT.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Matryoshka: Ratiometric biosensors from a nested cassette of green- and orange-emitting fluorescent proteins

2017 ◽  
Author(s):  
Cindy Ast ◽  
Jessica Foret ◽  
Luke M. Oltrogge ◽  
Roberto De Michele ◽  
Thomas J. Kleist ◽  
...  
Keyword(s):  
Fluorescent Protein ◽  
Dynamic Range ◽  
Fluorescent Proteins ◽  
Wide Spectrum ◽  
Stokes Shift ◽  
Ammonium Transport ◽  
Detection Range ◽  
Calcium Sensors ◽  
Acid Base Equilibrium

AbstractSensitivity, dynamic and detection range as well as exclusion of expression and instrumental artifacts are critical for the quantitation of data obtained with fluorescent protein (FP)-based biosensors in vivo. Current biosensors designs are, in general, unable to simultaneously meet all these criteria. Here, we describe a generalizable platform to create dual-FP biosensors with large dynamic ranges by employing a single FP-cassette, named GO-(Green-Orange) Matryoshka. The cassette nests a stable reference FP (large Stokes shift LSSmOrange) within a reporter FP (circularly permuted green FP). GO-Matryoshka yields green and orange fluorescence upon blue excitation. As proof of concept, we converted existing, single-emission biosensors into a series of ratiometric calcium sensors (MatryoshCaMP6s) and ammonium transport activity sensors (AmTryoshka1;3). We additionally identified the internal acid-base equilibrium as a key determinant of the GCaMP dynamic range. Matryoshka technology promises flexibility in the design of a wide spectrum of ratiometric biosensors and expanded in vivo applications.

Effects of chronic hyperkalemia on renal production and proximal tubule transport of ammonium in rats

1991 ◽  
Vol 260 (5) ◽  
pp. F680-F687 ◽  
Author(s):  
T. D. DuBose ◽  
D. W. Good
Keyword(s):  
Proximal Tubule ◽  
Renal Medulla ◽  
Proximal Convoluted Tubule ◽  
Ammonium Transport ◽  
Ammonium Excretion ◽  
High K ◽  
Collecting Ducts ◽  
Ammonium Production ◽  
K Concentration

Free-flow micropuncture experiments were performed to examine directly the effects of chronic hyperkalemia on renal ammonium production, urinary ammonium excretion, and proximal convoluted tubule ammonium transport in the rat in vivo. Munich-Wistar rats were pair-fed either a control or a high-K+ diet for 6-11 days. Chronic K+ loading was associated with an increase in plasma K+ concentration and significant systemic metabolic acidosis. Renal blood flow did not differ in control and high-K+ rats. In the hyperkalemic rats, urinary ammonium excretion was reduced by 40% and whole kidney ammonium production was reduced by 50% compared with controls. In contrast, chronic hyperkalemia had no significant effect on net ammonium transport by either the early or late segment of the proximal convoluted tubule. Chronic hyperkalemia also had no effect on the absolute rate of ammonium delivery to early or late proximal convoluted tubule sites. These results indicate that a change in renal ammonium production does not necessarily correlate with a change in proximal tubule ammonium transport and that reduced urinary ammonium excretion in chronic hyperkalemia is not due to impaired secretion of ammonium by the proximal convoluted tubule. Chronic hyperkalemia may reduce ammonium excretion by decreasing transfer of ammonium from proximal tubules to collecting ducts in the renal medulla.

Fine Structural Changes in the Microvasculature of the Mouse Pinna: Aging and Radiation Injury

1974 ◽  
Vol 32 ◽  
pp. 54-55
Author(s):  
S. Phyllis Steamer ◽  
Rosemarie L. Devine
Keyword(s):  
Structural Changes ◽  
Radiation Treatment ◽  
Arterial Stenosis ◽  
Ultrastructural Changes ◽  
Vascular Effects ◽  
Microvascular Changes ◽  
Surrounding Connective Tissue ◽  
Fission Neutrons ◽  
Total Body

The importance of radiation damage to the skin and its vasculature was recognized by the early radiologists. In more recent studies, vascular effects were shown to involve the endothelium as well as the surrounding connective tissue. Microvascular changes in the mouse pinna were studied in vivo and recorded photographically over a period of 12-18 months. Radiation treatment at 110 days of age was total body exposure to either 240 rad fission neutrons or 855 rad 60Co gamma rays. After in vivo observations in control and irradiated mice, animals were sacrificed for examination of changes in vascular fine structure. Vessels were selected from regions of specific interest that had been identified on photomicrographs. Prominent ultrastructural changes can be attributed to aging as well as to radiation treatment. Of principal concern were determinations of ultrastructural changes associated with venous dilatations, segmental arterial stenosis and tortuosities of both veins and arteries, effects that had been identified on the basis of light microscopic observations. Tortuosities and irregularly dilated vein segments were related to both aging and radiation changes but arterial stenosis was observed only in irradiated animals.

Induction and Differentiation of Dental Epithelium in Vivo and in Vitro

1982 ◽  
Vol 40 ◽  
pp. 142-145
Author(s):  
E. J. Kollar
Keyword(s):  
Connective Tissue ◽  
Oral Mucosa ◽  
Basal Lamina ◽  
Functional Derivatives ◽  
Specific Source ◽  
Dental Epithelium ◽  
Connective Tissue Stroma

The differentiation and maintenance of many specialized epithelial structures are dependent on the underlying connective tissue stroma and on an intact basal lamina. These requirements are especially stringent in the development and maintenance of the skin and oral mucosa. The keratinization patterns of thin or thick cornified layers as well as the appearance of specialized functional derivatives such as hair and teeth can be correlated with the specific source of stroma which supports these differentiated expressions.

Ultrastructural Correlations between Clonal Human Tumor Colonies and in Vivo Neoplasms

1982 ◽  
Vol 40 ◽  
pp. 210-211
Author(s):  
M.J. Murphy ◽  
R.R. Price ◽  
J.C. Sloman
Keyword(s):  
Cultured Cells ◽  
Human Tumor ◽  
Cell Type ◽  
Tumor Mass ◽  
Initial Cell ◽  
Cloning Assay ◽  
Human Tumor Cloning ◽  
The Relationship

The in vitro human tumor cloning assay originally described by Salmon and Hamburger has been applied recently to the investigation of differential anti-tumor drug sensitivities over a broad range of human neoplasms. A major problem in the acceptance of this technique has been the question of the relationship between the cultured cells and the original patient tumor, i.e., whether the colonies that develop derive from the neoplasm or from some other cell type within the initial cell population. A study of the ultrastructural morphology of the cultured cells vs. patient tumor has therefore been undertaken to resolve this question. Direct correlation was assured by division of a common tumor mass at surgical resection, one biopsy being fixed for TEM studies, the second being rapidly transported to the laboratory for culture.

Structural analysis of the photosynthetic membrane from Ectothiorhodospira halochloris

1983 ◽  
Vol 41 ◽  
pp. 740-741
Author(s):  
H. Engelhardt ◽  
R. Guckenberger ◽  
W. Baumeister
Keyword(s):  
Lattice Structure ◽  
Bacterial Species ◽  
Hexagonal Lattice ◽  
Reaction Centre ◽  
Photosynthetic Membrane ◽  
Rhodopseudomonas Viridis ◽  
Photosynthetic Membranes ◽  
Ectothiorhodospira Halochloris ◽  
Main Components

Bacterial photosynthetic membranes contain, apart from lipids and electron transport components, reaction centre (RC) and light harvesting (LH) polypeptides as the main components. The RC-LH complexes in Rhodopseudomonas viridis membranes are known since quite seme time to form a hexagonal lattice structure in vivo; hence this membrane attracted the particular attention of electron microscopists. Contrary to previous claims in the literature we found, however, that 2-D periodically organized photosynthetic membranes are not a unique feature of Rhodopseudomonas viridis. At least five bacterial species, all bacteriophyll b - containing, possess membranes with the RC-LH complexes regularly arrayed. All these membranes appear to have a similar lattice structure and fine-morphology. The lattice spacings of the Ectothiorhodospira haloohloris, Ectothiorhodospira abdelmalekii and Rhodopseudomonas viridis membranes are close to 13 nm, those of Thiocapsa pfennigii and Rhodopseudomonas sulfoviridis are slightly smaller (∼12.5 nm).

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