Aldosterone binding sites along nephron of Xenopus and rabbit

1989 ◽  
Vol 257 (1) ◽  
pp. R87-R95 ◽  
Author(s):  
A. Gnionsahe ◽  
M. Claire ◽  
N. Koechlin ◽  
J. P. Bonvalet ◽  
N. Farman
Keyword(s):  
Binding Sites ◽  
Direct Evidence ◽  
Distal Tubule ◽  
Distal Segment ◽  
The Other ◽  
Type I ◽  
Thick Ascending Limb ◽  
Type Ii ◽  
Straight Segment ◽  
Dry Film

Distal segment of several amphibians exhibits aldosterone-modulated ion transport properties. On the other hand, A6 cells, derived from Xenopus laevis (XL) kidney, are aldosterone sensitive. We examined the distribution of aldosterone binding sites in isolated tubules of XL compared with rabbit. After incubation with 2 nM [3H]aldosterone, microdissected tubular segments from proximal (PT), distal straight segment (DST), and flask cell collecting (CT) tubules from XL and from rabbit cortical thick ascending limb (CTAL), connecting (CNT), and collecting (CCD) tubules were processed for dry film autoradiography. In XL, specific nuclear labeling of type I (mineralocorticoid) sites was restricted to DST. Labeling of type II (glucocorticoid) sites was present all along the tubule. No specific cytoplasmic labeling was observed, except for type II sites in PT. In the rabbit, aldosterone binds to both type I and type II sites in the three tubular segments studied. In these segments, the binding was about fourfold higher than in DST of XL. These results bring direct evidence in designating the distal tubule of amphibians as a target epithelium for aldosterone. In addition, they suggest that A6 cell line may derive from DST of the Xenopus nephron.

scholarly journals Crystal structures of aconitase X enzymes from bacteria and archaea provide insights into the molecular evolution of the aconitase superfamily

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Seiya Watanabe ◽  
Yohsuke Murase ◽  
Yasunori Watanabe ◽  
Yasuhiro Sakurai ◽  
Kunihiko Tajima
Keyword(s):  
Molecular Evolution ◽  
Agrobacterium Tumefaciens ◽  
Crystal Structures ◽  
Epr Spectroscopy ◽  
Binding Sites ◽  
Active Sites ◽  
Type I ◽  
Type Ii ◽  
Thermococcus Kodakarensis ◽  
Evolutionary Scenario

AbstractAconitase superfamily members catalyze the homologous isomerization of specific substrates by sequential dehydration and hydration and contain a [4Fe-4S] cluster. However, monomeric and heterodimeric types of function unknown aconitase X (AcnX) have recently been characterized as a cis-3-hydroxy-L-proline dehydratase (AcnXType-I) and mevalonate 5-phosphate dehydratase (AcnXType-II), respectively. We herein elucidated the crystal structures of AcnXType-I from Agrobacterium tumefaciens (AtAcnX) and AcnXType-II from Thermococcus kodakarensis (TkAcnX) without a ligand and in complex with substrates. AtAcnX and TkAcnX contained the [2Fe-2S] and [3Fe-4S] clusters, respectively, conforming to UV and EPR spectroscopy analyses. The binding sites of the [Fe-S] cluster and substrate were clearlydifferent from those that were completely conserved in other aconitase enzymes; however, theoverall structural frameworks and locations of active sites were partially similar to each other.These results provide novel insights into the evolutionary scenario of the aconitase superfamilybased on the recruitment hypothesis.

Burn-in procedures for a generalized model

2001 ◽  
Vol 38 (02) ◽  
pp. 542-553 ◽  
Author(s):  
Ji Hwan Cha
Keyword(s):  
The Other ◽  
Replacement Policy ◽  
Type I ◽  
Type Ii ◽  
Failure Model ◽  
Minimal Repair ◽  
Optimal Replacement ◽  
Complete Repair ◽  
Optimal Replacement Policy ◽  
Type Of Failure

In this paper two burn-in procedures for a general failure model are considered. There are two types of failure in the general failure model. One is Type I failure (minor failure) which can be removed by a minimal repair or a complete repair and the other is Type II failure (catastrophic failure) which can be removed only by a complete repair. During a burn-in process, with burn-in Procedure I, the failed component is repaired completely regardless of the type of failure, whereas, with burn-in Procedure II, only minimal repair is done for the Type I failure and a complete repair is performed for the Type II failure. In field use, the component is replaced by a new burned-in component at the ‘field use age’ T or at the time of the first Type II failure, whichever occurs first. Under the model, the problems of determining optimal burn-in time and optimal replacement policy are considered. The two burn-in procedures are compared in cases when both the procedures are applicable.

Effects of dDAVP on rat juxtamedullary nephrons: stimulation of medullary K recycling

1985 ◽  
Vol 249 (2) ◽  
pp. F291-F298 ◽  
Author(s):  
J. M. Elalouf ◽  
N. Roinel ◽  
C. de Rouffignac
Keyword(s):  
Parathyroid Hormone ◽  
Adenylate Cyclase ◽  
Excretion Rate ◽  
Distal Tubule ◽  
Fractional Excretion ◽  
The Other ◽  
Thick Ascending Limb ◽  
Adenylate Cyclase System ◽  
Circulating Levels ◽  
Stimulation Of

The effects of 1-desamino-8-D-arginine vasopressin (dDAVP) on the handling of water and electrolytes by the juxtamedullary nephrons were studied on rats with reduced circulating levels of antidiuretic hormone (ADH), parathyroid hormone, calcitonin, and glucagon, all of which stimulate the adenylate cyclase system of the thick ascending limb and the distal tubule. In such hormone-deprived rats and in hormone-deprived + dDAVP rats, the concentration of Na, Cl, and total solutes was lower in the ascending than in the descending limbs, whereas the inulin concentration was similar at both sites. dDAVP did not alter the fraction of NaCl remaining in the thin limbs, but tended to reduce that of Mg and Ca. On the other hand, dDAVP significantly increased the fraction of filtered K remaining from 65.8 +/- 5.2 to 107.3 +/- 15.8%. A direct correlation was observed between the fraction of filtered K remaining at the tip of the juxtamedullary loops and the fractional excretion rate of K in urine. Since dDAVP enhances distal K net secretion, as previously shown in our laboratory, these results indicate that the medullary recycling of K from nephron terminal segments to Henle's loop of juxtamedullary nephrons is stimulated by this peptide.

Electrophysiological Characteristics of Classes of Neuron in the HVc of the Zebra Finch

1998 ◽  
Vol 80 (2) ◽  
pp. 914-923 ◽  
Author(s):  
Michinori Kubota ◽  
Ikuo Taniguchi
Keyword(s):  
Action Potential ◽  
Zebra Finch ◽  
Action Potential Duration ◽  
The Other ◽  
Time Dependent ◽  
Inward Rectification ◽  
Type I ◽  
Type Ii ◽  
Type Iii ◽  
Type Iv

Kubota, Michinori and Ikuo Taniguchi. Electrophysiological characteristics of classes of neuron in the HVc of the zebra finch. J. Neurophysiol. 80: 914–923, 1998. Whole cell recordings were made from zebra finch HVc neurons in slice preparations. Four distinct classes of neuron were found on the basis of their electrophysiological properties. The morphological characteristics of some of these neurons were also examined by intracellular injection of Lucifer yellow. Type I neurons (21 of 65 cells) had longer time-to-peak of an afterhyperpolarization following an action potential than the other classes. They exhibited both fast and time-dependent inward rectification and an initial high-frequency firing followed by a slower constant firing. Type I neurons had large somata and thick dendrites with many spines. The axons of some of the neurons in this class projected in the direction of area X of the parolfactory lobe. Type II neurons (30 of 65 cells) had a more negative resting membrane potential than the other classes. They exhibited fast inward rectification. Type II neurons could be divided into two subclasses by the absence (IIa; 22 cells) and the presence (IIb; 8 cells) of a low-threshold transient depolarization. Type IIa neurons had relatively small somata and thin, spiny dendrites. The axons of some of the neurons in this class projected in the direction of the robust nucleus of the archistriatum (RA). Type IIb neurons had relatively large somata and thick dendrites with many spines. Type III neurons (6 of 65 cells) had a shorter action-potential duration than the other classes. They exhibited prominent time-dependent inward rectification and a regular tonic firing with little or no accommodation. Type III neurons had beaded, aspiny dendrites. Type IV neurons (8 of 65 cells) had a longer action-potential duration, a much larger input resistance, and longer membrane time constant than the other classes. Type IV neurons had small somata and thin, short, sparsely spiny dendrites. The axons of some of the neurons in this class projected in the direction of the RA. These classes of neuron may play distinct roles in song production and representation in the HVc.

Corticosterone's metabolite is an agonist for Na+ transport stimulation in A6 cells

1988 ◽  
Vol 255 (4) ◽  
pp. F736-F748 ◽  
Author(s):  
R. L. Duncan ◽  
W. M. Grogan ◽  
L. B. Kramer ◽  
C. O. Watlington
Keyword(s):  
Binding Sites ◽  
Short Circuit ◽  
Type I ◽  
Type Ii ◽  
Na Transport ◽  
Single Class ◽  
Apparent Dissociation Constant ◽  
Lower Affinity ◽  
A6 Cells ◽  
Nuclear Binding

This study tests the hypothesis, in A6 epithelia, that 1) corticosterone stimulates active Na+ transport (short-circuit current, Isc) by an additional receptor mechanism to the type I (mineralocorticoid) and type II (glucocorticoid) mechanisms shared with aldosterone (Aldo) and 2) that the agonist may be 6 beta-OH-corticosterone made in the effector cell. The dose-response relationship of corticosterone at 24 h resolves into two components, by curve fitting, with a 50% effective concentration (EC50) for 10% of maximum Isc stimulation of 2 X 10(-9) M and an EC50 for the other 90% of 3 X 10(-7) M. The EC50 of the smaller component correlates with the apparent dissociation constant (K'd) of corticosterone for high affinity (type II) nuclear binding sites shared with Aldo. In unlabeled analogue competition studies Aldo and corticosterone displaced nuclear binding equally below 10(-8) M [3H]corticosterone, indicating only shared sites. However, nonshared saturable sites (displaced by corticosterone but not by Aldo) were found at [3H]-corticosterone concentrations above 10(-8) M. Concentration-binding curves performed with [3H]corticosterone, in presence of 1,000 X Aldo to displace shared sites, revealed a single class of binding sites with a half-maximal saturation of 2 X 10(-7) M, which is quite similar to the EC50 of the lower affinity component of Isc stimulation by corticosterone at 24 h. Reversed phase high-pressure liquid chromatography of nuclear extracts indicates that the saturable component of bound [3H] was 6 beta-OH-[3H]corticosterone derived from [3H]corticosterone. Thus, A6 cells metabolize corticosterone to 6 beta-OH-corticosterone, which in turn occupies lower-affinity receptors not shared with Aldo or corticosterone, to mediate most of the active Na+ transport stimulation by corticosterone.

Evaluation of an enzyme immunoassay kit for estrogen receptor measurement--report II.

1988 ◽  
Vol 34 (10) ◽  
pp. 2053-2057 ◽  
Author(s):  
S Raam ◽  
D M Vrabel
Keyword(s):  
Enzyme Immunoassay ◽  
Binding Sites ◽  
Solid Phase ◽  
Functional Characterization ◽  
Quantitative Agreement ◽  
Type I ◽  
Type Ii ◽  
Immunoreactive Protein ◽  
Estrogen Binding

Abstract We present evidence to show that monoclonal antibodies to estrogen receptors (ER) in solid phase recognize the secondary estrogen binding sites with moderate to low affinity for estradiol (E2). An excellent quantitative agreement was found in five cytosols between the ER values obtained by the enzyme immunoassay (ER-EIA) and the amount of secondary estrogen binding sites measured by the assay involving dextran-coated charcoal (Clin Chem 1986;32:1496). The immunoreactive protein recognized by the antibody-coated beads, when allowed to react with ER(+) cytosols, is shown to bind [3H]estradiol only when the ligand concentration exceeds 8 nmol/L. Further biochemical and functional characterization of the immunoreactive protein is required to establish similarities/dissimilarities between this protein, high-affinity Type I ER sites, and the secondary sites such as Type II sites.

scholarly journals Toxin–Antitoxin Systems in Bacillus subtilis

Toxins ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 262 ◽  
Author(s):  
Sabine Brantl ◽  
Peter Müller
Keyword(s):  
Bacillus Subtilis ◽  
Physiological Role ◽  
Present Knowledge ◽  
The Other ◽  
Type I ◽  
Type Ii ◽  
Free Living ◽  
Bacterial Chromosomes ◽  
Maintenance Systems ◽  
Living Bacteria

Toxin–antitoxin (TA) systems were originally discovered as plasmid maintenance systems in a multitude of free-living bacteria, but were afterwards found to also be widespread in bacterial chromosomes. TA loci comprise two genes, one coding for a stable toxin whose overexpression kills the cell or causes growth stasis, and the other coding for an unstable antitoxin that counteracts toxin action. Of the currently known six types of TA systems, in Bacillus subtilis, so far only type I and type II TA systems were found, all encoded on the chromosome. Here, we review our present knowledge of these systems, the mechanisms of antitoxin and toxin action, and the regulation of their expression, and we discuss their evolution and possible physiological role.

scholarly journals Rate constants rather than biochemical mechanism determine behaviour of genetic clocks

2008 ◽  
Vol 5 (suppl_1) ◽  
Author(s):  
Emery Conrad ◽  
Avraham E Mayo ◽  
Alexander J Ninfa ◽  
Daniel B Forger
Keyword(s):  
Transcription Regulation ◽  
Negative Feedback ◽  
Rate Constants ◽  
The Other ◽  
Type I ◽  
Type Ii ◽  
Biochemical Mechanism ◽  
Wide Range ◽  
Negative Feedbacks ◽  
Positive And Negative Feedbacks

Many biological systems contain both positive and negative feedbacks. These are often classified as resonators or integrators. Resonators respond preferentially to oscillating signals of a particular frequency. Integrators, on the other hand, accumulate a response to signals. Computational neuroscientists often refer to neurons showing integrator properties as type I neurons and those showing resonator properties as type II neurons. Guantes & Poyatos have shown that type I or type II behaviour can be seen in genetic clocks. They argue that when negative feedback occurs through transcription regulation and post-translationally, genetic clocks act as integrators and resonators, respectively. Here we show that either behaviour can be seen with either design and in a wide range of genetic clocks. This highlights the importance of parameters rather than biochemical mechanism in determining the system behaviour.

Pyrophosphates of Tetravalent Elements and a Mössbauer Study of SnP2O7

1975 ◽  
Vol 53 (1) ◽  
pp. 79-91 ◽  
Author(s):  
Chung-Hsi Huang ◽  
Osvald Knop ◽  
David A. Othen ◽  
Frank W. D. Woodhams ◽  
R. Allan Howie
Keyword(s):  
Chemical Shift ◽  
Electric Field ◽  
Electric Field Gradient ◽  
The Other ◽  
Type I ◽  
Type Ii ◽  
Transition Elements ◽  
Mössbauer Study ◽  
X Ray ◽  
Ionic Compounds

Cubic M4+P2O7 pyrophosphates of Ti, Zr, Hf, Sn, and Pb have been examined by X-ray powder diffractometry and by infrared, Raman, and Mössbauer 119Sn spectroscopy. The tin compound appeared to be of Chaunac's type I (with P2O7 groups oriented at random) and could be converted to type II (with ordered P2O7 groups) by heating to high temperatures. All the other preparations were of Chaunac's type II. Evidence from lattice parameters and intensity features of the Raman spectra suggests that the cubic MP2O7 pyrophosphates fall in two groups, one containing the compounds of the typical elements (Ge, Sn, Pb) and the other, the compounds of the transition elements. No support has been found for the view that the P—O—P groupings of the pyrophosphate anion in these compounds are linear. The 119Sn chemical shift in SnP2O7 is only slightly less negative than the shift in CuSnF6.4H2O, which makes SnP2O7 one of the most ionic compounds of tetravalent tin known. The observed quadrupole splitting in the Mössbauer spectrum of SnP2O7 arises largely from the contribution of the valence term to the electric field gradient at the Sn atom.

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