scholarly journals Renal countercurrent system: Role of collecting duct convergence and pelvic urea predicted from a mathematical model

1983 ◽  
Vol 16 (3) ◽  
Author(s):  
Peter Lory ◽  
Albert Gilg ◽  
Michael Horster
Keyword(s):  
Mathematical Model ◽  
Collecting Duct ◽  
Countercurrent System

The Impact of Light Polarisation on Light Field of Scenes with Multiple Reflections

2020 ◽  
pp. 108-115 ◽  
Author(s):  
Vladimir P. Budak ◽  
Anton V. Grimaylo
Keyword(s):  
Mathematical Model ◽  
Light Field ◽  
Global Illumination ◽  
Multiple Reflections ◽  
Software Environment ◽  
The Monte Carlo Method ◽  
Mueller Matrices ◽  
Volume Integration ◽  
The Impact

The article describes the role of polarisation in calculation of multiple reflections. A mathematical model of multiple reflections based on the Stokes vector for beam description and Mueller matrices for description of surface properties is presented. On the basis of this model, the global illumination equation is generalised for the polarisation case and is resolved into volume integration. This allows us to obtain an expression for the Monte Carlo method local estimates and to use them for evaluation of light distribution in the scene with consideration of polarisation. The obtained mathematical model was implemented in the software environment using the example of a scene with its surfaces having both diffuse and regular components of reflection. The results presented in the article show that the calculation difference may reach 30 % when polarisation is taken into consideration as compared to standard modelling.

scholarly journals Role of hepcidin in oxidative stress and cell death of cultured mouse renal collecting duct cells: protection against iron and sensitization to cadmium

2021 ◽  
Author(s):  
Stephanie Probst ◽  
Johannes Fels ◽  
Bettina Scharner ◽  
Natascha A. Wolff ◽  
Eleni Roussa ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Cell Death ◽  
Cell Fate ◽  
Catalase Activity ◽  
Metal Ion ◽  
Iron Homeostasis ◽  
Collecting Duct ◽  
Duct Cell ◽  
Plasmid Transfection

AbstractThe liver hormone hepcidin regulates systemic iron homeostasis. Hepcidin is also expressed by the kidney, but exclusively in distal nephron segments. Several studies suggest hepcidin protects against kidney damage involving Fe2+ overload. The nephrotoxic non-essential metal ion Cd2+ can displace Fe2+ from cellular biomolecules, causing oxidative stress and cell death. The role of hepcidin in Fe2+ and Cd2+ toxicity was assessed in mouse renal cortical [mCCD(cl.1)] and inner medullary [mIMCD3] collecting duct cell lines. Cells were exposed to equipotent Cd2+ (0.5–5 μmol/l) and/or Fe2+ (50–100 μmol/l) for 4–24 h. Hepcidin (Hamp1) was transiently silenced by RNAi or overexpressed by plasmid transfection. Hepcidin or catalase expression were evaluated by RT-PCR, qPCR, immunoblotting or immunofluorescence microscopy, and cell fate by MTT, apoptosis and necrosis assays. Reactive oxygen species (ROS) were detected using CellROX™ Green and catalase activity by fluorometry. Hepcidin upregulation protected against Fe2+-induced mIMCD3 cell death by increasing catalase activity and reducing ROS, but exacerbated Cd2+-induced catalase dysfunction, increasing ROS and cell death. Opposite effects were observed with Hamp1 siRNA. Similar to Hamp1 silencing, increased intracellular Fe2+ prevented Cd2+ damage, ROS formation and catalase disruption whereas chelation of intracellular Fe2+ with desferrioxamine augmented Cd2+ damage, corresponding to hepcidin upregulation. Comparable effects were observed in mCCD(cl.1) cells, indicating equivalent functions of renal hepcidin in different collecting duct segments. In conclusion, hepcidin likely binds Fe2+, but not Cd2+. Because Fe2+ and Cd2+ compete for functional binding sites in proteins, hepcidin affects their free metal ion pools and differentially impacts downstream processes and cell fate.

scholarly journals The Mathematical Model for Total Pubertal Growth in Idiopathic Growth Hormone (GH) Deficiency Suggests a Moderate Role of GH Dose

2003 ◽  
Vol 88 (10) ◽  
pp. 4748-4753 ◽  
Author(s):  
Michael B. Ranke ◽  
Anders Lindberg ◽  
David D. Martin ◽  
Bert Bakker ◽  
Patrick Wilton ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Growth Hormone ◽  
Gh Deficiency ◽  
Pubertal Growth ◽  
The Mathematical Model

scholarly journals Role of Collecting Duct AT1a Receptors in Concentrating Urine

2011 ◽  
Vol 22 (12) ◽  
pp. 2144-2145
Author(s):  
Oleh Pochynyuk ◽  
James D. Stockand
Keyword(s):  
Collecting Duct

scholarly journals Role of the medullary collecting duct in potassium excretion in potassium-adapted animals

1981 ◽  
Vol 20 (5) ◽  
pp. 655-662 ◽  
Author(s):  
Donald A. Schon ◽  
Karen A. Backman ◽  
John P. Hayslett
Keyword(s):  
Collecting Duct ◽  
Potassium Excretion ◽  
Medullary Collecting Duct

scholarly journals A Control Based Mathematical Model for the Evaluation of Intervention Lines in COVID-19 Epidemic Spread: The Italian Case Study

Symmetry ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 890
Author(s):  
Paolo Di Giamberardino ◽  
Rita Caldarella ◽  
Daniela Iacoviello
Keyword(s):  
Mathematical Model ◽  
Equilibrium Points ◽  
Italian Case ◽  
Control Actions ◽  
Containment Measures ◽  
Asymptomatic Subjects ◽  
The Impact

This paper addresses the problem of describing the spread of COVID-19 by a mathematical model introducing all the possible control actions as prevention (informative campaign, use of masks, social distancing, vaccination) and medication. The model adopted is similar to SEIQR, with the infected patients split into groups of asymptomatic subjects and isolated ones. This distinction is particularly important in the current pandemic, due to the fundamental the role of asymptomatic subjects in the virus diffusion. The influence of the control actions is considered in analysing the model, from the calculus of the equilibrium points to the determination of the reproduction number. This choice is motivated by the fact that the available organised data have been collected since from the end of February 2020, and almost simultaneously containment measures, increasing in typology and effectiveness, have been applied. The characteristics of COVID-19, not fully understood yet, suggest an asymmetric diffusion among countries and among categories of subjects. Referring to the Italian situation, the containment measures, as applied by the population, have been identified, showing their relation with the government's decisions; this allows the study of possible scenarios, comparing the impact of different possible choices.

Abstract 103: Soluble (Pro)Renin Receptor Targets Renal V2 Vasopressin Receptor to Enhance Urine Concentrating Capability

Hypertension ◽  
2016 ◽  
Vol 68 (suppl_1) ◽  
Author(s):  
Fei Wang ◽  
Nirupama Ramkumar ◽  
Kexin Peng ◽  
Xiaohan Lu ◽  
Long Zhao ◽  
...  
Keyword(s):  
Biological Fluid ◽  
Collecting Duct ◽  
Urine Volume ◽  
Neutralizing Antibody ◽  
Fold Increase ◽  
Medium Level ◽  
V2 Vasopressin Receptor ◽  
Receptor Targets ◽  
Renal Expression

The extracellular domain of (pro)renin receptor (PRR) is cleaved to produce a 28 kDa soluble receptor (sPRR) which is detected in biological fluid and elevated under certain pathological conditions. Our recent work suggests that sPRR derived from collecting duct intercalated cells acts in a paracrine fashion to regulate water transport in the principal cells. The present study attempted to further define the role of sPRR in vasopressin (AVP) signaling with emphasis on V2R regulation. In primary rat IMCD cells, treatment with a recombinant sPRR termed as sPRR-His at 10 nM for 12 h induced a 2.8 -fold increase in V2R protein and a 2-fold increase in V2R mRNA. Following AVP treatment, V2R protein expression was increased by 3-fold, which was blunted by a PRR antagonist (PRO20) and a PRR neutralizing antibody. Mice with CD-specific (CD PRR KO) developed a medium level of diabetes insipidus (urine volume: KO: 2.2±0.4 versus Floxed: 1.2±0.3 ml/day; P <0.05), accompanied with a 60% reduction of renal V2R protein and a 25% reduction of urinary sPRR excretion. Adminstration of sPRR-His at for 3 d almost completely rescued the polyuria phenotype of CD PRR KO mice (urine volume: KO+sPRR-His: 1.6±0.3 vs. KO: 2.4±0.5 ml/day, p <0.05) associated with restoration of renal V2R protein and AQP2 protein abundances. Interestingly, nephron-specific PRR KO (Neph PRR KO) exhibited more robust polyuria (urine volume: KO: 7.3±1.1 vs. Floxed: 1.2±0.5 ml/day, p <0.01) associated with suppressed renal expression of AQP2, NKCC2, and V2R. Administration of sPRR-His to Neph PRR KO mice partially attenuated polyuria (urine volume: KO+sPRR-His: 4.1±1.2 vs. KO: 7.3±1.1 ml/day, p <0.01) accompanied by restored renal expression of V2R and AQP2, as well as AVP sensitivity. In contrast, the downregulation of NKCC2 expression in the null mice was unaffected by sPRR-His infusion nor was the upregulation of autophagosome marker microtubule-associated protein 1A/1B-light chain 3 (LC3b). Together, our data suggests that sPRR selectively targets the CD to determine V2R expression and hence AVP sensitivity and urine concentrating capability, independently of autophagosome accumulation.

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