Cellular calcium transport in renal epithelia: measurement, mechanisms, and regulation

1995 ◽  
Vol 75 (3) ◽  
pp. 429-471 ◽  
Author(s):  
P. A. Friedman ◽  
F. A. Gesek
Keyword(s):  
Plasma Membranes ◽  
Single Channel ◽  
Calcium Absorption ◽  
Vital Role ◽  
Channel Blockers ◽  
Calcium Efflux ◽  
Cellular Calcium ◽  
Wide Range ◽  
Active Calcium ◽  
Convoluted Tubules

The kidneys play a vital role in mineral homeostasis. In this review, the handling of calcium and the methods currently applied to measuring its intracellular concentration are discussed. The bulk of calcium absorption proceeds in proximal tubules, with smaller fractions recovered by thick ascending limbs, distal convoluted tubules, and connecting tubules. Hormonally regulated transcellular calcium absorption is essentially limited to distal convoluted and connecting tubules. At physiological concentrations, parathyroid hormone, calcitonin, and vitamin D increase net calcium absorption. Calcium absorption by polarized epithelial cells is a two-step process wherein calcium enters the cell across apical plasma membranes and exits across basolateral membranes. Recent electrophysiological and pharmacological experiments demonstrate that apical entry is mediated by calcium channels, which are modestly calcium selective, sensitive to dihydropyridine-type calcium channel blockers, and exhibit a wide range of single-channel conductances. Cellular calcium efflux is mediated by Ca(2+)-ATPase and by Na+/Ca2+ exchange. Ca(2+)-ATPase activity is highest in segments that exhibit significant rates of active calcium absorption. Multiple plasma membrane Ca(2+)-ATPase isoforms have been found in the kidney. Several renal Na+/Ca2+ exchange isoforms have been identified, and their role in effecting calcium efflux is under investigation.

Glucose enhancement of transcellular calcium transport in the intestine

1988 ◽  
Vol 255 (3) ◽  
pp. G339-G345 ◽  
Author(s):  
K. M. Carroll ◽  
R. J. Wood ◽  
E. B. Chang ◽  
I. H. Rosenberg
Keyword(s):  
Calcium Transport ◽  
Calcium Uptake ◽  
Calcium Absorption ◽  
Membrane Integrity ◽  
Calcium Flux ◽  
Calcium Efflux ◽  
Cell Membrane Integrity ◽  
Active Calcium ◽  
Altered Cell

Glucose stimulates calcium transport in vitro in rat duodenal tissue and isolated enterocytes. Under short-circuited conditions, glucose increased mucosal to serosal calcium flux (JCa(m----s)) without altering serosal to mucosal calcium flux (JCa(s----m)) in the duodenum, the primary site of active calcium absorption in the rat small intestine. The half-maximal dose (ED50) of the glucose stimulatory effect was less than 1 mM, and an increase in JCa(m----s) of 80% over control was seen at a glucose concentration of 50 mM. Glucose did not increase calcium flux in the ileum where active calcium absorption is minimal. Glucose stimulated net calcium uptake by 35% in isolated duodenal enterocytes. Glucose did not alter calcium efflux from preloaded enterocytes suspended in calcium-free buffer. Glucose enhancement of net calcium uptake in enterocytes was not caused by altered cell membrane integrity or functional viability. The nonmetabolizable glucose analogue alpha-methylglucoside did not stimulate calcium transport. Our findings suggest that glucose can stimulate intestinal calcium absorption, at least partially, by enhancing transcellular calcium transport and that cellular glucose metabolism is necessary for stimulation of this route of calcium transport.

Active calcium absorption in primary cultures of cortical collecting duct cells

1993 ◽  
Vol 71 (7) ◽  
pp. 491-496 ◽  
Author(s):  
Lori G. Rochelle ◽  
Sangita Deveshwar ◽  
Anikó Náray-Fejes-Tóth ◽  
Géza Fejes-Tóth
Keyword(s):  
Cultured Cells ◽  
Calcium Absorption ◽  
Collecting Duct ◽  
Primary Cultures ◽  
Channel Blockers ◽  
Ca Channel ◽  
Cortical Collecting Duct ◽  
Cell Monolayers ◽  
Active Calcium ◽  
Plastic Surfaces

Primary cultures of rabbit cortical collecting duct (CCD) cells demonstrated accumulation of Ca at the basolateral (BL) side when cultured on either impermeable or permeable supports. Cell monolayers cultured on impermeable plastic surfaces absorbed Ca with such avidity that hydroxyapatite crystals formed. When cultured on a permeable matrix, the cells demonstrated significant net apical (A) to BL Ca transport against a lumen negative transepithelial potential difference. A steady-state BL/A [Ca] ratio of 120 developed across monolayers in 24 h on days 6 through 8 postseeding. Initial rates of unidirectional 45Ca fluxes on days 6 through 8 indicated a negligible BL to A flux (5.4 ± 2.6 nmol∙h−1∙cm−2) compared with A to BL 45Ca flux (99.4 ± 19.4 nmol∙h−1∙cm−2). Parathyroid hormone applied to the BL side had no significant effect on either unidirectional 45Ca flux, but the second messenger analog, 8-bromoadenosine cyclic monophosphate, increased the A to BL flux by 65%. Inhibiting the Na+–K+ ATPase with ouabain (10−4 M) reduced the A to BL flux by 77%; however, a significant net A to BL flux still remained. Apical addition of amiloride (2 × 10−5 M) did not affect either unidirectional 45Ca flux. In addition, the inorganic Ca channel blockers Ni2+ (100 μM and 1 mM), La3+ (100 μM and 1 mM), and Cd2+ (20 and 50 μM) did not significantly inhibit either unidirectional 45Ca flux. These results demonstrate that CCD monolayers actively absorb Ca and this can be stimulated by cyclic AMP, raising the possibility that apical Ca entry does not involve amiloride-sensitive channels, or typical Ca channels.Key words: calcium transport, cortical collecting duct, cultured cells.

Calcium-activated, voltage-dependent, non-selective cation currents in endosperm plasma membrane from higher plants

1989 ◽  
Vol 237 (1287) ◽  
pp. 213-231 ◽  
Keyword(s):  
Plasma Membranes ◽  
Single Channel ◽  
Higher Plants ◽  
Outward Current ◽  
Monovalent Cation ◽  
Channel Blockers ◽  
Whole Cell ◽  
Whole Cell Patch Clamp ◽  
Single Burst ◽  
Subsequent Exposure

Single-channel and whole-cell patch-clamp techniques were used to characterize the electrophysiological behaviour of plasma membranes from freshly isolated, non-enzyme-treated endosperm protoplasts. A non-selective monovalent cation channel with a single-channel conductance of 22 pS in solutions with physiological potassium concentrations was observed in inside-out patches. The channel passes outward current at depolarized potentials and is highly selective for cations over anions, but discriminates poorly between lithium, sodium, potassium, rubidium and caesium ions. Specific potassium channel blockers were ineffective. The channel kinetics were apparently complex, with burst-like openings and rapid closures within a single burst. Single-channel openings were more frequent both for depolarizing pulses and maintained positive potentials. Channel activity was also increased by elevated cytoplasmic concentrations of either calcium or barium. Subsequent exposure of patches to low calcium, EGTA-buffered solutions resulted in large decreases in activity. Under whole-cell current clamp, small negative resting potentials were observed. A slowly developing outward current evoked by depolarizing pulses was seen in whole-cell recordings.

An Investigation on the Performance of an Oxidation Catalyst Using Two-dimensional Simulation with Detailed Reaction Mechanism

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Sreeharsh Nair ◽  
Mayank Mittal
Keyword(s):  
Single Channel ◽  
Catalytic Converter ◽  
Oxidation Catalyst ◽  
Low Temperature Combustion ◽  
Wide Range ◽  
Detailed Reaction Mechanism ◽  
Temperature Combustion ◽  
High Concentrations ◽  
Dimensional Simulation ◽  
Surface Reaction Kinetics

AbstractThe advent of stricter emission standards has increased the importance of aftertreatment devices and the role of numerical simulations in the evolution of better catalytic converters in order to satisfy these emission regulations. In this paper, a 2-D numerical simulation of a single channel of the monolith catalytic converter is presented by using detailed surface reaction kinetics aiming to investigate the chemical behaviour inside the converter. The model has been developed to study the conversion of carbon monoxide (CO) in the presence of propene (C3H6) for low-temperature combustion (LTC) engine application. The inhibition effect of C3H6 over a wide range of CO inlet concentrations is investigated. Considering both low and high levels of CO concentration at the inlet, the 2-D model predicted better results than their corresponding 1-D counterparts when compared with the experimental data from literature. It was also observed that C3H6 inhibition at high temperatures was significant, particularly for high concentrations of CO compared to low concentrations of CO at the inlet.

Automatic Vulnerability Detection in Embedded Devices and Firmware

2021 ◽  
Vol 54 (2) ◽  
pp. 1-42
Author(s):  
Abdullah Qasem ◽  
Paria Shirani ◽  
Mourad Debbabi ◽  
Lingyu Wang ◽  
Bernard Lebel ◽  
...  
Keyword(s):  
Embedded Systems ◽  
Symbolic Execution ◽  
Vital Role ◽  
Security And Privacy ◽  
Embedded Devices ◽  
Security Vulnerabilities ◽  
Future Directions ◽  
Hybrid Approaches ◽  
Wide Range ◽  
The Internet Of Things

In the era of the internet of things (IoT), software-enabled inter-connected devices are of paramount importance. The embedded systems are very frequently used in both security and privacy-sensitive applications. However, the underlying software (a.k.a. firmware) very often suffers from a wide range of security vulnerabilities, mainly due to their outdated systems or reusing existing vulnerable libraries; which is evident by the surprising rise in the number of attacks against embedded systems. Therefore, to protect those embedded systems, detecting the presence of vulnerabilities in the large pool of embedded devices and their firmware plays a vital role. To this end, there exist several approaches to identify and trigger potential vulnerabilities within deployed embedded systems firmware. In this survey, we provide a comprehensive review of the state-of-the-art proposals, which detect vulnerabilities in embedded systems and firmware images by employing various analysis techniques, including static analysis, dynamic analysis, symbolic execution, and hybrid approaches. Furthermore, we perform both quantitative and qualitative comparisons among the surveyed approaches. Moreover, we devise taxonomies based on the applications of those approaches, the features used in the literature, and the type of the analysis. Finally, we identify the unresolved challenges and discuss possible future directions in this field of research.

scholarly journals Beehive Products as Antibacterial Agents: A Review

Antibiotics ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 717
Author(s):  
Rita Abou Nader ◽  
Rawan Mackieh ◽  
Rim Wehbe ◽  
Dany El El Obeid ◽  
Jean Marc Sabatier ◽  
...  
Keyword(s):  
Antibacterial Activity ◽  
Honey Bee ◽  
Antibacterial Agents ◽  
Royal Jelly ◽  
Biological Activities ◽  
Vital Role ◽  
Bee Venom ◽  
Bacterial Strains ◽  
Wide Range ◽  
Life Threatening

Honeybees are one of the most marvelous and economically beneficial insects. As pollinators, they play a vital role in every aspect of the ecosystem. Beehive products have been used for thousands of years in many cultures for the treatment of various diseases. Their healing properties have been documented in many religious texts like the Noble Quran and the Holy Bible. Honey, bee venom, propolis, pollen and royal jelly all demonstrated a richness in their bioactive compounds which make them effective against a variety of bacterial strains. Furthermore, many studies showed that honey and bee venom work as powerful antibacterial agents against a wide range of bacteria including life-threatening bacteria. Several reports documented the biological activities of honeybee products but none of them emphasized on the antibacterial activity of all beehive products. Therefore, this review aims to highlight the antibacterial activity of honey, bee venom, propolis, pollen and royal jelly, that are produced by honeybees.

scholarly journals Polymer cyclization for the emergence of hierarchical nanostructures

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Chaojian Chen ◽  
Manjesh Kumar Singh ◽  
Katrin Wunderlich ◽  
Sean Harvey ◽  
Colette J. Whitfield ◽  
...  
Keyword(s):  
Self Assembly ◽  
Three Dimensional ◽  
Hierarchical Structures ◽  
Structural Similarity ◽  
Vital Role ◽  
Nanomaterial Synthesis ◽  
Wide Range ◽  
Linear Poly ◽  
Polymer Folding ◽  
Dynamics Simulations

AbstractThe creation of synthetic polymer nanoobjects with well-defined hierarchical structures is important for a wide range of applications such as nanomaterial synthesis, catalysis, and therapeutics. Inspired by the programmability and precise three-dimensional architectures of biomolecules, here we demonstrate the strategy of fabricating controlled hierarchical structures through self-assembly of folded synthetic polymers. Linear poly(2-hydroxyethyl methacrylate) of different lengths are folded into cyclic polymers and their self-assembly into hierarchical structures is elucidated by various experimental techniques and molecular dynamics simulations. Based on their structural similarity, macrocyclic brush polymers with amphiphilic block side chains are synthesized, which can self-assemble into wormlike and higher-ordered structures. Our work points out the vital role of polymer folding in macromolecular self-assembly and establishes a versatile approach for constructing biomimetic hierarchical assemblies.

scholarly journals A modular microfluidic system based on a multilayered configuration to generate large-scale perfusable microvascular networks

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Tao Yue ◽  
Da Zhao ◽  
Duc T. T. Phan ◽  
Xiaolin Wang ◽  
Joshua Jonghyun Park ◽  
...  
Keyword(s):  
Large Scale ◽  
Circulatory System ◽  
Vertical Direction ◽  
Microfluidic System ◽  
Vital Role ◽  
Microvascular Networks ◽  
Biological Studies ◽  
Wide Range ◽  
High Flexibility

AbstractThe vascular network of the circulatory system plays a vital role in maintaining homeostasis in the human body. In this paper, a novel modular microfluidic system with a vertical two-layered configuration is developed to generate large-scale perfused microvascular networks in vitro. The two-layer polydimethylsiloxane (PDMS) configuration allows the tissue chambers and medium channels not only to be designed and fabricated independently but also to be aligned and bonded accordingly. This method can produce a modular microfluidic system that has high flexibility and scalability to design an integrated platform with multiple perfused vascularized tissues with high densities. The medium channel was designed with a rhombic shape and fabricated to be semiclosed to form a capillary burst valve in the vertical direction, serving as the interface between the medium channels and tissue chambers. Angiogenesis and anastomosis at the vertical interface were successfully achieved by using different combinations of tissue chambers and medium channels. Various large-scale microvascular networks were generated and quantified in terms of vessel length and density. Minimal leakage of the perfused 70-kDa FITC-dextran confirmed the lumenization of the microvascular networks and the formation of tight vertical interconnections between the microvascular networks and medium channels in different structural layers. This platform enables the culturing of interconnected, large-scale perfused vascularized tissue networks with high density and scalability for a wide range of multiorgan-on-a-chip applications, including basic biological studies and drug screening.

A Review on the Anti-Viral Activity of Houttuynia cordata: A Possible Herb for the Management and Treatment of COVID-19

2021 ◽  
Vol 4 (2) ◽  
pp. 3-10
Author(s):  
Emdormi Rymbai ◽  
Keyword(s):  
Vital Role ◽  
Viral Agent ◽  
Houttuynia Cordata ◽  
Traditional Medicines ◽  
Virulent Newcastle Disease Virus ◽  
Wide Range ◽  
Anti Cancer ◽  
The Family ◽  
Anti Oxidant

Plants are an important source of natural products and they play a vital role in the field of medicinal chemistry and pharmaceutical science. Traditional medicines have been practiced and used for thousands of years, mostly in Asian countries, where plants are the main sources of medicine. Houttuynia cordata, a herb that belongs to the family Saururaceae, has a wide range of pharmacological activities and is used traditionally in conditions like anisolobis sores, heatstroke, lung carbuncles, malaria, scrotal abscess, tonsillitis, salammoniac poison and has also been widely accepted to possess anti-cancer, anti-oxidant, anti-hypertension, anti-inflammatory, anti-mutagenic, antibacterial, anti-viral and anti-purulent activity. Moreover, it is one of the herbs that was recognized during pandemic outbreaks, such as Severe Acute Respiratory Syndrome Coronavirus (SARS CoV) in China, virulent Newcastle Disease Virus (VNDV) in Java (Indonesia) and Newcastle (England). In this review, we briefly discuss the role of H. cordata as an anti-viral agent and the possibility of developing a dosage form against Coronavirus disease-19 (COVID-19).

scholarly journals Adaptation of Newcastle Disease Virus (NDV) in Feral Birds and their Potential Role in Interspecies Transmission

2018 ◽  
Vol 12 (1) ◽  
pp. 52-68 ◽  
Author(s):  
Aziz-ul- Rahman ◽  
Momena Habib ◽  
Muhammad Zubair Shabbir
Keyword(s):  
Newcastle Disease ◽  
Potential Role ◽  
Vital Role ◽  
Wild Birds ◽  
Avian Species ◽  
Phylogenomic Analysis ◽  
Susceptible Host ◽  
Domestic Poultry ◽  
Wide Range

Introduction:Newcastle Disease (ND), caused by Avian avulavirus 1 (AAvV 1, avulaviruses), is a notifiable disease throughout the world due to the economic impact on trading restrictions and its embargoes placed in endemic regions. The feral birds including aquatic/migratory birds and other wild birds may act as natural reservoir hosts of ND Viruses (NDVs) and may play a remarkable role in the spread of the virus in environment. In addition, other 19 avulaviruses namely: AAvV 2 to 20, have been potentially recognized from feral avian species.Expalantion:Many previous studies have investigated the field prevailing NDVs to adapt a wide range of susceptible host. Still the available data is not enough to declare the potential role of feral birds in transmission of the virus to poultry and/or other avian birds. In view of the latest evidence related to incidences of AAvVs in susceptible avian species, it is increasingly important to understand the potential of viruses to transmit within the domestic poultry and other avian hosts. Genomic and phylogenomic analysis of several investigations has shown the same (RK/RQRR↓F) motif cleavage site among NDV isolates with same genotypes from domestic poultry and other wild hosts. So, the insight of this, various semi-captive/free-ranging wild avian species could play a vital role in the dissemination of the virus, which is an important consideration to control the disease outbreaks. Insufficient data on AAvV 1 transmission from wild birds to poultry and vice versa is the main constraint to understand about its molecular biology and genomic potential to cause infection in all susceptible hosts.Conclusion:The current review details the pertinent features of several historical and contemporary aspects of NDVs and the vital role of feral birds in its molecular epidemiology and ecology.

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