High concentrations of β‐hydroxybutyrate alter the kinetics of bovine spermatozoa

Andrologia ◽  
2021 ◽  
Author(s):  
Daniele Missio ◽  
Daniela dos Santos Brum ◽  
Lucas Dalle Laste Dacampo ◽  
Francielli Weber Santos Cibin ◽  
Fernando Silveira Mesquita ◽  
...  
Keyword(s):  
Bovine Spermatozoa ◽  
High Concentrations ◽  
Kinetics Of

scholarly journals Desensitization Contributes to the Synaptic Response of Gain-of-Function Mutants of the Muscle Nicotinic Receptor

2006 ◽  
Vol 128 (5) ◽  
pp. 615-627 ◽  
Author(s):  
Sergio Elenes ◽  
Ying Ni ◽  
Gisela D. Cymes ◽  
Claudio Grosman
Keyword(s):  
Nicotinic Receptor ◽  
Dissociation Rate ◽  
Gain Of Function ◽  
Naturally Occurring ◽  
Channel Opening ◽  
Speed Up ◽  
High Concentrations ◽  
Dissociation Rate Constants ◽  
Kinetics Of ◽  
Peak Value

Although the muscle nicotinic receptor (AChR) desensitizes almost completely in the steady presence of high concentrations of acetylcholine (ACh), it is well established that AChRs do not accumulate in desensitized states under normal physiological conditions of neurotransmitter release and clearance. Quantitative considerations in the framework of plausible kinetic schemes, however, lead us to predict that mutations that speed up channel opening, slow down channel closure, and/or slow down the dissociation of neurotransmitter (i.e., gain-of-function mutations) increase the extent to which AChRs desensitize upon ACh removal. In this paper, we confirm this prediction by applying high-frequency trains of brief (∼1 ms) ACh pulses to outside-out membrane patches expressing either lab-engineered or naturally occurring (disease-causing) gain-of-function mutants. Entry into desensitization was evident in our experiments as a frequency-dependent depression in the peak value of succesive macroscopic current responses, in a manner that is remarkably consistent with the theoretical expectation. We conclude that the comparatively small depression of the macroscopic currents observed upon repetitive stimulation of the wild-type AChR is due, not to desensitization being exceedingly slow but, rather, to the particular balance between gating, entry into desensitization, and ACh dissociation rate constants. Disruption of this fine balance by, for example, mutations can lead to enhanced desensitization even if the kinetics of entry into, and recovery from, desensitization themselves are not affected. It follows that accounting for the (usually overlooked) desensitization phenomenon is essential for the correct interpretation of mutagenesis-driven structure–function relationships and for the understanding of pathological synaptic transmission at the vertebrate neuromuscular junction.

scholarly journals Evaluation of the kinetics of oxidation and removal of organic matter in the self-purification of a mountain river

DYNA ◽  
2015 ◽  
Vol 82 (191) ◽  
pp. 183-193 ◽  
Author(s):  
Jorge Virgilio Rivera Gutiérrez
Keyword(s):  
Water Quality ◽  
Water System ◽  
The Self ◽  
Organic Load ◽  
Mountain River ◽  
Kinetics Of Oxidation ◽  
Kinetic Rates ◽  
High Concentrations ◽  
Kinetics Of

The study is based on the determination of the kinetic rates and assessment of self-purification of the Frio River, due to the uptake of organic load. The kinetic rates were calculated by applying differential and logarithmic methods on concentrations of water quality determinants present in each of the (7) reach of the river. The water system easily recovers the amount of oxygen, k<sub>d</sub>= 0.4, k<sub>a</sub> 3.2 d<sup>-1</sup>, only receives 27.7 Ton. d<sup>-1</sup>, the organic load, making high concentrations of carbon, ammonium and remain sediment. The length Influence of discharges, LIV- BOD yielded a mean per tranche of 10 km, compared to 3 km each way, means that the river can´t self- purification that need more length of travel. The study illustrates the modeling of the determinants of quality, developed by the QUAL2K, using the calculated rates.

In vitro survival kinetics of microfluidic‐sorted bovine spermatozoa

Andrology ◽  
2020 ◽  
Author(s):  
Kazuko Ogata ◽  
Maria Portia B. Nagata ◽  
Hirofumi Nishizono ◽  
Tadayuki Yamanouchi ◽  
Hideo Matsuda ◽  
...  
Keyword(s):  
Bovine Spermatozoa ◽  
Kinetics Of ◽  
In Vitro Survival

Impact of the Kinetics of Salt Crystallization on Stone Damage During Rewetting/Drying and Humidity Cycling

2013 ◽  
Vol 80 (2) ◽  
Author(s):  
Julie Desarnaud ◽  
François Bertrand ◽  
Noushine Shahidzadeh-Bonn
Keyword(s):  
Sodium Sulfate ◽  
Phase Contrast ◽  
Sulfate Solution ◽  
Salt Crystallization ◽  
Severe Damage ◽  
Contrast Microscopy ◽  
Salt Crystals ◽  
High Concentrations ◽  
The Impact ◽  
Kinetics Of

In this study, we show that the key to understand why the same salt can cause damage in some conditions and not in others is the kinetics of crystallization. We present experiments assessing the impact of the recrystallization dynamics of sodium sulfate on damage observed in sandstone after repeated cycles of rewetting/drying and humidification/drying. Macroscopic and microscopic scale experiments using magnetic resonance imaging and phase contrast microscopy demonstrate that sodium sulfate that has both hydrated and anhydrous phases can lead to severe damage in sandstone during rewetting/drying cycles, but not during humidity cycling. During rewetting (a rapid process) in regions (pores) that are highly concentrated in salt, anhydrous microcrystals dissolve only partially, giving rise to a heterogeneous salt solution that is supersaturated with respect to the hydrated phase. The remaining anhydrous crystals then act as seeds for the formation of large amounts of hydrated crystals, creating grape-like structures that expand rapidly. These clusters can generate stresses larger than the tensile strength of the stone, leading to damage. On the other hand, with humidification (a slow process) and after complete deliquescence of salt crystals, the homogeneous sodium sulfate solution can reach high concentrations during evaporation without any nucleation, favoring the formation of isolated anhydrous crystals (thenardite). The crystallization of the anhydrous salt generates only very small stresses compared to the hydrated clusters and therefore causes hardly any damage to the stone.

scholarly journals Determinants in 3Dpol Modulate the Rate of Growth of Hepatitis A Virus

2010 ◽  
Vol 84 (16) ◽  
pp. 8342-8347 ◽  
Author(s):  
Krishnamurthy Konduru ◽  
Gerardo G. Kaplan
Keyword(s):  
Hepatitis A ◽  
Hepatitis A Virus ◽  
Rna Replication ◽  
Virus Genome ◽  
Nucleotide Sequence Analysis ◽  
Reverse Genetic ◽  
Genetic Studies ◽  
High Concentrations ◽  
Kinetics Of ◽  
Atypical Member

ABSTRACT Hepatitis A virus (HAV), an atypical member of the Picornaviridae, grows poorly in cell culture. To define determinants of HAV growth, we introduced a blasticidin (Bsd) resistance gene into the virus genome and selected variants that grew at high concentrations of Bsd. The mutants grew fast and had increased rates of RNA replication and translation but did not produce significantly higher virus yields. Nucleotide sequence analysis and reverse genetic studies revealed that a T6069G change resulting in a F42L amino acid substitution in the viral polymerase (3Dpol) was required for growth at high Bsd concentrations whereas a silent C7027T mutation enhanced the growth rate. Here, we identified a novel determinant(s) in 3Dpol that controls the kinetics of HAV growth.

Kinetics of the cellular intake of a gene expression inducer at high concentrations

2015 ◽  
Vol 11 (9) ◽  
pp. 2579-2587 ◽  
Author(s):  
Huy Tran ◽  
Samuel M. D. Oliveira ◽  
Nadia Goncalves ◽  
Andre S. Ribeiro
Keyword(s):  
Gene Expression ◽  
Single Event ◽  
Transcription Activity ◽  
High Concentrations ◽  
Kinetics Of

Characterization of the cellular intake kinetics of a lactose analogue fromin vivosingle-event measurements of transcription activity.

scholarly journals In-depth Characterization of Firefly Luciferase as a Reporter of Circadian Gene Expression in Mammalian Cells

2016 ◽  
Vol 31 (6) ◽  
pp. 540-550 ◽  
Author(s):  
Kevin A. Feeney ◽  
Marrit Putker ◽  
Marco Brancaccio ◽  
John S. O’Neill
Keyword(s):  
Gene Expression ◽  
Mammalian Cells ◽  
Firefly Luciferase ◽  
Luciferase Reporter ◽  
Circadian Gene ◽  
Cultured Fibroblasts ◽  
High Concentrations ◽  
Lower Temperature ◽  
Kinetics Of

Firefly luciferase (Fluc) is frequently used to report circadian gene expression rhythms in mammalian cells and tissues. During longitudinal assays it is generally assumed that enzymatic substrates are in saturating excess, such that total bioluminescence is directly proportional to Fluc protein level. To test this assumption, we compared the enzyme kinetics of purified luciferase with its activity in mammalian cells. We found that Fluc activity in solution has a lower Michaelis constant (Km) for luciferin, lower temperature dependence, and lower catalytic half-life than Fluc in cells. In consequence, extracellular luciferin concentration significantly affects the apparent circadian amplitude and phase of the widely used PER2::LUC reporter in cultured fibroblasts, but not in SCN, and we suggest that this arises from differences in plasma membrane luciferin transporter activity. We found that at very high concentrations (>1 mM), luciferin lengthens circadian period, in both fibroblasts and organotypic SCN slices. We conclude that the amplitude and phase of circadian gene expression inferred from bioluminescence recordings should be treated with some caution, and we suggest that optimal luciferin concentration should be determined empirically for each luciferase reporter and cell type.

Influence of High Concentrations of Salts on the Kinetics of the Reaction of Bromide with Bromate in Acid Medium

1972 ◽  
Vol 250O (1) ◽  
Author(s):  
M. Wrońska ◽  
M. Wawrzeńczyk
Keyword(s):  
Acid Medium ◽  
High Concentrations ◽  
Kinetics Of

scholarly journals Slow kinetics of inositol 1,4,5-trisphosphate-induced Ca2+ release: is the release ‘quantal’ or ‘non-quantal’?

1997 ◽  
Vol 323 (1) ◽  
pp. 123-130 ◽  
Author(s):  
Ludwig MISSIAEN ◽  
Humbert DE SMEDT ◽  
Jan B. PARYS ◽  
Ilse SIENAERT ◽  
Henk SIPMA ◽  
...  
Keyword(s):  
Low Dose ◽  
Slow Phase ◽  
Quantal Response ◽  
Published Evidence ◽  
A7r5 Cells ◽  
Slow Kinetics ◽  
Inositol 1,4,5 Trisphosphate ◽  
Long Time ◽  
High Concentrations ◽  
Kinetics Of

Inositol 1,4,5-trisphosphate (InsP3)-induced Ca2+ release from intracellular stores is generally assumed to be a ‘quantal’ process because low InsP3 concentrations mobilize less Ca2+ than high concentrations and a submaximal concentration does not release all the InsP3-mobilizable Ca2+. However, some recent reports questioned the generally accepted view that a low dose of InsP3 is unable to empty the whole store. We have now challenged the stores of permeabilized A7r5 cells in InsP3 for much longer periods than previously reported, to assess directly whether the slow phase of the release would empty the whole store (a non-quantal response) or only a fraction of it (a quantal response). Addition of a maximal [InsP3] at the end of a prolonged (92 min) stimulation with a submaximal [InsP3] resulted in additional Ca2+ release. Experiments in which the stores were challenged with different submaximal InsP3 concentrations for long time periods revealed that a lower [InsP3] never released the same amount of Ca2+ as a higher [InsP3]. This quantal pattern of Ca2+ release occurred both at 25 °C and at 4 °C. There was a time-dependent increase in the fraction of Ca2+ recruited by the lower compared with the higher [InsP3]. This recruitment of Ca2+ persisted if the [InsP3] was decreased, but was largely prevented by palmitoyl-CoA, a potent blocker of the luminal Ca2+ translocation between individual store units. ATP, in the presence of InsP3, released Ca2+ under conditions permitting the recruitment of no additional InsP3 receptors, indicating that an all-or-none emptying of a fraction of the stores cannot be the only mechanism responsible for quantal Ca2+ release in A7r5 cells. We conclude that some of the previously published evidence for a non-quantal Ca2+ release pattern should be reinterpreted.

scholarly journals Cellular mechanisms underlying nitric oxide-induced vasodilation of descending vasa recta

2011 ◽  
Vol 300 (2) ◽  
pp. F441-F456 ◽  
Author(s):  
Aurélie Edwards ◽  
Chunhua Cao ◽  
Thomas L. Pallone
Keyword(s):  
Nitric Oxide ◽  
Cellular Mechanisms ◽  
Species Formation ◽  
Vasa Recta ◽  
Basal Tone ◽  
No Bioavailability ◽  
Low Levels ◽  
High Concentrations ◽  
Mlc Phosphorylation ◽  
Kinetics Of

It has been observed that vasoactivity of explanted descending vasa recta (DVR) is modulated by intrinsic nitric oxide (NO) and superoxide (O2−) production (Cao C, Edwards A, Sendeski M, Lee-Kwon W, Cui L, Cai CY, Patzak A, Pallone TL. Am J Physiol Renal Physiol 299: F1056–F1064, 2010). To elucidate the cellular mechanisms by which NO, O2− and hydrogen peroxide (H2O2) modulate DVR pericyte cytosolic Ca2+ concentration ([Ca]cyt) and vasoactivity, we expanded our mathematical model of Ca2+ signaling in pericytes. We incorporated simulations of the pathways that translate an increase in [Ca]cyt to the activation of myosin light chain (MLC) kinase and cell contraction, as well as the kinetics of NO and reactive oxygen species formation and their effects on [Ca]cyt and MLC phosphorylation. The model reproduced experimentally observed trends of DVR vasoactivity that accompany exposure to Nω-nitro-l-arginine methyl ester, 8-Br-cGMP, Tempol, and H2O2. Our results suggest that under resting conditions, NO-induced activation of cGMP maintains low levels of [Ca]cyt and MLC phosphorylation to minimize basal tone. This results from stimulation of Ca2+ uptake from the cytosol into the SR via SERCA pumps, Ca2+ efflux into the extracellular space via plasma membrane Ca2+ pumps, and MLC phosphatase (MLCP) activity. We predict that basal concentrations of O2− and H2O2 have negligible effects on Ca2+ signaling and MLC phosphorylation. At concentrations above 1 nM, O2− is predicted to modulate [Cacyt] and MCLP activity mostly by reducing NO bioavailability. The DVR vasoconstriction that is induced by high concentrations of H2O2 can be explained by H2O2-mediated downregulation of MLCP and SERCA activity. We conclude that intrinsic generation of NO by the DVR wall may be sufficient to inhibit vasoconstriction by maintaining suppression of MLC phosphorylation.

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