The effects of temperature, local anaesthetics, pH, divalent cations, and group-specific reagents on repriming and repolarization-induced contractures in frog skeletal muscle

1979 ◽  
Vol 57 (6) ◽  
pp. 619-630 ◽  
Author(s):  
J. G. Foulks ◽  
Florence A. Perry
Keyword(s):  
Resting State ◽  
Time Course ◽  
Divalent Cations ◽  
Local Anaesthetics ◽  
Alkaline Ph ◽  
Amino Groups ◽  
Small Reduction ◽  
Effects Of Temperature ◽  
Sufficient Reduction ◽  
Dependent Processes

Contractures appear during repolarization of frog toe muscles in media containing perchlorate in place of chloride. These contractures were suppressed or delayed by certain procedures which retard the repriming of K contractures, i.e., by sufficient reduction in temperature or by alkaline pH in solutions lacking divalent cations. They also were greatly reduced without interference with repriming after treatment with a reagent which selectively modifies free amino groups. In the presence of appropriate concentrations of procaine, repriming was markedly impaired with only a small reduction in the amplitude of repolarization-induced contractures. Small contractures were produced during repolarization in chloride solutions in the presence of 10 mM procaine at pH 8.0. None of these procedures affected the changes produced by perchlorate solutions in the potential dependence and the time course of K contractures. The results support the view that activation and inactivation of contraction following depolarization are separate potential dependent processes. Tension appears to develop during repolarization when the reversal of inactivation occurs before the reversal of activation is completed, both steps being necessary to recover the reprimed resting state.

The temperature dependence of ionic influences on contractile function in frog twitch muscle

1980 ◽  
Vol 58 (1) ◽  
pp. 74-84 ◽  
Author(s):  
J. G. Foulks ◽  
Lillian Morishita
Keyword(s):  
Temperature Dependence ◽  
Skeletal Muscles ◽  
Time Course ◽  
Contractile Function ◽  
Divalent Cations ◽  
Organic Anion ◽  
Ionic Composition ◽  
Amino Groups ◽  
Chloride Solutions ◽  
Reduced Temperature

Alterations in the ionic composition of the medium produce striking changes in the potential-dependent contractile responses of skeletal muscles. This study was undertaken to examine the temperature dependence of some of these effects. The suppression of maximal K contractures of frog toe muscles in media lacking divalent cations was largely overcome by a sufficient increase in temperature. The restoration of K contractures by perchlorate in the absence of divalent cations was prevented by a sufficient decrease in temperature. The effect of perchlorate was to shift the temperature dependence of these contractures toward lower temperatures. The reduction in the amplitude of maximal K contractures in the absence of divalent cations was less marked after pretreatment with a reagent (trinitrobenzenesulfonate) that selectively modifies free amino groups, although the temperature dependence of these contractures was unchanged. The reduction in the amplitude of K contractures in the presence of an organic anion (hexanoate) was partially antagonized both by an increase in temperature or by a decrease in temperature, effects that resemble those observed in solutions in which the divalent cation concentration was reduced. In chloride solutions, the relation between [K]0 and K contractures was shifted toward lower [K]0 by an increase in temperature, whereas in perchlorate solutions increased temperature produced a shift in the opposite direction. The shift in this relation toward lower [K]0 at reduced temperature, and the accelerated time course of K contractures with an increase in temperature were similar in perchlorate and in chloride solutions. Thermodynamic analysis by Arrhenius plots indicated that the influence of divalent cations and perchlorate anions on K contractures may be the result of their effects on hydrational factors.

Behaviour of Coli Phages in Oxidation Ponds

1985 ◽  
Vol 17 (10) ◽  
pp. 219-227 ◽  
Author(s):  
T. Omura ◽  
H. K. Shin ◽  
A. Ketratanakul
Keyword(s):  
Laboratory Experiments ◽  
Field Investigation ◽  
Host Cells ◽  
Coliform Bacteria ◽  
Alkaline Ph ◽  
Viral Inactivation ◽  
Effects Of Temperature ◽  
Oxidation Ponds ◽  
Incubation Temperatures ◽  
Inactivation Efficiency

Coliphages are among the most promising indicators of viral inactivation efficiency of wastewater treatment. Therefore, it is important to investigate the behaviour of coliphages in oxidation ponds from the viewpoint of predicting the inactivation of infectious viruses. In this study, numbers of coliphages were measured in oxidation ponds consisting of a series of facultative and maturation ponds. In parallel with this investigation, the effects of temperature and pH on the behaviour of coliphages were examined in the laboratory, employing three species of coliform bacteria as host cells. The field investigation showed that there was positive correlation between counts of coliphages and those of coliform bacteria, and that more than 99% of coliphages were inactivated. The inactivation efficiency of coliphages in the facultative pond was much higher than in the maturation pond. The results of the laboratory experiments indicated that at 30°C more than 99% of the coliform group were destroyed in 7 days of incubation and that coliphages counts increased from 105/100 ml to 107/100 ml with a lag time of 3 days. Greater reduction of the coliform count was obtained at higher incubation temperatures. It was observed that the coliphages possessed greater ability to attack coliform bacteria at acidic rather than alkaline pH.

Properties of NAD-dependent glutamate dehydrogenase from the tylosin producer Streptomyces fradiae

1997 ◽  
Vol 43 (11) ◽  
pp. 1005-1010 ◽  
Author(s):  
Kien Trung Nguyen ◽  
Lieu Thi Nguyen ◽  
Jan Kopecký ◽  
Vladislav Běhal
Keyword(s):  
Key Words ◽  
Glutamate Dehydrogenase ◽  
Reductive Amination ◽  
Divalent Cations ◽  
Ammonium Assimilation ◽  
Alkaline Ph ◽  
Streptomyces Fradiae ◽  
Oxidative Deamination

Glutamate dehydrogenase is an enzyme responsible for ammonium assimilation and glutamate catabolism in organisms. The tylosin producer Streptomyces fradiae possesses both NADP- and NAD-dependent glutamate dehydrogenases. The latter enzyme was purified 498-fold with a 7.5% recovery by a six-step protocol. The enzyme is composed of two subunits, each of Mr 47 000, and could form active aggregates of four or eight subunits. Its activity was inactivated by alkaline pH or temperatures of −20 °C or above 40 °C. Activities assayed in the direction of oxidative deamination and reductive amination were optimal at pH 9.2 and 8.8, respectively, and at temperatures of 30–35 °C. No activity was found when NAD(H) was replaced with NADP(H). The Km values were 32.2 mM for L-glutamate, 0.3 mM for NAD+, 3.4 mM for 2-ketoglutarate, 14.2 mM for NH4+, and 0.05 mM for NADH. Deamination activity was partially inhibited by adenyl nucleotides and several divalent cations; amination activity was not affected by the nucleotides but significantly inhibited by Cu2+ or Ni2+.Key words: Streptomyces fradiae, NAD-dependent glutamate dehydrogenase, purification, properties.

scholarly journals Self-assembly of highly ordered DNA origami lattices at solid-liquid interfaces by controlling cation binding and exchange

Nano Research ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 3142-3150 ◽  
Author(s):  
Yang Xin ◽  
Salvador Martinez Rivadeneira ◽  
Guido Grundmeier ◽  
Mario Castro ◽  
Adrian Keller
Keyword(s):  
Correlation Length ◽  
Self Assembly ◽  
High Speed ◽  
Time Course ◽  
Divalent Cations ◽  
Topological Analysis ◽  
Monovalent Cation ◽  
Cation Binding ◽  
Dna Origami ◽  
Lattice Order

Abstract The surface-assisted hierarchical self-assembly of DNA origami lattices represents a versatile and straightforward method for the organization of functional nanoscale objects such as proteins and nanoparticles. Here, we demonstrate that controlling the binding and exchange of different monovalent and divalent cation species at the DNA-mica interface enables the self-assembly of highly ordered DNA origami lattices on mica surfaces. The development of lattice quality and order is quantified by a detailed topological analysis of high-speed atomic force microscopy (HS-AFM) images. We find that lattice formation and quality strongly depend on the monovalent cation species. Na+ is more effective than Li+ and K+ in facilitating the assembly of high-quality DNA origami lattices, because it is replacing the divalent cations at their binding sites in the DNA backbone more efficiently. With regard to divalent cations, Ca2+ can be displaced more easily from the backbone phosphates than Mg2+ and is thus superior in guiding lattice assembly. By independently adjusting incubation time, DNA origami concentration, and cation species, we thus obtain a highly ordered DNA origami lattice with an unprecedented normalized correlation length of 8.2. Beyond the correlation length, we use computer vision algorithms to compute the time course of different topological observables that, overall, demonstrate that replacing MgCl2 by CaCl2 enables the synthesis of DNA origami lattices with drastically increased lattice order.

scholarly journals Time Course Based Artifact Identification for Independent Components of Resting-State fMRI

2013 ◽  
Vol 7 ◽  
Author(s):  
Christian Rummel ◽  
Rajeev Kumar Verma ◽  
Veronika Schöpf ◽  
Eugenio Abela ◽  
Martinus Hauf ◽  
...  
Keyword(s):  
Resting State ◽  
Time Course ◽  
Resting State Fmri ◽  
Independent Components ◽  
Artifact Identification

scholarly journals Effect of Water Chemistry on Antimony Removal by Chemical Coagulation: Implications of ζ-Potential and Size of Precipitates

2019 ◽  
Vol 20 (12) ◽  
pp. 2945 ◽  
Author(s):  
Muhammad Ali Inam ◽  
Rizwan Khan ◽  
Muhammad Akram ◽  
Sarfaraz Khan ◽  
Ick Tae Yeom
Keyword(s):  
Water Chemistry ◽  
Divalent Cations ◽  
Chemical Properties ◽  
Point Of Zero Charge ◽  
Hydrodynamic Diameter ◽  
Alkaline Ph ◽  
Solution Ph ◽  
Ζ Potential ◽  
Wide Group ◽  
Co Precipitation

The process of coagulation and precipitation affect the fate and mobility of antimony (Sb) species in drinking water. Moreover, the solubility and physico-chemical properties of the precipitates may be affected by the media chemistry. Accordingly, the present study aimed to investigate the removal of Sb(III, V) species by ferric chloride coagulation under various water chemistry influences with a particular focus on the role of the properties of the precipitates. The results indicated that the amount of Sb(III) removed increased with increasing solution pH, showing the insignificant effects of the hydrodynamic diameter (HDD) and ζ-potential of the precipitates. However, no Sb(V) removal occurred at alkaline pH values, while a highly negative ζ-potential and the complete dissolution of precipitates were observed in the aqueous solution. The solution pH was also useful in determining the dominant coagulation mechanisms, such as co-precipitation and adsorption. The Fe solubility substantially affects the Sb removal at a certain pH range, while the HDD of the precipitates plays an insignificant role in Sb removal. The presence of divalent cations brings the ζ-potential of the precipitates close to point of zero charge (pzc), thus enhancing the Sb(V) removal at alkaline pH conditions. Pronounced adverse effects of humic acid were observed on Sb removal, ζ-potential and HDD of the precipitates. In general, this study may provide critical information to a wide group of researchers dealing with environmental protection from heavy metal pollution.

scholarly journals Regular cannabis and alcohol use is associated with resting-state time course power spectra in incarcerated adolescents

2017 ◽  
Vol 178 ◽  
pp. 492-500 ◽  
Author(s):  
Sandra Thijssen ◽  
Barnaly Rashid ◽  
Shruti Gopal ◽  
Prashanth Nyalakanti ◽  
Vince D. Calhoun ◽  
...  
Keyword(s):  
Alcohol Use ◽  
Resting State ◽  
Time Course ◽  
Power Spectra ◽  
State Time ◽  
Incarcerated Adolescents

scholarly journals Increased calcium-ion influx is a component of capacitation of spermatozoa

1978 ◽  
Vol 172 (3) ◽  
pp. 549-556 ◽  
Author(s):  
J P Singh ◽  
D F Babcock ◽  
H A Lardy
Keyword(s):  
Calcium Ion ◽  
Time Course ◽  
Acrosome Reaction ◽  
Local Anaesthetics ◽  
Defined Medium ◽  
Ionophore A23187 ◽  
Net Uptake ◽  
Ion Influx ◽  
Triton X

Capacitation (modifications required for gamete fusion) is produced by incubating guinea-pig spermatozoa in vitro in a chemically defined medium. It is shown that during such incubation a net uptake of Ca2+ by the sperm occurs in two distinguishable phases. An initial loose association of Ca2+, possibly to surface sites, is unaffected by agents (Mg2+, inhibitors of mitochondiral function) that prevent or delay the exocytotic spermatozoal acrosome reaction. The time course of a secondary Ca2+ uptake parallels or slightly precedes the time course of the acrosome reaction. This parallelism is maintained during a variety of treatments that either expedite (local anaesthetics, ionophore A23187, Triton X-100) or delay (Mg2+, low external Ca2+) the acrosome reaction. We conclude that the secondary Ca2+ influx described herein apparently serves to link alterations of the spermatozoal membrane to subsequent contractile and secretory components of the capacitation sequence.

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