scholarly journals Catalatic activity of iron(III)-centred catalysts. Role of dimerization in the catalytic action of ferrihaems

1970 ◽  
Vol 117 (4) ◽  
pp. 741-744 ◽  
Author(s):  
S. B. Brown ◽  
T. C. Dean ◽  
Peter Jones
Keyword(s):  
Unique Feature ◽  
Specific Activity ◽  
Maximal Activity ◽  
Quantitative Comparison ◽  
Ion Concentration ◽  
Catalytic Activities ◽  
A Value ◽  
Equilibrium Data ◽  
The Difference

1. The specific stoicheiometric catalatic activity of deuteroferrihaem is 10–100-fold greater than that for protoferrihaem, depending on pH. It is suggested that the difference in activity may be related to quantitative differences in the extent of dimerization in aqueous solutions of proto- and deutero-ferrihaem (Brown, Dean & Jones, 1970b). 2. A quantitative comparison of the kinetic and equilibrium data implies that the catalytic activities of ferrihaems are determined by the proportion of monomer present. The specific activity of ferrihaem monomer calculated varies inversely with H+ ion concentration and attains a value equal to the maximal activity of catalase at pH>pKa(H2O2). 3. A comparison of catalatic behaviour in the series of iron(III)-centred catalysts aqua-iron(III) ion, ferrihaem monomer and catalase suggests that the unique feature of catalase action resides in the pH-independence of the reaction.

scholarly journals Role of Ca2+ in pyruvate dehydrogenase interconversion in brain mitochondria and synaptosomes

1985 ◽  
Vol 227 (1) ◽  
pp. 129-136 ◽  
Author(s):  
R G Hansford ◽  
F Castro
Keyword(s):  
Plasma Membrane ◽  
Steady State ◽  
Pyruvate Dehydrogenase ◽  
Maximal Activity ◽  
Brain Mitochondria ◽  
Ruthenium Red ◽  
Ion Concentration ◽  
Maximal Effect ◽  
State Content

The steady-state content of active (dephospho) pyruvate dehydrogenase (PDHA) of suspensions of coupled rat brain mitochondria oxidizing succinate was found to be markedly increased with increasing free Ca2+ ion concentration of the medium, with a half-maximal effect at 10(-6.43) M Ca2+. Other ions were present in these studies at concentrations appropriate for the cytosol. Depolarization of the plasma membrane of synaptosomes caused an increase in the steady-state content of PDHA, with veratridine giving a larger increase than depolarization by 33 mM-KCl. Values were 68 +/- 1% (n = 13) and 81 +/- 1% (n = 19) of maximal activity, for control incubations and incubations in the presence of 30 microM-veratridine, respectively. Measurements of cytosolic free Ca2+ concentrations ([Ca2+]cyt.) in these suspensions of synaptosomes, with the use of the fluorescent Ca2+-indicator Quin-2, indicated an increase on depolarization, with the change due to 30 microM-veratridine being larger in extent than that due to 33 mM-KCl. Values were 217 +/- 21 nM (n = 15), 544 +/- 48 nM (n = 15) and 783 +/- 75 nM (n = 14) for control, KCl-depolarized and veratridine-depolarized synaptosomes respectively. Experiments in which synaptosomes were treated with Ruthenium Red, an inhibitor of mitochondrial Ca2+ uptake, gave much lower resting contents of PDHA (42 +/- 2% of maximal), but failed to prevent totally an increase on depolarization. Addition of an excess of EGTA to the synaptosomal suspension just before the addition of veratridine resulted in a partial diminution in the response of PDHA content. Parallel studies with Quin-2 indicated no increase in [Ca2+]cyt. on addition of veratridine, under these conditions. Thus an increase in [Ca2+]cyt. forms only a part of the mechanism whereby pyruvate dehydrogenase interconversion responds to depolarization. A decrease in the ATP/ADP ratio may also be important, as inferred from the results of experiments with ouabain, which inhibits the Na+ + K+-dependent ATPase.

scholarly journals A new appraisal of the endoglucanases of the fungus Trichoderma reesei

1985 ◽  
Vol 231 (1) ◽  
pp. 75-81 ◽  
Author(s):  
M L Niku-Paavola ◽  
A Lappalainen ◽  
T M Enari ◽  
M Nummi
Keyword(s):  
Trichoderma Reesei ◽  
Specific Activity ◽  
Relative Proportion ◽  
Culture Liquid ◽  
Enzymic Activity ◽  
Soluble Form ◽  
Immunological Methods ◽  
A Value ◽  
And Storage

The properties and enzymic activity of endoglucanases (EC 3.2.1.4) of the fungus Trichoderma reesei were studied by means of immunological methods and by using polyglycosidic substrates. Endoglucanases exist in the culture liquid as a series of immunologically related components. The most active endoglucanase component has an Mr of 43 000 and pI value of 4.0. The most abundant components have a value of pI about 5.0, an Mr of 56 000-67 000 and specific activity only one-fifth of that of the pI-4.0 component. During purification and storage the endoglucanases are spontaneously modified; the relative proportion of components having greater Mr values, more alkaline pI values and lower specific activities is increased. The hexose content of the endoglucanase components is 2-7%. Endoglucanases hydrolyse soluble β-1,4 glycans. The enzymes described here differ from endoglucanase preparations described previously in not showing activity towards insoluble substrates. The role of endoglucanases in wood hydrolysis is consequently limited to the stage where wood constituents are already in soluble form.

scholarly journals The action of potassium and other ions on the injury potential and action current in maia nerve

1934 ◽  
Vol 115 (793) ◽  
pp. 216-260 ◽  
Keyword(s):  
Electrolyte Solutions ◽  
Ion Concentration ◽  
Action Current ◽  
A Value ◽  
Physico Chemical ◽  
Wide Range ◽  
The Difference ◽  
Living Tissues ◽  
The Relationship ◽  
Injury Potential

The electric currents in living tissues have interested physiologists ever since their existence was proved by Du Bois Reymond, but little was done towards explaining their origin and magnitude on a quantitative physico-chemical basis befor the pioneer researches og J. S. Macdonald. Work previous to Macdonald's has discussed fully by that anuthor (1902), hence it will not be mentioned here. macdonald found that the injury potential of medullated nerve, either frog's or mammal's (1900, a, b ; 1902), could be given a value greater or smaller than the normal by simply altering the concentration of the solution in contact with the external surfaces of the fibres. He showed that solutions of NaOH, HCl, NaCl, or KCl affected the potential according to their concentrations and that the relationship between the two variables was a logarithmic one, which fact was in agreement with the then new theory of concentration cells developed by Nernst. Macdonald went on to point out (1902) that the effects of potassium chloride solutions were particularly interesting, and to suggest that the difference between the concentration of potassium in the axis cylinder of the nerve and in the surrounding blood or salt solution was wholly responsible for the observed injury potential. Over a wide range of concentration, 1/8 to 1 molar, he demonstrated that there was nearly a linear relation between the injury potential and the logarithm of the potassium ion concentration. However, since he simply varied the concentrations of his electrolyte solutions, and made no effort to maintain them isotonic with blood by the addition of a non-electrolyte, exception might be taken to some of his results on the ground that the effects were due in part to the passage of water into or out of the nerve with a consequent dilution or concentration of the plasma.

scholarly journals SELF-DEVELOPMENT, ABILITY FOR SELF-DEVELOPMENT AND HIGHER ABILITY FOR SELF-DEVELOPMENT

2021 ◽  
pp. 190-198
Author(s):  
Галина Валентиновна Ожиганова
Keyword(s):  
Specific Activity ◽  
Point Of View ◽  
Subject Position ◽  
Key Factors ◽  
Life Problems ◽  
Self Development ◽  
Psychological Point ◽  
Inner World ◽  
The Difference

С психологической точки зрения анализируется понятие «саморазвитие», а также связанные с ним способности личности. Цель исследования – рассмотреть понятие «саморазвитие», а также «способность к саморазвитию», «высшую способность к саморазвитию» и выявить различие между этими способностями. В ходе проводимого анализа раскрывается понятие саморазвития, описываются его различные характеристики и параметры. Представлены определения способности к саморазвитию, охватывающие ее разные ракурсы. Показано, что единого представления о саморазвитии не существует. Многообразие факторов, способствующих саморазвитию, выделение множества его аспектов и компонентов, различных форм проявления представляется правомерным, так как отражает сложность и многомерность данного психологического феномена. Особое место занимает описание субъектности, которая трактуется автором в качестве одного из основных факторов, ведущих к саморазвитию. Подчеркивается важная роль позиции субъекта и субъектности в саморазвитии и ее значение для проявления высшей способности к саморазвитию. Отмечена специфика высшей способности к саморазвитию, связанная с ее принадлежностью к ментальному компоненту духовных способностей. Показано отличие обычной способности к саморазвитию от высшей способности к саморазвитию, которое связано с тем, что высшая способность к саморазвитию ориентирована на абсолютные ценности и высокие духовно-нравственные идеалы. The article analyzes the concept of “self-development” and the personality abilities associated with it from a psychological point of view. The purpose of the research is to consider the concept of “self-development”, as well as “the ability for self-development”, “the highest ability for self-development” and identify the difference between these abilities. In the course of the analysis the concept of self-development is described, its various characteristics and parameters are revealed. The article presents definitions of the ability for self-development, covering its different aspects, such as systemic, integrative, subjective, activity-oriented, life-oriented, transformative, motivational-value, evaluative-orientational, self-regulatory, reflexive-regulatory, cognitive. It is shown that there is no single concept of self-development. Some concepts emphasize the role of cognitive factors, while others give priority to self-regulatory skills; subject position; transformation of the inner world; specific activity for self-change, aimed at solving life problems. It is concluded that the variety of factors contributing to self-development, the identification of many its aspects and components, various forms of manifestation seems to be logical, since it reflects the complexity and multidimensionality of this psychological phenomenon. A special place in the article is occupied by the description of subjectiveness, which is interpreted by the author as one of the key factors determining self-development. The important role of the position of the subject and subjectiveness in self-development and its importance for the manifestation of the highest ability for self-development, when a person acts as a subject of activity, as a subject of development, and as a subject of life, is emphasized. The specificity of the highest ability for self-development is noted, associated with its belonging to the mental component of spiritual abilities. The difference between the ordinary ability for self-development and the higher ability for self-development is shown, which is due to the fact that the highest ability for self-development is focused on absolute values and high spiritual and moral ideals.

Modeling mechanical alternans in the beating heart: advantages of a systems-oriented approach

1987 ◽  
Vol 253 (3) ◽  
pp. H690-H698 ◽  
Author(s):  
D. Adler ◽  
Y. Mahler
Keyword(s):  
Functional Dependence ◽  
Critical Role ◽  
Beating Heart ◽  
Discrete Method ◽  
End Diastolic Volume ◽  
A Value ◽  
The Difference ◽  
Experimental Findings ◽  
The Relationship

A model employing an original discrete method is proposed to explain mechanical alternans in the beating heart. This is compared with analysis using the difference-equation method, which has been utilized in some other areas of science and found to better represent the cardiac beat-to-beat behavior. The model shows the critical role of a slope with an exact value of 2 in the functional dependence between stroke volume (SV) and the end-diastolic volume (EDV). The implications of this model with respect to the factors causing sustained mechanical alternans (SMA) in the heart are shown. A criterion for determining whether SMA is caused by variations in EDV is described. However, this possibility is ruled out on the basis of experimental findings. It is further shown that SMA caused primarily by alterations in the contractile state leads to secondary variations in EDV. In this case the model predicts that the mean slope of SV as a function of EDV, as determined by the two alternating beats, has a value of 2 and is independent of the SV-EDV relation. This prediction concerning the relationship between SV and EDV is confirmed by available experimental data. The implications and advantages of the modeling approaches are explored.

The Traditions of Technology

1979 ◽  
Vol 4 (3) ◽  
pp. 371-385 ◽  
Author(s):  
Ashis Nandy
Keyword(s):  
Industrial Revolution ◽  
Science And Technology ◽  
Modern Science ◽  
Modern Technology ◽  
Politics Of Technology ◽  
A Value ◽  
The Difference ◽  
World Image ◽  
Cross National

Modern technology is a particular form of traditional technology with about 300 years of history behind it. It has become the dominant tradition by marginalizing the other traditions of technology in the West and in the rest of the world. In this marginalization, important roles have been played by the ideology of Englightenment, by the Industrial Revolution, and nineteenth and twentieth century colonialism. They have blurred the difference between science and technology, underwritten the mechanomorphic world-image and promoted the concept of a value-free, ethically unrestrained technology seeking omnipotence and omniscience on behalf of man. However, the present crises of technological consciousness has brought to the fore alternative traditions of technology, not as ethnotechnologies from which a universal, secular, modern technology can draw lessons, but as competing philosophies of universality which can provide correctives to the alienating, exploitative, and dehumanizing role of modern science and technology. For this, an alternative ideology of science as well as a new legitimacy for the traditional technosystems and their cultural environments is necessary. Such a legitimacy will have to be based on a different set of values relating to the man-nature and man-man relationships and a deeper understanding of the politics of technology in its cross-national and cross-cultural contexts.

Diurnal rhythms in Ca transfer into bone, Ca release from bone, and bone resorbing activity in serum of rats

1992 ◽  
Vol 262 (2) ◽  
pp. R235-R240
Author(s):  
H. Shinoda ◽  
P. H. Stern
Keyword(s):  
Specific Activity ◽  
Humoral Factor ◽  
Diurnal Rhythms ◽  
Heat Inactivation ◽  
Mandibular Incisor ◽  
Fetal Rat ◽  
The Difference ◽  
Radionuclide Release ◽  
Bone Resorbing Activity

To characterize diurnal rhythms in calcium transfer in and out of bone, rats were adapted to a 12:12 h light-dark illumination program (with light from 0600 to 1800 h). For studies of deposition, rats were injected with 45CaCl2 at 0300, 0700, 1100, 1500, 1900 or 2300 h and killed with chloroform inhalation 60 min later, and radioactivity was determined in tibia and mandibular incisor. Peak deposition occurred at 2400 h, with a nadir at 1200 h. For studies of radionuclide release, rats were prelabeled with 45CaCl2 for 6 days and serum obtained from the tail at 4-h intervals. 45Ca and specific activity were maximal around 1200-1600 h and lowest late in the dark period. To determine the role of humoral factor(s), fetal rat limb bones were cultured in media prepared with sera from light-dark-adapted rats. Activity was maximal in serum collected at 0800 h and minimal at 1600 h. Heat inactivation at 100 degrees C for 5 min eliminated the difference between the peak and nadir. The results suggest that a heat-sensitive humoral factor(s) regulates diurnal rhythms in calcium metabolism.

The role of differential phase contrast in electron microscopy

1978 ◽  
Vol 36 (1) ◽  
pp. 176-177
Author(s):  
E.M. Waddell ◽  
J.N. Chapman ◽  
R.P. Ferrier
Keyword(s):  
Phase Contrast ◽  
Practical Method ◽  
Position Vector ◽  
Differential Phase ◽  
Pure Phase ◽  
Differential Phase Contrast ◽  
The Difference ◽  
Image Position ◽  
First Moment

Dekkers and de Lang (1977) have discussed a practical method of realising differential phase contrast in a STEM. The method involves taking the difference signal from two semi-circular detectors placed symmetrically about the optic axis and subtending the same angle (2α) at the specimen as that of the cone of illumination. Such a system, or an obvious generalisation of it, namely a quadrant detector, has the characteristic of responding to the gradient of the phase of the specimen transmittance. In this paper we shall compare the performance of this type of system with that of a first moment detector (Waddell et al.1977).For a first moment detector the response function R(k) is of the form R(k) = ck where c is a constant, k is a position vector in the detector plane and the vector nature of R(k)indicates that two signals are produced. This type of system would produce an image signal given bywhere the specimen transmittance is given by a (r) exp (iϕ (r), r is a position vector in object space, ro the position of the probe, ⊛ represents a convolution integral and it has been assumed that we have a coherent probe, with a complex disturbance of the form b(r-ro) exp (iζ (r-ro)). Thus the image signal for a pure phase object imaged in a STEM using a first moment detector is b2 ⊛ ▽ø. Note that this puts no restrictions on the magnitude of the variation of the phase function, but does assume an infinite detector.

On the Role of Transferrin in 67Ga Uptake by Tumor Cells

1988 ◽  
Vol 27 (04) ◽  
pp. 151-153
Author(s):  
P. Thouvenot ◽  
F. Brunotte ◽  
J. Robert ◽  
L. J. Anghileri
Keyword(s):  
Specific Binding ◽  
Subcellular Fractionation ◽  
Animal Blood ◽  
Tumor Bearing ◽  
Cell Structures ◽  
The Difference ◽  
Sarcoma Cells ◽  
In Vitro Uptake

In vitro uptake of 67Ga-citrate and 59Fe-citrate by DS sarcoma cells in the presence of tumor-bearing animal blood plasma showed a dramatic inhibition of both 67Ga and 59Fe uptakes: about ii/io of 67Ga and 1/5o of the 59Fe are taken up by the cells. Subcellular fractionation appears to indicate no specific binding to cell structures, and the difference of binding seems to be related to the transferrin chelation and transmembrane transport differences

REFLECTION COEFFICIENT OF AN ELECTROMAGNETIC WAVE IN CONDUCTIVE MEDIA

2018 ◽  
pp. 100-106
Author(s):  
M. S. Sudakova ◽  
M. L. Vladov ◽  
M. R. Sadurtdinov
Keyword(s):  
Reflection Coefficient ◽  
Ground Penetrating Radar ◽  
Electromagnetic Waves ◽  
Water Contamination ◽  
Survey Design ◽  
Direct And Inverse Problems ◽  
The Difference ◽  
Ground Penetrating ◽  
Ideal Dielectric

Within the ground penetrating radar bandwidth the medium is considered to be an ideal dielectric, which is not always true. Electromagnetic waves reflection coefficient conductivity dependence showed a significant role of the difference in conductivity in reflection strength. It was confirmed by physical modeling. Conductivity of geological media should be taken into account when solving direct and inverse problems, survey design planning, etc. Ground penetrating radar can be used to solve the problem of mapping of halocline or determine water contamination.

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