Protoplasmatologia Cell Biology Monographs – serie
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Häftad, Tyska, 1953
577 kr
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Häftad, Tyska, 1954
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Häftad, Engelska, 1954
562 kr
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obvious properties, its structure, composition, electrical properties, me chanical properties, and most particularly, its permeability properties. None of these properties are obviously associated with surface enzymes. What are the functions of the cell surface that may require the presence of enzymes? From a purely hypothetical point of view, the cellular activities in which cell surface enzymes are potentially functional can be divided into two categories; first, those activities related to the production and maintenance of the cell surface structure itself, and second, those activities which are concerned with interactions between the cell and its environment. During growth of a cell, as it enlarges, new structural ma terial must be synthesized and assembled in the cell membrane. Although it is conceivable that new structural material is synthesized in the interior of the cell, it is difficult to visualize its complete synthesis and final assembly in the periphery of the cell, without the assistance of enzymes at the site. In the case of non-growing cells, although no net synthesis of new structural material is necessary, the turnover of the various components by a continuous degradation and resynthesis must be considered as a pos sibility.
Häftad, Engelska, 1955
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I. Introduction Early estimatiOons Oof pH values in plant cells were based UPOon determina- tiOons Oof the electrOomOotive fOorce (EMF) develOoped between a standard hydrOo- gen electrOode and the fluid expressed frOom crushed tissues Oor liberated by cutting large algal cells such as thOose Oof Valonia, Chara Oor Nitella. These EMF values were then translated intOo terms Oof hydrQgen iOon CQncentratiQn Qn the assumptiQn that the numerical value Qf the EMF in VOolts depended entirely UPOon the cOoncentratiOon Qf hydrOogen iQns. Then hydrQgen iQn COoncentratiOon measured in this way was fQund tOo act in biOoIQgical reactiQns, mainly enzyme activity, in such a way that the apparent hydrQgen iOon cOoncentratiOon was related lQgarithmically tOo the prQcess investigated. SQ SORENSEN in 1909 intrQduced the pH scale based upOon what he called the 1 "hydrOogen-iOon eXPOonent. " He defined PH+ as -(1 (1909, p. 28, nQt p. 4) Oog PH;) and PH+ became pH as a matter Qf tYPOographical cQnvenience.As far as living, uncrushed, plant cells were cOoncerned, the available fluid was usually soo minute in amQunt, except in special cases, that hydrOogen electrQde methQds were nOot applicable tOo a general survey. AttentiOon was therefQre directed tOo pH indicatOors. These indicatQrs vary in cOoIQur, usually frQm Qne cQIOour tOo anOother cQIQur with dichrQic inter- mediate tints within a range Oof 1.
Häftad, Engelska, 1955
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Häftad, Tyska, 1955
577 kr
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Häftad, Engelska, 1956
562 kr
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Häftad, Engelska, 1956
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C. Chemistry 66 D. Medicine 67 Theories of Metachromasy 68 A. Optical Illusion 68 B Impurc Dyes 69 C. Dye Bases 69 D. Tautomers 70 E. pH-Indicators 72 F. Colloidal Theories 72 G. Dimerization and Polymerization 73 H. The Current Status ?4 Physiological Implications of Chromotropes 76 A. Some Properties of Polyacidic Colloids 77 B. Integrity of Connective Tissue 78 C. Blood Clotting 80 D. Cellular Activation and Inhibitiou 81 E. Metaphosphate (Volutin) ...82 F. An Evaluation of the Metachromatic Reaction 82 Acknowledgments 84 References 85 Introduction Metachromasy exists when a pure dye stains a tissue section in a hue perceptibly different from the color characteri,s.fically associated with the dye. Thus, a dilute solution of toluidine blue i8 blue. Cell nudei and certain basophilic components of the cytoplasm are stained in this color. A number of other histological elements are stained red by toluidine blue. The laNer is the metachromatic color of the dye. Both extremes of color, as well as intermediate hues, may prevail in the same histological pre- paration.
Häftad, Engelska, 1956
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It is also possible that contractile vacuoles originate by some form of phase separation not yet understood and possibly involving the contractile properties of proteins, and' it is possible that this process continues to operate in the walls of the vacuoles or feeder canals. This secretory process may be the function of that part of the vacuolar apparatus which blackens on impregnation with osmic acid, and which seems to possess some degree of permanence from vacuole to vacuole and in some cases from parent to daughter cell. Remarkably little is known about the mechanism of systole. General body turgor may contribute, but it is not essential. In ciliates the main force is local and probably comes from a tension in the wall of the vacuole itself, but it is not known whether or not this is an active contraction of an oriented protein layer. The critical process for the initiation of systole is probably the opening of the pore. It is possible that in ciliates there is a rhythmically operating independent timing mechani,sm by which the vacuolar cycle is controlled, but its existence has not been demonstrated.
Häftad, Tyska, 1957
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wiihrend das F i 1 a r p I a sma eine besondere Bedeutung fur Bewegungs- vorgiiIige haben sollte und daher von STRASBURGER auch mit dem Namen Kin 0 pIa Sma belegt wurde. HANSTEIN (1880) versuchte den im Innern des Cytoplasmas beobachteten Dif'ferenzierungen dadurch Rechnung zu tragen, daB er ein auReres, zaheres H y a lop I a sma oder E k t- p I a sma von einem inneren, leichter beweglichen, mit Mikrosomen aus- gestatteten Ene h y I e m a oder End 0 p I a sma unterschied. Von seiten der Zoologie wurde ebenfalls der mikroskopischen Morpho- logie schon friihzeitig Interesse zugewandt. Wahrend die alteren Forscher das Cytoplasma als eine mehr oder weniger homogene Masse ansahen, in deren Inneren kleinste Kornmen, die Mikrosomen, als Einschliisse auf- ireten, wurden gegen das Ende des 19. Jahrhunderts die bekannten Struk- turtheorien des Plasmas aufgestellt, denen im weiteren VerIauf der Ent- wicldung der Cytologie fast allgemein lediglich historisches Interesse ge- zollt wurde. So vertraten LEYDIG (1885), HEITZMANN (1873) und FROMMANN (1884) in der "R e t i k u I art h e 0 r i e" die Auffassung, daR das Plasma aus einem feinen Netzwerk von Fibrillen besteht, dessen Lii
Häftad, Tyska, 1957
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paper he discussed the results whim had been obtained from his studies of the adrenal gland. The results he obtained are probably best told in his own words:-"To see whether the adrenal cortex contains any such reducing agent the gland was cut with a knife into halves-which were immersed in a 0. 4% AgN0 solution. In a few minutes the cortical part 3 was seen to darken through the deposition of reduced metallic silver. In a quarter of an hour the cut surface of the cortex turned completely black while the medulla remained largely uncoloured. The black colouration ends towards the medulla with a sharp margin, which corresponds to the anatomical margin between the medulla and cortex. Like the medulla, other organs, such as brain, liver and muscle remain practically uncoloured. " When the gland was immersed in a mixture of potassium iodate and acetic acid-a reagent for adrenalin, the medulla became violet in colour and the cortex remained colourless. SZENT-GYORGYI therefore came to the conclusion that:-"The adrenal cortex therefore, contains some specific highly reducing agent which can be no arte fact, since its action is produced in the almost fresh material." Methyl alcohol extracts of the cortex reduced neutral silver nitrate almost instantaneously and when the portions of the interrenal glands of Elasmobranm fishes were treated with silver nitrate solutions they too went black-so that it appeared that this highly reducing factor was a funda- mental constituent of adrenal tissue.
Häftad, Engelska, 1958
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Häftad, Tyska, 1958
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Häftad, Tyska, 1958
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Häftad, Engelska, 1958
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Häftad, Tyska, 1958
577 kr
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Häftad, Tyska, 1958
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Häftad, Engelska, 1958
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In comparing plant and animal tumors it must bc remembered, however, that there are certain developmental and I'unctional characteristics C01- monly used in the differentiation of animal cancers that are more or less restricted to animals and cannot, therefore, be carried over and applied to plant tumors. These have been dealt with in detail by WHITE and BRAUN (1942) and by BLACK (1949), and will not be considered further here. The most essential characteristic of being able to grow independently of any morphogenetic restraint, upon which all of the other diagnostic features must ultimately depend, is, however, equaHy capable of expression in neoplasia of a11 higher organisms since it is a characteristic of the ceH itself. One striking aspect of tumor genesis is the multiplicity of diverse agencies that are seemingly capable of accomplishing essentially the same end result. Radiant energy, irritation, carcinogenic ehemicals, parasitic organisms, and virus es have all been shown to serve as incitors of tumors in animals. The effectiveness of these various I'actors in cliciting tumor formation appears to be a I'unction of the hereditary constitution of the host.Many of these same agencies have also beeIl found to be concerned etiologically in the inception of tumors in plants.
Häftad, Tyska, 1959
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Häftad, Tyska, 1959
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Häftad, Engelska, 1959
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Since CORTI (1774) observed for the first time a streaming in plant cells, a history oJ mnre than 180 years has already elapsed in the study of proto- plasmic streaming. Durling this period of time, many experiments have been conducted and various discussions have been made nn prntoplasmic streaming, each of them within the limits of the knowledge and techniques of its own times and mnre or less under the influence of the ideas that pre- vailed then. With such a long history of research, in spite of all the interest and efforts that have been devoted to it by many, the mechani'sm of this in- triguing and complicated binlogical phenomenon is still left far from clear. It is an undeniable fact that one important factor stood in the way in analysing this phenomenon, that is, the limitations in the techniques ap- plicable to thi,s research. Another factor lay in the fact that we still have not enough knowledge about the protoplasm regar1ding its structural organisation, mechanochemistry, energetics, rheology, etc., all of which con- stitute basic problems in understanding the nature of the streaming.
Häftad, Tyska, 1960
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Häftad, Tyska, 1960
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Häftad, Tyska, 1962
837 kr
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Häftad, Tyska, 1962
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Häftad, Tyska, 1963
577 kr
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Häftad, Tyska, 1964
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Häftad, Engelska, 1964
562 kr
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Häftad, Engelska, 1965
562 kr
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Häftad, Engelska, 1965
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Introduction When the study of heredity and variation first came to be treated as a scientific subject-and this, one must remember, was only just over a hundred years ago-there was an unfortunate separation between the disciplines of cytology and experimental breeding. This separation was based partly on a lack of understanding and partly on a lack of the desire to understand. Even WILLIAM BATESON, the first apostle of mendelism in England, had a blind spot for cytology and for many years dogmatically refused to believe that MENDEL'S determinants were transmitted and distributed by the chromosomes. This separation between cytology and experimental breeding is one which persists, in a measure, even today, simply because there are two quite different, though complementary, techniques available for the study of heredity and variation. On the one hand, one can study directly the structure and behaviour of the actual vehicles which transmit the genetic determinants from one generation to the next. This is the method employed by those who study genetics through a microscope. The alternative method is that used by the experimental breeder who, in default of being able to watch the hereditary factors segregate from each other directly, is obliged to examine the constitution of the germ cells indirectly by sampling, and usually at random, the products of a controlled mating.