scholarly journals Ascending from the Abstract to the Concrete as a Principle of Expansive Learning

2020 ◽  
Vol 25 (5) ◽  
pp. 31-43
Author(s):  
Y. Engeström
Keyword(s):  
Germ Cells ◽  
Concept Formation ◽  
School Transformation ◽  
Societal Transformation ◽  
Expansive Learning ◽  
In The Wild ◽  
Dialectical Principle ◽  
Transforming Practices

The article examines the potential of the dialectical principle of ascending from the abstract to the concrete for transforming practices of learning. It is shown that V.V. Davydov’s work has created a foundation for such transformation. The theory of expansive learning builds on Davydov’s legacy and brings the principle of ascending from the abstract to the concrete into learning and concept formation outside schools, “in the wild.” Three studies investigating different scales of expansive learning are discussed, focusing on the internally contradictory germ cells discovered and used in those studies. The article concludes by emphasizing the need to integrate Davydov’s revolutionary pedagogy and the broader agenda of school transformation as part of societal transformation.

Concept Formation in the Wild

2012 ◽  
Vol 19 (3) ◽  
pp. 201-206 ◽  
Author(s):  
Yrjö Engeström ◽  
Annalisa Sannino
Keyword(s):  
Concept Formation ◽  
In The Wild

scholarly journals Expansive Concept Formation in the Wild Tracing Trails From a Germ Cell Toward New Ways of Life and Work

2012 ◽  
Vol 51 (0) ◽  
pp. 170-176
Author(s):  
Yrjo¨ ENGESTRo¨M ◽  
Chikako TOMA ◽  
Yuji MORO ◽  
Hisao FUJII
Keyword(s):  
Germ Cell ◽  
Concept Formation ◽  
In The Wild ◽  
Ways Of Life

scholarly journals Germ cells and the seminiferous epithelium cycle in the wild rodent Oxymycterus rufus (Rodentia: Cricetidae)

2016 ◽  
Vol 11 (04) ◽  
pp. 61-71
Author(s):  
Ana Carolina T. Morais ◽  
Maytê K. Balarini ◽  
Tatiana P. Menezes ◽  
Fausto S. Ferraz ◽  
Marcos L. M. Gomes ◽  
...  
Keyword(s):  
Germ Cells ◽  
Seminiferous Epithelium ◽  
Wild Rodent ◽  
In The Wild

Freeze-etch observations on the tight junctions of sertoli cells grown in organ culture with FSH

1978 ◽  
Vol 36 (2) ◽  
pp. 340-341
Author(s):  
Rita Meyer ◽  
Zoltan Posalaky ◽  
Dennis Mcginley
Keyword(s):  
Organ Culture ◽  
Tight Junctions ◽  
Sertoli Cell ◽  
Germ Cells ◽  
Sertoli Cells ◽  
Barrier Function ◽  
Cell Junction ◽  
Intramembranous Particles ◽  
Junctional Complexes ◽  
Oriented Parallel

The Sertoli cell tight junctional complexes have been shown to be the most important structural counterpart of the physiological blood-testis barrier. In freeze etch replicas they consist of extensive rows of intramembranous particles which are not only oriented parallel to one another, but to the myoid layer as well. Thus the occluding complex has both an internal and an overall orientation. However, this overall orientation to the myoid layer does not seem to be necessary to its barrier function. The 20 day old rat has extensive parallel tight junctions which are not oriented with respect to the myoid layer, and yet they are inpenetrable by lanthanum. The mechanism(s) for the control of Sertoli cell junction development and orientation has not been established, although such factors as the presence or absence of germ cells, and/or hormones, especially FSH have been implicated.

Comparative Morphology of Intercellular Bridges Between Developing Germ Cells of the Ovary

1970 ◽  
Vol 28 ◽  
pp. 328-329
Author(s):  
J. R. Ruby ◽  
R. F. Dyer ◽  
R. G. Skalko ◽  
R. F. Gasser ◽  
E. P. Volpe
Keyword(s):  
Germ Cells ◽  
Rana Pipiens ◽  
Comparative Morphology ◽  
Dense Material ◽  
Individual Species ◽  
Microscope Examination ◽  
Electron Dense Material ◽  
Intercellular Bridges ◽  
Cytoplasmic Side ◽  
Intercellular Connections

An electron microscope examination of fetal ovaries has revealed that developing germ cells are connected by intercellular bridges. In this investigation several species have been studied including human, mouse, chicken, and tadpole (Rana pipiens). These studies demonstrate that intercellular connections are similar in morphology regardless of the species.Basically, all bridges are characterized by a band of electron-dense material on the cytoplasmic side of the tri-laminar membrane surrounding the connection (Fig.l). This membrane is continuous with the plasma membrane of the conjoined cells. The dense material, however, never extends beyond the limits of the bridge. Variations in the configuration of intercellular connections were noted in all ovaries studied. However, the bridges in each individual species usually exhibits one structural characteristic seldom found in the others. For example, bridges in the human ovary very often have large blebs projecting from the lateral borders whereas the sides of the connections in the mouse gonad merely demonstrate a slight convexity.

Hexachlorobenzene toxicity in the rat ovary: II. Ultrastructure induced by medium (10 mg/kg) dose exposure

1992 ◽  
Vol 50 (1) ◽  
pp. 668-669
Author(s):  
Amreek Singh ◽  
Warren G. Foster ◽  
Anna Dykeman ◽  
David C. Villeneuve
Keyword(s):  
Germ Cells ◽  
Primordial Germ Cells ◽  
Surface Epithelium ◽  
Morphological Parameters ◽  
Comprehensive Investigation ◽  
Ovary Surface Epithelium ◽  
Rat Ovary ◽  
High Doses

Hexachlorobenzene (HCB) is a known toxicant that is found in the environment as a by-product during manufacture of certain pesticides. This chlorinated chemical has been isolated from many tissues including ovary. When administered in high doses, HCB causes degeneration of primordial germ cells and ovary surface epithelium in sub-human primates. A purpose of this experiment was to determine a no-effect dose of the chemical on the rat ovary. The study is part of a comprehensive investigation on the effects of the compound on the biochemical, hematological, and morphological parameters in the monkey and rat.

Freeze-substituted fungal cells of Nectria haematococca: A comparison of the macroconidial walls of the adhesion-competent wild type with an adhesion-reduced mutant

1990 ◽  
Vol 48 (3) ◽  
pp. 688-689
Author(s):  
Thecan Caesar-Ton That ◽  
Lynn Epstein
Keyword(s):  
Freeze Substitution ◽  
Uranyl Acetate ◽  
Wild Type ◽  
Nectria Haematococca ◽  
Fruit Extract ◽  
Dialysis Tubing ◽  
Tube Emergence ◽  
Contrast Microscopy ◽  
In The Wild ◽  
Freeze Damage

Nectria haematococca mating population I (anamorph, Fusarium solani) macroconidia attach to its host (squash) and non-host surfaces prior to germ tube emergence. The macroconidia become adhesive after a brief period of protein synthesis. Recently, Hickman et al. (1989) isolated N. haematococca adhesion-reduced mutants. Using freeze substitution, we compared the development of the macroconidial wall in the wild type in comparison to one of the mutants, LEI.Macroconidia were harvested at 1C, washed by centrifugation, resuspended in a dilute zucchini fruit extract and incubated from 0 - 5 h. During the incubation period, wild type macroconidia attached to uncoated dialysis tubing. Mutant macroconidia did not attach and were collected on poly-L-lysine coated dialysis tubing just prior to freezing. Conidia on the tubing were frozen in liquid propane at 191 - 193C, substituted in acetone with 2% OsO4 and 0.05% uranyl acetate, washed with acetone, and flat-embedded in Epon-Araldite. Using phase contrast microscopy at 1000X, cells without freeze damage were selected, remounted, sectioned and post-stained sequentially with 1% Ba(MnO4)2 2% uranyl acetate and Reynold’s lead citrate. At least 30 cells/treatment were examined.

Electron microscope study of the effects of radiation on insect fertility

1990 ◽  
Vol 48 (3) ◽  
pp. 72-73
Author(s):  
Judy Ju-Hu Chiang ◽  
Robert Kuo-Cheng Chen
Keyword(s):  
Electron Microscopy ◽  
Germ Cell ◽  
Germ Cells ◽  
Electron Microscope Study ◽  
Radiation Treatment ◽  
Light And Electron Microscopy ◽  
Stem Borer ◽  
Metabolic Energy ◽  
Rice Stem Borer ◽  
Effects Of Radiation

Germ cells from the rice stem borer Chilo suppresalis, were examined by light and electron microscopy. Damages to organelles within the germ cells were observed. The mitochondria, which provide the cell with metabolic energy, were seen to disintegrate within the germ cell. Lysosomes within the germ cell were also seen to disintegrate. The subsequent release of hydrolytic enzymesmay be responsible for the destruction of organelles within the germ cell. Insect spermatozoa were seen to lose the ability to move because of radiation treatment. Damage to the centrioles, one of which is in contact with the tail, may be involved in causing sperm immobility.

A Cognitive-Linguistic Intervention Program: Basic Concept Formation Level

1977 ◽  
Vol 8 (1) ◽  
pp. 23-32
Author(s):  
Gerald E. Chappell
Keyword(s):  
Basic Concept ◽  
Concept Formation ◽  
Intervention Program ◽  
Cognitive Linguistic ◽  
Basic Concepts ◽  
Linguistic Skills ◽  
Linguistic Intervention

Test-teach questioning is a strategy that can be used to help children develop basic concepts. It fosters the use of multisensory exploration and discovery in learning which leads to the development of cognitive-linguistic skills. This article outlines some of the theoretical bases for this approach and indicates possibilities for their applications in child-clinician transactions.

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