The Role of Microfilaments in Frog Skin Ion Transport

Pratley, James N.; McQuillen, Nancy K.

doi:10.1083/jcb.56.3.850

Cited by 14 publications

(1 citation statement)

References 15 publications

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“…It is by no means clear which of the structural changes may be directly related to biochemical changes preceding keratinization and which may be ascribed to other physiological functions (or malfunctions) of the skin. Thus it is no longer generally believed that tonofilaments are related to keratinization (Budtz & Larsen, 1975;Spearman, 1977), and the decrease in the amount of filaments might, for example, be related to the decreased Ca2+-levels in plasma after hypophysectomy (Gerschman, 1943, cited by Houssay, 1949) since intercellular concentrations of Ca2+ appear to be important for normal epidermal filament structure in Rana pipiens, as indicated by their almost total disappearance in Ca-free Ringer's solution in vitro (Pratley & McQuillen, 1973). Also the relationship between keratinization and mucogenesis is unclear.…”

Section: Whichlorganelles Are Involved In Amphibian Keratinization ?mentioning

confidence: 99%

Epidermal structure and dynamics of the toad, Bufo bufo, deprived of the pars distalis of the pituitary gland

Budtz

1979

Journal of Zoology

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Structural changes and epidermal dynamics of the toad, Bufo bufo, were followed during 14 days after ablation of the pars distalis of the pituitary gland by taking skin biopsies 2, 17, 24, 40 and 65 hours, and 7 and 14 days after the operation. The rate of differentiation of new cornified layers was moderately increased during the first week, and highly increased during the second week after removal of the pars distalis. The keratinization process became gradually abnormal with regard to initial keratinization (formation of a peripheral dense band) as well as to final keratinization (laydown of an interfibrillar dense matrix). The structural manifestations of the keratinization process after pars distalis ablation are discussed in relation to those of intact toads. By counting the number of cells in the different “compartments” of the epidermis, it is shown that the total number of cells per length or square unit of stratum corneum remained constant in spite of at least five layers of stratum corneum being produced in a 14‐day period during which intact toads would have produced only one or two corneal layers. This shows that cell production can keep up with the increased rate of formation of corneal layers for at least 14 days after removal of the pars distalis, and consequently the rate of cell divisions must have increased. It was further shown that the ratio between the number of cells in the stratum germinativum and in the stratum intermedium was decreased, which is discussed in relation to epidermal dynamics. In Merkel cells, the number of granules increased, and eventually the granules became included within lysosome‐like bodies, indicating a secretory function of these cells. The findings are discussed in relation to the knowledge of mammalian Merkel cell structure and function. No significant change was observed in the flask cells. The control of amphibian epidermal proliferation, differentiation and moulting is discussed. It is concluded that these processes should be considered separately since they may not necessarily be coupled to one another and probably are differently controlled.

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Section: Whichlorganelles Are Involved In Amphibian Keratinization ?mentioning

confidence: 99%

Epidermal structure and dynamics of the toad, Bufo bufo, deprived of the pars distalis of the pituitary gland

Budtz

1979

Journal of Zoology

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Cytochalasin B and water transport

1978

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A morpho-functional study of the effects of cytochalasin B (CB) on Na and water transport was made in amphibian epithelia. The functional studies confirmed the dissociation of the natriferic and hydrosmotic effects of vasopressin in toad urinary bladders exposed to CB and showed in addition that the block of the hydrosmotic effect was reversible and could still be induced in epithelia maximally stimulated with the hormone. Scanning electron microscopy revealed that CB, per se, did not alter the apical surface of the bladders. An almost total loss of microvilli of granular cells was seen, however, if CB was associated with vasopressin and an osmotic gradient. The results suggest two points: a) the block of the hydrosmotic flow induced by CB is due to factors beyond the apical membrane; b) microfilaments may be important mechanochemical transducers in the chain of events leading to the hydrosmotic effect of vasopressin.

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Structure of the toad epidermis during the moulting cycle

Budtz

Larsen

1975

Cell Tissue Res.

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Changes in the ultrastructure of the toad epidermis during the moulting cycle are described on the basis of 17 skin preparations fixed in consecutive phases of the cycle. Our previous light microscopical findings that morphological changes are mainly restricted to a short period prior to and after shedding are confirmed. Differentiation of zonulae occludentes in the new replacement layer after shedding is described and discussed in relation to the changes in ion permeability after the moult. Changes in appearance and distribution of filaments and of two different types of granules during the moulting cycle are described and discussed in relation to current views on amphibian keratinization; it is concluded that the initial phase of keratinization in the toad is very rapid and with a high degree of synchrony, whereas the laying-down of interfibrillar, central dense matrix in the new stratum corneum takes up to 24 hours and is less synchronous. The separation of the old stratum corneum from the replacement layer is gradual; it may be accomplished by rupture of "pillars" bearing the desmosomal complexes between stratum corneum and the replacement layer, or by breaking within the desmosomes themselves. Observed changes in granular content of the replacement layer are considered of no importance for this process, since the time sequence of discharge into the subcorneal space is not correlated with the initiation of separation. Other possible mechanisms of separation are discussed.

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The Role of Microfilaments in Frog Skin Ion Transport

Cited by 14 publications

References 15 publications

Epidermal structure and dynamics of the toad, Bufo bufo, deprived of the pars distalis of the pituitary gland

Epidermal structure and dynamics of the toad, Bufo bufo, deprived of the pars distalis of the pituitary gland

Cytochalasin B and water transport

Structure of the toad epidermis during the moulting cycle

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