Structure-function relationships in the adipose cell. I. Ultrastructure of the isolated adipose cell
TL;DR: Structural responses of the isolated adipose cell to hormones, if such occur, must be dynamic rather than qualitative in nature; the extensive system of smooth surfaced membranes is suggestive of compartmentalized transport and metabolism.
Abstract: A method is described for preparing isolated rat adipose cells for electron microscopy. The ultrastructure of such cells and their production of 14CO2 from U-glucose-14C were studied simultaneously in the presence of insulin or epinephrine. Each adipose cell consists of a large lipid droplet surrounded by a thin rim of cytoplasm. In addition to typical subcellular organelles, a variety of small lipid droplets and an extensive system of membranes characterize the cell's cytoplasm. A fenestrated envelope surrounds the large, central lipid droplet. Similar envelopes surround cytoplasmic lipid droplets occurring individually or as aggregates of very small, amorphous droplets. Groups of individual droplets of smaller size also occur without envelopes. The system of membranes consists of invaginations of the cell membrane, vesicles possibly of pinocytic origin, simple and vesiculated vacuoles, vesicles deeper in the cytoplasm, flattened and vesicular smooth surfaced endoplasmic reticulum, and Golgi complexes. Neither insulin nor epinephrine produced detectable ultrastructural alterations even when cells were incubated under optimal conditions for the stimulation of 14CO2 evolution. Structural responses of the isolated adipose cell to hormones, if such occur, must, therefore, be dynamic rather than qualitative in nature; the extensive system of smooth surfaced membranes is suggestive of compartmentalized transport and metabolism.
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TL;DR: Epoxy embedding methods of Glauert and Kushida have been modified so as to yield rapid, reproducible, and convenientembedding methods for electron microscopy.
Abstract: Epoxy embedding methods of Glauert and Kushida have been modified so as to yield rapid, reproducible, and convenient embedding methods for electron microscopy. The sections are robust and tissue damage is less than with methacrylate embedding.
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TL;DR: This communication reports the use of a commercially available lead citratO to eliminate the lead citrate stain in electron microscopy.
Abstract: A disadvantage of the lead strains used in electron microscopy is the amount of time required for their preparation. One of the more stable and reliable stains, commonly called the lead citrate stain or Reynolds' stain (Reynolds, 1963), is made by mixing lead nitrate and sodium citrate in distilled water, allowing time for lead citrate to form, then adding sodium hydroxide to raise the pH of the solution to 12. This communication reports the use of a commercially available lead citratO to eliminate the
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TL;DR: Certain hitherto unobserved details are revealed and some sort of specificity exists, although the factors involved are not yet understood.
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TL;DR: Interpreted in the light of current physiological data, these findings suggest that the diffusion of water, ions, and small, water-soluble molecules is impeded along the intercellular spaces of the epidermis by zonulae occludentes while it is facilitated from cell to cell within the epidesis by z onulae and maculae OccludENTes.
Abstract: Cell junctions have been investigated in the amphibian epidermis, a stratified squamous epithelium, and compared to those described previously in simple columnar epithelia of mammalian cavitary organs In adult frogs and toads, and in larvae approaching metamorphosis, belts of membrane fusion or zonulae occludentes of considerable depth are regularly found between adjoining cells of the outermost layer of the stratum corneum, binding the cells together into a continuous, uninterrupted sheet Another set of occluding zonules appears in the second cornified layer (when such a layer is present), and a third set usually occurs in the outermost layer of the stratum granulosum Specialized elements described as "modified" and "composite" desmosomes are encountered along the lateral and basal aspects, respectively, of the cornified cells; ordinary desmosomes and maculae occludentes (ie, spots of membrane fusion) are found in all other strata The usual 200 A intercellular gap is generally maintained between the cells of the stratum germinativum at the basal ends of the intercellular spaces Hence, the intercellular spaces of the epidermis form a largely continuous network, closed to the external medium and open to the dermal interstitia The situation is comparable to that found in columnar epithelia, except that the intercellular spaces are much more extensive, and an extracellular subcompartment (or two) apparently exists in the stratum corneum and between the latter and the stratum granulosum The last subcompartment is usually filled with a dense substance, probably derived from discharged secretory granules The tripartite junctional complex characteristic of lumen-lining epithelia (ie, a zonula occludens followed by a zonula adhaerens, and desmosome) is seen only in early larvae; in adults and in larvae approaching metamorphosis, the occluding zonule is followed directly by a series of modified desmosomes Interpreted in the light of current physiological data, these findings suggest that the diffusion of water, ions, and small, water-soluble molecules is impeded along the intercellular spaces of the epidermis by zonulae occludentes while it is facilitated from cell to cell within the epidermis by zonulae and maculae occludentes
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