Quantitative variations in the disposition of the enteric surface coat in mouse jejunum

Sn, Rao; Tm, Mukherjee; Aw, Williams

doi:10.1136/gut.13.1.33

Cited by 15 publications

(3 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The thickness of the surface coat in replicas was found to be cell-specific; surface coat thickness was uniform for a particular cell, but varied markedly among different cells. These observations are in agreement with previous thin-section studies of surface coat distribution (7,10). However, freezeetching reveals some essential differences in the organization of surface coat filaments.…”

Section: Discussionsupporting

confidence: 92%

Demonstration of the fuzzy surface coat of rat intestinal microvilli by freeze-etching.

Swift¹,

Mukherjee²

1976

The Journal of Cell Biology

View full text Add to dashboard Cite

Interest in understanding the structural and functional organization of the surface coat of cell membranes of animal, plant, and bacterial cells has been widespread. In particular the ~'fuzzy" surface coat of intestinal epithelial cells has received special attention, mainly for its strategic location at the absorptive surface of the cell and its unique structural organization as shown by the studies to date (e.g. 2-5, 7, 1 I). However, much of this knowledge has been obtained from thin sections of conventionally processed tissues, and considerable differences have been observed in the organization of the surface coat (3,4,9). From these investigations it seems uncertain whether such differences in the organization of the surface coat demonstrate in vivo differences or artifactual differences due to variations in the tissue processing methods. It was felt, therefore, that an attempt to demonstrate the surface coat by a technique alternative to conventional thin sections, such as freeze-etching, would be of value in resolving this uncertainty.Previous freeze-etch studies have not yielded sufficient information to clarify details of the structural organization of the surface coat of epithelial cells or to enable meaningful comparison with our existing knowledge from thin-section techniques. Mukherjee and Staehelin (8) found that the surface coat of mouse intestine could not be readily identified in their freeze-etch preparations, lto (4) reported that the surface coat of aldehyde-fixed cat intestinal mucosa was not visible if tissue specimens were glycerinated before freezing, but was visible if fixed specimens were frozen in distilled water, lto's results showed the surface coat as consisting of a loose meshwork of filaments--a structure difficult to correlate with the surface coat structure seen in thin sections. Here we report that the surface coat of epithelial cells of rat rectum can be demonstrated clearly by standard freeze-etch procedures and that the appearance of the surface coat in replicas differs substantially from that found previously in both thin-section and freeze-etch studies. MATERIALS AND METHODSFor freeze-etching, small portions of mucosa from the rectum of D. A. Brown strain rats were fixed in 2.5% glutaraldehyde in 0.1 M phosphate buffer (pH 7.4) for l h at room temperature, rinsed in buffer, and transferred to 30% glycerol for 2 h. Pieces of mucosa of about I mm s were mounted on gold specimen disks, frozen in liquid Freon-22 at -150~ and stored in liquid nitrogen. Specimens were fractured at -100~ and etched for 5 s at -100~ in a Balzers freeze-etch apparatus (Balzers AG, Balzers, Liechtenstein). The replicas were cleaned in sodium hypochlorite, mounted on Formvar-coated grids, and examined in a Hitachi HU-IIE electron microscope.For thin sectioning, pieces of glutaraldehyde-fixed mucosa were postfixed in 2% OsO, for 0.5 h, dehydrated in ethanol, and embedded in Epon 812. Sections were stained with uranyl acetate and lead citrate. RESULTSIn replicas where the microvilli were fractured par...

show abstract

Section: Discussionsupporting

confidence: 92%

Demonstration of the fuzzy surface coat of rat intestinal microvilli by freeze-etching.

Swift¹,

Mukherjee²

1976

The Journal of Cell Biology

View full text Add to dashboard Cite

show abstract

“…Alternatively, Bock (1972Bock ( , 1973 proposed that this absorpiton is related to the surface charge of the cell coat. Surface absorption of ferritin molecules has also been related to the surface charge of the cell coat (Mukherjee, 1972;Rao et al, 1972). From our results it appears that there is a n interaction between the protein and the cell coat that is especially noticeable in the region of the bristle-coated pits and invaginations.…”

Section: Discussionmentioning

confidence: 64%

Transport across endodermal cells of the chick yolk sac during early stages of development

Mobbs

McMillan

1981

Am. J. Anat.

View full text Add to dashboard Cite

The endoderm of the chick yolk sac mediates the transfer of materials from the yolk mass to the embryonic circulation. There is little evidence of endocytotic activity in the area pellucida, but the endodermal cells of the area vasculosa possess many microvilli and bristle-coated pits and vesicles, as well as a canalicular system and vacuoles in the apical cytoplasm. Three tracers, horseradish peroxidase, ferritin, and latex spheres, were injected beneath the endoderm of both cultured embryos and embryos in ovo to study the pathway of uptake of extracellular materials. All tracers were sequestered in bristle-coated pits (200-500 nm in diameter) of the endodermal cells of the area vasculosa, but not those in the area pellucida. Both horseradish peroxidase and latex spheres (and probably ferritin) were incorporated into pleomorphic intracellular yolk drops through bristle-coated pits and vesicles, and then into apical vacuoles, which fuse with the intracellular yolk drops. Horseradish peroxidase and ferritin were also found within apical canaliculi. The apical junctions between endodermal cells prevented the intercellular passage of the tracers. A "topping-up" hypothesis is opposed whereby endodermal cells of the area vasculosa continually sequester extracellular yolk material, which is incorporated into a digesting intracellular yolk drop while, at the same time, digested yolk products are being transported across the vascular pole of the endoderm to the extraembryonic circulation and thence to the embryo.

show abstract

“…Close inspection showed that the sites at which the radioautographic reaction changed in intensity coincided exactly with the lateral limits of individual cells . After staining the apical microvilli of mouse jejunal cells with colloidal iron, great differences in staining were similarly observed between individual cells (57) . The individual differences may reflect different functional states in adjacent cells .…”

Section: Radioautographic Resultsmentioning

confidence: 97%

Migration of Glycoprotein From the Golgi Apparatus to the Surface of Various Cell Types as Shown by Radioautography After Labeled Fucose Injection Into Rats

Bennett

Leblond

Haddad

1974

The Journal of Cell Biology

314

View full text Add to dashboard Cite

A single intravenous injection of L-[ 3H]fucose, a specific glycoprotein precursor, was given to young 35-45 g rats which were sacrificed at times varying between 2 min and 30 h later. Radioautography of over 50 cell types, including renewing and nonrenewing cells, was carried out for light and electron microscope study .At early time intervals (2-10 min after injection), light microscope radioautography showed a reaction over nearly all cells investigated in the form of a discrete clump of silver grains over the Golgi region . This reaction varied in intensity and duration from cell type to cell type . Electron microscope radioautographs of duodenal villus columnar cells and kidney proximal and distal tubule cells at early time intervals revealed that the silver grains were restricted to Golgi saccules . These observations are interpreted to mean that glycoproteins undergoing synthesis incorporate fucose in the saccules of the Golgi apparatus . Since fucose occurs as a terminal residue in the carbohydrate side chains of glycoproteins, the Golgi saccules would be the site of completion of synthesis of these side chains.At later time intervals, light and electron microscope radioautography demonstrated a decrease in the reaction intensity of the Golgi region, while reactions appeared over other parts of the cells : lysosomes, secretory material, and plasma membrane . The intensity of the reactions observed over the plasma membrane varied considerably in various cell types ; furthermore the reactions were restricted to the apical surface in some types, but extended to the whole surface in others .Since the plasma membrane is covered by a "cell coat" composed of the carbohydraterich portions of membrane glycoproteins, it is concluded that newly formed glycoproteins, after acquiring fucose in the Golgi apparatus, migrate to the cell surface to contribute to the cell coat . This contribution implies turnover of cell coat glycoproteins, at least in nonrenewing cell types, such as those of kidney tubules . In the young cells of renewing populations, e .g . those of gastro-intestinal epithelia, the new glycoproteins seem to contribute to the growth as well as the turnover of the cell coat . The differences in reactivity among different cell types and cell surfaces imply considerable differences in the turnover rates of the cell coats .2 5 8

show abstract

Quantitative variations in the disposition of the enteric surface coat in mouse jejunum

Cited by 15 publications

References 17 publications

Demonstration of the fuzzy surface coat of rat intestinal microvilli by freeze-etching.

Demonstration of the fuzzy surface coat of rat intestinal microvilli by freeze-etching.

Transport across endodermal cells of the chick yolk sac during early stages of development

Migration of Glycoprotein From the Golgi Apparatus to the Surface of Various Cell Types as Shown by Radioautography After Labeled Fucose Injection Into Rats

Contact Info

Product

Resources

About