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R C Wagner

Publications and source records attributed to R C Wagner.

At least 37 records · Page 2Linked to original sources
PubMed1984

High-voltage electron microscopy of capillary endothelial vesicles.

Conventional electron microscopy of thin sections through capillary walls is inadequate to discern the relationships between endothelial vesicles and their association with the cell surface. High-voltage electron microscopy of thick sections through diaphragm muscle capillaries has been employed to visualize the three-dimensional structure of the vesicular system. Stereopairs of thick sections provide for direct three-dimensional observations of samples several vesicle diameters deep. A variety of simple and compound vesicular forms are present but not all are conjoined or maintain connections with the endothelial cell surface. This contributes to the concept of a dynamic interaction between free and attached vesicular structures where fission and fusion events compartmentalize and reconnect repeatedly. Such interactions would provide for a discontinuous pathway across the capillary wall but with a higher degree of complexity than a simple shuttling mechanism.

Animals↗
PubMed1983

Endocytosis and exocytosis of transferrin by isolated capillary endothelium.

Vesicular transport of solutes across capillary walls may be regulated by specific solute-endothelial interactions. Little data is available on the vesicular transport of serum proteins which may transit the capillary wall in situ. Capillaries were isolated from epididymal fat and incubated in fluorescent-labeled transferrin and radiolabeled sucrose. Endocytosis and exocytosis of these tracers were quantitated on a picomolar basis over timed intervals and standardized against the amount of endothelial DNA present in the isolate. The rate of vesicular endocytosis of transferrin was 6-7 times greater than that of sucrose indicating a mechanism of selection for transferrin. Endocytosis as a function of external concentration exhibited complex kinetics for transferrin that was consistent with an adsorptive component and a fluid component. Sucrose uptake appeared to be simple fluid endocytosis but with a rate-limiting concentration at 500-600 microM. Vesicular exocytosis of both solutes from preloaded capillaries appeared to occur more rapidly than their endocytosis. This was probably not due to different rates of filling and emptying of attached vesicles nor to an intrinsic difference in rates of vesicle interiorization and refusing with the plasma membrane. Different rates of endocytosis and exocytosis may only be apparent since exocytosis of marker before the capillaries reach ingestion equilibrium would reduce the measured uptake rate.

Animals↗
PubMed1980

Isolation and characterization of brain endothelial cells: morphology and enzyme activity.

Microvessels were isolated from rat brain using a double collagenase treatment which removed the endothelial basement membranes. The isolate was characterized by intact luminal and abluminal membranes and an absence of pericytes and astrocyte membranes. Minimal contamination by 5'-nucleotidase, an enzyme believed exclusively localized within the plasma membranes of neuroglia, established the purity of the isolated microvessels. Enrichment of alkaline phosphatase and gamma-glutamyl transpeptidase activity in microvessel preparations supports the endothelial localization of these enzymes.

5'-Nucleotidase↗
PubMed1975

Cytological differentiation in the uropygial gland.

Ultrastructural changes were studied in the cells undergoing secretory differentiation in zone I of the tubules of the uropygial gland of White Plymouth Rock chickens. A layer of basal cells and four secretory stages are recognized as the cells migrate from the periphery to the lumen of tubules and progressively elaborate a secretion product. Basal cells, containing rough endoplasmic reticulum and free ribosomes, rest on the basement membrane and are the source from which secretory cells arise. Dilated perinuclear cisternae and the proliferation of smooth endoplasmic reticulum in the form of vesicles, invaginated sacs and cusp-shaped cisternae indicate the onset of lipgenesis in stage I cells. The perinuclear cisternae are more dilated and the endoplasmic reticulum is composed on saccules and cisternae in stage II cells. Stage III cells are characterized by concentric lamellae of endoplasmic reticulum surrounding secretory droplets. Dilated cisternae of endoplasmic reticulum and secretory droplets both contain a reticular substance. The perinuclear cisternae of stage III cells have returned to normal dimensions. Large mature lucent secretory droplets, lined with electron-dense material, fill the cytoplasm ostage IV cells which degenerate and release their secretory product into the tubule lumen. Spherical membrane-bound compartments containing a mottled substance of moderate electron density occur in basal cells and all subsequent secretory stages. These mottled bodies are surrounded by saccules of endoplasmic reticulum in stage II cells and are intimately associated with secretory droplets in stage III cells, but there is no evidence that they give rise to secretory droplets and their role in secretory differentiation is unknown.

Animals↗