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D C Swartzendruber

Publications and source records attributed to D C Swartzendruber.

At least 37 records · Page 2Linked to original sources
PubMed1987

Presence of intact intercellular lipid lamellae in the upper layers of the stratum corneum.

The epidermal permeability barrier necessary for terrestrial life resides in the intercellular spaces of the stratum corneum and is composed of lipids. Membrane coating granules (MCGs), small intracellular organelles found in the uppermost layers of the living epidermis, contain stacks of membranous disks which are extruded into the intercellular space and undergo both biochemical and physical changes to form the lipid sheets which constitute this barrier. Using ruthenium tetroxide as a secondary fixative, we are able to demonstrate stacks of lamellae filling the intercellular spaces in the uppermost layers of the stratum corneum. The structure of these lipid lamellae is consistent with the proposed derivation of MCG lipid disks and also suggests that the lipid bilayer adjacent to the corneocyte cell envelope may be assembled from lipids not derived from MCGs.

Animals↗
PubMed1987

Composition and morphology of epidermal cyst lipids.

The contents of epidermal cysts were used as a source of desquamated human keratinocytes uncontaminated by sebaceous, subcutaneous, or bacterial lipids. Lipids extracted with chloroform:methanol mixtures included six series of ceramides (41% of the total extractable lipid), cholesterol (27%), cholesteryl esters (10%), fatty acids (9%), cholesteryl sulfate (1.9%), a novel class of ceramide esters (3.8%), and a sterol diester (0.9%). Electron microscopy revealed that the lipids in the cyst contents existed as multiple intercellular lamellae, as in stratum corneum. One lamella, adjacent to the horny cell protein envelope, was resistant to lipid extraction and is thought to represent covalently bound lipid on the outer surface of the keratinocyte. The results indicate that the degradation of intercellular lipid lamellae is not required for desquamation.

Ceramides↗
PubMed1987

Essential fatty acids and epidermal integrity.

The intercellular spaces of the stratum corneum contain multilamellar lipid sheets derived from the extruded contents of lamellar granules. In the absence of linoleic acid, lamellar granules appear empty, and only fragmentary extracellular sheets are found. This defective differentiation is attributable to substitution of oleate for linoleate in O-acylsphingolipids. Normally, linoleate is ester-linked to 30- to 34-carbon omega-hydroxyacids, which, in turn, are amide-linked to sphingosine. Acylglucosylceramides, bearing a beta-D-glucosyl moiety on the sphingosine, may provide the driving force for lamellar granule assembly. The omega-hydroxyacyl chains are long enough to span a lipid bilayer, while the linoleate inserts into an adjacent bilayer. This interaction could promote assembly of lamellar granules. It has also been proposed that acylceramides may stabilize the extracellular sheets by a similar mechanism. In addition, the horny cell has been found to possess a covalently bound lipid envelope consisting principally of omega-hydroxyacylsphingosines derived from O-acylsphingolipids.

Animals↗
PubMed1982

Establishment of two parental cell lines and three clonal cell strains from rat colonic carcinoma.

Two epithelial cell lines were established from separate pools of cells that were harvested by a sequential proteolytic treatment of a single specimen of rat transplantable colonic carcinoma. The cells were small (10-micrometer diameter) and cuboidal and displayed desmosomes and light junctions. Both cell lines grew rapidly with population-doubling times of 20 to 22 hr, were near diploid in chromosome number, contained A-2 and B-7 marker chromosomes, and were tumorigenic in rats. Each was distinguishable from the other by the shape of its cell clusters in monolayer culture, its serum requirement for growth, its modal chromosome number, and its karyotypic alterations. Undifferentiated cells, cystic cells, and vacuolated cells, but not mature mucous cells, were observed in monolayer cultures. Clonal cell strains mimic the morphological and growth properties of their respective parental cell line but display unique karyotypic alterations in addition to the A-2 and B-7 marker chromosomes.

Animals↗
PubMed1980

Mucous and argentaffin cells in colonic adenocarcinomas of tamarins and rats.

Primary and metastatic neoplasms of four naturally occurring colonic adenocarcinomas in the cotton-topped tamarin, Saguinus oedipus oedipus, and four chemically induced rat colonic adenocarcinomas were examined with light and electron microscopy. In each case, we observed mixtures of mucous and argentaffin cells in metastatic sites, proving that endocrine cells are an integral part of these tumors. The occurrence of mixed cell populations in metastases in both species suggests, but does not prove, that colonic tumor cells have the capacity for multi-directional differentiation and that neoplastic mucous and argentaffin cells in the colon have a common origin. We also observed mitotic figures in neoplastic argentaffin cells, confirming the observations of others that these cells can label with tritiated thymidine and divide.

Adenocarcinoma↗
PubMed1979

A morphometric study quantifying the mucus content of proliferating colonic epithelial cells.

We report a quantification of the maximum mucus accumulation in proliferating rat colonic epithelial cells. The proliferative potential was determined by radioautographic study of one-hour pulse exposures to tritiated thymidine, mucous content was determined by Periodic-acid Schiff (PAS) staining. We examined 55 labeled mucous cells in 0.5- to 1-micrometer serial sections. The maximum thecal and nuclear profiles of these cells were photographed and their surface areas were determined utilizing a coordinate sensor. The data were expressed as a theca-to-nucleus (T/N) ratio. The maximum (T/N) ratio for a labeled mucous cell was 3.0. We performed a similar analysis on 22 unlabeled mucous cells from upper crypt regions and surface epithelium to derive the range of (T/N) ratios for terminally differentiated mature mucous cells. The range of (T/N) ratios from these cells was from 4.8 to 16.4. Our study shows that proliferative potential of mucous cells is determined by the interrelationship between mucus accumulation and nuclear size.

Animals↗
PubMed1978

Spontaneous colonic adenocarcinoma in marmosets.

We find that colonic adenocarcinoma, which is an extremely rare neoplasm of all animals except man and carcinogen-treated rodents, occurs spontaneously in some marmosets. The cotton-topped Saguinus oedipus oedipus is particularly prone to develop it, but we have found it also at necropsy in Callimico goeldii (Goeldi's marmoset). Numerous metastases to regional lymph nodes develop. The cancers arise de novo in the mucosa and early invade the submucosa and lymphatic apparatus and paracolonic lymph nodes. These findings and the continuing occurrence of this cancer in our colony suggests that the marmoset may be the long-sought primate model for experimental intestinal carcinogenesis.

Adenocarcinoma↗
PubMed1976

A quantitative study of the subcellular localization of 67Ga.

This paper describes a quantitative procedure for the isolation of 67 Ga-binding granules (GBG) from normal rat liver and Morris 5123C hepatoma homogenates by a combination of rate and isopyknic density gradient zonal centrifugation. Another class of GBG has been found that is much smaller than the lysosomal GBG we have previously described. These smaller particles, or microvesicles, bind the largest portion of the 67Ga found in the hepatoma whereas, in the liver, the GBG lysosomes are the major binding component. Previously, we had shown that considerably more 67Ga is taken up in hepatoma than in liver (as percentage of administered dose per g of tissue). The preferential association of 67Ga with these microvesicles in the 5123C hepatoma may be indicative of a basic difference between normal and malignant tissue.

Animals↗
PubMed1970

Gallium-67 localization in rat and mouse tumors.

Various nonosseous tumors in mice and rats concentrate gallium-67-ESR-586 preputial gland carcinoma, P-1798 lymphosarcoma, C3H/ HeJ mammary tumor, AKR/J thymic lymphoma, R-3259 giant cell sarcoma, Walker-256 carcinosarcoma, and a new transplantable neoplasm of rats. This last tumor showed the greatest affinity for galliun. Viable tumor cells are mainly responsible for uptake of gallium-67; autoradiographic studies indicate it is chiefly located in tumor cytoplasm.

Animals↗