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Biomedical subjects

D Stetson

Publications and source records attributed to D Stetson.

8 recordsLinked to original sources
PubMed2001

Regulation of CD1 function and NK1.1(+) T cell selection and maturation by cathepsin S.

NK1.1(+) T cells develop and function through interactions with cell surface CD1 complexes. In I-A(b) mice lacking the invariant chain (Ii) processing enzyme, cathepsin S, NK1.1(+) T cell selection and function are impaired. In vitro, thymic dendritic cells (DCs) from cathepsin S(-/-) mice exhibit defective presentation of the CD1-restricted antigen, alpha-galactosylceramide (alpha-GalCer). CD1 dysfunction is secondary to defective trafficking of CD1, which colocalizes with Ii fragments and accumulates within endocytic compartments of cathepsin S(-/-) DCs. I-A(k), cathepsin S(-/-) mice do not accumulate class II-associated Ii fragments and accordingly do not display CD1 abnormalities. Thus, function of CD1 is critically linked to processing of Ii, revealing MHC class II haplotype and cathepsin S activity as regulators of NK T cells.

Animals↗
PubMed1996

The CPR: getting physicians on board.

The CPR is a powerful concept. In practice, it collects and presents information. It communicates among patients, health plans and all who participate in the healthcare delivery process. The CPR's value extends from supporting better clinical decision making to helping save time and money while making the clinical practice more rewarding. To get the CPR working in your organization, you must ensure that, aside from all the data collection and analysis benefits it might provide healthcare planners, the system must actively support and reward the clinicians who use it every time they come into contact with it.

Computer Security↗
PubMed1991

Ultrastructural characteristics of a cell line derived from a melanotic neuroectodermal tumor of infancy.

Thin section and freeze-fracture transmission electron microscopy were used to examine and identify the cytoplasmic and membrane structures in a cell line derived from a melanotic neuroectodermal tumor of infancy (MNTI). The cultured cells had a uniform appearance after 70 population doublings characterized by long dendritic processes and evidence of melanin production. The cytoplasm contained numerous melanosomes in various stages of development, vesiculated rough endoplasmic reticulum, microfilaments and uncoated as well as coated vesicles. The membrane specializations included caveoli, coated pits, gap junctions, microfilaments, desmosome-like structures and lamellipodia. The ultrastructural appearance of the cultured MNTI cells was similar to features previously seen in electron micrographs of MNTI tumor specimens. However, correlated freeze-fracture and thin section micrographs permitted further identification of structures previously described. The MNTI cell line represents one of the cell types of the tumor and provides an opportunity for further study of the pathogenesis of this rare tumor.

Cell Line↗
PubMed1990

Cellular basis of an avian countercurrent multiplier system.

A kidney from the budgerigar (budgie, parakeet; Melopsittacus undulatus) is composed of cortical reptilian-type nephrons (without loops of Henle) and mammalian-type nephrons (with loops) grouped together in medullary cones. The loop of the mammalian-type nephrons has a descending segment composed of thin and highly interdigitated cells. These thin limb cells have few mitochondria (15% of cell volume), undetectable Na+,K(+)-ATPase activity, and virtually no basolateral surface amplification. Prior to the hairpin turn, the descending limb thickens, but the cells continue to lack basolateral amplification. Cells just prior to and within the hairpin turn resemble cells of the entire ascending limb. These cells are thick (there is no thin ascending segment in the avian loop), with extensive infoldings of the basolateral membrane surrounding numerous mitochondria (45% of cell volume). The area of basolateral membrane is 25 times that of the apical membrane. The basolateral membrane (but not the apical membrane) is enriched in Na+,K(+)-ATPase activity. The structure of the avian mammalian-type nephron (as epitomized by the budgie nephron) and the fact that NaCl accounts for over 90% of the osmotic activity of avian urine leads to the conclusion that the countercurrent multiplier of the avian kidney functions by active NaCl transport from the entire ascending limb. No explanation is offered for the transport specializations found in the thick descending segment of the loop, just prior to the hairpin turn.

Animals↗
PubMed1988

Morphological heterogeneity of the rabbit collecting duct.

The localization of carbonic anhydrase by histochemistry, of Na-K-ATPase by immunocytochemistry and of rod-shaped intramembranous particles by freeze-fracture electron microscopy, was determined in the collecting duct of rabbits. In the cortical collecting duct (CCD), rod-shaped particles, which are abundant in intercalated cells were observed in both the apical and basolateral membrane of all intercalated cells examined. In the outer stripe of the outer medullary collecting duct (OMCDo) a high density of rod-shaped particles was found only in the apical membrane of intercalated cells. All cells of the inner stripe of the outer medullary collecting duct (OMCDi) had rod-shaped particles in the apical membrane but not in the basolateral membrane. As the collecting duct entered the inner medulla the density of rod-shaped particles decreased until they were virtually absent in the terminal segment. Na-K-ATPase, localized to the basolateral membrane, was more abundant in principal cells than in intercalated cells in the CCD. In the OMCDo, staining was equal in principal and intercalated cells. All cells of the OMCDi and the inner medullary collecting duct (IMCD) stained for Na-K-ATPase. Carbonic anhydrase in the CCD was localized to the cell membranes and cytoplasm of intercalated cells. Principal cells did not stain for carbonic anhydrase. A similar pattern was seen in the OMCDo. In the outer region of the OMCDi most cells did not stain for carbonic anhydrase, whereas in the inner region the apical and lateral membranes of all cells stained for carbonic anhydrase. Weak cytoplasmic staining was occasionally seen. A similar pattern was seen in the initial half of the IMCD, while the terminal half of the IMCD did not stain. In this study, the localization of enzymes and rod-shaped intramembranous particles associated with Na+, K+, and H+ transport shows both segmental and cellular heterogeneity, and correlates with the known transport properties of tubule segments. The distribution of these enzymes and rod-shaped intramembranous particles is different in rabbits and rats, and may explain some of the functional differences between homologous segments in these species.

Animals↗
PubMed1987

Hand-wrist disorders among investment casting plant workers.

A survey of the prevalence of chronic soft tissue disorders of the hand and wrist was conducted 3 years after an initial survey of workers in a midwestern investment casting plant. The second survey of 136 (90%) of the original participants disclosed that (1) approximately 25% had different jobs in 1986, (2) 35% of those who had different jobs in 1986 reported transfers because of disorders, and (3) of those workers with the same job during both surveys, 11% reported temporary job changes due to disorders in the preceding 3 years. Workers with hand-wrist disorders in high-force and high-repetitive jobs tended to transfer out of these jobs more frequently than those in low-force-low-repetitive jobs. We failed to detect a relationship between ergonomic changes and change in prevalence of chronic hand-wrist disorders. This may be because the changes did not substantially alter the force and repetitiveness characteristics of the jobs.

Accidents, Occupational↗
PubMed1984

Cellular ultrastructure of Amphiuma distal nephron: effects of exposure to potassium.

The cellular ultrastructure of the renal distal nephron of the salamander, Amphiuma means, was examined by electron-microscopic and stereological techniques before and after exposure to potassium in the ambient environment. The distal nephron of Amphiuma is composed of three ultrastructurally distinct segments: early distal (or diluting segment), late distal, and collecting tubule. The early distal tubule structurally resembles the mammalian thick ascending limb of Henle's loop. Large renin-like granules are present in the smooth muscle cells of the afferent arteriole in the vicinity of the early distal tubule, suggesting the presence of a rudimentary juxtaglomerular apparatus. Late distal tubules are composed of one large cell type characterized by extensive basal membrane invaginations, often extending to the luminal membrane. Collecting tubules contain principal and intercalated cells that are ultrastructurally similar to cells of the mammalian cortical collecting tubule. Exposure to potassium had no effect on the ultrastructure of early distal cells but led to a sharp increase in the basolateral membrane surface density of principal cells in the collecting tubule (1.17 +/- 0.08-1.63 +/- 0.13 micron2/micron3). Potassium adaptation leads to a similar structural response in the mammalian collecting tubule. Since Amphiuma collecting tubules can be isolated and perfused in vitro and impaled with ion- and voltage-sensitive microelectrodes, the observed structural adaptation suggests that the collecting tubule may be a useful preparation to study the cellular mechanisms of potassium adaptation.

Animals↗