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S K Powell

Publications and source records attributed to S K Powell.

28 records · Page 2Linked to original sources
PubMed1991

Thy-1 expresses two signals for apical localization in epithelial cells.

Recent work has shown that anchoring via glycosyl phosphatidylinositol (GPI) results in apical targeting for a variety of endogenous and transfected plasma membrane proteins expressed in epithelial cells. To further determine the correlation between GPI anchoring and apical localization, we expressed GPI-anchored and secretory forms of Thy-1 in Madin-Darby canine kidney cells by transfection. Native GPI-anchored Thy-1, normally expressed in thymocytes and neurons, was localized to the apical surface. A truncated form of Thy-1, lacking 22 out of 31 hydrophobic amino acids at the COOH-terminus, was also constructed; this deletion blocked attachment of the GPI anchor and resulted in apical secretion of Thy-1. In combination with previous results, our observations indicate that Thy-1 contains apical targeting information in its protein sequence as well as in the GPI anchor.

Animals↗
PubMed1991

New techniques lead to advances in epithelial cell polarity.

We have utilized cell surface biotinylation assays to study protein targeting signals and pathways in polarized epithelial cells. These studies have revealed that in MDCK cells, most proteins are sorted intracellularly and are targeted directly to the surface; in other cell types, protein targeting may be mediated by a selective retrieval event. Studies on both intact and permeabilized cells demonstrate that microtubules facilitate apical but not basolateral delivery. Recent transfection studies in MDCK cells have identified glycosyl phosphatidyl inositol (GPI) as an apical targeting signal; interaction of the GPI moiety with glycolipids preferentially expressed on the apical surface may mediate this process. Several proteinaceous basolateral targeting signals have also been recently described.

Animals↗
PubMed1990

The behaviour of human oral squamous cell carcinoma in cell culture.

This study examined the initial behaviour of 48 human oral squamous cell carcinomas (SCC) in cell culture. The early outcome of these cultures (contamination, absence of cell growth, epithelial cell senescence/fibroblast overgrowth, extended keratinocyte growth) did not reflect the clinical characteristics of the tumours of origin. Four new human oral SCC cell lines were characterized more extensively. Each cell line was immortal, 3T3-independent, and expressed low degrees of anchorage independence (CFE less than 4 per cent). Two of the four cell lines were tumorigenic in athymic mice. All of the cell lines expressed keratin intermediate filaments and two showed weak co-expression of vimentin. A wide range of keratins were expressed by the tumour xenografts; cornified keratins (K1, K10) were only expressed in the absence of K19 and vimentin, and vice versa. The nuclear:cytoplasmic ratio and the degree of serum independence correlated with each other and with the STNMP clinical grading of the tumours of origin.

Adult↗
PubMed1989

Autopsy services for dementia patients.

Chiefs of Pathology of every nonfederal hospital in Maryland were surveyed to determine their hospitals' experience with autopsies of dementia patients. Few pathology services had extensive, ongoing experience with these postmortem examinations, and many hospitals lacked special histochemical techniques or a referral system to evaluate them. Problems exist in obtaining postmortem examinations for dementia patients, especially those who die outside facilities with Autopsy Services.

Aged↗
PubMed1988

Efficient targeting to storage granules of human proinsulins with altered propeptide domain.

In neuronal and endocrine cells, peptide hormones are selectively segregated into storage granules, while other proteins are exported continuously without storage. Sorting of hormones by cellular machinery involves the recognition of specific structural domains on prohormone molecules. Since the propeptide of insulin is known to play an important role in its three-dimensional structure, it is reasonable to speculate that targeting of proinsulin to storage granules would require a functional connecting peptide. To test this hypothesis, we constructed two mutations in human proinsulin with different predicted structures. In one mutation, Ins delta C, the entire C peptide was deleted, resulting in an altered insulin in which the B and the A chains are joined contiguously. In the other mutation, Ins/IGF, the C peptide of proinsulin was replaced with the unrelated 12-amino acid connecting peptide of human insulin-like growth factor-I; this substitution should permit correct folding of the B and A chains to form a tertiary structure similar to that of proinsulin. By several biochemical and morphological criteria, we found that Ins/IGF is efficiently targeted to storage granules, suggesting that the C peptide of proinsulin does not contain necessary sorting information. Unexpectedly, Ins delta C, which presumably cannot fold properly, is also targeted to granules at a high efficiency. These results imply that either the targeting machinery can tolerate changes in the tertiary structure of transported proteins, or that the B and A chains of insulin can form a relatively intact three-dimensional structure even in the absence of C peptide.

Cell Compartmentation↗
PubMed1987

The trans-most cisternae of the Golgi complex: a compartment for sorting of secretory and plasma membrane proteins.

The intracellular site for the sorting of proteins destined for regulated or constitutive pathways is presently unknown for any one cell. By immunoelectron microscopy, we directly followed the routes taken by a regulated hormone, insulin, and a constitutive protein, hemagglutinin. Both proteins are present in individual Golgi stacks where they appear randomly distributed throughout the cisternae. In contrast, the two proteins do not colocalize outside the Golgi area:insulin is concentrated in dense-core secretory granules, while hemagglutinin is found predominantly in clear 100-300 nm vesicles. These vesicles do not label significantly with an endocytic tracer, indicating that they are exocytic carriers for hemagglutinin. The site at which the two proteins diverge is the clathrin-coated, trans-most cisterna of the Golgi, where the packaging of proinsulin takes place.

Adrenocorticotropic Hormone↗
PubMed1985

Genetics of exopolysaccharide production by mucoid Pseudomonas aeruginosa.

The secretion of the exopolysaccharide, alginate, is believed to contribute to the predilection for persistence of P. aeruginosa in respiratory tract infections of cystic fibrosis patients. To understand more about the pathway of alginate biosynthesis, we have cloned a gene, alg-50, which is involved in alginate biosynthesis. The alg-50 gene was physically mapped on a DNA fragment from P. aeruginosa by deletion analysis and transposition mutagenesis. The alginate trait is unstable, and another clone was found which may contain genes involved in this phenomenon. The two uronic acid components in alginate can vary, and a gene was cloned which increases the L-guluronate concentration of alginate produced by P. aeruginosa.

Alginates↗
PubMedDate not supplied

Enhanced gene transfer to rabbit jugular veins by an adenovirus containing a cyclic RGD motif in the HI loop of the fiber knob.

Gene therapy using recombinant adenoviral vectors represents a promising therapeutic tool to prevent vein graft stenosis, the main complication of coronary artery bypass grafting. However, the low transduction efficiency of vascular smooth muscle cells and endothelial cells (EC) is a potential limitation, presumably due to the low levels of functional adenovirus receptor (coxsackie:adenovirus receptor; CAR). Designing vectors specifically targeted to alpha(v) integrins is a strategy that might overcome the poor expression of CAR in vascular smooth muscle cells and EC. RGD, a receptor-binding motif that can interact with alpha(v) integrins, was inserted into the HI loop and at the C-terminus of the adenoviral fiber protein in two separate adenovirus vectors encoding a beta-galactosidase reporter gene. Av1nBgCRGD (C-terminus) and Av1nBgHIRGD (HI loop) were evaluated in EC in culture and in jugular vein organ culture. Transduction of primary rat and rabbit EC with Av1nBgHIRGD was significantly more efficient when compared to Av1nBgCRGD or Av1nBg. Transduction of mouse, rat and rabbit jugular veins in organ culture using Av1nBg showed that adenovirus-mediated gene expression was greatest in rabbit jugular veins compared to rat and mouse veins. Av1nBgHIRGD augmented gene expression approximately four-fold in rabbit jugular veins when compared to Av1nBg. Histochemical analysis showed that numerous EC but few smooth muscle cells were transduced at all vector concentrations. A substantial number of adventitial fibroblasts were transduced only at the highest vector concentrations of Av1nBgHIRGD. These findings demonstrate that integrin-targeted vectors allow for enhanced gene delivery to veins and strengthen the viability of adenoviral-mediated gene transfer of therapeutic transgenes to human veins prior to vein grafting.

Adenoviridae↗
PubMedDate not supplied

Job stress versus success factors for case management.

Job stress is all too common in the case management profession. Recognizing the signs and symptoms of stress and understanding its causes will help the nurse case manager minimize the deleterious effects of "burnout." The following article is an excerpt from the book. Nursing Case Management: A Practical Guide to Success in Managed Care. The author explores eight techniques to reduce stress and improve performance. The information can be used by the individual case manager or by supervisors and coworkers trying to help fellow case managers.

Adaptation, Psychological↗