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Biomedical subjects

L Warren

Publications and source records attributed to L Warren.

At least 55 records · Page 3Linked to original sources
PubMed1986

The internship--a prospective investigation of emotions and attitudes.

In a prospective survey for changes in emotions and attitudes of all medical interns of The Oregon Health Sciences University (N = 22) at six intervals during the 1982-1983 academic year, both positive and negative emotional changes were noted. Satisfaction with the decision to become a physician decreased during the period, a change that correlated directly with depression and fatigue and inversely with excitement and importance.

Attitude of Health Personnel↗
PubMed1985

Sialic acid lyase in differentiating murine teratocarcinoma cells.

N-Acetylneuraminic acid lyase (NAN-lyase) activity has been found to be much higher in the differentiated, murine parietal endodermal cell (PYS-2) in culture than in the related, undifferentiated embryonal teratocarcinoma cell (F9). The level of the enzyme rapidly increases in F9 cells exposed to an inducer of differentiation such as retinoic acid (RA) (10(-7) M). The level of the enzyme increases during log phase of growth of PYS-2 cells and decreases after the cells reach confluence. NAN-lyase from PYS-2 cells has been purified 365-fold and has been partially characterized. While most of the enzyme is freely soluble, at least 16% of the enzyme in PYS-2 cells is associated with the nucleus. The possible function of NAN-lyase in the cell and the significance of its marked elevation during growth and differentiation are discussed in view of the fact that the levels of NAN, neuraminidase, NAN transferases and the enzymes that synthesize and activate NAN, remain essentially unchanged during differentiation.

Animals↗
PubMed1985

Increased sialylation of complex glycopeptides during differentiation of mouse embryonal carcinoma cells.

High-molecular-weight, asparagine-linked glycopeptides--the lactosaminoglycans--are the major class of protein-bound carbohydrates synthesized by F9 cells; these cells synthesize only minor amounts of smaller glycopeptides. In contrast, F9ACC19, an endodermal cell line derived from F9 cells, synthesizes only minor amounts of lactosaminoglycans and a high proportion of smaller glycopeptides. Biochemical analysis of the small glycopeptides from F9ACC19 cells revealed that they are larger, bind less efficiently to concanavalin-A Sepharose and contain more sialic acid than their counterparts from F9 cells. Both cell types contain a small proportion of high-mannose glycopeptides. When synthesized by F9ACC19 cells, the glycopeptides of vesicular stomatitis virus show a high level of sialylation as compared to those synthesized by F9 cells, where few or no sialic-acid residues are present; this shows that the differences observed in total glycopeptides reflect differences in the glycosylation machinery of the cells. Consistent with this observation, sialyltransferase activity in vitro using a variety of acceptors was found to be markedly higher in F9ACC19 than in F9 cells, while galactosyltransferase activity was reduced several fold in F9ACC19 cells. These data support the hypothesis that the increased sialyltransferase activity in endodermal differentiated F9ACC19 cells may block the terminal galactose residue of glycopeptides, thereby inhibiting the synthesis of lactosaminoglycans in these cells.

Animals↗
PubMed1983

Selective management of lower gastrointestinal bleeding.

The management of lower gastrointestinal bleeding has evolved from a number of technological advances allowing precise diagnosis and localization of the bleeding site. This study of 40 angiographically demonstrated lower gastrointestinal bleeding lesions reinforces much of the data indicating the diagnostic and therapeutic trends. Twenty-four patients had bleeding diverticula with angiographic demonstration in 11 patients. Seven cases of vascular ectasia were identified, and nine patients had a variety of significant bleeding sites other than the two main sites that were listed. Pitressin was useful for control of bleeding in six of seven diverticular patients but was less useful in the vascular ectasia group in which only one patient was actively bleeding. Total abdominal colectomy and segmental resection were successful in control of hematochezia in 24 of 25 operative cases. Sixteen patients did not require surgical treatment.

Aged↗
PubMed1983

Urine excretion of 5-S-cysteinyldopa and serum sialic acid as tumor markers in human melanomas.

This study examines 5-S-cysteinyldopa, which is a melanoma-associated marker, and sialic acid whose increase appears to be a common feature of numerous cancers. In spite of some interferences due to sun exposure, 5-S-cysteinyldopa seems a significant indicator of metastases; the difference between 46 metastasis-negative and 34 metastasis-positive melanomas is significant at P less than 0.001. Cerebral metastases give little or no increase. In contrast with the 75% of patients who keep normal 5-S-cysteinyldopa excretion, all melanoma patients have elevated sialic acid. No difference occurs between glycoprotein carbohydrates of controls and patients after pronase digestion and con A chromatography. The use of those two parameters in association is proposed to have a proper index of tumor burden or success of therapy.

Adult↗
PubMed1982

Similarity in the bound carbohydrate groups of glycoproteins from cells of several vertebrate classes.

The carbohydrate groups of the glycoproteins of human, hamster, chick, reptile and fish cells growing in culture have been fractionated in succession according to size (Sephadex G-50), affinity for concanavalin A, charge (DEAE-Sephadex) and by thin-layer chromatography. It was found that despite the complexity of the array of separable glycopeptides in each type of cell, most of these structures seemed to be common to all of the cells. This suggests that they have existed in a relatively stable state for several hundreds of millions of years throughout the evolution of the vertebrates.

Animals↗
PubMed1982

Variation of the carbohydrates of glycoproteins of cells growing on different surfaces.

The carbohydrate components of some glycoproteins of hamster cells differ as a function of their growth on various substrates; glass, plastic, or plastic coated with collagen. This observation is interpreted as an effect of the environment on cellular structure at the molecular level. The basis of the change and its possible significance are discussed.

Animals↗
PubMed1982

Decreased synthesis of high-molecular-weight glycopeptides in human promyelocytic leukemic cells (HL-60) during phorbol ester-induced macrophage differentiation.

The human promyelocytic leukemia ell line, HL-60, synthesized a class of high-molecular-weight (M.W. 5000 to 7000), N-linked glycopeptides as the major class of protein-bound carbohydrates. Small glycopeptides (M.W. 2500 to 3500), typical of most mammalian cells except erythrocytes, represented a minor component in these cells. The large glycopeptides were labeled efficiently with fucose, glucosamine, and galactose but only poorly with mannose. They were found not to be glycolipids, glycosaminoglycans, or mucin-type glycopeptides and were not susceptible to exoglycosidases, but they were partially degraded by endo-beta-galactosidases. These characteristics are similar to those of the large glycopeptides synthesized by erythrocytes, by another human myeloid leukemia cell line (K562), and by human and murine teratocarcinoma cells. High-molecular-weight glycopeptides predominated on another human myeloid leukemia cell line KG1, but they were expressed at low levels on both a human monocytic leukemia cel line (THP-1) and a human T-lymphoblastoid cell line (Jurkat). When HL-60 cells were induced to differentiate into macrophage-like cells with phorbol esters, the proportion of large glycopeptides decreased, and the production of small glycopeptides predominated. This shift was observed within the first several hr after exposure to phorbol esters and was temporally related to the acquisition of adherent properties by the induced cells. In contrast, when HL-60 cells were induced to differentiate into granulocytes by dimethyl sulfoxide, hypoxanthine, or retinoic acid, they continued to synthesize glycopeptides similar to uninduced cells. Human peripheral blood granulocytes synthesized primarily large glycopeptides, whereas monocytes and lymphocytes synthesized mostly small glycopeptides. These results indicate that the synthesis of high-molecular-weight glycopeptides is a property of human myeloid leukemia cell lines and that it persists throughout myeloid differentiation. A proportionate decrease in the synthesis of these large glycopeptidase is a part of the differentiation program for monocytes and macrophages.

Cell Adhesion↗
PubMed1981

Aortic smooth muscle cells contain vimentin instead of desmin.

The 10-nm filament subunit proteins of smooth muscle cells in the mammalian aorta were analyzed by immunofluorescence and by two-dimensional gel electrophoresis. Indirect immunofluorescence studies on frozen sections of aorta showed intense staining of the tunica media by antibodies to vimentin, whereas no reaction could be detected with antibodies to desmin. Crude preparations from the tunica media contain a protein with molecular weight and isoelectric point similar to those of vimentin. Desmin was not detected on these same two-dimensional gels. We conclude that aortic smooth muscle cells contain vimentin as the predominant form of 10-nm filament protein subunit, unlike other muscle cells in which desmin predominates. Other immunofluorescence results indicate that the aorta may differ from smaller blood vessels which appear to contain both desmin and vimentin.

Animals↗
PubMed1980

Glycosaminoglycans and other carbohydrate groups bound to proteins of control and transformed cells.

The membrane glycoproteins from control (BHK21/C13) and Rous sarcoma virus-transformed (C13/B4) baby hamster kidney cells labeled with D-[14C]- or D-[3H]glucosamine, respectively, were purified by means of polyacrylamide electrophoresis and gel electrofocusing. The homogeneity of the isolated glycoproteins was demonstrated by analysis of the NH2-terminal peptides. Some purified glycoproteins were found to be hybrid molecules in terms of the type of oligosaccharides they bear. The majority of the oligosaccharides (approximately 90%) bound on thee glycoproteins are N-glycosidically linked (Mr approximately 3000 to 5000). Another 5% appears to be small groups linked O-glycosidically to several adjacent or closely spaced amino acid residues. The remainder (5%) of the carbohydrate groups appears to be small, covalently bound glycosaminoglycans. This is the first report of hybrid molecules bearing glycosaminoglycans in the cell surface. The ratio of the types of oligosaccharides varies among different glycoproteins. There is slightly more glycosaminoglycan present on glycoproteins from malignant cells. A remarkably complex but similar array of N-glyucosidically linked oligosccharides is bound to different individual membrane glycoproteins. Each individual polypeptide must contain only a small number of the total observed carbohydrate groups, i.e. the carbohydrate groups on individual polypeptides are grossly heterogeneous. This implies that purification is based largely on the characteristics of the polypeptide, and that overall charge and size of the carbohydrate groups are relatively constant in a single population of glycoproteins. Our results suggest that the differences between the carbohydrate groups derived from glycoproteins from control and transformed cells are mainly quantitative.

Animals↗
PubMed1980

Comparison of glycopeptides from control and virus-transformed baby hamster kidney fibroblasts.

Glucosamine-labeled glycopeptides from control and virus-transformed BHK fibroblasts were characterized by size, lectin affinity, charge, and composition. As already demonstrated, on the basis of elution position on a column of Sephadex G-50, transformed cells contained a greater proportion of large glycopeptides than did control cells. Transformed cells also contained a larger proportion of glycopeptides which do not bind to Con A-Sepharose. By sequential chromatography on Sephadex G-50, Con A-Sepharose, and DEAE-Sephadex, approximately 40 individual peaks were partially or completely resolved. If sialic acid was removed from the glycopeptides prior to analysis by ion-exchange chromatography, 95% of the glycopeptides from control cells and 85% of the glycopeptides from transformed cells were no longer bound by DEAE-Sephadex. It was concluded that the DEAE-Sephadex elution properties of the glycopeptides are determined almost entirely by the sialic acid content of the molecules. A comparison of the profiles of control and transformed cell glycopeptides simultaneously eluting from columns of DEAE-Sephadex revealed that the differences between the two cells were largely quantitative; however, the possibility of the existence of qualitative differences as well cannot be excluded. In particular, there was one component present on the surface of transformed cells that was virtually absent in control cells. It was degraded by nitrous acid hydrolysis and heparinase and appeared to be heparan sulfate like material. After fractionation, each isolated glycopeptide population was analyzed for carbohydrate and, in some cases, amino acid content. The apparently larger glycopeptides, group A, the dominant population in transformed cells, were found to contain 3 to 4 mannose residues/glycopeptide when the sugars were normalized to sialic acid content. On the basis of the same criteria, group B glycopeptides contained 4-6 mannose residues/glycopeptide. The carbohydrate and amino acid compositions of the glycopeptides from transformed cells were, with a few exceptions, similar to those from control cells. Some isolated glycopeptides appeared to contain both O-glycosidic anad N-glycosidic linkages on the same oligopeptide.

Amino Acids↗