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Biomedical subjects

E Higgins

Publications and source records attributed to E Higgins.

16 recordsLinked to original sources
PubMed1991

Increased UDP-GlcNAc:Gal beta 1-3GaLNAc-R (GlcNAc to GaLNAc) beta-1, 6-N-acetylglucosaminyltransferase activity in metastatic murine tumor cell lines. Control of polylactosamine synthesis.

Malignant transformation of rodent cell lines by polyoma virus and by activated ras genes is associated with increased UDP-GlcNAc:Man alpha-R beta-1,6-N-acetylglucosaminyltransferase V (GlcNAc-transferase V) activity and it product -GlcNAc beta 1-6Man alpha 1-6Man beta 1-branched Asn-linked oligosaccharides. In this report, we have compared beta 1-6GlcNAc branching of core O- and N-linked oligosaccharides in three experimental models of malignancy, namely (a) rat2 fibroblasts and their malignant T24H-ras-transfected counterpart; (b) benign SP1 mammary carcinoma cells and two metastic sublines of SP1; and (c) the metastatic MDAY-D2 lymphoma cell line and its poorly metastatic glycosylation mutant KBL-1. In addition to the previously reported increase in GlcNAc-transferase V activity, UDP-GlcNAc:Gal beta 1-3GalNAc alpha-R (GlcNAc to GalNAc) beta-1,6-N-acetylglucosaminyltransferase (core 2 GlcNAc-transferase, EC 2.4.1.102) activity was found to be elevated by 70% in the malignant rat2 and SP1 cell lines while several other glycosyltransferase activities were not significantly different. The action of core 2 GlcNAc-transferase followed by beta 1-4Gal-transferase provides an N-acetyllactosamine antenna that can be extended with polylactosamine (i.e. repeating Gal beta 1-4GlcNAc beta 1-3) provided UDP-GlcNAc:Gal beta-R beta 1-3GlcNAc-transferase (GlcNAc-transferase) (i)) activity is present. Polylactosamine content in microsomal membrane glycoproteins was quantitated by labeling the GlcNAc termini resulting from the action of Escherichia freundii endo-beta-galactosidase with bovine galactosyltransferase/UDP-[3H] Gal. Glycopeptidase F- sensitive and -insensitive fractions were measured to assess the N- and O-linked components. In the SP1 tumor model, the metastatic sublines showed increased core 2 GlcNAc-transferase and GlcNAc-transferase V activities but no change in GlcNAc-transferase (i) activity, yet polylactosamine was increased in both O- and N-linked oligosaccharides. In rat2 cells, down-regulation of GlcNAc-transferase (i) following transformation was associated with decreased polyactosamine even though core 2 GlcNAc-transferase and GlcNAc-transferase V were elevated in the cells. Finally, a 3-fold decrease in GlcNAc-transferase V in KBL-1, the glycosylation mutant of MDAY-D2 cells, resulted in complete loss of polylactosamine in N-linked but no change in O-linked polylactosamine content. These results suggest that, provided GlcNAc-transferase (i) is not limiting, the beta 1-6-branching enzymes core 2 GlcNAc-transferase and GlcNAc-transferase V regulate the levels of polyactosamine in O- and N-linked oligosaccharides, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Sugars↗
PubMed1991

Characterization of O-linked oligosaccharide biosynthesis in cultured cells using paranitrophenyl alpha-D-GalNAc as an acceptor.

Aryl-N-acetyl-alpha-galactosaminides (aryl-GalNAc) are acceptor substrates for UDP-Gal:alpha-GalNAc beta 1-3 galactosyltransferase and, in vivo, aryl-GalNAc have been shown to inhibit O-linked oligosaccharide biosynthesis (Kuan et al., J. Biol. Chem. 264, 19271, 1989). Since aryl-GalNAc, appears to enter viable cells and serve as an acceptor for O-glycosylation enzymes, the recovery and characterization of the aryl-oligosaccharides from cell culture medium may reflect cellular pattems of O-glycosylation. To pursue this possibility, the following paranitrophenyl-linked oligosaccharide standards were enzymatically synthesized and characterized by 1H-NMR: Gal beta 1-3(GlcNAc beta 1-6)Gal-NAc alpha-pNp; Gal beta 1-3(Gal beta 1-4GlcNAc beta 1-6)GalNAc alpha-pNp; SA alpha 2-3Gal beta 1-3(SA alpha 2-3Gal beta 1-4GlcNAc,beta 1-6)GalNAc alpha-pNp; SA alpha 2-3Gal beta 1-3GalNAc alpha-pNp. As a model system, MDAY-D2 lymphoid tumour cells were cultured for various periods in medium containing 2 mM GalNAc alpha-pNp. The secreted aryl-oligosaccharides were separated by Biogel P2 chromatography and DEAE HPLC, followed by further fractionation of the disialyl oligosaccharides on an Ultrahydrogel HPLC column. Absorbance of the paranitrophenyl aryl constituent at 303 nm allowed detection at the 10 pmol level and provided a relatively specific means of following the oligosaccharides. MDAY-D2 cells produced disialylated aryl-oligosaccharides at a rate of 20 pmol/h/10(6) cells with a half-time of transit to the cell surface of 13.6 min, a rate consistent with their movement from the Golgi to the cell surface by bulk flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylglucosamine↗
PubMed1991

Malignant melanoma--a review: early diagnosis is the key.

The face of malignant melanoma is changing. The incidence is rising, and the disease is tending to affect a younger age group. Publicity about the disease is intense, and the trend is towards earlier diagnosis. Early diagnosis is essential, as the only effective treatment remains surgical excision, which is curative for thin lesions.

Adult↗
PubMed1990

Delta Lys120, a mutation which destabilizes the ribosome-binding domain of ribosomal protein L7/L12.

Five-residue-long deletions centered on Ala63, Ala75, and Glu118 of ribosomal protein L7/L12 gave low mutant yields (5% or less) when the mutant genes were cloned in phage M13mp18 and controlled by the L10 promotor. Deletions of Glu118-Lys120 or Lys120 (the COOH-terminus of L7/L12) gave higher mutant yields, up to 50% with L7/L12 delta Lys120. L7/L12 delta Lys120 was not preferentially found in the S100 and not preferentially removed by LiCl washing, but was preferentially extracted from 70S ribosomes in the presence of 28-35% ethanol in 0.25-0.5 M NH4Cl. It follows that delta Lys120 destabilizes the ribosome-binding domain of ribosomal protein L7/L12 in an ethanol-containing solvent, which raises the question whether Lys120 is part of the ribosome-binding domain of L7/L12 during some step of protein synthesis or whether it is essential to preserve the conformation of the physiological ribosome-binding domain under structurally stressful conditions.

Amino Acid Sequence↗
PubMed1989

Relapse rates in moderately severe chronic psoriasis treated with cyclosporin A.

Seventeen patients with chronic psoriasis were given cyclosporin A (CsA) 5 mg/kg per day. Twelve patients cleared within 3 months and their relapse rate, 41% at 6 months, was not significantly different from that previously reported with dithranol or PUVA. This pilot study also suggests that continuing CsA for up to 4 weeks after clinical clearance confers no advantage with regard to relapse. Significant adverse effects on renal function and blood pressure did not occur.

Adult↗
PubMed1989

Altered expression of leucocyte sialoglycoprotein in Wiskott-Aldrich syndrome is associated with a specific defect in O-glycosylation.

The Wiskott-Aldrich syndrome (WAS) is an X-linked immune deficiency disorder characterized clinically by both lymphocyte and platelet dysfunction. Studies of WAS T lymphocytes have revealed deficient or defective cell surface expression of the highly O-glycosylated leucocyte sialoglycoprotein CD43. To further elucidate the basis for, and functional relevance of, CD43 modifications on WAS lymphocytes, we have studied lymphocytes from two WAS patients with regard to membrane glycoprotein profile and mitogen-induced proliferative responses. CD43 was found to be either absent or altered in size on peripheral blood lymphocytes and lectin-stimulated T cells from both patients. Compared with control cells, the WAS lymphocytes displayed reduced, but measurable proliferative responses to lectins and neuraminidase/galactose oxidase, and virtually no response to periodate, a mitogenic agent which targets sialic acid residues on membrane glycoproteins such as CD43. Analysis of activities of three glycosyltransferases involved in O-glycosylation revealed marked reduction in the level of activity of UDP-N-acetylglucosamine: Gal beta 1-3GalNAc-R beta-1,6-N-acetylglucosamine (beta-1,6-GlcNAc) transferase in one WAS patient and no detectable activity of this enzyme in a second. beta-1,6-GlcNAc transferase activity has recently been shown to increase during T cell activation coincident with changes in the O-linked glycans on CD43. A selective reduction of this glycosyltransferase in WAS lymphocytes suggests that O-linked oligosaccharides may be important to the structure of membrane glycoproteins involved in lymphocyte activation.

Cell Division↗
PubMed1988

Translational coupling between the ilvD and ilvA genes of Escherichia coli.

The hypothesis that translation of the ilvD and ilvA genes of Escherichia coli may be linked has been examined in strains in which lacZ-ilvD protein fusions are translated in all three reading frames with respect to ilvD. In these strains, the nucleotide sequence was altered to obtain premature termination of ilvD translation, and in one strain translation termination of ilvD DNA occurred two bases downstream of the ilvA initiation codon. In the wild-type strain, the ilvD translation termination site was located two bases upstream of the ilvA start codon. In each of the mutant strains, expression of ilvA, as determined by the level of threonine deaminase activity, was strikingly lower than in the wild-type strain. The data suggest that expression of ilvD and ilvA is translationally coupled. By inserting a promoterless cat gene downstream of ilvA, it was shown that the differences in enzyme activity were not the result of differences in the amount of ilvA mRNA produced.

DNA Mutational Analysis↗
PubMed1987

Investigations of factors influencing the prognosis of colon cancer.

Six hundred sixty patients from Downstate and Hackensack Medical Centers were restaged and reviewed to establish correlations with survival using Cox's proportional hazards model. Age, sex, tumor size, and total nodes examined in patients with involved nodes did not correlate with survival. Tumor depth, number of involved nodes, and total nodes examined in patients with uninvolved nodes did correlate with survival. Patients with metastatic invasion into an adjacent organ with uninvolved nodes had an excellent 5 year survival rate compared with patients who had full-thickness invasion into the serosa with uninvolved nodes. These observations need to be confirmed. The relationship of some of these factors to currently used staging systems has also been discussed.

Colonic Neoplasms↗
PubMed1978

Uncoupling activity of endogenous free fatty acids in rat liver mitochondria.

Changes in the respiratory control index (RCI) and ADP:O ratio were found to be related to alterations in the free fatty acids levels of rat liver mitochondria aging in 0.25 M sucrose- Tris buffer at 0 degrees C. Free fatty acid levels increased with time after isolation of mitochondria while a concomitant decrease in the RCI and ADP:O ratio occurred. The changes in free fatty acid levels corresponded with the reported increasing levels of phospholipase A activity in aged mitochondrial preparations. Washing these mitochondria with sucrose buffer containing 1% defatted bovine serum albumin (BSA) counteracted the aging effect on the RCI (E.G., 2.5 to 3.5) and reduced the free fatty acid levels (e.g., 50 to 16 nmol/mg protein). This reversible phenomenon could be repeated several times during the in vitro aging at 0 degrees C. Use of 125I-iodinated BSA showed that approximately 5 microgram BSA/mg mitochondria was adsorbed by the mitochondrial membranes during washing. These results indicate a direct correlation between the level of endogenous fatty acids and the uncoupling of mitochondrial oxidative phosphorylation. The mechanism of counteracting the aging effect by BSA involves the removal of some of the free fatty acids.

Adenosine Diphosphate↗
PubMed1977

The clinical diagnostic value of the carcinoembryonic antigen (CEA) in haematuria.

Plasma and urinary CEA levels in patients presenting with haematuria have been studied to assess whether they facilitate the differentiation between benign and malignant urothelial conditions. Plasma CEA is of no diagnostic value although, if raised, it may suggest an invasive tumour. Urinary CEA levels are only of value in the absence of urinary infection; even then, only 37% of the cases with overt urothelial tumours had raised titres. A knowledge of the urinary CEA level, therefore, would seem to contribute little to the diagnosis of patients presenting with haematuria and all patients must still be investigated by the conventional techniques of urinary bacteriology, cytology, intravenous pyelography and cystourethroscopy.

Carcinoembryonic Antigen↗