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Biomedical subjects

N Harris

Publications and source records attributed to N Harris.

At least 109 records · Page 6Linked to original sources
PubMed1992

Characterization of the murine macrophage mannose receptor: demonstration that the downregulation of receptor expression mediated by interferon-gamma occurs at the level of transcription.

The macrophage mannose receptor (MMR) is a 175-Kd cell-surface transmembrane glycoprotein that is expressed on tissue macrophages where it functions both to mediate the uptake of mannose-rich glycoproteins and as a phagocytic receptor for bacteria, yeasts, and other pathogenic microorganisms. In this report we describe the cloning of the full-length cDNA of the mouse macrophage mannose receptor and we investigate the level at which interferon gamma (IFN-gamma) downregulates mannose receptor expression. The latter is a marker of the functional state of the cell as high levels are expressed on resident and inflammatory macrophages, whereas cells activated by treatment with IFN-gamma have decreased-to-absent cell-surface mannose receptor expression. The murine MMR cDNA contains an open reading frame that predicts a protein of 1,456 amino acids. Transient expression of the protein in heterologous cells shows that this cDNA encodes a functional mannose receptor. The deduced amino acid sequence of this protein has an overall 82% homology with the human mannose receptor and as such, the ectodomain contains an N-terminus that is cysteine-rich followed by a fibronectin type II domain and eight carbohydrate recognition domains (CRDs). The ectodomain is linked to a hydrophobic transmembrane region and a 46-amino acid cytoplasmic tail. All of the eight CRDs are particularly well conserved, especially CRD4, which shows 92% homology with the equivalent region of the human protein. Steady-state levels of murine MMR mRNA were measured in the macrophage cell line J774E, which is known to express the protein at the cell surface. These levels were decreased by a 4- to 8-hour incubation with IFN-gamma, but were almost abolished by overnight treatment with this cytokine. Nuclear run-on experiments showed that IFN-gamma inhibits MMR gene transcription. Therefore, the regulation of mannose receptor expression by IFN-gamma provides a novel system in which to study the mechanisms by which this cytokine represses gene expression.

Amino Acid Sequence↗
PubMed1992

Interleukin 4 potently enhances murine macrophage mannose receptor activity: a marker of alternative immunologic macrophage activation.

Expression of the macrophage mannose receptor is inhibited by interferon gamma (IFN-gamma), a T helper type 1 (Th-1)-derived lymphokine. Interleukin 4 (IL-4), a Th-2 lymphocyte product, upregulates major histocompatibility class II antigen expression but inhibits inflammatory cytokine production by macrophages. We have studied the effect of IL-4 on expression of the macrophage mannose receptor (MMR) by elicited peritoneal macrophages. We found that recombinant murine IL-4 enhances MMR surface expression (10-fold) and activity (15-fold), as measured by the respective binding and degradation of 125I-mannose-bovine serum albumin. Polymerase chain reaction analysis of cDNAs from purified primary macrophage populations revealed that MMR, but not lysozyme or tumor necrosis factor alpha, mRNA levels were markedly increased by IL-4. The above effects were associated with morphologic changes. These data establish IL-4 as a potent and selective enhancer of murine MMR activity in vitro. IL-4 induces inflammatory macrophages to adopt an alternative activation phenotype, distinct from that induced by IFN-gamma, characterized by a high capacity for endocytic clearance of mannosylated ligands, enhanced (albeit restricted) MHC class II antigen expression, and reduced proinflammatory cytokine secretion.

Animals↗
PubMed1992

Temporal and spatial expression of a thiolprotease gene during pea ovary senescence, and its regulation by gibberellin.

Clones encoding a thiolprotease (tpp) have been isolated from a cDNA library of unpollinated, senescent pea ovaries and its pattern of expression during both ovary senescence and parthenocarpic development have been studied. The sequence of the tpp cDNA displays a high similarity with other plant and animal thiolproteases of the papain group. The homology is highest around the Cys-His of the active centre; a 109 amino acid sequence at the carboxy terminus was found to be homologous only to thiolproteases of plant origin; this part of the mRNA is also present in another pea mRNA that exhibits similar patterns of induction. tpp mRNA shows a temporal pattern of accumulation that precedes that observed for proteolytic activity. Such accumulation did not occur when ovaries were induced to grow parthenocarpically by gibberellic acid (GA) treatment; furthermore the initial low level of expression present in ovaries decreased after GA treatment, indicating that the gene is down-regulated by gibberellins. Spatially, tpp mRNA is localized mainly within the ovule and ovary vascular elements, and transiently within the endocarp of senescent ovaries. This pattern of expression precedes the development of the cytopathogenic effects observed as unpollinated ovaries undergo senescence.

Amino Acid Sequence↗
PubMed1992

Antiarrhythmic, electrophysiological and haemodynamic effects of prolonged oral dosing with Org 7797 in the anaesthetized rat.

The antiarrhythmic, electrophysiological and haemodynamic effects of chronic oral administration of Org 7797 ((16 alpha,17 beta)-17-methylamino-oestra-1,3,5(10)-triene-3, 16-diol-(Z)-2-butonedioate) were studied in rats. During dosing (10 mg kg-1 twice a day for 10 days) no effects on the electrocardiogram, monitored in conscious animals, were observed despite modest reductions (15-18%) in the maximum rate of depolarization of papillary muscle excised 1 or 6 h after completion of the dosing regime. Following anaesthesia, Org 7797 reduced the severity of arrhythmias induced by coronary artery occlusion and prevented the accompanying decrease in the ventricular fibrillation threshold (VFT) at 1 h after completion of dosing. By 6 h the effect on VFT had waned but protection against ischaemia-induced arrhythmias was retained despite a substantial decrease in Org 7797 plasma levels. Drug treatment did not modify arterial blood pressure, heart rate or stroke volume. We conclude that Org 7797 given chronically via the oral route exerts antiarrhythmic actions which may, at least in part, be due to sodium-channel block. In addition, our results suggest the presence of an active metabolite. The protective effects of Org 7797 were seen in the absence of electrocardiographic or haemodynamic changes suggesting that multiple oral doses of Org 7797 do not compromise normal cardiac function.

Action Potentials↗
PubMed1991

Gonadotropin-releasing hormone gene expression in MDA-MB-231 and ZR-75-1 breast carcinoma cell lines.

The presence of gonadotropin-releasing hormone (GnRH)-binding sites in human breast carcinomas and breast tumor cell lines as well as the demonstration of the inhibitory effects of GnRH analogues on the growth of these cells raised the possibility that GnRH is produced locally by breast tumor cells themselves. Immunoreactive GnRH was shown to be present in acetic acid extracts of cultured MDA-MB-231 and ZR-75-1 breast carcinoma cells. These extracts were separated by high-performance liquid chromatography and were analyzed by means of region-specific antisera with differing GnRH sequence specificities. A peak of GnRH which coeluted with synthetic mammalian GnRH in 2 different high-performance liquid chromatography systems was similarly detected by antisera directed at the NH2 terminus, at the middle portion and at the N and COOH termini together. The GnRH gene is expressed in these breast tumor lines, as determined by S1 nuclease protection assay, oligonucleotide primer extension studies, and polymerase chain reaction amplification of complementary DNA using oligonucleotides. The primer extension studies indicate that several forms of mRNA are present. The predominant form corresponds to the excision of intron I and the use of a start site about 60 bases upstream of intron I as in the human hypothalamus. Less usage is made of other start sites further upstream. Much larger species of mRNA were also present and correspond to the retention of intron I as in human placenta. The demonstration of GnRH gene expression and the presence of immunoreactive GnRH in mammary carcinoma cells known to have GnRH-binding sites and to be affected by GnRH analogues suggests that GnRH may serve an autocrine regulatory role.

Base Sequence↗
PubMed1991

The mitogenic effects of sera from psoriatic subjects on normal dermal fibroblasts: an absence of correlation with the clinical activity of psoriasis.

Serum was obtained from 21 normal and 22 psoriatic subjects, and the severity of skin disease in the psoriatic patients was recorded using the PASI score. The scores ranged from 1.8 to 51.0. The growth stimulatory effect of the sera on normal dermal fibroblasts in cell culture was assessed by measuring [3H]-thymidine uptake. Each serum was assessed at four concentrations (2,5, 10,20%). The psoriatic sera were more growth stimulatory than normal sera, but this difference was statistically significant (P less than 0.02) only at 20% serum concentration. Eleven of the 22 psoriatic serum samples had a mitogenic effect greater than the mean +/- SEM of all the normal sera; these sera were then from patients with PASI scores of 4.5-51.0. Six of these psoriatic subjects were recalled after 5 months; their PASI scores were reassessed, and the mitogenic effect of new serum samples was compared with that of the initial samples. All of these patients displayed a change in serum mitogenic effect, but this was not consistent with the change in severity of skin disease over the corresponding time period. In one subject, the severity of the psoriasis had increased marginally over the 5 months, while the mitogenic effect of her serum decreased significantly (mean counts of 43808 vs. 32660; P = 0.0029).

Adult↗