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D G Russell

Publications and source records attributed to D G Russell.

At least 91 records · Page 5Linked to original sources
PubMed1992

Recombinant Escherichia coli express a defined, cytoplasmic epitope that is efficiently processed in macrophage phagolysosomes for class II MHC presentation to T lymphocytes.

Although the processing of soluble Ag for presentation to T cells has been extensively studied in vitro, similar studies of phagocytic Ag processing have been limited. We have developed an in vitro model system to study the ability of macrophages to process recombinant Escherichia coli strain HB101 with cytoplasmic or surface expression of the well characterized T cell epitope of hen egg lysozyme (HEL) 52-61. This epitope was expressed within full length HEL or within a fusion protein containing the HEL epitope. Phagocytosis of E. coli with cytoplasmic expression of HEL or the HEL fusion protein resulted in strong presentation of HEL(52-61) to T cells. Surface-conjugated HEL was processed with even greater efficiency. Processing required viable macrophages, was inhibited by cytochalasin D, and was achieved within 20 min of bacterial contact with the macrophages. Within this time span, phagosomes containing bacteria fused with lysosomes, and the bacteria were extensively degraded. Uptake of as few as four bacteria per macrophage produced an Ag-specific T cell response. We conclude that bacterial compartmentalization of the antigenic epitope (cytoplasmic vs surface) had some effect on its processing, but that phagocytic Ag processing organelles contain extensive capacity to degrade internalized bacteria and liberate intracellular Ag epitopes for recycling and presentation, consistent with a central role for phagolysosomes. Thus, future recombinant bacterial vaccines may be effectively designed with T cell epitopes expressed either on the surface or within the bacterial cytoplasm.

Animals↗
PubMed1992

Blood pressure in a random sample of the New Zealand population.

Blood pressures were measured as part of a health check in a randomly selected sample of the New Zealand population. One thousand, four hundred and ten men and 1605 women over 15 years were studied. Measurements were made by trained observers using the Hawksley Random Zero instrument. Systolic and diastolic pressures increased with age in men and women. There were 29% of men and 24% of women over the age of 45 with pressures over 160/95 mmHg of whom 24% of men and 33% of women were on treatment for hypertension. Of all subjects 9% of men and 12% of women were on treatment for hypertension. Systolic and diastolic pressures correlated significantly with body mass index, waist/hip ratio and skinfold measurements in men and women. The most significant correlation was with the body mass index. No regional or urban/rural differences were seen in systolic or diastolic pressures. A history of hypertension in the fathers of respondents related to blood pressures in the highest tertile of diastolic blood pressures in males, and systolic pressure of females. The association was not seen between mothers of respondents in respect of diastolic pressure.

Adult↗
PubMed1992

The Crl protein activates cryptic genes for curli formation and fibronectin binding in Escherichia coli HB101.

Curli are thin, coiled, temperature-regulated fibres on fibronectin-binding Escherichia coli. The subunit protein of curli was highly homologous at its amino terminus to SEF-17, the subunit protein of thin, aggregative fimbriae of Salmonella enteritidis 27655 strain 3b, suggesting that these fibres form a novel class of surface organelles on enterobacteria. E. coli HB101 is non-curliated and unable to bind soluble, iodinated fibronectin. The phenotypically cryptic curlin subunit gene, csgA, in HB101 is transcriptionally activated by expressing the cytoplasmic Crl on a multicopy plasmid. Transcriptional activation of csgA by Crl was observed after growth at 26 degrees C but not at 37 degrees C, even though crl transcription was not thermoregulated. A deletion of the 39 carboxy-terminal residues abolished Crl activity, whereas a deletion of 10 residues at the C-terminus did not, implying that a region between residue 93 and 122 in the 132-amino-acid-residue large Crl protein is required for activating curli expression in E. coli HB101. crl is a normal housekeeping gene in E. coli and it is suggested that its gene product may either be a DNA-binding protein affecting chromatin structure as has been suggested for histone-like protein H1 or interact with specific regulatory protein(s) controlling transcription of genes required for curli formation and fibronectin binding.

Amino Acid Sequence↗
PubMed1992

Intracellular trafficking and the parasitophorous vacuole of Leishmania mexicana-infected macrophages.

The continued success of Leishmania as an intramacrophage parasite is dependent on its ability to survive within an acidic intracellular compartment, resist degradation by lysosomal hydrolases, exploit the host cell as a source of nutrients, and avoid the macrophage's antigen-presenting capabilities. All these requirements are dependent on the properties of the parasitophorous vacuole in which Leishmania resides. This study shows that the vacuole possesses membrane proteins characteristic of a lysosome, and has MHC class II molecules. The trafficking of a variety of endocytic markers supports this finding. However, a temporal study up to 14 days post-infection indicates that, as it matures, the vacuole gains mannose 6-phosphate receptor, and becomes more accessible to endocytosed ligand, suggesting that the vacuole has functionally translocated from a lysosomal to late endosomal compartment. Endocytosed material was detected in the flagellar pocket and inside the amastigote, demonstrating parasite uptake of intra-vacuolar material. Careful analysis of amastigotes suggests that they avoid antigen presentation by their host cell by limiting the release of potential antigens. These findings significantly extend our understanding of the mechanisms employed by Leishmania to ensure its survival in the macrophage.

Animals↗
PubMed1991

Blood lipid levels in New Zealand.

OBJECTIVES: the study aimed to determine age and gender specific levels of lipids and lipoproteins in New Zealanders. Participants were randomly selected from 20 general electoral roles, and from a sample of 15-18 year olds. METHODS: plasma cholesterol, LDL cholesterol, HDL cholesterol and triglyceride levels were measured in 2941 men and women aged 15-99 years. RESULTS: mean (SD) plasma cholesterol was 6.0 (1.3) mmol/L in men and 6.1 (1.3) mmol/L in women. There was a marked variation in total cholesterol and calculated LDL cholesterol with age, and the pattern was different in men and women. There was also a considerable regional variation; levels tending to increase from north to south. Overall mean cholesterol levels adjusted for age and geographical distribution were 5.8 and 6.0 mmol/L for men and women respectively. CONCLUSION: the fact that approximately a third of the adult population in New Zealand under 65 years have cholesterol levels greater than 6.5 mmol/L indicates the need for effective diet and lifestyle changes to reduce the high rates of CHD.

Adolescent↗
PubMed1991

The interaction between CD8+ cytotoxic T cells and Leishmania-infected macrophages.

Leishmania is resident within the macrophages of its vertebrate host. In any intramacrophage infection, where the pathogen is present in a form capable of mediating cell to cell transmission, the contribution of a cytotoxic T cell response to protective immunity is questionable. This study presents data from an in vitro model designed to elucidate the outcome of an interaction between CD8+, cytotoxic T cells and infected macrophages. Experiments were conducted with an H-2d-restricted, cytotoxic CD8+ T cell clone and Leishmania parasites present in mixed macrophage cultures, with the parasites confined to either histocompatible BALB/c macrophages, or incompatible CBA macrophages. Initial experiments indicated that the viability of Leishmania was unaffected by the lysis of its host macrophage by cytotoxic T cells. However, extended experiments showed that the parasites were killed between 24 and 72 h. The same results were obtained regardless of whether the parasites were resident in the target, BALB/c, macrophages or the bystander, CBA, macrophages. Addition of neutralizing, anti-IFN-g antibody to the cultures ablated most of the leishmanicidal behavior, indicating that parasite death was attributable to macrophage activation, resulting from cytokine secretion from the T cells following the initial recognition event.

Animals↗
PubMed1991

Validation of the physical activity instrument for the Life in New Zealand national survey.

A physical activity recall instrument suitable for self-administration by the adult New Zealand population was devised and validated for 140 subjects selected randomly from urban electoral rolls. Validation used bootstrapping to compare correlations between subjective measures derived from the instrument, the Stanford 7-day recall questionnaire and other questionnaires, and objective measures derived from an exercise test. Subjective measures were grouped as measures of high intensity activity, low intensity activity, or total activity metabolism. The high intensity measures correlated moderately with each other (mean r = 0.39), but poorly with metabolism and low intensity measures (r = 0.16, -0.02, respectively). The mean correlation between the metabolism and low intensity groups (r = 0.26) was similar to those within these groups (r = 0.31, 0.25, respectively). Thus, the high intensity measures formed a group distinct from the metabolism and low intensity groups, which represented similar measures. The objective measures that correlated with high intensity measures (mean r = 0.25) are predominantly recognized risk factors for cardiovascular disease; these did not correlate with the metabolism or low intensity measures (mean r = 0.03, -0.07, respectively). Activity measures from the instrument had mean correlations with subjective and objective measures that equaled or surpassed those of the Stanford measures from the same group. The authors conclude that 1) population health studies that assay physical activity should include well-defined measures of high intensity activity, and 2) valid measures of physical activity in the New Zealand population are achievable with this instrument.

Adolescent↗
PubMed1991

Analysis of the human T cell responsiveness to purified antigens of Leishmania: lipophosphoglycan (LPG) and glycoprotein 63 (gp 63).

The responsiveness of peripheral blood lymphocytes from 15 cutaneous leishmaniasis patients and five healthy volunteers to purified surface antigens of Leishmania was studied. The following purified antigens were independently used as stimuli for lymphocyte proliferation in vitro: lipophosphoglycan of L. braziliensis, (Lb-LPG), lipophosphoglycan of L. mexicana (Lm-LPG), glycoprotein 63 of L. braziliensis (Lb-gp 63) and glycoprotein 63 of L. mexicana (Lm-gp 63). Among six patients tested with Lb-gp 63 and Lm-gp 63, two borderline responses and two positive responses were observed, respectively, all the others being negative. Lb-LPG and Lm-LPG induced positive responses in all patients tested (11 with Lb-LPG and five with Lm-LPG). A positive dose-response correlation was observed in the responses of the patients to both Lb-LPG and Lm-LPG. Significant differences (P less than 0.01) were found between the two groups (patients and healthy subjects) with regard to the responses to Lb-LPG. The proliferating cells after stimulation with Lb-LPG were shown to belong to the CD4+ T cell subset by flow cytometry. However, the following evidence suggests that the T cell responses were not induced by LPG itself but rather by protein contaminants in the LPG preparations: a highly purified Lb-LPG batch that had undergone additional purification induced positive responses in cells from only three out of six patients and a proteinase K-treated Lb-LPG batch did not stimulate any positive response among the same six patients.

Adult↗
PubMed1991

Monoclonal antibodies to Leishmania mexicana promastigote antigens. I. Secreted acid phosphatase and other proteins share epitopes with lipophosphoglycan.

The abundant surface glycolipid, lipophosphoglycan (LPG), of Leishmania promastigotes is composed of phosphosaccharide repeating units linked via a phosphosaccharide core to a conserved lyso alkylphosphatidylinositol membrane anchor. It is shown in this paper that monoclonal antibodies (mAbs) directed against LPG also react with an acid phosphatase secreted by L. mexicana promastigotes. Acid phosphatase purified by column chromatography (apparent Mr = 100,000) reacts in immunoblots with the anti-LPG mAb AP3 and another mAb, L3.13, which does not recognize LPG. mAb L3.13 was used to purify the enzyme by affinity chromatography. The resulting glycoprotein has the same molecular weight and binds AP3 on immunoblots. The secreted phosphatase is non-covalently associated with a high molecular weight, galactose-containing glycan or proteoglycan that is recognized by both AP3 and L3.13. In addition to acid phosphatase, other parasite proteins appear to be modified by LPG epitopes.

Acid Phosphatase↗
PubMed1991

Monoclonal antibodies to Leishmania mexicana promastigote antigens. II. Cellular localization of antigens in promastigotes and infected macrophages.

In the accompanying paper by Ilg et al., it was shown that Leishmania mexicana promastigotes covalently modify a secreted acid phosphatase and other proteins by carbohydrate epitopes characteristic for lipophosphoglycan (LPG). In this study, the reaction of the anti-LPG monoclonal antibodies (mAbs AP3 and L7.25) and of mAb L3.13, an antibody directed against an epitope present on the secreted acid phosphatase but not on LPG, with promastigotes and infected peritoneal macrophages is studied by immunofluorescence and immunoelectron microscopy. AP3 labels the surface, the flagellar pocket and intracellular structures in promastigotes, while L3.13 reacts predominantly with an antigen located in the flagellar pocket. Early after infection with promastigotes, but not amastigotes, AP3 or L7.25 transiently label epitopes at the surface of live macrophages. No L3.13-reactive material is detected at the surface of infected macrophages. In permeabilized, infected macrophages, AP3 heavily labels the surface of amastigotes and the lumen of the parasitophorous vacuole, while L3.13 reveals antigen in the flagellar pocket, intracellular vesicles of amastigotes, and components in the lumen of the parasitophorous vacuole. Possible mechanistic implications for Leishmania-macrophage interaction raised by these findings are discussed.

Animals↗
PubMed1991

The interface between the Leishmania-infected macrophage and the host's immune system.

The protozoan parasite Leishmania exploits the lysosomal compartment of the macrophages of its vertebrate host. Given that the macrophage is capable of killing the parasite if supplied with the correct stimulus from the host's immune system, the successful continuation of the infection is in the balance. This paper examines certain aspects of the Leishmania/macrophage interplay, with particular emphasis on the nature of defined protective antigens, and of the interface between the infected macrophage and the host's immune system.

Animals↗
PubMed1990

Lipophosphoglycan from Leishmania mexicana promastigotes binds to members of the CR3, p150,95 and LFA-1 family of leukocyte integrins.

The abundant surface glycolipid, promastigote lipophosphoglycan (LPG), of Leishmania promastigotes was isolated and reconstituted onto the surface of hydrophobic silica beads. These beads bound to both macrophages and monocytes, suggesting that phagocytes possess a receptor(s) capable of recognizing LPG. LPG beads were unable to bind to macrophages isolated from individuals with a genetic deficiency in the CD18 complex of leukocyte integrins (CR3, p150,95, and LFA-1), suggesting that one or more of these receptors were required for binding of LPG. Individual members of the CD18 complex were depleted from macrophages by plating cells on surfaces coated with anti-receptor mAb. These experiments indicated that CR3 and p150,95 from the CD18 complex, were the predominant mediators of attachment of LPG. The phagocyte receptor CR3 expresses two distinct binding sites, one that binds peptide ligands, such as C3bi, and a second site, that recognizes bacterial LPS. Antibody inhibition experiments and competition binding studies with synthetic peptides and soluble LPG indicated that LPG is recognized by the nonpeptide, or "LPS" binding site on CR3.

Animals↗
PubMed1990

Leishmania mexicana mexicana gp63 is a site-specific neutral endopeptidase.

Leishmania mexicana, like other species of the genus, has a major 63-kDa surface glycoprotein (gp63) that is an active protease. Reports differ as to whether gp63 is a neutral or an acidic protease. Using three radiolabeled synthetic peptide substrates, gp63 purified from L. m. mexicana is most active at pH 6.5-7.5, in three different buffer systems, and appears to be a sequence-specific endopeptidase. The full extent of sequence specificity is undetermined, but these experiments suggest a strong preference for cleavage at serine or threonine residues. In common with other metalloproteases, the cleavage is on the amino side of the recognition residue.

Amino Acid Sequence↗
PubMed1990

Characterization of a cDNA encoding a cysteine-rich cell surface protein located in the flagellar pocket of the protozoan Trypanosoma brucei.

We have characterized a cDNA encoding a cysteine-rich, acidic integral membrane protein (CRAM) of the parasitic protozoa Trypanosoma brucei and Trypanosoma equiperdum. Unlike other membrane proteins of T. brucei, which are distributed throughout the cell surface, CRAM is concentrated in the flagellar pocket, an invagination of the cell surface of the trypanosome where endocytosis has been documented. Accordingly, CRAM also locates to vesicles located underneath the pocket, providing evidence of its internalization. CRAM has a predicted molecular mass of 130 kilodaltons and has a signal peptide, a transmembrane domain, and a 41-amino-acid cytoplasmic extension. A characteristic feature of CRAM is a large extracellular domain with a roughly 66-fold acidic, cysteine-rich 12-amino-acid repeat. CRAM is conserved among different protozoan species, including Trypanosoma cruzi, and CRAM has structural similarities with eucaryotic cell surface receptors. The most striking homology of CRAM is to the human low-density-lipoprotein receptor. We propose that CRAM functions as a cell surface receptor of different trypanosome species.

Amino Acid Sequence↗
PubMed1990

Blood pressures in a random sample of the New Zealand population: preliminary data from the life in New Zealand survey.

Blood pressures (BPs) were measured as part of a health check in a randomly selected sample of the New Zealand population in the Life in New Zealand survey. A total of 1,410 men and 1,605 women over 15 years of age were studied. Measurements were made by trained observers using the Hawksley random zero instrument. Systolic BP (SBP) and diastolic BP (DBP) increased with age in men and women. There were 29% of men and 24% of women over the age of 45 years with BPs over 160/95 mm Hg, of whom 24% of men and 33% of women indicated they were on treatment for hypertension. No regional or urban/rural differences were seen in either SBPs or DBPs. A history of hypertension in the fathers of respondents related to BPs in the highest tertile of SBPs in males, and SBPs in females. The association was not seen between mothers of respondents, except for DBP in women respondents.

Adolescent↗
PubMed1989

Genes encoding the major surface glycoprotein in Leishmania are tandemly linked at a single chromosomal locus and are constitutively transcribed.

The major surface glycoprotein of Leishmania, gp63, is encoded by a small multi-gene family of tandemly linked genes which map to a single chromosome. For Leishmania major, there are five 3.1 kilobasepair (kb) direct repeat units which include a 1.8-kb open reading frame and a 1.3-kb intergenic or spacer region. In addition, there is a single gene copy linked as a direct repeat but separated from the tandem array of gp63 genes by about 8 kb. The restriction enzyme map of the repeat unit is highly conserved among the gene copies. The regions which flank the tandemly repeated genes diverge outside of the 3.1-kb repeat unit. Transcription of the gp63 gene locus is constitutive as the 3-kb transcript was present in promastigotes as well as in amastigotes. A minor 6-kb gp63 gene transcript was also detected in Northern blot analysis which could signify the transcription of the genes as a polycistronic or multigene precursor RNA.

Animals↗