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Biomedical subjects

D G Russell

Publications and source records attributed to D G Russell.

At least 73 records · Page 4Linked to original sources
PubMed1994

Leishmania major: organization and conservation of genes encoding repetitive peptides and subcellular localization of the corresponding proteins.

Proteins containing tandemly repeating peptide sequences are characteristic of several parasite antigens. Previously it was reported that Leishmania major contain two genes, Lm20 and Lm39, consisting of two unrelated repeat sequences of 42 and 30 base pairs (bp), respectively. In present study L. major was shown to contain two genes that contained the Lm20 42-BP repeat sequence and that the 42-BP repeat sequence was highly conserved among both Old and New World Leishmania species. The two L. major genes varied in the number of 42-BP tandem repeat sequences with Lm20.1 containing over 100 repeat units while Lm20.2 contained only 8 repeat units. Furthermore, these two L. major genes were distinct with respect to the nonrepetitive sequence. The unrelated Lm39 30 BP tandem repeat was also shown to be highly conserved among Leishmania species. The subcellular localization of the proteins encoded by Lm20 42-BP repeat and the Lm39 30-BP repeat were determined by immunoelectron microscopy. Antibodies raised against synthetic peptides corresponding to the Lm39 30-BP repeat sequence reacted with proteins that localized to the endoplasmic reticulum and membraneous structures within the promastigote cytoplasm.

Amino Acid Sequence↗
PubMed1994

Characterization of polymer release from the flagellar pocket of Leishmania mexicana promastigotes.

Trypanosomatids contain a unique compartment, the flagellar pocket, formed by an invagination of the plasma membrane at the base of the flagellum, which is considered to be the sole cellular site for endocytosis and exocytosis of macromolecules. The culture supernatant of Leishmania mexicana promastigotes, the insect stage of this protozoan parasite, contains two types of polymers: a filamentous acid phosphatase (sAP) composed of a 100-kD phosphoglycoprotein with non-covalently associated proteo high molecular weight phosphoglycan (proteo-HMWPG) and fibrous material termed network consisting of complex phosphoglycans. Secretion of both polymers is investigated using mAbs and a combination of light and electron microscopic techniques. Long filaments of sAP are detectable in the lumen of the flagellar pocket. Both sAP filaments and network material emerge from the ostium of the flagellar pocket. While sAP filaments detach from the cells, the fibrous network frequently remains associated with the anterior end of the parasites and can be found in the center of cell aggregates. The related species L. major forms similar networks. Since polymeric structures cannot be detected in intracellular compartments, it is proposed that monomeric or, possibly, oligomeric subunits synthesized in the cells are secreted into the flagellar pocket. Polymer formation from subunits is suggested to occur in the lumen of the pocket before release into the culture medium or, naturally, into the gut of infected sandflies.

Acid Phosphatase↗
PubMed1994

Formation and intracellular localization of hepatitis C virus envelope glycoprotein complexes expressed by recombinant vaccinia and Sindbis viruses.

Hepatitis C virus (HCV) encodes two putative virion glycoproteins (E1 and E2) which are released from the polyprotein by signal peptidase cleavage. In this report, we have characterized the complexes formed between E1 and E2 (called E1E2) for two different HCV strains (H and BK) and studied their intracellular localization. Vaccinia virus and Sindbis virus vectors were used to express the HCV structural proteins in three different cell lines (HepG2, BHK-21, and PK-15). The kinetics of association between E1 and E2, as studied by pulse-chase analysis and coprecipitation of E2 with an anti-E1 monoclonal antibody, indicated that formation of stable E1E2 complexes is slow. The times required for half-maximal association between E1 and E2 were 60 to 85 min for the H strain and more than 165 min for the BK strain. In the presence of nonionic detergents, two forms of E1E2 complexes were detected. The predominant form was a heterodimer of E1 and E2 stabilized by noncovalent interactions. A minor fraction consisted of heterogeneous disulfide-linked aggregates, which most likely represent misfolded complexes. Posttranslational processing and localization of the HCV glycoproteins were examined by acquisition of endoglycosidase H resistance, subcellular fractionation, immunofluorescence, cell surface immunostaining, and immunoelectron microscopy. HCV glycoproteins containing complex N-linked glycans were not observed, and the proteins were not detected at the cell surface. Rather, the proteins localized predominantly to the endoplasmic reticular network, suggesting that some mechanism exists for their retention in this compartment.

Animals↗
PubMed1993

Effective immunization against cutaneous leishmaniasis with recombinant bacille Calmette-Guérin expressing the Leishmania surface proteinase gp63.

Leishmania parasites cause a spectrum of diseases that afflict the populations of 86 countries in the world. The parasites can survive within the lysosomal compartments of the host's macrophages, unless those macrophages are appropriately activated. Despite the fact that protective immunity can be induced by vaccination with crude parasite preparations, little progress has been made toward a defined vaccine for humans. In this study the gene encoding the Leishmania surface proteinase gp63 was cloned and expressed as a cytoplasmic protein in a bacille Calmette-Guérin (BCG) vaccine strain. BALB/c and CBA/J mice were inoculated with a single dose of recombinant BCG and challenged with infective Leishmania major or Leishmania mexicana promastigotes. Significant protection was observed in both mouse strains against L. mexicana and in CBA/J against L. major, whereas only a delay in L. major growth was seen in BALB/c mice. Recombinant BCG also engendered a strong protective response against challenge with amastigotes of L. mexicana, demonstrating that the induced immune response recognized the intracellular form of the parasite. The results support the view that recombinant BCG expressing gp63 may prove a useful vaccine for inducing protective cell-mediated immune responses to Leishmania species causing American cutaneous leishmaniasis.

Animals↗
PubMed1993

Disseminated tuberculosis in interferon gamma gene-disrupted mice.

The expression of protective immunity to Mycobacterium tuberculosis in mice is mediated by T lymphocytes that secrete cytokines. These molecules then mediate a variety of roles, including the activation of parasitized host macrophages, and the recruitment of other mononuclear phagocytes to the site of the infection in order to initiate granuloma formation. Among these cytokines, interferon gamma (IFN-gamma) is believed to play a key role is these events. In confirmation of this hypothesis, we show in this study that mice in which the IFN-gamma gene has been disrupted were unable to contain or control a normally sublethal dose of M. tuberculosis, delivered either intravenously or aerogenically. In such mice, a progressive and widespread tissue destruction and necrosis, associated with very high numbers of acid-fast bacilli, was observed. In contrast, despite the lack of protective immunity, some DTH-like reactivity could still be elicited. These data, therefore, indicate that although IFN-gamma may not be needed for DTH expression, it plays a pivotal and essential role in protective cellular immunity to tuberculosis infection.

Animals↗
PubMed1993

Ligand specificity of purified complement receptor type three (CD11b/CD18, alpha m beta 2, Mac-1). Indirect effects of an Arg-Gly-Asp (RGD) sequence.

We have purified CR3 to homogeneity by affinity chromatography on C3bi-Sepharose and elution with EDTA. C3bi-coated erythrocytes bound to this purified CR3, and binding was dependent on the concentration of both C3bi and CR3, as well as on temperature and the presence of divalent cations. Moreover, binding could be blocked by mAb against CR3 or C3bi and could be enhanced by the addition of integrin modulating factor-1. We used the purified CR3 to test whether several putative ligands of CR3 directly bound the receptor. The interaction of purified CR3 with fibrinogen, filamentous hemagglutinin of Bordetella pertussis, lipophosphoglycan and glycoprotein 63 of Leishmania mexicana, and lipopolysaccharide from Escherichia coli was confirmed. However the interaction of CR3 with zymosan or its major component, beta-glucan, was not observed in these assays. Previous studies showed that binding of C3bi to PMN could be blocked with Arg-Gly-Asp (RGD) containing peptides and were interpreted to indicate that the RGD sequence in C3bi interacts directly with CR3. We found, however, that RGD containing peptides were unable to block the interaction of C3bi with purified CR3, yet retained the ability to block binding of C3bi to cells. We conclude that RGD-peptides do not directly bind CR3, but instead indirectly effect CR3 function. Inasmuch as the effect of RGD-peptides could be mimicked with antibodies against leukocyte response integrin, we suggest that RGD-peptides may bind to leukocyte response integrin on polymorphonuclear leukocytes and influence CR3 activity via this receptor.

Amino Acid Sequence↗
PubMed1993

Obesity and body fat distribution in New Zealanders: a pattern of coronary heart disease risk.

AIMS: To describe the prevalence of obesity and the body fat distribution of New Zealanders. To discuss this in the context of the coronary heart disease risk. METHODS: Body weight and height, body mass index (BMI), waist:hip ratio (WHR) and six skinfold measurements were determined for 3204 randomly selected New Zealanders who responded to an invitation to a health check (response rate 56%). RESULTS: In the study sample BMI generally increased with age. Fifty five percent of men and 38 per cent of women aged 18-64 had a BMI exceeding 25, and of these 13 per cent and 10 per cent were obese (BMI > 30). WHR was greater in men than in women of all ages, and a third of the men and a quarter of the women had values exceeding 0.9 and 0.8 respectively. Central skinfold measurements (subscapular, suprailiac and abdominal) were lowest in young men, but rose markedly with age and were similar to women above age 35. Limb skinfolds were lower in men. CONCLUSIONS: This survey indicates that a large percentage of New Zealanders are overweight or obese and their excess body fat tends to be centrally distributed, especially in men. Obesity is thus a significant health problem in New Zealand.

Adipose Tissue↗
PubMed1993

Structurally distinct genes for the surface protease of Leishmania mexicana are developmentally regulated.

gp63 is a highly abundant glycosylphosphatidylinositol (GPI)-anchored membrane protein expressed in both the promastigote and the amastigote forms of Leishmania species. In Leishmania mexicana, gp63 exists as a heterogeneous family of proteins that are differentially processed and localized during the 2 developmental stages. In this study we determined the molecular organization of the L. mexicana gp63 gene family, demonstrating that the gp63 genes fall into 3 linked families of tandemly repeated, but structurally distinct, entities designated as C1, C2 and C3. The C1 and C2 gene clusters contain 4-5 copies each, while the C3 gene may be single copy. Whilst promastigotes contain transcripts from all 3 gene classes, the intracellular amastigote only expresses detectable transcript from the C1 gene class. Moreover, the sequence of the C1 genes predicts a unique carboxy terminus substantially different from the GPI anchor addition signal sequence found in other Leishmania spp. and which has characteristics incompatible with substitution with a GPI anchor. These findings have significance for both the diversity of gp63 and for the regulation of tightly clustered, tandem gene arrays.

Amino Acid Sequence↗
PubMed1993

Crithidia fasciculata contains a transcribed leishmanial surface proteinase (gp63) gene homologue.

We have cloned and analysed a gene from the insect parasite, Crithidia fasciculata, with homology to the gp63 metalloendoproteinase gene of Leishmania. The Crithidia gene homologue is arranged as a multicopy family comprised of approximately 7 genes. The mature transcript is 4.0 kb. The predicted amino acid sequence has significant homology with Leishmania gp63s, contains a zinc-binding motif and a potential site for addition of a glycosylphosphatidylinositol anchor. Demonstration of a gp63 homologue in C. fasciculata, a monogenetic parasite, suggests that the molecule may play a role in parasite survival within the insect gut.

Amino Acid Sequence↗
PubMed1993

The flagellar pocket of trypanosomatids.

The surface of the trypanosomatid forms the interface between the parasite and its host, and has evolved to repel a variety of host anti-microbial defences. The flagellar pocket constitutes a highly differentiated region of the trypanosomatid surface that facilitates internalization of host macromolecules, while restricting host access to the exposed, endocytic receptors of the parasite. In this review, Paul Webster and David Russell discuss the ability of this organelle to accumulate efficiently nutrients obtained from the host as a major factor in the success of this group of parasites.

Journal Article↗
PubMed1993

Inhibition of growth of Mycobacterium avium in murine and human mononuclear phagocytes by migration inhibitory factor.

Infections caused by Mycobacterium avium, the most common form of diseminated bacterial disease in AIDS patients, are difficult to treat because of their resistance to many antimycobacterial drugs. The results of the present study show that recombinant migration inhibitory factor, a 12-kDa molecule recently isolated by COS-1 cell expression screening of cDNA from a human T-cell hybridoma, has potent inhibitory activity on the growth of a panel of clinical isolates of M. avium within both bone-marrow-derived murine macrophages and cultured human blood monocytes. These cells cultured in recombinant migration inhibitory factor exhibit various signs of activation, including cell division, morphological changes such as evidence of substantial phagolysosomal fusion, and enhanced secretion of tumor necrosis factor.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Paracrystalline inclusions of a novel ferritin containing nonheme iron, produced by the human gastric pathogen Helicobacter pylori: evidence for a third class of ferritins.

An abundant 19.3-kDa Helicobacter pylori protein has been cloned, and the sequence is homologous with a ferritin-like protein produced by Escherichia coli K-12. Homologies are also present with a number of eucaryotic ferritins, as well as with the heme group-containing bacterioferritins. All amino acids involved in chelation of inorganic iron by ferritins from humans and other higher species are conserved in the H. pylori protein. Consistent with the structural data indicating an iron-binding function, E. coli overexpressing the H. pylori ferritin-like protein accumulates almost 10 times more nonheme iron than vector controls, and the iron-binding activity copurifies with the 19.3-kDa protein. Immunoelectron microscopy of H. pylori, as well as of E. coli overexpressing the H. pylori gene, demonstrates that the gene product has a cytoplasmic location where it forms paracrystalline inclusions. On the basis of these structural and functional data, we propose that the H. pylori gene product (termed Pfr) forms the basis for a second class of bacterial ferritins designed to store nonheme iron.

Amino Acid Sequence↗
PubMed1993

Characterization of the internalization of bacillus Calmette-Guerin by human bladder tumor cells.

Adjuvant intravesical Mycobacterium bovis BCG is the treatment of choice for recurrent superficial bladder cancer. Fibronectin (FN) was previously demonstrated to be necessary for the retention of BCG within the bladder and for the expression of antitumor activity. Recent studies have demonstrated that BCG attach and are ingested by bladder epithelial cells, suggesting the existence of a second bacterial attachment mechanism. We report the characterization of the molecules involved in BCG attachment and internalization by the human bladder transitional cell carcinoma cell line T-24. Pretreatment of T-24 cells with monoclonal antibodies to either alpha 5 or beta 1 integrin subunits significantly inhibited both BCG attachment and ingestion. Exogenous FN was observed to enhance both attachment and ingestion of BCG, and anti-FN was observed to inhibit both phenomena. Latex beads precoated with either FN or laminin (LN) but not BSA were ingested by T-24 cells, but only FN-coated beads inhibited BCG attachment and ingestion. Pretreatment of BCG with FN augmented both attachment and ingestion. The role of bacterial FN binding proteins was evaluated. A monoclonal antibody to a 55-kD FN-binding protein was observed to abrogate attachment and ingestion. These results demonstrate that attachment and ingestion of BCG are mediated in part by the alpha 5 beta 1 integrin receptor and are dependent on FN. These studies demonstrate a mechanism of entrance of mycobacteria into epithelial cells and suggest a second role for FN in the adjuvant antitumor effect of BCG.

Amino Acid Sequence↗
PubMed1993

Evolution and expression of the Leishmania surface proteinase (gp63) gene locus.

The Leishmania surface proteinase, gp63, is the most abundant, surface-exposed protein on the promastigote form of the parasite. It is the product of a multigene family that, in some Leishmania species, shows marked heterogeneity among its members. The differential expression of structurally distinct gp63 genes shows circumstantial correlation with the differential processing and localization of the protein in the intracellular, amastigote form of Leishmania mexicana. The recent cloning and sequencing of a homologous gene in the monoxenous trypanosomatid, Crithidia fasciculata, provides a reference sequence for comparison with ten Leishmania gp63 genes sequenced to date. The amino terminal and the carboxy terminal regions of the protein sequences suggest different evolutionary histories within some of the genes. The evolutionary significance of the structure, organization, and regulation of the gp63 genes from different Leishmania species is described and speculated upon.

Amino Acid Sequence↗