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G Sayers

Publications and source records attributed to G Sayers.

At least 19 recordsLinked to original sources
PubMed1992

Plasmacyte-reticulum cell satellitism in multiple myeloma associated with amyloidosis.

A novel morphological feature is described in a patient with myeloma and associated amyloidosis: characteristic clustering (satellitism) of neoplastic plasma cells around macrophages in bone marrow aspirates. Although described in myeloma cell culture, as far as is known, this is the first description of this phenomenon in a patient. This unique association may partly explain the origin of amyloid deposition in tissues and organs.

Aged↗
PubMed1989

Identification, synthesis and immunogenicity of cuticular collagens from the filarial nematodes Brugia malayi and Brugia pahangi.

The major structural proteins of the cuticle of the filarial nematode parasites Brugia malayi and Brugia pahangi were identified by extrinsic iodination and sensitivity to clostridial collagenase. At least 16 acidic components were identified in adult worms by 2-dimensional electrophoresis, with molecular weights ranging from 35,000 to 160,000. These proteins appear to be cross-linked by disulphide bonds, and localised in the basal and inner cortical layers of the cuticle. The outer cortex, containing the epicuticle, is insoluble in 1% sodium dodecyl sulphate and 5% 2-mercaptoethanol, and can be isolated free of cellular material. Despite their inaccessibility to the immune system in intact worms, antibodies to the cuticular collagens are provoked in humans infected with a variety of filarial parasites. Immunological cross-reactivity was demonstrated between a 35 kDa component and human type IV (basement membrane) collagen. Autoantibodies to type IV collagen were detected in a number of individuals with lymphatic filariasis, although no correlation could be drawn with observed pathology. Synthesis of cuticular collagens is discontinuous, occurs at negligible levels in mature adult male worms, and does not appear to involve the production of small molecular weight precursors, in contrast to Caenorhabditis elegans. Hybridisation with a heterologous cDNA probe coding for the alpha 2 chain of chicken type 1 collagen suggests that they are encoded by a multigene family.

Animals↗
PubMed1987

Leishmania donovani metacyclic promastigotes: transformation in vitro, lectin agglutination, complement resistance, and infectivity.

Freshly transformed Leishmania donovani amastigotes from hamster spleen were used to establish axenic cultures at high density in a modified Grace's medium, which was only partly replenished when cultures were fed. Small, free-swimming, highly active stationary phase promastigotes with a short cell body and long flagellum were induced in this medium. The freshly transformed stationary phase promastigotes so induced were less able to bind peanut agglutinin, had more than 40-fold increased resistance to killing by normal human serum, and 15-fold increased infectivity both in vivo and in vitro when compared to freshly transformed logarithmic phase or long term culture promastigotes. These short form promastigotes may correspond to the metacyclic promastigote forms in the sand fly vector.

Agglutination↗
PubMed1986

Macrophage type 3 complement receptors mediate serum-independent binding of Leishmania donovani. Detection of macrophage-derived complement on the parasite surface by immunoelectron microscopy.

In this study, direct visual evidence for local opsonization of L. donovani by macrophage (M phi)-derived complement components was obtained using immunoelectron microscopy. C3 deposition was detected on the surface of both promastigotes and amastigotes after 20 min serum-free incubation with murine resident peritoneal M phi (RPM), followed by fixation and incubation first with specific antibody directed against C3 and then with gold-labelled protein A. Gold deposition was not observed around either form of the parasite if the anti-C3 antibody was omitted. For promastigotes, the degree of C3 deposition under serum-free conditions was comparable with that observed in the presence of an exogenous (serum) source of C3, but did not result in the same severe damage to the parasite as did the latter. Addition of sodium salicyl hydroxamate, which prevents covalent binding of C3 to activator surfaces, abrogated promastigote binding. Hence, although the anti-C3 antibody did not distinguish between native C3 and its breakdown product iC3b, these data support our earlier conclusion that promastigote binding to the CR3 of murine RPM is complement dependent. For amastigotes, gold deposition and binding to murine RPM were not eliminated by sodium salicyl hydroxamate. The presence of normal mouse serum resulted in increased gold deposition, but did not mediate either enhanced binding to M phi or damage to the amastigote. These data suggest that a proportion of C3 binding to the amastigote surface may be via noncovalent linkages, and that the C3 bound may not be in the correct form to mediate binding to CR3.

Animals↗
PubMed1985

Oxygen radical release by adherent cell populations during the initial stages of a lethal rodent malarial infection.

A series of experiments was carried out to assess the levels of reactive oxygen intermediates (ROI) released by macrophages and monocytes during an acute malarial infection, and to consider the importance of oxidant-induced parasite killing in host protection. Adherent cell populations were removed from the peritoneum and spleen of BALB/c and B10/D2/n mice between Days 0-5 of a Plasmodium yoelii nigeriensis infection. These cell populations were quantified, characterized and their ROI-releasing capacity was measured by following ferricytochrome c reduction upon stimulation with phorbol myristate acetate (PMA). Both strains of mice displayed higher numbers of macrophages and macrophage precursors as the infection progressed; this rise was more marked and accompanied by splenomegaly in BALB/c mice. A concurrent decrease in peritoneal cell numbers was observed. Splenic adherent cell populations released much lower levels of ROI than peritoneal macrophages upon triggering. The levels of ROI released from BALB/c splenic adherent cells rose gradually until Day 3, when the parasitaemia was slightly decreased. In contrast, splenic populations from B10 mice had a decreased capacity to release ROI, particularly after Day 3, when the parasitaemia rose sharply. In further studies, electron microscopy was used to detect H2O2 release during the in vitro interaction of peritoneal macrophages and parasitized erythrocytes. Cerium chloride staining techniques demonstrated that H2O production was not dependent on phagocytosis or the presence of immune serum, although levels were increased by the presence of the latter.

Animals↗
PubMed1984

Biochemical surface components of Brugia pahangi microfilariae.

The sheath and cuticle of microfilariae of Brugia pahangi were examined by electron microscopy and the presence of various proteins, carbohydrate and enzymes sought. The epicuticle of microfilariae consists of a pentalaminate structure (24.0 +/- 1.4 nm), a cortex (13.7 +/- 3.6 nm) and a basal zone (27.8 +/- 4.8 nm) which is often banded in appearance. The pentalaminate layers are not continuous at the base of the interannular grooves. The sheath and the epicuticle of B. pahangi stained positively with concanavalin A and saccharated iron oxide. The sheath of approximately 50% of microfilariae showed activity for acid phosphatase, 5' nucleotidase and peroxidase, but not for ATPases, alkaline phosphatase or esterase. No enzymes were detected in the epicuticle although the cortex and basal layers of the cuticle did show enzymic activity. Structures beneath the cuticle in the main body of the worms contained considerable enzymic activity. Microfilariae directly isolated from the blood of infected cats were found by immunochemical means to carry serum proteins on their sheaths but not on their cuticles. These studies extend the definition of the outer structures of microfilariae and confirm that they significantly differ in morphology and enzyme content from typical mammalian cell membranes.

Acid Phosphatase↗
PubMed1973

Isolated adrenal cortex cells: hypersensitivity to adrenocorticotropic hormone after hypophysectomy.

Cells from the adrenals of hypophysectomized rats (up to 28 days after operation) require less adrenocorticotropic hormone to induce one-half maximal rate of production of 3',5'-adenosine monophosphate than do cells from the adrenals of intact rats. A corresponding increase in sensitivity is reflected in the steroidogenic response to adrenocorticotropic hormone up to 2 days after hypophysectomy.

Adenine↗