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Biomedical subjects

T M Preston

Publications and source records attributed to T M Preston.

29 records · Page 2Linked to original sources
PubMed1977

Studies of anionic sites on the cell surface of the amoeba Naegleria gruberi using cationized ferritin.

Interaction of cationized ferritin with the anionic groups on the cell surface of Naegleria was studied using transmission electron microscopy in conjunction with fluorescence microscopy. Most of the experiments involved the use of fluorescein-labelled cationized ferritin (FITC-CF) incubated with living amoebae. Initially the FITC-CF was located over the posterior two-thirds of the amoebae but the label was rapidly redistributed to form a cap at the posterior end in the region of the uroid; frequently this cap was shed. Pinosomes containing FITC-CF were clearly visible within the amoebae. Amoebae prefixed in glutaraldehyde were uniformly stained and did not show redistribution of the label. Exposure of live amoebae, previously incubated with cationized ferritin and allowed to cap, to fresh FITC-CF failed to produce fluorescent staining of the general cell surface, i.e. depletion of binding sites had occurred. The binding of the FITC-CF was not affected by pretreatment of the amoebae with neuraminidase or pronase. The possible nature of the anionic sites on the membrane is discussed.

Amoeba↗
PubMedDate not supplied

Biological characteristics of the Calliphora vomitoria agglutinin.

The galactose specific agglutinin from Calliphora vomitoria was found to be expressed in the haemolymph of all the larval instars, but could not be detected at any other time during the life cycle. The haemagglutinating activity was insensitive to wounding of the tegument or injection of saline; however, a significant increase in haemagglutinating titre could be induced upon inoculation of the haemocoel with biotic or abiotic particulate material. The agglutinin also actively agglutinated several bacterial species and appeared capable of playing a role in particle--haemocyte interaction. The presence of the purified agglutinin significantly increased the attachment of fetuin-derivatized beads to haemocytes in vitro, and this activity could be specifically reduced by the addition of galactose, suggesting that the agglutinin may act as an opsonin.

Animals↗
PubMedDate not supplied

Functional studies on Calliphora vomitoria haemocyte subpopulations defined by lectin staining and density centrifugation.

Haemocyte subpopulations of Calliphora vomitoria have been categorized by their surface staining properties using fluorescently labelled lectins, and their mobilities in Percoll density gradients. These methods of identification were exploited to determine the roles of these cell types in cellular defence reactions. Soybean agglutinin clearly defined the cell subpopulation involved in phagocytosis, while purified thrombocytoid fragments proved to be the main haemocyte population involved in encapsulation and nodule formation.

Animals↗
PubMedDate not supplied

Purification and characterization of a galactose-specific agglutinin from the haemolymph of the larval stages of the insect Calliphora vomitoria.

A lectin was isolated from the haemolymph of the blowfly larva Calliphora vomitoria. It agglutinated a variety of mammalian erythrocytes with varying specificities and was strongly inhibited by D-galactose and fetuin. The activity was also sensitive to chelators of metal ions, heating above 50 degrees C and proteolytic digestion. SDS-PAGE identified a glycoprotein with an Mr of 32,000 under reducing and nonreducing conditions which resolved to a band at pH 5.4 using isoelectric focusing. Using FPLC gel filtration the activity was isolated in a fraction with an Mr of 130,000. It is suggested that the native form of the molecule is a noncovalently associated tetramer.

Animals↗
PubMedDate not supplied

Amoeboid locomotion of Naegleria gruberi: the effects of cytochalasin B on cell-substratum interactions and motile behavior.

The major manifestations of amoeboid locomotion in Naegleria-cytoplasmic streaming, pseudopod production, cell polarity and focal contact production-require that the actin-based cytoskeleton be extremely dynamic. Whether these features are causally linked is unclear. In an attempt to answer this question we have used the fungal product cytochalasin B (cyt B) to dissect the motility process. This drug can perturb the organisation of actin filaments both in vivo and in vitro. Essentially cyt B acts as a molecule which can cap the barbed ends of actin filaments. Not surprisingly, therefore cyt B has an effect on rates of actin polymerization and the dynamic state of actin in the cytoplasm. We have found that cyt B has a profound effect on focal contact production and breakdown. Within minutes of addition of cyt B focal contact production ceases, existing focal contacts are stabilised but cytoplasmic streaming and pseudopod production are not blocked. In conclusion it is now clear that the state of actin required for focal contact production is different from that required for pseudopod extension and cytoplasmic streaming.

Actins↗