Inhibition of immune opsonin-independent phagocytosis by antibody to a pulmonary macrophage cell surface antigen

Unlike other hamster phagocytes, hamster pulmonary macrophages (PM) avidly ingest albumin-coated latex particles in the absence of serum. They also possess a highly specific cell surface antigen. To evaluate the relationship between these two characteristics, PM were incubated with mouse monoclonal antibody directed against the PM antigen. After unbound antibody was removed, the amount of bound antibody and the phagocytic capability of PM were measured by flow cytometry and fluorescence microscopy. Maximum antibody binding produced a 25% inhibition of ingestion. Particle attachment was not affected. This effect was antigen specific, since neither a nonspecific mouse myeloma protein of the same subclass nor a mouse antibody that bound to another hamster surface antigen had any effect on binding or ingestion. If antigen-specific F(ab')2 fragments were introduced both before and during the period of phagocytosis, the inhibition of particle ingestion approached 100%. Particle binding increased at low F(ab')2 concentrations but declined at higher concentrations. Because calcium may play a role in the ingestion process, the effect of antibody on 45Ca uptake was evaluated. It was observed that antigen-specific F(ab')2 fragments stimulated 45Ca uptake, whereas control antibodies did not. These results suggest that the antigen reacting with our anti-hamster PM monoclonal antibody is involved in immune opsonin-independent phagocytosis and that calcium participates in this phagocytic process.     

Phylogeny of Myrmeleontiformia based on larval morphology (Neuropterida: Neuroptera)

The suborder Myrmeleontiformia is a derived lineage of lacewings (Insecta: Neuroptera) including the families Psychopsidae, Nemopteridae, Nymphidae, Ascalaphidae and Myrmeleontidae. In particular, Myrmeleontidae (antlions) are the most diverse neuropteran family, representing a conspicuous component of the insect fauna of xeric environments. We present the first detailed quantitative phylogenetic analysis of Myrmeleontiformia, based on 107 larval morphological and behavioural characters for 36 genera whose larvae are known (including at least one representative of all the subfamilies of the suborder). Four related families were used as outgroups to polarize character states. Phylogenetic analyses were conducted using both parsimony and Bayesian methods. The reconstructions resulting from our analyses corroborate the monophyly of Myrmeleontiformia. Within this clade, Psychopsidae are recovered as the sister family to all the remaining taxa. Nemopteridae (including both subfamilies Nemopterinae and Crocinae) are recovered as monophyletic and sister to the clade comprising Nymphidae + (Myrmeleontidae + Ascalaphidae). Nymphidae consist of two well‐supported clades corresponding to the subfamilies Nymphinae and Myiodactylinae. Our results suggest that Ascalaphidae may not be monophyletic, as they collapse into an unresolved polytomy under the Bayesian analysis. In addition, the recovered phylogenetic relationships diverge from the traditional classification scheme for ascalaphids. Myrmeleontidae are reconstructed as monophyletic, with the subfamilies Stilbopteryginae, Palparinae and Myrmeleontinae. We retrieved a strongly supported clade comprising taxa with a fossorial habit of the preimaginal instars, which represents a major antlion radiation, also including the monophyletic pit‐trap building species.     

Detection and side-chain specificity of IgE antibodies to flucloxicillin in allergic subjects

Unlike studies on the antigenicity of penicillins in laboratory animals, limited information is available on the allergenicity of penicillins in man, especially with regard to fine structural allergenic differences between the many different penicillins. Inconsistent with the earlier conclusions of others, our studies suggest that side-chain structures to flucloxacillin-reactive IgE antibodies. Quantitative hapten inhibition studies revealed potent inhibition by flucloxacillin and three structurally related penicillins: oxacillin, cloxacillin and dicloxacillin. Analysis of the results showed that the side-chain group of flucloxacillin, 3-2(-chloro-6-fluorophenyl)-5-methyl-4-isoxazolyl, is recognized by some antibodies and that the 5-methyl-3-phenyl-4-isoxazolyl group, with or without halogen substituents, accounts for the reactivity of other antibodies and for the cross-reactions seen with some other penicillins. Since it is the side-chain group that distinguishes the many different types of penicillin, and since IgE antibodies in many of the allergic reactions recognize the side-chain groups, it is becoming clear that specific assays are required for the detection of IgE antibodies to each of the different penicillins.     

Attempts to determine the status of electroshock-induced attack in male laboratory mice

An attempt was made using a combination of simple experimental manipulations and videotape recorder (VTR) analysis of bite targets employed to determine whether electroshock-induced attack on anosmic opponents in laboratory mice was an offensive or a defensive behaviour. VTR analysis suggested that ventral surface biting was more evident in this form of attack than in social conflict. Individually- and group-housed males showed similar levels of fighting on exposure to electroshock, but dominant males from pairs showed greater attack than their subordinate partners. Zinc sulphate-induced anosmia, 36 h of food deprivation, castration and lithium chloride treatment reduced electroshock-induced attack. Although significant changes were not obtained, there was some evidence that acute treatment with dexamethasone or ACTH augmented this behaviour. The direction of these changes is similar to that seen with social conflict, and it is suggested that electroshock-induced attack in the mouse (unlike the rat) is largely an aggressive offensive behaviour. The high incidence of ventral surface biting may be a consequence of the upright postures assumed on subjecting the animals to electroshock.     

The effect of chemical modification of Saccharomyces cerevisiae on electrophoretic mobility, cell-wall structure and amphotericin B uptake

Saccharomyces cerevisiae NCYC 239 suspended in solutions of NaCl showed two distinct plateaus in plots of electrophoretic mobility vs. pH, corresponding to pKa values of approx. 2 and 5. This is in contrast to cells suspended in buffer where only a single pKa (4) can be determined. Modification of cells with KI/I2 or nitrous acid led to altered electrophoretic mobility, indicating the presence of sulphydryl and amino groups, respectively, in the yeast cell surface, whereas uranyl nitrate modification had little effect, suggesting phosphate groups to be absent. Electron micrographs showed visible effects of KI/I2 and nitrous acid modification on cell membrane structure, and in these modified cells amphotericin B uptake was rapid. It is suggested that diffusion through the cell wall is the rate-limiting step for amphotericin B uptake. An activation energy of 20 kJ X mol-1 was determined for uptake of amphotericin B by unmodified cells.     

Freeze-fracture electron microscopic observations on the effects of sulphydryl group reagents on human erythrocyte membranes

Freeze-fracture electron microscopy of human red blood cells at pH 7.4 and 5.5 reveals the presence of membrane elevations (50-100 nm diameter). These are also observed after incubation of the erythrocytes with N-ethylmaleimide but not after incubation with p-chloromercuribenzene sulphonate. Neither of the sulphydryl-group reagents affects the distribution or size of intramembrane particles. The findings are discussed in the light of the effects of mercurials on erythrocyte membrane proteins.