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.     

Cathepsin B from human renal cortex.

Cysteine-proteinase activity was observed in homogenates of human-cadaver renal cortex. This activity co-purified with renin enzymic activity until separation by aminohexyl-Sepharose--pepstatin affinity chromatography. The cysteine proteinase was purified 1780-fold after the following successive chromatographic procedures: Sephadex G-75, DEAE-cellulose DE-52, and an organomercurial affinity resin. The proteinase activity was dependent upon activation by thiol-containing compounds such as dithiothreitol, as well as by EDTA, and was inhibited by the thiol-group-specific alkylating reagents iodoacetic acid and N-ethylmaleimide. DE-52 cellulose chromatography resolved the cysteine proteinase into two components. On the basis of molecular size (26 000 daltons), activity as a function of pH, stability as a function of pH, substrate specificity and thermal lability, the major component (95%) has been identified as cathepsin B. The DE-52 cellulose elution pattern of the minor component (5%) is suggestive of cathepsin H [Schwartz & Barrett (1980) Biochem. J. 191, 487-497] Enzymic activity was determined with synthetic substrates, in particular alpha-N-benzoyl-DL-arginine 2-naphthylamide (Bz-Arg-NNap), thus precluding the detection of cathepsin L [Kirschke, Langner, Wiederanders, Ansorge, Bohley & Broghammer (1976) Acta Biol. Med. Germ. 35, 285-299]. Inhibition by dimethyl sulphoxide was observed in the determination of Km = 7.0 +/- 0.4 mM for the substrate Bz-Arg-NNap, and care must therefore be taken in the preparation of substrate solutions.     

Respiration rates of some greenhouse cultivated tropical and subtropical species

A comparative study of dark respiration and effects of high and low temperature on dark respiration in five greenhouse cultivated tropical and sub-tropical species was made. The respiration rates determined manometrically were low in all species. Respiration rates increased with increasing temperature. Low temperature treatment accelerated the rate of respiration at 25 °G except in two species. An attempt has been made to determine the critical and optimum temperature for these species. The respiratory behaviour of these species has been discussed with respect to their original habitats and prevailing environmental conditions.     

Enhanced activation of a T cell line specific for acetylcholine receptor (AChR) by using anti-AChR monoclonal antibodies plus receptors

Immune complex-mediated regulation of the immune response has been studied by using T cell lines and monoclonal antibodies (MAb), both specific for the acetylcholine receptor (AChR). Rat T lymphocytes bearing the W3/25 phenotype and specific for AChR from Torpedo californica have been propagated in vitro for nearly 1 yr. These T cells proliferate in response to optimal concentrations of AChR presented by irradiated syngeneic thymus cells. At suboptimal concentrations of antigen there is little activation of the T cell line. We report here that the addition of small amounts of anti-AChR MAb produces dramatic stimulation of the T cell lines at suboptimal doses of AChR. Enhanced activation depends on the isotype and not the fine specificity of the MAb that are used. The observed phenomenon is antigen specific, and in fact, the immune complexes may actually suppress the proliferative response of irrelevant T cells to some extent. The MAb plus antigen are rapidly bound to the surface of the antigen-presenting cell, which we have shown is the dendritic cell.     

Intramuscular loading dose of quinine for falciparum malaria: pharmacokinetics and toxicity.

In a study of intramuscular injection of quinine eight adults with moderately severe falciparum malaria resistant to chloroquine were treated with quinine dihydrochloride, being given a loading dose of 20 mg salt (16.7 mg base)/kg followed by three or four eight hourly maintenance doses of 10 mg salt (8.3 mg base)/kg injected into the anterior thigh. All patients responded to treatment. Fever and parasite clearance times (mean (SD) 60 (23) h and 53 (22) h respectively) were comparable with those obtained with intravenous quinine. The mean peak plasma quinine concentration of 11.0 mg/l (34.4 mu mol/l) [corrected] was reached a median of five hours after administration of the loading dose. In all patients plasma quinine concentrations exceeded the high minimum inhibitory concentration for Plasmodium falciparum malaria prevalent in Thailand within four hours of the start of treatment but did not cause toxicity other than mild cinchonism. When intravenous infusion is not possible an intramuscular quinine loading dose is an effective means of starting treatment in patients with moderately severe falciparum malaria who cannot swallow tablets.     

The diet of coastal breeding hooded crows corvus corone comix

Three methods of analysis were used to determine the diet of territorial hooded crows at Lough Hyne Marine Reserve, Co Cork, Ireland The regular collection of prey Items from these sites at Lough Hyne was integrated with pellet and stomach analysis to determine diet Intertidal organisms occurred in over 80% of pellets and 43% of stomachs and occupied over 77% of the total wet weight of foods identified in pellets All prey items recovered from drop sites originated from the intertidal habitat, involved either large-sized species or larger individuals of smaller-sized species, and were only dropped during October to February Twenty-five intertidal species were identified but only a few of these species contributed to the bulk of the diet Hooded crows were shown to consume a wide range of intertidal species throughout the year, though the species composition in the diet was seasonally influenced Depletion and weight loss of intertidal molluscs through the winter was shown to have a minimal effect on selection suggesting that prey switching was driven by the birds nutritional requirements     

Androgenic stimulation of endocytosis, amino acid and hexose transport in mouse kidney cortex involves increased calcium fluxes

Testosterone was previously shown to induce an early (less than 1 min) receptor-dependent stimulation of endocytosis, hexose and amino acid transport in mouse kidney cortex (Koenig, H., Goldstone, A. and Lu, C.Y. (1982) Biochem. Biophys. Res. Commun. 104, 165-172). Testosterone (10(-8) M) has now been found to stimulate rapidly (less than 30 s) the influx and efflux of 45Ca2+ in cortex slices. Testosterone also decreased mitochondrial 45Ca and augmented soluble 45Ca, indicating a mobilization of intracellular calcium. Incubation of cortex slices in calcium-free medium without or with 2.5 mM EGTA decreased basal endocytosis, hexose and amino acid transport and blocked the hormonal response. 100 microM verapamil blocked the hormonal response without affecting basal transport. The calcium ionophore A23187 rapidly stimulated endocytosis, hexose and amino acid transport. These data indicate that androgenic stimulation of membrane transport functions involves an increased influx of extracellular calcium and a mobilization of intracellular calcium. Increased cytosolic Ca2+ is probably the regulatory signal for these transport processes.