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.     

Mysterious bio-duck sound attributed to the Antarctic minke whale (Balaenoptera bonaerensis)

For decades, the bio-duck sound has been recorded in the Southern Ocean, but the animal producing it has remained a mystery. Heard mainly during austral winter in the Southern Ocean, this ubiquitous sound has been recorded in Antarctic waters and contemporaneously off the Australian west coast. Here, we present conclusive evidence that the bio-duck sound is produced by Antarctic minke whales (Balaenoptera bonaerensis). We analysed data from multi-sensor acoustic recording tags that included intense bio-duck sounds as well as singular downsweeps that have previously been attributed to this species. This finding allows the interpretation of a wealth of long-term acoustic recordings for this previously acoustically concealed species, which will improve our understanding of the distribution, abundance and behaviour of Antarctic minke whales. This is critical information for a species that inhabits a difficult to access sea-ice environment that is changing rapidly in some regions and has been the subject of contentious lethal sampling efforts and ongoing international legal action.     

A DNA Damage Checkpoint Pathway Coordinates the Division of Dikaryotic Cells in the Ink Cap Mushroom Coprinopsis cinerea

The fungal fruiting body or mushroom is a multicellular structure essential for sexual reproduction. It is composed of dikaryotic cells that contain one haploid nucleus from each mating partner sharing the same cytoplasm without undergoing nuclear fusion. In the mushroom, the pileus bears the hymenium, a layer of cells that includes the specialized basidia in which nuclear fusion, meiosis, and sporulation occur. Coprinopsis cinerea is a well-known model fungus used to study developmental processes associated with the formation of the fruiting body. Here we describe that knocking down the expression of Atr1 and Chk1, two kinases shown to be involved in the response to DNA damage in a number of eukaryotic organisms, dramatically impairs the ability to develop fruiting bodies in C. cinerea, as well as other developmental decisions such as sclerotia formation. These developmental defects correlated with the impairment in silenced strains to sustain an appropriated dikaryotic cell cycle. Dikaryotic cells in which chk1 or atr1 genes were silenced displayed a higher level of asynchronous mitosis and as a consequence aberrant cells carrying an unbalanced dose of nuclei. Since fruiting body initiation is dependent on the balanced mating-type regulator doses present in the dikaryon, we believe that the observed developmental defects were a consequence of the impaired cell cycle in the dikaryon. Our results suggest a connection between the DNA damage response cascade, cell cycle regulation, and developmental processes in this fungus.     

Immunocytochemical detection of the growth-associated protein B-50 by newly characterized monoclonal antibodies in human brain and muscle

The growth-associated protein B-50 also termed GAP-43, F1, pp46, P-57 and neuromodulin is a nervous tissuespecific protein kinase C (PKC) substrate that is considered to play a major role in neurite formation, regeneration, and neuroplasticity. We describe the isolation of seven mouse monoclonal antibodies (Mabs) directed against B-50. The Mabs are produced against the bovine B-50, selected by ELISA for cross-reactivity with its human counterpart, and evaluated on Western blots in comparison with the well-characterized affinity-purified rabbit polyclonal antibodies to rat-B-50. The Western blots show that the Mabs NM1, NM4, and NM6 recognize specifically the B-50 of bovine, human, and rat brain extract and the purified PKC phosphorylated and unphosphorylated rat B-50 isoforms. The Mabs NM2 and NM3 cross-react with bovine B-50 immunoreactive c-kinase substrate (BICKS), a protein sharing a 17 amino acid sequence homology with B-50. Two Mabs are useful for the detection of B-50 immunoreactivity in formalin-fixed human and rat brain tissues. In human specimen of the hippocampus, a characteristic neuropil distribution of B-50 is detected by the Mabs. In human muscle, Mabs reveal B-50 in nerve bundles and in axons at motor end plates. Thus, these Mabs are useful in investigating the function and localization of the B-50 protein.     

INTERRELATIONSHIPS BETWEEN POLYAMINES AND NUCLEIC ACIDS. CHANGES OF POLYAMINE AND NUCLEIC ACID CONCENTRATIONS IN THE GROWING FISH BRAIN (SALMO IRIDEUS GIBB.)

Abstract— In contrast to mouse brain, the content of putrescine in fish brain considerably exceeds that of spermine and spermidine. While we observed constant protein, RNA and spermidine concentrations in fish brains of weights between 60 and 800 mg, DNA and spermine concentrations diminished with increasing brain weight, the content of spermine per cell being constant throughout life. It can be concluded from our results that growth of fish brain results both from cell enlargement and cell proliferation. The concomitant changes of spermine and DNA concentrations in the growing fish brain are the first example of a direct quantitative relationship between these cell constituents and provides evidence on their possible functional relationship in the cell nucleus.     

A proposed neural pathway for vocalization in South African clawed frogs,Xenopus laevis

Vocalizations of South African clawed frogs are produced by contractions of laryngeal muscles innervated by motor neurons of the caudal medulla (within cranial nerve nucleus IX-X). We have traced afferents to laryngeal motor neurons in male and female frogs using retrograde axonal transport of horseradish peroxidase conjugated to wheat germ agglutinin (HRP-WGA). After iontophoretic injection of HRP-WGA into n. IX-X, retrogradely labelled neurons were seen in the contralateral n. IX-X, in rhombencephalic reticular nuclei, and in the pre-trigeminal nucleus of the dorsal tegmental area (DTAM) of both males and females.     

The type IC hsd loci of the enterobacteria are flanked by DNA with high homology to the phage P1 genome: implications for the evolution and spread of DNA restriction systems

Eco R124I, Eco DXXI and Eco prrI are the known members of the type IC family of DNA restriction and modification systems. The first three are carried on large, conjugative plasmids, while Eco prrI is chromosomally encoded. The enzymes are coded by three genes, hsdR , hsdM and hsdS . Analysis of the DNA sequences upstream and downstream of the type IC hsd loci shows that all are highly homologous to each other and also to sequences present in the bacteriophage P1 genome. The upstream sequences include functional phd and doc genes, which encode an addiction system that stabilizes the P1 prophage state, and extend to and beyond pac , the site at which phage DNA packaging begins. Downstream of the hsd loci, P1 DNA sequences begin at exactly the same place for all of the systems. For Eco DXXI and Eco prrI the P1 homology extends for thousands of base pairs while for Eco R124I an IS 1 insertion and an associated deletion have removed most of the P1-homologous sequences. The significance of these results for the evolution of DNA restriction and modification systems is discussed.