Behavioral interactions between three birch aphid species and Adalia bipunctata larvae

First and fourth instars of three birch aphid species were exposed to first and fourth instars of Adalia bipunctata (L.), the most common aphid predator on silver birch, Betula pendula Roth, in northern California. Defensive behavior differed by aphid species. Euceraphis betulae (Koch) (Eb), the most successful escapee, was highly mobile and frequently walked away from coccinellid larvae. Betulaphis brevipilosa Börner (Bb), a flat, sessile species, was the least successful aphid at actively escaping from A. bipunctata larvae, but could passively escape detection when coccinellid larvae walked over nymphs and did not perceive them. Active escape behavior was much safer for aphids than passive avoidance of detection. Both instars of Eb and fourth instars of Callipterinella calliptera (Hartig) (Cc) escaped from coccinellid larvae more frequently when approached from the front, apparently using vision for pre-contact detection of A. bipunctata. These aphids avoided physical contact with larger predators more often than with smaller predators. Level of predation by A. bipunctata on these three aphid species is dependent upon types of aphid defense.

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Résumé Des larves de premier et troisième stades de 3 espèces de pucerons du bouleau: Betulaphis brevipilosa, Callipterinella calliptera et Euceraphis betulae ont été exposées aux attaques des larves du premier et du quatrième stades d'Adalia bipunctata, prédateur le plus fréquent de pucerons sur Betula pendula en Californie du Nord. Le comportement défensif dépend beaucoup de l'espèce de puceron. E. betulae, qui s'échappe avec le plus de succès, est très mobile et s'écarte fréquemment des larves agressives de coccinelles. B. brevipilosa, espèce plate, sessile, a le moins de succès dans la protection active contre les attaques des larves de A. bipunctata, mais elle peut échapper passivement à la détection des larves de coccinelles qui ne peuvent pas les discerner lorsqu'elles circulent parmi les larves de pucerons. E. betulae (aux deux stades) et C. calliptera (au quatrième) échappent le plus aux larves de coccinelles qui attaquent de front, ce qui laisse supposer que la vision permet de détecter A. bipunctata avant le contact. Le succès des larves de coccinelles varie selon les stades du puceron et de la coccinelle. Les possibilités d'obtention de niveaux de prédation élevés de ces 3 pucerons par A. bipunctata dépend du type de protection du puceron.

     

Plasmid profiles and antibiotic susceptibility of Haemophilus pleuropneumoniae serotypes 1, 3, 5, and 7

Abstract This paper describes the plasmid profiles obtained for 73 of 96 field isolates of Haemophilus pleuropneumoniae serotypes 1, 3, 5, and 7. We also characterized the antibiotic susceptibilities of these 96 isolates. Because of the high proportion of isolates resistant to some of the antibiotics, no conclusions can be drawn as to the role of plasmids in antibiotic resistance.     

Canine lymphoma-associated antigens defined by murine monoclonal antibodies

Summary Lymphoma in dogs resembles human non-Hodgkin's lymphoma in pathological presentation, immunophenotype, and response to therapy, thus representing a good model for comparative studies with human disease. Monoclonal antibodies (MAbs) were derived from mice immunized with a dog lymphoma cell line. Three MAbs were selected for further application in immunophenotyping and immunotherapy. The binding specificities, antigen characterization, and isotypes for these MAbs are described.Supported by NCI grant CA-10815     

Consequences of terbium (111) binding on the conformation and enzymatic activity of Guinea pig liver transglutaminase

Calcium ions are crucial for expression of transglutaminase activity. Although lanthanides have been reported to substitute for calcium in a variety of protein functions, they did not replace the calcium requirement during transglutaminase activity measurements. Furthermore, lanthanides strongly inhibited purified liver transglutaminase activity using either casein or fibrinogen as substrates. Terbium (III) inhibition of transglutaminase-catalyzed putrescine incorporation into casein was not reversed by the presence of 10–200 fold molar excess of calcium ions (Ki for Tb(III)=60 µM). Conformational changes in purified liver transglutaminase upon Tb(III) binding were evident from a biphasic effect of Tb(III) on transglutaminase binding to fibrin. Low concentrations of Tb(III) (1 µM to 10 µM inhibited the binding of transglutaminase to fibrin, whereas higher concentrations (20 µM to 100 µM promoted binding. Conformational changes in purified liver transglutaminase consequent to Tb(III) binding were also demonstrated by fluorescence spectroscopy due to Forster energy transfer. Fluorescence emission was stable to the presence of 200 mM NaCl and 100 mM CaCl₂ only partially quenched emission. Purified liver transglutaminase strongly bound to Tb(III)-Chelating Sepharose beads and binding could not be disrupted by 100 mM CaCl₂ solution. Our data suggest that Tb(III)-induced conformational changes in transglutaminase are responsible for the observed effects on enzyme structure and function. The potential applications of Tb(III)-transglutaminase interactions in elucidating the structure-function relationships of liver transglutaminase are discussed.     

Growth dynamics of a ctenophore (Mnemiopsis) in relation to variable food supply. I. Carbon biomass, feeding, egg production, growth and assimilation efficiency

This paper contains new experimental data on the growth dynamicsof a lobate coastal ctenophore, Mnenmiopsis mccradyi, whichadd significantly to our understanding of the nutritional ecologyof ctenophores and their role as opportunistic predators. Theseexperimental observations were necessary to refine the dynamiccarbon budget presented as a simulation model in another report.The ratio of carbon biomass to dry weight may vary several-folddepending on the nutritional state and size from >12% inwell-fed larvae to <1% in starved adults. Feeding effort(clearance rate) is higher for previously starved animals, fallingsharply within a few hours after re-exposure to food. Directvisual observations of feeding activity of animals confirmedthis. Assimilation efficiency can be high (72%) in these animalsbut if they continue to feed at high food concentrations, incomingfood displaces material which is only partially digested andassimilation efficiency decreases substantially. Except at verylow food concentrations, growth efficiency ranges between 20and 45%. Mnemiopsis, begins to produce eggs at a size much lessthan its maximum. Egg production is very sensitive to food supply,and somatic growth is favored over egg production at low fooddensities. Even though several thousand eggs may be producedover a few days, they represent <2% day^–1 of the carbonbiomass of the ctenophore and several-fold less than respiratorycarbon.     

Neuromedin U-immunoreactivity in the nervous system of the small intestine of the pig and its coexistence with substance P and CGRP

Summary In the small intestine of the pig, neuromedin U (NMU)-immunoreactivity was mainly confined to the nerve plexus of the inner submucosal and mucosal regions. After colchicine treatment, a high number of immunoreactive nerve cell bodies was observed in the plexus submucosus internus (Meissner), whereas only a low number was found in the plexus submucosus externus (Schabadasch). The plexus myentericus as well as the aganglionic nerve meshworks in the circular and longitudinal smooth muscle layers almost completely lacked NMU-immunoreactivity. Double-labeling experiments demonstrated the occurrence of distinct NMU-containing neuron populations in the plexus submucosus internus: (1) relatively large type-II neurons revealing immunoreactivity for NMU and calcitonin gene-related peptide (CGRP) and/or substance P (SP); (2) a group of small NMU- and SP-immunoreactive neurons; (3) a relatively low number of small neurons displaying immunoreactivity for NMU but not for SP. Based on its distributional pattern, it is concluded that NMU plays an important role in the regulation and control of mucosal functions.     

Functional role of newly formed pore complexes in postmitotic nuclear reorganization

Many nuclear proteins are released into the cytoplasm at prometaphase and are transported back into the daughter nuclei at the end of mitosis. To determine the role of this reentry in nuclear remodelling during early interphase, we experimentally manipulated nuclear protein uptake in dividing cells. Recently we and others have shown that signal-dependent, pore complex-mediated uptake of nuclear protein is blocked in living cells on microinjection of the lectin wheat germ agglutinin (WGA), or of antibodies such as PI1 that are directed against WGA-binding pore complex glycoproteins. In the present study, we microinjected mitotic PtK₂ cells with WGA or antibody PI1 and followed nuclear reorganization of the daughter cells by immunofluorescence and electron microscopy. The inhibitory effect on nuclear protein uptake was monitored by co-injection of the karyophilic protein nucleoplasmin. When injected by itself early in mitosis, nucleoplasmin became sequestered into the daughter nuclei as they entered telophase. In contrast, nucleoplasmin was excluded from the daughter nuclei in the presence of WGA or antibody PI1. Although PtK₂ cells with blocked nuclear protein uptake completed cytokinesis, their nuclei showed a telophaselike organization characterized by highly condensed chromatin surrounded by a nuclear envelope containing a few pore complexes. These findings suggest that pore complexes become functional as early as telophase, in close coincidence with nuclear envelope reformation. They further indicate that the extensive structural rearrangement of the nucleus during the telophase-G1 transition is dependent on the influx of karyophilic proteins from the cytoplasm through the pore complexes, and is not due solely to chromosome-associated components.Abbreviations WGA wheat germ agglutinin - GlcNAc N-acetylglucosamine     

Expression of a cytochrome c2 isozyme restores photosynthetic growth of Rhodobacter sphaeroides mutants lacking the wild-type cytochrome c2 gene

Deletion of the cytochrome c2 gene in the purple bacterium Rhodobacter sphaeroides renders it incapable of phototrophic growth (strain cycA65). However, suppressor mutants which restore the ability to grow phototrophically are obtained at relatively high frequency (1-10 in 10(7)). We examined two such suppressors (strains cycA65R5 and cycA65R7) and found the expected complement of electron transfer proteins minus cytochrome c2: SHP, c', c551.5, and c554. Instead of cytochrome c2 which elutes from DEAE-cellulose between SHP and cytochrome c', at about 50 mM ionic strength in wild-type extracts, we found a new high redox potential cytochrome c in the mutants which elutes with cytochrome c551.5 at about 150 mM ionic strength. The new cytochrome is more acidic than cytochrome c2, but is about the same size or slightly smaller (13,500 Da). The redox potential of the new cytochrome from strain cycA65R7 (294 mV) is about 70 mV lower than that of cytochrome c2. The 280 nm absorbance of the new cytochrome is smaller than that of cytochrome c2, which suggests that there is less tryptophan (the latter has two residues). In vitro kinetics of reduction by lumiflavin and FMN semiquinones show that the reactivity of the new cytochrome is similar to that of cytochrome c2, and that there is a relatively large positive charge (+2.6) at the site of reduction, despite the overall negative charge of the protein. This behavior is characteristic of cytochromes c2 and unlike the majority of bacterial cytochromes examined. Fourteen out of twenty-four of the N-terminal amino acids of the new cytochrome are identical to the sequence of cytochrome c2. The N-termini of the cycA65R5 and cycA65R7 cytochromes were the same. The kinetics and sequence data indicate that the new protein may be a cytochrome c2 isozyme, which is not detectable in wild-type cells under photosynthetic growth conditions. We propose the name iso-2 cytochrome c2 for the new cytochrome produced in the suppressor strains.     

GPIIb and GPIIIa amino acid sequences deduced from human megakaryocyte cDNAs

Platelet GPIIbIIIa is only synthesized in megakaryocyte or in cell lines with megakaryocytic features. The sequence for GPIIb and GPIIIa have recently been derived from cDNAs obtained from HEL cells. The sequence of these proteins produced by the megakaryocyte, has however, not been determined yet. This study describes full length cDNAs for GPIIb and GPIIIa isolated from megakaryocyte cDNA libraries. The cDNA sequences indicate the presence of nucleotide differences, between the sequence of the GPIIIa cDNAs from HEL cells, endothelial cells and megakaryocytes. One difference was also observed between HEL and megakaryocyte GPIIb at position 633 where a cystein in the megakaryocyte GPIIb, is replaced by a serine in the HEL sequence. The mRNA species for GPIIb (3.4kb) and GPIIIa (6.1 kb) were of the same size in HEL cells and human megakaryocytes.     

Cystic fibrosis typing with DNA probes and screening for ΔF508 deletion in families from Southern France

Summary A sample of 235 individuals from 49 French cystic fibrosis (CF) families with at least one living affected child was typed with probes for restriction fragment length polymorphisms (RFLPs) known to be linked to the CF gene, and was screened for the ΔF508 mutation. Using a combination of six probes, 44 out of the 49 families were sufficiently informative to enable prenatal diagnosis or carrier determination. As in many other populations, linkage disequilibrium was found between the CF locus and the haplotype B (XV2c: allele 1; KM19: allele 2), which accounts for about 78% of CF chromosomes in our families. The ΔF508 deletion was present in 64.3% of CF chromosomes.