Plant phylogeny drives arboreal caterpillar assemblages across the Holarctic

1. Assemblages of insect herbivores are structured by plant traits such as nutrient content, secondary metabolites, physical traits, and phenology. Many of these traits are phylogenetically conserved, implying a decrease in trait similarity with increasing phylogenetic distance of the host plant taxa. Thus, a metric of phylogenetic distances and relationships can be considered a proxy for phylogenetically conserved plant traits and used to predict variation in herbivorous insect assemblages among co‐occurring plant species.
2. Using a Holarctic dataset of exposed‐feeding and shelter‐building caterpillars, we aimed at showing how phylogenetic relationships among host plants explain compositional changes and characteristics of herbivore assemblages.
3. Our plant–caterpillar network data derived from plot‐based samplings at three different continents included >28,000 individual caterpillar–plant interactions. We tested whether increasing phylogenetic distance of the host plants leads to a decrease in caterpillar assemblage overlap. We further investigated to what degree phylogenetic isolation of a host tree species within the local community explains abundance, density, richness, and mean specialization of its associated caterpillar assemblage.
4. The overlap of caterpillar assemblages decreased with increasing phylogenetic distance among the host tree species. Phylogenetic isolation of a host plant within the local plant community was correlated with lower richness and mean specialization of the associated caterpillar assemblages. Phylogenetic isolation had no effect on caterpillar abundance or density. The effects of plant phylogeny were consistent across exposed‐feeding and shelter‐building caterpillars.
5. Our study reveals that distance metrics obtained from host plant phylogeny are useful predictors to explain compositional turnover among hosts and host‐specific variations in richness and mean specialization of associated insect herbivore assemblages in temperate broadleaf forests. As phylogenetic information of plant communities is becoming increasingly available, further large‐scale studies are needed to investigate to what degree plant phylogeny structures herbivore assemblages in other biomes and ecosystems.

     

Concentrations of glandular kallikrein in human nasal secretions increase during experimentally induced allergic rhinitis

We have previously demonstrated that a mixture of bradykinin and lysylbradykinin is generated in nasal secretions during the immediate allergic response to allergen. The present studies were performed to determine whether glandular kallikrein plays a role in kinin formation during the allergic reaction. Allergic individuals (n = 7) and nonallergic controls (n = 7) were challenged intranasally with appropriate allergen, and nasal lavages obtained before and after challenge were assayed for immunoreactive glandular kallikrein as well as for histamine, kinins, and N-alpha-tosyl-L-arginine methyl esterase (TAME-esterase) activity. The increase in postchallenge immunoreactive glandular kallikrein levels above baseline was significantly greater (p less than 0.01) for the allergic group (16.3 +/- 14 ng/ml; means +/- SD) than for the nonallergic controls (1.0 +/- 1.9 ng/ml). Increased levels of immunoreactive glandular kallikrein correlated with increases in kinins, histamine, and TAME-esterase activity and with the onset of clinical symptoms. Characterization of immunoreactive glandular kallikrein purified from postchallenge lavages by immunoaffinity chromatography confirmed the identity of this material as an authentic glandular kallikrein on the basis of its inhibition by protease inhibitors and by monospecific antibody to tissue kallikrein, its chromatographic behavior on gel filtration, and its ability to generate lysylbradykinin from highly purified human low m.w. kininogen. The specific activity of this purified material, in terms of kinin generation from kininogen, was very similar to that for authentic glandular kallikrein, suggesting that most if not all of the immunoreactive material purified from nasal lavages represented active enzyme. Inhibition studies by using pooled postchallenge lavages suggest that the majority of the kinin generating activity in these samples was due to glandular kallikrein. We conclude, therefore, that glandular kallikrein is secreted during the allergic response and can contribute to the formation of the lysylbradykinin produced during the allergic reaction.     

Observations on lesser-known flatworms: temnocephala

Temnocephala novae-zealandie, a flatworm epizoic on crayfish, was examined by light and electron microscopy to investigate the variation within rhabdocoel turbellarians and to provide information on the possible structural modifications in the evolution of parasitism. The sucker is clearly glandular; the tentacular glands are eosinophilic and at the surface store and often release mucus as a coiled thread; the epidermis is clearly not reduced in structure and contains septate junctions in the anterior portion. Light microscope studies documented the presence of ten pair of paranephrocytes (athrocytes). In the laboratory, egg deposition, survival on and apart from the host and another crayfish, and behavior during the host molt were observed.     

The time course of hydrolysis of a beta-lactam antibiotic by intact gram-negative bacteria possessing a periplasmic beta-lactamase.

An equation is derived from first principles for describing the change in concentration with time of a beta-lactam antibiotic in the presence of intact Gram-negative bacteria possessing a beta-lactamase located in the periplasmic space. The equation predicts a first-order decline in beta-lactam concentration of the form [S] = [Si]e lambda t, where [S] is the exogenous concentration of beta-lactam, [Si] is the value of [S] at time zero, t is the time from mixing of cells and antibiotic and lambda (less than 0) is the decay constant. The value of lambda is exactly described by the theory in terms of experimentally measurable quantities. Quantitative data concerning cephaloridine hydrolysis by intact cells of Haemophilus influenzae agreed well with the theory, as did data concerning the uptake of 2-nitrophenyl galactoside by intact cells of Escherichia coli. Cephalosporin C hydrolysis by intact cells of Pseudomonas aeruginosa did not progress as predicted by the theory. The theory is applicable to any substrate which is acted on by an enzyme that is located solely in the periplasmic space and that obeys the Michaelis-Menten equation of enzyme kinetics.     

Nerve growth factor treatment or cAMP elevation reduces Ca2+/calmodulin-dependent protein kinase III activity in PC12 cells

Ca2+/calmodulin-dependent protein kinase III (Ca2+/CaM kinase III) phosphorylates a protein of Mr = 100,000 (the 100-kDa protein), a major substrate for Ca2+/CaM-dependent protein phosphorylation found in many mammalian tissues and cell lines (Nairn, A.C., Baghat, B., and Palfrey, H.C. (1985) Proc. Natl. Acad. Sci. U.S.A. 82, 7939-7943). Treatment of PC12 cells with nerve growth factor (NGF) or forskolin resulted in a decrease in the depolarization-dependent phosphorylation of the 100-kDa protein in intact cells and in a decrease in the Ca2+/CaM-dependent phosphorylation of the 100-kDa protein in cytosolic extracts. In experiments using cytosolic extracts, the initial effect of NGF on the phosphorylation of the 100-kDa protein was observed in less than 1 h, was maximal (70% decrease) after 12 h, and began to recover after 24 h. The effect of forskolin was more rapid and the maximal effect was greater (90-95% decrease). Decreased Ca2+/CaM kinase III activity was also found in PC12 cells treated with epidermal growth factor, 2-chloroadenosine plus isobutylmethylxanthine, or dibutyryl cAMP. The effect of forskolin did not reverse unless it was removed. Cycloheximide blocked the recovery of Ca2+/CaM kinase III activity observed following the removal of forskolin but did not affect the ability of forskolin to reduce kinase activity. Short-term treatment with phorbol ester had little effect on Ca2+/CaM kinase III activity; long-term treatment with phorbol ester, which results in the disappearance of enzymatically detectable protein kinase C, had no effect on the ability of NGF or 2-chloroadenosine to reduce Ca2+/CaM kinase III activity. The level of the 100-kDa protein as determined by immunological techniques was not changed by any treatment. These results suggested that the effect of treatment of PC12 cells with NGF or forskolin was to reduce the level of Ca2+/CaM kinase III per se.     

Genetic mechanisms of tumor-specific loss of 11p DNA sequences in Wilms tumor.

Wilms tumor, a common childhood renal tumor, occurs in both a heritable and a nonheritable form. The heritable form may occasionally be attributed to a chromosome deletion at 11p13, and tumors from patients with normal constitutional chromosomes often show deletion or rearrangement of 11p13. It has been suggested that a germinal or somatic mutation may occur on one chromosome 11 and predispose to Wilms tumor and that a subsequent somatic genetic event on the normal homologue at 11p13 may permit tumor development. To study the frequency and mechanism of such tumor-specific genetic events, we have examined the karyotype and chromosome 11 genotype of normal and tumor tissues from 13 childhood renal tumor patients with different histologic tumor types and associated clinical conditions. Tumors of eight of the 12 Wilms tumor patients, including all viable tumors examined directly, show molecular evidence of loss of 11p DNA sequences by somatic recombination (four cases), chromosome loss (two cases), and recombination (two cases) or chromosome loss and duplication. One malignant rhabdoid tumor in a patient heterozygous for multiple 11p markers did not show any tumor-specific 11p alteration. These findings confirm the critical role of 11p sequences in Wilms tumor development and reveal that mitotic recombination may be the most frequent mechanism by which tumors develop.     

Ultrastructure of neural crest formation in the midbrain/rostral hindbrain and preotic hindbrain regions of the mouse embryo

In the mouse embryo, neural crest mesenchyme associated with the first and second pharyngeal arches escapes from the epithelium that forms the tips of the midbrain/rostral hindbrain and preotic hindbrain neural folds. To investigate the ultrastructure of crest formation, embryos with four to eight pairs of somites were processed for transmission electron microscopy. In the earliest event related to crest formation, crest precursors in the midbrain/rostral hindbrain elongated and moved all or most of their contents to the basal region of the epithelium. Elongation was probably mediated by apical bands of microfilaments and longitudinally oriented microtubules. Elongated cells then relinquished apical associations while nonelongated cells maintained those associations and withdrew from the basal lamina. This resulted in an epithelium stratified into apical and basal (crest precursor) layers. The coalescence of enlarging extra-cellular spaces opened a delaminate gap between the two layers. Additional crest precursors entered this gap from the apical layer. From the time crest precursors began moving basally, some formed microfilament- and/or microtubule-containing processes, which penetrated the basal lamina. Some of these cells moved their contents into the larger, microtubule-containing processes, perhaps thereby escaping from the epithelium. Soon after elongating cells appeared, the basal lamina beneath the epithelium began to degrade in a pattern unrelated to process formation. This ultimately resulted in disruption of the lamina, dispersal of the basal layer of the epithelium, and release of the crest precursors in the delaminate gap. Once crest formation was complete, the apical layer reformed a basal lamina on a patch-by-patch, cell-by-cell basis. In the preotic hindbrain, elongating crest precursors apparently forced their basal faces through the basal lamina and then relinquished apical association to escape. As a result, the lamina was disrupted before the epithelium could stratify, and enlarged extracellular spaces appeared among mesenchymal cells rather than creating a delaminate gap. The failure of elongation to disrupt the basal lamina in the midbrain/rostral hindbrain and its success in the preotic hindbrain might be due to less-vigorous, less-concerted elongation in the midbrain/rostral hindbrain or to earlier, more rapid degradation of the lamina in the preotic hindbrain.     

Escherichia coli tryptophan synthase: synthesis of catalytically competent alpha subunit in a cell-free system containing preacylated tRNAs

A cell-free protein biosynthesizing system prepared from Escherichia coli CF300 was found to synthesize E. coli tryptophan synthase alpha subunit in a time-dependent manner when programmed with pBN69 plasmid DNA. This plasmid contains the trp promoter from Serratia marcescens adjacent to the coding region of E. coli tryptophan synthase alpha protein [Nichols, B.P., & Yanofsky, C. (1983) Methods Enzymol. 101, 155-164]. The synthesized tryptophan synthase alpha subunit was found to be indistinguishable from authentic alpha subunit protein when analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and to have the same specific activity for catalyzing the conversion of indole----L-tryptophan by tryptophan synthase beta 2 subunit, as well as the conversion of indole + glyceraldehyde 3-phosphate to indole-3-glycerol phosphate. In the absence of exogenously added phenylalanine, admixture of E. coli phenylalanyl-tRNAPhe to the protein biosynthesizing system stimulated the production of functional alpha protein; the analogous result was obtained when valine was replaced by E. coli valyl-tRNAVal. The ability of a misacylated tRNA to participate in alpha protein synthesis in this system was established by the use of E. coli phenylalanyl-tRNAVal in the absence of added valine. Protein biosynthesis proceeded normally and gave a product having the approximate molecular weight of tryptophan synthase alpha subunit; as expected, this polypeptide lacked catalytic activity.     

Conversion of apolipoprotein-specific high-density lipoprotein populations during incubation of human plasma

Incubation studies were performed on plasma obtained from subjects selected for relatively low levels of high-density lipoprotein cholesterol (HDL-C) (no greater than 30 mg/dl) and particle size distributions enriched in the HDL3 subclass. Incubation (12 h, 37 degrees C) of plasma in the presence or absence of lecithin: cholesterol acyltransferase activity produces marked alteration in size profiles of both major apolipoprotein-specific HDL3 populations (HDL3(AI w AII), HDL3 species containing both apolipoprotein A-I and apolipoprotein A-II, and HDL3(AI w/o AII), HDL3 species containing apolipoprotein A-I) as isolated by immunoaffinity chromatography. In the presence or absence of lecithin: cholesterol acyltransferase activity, plasma incubation results in a shift of HDL3(AI w AII) species (initial mean sizes of major components, approx. 8.8 and 8.0 nm) predominantly to larger particles (mean size, 9.8 nm). A less prominent shift to smaller particles (mean size, 7.8 nm) accompanies the conversion to larger particles only when the enzyme is active. Combined shifts to larger (mean size, 9.8 nm) and smaller (mean size, 7.4 nm) particles are observed for HDL3(AI w/o AII) particles (mean size, 8.3 nm) also only in the presence of enzyme activity. However, in the absence of enzyme activity, HDL3(AI w/o AII) species, unlike the HDL3(AI w AII) species, are converted to smaller (mean size 7.4 nm) rather than to larger particles. Like native HDL2b(AI w/o AII) particles, the larger HDL3(AI w/o AII) conversion products exhibit a protein moiety with molecular weight equivalent to four apolipoprotein A-I molecules per particle; small HDL3(AI w/o AII) products are comprised predominantly of particles with two apolipoprotein A-I per particle. Incubation-induced conversion of HDL3 particles in the presence of lecithin: cholesterol acyltransferase activity is associated with increased binding of both apolipoprotein-specific HDL populations to low-density lipoproteins (LDL). The present studies indicate that, in the absence of lecithin: cholesterol acyltransferase activity, the two HDL3 populations follow different conversion pathways, possibly due to apolipoprotein-specific activities of lipid transfer protein or conversion protein in plasma. Our studies also suggest that lecithin: cholesterol acyltransferase activity may play a role in the origins of large HDL2b(AI w/o AII) species in human plasma by participating in the conversion of HDL3(AI w/o AII) particles, initially with three apolipoprotein A-I, to larger particles with four apolipoprotein A-I per particle.     

An evolutionary comparison of Acinetobacter calcoaceticus trpF with trpF genes of several organisms

The deduced amino acid sequence of Acinetobacter calcoaceticus N-(5'-phosphoribosyl) anthranilate isomerase (PRAI), which is coded by trpF, was compared with TrpF of Caulobacter crescentus, Escherichia coli, Bacillus subtilis, Saccharomyces cerevisiae, Neurospora crassa, and Aspergillus nidulans. Sixty percent of identical or similar amino acids were located in alpha/beta TIM (triose-phosphate isomerase) barrels and in residues important in substrate binding and catalysis. In addition, the analysis of trpF genes presented here supports a model by which fusion between separate trpC and trpF genes arose in some cases by in-frame deletions.