Analysis of Proteins Binding to the ITAM Motif of the β-Subunit of the High-Affinity Receptor for IgE (FcεRI)

Aggregation of the multichain (α β γ₂) high-affinity IgE receptor (Fcε RI) initiates a signaling cascade that results in the release of allergic mediators. The cytoplasmic tails of the Fcε RI-β and -γ subunits contain immunoreceptor tyrosine-based activation motifs (ITAMs). Phosphorylation of the γ ITAM mediates activation of Syk kinase and is sufficient for triggering the responses induced by Fcε RI crosslinking. Phosphorylation of the β ITAM is insufficient to mediate cell activation. The rat β ITAM contains three tyrosines (Tyr²¹⁸, Tyr²²⁴, and Tyr²²⁸) with an intermediate noncanonical tyrosine. Synthetic peptides based on the ITAM of the Fcε RI-β subunit were used to investigate the role of each phosphotyrosine in the binding of signaling proteins to this motif. Among the proteins that bind to phosphorylated β ITAM are Syk, Grb2, Shc, SHIP, and SHP-1, and binding does not depend on previous cell activation. Nonphosphorylated peptides do not bind these proteins. Syk binding to β -peptides is dependent on the number and position of phosphotyrosines in the ITAM. Phosphorylation of Tyr²¹⁸ seems to be most important for Syk binding. Recruitment of Syk and other signaling proteins to the β -subunit might be important for its amplifier role.     

Species-Specific Aggregation Factor in Sponges

An aggregation factor (AF) from the siliceous sponge Suberites domuncula has been isolated and purified by the following steps: Sepharose 2 B gel chromatography, sucrose gradient, Nonidet treatment, Sephadex G-100 gel chromatography and DEAE-Sephadex ion-exchange chromatography. By this procedure the AF was purified 1340-fold with a 63% yield nearly to homogeneity. The AF is originally associated with large particles, characterized by a sedimentation of 2200 S. These particles have been visualized electron microscopically; they are characterized by a filament-like shape of a length of 3400 Å and a cross-sectional diameter of 230 Å.
The purified, low-molecular weight AF has a buoyant density of 1.38 g/cm³ and an absorbance maximum at 282 nm. The isoelectric pH is approximately 5.75. The molecular weight of the AF has been determined to be 55,000. Chemical analysis revealed that AF consists mainly of protein.
The reaggregation process of Suberites cells to large aggregates (>1000 μm), mediated by Suberites AF, is strongly dependent on pH, ionic strength and the presence of calcium ions, and independent of incubation temperature between 0°C and 20°C. Aggregation can be inhibited by trypsin, D-glucosamine and dodecyl sulphate.
The Suberites AF is species-specific if tested in a system containing cells from the siliceous sponge Geodia cydonium .     

Geochemistry of Persististrombus latus Gmelin from the Pleistocene Iberian Mediterranean realm

De Torres, T., Ortiz, J.E., Arribas, I., Delgado, A., Julià, R. & Martín‐Rubí, J.A. 2009: Geochemistry of Persististrombus latus Gmelin from the Pleistocene Iberian Mediterranean realm. Lethaia, Vol. 43, pp. 149–163. In this paper the organic and inorganic geochemistry of fossil and extant Persististrombus latus are compared, together with other strombid species (Lentigo lentiginosus, Lobatus gigas, Strombus alatus, Lobatus raninus, Laevistrombus canarium and Tricornis latissimus). Using a large sample of well‐preserved fossil P. latus shells from the Mediterranean realm, we examined the warming period of sea water in the Middle Pleistocene. A mineralogical study of the shells demonstrates the continuous presence of calcite and a complex organic matter distribution, which was well preserved in many cases, thereby making the U/Th dating of strombid shells unreliable. U/Th analysis of coral samples and amino acid racemization dating of pelecypod shells confirmed that P. latus entered the Mediterranean realm in MIS 7 and 5. The oscillations of the δ¹⁸O values reflect annual growth periods and provide a mixing of the first signal record (primary growth) and successive overgrowths. □Amino acid racemization, Mediterranean Sea, Persististrombus latus, shell mineralogy, U/Th, δ¹⁸O.     

Phylloclade development in the Asparagaceae: an example of homoeosis

Phylloclades are traditionally defined as flattened, determinate, leaf-like stems primarily on the basis of their axillary position. However, because the literature is replete with controversy over the morphological interpretation of these organs, a study of phylloclade development in comparison with leaf and stem development was undertaken in four closely related species of the Asparagaceae: Ruscus aculeatus, Danae racemosa, Semele androgyna and Asparagus densiflorus. Results reveal a continuum in phylloclade development from very leaf-like forms, such as those of Danae, via the more intermediate types of Ruscus, to the gradually more shootlike forms of Semele and Asparagus. This continuum results from a differential expression of stem (or shoot) and leaf characteristics in an axillary position. When stem (or shoot) and leaf features are combined, as in the fertile phylloclade of Ruscus, an intermediate organ is formed. Phylloclades are a form of evolutionary novelty that exemplifies the phenomenon of homoeosis, which is the transference of features from one organ to another. Developmentally, this means that leaf features are expressed by the axillary meristem.     

New Culture Medium for Maintenance of Tsetse Tissues and Growth of Trypanosomatids*

SYNOPSIS. A new culture medium (SM), based on the amino-acid composition of tsetse hemolymph and containing fetal bovine serum, was designed for the maintenance of tsetse organs and the cultivation of various trypanosomatids. For optimum growth 20% (v/v) serum was required. The medium supported prolonged peristalsis of the alimentary tract and salivary glands of pre-emerged Glossina morsitans morsitans. In established cultures, derived from bloodstream forms of pleomorphic Trypanosoma brucei brucei and Trypanosoma brucei rhodesiense strains, inocula of ～ 10⁶ procyclics/ml yielded 4–5 × 10⁷ organisms/ml after 4 or 5 days of incubation at 28 C. Bloodstream forms of a cloned monomorphic T. b. brucei strain were also able to transform into procyclics, which, however, multiplied at a lower rate, with maximum yields of ～ 2 × 10⁷ after 5 days. Cultures of Trypanosoma congolense and of a nearly monomorphic Trypanosoma brucei gambiense strains could be established in SM medium only in the presence of tsetse alimentary tract. The procyclic trypomastigotes of these species, adapted to SM medium and able to grow in it without Glossina organs, gave maximum populations of ～ 4.5 × 10⁷ cells/ml. Promastigotes of Leishmania donovani, cultivated routinely in a diphasic Table's medium, multiplied actively upon being transferred into SM medium, producing yields of ～ 4 × 10⁷ cells/ml.     

Influence of bacterial density and water temperature on the grazing activity of two freshwater ciliates

1. The influences of bacterial density and water temperature on the grazing activity of the ciliates Uronema sp. and Colpoda inflata were studied. The conditions assayed were two prey densities (10⁶ and 4 × 10⁷ bacteria ml^?1) and three water temperatures (10, 15 and 22 °C). 2. The response of the ciliates was measured from changes in protistan biovolumes and specific clearance rates. At high prey density, both ciliates showed lower biovolumes as water temperature increased, while at low prey density this tendency was minimized. 3. At the intermediate temperature of 15 °C both ciliates filtered ten times more body volume when bacteria were scarce; however, the ingested bacteria were fewer than at high prey density. At low prey density, a decrease from 15 to 10 °C evidenced different strategies of the two ciliates, which led to a similar ingestion of bacteria: C. inflata reduced its specific clearance rates and increased its biovolume, while Uronema sp. did not show changes. At high prey density, an increase from 15 to 22 °C caused lower biovolumes and a noticeable increase in specific clearance rates in both ciliates, indicating opportunist behaviour.     

Patterns of animal dispersal, vicariance and divsrsification in the Holarctic

We analysed patterns of animal dispersal, vicariance and diversification in the Holarctic based on complete phylogenies of 57 extant non‐marine taxa, together comprising 770 species, documenting biogeographic events from the Late Mesozoic to the present. Four major areas, each corresponding to a historically persistent landmass, were used in the analyses: eastern Nearctic (EN), western Nearctic (WN), eastern Palaeoarctic (EP) and western Palaeoarctic (WP). Parsimony‐based tree fitting showed that there is no significantly supported general area cladogram for the dataset. Yet, distributions are strongly phylogenetically conserved, as revealed by dispersal‐vicariance analysis (DIVA). DIVA‐based permutation tests were used to pinpoint phylogenetically determined biogeographic patterns. Consistent with expectations, continental dispersals (WP?EP and WN?EN) are significantly more common than palaeocontinental dispersals (WN?EP and EN?WP), which in turn are more common than disjunct dispersals (EN?EP and WN?WP). There is significant dispersal asymmetry both within the Nearctic (WN→EN more common than EN→WN) and the Palaeoarctic (EP→WP more common than WP→EP). Cross‐Beringian faunal connections have traditionally been emphasized but are not more important than cross‐Atlantic connections in our data set. To analyse changes over time, we sorted biogeographic events into four major time periods using fossil, biogeographic and molecular evidence combined with a ‘branching clock’. These analyses show that trans‐Atlantic distributions (EN‐WP) were common in the Early‐Mid Tertiary (70‐20 Myr), whereas trans‐Beringian distributions (WN‐EP) were rare in that period. Most EN‐EP disjunctions date back to the Early Tertiary (70‐45 Myr), suggesting that they resulted from division of cross‐Atlantic rather than cross‐Beringian distributions. Diversification in WN and WP increased in the Quaternary (< 3 Myr), whereas in EP and EN it decreased from a maximum in the Early‐Mid Tertiary.     

Affinities in C3Cyperus lineages (Cyperaceae) revealed using molecular phylogenetic data and carbon isotope analysis

Maximum likelihood and Bayesian analyses of nrDNA (ETS1f) and plastid DNA (rpl32‐trnL, trnH‐psbA) sequence data are presented for ‘C₃Cyperus’ (Cyperaceae). The term ‘C₃Cyperus’ indicates all species of Cyperus s.l. that use C₃ photosynthesis linked with eucyperoid vegetative anatomy. Sampling comprises 77 specimens of 61 different taxa, representing nearly all previously recognized subdivisions of C₃Cyperus and the segregate genera Courtoisina, Kyllingiella and Oxycaryum. According to our results, the Cyperus clade is divided in six well‐supported clades. The first of these clades (clade 1) forms three subclades largely corresponding to Cyperus sections Haspani, Incurvi and Diffusi. Clade 2 comprises the entirely New World C. section Luzuloidei sensu Denton (1978). Clade 3 is a highly diverse clade including two subclades: clade 3a, C. sections Pseudanosporum and Anosporum plus the segregate genera Courtoisina and Oxycaryum; and clade 3b, C. section Fusci. Clade 4 corresponds to C. section Alternifolii and clade 5 to C. section Leucocephali plus the segregate genus Kyllingiella. The sixth clade is a well‐supported monophyletic clade encompassing all C₄Cyperus s.l. species (‘C₄Cyperus’). This study establishes a phylogenetic framework for future studies. © 2011 The Linnean Society of London, Botanical Journal of the Linnean Society, 2011, 167 , 19–46.