The bell-shaped Ca2+ dependence of the inositol 1,4, 5-trisphosphate-induced Ca2+ release is modulated by Ca2+/calmodulin.

Calmodulin inhibits inositol 1,4,5-trisphosphate (IP3) binding to the IP3 receptor in both a Ca2+-dependent and a Ca2+-independent way. Because there are no functional data on the modulation of the IP3-induced Ca2+ release by calmodulin at various Ca2+ concentrations, we have studied how cytosolic Ca2+ and Sr2+ interfere with the effects of calmodulin on the IP3-induced Ca2+ release in permeabilized A7r5 cells. We now report that calmodulin inhibited Ca2+ release through the IP3 receptor with an IC50 of 4.6 microM if the cytosolic Ca2+ concentration was 0.3 microM or higher. This inhibition was particularly pronounced at low IP3 concentrations. In contrast, calmodulin did not affect IP3-induced Ca2+ release if the cytosolic Ca2+ concentration was below 0.3 microM. Calmodulin also inhibited Ca2+ release through the IP3 receptor in the presence of at least 10 microM Sr2+. We conclude that cytosolic Ca2+ or Sr2+ are absolutely required for the calmodulin-induced inhibition of the IP3-induced Ca2+ release and that this dependence represents the formation of the Ca2+/calmodulin or Sr2+/calmodulin complex.     

Pattern of movements of adult Barbus haasi in a small Mediterranean stream

Most adult Barbus haasi , at a 1950 m-long site in Vallvidrera creek, were highly sedentary and resided within a home range <20 m (32 m²), while a small group were more mobile. On successive sampling occasions, between 52·3 and 64·9% of fish were recaptured in the same 10-m-long section in which they had previously been captured. Movements over long distances were infrequent, and only 5·6% of the fish moved >100 m. The movement pattern of the population was seasonally stable, although the mean distances were slightly greater in summer because of the medium-range movements of a few individuals. Overall, upstream and downstream movements were equally common but a significant downstream movement occurred in spring. The size of the fish did not influence the movement rate. Fish inhabiting those sections of the stream with greater depth, slower current and more cover had a lower movement rate than fish occupying shallower, exposed sections. The restricted movement of B. haasi could increase the survival of fish by increasing the probability of staying in the remaining pools during summer dry-out, and may therefore be of adaptive significance.     

Dipstick enzyme immunoassay to detect Fusarium T-2 toxin in wheat.

A dipstick enzyme immunoassay for the rapid detection of Fusarium T-2 toxin in wheat was developed. An Immunodyne ABC membrane was precoated with rabbit anti-mouse immunoglobulins. After the strips were immersed in a solution of monoclonal anti-T-2 toxin antibodies, a direct competitive enzyme immunoassay was performed. This assay included the incubation of the antibody-coated dipsticks in a mixture of sample and T-2 toxin-horseradish peroxidase conjugate. Afterwards, the strips were placed in a chromogen-containing substrate solution (H202-3,3',5,5'-tetramethylbenzidine) for color reaction. The dot color intensity of toxin-positive dipsticks was visually distinguishable from that of the negative control. A portable colorimeter was used to confirm and quantify the visual observations. With coated strips, the tests could be performed in 45 min. The visual detection limit for T-2 toxin in buffer solution was 0.25 ng/ml. Artificially infected wheat samples were extracted with 80% methanol-water. A dilution of the raw extract of 1:8 was sufficient to avoid matrix effects. It was possible to make visually a clear distinction between the negative control and a wheat extract spiked with 12 ng/g.     

Presence and Analysis of Plasmids in Human and Animal Associated Arcobacter Species

In this study, we report the screening of four Arcobacter species for the presence of small and large plasmids. Plasmids were present in 9.9% of the 273 examined strains. One Arcobacter cryaerophilus and four Arcobacter butzleri plasmids were selected for further sequencing. The size of three small plasmids isolated from A. butzleri and the one from A. cryaerophilus strains ranged between 4.8 and 5.1 kb, and the size of the large plasmid, isolated from A. butzleri, was 27.4 kbp. The G+C content of all plasmids ranged between 25.4% and 26.2%. A total of 95% of the large plasmid sequence represents coding information, which contrasts to the 20 to 30% for the small plasmids. Some of the open reading frames showed a high homology to putative conserved domains found in other related organisms, such as replication, mobilization and genes involved in type IV secretion system. The large plasmid carried 35 coding sequences, including seven genes in a contiguous region of 11.6 kbp that encodes an orthologous type IV secretion system found in the Wolinella succinogenes genome, Helicobacter pylori and Campylobacter jejuni plasmids, which makes this plasmid interesting for further exploration.     

The prickly pear (Opuntia ficus-indica [Cactaceae]) in South Africa: Utilization of the naturalized weed,and of the cultivated plants

In spite of successful biological control efforts, vast areas of South Africa remain infested with the spiny prickly pear weed, Opuntia ficus-indica. These remnant populations, which vary from sparse to dense and which are more or less stable, are confined mainly to the eastern Cape. They provide a popular fruit and a limited source of income for certain sectors of the population in these areas. In terms of existing legislation, there are, however, restrictions on the large-scale utilization of these fruit. A novel method for mass-rearing the cochineal insect, Dactylopius coccus, for the commercial production of a red dye (carminic acid) has been developed. The cultivated spineless prickly pear has recently been enjoying renewed attention from researchers and growers alike. Whereas it has traditionally been cultivated mainly as a droughtresistant fodder crop, and is still popular as such, it is now increasingly recognised as a fruit, in its own right, with considerable promise as a commercial crop for local and export markets. There is also a need to encourage the use of very young cladodes (nopalitos) as a highly nutritious vegetable for human consumption in South Africa.     

Quorum Sensing Peptides Selectively Penetrate the Blood-Brain Barrier

Bacteria communicate with each other by the use of signaling molecules, a process called ‘quorum sensing’. One group of quorum sensing molecules includes the oligopeptides, which are mainly produced by Gram-positive bacteria. Recently, these quorum sensing peptides were found to biologically influence mammalian cells, promoting i.a. metastasis of cancer cells. Moreover, it was found that bacteria can influence different central nervous system related disorders as well, e.g. anxiety, depression and autism. Research currently focuses on the role of bacterial metabolites in this bacteria-brain interaction, with the role of the quorum sensing peptides not yet known. Here, three chemically diverse quorum sensing peptides were investigated for their brain influx (multiple time regression technique) and efflux properties in an in vivo mouse model (ICR-CD-1) to determine blood-brain transfer properties: PhrCACET1 demonstrated comparatively a very high initial influx into the mouse brain (K_in = 20.87 μl/(g×min)), while brain penetrabilities of BIP-2 and PhrANTH2 were found to be low (K_in = 2.68 μl/(g×min)) and very low (K_in = 0.18 μl/(g×min)), respectively. All three quorum sensing peptides were metabolically stable in plasma (in vitro) during the experimental time frame and no significant brain efflux was observed. Initial tissue distribution data showed remarkably high liver accumulation of BIP-2 as well. Our results thus support the potential role of some quorum sensing peptides in different neurological disorders, thereby enlarging our knowledge about the microbiome-brain axis.     

Anatomical and ultrastructural examination of adventitious root formation in stem slices of apple

Adventitious root formation in vitro in 1-mm stem slices cut from microshoots of apple cv. Jork 9 was studied using light and electron microscopy. When indole-3-butyric acid (IBA) had been added to the medium, starch grains accumulated during the first 24 h of culture in cells of the cambial region and in cells in the vicinity of vascular tissue and in the primary rays. This accumulation occurred only in the basal part of explants. After that, the nuclei in these cells were activated, and the density of the cytoplasm and the number of cell organelles increased, whereas starch was broken down. Cambium cells started to divide transversely and at 96 h, after several divisions, a continuous ring of isodiametric cytoplasmic cells had appeared around the xylem near the basal cutting surface. The cells in this ring were rich in cell structures, and did not contain large starch grains and a central vacuole. Root meristemoids regenerated from the portions of the ring that were localized in the primary rays. From the other cells in the ring, callus developed. The meristemoids did not grow into the direction of the epidermis as in shoots, but along the vascular bundles. After emergence from the cutting surface, the meristemoids were transformed into small, dome-like primordia. They developed a typical root apex with root cap, root ground meristem and tracheid connection with shoot vascular tissue. This revised version was published online in July 2006 with corrections to the Cover Date.     

Malaria Parasite-Infected Erythrocytes Secrete PfCK1, the Plasmodium Homologue of the Pleiotropic Protein Kinase Casein Kinase 1

Casein kinase 1 (CK1) is a pleiotropic protein kinase implicated in several fundamental processes of eukaryotic cell biology. Plasmodium falciparum encodes a single CK1 isoform, PfCK1, that is expressed at all stages of the parasite’s life cycle. We have previously shown that the pfck1 gene cannot be disrupted, but that the locus can be modified if no loss-of-function is incurred, suggesting an important role for this kinase in intra-erythrocytic asexual proliferation. Here, we report on the use of parasite lines expressing GFP- or His-tagged PfCK1 from the endogenous locus to investigate (i) the dynamics of PfCK1 localisation during the asexual cycle in red blood cells, and (ii) potential interactors of PfCK1, so as to gain insight into the involvement of the enzyme in specific cellular processes. Immunofluorescence analysis reveals a dynamic localisation of PfCK1, with evidence for a pool of the enzyme being directed to the membrane of the host erythrocyte in the early stages of infection, followed by a predominantly intra-parasite localisation in trophozoites and schizonts and association with micronemes in merozoites. Furthermore, we present strong evidence that a pool of enzymatically active PfCK1 is secreted into the culture supernatant, demonstrating that PfCK1 is an ectokinase. Our interactome experiments and ensuing kinase assays using recombinant PfCK1 to phosphorylate putative interactors in vitro suggest an involvement of PfCK1 in many cellular processes such as mRNA splicing, protein trafficking, ribosomal, and host cell invasion.