A membrane-bound activity catalysing phosphatidylinositol breakdown to 1,2-diacylglycerol, d-myoinositol 1:2-cyclic phosphate and d-myoinositol 1-phosphate. Properties and subcellular distribution in rat cerebral cortex

1. Breakdown of phosphatidylinositol was studied in homogenates and subcellular fractions of rat cerebral cortex by using both membrane-bound and externally added [(32)P]phosphatidylinositol as substrate. 2. In the presence of deoxycholate breakdown followed first-order kinetics at low substrate concentrations ([unk]1mm) and zero-order kinetics at higher concentrations (6-9mm). 3. Maximum breakdown by cerebral-cortex homogenates was approximately 0.5mumol/h per mg of protein and occurred at pH7.0 in the presence of 8mm-phosphatidylinositol, 2mm-CaCl(2) and 2mg of deoxycholate/ml. Activity was abolished by 1mm-ethanedioxybis(ethylamine)tetra-acetate. 4. The products of phosphatidylinositol breakdown were 1,2-diacylglycerol and a mixture of d-myoinositol 1:2-cyclic phosphate (55%) and d-myoinositol 1-phosphate (45%). The two phosphate esters appeared to be produced together and in constant proportions. 5. Some 51% of the activity was particle-bound, with the highest activities in small nerve endings, microsomal material and two synaptic membrane fractions (fractions Mic(20), Mic(100), M(1) 1.0 and M(1) 0.9 respectively), all of which were also rich in acetylcholinesterase and which have been shown to be rich in other surface-membrane enzymes. Much of the particle-bound activity therefore appears to be present in cerebral-cortex plasma membranes. 6. The results are discussed in relation to previously described soluble activities that catalyse the same reaction, and to a possible role of the membrane-bound enzyme in enhanced phosphatidylinositol turnover in externally stimulated cells.     

The effects of continuous exposure to low concentrations of the δ-endotoxin of Bacillus thuringiensis on the development of the tobacco budworm,Heliothis virescens

The tobacco budworm, Heliothis virescens, was reared on diets containing various low concentrations of the spore-δ-endotoxin complex of Bacillus thuringiensis var. kurstaki. As the concentration of the complex was increased, the development time increased, pupal weights of the surviving larvae decreased, and the numbers of larvae able to complete the cycle and reach adulthood was reduced. In all these cases, the changes were directly proportional to the log of the concentration of the complex in the diet. Fertility and fecundity were reduced in adult tobacco budworms emerging from larvae reared in the presence of the toxin, but these effects seemed to result indirectly from the general debilitation produced by the toxin, since their occurrence was not related to the concentration of the toxin in the diet.     

SOME FEATURES OF THE SUBMICROSCOPIC MORPHOLOGY OF SYNAPSES IN FROG AND EARTHWORM

Electron micrographs are presented of synaptic regions encountered in sections of frog sympathetic ganglia and earthworm nerve cord neuropile. Pre- and postsynaptic neuronal elements each appear to have a membrane 70 to 100 A thick, separated from each other over the synaptic area by an intermembranal space 100 to 150 A across. A granular or vesicular component, here designated the synaptic vesicles, is encountered on the presynaptic side of the synapse and consists of numerous oval or spherical bodies 200 to 500 A in diameter, with dense circumferences and lighter centers. Synaptic vesicles are encountered in close relationship to the synaptic membrane. In the earthworm neuropile elongated vesicles are found extending through perforations or gaps in the presynaptic membrane, with portions of vesicles appearing in the intermembranal space. Mitochondria are encountered in the vicinity of the synapse, and in the frog, a submicroscopic filamentary component can be seen in the presynaptic member extending up to the region where the vesicles are found, but terminating short of the synapse itself.     

Influence of clay licks on the diversity and structure of an Amazonian forest

The spatial heterogeneity of resource availability is a major driver of biodiversity patterns. Some environmental conditions and resources are characterized by large‐scale patterns of variation within the landscape. Clumped local discontinuities or discrete elements also increase spatial heterogeneity, promoting local ‘biodiversity hot spots’ by modifying habitat characteristics and promoting plant–animal interactions. Clay licks are faunal attractors owing to their role in the nutritional ecology of the user species; nevertheless, the effect of their presence on the surrounding vegetation has been poorly quantified. Here, we use data from 100 × 10 m transects and evaluate the effects of the presence of clay licks on forest diversity and structure at local and landscape scales. In clay lick areas, there was a higher abundance of certain species, which helps to homogenize species composition between localities counteracting the natural distance‐decay of compositional similarity between transects without clay lick influence (controls). Compared to control sites, clay lick′s forests had higher palm densities, shorter but more variable individuals in the canopy and understory, a thinner canopy layer, and denser herbaceous and ground level covers. These differences were found along the whole length of transects in both sampled areas types. These results reveal that the presence of discrete elements (i.e., clay licks) may help to explain the compositional and structural heterogeneity of Amazonian forests influencing ecological processes such as seed dispersal and trampling. These considerations may be relevant for other biomes where clay licks are present and give weight to their inclusion in conservation initiatives in tropical forests.     

Spike‐dip transformation of Setaria viridis

Traditional method of Agrobacterium‐mediated transformation through the generation of tissue culture had limited success for Setaria viridis, an emerging C4 monocot model. Here we present an efficient in planta method for Agrobacterium‐mediated genetic transformation of S. viridis using spike dip. Pre‐anthesis developing spikes were dipped into a solution of Agrobacterium tumefaciens strain AGL1 harboring the β‐glucuronidase (GUS) reporter gene driven by the cauliflower mosaic virus 35S (CaMV35S) promoter to standardize and optimize conditions for transient as well as stable transformations. A transformation efficiency of 0.8 ± 0.1% was obtained after dipping of 5‐day‐old S3 spikes for 20 min in Agrobacterium cultures containing S. viridis spike‐dip medium supplemented with 0.025% Silwet L‐77 and 200 μm acetosyringone. Reproducibility of this method was demonstrated by generating stable transgenic lines expressing β‐glucuronidase plus (GUSplus), green fluorescent protein (GFP) and Discosoma sp. red fluorescent protein (DsRed) reporter genes driven by either CaMV35S or intron‐interrupted maize ubiquitin (Ubi) promoters from three S. viridis genotypes. Expression of these reporter genes in transient assays as well as in T1 stable transformed plants was monitored using histochemical, fluorometric GUS activity and fluorescence microscopy. Molecular analysis of transgenic lines revealed stable integration of transgenes into the genome, and inherited transgenes expressed in the subsequent generations. This approach provides opportunities for the high‐throughput transformation and potentially facilitates translational research in a monocot model plant.     

Intertidal benthic communities associated with the macroalgae <Emphasis Type="Italic">Iridaea cordata</Emphasis> and <Emphasis Type="Italic">Adenocystis utricularis</Emphasis> in King George Island,Antarctica

Antarctic benthos has been a main target in Antarctic research, but very few quantitative studies have been carried out in the littoral zone, which may be seasonally covered by macroalgae. In this work, we studied (1) cover and biomass of the macroalgae Iridaea cordata and Adenocystis utricularis, and (2) composition of macrobenthic assemblage associated with these macroalgal species at three locations at King George Island: Mareograph Beach (1 M), Tank’s Bay (2R) and Ardley Bay (3R). Iridaea cordata was collected by completely detaching the algae from the substrate, while A. utricularis was scraped. Adenocystis utricularis covered more than 80 % of the substrate at all locations, while coverage of Iridaea cordata was below 53 % or absent (3R). Fresh biomass of I. cordata was 0.8–61.4 g/individual and 4.7–93.0 g/100 cm² for A. utricularis. The assemblage associated with both macroalgae differed significantly between sites. The studied fauna was composed mainly of amphipods, gastropods and bivalves. Species diversity was higher in the community associated with A. utricularis. A total of ~27 ind/g DW were found associated with I. cordata, while ~112 ind/g DW were found associated with A. utricularis. The most abundant groups associated with I. cordata were amphipods at 1 M (57 %) and gastropods at 2R (46 %). Both groups were responsible for the dissimilarity between localities (62.50 %). The most abundant groups associated with A. utricularis were the gastropods at all localities reaching up to 82 % at 1 M. This study provides a first baseline on the diversity and abundance of benthic assemblages associated with intertidal macroalgae in the southwest of King George Island.