Cell adhesion in invasion and metastasis.

Metastatic cells exhibit considerable flexibility in their adhesive interactions with other cells or components of the extracellular matrix. This review will describe the involvement of specific adhesion receptors, extracellular matrix molecules and cell dissociating cytokines in the metastatic cascade. We will particularly focus on disturbance of intercellular adhesion as a prerequisite for the release of invasive cells from carcinomas. We suggest that cell dissociation in these tumours is accomplished by loss of function or expression of the epithelial cell adhesion molecule E-cadherin, and through the activity of cell motility factors such as the scatter factor.     

Genome sequence of the soybean symbiont Sinorhizobium fredii HH103

Sinorhizobium fredii HH103 is a fast-growing rhizobial strain that is able to nodulate legumes that develop determinate nodules, e.g., soybean, and legumes that form nodules of the indeterminate type. Here we present the genome of HH103, which consists of one chromosome and five plasmids with a total size of 7.22 Mb.     

Galactosemic nephropathy in the rat

The effect of 30% galactose feeding on kidney function and structure was compared to the effect of streptozotocin-induced diabetes in the rat. In the galactose-fed rats there was increased urine volume (500%), creatinine clearance (40%), urinary albumin excretion (100%), urinary N-acetyl glucosaminidase (600%) and relative kidney weight (21%). These changes were similar to that observed in streptozotocin-induced diabetic animals. Galactitol in the kidney cortex of galactose-fed rats was increased 4 times similar to that observed for sorbitol in the streptozotocin-induced diabetic animals. Glycosylated hemoglobins were also increased in both galactose-fed animals and streptozotocin-treated animals. These data suggest that galactose feeding may be a useful model for investigating some aspects of diabetic nephropathy.     

Modelling the longitudinal distribution,abundance, and habitat use of the giant freshwater shrimp (Macrobrachium spinipes) in a large intermittent,tropical Australian river to inform water resource policy

1. Water development threatens rivers and their biodiversity. Amphidromous shrimp are particularly vulnerable as they require migration between freshwater and estuaries to complete their life cycle. The Fitzroy River is a large tropical intermittent river undergoing water development that is home to the amphidromous shrimp Macrobrachium spinipes (cherabin), yet little is known about its habitat use and flow-ecology making it difficult to inform sustainable water-take.
2. We investigated habitat associations, distributional patterns suggestive of amphidromy, and the influence of water availability by sampling main channel and floodplain pools along a 350-km river length during 2 contrasting flow years. Applying a size-specific abundance model, we estimated abundance per size class, site, and year. We then predicted abundance at the landscape scale with remotely sensed water to reveal the impact of water availability on the meta-population.
3. Our model revealed that juveniles were in greatest abundance in downstream main channel pools, whereas adults were in greatest abundance in upstream floodplain pools. Abundance varied by year with lower numbers predicted in the low-flow year. Longitudinal and habitat patterns remained when our pool-level results were scaled to the landscape, and the positive relationship of abundance to wet-season flow was strengthened. The predominance of smaller cherabin in the lower reaches of the river provides indirect support for an estuarine nursery and amphidromous life history; however, small individuals observed in landlocked pools, during late dry season suggests possible within-river recruitment.
4. The importance of water development policies that protect wet-season flow and passage along the Fitzroy River is supported by this work. These types of policies are likely to be important for this and other amphidromous shrimp species across Australia, Southeast Asia and further afield. Further research detailing the species life history and describing flow–recruitment relationships will be important contributions to understanding this important taxonomic group and refining policies for current and future water resource development.

     

Possible involvement of the cytoskeleton in the regulation of barley caryopsis dormancy and germination

This study was conducted on barley cv. Ars. caryopses collected at full ripeness and divided into two batches. From one batch (dormant caryopses) polysomes were isolated from embryos immediately after harvesting and after two days of germination. From the other batch (non-dormant caryopses) the same was done after eight months storage in a dry state. A low ionic strength cytoskeleton-stabilizing buffer was used for the isolation of polysomes. Four different fractions of polysomes were examined: free polysomes (FP), membrane-bound polysomes (MBP), cytoskeleton-bound polysomes (CBP) and cytoskeleton-membrane-bound polysomes (CMBP). In germs grown from non-dormant caryopses, the first two fractions (FP + MBP) made up about 78 % of the total ribosomal material, whereas in embryos of dormant, imbibed caryopses, two last fractions (CBP + CMBP) made up about 71 %. The percentage of polysomes after 48 hours of imbibition of dormant caryopses in the FP, MBP and CBP was only about 13 % (i.e., 87 % monosomes), whereas a greater proportion (19.4 %) was found in the CMBP. The highest incorporation of ³H-uridine and ¹⁴C-amino acids (after 48 hours of germination and 0.5, 3 and 6 hrs incubation with precursors) took place in trhc CMBP both in dormant and non-dormant caryopses The major amount of the two polysome fractions associated with the cytoskeleton (CBP and CMBP) and the higher activity of CMBP in protein synthesis in embryos of dormant, imbibed triticale caryopses may indicate a significant role for polysomes associated with the cytoskeleton in the control of protein synthesis in dormant and germinating caryopses.     

Temporal and stoichiometric patterns of algal stimulation of litter-associated heterotrophic microbial activity

1. Periphyton communities associated with submerged plant detritus contain interacting autotrophic and heterotrophic microbes, and are sites of extracellular enzymatic activity. The strength and nature of these interactions might be expected to change over time as microbial communities develop on plant litter. Microbial interactions and enzymatic activity can be altered by nutrient availability, suggesting that litter stoichiometry could also affect these phenomena.
2. We grew wetland plants under ambient and nutrient-enriched conditions to generate plant litter of differing nutrient content. In two experiments, we investigated: (1) the influence of algal photosynthesis on fungal and bacterial production and the activities of four extracellular enzymes throughout a 54-day period of microbial colonisation and growth; and (2) the influence of litter stoichiometry on these relationships.
3. Ambient and nutrient-enriched standing-dead plant litter was collected and then submerged in wetland pools to allow for natural microbial colonisation and growth. Litter samples were periodically retrieved and transported to the laboratory for experiments manipulating photosynthesis using the photosystem II inhibitor DCMU (which effectively prevents algal photosynthetic activity). Algal (¹⁴C-bicarbonate), bacterial (³H-leucine), and fungal (¹⁴C-acetate) production, and β-glucosidase, β-xylosidase, leucine aminopeptidase, and phosphatase activities (MUF- or AMC-labelled fluorogenic substrates) were measured under conditions of active and inhibited algal photosynthesis.
4. Photosynthesis stimulated overall fungal and bacterial production in both experiments, although the strength of stimulation varied amongst sampling dates. Phosphatase activity was stimulated by photosynthesis during the first, but not the second, experiment. No other enzymatic responses to short-term photosynthesis manipulations were observed.
5. Microbial communities on high-nutrient litter occasionally showed increased extracellular enzyme activity, fungal growth rates, and bacterial production compared to communities on non-enriched litter, but algal and fungal production were not affected. Litter stoichiometry had no effects on fungal, bacterial, or enzymatic responses to photosynthesis, but the mean enzyme vector analysis angle (a measure of P- versus N-acquiring enzyme activity) was positively correlated to litter N:P, suggesting that elevated litter N:P led to an increase in the relative activity of P-acquiring enzymes.
6. These results supported the hypothesis that algal photosynthesis strongly influences heterotrophic microbial activity on macrophyte leaf litter, especially that of fungi, throughout microbial community development. However, the strength of this photosynthetic stimulation does not generally depend on small differences in litter nutrient content.
7. Stimulation of microbial heterotrophs by algal photosynthesis could drive diurnal shifts in periphyton community and aquatic ecosystem function, as well as linking green (photoautotroph-based) and brown (detrital-based) food webs.