Dopamine D1 receptor-induced signaling through TrkB receptors in striatal neurons

In addition to its role as a neurotransmitter, dopamine can stimulate neurite outgrowth and morphological effects upon primary neurons. To investigate the signal transduction mechanisms used by dopamine in developing striatal neurons, we focused upon the effects of activating the dopamine D1 receptor. Using the D1 receptor agonist SKF38393, we found that Trk neurotrophin receptors were activated in embryonic day 18 striatal neurons. K-252a, a Trk tyrosine kinase inhibitor, and a dopamine D1 receptor antagonist could block the effects of SKF38393. The increase in TrkB phosphorylation was not the result of increased neurotrophin production. Induction of TrkB activity by SKF38393 was accompanied by the phosphorylation of several Trk signaling proteins, including phospholipase Cgamma, Akt, and MAPK. Biotinylation experiments followed by immunostaining by phospho-TrkB-specific antibodies indicated that the mechanism involved increased TrkB surface expression by dopamine D1 receptor activation. This increase in cell surface TrkB expression was dependent upon an increase in intracellular Ca(2+). These results indicate that stimulation of dopamine D1 receptors can be coupled to the neurotrophin receptor signaling to mediate the effects of dopamine upon striatal neurons.     

Micromechanical evaluation of mineralized multilayers

The biomechanical stability of osseointegrated implants is of particular importance, especially the stability which is achieved from structural manipulation at the interface between the implant surface and the bone tissues. Nanoscale β-tricalcium phosphate-immobilized titanium was prepared by discharge into a physiological buffered saline solution. Compared with hydroxyapatite, it has been shown to be effective in generating a bone-like chemical structure on the surface by cooperative interaction between osteoblastic cells and the β-tricalcium phosphate. The present study, after cell cultivation, investigates the nanostructures and biomechanical property differences of a mineralized layer formed on two samples of nano-calcium phosphate-immobilized titanium. A scanning probe microscope study revealed that the mineralized tissue formed on the β-tricalcium phosphate samples after 1 week of cell culture showed significantly higher roughness, compared with hydroxyapatite samples. Nanoindentation micromechanical evaluation of the in vitro generated multilayered structures exhibited thicker bone-like mineralized layers on the β-tricalcium phosphate samples. A successful modification of titanium implants through the cooperative interaction between osteoblastic cells and nano β-tricalcium phosphate is anticipated.     

Mimicking a semi-arid tropical environment achieves dormancy alleviation for seeds of Australian native Goodeniaceae and Asteraceae

Background and Aims: Seed physiological dormancy (PD) limits the use and conservationof some of Queensland's (Qld) native forb species. It was hypothesisedthat optimum dormancy-alleviating treatments would reflect environmentalconditions that seeds experience in situ, and this premise wastested for PD seeds of four species native to south-west Qld. Methods: High temperatures and increased rainfall during summer are characteristicof this semi-arid tropical environment. Ex situ treatments weredesigned to mimic conditions that seeds dispersed in springexperience during the summer months before germinating in coolerautumn temperatures. Seeds received between 4 and 20 weeks ofa dry after-ripening (DAR), warm stratification or dry/wet cyclingtreatment (DAR interspersed with short periods of warm stratification),in darkness, before being transferred to germination test conditions.In addition, natural dormancy alleviation of one of the Goodeniaceaespecies was investigated in situ. Key Results: Dry/wet cycling resulted in higher levels of germination ofActinobole uliginosum (Asteraceae), Goodenia cycloptera andVelleia glabrata (Goodeniaceae) when compared with constantDAR or stratification, while Goodenia fascicularis (Goodeniaceae)responded better to short durations of warm stratification.Long durations of DAR partially alleviated PD of A. uliginosum;however, stratification induced and maintained dormancy of thisspecies. Modifications to the dry/wet cycling treatment andgermination test conditions based on data collected in situenabled germination of G. cycloptera and V. glabrata to be furtherimproved. Conclusions: Treatments designed using temperature, relative humidity andrainfall data for the period between natural seed dispersaland germination can successfully alleviate PD. Differences betweenthe four species in conditions that resulted in maximum germinationindicate that, in addition to responding to broad-scale climatepatterns, species may be adapted to particular microsites and/orseasonal conditions.     

Mutations in foregut SOX2+ cells induce efficient proliferation via CXCR2 pathway

Identification of the precise molecular pathways involved in oncogene-induced transformation may help us gain a better understanding of tumor initiation and promotion. Here, we demonstrate that SOX2⁺ foregut epithelial cells are prone to oncogenic transformation upon mutagenic insults, such as Kras^G12D and p53 deletion. GFP-based lineage-tracing experiments indicate that SOX2⁺ cells are the cells-of-origin of esophagus and stomach hyperplasia. Our observations indicate distinct roles for oncogenic KRAS mutation and P53 deletion. p53 homozygous deletion is required for the acquisition of an invasive potential, and Kras^G12D expression, but not p53 deletion, suffices for tumor formation. Global gene expression analysis reveals secreting factors upregulated in the hyperplasia induced by oncogenic KRAS and highlights a crucial role for the CXCR2 pathway in driving hyperplasia. Collectively, the array of genetic models presented here demonstrate that stratified epithelial cells are susceptible to oncogenic insults, which may lead to a better understanding of tumor initiation and aid in the design of new cancer therapeutics.     

The physiological basis of seed dormancy in Avena fatua. VIII. Action of malonic acid

Adkins, S. W., Symons, S. J. and Simpson, G. M. 1988. The physiological basis of seed dormancy in Avena fatua . VIII. Action of malonic acid - Physiol. Plant, 72: 477–482.
A low concentration of malonic acid (50 m M ) induced germination in four genetically pure dormant lines of Avena fatua L. Sensitivity to this treatment was poor immediately after harvest but increased markedly during after-ripening, indicating that the mode of action of malonic acid (50 m M ) was similar to that of another organic acid, citric acid. Over the concentration range (10–50 m M ) where malonic acid promoted germination, oxygen uptake was also stimulated, and this was before the first visible signs of germination. At higher concentrations (100–300 m M ) where there was no promotion of germination, malonic acid strongly inhibited oxygen uptake. These results show that malonic acid has a dual effect on oxygen uptake and subsequent germination. Low concentrations (10–50 m M ) act by stimulating the Krebs cycle and germination through an acidification reaction like citric acid, and high concentrations (100–300 m M ) act by inhibiting germination through enzymatic restraint of the Krebs cycle.
The stimulation of both oxygen uptake and germination by three established germination promoters (sodium nitrate, citric acid and ethanol) was inhibited by a high concentration of malonic acid (200 m M ) but unaffected by a low concentration (50 m M ). These results show that oxygen uptake, and hence the activity of the Krebs cycle, are important processes involved in the dormancy breaking mechanism of these three promotors.     

Genotype-Based Ancestral Background Consistently Predicts Efficacy and Side Effects across Treatments in CATIE and STAR*D

Only a subset of patients will typically respond to any given prescribed drug. The time it takes clinicians to declare a treatment ineffective leaves the patient in an impaired state and at unnecessary risk for adverse drug effects. Thus, diagnostic tests robustly predicting the most effective and safe medication for each patient prior to starting pharmacotherapy would have tremendous clinical value. In this article, we evaluated the use of genetic markers to estimate ancestry as a predictive component of such diagnostic tests. We first estimated each patient’s unique mosaic of ancestral backgrounds using genome-wide SNP data collected in the Clinical Antipsychotic Trials of Intervention Effectiveness (CATIE) (n = 765) and the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) (n = 1892). Next, we performed multiple regression analyses to estimate the predictive power of these ancestral dimensions. For 136/89 treatment-outcome combinations tested in CATIE/STAR*D, results indicated 1.67/1.84 times higher median test statistics than expected under the null hypothesis assuming no predictive power (p<0.01, both samples). Thus, ancestry showed robust and pervasive correlations with drug efficacy and side effects in both CATIE and STAR*D. Comparison of the marginal predictive power of MDS ancestral dimensions and self-reported race indicated significant improvements to model fit with the inclusion of MDS dimensions, but mixed evidence for self-reported race. Knowledge of each patient’s unique mosaic of ancestral backgrounds provides a potent immediate starting point for developing algorithms identifying the most effective and safe medication for a wide variety of drug-treatment response combinations. As relatively few new psychiatric drugs are currently under development, such personalized medicine offers a promising approach toward optimizing pharmacotherapy for psychiatric conditions.     

Age and growth of the cold-water scleractinian Solenosmilia variabilis and its reef on SW Pacific seamounts

Little is known about growth rates of deep-water reef-forming corals or the rates at which these reefs accumulate. Such information is critical for determining the resilience of the reefs to anthropogenic impacts such as trawling and climate change. We radiocarbon date live-caught and sub-fossil samples of the bioherm-forming coral Solenosmilia variabilis collected from precisely known depths and locations by means of a remotely operated vehicle on seamounts south of Tasmania, Australia. The growth rate of colonies live-caught between 958 and 1,454 m, which spans most of the depth range of the species locally, ranged from 0.84 to 1.25 mm linear extension yr^?1 and tended to be higher in the deeper-caught material. Analysis of skeletal microstructure suggests annual deposition of growth increments near the growing tips, but not closer to the base, as the skeleton is extended and thickened. Dating of sub-fossil material indicates S. variabilis has been present on Tasmanian seamounts for at least the last 47,000 yrs and a reef accumulation rate of 0.27 mm yr^?1.     

The crystal structure of the tryptophan synthase beta subunit from the hyperthermophile Pyrococcus furiosus. Investigation of stabilization factors.

The structure of the tryptophan synthase beta2 subunit (Pfbeta2) from the hyperthermophile, Pyrococcus furiosus, was determined by X-ray crystallographic analysis at 2.2 A resolution, and its stability was examined by DSC. This is the first report of the X-ray structure of the tryptophan synthase beta2 subunit alone, although the structure of the tryptophan synthase alpha2beta2 complex from Salmonella typhimurium has already been reported. The structure of Pfbeta2 was essentially similar to that of the beta2 subunit (Stbeta2) in the alpha2beta2 complex from S. typhimurium. The sequence alignment with secondary structures of Pfbeta and Stbeta in monomeric form showed that six residues in the N-terminal region and three residues in the C-terminal region were deleted in Pfbeta, and one residue at Pro366 of Stbeta and at Ile63 of Pfbeta was inserted. The denaturation temperature of Pfbeta2 was higher by 35 degrees C than the reported values from mesophiles at approximately pH 8. On the basis of structural information on both proteins, the analyses of the contributions of each stabilization factor indicate that: (a) the higher stability of Pfbeta2 is not caused by either a hydrophobic interaction or an increase in ion pairs; (b) the number of hydrogen bonds involved in the main chains of Pfbeta is greater by about 10% than that of Stbeta, indicating that the secondary structures of Pfbeta are more stabilized than those of Stbeta and (c) the sequence of Pfbeta seems to be better fitted to an ideally stable structure than that of Stbeta, as assessed from X-ray structure data.