A novel concept of radiosynthesis of a 99mTc-labeled dimeric RGD peptide as a potential radiotracer for tumor imaging

Radiolabeled Arg-Gly-Asp (RGD) peptides are promising agents for non invasive imaging of α_vβ₃ expression in malignant tumors. The integrin α_vβ₃ binding affinity and consequent tumor uptake could be improved when a dimeric RGD peptide is used as the targeting moiety instead of a monomer. Towards this, a novel approach was envisaged to synthesize a ^99mTc labeled dimeric RGD derivative using a RGD monomer and [^99mTcN]⁺² intermediate. The dithiocarbamate derivative of cyclic RGD peptide G₃-c(RGDfK) (G₃ = Gly-Gly-Gly, f = Phe, K = Lys) was synthesized and radiolabeled with [^99mTcN]⁺² intermediate to form the ^99mTcN-[G₃-c(RGDfK)]₂ complex in high yield (～98%). Biodistribution studies carried out in C57/BL6 mice bearing melanoma tumors showed good tumor uptake [4.61 ± 0.04% IA/g at 30 min post-injection] with fast clearance of the activity from non-target organs/tissue. Scintigraphic imaging studies showed visible accumulation of activity in the tumor with appreciable target to background ratio.     

C3′-endo-puckered pyrrolidine containing PNA has favorable geometry for RNA binding: Novel ethano locked PNA (ethano-PNA)

A novel peptide nucleic acid (PNA) analogue is designed with a constraint in the aminoethyl segment of the aegPNA backbone so that the dihedral angle β is restricted within 60–80°, compatible to form PNA:RNA duplexes. The designed monomer is further functionalized with positively charged amino-/guanidino-groups. The appropriately protected monomers were synthesized and incorporated into aegPNA oligomers at predetermined positions and their binding abilities with cDNA and RNA were investigated. A single incorporation of the modified PNA monomer into a 12-mer PNA sequence resulted in stronger binding with complementary RNA over cDNA. No significant changes in the CD signatures of the derived duplexes of modified PNA with complementary RNA were observed.     

Massively Parallel Sequencing Reveals the Complex Structure of an Irradiated Human Chromosome on a Mouse Background in the Tc1 Model of Down Syndrome

Down syndrome (DS) is caused by trisomy of chromosome 21 (Hsa21) and presents a complex phenotype that arises from abnormal dosage of genes on this chromosome. However, the individual dosage-sensitive genes underlying each phenotype remain largely unknown. To help dissect genotype – phenotype correlations in this complex syndrome, the first fully transchromosomic mouse model, the Tc1 mouse, which carries a copy of human chromosome 21 was produced in 2005. The Tc1 strain is trisomic for the majority of genes that cause phenotypes associated with DS, and this freely available mouse strain has become used widely to study DS, the effects of gene dosage abnormalities, and the effect on the basic biology of cells when a mouse carries a freely segregating human chromosome. Tc1 mice were created by a process that included irradiation microcell-mediated chromosome transfer of Hsa21 into recipient mouse embryonic stem cells. Here, the combination of next generation sequencing, array-CGH and fluorescence in situ hybridization technologies has enabled us to identify unsuspected rearrangements of Hsa21 in this mouse model; revealing one deletion, six duplications and more than 25 de novo structural rearrangements. Our study is not only essential for informing functional studies of the Tc1 mouse but also (1) presents for the first time a detailed sequence analysis of the effects of gamma radiation on an entire human chromosome, which gives some mechanistic insight into the effects of radiation damage on DNA, and (2) overcomes specific technical difficulties of assaying a human chromosome on a mouse background where highly conserved sequences may confound the analysis. Sequence data generated in this study is deposited in the ENA database, Study Accession number: ERP000439.     

Polarization of Diploid Daughter Cells Directed by Spatial Cues and GTP Hydrolysis of Cdc42 in Budding Yeast

Cell polarization occurs along a single axis that is generally determined by a spatial cue. Cells of the budding yeast exhibit a characteristic pattern of budding, which depends on cell-type-specific cortical markers, reflecting a genetic programming for the site of cell polarization. The Cdc42 GTPase plays a key role in cell polarization in various cell types. Although previous studies in budding yeast suggested positive feedback loops whereby Cdc42 becomes polarized, these mechanisms do not include spatial cues, neglecting the normal patterns of budding. Here we combine live-cell imaging and mathematical modeling to understand how diploid daughter cells establish polarity preferentially at the pole distal to the previous division site. Live-cell imaging shows that daughter cells of diploids exhibit dynamic polarization of Cdc42-GTP, which localizes to the bud tip until the M phase, to the division site at cytokinesis, and then to the distal pole in the next G1 phase. The strong bias toward distal budding of daughter cells requires the distal-pole tag Bud8 and Rga1, a GTPase activating protein for Cdc42, which inhibits budding at the cytokinesis site. Unexpectedly, we also find that over 50% of daughter cells lacking Rga1 exhibit persistent Cdc42-GTP polarization at the bud tip and the distal pole, revealing an additional role of Rga1 in spatiotemporal regulation of Cdc42 and thus in the pattern of polarized growth. Mathematical modeling indeed reveals robust Cdc42-GTP clustering at the distal pole in diploid daughter cells despite random perturbation of the landmark cues. Moreover, modeling predicts different dynamics of Cdc42-GTP polarization when the landmark level and the initial level of Cdc42-GTP at the division site are perturbed by noise added in the model.     

Can Carnosine Prevent the Aging-Induced Changes of Blood Platelet and Brain Regional Monoamine Oxidase-A mRNA in Relation to its Activity?

It is well known that the monoamine oxidase (MAO) activity deregulates during aging along with anti-oxidant activity. Carnosine (β-Ala-l-His) is an endogenous dipeptide biomolecule, having both anti-oxidant and anti-glycating properties. The present study deals with the effect of carnosine on aging-induced changes in MAO-A mRNA expression of brain regions and blood platelets in relation to their MAO-A activity. Results showed that aging significantly and characteristically increased the brain regional MAO-A mRNA whereas, in blood platelets it was significantly reduced with an increase in blood platelet counts. Carnosine attenuated both aging-induced (i) increase in brain regional MAO-A mRNA expression and blood platelet count, (ii) decrease in blood platelet MAO-A mRNA expression and its (platelet MAO-A) activity without affecting the young rats’ brain regions and platelet. The present results thus suggest that carnosine attenuated and restored the aging-induced (a) increase of platelet count and (b) changes in brain regional and blood platelet MAO-A mRNA expression and (c) decrease in platelet MAO-A activity, towards their respective basal level that were observed in young rats.