Massively parallel electro-optic sampling of space-encoded optical pulses for ultrafast multi-dimensional imaging

High-speed and high-resolution imaging of surface profiles is critical for the investigation of various structures and mechanical dynamics of micro- and nano-scale devices. In particular, recent emergence of various nonlinear, transient and complex mechanical dynamics, such as anharmonic vibrations in mechanical resonators, has necessitated real-time surface deformation imaging with higher axial and lateral resolutions, speed, and dynamic range. However, real-time capturing of fast and complex mechanical dynamics has been challenging, and direct time-domain imaging of displacements and mechanical motions has been a missing element in studying full-field structural and dynamic behaviours. Here, by exploiting the electro-optic sampling with a frequency comb, we demonstrate a line-scan time-of-flight (TOF) camera that can simultaneously measure the TOF changes of more than 1000 spatial coordinates with hundreds megapixels/s pixel-rate and sub-nanometre axial resolution over several millimetres field-of-view. This unique combination of performances enables fast and precise imaging of both complex structures and dynamics in three-dimensional devices and mechanical resonators.

Simple-structured, subfemtosecond-resolution optical-microwave phase detector

We demonstrate a simple all-fiber photonic phase detector that can measure the phase (timing) difference between an optical pulse train and a microwave signal with subfemtosecond resolution and -60  dB-level amplitude-to-phase conversion coefficient. It is based on passive phase biasing of a Sagnac loop by the intrinsic phase shift of a symmetric 3×3 fiber coupler. By eliminating the necessity of magneto-optic components or complex radio frequency (RF) electronics for phase biasing of the Sagnac loop, this phase detector has potential to be implemented as an integrated photonic device as well. When using this device for synchronization between a 250 MHz mode-locked Er-fiber laser and an 8 GHz microwave oscillator, the minimum residual phase noise floor reaches <-154  dBc/Hz (at 8 GHz carrier) with integrated root mean square (rms) timing jitter of 0.97 fs [1 Hz-1 MHz]. The long-term rms timing drift and frequency instability are 0.92 fs (over 5000 s) and 4×10^-19 (at 10,000 s averaging time), respectively.

Prognostic significance of Id-1 and its association with EGFR in renal cell cancer

AIMS

Epidermal growth factor receptor (EGFR) is suggested as one of the positive regulators in the invasive progression of renal cell cancer (RCC). Recently, Id-1 (inhibitor of differentiation or DNA binding), a helix-loop-helix transcription factor, has been identified as one of the key factors in the EGFR signalling pathway. The aim of this study was to investigate the significance of Id-1 expression in renal cell cancer and to study its relationship with EGFR.

METHODS AND RESULTS

Id-1 and EGFR expression was examined in tissue microarray (TMA) samples of 107 RCC and 32 normal kidney specimens by immunohistochemistry. Relative Id-1 and EGFR protein expression was quantified by estimating the staining intensity on a four-grade scale. We found that while negative to weak expression of Id-1 and EGFR was observed in non-malignant kidney tissues, most RCCs showed significant positive Id-1 and EGFR expression in tumour cells. In addition, Id-1 immunostaining intensity was positively associated with increased tumour staging, grading and EGFR expression.

CONCLUSION

Overexpression of Id-1 is a novel marker for advanced RCC which is positively correlated with EGFR expression. Our results suggest that Id-1 may play an important role in the development of RCC and indicate that Id-1 is a potential marker of patients with a poor prognosis.

Global analysis of differentially expressed genes in androgen-independent prostate cancer

Progression to androgen independent (AI) is the main cause of death in prostate cancer, and the mechanism is still unclear. By reviewing the expression profiles of 26 prostate cancer samples in a holistic view, we found a group of genes differentially expressed in AI compared with androgen-dependent groups (P-value<0.01, t-test). Focusing on apoptosis, proliferation, hormone and angiogenesis, we found a group of genes such as thioredoxin domain containing 5 , tumor necrosis factor receptor superfamily, member 10a , ribosomal protein S19 and Janus kinase 2 upregulated in AI prostate cancer, could play important roles in the transition from AD to AI and could be biomarkers of prognosis.

Silencing mediator of retinoid and thyroid hormone receptors and activating signal cointegrator-2 as transcriptional coregulators of the orphan nuclear receptor Nur77

For the orphan nuclear receptor subfamily that includes Nur77 (NGFI-B), Nurr1, and NOR-1, no transcriptional coregulators have been identified thus far. In this report, we found that Ca(2+)/calmodulin-dependent protein kinase IV enhances Nur77 transactivation in cotransfections either alone or in synergy with AF2dependent coactivator ASC-2, whereas corepressor silencing mediator for retinoid and thyroid hormone receptors (SMRT) is repressive. Interestingly, Nur77 interacted with SMRT but did not directly bind ASC-2, and accordingly, the putative AF2 core domain of Nur77 did not affect the Nur77 transactivation. SMRT harbors transferable repression domains that associate with various histone deacetylases. Surprisingly, histone deacetylase inhibitor trichostatin A was unable to block the repressive effect of SMRT while dramatically stimulating the Nur77 transactivation. These results suggest that SMRT and ASC-2 are specific coregulators of Nur77 and that SMRT may dynamically compete with a putative adaptor molecule, which links ASC-2 to Nur77, for the identical binding sites within Nur77 in vivo.

Synthesis, DNA cross-linking activity, and cytotoxicity of dimeric mitomycins

Dimeric DNA cross-linking compounds have emerged as important new antitumor agents. We report the synthesis and biochemical evaluation of a select set of dimeric mitomycins in which the two mitomycin units are tethered at either the mitomycin C(7) amino or the aziridine N(1a) positions. Significantly, mitomycin C (1) itself is the prototypical bioreductive DNA cross-linking agent. DNA cross-linking experiments using a denaturing-gel-electrophoresis-based assay showed that the extent of DNA cross-linking for select dimeric mitomycins can exceed that of the parent compound, mitomycin C, and that the reaction proceeds, in part, at the two distal C(1) sites in the mitomycins. The efficiency of DNA cross-linking depended on the nature of the linker and the position of linker unit's attachment. When we compared the efficiency of DNA cross-linking for the dimeric mitomycins with their in vitro cytotoxicities in cultured human tumor cells, we observed a poor correlation. The mitomycins that gave the highest levels of DNA cross-linked adducts displayed the weakest cytotoxicities. These findings determined that the denaturing-gel-electrophoresis-based assay was a poor predictor of cytotoxic activity.

Suppression subtractive hybridization for identifying differentially expressed genes in renal cell carcinoma

OBJECTIVE

To construct a renal cell carcinoma (RCC) cDNA subtractive library using suppression subtractive hybridization.

METHODS

Polyadenylated RNA [Poly (A)+ RNA] was isolated from tissues of RCC and normal kidney, and single-strand cDNAs and double-strand cDNAs were synthesized in turn. RCC cDNAs were divided into two groups and ligated to the specific adaptors I and 2, and then hybridized with normal kidney cDNA twice with two rounds of suppression PCR. Second round PCR products were cloned to T/A plasmid vectors to set up the subtractive library. One hundred clones were randomly picked to perform enzyme digest analysis, and some underwent sequence analysis and Northern blot to identify RCC specifically expressed genes. SMART RACE procedure was operated to clone full length novel RCC specifically expressed genes.

RESULTS

A human RCC subtractive library with high subtractive efficiency was successfully set up. The amplified library contains 350 positive clones. Random analysis of 100 clones with enzyme restriction showed that 85 plasmids in the clones contained 50-400 bp inserts. Sequence analysis was performed for 10 clones. All the 10 sequences were unknown before and derived from 6 unique, novel genes among which the cDNA insert RCC18 had five copies. Northern blot analysis showed that RCC18 cDNA was highly expressed in RCC, but no signal could be detected in normal kidney. Using SMART RACE technique, we obtained the full length of the novel gene RCC18.

CONCLUSIONS

The constructed cDNA subtractive library of human RCC is a highly efficient one and lays a solid foundation for large scale screening and cloning new and specific oncogenes or tumor suppressor genes of RCC. The novel specifically expressed genes provided an important clue for studying the mechanisms of occurrence and development of RCC.