Surpassing the limitation of a coherence length in lidar by digital coherence.

In this manuscript, we propose a digital coherent detection method to surpass the limitation of a coherent length on the detection range of a coherent lidar. This method rapidly reconstructs the laser phase noise utilizing the multi-channel delay self-homodyne and the generalized inverse of the system observation matrix. Subsequently, the reconstructed phase noise is utilized to expunge its perturbation onto the target information in the digital domain, thereby effectively surmounting the coherence length limitation. Through experimentation, the proposed method is verified to produce stable and high-quality interference even when the optical path difference between two beams exceeds 1000 times the coherence length. Additionally, the equivalent laser linewidth is compressed by 105 times.

Antibody responses to SARS-CoV-2 in patients with COVID-19.

We report acute antibody responses to SARS-CoV-2 in 285 patients with COVID-19. Within 19 days after symptom onset, 100% of patients tested positive for antiviral immunoglobulin-G (IgG). Seroconversion for IgG and IgM occurred simultaneously or sequentially. Both IgG and IgM titers plateaued within 6 days after seroconversion. Serological testing may be helpful for the diagnosis of suspected patients with negative RT-PCR results and for the identification of asymptomatic infections.

Identification and characterization of a novel freezing inducible gene, li16, in the wood frog Rana sylvatica.

The wood frog Rana sylvatica survives for weeks during winter hibernation with up to 65% body water frozen as ice. Natural freeze tolerance includes both seasonal and freeze-induced molecular adaptations that control ice formation, deal with long-term ischemia, regulate cell volume changes, and protect macromolecules. This report identifies and characterizes a novel freeze-inducible gene, li16, that codes for a protein of 115 amino acids. Northern blot analysis showed that li16 transcript levels rose quickly during freezing to reach levels 3.7-fold higher than control values after 24 h; immunoblotting showed a parallel 2.4-fold rise in Li16 protein. Regulatory influences on gene expression were assessed. Nuclear runoff assays confirmed that freezing initiated an increase in the rate of li16 transcription, and analysis of signal transduction pathways via in vitro incubation of liver slices implicated a cGMP-mediated pathway in li16 expression. Gene and protein expression in liver was also strongly stimulated by anoxia exposure, whereas the gene was less responsive to dehydration stress. The strong response of li16 to both freezing and anoxia, and the rapid down-regulation of the gene when oxygen was reintroduced, suggest that the Li16 protein may play a role in ischemia resistance during freezing.

[The mechanism of topotecan resistance in ovarian cancer cell line].

OBJECTIVE: To study the mechanism of topotecan (TPT) resistance in ovarian cancer cell line. METHODS: A TPT-resistant ovarian cancer cell line A2780/TPT established in this laboratory was used in this study. Intracellular rhodamine fluorescence intensity of the TPT-resistant cells and parental cells were measured by flow cytometry. The gene expression of membrane protein transporter such as transporter P-glycoprotein (P-gp), multidrug resistance associated protein (MRP), breast cancer resistance protein (BCRP) was evaluated by RT-PCR. The antisense-phosphorothioate oligonucleotide (ASODN) including a translation initiation site of BCRP mRNA was transferred into resistant cells by liposome. RESULTS: Intracellular rhodamine fluorescence intensity of the resistant cells was 31.19% of that in the parental cells (P < 0.01). No expression of P-gp was demonstrated, and that of MRP was very weak in the TPT-resistant cells (relative expression value = 0.057). BCRP was overexpressed in the TPT-resistant cells (relative expression = 0.66), but not in the parental cells. Transfer of ASODN into resistant cells resulted in a 59.42% reduction of BCRP gene expression (P < 0.05) and an obviously increased intracellular rhodamine fluorescence intensity from 5.42 to 16.63 (P < 0.05). CONCLUSION: The overexpression of BCRP which mediated drug efflux may play an important role in the induction of TPT-resistance in ovarian cancer.

Involvement of cyclin dependent kinase 5 and its activator p35 in staurosporine-induced apoptosis of cortical neurons.

AIM: To investigate whether cyclin-dependent kinase 5 and its regulatory protein p35 was involved in staurosporine-induced apoptosis of cortical neuronal cultures. METHODS: Primary cerebral cortical neurons were exposed to 300 nmol/L staurosporine. After incubation for different time, morphological alterations were observed with phase-contrast microscopy, fluorescence microscopy, and transmission electron microscopy. DNA fragmentation was detected by agarose gel electrophoresis. The protein levels of Cdk4, p53, Cdk5, and its regulatory protein p35 following staurosporine treatment were measured by Western blotting. The Cdk5 activity was assayed for histone H1 kinase activity by autoradiography. RESULTS: The typical morphological changes of apoptosis were observed and the nuclear DNA fragmentation showed the characteristic "ladder" pattern after the cells were treated by staurosporine. The Cdk5 protein level increased markedly at 3 h and continued to 24 h. The p35 level increased at 3 h after being exposed to staurosporine, and decreased at 12 h. The cleavage of p35 to p25 was also detected at 12 h and increased at 24 h. There was no increase in Cdk5 kinase activity despite the increased cleavage of p35. The protein level of Cdk4 protein increased at 3 h and then decreased gradually from 6 h, but it was still higher than that in the vehicle cultures at 12 h. The p53 level decreased obviously at 3 h after staurosporine treatment and then seemed to increase at 12 h, but remained lower than that of vehicle cultures. CONCLUSION: Staurosporine-induced increase in Cdk5 protein levels and the cleavage of p35 to p25 may contribute to neuronal apoptosis.

[Antisense oligonucleotide reverses topotecan-resistant ovarian cancer cells].

BACKGROUND & OBJECTIVE: Breast cancer resistance protein (BCRP) was overexpressed in topotecan (TPT)-selected human ovarian cancer cell line A2780/TPT, strongly suggesting BCRP to be responsible for the drug-resistance of ovarian cancer. The current study was designed to investigate the reversal effect of BCRP antisense oligonucleotide (ASODN) on topotecan- resistant A2780/TPT cells. METHODS: The antisense-phosphorothioate oligonucleotide including the translation initiation site of BCRP mRNA was artificially synthesized, and the sense oligonucleotide (SODN) corresponding to the ASODN was also synthesized as control. Lipofect-2000 (LF) was used for the transfer of either ASODN or SODN into A2780/TPT cells. The changes of BCRP mRNA expression, intracellular fluorescence intensity of rhodamine and resistance index to topotecan of in vitro transfected A2780/TPT cells were detected respectively by reverse transcription-polymerase chain reaction (RT-PCR),flow cytometry (FCM),and methyl thiazolyl tetrazolium (MTT) assay. RESULTS: The transfer of ASODN/LF into A2780/TPT cells resulted in:(1)a 59.42% reduction of BCRP mRNA level (P< 0.05); (2)an obviously increased intracellular rhodamine fluorescence intensity from 5.42 to 16.63(P< 0.05); (3)a decreased resistance index to topotecan from 25 to 5 indicating sensitivity to topotecan in A2780/TPT cells recovered, as compared with non-transfected cell. But after transfecting SODN, no significant change could be measured. CONCLUSION: ASODN transfection may partly reverse BCRP-mediated drug- resistance of ovarian cancer cells.