Axons find their way in the snow

In February 2009, Keystone, Colorado, hosted the third Symposium on; Axonal Connections: Molecular Cues for Development and Regeneration', organized by Marie Filbin, John Flanagan and Liqun Luo. Researchers from diverse backgrounds spent the week discussing the latest findings in axon guidance, synapse formation, dendrite development and axon regeneration. The meeting was held jointly with another Keystone Symposium on ;Neurodegenerative Diseases: New Molecular Mechanisms', and the two meetings profited from the lively discussions fuelled with questions from both fields in the joint sessions, which featured topics of common interest, such as axon degeneration, regeneration and neural stem cells.

Effect of short term calorie restriction on pro-inflammatory NF-kB and AP-1 in aged rat kidney

OBJECTIVE

To compare the effect of short-term calorie restriction (CR) on aging with that of already known long-term CR, the anti-inflammatory efficacy of 10-day CR was explored in aged rat kidney.

TREATMENT

Two different age groups, 6 months (young) and 24 months (old) were used. In the old group, one sub-group was control, fed ad libitum (AL) and the other was fed CR for 10 days with 40 % of the food intake of the AL subgroup (n = 5).

METHODS

Reactive species (RS), lipid peroxides and COX-2 activity were measured. The activities of proinflammatory transcription factors NF-kB and AP-1 were measured by electro-mobility shift assay (EMSA). Upstream signaling cascades of NF-kB and AP-1 as well as proinflammatory gene expression were detected by Western blot.

RESULTS

10-day CR suppressed RS, lipid peroxides, and COX-2 activity in aged rat kidney. CR also inhibited upstream signaling cascades and DNA binding activity of NF-kB and AP-1, and thioredoxin/Ref-1 pathway. CR blocked expression of NF-kB-and AP-1-responsive gene COX-2, iNOS, VCAM-1 and ICAM-1.

CONCLUSIONS

We report for the first time that 10-day CR can attenuate the altered signaling transduction for inflammatory processes which is mediated through RS-induced NF-kB and AP-1 in aged kidney.

MRP- and BCL-2-mediated drug resistance in human SCLC: effects of apoptotic sphingolipids in vitro

Multidrug-resistance-associated protein (MRP) and BCL-2 contribute to drug resistance expressed in SCLC. To establish whether MRP-mediated drug resistance affects sphingolipid (SL)-induced apoptosis in SCLC, we first examined the human SCLC cell line, UMCC-1, and its MRP over-expressing, drug-resistant subline, UMCC-1/VP. Despite significantly decreased sensitivity to doxorubicin (Dox) and to the etoposide, VP-16, the drug-selected line was essentially equally as sensitive to treatment with exogenous ceramide (Cer), sphingosine (Sp) or dimethyl-sphingosine (DMSP) as the parental line. Next, we observed that high BCL-2-expressing human H69 SCLC cells, that were approximately 160-fold more sensitive to Dox than their combined BCL-2 and MRP-over-expressing (H69AR) counterparts, were only approximately 5-fold more resistant to DMSP. Time-lapse fluorescence microscopy of either UMCC cell line treated with DMSP-Coumarin revealed comparable extents and kinetics of SL uptake, further ruling out MRP-mediated effects on drug uptake. DMSP potentiated the cytotoxic activity of VP-16 and Taxol, but not Dox, in drug-resistant UMCC-1/VP cells. However, this sensitization did not appear to involve DMSP-mediated effects on the function of MRP in drug export; nor did DMSP strongly shift the balance of pro-apoptotic Sps and anti-apoptotic Sp-1-Ps in these cells. We conclude that SL-induced apoptosis markedly overcomes or bypasses MRP-mediated drug resistance relevant to SCLC and may suggest a novel therapeutic approach to chemotherapy for these tumors.

High precision high voltage divider and its application to electron beam ion traps

A high precision high voltage divider has been developed for the electron beam ion trap in Shanghai. The uncertainty caused by the temperature coefficient of resistance (TCR) and the voltage coefficient of resistance has been studied in detail and was minimized to the level of ppm (10(-6)) range. Once the TCR was matched between the resistors, the precision of the dividing ratio finally reached the ppm range also. We measured the delay of the divider caused by the capacitor introduced to minimize voltage ripple to be 2.35 ms. Finally we applied the divider to an experiment to measure resonant energies for some dielectronic recombination processes for highly charged xenon ions. The final energies include corrections for both space charge and fringe field effects are mostly under 0.03%.

Wnts acting through canonical and noncanonical signaling pathways exert opposite effects on hippocampal synapse formation

Background

Wnt proteins comprise a large class of signaling molecules that regulate a variety of developmental processes, including synapse formation. Previous studies have shown Wnts to be involved in both the induction and prevention of synapses in a number of different organisms. However, it is not clear whether the influence of Wnts on synapses is a result of Wnts' behavior in different organisms or differences in the activity of different Wnt ligands.

Results

We used in situ hybridization to show that several Wnt ligands (Wnt3, Wnt5a, Wnt7a, and Wnt7b) and their receptors, Frizzled, are expressed in the developing hippocampus during the period of synapse formation in rodents. We used recombinant Wnt protein or Wnt conditioned media to explore the effects of Wnts on synapses in hippocampal cultures. We found that Wnt7a and Wnt7b activate canonical signaling, whereas Wnt5a activates a noncanonical pathway. The activation of the canonical pathway, either through pathway manipulations or through Wnt stimulation, increases presynaptic inputs. In contrast, exposure to Wnt5a, which activates a noncanonical signaling pathway, decreases the number of presynaptic terminals.

Conclusion

Our observations suggest that the pro- and antisynaptogenic effects of Wnt proteins are associated with the activation of the canonical and noncanonical Wnt signaling pathways.

Wnt signaling in neural circuit assembly

The Wnt family of secreted proteins plays a crucial role in nervous system wiring. Wnts regulate neuronal positioning, polarization, axon and dendrite development, and synaptogenesis. These diverse roles of Wnt proteins are due not only to the large numbers of Wnt ligands and receptors but also to their ability to signal through distinct signaling pathways in different cell types and developmental contexts. Studies on Wnts have shed new light on novel molecular mechanisms that control the development of complex neuronal connections. This review discusses recent advances on how Wnt signaling influences different aspects of neuronal circuit assembly through changes in gene expression and/or cytoskeletal modulation.

High resolution flat crystal spectrometer for the Shanghai EBIT

We report on a high resolution flat crystal spectrometer designed for the Shanghai EBIT. Its energy range is from 0.5 to 10 keV. Three crystals can be installed in the vacuum chamber simultaneously, and its effective Bragg angle can be covered from 15 degrees to 75 degrees . A vacuum version charge-coupled device detector is used for detection of photons. An energy resolution under 1 eV was reached in measurements of the 4.5 keV Kalpha(1) line by using an x-ray generator with a titanium anode. The spectrometer was also tested to operate well on the Shanghai EBIT by observing the lines of tungsten at around 3.2 keV.

Exon skipping mutations in collagen VI are common and are predictive for severity and inheritance

Mutations in the genes encoding collagen VI (COL6A1, COL6A2, and COL6A3) cause Bethlem myopathy (BM) and Ullrich congenital muscular dystrophy (UCMD), two related conditions of differing severity. BM is a relatively mild dominantly inherited disorder characterized by proximal weakness and distal joint contractures. UCMD was originally regarded as an exclusively autosomal recessive condition causing severe muscle weakness with proximal joint contractures and distal hyperlaxity. We and others have subsequently modified this model when we described UCMD patients with heterozygous in-frame deletions acting in a dominant-negative way. Here we report 10 unrelated patients with a UCMD clinical phenotype and de novo dominant negative heterozygous splice mutations in COL6A1, COL6A2, and COL6A3 and contrast our findings with four UCMD patients with recessively acting splice mutations and two BM patients with heterozygous splice mutations. We find that the location of the skipped exon relative to the molecular structure of the collagen chain strongly correlates with the clinical phenotype. Analysis by immunohistochemical staining of muscle biopsies and dermal fibroblast cultures, as well as immunoprecipitation to study protein biosynthesis and assembly, suggests different mechanisms each for exon skipping mutations underlying dominant UCMD, dominant BM, and recessive UCMD. We provide further evidence that de novo dominant mutations in severe UCMD occur relatively frequently in all three collagen VI chains and offer biochemical insight into genotype-phenotype correlations within the collagen VI-related disorders by showing that severity of the phenotype depends on the ability of mutant chains to be incorporated in the multimeric structure of collagen VI.

Administration of intracoronary bone marrow mononuclear cells on chronic myocardial infarction improves diastolic function

BACKGROUND

Regeneration of the myocardium and improved ventricular function have been demonstrated in patients with acute myocardial infarction (MI) treated by intracoronary delivery of autologous bone marrow mononuclear cells (BMC) a few days after successful myocardial reperfusion by percutaneous coronary intervention (PCI); however, the effects of intracoronary cell infusion in chronic MI patients are still unknown.

AIMS

To investigate whether intracoronary infusion of BMC into the infarct-related artery in patients with healed MI could lead to improvement in left ventricular (LV) function.

METHODS

Among 47 patients with stable ischaemic heart disease due to a previous MI (13 (SD 8) months previously), 24 were randomised to intracoronary infusion of BMC (BMC group) and 23 to a saline infusion (control group) into the target vessel after successful PCI within 12 hours after chest pain occurred. LV systolic and diastolic function, infarct size and myocardial perfusion defect were assessed with the use of echocardiography, magnetic resonance imaging (MRI) or (201)Tl single-photon-emission computed tomography (SPECT) at baseline and repeated at the 6-month follow-up examination.

RESULTS

BMC treatment did not result in a significant increase in LV ejection fraction in any of the groups by any of the methods used, and the apparent tendency of an improvement was not statistically different between the two groups. The two groups also did not differ significantly in changes of LV end-diastolic and systolic volume, infarct size or myocardial perfusion. However, there was an overall effect of BMC transfer compared with the control group with respect to early/late (E/A) (p<0.001), early diastolic velocity/late diastolic (Aa) velocity (Ea/Aa) ratio (p = 0.002) and isovolumetric relaxation time (p = 0.038) after 6 months, as evaluated by tissue Doppler echocardiography. We noted no complications associated with BMS transfer.

CONCLUSION

Intracoronary transfer of autologous BMC in patients with healed MI did not lead to significant improvement of cardiac systolic function, infarct size or myocardial perfusion, but did lead to improvement in diastolic function.

Cryoablation induces necrosis and apoptosis in lung adenocarcinoma in mice

This study evaluated cryoablation on subcutaneously transplanted tumors of lung adenocarcinoma LA795 in T739 mice in vivo, in an effort to assess the feasibility of cryoablation in treatment of NSCLC. Subcutaneously transplanted lung adenocarcinoma LA795 was implanted into T739 mice yielding tumors of approximately 2.5 cm in diameter. Following cryoablation, the various modes of cell death were studied: necrosis in the central frozen zone by light microscopy and apoptosis in periphery of the frozen zone by in situ end labeling (TUNEL). Bc1-2 and bax expression were detected by immunohistochemical SABC procedures, and the cleavage and activation of Caspase 3 and PARP in peripheral zone by Western blot. We find that in central cryoablated zone, necrosis was the dominant mode of cell death occurring at three hours and four days post-thaw. The first three-hour necrosis peak involved approximately 47% of the tumor while the four-day peak increased in volume to 68% of the tumor. In peripheral cryoablation zone, definite cell apoptosis could be observed by morphological examination under light microscope and TUNEL staining, peaking at 8-16 h after cryoablation. Immunohistochemical results yielded little change in bcl-2 protein expression before and after cryoablation. However, bax protein expression was up-regulated significantly after cryoablation. In addition, cleavage and activation of Caspase-3 and PARP occurred in the peripheral freeze zone after the treatment. It indicated that Cryoablation efficiently induces cell death both by necrosis and apoptosis. Cryoablation appears to induce apoptosis in the peripheral freeze zone through the intrinsic mitochondrial caspase pathway based on bax upregulation. This observation allows us to suggest that cryoablation may be combined with chemotherapy to increase cancer destruction.