Disruption of Trkb-mediated signaling induces disassembly of postsynaptic receptor clusters at neuromuscular junctions

Neurotrophins and tyrosine receptor kinase (Trk) receptors are expressed in skeletal muscle, but it is unclear what functional role Trk-mediated signaling plays during postnatal life. Full-length TrkB (trkB.FL) as well as truncated TrkB (trkB.t1) were found to be localized primarily to the postsynaptic acetylcholine receptor- (AChR-) rich membrane at neuromuscular junctions. In vivo, dominant-negative manipulation of TrkB signaling using adenovirus to overexpress trkB.t1 in mouse sternomastoid muscle fibers resulted in the disassembly of postsynaptic AChR clusters at neuromuscular junctions, similar to that observed in mutant trkB+/- mice. When TrkB-mediated signaling was disrupted in cultured myotubes in the absence of motor nerve terminals and Schwann cells, agrin-induced AChR clusters were also disassembled. These results demonstrate a novel role for neurotrophin signaling through TrkB receptors on muscle fibers in the ongoing maintenance of postsynaptic AChR regions.

Glucose-induced microautophagy in Pichia pastoris requires the alpha-subunit of phosphofructokinase

We have characterized biochemically, morphologically, and genetically two distinct pathways for the selective degradation of peroxisomes in Pichia pastoris. These pathways are independently regulated and analogous to microautophagy and macroautophagy that have been defined in mammalian cells. When P. pastoris is grown in methanol, cytosolic and peroxisomal enzymes necessary for methanol assimilation are synthesized. During adaptation from methanol to glucose, these enzymes are rapidly and selectively degraded within the yeast vacuole by microautophagy. We have isolated gsa mutants that are defective in glucose-induced selective autophagy of peroxisomes. In this study, we have shown that gsa1 is unable to sequester peroxisomes into the yeast vacuole. In addition, we provide evidence that the glucose-induced selective autophagy 1 (GSA1) protein is the alpha subunit of the phosphofructokinase enzyme complex encoded by PFK1. First, we can rescue the gsa1 mutant by transformation with a vector containing PFK1. Second, cellular levels of both PFK1 mRNA and phosphofructokinase activity are dramatically reduced in gsa1 when compared to the parental GS115. Third, a PFK1 knockout (delta pfk1) is unable to degrade alcohol oxidase during glucose adaptation. As observed in gsa1, the peroxisomes in delta pfk1 remain outside the vacuole during adaptation. Our data are consistent with the concept that PFK1 protein is required for an event upstream of vacuole degradation (i.e. signaling, selection, or sequestration). However, the degradation of peroxisomes does not require a catalytically active phosphofructokinase. The inability of delta pfk1 cells to degrade alcohol oxidase can be rescued by transformation with either normal PFK1 or mutant pfk1 whose catalytic site had been inactivated by a single amino acid mutation. We propose that PFK1 protein directly modulates glucose-induced microautophagy independent of its ability to metabolize glucose intermediates.

Neurochemistry of the mammalian cone 'synaptic complex'

The cone 'synaptic complex' is a unique structure in which a single presynaptic axon secretes glutamate onto processes of bipolar cells (both ON and OFF) and horizontal cells. In turn, the horizontal cell processes antagonize cone and bipolar responses to glutamate (probably by GABA). What still remains largely unknown is the molecular identity of the postsynaptic receptors and their exact locations. We identified several subunits of the glutamate receptor and the GABAA receptor expressed at the cone synaptic complex and localized them ultrastructurally. Glutamate receptors: (i) Invaginating (probably ON) bipolar dendrites in the monkey and rat express the metabotropic glutamate receptor, mGluR6. The stain is intense on the dendritic membrane where it first enters the invagination, and weak at the tip nearest to the ribbon. The cone membrane is electron-dense where it apposes the intense stain for mGluR6. Surprisingly, invaginating bipolar dendrites in the cat also express the AMPA receptor subunits, GluR2/3 and GluR4. (ii) Dendrites forming basal contacts in the cat (probably OFF) express the AMPA subunits GluR2/3, GluR4, and also the kainate subunit, GluR6/7. The stain is especially intense at the dendritic tips in apposition to electron-dense regions of cone membrane. (iii) Horizontal cells in the cat express the AMPA subunits GluR2/3, GluR4 and the kainate subunit, GluR6/7. The stain is strongest in the cytosol of somas and primary dendrites, but is also present in the invaginating terminals where it localizes to the membrane subjacent to the ribbon. GABAA receptors: (i) ON and OFF bipolar dendrites in the monkey express the alpha 1 and beta 2/3 subunits. The stain is localized to the bipolar cell membrane in apposition to horizontal cell processes. (ii) Cones did not express the GABAA subunits tested by immunocytochemistry, but beta 3 mRNA was amplified by RT-PCR from rat photoreceptors.

CONCLUSIONS

(i) mGluR6 receptors concentrate on dendrites at the base of the invagination rather than at the apex. This implies that receptors at both 'invaginating' and 'basal' contacts lie roughly equidistant from the release sites and should therefore receive similar spatiotemporal concentrations of glutamate. (ii) The 'cone' membrane is electron-dense opposite to the receptor sites on both ON and OFF bipolar cells. This suggests a special role for this region in synaptic transmission. Possibly, these densities signify a transporter that would regulate glutamate concentration at sites remote (> 200 nm) from the locus of vesicle release.

Detection of circulating thyroid cells in peripheral blood

BACKGROUND

Detection of circulating malignant thyroid cells may provide a method to identify postoperative patients at risk for metastatic thyroid cancer.

METHODS

On the basis of tissue specificity of thyroglobulin gene expression and the sensitivity of the reverse transcriptase-polymerase chain reaction (RT-PCR) analysis, we performed RT-PCR using primers for thyroglobulin on blood samples from patients with thyroid disease to detect thyroglobulin RNA transcripts. Postoperative peripheral blood samples from 100 patients, including patients with known metastatic thyroid cancer (six papillary and three follicular), thyroid cancer and no evidence of current metastases (63 papillary, 10 follicular, and five patients with both papillary and follicular), benign thyroid disease (six nontoxic nodular goiters), and normal volunteers (seven).

RESULTS

Thyroglobulin transcripts were detected in nine of nine patients with metastatic thyroid cancer, seven of 78 patients with thyroid cancer and no current metastases (although of these seven patients, five had a history of metastatic disease that had been previously treated by surgery, one had a coexisting parathyroid cancer, and one had both papillary and follicular thyroid cancers), zero of six patients with benign thyroid disease, and zero of seven normal volunteers. Identity of amplicons was confirmed by restriction enzyme digestion and by cloning and sequencing of RT-PCR amplified thyroglobulin fragment (the latter in a limited number of cases).

CONCLUSIONS

These data indicate that RT-PCR can be used to detect thyroglobulin mRNA in peripheral blood. The presence of these transcripts correlates with the existence of extrathyroidal disease.

Duchenne muscular dystrophy gene expression in normal and diseased human muscle

A probe for the 5' end of the Duchenne muscular dystrophy (DMD) gene was used to study expression of the gene in normal human muscle, myogenic cell cultures, and muscle from patients with DMD. Expression was found in RNA from normal fetal muscle, adult cardiac and skeletal muscle, and cultured muscle after myoblast fusion. In DMD muscle, expression of this portion of the gene was also revealed by in situ RNA hybridization, particularly in regenerating muscle fibers.

An adenoviral vector can transfer lacZ expression into Schwann cells in culture and in sciatic nerve

Although a number of genetic defects in the P0, peripheral myelin protein-22, and connexin-32 genes recently were shown to cause the demyelinating forms of Charcot-Marie-Tooth disease, there is yet no effective treatment for these patients. Recent studies showed that replication defective adenoviral vectors can efficiently introduce genes into muscle, brain, lung, and other tissues, suggesting that this vector system may be useful for the treatment of a number of genetic diseases. In this work, we demonstrated that a replication deficient adenovirus expressing the Escherichia coli beta-galactosidase gene (AdCMVLacZ) can introduce genes into Schwann cells, in culture as well as in sciatic nerve. Schwann cells cultured at a multiplicity of infection of 250:1 did not demonstrate cytopathic effects. Following injection of AdCMVLacZ into sciatic nerve of rats, lacZ-expressing, myelinating Schwann cells could be detected for at least 45 days. These data suggest that in the future, these vectors may be useful both in perturbing Schwann cell gene expression and in designing therapies for the treatment of Charcot-Marie-Tooth disease.

Inhibition of connective tissue growth factor by small interfering RNA prevents renal fibrosis in rats undergoing chronic allograft nephropathy

AIM

Connective tissue growth factor (CTGF) is a highly profibrogenic molecule implicated in renal fibrogenesis. Small interfering RNA (siRNA) is an effective tool to silence gene expression. This study determined whether caudal vein injection of siRNA targeting CTGF inhibited its expression in rat kidneys in vivo, and furthermore whether it protected the kidney from renal fibrosis in chronic allograft nephropathy (CAN).

METHODS

Male inbred Fischer (F344, RT1(lv1)) rat renal grafts were orthotopically transplanted into Lewis (LEW, RT1(1)) rats following the procedure of Kamada with our modification. At 6 weeks, recipients were divided into siRNA, normal saline (NS), and control siRNA groups, using daily siRNA-targeting CTGF (0.1 mg/kg), or NS, or a control siRNA via caudal vein injection for 14 days. At 4, 6, and 8 weeks, we observed the pathologic changes, expression of CTGF, E-cadherin, collagen I and IV, and anti-smooth muscle actin (alpha-SMA).

RESULTS

Serum creatinine level, Banff score, and the expression of CTGF were significantly lower among the siRNA than the NS or the control siRNA groups at 8 weeks (P < .05). The expressions of collagen I and IV, and alpha-SMA were also significantly downregulated and E-cadherin was lost in the siRNA versus the NS and control siRNA groups at 8 weeks.

CONCLUSIONS

This study showed that delivery of CTGF siRNA via the caudal vein significantly inhibited expression of CTGF in rat kidneys, effectively preventing fibrosis in CAN. The results suggest that siRNA-targeting of CTGF has the potential to be a novel strategy for amelioration of CAN.

An overview of organic molecule soft ionization using vacuum ultraviolet laser radiation

The utility of coherent vacuum ultraviolet (VUV) single-photon ionization (SPI) combined with time-of-flight mass spectrometry (TOF-MS) for organic molecule detection by parent mass is explored in this short review. Nonresonant tripling in phase-matched Xe–Ar gas mixtures was used to generate photons at a fixed energy of 10.5 eV. Representative organic molecules with different functional groups were examined, including aliphatic and aromatic alkanes, alkenes, alkynes, alkanols, ethers, amines, aldehydes, ketones, carboxylic acids, and esters. In almost every case, the intensity of the resultant parent molecular ion peak detected by TOF-MS was found to be superior to that obtained using 70 eV electron impact (EI), and comparable to that obtained with 12 eV EI. In those instances when fragmentation reactions did occur, the resultant ions were similar to those found using EI but with significantly reduced mass spectral intensities. It was still possible to establish one dominant fragmentation pathway that could be used for molecular identification even if the parent molecular ion was not the strongest feature in the spectrum, for example, in the case of alcohols, alcohol clusters, and alcohol–ether adducts. Several of the fragment ions were metastably broadened. Not surprisingly, their known appearance energies or estimated reaction enthalpies were very similar to the fixed photon energy used. The success of using VUV for organic molecule soft ionization is attributed to the low photon energy that removes predominantly a π- or non-bonding electron from the functionalized species. As most organic compounds have ionization potentials in the 10.5 eV region, this approach is expected to be near universal.Key words: vacuum ultraviolet laser, single photon ionization, organic molecule detection, soft-ionization, mass spectrometry.

Epidermal permeability barrier recovery is delayed in vitiligo-involved sites

BACKGROUND/OBJECTIVES

Prior studies have demonstrated that both the skin surface pH and epidermal permeability barrier function vary with skin pigmentation types. Although melanin deficiency is the main feature of vitiligo, alterations in cutaneous biophysical properties in vitiligo have not yet been well defined. In the present study, stratum corneum (SC) hydration, the skin surface pH and epidermal permeability barrier function in vitiligo were evaluated.

METHODS

A total of 30 volunteers with vitiligo comprising 19 males and 11 females aged 13-51 years (mean age: 27.91 +/- 2.06 years) were enrolled in this study. The skin surface pH, SC hydration, melanin/erythema index and transepidermal water loss (TEWL) were measured by respective probes connected to a Courage-Khazaka MPA5. SC integrity was determined by measuring the TEWL following each D-Squame application. The barrier recovery rate was assessed at 5 h following barrier disruption by repeated tape stripping.

RESULTS

In addition to SC hydration, both melanin and erythema index were significantly lower in vitiligo lesions than in contralateral, nonlesional sites, while no difference in skin surface pH between vitiligo-involved and uninvolved areas was observed. In addition, neither the basal TEWL nor SC integrity in the involved areas differed significantly from that in the uninvolved areas. However, barrier recovery in vitiligo-involved sites was significantly delayed in comparison with uninvolved sites (40.83 +/- 5.39% vs. 58.30 +/- 4.71%; t = 2.441; p < 0.02).

CONCLUSION

Barrier recovery following tape stripping of the SC is delayed in vitiligo. Therefore, improvement in epidermal permeability barrier function may be an important unrecognized factor to be considered in treating patients with vitiligo.

Sun-induced changes in stratum corneum function are gender and dose dependent in a Chinese population

Previous studies have demonstrated that UVB radiation changes the epidermal permeability barrier and stratum corneum (SC) hydration. It is well known that sun exposure causes erythema, sunburn and melanoma. However, whether daily sun exposure alters SC integrity and epidermal permeability barrier function is largely unknown, especially in Chinese subjects. In the present study, we assess the SC integrity, SC hydration and epidermal permeability barrier function following various doses of sun exposure. A total of 258 subjects (124 males and 134 females) aged 18-50 years were enrolled. A multifunctional skin physiology monitor (Courage & Khazaka MPA5) was used to measure SC hydration and transepidermal water loss (TEWL) on the forearms. In males, basal TEWL was higher with higher doses of sun exposure than with lower doses and control, whereas in females, basal TEWL was higher with lower doses of sun exposure than with higher doses and control. In the group with higher doses of sun exposure, TEWL in females was significantly lower than that in males. The barrier recovery was faster in females than in males in both control and lower-dose groups. In both males and females, barrier recovery was delayed with higher doses of sun exposure. In males, sun exposure did not alter SC hydration, while in females SC hydration was lower with lower doses of sun exposure as compared with control and higher doses of sun exposure. These results demonstrated that sun-induced changes in SC function and SC hydration vary with gender and the extent of sun exposure.

Decomposition of 1,1-dimethyl-1-silacyclobutane on a tungsten filament--evidence of both ring C-C and ring Si-C bond cleavages

The decomposition of 1,1-dimethyl-1-silacyclobutane (DMSCB) on a heated tungsten filament has been studied using vacuum ultraviolet laser single photon ionization time-of-flight mass spectrometry. It is found that the decomposition of DMSCB on the W filament to form ethene and 1,1-dimethylsilene is a catalytic process. In addition, two other decomposition channels exist to produce methyl radicals via the Si-CH(3) bond cleavage and to form propene (or cyclopropane)/dimethylsilylene. It has been demonstrated that both the formation of ethene and that of propene are stepwise processes initiated by the cleavage of a ring C-C bond and a ring Si-C bond, respectively, to form diradical intermediates, followed by the breaking of the remaining central bonds in the diradicals. The formation of ethene via an initial cleavage of a ring C-C bond is dominant over that of propene via an initial cleavage of a ring Si-C bond. When the collision-free condition is voided, secondary reactions in the gas-phase produce various methyl-substituted 1,3-disilacyclobutane molecules. The dominant of all is found to be 1,1,3,3-tetramethyl-1,3-disilacyclobutane originated from the dimerization of 1,1-dimethylsilene.

In situ diagnostics of the decomposition of silacyclobutane on a hot filament by vacuum ultraviolet laser ionization mass spectrometry

The gas-phase reaction products of silacyclobutane (SCB) and 1, 1-dideuterio-silacyclobutane (SCB-d(2)) from a hot-wire chemical vapor deposition (HWCVD) chamber were diagnosed in situ using vacuum ultraviolet (VUV) laser single-photon ionization (SPI) coupled with time-of-flight (TOF) mass spectrometry. The SCB molecule was found to decompose at a filament temperature as low as 900 degrees C. Both Si- (silylene, methylsilylene, and silene) and C-containing (ethene and propene) species were produced from the SCB decomposition on the filament. Ethene and propene were detected by the mass spectrometer. It is demonstrated that the formation of ethene is favored over that of propene. The experimental study of hot-wire decomposition of SCB-d(2) shows that propene is most likely produced by a process that is initiated by a 1,2-H(D) migration to form n-propylsilylene, followed by an equilibration with silacyclopropane, which then decomposes to propene. The detection of ethene in our experiment indicates that a competitive route of fragmentation exists for SCB decomposition on the filament. It has been shown that this competitive route occurs without H/D scrambling. The highly reactive silylene, silene, and methylsilylene species produced from SCB decomposition underwent either insertion reactions into the Si-H bonds of the parent molecule or pi-type addition reaction across the double and triple CC bonds. The dimerization product of silene, 1,3-disilacyclobutane, at m/z = 88 was also observed.

The effects of SOCS-1 on liver endotoxin tolerance development induced by a low dose of lipopolysaccharide are related to dampen NF-kappaB-mediated pathway

BACKGROUND

Endotoxin tolerance is an important mechanism to maintain the homeostasis of liver. It was reported that suppressors of cytokine signalling-1 was a negative regulator of lipopolysaccharide-induced macrophages activation, however, the mechanism underlying endotoxin tolerance and suppressors of cytokine signalling-1 has not been fully elucidated.

AIM

Our aim here is to clarify whether suppressors of cytokine signalling-1 was involved in the mechanisms of endotoxin tolerance in liver through dampening nuclear factor-kappaB-mediated pathway.

METHODS

Endotoxin tolerance models of C57BL/6J mice and isolated Kupffer cells were established by pretreating them with a low dose of lipopolysaccharide to observe the changes of suppressors of cytokine signalling-1 expression during endotoxin tolerance inducement. Moreover, a vector-based short hairpin RNA expression system was used to specifically inhibit suppressors of cytokine signalling-1 expression in RAW264.7 macrophage cells to further explore the role of suppressors of cytokine signalling-1 in endotoxin tolerance inducement. The expression of suppressors of cytokine signalling-1 was analysed by immunohistochemistry, reverse transcription-polymerase chain reaction and Western blotting, respectively. The responses to lipopolysaccharide were assessed by the activation of nuclear factor-kappaB and the production of tumour necrosis factor-alpha, which were analysed by ELISA.

RESULTS

The histopathologic changes in the liver of the non-endotoxin tolerance group were more serious than those of the endotoxin tolerance group. The phagocytic activity of Kupffer cells were depressed and suppressors of cytokine signalling-1 expression in the endotoxin tolerance group obviously increased. Endotoxin tolerance also led to a hyporesponse of Kupffer cells to lipopolysaccharide with less activation of nuclear factor-kappaB, less production of tumour necrosis factor-alpha and more expression of suppressors of cytokine signalling-1 than those of non-endotoxin tolerance group. Moreover, the inhibitive effect was partly refracted in pSOCS-1-short hairpin RNA transfected RAW264.7 cells.

CONCLUSIONS

Endotoxin tolerance induced by lipopolysaccharide pretreatment was accompanied with upregulation of suppressors of cytokine signalling-1 and the silence of suppressors of cytokine signalling-1 by RNA interference obviously attenuated this inhibitive effect, indicating that the absence of suppressors of cytokine signalling-1 caused abnormal enhancement of inflammatory cytokine production and suppressors of cytokine signalling-1 was involved in endotoxin tolerance inducement through dampening nuclear factor-kappaB-mediated pathway. Therefore, suppressors of cytokine signalling-1 may be a new target for the clinical treatment of sepsis.

[Analysis on the epidemiological features of human brucellosis in northern and southern areas of China, 2015-2016]

Different epidemiological features of human brucellosis appeared in both northern and southern areas of China. The disease was seen endemic in the northern and dispersal in the southern provinces. Appropriate strategies for brucellosis prevention and control should be developed, according to the different epidemiological characteristics in the northern or southern areas.

Geometries and energetics of methanol–ethanol clusters: a VUV laser/time-of-flight mass spectrometry and density functional theory study

Hydrogen-bonded clusters, formed above liquid methanol (Me) and ethanol (Et) mixtures of various compositions, were entrained in a supersonic jet and probed using 118 nm vacuum ultraviolet (VUV) laser single-photon ionization/time-of-flight mass spectrometry. The spectra are dominated by protonated cluster ions, formed by ionizing hydrogen-bonded MemEtn neutrals, m = 0–4, n = 0–3, and m + n = 2–5. The structures and energetics of the neutral and ionic species were investigated using both the all-atom optimized potential for liquid state, OPLS-AA, and the density functional (DFT) calculations. The energetic factors affecting the observed cluster distributions were examined. Calculations indicate that the large change in binding energy going from trimer to tetramer can be attributed more to pair-wise interactions than to cooperativity effects.Key words: alcohol clusters, cluster formation, DFT calculations, mass spectrometry, vacuum ultraviolet laser.

Field evaluation of a test for praziquantel resistance in Schistosoma sp

A simple rapid test for detecting praziquantel resistance in Schistosoma sp., involving change in shape of miracidia on exposure to praziquantel, was evaluated in China. Tests on miracidia hatched from eggs collected from naturally infected goats were run in a field laboratory in Jiangxi Province and a research laboratory in Shanghai. The mean values in the two laboratories were not significantly different, but the variation between individual samples in the two laboratories suggests that a delineating dose will be required for routine diagnosis of resistance. Confirmation that resistance would have been detected in Schistosoma japonicum must await the isolation of a resistant isolate. The tests suggested that the infection in the goats was susceptible to praziquantel as did chemotherapy of water buffaloes with 25mg/kg. This gave a 95% cure rate on the first treatment and 100% with a second treatment, similar to that found previously in human patients.

Mechanism for the formation of gas-phase protonated alcohol-ether adducts by VUV laser ionization and density-functional calculations

The neutral vapors above liquid alcohol/ether mixtures, (diethyl ether/methanol, diethyl ether/ethanol, tetrahydrofuran/methanol, and tetrahydrofuran/ethanol) were co-expanded with He in a supersonic jet, ionized with a 118-nm vacuum ultraviolet laser, and detected in a time-of-flight mass spectrometer. In each case, features attributed to protonated alcohol-ether dimers and protonated ether monomers were observed, as well as those ions obtained by ionizing neat alcohol or ether samples alone. Theoretical calculations, carried out to establish the energetics of the various possible reactions leading to the formation of the observed binary adducts, indicate that the most thermodynamically favorable pathway corresponds to the addition of a protonated alcohol monomer to neutral ether.

Development of the charge exchange recombination spectroscopy and the beam emission spectroscopy on the EAST tokamak

Charge eXchange Recombination Spectroscopy (CXRS) and Beam Emission Spectroscopy (BES) diagnostics based on a heating neutral beam have recently been installed on EAST to provide local measurements of ion temperature, velocity, and density. The system design features common light collection optics for CXRS and BES, background channels for the toroidal views, multi-chord viewing sightlines, and high throughput lens-based spectrometers with good signal to noise ratio for high time resolution measurements. Additionally, two spectrometers each has a tunable grating to observe any wavelength of interest are used for the CXRS and one utilizes a fixed-wavelength grating to achieve higher diffraction efficiency for the BES system. A real-time wavelength correction is implemented to achieve a high-accuracy wavelength calibration. Alignment and calibration are performed. Initial performance test results are presented.

Promotion of exocyclic bond cleavages in the decomposition of 1,3-disilacyclobutane in the presence of a metal filament

The primary decomposition of 1,3-disilacyclobutane (DSCB) on a tungsten filament and its secondary gas-phase reactions in a hot-wire chemical vapor deposition (CVD) reactor have been studied using laser ionization mass spectrometry. Under the collision-free conditions, DSCB decomposes on the W filament to produce H2 molecules with an activation energy of 43.6 ± 4.1 kJ·mol(-1). With the help of the isotope labeling and chemical trapping methods, the mechanistic details in the secondary gas-phase reactions important in the hot-wire CVD reactor setup have been examined. The dominant pathway has been demonstrated to be the insertion of the cyclic 1,3-disilacyclobut-1-ylidene, generated by exocyclic Si-H bond rupture, into the Si-H bond in DSCB to form 1,1'-bis(1,3-disilacyclobutane) (174 amu). The successful trapping of 1,3-disilacyclobut-1-ylidene by both 1,3-butadiene and trimethylsilane provides compelling evidence for the existence of this cyclic silylene species in the hot-wire CVD reactor with DSCB. Other reactions operating in the reactor include the DSCB cycloreversion to form silene and the ring opening of DSCB via 1,2-H shift to produce silene/methylsilylene and 1-methylsilene/silylene. The introduction of an additional Si atom in the four-membered ring monosilacyclobutane molecule has caused two major changes in the reaction chemistry assumed by DSCB: (1) The endocyclic cycloreversion reactions that dominate in the decomposition of monosilacyclobutane molecules only play a much less important role in the dissociation of DSCB; and (2) the exocyclic bond cleavages are promoted in DSCB due to the ring stabilization caused by the introduction of one additional Si atom.

Effect of long-term organic fertilization on the soil pore characteristics of greenhouse vegetable fields converted from rice-wheat rotation fields

The shift from rice-wheat rotation (RWR) to greenhouse vegetable soils has been widely practiced in China. Several studies have discussed the changes in soil properties with land-use changes, but few studies have sought to address the differences in soil pore properties, especially for fields based on long-term organic fertilization under greenhouse vegetable system from RWR fields. This study uses the X-ray computed tomography (CT) scanning and statistical analysis to compare the long-term effects of the conversion of organic greenhouse vegetable fields (over one year, nine years, and fourteen years) from RWR fields on the soil macropore structure as well as the influencing factors from samples obtained in Nanjing, Jiangsu, China, using the surface soil layer and triplicate samples. The results demonstrated that the macropore structure became more complex and stable, with a higher connectivity, fractal dimension (FD) and a lower degree of anisotropy (DA), as the greenhouse vegetable planting time increased. The total topsoil macroporosity increased considerably, but the rate of increase gradually decelerated with time. The transmission pores (round pores ranging from 50 to 500μm) increased with time, but the biopores (>2000μm) clearly decreased after nine years of use as greenhouse vegetable fields. Soil organic matter (OM) has a significant relationship with the soil pore structure characteristics, especially for the transmission pores. In addition, organic fertilization on the topsoil had a short-term effect on the pores, but the effect stabilized and had a weak influence on the pores over longer periods. These results suggested that organic fertilization was conducive for controlling soil degradation regarding it physical quality for water and oxygen availability in the short term.

A vacuum ultraviolet laser single-photon zero kinetic energy photoelectron spectroscopic study of the 2E3/2 ground electronic state of CH3Br+

The vacuum ultraviolet laser single-photon zero kinetic energy (ZEKE) photoelectron spectrum of the [Formula: see text]2E3/2 ground electronic state of the methyl bromide cation is reported. The spectrum is dominated by the origin band 000 of the transition [Formula: see text]2E3/2 ← [Formula: see text]1A1. In addition, the 210 band and the 311 hot band are observed. All observed bands show similar rotational contours. Simulation of the rotational contour of the origin band yields the first ionization energy of methyl bromide (85 031.2 ± 1.0 cm–1) and the rotational constants of the cation in its ground electronic state. Key words: methyl bromide, vacuum ultraviolet laser, single-photon excitation, zero kinetic energy photoelectron spectroscopy.

Epithelial to mesenchymal transformation in tubular epithelial cells undergoing anoxia

AIM

Epithelial-mesenchymal transformation (EMT) has been proved to be a critical event in fibrogenesis of renal allografts. This study sought to determine whether anoxia could induce EMT from tubular epithelial cells (TEC).

METHODS

Rat TEC-line (NRK-52E) was cultured in Dulbelco's modified Eagle's medium (DMEM) without glucose under 100% N2 for 4 hours. After 6, 12, 24, 48, and 72 hours, the expressions of connective tissue growth factor (CTGF) mRNA and protein were measured by real-time RT-PCR and Western blot, respectively. Morphologic changes and cytoskeleton remodeling were observed in NRK-52E cells under laser confocal microscopy. Immunohistochemistry and flow cytometry were used to detect expression changes of E-cadherin, alpha-smooth muscle actin (SMA), types I and IV collagen, all of which are involved in TEC, EMT.

RESULTS

After stimulation by anoxia, NRK-52E cells became round and enlarged with a remodeled cytoskeleton. The expressions of CTGF mRNA and protein were upregulated after 6 hours, reaching their peak at 48 hours. The expressions of types I and IV collagen, and alpha-SMA were all upregulated except for E-cadherin.

CONCLUSIONS

Anoxia upregulated the expression of CTGF and other EMT-associated genes in NRK-52E cells.

Carburization of tungsten filaments in a hot-wire chemical vapor deposition process using 1,1,3,3-tetramethyl-1,3-disilacyclobutane

The alloying of tungsten filament when using 1,1,3,3-tetramethyl-1,3-disilacyclobutane (TMDSCB) in a hot-wire chemical vapor deposition reactor was systematically studied by scanning electron microscopy, Auger electron spectroscopy, analysis of the power consumed by the filament, and in situ mass spectrometric measurements of the gas-phase species produced in the process. Only carburization of the W filament was observed. The carburization is mainly caused by the interaction of methyl radicals with the filament. Graphite as well as both WC and W2C alloys can form on the filament surface, depending on the filament temperatures and source gas pressures. Both WC and graphite are converted to W2C with the diffusion of C into the filament. It is shown that filament carburization affects the consumption rate of the source gas and the intensities of gas-phase reaction products. Gas-phase reactions dominate at T < or = 1400 degrees C. The carburization rate increases with increasing filament temperatures and dominates at T > or = 1800 degrees C.