Enhanced adhesion and field emission of CuO nanowires synthesized by simply modified thermal oxidation technique.

Metal oxide nanowires (NWs) can be easily grown by the thermal oxidation method, but the low adhesion between the NWs and the substrate restricts their practical applications in functional devices. In this work, the conventional hotplate technique is simply modified by introducing one or two stainless steel plates to supply a more stable oxidation environment, which is found to be beneficial to the growth and adhesion of CuO NWs on the Cu substrate. In detail, the Cu foils were heated on the hotplate directly, on one plate over the hotplate, and between two plates over the hotplate at 400 °C in ambient condition. It is found that the NWs obtained between two plates exhibit large length and diameter with moderate density. The sufficient activated oxygen, stable temperature, and proper temperature gradient configuration caused by the two plates accelerate the formation of CuO NWs, and result in the longest NWs with enhanced adhesion. The grain-boundary diffusion and Kirkendall effect are proposed to explain the mechanism of NWs growth and the formation of cracks. The NWs obtained between two plates also showed the best field emission properties, with lowest turn-on field (5.31 V µm(-1)) and threshold field (9.8 V µm(-1)). Excellent field emission properties and enhanced NW-substrate adhesion indicate that these NW arrays could be potentially used as the cathode of field emission displays.

microRNA-221 and microRNA-18a identification in stool as potential biomarkers for the non-invasive diagnosis of colorectal carcinoma.

BACKGROUND: The detection of microRNA (miRNA) dysregulation in stool is a novel approach for the diagnosis of colorectal carcinoma (CRC). The aim of this study is to investigate the use of miR-221 and miR-18a in stool samples as non-invasive biomarkers for CRC diagnosis. METHODS: A miRNA expression array containing 667 miRNAs was performed to identify miRNA dysregulation in CRC tissues. We focused on miR-221 and miR-18a, two significantly upregulated miRNAs which were subsequently verified in 40 pairs of CRC tissues and 595 stool samples (198 CRCs, 199 polyps and 198 normal controls). RESULTS: miR-221 and miR-18a were upregulated in the miRNA expression array. miR-221 and miR-18a levels were also significantly higher in 40 CRC tumours compared with their respective adjacent normal tissues. In stool samples, miR-221 and miR-18a showed a significant increasing trend from normal controls to late stages of CRC (P<0.0001). The levels of stool miR-221 and miR-18a were both significantly higher in subjects with stages I+II (miR-221: P<0.0001, miR-18a: P<0.0001) and stages III+IV of CRC (miR-221: P=0.0004, miR-18a: P<0.0001) compared with normal controls. The AUC of stool miR-221 and miR-18a were 0.73 and 0.67 for CRC patients as compared with normal controls, respectively. No significant differences in stool miR-221 and miR-18a levels were found between patients with proximal and distal CRCs. The use of antibiotics did not influence stool miRNA-221 and miRNA-18a levels. CONCLUSIONS: Stool-based miR-221 can be used as a non-invasive biomarker for the detection of CRC.

Biocontrol of verticillium wilt and colonization of cotton plants by an endophytic bacterial isolate.

AIMS: To explore biocontrol potential of 39 DAEB isolates (doubly antagonistic towards both Verticillium dahliae Kleb and Fusarium oxysporum) against verticillium wilt of cotton and to elucidate colonization and category characteristics of an endophytic bacterium with significant biocontrol activity. METHODS AND RESULTS: Thirty-nine antagonistic endophytic bacteria strains were tested for their ability to control verticillium wilt in cotton plants caused by a defoliating pathotype of V. dahliae 107 in cotton under controlled conditions. The biocontrol trial revealed that an endophytic bacterium, designated HA02, showed a significant biocontrol activity to V. dahliae 107. After cotton seedlings were inoculated with a gfp gene-tagged HA02 (HA02-gfp), HA02-gfp populations were higher in the root than in the stem; in addition, the HA02-gfp was distributed in the maturation zone of cotton root. Furthermore, HA02-gfp also colonized seedlings of maize, rape and soybean after the bacteria inoculation. Phylogenetic trees based on 16S rDNA sequences combined with morphological, physiological and identification showed that the bacterium belongs to the Enterobacter genus. CONCLUSIONS: Our results showed that only 1 of 39 DAEB isolates demonstrated more efficient biocontrol potential towards V. dahliae 107 in greenhouse and field trials. HA02-gfp mainly colonized cotton in roots. In addition, we quantitatively observed HA02 colonization in other hosts. HA02 belongs to the Enterobacter genus. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study on biocontrol to defoliating pathotype of V. dahliae Kleb by endophytic bacteria. The HA02 showed effective biocontrol to V. dahliae 107 in greenhouse and field trials. Furthermore, we assessed the quantitative and qualitative colonization of HA02 in cotton seedlings. Our study provides basic information to further explore managing strategies to control this critical disease.

Functional genomics of Neisseria meningitidis pathogenesis.

The pathogenic bacterium Neisseria meningitidis is an important cause of septicemia and meningitis, especially in childhood. The establishment and maintenance of bacteremic infection is a pre-requisite for all the pathological sequelae of meningococcal infection. To further understand the genetic basis of this essential step in pathogenesis, we analyzed a library of 2,850 insertional mutants of N. meningitidis for their capacity to cause systemic infection in an infant rat model. The library was constructed by in vitro modification of Neisseria genomic DNA with the purified components of Tn10 transposition. We identified 73 genes in the N. meningitidis genome that are essential for bacteremic disease. Eight insertions were in genes encoding known pathogenicity factors. Involvement of the remaining 65 genes in meningocoocal pathogenesis has not been demonstrated previously, and the identification of these genes provides insights into the pathogenic mechanisms that underlie meningococcal infection. Our results provide a genome-wide analysis of the attributes of N. meningitidis required for disseminated infection, and may lead to new interventions to prevent and treat meningococcal infection.

Effect of Cobalt Precursors on Cobalt-Hydroxyapatite Used in Bone Regeneration and MRI.

In clinical dentistry practice, supplemental bone surgery or jawbone defect after tooth extraction must be assisted by a bone-filling material. Cobalt-substituted hydroxyapatite (COHA) effectively promotes bone cell growth, reduces the inflammatory response, and is an antibacterial agent. COHA can therefore be used as an alveolar bone-filling material or guided bone regeneration membrane. Meanwhile, COHA can be used in magnetic resonance imaging (MRI) with negative contrast agents and targeting materials without causing metal interference with the image. Hence, COHA has received increasing amounts of attention in recent years. However, the influence of different cobalt precursors on the synthesized COHA is still unknown. Therefore, COHA synthesized from 3 cobalt precursors (cobalt chloride, cobalt nitrate, and cobalt sulfate) was compared in this study. The results show that COHA synthesized by the precursor with the smallest anion radius, cobalt chloride, has a larger particle size (239 nm) and a higher cobalt ion substitution rate (15.6%). When the cobalt ion substitution rate increases, the MRI has a stronger contrast. Bioactivity data indicate that COHAC is more susceptible to degradation and therefore releases more cobalt ions to contribute to the differentiation of bone cells. Based on these studies, COHAC prepared with the cobalt chloride precursor has a higher cobalt ion substitution rate, faster degradation rate, better image contrast, and better bioactivity. It is therefore the preferred choice of bone-filling material for alveolar bone regeneration.

Dynamic infection of Verticillium dahliae in upland cotton.

Verticillium wilt, an infection caused by the soilborne fungus Verticillium dahliae, is one of the most serious diseases in cotton. No effective control method against V. dahliae has been established, and the infection mechanism of V. dahliae in upland cotton remains unknown. GFP-tagged V. dahliae isolates with different pathogenic abilities were used to analyse the colonisation and infection of V. dahliae in the roots and leaves of different upland cotton cultivars, the relationships among infection processes, the immune responses and the resistance ability of different cultivars against V. dahliae. Here, we report a new infection model for V. dahliae in upland cotton plants. V. dahliae can colonise and infect any organ of upland cotton plants and then spread to the entire plant from the infected organ through the surface and interior of the organ. Vascular tissue was found to not be the sole transmission route of V. dahliae in cotton plants. In addition, the rate of infection of a V. dahliae isolate with strong pathogenicity was notably faster than that of an isolate with weak pathogenicity. The resistance of upland cotton to Verticillium wilt was related to the degree of the immune response induced in plants infected with V. dahliae. These results provide a theoretical basis for studying the mechanism underlying the interaction between V. dahliae and upland cotton. These results provide a theoretical basis for studying the mechanism underlying the interaction between V. dahliae and upland cotton.

Quisqualate activates a rapidly inactivating high conductance ionic channel in hippocampal neurons.

Glutamate activates a number of different receptor-channel complexes, each of which may contribute to generation of excitatory postsynaptic potentials in the mammalian central nervous system. The rapid application of the selective glutamate agonist, quisqualate, activates a large rapidly inactivating current (3 to 8 milliseconds), which is mediated by a neuronal ionic channel with high unitary conductance (35 picosiemens). The current through this channel shows pharmacologic characteristics similar to those observed for the fast excitatory postsynaptic current (EPSC); it reverses near 0 millivolts and shows no significant voltage dependence. The amplitude of the current through this channel is many times larger than that through the other non-NMDA (N-methyl-D-aspartate) channels. These results suggest that this high-conductance quisqualate-activated channel may mediate the fast EPSC in the mammalian central nervous system.

Amiloride selectively blocks the low threshold (T) calcium channel.

More than one type of voltage-gated calcium channel has been identified in muscle cells and neurons. Many specific organic and inorganic blockers of the conventional, slowly inactivating high threshold (L) calcium channel have been reported. No specific blockers of the low threshold (T) channel have been as yet identified. Amiloride, a potassium sparing diuretic, has now been shown to selectively block the low threshold calcium channel in mouse neuroblastoma and chick dorsal root ganglion neurons. The selective blockade of the T-type calcium channel will allow identification of this channel in different tissues and characterization of its specific physiological role.

Modulation of the time course of fast EPSCs and glutamate channel kinetics by aniracetam.

It is generally accepted that glutamate serves as the neurotransmitter at most excitatory synapses in the mammalian central nervous system (CNS). Synaptic release of glutamate may trigger a fast and a slow excitatory postsynaptic current (EPSC). The slow EPSC is mediated by N-methyl-D-aspartate (NMDA) receptor channels, whereas the fast EPSC is mediated by non-NMDA receptor channels. The nootropic agent aniracetam selectively and reversibly slows the desensitization kinetics of non-NMDA channels and lengthens their single-channel open times. Antiracetam also modulates the kinetics of the fast EPSC in a manner that mirrors its action on the kinetics of the non-NMDA channels. These results support the hypothesis that the properties of the non-NMDA glutamate channels rather than the rate of neurotransmitter clearance are the primary determinants of the kinetics of the fast EPSC in the mammalian CNS.

Compartmentalized and binary behavior of terminal dendrites in hippocampal pyramidal neurons.

The dendritic arbor of pyramidal neurons is not a monolithic structure. We show here that the excitability of terminal apical dendrites differs from that of the apical trunk. In response to fluorescence-guided focal photolysis of caged glutamate, individual terminal apical dendrites generated cadmium-sensitive all-or-none responses that were subthreshold for somatic action potentials. Calcium transients produced by all-or-none responses were not restricted to the sites of photolysis, but occurred throughout individual distal dendritic compartments, indicating that electrogenesis is mediated primarily by voltage-gated calcium channels. Compartmentalized and binary behavior of parallel-connected terminal dendrites can greatly expand the computational power of a single neuron.

Saturation of postsynaptic glutamate receptors after quantal release of transmitter.

Miniature excitatory postsynaptic currents (mEPSCs) were elicited from small numbers of release sites after brief microperfusion of Ba2+ and K+ onto proximal dendritic processes of hippocampal neurons in culture. Temporal summation of closely timed mEPSCs deviated significantly from linearity. The number of instances of closely timed mEPSCs that were also closely matched in terms of peak amplitudes was significantly greater than that expected by chance. Amplitude pairing became statistically more significant after prolongation of mEPSC duration and inhibition of glutamate receptor desensitization with cyclothiazide. These results are best explained by postsynaptic receptors that approach saturation after quantal release of transmitter.

Structure-based design of chimeric antigens for multivalent protein vaccines.

There is an urgent need to develop vaccines against pathogenic bacteria. However, this is often hindered by antigenic diversity and difficulties encountered manufacturing membrane proteins. Here we show how to use structure-based design to develop chimeric antigens (ChAs) for subunit vaccines. ChAs are generated against serogroup B Neisseria meningitidis (MenB), the predominant cause of meningococcal disease in wealthy countries. MenB ChAs exploit factor H binding protein (fHbp) as a molecular scaffold to display the immunogenic VR2 epitope from the integral membrane protein PorA. Structural analyses demonstrate fHbp is correctly folded and the PorA VR2 epitope adopts an immunogenic conformation. In mice, immunisation with ChAs generates fHbp and PorA antibodies that recognise the antigens expressed by clinical MenB isolates; these antibody responses correlate with protection against meningococcal disease. Application of ChAs is therefore a potentially powerful approach to develop multivalent subunit vaccines, which can be tailored to circumvent pathogen diversity.

Haemophilus influence: the impact of whole genome sequencing on microbiology.

The publication of the Haemophilus influenzae genome sequence in 1995 was a landmark in microbiological research. It has changed our understanding of the prokaryotic world, and will influence the approach and focus of research on microorganisms over the next few years. In this article we outline what has been learned from this and other genome sequencing projects, and discuss some of the potential avenues of investigation that will follow in the 'post-genome era'.

trans repression of the human metallothionein IIA gene promoter by PZ120, a novel 120-kilodalton zinc finger protein.

Metallothioneins are small, highly conserved, cysteine-rich proteins that bind a variety of metal ions. They are found in virtually all eukaryotic organisms and are regulated primarily at the transcriptional level. In humans, the predominant metallothionein gene is hMTIIA, which accounts for 50% of all metallothioneins expressed in cultured human cells. The hMTIIA promoter is quite complex. In addition to cis-acting DNA sequences that serve as binding sites for trans-acting factors such as Sp1, AP1, AP2, AP4, and the glucocorticoid receptor, the hMTIIA promoter contains eight consensus metal response element sequences. We report here the cloning of a novel zinc finger protein with a molecular mass of 120 kDa (PZ120) that interacts specifically with the hMTIIA transcription initiation site. The PZ120 protein is ubiquitously expressed in most tissues and possesses a conserved poxvirus and zinc finger (POZ) motif previously found in several zinc finger transcription factors. Intriguingly, we found that a region of PZ120 outside of the zinc finger domain can bind specifically to the hMTIIA DNA. Using transient-transfection analysis, we found that PZ120 repressed transcription of the hMTIIA promoter. These results suggest that the hMTIIA gene is regulated by an additional negative regulator that has not been previously described.

Microbial genome sequencing and pathogenesis.

The year 1997 saw the publication of the complete nucleotide sequence of Helicobacter pylori and Escherichia coli. It is conceivable that the complete nucleotide sequence for all the major human bacterial pathogens will be available by the end of the century. Database alignments have been used to ascribe the putative functions of open reading frames in the sequenced isolates and to define the differences between bacterial species at the nucleotide level. The most striking finding from all genome projects has been the high proportion of open reading frames that have no known function. Experimental data demonstrating the utility of the genome sequencing projects are only just beginning to emerge.

Sodium ramping reduces hypotension and symptoms during haemodialysis.

OBJECTIVES: To evaluate the effectiveness of sodium ramping (profiling) in reducing hypotensive episodes and symptoms during haemodialysis. DESIGN: Prospective study. SETTING: Regional hospital, Hong Kong. PATIENTS: Thirteen patients who experienced frequent episodes of hypotension and/or symptoms such as cramps, dizziness, chest pain, nausea, vomiting, and headache during haemodialysis in the preceding 4 weeks. INTERVENTIONS: Each patient was switched from standard haemodialysis with a constant dialysate sodium concentration of 135 to 140 mmol/L to a ramped sodium haemodialysis for a period of 4 weeks. During this time the dialysate sodium concentration was ramped linearly downwards from 150 mmol/L at the beginning of dialysis to 140 mmol/L at the end of dialysis. MAIN OUTCOME MEASURES: Intradialytic hypotensive episodes, intradialytic symptoms, nursing interventions, systolic and diastolic blood pressures, and interdialytic weight gain. RESULTS: A total of 248 haemodialysis sessions undertaken by 13 patients were analysed. Switching from constant sodium haemodialysis to ramped sodium haemodialysis resulted in a significant reduction in the number of intradialytic hypotensive episodes from 5.8 (standard deviation, 6.4) to 2.2 (3.3) [P<0.05], the total number of intradialytic symptoms from 7.1 (3.4) to 0.9 (1.3) [P<0.01], and nursing interventions from 11.3 (6.3) to 1.7 (3.9) [P<0.01]. Post-dialysis systolic and diastolic blood pressures were higher during ramped sodium haemodialysis compared with constant sodium haemodialysis (systolic blood pressure, 139 [standard deviation, 23] vs 133 [22] mm Hg, P<0.001; diastolic blood pressure, 77 [11] vs 74 [13] mm Hg, P<0.01), and there was a trend towards a smaller drop in blood pressure after dialysis. The interdialytic weight gain with sodium ramping haemodialysis was greater compared with constant sodium haemodialysis (3.1 [standard deviation, 1.0] vs 2.7 [1.1] kg, P<0.001). CONCLUSION: Sodium ramping during haemodialysis effectively reduces hypotensive episodes and intradialytic symptoms. Post-dialysis blood pressure is better maintained. A side-effect of sodium ramping is a greater interdialytic weight gain.

Sodium channels in axons and glial cells of the optic nerve of Necturus maculosa.

Experiments investigating both the binding of radioactively labelled saxitoxin (STX) and the electrophysiological response to drugs that increase the sodium permeability of excitable membranes were conducted in an effort to detect sodium channels in glial cells of the optic nerve of Necturus maculosa, the mudpuppy. Glial cells in nerves from chronically enucleated animals, which lack optic nerve axons, show no saturable uptake of STX whereas a saturable uptake is clearly present in normal optic nerves. The normal nerve is depolarized by aconitine, batrachotoxin, and veratridine (10(-6)-10(-5) M), whereas the all-glial preparation is only depolarized by veratridine and at concentrations greater than 10(-3) M. Unlike the depolarization caused by veratridine in normal nerves, the response in the all-glial tissue is not blocked by tetrodotoxin nor enhanced by scorpion venom (Leiurus quinquestriatus). In glial cells of the normal nerve, where axons are also present, the addition of 10(-5) M veratridine does lead to a transient depolarization; however, it is much briefer than the axonal response to veratridine in this same tissue. This glial response to veratridine could be caused by the efflux of K+ from the drug-depolarized axons, and is similar to the glial response to extracellular K+ accumulation resulting from action potentials in the axon.

Functional synapses are formed between human NTera2 (NT2N, hNT) neurons grown on astrocytes.

The formation of functional synapses is a late milestone of neuronal differentiation. The establishment of functional synapses can be used to assess neuronal characteristics of different cell lines. In the present study, we examined the in vitro conditions that influence the ability of human neurons derived from the NT2 cell line (NT2N neurons) to establish synapses. The morphologic, immunologic, and electrophysiologic characteristics of these synapses was examined. In the absence of astrocytes, NT2N neurons rarely formed synapses and their action potentials were weak and uncommon. In contrast, when plated on primary astrocytes, NT2N neurons were able to form both glutamatergic excitatory (71%) and GABAergic inhibitory (29%) functional synapses whose properties (kinetics, ion selectivity, pharmacology, and ultrastructure) were similar to those of synapses of neurons in primary cultures. In addition, coculture of NT2N neurons with astrocytes modified the morphology of the neurons and extended their in vitro viability to more than 1 year. Because astrocyte-conditioned medium did not produce these effects, we infer that direct contact between NT2N neurons and astrocytes is required. These results suggest that NT2N neurons are similar to primary neurons in their synaptogenesis and their requirement for glial support for optimal survival and maturation. This system provides a model for further investigations into the neurobiology of synapses formed by human neurons.

p53 mutational spectrum of esophageal carcinomas from five different geographical locales in China.

A mutational spectrum for exons 5-8 of the p53 tumor suppressor gene in esophageal carcinomas in mainland China and Hong Kong was established. This study involved 209 squamous cell carcinoma specimens obtained from five different geographical locales in China: Zhengzhou, Taiyuan, Shantou, Guangzhou, and Hong Kong. Zhengzhou and Shantou were high-incidence regions for esophageal cancer, whereas the other three regions had low or intermediate incidence of the disease. Analysis by single-strand conformation polymorphism and DNA sequencing showed that 87 specimens (41.6%) contained mutations in exons 5-8 of the p53 gene compared to 163 cases (78%) that had accumulation or aberrant expression of the protein, as detected by immunohistochemical staining. Point mutations accounted for 80.4% (87/107) of all genetic changes. The specimens from northern China exhibited fewer p53 gene aberrations and a more even distribution of mutations in exons 5-8 compared to those from southern China in which 60% of all mutations were found in exon 5. A major hot spot was found at codon 176 in exon 5, where 41 samples from Shantou, Guangzhou, and Hong Kong had a G-->T transversion. It is likely that among southern Chinese this codon is susceptible to mutagenesis by carcinogens. Codons 175, 203, 245, 250, 273, and 282 were also shown to be mutational hot spots, with three or more mutations observed at each site. The p53 mutational data obtained in this study showed that Chinese esophageal carcinomas are often associated with some unique genetic alterations, which may be attributed to specific dietary or environmental carcinogens that affect the Chinese but not Caucasians.

p53 mutations detected in colorectal carcinoma patients in Hong Kong.

A mutational spectrum for exons 5-8 of the p53 tumor suppressor gene in colorectal carcinomas in Hong Kong Chinese was established. Ninety-nine colorectal carcinomas from Hong Kong patients were analyzed for mutations in p53 gene by PCR-single-strand conformation polymorphism analysis and direct DNA sequencing. Thirty-five of the 99 tumors (35.4%) contained mutations. Point mutations accounted for 80% of all genetic changes and were predominantly base transitions at CpG dinucleotide sites, mutations that were also predominant in Caucasian carcinomas. The major hot spots at codons 175 and 248 of p53 in Caucasians are also hot spots in the Chinese gene. Identical mutations in codons 152 and 306 were detected in two independent tumors in the Chinese, which were reported only rarely in Caucasians. Moreover, a significantly higher frequency (20%) of deletion and insertion mutations was observed in Hong Kong colorectal cancer patients. Distinct genetic and/or environmental factors may contribute to these findings.