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Biomedical subjects

X L Feng

Publications and source records attributed to X L Feng.

17 recordsLinked to original sources
PubMed2006

Zeptogram-scale nanomechanical mass sensing.

Very high frequency (VHF) nanoelectromechanical systems (NEMS) provide unprecedented sensitivity for inertial mass sensing. We demonstrate in situ measurements in real time with mass noise floor approximately 20 zg. Our best mass resolution corresponds to approximately 7 zg, equivalent to approximately 30 xenon atoms or the mass of an individual 4 kDa molecule. Detailed analysis of the ultimate sensitivity of such devices based on these experimental results indicates that NEMS can ultimately provide inertial mass sensing of individual intact, electrically neutral macromolecules with single-Dalton (1 amu) resolution.

Equipment Design↗
PubMed2005

Incoherent subharmonic light scattering in isotropic media.

Incoherent subharmonic light scattering in isotropic media is a new kind of nonlinear light scattering, which involves single input photon and multiple output photons of equal frequency. We investigate theoretically the dependence of the subharmonic scattering intensity on the hyperpolarizability of molecules and the incident intensity using nonlinear optics theory similar to that used for Hyper-Rayleigh scattering and degenerate optical parametric oscillators. It is derived that the subharmonic scattering intensities grow exponentially or superexponentially with the hyperpolarizability of molecules and the incident intensity.

Light↗
PubMed2001

Bis(beta-alaninium) biphenyl-4,4'-disulfonate.

In the crystal structure of the title compound, 2C(3)H(8)NO(2)(+).C(12)H(8)O(6)S(2)(2-), N-H...O hydrogen bonds formed between the amino H atoms and the sulfonate O atoms give rise to the assembly of cationic beta-alaninium dimers and centrosymmetric biphenyl-4,4'-disulfonate anions into an extended two-dimensional layer. The resulting hydrogen-bonded ribbons can be described as C(2)(2)(6)R(4)(4)(12) according to graph-set notation. C-H...O hydrogen bonds between adjacent sheets further extend the structure into a three-dimensional arrangement.

Alanine↗
PubMed2001

Diaquabis(ethylenediamine)copper(II) bis[tris(ethylenediamine)nickel(II)] tris(naphthalene-2,6-disulfonate) tetrahydrate.

The title mixed-metal compound, [Cu(C(2)H(8)N(2))(2)(H(2)O)(2)][Ni(C(2)H(8)N(2))(3)](2)(C(10)H(6)O(6)S(2))(3).4H(2)O, was obtained during investigations of the porous frameworks constructed by amino-coordinated metal complex cations and large organic anions. All three naphthalene-2,6-disulfonate anions and the [Cu(en)(2)(H(2)O)(2)](2+) cation are located on crystallographic inversion centers and assemble into an extended two-dimensional network through intermolecular hydrogen bonds, creating cavities in which the [Ni(en)(3)](2+) cations and water molecules are included.

Journal Article↗
PubMed2001

Solid-state structures of group 1 and group 2 metal 1,5-naphthalenedisulfonates: systematic investigation of lamellar three-dimensional networks constructed by metal arenedisulfonate.

Seven Group 1 and Group 2 1,5-naphthalenedisulfonates (1,5-nds) have been synthesized and structurally characterized by single-crystal X-ray diffraction, IR spectroscopy and thermal gravimetric analysis. For Group 1 metal complexes, with M = Li(+) (1), Na(+) (2) and K(+) (3), all crystallize in the same space group (P2(1)/c) with the same composition, [M(2)(1,5-nds)(H(2)O)(2)]. They adopt similar three-dimensional packing arrangements with the metal-sulfonate inorganic layers pillared by naphthalene rings. However, the coordination behavior of three metal cations toward the SO(3)(-) group and water molecule are different, resulting in different architectures for the inorganic portion. For Group 2 complexes with M = Mg(2+) (4), Ca(2+) (5), Sr(2+) (6) and Ba(2+) (7), Mg(2+) shows no direct coordination by the SO(3)(-) group while Ca(2+) is coordinated by four SO(3)(-) groups and a two-dimensional network is formed. Complexes (6) and (7) are isostructural, adopting the same three-dimensional, inorganic-organic pillared framework as seen for (1)-(3). The coordination behavior of the metal cations in these structures neatly illustrates the increase in coordination strength with decreasing charge/radius ratio for Group 1 and Group 2 metal cations with large organic anions.

Journal Article↗
PubMed2001

Alterations in metastatic properties of hepatocellular carcinoma cell following H-ras oncogene transfection.

AIM: To demonstrate the relationship between H-ras oncogene and hepatocellular carcinoma (HCC) metastasis. METHODS: Activated H-ras oncogene was transfected into SMMC 7721, a cell line derived from human HCC, by calcium phosphate transfection method. Some metastasis-related parameters were detected in vitro, including adhesion assay, migration assay, expression of collagenase IV(c IV ase) and epidermal growth factor receptor (EGFR). RESULTS: The abilities of H-ras-transfected cell clones in adhesion to laminin (LN) or fibronectin (FN), migration, c IV ase secretion increased markedly, and the expression of EGFR elevated moderately. More importantly, these alterations were consistent positively with the expression of p21, the protein product of H-ras oncogene. CONCLUSION: H-ras oncogene could induce the metastatic phenotype of HCC cell in vitro to raise its metastatic potential.

Carcinoma, Hepatocellular↗
PubMed2001

[Removal of PEG and salt from recombinant human tumor necrosis factor-alpha(rhTNF-alpha) with serial operation of gel filtration chromatography].

A serial gel filtration operation with the combination of G25 and G100 in one column was developed to remove salt and PEG from upper phase rich in recombinant human tumor necrosis factor alpha after simultaneous cell disruption and two-phase aqueous extraction. Buffer exchanging and primary purification were also achieved at same time. The purification factor of 4.4 was obtained with an activity recovery of 97% by one single step of serial operation.

Chromatography, Gel↗
PubMed1998

Biological behavior of plasmid in Rhizobium sp. strain S25 from Tephrosia candida.

Rhizobium sp. strain S25 was isolated from the nodule on Tephrosia candida in Hainan Province, China. The strain showed high stress tolerance. The plasmid profile of strain S25, examined by the Eckhardt procedure, indicated that the strain harbors only one plasmid with an estimated size of 150 kb. The plasmid was shown to carry nod and nif genes by hybridization with probes of nodABC and nifHDK genes. Plasmid curing was carried out using the Bacillus subtilis sacB to generate derivatives of strain S25. In comparison with the parent strain S25, the cured derivative lost its ability to nodulate the host plant. Loss of the plasmid reduced significantly the strain's tolerance to acid, nitrous, and multiple antibiotics. The properties of the cured strain also indicated that the plasmid was involved in carbon and nitrogen metabolism. Reintroduction of the plasmid from S25 in the cured derivative restored its original biological phenotypes.

DNA, Bacterial↗
PubMed1998

Postnatal developmental changes in NSE and NNE mRNA expression in the rat pineal gland: in situ hybridization histochemistry.

By in situ hybridization, neuron-specific enolase (NSE) and non-neuronal enolase (NNE) mRNAs were examined in the rat pineal gland at the postnatal developmental and adult stages. The distributions of hybridized signals were analyzed in comparison with immunohistochemical staining of synaptophysin (SYN), which is a marker for pinealocytes. In SYN-positive areas that were observed throughout postnatal developmental and adult stages, we detected both NSE and NNE signals, which increased simultaneously during early postnatal development and thereafter became stationary. Quantitative analysis revealed that NNE signals were 2- to 3-fold greater in number than NSE signals at any given stage. This predominant expression pattern of NNE differed from that in neurons, which usually showed both signals at similar levels and seemed to reflect the difference in physiological function from neurons. During the early postnatal stages, a cord-like arrangement of cells without distinct SYN staining was observed. This arrangement was the thickest at postnatal day 0 and became dispersed and thinner with development, showing a relationship with formation of vascularized connective tissue stroma. By in situ hybridization, many of the constituent cells showed weak NNE signals but no distinct NSE signals. However, some cells also showed weak NSE signals, suggesting heterogeneity of these cells. The characteristic NSE and NNE expression patterns in the pineal gland cells clarified in this study might provide a basis for further studies of the differentiation and function of the pineal gland.

Animals↗
PubMed1998

The abundance of NM23-H1 mRNA is related with in situ microenvironment and intrahepatic metastasis in hepato-cellular carcinoma.

In HCC specimens from 25 patients, the levels of nm23-H1 and H-ras mRNA were analyzed by quantitative reverse transcription-polymerase-chain reaction (RT-PCR). Tumor microvessel density (MDV), the essential factor of microenvironment and proliferating cell nucleus antigen (PCNA), indexes as tumor cell proliferating in its microenvironment are also analyzed by immunohistochemical methods using antibodies against endothelial protein factor VIII related antigen (F8RA) and antibody PC-10. Results show that The MDV and PCNA index in the group with intrahepatic metastasis is remarkably higher than that in without one (p<0.01), but the abundance of nm23-H mRNA is opposite (p<0.01). The abundance of H-ras mRNA shows little difference (p>0.05). MDV index shows directly relationship with PCNA index (p<0.01), the abundance of nm23-H1 mRNA show an inverse one with PCNA index (p<0.05). We conclude that in HCC, tumor in situ microenvironment, especially a deteriorative one, plays an important selective role. The decline of nm23-H1 mRNA abundance implies the increase of highly potential metastatic cancer cells which adapt to their microenvironment.

Biomarkers, Tumor↗
PubMed1994

[The correlation between occurrence of intracranial germ cell tumors and p53 tumor suppressor gene mutations].

Using PCR-SSCP molecular biological techniques and sequencing analysis, an investigation on intracranial germ cell tumors for a correlation between the p53 tumor suppressor gene mutations and the occurrence of these tumors was performed. The results were as follows: 1. The p53 gene mutations were closely related with the development of intracranial germ cell tumors; 2. Among the germ cell tumors, different types of tumors had different p53 tumor gene mutations.

Adolescent↗
PubMed1992

Direct chromosome analysis of seven primary colorectal carcinomas.

Chromosome studies were performed on direct preparations of seven cases of primary colorectal carcinomas. Two cases had relatively simple chromosome changes: 48,XY,+8,+21/51, XY,+8,+9,+10,+i(17q),+21, and 47,der(X)t(X;14)(q11;q11)-Y,t(6;18)(p22;q24)+7,+8,der(19)t (19;?)(q13;?). The five others had complicated deletions and translocations; 1p- was noted in five cases, and i(17q) was noted in three cases.

Adenocarcinoma↗
PubMed1992

Cytogenetic studies of eight primary gastric cancers.

Cytogenetic analysis was performed on eight primary gastric cancers. Three of them had simple chromosome changes: 47,XX,+X/48,XX,+X,+X; 48,XX,+8,+19,t(3;5) (q21;q31) and 47,XY,+del(7)(q22). The five others had complicated chromosome changes; both 3p- and 7q- were noted in four cases and i(5p) was noted in two cases.

Adenocarcinoma↗
PubMed1992

Cytogenetic abnormalities in a squamous cell carcinoma of the penis.

Cytogenetic findings in a squamous cell carcinoma (SCC) of the penis in a 60-year-old patient was observed for the first time. The stemline karyotype of the tumor was 46,XY,del(2) (q33q36),der(4)t(4;?)(p16;?),der(5;15)(q10;q10),der(8)t(8;?13)(p21 ;?),-13,- 13,-15,+3mar.

Carcinoma, Squamous Cell↗
PubMed1991

Cytogenetic studies of five primary esophageal cancers.

In direct preparation of five primary esophageal cancers, chromosomes 1, 3, and 12 were most frequently involved in structural abnormalities; 12p- was consistently seen in all five cases and, thus, could be considered as one of the characteristic chromosome changes in esophageal cancer. Moreover, 2p-, 4p-, and 7q- were seen in three cases.

China↗
PubMed1988

Studies on the sites expressing evolutionary changes in the structure of eukaryotic 5S ribosomal RNA.

We have determined the complete sequences of 5S rRNAs from a lamprey (Lampetra reissneri), a lancelet (Branchiostoma belcheri), silkworms (Philosamia cynthia ricini, Bombyx mori, Antheraea pernyi), and a silkworm hybrid (artificially fertilized hybrid species of Philosamia cynthia ricini male x Bombyx mori female), as well as those of cotton seeds (Gossypium hirsutum L.). Having compared more than 170 eukaryotic 5S rRNAs of which seven sequences have been determined by our group as mentioned above, we have found that the "evolutionary sites" that exist at special locations in these structures are closely related to the evolution of eukaryotes. The changes proceed step by step in an orderly way, i.e., the change in nucleotide residues of the "evolutionary sites" depends on the order of the evolution of the species and shows group-specific patterns.

Animals↗