Search PubMed⌕ Search

Biomedical subjects

X Kong

Publications and source records attributed to X Kong.

At least 37 records · Page 2Linked to original sources
PubMed2001

Latency change estimation for evoked potentials: a comparison of algorithms.

Evoked potentials (EPs) have been widely used to quantify neurological system properties. Changes in EP latency may indicate impending neurological dysfunctions. This paper provides a review and a performance comparison of three classes of latency change estimation algorithms: correlation based, adaptive least mean square (LMS) based, and p-norm based algorithms. Data analysis based on computer simulated data and data from impact acceleration and hypoxia experiments were conducted. This concluded that correlation-based algorithms should only be used when the expected latency change is fixed and the noises are not correlated. While all adaptive LMS type algorithms were capable of tracking and estimating latency changes (fixed or variable) under Gaussian noise conditions, the direct LMS-based algorithm reduced the estimation error power given by traditional filter type LMS algorithms as much as 93%. When periodic interference was present, the frequency selective LMS algorithms outperformed other LMS-based algorithms and reduced of the estimation error power by 89%. Alpha-stable noise processes are better approximations of noises found in various EP analysis applications and adaptive p-norm based algorithms are found to be very robust under such noise conditions, eliminate erroneous abrupt latency changes other algorithms would have produced.

Algorithms↗
PubMed2001

Anti-viral activity of hairpin ribozyme directed against HBV core region in vitro.

To study the preparation and cleavage of hairpin ribozyme (HpRz) directed against the transcript of HBV core region in vitro, HRz gene designed by computer targeting the transcript of HBV core gene was cloned into the vector p1.5 between 5'-cis-Rz and 3'-cis-Rz. 32P-labeled HpRz transcript proved whether the vector fit for the preparation of hairpin ribozyme. 32P-labeled pKC transcript containing HBV core region as targets-RNA was transcribed by using T7 RNA polymerase and purified by PAGE. Cold HpRz transcript was incubated with 32P-labeled target-RNAs under different conditions and radioautographed after denaturing polyacrylamide gel electrophoresis. The results showed that HpRz had the ability of cleavage at 37 degrees C and 12 mmol/L MgCl2 and the design of ribozyme was correct. It is concluded that HpRz prepared in vitro possesses specific catalytic activity, indicating that it is possible for HpRz to intracellularly inhibit the replication of HBV. It may be developed into a nucleic acid drug in the treatment of hepatitis B in the future.

Antiviral Agents↗
PubMed2001

Pulmonary sequestration: three dimensional dynamic contrast-enhanced MR angiography and MRI.

In order to evaluate the diagnostic value of three-dimensional contrast-enhanced MR angiography and MRI for pulmonary sequestration, 5 patients with pulmonary sequestration underwent 3D fast imaging by steady state precession (FISP) with a contrast medium and breath holding following chest radiography, CT and MR scans. The reconstructed MR angiography was performed using maximum intensity projection (MIP) and multiplanar reconstruction (MPR) techniques. It was found that the chest radiography showed pulmonary sequestration as a persistent area of opacity in the posterior basal segment of the left lower lobe, which was close to mediastinum in 2 cases and close to diaphragma in 3 cases. CT revealed a soft issue mass beyond descending aorta and lobar emphysema around the pulmonary sequestration. And the supplying vessel was documented in 2 cases on enhanced CT. MRI demonstrated a hyperintensity mass with respect to normal lung parenchyma on T1WI and T2WI, and the origin of the supplying vessel in 3 cases. The reconstructed CE MRA using MIP or MRP techniques clearly showed the supplying vessel and its course, branches as well as draining vessels. It was concluded that 3D CE MRA of demonstrating the supplying and draining vessels to pulmonary sequestration, together with plain MRI, can provide a diagnosis and aid in surgical planning without the need for DSA.

Adolescent↗
PubMed2001

Dentinogenesis imperfecta 1 with or without progressive hearing loss is associated with distinct mutations in DSPP.

Dentinogenesis imperfecta 1 (DGI1, MIM 125490) is an autosomal dominant dental disease characterized by abnormal dentin production and mineralization. The DGI1 locus was recently refined to a 2-Mb interval on 4q21 (ref. 1). Here we study three Chinese families carrying DGI1. We find that the affected individuals of two families also presented with progressive sensorineural high-frequency hearing loss (gene DFNA39). We identified three disease-specific mutations within the dentin sialophosphoprotein gene (DSPP) in these three families. We detected a G-->A transition at the donor-splicing site of intron 3 in one family without DFNA39, a mutation predicted to result in the skipping of exon 3. In two other families affected with both DGI1 and DFNA39, however, we identified two independent nucleotide transversions in exons 2 and 3 of DSPP, respectively, that cause missense mutations of two adjacent amino-acid residues in the predicted transmembrane region of the protein. Moreover, transcripts of DSPP previously reported to be expressed specifically in teeth are also detected in the inner ear of mice. We have thus demonstrated for the first time that distinct mutations in DSPP are responsible for the clinical manifestations of DGI1 with or without DFNA39.

Asian People↗
PubMed2001

Watermarking medical signals for telemedicine.

Modern telecommunication infrastructure supports the possibility of delivering quality health care without the physical presence of medical experts. The integrity of biomedical signals being transmitted through communication channels must be established before their utilization. This paper investigates three digital watermarking techniques for signal integrity verification in an electroencephalogram (EEG) monitoring application for brain injury detection. The techniques studied are patchwork, least significant bit, and quantization watermarking methods. The three techniques are evaluated and compared in the following areas: sensitivity to noise contamination, robustness to EEG signal characteristic changes due to brain injury, and consistency under various communication channel models. The patchwork method performs best for noise contamination rejection among the three methods. The noise contamination detection rates of all three methods remain relatively stable across a wide range of EEG characteristics.

Brain Injuries↗
PubMed2001

Transcatheter closure of secundum atrial septal defect with a new self-expanding nitinol double disk device (Amplatzer device): experience in Nanjing.

PURPOSE: Various devices have been developed for the transcatheter closure of secundum atrial septal defect (ASD II) to avoid the morbidity, discomfort, and thoracotomy scar associated with surgical closure. The purpose of this study was to evaluate the safety and efficacy of the Amplatzer septal occluder for transcatheter closure of ASD II. PATIENTS AND METHODS: Only patients who were clinically diagnosed with ASD II were selected. The anatomy of ASD had to meet certain echocardiographic criteria. Under the guidance of echocardiography and fluoroscopy, the implantation of the device was accomplished as recommended by the manufacturer. RESULTS: Thirty patients (median age 18.4 years) with an ASD II underwent transcatheter closure. Procedure time ranged from 30-200 minutes and fluoroscopy time from 10-50 minutes. The diameter of the ASD measured by echocardiography ranged from 13-25 mm, while both the stretched diameters of the ASDs and the sizes of the devices ranged from 18-34 mm. The successful placement rate was 100%. The residual shunt rate was 100% immediately after device implantation and 10% after 24 hours. After 3 months, 3.3% of the patients had a (trivial) residual shunt. The device did not affect the surrounding structures of ASD. No embolization of the device occurred. CONCLUSION: The Amplatzer device designed for the closure of ASD II can be implanted easily and also is retrievable. Due to a low ratio of residual shunt and few complications, this device is a good choice for transcatheter closure of ASD II. Long-term follow-up will be required for widespread clinical use.

Adolescent↗
PubMed2001

[Effect of pentoxifylline on promoter activity of human alpha 1(I) procollagen gene].

OBJECTIVE: To study the effect of pentoxifylline (PTX) on promoter activity of human alpha 1(I) procollagen (COL1A1) gene and the influence of PTX on the promoter activity induced by insulin-like growth factor 1 and insulin. METHODS: The constructs of pCOLH2.5 containing -2483 approximately +42bp of the procollagen gene and chloramphenicol acetyltransferase (CAT) as reporter gene were transiently transfected into human skin fibroblasts. The cells were subsequently treated with PTX or IGF-1 or insulin, or PTX plus IGF-1 or insulin. The CAT activity was assessed 24h after PTX and the cytokines added. RESULTS: PTX of 0.4 mmol/L, 2 mmol/L, and 10 mmol/L decreased the CAT activity of pCOLH 2.5 to 82%+/-9%, 58%+/-8%, and 32%+/-13% of the control level, respectively. IGF-1 and insulin increased the activity of the construct. PTX could inhibit the CAT activity of pCOLH2.5 induced by IGF-1 and insulin. CONCLUSIONS: These studies indicate that PTX downregulates the promoter activity of the human COL1A1 gene, while IGF-1 and insulin upregulates it. PTX can inhibit the promoter activity induced by IGF-1 and insulin.

Collagen↗
PubMed2001

[Decomposition of aqueous sodium pentachlorophenolate (PCP-Na) by using TiO2 coating photocatalyst].

Titanium dioxide (TiO2) photocatalysts were coated on hollow glass beads by sodium silicate (Na2SiO3.9H2O) solution. The coated catalysts were characterized by BET, XRD. Their photoactivity were examined using photocatalytic degradation of sodium pentachlorophenolate(PCP-Na) and glucose solution. The impact of catalysts dosage, PCP-Na initial concentration, initial pH and oxygen concentration on reaction kinetics were also studied in detail. The experiments illustrated that the performance of C3-type catalysts was satisfactory. Conditions of the experiments were following: The initial concentration of PCP-Na and CODCr were 10 mg.L-1 and 400 mg.L-1, respectively, and illumination time was 2 hours and catalysts dosage was 2 g.L-1, the removal rates of CODCr and PCP-Na were above 65% and 92% respectively. Optimum dosage of C3-type catalysts was 2-2.5 g.L-1, DO was no less than 3 mg.L-1.

Catalysis↗
PubMed2001

Glycosaminoglycan mimetics: a therapeutic approach to cerebral amyloid angiopathy.

Amyloid deposits characteristic of cerebral amyloid angiopathy lead to vessel rupture and intracerebral hemorrhage. Proteoglycans associate with the amyloid fibril deposits and are thought to play a role in the polymerization of amyloid proteins and the propagation of the deposition process. A series of low molecular weight anionic compounds was developed to mimic the glycosaminoglycan moieties of these proteoglycans. These compounds were tested in different in vitro systems to determine their anti-Abeta amyloid activity. Specific compounds were identified as being anti-fibrillogenic and protective against Abeta-induced cvtotoxicity. Such compounds also did not show intrinsic cellular toxicity could cross the blood-brain barrier (BBB) in vivo, and showed a good safety profile following chronic' exposure. Molecules showing an anti-amyloid profile combined with the ability to cross the BBB represent promising therapeutics for CAA.

Amyloid beta-Peptides↗
PubMed2001

Molecular epidemiology of respiratory syncytial virus.

OBJECTIVE: To determine the epidemiologic pattern of subgroups A and B and genotypes of respiratory syncytial virus (RSV) during two noncontinuous epidemics during 1990-1991 and 1997-1998 in Beijing. METHODS: Nasopharyngeal secretion (NPS) samples of RSV positive or RSV isolates tested by indirect immunofluorescence (IIF) assay were classified into subgroups A and B. Isolates of RSV were divided into at least six different lineages, designated NP1-NP6, by restriction mapping of the N gene. Np1, 3 and 6 were given by subgroup B isolates, while NP2, 4 and 5 were given by subgroup A isolates. Strains of subgroup A were further subdivided into six lineages SHL1-SHL6 on the basis of the SH gene sequence. SH lineages were closely related to each other and to NP1-NP6. Strains of SHL1, 3 and 4 were closely related and belonged to NP2, SHL2 and 6 to NP4, and SHL5 to NP5. RESULTS: Of 145 RSV NPS samples from the 1997-1998 epidemic, 83 (57.2%) were of subgroup B RSV positive, 62 (42.8%) of subgroup A RSV positive. The rate of occurrence of subgroup A to B strains was about 1:1.3. Two of 10 isolates during the epidemic were subgroup A strains, whereas 8 were subgroup B strains. The rate of occurrence of subgroup A to B strains was 1:4. Eight subgroup A strains of 10 isolates from the 1990-1991 epidermic were dominant; the proportion of subgroup A to B strains was 4:1. With 10 RSV isolates in 1997-1998, all 2 subgroup A strains gave N gene fragment restriction pattern NP4, and fell into SH lineage SHL2, whereas 8 subgroup B strains all belonged to NP3. All 8 subgroup A isolates from the 1990-1991 epidemic gave pattern NP4, and fell into SHL2, while 2 subgroup B strains all belonged to NP3. The classification of subgroups A and B deduced from NP patterns corresponded to the definition of these subgroups by monoclonal antibodies. CONCLUSIONS: These observations confirm that subgroups A and B or multiple lineages of RSV co-circulated in Beijing, but different genome types predominated each year. Moreover, very similar viruses were isolated up to more than 5 years ago, indicating that despite apparent diversity of the subgroup A strains, the separate lineages might be relatively stable.

Genotype↗
PubMed2001

[Carcinoma of kidney collecting duct: an analysis of 10 cases].

OBJECTIVE: To study the clinicopathologic characteristics of renal collecting duct carcinoma (CDC). METHODS: A retrospective study was done in 10 cases of CDC. RESULTS: Among 466 cases of renal cell carcinoma admitted in our Institute between January 1989 and June 30, 1999, 10(2.1%) cases of CDC were identified. Seven presented with gross hematuria and 3 with abdominal pain. Radical nephrectomy was done in 9 patients, enucleation of tumor in one. The primary tumor was located predominantly in the renal medulla. Histologic examination showed prominent tubular or tubulopapillary structures. Sarcomatoid carcinoma, cystadenocarcinoma, nests and cords of tumor cells in desmoplastic stroma were identified in some cases. High molecular weight cytokeratin 34 beta E12 was positive in 8 cases and peanut agglutinin in 7 cases. According to Fuhrman's nuclear grade, one was in G2, 4 were in G3 and 5 in G4. Six patients died of metastases within 3 to 23 months (mean 13.3 months), one died of heart disease with tumor free after 19 months, two survived with tumor free for 14 months and 39 months, respectively, one lost from follow-up. CONCLUSION: CDC is a distinctive renal cell carcinoma with prominent clinical appearance and progressive clinical course.

Adult↗
PubMed2000

Near-infrared spectrophotometric determination of tri- and tetrapeptides.

A new method based on the near infrared technique has been developed for the noninvasive and nondestructive determination of the identity and sequences of amino acid residues in small peptides. The method is capable of distinguishing not only peptides with very similar structures (e.g., Gly-Ala-Ala, Gly-Ala-Leu, Leu-Gly-Gly and Gly-Leu-Leu-Gly, Gly-Leu-Gly-Gly, Gly-Gly-Ala-Gly) but also peptides with the same amino acid residues but different sequences (e.g., Gly-Ala-Ala, Ala-Gly-Ala, Ala-Ala-Gly and Gly-Gly-Gly-Ala, Gly-Gly-Ala-Gly).

Peptides↗
PubMed2000

Refinement of the locus for autosomal dominant hereditary gingival fibromatosis (GINGF) to a 3.8-cM region on 2p21.

Hereditary gingival fibromatosis (HGF, MIM 135300; approved gene symbol GINGF) is an oral disease characterized by enlargement of gingiva. Recently, a locus for autosomal dominant HGF has been mapped to an 11-cM region on chromosome 2p21. In the current investigation, we genotyped four Chinese HGF families using polymorphic microsatellite markers on 2p21. The HOMOG test provided evidence for genetic homogeneity, with evidence for linkage in four families (heterogeneity versus homogeneity test HOMOG, chi(2) = 0. 00). A cumulative maximum two-point lod score of 5.04 was produced with marker D2S390 at a recombination frequency of θ = 0 in the four linked families. Haplotype analysis localized the hereditary gingival fibromatosis locus within the region defined by D2S352 and D2S2163. This region overlaps by 3.8 cM with the previously reported HGF region. Single-strand conformation polymorphism and sequence analysis of the coding region of cytochrome P450 1B1 (CYP1B1) excluded it as a likely candidate gene.

Aryl Hydrocarbon Hydroxylases↗
PubMed2000

Sensitivity enhancement of HCACO by using an HMQC magnetization transfer scheme.

Previous theoretical calculations have demonstrated that the multiquantum relaxation rate of (1)H(alpha)-(13)C(alpha)(R(MQ)) is, on average, 1.3 +/- 0.4 or 1.7 +/- 0.6 times slower than the single-quantum relaxation rate of (13)C(alpha)(R(C)) for a sample with or without, respectively, amide protons. By taking advantage of this fact and by using the PEP sensitivity enhancement scheme, an HMQC version of the HCACO experiment has been developed. We demonstrate that this new experiment is 23 and 55% more sensitive than the original HSQC version of the HCACO experiment, at constant times of 7 and 27 ms, respectively, for a sample of the BC domain of the ciliary neurotrophic factor receptor protein dissolved in D(2)O at 20 degrees C.

Algorithms↗
PubMed2000

A J-multiplied HMQC (MJ-HMQC) experiment for measuring (3)J(HNHalpha) coupling constants.

The J-multiplied HSQC experiment (MJ-HSQC: S. Heikkinen et al., J. Magn. Reson 137, 243 (1999)) amplifies J coupling constants m times and allows direct observation of the (3)J(HNHalpha) coupling constants of peptides and proteins (<10 kDa). The drawbacks to this method are line broadening in the f(1)-dimension and lower sensitivity. In the J-multiplied HMQC (MJ-HMQC) experiment described here, the PEP-HSQC pulse sequence is replaced by a sensitivity-enhanced HMQC section, and the total decay time for the J-coupling and the chemical shift evolution is shortened by a period of t(1). This experiment affords narrower linewidth and enhances the sensitivity by 34%, on an average of 105 well-isolated peaks, when compared with the MJ-HSQC experiment.

Algorithms↗
PubMed2000

Determination of internucleotide (h)J(HN) couplings by the modified 2D J(NN)-correlated [(15)N, (1)H] TROSY.

Recent developments in the direct observation of J couplings across hydrogen bonds in proteins and nucleic acids provide additional information for structure and function studies of these molecules by NMR spectroscopy. A J(NN)-correlated [(15)N, (1)H] TROSY experiment proposed by Pervushin et al. (Proc. Natl. Acad. Sci. USA 95, 14147-14151, 1998) can be applied to measure (h)J(HN) in smaller nucleic acids in an E.COSY manner. However, it cannot be effectively applied to large nucleic acids, such as tRNA(Trp), since one of the peaks corresponding to a fast relaxing component will be too weak to be observed in the spectra of large molecules. In this Communication, we proposed a modified J(NN)-correlated [(15)N, (1)H] TROSY experiment which enables direct measurement of (h)J(HN) in large nucleic acids.

Bacillus subtilis↗
PubMed2000

The value of in-phase and opposed-phase T1-weighted breath-hold FLASH sequences for hepatic imaging.

The value of the combined in-phase (IP) and opposed-phase (OP) T1-weighted (T1-W) breath-hold FLASH sequences for hepatic imaging, especially for fat content, was evaluated. Non-contrast-enhanced IP and OP T1-W GRE breath-hold images were obtained in 76 patients refereed for abdominal MRI at 1.5T. 76 patients were divided into three groups for analysis: (1) liver without mass (n = 8); (2) liver with hepatoma (n = 34); (3) liver with haemangioma or cyst (n = 34). Liver/spleen and liver/lesion signal-to-noise (SNR) and contrast-to-noise ratio (CNR) were assessed for lesion detection. Images between IP and OP sequences were compared quantitatively. The results showed that there was not statistically significant difference in liver/spleen and liver/lesion SNR between IP and OP sequences. In the patients with fatty infiltration, the OP sequences yielded substantially lower values for liver/spleen and liver/lesion SNR than those of the IP sequences. Furthermore, OP imaging showed fatty infiltration in 14 cases and demonstrated hyperintense peritumor rim in 4 cases. In 14 cases of fatty infiltration, many lesions were identified using IP images. The use of IP and OP GRE sequences provides complementary diagnostic information for hepatic lesions and fat content. Focal hepatic lesions may be obscured in the setting of fatty infiltration if only OP sequences are employed. A complete assessment of the liver with MR should include both IP and OP imaging.

Adolescent↗