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Biomedical subjects

Z Lin

Publications and source records attributed to Z Lin.

At least 55 records · Page 3Linked to original sources
PubMed2001

Versican modulates embryonic chondrocyte morphology via the epidermal growth factor-like motifs in G3.

This investigation was designed to characterize the effect of the extracellular matrix molecule versican on chondrocyte morphology, using the well-studied chondrocyte cell culture system. When cultured chondrocytes reverted or "dedifferentiated" to a fibroblast-like morphology, we found that versican expression was significantly enhanced. Transfection of chondrocytes, isolated from embryonic chicken sterna, with a chicken miniversican construct accelerated the reversion process, while expression of an antisense construct inhibited it. A mutant miniversican lacking two epidermal growth factor-like motifs (versicanDeltaEGF) promoted differentiation, as shown by morphological changes and changes in the expression of other extracellular matrix molecules. A truncated versican mutant, the G3DeltaEGF, a G3 domain lacking its two epidermal growth factor-like motifs, also enhanced differentiation. This effect is related to G3DeltaEGF-induced change in cytoskeleton, since transfected cells exhibited misassembly of actin filaments. This article thus provides the first evidence that versican modulates chondrocyte morphology via changes in cytoskeletal structure, and may imply that extracellular matrix molecules play an important role in cell differentiation.

Actins↗
PubMed2001

Fatty aldehyde dehydrogenase: genomic structure, expression and mutation analysis in Sjögren-Larsson syndrome.

Fatty aldehyde dehydrogenase (FALDH) is a microsomal enzyme that catalyzes the oxidation of medium- and long-chain aliphatic aldehydes derived from metabolism of fatty alcohol, phytanic acid, ether glycerolipids and leukotriene B4. The FALDH gene (ALDH3A2) in man and mouse consists of 11 exons and is closely linked to the gene for ALDH3. In both species, alternative splicing results in formation of a second minor protein, FALDHv, that has a unique carboxy-terminal end. The functional significance of this alternate protein is not known. In humans, mutations in the FALDH gene cause Sjögren-Larsson syndrome (SLS), which is characterized by ichthyosis, mental retardation and spasticity. Missense mutations involving 24 amino acid positions in FALDH have been identified. These amino acids are more highly conserved among related class 3 aldehyde dehydrogenase enzymes than expected, suggesting that they are critically important for protein folding, catalysis or stability. Studies of mutations in SLS should prove useful for understanding structure-function correlations in FALDH and other aldehyde dehydrogenase proteins.

Aldehyde Oxidoreductases↗
PubMed2001

Synthesis, characterisation, crystal structures, reactivity, and electrochemistry of ruthenium-nitrido, ruthenium-cobalt-imido and ruthenapyrrolidone carbonyl clusters containing alkyne ligands.

Thermolysis of [Ru3(CO)9(mu3-NOMe)(mu3-eta2-PhC2Ph)] (1) with two equivalents of [Cp*Co(CO)2] in THF afforded four new clusters, brown [Ru5(CO)8(mu-CO)3(eta5-C5Me5)(mu5-N)(mu4-eta2-PhC2Ph)] (2), green [Ru3Co2(CO)7(mu3-CO)(eta5-C5Me5)2(mu3-NH)[mu4-eta8-C6H4-C(H)C(Ph)]] (3), orange [Ru3(CO)7(mu-eta6-C5Me4CH2)[mu-eta3-PhC2(Ph)C(O)N(OMe)]] (4) and pale yellow [Ru2(CO)6[mu-eta3-PhC2(Ph)C(O)N(OMe)]] (5). Cluster 2 is a pentaruthenium mu5-nitrido complex, in which the five metal atoms are arranged in a novel "spiked" square-planar metal skeleton with a quadruply bridging alkyne ligand. The mu5-nitrido N atom exhibits an unusually low frequency chemical shift in its 15N NMR spectrum. Cluster 3 contains a triangular Ru2Co-imido moiety linked to a ruthenium-cobaltocene through the mu4-eta8-C6H4C(H)C(Ph) ligand. Clusters 4 and 5 are both metallapyrrolidone complexes, in which interaction of diphenylacetylene with CO and the NOMe nitrene moiety were observed. In 4, one methyl group of the Cp* ring is activated and interacts with a ruthenium atom. The "distorted" Ru3Co butterfly nitrido complex [Ru3Co(CO)5(eta5-C5Me5)(mu4-N)(mu3-eta2-PhC2Ph)(mu-I)2I] (6) was isolated from the reaction of 1 with [Cp*Co(CO)I2] heated under reflux in THF, in which a Ru-Ru wing edge is missing. Two bridging and one terminal iodides were found to be placed along the two Ru-Ru wing edges and at a hinge Ru atom, respectively. The redox properties of the selected compounds in this study were investigated by using cyclic voltammetry and controlled potential coulometry. 15N magnetic resonance spectroscopy studies were also performed on these clusters.

Journal Article↗
PubMed2001

A new method of Fourier-transform smoothing with ratio spectra derivative spectrophotometry.

A new method which combines Fourier-transform smoothing with ratio spectra derivative spectrophotometry has been developed for analysis of binary and ternary mixtures. The method proposed has been applied to the simultaneous determination of a binary mixture of 0.974-2.026 x 10(-2) g L(-1) nitrate and nitrite and to a ternary mixture of 1.840-3.888 x 10(-3) g L(-1) histidine, phenylalanine, and tryptophan. The relative standard derivations are between 0.07 and 5.3% for the former system, and between 0.5 and 7.3% for the latter. The results show that the method proposed is more accurate than multiple linear regression.

Journal Article↗
PubMed2001

Development of the fragment constant method for estimating the partition coefficients of nonionic organic mixtures.

The fragment constant model for estimating partition coefficient of nonionic organic mixtures is developed based on group contribution theory. For 60 mixtures randomly composed of eight substituted benzenes, the C(18)-Empore disks/water partition coefficients (K(MD)) are determined. Establishment of a model between these K(MD) and the mole fraction of the fragments (Cl, Br, I, NO(2), CH(3)) acquires the fragments constants for K(MD). The significant linear regression equation, between these fragment constants and that of Hansch, provides an approach for calculating K(MD) of untested nonionic organic mixtures by using the fragment constants of Hansch.

Benzene↗
PubMed2001

Characterization of a SINE species from vicuna and its distribution in animal species including the family Camelidae.

Twenty-six sequences of a short interspersed repetitive element (SINE) with a size of approximately 150 base pairs (bp) were isolated from the genomic DNA of Vicugna vicugna (vicuna). RNA polymerase III split promoter sequence was observed in most of them, and many had direct repeats flanking to SINEs as well as a poly(A)-like structure. The SINE sequences were designated as "vic-1" sequences. Comparison of the vic-1 consensus sequence with sequences registered in the DNA database (DDBJ/ EMBL/GENBANK) revealed that the vic-1 sequence had a 79% homology with mouse ala-tRNA gene. In addition, the tRNA-related region of the consensus sequence was folded into a cloverleaf structure as with mouse ala-tRNA. These findings strongly indicated that vic-1 was a retroposon derived from ala-tRNA gene. The vic-1 sequences were used as a probe for dot-blot hybridization to examine the distribution of their homologous sequences in the genomes of various animal species spanning 14 orders, of which, homologous sequences were found only in the Camelidae family. In order to examine the phylogenetical relationship among vicuna, llama, and camel, vic-1 insertion analysis and homology analysis of vic-1 sequences were performed at each locus. The analyses indicated that vic-1 sequences were generated in a common ancestor of the animal species, and that camels first branched off from the clade Camelidae, followed by vicunas and llamas.

Animals↗
PubMed2001

Down-regulation of telomerase activity in malignant lymphomas by radiation and chemotherapeutic agents.

The effects of radiation and cytotoxic agents on telomerase activity in lymphoma cells were analyzed by a polymerase chain reaction-based telomeric repeat amplification protocol coupled with an enzyme-linked immunosorbent assay, reverse transcriptase-polymerase chain reaction for the expression of the catalytic subunit of telomerase (hTERT), and by Western blot analysis in three lymphoma cell lines (Jurkat, Raji, CEM-6). Telomeric repeat amplification protocol-enzyme-linked immunosorbent assay demonstrated high basal levels of telomerase activity in all cell lines compared to normal and activated peripheral blood lymphocytes. A significant decrease in telomerase activity was observed in all cell lines after exposure to vincristine for 24 hours. The decrease in telomerase activity paralleled the decrease in cell viability in Jurkat and CEM-6 cells but not in Raji cells. Radiation exposure inhibited the telomerase activity of Jurkat and CEM-6 cells whereas Raji cells were unaffected. Cell cycle analysis demonstrated a significant G(2)/M arrest by cisplatin, VP-16, and vincristine. In contrast to the decline in telomerase activity, the level of hTERT RNA and protein increased. Furthermore, the induction of hTERT was preceded by increased expression of the cyclin-dependent kinase inhibitor, p27/Kip1 protein, and p53. These results indicate that telomerase activity is down-regulated by anti-neoplastic agents in lymphoma cells, however expression of hTERT may not be correlated with telomerase activity. We also show that p27/Kip1 may be involved in the G(2)/M growth arrest induced by anti-neoplastic agents.

Antineoplastic Agents↗
PubMed2001

Gastric pacing is a new surgical treatment for gastroparesis.

BACKGROUND: Gastroparesis is a chronic gastric motility disorder affecting mostly young and middle-aged women who present with nausea, abdominal pain, early satiety, vomiting, fullness, and bloating. METHODS: From April 1998 to September 2000, 25 patients underwent gastric pacemaker placement. All had documented delayed gastric emptying by a radionucleotide study. Nineteen patients had diabetic gastroparesis, 3 had developed postsurgical gastroparesis, and 3 had idiopathic gastroparesis. Baseline and postoperative follow-ups were done by a self-administered questionnaire on which the patients rated the severity and frequency of nausea and vomiting. Gastric emptying times were also followed up using a radionucleotide technique. RESULTS: Both the severity and frequency of nausea and vomiting improved significantly at 3 months and was sustained for 12 months. Gastric emptying time was also numerically faster over the 12-month period. Three of the devices have been removed. One patient died of causes unrelated to the pacemaker 10 months postoperatively. CONCLUSIONS: After placement of the gastric pacemaker, patients rated significantly fewer symptoms and had a modest acceleration of gastric emptying.

Adult↗
PubMed2001

Single-clamp technique does not protect against cerebrovascular accident in coronary artery bypass grafting.

OBJECTIVES: By potentially avoiding the embolic consequences of a side-biting aortic clamp, the single-clamp technique may decrease cerebrovascular accidents in coronary artery bypass grafting. However, this theoretical superiority in stroke prevention has not been conclusively demonstrated and use of this technique may lead to adverse myocardial effects due to longer cross-clamp times. In this study, we sought to determine if the single-clamp technique prevents postoperative stroke in clinical practice. METHODS: Of 607 consecutive isolated coronary bypass operations completed over a 3 year period, 301 (50%) were performed by one surgeon using exclusively the single-clamp technique and 306 (50%) were performed by a second surgeon using exclusively the two-clamp technique. Postoperative adverse events were retrospectively compared between these two groups. RESULTS: There were no differences between groups in terms of postoperative stroke (1.7% single-clamp vs. 2.0% two-clamp, P=0.78), hospital mortality (2.7% single-clamp vs. 1.6% two-clamp, P=0.38), or perioperative myocardial infarction (2.6% single-clamp vs. 0.7% two-clamp, P=0.052). The two-clamp technique was not a significant predictor of stroke by logistic regression analysis (P=0.72). CONCLUSIONS: We conclude that there are no statistically significant differences between clamp techniques with regard to stroke prevention or myocardial protection. We find no compelling evidence for surgeons successfully utilizing one technique to change to the other.

Aged↗
PubMed2001

Frequent cyclin D1 gene amplification and protein overexpression in oral epithelial dysplasias.

Amplification of the cyclin D1 gene has been identified in 17-55% of head and neck squamous cell carcinoma. In some tumors, this alteration has been associated with decreased survival and increased recurrence rates. In precancerous lesions of the mouth, the frequency of cyclin D1 gene amplification is not known. In addition, it is unknown whether amplification of the gene translates to overexpressed cyclin D1 protein in these lesions. We examined 59 formalin-fixed, paraffin embedded tissue biopsies of oral epithelial dysplasias (OED) and 25 oral squamous cell carcinoma (SCC) from the floor of the mouth for cyclin D1 gene and protein levels. Genomic DNA was extracted from laser microdissected lesional tissue and a duplex, quantitative PCR assay was used to determine the amplification of the cyclin D1 gene relative to interferon-gamma. Cyclin D1 protein expression was determined using immunohistochemistry and counting positive nuclei by computer image analysis. We found cyclin D1 gene amplification in 41% of mild, 45% of moderate and 24% of severe OEDs. Cyclin D1 was amplified in 36% of SCC. Overexpression of cyclin D1 protein was identified in 29% of mild, 47% of moderate, 29% of severe OED's, and in 32% of SCC. Overexpression of cyclin D1 protein was identified in similar proportions of all grades of dysplasia and SCC. There were statistically significant correlations identified between gene and protein levels in all categories of disease. We concluded that amplification of the cyclin D1 gene is frequent in OED and that duplex, quantitative polymerase chain reaction is a reliable method to detect this change in routinely processed biopsies. The strong correlation between cyclin D1 gene amplification and protein levels suggests that this method may be suitable to assess cyclin D1 gene status in tissues not suitable for protein analysis.

Adult↗
PubMed2001

Prevalence of gastric myoelectrical abnormalities in patients with nonulcer dyspepsia and H. pylori infection: resolution after H. pylori eradication.

The aims of this study were to investigate the effects of H. pylori eradication on gastric myoelectrical activity and dyspeptic symptoms. Sixty-two subjects with H. pylori infection and no active peptic ulcer participated in this study, which involved three sessions. Anti-H. pylori therapy consisting of clarithromycin and omeprazole was given for two weeks. Gastric myoelectrical activity was measured using surface electrogastrography and dyspeptic symptoms were scored at each session. A [14C] urea breath test was performed at baseline and one month after treatment. In comparison with baseline, the percentage of normal slow waves was significantly increased and the mean total symptom score was significantly reduced one and three months after therapy (P < 0.05). Approximately 40% of patients with nonulcer dyspepsia' symptoms and H. pylori infection have abnormal gastric myoelectrical activity, which may be normalized following the eradication of H. pylori infection. The normalization of gastric myoelectrical activity may be one explanation for the significant symptom improvement in this subset of the dyspepsia population after H. pylori eradication.

Adult↗
PubMed2001

Accurate prediction of protein secondary structural content.

An improved multiple linear regression (MLR) method is proposed to predict a protein's secondary structural content based on its primary sequence. The amino acid composition, the autocorrelation function, and the interaction function of side-chain mass derived from the primary sequence are taken into account. The average absolute errors of prediction over 704 unrelated proteins with the jackknife test are 0.088, 0.081, and 0.059 with standard deviations 0.073, 0.066, and 0.055 for alpha-helix, beta-sheet, and coil, respectively. That the sum of predicted secondary structure content should be close to 1.0 was introduced as a criterion to evaluate whether the prediction is acceptable. While only the predictions with the sum of predicted secondary structure content between 0.99 and 1.01 are accepted (about 11% of all proteins), the absolute errors are 0.058 for alpha-helix, 0.054 for beta-sheet, and 0.045 for coil.

Algorithms↗
PubMed2001

Aggregated proteins accelerate but do not increase the aggregation of D-glyceraldehyde-3-phosphate dehydrogenase. Specificity of protein aggregation.

The effect of protein aggregates on the aggregation of D-glyceraldehyde-3-phosphate dehydrogenase (GAPDH) during unfolding and refolding has been studied. The aggregation of GAPDH follows a sigmoid course. The presence of protein aggregates increases the aggregation rate during unfolding and refolding of GAPDH but does not change the extent of aggregation and the final renaturation yield. It is suggested that protein aggregates function as seeds for aggregation via hydrophobic interaction with only GAPDH folding intermediates destined to aggregate and do not affect the distribution between pathways leading to correct folding and aggregation. Moreover, two different proteins do not interfere with each other during their simultaneous refolding together in a buffer. These findings provide insight into a mechanism by which cells prevent protein folding against the interference from aggregation of other proteins.

Animals↗
PubMed2001

Dispersion of atrial repolarization in patients with paroxysmal atrial fibrillation.

UNLABELLED: To study the role of the dispersion of atrial repolarization (DAR) in the genesis of atrial fibrillation (AF), monophasic action potentials (MAP) were recorded simultaneously from a catheter at the high lateral right atrium (HLRA) and a catheter moving around the high, middle and low lateral right atrium (RA) the high, anterior and posterior septal RA and the RA appendage in 15 patients with paroxysmal AF and 15 patients with atrioventricular nodal re-entry tachycardia (AVNRT) or concealed Wolff-Parkinson-White syndrome (WPW) without history of AF. After recordings during sinus rhythm (SR), MAPs were recorded during programmed stimulation (PS) via the HLRA catheter at a drive cycle length (CL) of 500 ms. Thus, MAPs were recorded simultaneously from 2 sites at a time and sequentially from 4 to 12 sites during SR, drive pacing and PS. Taking the MAP at the HLRA as reference, the dispersion of repolarization time (dispersion of RT) and its two components, the dispersions of activation time (dispersion of AT) and MAP duration (dispersion of MAP duration) among the 4 to 12 sites were calculated and taken as parameters of DAR. RESULTS: During SR and PS, the maximal dispersion of RT was significantly greater in AF than in control patients, 113+/-49 ms vs 50+/-28 ms (P<0.001) and 114+/-56 vs 70+/-43 ms (P<0.05) respectively. The increased dispersion of RT in the AF group was caused by increases in both dispersion of MAP duration and dispersion of AT. CONCLUSION: During SR and PS, DAR increased in patients with paroxysmal AF due to increases in dispersion of MAP duration and dispersion of AT, which suggests the involvement of both repolarization and conduction disturbances in the development of paroxysmal AF.

Action Potentials↗
PubMed2001

Characterization of the biologic activities of a recombinant human zona pellucida protein 3 expressed in human ovarian teratocarcinoma (PA-1) cells.

OBJECTIVE: This study was undertaken to clone and express a recombinant human zona pellucida protein 3 and to characterize its biologic activities as a sperm ligand and an inducer of the acrosome reaction. STUDY DESIGN: Human ovarian teratocarcinoma (PA-1) cells were transfected with an expression vector containing human zona pellucida protein 3 complementary deoxyribonucleic acid with a sequence coding for a 6-histidine tail introduced into its 3' end. Purification of the secreted glycoprotein was performed by sequential affinity (lectin and nickel--nitrilotriacetic acid) and ion-exchange chromatography. RESULTS: Western blot analysis confirmed a molecular weight of approximately 65 kd for the purified product. A cell-free translation system revealed a correctly sized protein backbone of 47 kd. The recombinant human zona pellucida protein 3 demonstrated specific, potent, and dose-dependent competitive inhibition of sperm-zona pellucida binding in vitro under hemizona assay conditions. Recombinant human zona pellucida protein 3 also stimulated the acrosome reaction of live sperm. This effect was fast, dose dependent, and capacitation time dependent. Furthermore, advance incubation with pertussis toxin, an inactivator of heterotrimeric G proteins, blocked recombinant human zona pellucida protein 3--induced acrosomal exocytosis. CONCLUSION: The recombinant human zona pellucida protein 3 expressed in PA-1 cells manifested the full spectrum of expected biologic activities. It therefore represents a valuable tool for examination of human fertilization and the design of new strategies in diagnosis of male factor infertility and in contraception.

Acrosome Reaction↗
PubMed2001

Biosorption and desorption of cadmium(II) by biomass of Laminaria japonica.

Biosorption and desorption properties of cadmium(II) from aqueous solutions by the biomass of marine alga Laminaria japonica were investigated. Results indicated that the uptake capacities were solution pH dependent and a maximum uptake capacity of about 1.3 mmol g-1 (dry weight) was observed at pH 6. The adsorbed cadmium cannot be desorbed by distilled water, but it can be effectively recovered by using acidic or EDTA solutions. The equilibrium isotherms can be described well with the Langmuir adsorption equation. Biomass, pre-treated with calcium solution exhibited a higher (about 30%) uptake capacity and can be easily settled from aqueous solutions. Batch kinetics experiments indicated that more than 90% of the adsorption occurred within 20 minutes of agitation and equilibrium was reached within one hour. Fixed-bed experiments showed similar uptake capacities to those of batch results and sharp breakthrough curves were obtained. This study indicated that the biomass of L. japonica can be used as an efficient biosorbent for the removal and recovery of cadmium(II) from waste water streams.

Adsorption↗