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Biomedical subjects

B Yu

Publications and source records attributed to B Yu.

At least 91 records · Page 5Linked to original sources
PubMed1999

The influence of the p53 gene on the in vitro chemosensitivity of colorectal cancer cells.

PURPOSE: The p53 gene is considered one of the most important in the control of apoptosis, and its mutations have a close relationship with chemosensitivity. The aim of this work was to investigate the role of p53 in the apoptosis of colorectal cancer cells in vitro, induced by 5-fluorouracil (5-FU) and hydroxy-camptothecin (HCPT). METHODS: A total of 39 colorectal cancer samples from patients were treated in vitro with 5-FU (10 microg/ml), 5-FU (10 microg/ml) + leucovorin (5 microg/ml), HCPT (0.1 microg/ml) and HCPT (0.1 microg/ml) + Salvia mitorrhiza (6 microl), using an in situ terminal deoxynucleotidyltransferase assay to detect chemosensitivity. p53 gene mutations from tumor DNA were detected, after amplification by the polymerase chain reaction of exons 5-8, by non-radioactive single-strand conformation polymorphism. RESULTS: p53 gene mutations were observed in 43.6% (17/39) of colorectal carcinomas, when the terminal deoxynucleotidyltransferase assay was used to detect the tumor apoptotic rate. Cells with mutated p53 had lower chemosensitivity than those without (p < 0.01). CONCLUSION: Routine assessment of p53 status may be helpful in selecting patients with the wildtype p53 gene, who have a predictably better response to chemotherapy.

Adult↗
PubMed1999

GABA(B) auto- versus hetero-receptor sensitivity: implications for novel pharmacotherapy.

After uncoupling G-protein dependent post-synaptic GABA(B) receptors--without altering GABA(B) nerve terminal receptors--we demonstrate that the GABA(B) agonist, CGP44533, exhibits less efficacy and potency at GABA(B) auto- versus hetero-receptors. CGP44533 (1 and 10 microM) depressed monosynaptic GABA(A)-mediated transmission by 2 and 35%, but depressed glutamate mediated transmission by 41 and 78%, respectively. These data suggest a differential pharmacological sensitivity for CGP44533 at glutamate versus GABA releasing neurons.

Animals↗
PubMed1999

Horizontal-to-vertical velocity conversion in the triple jump.

The aim of this study was to determine the effects of selected factors on horizontal-to-vertical velocity conversion in the triple jump. An understanding of this conversion is important not only for studies on the techniques of the triple jump, but also for other jumping events. Ten elite jumpers were studied. Three-dimensional kinematic data were collected for at least four complete trials in the same competition for each athlete. The loss in horizontal velocity and the gain in vertical velocity during each support phase were calculated for each trial. The loss in horizontal velocity was found to be a linear function of the gain in vertical velocity. The slope of this linear function, A1, is referred to as the horizontal-to-vertical velocity conversion coefficient. The loss in horizontal velocity increased as the gain in vertical velocity increased. The sensitivity of the loss in horizontal velocity to the gain in vertical velocity increased as the magnitude of A1 increased. Further studies are required on the optimum techniques of the triple jump.

Biomechanical Phenomena↗
PubMed1999

Drug resistance mutations can effect dimer stability of HIV-1 protease at neutral pH.

The monomer-dimer equilibrium for the human immunodeficiency virus type 1 (HIV-1) protease has been investigated under physiological conditions. Dimer dissociation at pH 7.0 was correlated with a loss in beta-sheet structure and a lower degree of ANS binding. An autolysis-resistant mutant, Q7K/L33I/L63I, was used to facilitate sedimentation equilibrium studies at neutral pH where the wild-type enzyme is typically unstable in the absence of bound inhibitor. The dimer dissociation constant (KD) of the triple mutant was 5.8 microM at pH 7.0 and was below the limit of measurement (approximately 100 nM) at pH 4.5. Similar studies using the catalytically inactive D25N mutant yielded a KD value of 1.0 microM at pH 7.0. These values differ significantly from a previously reported value of 23 nM obtained indirectly from inhibitor binding measurements (Darke et al., 1994). We show that the discrepancy may result from the thermodynamic linkage between the monomer-dimer and inhibitor binding equilibria. Under conditions where a significant degree of monomer is present, both substrates and competitive inhibitors will shift the equilibrium toward the dimer, resulting in apparent increases in dimer stability and decreases in ligand binding affinity. Sedimentation equilibrium studies were also carried out on several drug-resistant HIV-1 protease mutants: V82F, V82F/I84V, V82T/I84V, and L90M. All four mutants exhibited reduced dimer stability relative to the autolysis-resistant mutant at pH 7.0. Our results indicate that reductions in drug affinity may be due to the combined effects of mutations on both dimer stability and inhibitor binding.

Circular Dichroism↗
PubMed1999

Transport of fluid by lens epithelium.

We report for the first time that cultured lens epithelial cell layers and rabbit lenses in vitro transport fluid. Layers of the alphaTN4 mouse cell line and bovine cell cultures were grown to confluence on permeable membrane inserts. Fluid movement across cultured layers and excised rabbit lenses was determined by volume clamp (37 degrees C). Cultured layers transported fluid from their basal to their apical sides against a pressure head of 3 cmH2O. Rates were (in microliter. h-1. cm-2) 3.3 +/- 0.3 for alphaTN4 cells (n = 27) and 4.7 +/- 1.0 for bovine layers (n = 6). Quinidine, a blocker of K+ channels, and p-chloromercuribenzenesulfonate and HgCl2, inhibitors of aquaporins, inhibited fluid transport. Rabbit lenses transported fluid from their anterior to their posterior sides against a 2.5-cmH2O pressure head at 10.3 +/- 0.62 microliter. h-1. lens-1 (n = 5) and along the same pressure head at 12.5 +/- 1.1 microliter. h-1. lens-1 (n = 6). We calculate that this flow could wash the lens extracellular space by convection about once every 2 h and therefore might contribute to lens homeostasis and transparency.

4-Chloromercuribenzenesulfonate↗
PubMed1999

Mobilization of GLUT-4 from intracellular vesicles by insulin and K(+) depolarization in cultured H9c2 myotubes.

The insulin-responsive glucose transporter, GLUT-4, moves from an intracellular compartment to the cell surface in response to insulin and/or muscle contraction. Treatment of H9c2 myotubes with insulin significantly increased uptake of 2-deoxyglucose. Depolarization of the myotubes by increasing extracellular [K(+)], which mimics the initial phases of excitation-contraction coupling, also increased 2-deoxyglucose uptake. The K(+)- but not insulin-evoked increase was blocked by dantrolene, an inhibitor of Ca(2+) release from the sarcoplasmic reticulum. In contrast, wortmannin, an inhibitor of phosphatidylinositol 3-kinase, blocked insulin- but not K(+)-stimulated 2-deoxyglucose uptake. Increased glucose uptake in response to insulin or K(+) depolarization was associated with increased GLUT-4 in plasma membranes and depletion of a population of small intracellular GLUT-4-containing vesicles. Similarly, in H9c2 cells transfected with c-myc-tagged GLUT-4, translocation of c-myc GLUT-4 to the cell surface was increased after stimulation with insulin or K(+) depolarization. Taken together, these data demonstrate that insulin and K(+) depolarization increase glucose uptake by recruiting GLUT-4 from intracellular vesicles to the plasma membrane of H9c2 myotubes via distinct signaling mechanisms.

Androstadienes↗
PubMed1999

Different subtypes of GABAB receptors are present at pre- and postsynaptic sites within the rat dorsolateral septal nucleus.

GABAB receptor activation modulates neuronal activity mediated by multiple CNS transmitters and can occur at pre- and postsynaptic sites. In low concentrations, baclofen acts presynaptically to diminish transmitter release via both hetero- and autoreceptors, whereas at increasing concentrations, the same compound alters postsynaptic membrane excitability by inducing a membrane hyperpolarization. We have utilized electrophysiological techniques in vitro to focus on the possibility that pharmacologically different subtypes of GABAB receptors are present on presynaptic sites of glutamatergic terminals when compared with GABAB receptors on postsynaptic sites within the dorsolateral septal nucleus (DLSN). The glutamatergic terminal within the DLSN originates from a pyramidal cell body located within the hippocampus and most likely terminates on a GABAergic neuron from which recordings were made. Whole cell patch voltage-clamp methods were employed to record pharmacologically isolated excitatory postsynaptic currents (EPSCs) from DLSN neurons as an index of glutamatergic transmission. Using a modified internal pipette solution containing QX-314 and in which CsGluconate and GDPbetaS replaced Kgluconate and GTP, respectively, we recorded isolated monosynaptic EPSCs. The GABAA receptor antagonists bicuculline and picrotoxin were included in the external standard superfusion solution. Application of the GABAB receptor agonists, (+/-)-baclofen, CGP44533, and CGP35024 (10 nM to 10 microM) depressed glutamate-mediated EPSCs in a concentration-dependent manner. With the use of this combination of solutions, CGP44533 did not produce postsynaptic membrane property changes. Under these conditions, both (+/-)-baclofen and CGP35024 still induced increases of postsynaptic membrane conductance associated with an outward current. The GABAB receptor antagonist CGP55845A (1 microM) blocked the presynaptic CGP44533-mediated depressant effects of EPSCs, whereas CGP35348 (100 microM) or barium (2 mM) was ineffective. Furthermore, both CGP35348 (100 microM) and CGP55845A (1 microM) were effective in blocking the postsynaptic conductance changes associated with baclofen and CGP35024, whereas barium was ineffective. Our results demonstrate a distinct pharmacology for GABAB agonists acting at putative subtypes of GABAB receptors located on presynaptic sites of a glutamatergic terminal versus GABAB receptors on postsynaptic sites of a DLSN neuron. Furthermore, our results also suggest a different pharmacology and/or coupling of a GABAB receptor to different effectors at postsynaptic sites within the DLSN. Thus there may be three or more pharmacologically distinct GABAB receptors or receptor complexes associated with DLSN neurons: at least one pre- and two postsynaptic. If this distinct pharmacology and GABAB receptor distribution also extends to other CNS structures, such differences could provide development of selective drugs to act at these multiple sites.

Animals↗
PubMed1999

Morphological and biochemical analysis of anti-nuclear matrix protein antibodies in human sera.

Autoimmune sera have been used in the diagnosis of autoimmune diseases as well as the analysis of nuclear substructures. In an attempt to study the biological characteristics of the nuclear matrix, we screened human sera using immunofluorescent staining and immunoblot. We detected antibodies against nuclear matrix (NM), a remnant nonchromatin protein compartment after the treatment of detergent, salt and nuclease, in 212 out of 284 tested sera (74.6%) by immunoblot. Peptides with molecular weights of 70 kDa, 50 kDa and 25 kDa were detected in the order of frequency. Clinical informations of 198 out of 212 cases were available and went as follows: 38 cases were autoimmune diseases, such as systemic lupus erythematosus and rheumatoid arthritis; 132 non-autoimmune and non-neoplastic diseases; 16 neoplastic diseases and 12 cases unclassified. The immunofluorescent staining intensity by anti-nuclear matrix protein (NMP) antibodies decreased variably, but fibrillogranular, speckled and nucleolar immunolocalization patterns were retained after in situ fractionation. Ku70 and La protein were detected by anti-NMP antibodies. Immunolocalization by anti-NMP antibodies indicates that the NMPs constitute a variety of characteristic nuclear substructures and may serve as autoantigens in diverse human diseases. In addition, the presence of Ku70 and La protein as NMPs suggests that the NM can be functionally active in association with DNA or RNA.

Antigens, Nuclear↗
PubMed1999

[Study of the relation between mutant gene in bile and hepatic metastasis of large intestinal carcinoma].

OBJECTIVE: To study the value of point mutant genes in the diagnosis of hepatic metastasis of large intestinal carcinoma. METHODS: Techniques of PCR-SSCP and DNA sequencing were used to detect point mutations of p53 and k-ras genes in primary focus, hepatic metastatic focus, and bile. RESULTS: 50 cases of large intestinal cancer were detected. 38 cases (76.0%) had p53 and k-ras gene mutations. p53 gene mutations were detected in 28 cases (56.0%) and k-ras gene mutations in 16 cases (32.0%). The same point mutant genes in bile with primary focus were detected in 10 out of 12 patients with hepatic metastasis (83.3%). CONCLUSIONS: The tumor cells of hepatic metastasis show the same clonal origin with primary focal cells that had same point mutant genes. Detection of the point mutant genes in bile is of value in the diagnosis of hepatic metastasis of large intestinal carcinoma.

Bile↗
PubMed1999

[The effect of sandostatin and 5-fluorouracil on apoptosis in breast cancer].

OBJECTIVE: To investigate the effect of 5-FU plus sandostatin on apoptosis in breast cancer. METHODS: Breast cancer samples from 16 patients were treated with 5-FU (10 microg/ml) and sandostatin (0.1 microg/ml) in vitro using the in situ terminal deoxynucleotidyl transferase assay (TDT) to detect apoptosis. The patients were female (mean age 54.4 years). In the 16 patients, 10 had positive estrogen receptor (ER) and positive progestogen receptor (PR), and the rest had negative ER and PR. RESULTS: 18 hours after addition of 5-FU, sandostatin and both, the apoptotic rate of tumor cells was (21.8 +/- 6.6)%, (14.3 +/- 8.8)%, and (26.7 +/- 6.9)% respectively. When samples were divided into 2 groups according to the sensitivity of ER and PR, the apoptotic rate of 5-FU plus sandostatin was (32.2 +/- 7.9)%, in positive ER and PR group, but (20.5 +/- 5.5)% in negative ER and PR group (P < 0.05). CONCLUSIONS: 5-FU plus sandostatin is more sensitive in the positive ER and PR group than in the negative ER and PR group. 5-FU plus sandostatin would be helpful in the biotherapy of breast cancer patients with positive ER and PR.

Adult↗
PubMed1999

[The correlation of free radicals induced by cadmium toxicess with erythrocyte injury and band3 expression].

OBJECTIVE: To study the correlation of hydrogen peroxide induced by cadmium ion with erythrocyte injury and band3 expression. METHODS: It was application immunoscanning electronmicroscopy and cytochemistry and EDX methods. RESULT: Cadmium ion not only induced a lot of hydrogen peroxide but also caused serious distortion of erythrocyte. CONCLUSION: Cadmium ion-induced free radicals lead to oxygen free radical damage of membrane and crytoskelecton of erythrocyte, affecting the stability and deformability and band3 expression in erythrocyte.

Animals↗
PubMed1999

[Application of cerium cytochemical method in observation of renal injury caused by oxygen free radical with cadmium induction].

OBJECTIVE: To study acute renal injury caused by oxygen free radical with cadmium induction. METHODS: Electron microscopy cytochemical and energy dispersive X-ray (EDX) analysis techniques were used. RESULTS: Cadmium ions could enter the epithelial cells of renal proximal convoluted tubules. Excessive production of oxygen free radical was found in the kidney tissues, which located mainly in the endothelial cells of blood vessels, mitochondria of epithelial cells of renal proximal convoluted tubules, microvilli and basement membrane. Swelling of epithelial cells and mitochondria and drop of epithelial cells could occur in renal proximal convoluted tubules. CONCLUSION: It suggests that cadmium ions can induce the formation of large amount of oxygen free radical and cause renal injury.

Acute Kidney Injury↗
PubMed1999

[Qualitative and quantitative studies on Chinese drug maidong].

OBJECTIVE: To explore a better approach to controlling the quality of Maidong. METHOD: The differences between Ophiopogon japonicus and the plants belonging to Liriope genus were identified by TLC. The total saponins in plants collected from different areas were determined by spectrophotometry, using HClO4 as the staining agent. RESULTS: The quantity of Maidong markedly varies with producing areas. CONCLUSION: This method is convenient and effective, and the MeOH extract of samples can be determined directly after reaction with HClO4 without preliminary treatment. The RSD was 0.75% (n = 5).

Chromatography, Thin Layer↗
PubMed1999

[A comparative study of three-dimensional movements of lumbar spine in the old and the young people].

This article is aimed at the differences in lumbar vertebral three-dimensional movement and in stability between the old and the young people, and at the reasons which lead to the differences. Fifteen fresh adult male cadavers were divided into two groups: the young group, 20-30 years old, comprising 7 cases; the old group, 60-70 years old, 8 caes. Lumbar spine(L1-S1) was cut down. Three-dimensional movements under a loading system were measured by a compute system. The result showed that the range of the motion of the old group was lower than that of the young group. It suggests that the lumbar spine of the old people is more stable than that of the young people. This may be associated with the degeneration of the lumbar vertebra, which arouses biocompensatory changes, so the lumbar spine becomes re-stable.

Adult↗
PubMed1999

[Removal of a broken needle in the left pterygoid fossa:report of one case]

OBJECTIVE:To research the application of orthodontic techniques of edgewise brackets to enhance the curative effect of stabilizing the loose teeth.METHODS: Between 1993-1998,we applied orthodontic techniques of Edgewise brackets to treat 35 cases of patients which include 58 loosen teeth caused by trauma factors,most adopting edgewise brackets plus round wire.RESULTS: We have obtained excellent curative effect in 45 teeth,good curative effect in 9 teeth,and 4 teeth failed.CONCLUSION: Orthodontic technique of Edgewidw brackets is a reliable method to stabilize the loose teeth.Compared with conventional arch bar splint fixation,the Edgewise technique has its unique advantage.

Journal Article↗
PubMed1998

Unsymmetric nonpeptidic HIV protease inhibitors containing anthranilamide as a P2' ligand.

A series of novel unsymmetrical anthranilamide-containing HIV protease inhibitors was designed. The structure-activity studies revealed a series of potent P2-P3' inhibitors that incorporate an anthranilamide group at the P2' position. A reduction in molecular weight and lipophilicity is achieved by a judicious choice of P2 ligands (i.e., aromatic, heteroaromatic, carbamate, and peptidic). A systematic investigation led to the 5-thiazolyl carbamate analog 8 m, which exhibited a favorable Cmax/EC50 ratio (> 30), plasma half-life (> 8 h), and potent in vitro antiviral activity (EC50 = 0.2 microM).

Amides↗