Biomedical subjects

B Liu

Publications and source records attributed to B Liu.

At least 379 records · Page 21Linked to original sources

PubMed1998

Overexpression of ErbB2 blocks Taxol-induced apoptosis by upregulation of p21Cip1, which inhibits p34Cdc2 kinase.

Overexpression of the receptor tyrosine kinase p185ErbB2 confers Taxol resistance in breast cancers. Here, we investigated the underlying mechanisms and found that overexpression of p185ErbB2 inhibits Taxol-induced apoptosis. Taxol activates p34Cdc2 kinase in MDA-MB-435 breast cancer cells, leading to cell cycle arrest at the G2/M phase and, subsequently, apoptosis. A chemical inhibitor of p34Cdc2 and a dominant-negative mutant of p34Cdc2 blocked Taxol-induced apoptosis in these cells. Overexpression of p185ErbB2 in MDA-MB-435 cells by transfection transcriptionally upregulates p21Cip1, which associates with p34Cdc2, inhibits Taxol-mediated p34Cdc2 activation, delays cell entrance to G2/M phase, and thereby inhibits Taxol-induced apoptosis. In p21Cip1 antisense-transfected MDA-MB-435 cells or in p21-/- MEF cells, p185ErbB2 was unable to inhibit Taxol-induced apoptosis. Therefore, p21Cip1 participates in the regulation of a G2/M checkpoint that contributes to resistance to Taxol-induced apoptosis in p185ErbB2-overexpressing breast cancer cells.

Animals↗

PubMed1998

Transcriptional activation and redox regulation of the tumor necrosis factor-alpha promoter in human T cells: role of the CRE/kappa3 promoter region.

Aberrancies in T cell expression of tumor necrosis factor-alpha (TNF-alpha) are frequently observed in inflammatory states characterized by oxidative stress due to excessive generation of hydrogen peroxide (H2O2) and other reactive oxygen species (ROS). In this study, we examined the possible effects of oxidative stress on the expression of TNF-alpha protein and transcriptional activation of the TNF-alpha promoter in human T cells. Results show that exposure of resting T cells to micromolar concentrations of H2O2 did not induce TNF-alpha protein production or transcriptional activation of the TNF-alpha promoter. However, oxidative signals resulted in a dose-dependent suppression of TNF-alpha protein production and transcriptional activation in T cells stimulated with the lectin phytohemagglutinin (PHA) and phorbol myristate acetate (PMA). Optimal suppression of TNF-alpha promoter activity was observed when cells were exposed to oxidative stress during early T cell activation, and other experiments demonstrated that the transactivation responses of the TNF-alpha promoter were quite susceptible to inhibition by both oxidative and reducing changes in cellular redox. Furthermore, reporter gene assays with 5' deletion mutants of the TNF-alpha promoter showed that the CRE/kappa3 composite site played a major role in activation of the TNF-alpha promoter by dual stimulatory signals and suppression of the TNF-alpha promoter by oxidative signals. Thus, T cell expression of TNF-alpha at the protein and transcriptional levels is highly regulated by changes in cellular redox, and the CRE/kappa3 composite site is important for both activation and redox regulation of the TNF-alpha promoter.

Humans↗

PubMed1998

Homologues for prolactin-like proteins A and B are present in the mouse.

The prolactin (PRL) family consists of a collection of proteins expressed in the uterus, placenta, and anterior pituitary. These cytokines/hormones are hypothesized to control maternal-fetal adaptations to pregnancy. Establishment of mouse models for members of the PRL family expands the experimental repertoire available for investigations on their biological activities. In this report, we establish the presence of mouse homologues for two rat members, PRL-like protein-A (PLP-A) and PLP-B. We present data on their cDNAs and describe aspects of their expression in uteroplacental tissues. A mouse genomic DNA fragment was found to hybridize with a rat PLP-A cDNA. Perusal of the National Center for Biotechnology Information dbEST database resulted in the identification of several putative mouse PLP-A cDNAs and a single putative mouse PLP-B cDNA. The cDNAs were obtained from the IMAGE consortium and Research Genetics and sequenced, and their corresponding mRNAs and proteins were characterized. Overall, mouse PLP-A and PLP-B showed considerable similarities with rat PLP-A and PLP-B in both structure and expression. PLP-A was expressed in both trophoblast giant cells and spongiotrophoblast cells, whereas PLP-B was expressed in decidual and spongiotrophoblast cells. However, some notable exceptions were evident. Mouse PLP-A contained a single putative N-linked glycosylation site and consisted of a single 29-kDa protein species, whereas rat PLP-A contained two putative N-linked glycosylation sites and consisted of two protein species, of 29 and 33 kDa. Subtle differences in the expression patterns in the mouse and rat are also apparent. In summary, we have established the presence of PLP-A and PLP-B in the mouse. The findings expand our knowledge of these two cytokines/hormones and provide additional strategies for studying their function.

Amino Acid Sequence↗

PubMed1998

Automatic adjustment of pacemaker stimulation output correlated with continuously monitored capture thresholds: a multicenter study. European Microny Study Group.

Pacing threshold is affected by many factors. A pacing system able to confirm capture at each beat and automatically adjust its output close to the actual pacing threshold is highly desirable. This study evaluates the safety and efficacy of the Autocapture function of the Pacesetter Microny SR+. One hundred thirteen patients were recruited from 16 centers in 7 European countries and followed up for 1 year. All pacemakers were implanted with Pacesetter's low polarization, bipolar leads. The key feature of Autocapture is the immediate delivery of a 4.5 V safety backup pulse 62.5 ms after any ineffective ongoing low output pulse. Holter recordings confirmed total reliability of this feature without any exit block. The measured evoked response (ER) signal was stable over time. Acute and chronic pacing thresholds measured by VARIO and Autocapture tests correlated (r > 0.79) over the period of the study. The incidence of backup pulses was 1.1% during pacing. With Autocapture programmed ON, the overall total current consumption was 4.1 microA for VVI and 5.0 microA for VVIR pacing. This study proved that the Autocapture safely and reliably regulates the pacemaker's output according to the prevailing threshold thus providing maximum patient safety and prolonging service life.

Aged↗

PubMed1998

Classification of compressed breast shapes for the design of equalization filters in x-ray mammography.

We are developing an external filter method for equalizing the x-ray exposure in mammography. Each filter is specially designed to match the shape of the compressed breast border and to preferentially attenuate the x-ray beam in the peripheral region of the breast. To be practical, this method should require the use of only a limited number of custom built filters. It is hypothesized that this would be possible if compressed breasts can be classified into a finite number of shapes. A study was performed to determine the number of shapes. Based on the parabolic appearance of the outer borders of compressed breasts in mammograms, the borders were fit with the polynomial equations y = ax2 + bx3 and y = ax2 + bx3 + cx4. The goodness-of-fit of these equations was compared. The a,b and a,b,c coefficients were employed in a K-Means clustering procedure to classify 470 CC-view and 484 MLO-view borders into 2-10 clusters. The mean coefficients of the borders within a given cluster defined the "filter" shape, and the individual borders were translated and rotated to best match that filter shape. The average rms differences between the individual borders and the "filter" were computed as were the standard deviations of those differences. The optimally shifted and rotated borders were refit with the above polynomial equations, and plotted for visual evaluation of clustering success. Both polynomial fits were adequate with rms errors of about 2 mm for the 2-coefficient equation, and about 1 mm for the 3-coefficient equation. Although the fits to the original borders were superior for the 3-coefficient equation, the matches to the "filter" borders determined by clustering were not significantly improved. A variety of modified clustering methods were developed and utilized, but none produced major improvements in clustering. Results indicate that 3 or 4 filter shapes may be adequate for each mammographic projection (CC- and MLO-view). To account for the wide variations in exposures observed at the peripheral regions of breasts classified to be of a particular shape, it may be necessary to employ different filters for thin, medium and thick breasts. Even with this added requirement, it should be possible to use a small number of filters as desired.

Biophysical Phenomena↗

PubMed1998

Rapid genomic changes in newly synthesized amphiploids of Triticum and Aegilops. II. Changes in low-copy coding DNA sequences.

We recently reported that formation of allopolyploid wheat was accompanied by rapid nonrandom changes in low-copy noncoding DNA sequences. In this report we show that following allopolyploidization, changes also occurred in coding sequences. Genomic DNA of nine different newly synthesized amphiploids of different ploidy levels and their parental lines was digested with five restriction enzymes and probed with 43 coding sequences. The sequences, 19 genomic and 24 cDNA sequences, are group (homoelogous) specific and represent the proximal and distal regions of the short and long arms of the seven homoeologous groups of the Triticeae. We revealed three types of changes: disappearance of a parental hybridization fragment(s), appearance of a novel fragment(s), and simultaneous disappearance of a parental fragment(s) and appearance of a novel fragment(s). No elimination of sequences took place, since in every sequence studied the parental hybridization fragments were present in at least one of the enzyme digests. Variations in pattern among individual plants of the same amphiploid, as well as a between several synthetic and natural amphiploids, indicated that at least some of the genomic changes occurred at random. Intergenomic recombination was not the cause of the observed changes. Evidence was obtained, however, that changes were also brought about by DNA methylation. Methylation may cause inactivation of genes or modify their expression levels in some of the newly synthesized amphiploid plants, leading to genetic diploidization and gene-dosage compensation and thus increasing variation among individuals.

Avena↗

PubMed1998

Microvascular permeability and number of tight junctions are modulated by cAMP.

We tested the hypothesis that increased endothelial cell adenosine 3',5'-cyclic monophosphate (cAMP) decreases microvascular permeability in vivo. The effects of cAMP-specific phosphodiesterase type IV inhibition and adenylate cyclase activation on microvascular hydraulic conductivity (Lp) were investigated in intact individual capillaries and postcapillary venules in mesentery of pithed frogs (Rana pipiens). Treatment with rolipram (10 microM) and forskolin (5 microM) for 25 min decreased Lp to 37% of control. Rolipram alone also significantly decreased Lp. Isoproterenol (10 microM) decreased Lp to 27% of control within 20 min. A subgroup of eight vessels treated with rolipram and forskolin, in which mean Lp fell to 25% of control, was examined with transmission electron microscopy. The mean number of tight junctions in the treated vessels was 2.2 per cleft (303 clefts), significantly higher than in a matched control group (192 clefts), which was 1.7 per cleft. The results indicate that microvascular Lp can be modulated by intracellular cAMP and that one of the structural end points of stimulated cAMP levels is an increase in the mean number of tight-junction strands between endothelial cells.

Adrenergic beta-Agonists↗

PubMed1998

A new member of the mouse prolactin (PRL)-like protein-C subfamily, PRL-like protein-C alpha: structure and expression.

In this study, we establish the presence of a unique member of the PRL-like protein-C (PLP-C) subfamily in the mouse, PLP-C alpha, characterize its complementary DNA and gene, and map its chromosomal location and pattern of expression during pregnancy. Mouse PLP-C alpha encodes for a 239 amino acid protein and possesses from 69-71% identity with rat PLP-C, PLP-Cv, PLP-D, and PLP-H. Another feature characteristic of PLP-C subfamily members that is also present in mouse PLP-C alpha is a 6-exon/5-intron gene structure including an aromatic domain encoded by exon 3. Southern analysis with mouse and rat PLP-C subfamily probes suggested the existence of a single mouse PLP-C alpha gene. Mouse PLP-C alpha maps to chromosome 13 along with other members of the mouse PRL family. Expression of mouse PLP-C alpha increases dramatically as gestation advances and is restricted to spongiotrophoblast and trophoblast giant cells of the junctional zone. In summary, we have established the presence of a new PLP-C subfamily member in the mouse and demonstrated its similarity in structure and expression to rat PLP-C subfamily members. This level of conservation between species expands the biological significance of the PLP-C subfamily and provides additional opportunities for genetically evaluating its function.

Amino Acid Sequence↗

PubMed1998

What is anatomy for? Considerations on the body as a whole and whole anatomy.

In anatomy today, construction of the body is devoid of the water element, and the framework of the discipline is sectionalized (segmented, specialized, and divided), so that the body is not described in an integrated, harmonious manner. In this paper, the present authors selected the body, body water, and skin as objects of contemplation and deliberated on the history, significance, and resuscitation of anatomy. (1) Living things are dependent on water, and water is a vital component of the body. Therefore, greater consideration should be given to the presence of body water in morphological description of the body. (2) Since anatomy is sectionalized, understanding of the body is dwarfed and distorted. Whole anatomy, which described the body as a whole is the ideal style. (3) The body as a whole should always be placed in the center of anatomy. This should be the ultimate form of teaching anatomy.

Anatomy↗

PubMed1998

Electron microscopic study of intercalated duct cells in the chicken pancreatic islet and effects of tolbutamide administration.

Intercalated duct cells are present in the alpha and beta islets of chicken. The intercalated duct cells adhere to each other via intercellular junctional complexes at the apical side, projecting many microvilli and a few cilia into the lumen. They also extend slender cytoplasmic processes between the islet endocrine cells. These intercalated cells appear to have a stellate form, and to wrap their cytoplasm around endocrine cells. Administration of tolbutamide led to increased electron density in the cytoplasm of intercalated duct cells. Lysosomes are present in these cells in various numbers and sizes and tend to increase with time after administration of tolbutamide. These observations suggested that the intercalated ducts not only pass through the islet, but also play a role in supplying islet cells.

Animals↗

PubMed1998

Effects of metallothionein on action potentials of anoxic and reoxygenated papillary muscles of guinea pigs.

AIM: To study anti-arrhythmic effects of metallothionein (MT). METHODS: Standard microelectrode technique was used to study the effects of MT on action potentials (AP) in anoxic and reoxygenated papillary muscles of guinea pigs. RESULTS: MT (0.02 mmol.L-1) had no effects on AP of the normal papillary muscles; when the muscles were exposed to ischemic solution without MT, there was a marked shortening of action potential duration (APD) at 20%, 50%, and 90% of repolarization (APD20, APD50, APD90) from 82 +/- 7 to 37 +/- 7, 131 +/- 35 to 63 +/- 11, and 167 +/- 12 to 100 +/- 19 ms, respectively, (P < 0.01); and an obvious reduction of resting potential (RP), action potential amplitude (APA), and the maximal upstroke velocity of phase 0 (Vmax) from -92 +/- 9 to -63 +/- 12 mV, 135 +/- 13 to 80 +/- 8 mV, and 286 +/- 55 to 164 +/- 42 V.s-1, respectively (P < 0.01). However, in the presence of MT, the AP parameters (RP, APA, and Vmax) changed from -63 +/- 2 to -82 +/- 1 mV, 80 +/- 8 to 104 +/- 25 mV, and 164 +/- 42 to 237 +/- 43 V.s-1, respectively, (P < 0.01), except that APD20, APD50, and APD90 shortened further from 37 +/- 7 to 12 +/- 3, 63 +/- 11 to 28 +/- 7, and 100 +/- 19 to 82 +/- 11 mV, respectively (P < 0.01). MT decreased the incidence of automaticity during reoxygenation from 91% to 33%. CONCLUSION: MT possesses a calcium regulatory property.

Action Potentials↗

PubMed1998

[The flow cytometric analysis of activated platelets of severed finger by severe injury before and after replantation].

To investigate the significance of activated platelet levels before and after surgical operation in patients with severed finger by severe injury, the P-selectin (CD62p) positive platelet percent in peripheral blood was studied in 32 patients before and after operation by flow cytometric immunology. At the second and third day after operation, seventeen patients, which in a high positive platelet percent, were measured again after anticoagulation treatment with a large dose of urokinase etc. The results were that the levels of CD62p positive platelet in peripheral blood before and after operation were significantly higher than that of the normal group (P < 0.01). The CD62p positive platelet percent was increased not much more in the anti-coagulation patients than in the normal ones (P > 0.05). There were a few vascular crisis observed. This study suggested that severed fingers by a crushing or wringing injury enhance the platelet activity and resulted in hypercoagulation, thus anti-coagulation measures should be taken to avoid possible thrombosis and improve the survival rate of replantation. CD62p was one of the sensitive indices of activated platelet, which could be used in calculating hypercoagulation accurately.

Adolescent↗

PubMed1998

Studies on dynamics of growth and biosynthesis of artemisinin in hairy roots of Artemisia annua L.

Seven hairy root lines with the properties of fast growth and high artemisinin contents were selected from 747 hairy roots induced by transformation of Artemisia annua L. strain 025 with Agrobacterium rhizogenes ATCC15834. The differences of growth rates and artemisinin contents among the 7 selected hairy root lines were extremely significant, of which HR-9 gave the highest yield of artemisinin, reaching 33.25 mg/y.L. The differences of growth rates and artemisinin contents among hairy roots, untransformated roots and callus were also significant. There were no obvious lag phase in batch culture of hairy roots of Artemisia annua L. The exponential growth phase was 7 approximately 15 days after inculation. The growth rate reached the highest on the 11th day, and the cultures reached a stationary phase on the 20th day. The properties of artemisinin content of hairy roots were obviously "related to growth". The artemisinin content decreased slowly during the exponential phase, increased while the growth rate slowed down and remained consistent after the growth stopped. The optimum culture time for hairy roots of Artemisia annua L. was 21 days in our system.

Artemisia↗

PubMed1998

[Application and analysis of biochemical indices for the evaluation of antisilicosis treatment. Study on anti-silicosis therapy and its evaluation research group].

The levels of serum Ceruloplasmin (Cp), Superoxide dismutase (SOD) and IgG of 296 silicosis patients treated by tetrandrine, polyvinylpridine-N-Oxide, hydroxypiperaquinoline phosphate and aluminium citrate were measured. Sera were collected before and after the 1st, 3rd and 6th therapy courses. 144 Silicosis patients without treatment were observed as controls. The levels of these three indices decreased by the end of treatment. The levels of SOD were fluctuated, which were increased after the 3rd course, but decreased after the 1st and 6th courses. The decrease of Cp, SOD and IgG consisted with the clinical effectiveness of the treatment, indicating that Cp, SOD and IgG were appropriate biochemical indicators for the evaluation of antisilicosis drugs. The quality control and the statistics standardization for data analysis are important.

Alkaloids↗

PubMed1998

[Ceruloplasmin gene expression in silicotic rat lung].

In order to investigate the existence of extrahepatic ceruloplasmin (Cp) gene expression during silicotic process, molecular hybridization technique including dot blotting, in situ hybridization and Northern blotting was used. Twenty one days after silica dust intratracheal injection, Cp mRNA was detectable in lung, which was nearly double the content of that in the control (saline injection). In situ hybridization and Northern blotting revealed that the alveolar macrophages in silicosis could express Cp mRNA. It is concluded that lung is a prominent site for Cp gene expression during silicosis and Cp may play a previously unknown role in pulmonary injury or repair.

Animals↗

PubMed1998

[Study on the relationship between deoxyribonucleoside triphosphate (dNTP) pools and cell transformation].

Deoxyribonucleoside triphosphate (dNTP) pools were measured in normal BALB/c3T3 cells, transformation-treated cells and transformed cells with reverse-phase HPLC. The fluctuation of dNTP pools was similar after cells were treated with alkylating mutagens glycidyl methacrylate (GMA) and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). The gap between (dGTP + dATP) pools and (dTTP + dCTP) pools was greatly intensified. The measurements also indicated that the dNTP pools in transformed cells were quite different from those in normal cells. The results suggest that dNTP pools may play an important role in cell transformation.

3T3 Cells↗

PubMed1998

[Relationship between the expression level of alpha-MHC gene and cardiac contractility during heart failure].

To investigate the molecular basis of the decrease in myocardial contractility during heart failure, an animan model of heart failure was set up by means of deoxycorticosterone-acetate impregnated silicone rubber implants in wistar rats. Cardiac contractility in normal and heart failure rats was examined, and gene expression of its myocardial contractile protein, alpha-MHC, was quantitatively analyzed at gene transcription level by using RNA slot blot hybridization. The results showed that the cardiac contractility and the alpha-MHC mRNA levels in heart failure rats were all lower than those in the normal. Statistical analysis showed a positive correlation between the cardiac contractility and the gene expression of alpha-MHC (r = 0.4143, n = 43, P < 0.05). The above results indicate that gene expression level of alpha-MHC is one of the key factors determining cardiac contractility.

Animals↗

PubMed1998

[Study on the beta-lactamases of the Escherichia coli HX88108 resistant to ceforperazon].

E. coli HX88108 was isolated from a patient and found to produce plasmid-encode beta-lactamases with conferring highly resistance to ceforperazone(CPZ). The beta-lactamases of the E. coli HX88108 and transformants pFC, pFT1, pFT2 and pFT3 were studied. The beta-lactamases stability test among 11 beta-lactam antibiotics showed that beta-lactamases from E. coli HX88108. pFC, pFT1, readily hydrolyzed penicillins, the first, second-generation cephalosporins and CPZ. beta-lactamases of pFT2 and pFT3 hydrolyzed penicillins more strongly than cephalosporins. On the other hand, experiments of inhibiting enzyme were carried out. The results indicated that beta-lactamases of HX88108, pTF1, pFT2 and pFT3 were inhibited by clavulanic acid(CA) and sulbactam (SBT). Enzyme of pFC was inhibited poorly by CA and SBT. Through isoelectric focusing technique, the PIs were as follows: HX88108 contained three beta-lactamases, of which the PIs were 5.25, 5.3 and 5.6 respectively; the PIs of beta-lactamases from pFT2, pFT3, were 5.3 and 5.6. pFC and pFT1 were different plasmids encoded beta-lactamases with the same PI 5.25. The results indicate that the beta-lactamases of E. coli HX88108 may be a new member in TEM farmily.

Anti-Bacterial Agents↗