Biomedical subjects

T Liu

Publications and source records attributed to T Liu.

At least 145 records · Page 8Linked to original sources

PubMed2000

Active ion secretion and permeability of rabbit maxillary sinus epithelium, impact of staphylococcal enterotoxin B.

The aim of this study was to investigate the impact of staphylococcal enterotoxin B (SEB), a model superantigen, on the physiologic functions of rabbit maxillary sinus epithelium. Rabbit sinus mucosae were separated under a surgical microscope and mounted in Ussing chambers to record short-circuit current, conductance, and permeability to horseradish peroxidase. The results showed that SEB evoked increases in sinus epithelial cell baseline short-circuit current, conductance, and permeability to horseradish peroxidase. When tumor necrosis factor-alpha (TNF-alpha) was added to the Ussing chambers, we got results similar to those obtained by SEB stimulation in vitro; the effects of SEB on sinus epithelial cells could be blocked by pretreatment with anti-TNF-alpha antibody. These results demonstrate that SEB is able to alter the function of sinus epithelial cells and to affect the capability of the epithelial defensive barrier, which may be mediated by TNF-alpha.

Animals↗

PubMed2000

Value of troponin-T rapid assay, cardiac enzymes, electrocardiogram and history of chest pain in the initial diagnosis of myocardial infarction in the emergency department.

We conducted a prospective study of 152 adult patients presenting to an emergency department with chest pain or symptoms suggestive of acute myocardial infarction (AMI) to evaluate the first electrocardiogram (ECG), creatine kinase (CK)-MB and Troponin-T Rapid Assay (TnT) alone or in combination with chest pain in the initial diagnosis of AMI. A provisional diagnosis was made after the history, physical examination and the first ECG reading. Blood specimens were taken for TnT, CK and CK-MB mass. A final discharge diagnosis of AMI was made according to World Health Organization criteria. Seventy-six (50%) of patients had a final diagnosis of AMI. The sensitivities of the first ECG, first CK-MB mass and first TnT were 76.3% (95% confidence interval (CI), 66.8-85.9), 38.2% (95% CI, 27.2-49.1) and 31.6% (95% CI, 21.2-42.0) respectively. The area under the curve for a combination of ECG, CK-MB mass, TnT and chest pain was the highest at 0.937 when compared with chest pain with varying combinations of tests. A combination of the first ECG, CK-MB mass and TnT had a negative predictive value (NPV) of 87.9% (95% CI, 80.0-95.8). The first ECG was the most sensitive test while the combination of chest pain, ECG, cardiac enzymes and TnT gave the best results in the initial diagnosis of AMI. If the first ECG, CK-MB mass and TnT are all negative, the probability of having an AMI is 12%.

Adult↗

PubMed2000

The influence of backward wave transmission on quantitative ultrasonic evaluation using Lamb wave propagation

In view of the various novel quantitative ultrasonic evaluation techniques developed using Lamb wave propagation, the influence of an important related phenomenon, backward transmission, is investigated in this paper. Using the discrete layer theory and a multiple integral transform method, the surface displacement and velocity responses of isotropic plates and cross-ply laminated composite plates due to the Lamb waves excited by parabolic- and piston-type transmitting transducers are evaluated. Analytical expressions for the surface displacement and velocity frequency response functions are developed. Based on this a large volume of calculations is carried out. Through examining the characteristics of the surface displacement and velocity frequency response functions and, especially, the different propagation modes' contributions to them, the influence of the backward wave transmission related to quantitative ultrasonic nondestructive evaluation applications is discussed and some important conclusions are drawn.

Journal Article↗

PubMed2000

Molecular characterization of the Mycoplasma gallisepticum pvpA gene which encodes a putative variable cytadhesin protein.

A putative cytadhesin-related protein (PvpA) undergoing variation in its expression was identified in the avian pathogen Mycoplasma gallisepticum. The pvpA gene was cloned, expressed in Escherichia coli, and sequenced. It exhibits 54 and 52% homology with the P30 and P32 cytadhesin proteins of the human pathogens Mycoplasma pneumoniae and Mycoplasma genitalium, respectively. In addition, 50% homology was found with the MGC2 cytadhesin of M. gallisepticum and 49% homology was found with a stretch of 205 amino acids of the cytadherence accessory protein HMW3 of M. pneumoniae. The PvpA molecule possesses a proline-rich carboxy-terminal region (28%) containing two identical directly repeated sequences of 52 amino acids and a tetrapeptide motif (Pro-Arg-Pro-X) which is repeated 14 times. Genetic analysis of several clonal isolates representing different expression states of the PvpA product ruled out chromosomal rearrangement as the mechanism for PvpA phase variation. The molecular basis of PvpA variation was revealed in a short tract of repeated GAA codons, encoding five successive glutamate resides, located in the N-terminal region and subject to frequent mutation generating an in-frame UAA stop codon. Size variation of the PvpA protein was observed among M. gallisepticum strains, ranging from 48 to 55 kDa and caused by several types of deletions occurring at the PvpA C-terminal end and within the two directly repeated sequences. By immunoelectron microscopy, the PvpA protein was localized on the mycoplasma cell surface, in particular on the terminal tip structure. Collectively, these findings suggest that PvpA is a newly identified variable surface cytadhesin protein of M. gallisepticum.

Adhesins, Bacterial↗

PubMed2000

Expression of mouse mammary tumor virus superantigen accelerates tumorigenicity of myeloma cells.

To investigate whether superantigen (SAG) from endogenous mouse mammary tumor virus functions as an immunogenic or a tumorigenic factor in tumor development, the BALB/c myeloma cell line FO was transfected with the SAG gene from the 3' Mtv-50 long terminal repeat (LTR) open reading frame (ORF), the product of which was specific for Vbeta6. All five transfectants expressing Mtv-50 LTR ORF mRNA showed stimulatory activity for Vbeta6 T-cell hybridomas in vitro; this activity was inhibited by the addition of anti-Mtv-7 monoclonal antibody (MAb) or anti-major histocompatibility complex class II I-A(d) and I-E(d) MAb. All transfectants with the SAG gene grew more rapidly than did mock transfectants in BALB/c mice after subcutaneous inoculation, whereas all clones, including mock transfectants, grew equally well in athymic nude mice. A significant fraction of Vbeta6 T cells selectively expressed activation markers, including CD44(high), CD62L(low), and CD69(high), and produced large amounts of interleukin 5 (IL-5) and IL-6 in BALB/c mice inoculated with transfectants. These results suggested that the expression of viral SAG enhances the tumorigenicity of a myeloma cell line through the stimulation of SAG-reactive T cells.

Animals↗

PubMed2000

Induction of telomerase activity in fibroblasts from bleomycin-injured lungs.

Bleomycin-induced lung injury causes increased fibroblast numbers in the lung and pulmonary fibrosis. Studies of fibroblasts isolated from such injured lungs have revealed evidence of increased intrinsic proliferative capacity, but the mechanism is unknown. Telomerase catalyzes the addition of telomeric DNA repeats onto chromosomal ends, which is associated with increased cellular life span or immortality. To examine whether telomerase might play a role in regulating fibroblast proliferative capacity in pulmonary fibrosis, lung fibroblasts were isolated from rats treated with endotracheal injections of phosphate-buffered saline or bleomycin. At selected time points, the rats were killed and lung fibroblasts isolated. The isolated cells and lung tissue were then used in experiments for measurement of telomerase activity. The results show undetectable telomerase activity in fibroblasts isolated from control uninjured lungs, or in the control lung tissue extracts. Similar results were obtained in cells and lung tissue from Days 1, 3, and 28 bleomycin-injured lungs. However, significant telomerase activity was detected in fibroblasts and tissue extracts isolated from Days 7, 14, and 21 bleomycin-treated rat lungs, with maximal activity observed in the Day 14 samples. Analysis of the isolated cells for telomerase messenger RNA or reverse transcriptase expression, combined with alpha-smooth-muscle actin expression by immunohistochemistry, revealed that telomerase expression localized primarily to nonmyofibroblasts. These findings suggest that in addition to elevated growth factor expression, the injured lung fibroblast population may contain cells with increased life span, which could contribute to the observed overall increase in lung fibroblast numbers.

Animals↗

PubMed2000

The Outcasts: a family romance.

The following short impression is meant to be neither academic nor comprehensive. It is, rather, just that-an impression, a series of floating thoughts on a film that sticks in the mind.

Art↗

PubMed2000

Effects of captopril treatment of renovascular hypertension on beta-adrenergic modulation of L-type Ca(2+) current.

beta-Adrenergic stimulation of cardiac L-type Ca(2+) channels is severely impaired in hypertrophied and failing hearts of both experimental animals and humans. The aim of this study was to test the hypothesis that chronic treatment of renovascular hypertension with captopril restores normal beta-adrenergic responsiveness of L-type Ca(2+) channels in cardiac myocytes. Left ventricular hypertrophy was induced in rabbits by unilateral renal artery banding and contralateral nephrectomy. Beginning at 3 months after banding, hypertensive rabbits were treated with captopril for 3 months. The responsiveness of L-type Ca(2+) current (I(Ca,L)) to (+/-)-isoproterenol was investigated with the whole-cell patch-clamp technique. (+/-)-Isoproterenol (1 microM) induced an increase of I(Ca,L) at 0 mV of 126 +/- 20% (n = 13) in control myocytes versus 69 +/- 11% (n = 18) in hypertrophied myocytes from rabbits 3 months after banding. The half-maximal activation concentration of (+/-)-isoproterenol was similar between control and hypertrophied myocytes. Forskolin (10 microM) induced a similar percentage of increase of I(Ca,L) in control and hypertrophied myocytes, 109 +/- 13% (n = 12) versus 120 +/- 14% (n = 11) at 0 mV. The responsiveness of I(Ca,L) to (+/-)-isoproterenol remained depressed in untreated hypertensive rabbits. (+/-)-Isoproterenol (1 microM) increased I(Ca, L) at 0 mV by 64 +/- 8% (n = 14) in myocytes isolated from rabbits 6 months after banding versus 111 +/- 15% (n = 16) in age-matched controls. In captopril-treated rabbits, 1 microM (+/-)-isoproterenol increased I(Ca,L) by 110 +/- 11% (n = 17). We conclude that the maximal response of I(Ca,L) to (+/-)-isoproterenol was severely depressed in hypertrophied myocytes. Chronic treatment of renovascular hypertension with captopril can restore normal responsiveness of I(Ca,L) to (+/-)-isoproterenol in cardiac myocytes.

Animals↗

PubMed2000

[The promoter sequence of human nitric-oxide-synthase gene: functional study].

OBJECTIVE: Endothelial nitric oxide synthase (ecNOS) catalyzes the NADPH and O(2) to nitric oxide(NO). This study aimed at the regulation mechanism of the transcription of ecNOS gene. METHODS: The promoter regions of ecNOS gene were analyzed by gel mobility shift assay and DNase I footprinting assay using nuclear extract from endothelial cells. RESULTS: Three regions were protected by protein/transcription-factors. One of these regions, (-106 to -88) was demonstrated to be SP1 binding consensus sequence which was extremely rich in GC content. The other two regions, (-79 to -64) and (-58 to -44), covered the CTCF binding regions, but showed various binding modes. CONCLUSION: The protected regions are bound either with aggregated SP1/SP1- like proteins or with new transcription factor which have not been reported yet.

DNA Footprinting↗

PubMed2000

[Effect of anti-endotoxin therapy on vaso-active substances in decompensated liver cirrhosis].

OBJECTIVE: To study the anti-endotoxin therapy on the plasma levels of nitric oxide, prostacyclin, tumor necrosis factor-alpha in patients with liver cirrhosis after hepatitis. METHODS: Thirty patients with decompensated liver cirrhosis accepted anti-endotoxin therapy with oral Amoxycillin and Smedta for 2 weeks. Plasma levels of endotoxin, nitric oxide, prostacyclin and tumor necrosis factor-alpha were detected before and after therapy in study group and control group, respectively. The relationship between endotoxin and vasoactive substances and between the four substances and the status of patients were analyzed. RESULTS: The four substances were all increased significantly (P<0.01) in patients with liver cirrhosis compared with control group and decreased obviously after treatment for 2 weeks (endotoxin from 0.546X10(21) U/L to 0. 347X10(21) U/L, no from 56.498 mumol/L to 31.256 mumol/L, 6-keto-PGF1 alpha from 716.964 ng/L to 539.867ng/L, and TNF-alpha from 3.090 mug/L to 1.750 mug/L (P<0.01). CONCLUSION: The plasma levels of nitric oxide, prostacyclin and tumor necrosis factor-alpha increased because of endotoxemia. Amoxycillin and Smecta can clear endotoxin out effectively.

Adult↗

PubMed2000

[The alpha-dissipation characteristic of human auricular points].

We researched into the dissipative characteristic of human auricular points in 40 cases of myopia. The logZ-logf curve of the dissipative characteristic of the otopoint is similiar to the dermal alpha-Dispersion in 1-100 kHz of the alternating electric field. The dissipative effect of the otopoint is generated mainly by the skin of the body surface. The characteristic frequency f0 has intimate relation to patholgic change, correlation coefficent r approximately 0.8. The f0 has characteristic reflecting pathologic change, P < 0.01. The relexation time tau signifies the space constructive characteristic of the tissue. So we suppose that the otopoint and its characteristic reflecting pathologic change essentially relate to the change of biological macromolecule conformation of the dermatic tissue under acupoint.

Acupuncture Points↗

PubMed2000

[Evolution of distribution patterns of cis-acting elements in 5' regulative regions of vertebrate actin].

Actins are expressed in a rigorous tissue- and development-manner which implies tthat there most probably are some unique distribution patterns of cis-acting elements in their 5' regulative regions. We improved a method to predict cis-acting element and constructed nucleotide distribution weight matrixes of 5 cis-acting elements which are concerned in vertebrate actin genes' transcription regulation. Using this method, we matched these factors in 5' regulative regions of vertebrate actin genes by comparing the sequences with these matrixes, and got six isotype-specific distribution models of these cis-acting elements. The evolutionary trends of the six models were also analyzed.

Actins↗

PubMed2000

[Prognostic evaluation of heart-liver ratio of (99m)Tc-MIBI on liver cirrhosis].

OBJECTIVE: To evaluate heart-liver ratio (H/L) of (99m)Tc-MIBI on the prognosis of cirrhotic patients. METHODS: Retrospective cohort study was used to analyze the survival rate among the patients who had received H/L detection, and the H/L value was classified by Child-Pugh class. RESULTS: All the patients were followed up for 0.1 to 63 months. H/L ratio was significantly different among Child-Pugh A, B, C groups (0.85 +/- 0.15, 0.99 +/- 0.19, 1.15 +/- 0.27, F=5.09, P<0.01); 6-month, 1-year, and 2-year survival rates in H/L<1.0 group were significantly higher than those in H/L>1.0 group (85.9%, 57.4%, 57. 4% vs 50.0%, 39.4%, 19.7%, P<0.01 ). Among patients with Child-Pugh degree C, 6-month, 1-year, and 2-year survival rates in H/L<1.0 group were significantly higher than those in H/L>1.0 group (71.4%, 42.9%, 42.9% vs 27.3%, 18.2%, 0). CONCLUSION: H/L is an effective index for evaluating prognosis of cirrhotic patients, and it could be complemented by Child-Pugh classification.

Adult↗

PubMed2000

Three-dimensional ultrasound analyses of the prostate.

Although conventional ultrasonography has proven to be clinically useful for depicting many types of cancerous lesions, it cannot distinguish reliably between cancerous and noncancerous tissue of the prostate. Therefore, conventional transrectal ultrasonography (TRUS) is used primarily for general evaluations of the gland and for guiding biopsies based on clearly imaged anatomic features such as the capsule, seminal vesicles, and urethra. Spectrum analysis extracts ultrasound signal parameters associated with biopsy-proven tissue types, and these parameters are then classified using neural network tools such as learning vector quantization, radial basis, and multilayer perceptron algorithms. Classification of cancerous and noncancerous prostate tissue using neural networks produces receiver operating characteristic (ROC) curves of 0.87 +/- 0.04 compared with 0.64 +/- 0.04 for conventional ultrasonography. To image the prostate using these methods, parameter values are computed at each pixel location, then translated into a score for the likelihood of cancer using a look-up table generated using the best classification algorithm. The score for cancer likelihood is expressed as a gray-scale or color value, and the resulting image may be useful to guide biopsies or therapy. Changes in parameter or score values over time potentially can be used to assess progression of disease or efficacy of therapy.

Adenocarcinoma↗

PubMed2000

[Status of methylation of promoter of mis-match repair gene hMLH1 in lung cancer].

OBJECTIVE: To study the relationship between status of methylation of hMLH1 promoter and expression of its protein in lung cancer. METHODS: Methylation of the hMLH1 gene promoter and hMLH1 protein was examined in 50 primary lung cancer tissues by Hpa II digestion-PCR and immunohistochemistry. RESULTS: The incidence of the hMLH1 promoter methylation was 32.0% (16/50). Methylation frequeney did not correlate with sex, smoking and clinicopathological characteristics. Negative expression of hMLH1 protein occurred in 14/46 tumors, of which 11 tumors had hMLH1 promoter methylation (78.6%, 11/14), while only 5 had methylation in 32 specimens positive for hMLH1 protein expression. CONCLUSION: In about one-third of lung cancer tissues examined there exists methylation of hMLH1 promoter, which correlates well with the absence of expression of hMLH1 protein.

Adaptor Proteins, Signal Transducing↗

PubMed2000

[Evaluation of performance and blood compatibility of polyethersulfone hollow fiber plasma separator].

In this study, we evaluated the performance and blood compatibility of polyethersulfone hollow fiber membrane plasma separator by animal experiment. Hemolysis did not occur under the usual conditions of plasma separation. The sieving coefficients of total protein, albumin and globulin were over 95%, and about 60% of total plasma were extracted from the whole blood. White blood cells, platelets, fibrinogen, and coagulation factors were decreased during the early stage of plasma separation and appeared to be within acceptable ranges for clinical use.

Animals↗

PubMed2000

[Impact of starvation on predation by male adult Chrysopa septempunctata].

The predation on Schizaphis graminum by male adult Chrysopa septempunctatata at various levels of starvation was examined in this paper. Th results showed that the functional reactive types of predator were not altered by its starvation duration, and the amount(Na) of catched S. graminum by C. septempunctata within 24 hrs varied with duration time(t), which could be expressed by the model: Na = 100/(1 + e-0.3088 - 0.0996t). The relationship between predation rate(v) and time(x) could be described as v = 6.7117 x-0.7928. The male adult predators preferred feeding on the young preys.

Animals↗

PubMed2000

Immune response to plasmid DNA encoding HPV16-L1 protein.

OBJECTIVE: To test the immunogenicity of recombinant plasmid DNA containing human papillomavirus type 16-L1 (HPV16-L1) coding sequence of mice. METHODS: The HPV16-L1 encoding sequence was generated by polymerase chain reaction (PCR), and inserted into TA cloning vector PCR II, then cloned in the eukaryotic expression vector pcDNA3.1 with CMV promoter. The recombinant plasmid DNA pcDNA-L1 was transferred into Cos-7 cells and used to immunize BALB/c mice via muscular injection. The expression of HPV16-L1 in transferred cells was identified by immunospot and immunocytochemistry, which tested specific anti-HPV16-L1 antibody in the serum of immunized mice. RESULTS: Using the immunospot technique, we found L1 protein expression in pcDNA-L1 transferred cells. The immunocytochemistry studies demonstrated that the L1 protein was located in nuclei. In immunized mice, specific anti-HPV16-L1 antibodies could be detected by immunospot and immunocytochemistry 28 days after the first immunization and last at least 41 days. CONCLUSIONS: We constructed HPV16-L1 eukaryotic expressing plasmid whose DNA could induce immunohumoral response in mice. This observation will be helpful in designing HPV16 prophylactic vaccine.

Animals↗