Biomedical subjects

Z Liang

Publications and source records attributed to Z Liang.

At least 55 records · Page 3Linked to original sources

PubMed2000

Geometric and Topological Analysis of Three-Dimensional Porous Media: Pore Space Partitioning Based on Morphological Skeletonization.

This article presents a versatile, rigorous, and efficient methodology for extracting various geometric and topological parameters of 3D discrete porous media. The new approach takes advantage of the morphological skeleton of the pore structure-a lower dimensional representation of the pore space akin to the topological "deformation retract". The skeleton is derived by a fully parallel thinning algorithm that fulfils two essential requirements: it generates a medial axis and preserves the connectivity of the pore space. Topological analysis is accomplished by classifying all skeleton points as node or link (branch) points according to the concept of lambda-adjacency in 3D discrete space. In this manner, node coordination number and link length distributions are directly obtained from the skeleton. Pore necks (throats) are identified through a search for minima in the hydraulic radius of individual pore space channels outlined by skeleton links. In addition to the determination of the size distribution of the constrictions (pore necks) that control nonwetting phase invasion, improved estimates of the distributions of effective hydraulic and electric conductivity of individual pore space channels are obtained. Furthermore, erection of planes at the location of pore necks results in partitioning of the pore space into its constituent pores. This enables the characterization of the pore space in terms of a pore volume distribution. The new methodology is illustrated by application to a regular cubic pore network and irregularly shaped 2D and 3D pore networks generated by stochastic simulation. In the latter case, important new results are obtained concerning the sensitivity of geometric and topological properties of the microstructure to the parameters of stochastic simulation, namely, the porosity and correlation function. It is found that model porous media reconstructed from the same porosity and correlation function can exhibit marked differences in geometry and connectivity, which correlate with differences in specific surface area. Copyright 2000 Academic Press.

Journal Article↗

PubMed2000

A total fibrinogen deficiency is compatible with the development of pulmonary fibrosis in mice.

In addition to their well-known roles in hemostasis, fibrinogen (Fg) and fibrin (Fn) have been implicated in a number of other physiological and pathophysiological events. One of these involves the fibroproliferative response after acute lung injury, which is the focus of the current study. Mice with a total Fg deficiency (FG(-/-)) were generated by breeding heterozygous (FG(+/-)) pairs, each of which contained an allele with a targeted deletion of its Fg-gamma-chain gene. The resulting FG(-/-) animals did not possess detectable plasma Fg. FG(-/-) mice were then used to assess the roles of Fg and Fn in a bleomycin-induced acute lung injury model. Intratracheal administration of bleomycin in wild-type and FG(-/-) mice resulted in equivalent deposition of interstitial collagen and fibrotic lesions at days 7 and 14 after administration. This indicates that Fg and/or Fn are not essential for the development of bleomycin-induced pulmonary fibrosis.

Afibrinogenemia↗

PubMed2000

Prefrontal regions play a predominant role in imposing an attentional 'set': evidence from fMRI.

fMRI was used to determine whether prefrontal regions play a predominant role in imposing an attentional 'set' that drives selection of task-relevant information. While monitoring for an atypical item, individuals viewed Stroop stimuli that were either colored words or colored objects. Attentional demands were varied, being greater when the stimuli contained two distinct and incongruent sources of information about the task-relevant attribute (e.g., when attending to color, seeing the word 'blue' in red ink) as compared to only one source (e.g., seeing the word 'late' in red ink). Prefrontal but not anterior cingulate regions exhibited greater activation on incongruent than neutral trials, suggesting that prefrontal cortex has a major role in imposing an attentional 'set'. In addition, we found that prefrontal activation is most likely to occur when that attentional set is difficult to impose.

Attention↗

PubMed2000

A novel approach to extract colon lumen from CT images for virtual colonoscopy.

An automatic method has been developed for segmentation of abdominal computed tomography (CT) images for virtual colonoscopy obtained after a bowel preparation of a low-residue diet with ingested contrast solutions to enhance the image intensities of residual colonic materials. Removal of the enhanced materials was performed electronically by a computer algorithm. The method is a multistage approach that employs a modified self-adaptive on-line vector quantization technique for a low-level image classification and utilizes a region-growing strategy for a high-level feature extraction. The low-level classification labels each voxel based on statistical analysis of its three-dimensional intensity vectors consisting of nearby voxels. The high-level processing extracts the labeled stool, fluid and air voxels within the colon, and eliminates bone and lung voxels which have similar image intensities as the enhanced materials and air, but are physically separated from the colon. This method was evaluated by volunteer studies based on both objective and subjective criteria. The validation demonstrated that the method has a high reproducibility and repeatability and a small error due to partial volume effect. As a result of this electronic colon cleansing, routine physical bowel cleansing prior to virtual colonoscopy may not be necessary.

Adult↗

PubMed2000

Species-specific monoclonal antibodies for rapid identification of Bartonella quintana.

Seven species-specific monoclonal antibodies (MAbs) to Bartonella quintana were produced and characterized. The MAbs were of the immunoglobulin G class and reacted only with 13 B. quintana strains in indirect microimmunofluorescence and Western immunoblotting assays. They did not react with eight other Bartonella spp., including Bartonella henselae, the most closely related species, and a selected MAb did also not react with nine other strains of gram-negative bacteria. The MAbs reacted mainly with a 34-kDa protein epitope of B. quintana which was shown to be species specific by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Four of five body lice experimentally infected with B. quintana were found to be positive for the organism in microimmunofluorescence assays with one MAb. These MAbs may provide a specific, simple, rapid, and low-cost tool for the identification of B. quintana and the diagnosis of infections due to the microorganism.

Animals↗

PubMed2000

Differentiation of Bartonella species by a microimmunofluorescence assay, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and Western immunoblotting.

Bartonella species can be differentiated by microimmunofluorescence assay, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), and immunoblotting with murine polyclonal antisera to Bartonella henselae, B. quintana, B. elizabethae, and B. bacilliformis. A pairwise comparison on the basis of SDS-PAGE protein profiles demonstrated similarity values for proteins of different Bartonella species ranging from 28.6 to 86.4%. Antigenic relationships revealed by immunoblotting with murine antisera were equivalent to those of proteins observed by SDS-PAGE. A dendrogram obtained on the basis of protein bands of SDS-polyacrylamide gels showed that Bartonella species could be divided into three groups. B. bacilliformis was distinct from all other Bartonella species; B. grahamii, B. taylorii, B. doshiae, and B. vinsonii formed a cluster, as did B. henselae, B. quintana, B. elizabethae, and B. clarridgeiae. These relationships were consistent with those revealed by parsimony trees derived from 16S rRNA and gltA gene sequencing. SDS-PAGE analysis showed that 120-, 104-, 85-, 71-, 54-, 47-, 40-, 33-, 30-, and 19-kDa proteins were present in all species, with the 54-kDa protein being the most dominant. Proteins with a molecular mass of less than 54 kDa allow the differentiation of species and are a possible target for future species-specific antibodies and antigens.

Bacterial Typing Techniques↗

PubMed2000

Evolution of arginine biosynthesis in the bacterial domain: novel gene-enzyme relationships from psychrophilic Moritella strains (Vibrionaceae) and evolutionary significance of N-alpha-acetyl ornithinase.

In the arginine biosynthetic pathway of the vast majority of prokaryotes, the formation of ornithine is catalyzed by an enzyme transferring the acetyl group of N-alpha-acetylornithine to glutamate (ornithine acetyltransferase [OATase]) (argJ encoded). Only two exceptions had been reported-the Enterobacteriaceae and Myxococcus xanthus (members of the gamma and delta groups of the class Proteobacteria, respectively)-in which ornithine is produced from N-alpha-acetylornithine by a deacylase, acetylornithinase (AOase) (argE encoded). We have investigated the gene-enzyme relationship in the arginine regulons of two psychrophilic Moritella strains belonging to the Vibrionaceae, a family phylogenetically related to the Enterobacteriaceae. Most of the arg genes were found to be clustered in one continuous sequence divergently transcribed in two wings, argE and argCBFGH(A) ["H(A)" indicates that the argininosuccinase gene consists of a part homologous to known argH sequences and of a 3' extension able to complement an Escherichia coli mutant deficient in the argA gene, encoding N-alpha-acetylglutamate synthetase, the first enzyme committed to the pathway]. Phylogenetic evidence suggests that this new clustering pattern arose in an ancestor common to Vibrionaceae and Enterobacteriaceae, where OATase was lost and replaced by a deacylase. The AOase and ornithine carbamoyltransferase of these psychrophilic strains both display distinctly cold-adapted activity profiles, providing the first cold-active examples of such enzymes.

Acetyltransferases↗

PubMed2000

Comparison of occurrence of oro-maxillo-facial tumor types in different regions of the People's Republic of China.

The frequencies of oro-maxillo-facial tumors, by type, seen at the Guangxi Medical College Hospital were surveyed in order to compare different regions of the People's Republic of China. Computer analysis was performed on data for all oro-maxillo-facial tumors, as confirmed by the hospital between 1957 and 1987, inclusive. The results were then used in a comparative study with those of five other medical colleges. Among a total of 4,052 cases, there were 1,593 benign tumors, 2,049 malignant tumors and 410 unknown tumors. Tumors derived from the epithelium were the most common type (42.0% of the total), whereas in the other five medical colleges the mean corresponding proportion was 27.8%, the difference being significant (p < 0.05). Epithelial tumors were also the most common type of malignant tumor (70.5% of the total), whereas the corresponding proportion reported by the other five institutions was 60.6%, which was also significantly different (p < 0.05). The proportion of malignant tumors among the total was more than 50.6%, which was higher than that reported by the other five colleges. This study shows that epithelium-derived tumors and malignant tumors were encountered more frequently at Guangxi Medical College than at the other five medical colleges in China.

Carcinoma↗

PubMed2000

Blood coagulation factor X deficiency causes partial embryonic lethality and fatal neonatal bleeding in mice.

Mice with a total deficiency in blood coagulation Factor X (FX) were generated by targeted replacement of an 18-kb fragment of the FX gene, comprising all exons encoding the mature FX protein, with a neo(r) cassette. The genotype distribution among the offspring from heterozygous breeding pairs suggested that FX deficiency resulted in partial embryonic lethality, with approximately one-third of the FX-/- embryos dying around embryonic day (E) 11.5-12.5. Two of 44 non-resorbed FX-/- embryos analyzed at these stages showed signs of massive bleeding, one of which into the brain ventricles, but no histological defects in the vasculature of these embryos or their yolk sac were observed. The remainder of the FX-/- embryos appeared normal and survived to term, but the majority of neonates (90%) died within 5 days, most frequently from intraabdominal bleeding. The remaining FX-/- animals succumbed between postnatal day (P)5 and P20 with intraabdominal, subcutaneous, or intracranial bleeding or a combination thereof. The lethal phenotype of the FX-/- mice illustrates the importance of FX function in embryonic and postnatal survival and demonstrates that these mice serve as effective models of the bleeding disorders observed in severe FX deficiency in humans.

Animals↗

PubMed2000

Cloning and characterization of the murine coagulation factor X gene.

The gene encoding murine coagulation factor X (fX) was isolated and characterized from a lamdaFIX II library generated from murine genomic DNA. The 20130 bp sequence contains 18049 nucleotides that extend from the initiating methionine to the polyadenylation site. 1056 nucleotides 5' of the start codon were determined and contain putative start sites for the FX mRNA as well as sites for binding of putative transcription factors. The sequence extends 1024 3' of the polyadenylation site. The gene contains 8 exons and 7 introns which were determined by comparing the mouse FX cDNA and gene sequences. The exonic structure of the gene is similar to that of the other mammalian vitamin K-dependent serine proteases of the coagulation system. These include an exon encoding the prepropepetide, the gla-domain, a short helical stack, two exons for the two EGF domains, the activation pepetide, and two exons encoding the serine protease domain. The 5' sequence of the mouse FX gene overlaps with the 3' region of the FVII gene indicating that the murine FVII and FX gene are arranged in a head to tail arrangement as they are in humans.

Animals↗

PubMed2000

The disposition of saquinavir in normal and P-glycoprotein deficient mice, rats, and in cultured cells.

Protease inhibitors are very effective in treating patients infected with HIV. However, many drugs in this class penetrate poorly into the central nervous system (CNS) and may permit this site to be a sanctuary from which resistant virus can emerge. Previous studies have shown that the protease inhibitor saquinavir (SQV) interacts with the multidrug transport system, P-glycoprotein (P-gp), expressed in epithelial cells in the gut mucosa and at the blood-brain barrier, and thus might affect both the oral absorption and the penetration of SQV into the CNS. To determine whether SQV is a substrate for P-gp, its uptake was determined in cancer cells, which do (Dx5) and do not (MES-SA) express P-gp. The distribution of SQV between brain tissue and plasma was also investigated in rats and in normal and P-gp-deficient mdr1a(-/-) mice. The distribution ratio of SQV in plasma:brain:cerebrospinal fluid was approximately 100:10:0.2 in rats. The accumulation of SQV was enhanced in MES-SA cells (P-gp-negative) versus Dx5 cells (P-gp-positive). Bolus i.v. injection of [(14)C]SQV (2 and 5 mg/kg) into mdr1a(-/-) and normal mice (n = 3 or 4) resulted in 3-fold higher radioactivity in brains from mdr1a(-/-) mice. Similarly, oral administration of [(14)C]SQV (500 mg/kg) resulted in a 5-fold increase in systemic exposure and a 10-fold increase in brain levels in mdr1a(-/-) mice. These data demonstrate that saquinavir is a substrate for P-gp and that this transport system may play a role in limiting oral absorption and CNS exposure to this protease inhibitor.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2000

[Antigen presenting role of dendritic cell proliferated from peripheral blood monocytes in patients with chronic hepatitis B].

OBJECTIVE: To study the presenting effect of dendritic cell (DC) proliferated from peripheral blood monocytes in patients with chronic hepatitis B on HBsAg. METHODS: DC proliferated from patient's peripheral blood monocytes by adding GM-CSF and IL-4 were incubated with HBsAg for 1.5h at different concentrations, then mixed with autologous T cell and cocultured in 96-well flat-bottomed microtiter plates for 5 d at 37 degrees C and 5% CO(2). (3)H-TdR was added 13h before the culture completion, and finally the cells were gathered and the cpm was tested. RESULTS: The proliferation of T cell by DC treated by HBsAg is significantly higher than untreated. CONCLUSION: DC cultured from peripheral blood monocytes in patients with chronic hepatitis B plays a role in presenting HBsAg.

Antigen Presentation↗

PubMed2000

[Detection of circulating pemphigus vulgaris antibodies in families of patients with pemphigus vulgaris].

OBJECTIVE: To detect the autoantibodies on 30 first-degree relatives of 12 patients with pemphigus vulgaris (PV), who may share the same susceptible gene with the patients. METHODS: Immunoblot and indirect immunofluorescence (IIF) method were used to detect circulatory PV antibodies in the peripheral blood. RESULTS: PV antibodies were found in 19 of 30 (63%) relatives by both methods, but 10 control serum were all negative by both methods. CONCLUSION: Healthy PV antibody carriers may also exist in high frequency in the first-degree relatives of Chinese PV patients.

Adolescent↗

PubMed2000

Kinetic study of eosinophil apoptosis and its relationship to Th2 cytokines in asthmatic murine model.

OBJECTIVE: To investigate the significance and regulatory mechanism of eosinophil apoptosis in asthmatic airway inflammation using an animal models, as well as its relationship to IL-5 and IL-10. METHODS: An animal model of asthma was established by ovalbumin (OVA) sensitizing-challenging BALB/C mice. At seven points in the time course after challenge, bronchoalveolar lavage (BAL) was performed to obtain BAL cells. Levels of two Th2 cytokines, IL-5 and IL-10 were detected by ELISA. A double label technique combining CD15 with CD49d was used to distinguish eosinophils from other cell types. Cell apoptosis was assayed by PI stain using a flow cytometer. RESULTS: Eosinophil apoptosis was identified and a two-phase elevation of apoptosis percentages was observed, although no significant difference was found between average apoptosis in the asthmatic group and that in the control. Analysis of kinetic changes of eosinophil apoptosis and cytokine levels revealed a negative correlation between apoptosis percentages and levels of IL-5, and a closer correlation between apoptosis percentages and the IL-5/IL-10 ratio. Dexamethasone pretreatment markedly reduced IL-5 levels in BAL, elevated eosinophil apoptosis percentages, but had no effect on IL-10 levels. CONCLUSION: Eosinophils underwent apoptosis in asthmatic airways. Equilibrium between IL-5 and IL-10 not only regulated eosinophil infiltration, but also modulated cell apoptosis.

Animals↗

PubMed2000

[Determination of tumor necrosis factor-alpha and interleukin-6 levels of the tubal fluids in patients with infertility caused by infection of Chlamydia trachomatis].

OBJECTIVE: To study the levels of tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) in tubal fluids of tubal factor infertile (TFI) women due to chlamydia trachomatis (CT) infection and its implication. METHODS: Twenty-two TFI women with CT infection (group A), twenty-three TFI women without CT infection (group B) and nineteen fertile women with normal tubes (group control) were enrolled for study. Levels of TNF-alpha and IL-6 in tubal fluids were measured by enzyme-linked immunosorbent assay. RESULTS: Group A had significantly higher TNF-alpha levels than those of group control (178 ng/L versus 124 ng/L, P < 0.01). Moreover, women with tubal blocks had significantly higher TNF-alpha those of tubal adhesions (199 ng/L versus 142 ng/L, P < 0.01). IL-6 levels of group A were significantly higher than those of group B and group control (681 ng/L versus 264 ng/L and 229 ng/L, both P < 0.01), but there is no difference between group B and group control. CONCLUSIONS: Local TNF-alpha and IL-6 levels increased in silent tubal infection of CT. TNF-alpha had a positive relevance with the degree of tubal damage.

Adult↗

PubMed2000

[Genes of micrometastasis in bone marrow of patients with colorectal cancer].

OBJECTIVE: To detect the gene of micrometastasis in bone marrow of patients with colorectal cancer. METHODS: PCR-SSCP/silver stain technique was used to find out the metastatic cancer cells in 51 bone marrow samples in different time. RESULTS: The total positive rate of mutations of p53 and K-ras in bone marrow was 37.25% before operation. The incidence of mutations was obviously correlated with Duke's stage and lymphatic metastasis. After postoperative chemotherapy mutation in 11 patients turned to be negative. CONCLUSIONS: Detection of micrometastasis in bone marrow may contribute to early diagnosis of blood stream metastasis of colorectal cancer.

Bone Marrow Neoplasms↗

PubMed2000

[Expression of thymidylate synthase gene and recurrence of colorectal carcinoma: their relation and clinical significance].

OBJECTIVE: To study the relationship between expression of thymidylate synthase (TS) gene and recurrence of colorectal carcinoma and its effect on clinical treatment. METHODS: RT-PCR was used to detect the expression of TS gene in primary foci, para-tumoral intestine mucosa, local recurrence, abdominal-pelvic dissemination and hepatic metastasis in 68 cases of colorectal carcinoma, and TS protein was examined with western blot. RESULTS: In 68 cases of colorectal carcinoma, the expression of TS gene in primary foci was 22.1% (15/68); and the positive rates of TS gene expression in local recurrence, abdominal-pelvic dissemination and hepatic metastasis were 88.5% (23/26), 85.0% (17/20), 40.9% (9/20) respectively. The rates of TS protein expression in primary foci, local recurrence, abdominal-pelvic dissemination and hepatic metastasis were 22.1% (15/68), 84.6% (22/26), 80.0% (16/20), 36.4% (8/22) respectively. The negative expression of TS gene and TS protein was detected in paratumoral intestinal mucosa. The results of TS gene and TS protein expression were identical with those the two methods. The positive rates of TS gene and TS protein expression in diversified recurrence foci and metastasis were higher than those in primary foci (P < 0.01). The differences of TS gene and TS protein expression rates between recurrence and hepatic metastasis were significant (P < 0.01). The expression rates of TS gene and TS protein in local recurrence and abdominal-pelvic dissemination tissues were higher than those in hepatic metastasis. CONCLUSION: Overexpression of TS gene plays an important role in the process of local recurrence and abdominal-pelvic dissemination of colorectal carcinoma.

Adult↗

PubMed2000

[The relationship between effects and radiation doses of intra-arterial phosphorus-32 glass microspheres embolization therapy for patients with advanced liver cancer].

OBJECTIVE: To evaluate the relationship between effects and internal radiation of phosphorus-32 glass microspheres embolization therapy for liver cancer patients. METHODS: From 1994 to 1998, 44 patients with unresectable liver cancer received intra-arterial radio-embolization therapy using (32)P-GMS. Preoperative and postoperative function and energy level of the liver were tested by liver function test and arterial blood ketone body ratio (AKBR). CT, single photon emission computer tomography (SPECT), and AFP were used to judge the effect of the therapy; multivariate analysis was made. RESULTS: In the moderate dose group, low incidence of complication, high tumor shrinking rate and AFP decreasing rate, and long-term survival rate were observed. In the larger dose group, high incidence of liver failure, high tumor shrinking rate and AFP decreasing rate, and long-term survival rate were also observed. In the low dose group, low incidence of complication, but low tumor shrinking rate and AFP decreasing rate and long-term survival rate were not observed. CONCLUSIONS: The reasonable radiation doses for liver cancer patients may be about 30 Gy; if liver cirrhosis is serious, the doses can be reduced.

Adult↗