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Biomedical subjects

L Yang

Publications and source records attributed to L Yang.

At least 145 records · Page 8Linked to original sources
PubMed2001

Light scattering and ink penetration effects on tone reproduction.

Light scattering, or the so-called Yule-Nielsen effect, and ink penetration into the substrate paper play important roles in tone reproduction. We develop a framework in which the influences of both of these effects on the reflectance and tristimulus values of a halftone sample are investigated. The properties of the paper and the ink and their bilateral interaction can be parameterized by the reflectance Rp(o) of the substrate paper, the transmittance Ti of the ink layer, the parameter gamma describing the ink penetration, and p describing the Yule-Nielsen effect. We derive explicit expressions that relate the reflectance of the ink dots (Ri), the paper (Rp) and the halftone image (R) as functions of these parameters. We also describe the optical dot gain as a function of these parameters. We further demonstrate that ink penetration leads to a decrease in optical dot gain and that scattering in the paper results in the printed image's being viewed as more saturated in color.

Journal Article↗
PubMed2001

Administration of unmodified prolactin (U-PRL) and a molecular mimic of phosphorylated prolactin (PP-PRL) during rat pregnancy provides evidence that the U-PRL:PP-PRL ratio is crucial to the normal development of pup tissues.

During rat pregnancy initial high concentrations of prolactin (PRL) decline by about day 9, concomitant with an increase in the ratio of unmodified to phosphorylated PRL. The physiological significance of both the decline in total PRL and the change in ratio of the two PRLs is unknown. To test the importance of each, either unmodified PRL (U-PRL) or a molecular mimic of phosphorylated PRL (PP-PRL) were continuously administered to rats throughout pregnancy. A dose of 6 microg/24 h resulted in circulating concentrations of 50 ng/ml of each administered PRL and had little effect on the pregnancy itself. After birth, pups were killed and various tissues examined. In the pup lungs, exposure to additional PP-PRL caused a reduction in epithelial integrity and an increase in apoptosis, whereas exposure to additional U-PRL had beneficial, anti-apoptotic effects. In the heart, PP-PRL caused an apparent developmental delay, whereas U-PRL promoted tissue compaction. In the blood, U-PRL increased the number of mature red blood cells at the expense of white blood cell production. Within the white blood cell population, myelopoiesis was favored at the expense of lymphopoiesis. PP-PRL, in contrast, had a less dramatic influence on the hematopoietic compartment by promoting red blood cell maturation and granulocyte production. In the thymus, exposure to PP-PRL caused accumulation of apoptotic thymocytes in enlarged glands, whereas exposure to U-PRL resulted in smaller thymi. In the spleen, exposure to U-PRL increased cellularity, with the majority of cells belonging to the erythroid series - a finding consistent with increased red blood cells in the circulation. Exposure to PP-PRL was without discernible effect. In all of these tissues, the contrasting effects of the two PRLs indicate that the absolute concentration of PRL is not crucial, but that the ratio of U-PRL to PP-PRL has a profound effect on tissue development. In brown fat, both PRL preparations decreased the number of lipid droplets. This result is therefore probably a consequence of the increase in total PRL. The results of this study attest to the importance of the U-PRL:PP-PRL ratio normally present during pregnancy and have provided clues as to the possible pathogenesis of a variety of neonatal problems.

Animals↗
PubMed2001

Telomerase activity in primary cultures of normal adrenocortical cells.

Telomerase activity was measured in isolated cells from bovine and human adrenal cortex, in cells in primary culture, in cells in later passages in culture, and in cells genetically modified by expression of hTERT (human telomerase reverse transcriptase). Telomerase activity in freshly isolated bovine adrenocortical cells and in human adrenal cells from donors of various ages (6-79 years) was very low or undetected. However, primary bovine adrenocortical cell cultures were strongly positive for telomerase activity, and primary human adrenocortical cell cultures were weakly positive. Both cell types proliferate in primary culture but proliferation of bovine cells is much more vigorous. When primary bovine cells were subcultured to make successively secondary and tertiary cultures, telomerase activity declined strongly, and was undetected by the third passage. There was only a slight decrease in growth rate over this period. Levels of the telomerase RNA component did not change with passage number when assessed by semi-quantitative competitive RT-PCR. When both bovine and human cells were infected with a retrovirus encoding hTERT, telomerase activity in the cells was very high. We conclude that in the adrenal cortex, as in some other tissues, TERT expression is regulated and upregulation of telomerase activity is associated with rapid proliferation in primary culture. Telomerase activity is not maintained, and introduction of TERT is required for stable telomerase activity and for immortalization.

Adolescent↗
PubMed2001

Serum-free recombinant production of adenovirus using a hollow fiber capillary system.

A novel method for the production of adenoviral vectors on a scale sufficient to support most research applications and early phase clinical trials is presented. This method utilizes serum-free cell culture medium and a hollow fiber cell culture apparatus. Significantly less time and space are required than in conventional methods, and the resulting adenovirus is collected in a much smaller volume, simplifying the purification steps. The protocol described is a reproducible, convenient, biologically safe, and environmentally sound method for the production of adenoviral vectors for laboratory use and has the potential to scale-up the adenovirus production for clinical use.

Adenoviridae↗
PubMed2001

Comparison of a new stent and Wallstent for transjugular intrahepatic portosystemic shunt in a porcine model.

AIM: To evaluate a new balloon-expandable stainless steel stent (Cordis stent) in a transjugular intrahepatic portosystemic shunt (TIPS) porcine model and compared with Wallstent. METHODS: TIPS was performed in 26 normal domestic pigs weighing 20 kg-30 kg using a Cordis stent or Wallstent (13 pigs in each stent). All pigs were sacrificed at the 14th day after TIPS. The stent deployment delivery system, stent patency, and stent recoil after placement were evaluated. Proliferative response in representative histological sections from the center,hepatic and portal regions of the two stent designs were quantified. RESULTS: The shunt was widely patent in 4 pigs in the Cordis stent group (4/12, premature dead in 1 pig), and in 5 pigs in the Wallstent group (5/13). All remaining stents of both designs were occluded or stenotic. The mean quantified proliferation including thickness of the proliferation and the ratio of proliferation: total area in three assayed regions in Cordis stent and Wallstent was 2.18 mm:2.00 mm, and 59.18 mm2:51.66 mm2, respectively (P > 0.05). The delivery system and mechanical properties of the Cordis stent functioned well. CONCLUSION: The new Cordis stent is appropriate for TIPS procedure.

Animals↗
PubMed2001

Induction of topoisomerase II activity after ErbB2 activation is associated with a differential response to breast cancer chemotherapy.

ErbB2 (HER-2) gene amplification and overexpression have been shown to predict a better outcome with doxorubicin-based chemotherapy as opposed to alkylator-based chemotherapy in early stage breast cancer. To understand the mechanism of differential response to these two regimens, we have evaluated the effect of signaling through the ErbB2 receptor on downstream enzymes that may affect drug response, using two different models. The first system employs breast cancer cells that have high levels of endogenous ErbB2 by gene amplification (BT-474 and SKBR3 cells). The second system allows us to isolate the effect of ErbB2 receptor-mediated intracellular signaling using an epidermal growth factor receptor-ErbB2 chimeric receptor activated by epidermal growth factor. Our experiments show that the cytotoxicity of doxorubicin is inhibited in ErbB2+ breast cancer cells by the anti-ErbB2 antibody, Herceptin. This is accompanied by a decrease in topoisomerase (topo) IIalpha protein and activity, suggesting that this is the mechanism of change in doxorubicin response. In addition, a 10-100-fold (1-2 log) decrease in the LD(50) of doxorubicin is seen after ErbB2 activation using the chimeric receptor model. Furthermore, we see a 100-fold decrease in the LD(50) of etoposide, another topo II inhibitor. This increase in doxorubicin sensitivity is associated with a 4.5-fold increase in the amount of topo IIalpha protein and an increase in topo II activity as measured by DNA decatenating and unknotting activities, as well as cleavable complex formation. In contradistinction to doxorubicin, we have observed an increased resistance to cyclophosphamide chemotherapy after chimeric receptor activation. We propose that the differential benefit seen with doxorubicin- versus alkylator-based chemotherapy in ErbB2+ breast cancer is due, in some cases, to ErbB2-mediated topo IIalpha activation. These data also suggest hypotheses for the optimal sequencing of Herceptin and chemotherapy agents in ErbB2+ breast cancer.

3T3 Cells↗
PubMed2001

[Organochlorine residues in eggs of night heron breeding in Yuantouzhu, Wuxi and their functions as bioindicator].

This study analyzed chlorinated pesticides in eggs of night heron breeding in Yuantouzhu, Tai lake. The HCH isomers, DDT, DDD, DDE, endrine and heptachlor epoxide were detected out in egg samples. The residue level and the percent of detection of beta-HCH and p,p'-DDE were significantly high. The mean value of p,p'-DDE was 0.906 microgram/g dry weight. Most of the chlorinated pesticides in samples from Wuxi were higher than those of Gongqing city, Jiangxi province. Oppositely, the hatching rate of night heron egg in Wuxi region was lower than that in Gongqing city. It may be related to the difference of DDE residual levels. Using organochlorine residue in eggs of water-fowls as an indicator for environmental quality assessment is feasible.

Animals↗
PubMed2001

[Overexpression of artificial synthetic gene of Aspergillus niger NRRL3135 phytase in Pichia pastoris].

The phytase gene of Aspergillus niger NRRL3135 was modified with a deletion of intron and signal coding sequence. Then, according to the codon preference of Pichia pastoris, modified phyA gene was artificially synthesized and cloned into expression vector of pPICZ alpha A. The recombinant plasmid was transformed into chromosome of Pichia pastoris X-33 strain by electroporation. The results of SDS-PAGE and enzymatic kinetic analysis proved that the recombinant phytase was secreted into culture medium with nearly same character of natural phytase. After screening for high level productive yeast strains, a strain named SPAN-III produced recombinant phytase with 165,000 u/mL under the condition of shake cultivation. It will satisfy the demand for industrialized production in some degree.

6-Phytase↗
PubMed2001

Arachidonate metabolism and the signaling pathway of induction of apoptosis by oxidized LDL/oxysterol.

Owing at least in part to oxysterol components that can induce apoptosis, oxidized LDL (oxLDL) is cytotoxic to mammalian cells with receptors that can internalize it. Vascular cells possess such receptors, and it appears that the apoptotic response of vascular cells to the oxysterols borne by oxLDL is an important part of the atherogenic effects of oxLDL. Thus, an analysis of the signaling pathway of apoptotic induction by oxysterols is of value in understanding the development of atherosclerotic plaque. In a prior study, we demonstrated an induction of calcium ion flux into cells treated with 25-hydroxycholesterol (25-OHC) and showed that this response is essential for 25-OHC-induced apoptosis. One possible signal transduction pathway initiated by calcium ion fluxes is the activation of cytosolic phospholipase A2 (cPLA2). In the current study, we demonstrate that activation of cPLA2 does occur in both macrophages and fibroblasts treated with 25-OHC or oxLDL. Activation is evidenced by 25-OHC-induced relocalization of cPLA2 to the nuclear envelope and arachidonic acid release. Loss of cPLA2 activity, either through genetic knockout in mice, or by treatment with a cPLA2 inhibitor, results in an attenuation of arachidonic acid release as well as of the apoptotic response to oxLDL in peritoneal macrophages or to 25-OHC in cultured fibroblast and macrophage cell lines.

Animals↗
PubMed2001

[Studies on asymmetric synthesis of R-phenylethanolamine by whole cells of Arachnia sp. P163].

Effects of various factors on asymmetric synthesis of R-phenylaminoethanol from aminoacetophenone by the whole cells of Arachnia sp. P163 producing alcohol dehydrogenase for phenylethanol amine was investigated. It found that, although the reduction was inhibited by the substrate and the product, but it has the very high stereoselectivity. The reduction was normaly carried out with 2% glucose for reproduction of coenzyme in the reaction system without oxygen. The conversion yield and ee value of the product achieved 65% and 100%, respectively.

2-Hydroxyphenethylamine↗
PubMed2001

[Cytokine networks and their endogenous modulators in patients with congestive heart failure].

OBJECTIVE: To explore the pathophysiological role of cytokine network and their endogenous modulators in the development of congestive heart failure (CHF). METHODS: Plasma levels of tumor necrosis factor-alpha (TNF-alpha), interleukin-6(IL-6), soluble TNF receptor I (sTNF-RI) and transforming growth factor (TGF)-beta were measured by enzyme-linked immunoassay in 52 CHF patients with various degrees of heart failure and in 30 healthy controls. RESULTS: Patients with CHF had increased plasma concentrations of TNF alpha, IL-6 and sTNF-RI, but decreased levels of TGF-beta. They also had elevated ratios of TNF-alpha/sTNF-RI and TNF-alpha/TGF-beta, particularly those in functional class IV. The levels of TNF-alpha were positively correlated with IL-6 and sTNF-RI but negatively correlated with TGF-beta(P < 0.01). CONCLUSIONS: The imbalance in the cytokine network were most pronounced in patients with the most severe heart failure. CHF may be accompanied by a shift toward enhanced levels of inflammatory cytokines combined with inadequately raised or even decreased levels of anti-inflammatory cytokines. A poorly regulated cytokine network may be involved in the development and progression of CHF.

Antigens, CD↗
PubMed2001

[An analysis of the clinical and pathological characteristics of mu-tong (a Chinese herb) induced tubulointerstitial nephropathy].

OBJECTIVES: To investigate the clinical and pathological characteristics of Mutong (a Chinese herb, caulis aristolochiae manshuriensis) induced tubulointerstitial nephropathy (MT-TIN), and analyze the related to renal function decline and clinical prognosis. METHODS: 51 patients with MT-TIN were studied retrospectively. They were divided into acute, mild chronic and severe chronic groups according to the pathological lesion. Clinical and pathological data were semi-quantitatively assessed. Correlation and regression of the parameters were further tested. Relationship between medication and the illness, incidence, clinical characteristics, therapy and regression of the disease were analyzed. The results of the acute group of MT-TIN were compared with those of the antibiotics-induced acute tubular necrosis (A-ATN) and acute interstitial nephritis (A-AIN). RESULTS: The common clinical symptoms of MT-TIN were fatigue, polyuria, nocturia, usually accompanied by renal tubular dysfunction with or without an elevated serum creatinine (Scr) level. It was rare to find urine abnormality and anemia in the acute and mild chronic groups. The pathological examination of MT-TIN revealed that there were severe degradation, necrosis and collapse of the renal epithelial cells leaving the basement membrane naked. Regeneration was rarely seen as in A-ATN. Cellular infiltrate in the interstitium was also rarely seen as in A-AIN. However, marked tubular atrophy and early occurrence of diffuse interstitial fibrosis were detected in the chronic groups. Correlation and regression tests showed that the level of Scr correlates obviously with the degree of anemia and renal interstitial fibrosis. After withdrawal of medication containing MT, most patients' Scr level became steady within 2 months. Both the clinical and pathological characteristics were different with those of A-ATN or A-AIN. Most of the patients suffering from MT-TIN got the disease by over-dose or long-term taking of medicines containing Mu-Tong. Few patients had it when taking regular dose of the medicine. CONCLUSION: MT-TIN is a special type of drug-induced tubulointerstitial nephropathy, which is mainly related to over-dose or long-term taking of Mu-Tong, which contains aristolochic acid. One should try to avoid using Mu-Tong containing aristolochic acid and pay attention to monitor the renal function if the medication has to be given.

Adult↗
PubMed2001

Stable clonal expansion of the T-cell receptor V beta 6, V beta 17 and V beta 19 T cells in a cGVHD case using genescan analysis.

OBJECTIVE: To investigate the distribution and clonality of the T-cell receptor (TCR) V beta repertoire in chronic graft versus host disease (cGVHD). METHODS: The complementarity determining region 3 (CDR3) of the TCR beta gene with 24 variable regions was amplified in peripheral blood mononuclear cells drawn from one cGVHD patient after allogenic bone marrow transplantation (allo-BMT) 35, 39, 43 or 45 months respectively, using RT-PCR, to observe the expression of TCR V beta repertoire T cells. The PCR products were further analyzed by genescan to evaluate clonality of T cells. RESULTS: Fourteen or 16 TCR V beta subfamily T cells were detected in each sample of cGVHD case. Oligoclonal T cells were identified in TCR V beta 6, 16, 17, 19 and 21 subfamilies. The stable clonal T cells in all samples were identified in V beta 6, V beta 17 and V beta 21 subfamilies. CONCLUSION: Skewing distribution and stable clonal expansion of T cells can be found in cGVHD cases and it may be related to the initiation of cGVHD.

Adult↗
PubMed2001

An epidemiological survey on neonatal jaundice in China.

OBJECTIVE: To provide epidemiological data for revising the diagnostic criteria of neonatal hyperbilirubinemia in China. METHODS: A survey was performed among full-term infants in multiple centers throughout the country. From less than 24 hours after birth, the infants' bilirubin levels were measured every day until the peak level fell to less than 68.4 mumol/L. Auditory brainstem responses were assessed in 56 infants randomly chosen from those with serum bilirubin levels of higher than 220.5 mumol/L. RESULTS: Jaundice in most infants was detected at 2-3 days after birth. The bilirubin level usually reached a peak level of 204 +/- 54.69 mumol/L at 5 days after birth and then fell. Among the 875 infants, the serum bilirubin levels in 34.4% of neonates were higher than 220.5 mumol/L. The mean serum bilirubin level of the infants during the first week after birth varied with geography (P < 0.001) and season (P < 0.001). The serum bilirubin level was significantly associated with gestation age (P < 0.01), delivery method (P < 0.01), weight loss (P < 0.001), and PCV elevation (P < 0.001) during the first three days after birth. CONCLUSIONS: The start time of neonatal jaundice was similar to that reported elsewhere, but the mean peak level in our study was higher than the reported. It is suggested that the diagnostic criteria for neonatal hyperbilirubinemia in China should be strict.

Bilirubin↗
PubMed2001

Genetic analysis of wild-type hepatitis A virus strains.

OBJECTIVE: To clarify the distribution of hepatitis A virus (HAV) genotype in geographical regions of China. METHODS: Seventeen representative HAV strains were isolated from the stool or serum of hepatitis A patients in different geographical regions. Viral RNA was recovered from stool or serum by proteinase K digestion and phenol-chloroform extraction, followed by ethanol precipitation prior to reverse transcription and polymerase chain reaction (RT-PCR) amplification. The nucleotide sequences of VP1/2A junction region were tested by using a direct sequencing technique. RESULTS: A pairwise comparison of sequences within 168 bases at the VP1/2A junction revealed that all the sequences clustered within genotype I. About 53% of strains clustered in genotype I B, with less than 6% variability; while the others clustered in genotype I A, with less than 5.3% variability. Sequence homology between genotype I A and I B varied from 88.7% to 92.3%. CONCLUSION: Epidemic or sporadic HAV strains in China may belong to HAV genotype I A or I B. Epidemiologically related strains may be identical or closely related in sequence.

Genotype↗
PubMed2001

[Changes of the expression of integrin alpha6beta1 and the activity of focal adhesion kinase in the liver sinusoidal endothelial cell in experimental fibrotic rats].

OBJECTIVE: To investigate the expression of integrin alpha(6)beta(1) and the activity of focal adhesion kinase (FAK) in liver sinusoidal endothelial cells (SECs) from experimental fibrotic rats induced by CCl(4). METHODS: By in situ collagenase perfusion and two-step Percoll gradient centrifugation, SECs were isolated and cultured from normal and CCl(4) -treated Wistar rats. The expression of integrin alpha(6)beta(1) was determined by cell-ELISA, and the activity of FAK was assessed by immunoprecipitation-tyrosine kinase assay. RESULTS: The integrin alpha(6)beta(1) was almost absent in the normal SECs and was up-regulated during the fibrotic process; SECs from experimental fibrotic rats possessed higher expression level of integrin alpha(6)beta(1) than normal SECs (P<0.05). The FAK activity in SECs from experimental fibrotic rats increased significantly as compared with the normal controls (P<0.05). CONCLUSIONS: The expression of integrin alpha(6)beta(1) on SECs and the increase of FAK in SECs may be important in the phenotype and function changes of SECs during hepatic fibrogenesis.

Animals↗
PubMed2001

[The clinical effect of Tropisetron in the prevention of nausea and vomiting induced by anti-cancer drugs].

OBJECTIVE: To compare the efficacy and adverse effects of Tropisetron with Kytril in the prevention of nausea and vomiting induced by anti-cancer drugs. METHODS: In a clinical randomized controlled cross-over trial, 34 patients (19 among them treated with regimens containing cisplatin) were randomized into A and B group. In group A, Tropisetron was given in the first cycle and Kytril in the second cycle, while in group B Kytril was given in the first and Tropisetron in the second cycle of the same chemotherapy. RESULTS: In the Tropisetron treated group, the response rate was 97.1% with 4.5 episodes of vomiting on the first day of chemotherapy, while that in the Kytril treated patients was 94.1% with 3 episodes of vomiting. There was no statistical difference between the 2 groups. Control of delayed emesis and other adverse reactions were comparable in both arms and there was no notable difference between Tropisetron and Kytril. CONCLUSION: Tropisetron is an effective anti-emetic drug to prevent nausea and vomiting caused by anti-tumor agents, and its adverse reactions are mild.

Adolescent↗