Search PubMed⌕ Search

Biomedical subjects

Z Shao

Publications and source records attributed to Z Shao.

At least 73 records · Page 4Linked to original sources
PubMed1999

A different approach to treatment of phenylketonuria: phenylalanine degradation with recombinant phenylalanine ammonia lyase.

Phenylketonuria (PKU), with its associated hyperphenylalaninemia (HPA) and mental retardation, is a classic genetic disease and the first to have an identified chemical cause of impaired cognitive development. Treatment from birth with a low phenylalanine diet largely prevents the deviant cognitive phenotype by ameliorating HPA and is recognized as one of the first effective treatments of a genetic disease. However, compliance with dietary treatment is difficult and when it is for life, as now recommended by an internationally used set of guidelines, is probably unrealistic. Herein we describe experiments on a mouse model using another modality for treatment of PKU compatible with better compliance using ancillary phenylalanine ammonia lyase (PAL, EC 4.3.1.5) to degrade phenylalanine, the harmful nutrient in PKU; in this treatment, PAL acts as a substitute for the enzyme phenylalanine monooxygenase (EC 1.14.16.1), which is deficient in PKU. PAL, a robust enzyme without need for a cofactor, converts phenylalanine to trans-cinnamic acid, a harmless metabolite. We describe (i) an efficient recombinant approach to produce PAL enzyme, (ii) testing of PAL in orthologous N-ethyl-N'-nitrosourea (ENU) mutant mouse strains with HPA, and (iii) proofs of principle (PAL reduces HPA)-both pharmacologic (with a clear dose-response effect vs. HPA after PAL injection) and physiologic (protected enteral PAL is significantly effective vs. HPA). These findings open another way to facilitate treatment of this classic genetic disease.

Animals↗
PubMed1999

Cyclin D1 associates with the TBP-associated factor TAF(II)250 to regulate Sp1-mediated transcription.

We have previously shown that Sp1-mediated transcription is stimulated by Rb and repressed by cyclin D1. The stimulation of Sp1 transcriptional activity by Rb is conferred, in part, through a direct interaction with the TBP-associated factor TAF(II)250. Here we investigated the mechanism(s) through which cyclin D1 represses Sp1. We examined the ability of cyclin D1 to regulate transcription mediated by Gal4-Sp1 fusion proteins, which contain the Gal4 DNA-binding domain and Sp1 trans-activation domain(s). The domain of Sp1 sufficient to confer repression by cyclin D1 was mapped to a region important for interaction with TAF(II)110. We further demonstrate that TAF(II)250-cyclin D1 complexes can be immunoprecipitated from mammalian and baculovirus-infected insect cells and that recombinant GST-TAF(II)250 (amino acids 1-434) associates with cyclin D1 in vitro. Moreover, the overexpression of Rb or CDK4 reduced the level of TAF(II)250-cyclin D1 complex. The amino terminus of cyclin D1 (amino acids 1-100) was sufficient for association with TAF(II)250 and for repressing Sp1-mediated transcription. Taken together, the results suggest that cyclin D1 may regulate transcription by interacting directly or indirectly with TAF(II)250.

3T3 Cells↗
PubMed1999

Parallel electron energy-loss spectroscopy free from gain variation.

A new method is presented for removing the effect of the gain variation of parallel detectors used for the quantitation of trace elements with electron energy loss spectroscopy (EELS). Use of the ratio of two first-difference spectra eliminates the effect of gain variation of the detector, therefore eliminating the need for gain normalization and dark current subtraction. This method is particularly suitable for revealing small signals superimposed on a large background, a typical scenario for trace element quantitation of both biological and inorganic materials. This method has been tested on a system with a cooled CCD camera as the parallel detector and illustrated by the analysis of low concentration Ca in an organic matrix. The method is expected to be generally applicable to spectral analysis affected by gain variations of parallel detectors.

Calcium↗
PubMed1999

Calcium Quantitation with a Parallel Electron Energy Loss Spectroscopy/Cooled Charge-Coupled Device/200 keV System.

: We evaluated factors affected the accuracy and precision of quantitating trace concentration of Ca with electron energy loss spectroscopy (EELS). These factors include internal reflection in the spectrometer, precision of correlation between standards and experimental spectra, and radiation damage-induced spectral changes. We present methods of correcting for these effects and improving the reliability of trace Ca quantitation. A two-step fitting procedure is described that improves the retrieval of small Ca signals from the large background common to biological specimens. After optimizing the experimental conditions and data processing procedures, our current system can detect about 2.2 mmol/kg Ca in a 730-Å thick specimen at a total dose of about 410 nA. sec at 95% confidence level by fitting the first difference spectra. Because of the 0.1% residual gain variation after gain normalization, the first difference spectrum fitting is still the preferred method for trace Ca quantitation. Our study also demonstrates the clear advantage of using a 200 keV system, instead of 120 keV or lower accelerating voltages, for EELS analysis of relatively thick biological cryosections.

Journal Article↗
PubMed1999

Role of reactive oxygen species in acetylcholine-induced preconditioning in cardiomyocytes.

We examined the ability of ACh to mimic ischemic preconditioning in cardiomyocytes and the role of ATP-sensitive potassium (KATP) channels and mitochondrial reactive oxygen species (ROS) in mediating this effect. Chick embryonic ventricular myocytes were studied in a flow-through chamber while flow rate, pH, PO2, and PCO2 were controlled. Cell viability was quantified with propidium iodide (5 microM), and production of ROS was measured using 2', 7'-dichlorofluorescin diacetate. Data were expressed as means +/- SE. Preconditioning with 10 min of ischemia followed by 10 min of reoxygenation or 10 min of ACh (1 mM) followed by a drug-free period before 1 h of ischemia and 3 h of reoxygenation reduced cell death to the same extent [preconditioning 19 +/- 2% (n = 6, P < 0.05) ACh 21 +/- 5% (n = 6, P < 0.05) vs controls 42 +/- 5% (n = 9)]. Like preconditioning, ACh increased ROS production threefold before ischemia [0.60 +/- 0.16 (n = 7, P < 0.05) vs. controls, 0.16 +/- 0. 03 (n = 6); arbitrary units]. Protection and increased ROS production during ACh preconditioning were abolished with 5-hydroxydecanoate (5-HD, 100 microM), a selective mitochondrial K(ATP) channel antagonist, and the thiol reductant 2-mercaptopropionyl glycine (2-MPG, 1 mM), an antioxidant [cell death: 5-HD+ACh 37 +/- 7% (n = 5), 2-MPG+ACh 47 +/- 6% (n = 6); ROS signals: 5-HD+ACh 0.09 +/- 0.03 (n = 5), 2-MPG+ACh 0.01 +/- 0.04 (n = 4)]. In addition, ACh-induced ROS signaling was blocked by the mitochondrial site III electron transport inhibitor myxothiazol (0.02 +/- 0.07, n = 5). These results demonstrate that activation of mitochondrial K(ATP) channels and increased ROS production from mitochondria are important intracellular signals that participate in ACh-induced preconditioning in cardiomyocytes.

Acetylcholine↗
PubMed1999

Role of GABAB receptor-mediated inhibition in reciprocal interareal pathways of rat visual cortex.

In neocortex, synaptic inhibition is mediated by gamma-aminobutyric acid-A (GABAA) and GABAB receptors. By using intracellular and patch-clamp recordings in slices of rat visual cortex we studied the balance of excitation and inhibition in different intracortical pathways. The study was focused on the strength of fast GABAA- and slow GABAB-mediated inhibition in interareal forward and feedback connections between area 17 and the secondary, latero-medial visual area (LM). Our results demonstrate that in most layer 2/3 neurons forward inputs elicited excitatory postsynaptic potentials (EPSPs) that were followed by fast GABAA- and slow GABAB-mediated hyperpolarizing inhibitory postsynaptic potentials (IPSPs). These responses resembled those elicited by horizontal connections within area 17 and those evoked by stimulation of the layer 6/white matter border. In contrast, in the feedback pathway hyperpolarizing fast and slow IPSPs were rare. However weak fast and slow IPSPs were unmasked by bath application of GABAB receptor antagonists. Because in the feedback pathway disynaptic fast and slow IPSPs were rare, polysynaptic EPSPs were more frequent than in forward, horizontal, and interlaminar circuits and were activated over a broader stimulus range. In addition, in the feedback pathway large-amplitude polysynaptic EPSPs were longer lasting and showed a late component whose onset coincided with that of slow IPSPs. In the forward pathway these late EPSPs were only seen with stimulus intensities that were below the activation threshold of slow IPSPs. Unlike strong forward inputs, feedback stimuli of a wide range of intensities increased the rate of ongoing neuronal firing. Thus, when forward and feedback inputs are simultaneously active, feedback inputs may provide late polysynaptic excitation that can offset slow IPSPs evoked by forward inputs and in turn may promote recurrent excitation through local intracolumnar circuits. This may provide a mechanism by which feedback inputs from higher cortical areas can amplify afferent signals in lower areas.

Animals↗
PubMed1999

AFM tips: how sharp are they?

From both simple estimates and a 'blind' reconstruction based on cryo-AFM images of filamentous actin, we find that the radius of curvature at the apex of Si3N4 tips can be as small as 1 nm with a conical angle in the range 30 approximately 40 degrees, revealing a relatively high aspect ratio that is much greater than previously anticipated. Our results show that commercially available cantilevers are often sharp enough for routine high resolution imaging of biological materials, and suggest that factors other than an inherent blunt tip are probably responsible for frequent occurrences of poor resolution.

Actins↗
PubMed1999

[Immunophenotyping in myelodysplastic syndromes].

OBJECTIVE: To evaluate the values of immunophenotyping in the diagnosis and prognosis of myelodysplastic syndromes (MDS). METHODS: Surface markers of mononuclear marrow cells were analyzed by indirect immunofluorescence for a panel of monoclonal antibodies in 32 patients with MDS. RESULTS: Expression of myeloid antigen increased significantly while lymphoid antigen decreased. The antigen expression was correlated with the FAB subtype of MDS, Immature myeloid cells (CD13+, CD33+) was being increased and the lymphoid antigen expression decreased with the RA/RAS evolving to RAEB and RAEB-t. Compared with normal marrow, the number of CD34+ cells was not significantly different in RA/RAS subtypes but significantly higher in RAEB/RAEB-t subtypes. The expression of early marrow cell antigens (CD38, HLA-DR, CD99R and CD9) was significantly increased. The expression of CD34 and other early antigen was predictive for transformation and poor survival. CONCLUSION: Surface marker analysis of mononuclear marrow cells may be a useful tool for the diagnosis and prognosis of MDS.

Adult↗
PubMed1999

[Human breast myoepithelial cell blocks estrogen receptor-negative breast carcinoma cell invasion].

OBJECTIVE: To investigate the effect of mammary myoepithelial cell on breast cancer cell infiltration. METHODS: By immunohistochemistry, Western Blot, Northern Blot and Matrigel invasion experiments, we detected the maspin in breast cancer cell and myoepithelial cell, and studied the machanism of breast cancer cell invasion inhibition by myoepithelial cell. RESULTS: Histologically, ducts and ductal carcinoma in situ (DCIS) were surrounded by an intact circumferential layer of myoepithelial cells. In invasive carcinoma, the myoepithelial cell layer appeared disrupted. In matrigel invasion experiments, myoepithel cell and its condition medium could block the ER-negative breast carcinoma cell line MDA-MB-231 cell invasion. The proteinase inhibitor most dramatically up-regulated in myoepithelial cells was the tumor suppressor maspin which was only highly expressed in myoepithelial cells, not in breast cancer cells. CONCLUSION: Mammary myoepithelial cells could inhibit tumor cell invasion, suggesting that myoepithelial cell might have antitumor effect in the regulation of breast cancer development and progression in vivo.

Breast↗
PubMed1999

[Antilymphocyte globulin combining with cyclosporine A in the treatment of severe aplastic anemia].

OBJECTIVE: To explore more effective regimen for severe aplastic anemia (SAA). METHODS: A prospective, randomized clinical trial was conducted to determine whether the outcome of SAA patients treated with the combination of antilymphocyte globulin(ALG) and cyclosporine A(CsA) (intensive immunosuppressive therapy, IIST) was better than that with ALG alone (non-intensive immunosuppressive therapy, NIIST). RESULTS: The response rate of IIST group(83.7%) was significantly higher than that of NIIST group(57.6%), with a lower risk of early mortality and a shorter time to red cell transfusion independence. Furthermore, the recovery of bone marrow BFU-E and CFU-GM of the responding patients was more complete in IIST group than in NIIST group. CONCLUSIONS: The treatment outcome was better with IIST than with NIIST for SAA.

Adolescent↗
PubMed1999

Subclasses of warm autoantibody IgG in patients with autoimmune hemolytic anemia and their clinical implications.

OBJECTIVE: To explore the mechanism of autoimmune hemolysis and establish a more sensitive test for autoimmune hemolytic anemia (AIHA). METHODS: IgG subclasses were tested in 40 patients with idiopathic or secondary AIHA by Coombs test with monoclonal antibodies. Hb, TBil, RC and FHb, as hemolytic parameters, were used to analyze the clinical implications of subclasses of AIHA warm autoantibody IgG. RESULTS: In most patients IgG incomplete warm autoantibody was IgG1 (27 patients), but IgG3 (20 patients), rarely IgG2 (14 patients) and IgG4 (9 patients) also occurred. Three groups were analyzed: Group A included 20 patients with IgG3; Group B included 14 patients with IgG1 bit without IgG3; Group C included 6 patients without IgG1 and IgG3. There were significant differences (P < 0.01) between groups in Hb, TBil, RC and FHb. Moreover, we also found that the sensitivity of Coombs test with polyclonal antiserums was 90.0%, while that of Coombs test with monoclonal antibodies was 97.5%. The effect of treatment was worst in patients with positive IgG3 autoantibody, whose hemolysis recurred frequently. CONCLUSION: IgG3 autoantibody was the most effective in bringing about red cell destruction, IgG1 autoantibody was less effective, IgG2 even less, whereas IgG4 autoantibody was shown to hardly affect red cell survival. Coombs test with monoclonal antibodies was more sensitive than that with polyclonal antiserums. Patients' respondence to treatment correlated with the type of IgG subclasses.

Adult↗
PubMed1999

[The clinical implications of IgG subclass in 84 patients with autoimmune hemolytic anemia].

OBJECTIVE: To evaluate the clinical implications of IgG subclass in autoimmune hemolytic anemia(AIHA). METHODS: Data of 84 AIHA patients were retrospectively analyzed. RESULTS: In the 84 patients, IgG1 + IgG3 + C3d accounted for 45.0%, IgG1 + IgG3 15.5%, IgG1 + C3d 11.0%, C3d 10.7%, IgG1 9.5% and IgG3 + C3d 8.3%. IgG3 patients had the most severity of clinical and laboratory findings, followed by IgG1 patients. In IgG1 and IgG3 subgroups, the severity of hemolysis was positively correlated with the score of Coombs' test. The response rates of IgG3 and IgG1 patients were 68.2% and 100%, respectively. CONCLUSION: In AIHA, the basic predominant IgG subclass is IgG1. IgG3 has a greater potential for red-cell destruction than IgG1 and C3d.

Adolescent↗
PubMed1999

[In vitro proliferation and differentiation of bone marrow stem cells of aplastic anemia patients].

OBJECTIVE: To investigate the quality of bone marrow stem cells from aplastic anemia patients and their in vitro responses to hemopoietic growth factors(HGF). METHODS: CD34 positive bone marrow cells from 10 chronic aplastic anemia(CAA), 5 severe aplastic anemia(SAA) patients and 5 healthy subjects were detected with immunoflurescence assay, enriched by Panning way, and then cultured in vitro for CFU-GM, BFU-E and CFU-E in the presence of recombinant HGFs. RESULTS: CD34 positive rates of the bone marrow mononuclear cells(MNC) of CAA, SAA and control groups were (1.05 +/- 0.51)%, (0.70 +/- 0.37)% and (1.27 +/- 0.45)%, respectively, and there was no difference among them (P > 0.05). After being enriched, CD34 positive cells in MNC of CAA, SAA and control groups increased to a similar level(P > 0.05). In the presence of G-CSF or GM-CSF, the enriched CD34 positive MNC of CAA and SAA patients formed similar CFU-GM number to those of normal controls. The numbers of BFU-E and CFU-E formed from the enriched CD34 positive MNC of CAA and SAA patients were also the same as that of normal control groups under the stimulation of erythropoietin and interleukin-3. Stem cell factor could cooperate with G-CSF, GM-CSF, and erythropoietin significantly increasing the numbers of CFU-GM, BFU-E and CFU-E of CAA, SAA and normal control's enriched CD34 positive MNC. CONCLUSION: The bone marrow CD34 positive cells from aplastic anemia patients appears to be normal in percentages and in in vitro proliferation/differentiation capacities.

Adolescent↗
PubMed1999

[Expression of c-kit receptor on the hemopoietic stem/precursor cells of aplastic anemia patients].

OBJECTIVE: To explore the expression of c-kit receptor(CD117) on the hemopoietic stem/precursor cells of aplastic anemia patients and its role in the genesis of aplastic hematopoiesis failure. METHODS: c-kit expression on the bone marrow mononuclear cells(MNC) and CD34 positive cells from 11 chronic aplastic anemia (CAA), 9 severe aplastic anemia(SAA), 10 non-aplastic anemia(NAA) patients (5 iron deficiency anemia and 5 autoimmune hemolytic anemia) and 5 healthy controls was measured with flow cytometric immunofluorescence assay and anti-CD117 monoclonal antibody. RESULTS: The CD117 positive rates of MNC in CAA, SAA, NAA and control groups were (2.08 +/- 1.96)%, (0.89 +/- 0.32)%, (0.67 +/- 0.39)% and (0.45 +/- 0.16)%, respectively, and the rates were significantly higher in CAA and SAA groups than in NAA and control groups(P < 0.05). The CD117 and CD34 double positive cells of MNC in CAA, SAA, NAA and control groups were (0.87 +/- 0.57)%, (0.65 +/- 0.41)%, (0.46 +/- 0.26)% and (0.41 +/- 0.15)%, respectively, and were significantly higher in CAA and SAA groups than in NAA and control groups (P < 0.05). The CD117 positive cells of CD34 positive cells were also higher in CAA[(71.6 +/- 12.4)%] and SAA[(88.9 +/- 23.5)%] groups than in NAA[(41.8 +/- 10.3)%] and control [(46.3 +/- 9.7)%] groups (P < 0.01). CONCLUSION: Hemopoietic stem/precursor cells of aplastic anemia patients expressed more c-kit receptors than those of NAA patients and healthy controls. The hematopoiesis failure occurred in aplastic anemia is not attributed to low expression of c-kit receptor on the hemopoietic stem/precursor cells.

Adolescent↗
PubMed1999

Evi-1 and MDS1-Evi-1 genes in pathogenesis of myelodysplastic syndromes and post-MDS acute myeloid leukemia.

OBJECTIVE: To investigate expression of Evi-1 and MDS1-Evi-1 genes in myelodysplastic syndromes (MDS) and post-MDS acute myeloid leukemia (post-MDS AML), and its role in pathogenesis or progression of MDS and post-MDS AML. METHODS: Expression of Evi-1 and MDS1-Evi-1 genes was examined in 31 MDS, 11 post-MDS AML, and 34 de novo AML patients by a semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: Evi-1 expression was not detected in bone marrow samples of 8 normal controls, but low MDS1-Evi-1 expression levels (MDS1-Evi-1/GAPDH < 0.1) were detected in 3 of the 8 controls. Evi-1 RNA was expressed in 1 of 8 RA, 8 of 13 RAEB and 6 of 9 RAEB-T patients, and the percentage of Evi-1 expression in RAEB(T) patients was higher than that in RA (P < 0.05). MDS1-Evi-1 expression was detected in 5 of 8 RA, 9 of 13 RAEB and 5 of 9 RAEB-T patients, and MDS1-Evi-1 expression levels (MDS1-Evi-1/GAPDH > 0.1) were markedly higher than those in the controls. Evi-1 expression was gradually increased in 4 of 5 RAEB-T patients with transformation from MDS to AML. The percentages of Evi-1 and MDS1-Evi-1 expression in post-MDS AML patients were significantly (P < 0.01 and P < 0.05 respectively) higher than those in de novo AML. The colonies of hematopoietic progenitor cells were decreased in Evi-1 and MDS1-Evi-1-positive MDS patients as compared with those in Evi-1 and MDS1-Evi-1-negative patients. CONCLUSION: Abnormal expression of the Evi-1 gene and overexpression of MDS1-Evi-1 gene may play a role in the pathogenesis or progression of MDS and post-MDS AML.

Adult↗