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Biomedical subjects

A Liu

Publications and source records attributed to A Liu.

At least 127 records · Page 7Linked to original sources
PubMed1999

A method for patient-specific absorbed dose estimation for internal beta emitters.

The purpose of the study was to determine a technique for estimating patient-specific absorbed radiation doses in radioimmunotherapy and other internal emitter therapies. Beta Radiation sources were considered, with 90Y being the radionuclide of primary interest. Organ uptake of activity was determined using a merged set of computed tomography and planar nuclear images. Estimation of local absorbed dose was accomplished using a voxel source kernel. Voxel size was 0.2 x 0.2 x 0.5 cm; dimensions were from the digital resolution of the nuclear and computed tomography data sets. Dose-volume histograms were also obtained due to the voxel nature of the estimations. Organ dose estimates were made for two patients receiving the chimeric anticarcinoembryonic antigen antibody cT84.66. Considerable variation was observed when comparing the voxel kernel results with medical internal radiation dosimetry values obtained via the MIRDOSE3 program. Primary uncertainty in the organ dose estimates was determined to be due to the variation in organ mass. By correcting the S values in that program by the organ mass ratio, we found generally good agreement between our method and MIRDOSE3. We conclude that patient-specific absorbed doses can be estimated for 90Y-labeled antibodies.

Beta Particles↗
PubMed1999

Initial clinical experience evaluating Yttrium-90-chimeric T84.66 anticarcinoembryonic antigen antibody and autologous hematopoietic stem cell support in patients with carcinoembryonic antigen-producing metastatic breast cancer.

cT84.66 is a human/murine IgG1 with high affinity and specificity for carcinoembryonic antigen (CEA). An earlier Phase I trial defined the maximum tolerated dose for 90Y-diethylenetriaminepentaacetic acid (DTPA)-cT84.66 at 22 mCi/m2. Dose-limiting toxicities were reversible leukopenia and thrombocytopenia. The purpose of this Phase I trial was to evaluate the feasibility and toxicities of administering higher activities of 90Y-DTPA-cT84.66 with stem cell support in patients with CEA-producing breast cancer. Patients with CEA-producing breast cancer refractory to standard therapies underwent peripheral stem cell collection followed by infusion of 111indium-DTPA-cT84.66. Those patients demonstrating tumor targeting received a single therapy dose of 90Y-DTPA-cT84.66, followed by Ca-DTPA infusion for 72 h posttherapy. Stem cells were reinfused following a divided schedule. To date, seven patients have been accrued to this trial. Each patient received an imaging dose of (111)In-cT84.66. Six patients demonstrated tumor imaging and received a single cycle of 90Y-cT84.66 at 15 mCi/m2 (three patients) and 22.5 mCi/m2 (three patients). One patient did not demonstrate tumor imaging and was not treated. At these administered activities, 90Y-cT84.66 was well tolerated. No dose-limiting toxicities have been observed. All patients demonstrated hematopoietic recovery after stem cell infusion. One patient demonstrated stable disease for 4 months; one patient had stable disease and reduction of bone pain for 3 months; and a third patient experienced >50% reduction of an ovarian metastasis, resolution of malignant pleural effusion, stable pleural metastases, and stable bone scan for 14 months. Preliminary results from this ongoing Phase I trial are promising and demonstrate the feasibility and potential for antitumor effects of stem cell supported 90Y-cT84.66 therapy in patients with CEA-producing breast cancers.

Animals↗
PubMed1999

A comparison of the preventive effects of lanthanides and fluoride on human experimental root surface carious-like lesions.

OBJECTIVE: To investigate the mechanisms of lanthanides prevention of human root surface carious-like lesions and to compare the effectiveness of lanthanum (La) with that of cerium (Ce) and fluoride (F). Various treatment procedures were also compared. MATERIALS AND METHODS: Acetic buffers containing lanthanum, cerium, and fluoride (500 ppm) were used individually or in combination to treat 48 cementum-dentin samples. The acid-resistant capacity of various treatment procedures was evaluated by means of scanning electron microscope, electron microprobe, and polarizing light microscope analyses. RESULTS: The acid-resistant effects of lanthanide element were comparable to those of fluoride, and their acid-resistant effects were even stronger when combined with fluoride and cerium. These effects are likely due to the formation of La(Ce)HAP, FLa(Ce)HAP, and lanthanum/cerium phosphate compounds. CONCLUSION: Combined F/La(Ce) was more effective in the prevention of root surface caries than were lanthanides alone.

Acetic Acid↗
PubMed1999

Relationship between fossa-condylar position, meniscus position, and morphologic change in patients with Class II and III malocclusion.

OBJECTIVE: To evaluate fossa-condylar-meniscus morphologic changes in patients with skeletal and dental Class III and Class II division 1 and 2 malocclusion to determine which type is related to internal derangement of the temporomandibular joint (TMJ) and whether the variation of TMJ structure is related to a particular type of malocclusion. MATERIALS AND METHODS: Seventy-two pretreatment orthodontic patients, ranging in age from 10 to 27 years, underwent examination of the right and left TMJs with corrected Schöller's position radiographs. Bilateral TMJ relationships of the fossa-condyle were examined through subjective evaluation and linear and area measurements. In addition, in 20 of the 72 patients, meniscus positions and morphologic changes were imaged with a 0.5 T sagittal magnetic resonance imaging system on the right and left TMJ. RESULTS: (1) The variation of condyle-fossa positions for identical types of malocclusion was very large. (2) Skeletal and functional Class III malocclusion patients demonstrated significantly more anteriorly positioned condyles. (3) Class II division 1 patients showed concentrically positioned condyles, but with slightly anterior displacement. (4) Class II division 2 patients demonstrated more posteriorly positioned condyles. (5) When condyles were in anterior or concentric positions, meniscus positions and morphology were normal and in concavoconcave shapes. (6) When condyles were in posterior positions, most meniscus positions were in normal or slightly anterior range and their shapes were also concavoconcave. The rest were significantly more anterior and their shapes were abnormal, as evidenced by thickened anterior bands. CONCLUSION: Class III and Class II division 1 malocclusion demonstrated normal structure and function of the TMJ. Class II division 2 malocclusion was obviously associated with abnormal structure and function of the TMJ.

Adolescent↗
PubMed1999

Dendritic cells stimulate the expansion of PML-RAR alpha specific cytotoxic T-lymphocytes: its applicability for antileukemia immunotherapy.

Dendritic cells (DC), the most potent "professional" antigen-presenting cells, hold promise for improving the immunotherapy of cancer. In this study, we investigated the ability of normal donor DC pulsed ex vivo with 12 mer PML-RAR alpha (A) peptide (SGAGEAAIETQS) to generate peptide specific autologous cytotoxic T-lymphocytes. The peptide pulsed DC-primed peripheral blood lymphocytes (PBL) displayed significantly higher cytotoxic activity compared with that of peptide non-pulsed DC-primed PBL against peptide-pulsed autologous macrophages (P<0.001). Both CD8+ and CD4+ T lymphocytes were involved in the effector cell populations. The PML-RAR alpha peptide-pulsed DC-primed T-cells were significantly superior in their production of GM-CSF and TNF-alpha, compared with peptide non-pulsed DC-primed T-cells. These intriguing preclinical studies, suggest that PML-RAR alpha pulsed-DC could be a promising immunotherapeutic modality for patients with acute promyelocytic leukemia.

CD4-Positive T-Lymphocytes↗
PubMed1999

[The effect of EBNA-1 ribozyme on the ability of tumor genesis of lymphoblastoid cell lines in SCID mice].

OBJECTIVE: To explore the effect of EBNA-1 specific ribozyme on the tumor genesis ability of lymphoblastoid cell lines (LCLs) in severe combined immunodeficiency (SCID) mice. METHODS: Using molecular cloning technique, recombinant adenovirus vectors expressing EBNA-1 ribozyme (RZ1) or its inactive mutant (RZ1mut) were constructed as Ad.RZ1 or Ad.RZ1mut. Recombinant adenoviruses were generated by homologous recombination and isolated by plaque formation. LCLs were established and infected with recombinant adenovirus and then injected in SCID mice (1 x 10(7) cells/animal). The SCID mice were sacrificed six weeks after injection, then the tumors were excised from these mice and their size and weight were measured. The expression of EBNA-1 ribozyme and EBNA-1 mRNA in the tumor was analyzed by RT-PCR, and the expression of EBNA-1 protein in the tumor was detected by Western blot. RESULTS: The tumors (0.27 +/- 0.18) g formed from the Ad.RZ1-treated LCLs were much smaller than those of the untreated LCLs (1.04 +/- 0.27) g or LCLs treated with control vector of adenovirus (1.12 +/- 0.32) g (P < 0.01), and also smaller than those of Ad.RZ1mut-treated LCLs (0.76 +/- 0.28) g (P < 0.05). The expression of EBNA-1 mRNA and protein in the tumors of Ad.RZ1-treated LCLs decreased significantly than that of other groups. CONCLUSIONS: Adenovirus delivery of EBNA-1 ribozyme was able to suppress LCL tumors significantly and depress the tumor genesis ability of B lymphocyte induced by EBV.

Adenoviruses, Human↗
PubMed1999

[The role of activation of p38 MAPK induced by LPS in TNF-alpha gene expression].

OBJECTIVE: To study the molecular mechanisms of TNF-alpha expression induced by LPS for the exploring of novel methods to prevent and treat clinical patients of endotoxic shock. METHODS: Protein kinase assay was used to detect the kinase activity stimulated by LPS; Confocal laser scan technique was used to show the translocation of p38 on the activation; RT-PCR and reporter gene system were used to study the molecular mechanism of TNF-alpha gene transcription. RESULTS: In RAW cells, p38 was activated on the stimulation of LPS, and activated p38 moved into nucleus from cytosol. TNF-alpha mRNA increased on the stimulation of LPS and the increased promoter transactivity induced by LPS could be inhibited significantly by specific inhibitor for p38. CONCLUSION: p38 MAPK was activated on the stimulation of LPS, which brought about its translocation to the nucleus to act on transcription factors to regulate cellular processes. p38 MAPK is an important regulator of TNF-alpha gene expression induced by LPS.

Cells, Cultured↗
PubMed1999

[PCR for the detection of 16S rRNA gene bacteria].

According to the high conservative region of 16S rRNA gene in bacteria, PCR primers of the broad-range bacteria, gram-positive bacteria and gram-negative bacteria were synthesized to detect 13 bacterium species and (40) clinical specimens. All the tested bacterium species were positive. The lowest concentration of Escherichia Coli detected by serial dilution was 4 CFU.ml-1. The positive rate of PCR (27/40) was higher than that of bacterium culture(18/40). The results indicate that these PCR primers possess high specificity and sensitivity in identifying 16S rRNA gene of bacteria.

Bacteriuria↗
PubMed1999

[Determination of TNF-alpha and endotoxemia in patients with chronic liver diseases].

The incidence of endotoxemia in 153 patients with different liver diseases was determined by Limulus Lysaite Test(LLT). Comparative studies were carried out on the levels of tumour necrosis factor-alpha(TNF-alpha) between positive and negative endotoxemia in patients suffering from chronic liver diseases. At the same time, 58 patients of positive endotoxemia were divided into two groups--bifidobiogen group (38 cases) and control group(20 cases). The patients in bifidobiogen group were treated mainly with daily administration of bifidobiogen for 1 month besides general liver--protection therapy and the bifidobiogen was not given to the control group. The results showed that: 1. Incidence of endotoxemia in 153 patients suffering from various types of liver diseases was 65.36%; the highest rate was found in the patients with severe hepatitis; 2. The TNF-alpha level was obviously increased in the patients of positive endotoxemia; 3. The total efficacy in bifidobiogen group was significantly higher than that in control group. The data suggest that chronic liver diseases are generally complicated with endotoxemia, and TNF-alpha plays an important role in the pathogenesis of endotoxemia. The serum endotoxin level may be reduced after the treatment with bifidobiogen.

Adult↗
PubMed1999

[A wavelet neural network algorithm of EEG signals data compression and spikes recognition].

A novel method of EEG signals compression representation and epileptiform spikes recognition based on wavelet neural network and its algorithm is presented. The wavelet network not only can compress data effectively but also can recover original signal. In addition, the characters of the spikes and the spike-slow rhythm are auto-detected from the time-frequency isoline of EEG signal. This method is well worth using in the field of the electrophysiological signal processing and time-frequency analyzing.

Adult↗
PubMed1999

[Diagnosis and surgical treatment of brain-stem vascular malformations].

OBJECTIVE: To study the various aspects of the brain-stem vascular malformations, including the histopathology, clinical presentation, neuroimaging, techniques of surgical operation. METHODS: A retrospective analysis of 100 patients with 105 brain-stem vascular malformations had underwent microsurgery from 1987 to 1997 in the institute. RESULTS: Most brain-stem vascular malformations are cavernoma, some of them are not easily differentiated from telangiectasis. Meanwhile, they could also associate with venous malformation. In our group, 67% patients suffered from hemorrhage more than one time. The average number of bleeding in female is higher than in male's. There was no operative mortality. The outcome was improved and stable in 65% patients. Ninety-two patients have followed-up half a year to 11 years. Rebleeding after operation occurred in 4% cases. CONCLUSIONS: Active microsurgery should be adopted carefully for the patients with symptomatic brain-stem vascular malformations, while those with asymptomatic lesions need long-term clinical observations and neuroimaging follow-up.

Adolescent↗
PubMed1999

[Differential diagnosis and operative timing of intramedullary spinal cord tumors].

OBJECTIVE: To discuss the differential diagnosis of various kinds of intramedullary spinal cord tumors, and choose the right operative timing. METHODS: On grading the dysfunction of the movement, an analysis has been made statistically for 147 cases with 160 tumors resected by microneurosurgery and confirmed pathologically. Their neuroimage have been also compared. RESULTS: The clinical manifestations of main kinds of intramedullary spinal cord tumors are not significantly different, but there are certain characteristic features in their neuroimage. The tumors of grade 0 group (normal movement) are obviously smaller than those of other grades groups. The pre- and post-operative grades of motor disturbance show a better, positive linear correlation. CONCLUSIONS: MRI, particularly its enhancement, can differentiate an ependymoma from astrocytoma and hemangioblastoma in most cases. A satisfactory result can be achieved to resect the tumor immediately by using the minimally invasive, microsurgical techniques.

Adolescent↗
PubMed1998

The tyrosyl free radical of recombinant ribonucleotide reductase from Mycobacterium tuberculosis is located in a rigid hydrophobic pocket.

The tyrosyl free radical in protein R2-2 of class Ib ribonucleotide reductase (RNR) fromMycobacterium tuberculosis is essential for the enzymatic activity and has an EPR spectrum remarkably similar to that of the tyrosyl radical YD* in PSII. The EPR relaxation properties of the radical suggest a very weak exchange coupling between the two redox centers, the radical and the diferric cluster. The tyrosyl radical gives almost identical EPR spectra in the temperature interval 10-293 K. We conclude that the tyrosyl radical sits in a rigid pocket. Two ring protons and one beta-methylene proton account for the major anisotropic hyperfine interactions. A high-frequency EPR spectrum of the radical showed a resolved gx = 2. 0092, indicating that a hydrogen bond to the phenolic oxygen of the radical is absent. Theoretical modeling studies based on the structural data known for Salmonella typhimurium class Ib RNR protein R2F revealed a hydrophobic wall aligned with the radical harboring residue Y110. The distance between the phenolic oxygen of the radical and the diferric cluster is longer in the two class Ib nrdF R2 proteins than in other characterized class Ia R2 proteins. The tyrosyl radical in protein R2-2 from M. tuberculosis was accessible to direct reduction by dithionite in the absence of a mediator. The radical could be partly regenerated when the system was exposed to O2 after the completion of anaerobic reduction. This indicates that the Fe3+ ions also had become reduced by dithionite.

Bacterial Proteins↗
PubMed1998

Photorefractive materials for nonvolatile volume holographic data storage

Optically gated recording and nonvolatile readout in a digital volume holographic data storage system that uses a pair of mutually incoherent light sources during recording and only one for readout were demonstrated recently. This approach used stoichiometric lithium niobate, which after post-growth processing gave rise to an at least two orders of magnitude improvement in sensitivity over the best materials reported previously. It is also shown that by adding certain dopants (iron and manganese) to near-stoichiometric lithium niobate, the dark storage time and gating efficiency can be increased compared with previous work. The underlying physical mechanisms of gated recording and the effectiveness of the gating process responsible for this manifold improved performance are discussed, and bipolarons and small polarons are identified as the responsible photorefractive species.

Journal Article↗
PubMed1998

New paramagnetic species formed at the expense of the transient tyrosyl radical in mutant protein R2 F208Y of Escherichia coli ribonucleotide reductase.

The highly conserved residue F208 in protein R2 of E. coli ribonucleotide reductase is close to the binuclear iron center, and found to be involved in stabilizing the tyrosyl radical Y122. in wild type R2. Upon the reconstitution reaction of the mutant R2 F208Y with ferrous iron and molecular oxygen, we observed a new EPR singlet signal (g = 2.003) formed concomitantly with decay of the transient tyrosyl radical Y122. (g = 2.005). This new paramagnetic species (denoted Z) was stable for weeks at 4 degrees C and visible by EPR only below 50 K. The EPR singlet could not be saturated by available microwave power, suggesting that Z may be a mainly metal centered species. The maximum amount of the compound Z in the protein purified from cells grown in rich medium was about 0.18 unpaired spin/R2. An identical EPR signal of Z was found also in the double mutant R2 F208Y/Y122F. In the presence of high concentration of sodium ascorbate, the amounts of both the transient Y122. and the new species Z increased considerably in the reconstitution reaction. The results suggest that Z is most likely an oxo-ferryl species possibly in equilibrium with a Y208 ligand radical.

Binding Sites↗
PubMed1998

Simultaneous HLA Class I and Class II antibodies screening with flow cytometry.

A flow cytometric method of simultaneously screening both HLA Class I and Class II panel reactive antibodies (PRA) was developed using a pool of 30 different Class I and 30 different Class II microbeads coated with purified HLA antigens. The antibodies in the serum that react specifically to the coated HLA antigens are detected by using a FITC-conjugated antibody against human IgG. Percent PRA can be determined by the percentage of microbeads that react positively to the serum. There is no cross-reactivity between the Class I and Class II microbeads. A mixture of Class I and Class II microbeads can be distinguished by their different fluorescent properties on the flow cytometry analysis. Thus, both Class I and Class II PRA can be detected from a single tube reaction.

Antibodies↗