Biomedical subjects

X Xu

Publications and source records attributed to X Xu.

At least 883 records · Page 49Linked to original sources

PubMed1995

Characteristics of an established retinoblastoma cell line HXO-Rb44.

PURPOSE: To study the retinoblastoma cell culture and to establish a new retinoblastoma cell line. METHODS: 22 retinoblastomas were cultured by using the method of single cell suspension. Characteristics of the cultured cells were studied in the following programs: tumor cell morphology in vitro, electron microscopic, growth curve, cloning in soft agar, immunohistochemistry, karyotype and tumorigenicity. RESULTS: 22 retinoblastomas were cultured successfully in vitro, only a continued cell line HXO-Rb44 was established (more than 3 years). The characteristics of this cell line are that it grew as a suspension of round cell in graps like clusters in vitro, its population doubling time was 44 hours, and it could be cloned in soft agar. Histopathologic and ultrastructured pictures showed the characteristics of Rb. HXO-Rb44 cell was positive to NSE and negative to GFAP in immunohistochemical staining. A subcutaneous injection of HXO-Rb44 cells produced a retinoblastoma in BALB/C athumic nude mice. CONCLUSIONS: HXO-Rb44 has the characteristics of retinoblastoma and is a new retinoblastoma cell line. It is a useful material for study this tumor both in basic and clinical fields.

Animals↗

PubMed1995

Treatment of 23 patients with advanced gastric cancer by intravenously transfer of autologous tumor-infiltrating lymphocytes combined with rIL-2.

Tumor-infiltrating lymphocytes (TIL) isolated from metastatic lymph nodes in patients with nonoperable advanced gastric cancer were induced to become LAK-like cytotoxic activity of TIL after in vitro culture with rIL-2. Twenty-three patients with advanced gastric cancer were treated by intravenously transfer of autologous TIL combined with rIL-2. The tumor focus disappeared (complete remission, CR) in 3 patients (13.0%) and significantly decreased (partial remission, PR) in 5 patients (21.7%). Fifteen patients did not respond to the treatment. The amount of soluable IL-2 receptor in serum was significantly decreased after treatment, the cytotoxicity of NK cells and OT test were significantly increased. No significant difference in CD4/CD8 was found between before and after treatment. No serious side effect was observed in the treatment.

Adenocarcinoma↗

PubMed1995

[Multivariable analysis of survival in patients with transitional cell bladder carcinoma].

In 82 transitional cell bladder cancer patients with adequate follow-up, the prognostic value of histological grade, depth of invasion, size, site, appearance, number of primary tumours, surgical treatment and ages of patients were assessed. Univariable analysis showed the statistically significant relation of histological grade, depth of invasion, size, site, appearance and number of tumours to survival. Survival analysis with Cox's regression model indicated that the histological grade is the most important prognostic factor, followed by site of tumours and depth of invasion. The results suggest that the information of site should not be omitted.

Adult↗

PubMed1995

[Effects of thymectomy and glucocorticoid therapy on peripheral lymphocytes in myasthenia gravis].

Clinical manifestations and peripheral blood lymphocyte subset changes were studied in patients with myasthenia gravis (MG) to elucidate the mechanism of clinical improvement following treatment, with thymectomy (Tx) or glucocorticoid (GC) therapy. The changes found were: 1. There was a significant increase in percentages of CD3+, CD29+ CD4+ cells and CD4/CD8 ratio and a significant decrease in percentages of CD8+ and CD16,56+ cells in patients who had never been treated with any immune therapy. 2. After Tx or GC therapy, CD3+ and CD4+, CD29+ cells were decreased, but the number CD19+ and CD16, CD56 cells did not change. 3. Tx had a special effect on CD8+ cells. In most of the patients who showed clinical improvement after Tx, CD8+ cells were increased and CD4/CD8 ratio wad decreased. 4. Anti-acetylcholine receptor (AChRAb) titers were markedly decreased after GC therapy. These results indicate that there were obvious abnormalities in cell-mediated immunity in addition to those in humoral immunity in myasthenia gravis. These abnormalities tended to be normalized after Tx or GC therapy.

Adolescent↗

PubMed1995

[Direct genotyping and antenatal diagnosis of deletional alpha-thalassemia of the southeast Asian type by polymerase chain reaction technique].

OBJECTIVE: To study the gene of deletional alpha-thalassemia of the Southeast Asian type (SEA) and to perform the antenatal diagnosis. METHODS: A new method of polymerase chain reaction technique using three primers bridging the breakpoints was carried out for carrier detection and antenatal diagnosis of deletional alpha-thalassemia of the Southeast Asian type. A DNA fragment of about 630bp in size was amplified in case of--SEA alleles, while a 224 bp fragment was amplified in samples without the deletion. Homozygotes, heterozygotes, and normal subjects could be clearly distinguished with the present method. RESULTS: We used this method in the genotyping and antenatal diagnosis of 10 high risk pregnancies of alpha-thalassemia. 2 homozygotes, 4 heterozygotes, and 4 normal infants were found. CONCLUSION: The present method is simple and rapid in detection of carriers and antenatal diagnosis of the alpha-thalassemia of southeast Asian type.

Base Sequence↗

PubMed1995

[The damped torsion swing test in guinea pigs].

The damped torsion swing test (DTST) was carried out for assessing the vestibular function in guinea pigs. Twenty guinea pigs which had normal pinna reflexes and normal tympanic membranes were used. In the formula, L represented the number of the left nystagmus, and R the right nystagmus during DTST. The symmetric rate [formula: see text] between left and right nystagmus was calculated. Then the animals were randomly divided into two groups: (1) Gentamicin group (n = 10): DTST was reexamined, Animals were injected with gentamicin (250 mg/kg) for three days. (2) Endolymphatic hydrops group (n = 10): Surgical obliteration of the right endolymphatic sac and duct was done, 30 days later DTST was carried out again. The results showed: (1) The normal value [formula: see text] of DTST in the 20 healthy guinea pigs is less than 8.25%. (2) Both of left and right nystagmus were reduced (P < 0.01) in gentamicin group. (3) The number of the right nystagmus was reduced in endolymphatic hydrops group (P < 0.01) and the symmetric rate of 6 animals was more than 8.25%. It is concluded that DTST is an important method of evaluating vestibular function in guinea pigs.

Animals↗

PubMed1995

[Promoter activity detection and transcription initiation site determination of the D-xylose isomerase gene of Streptomyces diastaticus strain No.7 M1033].

The DNA segment of the Streptomyces diastaticus strain No.7 M1033 D-xylose Isomerase gene, from -192 to +581 bp according to the translation start site (tss), was cloned in Streptomyces promoter-probe plasmid pIJ4083 from recombination plasmid pUB1 and its M13 subclone S1 respectively. The protoplasts of S. lividans TK24 were transformed with the recombinant, and then detected the promoter activity by measuring the catethol dioxygenase expression. Results of S1 mapping of total RNA of S. di. M1033 indicatedthat: the transcription initiation site of D-XI gene was 40bp upstream the coding region; there was another gene encoded on the antisense strand upstream D-XI gene, with a 114-nucleotide sequence separating their coding regions. According to its DNA sequence, we believed it was the xylulose kinase gene. Data from quantitive S1 mapping also suggested that transcription of the two genes was induced by D-xylose and repressed by glucose.

Aldose-Ketose Isomerases↗

PubMed1995

The intracellular assembly of antigenic-peptide-class II complexes.

The immune system employs remarkable strategies to ensure that foreign antigens, from the most complex pathogens to the simplest proteins, are displayed on the surfaces of cells which are targets of T lymphocyte recognition. At the heart of these strategies is the molecular transformation of a soluble protein antigen to a complex of a small peptide containing the antigenic determinant bound to a cell surface Major Histocompatibility Complex class I or class II protein. This process is termed antigen presentation. Progress in a variety of laboratories over the last several years has yielded a wealth of information about the molecular mechanisms underlying antigen presentation, providing potential new approaches to vaccine design. Here we describe recent studies in our laboratory aimed at elucidating the intracellular site in B lymphocytes in which antigenic peptide-class II complexes are assembled for recognition by helper T cells and the regulation of this assembly process. Our results suggest that processed antigen-class II complexes are assembled in a unique compartment in the endocytic route which contains all the necessary cellular and molecular machinery for assembly and that B cells regulate the assembly process in response to external and internal signals.

Antigen-Presenting Cells↗

PubMed1994

Two murine GSTpi genes are arranged in tandem and are differentially expressed.

An 8-kilobase mouse genomic fragment containing two intact glutathione S-transferase (GST) genes has been isolated from a mouse lambda genomic library. Each of the genes (designated mGSTpiA and mGSTpiB) is less than 3 kilobases in size and is comprised of seven exons that give rise to a 630-base pair open reading frame encoding 209 amino acids. The deduced amino acid sequences of the gene products differ in only 6 amino acids at positions 10, 11, 89, 104, 106, and 109. These two genes are highly homologous to rat GST-P and to a lesser extent to human GST-pi. Northern blot analysis of mRNAs from a variety of mouse tissues demonstrated that mGSTpiB is ubiquitously expressed, whereas mGST-piA is more selectively expressed in gallbladder, colon, heart, and skeletal muscle. Primer extension analysis revealed four potential transcription start sites in mGST-piB and one in mGSTpiA. Although both genes were expressed in vitro and in vivo only mGSTpiB product metabolized 1-chloro-2,4-dinitrobenzene, a common GST substrate. Further in vitro expression studies of three chimeric mGSTpi genes suggested that one or both of the amino acids at positions 10 and 11 of mouse GSTpi enzymes are important for the enzyme's ability to metabolize 1-chloro-2,4-dinitrobenzene.

Amino Acid Sequence↗

PubMed1994

Compartmentalization of Ca2+ signaling and Ca2+ pools in pancreatic acini. Implications for the quantal behavior of Ca2+ release.

Streptolysin O-permeabilized pancreatic acini were used to study compartmentalization of Ca2+ signaling and Ca2+ pools. In these cells, the inositol 1,4,5-trisphosphate (IP3)-dependent Ca2+ channels could be activated by a number of agonists (carbachol, cholecystokinin, or bombesin) or by activation of the entire cellular phospholipase C pool with GTP gamma S. Surprisingly, each of the antagonists interacting with acinar cells inactivated the channels after stimulation with GTP gamma S. In addition, when permeabilized cells were stimulated with more than one agonist, any antagonist to the specific agonists employed inactivated the channels. The aberrant behavior of the antagonists in permeable cells was not related to a loss of specificity since (a) when added before GTP gamma S, the antagonists had no effect on Ca2+ release and (b) when cells were stimulated with a single agonist, the antagonists prevented only the effect of their specific agonist. The differential behavior of the antagonists in intact and permeable cells suggests a compartmentalization of Ca2+ signaling into separate, agonist-specific units that is modified by cell permeabilization. Further evidence for compartmentalization of signaling was obtained by showing that the partial agonist (the CCK octapeptide analogue JMV-180) can access and release only 50% of the cholecystokinin- or IP3-mobilizable Ca2+ pool in intact and permeable cells. Kinetic measurements revealed a multiphasic time course of agonist-evoked Ca2+ release in permeable cells. At high agonist concentrations, all phases were fast and merged into an apparent single event of Ca2+ release. The phases were separated by three independent protocols: reduction in agonist concentrations, addition of heparin, or addition of guanosine-5'-O-(thio)diphosphate. Since all protocols that caused phase separation reduce IP3-mediated Ca2+ release, these findings demonstrate heterogeneity in the affinity for IP3 of channels present in compartmentalized Ca2+ pools of the same cells. Compartmentalization of signaling and the heterogeneity in the affinity for IP3 resulted in a quantal agonist-evoked Ca2+ release. The overall findings are discussed in the context of an integrated model of compartmentalization of signaling complexes, Ca2+ pools, and IP3-activated Ca2+ channels.

Animals↗

PubMed1994

Simultaneous determination of urinary creatinine, calcium and other inorganic cations by capillary zone electrophoresis with indirect ultraviolet detection.

A method for the rapid analysis of calcium and creatinine in urine has been developed using capillary zone electrophoresis without sample pretreatment other than dilution. Cations of NH3, K, Na, Mg, Ca, Li, Ba and creatinine in human urine samples could be separated within 7 min. Background electrolyte (BGE) was composed of 5 mmol/l pyridine (chromophore), 3.6 mmol/l tartaric acid and 2 mmol/l 18-crown-6, having a pH of 4.05. An indirect UV detection mode was employed at 255 nm. Efforts were made to eliminate the interaction between cations and proteins and to minimize the electromigrative dispersion (EMD) for the analytes of interest by selecting a suitable BGE and sample dilution solution. Quantitative analyses were performed for calcium and creatinine. The calibration plots showed good linearity over the concentration range of interest to clinical analysis. Data on recoveries and reproducibilities are also reported. Results for urine samples (previously collected and frozen) from a variety of healthy and pathological individuals were in good agreement with those obtained by the Technicon SMA II calcium and creatinine methods.

Ammonia↗

PubMed1994

SmgGDS stabilizes nucleotide-bound and -free forms of the Rac1 GTP-binding protein and stimulates GTP/GDP exchange through a substituted enzyme mechanism.

The Rac proteins, Rac1 and Rac2, are essential components of the NADPH oxidase system of phagocytes and regulate the actin assembly associated with membrane ruffling. These functions are controlled by the GTP-bound form of Rac. The biochemical interaction between Rac and its only known GDP-dissociation stimulator (termed smgGDS) was characterized. SmgGDS was able to stimulate the incorporation of guanosine 5'-[gamma-thio]-triphosphate GTP[gamma S] into the RhoA, Rac2, Rac1, Rap1A and CDC42Hs GTP-binding proteins, but the activity was greatest toward RhoA and Rac2. Isoprenoid modification of these proteins was not absolutely required for the interaction with smgGDS. Interestingly, the activity of smgGDS toward Rac1 could not be observed in a [3H]GDP/GTP exchange assay under conditions where it stimulated incorporation of GTP[gamma S] into Rac1. We determined that smgGDS prevented the loss of Rac1 activity during the [3H]GDP/GTP exchange assay by demonstrating the ability of smgGDS to inhibit the loss of Rac1 GTP[gamma S]-binding during incubations at 30 degrees C. This stabilizing effect was exactly counterbalanced by the ability of smgGDS to stimulate the release of [3H]GDP from Rac1, thereby producing no net observable effect in the exchange assay. SmgGDS was able to effectively stimulate the release of GDP but not GTP[gamma S] from Rac1. SmgGDS maintains Rac1 in a nucleotide-free form after release of GDP, indicating that the reaction between Rac1 and smgGDS involves a substituted enzyme mechanism.

Animals↗

PubMed1994

Effect of phosphorothioate modification of oligodeoxynucleotides on specific protein binding.

Phosphorothioate modification of internucleoside linkages is widely used to prevent degradation of oligodeoxynucleotide (ODN) therapeutic agents in serum and cells. This modification generally increases ODN potency, but in many instances it is associated with an increase of poorly understood nonspecific effects. In this study, we have found that both cellular retention and nonspecific protein binding are dependent upon the extent of the oligonucleotide's modification. Flow cytometry of cells treated with fluorescein-labeled single-stranded (ss) or double-stranded (ds) ODNs demonstrated that fully phosphorothioate-modified ODNs exhibit much greater cellular association than 3'-terminally modified ODNs (with three 3'-terminal phosphorothioate linkages). Additionally, gel shift assays with either ss- or ds-probes showed that fully phosphorothioate-modified ODNs also exhibit much greater cytoplasmic and nuclear protein binding than either 3'-terminally modified or unmodified ODNs. However, gel shift competition assays showed that transcription factor binding by fully phosphorothioate-modified ds-ODNs was completely nonspecific relative to 3'-terminally modified and unmodified ds-ODNs. These results suggest that the benefits derived from full phosphorothioate modification of ODNs may be negated by increases of nonspecific protein binding and associated sequence-independent effects.

3T3 Cells↗

PubMed1994

The complete mitochondrial DNA sequence of the horse, Equus caballus: extensive heteroplasmy of the control region.

The sequence of the mitochondrial (mt) DNA of the horse (Equus caballus) was determined. The length of the sequence presented is 16,660 bp. This figure, however, is not absolute due to pronounced heteroplasmy caused by variable numbers of the motif GTGCACCT in the control region of different molecules. Boundaries of the 13 peptide-coding genes were determined by the presence of start and stop codons, and by analogy with other eutherian mtDNAs. Three genes (COIII, NADH3 and NADH4) were not terminated by a stop codon. Comparison among the peptide-coding genes of the horse and eight other mammals suggests that the boundaries of some mt genes should be redefined. The number of repeats in the control region was determined by sequencing 77 different clones (20 direct plus 57 PCR clones). The number of repeats ranged from 2 to 29. There was a pronounced overrepresentation of clones with many repeats (22-27). Very few clones had a repeat number that was close to the mean number of repeats.

Animals↗

PubMed1994

Activation of neutrophils by a chemically separated but optically coupled neutrophil population undergoing respiratory burst.

Neutrophils from pig blood were used as a model system to investigate the optical communication between cells. It was found that neutrophils stimulated to undergo respiratory burst can activate a second, chemically separated, but optically coupled population of neutrophils. The response of the latter was visualized as a temporary rising of their low-level chemiluminescence and an enhanced generation of superoxide radicals detected by both the reduction of ferricytochrome c and spin trapping. The results provide evidence that a long-range optical coupling of biological significance between living cells exists.

Animals↗

PubMed1994

Differing structural requirements for GTPase-activating protein responsiveness and NADPH oxidase activation by Rac.

The Rac GTP-binding proteins regulate the actin cytoskeleton and the superoxide-forming NADPH oxidase of phagocytic leukocytes. These functions of Rac are determined by the GTP/GDP state of the protein, which can be modulated by GTPase-activating proteins (GAPs). The interaction of Ras with both downstream signaling targets and GAPs is mediated via an "effector" domain (amino acids 30-40). We demonstrate that the effector domain of Rac2 is required for both NADPH oxidase activation and actin assembly, but that mutations in this region do not decrease the responsiveness of Rac to GAPs. In contrast, mutations of residues 12 (Gly-->Val) or 61 (Gln-->Leu) inhibit both intrinsic- and GAP-stimulated GTP hydrolysis by Rac2. A double mutation in which both the effector domain and Q61L were modified restored NADPH oxidase activation and membrane ruffling, while the equivalent effector domain and G12V double mutation did not. The Rac2 Q61L mutant had an increased "affinity" for NADPH oxidase activation and for GAP binding as compared to the wild type or G12V proteins. These experiments suggest that Rac contains at least two "effector" interaction sites, and that changes in binding interactions at one of these sites may influence the function of the other.

Base Sequence↗

PubMed1994

Antagonists inactivate the inositol 1,4,5-trisphosphate (Ins-1,4,5-P3)-dependent Ca2+ channel independent of Ins-1,4,5-P3 metabolism.

Streptolysin O-permeable pancreatic acini, which retain intact signaling systems, were used to study the regulation of the inositol 1,4,5-trisphosphate (Ins-1,4,5-P3)-activated Ca2+ channel during agonist stimulation and antagonist inhibition. Stimulation of permeable cells with carbachol induced rapid Ca2+ release from internal stores. Addition of heparin prior to or after agonist stimulation inhibited the release, indicating the activation of the Ins-1,4,5-P3-dependent Ca2+ channels by the agonist. Termination of cell stimulation with the specific antagonist atropine rapidly inactivated the release channels. Channel inactivation by the antagonist was independent of Ins-1,4,5-P3 levels since (a) addition of atropine to carbachol-stimulated cells resulted in a slow hydrolysis of Ins-1,4,5-P3, (b) addition of 10-fold excess Ins-1,4,5-P3 together with the agonist did not prevent channel inactivation by the antagonist, and (c) the antagonist inactivated Ca2+ release in the presence of saturating concentration of the nonhydrolyzable Ins-2,4,5-P3. Hence, the antagonist appears to stabilize the Ins-1,4,5-P3-activated Ca2+ channel in a state refractory to Ins-1,4,5-P3. These findings are the first direct evidence that the channel can exist in such a refractory state.

Animals↗

PubMed1994

Chromium-induced early changes in renal function among ferrochromium-producing workers.

Urinary biochemical indicators of renal injury were examined in 84 male and 38 female ferrochromium-producing workers exposed to water-soluble chromium compounds [Cr(VI)]. The indicators examined included urinary chromium (U-Cr), alkaline phosphatase (ALP), gamma-glutamyl transferase (gamma-GT), glutamic-oxalacetic and glutamic-pyruvic transaminases (GOT & GPT), lactate dehydrogenase (LDH), N-acetyl-beta-D-glucosaminidase (NAG), total protein (TPr) and beta 2-microglobulin (beta 2-MG). The U-Cr levels in the exposed group were approximately 1.8 times that of the control group. Compared to controls, the activities of gamma-GT, NAG, ALP, GOT and LDH in the urine of workers were significantly increased whenever U-Cr concentration exceeded 45 microgram/g creatinine. The activities of gamma-GT, GOT and NAG were elevated in workers employed for longer than ten years. However, no clear dose-response relationships nor time-effect relationships were found. The present results suggest that long-term exposure to water-soluble chromium [Cr(VI)] produces chronic renal injury. The site of the injury appears to mainly involve the proximal tubule. U-Cr concentrations of > 15 microgram/g creatinine can be proposed as a threshold dosage for nephrotoxicity, and gamma-GT, NAG and ALP are early sensitive indicators of the most valuable for evaluating the renal injury.

Acetylglucosaminidase↗