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Biomedical subjects

L Gu

Publications and source records attributed to L Gu.

At least 91 records · Page 5Linked to original sources
PubMed1997

Expression and regulation of Bcl-2, Bcl-xl, and Bax correlate with p53 status and sensitivity to apoptosis in childhood acute lymphoblastic leukemia.

Bcl-2 and its homologue, Bcl-x1, encode membrane-associated proteins that protect neoplastic cells from DNA damage-induced apoptosis, whereas Bax is a Bcl-2 antagonist that promotes cell death. In the present study, we examined the expression and regulation of these genes at both the mRNA and protein level in 22 pediatric acute lymphoblastic leukemia (ALL) cell lines, as well as their sensitivity to apoptosis after exposure to ionizing radiation (IR). Eleven of 22 lines expressed wild-type (wt) p53, 4 expressed mutant p53, and 7 did not express p53 (p53-null). Nine of 22 (41%) lines expressed Bcl-2; of these, 8 were wt-p53+ and 1 expressed mutant p53. Bcl-2 was not expressed in any p53-null lines. In contrast, all 22 lines were positive for Bcl-x1 and Bax, although expression level varied. Treatment with IR (10 Gy) induced both downregulation of Bcl-2 and upregulation of Bax at 2 to 5 hours post-IR in 5 of 8 (63%) wt-p53+ lines, leading to apoptosis. Conversely, lines that failed to both downregulate Bcl-2 and upregulate Bax after IR were resistant to apoptosis. Although levels of Bcl-x1 expression varied among the 22 lines, high levels of Bcl-x1 were observed in 5 of 7 (71%) p53- lines. There were no obvious changes in the expression of Bcl-x1 in these lines after IR. However, among the p53-null lines, resistance to IR was observed only in those expressing high levels of Bcl-x1. These results suggest that expression of Bcl-2 but not Bcl-x1 is p53-dependent and that IR-induced downregulation of Bcl-2 and upregulation of Bax occur in most wt-p53+ lines and are associated with radiosensitivity. Furthermore, high-level expression of Bcl-x1 occurs predominantly in p53-null lines and is associated with resistance to IR-induced apoptosis in these lines, indicating differential expression and regulation of Bcl-2 and Bcl-x1 in pediatric ALL.

Apoptosis↗
PubMed1997

In vivo properties of monocyte chemoattractant protein-1.

Monocyte chemoattractant protein-1 (MCP-1) attracts monocytes, memory T lymphocytes, and natural killer (NK) cells in vitro. Its expression has been documented in disorders characterized by mononuclear cell infiltrates, suggesting that it may contribute to the inflammatory component of such diseases as atherosclerosis, multiple sclerosis, or rheumatoid arthritis. To prove a causal association, the in vivo properties of MCP-1 must be understood. Several lines of transgenic mice have been constructed to address this question. A transgenic line in which MCP-1 expression is controlled by the MMTV-LTR expressed high levels of MCP-1 in multiple organs but showed no evidence for monocyte infiltration. Instead, these mice were more susceptible to infection by the intracellular pathogens, Listeria monocytogenes and Mycobacterium tuberculosis. These mice had high serum levels of MCP-1, suggesting that their circulating monocytes may have been desensitized or that MCP-1 stimulated a Th2-dominant response. In contrast, another model in which MCP-1 expression was controlled by the insulin promoter demonstrated a monocytic infiltrate in pancreatic islets. These results indicate that MCP-1 expression at low levels in an anatomically confined area results in monocyte infiltration, suggesting that when properly expressed, MCP-1's in vitro properties are reproduced in vivo. This justifies the examination of MCP-1-deficient mice in disease models in order to explore MCP-1's role in pathogenesis.

Animals↗
PubMed1997

Cytoplasmic redox potential affects energetics and contractile reactivity of vascular smooth muscle.

Variations in the cytoplasmic redox potential (Eh) and NADH/NAD ratio as determined by the ratio of reduced to oxidized intracellular metabolite redox couples may affect mitochondrial energetics and alter the excitability and contractile reactivity of vascular smooth muscle. To test these hypotheses, the cytoplasmic redox state was experimentally manipulated by incubating porcine carotid artery strips in various substrates. The redox potentials of the metabolite couples [lactate]/[pyruvate]i and [glycerol 3-phosphate]/[dihydroxyacetone phosphate]i varied linearly (r=0.945), indicating equilibrium between the two cytoplasmic redox systems and with cytoplasmic NADH/NAD. Incubation in physiological salt solution (PSS) containing 10 mm pyruvate ([lact]/[pyr]=0.6) increased O2 consumption approximately 45% and produced anaplerosis of the tricarboxylic acid (TCA cycle), whereas incubation with 10 mm lactate-PSS ([lact]/[pyr]i=47) was without effect. A hyperpolarizing dose of external KCl (10 mM) produced a decrease in resting tone of muscles incubated in either glucose-PSS (-0.8+/-0.8 g) or pyruvate-PSS (-2.1+/-0.8 g), but increased contraction in lactate-PSS (1.5+/-0.7 g) (n=12-18, P<0.05). The rate and magnitude of contraction with 80 mm KCl (depolarizing) was decreased in lactate-PSS (P=0.001). Slopes of KCl concentration-response curves indicated pyruvate>glucose>lactate (P<0.0001); EC50 in lactate (29. 1+/-1.0 mM) was less than that in either glucose (32.1+/-0.9 mm) or pyruvate (32.2+/-1.0 mM), P<0.03. The results are consistent with an effect of the cytoplasmic redox potential to influence the excitability of the smooth muscle and to affect mitochondrial energetics.

Aerobiosis↗
PubMed1997

Expression of interleukin-6 receptors by pediatric acute lymphoblastic leukemia cells with the t(4;11) translocation: a possible target for therapy with recombinant IL6-Pseudomonas exotoxin.

We have detected expression of interleukin-6 receptors (IL-6R) by primary leukemic cells from three of six patients with t(4;11)+ ALL. Scatchard analysis revealed from 960 to 2100 high-affinity IL-6R/cell on these cells (median, 1560; mean, 1540). All three IL-6R+ cases also expressed CD33, which was not expressed on IL-6R-negative cases. To determine if these receptors could serve as a target for a recombinant ligand-toxin, we examined the sensitivity of primary IL-6R+ ALL cells to a recombinant IL6-Pseudomonas exotoxin (IL6-PE4E) fusion protein, in which the toxicity and specificity of the chimeric toxin was enhanced by substitution of four glutamine residues for naturally occurring amino acids in PE domain I. Primary cells from IL-6R+ cases were sensitive to IL6-PE4E in a 48-h cytotoxicity assay, with ID50 values (concentrations causing 50% decrease in viability) ranging from 23 ng/ml to 92 ng/ml (median, 61; mean, 58). Furthermore, incubation of these cells with 10(3) ng/ml IL6-toxin for 24 h prevented their subsequent engraftment in SCID mice. Thus, IL6-PE4E may be useful for ex vivo purging of IL-6R+ leukemic cells in an autologous bone marrow transplantation setting and possibly for therapy of residual, chemotherapy-resistant disease.

ADP Ribose Transferases↗
PubMed1997

Conserved structure, regulatory elements, and transcriptional regulation from the GATA-1 gene testis promoter.

Transcription factor GATA-1 was first identified in erythroid cells, but was later shown to also be expressed in Sertoli cells of the mouse testis. GATA-1 transcription in testis initiates from a different first exon (exon IT) than the erythroid mRNA (transcribed from exon IE). To begin to address the question of how expression of GATA-1 might be differentially regulated in Sertoli and erythroid cells, we have cloned and determined the structure of the IT promoters of both the rat and mouse GATA-1 genes. The transcription regulatory mechanism(s) controlling the synthesis of exon IT-derived mRNA was investigated by transfection of wild-type and mutant reporter genes, with and without co-transfected GATA factor expression plasmids, into either fibroblasts or Sertoli cell lines. Two GATA binding sites in the IT promoter were found to be required for GATA factor-mediated activation in fibroblasts: GATA-IT-directed reporter gene expression was activated only after co-transfection with GATA-1, implying that transcriptional activation of GATA-1 in the testis might be at least partially mediated through these GATA regulatory elements. We also found that the endogenous GATA-1 gene was silent in primary culture and two different Sertoli cell lines, and that the repression of co-transfected GATA-1 reporter genes could not be relieved by forced expression of GATA-1 in Sertoli cells. Thus the GATA-IT promoter may be under the control of a regulatory network in Sertoli cells which involves both positive and negative regulation of transcription, and conserved GATA motifs found in the IT promoter may be required for transducing these effects.

Animals↗
PubMed1997

A transglutaminase-related antigen associates with keratin filaments in some mouse epidermal cells.

A mouse monoclonal IgG, G82, directed against guinea pig liver transglutaminase recognizes a transglutaminase-related antigen that is associated with the keratin intermediate filament network in some primary mouse keratinocytes. The association can be seen at the resolution of individual keratin tonofibrils following fixation and staining for double-label indirect immunofluorescence. Western blots indicate that G82 reacts with two proteins of 95 kDa and 280 kDa, respectively, in extracts of these cells. The 95-kDa band is also recognized by a polyclonal antibody against purified guinea pig liver transglutaminase, and the 280-kDa protein seems to correspond to a similar protein that was shown to be recognized by G92.1.2 in the intermediate filament fraction of primary mouse fibroblasts. The transglutaminase-related antigen was shown by confocal microscopy to co-localize only with nonbasal cell specific keratin intermediate filaments.

Animals↗
PubMed1997

[Determination of the selenomethionine content in grain and human blood].

The authors used the method of cyanogen bromide-fulorimetry to determine the trace amounts of bound selenomethionine (SeMet) in corn, rice, wheat, soybean and human blood. The contents of SeMet in corn samples were found to be 9.2-19014.1 ng/g, and 45.5% to 82% of the total Se in corn samples were in the form of SeMet. Like corn, the proportion of Se in the form of SeMet in total Se in rice, wheat and soybean were 54.9%-86.5%, 50.4%-81.4% and 62.9%-71.8% respectively. The results showed that SeMet is the major chemical form of Se in grain samples determined. The contents of SeMet in two human blood samples (Se content 56.4 ng/g and 71.8 ng/g) were determined as 28.3 ng/g and 53.4 ng/g respectively.

Edible Grain↗
PubMed1996

HLA-DM is present in one-fifth the amount of HLA-DR in the class II peptide-loading compartment where it associates with leupeptin-induced peptide (LIP)-HLA-DR complexes.

HLA-DM has been shown in vitro to catalyze the release of invariant chain (Ii) derived peptides from the peptide-binding groove of class II molecules, thereby facilitating the binding of antigenic peptides. Previous studies showed that at steady state, the majority of DM resides in the class II peptide-loading compartment (IIPLC) where Ii dissociates from class II molecules and antigenic peptides are bound. Here we characterize the expression of DM in vivo in subcellular fractions containing the IIPLC. Using quantitative immunoblotting, we show that in the cell as a whole, class II molecules are expressed in 23-fold molar excess of DM. However, DM is concentrated in the IIPLC, where it is present in a considerably higher concentration relative to the class II molecules, in a molar ratio of 5DR:1 DM. This molar ratio of DM to DR in the IIPLC in vivo is consistent with the catalytic function proposed for DM from studies in vitro. We also provide both biochemical and genetic evidence that DM associates with complexes which contain Ii fragments and class II molecules in the IIPLC. Such complexes are only observed in leupeptin-treated cells in which Ii fails to be completely degraded and complexes containing the leupeptin-induced fragment of Ii (LIP) and class II molecules accumulate in the IIPLC. This observation is consistent with LIP-class II complexes being a substrate for DM in vivo and suggests that interactions of DM and LIP-class II are extremely transient under normal conditions.

Antigens, Differentiation, B-Lymphocyte↗
PubMed1996

Tissue-specific inactivation of p53 tumor suppression in the mouse.

The p53 gene is the most frequent target of structural and functional genetic mutations in human cancer. Thus, considerable effort has been devoted to mapping the functional domains of p53 with regard to their impact on tumorigenesis in vivo. Studies have shown that the carboxy-terminal domain of p53 is sufficient for transformation in vitro. To determine whether a transdominant-negative p53 protein could be used to elicit a tissue-specific p53-null effect in vivo, we tested whether a carboxy-terminal p53 fragment (amino acids 302-390) could abolish p53-dependent apoptosis in an established tumor progression model. We showed previously that loss of p53-dependent apoptosis accelerates brain tumorigenesis in a transgenic mouse model. Here, we show that the same effect can be elicited by expressing a dominant-negative p53 protein tissue specifically in the presence of wild-type p53. Transgenic mice in which pRb function has been disrupted and that coexpress a p53 carboxy-terminal dominant-negative fragment (p53DD) develop aggressive brain tumors mimicking genetic loss of p53 in this model. Inactivation of endogenous p53, which we show to be complexed with p53DD, results in a reduction in apoptosis and acceleration of tumorigenesis. These studies establish a mechanism for tissue-specific knock out of p53 function in vivo.

Animals↗
PubMed1996

Genetic-dietary regulation of serum paraoxonase expression and its role in atherogenesis in a mouse model.

In an effort to identify genetic factors contributing to atherogenesis, we have studied inbred strains of mice that are susceptible (C57BL/6J) and resistant (C3H/HeJ) to diet-induced aortic fatty streak lesions. When maintained on a low-fat diet, HDL isolated from both strain C57BL/6J (B6) and C3H/HeJ (C3H) mice protect against LDL oxidation in a coculture model of the artery wall. However, when maintained on an atherogenic diet high in fat and cholesterol, the HDL isolated from B6 mice lose the capacity to protect, whereas HDL from C3H mice protect equally well. Associated with the loss in the ability of HDL to protect is a decrease in the activity of serum paraoxonase, a serum esterase carried on HDL that has previously been shown to protect against LDL oxidation in vitro. The levels of paraoxonase mRNA decreased in B6 mice upon challenge with the atherogenic diet but increased in C3H, indicating that paraoxonase production is under genetic control. In a set of recombinant inbred strains derived from the B6 and C3H parental strains, low paraoxonase mRNA levels segregated with aortic lesion development, supporting a role for paraoxonase in atherogenesis.

Amino Acid Sequence↗
PubMed1996

Genetic mapping of two blood pressure quantitative trait loci on rat chromosome 1.

A genetic map for rat chromosome 1 was constructed using 66 microsatellite markers typed on either or both of two populations derived from inbred Dahl salt-sensitive (S) rats: F2(LEW x S) n = 151, and F2(WKY x S) n = 159. These populations had been raised on a high salt (8% NaCl) diet. Systolic blood pressure and heart weight were found to be genetically linked to two separate regions on rat chromosome 1 in the F2(LEW x S) population. One region was centered around the anonymous SA locus and accounted for 24 mmHg of blood pressure. The other region was 55 cM from the SA locus centered around a cluster of cytochromes P450 loci, and accounted for 30 mmHg of blood pressure. Since blood pressure and heart weight were highly correlated these same regions were also linked to heart weight. These results were cross-specific as linkage of these chromosome 1 regions to blood pressure and heart weight was not observed in several other F2 populations derived by crossing S and other normotensive control strains. This is presumably due to different alleles and/or different genetic backgrounds in the various populations. The SA region of chromosome 1 was found to influence body weight in F2(LEW x S) rats. Combining the present data with our previously published data on the F2(LEW x S) population showed that four separate quantitative trait loci with additive effects accounted for 106 mmHg and 38% of the total variance of blood pressure and for 506 mg and 34% of the total variance of heart wt.

Animals↗
PubMed1996

Long-term follow-up of minimal residual disease in childhood acute lymphoblastic leukemia patients by polymerase chain reaction analysis of multiple clone-specific or malignancy-specific gene markers.

Two types of markers, namely the clone-specific markers including T-cell receptor (TCR) gamma, TCR delta, and Ig heavy-chain (IgH) gene rearrangements, and malignancy-specific fusion gene mRNA such as SIL-TAL-1, BCR-ABL, and HRX-partner genes, were investigated by molecular biology techniques in 65 Chinese patients with acute lymphoblastic leukemia (ALL). In combination, these markers were informative among 96% of patients. Minimal residual disease (MRD) was followed up in 23 of these patients with available materials over a period varying from 8 to 54 months with at least one leukemia-specific probe. In most children, MRD was decreased continuously to an ultimately undetectable level within 6 to 12 months after remission induction therapy. One patient exhibited low-level residual leukemic cells for 4 years before the MRD turned negative. Another patient remained in complete remission for 45 months, although a positive signal was detected at 34 months using TCR delta probe, but was negative with a TCR gamma marker which was positive at presentation. In three patients who relapsed, MRD either persisted through the clinical course or became positive and eventually increased 3-11 months before clinical relapse. These data suggested that the combined use of multiple gene markers is a valuable tool for the PCR-based MRD detection, since it can cover most ALL patients. Furthermore, long-term follow-up of MRD is helpful for determining the dosage as well as the period of maintenance chemotherapy and for predicting impending relapse.

Base Sequence↗
PubMed1996

[Capsaicin-sensitive afferent neurons and endogenous nitric oxide (NO) mediate the gastric acid secretion and hyperemic responses to intragastric peptone].

Using hydrogen gas clearance technique to measure gastric mucosal blood flow (GMBF) and a high dose of capsaicin to ablate the capsaicin-sensitive afferent neurons, the role of capsaicin-sensitive neurons in the gastric acid secretion and hyperemic response to intragastric peptone was investigated. The results were as follows: (1) there was an increase in acid secretion associated with the hyperemic response to intragastric peptone; (2) pretreatment with a high dose of capsaicin to ablate afferent neurons completely abolished the gastric hyperemic response to intragastric peptone and partially inhibited the acid secretion; (3) the gastric hyperemic response to intragastric peptone was completely blocked by pretreatment with L-nitro-arginine methyl ester (L-NAME), whereas the acid secretion was significantly attenuated; (4) inhibited effects of L-NAME on acid secretion and GMBF could be reversed by pretreatment with L-arginine (L-ARG); (5) pretreatment with atropine inhibited gastric acid output (GAO) and partially attenuated GMBF. These results suggested that capsaicin-sensitive afferent neurons and endogenous NO were involved in the gastric acid secretion and hyperemic response to intragastric peptone and the hyperemic response was mediated by both cholinergic and noncholinergic neurons.

Animals↗
PubMed1996

[A prospective study on causal factors of female infertility with laparoscopy and transvaginal B-ultrasound].

OBJECTIVE: To study the casual factors of female infertility with laparoscopy and B-ultrasound. METHODS: Eighty-five infertile women were evaluated by serial transvaginal B-ultrasound scans for follicular development and ovulation and by laparoscopic examinations 2 to 6 days after ovulation. RESULTS: The patterns of follicular development and ovulation detected by B-ultrasound were: (1) ovulation from normal follicle (ONF) (56.47%); (2) ovulation from two follicles at the same time (O2F) (5.88%); (3) ovulation from small follicle (OSF) (16.47%); (4) ovulation from polycystic ovaries (PCO) (3.53%); (5) luteinized unruptured follicle syndrome (LUFS) (7.06%); (6) anovulation (10.90%). Laparoscopic examinations showed that the incidence of partial and complete tubal obstruction was 32.94% and pelvic adhesions 35.29%. Pelvic tuberculosis was found in 20.00%, which was the main disease leading to pelvic adhesions (46.67%), and tubal obstruction (60.71%). Endometriosis (EMS) was discovered in 36 cases (42.35%), among them, 30 (83.33%) had patent tubes. The stigmas or/and corpus hemorrhagica were seen in 60 out of 70 patients in whom ovulation had been diagnosed by B-ultrasound. 6 cases were defined as "mechanically unruptured follicle syndrome". CONCLUSIONS: Abnormal follicular development may result in female infertility. Pelvic tuberculosis is another main causal factor of infertility. Endometriosis related infertility may rather result from other factors than tubal obstruction. Laparoscopic examinations combined with transvaginal B-ultrasound scans are very useful approaches in the etiological study of female infertility.

Adult↗
PubMed1996

[Histologic examination and immunohistochemical analysis of estrogen and progesterone receptors of eutopic and ectopic endometrium in patients with endometriosis].

OBJECTIVE: To study the differences of histologic dating and steroid receptors between ectopic and eutopic endometrium in patients with endometriosis. METHODS: Histologic examinations were done on eutopic and ectopic endometrium in 28 patients with pelvic endometriosis, and estrogen and progestrone receptors concentrations were determined by immunochemical ABC method in 15 patients. All the ectopic tissues were biopsied from peritoneal lesions. RESULTS: In 67.9% patients, the ectopic endometrium development was retardated and 14.3% accelerated as compared with eutopic endometrium, and only 17.9% identical. The estrogen receptors (ER) and progesterone receptors (PR) contents of ectopic endometrium were significantly lower than those of eutopic endometrium in glandular cells (P < 0.01, P < 0.05 respectively), while differences were not significant in stroma cells. CONCLUSIONS: The advantage of the immunochemical technique is that it can definitely locate the site of receptors in the histologic section. The difference in histologic dating and ER and PR concentrations in the eutopic and ectopic endometrium may be accounted for by the different steroid environments and pathogenic theory of peritoneum metaplasia.

Endometriosis↗
PubMed1996

[Effects of gastric mucosal blood flow (GMBF) on the role of adaptive cytoprotection of rat gastric mucosa].

By the use of hydrogen gas clearance technique, we have investigated the role of GMBF in the adaptive cytoprotection induced by intragastric perfusion with low concentration prior to high concentration of HCl plus ethanol. The results were as follows: (1) intragastric perfusion with low concentration prior to high concentration of HCl plus ethanol led to an adaptive cytoprotection, i.e., the gross and the deep damage were decreased by 47.09% and 44.57% respectively, as compared with those caused by high concentration of HCl plus ethanol alone; correspondingly, GMBF also showed an adaptive hyperemic response, i.e., GMBF was increased by 28.02% as compared with that due to high concentration alone; (2) close arterial infusion of vasopressin blocked the adaptive hyperemic response and abolished the adaptive cytoprotection; (3) intravenous indomethacin reduced the basal GMBF, and abolished both the adaptive hyperemic response and cytoprotection; furthermore, the gross and deep damage were aggravated compared with that caused by high concentration alone. The results showed that the adaptive hyperemic response of gastric mucosa was involved in the adaptive cytoprotection and suggested that the adaptive cytoprotection of endogenous prostaglandin might be partially related to the increase of GMBF.

Adaptation, Physiological↗
PubMed1995

Relationship of DNA topoisomerase II alpha and beta expression to cytotoxicity of antineoplastic agents in human acute lymphoblastic leukemia cell lines.

The levels of expression of topoisomerase II alpha and topoisomerase II beta were investigated in six established cell lines of human childhood acute lymphoblastic leukemia (ALL) as a function of doubling time, cell cycle distribution, and of sensitivity to the antineoplastic agents Adriamycin and etoposide. The slowest growing cell line, ALL-G, was most sensitive to both drugs, whereas the fastest growing cell line, ALL-C, was 15.3- and 6.4-fold more resistant than ALL-G to Adriamycin and etoposide, respectively. Furthermore, ALL-W, the second most rapidly dividing cell line, was most resistant to both Adriamycin (22.8-fold) and etoposide (14.1-fold). Expression of topoisomerase II alpha varied inversely with doubling time, whereas no correlation was found between topoisomerase II beta levels and doubling time. Expression of topoisomerase II beta varied inversely with that of topoisomerase II alpha. The level of topoisomerase II alpha correlated directly with the percentage of cells in S and G2-M phases, whereas topoisomerase II beta expression varied directly with the number of cells in G1. An inverse correlation was found between the level of expression of topoisomerase II beta and resistance to Adriamycin, whereas a direct correlation was observed between the level of expression of topoisomerase II alpha and resistance to Adriamycin. Studies with etoposide, although not statistically significant, were consistent with the pattern observed with Adriamycin. These findings suggest that in ALL cells, cytocidal activity of Adriamycin and etoposide may be mediated, at least in part, by topoisomerase II beta.

Antineoplastic Agents↗