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Biomedical subjects

A Ma

Publications and source records attributed to A Ma.

At least 37 records · Page 2Linked to original sources
PubMed2000

Regulation of c-SRC activity and function by the adapter protein CAS.

SRC family kinases play essential roles in a variety of cellular functions, including proliferation, survival, differentiation, and apoptosis. The activities of these kinases are regulated by intramolecular interactions and by heterologous binding partners that modulate the transition between active and inactive structural conformations. p130(CAS) (CAS) binds directly to both the SH2 and SH3 domains of c-SRC and therefore has the potential to structurally alter and activate this kinase. In this report, we demonstrate that overexpression of full-length CAS in COS-1 cells induces c-SRC-dependent tyrosine phosphorylation of multiple endogenous cellular proteins. A carboxy-terminal fragment of CAS (CAS-CT), which contains the c-SRC binding site, was sufficient to induce c-SRC-dependent protein tyrosine kinase activity, as measured by tyrosine phosphorylation of cortactin, paxillin, and, to a lesser extent, focal adhesion kinase. A single amino acid substitution located in the binding site for the SRC SH3 domain of CAS-CT disrupted CAS-CT's interaction with c-SRC and inhibited its ability to induce tyrosine phosphorylation of cortactin and paxillin. Murine C3H10T1/2 fibroblasts that expressed elevated levels of tyrosine phosphorylated CAS and c-SRC-CAS complexes exhibited an enhanced ability to form colonies in soft agar and to proliferate in the absence of serum or growth factors. CAS-CT fully substituted for CAS in mediating growth in soft agar but was less effective in promoting serum-independent growth. These data suggest that CAS plays an important role in regulating specific signaling pathways governing cell growth and/or survival, in part through its ability to interact with and modulate the activity of c-SRC.

Animals↗
PubMed2000

Conservation of heterochromatin protein 1 function.

Heterochromatin represents a cytologically visible state of heritable gene repression. In the yeast, Schizosaccharomyces pombe, the swi6 gene encodes a heterochromatin protein 1 (HP1)-like chromodomain protein that localizes to heterochromatin domains, including the centromeres, telomeres, and the donor mating-type loci, and is involved in silencing at these loci. We identify here the functional domains of swi6p and demonstrate that the chromodomain from a mammalian HP1-like protein, M31, can functionally replace that of swi6p, showing that chromodomain function is conserved from yeasts to humans. Site-directed mutagenesis, based on a modeled three-dimensional structure of the swi6p chromodomain, shows that the hydrophobic amino acids which lie in the core of the structure are critical for biological function. Gel filtration, gel overlay experiments, and mass spectroscopy show that HP1 proteins can self-associate, and we suggest that it is as oligomers that HP1 proteins are incorporated into heterochromatin complexes that silence gene activity.

Amino Acid Sequence↗
PubMed2000

Selective denervation and resection of cervical muscles in the treatment of spasmodic torticollis: long-term follow-up results in 207 cases.

OBJECT: To report the outcome of patients with selective denervation and resection of cervical muscles for spasmodic torticollis. METHODS: We reviewed 362 cases of surgically treated spasmodic torticollis. 207 patients were followed from 2 years to 29 years. RESULTS: Total or marked relief of symptoms with preservation of normal of nearly normal movements has been obtained in 87.9%. CONCLUSION: This procedure may be recommended if one to two years of conservative therapy does not offer satisfactory relief of symptoms.

Adolescent↗
PubMed2000

Correlative factors of insulin resistance in essential hypertension.

Essential Hypertension (EH) is correlated with a metabolic disturbance characterized by insulin resistance (IR). In this study, there were observed in 47 subjects with EH and 30 subjects with normal blood pressure. Serum levels of insulin-like growth factor-1 (IGF-1), serum levels of growth hormone (GH), the activity of erythrocyte insulin receptors (EIR), and ATP levels in erythrocytes, the insulin sensitivity index (ISI) was used to study the correlative factors of essential hypertension. 1. Among patients with EH, ISI, GH, and low-affinity insulin binding sites of EIRs (RT2) were found to be in significantly lower amounts, IGF-1 levels and the KD2 of the erythrocyte insulin receptors were noted to be significantly higher. Compared with the control group, there was a marked difference between EH group and the control group. However, no statistical difference was observed between the hypertensive group and the group with normal blood pressure as regards erythrocyte ATP levels, high-affinity insulin binding sites of EIRs (RT1), and the KD1 of EIRs. 2. In the hypertensive group, the ISI was negatively correlated with mean arterial blood pressure (MBP), a family history of hypertension, the body mass index (BMI), the waist-hip ratio (WHR) and IGF-1 levels (r=-0.614delta, -0.354**, -0.386**, -0.472**, -0.298*, delta p < 0.001, **p < 0.01, *p < 0.05), were positively correlated with RT2 and GH levels (r=0.301**, 0.275*, **p < 0.01, *p < 0.05). There were no statistically significant differences between ISI and age, sex, smoking history, drinking, RT1, KD1, and ATP levels in erythrocytes. 3. The ISI was used as the dependent variable in multiple linear stepwise regression analysis. MBP (X1), a family history of EH (X2), WHR (X3), GH (X4), IGF-1 (X5), RT2 (X6), and the body mass index (X7) was used as independent variables. X1, X2, X3, X5, X6, and X7 were used in the equations. The results indicate that patients with EH also tend to have IR. We suggest that MBP, a family history of hypertension, BMI, WHR, IGF-1, and RT2 might be independent factors affecting IR in cases of essential hypertension.

Adenosine Triphosphate↗
PubMed2000

[Effect of Nerium indicum on killing Oncomelania hupensis].

A laboratory experiment at 20 +/- 5 degrees C shows that the water extract of fresh Nerium indicum had an obvious effect on killing Oncomelania hupensis. Treated with 0.1% water extract for four days, the mortality of O. hupensis was up to 100%. The effect of different tissues of N. indicum on O. hupensis was in order of stem phloem > leaf > root phloem > flower. The effect of N. indicum on O. hupensis was about ten times higher than that of Pterocarya stenoptera and Rumex japonicus, and was equal to that of 1 x 10(-3) mg.L-1 niclosamidum.

Animals↗
PubMed2000

[The St14 (DXS 52) VNTR in a Guangdong Han population and detection of hemophilia A carriers].

OBJECTIVE: To investigate the genetic polymorphism of the St14 (DXS 52) variable number tandem repeat (VNTR) in normal individuals in Guangdong, and to evaluate the efficacy of this marker for the gene diagnosis of hemophilia A. METHODS: 125 unrelated healthy individuals (male 21, female 104) and 4 hemophilia A families were detected using amplified-fragment-length polymorphism (Amp-FLP). RESULTS: 11 allelic fragments ranging from 700 to 1,810 bp in size and 7 different genotypes in males, 17 different genotypes in females were observed, respectively. The allele frequencies were 0.0044 to 0.4803. The polymorphism information contents (PIC) was 0.7335, and the heterozygosity was 0.432. Four families with hemophilia A were analyzed and 2 of them were informative for linkage analysis. In one family, 2 females were determined to be normal individuals, not carriers, one female carrier was detected in the other family. CONCLUSION: St14 (DXS 52) was a useful polymorphism marker for carrier detection of hemophilia A in southern Chinese population, and it was different from those in Caucasian.

China↗
PubMed2000

[Study on extraction process for psoralen in compound prescription by orthogonal design].

The study on water volume, extraction time and times for the extraction of psoralen in compound prescription Yiniao Tong capsule has been carried out by orthogonal design. The process condition has been determinated, extracting prescription herbs with water for 3 times(2 hour and 16 time amount of water all told). The determination method used in this experiment was TLC-scanning.

Capsules↗
PubMed1999

GATA-1 and erythropoietin cooperate to promote erythroid cell survival by regulating bcl-xL expression.

The transcription factor GATA-1 is essential for normal erythropoiesis. By examining in vitro-differentiated embryonic stem cells, we showed previously that in the absence of GATA-1, committed erythroid precursors fail to complete maturation and instead undergo apoptosis. The mechanisms by which GATA-1 controls cell survival are unknown. Here we report that in erythroid cells, GATA-1 strongly induces the expression of the anti-apoptotic protein bcl-xL, but not the related proteins bcl-2 and mcl-1. Consistent with a role for bcl-xL in mediating GATA-1-induced erythroid cell survival, in vitro-differentiated bcl-xL-/- embryonic stem cells fail to generate viable mature definitive erythroid cells, a phenotype resembling that of GATA-1 gene disruption. In addition, we show that erythropoietin, which is also required for erythroid cell survival, cooperates with GATA-1 to stimulate bcl-xL gene expression and to maintain erythroid cell viability during terminal maturation. Together, our data show that bcl-xL is essential for normal erythroid development and suggest a regulatory hierarchy in which bcl-xL is a critical downstream effector of GATA-1 and erythropoietin-mediated signals.

Animals↗
PubMed1999

A study of early pregnancy factor activity in the sera of women with trophoblastic tumor.

PROBLEM: To detect whether or not the early pregnancy factor (EPF)-like activity, or chaperonin 10, could be in the sera of patients with trophoblastic tumor in order to find another more efficient means to diagnose this kind of tumor. METHOD OF STUDY: The rosette inhibition assay was used to detect EPF-like activity in 216 sera, collected from patients with gestational trophoblastic tumor, including 47 sera of patients with choriocarcinoma, 68 sera of patients bearing invasive mole, and 101 sera of patients with vesicular mole. RESULTS: The accuracy of diagnosing malignant trophoblastic tumor by detecting EPF-like activity is 91.3% (105/115), with a false positive rate of 14.58% and a false negative rate of 4.8% by this method. Furthermore, the rosette inhibition titer (RIT) values have significant difference (P < 0.001) between the sera in patients with malignant trophoblastic tumor before treatment and those after treatment. CONCLUSIONS: This study demonstrated that diagnosis of malignant trophoblastic tumor could be made with an accuracy of 91.3% by detecting EPF-like activity and that EPF-like activity could be used as an indicator to distinguish benign from malignant trophoblastic tumor.

Adult↗
PubMed1999

[Effects of vitamins E, C and beta-carotene on DNA damage].

OBJECTIVE: To investigate their effects on lymphocyte damage with supplementation of high-dose vitamins E, C and beta-carotene. METHODS: Healthy men aged 50 - 59 years were selected and randomized into the trial and control groups with 50 in each one. In the trial group, 25 mg of beta-carotene, 100 mg vitamin C and 280 mg vitamin E were given to each subject every day for 20 weeks. Whole blood was collected in both the trial and control groups and its lymphocytes separated. Damage to DNA was analyzed with a"comet" electrophoresis technique, and serum levels of vitamin C, beta-carotene and alpha-tocopherol were determined by high performance liquid chromatography. RESULTS: There was no significant difference in the proportions of spontaneous damage to DNA in lymphocytes between the trial and control groups (6.1% vs. 6.8%). But, proportions of damage to DNA in peripheral lymphocytes increased to 36.14%, 59.45, and 69.62%, respectively, after treatment with 30 micromol/L, 100 micromol/L and 300 micromol/L of H(2)O(2). CONCLUSION: Supplementation of vitamin E, C and beta-carotene could effectively reduce the damage to DNA caused by H(2)O(2).

Antioxidants↗
PubMed1998

IL-15 receptor maintains lymphoid homeostasis by supporting lymphocyte homing and proliferation.

The IL-15 receptor alpha subunit (IL-15Ralpha) mediates high-affinity binding of IL-15, a pleiotropic cytokine implicated in the development of innate immune cells. We have generated IL-15Ralpha null (IL-15Ralpha-/-) mice to understand the role of IL-15Ralpha in immune development and function. IL-15Ralpha-/- mice are markedly lymphopenic despite grossly normal T and B lymphocyte development. This lymphopenia is due to decreased proliferation and decreased homing of IL-15Ralpha-/- lymphocytes to peripheral lymph nodes. These mice are also deficient in natural killer cells, natural killer T cells, CD8+ T lymphocytes, and TCRgammadelta intraepithelial lymphocytes. In addition, memory phenotype CD8+ T cells are selectively reduced in number. Thus, IL-15Ralpha has pleiotropic roles in immune development and function, including the positive maintenance of lymphocyte homeostasis.

Animals↗
PubMed1998

[Effect of radix Achyranthis bidentatae on memory and endurance].

After P. O. decoction of Radix Achyranthis Bidentatae, continuously for seven days in mice, the drug could effectively improve the acquisition of memory of mice, significantly enhance the endurance of mice. The results indicated that the decoction of Radix Achyranthis Bidentatae has the actions of enhancing memory and endurance.

Achyranthes↗
PubMed1997

Gene structure, cDNA sequence, and expression of murine Bak, a proapoptotic Bcl-2 family member.

To facilitate the creation of Bak knockout mice and the further analysis of this Bcl-2 family member, we have isolated and sequenced the complete mouse Bak cDNA. The cDNA is 2 kb long and shares an overall nucleotide identity to the human Bak cDNA of 62%. The mouse Bak protein is 208 amino acids long with a predicted molecular weight of 23 kDa. The mouse Bak mRNA could be detected in all mouse tissues examined. In addition we mapped the murine bak gene. It consists of six exons spanning about 10 kb on chromosome 17B. The 5' region of the murine bak gene is unmethylated on the dinucleotide CpG in the area around exon 1. Furthermore, it contains potential binding sites for transcription factors such as Sp1 and c-Myb.

Amino Acid Sequence↗
PubMed1997

Dietary L-arginine supplementation normalizes platelet aggregation in hypercholesterolemic humans.

OBJECTIVES: The present study was designed to test the hypothesis that long-term dietary supplementation with the nitric oxide precursor L-arginine would enhance vascular or platelet-derived nitric oxide activity, or both, and thereby inhibit platelet reactivity in hypercholesterolemic humans. BACKGROUND: We have shown that reduced vascular activity of nitric oxide in hypercholesterolemic rabbits can be restored by L-arginine supplementation. The improvement in nitric oxide activity is associated with an inhibition of platelet aggregation ex vivo. This effect is most likely due to increased elaboration of endothelium- or platelet-derived nitric oxide, or both, because the inhibition of platelet reactivity was associated with elevation of intraplatelet cyclic guanosine monophosphate and was reversed by the nitric oxide synthase antagonist N-methyl-arginine. METHODS: In a double-blinded, randomized, placebo-controlled trial, hypercholesterolemic patients were assigned to L-arginine hydrochloride, 8.4 g/day orally, or placebo for 2 weeks. Platelet-rich plasma was obtained for aggregometry induced by collagen (1 to 10 micrograms/ml) at four points: baseline, after 2 weeks of treatment, after a 2-week washout and after a long-term washout of 16 weeks on average. Aggregation was quantified by light transmittance and expressed as a percent transmittance observed with platelet-poor plasma. RESULTS: Compared with normocholesterolemic control subjects, platelets from hypercholesterolemic subjects stimulated with 5 micrograms/ml of collagen showed increased aggregability (68.6% in hypercholesterolemic patients vs. 54.5% in normocholesterolemic control subjects, p < or = 0.02). After 2 weeks of treatment with L-arginine (but not placebo), platelet reactivity was modestly reduced; this effect persisted for 2 weeks after discontinuation of arginine (52.6% in arginine-treated patients vs. 65.1% in normocholesterolemic control subjects, p = 0.07). After 18 weeks (i.e., 16 weeks after discontinuing arginine treatment), the platelets of hypercholesterolemic patients once again became hyperaggregable, and the extent of platelet aggregation was significantly increased compared with the 4-week point (73.6% after vs. 52.6% during arginine treatment, p < 0.01). No significant change in platelet reactivity was seen in placebo-treated hypercholesterolemic patients throughout the study. L-Arginine treatment was well tolerated without side effects. CONCLUSIONS: This double-blinded, placebo-controlled study demonstrates that dietary supplementation with L-arginine can modestly attenuate the increased platelet reactivity seen in hypercholesterolemic patients. The data are consistent with our previous studies in hypercholesterolemic animals, demonstrating that L-arginine restores endogenous nitric oxide activity and inhibits platelet aggregation. Enhancement of endogenous nitric oxide activity is a potential novel therapeutic strategy worthy of further study.

Arginine↗