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Biomedical subjects

Y Tao

Publications and source records attributed to Y Tao.

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

Effects of glucagon on axoplasmic transport in mouse superior cervical ganglion cells.

The effects of glucagon on the axoplasmic transport of cultured mouse superior cervical ganglion cells were analyzed with the video-enhanced DIC microscope system. Glucagon increased the rate of fast axoplasmic transport by 30% in both anterograde and retrograde directions. The average velocity was increased from 1.36 +/- 0.48 microns/s to 1.74 +/- 0.43 microns/s (anterograde, n = 60) and from 1.37 +/- 0.48 microns/s to 1.62 +/- 0.39 microns/s (retrograde, n = 60). The stimulatory effect of glucagon on the axoplasmic transport was reversed in a glucose-free medium, whereas blocking the citrate cycle by pretreating neuronal cells with malonate did not alter the effect of glucagon. Together with our previous findings, our data suggest that neurotransmitters and hormones play a major role in the regulation of fast axoplasmic transport.

Animals↗
PubMed1999

Prospective study of colorectal cancer risk in men and plasma levels of insulin-like growth factor (IGF)-I and IGF-binding protein-3.

BACKGROUND: Insulin-like growth factor-I (IGF-I) is a potent mitogen for normal and neoplastic cells, whereas IGF-binding protein-3 (IGFBP-3) inhibits cell growth in many experimental systems. Acromegalics, who have abnormally high levels of growth hormone and IGF-I, have higher rates of colorectal cancer. We therefore examined associations of plasma levels of IGF-I and IGFBP-3 with the risk of colorectal cancer in a prospective case-control study nested in the Physicians' Health Study. METHODS: Plasma samples were collected at baseline from 14916 men without diagnosed cancer. IGF-I, IGF-II, and IGFBP-3 were assayed among 193 men later diagnosed with colorectal cancer during 14 years of follow-up and among 318 age- and smoking-matched control subjects. All P values are two-sided. RESULTS: IGFBP-3 levels correlated with IGF-I levels (r=.64) and with IGF-II levels (r=.90). After controlling for IGFBP-3, age, smoking, body mass index (weight in kg/[height in m]2), and alcohol intake, men in the highest quintile for IGF-I had an increased risk of colorectal cancer compared with men in the lowest quintile (relative risk [RR]=2.51; 95% confidence interval [CI]=1.15-5.46; P for trend = .02). After controlling for IGF-I and other covariates, men with higher IGFBP-3 had a lower risk (RR=0.28; 95% CI=0.12-0.66; P for trend = .005, comparing extreme quintiles). The associations were consistent during the first and the second 7-year follow-up intervals and among younger and older men. IGF-II was not associated with risk. CONCLUSIONS: Our findings suggest that circulating IGF-I and IGFBP-3 are related to future risk of colorectal cancer.

Case-Control Studies↗
PubMed1999

The human homologue of Drosophila TRF-proximal protein is associated with an RNA polymerase II-SRB complex.

Mammalian RNA polymerase II holoenzymes are large complexes that have been reported to contain, in addition to RNA polymerase II, homologues of several yeast SRBs, various general transcription factors, and other polypeptides. On the basis of its copurification with an SRB-containing RNA polymerase II complex by conventional chromatography procedures, we have identified a human homologue of Drosophila TRF-proximal protein, designated hTRFP, and isolated its cognate cDNA. Antibody specific for SRB7 can immunoprecipitate hTRFP and RNA polymerase II and, reciprocally, antibody specific for hTRFP can immunoprecipitate RNA polymerase II and SRB7. These data indicate that hTRFP is an integral component of an RNA polymerase II-SRB complex. Whereas the precise function of hTRFP remains to be determined, the hTRFP-containing RNA polymerase II-SRB complex supports basal level transcription and, relative to RNA polymerase II alone, enhances transcriptional activation by Gal4-VP16 in the presence of cofactor PC4. Thus, hTRFP may regulate transcription of class II genes through association with the RNA polymerase II-SRB complex.

Amino Acid Sequence↗
PubMed1999

The NIT2 nitrogen regulatory protein of Neurospora: expression and stability of nit-2 mRNA and protein.

In Neurospora crassa, NIT2 is a global transcription factor that positively regulates the expression of up to 100 genes that are related to nitrogen metabolism. NIT2 is responsible for the lifting of nitrogen catabolite repression when the cellular levels of glutamine or other favored nitrogen sources become limited. Immunoprecipitation of the NIT2 protein showed that it is constitutively expressed, although its expression level is elevated a few-fold when nitrate instead of glutamine is used as the sole nitrogen source. The NIT2 protein is very stable and its stability is not affected by the nitrogen sources. The nit-2 transcripts appear to be very stable as well. The lack of significant regulation of cellular levels of nit-2 mRNA and of NIT2 protein suggests that its interactions with other proteins, e.g., in the nitrate assimilation pathway, with NIT4 and NMR, or post-translational modification of NIT2, may play important roles in modulating the function of NIT2 in response to environmental stimuli.

Blotting, Western↗
PubMed1999

Effects of ALCAR on the fast axoplasmic transport in cultured sensory neurons of streptozotocin-induced diabetic rats.

The effects of acetyl-L-carnitine (ALCAR) on fast axoplasmic transport were studied in cultured dorsal root ganglion (DRG) neurons of diabetic rats. Three-month-old male rats were used 7 days after streptozotocin injection. Neurons obtained from ganglia were cultured with a high concentration of glucose. The amount and the mean velocity of retrogradely transported particles, reduced in the diabetic animal, were transiently recovered by 1 mM ALCAR. The number of particles moving at 0.8-1.2 microm/s, considered to be lysosomes, increased in the velocity distribution. ALCAR did not modify the amount and mean velocity of anterograde particles which were unaffected by diabetes, or of bidirectional particles in neurons of control rats. This study suggests that diabetic neuropathy may be relieved by ALCAR via recovering retrograde axoplasmic transport.

Acetylcarnitine↗
PubMed1999

Structural insight into insect viruses.

The first structure of an insect picorna-(small RNA-containing) virus is now available. Although there is considerable similarity in the structures of mammalian and insect picornaviruses, there are also remarkable differences, the most noteworthy being associated with the small, internal, functionally essential, VP4 protein.

Insect Viruses↗
PubMed1999

NF-kappaB functions as both a proapoptotic and antiapoptotic regulatory factor within a single cell type.

Recently NF-kappaB has been shown to have both proapoptotic and antiapoptotic functions. In T cell hybridomas, both T cell activators and glucocorticoids induce apoptosis. Here we show that blockade of NF-kappaB activity, using a dominant negative IkappaBalpha, has opposite effects on these two apoptotic signals. Treatment with PMA plus ionomycin (P/I) results in the upregulation of Fas Ligand (FasL) and induction of apoptosis. Inhibition of NF-kappaB activity inhibits the P/I mediated induction of FasL mRNA and decreases the level of apoptosis in these cultures, thus establishing NF-kappaB as a proapoptotic factor in this context. Conversely, inhibition of NF-kappaB confers a tenfold increase in glucocorticoid mediated apoptosis, establishing that NF-kappaB also functions as an antiapoptotic factor. We conclude that NF-kappaB is a context-dependent apoptosis regulator. Our data suggests that NF-kappaB may function as an antiapoptotic factor in thymocytes while functioning as a proapoptotic factor in mature peripheral T cells.

Apoptosis↗
PubMed1999

Quantitation of RNA polymerase II and its transcription factors in an HeLa cell: little soluble holoenzyme but significant amounts of polymerases attached to the nuclear substructure.

Various complexes that contain the core subunits of RNA polymerase II associated with different transcription factors have been isolated from eukaryotes; their precise molecular constitution depends on the purification procedure. We estimated the numbers of various components of such complexes in an HeLa cell by quantitative immunoblotting. The cells were lysed with saponin in a physiological buffer; approximately 140,000 unengaged polymerases (mainly of form IIA) were released. Only approximately 4,000 of these soluble molecules sedimented in glycerol gradients as holoenzyme-sized complexes. About 180,000 molecules of polymerases (approximately 110,000 molecules of form IIO) and 10,000 to 30,000 molecules of each of TFIIB, TFIIEalpha, TFIIEbeta, TFIIF-RAP74, TFIIF-RAP30, and TFIIH-MAT1 remained tightly associated with the nuclear substructure. Most proteins and run-on activity were retained when approximately 50% of the chromatin was detached with a nuclease, but approximately 45,000 molecules of bound TATA binding protein (TBP) were detached. Similar results were obtained after cross-linking living cells with formaldehyde. The results provide little support for the existence of a large pool of soluble holoenzyme; they are consistent with TBP-promoter complexes in nuclease-sensitive chromatin being assembled into preinitiation complexes attached to the underlying structure.

Cell Nucleus↗
PubMed1999

[Investigation of Y chromosome and polymorphism of 5 Chinese ethnic groups in Yunnan Province, China].

OBJECTIVE: To investigate the polymorphism of DYS287 in the Han, Dai, Lahu, Wa and Tibetan groups living in Yunnan Province, China. METHODS: YAP element was detected by PCR amplification and agarose gel electrophoresis. RESULTS: With 150bp product in all Han,Dai, Lahu and Wa individuals, YAP element is absent. In 11 Tibetan individuals out of 30, YAP element is present and the PCR product is 455bp. CONCLUSION: As an important and stable genetic marker, DYS287 can provide reliable evidence in evolution study.

China↗
PubMed1999

Racial variation in insulin-like growth factor-1 and binding protein-3 concentrations in middle-aged men.

African-American men have the highest and Asian-American men have the lowest prostate cancer incidence rates in the United States; internationally, rates for the Asian continent are among the lowest. Higher insulin-like growth factor (IGF)-1, which participates in the control of cellular growth and differentiation and is modulated by IGF-binding protein-3 (IGFBP-3), was associated with an increased prostate cancer risk in three recent studies. We, therefore, investigated whether plasma levels of IGF-1 and IGFBP-3 vary by race in United States men selected from among members of the Health Professionals Follow-up Study who were 47-78 years old in 1993-1995 when they provided blood (n = 18,000). All of the men who described their major ancestry as African American (n = 63) and a random sample of 75 Asians and 75 Caucasians were invited to provide a second blood sample in 1997, of whom 42, 52, and 55, respectively, did so. IGF-1 and IGFBP-3 concentrations were determined by ELISA. We used nonparametric methods to assess racial variation in age-adjusted levels. Caucasians had the highest median IGF-1 level (224 ng/ml), followed by Asians (208 ng/ml) and African Americans (205 ng/ml). Median IGFBP-3 concentration was similar between Caucasians and Asians but was more than 13% lower in African Americans. Median molar IGF-1:IGFBP-3 ratio was greatest in Caucasians and lowest in Asians. The lower IGF-1 blood levels relative to IGFBP-3 levels among Asian men are consistent with their lower prostate cancer incidence. Although differences in circulating IGF-1 do not seem to account for the greater prostate cancer risk among African-American men, their absolute lower levels of IGFBP-3 may be contributory.

Age Distribution↗
PubMed1999

[Treatment of polycystic ovary syndrome and related infertility with clomiphene resistance by compound cyproterone acetate].

OBJECTIVE: To assess the efficacy and safety of compound cyproterone acetate (CPA Co, or Diane-35) in the treatment of polycystic ovary syndrome (PCOS) and to explore its potential role in improving the outcome of ovulation induction in clomiphene (CC) resistant cases. METHODS: Twenty-nine proven PCOS patients were enrolled. Seventeen out of them, including 16 who were resistant to CC, had anovulatory infertility. CPA Co was given for 4-6 cycles. Serum luteinizing hormone(LH), follicle stimulating hormone(FSH), estradiol(E2), testosterone(T), androstenedione(A), dehydroepiandrosterone (Ds), sex hormone binding globvlin (SHBG), insulin concentrations, total cholesterol, triglycerides(TG), high density lipoprotein-cholesterol(HDL-C), low density lipoprotein-cholesterol (LDL-C), apolipoprotein A, apolipoprotein B and transvaginal pelvic ultrasonography were determined before, 2-3 cycles and 4-6 cycles after treatment. After stopping the drug, CC or human menopausal gonadotropin were re-administered in 12 patients (22 cycles) and 5 cases (6 cycles) respectively for induction of ovulation. RESULTS: All patients had regular uterine bleeding during CPA Co therapy. Acne improved in 8 cases. Hirsute score didn't decrease significantly. Serum LH, FSH, E2, A, T, Ds concentrations decreased significantly (P < 0.05-0.01), while SHBG levels increased by 5.1 times after treatment. Meanwhile, bilateral ovarian volumes shrunk and follicle numbers decreased significantly (P < 0.05-0.01). Serum insulin levels did not change significantly. As to the lipid profile, the most striking change was 55.1% increase of HDL-C and 23.0% decrease of LDL-C, although TG also increased by 36.2%. 58.6% of patients had mild and transient adverse effects. Serum alanine transaminase increased in 3 cases. After stopping treatment, CC induced 5.3% (by cases) or 45.4% (by cycles) ovulation rate and 2 pregnancies achieved in 12 CC resistant patients. CONCLUSION: CPA Co has antiandrogenic effects on PCOS patients clinically, biochemically and in ovarian morphology. Pretreatment of CPA Co may play a role in improving the outcome of ovulation induction in CC resistant cases.

Adult↗
PubMed1999

[Mutations of several tumor suppressor genes in primary retinoblastoma].

OBJECTIVE: To study the status of several tumor suppressor genes in primary retinoblastoma. METHODS: Single stranded conformation polymorphism (SSCP) analysis associated with direct DNA sequencing was used to identify point mutations in the coding sequence of Rb, p53, p16, p15 and p21 tumor suppressor genes, and multiplex PCR was used to detect big deletion in p16 and p15 genes. RESULTS: Rb gene point mutation was detected in 74% of retinoblastoma and p16 gene big deletions in 16% of retinoblastoma with or without Rb gene mutation. However, despite polymorphism, no real mutation was detected in p53 or p21 gene in retinoblastoma. CONCLUSION: The evidence from this study suggests that retinoblastoma is resulted exclusively from alterations of genes in Rb pathway.

Cell Cycle Proteins↗
PubMed1999

[Endogenous protective effects of superoxide dismutases on infectious brain injury in rats].

We studied the alterations of MDA and three forms of SOD activities such as T-SOD, CuZn-SOD, and Mn-SOD in rat cerebral tissues injected by bordetella pertussis (BP) to elucidate protective mechanism of SOD against the infectious brain injury. The results were that water content(WC), Evans blue content(EB), MDA, and Mn-SOD activities in 4 h and 24 h BP-treated groups increased and T-SOD and CuZn-SOD decreased compared to corresponding normal saline(NS)-treated groups, respectively(P < 0.01); MDA increased and had a positive correlation with WC and EB in 4 h BP treated group (r = 0.9650, r = 0.9441, P < 0.01, P < 0.01, respectively); Mn-SOD activities were elevated and had a negative correlation with WC, EB, and MDA (r = -0.8650, r = -0.9021, r = -0.9346, P < 0.01, P < 0.01, P < 0.01, respectively) in 24 h BP-treated group. The results suggest that the increase of component Mn-SOD activities may play an important role in vivo endogenous protective mechanism against delayed infectious brain injury.

Animals↗
PubMed1999

[Microwave therapy of radiotherapeutical choanal atresia under nasal endoscope].

OBJECTIVE: In order to know efficacy of microwave to treat the secondary choanal atresia under nasal endoscope. METHOD: Three patients suffering from membranous choanal atresia due to radiotherapy of nasopharyngeal carcinoma (NPC) were treated by microwave under nasal endoscope. RESULT: Satisfing recoveries were accomplished in all patients and no relapse was found within the 7-13 months' follow-up. CONCLUSION: This method has many advantages, such as: processing available under local anesthesia without incision, mild damage to normal tissues, clear operation visual field, less hemorrhage and postoperative pain, complete coagulation and gasification of atresic membrane, no need of postoperative dilation and stable therapeutical effect.

Adult↗
PubMed1998

Assembly of a tailed bacterial virus and its genome release studied in three dimensions.

We present the first three-dimensional reconstruction of a prolate, tailed phage, and its empty prohead precursor by cryo-electron microscopy. The head-tail connector, the central component of the DNA packaging machine, is visualized for the first time in situ within the Bacillus subtilis dsDNA phage phi29. The connector, with 12- or 13-fold symmetry, appears to fit loosely into a pentameric vertex of the head, a symmetry mismatch that may be required to rotate the connector to package DNA. The prolate head of phi29 has 10 hexameric units in its cylindrical equatorial region, and 11 pentameric and 20 hexameric units comprise icosahedral end-caps with T=3 quasi-symmetry. Reconstruction of an emptied phage particle shows that the connector and neck/tail assembly undergo significant conformational changes upon ejection of DNA.

Bacillus Phages↗
PubMed1998

Structure of bacteriophage T4 fibritin M: a troublesome packing arrangement.

Fibritin, a 52 kDa product of bacteriophage T4 gene wac, forms 530 A long fibers, named whiskers, that attach to the phage neck and perform a helper function during phage assembly. Fibritin is a homotrimer, with its predominant central domain consisting of 12 consecutive alpha-helical coiled-coil segments linked together by loops. The central domain is flanked by small globular domains at both ends. Fibritin M is a genetically engineered fragment of the wild type and contains 74 amino-acid residues corresponding to the last coiled-coil segment and the complete carboxy-terminal domain. The crystals of fibritin M belong to the rare space group P3 with three crystallographically independent trimers in the unit cell. The structure has been established at 1.85 A resolution by combining molecular and isomorphous replacement techniques. One of the two heavy-atom derivatives used was gaseous xenon. A substantial fraction of residues in each independent trimer is disordered to various extents in proportion to the lack of restraints on the molecules provided by the lattice contacts. Accurate modeling of the solvent present in the crystals was crucial for achieving good agreement with experimental data.

Amino Acid Sequence↗