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Biomedical subjects

D Guo

Publications and source records attributed to D Guo.

At least 127 records · Page 7Linked to original sources
PubMed1996

Childhood lead poisoning in China.

In China, comprehensive epidemiological data relating to the prevalence of childhood lead poisoning are not available. However, existing data suggest that this disease may be widely pervasive as a result of rapid industrialization and the use of leaded gasoline. Seventeen publications have reported elevated blood lead levels in children from different areas of the country. Children residing in industrial and busy traffic areas had average blood lead levels(BPb) of 21.8-67.9 mu g/dl. The percentages of BPb values above 10 mu g/dl, which is the definition of lead poisoning in children, ranged from 64.9% to 99.5%. Even for 'unexposed' children, about 50% of them had BPb values above 10 mu g/dl. Furthermore, several retrospective pilot studies were conducted in Shanghai, Shenyang, Fuzhou and Beijing to evaluate the health effects of lead at current degree of exposure. The link between low-level lead exposure and deficits in IQ, neurobehavioral development and physical growth is remarkably consistent without exception. In summary, the harmful health effects of childhood lead poisoning in limited studies of exposed and 'unexposed' children demonstrate that this totally preventable disease warrants considerable public health attention in China.

Child↗
PubMed1996

Tumor necrosis factor promotes phosphorylation and binding of insulin receptor substrate 1 to phosphatidylinositol 3-kinase in 3T3-L1 adipocytes.

Chronic incubation of 3T3-L1 adipocytes with tumor necrosis factor (TNF) induces a state of insulin resistance characterized by a diminished ability of insulin to induce phosphorylation of the beta subunit of its own receptor and insulin receptor substrate 1 (IRS-1). When adipocytes are briefly pretreated with TNF and then stimulated with insulin, tyrosine phosphorylation of IRS-1 increases above the level induced by insulin alone. By itself, TNF induces the time-dependent tyrosine phosphorylation of proteins in 3T3-L1 adipocytes. Among these is IRS-1, a docking protein with tyrosine phosphorylation sites that bind cytoplasmic signaling molecules that contain Src homology 2 (SH2) domains. TNF stimulation of 3T3-L1 adipocytes also promotes the association of the p85 regulatory subunit of phosphatidylinositol 3-kinase (PI 3-kinase) with IRS-1 and also its tyrosine phosphorylation. In murine 3T3-L1 adipocytes, IRS-1 and PI 3-kinase phosphorylation and the association of these proteins are promoted by murine TNF, which interacts with the type 1 and type 2 TNF receptors. Human TNF, which binds to the murine type 1 TNF receptor selectively, also promotes IRS-1 phosphorylation and binding of IRS-1 to PI 3-kinase. This is the first demonstration that a member of the TNF/nerve growth factor receptor superfamily can use an IRS-1 signaling system as a component of its cellular response and provides a mechanism through which TNF receptors may engage downstream elements in signaling pathways.

Adipocytes↗
PubMed1996

The Myxococcus xanthus rfbABC operon encodes an ATP-binding cassette transporter homolog required for O-antigen biosynthesis and multicellular development.

A wild-type sasA locus is critical for Myxococcus xanthus multicellular development. Mutations in the sasA locus cause defective fruiting body formation, reduce sporulation, and restore developmental expression of the early A-signal-dependent gene 4521 in the absence of A signal. The wild-type sasA locus has been located on a 14-kb cloned fragment of the M. xanthus chromosome. The nucleotide sequence of a 7-kb region containing the complete sasA locus was determined. Three open reading frames encoded by the genes, designated rfbA, B and C were identified. The deduced amino acid sequences of rfbA and rfbB show identity to the integral membrane domains and ATPase domains, respectively, of the ATP-binding cassette (ABC) transporter family. The highest identities are to a set of predicted ABC transporters required for the biosynthesis of lipopolysaccharide O-antigen in certain gram-negative bacteria. The rfbC gene encodes a predicted protein of 1,276 amino acids. This predicted protein contains a region of 358 amino acids that is 33.8% identical to the Yersinia enterocolitica O3 rfbH gene product, which is also required for O-antigen biosynthesis. Immunoblot analysis revealed that the sasA1 mutant, which was found to encode a nonsense codon in the beginning of rfbA, produced less O-antigen than sasA+ strains. These data indicate that the sasA locus is required for the biosynthesis of O-antigen and, when mutated, results in A-signal-independent expression of 4521.

ATP-Binding Cassette Transporters↗
PubMed1996

Biological activities of human tumor necrosis factor-alpha and its novel mutants.

Biological activities of human tumor necrosis factor-alpha (hTNF-alpha) and its mutants were compared. In cytotoxicity assay with L929 cells, one mutant, designated as TNF-B, showed 4.5-fold higher activity than TNF examined. And TNF-B also increased cytostatic activity and decreased protein synthesis against U937 cells. In receptor binding assay, TNF-B had almost the same affinity for TNF receports on L929 cells as hTNF-alpha. But another mutant, TNFarg, markedly decreased the all activities of hTNF-alpha and had lower affinity for receports on different types of target cell. These results indicated that the relative activity of TNFs to target cells may correlate with their affinity for receports. We also found that TNF-B retained the cytotoxicity of hTNF-alpha for HEp-2 cells. TNF-B also had two-fold higher affinity than hTNF-alpha for receptors on HEp-2 cells (only carrying hTNF-R55) and lower affinity for receptors on U937 cells (expressing mainly hTNF-R75). These results suggested that TNF-B might still interact with the human TNF-R55 receptor, but it might largely lose its ability to bind to human TNF-R75. Changes of biological activity of TNFs might be due to an altered affinity to the different types of TNF receptor on the target cells.

Amino Acid Sequence↗
PubMed1996

Biological activities of human tumor necrosis factor-alpha and its novel mutants.

Biological activities of human tumor necrosis factor-alpha (hTNF-alpha) and its mutants were compared. In cytotoxicity assay with L929 cells, one mutant, designated as TNF-B, showed 4.5-fold higher activity than TNF examined. In receptor binding assay, TNF-B had almost the same affinity for TNF receptors on L929 cells as hTNF-alpha. We also found that TNF-B retained the cytotoxicity of hTNF-alpha for HEp-2 cells. TNF-B also had two-fold higher affinity than hTNF-alpha for receptors on HEp-2 cells (only carrying hTNF-R55) and lower affinity for receptors on U937 cells (expressing mainly hTNF-R75). These results suggested that TNF-B might still interact with the human TNF-R55 receptor, but it might largely lose its ability to bind to human TNF-R75. Changes of biological activity of TNFs might be due to an altered affinity to the different types of TNF receptor on the target cells.

Amino Acid Sequence↗
PubMed1996

[Clinical study on the effect of TCM treatment in decreasing frequency of peritoneal dialysis].

Traditional Chinese herbal medicine was used in combination with peritoneal dialysis (PD) in order to improve the renal function and reduce the frequency of PD. The results indicated that, after 3 months of PD+TCM, the serum BUN, creatinine and mean arterial pressure of therapeutic group lowered and the hemoglobin elevated as compared with those after 1 month of PD (P < 0.01), the difference of above-mentioned criteria between PD+TCM group and less frequent PD (LEPD) group was significant too, while there was no obvious difference in comparison of the PD+TCM group with regular PD group (P > 0.05). The effective rate and the edema cure rate of TCM+PD group were superior to the LFPD group, but had no evident difference as compared with the regular PD group. The results revealed that PD combined with TCM treatment might reduce the frequency of PD for the uremia patient deserved long-term PD therapy.

Adult↗
PubMed1996

[Segmental influence of dorsal root action potentials evoked by stimulating the acupoints after acupuncture along meridians].

Using the method of recording the corresponding dorsal root action potentials evoked by stimulating the acupoints, we found that electro-acupuncture could not only expand the segmental of potentials, but also amplitude the potentials. The results proved the acupuncture sensation may be transsegmental afferent after acupuncture along the meridians. This study gave a new evidence for the mechanism's explanation of propagated sensation along the meridians.

Acupuncture Points↗
PubMed1996

[A study on the effect of emodin on smooth muscle cell proliferation].

By using smooth muscle cell (SMC) culture in vitro and H3-TdR incorporation technique, we tested the effect of Emodin on SMC proliferation in three groups: (1) Normal rabbit iliac artery, (2) atherosclerotic rabbit iliac artery, (3) atherosclerotic rabbit iliac artery after PTA. These data indicated: Emodin has antiproliferative effect on SMC, which is dose dependent; it blocks the transition of SMC cycle from G0 to S. In PTA group it exerts a more significant proliferative effect than in the normal one. This is a the first report of Emodin's effect on SMC proliferation, it implies that the drug may be used clinically to prevent restenosis after PTCA.

Angioplasty, Balloon↗
PubMed1996

[Electroacupuncture along meridians activating subcutaneous primary afferents in acupoints--CB-HRP tracing study].

The experiment was performed to observe the segmental distribution of sensory afferent nerves in acupoints and the influence of electroacupuncture (EA) along meridians on it. 1% CB-HRP solution (5 microliters) was injected subcutaneously at unilateral "Zusanli" or "Ruzhong" acupoint of rats. The HRP labeled cells were counted in the related spinal dorsal root ganglia (DRG). The results were as follows: the sensory nerve terminals of "Zusanli" acupoint mainly projected to the neurons of L4 and L5 DRG and that of "Ruzhong" acupoint projected to the neurons of T4, T5 and T6 DRG; sensory nerve terminals of "Zusanli" or "Ruzhong" acupoint were activated by the EA stimulation along meridians, their ability of uptaking HRP was enhanced, so the HRP labeled cells increased in the related DRG, the HRP labeled DRG segments spread. This study provides a new morphological evidence for the mechanism's explanation of propagated sensation along the meridians.

Acupuncture Points↗
PubMed1996

[Loss of p16 gene in bladder cancer and genitourinary carcinoma cell lines].

To determine whether p16, a novel antioncogene, is altered in human bladder cancer and urogenital carcinoma cell lines, we examined a series of 10 primary bladder cancer and 4 urogenital carcinoma cell lines (BIU-87, EJ, GRC and PC-3M) by southern blot. Two cases of 10 primary bladder cancer and EJ, BIU-87 PC-3M had homozygous deletion of p16, and 2 cases of 10 primary bladder cancer had loss of heterozygous. Loss of p16 may provide an additional growth advantage and carcinogenesis.

Carcinoma, Squamous Cell↗
PubMed1996

[Selection of surgical approaches in the treatment of aortoiliac arterial occlusive disease].

31 patients with aortoiliac occlusive disease with or without infrainguinal occlusion was treated with thromboendarterectomies, aortoiliac or aortofemoral arterial bypasses, extra-anatomic bypasses and sequential arterial bypasses in the past 5 years. The results were satisfactory. The surgical mortality was 3.2%, the primary 5-year patent rate was 84.2%, and the secondary 5-year patent rate was 96.5%. We emphasize the value of ABI to indicate arterial reconstruction.

Aged↗
PubMed1996

[In situ saphenous vein arterial bypass for lower limb ischemia].

28 patients with 30 ischemic lower limbs were treated by in situ saphenous vein femorodistal arterial bypass using self-made valvulotome at Zhongshan Hospital from 1989 to 1994. All patients had claudication in the lower extremities and were diagnosed angiographically. The preoperative ABI was from 0 to 0.57 (mean 0.41). All the vein grafts were patent postoperation and the dorsalis pedis or posterior tibial arteries were palpable in 18 legs immediately postoperation and the dorsalis pedis or comitant arterial reconstruction. Graft occlusion within 3 days after original operations occurred in three cases and secondary surgical corrections were successful. Postoperative mean ABI increased from 0.41 to 0.84. The limb salvage rate was 100% and the cumulative patency rate, by the lifetable analysis in 1, 2, 3, 4 and 5 years, were 92%, 88%, 86%, 78% and 71% respectively. The results suggest that the in situ saphenous vein arterial bypass is the superior method for distal arterial reconstruction and concomitant procedures to ensure sufficient inflow as well as outflow are essential to the patency of the graft.

Aged↗
PubMed1995

Use of 'random-atom" phasing models to determine macromolecular heavy-atom replacement positions.

A procedure is described by which the phase-invariant translation function may be used to provide starting set phases for the minimal function that are significantly better than those generated from random-atom coordinates. Applications to determine the heavy-atom positions for single isomorphous replacement data from macromolecular structures are very encouraging. In the case of chiral space groups, e.g. P4(1)2(1)2 versus P4(3)2(1)2, unlike Patterson functions, these methods provide the correct enantiomorph coordinates for the heavy-atom sites for whichever space group is chosen.

Journal Article↗
PubMed1995

Inhibition by chlorophyllin of 2-amino-3-methylimidazo-[4,5-f]quinoline-induced tumorigenesis in the male F344 rat.

This report describes a 1-year carcinogenicity bioassay in which male F344 rats received 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) by gavage 2-3 times per week throughout the first 35 weeks of study, while 0.1% sodium/copper chlorophyllin (CHL) was given concomitantly in the drinking water. The carcinogen dose was calculated to provide an average exposure of 4.2 mg IQ/rat per day, equivalent to that reported in previous carcinogenicity study in which rats were given 0.03% IQ in the diet. Adjusted for length of follow-up, inhibition was highly significant for total tumor burden (P < 0.001), and for specific sites was significant in the small intestine and Zymbal's gland (P < or = 0.1), and in the liver (P < 0.01). In rats given CHL, the first onset of tumors in the Zymbal's gland was delayed from week 20 to 36, but was shortened from week 31 to 26 in the skin (P < 0.05). These results support a chemopreventive role for CHL in several of the major target organs for IQ tumorigenesis in the rat, but raise concerns over possible deleterious effects in the skin.

Animals↗
PubMed1995

TDSIR phasing: direct use of phase-invariant distributions in macromolecular crystallography.

A new strategy for employing three phase triples invariant estimates from Hauptman's single isomorphous replacement (SIR) and anomalous dispersion (SAS) joint probability distribution formulae is outlined which produces a single unique phase-invariant solution in the case where the positions of the heavy-atom scatterers is known. A similar but non-identical result is obtained for the phase invariants of a structure for which a molecular-replacement solution has been obtained. It is important to note that the values of the individual native/derivative phases can be determined directly from the probability distribution formulae without having to utilize the phase-invariant estimates in an active way. Elimination of the multisolution aspect of utilizing phase-invariant estimates should have important repercussions with regard to phasing macromolecular sets of derivatized data. Trial calculations based on experimentally measured 2.5 A data for three derivatives of cytochrome c550 are encouraging. The average of the three SIR maps resolves a number of structural ambiguities seen in the published multiple isomorphous replacement (MIR) map obtained from eight derivatives.

Crystallography, X-Ray↗
PubMed1995

Vascular endothelial cell growth factor promotes tyrosine phosphorylation of mediators of signal transduction that contain SH2 domains. Association with endothelial cell proliferation.

Vascular endothelial cell growth factor (VEGF), an endothelial cell-specific mitogen that plays an important role in angiogenesis, promotes the tyrosine phosphorylation of at least 11 proteins in bovine aortic endothelial cells (BAEC). Proteins immunoprecipitated from lysates of control- and VEGF-stimulated BAEC with antisera to phospholipase C-gamma (PLC-gamma) were fractionated by SDS-polyacrylamide gel electrophoresis and transferred to Immobilon-P. Evaluation of the Western blots with antisera to phosphotyrosine demonstrated that PLC-gamma and two proteins (100 and 85 kDa) that associate with PLC-gamma were phosphorylated in response to VEGF. By using antisera specific to other mediators of signal transduction that contain SH2 domains for immunoprecipitation, it was demonstrated that VEGF promotes phosphorylation of phosphatidylinositol 3-kinase, Ras GTPase activating protein (GAP), and the oncogenic adaptor protein NcK. Proteins of M(r) consistent with the VEGF receptors Flt-1 and Flk-1/KDR were also tyrosine phosphorylated in stimulated cells. Tyrosine-phosphorylated Nck, PLC-gamma, and two GAP-associated proteins, p190 and p62, were in GAP immunoprecipitates of VEGF-stimulated BAEC, and tyrosine-phosphorylated NcK was in phosphatidylinositol 3-kinase immunoprecipitates. These observations suggest that VEGF promotes formation of multimeric aggregates of VEGF receptors with proteins that contain SH2 domains and activate various signaling pathways. VEGF-promoted proliferation of endothelial cells and tyrosine phosphorylation of SH2 domain containing signaling molecules were inhibited by the tyrosine kinase inhibitor genistein.

Adaptor Proteins, Signal Transducing↗
PubMed1995

Creation of a high cytotoxic active human tumor necrosis factor having the truncated and more basic amino terminus.

In order to define the structure-functional relationship of tumor necrosis factor(TNF), a mutant TNF gene was created by site-specific mutagenesis based on the PCR technique. This gene was highly expressed in E.coli cells. The amount of the recombinant protein was up to about 80% of the total cellular proteins. Through one-step ion exchange chromatography, the mutant TNF could be purified to homogeneity. This mutein showed the molecular weight of a dimer but not a trimer. It bears the features of truncated amino terminus and increase of the basicity of amino terminal residues. Compared with the wild type TNF, the specific activity of mutant TNF was increased by fourfold.

Amino Acid Sequence↗