Biomedical subjects

H Yan

Publications and source records attributed to H Yan.

At least 55 records · Page 3Linked to original sources

PubMed2001

[Toxic effects of Cu, Zn and Mn on the inhibition of Chlorella pyrenoidosa's growth].

A standard method of algal bioassay for evaluating the toxicity of toxic chemicals was applied in the study. It was found that safety concentrations of Cu, Zn and Mn for Chlorella pyrenoidosa's growth were 31.8 micrograms/L, 65.0 micrograms/L and 5.5 mg/L, and 96 h-EC50 were 67.3 micrograms/L, 473.0 micrograms/L and 17.0 mg/L, respectively. According to both safety concentration and 96 h-EC50, the toxic sequences of these metals from high to low on the inhibition of C. pyrenoidosa's growth were Cu, Zn and Mn. The different affinities between different metal ions and algal cells are mainly responsible for the different inhibitions of C. pyrenoidosa's growth.

Chlorella↗

PubMed2001

[The growth hormone and insulin-like growth factors axis in liver failure patients].

OBJECTIVE: To measure circulating concentration of growth hormone (GH), insulin-like growth factors 1 (IGF-1), and it's binding protein 1 (IGFBP1) and binding protein 3 (IGFBP3) in patients with sever hepatitis, and to survey the clinical significance of GH-IGFS axis. METHODS: The study population consisted of 18 patients with liver failure caused by serious virous hepatitis, and of 20 normal volunteers. Serum concentration of GH, IGF-1, IGFBP1 and IGFBP3 was determined by ELISA. Liver biochemistric functions were measured by routine methods. RESULTS: Serum concentrations of IGF-1 and IGFBP3 were equally reduced (5.5microgram/ml +/- 6.2 microgram/ml vs 17.6 microgram/ml +/-7.0 microgram/ml, and 2.4 microgram/ml +/-1.3 microgram/ml vs 9.4 microgram/ml +/- 1.7microgram/ml, P<0.001, respectively); increased serum GH and IGFBP1 were observed (9.1ng/ml +/-12.4ng/ml vs 1.6ng/ml +/-2.4ng/ml, P<0.05; 67.9ng/ml+/-50.2ng/ml vs 45.8ng/ml+/-33.1ng/ml, P<0.01) in liver failure patients as compared with the controls. The positive relationship between IGF-1 and IGFBP3 (r=0.91, P<0.001) was observed. The closed relation between the serum IGF-1 and the prognosis of patients was also obtained. IGF-1<10 microgram/ml was in accord with 90% accurate rate of predicted death. CONCLUSIONS: The GH-IGFs axis is significantly abnormal in liver failure patients, suggesting the existence of GH resistance in these patients. Serum IGF-1 may act as a predictor for their prognosis.

Adult↗

PubMed2001

[Sequencing-based typing of HLA-DPB1 and DQB1 exon 2 in patients with type 1 diabetes mellitus].

OBJECTIVE: To investigate the correlation between type 1 diabetes mellitus susceptibility and HLA-DPB1 and DQB1 genes in Shandong Han population. METHODS: HLA-DPB1 and DQB1 genes analysis were performed by sequencing-based typing in 52 type 1 diabetes mellitus patients and 38 normal controls. RESULTS: The frequency of DPB1*2201 in diabetics was significantly higher than that in controls(26.92% vs 5.26%, P<0.01), but the frequency of DPB1*0402 in diabetics was significantly lower than that in controls(11.54% vs 34.21%, P<0.01). The frequencies of DQB1*0201, *0303 and *0604 in diabetics were higher than those in controls (24.04% vs 10.53%, P< 0.01; 22.12% vs 6.58%, P<0.05; 19.23% vs 7.89%, P<0.05), while the frequency of DQB1*0301 in diabetics was significantly lower than that in controls (4.81% vs 25.00%, P<0.01). CONCLUSION: DPB1*2201, DQB1*0201, *0303 and *0604 may be susceptible alleles, and DPB1*0402 and DQB1*0301 may be protective alleles in patients with type 1 diabetes mellitus.

Adolescent↗

PubMed2001

[Hypercoagulation aggravates renal dysfunction in patient with diabetic nephropathy].

OBJECTIVE: To investigate the relationship of hypercoagulation and renal dysfunction in patients with diabetic nephropathy(DN). METHODS: Forty six diabetes type II patients with nephrotic syndrome were divided into 3 groups according to 24 hr creatinine clearance (Ccr) as high, middle and low groups. Fourteen of the 46 patients received warfarin therapy. The parameters of coagulation and fibrolysis as well as renal function were examined. RESULTS: Patients with moderate and major renal dysfunction (M group and L group) displayed higher activities of coagulation than those with mild renal dysfunction (H group) did. Warfarin could obviously improve the status of coagulation and fibrolysis in patients with DN and delay the progress of renal dysfunction. CONCLUSION: Hypercoa-gulation was one of the causes of renal dysfunction in patients with DN.

Creatinine↗

PubMed2001

[Pathogenecity and replication of transfusion transmitted virus in liver tissue by in situ hybridization].

OBJECTIVE: To study its pathogenecity based on infection status and replication of transfusion transmitted virus (TTV) in the liver tissues. METHODS: Using recombinant plasmid as template and symmetrical and asymmetrical polymerase chain reaction (PCR), double-strand and single-strand TTV probes were labeled with digoxigenin. Fifty-six cases of liver biopsy specimens were detected by in situ hybridization, and six positive cases of them were tested further with single-strand probes. RESULTS: TTV DNA was found in 14 of 51 patients with non A and non G hepatitis (27.5%), and five cases in the control group were negative. TTV DNA was mainly observed in the nuclei of hepatocytes and pathologic changes and necrosis in the infected liver cells were not so apparent, but they could be seen in the liver tissues of acute, chronic and severe hepatitis, as well as of liver cirrhosis. TTV genome strand hybridization detected by single-strand probe was consistent with that by double-strand probe. Both TTV genome strand and its complementary strand were present in the two cases of liver specimens, but hybridizational signals were weaker in the latter than those in the former. CONCLUSION: TTV could cause injury and replicate itself in the liver, but no obvious and direct injury to hepatocytes.

DNA, Viral↗

PubMed2001

[HCV-PCR-Hybrid.ELISA for the detection of HCV RNA in serum samples from hepatitis patients].

BACKGROUND: To detect HCV RNA in serum samples from hepatitis patients by using the methods of HCV-Reverse transcription polymerase chain reaction and hybrid ELISA. METHODS: HCV RNA in serum samples was amplified by RT-PCR with one of the primer labeled with biotin. PCR amplified products were detected with microtiter plate hybridization with HCV specific probe, then determined with steptavidin-HRP assay. Anti-HCV in these samples was also detected with ELISA simultaneously. RESULTS: The positive rates of HCV RNA were 81.8% (72/88) in anti-HCV positive group and 57.9% (88/152) in the whole patients group. Serum HCV RNA and anti-HCV positive rates were compared and the consistent rate was 78.9% (120/152, P>0.05). The positive rate of HCV RNA was higher in H.ELISA (57.9%, 88/152) than that in electrophoresis (35.5%, 54/152)(P<0.01). CONCLUSIONS: The HCV-PCR-H.ELISA was a sensitive, specific, stable, semi-quantitative and easy to operate method. This HCV RNA detection was especially beneficial to early diagnosis during viramia period and was helpful for the evaluation of anti-HCV therapy.

Adolescent↗

PubMed2001

[Detection of TTV DNA in liver tissues of patients with non A-G hepatitis by in situ hybridization].

OBJECTIVE: To demonstrate the existence of TT virus(transfusion-transmitted virus, TTV) in liver tissues of patients with unknown etiology. METHODS: Paraffin-embedded liver tissues from 51 cases who were non A-E hepatitis serologically and immunohistochemically negative for HBsAg, HCV NS3 antigen and HGV NS5 antigen were tested by in situ hybridization with Dig TTV DNA probe. RESULTS: The total positive rate of TTV DNA was 27.5% (14/51). Among the different pathological types, the positive rates were 30.8% (4/13) in acute mild hepatitis, 12.5% (1/8) in acute fulminante hepatitis, 42.9% (3/7) in subacute fulminante hepatitis, 33.3% (2/6) in chronic hepatitis, 22.2% (2/9) in active liver cirrhosis, 25% (1/4) in chronic fulminante hepatitis and 25% (1/4) in primary liver carcinoma respectively. Hybridization signals were detected within the nuclei or cytoplasm of the hepatocyte and most of them in nuclei. The positive cells were diffusely scattered in the intralobular areas in acute hepatitis and aggregated in periportal areas in chronic hepatitis or in the form of clustering in pseudolobules in active liver cirrhosis. CONCLUSION: Our results suggest that the TTV detected from liver tissues or sera from patients with unknown etiology is a novel virus, which belongs to hepadnavirus.

Adolescent↗

PubMed2001

Change of visual acuity and related factors in idiopathic optic neuritis.

PURPOSE: To study the change of visual acuity and related factors in idiopathic optic neuritis. METHODS: Retrospectively studying 136 cases (210 eyes) of idiopathic optic neuritis hospitalized in our department during last 5 years. The data was analyzed with the methods of multivariate stepwise regression analysis by SPSS statistic package. RESULTS: The final visual acuity was very strongly related positively to the initial visual acuity at the time point of starting treatment and negatively to the time span beginning the treatment to the time showing improvement, age of patient and the duration from onset of the disorder to the time point of treatment beginning. CONCLUSIONS: Promptly right treatment can significantly change the natural course and the final vision of optic neuritis. Severe visual loss, old age, longer time without right therapy and slow improvement after the treatment may indicate an unfavorable final visual recovery. The different dosages of steroid applied in this study was not significant in view of the final visual acuity.

Adolescent↗

PubMed2001

[Character of alpha-crystallin molecular chaperone activity in selenite cataract].

PURPOSE: To evaluate the character of alpha-crystallin molecular chaperone activity in selenite cataract. METHODS: alpha-Crystallin from lenses of normal young rats and lenses with selenite cataract were separated and purified by gel filtration chromatography. The chaperone activity of alpha-crystallin was assayed by mearsuring heat-induced aggregation and scattering of catalase. RESULTS: alpha-Crystallin in both normal and cataractous lenses specifically prevented catalase against thermal aggregation compared with control proteins. The preventive ability in alpha H-crystallin was less than in alpha L-crystallin. Chaperone activity was diminished in selenite cataract. There was statistically significant difference in chaperone activity between normal and cataractous lenses in both alpha H-crystallin and alpha L-crystallin respectively. CONCLUSION: The reduction of alpha-crystallin chaperone activity in selenite cataract by preventing thermal aggregation of catalase is an important process in cataract formation.

Animals↗

PubMed2001

[Effect of tetrandrine on expression of bFGF in lung tissue of rat with chronic hypoxic pulmonary hypertension].

OBJECTIVE: To evaluate effect of tetrandrine (Tet) on chronic hypoxic pulmonary by observing expression of bFGF in lung tissue of rat with chronic hypoxic pulmonary hypertension. METHODS: 30 rats were divided into 3 groups: hypoxia group, hypoxia + Tet group and control group. On the 21st day of hypoxia, the hemodynamic parameters were measured and the intra acinar pulmonary arteries (IAPA) changes were studied under light microscopes. Immunohistochemical staining with monoclonal antibody against human recombinant bFGF was performed in the paraffin section of rat lung. RESULTS: Tetrandrine could reduce pulmonary artery mean pressure (mPAP) and pulmonary vascular resistance (PVR), (P < 0.01), decrease the expression of bFGF in wall of IAPA, and inhibit hypoxic structural remodeling of IAPA. CONCLUSION: Tetrandrine could decrease the expression of bFGF in wall of IAPA and in that connection to inhibit remodeling of IAPA and pulmonary hypertension.

Alkaloids↗

PubMed2001

[Simultaneous determination of aspirin, phenacetin and caffeine in compound APC by derivative ratio UV adsorption spectrum method].

The principle of derivative spectrum is described, which is based on the simultaneous use of the first derivative of ratio spectra and measurements of zero-crossing wavelengths. The method can be used to analyze one of three components in ternary mixture and eliminate the interference of others. This method is used to determine the ternary mixture of aspirin, phenacetin and caffeine in APC simultaneous with satisfactory results. The regression coefficient is higher than 0.9992, the relative standard derivatives (RSD) is less than 3.2%, the recovery is between 93.3%-106.3%.

Aspirin↗

PubMed2000

Effect of CO(2) and CHF(3) on the Solubilization of Protein in Reverse Micelles.

The effect of dissolved CO(2) and CHF(3) on the precipitation of bovine serum albumin (BSA) from reverse micelles of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in 2,2,4-trimethylpentane (iso-octane) has been studied at 308.15 K. It was found that BSA can be precipitated completely by CO(2) while the AOT and water remain in the iso-octane continuous phase. This opens up a possibility for recovery of protein solids directly from reverse micellar solutions. CHF(3) is also an effective agent for precipitation of BSA in the reverse micelles when the expansion coefficient of CHF(3) exceeds 0.4. However, the condition required for complete removal of the BSA using CHF(3) results in some precipitation of AOT and water from the solution. Copyright 2000 Academic Press.

Journal Article↗

PubMed2000

Interaction of polyphemusin I and structural analogs with bacterial membranes, lipopolysaccharide, and lipid monolayers.

Three structural variants (PV5, PV7, and PV8) of the horseshoe crab cationic antimicrobial peptide polyphemusin I were designed with improved amphipathic profiles. Circular dichroism spectroscopy analysis indicated that in phosphate buffer polyphemusin I, PV7, and PV8 displayed the spectrum of a type II beta-turn-rich structure, but, like polyphemusin I, all three variants adopted a typical beta-sheet structure in an anionic lipid environment. Both polyphemusin I and variants were potent broad spectrum antimicrobials that were clearly bactericidal at their minimal inhibitory concentrations. The variants were moderately less active in vitro but more effective in animal models. Moreover, these variants exhibited delayed bacterial killing, whereas polyphemusin I killed Escherichia coli UB1005 within 5 min at 2.5 microg/mL. All the peptides showed similar abilities to bind to bacterial lipopolysaccharide (LPS) and permeabilize bacterial outer membranes. Consistent with this was the observation that all peptides significantly inhibited cytokine production by LPS-stimulated macrophages and penetrated polyanionic LPS monolayers to similar extents. None of the peptides had affinity for neutral lipids as evident from both tryptophan fluorescence spectroscopy and Langmuir monolayer analysis. As compared to polyphemusin I, all variants showed reduced ability to interact with anionic lipids, and the hemolytic activity of the variants was decreased by 2-4-fold. In contrast, polyphemusin I efficiently depolarized the cytoplasmic membrane of E. coli, as assessed using a membrane potential sensitive fluorescent dye 3,3-dipropylthiacarbocyanine (diSC(3)5) assay, but the variants showed a substantially delayed and decreased depolarizing ability. The coincident assessment of cell viability indicated that depolarization of the bacterial cytoplasmic membrane potential by polyphemusin I occurred prior to lethal damage to cells. Our data suggest that increase of amphipathicity of beta-sheet polyphemusin I generally resulted in variants with decreased activity for membranes. Interestingly, all variants showed an improved ability to protect mice both against infection by Pseudomonas aeruginosa and from endotoxaemia.

Animals↗

PubMed2000

NT-3 weakly stimulates proliferation of adult rat O1(-)O4(+) oligodendrocyte-lineage cells and increases oligodendrocyte myelination in vitro.

The transplantation of fibroblasts, genetically modified to secrete neurotrophin-3 (NT-3) and/or brain-derived neurotrophic factor (BDNF), into spinal cord-injured rats increases the production of new oligodendrocytes and myelination (McTigue et al. [1998] J. Neurosci. 18:5354-5365). This experiment did not fully resolve whether the effect was exerted on oligodendrocyte precursors or on oligodendrocytes, or whether there was stimulation of both proliferation and differentiation of the oligodendrocyte lineage cells. To clarify the effects of NT-3 and BDNF, adult rat spinal cord was dissociated to produce cultures in which both oligodendrocyte precursors (O1(-)O4(+)) and oligodendrocytes (O1(+)) were present. Thymidine labeling of cells was determined in the presence and absence of added NT-3 and/or BDNF. In addition, the effect of these neurotrophins on myelination was determined by treating purified adult O1(+) oligodendrocyte/embryonic dorsal root ganglion (DRG) neuron cocultures with neurotrophins, only during the myelination period. O1(+) oligodendrocyte proliferation was not stimulated by NT-3 or BDNF; however, the proliferation of O1(-)O4(+) cells was increased in NT-3-treated cultures to a labeling index (LI: 24 hr) of 15-20%. This effect was observed at 5 but not at 10 days in vitro. In comparison, basic fibroblast growth factor (bFGF) induced the proliferation of both O1(+) oligodendrocytes (LI approximately 60%) and O1(-)O4(+) cells (LI approximately 75%). The amount of myelin formed in purified O1(+) oligodendrocyte/DRG neuron cocultures was significantly increased in NT-3-treated cultures compared to untreated cultures. These results indicate that NT-3 is weakly but transiently mitogenic for adult-derived oligodendrocyte precursors and support the suggestion that NT-3 promotes the maturation of O1(+) oligodendrocytes into myelin-forming cells.

Animals↗

PubMed2000

Catalytic center assembly of HPPK as revealed by the crystal structure of a ternary complex at 1.25 A resolution.

BACKGROUND: Folates are essential for life. Unlike mammals, most microorganisms must synthesize folates de novo. 6-Hydroxymethyl-7, 8-dihydropterin pyrophosphokinase (HPPK) catalyzes pyrophosphoryl transfer from ATP to 6-hydroxymethyl-7,8-dihydropterin (HP), the first reaction in the folate pathway, and therefore is an ideal target for developing novel antimicrobial agents. HPPK from Escherichia coli is a 158-residue thermostable protein that provides a convenient model system for mechanistic studies. Crystal structures have been reported for HPPK without bound ligand, containing an HP analog, and complexed with an HP analog, two Mg(2+) ions, and ATP. RESULTS: We present the 1.25 A crystal structure of HPPK in complex with HP, two Mg(2+) ions, and AMPCPP (an ATP analog that inhibits the enzymatic reaction). This structure demonstrates that the enzyme seals the active center where the reaction occurs. The comparison with unligated HPPK reveals dramatic conformational changes of three flexible loops and many sidechains. The coordination of Mg(2+) ions has been defined and the roles of 26 residues have been derived. CONCLUSIONS: HPPK-HP-MgAMPCPP mimics most closely the natural ternary complex of HPPK and provides details of protein-substrate interactions. The coordination of the two Mg(2+) ions helps create the correct geometry for the one-step reaction of pyrophosphoryl transfer, for which we suggest an in-line single displacement mechanism with some associative character in the transition state. The rigidity of the adenine-binding pocket and hydrogen bonds are responsible for adenosine specificity. The nonconserved residues that interact with the substrate might be responsible for the species-dependent properties of an isozyme.

Adenosine Triphosphate↗

PubMed2000

The function of Xenopus Bloom's syndrome protein homolog (xBLM) in DNA replication.

The Bloom's syndrome gene (BLM) plays a pivotal role in the maintenance of genomic stability in somatic cells. It encodes a DNA helicase (BLM) of the RecQ family, but the exact function of BLM remains elusive. To study this question, we have cloned the BLM homolog of the frog Xenopus laevis (xBLM) and have raised antibodies to it. Immunodepletion of xBLM from a Xenopus egg extract severely inhibits the replication of DNA in reconstituted nuclei. Moreover, the inhibition can be rescued by the addition of the recombinant xBLM protein. These results provide the first direct evidence that BLM plays an important role in DNA replication, suggesting that Bloom's syndrome may be the consequence of defective DNA replication.

Adenosine Triphosphatases↗

PubMed2000

Co-expression of the Bordetella pertussis leader peptidase I results in enhanced processing and expression of the pertussis toxin S1 subunit in Escherichia coli.

Bordetella pertussis is the causative agent of whooping cough. Traditional vaccines against this disease are inherently reactogenic, thus research is currently focussed on the production of less reactive, acellular vaccines. Expression of candidate antigens for these vaccines in Escherichia coli would be preferable, however, several B. pertussis antigens undergo incorrect post-translational processing in E. coli. The leader peptidase gene (lep) of B. pertussis encodes a protein of 294 amino acid residues that shares homology with other prokaryote leader peptidase I sequences. Hydrophilicity analysis based on the predicted amino acid sequence has demonstrated a similar membrane topology to that of E. coli and Salmonella typhimurium leader peptidase I. Co-expression of the B. pertussis lep gene in E. coli strain TOPP2 expressing the pertussis toxin S1 subunit was found to markedly increase the expression and post-translational processing of the S1 protein.

Amino Acid Sequence↗

PubMed2000

Combinatorial signaling in the specification of unique cell fates.

How multifunctional signals combine to specify unique cell fates during pattern formation is not well understood. Here, we demonstrate that together with the transcription factor Lozenge, the nuclear effectors of the EGFR and Notch signaling pathways directly regulate D-Pax2 transcription in cone cells of the Drosophila eye disc. Moreover, the specificity of D-Pax2 expression can be altered upon genetic manipulation of these inputs. Thus, a relatively small number of temporally and spatially controlled signals received by a set of pluripotent cells can create the unique combinations of activated transcription factors required to regulate target genes and ultimately specify distinct cell fates within this group. We expect that similar mechanisms may specify pattern formation in vertebrate developmental systems that involve intercellular communication.

Animals↗