Biomedical subjects

H Yang

Publications and source records attributed to H Yang.

At least 595 records · Page 33Linked to original sources

PubMed1998

[Study on invasibility and multiplication of Toxoplasma strains with different virulence toward Vero-cells].

AIM: To investigate the pathogenic mechanisms of Toxoplasma strains with different virulence. METHODS: Tachyzoites from 3 strains, Viz. RH, B36 and Fukaya strains, were challenged to in vitro cultivated Vero-cells. Systematic examinations on the earliest invasion time, the invasion rate and intracellular multiplication were performed under different cultivation conditions. RESULTS: The tachyzoites of all the 3 strains invaded the host cells within a short period after inoculation. Invasion rates were all increased along with the prolonged duration of infection. The intracellular multiplication was found to be most active in RH strain, moderate in B36, and comparatively slow in Fukaya strains. Using purified tachyzoites freed from host debris and proteins and adding sufficient FCS in the medium may facilitate the invasion and subsequent multiplication of the parasite. CONCLUSION: Strain differences in pathogenicity to the host may be correlated to the genetically predetermined multiplication capabilities of the parasites after being invaded to the host cell, and that environmental factors may give certain impact on the invasibility of the parasite.

Animals↗

PubMed1998

[Correlation between the dose and the anti-Toxoplasma effect of activated mouse macrophages induced by IFN-gamma and the synergism between IFN-gamma and TNF-alpha].

AIM: To find out the dose dependence of the anti-Toxoplasma effect induced by IFN-gamma and to determine the possible synergistic activity between TNF-alpha and IFN-gamma. METHODS: The in vitro effect of cultivated mouse peritoneal macrophages activated by IFN-gamma alone or IFN-gamma combined with different doses of TNF-alpha on the intracellular tachyzoites of RH strains and the nitric oxide (NO) level in the culture medium supernatant were simultaneously determined. RESULTS: With the increase in the dose of IFN-gamma, the anti-Toxoplasma effect was augmented and the NO level was enhanced. At 24 hours after tachyzoite invasion, a significant reversed correlation was demonstrated between the NO level and the number of intracellular parasites. CONCLUSION: The anti-Toxoplasma effect of macrophages activated by IFN-gamma appears to be dose-dependent and TNF-alpha acts synergitically with IFN-gamma in the activation of macrophages. The production of reactive NO could be an important effector in the IFN-gamma primed anti-Toxoplasma action.

Animals↗

PubMed1998

[Structure and function of saw1--a gene related to differentiation of Streptomyces ansochromogenes].

The DNA sequence of double strands of saw1 gene was determined by the method of chaintermination inhibitors. The result indicated that the 1500 bp of DNA fragment displayed a complete open reading frame (ORF), the encoding regions were located in 419 to 1252 bp positions, saw1 product has 89% identity to amino acids of sigma whiG of Streptomyces coelicolor. When recombinant plasmid containing a 1500 bp saw1 DNA fragment insert in plasmid pIJ702 was introduced into Streptomyces coelicolor C71, the sporulation deficient mutant C71 could form spore and produce grey pigment. The gene function was studied by using the method of gene disruption and the result showed that the saw1 played an important role in developmental changes from aerial hypha to spore formation of Streptomyces ansochromogenes.

Amino Acid Sequence↗

PubMed1998

[Studies on reduction of hexavalent chromium by fungi].

Several fungal strain, isolated from activated sludge, sewage and soil, were able to grow in the medium containing 300-500 mg/L K2Cr2O7, and strain BS-1 was capable of resistance to K2Cr2O7 up to 900 mg/L. After 4-6 d growing of the strain BS-1 and other 3 strains in the liquid medium added 200 mg/L K2Cr2O7, the Cr(VI) content of the medium disappeared completely. These strain were identified as Penicillium sp. BS-1, BS-3, Aspergillus niger BR-4, Aspergillus flavus BX-1 respectively. The results from the detection of the fungal culture by UV-absorbance spectrum and chemical analysis showed that high-toxic Cr(VI) was reduced to lesstoxic Cr(III). Reaction conditions and effectors of Cr(VI) reduction by intact cells of Penicillium sp. BS-1 were studied. The optimum temperature was 30 degrees C, the optimum pH was 7.0. Addition of glucose (0.25%) enhanced Cr(VI) reduction, but high concentrations of Cr(VI) inhibited the reduction of Cr(VI) to Cr(III).

Aspergillus↗

PubMed1998

[Determination of trace Pb, Cu and Cd in environmental sample by slotted-tube atom-trapping atomic absorption spectrometry].

The optimal measuring conditions of slotted-tube atom-trapping atomic absorption spectrometry of Pb, Cu and Cd were examined in detail. The results show that the characteristic concentrations measured after trapping for 1min under definite conditions were 1.82 x 10(-3), 1.26 x 10(-3) and 6.7 x 10(-5) mg/L for Pb, Cu and Cd, respectively. Thus slotted tube atom-trapping AAS yields increase in sensitivety for Pb, Cu and Cd by 110, 39 and 150 fold, respectively, in comparison with the conventional FAAS. Trace elements Pb, Cu and Cd in earth surface water, tea and hair were determined by slotted tube atom-trapping. Satisfactory results were obtained.

English Abstract↗

PubMed1998

[Respective determination of inorganic germanium and germanium-132 in foods].

Inorganic germanium and carboxyethyl germanium sesquioxide (germanium-132) in health drinks were respectively determined by hydride generation-atomic fluorescence spectrometry (HG-AFS). The conditions of respective determination of inorganic germanium and germanium-132 in natural foods were preliminarily discussed.

Beverages↗

PubMed1998

The changes and significance of c-kit expression in the irradiated bone marrow of mice.

There have been only a few studies on the expression of c-kit in bone marrow after radiation and radiation-induced apoptosis of hematopoietic cells. LACA mice were examined after irradiation with a dose of 60Co gamma-rays. Using a light microscope, electron microscope, and immunohistochemistry, we studied radiation-induced apoptosis of hematopoietic cells and the expression of c-kit. We found that 5.5 Gy total body irradiation was a sublethal dose for LACA mice, induced suppression of leukocytes in blood, and of nucleated cells in bone marrow. Apoptosis of the hematopoietic cells occurred within 1 day after irradiation. The expression of c-kit was related to the recovery of hematopoiesis and played an important role in early hematopoiesis.

Animals↗

PubMed1998

Interleukin-3 gene expression in irradiated mouse bone marrow.

The expression of endogenous interleukin-3 (IL-3) gene in mouse bone marrow after whole body irradiation was assessed by immunocytochemistry, in situ hybridization (ISH), and in situ reverse transcription PCR (IS RT-PCR). The results showed obvious injury to the bone marrow followed by recovery 4 weeks after radiation. IL-3 protein was increased in the cytoplasm of recovering hematopoietic cells, especially at 21 days after radiation, while the mRNA was negative, except at 15 days when the mRNA was weakly positive by ISH. IS RT-PCR showed that IL-3 mRNA was strongly positive in the cytoplasm of recovering hematopoietic cells, especially at 10 to 15 days after radiation. We postulate that endogenous IL-3 gene may accelerate hematopoietic recovery in irradiated bone marrow and that IS RT-PCR may objectively report the regulation of IL-3 gene expression.

Animals↗

PubMed1998

Kinetic alterations of angiotensin-II and nitric oxide in radiation pulmonary fibrosis.

We studied the kinetic alterations of angiotensin-II (A-II) and nitric oxide (NO) in radiation pulmonary fibrosis (RPF) to determine the roles of these two types of vasoactive substances in the pathogenesis of RPF. We irradiated the right hemithorax of male Wistar rats with single doses of 0, 15, and 30 Gy of 60Co gamma rays and we examined the lung parenchyma at 1, 3, 5, and 7 months following the radiation. The rats were killed at the stated intervals and samples were obtained from the right lung. We measured types I and III procollagen mRNA by in situ hybridization and demonstrated the synthesis and distribution of A-II in the pulmonary tissue by immunohistochemistry. The formation and kinetic alterations of types I and III collagen were analyzed under polarized light microscope using Sirius Red stain. The hydroxyproline (Hyp) content was measured in the pulmonary tissue after digestion with HCl. A-II radiation immunoactivity (RIA) was assayed in pulmonary tissue homogenate. Pulmonary NO content, NO synthase (NOS), and the angiotensin converting enzyme (ACE) activities were also measured. Our results showed that types I and III collagen genes began to be expressed 1 month after irradiation. Type I collagen gene increased significantly, reaching its peak 3 months after irradiation. As the irradiation dosage was increased from 15 to 30 Gy, the type I collagen gene content increased significantly, while type III significantly decreased. The Hyp content increased with the passage of time after irradiation. Pulmonary A-II RIA increased significantly with the dose of irradiation and was chiefly produced by fibroblasts and macrophages in the interstitium, bronchiolar epithelium, and the anteriolar wall. Pulmonary NO and NOS activities decreased following irradiation. One month following irradiation, the expression of the type I collagen gene begins to increase, with a significant increase in both Hyp and type I collagen 3 months after irradiation. The histogenesis of RPF may be related to A-II. The interstitial cells, the bronchiolar epithelium, and the arteriolar wall can produce A-II and need not pass through the ACE pathway. Our results suggest that the A-II increase and NO decrease may have a role in the pathogenesis of RPF.

Angiotensin II↗

PubMed1998

The effect of translation of the C1-C2 on the spinal canal.

The stability of the atlantoaxial articulation depends fundamentally on the integrity of the odontoid process and the ligaments. Ligament stability mostly is maintained by two ligaments: the transverse ligament and the alar, apical ligaments. Failure of the transverse ligament can result in anterior translation of the atlas on the axis. The anteroposterior diameter of the ring of the atlas is approximately 3 cm. The spinal cord and the odontoid process are each approximately 1 cm in diameter, approximately 1/3 the diameter of the ring. According to Steel's rule of thirds, the remaining centimeter of free space allows for some degree of pathologic displacement. The current anatomic study showed that the space available for the spinal cord was limited. The sagittal diameter C1-C2 canal is 18.71 +/- 2.88 mm (excluding 10 mm thickness of the dens and 2.91 +/- 0.69 mm thickness of transverse ligament), with the spinal cord occupying 7.73 +/- 0.87 mm of the available space. Space available for spinal cord at the level of the atlas is 3.44 +/- 1.19 mm plus 1.01 +/- 0.20 mm space anterior to the cord (anterior epidural space) and 5.64 +/- 2.22 mm space posterior to the cord (posterior epidural space), which is approximately in agreement with the normal diameter by Steel's rule of thirds.

Aged↗

PubMed1998

Anatomic considerations of the vertebral artery: implications for anterior decompression of the cervical spine.

Anatomic dissection and measurements of the vertebral artery relative to the medial margin of the longus colli and the anterior margin of the vertebral body from C6 to C3 were performed in this study. The average angle of the vertebral artery relative to the midline was 4.3 +/- 2.6 degrees overall. The average distance between the medial margin of the longus colli and medial margin of the vertebral artery gradually decreased from the C6 level (11.5 +/- 1.0 mm) to the C3 level (9.0 +/- 1.3 mm). The average distance between anterior margin of the vertebral body and anterior margin of the vertebral artery gradually increased from the C6 level (7.2 +/- 1.9 mm) to the C3 level (9.6 +/- 2.1 mm). The distance between medial borders of the longus colli muscles gradually decreased from the C6 level (13.8 +/- 2.2 mm) to the C3 level (7.9 +/- 2.2 mm). Relative to the medial margin of the longus colli muscle and the anterior margin of the vertebral body, the vertebral artery is more lateral and anterior at the C6 level but more medial and posterior at C3 level. This knowledge may facilitate effective decompression of the lateral cervical canal and improve the margin of safety of the surgeon.

Aged↗

PubMed1998

[Application of chromosome painting to analysis of structural aberration in five cases].

OBJECTIVE: This article reports that competitive hybridization using entire chromosome specific libraries as probe and human genomic DNA as the competitor allows intense and specific fluorescent staining of human chromosome in metaphase. This general approach is called "chromosome painting". METHODS: The probes comprising chromosomes 2, 5, 6, 7, 13, 14, X specific libraries were used to analyse five cases which had been suspected of subtle translocation and deletion in karyotype analysis by G-banding of metaphase cells. The authors selected entire chromosome-specific DNA libraries hybridizing with the five cases. Unlabeled human genomic DNA was used to inhibit the hybridization of sequences in the library that bind to multiple chromosome. RESULTS: The target chromosome was made at least 20 times brighter parunit length than the others. Translocations and deletions were detected clearly in metaphase and were consistent with G-banding. However, the result was clearer and the detection easier, compared with G-banding. CONCLUSION: Chromosome painting is very powerful for identification of chromosome structural aberrations. Translocation and deletion involving these chromosomes can be strikingly visualized. The hybridization intensity and specificity are such that even very small portions of the involved chromosome can be detected. This technique is especially useful in settings where high-quality banding is difficult.

Adult↗

PubMed1998

In vitro IgG1 alloreactive antibody production by circulating memory cells in humans.

This study was designed to investigate the presence of IgG1 alloreactive memory cells in the peripheral blood in humans and their in vitro activation requirements. Alloreactive antibody production was measured after cell activation with cytokines: Interleukin (IL) 2, IL-4 and IL-10, interferon gamma, alloantigens and/or OKT3, lipopolysaccharide or Pokeweed mitogen and Epstein-Barr virus transformation. The examined cells were taken from ten sensitized and five nonsensitized uremic patients with previous graft loss and five normal controls. The titers and percentage panel reactive IgG1 antibody reactivity present in the respective sera was further compared with the in vitro profile. Alloreactive antibody reactivity was measured by PRA-STAT ELISA method. The results show that: 1) Short term control T cell lines or nonsensitized cells were unable to provide the necessary help to autologous B cells to produce alloreactive antibodies of the IgG subclass. 2) Activated cells from sensitized patients produced low levels of alloreactive IgGl antibodies. 3) Stimulation with any of the cytokines and/or mitogens or alloantigens or allopeptides was not sufficient to produce consistent levels of alloreactive IgG 1 antibodies, in spite of its presence in the respective sera.

Adult↗

PubMed1998

Factors influencing malaria endemicity in Yunnan Province, PR China (analysis of spatial pattern by GIS). Geographical Information System.

This study is an initial attempt to apply disease mapping through Geographical Information System (GIS) with multiple regression analysis to determine the nature and extent of factors influencing malaria transmission in Yunnan Province, PR China, particularly in border areas. Secondary county-based data covering the period 1990 to 1996 were collected and analyzed. The malaria situation in Yunnan Province as a whole is influenced mainly by the combined effects of the physical environment, the presence of efficient vector species, and mobile population along international borders with Myanmar, Lao PDR and Vietnam.

China↗

PubMed1997

Kinetics of cytochrome c folding examined by hydrogen exchange and mass spectrometry.

Pulsed hydrogen exchange/mass spectrometry, a new method for studying protein folding, has been used to investigate folding of cytochrome c on the 5 ms to 15 s time scale. Cytochrome c, unfolded in guanidine hydrochloride/D2O, was allowed to refold in a high-speed quenched-flow apparatus and pulse-labeled with protium to identify unfolded regions. Intact, labeled cytochrome c was digested into fragments which were analyzed by HPLC electrospray ionization mass spectrometry to determine the level of deuterium in each fragment. Bimodal distributions of deuterium were found for most segments, indicating that regions represented by these segments were either unfolded or completely folded in the intact polypeptide prior to labeling. This behavior is consistent with cooperative, localized folding which occurs in less than 10 ms in individual molecules. Deuterium levels found in the fragments were normalized to levels found in the same fragments derived from folded cytochrome c, pulse-labeled in the same manner, to indicate the percentage of cytochrome c that was folded. These results show that the N/C-terminal regions fold cooperatively on a time scale extending from less than the mixing time of the apparatus (5 ms) to as long as 15 s, and that the other regions also fold cooperatively. However, these regions do not begin to fold until 30 ms after mixing. In addition to providing new information on cytochrome c folding, these results demonstrate that pulse-hydrogen exchange/mass spectrometry is complementary to NMR in some respects and advantageous in others. Results of this study form the foundation required to extend the pulsed hydrogen exchange approach to folding studies of proteins too large to be analyzed by NMR.

Cytochrome c Group↗

PubMed1997

Cloning and characterization of the arginine-specific carbamoyl-phosphate synthetase from Bacillus stearothermophilus.

Bacillus stearothermophilus contains two carbamoyl-phosphate synthetases (CPS), one specific for pyrimidine biosynthesis and the other for arginine biosynthesis. The pyrimidine-specific CPS is repressed by exogenous pyrimidines, and its activity is inhibited by UMP and activated by 5-phospho-alpha-D-ribosyl diphosphate. The arginine-specific CPS is similarly repressed by exogenous arginine but its activity is not sensitive to these or other potential effectors. Each of the two enzymes consist of two unequal subunits, as is the case for other microbial CPS; however, the large subunit for the arginine-specific CPS is smaller than that for the pyrimidine-specific enzyme. Comparison of the derived amino acid sequence for the cloned large subunit of the arginine-specific CPS with those for subunits from pyrimidine-sensitive CPS showed significant similarity throughout the polypeptides except at the carboxy terminus, which was identified by other laboratories to contain the binding site for the pyrimidine effector. Unlike the results previously reported for CPS from an enteric mesophile, the kinetic properties of the arginine-specific CPS were not affected by growth of B. stearothermophilus at temperatures near the minimal growth temperature. Furthermore, calorimetric studies showed that the thermal stability of cloned CPS was identical regardless of the growth temperature of B. stearothermophilus between 42 degrees C and 63 degrees C. The thermal stability of cloned CPS was not affected by expression at 37 C in Bacillus subtilis or Escherichia coli. In contrast, the thermal stabilities for CPS and other proteins were higher in extracts of cells grown at higher temperatures. These results indicate that cellular factors, probably chaperonins, are necessary for thermal stability of proteins at and below the optimal temperature for this thermophile.

Allosteric Regulation↗

PubMed1997

High potency antagonists of the pancreatic glucagon-like peptide-1 receptor.

GLP-1-(7-36)-amide and exendin-4-(1-39) are glucagon-like peptide-1 (GLP-1) receptor agonists, whereas exendin-(9-39) is the only known antagonist. To analyze the transition from agonist to antagonist and to identify the amino acid residues involved in ligand activation of the GLP-1 receptor, we used exendin analogs with successive N-terminal truncations. Chinese hamster ovary cells stably transfected with the rat GLP-1 receptor were assayed for changes in intracellular cAMP caused by the test peptides in the absence or presence of half-maximal stimulatory doses of GLP-1. N-terminal truncation of a single amino acid reduced the agonist activity of the exendin peptide, whereas N-terminal truncation of 3-7 amino acids produced antagonists that were 4-10-fold more potent than exendin-(9-39). N-terminal truncation of GLP-1 by 2 amino acids resulted in weak agonist activity, but an 8-amino acid N-terminal truncation inactivated the peptide. Binding studies performed using 125I-labeled GLP-1 confirmed that all bioactive peptides specifically displaced tracer with high potency. In a set of exendin/GLP-1 chimeric peptides, substitution of GLP-1 sequences into exendin-(3-39) produced loss of antagonist activity with conversion to a weak agonist. The results show that receptor binding and activation occur in separate domains of exendin, but they are more closely coupled in GLP-1.

Amino Acid Sequence↗

PubMed1997

The enantiomeric purity of alcohols formed by enzymatic reduction of ketones can be improved by optimisation of the temperature and by using a high co-substrate concentration.

The stereoselective reduction of ketones by alcohol dehydrogenase from Thermoanaerobium brockii was studied in organic reaction media. 2-Propanol was used as co-substrate to regenerate the coenzyme NADPH. The enantiomeric excess of the alcohol formed from the ketone decreased during the course of the reaction (from 53 to 0% e.e. in the formation of (R)-2-butanol). This was interpreted as being due to the reversibility of all the reactions involved. By using a large excess of 2-propanol this effect was suppressed. In the reduction of 2-butanone to (R)-2-butanol, the enantiomeric excess increased with increasing temperature, but in the reduction of 2-pentanone to (S)-2-pentanol the enantiomeric excess decreased with increasing temperature. The data were evaluated in terms of free energy of activation of the reaction pathways leading to the different possible products.

1-Propanol↗