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Biomedical subjects

B Hu

Publications and source records attributed to B Hu.

At least 91 records · Page 5Linked to original sources
PubMed2001

[An evaluation on corrosion resistance of magnetic retainers].

OBJECTIVE: The present study was to explore the corrosion resistance of three kinds of magnetic retainers which named neodymium-iron-boron magnet and encapsulated in stainless steel. METHODS: Three kinds of magnetic retainers were exposed for 6 months to artificial saliva thermostated at 36.5 degrees C. This study included a electrochemical test as polarization curves and a chemical test as immersion test. RESULTS: In the electrochemical test, current density of the national keeper was 7.015 microA/cm2 and magnet was 0.119 microA/cm2. In the chemical test, corrosion rate of national keeper was 3.67 x 10(-5) mg/cm2.h and magnet was 1.77 x 10(-5) mg/cm2.h. The corrosion resistance of the national magnetic retainer had little difference with the imported ones. CONCLUSION: Transient exposure of stainless steel to artificial saliva environment is likely to significantly increase elemental release. It would affect the useful life span of magnets.

Corrosion↗
PubMed2001

[Gene dispersal risk of transgenic plants].

Gene flow is a key problem and top topic in risk assessment and management of transgenic plants. Five major study areas of gene dispersal in transgenic plants were reviewed in this paper, which include gene flow from transgenic plant to its wild species, characteristics of gene flow based on pollen, methods of doing experiment and risk assessment for gene flow, safety standards of risk assessment of transgenic plants, and long-term ecological impact of gene flow in the future. Some areas needed to be studied further were also proposed.

Ecosystem↗
PubMed2001

[The prevalence of beta-thalassemia heterozygotes compound alpha-thalassemia in Guangdong district].

OBJECTIVE: To investigate the prevalence of beta-thalassemia (beta-thal) heterozygotes compound alpha-thal in Guangdong area. METHODS: alpha-thal 1 genes were amplified in 500 beta-thal carriers diagnosed by reverse dot blotting (RDB) using gap-PCR method, alpha-thal 2 genes were detected in 400 of the 500 beta-thal carriers using Southern blotting with alpha-globin DNA probe and restrict endonuclease zymogram analytical method. RESULTS: Forty three alpha-thal-1(alpha alpha/- -SEA) cases were identified in the 500 beta-thal traits, and 26 alpha-thal 2 including 17 rightward deletion (alpha alpha/- alpha 3.7) and 9 leftward deletion(alpha alpha/-alpha 4.2) cases were identified in the 400 beta-thal traits. CONCLUSION: The prevalence of beta-thal heterozygote carrying alpha-thal-1 gene was 8.6% and that of beta-thal heterozygote carrying alpha-thal-2 gene was 6.5% (4.2% rightward deletion and 2.2% leftward deletion).

Adult↗
PubMed2001

Dynamic changes of interleukin-1, interleukin-6 and tumor necrosis factor in intermingled skin graft in burned rats.

OBJECTIVE: To compare the dynamic changes of interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor (TNF) in intermingled skin graft with those in other types of skin grafts in rats. METHODS: A 10%-15% third-degree burn was created in 180 Sprague-Dawley (SD) rats. After removing the scar, skin grafts were performed on the open wounds immediately with autoskin (aus, n=54), alloskin (als, n=54) and intermingled skin (n=36). That is to say, in the intermingled skin graft, a big piece of alloskin (mals) was grafted first, and 3 days later, small pieces of autoskin (maus) wer e embedded in the alloskin. The rest 36 rats were taken as the controls. And the biological activities of IL-1, IL-6 and TNF in graft sheets in each group were detected after skin graft. RESULTS: The levels of IL-1, IL-6 and TNF in the aus group decreased steadily after their initial elevations, whereas in the als group they increased significantly and kept on the peak level in the later phases. In the in termingled group, there appeared a lowest IL-1 level in the mals and a highest one in the maus simultaneously at 7 (4) days (The number out of parenthesis is t he days after transplanting with alloskin sheets, and the number in parenthesis is the days after embedding autoskin sheets in the intermingled skin graft. Similarly hereinafter.) after skin graft (P<0.01), and the high level in the maus abruptly decreased at 14 (11) days after skin graft. At exactly the same phase on day 7 (4), a prominent peaked IL-6 in the mals occurred. In the later phases, the levels of TNF remained relatively low both in the m als and in the maus. From day 7 (4) on, each cytokine fluctuation in the mals synchronized with that in the maus. The longer the post transplantation period lasted, the more the positive cytokine correlated between the mals and the maus. CONCLUSIONS: The low levels of IL-1 and TNF may be important f actors to lighten the intensity of local rejection in the intermingled skin graft. The temporarily peaked IL-6 is both an inducer which induces the production of local IL-1 receptor antagonists and soluble TNF receptors and a signal which indicates a local enhancement of Th(2) cells. The mild rejection process and th e synchronized cytokine level during the later phases suggest a possible chimerism between the mals and the maus.

Animals↗
PubMed2001

[Synergetic protective effects of glial cell line-derived neurotrophic factor combined with neurotrophin-3 in F-actin on hair cell after noise trauma].

OBJECTIVE: To investigate if glial cell line-derived neurotrophic factor (GDNF) combined with neurotrophin-3 (NT-3) provides synergetic protection in filamentous actin (F-actin) on hair cell (HC) from acoustic trauma. METHODS: Guinea pigs were exposed to 4 kHz narrow band noise at 115 dB SPL for 4 h. Test group (n = 12) with a mixture of GDNF (100 ng/ml) and NT-3(2.5 micrograms/ml) or control group (n = 9) with artificial perilymph (AP) was delivered to the scala tympani via a mini-osmotic pump (0.5 microliter/h) for a total of 14 days. Auditory function was assessed by measuring thresholds of auditory brainstem responses (ABRs) elicited by clicks prior to surgery, 3 days after surgery (1 day before noise exposure) and 10 days following noise exposure (before animals were sacrificed), respectively. F-actin, labeled by rhodamine-phalloidin, was examined in the guinea pig cochlea using fluorescence microscopy for quantitative assessment of hair cell damage. RESULTS: There was a statistically significant increase the survival of out hair cell(P < 0.001, P < 0.01) and inner hair cell(P < 0.01, P < 0.01) and decrease in ABR threshold (P < 0.05, P < 0.01) in both the GDNF and NT-3 treated and untreated ear of animals. CONCLUSION: Our findings indicate that GDNF combined with NT-3 may effectively protect the inner ear from noise--induced hearing loss.

Actins↗
PubMed2001

[The role of fibrinolysis in pathogenesis of middle ears adhesions].

OBJECTIVE: To investigate the role of fibrinolysis in pathogenesis of middle ears adhesions. METHODS: The amount of Tissue-type Plasminogen Activator (tPA) of 28 sections from 6 ears with adhesive otitis media (AOM) and of 22 sections from 6 normal ears was examined by Super Sensitive Biotin-Streptavidin (SSBSA) method. Amount of Fibrin of 11 sections from 3 ears with significant adhesions was compared with that of 12 sections from 3 normal ears. Qualitative analysis of light microscopy with computer-assisted image system was employed. RESULTS: In adhesive ears, tPA stains were negative in 11 of 28 sections and faint positive were 10 of 28 sections, while Fibrin stains were positive in 6 of 11 sections and strong positive were in 3 of 11 sections. In normal ears, tPA stains positive were in 8 of 22 sections and strong positive were 10 of 22 sections, meanwhile, fibrin stains were negative in 8 of 12 sections and faint positive were in 3 of 12 sections. Quantitative analysis showed that the amount of tPA was 16.70 +/- 5.11 and 39.84 +/- 6.26 in ears with AOM and normal ones respectively (P < 0.05). CONCLUSION: In adhesive ears the amount of tPA was less than that in the normal ears, whereas, the amount of Fibrin was greater in ears with AOM than that in normal ears. It indicates that fibrinolysis involved in the process of adhesion formation of AOM, which may acts as a key factor.

Fibrin↗
PubMed2001

[Studies on the arbutin biosynthesis by hairy root of Panax ginseng C.A. Mayer].

OBJECTIVE: To study basic conditions for biosynthesis arbutin by the hairy root of Panax ginseng. METHOD: Based on the content of arbutin and the biotransformation rate of hydroquione, these conditions such as the culture stage, the lasting time and the concentration of hydroquione fitting for biosynthesis were found. RESULT: After cultured for 22 days, transferred in fresh B5 medium having 2 mmol.L-1 hydroquione, the hairy root biotransformated hydroquione into arbutin in 24 hours, the bioconversion rate was 89.0% and the content of arbutin in dry root was 13.0%. CONCLUSION: Arbutin, was which never found in the genus of Panax ginseng, can be biosynthesized by the hairy root of Panax ginseng.

Arbutin↗
PubMed2000

Immunolocalization of p38 MAP kinase in mouse brain.

p38 has been implicated to play a critical role in regulating apoptosis in PC12 and cerebellar granule cells, and is inactivated in cultured fetal neurons in response to insulin. Though p38 is activated in microglia after ischemia, the physiological functions of p38 in the brain are not well understood. As a first step to elucidate the physiological functions of p38 in the central nervous system, we raised a polyclonal antibody against p38 and performed immunohistochemical examination to demonstrate the localization of p38 in mouse brain. Strong p38 immunoreactivity was apparent in fiber bundles including the olfactory tract, anterior commissure, corpus callosum, cingulum, internal capsule, stria terminalis, fimbria and alveus hippocampi, fornix, stria medullaris, optic chiasm and optic tract. Although similar regions were stained with both anti-p38 and anti-neurofilament antibodies, intense p38 immunoreactivity was often observed in myelin sheath-like structures but not in axons. This is the first demonstration of the localization of p38 in the central nervous system and provides an anatomical basis for understanding physiological roles of p38.

Animals↗
PubMed2000

Effects of bicuculline on direction-sensitive relay cells in the dorsal lateral geniculate nucleus (LGNd) of cats.

The direction sensitivity of relay cells in the cat's dorsal lateral geniculate (LGNd) was measured using sinusoidal grating stimuli before and during local bicuculline administration. One hundred and twenty-eight LGNd relay cells were recorded in laminae A and A1, of which 44 relay cells (34%) were found to be sensitive to direction of stimulus movement. The direction-sensitive LGNd relay cells could be differentiated into two subgroups based on different measures of their response amplitude. Type I cells exhibited their direction sensitivity when the fundamental Fourier component (FFC) of the poststimulus time histograms (PSTHs) was used as response measure, but did not show significant direction sensitivity when mean firing rate was used. Type II cells exhibited their direction sensitivity, no matter whether the FFC or mean firing rate was used as the measure. Of 35 cells analyzed, 27 cells remained direction sensitive during bicuculline administration. At the population level, the direction bias of type I cells did not change systematically, while the direction bias of type II cells decreased significantly during bicuculline administration. These results suggest that the direction bias of these two types of relay cells are mediated by different neural mechanisms. The direction bias of type I cells may involve multiple inputs from spatio-temporally separate subunits within retinal ganglion cells receptive fields. The direction bias of type II cells may involve GABAergic neuronal circuits within the LGNd.

Animals↗
PubMed2000

Neurobeachin: A protein kinase A-anchoring, beige/Chediak-higashi protein homolog implicated in neuronal membrane traffic.

We describe the identification and initial characterization of neurobeachin, a neuron-specific multidomain protein of 327 kDa with a high-affinity binding site (K(d), 10 nm) for the type II regulatory subunit of protein kinase A (PKA RII). Neurobeachin is peripherally associated with pleomorphic tubulovesicular endomembranes near the trans sides of Golgi stacks and throughout the cell body and cell processes. It is also found in a subpopulation of synapses, where it is concentrated at the postsynaptic plasma membrane. In live cells, perinuclear neurobeachin is dispersed by brefeldin A (BFA) within 1 min, and in permeabilized cells a recruitment of neurobeachin from cytosol to Golgi-near membranes is stimulated by GTPgammaS and prevented by brefeldin A. Spots of neurobeachin recruitment are close to but distinct from recruitment sites of COP-I, AP-1, and AP-3 coat proteins involved in vesicle budding. These observations indicate that neurobeachin binding to membranes close to the trans-Golgi requires an ADP-ribosylation factor-like GTPase, possibly in association with a novel type of protein coat. A neurobeachin isoform that does not bind RII, beige-like protein (BGL), is expressed in many tissues. Neurobeachin, BGL, and approximately 10 other mammalian gene products share a characteristic C-terminal BEACH-WD40 sequence module, which is also present in gene products of invertebrates, plants, protozoans, and yeasts, thus defining a new protein family. The prototype member of this family of BEACH domain proteins, lysosomal trafficking regulator (LYST), is deficient in genetic defects of protein sorting in lysosome biogenesis (the beige mouse and Chediak-Higashi syndrome). Neurobeachin's subcellular localization, its coat protein-like membrane recruitment, and its sequence similarity to LYST suggest an involvement in neuronal post-Golgi membrane traffic, one of its functions being to recruit protein kinase A to the membranes with which it associates.

Animals↗
PubMed2000

The vitamin D response element-binding protein. A novel dominant-negative regulator of vitamin D-directed transactivation.

Vitamin D resistance in certain primate genera is associated with the constitutive overexpression of a non-vitamin D receptor (VDR)-related, vitamin D response element-binding protein (VDRE-BP) and squelching of vitamin d-directed transactivation. We used DNA affinity chromatography to purify proteins associated with non-VDR-VDRE binding activity from vitamin d-resistant New World primate cells. In electrophoretic mobility shift assays, these proteins bound specifically to either single-strand or double-strand oligonucleotides harboring the VDRE. Amino acid sequencing of tryptic peptides from a 34-kDa (VDRE-BP1) and 38-kDa species (VDRE-BP-2) possessed sequence homology with human heterogeneous nuclear ribonucleoprotein (hnRNP) A1 and hnRNPA2, respectively. cDNAs bearing the open reading frame for both VDRE-BPs were cloned and used to transfect wild-type, hormone-responsive primate cells. Transient and stable overexpression of the VDRE-BP2 cDNA, but not the VDRE-BP1 cDNA, in wild-type cells with a VDRE-luciferase reporter resulted in significant reduction in reporter activity. These data suggest that the hnRNPA2-related VDRE-BP2 is a dominant-negative regulator of vitamin D action.

Amino Acid Sequence↗
PubMed2000

Intervesicle cross-linking with integrin alpha IIb beta 3 and cyclic-RGD-lipopeptide. A model of cell-adhesion processes.

We report the synthesis of a new integrin alpha(IIb)beta(3)-specific cyclic hexapeptide that contains an Arg-Gly-Asp (RGD) sequence and is coupled to a dimyristoylthioglyceryl anchor. We demonstrate that this ligand is useful to study specific integrin binding to membrane surfaces. With the help of biotinylated analogues of the peptide, a spacer of optimal length between the peptide and lipid moieties was searched for by evaluating the binding strength with an enzyme-coupled immunosorbent assay (ELISA) and by surface plasmon resonance (SPR). It was found to be strongly dependent on the length of the spacer introduced between the biotin and peptide moieties of the ligands, which consisted either of epsilon-aminohexanoic acid (epsilonAhx) or of epsilonAhx with two additional glycine units. Best results were obtained with c[Arg-Gly-Asp-D-Phe-Lys(Biot-Ahx-Gly-Gly)-Gly-] with dissociation constants of K(D) = 0.158 microM from ELISA and K(D) = 1.1 microM from SPR measurements. The analogous lipopeptide, c[Arg-Gly-Asp-D-Phe-Lys([dimyristoyl-3-thioglyceryl-succinimido -propanoyl]Ahx-Gly-Gly)-Gly], was used as a membrane-anchored integrin ligand. It is shown by fluorescence microscopy and cryo electron microscopy that integrin reconstituted into phospholipid vesicles binds to vesicles decorated with the lipopeptide, forming regularly spaced bridges between the two kinds of vesicles. The novel integrin-specific ligand allows establishment of new model systems for systematic studies of the self-organization of integrin clusters and focal adhesion complexes.

Binding Sites↗
PubMed2000

Deficient in vitro and in vivo phagocytosis of apoptotic T cells by resident murine alveolar macrophages.

Apoptotic lymphocytes are readily identified in murine lungs, both during the response to particulate Ag and in normal mice. Because apoptotic lymphocytes are seldom detected in other organs, we hypothesized that alveolar macrophages (AMphi) clear apoptotic lymphocytes poorly. To test this hypothesis, we compared in vitro phagocytosis of apoptotic thymocytes by resident AMphi and peritoneal macrophages (PMphi) from normal C57BL/6 mice. AMphi were deficient relative to PMphi both in percentage containing apoptotic thymocytes (19.1 +/- 1% vs 96 +/- 2.6% positive) and in phagocytic index (0.23 +/- 0.02 vs 4.2 +/- 0.67). This deficiency was not due to kinetic differences, was seen with six other inbred mouse strains, and was not observed using carboxylate-modified polystyrene microbeads. Annexin V blockade indicated that both Mphi types cleared apoptotic T cells by a mechanism involving phosphatidylserine expression. By contrast, neither mAb blockade of a variety of receptors (CD11b, CD29, CD51, and CD61) known to be involved in clearance of apoptotic cells, nor the tetrapeptide RGDS (arginine-glycine-aspartic acid-serine) blocked ingestion by either type of macrophage. To confirm these studies, apoptotic thymocytes were given intratracheally or i.p. to normal mice, and then AMphi or PMphi were recovered 30-240 min later. Ingestion of apoptotic thymocytes by AMphi in vivo was significantly decreased at all times. Defective ingestion of apoptotic lymphocytes may preserve AMphi capacity to produce proinflammatory cytokines in host defense, but could contribute to development of autoimmunity by failing to eliminate nucleosomes.

Animals↗
PubMed2000

Changes of reliability and efficiency of micronucleus bioassay in Vicia faba after exposure to metal contamination for several generations.

Mitotic root micronucleus (MCN) frequency in Vicia faba as a bioassay, is primarily based on the extent of the sentinel Vicia response in terms of cytogenetic damage quantitatively or qualitatively to indicate the presence of mutagenic contaminants. This paper describes an investigation designed to assess changes in MCN frequencies of Vicia faba from three generation plants obtained, respectively from a reference site (RS) and a metal-contaminated experimental field (EF) in the bioassay of mutagenic Cd(2+) and NaN(3). The background value, dose-response to Cd(2+) and to NaN(3) in three generation (F(1), F(2) and F(3)) plants of the EF and the initial (F(0)) plants were determined in terms of MCN frequencies. With more generations of growing Vicia plants in the EF, a higher background value of MCN frequency, a lower slope value in the regression equation, a smaller ratio of MCN frequency between the control and treatment in the same generation and larger perturbation values were observed. This denotes that the decreased reliability and efficiency are represented in Vicia plants from the EF if the plants are used as sentinels in the bioassay of mutagenic Cd(2+) and NaN(3). It was concluded that the Vicia MCN bioassay should be used as an endpoint biomarker acceptable in biomonitoring environmental mutagens when the sentinel plants were collected from clean areas. Because no place is absolutely without pollutants, it is suggested that several seed stock centers should be established for providing sentinel Vicia if Vicia MCN bioassay is used as a biomarker to identify the global environmental status.

Journal Article↗
PubMed2000

Regulation of Na+,K+-ATPase by persistent sodium accumulation in adult rat thalamic neurones.

The present study investigated the regulatory mechanism of the Na+, K+-ATPase and the level of internal Na+ and Ca2+ in response to persistent Na+ influx in acutely dissociated rat thalamic neurones. Whole-cell patch-clamp recordings and Na+ imaging revealed a stable [Na+]i and low background pump activity. Exposure to veratridine (50 microM) for 1 h resulted in a progressive rise in [Na+]i (DeltaFNa = 64 +/-22%) and [Ca2+]i (DeltaFCa = 44 +/- 14%) over 3 h. Increases in [Na+]i and [Ca2+]i were also observed during neuronal exposure to the Na+ ionophore monensin (50 microM). Subcellular confocal immunofluorescence quantification of alpha3 catalytic Na+-K+ pump subunits showed that a veratridine-induced rise in [Na+]i was accompanied by a significant increase in pump density in both membrane and cytoplasmic compartments, by 39 and 54%, respectively. Similar results were also obtained in experiments when neurones were treated with monensin. A fluorescent 9-anthroylouabain binding assay detected a 60 and 110% increase in phosphorylated (active) pumps after veratridine and monensin exposure, respectively. During the entire experiment, application of ouabain or veratridine alone induced little cell swelling and death, but pump inhibition in cells pre-loaded with Na+ led to rapid cell swelling and necrosis. The above results indicate that a persistent influx of Na+ may trigger rapid enhancement of pump synthesis, membrane redistribution and functional activity. However, these compensatory mechanisms failed to prevent persistent Na+ accumulation.

Animals↗
PubMed2000

Repeated intratracheal challenge with particulate antigen modulates murine lung cytokines.

When lungs of experimental animals are repeatedly challenged with Ag, pulmonary inflammation wanes via unknown mechanisms. We hypothesized that changes in the balance of lung cytokines are responsible for immune down-regulation to repeated Ag challenge. We used intratracheal (IT) challenge of primed C57BL/6 mice with SRBC and on various days after single (1IT) or triple (3IT) challenge counted lung inflammatory cells and measured whole-lung cytokine mRNA and protein concentrations using RT-PCR and ELISA. We found that lung lymphocyte numbers and parenchymal lung inflammation decreased significantly at days 6 and 9 after final Ag challenge in 3IT mice compared with 1IT mice. Lungs of 3IT mice showed the following changes in relative mRNA expression: an earlier peak in IL-10, decreased IL-1beta, and a change from a Th2 response in 1IT mice to a Th1 response in 3IT mice (with pronounced increases in IL-12, IL-18, and IFN-gamma and decreased IL-4, IL-13, and IL-5). Similar types of changes were seen in whole-lung protein concentrations for TNF-alpha, IL-10, IL-12 p40, IFN-gamma, and IL-4. Additionally, mRNA expression of the endothelial selectins CD62E and CD62P decreased and lung lymphocyte apoptosis increased in the 3IT group. Thus, physiologic down-regulation of the pulmonary immune response to repeated Ag exposure is characterized by increased anti- and decreased proinflammatory cytokines that accompanies Th1 polarization. Similar mechanisms may act to minimize chronic lung inflammation in the majority of normal humans who do not develop progressive lung pathology when repeatedly exposed to inhaled or aspirated environmental Ags.

Animals↗
PubMed2000

Immune deviation and Fas-mediated deletion limit antitumor activity after multiple dendritic cell vaccinations in mice.

Genetic immunization with a single injection of dendritic cells (DCs) expressing a model melanoma antigen generates antigen-specific, MHC-restricted, protective immune responses. After initiating the immune response, additional vaccinations may increase the protection or conversely downregulate the immune response. Groups of mice were vaccinated several times with DCs transduced with the MART-1 gene, and the anti-tumor protection was compared with that of mice receiving a single vaccination. C3H mice had poorer protection from a syngeneic MART-1-expressing tumor challenge with multiple vaccinations. This was accompanied by lower levels of splenic CTL effectors and a shift from a type 1 to a type 2 cytokine profile. On the contrary, multiple vaccinations in C57BL/6 mice generated greater in vivo antitumor protection with no decrease in splenic CTLs and no cytokine shift. Antiadenoviral humoral or cellular immune responses did not seem to contribute to these effects. When studies were performed in Fas receptor-negative C3H.(lpr) mice, the adverse effect of multiple vaccinations disappeared, and there was no cytokine shift pattern. In conclusion, C3H mice but not C57BL/6 mice receiving multiple vaccinations with DCs expressing the MART-1 tumor antigen show decreased protection associated with deviation from a type 1 to a type 2 cytokine response attributable to a Fas-receptor mediated clearance of antigen-specific IFN-gamma-producing cells.

Adenoviridae↗