Biomedical subjects

D He

Publications and source records attributed to D He.

At least 37 records · Page 2Linked to original sources

PubMed2000

alpha-Amylase immobilized on bulk acoustic-wave sensor by UV-curing coating.

A new method for immobilization of alpha-amylase by UV-curing coating is proposed in this paper. The immobilization procedure of UV-curing coating on piezoelectric quartz crystal is simple and convenient, and causes less loss of enzymatic activity. The activity of the immobilized alpha-amylase is monitored by a technique based on bulk acoustic-wave (BAW) sensor. The frequency shift of BAW sensor can reflect the degree of hydrolysis of starch by the immobilized alpha-amylase. It is appropriate for the immobilized alpha-amylase to hydrolyze the soluble starch under pH 7.0 condition, which is similar to that of the free alpha-amylase. Kinetic parameters (the Michaelis constant, K(m), and the maximum initial rate V(max)) of the enzymatic hydrolysis of starch by the immobilized alpha-amylase are estimated by using a linear method of Lineweaver-Burk plot. K(m)=12.7mgml(-1) and V(max)=15.9Hzmin(-1). And the experimental results show that the immobilized alpha-amylase entrapped by the UV-curing coating retains adequate enzymatic activity and can be reused more than 50 times under certain experimental conditions.

Journal Article↗

PubMed2000

Determination of the binding parameters of drug to protein by equilibrium dialysis/piezoelectric quartz crystal sensor.

A novel method, equilibrium dialysis/piezoelectric quartz crystal sensor, applied to determine the binding parameters of diethyldithiocarbamate to human plasma protein is proposed. Based on the investigation of the equilibrium reaction for the binding of drug to protein, the related theoretical equations for this binding were derived. By monitoring the frequency responses of a copper-plated piezoelectric quartz crystal sensor to drug in and out of a dialysis membrane after equilibrium, the binding parameters were determined, i.e., 0.375 micromol g(-1) for beta(p), 6.496 microM for K(dp), 141.99 L mmol(-1) for K(p), and 0.043 for N. These values were in good agreement with reference values. It was found that this method may have application for studying the characteristics of the interaction between other drugs and proteins.

Biosensing Techniques↗

PubMed2000

Transforming growth factor beta -inducible independent binding of SMAD to the Smad7 promoter.

SMAD proteins can mediate transforming growth factor beta (TGF-beta)-inducible transcriptional responses. Whereas SMAD can recognize specific DNA sequences, it is usually recruited to a promoter through interaction with a DNA-binding partner. In an effort to search for TGF-beta-inducible genes, we used a subtractive screening method and identified human Smad7, which can antagonize TGF-beta signaling and is rapidly up-regulated by TGF-beta. In this report, we show that TGF-beta can stabilize Smad7 mRNA and activate Smad7 transcription. The Smad7 promoter is the first TGF-beta responsive promoter identified in vertebrates that contains the 8-bp palindromic SMAD-binding element (SBE), an optimal binding site previously identified by a PCR-based selection from random oligonucleotides by using recombinant Smad3 and Smad4. We demonstrate that on TGF-beta treatment, endogenous SMAD complex can bind to a Smad7 promoter DNA as short as 14 or 16 bp that contains the 8-bp SBE in gel mobility shift and supershift assays. Our studies provide strong evidence that SMAD proteins can bind to a natural TGF-beta responsive promoter independent of other sequencespecific transcription factors. We further show that, whereas recombinant Smad3 binds to the SBE, endogenous or even transfected Smad3 cannot bind to the SBE in the absence of Smad4. These findings have important implications in the identification of target genes of the TGF-beta/SMAD signaling pathways.

Base Sequence↗

PubMed2000

Effects of naloxone on the serum luteinizing hormone level and the number of Fos-positive gonadotropin-releasing hormone neurons in immature female rats.

To examine developmental changes in the number of gonadotropin-releasing hormone (GnRH) neurons activated by an opioid receptor antagonist in female rats, blood sampling and double-labeled immunocytochemistry for Fos and GnRH were performed after the injection of naloxone (NAL) in immature (postnatal d16 and d30) and mature female rats. Three age groups of rats were perfused with 4% paraformaldehyde-PB 90 min after the subcutaneous injection of NAL (2.5 mg/kg) or saline. All tissue incubation and staining for double-labeled immunocytochemistry were simultaneously performed. Although no significant developmental change was observed in the total number of GnRH neurons (p0.05), NAL-induced increases in serum luteinizing hormone (LH) concentrations were much greater in the d16 group than those in the d30 and mature groups (p<0.01). Conversely, Fos-positive GnRH neurons were rarely observed in d16, and some Fos-positive GnRH neurons were observed in the d30 group (p<0.05 vs. saline) and the mature group (p<0.01 vs. saline). These results suggest that opiatergic inhibitory system on GnRH neuron in immature female rats is different from that in mature female rats.

Age Factors↗

PubMed2000

Induction of Alzheimer-specific Tau epitope AT100 in apoptotic human fetal astrocytes.

In Alzheimer's and other neurodegenerative diseases, hyperphosphorylated tau accumulates in affected neuronal and glial cells in the form of paired helical filaments (PHFs). This tau binds antibody AT100, which recognizes the double phosphorylation site (Thr212/Ser214) that is not present in normal biopsy tau. In primary cultures, highly enriched (>98%) in astrocytes of human fetal brain, three polypeptides of 52, 64, and 70 kD showed immunoreactivity with tau antibodies against non-phosphorylated epitopes, accounting for 88, 12, and <1%, respectively, of the total reactivity. All three polypeptides were phosphorylated at the PHF-1 epitope but not at the epitopes Tau-1, 12E8, AT8, and AT100. Treatment of cultures with okadaic acid resulted in apoptosis characterized by the blebbing of the plasma membrane, condensation of nuclear chromatin, and fragmentation of the nucleus. This treatment also resulted in a 3- to 5-fold increase in the content of both tau protein and phosphorylation. The increases were observed in all phosphorylation sites examined, and included the AT100 site. The AT100 site has been proposed to be generated by protein kinase B/Akt and Cdc2. Since okadaic acid can induce an AD-like hyperphosphorylated state of normal tau in primary cultures of human brain cells, a simple cellular model is available permitting study of self-aggregation of tau and phosphorylation events characteristic of neurodegeneration.

Alternative Splicing↗

PubMed2000

CENP-G in neocentromeres and inactive centromeres.

CENP-G is a novel constitutive centromere-specific protein localized to the kinetochore inner plate and subjacent region. It has been identified as associating specifically with the alpha-1 subfamily of alpha-satellite DNA. In the present work, the localization of CENP-G was compared with that of other CENPs by immunofluorescence and fluorescence in situ hybridization. Studies were carried out on four abnormal human centromeres: two neocentromeres and two inactive centromeres. CENP-G was detected in one of the two inactive centromeres but not in the other that shows a partial deletion of the alphoid DNA. Interestingly, CENP-G is also present in neocentromeres, which lack alphoid DNA sequences, and in the human Y chromosome, which lacks the alpha-1 type of satellite DNA. These data provide further evidence that CENP-G may be an essential factor in centromeric function and that in centromeres lacking the alpha-1 subfamily of alphoid DNA, other DNA sequences are able to bind CENP-G.

Aged↗

PubMed2000

Clostridium difficile toxin A causes early damage to mitochondria in cultured cells.

BACKGROUND & AIMS: The mechanism by which Clostridium difficile toxin A causes actin depolymerization and cell rounding involves toxin internalization and subsequent monoglucosylation of the Rho family of proteins. This study explored toxin internalization and effects on mitochondrial function before cell rounding. METHODS: Chinese hamster ovary (CHO) cells were exposed to toxin A, and mitochondrial localization was assayed by confocal microscopy. Mitochondrial function was measured by adenosine triphosphate (ATP) concentration, mitochondrial permeability, and leakage of cytochrome c. RESULTS: Confocal microscopy showed toxin A colocalization with the mitochondrial protein GRP 75 at 5 minutes after toxin exposure. Between 5 and 15 minutes, toxin A caused an 80% diminution in cellular ATP levels; cell rounding and Rho glucosylation commenced between 15 and 30 minutes. Toxin A also resulted in reduction of mitochondrial membrane potential and a 2-3-fold increase in reactive oxygen radicals. Preincubation of CHO cells with the antioxidants butylated hydroxyanisole or butylated hydroxytoluene blocked the toxin A-induced increase in oxygen radicals and diminished cell rounding. Western blot analysis of toxin A-exposed isolated mitochondria showed a direct effect of toxin A on leakage of cytochrome c. CONCLUSIONS: The results show that extensive mitochondrial damage occurs within 15 minutes in CHO cells exposed to toxin A. Diminished ATP concentrations and increased oxygen radicals are likely to contribute to cytotoxicity from this bacterial toxin.

Adenosine Triphosphate↗

PubMed2000

A z gain nonuniformity correction for multislice volumetric CT scanners.

This paper presents a calibration and correction method for detector cell gain variations. A key functionality of current CT scanners is to offer variable slice thickness to the user. To provide this capability in multislice volumetric scanners, while minimizing costs, it is necessary to combine the signals of several detector cells in z, when the desired slice thickness is larger than the minimum provided by a single cell. These combined signals are then pre-amplified, digitized, and transmitted to the system for further processing. The process of combining the output of several detector cells with nonuniform gains can introduce numerical errors when the impinging x-ray signal presents a variation along z over the range of combined cells. These numerical errors, which by nature are scan dependent, can lead to artifacts in the reconstructed images, particularly when the numerical errors vary from channel-to-channel (as the filtered-backprojection filter includes a high-pass filtering along the channel direction, within a given slice). A projection data correction algorithm has been developed to subtract the associated numerical errors. It relies on the ability of calibrating the individual cell gains. For effectiveness and data flow reasons, the algorithm works on a single slice basis, without slice-to-slice exchange of information. An initial error vector is calculated by applying a high-pass filter to the projection data. The essence of the algorithm is to correlate that initial error vector, with a calibration vector obtained by applying the same high-pass filter to various z combinations of the cell gains (each combination representing a basis function for a z expansion). The solution of the least-square problem, obtained via singular value decomposition, gives the coefficients of a polynomial expansion of the signal z slope and curvature. From this information, and given the cell gains, the final error vector is calculated and subtracted from the projection data.

Algorithms↗

PubMed2000

Sound absorption of cellular metals with semiopen cells.

A combined experimental and theoretical study is presented for the feasibility of using aluminum foams with semiopen cells for sound-absorption applications. The foams are processed via negative-pressure infiltration, using a preform consisting of water-soluble spherical particles. An analytical model is developed to quantify the dependence of pore connectivity on processing parameters, including infiltration pressure, particle size, wetting angle, and surface tension of molten alloy. Normal sound-absorption coefficient and static flow resistance are measured for samples having different porosity, pore size, and pore opening. A theory is developed for idealized semiopen metallic foams, with a regular hexagonal hollow prism having one circular aperture on each of its eight surfaces as the unit cell. The theory is built upon the acoustic impedance of the circular apertures (orifices) and cylindrical cavities due to viscous effects, and the principle of electroacoustic analogy. The predicted sound-absorption coefficients are compared with those measured. To help select processing parameters for producing semiopen metallic foams with desirable sound-absorbing properties, emphasis is placed on revealing the correlation between sound absorption and morphological parameters such as pore size, pore opening, and porosity.

Acoustics↗

PubMed2000

[Quantitative characteristics of rare and endangered Castanopsis kawakamii population].

In this paper, a new self-adaptive model for population growth, i.e. S = exp(alpha ln2(1 + ce-rt) + beta ln(1 + ce-rt) + gamma) was established, which combined Logistic, Smith, Gompertz, Gui-Lawson, Zhang-Logistic and Liu-Logistic models. Estimations with genetic algorithm showed that the new model was more suitable than other models to simulate the actual growth trend of Castanopsis kawakamii population.

China↗

PubMed2000

[Energy distribution of Phyllostachys pubescens ecosytem in north Fujian].

Based on the data obtrained from 40 Phyllostachys pubescens plots in Jianou City of Fujian Province, the distribution of energy was studied in this paper. The results showed that the energy contained in stems, branches and leaves, and underground parts of P. pubescens ecosystem were 4.2322 x 10(8) kJ.hm-2, 0.9230 x 10(8) kJ.hm-2 and 1.7643 x 10(8) kJ.hm-2, accounting for 61.32%, 13.11% and 25.57% of the total energy respectively.

China↗

PubMed2000

[An experimental study on physiotherapy for traumatic facial nerve injury].

OBJECTIVE: To investigate the effects of electric stimulation, iontophoresis and electric stimulation with iontophoresis therapy in treating traumatic facial nerve injury. METHODS: Fifty rabbits were used. All right buccal branch of facial nerve were injured. The rabbits were randomly divided into five groups and treated by different stimulation pattern: (a) electric stimulation group; (b) iontophoresis group; (c) iontophoresis with electric stimulation group; (d) routine therapy group; (e) control group. The histologic morphology, quantitative indices of nerve fibers and electroneurography(ENoG) indices were analyzed. RESULTS: (a) Iontophoresis with Vitamin B1 and Vitamin B12 improved the regeneration of facial nerve myelin sheath. And had the best effect among these groups. (b) Electric stimulation had great effect on axon regeneration. (c) The group of electric stimulation with iontophoresis therapy had the best comprehensive effect on the nerve injury. CONCLUSIONS: Both electric stimulation and iontophoresis have good effects on nerve regeneration, when they are used in combination, the best comprehensive effect will be expected.

Animals↗

PubMed1999

Effects of glucose and related substrates on the recovery of the electrical activity of gonadotropin-releasing hormone pulse generator which is decreased by insulin-induced hypoglycemia in the estrogen-primed ovariectomized rat.

We investigated the effect of glucose and its related substrates on the recovery of pulsatile luteinizing hormone (LH) secretion which was suppressed by insulin in estrogen-primed ovariectomized rats. We also examined the effect of glucose on the electrical activity of the gonadotropin-releasing hormone (GnRH) pulse generator which was suppressed by insulin. The intravenous (i.v.) injection of insulin (5 units/rat) suppressed the pulsatile LH secretion for 3 h in estrogen-primed ovariectomized rats. This suppressive effect of insulin on the LH secretion was rapidly reversed by the i.v. injection of glucose and mannose but not by the injection of lactate and saline. Fructose could recover the LH secretion suppressed by insulin, but took a longer time than glucose did. By monitoring the electrical activity of the GnRH pulse generator, we found that i.v. injection of insulin suppressed the pulsatile LH secretion by decreasing the activity of the GnRH pulse generator. Again, the i.v. injection of glucose, but not saline, immediately recovered the decrease in the electrical activity of the GnRH pulse generator. Fructose could recover the activity of the GnRH pulse generator, but it took a longer time than glucose did. We suggest that glucose availability, but not simply a metabolic state such as the ATP level, is an essential factor for maintaining the electrical activity of the GnRH pulse generator which is responsible for pulsatile LH secretion.

Animals↗

PubMed1999

HCA, an immunoglobulin-like adhesion molecule present on the earliest human hematopoietic precursor cells, is also expressed by stromal cells in blood-forming tissues.

We have previously shown that the HCA/ALCAM (CD166) glycoprotein, a member of the immunoglobulin family that mediates both homophilic and heterophilic cell-cell adhesion, via the CD6 ligand, is expressed at the surface of all of the most primitive CD38(-/lo), Thy-1(+), rho123(lo), CD34(+) hematopoietic cells in human fetal liver and fetal and adult bone marrow. In the present report we show that HCA is also expressed by subsets of stromal cells in the primary hematopoietic sites that sequentially develop in the human embryo and fetus, ie, the paraaortic mesoderm, liver, thymus, and bone marrow. Adult bone marrow stromal cells established in vitro, including those derived from Stro-1(+) progenitors and cells from immortalized cell lines, express HCA. In contrast, no HCA expression could be detected in peripheral lymphoid tissues, fetal spleen, and lymph nodes. HCA membrane molecules purified from marrow stromal cells interact with intact marrow stromal cells, CD34(+) CD38(-) hematopoietic precursors, and CD3(+) CD6(+) peripheral blood lymphocytes. Finally, low but significant levels of CD6 are here for the first time detected at the surface of CD34(+) rho123(med/lo) progenitors in the bone marrow and in mobilized blood from healthy individuals. Altogether, these results indicate that the HCA/ALCAM surface molecule is involved in homophilic or heterophilic (with CD6) adhesive interactions between early hematopoietic progenitors and associated stromal cells in primary blood-forming organs.

Adult↗

PubMed1999

A cluster of five cell wall-associated receptor kinase genes, Wak1-5, are expressed in specific organs of Arabidopsis.

WAK1 (wall-associated kinase 1) is a cytoplasmic serine/threonine kinase that spans the plasma membrane and extends into the extracellular region to bind tightly to the cell wall. The Wak1 gene was mapped and found to lie in a tight cluster of five highly similar genes (Wak1-5) within a 30 kb region. All of the Wak genes encode a cytoplasmic serine/threonine protein kinase, a transmembrane domain, and an extracytoplasmic region with several epidermal growth factor (EGF) repeats. The extracellular regions also contain limited amino acid identities to the tenascin superfamily, collagen, or the neurexins. RNA blot analysis with gene-specific probes revealed that Wak1, Wak3 and Wak5 are expressed primarily in leaves and stems of Arabidopsis. Wak4 mRNA is only detected in siliques, while Wak2 mRNA is found in high levels in leaves and stems, and in lower levels in flowers and siliques. A trace amount of Wak2 can also be detected in roots. Wak1 is induced by pathogen infection and salicylic acid or its analogue INA and is involved in the plant's response, and Wak2, Wak3 and Wak5 also can be greatly induced by salicylic acid or INA. The WAK proteins have the potential to serve as both linkers of the cell wall to the plasma membrane and as signaling molecules, and since Wak expression is organ-specific and the isoforms vary significantly in the cell wall associated domain this family of proteins may be involved in cell wall-plasma membrane interactions that direct fundamental processes in angiosperms.

Amino Acid Sequence↗

PubMed1999

Construction and analytical application of ion-selective piezoelectric sensor for atropine sulfate.

The method describes the use of a piezoelectric quartz crystal (PQC) as a substitute for ion-selective electrodes. The approach is feasible when the membrane materials are electrically non-conductive and membrane potential measurements are consequently not possible. An ion-selective piezoelectric sensor sensitive to atropine sulfate was constructed by coating a PVC membrane containing activant on one the side of a PQC. On the basis of selective adsorption of atropine ions across the modified film and the sensitive mass response of PQC, the method exhibits a sensitive, rapid response and is easy to operate without pretreatment of the sample. The logarithm of the frequency shift gave a linear relationship with the logarithm of atropine sulfate concentration in the 1.0 x 10(-8)-1.0 x 10(-3) M range with a detection limit of 5.0 x 10(-9) M at pH 7.0. Recoveries were from 98.7-102.2%. Two activants, atropine tetraphenylborate and atropine dipicrylaminate, were synthesized and investigated. Influencing factors were also examined and optimized. The results for real samples obtained by the proposed method agreed with those obtained by conventional methods.

Atropine↗

PubMed1999

Computer simulation of random packing of unequal particles.

A Monte Carlo simulation model for the random packing of unequal spherical particles is presented in this paper. With this model, the particle radii obeying a given distribution are generated and randomly placed within a cubic packing domain with high packing density and many overlaps. Then a relaxation iteration is applied to reduce or eliminate the overlaps, while the packing space is gradually expanded. The simulation is completed once the mean overlap value falls below a preset value. To simulate the random close packing, a "vibration" process is applied after the relaxation iteration. For log-normal distributed particles, the effect of particle size standard deviation, and for bidisperse particles, the effects of particle size ratio and the volume fraction of large particles on packing density and on coordination number are investigated. Simulation results show good agreement with that obtained by experiments and by other simulations. The randomness, homogeneity, and isotropy, which have not been evaluated before for packing of distributed particles, are also examined using statistical measures.

Journal Article↗

PubMed1998

Inducible nitric oxide synthase expression is selectively induced in astrocytes isolated from adult human brain.

Inducible nitric oxide synthase (iNOS) expression has been shown to be differentially regulated among different cell types and species. In cultures of primary human fetal glial cells, we have shown that astrocytes rather than microglia express iNOS. In the present study, we extended these findings to primary cultures of astrocytes and microglia derived from adult human brains. Mixed cultures of adult brain tissue were stimulated with IL-1beta and IFNgamma, a combination known to induce iNOS maximally in human fetal cells, and the expression of iNOS was determined by immunocytochemistry. Cell types were determined by morphology as well as immunocytochemistry for GFAP (astrocytes) and CD68 (microglia). The results showed that in cultures of adult human glia, iNOS was expressed following stimulation with cytokines, and the expression was restricted to astrocytes. Astrocyte iNOS immunoreactivity was detected both in the cytosol and in a discrete paranuclear region, a pattern noted in human fetal astrocytes. These results demonstrate that the ability to express iNOS is common to both fetal and adult human astrocytes.

Adult↗