Biomedical subjects

H Zou

Publications and source records attributed to H Zou.

At least 73 records · Page 4Linked to original sources

PubMed1999

Membrane supports as the stationary phase in high-performance immunoaffinity chromatography.

The membrane with a composite of cellulose grafted with acrylic polymers formed by polymerizing a glycidyl methacrylate in the presence of dispersed cellulose fiber was prepared as the stationary phase; the column (40 x 4 mm i.d.) which was compatible with the HPLC instrument was packed with pieces of the cut membrane. Protein A and human IgG were immobilized on the membrane stationary phase. The column based on the membrane support provided us good reproducibility, high efficiency, and low back pressure. High-performance immunoaffinity chromatographic analysis of human IgG in serum and polyclonal antibody to human IgG raised in goat was performed within 2.5 min. The fast-speed immunoaffinity analysis was developed by increasing the flow rate of the mobile phase and decreasing the duration time for the switch of the mobile phase; an operation for immunoaffinity analysis of human IgG could be finished within 30 s.

Cellulose↗

PubMed1999

Immobilized iminodiacetic acid (IDA)-type Cu2+ -chelating membrane affinity chromatography for purification of bovine liver catalase.

A metal ion chelating membrane medium based on iminodiacetate-substituted modified short cotton cellulose was examined for the purification of bovine liver catalase (BLC). The effect of buffer pH, chelator surface density, initial concentration of crude enzyme and flow rate on BLC binding efficiency to the copper ion chelating membrane adsorbent were examined. Under the chromatographic conditions chosen, 67.7% recovery of BLC was attained with an overall 4.2-fold increase in specific activity in a single step. After performance of BLC purification, the chelating membrane adsorbent can be easily regenerated by imidazole or EDTA buffer with higher reviving effectiveness with the latter.

Animals↗

PubMed1999

Protein A tangential flow affinity membrane cartridge for extracorporeal immunoadsorption therapy.

Tangential flow affinity membrane cartridge (TFAMC) is a new model of immunoadsorption therapy for hemoperfusion. Recombinant Protein A was immobilized on the membrane cartridge through Schiff base formation for extracorporeal IgG and immune complex removal from blood. Flow characteristics, immunoadsorption capacity and biocompatibility of protein A TFAMC were studied. The results showed that the pressure drop increased with the increasing flow rate of water, plasma and blood, demonstrating reliable strength of membrane at high flow rate. The adsorption capacities of protein A TFAMC for IgG from human plasma and blood were measured. The cartridge with 139 mg protein A immobilized on the matrix (6 mg protein A/g dry matrix) adsorbed 553 mg IgG (23.8 mg IgG/g dry matrix) from human plasma and 499.4 mg IgG (21.5 mg IgG/g dry matrix) from human blood, respectively. The circulation time had a major influence on IgG adsorption capacity, but the flow rate had little influence. Experiments in vitro and in vivo confirmed that protein A TFAMC mainly adsorbed IgG and little of other plasma proteins, and that blood cell damage was negligible. The extracorporeal circulation system is safe and reliable.

Animals↗

PubMed1999

Study of physically absorbed stationary phases for open tubullar capillary electrochromatography.

A novel method based on the adsorption of positively charged compounds on the wall of a fused-silica capillary was applied to prepare stationary phases for open tubular capillary electrochromatography (OTCEC). The positively charged substances including cationic surfactant such as cetyltrimethylammonium bromide (CTAB) and basic chiral selectors such as protein, peptide and amino acid were physically adsorbed onto the capillary wall under specially selected conditions. The adsorbed stationary phase of CTAB was used to separate neutral compounds, while the others were used for chiral separations. The run-to-run reproducibility of retention time was rather good with relative standard deviation (RSD) values of less than 2.3%. The separation efficiency was excellent with the highest theoretical plate number of up to 590000/m and the average one above 250000/m. Stored at 2-8 degrees C in the refrigerator, the adsorbed stationary phase can last at least one month. It was observed that the UV spectra for the enantiomers are significantly different due to the diastereomeric interactions of enantiomers with the chiral stationary phase in the detection window. With the use of the same capillary, the same instrument, and the same mobile phase, the superiority of OTCEC over open tubular liquid chromatography (OTLC) and capillary zone electrophoresis (CZE) was illustrated.

Animals↗

PubMed1999

Effects of organic modifiers on solute retention and electrokinetic migrations in micellar electrokinetic capillary chromatography.

Influences of seven organic modifiers, including urea, methanol (MeOH), dioxane (DIO), tetrahydrofuran (THF), acetonitrile (ACN), 1-propanol (1-PrOH) and 2-propanol (2-PrOH), on the solute retention and the electrokinetic migrations in micellar electrokinetic capillary chromatography (MEKC) are investigated with sodium dodecyl sulfate (SDS) micelle as pseudostationary phase. It is observed that in the limited concentration ranges used in the MEKC systems the effect of organic modifier concentration on the retention can be described by the equation logk1=logk1w-SC for most binary aqueous-organic buffer, but deviations from this retention equation are observed at ACN and particularly THF as organic modifiers. With parameter S as a measure of the elutropic strength, the elutropic strength of the organic modifiers is found to follow a general order urea <MeOH<ACN<2-PrOH<DIO, while THF is found to be the most abundant modifier in selectivity among the organic modifiers studied. The electroosmotic mobility decreases linearly with increasing modifier concentrations. The strength of modifiers to suppress the electroosmotic mobility follows the order urea < MeOH, ACN < DIO, THF, 1-PrOH, 2-PrOH. The addition of ACN affects the electrophoretic mobility of the SDS micelle in different patterns depending on the buffer composition used, while the addition of the other modifiers leads to a rough linear decrease of the electrophoretic mobility of the SDS micelle. The suppressing strength of THF on the electrophoretic mobility of the SDS micelle is strongly related to the buffer composition, whereas the suppressing strength for the other modifiers follows the sequence urea < MeOH < DIO, 1-PrOH, 2-PrOH. The migration time window is expanded by the use of organic modifiers. Urea and MeOH have the least expanding strength while ACN, DIO, THF, 1-PrOH and 2-PrOH have the highest expanding strength on the migration time window.

Chromatography, Micellar Electrokinetic Capillary↗

PubMed1999

Dark is a Drosophila homologue of Apaf-1/CED-4 and functions in an evolutionarily conserved death pathway.

Here we identify a new gene, dark, which encodes a Drosophila homologue of mammalian Apaf-1 and Caenorhabditis elegans CED-4, cell-death proteins. Like Apaf-1, but in contrast to CED-4, Dark contains a carboxy-terminal WD-repeat domain necessary for interactions with the mitochondrial protein cytochrome c. Dark selectively associates with another protein involved in apoptosis, the fly apical caspase, Dredd. Dark-induced cell killing is suppressed by caspase-inhibitory peptides and by a dominant-negative mutant Dredd protein, and enhanced by removal of the WD domain. Loss-of-function mutations in dark attenuate programmed cell deaths during development, causing hyperplasia of the central nervous system, and other abnormalities including ectopic melanotic tumours and defective wings. Moreover, ectopic cell killing by the Drosophila cell-death activators, Reaper, Grim and Hid, is substantially suppressed in dark mutants. These findings establish dark as an important apoptosis effector in Drosophila and raise profound evolutionary considerations concerning the relationship between mitochondrial components and the apoptosis-promoting machinery.

Amino Acid Sequence↗

PubMed1999

Imaging Ca(2+) entering the cytoplasm through a single opening of a plasma membrane cation channel.

Discrete localized fluorescence transients due to openings of a single plasma membrane Ca(2+) permeable cation channel were recorded using wide-field digital imaging microscopy with fluo-3 as the Ca(2+) indicator. These transients were obtained while simultaneously recording the unitary channel currents using the whole-cell current-recording configuration of the patch-clamp technique. This cation channel in smooth muscle cells is opened by caffeine (Guerrero, A., F.S. Fay, and J.J. Singer. 1994. J. Gen. Physiol. 104:375-394). The localized fluorescence transients appeared to occur at random locations on the cell membrane, with the duration of the rising phase matching the duration of the channel opening. Moreover, these transients were only observed in the presence of sufficient extracellular Ca(2+), suggesting that they are due to Ca(2+) influx from the bathing solution. The fluorescence transient is characterized by an initial fast rising phase when the channel opens, followed by a slower rising phase during prolonged openings. When the channel closes there is an immediate fast falling phase followed by a slower falling phase. Computer simulations of the underlying events were used to interpret the time course of the transients. The rapid phases are mainly due to the establishment or removal of Ca(2+) and Ca(2+)-bound fluo-3 gradients near the channel when the channel opens or closes, while the slow phases are due to the diffusion of Ca(2+) and Ca(2+)-bound fluo-3 into the cytoplasm. Transients due to short channel openings have a "Ca(2+) spark-like" appearance, suggesting that the rising and early falling components of sparks (due to openings of ryanodine receptors) reflect the fast phases of the fluorescence change. The results presented here suggest methods to determine the relationship between the fluorescence transient and the underlying Ca(2+) current, to study intracellular localized Ca(2+) handling as might occur from single Ca(2+) channel openings, and to localize Ca(2+) permeable ion channels on the plasma membrane.

Animals↗

PubMed1999

Bound volatile general anesthetics alter both local protein dynamics and global protein stability.

BACKGROUND: Recent studies have demonstrated that volatile general anesthetic agents such as halothane and isoflurane may bind to discrete sites on protein targets. In the case of bovine serum albumin, the sites of halothane and chloroform binding have been identified as being located in the IB and IIA subdomains. This structural information provides a foundation for more detailed studies into the potential mechanisms of anesthetic action. METHODS: The effect of halothane and isoflurane and the nonimmobilizer 1,2-dichlorohexafluorocyclobutane on the mobility of the indole ring in the tryptophan residues of albumin was investigated using measurements of fluorescence anisotropy. Myoglobin served as a negative control. In addition, the effect of bound anesthetic agents on global protein stability was determined by thermal denaturation experiments using near-ultraviolet circular dichroism spectroscopy. RESULTS: The fluorescence anisotropy measurements showed that halothane and isoflurane decreased the mobility of the indole rings in a concentration-dependent manner. The calculated dissociation constants were 1.6+/-0.4 and 1.3+/-0.3 mM for isoflurane and halothane, respectively. In contrast, both agents failed to increase the fluorescence anisotropy of the tryptophan residues in myoglobin, compatible with lack of binding. The nonimmobilizer 1,2-dichlorohexafluorocyclobutane caused no change in the fluorescence anisotropy of albumin. Binding of the anesthetic agents stabilized the native folded form of albumin to thermal denaturation. Analysis of the thermal denaturation data yielded dissociation constant values of 0.98+/-0.10 mM for isoflurane and 1.0+/-0.1 mM for halothane. CONCLUSIONS: Attenuation of local side-chain dynamics and stabilization of folded protein conformations may represent fundamental modes of action of volatile general anesthetic agents. Because protein activity is crucially dependent on inherent flexibility, anesthetic-induced stabilization of certain protein conformations may explain how these important clinical agents change protein function.

Algorithms↗

PubMed1999

Marked inhibition of tumor growth in a malignant glioma tumor model by a novel synthetic matrix metalloproteinase inhibitor AG3340.

Synthetic matrix metalloproteinase (MMP) inhibitors have activity against a variety of tumors in preclinical models but have not been studied in gliomas. We determined the effect of AG3340, a novel synthetic MMP inhibitor with Ki values against gelatinases in the low picomolar range, on the growth of a human malignant glioma cell line (U87) in SCID-NOD mice. Mice were injected s.c. with U87 cells. Tumors were allowed to grow to a size of approximately 0.5 x 0.5 cm (after about 3 weeks), and the mice were randomized to receive either: (a) 100 mg/kg AG3340 in vehicle; or (b) vehicle control (0.5% carboxymethyl cellulose, 0.1% pluronic F68), both given daily i.p. Tumor area was measured twice weekly, and animals were sacrificed when moribund, or earlier if premorbid histology was examined. In vivo inhibition of tumor growth was profound, with AG3340 decreasing tumor size by 78% compared with controls after 31 days (when controls were sacrificed; P < 0.01, Wilcoxon test). Control animals survived 31 days after the i.p. injections began, and AG3340 mice survived 71 days, representing a >2-fold increase in survival associated with tumor growth delay. Histological examination found that AG3340-treated tumors were smaller, had lower rates of proliferation, and significantly less invasion than control-treated tumors. Hepatic or pulmonary metastases were not seen in either group. In a separate experiment, the tumors were smaller and sampled after a shorter duration of treatment; the changes in proliferation were more marked and occurred earlier than differences in tumor invasion between the two groups. Furthermore, in vitro cell growth was not inhibited at AG3340 concentrations of <1 mM. AG3340 plasma concentrations in vivo, 1 h after administration, ranged from 67 to 365 nM. Thus, AG3340 produced a profound inhibition of glioma tumor growth and invasion. AG3340 markedly increased survival in this in vivo glioma model. Treatment with AG3340 may be potentially useful in patients with malignant gliomas.

Animals↗

PubMed1999

Marked antiangiogenic and antitumor efficacy of AG3340 in chemoresistant human non-small cell lung cancer tumors: single agent and combination chemotherapy studies.

Effective therapy is needed to improve the survival of patients with advanced lung cancers. We studied the effects of a selective metalloprotease inhibitor, AG3340, on chemoresistant human non-small cell lung cancer tumors (line MV522) in vivo. Mice bearing s.c. tumors were given twice-daily oral doses of AG3340. As a single agent, AG3340 inhibited angiogenesis (up to 77%) and tumor growth (up to 65%) in a dose-dependent manner at well-tolerated daily doses up to 400 mg/kg/day and induced significant tumor necrosis. In contrast, tumors were relatively insensitive to carboplatin with approximately 25% growth inhibition observed at a maximum tolerated dose of approximately 30 mg/kg/week (given i.p., twice weekly). Carboplatin inhibited tumor growth markedly only at toxic doses, demonstrating a superior therapeutic index of AG3340 to carboplatin in this tumor model. A suboptimal dose of AG3340, when used in combination with an ineffective maximum tolerated dose of carboplatin, resulted in greater tumor growth inhibitions than those produced by either agent alone. Similarly, growth inhibition was enhanced when AG3340 was used in combination with paclitaxel. Cotreatment with carboplatin did not alter AG3340 plasma concentrations achieved acutely after oral dosing. These data demonstrate an antiangiogenic and antitumor effect of AG3340 when used as a single agent and enhanced growth inhibitions when AG3340 is used in combination with cytotoxic agents. These data suggest that treatment with this novel matrix metalloprotease inhibitor may be beneficial in advanced lung cancers and other chemoresistant malignancies.

Animals↗

PubMed1999

[Efficacy of 40-O-(2-hydroxyethyl)-rapamycin in preventing chronic renal allograft rejection in rats].

OBJECTIVE: To study the efficacy of 40-O-(2-hydroxyethyl)-rapamycin (SDZ RAD) in preventing chronic renal allograft rejention in rats. METHODS: The rat model of chronic renal allograft rejection was made with micro-surgery. The recipients were divided into two groups. The recipients in the study group were treated with SDZ RAD at a dose of 0.5 mg x kg(-1) x d(-1) by means of gavage and the controls with vehicle. RESULTS: After 24 weeks of treatment, proteinuria, glomerular sclerosis, vascular intimal thickening and the infiltration of monocytesmacrophages and lymphocytes in the study group were decreased, in consistence with the reduced expression of ICAM-1, VCAM-1, TGF-beta(1) and PDGF-AA mRNA. CONCLUSION: It is suggested that SDZ RAD can prevent chronic renal allograft rejection and the reduced expression of above adhesion molecules and growth factors may be involved in the mechanism.

Animals↗

PubMed1999

[Re-assessment of indicators for screening lead poisoning].

OBJECTIVE: To determine the accuracy of the indicators for detecting lead poisoning. METHODS: Blood and urine specimens in 157 workers exposed to lead were collected. Their blood levels of lead, free erythrocyte protoporphyrin (FEP), zinc protoporphyrin (ZPP), urine delta-aminolevulinic acid and activity of red cell pyrimidine 5'-nucleotidase were determined, with gold standards of blood lead levels of >or= 1.93 micromol/L and >or= 2.90 micromol/L. Accuracy assessment of the indicators mentioned above for detecting lead poisoning was based on the area under the receiver operative characteristic (AUC(ROC)) curve with a software specially for ROC curve analysis and software of Epi-Info, after determining the optimal cut-off points for the above mentioned indicators in detecting those with blood lead >or= 1.93 micromol/L and >or= 2.90 micromol/L. The sensitivity of screening in parallel for detecting those with blood lead >or= 1.93 micromol/L and >or= 2.90 micromol/L was calculated and compared. RESULTS: For detecting those with blood lead level >or= 1.93 micromol/L, the area under ROC curve (AUC(ROC)) of above indicators was 0.978 for ZPP, 0.973 for red cell P5'N, 0.937 for FEP, 0.890 for urine delta-ALA (significantly different from that for ZPP with P < 0.05), and 0.845 for urine lead level (significantly different from that for ZPP with P < 0.05), respectively. For detecting those with blood lead level >or= 2.90 micromol/L, the area under ROC curve (AUC(ROC)) of above indicators was 0.975 for red cell P5'N, 0.954 for ZPP, 0.906 for FEP (significantly different from that for red cell P5'N with P < 0.05), 0.900 for urine delta-ALA (significantly different from that for red cell P5'N with P < 0.05), and 0.750 for urine lead level (significantly different from that for red cell P5'N with P < 0.05). Sensitivity of screening in parallel with ZPP and P5'N was significantly higher than that with urine levels of lead and delta-ALA. CONCLUSION: Determinations of red cell P5'N and ZPP for detecting those with blood lead >or= 1.93 micromol/L and >or= 2.90 micromol/L are more accurate.

5'-Nucleotidase↗

PubMed1999

[Selectivity tuning in multi-binary eluents for reversed-phase liquid chromatography (RPLC)].

In this article, the retention equation and the relationship between retention parameters and the parameters of molecular structure deduced from statistical thermodynamics in RPLC have been used to explain the difference of selectivity towards a particular species of compounds polycyclic aromatic hydrocarbons (PAHs). Methanol/water, acetonitrile/water and isopropanol/acetonitrile have been provided in advance, then the retention behaviors of sixteen PAHs under three binary solvent systems have been investigated. It is found that each pair of binary solvents of methanol/water, acetonitrile/water and isopropanol/acetonitrile has its own unique selectivity. The best selectivity obtained for acenaphthene and fluorene is methanol/water system for fluoranthene and pyrene is acetonitrile/water, and for benzo[g,h,i]perylene and dibenzo[a,h]anthracene is isopropanol/acetonitrile. So a three-stepwise gradient elution of multi-binary mobile phase can be chosen for separation of 16 PAHs.

Acenaphthenes↗

PubMed1999

Method development of adsorbed stationary phase open tubular capillary electrochromatography.

The adsorption effect of capillary wall, which was usually considered as a troublesome factor, has been used as driving force for preparing stationary phase for open tubular capillary electrochromatography (OTCEC). A number of compounds have been applied as stationary phase materials, which include cationic surfactants such as cetyltrimethylammonium bromide (CTAB), basic proteins such as lysozyme and cytochrome C, basic peptides such as Lys-Tyr and Lys-Ser-Tyr, and basic amino acid L-lysine. The adsorbed CTAB phase is used for separation of neutral compounds while other adsorbed stationary phases are used for chiral separation. The run-to-run reproducibility of retention time is rather good with RSD values less than 2.3%. The separation efficiency is excellent with the highest theoretical plate number of up to 590,000/m and the average plate number of more than 250,000/m. Being stored at 2-8 degrees C in refrigerator, the adsorbed stationary phase can last at least one month.

Adsorption↗

PubMed1999

[Protein A tangential flow membrane chromatographic column used for immunoadsorption therapy].

Tangential flow membrane chromatographic column is a new model of immunoadsorption therapy from blood. The results showed that the structure of the column and the flowing channel had a little damages for blood cells. The relation of flow-rate and backpressure with water, plasma and blood individually as the fluid flowing through the column has been studied. It was observed that backpressures increased with fluid viscosity, when flow-rate of blood was 120 mL/min and the backpressure reached 0.093 MPa; The adsorption capacity of protein A of the column for IgG from human plasma has been measured. When plasma and blood individually circulated through the column for 1 h, the column with 139 mg protein A immobilized on the matrix (6 mg protein A/g dry matrix) adsorbed 553 mg IgG (23.8 mg IgG/g dry matrix) from human plasma and 499.4 mg IgG (21.5 mg IgG/g dry matrix) from human blood respectively. The circulation time had a great influence on IgG adsorption capacity; but the circulation rate had a little influence on IgG adsorption capacity. The result of extracoporeal blood perfusion for dog showed that the Protein A column has good blood biocompatibility.

Chromatography↗

PubMed1999

[The application of artificial neural network in QSAR research of PCDD].

The study of QSAR between molecular structure and retention behavior of solutes is an important topic of chromatographic basic theory. PCDD (polychlorinated dioxin) is a kind of important environmental toxin. The basic skeleton of PCDD is [symbol: see text]. PCDDs are all chlorine substituted, so they are only different from each other in the number and position of chlorine substitutents on the skeleton. There are 76 kinds of homologues (1 to 8 chlorine substituent) for 3, 4, 5 and 6 chlorine substituted compounds including more than ten kinds of isomerides. In this paper, the description of molecular structure and feature selection have been investigated. Artificial neural network (ANN) is used to relate the molecular structure and retention time of PCDD. The predicted results of 49 PCDDs retention time by ANN are listed. It was shown that as to the relative error more than 95% data was less than 10% and more than 80% data was less than 5%.

Chromatography↗

PubMed1999

[Screening and analysis of biologically active components in traditional Chinese medicine by molecular biochromatography].

Screening of biologically active components from Chinese medicines by molecular biochromatography has been first proposed by authors. This paper summarizes their recent progresses on screening and analysis of Chinese medicines by molecular chromatography, including the comparison of the chromatograpic pattern for a number of herbal medicines, and the same kind of medicines but different sources, method development for screening and quality control of Chinese medicines, and the study on the interactions between the biologically active compounds in Chinese medicines and protein. The prospect of molecular biochromatography on study of Chinese medicines has also been highlighted.

4-Butyrolactone↗

PubMed1999

[Preparation and evaluation of open tubular capillary electrochromatographic columns by sol-gel method].

Open-tubular capillary electrochromatographic columns were prepared by sol-gel method. The influence of pH of gel solution on the column performance was investigated with a series of gel solution prepared by hydrochloric acid at different pH value. The results show that the pH of gel solution influences the capacity factors (k') of solutes in a complex way. The general trend is that the values of k' increase as the pH value increases except that at pH of 2.0. The gel solution of pH 2.8 was selected to prepare the column, at which the greatest capacity factors can be obtained within an acceptable reaction rate. The influence of reaction time of gel solution in column was also investigated. Out of expectation, the k' value didn't increase with increase in reaction time. The reason may be that the pore of silica gel is so small that the sample molecule can't migrate into it. The surface area is only offered by outer surface of silica gel, so the phase ratio of column prepared by this method is still not large enough. It was found that the joule heat effect can be neglected since the capillaries used were very small in inner diameter. The electroosmotic flow plays an important role in the separation as it determines the separation time. In order to accelerate the separation, high pH condition is necessary. Therefore, the stability of column under high pH is very important. The column shows a good stability under pH 9 of the mobile phase. The relative standard deviations (RSD) of capacity factor of four solutes were less than 3.7% for 100 times of operations. The separation efficiency was evaluated and the average theoretical plate numbers under optimal conditions for thiourea, phenetole, naphthalene, biphenyl, and 2,6-dimethyl naphthalene were 4.66 x 10(5), 5.24 x 10(5), 5.02 x 10(5), 4.77 x 10(5), and 3.58 x 10(5)/m, respectively. The column shows good repeatability. The RSD values for k' are less than 1% and the RSD values for efficiency are less than 8% (n = 5). In addition, fast separation was obtained with shorter column and higher voltage used, where four aromatic compounds were baseline separated in 101 s.

English Abstract↗