Search PubMed⌕ Search

Biomedical subjects

Z Hu

Publications and source records attributed to Z Hu.

At least 181 records · Page 10Linked to original sources
PubMed1999

Specificity of polyhedrin in the generation of baculovirus occlusion bodies.

The role of polyhedrin in the occlusion of virions was studied by substituting two heterologous polyhedrin-coding sequences, one from a multiple-nucleocapsid (M) nucleopolyhedrovirus (NPV) of Spodoptera exigua (Se) and one from a single-nucleocapsid (S) NPV of Buzura suppressaria (BusuNPV), into the genome of Autographa californica (Ac) MNPV. Both heterologous polyhedrin genes were highly expressed and polyhedra were produced in the nuclei of cells infected with the respective recombinant AcMNPVs. Polyhedra produced by the recombinant with BusuNPV polyhedrin showed normal occlusion of multiple-nucleocapsid virions and were equally as infectious to S. exigua larvae as were wild-type AcMNPV polyhedra. This indicates that virion occlusion is not specific with respect to whether the virions or polyhedrin are from an SNPV or MNPV. Polyhedra produced by the recombinant containing the SeMNPV polyhedrin had an altered morphology, being pyramidal rather than polyhedral in shape, and many fewer virions were occluded. These occlusion bodies were less infectious to S. exigua larvae than were those of wild-type AcMNPV. These results indicate that virion occlusion is a finely controlled process that is to some extent specific to the polyhedrin involved and may also require other viral or host factors for optimal morphogenesis.

Amino Acid Sequence↗
PubMed1999

Molecular analysis of (R)-(+)-mandelonitrile lyase microheterogeneity in black cherry.

The flavoprotein (R)-(+)-mandelonitrile lyase (MDL; EC 4.1.2.10), which plays a key role in cyanogenesis in rosaceous stone fruits, occurs in black cherry (Prunus serotina Ehrh.) homogenates as several closely related isoforms. Biochemical and molecular biological methods were used to investigate MDL microheterogeneity and function in this species. Three novel MDL cDNAs of high sequence identity (designated MDL2, MDL4, and MDL5) were isolated. Like MDL1 and MDL3 cDNAs (Z. Hu, J.E. Poulton [1997] Plant Physiol 115: 1359-1369), they had open reading frames that predicted a flavin adenine dinucleotide-binding site, multiple N-glycosylation sites, and an N-terminal signal sequence. The N terminus of an MDL isoform purified from seedlings matched the derived amino acid sequence of the MDL4 cDNA. Genomic sequences corresponding to the MDL1, MDL2, and MDL4 cDNAs were obtained by polymerase chain reaction amplification of genomic DNA. Like the previously reported mdl3 gene, these genes are interrupted at identical positions by three short, conserved introns. Given their overall similarity, we conclude that the genes mdl1, mdl2, mdl3, mdl4, and mdl5 are derived from a common ancestral gene and constitute members of a gene family. Genomic Southern-blot analysis showed that this family has approximately eight members. Northern-blot analysis using gene-specific probes revealed differential expression of the genes mdl1, mdl2, mdl3, mdl4, and mdl5.

Aldehyde-Lyases↗
PubMed1999

The relationship between effector binding and inhibition of activity in D-3-phosphoglycerate dehydrogenase.

The binding of L-serine to phosphoglycerate dehydrogenase from Escherichia coli displays elements of both positive and negative cooperativity. At pH 7.5, approximately 2 mol of serine are bound per mole of tetrameric enzyme. A substantial degree of positive cooperativity is seen for the binding of the second ligand, but the binding of the third and fourth ligand display substantial negative cooperativity. The data indicate a state of approximately 50% inhibition when only one serine is bound and approximately 80-90% inhibition when two serines are bound. This is consistent with the tethered domain hypothesis that has been presented previously. Comparison of the data derived directly from binding stoichiometry to the binding constants determined from the best fit to the Adair equation, produce a close agreement, and reinforce the general validity of the derived binding constants. The data also support the conclusion that the positive cooperativity between the binding to the first and second site involves binding sites at opposite interfaces over 110 A apart. Thus, an order of binding can be envisioned where the binding of the first ligand initiates a conformational transition that allows the second ligand to bind with much higher affinity at the opposite interface. This is followed by the third ligand, which binds with lesser affinity to one of the two already occupied interfaces, and in so doing, completes a global conformational transition that produces maximum inhibition of activity and an even lower affinity for the fourth ligand, excluding it completely. Thus, maximal inhibition is accomplished with less than maximal occupancy of effector sites through a mechanism that displays strong elements of both positive and negative cooperativity.

Binding Sites↗
PubMed1999

Hepatitis B virus X protein is both a substrate and a potential inhibitor of the proteasome complex.

The hepatitis B virus X protein (HBX) is essential for the establishment of HBV infection in vivo and exerts a pleiotropic effect on diverse cellular functions. The yeast two-hybrid system had indicated that HBX could interact with two subunits of the 26S proteasome. Here we demonstrate an association in vivo of HBX with the 26S proteasome complex by coimmunoprecipitation and colocalization upon sucrose gradient centrifugation. Expression of HBX in HepG2 cells caused a modest decrease in the proteasome's chymotrypsin- and trypsin-like activities and in hydrolysis of ubiquitinated lysozyme, suggesting that HBX functions as an inhibitor of proteasome. In these cells, HBX is degraded with a half-life of 30 min. Proteasome inhibitors retarded this rapid degradation and caused a marked increase in the level of HBX and an accumulation of HBX in polyubiquitinated form. Thus, the low intracellular level of HBX is due to rapid proteolysis by the ubiquitin-proteasome pathway. Surprisingly, the proteasome inhibitors blocked the transactivation by HBX, and this effect was not a result of a squelching phenomenon due to HBX accumulation. Therefore, proteasome function is possibly required for the transactivation function of HBX. The inhibition of protein breakdown by proteasomes may account for the multiple actions of HBX and may be an important feature of HBV infection, possibly in helping stabilize viral gene products and suppressing antigen presentation.

Acetylcysteine↗
PubMed1999

Identification of CHIP, a novel tetratricopeptide repeat-containing protein that interacts with heat shock proteins and negatively regulates chaperone functions.

The chaperone function of the mammalian 70-kDa heat shock proteins Hsc70 and Hsp70 is modulated by physical interactions with four previously identified chaperone cofactors: Hsp40, BAG-1, the Hsc70-interacting protein Hip, and the Hsc70-Hsp90-organizing protein Hop. Hip and Hop interact with Hsc70 via a tetratricopeptide repeat domain. In a search for additional tetratricopeptide repeat-containing proteins, we have identified a novel 35-kDa cytoplasmic protein, carboxyl terminus of Hsc70-interacting protein (CHIP). CHIP is highly expressed in adult striated muscle in vivo and is expressed broadly in vitro in tissue culture. Hsc70 and Hsp70 were identified as potential interaction partners for this protein in a yeast two-hybrid screen. In vitro binding assays demonstrated direct interactions between CHIP and both Hsc70 and Hsp70, and complexes containing CHIP and Hsc70 were identified in immunoprecipitates of human skeletal muscle cells in vivo. Using glutathione S-transferase fusions, we found that CHIP interacted with the carboxy-terminal residues 540 to 650 of Hsc70, whereas Hsc70 interacted with the amino-terminal residues 1 to 197 (containing the tetratricopeptide domain and an adjacent charged domain) of CHIP. Recombinant CHIP inhibited Hsp40-stimulated ATPase activity of Hsc70 and Hsp70, suggesting that CHIP blocks the forward reaction of the Hsc70-Hsp70 substrate-binding cycle. Consistent with this observation, both luciferase refolding and substrate binding in the presence of Hsp40 and Hsp70 were inhibited by CHIP. Taken together, these results indicate that CHIP decreases net ATPase activity and reduces chaperone efficiency, and they implicate CHIP in the negative regulation of the forward reaction of the Hsc70-Hsp70 substrate-binding cycle.

Adenosine Triphosphatases↗
PubMed1999

Efficiency of leukocyte removal by filters made of superfine glass fiber membranes.

BACKGROUND AND OBJECTIVES: To demonstrate the application of leukocyte removal filters made of a new type of filter material - superfine glass fiber - for depleting leukocytes in SAGM red cell suspensions and preventing nonhemolytic transfusion reactions. MATERIALS AND METHODS: The extent of leukocyte depletion and red cell recovery was based on cell counts. Trace leukocytes were counted in a 50-microl Nageotte counting chamber or by using a flow cytometer. The chemical stability of the glass fiber membranes was studied by plasma emission spectrometer and by measuring the ion content and weighing nonvolatile matter in water extract. The structural stability of the glass fiber membranes was studied by a micropore-filter membrane method. RESULTS: Leukocyte removal filters made of superfine glass fiber membranes removed more than 99.0% of leukocytes in SAGM red cell suspensions prepared from 400 ml whole blood. Red cell recovery exceeded 90%, and the total number of residual leukocytes was less than 5x10(6). A water extract of the glass fiber membranes contained only traces of Si4+ and Ca2+ and less than 2 mg/100 ml of nonvolatile matter. No broken or loose fibers were found in the filters. Scanning electron microscopy showed that the web structure of the glass fiber membranes was instrumental in trapping and holding leukocytes. CONCLUSION: A filter made of glass fiber membranes is effective in leukocyte depletion.

Adenine↗
PubMed1999

A dissolution test for a pressure-controlled colon delivery capsule: rotating beads method.

The rotating beads method is a new in-vitro dissolution test proposed for drugs formulated as pressure-controlled colon delivery capsules (PCDCs). The apparatus consisted of a glass vessel (500 mL) containing 4-mm (i.d.) glass beads (5000, 10000 or 15000) and dissolution medium (0-067 M phosphate buffer, pH 7; 25, 50 or 100 mL) containing polyvinyl alcohol (PVA; 5, 10 or 20 w/v%) to simulate the viscosity of the colon. The vessel was rotated at 5, 10 or 25 rev min(-1) and the temperature was maintained at 37 degrees C. Fluorescein was used as a model drug to explore the optimized conditions under which differences in the drug dissolution rate are detected between colon delivery systems. Fluorescein was formulated in four types of colon delivery systems. One was a tablet coated with an enteric polymer, Eudragit S-100, and the other three were PCDCs prepared with different thicknesses of ethylcellulose coating membrane (type I, II, III). The dissolution behaviour of fluorescein from the PCDC formulation was significantly different from that of the Eudragit S-100-coated tablets, when the dissolution conditions were as follows: rotation speed, 10 rev min(-1); bead number, 10000; dissolution medium, 50mL with 10% PVA. This dissolution method was applied to acetaminophen sustained-release tablets and two other drugs having low solubility in the colon, tegafur and 5-aminosalicylic acid. Similarly, significant differences in the dissolution rates of drugs from the PCDC formulation and the enteric tablet were detected. There was good correlation between the in-vitro dissolution rates and in-vivo absorption rates using T50 (the time for half of the amount of drug to be released from the preparation) and Cmax/Tmax (enteric tablet) or Cmax/(Tmax-Ti) (PCDC), where Ti is the first appearance time in the systemic circulation. The rotating beads method is a valuable technique for evaluating the dissolution rate of drugs formulated in PCDC.

Administration, Rectal↗
PubMed1999

Technology to obtain sustained release characteristics of drugs after delivered to the colon.

To determine the necessary technology by which sustained drug release is obtained after drug is delivered to the colon, two kinds of microcapsules were prepared and were filled in a pressure-controlled colon delivery capsule (PCDC). As a model drug 5-aminosalicylic acid (5-ASA) was used, because the target site of 5-ASA is the entire large intestine. 5-ASA was microencapsulated using a water-insoluble polymer, ethylcellulose (EC) or with pH-sensitive polymers, Eudragit L-100 or S-100 and encased in PCDC. The particle size of these microcapsules was around 800 microns and the loading efficiencies of 5-ASA were approximately 90%. In vitro dissolution tests were performed with the prepared microcapsules. The release rate of 5-ASA from the microcapsules was significantly prolonged as compared to 5-ASA powder, although there were no significant differences in the release rates between these microcapsules. By incorporating the 5-ASA microcapsules into PCDC, sustained release PCDCs for colon delivery were prepared and in vivo evaluation was performed using beagle dogs. As a fast release colon delivery system, PCDCs were prepared with 5-ASA powder suspended in suppository base. After oral administration of the test preparations to beagle dogs, plasma 5-ASA concentrations were measured and sustained release characteristics of 5-ASA from the test preparations were evaluated from the plasma 5-ASA concentration-time profiles. The first appearance time of 5-ASA into the systemic circulation after oral administration were 3 h for all the colon delivery preparations and it was thought that these test preparations were delivered to the colon. Both EC microcapsules and Eudragit S-100/RS-100 microcapsules in PCDC showed longer the mean residence time MRT, 8.2 +/- 0.6 h and 8.7 +/- 0.9 h, than Eudragit L-100/RS-100 microcapsules in PCDC where the MRT was 6.6 +/- 0.2 h. Since PCDCs containing 5-ASA powder exhibited a MRT of 7.0 +/- 1.0 h, these two types of preparations have suggested sustained release characteristics.

Algorithms↗
PubMed1999

Characterization of norfloxacine release from tablet coated with a new pH-sensitive polymer, P-4135F.

A new pH-sensitive polymer, P-4135F, was evaluated as a colon delivery device for norfloxacine (NFLX) which is used for the therapy of patients with Vero toxin-producing Escherichia coli gastroenteritis. P-4135F has a dissolution threshold pH of 7.2 which is higher than the conventional pH-sensitive polymers, Eudragit S100 and L100. To compare the dissolution site of P-4135F coated tablets with other enteric polymer coatings, mini-tablets containing sodium fluorescein (FL) as a model drug were prepared by coating them with the three polymers. After oral administration of FL mini-tablets to rats, the first-appearance time, Ti, of FL into the systemic circulation was measured. The Tis were 0.7+/-0.2 h for Eudragit L100, 1.8+/-0.4 h for S100 and 2.0+/-0.3 h for P-4135F. Direct inspection of the dissolution process of the FL mini-tablets after oral administration to rats was performed by abdominal incision studies. All of the coated FL mini-tablets started to dissolve in the rat ileum. The dissolution sites were identified to be proximal to the ileocecal junction for P-4135F, at the middle part of the ileum for Eudragit S100 and at the proximal part of the ileum for Eudragit L100. NFLX tablets with different membrane thicknesses of P-4135F were prepared and were orally administered to beagle dogs. The colon delivery efficiency was evaluated by measuring the Ti of NFLX into the systemic circulation. The mean Tis were 1.33+/-0.33 h for 56.8+/-0.5 microm membranes, 3.75+/-0.25 h for 64.6+/-0.7 microm membranes, 4.00+/-1.00 h for 70.5+/-0.5 microm membranes and 3.00+/-1.00 h for 74.9+/-0.4 microm membranes. By comparing the Ti, 4.33+/-0.33 h, obtained after oral administration of NFLX in a pressure-controlled colon delivery capsule, and the colon arrival time, 3.5+/-0.3 h, determined by a sulfasalazine test in beagle dogs. P-4135F coated NFLX tablets appeared to dissolve and disintegrate before reaching the colon. Studies using rats and beagle dogs have suggested that P-4135F dissolves in the lower part of the small intestine, i.e., the ileum. These studies also suggest that this new polymer will be useful for the delivery of NFLX to the lower part of the small intestine.

Acrylic Resins↗
PubMed1999

Different responses of cerebral vessels to -30 degrees head-down tilt in humans.

This study explored changes of the cerebral circulation and evaluated the responses to weightlessness in 12 volunteers (18-22 yr of age). The velocities, diameters and blood flow volume of the common carotid artery (CCA), internal carotid artery (ICA), vertebral artery (VA) and internal jugular vein (IJV) were measured with color Doppler echogram before and during simulated weightlessness. -30 degrees head-down tilt (HDT) for 45 min was used as a weightlessness simulation model. When the subjects' positions were changed from the supine to -30 degrees HDT, blood flow velocities along the CCA, ICA and IJV decreased significantly (p< 0.05), and their diameters were increased. The subjects were divided into two groups according to measured changes in flow volume of the ICA and IJV: group I with a net in-flow of cerebral blood flow (CBF) and group II with a net out-flow of CBF during HDT. Symptoms were recorded in the two groups during HDT (nasal congestion, sensation of head fullness, headache, and others) and graded on a four-point scale, from absent to serious. Results showed that group I had a higher symptoms score while group II had a lower symptoms score. Although this difference did not reach statistical significance, it suggests that cerebral blood flow changes may be partly responsible for the symptoms observed in subjects during HDT.

Adolescent↗
PubMed1999

Determination of blood flow and endothelial shear stress in human coronary artery in vivo.

This paper describes a system that permits, for the first time, the in vivo determination of local velocity and endothelial shear stress in the major human coronary arteries. The purpose of the system is to facilitate the study of plaque growth and the relationships between local hemodynamic factors and atherogenesis and restenosis. The three-dimensional anatomy of a segment of the right coronary artery was determined immediately after directional atherectomy via a combination of intracoronary ultrasound and biplane angiography. The highly irregular geometry of the segment was then represented in curvilinear coordinates and a computational fluid dynamics technique was used to investigate the detailed, intravascular velocity profile and shear stress distribution. We found minor flow reversals, significant swirling and a large variation of local velocity and shear stress, both axially and circumferentially, within the artery, even in the absence of significant luminal obstruction. The flow phenomena exhibit characteristics consistent with the focal nature of atherogenesis and restenosis. It is concluded that the technology now exists to determine luminal geometry and local variations in flow fields and endothelial shear stress, in vivo.

Arteries↗
PubMed1999

[Clinical study on pathologic changes of umbilical cord vessels in pregnancy induced hypertension].

OBJECTIVE: To evaluate the relationship between the pathologic features of umbilical cord vessels and the severity of disease in pregnancy induced hypertension (PIH). METHODS: The umbilical cord vessels of forty-five women with PIH and thirty normal term-pregnant women (control group) were observed under light microscopy; the three parts of cord i.e. near placenta, near fetus and middle section of twenty women with PIH selected randomly were observed as well. RESULTS: There were no different pathologic changes in the 3 parts of umbilical cord in PIH; Forty-five women with PIH were categorized into three groups according to the degree of lesions: no lesion (n = 6), mild (n = 13) and severe (n = 26). The pathologic changes of umbilical vessels in moderate and severe PIH were more severe than those in mild PIH (P < 0.05, P < 0.01). However, there were no apparent pathologic changes in the control. The pathologic changes of umbilical vessels in PIH had significant relationship with mean arterial pressure (MAP), neonatal outcome and urinary protein. CONCLUSIONS: The pathologic changes of umbilical vessels can reflect the characteristic lesion of PIH and are parallel with the severity of disease; and there is a homogeneity in pathomorphology of umbilical cord.

Adult↗
PubMed1999

[Study on relationship between two different syndromes and three soluble cytokine receptors in patients with rheumatoid arthritis].

OBJECTIVE: To study the relationship between two different Syndromes (Cold-Damp Syndrome and Damp-Heat Syndrome) and three soluble cytokine receptors (sCKR, soluble interleukin-2 receptor, sIL-2R, soluble interleukin-6 receptor, sIL-6R, soluble tumor necrosis factor receptor 1, sTNFR1) in rheumatoid arthritis (RA). METHODS: The serum levels of three soluble receptors were measured by ELISA in patients with RA. RESULTS: The serum levels of 3 sCKR were significantly elevated in RA patients compared to healthy controls and obviously lowered after treatment (P < 0.01). The level of sIL-2R was significantly higher in Cold-Damp Syndrome than that in Damp-Heat Syndrome (P < 0.01), but serum sTNFR1 was significantly higher in Damp-Heat Syndrome than that in Cold-Damp Syndrome, there was no obvious difference between sIL-6R of two Syndromes. CONCLUSION: The high serum sIL-2R and low sTNFR1 might be a criterion of Cold-Damp Syndrome, but the high sTNFR1 and low sIL-2R might be a criterion of Damp-Heat Syndrome, these criteria reflected some states of different functions in immune system in patients with RA.

Adolescent↗
PubMed1999

[Experimental study of influence of yiqi huoxue serial recipes on basement membrane in membranous nephritis in rabbits].

OBJECTIVE: To clucidate the mechanism of the therapeutic effect of Yiqi Huoxue (YQHX) serial recipes on membranous nephritis. METHODS: Forty-nine New Zealand male rabbits were made to menbranous nephritis model by cation bovine serum albumin and divided into 5 groups, the group A (treated by Qingre Moshen granule), B (treated by Bushen Moshen granule), C (treated by steroid), D (the control group) and E (the normal group). Twenty-four hours' urinary protein content of the animals was determined every week, and plasma albumin, blood lipid, renal function and prostaglandins were tested by the end of experiment. And pathological changes of basement membrane were observed by using light, electronic and immunofluorescent microscopy with polyethylene imine stain. RESULTS: The 24 hours urinary protein content, plasma albumin and blood lipid in the group A and B were lower than those in the control group significantly, P < 0.01 or 0.05, while those in the group C and the D were similar, P > 0.05. In comparing the group A and B with the group C, the difference was also significant, P < 0.05. Light, electronic and immunofluorescent microscopic examination all showed that the pathologic changes in the group A, B and C were lesser than that of the control, the effect was in the order A > B > C. CONCLUSION: YQHX serial recipes can reduce urinary protein content, elevate plasma albumin level, restore the charge barrier effect of and attenuate the immune complex deposition on the basement membrane of glomeruli.

6-Ketoprostaglandin F1 alpha↗
PubMed1999

[Axial aponeurotic flap combined with skin graft in the treatment of lower lid ectropion and severe infra-orbital soft tissue depression].

OBJECTIVE: The correction of ectropion of lower lid and severe infra-orbital soft tissue depression is very difficult. Former methods included simple skin graft, tubed graft, transfer of local skin flap and so on. These methods had some disadvantages, such as not enough tissue to fill the depression, too much damage done to the donor area and operation in stages required. METHODS: After investigation on the anatomy of temporal region, designed the following method. Combined transfer of the galea aponeurotica and temporal fascia was used to repair severe infra-orbital soft tissue depression and ectropion of lower lid in 6 cases. RESULTS: It was discovered that the combined transfer of the galea aponeurotica and temporal fascia was rich in blood circulation because they received blood supply from parietal branch of superficial temporal artery and could be transferred to a distance as far as 15-18 cm. The skin graft used to cover the fascia usually resulted in good survival. This technique was used in 6 cases with good success. CONCLUSION: This method had some merits such as the tissue flap had good blood supply, little damage done to the donor area, good correction of the severe depression, good appearance following correction, operation done under local anesthesia and completed in one-stage operation.

Adolescent↗