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D Zhu

Publications and source records attributed to D Zhu.

At least 181 records · Page 10Linked to original sources
PubMed1997

Ligand linked assembly of Scapharca dimeric hemoglobin.

The assembly of Scapharca dimeric hemoglobin as a function of ligation has been explored by analytical gel chromatography, sedimentation equilibrium, and oxygen binding experiments to test the proposal that its cooperativity is based on quaternary enhancement. This hypothesis predicts that the liganded form would be assembled more tightly into a dimer than the unliganded form and that dissociation would lead to lower oxygen affinity. Our experiments demonstrate that although the dimeric interface is quite tight in this hemoglobin, dissociation can be clearly detected in the liganded states with monomer to dimer association constants in the range of 10(8) M-1 for the CO-liganded state and lower association constants measured in the oxygenated state. In contrast, the deoxy dimer shows no detectable dissociation by analytical ultracentrifugation. Thus, the more highly hydrated deoxy interface of this dimer is also the more tightly assembled. Equilibrium oxygen binding experiments reveal an increase in oxygen affinity and decrease in cooperativity as the concentration is lowered (in the muM range). These experiments unambiguously refute the hypothesis of quaternary enhancement and indicate that, as in the case of human hemoglobin and other allosteric proteins, quaternary constraint underlies cooperativity in Scapharca dimeric hemoglobin.

Animals↗
PubMed1997

Increased monocyte TNF-alpha message stability contributes to trauma patients' increased TNF production.

Post-trauma elevation of tumor necrosis factor alpha (TNF-alpha) appears to be critical in mediating many symptoms of systemic inflammatory response syndrome (SIRS), resulting in late mortality. Although increased monocyte (mphi) TNF-alpha production plays a pivotal role in this TNF-alpha elevation, the molecular mechanisms leading to increased mphi TNF-alpha production have yet to be elucidated. We demonstrate that, although TNF-alpha mRNA levels are increased in all trauma patients' mphi, which produce elevated levels of TNF-alpha protein, in the majority of patients, these increased TNF-alpha mRNA levels are under normal transcriptional and posttranscriptional control. Consequently, the increased TNF-alpha production by these patients' mphi is probably due to preactivation of these mphi by trauma-released mediators. However, a small minority of patients, whose mortality rate was 57%, produce TNF-alpha of primarily the membrane-associated type. The mphi TNF-alpha mRNA accumulation of these patients in response to in vitro stimulation is significantly augmented. All of these patients experienced SIRS. In this subset of patients' mphi, TNF-alpha mRNA stability was aberrantly increased. Such an increase in TNF-alpha mRNA stability could lead to devastatingly prolonged production of TNF-alpha protein. This demonstration of increased TNF-alpha mRNA stability in post-trauma mphi represents a novel correlation of elevated membrane-associated TNF-alpha protein, increased mortality, and a mechanism for this occurrence.

Adult↗
PubMed1997

Dominant inheritance of optic pits.

PURPOSE: To report the familial occurrence of optic pits and to screen the candidate PAX2 gene for mutations in this family. METHODS: Clinical family study. Standard mutation analysis of the PAX2 exons. RESULTS: Unilateral optic pits were present in three generations of one family and were inherited in an autosomal dominant fashion. No mutations in the PAX2 gene, responsible for the renal-optic coloboma syndrome, were found. CONCLUSION: Unilateral optic pits may be inherited in an autosomal dominant fashion and not in association with mutation in the PAX2 gene.

Adolescent↗
PubMed1997

Mutation of Arg154 to Gly154 in urokinase augments its fibrin-specificity.

Rscu-PA and its mutant constructed by in vitro site specific mutagenesis of Arg154 in rscu-PA to Gly154 (mscu-PA) were both expressed in Escherichia coli. After in vitro denaturation and renaturation, the rscu-PA and mscu-PA were purified to homogeneity by Zn2+ selective precipitation, anti-u-PA IgG-sepharose CL 4B affinity chromatography. After activation by plasmin, the kinetic constants for the resultant mtcu-PA against synthetic substrate S2444 hydrolysis were found to be essentially identical to rtcu-PA, suggesting that no impairment had been exerted on the catalytic active site of mtcu-PA. However, both 125I-fibrin plasma-clot lysis and fibrinogenolysis showed that mtcu-PA possessed a higher fibrinolytic activity but hardly any degradation of fibrinogen in plasma compared to rtcu-PA and rscu-PA. It was concluded that the substitution of Arg154 by Gly154 in tcu-PA promoted the fibrin-specificity of urokinase.

Arginine↗
PubMed1997

GroE assists refolding of recombinant human pro-urokinase.

GroE, one of the molecular chaperones, facilitates correct protein folding both in vitro and in vivo. The refolding of recombinant human pro-urokinase, a protein with a high content of disulfide bonds, was used as a model system to illustrate the mechanism of action of GroE. Aggregation of this protein predominates during its in vitro refolding, as indicated by a strong, concentration-dependent increase in light scattering. The addition of GroE and Mg-ATP significantly increases the yield of the active protein. GroE specifically inhibits the aggregation reaction that competes with correct folding, as shown by a strong decrease in the intensity of light scattering. GroEL rapidly binds to unfolded or partially folded pro-urokinase molecules and thus protects them from the aggregation reaction. Interaction with GroES and ATP hydrolysis are required for the release of the polypeptide chain from GroEL and further acquisition of the completely folded, native conformation.

Adenosine Triphosphate↗
PubMed1997

Renaturation, purification, and characterization of human plasminogen activator inhibitor type 2 (PAI-2) accumulated at high level in Escherichia coli.

Plasminogen activator inhibitor 2 (PAI-2) is an important regulator of plasminogen activation, which inhibits both tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA). In this study we have developed a high-level expression system by inserting a modified PAI-2 gene downstream of the T7 promoter. The expression level of recombinant PAI-2 amounted to 55-60% of total microbial protein. By efficient renaturation and one-step purification, the recombinant protein was purified to homogeneity. The specific activity and yield of recombinant PAI-2 reached 33,000 IU/mg and 10 mg per gram wet weight of Escherichia coli cells, respectively. The second-order rate constant for uPA was 2.6-2.8 x 10(6) M(-1) x s(-1).

Cloning, Molecular↗
PubMed1997

Effects of exogenous recombinant ovine interferon tau on circulating concentrations of progesterone, cortisol, luteinizing hormone, and antiviral activity; interestrous interval; rectal temperature; and uterine response to oxytocin in cyclic ewes.

Interferon tau (IFN tau) is the conceptus-produced antiluteolytic signal in ruminants. Three experiments examined the effects of s.c. administration of recombinant ovine (ro)IFN tau on interestrous interval (IEI), oxytocin (OT)-induced uterine prostaglandin F2alpha metabolite (PGFM) production, rectal temperature (RT), respiration rate (RR), and plasma concentrations of progesterone, cortisol, LH, and antiviral activity (AVA) in plasma and uterine flushings. In experiment I, 20 ewes were treated s.c. with either 0, 1, 2, or 4 mg/day roIFN tau (0.7 x 10(8) U/mg; 5 ewes/dosage) from Days 11 to 15 of the estrous cycle (estrus = Day 0) and were challenged with OT (30 IU) on Day 15. Jugular blood samples were collected at -10, 0, 10, 20, 30, 40, 50, and 60 min relative to the OT challenge and assayed for PGFM. Recombinant oIFN tau increased IEI (16.7, 18.7, and 22.6 +/- 0.6 days for 0, 2, and 4 mg roIFN tau, respectively, p < 0.01). Recombinant oIFN tau did not affect peak PGFM response to OT (2309 +/- 172 pg/ml; p > 0.1). However, the 4 mg/day dosage delayed the time to peak PGFM (32.4 vs. 47.5 +/- 3.4 min; p < 0.01, 0 vs. 4 mg) and resulted in approximately 200% higher concentrations of PGFM at 60 min post-OT (0 vs. 4 mg/day, p < 0.07). Experiment II was similar to experiment I, except that only the 0- and 4-mg/day dosages of roIFN tau were administered. Ewes were hysterectomized on Day 16, and assay of uterine flushes detected no AVA from ewes treated with either 0 or 4 mg/day roIFN tau. In experiment III, 20 ewes were treated s.c. with either 0, 2, 4, or 6 mg roIFN tau on Day 12. Blood samples, RT, and RR were obtained at frequent intervals for 24 h, and plasma was assayed for progesterone, cortisol, LH, and AVA. Plasma AVA, which increased in a dose-dependent manner, was detectable within 60 min and remained elevated at 24 h compared to control values. RT (elevated 0.5-1.0 degrees C), RR, and cortisol increased in response to all dosages of roIFN tau, with peak values occurring 150-180 min postinjection. For all dosages of roIFN tau, plasma progesterone declined from 120 to 360 min posttreatment and then returned to pretreatment values by 24 h (p < 0.01) as compared to controls. Overall, exogenous roIFN tau altered uterine PGFM response to OT from a pulse to a gradual and sustained elevation and extended IEI with only a transient decline in progesterone and mild hyperthermia, effects that are not expected to compromise pregnancy.

Animals↗
PubMed1997

HSP70-2 is required for CDC2 kinase activity in meiosis I of mouse spermatocytes.

Cyclin B-dependent CDC2 kinase activity has a key role in triggering the G2/M-phase transition during the mitotic and meiotic cell cycles. The Hsp70-2 gene is expressed only in spermatogenic cells at a significant level. In Hsp70-2 gene knock-out (Hsp70-2(-/-)) mice, primary spermatocytes fail to complete meiosis I, suggesting a link between HSP70-2 heat-shock protein and CDC2 kinase activity during this phase of spermatogenesis. Members of the HSP70 protein family are molecular chaperones that mediate protein de novo folding, translocation and multimer assembly. This study used immunoprecipitation-coupled western blot and in vitro reconstitution experiments to show that HSP70-2 interacts with CDC2 in the mouse testis, appears to be a molecular chaperone for CDC2, and is required for CDC2/cyclin B1 complex formation. Previous studies reported that most CDC2 kinase activity in the mouse testis is present in pachytene spermatocytes. Although CDC2 kinase activity for histone H1 was present in the testis of wild-type mice, it was nearly absent from the testis of Hsp70-2(-/-) mice, probably due to defective CDC2/cyclin B1 complex formation. Furthermore, addition of HSP70-2 to freshly prepared extracts of testis from Hsp70-2(-/-) mice not only restored CDC2/cyclin B1 complex formation but also reconstituted CDC2 kinase activity in vitro. It appears that one cause of failure to complete meiosis I during spermatogenesis in Hsp70-2(-/-) mice is disruption of CDC2/cyclin B1 assembly in pachytene spermatocytes, thereby preventing development of the CDC2 kinase activity required to trigger G2/M-phase transition. These studies provide novel in vivo evidence for a link between an HSP70 molecular chaperone and CDC2 kinase activity essential for the meiotic cell cycle in spermatogenesis.

Animals↗
PubMed1997

[Optimization of technical parameters for processing radix Aconiti coreani].

Based on the determination of guanfu A, hypaconitine, and total alkaloids, along with the experiment of acute toxicity of sliced Radix Aconiti Coreani and in compliance with the quality standard stipulated in pharmacopeia-surface features cross section colour and odor of sliced Radix Aconiti Co-reani the technology of processing Radix Aconiti Coreani has been optimized to be steaming the drug for four hours.

Aconitine↗
PubMed1997

[Oral candidiasis in Sjögren's syndrome: prevalence, clinical features and treatment].

The clinical feature of 20 cases with oral candidiasis in Sjögren's syndrome (SS) were reported, and the treatment effect by topical nystatin smearing, 2% sodium bicarbonate solution rinsing, and transfer factor injecting for about 2 months were analysed. The results showed that the diagnostic criterion of oral candidiasis in SS included two aspects: the SS changes confirmed by labial gland biopsy and candidal hyphae and spores found in a smear. The results indicated that the comprehensive treatments were proved to be effective for oral candidiasis in SS.

Adolescent↗
PubMed1997

[Recombinant human macrophage colony-stimulating factor expressed in silkworm accelerates hematopoietic recovery of radiolesion mice].

OBJECTIVE: To demonstrate the hematopoietic enhancement activity of recombinant human macrophage colony-stimulating factor (rhM-CSF). METHODS: Balb/c mice were sublethally irradiated with 60Co gamma-rays and then the rhM-CSF expressed in silkworm (10(3)U per individual for 7 days) was administered intraperitoneally. RESULTS: (1) The peripheral white blood cell counts of treatment group at day 15 and day 20 after irradiation were significantly higher than those of normal control group; (2) At days 10, 15, 20, 25 and 30 after irradiation, the difference between the peripheral monocyte counts of the treatment and control group were statistically significant; (3) At days 15, 20 and 25 after irradiation, the difference between the peripheral granulocyte counts of the two groups were also significant; (4) At day 9 after irradiation, the bone marrow CFU GM yield of the control group were significantly lower than those of the treatment group. CONCLUSION: rhM-CSF expressed in silkworm could accelerate hematopoietic recovery in irradiated mice.

Animals↗
PubMed1997

[The development of a gas chromatograph used in gas analysis below atmospheric pressure].

During the process of setting up a carbon monoxide infrared laser generator, it's necessary to analyze the gaseous components produced in laser cavity under reduced pressure for understanding its charging regularity. In this paper a self-made gas chromatograph for analysis of some special gas mixtures is described. This instrument can analyze O2, N2, CO (with normal contents) and trace CO2 simultaneously below atmospheric pressure. The gas sample below atmospheric pressure was taken into a small piston cylinder and then compressed by pushing the piston for injection. The injected sample was carried by He into two parallel chromatographic columns and detected separately. The gases with normal contents were detected by a thermalconductivity detector (TCD) and the trace CO2 was detected by a He ionization detector (HeID). The detection sensitivity of CO2 is in the order of magnitude of 10(-6) V/V. The experimental results show that this instrument with advantages of simple design, easy operation and good stability is suitable for on-line analysis of gas samples below atmospheric pressure. We have successfully analyzed on-line the gaseous components produced in the laser cavity by using this equipment. The technique described here can be used for complete analysis of gas samples below atmospheric pressure in many other fields.

English Abstract↗
PubMed1997

[X-ray photoelectron spectroscopy (XPS) and mass spectrum (MS) study of organic tin compounds II].

Seven new synthetical (Z)-1-[2-(Triarylstannyl) vinyl]-1-cycloheptanols organic tin compounds were studied by X-ray photoelectron spectroscopy and mass spectrum method. The influence of different replacement radical in compounds on the d orbit of tin atom was discussed. The coordinate substance had an effect on the chemical displacement of Ols binding energy. The O-->Sn bond was affected by the different replacement radical. The results of X-ray photoelectron spectroscopy and mass spectrum show that Cl, Br and I had the important action.

Electrons↗
PubMed1997

Sporadic and Thorotrast-induced angiosarcomas of the liver manifest frequent and multiple point mutations in K-ras-2.

Hepatic angiosarcoma (HA) is an uncommon neoplasm associated with known etiologic factors in 25% to 42% of cases. It is, however, one of the most common sarcomas found in the liver. The aim of this study was to find was to find mutations in the K-ras-2 oncogene in sporadic and Thorotrast (TT)-induced HA. Point mutations in K-ras-2 were sought in archival, formalin-fixed tissue blocks from 24 patients with angiosarcoma. Of these, 19 cases were sporadic and 5 were TT-induced. Mutational analysis was performed by topographic microdissection with PCR amplification followed by genotyping. Specific mutations were determined by two independent methods: (a) direct sequencing of the PCR product confirmed by rePCR and by using a different sequencing primer, and (b) PCR-based selective enrichment of mutant DNA by endonuclease digestion followed by heteroduplex DNA analysis using denaturing gradient gel electrophoresis. Eleven K-ras-2 point mutations were detected in 7 of 24 (29%) tumors, including 5 of 19 (26%) sporadic HA and 2 of 5 (40%) TT-induced HA. There were seven G:C > A:T and four G:C > T:A mutations. All seven mutated tumors contained a codon 12-aspartate amino acid substitution. In addition, a second codon 12-cysteine mutant cell population was present in one of two codon 12-aspartate mutated TT-induced HA and in three of five codon 12-aspartate sporadic tumors. Of these four tumors, three contained both aspartate and cysteine mutations and were composed of multiple nodules; the fourth was a single mass. Seventeen tumors had multiple nodules; whereas 5 had a K-ras-2 mutation, 12 were wild-type. The molecular pathology of both sporadic and TT-induced HA is characterized by a high rate of K-ras-2 mutations characteristic of oxidative damage (ie, G:C > A:T and G:C > T:A mutations) resulting in two mutated population sets: codon 12 GGT > GAT and GGT > TGT (glycine to aspartic acid and cysteine). This is, to date, the first study to characterize the K-ras-2 gene mutations within human sporadic and TT-induced HA by direct sequence analysis and denaturing gradient gel electrophoresis. These data further support the hypothesis linking adduct-forming vinyl chloride exposure to HA containing a much higher frequency of K-ras-2 mutations and a mutational spectrum characteristic of chloroethylene oxide, a carcinogenic metabolite of vinyl chloride.

Adult↗
PubMed1997

Phage surface expression for analysis of recognition sites of human autoantibodies: comparison of single chain Fv and Fab.

Human autoantibodies can mediate the pathology of autoimmune disease. To plan therapeutic intervention based on inhibition of binding to autoantigen, it is desirable to map the amino acid residues involved in recognition. Bacterial expression provides a simple and rapid system for production and mutagenesis of recombinant antibody fragments, but there are problems with reproducible folding and dispersity of soluble products. Expression at the surface of phage particles avoids both these problems, and allows variable region gene sequences to be expressed as functional monomers. To apply this technology, we have expressed a human anti-DNA monoclonal antibody, derived from a hybridoma, at the surface of the phage. The presence of the phage particle allowed highly sensitive detection of antibody activity by ELISA, so that minimal levels of expression were required. By measuring the amount of expressed antibody protein, it was possible to analyze the antibody activity/microgram. We expressed the antibody as FAB or single chain (sc) Fv, and found binding activities to be closely similar. The parental anti-DNA antibody utilizes the human V4-34 gene and displays the associated conformation-dependent 9G4 idiotope. Both the Fab and scFv expressed the idiotope, confirming similar molecular folding. This technology can be applied rapidly and efficiently to investigations of human autoantibody structure, with the option for expression as either Fab or scFv, and the only requirement being knowledge of VH and VL sequences.

Antibodies, Anti-Idiotypic↗
PubMed1997

[Study on the recognition and evolutionary genetics of the courtship song of species in Drosphila nasuta species subgroup].

The subgroup of Drosophila nasuta consists of 14 species, subspecies and taxa. It has a wide distribution in area of Indo-Pacific Ocean. The courtship song of species in nasuta subgroup is recorded for the first time in the paper. Some parameters of temporal pattern of pulse song were measured: the inter burst interval (IBI), the interpulse interval (IPI), the length of a pulse train (PTL), the number of pulses in a train (PN), the length of a pulse (PL) and the length of a cycle (CL). Computer analysis techniques were used to make spectral analysis of sine song. A three-dimensional power spectra of the sound was made. In this subgroup, the male of D. pulauna and Taxon-F didn't produce any sound signals during courtship, suggesting that the visual stimuli play an important role in mating process. By analysing the courtship sound signals of other species, subspecies and taxa, the sounds produced by courting male could be described as pulse song or as sine song. By studying the sounds of intra- or interspecific F1 hybrids we have found that the parameters of the temporal pattern of pulse song, for example, the mean value of IPI is controlled by X-linked and autosomal polygene and the sine song frequency is predisposed to the maternity. The phylogenetic tree of the subgroup is constructed based on the temporal pattern of the pulse sounds in different species, subspecies and taxa. The relationship within the members of the Drosophila nasuta subgroup is discussed.

Animals↗