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Biomedical subjects

D Zhao

Publications and source records attributed to D Zhao.

At least 19 recordsLinked to original sources
PubMed2000

Dynamics of non-structural carbohydrates in developing leaves, bracts and floral buds of cotton.

Development of cotton (Gossypium hirsutum L.) squares (i.e. floral buds with bracts) is fundamental for yield formation. A 2-year field study was conducted to determine dry weight (DW) accumulations of cotton leaves, floral bracts and floral buds, and the changes in concentrations of non-structural carbohydrates (hexoses, sucrose and starch) in these tissues during square ontogeny as affected by fruiting positions within the plant canopy. During square development, DW accumulation of a subtending sympodial leaf and floral bracts followed a sigmoid growth curve with increasing square age, whereas the DW increase of a floral bud followed an exponential curve. Main-stem node (Node 8, 10 or 12) and branch position (proximal vs. distal) within a plant canopy significantly affected DW accumulations of the leaf, bracts and floral bud. Starch was the dominant non-structural carbohydrate in the three tissues, accounting for more than 65% of total non-structural carbohydrates (TNC). Subtending leaf TNC increased as square age increased. The bracts exhibited a smaller change in TNC than leaves. Non-structural carbohydrate concentration was the lowest in 10-day-old floral buds, and had little change during the first 15 days of square development. Within 5 days prior to anthesis, the floral-bud TNC increased dramatically, tripling at the time of floral anthesis compared with 15-day-old floral buds. Square age and fruiting position significantly affected non-structural carbohydrate concentrations of subtending leaves, bracts, and floral buds. The correlation did not exist between final boll retention and non-structural carbohydrate concentrations of floral buds at different fruiting positions under normal growth conditions. The pattern of floral-bud non-structural carbohydrates during square ontogeny suggests that major events in carbohydrate metabolism occur just prior to anthesis.

Journal Article↗
PubMed2000

Structure and stability effects of the mutation of glycine 34 to serine in Rhodobacter capsulatus cytochrome c(2).

Gly 34 and the adjacent Pro 35 of Rhodobacter capsulatus cytochrome c(2) (or Gly 29 and Pro 30 in vertebrate cytochrome c) are highly conserved side chains among the class I c-type cytochromes. The mutation of Gly 34 to Ser in Rb. capsulatus cytochrome c(2) has been characterized in terms of physicochemical properties and NMR in both redox states. A comparison of the wild-type cytochrome c(2), the G34S mutation, and the P35A mutation is presented in the context of differences in chemical shifts, the differences in NOE patterns, and structural changes resulting from oxidation of the reduced cytochrome. G34S is substantially destabilized relative to wild-type (2.2 kcal/mol in the oxidized state) but similarly destabilized relative to P35A. Nevertheless, differences in terms of the impact of the mutations on specific structural regions are found when comparing G34S and P35A. Although available data indicates that the overall secondary structure of G34S and wild-type cytochrome c(2) are similar, a number of both perturbations of hydrogen bond networks and interactions with internal waters are found. Thus, the impact of the mutation at position 35 is propagated throughout the cytochrome but with alterations at defined sites within the molecule. Interestingly, we find that the substitution of serine at position 34 results in a perturbation of the heme beta meso and the methyl-5 protons. This suggests that the hydroxyl and beta carbon are positioned away from the solvent and toward the heme. This has the consequence of preferentially stabilizing the oxidized state in G34S, thus, altering hydrogen bond networks which involve the heme propionate, internal waters, and key amino acid side chains. The results presented provide important new insights into the stability and solution structure of the cytochrome c(2).

Amino Acid Substitution↗
PubMed2000

Changes in phospholipase D isoform activity and expression in multidrug-resistant human cancer cells.

Multidrug resistance (MDR) is a major cause of failure of cancer chemotherapy and is often associated with elevated expression of drug transporters such as P-glycoprotein (P-gp) in the cancer cells. MDR is, however, accompanied by additional biochemical changes including modifications of membrane composition and properties. We have shown that MDR is associated with a massive up-regulation of caveolin expression and an elevated surface density of caveolae. We report that phospholipase D (PLD), a constituent enzyme of caveolae and detergent-insoluble glycolipid-rich membranes (DIGs), is up-regulated in human MDR cancer cells. Lysates of HT-29-MDR human colon adenocarcinoma cells, MCF-7 AdrR human breast adenocarcinoma cells and the corresponding parental drug-sensitive cells, were fractionated on discontinuous sucrose density gradients. PLD activity was found to be enriched in low density fractions that contain DIGs and caveolar membranes, and the activity in these fractions was 4- to 6-fold higher in the MDR cells compared with the parental drug- sensitive cells. Utilizing specific antibodies to PLD1 and PLD2, the distribution of PLD isoforms along the gradient was determined and the PLD localized in DIGs and caveolar membranes has been identified as PLD2. Northern blot analysis of PLD1 and PLD2 mRNA levels has indicated that PLD2 mRNA is elevated in both HT-29-MDR and MCF-7 AdrR cells. PLD1 mRNA levels were either unchanged or reduced in the MDR cells. Finally, in vivo experiments have confirmed previous results showing that activation of PLD by phorbol esters is markedly potentiated in the MDR cells. We conclude that MDR is accompanied by an increase in PLD2 activity in DIGs and caveolar membranes.

Adenocarcinoma↗
PubMed2000

Three new taxoids from the seeds of Japanese yew, Taxus cuspidata.

Five taxane diterpenoids were isolated from the seeds of the Japanese yew, Taxus cuspidata Sieb. et Zucc. The structures were established as 2 alpha,7 beta,13 alpha-triacetoxy-5 alpha-(3'-dimethylamino-3'-phenyl)-propionyloxy-2(3-->20)-aboe+ ++-taxa-9,10-dione (1) and 2 alpha,7 beta,9 alpha,10 beta-tetraacetoxy-5 alpha-[(2R,3S),N,N-dimethyl-3-phenylisoseryloxy]-taxa-4(20),11- dien-13-one (2), 2 alpha, 9 alpha, 10 beta-triacetoxy-5 alpha-cinnamoxy-taxa-4(20),11-diene-13 alpha-ol (3), taxezopidine J (4), and taxuspine D (5) on the basis of 1D, 2D NMR, and MS spectral analysis. Compounds 1, 2, and 3 are new compounds.

Diterpenes↗
PubMed2000

New taxane diterpenoid from seed of the Chinese yew, Taxus yunnanensis.

A novel taxane diterpenoid with a rearranged 5/7/6-membered ring system was isolated from seeds of the Chinese yew, Taxus yunnanensis. Its structure was established as 9alpha,13alpha-diacetoxy-10beta-benzoxy-5alpha- cinnamoyl-11(1 5-->1)-abeotaxa-4(20),11-dien-15-ol on the basis of a spectroscopic analysis. Its relative stereochemistry is proposed from the results of NOESY experiments.

Bridged-Ring Compounds↗
PubMed1999

Crystal structure of colicin E3 immunity protein: an inhibitor of a ribosome-inactivating RNase.

BACKGROUND: Colicins are antibiotic-like proteins of Escherichia coli that kill related strains. Colicin E3 acts as an RNase that specifically cleaves 16S rRNA, thereby inactivating the ribosomes in the infected cell. The producing organism is protected against colicin E3 by a specific inhibitor, the immunity protein Im3, which forms a tight 1:1 complex with colicin E3 and renders it inactive. Crystallographic studies on colicin E3 and Im3 have been undertaken to unravel the structural basis for the ribonucleolytic activity and its inhibition. RESULTS: The crystal structure of Im3 has been determined to a resolution of 1.8 A. The structure consists of a four-standard antiparallel beta sheet flanked by three alpha helices on one side of the sheet. Thr7, Phe9, Phe16 and Phe74 form a hydrophobic cluster on the surface of the protein in the vicinity of Cys47. This cluster is part of a putative binding pocket which also includes nine polar residues. CONCLUSIONS: The putative binding pocket of Im3 is the probable site of interaction with colicin E3. The six acidic residues in the pocket may interact with some of the numerous basic residues of colicin E3. The involvement of hydrophobic moieties in the binding is consistent with the observation that the tight complex can only be dissociated by denaturation. The structure of Im3 resembles those of certain nucleic acid binding proteins, in particular domain II of topoisomerase I and RNA-binding proteins that contain the ribonucleoprotein (RNP) sequence motif. This observation suggests that Im3 has a nucleic acid binding function in addition to binding colicin E3.

Bacterial Proteins↗
PubMed1999

The ASK1 gene regulates development and interacts with the UFO gene to control floral organ identity in Arabidopsis.

Normal flower development likely requires both specific and general regulators. We have isolated an Arabidopsis mutant ask1-1 (for -Arabidopsis skp1-like1-1), which exhibits defects in both vegetative and reproductive development. In the ask1-1mutant, rosette leaf growth is reduced, resulting in smaller than normal rosette leaves, and internodes in the floral stem are shorter than normal. Examination of cell sizes in these organs indicates that cell expansion is normal in the mutant, but cell number is reduced. In the mutant, the numbers of petals and stamens are reduced, and many flowers have one or more petals with a reduced size. In addition, all mutant flowers have short stamen filaments. Furthermore, petal/stamen chimeric organs are found in many flowers. These results indicate that the ASK1 gene affects the size of vegetative and floral organs. The ask1 floral phenotype resembles somewhat that of the Arabidopsis ufo mutants in that both genes affect whorls 2 and 3. We therefore tested for possible interactions between ASK1 and UFO by analyzing the phenotypes of ufo-2 ask1-1 double mutant plants. In these plants, vegetative development is similar to that of the ask1-1 single mutant, whereas the floral defects are more severe than those in either single mutant. Interior to the first whorl, the double mutant flowers have more sepals or sepal-like organs than are found in ufo-2, and less petals than ask1-1. Our results suggest that ASK1 interacts with UFO to control floral organ identity in whorls 2 and 3. This is very intriguing because ASK1 is very similar in sequence to the yeast SKP1 protein and UFO contains an F-box, a motif known to interact with SKP1 in yeast. Although the precise mechanism of ASK1 and UFO action is unknown, our results support the hypothesis that these two proteins physically interact in vivo.

Arabidopsis↗
PubMed1999

Misexpression of argos, an inhibitor of EGFR signaling in oogenesis, leads to the production of bicephalic, ventralized, and lateralized Drosophila melanogaster eggs.

Epidermal growth factor receptor (EGFR) signaling pathways are frequently involved in generating cell fate diversity in a number of organisms. During anterior-posterior and dorso-ventral polarity in the Drosophila egg chamber and eggshell, EGFR signaling leads to a number of determinative events in the follicle cell layer. A high level of Gurken signal leads to the expression of argos in dorsal midline cells. Lateral follicle cells, receiving a lower level of Gurken signal, can continue to express the Broad-Complex (BR-C) and differentiate into cells which produce chorionic appendages. Misexpression of argos in mid-oogenesis causes the midline cells to retain expression of BR-C, resulting in a single fused large appendage. Evidence that argos can directly repress Gurken-induced EGFR signaling is seen when premature expression of argos is induced earlier in oogenesis. It represses the Gurken signal at stage 5-6 of oogenesis which determines posterior follicle cells and occasionally leads to eggs with anteriors at both ends. We propose that the Gurken signal at stage 9 of oogenesis induces follicle cells to take on two fates, dorsal midline and lateral, each producing different parts of the eggshell and that argos is one of the key downstream genes required to select between these two fates.

Animals↗
PubMed1999

Expression of P27kip1 and Ki-67 in pituitary adenomas: an investigation of marker of adenoma invasiveness.

Mirroring the ambiguities noted with other endocrine tumours, histology is a poor predictor of the invasiveness of pituitary adenomas. Accordingly, the proteins p27Kip1 (p27) and Ki-67, which respectively block cell-cycle progression and reflect proliferative activity of cells, were studied immunohistochemically in 123 specimens of pituitary adenomas including 57 clinically verified invasive cases. Only Ki-67 had a significant association with invasiveness; only p27 differed significantly between functioning and nonfunctioning adenomas, with a higher frequency of cell labelling in the former. No relationship between Ki-67 and p27 was obtained. Ki-67 detected by MIB-1 is thus an important marker related to the invasive potential of adenomas, and thereby may be helpful in planning postoperative management of patients with pituitary adenomas.

Adolescent↗
PubMed1999

Myofibroblasts in the cirrhotic rat liver reflect hepatic remodeling and correlate with fibrosis and sinusoidal capillarization.

BACKGROUND/AIMS: Myofibroblasts are essential in fibrogenesis during development of cirrhosis. In the present study we stereologically quantitated MFB's and correlated them with fibrosis and sinusoidal capillarization. METHODS: Male SD rats were rendered cirrhotic by chronic exposure to phenobarbital/CCl4, (CIR; n = 16); untreated littermates served as controls (CTR; n = 10). Sinusoidal capillarization was assessed by a multiple indicator dilution technique as previously described. The volume fractions of myofibroblasts and other liver components were estimated by morphometry. RESULTS: Myofibroblasts averaged 15.7 +/- SD 0.7% in CIR as compared to 6.7% +/- SD 0.4% in CTR (p < 0.01). An extra-littoral compartment of myofibroblasts was found in portal tracts and within fibrous septa. In CIR, hepatocytes showed a bimodal distribution of volume fractions, and hepatocyte volume distribution disclosed a mirror image of that of myofibroblasts. Connective tissue was markedly increased in CIR, averaging 13.2 +/- 1.2% in CIR vs. 1.2 +/- 0.3% in CTR (p < 0.0001). Extravascular albumin space--a measure of sinusoidal capillarization--was reduced by 44% in CIR (0.028 +/- 0.017 vs. 0.050 +/- 0.010 ml/g; p < 0.001). The volume fraction of myofibroblasts correlated best with extravascular albumin space (r = -0.84, p < 0.001). Multiple regression analysis selected only extravascular albumin space and connective tissue to be determined by the volume fraction of myofibroblasts (r = 0.923; p < 0.001). CONCLUSION: We conclude that increased myofibroblasts reflect the degree of hepatic remodeling rather than cirrhosis inasmuch as myofibroblast volume fraction inversely reflects that of hepatocyte bimodality. Myofibroblasts form an extra-littoral compartment in this model of CIR and correlate with hepatic fibrosis and sinusoidal capillarization.

Actins↗
PubMed1999

Conopeptides from Conus striatus and Conus textile by cDNA cloning.

Conopeptide content in Conus textile and Conus striatus venoms were examined by polymerase chain reaction amplification of alpha-conopeptide cDNA and rapid amplification of 3' cDNA ends of O-superfamily conopeptide cDNA. Two new alpha-conopeptide sequences and six new O-superfamily conopeptide sequences from C. textile, four new O-superfamily conopeptide sequences, and four previously biochemically characterized conopeptide sequences from C. striatus were identified. The results suggest that this cDNA method is rapid and requires less material for the study of conopeptides.

Amino Acid Sequence↗
PubMed1999

Trial of antiepilepsirine (AES) in children with epilepsy.

Antieplepsirine (AES) is a new antiepileptic drug (AED) which was originally extracted from a Chinese folk remedy, and is now chemically characterized and synthesized. Its chemical structure is different from those of other available AEDs. Animal experiments involving AES demonstrated significant antiepileptic activity. Only a few clinical studies of AES with open trial have been resorted, none of which were on children. A 6.5 month, add-on, double-blind, placebo-controlled, randomized, cross-over study on AES (10 mg/kg per day) was conducted on epileptic children (aged 1-14 years) refractory to treatment with standard AEDs. The seizure frequency was recorded, and the blood levels of AES and other co-medicated AEDs (phenobarbital, phenytoin, carbamazepine and valproate) were determined. Although not planned, patients or parents were allowed to refuse to cross-over to the alternate therapy. The results were compared to the children who crossed-over as well as for the entire group during the first 3 months of randomized treatment. A total of 58 children entered, but only 34/58 children completed the cross-over study. The 24 children whose parents refused to let them be crossed-over continued the original study treatment (AES or placebo) for the entire 6 months. There was no statistically significant difference in seizure control when the entire group of 58 patients was compared to a parallel study group for the first 3 months of therapy (P = 0.178). There was a significant difference (P<0.01) in seizure control between AES and placebo treatment for the 34 patients who completed the entire cross-over study. No significant changes were seen in the blood level of other AEDs, and no serious acute side effects were observed. The results of the present study indicate the efficacy of AES for epileptic children with refractory seizures.

Adolescent↗
PubMed1999

Upregulation of heme oxygenase-1 protects genetically fat Zucker rat livers from ischemia/reperfusion injury.

We examined the effects of upregulation of heme oxygenase-1 (HO-1) in steatotic rat liver models of ex vivo cold ischemia/reperfusion (I/R) injury. In the model of ischemia/isolated perfusion, treatment of genetically obese Zucker rats with the HO-1 inducer cobalt protoporphyrin (CoPP) or with adenoviral HO-1 (Ad-HO-1) significantly improved portal venous blood flow, increased bile production, and decreased hepatocyte injury. Unlike in untreated rats or those pretreated with the HO-1 inhibitor zinc protoporphyrin (ZnPP), upregulation of HO-1 by Western blots correlated with amelioration of histologic features of I/R injury. Adjunctive infusion of ZnPP abrogated the beneficial effects of Ad-HO-1 gene transfer, documenting the direct involvement of HO-1 in protection against I/R injury. Following cold ischemia/isotransplantation, HO-1 overexpression extended animal survival from 40% in untreated controls to about 80% after CoPP or Ad-HO-1 therapy. This effect correlated with preserved hepatic architecture, improved liver function, and depressed infiltration by T cells and macrophages. Hence, CoPP- or gene therapy-induced HO-1 prevented I/R injury in steatotic rat livers. These findings provide the rationale for refined new treatments that should increase the supply of usable donor livers and ultimately improve the overall success of liver transplantation.

Adenoviridae↗
PubMed1999

A comparative study on the treatment of migraine headache with combined distant and local acupuncture points versus conventional drug therapy.

UNLABELLED: According to Chinese medicine, the differential diagnosis of migraine headache may be classified based on the state of the viscera, channels and collaterals. In this study, acupuncture treatment prescriptions combining distant and local acupoints were selected according to the differential diagnosis. Sixty-four patients were divided into two equal groups: one group received acupuncture, and the other group underwent conventional drug treatment. RESULTS: The efficacy rates in the acupuncture and control groups were as follows, respectively: Cure: 75% versus 34.4%, marked improvement: 18.8% versus 28.1%, no effect: 6.3% versus 37.5%. The overall effective rates for the acupuncture and control groups were 93.8% and 62.5%, respectively, indicating a significantly greater effect in the acupuncture group (P < 0.01, x = 13.475).

Acupuncture Therapy↗
PubMed1998

Hierarchically ordered oxides

Porous silica, niobia, and titania with three-dimensional structures patterned over multiple length scales were prepared by combining micromolding, polystyrene sphere templating, and cooperative assembly of inorganic sol-gel species with amphiphilic triblock copolymers. The resulting materials show hierarchical ordering over several discrete and tunable length scales ranging from 10 nanometers to several micrometers. The respective ordered structures can be independently modified by choosing different mold patterns, latex spheres, and block copolymers. The examples presented demonstrate the compositional and structural diversities that are possible with this simple approach.

Journal Article↗
PubMed1998

Developmental changes in phospholipase D activity and mRNA levels in rat brain.

Phospholipase D (PLD) activity and PLD1 mRNA levels were determined in rat brain at ages ranging from embryonic day (E) 19 to postnatal day (P) 49. Basal, oleate-, and phosphatidylinositol-4, 5-bisphosphate-stimulated PLD activity increased between E19 and P24 by approximately 3-fold and remained unaltered thereafter. A similar developmental pattern of mRNA levels of PLD1 isoform was found by Northern blotting. The development of PLD correlates with synaptogenesis and myelination suggesting that the enzyme might have an important function in these processes.

Animals↗
PubMed1998

Biochemical characterization of selenium-containing catalytic antibody as a cytosolic glutathione peroxidase mimic.

A selenium-containing catalytic antibody (Se-4A4), prepared by converting reactive serine residues of a monoclonal antibody (4A4) raised against a GSH derivative into selenocysteines, acts as a mimic of cytosolic glutathione peroxidase (cGPX). To clarify the mechanism of action of this catalytic antibody, detailed studies on kinetic behaviour and biological activity were carried out. A rate of acceleration (kcat/Km/kuncat) 10(7)-fold that of the uncatalytic reaction is observed. Under similar conditions, the turnover number (kcat) of Se-4A4 is 42% of that of the natural rabbit liver cGPX. The Se-4A4 reaction involves a Ping Pong mechanism, which is the same as that of the natural cGPX. The selenocysteine residue is located in the binding site of the antibody and is shown to be crucial for this activity. Of the thiol compounds tested, only GSH is able to serve as substrate for Se-4A4. It was demonstrated, using the free-radical-damage system (hypoxanthine/xanthine oxidase) of cardiac mitochondria, that Se-4A4 can protect mitochondria from free-radical damage at least 10(4)-fold more effectively than the natural cGPX.

Antibodies, Catalytic↗