Biomedical subjects
Publications and source records attributed to Y Zou.
A 170bp PCR products was amplified the DNA in a dinosaur egg using primers designed from the conserved regions of human cytochrome b gene and was sequenced. BLAST search through INTERNET for homology detection showed that the sequence was almose identical with the human mitochondria cytochrome b gene(96-100% similarity). Therefore we can conclude that the dinosaur egg itself has been seriously contaminated.
This paper report a sensitive and rapid method for the determination of metronidazole (MTZ) using theophylline as the internal standard. High performance liquid chromatograph model 344 (Beckman) with a 254 nm wavelength UV detector and YWG-C18H37 column (10 microns, 250 x 4.6 mm) was used. To the serum sample 200 microliters, 100 microliters phosphate buffer (0.8 mol/L, pH 7.5) was added, then extracted with 3 ml chloroform containing 5% isopropyl alcohol. The organic layer was removed and evaporated to dryness under an air stream in a 40 degrees C water bath. The residue was dissolved in 30 microliters mobile phase and 20 microliters injected. The mobile phase of water-methanol (73:27) was pumped at 1.0 ml/min through the column. The detector operated at 0.005 aufs. The retention times for MTZ and theophylline were 5.78 and 6.81 min respectively. Standard curve was linear in the concentration range of 0.3125 to 20 mg/L. The detection limit in serum was 0.02 mg/L. Extraction recovery was 77%-82%; method recovery 99%-102%; withinday RSD less than 3.0%; inter-day RSD less than 3.5%.
This paper reports the preparation of the coupling compound between thiogalactose and cytochrome C(Cyt-C). The binding tests of this compound to asialoglycoprotein receptor have also been carried out in vivo. The results show that the pharmacokinetics of this compound is in accordance with the basic characteristic of receptor induced binding. The highest uptake of liver reaches to 32.9% and at the same time the conjugate remains 78.6% the biological activity of Cyt-C. It is possibly a hepatic targeting drug or a hepatic targeting carrier.
The DNA binding profile of a series of dinuclear platinum complexes [{trans-PtCl-(L)2}2H2N(CH2)nNH2]2+ (L = NH3 or py; 1,1/t,t/NH3 and 1,1/t,t/py, respectively) and [{cis-PtCl-(NH3)2H2N(CH2)nNH2]2+ (1,1/c,c/NH3) was examined to compare the effects of geometrical isomerism and the presence of ligands other than NH3 in the coordination sphere. Steric effects, because of the geometry of the leaving groups cis to the diamine bridge or the presence of planar pyridine ligands, result in diminished binding to calf thymus DNA for these isomers. In contrast, the pyridine derivative shows a distinct binding preference for poly(dG-dC).poly(dG-dC) in comparison to both NH3 isomers. Both NH3 complexes induced the B-->Z transition in poly(dG-dC).poly(dG-dC), but the presence of a pyridine ligand stabilized the B conformation. The bifunctional binding of the NH3 isomers results in unwinding of supercoiled pUC19 plasmid DNA equivalent to cis-DDP, while the unwinding of the pyridine derivative is approximately twice that of the mononuclear trans-[PtCl2(py)2]. DNA-DNA interstrand cross-linking is very efficient for all three agents, but sequencing studies indicated that only the 1,1/t,t/NH3 derivative is capable of forming a (Pt,Pt) intrastrand cross-link to the adjacent guanines of a d(GpG) sequence. The effects on DNA caused by bifunctional binding of dinuclear complexes are compared with those from the mononuclear [PtCl2(NH3)2] isomers. The results are discussed with respect to the antitumor activity of the dinuclear series.
Oligonucleotides containing site-specifically-modified N2-guanine (+)-trans-, (-)-trans-, (+)-cis-, and (-)-cis-BPDE adducts were ligated into 50-base-pair DNA fragments. These substrates were used in reactions with the Escherichia coli UvrABC nuclease system. The interaction of the UvrA2 and UvrA2B complexes with these four stereoisomers was probed using DNase I footprinting and gel mobility shift assays. DNase I digestion of substrates containing each stereoisomer of BPDE displayed a unique pattern which was consistent with the known structure of these DNA adducts. UvrA and UvrA2B appeared to interact very similarly with all four substrates. Binding of UvrA2 to these substrates produced a 33-bp footprint, and the UvrB--DNA complex resulted in footprint of 24 bp. The UvrABC nuclease system produced bimodal incisions at the eighth phosphate 5' and the fifth, sixth, or seventh phosphate 3' to the modified guanine. The variation of the 3' incision site was linked to the stereochemistry and orientation of the BPDE adduct. For example, the 3' incision of the 50-bp duplex containing (-)-trans-BPDE-N2-guanine was inhibited at the fifth phosphate. UvrABC nuclease incision kinetics revealed a hierarchy of specificity. The intercalative cis isomers were incised more efficiently than the corresponding trans isomers which lie in the minor groove. The (+) enantiomers were incised more efficiently than the (-) form for both cis and trans isomers. These observations reveal that UvrABC nuclease recognition and incision are directly influenced by the conformation of the DNA adduct.
Explore the source record for details and available documents.
Annamycin (Ann) is a non-cross-resistant lipophilic anthracycline antiobiotic optimally suited for liposome delivery. We studied how vesicle size and presence of phospholipids with a high phase transition temperature and monosialoganglioside (GM I) in the liposome bilayers affect the pharmacokinetics, tumor selectivity and toxicity of Ann. Entrapment of Ann in multilamellar vesicles (L-Ann) resulted in a 20% lower heart AUC and a 30-40% higher tumor and liver AUC. Reduction of the liposome size from 1.6 to 0.03 microns increased Ann plasma circulation time and tumor AUC by 2-fold, enhanced Ann tumor selectivity and decreased Ann subacute toxicity by 2-fold. The presence of phospholipids with a high phase transition temperature and GMI in the liposome bilayers further prolonged Ann plasma circulation time by 2- to 4-fold, did not increase Ann tumor AUC and moderately increased Ann subacute toxicity. The anti-tumor activity of Ann correlated with the tumor AUC achieved with each particular formulation. Our results strongly suggest that vesicle size may be an important determinant of the therapeutic index of liposomal Ann, but they fail to demonstrate a beneficial tumor-targeting effect of liposomes composed of GMI and phospholipids with a high phase transition temperature, as has been reported for the hydrophilic parent compound doxorubicin.
Explore the source record for details and available documents.
The interactions of cyanide and phenylhydrazine with porcine kidney diamine oxidase (PKDAO) and bovine plasma amine oxidase (BPAO) (EC 1.4.3.6) have been investigated. Cyanide displays mixed noncompetitive inhibition against amine substrates and also against O2. EPR spectroscopy shows that cyanide binds to an equatorial site on Cu(II) and can be displaced by chloride, which is not an inhibitor, without recovery of activity, indicating that Cu(II)-bound cyanide is not inhibitory. 14CN-. studies have shown that one cyanide in PKDAO and two in BPAO are covalently and irreversibly bound per enzyme dimer at an unknown site, even under conditions where cyanide is not bound to Cu(II). These cyanides have no effect on activity or on binding of phenylhydrazine to the enzymes. Cyanide also binds reversibly to the organic cofactor in both enzymes, presumably as a cyanohydrin, leading to the observed mixed noncompetitive inhibition against substrate. In both enzymes, two phenylhydrazines react per enzyme dimer. The kinetics of phenylhydrazine titration are affected by cyanide, which indicates that phenylhydrazine and cyanide react at the same carbonyl group in the enzymes. The results suggest that inhibition of amine oxidases by cyanide is through a carbonyl reagent and a Cu(I) ligand rather than through a Cu(II) ligand.
We studied the subcellular and subnuclear distributions of the partially cross-resistant anthracycline Annamycin (Ann) in KB-3-1 and multi-drug resistant KB-VI cells. Subcellular drug localization was assessed qualitatively by fluorescence microscopy and quantitatively by cell fractionation and fluorescence measurements. Doxorubicin (Dox) localized predominantly in the nucleus in KB-3-1 cells and in the membranes in KB-VI cells. In contrast, the subcellular distribution of Ann was identical in both cell lines, with preferential drug localization in the perinuclear region, Golgi apparatus, endoplasmic reticulum and endosomes. Dox rate of efflux from the nucleus was negligible in KB-3-1 cells but markedly enhanced in KB-VI cells, whereas Ann was lost at a similar rate from the nucleus in both cell lines. In KB-3-1 cells Dox levels in the nuclear non-matrix were about 2-fold higher than those of Ann, while in the matrix the inverse relationship was observed. In spite of these differences, Dox and Ann had a similar inhibitory effect on new DNA synthesis in the nuclear matrix and non-matrix of KB-3-1 cells. Dox levels were reduced by 10-fold in the nuclear non-matrix and 2-fold in the matrix in KB-VI cells compared with KB-3-1 cells, whereas Ann levels were reduced by about 2- to 3-fold in the non-matrix and were unchanged in the matrix. In correlation with these findings, Dox did not cause inhibition of new DNA synthesis in either nuclear fraction in KB-VI cells, whereas inhibition of new DNA synthesis in the matrix by Ann was similar in both cell lines. Our results indicate that Ann's partial circumvention of multi-drug resistance is associated with its ability to cause comparable new DNA synthesis inhibition in the nuclear matrix of sensitive and resistant cells.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Transient assays in cultured ventricular muscle cells and studies in transgenic mice have identified two adjacent regulatory elements (HF-1a and HF-1b/MEF-2) as required to maintain ventricular chamber-specific expression of the myosin light-chain 2v (MLC-2v) gene. A rat neonatal heart cDNA library was screened with an HF-1a binding site, resulting in the isolation of EFIA, the rat homolog of human YB-1. Purified recombinant EFIA/YB-1 protein binds to the HF-1a site in a sequence-specific manner and contacts a subset of the HF-1a contact points made by the cardiac nuclear factor(s). The HF-1a sequence contains AGTGG, which is highly homologous to the inverted CCAAT core of the EFIA/YB-1 binding sites and is found to be essential for binding of the recombinant EFIA/YB-1. Antiserum against Xenopus YB-3 (100% identical in the DNA binding domain and 89% identical in overall amino acid sequence to rat EFIA) can specifically abolish a component of the endogenous HF-1a complex in the rat cardiac myocyte nuclear extracts. In cotransfection assays, EFIA/YB-1 increased 250-bp MLC-2v promoter activity by 3.4-fold specifically in the cardiac cell context and in an HF-1a site-dependent manner. EFIA/YB-1 complexes with an unknown protein in cardiac myocyte nuclear extracts to form the endogenous HF-1a binding activity. Immunocoprecipitation revealed that EFIA/YB-1 has a major associated protein of approximately 30 kDa (p30) in cardiac muscle cells. This study suggests that EFIA/YB-1, together with the partner p30, binds to the HF-1a site and, in conjunction with HF-1b/MEF-2, mediates ventricular chamber-specific expression of the MLC-2v gene.
We have previously shown that mechanical stress induces activation of protein kinases and increases in specific gene expression and protein synthesis in cardiac myocytes, all of which are similar to those evoked by humoral factors such as growth factors and hormones. Many lines of evidence have suggested that angiotensin II (Ang II) plays a vital role in cardiac hypertrophy, and it has been reported that secretion of Ang II from cultured cardiac myocytes was induced by mechanical stretch. To examine the role of Ang II in mechanical stress-induced cardiac hypertrophy, we stretched neonatal rat cardiac myocytes in the absence or presence of the Ang II receptor antagonists saralasin (an antagonist of both type 1 and type 2 receptors), CV-11974 (a type 1 receptor-specific antagonist), and PD123319 (a type 2 receptor-specific antagonist). Stretching cardiac myocytes by 20% using deformable silicone dishes rapidly increased the activities of mitogen-activated protein (MAP) kinase kinase activators and MAP kinases. Both saralasin and CV-11974 partially inhibited the stretch-induced increases in the activities of both kinases, whereas PD123319 showed no inhibitory effects. Stretching cardiac myocytes increased amino acid incorporation, which was also inhibited by approximately 70% with the pretreatment by saralasin or CV-11974. When the culture medium conditioned by stretching cardiocytes was transferred to nonstretched cardiac myocytes, the increase in MAP kinase activity was observed, and this increase was completely suppressed by saralasin or CV-11974. These results suggest that Ang II plays an important role in mechanical stress-induced cardiac hypertrophy and that there are also other (possibly nonsecretory) factors to induce hypertrophic responses.
We have previously shown that stretching cardiac myocytes evokes activation of protein kinase C (PKC), mitogen-activated protein kinases (MAPKs), and 90-kD ribosomal S6 kinase (p90rsk). To clarify the signal transduction pathways from external mechanical stress to nuclear gene expression in stretch-induced cardiac hypertrophy, we have elucidated protein kinase cascade of phosphorylation by examining the time course of activation of MAP kinase kinase kinases (MAPKKKs), MAP kinase kinase (MAPKK), MAPKs, and p90rsk in neonatal rat cardiac myocytes. Mechanical stretch transiently increased the activity of MAPKKKs. An increase in MAPKKKs activity was first detected at 1 min and maximal activation was observed at 2 min after stretch. The activity of MAPKK was increased by stretch from 1-2 min, with a peak at 5 min after stretch. In addition, MAPKs and p90rsk were maximally activated at 8 min and at 10 approximately 30 min after stretch, respectively. Raf-1 kinase (Raf-1) and (MAPK/extracellular signal-regulated kinase) kinase kinase (MEKK), both of which have MAPKKK activity, were also activated by stretching cardiac myocytes for 2 min. The angiotensin II receptor antagonist partially suppressed activation of Raf-1 and MAPKs by stretch. The stretch-induced hypertrophic responses such as activation of Raf-1 and MAPKs and an increase in amino acid uptake was partially dependent on PKC, while a PKC inhibitor completely abolished MAPK activation by angiotensin II. These results suggest that mechanical stress activates the protein kinase cascade of phosphorylation in cardiac myocytes in the order of Raf-1 and MEKK, MAPKK, MAPKs and p90rsk, and that angiotensin II, which may be secreted from stretched myocytes, may be partly involved in stretch-induced hypertrophic responses by activating PKC.
This paper presents the morphologic charactistic of substance P immunoreactivity (SP-IR) in the facial nerve and geniculate ganglion of normal cats by using immunohistochemical technique and immunoelectronic microscopy. SP-IR positive cells are more in geniculate ganglion than the other parts of the facial nerve. These cells are black. The sizes of their somata are different, and the shapes are round, elliptic or irregular. The somata are connected with each other by their central and peripheral synapses in the shapes of spider's web or root of a tree. Among the cells the bipolar and pseudounipolar cells are also found. SP-IR positive fibers curve and some of them have obvious expansive bodies, which are beaded, different in diameter. Under electronic microscope SP-IR positive cells show thicker electronic density than the others, and SP-IR positive products with thick electronic density are found in the nuclei, nucleomembranes, outer membranes of mitochndria and plasma. The nerve fibers are myelinated and the myelin sheath is concentric, and in the axoplasms there are nervous microfilament and a bit of mitochndria.