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Biomedical subjects

D Yang

Publications and source records attributed to D Yang.

At least 379 records · Page 21Linked to original sources
PubMed1995

[Inhibition of antisense DNA and its derivative on gastric transformed cell carcinogenicity].

In this study, an antisense c-Ha-ras DNA was synthesized. It was a complementary oligonucleotide chain to the sequence of initiation position of c-Ha-ras gene transcription. We found that the antisense DNA blocked the gene expression at the level of transcription and translation and partially reverted the malignant phenotyped of gastric transformed cells, including their growth rate, colonies formation in soft agar, tumorigenicity in nude mice and different grade. When the 5'-end of the antisense DNA was covalently linked with psoralen group, its biological effects were significantly enhanced. No effect of tumor inhibition was found in control oligonucleotide chains not complete complementary to the sequence of target gene. These results indicate that antisense DNA and its derivative are effective in tumor gene therapy.

Animals↗
PubMed1995

[Dynamic observation and significance of autoantibody against ADP/ATP carrier in dilated cardiomyopathy].

The presence and dynamic change of autoantibody against ADP/ATP carrier in patients with dilated cardiomyopathy (DCM) was studied by using indirect micro-solid-phase radioimmunoassay. A significant antibody titre was present in 16 of 48 DCM patients and most of them were in early stage of the disease. The titre of anti-ADP/ATP carrier antibody in DCM patients decreased gradually in a follow-up period of three months. The titre of this antibody in the serum from patients with coronary and rheumatic heart disease were within normal limits. Anti-ADP/ATP carrier antibody may play an important role in the pathogenesis, diagnosis and treatment of DCM.

Adult↗
PubMed1995

High expression of synthetic human interferon-gamma cDNA in E. coli.

Human interferon-gamma (IFN-gamma) cDNA was synthesized, and it makes the usage of favorable codons in E. coli. The authors got 9 different expression plasmids which contain the synthetic IFN-gamma-cDNA and have different spaces between SD sequence and ATG. The free energies G0f298 in the formation of stable secondary structure in the translation initiation region (TIR) are different in various expression plasmids. One of them, pLY4-gamma 5, can highly yield INF-gamma which will be about 60%-80% of the total bacterial proteins, such a high expression was hardly noted in literature. The reasons of high expression in this work are optimal spaces between SD and ATC, favorable delta G0f298, favourable condons usage for E. coli.

Amino Acid Sequence↗
PubMed1995

[p53 gene point mutation in human colorectal carcinoma].

We introduced two modified assay systems, PCR-SSCP and PCR-direct sequencing for the identification of structure aberration at p53 exon 7 in 22 colorectal carcinomas and 1 metastatic lymph node. The data indicated that 27.2% (6/22) colorectal carcinomas and one metastatic lymph node were shown to contain the point mutations in codons 245, 251, 259 and 260 of exon 7. One half of all the mutations was G:c to A:T transition in codon 245. Other mutation patterns were base insertion and deletion. All positive point mutations of p53 exon 7 existed in colon carcinomas in this study. The point mutation in p53 exon 7 was usually associated with poorly differentiated primary carcinomas (P = 0.0178) and the mutation rate of was higher in Duckes C stage of the disease than in stage Duckes A and B (P = 0.0361). Thus p53 exon 7 point mutation in primary colorectal tumors and regional lymph nodes may identity a subgroup of colorectal cancer patients with more aggressive disease and may be as a new tumor markers for assessing the prognosis of colorectal carcinomas.

Adult↗
PubMed1995

[Preventive effect of 10% (NH4)2MoO2F4 solution on artificial root-surface caries in vitro].

The aim of this study is to determine the preventive effect of F-Mo preparation on artificial root-surface caries. 60 premolar teeth extraced for orthodontic purpose were divided into five groups. A window was prepared on every tooth. They were treated by 10% (NH4)2MoO2F4, 38%Ag (NH4)2F, 2% NaF, 7.3% (NH4)2MoO4 and deionized water for 2 minutes and three times. They were then put in the fluid contained cariogenic bacteria for 96 hours to produce root caries. The root surface lesion of every tooth was examined and analysed by micro-radiography, SEM and spectrum. The result showed that the lesion depth of the groups treated by 10% (NH4)2MoO2F4 and 38%Ag (NH4)2F were significantly smaller than the other groups, and the surface of windows are more integrate and smooth, and mean mineral concentration is more higher than those of the other groups. It can be concluded that 10% (NH4)2MoO2F4 solution has greater inhibit effect to the development of root caries, so as the 38% Ag(NH4)2F solution. But the former discolored the tooth much less than the latter.

Administration, Topical↗
PubMed1995

[Immunohistochemical study of hepatitis C virus (HCV) antigen in liver tissue of patients with HCV infection].

Hepatitis C virus antigen (HCV Ag) and HCV-NS3 protein in paraffin-embedded liver tissue of patients with HCV infection were detected with immunohistochemical method by using polyclonal anti-HCV and monoclonal anti-HCV-NS3 for studying the expression of HCV in liver tissue. The results showed that the detection rate of HCV Ag and HCV-NS3 were 38.3% and 30.0% respectively. All the specimens with HCV-NS3 positive tissue were also those with HCV Ag positive. The stained substance located in the cytoplasm of liver cell, and the stained cells distributed scattered, clustered or diffuse in liver lobular. No obvious infiltration or necrosis was observed around the positive cells. There was obvious difference of the detection rate between different models of serum HCV markers. These results provided some help in understanding the pathogenesis of HCV.

Adolescent↗
PubMed1995

[Association of plasma insulin with blood pressure and sodium sensitivity in children].

To study the relationship between plasma insulin level, sodium sensitivity and blood pressure, 150 children aged from 10 to 15 years with high blood pressure and 150 children matched for age and sex but with normal blood pressure were measured for plasma insulin with radioimmunoassay and sodium sensitivity with the tests of oral saline load and furosemide sodium-volume depletion and followed for 5 years. The results showed that (1) In children with HBP and positive family history of hypertension (FH+), the plasma insulin level was significantly higher than that in the respective control group (P < 0.01); (2) In children with high plasma insulin level, the percentiles of systolic blood pressure kept high and had a rising tendency during the follow-up period; (3) In children with sodium sensitivity, the plasma insulin level was higher than that in children with sodium resistance (P < 0.01) and the plasma insulin level correlated positively with blood pressure increasing rate of post-load (P < 0.05). It is suggested that insulin resistance was associated with sodium sensitivity, and they might play a role in the development of hypertension in childhood.

Adolescent↗
PubMed1994

Repair of a specific double-strand break generated within a mammalian chromosome by yeast endonuclease I-SceI.

We established a mouse Ltk- cell line that contains within its genome a herpes simplex virus thymidine kinase gene (tk) that had been disrupted by the insertion of the recognition sequence for yeast endonuclease I-SceI. The artificially introduced 18 bp I-SceI recognition sequence was likely a unique sequence in the genome of the mouse cell line. To assess whether an induced double-strand break (DSB) in the genomic tk gene would be repaired preferentially by gene targeting or non-homologous recombination, we electroporated the mouse cell line with endonuclease I-SceI alone, one of two different gene targeting constructs alone, or with I-SceI in conjunction with each of the two targeting constructs. Each targeting construct was, in principle, capable of correcting the defective genomic tk sequence via homologous recombination. tk+ colonies were recovered following electroporation of cells with I-SceI in the presence or absence of a targeting construct. Through the detection of small deletions at the I-SceI recognition sequence in the mouse genome, we present evidence that a specific DSB can be introduced into the genome of a living mammalian cell by yeast endonuclease I-SceI. We further report that a DSB in the genome of a mouse Ltk- cell is repaired preferentially by non-homologous end-joining rather than by targeted homologous recombination with an exogenous donor sequence. The potential utility of this system is discussed.

Animals↗
PubMed1994

Targeted amplification of alternatively spliced transcripts of major histocompatibility complex class I heavy chain.

The RPMI1788 cell line was found to produce soluble form of HLA class I molecules (sHLA) constitutively, due at least in part to an alternative splicing mechanism in which exon 5 of HLA class I heavy chain transcripts is deleted. Reverse transcription-polymerase chain reaction (RT-PCR) of cytoplasmic RNA of RPMI1788 cells using a pair of primers (A,B) complementary to the conserved sequences of HLA class I exon 4 and 6 yielded almost exclusively the full-length class I heavy chain cDNA. In order to amplify the alternatively spliced transcripts, primer C corresponding to the 5' boundary conserved region of exon 6 juxtaposed with three conserved nucleotides in 3' boundary region of exon 4 was synthesized. Using the primers A and C the spliced transcripts of RPMI1788 cells can be selectively or preferentially amplified by RT-PCR with three different DNA polymerases. Cloning and sequencing of the resulting cDNA confirmed that the spliced transcript lacks exon 5. The targeted amplification method may be useful and important for studies with respect to the regulation of class I sHLA expression and the mechanism by which alternative splicing of HLA class I heavy chain mRNA is induced.

Alternative Splicing↗
PubMed1994

Rat kidney carboxylesterase. Cloning, sequencing, cellular localization, and relationship to rat liver hydrolase.

We recently purified from rat liver microsomes a carboxylesterase, designated hydrolase B, that catalyzes the hydrolysis of para-nitrophenylacetate with low affinity (Km approximately 400 microM) and is relatively insensitive to the inhibitory effects of phenylmethylsulfonyl fluoride. A carboxylesterase with identical properties is also present in rat kidney microsomes, at levels comparable to those in liver microsomes. The kidney enzyme is immunochemically indistinguishable from hydrolase B by Western immunoblotting and Ouchterlony double diffusion analysis. This study describes the cloning and sequencing of hydrolase B. A 1809-base pair (bp) cDNA was isolated from a rat kidney cDNA library screened with antibody against hydrolase B. Screening the same cDNA library by two-step polymerase chain reaction with external and internal primers based on the sequence of the 1809-bp cDNA and a primer based on the sequence of the adjoining lambda gt11 arm yielded a 279-bp cDNA that overlapped by 179 bp with the 1809-bp-sequence. Together these two cDNAs spanned a 1909-bp sequence with an opening reading frame encoding 561 amino acids, which includes all 543 amino acid residues in the mature protein plus an 18-amino acid signal peptide at the N terminus. The mature protein encoded by this kidney cDNA matches perfectly the N-terminal amino acid sequence of purified hydrolase B for 30 amino acid residues, as determined by automated Edman degradation. The mature protein contains 5 cysteine residues, two potential N-linked glycosylation sites, and a C-terminal tetrapeptide (His-Asn-Glu-Leu) that matches the HXEL consensus sequence for retaining proteins in the lumen of the endoplasmic reticulum. Based on alignment of conserved amino acid sequences in several mammalian carboxylesterases, and based on the mechanism of catalysis of serine proteases, the catalytic triad in hydrolase B is apparently composed of the nucleophile Ser203, the basic amino acid His448, and the acidic amino acid Asp97 or Glu228. Northern blots probed with the 1809-bp cDNA identified high levels of a approximately 2-kilobase mRNA for hydrolase B in liver and kidney. Little or no mRNA for hydrolase B was detected in testis, lung, prostate, brain, and heart, which confirms the tissue distribution of hydrolase B based on catalytic activity and Western immunoblotting. Immunocytochemical studies established that hydrolase B is localized in the centrilobular region of the liver and in the proximal tubules of the kidney, where it presumably plays a role in the metabolism of xenobiotics and possibly endogenous lipids, although a precise physiological role for hydrolase B remains to be determined.

Amino Acid Sequence↗
PubMed1994

Expression of two variants of the human mu opioid receptor mRNA in SK-N-SH cells and human brain.

A partial mu opioid receptor gene was isolated from a human genomic library using a mouse delta opioid receptor cDNA as a probe. Using information from this genomic clone and the published human mu receptor, MOR1, a cDNA was isolated from SK-N-SH mRNA that codes for a variant of the MOR1 mRNA, MOR1A. The presence of MOR1A is also shown in human brain using RT-PCR. MOR1A differs from MOR1 in that the 3' terminal intron has not been removed. An in-frame termination codon is found four amino acids after the 5' consensus splice site, making MOR1A eight amino acids shorter than MOR1. Both receptors show similar ligand binding and coupling to cAMP in CHO-K1 cells. The C-terminal differences between MOR1 and MOR1A could have effects on receptor coupling or receptor transport and localization.

Alternative Splicing↗
PubMed1994

Structure and dynamics of the antitumor drugs nogalamycin and disnogalamycin complexed to d(CGTACG)2: comparison of crystal and solution structures.

The nuclear magnetic resonance (NMR) solution structures of the 2:1 complexes of nogalamycin-d(CGTACG)2 (Ng-CGTACG) and disnogalamycin-d(CGTACG)2 (DNg-CGTACG) have been determined by a quantitative treatment of two-dimensional nuclear Overhauser effect (2D-NOE) crosspeak intensities. The 1.3 A resolution crystal structure of the 2:1 complex of Ng-CGTACG was used as a starting model for refinement using the procedure, SPEDREF [Robinson and Wang, Biochemistry 31 (1992) 3524-3533], which incorporates full matrix relaxation theory and simulated annealing minimization. The refined solution structures have R-factors of 16.1 and 19.6% between the observed and simulated NOEs for Ng-CGTACG and DNg-CGTACG, respectively. The refined NMR structures retain major features of the crystal structure in which the elongated aglycone chromophore is intercalated between the CpG steps with its nogalose and aminoglucose lying in the minor and major grooves, respectively. The root mean square deviation between the solution and crystal structure for the complexes is 1.01 A (Ng-CGTACG) and 1.20 A (DNg-CGTACG) for the drug, plus the three base pairs surrounding the drug, indicating a very similar local structure at the intercalation site. In the NMR structure, the two G:C Watson-Crick base pairs (C1:G12 and G2:C11) that wrap around the aglycone have large buckles, as do those seen in the crystal structure. There is a 22 degree bend at the T3-A4 step in the refined solution structure. This rearrangement of the solution conformation is likely due to the absence of crystal packing. Specific hydrogen bonds between the drug and G:C bases in both grooves of the helix are preserved in the solution structure. A separate study of the 2:1 complex at low pH showed that the terminal G-C base pairing is destabilized.

Crystallography, X-Ray↗
PubMed1994

Isolation of a human kappa opioid receptor cDNA from placenta.

By using a mouse delta opioid receptor cDNA as a probe, a kappa opioid receptor gene was isolated from a human genomic library. Reverse transcriptase/PCR was subsequently used to isolate the corresponding cDNA from human placenta mRNA. Characterization of the cloned receptor with a kappa agonist in transfected COS-7 cells, revealed a Kd of 0.67 nM, which is similar to rodent kappa 1 receptors. In competition binding experiments, non-kappa agonists had kis > 1000nM. Furthermore, when expressed in COS-7 cells, the kappa receptor is negatively linked to cAMP. A Northern blot showed the presence of two transcripts, 6 and 7 kB in size, in both placenta and brain mRNA, which hybridized to the kappa cDNA.

Amino Acid Sequence↗
PubMed1994

Crystal and solution structures of d(CGC[e6G]AATTCGCG)-drug complexes reveal conformational polymorphism of O6-ethyl-guanine:cytosine base pair.

O6-ethyl-guanine (e6G) is a relatively persistent alkylation lesion caused by the exposure of DNA to carcinogen N-ethyl-N-nitrosourea. We have studied the structural consequences of the e6G incorporation in DNA by X-ray crystallography and NMR. We have obtained crystals of the modified DNA dodecamer d(CGC[e6G]AATTCGCG) complexed to several minor groove binding drugs including Hoechst 33258, Hoechst 33342, netropsin, and SN6999. The space group of the crystals from those complexes is P2(1)2(1)2(1). However the crystal structure of the SN6999 complex is not isomorphous to that from the other three complexes. In all four refined crystal structures the drugs bind in the narrow minor groove at or close to the central AATT region of the dodecamer B-DNA duplex. The DNA conformation is influenced by the binding of drugs. The eight independent e6G:C base pairs have a conformation ranging from one with three-centered hydrogen bonds between the bases to a wobble conformation with two hydrogen bonds. The ethyl group of the eight e6G bases is mostly in the proximal orientation to N7. Our 1D and 2D-NMR studies of the same (free) dodecamer reveal that the e6G:C base pairs in the duplex are likely to adopt a wobble conformation in solution. Those results suggest that the e6G:C base pair has a dynamic equilibrium among various conformations, which may present an ambiguous signal to cells. In contrast, the e6G:T base pair adopts a Watson-Crick-like conformation. This may be a plausible explanation of why thymine is found preferentially incorporated across the e6G during replication.

Base Composition↗
PubMed1994

Heterogeneities in ferritin dimers as characterized by gel filtration, nuclear magnetic resonance, electrophoresis, transmission electron microscopy, and gene engineering techniques.

To understand the mechanism underlying the preferential dimerization of ferritin shells, we studied monomers and dimers from both horse spleen and recombinant horse L-apoferritin by using gel filtration, nuclear magnetic resonance, electrophoresis, transmission electron microscopy, and gene engineering techniques. Our study of the kinetics of dimer-monomer dissociation that is produced by heating revealed the presence of at least two types of dimers, namely, weakly and strongly linked dimers with activation energies of 124 +/- 14 and 157 +/- 16 kJ/mol, respectively. Our study using thiol reagents indicated that the dimerization in horse spleen ferritin is partially mediated by disulfide bridges being formed between H-chains. Our analysis of the components that resulted from the dimer-monomer dissociation further clarified that these dimers form interdigitation structures. In summary, five types of dimers were identified in horse spleen apoferritin: reversible dimers with very weak interaction, non-sulfide dimers with weak interaction, non-sulfide dimers with strong interaction, disulfide dimers linked only by disulfide bridges, and disulfide dimers linked by disulfide bridges and having other interactions.

Animals↗
PubMed1994

Structure by NMR of antitumor drugs aclacinomycin A and B complexed to d(CGTACG).

Aclacinomycins A and B are anthracycline antibiotics with potent antitumor activity. Each consists of an alkavinone aglycon chromophore and a trisaccharide (rhodosamine-deoxyfucose-cinerulose A or B) tail attached at the C7 of ring A of the alkavinone. The structures of the 2:1 aclacinomycin-d(CGTACG) complexes have been studied in solution by 2D NMR spectroscopy using nuclear Overhauser effect data. SPEDREF refinement procedure (incorporating simulated annealing within the program X-PLOR) was used to obtain an ensemble of refined structures which reveal that the elongated alkavinone is intercalated between the CpG steps and the trisaccharide lies in the minor groove. In the complex, the two GC Watson-Crick base pairs (C1:G12 and G2:C11) that wrap around the aglycon have large buckles, consistent with those seen in the crystal structures of other anthracycline-DNA complexes. The intercalation geometry of aclcainomycin is a hybrid between those of daunorubicin and nogalamycin. Ring D of alkavinone is sandwiched by the C1 and C11 bases. The deoxyfucose ring of the trisaccharide is close to the DNA backbone at the A4 nucleotide, forcing the DNA helix to kink toward the major groove (with the opening in the minor groove). The kink between two adjacent A-T base pairs (T3-A10 and A4-T9) causes the adenine A4N6 to form two hydrogen bonds to T9O4 (interstrand) and T3O4 (intrastrand) simultaneously. There is a small unwinding of the helix resulting from the intercalated aclacinomycin. Several potential hydrogen bonds exist between the drug and the guanine bases in the minor groove of the helix.(ABSTRACT TRUNCATED AT 250 WORDS)

Aclarubicin↗
PubMed1994

Altered body composition and increased frequency of diverse malignancies in insulin-like growth factor-II transgenic mice.

The physiological role of insulin-like growth factor (IGF) II (IGF-II) in adult humans is poorly understood. Rather high levels of IGF-II persist in adult human serum, whereas, in rodents, IGF-II levels are very low. To investigate the physiological and carcinogenic effects of persistently elevated IGF-II in adults, we have produced two lines of transgenic mice in which high levels of IGF-II (20- or 30-fold increase above normal) are persistently maintained in the blood. The transgene is driven by the major urinary protein promoter, and it is highly expressed in the liver and perputial glands in both lines. The adult transgenic mice are smaller than controls, and their body composition is altered. Their lean body mass is reduced by 5-8%, whereas fat mass is reduced between 44 and 77%. The mice expressing the highest level of IGF-II (30x) develop hypoglycemia and hypoinsulinemia and IGF-I levels are normal. Mice in the lower expression line (20-fold elevated IGF-II) develop hypoglycemia progressively over their lifetime. Mice from both lines also develop a diverse spectrum of tumors at a higher frequency than controls after 18 months of age, and the most frequent types of tumors are hepatocellular carcinomas and lymphomas. Squamous cell carcinoma, sarcoma, and thyroid carcinomas also occurred in our test group. The long latent period before tumors arise and the wide spectrum of tumor types suggest that IGF-II may function primarily as a tumor progression factor in mice via autocrine and endocrine mechanisms of action.

Animals↗