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F Fang

Publications and source records attributed to F Fang.

At least 127 records · Page 7Linked to original sources
PubMed1995

[The variable number of tandem repeats in the renin gene of rats and possible significance in hypertension].

The variable number of tandem repeats (VNTR) in the first intron of renin gene for the spontaneously hypertensive rat (SHR), its controls Wistar-Kyoto (WKY), renal hypertensive rat, and Sprague-Dawley rat (SD) were compared by polymerase chain reaction (PCR) method. An analysis of VNTR from WKY, Wistar and SD showed that there are two different renin gene alleles and three genetypes 2.0kb/2.0kb, 2.0kb/1.8kb, 1.8kb/1.8kb. The genetype from renal hypertensive rats is same as those seen in the normal controls. However, compared with the WKY, Wistar and SD genes, a "deletion" of approximately 1.0kb was found in the first intron of the SHR renin gene. Our results strongly suggest that the cause and mechanism of elevated blood pressure is complex, and the molecular basis of the genetic-prone hypertension is existed.

Animals↗
PubMed1994

Substrate specificity in short-chain phospholipid analogs at the active site of human synovial phospholipase A2.

The substrate specificity at the active site of recombinant human synovial fluid phospholipase A2 (hs-PLA2) was investigated by the preparation of a series of short-chain phospholipid analogs and measurement of their enzymatic hydrolysis at concentrations well below the critical micelle concentration. Substrates used in the study included 1,2-dihexanoylglycerophospholipids, 1,2-bis(alkanoylthio)glycerophospholipids, and 1-O-alkyl-2-(alkanoylthio)phospholipids. Turnover was observed for only a few of the 1,2-dihexanoylglycerophospholipids, and the rate of hydrolysis was very low, near the limit of detection of the assay. In contrast, selected 2-(alkanoylthio)-glycerophospholipids were hydrolyzed by hs-PLA2 at much higher rates at concentrations well below their critical micelle concentration (cmc). Thus, the 1,2-bis(hexanoylthio)glycerophosphatidylmethanol exhibits a k(cat)/K(M) = 1800 L mol-1 s-1. Over the calculated log P (cLogP) range of 3-9, cLogP and log(k(cat)/K(M) were linearly related for compounds with straight-chain sn-1 and sn-2 substituents. At comparable cLogP's, the sn-1 ethers and thioesters were hydrolyzed at comparable rates. A negative charge in the phosphate head group was required for enzyme activity. Unsaturation, aromaticity, and branching in the sn-2 substituent reduce turnover dramatically. The same structural modifications in the sn-1 substituent have less effect on turnover. Certain of these substrates, e.g., 1,2-bis(hexanoylthio)glycerophosphatidylmethanol, may be useful in assaying for active site inhibitors of PLA2. The structure--activity relationships established here for substrates should serve as a reference for the structure--activity relationships of substrate-based inhibitors.

Binding Sites↗
PubMed1994

Aggregation of the chemokine MIP-1 alpha is a dynamic and reversible phenomenon. Biochemical and biological analyses.

Macrophage inhibitory protein (MIP)-1 alpha is a potent inhibitor of hemopoietic stem cell proliferation and is a member of a family of pro-inflammatory mediators, the chemokine family. This molecule along with other members of the chemokine family exists as a peptide of 8 kDa but has a strong tendency for noncovalent extensive self-aggregation. As this aggregation may interfere with biological activity, we have produced nonaggregating variants of MIP-1 alpha which display a range of molecular sizes. The mutants, produced by sequential neutralization of carboxyl-terminal acidic residues, display native molecular masses representative of tetramers, dimers, and monomers. Intriguingly when these mutants are assessed in comparison with native MIP-1 alpha for bioactivity in vitro, they are seen to be equipotent in both stem cell assays and in monocyte shape-change assays, suggesting that there is no requirement for aggregation in either of these biological contexts. This indicates that the aggregated MIP-1 alpha and the aggregated mutants spontaneously disaggregate under assay conditions and ultimately function as monomers. We have further demonstrated the ability of MIP-1 alpha to disaggregate spontaneously in dilute solution by enzyme-linked immunosorbent assay analysis of fractions obtained from gel filtration of varying concentrations of MIP-1 alpha. The aggregation of MIP-1 alpha is therefore a dynamic and reversible phenomenon which has little, if any, impact on bioactivity in vitro.

Amino Acid Sequence↗
PubMed1994

Toward cataloguing all rice genes: large-scale sequencing of randomly chosen rice cDNAs from a callus cDNA library.

A large-scale sequence analysis of rice cDNA was performed for a library from rice callus cultured in a medium containing 1 p.p.m. of 2,4-dichlorophenoxyacetic acid. Random sequencing of 2778 cDNA clones generated 2259 non-redundant expressed sequence tags (ESTs). The strategy of sequencing cDNAs can yield quickly a large number of novel genes. After translation, 690 sequences showed a significant amino acid sequence similarity to sequences already known from PIR. The source of known proteins ranged from bacteria to human. In this report, the non-redundant set of 280 identified ESTs is analyzed in detail.

Animals↗
PubMed1994

[Mapping of full-length murine renin-2 gene].

A 24kb fragment containing full-length renin-2 gene and its flanking sequence was obtained by digesting the pKG-R2D with XhoI. This fragment was cleaved with single enzyme (EcoRI, KpnI and BamHI), and combined enzymes (EcoRI/KpnI, KpnI/BamHI and BamHI/EcoRI), respectively. The digests were electrophoresed on 0.8% agarose plates and transferred onto NC membranes. Radioactive probes of 735bp and 1400bp, templates of which were from half and full-length of renin-1 cDNA, respectively were used for Southern hybridization. On the basis of electrophoresis and hybridization patterns, a restriction map was constructed in this paper.

Animals↗
PubMed1994

Molecular mutagenesis induced by glycidyl methacrylate.

Glycidyl methacrylate (GMA) is a recently recognized mutagen. In order to explore the mutagenicity and mechanism of GMA, plasmid pBR322 was used for in vitro binding, mutant screening, restriction enzyme mapping, and DNA sequencing. To explore the mechanism by which an initial premutational event is converted into a stable heritable mutation, pBR322 and GMA-bound pBR322 were transformed into E. coli HB101, and the following results were obtained: 1) GMA-bound pBR322 induced phenotype changes in competent cells. Two stable and heritable mutants were isolated (ApRTcS and ApSTcR). 2) When restriction enzyme mapping was used to analyze the mutant ApRTcS, four of seven maps showed changes, but no large DNA insertion or deletion were observed. 3) The frequency of deletion and insertion forms counted about 10%. Sequence specificity and hot spot regions were evident in the sequence analysis of mutated plasmid. The above results indicate that the premutagenic lesions of plasmid induced by GMA can be converted into point mutations in vivo.

Amino Acid Sequence↗
PubMed1993

Effect of the mutation of tyrosine 713 in p93c-fes on its catalytic activity and ability to promote myeloid differentiation in K562 cells.

The protooncogene protein-tyrosine kinase c-fes plays an active role in the induction of terminal myeloid differentiation in myeloid leukemia cells. Although p93c-fes contains two autophosphorylation sites, it is not known what role they play in its catalytic or biological activities. To address this question, the major autophosphorylation site at tyrosine 713 was mutated to phenylalanine (YF713), and the mutated cDNA was expressed in a baculovirus system to assess catalytic activity, as well as in an inducible retrovirus to determine its biological activity. The major phosphopeptide in p93c-fes in vitro contained Y713 and was absent in the YF713 mutant, which exhibited an 85% loss of autophosphorylation activity. The catalytic activity of p93c-fesYF713 with either RCM-lysozyme or poly(Glu,Tyr)4:1 as substrate was reduced by 85 and 78%, respectively, in comparison to p93c-fes. Retroviral infection of K562 cells with the c-fes cDNA under the control of the mouse metallothionein promoter increased superoxide formation, phagocytosis, CD13 and CD33 antigen expression, and doubling time 4-6 days after induction. Cells infected with c-fesYF713 exhibited 40% less superoxide formation but similar levels of phagocytosis, CD13/CD33 antigen, and doubling time in comparison to cells infected with c-fes. The level of phosphotyrosine-containing proteins did not markedly differ between K562 cells expressing either neo, c-fes, or c-fesYF713, with the exception of a reduction in the level of a 210-kDa protein specifically in both c-fes-expressing cell lines. The p210 was tentatively identified as bcr-abl, whose level was also reduced in cells expressing c-fes or c-fesYF713.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

Hepatitis C virus infection in different groups of children in Wuhan area.

To investigate the incidence of child's HCV infection in our area, 637 children with different background, including 65 posttransfusion cases, 419 hepatitis patients (250 cases of acute hepatitis A, 156 cases of chronic hepatitis B and 13 cases of non-A, non-B hepatitis), 50 infantile hepatitis syndrome (IHS) infants and 103 healthy day-cared children were tested for serum anti-HCV antibody (EIA) and HCV RNA (nested PCR). It was found that posttransfusion children had significantly higher anti-HCV positive rate (30.8%) and HCV infection incidence (43.1%) than hepatitis patients (4.3% and 5.3%), IHS infants (6.0% and 8.0%) and day-cared children (2.9% and 2.9%). 25 of 33 cases with posttransfusion hepatitis (PTH) developed hepatitis C, which was the leading cause of PTH (75.8%) and NANB PTH (25/30, 83.3%). The incidence of HCV infection in NANBH patients was 23.1% (3/13) which was apparently higher than that in day-cared children (P < 0.02) and lower than that in PTH patients (P < 0.001), but not statistically different from that in AHA and CHB patients (P > 0.05). Mother-infant paired study in IHS group showed that 4 pairs of mother-infant had HCV infection, one boy aged 8 months and his mother were anti-HCV positive, and another 3 pairs possessed HCV RNA in sera. 3 of 103 healthy day-cared children were found to have inapparent HCV infection, who were anti-HCV and HCV RNA positive.

Adolescent↗
PubMed1993

Expression of the Salmonella virulence plasmid gene spvB in cultured macrophages and nonphagocytic cells.

Certain serotypes of salmonellae carry virulence plasmids that greatly enhance the pathogenicity of these bacteria in experimentally infected mice. This phenotype is largely attributable to the 8-kb spv regulon. However, spv genes are not expressed while bacteria grow in vitro. We now show that spvB, which is required for virulence, is expressed rapidly after Salmonella dublin is ingested by cultured J774 and murine peritoneal macrophages and that expression is not affected by the alkalinization of intracellular vesicles. The level of induction of spvB is reduced when macrophages are pretreated with gamma interferon. spvB is also expressed in human and canine epithelial cell lines and a human hepatoma cell line. In all cases, spvB expression is dependent on the spvR gene, just as it is in stationary-phase cultures in vitro. These data suggest that spv virulence genes are expressed by intracellular salmonellae in vivo in response to a signal that is common to the intracellular compartments of cells that are invaded by salmonellae.

Animals↗
PubMed1993

Distinct roles of cdk2 and cdc2 in RP-A phosphorylation during the cell cycle.

RP-A is a single-stranded DNA-binding protein, which has been shown to be required for DNA replication using an SV40 model system. The protein has also been shown to be phosphorylated at the G1-S phase transition. Using Xenopus cell-free extracts we have investigated the role of RP-A in nuclear replication and characterized the kinases and conditions that lead to phosphorylation of RP-A during the cell cycle. By immunodepleting RP-A from Xenopus extracts we have shown that RP-A is essential for replication of chromosomal DNA. Our results show that, during S phase, only that RP-A which is associated with nuclei is phosphorylated. Furthermore our results indicate that during S phase RP-A is only phosphorylated when associated with single-stranded DNA. By immunodepleting cdk2 kinase we show that cdk2 kinase is required for the observed phosphorylation of RP-A in nuclei during S phase. However, using purified cdk2 kinase and RP-A we are unable to detect a direct phosphorylation of RP-A by cdk2 kinase. This observation suggests that phosphorylation of DNA-bound RP-A at S phase is carried out by a kinase distinct from cdk2. Consistent with this we find that when single-stranded DNA is added to S phase extracts depleted of cdk2 kinase, RP-A is phosphorylated. Together these results suggest that cdk2 kinase participates in the activation of DNA replication at a stage prior to the binding of RP-A to the initiation complex. In addition to RP-A phosphorylation in S phase, we have also found that at the onset of mitosis RP-A is quantitatively phosphorylated and that phosphorylation is directly mediated by cdc2 kinase. However, at this time during the cell cycle, cdc2-dependent phosphorylation of RP-A is independent of DNA binding. These observations further demonstrate the distinctions between cdk2 and cdc2 kinases.

Animals↗
PubMed1993

[Effects of epidermal growth factor on growth and differentiation of rat granulosa cells].

It was known that epidermal growth factor (EGF) plays an important role in the regulation of reproduction. The present study was undertaken to investigate the effect of EGF on the proliferation and differentiation of cultured rat granulosa cells. The results showed that EGF inhibited the 3H-TdR incorporation into DNA of granulosa cells, while the progesterone production was increased due to enhanced 3 beta-HSD activity. Radioreceptor assay (RRA) suggested that there were specific receptors for EGF on the granulosa cell with a Kd of 1.83 +/- 0.30 x 10(-8) mol/L and a Bmax of 1.75 +/- 0.29 x 10(4) sites/cell. Using method of immunohistochemistry, no EGF-like immunoreactivity was found in the granulosa cells at different age or different estrous cycle, but in the theca folliculi, interstitium and corpus luteum. These results suggest that EGF can regulate the growth and differentiation of the granulosa cells in the course of maturation of the folliculi and granulosa cells.

3-Hydroxysteroid Dehydrogenases↗
PubMed1991

Evidence that the G1-S and G2-M transitions are controlled by different cdc2 proteins in higher eukaryotes.

Xenopus eggs contain two distinct cdc2 homologs of 34 and 32 kd. We show that the 32 kd cdc2 protein, like the 34 kd protein, is a kinase. However, unlike the 34 kd homolog, the 32 kd cdc2 kinase activity does not decrease dramatically at the end of mitosis. The 32 kd protein does not associate with mitotic cyclins B1 and B2 but does associate with cyclin A and a novel doublet of proteins of 54 kd that may regulate its activity. We also show that depletion of the 32 kd cdc2 homolog from a Xenopus extract blocks DNA replication, but does not inhibit entry into mitosis. By contrast, depletion of the 34 kd cdc2 homolog or absence of mitotic cyclins from an extract does not inhibit replication, but does block entry into mitosis. Our results indicate that in higher eukaryotes, DNA replication (G1-S) and mitosis (G2-M) may be controlled by distinctly different cdc2 proteins.

Animals↗
PubMed1991

Effects of cytomegalovirus hepatitis on growth, development and nervous system of infants. A follow-up study.

Twenty-seven infants with cytomegalovirus hepatitis were followed up for 15-40 months after onset of the illness. They had recovered from the hepatitis, but microcephaly was present in 2 (7.4%), sensorineural hearing loss in 5 (18.5%), quadriplegia, mental retardation, ventricular septal defect and tooth defects in 1 (3.7%) each. The patients with congenital infection had more severe and complex defects, some with perinatal infection had mild defects, those with postnatally acquired infection had no sequelae. The mean MDI and frequency of expressive language delay in the former group differed significantly from those of the other 2. Five patients still excreted cytomegalovirus in the urine at follow-up.

Child Development↗
PubMed1991

[The preparation of highly purified insulin and its clinical use. Insulin Cooperative Study Group].

Antigenicity of insulin preparations is obviously related to their purity. The average contents of proinsulin, glucagon and pancreatic polypeptide in highly purified insulin (HP-I) produced by us are 76.0, 2.11 and 0.11 ppm respectively. These results are superior to those for domestic conventional crystalline insulin and single peak insulin (SP-I). The antibodies to insulin, proinsulin and pancreatic polypeptide in serum were examined in 24 diabetic patients treated with HP-I for more than 6 months. The positive rates for the above three antibodies were 37.5%, 0% and 0% respectively. The results showed that the antigenicity of HP-I was much lower than that of domestic conventional crystalline insulin and almost the same as that of MC-I from Nordisk, Denmark.

Autoantibodies↗
PubMed1991

[Plasmid pBR322 drug-resistance gene changes induced by glycidyl methacrylate].

A mutagen, glycidyl methacrylate (GMA), discovered by us a few years ago has been used to investigate the mutation mechanism of drug-resistance genes of plasmid pBR322. The results indicated that GMA binds strongly to pBR322 DNA, and this binding decreased the relative transformation efficiency using E. coli HB1O1 strain on LB plates containing ampicillin (Ap) or tetracycline (Tc). The mutants, ARpTSc, AspTRc and ASpTSc, have been isolated and their drug-resistance proved to be heritable.

Ampicillin Resistance↗
PubMed1990

Mutations in the trfA replication gene of the broad-host-range plasmid RK2 result in elevated plasmid copy numbers.

Mutated forms of trfA, the replication protein gene of plasmid RK2, that support a minimal RK2 origin plasmid in Escherichia coli at copy numbers up to 23-fold higher than normal have been isolated. Six such high-copy-number (copy-up) mutations were mapped and sequenced. In each case, a single base transition led to an amino acid substitution in the TrfA protein primary sequence. The six mutations affected different residues of the protein and were located within a 69-base-pair region encoding 24 amino acids. Dominance tests showed that each of the mutants can be suppressed by wild-type trfA in trans, but suppression is highly dependent on the amount of wild-type protein produced. Excess mutant TrfA protein provided in trans significantly increased the copy number of RK2 and other self-replicating derivatives of RK2 that contain a wild-type trfA gene. These observations suggest that the mutations affect a regulatory activity of the TrfA replication protein that is a key factor in the control of initiation of RK2 replication.

Alleles↗