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Biomedical subjects

P Liang

Publications and source records attributed to P Liang.

At least 91 records · Page 5Linked to original sources
PubMed1995

N-ras mutation in 7,12-dimethylbenz[a]anthracene (DMBA)-induced erythroleukemia in Long-Evans rats.

Intravenous injections of 7,12-dimethylbenz[a]anthracene (DMBA) induce erythroblastic leukemia (erythroleukemia) with No.2 trisomy in Long-Evans rats. Activation of some oncogenes such as abl and Ha-ras has been reported to occur in relation to the secondary chromosomal translocations. In the present studies, a consistent type of mutation, A to T transversion in codon 61 of N-ras gene, was found in all of 6 cultured leukemia cell lines and 5 primary leukemias induced by DMBA. The N-ras mutation was also found in bone marrow cells of 2 out of 8 preleukemias. On the contrary, no mutation was observed in Ha- and Ki-ras genes in all leukemias and preleukemias. The consistent occurrence of above N-ras mutation in leukemias indicates that it plays an important role in DMBA-leukemogenesis.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1995

Prenatal diagnosis of Charcot-Marie-Tooth disease type 1A (CMT1A) using molecular genetic techniques.

Charcot-Marie-Tooth disease type 1A (CMT1A) is a frequent hereditary motor and sensory neuropathy of the peripheral nerves. In most cases, the disease is associated with a 1.5 Mb tandem duplication at 17p11.2. A 42-year-old pregnant women requested prenatal diagnosis because of her age and since both her husband and two children were severely affected with CMT1. The CMT1A duplication was demonstrated in the father's, the two children's, and the fetus's DNA using different molecular genetic methods. Although cytogenetical analysis showed a normal female karyotype in the fetus, the parents decided to terminate the pregnancy because of the genetic risk associated with the CMT1A duplication.

Adult↗
PubMed1995

Nuclear-cytoplasmic translocations of protein p26 during aerobic-anoxic transitions in embryos of Artemia franciscana.

Embryos of the crustacean Artemia franciscana survive continuous anoxia for periods of years, during which their metabolism comes to a reversible stand-still. A question of some interest concerns the maintenance of cellular integrity in the absence of biosynthesis and an ongoing energy metabolism. The present paper continues previous work on an abundant protein (p26) that undergoes extensive intracellular translocation during aerobic-anoxic transitions, exhibits several characteristics of stress proteins, and might be involved in metabolic regulation during aerobic-anoxic transitions. Since it has been established that intracellular pH (pHi) plays a major role in aerobic-anoxic transitions in this system we examined the pH-dependence of nuclear-cytoplasmic translocations of p26. In unincubated and aerobic-incubated embryos (pHi > or = 7.9) p26 was located in the "soluble" fraction, whereas in anoxic embryos (pH about 6.3) roughly 50% was translocated into the nucleus as shown by immunocolloidal gold electron microscopy. These nuclear translocations also took place in vitro, simply by manipulating buffer pH in a physiologically appropriate fashion. Immunostaining of Western blots prepared after two-dimensional electrophoresis revealed several isoforms of native p26. The isoelectric point of the major isoform was 7.10 +/- 0.05, a value close to the pH at which p26 translocation into the nucleus was first initiated in vitro. 31P-NMR measurements indicated that pHi was maintained at acidic levels (about 6.3) during prolonged anoxia. We also found that pHi of hydrated (0 degree C) but otherwise unincubated embryos was alkaline, allowing for rapid resumption of metabolism under permissive conditions. The significance of these pH-dependent translocations of p26 is discussed.

Aerobiosis↗
PubMed1995

Recent advances in differential display.

Differential display and RNA arbitrary primed polmerase chain reaction are methods recently designed to identify and isolate differentially expressed genes. Methodological modifications have since been introduced to streamline the techniques. The major effort has centered on how to eliminate false positives as approached from a variety of angles, ranging from RNA sample preparation, northern blot confirmation, primer length variation, to better experimental design.

Base Sequence↗
PubMed1995

Molecular characterization of the murine thymidylate kinase gene.

Thymidylate kinase (TMK) catalyzes an essential reaction of converting dTMP to dTDP, leading to formation of the DNA precursor dTTP. Unlike the preceding enzymes, thymidine kinase and thymdylate synthase, little is known about regulation of TMK after mammalian cells exit from quiescence and enter the cell cycle. In this study, cDNA of murine TMK was isolated and characterized. Murine TMK gene expression in nontransformed BALB/c 3T3 cells was shown to be regulated during Gø to S-phase transit at both mRNA and enzyme activity levels. Its timing was distinctive from that of thymidine kinase and thymdylate synthase. In contrast, the regulation of TMK in response to serum growth factor stimulation was abolished in cells transformed by either SV40 or Kirsten viruses, and tmk expression became constitutively elevated. This finding is in concordance with previous results showing that transformed cells exhibit more relaxed control than normal cells in their initiation of DNA replication.

3T3 Cells↗
PubMed1994

Ras activation of genes: Mob-1 as a model.

The ras oncogenes function by indirectly controlling expression of a subset of yet-undefined genes that are crucial for cell growth and differentiation. In a differential display strategy, numerous genes were identified on the basis of their differential expression in rat embryo fibroblasts transformed by the cooperation of mutant Ha-ras and p53 genes. We demonstrate here that one such gene, designated mob-1, is a downstream target of the Ras signaling pathway. The 417-bp mob-1 promoter, which contains dual NF-kappa B and AP-1 binding sites, confers the Ras inducibility. Oncogenic Ras as well as serum growth factors that activate endogenous Ras can induce mob-1 expression, but with a fundamental difference in that the oncogenic induction is constitutive whereas the serum induction is transient. mob-1 encodes a small secretory protein with a high degree of homology to IP-10, a member of a proinflammatory cytokine family. These findings link chronic inflammatory response to constitutive ras activation and tumorigenesis. Mob-1 may serve as a secreted marker for oncogenic Ha-ras mutations.

Amino Acid Sequence↗
PubMed1994

Chronic cardiac rejection: identification of five upregulated genes in transplanted hearts by differential mRNA display.

Transplant arteriosclerosis, the major manifestation of chronic rejection, develops after allogeneic (Lewis to F344) but not syngeneic (Lewis to Lewis) rat cardiac transplantation. To identify transcriptionally regulated mediators associated with chronic cardiac rejection, we adapted the differential mRNA display technique for in vivo transplant specimens. Gene transcript patterns in four allogeneic hearts showing early signs of chronic rejection were compared with those in two syngeneic hearts exposed to the same surgical procedure but histologically normal. Twelve differentially expressed cDNA bands were identified. We improved the probability of isolating one or more allograft-specific cDNAs from a single display band by first using recovered and reamplified PCR products as probes in RNA blot analysis. cDNA fragments cloned from individual bands were then used in a second RNA blot analysis, which allowed for the correlation of specific mRNA transcripts with cDNA clones. Five cDNA clones produced time-dependent, allograft-specific hybridization. Sequence analysis demonstrated that two of these cDNAs corresponded to unknown genes, whereas the other three represented known genes not previously associated with chronic rejection. The latter group included the macrophage lectin specific for galactose/N-acetylgalactosamine (a cell-surface receptor), the nuclear P1 gene (a homologue of a yeast replication protein), and a ubiquitin-like gene. Our application of the differential display technique allowed the direct identification of potential mediators under in vivo conditions that preserve the environment of the disease process--including infiltrating cell populations critical to the inflammatory response.

Animals↗
PubMed1994

The closed conformation of a highly flexible protein: the structure of E. coli adenylate kinase with bound AMP and AMPPNP.

The structure of E. coli adenylate kinase with bound AMP and AMPPNP at 2.0 A resolution is presented. The protein crystallizes in space group C2 with two molecules in the asymmetric unit, and has been refined to an R factor of 20.1% and an Rfree of 31.6%. In the present structure, the protein is in the closed (globular) form with the large flexible lid domain covering the AMPPNP molecule. Within the protein, AMP and AMPPNP, and ATP analog, occupy the AMP and ATP sites respectively, which had been suggested by the most recent crystal structure of E. coli adenylate kinase with Ap5A bound (Müller and Schulz, 1992, ref. 1) and prior fluorescence studies (Liang et al., 1991, ref. 2). The binding of substrates and the positions of the active site residues are compared between the present structure and the E. coli adenylate kinase/Ap5A structure. We failed to detect a peak in the density map corresponding to the Mg2+ ion which is required for catalysis, and its absence has been attributed to the use of ammonium sulfate in the crystallization solution. Finally, a comparison is made between the present structure and the structure of the heavy chain of muscle myosin.

Adenosine Monophosphate↗
PubMed1994

Identification and upregulation of galactose/N-acetylgalactosamine macrophage lectin in rat cardiac allografts with arteriosclerosis.

Using differential mRNA display to uncover potential mediators associated with chronic rejection, we identified a cDNA fragment induced in Lewis to F344 rat cardiac allografts with arteriosclerosis but not Lewis syngrafts. The full-length cDNA (1.4 kb) isolated from a rat cardiac allograft cDNA library was 99% identical to galactose/N-acetylgalactosamine (Gal/GalNAc) macrophage lectin, a cell-surface receptor. This cDNA hybridized in Northern analysis with total RNA from eight cardiac allografts but not with host hearts, syngrafts, or other organs. There was a significant allograft-specific increase in transcript levels measured by reverse transcriptase PCR at days 7, 14, 28, and 75 in comparison with paired F344 host hearts (subject to same circulation but histologically normal), day-0 hearts, and syngrafts (P < 0.008, n = 4 at each time). Transcript levels in cardiac allografts were higher than those in paired host spleens (a major source of inflammatory cells) (P < 0.0001), indicating the localized nature of Gal/GalNAc lectin induction. By in situ hybridization and immunostaining, Gal/GalNAc lectin expression localized to a subset of inflammatory cells in cardiac allografts. These findings link Gal/GalNAc macrophage lectin to the chronic rejection process, as a possible mediator of macrophage infiltration.

Acetylgalactosamine↗
PubMed1994

The effect of fibronectin on re-epithelialization of rabbits cornea after alkali burn.

The authors found experimentally that (1) fibronectin enhanced the healing of rabbit corneal epithelium after alkali burn and prevented the secondary breakdown; (2) it rapidly deposited on the denuded basement membrane to disappear as epithelial cells slid over, and (3) ultrastructurally, the neighbouring epithelial cells became flattened, with filopodia at the advancing edge, and extended to the wounded areas at 24 hours after the burn. However, the epithelial defects recurred 72 hours after the burn when the basement membrane vanished till after the 8th week, indicating that the latter was associated with the secondary epithelial breakdown.

Animals↗
PubMed1994

[Preoperative evaluation of resectability of hilar bile duct carcinoma by color Doppler flow imaging and duplex Doppler].

Color flow images of hilar bile duct carcinoma and the relationship between tumors and hilar important blood vessals were observed in 22 patients with hilar bile duct carcinoma by color Doppler flow imaging (CDFI) and Duplex Doppler. It was found that most of bile duct carcinoma were of oligovascularity. Accurate rate were 81.82% and 77.28% respectively by preoperative ultrasound evaluation of the relationship between the tumor and the portal vein, and the tumor and the hepatic artery. CDFI and Duplex Doppler are sensitive, convenient and noninvasive methods for preoperative evaluation of resectability of hilar bile duct carcinoma and provide important information for surgery.

Adult↗
PubMed1994

Transfer of shuttle vectors containing Bacillus thuringiensis toxin gene into wild-type B. cereus, B. brevis and B. subtilis by electroporation.

Gram positive and negative bacterial shuttle vectors carrying Bacillus thuringiensis (B.t.) toxin gene were introduced by electroporation into wild-type Bacillus cereus, B. brevis and B. subtilis. The transformation efficiencies for these bacteria were around 10(1)-10(4) transformants per micrograms DNA based on the numbers of neomycin- and ampicillin-resistant colonies produced. The structure of the transferred plasmids proved identical with the original ones both in size and restriction pattern. Toxicity assays showed that the transformants gave a mortality of 90-100% against caterpillar of Heliothis assulta, indicating that the gene function was not changed by electroporation.

Bacillus↗
PubMed1994

[Combined treatment of hepatic carcinoma: percutaneous intratumoral injection of Y-90 glass treatment microspheres with sonographic guidance].

Twenty-eight patients with hepatic carcinoma were treated with a percutaneous injection of Y-90 glass treatment microspheres (GTMS) with sonographic guidance. Of these patients, some were also given alcohol around the lesions and intraportal vein chemotherapy alternatively. Diagnoses were confirmed by biopsy in all patients preoperatively. All patients were alive after 2-16 months follow up. In this group, 91% patients had their tumor size reduced. All lesions showed changes in echo pattern on US scans after the treatment, most of them being hyperechogenic, then being mixed echogenic or isoechogenic. Blood flow sign decreased within lesions and at periphery on color Doppler scans. Of the 13 patients with increased AFP level before injection, 11 had AFP titer dropped with 6 falling to normal after treatment. All patients experienced relief of symptoms and improved general conditions. Histopathologic examination performed in 8 patients after treatment showed complete necrosis and fibrosis of the tumor in 7. Small focus of tumor tissue was detected in one patient only. The therapeutic outcome indicated that the percutaneous intratumoral injection of Y-90 is an appropriate first-line treatment for patients with hepatic carcinoma.

Adult↗
PubMed1993

Distribution and cloning of eukaryotic mRNAs by means of differential display: refinements and optimization.

Differential display has been developed as a tool to detect and characterize altered gene expression in eukaryotic cells. The basic principle is to systematically amplify messenger RNAs and then distribute their 3' termini on a denaturing polyacrylamide gel. Here we provide methodological details and examine in depth the specificity, sensitivity and reproducibility of the method. We show that the number of anchored oligo-dT primers can be reduced from twelve to four that are degenerate at the penultimate base from the 3' end. We also demonstrate that using optimized conditions described here, multiple RNA samples from related cells can be displayed simultaneously. Therefore process-specific rather than cell-specific genes could be more accurately identified. These results enable further streamlining of the technique and make it readily applicable to a broad spectrum of biological systems.

Animals↗