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Z Cui

Publications and source records attributed to Z Cui.

18 recordsLinked to original sources
PubMed1995

Expression of phosphatidylethanolamine N-methyltransferase-2 cannot compensate for an impaired CDP-choline pathway in mutant Chinese hamster ovary cells.

Phosphatidylcholine is a product of the CDP-choline pathway and the pathway that methylates phosphatidylethanolamine. We have asked the question: are the two pathways functionally interchangeable? We addressed his question by investigating the expression of phosphatidylethanolamine N-methyltransferase-2 (PEMT2) of rat liver in mutant Chinese hamster ovary cells (MT-58) (Esko, J. D., Wermuth, M.M., and Raetz, C. R. H. (1981) J. Biol. Chem. 256, 7388-7393) defective in the CDP-choline pathway for phosphatidylcholine biosynthesis. Cell lines stably expressing different amounts of PEMT2 activity (up to 700 pmol/min.mg protein) were isolated. A positive correlation between the amount of PEMT2 activity expressed and the incorporation of [3H]methionine into phosphatidylcholine at both the permissive and restrictive temperatures showed that PEMT2 was functional in the Chinese hamster ovary MT-58 cells. In contrast to mutant cell lines stably expressing transfected CTP:phosphocholine cytidylyltransferase, the cell lines stably expressing PEMT2 did not survive at the restrictive temperature. Determination of the phosphatidylcholine mass in wild type cells, mutant MT-58 cells, and cells with the highest level of PEMT2 expression showed that PEMT2 was functional and synthesized the same amount of phosphatidylcholine as did wild type cells at the restrictive temperature. Indirect immunofluorescence studies showed that localization of the over-expressed cytidylyltransferase in MT-58 cells was largely nuclear, whereas PEMT2 was predominantly located outside the nucleus. Our data show that methylation of phosphatidylethanolamine to phosphatidylcholine cannot substitute for the CDP-choline pathway.

Animals↗
PubMed1995

Triterpenoid glycosides from the fruits of Kochia scoparia.

From the fruits of Kochia scoparia (L.) Schrad, five triterpenoid glycosides were isolated for the first time from this plant. They were elucidated as momordin Ic, the 6'-methyl ester of momordin Ic, momordin IIc, 2'-O-beta-D-glucopyranosylmomordin Ic, and 2'-O-beta-D-glucopyranosylmomordin IIc on the basis of spectral and chemical methods. The last two saponins are new natural products.

Carbohydrate Sequence↗
PubMed1995

Bradyrhizobium liaoningense sp. nov., isolated from the root nodules of soybeans.

Seventeen strains of extra-slowly growing (ESG) soybean rhizobia isolated from root nodules of Glycine soja and Glycine max growing in five provinces (Liaoning, Heilongjiang, Shanxi, Hubei, and Anhui) in the People's Republic of China were compared with 48 reference strains belonging to the genera Bradyrhizobium, Rhizobium, and Agrobacterium by performing a numerical analysis of 191 phenotypic features. Our results showed that all of the ESG strains examined clustered closely in the genus Bradyrhizobium but were separated from Bradyrhizobium japonicum at the species level and that they could be differentiated from Rhizobium and Agrobacterium species at the genus level. On the basis of the results of our numerical taxonomy analysis, a genomic DNA G & C content analysis, DNA-DNA hybridization experiments, a partial 16S rRNA sequence analysis, a serological analysis, an N and C content analysis, and an N/C ratio analysis of members of the three groups of soybean rhizobia, we propose the name Bradyrhizobium liaoningense sp. nov. for the ESG strains; the type strain of this species is strain 2281.

Base Composition↗
PubMed1994

A unique mitochondria-associated membrane fraction from rat liver has a high capacity for lipid synthesis and contains pre-Golgi secretory proteins including nascent lipoproteins.

An endoplasmic reticulum-like membrane fraction, termed the "mitochondria-associated membrane" (MAM), that co-isolates with mitochondria from rat liver has been characterized. One potential function of the MAM is as a membrane bridge between the endoplasmic reticulum and mitochondria that may be involved in transfer of phospholipids between these two organelles (Vance, J. E. (1990) J. Biol. Chem. 265, 7248-7256). A polyclonal antibody directed against a peptide corresponding to the C terminus of phosphatidylethanolamine N-methyltransferase-2, a specific marker protein of the MAM (Cui, Z., Vance, J. E., Chen, M. H., Voelker, D. R., and Vance, D. E. (1993) J. Biol. Chem. 268, 16655-16663), was used in immunofluorescence and immunogold electron microscopy localization studies in rat hepatocytes. Immunoreactive protein was clustered in regions of the cell that did not correspond to the bulk of endoplasmic reticulum. A second potential role for the MAM, as a component of the secretory pathway that supplies lipids for assembly into very low density lipoproteins, has been examined. The MAM contains enzymes of similar, or higher, specific activities to those enzymes in the endoplasmic reticulum for the synthesis of phospholipids, triacylglycerols, cholesterol, and cholesteryl esters. Specific activities of diacylglycerol acyltransferase, acyl-coenzyme A:cholesterol acyltransferase, and phosphatidylserine synthase (base exchange enzyme) are enriched 2.2-3.4-fold in the MAM compared with endoplasmic reticulum. In addition, the microsomal triacylglycerol transfer protein, which is required for the assembly/secretion of apolipoprotein B-containing lipoproteins, was present in the MAM. Nascent apolipoprotein B-containing lipoproteins were isolated from the lumen of the MAM. These lipoproteins had the same average density and composition as nascent apolipoprotein B-containing lipoproteins isolated from heavy and light endoplasmic reticulum fractions, from the Golgi, and lipoproteins newly secreted by cultured rat hepatocytes. The MAM is a pre-Golgi compartment of the secretory route, as shown by pulse-chase studies with apolipoprotein B and albumin, as well as the sensitivity of luminal apolipoprotein B to endoglycosidase H.

Animals↗
PubMed1994

Suppression of rat hepatoma cell growth by expression of phosphatidylethanolamine N-methyltransferase-2.

The expression of rat liver phosphatidylethanolamine N-methyltransferase-2 (PEMT2) in McA-RH7777 rat hepatoma cells resulted in the unexpected inhibition of cell growth. There was a strict correlation (r = 0.973) between the level of expression of the enzyme activity and the generation time for hepatoma cell division. Expression of other foreign proteins via the same vector did not inhibit McA-RH7777 cell growth; thus, retardation of cell division was specific for the methyltransferase. Addition of 1 microM 3-deazaadenosine, which causes inhibition of phosphatidylethanolamine methylation, reversed the PEMT2-mediated inhibition of cell division. Transfection of a line of Chinese hamster ovary cells with PEMT2 had no effect on the division of these cells. Induction of hepatic tumors in rats with N-nitrosodiethylamine coincided with a striking decrease in methyltransferase activity and immunoreactive protein in the tumor nodules. Thus, data from studies in cell culture and intact rats suggest a regulatory role for PEMT2 in hepatocyte cell growth and possibly in the development of liver cancer.

Animals↗
PubMed1994

Using interval logic for order assembly.

Temporal logic, in particular, interval logic has been used to represent genome maps and to assist genome map constructions. However, interval logic itself appears to be limited in its expressive power because genome mapping requires various information such as partial order, distance and local orientation. In this paper, we first propose an integrated formalism based on a spatial-temporal logic where the concepts of metric information, local orientation and uncertainty are merged. Then, we present and discuss a deductive and object-oriented data model based on this formalism for a genetic deductive database, and the inference rules required. The formalism supports the maintenance of coarser knowledge of unordered, partially ordered and completely ordered genetic data in a relational hierarchy. We believe that this integrated formalism also provides a formal basis for designing a declarative query language.

Animals↗
PubMed1994

Prototyping a genetics deductive database.

We are developing a laboratory notebook system known as the Genetics Deductive Database. Currently our prototype provides storage for biological facts and rules with flexible access via an interactive graphical display. We have introduced a formal basis for the representation and reasoning necessary to order genome map data and handle the uncertainty inherent in biological data. We aim to support laboratory activities by introducing an experiment planner into our prototype. The Genetics Deductive Database is built using new database technology which provides an object-oriented conceptual model, a declarative rule language, and a procedural update language. This combination of features allows the implementation of consistency maintenance, automated reasoning, and data verification.

Animals↗
PubMed1994

[Immunological cross-reaction of serotype I Marek's disease virus 38kD phosphorylated protein with serotype II and III viruses].

Marek's disease virus (MDV) 38kD phosphorylated protein (pp38), which was identified by monoclonal antibody (mAb) H19 specific to pathogenic serotype I of MDV, has been recognized as a transformation-associated antigen specific to serotype I of MDV. The recombinant pp38 was prepared and purified from pp38-expressing recombinant baculovirus infected Sf9 cell lysates through a mAb H19-affinity column. In indirect fluorescence antibody test, the mouse sera against the purified recombinant pp38 not only gave a high titer to serotype I strain GA-infected CEF but also gave a reasonable titers to serotype II strain Z4- and serotype III HVT strain Fc126-infected CEF. In another way, the pp38- expressing recombinant baculovirus infected Sf9 cells reacted with anti-serotype I MDV chicken sera as well as with anti-serotype II and serotype III MDV chicken sera respectively. The results imply that both serotypes II and III of MDV probably contain a homologue to pp38 of serotype I.

Antigens, Viral↗
PubMed1994

Purification of recombinant 38-kDa phosphorylated protein of Marek's disease virus from insect cells through an affinity column.

The 38-kDa phosphorylated protein (pp38) of Marek's disease virus (MDV) expressed in insect cell line Sf9 cells infected with recombinant baculovirus BP38II was purified through an affinity column made of CNBr-Sepharose 4B linked with monoclonal antibody (Mab) H19 specific to serotype I MDV. The result of SDS-PAGE showed a main band of 38 kDa in the lane loaded with the purified pp38, and this band was specifically recognized by MAb H19 in Western blot. The serum from mice immunized with the purified recombinant pp38 reacted only to Sf9 cells infected with the recombinant baculovirus BP38II but not with wild baculovirus. It also gave a titer of 1:128 in indirect fluorescence antibody test to MDV-infected chick embryo fibroblast cells. These results indicated that the purification procedure was effective and that it would be useful for investigating the biological functions of MDV pp38.

Animals↗
PubMed1993

Incorporation of the pancreatic membrane protein GP-2 into secretory granules in exocrine but not endocrine cells.

The pancreatic zymogen granule membrane protein GP-2 was introduced into cells of exocrine or endocrine origin by transfection of its cDNA in order to investigate the mechanisms by which proteins are specifically incorporated into the membranes of secretory granules. Permanent transformants expressing GP-2 were isolated from exocrine pancreatic-derived AR42J cells as well as AtT20 cells of anterior pituitary origin and insulinoma-derived Rin5F cells. In AR42J cells, GP-2 was localized by immunofluorescence and immunoelectron microscopy to the endogenous zymogen-like granules as well as to the plasma membrane. In experiments supporting the localization data, incubation of the AR42J transformants with the secretagogue cholecystokinin (CCK8) resulted in enhanced release of a shed form of GP-2 into the medium in parallel with amylase, suggesting that the two proteins were secreted from the same compartment. By contrast, when expressed in AtT20 cells, the protein was found by immunofluorescence microscopy on the plasma membrane as well as in intracellular vesicles that differed in size and location from the endogenous secretory vesicles. By electron microscopy, large (approximately 0.5 micron) multivesicular structures were observed. Single- and double-label immunoelectron microscopy demonstrated that these large organelles labeled with anti-GP-2 antibodies, whereas the smaller adrenocorticotropic hormone (ACTH)-containing secretory vesicles did not. In permanent transformants of Rin5F cells, GP-2 was also excluded from the insulin-containing granules and found in multivesicular bodies similar to those in the AtT20 cells and containing the endosomal/lysosomal marker endolyn-78. Despite the apparent accumulation of GP-2 in lysosome-like structures, it turned over slowly and did not undergo rapid endocytosis from the cell surface. We conclude that GP-2 is targeted to secretory granule membranes by cell type-specific mechanisms that likely involve its interaction with other membrane or content proteins expressed only in the exocrine cells.

Amylases↗
PubMed1992

Cloning and molecular analysis of cDNA encoding a carboxymethylcellulase of the yeast Cryptococcus flavus.

A cDNA copy for carboxymethylcellulase (CMCase 1) of the yeast Cryptococcus flavus was cloned by screening an expression cDNA library with anti-CMCase 1 antibody. The sequence of the cDNA had an open reading frame of 1023 bp that encoded a preprotein of 341 amino acids with a molecular weight of 35,698. The putative precursor begins with a hydrophobic segment that possibly acts as a signal sequence for secretion, which is followed by a presumed prosequence and a sequence consistent with the N-terminal amino acid sequence of secreted CMCase 1. No potential N-glycosylation site was found in the sequence of putative pro-CMCase 1. Comparison of the deduced protein sequence shows that the C. flavus CMCase 1 is partially homologous to the Trichoderma reesei endoglucanase EGIII. Alignment of the cDNA copy and the chromosomal DNA showed seven putative introns of 45 to 134 bp. When introduced into E. coli, the cDNA directed the synthesis of CMCase 1 as seen by CMCase activity and Western blotting using anti-CMCase 1 antibody.

Amino Acid Sequence↗
PubMed1991

Expression of a G protein subunit, alpha i-1, in Balb/c 3T3 cells leads to agonist-specific changes in growth regulation.

Cellular receptors for many hormones, neurotransmitters, and growth factors are coupled to intracellular effector enzymes or ion channels through a set of heterotrimeric G proteins. In order to determine whether isoforms of G protein alpha subunits contribute differentially to mitogenic responses, we introduced an alpha subunit isoform, alpha i-1, into Balb/c 3T3 cells that normally lack this subtype. Balb/c 3T3 cells transfected with a plasmid containing cDNA encoding alpha i-1 expressed the alpha i-1 protein as judged both by the appearance of immunoreactive alpha i-1 protein on Western blots and by two-dimensional analysis of the proteins [32P]ADP-ribosylated by pertussis toxin. The amount of alpha i-1 expressed is less than the amount of alpha subunits endogenously present in these cells. Expression of alpha i-1 in the transfected cells slightly blunts stimulation of adenylylcyclase by GTP, guanosine 5'-3-O-(thio)triphosphate, or forskolin, but has no major effect on the ability of thrombin to inhibit the enzyme. In contrast, the expression of alpha i-1 has significant effects on cell growth and on the mitogenic response to thrombin. The alpha i-1-transfected cells have a doubling time that is twice as long as control cells transfected with the same plasmid without a cDNA insert. Despite their slower growth, thymidine incorporation in response to thrombin is greater in transfected than in control cells. Thrombin-stimulated DNA synthesis is sensitive to inhibition by pertussis toxin and is 5-fold more sensitive to inhibition by pertussis toxin in transfected cells than in control cells. The changes are receptor-specific since the mitogenic response to platelet-derived growth factor is indistinguishable between control and transfected cells. These studies suggest that the alpha i subunit composition of the cell may have profound effects on its growth and its response to stimulation through a specific cell surface receptor.

3T3 Cells↗
PubMed1991

[Androgen-like and anabolic action of Antheraea pernyi Guerin-Meneville Pas].

It has been found that the ethyl acetate extract isolated from Antheraea pernyi Pas is able to increase the weight of prostate-semina and levator ani muscle-bulbocavarnosus muscle of castrated mice. In addition, the extract also accelerates the growth of younger male mice and enhances the contents of RNA, DNA and protein in the liver tissue of mice. It has been determined that beta-ecdysone is one of the effective constituents for the androgen-like and anabolic action.

Animals↗
PubMed1989

A single nucleotide substitution at the rib2 locus of the yeast mitochondrial gene for 21S rRNA confers resistance to erythromycin and cold-sensitive ribosome assembly.

We have studied a mutation (cs23) in the mitochondrial gene for 21S rRNA that affects the peptidyl transferase center of the ribosome and conditionally blocks the assembly of the 54S ribosomal subunit. Strains carrying this mutation are resistant to erythromycin and cold-sensitive for growth on nonfermentable carbon sources (Singh et al. 1978) Mitochondria isolated from mutant cells grown on glucose at 20 degrees C, the nonpermissive temperature, were depleted of the 54S subunit and instead contained a novel 45S ribosomal particle. After mutant cells were shifted from 20 degrees C to 32 degrees C, 54S subunits were assembled, apparently from the 45S particles and pre-existing ribosomal proteins. DNA sequencing revealed that the mutant phenotype is a consequence of a C to A transversion at position 3993 of the 21S rRNA gene. Previously, C to U and C to G mutations have been identified at the same position in the 21S rRNA sequence. This position corresponds to C-2611 in the E. coli 23S RNA, a nucleotide that appears to be conserved in the large rRNA of all erythromycin-sensitive ribosomes.

Base Sequence↗
PubMed1987

Serologic differences among nondefective reticuloendotheliosis viruses.

Antigenic relationships among 26 isolates of reticuloendotheliosis virus (REV) obtained from several avian species were compared by cross neutralization tests with polyclonal chicken sera and by immunofluorescent assays with monoclonal antibodies to REV strain T. The isolates were all strongly related by neutralization assays and thus probably constitute a single serotype. However, 3 antigenic subtypes were suggested by minor but distinct differences in neutralization titers. The validity of these 3 subtype designations was confirmed by differential reactivity of viral isolates to selected monoclonal antibodies. Subtype-associated differences in serum antibody titers were noted following the inoculation of chickens with the REV isolates.

Animals↗