PubMed Health⌕ Search

Biomedical subjects

X Zhao

Publications and source records attributed to X Zhao.

At least 631 records · Page 35Linked to original sources
PubMed1993

Cloning and expression of the gene from Candida albicans that encodes a high-affinity corticosteroid-binding protein.

We have previously demonstrated the presence of a corticosteroid-binding protein (CBP) in Candida albicans and speculated on its homology to the glucocorticoid receptor. To explore this relationship further, we cloned the CBP gene. Our strategy employed sequencing enzymatically derived peptide fragments from purified CBP and using this information to synthesize degenerate oligonucleotide primers for use in the PCR. A 117-bp fragment amplified from C. albicans DNA was then used to screen a genomic library. Hybridizing clones were isolated, and DNA sequencing revealed an open reading frame of 1467 bp which encoded a protein with a molecular weight of 55,545. Southern analysis demonstrated that the gene was present at a unique locus within chromosome R of the Candida genome, while Northern analysis showed that the gene was expressed in C. albicans as a 1.8-kb transcript. CBP was over-expressed in Saccharomyces cerevisiae, and it exhibited an apparent dissociation constant (Kd) of 7 nM for [3H]corticosterone and displayed a steroid hormone binding profile comparable to that of the native protein. Searches of the data banks revealed little overall similarity to other cloned genes. However, the amino acid sequence contains a dinucleotide-binding fingerprint. In conclusion, we have cloned the gene encoding the CBP from C. albicans and have shown that the expressed protein has the properties of the native CBP. A comparison of the cloned gene to members of the steroid-thyroid-retinoic acid receptor gene superfamily showed that CBP is unrelated to these hormone receptors.

Adrenal Cortex Hormones↗
PubMed1993

Microsatellite mapping of the gene causing weaver disease in cattle will allow the study of an associated quantitative trait locus.

A genetic disease in cattle, progressive degenerative myeloencephalopathy (weaver disease), is associated with increased milk production. This association could result from population stratification, from a pleiotropic effect of a single gene, or from linkage disequilibrium between the gene causing weaver disease and a quantitative trait locus (QTL) for milk production. To test these hypotheses, we performed an extensive linkage study in a bovine pedigree segregating for the weaver condition and identified a microsatellite locus (TGLA116) closely linked to the weaver gene (zmax, 8.15; theta, 0.03). TGLA116 and, by extension, the weaver locus were assigned to bovine synteny group 13. This microsatellite can be used to identify weaver carriers, to select against this genetic defect, and to study the effect of the corresponding chromosomal region on milk production in Brown Swiss and other breeds of cattle.

Animals↗
PubMed1993

Quantitative estimation of chimerism in mice using microsatellite markers.

An embryonic stem cell line was established from SV129 mouse blastocysts and used to generate chimeric mice by injection into OF1 blastocysts; 18 out of the 30 resulting offspring appeared chimeric as judged from their coat color patterns, and 3 of the 13 males proved to be germ-line chimeras as they transmitted the SV129 agouti phenotype to all or part of their offspring. The degree of chimerism of these males was evaluated for different tissues using polymorphic microsatellite markers amplified by the polymerase chain reaction. It was shown that these new markers can be effectively used to quantitatively estimate levels of chimerism. The CKMM (creatine kinase, muscle) microsatellite system was used to distinguish the SV129 from the OF1 genotype. In all performed tests, the correlation between DNA ratio and signal ratio, expressed as a base 10 logarithm, was shown to exceed or equal 0.98 for known DNA ratios (SV129/OF1) ranging from 1/99 to 99/1. Linear calibration methods were used to predict the % SV129 DNA of a test sample based on the obtained signal ratio. The accuracy of the prediction was evaluated by performing repeated measurements. Differences among three repeated estimates ranged from 2 to 17% for a given sample. Microsatellite systems should be very useful to monitor chimerism involving strains that can not be discerned with coat color or biochemical markers. This will be particularly important when ES methodology becomes available in species other than mice.

Animals↗
PubMed1993

Regulation of cytochrome P450 expression in a novel liver cell line from zebrafish (Brachydanio rerio).

The expression and induction of cytochrome P450 by 2,3,7,8-tetrachlordibenzo-p-dioxin (TCDD) and beta-naphthoflavone (BNF) in a new liver cell line from adult zebrafish (Brachydanio rerio) were studied. Subcellular fractions from control, BNF- or TCDD-treated cells did not show detectable bands in immunoblots probed with antibodies to the constitutive forms of trout P450 (LMC1, LMC2, LMC3, LMC4, and LMC5), suggesting that either zebrafish liver cells lack P450s closely related to those constitutively expressed in trout or that the concentrations of the orthologous P450s were too low to be detected. However, upon exposure to TCDD, the cells expressed a major immunoreactive 54-kDa protein and a minor 50-kDa protein recognized by antibodies to rainbow trout P4501A1. These immunoreactive proteins were observed in microsomal and mitochondrial fractions of TCDD-treated cells but were not detected in cell cultures treated with dimethyl sulfoxide (DMSO) (vehicle control) or BNF. The activities of ethoxyresorufin O-deethylase (EROD) and 7,12-dimethylbenzanthracene (DMBA) hydroxylase were markedly increased by TCDD but not by BNF in this cell line. EROD activity was more sensitive than DMBA hydroxylase activity of TCDD-treated liver cells to diagnostic inhibitors such as alpha-naphthoflavone and anti-trout P4501A1 IgG. The TCDD-treated cells converted DMBA to various metabolites, one of which is the putative proximate carcinogen, DMBA-3,4-diol. These results suggest that TCDD, but not BNF, induces one or possibly two forms of P450 immunochemically and functionally related to trout P4501A1, in cultured zebrafish liver cells.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1993

Presence of subgenomic mRNAs in virions of coronavirus IBV.

The presence of subgenomic mRNAs in virions of IBV was examined by probing Northern blots of RNA extracted from virions using as a probe a cDNA of the 3'-terminal nucleocapsid protein (N) gene. This detects all five mRNAs because of the 3'-coterminal, nested-set arrangement of coronavirus mRNAs. The mRNAs were readily detected even after extensive purification of virions and after RNase A treatment of virions. In sucrose gradients the peaks of virus particles, genomic RNA (gRNA), and mRNAs were coincident. Cellular mRNA was not detected in virions. The molar ratio of gRNA to each mRNA ranged from about 10 to 30 for IBV-Beaudette and 25 to 800 for IBV-M41. The molar ratio of genomic to intracellular viral mRNAs was also determined. From this it was estimated that the efficiency of incorporation of gRNA into virions was at least 20- to 100-fold greater, depending on the mRNA species, for IBV-Beaudette and 100- to 500-fold for IBV-M41. It is concluded that most virions contain only gRNA or contain only one species of mRNA on average in addition to gRNA.

Animals↗
PubMed1993

Analysis of messenger RNA within virions of IBV.

The presence of subgenomic mRNAs (sgRNAs) in virions of infectious bronchitis virus was examined by probing Northern blots of RNA extracted from virions using as a probe a cDNA of the 3'-terminal nucleocapsid protein (N) gene. The sgRNAs were readily detected even after extensive purification of virions and after RNase A treatment of virions. The molar ratio of gRNA to each sgRNA was in the range 25 to 400 for IBV-M41 and 10 to 30 for IBV-Beaudette. After comparison with the molar ratios of genomic to intracellular viral sgRNAs it was estimated that the efficiency of incorporation of gRNA into virions was approximately 100 to 500-fold greater than for sgRNAs in the case of M41 and 20 to 100-fold for Beaudette, depending on the sgRNA species. It is concluded that sgRNAs can be present within IBV virions. Approximately 1 in 3 Beaudette virions and 1 in 20 M41 particles might contain a single copy of one sgRNA.

Animals↗
PubMed1993

Phylogenetic distribution and genetic mapping of a (GGC)n microsatellite from rice (Oryza sativa L.).

DNA microsatellites are ubiquitously present in eukaryotic genomes and represent a vast source of highly informative markers. We describe in this article a (GGC)n microsatellite which is widely distributed in eukaryotic genomes. Using polymerase chain reaction (PCR) techniques and DNA sequencing, we demonstrated for the first time in plant species that a (GGC)n microsatellite locus is moderately polymorphic. Six alleles are present at this locus in rice and length polymorphisms are caused by variation in the number of tandem GGC repeats. By scoring a backcross mapping population, we were able to demonstrate that this locus is stably inherited and does not link to any known RFLP markers on the rice RFLP map. Our results suggest that DNA microsatellites should be useful in plants for construction of genetic linkage maps, extension of the existing genetic linkage maps, linkage analysis of disease and pest resistance genes, and the study of population genetics.

Base Sequence↗
PubMed1993

The effect of a depot injection of recombinant bovine somatotropin on follicular development and embryo yield in superovulated Holstein heifers.

Superovulated Holstein heifers (n = 32) were given a depot injection of 500 mg recombinant bovine somatotropin (rBST) or vehicle at Day 4 of the estrous cycle (7 days before the first FSH injection); at Day 11, coincidentally with the first FSH injection; or at Day 15, the time of artificial insemination. Embryos were collected nonsurgically, and the number of corpora lutea was counted by ultrasonography at Day 7 after insemination. Blood samples were taken every second day, from Day 2 of the superovulatory cycle until the day of embryo collection, and were analyzed for progesterone, somatotropin and insulin-like growth factor-1 (IGF-1). Somatotropin-treated heifers at Day 11 had a significantly higher mean number of corpora lutea than the controls (18.1 vs 13.4; P </= 0.05). Day 4 treatment tended to increase the mean number of corpora lutea (15.4; P <- 0.10), and significantly increased the overall percentage of transferable embryos (74.6 vs 58.6%; P </= 0.01). In the control animals, plasma IGF-1 was uncorrelated to somatotropin (P > 0.63), but it was negatively correlated with progesterone (P </= 0.01), suggesting that IGF-1 production in the superovulated heifer may be related to ovarian development.

Journal Article↗
PubMed1993

Comparative toxicity of amyloid beta-peptide in neuroblastoma cell lines: effects of albumin and physalaemin.

1. Synthetic amyloid beta-peptide was toxic to NB41A3 neuroblastoma cells in serum-free culture as judged by decreasing cell numbers and release of the cytosolic enzyme, lactic dehydrogenase. 2. Without amyloid beta-peptide, bovine serum albumin increased the number of cells surviving in culture. 3. In the presence of amyloid beta-peptide, BSA appeared to potentiate the amyloid beta-peptide toxicity. 4. The toxic dose response for amyloid beta-peptide varied between different cell lines (NB41A3, NB2a and IMR32), in a range of 100-1000 nM amyloid beta-peptide. 5. Amyloid beta-peptide toxicity was inhibited by the concurrent treatment of the cells with the tachykinin physalaemin with an ED50 of 10(-6) M.

Amyloid beta-Peptides↗
PubMed1993

Microsatellite mapping of a gene affecting horn development in Bos taurus.

The presence or absence of horns in Bos taurus is thought to be under the genetic control of the autosomal polled locus, characterized by two alleles: P dominant over p, and causing the polled or hornless phenotype. We have demonstrated genetic linkage between the polled locus and two microsatellite markers, GMPOLL-1 and GMPOLL-2, and have assigned the corresponding linkage group to bovine chromosome 1. This confirms the existence of the postulated polled locus and the hypothesized inheritance pattern. It will allow marker assisted selection for the polledness trait in breeding programs and is a first step towards positional cloning and molecular study of a gene that has been subjected to both natural and artificial selection.

Alleles↗
PubMed1993

Clusters of interspersed repeated DNA sequences in the rice genome (Oryza).

We have characterized a repeated DNA sequence (RTL122) from rice (Oryza sativa L.) with respect to its organization in the rice genome and its distribution among rice and other plants. The results indicate that the RTL122 sequence is interspersed in the rice genome and limited to the genus Oryza. It is highly polymorphic and can be used to fingerprint rice varieties. A structure was observed in which several repeated sequences were clustered in DNA regions of 15-20 kb. We characterized three bacteriophage lambda clones that contained the RTL122 sequence. Southern analysis using probes derived from restriction fragments of the three lambda clones indicated that all fragments except one are interspersed repeated sequences and belong to different repeated sequence families. Subsequent slot blot hybridization showed that most of them are only present within the genus Oryza. Some of the Oryza-specific, physically linked sequences show the same phylogenetic distribution, which suggests that these sequences might have evolved in a coordinate fashion. On the other hand, some of the repeated sequences have a different distribution even though they are physically adjacent in the genome. We speculate that such blocks of interspersed repeated sequences may serve as hotspots for rapid changes in the rice genome.

Bacteriophage lambda↗
PubMed1993

Regulation of vitamin D receptor abundance and responsiveness during differentiation of HT-29 human colon cancer cells.

We have studied the effects of 1,25-dihydroxyvitamin D [1,25-(OH)2D3] on cellular differentiation in the HT-29 human colon cancer cell line. Our aim was to evaluate the regulation of 1,25-dihydroxyvitamin D receptor (VDR) abundance and hormone responsiveness during the transition of rapidly proliferating to differentiated cells. Differentiation was induced by three means: cells were cultured in galactose-supplemented medium without glucose (GAL), grown on Matrigel-coated surfaces (MTG), or treated with 1,25(OH)2D3. Cell proliferation, assessed by [3H]thymidine incorporation, was equivalently inhibited by treatment with 1,25(OH)2D3, GAL or MTG. Differentiation was assessed by the induction of amino-oligo peptidase activity which was low in the proliferating cells. Following treatment with 1,25(OH)2D3, or growth in GAL or on MTG, amino-oligo peptidase activity increased 8- to 9-fold. The abundance of VDR measured by [3H]1,25(OH)2D3 binding, decreased to half without significant change in affinity, in cells differentiated by all three means compared to proliferating cells. Northern blot analyses of differentiated cells showed decreased steady-state levels of VDR messenger RNA (mRNA), indicating that all three treatments similarly decreased the abundance of VDR, at least in part, at the mRNA level. When exposed to 1,25(OH)2D3, the proliferating cells exhibited homologous up-regulation of VDR as well as the induction of 24-hydroxylase mRNA; the differentiated cells failed to exhibit both of these biological responses. Our findings demonstrate that 1,25(OH)2D3, GAL and MTG treatment all inhibit HT-29 cell proliferation and stimulate differentiation. Postproliferative differentiation achieved by the three approaches was associated with decreased VDR abundance, loss of VDR homologous up-regulation, and development of hormone unresponsiveness to 1,25(OH)2D3.

Calcitriol↗
PubMed1993

Effects of insulin-like growth factor-I and its analogues on bovine hydrogen peroxide release by neutrophils and blastogenesis by mononuclear cells.

The biological potencies of recombinant human insulin-like growth factor-I (IGF-I) and two of its analogues were examined for hydrogen peroxide release by neutrophils and blastogenesis by mononuclear cells. The binding affinities of these peptides for bovine serum IGF-binding proteins (IGFBPs) and IGF-I receptors on bovine neutrophils and mononuclear cells were also investigated. Relative to control treatment containing no IGF-I, preincubation of neutrophils with 12.5 micrograms/l of IGF-I, des(1-3)IGF-I (an analogue of human IGF-I lacking the N-terminal tripeptide Gly-Pro-Glu) and long R3 IGF-I (an analogue of human IGF-I with arginine replacing glutamate at position 3 of human IGF-I and the N-terminal extension Met-Phe-Pro-Ala-Met-Pro-Leu-Ser-Ser-Leu-Phe-Val-Asn) increased the release of H2O2 by 65%, 64% and 32% respectively. However, the difference in stimulating the release of H2O2 between long R3 IGF-I and other two (IGF-I and des(1-3)IGF-I) was reduced at a dosage of 100 micrograms/l. In the absence or presence of 2.5% fetal calf serum (FCS), 100 micrograms/l of IGF-I, des(1-3)IGF-I but not long R3 IGF-I significantly stimulated thymidine incorporation into mononuclear cells. In addition, des(1-3)IGF-I was more potent than IGF-I in stimulating thymidine incorporation into mononuclear cells in the presence of 2.5% FCS.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Decreased insulin-like growth factor-I (IGF-I) receptor sites on circulating mononuclear cells from cows with persistent lymphocytosis.

Plasma IGF-I concentrations and IGF-I receptor binding on mononuclear cells have been studied on bovine leukemia virus (BLV)-negative (CO), BLV-infected aleukemic (AL) cows or cows with persistent lymphocytosis (PL). No significant differences in plasma IGF-I concentrations were demonstrated among the three groups of animals. However, a linear negative correlation existed between the number of circulating mononuclear cells and the number of IGF-I binding sites on these cells from control cows. In addition, mononuclear cells from PL cows had fewer IGF-I binding sites per cell when compared with control cows. These results suggest involvement of IGF-I in etiology of BLV infection and progression and warrant further studies to establish whether IGF-I plays a major physiological role in these conditions.

Animals↗
PubMed1993

Intelligence function in children with acute lymphoblastic leukemia after treatment.

In order to evaluate the effects of chemotherapy and central nervous system prophylaxis on the intelligence function of children with acute lymphoblastic leukemia (ALL), 147 patients were divided into 2 groups according to their different treatment regimens. Group A included 75 patients with ALL who were diagnosed and treated from 1981 to 1986. Group B included 72 ALL patients diagnosed and treated from 1988 to 1990. A control group included 73 healthy children who shared the same education and environmental background with the patients. Chinese revisions of Wechsler measures of intelligence quotient were used to estimate verbal IQ, performance IQ and total IQ in the 3 groups. American-produced Systate software was used to analyze the data. Results showed that IQ distribution, verbal IQ, performance IQ and total IQ of group A were obviously lower than those in the control group. Verbal IQ and total IQ of group B were also reduced. Significant differences of verbal IQ and performance IQ as well as total IQ were also found between groups A and B. Multiple regression analysis showed negative correlations between IQ and cranial irradiation dosage, times of intrathecal MTX and time after irradiation.

Antineoplastic Combined Chemotherapy Protocols↗