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Biomedical subjects

S Luo

Publications and source records attributed to S Luo.

At least 181 records · Page 10Linked to original sources
PubMed1994

The severe phenotype of females with tiny ring X chromosomes is associated with inability of these chromosomes to undergo X inactivation.

Mental retardation and a constellation of congenital malformations not usually associated with Turner syndrome are seen in some females with a mosaic 45,X/46,X,r(X) karyotype. Studies of these females show that the XIST locus on their tiny ring X chromosomes is either not present or not expressed. As XIST transcription is well correlated with inactivation of the X chromosome in female somatic cells and spermatogonia, nonexpression of the locus even when it is present suggests that these chromosomes are transcriptionally active. We examined the transcriptional activity of ring X chromosomes lacking XIST expression (XISTE-), from three females with severe phenotypes. The two tiny ring X chromosomes studied with an antibody specific for the acetylated isoforms of histone H4 marking transcribed chromatin domains were labeled at a level consistent with their being active. We also examined tow of the XISTE- ring chromosomes to determine whether genes that are normally silent on an inactive X are expressed from these chromosomes. Analyses of hybrid cells show that TIMP, ZXDA, and ZXDB loci on the proximal short arm, and AR and PHKA1 loci on the long arm, are well expressed from the tiny ring X chromosome lacking XIST DNA. Studies of the ring chromosome that has XIST DNA but does not transcribe it show that its AR allele is transcribed along with the one on the normal X allele.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylation↗
PubMed1993

Deficient transcription of XIST from tiny ring X chromosomes in females with severe phenotypes.

The severe phenotype of human females whose karyotype includes tiny ring X chromosomes has been attributed to the inability of the small ring X chromosome to inactivate. The XIST locus is expressed only from the inactive X chromosome, resides at the putative X inactivation center, and is considered a prime player in the initiation of mammalian X dosage compensation. Using PCR, Southern blot analysis, and in situ hybridization, we have looked for the presence of the XIST locus in tiny ring X chromosomes from eight females who have multiple congenital malformations and severe mental retardation. Our studies reveal heterogeneity within this group; some rings lack the XIST locus, while others have sequences homologous to probes for XIST. However, in the latter, the locus is either not expressed or negligibly expressed, based on reverse transcription-PCR analysis. Therefore, what these tiny ring chromosomes have in common is a level of XIST transcription comparable to an active X. As XIST transcription is an indicator of X chromosome inactivity, the absence of XIST transcription strongly suggests that tiny ring X chromosomes in females with severe phenotypes are mutants in the X chromosome inactivation pathway and that the inability of these rings to inactivate is responsible for the severe phenotypes.

Adolescent↗
PubMed1993

DNA methylation of the fragile X locus in somatic and germ cells during fetal development: relevance to the fragile X syndrome and X inactivation.

To obtain insights into mechanisms responsible for methylation of CpG islands on the inactive X chromosome of normal females, we examined methylation of the fragile X (FraX) locus in a variety of tissues from normal fetuses and adults, and from males with the FraX syndrome. We identified 20 CCGG sites (MspI-HpaII sites M1-M20) within a 12-kb BglII fragment that includes the CpG island. Sites M3-M18, within the 1.2-kb CpG island are unmethylated on the active X in normal males and females at all ages and in all tissues studied. In contrast, these sites are at least partially methylated on the inactive X chromosome in a variety of tissues from normal females by six weeks from conception. The exceptional tissues are chorionic villi and gonads, which are significantly undermethylated. In addition, fetal germ cells are unmethylated at site M3, which is methylated on the inactive X in other tissues; thus, the methylation imprint of the inactive X has been erased. Methylation of the locus on the fragile X chromosome is similar to that of the normal inactive X but is more extensive and less heterogeneous. This suggests that the expansion of the island and the greater number of CpGs that result from amplification of the CGG repeat enhance the methylatibility of the island. Additional studies show that the chromatin of the CpG island is nuclease hypersensitive on the active X but insensitive on both inactive and FraX.

Adult↗
PubMed1993

Buspirone-induced carbohydrate feeding is not influenced by route of administration and nutritional status.

Rats were habituated to ad lib food intake from two isoenergetic diets that differed in carbohydrate and protein content. To examine the route of administration effect, buspirone (0.6, 1.0, and 1.4 mg/kg) was injected into satiated rats either subcutaneously or intraperitoneally. Overall, no route of administration effect was observed; however, when results of the lowest dose were analyzed separately, the subcutaneous route was more effective than the intraperitoneal route. Regardless of route of administration, buspirone increased food intake over the first 2 h of food presentation in a dose-dependent manner. Moreover, the increase was entirely attributed to increases in intake from the high carbohydrate diet. In the subsequent experiment, the effect of buspirone (0.6 mg/kg) was examined in both satiated (early light period) and nonsatiated rats (early dark period). Both groups responded to buspirone with an increase in carbohydrate intake. Despite differences in baseline intake, the absolute increase was similar between satiated and nonsatiated rats. These data suggest that both sensitivity and selectively of buspirone-induced feeding are neither influenced by route of administration nor nutritional status of rats.

Animals↗
PubMed1993

Developmental and cAMP-mediated regulation of glycogen phosphorylase 1 in Dictyostelium discoideum.

The Dictyostelium discoideum glycogen phosphorylase-1 (gp-1) exhibits a complex pattern of developmental expression in which differential temporal regulation of enzyme activity, protein levels and mRNA levels is observed. This pattern of expression implies that gp-1 regulation occurs at multiple levels, probably involving both transcriptional and post-transcriptional events. Post-translational control of gp-1 activity, in effect, actually regulates the protein from a developmental perspective. In this report we have examined several facets of this regulation. We show that addition of exogenous cAMP to cells in suspension culture caused changes in gp-1 enzyme activity and mRNA levels that are identical to those observed during normal development, suggesting that cAMP is involved in the regulation of gp-1. Exogenous cAMP could regulate gp-1 mRNA expression at concentrations as low as 1.0 microM. cAMP regulation of gp-1 mRNA appeared to occur through a mechanism that required intracellular cAMP signalling. We identified regions of the promoter necessary for gp-1 expression by using gp-1 promoter deletions to drive the expression of a luciferase reporter gene. Results of these experiments suggested that developmental and cAMP-mediated changes in gp-1 mRNA levels were the result of alterations in transcription. The promoter analysis also suggested that a vegetative specific element is located between -785 and -1894 nucleotides from the transcriptional start site. Elements necessary for maximal developmental and cAMP-mediated expression appear to be located between -1153 and -1894 nucleotides from the cap site. Sequence elements located between -180 and -1153 appear to be required for a basal level of late developmental expression.

Animals↗
PubMed1993

[Pathologic observation of 298 rat mesotheliomas induced by asbestos].

Two hundred and ninety eight rat mesotheliomas induced by chrysotile or crocidolite were studies. The results demonstrated that tumor masses were scattered extensively. The appearance of tumor was polymorphous. According to the microscopic features, the 298 cases of mesothelioma could be histologically classified into three types, i.e. epithelial type, fibrous type and mixed cell type. The malignant mesothelioma is characteristic of its polymorphism and the clear cancernation of mesothelial cells.

Animals↗
PubMed1992

Characterization and cloning of glycogen phosphorylase 1 from Dictyostelium discoideum.

We have cloned cDNA and genomic DNA fragments from Dictyostelium discoideum that represent the entire coding region of glycogen phosphorylase 1 (gp1, alpha-D-glucosyltransferase, EC 2.4.1.1). Nucleic acid sequencing of the gp1 clones revealed a single 139 bp intron separating the two exons that encode the 853 amino acids of gp1. The gp1 sequences are similar to other genes and proteins described for Dictyostelium in terms of G + C composition of coding and noncoding regions, splice junctions, intron length, codon preference and termination signals. Genomic Southern blot hybridizations suggest that gp1 exists as a single or low copy number gene in Dictyostelium. Northern analyses demonstrate that gp1 is a developmentally regulated transcript. In alignments of the gp1 peptide sequence to glycogen phosphorylase sequences from other organisms, a high degree of amino acid conservation at many active and regulatory sites was found; however, critical residues in the AMP and purine binding sites were not conserved.

Amino Acid Sequence↗
PubMed1992

Cloning, structural analysis, and expression of the glycogen phosphorylase-2 gene in Dictyostelium.

The glycogen phosphorylase-2 (GP2) activity that appears during the cell differentiation of Dictyostelium was purified to homogeneity. The molecular weight of the nondenatured enzyme was 200,000 as determined by Sephacryl S-300 gel filtration and was 107,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, suggesting that the native enzyme consists of two similar subunits. The intact protein was digested with trypsin and protease V8, and the resulting peptides were purified by microbore high pressure liquid chromatography. The peptides were sequenced, and oligonucleotides were constructed for polymerase chain reaction amplification of the GP2 gene from Dictyostelium genomic DNA template. The resulting polymerase chain reaction products were sequenced directly and were confirmed to encode portions of the GP2 gene. These fragments were used to probe a partial EcoRI genomic library for the remainder of the GP2 gene. The nucleotide sequence of the GP2-selected clones revealed an open reading frame of 2975 base pairs that was interrupted by two introns of 109 and 105 base pairs, respectively. The open reading frame encoded a protein of 992 amino acids with a calculated molecular mass of 112,500 Da and an isoelectric point of 6.4. An unusual sequence within the second exon of GP2, in which the triplet CAA was repeated 11 times, resulted in 11 in-frame glutamine residues of a possible 15 amino acids coded for by this region. The CAA repeat was transcribed, as shown by the sequence of cDNA. Comparison of the amino acid sequence of Dictyostelium GP2 to the phosphorylases from other organisms revealed that the Dictyostelium protein was 50 and 44% identical to yeast and rabbit muscle phosphorylases, respectively. Northern blot analysis showed that GP2 mRNA was absent in amebas and the early stages of development, reached a maximum level of expression at the slug stage, and then decreased in the terminal stages of development. Comparison of the mRNA expression with the appearance of GP2 enzyme protein and enzyme activity revealed that gp2 mRNA and a 113-kDa GP2 enzyme peptide were expressed concurrently at 10 h of development. However, enzyme activity did not appear until 18 h, coincident with a decrease in the level of the 113-kDa peptide and a corresponding increase in the amount of a 106-kDa GP2 peptide. Addition of cAMP to aggregation-competent cells in liquid culture resulted in the induction of GP2 mRNA, GP2 protein, and GP2 enzyme activity.

Amino Acid Sequence↗
PubMed1992

Effect of 5-HT agonists on rats fed single diets with varying proportions of carbohydrate and protein.

Low doses of 5-HT agonists have been shown to selectively suppress carbohydrate intake in rats given dietary choices. To investigate further the relationship between dietary macronutrient composition and 5-HT-induced anorexia, the present study examined the effects of three 5-HT agonists on rats fed single isocaloric diets containing varying proportions of carbohydrate (CHO) and protein (PRO). Rats were habituated to eat one of the three diets (73.5% CHO--10% PRO, 58.5% CHO--25% PRO or 43.5% CHO--40% PRO) during the dark period (1900-0700 h). Saline or 5-HT agonists (fluoxetine, RU 24969 and dexfenfluramine) were administered intraperitoneally at 1845 hours, 15 min prior to food access. At the doses used, food intake was significantly affected only during the first hour of eating. All 5-HT agonists caused dose-dependent decreases in food intake (P < 0.01). The magnitude of decrease, however, was significantly influenced by diet composition. Reduction in intake was greatest in rats fed the 73.5% CHO--10% PRO diet. Thus, rats chronically fed a diet high in carbohydrate content were more sensitive to the anorectic effect of 5-HT agonists than rats fed diets containing moderate to low levels of carbohydrate.

Animals↗
PubMed1992

The electrode system in impedance-based ventilation measurement.

In this paper, we determined which electrode types, sizes, and locations were best suited for impedance-based ventilation measurement. Optimal electrodes provide high signal-to-(motion) artifact ratio (SAR) and reliability by meeting the following criteria: 1) low baseline impedance, 2) high adhesion, 3) good physical stability, 4) large effective area, 5) thin with high flexibility. We compared 14 electrodes from two main groups: adhesive-gel and conductive rubber electrodes. Adhesive-gel electrodes are easy to apply, make good body contact, and do not slip during the course of an experiment. We found that higher SAR's are obtained when electrode area is increased by connecting several small electrodes together rather than by using a single electrode with a larger area. The peak SAR is achieved when two electrode arrays (area = 70 cm2) are centered at the 8th intercostal spaces on opposite midaxillary lines. To determine the optimal electrode locations, we placed 32 electrodes on the trunk and recorded impedance between 171 electrode combinations on ten normal adult subjects. Based on these data, we conclude that the SAR's are highest when one electrode is placed on the midpoint between the left and right second intercostal spaces on the sternum and the other electrode is placed in the opposite position on the back.

Adult↗
PubMed1992

[Determination of naphthoquinone in zicao].

A TLC-spectrophotometric method for the separation and determination of the naphthoquinones in Zicao is described. The sample solution was applied at a point 1 cm from the bottom edge of a silica gel G plate. A mixture of n-hexane-acetone-chloroform-glacial acetic acid was used as the developing solvent. The plate was saturated for 30 min and developed. The spots were scraped and extracted with chloroform for spectrophotometric determination at 523nm. The method has been applied to the analysis of different samples.

Chromatography, Thin Layer↗
PubMed1992

[Observation of the morphological genesis of pleural mesothelioma induced by asbestos in rats].

In order to observe the lesions of pleural mesothelia caused by asbestos, we injected asbestos fiber into the pleural cavity of Wistar rats. The result showed that there Was an obvious process for the morphological genesis of mesothelioma. Simple hyperplasia and stratified pleomorphic hyperplasia of mesothelial cells were found on the 30th and 106th day after the injection of asbestos fiber, respectively. The benign and malignant mesotheliomas were noted on the 300th day. Meanwhile, a two-way differentiation may be observed in the process of mesothelial hyperplasia.

Animals↗
PubMed1991

[Chemical constituents of the aerial parts of six species of Bupleurum genus medicinally used in south-west region of China].

The chemical constituents of the aerial parts of six species of Bupleurum genus (B. kunmingense, B. polyclonum, B. wenchuanense, B. longicaule var. franchetii, B. rockii and B. chaishoui) medicinally used in south-west region of China have been investigated with the results of obtaining eight flavonoid compounds and six triterpenoid saponins. The aglycones of these eight flavonoid compounds are quercetin and isorhamnetin, which are different from the aglycones of the flavonoid compounds isolated from the aerial parts of B. chinense, the official species in Chinese Pharmacopoeia. In the latter case, the aglycone is kaempferol. This difference may be of chemotaxonomic value in Bupleurum genus.

Antiviral Agents↗
PubMed1991

[A control study of some hair trace elements content of schizophrenics before and after treatment].

This is a comparative survey of hair trace elements of 69 schizophrenics matched with normals, the result of which is summarized as follows: It was found that the hair Cu Fe Mg in all patients and Mn in females had significantly lower quantities than normals, in addition to which no significant difference of CU/ZN ratio was found between the patients and the normals and there were no significant differences of hair Cu Fe Mn Zn Mg in schizophrenics before and after chlorpromazine treatment. The hair Fe Mn in recovered group were significantly higher than the improved group, it was probably related to the former had more patients with extrapyramidal symptoms than the later. That was coincident with the hair Fe was increased significantly in the patients with extrapyramidal symptoms of study group after Chlorpromazine treatment. The authors suggest the need for further study on the theory of Parkinson-like Syndrome could probably be related to free-radical formation.

Adolescent↗