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T Ley

Publications and source records attributed to T Ley.

9 recordsLinked to original sources
PubMed1990

The Psychopathology Instrument for Mentally Retarded Adults. Internal consistencies and relationship to behaviour problems.

The Psychopathology Instrument for Mentally Retarded Adults, a recently developed, empirically derived measure of psychiatric disturbance for the mentally handicapped, gives a total of eight scales which correspond to DSM-III diagnostic categories. This paper reports its psychometric properties in a British population and the psychometric properties of three scales derived by factor analysis. The internal consistencies of the scales were only barely acceptable in this sample and less acceptable than in previous studies.

Humans↗
PubMed1985

5-Azacytidine acts directly on both erythroid precursors and progenitors to increase production of fetal hemoglobin.

The effect of 5-azacytidine on erythroid precursors and progenitors was studied in nine patients with sickle cell anemia or severe thalassemia. Each patient received the drug intravenously for 5 or 7 d. 5-Azacytidine caused a four- to sixfold increase in gamma-messenger RNA concentration in bone marrow cells of eight of the nine patients and decreased the methylation frequency of a specific cytosine residue in the gamma-globin gene promoter in all nine patients. Within 2 d of the start of drug treatment there was a rise in the percentage of reticulocytes containing fetal hemoglobin (HbF; F-reticulocytes) without a significant change in the total number of reticulocytes, which suggested that there was a direct action of 5-azacytidine on erythroid precursors. Late erythroid progenitors (CFU-E), present in bone marrow after 2 d of drug administration, formed colonies containing an increased amount of HbF as compared with control colonies. Moreover, the number of CFU-E derived colonies was not decreased at these early times, which suggested that there was a direct action of 5-azacytidine on erythroid progenitors in the absence of cytotoxicity. Exposure of normal bone marrow cells in tissue culture to 5-azacytidine for 24 h reproduced both of these effects as judged during subsequent colony formation. The combined direct effects of 5-azacytidine on both the erythroid precursor and progenitor compartments resulted in an increase in HbF synthesis that was sustained for 2-3 wk. Toxicity to bone marrow as reflected by cytoreduction was evident after treatment in some patients but was not accompanied by an increase in HbF production. A correlation was found between the effects of 5-azacytidine on bone marrow, as assessed by in vitro measurements, and the hematological response of the individual patients to drug treatment.

Adult↗
PubMed1985

Pharmacologic manipulation of fetal hemoglobin synthesis.

The ease with which HbF production can be increased in subjects with SS disease was a totally unexpected phenomena on the basis of previous models of HbF synthesis. The fact that these drugs induce rapid increases in F cell production and increase HbF per F cell and HbS in non-F cells, may be important clues as to the mechanism of the action of these drugs. It is far from clear whether either one of these agents will be eventually used as therapy for subjects with SS disease. The more recent problems with cytotoxicity illustrated by HU, and the potential carcinogenic effect of 5-aza limit our ability to perform large controlled clinical trials at this time. The observation that HbF production is increased by two agents which perturb DNA replication may be important clues in understanding not only the origins of differential gamma versus beta globin gene expression but also the mechanism by which HbF is restricted to expression in only certain cells during normal erythroid maturation.

Anemia, Sickle Cell↗
PubMed1983

"Silent" nucleotide substitution in a beta+-thalassemia globin gene activates splice site in coding sequence RNA.

A beta+-thalassemia globin gene was isolated from the genome of a Black individual by molecular cloning. DNA sequence analysis revealed only a single difference between this gene and the normal human beta-globin gene--adenine is substituted for thymine in the third position of codon 24. Codon 24 in both the normal gene (GGT) and the beta+-thalassemia gene (GGA) encodes glycine. The function of this beta+-thalassemia gene was compared to the function of the normal human beta-globin gene in monkey kidney cells by using plasmid expression vectors. The codon 24 substitution activates a 5' splice site that involves the guanine-thymine dinucleotide present in codon 25, 16 nucleotides upstream from the normal exon 1-intron I boundary. The splice, involving the abnormal 5' site in codon 25, is completed with the normal 3' splice site at the end of intron I. This splicing abnormality leads to a 75% decrease in the accumulation of normally processed beta-globin mRNA, thereby causing the beta+-thalassemia phenotype.

Base Sequence↗
PubMed1983

"Silent" nucleotide substitution in codon 24 of a beta+ thalassemia globin gene activates splice site in coding sequence RNA.

A beta+-thalassemia globin gene was isolated from the genome of a black patient by molecular cloning. DNA sequence analysis revealed only a single difference between this gene and the normal human beta-globin gene--adenine is substituted for thymine in the third position of codon 24. This mutation is silent at the protein sequence level. We compared the function of this beta+-thalassemia gene with the normal human beta-globin gene in monkey kidney cells using plasmid expression vectors. The codon 24 substitution activates a 5' splice site that involves the guanine-thymine dinucleotide present in codon 25, 16 nucleotides upstream from the normal exon 1-intron I boundary. Splices at the abnormal 5' site in the coding sequence are completed with the normal 3' splice site at the end of intron I. This splicing abnormality leads to a fourfold decrease in the accumulation of normally processed beta-globin mRNA, thereby causing the beta+-thalassemia phenotype.

Base Sequence↗
PubMed1982

Differences in human alpha-, beta- and delta-globin gene expression in monkey kidney cells.

We have compared the function of the human alpha-, beta- and delta-globin genes using various plasmid expression vectors derived from pBR322. Amplification of recombinants occurred after their introduction, by calcium-phosphate-mediated DNA transfer, into monkey kidney cells that constitutively produce T antigen (COS cells). The human alpha-globin gene promoter functioned independently, but the beta-globin gene promoter was nearly totally dependent on the enhancing activity of the 72 bp direct repeats from the SV40 genome. Furthermore, when the human alpha- and beta-globin genes were linked in the same vector, the alpha promoter was active but the beta promoter was not. Function of the delta-globin gene promoter also depended on the enhancer element. In vectors containing the 72 bp repeats and the beta- or delta-globin gene, the activity of the beta-globin gene was approximately 50 times greater than that of the delta-globin gene, approximating the ratio of beta and delta mRNA observed in normal human bone marrow cells.

Animals↗
PubMed1982

Molecular defects in beta-thalassemia.

Our studies have shown that globin-gene structure, as revealed by Southern blot analysis, is normal in most patients who are homozygous for beta-thalassemia. In many, but not all patients, evidence for mutations which alter the metabolism of beta-globin RNA molecules was obtained by several methods of analysis. The most specific and sensitive of these involves the use of single-stranded, highly radioactive probes generated using the M13 cloning system. Such probes allow detection of aberrantly processed RNA molecules by S1 nuclease analysis, thereby providing clues as to the position and nature of mutations within individual thalassemic globin genes. Of greatest potential interest are those genes which provide no evidence, in bone marrow RNA, of aberrantly processed intermediates. Analysis of these genes by molecular cloning and DNA sequencing may lead to identification of sequences which are important for initiation or termination of RNA transcription. Mutations which cause beta-thalassemia continue to provide a rich source of information about the nature of DNA sequences which are essential for efficient gene expression. By study of thalassemic patients, new insights are obtained into normal mRNA metabolism.

Base Sequence↗