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Biomedical subjects

B D Young

Publications and source records attributed to B D Young.

126 records · Page 7Linked to original sources
PubMed1981

High-resolution analysis of human peripheral lymphocyte chromosomes by flow cytometry.

A method for high-resolution analysis of the human karyotype by flow cytometry has been developed. Metaphase chromosomes are prepared from short-term peripheral blood cultures, stained with ethidium bromide, and analyzed on a standard fluorescence-activated cell sorter (FACS-II). Flow karyotypes with up to 20 peaks can be obtained with coefficients of variation in the range 1-2%. At this level of resolution the contribution of many of the human chromosomes can be evaluated separately. Significant and reproducible differences between normal individuals have been detected and have been correlated with differences in the centric heterochromatin of certain chromosomes as revealed in their C-banded karyotypes.

Cell Separation↗
PubMed1981

A new method for the preparation of metaphase chromosomes for flow analysis.

A new method for the preparation of metaphase chromosomes for flow analysis has been evaluated. It has been shown that this method, which involves detergent lysis of metaphase cells and polyamines to stabilize the DNA, yields lower coefficients of variation and background levels in the DNA histograms than is currently obtained by hexylene glycol based methods. A conventional flow cytometer (FACS-II) has been used to resolve the human karyotype into about 14 peaks after ethidium bromide staining and excitation with a relatively low level of illumination (0.4 W at 488 nm). Flow karyotypes have also been obtained from suspension cell lines, in particular from the mouse cell line, Friend 707/B10. The only disadvantage of this method is that the chromosomes are highly condensed and therefore banding studies on sorted chromosomes may not be possible.

Animals↗
PubMed1977

Comparison of the base-sequence complexities of polysomal and nuclear RNAs in growing Friend erythroleukemia cells.

The base-sequence complexities of polysomal poly(A)+ RNA, nuclear poly(A)+ RNA, and total nuclear RNA from Friend erythroleukemia cells in logarithmic phase of growth were determined by measuring the proportion of labeled unique mouse DNA sequences which formed hybrids when incubated with a vast excess of each RNA. It was estimated that the RNAs had been transcribed from 1.8, 7.6, and 8.3%, respectively, of the haploid mouse genome. Although these estimates for polysomal and nuclear poly(A)+ RNAs were 2.5 times greater than those previously determined by analysis of the kinetics of the hybridization reactions between the RNAs and the cDNAs transcribed from them, they confirmed that the base-sequence complexity of nuclear poly(A)+ RNA in these cells is at least four times greater than that of polysomal poly(A)+ RNA.

Base Sequence↗
PubMed1976

A new estimate of human ribosomal gene number.

Radioactively labelled DNAs (5 X 10(6) cpm/mug) complementary to human 18 S and 28 S ribosomal RNA were synthesized using RNA-directed DNA polymerase (EC 2.7.7.7). These complementary DNAs were used to measure human ribosomal gene numbers by two independent methods, both of which indicated numbers at least four-fold lower than those previously reported. First, the kinetics of the annealing of the complementary DNAs with total human placental DNA indicated that the number of both 18-S and 28-S ribosomal genes per haploid genome is approximately 50. Second, saturation experiments in which a constant amount of DNA was annealed with increasing amounts of complementary DNA also indicated that the number of 28 S ribosomal RNA genes in human placental and spleen DNA is is about 50 per haploid genome.

DNA↗
PubMed1976

Synthesis of DNAs complementary to human ribosomal RNAs polyadenylated in vitro.

Conditions are described under which poly(A) polymerase from Escherichia coli ribosomes will catalyse the addition of AMP residues onto the 3'-ends of human 18 S and 28 S ribosomal RNAs at an average rate of 40 AMP residues per 1000 nucleotides in 20 min. Single-stranded complementary DNAs (cDNAs) can then be transcribed from the polyadenylated RNAs with RNA-directed DNA polymerase from avian myeloblastosis virus. All of the sequences in the RNAs are represented in the cDNAs; measurements of the rates at which the cDNAs hybridize with their template RNAs showed that, when appropriate adjustments for differences in lengths and G + C contents of the reacting sequences are taken into account, the Rot 1/2 values of homologous RNA-cDNA hybridization reactions are directly proportional to the base-sequence complexity of the RNAs.

DNA↗
PubMed1976

Complexity and specificity of polysomal poly(A+) RNA in mouse tissues.

Base sequence complexities of polysomal poly(A+)RNA from mouse embryo, brain, and liver have been estimated by hybridization to homologous cDNA to be approximately 7 x 109, 1.5 x 1010, and 7 x109 daltons, respectively. By annealing each cDNA with a large excess of total mouse embryo DNA, the genes coding for the polysomal poly(A+) sequences were shown to be unique. Heterologous hybridization experiments showed that the high abundance class of poly(A+) sequences in one tissue is not identical with the high abundance class in other tissues. However, at least 55%, and possibly more, of the poly(A+) RNA in one tissue is present in the poly(A+) RNA of another tissue.

Animals↗
PubMed1975

A kinetic estimation of base sequence complexity of nuclear poly(A)-containing RNA in mouse Friend cells.

Complementary DNA (cDNA) has been transcribed by viral reverse transcriptase from poly(A)-containing nuclear RNA prepared from growing mouse Friend cells (clone M2). Annealing experiments with this cDNA have demonstrated that a large proportion of the poly(A) tracts in M2 cell nuclear RNA are adjacent to RNA sequences which are transcribed from nonrepetitive DNA in the mouse genome. The kinetics of hybridization of cDNA to template RNA indicate that nuclear poly(A)-containing RNA consists of at least two abundance classes, the more complex of which is transcribed from approximately 3 percent of the genome. Thus there are at least 5 times more unique DNA sequences represented in nuclear polyadenylated RNA than in polysomal polyadenylated RNA. Moreover, there is evidence for posttranscriptional mechanisms which alter the relative concentrations of some (at least) gene transcripts between nucleus and cytoplasm.

Adenine Nucleotides↗
PubMedDate not supplied

Novel chimaeric protein expressed in Philadelphia positive acute lymphoblastic leukaemia.

Cytogenic changes are becoming increasingly important in understanding the pathogenesis of human malignancies. The t(9;22) (q34;q11) translocation is one of the most consistent and generates the Philadelphia chromosome (Ph1) (ref. 1) in chronic myeloid leukaemia (CML); it has also been observed in some acute lymphoblastic leukaemias (ALL) (ref. 2). In CML the breakpoints occur on chromosome 22 in the region designated bcr (ref. 3) and result in the expression of a bcr-abl fusion product of relative molecular mass (MT) 210,000 (210K) with associated in vitro tyrosine kinase activity (P210bcr-abl). In some cases of Ph1-positive ALL, a novel abl-related protein (P190all-abl) of 190K has been shown to have tyrosine kinase activity. In this report we demonstrate that the P190all-abl protein has a bcr determinant from the amino-terminal region, but is lacking a bcr determinant normally found in the P210bcr-abl near the bcr-abl junction. The chimaeric nature of the P190all-abl was confirmed by sequential immunoprecipitation with antisera against abl and bcr peptides.

Cell Line↗
PubMedDate not supplied

Molecular abnormalities in leukemia: the 11q23 story so far.

Various hematopoietic malignant disorders have been shown to bear chromosome abnormalities of the 11q23 band, which can be rearranged with many different chromosomal regions in a wide variety of different leukemia subtypes. Several laboratories have identified a trithorax-related gene that is involved in most of the 11q23 abnormalities. Although some patterns and associations between the partner genes are beginning to emerge, it is not yet possible to frame a single unifying hypothesis for 11q23 leukaemic transformation. The aim of this review is to summarise the recent data concerning these 11q23 rearrangements and the understanding of their consequences.

Chromosomes, Human, Pair 11↗