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S G Ballard

Publications and source records attributed to S G Ballard.

6 recordsLinked to original sources
PubMed1992

Two diverged human homeobox genes involved in the differentiation of human hematopoietic progenitors map to chromosome 1, bands q41-42.1.

Proteins encoded by homeobox containing genes are sequence-specific DNA binding proteins implicated in the control of gene expression in both developing and adult tissues. Two recently characterized human homeobox genes, HB9 and HB24, are highly expressed in CD34-positive marrow cells but not in CD34-depleted marrow cells. Their expression is readily down-regulated during the differentiation of hematopoietic progenitors to specific cell lineages. In this study, genomic DNA fragments isolated with HB9 (3 kb) and HB24 (6 kb) cDNAs were used to map their chromosomal location by fluorescence in situ hybridization. Both HB9 and HB24 DNA probes gave specific hybridization signals on chromosome 1. The hybridization loci were identified by combining fluorescence images of the probe signals with fluorescence banding patterns generated by cohybridization in situ with an Alu probe (R-like banding) and by DAPI staining (G-like). The results demonstrate that the loci of the HB24 and HB9 genes are within bands 1q41-q42.1. A cohybridization experiment utilizing both probes with two-color fluorescence imaging could not resolve separate loci for the two genes.

Cell Differentiation↗
PubMed1992

The gene for human erythrocyte protein 4.2 maps to chromosome 15q15.

Protein 4.2 (P4.2), one of the major components of the red-blood-cell membrane, is located on the interior surface, where it binds with high affinity to the cytoplasmic domain of band 3. Individuals whose red blood cells are deficient in P4.2 have osmotically fragile, abnormally shaped cells and moderate hemolytic anemia. cDNA clones from both the 5' and the 3' coding regions of the P4.2 gene were used to map its chromosomal location by fluorescence in situ hybridization. The probes, individually or in combination, gave specific hybridization signals on chromosome 15. The hybridization locus was identified by combining fluorescence images of the probe signals with fluorescence banding patterns generated by Alu-PCR (R-like) probe and by DAPI staining (G-like). Our results demonstrate that the locus of the P4.2 gene is located within 15q15.

Biotin↗
PubMed1990

Differential distribution of long and short interspersed element sequences in the mouse genome: chromosome karyotyping by fluorescence in situ hybridization.

Fluorescence in situ hybridization has been used to demonstrate the differential distribution of interspersed repetitive elements in the genome of Mus musculus domesticus. Hybridization with a mouse long interspersed element sequence results in a sharp, highly reproducible banding pattern on metaphase chromosomes, which is quite similar to Giemsa banding for all chromosomes except 7 and X. The families of short interspersed elements, B1 and B2, preferentially cluster in the R, or reverse, bands. There is no evidence of any interspersed repeat present in the centromeric heterochromatic regions. Both the long interspersed element and B2 probes give banding patterns suitable for karyotype analysis. Simultaneous hybridization of the biotinylated long interspersed element probe and a digoxigenin-labeled cosmid to metaphase spreads allows rapid localization of a probe of interest to a particular cytogenetic band on a chromosome.

Animals↗
PubMed1978

Photo-initiated ion formation from octaethyl-porphyrin and its zinc chelate as a model for electron transfer in reaction centers.

Ion formation from the reaction of triplet (T) and ground state (P) octaethyl-porphyrin (OEP) and zinc octaethyl porphyrin (ZnOEP) and the corresponding cross-reactions have been measured in dry acetonitrile. A uniquely sensitive and fast conductance apparatus and a pulsed dye laser allowed the measurements to be made at the necessarily very low concentrations of T. The hemogeneous reaction of T (ZnOEP) and P (ZnOEP) occurs with rat constant k(1) = 2.0 x 10(8) M(-1)s(-1) and an ion yield of 67%. The similar homogeneous reaction of OEP has k(2) = 1.3 x 10(8)M(-1)s(-1) but an ion yield of only 3%. The cross-reaction of T (OEP) with P (ZnOEP) has k(3) = 1.5 x 10(8) M(-1)s(-1) and an ion yield of 27%, while the inverse cross-reaction of T (ZnOEP) with P (OEP) has k(4) = 3 x 10(8) M(-1)s(-1) and an ion yield of 20%. Thus, the rate constants are only slightly affected but the yields are sensitive to the porphyrin. The possible formation of the heterogeneous ions ZnOEP+ + OEP-, thermodynamically favored by 0.3 V over the homogeneous ions, has little influence on the observed yields. The data are explained by electron transfer and Coulomb field-electon spin-controlled escape of the initial ion-pair.

Electric Conductivity↗