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Biomedical subjects

O J Miller

Publications and source records attributed to O J Miller.

At least 73 records · Page 4Linked to original sources
PubMed1981

Amplified ribosomal RNA genes in a rat hepatoma cell line are enriched in 5-methylcytosine.

In a rat hepatoma cell line, H4-IIE-C3, a 10-fold excess of 18S and 28S rRNA genes has been found in amplified chromosome regions. Antibodies to 5-methylcytidine bound extensively to the DNA of these regions, indicating a high level of DNA methylation. Most of the amplified rRNA genes were transcriptionally inactive, as shown by their failure to stain with silver. DNAs from the tumor cells and control rat hepatocytes grown with L-[methyl-14C]methionine were digested with restriction endonuclease EcoRI; the DNA fragments were separated by agarose gel electrophoresis, denatured, transferred to nitrocellulose filters, and hybridized to 32P-labeled rRNA or cDNA. Fragments containing the 18S or 28S rRNA coding sequences occurred in three major size classes; all three were rich in 5-methylcytosine. Analysis of EcoRI fragments of DNA from the tumor and control cells after digestion with Hpa II or Msp I endonuclease indicated that the 5'-C-C-G-G-3' sequences in most of the amplified rRNA genes were methylated. Analysis of the fragments produced by digestion with Hha I endonuclease indicated a high degree of methylation within its recognition sequence in the amplified rRNA genes as well. The association of hypermethylation with restricted transcriptional activity suggests that DNA methylation may regulate the activity of the rRNA genes.

5-Methylcytosine↗
PubMed1980

H-Y antigen in 46,XY gonadal dysgenesis.

Presence of H-Y antigen has been correlated with testicular differentiation, and absence of H-Y with failure of testicular differentiation, in a variety of mammalian species. To determine more precisely the relationship between expression of H-Y antigen and development of the testis, we studied the cells of phenotypic females with the 46,XY male karyotype. Blood leukocytes were typed H-Y+ in five XY females with gonadal dysgenesis, although in other studies blood leukocytes from XY females with gonadal dysgenesis were typed H-Y-. Thus mere presence of H-Y antigen is not sufficient to guarantee normal differentiation of the testis. In the present paper we review evidence for an additional factor in gonadal organogenesis, the H-Y antigen receptor. We infer that testicular development requires engagement of H-Y and its receptor. It follows that XY gonadal dysgenesis is the consequence of functional absence of the H-Y testis inducer as in the following conditions: failure of synthesis of H-Y or failure of specific binding of H-Y.

Adolescent↗
PubMed1980

The organization of DNA in the mitotic and polytene chromosomes of Sciara corprophila.

The organization of DNA in the mitotic metaphase and polytene chromosomes of the fungus gnat, Sciara coprophila, has been studied using base-specific DNA ligands, including anti-nucleoside antibodies. The DNA of metaphase and polytene chromosomes reacts with AT-specific probes (quinacrine, DAPI, Hoechst 33258 and anti-adenosine) and to a somewhat lesser extent with GC-specific probes (mithramycin, chromomycin A3 and anti-cytidine). In virtually every band of the polytene chromosomes chromomycin A3 fluorescence is almost totally quenched by counterstaining with the AT-specific ligand methyl green. This indicates that GC base pairs in most bands are closely interspersed with AT base pairs. The only exceptions are band IV-8A3 and the nucleolus organizer on the X. In contrast, quinacrine and DAPI fluorescence in every band is only slightly quenched by counterstaining with the GC-specific ligand actinomycin D. Thus, each band contains a moderate proportion of AT-rich DNA sequences with few interspersed GC base pairs. - The C-bands in mitotic and polytene chromosomes can be visualized by Giemsa staining after differential extraction of DNA and those in polytene chromosomes by the use of base-specific fluorochromes or antibodies without prior extraction of DNA. C-bands are located in the centromeric region of every chromosome, and the telomeric region of some. The C-bands in the polytene chromosomes contain AT-rich DNA sequences without closely interspered GC base pairs and lack relatively GC-rich sequences. However, one C-band in the centromeric region of chromosome IV contains relatively GC-rich sequences with closely interspersed AT base pairs. - C-bands make up less than 1% of polytene chromosomes compared to nearly 20% of mitotic metaphase chromosomes. The C-bands in polytene chromosomes are detectable with AT-specific or GC-specific probes while those in metaphase chromosomes are not. Thus, during polytenization there is selective replication of highly At-rich and relatively GC-rich sequences and underreplication of the remainder of the DNA sequences in the constitutive heterochromatin.

Animals↗
PubMed1980

5-methylcytosine in the DNA of the polytene chromosomes of the diptera Sciara coprophila, Drosophila melanogaster and D. persimilis.

5-Methylcytosine has been detected in the DNA of the polytene chromosomes of Sciara coprophila, Drosophila melanogaster and D. persimilis, using specifically purified antibodies to 5-methylcytidine. The 5-methylcytosine is present in GC-rich sequences in the bands. Virtually no 5-methylcytosine is detectable in mitotic metaphase chromosomes of S. coprophila. Thus, methylation is associated with polytenization in these diptera. Restriction enzyme studies using HpaII, MspI, HhaI and AluI indicate that unmethylated 5'-CCGG-3', 5'-GCGC-3' and 5'-AGCT-3' sequences are abundant in polytene chromosome DNA. These sequences are probably not major sites of methylation. Since the DNA in the bands of polytene chromosomes is generally transcriptionally inactive, as well as extensively methylated, these results are consistent with the hypothesis that genes in the bands have been inactivated by a process involving DNA methylation.

5-Methylcytosine↗
PubMed1979

Marked increase in ribosomal RNA gene multiplicity in a rat hepatoma cell line.

An H4-IIE-C3 hepatoma cell line derived from an ACI rat has been shown to have differentially stained regions attached to the short arms of chromosomes 3, 11 and 13 and the long arm of an unidentified small chromosome. There is cell to cell variability in the number and size of the differentially stained regions, which contain, on the average, about 5% of the total DNA. A series of secondary constrictions occur at intervals along the length of each differentially stained region. These stain with silver by the Ag-AS method, indicating that the differentially stained regions contain sites of active 45S ribosomal precursor RNA transcription. In situ hybridization to metaphase chromosomes shows that the hepatoma cells have a 10 fold increase in DNA coding for 18S and 28S ribosomal RNA, 90% of it located in the differentially stained regions, and no change in the number of genes coding for 5S RNA. These results have been confirmed by filter disc hybridization.

Animals↗
PubMed1979

Sexual and somatic determinants of the human Y chromosome: studies in a 46,XYp- phenotypic female.

A case of a 46,XYp- phenotypic female provided an opportunity to evaluate both sexual and somatic determinants for the Y chromosome. The patient had multiple stigmata of Turner syndrome, but normal stature. Laparotomy revealed a normal uterus and tubes, with 1.5 cm undifferentiated gonads. Serological tests for H-Y antigen (ostensibly the product of Y-chromosomal testis-determining genes) indicated absence of the H-Y+ phenotype normally associated with the intact Y chromosome. We conclude that genes exist on the short arm of the human Y chromosome which both suppress some of the somatic stigmata of Turner syndrome and determine normal expression of H-Y antigen and testicular differentiation of the primitive gonad. Our data are consistent with the view that H-Y genes comprise a family of testis-determinants, and that loss of a critical moiety is inconsistent with normal development of the male gonad.

Body Height↗
PubMed1978

Spreading of inactivation in an (X;14) translocation.

In the KOP translocation, t(X;14)(q13;q32), virtually the entire long arm of the X has been translocated to the end of the long arm of chromosome 14. Meiotic secondary nondisjunction in a female balanced carrier of the translocation has led to a son with two der(14) or 14-X chromosomes. The normal X chromosome is late replicating in the mother. One of the two 14-X chromosomes is late replicating in the son, with heavy terminal labeling of all but the centromeric end of the chromosome. This suggests that genetic inactivation has spread from the Xq segment of the translocation chromosome to at least two thirds of the segment derived from chromosome 14, and that the remaining proximal segment of chromosome 14 is possibly still genetically active. These findings provide an explanation for the phenotype: Klinefelter syndrome plus a few mild malformations that are sometimes seen in this syndrome but are also seen in duplication of the proximal portion of chromosome 14. Although the proband has a duplication of virtually an entire chromosome 14, 14(pter leads to q32), the phenotypic effect of the autosomal duplication has been mostly nullified by the spread of inactivation.

Centromere↗
PubMed1978

Human semen as a source of epithelial cells for culture.

When washed cells from human semen samples were plated out, epithelial cultures were obtained. The human ejaculates used as starting material contained, in addition to spermatazoa, 10(3) to 10(7) cells of other types, including granulocytes, macrophages, lymphocytes, spermatocytes and epithelial cells. Although no fractionation of cell types was attempted, semen samples yielded epithelial cultures uncontaminated by fibroblasts. The cultured cells appeared characteristically epithelial with a polygonal shape, interdigitating cell membranes, and desmosomes. ABH blood-group antigenic determinants of the donor were expressed with variable frequency as a surface antigen on these cells. About half the trials gave some cell attachment. Most cultures remained as small, tight colonies, but a few reached confluency in about 5 weeks and could be subcultured successfully. Cell proliferation, as monitored by (3H) thymidine incorporation into nuclear macromolecules, ceased in less than 2 months.

Antigens, Surface↗