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M L Pardue

Publications and source records attributed to M L Pardue.

At least 91 records · Page 5Linked to original sources
PubMed1977

Localization of sequences coding for histone messenger RNA in the chromosomes of Drosophila melanogaster.

In situ hybridization of sea urchin (Psammechinus miliaris, Lytechinus pictus and Strongylocentrotus purpuratus) histone messenger RNA has been used to map complementary sequences on polytene chromosomes from Drosophila melanogaster. The sea urchin RNA hybridizes to the polytene regions from 39D3 through 39E1-2, including both of these bands (39D2 may also be included). This region is identical to the one which hybridizes most heavily with non-polyadenylated cytoplasmic RNA from D. melanogaster tissues. Sea urchin mRNAs coding for several individual histones each hybridize across the entire region from 39D3 (or D2) through 39E1-2, as would be expected if the individual mRNA sequences are interspersed. In view of the apparently even distribution of sequences complementary to histone mRNA within the 39D3-39E1-2 region, the significance of the several polytene bands in this region remains an open question. Biochemical characterization of the hybrids between sea urchin histone mRNA and D. melanogaster DNA suggest that sea urchin mRNAs for several of the histone classes have some portions which retain enough sequence homology with the D. melanogaster sequences to form hybrids, although the hybrids have base pair mismatches. In situ hybridization of chromosomes in which region 39-E is ectopically paired show no evidence of seqence homology in the chromosome region with which 39D-E is associated.

Animals↗
PubMed1977

Ecdysone-stimulated RNA synthesis in salivary glands of drosophila melanogaster: assay by in situ hybridization.

3H-RNA was isolated from nuclei and cytoplasm of Drosophila melanogaster larval salivary glands after labeling in organ culture in the presence or absence of ecdysone. Hybridization to the sites of the ecdysone-induced puffs 74EF and 75B could be detected only if the RNA was labeled in the presence of ecdysone, while hybridization to the ecdysone-repressed puff 68C was found primarily in the cytoplasmic RNA sample labeled in the absence of ecdysone. Hybridization at the site of an ecdysone-insensitive puff, 50CD, was readily detectable in all RNA samples. RNA hybridizing to the unpuffed region 60D seemed to be restricted to the nucleus of salivary gland cells and was present at only a low level in cytoplasmic RNA samples. The data indicate that in situ hybridization can be used to detect specific hormone-induced changes in transcription.

Cell Nucleus↗
PubMed1977

Polytene chromosome puffing and in situ hybridization measure different aspects of RNA metabolism.

Direct autoradiography of Drosophila melanogaster polytene chromosomes which have incorporated 3H-uridine suggests that the chromosomal puffs are the most active sites of incorporation; that the puffs are not the only sites of incorporation; and that there are sites which do not incorporate at all. In situ hybridization of 3H-RNA from salivary gland nuclei labels all three types of chromosomal sites. Labeling by in situ hybridization is not proportional to labeling by direct autoradiography. The differences may be explained by several models. Nuclear RNA of salivary glands probably contains transcripts from multiply repeated genes; these transcripts may hybridize to many chromosomal sites. The data furthermore suggest that the phenomenon of puffing may not be a simple reflection of transcription rate, since several puffs hybridize RNAs with quite different metabolic characteristics.

Autoradiography↗
PubMed1976

Ecdysone-stimulated RNA synthesis in imaginal discs of Drosophila melanogaster. Assay by in situ hybridization.

Cytoplasmic RNA from imaginal discs of Drosophila melanogaster, labeled by uridine incorporation in organ culture, has been assayed by hybridization to cytological preparations of polytene chromosomes. RNA labeled during the early stages (first four hours) of ecdysone stimulation was compared to RNA labeled in the absence of the hormone. For the poly(A)-containing fraction (oligo-dT bound), several loci hybridize only RNA labeled in the presence of ecdysone; one locus hybridizes only control RNA. The majority of hybridizing loci are unaffected by the hormone. Of the loci hybridizing RNA not bound to oligo-dT, several appear specific for the ecdysone-treated sample, though most are labeled more heavily with this RNA than with the control. None of the ecdysone-sensitive loci visualized by in situ hybridization are the sites of salivary gland puffs induced by ecdysone on the same time scale.

Animals↗
PubMed1976

The effect of heat shock on RNA synthesis in Drosophila tissues.

Total RNA from Drosophila imaginal discs, labeled under conditions of heat shock, is analyzed by hybridization in situ to salivary gland polytene chromosomes. Grain densities over the hybridizing bands are compared, showing that the response to heat shock is similar for several disc types and fly stocks. Alteration of the culture medium used for labeling during heat shock results in the specific induction (in discs, salvary glands, or fat body) of one of the heat-shock loci to a level far beyond that normally seen. We discuss the implications of this specific induction regarding the mechanism of response. We also discuss the observed difference between transcription labeling of salivary gland chromosomes and labeling by in situ hybridization.

Culture Media↗
PubMed1976

Electron microscopy of DNA crosslinked with trimethylpsoralen: test of the secondary structure of eukaryotic inverted repeat sequences.

It has been suggested that inverted repeat (palindrome) sequences, which are widespread in eukaryotic genomes, exist in two alternate configurations, a linear form and a cruciform. To investigate the relative frequency of these forms, the DNA of intact mouse tissue culture cells was covalently crosslinked with 4,5',8-trimethylpsoralen (me3-psoralen) in order to prevent rearrangement of the DNA secondary structure during DNA isolation. The distribution of me3-psoralen crosslinks was determined by electron microscopy after denaturation of the DNA in the presence of glyoxal. Because of the high frequency and the relatively uniform distribution of the me3-psoralen crosslinks, it could be concluded that almost all of the inverted repeat sequences had been crosslinked. In spite of this, no significant number of cruciforms was detected by electron microscopy. To determine whether the me3-psoralen might itself be disrupting cruciform structures, cruciforms were first produced in isolated Tetrahymena rDNA by heat treatment and then crosslinked in vitro. The crosslinking was found to stabilize rather than disrupt these cruciforms. We conclude that the inverted repeat sequences of the mouse tissue culture cells we tested are predominantly in linear forms rather than in cruciform structures inside the cell.

Base Sequence↗
PubMed1975

Distribution of 18+28S ribosomal genes in mammalian genomes.

In situ hybridization with 3H 18S and 28S ribosomal RNA from Xenopus laevis has been used to study the distribution of DNA sequences coding for these RNAs (the nucleolus organizing regions) in the genomes of six mammals. Several patterns of distribution have been found: 1) A single major site (rat kangaroo, Seba's fruit bat), 2) Two major sites (Indian muntjac), 3) Multiple sites in centromeric heterochromatin (field vole), 4) Multiple sites in heterochromatic short arms (Peromyscus eremicus), 5) Multiple sites in telomeric regions (Chinese hamster). - The chromosomal sites which bind 3H 18S and 28S ribosomal RNA correspond closely to the sites of secondary constrictions where these are known. However, the correlation is not absolute. Some secondary constrictions do not appear to bind 3H ribosomal RNA. Some regions which bind ribosomal RNA do not appear as secondary constrictions in metaphase chromosomes. - Although the nucleolus organizing regions of most mammalian karyotypes are found on the autosomes, the X chromosomes in Carollia perspicillata and C. castanea carry large clusters of sequences complementary to ribosomal RNA. In situ hybridization shows that the Y chromosome in C. castanea also has a large nucleolus organizing region.

Animals↗
PubMed1975

The mitotic chromosomes of Notophthalmus (=Triturus) viridescens: localization of C banding regions and DNA sequences complementary to 18S, 28S and 5S ribosomal RNA.

The metaphase chromosomes of Notophthalmus (Triturus) viridescens have been studied by C-banding and in situ hybridization. The chromosomes show the pericentric C-banding seen in many organisms and in addition have interstitial C-bands located a short distance from the pericentric C-bands on each chromosome arm. A few C-bands are seen in telomeric regions. Regions which hybridize in situ with 18S and 28S ribosomal RNA were found on three chromosome pairs. The animals studied fell into three groups with respect to which of the six possible sites showed detectable hybridization with 18S and 28S RNA. Individual animals differed not only in the pattern of in situ hybridization of ribosomal RNA but also in the number of ribosomal RNA cistrons in the genome as measured by saturation hybridization on purified DNA. In situ hybridization showed five pairs of chromosomes which contained DNA complementary to 5S RNA. The four pairs of subtelocentric chromosomes in the N. viridescens karyotype all have 5S DNA in the pericentric regions. The fifth cluster of 5S DNA is in the middle of one arm of the chromosomes in one of the two smallest submetacentric pairs in the genome. The five sites of 5S DNA differ markedly in the level of in situ hybridization with 5S cRNA.

Animals↗
PubMed1975

Analysis of drosophila mRNA by in situ hybridization: sequences transcribed in normal and heat shocked cultured cells.

Messenger RNA transcribed in cultured Drosophila cells adapted for growth under conditions permitting labeling to high specific acitivty has been analyzed by the technique of in situ hybridization. Poly(A)-containing cytoplasmic RNA binds specifically and reproducibly to about 50 bands in the salivary gland polytene chromosomes. In addition heavy labeling of the beta-heterochromatin associated with each of the chromosome arms is observed. The species which are detected probably belong to the more abundant classes of RNA. When the cultured Drosophila cells are subjected to heat shock immediately before labeling with 3H-uridine, there is a drastic alteration in the pattern of gene transcription detected by in situ hybridization. Most of the mRNA synthesis which could be detected in the normal cell is shut off. Newly synthesized RNA hybridizes strongly to seven new sites which do not bind mRNA from control cells. The new loci correspond almost exactly to the regions of Drosophila polytene chromosomes which puff when intact larvae are subjected to an identical heat treatment.

Animals↗
PubMed1975

Locations of 18S and 28S ribosomal genes on the chromosomes of the Indian muntjac.

The locations of genes coding for 18S and 28S ribosomal RNA have been mapped on metaphase chromosomes of the Indian muntjac M. muntjak by in situ hybridization with (3H)rRNA from the toad X. laevis. The results show that, in the muntjac, rDNA clusters are associated with the prominent secondary constrictions on the X and the Y1 chromos. In addition a cluster of rDNA is found near the tip of one arm on the longest pair of autosomes. The autosomal cluster of rDNAs usually does not express as a secondary constriction at metaphase.

Animals↗