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A Balmain

Publications and source records attributed to A Balmain.

At least 109 records · Page 6Linked to original sources
PubMed1981

Sequence divergence of nucleus-confined polyadenylated ribonucleic acids in Friend erythroleukemic cells.

For determination of whether any potential protein-coding RNA sequences are confined to the nucleus in Friend cells, a comparison has been made of the sequence divergence of polyadenylated RNA molecules which are either nucleus confined or transported to the cytoplasm. Both unique DNA and cDNA probes enriched in such sequences were reacted with a large excess of mouse or rat DNA. The extent of hybridization and the thermal stability of hybrids formed under various stringency conditions were used as a measure of the amount of sequence divergence which had taken place. The results confirmed that messenger sequences are relatively conserved during evolution. Furthermore, experiments involving both unique DNA probes representative of the full length of nucleus-confined RNA molecules and cDNA probes complementary to their poly(A)-adjacent fragments indicated that the polyadenylated nucleus-confined sequences have, on average, diverged during evolution much more than mRNA sequences. The vast majority of these sequences therefore probably do not represent potential mRNAs which are confined to the nucleus and subject to posttranscriptional control in a manner similar to those which have been demonstrated in sea urchins [Wold, B., Klein, W. H., Hough-Evans, B. R., Britten, R. J., & Davidson, E. H. (1978) Cell (Cambridge, Mass.) 14, 941-950].

Animals↗
PubMed1980

Frequency distribution of pre-messenger RNA sequences in polyadenylated and non-polyadenylated nuclear RNA from Friend cells.

Hybridisation of cDNA probes for abundant and rare polysomal polyadenylated RNAs with polyadenylated and non-polyadenylated nuclear RNA from Friend cells indicated that the abundant polysomal polyadenylated RNA sequences were present at a higher concentration in the nucleus than rare polysomal sequences, but at a reduced range of concentrations. The ratio of the concentrations of abundant and rare sequences was about 3 in non-polyadenylated nuclear RNA, 9 in polyadenylated nuclear RNA and 13 in polysomal polyadenylated RNA. This suggests that polyadenylation may play a role in the quantitative selection of sequences for transport to the cytoplasm. Polyadenylation cannot be the only signal for transport, since a highly complex population of nucleus-confined polyadenylated molecules exists, each of which is present on average at less than one copy per cell.

Animals↗
PubMed1979

The effects of mercury-substitution on the hybridisation characteristics of nucleic acids.

The effect of different levels of mercury substitution on the rate and extent of hybridisation of globin mRNA with a complementary DNA (cDNA) copy has been investigated. It was found that mercuration significantly reduces both the rate of hybridisation and the extent of the reaction, but that these effects are abolished when at least stoichiometric amounts of 2-mercaptoethanol are included in the hybridisation medium. As a preliminary to using this technique to isolate specific groups of sequences after long-term hybridisations, we have investigated both the rate of demercuration of RNA and its retention on thiol-sepharose columns after extended incubation under commonly employed hybridisation conditions at 43 degrees or 60 degrees. Retention was essentially quantitative even after incubation times of 300 hours at 43 degrees, but decreased significantly after 48 hours at 60 degrees. It is concluded that thiol-sepharose chromatography offers considerable advantages over hydroxyapatite chromatography for the recovery of hybridised sequences, particularly with regard to the lower levels of non-specific binding obtained and its ability to distinguish directly between DNA-DNA and DNA-Hg RNA hybrids.

Animals↗
PubMed1979

Nick translation of mammalian DNA.

The labelling of mouse DNA by nick translation with DNA polymerase I has been investigated with respect to the time of incubation, requirement for DNAase I, size of the product, and uniformity of labelling, and the hybridisability and stability of the resultant labelled probes. Total mouse DNA and reannealed unique mouse DNA sequences can be labelled by nick translation in the presence of [3H]dCTP and [3H]TTP to a specific activity of 7 . 10(6)--20 . 10(6) cpm/microgram DNA. The hybridisation characteristics of nick-translated whole DNA with an excess of unlabelled mouse-embryo driver DNA indicates that no preferential labelling of repetitive or unique DNA sequence classes occurs. In addition, the proportion of unique DNA sequences labelled by nick translation which hybridises with polyadenylated nuclear RNA from Friend cells is the same as that of unique DNA sequences isolated from cells labelled with [3H]thymidine in vivo, indicating that few (if any) of the unique DNA sequences are unrepresented in the nick-translated probe. Probes which contain [3H]dTMP are unstable, and show a considerable reduction in hybridisability over a period of 6 months at --20 degrees C. The decrease is accompanied by an increase in the number of mismatched sites in duplexes containing the labelled probe (as shown by thermal stability measurements of hybrid molecules) and a decrease in the rate of hybridisation of the probe with total mouse DNA. In contrast, DNA which is labelled with [3H]dCMP alone is stable, and does not show any decrease in hybridisability on prolonged storage.

Animals↗
PubMed1979

Diversity and complexity of uterine mRNA from rats of differing hormonal states.

The diversity and complexity of the uterine mRNA population has been compared at two different stages of uterine growth and development in the rat. Analysis by cDNA hybridization to homologous mRNA indicates that there are 8000 different sequences expressed in the immature rat uterus responding to just 4 h of oestradiol-17 beta-induced growth while the fully developed uterus expresses 36 000 sequences. As a check on our results, the complexity is re-analysed by hybridization of mercurated mRNA to total unique DNA. Analysis by this method indicates that the hormone-stimulated immature rat uterus contains 12 000 poly(A)-containing mRNA sequences while the fully differentiated adult tissue contains 53 000 diverse sequences.

Aging↗
PubMed1979

Qualitative and quantitative changes in uterine mRNA populations in response to oestradiol treatment of rats.

The mRNA population of immature rat uteri, responding to different lengths of oestradiol-induced differentiation, have been compared by the technique of DNA hybridization with heterogeneous RNA. Over the first 4 h of hormone induction there are continuing qualitative and quantitative changes in the poly(A)-containing mRNA such that, by 4 h after oestradiol administration, the population bears little resemblance to that of the unstimulated animal. Between 2 h and 4 h after oestradiol administration, the most striking changes appear to be in sequences of intermediate abundance. The possible significance of these findings is discussed.

Animals↗
PubMed1978

On the existence of 'arrested G2 cells' in mouse epidermis.

It has been postulated that mouse epidermis contains two populations of resting cells, one of which is blocked at the G1-S boundary and the other between G2 and mitosis. The 'arrested G2 cells' were estimated, by the labelled mitosis method, to comprise 5-10% of the epidermal population and presumed to function as a 'reserve pool' which could be activated by wounding. A comprehensive search has now been carried out for arrested G2 cells in mouse epidermis using the direct methods of single cell and flow through cytophotometry. No evidence was obtained which supports the existence of such a cell compartment. Suitable control experiments were carried out to ensure that G2 cells were not lost during the isolation of epidermal nuclei.

Aging↗
PubMed1977

Histone phosphorylation and synthesis of DNA and RNA during phases of proliferation and differentiation induced in mouse epidermis by the tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate.

The tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate (TPA) induces discrete waves of proliferation and differentiation when applied to mouse epidermis. The aim of this study was to elucidate the temporal relationship between histone phosphorylation and synthesis of DNA and RNA in mouse epidermis during the process of tumor promotion. This investigation as facilitated by choosing a low but nevertheless strongly tumor-promoting dose of TPA (0.002 micronmole/mouse), which induced the epidermal cells to go through only one round of DNA synthesis and cell division. Histones were isolated from mouse epidermis, and the rates of phosphorylation of the individual histone species were determined at different times after treatment with TPA. The results demonstrated that the phosphorylation of H1 histone was initiated at about the same time as the synthesis of DNA but continued past the S phase and reached a maximum simultaneously with the maximum in the epidermal mitotic rate. The only other histone that phosphorylated to any significant extent was Histone H2A. From the results obtained, it was concluded that histone phosphorylation in the epidermis is related to the processes of DNA replication and mitosis after stimulation with TPA. Positive evidence for the activation of specific genes, which has been proposed by other authors to be important in the promotion of epidermal tumors, was not found in this investigation.

Animals↗
PubMed1976

On the biochemical mechanism of tumorigenesis in mouse skin. VII. The effects of tumor promoters on 3H-choline and 3H-glycerol incorporation into mouse epidermal phosphatidylcholine in relation to their effects on 3H-thymidine incorporation into DNA.

The kinetics of the stimulation of phospholipid and DNA biosynthesis in mouse epidermis after treatment with various tumor promoting agents has been investigated. 3H-choline and 3H-glycerol were used as precursors for phosphatidylcholine. An early stimulation of 3H-choline incorporation into phosphatidylcholine is observed which always precedes the stimulation of 3H-thymidine incorporation into epidermal DNA. This is interpreted as being a manifestation of the proliferation of cellular membranes in preparation for cell division. Appreciable differences are observed in the incorporation of 3H-choline and 3H-glycerol into phosphatidylcholine, the possible reasons for which are discussed. It is concluded that 3H-choline incorporation is a more reliable parameter for the measurement of phosphatidylcholine biosynthesis than 3H-glycerol incorporation. The relationship between those effects on phospholipid synthesis and the tumor promoting activity of the substances tested is discussed.

Animals↗
PubMed1976

The synthesis of specific proteins in adult mouse epidermis during phases of proliferation and differentiation induced by the tumor promoter TPA, and in basal and differentiating layers of neonatal mouse epidermis.

Mouse epidermis can be induced to undergo sequential waves of proliferation and keratinization by treatment with the tumor promoter TPA (12-O-tetradecanoyl-phorbol-13-acetate). This model system offers a unique possibility to study the synthesis of differentiation-specific proteins in the epidermis. During these studies it could be shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis that several previously undetected proteins appear in the epidermis during the phase of differentiation. These have been fractionated according to solubility in 1 M phosphate buffer, pH 7.0, or 0.1 M sodium citrate buffer, pH 2.6. Of the soluble proteins, a band of approximate molecular weight 13,500 (band 1) appears early during the differentiative phase (24 hr after treatment with TPA). Another previously undetected protein of approximate molecular weight 27,000 (band 2) appears in the soluble fraction after 48 hr, at a time when many of the typical manifestations of increased keratinization can be observed. Both of these soluble proteins, although not detectable in normal adult mouse epidermis, are shown to be present in newborn mouse epidermis, which demonstrates histologically a well-developed layer of keratinizing and cornified cells. In addition, by separation of neonatal and TPA-treated adult mouse epidermis into "basal" and "cornified" layers, it could be demonstrated that these two proteins are localized exclusively in the upper layer of the epidermis.

Animals↗
PubMedDate not supplied

Mouse skin carcinomas induced in vivo by chemical carcinogens have a transforming Harvey-ras oncogene.

Several groups have shown that the malignant phenotype can be transferred to NIH/3T3 fibroblasts by incorporation of DNA isolated from tumour cell lines. These studies have demonstrated that the transforming activity of DNA isolated from human bladder, lung and colon carcinoma cell lines is related to an alteration of the cellular homologues of the ras genes of Harvey or Kirsten murine sarcoma viruses. It is, however, unclear what relevance these observations have to the multi-stage nature of tumorigenesis in vivo, in which several independent events are required in both humans and experimental animals. The activation of a cellular oncogene in a defined experimental system for the progressive induction of solid tumours has not yet been demonstrated. We report here that high molecular weight DNA from transplanted squamous cell carcinomas induced by sequential treatment of mouse skin with initiators and promoters of carcinogenesis causes morphological transformation of NIH/3T3 fibroblasts at high frequency. The transforming properties are due to the transfer of an activated cellular homologue of the Harvey-ras (rasH) oncogene.

Animals↗
PubMedDate not supplied

Activation of the mouse cellular Harvey-ras gene in chemically induced benign skin papillomas.

An important feature of the development of many human and animal tumours is the appearance of pre-malignant benign lesions, some of which undergo further changes during progression to malignancy. Many of the currently accepted concepts of multi-stage carcinogenesis have been developed using an experimental model based on the chemical induction of tumours in mouse skin. In this system, many of the premalignant papillomas which arise are promoter-dependent, and appear to regress if promoter treatment is interrupted, whereas others progress to form autonomous benign lesions and, in some cases, malignant carcinomas. Although the number and nature of the events leading to malignancy are not known, DNA transfection experiments have led to the identification of several genes which may be qualitatively altered in tumour cells (see ref. 6 for review). We have previously shown that DNA from transplantable mouse skin carcinomas induced by chemical carcinogens has the ability to transform NIH/3T3 cells, and that the gene responsible for the transformation is an activated form of the mouse cellular Harvey-ras gene (c-rasH). We have now investigated the stage of carcinogenesis at which the proto-oncogene acquires transforming activity. We demonstrate that primary papillomas induced by chemical carcinogens in two different mouse strains have an activated c-rasH gene. This constitutes the first report of a benign tumour which contains DNA with detectable transforming activity. In addition, steady-state levels of c-rasH gene transcripts are elevated in the papillomas as compared with normal epidermis.

Animals↗
PubMedDate not supplied

Carcinogen-specific mutation and amplification of Ha-ras during mouse skin carcinogenesis.

Cellular proto-oncogenes can be activated by both point mutations and chromosomal translocations, suggesting that there may be a direct link between exposure to agents which damage DNA and genetic change leading to malignancy. Several groups have therefore analysed mutations found in cellular oncogenes of tumours induced by particular physical or chemical carcinogens. Here, we have analysed the molecular changes at different stages of carcinogenesis in mouse skin tumours induced by initiating and promoting agents. Over 90% of tumours, including premalignant papillomas, initiated with dimethylbenzanthracene (DMBA) have a specific A----T transversion at the second nucleotide of codon 61 of the Harvey-ras (Ha-ras) gene. The frequency of this mutation was dependent on the initiating agent used, but not on the promoter, suggesting that the mutation occurs at the time of initiation. The mutation was heterozygous in most papillomas tested, but was homozygous or amplified in some carcinomas. The development of further chromosomal changes at the c-Ha-ras gene locus is therefore a common feature of tumour progression.

9,10-Dimethyl-1,2-benzanthracene↗