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S Malcolm

Publications and source records attributed to S Malcolm.

At least 181 records · Page 10Linked to original sources
PubMed1984

Size heterogeneity of the largest subunit of nuclear RNA polymerase II. An immunological analysis.

Antibodies raised against the 180-kDa subunit of cauliflower RNA polymerase II bind selectively to the largest subunit of RNA polymerase II purified from a variety of plant species. The selective binding of this antibody to the largest RNA polymerase II subunit has allowed us to probe for the size of this subunit in crude cell extracts, in fractions containing partially purified RNA polymerase II, and in isolated nuclei. Fractions containing RNA polymerase II were subjected to electrophoresis in the presence of sodium dodecyl sulfate, blotted onto nitrocellulose, and blots were probed with antibody. Immunoglobulin complexes were revealed with 125I-Protein A. Published purification procedures result in rapid conversion of a 220-kDa subunit to a 180-kDa polypeptide, but purification at high pH (pH 9.0) retards this proteolysis. RNA polymerase II associated with isolated nuclei is largely protected from proteolytic degradation, and a 240-kDa polypeptide as well as a 220-kDa polypeptide can be detected. These results suggest that the 180-kDa subunit of RNA polymerase II arises artificially during cell lysis and enzyme purification, and that even the 220-kDa polypeptide may be a degradation product of a 240-kDa polypeptide in plants.

Animals↗
PubMed1984

Immunological studies on plant DNA-dependent RNA polymerases with antibodies raised against individual subunits.

Antibodies were raised against native soybean RNA polymerase II and individual subunits of RNA polymerase II purified from soybean, cauliflower, and wheat. These antibodies were used to study the immunological relationships of plant RNA polymerases I, II, and III at the subunit level. RNA polymerases I and II from soybean, I, II, and III from cauliflower and wheat, and II from turnip were purified to homogeneity, and enzyme subunits were separated on polyacrylamide gels containing sodium dodecyl sulfate. Separated RNA polymerase subunits were electrophoretically transferred to nitrocellulose, reacted with antibodies, and the immunoglobulin complexes were revealed by reaction with 125I-labeled Protein A. Antibodies directed against native soybean RNA polymerase II bind to all or most of the subunits of soybean and wheat RNA polymerase II and to the putative common subunits in RNA polymerases I and III. Antibodies directed against individual subunits of RNA polymerase II enzymes react specifically with the subunit to which the antibody was raised and to related or identical subunits in RNA polymerases I and III. These studies confirm the presence of common subunits in the three classes of nuclear RNA polymerase and provide information on analogous or related subunits within each class of enzyme purified from different plant species.

Animals↗
PubMed1984

A note on the use of the non-central t-distribution in setting numerical microbiological specifications for foods.

An exact procedure is described and used to determine k values and probabilities of rejection used in the application of variables sampling plans to foods. Comparison of quantities so obtained to those calculated by Kilsby et al. (1979), who used an approximation procedure, reveals that for small samples the approximation can lead to probabilities of rejection which are larger than those obtained using the exact procedure. It is recommended that the exact procedure be used in the application of these plans.

Food Microbiology↗
PubMed1984

c-myc Gene activation and chromosomal translocation.

Burkitt's lymphoma cells are characterized by the presence of specific chromosomal translocation bringing the immunoglobulin and the c-myc proto-oncogenes into the proximity of each other. Different translocations involve each of the three immunoglobulin loci but the breakpoint with respect to the c-myc gene is shown to be very variable. In t8/14 the breakpoint occurs upstream from the c-myc gene whilst in the variant lymphomas it occurs downstream from the gene. Possible ways in which the translocation affects the c-myc gene are discussed.

Animals↗
PubMed1983

Localisation of the human N-ras oncogene to chromosome 1cen - p21 by in situ hybridisation.

The N-ras gene is a transforming gene isolated from a variety of human tumour cell lines and is a member of a family of related ras genes. Somatic cell hybrids have previously shown that the N-ras gene is located on chromosome 1. We have confirmed this localisation by in situ hybridisation to metaphase preparations of lymphocytes and localised the gene to the region 1cen - p21. A survey has found 47 reported cases of malignancy involving deletions in the short arm of chromosome 1. Fifteen of the 47 involved a deletion in this region.

Chromosome Mapping↗
PubMed1983

Colony counting on hydrophobic grid-membrane filters.

A device to facilitate manual scoring of hydrophobic grid-membrane filters (HGMF) is described. Variations in scores were generally less than 2.5% between 41 analysts from six laboratories, who, using the apparatus, scored a set of five specimen HGMF in different ways, and there was good agreement between scores from positive and negative grid-cell counts by each analyst. A scoring procedure for use in routine microbiological analysis, suitable for HGMF at various degrees of saturation, is recommended.

Bacteriological Techniques↗
PubMed1983

Collaborative study of the MPN, Anderson-Baird-Parker direct plating, and hydrophobic grid-membrane filter methods for the enumeration of Escherichia coli biotype I in foods.

Five Health Protection Branch laboratories compared two membrane filter methods (the Anderson-Baird-Parker direct plating, and a hydrophobic grid-membrane filter method) against the most probable number procedure (MPN) for enumerating Escherichia coli biotype I in foods. Results were available in 24 h by both membrane filter methods, compared with 10-14 days by the MPN procedure. For ground beef, Parmesan cheese, and cut green beans, the hydrophobic grid method generally gave the highest recovery, although the two membrane filter methods were not significantly different. Both these methods gave significantly higher recoveries than the MPN procedure, and for most foods, either method would be preferable. Further work is required before either membrane filter method can be recommended for bean and alfalfa sprouts, which may contain very high levels of Klebsiella spp.

Animals↗
PubMed1982

Localization of human immunoglobulin kappa light chain variable region genes to the short arm of chromosome 2 by in situ hybridization.

The genes for human immunoglobulin kappa light chains have been localized in normal lymphocyte and fibroblast chromosomes by in situ hybridization of probes from cloned DNA fragments of the kappa variable region locus. The localization was achieved by counting grains (after autoradiography) over chromosomes in a number of karyotypes. The variable region gene probes hybridized in a cluster on a region of the chromosome 2 short arm close to the centromere (2cen leads to p12). This location was confirmed in lymphocytes from a balanced translocation carrier 46XXt (2; 16) (q13; q22). Our results show that human kappa light chain genes are located in the region of the break point observed in specific chromosomal translocations associated with Burkitt lymphoma.

Binding Sites, Antibody↗
PubMed1981

The chromosomal distribution of repetitive DNA sequences within the human beta globin gene cluster.

The chromosomal distribution and degree of repetitiveness of the sequences within the human beta globin gene cluster has been studied by in situ hybridisation. A genomic recombinant, H beta G1, which contains 15.9 thousand base pairs (kb) of DNA inserted into lambda charon 4A, was used as a template for the [3H] complementary RNA used for hybridisation. The inserted DNA contains sequences 4.7 kb to the 5' side of the delta gene and continues through the delta and beta genes to a site 2.8 kb to the 3' side of the beta gene. Two highly repetitive sequences, which are distributed evenly over all the chromosomes, have been identified within this DNA. Another somewhat less repetitive sequence has been identified between the beta and delta genes.

Base Sequence↗
PubMed1981

Chromosomal localization of a single copy gene by in situ hybridization--human beta globin genes on the short arm of chromosome 11.

1. The localization of the beta globin genes by in situ hybridization to fixed chromosomes is described. 2. The probe used was a [3H]cRNA copy of a genomic clone containing in total 4.4 kb of DNA and including the beta globin gene. 3. The evidence for the localization of the gene comes from three pieces of data. (a) Chromosome 11 is labelled to double the extent expected if the grains were randomly distributed, (b) the extra grains above background are clustered on the short arm of 11 close to the centromere, and (c) the absolute number of grains observed is very close to that predicted for a probe of that length by comparison with ribosomal genes. The localization is in agreement with that obtained by other methods. 4. This method could be extended to any gene for which a genomic clone containing at least 5 kb of single copy DNA is available.

Chromosome Mapping↗
PubMed1979

Use of chromosomal translocations with in situ DNA hybridisation to confirm localisation of human 5S ribosomal RNA genes.

Two cases of chromosomal translocations involving the long arm of chromosome 1 were investigated for 5S ribosomal gene localisation using in situ hybridisation. In the first family, there was an interstitial translocation of 1q25-32 to chromosome 5; the 5S genes remained on chromosome 1. In the second family, there was a translocation of 1q42-44 to chromosome 21q12; the 5S gene locus in this case was translocated. This shows that the 5S ribosomal genes are at position 1q42-44, confirming a previous assignment based on adenovirus-induced uncoiling and on a partial trisomy (Steffensen et al., 1977).

Chromosome Banding↗