Search PubMed⌕ Search

Biomedical subjects

C Mulder

Publications and source records attributed to C Mulder.

At least 73 records · Page 4Linked to original sources
PubMed1984

The effect of dietary saturated fat versus polyunsaturated fat on serum cholesterol and phospholipid concentrations in rabbits with partial ileal bypass.

Rabbits were fed semipurified diets containing either corn oil or coconut fat. Dietary coconut fat significantly elevated serum total cholesterol and phospholipid concentrations. Rabbits with partial ileal bypass (PIB) had significantly lower serum cholesterol and phospholipid values, irrespective of whether the diet contained corn oil or coconut fat. The effect on serum lipids of the type of fat was similar in control and PIB animals. Since PIB rabbits are known to excrete extremely high amounts of steroids with the feces, we suggest that our data point to a lack of interaction of the type of dietary fat with the fecal excretion of steroids.

Animals↗
PubMed1984

Detection of circular and linear herpesvirus DNA molecules in mammalian cells by gel electrophoresis.

A simple gel technique is described for the detection of large, covalently closed, circular DNA molecules in eucaryotic cells. The procedure is based on the electrophoretic technique of Eckhardt (T. Eckhardt, Plasmid 1:584-588, 1978) for detecting bacterial plasmids and has been modified for the detection of circular and linear extrachromosomal herpesvirus genomes in mammalian cells. Gentle lysis of suspended cells in the well of an agarose gel followed by high-voltage electrophoresis allows separation of extrachromosomal DNA from the bulk of cellular DNA. Circular viral DNA from cells which carry the genomes of Epstein-Barr virus, Herpesvirus saimiri, and Herpesvirus ateles can be detected in these gels as sharp bands which comigrate with bacterial plasmid DNA of 208 kilobases. Epstein-Barr virus producer cell lines also show a sharp band of linear 160-kilobase DNA. The kinetics of the appearance of this linear band after induction of viral replication after temperature shift parallels the known kinetics of Epstein-Barr virus production in these cell lines. Hybridization of DNA after transfer to filters shows that the circular and linear DNA bands are virus specific and that as little as 0.25 Epstein-Barr virus genome per cell can be detected. The technique is simple, rapid, and sensitive and requires relatively low amounts of cells (0.5 X 10(6) to 2.5 X 10(6)).

Animals↗
PubMed1984

Deletion of DNA sequence in a nononcogenic variant of Herpesvirus saimiri.

The 110-kilobase-pair stretch of unique sequence DNA of Herpesvirus saimiri is flanked by highly repetitive DNA. Detailed restriction endonuclease mapping has localized the left junction of repetitive and unique DNA to a 100-base-pair region. H. saimiri 11att, a replication competent nononcogenic variant of strain 11, has a deletion of 2.3 kilobase pairs of sequence information that spans this left junction of repetitive and unique DNA.

Animals↗
PubMed1984

Classification of herpesvirus saimiri into three groups based on extreme variation in a DNA region required for oncogenicity.

The leftmost 7 kilobase pairs of unique sequence L-DNA of herpesvirus saimiri was found to be highly variable among different strains as determined by restriction endonuclease analysis and blot hybridization. This region in one group of viruses (group A) showed only very weak hybridization with the DNA of two other groups. Similarly, a fragment of group B hybridized to DNA of its own group much more strongly than to group A. No homology was detected within a 1.2-kilobase-pair region between strain 11 (group A virus) and strain SMHI (group B) even under reduced stringency, and the adjacent 5.5-kilobase-pair segment of the region showed only a very weak intergroup hybridization. DNA of a third group of viruses (non-A, non-B) did not hybridize significantly with cloned fragments representing the leftmost 7-kilobase-pair region of either group A or group B. Since sequences in the highly variable region are required for the oncogenicity of the virus, these results raise interesting questions regarding the origin and function of this region of the genome.

Animals↗
PubMed1983

Determination of free fatty acids: a comparative study of the enzymatic versus the gas chromatographic and the colorimetric method.

We determined the concentration of free fatty acids in 51 plasma samples by three different methods: a gas-liquid chromatographic, a colorimetric and an enzymatic method. Values obtained by the three methods show a good correlation. The gas-liquid chromatographic method was used as the reference method. The results of the enzymatic method are about 5% too high and the colorimetric results have a bias of +27%. The coefficients of variation of the three assays are 4, 7 and 5% respectively. Storage of the samples at -18 degrees C gives no change in the total amount of free fatty acids, enzymatically determined. Because of low costs (time, reagents and apparatus), combined with a sufficient accuracy and precision, the enzymatic method for the determination of total free fatty acids is the method of choice.

Chromatography, Gas↗
PubMed1982

Methylation of the viral genome in an in vitro model of herpes simplex virus latency.

An in vitro model of latency of herpes simplex virus type 1 (HSV-1) in a lymphoid cell line has been developed recently. CEM cells persistently infected with HSV-1 transiently ceased to produce virus for 24 days. This nonproductive state could either be reversed with phytohemagglutinin or maintained with concanavalin A. This system was used to study the relationship between DNA methylation and HSV-1 latency. DNA was probed for methylation by comparing the cleavage patterns generated by two pairs of restriction endonucleases (Sma I vs. Xma I and Hpa II vs. MspI); these enzymes show differential activity reflecting methylation of the recognition sequences. Viral DNA in the concanavalin A-treated cells (not producing virus) was found to be extensively methylated. By contrast, no methylated copies were detected in viral DNA from producer cells. About 800 days after the initial infection, the productive culture once again became nonproductive. Viral sequences in the latter cells were also methylated. Reconstitution experiments revealed 1-2 copies of viral DNA in cells from the latent stages and 40-80 copies in cells from productive stages. Most (if not all) of the viral genome is present in cells from various productive and latent stages. No differences in sequence arrangement were detected (although a terminal fragment of intracellular HSV-1 DNA appeared to be under-represented in latent cells). These results suggest a role for DNA methylation in the mechanism of HSV-1 latency in this system.

Cell Line↗
PubMed1979

Methylation of Herpesvirus saimiri DNA in lymphoid tumor cell lines.

Several continuous lymphoid cell lines have been established from tumors induced by Herpesvirus saimiri. At least a portion of the viral DNA in the marmoset lymphoid cell line 1670, which does not produce detectable virus, is present as covalently closed circular episomal DNA. The use of restriction endonuclease digestion, transfer to nitrocellulose filters, and hybridization of the virus-specific DNA has produced strong evidence that viral DNA sequences present in total 1670 cell DNA and in isolated episomes are extensively methylated. The restriction endonuclease Hpa II has the same recognition sequence as Msp I but, unlike Msp I, fails to cleave when the C of the C-G dinucleotide is methylated. Viral DNA sequences of 1670 cells are refractory to cleavage by Hpa II but not Msp I; greater than 80% of the Hpa II cleavage sites appear to be methylated. Similarly, viral DNA sequences of 1670 cells are refractory to cleavage by Sma I (C-C-C-G-G-G) and Sac II (C-C-G-C-G-G) but not Sac I, Pvu II, or Pst I, which lack the dinucleotide C-G in their recognition sequences. Methylation of mammalian DNA has been previously found exclusively at C residues in the dinucleotide C-G. H. saimiri DNA sequences of another nonproducer cell line, 70N2, also appeared to be extensively methylated, but analysis of total cell DNA extracted from three virus-producing lymphoid lines revealed no evidence of methylation of viral DNA sequences. It remains to be seen if methylation of viral DNA plays a role in the lack of complete expression of H. saimiri genome information in nonproducing lymphoid cell lines.

Animals↗
PubMed1978

Herpesvirus ateles DNA and its homology with Herpesvirus saimiri nucleic acid.

Analysis of the structural organization of Herpesvirus ateles DNA shows that two types of viral DNA molecules are encapsidated in virions: (i) M-genomes, which contain 74% light sequences (L-DNA, 38% guanine plus cytosine) and 26% highly repetitive heavy sequences (H-DNA, 75% guanine plus cytosine), and (ii) defective H-genomes, which consist exclusively of repetitive H-DNA. The structure of M-genomes from H. ateles consists of an L-DNA region of about 70 x 10(6) daltons inserted between H-DNA termini of variable length. M-genomes with a shorter H-DNA region at one end of the molecule have a long stretch of H-DNA at the other end, resulting in a total molecular weight of 89.8 +/- 8.5 x 10(6). Thus it resembles the structure of M-genomes of H. saimiri. H-DNA of the two independent H. ateles isolates, strains 810 and 73, reveals different patterns after cleavage with restriction endonuclease Sma I. H-DNA of H. ateles 810 appears to consist of identical tandem repeat units with a molecular weight of 1,035,000; the H-DNA repeat unit of strain 73 is shorter (930,000 molecular weight). Corresponding DNA sequences of the two H. ateles strains (810 and 73) are completely homologous in cross-hybridizations. However, a discrete nucleotide sequence divergence between these virus strains is detected by measuring melting temperatures (T(m)) of DNA hybrid molecules. Some homology exists between H. ateles and H. saimiri DNA. Hybridization of L-DNA from H. ateles with L-DNA from H. saimiri shows about a 35% homology between the respective L-DNA sequences; the resulting heteroduplex molecules show a decrease of T(m) by 13.5 degrees C, corresponding to about a 9% mismatching in cross-hybridizing parts of L-regions. Very little homology is found between H-DNA of H. ateles and H. saimiri.

Base Sequence↗
PubMed1978

DNA of Bacillus subtilis bacteriophage SPP1: physical mapping and localization of the origin of replication.

The genome of Bacillus subtilis bacteriophage SPP1, a linear, 28.5-megadalton DNA duplex, was mapped by analysis with the restriction endonucleases endo R.Sal I, Sma I, Xba I, Bgl I, Bgl II, and EcoRI. The SPP1 genome, like that of the Salmonella typhimurium phage, P22, was found to be a terminally repetitious, circularly permuted molecule. 6-(p-Hydroxyphenylazo)uracil, a selective, reversible inhibitor of SPP1 DNA synthesis, was exploited to synchronize the initiation of genome replication and to selectively label the site of its initiation with radioactive thymidine. Restriction endonuclease analysis of the distribution of the label located the origin of replicative synthesis at an area approximately 0.2 genome length from one molecular terminus.

Bacillus subtilis↗
PubMed1978

Episomal viral DNA in herpesvirus saimiri-transformed lymphoid cell lines.

Structural analysis of episomal viral genomes from two herpesvirus saimiri (HVS)-transformed tumour cell lines (No. 1670 and 70N2) showed that both types of episomes have a higher molecular weight than linear virion DNA. The arrangement of unique (L) and repetitive (H) DNA in No. 1670 episomes was studied by partial denaturation mapping. Part of the L-sequences present in linear virion DNA was found to be missing, part was found to be duplicated in the episomes. The episomal L-DNA regions were correlated with the known physical gene maps of linear HVS DNA.

Animals↗
PubMed1976

Structure of Herpesvirus saimiri genomes: arrangement of heavy and light sequences in the M genome.

Herpesvirus saimiri contains two species of DNA molecules. (i) The M genome is composed of 70% light (L) DNA (36% cytosine plus guanine; density in CsCl, 1.695 g/ml), which consists of unique sequences, and 30% heavy (H) DNA (71% cytosine plus guanine; density, 1.729 g/ml). (ii) The H genome contains heavy sequences exclusively. H sequences in M and H genomes cross-hybridize completely and are cleaved identically by restriction endonuclease R-Sma I into four classes of fragments with molecular weights of about 360,000, 300,000, 130,000 and 40,000, respectively. H sequences are chains of identical repeat units in tandem arrangement. The molecular weight of each repeat unit is about 830,000. L sequences have no cleavage site for endo R-Sma I H sequences are terminally arranged at both ends of the M genome, as seen by electron microscopy after partial denaturation. The length of the individual heavy ends varies between 21 mum and less than 1 mum, whereas the light region is uniform in size (35.3+/-0.35 mum). As a rule, molecules with a long heavy end at one side have a short heavy end at the other side, thus giving rise to a limited size heterogeneity. Orientation of M DNA molecules by the denaturation map of the light region shows that the longer heavy end may be located at the left or at the right side of the M genome.

Base Sequence↗