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J Bonner

Publications and source records attributed to J Bonner.

At least 37 records · Page 2Linked to original sources

Weight reduction methods of college women.

Weight reduction attitudes and practices were obtained from a sample of 400 female students. Forty-eight percent reported using a weight loss program since admission to college. The programs most often selected included hypocaloric diets and exercise. Although the majority of subjects rated hypocaloric diets and exercise as good methods for weight reduction and indicated that they would recommend them to others, these methods supported the slowest rate of weight loss. Evidently, the side effects and costs of the other programs offset the rapid weight loss. Other methods, in descending order of use, included the Cambridge diet, drugs, weight loss clinics, and low-carbohydrate diets. Improved appearance was most often given as the reason for losing weight.

Adolescent

Turtle headaches.

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Headache

Studies on histone acetyltransferase. Partial purification and basic properties.

A rapid and reproducible method for the purification of rat liver histone acetyltransferase is presented. Extraction of nuclei in low salt, followed by phenyl-Sepharose hydrophobic affinity chromatography, G-200 gel filtration in the presence of 1 M urea, CM-cellulose ion exchange and acetyllysine affinity chromatography minimize exposure of the enzyme to high salt. Evidence is provided which indicates that the instability of the enzyme activity is due in part to hydrophobic interactions. The molecular weight of the enzyme is 96,000 as judged by gel filtration. In agreement with others, the enzyme is unstable in the presence of divalent cations, although a requirement for low concentration of Mg2+ or Ca2+ was observed. The enzyme is also sensitive to sulfhydryl blocking agents and is susceptible to rapid thermal denaturation at 37 and 45 degrees C (t1/2 = 22.2 and 9.54 min, respectively). The optimum pH and the energy of activation for the reaction were pH 7.5 and 5230 +/- 378 cal/mol, respectively. In the presence of all five histones, the enzyme catalyzes the acetylation in the order of H3 greater than H4 greater than H2b greater than H2a greater than H1 and appears to operate in a nonprocessive manner. While no other isozymic forms of nuclear acetyltransferase were detected, the enzyme exhibits the properties of both nuclear isozymic forms which have been reported, histone acetyltransferase A and DB, observed in calf thymus and bovine lymphocytes, respectively.

Acetyltransferases

Purification and some properties of a deoxyribonucleic acid endonuclease endogenous to rat liver chromatin.

A deoxyribonucleic acid (DNA) endonucleolytic activity has been purified from a 0.3 M KCl extract of rat liver chromatin by a combination of selective precipitation and ion-exchange and gel filtration chromatography. The purified protein has a molecular weight of 35 000 as determined by Sephadex G-200 gel filtration and sodium dodecyl sulfate-acrylamide gel electrophoresis. The nuclease activity is stimulated by the addition of Mg2+ and thus may represent the Mg2+-activated DNase endogenous to chromatin. The purified enzyme has the ability to make both single-strand nicks and double-strand cuts in DNA.

Animals

Substrate and product inhibition initial rate kinetics of histone acetyltransferase.

Initial velocity and product inhibition kinetics of the histone acetyltransferase (EC 2.3.1.48) reaction indicate that the rat liver nuclear enzyme operates under a rapid equilibrium ordered bireactant mechanism. Histone adds first to the enzyme, and under the conditions of the experiment Ka = 0 as acetyl coenzyme A (CoA) concentration approaches saturating conditions. The Km for acetyl-CoA was 2.10 +/- 0.48 micrometer. Inhibition with acetyllysine resulted in a Kiq for the enzyme-acetyllysine complex of 1.96 +/- 0.30 mM. Inhibition with CoA yielded Kip for the ternary complex of 3.19 +/- 0.48 micrometer. These results indicate that the enzyme activity is comparatively independent of histone concentration, and, since the enzyme is sensitive only to acetyl-CoA and CoA concentrations, the enzyme will tend to maintain histones in the acetylated state.

Acetyltransferases

Nucleotide sequence of cloned rat serum albumin messenger RNA.

The nucleotide sequences of the recombinant DNA inserts of three bacterial plasmid clones containing nearly all of the rat serum albumin mRNA have been determined. A statistical analysis of the nucleotide sequence reveals a pattern of repeated internal homology that confirms the "intragenic triplication" model of albumin evolution.

Amino Acid Sequence

Sequence homology between RNAs encoding rat alpha-fetoprotein and rat serum albumin.

We have determined the sequences of the recombinant DNA inserts of three bacterial plasmid cDNA clones containing most of the rat alpha a-fetoprotein mRNA. The resultant nucleotide sequence of alpha-fetoprotein was exhaustively compared to the nucleotide sequence of the mRNA encoding rat serum albumin. These two mRNAs have extensive homology (50%) throughout and the same intron locations. The amino acid sequence of rat alpha-fetoprotein has been deduced from the nucleotide sequence, and its comparison to rat serum albumin's amino acid sequence reveals a 34% homology. The regularly spaced positions of the cysteines found in serum albumin are conserved in rat alpha-fetoprotein, indicating that these two proteins may have a similar secondary folding structure. These homologies indicate that alpha-fetoprotein and serum albumin were derived by duplication of a common ancestral gene and constitute a gene family.

Amino Acid Sequence

Fine structure and evolution of the rat serum albumin gene.

The exons, their boundaries, and approximately half of the intronic deoxyribonucleic acid of the rat serum albumin gene were sequenced. In addition to the 14 exons identified earlier by R-loop analysis, a small exon was detected between the "leader" exon (Z) and exon B. The leader exon encoded the 5'-untranslated portion of albumin messenger ribonucleic acid and the "pre-pro" oligopeptide present on the nascent protein. The sites of initiation and termination of transcription were tentatively identified by comparison of the 5' and 3' gene-flanking sequences with those of other eucaryotic genes. All 28 intron/exon junctions conformed to the "GT-AG rule" (Breathnach et al., Proc. Natl. Acad. Sci. 75:4853-4857, 1978). The three homologous domains of albumin were encoded by three subgenes that consisted of four exons each and evolved by intragenic duplication of a common ancestor. The second and forth exons of each subgene appeared to be the result of an even earlier duplication event. We propose a model for the evolution of this gene that accounts for the observed patterns of exon size and homology.

Animals

Molecular mechanisms of control of albumin and alphafetoprotein production: a system to study the early effects of chemical hepatocarcinogens.

The cellular mechanism of control of alphafetoprotein (AFP) and albumin (ALB) production during normal and pathologic permissive states is being examined using complementary DNA probes. AFP is the major serum protein for most of fetal life, but normally is produced in very small amounts in the adult. AFP production recurs in the adult during restitutive proliferation of the liver following partial hepatectomy or chemical injury, early after the exposure to chemical carcinogens and in animals with hepatocellular or yolk sac carcinomas. AFP production is roughly proportional in each case examined so far to the amount of mRNA available. On the other hand, there appears to be no difference in the gene number or gene organization in permissive or non-permissive states and there is no evidence of selective degradation of AFP or AFP (and ALB) production is probably at the level of gene transcription. Understanding of how carcinogens act to permit expression of the AFP gene may lead to important insights into carcinogenic mechanisms.

Albumins

Isolation of newly replicated chromatin by using shallow metrizamide gradients.

The properties of chromatin containing newly synthesized DNA and protein were investigated. A fraction of chromatin enriched in newly replicated DNA was isolated by means of its increased density in metrizamide relative to bulk chromatin. The DNA of this fraction appeared to be packaged into nucleosomes but at a reduced nucleosomal spacing. Although pulse-labeled DNA was present in this dense fraction, nucleosomes labeled with short pulses of arginine or acetate were of normal density. The data presented are consistent with the conclusion that newly replicated DNA is associated with preexisting histones in a short-lived, compact structure whereas newly synthesized histones are deposited at normal spacing some distance from the replication fork.

Animals

Purification and the histones of Dictyostelium discoideum chromatin.

Dictyostelium chromatin has been purified from nuclei in high yield by differential centrifugation and nuclease cleaving. Its chemical composition has been assayed, and its histones have been analyzed by gel electrophoresis, peptide fingerprints, amino acid composition, and ion-exchange chromatography. The mass ratios of DNA/RNA/histone/nonhistone are 1.0:0.18:0.98:1.02. There are four histones including one unusual histone, H7, which is the most abundant histone in the slime mold. The H4-like protein is the most conserved protein, while the other histones show both similarities and differences with mammalian histones.

Amino Acids

Control of albumin and alpha-fetoprotein expression in rat liver and in some transplantable hepatocellular carcinomas.

Albumin and alpha-fetoprotein production by rat liver and by four selected transplantable hepatocellular carcinomas is compared to the messenger RNA present in these tissues. Albumin and alpha-fetoprotein were measured by radioimmunoassay of serum concentration, immunofluorescence, and in vitro incorporation of labeled amino acids into proteins specifically precipitated by antisera. The number of mRNA molecules per cell was calculated from the hybridization of specific cDNA probes to polysomal mRNA and by translational activity of polysomal RNA in a wheat germ system. The amount of albumin and alpha-fetoprotein produced by the different tissues is directly related to the number of functional mRNA molecules per cell for each protein.

Animals

Computer programs for analysis of nucleic acid hybridization, thermal denaturation, and gel electrophoresis data.

Computer programs for the analysis of data from techniques frequently used in nucleic acids research are described. In addition to calculating non-linear, least-squares solutions to equations describing these systems, the programs allow for data editing, normalization, plotting and storage, and are flexible and simple to use. Typical applications of the programs are described.

Computers

Hybridization of synthetic oligodeoxyribonucleotides to phi chi 174 DNA: the effect of single base pair mismatch.

Oligodeoxyribonucleotides complementary to the DNA of the wild type (wt) bacteriophage phi chi 174 have been synthesized by the phosphotriester method. The oligomers, 11, 14, and 17 bases long, are complementary to the region of the DNA which accounts for the am-3 point mutation. When hybridized to am-3 DNA, the oligonucleotides form duplexes with a single base pair mismatch. The thermal stability of the duplexes formed between wt and am-3 DNAs has been measured. The am-3 DNA:oligomer duplexes dissociate at a temperature about 10 degrees C lower than the corresponding wt DNA:oligomer duplexes. This dramatic decrease in thermal stability due to a single mismatch makes it possible to eliminate the formation of the mismatched duplexes by the appropriate choice of hybridization temperature. These results are discussed with respect to the use of oligonucleotides as probes for the isolation of specific cloned DNA sequences.

Bacteriophage phi X 174

Determination of the size of rat ribosomal deoxyribonucleic acid repeating units by electron microscopy.

The empoyment of a novel method of affinity chromatography, which makes use of antibodies that specifically bind DNA/RNA hybrids, has made it possible to enrich for rat rDNA molecules which contain R loops formed with the 18S and 28S rRNAs. An approximately 150-fold enrichment of the ratrRNA coding sequences was obtained by this affinity chromatography procedure. This degree of enrichment made it possible to visualize these R loop containing molecules in the electron microscope and, thus, to obtain a map of the transcribed and spacer regions of rat rDNA. Eleven of the molecules that were observed contained either 3 or 4 R loops, or else 2 R loops separated by a long spacer. Thus, these molecules provided direct information in regard to the length of rat rDNA repeating units. The mean length of the repeating units was 37.2 kbp with a standard deviation of 1.3 kbp. Within the errors of the measurements, these could all represent repeating units of exactly the same length, although a certain degree of length heterogeneity, possibly up to 4 or 5 kbp, cannot be ruled out by the data. If significantly longer or shorter rDNA repeating units exist in the rat genome, they are probably much less common than the 37.2 kbp unit. These electron microscopic measurements provide the most definitive data yet available on the size of the repeating units of mammalian rRNA genes.

Animals

Changes in expression of albumin and alpha-fetoprotein genes during rat liver development and neoplasia.

Albumin mRNA was isolated and purified from rat liver polysomes by a combination of immunoprecipitation of specific polysomes, poly(U)-Sepharose 4B chromatography, and fractionation of the resulting poly(A)-containing RNA on a sucrose gradient. alpha-Fetoprotein (AFP) mRNA was isolated from Morris hepatoma 7777 by a similar procedure. The purity of the mRNA preparations was determined by analytical gel electrophoresis under denaturing conditions, analysis of sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the polypeptides synthesized in a wheat germ cell-free system, and the kinetics of hybridization to cDNA transcribed from albumin mRNA and AFP mRNA. The albumin mRNA possessed a chain length of approximately 2265 nucleotides and the AFP mRNA possesed a length of approximately 2235 nucleotides when examined under stringent denaturing conditions on agarose gels containing 10 mM methylmercury hydroxide. Analysis of poly(A) content by a hybridization assay with [3H]poly(U) revealed the presence in albumin mRNA of a poly(A) region containing approximately 100 adenosine residues. The AFP mRNA preparation was found to contain an average poly(A) tract of approximately 190 bases. Thus, albumin mRNA appears to contain approximately 330 untranslated nucleotides, and AFP mRNA appears to contain a similar number (approximately 285) of noncoding, nonpoly(A) bases. The purified albumin and AFP mRNA's were used as templates for synthesis of full-length cDNA hybridization probes. Both of the probes selectively hybridized to their templates with kinetics expected for single RNA species the sizes of albumin and AFP mRNA. ROt analysis was used to quantitate albumin and AFP mRNA sequences during normal liver postnatal development and liver oncogenesis. The number of polysomal AFP mRNA molecules per liver was found to drastically decrease during the first weeks of postnatal life, concomitant with a decline in the AFP synthetic capacity of the livers and in the serum concentrations of AFP. During this period, the concentration of albumin mRNA molecules per cell in the liver remained at high, approximately constant levels. In Morris hepatoma 7777, the concentration of AFP-specifying sequences was at least 10(3)-fold higher than that found in normal adult liver, whereas the content of albumin nRNA was four- to five-fold lower. These changes in concentration of albumin and AFP mRNA sequences closely correlated with a parallel variation in the specific protein synthetic capacity of the tissues.

Animals