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B Dunn

Publications and source records attributed to B Dunn.

At least 73 records · Page 4Linked to original sources
PubMed1989

Calcium-dependent proteolysis of actin during storage of platelet concentrates.

In an ongoing study of the changes that occur in platelet concentrates during storage, we investigated two 28-26-Kd proteins designated SP-1 and SP-2, respectively, which increase markedly during blood-bank storage of platelet concentrates at room temperature. Formation of SP-1 and SP-2 was inhibited by storage at 4 degrees C as well as by treatment of the concentrates with leupeptin, N-ethylmaleimide, and EDTA; DFP and PPACK had no effect. The calcium ionophore A23187 markedly stimulated production of SP-1 and SP-2. After partial purification, the two proteins were found to be associated with platelet cytoskeletal protein. Two-dimensional peptide mapping and amino acid sequencing identified SP-1 and SP-2 as fragments of actin formed by cleavage on the N-terminal side of residues Thr-106 and Ala-114, respectively. Generation of SP-1 and SP-2 during storage of platelet concentrate is likely attributable to calcium-dependent neutral protease degradation of actin and may have implications for development of the platelet storage lesion.

Actins↗
PubMed1988

The effect of histone gene deletions on chromatin structure in Saccharomyces cerevisiae.

As a way of studying nucleosome assembly and maintenance in Saccharomyces cerevisiae, mutants bearing deletions or duplications of the genes encoding histones H2A and H2B were analyzed. Previous genetic analysis had shown that only one of these mutants exhibited dramatic and pleiotropic phenotypes. This mutant was also the only one that contained disrupted chromatin, suggesting that the original phenotypes were attributable to alterations in chromosome structure. The chromatin disruption in the mutant, however, did not extend over the entire genome, but rather was localized to specific regions. Thus, while the arrangement of nucleosomes over the HIS4 and GAL1 genes, the telomeres, and the long terminal repeats (delta sequences) of Ty retrotransposons appeared essentially normal, nucleosomes over the CYH2 and UBI4 genes and the centromere of chromosome III were dramatically disrupted. The observation that the mutant exhibited localized chromatin disruptions implies that the assembly or maintenance of nucleosomes differs over different parts of the yeast genome.

Centromere↗
PubMed1987

Phylogenetic diversity and position of the genus Campylobacter.

RNA sequence analysis has been used to examine the phylogenetic position and structure of the genus Campylobacter. A complete 5S rRNA sequence was determined for two strains of Campylobacter jejuni and extensive partial sequences of the 16S rRNA were obtained for several strains of C. jejuni and Wolinella succinogenes. In addition limited partial sequence data were obtained from the 16S rRNAs of isolates of C. coli, C. laridis, C. fetus, C. fecalis, and C. pyloridis. It was found that W. succinogenes is specifically related to, but not included, in the genus Campylobacter as presently constituted. Within the genus significant diversity was noted. C. jejuni, C. coli and C. laridis are very closely related but the other species are distinctly different from one another. C. pyloridis is without question the most divergent of the Campylobacter isolates examined here and is sufficiently distinct to warrant inclusion in a separate genus. In terms of overall position in bacterial phylogeny, the Campylobacter/Wolinella cluster represents a deep branching most probably located within an expanded version of the Division containing the purple photosynthetic bacteria and their relatives. The Campylobacter/Wolinella cluster is not specifically includable in either the alpha, beta or gamma subdivisions of the purple bacteria.

Base Sequence↗
PubMed1985

Antibodies to 5 M urea soluble chromosomal proteins from HeLa cells.

The tissue specificity of a chromosomal protein fraction, extractable from chromatin with 5 M urea at low ionic strength, has been examined in HeLa, A549 and HT 29 cells. Electrophoresis in polyacrylamide gels indicates that each cell type has a different content of 5 M urea soluble proteins which are distinguishable from the histones, from the tight DNA-binding proteins and from the high-mobility-group chromosomal proteins. Antibodies against 5 M urea soluble proteins extracted from HeLa cells were produced in mice. Although each of the mice tested prior to immunization contained a detectable amount of antibodies against both the 5 M urea soluble proteins and tight DNA-binding proteins, immunization elevated the level of the antibodies in the serum over 100-fold. The antibodies do not distinguish between the 5 M urea extracts obtained from different sources because most of the antibodies are directed against antigens shared by the cells studied. Immunofluorescence studies reveal that components which cross-react with 5 M urea soluble chromosomal proteins are also present in the cytoplasm. We conclude the following. (1) 5 M urea extracts from chromatin a group of proteins which differs among cells. (2) Mice contain detectable amounts of autoantibodies against these chromosomal proteins. (3) Immunization with the 5 M urea extractable fraction elicits antibodies against a restricted number of antigenic components which are shared among the cells studied. (4) 5 M urea extractable proteins are found both in the nucleus and cytoplasm; part of these may be cytoskeletal elements. Because the antisera do not react with histones, high-mobility-group proteins and tight DNA-binding proteins, they may be used for various functional studies on the 5 M urea extractable chromosomal protein fraction.

Animals↗
PubMed1984

True sensitivity of cardiac exercise testing. A combined clinical evaluation of multiple parameters.

Maximal exercise tests were performed in 308 patients with angiographically defined coronary disease, in 38 patients whose coronary vessels were not obstructed, and in 236 clinically normal volunteers. The sensitivity of parameters indicating ischaemia was evaluated singly and in combination in each group. The most sensitive individual parameters were work capacity restriction (65%), ST segment depression (56%) and test angina (55%). When the sequence of parameters were assessed successively in the coronary group, the sensitivity rose from 56% with ST depression to 70% with the addition of test angina, to 85% when work capacity restriction was added, and to 87% when inadequate heart rate or blood pressure responses or repetitive ventricular arrhythmias were included. In the group of patients whose coronary vessels were not obstructed, substantial clinical abnormalities and a bias to carry out angiography in those with abnormal exercise responses led to false ST segment changes in 34%, and, in a further 20%, to positivity in the other parameters. In clinically normal subjects a 15% "false" positive rate occurred. One parameter (R wave amplitude change) was falsely positive in 24%, and was therefore excluded. Grouped parameter sensitivity for patients who exercised on a bicycle and those who used a treadmill was similar.

Coronary Disease↗
PubMed1984

Transfer of yeast telomeres to linear plasmids by recombination.

We have characterized two types of recombination events between linear plasmids and yeast chromosomal telomere-adjacent sequences (Y' elements). In one type of event, a linear plasmid restriction-cut within a Y' element regains the missing Y' DNA, and may also acquire additional Y' elements. This process is similar to the healing of broken chromosomes by recombination. In a second type of event, terminally added C1-3A sequences on the linear plasmid interact with C1-3A sequences located just internal to the chromosomal Y' elements, resulting in the addition of one to four Y' elements to the plasmid. Similar recombination events occurring between different chromosome ends could lead to the dispersal and amplification of telomere-adjacent sequences.

Base Sequence↗
PubMed1983

Specific binding of Alu sequences by HeLa nuclear extracts.

Plasmid Blur 8 which contains the 300bp human Alu consensus sequence and plasmid pBR322 were digested with restriction enzymes and the fragments obtained end labelled with 32P-gamma-ATP. The end labelled fragments were incubated with HeLa nuclear extracts and the incubation mixtures passed through a nitrocellulose filter. The 300bp alu consensus sequence was preferentially retained on the filter. The HeLa nuclear extract did not preferentially bind any fragments generated from pBR322 and histones which bind nonspecifically all DNA fragments did not preferentially bind the alu sequence. We conclude that the HeLa nuclear extract contains components which specifically bind the human alu sequence.

Base Sequence↗
PubMed1983

Thermal characterization of electrosurgery.

The volumetric heating response of soft tissues to electrosurgical cutting and coagulation was studied. A series of experiments was conducted with thermistor probes embedded in a surrogate medium during controlled application of the electrosurgery current. A series of temperature profiles was obtained for various thermistor probe locations. These temperature profiles were found to be linear, exponential, or double exponential, depending upon the probe-incision distance. Temperatures next to the site of tissue destruction approached 70 degrees C, within 2 seconds of application of power. Temperature changes due to lateral heating were an order of magnitude greater than temperature changes directly under the incision. Anisotropic heat conduction was observed for muscle fibers oriented in different directions.

Electrocoagulation↗
PubMed1982

Antigenic determinants of high mobility group chromosomal proteins 1 and 2.

The antigenic determinants of nonhistone high mobility group chromosomal proteins 1 (HMG-1) and 2 (HMG-2) were studied with rabbit antisera elicited against HMG-1 and against HMG-2 and monoclonal antibodies elicited by HMG-1. The monoclonal antibodies did not distinguish between the two proteins, suggesting that they have specificity toward a shared determinant. Whereas anti-HMG-1 did not, anti-HMG-2 did distinguish between the proteins, suggesting that the anti-HMG-2 serum contains antibodies against peptides which differ between the proteins. Peptides were generated from HMG-1 and HMG-2 by controlled digestion with trypsin and pepsin. Analysis of the digests by ELISA and by sodium dodecyl sulfate electrophoresis followed by diazobenzyloxymethyl transfer, antibody binding and autoradiography revealed that most of the antibodies are against sequential determinants some of which are smaller than 3000 in molecular weight.

Animals↗
PubMed1982

Antibodies against the folding domain of histone H5 cross-react with H1(0) but not with H1.

Antibodies to the folding domain (residues 22-100) of histone H5 were elicited in rabbits. Analysis of the specificity of these antibodies by enzyme-linked immunoassay and by diazobenzyloxymethyl cellulose transfer techniques revealed that the antibody cross-reacts strongly with intact H5 and histones H1(0)a and H1(0)b purified from ox liver but not with the four core calf thymus, or with high mobility group proteins. We conclude that the globular region of H5 is serologically homologous to that of H1 degrees and suggest that possible functional similarities between the two proteins reside in this region.

Animals↗