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Biomedical subjects

B Keller

Publications and source records attributed to B Keller.

At least 109 records · Page 6Linked to original sources
PubMed1989

Anthropometric measurements of adolescent and professional classical ballet dancers.

This study examined anthropometric measures of 83 female adolescent students attending the Boston Ballet summer program and 15 professional dancers from the Boston Ballet Company. Thirty-one were in the least advanced level (group A), 38 were in the moderately advanced level (group B) and 14 were in the most advanced level (group C). The adolescent dancers devoted between 17 and 23 hours per week in dance training, while professional dancers spent 39.2 hours per week in class and rehearsals. Compared to normative data, the dancers tended to be tall and slim. The skinfold, diameter, and circumference measurements were found to be very similar among groups A, B and C, and between group C and the company members. The somatograms demonstrated that the ballet dancers had relatively smaller upper arms and larger calves and ankles compared with the reference female. The data from this study suggest that the body type characteristics associated with professional classical ballet dancers are already apparent in the pre-professional adolescent dancers.

Adolescent↗
PubMed1988

Glycine-rich cell wall proteins in bean: gene structure and association of the protein with the vascular system.

A single genomic clone (14 kb) isolated from bean (Phaseolus vulgaris L.) contains two genes that encode glycine-rich proteins. These genes are present as single copies in the genome, are separated by 2.85 kb and encode transcripts of 1.8 kb and 1.0 kb respectively. The encoded proteins contain 60% glycine and have amino-terminal signal peptides. The 1.8 kb transcript is present in young hypocotyls and in ovary tissue. Excision-wounding transiently induced this transcript in old, but not in young hypocotyl tissue. Antibodies raised against regions of the glycine-rich protein 1.8, expressed as a lacZ fusion protein in bacteria, react with a protein of 53 kd in a protein fraction extracted from cell walls of bean ovaries. Tissue imprints of bean ovaries treated with anti-glycine-rich protein antibodies showed that the glycine-rich protein was distributed in a regular pattern of small, highly localized discrete sites. The immunoreactive regions correspond to the pattern of vascular tissue in the pod. In young hypocotyls, glycine-rich protein is present at four pairs of discrete sites symmetrically arranged on the inner side of the vascular ring. These results suggest a close relationship between glycine-rich proteins and development of the vascular system.

Amino Acid Sequence↗
PubMed1988

Length and shape variants of the bacteriophage T4 head: mutations in the scaffolding core genes 68 and 22.

The shape and size of the bacteriophage T4 head are dependent on genes that determine the scaffolding core and the shell of the prohead. Mutants of the shell proteins affect mainly the head length. Two recently identified genes (genes 67 and 68) and one already known gene (gene 22), whose products are scaffold constituents, have been investigated. Different types of mutants were shown to strongly influence the proportion of aberrantly shaped particles. By model building, these shape variants could be represented as polyhedral bodies derived from icosahedra, through outgrowths along different polyhedral axes. The normal, prolate particle is obtained by elongation along a fivefold axis. The mutations of the three core genes (genes 67, 68, and 22) affect the width mainly by lateral outgrowths of the prolate particle, although small and large isometric particles are also found. Many of the aberrant particles are multitailed, suggesting a correlation between tail attachment sites and shape.

DNA Mutational Analysis↗
PubMed1987

Prohead core of bacteriophage T4 can act as an intermediate in the T4 head assembly pathway.

Bacteriophage T4 assembly was impaired in Escherichia coli hdB3-1 at an incubation temperature below 30 degrees C. Naked prohead cores (head scaffold) bound to the inner surface of the plasma membrane accumulated, and the major shell protein (gp23) precipitated into visible intracellular aggregates in the cytoplasm. Shifting the temperature to 42 degrees C allowed newly synthesized gp23 to assemble around the accumulated cores. We conclude that synchronous assembly of the scaffold and shell is not obligatory and that naked cores can serve as intermediates in the T4 assembly pathway.

Cell Membrane↗
PubMed1986

Amber mutants in gene 67 of phage T4. Effects on formation and shape determination of the head.

Two amber mutations in gene 67 of bacteriophage T4 were constructed by oligonucleotide-directed mutagenesis and the resulting mutated genes were recombined back into the phage genome and their phenotype was studied. The 67amK1 mutation is close to the amino terminus of the gene, and phage carrying this mutation are unable to form plaques on suppressor-negative hosts. A second mutation, 67amK2, which lies in the middle of the gene, three codons N-terminal to a proteolytic cleavage site, produces a small number of viable phage particles. In suppressor-negative hosts, both mutants produce polyheads and proheads. 67amK1 assembles only few proheads that have a disorganized core structure, as judged from thin sections of infected cells. The proheads and the mature phages of both mutants are mainly isometric rather than having the usual prolate shape. Depending on the 67 mutant and the host, between 20% and 73% of the particles that are produced are isometric, and 1 to 10% are two-tailed biprolate particles. 67amK2 phages grown on a supD suppressor strain that inserts serine in place of the wild-type leucine do not contain gp67* derived from gene product 67 (gp67) by proteolytic cleavage. This demonstrates the importance of the correct amino acid at this position in the protein. Other abnormalities in these 67amK2 phages are the presence of uncleaved scaffolding core proteins (IPIII and gp68), indicating a structural alteration in the prohead scaffold, resulting in only partial cleavage. In wild-type phages these proteins are found in the head only in the cleaved form. With double-mutants of 67 with mutations in the major shell protein gp23 no naked scaffolding cores were found, confirming the necessity of gp67 for the assembly or persistence of a "normal" core.

Genes, Viral↗
PubMed1986

The nucleotide sequence of gene 21 of bacteriophage T4 coding for the prohead protease.

We have sequenced gene 21 coding for the bacteriophage T4 prohead protease. The sequence codes for a protein of 212 amino acids (aa) with an Mr of 23,251. A second possible in-frame initiation site was also found which would code for an Mr 18,440 protein. Evidence is presented that this second site is used in vivo. The only striking homology of gp21 to other proteins is with the serine proteases. The protein is homologous to a short aa sequence around the active site, but has a His where the active site Ser is normally found. However, mutation of this His to Ser gave a functional protein that could not be inhibited by serine protease inhibitors. We have located three sites in the gene that give rise to temperature-sensitive mutations. One of these is towards the N-terminus of the gene, the other two flank the region that shows homology with serine proteases. Attempts to overproduce the protein in Escherichia coli failed due to the extreme lability of the enzyme. A frame-shift mutation in the gene was therefore constructed which allowed the synthesis of large amounts of a stable N-terminal fragment of the protein.

Amino Acid Sequence↗
PubMed1986

A distribution-free, multivariate discriminating method. Initial experience with the discrimination of patient groups by 2 or more clinical chemical parameters.

We communicate a distribution-free quasi graphic procedure for obtaining a linear discriminating function. The method is based on the following considerations: Suppose a group A is to be separated from a group B using two parameters X and Y. The centre of each group is defined as the median (or mean or mode) of its points. Of all straight lines passing through any point of A and any point of B those are retained which intersect the segment joining the centres of A and B. For each of these the number of wrongly allocated points is calculated (i.e. the points which do not lie on the same side of the straight line as their group centres). In this way one obtains straight lines with maximal separating power (for the two groups given). Finally, each optimal line is rotated in such a way that its defining points are also correctly allocated. If more than two parameters are available a stepwise procedure can be used: the distance from the separating straight line obtained from the first two parameters is introduced as a new parameter, which is then combined with the third parameter to yield a new discriminating function which depends on all three parameters. Iterating this step one can combine any number of parameters. The method was implemented on a personal computer. It was first applied to a textbook model (chances of survival for M. haemolyticus neonatorum estimated by concentrations of haemoglobin and bilirubin in cord blood).(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium↗
PubMed1986

Potential for real-time processing of the continuously monitored electrocardiogram in the detection, quantitation, and intervention of silent myocardial ischemia.

Current technology for monitoring and analyzing the ST segment allows for accurate description of ST-segment deviation, which in most cases is a valid measure of myocardial ischemia. In this article, the authors describe a new method that utilizes microprocessor analysis of the electrocardiogram to detect ST-segment deviation in ambulatory subjects. This technique results in the ability to characterize the total ischemic burden over long periods of time and to intervene acutely in order to treat myocardial ischemia and possibly to prevent complications of coronary artery disease.

Algorithms↗
PubMed1985

Determination of the cleavage site of the phage T4 prohead protease in gene product 68. Influence of protein secondary structure on cleavage specificity.

The cleavage site of the T4 prohead protease in gene product 68 of bacteriophage T4 has been determined by direct protein sequencing. It is located close to the carboxy-terminal end of a predicted alpha-helix in the sequence Asn-Val-Glu-Ala between the Glu and Ala residues. Secondary structure seems to be more important in determining cleavage than the presence of an aliphatic amino acid three residues before the cleavage site that was proposed earlier. In this case, that position is occupied by Asn, a hydrophilic residue. A second potentially cleavable Glu-Ala is found five residues after the cleaved sequence and this is preceded by an Ile at the -3 position. Despite this, the sequences of the amino and carboxyl termini of the uncleaved protein are identical to those previously proposed from an analysis of the DNA sequence of the gene.

Peptide Hydrolases↗
PubMed1985

Purification of arogenate dehydrogenase from Phenylobacterium immobile.

Phenylobacterium immobile, a bacterium which is able to degrade the herbicide chloridazon, utilizes for L-tyrosine synthesis arogenate as an obligatory intermediate which is converted in the final biosynthetic step by a dehydrogenase to tyrosine. This enzyme, the arogenate dehydrogenase, has been purified for the first time in a 5-step procedure to homogeneity as confirmed by electrophoresis. The Mr of the enzyme that consists of two identical subunits amounts to 69000 as established by gel electrophoresis after cross-linking the enzyme with dimethylsuberimidate. The Km values were 0.09 mM for arogenate and 0.02 mM for NAD+. The enzyme has a high specificity with respect to its substrate arogenate.

Electrophoresis, Polyacrylamide Gel↗
PubMed1985

Deletion analysis of a bacteriophage T4 late promoter.

We have conducted a BAL 31 unidirectional deletion analysis to determine whether the conserved consensus sequence found upstream of all sequenced phage T4 late genes represents the late T4 promoter or is only part of the promoter. The results confirm those of Elliott and Geiduschek [Cell 36 (1984) 211-219] that no sequences upstream from the consensus sequence are necessary for late transcription activity. In addition, they provide evidence that sequences downstream from the consensus sequence are important. We have also constructed a sequence that differs in several positions from the consensus but which still shows the properties of a late T4 promoter. Finally, we have noticed a remarkable homology between the consensus sequence for late T4 promoters and mitochondrial promoters from Saccharomyces cerevisiae and Kluyveromyces lactis.

Base Sequence↗
PubMed1985

Arogenate dehydrogenase from Streptomyces phaeochromogenes. Purification and properties.

Arogenate dehydrogenase, the terminal enzyme of tyrosine biosynthesis in Streptomyces phaeochromogenes, was purified to homogeneity by a five-step procedure. The enzyme is a dimer of Mr 57 600 as determined by dodecyl sulfate polyacrylamide gel electrophoresis after cross-linking of the monomers, or of 66 300 as found by gel permeation chromatography, and consists of two identical subunits of Mr 28 100. The pI of the enzyme is 4.45, and the Km values are 0.105mM for arogenate and 0.01 mM for NAD.

Ammonium Sulfate↗