Search PubMed⌕ Search

Biomedical subjects

W Keller

Publications and source records attributed to W Keller.

At least 127 records · Page 7Linked to original sources
PubMed1979

Nucleotide sequence analysis of the leader segments in a cloned copy of adenovirus 2 fiber mRNA.

Fiber mRNA of adenovirus 2 has been used as a template for RNA-dependent DNA polymerase. The resulting cDNA/RNA hybrids have been inserted at the Pst I site of the plasmid vector pBR322 after A:T tailing. One recombinant plasmid, pJAW 43, has been characterized in detail and shown to contain sequences from the main body of fiber mRNA, the three leaders common to most late adenoviral mRNAs and a fourth leader found in some species of fiber mRNA. The complete DNA sequence of the leader region has been determined and does not contain the initiation codon AUG, although this codon does occur immediately downstream from the junction between the fourth leader and the main body of the fiber mRNA. The first leader (map coordinate 16.6) is 41 nucleotides long, the second (from 19.6) is 71 nucleotides, the third (from 26.6) is 88 nucleotides and the fourth (from 78.5) is 181 nucleotides. The location of junctions between viral leaders and intervening sequences has been determined by reference, where possible, to sequences of the adenovirus 2 genome. Although the presence of short repeated sequences at the boundaries of intervening sequences and leaders makes it impossible to locate the splice point unambiguously, all of the leader-intervening sequence junctions can be arranged to stress a common feature--the presence of the dinucleotides GT and AG at the 5' and 3' ends, respectively, of the intervening sequences. This prototype sequence, which has also been recognized at or near the splice points in other eucaryotic systems, is possibly part of a larger unit which serves as a recognition site for specific excision-ligation events that ultimately lead to the production of mature mRNAs.

Adenoviruses, Human↗
PubMed1978

Treatment of demyelinating and degenerative diseases by electro stimulation of the spinal cord.

Electrical stimulation was applied to the spinal cord of 75 patients who had demyelinating and degenerative diseases of the central nervous system, and 3 patients who had sustained spinal cord injuries. The electrical energy was delivered to the central nervous system by the percutaneous technique. The amount of electrical energy required to produce the perception of paresthesias was measured in 11 patients. The minimum power necessary was 76.89 muW, the maximum was 868 muW, and the average was 448.8 muW. The patients were evaluated by 4 examiners by means of routine neurologic examination, videotape movies, and measurement of urinary bladder function. Continued improvement in neurological status, which allowed the patient to live a better lifestyle, occurred in 30 of the 61 patients with multiple sclerosis, and 6 of the 10 patients with ataxia. The patient with transverse Myelitis, the patient with primary lateral sclerosis, and 1 patient with olivopontocerebellar atrophy; also noted similar enhancement of neurological function. The patients with amyotrophic lateral sclerosis and spinal cord injuries had no changes of significance. Thirty-two out of 44 patients who were ambulatory had significant improvement, whereas 10 of the 19 patients who were not ambulatory had improvement. There was no evidence that electrical stimulation of the spinal cord, when applied via dorsally placed percutaneous electrodes and when carried only to the perception of a paresthesias, has any adverse effect on neurological function. It is hypothecated that the electrical current alters neurotransmitters to enhance the transmission along nervous and neurochemical pathways. The exact mechanisms are unknown at the present time.

Amyotrophic Lateral Sclerosis↗
PubMed1978

Higher order structure of simian virus 40 chromatin.

Simian virus 40 nucleoprotein complexes undergo an ionic strength-dependent structural transition. At moderate ionic strength they contain histone H1 as well as the nucleosomal histones and have a compact conformation with globular subunits 190 angstroms in diameter. At high ionic strength histone H1 is released, and the structure unfolds into chains with an average of 24 nucleosomes. The extended viral chromatin converts to the compact form by the addition of histone H1. Transcriptionally active simian virus 40 chromatin undergoes the same structural transitions. The higher order structure of viral chromatin may be analogous to the compact state of cellular chromatin fibers observed at physiological ionic strength.

Chromatin↗
PubMed1978

The structure of SV 40 chromatin.

Simian virus 40 (SV40) nucleoprotein complexes were studied with the electron microscope. Depending on the isolation procedure, SV40 chromatin has two different conformations: complexes isolated in the presence of 0.15 M NaCl appeared as very compact globular structures, while those isolated in the presence of 0.6 M NaCl had the typical 'beads-on-a-string' appearance of the primary nucleofilament. Concomitant with this structural change was a variation in the histone pattern and sedimentation behaviour of the complexes: with NaCl at 0.15 mol 1(-1) the isolated complexes contained both the nucleosomal histones and histone H1, and sedimented in sucrose gradients at 70S. Increasing the ionic strength to 0.6 M NaCl resulted in the removal of histone H1 from the complexes and in a decrease of the sedimentation coefficient to 40S. DNA relaxing enzyme is associated with the SV40 nucleoprotein complexes. The numbers of superhelical turns in DNA from compact and open types of complexes were found to be the same. Therefore the transition from the condensed to the open structure of viral chromatin does not require a change in the topological winding number of its DNA.

Centrifugation, Density Gradient↗
PubMed1978

Biochemical and ultrastructural analysis of SV40 chromatin.

SV40 chromatin can be isolated in two forms: At moderate ionic strength (mu = 0.1-0.3) it contains histone H1 in addition to the four nucleosomal histones and has a highly condensed appearance in the electron microscope, being composed of a few closely connected large spheres [190 A (160, 220) diameter]. At high ionic strength (mu = 0.6-0.8) or after prolonged exposure to very low ionic strengths (mu less than 0.02), the compact form unfolds and the chromatin shows a typical nucleosomal morphology. Native SV40 DNA-protein complexes contain a median number of 24 nucleosomes. The number of superhelical turns does not differ in DNA obtained from the compact and the unfolded forms of chromatin. DNA-relaxing enzyme is found associated with SV40 chromatin and is capable of acting both on extraneously added circular DNA and on its own DNA in the nucleoprotein complex. Purified DNA-relaxing enzyme forms transiently nicked DNA intermediates where the enzyme can be found covalently attached to the site of the nick in the DNA. Transcriptionally active SV40 complexes undergo the same ionic-strength-dependent structural transition as that of bulk SV40 chromatin and may therefore also have a compact configuration at physiological salt concentrations.

Cell Line↗
PubMed1978

[Postoperative feeding of patients after maxillofacial surgery with Sokoham--a new parenteral nutritive solution].

20 patients--15 to 71 years old--, who underwent maxillofacial operations received Sokoham for 10 days via a nasogastric tube. In 0.8% of all applications vomiting occurred. Wound healing and time of hospitalisation were the same as in a control group. Mean frequency of defecation was 0.5/24 hours. Body weight, serum electrolytes, fat content of the blood, blood gases, pH, base deficit, serum transaminases, urea-nitrogen and creatinine in the serum did not change significantly.

Adolescent↗
PubMed1977

[Experimental investigations on the tumorigenic activity of cigarette smoke condensate on mouse skin. VII. Comparative studies of condensates from different modified cigarettes (author's transl)].

Condensate from different modified cigarettes were compared with condensate from a standard cigarette with regard to its tumorigenic activity on mouse skin. Significant lower effects were observed in test series with cigarettes from expanded tobacco. Different results were obtained in experiments with cigarettes from the new smoking materials. In one case the effect was higher, in two another cases the effect was lower in comparison to the effect of condensate from reference cigarettes. A certain influence may be referred to the diameter of the cigarette, i.e. a thinner cigarette shows a lower biological effect. The lowest tumoringenic effect was observed in tests with cigarettes with a high content of Burley-stems.

Animals↗
PubMed1977

The presentation and use of height and weight data for comparing the nutritional status of groups of children under the age of 10 years.

This paper presents recommendations for the analysis and presentation of height and weight data from surveillance or surveys involving nutrition and anthropometry in young children up to the age of 10 years. These recommendations are only for the analysis of data collected on a cross-sectional basis. The basic indices recommended are height for age and weight for height, each considered either in terms of centiles or in a cross-classification scheme using standard deviation scores. It is hoped that these methods of analysis and presentation will prove widely acceptable, so that international comparisons will be made easier.

Anthropometry↗
PubMed1976

Genes inhibiting senescence in the ascomycete Podospora anserina.

Senescence occurs in all wild strains of Podospora anserina after continued growth. This syndrome can be inhibited by a synergistic interaction of two linked genes, incoloris and vivax. Whereas the wild strain starts to become senescent after 26 d and the mutants incoloris and vivax after 42 and 66 d respectively, the double mutant shows no signs of aging after culture for more than one year.

Ascomycota↗
PubMed1975

Determination of the number of superhelical turns in simian virus 40 DNA by gel electrophoresis.

Closed-circular, superhelical DNA from simian virus 40 (SV40 DNA I) was treated with an excess of DNA-relaxing enzyme in the presence of increasing amounts of ethidium bromide (EtdBr). After removal of the ethidium, each sample consisted of a group of close-circular DNA molecules differing in their number of superhelical turns (tau) around a mean value of tau in a Gaussian-like distribution. The DNA samples were analyzed by electrophoresis in agarose gels under conditions where the electrophoretic mobility was a function of the number of superhelical turns. Since the distributions around tau of DNA molecules of different samples overlappped, the difference in the mean number of superhelical turns from sample to sample, delta tau, could be determined and used to measure the mean number (tau) for native SV40 DNA I. By this criterion, SV40 DNA I contains a Gaussian-like distribution of molecules differing by integral numbers around a mean value of tau = -24 +/- 2 at 37 degree C [in 0.2 M NaC1, 10 mM Tris-HC1 (pH 7.9), and 0.2 mM EDTA]. The heterogeneity in tau is probably a consequence of thermal fluctuations in the DNA helix at the time when the last phospholiester bond is closed in vivo. When correlated to the buoyant shift of completely relaxed SV40 DNA in a CsC1-propidium diiodide gradient, the number of delta tau = 24 +/- 2 of superhelical versus relaxed DNA implies an unwinding of the DNA helix by 26-28 degree upon intercalation of one molecule of EtdBr.

DNA, Circular↗
PubMed1975

Characterization of purified DNA-relaxing enzyme from human tissue culture cells.

Superhelical simian virus 40 DNA migrates more rapidly during electrophoresis in agarose gels than covalently closed DNA free of superhelical turns (relaxed DNA). The difference in electrophoretic mobility between superhelical and relaxed DNA was used to monitor the activity of a protein from human tissue culture cells which converts superhelical DNA into relaxed DNA. Purified DNA-relaxing protein removes both negative and positive superhelical turns and acts in a catalytic manner. The relaxation of DNA proceeds in a stepwise fashion and DNA intermediates with decreasing numbers of superhelical turns are seen during the course of the reaction.

Cell Line↗
PubMed1975

Stepwise relaxation of supercoiled SV40 DNA.

We have shown in this paper that agarose gel electrophoresis can be used to examine the tertiary structure of supercoiled SV40 DNA. Differences as small as one superhelical turn can be detected by this method. When used as an assay, it enabled us to purify from human tissue culture cells a protein which acts on supercoiled DNA, leading to a gradual removal of its superhelical turns. Using in turn the purified DNA relaxing protein to generate reaction intermediates of DNAs with different numbers of superhelical turns, we deduced that native SV40 DNA contains a minimum of 20 physical superhelical turns. The upper limit of this number is less accurately defined, but we think that it is not higher than 24. These numbers agree within very close limits with the numbers determined previously by various indirect physical methods.

Cell Fractionation↗
PubMed1974

The length of the terminal repetition in adenovirus-2 DNA.

Adenovirus-2 DNA was end-labeled by partial digestion with Escherichia coli exonuclease III and resynthesis with the DNA polymerase from avian myeloblastosis virus and alpha-(32)P-labeled deoxyribonucleoside triphosphates. This end-labeled DNA was cleaved with several specific endonucleases and the terminal fragments were characterized by gel electrophoresis and pyrimidine tract analysis. Two endonucleases gave identical fragments from both ends, presumably from cleavage within the inverted terminal repetition, while all other endonucleases gave dissimilar fragments from the two ends. From the sizes of these fragments it is estimated that the inverted terminal repetition is between 100 and 140 nucleotide pairs long.

Adenoviridae↗