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B Wold

Publications and source records attributed to B Wold.

At least 37 records · Page 2Linked to original sources
PubMed1993

HLH forced dimers: tethering MyoD to E47 generates a dominant positive myogenic factor insulated from negative regulation by Id.

Basic-helix-loop-helix (bHLH) class transcription factors bind DNA as hetero- and homodimers. In murine myogenic cells the HLH network includes multiple members of the E protein, MyoD, and Id families; changes in the network characterize muscle determination and differentiation and have been proposed as causal for these developmental transitions. To test the importance of HLH partner choice in these cellular decisions, we have designed a strategy in which the identity of a bHLH dimer is specified by joining two monomers via a flexible polypeptide linker. A MyoD-E47 polyprotein avidly bound the same DNA targets as its unlinked counterpart, but, unlike intermolecular dimers that are very sensitive to inhibition by Id, MyoD-E47 was resistant to Id challenge. In cells MyoD-E47 acted as a dominant positive myogenic factor, capable of initiating myogenic determination and also substantially bypassing negative regulation of differentiation by serum growth factors.

3T3 Cells↗
PubMed1993

Nucleolar localization of myc transcripts.

In situ hybridization has revealed a striking subnuclear distribution of c-myc RNA transcripts. A major fraction of the sense-strand nuclear c-myc transcripts was localized to the nucleoli. myc intron 1-containing RNAs were noticeably absent from nucleoli, accumulating instead in the nucleoplasm. The localization of myc RNA to nucleoli was shown to be common to a number of diverse cell types, including primary Sertoli cells and several cell lines. Furthermore, nucleolar localization was not restricted to c-myc and N-myc and myoD transcripts also displayed this phenomenon. In contrast, gamma-actin or lactate dehydrogenase transcripts did not display nucleolar localization. These observations suggest a new role for the nucleolus in transport and/or turnover of potential mRNAs.

3T3 Cells↗
PubMed1993

Isolated sequences from the linked Myf-5 and MRF4 genes drive distinct patterns of muscle-specific expression in transgenic mice.

In developing mouse embryos, MyoD family regulatory genes are expressed specifically in muscle precursors and mature myofibers. This pattern, taken together with the well-established ability of MyoD family members to convert a variety of cell types to skeletal muscle, suggests a significant role for these genes in regulating skeletal myogenesis. The possibility that expression of these genes may be causally associated with segregation of the myogenic lineage from other mesodermal derivatives, or with the subsequent maintenance of muscle phenotypes at later times, raises the issue of how MyoD family genes are themselves regulated during development. In this work, we have initiated studies to identify DNA sequences that govern Myf-5 and MRF4 (herculin, myf-6) transcription. Myf-5 is the first of the MyoD family to be expressed in the developing mouse embryo, while MRF4 is the most abundantly expressed myogenic factor in postnatal animals. In spite of their strikingly divergent patterns of expression, Myf-5 and MRF4 are tightly linked in the mouse genome; their translational start codons are only 8.5 kilobases apart. Here, the 5' flanking regions of the mouse Myf-5 and MRF4 genes were separately linked to a bacterial beta-galactosidase (lacZ) gene, and these constructs were each used to produce several lines of transgenic mice. Transgene expression was monitored by X-gal staining of whole embryos and by in situ hybridization of embryo sections. For the Myf-5/lacZ lines, the most intense transgene expression was in the visceral arches and their craniofacial muscle derivatives, beginning at day 8.75 post coitum (p.c.). This correlates with endogenous Myf-5 expression in visceral arches.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Analysis of promoter-specific repression by triple-helical DNA complexes in a eukaryotic cell-free transcription system.

A site-specific triple-helical DNA complex has previously been shown to inhibit DNA binding by eukaryotic transcription factor Sp1. To examine the functional consequences of such inhibition, homopurine target sequences for oligonucleotide-directed triple-helix formation were inserted in various configurations relative to Sp1 transcription activator binding sites, upstream of the TATA element of recombinant eukaryotic promoters. The resulting promoters were tested for activity in the presence or absence of recombinant human Sp1 in a Drosophila in vitro transcription system lacking endogenous Sp1. When triple-helical complexes were assembled on the promoters by incubation with specific oligodeoxyribonucleotides, promoter-specific repression of basal transcription was observed in the absence of Sp1. Transcriptional repression required the preassembly of triple-helical complexes before addition of nuclear extract. The degree of basal repression was a function of the number and proximity of triple-helical complexes relative to the basal promoter complex. Repression did not result from triple-helix-induced template degradation. Addition of recombinant Sp1 did not cause derepression. These results suggest that triple-helical complexes can repress transcription primarily by blocking promoter DNA assembly into initiation complexes rather than by occluding Sp1 binding. One of several plausible mechanisms for triple-helix-induced repression involves changes in DNA flexibility. Evidence in favor of this model is provided by a permutation-dependent gel mobility assay in which formation of site-specific triple-helical complexes is shown to stiffen double-helical DNA.

Animals↗
PubMed1992

Parental and peer influences on leisure-time physical activity in young adolescents.

Influence from parents and friends on adolescents' self-reported level of leisure-time physical activity was examined through measures of (a) perceived leisure-time physical activity of parents and best friend, (b) perceived direct support for physical activity from parents and friends, (c) direct help from parents in exercising vigorously, and (d) perceived value of physical activity of parents and friends. The present analysis included 904 students in western Norway (M age 13.3 years, SD 0.3) who took part in a health behavior survey, which included questions regarding physical activity. Students completed a confidential questionnaire at school. All four measures of influence were positively related to students' activity levels. None of the examined measures was clearly stronger than the other. Parental and peer physical activity level and parental and peer support for physical activity seem to influence the reported physical activity level of the respondents. The findings indicate that, by serving as models and supporters, significant others have an important impact in promoting physical activity in young adolescents.

Adolescent↗
PubMed1991

[Smoking and use of alcohol among Norwegian school children: trends in the 1980s].

Large-scale, national surveys to assess smoking and use of alcohol among representative samples of Norwegian school children were conducted in November 1983, 1985, and 1989. The surveys were part of the international WHO-study: Health Behaviour in Schoolchildren. A total of 3,391 (1983), 3,955 (1985) and 5,037 (1989) 5th, 7th and 9th grade students completed an anonymous questionnaire. The results clearly show that both experimentation and regular use of cigarettes and alcohol take place as early as in the 5th grade. There is a strong increase in reported use from the 5th to the 9th grade. In 1989, by the time they reached the 9th grade the large majority of students had tried smoking at least one cigarette (60% of the boys and 58% of the girls) or had tried drinking alcohol (85% of the boys and 80% of the girls). Furthermore, a substantial proportion of the students reported regular use of these substances. In 1989, 22% of the 9th grade boys and girls reported smoking every day or every week. Similarly, 29% of the boys and 27% of the girls reported drinking alcoholic beverages at least once a month. Comparing the results across the three surveys, we find that an encouraging decline in self-reported use of cigarettes and alcohol seems to have taken place from 1983 to 1989 among school children 11-16 years old.

Adolescent↗
PubMed1991

[Self-reported accident frequency among children and adolescents].

The article presents self-reported accidents among a representative group of Norwegian children from grades 5, 7 and 9. About half of the girls and 2/3 of the boys report having had at least one accident which had to be treated by a physician during their lifetime. This number is less than expected on the basis of accident-report figures, and may indicate that a small group of children have an unproportionally large number of accidents. About 35% of the children surveyed report having had an accident sometime during the past year. This is significantly more than expected and thus indicates report bias. There are important methodological difficulties associated with self-reporting of accidents among children. The difficulties can be minimized if the time period is limited and the types of accident are well-defined. If these conditions are fulfilled, self-reporting can be an important complement to accident-report figures.

Accidents↗
PubMed1991

[Use of safety devices among children and adolescents].

5,000 Norwegian children from grades 5, 7 and 9 participated in a survey which questioned to what extent they use various kinds of safety equipment: safety belt, bicycle helmet, reflector, life-vest when in small boats, skateboard helmet and other skateboard safety devices. Use of all types of equipment decreases with increasing age. Except for reflectors, which are used most often by girls, there are no difference between girls and boys as regards use of safety equipment. The results indicate that there is a large potential for increasing the use of safety equipment among children. The consistent decrease in use of such equipment as children grow older shows the importance of understanding the social processes associated with use of safety equipment.

Accident Prevention↗
PubMed1991

Distribution of dental health behaviors in Nordic schoolchildren.

The present study was part of the project "Health Behavior in Schoolchildren. A WHO Cross National Survey". The distribution of eight dental health behaviors among Finnish, Norwegian, and Swedish schoolchildren aged 11, 13, and 15 yr was studied separately for boys and girls. The sample size approximated 3000 individuals for each country, and the samples are considered to be representative for whole countries. The distinction between individual and collective behavior was empirically supported in this study. Thus collective behaviors (supervised fluoride rinsing and distribution of fluoride tablets) did not vary according to sex but declined with increasing age. On the other hand, individual behaviors varied according to sex and tended to increase in frequency with increasing age. The levels of the studied dental health behaviors were different among the three countries. This may be related to country-specific preventive policies as well as social and cultural norms.

Adolescent↗
PubMed1991

Determinants of dental health behaviors in Nordic schoolchildren.

As part of the comprehensive study "Health Behavior in Schoolchildren. A WHO Cross National Survey", this paper set out to identify determinants of four dental health behavioral dimensions in Finnish, Norwegian, and Swedish schoolchildren aged 11, 13, and 15. The data were collected by means of self-administered questionnaires, and the results are considered to be representative of each country. The total sample size approximated 3000 pupils in each country. The four dependent variables, fluoride, interdental cleaning, sugar, and brushing behavior, were all based upon sum-scores of several questions, and were subsequently regressed upon five predictors: school achievement, sex, time spent with friends, educational plans, and family meal pattern. This model provided a far better fit to the data on sugar and brushing behavior than to fluoride and interdental cleaning behavior. However, brushing seems to be different from sugar behavior, being influenced by different factors. While brushing is closely linked to the prevailing sex-role pattern, sugar behavior is stronger related to peer group norms. Thus, the symbolic function of sweet consumption of the youth culture should have implications for the design of intervention strategies. For example, the provision of alternative behaviors will only be successful if the behaviors serve the same function as sugar consumption.

Adolescent↗
PubMed1991

Oligonucleotide-directed DNA triple-helix formation: an approach to artificial repressors?

Pyrimidine oligonucleotides exhibit sequence-specific binding to purine sequences in double-helical DNA. Molecular recognition occurs through triple-helix formation, mediated by Hoogsteen hydrogen bonding of the pyrimidine strand parallel to the double-helical DNA purine strand. Oligonucleotide-directed DNA triple-helix formation has been shown to inhibit the recognition of double-helical DNA by sequence-specific binding proteins. This observation provides the potential for new approaches to both the analysis of nucleic acids, and the study of nucleic acid-protein interactions. We wish to understand molecular mechanisms whereby such complexes affect protein-DNA interactions involved in eukaryotic transcription.

Base Sequence↗
PubMed1991

The lifestyle concept and health education with young people. Results from a WHO international survey.

This article draws upon data from a unique, 11-country study of young people's health behaviour, facilitated by the WHO Regional Office for Europe. Analyses of the data available on individual health behaviours cluster into two groups: (i) health enhancing behaviours; and (ii) health-compromising behaviours. The results were analysed to identify the strength and consistency of these lifestyles across countries. A relatively modest proportion of the variance of the original variables was explained by these two lifestyle factors, but a consistent pattern emerged between countries. This consistency indicates that the health-related lifestyles of young people may not vary greatly between the countries in the study, a finding which might be used as an encouragement for greater international cooperation in the development and use of health education materials for young people, which may be easily transferable between countries. The data also support a more integrated approach to health education based on the promotion of healthy lifestyles, rather than a focus on individual health behaviours.

Adolescent↗
PubMed1990

Herculin, a fourth member of the MyoD family of myogenic regulatory genes.

We have identified and cloned herculin, a fourth mouse muscle regulatory gene. Comparison of its DNA and deduced amino acid sequences with those of the three known myogenic genes (MyoD, myogenin, and Myf-5) reveals scattered short spans with similarity to one or more of these genes and a long span with strong similarity to all three. This long span includes a sequence motif that is also present in proteins of the myc, achaete-scute, and immunoglobulin enhancer-binding families. The herculin gene is physically linked to the Myf-5 gene on the chromosome; only 8.5 kilobases separate their translational start sites. A putative 27-kDa protein is encoded by three exons contained within a 1.7-kilobase fragment of the herculin gene. When expressed under the control of the simian virus 40 early promoter, transfected herculin renders murine NIH 3T3 and C3H/10T1/2 fibroblasts myogenic. In doing so, it also activates expression of myogenin, MyoD, and endogenous herculin in NIH 3T3 recipients. In adult mice, herculin is expressed in skeletal muscle but is absent from smooth muscle, cardiac muscle, and all nonmuscle tissues assayed. Direct comparison of the four known myogenic regulators in adult muscle showed that herculin is expressed at a significantly higher level than is any of the others. This quantitative dominance suggests an important role in the establishment or maintenance of adult skeletal muscle.

Aging↗
PubMed1989

In vivo footprinting of a muscle specific enhancer by ligation mediated PCR.

In vivo protein-DNA interactions at the developmentally regulated enhancer of the mouse muscle creatine kinase (MCK) gene were examined by a newly developed polymerase chain reaction (PCR) footprinting procedure. This ligation mediated, single-sided PCR technique permits the exponential amplification of an entire sequence ladder. Several footprints were detected in terminally differentiated muscle cells where the MCK gene is actively transcribed. None were observed in myogenic cells prior to differentiation or in nonmuscle cells. Two footprints appear to correspond to sites that can bind the myogenic regulator MyoD1 in vitro, whereas two others represent muscle specific use of apparently general factors. Because MyoD1 is synthesized by undifferentiated myoblasts, these data imply that additional regulatory mechanisms must restrict the interaction between this protein and its target site prior to differentiation.

Animals↗
PubMed1989

Genomic sequencing and methylation analysis by ligation mediated PCR.

Genomic sequencing permits studies of in vivo DNA methylation and protein-DNA interactions, but its use has been limited because of the complexity of the mammalian genome. A newly developed genomic sequencing procedure in which a ligation mediated polymerase chain reaction (PCR) is used generates high quality, reproducible sequence ladders starting with only 1 microgram of uncloned mammalian DNA per reaction. Different sequence ladders can be created simultaneously by inclusion of multiple primers and visualized separately by rehybridization. Relatively little radioactivity is needed for hybridization and exposure times are short. Methylation patterns in genomic DNA are readily detectable; for example, 17 CpG dinucleotides in the 5' region of human X-linked PGK-1 (phosphoglycerate kinase 1) were found to be methylated on an inactive human X chromosome, but unmethylated on an active X chromosome.

5-Methylcytosine↗
PubMed1989

Inhibition of DNA binding proteins by oligonucleotide-directed triple helix formation.

Oligonucleotides that bind to duplex DNA in a sequence-specific manner by triple helix formation offer an approach to the experimental manipulation of sequence-specific protein binding. Micromolar concentrations of pyrimidine oligodeoxyribonucleotides are shown to block recognition of double helical DNA by prokaryotic modifying enzymes and a eukaryotic transcription factor at a homopurine target site. Inhibition is sequence-specific. Oligonucleotides containing 5-methylcytosine provide substantially more efficient inhibition than oligonucleotides containing cytosine. The results have implications for gene-specific repression by oligonucleotides or their analogs.

5-Methylcytosine↗
PubMed1988

Isolation and characterization of a Xenopus laevis C protein cDNA: structure and expression of a heterogeneous nuclear ribonucleoprotein core protein.

The C proteins are major components of heterogeneous nuclear ribonucleoprotein complexes in nuclei of vertebrate cells. To begin to describe their structure, expression, and function we isolated and determined the DNA sequence of Xenopus laevis C protein cDNA clones. The protein predicted from the DNA sequence has a molecular mass of 30,916 kDa and is very similar to its human counterpart. Although mammalian genomes contain many copies of C protein sequence, the Xenopus genome contains few copies. When C protein RNA was synthesized in vitro and microinjected into stage-VI Xenopus oocytes, newly synthesized C proteins were efficiently localized in the nucleus. In vitro rabbit reticulocyte lysate and in vivo Xenopus oocyte translation systems both produce from a single mRNA two discrete polypeptide species that accumulate in a ratio similar to that of mammalian C1 and C2 proteins in vivo.

Animals↗