The Drosophila embryo proceeds through thirteen mitotic divisions as a syncytium. Its nuclei distribute in the embryo's interior during the first six divisions, dividing synchronously with a cycle ...time of less than ten minutes. After seven divisions (nuclear cycle 8), the syncytial blastoderm forms as the nuclei approach the embryo surface and slow their cycle time; subsequent divisions proceed in waves that initiate at the poles. Because genetic studies have not identified zygotic mutants that affect the early divisions and because transcription has not been detected before cycle 8, the early, pre-blastoderm embryo has been considered to rely entirely on maternal contributions and to be transcriptionally silent. Our studies identified several abnormal phenotypes in live engrailed (en) mutant embryos prior to cycle 8, as well as a small group of genes that are transcribed in embryos prior to cycle 7. Nuclei in en embryos divide asynchronously, an abnormality that was detected as early as nuclear cycle 2-3. Anti-En antibody detected nuclear En protein in embryos at cycle 2, and expression of an En:GFP fusion protein encoded in the paternal genome was also detected in cycle 2 nuclei. These findings demonstrate that the Drosophila embryo is functionally competent for gene expression prior to the onset of its rapid nuclear divisions and that the embryo requires functions that are expressed in the zygote in order to faithfully prosecute its early, pre-cellularization mitotic cycles.
Provides evidence that interpersonal attitudes can be validly inferred from indirect behavioral indexes which do not require self-disclosure. Study 1, utilizing 20 children aged 6-16 enrolled in a ...summer recreation program, and Study 2, utilizing 48 boys aged 8-14 living together during a 2- wk camp session, both found positive relations between a 15-step Liking Scale and each of 2 oblique measures adapted from J. C. Nunnally and his associates (see 39:4 and 41:9): a looking box measure of selective looking and a treasure hunt game reflecting anticipation of desirable consequences. 23 1st graders in Study 3 provided data indicating that 3 levels of attraction toward peers, as measured by a Sociometric Test, may be reliably inferred from 2 objective measures of drawings made of their classmates: percentage of head relative to total length and relative degree of detail. A perceptual measure of recognition of peers under conditions of .01-.04 sec. slide exposure time yielded ambiguous sex-related results. (21 ref.)
When a point source of light is placed low over one side of a gramophone record and the eye is diametrically opposite it at about the same height, then the bright reflections on the record take the ...form of a rectangular cross, symmetrically placed. The direct image of the source is coincident with the centre of the record.
Coronavirus disease 2019 (COVID-19) has had a substantial impact on the incidence of cardiac arrest and survival. The challenge is to find the correct balance between the risk to the rescuer when ...undertaking cardiopulmonary resuscitation (CPR) on a person with possible COVID-19 and the risk to that person if CPR is delayed. These guidelines focus specifically on patients with suspected or confirmed COVID-19. The guidelines include the delivery of basic and advanced life support in adults and children and recommendations for delivering training during the pandemic. Where uncertainty exists treatment should be informed by a dynamic risk assessment which may consider current COVID-19 prevalence, the person’s presentation (e.g. history of COVID-19 contact, COVID-19 symptoms), likelihood that treatment will be effective, availability of personal protective equipment (PPE) and personal risks for those providing treatment. These guidelines will be subject to evolving knowledge and experience of COVID-19. As countries are at different stages of the pandemic, there may some international variation in practice.
To better characterize how variation in regulatory sequences drives divergence in gene expression, we undertook a systematic study of transcription factor binding and gene expression in blastoderm ...embryos of four species, which sample much of the diversity in the 40 million-year old genus Drosophila: D. melanogaster, D. yakuba, D. pseudoobscura and D. virilis. We compared gene expression, measured by mRNA-seq, to the genome-wide binding, measured by ChIP-seq, of four transcription factors involved in early anterior-posterior patterning. We found that mRNA levels are much better conserved than individual transcription factor binding events, and that changes in a gene's expression were poorly explained by changes in adjacent transcription factor binding. However, highly bound sites, sites in regions bound by multiple factors and sites near genes are conserved more frequently than other binding, suggesting that a considerable amount of transcription factor binding is weakly or non-functional and not subject to purifying selection.
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