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  • 1
    ISSN: 1432-041X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have visualized segmentation in theDrosophila embryoniccentral nervous system (CNS) by staining for acetylcholinesterase activity. This technique was used to evaluate the effect of ligation on segments in the ventral CNS. When embryos were ligated prior to cellularization (60 min) fewer segmental ganglia developed in posterior fragments than when embryos were ligated at the blatoderm stage (3 h). This result is consistent with previous ligation experiments in which hypodermal segments were counted (Schubiger and Wood 1977). The number of ganglia scored exceeded the number of hypodermal segments scored especially after ligations at 60 min. Possible explanations for this difference are discussed.
    Type of Medium: Electronic Resource
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  • 2
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    PANGAEA
    In:  Supplement to: Brown, Elizabeth E; Baumann, Hannes; Conover, David O (2014): Temperature and photoperiod effects on sex determination in a fish. Journal of Experimental Marine Biology and Ecology, 461, 39-43, https://doi.org/10.1016/j.jembe.2014.07.009
    Publication Date: 2018-09-27
    Description: In some gonochoristic species, sex is influenced not only by genotype at conception but also by the environment that offspring experience during early ontogeny (termed environmental sex determination or ESD). ESD is thought to be adaptive when seasonal variations in environmental conditions provide a sex-specific fitness advantage. In vertebrates, temperature is the most common determinant of sex, and seasonal variation in temperature serves as a temporal cue of environmental quality such as length of the growing season. Some environments, however, lack strong seasonal temperature fluctuations and other cues, particularly photoperiod, may provide a more reliable indicator of the environment offspring enter. We tested this hypothesis by rearing the offspring of the California grunion (Leuresthes tenuis, Ayres), which experiences low seasonal temperature variation in nature, under common garden conditions at three temperature and two photoperiod treatments. Our experiments revealed that both temperature and photoperiod significantly affected sex ratios in L. tenuis. More females were produced at cooler temperatures and longer day lengths, which is consistent with female biased sex ratios early in the breeding season, and likely adaptive through increased female size and fecundity. To our knowledge, this is the first documented case of photoperiod-dependent sex determination in a gonochoristic vertebrate.
    Type: Dataset
    Format: text/tab-separated-values, 4248 data points
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  • 3
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Diabetes mellitus is a chronic disease that leads to complications including heart disease, stroke, kidney failure, blindness and nerve damage. Type 2 diabetes, characterized by target-tissue resistance to insulin, is epidemic in industrialized societies and is strongly associated with obesity; ...
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1520-510X
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1752-1688
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: : A macroscale hydrologic model is developed for regional climate assessment studies under way in the southeastern United States. The hydrologic modeling strategy is developed to optimize spatial representation of basin characteristics while maximizing computational efficiency. The model employs the “grouped response unit” methodology, which follows the natural drainage pattern of the area. First order streams are delineated and their surface characteristics are tested so that areas with statistically similar characteristics can be combined into larger computational zones for modeling purposes. Hydrologic response units (HRU) are identified within the modeling units and a simple three-layer water balance model, Soil and Water Assessment Tool (SWAT), is executed for each HRU. The runoff values are then convoluted using a triangular unit hydrograph and routed by Muskingum-Cunge method. The methodology is shown to produce accurate results relative to other studies, when compared to observations. The model is used to evaluate the potential error in hydrologic assessments when using GCM predictions as climatic input in a rainfall-runoff dominated environment. In such areas, the results from this study, although limited in temporal and spatial scope, appear to imply that use of GCM climate predictions in short term quantitative analyses studies in rainfall-runoff dominated environments should proceed with caution.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1539-6924
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Using physiologically-based pharmacokinetic (PBPK) modeling, occupational, personal, and environmental benzene exposure scenarios are simulated for adult men and women. This research identifies differences in internal exposure due to physiological and biochemical gender differences. Physiological and chemical-specific model parameters were obtained from other studies reported in the literature and medical texts for the subjects of interest. Women were found to have a higher blood/air partition coefficient and maximum velocity of metabolism for benzene than men (the two most sensitive parameters affecting gender-specific differences). Additionally, women generally have a higher body fat percentage than men. These factors influence the internal exposure incurred by the subjects and should be considered when conducting a risk assessment. Results demonstrated that physicochemical gender differences result in women metabolizing 23–26% more benzene than men when subject to the same exposure scenario even though benzene blood concentration levels are generally higher in men. These results suggest that women may be at significantly higher risk for certain effects of benzene exposure. Thus, exposure standards based on data from male subjects may not be protective for the female population.
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  • 8
    ISSN: 0192-253X
    Keywords: Gene cluster ; Transposon ; Enhancer ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Genes that encode 3rd instar larval cuticle proteins (LCP's) of Drosophila melanogaster are located in at least two chromosomal sites. The genes encoding four of the five predominant LCP's are located in a cluster at the chromosomal region 44D. They are organized in pairs that are transcribed divergently, and expressed with different timing during the third larval instar. Towards understanding the basis of gene regulation within the 44D cluster, we have analyzed genetic variants, including the 2-3 variant, which has an insertion of a copia-like transposable element, H.M.S. Beagle, within the 44D cluster. The Beagle element appears to inactivate the LCP-3 gene by inserting into its TATA box, but also may cause the precocious expression of two other LCP genes, LCP-1 and LCP-f2, in the cluster. The long terminal repeat (LTR) of the Beagle element apparently contains a sequence, perhaps an enhancer-like element, which causes altered expression of these genes. We have also investigated the cis-regulatory elements involved in expression of the LCP-2 gene in wild-type larvae. We have identified two upstream regions that may contain separate cisregulatory elements. The region between -252 bp and -515 bp may be essential for any expression of LCP-2. Additionally, the region between -515 bp and -795 bp appears to be required for the normal level of expression of the LCP-2 gene.
    Additional Material: 7 Ill.
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  • 9
    ISSN: 1546-1718
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] Allotypes of the natural killer (NK) cell receptor KIR3DL1 vary in both NK cell expression patterns and inhibitory capacity upon binding to their ligands, HLA-B Bw4 molecules, present on target cells. Using a sample size of over 1,500 human immunodeficiency virus (HIV)+ individuals, we show that ...
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  • 10
    ISSN: 0739-4462
    Keywords: Ecdysone ; cuticle proteins ; gene expression ; Drosophila ; Chemistry ; Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The deposition and apolysis of insect cuticles have long been known to be regulated by ecdysone. Unsclerotized, chitin-containing procuticles contain evolutionarily conserved, hydrophobic proteins that are soluble in solutions of denaturing agents. The pupal procuticle of Drosophila is deposited by larval and imaginal epidermis starting 9 h after puparium formation when the ecdysone titer is low. Initially, a set of low molecular weight proteins (less than 25,000 daltons; low molecular weight pupal cuticle proteins = S-PCPs) is synthesized. However, about the time of pupation, synthesis of S-PCPs ceases, and high molecular weight proteins (greater than 50,000 daltons; H-PCPs) are synthesized. In vitro experiments indicate that the initial formation of the procuticle with synthesis of the S-PCPs requires a pulse of hormone followed by withdrawal (6 h with 20-hydroxyecdysone, 1 μg/ml). The switch from synthesis of S-PCPs to H-PCPs is facilitated by a second, short pulse of 20-hydroxyecdysone (0.1 μg/ml, 3 h). Ultrastructural localization demonstrates that the S-PCPs are located only in the external lamellae of the procuticle, while the H-PCPs are present only in internal lamellae. Developmental analyses with cloned genes indicate that cuticle protein genes are expressed during only one stage of Drosophila development. Some of the genes encoding S-PCPs are limited in their expression to larval (posterior) or imaginal (anterior) epidermis. Preliminary molecular analyses of the larval and pupal cuticle protein genes indicate that they are organized in different ways. For example, four larval genes exist in a cluster with divergent transcription, and one PCP gene, PCP-GART, is located within an intron of a “housekeeping” gene.
    Additional Material: 5 Ill.
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