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  • Articles  (109)
  • Biology  (109)
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  • Articles  (109)
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  • 1
    Publication Date: 2016-09-21
    Description: Although most organisms thermoregulate behaviorally, biologists still cannot easily predict whether mobile animals will thermoregulate in natural environments. Current models fail because they ignore how the spatial distribution of thermal resources constrains thermoregulatory performance over space and time. To overcome this limitation, we modeled the spatially explicit movements of animals...
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 135 (1980), S. 259-268 
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Some insects stridulate when attacked by a predator. This behavior has been interpreted as a defensive response, the sound being a warning to predators of the insect's noxiousness. Since to humans many such disturbance sounds are audibly similar, it is possible that they may in fact be mutually mimetic. This idea was investigated through analysis of the temporal and spectral characteristics of the disturbance sounds of a variety of insects that stridulate by a file- and -scraper device. Properties of both the airborne sound and the underlying cuticular vibration (detected by a special vibration measuring instrument) were examined, and four characteristic features found: 1. The temporal pattern is simple. Bursts of toothstrike impulses are about 80 ms long, and are separated by pauses about 90 ms long. Bursts occur at a rate of about 5 to 10/s. 2. The temporal pattern is irregular. For toothstrike interval, burst duration, pause duration and interburst interval, the standard deviation is usually 〉30% of the mean. Much of the irregularity is presumably caused by the insect struggling at the same time it stridulates. Some insects show less variability, and these appear to lack tight coupling between stridulatory movements and struggling movements, so struggling does not interfere with stridulation. 3. The airborne sound pressure waveform is impulsive. The frequency coverage of the sounds is quite broad with an average 10-dB bandwidth of about 40 kHz centered at 25 kHz. The sounds are not intense, ranging from about 10 to 60 dB (re 20×10−6 Pa) at 10 cm. 4. The cuticular vibration waveform is sharply peaked and contains maximum energy at a frequency determined by the tooth-strike rate, usually about 1 kHz. The average decrease in power above this frequency is about 12 dB/octave. The maximum peak-to-peak amplitude of cuticular motion is about 1 to 10 μm. These common characteristics may lead predators to treat insects producing disturbance sounds similarly, although this possibility should be tested empirically. If acoustic mimicry exists, the communicatory interchange between predator and prey may be subtler than is commonly appreciated.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 166 (1989), S. 65-73 
    ISSN: 1432-1351
    Keywords: Bats ; Range discrimination ; Echo ; Filtering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Big brown bats (Eptesicus fuscus) were tested for their ability to detect an electronically simulated target, and to discriminate differences in range to two simulated targets, when receiving either a model of their own sonar emissions or the model reversed in time as the ‘echo’. The theory of matched detection predicts a large decrease in performance if bats use matched filtering, unless they are somehow able to adjust their filter to match the novel, time-reversed signal. The detection thresholds we obtained were much lower than Møhl's (1986), but like him we found no difference in threshold for reversed models (Table 2). This suggests either that bats do not use matched filtering for target detection, or, possibly, that they are able to adapt their filter to a highly unnatural signal in some way as yet unknown. Unlike detection, range discrimination was much poorer with reversed echoes (Table 3). Threshold increased from about 1 cm range difference with normal model echoes to 18 cm or more with reversed model echoes. This suggests that range determination, which is based on measuring the time of arrival of echoes, does involve matched filtering. Whether such filtering is ‘ideal’ (i.e., equivalent to cross-correlation detection) cannot be decided by our results, but there are some indications that the match between an echo and the presumed internal template (the ‘match’ of matched filtering) must be fairly precise. Also, since performance with phantom targets generated using model echoes was as good as has been found with real targets, the internal template is probably fixed (or only slowly modifiable) rather than re-programmed with each sonar emission. Finally, because synchronization of emission and model echo was not perfect, the apparent distance to targets probably varied by 2 to 4 cm from emission to emission, although both targets would appear to move together thus keeping the range difference constant. This suggests that bats determined range to the targets simultaneously rather than sequentially, as is usually assumed.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 212 (1966), S. 405-405 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] During the course of toxicity investigations on the isolated innervated guinea-pig atrium, it was observed that a 0-4 M bath concentration of DMSO in the Krebs-Henseleit bicarbonate buffer6 depressed the vagal threshold to electrical stimulation by about 50 per cent, an effect also produced by 3-3 ...
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of insect behavior 3 (1990), S. 143-157 
    ISSN: 1572-8889
    Keywords: Chrysopidae ; Araneidae ; lacewings ; spiders ; orb webs ; escape behavior ; prey capture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract When green lacewings (Neuroptera: Chrysopidae) fly into spider orb webs, they often simply reverse their flight direction and pull away (Table I). If a lacewing is trapped, it uses a specialized escape behavior. It first cuts away the sticky strands entangling head, feet, and antennae. If an antenna cannot be freed by tugging, it uses an “antenna climb” (Fig. 5A). After its body is free, the lacewing remains suspended by its hair-covered wings, which are held in a characteristic cruciform position (Fig. 5B). Orb web sticky strands adhere poorly to the hairy wings (Fig. 7), so the chrysopid may just wait until the strands slide off and it falls free. If placed in an orb web when the spider is at the web hub and ready to attack, a lacewing usually does not have time to escape (Fig. 1). When the spider is at the hub but eating, the chances of escape improve, and when the spider is away from the hub attacking other prey, nearly all lacewings in our experiment were able to escape. This finding emphasizes the importance of the spider's activity in its capture success.
    Type of Medium: Electronic Resource
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  • 6
    Publication Date: 2014-09-10
    Description: Article Production of male and female forms of the malaria parasite in an infected person is crucial for transmission of the disease. Here, Tran et al. show that an ABC transporter protein of the parasite, expressed in the female cells, modulates lipid accumulation and formation of sexual cells. Nature Communications doi: 10.1038/ncomms5773 Authors: Phuong N. Tran, Simon H. J. Brown, Todd W. Mitchell, Kai Matuschewski, Paul J. McMillan, Kiaran Kirk, Matthew W. A. Dixon, Alexander G. Maier
    Electronic ISSN: 2041-1723
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General , Physics
    Published by Springer Nature
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  • 7
    Publication Date: 2014-08-20
    Description: Ribosomally synthesized and posttranslationally modified peptides (RiPPs) are a growing class of natural products that are found in all domains of life. These compounds possess vast structural diversity and have a wide range of biological activities, promising a fertile ground for exploring novel natural products. One challenging aspect of RiPP...
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 8
    Publication Date: 1998-10-23
    Description: Analysis of the 1,042,519-base pair Chlamydia trachomatis genome revealed unexpected features related to the complex biology of chlamydiae. Although chlamydiae lack many biosynthetic capabilities, they retain functions for performing key steps and interconversions of metabolites obtained from their mammalian host cells. Numerous potential virulence-associated proteins also were characterized. Several eukaryotic chromatin-associated domain proteins were identified, suggesting a eukaryotic-like mechanism for chlamydial nucleoid condensation and decondensation. The phylogenetic mosaic of chlamydial genes, including a large number of genes with phylogenetic origins from eukaryotes, implies a complex evolution for adaptation to obligate intracellular parasitism.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Stephens, R S -- Kalman, S -- Lammel, C -- Fan, J -- Marathe, R -- Aravind, L -- Mitchell, W -- Olinger, L -- Tatusov, R L -- Zhao, Q -- Koonin, E V -- Davis, R W -- AI 39258/AI/NIAID NIH HHS/ -- New York, N.Y. -- Science. 1998 Oct 23;282(5389):754-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Program in Infectious Diseases, University of California, Berkeley, CA 94720, USA. ctgenome@socrates.berkeley.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9784136" target="_blank"〉PubMed〈/a〉
    Keywords: Aerobiosis ; Amino Acid Sequence ; Amino Acids/biosynthesis ; Bacterial Outer Membrane Proteins/genetics ; Bacterial Proteins/chemistry/genetics ; Biological Evolution ; Chlamydia trachomatis/classification/*genetics/metabolism/physiology ; DNA Repair ; Energy Metabolism ; Enzymes/chemistry/genetics ; *Genome, Bacterial ; Humans ; Lipids/biosynthesis ; Molecular Sequence Data ; Peptidoglycan/biosynthesis/genetics ; Phylogeny ; Protein Biosynthesis ; Recombination, Genetic ; *Sequence Analysis, DNA ; Transcription, Genetic ; Transformation, Bacterial ; Virulence
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 9
    Publication Date: 1988-01-15
    Description: By means of a selective DNA amplification technique called polymerase chain reaction, proviral sequences of the human immunodeficiency virus (HIV-1) were identified directly in DNA isolated from peripheral blood mononuclear cells (PBMCs) of persons seropositive but not in DNA isolated from PBMCs of persons seronegative for the virus. Primer pairs from multiple regions of the HIV-1 genome were used to achieve maximum sensitivity of provirus detection. HIV-1 sequences were detected in 100% of DNA specimens from seropositive, homosexual men from whom the virus was isolated by coculture, but in none of the DNA specimens from a control group of seronegative, virus culture-negative persons. However, HIV-1 sequences were detected in 64% of DNA specimens from seropositive, virus culture-negative homosexual men. This method of DNA amplification made it possible to obtain results within 3 days, whereas virus isolation takes up to 3 to 4 weeks. The method may therefore be used to complement or replace virus isolation as a routine means of determining HIV-1 infection.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ou, C Y -- Kwok, S -- Mitchell, S W -- Mack, D H -- Sninsky, J J -- Krebs, J W -- Feorino, P -- Warfield, D -- Schochetman, G -- New York, N.Y. -- Science. 1988 Jan 15;239(4837):295-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Center for Infectious Diseases, Centers for Disease Control, Atlanta, GA 30333.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3336784" target="_blank"〉PubMed〈/a〉
    Keywords: Acquired Immunodeficiency Syndrome/*microbiology ; Base Sequence ; DNA, Viral/*blood ; DNA-Directed DNA Polymerase ; *Gene Amplification ; HIV/*genetics/isolation & purification ; HIV Seropositivity ; Homosexuality ; Humans ; Leukocytes, Mononuclear/*analysis ; Male ; Nucleic Acid Amplification Techniques ; Nucleic Acid Hybridization ; Virus Cultivation
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 10
    Publication Date: 2003-10-18
    Description: Despite a central circadian role in Drosophila for the transcriptional regulator Timeless (dTim), the relevance of mammalian Timeless (mTim) remains equivocal. Conditional knockdown of mTim protein expression in the rat suprachiasmatic nucleus (SCN) disrupted SCN neuronal activity rhythms, and altered levels of known core clock elements. Full-length mTim protein (mTIM-fl) exhibited a 24-hour oscillation, where as a truncated isoform (mTIM-s) was constitutively expressed. mTIM-fl associated with the mammalian clock Period proteins (mPERs) in oscillating SCN cells. These data suggest that mTim is required for rhythmicity and is a functional homolog of dTim on the negative-feedback arm of the mammalian molecular clockwork.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Barnes, Jessica W -- Tischkau, Shelley A -- Barnes, Jeffrey A -- Mitchell, Jennifer W -- Burgoon, Penny W -- Hickok, Jason R -- Gillette, Martha U -- GM07143/GM/NIGMS NIH HHS/ -- HL67007/HL/NHLBI NIH HHS/ -- NS10170/NS/NINDS NIH HHS/ -- NS11134/NS/NINDS NIH HHS/ -- NS11158/NS/NINDS NIH HHS/ -- NS22155/NS/NINDS NIH HHS/ -- NS35859/NS/NINDS NIH HHS/ -- R01 HL067007/HL/NHLBI NIH HHS/ -- R01 NS022155/NS/NINDS NIH HHS/ -- R01 NS035859/NS/NINDS NIH HHS/ -- New York, N.Y. -- Science. 2003 Oct 17;302(5644):439-42.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Cell and Structural Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/14564007" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Biological Clocks ; Cell Cycle Proteins ; Cell Line ; *Circadian Rhythm ; Cryptochromes ; *Drosophila Proteins ; Electrophysiology ; *Eye Proteins ; Flavoproteins/metabolism ; Humans ; In Vitro Techniques ; Intracellular Signaling Peptides and Proteins ; Neurons/physiology ; Nuclear Proteins/metabolism ; Oligonucleotides, Antisense/pharmacology ; Period Circadian Proteins ; *Photoreceptor Cells, Invertebrate ; RNA Interference ; RNA, Messenger/genetics/metabolism ; Rats ; Rats, Inbred Strains ; Receptors, G-Protein-Coupled ; Reverse Transcriptase Polymerase Chain Reaction ; Suprachiasmatic Nucleus/*physiology ; Transcription Factors/chemistry/genetics/*metabolism ; Transfection
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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