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We suggest applying the log-periodic law formerly used to describe various crisis phenomena, in biology (evolutionary leaps), inorganic systems (earthquakes), societies and economy (economic crisis, market crashes) to the various steps of human ontogeny. We find a statistically significant agreement between this model and the data. 相似文献
24.
Joseph M. Culp Cheryl L. Podemski Kevin J. Cash Richard B. Lowell 《Journal of Aquatic Ecosystem Stress and Recovery (Formerly Journal of Aquatic Ecosystem Health)》2000,7(4):359-360
Authors Index
Author Index, Volume 7 相似文献25.
Effects of three different handling aids on calf behavior were determined. Group 1 calves were intensively-reared intact Holstein males (mean 180 days old); Group 2, extensively-reared beef-breed females (mean 230 days); Group 3, extensively-reared castrated beef-breed males (mean 253 days). Calves in each group were assigned to one of three handling aid treatments (n=5 per treatment subgroup; total n=45): electric prod (Prod), oar with rattles (Oar), manual urging (Manual). Treatments were applied only as needed to encourage forward movement of calves through the length of a solid-sided semicircular chute system. Number of treatment applications, length of time required to move through the entire chute system, and behavior during movement through the chute were recorded. An approach test was conducted 1 day before and 1 day and 1 week after chute tests to evaluate changes in behavior due to handling aid application. During chute tests, Group 1 Prod calves required the fewest treatment applications (4.9) vs. 23.5 (Oar) or 13.5 (Manual), ran most often (1.40 times) vs. 0.20 times (Manual) or 0.33 times (Oar), and made contact with chute sides most often (1.8 times vs. 0.2 times (Manual) or 0.7 times (Oar), respectively (all P<0.05). Similar trends were observed for calves in Groups 2 and 3. There were no significant differences between behaviors observed during the approach tests conducted before and after handling aid treatments had been imposed. Regardless of treatment, intensively-reared Group 1 calves appeared markedly less fearful of handlers during approach tests compared to extensively-reared calves in Groups 2 and 3, which demonstrated overt attempts to escape from the test facilities. One week after chute tests, 13 of 15 Prod calves from all three groups walked, rushed, or backed >1 m away from the handler when the prod was buzzed but not applied, suggesting that the buzzing sound alone may have sufficed to encourage movement by calves that had previously experienced both the sensation and sound associated with electric prodding. 相似文献
26.
Rod and cone photoreceptors project from the outer retinal surface into a
carbohydrate-rich interphotoreceptor matrix (IPM). Unique IPM
glycoconjugates are distributed around rods and cones. Wheat germ
agglutinin (WGA) strongly decorates the rod matrix domains and weakly
decorates the cone matrix domains. This study characterizes the major
WGA-binding glycoprotein in the human IPM, which we refer to as SPACR
(sialoprotein associated with cones and rods). SPACR, which has a molecular
weight of 147 kDa, was isolated and purified from the IPM by lectin
affinity chromatography. A polyclonal antibody to SPACR was prepared that
colocalizes in tissue preparations with WGA-binding domains in the IPM.
Sequential digestion of SPACR with N- and O- glycosidases results in a
systematic increase in electrophorectic mobility, indicating the presence
of both N- and O-linked glycoconjugates. Complete deglycosylation results
in a reduction in the relative molecular mass of SPACR by about 30%.
Analysis of lectin binding allowed us to identify some of the structural
characteristics of SPACR glycoconjugates. Treatment with neuraminidase
exposes Galbeta1- 3GalNAc disaccharide as indicated by positive peanut
agglutinin (PNA) staining, accompanied by the loss of WGA staining. Maackia
amurensis agglutinins (MAA-1 and MAA-2), specific for sialic acid in
alpha2-3 linkage to Gal, bind SPACR, while Sambucus nigra agglutinin (SNA),
specific for alpha2-6 linked sialic acid, does not, indicating that the
dominant glycoconjugate determinant on SPACR is the O-linked carbohydrate,
NeuAcalpha2-3Galbeta1-3GalNAc. The abundance of sialic acid in SPACR
suggests that this glycoprotein may contribute substantially to the
polyanionic nature of the IPM. The carbohydrate chains present on SPACR
could also provide sites for extensive crosslinking and participate in the
formation of the ordered IPM lattice that surrounds the elongate
photoreceptors projecting from the outer retinal surface.
相似文献
27.
The recent structure determinations of the mammalian effector enzyme adenylyl cyclase reveal the structure of its catalytic core, provide new insights into its catalytic mechanism and suggest how diverse signaling molecules regulate its activity. 相似文献
28.
Proteomic changes in the brain of the western painted turtle (Chrysemys picta bellii) during exposure to anoxia
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During anoxia, overall protein synthesis is almost undetectable in the brain of the western painted turtle. The aim of this investigation was to address the question of whether there are alterations to specific proteins by comparing the normoxic and anoxic brain proteomes. Reductions in creatine kinase, hexokinase, glyceraldehyde‐3‐phosphate dehydrogenase, and pyruvate kinase reflected the reduced production of adenosine triphosphate (ATP) during anoxia while the reduction in transitional endoplasmic reticulum ATPase reflected the conservation of ATP or possibly a decrease in intracellular Ca2+. In terms of neural protection programed cell death 6 interacting protein (PDCD6IP; a protein associated with apoptosis), dihydropyrimidinase‐like protein, t‐complex protein, and guanine nucleotide protein G(o) subunit alpha (Go alpha; proteins associated with neural degradation and impaired cognitive function) also declined. A decline in actin, gelsolin, and PDCD6IP, together with an increase in tubulin, also provided evidence for the induction of a neurological repair response. Although these proteomic alterations show some similarities with the crucian carp (another anoxia‐tolerant species), there are species‐specific responses, which supports the theory of no single strategy for anoxia tolerance. These findings also suggest the anoxic turtle brain could be an etiological model for investigating mammalian hypoxic damage and clinical neurological disorders. 相似文献
29.
Nima Dehghani Claude Bédard Sydney S. Cash Eric Halgren Alain Destexhe 《Journal of computational neuroscience》2010,29(3):405-421
The resistive or non-resistive nature of the extracellular space in the brain is still debated, and is an important issue
for correctly modeling extracellular potentials. Here, we first show theoretically that if the medium is resistive, the frequency
scaling should be the same for electroencephalogram (EEG) and magnetoencephalogram (MEG) signals at low frequencies (<10 Hz).
To test this prediction, we analyzed the spectrum of simultaneous EEG and MEG measurements in four human subjects. The frequency
scaling of EEG displays coherent variations across the brain, in general between 1/f and 1/f
2, and tends to be smaller in parietal/temporal regions. In a given region, although the variability of the frequency scaling
exponent was higher for MEG compared to EEG, both signals consistently scale with a different exponent. In some cases, the
scaling was similar, but only when the signal-to-noise ratio of the MEG was low. Several methods of noise correction for environmental
and instrumental noise were tested, and they all increased the difference between EEG and MEG scaling. In conclusion, there
is a significant difference in frequency scaling between EEG and MEG, which can be explained if the extracellular medium (including
other layers such as dura matter and skull) is globally non-resistive. 相似文献
30.
JG Hansen W Gao J Dupuis GT O’Connor W Tang M Kowgier A Sood SA Gharib LJ Palmer M Fornage SR Heckbert BM Psaty SL Booth SUNLIGHT Consortium Patricia A Cassano 《Respiratory research》2015,16(1)