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Jesse L. Steinfeld 《The Western journal of medicine》1984,141(6):878-883
Although cigarette smoking is the number one public health problem in the United States, physicians have failed to take the lead either in convincing youngsters not to begin smoking or in aiding adults to quit smoking. To be most effective and convincing in combating the smoking epidemic, practicing physicians must have the same basic fund of knowledge about the short- and long-term consequences of smoking as they do about other commonly encountered medical problems. By acting on such knowledge and adopting a definite set of attitudes and activities in their offices and with patients, physicians can make a significant contribution to their patients and to the entire community in which they practice. 相似文献
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Allison McNamara Noah T. Dunham Liza J. Shapiro Jesse W. Young 《American journal of primatology》2019,81(9)
Wild primates encounter complex matrices of substrates that differ in size, orientation, height, and compliance, and often move on multiple, discontinuous substrates within a single bout of locomotion. Our current understanding of primate gait is limited by artificial laboratory settings in which primate quadrupedal gait has primarily been studied. This study analyzes wild Saimiri sciureus (common squirrel monkey) gait on discontinuous substrates to capture the realistic effects of the complex arboreal habitat on walking kinematics. We collected high‐speed video footage at Tiputini Biodiversity Station, Ecuador between August and October 2017. Overall, the squirrel monkeys used more asymmetrical walking gaits than symmetrical gaits, and specifically asymmetrical lateral sequence walking gaits when moving across discontinuous substrates. When individuals used symmetrical gaits, they used diagonal sequence gaits more than lateral sequence gaits. In addition, individuals were more likely to change their footfall sequence during strides on discontinuous substrates. Squirrel monkeys increased the time lag between touchdowns both of ipsilaterally paired limbs (pair lag) and of the paired forelimbs (forelimb lag) when walking across discontinuous substrates compared to continuous substrates. Results indicate that gait flexibility and the ability to alter footfall patterns during quadrupedal walking may be critical for primates to safely move in their complex arboreal habitats. Notably, wild squirrel monkey quadrupedalism is diverse and flexible with high proportions of asymmetrical walking. Studying kinematics in the wild is critical for understanding the complexity of primate quadrupedalism. 相似文献
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Big, beautiful organisms are useful for biological education, increasing evolution literacy, and biodiversity conservation. But if educators gloss over the ubiquity of streamlined and miniaturized organisms, they unwittingly leave students and the public vulnerable to the idea that the primary evolutionary plot of every metazoan lineage is “progressive” and "favors" complexity. We show that simple, small, and intriguingly repulsive invertebrate animals provide a counterpoint to misconceptions about evolution. Our examples can be immediately deployed in biology courses and outreach. This context emphasizes that chordates are not the pinnacle of evolution. Rather, in the evolution of animals, miniaturization, trait loss, and lack of perfection are at least as frequent as their opposites. Teaching about invertebrate animals in a “tree thinking” context uproots evolution misconceptions (for students and the public alike), provides a mental scaffold for understanding all animals, and helps to cultivate future ambassadors and experts on these little‐known, weird, and fascinating taxa. 相似文献
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F Hudecz S Kutassi-Kovács G Mez? M Szekerke 《Biological chemistry Hoppe-Seyler》1989,370(9):1019-1026
A detailed investigation is reported about the biodegradation of poly[Lys(DL-Alam)], m approximately 3, (AK) the common inside area of a branched polypeptide model system developed by our group over the last decade. Enzymatic hydrolysis was carried out by the exopeptidase aminopeptidase M, or the endopeptidase trypsin, or their mixture. Ion-exchange column chromatography, paper electrophoresis and thin-layer chromatography were utilised to achieve separation of metabolites. Breakdown products were identified by the aid of synthetic oligopeptides representing the potential fragments (DL-Ala2, DL-Ala3, Lys(DL-Alam), m = 1-3). The kinetics and the degree of enzymatic degradation were determined. The ratio of peptide/amino acid amounts in the hydrolysate was found to be 1.07 after 24 h treatment with aminopeptidase M, 3.0 with trypsin and 1.3 with aminopeptidase - trypsin mixture. The overall results indicated that the proteolysis of AK by an aminopeptidase M and trypsin mixture proceeds stepwise at multiple sites on the polypeptide chain. The degradation is significantly retarded as compared to that of alpha- or epsilon-polylysine. A mechanism of degradation is suggested based on the experimental results. 相似文献
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1. The apparent acid and basic dissociation constants were determined potentiometrically by the methods of hydrolysis and of titration for the following ampholytes: Glycocoll, glycylglycocoll, alanylglycocoll, valylglycocoll, leucylglycocoll, methylleucylglycocoll, phenylalanylglycocoll and glycylglycylglycocoll. The constants were also determined in the presence of KCl and of K2SO4 at equal ionic strength. 2. In general, the relative order of magnitude of the constants decreased as the number of carbon atoms between amino and carboxyl groups increased. An explanation of this is offered on the basis of theories of electronic structure. 3. The application of the modern concepts of solutions to the case of the ampholytic ions is discussed. The inadequacy of the present theories is pointed out. 4. The constants were found, in general, to be functions of the hydrogen ion activity and the ionic strength of the solutions. Apparent contradictions to the Debye-Hückel theory are pointed out and partially explained on the basis of specific ion effects. 相似文献
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This review focuses on new aspects of extracellular roles of the calgranulins. S100A8, S100A9 and S100A12 are constitutively
expressed in neutrophils and induced in several cell types. The S100A8 and S100A9 genes are regulated by pro- and anti-inflammatory
mediators and their functions may depend on cell type, mediators within a particular inflammatory milieu, receptors involved
in their recognition and their post-translational modification. The S100A8 gene induction in macrophages is dependent on IL-10
and potentiated by immunosuppressive agents. S100A8 and S100A9 are oxidized by peroxide, hypochlorite and nitric oxide (NO).
HOCl generates intra-chain sulfinamide bonds; stronger oxidation promotes cross-linked forms that are seen in human atheroma.
S100A8 is >200-fold more sensitive to oxidative cross-linking than low-density lipoprotein and may reduce oxidative damage.
S100A8 and S100A9 can be S-nitrosylated. S100A8–SNO suppresses mast cell activation and inflammation in the microcirculation
and may act as an NO transporter to regulate vessel tone in inflammatory lesions. S100A12 activates mast cells and is a monocyte
and mast cell chemoattractant; a G-protein-coupled mechanism may be involved. Structure–function studies are discussed in
relation to conservation and divergence of functions in S100A8. S100A12 induces cytokines in mast cells, but not monocytes/macrophages.
It forms complexes with Zn2+ and, by chelating Zn2+, S100A12 significantly inhibits MMPs. Zn2+ in S100A12 complexes co-localize with MMP-9 in foam cells in atheroma. In summary, S100A12 has pro-inflammatory properties
that are likely to be stable in an oxidative environment, because it lacks Cys and Met residues. Conversely, S100A8 and S100A9
oxidation and S-nitrosylation may have important protective mechanisms in inflammation. 相似文献