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51.
52.
Pedersen, O. F., T. F. Pedersen, and M. R. Miller. Gascompression in lungs decreases peak expiratory flow depending onresistance of peak flowmeter. J. Appl.Physiol. 83(5): 1517-1521, 1997.It has recentlybeen shown (O. F. Pedersen T. R. Rasmussen, Ø. Omland, T. Sigsgaard, P. H. Quanjer, and M. R. Miller. Eur. Respir. J. 9: 828-833, 1996) that the addedresistance of a mini-Wright peak flowmeter decreases peak expiratoryflow (PEF) by ~8% compared with PEF measured by a pneumotachograph.To explore the reason for this, 10 healthy men (mean age 43 yr, range33-58 yr) were examined in a body plethysmograph with facilitiesto measure mouth flow vs. expired volume as well as the change inthoracic gas volume (Vb) and alveolar pressure(PA). The subjects performed forced vital capacity maneuvers through orifices of different sizes andalso a mini-Wright peak flowmeter. PEF with the meter and other addedresistances were achieved when flow reached the perimeter of theflow-Vb curves. The mini-Wright PEF meter decreased PEF from 11.4 ± 1.5 to 10.3 ± 1.4 (SD) l/s(P < 0.001),PA increased from 6.7 ± 1.9 to 9.3 ± 2.7 kPa (P < 0.001), anincrease equal to the pressure drop across the meter, and caused Vb atPEF to decrease by 0.24 ± 0.09 liter(P < 0.001). We conclude that PEF obtained with an added resistance like a mini-Wright PEF meter is awave-speed-determined maximal flow, but the added resistance causes gascompression because of increasedPA at PEF. Therefore, Vb at PEFand, accordingly, PEF decrease. 相似文献
53.
Else Marie Friis Kaj Raunsgaard Pedersen Peter R. Crane 《American journal of botany》1995,82(7):933-943
A new genus and species of fossil angiosperm (Appomattoxia ancistrophora) is established based on well-preserved fruiting units and associated pollen from the Early Cretaceous (Early or Middle Albian) Puddledock locality in the Potomac Group sequence of Virginia, eastern North America. Fruiting units are small, unilocular, and with a single, pendulous, orthotropous seed. The fruit surface is characterized by densely spaced unicellular spines with hooklike tips, which probably functioned in biotic dispersal. Pollen grains adhering to the stigmatic area of many specimens are monocolpate and tectate with granular to columellate infratectal structure, and are similar to dispersed grains assigned to Tucanopollis and Transitoripollis. Comparison of fossil Appomattoxia ancistrophora with extant plants reveals an unusual combination of characters that includes similarities with some magnoliid taxa, particularly Piperales (Piperaceae, Saururaceae) and Laurales (Chloranthaceae), as well as the monotypic ranunculid family Circaeasteraceae. Appomattoxia ancistrophora differs from extant Piperales in having a pendulous rather than erect ovule, and differs from extant Circaeaster in details of the fruit wall, as well as the presence of monosulcate rather than tricolpate pollen. 相似文献
54.
Site selective bis-intercalation of a homodimeric thiazole orange dye in DNA oligonucleotides. 总被引:2,自引:1,他引:1 下载免费PDF全文
We have used one and two dimensional 1H NMR spectroscopy to characterize the binding of a homodimeric thiazole orange dye, 1,1'-(4,4,8,8-tetramethyl-4,8-diaza-undecamethylene)-bis-4- (3-methyl-2,3-dihydro-(benzo-1,3-thiazole)-2-methylidene)-quinolin ium tetraiodide (TOTO), to various double stranded DNA oligonucleotides. TOTO binds strongly to all the oligonucleotides used, but usually more than one complex is observed and exchange between different binding sites broadens the lines in the NMR spectra. Complete precipitation occurs when TOTO is bound to small oligonucleotides. Binding to larger oligonucleotides occurs by bis-intercalation. The 1:1 complex of TOTO with the oligonucleotide d(CCGACTGATGC):d (GCATCAGTCGG) gave only one complex that was shown to be a bis-intercalation in the CTGA:TCAG binding site. The binding to this site was also characterized by studying the TOTO complex with the d(CCGCTGAGC):d(GCTCAGCGG) oligonucleotide. NOE connectivities and molecular modelling were used to characterize the complex. The 1:1 complex of TOTO with the oligonucleotide d(CCGCTAGCG):d(CGCTAGCGG) containing a CTAG:CTAG binding site was similarly characterized by NMR. It was concluded that the binding of TOTO to larger oligonucleotides is site selective with CTAG:CTAG as the preferred binding site. 相似文献
55.
David W. Deerfield Douglas J. Fox Martin Head-Gordon Richard G. Hiskey Lee G. Pedersen 《Proteins》1995,21(3):244-255
The first coordination shell of an Mg(II) ion in a model protein environment is studied. Complexes containing a model carboxylate, an Mg(II) ion, various ligands (NH3, H2S, imidazole, and formaldehyde) and water of hydration about the divalent metal ion were geometry optimized. We find that for complexes with the same coordination number, the unidentate carboxylate–Mg(II) ion is greater than 10 kcal mol?1 more stable than the bidentate orientation. Imidazole was found to be the most stable ligand, followed in order by NH3 formaldehyde, H2O, and H2S. © 1995 Wiley-Liss, Inc. 相似文献
56.
Exogenous nucleosides, either singly or in combination, do not enhance postimplantation development of mouse embryos in vitro, and adenosine, guanosine and thymidine are toxic to the embryos at high concentrations. 相似文献
57.
Polyol accumulation by two filamentous fungi grown at different concentrations of NaCl 总被引:1,自引:0,他引:1
The accumulation of polyols by Aspergillus niger (van Tiegh) strain S 1 and Penicillium chrysogenum (Thom) strain S 30 was followed during growth in media of different concentrations of NaCl. The major polyols found were glycerol, erythritol and mannitol. The total polyol pool increased in both organisms in response to raised salinity, and the proportion of glycerol and erythritol was markedly enhanced at high salinity. 相似文献
58.
S. C. Rastogi J. Clausen H. J. Hansen E. Pedersen W. W. Tourtellotte 《Neurochemical research》1983,8(10):1261-1269
The binding of partially purified multiple sclerosis (MS) specific brain antigens (MSG2) and of the corresponding antigens of non-MS brains (KG2) to cerebrospinal fluid IgG of patients with MS and other neurological diseases was assayed employing sandwich enzyme linked immunosorbent assay (ELISA). Assay of the antigen-antibody binding revealed that the concentration of MSG2 required for the optimum binding to IgG in the undiluted MS CSFs was lower than that of KG2 in all cases. The index for IgG binding capacity of an antigen (IgBC) was expressed as a ratio of the optical density of the enzymic products in ELISA at the optimal antigen-antibody binding to the lowest concentration of the antigen required for the optimal binding. The IgBC of MSG2 was found to be linearly correlated with the IgG concentration in the CSF of MS patients. These results indicate that IgG with specificity to MSG2 may be present in the CSF of MS patients. 相似文献
59.
A soluble, ligand binding mutant of the human urokinase plasminogen activator receptor. 总被引:6,自引:0,他引:6
A truncated version of the human urokinase plasminogen activator receptor has been obtained by in vitro mutagenesis by insertion of a premature nonsense codon in the urokinase plasminogen activator receptor cDNA. This results in a protein truncated immediately upstream of the region which appears to be required for membrane attachment of the receptor via a glycolipid anchor. The modified receptor cDNA inserted into an expression vector has been transfected into mouse LB6 cells. Transfectants produce a urokinase plasminogen activator (u-PA)-binding protein that is secreted into the medium. It can be cross-linked to iodinated ATF (amino-terminal fragment of u-PA) and can also inhibit binding of iodinated ATF to mouse LB6 cells that express the wild type human receptor. The soluble u-PA receptor will be used in a variety of experiments aimed at identifying the role and mechanism of u-PA in physiological and pathological invasive processes, as well as in therapeutical attempts to block or decrease cancer cell invasion and in general u-PA-mediated tissue destruction. 相似文献
60.
Frank A. Pedersen 《Human nature (Hawthorne, N.Y.)》1991,2(3):271-291
Secular change in sex ratios is examined in relation to experience in the family. Two theoretical perspectives are outlined: Guttentag and Secord’s (1983) adaptation of social exchange theory, and sexual selection theory. Because of large-scale change in number of births and typical age differentials between men and women at marriage, low sex ratios at couple formation ages existed in the U.S. between 1965 and the early 1980s. The currently high sex ratios, however, will persist until the end of the century. High sex ratios appear to be associated with lower divorce rates, male commitment to careers that promise economic rewards, male willingness to engage in child care, higher fertility, and higher rates of sexual violence. Sexual selection theory calls attention to intrasexual competition in the numerically larger sex. 相似文献