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71.
72.
Hubmayr, Rolf D., and Susan S. Margulies. Regionalventilation in statically and dynamically hyperinflated dogs.J. Appl. Physiol. 81(4):1815-1821, 1996.Using the parenchymal marker technique innormal anesthetized dogs, we compared the dynamics of regional lungexpansion between two ventilation strategies designed to increase meanthoracic volume. Dynamic hyperinflation (DH) was produced byventilating the lungs at a rate of 50 breaths/min and with a duty cycleof 0.5. Static hyperinflation (SH) was produced throughthe application of extrinsic positive end-expiratory pressure while thelungs were ventilated at a rate of 15 breaths/min and with a duty cycleof 0.15. Regional tidal volume(VT,r), regional functionalresidual volume, and the time delay between regional expansion and the flow signal at the common airway were computed for upto 100 regions/lobe in 5 animals. Ventilation strategy had no effect onthe overall variance of VT,rwithin lobes. Although the VT,rmeasured during SH correlated withVT,r measured during DH, theaverage correlation coefficient was only 0.69. Ventilation rate-relateddifferences in VT,r and regionalfunctional residual capacity varied with the regional time delay inways qualitatively consistent with parallel inhomogeneity of unit timeconstants. However, a large component of frequency-dependent behaviorremains unexplained by established mechanisms. We conclude that DH and SH should not be considered equivalent lung unit recruitmentstrategies. 相似文献
73.
74.
Josef Hermanns Fons Debets Rolf Hoekstra Heinz D. Osiewacz 《Molecular & general genetics : MGG》1995,246(5):638-647
Three recently isolated wild-type strains of the ascomycete Podospora anserina were analyzed for the presence of linear mitochondrial plasmids. In one of these strains, designated Wa6, at least 12 distinct plasmid-like elements were identified. From molecular analyses a minimum number of 78 individual linear molecules with proteins bound to their 5 ends was estimated. In addition, the different members of this family of typical linear plasmids were shown to possess a common central region and terminal sequences which differ from one plasmid to another due to the presence of different numbers of a 2.4 kb sequence module. Finally, the pWa6 plasmids share a high degree of sequence similarity with pAL2-1, a linear plasmid previously identified in mitochondria of a long-lived mutant of P.anserina. A mechanism is proposed which explains the generation of these distinct, closely related extrachromosomal genetic traits. 相似文献
75.
Therese Mandel Andrew J. Fleming Rolf Krähenbühl Cris Kuhlemeier 《Plant molecular biology》1995,29(5):995-1004
The NeIF-4A10 gene belongs to a family of at least ten genes, all of which encode closely related isoforms of translation initiation factor 4A. The promoter region of NeIF-4A10 was sequenced, and four mRNA 5 ends were determined. Deletions containing 2750, 689 and 188 bp of untranscribed upstream DNA were fused to the GUS reporter gene and introduced into transgenic tobacco. The three constructs mediated GUS expression in all cells of the leaf, stem and shoot apical meristem. Control experiments using in situ hybridization and tissue printing indicated that the observed GUS expression matches the expression patterns of NeIF-4A mRNA and protein. This detailed analysis at the level of mRNA, protein and reporter gene expression shows that NeIF-4A10 is an ideal constitutively expressed control gene. We argue that inclusion of such a control gene in experiments dealing with specifically expressed genes is in many cases essential for the correct interpretation of observed expression patterns. 相似文献
76.
Calcitonin gene-related peptide and its receptor in the thymus 总被引:2,自引:0,他引:2
Bodo Kurz Brita von Gaudecker Andrea Kranz Brigitte Krisch Rolf Mentlein 《Peptides》1995,16(8):1497-1503
Calcitonin gene-related peptide (CGRP), a 37-amino acid residue neuropeptide, was immunostained in rat thymus at two sites: a subpopulation of thymic epithelial cells, namely subcapsular/perivascular cells, were heavily stained besides some nerve fibers surrounding arteries and arterioles. The administration of nanomolar concentrations of rat -CGRP dose-dependently raised intracellular cyclic adenosine monophosphate (cAMP) levels in isolated rat thymocytes (half-maximum stimulation 1 nM) but not in cultured rat thymic epithelial cells. Peptides structurally related to CGRP (i.e., rat calcitonin or amylin) had no effect. CGRP(8–37), an N-terminally truncated form, acted as an antagonist. Peripheral blood lymphocytes did not respond to CGRP, suggesting that receptors are present only on a subpopulation of thymocytes but not on mature T cells. This was substantiated by visualization of CGRP receptors on single cells by use of CGRP-gold and -biotin conjugates of established biological activity: only a small proportion of isolated thymocytes was surface labeled. In situ, the CGRP conjugates labeled receptors on large thymocytes residing in the outer cortical region of rat thymus pseudolobules. Thus, immunoreactive CGRP is found in subcapsular/perivascular thymic epithelial cells and acts via specific CGRP receptors on thymocytes by raising their intracellular cAMP level. It is suggested that CGRP is a paracrine thymic mediator that might influence the differentiation, maturation, and proliferation of thymocytes. 相似文献
77.
Tibor Harrach Klaus Eckert Kai Schulze-Forster Rolf Nuck Detlef Grunow H. Rainer Maurer 《Journal of Protein Chemistry》1995,14(1):41-52
Crude bromelain extracts from pineapple stems (Ananas comosus) were fractionated by two-step FPLC-cation-exchange chromatography. At least eight basic proteolytically active components were detected. The two main components F4 and F5 together with the most active proteinase fraction F9 were characterized by SDS-PAGE, mass spectroscopy, multizonal cathodal electrophoresis, partial amino acid sequence, and monosaccharide composition analysis. F9 amounts to about 2% of the total protein and has a 15 times higher specific activity against the substratel-pyroglutamyl-l-phenylanalyl-l-leucine-p-nitroanilide (PFLNA) than the main component F4. The molecular masses of F4, F5, and F9 were determined to 24,397, 24,472, and 23,427, respectively, by mass spectroscopy. Partial N-terminal amino acid sequence analysis (20 amino acids) revealed that F9 differs from the determined sequence of F4 and F5 by an exchange at position 10 (tyrosineserine) and position 20 (asparagine glycine). F4 and F5 contained fucose, N-acetylglucosamine, xylose, and mannose in ratio of 1.02.01.02.0, but only 50% of the proteins seem to be glycosylated, whereas F9 was found to be unglycosylated. Polyclonal antibodies (IgG) against F9 detected F4 and F5 with tenfold reduced reactivity. ThepH optimum of F4 and F5 was betweenpH4.0 and 4.5 and for F9 close to neutralpH. The kinetic parameters for PFLNA hydrolysis were similar for F4 (K
m 2.30 mM,k
cat 0.87 sec–1 and F5 (K
m 2.42 mM,k
cat 0.68 sec–1), and differed greatly from F9 (K
m 0.40 mM,k
cat 3.94 sec–1).Dedicated to H. Tschesche, Bielefeld, Germany, on behalf of his 60th anniversary. 相似文献
78.
Petra Düx Brian Whitehead Rolf Boelens Robert Kaptein Geerten W. Vuister 《Journal of biomolecular NMR》1997,10(3):301-306
A modified HNHB experiment is presented that allows thedetermination of J(NH) coupling constants directly from the ratio ofcross-peak to diagonal-peak intensities. The experiment was applied to thephotoactive yellow protein (PYP) and yielded the magnitude of 1173J(NH) coupling constants. In addition, 293J(NH(i–1)) coupling constantscould be measured, providing information about the backbone angle .These data, in conjunction with the magnitudes of the3J(HNH) coupling constantsobtained from the HNHA spectrum, effectively discriminate the twopossibilities for the stereospecific assignment of theH resonances in glycine residues. For all eight glycineresidues in PYP that were not subject to conformational averaging and hadnon-degenerate H resonance frequencies, the J-couplingdata, together with limited NOE data, yielded the stereospecific assignmentof the H resonances for these residues. In addition,reliable and precise , dihedral constraints were also derived forthese residues from the J-coupling data. 相似文献
79.
Stable carbon isotopes in tree rings of beech: climatic versus site-related influences 总被引:11,自引:0,他引:11
M. Saurer Silvio Borella Fritz Schweingruber Rolf Siegwolf 《Trees - Structure and Function》1997,11(5):291-297
Stable carbon isotopes in tree rings are a promising tool in palaeoclimate research, provided attempts are made to disentangle
climatic from local effects (e.g. soil properties, competition, light). The 13C/12C variations in cellulose of tree rings of beech (Fagus sylvatica) were determined at several sites in the Swiss Central Plateau covering the last 50 years. We chose sites which differ in
moisture conditions and sampled cores from four to six trees per site. The mean 13C/12C series from the different dry sites (distant by up to 40 km) are closely interrelated suggesting a common external cause.
Correlation analysis with climate data proved the total precipitation in the months May, June and July to have the strongest
effect on the carbon isotopes (r = – 0.73). This result is in agreement with the commonly used model which relates the isotope discrimination to the water
use efficiency. On the other hand, the isotope series of the wet sites are not as well correlated to the climate. At two of
the sites (a dry and a humid) tree ring width suddenly increased. We used this effect as a test-case to study the influence
of local growth conditions on the climate-isotope relationship.
Received: 17 April 1996 / Accepted: 2 September 1996 相似文献
80.
Jarl S:son Torgerson Anna-Karin Lindroos C. David Sjstrm Rolf Olsson Lauren Lissner Lars Sjstrm 《Obesity (Silver Spring, Md.)》1997,5(2):105-114
Abnormal liver tests, as well as morphological changes in the liver, are frequent among obese patients. Other frequent disturbances are visceral fat accumulation, insulin resistance, non-insulin-dependent diabetes mellitus (NIDDM), hypertriglyceridemia, and hypertension; these are a set of aberrations known as the metabolic syndrome. In order to investigate a possible relationship between the metabolic syndrome and impaired liver status we examined associations between liver tests, metabolic variables (insulin, glucose, and triglycerids), body composition and nutrition in 1083 men (BMI 28.8–63.8 kg/m2) and 1367 women (BMI 26.7–68.0 kg/m2) in the ongoing intervention study of Swedish Obese Subjects (SOS). Standard biochemical techniques were used to assess liver status and metabolic variables. Lean body mass (LBM) and masses of visceral and subcutaneous adipose tissue (AT) were estimated by means of computed tomography (CT) calibrated anthropometric equations. In both genders aspartate aminotransferase and alanine aminotransferase were, or tended to be, positively correlated to fasting serum insulin, visceral AT (women), and alcohol intake. In women, the aminotransferases were also correlated with fasting blood glucose. In both genders alkaline phosphatase was, or tended to be, positively associated with visceral AT, insulin (women), and glucose. Bilirubin was negatively correlated to insulin and visceral AT in men and women. Additional multivariate analyses indicated that alcohol had less explanatory power than serum insulin for the examined liver tests, especially among women. These results suggest that pathological liver tests in the obese may represent an expression of the metabolic syndrome. 相似文献