Volatile fatty acid metabolism by epithelial cells isolated from different areas of the ewe rumen     

Waldron MR  Schrick FN  Quigley JD  Klotz JL  Saxton AM  Heitmann RN 《Journal of animal science》2002,80(1):270-278

Cells were harvested from four rumen locations in four 2- to 3-yr-old ewes fed fescue hay to determine whether cell origin has an effect on cellular VFA metabolism. Tissue (approximately 150 cm2) was excised from the anterior cranial pillar, ventral sac floor, caudal pillar surface, and dorsal sac ceiling. Cells were isolated using serial tryptic digestion. One milliliter of isolate was incubated for 2 h in 6 mL of medium containing 25 mM propionate and 10 mM butyrate. Incubations were terminated at 0, 30, 60, 90, and 120 min and analyzed for beta-hydroxybutyrate, acetoacetate, lactate, and pyruvate. Cell yield was 22, 22, 24, and 14 (+/- 6) x 106 cells/mL, and viability was 92, 92, 94, and 87% for anterior cranial pillar, ventral sac floor, caudal pillar surface, and dorsal sac ceiling, respectively. All metabolite concentrations and ratios of redox pairs increased throughout the incubations, indicating continuous cellular activity. Final 2-h concentrations (nmol/10(6) cells) were 123, 113, 163, and 158 (+/- 35) for beta-hydroxybutyrate; 38, 42, 24, and 45 (+/- 10) for acetoacetate; 25.3, 20.6, 10.1, and 20.4 (+/- 5.6) for lactate; and 2.54, 0.98, 1.06, and 1.31 (+/- 0.61) for pyruvate in the anterior cranial pillar, ventral sac floor, caudal pillar surface and dorsal sac ceiling incubations, respectively. Origin of rumen tissue had no significant effect on metabolite production, indicating that cellular location is not a critical factor that affects rate of rumen epithelial cell VFA metabolism under these specific in vitro conditions.  相似文献   

Using model scenarios to predict and evaluate forest-management impacts on soil base saturation at landscape level     

Dietmar?Zirlewagen  Klaus?von?WilpertEmail author 《European Journal of Forest Research》2004,123(4):269-282

Silviculture, forest conversion and technical tools of ecosystem management, such as forest liming, display their effects at the landscape level. Therefore their planning and control should take place at the same scale. The primary objective of this work was to assess soil chemical properties and their changes in relationship to ecosystem management, especially forest conversion and forest liming. We calculated scenario models, based on regression analysis, which allow such an examination in the context of understanding landscape processes which can be expected to operate in the sampling region. Stepwise multiple linear regression analysis was used to predict soil chemical attributes (base saturation, pH, C/N content and stock, exchangeable stocks of Ca and Mg) as indicators of site stability or off-site effects of forest ecosystems such as effects on clean drinking water from forested watersheds. Because of space limitations, in this paper only the modelling results of base saturation are presented. Base saturation was used as an integrative example for other soil chemical properties. The transformation of measurements to the regional scale, i.e., the regionalization, was calculated for the forested parts of two test regions in the Black Forest on the basis of measured chemical properties of 90–150 soil profiles per test region. The models have a spatial resolution of 50×50 m, which is a spatial scale relevant for forestry practice and forest management. Topographic variables (e.g., elevation, aspect, slope gradient, and slope length), the stratigraphic classification of the geologic substrate, stand characteristics from forest inventory data, and finally technical information about forest liming were the auxiliary variables (secondary site properties) that provided indirect information about base saturation and were available for the whole forested area of the test regions. Base saturation could be predicted with an accuracy of ~50–70% (in terms of the multiple R²) by using these properties as predictor variables in multiple linear regression analyses. The explained proportion of variance was unexpectedly high considering the high geomorphological heterogeneity of the two test regions. Based upon the regionalization models, it was possible to establish scenarios showing the landscape-related effects on base saturation that may be achieved by forest conversion towards a higher proportion of forests with broad-leaved mixed stands and by forest liming. These scenarios allow the interactions between several influencing factors and management strategies and the impacts on the target variable to be synoptically judged. Thus the presented regionalization models achieve the role of decision support tools for the planning of forest management at the landscape level. They allow an assessment of the environmental effects of forest management strategies in terms of site sustainability or preservation of water resources in forested catchments.  相似文献   

A BACTERIAL PATHOGEN OF THE CITRUS RED SCALE     

Sokoloff VP  Klotz LJ 《Science (New York, N.Y.)》1941,94(2428):40-41

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MICROSEISMS     

Klotz O 《Science (New York, N.Y.)》1910,32(816):252-254

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Urbanization and homogenization - Comparing the floras of urban and rural areas in Germany     

Ingolf Kühn  Stefan Klotz 《Biological conservation》2006,127(3):292-300

The process of urbanization has resulted in an expansion of alien plant species and declines of native species, in particular already rare species. These processes may cause a greater similarity between different urban regions, i.e. biotic homogenization. We explored the relationship between urban regions and homogenization for plant species in Germany using (i) all plant species, (ii) only native species, (iii) all alien species and only those introduced (iv) before or (v) after 1500, respectively. We used the database FLORKART for species distribution on a 6 min latitude × 10 min longitude (ca. 130 km²) scale. We calculated mean similarities for the 60 “most urbanized” cells. We then resampled 60 randomly drawn “less urbanized” cells and 60 “rural” cells and compared these results to the “most urbanized” cells taking distance effects into account. Urbanization does not have an overall effect on homogenization of all species, but native species as well as pre-1500 alien plant assemblages show effects of homogenization while post-1500 alien plant assemblages show the opposite effect. On a regional scale, urbanization is not unequivocally related to homogenization. This might be different when extending the analysed range across several bioclimatic regions. Specific urban habitats, or what remains of them, require special protection and management if the trend towards homogenization is to be avoided.  相似文献   

Chemical composition of precipitation at Long Island,NY     

Yin-Nan Lee  Ji Shen  Paul J. Klotz 《Water, air, and soil pollution》1986,30(1-2):143-152

Chemical analyses were performed on 387 sequential precipitation samples, both rain and snow, collected at Brookhaven National Laboratory, Long Island, New York, on 96 different days during the period from October 1983 to June 1985. The collection time for each individual sample was typically 30 min. The chemical species determined and the volume-weighted average and maximum concentrations (in parentheses) in units of μM were: H₂0₂:7(120), H₂CO:6(60), H⁺:51(500), N0₃ ^?:30(350), S0₄ ^2?:25(270), NH₄ ⁺:18(250), Ca²⁺:3(48), Na⁺:32(400), and Cl^?:37(380). A strong seasonal dependence was observed for H₂0₂ concentration, the maximum concentration in summer (120 μM) being 6 times greater than in winter. In addition, H₂0₂ concentration also exhibited a strong diurnal variation, with a maximum peaking in the afternoon and a minimum after midnight. These observations suggest that the production of H₂0₂ may be governed by photochemical activity. Nitrate concentration also displayed a strong diurnal variation, having a maximum around noon, but did not show a seasonal dependence. Relationships between various species and their possible sources are briefly discussed.  相似文献   

Identification and quantification of astaxanthin esters in shrimp (Pandalus borealis) and in a microalga (Haematococcus pluvialis) by liquid chromatography-mass spectrometry using negative ion atmospheric pressure chemical ionization     

Breithaupt DE 《Journal of agricultural and food chemistry》2004,52(12):3870-3875

Negative ion liquid chromatography-atmospheric pressure chemical ionization mass spectrometry [negative ion LC-(APCI)MS] was used for the identification of astaxanthin esters in extracts of commercial shrimp (Pandalus borealis) and dried microalga (Haematococcus pluvialis) samples. A cleanup step using a normal phase solid phase extraction (SPE) cartridge was applied prior to analysis. Recovery experiments with astaxanthin oleate as model compound proved the applicability of this step (98.5 +/- 7.6%; n = 4). The assignment of astaxanthin esters in negative ion LC-(APCI)MS was based on the detection of the molecular ion (M*-) and the formation of characteristic fragment ions, resulting from the loss of one or two fatty acids. Quantification of individual astaxanthin esters was performed using an astaxanthin calibration curve, which was found to be linear over the required range (1-51 micromol/L; r2 = 0.9996). Detection limits, based on the intensity of M*-, a signal-to-noise ratio of 3:1, and an injection volume of 20 microL, were estimated to be 0.05 microg/mL (free astaxanthin), 0.28 microg/mL (astaxanthin-C16:0), and 0.78 microg/mL (astaxanthin-C16:0/C16:0), respectively. This LC-(APCI)MS method allows for the first time the characterization of native astaxanthin esters in P. borealis and H. pluvialis without using time-consuming isolation steps with subsequent gas chromatographic analyses of fatty acid methyl esters. The results suggest that the pattern of astaxanthin-bound polyunsaturated fatty acids of P. borealis does not reflect the respective fatty acid pattern found in triacylglycerides. Application of the presented LC-(APCI)MS technique in common astaxanthin ester analysis will forestall erroneous xanthophyll ester assignment in natural sources.  相似文献   

Carotenoids and carotenoid esters in potatoes (Solanum tuberosum L.): new insights into an ancient vegetable     

Breithaupt DE  Bamedi A 《Journal of agricultural and food chemistry》2002,50(24):7175-7181

The carotenoid pattern of four yellow- and four white-fleshed potato cultivars (Solanum tuberosum L.), common on the German market, was investigated using HPLC and LC(APCI)-MS for identification and quantification of carotenoids. In each case, the carotenoid pattern was dominated by violaxanthin, antheraxanthin, lutein, and zeaxanthin, which were present in different ratios, whereas neoxanthin, beta-cryptoxanthin, and beta,beta-carotene generally are only minor constituents. In contrast to literature data, antheraxanthin was found to be the only carotenoid epoxide present in native extracts. The total concentration of the four main carotenoids reached 175 microg/100 g, whereas the sum of carotenoid esters accounted for 41-131 microg/100 g. Therefore, carotenoid esters are regarded as quantitatively significant compounds in potatoes. For LC(APCI)-MS analyses of carotenoid esters, a two-stage cleanup procedure was developed, involving column chromatography on silica gel and enzymatic cleavage of residual triacylglycerides by lipases. This facilitated the direct identification of several potato carotenoid esters without previous isolation of the compounds. Although the unequivocal identification of all parent carotenoids was not possible, the cleanup procedure proved to be highly efficient for LC(APCI)-MS analyses of very low amounts of carotenoid esters.  相似文献   

Protein subunits: a table (second edition)   总被引：7，自引：0，他引：7  

I M Klotz  D W Darnall 《Science (New York, N.Y.)》1969,166(901):126-128

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Real-space observation of molecular motion induced by femtosecond laser pulses     

Bartels L  Wang F  Möller D  Knoesel E  Heinz TF 《Science (New York, N.Y.)》2004,305(5684):648-651

Femtosecond laser irradiation is used to excite adsorbed CO molecules on a Cu110 surface; the ensuing motion of individual molecules across the surface is characterized on a site-to-site basis by in situ scanning tunneling microscopy. Adsorbate motion both along and perpendicular to the rows of the Cu110 surface occurs readily, in marked contrast to the behavior seen for equilibrium diffusion processes. The experimental findings for the probability and direction of the molecular motion can be understood as a manifestation of strong coupling between the adsorbates' lateral degrees of freedom and the substrate electronic excitation produced by the femtosecond laser radiation.  相似文献