The purpose of this study was to evaluate the possibility to delineate artificial osseous lesions with direct digital radiography (DDR) in comparison to conventional radiography (Rx). Defined lesions ...of nine different depths were created on ten mandibular segments of pigs. A conventional and a direct digital radiography was made of each lesion. 400 pairs of images were evaluated by ten dentists on the basis of a 5-point rating scale. The statistical evaluation included the interexaminer agreement and ROC-analyses. The mean interexaminer agreement was low and not significantly different between the two methods (Rx: kappa = 21.87 +/- 5.08; DDR: kappa = 20.25 +/- 3.79; p > 0.05). The ROC-analyses showed no significant differences between the two methods for the smallest lesions (Rx: 0.72 +/- 0.12; DDR: 0.64 +/- 0.12; p > 0.05). Defects between 0.5 mm and 1.0 mm of size were significantly better depicted with conventional radiographs (p > 0.05). Lesions from 1.25 to 2.0 mm were statistically not significantly different (p > 0.05). The diagnosis of lesions of 1.0 mm diameter and less than 1.25 mm depth was better delineated by conventional radiographs than by direct digital radiographs. However, proper diagnostic results were only achieved in lesions bigger than 2.0 mm. During the time this study was conducted many technical improvements were introduced for direct digital equipment with higher spatial resolutions. The presented methodology is proposed for the examination of the diagnostic properties of new imaging tools in comparison to conventional radiography.
The present study evaluated the effects of linseed supplementation on CH4 emission and milk fatty acid composition in dairy cows measured at the group level in an experimental dairy loose housing ...using a tracer gas technique and individually in tied stalls and respiration chambers. Cows (2 × 20) were maintained in two separate sections under loose-housing conditions and received a diet supplemented with extruded linseed (L) lipids (29 g·kg−1 dry matter) or a control (C) diet containing corn flour. Subsequently, 2 × 6 cows per dietary group were investigated in a tied-housing system and respiration chambers. Substantially higher proportions of favorable milk fatty acids were recovered in L cows when compared with C cows at the group level, making the analysis of bulk milk a suitable control instrument for retailers. Linseed supplementation resulted in a slightly lower diurnal course of CH4 emission intensity than the control at the group and individual levels. However, we found no more than a trend for a CH4 mitigating effect, unlike in other studies supplementing similar linseed lipid levels. Feed supplements in concentrations that lead to a significant reduction in CH4 emissions must show whether the reduction potential determined at the group and individual levels is comparable.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The present study evaluated the effects of linseed supplementation on CH.sub.4 emission and milk fatty acid composition in dairy cows measured at the group level in an experimental dairy loose ...housing using a tracer gas technique and individually in tied stalls and respiration chambers. Cows (2 * 20) were maintained in two separate sections under loose-housing conditions and received a diet supplemented with extruded linseed (L) lipids (29 g * kg.sup.-1 dry matter) or a control (C) diet containing corn flour. Subsequently, 2 * 6 cows per dietary group were investigated in a tied-housing system and respiration chambers. Substantially higher proportions of favorable milk fatty acids were recovered in L cows when compared with C cows at the group level, making the analysis of bulk milk a suitable control instrument for retailers. Linseed supplementation resulted in a slightly lower diurnal course of CH.sub.4 emission intensity than the control at the group and individual levels. However, we found no more than a trend for a CH.sub.4 mitigating effect, unlike in other studies supplementing similar linseed lipid levels. Feed supplements in concentrations that lead to a significant reduction in CH.sub.4 emissions must show whether the reduction potential determined at the group and individual levels is comparable. Keywords: methanogenesis; methane mitigation; lipid; ruminant; cattle; emission measurement Cows emit the greenhouse gas methane (CH.sub.4) as a result of microbial feed digestion. Methane emissions can be reduced by adopting nutritional strategies, such as dietary supplementation of linseed. Additionally, the oil in linseed increases the proportion of favorable fatty acids in milk fat. This study evaluated the effect of linseed on CH.sub.4 emission and milk fatty acid composition measured in a group of cows in a naturally ventilated bam and in individual cows in respiration chambers. The substantially higher proportions of favorable fatty acids in the milk of linseed-fed cows were detected in individual milk samples and in the milk of the herd. Therefore, the analysis of bulk milk could be a suitable control instrument for retailers. Visualizing the course of CH.sub.4 emissions over a whole day showed slightly lower CH.sub.4 values in linseed-supplemented individuals and groups. However, we found no significant reduction of CH.sub.4 as a result of linseed supplementation. Feed supplements in concentrations that are effective in reducing CH.sub.4 must show whether the reduction potential is comparable when determined at the group and individual levels.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The flow of new and native plant-derived C in the rhizosphere of an agricultural field during one growing season was tracked, the ratios in different soil C pools were quantified, and the residence ...times (τs) were estimated. For this the natural differences in ^sup 13^C abundances of: (1) C^sub 4^ soil (with a history of C^sub 4^ plant, Miscanthus sinensis, cultivation), (2) C^sub 3^ soil (history of C^sub 3^ plant cultivation), and (3) C^sub 4/3^ soil (C^sub 4^ soil, planted with a C^sub 3^ plant, Triticum aestivum) were used. Total amounts and δ^sup 13^C values of total soil C, non-hydrolysable C, light fraction C, water-soluble C, microbial biomass C, and phospholipid fatty acids (PLFA) were determined. Using the δ^sup 13^C values of soil C in a mixing and a 1-box model enabled the quantification of relative contributions of C^sub 3^ plant and C^sub 4^ plant C to the total amount of the respective C pools in the C^sub 4/3^ soil and their τs. Compared to early spring (March), the percentage of C^sub 3^ plant C increased in all pools in June and August, showing the addition of new C to the different soil C fractions. In August the contribution of new C to microbial biomass C and water-soluble C reached 64 and 89%, respectively. The τs of these pools were 115 and 147 days. The δ^sup 13^C values of the dominant soil PLFA, 18:1ω7c, cy19:0, 18:1ω9c, 16:0, and 10Me16:0, showed wide ranges (-35.1 to -13.0per thousand) suggesting that the microbial community utilized different pools as C sources during the season. The δ^sup 13^C values of PLFA, therefore, enabled the analysis of the metabolically active populations. The majority of δ^sup 13^C values of PLFA from the C^sub 4/3^ soil were closely related to those of PLFA from the C^sub 3^ soil when T. aestivum biomass contributions to the soil were high in June and August. Specific populations reacted differently to changes in environmental conditions and supplies of C sources, which reflect the high functional diversity of soil microorganisms.PUBLICATION ABSTRACT
Comamonas sp. strain CNB-1 can utilize 4-chloronitrobenzene (4CNB) as sole carbon and nitrogen source for growth. Previous studies were focused on 4CNB degradative pathway and have showed that CNB-1 ...contained a plasmid pCNB1 harboring the genes (cnbABCaCbDEFGH, cnbZ) for the enzymes involving in 4CNB degradation, but only three gene products (CnbCa, CnbCb, and CnbZ) were identified in CNB-1 cells. Comamonas strain CNB-2 that lost pCNB1 was not able to grow on 4CNB. In this study, physiological adaptation to 4CNB by CNB-1 was investigated with proteomic and molecular tools. Comparative proteomes of strains CNB-1 and CNB-2 grown on 4CNB and/or succinate revealed that adaptation to 4CNB by CNB-1 included specific degradative pathway and general physiological responses: (1) Seven gene products (CnbA, CnbCa, CnbCb, CnbD, CnbE, CnbF, and CnbZ) for 4CNB degradation were identified in 4CNB-grown cells, and they were constitutively synthesized in CNB-1. Two genes cnbE and cnbF were cloned and simultaneously expressed in E. coli. The CnbE and CnbF together catalyzed the conversion of 2-oxohex-4-ene-5-chloro-1,6-dioate into 2-oxo-4-hydroxy-5-chloro-valeric acid; (2) Enzymes involving in glycolysis, tricarboxylic acid cycle, and synthesis of glutamate increased their abundances in 4CNB-grown cells.
Microcosms were inoculated with sediments from both a petroleum-hydrocarbon (PHC)-contaminated aquifer and from a nearby pristine aquifer and incubated under anoxic denitrifying conditions with ...methyl-13Ctoluene. These microcosms served as a laboratory model system to evaluate the combination of isotope (13C-labeling of polar-lipid-derived fatty acids) and molecular techniques (16S rRNA-targeting gene probes) to identify the toluene-metabolizing population. After total depletion of toluene, the following bacterial phospholipid fatty acids (PLFA) were 13C-enriched: 16:1omega7c, 16:1omega7t, 16:0, cy17:0, and 18:1omega7c. Pure culture experiments demonstrated that these compounds were also found in PLFA profiles of PHC-degrading Azoarcus spp. (beta-Proteobacteria) and related species. The origin of the CO2 evolved in the microcosms was determined by measurements of stable carbon isotope ratios. Toluene represented 11% of the total pool of mineralized substrates in the contaminated sediment and 54% in the pristine sediment. The microbial community in the microcosm incubations was characterized by using DAPI staining and whole-cell hybridization with specific fluorescently labeled 16S rRNA-targeted oligonucleotide probes. Results revealed that 6% of the DAPI-stained cells in the contaminated sediment and 32% in the pristine sediment were PHC-degrading Azoarcus spp. In biotic control microcosms (incubated under denitrifying conditions, no toluene added), Azoarcus spp. cells remained at less than 1% of the DAPI-stained cells. The results show that isotope analysis in combination with whole-cell hybridization is a promising approach to identify and to quantify denitrifying toluene degraders within microbial communities.
The decomposition of leaves of
Taraxacum officinale,
Hypericum perforatum,
Dipsacus silvester and
Miscanthus sinensis was monitored under laboratory conditions (20°C, 90 to 100% relative humidity) ...for 2 to 4
weeks. At weekly intervals, weight loss, C-to-N-ratio, secondary plant metabolites, bacterial biomass and palatability to the earthworm
Lumbricus terrestris were determined. The first order constants for dry weight loss were 0.092, 0.012, 0.005 and 0.004
d
−1 for
T. officinale,
H. perforatum,
D. silvester and
M. sinensis, respectively. Secondary metabolites in green leaves of all plants mainly comprised polyphenolic compounds (bitter drugs, coumarins, flavonoids). During initial decomposition, the overall pattern of secondary plant metabolites was characterized by a qualitative and quantitative reduction. After one week of decomposition, the patterns of secondary plant metabolites became similar in all species and remained visually unchanged during further decomposition. A potential inhibition of bacterial growth and palatability to
L. terrestris could be demonstrated in bioassays with extracts of secondary plant metabolites from
H. perforatum and
D. silvester. On plants, however, an inhibition of bacterial growth and a reduction of palatability to
L. terrestris was only obtained during the initial decomposition of senescent leaves of
H. perforatum which is known to possess toxic secondary plant metabolites. The bacterial growth and the palatability to
L. terrestris on leaves of
T.
officinale,
D.
silvester and
M. sinensis were mainly influenced by the C-to-N-ratio of the leaves.
A food chain consisting of toluene, toluene-degrading Pseudomonas sp. PS+ and a bacterivorous flagellated amoebae Vahlkampfia sp. was established in a batch culture. This culture was amended with U- ...super(13)Ctoluene and served as a model system to elucidate the flux of carbon in the food chain by quantifying bacterial biovolumes and super(13)C enrichment of phospholipid fatty acid (PLFA) biomarkers of the bacteria and the heterotrophic protists. Major PLFA detected in the batch co-culture included those derived from Pseudomonas sp. PS+ (16:1 omega 7c and 18:1 omega 7c) and Vahlkampfia sp. (20:4 omega 6c and 20:3 omega 6c). A numerical model including consumption of toluene by the bacteria and predation of the bacteria by the heterotrophic protists was adjsuted to the measured toluene carbon, bacterial carbon and delta super(13)C values of bacterial and protist biomass. Using this model, we estimated that 28 plus or minus 7% of the consumed toluene carbon was transformed into bacterial biomass, and 12 plus or minus 4% of the predated bacterial carbon was incorporated into heterotrophic protist biomass. Our study showed that the super(13)C enrichment of PLFA biomarkers coupled to biomass determination via biovolume calculations is a suitable method to trace carbon fluxes in protist-inclusive microbial food chains because it does not require the separation of protist cells from bacterial cells and soil particles.
PDF
