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- Inzunza, J, et al.
(författare)
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Germfree status of mice obtained by embryo transfer in an isolator environment
- 2005
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Ingår i: Laboratory animals. - : SAGE Publications. - 0023-6772 .- 1758-1117. ; 39:4, s. 421-427
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Tidskriftsartikel (refereegranskat)abstract
- The technique of embryo transfer has been evaluated for the purpose of changing the mouse stocks to a germfree (GF) status. Our results show reproducible and quality-assured conversion of animals to those which are negative for the presence of microorganisms. Rapid and easy access to GF mice is advantageous for studies of selected microflora and their cross-talks with the host, when applying, e.g. genomic, proteomic and metabolic methodology. The study involved embryo transfer in an isolator environment, thereby allowing implantation of cleansed embryos into GF recipients under well-controlled conditions. The recipient females gave birth normally and took care of the offspring as if they were their own pups, thus enhancing the survival rate. Access to full technical resources required to maintain GF isolators are, however, a prerequisite. In this study, we used stainless steel isolators designed by Gustafsson (1959), on which a stereomicroscope was mounted to facilitate embryo transfer inside the isolator. The use of embryo transfer and isolator techniques will facilitate the availability of various mouse mutant models under different gnotobiotic conditions, GF, monoxenic or polyxenic animals, to enable comparison with conventional animals for physiological and pathophysiological studies.
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- Kotov, P. V., et al.
(författare)
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Recovery of the ponderomotive parametric instability after long pumping of the ionosphere
- 2007
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Ingår i: Advances in Space Research. - : Elsevier BV. - 0273-1177 .- 1879-1948. ; 40:3
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Tidskriftsartikel (refereegranskat)abstract
- We show that during high frequency (HF) pumping of the overhead ionosphere with a pump wave frequency slightly above the local fifth electron gyroharmonic, when one switches the pump wave from continuous pumping to low duty cycle pulse pumping, the stimulated electromagnetic emission (SEE) features related to the ponderomotive parametric instability (PPI) near the pump wave reflection point, such as the ponderomotive narrow continuum and the narrow continuum maximum, recover and become dominating in the SEE spectra after a few seconds after the switch. Simultaneously, the ionospherically reflected pump wave signal exhibits a recovery of ponderomotive self-action and the damped quasi-periodical oscillations (spikes) of the reflected pump wave, also related to the PPI development. The intensity of the down-shifted maximum (DM) feature in the SEE spectra increases for about 1–2 s after the switch to the pulse mode, but later, together with PPI related phenomena recovery, the DM intensity decreases noticeably. The phenomena described are attributed to the relaxation of small-scale irregularities (striations). The latter provide strong scattering of the pump wave into upper hybrid waves, strong shielding of the pump wave reflection point, and generation of the upper-hybrid related DM feature.
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- Kovacev, M, et al.
(författare)
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Extreme ultraviolet fourier-transform spectroscopy with high order harmonics
- 2005
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Ingår i: Physical Review Letters. - 1079-7114. ; 95:22
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a new scheme for extreme ultraviolet (xuv) Fourier-transform spectroscopy based on the generation of two phase-locked high-harmonic beams. It allows us to measure for the first time interferograms at wavelengths as short as 90 nm, and open the perspective of performing high-resolution Fourier-transform absorption spectroscopy in the xuv. Our measurements also demonstrate that a precise control of the relative phase of harmonic pulses can be obtained with an accuracy on an attosecond time scale, of importance for future xuv pump-xuv probe attosecond spectroscopy.
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- Mårtensson, Olof, et al.
(författare)
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Fermented, ropy, oat-based products reduce cholesterol levels and stimulate the bifidobacteria flora in humans
- 2005
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Ingår i: Nutrition Research. - : Elsevier BV. - 0271-5317. ; 25:5, s. 429-442
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Tidskriftsartikel (refereegranskat)abstract
- This investigation determined the effects of fermented oat-based products containing both native and microbial beta-glucans on plasma lipids and on fecal total bacterial count and Bifidobacterium ssp. The study was randomized, double blind with 3 parallel groups. Sixty-two free-living volunteers with moderately increased plasma cholesterol levels were recruited. In the final analysis, 56 subjects remained, as 6 subjects had left the study either due to lack of time (n = 2), unwillingness to continue the regimen (n = 2), or for other reasons (n = 2). During the first 3 weeks, all subjects received a fermented dairy-based product (control product, run-in period). On the following 5 weeks, I group continued with the control product, whereas the other 2 groups were given fermented oat-based products (intervention period, 3-3.5 g native beta-glucans per day). One of the oat products (ropy) was cofermented with an exopolysaccharide-producing strain, Pediococcus damnosus 2.6. A significant (P = .022) reduction in total cholesterol by 6% was observed in volunteers who had eaten the fermented, ropy, oat-based product compared with the control group. No other significant changes in plasma lipids were found. A significant increase in total bacterial count (P = .001) and Bifidobacterium ssp (P = .012) was observed in fecal samples from volunteers in the group who had eaten the fermented, ropy, oat-based product. This study shows that a fermented, ropy, oat-based product, containing both native and microbial glucans, can reduce the blood cholesterol level and also stimulate the bifidobacteria flora in the gastrointestinal tract. (c) 2005 Elsevier Inc. All rights reserved.
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- Norin, E
(författare)
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Intestinal cholesterol conversion in adults and elderly from four different European countries
- 2008
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Ingår i: Annals of nutrition & metabolism. - : S. Karger AG. - 1421-9697 .- 0250-6807. ; 5252 Suppl 1, s. 12-14
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Tidskriftsartikel (refereegranskat)abstract
- The growing healthy aging population in Europe is a heterogeneous group with varying nutritional needs, especially in association with problems like decreased sense of smell and taste, saliva production, chewing and swallowing problems besides all disease problems that put specific demands on the dietary intake and the role of the intestinal metabolism. To investigate this, one must clarify which functions are related to the host itself and which actions are related to the microflora. In short, the host’s side of the ecosystem can be defined as <X_Underline>m</X_Underline>ilieu <X_Underline>i</X_Underline>nterieur (MI), the non-host side as <X_Underline>m</X_Underline>ilieu <X_Underline>e</X_Underline>xterieur (ME) and MI plus ME together as <X_Underline>m</X_Underline>ilieu <X_Underline>t</X_Underline>otal (MT). We have investigated the role of the intestinal flora and its functions in adults and elderly from different European countries and this publication is concentrated on the microbial conversion of intestinal cholesterol to coprostanol, aiming to investigate the hepatic-intestinal flora co-cross-talk.
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- Norin, Lars, et al.
(författare)
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Ionospheric plasma density irregularities measured by stimulated electromagnetic emission
- 2008
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 113:A9, s. A09314-
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Tidskriftsartikel (refereegranskat)abstract
- It is well known that ionospheric plasma turbulence can be conveniently generated by controlled injection of powerful high-frequency radio beams from the ground. Irradiation of the ionosphere with such radio waves leads to the formation of plasma density structures, striations, and the generation of secondary electromagnetic radiation, a phenomenon known as stimulated electromagnetic emission (SEE). In this paper we present experimental results of the dependence of SEE on decreasing excitation levels of the striations. In the experiments the frequency of the injected radio beam was varied near the fifth harmonic of the local ionospheric electron gyro frequency. We use the SEE measurements to obtain transverse length scales of the striations involved in the generation of the SEE. Our results show that different spectral features of the SEE display different temporal dynamics, suggesting that they are related to striations with different transverse length scales (1 less than or similar to L-perpendicular to less than or similar to 25 m).
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| 16. |
- Norin, Lars, et al.
(författare)
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Transient dynamics of secondary radiation from an HF pumped magnetized space plasma
- 2007
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 119:A9
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Tidskriftsartikel (refereegranskat)abstract
- In order to systematically analyze the transient wave and radiation processes that are excited when a high-frequency (HF) radio wave is injected into a magnetized space plasma, we have measured the secondary radiation, or stimulated electromagnetic emission (SEE), from the ionosphere, preconditioned such that geomagnetic field-aligned plasma irregularities are already present. The transient dynamics experiments were made using a duty cycle of the HF radio wave of 200 ms (180 ms on and 20 ms off) and 100 ms (80 ms on and 20 ms off) for various frequencies near the fifth harmonic of the local ionospheric electron cyclotron frequency. Within the first 10 ms after the radio pulse turn-on, frequency downshifted structures of the SEE exhibit an overshoot with a maximum at 3 ms < t < 8 ms, whereas the upshifted spectral components do not exhibit this feature. The relative magnitude of the overshoot is strongly dependent on the frequency offset of the pump from the harmonic of the electron cyclotron frequency. A transient blue-shifted frequency component is identified. This component is upshifted from the pump by 14 kHz < Δ f< 55 kHz and exists only within the first 10 ms after the radio pulse turn-on. On a longer time scale we analyze the amplitude modulation, or "ringing," of the reflected radio wave, (also known as "quasi-periodic oscillations" or "spikes"). The ringing has a frequency of the order 15-20 Hz and we show that this phenomenon is also present in the SEE sidebands and is synchronized with the ringing of the reflected HF wave itself.
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- Tjellström, Bo, et al.
(författare)
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Gut microflora associated characteristics in children with celiac disease
- 2005
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Ingår i: American Journal of Gastroenterology. - : Ovid Technologies (Wolters Kluwer Health). - 0002-9270 .- 1572-0241. ; 100:12, s. 2784-2788
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: The aim of the study was to investigate the metabolic function of intestinal microflora in children with celiac disease (CD) in order to find out if there is a deviant gut flora in CD patients compared to healthy controls. METHODS: The study group comprised children with CD, consecutively diagnosed according to current criteria given by the European Society for Paediatric Gastroenterology, Hepatology, and Nutrition. Thirty-six children were studied at presentation, i.e., on a normal gluten-containing diet, with clinical symptoms and signs indicative of CD, positive celiac serology markers, and a small bowel biopsy showing severe enteropathy. Forty-seven patients were studied when they had been on a gluten-free diet (GFD) for at least 3 months. For comparison, a group of 42 healthy controls (HC) were studied. The functional status of the intestinal microflora was evaluated by gas-liquid chromatography of short chain fatty acids (SCFAs) in fecal samples. RESULTS: There was a significant difference between untreated CD children and HC as well as between treated CD children and HC regarding acetic, i-butyric, i-valeric acid, and total SCFAs. The propionic and n-valeric acids differed significantly between CD children on GFD and HC. Moreover, there was a strong correlation between i-butyric and i-valeric acids in all study groups. CONCLUSIONS: This is the first study of the SCFA pattern in fecal samples from children with CD. The results indicate that there is a difference in the metabolic activity of intestinal microbial flora in children with CD compared to that in HC. The finding of a different pattern of some SCFAs in celiacs both at presentation and during treatment with GFD indicates that it is a genuine phenomenon of CD not affected by either the diet, the inflammation, or the autoimmune status of the patient. © 2005 by Am. Coll. of Gastroenterology Published by Blackwell Publishing.
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