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11.
The effect of oral administration, for 24 or 48 hr, of different octadeca fatty acids containing a 9,12-dienoic structure
on the fatty acid composition and Δ9 desaturation activity of liver microsomes of rat fed a fat-free diet was studied. The
ethyl esters of linoelaidic and γ-linolenic acids, the methyl ester of linoleic acid and free columbinic acid were administered
to rats maintained on a fat-free diet. The supplementation of the fat-free diet with linoelaidate produced no relevant changes
in the fatty acid composition pattern of liver microsomes and did not modify the percentage of conversion of palmitic to palmitoleic
acid. The addition of linoleate or γ-linolenate to the fat-free diet returned liver microsome Δ9 desaturation activity toward
the control and partially restored the liver microsome fatty acid spectrum found in the fat-free diet. Columbinic acid (5-trans-9-cis,12-cis-18∶3), which cannot be transformed into arachidonic acid, also decreased the Δ9 desaturation activity enhanced by the fat-free
diet and evoked changes in the microsomal fatty acid composition similar to those produced by the ω6 fatty acids. These results
suggest that the modulation of Δ9 desaturase activity evoked by dietary administration of unsaturated acids of ω6 series would
depend on thecis double bond configuration of these acids. 相似文献
12.
The incorporation of L-4,5-[3H]leucine into the ultracentrifugally separated apolipoproteins of very low, low, and high density lipoproteins (VLDL, LDL,
HDL) and into serum albumin was found three-to four-fold higher in nephrotic than in normal rats one hour after intravenous
injection. Incorporation of leucine into the circulating lipids was negligible. Increases of similar magnitude were obtained
in the incorporation of simultaneously injected 1,5[14C] citrate into the lipids of VLDL, LDL, and HDL of nephrotic rats. Of the citrate carbons incorporated into serum and liver
lipids, the proportion in cholesterol was higher in nephrotic rats when compared to normal rats. The incorporation of both
precursors into total proteins and lipids of the liver vs. the incorporation into the lipoproteins was relatively lower in
nephrotic than in control rats, indicating a preferential channeling into secretable products. The occurrence of enhanced
new lipid synthesis in nephrosis was corroborated by the finding of markedly enhanced synthesis of lipoprotein-borne fatty
acids and cholesterol from3H2O. These results point out that while leucine is not an efficient in vivo precursor of lipoprotein lipids in nephrosis, de
novo lipogenesis proceeds from other precursors. Similar trend of changes, though of smaller magnitude, was elicited in rats
after double plasmapheresis, 18 hr apart, when measured 3 hr after the second plasma withdrawal. This indicates that the loss
of circulating proteins either by direct removal or through kidney lesion stimulates the compensatory hepatic response involving
excessive lipoprotein synthesis. Time-course studies showed that peak incorporation of leucine and citrate into the protein
and lipid components of lipoproteins, respectively, as well as into serum albumin, occurred coincidentally 3 hr after the
second plasmapheresis, suggesting an interdependence of the enhanced protein and lipid synthesis. 相似文献
13.
Liver nuclear incorporation of stearic (18∶0), linoleic (18∶2n−6), and arachidonic (20∶4n−6) acids was studied by incubation
in vitro of the [1-14C] fatty acids with nuclei, with or without the cytosol fraction at different times. The [1-14C] fatty acids were incorporated into the nuclei as free fatty acids in the following order: 18∶0>20∶4n−6≫18∶2n−6, and esterified
into nuclear lipids by an acyl-CoA pathway. All [1-14C] fatty acids were esterified mainly to phospholipids and triacylglycerols and in a minor proportion to diacylglycerols.
Only [1-14C] 18∶2n−6-CoA was incorporated into cholesterol esters. The incorporation was not modified by cytosol addition. The incorporation
of 20∶4n−6 into nuclear phosphatidylcholine (PC) pools was also studied by incubation of liver nuclei in vitro with [1-14C]20∶4n−6-CoA, and nuclear labeled PC molecular species were determined. From the 15 PC nuclear molecular species determined,
five were labeled with [1-14C]20∶4n−6-CoA: 18∶0–20∶4, 16∶0–20∶4, 18∶1–20∶4, 18∶2–20∶4, and 20∶4–20∶4. The highest specific radioactivity was found in
20∶4–20∶4 PC, which is a minor species. In conclusion, liver cell nuclei possess the necessary enzymes to incorporate exogenous
saturated and unsaturated fatty acids into lipids by an acyl-CoA pathway, showing specificity for each fatty acid. Liver cell
nuclei also utilize exogenous 20∶4n−6-CoA to synthesize the major molecular species of PC with 20∶4n−6 at the sn-2 position. However, the most actively synthesized is 20∶4–20∶4 PC, which is a quantitatively minor component. The labeling
pattern of 20∶4–20∶4 PC would indicate that this molecular species is synthesized mainly by the de novo pathway. 相似文献
14.
Fabrication of planar microlens arrays by silver-sodium ion exchange is possible by using a new glass type, optimized for this technology. Because of its nonlinear diffusion response it is well suited to the fabrication of microlens arrays. We show that the diffusion coefficient can be described theoretically by an exponential concentration dependence. The parameters of the planar microlenses are measured interferometrically and by imaging experiments. Because of the specific index distribution, new evaluation techniques for the determination of lens parameters from interferometric measurements have been applied. We also present a simple model that relates the achievable lens parameters to the diffusion conditions. 相似文献
15.
For the conversion of light from edge-emitting laser diodes into symmetric laser beams two main tasks have to be performed: collimation and beam shaping. Generally these two jobs are performed separately. Because of the inherently different divergence angles of the emitted light, collimation with astigmatic lenses generally results in a beam with an elliptically shaped amplitude distribution. This asymmetry has to be compensated for by an anamorphic imaging step to obtain the desired spherical beam profile. It can be advantageous to combine both jobs in one element. We demonstrate the design, the fabrication, and the application of refractive gradient-index elements, which allow one to perform both jobs with a single element. Our astigmatic lenses were fabricated by silver-sodium ion exchange in glass. 相似文献
16.
Dieter Schneider Berndt Brenner Thomas Schwarz 《Journal of Nondestructive Evaluation》1995,14(1):21-29
Ultrasonic surface waves are suitable for the characterization of surface hardened materials. This is shown on laser hardened turbine blades. The martensitic microstructure within the surface layer of surface hardened steels has a lower surface wave propagation velocity than the annealed or normalized substrate material. Because the propagation velocity depends on the ratio of layer thickness to wavelengthd/, its measurement allows the determination of the hardening depth. If the surface wave frequency is high enough, the surface wave propagates mainly within the hardened layer. A correlation of the surface wave velocity to the surface hardness has been found. Because the variation of the surface velocity in hardened steels is small, a high measurement accuracy is necessary to obtain the interesting hardening parameters with sufficient certainty. Therefore, a measuring arrangement has been developed where laser pulses, guided by optical fibers to the surface hardened structure, generate simultaneously surface wave pulses at two different positions. The two ultrasonic pulses are received by a piezoelectric transducer. The surface wave velocity is obtained from the time delay between these pulses which is determined by the cross-correlation method. To evaluate simultaneously surface waves with different penetration depths from the same signal acquisition, digital filtering has been used in connection with the cross-correlation. 相似文献
17.
Passon C Moisel J McArdle N Eckert W Brenner KH Kuijk M Heremans P 《Applied optics》1996,35(8):1205-1211
We demonstrate a refractive micr-optical system by using ion-exchange microlenses and microprisms, which are combined to generate a superposition of two shifted images. The microlenses, fabricated with field-assisted Ag-Na exchange, achieve diffraction-limited imaging with a single-lens system and with a double-lens system for a field of 800 μm × 800 μm. Furthermore, we demonstrate cascading of two separate differential-pair optical-thyristor arrays by transcribing the information of a source array onto a second destination array. 相似文献
18.
Six asthmatic children were studied to determine whether supplemental, parenteral atropine would increase the effects of bronchodilation and protection against exercise-induced bronchoconstriction after maximal effects had been achieved by inhalation. First, we determined the amount of inhaled atropine sulfate that would give maximal bronchodilation for each patient at rest. This quantity of atropine was designated as "A." Then all subjects exercised for five sessions with the following pre-exercise treatments in a random order: (a) inhaled distilled water plus intramuscular (IM) saline solution; (b) inhaled A dose of atropine plus IM saline solution; (c) inhaled distilled water plus 0.35 mg IM atropine; (d) inhaled A dose of atropine plus 0.35 mg IM atropine; and (e) inhaled double the A dose plus IM saline solution. The results showed that the combination of inhaled and IM atropine had the greatest bronchodilation effect and the greatest protection against exercise-induced bronchoconstriction. Atropine inhalation alone (A dose) or IM injection (0.35 mg) was not as effective in bronchodilation or in alleviation of exercise-induced bronchoconstriction. Doubling the dose of inhalation (2A) did not increase the effects of the A dose. These results support the hypothesis that inhaled atropine does not reach all the airways where cholinergic receptors are present. 相似文献
19.
必需脂肪酸在美容化妆品中的应用 总被引:4,自引:0,他引:4
必需脂肪酸(EFAs)可以使皮肤增益,加强细胞膜结构与功能,维持并恢复皮肤天然屏障,预防皮肤刺激和炎症,以及增强细胞膜的通透性。详述了必需脂肪酸的新陈代谢过程和其在美容化妆品中的应用。 相似文献
20.
J Innitzer K Ehrenberger M Emami-Nouri H Brenner 《Canadian Metallurgical Quarterly》1976,88(20):668-669
A patient studied preoperatively by a neuro-otological test battery showed signs of an extensive cerebellopontine angle tumour. During the operation dense fibrotic tissue was found extending from the choroid plexus to the right acoustic nerve, which was freed and thus decompressed. Postoperatively, low frequency hearing improved markedly in the right ear. In contrast to the well-known documented cases of successful decompression of the optic nerve it has not been possible up to now to achieve a successful outcome in similar procedures on the acoustic nerve. In the described case the fibrotic lesion had obviously just caused reversible damage to the myelin sheaths of the eighth nerve, which can be interpreted as "neurapraxia" (Seddon, 1943). Further investigations in regard to the systematic elucidation of possibly reversible damage to the acoustic nerve are currently being performed at the IInd ENT department of Vienna University. 相似文献