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31.
Katharina S. Buser Bernhard Kopp Peter Gehr Ewald R. Weibel Dr. Hans Hoppeler 《Cell and tissue research》1982,225(2):427-436
Summary Growing rats (4 weeks old) were kept for 3 weeks at 11° C and 24° C respectively. The cold-adapted animals showed a significantly higher oxygen consumption (64%). Volume density of subsarcolemmal and interfibrillar mitochondria as well as volume density of fat droplets were estimated in M. soleus and the diaphragm of both groups. In cold-adapted animals, the total volume of mitochondria was significantly increased by 24% in diaphragm and 37% in M. soleus. The volume of subsarcolemmal mitochondria was almost doubled in each muscle, but the volume of interfibrillar mitochondria did not change significantly. The surface of the inner mitochondrial membranes per unit volume of mitochondrion in M. soleus was significantly increased both in interfibrillar and subsarcolemmal mitochondria, whereas the surface of the outer mitochondrial membranes per unit volume of mitochondrion was increased only in the subsarcolemmal mitochondria. The volume of fat droplets in the diaphragm and M. soleus of cold adapted animals increased significantly by 62% and 150% respectively. 相似文献
32.
Katharina Dalton 《BMJ (Clinical research ed.)》1982,284(6325):1332-1333
33.
A model arterial system of heparin immobilized on an agarose gel was used to study the amount and kinetics of binding of porcine serum lipoproteins to heparin. Binding occurred to lipoproteins in the density range 1.006 less than d less than 1.062, but there was no binding with high density lipoprotein. A theoretical model of the kinetic experiments was formulated and used to demonstrate that the rate of the binding reaction could be considered instantaneous relative to the rate of transport of lipoproteins. Extrapolation of these results to arterial levels of glycosaminoglycans and lipoprotein indicate that complexes of lipoprotein and the glycosaminoglycans could account for much of the cholesterol entrapment in atherosclerotic lesions. 相似文献
34.
The biogenesis of plasmalemma glycoproteins of rat small-intestinal villus cells was studied by following the incorporation of l-[1,5,6-(3)H]fucose, given intraperitoneally with and without chase, into Golgi, lateral basal and microvillus membranes. Each membrane fraction showed distinct kinetics of incorporation of labelled fucose and was differently affected by the chase, which produced a much greater decrease in incorporation of label into Golgi and microvillus than into lateral basal membranes. The kinetic data suggest a redistribution of newly synthesized glycoproteins from the site of fucosylation, the Golgi complex, directly into both lateral basal and microvillus membranes. The observed biphasic pattern of label incorporation into the microvillus membrane fraction may be evidence for a second indirect route of incorporation. The selective effect of the chase suggests the presence of two different pools of radioactive fucose in the Golgi complex that differ in (1) their accessibility to dilution with non-radioactive fucose, and (2) their utilization for the biosynthesis of membrane glycoproteins subsequently destined for either the microvillus or the lateral basal parts of the plasmalemma. The radioactively labelled glycoproteins of the different membrane fractions were separated by sodium dodecyl sulphate/polyacrylamide-slab-gel electrophoresis and identified by fluorography. The patterns of labelled glycoproteins in Golgi and lateral basal membranes were identical at all times. At least 14 bands could be identified shortly after radioactive-fucose injection. Most seemed to disappear at later times, although one of them, which was never observed in microvillus membranes, increased in relative intensity. All but two of the labelled glycoproteins present in the microvillus membrane corresponded to those observed in Golgi and lateral basal membranes shortly after fucose injection. The patterns of labelled glycoproteins in all membrane fractions were little affected by the chase. These data support a flow concept for the insertion of most surface-membrane glycoproteins of the intestinal villus cells. 相似文献
35.
Summary The localization of two carbohydrate binding proteins, so-called lectins, was studied in the sponge tissue of Axinella polypoides by light and immunofluorescence microscopy. They do not occur at the cellular surface of any cell type, but they are stored in vesicles of the spherulous cells. After short formaldehyde fixation spherulous cells can be isolated and they release the active lectins upon lysis in distilled water.Electron microscopical studies of spherulous cells show that they contain almost nothing else but a small nucleus and vesicles of different size and number. Small vesicles are full of an electron dense material, whereas the content of large vesicles has a fluffy and fibrillar structure. Spherulous cells are large and tightly packed in the outer layer of the ectosome and in the mesh work of the spongin fibres of the central axis. They are small and scattered in the inner layer of the ectosome, and they are found throughout the choanosome. The function of the lectins is not clearly defined, and different alternatives such as participation in glycoprotein synthesis, immunological defense, or carbohydrate transport are possible.This study was supported by a grant from the Deutsche ForschungsgemeinschaftWe are gratefully indebted to Dr. D. Keyser for his help in our electron microscopical studies 相似文献
36.
Todd J Menkhaus Sara U Eriksson Paul B Whitson Charles E Glatz 《Biotechnology and bioengineering》2002,77(2):148-154
Host selection can be a strategy to simplify downstream processing for protein recovery. Advancing capabilities for using plants as hosts offers new host opportunities that have received only limited attention from a downstream processing perspective. Here, we investigated the potential of using a polycationic precipitating agent (polyethylenimine; PEI) to precipitate an acidic model protein (beta-glucuronidase; GUS) from aqueous plant extracts. To assess the potential of host selection to enhance the ease of recovery, the same procedure was applied to oilseed extracts of canola, corn (germ), and soy. For comparison, PEI precipitation of GUS was also evaluated from a crude bacterial fermentation broth. Two versions of the target protein were investigated--the wild-type enzyme (WTGUS) and a genetically engineered version containing 10 additional aspartates on each of the enzyme's four homologous subunits (GUSD10). It was found that canola was the most compatible expression host for use with this purification technique. GUS was completely precipitated from canola with the lowest dosage of PEI (30 mg PEI/g total protein), and over 80% of the initial WTGUS activity was recovered with 18-fold purification. Precipitation from soy gave yields over 90% for WTGUS but only 1.3-fold enrichment. Corn, although requiring the most PEI relative to total protein to precipitate (210 mg PEI/g total protein for 100% precipitation), gave intermediate results, with 81% recovery of WTGUS activity and a purification factor of 2.6. The addition of aspartate residues to the target protein did not enhance the selectivity of PEI precipitation in any of the systems tested. In fact, the additional charge reduced the ability to recover GUSD10 from the precipitate, resulting in lower yields and enrichment ratios compared to WTGUS. Compared to the bacterial host, plant systems provided lower polymer dosage requirements, higher yields of recoverable activity and greater purification factors. 相似文献
37.
Steffen Kaiser Katharina Rimbach Tatjana Eigenbrod Alexander H. Dalpke Mark Helm 《RNA (New York, N.Y.)》2014,20(9):1351-1355
RNA can function as a pathogen-associated molecular pattern (PAMP) whose recognition by the innate immune system alerts the body to an impending microbial infection. The recognition of tRNA as either self or nonself RNA by TLR7 depends on its modification patterns. In particular, it is known that the presence of a ribose methylated guanosine at position 18, which is overrepresented in self-RNA, antagonizes an immune response. Here, we report that recognition extends to the next downstream nucleotide and the effectively recognized molecular detail is actually a methylated dinucleotide. The most efficient nucleobases combination of this motif includes two purines, while pyrimidines diminish the effect of ribose methylation. The constraints of this motif stay intact when transposed to other parts of the tRNA. The results argue against a fixed orientation of the tRNA during interaction with TLR7 and, rather, suggest a processive type of inspection. 相似文献
38.
Changes to land use affect streams through nutrient enrichment, increased inputs of sediment and, where riparian vegetation has been removed, raised water temperature. We manipulated all three stressors in experimental streamside channels for 30 days and determined the individual and pair-wise combined effects on benthic invertebrate and algal communities and on leaf decay, a measure of ecosystem functioning. We added nutrients (phosphorus+nitrogen; high, intermediate, natural) and/or sediment (grain size 0.2 mm; high, intermediate, natural) to 18 channels supplied with water from a nearby stream. Temperature was increased by 1.4°C in half the channels, simulating the loss of upstream and adjacent riparian shade. Sediment affected 93% of all biological response variables (either as an individual effect or via an interaction with another stressor) generally in a negative manner, while nutrient enrichment affected 59% (mostly positive) and raised temperature 59% (mostly positive). More of the algal components of the community responded to stressors acting individually than did invertebrate components, whereas pair-wise stressor interactions were more common in the invertebrate community. Stressors interacted often and in a complex manner, with interactions between sediment and temperature most common. Thus, the negative impact of high sediment on taxon richness of both algae and invertebrates was stronger at raised temperature, further reducing biodiversity. In addition, the decay rate of leaf material (strength loss) accelerated with nutrient enrichment at ambient but not at raised temperature. A key implication of our findings for resource managers is that the removal of riparian shading from streams already subjected to high sediment inputs, or land-use changes that increase erosion or nutrient runoff in a landscape without riparian buffers, may have unexpected effects on stream health. We highlight the likely importance of intact or restored buffer strips, both in reducing sediment input and in maintaining cooler water temperatures. 相似文献
39.
40.
Katrin Paul Katharina Bttinger Bernd M. Mitic Georg Scherfler Christoph Posch Dirk Behrens Christian G. Huber Christoph Herwig 《Engineering in Life Science》2020,20(8):368-378
Large‐scale bioreactors for the production of monoclonal antibodies reach volumes of up to 25 000 L. With increasing bioreactor size, mixing is however affected negatively, resulting in the formation of gradients throughout the reactor. These gradients can adversely affect process performance at large scale. Since mammalian cells are sensitive to changes in pH, this study investigated the effects of pH gradients on process performance. A 2‐Compartment System was established for this purpose to expose only a fraction of the cell population to pH excursions and thereby mimicking a large‐scale bioreactor. Cells were exposed to repeated pH amplitudes of 0.4 units (pH 7.3), which resulted in decreased viable cell counts, as well as the inhibition of the lactate metabolic shift. These effects were furthermore accompanied by increased absolute lactate levels. Continuous assessment of molecular attributes of the expressed target protein revealed that subunit assembly or N‐glycosylation patterns were only slightly influenced by the pH excursions. The exposure of more cells to the same pH amplitudes further impaired process performance, indicating this is an important factor, which influences the impact of pH inhomogeneity. This knowledge can aid in the design of pH control strategies to minimize the effects of pH inhomogeneity in large‐scale bioreactors. 相似文献