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排序方式: 共有1902条查询结果,搜索用时 218 毫秒
1.
The Korean species of the genus Eudorylas Aczél have been studied. A total of 16 species are arranged herein. Among them, E. paraappendiculatus sp. nov. is new to science, and E. nomurai Morakote et Yano, 1990 is newly recorded in the Korean fauna. 相似文献
2.
H+/sugar symport in the obligatory aerobic yeastRhodotorula glutinis was analyzed under conditions where the plasma membrane was selectively depolarized by the lipophilic cation tetraphenylphosphonium (TPP+). Control experiments showed that this treatment did not impair the transmembrane pH, the cell energy charge, and the function of plasma membrane H+-ATPase. The kinetic data were fitted to elementary functions derived from a model constructed on the basis of some simplifying premises for ordered (either C + H+ + S or C + S + H+) and random reaction mechanisms. In addition, the comparison of the kinetic parameters in fully energized and depolarized cells provided information about the free carrier charge. It was concluded that the binding sequence of formation of the ternary carrier/H+/substrate complex follows a random mechanism and that the carrier bears a negative charge. 相似文献
3.
Milan Höfer Klaas Nicolay George Robillard 《Journal of bioenergetics and biomembranes》1985,17(3):175-182
The electrochemical gradient of protons,
, was estimated in the obligatory aerobic yeastRhodotorula glutinis in the pH0 range from 3 to 8.5. The membrane potential, , was measured by steady-state distribution of the hydrophobic ions, tetraphenylphosphonium (TPP+) for negative above pH0 4.5, and thiocyanate (SCN–) for positive below pH0 4.5. The chemical gradient of H+ was determined by measuring the chemical shift of intracellular Pi by31P-NMR at given pH0 values. The values of pHi increased almost linearly from 7.3 at pH0 3 to 7.8 at pH0 8.5. In the physiological pH0 range from 3.5 to 6,
was fairly constant at values between 17–18 KJ mol–1, gradually decreasing at pH0 above 6. In deenergized cells, the intracellular pHi decreased to values as low as 6, regardless of whether the cell suspension was buffered at pH0 4.5 or 7.5. There was no membrane potential detectable in deenergized cells. 相似文献
4.
5.
A simple procedure for obtaining useful narrow-pH-range ampholytes from inexpensive laboratory-synthesized ampholytes by preparative isoelectric focusing in Pevikon is described. The narrow range ampholytes prepared in this way are comparable to commercial ampholyte preparation as judged by conductivity, buffer capacity, pH gradient formation, and resolving power. These inexpensive narrow-range ampholytes are particularly well suited to preparative isoelectric focusing applications requiring large quantities of ampholytes. 相似文献
6.
In vivo and in vitro uptake and degradation of acetylated low density lipoprotein by rat liver endothelial, Kupffer, and parenchymal cells 总被引:27,自引:0,他引:27
J F Nagelkerke K P Barto T J van Berkel 《The Journal of biological chemistry》1983,258(20):12221-12227
Isolation and separation of rat liver cells into endothelial, Kupffer, and parenchymal cell fractions were performed at different times after injection of human 125I-acetyl low density lipoproteins (LDL). In order to minimize degradation and redistribution of the injected lipoprotein during cell isolation, a low temperature (8 degrees C) procedure was applied. Ten min after injection, isolated endothelial cells contained 5 times more acetyl-LDL apoprotein per mg of cell protein than the Kupffer cells and 31 times more than the hepatocytes. A similar relative importance of the different cell types in the uptake of acetyl-LDL was observed 30 min after injection. For studies on the in vitro interaction of endothelial and Kupffer cells with acetyl-LDL, the cells were isolated with a collagenase perfusion at 37 degrees C. Pure endothelial (greater than 95%) and purified Kupffer cells (greater than 70%) were obtained by a two-step elutriation method. It is demonstrated that the rat liver endothelial cell possesses a high affinity receptor specific for the acetyl-LDL because a 35-fold excess of unlabeled acetyl-LDL inhibits association of the labeled compound for 70%, whereas unlabeled native human LDL is ineffective. Binding to the acetyl-LDL receptor is coupled to rapid uptake and degradation of the apolipoprotein. Addition of the lysosomotropic agents chloroquine (50 microM) or NH4Cl (10 mM) resulted in more than 90% inhibition of the high affinity degradation, indicating that this occurs in the lysosomes. With the purified Kupffer cell fraction, the cell association and degradation of acetyl-LDL was at least 4 times less per mg of cell protein than with the pure endothelial cells. Although cells isolated with the cold pronase technique are also still able to bind and degrade acetyl-LDL, it appeared that 40-60% of the receptors are destroyed or inactivated during the isolation procedure. It is concluded that the rat liver endothelial cell is the main cell type responsible for acetyl-LDL uptake. 相似文献
7.
Summary The gross primary production of periphyton, grown on artificial substrata in the littoral of the Danube, was measured by the light and dark bottle method from April 1970 to March 1971. The periphyton used for the measurements was sampled from various depths, in order to cover the production of the whole littoral. In connection with this, the littoral area was divided into four zones limited by the heights 600 to 200 cm, according to the local water level gauge. The highest localized zone A (500–600 cm) was inundated only at maximum water levels for rather short period of time, the deepest zone D (200–300 cm) was permanently flooded.The zone A showed an average periphyton primary production of 22.5, the zone B of 54.8, the zone C of 28.9 and the zone D of 9.1 mg O2/dm2/day. When recalculated to periods when the individual zones were inundated, the annual production was as follows: in zone A: 0.94, zone B: 9.20, zone C: 7.29 and zone D: 3.06g O2/dm2. The highest primary production was always found in the zone just below the water level. Exceptions occurred only when this zone was inundated for a short time as a result of a temporary rise of the water level and the periphyton was insufficiently developed.In order to compare the values of primary production of periphyton obtained from shallower rivers, where the whole bottom is well illuminated, or from rivers that do not exhibit such frequent and extensive level oscillations as the Danube, average value calculated from results obtained from the zone closest to the water level at the time of measurements, were always used. These results represent a special zone following the water level changes which is called surface zone. Primary periphytic production in the surface zone was 43.8 mg O2/dm2/day. For the annual period it corresponds to the value of 14.74 g O2/dm2. Efficiently of gross photosynthesis in this zone was on the average 1.72%.The height of the water level and the water temperature were higly correlated with gross periphytic production. Close relationships between chlorophyll a concent, biomass and gross primary production of periphyton were found.
Zusammenfassung Die Bruttoprimärproduktion des auf künstlichem Substrat im litoralen Bereich der Donau wachsenden Periphytons, wurde vom April 1970 bis zum März 1971, mit Hilfe der Hell-Dunkelflaschenmethode, gemessen. Das für die Messung herangezogene Periphyton wurde aus verschiedenen Tiefenzonen entnommen, um die Produktion der gesamten Uferzone festzuhalten. Im Zusammenhang damit wurde der litorale Bereich der Donau in 4 Zonen gegliedert, welche ihre Grenzen bei einem Pegelstand von 600–200 cm des Ortspegels hatten. Die höchste Zone A (500–600 cm) wurde nur bei den höchsten Wasserstanden und nur für kurze Zeit vom Wasser überflutet, die tiefste Zone D (200–300 cm) war dauernd unter Wasser.In der Zone A war die durchschnittliche Produktion des Periphytons 22,5 mg O2/dm2/Tag, in Zone B 54,8 mg, in Zone C 28,9 mg und in Zone D 9.1 mg. Nach Berechnung für die Zeit, in der die einzelnen Zonen vom Wasser bedeckt waren war folgende Produktion in den einzelnen Zonen festzustellen: in Zone A 0,94 g O2/dm2, in Zone B 9,20 g, in Zone C 7,29 g und in Zone D 3,06 g. Die höchste Periphytonproduktion wurde jeweils in der Zone festgestellt, welche dem Wasserspiegel am nächsten war. Eine Ausnahme bildeten nur jene Fälle, in denen these Zone nach vorübergehender Erhöhung des Wasserspiegels erst kurze Zeit vom Wasser bedeckt war und das Periphyton ungenügend entwickelt war.Zum Vergleich mit den Werten der Primärproduktion des Aufwuchses aus seichteren Gewässern mit gut belichteter Sohle, oder aus Flüssen welche nicht so häufige und weitreichende Spiegelschwankungen aufweisen wie die Donau, wird in der vorgelegten Arbeit der Durchschnittswert aus den Ergebnissen der Zone verwendet, welche zur Zeit der Messungen dem Wasserspiegel am nächsten war. Diese Ergebnisse repräsentieren eine besondere Zone, welche den Schwankungen des Wasserspiegels folgt und von den Autoren durch den Begriff Oberflachenzone bezeichnet wird. Die Primärproduktion des Periphytons in dieser Oberflächenzone war 43,8 mg O2/dm2/Tag. Dem entspricht im Jahresverlauf ein Wert von 14,74 g O2/dm2. Die Ausnützung der Sonnenenergie war in dieser Zone im Durchschnitt 1,72%.Von den Umweltfaktoren zeigt die Höhe des Wasserspiegels und die Wassertemperatur den engsten Zusammenhang mit der Höhe der Bruttoprimärproduktion des Periphytons. In kürzeren Zeitabschnitten, in denen es zu keinen raschen ausgeprägten Schwankungen des Wasserspiegels des Flusses kommt, wurde eine enge Abhängigkeit zwischen den Werten der Primärproduktion und dem a-Chlorophylgehalt und auch der Biomasse festgestellt.相似文献
8.
Milan Fiala 《Applied microbiology》1968,16(10):1445-1450
Plaque production by 55 rhinoviruses in several lines of HeLa cells is reported. Forty-nine types produced macroscopic plaques under the conditions described previously employing 30 mM MgCl(2) and 30 mug/ml of DEAE-dextran in overlay and M HeLa cells. Basically three kinds of plaques were observed: clear large and intermediate sized plaques and small turbid plaques. Five rhinoviruses produced plaques only in a sensitive clonal line isolated from the M HeLa line. Rhinovirus type 4 produced plaques after the pretreatment of cells with actinomycin D. Enhancement of plaque formation by MgCl(2) has been demonstrated to date with 17 rhinoviruses. Some rhinoviruses were enhanced either by DEAE-dextran or by dextran sulfate in the overlay. No inhibitors were found in any of 10 bovine sera tested. Rhinovirus type 2 was visualized inside HeLa cells by electron microscopy and there appeared to be a very high ratio of physical particles per infectious unit of virus. 相似文献
9.
Biologia Plantarum - New Chromatographic methods, chromatography in centrifugal field and thin-layer chromatography on alumina, were used for separating physiologically active gibberellins A1 and... 相似文献
10.
Summary
Lambertz (1954) did not mention Gramineae as plants containing ectodesmata, although he stated that ectodesmata are not bound to special groups of angiosperms but should occur in all families of angiosperms. Schnepe (1959) expressly pointed out that he never succeeded in demonstrating such structures in leaves of Gramineae with his method. In our studies, however, ectodesmata could be shown in leaves of wheat and maize if the fixation mixture contained nitric acid. As in other objects, including species of gymnosperms and pteridophytes, the same distribution of ectodesmata could be observed which was characterized by the formation of rows along the anticlinal walls, crowding in guard-cells and seattering in periclincal walls. 相似文献