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661.
M. P. Saiz M. T. Marti M. T. Mitjavila J. Planas 《Biological trace element research》1980,2(4):255-267
Intestinal iron absorption in chickens was studied in vivo, using an intestinal perfusion technique in closed circuit.
The results obtained show that iron absorption, at 30 min intervals, is a linear function of test solution iron concentrations
of up to 776 μg Fe/20 mL. At higher concentrations, iron saturation occurs. The mucosal epithelial cells seem to be less a
limiting factor than in rats. However, in chickens, the binding capacity of plasma might play an important role in the regulation
of iron absorption.
Iron absorption versus time was analyzed in 15, 30, 60, and 120 min periods for the iron concentration of 14 μg Fe/20 mL.
Intestinal iron absorption showed a linear relationship between these two parameters.
A period of perfusion of either 30 or 60 min by a solution of 14 μg Fe/20 mL appears suitable since no interference by a saturation
process can then occur. 相似文献
662.
O.-W. Merten 《Cytotechnology》2000,34(1-2):175-179
The use of the ultrasonic separation deviceis a very important step in the direction forimproving animal cell bioreactor cultures. However,the normal construction of the ultrasonic separationdevice ADI 1015 has an inherent disadvantage inpumping the cell suspension continuously through thedevice by using a peristaltic pump. The cells aretaken out of the reactor and are transported to theside inlet located below the separation chamber of thedevice. This cycling leads to cell death and aconsiderable reduction of the viable cell density. Themodification of the configuration of the device (nocirculation of the cell suspension through theretention device; during approximately 9 minutescell-free supernatant is extracted; every 9 minute forabout one minute, the volume which is equivalent tothe interior volume of the chamber and the tubingconnecting the device to the reactor, is flushed backin order to return the retained cells back to thereactor) allows cell densities from 106 to2.7 × 106 c/ml with a viability of at least90% (tested for the shear sensitive insect cell lineHigh Five), whereas the maximal cell densitiesobtained were 0.76 × 106 c/ml for the periodof continuous culture and 105 c/ml at the end ofthe use of the device in the classical mode. 相似文献
663.
Production of testosterone by highly purified Leydig cells prepared from rat and mouse testes is compared. Testosterone formation is improved to a higher degree in rat (2.7-fold) than in mouse (1.7-fold) cells by collagenase treatment of the testis compared with mechanical isolation. Mouse Leydig cells respond to exogenous stimuli (choriogonadotropin, dibutyryl cyclic AMP) with 2.4-fold higher testosterone secretion than rat cells. A 1.7-fold increased conversion of androgen precursors to testosterone by mouse compared with rat Leydig cells is demonstrated in static incubations as well as in steady-state superfusion experiments and can be derived from enhanced androstenedione reduction and a less inhibitory effect of progesterone on this process in mouse Leydig cells. 相似文献
664.
Arteriovenous anastomoses (AVA) in acral skin (palms and soles) have a huge capacity to shunt blood directly from the arteries to the superficial venous plexus of the extremities. We hypothesized that acral skin, which supplies blood to the superficial venous plexus, has a stronger influence on blood flow adjustments during cooling in thermoneutral subjects than does non-acral skin. Thirteen healthy subjects were exposed to stepwise cooling from 32 °C to 25 °C and 17 °C in a climate chamber. Laser Doppler flux and skin temperature were measured simultaneously from the left and right third finger pulp and bilateral upper arm skin. Coherence and correlation analyses were performed of short-term fluctuations at each temperature interval. The flux from finger pulps showed the synchronous spontaneous fluctuations characteristic of skin areas containing AVAs. Fluctuation frequency, amplitude and synchronicity were all higher at 25 °C than at 32 °C and 17 °C (p<0.02). Bilateral flux from the upper arm skin showed an irregular, asynchronous vasomotor pattern with small amplitudes which were independent of ambient temperature. At 32 °C, ipsilateral median flux values from the right arm (95% confidence intervals) were 492 arbitrary units (au) (417, 537) in finger pulp and 43 au (35, 60) in upper arm skin. Flux values gradually decreased in finger pulp to 246 au (109, 363) at 25 °C, before an abrupt fall occurred at a median room temperature of 24 °C, resulting in a flux value of 79 au (31, 116) at 17 °C. In the upper arm skin a gradual fall throughout the cooling period to 21 au (13, 27) at 17 °C was observed. The fact that the response of blood flow to ambient cooling is stronger in acral skin than in non-acral skin suggests that AVAs have a greater capacity to adjust blood flow in thermoneutral zone than arterioles in non-acral skin. 相似文献
665.
A method is described using an extended (8 h), rat liver perfusion that produces approx. 100 mg of selectively radiolabelled, mature, very-low-density lipoprotein suitable for use in subsequent whole organ perfusion experiments. 相似文献
666.
Topsoil stockpiled for 4 years resulted in an accumulation of NH4-N at depths of 1m or more in mound, as measured by an ammonia gas-sensing electrode. When leached with water these soils were also found to contain high concentrations of dissolved organic C below 1m. Both NH4-N and DOC were products of microbial mineralisation of soil organic matter that accumulated under anaerobic conditions. When these soils were restored a flush of decomposition took place, fuelled by labile organic matter and soluble nitrogen.Stockpiled soil which underwent an ammonium-rich perfusion regime in the laboratory indicated that in-mound soils rapidly attained greater nitrification potential than surface mound soils and also had greater potential for further mineralisation of organic matter to NH4-N. This further production was seen as a contribution from the bacterial flush, stimulated by the large labile-C pool already present.As the bulk of stored soil was anaerobic, restored soils were seen as potentially wasteful of their N-reserves; the fate of nitrogen and soluble carbon compounds in restored soils is discussed. 相似文献
667.
Martina Klöppinger Georg Fertig Elisabeth Fraune Herbert G. Miltenburger 《Cytotechnology》1990,4(3):271-278
The aim of our study was to establish an efficient system for thein vitro production of the insect pathogenic Autographa californica nuclear polyhedrosis virus in a Spodoptera frugiperda cell line. We optimized cultivation conditions for cell proliferation as well as for virus replication in a 1.5 litre stirred tank bioreactor. Cell and virus propagation were found to be optimal at a constant oxygen tension of 40%. In order to provide sufficient nutrients during virus synthesis filtration and perfusion devices were connected to the bioreactor. A virus production procedure in a repeated batch mode by using a two stage bioreactor system is described. Stage I was optimized for cell production and stage II for virus production.Abbreviations Ac-NPV
Autographa californica Nuclear Polyhedrosis Virus
- BV
Baculovirus
- MOI
Multiplicity Of Infection
- ECV
Extracellular Virus 相似文献