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排序方式: 共有428条查询结果,搜索用时 15 毫秒
1.
Denis A. Magoffin Gregory F. Erickson 《In vitro cellular & developmental biology. Plant》1988,24(9):862-870
Summary Although luteinizing hormone (LH) alone stimulates ovarian interstitial cells cultured in serum-free medium to synthesize
large amounts of androgens, there seem to be additional factors in vivo that modulate the time course and magnitude of the
cellular responses to LH. In an attempt to develop a more nearly physiologic cell culture model, lipoproteins, insulin, and
insulinlike growth factor-I (IGF-I) were added to the serum-free medium. The effects of these modifications on androgen biosynthesis
by dispersed cells from ovaries of hypophysectomized immature rats cultured in 96-well tissue culture plates were examined.
A saturating dose of LH stimulated a 25-fold increase in androsterone synthesis at 2 d, which decreased at 4 and 6 d. Addition
of human high density (hHDL) or human low density lipoprotein (hLDL) caused a 2.5-fold increase in LH-stimulated androsterone
synthesis. Cells were approximately twice as sensitive to hHDL (ED50=5.5±0.5 μg cholesterol/ml) compared to hLDL (ED50=9.1±1.1 μg cholesterol/ml). Surprisingly, rat HDL caused only a 40% increase in LH-stimulated androsterone synthesis. When
insulin alone was added to cells cultured with a saturating dose of LH, there was a 2.8-fold increase in androsterone synthesis.
Addition of hHDL and insulin together caused a synergistic increase in LH-stimulated androsterone synthesis. In contrast to
hHDL, which did not change the time course of LH-stimulated androsterone production, insulin prolonged maximal LH-stimulated
androsterone synthesis at 4 and 6 d. Inasmuch as the ED50 for insulin action (1.3±0.1 μg/ml) was supraphysiologic, the effects of IGF-I on LH-stimulated androgen synthesis were examined.
IGF-I mimicked all of the effects of insulin, but at a physiologic concentration (ED50=2.5±0.3 ng/ml). Ovarian cells cultured in serum-free medium supplemented with hHDL and insulin or IGF-I exhibit responses
that closely approximate the physiologic responses observed in vivo. These results suggest that lipoproteins and IGF-I are
important physiologic stimulators of ovarian theca-interstitial cell androgen biosynthesis which, when added to the serum-free
medium, make the cellular responses in this in vitro model more nearly approximate the responses in vivo.
This research was supported by research center grant HD 12303 from the National Institute of Child Health and Human Development,
Bethesda, MD, and USCD Academic Senate grant RM-169M 相似文献
2.
A sampler for collection of interstitial water from wetland sediments is described. It differs from other sampling devices because it does not have to be filled with solution to facilitate diffusion, it does not have to be removed from the wetland to collect samples, and it can be used to draw repeated samples over time from identical locations. The device facilitates in situ measurement of a wide range of abiotic parameters such as electrical conductivity, redox potential, and pH in wetland sediments. The device has application in ecological investigations of sediment-borne wildlife diseases, studies of benthic invertebrates, measurement of nutrient exchange, and other aspects of wetland ecology. 相似文献
3.
Preliminary data on rotifers in the interstitial of the Ninnescah river, Kansas, USA 总被引:1,自引:1,他引:0
Paul N. Turner 《Hydrobiologia》1996,319(3):179-184
One-hundred five rotifer species were identified from a sandy, plains river in Kansas, USA (the Ninnescah river). Of those
rotifers identified, eighty occurred only in the interstitial sand, fifty-six in only the flow as plankton, and thirty-one
from both habitats. Most species can be characterized as being more commonly found in littoral habitats, and not the interstitial
or plankton. Lecane inermis (Bryce, 1892) had the highest density in the hygropsammon interstitial with an average 401 ind. 10 cm−3 at 1–3 cm depth in September 1993.
New records for the US include Encentrum wiszniewski Wulfert (1939), E. longidens Donner (1943) ant E. (Parencentrum) longipes Wulfert (1960). A small form of Lecane levistyla Olofsson (1917) is further examined and discussed. 相似文献
4.
Obst O. O. Linssen M. C. J. G. Vusse G. J. v. d. Kammermeier H. 《Molecular and cellular biochemistry》1996,163(1):173-180
Marked concentration differences of noradrenaline (NA) between the vascular and the interstitial compartment were detected by sampling interstitial transudate from isolated perfused rat hearts. The ratios of vascular/interstitial concentration amounted to 7.4 to 1.3 depending on the concentration of NA administered (3 × 10–9 to 10–6 M). These concentration differences were abolished by inhibitors of uptake1 desipramine (DMI) I and uptake, (O-methyl-isoprenaline (OMI)). Neuronal uptake, was characterized by a Km of 0.22 mol/l and a Vmax of 370 pmol × min–1 × gWWT–1, extraneuronal uptake2 by a KUPTAKE of = 0.313 min–4.The apparent permeability surface area (P×S)-product calculated from uptake rate and transcapillary concentration difference was significantly decreased by administrating 100 mol/l (NA) in presence of DMI. A presumed endothelial uptake mechanism contributing to catecholamine translocation was investigated in endothelial cells in culture. These cells showed a specific noradrenaline uptake with a Km of 4.35 mol/l and a Vmax of about 75 pmol × min–1 x gWWT–1. Any inhibiton by inhibitors of both of the two noradrenaline uptakes was lacking. The uptake rate of this mechanism is insufficient to contribute to the diffusive conductivity of the capillary wall (P × S-product). We conclude from our investigations on interstitial concentrations of catecholamines and transcapillary concentration differences, that the capillary wall, owing to its metabolic and diffusional characteristics, influences the exchange of catecholamines to a substantial and physiologically relevant extent. 相似文献
5.
6.
H. tageae sp. n. and Halicyclops ytororoma sp. n. are described from the intertidal interstitial water of Brazilian beaches.
H. tageae is distinguished from all congeneric species by the number of setae on legs 1–4 endopodite 2 (1, 1, 2, 2) and by possessing a reduced inner spine on the leg 5 exopodite. It shares with H. brevispinosus, H. pusillus and H. canui the spine formula 2, 3, 3, 3 on exopodite 3 of swimming legs 1–4.
H. ytororoma closely resembles H. gauldi and differs from this species by having 4 setae on leg 1 endopodite 3; H. gauldi has 3 setae on this segment.This is the first record of Halicyclops from marine interstitial water in Brazil. 相似文献
7.
Binding, internalization and intracellular processing of 125I-epidermal growth factor purified by isoelectric focusing 总被引:1,自引:0,他引:1
B E Magun S R Planck L M Matrisian J S Finch 《Biochemical and biophysical research communications》1982,108(1):299-306
When epidermal growth factor (EGF) which had been extensively purified by HPLC was subjected to iodination with sodium 125iodide, 5 major species of differing isoelectric points were produced. Some of these species bound to rat fibroblasts with different affinities but were internalized with equal efficiency. Examination of the internalized 125I-labelled molecules revealed processing of all the 125I-EGF species to macromolecules with more acidic isoelectric points. The 125I-EGF species with a pI of 4.5 corresponded in electrofocusing behavior with intact non-iodinated EGF. Other EGF species probably represented molecules which were covalently modified as a result of the iodination procedure. 相似文献
8.
Sediment pore water concentrations of Fe2+, Mn2+, NH
inf4
sup+
and CH4 were analyzed from both diver-collected cores and anin situ equilibration device (peeper) in Lake Erie's central basin. Sediment oxygen demand (SOD) was measured at the same station
with a hemispheric chamber (including DO probe and recorder) subtending a known area of sediments. The average SOD was 9.4
mM m−2 day−1 (0.3 g m−2 day−1). From pore water gradients within the near-surface zone, the chemical flux across the interface was calculated indirectly
using Fick's first law modified for sediments. These calculations, using core and peeper gradients, always showed sediment
loss to overlying waters, and variations between the two techniques differed by less than an order of magnitude for Fe2+ and CH4. The transport of these reduced constituents can represent a sizeable oxygen demand, ranging from less than 1% for Fe2+ and Mn2+ to as high as 26% for NH
inf4
sup+
, and 30% for CH4. The average flux of these constituents could account for about a third of the SOD at the sediment-water interface of this
station. 相似文献
9.
H. Stam H. Jansen W.C. Hülsmann 《Biochemical and biophysical research communications》1980,96(2):899-906
Chylomicron degradation by hearts from fed and fasted rats was studied using a perfusion technique, which allows the separate collection of coronary (Qrv) and interstitial effluent (Qi). Upon perfusion with [3H]-cholesterol-containing chylomicrons the tissue recovery of label was highest in the fasted state, while label recovered in Qi was highest in the fed state. Density gradient centrifugation of Qi indicated that the label was recovered in lipoproteins with higher densities: low density lipoproteins (1.019<d<1.050), high density lipoproteins (1.050<d<1.21) and a fraction of d>1.21. These particles probably represent chylomicron degradation products (remnants and “surface fragments”). Our results indicate that tissue cholesterol uptake during chylomicron degradation may be inhibited in the fed state. Furthermore, the role of the myocyte (or interstitial) lipoprotein lipase in chylomicron degradation is discussed. 相似文献
10.
Sigong Zhang Xueqin Jia Qiuyue Zhang Li Zhang Jing Yang Caihong Hu Junnian Shi Xiao Jiang Jinyue Lu Haili Shen 《Journal of cellular and molecular medicine》2020,24(2):1658-1669
Excessive neutrophil extracellular trap (NET) formation may contribute to polymyositis (PM)‐associated interstitial lung diseases (ILD), but the underlying mechanism is not fully revealed. In this study, we found that NET accelerated the progression of ILD and promoted pulmonary fibrosis (PF) in vivo. miR‐7 expression was down‐regulated in lung tissue of PM group than control group, and NETs further decreased miR‐7 expression. TLR9 and Smad2 were up‐regulated in lung tissue of PM group than control group, and NETs further increased TLR9 and Smad2 expressions. In vitro experiments showed that PMA‐treated NETs accelerated the proliferation of LF and their differentiation into myofibroblast (MF), whereas DNase I decreased the promotion effect of NETs. Neutrophil extracellular trap components myeloperoxidase (MPO) and histone 3 also promoted the proliferation and differentiation of LF. In addition, we demonstrated that TLR9 involved in the regulation of NETs on LF proliferation and differentiation, and confirmed the interaction between miR‐7 and Smad2 in LF. Finally, miR‐7‐Smad2 pathway was confirmed to be involved in the regulation of TLR9 on LF proliferation and differentiation. Therefore, NETs promote PM‐related ILD, and TLR9‐miR‐7‐Smad2 signalling pathway is involved in the proliferation of LFs and their differentiation into MFs. 相似文献