排序方式: 共有16条查询结果,搜索用时 0 毫秒
1.
Maria Ponec Arij Weerheim Louis Havekes Johannes Boonstra 《Experimental cell research》1987,171(2):426-435
The relationship among keratinocyte differentiation capacity, lipid synthesis, low-density lipoprotein (LDL) metabolism, plasma membrane composition, and epidermal growth factor (EGF) binding has been studied in SCC-12F2 cells. The differentiation capacity of the cells, i.e., ionophore-induced cornified envelope formation, was inhibited by various retinoids and stimulated by hydrocortisone. Retinoids that caused a significant reduction of cornified envelope formation, i.e., retinoic acid and 13-cis-retinoic acid, caused only minor changes in lipid synthesis and plasma membrane composition. Arotinoid ethylsulfone, having a minor effect on cornified envelope formation, caused a drastic inhibition of cholesterol synthesis, resulting in changes in the plasma membrane composition. Hydrocortisone stimulated cornified envelope formation but had only minor effects on lipid synthesis and plasma membrane composition. Of all retinoids tested, only arotinoid ethylsulfone caused a drastic increase in EGF binding, while hydrocortisone had no effect. Retinoic acid, arotinoid ethylsulfone, and hydrocortisone had no effects on LDL binding and only minor effects on LDL degradation. These results clearly demonstrate that the plasma membrane composition is not related to keratinocyte differentiation capacity, but most likely does determine EGF binding. Furthermore, EGF binding does not determine keratinocyte differentiation capacity. 相似文献
2.
Katny MA Hoffmann-Thoma G Schrier AA Fangmeier A Jäger HJ van Bel AJ 《Journal of plant physiology》2005,162(4):429-438
Potato plants (Solanum tuberosum cv. Bintje) were grown in open top chambers under ambient (400 microL L(-1)) and elevated CO2 (720 microL L(-1)). After 50 days one half of each group was transferred to the other CO2 concentration and the effects were studied in relation to leaf age (old, middle-aged and young leaves) in each of the four groups. Under long-term exposure to elevated CO2, photosynthesis increased between 10% and 40% compared to ambient CO2. A subsequent shift of the same plants to ambient CO2 caused a 20-40% decline in photosynthetic rate, which was most pronounced in young leaves. After shifting from long-term ambient to elevated CO2, photosynthesis also increased most strongly in young leaves (90%); these experiments show that photosynthesis was downregulated in the upper young fully expanded leaves of potato growing long-term under elevated CO2. Soluble sugar content in all leaf classes under long-term exposure was stable irrespective of the CO2 treatment, however under elevated CO2 young leaves showed a strongly increased starch accumulation (up to 400%). In all leaf classes starch levels dropped in response to the shift from 720 to 400 microL L(-1) approaching ambient CO2 levels. After the shift to 720 microL L(-1), sucrose and starch levels increased, principally in young Leaves. There is clear evidence that leaves of different age vary in their responses to changes in atmospheric CO2 concentration. 相似文献
3.
Zhang X Daou A Truong TM Bertram R Roper MG 《American journal of physiology. Endocrinology and metabolism》2011,301(4):E742-E747
Pancreatic islets secrete insulin in a pulsatile manner, and the individual islets are synchronized, producing in vivo oscillations. In this report, the ability of imposed glucose waveforms to synchronize a population of islets was investigated. A microfluidic system was used to deliver glucose waveforms to ~20 islets while fura 2 fluorescence was imaged. All islets were entrained to a sinusoidal waveform of glucose (11 mM median, 1 mM amplitude, and a 5-min period), producing synchronized oscillations of fura 2 fluorescence. During perfusion with constant 11 mM glucose, oscillations of fura 2 fluorescence were observed in individual islets, but the average signal was nonoscillatory. Spectral analysis and a synchronization index (λ) were used to measure the period of fura 2 fluorescence oscillations and evaluate synchronization of islets, respectively. During perfusion with glucose waveforms, spectral analysis revealed a dominant frequency at 5 min, and λ, which can range from 0 (unsynchronized) to 1 (perfect synchronization), was 0.78 ± 0.15. In contrast, during perfusion with constant 11 mM glucose, the main peak in the spectral analysis corresponded to a period of 5 min but was substantially smaller than during perfusion with oscillatory glucose, and the average λ was 0.52 ± 0.09, significantly lower than during perfusion with sinusoidal glucose. These results indicated that an oscillatory glucose level synchronized the activity of a heterogeneous islet population, serving as preliminary evidence that islets could be synchronized in vivo through oscillatory glucose levels produced by a liver-pancreas feedback loop. 相似文献
4.
5.
Acer monspessulanum (maple) is an endemic endangered tree with a wide but fragmented distribution in the Mediterranean mountains. The persistence of its small populations depends often on few adults, which makes it is highly vulnerable to limiting recruitment factors. In this paper, we examined the regeneration status of this maple in three populations through its geographical distribution in the mountain range of the Tunisian dorsal (Jbel Srerej national park and sacred site). Morphological parameters, genetic variability, and diversity were analyzed as species viability indicators. The ecological site of maple was studied based on the soil texture and structure under the population, additionally to the role of shrubs as nurse plants in maple regeneration dynamic. Here, the maple population in Tunisia was investigated for the first time. The results show that Acer monspessulanum population has a variation terms of height, stem diameter and crown diameter, it also shows that there is a good natural regeneration. Analysis of the soil’s physicochemical parameters showed that the species grows on sandy loam and clay loam soil, shallow and slightly alkaline pH. This study contributes to better characterization of the Tunisian maple population and its ecological niche from the standpoint of soil and vegetation. 相似文献
6.
Maria Ponec Arij Weerheim Johanna Kempenaar Peter M. Elias Mary L. Williams 《In vitro cellular & developmental biology. Plant》1989,25(8):689-696
Summary Differentiation in keratinocytes can be experimentally modulated by changing the culture conditions. When cultured under conventional,
submerged conditions, the extent of cellular differentiation is reduced in the presence of low calcium medium and is enhanced
in medium containing physiologic calcium concentrations. Moreover cultures grown at the air-medium interface or on a dermal
substrate, or both, differentiate even further. Herein we report the effect of culture conditions on lipid composition in
normal human keratinocytes and three squamous carcinoma cell (SCC) lines that vary in their capacity to differentiate as assessed
by cornified envelope formation. Under submerged conditions, the total phospholipid content was lower, triglyceride content
higher, and phospholipid: neutral lipid ratio lower in direct correlation to the degree of differentiation in these cultures.
When grown at the air-medium interface on the-epidermized dermis, evidence of further morphologic differentiation was found
only for well-differentiated SCC cells and normal keratinocytes. Similarly, the phospholipid content remained high in poorly
differentiated SCC cells and it, decreased modestly in well-differentiated SCC cells and markedly in normal keratinocytes.
In all cell lines the triglyceride content was increased and cholesterol content decreased when compared to parallel submerged
cultures, but these differences were most pronounced in well-differentiated cell lines. Acylceramides and acylglucosylceramides
were found only in normal keratinocytes and only under the most differentiation-enhancing conditions. These studies demonstrate
differentiation-related changes in the lipid content of both normal and neoplastic keratinocytes.
This work was supported in part by NATO Scientific Award (RG 8510056). 相似文献
7.
Arij Mechergui Wafa Achour Assia Ben Hassen 《World journal of microbiology & biotechnology》2014,30(8):2181-2188
We aimed to compare accuracy of genus and species level identification of Neisseria spp. using biochemical testing and 16S rRNA sequence analysis. These methods were evaluated using 85 Neisseria spp. clinical isolates initially identified to the genus level by conventional biochemical tests and API NH system (Bio-Mérieux®). In 34 % (29/85), more than one possibility was given by 16S rRNA sequence analysis. In 6 % (5/85), one of the possibilities offered by 16S rRNA gene sequencing, agreed with the result given by biochemical testing. In 4 % (3/85), the same species was given by both methods. 16S rRNA gene sequencing results did not correlate well with biochemical tests. 相似文献
8.
Ng T Chand D Song L Al Chawaf A Watson JD Boutros PC Belsham DD Lovejoy DA 《Regulatory peptides》2012,174(1-3):79-89
9.
José Oliveira Bruno Etain Mohamed Lajnef Nora Hamdani Meriem Bennabi Djaouida Bengoufa Aparna Sundaresh Arij Ben Chaabane Frank Bellivier Chantal Henry Jean-Pierre Kahn Dominique Charron Rajagopal Krishnamoorthy Marion Leboyer Ryad Tamouza 《PloS one》2015,10(3)
Gene-environment interactions may play an important role in modulating the impact of early-life stressful events on the clinical course of bipolar disorder (BD), particularly associated to early age at onset. Immune dysfunction is thought to be an important mechanism linking childhood trauma with early-onset BD, thus the genetic diversity of immune-related loci may account for an important part of the interindividual susceptibility to this severe subform. Here we investigated the potential interaction between genetic variants of Toll-like receptors 2 (TLR2) and 4 (TLR4), major innate immune response molecules to pathogens, and the childhood trauma questionnaire (CTQ) in age at onset of BD. We recruited 531 BD patients (type I and II or not otherwise specified), genotyped for the TLR2 rs4696480 and rs3804099 and TLR4 rs1927914 and rs11536891 single-nucleotide polymorphisms and recorded for history of childhood trauma using the CTQ. TLR2 and TLR4 risk genotype carrier state and history of childhood emotional, physical and sexual abuses were evaluated in relation to age at onset as defined by the age at first manic or depressive episode. We observed a combined effect of TLR2 rs3804099 TT genotype and reported sexual abuse on determining an earlier age at onset of BD by means of a Kaplan-Meier survival curve (p = 0.002; corrected p = 0.02). Regression analysis, however, was non-significant for the TLR2-CTQ sexual abuse interaction term. The negative effects of childhood sexual abuse on age at onset of BD may be amplified in TLR2 rs3804099 risk genotype carriers through immune-mediated pathways. Clinical characteristics of illness severity, immune phenotypes and history of early life infectious insults should be included in future studies involving large patient cohorts. 相似文献
10.