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121.
Varpu Ranta Tomi Mikkola Olavi Ylikorkala Lasse Viinikka Arto Orpana 《Journal of cellular physiology》1998,176(1):92-98
Optimal vascular homeostasis requires efficient control of both proliferation and elimination of vascular endothelial cells. Programmed cell death, or apoptosis, is the main mechanism controlling cell elimination, and it is an essential component of vascular formation. Human vascular endothelial cells die in vitro, if prevented from obligatory survival factors like growth factors or attachment and cell spreading, but very little is known about the mechanisms controlling endothelial cell elimination. Signaling from the extracellular matrix affects the behavior and functions of human umbilical vein endothelial cells (HUVECs), and we have recently demonstrated the beneficial effects of plating on the reconstituted extracellular matrix Matrigel™, on the inducible nitric oxide production of freshly isolated HUVECs. In this work we observed that cultured HUVECs formed typical capillary-like structures on Matrigel, but unexpectedly, after 24–48 hours their viability was gradually lost. Viability was measured with an assay based on mitochondrial reduction of reagent XTT. No decrease in viability was seen in freshly isolated HUVECs or in cultured fibroblasts during this time. It is known that cells often turn into apoptosis if they receive conflicting information from their surroundings, and apparently signaling from Matrigel to HUVECs, while at their in vitro proliferating phenotype, resulted in launching of the apoptotic machinery. Thus, proliferating and differentiated phenotypes of endothelial cells seemed to have different sensitivity to signals that induce apoptosis. J. Cell. Physiol. 176:92–98, 1998. © 1998 Wiley-Liss, Inc. 相似文献
122.
Arto Orpana Varpu Ranta Tomi Mikkola Lasse Viinikka Olavi Ylikorkala 《Journal of cellular biochemistry》1997,64(4):538-546
Both cell-matrix and cell-cell interactions are important regulators of the function of most human cells. In this study we investigated how these interactions controlled the production of vasodilators nitric oxide (NO), and prostacyclin (PGI2), in freshly isolated human umbilical vein endothelial cells (HUVECs). On the reconstituted extracellular matrix (ECM) Matrigel freshly isolated HUVECs treated with interleukin-1β, lipopolysaccharide, and interferon-γ, produced more NO, but less PGI2, than on gelatin substratum. High cell density was essential for inducibility of NO production in cells plated on gelatin substratum, but not on ECM. In cells plated on gelatin substratum at low cell density, which mimicked conventional HUVEC culturing conditions, both inducible NO production and the inducible NO synthase (iNOS) mRNA levels, detected by competitive RT-PCR, were low. However, inducible PGI2 production remained high in these cells. Highest inducible NO productions were observed in HUVECs that presumably had best maintained their original differentiated phenotype. Thus our data imply that the inducible NO and PGI2 productions of freshly isolated HUVECs were differently controlled by the extracellular matrix and cell density. Our data suggest that both cell-matrix and cell-cell interactions may have a strong influence on the proinflammatory cytokine responses of human vascular endothelial cells. J. Cell. Biochem. 64:538–546. © 1997 Wiley-Liss, Inc. 相似文献
123.
Summary A freeze-drying apparatus with a practical temperature regulating system is described. Degassing, drying and embedding all take place in the drying chamber. The drying temperature can be set at a number of fixed temperature levels which may be chosen anywhere between -70° C and +60° C. 相似文献
124.
125.
The Baltic herring is one of the key elements of the pelagic ecosystem of the Baltic Sea, being of the most important commercial
species of the sea. The structure and dynamics of herring populations (stocks) have been assessed and managed on international
level since 1970s. Since 1990, all local herring populations have been combined and assessed as one stock (Central Baltic
Herring in Sub-divisions 25–29 and 32). However, the continuously decreasing trend in stock biomass throughout almost 30-years
period of observations indicates the failure of the stock management implementation of the scientific advice. The separate
assessments of different stocks and results of hydro-acoustic surveys of different sub-units (herring in Sub-divisions 25–27,
Sub-divisions 28, 29 and 32 and the Gulf of Riga herring) have revealed rather different situation within combined assessment
unit: e.g. fishing mortality of the Gulf of Riga herring has decreased while a sharp increase in mortality is observed in
the herring stocks of the North-eastern Baltic (Sub-divisions 28, 29 and 32). At the same time stock abundance and biomass
of the Gulf of Riga herring have increased to record high in early 2000s allowing also higher catches. It is concluded that
only separate analytical assessment of local populations combined with regular acoustical surveys and following different
protection measures have proved to be a successful way in managing the herring stocks. Joint assessment and management of
several populations with different structure and dynamics as one combined stock do not allow revealing the real situation
and trends in its parts. 相似文献
126.
Olavi Ukkola Tuomo Rankinen Timo Lakka Arthur S. Leon James S. Skinner Jack H. Wilmore D.C. Rao Y.A. Kesniemi Claude Bouchard 《Obesity (Silver Spring, Md.)》2005,13(5):829-834
Protein tyrosine phosphatase 1B (PTPN1) affects the regulation of insulin signaling and energy metabolism. We studied whether polymorphisms in the PTPN1 gene impact body fat distribution in the HERITAGE Family Study cohort in 502 white and 276 black subjects. Insulin sensitivity index, glucose disappearance index, acute insulin response to glucose (AIRglucose), and the disposition index (DI) were obtained from the frequently sampled intravenous glucose tolerance test. White subjects with the G82G at the PTPN1 IVS6+G82A polymorphism had higher body fat levels (p = 0.031) and sum of eight skinfolds (p = 0.003) and highest subcutaneous fat on the limbs (p = 0.002). G82A subjects had the lowest AIRglucose (p = 0.005) and disposition index (p = 0.040). Interaction effects between PTPN1 and leptin receptor gene variants influenced insulin sensitivity index and AIRglucose (p from 0.006 to 0.010). The variant PTPN1 Pro387Leu was associated with lower fasting insulin level (p = 0.035) and glucose disappearance index (p = 0.038). In summary, PTPN1 IVS6+G82G homozygotes showed higher levels of all measures of adiposity. G82 allele heterozygotes are potentially at higher risk for type 2 diabetes. Gene‐gene interactions between the PTPN1 and leptin receptor genes contributed to the phenotypic variability of insulin sensitivity. The PTPN1 Pro387Leu variant was associated with lower glucose tolerance. 相似文献
127.
Indolyl-3-acetic acid from vegetative shoots of Salix pentandra L. has been isolated and identified by high performance liquid chromatography and combined gas chromatography-mass spectrometry. 相似文献
128.
129.
Olavi Junttila Ola M. Heide Bente Lindgård Arild Ernstsen 《Physiologia plantarum》1997,101(3):599-605
The role of gibberellins (GAs) in photoperiodic control of leaf elongation in Poa pratensis was studied by both application of exogenous GAs and analysis of endogenous GAs. Leaf elongation was strongly increased under long day (LD, 24 h) conditions at both 9 and 21°C, leaf length at 9°C LD being similar to that in plants grown in short days (SD, 8 h) at 21°C. However, even at 21°C leaf elongation was enhanced by LD. Exogenous GA1 could completely compensate for LD at both 9 and 21°C. Gibberellins A20, A19 and A44 could also partly replace LD, but they were significantly less active than GA1, GA53 was inactive when applied to plants grown at 9°C in SD and exhibited only marginal activity at 9°C LD and 21°C SD. The total level of GAs of the early 13-hydroxylation pathway (A53, A44, A19, A20 and A1) increased rapidly when plants were transferred from SD to LD at 9°C. After transfer from 9 to 21°C, there was an increase in GA levels at both LD and SD, followed by a decrease under LD conditions. In all cases, GA19 was the predominant GA, accounting for 60 to 80% of the analysed GAs. Levels of the bioactive GA1 were low and increased transiently by LD four days after transfer from SD to LD. At both temperatures, the ratio GA19 to GA20 and GA20 to GA1 at 9°C was enhanced by LD compared with SD. Taken together, these results support the hypothesis that photoperiodic regulation of leaf elongation in Poa pratensis is GA-mediated, and they indicate a photoperiodic control of oxidation of GA53 to GA44 and GA19 to GA20, and perhaps also of 3β-hydroxylation of GA20 to GA1. 相似文献
130.
Frost tolerance and biochemical changes during hardening and dehardening in contrasting white clover populations 总被引:4,自引:0,他引:4
Successful winter survival of perennial plants, like white clover, is dependent on proper timing of both hardening and dehardening. The purpose of this study was to investigate the regulation of these processes in two cultivars (AberCrest and AberHerald) and two Norwegian ecotypes (Særheim collected at 58°46′N lat. and Bodø at 67°20′N lat.) of white clover (Trifolium repens L.). For hardening and dehardening, plants were exposed to controlled temperature conditions and frost hardiness of stolons was tested by programmed freezing at the rate of 3°C per hour. In addition, stolons were analysed for starch, soluble sugars and soluble amino acids. Cultivars AberCrest and AberHerald, selected for growth at low temperature and winter hardiness in the United Kingdom, were significantly less hardy than the Norwegian populations. After six weeks of hardening (2 weeks at 6°C and 4 weeks at 0.5°C), estimated LT50 values were ?13.8, ?13.0, ?17.8 and ?20.3°C for AberCrest, AberHerald, Saerheim and Bodø, respectively. The rate of dehardening increased with increasing temperature. At low temperature (6°C), the northern ecotype from Bodø was more resistant to dehardening than AberHerald. However, at 18°C the absolute rate of dehardening (°C day?1) was twice as high in Bodø as in AberHerald plants. Stolon elongation during dehardening was initiated at lower temperatures in AberHerald than in plants of the Bodø ecotype. The content of total soluble sugars, sucrose and the amino acids proline and arginine were significantly higher in hardy plants of Bodø than in those of AberHerald. Sucrose levels decreased during dehardening and correlations between sucrose content and LT50 during this process were statistically highly significant for both Bodø and AberHerald. The least hardy populations of white clover were characterized by thick stolons, long internodes and large leaves. 相似文献