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61.
Abstract: Krox proteins are important regulators of development and terminal differentiation. Using the rat glial progenitor cell line CG-4 as a model system for oligodendrocyte differentiation, we show that on the RNA level Krox-24 is the predominant member of the Krox family in these cells. Similar results were also obtained on the protein level as the major Krox protein from CG-4 cell extracts reacted specifically with an antibody against Krox-24. Whereas Krox-24 RNA and protein were abundant in undifferentiated CG-4 cells, a dramatic decrease in expression was detected after a 3–5-day period of differentiation during which we observed a reciprocal increase in the levels of myelin basic protein expression. Importantly, regulation of Krox-24 expression was very similar in CG-4 cells and primary oligodendrocyte cultures. When expression of Krox-24 in differentiating CG-4 cells was followed on a closer time scale, we observed a sharp and transient increase in Krox-24 RNA, protein, and DNA binding activity immediately after the onset of differentiation followed by an equally rapid decrease. This expression pattern implicates Krox-24 both in maintenance of the undifferentiated state and in the immediate early phase of differentiation of CG-4 cells and possibly oligodendrocytes.  相似文献   
62.
Wildfires produce a charcoal layer, which has an adsorbing capacity resembling activated carbon. After the fire a new litter layer starts to accumulate on top of the charcoal layer, which liberates water‐soluble compounds that percolate through the charcoal and the unburned humus layer. We first hypothesized that since charcoal has the capacity to adsorb organic compounds it may form a new habitat for microbes, which decompose the adsorbed compounds. Secondly, we hypothesized that the charcoal may cause depletion of decomposable organic carbon in the underlying humus and thus reduce the microbial biomass. To test our hypotheses we prepared microcosms, where we placed non‐heated humus and on top one of the adsorbents: non‐adsorptive pumice (Pum), charcoal from Empetrum nigrum (EmpCh), charcoal from humus (HuCh) or activated carbon (ActC). We watered them with birch leaf litter extract. The adsorbing capacity increased in the order Pumorg in the litter extract, respectively. After one month, all adsorbents harboured microbes, but their amount and basal respiration was largest in EmpCh and HuCh, and smallest in Pum. In addition, different kinds of microbial communities with respect to their phospholipid fatty acid and substrate utilization patterns were formed in the adsorbents. The amount of microbial biomass and number of bacteria did not differ between humus under different adsorbents, although different microbial communities developed in humus under EmpCh compared with Pum, which is obviously related to the increased pH of the humus under EmpCh, and also ActC. We suggest that charcoal from burning can support microbial communities, which are small in size but have a higher specific growth rate than those of the humus. Although the charcoal layer induces changes in the microbial community of the humus, it does not reduce the amount of humus microbes.  相似文献   
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64.
Basal aryl hydrocarbon hydroxylase (AHH) activity and its kinetic properties were studied as a function of proliferation in C3H mouse embryo 10T12 CL8 cells. Activity was low in freshly plated cells, increased during exponential growth, peaked at confluency, and then declined. The apparent Km-values for benzo[a]pyrene (BP) and NADPH were less in proliferating (approx. 0.37 μM BP, 3.3 nM NADPH) than in confluent cells (0.74–1.39 μM BP, 33.4–53.4 nM NADPH). Cells at different growth states responded differently to benz[a]anthracene (BA) and aminophylline, an inhibitor of cyclic nucleotide phosphodiesterases. When cells were harvested at the mid log phase of growth, 12 h of exposure to aminophylline caused maximum induction, while 24 h of BA treatment were required. In contrast, at early confluence, 12 h of BA treatment gave the greatest levels of activity, while exposure to aminophylline did not induce AHH. In fact, decreases in activity were observed. These differences are indicative of different regulatory mechanisms for BA and aminophylline induction. They also suggest the regulation of basal AHH by cyclic nucleotides changes during growth. The exposure times giving maximum activity were used to determine the kinetic properties of BA-induced activity. As with basal AHH, the Km-value for BP was less in log phase (0.2–0.4 μM BP) than in confluent cells (0.64–1.05 μM BP). Moreover, the Km-values for BP and NADPH in control cultures at confluency (0.10–0.14 μM BP, 15.4–23.2 nM NADPH) were less than those for BA-treated cells (0.64 μM BP, 37.9–54.8 nM NADPH) under the same nutritional conditions. The finding that the Km-value for BP is lower in rapidly dividing cells than in confluent cells may help to explain why proliferating cells are more susceptible to transforming agents.  相似文献   
65.
Twin-pregnant ewes underwent unilateral fetectomy (Fetx) at 50 days of gestation and were studied at 136 days. Aspects of conceptus growth and placental cellularity and metabolism in vitro were compared to those of unoperated control groups of twin-pregnant or single-pregnant ewes. Mean fetal weight in Fetx ewes tended to be greater than that of twin-pregnant ewes and was similar to that of single-pregnant ewes. Mean placental wet and dry weights were intermediate between those for naturally single- and twin-pregnant animals. Fetectomy caused a significant increase in placental protein:DNA ratio but an unchanged DNA concentration, apparently due to cellular hypertrophy in the placenta of the remaining fetus. Weight-specific rate of oxygen consumption (VO2) of fetal placental tissue in twin-pregnant ewes was higher than in Fetx or singles while maternal placental VO2 in twins tended to be lower than in either of the other two groups. These results highlight the plasticity of placental metabolism and growth, perhaps in response to altered trophic signals from the fetus. Unilateral fetectomy should prove useful in studies designed to identify these signals.  相似文献   
66.
Molecular pathogen detection from blood is still expensive and the exact clinical value remains to be determined. The use of biomarkers may assist in preselecting patients for immediate molecular testing besides blood culture. In this study, 140 patients with ≥ 2 SIRS criteria and clinical signs of infection presenting at the emergency department of our hospital were included. C-reactive protein (CRP), neutrophil-lymphocyte count ratio (NLCR), procalcitonin (PCT) and soluble urokinase plasminogen activator receptor (suPAR) levels were determined. One ml EDTA blood was obtained and selective pathogen DNA isolation was performed with MolYsis (Molzym). DNA samples were analysed for the presence of pathogens, using both the MagicPlex Sepsis Test (Seegene) and SepsiTest (Molzym), and results were compared to blood cultures. Fifteen patients had to be excluded from the study, leaving 125 patients for further analysis. Of the 125 patient samples analysed, 27 presented with positive blood cultures of which 7 were considered to be contaminants. suPAR, PCT, and NLCR values were significantly higher in patients with positive blood cultures compared to patients without (p < 0.001). Receiver operating characteristic curves of the 4 biomarkers for differentiating bacteremia from non-bacteremia showed the highest area under the curve (AUC) for PCT (0.806 (95% confidence interval 0.699–0.913)). NLCR, suPAR and CRP resulted in an AUC of 0.770, 0.793, and 0.485, respectively. When compared to blood cultures, the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for SepsiTest and MagicPlex Sepsis Test were 11%, 96%, 43%, 80%, and 37%, 77%, 30%, 82%, respectively. In conclusion, both molecular assays perform poorly when one ml whole blood is used from emergency care unit patients. NLCR is a cheap, fast, easy to determine, and rapidly available biomarker, and therefore seems most promising in differentiating BSI from non-BSI patients for subsequent pathogen identification using molecular diagnostics.  相似文献   
67.
68.
In a previous article modifications were proposed in the preparation of the so-called two-donor fibrinogen, used in the treatment of patients suffering from hemophilia A. Only the freshly prepared product could be used, as lyophilization by the usual method caused varying, and at times considerable, losses in Factor VIII activity.In the present communication a method is described for lyophilization of the product by which the advantageous properties of the modified two-donor fibrinogen can be retained for a longer period. Factor VIII activity of this dried product was found to be nearly unchanged after storage for several months.  相似文献   
69.
Improved methods are needed for in situ characterization of post-translational modifications in cell lines and tissues. For example, it is desirable to monitor the phosphorylation status of individual receptor tyrosine kinases in samples from human tumors treated with inhibitors to evaluate therapeutic responses. Unfortunately the leading methods for observing the dynamics of tissue post-translational modifications in situ, immunohistochemistry and immunofluorescence, exhibit limited sensitivity and selectivity. Proximity ligation assay is a novel method that offers improved selectivity through the requirement of dual recognition and increased sensitivity by including DNA amplification as a component of detection of the target molecule. Here we therefore established a generalized in situ proximity ligation assay to investigate phosphorylation of platelet-derived growth factor receptor beta (PDGFRbeta) in cells stimulated with platelet-derived growth factor BB. Antibodies specific for immunoglobulins from different species, modified by attachment of DNA strands, were used as secondary proximity probes together with a pair of primary antibodies from the corresponding species. Dual recognition of receptors and phosphorylated sites by the primary antibodies in combination with the secondary proximity probes was used to generate circular DNA strands; this was followed by signal amplification by replicating the DNA circles via rolling circle amplification. We detected tyrosine phosphorylated PDGFRbeta in human embryonic kidney cells stably overexpressing human influenza hemagglutinin-tagged human PDGFRbeta in porcine aortic endothelial cells transfected with the beta-receptor, but not in cells transfected with the alpha-receptor, and also in immortalized human foreskin fibroblasts, BJ hTert, endogenously expressing the PDGFRbeta. We furthermore visualized tyrosine phosphorylated PDGFRbeta in tissue sections from fresh frozen human scar tissue undergoing wound healing. The method should be of great value to study signal transduction, screen for effects of pharmacological agents, and enhance the diagnostic potential in histopathology.  相似文献   
70.
The self-fertile nematode worms Caenorhabditis elegans, C. briggsae, and C. tropicalis evolved independently from outcrossing male-female ancestors and have genomes 20-40% smaller than closely related outcrossing relatives. This pattern of smaller genomes for selfing species and larger genomes for closely related outcrossing species is also seen in plants. We use comparative genomics, including the first high quality genome assembly for an outcrossing member of the genus (C. remanei) to test several hypotheses for the evolution of genome reduction under a change in mating system. Unlike plants, it does not appear that reductions in the number of repetitive elements, such as transposable elements, are an important contributor to the change in genome size. Instead, all functional genomic categories are lost in approximately equal proportions. Theory predicts that self-fertilization should equalize the effective population size, as well as the resulting effects of genetic drift, between the X chromosome and autosomes. Contrary to this, we find that the self-fertile C. briggsae and C. elegans have larger intergenic spaces and larger protein-coding genes on the X chromosome when compared to autosomes, while C. remanei actually has smaller introns on the X chromosome than either self-reproducing species. Rather than being driven by mutational biases and/or genetic drift caused by a reduction in effective population size under self reproduction, changes in genome size in this group of nematodes appear to be caused by genome-wide patterns of gene loss, most likely generated by genomic adaptation to self reproduction per se.  相似文献   
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