Declining expression of a single epithelial cell‐autonomous gene accelerates age‐related thymic involution

Age‐related thymic involution may be triggered by gene expression changes in lymphohematopoietic and/or nonhematopoietic thymic epithelial cells (TECs). The role of epithelial cell‐autonomous gene FoxN1 may be involved in the process, but it is still a puzzle because of the shortage of evidence from gradual loss‐of‐function and exogenous gain‐of‐function studies. Using our recently generated loxP‐floxed‐FoxN1(fx) mouse carrying the ubiquitous CreER^T (uCreER^T) transgene with a low dose of spontaneous activation, which causes gradual FoxN1 deletion with age, we found that the uCreER^T‐fx/fx mice showed an accelerated age‐related thymic involution owing to progressive loss of FoxN1⁺ TECs. The thymic aging phenotypes were clearly observable as early as at 3–6 months of age, resembling the naturally aged (18–22‐month‐old) murine thymus. By intrathymically supplying aged wild‐type mice with exogenous FoxN1‐cDNA, thymic involution and defective peripheral CD4⁺ T‐cell function could be partially rescued. The results support the notion that decline of a single epithelial cell‐autonomous gene FoxN1 levels with age causes primary deterioration in TECs followed by impairment of the total postnatal thymic microenvironment, and potentially triggers age‐related thymic involution in mice.     

白介素-6对NMDA诱导的小脑神经元放电活动的抑制作用及其机制

目的：观察白介素-6（IL-6）对N-甲基-D-天冬氨酸（NMDA）激发的神经元放电活动的影响及其可能的作用机制。方法：用含IL-6、NMDA和JAK抑制剂ACA90的人工脑脊液（ACSF）灌流小脑脑片,利用离体脑片神经元单位放电细胞外记录技术,记录药物对小脑间位核神经元放电的影响。用Western blot法测定间位核神经元NMDA受体亚单位1（NRI）的磷酸化水平。结果：单独用12．5μmol／L和25μmol／LNMDA灌流,神经元放电频率均较基础放电频率增加;用不同浓度IL-6（50,100,200μg／ml）联合NMDA作用后,神经尤的放电频率出现浓度依赖性地降低;AG490可部分阻断IL-6对NMDA兴奋神经元放电的抑制作用。与单独NMDA处理组比较,用IL-6联合NMDA处理神经元后,神经元的NR1磷酸化水平出现浓度依赖性地降低。AG490可阻断IL-6所致的神经元NR1磷酸化水平的降低。结论：IL-6可抑制NMDA激发的小脑间位核神经元的放电兴奋活动;并同时下调神经元的NR1磷酸化水平。     

Tumour necrosis factor-alpha receptor 1 polymorphisms and serum soluble TNFR1 in early spontaneous miscarriage

OBJECTIVES: The study investigated the association of TNFR1 gene polymorphism with early recurrent spontaneous miscarriage (ERSM) in Chinese women, and soluble TNFR1 (sTNFR1) expression in ERSM women. STUDY DESIGN: Two single nucleotide polymorphisms (SNPs) located at -383 (AGA to AGC) in the promoter region and +36 (CCA to CCG) in exon 1 of TNFR1 were investigated in 188 non-pregnant ERSM Chinese women. The serum sTNFR1 was measured by the ELISA method. RESULTS: Both SNPs were not associated with ERSM. The non-pregnant ERSM women had significantly higher levels of serum sTNFR1, compared with the non-pregnant, normal women (1.84+/-0.54 ng/ml versus 1.62+/-0.38 ng/ml; t=-2.053; p<0.05). CONCLUSIONS: The data do not provide evidence that TNFR1 gene polymorphism is etiologically important for ERSM in Chinese women. But, a significantly raised sTNFR1 level in non-pregnant ERSM women was recorded compared to women with normal pregnancies. The result suggests that pregnancy failure is associated with an increase of sTNFR1.     

Listeria monocytogenes in spontaneous abortions in humans and its detection by multiplex PCR

AIM: To assess the extent of Listeria monocytogenes in causation of human spontaneous abortions by isolation methods and PCR analysis for the presence of virulence-associated genes. METHODS AND RESULTS: A total of 305 samples comprising blood, urine, placental bits, faecal and vaginal swabs were collected from 61 patients with spontaneous abortions. Listeria spp. were isolated from 10 samples collected from nine (14.8%) patients. Confirmation of these isolates was based on biochemical tests, haemolysis on blood agar, CAMP test, phosphatidylinositol-specific phospholipase C (PI-PLC) assay followed by in vivo pathogenicity tests and multiplex PCR to detect virulence-associated genes (prfA, plcA, hlyA, actA and iap). Three isolates were confirmed as L. monocytogenes. Of these, two isolates turned out to be pathogenic and found to posses all five genes. However, the remaining two haemolytic L. monocytogenes isolates lacking the plcA gene and activity in the PI-PLC assay were found to be nonpathogenic by in vivo tests. CONCLUSIONS: The occurrence of pathogenic L. monocytogenes in cases of spontaneous abortions was 3.3%. It seems that the plcA gene and its expression have an important role as essential virulence determinants in pathogenic Listeria spp. SIGNIFICANCE AND IMPACT OF THE STUDY: The recovery of pathogenic L. monocytogenes isolates from cases of spontaneous abortion indicates the significance of listeric infection in pregnant women.     

The red death meets the abdominal bristle: Polygenic mutation for susceptibility to a bacterial pathogen in Caenorhabditis elegans

Understanding the genetic basis of susceptibility to pathogens is an important goal of medicine and of evolutionary biology. A key first step toward understanding the genetics and evolution of any phenotypic trait is characterizing the role of mutation. However, the rate at which mutation introduces genetic variance for pathogen susceptibility in any organism is essentially unknown. Here, we quantify the per‐generation input of genetic variance by mutation (VM) for susceptibility of Caenorhabditis elegans to the pathogenic bacterium Pseudomonas aeruginosa (defined as the median time of death, LT50). VM for LT50 is slightly less than VM for a variety of life‐history and morphological traits in this strain of C. elegans, but is well within the range of reported values in a variety of organisms. Mean LT50 did not change significantly over 250 generations of mutation accumulation. Comparison of VM to the standing genetic variance (VG) implies a strength of selection against new mutations of a few tenths of a percent. These results suggest that the substantial standing genetic variation for susceptibility of C. elegans to P. aeruginosa can be explained by polygenic mutation coupled with purifying selection.     

Lipid‐dependent pore formation by antimicrobial peptides arenicin‐2 and melittin demonstrated by their proton transfer activity

This work presents a comparative study of proton transfer activity (PTA) of two cationic (+6) antimicrobial peptides, β‐structural arenicin‐2 and α‐helical melittin. A new approach was proposed for the detection of passive proton transfer by using proteoliposomes containing bacteriorhodopsin, which creates a small light‐induced electrochemical proton gradient ?ΔpH. Addition of several nanomoles of the peptides lowers ?ΔpH that is proximately indicative of the pore formation. The quantitative analysis of sigmoidal dependences of ?pH on the peptides concentration was carried out using liposomes prepared from PC, PC/PE, PC/PE/PI and PC/PG. Substitution of PC‐containing liposomes with PE‐containing ones, having negative spontaneous curvature, reduced the PTA of α‐helical melittin and increased that of β‐structural arenicin‐2. This result indicates an essential difference in the pore formation by these peptides. Further increase of PTA in response to arenicin‐2 (in contrast to melittin) was observed in the liposomes prepared from PC/PE/PI. The data analysis leads to the conclusion that PTA is influenced by (i) efficiency of the pore assemblage, which depends on the structure of pore‐forming peptides, and the spontaneous curvature of lipids and (ii) the presence of mobile protons in the polar head groups of phospholipids. Copyright © 2014 European Peptide Society and John Wiley & Sons, Ltd.     

Carnivorous Utricularia: The buckling scenario

We review recent results about the functioning of aquatic carnivorous traps from the genus Utricularia. The use of high speed cameras has helped to elucidate the mechanism at the origin of the ultra fast capture process of Utricularia, at a millisecond time scale. As water is pumped out of the trap, pressure decreases inside the trap and elastic energy is stored due to the change of shape of the trap body. This energy is suddenly released when the trap is fired: the trap door undergoes an elastical instability: buckling, which allows its fast and passive opening and closure. This mechanism is used by Utricularia both to catch preys touching its trigger hairs and to fire spontaneously at regular time intervals. The results leading to this interpretation are reviewed and discussed and suggestions for further work are briefly presented.     

Evaluation of the reproductive and developmental risks of caffeine

A risk analysis of in utero caffeine exposure is presented utilizing epidemiological studies and animal studies dealing with congenital malformation, pregnancy loss, and weight reduction. These effects are of interest to teratologists, because animal studies are useful in their evaluation. Many of the epidemiology studies did not evaluate the impact of the "pregnancy signal," which identifies healthy pregnancies and permits investigators to identify subjects with low pregnancy risks. The spontaneous abortion epidemiology studies were inconsistent and the majority did not consider the confounding introduced by not considering the pregnancy signal. The animal studies do not support the concept that caffeine is an abortafacient for the wide range of human caffeine exposures. Almost all the congenital malformation epidemiology studies were negative. Animal pharmacokinetic studies indicate that the teratogenic plasma level of caffeine has to reach or exceed 60 μg/ml, which is not attainable from ingesting large amounts of caffeine in foods and beverages. No epidemiological study described the "caffeine teratogenic syndrome." Six of the 17 recent epidemiology studies dealing with the risk of caffeine and fetal weight reduction were negative. Seven of the positive studies had growth reductions that were clinically insignificant and none of the studies cited the animal literature. Analysis of caffeine's reproductive toxicity considers reproducibility and plausibility of clinical, epidemiological, and animal data. Moderate or even high amounts of beverages and foods containing caffeine do not increase the risks of congenital malformations, miscarriage or growth retardation. Pharmacokinetic studies markedly improve the ability to perform the risk analyses.     

D-Tubocurarine-Sensitive Component of Calcium-Dependent Potassium Current in Guinea Pig <Emphasis Type="Italic">Taenia Coli</Emphasis> Myocytes

Using a patch-clamp technique in the whole-cell configuration, we studied transmembrane ion currents in isolated single smooth muscle cells of the guinea pig taenia coli. A depolarizing step shift of the membrane potential from −50 mV was accompanied by the appearance of an outward current. Application of d-tubocurarine (d-TK) or a nonselective blocker of voltage-dependent potassium channels, tetraethylammonium (TEA), led to a decrease in the outward current. Application of d-TK against the background of the action of TEA additionally decreased the outward current. Analysis of the current-voltage (I–V) relationships of the d-TK-sensitive current showed that this current is practically voltage-independent. At the same time, an inflection of the I–V curve of the potassium current within the segment of maximum activation of the voltage-dependent potassium current is indicative of the sensitivity of this current to the intracellular Ca²⁺ concentration. Therefore, the calcium-activated potassium current through small-conductance calcium-dependent potassium channels includes a d-TK-sensitive voltage-independent component. Using depolarizing shifts of the membrane potential, we observed high- and low-amplitude spontaneous outward currents (SOCs) in many studied cells, i.e., the effect of an increase in the conductance of calcium-dependent potassium channels as a result of periodic release of Ca²⁺ from the intracellular stores. Application of d-TK led to a decrease in the frequency of low-amplitude SOCs and exerted nearly no influence on the high-amplitude SOCs under study. Neirofiziologiya/Neurophysiology, Vol. 37, No. 3, pp. 271–277, May–June, 2005.     

Surprising Effects of Synaptic Excitation

Typically, excitatory synaptic coupling is thought of as an influence that accelerates and propagates firing in neuronal networks. This paper reviews recent results explaining how, contrary to these expectations, the presence of excitatory synaptic coupling can drastically slow oscillations in a network and how localized, sustained activity can arise in a network with purely excitatory coupling, without sustained inputs. These two effects stem from interactions of excitatory coupling with two different forms of intrinsic neuronal dynamics, and both serve to highlight the fact that the influence of synaptic coupling in a network depends strongly on the intrinsic properties of cells in the network.This work was partially supported by the National Science Foundation, under award DMS-0414023