High CO2 levels impair alveolar epithelial function independently of pH

Background

In patients with acute respiratory failure, gas exchange is impaired due to the accumulation of fluid in the lung airspaces. This life-threatening syndrome is treated with mechanical ventilation, which is adjusted to maintain gas exchange, but can be associated with the accumulation of carbon dioxide in the lung. Carbon dioxide (CO₂) is a by-product of cellular energy utilization and its elimination is affected via alveolar epithelial cells. Signaling pathways sensitive to changes in CO₂ levels were described in plants and neuronal mammalian cells. However, it has not been fully elucidated whether non-neuronal cells sense and respond to CO₂. The Na,K-ATPase consumes ∼40% of the cellular metabolism to maintain cell homeostasis. Our study examines the effects of increased pCO₂ on the epithelial Na,K-ATPase a major contributor to alveolar fluid reabsorption which is a marker of alveolar epithelial function.

Principal Findings

We found that short-term increases in pCO₂ impaired alveolar fluid reabsorption in rats. Also, we provide evidence that non-excitable, alveolar epithelial cells sense and respond to high levels of CO₂, independently of extracellular and intracellular pH, by inhibiting Na,K-ATPase function, via activation of PKCζ which phosphorylates the Na,K-ATPase, causing it to endocytose from the plasma membrane into intracellular pools.

Conclusions

Our data suggest that alveolar epithelial cells, through which CO₂ is eliminated in mammals, are highly sensitive to hypercapnia. Elevated CO₂ levels impair alveolar epithelial function, independently of pH, which is relevant in patients with lung diseases and altered alveolar gas exchange.     

Correlation between physico-chemical properties of quaternary ammonium salts of heptacaine and their inhibitory activity against photosynthesizing organisms

Photosynthesis inhibition in algae (Chlorella) and plant (spinach) chloroplasts by quaternary ammonium salts of heptacaine {N-[2-(2-heptyloxyphenylcarbamoyloxy)-ethyl]-N-alkylpiperidinium bromides} depended on the alkyl chain length of the alkyl substituent and showed good correlations with theoretical hydrophobic fragment constants as well as with experimentally determined physico-chemical parameters, namely extraction constants and surface activities. Communicated by. Z. ŠESTáK     

EUF-nutrient contents required for optimal nutrition of grapes

Summary Our field surveys conducted in 10 Hungarian grape producing areas have revealed that the nutrient contents of vine leaves of different grape varieties were closely correlated with the EUF-nutrient contents of different soil types with different contents of clay. Resulting from these relationships the following EUF-nutrient values are considered as required for optimal nutrition of the vine-stock to attain grape yields of 10–12 t/ha in the areas under investigation:     

From Mesolithic hunters to Iron Age herders: a unique record of woodland use from eastern central Europe (Czech Republic)

Vegetation History and Archaeobotany - In a continuous, perfectly stratified sedimentary sequence which was discovered under a large sandstone overhang in northern Bohemia, Czech Republic, we...     

Protein oligomerization mediated by the transmembrane carboxyl terminal domain of Bcl-XL

Bcl-XL is a pro-survival member of the Bcl-2 family that can be found in the outer mitochondrial membrane and in soluble cytosolic homodimers. Bcl-XL can bind pro-apoptotic members of this family preventing them from activating the execution phase of apoptosis. Bcl-XL has been shown to homodimerize in different ways, although most binding and structural assays have been carried out in the absence of its carboxyl terminal transmembrane domain. We show here that this domain can by itself direct protein oligomerization, which could be related to its previously reported role in mitochondrial morphology alterations and apoptosis inhibition.     

Bioengineering potato plants to produce benzylglucosinolate for improved broad-spectrum pest and disease resistance

Transgenic Research - In traditional, small-scale agriculture in the Andes, potatoes are frequently co-cultivated with the Andean edible tuber Tropaeolum tuberosum, commonly known as mashua, which...     

The potential role of polyploidy and hybridisation in the further evolution of the highly invasive <Emphasis Type="Italic">Fallopia</Emphasis> taxa in Europe

Japanese knotweed s.l. comprises Fallopia japonica, F. sachalinensis, F. × bohemica and any F2s or backcrosses. The parental taxa were introduced from the East to the West as garden ornamentals in the nineteenth century, and soon spread beyond the confines of the garden to become widespread and persistent weeds. Since only female F. japonica var. japonica was introduced, its impressive spread has occurred solely by vegetative means. However, the initial lack of genetic variability has been complemented by an extensive series of hybridisations in the adventive range. We examine the history, spread, reproductive biology and ecological impact of these species in the West. The role and importance of polyploidy and hybridisation in their invasion of the West is discussed, as are the implications of these factors for the potential further evolution of the group.     

Evolution of GnRH ligands and receptors in gnathostomata

Gonadotropin-releasing hormone (GnRH) is the final common signaling molecule used by the brain to regulate reproduction in all vertebrates. Until now, a total of 24 GnRH structural variants have been characterized from vertebrate, protochordate and invertebrate nervous tissue. Almost all vertebrates already investigated have at least two GnRH forms coexisting in the central nervous system. Furthermore, it is now well accepted that three GnRH forms are present both in early and late evolved teleostean fishes. The number and taxonomic distribution of the different GnRH variants also raise questions about the phylogenetic relationships between them. Most of the GnRH phylogenetic analyses are in agreement with the widely accepted idea that the GnRH family can be divided into three main groups. However, the examination of the gnathostome GnRH phylogenetic relationships clearly shows the existence of two main paralogous GnRH lineages: the 'midbrain GnRH" group and the "forebrain GnRH" group. The first one, represented by chicken GnRH-II forms, and the second one composed of two paralogous lineages, the salmon GnRH cluster (only represented in teleostean fish species) and the hypophysotropic GnRH cluster, also present in tetrapods. This analysis suggests that the two forebrain clades share a common precursor and reinforces the idea that the salmon GnRH branch has originated from a duplication of the hypophysotropic lineage. GnRH ligands exert their activity through G protein-coupled receptors of the rhodopsin-like family. As with the ligands, multiple GnRHRs are expressed in individual vertebrate species and phylogenetic analyses have revealed that all vertebrate GnRHRs cluster into three main receptor types. However, new data and a new phylogenetic analysis propose a two GnRHR type model, in which different rounds of gene duplications may have occurred in different groups within each lineage.     

From lignocellulosic residues to market: Production and commercial potential of xylooligosaccharides

The updated definition of prebiotic expands the range of potential applications in which emerging xylooligosaccharides (XOS) can be used. It has been demonstrated that XOS exhibit prebiotic effects at lower amounts compared to others, making them competitively priced prebiotics. As a result, the industry is focused on developing alternative approaches to improve processes efficiency that can meet the increasing demand while reducing costs. Recent advances have been made towards greener and more efficient processes, by applying process integration strategies to produce XOS from costless lignocellulosic residues and using genetic engineering to create microorganisms that convert these residues to XOS. In addition, collecting more in vivo data on their performance will be key to achieve regulatory claims, greatly increasing XOS commercial value.