Targeted deletion of Gpbar1 protects mice from cholesterol gallstone formation

The Gpbar1 [G-protein-coupled BA (bile acid) receptor 1] is a recently identified cell-surface receptor that can bind and is activated by BAs, but its physiological role is unclear. Using targeted deletion of the Gpbar1 gene in mice, we show that the gene plays a critical role in the maintenance of bile lipid homoeostasis. Mice lacking Gpbar1 expression were viable, developed normally and did not show significant difference in the levels of cholesterol, BAs or any other bile constituents. However, they did not form cholesterol gallstones when fed a cholic acid-containing high-fat diet, and liver-specific gene expression indicated that Gpbar1-deficient mice have altered feedback regulation of BA synthesis. These results suggest that Gpbar1 plays a critical role in the formation of gallstones, possibly via a regulatory mechanism involving the cholesterol 7alpha-hydroxylase pathway.     

Structural and Functional Characteristics of Ajuga reptansPhotosynthesis under Cold Climate Conditions

Structural, functional, and biochemical characteristics of the photosynthetic apparatus of a nemoral herbaceous perennial plant Ajuga reptansL. inhabiting the middle taiga subzone were investigated. Plant leaves were characterized by a high content of green (3.1 mg/dm²) and yellow (0.64 mg/dm²) pigments and contained moderate-sized chloroplasts with grana consisting of ten thylakoids or more. The maximum rate of photosynthesis in summergreen leaves (5–8 mg CO₂/(dm²h)) was observed at 14–16°C under a saturating photosynthetically active radiation of 50 W/m². At 6–7°C, the rate of CO₂assimilation was reduced to 60–80% of the maximum one. The temperature optimum of photosynthesis was not constant and shifted by 2–6°C depending on the changes in the ambient temperature. Wintergreen leaves were capable of photosynthesis in late autumn after heavy freezes and in early spring after a long winter. The accumulation of soluble carbohydrates and free amino acids in leaves helps to maintain the functional activity of the photosynthetic apparatus.     

Genetic transformation of sugar beet: evolution of theoretical and experimental approaches

The review is dedicated to several aspects of sugar beet (Beta vulgaris L.) biotechnology: in vitro cultivation, callus induction, plant regeneration and genetic transformation. Media composition, methods of plant regeneration via somatic embryogenesis and protoplast culture are analysed. The use of Agrobacterium tumefaciens and gold particle bombardment is the base for modern genetic transformation methods.     

Underground Metameric Complex in the Source-Sink System of Rhizome-Forming Perennial Cereals <Emphasis Type="Italic">Bromopsis inermis</Emphasis> and <Emphasis Type="Italic">Phalaroides arundinacea</Emphasis>

Morphophysiological characteristics of rhizomes and growth relationships between underground shoots and aboveground orthotropic shoots were studied in two species of perennial monocotyledonous plants—Hungarian brome (Bromopsis inermis (Leyss.) Holub.) and reed canary-grass (Phalaroides arundinacea (L.) Rauschert.). The underground metameric complex was shown to be comparable with the aerial shoots in terms of the number, biomass, and metabolic activity of the shoots. The role of the underground metameric complex in the source-sink system of perennial rhizome-forming cereals is determined by a significant proportion of rhizomes in plant biomass (30–50%), formation of a large amount of meristems in the underground stock of vegetative reproduction (more than 1000 per plant), a comparatively high respiration rate (1.5 mg CO₂/(g dry wt h)), and a high nitrogen content (3.5%). No pronounced growth response was found in the rhizome upon plant treatment with growth regulators (GA and chlorocholine chloride) and upon decapitation of plant shoots. It is concluded that the underground metameric complex of the perennial monocotyledonous herbaceous plants is relatively autonomous from the orthotropic shoots.     

Single and multiple early afterdepolarization caused by nickel in rat atrial muscle

We examined the possible role of the Na-Ca exchange (NCX) in the arrhythmogenesis in rat atrial preparations applying microelectrode technique. In control Tyrode solution preparations isolated from the sinoatrial area contracted with frequency of 48+/-4 min(-1) (group I) or 84+/-7 min(-1) (group II). In preparation beating with low frequency partial inhibition of NCX by administration of Ni2+ (0.3 mmol/l) to the bath solution caused single early afterdepolarization (EAD) on the 15th min. During the following five minutes they were transformed into multiple EADs from 4 to 47 (action potentials) with general duration of 1-12 s. The effects were reversible. Ni2+ (0.3 mmol/l) in the preparations beating with higher rate (group II) did not cause multiple EADs, but after higher Ni2+ concentration (0.5 mmol/l) single EAD was observed more often. It was concluded that Ca2+ overload due to partial block of the NCX can contribute to the development of atrial tachyarrhythmias.     

Genetic variability of somatic embryogenesis in tissue cultures of sugar beet breeding lines

Genetic variability of callus initiation and plant regeneration has been investigated among three sugar beet genotypes. It was found that TDZ has a genotype-independent effect on callus initiation and is responsible for more than a two-fold increase in the friable callus induction rate and more than a three-fold increase in the shoot regeneration rate from this callus. Along with the genotype-independent organogenesis, regeneration from callus occasionally went through the process of somatic embryogenesis in a highly genotype-specific manner. Despite fast and uncontrollable conversion of embryos to normal plants, it was possible to select and maintain repetitive embryogenic culture without loosing regeneration and root formation capabilities. Extensive experimenting with medium composition and culture conditions resulted in an optimal medium for maintenance of repetitive embryos. Comparing with BAP, low concentrations of TDZ provide higher level of adventitious shoot formation and do not induce vitrification of tissues.     

Amphipathic CRAC-Containing Peptides Derived from the Influenza Virus A M1 Protein Modulate Cholesterol-Dependent Activity of Cultured IC-21 Macrophages

Entry of many viral and bacterial pathogens into host cells depends on cholesterol and/or cholesterol-enriched domains (lipid rafts) in the cell membrane. Earlier, we showed that influenza virus A matrix protein M1 contains amphipathic α-helices with exposed cholesterol-recognizing amino acid consensus (CRAC) motifs. In order to test possible functional activity of these motifs, we studied the effects of three synthetic peptides corresponding to the CRAC-containing α-helices of the viral M1 protein on the phagocytic activity of cultured mouse IC-21 macrophages. The following peptides were used: LEVLMEWLKTR (M1 α-helix 3, a.a. 39–49; further referred to as peptide 1), NNMDKAVKLYRKLK (M1 α-helix 6, a.a. 91–105; peptide 2), and GLKNDLLENLQAYQKR (M1 α-helix 13, a.a. 228–243; peptide 3). We found that all three peptides modulated interactions of IC-21 macrophages with non-opsonized 2-μm target particles. The greatest effect was demonstrated by peptide 2: in the presence of 35 μM peptide 2, the phagocytic index of IC-21 macrophages exceeded the control value by 60%; 10–11 mM methyl-β-cyclodextrin abolished this effect. Peptides 1 and 3 exerted weak inhibitory effect in a narrow concentration range of 5–10 μM. The dose-response curves could be approximated by a sum of two (stimulatory and inhibitory) components with different Hill coefficients, suggesting existence of at least two peptide-binding sites with different affinities on the cell surface. CD spectroscopy confirmed that the peptides exhibit structural flexibility in solutions. Altogether, our data indicate that amphipathic CRAC-containing peptides derived from the viral M1 protein modulate lipid raft-dependent processes in IC-21 macrophages.     

Assessing the utility of metabarcoding for diet analyses of the omnivorous wild pig (Sus scrofa)

Wild pigs (Sus scrofa) are an invasive species descended from both domestic swine and Eurasian wild boar that was introduced to North America during the early 1500s. Wild pigs have since become the most abundant free‐ranging exotic ungulate in the United States. Large and ever‐increasing populations of wild pigs negatively impact agriculture, sport hunting, and native ecosystems with costs estimated to exceed $1.5 billion/year within the United States. Wild pigs are recognized as generalist feeders, able to exploit a broad array of locally available food resources, yet their feeding behaviors remain poorly understood as partially digested material is often unidentifiable through traditional stomach content analyses. To overcome the limitation of stomach content analyses, we developed a DNA sequencing‐based protocol to describe the plant and animal diet composition of wild pigs. Additionally, we developed and evaluated blocking primers to reduce the amplification and sequencing of host DNA, thus providing greater returns of sequences from diet items. We demonstrate that the use of blocking primers produces significantly more sequencing reads per sample from diet items, which increases the robustness of ascertaining animal diet composition with molecular tools. Further, we show that the overall plant and animal diet composition is significantly different between the three areas sampled, demonstrating this approach is suitable for describing differences in diet composition among the locations.     

Developmental changes in energy dissipation in etiolated wheat seedlings during the greening process

We studied the developmental changes in photosynthetic and respiration rates and thermal dissipation processes connected with chloroplasts and mitochondria activity in etiolated wheat (Triticum aestivum L., var. Irgina) seedlings during the greening process. Etioplasts gradually developed into mature chloroplasts under continuous light [190 μmol(photon) m^?2 s^?1] for 48 h in 5-day-dark-grown seedlings. The net photosynthetic rate of irradiated leaves became positive after 6 h of illumination and increased further. The first two hours of de-etiolation were characterized by low values of maximum (F_v/F_m) and actual photochemical efficiency of photosystem II (PSII) and by a coefficient of photochemical quenching in leaves. F_v/F_m reached 0.8 by the end of 24 h-light period. During greening, energy-dependent component of nonphotochemical quenching of chlorophyll fluorescence, violaxanthin cycle (VXC) operation, and lipoperoxidation activity changed in a similar way. Values of these parameters were the highest at the later phase of de-etiolation (4–12 h of illumination). The respiration rate increased significantly after 2 h of greening and it was the highest after 4–6 h of illumination. It was caused by an increase in alternative respiration (AP) capacity. The strong, positive linear correlation was revealed between AP capacity and heat production in greening tissues. These results indicated that VXC in chloroplasts and AP in mitochondria were intensified as energy-dissipating systems at the later stage of greening (after 4 h), when most of prolamellar bodies converted into thylakoids, and they showed the greatest activity until the photosynthetic machinery was almost completely developed.