Design,synthesis, and in vitro evaluation of BP-1-102 analogs with modified hydrophobic fragments for STAT3 inhibition

Twelve novel analogs of STAT3 inhibitor BP-1-102 were designed and synthesised with the aim to modify hydrophobic fragments of the molecules that are important for interaction with the STAT3 SH2 domain. The cytotoxic activity of the reference and novel compounds was evaluated using several human and two mouse cancer cell lines. BP-1-102 and its two analogs emerged as effective cytotoxic agents and were further tested in additional six human and two murine cancer cell lines, in all of which they manifested the cytotoxic effect in a micromolar range. Reference compound S3I-201.1066 was found ineffective in all tested cell lines, in contrast to formerly published data. The ability of selected BP-1-102 analogs to induce apoptosis and inhibition of STAT3 receptor-mediated phosphorylation was confirmed. The structure–activity relationship confirmed a demand for two hydrophobic substituents, i.e. the pentafluorophenyl moiety and another spatially bulky moiety, for effective cytotoxic activity and STAT3 inhibition.     

Nest microhabitats and tree size mediate shifts in ant community structure across elevation in tropical rainforest canopies

Declines or mid-elevation peaks in invertebrate diversity with elevation are often attributed to climate and geometric constraints. However, vegetation structure may also drive diversity patterns, especially for tree-dwelling species, via its effects on microhabitat use and competitive interactions. Here we investigate these effects on the diversity and community structure of tree-nesting ants over elevation. We exhaustively sampled ant nests in 1254 trees within continuous plots of primary rainforest at low (200 m a.s.l.), mid (900 m a.s.l.) and high (1800 m a.s.l.) elevation in Papua New Guinea. Ant diversity, nest abundance and tree occupancy peaked at mid-elevation. Although host tree diversity also peaked at mid-elevation, there was low specialisation of ant species to tree species at all elevations. Mid-elevation trees hosted more species, more nests and a greater diversity of nest types than trees of a similar size at low or high elevation. Tree size and nest microhabitat use were the strongest predictors of species composition, explaining twice as much of the variability in the communities than elevation. At mid to high elevation there were proportionally fewer large nests than in the lowlands, with an increase in smaller nests in live hollow twigs and epiphytes. There was high species turnover between elevations, and between trees within elevations. Species co-occurrence patterns within trees differed with tree size, and with elevation. In large trees species tended to co-occur at random at low and high elevation, but co-occurred more often than expected by chance at mid elevation, indicating an elevational shift in competitive interactions. We conclude that the more extreme diurnal temperatures at higher elevations, combined with increased epiphyte availability, drive ants to nest in more insulated microhabitats. This results in smaller colony sizes and a decrease in interspecific competition, thereby boosting species co-existence at mid elevation.     

Insect herbivory and herbivores of Ficus species along a rain forest elevational gradient in Papua New Guinea

Classic research on elevational gradients in plant–herbivore interactions holds that insect herbivore pressure is stronger under warmer climates of low elevations. However, recent work has questioned this paradigm, arguing that it oversimplifies the ecological complexity in which plant–insect herbivore interactions are embedded. Knowledge of antagonistic networks of plants and herbivores is however crucial for understanding the mechanisms that govern ecosystem functioning. We examined herbivore damage and insect herbivores of eight species of genus Ficus (105 saplings) and plant constitutive defensive traits of two of these species, along a rain forest elevational gradient of Mt. Wilhelm (200–2,700 m a.s.l.), in tropical Papua New Guinea. We report overall herbivore damage 2.4% of leaf area, ranging from 0.03% in Ficus endochaete at 1,700 m a.s.l. to 6.1% in F. hombroniana at 700 m a.s.l. Herbivore damage and herbivore abundances varied significantly with elevation, as well as among the tree species, and between the wet and dry season. Community-wide herbivore damage followed a hump-shaped pattern with the peak between 700 and 1,200 m a.s.l. and this pattern corresponded with abundance of herbivores. For two tree species surveyed in detail, we observed decreasing and hump-shaped patterns in herbivory, in general matching the trends found in the set of plant defenses measured here. Our results imply that vegetation growing at mid-elevations of the elevational gradient, that is at the climatically most favorable elevations where water is abundant, and temperatures still relatively warm, suffers the maximum amount of herbivorous damage which changes seasonally, reflecting the water availability.     

Rickettsia slovaca and Rickettsia raoultii in Dermacentor marginatus and Dermacentor reticulatus ticks from Slovak Republic

Rickettsiae, obligate intracellular Gram-negative bacteria, responsible for mild to severe diseases in humans are associated with arthropod vectors. Dermacentor marginatus and Dermacentor reticulatus are known vectors of Rickettsia slovaca and Rickettsia raoultii distributed across Europe. A total of 794 D. marginatus, D. reticulatus and Ixodes ricinus adult ticks were collected from the vegetation, removed from horses, sheep, goats and dogs in Slovakia. The DNA of Rickettsia sp. was found in 229 ticks by PCR amplifying parts of gltA, ompA and sca4 genes. Next analyses of Rickettsia-positive samples by PCR-RFLP and/or sequencing showed D. reticulatus ticks were more infected with R. raoultii and D. marginatus were more infected with R. slovaca. The prevalence of R. raoultii was 8.1-8.6% and 22.3-27% in D. marginatus and D. reticulatus, respectively. The prevalence of R. slovaca was 20.6-24.3% in D. marginatus and 1.7-3.4% in D. reticulatus. Intracellular growth of R. raoultii isolate from D. marginatus tick was evaluated by rOmpA-based quantitative SybrGreen PCR assay. The highest point of multiplication was recorded on the 7th and 8th day postinfection in Vero and L929 cells, respectively. R. raoultii was transmitted during feeding of R. raoultii-positive ticks to guinea pigs and subsequently rickettsial infection was recorded in all organs, the highest infection was in spleen, liver and heart. Our study describes the detection and isolation of tick-borne pathogens R. raoultii and R. slovaca, show that they are spread in Slovakia and highlight their risk for humans.     

Use of the Frank-Starling mechanism during exercise is linked to exercise-induced changes in arterial load

Effective arterial elastance(E(A)) is a measure of the net arterial load imposed on the heart that integrates the effects of heart rate(HR), peripheral vascular resistance(PVR), and total arterial compliance(TAC) and is a modulator of cardiac performance. To what extent the change in E(A) during exercise impacts on cardiac performance and aerobic capacity is unknown. We examined E(A) and its relationship with cardiovascular performance in 352 healthy subjects. Subjects underwent rest and exercise gated scans to measure cardiac volumes and to derive E(A)[end-systolic pressure/stroke volume index(SV)], PVR[MAP/(SV*HR)], and TAC(SV/pulse pressure). E(A) varied with exercise intensity: the ΔE(A) between rest and peak exercise along with its determinants, differed among individuals and ranged from -44% to +149%, and was independent of age and sex. Individuals were separated into 3 groups based on their ΔE(A)I. Individuals with the largest increase in ΔE(A)(group 3;ΔE(A)≥0.98 mmHg.m(2)/ml) had the smallest reduction in PVR, the greatest reduction in TAC and a similar increase in HR vs. group 1(ΔE(A)<0.22 mmHg.m(2)/ml). Furthermore, group 3 had a reduction in end-diastolic volume, and a blunted increase in SV(80%), and cardiac output(27%), during exercise vs. group 1. Despite limitations in the Frank-Starling mechanism and cardiac function, peak aerobic capacity did not differ by group because arterial-venous oxygen difference was greater in group 3 vs. 1. Thus the change in arterial load during exercise has important effects on the Frank-Starling mechanism and cardiac performance but not on exercise capacity. These findings provide interesting insights into the dynamic cardiovascular alterations during exercise.     

Inter-species differences in the growth of bifidobacteria cultured on human milk oligosaccharides

Human milk (HM) contains as the third most abundant component around 200 different structures of human milk oligosaccharides (HMOs). HMOs are the first and irreplaceable prebiotics for infants, supporting bifidobacteria as the most important bacterial group in an infant intestine. The aim of our study was to test the growth of bifidobacteria in HM and on HMOs. Bifidobacteria were isolated from two groups of infants. The first one (eight strains) were isolated from infants who had bifidobacteria in their feces but, after a short period of time (4 to 24 days), bifidobacteria were no longer detected in their feces (disappeared bifidobacteria [DB]). The second group of bifidobacteria (eight strains) originated from infants with continual presence of bifidobacteria in their feces (persistent bifidobacteria [PB]). There were significant differences (p?Bifidobacterium bifidum and B. breve species were able to utilize HMOs, while B. adolescentis and B. longum subsp. longum species did not. The ability to grow in HM and to utilize HMOs seem to be important properties of bifidobacteria which are able to colonize infant intestinal tract.     

Key amino acid residues within the third membrane domains of NR1 and NR2 subunits contribute to the regulation of the surface delivery of N-methyl-D-aspartate receptors

N-methyl-d-aspartate (NMDA) receptors are glutamate ionotropic receptors that play critical roles in synaptic transmission, plasticity, and excitotoxicity. The functional NMDA receptors, heterotetramers composed mainly of two NR1 and two NR2 subunits, likely pass endoplasmic reticulum quality control before they are released from the endoplasmic reticulum and trafficked to the cell surface. However, the mechanism underlying this process is not clear. Using truncated and mutated NMDA receptor subunits expressed in heterologous cells, we found that the M3 domains of both NR1 and NR2 subunits contain key amino acid residues that contribute to the regulation of the number of surface functional NMDA receptors. These key residues are critical neither for the interaction between the NR1 and NR2 subunits nor for the formation of the functional receptors, but rather they regulate the early trafficking of the receptors. We also found that the identified key amino acid residues within both NR1 and NR2 M3 domains contribute to the regulation of the surface expression of unassembled NR1 and NR2 subunits. Thus, our data identify the unique role of the membrane domains in the regulation of the number of surface NMDA receptors.     

Citraconylation--a simple method for high protein sequence coverage in MALDI-TOF mass spectrometry

Lysine epsilon -amino group reacts with citraconic anhydride forming a derivative, which is stable on terms for trypsin cleavage. This modification changes the spectrum of peptides formed by the trypsin action; as the number of trypsin-sensitive sites is reduced, the peptides with higher molecular mass can survive in the digest. The various studies of proteins by MALDI-TOF mass spectrometry are often complicated by the low sequence coverage of the peptide chain. This paper demonstrates that the modification of proteins by citraconylation before trypsin cleavage represents a simple experimental technique, which allows a significant increase of sequence coverage in MALDI-TOF mass spectrometry. This improvement is caused both by change of trypsin fragmentation pattern and by disturbance of the protein's native tertiary structure.