AMP-deaminase from hen stomach smooth muscle--physico-chemical properties of the enzyme

AMP-deaminase from hen stomach smooth muscle was isolated and physico-chemical properties of the purified enzyme were investigated. The enzyme had an activity optimum at pH 6.5, and poorly deaminated the substrate analogues tested. At optimum pH (6.5), in the absence of regulatory ligands (control conditions), the enzyme manifested hyperbolic substrate-saturation kinetics with half-saturation constant (S(0.5)) of about 4.5 mM. Additions of adenine nucleotide effectors (ATP, ADP) activated the enzyme strongly at all the concentrations tested, diminishing significantly the value of S(0.5) constant. In contrast, the regulatory effect of orthophosphate was variable, and depended on the orthophosphate concentration used. The molecular mass of the enzyme subunit determined in SDS/PAG electrophoresis was about of 37kDa. The obtained results suggest that in different types of hen muscle, similarly as in humans and rats, expression of AMP-deaminase is under the control of independent genes.     

Can inhibition of angiogenesis and stimulation of immune response be combined into a more effective antitumor therapy?

Cancer initiation and progression is strongly influenced by the tumor microenvironment consisting of various types of host cells (inflammatory cells, vascular cells and fibroblasts), extracellular matrix and non-matrix molecules. Host cells play a defining role in two major processes crucial for tumor growth: angiogenesis and escape from immune surveillance. The interdependence of these processes resemble the principles of Yin and Yang, as the stimulation of tumor angiogenesis inhibits effective immune responses, while angiogenesis inhibition may have the opposite effect. These considerations may be useful in developing anticancer strategies based on the potentially synergistic combinations of antiangiogenic and immunostimulatory drugs.     

Low endotoxic activity of lipopolysaccharides isolated from Bradyrhizobium, Mesorhizobium, and Azospirillum strains

The endotoxic activities of lipopolysaccharides (LPS) isolated from different strains of rhizobia and rhizobacteria (Bradyrhizobium, Mesorhizobium, and Azospirillum) were compared to those of Salmonella enterica sv. Typhimurium LPS. The biological activity of all the examined preparations, measured as Limulus lysate gelation, production of tumor necrosis factor (TNF), interleukin-1β (IL-1β), and interleukin-6 (IL-6), and nitrogen oxide (NO) induction in human myelomonocytic cells (line THP-1), was considerably lower than that of the reference enterobacterial endotoxin. Among the rhizobial lipopolysaccharides, the activities of Mesorhizobium huakuii and Azospirillum lipoferum LPSs were higher than those of the LPS preparations from five strains of Bradyrhizobium. The weak endotoxic activity of the examined preparations was correlated with differences in lipid A structure compared to Salmonella.     

Evaluation of genetic biodiversity in farm-bred and wild raccoon dogs in Poland

The aim of the study was to analyze the intra- and inter-group diversity in farm-raised and wild raccoon dogs with the use of molecular markers. Genetic differences between the particular raccoon dog groups were observed, accompanied by a relatively high intra-group genetic variation. It was noted that the wild raccoon dogs were characterized by the highest genetic diversity, compared to the three study groups of farm-bred raccoon dogs. Wild raccoon dogs and farm-bred raccoon dogs constitute separate phylogenetic groups. The results obtained suggest that farm breeding may lead to differentiation into a different phylogenetic lineage than that of the wild raccoon dogs. In each case, the genetic distance between the animals bred on the individual farms was lower than the distances between the farm-raised and wild animals. Since the Polish farm breeding is based entirely on phenotype ranking, the genotype of "native" animals is still closely related to that of wild animals.     

Unexpected genetic diversity of Fallopia japonica from Central Europe revealed after AFLP analysis

Recently much attention has been paid to genetic aspects of invasive success in Japanese knotweed s.l. One hypothesis to explain the invasive spread of these species is a multiple introduction, which leads to a higher level of genetic diversity in the invaded range. Fallopia japonica is considered to be genetically uniform in Europe, introduced as a single female clone. However, there is some evidence suggesting that invasion history and dynamics differ between Western and Central-Eastern Europe. We used AFLP markers to characterize genetic diversity of three Fallopia taxa that occur in Poland: F. japonica, F. sachalinensis and their hybrid Fallopia × bohemica, growing in so-called ‘homogeneous’ populations, consisting of one taxon and ‘heterogeneous’ populations, composed of the three taxa cohabiting together. No polymorphism, resp. an insignificantly low variability was observed in the ‘homogeneous’ populations. In the ‘heterogeneous’ stands polymorphism was detected within each taxa, with one exception that concerns individuals of F. sachalinensis from a riparian habitat. The highest level of polymorphism was found among individuals of F. × bohemica. The most striking result of our study is the observation of polymorphism between individuals of F. japonica. The AFLP data also showed that F. × bohemica is most diverse when occurring in a heterogeneous configuration with F. japonica and F. sachalinensis in the same habitat. Our results are the first evidence of genetic diversity in F. japonica populations in Central Europe and can implicate the possibility of its multiple introduction in this region or the existence of sexual reproduction of this species.     

Antimetabolic effect of phytohemagglutinin to the grain aphid Sitobion avenae fabricius

The insecticidal activity of plant lectins against a wide range of insect species have been intensively studied. Understanding the mechanism of the toxicity of lectins is one of the studied aspects. In the present research, the first step was determine the effect of phytohemagglutinin (PHA) on the development, fecundity and mortality of grain aphid. Next, the effect of PHA lectin on the activity of such enzymes as: α- and β-glucosidases, alkaline (AkP) and acid (AcP) phosphatases, aminopeptidase N and cathepsin L involved in the metabolism of sugar, phosphorus and proteins of an adult apterae aphids was investigated. The PHA lectin added into the liquid diet increased the pre-reproductive period, mortality of Sitobion avenae, the time of generation development and decreased its fecundity and the intrinsic rate of natural increase. In addition, activity of α-glucosidase, alkaline phosphatase and aminopeptidase N of adult apterae exposed to PHA were reduced. The results indicate that the insecticidal activity of PHA on S. avenae may involve changes in activity of the enzymes in the midgut and it may be part of its toxicity.     

Differential responses of oat cultivars to phosphate deprivation: plant growth and acid phosphatase activities

The effect of phosphate starvation on growth and acid phosphatases (APases) localization and activity in oat tissues was investigated. Oat cultivars (Avena sativa L.??Arab, Polar, Szakal) were grown for 1?C3?weeks in complete nutrient medium (+P) and without phosphate (?P). Pi concentration in plant tissues decreased strongly after culturing on ?P medium. Pi deficit reduced shoot growth, stimulated root elongation and increased ratio of root/shoot in all oat cultivars. Pi deficit had a greater impact on growth of oat cv. Polar than other varieties. A decrease in the internal Pi status led to an increase of acid phosphatase activities in extracts from shoots and roots, and in root exudates. The highest activity of secreted APases was observed for oat cv. Arab, during the third week of growth under Pi-deficient conditions. The activity of extracellular APase was high in young, growing zones of roots of ?P plants. Histochemical visualization indicated high activity of APases in the epidermis and vascular tissues of ?P plants. Pi deficiency increased intracellular APase activity in shoot mainly in oat cv. Polar, whereas APase activity in roots was the highest in oat cv. Szakal. Protein extracts from roots and shoots were run on native discontinuous PAGE to determine which isoform(s) may be affected by Pi deficiency. Three major APase isoforms were detected in all oat plants; one was strongly induced by Pi deficit. The studied oat cultivars differed in terms of acclimation to deficiency of phosphate??used various pools of APases to acquire Pi from external or internal sources.