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Ewa A. Zaobidna, Kamila Dmochowska, Regina Frączek, Ewa Dymczyk and Krystyna Żółtowska

Abstract

Osmia rufa is a solitary bee that is used commercially for pollinating crops. The bee enters obligatory diapause as an imago. The activity of proteolytic enzymes during diapause has not been investigated. We studied the proteinase activity on four substrates - casein, haemoglobin, bovine serum albumin (BSA ), and gelatine - during diapause (from October to March) and in newly hatched males and females in April. During diapause, greater fluctuations in enzyme activity levels were noted in males than in females, and a significant decrease in male enzyme activity was observed in January and March. Male enzymes were most effective in decomposing gelatine; whereas, female enzymes were equally effective in hydrolysing gelatine and BSA . The differences in substrate preferences between male and female enzymes were particularly pronounced in October and in the newly hatched individuals. The levels of gelatinolytic activity likely indicate that a high proportion of proteinases in O. rufa are elastase-like enzymes. They are involved in the digestion and remodelling of proteins with numerous peptide bonds formed by amino acids with short side-chains.

Open access

Ewa A. Zaobidna, Krystyna Żółtowska and Elżbieta Łopieńska-Biernat

Abstract

The pathogenesis of varroasis has not been fully explained despite intensive research. Earlier studies suggested that parasitic infections caused by Varroa destructor mites were accompanied by immunosuppression in the host organism. The objective of this study was to analyse the influence of varroasis on one of the immune pathway in Apis mellifera measured by the expression of the prophenoloxidase (proPO) gene and the enzymatic activity of this gene’s product, phenoloxidase (EC 1.14.18.1). An evaluation was done of five developmental stages of honey bee workers and drones. The relative expression of proPO decreased in infected individuals. The only exceptions were worker prepupae (PP) and drone pupae with brown eyes and dark brown thorax (P5) where propo gene expression was 1.8-fold and 1.5-fold higher, respectively, than in the control. Phenoloxidase (PO) activity was 2.8-fold higher in infected pp workers and 2-fold higher in p5 drones in comparison with uninfected bees. Phenoloxidase activity was reduced in the remaining developmental stages of infected workers and drones. The relative expression of proPO was positively correlated with the relative PO activity in both workers (r = 0.988) and drones (r = 0.996). The results of the study indicate that V. destructor significantly influences the phenoloxidase-dependent immune pathway in honey bees.

Open access

Ewa A. Zaobidna, Krystyna Żółtowska and Elżbieta Łopieńska-Biernat

Abstract

Varroa destructor is a parasitic mite that attacks the honey bee, and previous studies have suggested that parasitosis caused by this mite is accompanied by immunosuppresion in the host. In this study, the effect of mite infestation on the expression of the lysozyme-1 (lys-1) gene and lysozyme activity in Apis mellifera carnica was determined. The experiment was carried out on the five developmental stages of honey bee workers and drones. Developmental and gender-related differences in gene expression and lysozyme activity were observed in a Varroa destructor-infested brood. The relative expression of the lys-1 gene increased in a infested worker brood and decreased in a drone brood except for P3 pupae. In the final stage of development, the lys-1 gene expression was significantly lower in infested newly emerged workers and drones. Changes in the relative expression of the lys-1 gene in infested individuals was poorly manifested at the level of enzyme activity, whereas at the two final stages of development (P5 and I) there was a positive correlation between relative lys-1 expression and lysozyme activity in infested bees of both genders (r=0.988, r=0.999, respectively). The results of this study indicate that V. destructor influences the lysozyme-linked immune response in bees.

Open access

Elżbieta Łopieńska–Biernat, Małgorzata Dmitryjuk, Ewa Zaobidna, Zbigniew Lipiński and Krystyna Żółtowska

Abstract

The aim of the present research was to determine the basic composition of the organic compounds present in extracts from Varroa destructor, a parasitic mite of the honeybee. The total protein content was 9.16 ± 0.82 mg/100 mg of body weight, lipid content was 9.81 ± 1.99 mg/100 mg, and carbohydrate content was 26.67 ± 4.52 mg/100 mg. The triacylglycerol content was 2.40 ± 0.86 mg/100 mg and the cholesterol content was 0.14 ± 0.02 mg/100 mg. Thin layer chromatography indicated that phospholipids comprised the major part of the lipid component; cephalins (78%), cerebrosides (16%), and lecithins (6%) were identified in the phospholipid pool. Glucose (23.6 ± 4.52 mg/100 mg) was the main carbohydrate, followed by glycogen (5.43 ± 1.23 mg/100 mg) and trehalose (0.35 ± 0.07 mg/100 mg). Enzyme-linked immunosorbent assays detected two major glycogen metabolism enzymes, glycogen phosphorylase and glycogen synthase. Among the enzymes metabolising disaccharides, maltase (24.7 ± 2.38 μmol/mg protein) and trehalase (14.81 ± 5.21 μmol/mg protein) presented the highest activity. Saccharose and lactose were hydrolysed to a minor extent. These are the first measurements of the basic composition of the mite body. Although these data are not exhaustive, they may serve as the basis for further research on the metabolism of V. destructor, particularly concerning lipid metabolism.

Open access

Kamila Dmochowska-Ślęzak, Małgorzata Dmitryjuk, Ewa Zaobidna and Krystyna Żółtowska

Abstract

Varroa destructor is a parasitic mite of the Western honey bee. The activity of five antioxidant enzymes of V. destructor were analysed. Glutathione content and total antioxidant status was also evaluated. Our results suggest that antioxidant enzymes constitute the main line of defense against ROS in V. destructor, whereas low-molecular-weight antioxidants play a limited role in the antioxidant system of mites.

Open access

Elżbieta Łopieńska-Biernat, Marta Pastorczyk, Irena Giełwanowska, Krystyna Żółtowska, Robert Stryiński and Ewa Zaobidna

Abstract

Plants adapt to extremely low temperatures in polar regions by maximizing their photosynthetic efficiency and accumulating cryoprotective and osmoprotective compounds. Flowering plants of the family Poaceae growing in the Arctic and in the Antarctic were investigated. Their responses to cold stress were analyzed under laboratory conditions. Samples were collected after 24 h and 48 h of cold treatment. Quantitative and qualitative changes of sugars are found among different species, but they can differ within a genus of the family Poaceae. The values of the investigated parameters in Poa annua differed considerably depending to the biogeographic origin of plants. At the beginning of the experiment, Antarctic plants were acclimatized in greenhouse characterized by significantly higher content of sugars, including storage reserves, sucrose and starch, but lower total protein content. After 24 h of exposure to cold stress, much smaller changes in the examined parameters were noted in Antarctic plants than in locally grown specimens. Total sugar content and sucrose, starch and glucose levels were nearly constant in P. annua, but they varied significantly. Those changes are responsible for the high adaptability of P. annua to survive and develop in highly unsupportive environments and colonize new regions.