AMP-deaminase from normal and cirrhotic human liver: A comparative study

AMP-deaminase (EC 3.5.4.6) is an enzyme of nucleotide breakdown involved in regulation of adenine nucleotide pool in mammalian cells. Reaction catalysed by AMP-deaminase constitutes a rate-limiting step in adenine nucleotide catabolism in liver. In this study kinetic and regulatory properties of AMP-deaminase purified from normal and cirrhotic human liver were investigated. In comparison to AMP-deaminase extracted from the normal human liver, AMP-deaminase extracted from the cirrhotic liver was less sensitive towards substrate analogues, and only a very limited response towards pH and adenylate energy charge changes tested for enzyme isolated from this tissue source had been observed. At physiological pH 7.0, in the absence and in the presence of important allosteric effectors (ATP, ADP, GTP and orthophosphate), AMP-deaminases from the two sources studied manifested different regulatory profiles, with half-saturation constant (S0.5) values being distinctly higher for the enzyme extracted from the pathological organ. In contrast to AMP-deaminase isolated from the normal, healthy liver, where presence of relatively large (68 kDa) protein fragment was also detected, only smaller protein fragments were identified, while SDS-PAG electrophoresis of AMP-deaminase isolated from the cirrhotic liver was performed. The obtained results indicate clearly that advanced proteolytic processes occurring in the cirrhotic liver may affect structural integrity of AMP-deaminase studied, making enzyme less active and less sensitive to regulatory action of important allosteric effectors.     

Stability of Prussian Blue in Soils of a Former Manufactured Gas Plant Site

Soil contamination with iron-cyanide complexes is a common problem at former manufactured gas plant (MGP) sites. Dissolution of the cyanide, from Prussian Blue (ferric ferrocyanide), creates an environmental hazard, whereas the risk of groundwater contamination depends on the stability of dissolved iron–cyanide complexes. Lack of a standard leaching method to determine the water-soluble (plant-available) cyanide fraction generates potential limitations for implementing remediation strategies like phytoremediation. Applicability of neutral solution extraction to determine the water-soluble cyanide fraction and the stability of Prussian Blue in surface and near-surface soils of an MGP site in Cottbus, undersaturated and unsaturated water conditions, was studied in column leaching and batch extraction experiments. MGP soils used in the long-term tests varied according to the pH (5.0–7.7) and the total cyanide content (40–1718 mg kg^?1). Column leaching, after four months of percolation, still yielded effluent concentrations exceeding the German drinking water limit (> 50 μg L^?1) and the solubility of Prussian Blue reported in the literature (< 1 mg L^?1) from both alkaline and acidic soils. Long-term (1344 h) extraction of MGP soils with distilled water was sufficient to dissolve 97% of the total cyanide from the slightly alkaline soils and up to 78% from the acidic soils. Both experiments revealed that dissolution of ferric ferrocyanide under circum-neutral pH and oxic water conditions is a function of time, where the released amount is dependent on the soil pH and total cyanide content. Unexpectedly high and continuous solubility of Prussian Blue, both in acidic and slightly alkaline MGP soils, implies the need to introduce an additional cyanide fraction (“readily soluble fraction”) to improve and specify cyanide leaching methods. Long-term extraction of cyanide-contaminated soil in neutral solution seems to be a promising approach to evaluate the potential hazard of groundwater pollution at the MGP sites.     

Patterns of host–parasite associations in tropical lice and their passerine hosts in Cameroon

Coevolutionary processes that drive the patterns of host–parasite associations can be deduced through congruence analysis of their phylogenies. Feather lice and their avian hosts have previously been used as typical model systems for congruence analysis; however, such analyses are strongly biased toward nonpasserine hosts in the temperate zone. Further, in the Afrotropical region especially, cospeciation studies of lice and birds are entirely missing. This work supplements knowledge of host–parasite associations in lice using cospeciation analysis of feather lice (genus Myrsidea and the Brueelia complex) and their avian hosts in the tropical rainforests of Cameroon. Our analysis revealed a limited number of cospeciation events in both parasite groups. The parasite–host associations in both louse groups were predominantly shaped by host switching. Despite a general dissimilarity in phylogeny for the parasites and hosts, we found significant congruence in host–parasite distance matrices, mainly driven by associations between Brueelia lice and passerine species of the Waxbill (Estrildidae) family, and Myrsidea lice and their Bulbul (Pycnonotidae) host species. As such, our study supports the importance of complex biotic interactions in tropical environments.     

Polyamines induce adaptive responses in water deficit stressed cucumber roots

The aim of this study was to investigate the effect of exogenous polyamines (PAs) on the membrane status and proline level in roots of water stressed cucumber (Cucumis sativus cv. Dar) seedlings. It was found that water shortage resulted in an increase of membrane injury, lipoxygenase (LOX) activity, lipid peroxidation and proline concentration in cucumber roots during progressive dehydration. PA pretreatment resulted in a distinct reduction of the injury index, and this effect was reflected by a lower stress-evoked LOX activity increase and lipid peroxide levels at the end of the stress period. In contrast, PA-supplied stressed roots displayed a higher proline accumulation. The presented results suggest that exogenous PAs are able to alleviate water deficit-induced membrane permeability and diminish LOX activity. Observed changes were accompanied by an accumulation of proline, suggesting that the accumulation of this osmolyte might be another possible mode of action for PAs to attain higher membrane stability, and in this way mitigate water deficit effects in roots of cucumber seedlings.     

Design and synthesis of new substrates of HtrA2 protease

HtrA2 belongs to the HtrA (high temperature requirement A) family of ATP-independent serine proteases. The primary function of HtrA2 includes maintaining the mitochondria homeostasis, cell death (by apoptosis, necrosis, or anoikis), and contribution to the cell signaling. Several recent reports have shown involvement of HtrA2 in development of cancer and neurodegenerative disorders. Here, we describe the profiling of HtrA2 protease substrate specificity via the combinatorial chemistry approach that led to the selection of novel intramolecularly quenched substrates. For all synthesized compounds, the highest HtrA2-mediated hydrolysis efficiency and selectivity among tested HtrA family members was observed for ABZ-Ile-Met-Thr-Abu-Tyr-Met-Phe-Tyr(3-NO₂)-NH₂, which displayed a specificity constant k_cat/K_M value of 14,535 M⁻¹ s⁻¹.     

The effect of polyphenols and vitamin E on the antioxidant status and meat quality of broiler chickens exposed to high temperature

The aim of this study was to determine the effect of a polyphenol product (PP) (Proviox) and vitamin E on the antioxidant status and meat quality of broiler chickens exposed to high temperature. The experimental materials comprised 120 ROSS 308 broilers (6 treatments, 10 replications, 2 birds per replication). Dietary supplementation with vitamin E and PP was applied in the following experimental design: group I (negative control) – without supplementation; group II (positive control) – without supplementation; group III – supplementation with 100 mg vitamin E/kg; group IV – 200 mg vitamin E/kg; group V – 100 mg vitamin E/kg and 100 mg PP/kg; group VI – 200 mg PP/kg. In groups II–VI, broiler chickens aged 21–35 d were exposed to increased temperature (34°C for 10 h daily). In chickens exposed to high temperature, dietary supplementation with antioxidants, mostly PP, improved growth performance parameters, including body weight, body weight gain and feed intake until 28 d of age. Vitamin E added to broiler chicken diets at 200 mg/kg and vitamin E combined with PP was most effective in improving the total antioxidant status of birds, enhancing blood antioxidant enzyme activities and increasing vitamin E concentrations in the liver and breast muscles. Broilers fed diets supplemented with 200 mg/kg of vitamin E alone and vitamin E in combination with PP were characterised by a higher percentage content of breast muscles in the carcass. Dietary supplementation with antioxidants improved the water-holding capacity of meat, reduced natural drip loss and increased the crude ash content of meat. The breast muscles of chickens fed diets supplemented with PP had a lower contribution of yellowness. The breast muscles of chickens receiving diets with 100 mg vitamin E/kg(group III) and diets supplemented with PP (groups V and VI) were characterised by the highest concentrations of polyunsaturated fatty acids. The PP can be a valuable component of diets for broiler chickens exposed to high temperature.