Ligand Binding Properties of Bovine Liver Adenosine Kinase

Abstract

Bovine liver adenosine kinase displays a characteristic intrinsic fluorescence due to 3 tryptophans/mol. This fluorescence is very sensitive to ligand binding and was used to characterize the ligand binding sites of the enzyme. ADP or ATP showed a monophasic saturation curve consistent with the existence of one binding site. In contrast, adenosine and AMP gave biphasic saturation curves suggesting the existence of at least two binding sites with high and low affinity. These binding sites were further characterized by studying the complexation of adenosine kinase with O-(N-methylanthraniloyl)adenosine nucleoside or nucleotide analogues.     

Priming of Nicotiana benthamiana antioxidant defences using brown seaweed extracts

Extracts from the brown seaweeds Cystoseira myriophylloides, Laminaria digitata and Fucus spiralis were evaluated as plant defence inducers against the wild fire disease of Nicotiana benthamiana. Seeds’ imbibition in aqueous seaweed extracts (SE) results in plants with reduced disease severity. In addition, bacterial populations were significantly reduced in these plants when compared to those germinated in sterile distilled water. They primed N. benthamiana for H₂O₂ accumulation and for enhanced activity of several antioxidant enzymes including catalase, ascorbate peroxidase, guaiacol peroxidase and polyphenol oxidase. These results revealed that soaking of seeds in SE before sowing allows N. benthamiana to reduce pathogen attack and can be easily applied in practice.     

Competitive exclusion against Salmonella Enteritidis in layer chickens by yoghurt microbiota: impact on egg production, protection and yolk-antibody and cholesterol levels

AIMS: This work aims at studying the impact of competitive exclusion of Salmonella serotype Enteritidis infection in layer chickens, by microbiota of fresh and dried-modified yoghurt, on egg production and weight, protection against infection, and on yolk-antibody and cholesterol levels. METHODS AND RESULTS: Four groups of 27-week-old layer chickens were included in this study. After an initial enrofloxacin treatment, groups 1 and 2 were administered fresh or dry yoghurt (respectively) for 14 days. Groups 1, 2 and 3 were challenged intraoesophageally with Salm. Enteritidis, on the sixth day of yoghurt administration, while group 4 was left unchallenged and without yoghurt administration. No significant difference in percent infectivity of visceral organs with Salm. Enteritidis was observed between the groups. The yoghurt administered groups showed an early significant antibody response in their yolk on the seventh day postchallenge (P < 0.05) and highest egg production and weight. Finally, the egg yolk cholesterol concentration was higher in Salm. Enteritidis-challenged groups than that observed in the unchallenged group. CONCLUSIONS: The results point to the possible involvement of yoghurt administration in immunopotentiation and improvement of egg production and weight. SIGNIFICANCE AND IMPACT OF THE STUDY: These findings warrant further research that could improve immunity and production in layer chickens infected with Salm. Enteritidis.     

II. Plasma and brain catecholamines in experimental uremia: Acute and chronic studies

To evaluate the role of catecholamines (CA) in uremia, we used “high performance” liquid chromatographic technique with electrodetection to determine plasma and brain concentration of dopamine (DA), norepinephrine (NE) and epinephrine (E) in rats with acute and chronic uremia. The results revealed a steady elevation in plasma CA (p < 0.05) in both acutely and chronically uremic rats when compared to the level of these neurotransmitters in controls. The highest changes were observed in DA and the least in NE (16.8 ± 3.2 vs. 0.5 ± 0.2 ng/ml and 93.2 ± 11.1 vs. 68.1 ± 16.3 ng/ml. There was a positive correlation between plasma CA and the duration of uremia (r = 0.97; p < 0.05). The elevations were more pronounced in acutely uremic rats than in chronically uremic rats. This was followed by a concomitant depletion in the concentration of DA, NE and E in the brain. The defects in catecholaminergic neurotransmission as evidence of dysfunction in the autonomic nervous system may contribute to the development of neuropathy.     

Computational algorithms for optimal feed rates for a class of fed-batch fermentation: Numerical results for penicillin and cell mass production

Based upon the general characteristics of the optimal feed rate profiles presented in an earlier article, efficient computational algorithms have been developed for fed-batch fermentation processes described by four or less mass balance equations. These algorithms make computations of optimal substrate feed rate profiles straight forward and simple for various fed-batch cultures for such products as antibiotics, amino acids, enzymes, alcohols, and cell mass. Numerical examples of penicillin fermentation and bacterial cell mass production are given in detail, illustrating the use of these algorithms.     

Complex dynamics of osteoclast formation and death in long-term cultures

Background

Osteoclasts, cells responsible for bone resorption, contribute to the development of degenerative, metabolic and neoplastic bone diseases, which are often characterized by persistent changes in bone microenvironment. We aimed to investigate the dynamics of osteoclast formation and death in cultures that considerably exceeded the length of standard protocol and to design a mathematical model describing osteoclastogenesis.

Methodology/Principal Findings

RAW 264.7 monocytic cells fuse to form multinucleated osteoclasts upon treatment with pro-resorptive cytokine RANKL. We have found that in long-term experiments (15–26 days), the dynamics of changes in osteoclast numbers was remarkably complex and qualitatively variable in different experiments. Whereas 19 of 46 experiments exhibited single peak of osteoclast formation, in 27 experiments we observed development of successive waves of osteoclast formation and death. Periodic changes in osteoclast numbers were confirmed in long-term cultures of mouse bone marrow cells treated with M-CSF and RANKL. Because the dynamics of changes in osteoclast numbers was found to be largely independent of monocytes, a two-species model of ordinary differential equations describing the changes in osteoclasts and monocytes was ineffective in recapitulating the oscillations in osteoclast numbers. Following experimental observation that medium collected from mature osteoclasts inhibited osteoclastogenesis in fresh cultures, we introduced a third variable, factor f, to describe osteoclast-derived inhibitor. This model allowed us to simulate the oscillatory changes in osteoclasts, which were coupled to oscillatory changes in the factor f, whereas monocytes changed exponentially. Importantly, to achieve the experimentally observed oscillations with increasing amplitude, we also had to assume that osteoclast presence stimulates osteoclast formation.

Conclusions/Significance

This study identifies the critical role for osteoclast autocrine regulation in controlling long-term dynamic of osteoclast formation and death and describes the complementary roles for negative and positive feedback mediators in determining the sharp dynamics of activation and inactivation of osteoclasts.     

Early experience with the Venus p‑valve for percutaneous pulmonary valve implantation in native outflow tract

Introduction

The Venus p?valve (MedTech, Shanghai, China) is a self-expanding percutaneous heart valve designed to be implanted in a native patched right ventricle outflow tract. The worldwide clinical experience with this valve is just beginning and the results have so far been encouraging. We present our initial early experience implanting the Venus p?valve in the native right ventricle outflow tract of patients with Tetralogy of Fallot repaired with a transannular patch.

Methods

In 10 selected patients a procedure for percutaneous pulmonary valve implantation was performed using the Venus p?valve. The patients mean age was 32 years (13–57), mean weight 59.6?kg (40–80). All patients had Tetralogy of Fallot with moderate to severe pulmonary regurgitation and an indication for pulmonary valve replacement.

Results

The implantation procedure was successful in all the patients resulting in an immediately functional valve. No procedure-related complications were observed. Follow-up after 12 months (4–21) resulted in an improvement in NYHA class. There was a reduction of the mean right ventricle diastolic volume from 139?ml/m² (105–179) to 78?ml/m² (65–100) and improvement in the regurgitation fraction from 42% (29–58) to 1% (0–5), as seen on routine cardiac magnetic resonance 6 months after the implantation. No stent fractures have been observed so far.

Conclusion

Percutaneous pulmonary valve implantation with the Venus p?valve resulted in a safe and effective procedure. The valve has predictable and sustained functional competence, resulting in clinical improvement in the patients.

     

Biotransformations of α,β-Epoxyalcohols Catalyzed by Epoxide Hydrolases

Microsomal and cytosolic fractions of mammalian livers were screened for their capacity to resolve racemic mixtures of trans -2,3-epoxy-l-alkanols. The epoxide hydrolase activities showed some specificity for the 2S, 3S enantiomers which were attacked at the proximate carbon atom. The best resolutions were observed with guinea pig liver microsomal enzymes.