Identification and characterization of the proBA operon of Streptococcus bovis.

A genomic DNA library of the rumen bacterium Streptococcus bovis was constructed in Escherichia coli, and recombinant plasmids able to complement proA and proB mutations of the host were found. Southern hybridization and restriction analysis showed that a 3.5-kb fragment of S. bovis DNA contained two genes, organized in an operon and coding for enzymes functionally similar to the glutamyl phosphate reductase-glutamyl kinase enzyme complex that in E. coli catalyzes the first step of proline biosynthesis. Complementation of the E. coli mutations was observed with the fragment inserted in both orientations, which suggested that the S. bovis proBA operon was transcribed from its own promoter. Genetic and biochemical data suggested that the proline biosynthetic pathway of S. bovis is similar to the one previously characterized for E. coli.     

In Vivo and in Vitro Experimental Analysis of Lens Regeneration in Larval Xenopus laevis

After lentectomy of larval Xenopus laevis , the outer cornea undergoes tissue transformation resulting in formation of a new lens. This lens regeneration is triggered and sustained by neural retina. In the present study, lens-forming transformation of the outer cornea was completed in vitro when the outer cornea was cultured within the lentectomized eye-cup. Well-differentiated lens fiber cells, which showed positive immunofluorescence for total crystallins, were also formed when the outer cornea was cultivated with the retina. No lens tissue was formed when the cornea was cultured alone. Lens-forming transformation, originating from the cornea three and five days after lentectomy, completely regressed when the tissue was isolated in vitro . Fom the present and previous findings, we concluded that, the interaction of corneal cells with the retina plays a decisive role in lens regeneration in situ .     

The evolution and ecology of multiple antipredator defences

Prey seldom rely on a single type of antipredator defence, often using multiple defences to avoid predation. In many cases, selection in different contexts may favour the evolution of multiple defences in a prey. However, a prey may use multiple defences to protect itself during a single predator encounter. Such “defence portfolios” that defend prey against a single instance of predation are distributed across and within successive stages of the predation sequence (encounter, detection, identification, approach (attack), subjugation and consumption). We contend that at present, our understanding of defence portfolio evolution is incomplete, and seen from the fragmentary perspective of specific sensory systems (e.g., visual) or specific types of defences (especially aposematism). In this review, we aim to build a comprehensive framework for conceptualizing the evolution of multiple prey defences, beginning with hypotheses for the evolution of multiple defences in general, and defence portfolios in particular. We then examine idealized models of resource trade-offs and functional interactions between traits, along with evidence supporting them. We find that defence portfolios are constrained by resource allocation to other aspects of life history, as well as functional incompatibilities between different defences. We also find that selection is likely to favour combinations of defences that have synergistic effects on predator behaviour and prey survival. Next, we examine specific aspects of prey ecology, genetics and development, and predator cognition that modify the predictions of current hypotheses or introduce competing hypotheses. We outline schema for gathering data on the distribution of prey defences across species and geography, determining how multiple defences are produced, and testing the proximate mechanisms by which multiple prey defences impact predator behaviour. Adopting these approaches will strengthen our understanding of multiple defensive strategies.     

PYK2 is overexpressed in chronic lymphocytic leukaemia: A potential new therapeutic target

Chronic Lymphocytic Leukaemia (CLL) is the most common adult B-cell leukaemia and despite improvement in patients' outcome, following the use of targeted therapies, it remains incurable. CLL supportive microenvironment plays a key role in both CLL progression and drug resistance through signals that can be sensed by the main components of the focal adhesion complex, such as FAK and PYK2 kinases. Dysregulations of both kinases have been observed in several metastatic cancers, but their role in haematological malignancies is still poorly defined. We characterized FAK and PYK2 expression and observed that PYK2 expression is higher in leukaemic B cells and its overexpression significantly correlates with their malignant transformation. When targeting both FAK and PYK2 with the specific inhibitor defactinib, we observed a dose–response effect on CLL cells viability and survival. In vivo treatment of a CLL mouse model showed a decrease of the leukaemic clone in all the lymphoid organs along with a significant reduction of macrophages and of the spleen weight and size. Our results first define a possible prognostic value for PYK2 in CLL, and show that both FAK and PYK2 might become putative targets for both CLL and its microenvironment (e.g. macrophages), thus paving the way to an innovative therapeutic strategy.     

Immunocytochemical analysis of phosphatidylinositol-specific phospholipase C in PC12 cells: predominance of the δ isoform during neural differentiation

The rat pheochromocytoma PC12 cell line, which differentiates into sympathetic neurons under nerve growth factor (NGF) treatment, contains at least three phosphoinositidase C (PIC) isozymes, PIC , PIC , PIC . These isozymes have been previously shown to display a different subcellular localization. To determine whether or not NGF induces changes in the presence and/or distribution of PIC isozymes during PC12 neural differentiation, studies were carried out by means of in situ immunocytochemistry. After NGF administration the proliferative activity was progressively reduced to very low levels, as measured by bromodeoxyUridine incorporation, and a neuron-like morphology was displayed by almost all cells. In unstimulated PC12 cells, PIC was detected in the nucleus whereas PIC was only cytoplasmic; PIC was found in both cell compartments. In cells treated with NGF for 3 days, neural processes extended to twice the diameter of the cell body; the isoform was concentrated near the nucleus, while the immunoreactivity of the form remained constant and the form was increased. After 10 days of treatment with NGF, PIC was hardly detectable and PIC immunostaining was considerably decreased. On the contrary, PIC progressively increased and, after 14 days of NGF exposure, fully differentiated cells displayed an intense labelling of cell body and neurites. In the same cells, PIC and PIC were almost negative. These results suggest that NGF dependent neural differentiation is related to the selective down regulation of PIC and and the increase of PIC isozyme associated with the decrease of cell proliferation.     

Inhibition of pea ferredoxin-NADP(H) reductase by Zn-ferrocyanide.

Ferredoxin-NADP(H) reductases (FNRs) represent a prototype of enzymes involved in numerous metabolic pathways. We found that pea FNR ferricyanide diaphorase activity was inhibited by Zn2+ (Ki 1.57 microM). Dichlorophenolindophenol diaphorase activity was also inhibited by Zn2+ (Ki 1.80 microM), but the addition of ferrocyanide was required, indicating that the inhibitor is an arrangement of both ions. Escherichia coli FNR was also inhibited by Zn-ferrocyanide, suggesting that inhibition is a consequence of common structural features of these flavoenzymes. The inhibitor behaves in a noncompetitive manner for NADPH and for artificial electron acceptors. Analysis of the oxidation state of the flavin during catalysis in the presence of the inhibitor suggests that the electron-transfer process between NADPH and the flavin is not significantly altered, and that the transfer between the flavin and the second substrate is mainly affected. Zn-ferrocyanide interacts with the reductase, probably increasing the accessibility of the prosthetic group to the solvent. Ferredoxin reduction was also inhibited by Zn-ferrocyanide in a noncompetitive manner, but the observed Ki was about nine times higher than those for the diaphorase reactions. The electron transfer to Anabaena flavodoxin was not affected by Zn-ferrocyanide. Binding of the apoflavodoxin to the reductase was sufficient to overcome the inhibition by Zn-ferrocyanide, suggesting that the interaction of FNRs with their proteinaceous electron partners may induce a conformational change in the reductase that alters or completely prevents the inhibitory effect.     

Synthesis and biological activity of tachykinin analogs containing the adamantane moiety

Summary The adamantane moiety was introduced in the tachykinin NK₂ receptor-selective agonist [-Ala⁸]-NKA(4–10) (H-Asp-Ser-Phe-Val--Ala-Leu-Met-NH₂, MEN 10210) and in different positions of the NK₂ receptor antagonist MEN 10376 (H-Asp-Tyr-d-Trp-Val-d-Trp-d-Trp-Lys-NH₂) in order to investigate how this substitution affects their biological activity at tachykinin NK₁, NK₂ and NK₃ receptors. 1-Adamantaneacetic acid (1-Ada-CH₂COOH) was directly conjugated in the solid phase as the preformed OBt active ester to the N-terminal position of MEN 10210, obtaining MEN 10586 (1-Ada-CH₂CO-Asp-Ser-Phe-Val--Ala-Leu-Met-NH₂). The Pfp ester of adamantaneacetic acid (1) was prepared and used for the acylation of the N-terminal position of MEN 10376, yielding MEN 10606 (1-Ada-CH₂CO-Asp-Tyr-d-Trp-Val-d-Trp-d-Trp-Lys-NH₂). Compound 1 was then used to obtain the building block Fmoc-Lys(1-Ada-CH₂CO)-OH as a modified amino acid for the synthesis of MEN 10818 [H-Asp-Tyr-d-Trp-Val-d-Trp-d-Trp-Lys(1-Ada-CH₂CO)-NH₂]. In order to investigate the biological activity of the peptide bearing the adamantane group together with the free N-terminal amino function, we synthesised MEN 10676 [H-Asp(O-2-Ada)-Tyr-d-Trp-Val-d-Trp-d-Trp-Lys-NH₂] using Fmoc-Asp(O-2-Ada)-OH, in which 2-adamantanole was the protecting group of the aspartate -COOH moiety during the peptide synthesis and survived the final peptide cleavage and deprotection carried out under controlled conditions. MEN 10586 showed an agonist activity comparable to that of the parent compound MEN 10210 at NK₁ and NK₂ receptors of guinea pig ileum, rabbit isolated pulmonary artery and hamster isolated trachea preparations, while it showed a 25-fold higher agonist activity at NK₃ receptors of rat isolated portal vein. The three modified antagonist analogs displayed similar or reduced affinity at NK₁, NK₂ and NK₃ receptors as compared to MEN 10376. The drop was particularly evident (>2 log units) at the NK₂ receptors of the rabbit isolated pulmonay artery.