Identification, synthesis and biological activity of alkyl-guanidine oligomers as potent antibacterial agents.

In the last two decades, the repertoire of clinically effective antibacterials is shrinking due to the rapidly increasing of multi-drug-resistant pathogenic bacteria. New chemical classes with innovative mode of action are required to prevent a return to the pre-antibiotic era. We have recently reported the identification of a series of linear guanidine derivatives and their antibacterial properties. A batch of a promising candidate for optimization studies (compound 1) turned out to be a mixture containing two unknown species with a better biological activity than the pure compound. This serendipitous discovery led us to investigate the chemical nature of the unknown components of the mixture. Through MS analysis coupled with design and synthesis we found that the components were spontaneously generated oligomers of the original compound. Preliminary biological evaluations eventually confirmed the broad-spectrum antibacterial activity of this new family of molecules. Interestingly the symmetric dimeric derivative (2) exhibited the best profile and it was selected as lead compound for further studies.

Melatonin reduces excitotoxic blood-brain barrier breakdown in neonatal rats.

The blood-brain barrier (BBB) is a complex structure that protects the central nervous system from peripheral insults. Understanding the molecular basis of BBB function and dysfunction holds significant potential for future strategies to prevent and treat neurological damage. The aim of our study was (1) to investigate BBB alterations following excitotoxicity and (2) to test the protective properties of melatonin. Ibotenate, a glutamate analog, was injected intracerebrally in postnatal day 5 (P5) rat pups to mimic excitotoxic injury. Animals were than randomly divided into two groups, one receiving intraperitoneal (i.p.) melatonin injections (5mg/kg), and the other phosphate buffer saline (PBS) injections. Pups were sacrificed 2, 4 and 18 h after ibotenate injection. We determined lesion size at 5 days by histology, the location and organization of tight junction (TJ) proteins by immunohistochemical studies, and BBB leakage by dextran extravasation. Expression levels of BBB genes (TJs, efflux transporters and detoxification enzymes) were determined in the cortex and choroid plexus by quantitative PCR. Dextran extravasation was seen 2h after the insult, suggesting a rapid BBB breakdown that was resolved by 4h. Extravasation was significantly reduced in melatonin-treated pups. Gene expression and immunohistochemical assays showed dynamic BBB modifications during the first 4h, partially prevented by melatonin. Lesion-size measurements confirmed white matter neuroprotection by melatonin. Our study is the first to evaluate BBB structure and function at a very early time point following excitotoxicity in neonates. Melatonin neuroprotects by preventing TJ modifications and BBB disruption at this early phase, before its previously demonstrated anti-inflammatory, antioxidant and axonal regrowth-promoting effects.

[Newborn resuscitation: from necessity of continous practice to professional liability]. / Rianimazione neonatale:dalla necessità di formazione continua ai profili di responsabilità civile del neonatologo.

The immediately postbirth extra uterine adaptation is the most important cause of death in the first two hours of life. In all risky cases, it is necessary to effect efficient and on time techniques of newborn resuscitation, because dubitation or delay may be very dangerous for the infant. In Italy courses of equipment in newborn resuscitation are regularly performed, but an excellent level of technique can be obtained only with continuous daily practice. Then, particularly in little hospitals where it is unusually necessary to act resuscitation on a newborn, courses of simulation for medical and nursering staff would be opportune to prevent neonatal handicap and to deal with the professional liability in the best way. The Italian current jurisprudence, in fact, has slowly confined the application of 2236 article of Civil code about professional liability in particularly difficult efforts. The Italian law asserts that a professional specialist is trained to be able resolve any type of problem among those of his specialistic competence, even if technically very difficult. It should be opportune to train health staff with practical exercises, in order to obtain complete technical skills in all neonatal centers.

Optimization of emergency department management of infants with bronchiolitis.

Bronchiolitis is the most common lower respiratory tract infection in infants < 2 years of age; in the last decades both incidence and hospitalization rate had increased, thus increasing sanitary burden. From November 2006 to March 2007, an experimental protocol was followed in the Emergency Department at G. Gaslini Children's Hospital, Genoa, Italy, which attempted to optimise the management of patients with bronchiolitis and to reduce the overall hospitalization rate therefore admitting only those patients with severe illness. All clinical evaluations of the patients were obtained administering a score (Bronchiolitis Clinical Score - BCS), to quantify both initial severity of illness and response to treatment. All patient were at first treated with inhaled epinephrine, supplemented with or substituted by other drugs, if needed, according to clinical evolution. Moreover, strict admission and discharge criteria were defined, taking into consideration the BCS, response to treatment and the presence of risk factors for severe disease, attempting to increase the role of the Short Stay Unit (SSU). The outcome evaluated were the percentage of patients discharged, admitted and managed through the SSU respectively, the length of stay and the readmission rate after discharge; data collected were then compared to that regarding patients with bronchiolitis presented at the ED from November 2005 to March 2006. Our data showed an increasing of both discharged patients (37.5% vs 25.22%) and patients managed through the SSU (25.83% vs 19.57%) and a related decrease of hospitalization (36.67% vs 55.22%); no significative difference was observed regarding the readmission rate between the two populations. We also observed a statistically significant reduction of the length of stay in the study population (2.07 +/- 2.56 vs 2.84 +/- 3.25, p = 0.005). In conclusion, the protocol proposed showed to be useful in optimizing the ED management of the patient with bronchiolitis, being able to safely reduce both admission rate and lenght of stay.

Characterization of the response of the Arabidopsis response regulator gene family to cytokinin.

We examined the expression of a family of Arabidopsis response regulators (ARR) and found that the steady-state levels of RNA for most are elevated very rapidly by cytokinin. Using nuclear run-on assays we demonstrated that this increase in ARR transcript levels in response to cytokinin is due, at least in part, to increased transcription. The start site of transcription for the ARR5 gene was identified using primer extension analysis. A DNA fragment comprised of 1.6 kb upstream of the ARR5 transcript start site conferred cytokinin-inducible gene expression when fused to a beta-glucuronidase reporter, confirming that the transcription rate of ARR5 is elevated by cytokinin. This reporter construct was also used to examine the spatial pattern of ARR5 expression. The highest levels of expression were observed in the root and shoot apical meristems, at the junction of the pedicle and the silique, and in the central portion of mature roots. The expression of ARR5 in the apical meristems was confirmed by whole mount in situ analysis of seedlings and is consistent with a role for cytokinin in regulating cell division in vivo.

Phosphorelay signal transduction: the emerging family of plant response regulators.

Homologs of bacterial two-component signal transduction elements are emerging as key players in eukaryotic signaling systems. The recent identification of a large gene family in Arabidopsis that is similar to two-component response regulators emphasizes the importance of this signaling mechanism in plants. The understanding of the function of these response regulator genes is only rudimentary but the transcriptional induction of a subset by cytokinin suggests a role for some of these regulators in the response to this important plant hormone.

Molecular mechanisms of cytokinin action.

Cytokinins have been implicated in many aspects of plant development, including a crucial role in regulating cell proliferation. Recent studies indicate that cytokinins may elevate cell division rates by induction of expression of CycD3, which encodes a D-type cyclin thought to play a role in the G1-->M transition of the cell cycle. Progress has also been made in our understanding of cytokinin perception as homologs of two-component phosphorelay systems have emerged as likely signaling elements.

The effect of monensin and chloroquine on the endocytosis and toxicity of chimeric toxins.

The toxicity of two conjugates containing ribosome-inactivating proteins (RIPs, i.e. saporin and ricin-A chain x-linked to transferrin) has been measured on a prostatic cancer line (PC3) naturally overexpressing the transferrin receptor, in the presence of monensin and chloroquine. This paper investigates whether the increased toxicity of Tf-RIPs induced by monensin and chloroquine may be due to alterations of the normal endocytotic pathway of the complexes mediated by the transferrin receptor. Monensin, besides inducing alkalinization of normally acid intracellular compartments, causes an accumulation of the receptor-bound Tf-RIP in a perinuclear region contiguous to the cisternae of the trans-Golgi network. Chloroquine, though increasing the intracellular pH, seems not to modify the endocytotic pathway of these chimeric molecules. We believe that the enhanced toxicity of the Tf-RIPs may be related to intracellular alkalinization (i.e., endosomal or lysosomal pH) rather than to the effects on the recycling of transferrin receptor-bound toxins. We conclude that the efficacy of chimeric toxins may be modulated not only by the carrier used for their engineering but also by addition of drugs able to influence the stability and activation of the toxins inside the cell.

Liposomal targeting of leukaemia HL60 cells induced by transferrin-receptor endocytosis.

A liposomal carrier system able to interact specifically with HL60 leukaemia cells was produced using small unilamellar liposomes made of pure phospholipids chemically cross-linked to human transferrin. The conjugation of transferrin to liposomes was carried out using N-succinimidyl 3-(2-pyridyldithio)-propionate and 2-iminothiolane as activating agents for the liposomes and the protein. The reaction occurred under conditions set to covalently link on the surface of a single vesicle a limited number (one to ten) of transferrin molecules, as verified by means of electron microscopy and immunoenzymic measurements. Before conjugation, the ultrastructure of the liposomes, and the content and distribution of the amino groups within the bilayer, were determined. The reactivity of the liposomes towards amino-derivatizing or thiolating compounds was also measured. Kinetic spectroscopic measurements confirmed that the distribution of the phosphatidylethanolamine in the vesicle bilayer is asymmetrical: 22% of phosphatidylethanolamine was found exposed to the external surface of the liposomes and accessible to the cross-linker. The modified liposomes were able to interact specifically with the cells and to be internalized by active receptor-mediated endocytosis, as demonstrated by the full inhibition of internalization induced by free transferrin.

A chimeric saporin-transferrin conjugate compared to ricin toxin: role of the carrier in intracellular transport and toxicity.

Human transferrin (Tf) and saporin-6 (Sap), a ribosome inactivating protein from Saponaria officinalis, were chemically conjugated: the reaction generated two chimeras (called Tf-Sap) that proved to be cytotoxic to HepG2 cells. Electrophoretic and chromatographic analysis revealed that the two conjugates contained saporin and Tf in a 2:1 or 1:1 molar ratio (140 and 110 KDa, respectively). Free saporin is essentially nontoxic, whereas Tf-Sap efficiently kills HepG2 cells, although its ID50 (= 6 nM) is 1000-fold greater than that of ricin. Intracellular transport of these toxins was followed by in vivo fluorescence video microscopy, preparing the conjugates starting from rhodamine isothiocyanate-labeled saporin. Image analysis of living HepG2 cells exposed to fluorescent Tf-Sap revealed that the endocytotic pathway involving passage through secondary endosomes is dictated by Tf and is different from that of ricin (the dimeric toxin from Ricinus communis), which is delivered to the Golgi apparatus, the probable site of activation. We discuss whether differences in toxicity between ricin and Tf-Sap can be attributed to the different mechanisms of transport and activation.