Stable adhesion of phospholipid vesicles to modified gold surfaces

Phospholipid vesicles are well-studied biomembrane mimics that are of increasing interest in drug delivery, immunoassays, and sensor chips. In a number of biosensor applications it is desirable to be able to adhere vesicles to a surface in a manner which does not result in their rupture or fusion. Such behavior should, in principle, be achievable by controlling the vesicle-surface and vesicle-vesicle interactions. We have varied vesicle composition and charge (phosphatidylcholine, phosphatidylcholine-phosphatidic acid 18 mol%) and solution ionic strength, to study the adhesion of fluorescent vesicles to glass, gold, and gold modified with chemisorbed acetyl-cysteine. The extent of chemisorption was characterized with angle-resolved X-ray photoelectron spectroscopy (ARXPS), and vesicle integrity and behavior was studied using entrapped and lipophilic fluorescent markers, together and in separate measurements. Vesicle fusion (by energy transfer), adhesion of intact vesicles (with entrapped calcein) and diffusion coefficients (by photobleaching recovery) were monitored using confocal fluorescence microscopy. Acetyl-cysteine modified gold surfaces were shown to be appropriate substrates for adhesion of intact vesicles. Finally, as a 'proof of principle' for fluorescence amplification, release of a self-quenching entrapped reporter dye (calcein) by the detergent Triton X-100 was followed in real time.     

Miscibility study of chitosan/2-hydroxyethyl starch blends and evaluation of their effectiveness as drug sustained release hydrogels

Polymeric matrices of chitosan (CS), 2-hydroxyethyl starch (HES) and their blends prepared by solvent evaporation technique, have been tested as sustained release hydrogels of ropinirole drug. X-Ray diffraction (XRD), infrared spectroscopy (FT-IR) and viscometry measurements showed that the two polymers can form miscible blends. This miscibility is owed to formed hydrogen bonds taking place between the reactive groups of CS and HES and one glass transition is recorded in all blends. Neat polymers were used to prepare solid dispersion formulations with ropinirole drug. It was found that drug was released immediately within 15-30 min from HES while the release was slower from CS matrix. Completely different were the release rates from ropinirole with physical mixtures using neat polymers and their blends. Due to the different solubility and swelling behaviour of CS and HES the release rates showed a sustained profile from the blends containing high amounts of CS.     

Medical confidentiality: legal and ethical aspects in Greece

Respect for confidentiality is firmly established in codes of ethics and law. Medical care and the patients' trust depend on the ability of the doctors to maintain confidentiality. Without a guarantee of confidentiality, many patients would want to avoid seeking medical assistance The principle of confidentiality, however, is not absolute and may be overridden by public interests. On some occasions (birth, death, infectious disease) there is a legal obligation on the part of the doctor to disclose but only to the appropriate authorities. Permissible disclosure can be granted by the patients' consent, for example, for the purpose of insurance they may wish to take out. Moreover, there are some ambivalent situations (such as criminal acts, or notification of sexual partner in case of a patient with AIDS) for which Greek law does not include relevant provisions, and the Codes of Medical Ethics do not offer clear guidelines. Therefore, the Greek doctor is called to estimate the situation and assume full responsibility for his decision. Finally, new considerations have arisen in the context of the recent advances in the field of telemedicine and electronic archiving. The paper discusses the current situation and legislation in Greece.     

Clinical and subclinical ACTH-independent macronodular adrenal hyperplasia and aberrant hormone receptors

ACTH-independent macronodular adrenal hyperplasia (AIMAH) is a very rare cause of endogenous Cushing's syndrome (CS). In this review, the clinical characteristics, the pathophysiology, and the management of AIMAH are described. AIMAH typically presents with overt CS, but subclinical oversecretion of cortisol has been increasingly described. The diagnosis is suspected by adrenal nodular enlargement on conventional imaging following the demonstration of ACTH-independent hypercortisolism. Final diagnosis is established by histological examination of the adrenal tissue. Bilateral adrenalectomy is the treatment of choice but unilateral adrenalectomy has been proposed in selected cases. In patients with subclinical CS, the decision to treat should be individualized. The pathophysiology of this condition has begun to be elucidated in recent years. Diverse aberrant membrane-bound receptors expressed in a non-mutated form in the adrenal gland have been found to be implicated in the regulation of steroidogenesis in AIMAH. When systematically screened, most patients with AIMAH and CS or subclinical CS exhibit an in vivo aberrant cortisol response to one or various ligands suggesting the presence of aberrant adrenal receptors. A protocol designed to screen patients for the presence of these aberrant receptors should be undertaken in all patients with AIMAH. The identification of these receptors provides the potential for novel pharmacological therapies by suppressing the endogenous ligands or blocking the receptor with specific antagonists.     

Fixation of transposable elements in the Drosophila melanogaster genome

We have investigated at the molecular level four cases in which D. melanogaster middle repetitive DNA probes consistently hybridized to a particular band on chromosomes sampled from a D. melanogaster natural population. Two corresponded to true fixations of a roo and a Stalker element, and the others were artefacts of the in situ hybridization technique caused by the presence of genomic DNA flanking the transposable elements (TEs) in the probes. The two fixed elements are located in the beta-heterochromatin (20A and 80B, respectively) and are embedded in large clusters of other elements, many of which may also be fixed. We also found evidence that this accumulation is an ongoing process. These results support the hypothesis that TEs accumulate in the non-recombining part of the genome. Their implications for the effects of TEs on determining the chromatin structure of the host genomes are discussed in the light of recent evidence for the role of TE-derived small interfering-RNAs as cis -acting determinants of heterochromatin formation.     

Resistance to vesicular stomatitis virus infection requires a functional cross talk between the eukaryotic translation initiation factor 2alpha kinases PERK and PKR

Phosphorylation of the alpha (alpha) subunit of the eukaryotic translation initiation factor 2 (eIF2) leads to the inhibition of protein synthesis in response to diverse stress conditions, including viral infection. The eIF2alpha kinase PKR has been shown to play an essential role against vesicular stomatitis virus (VSV) infection. We demonstrate here that another eIF2alpha kinase, the endoplasmic reticulum-resident protein kinase PERK, contributes to cellular resistance to VSV infection. We demonstrate that mouse embryonic fibroblasts (MEFs) from PERK(-/-) mice are more susceptible to VSV-mediated apoptosis than PERK(+/+) MEFs. The higher replication capacity of VSV in PERK(-/-) MEFs results from their inability to attenuate viral protein synthesis due to an impaired eIF2alpha phosphorylation. We also show that VSV-infected PERK(-/-) MEFs are unable to fully activate PKR, suggesting a cross talk between the two eIF2alpha kinases in virus-infected cells. These findings further implicate PERK in virus infection, and provide evidence that the antiviral and antiapoptotic roles of PERK are mediated, at least in part, via the activation of PKR.