The different steps of skin formation in vertebrates

Skin morphogenesis occurs following a continuous series of cell-cell interactions which can be subdivided into three main stages: 1- the formation of a dense dermis and its overlying epidermis in the future appendage fields (macropattern); 2- the organization of these primary homogeneous fields into heterogeneous ones by the appearance of cutaneous appendage primordia (micropattern) and 3- cutaneous appendage organogenesis itself. In this review, we will first show, by synthesizing novel and previously published data from our laboratory, how heterogenetic and heterospecific dermal/epidermal recombinations have allowed us to distinguish between the respective roles of the dermis and the epidermis. We will then summarize what is known from the work of many different research groups about the molecular signaling which mediates these interactions in order to introduce the following articles of this Special Issue and to highlight what remains to done.     

Effect of hypercholesterolemia and of oxidative stress on the nitric oxide-cGMP pathway

Soluble guanylyl cyclase (sGC) is a key enzyme of the NO-cGMP pathway which is believed to mediate vasoprotective actions. In cardiovascular diseases such as hypercholesterolemia and atherosclerosis, these important functions of the vascular endothelium are strongly impaired. One of the major reasons for this so-called endothelial dysfunction is the increased vascular generation of reactive oxygen species such as superoxide and peroxynitrite. We aimed to investigate whether superoxide and peroxynitrite impacts on the expression and function of sGC and if such a mechanism occurs in a hypercholestemia-induced atherosclerosis. Our experiments with isolated rat aortic rings showed that extracellular superoxide has no effect on expression and function of sGC, while subjection of these rings to continuously generated extracellular peroxynitrite reduced sGC activity. Furthermore, intracellular superoxide as generated by LY85385 almost completely inhibited sGC-activity and increased its expression. In the cholesterol-fed White New Zealand rabbit, we found a 3.5-fold upregulation of sGC, while basal and NO-stimulated sGC-activities were only slightly enhanced and the vasodilator potency of SNAP was decreased by 10-fold. A great portion of the overexpressed dysfunctional sGC is located in intimal lesions. Finally, platelet sGC-activity and the anti-aggregatory effect of SNAP were not changed. These data suggest that endothelial dysfunction in hypercholesterolemia is associated with an oxidative stress-dependent and reversible overexpression of a dysfunctional vascular sGC, while inhibition of platelet sGC-activity is most likely not involved in hypercholesterolemia-induced platelet hyperreactivity.     

Evidences for the formation of bisbenzamidine-heme complexes in cell-free systems

Infrared and colorimetry data suggest that bisbenzamidines connected by various rigid or flexible linkers are able to interact with heme in cell-free systems. At pH 5.0 the inhibition of formation of beta-hematin could be ascertained by infrared spectroscopy whereas at pH 7.0 the interaction yielded insoluble complexes for which a sandwich-type structure of stoichiometry 2:1, heme-drug, is tentatively proposed.     

Covalent binding of the 13C-labeled skin sensitizers 5-chloro-2-methylisothiazol-3-one (MCI) and 2-methylisothiazol-3-one (MI) to a model peptide and glutathione

The reactivity of 4-[13C]- and 5-[13C]-5-chloro-2-methylisothiazol-3-one (MCI) and 2-methylisothiazol-3-one (MI) towards a model peptide and glutathione was followed by 13C and 1H[13C] NMR spectroscopy. Both molecules were found to react with GSH but in addition MCI was found to react with histidine and lysine to form adducts of a different nature. Reaction with histidine led to stable substitution adducts through an addition-elimination reaction at position 5 while reaction with lysine led to the formation of open adducts of the thioamide or amide type.     

Synthesis of N,N'-disubstituted 3-aminobenzo[c] and [d]azepin-2-ones as potent and specific farnesyl transferase inhibitors

A structure-activity study was performed by synthesis on N,N'-disubstitution of 3-aminobenzo[c] and [d]azepin-2-one 2 and 3 to afford potent and specific farnesyl transferase inhibitors with low nM enzymatic and cellular activities.     

Novel bisbenzamidines as potential drug candidates for the treatment of Pneumocystis carinii pneumonia

A series of pentamidine congeners has been synthesized and screened for their in vitro activity against Pneumocystis carinii. Among the tested compounds, bisbenzamidines linked by a flexible pentanediamide or hexanediamide chain (7 and 9) emerged as exceptionally potent agents that were more effective and less toxic than pentamidine in the assays described in this study.     

Kinesin II mediates Vg1 mRNA transport in Xenopus oocytes

The subcellular localization of specific mRNAs is a widespread mechanism for regulating gene expression. In Xenopus oocytes microtubules are required for localization of Vg1 mRNA to the vegetal cortex during the late RNA localization pathway. The factors that mediate microtubule-based RNA transport during the late pathway have been elusive. Here we show that heterotrimeric kinesin II becomes enriched at the vegetal cortex of stage III/IV Xenopus oocytes concomitant with the localization of endogenous Vg1 mRNA. In addition, expression of a dominant negative mutant peptide fragment or injection of a function-blocking antibody, both of which impair the function of heterotrimeric kinesin II, block localization of Vg1 mRNA. We also show that exogenous Vg1 RNA or Xcat-2, another RNA that can use the late pathway, recruits endogenous kinesin II to the vegetal pole and colocalizes with it at the cortex. These data support a model in which kinesin II mediates the transport of specific RNA complexes destined for the vegetal cortex.     

Organogenesis: cutting to the chase

Gonad morphogenesis in Caenorhabditis elegans requires two secreted proteases. Recent studies show that alterations of the extracellular matrix component fibulin-1 rescue gonadogenesis in the absence of these proteases. This finding is a critical step toward understanding the role of extracellular matrix in organogenesis.     

Hepatitis A virus attachment to agri-food surfaces using immunological, virological and thermodynamic assays

AIMS: This study was designed to investigate the ability of hepatitis A virus (HAV) to attach to various food contact surfaces. METHODS AND RESULTS: HAV attachment was demonstrated after elution of attached viruses from solid surfaces by an immunofluorescent method using anti-HAV-specific antibodies and confocal microscopy. Attachment and survival of HAV on stainless steel, copper, polythene and polyvinyl chloride (PVC) at 20 and 4 degrees C after 2 and 4 h were quantified by plaque assay. HAV was shown to attach almost instantaneously to all four surfaces tested. Attachment of HAV depended on initial viral concentration and was slightly greater at 4 degrees C. The total surface energy (gammaTOT), nonpolar Lifshitz-Van der Waals (gammaLW) and polar short range (gammaSR) hydrogen-bonding components for HAV and each surface as well as total free energy of the system were determined by contact angle measurements using an extended Young equation [Young (1805) Philosophical Transactions of The Royal Society (London) 95, 65-87). The calculation of these parameters predicted the favourable conditions for attachment of HAV to all four surfaces tested. CONCLUSION: HAV particles attach to stainless steel, copper, polythene and PVC at 20 and 4 degrees C and the total free energy of the interaction is optimal for this attachment. SIGNIFICANCE AND IMPACT OF THE STUDY: Comprehension of viral attachment to the solid surfaces will permit to successfully disinfect these surfaces and to establish a better surveillance programme for control of viral food-borne illnesses.