Naevus vascularis mixtus and mixed vascular naevus syndrome.

Naevus vascularis mixtus (NVM), or mixed vascular naevus (MVN), is a binary phenotype resulting from allelic twin spotting, consisting of a naevus anaemicus paired with a telangiectatic naevus reminiscent of naevus roseus, and caused by a mosaic GNA11 mutation. MVN syndrome is characterized by an NVM associated with soft tissue hypotrophy or central nervous system abnormalities, mainly involving the cerebral vasculature. The differential diagnoses of NVM and its syndrome include vascular twin naevi, syndromes featuring naevus flammeus and other port-wine naevi, and the various types of phacomatosis pigmentovascularis. NVM and MVN syndrome are rare but probably underdiagnosed and under-reported.

Melanocytic naevi clustered on normal background skin.

Several types of maculopapular melanocytic naevi can occur in a multiple form, and be arranged in a nonrandom fashion on the skin. The most frequently reported segmentally grouped naevi are lentigines. Two types of segmentally arranged lentigines probably exist. The first is associated with neurofibromatosis (NF)1 or NF1 signs, features scattered light-brown lesions and can be considered a type of mosaic NF1. By contrast, non-NF1 associated lesions are characterized by densely packed, dark lesions, and can be defined as 'non-NF1 checkerboard-arranged lentigines'. Blue naevi, Spitz naevi and common acquired melanocytic naevi can occur, clustered in an agminated (or cannonball) shape. However, if large enough, they always follow a checkerboard pattern. Hence, such mosaic conditions should be termed 'checkerboard-arranged blue naevi', 'checkerboard-arranged Spitz naevi' and 'checkerboard-arranged common acquired melanocytic naevi'. Segmentally arranged dysplastic melanocytic naevi probably represent a mosaic form of dysplastic naevus syndrome. Dysplastic melanocytic naevi confined to a cutaneous segment could be defined as 'isolated segmental dysplastic naevus syndrome', while segmentally arranged dysplastic melanocytic naevi co-occurring with widespread, nonsegmental dysplastic melanocytic naevi might configure a 'superimposed segmental dysplastic naevus syndrome'. Small congenital melanocytic naevi are always grouped along Blaschko lines. The only other instances following Blaschko lines are the so-called 'linear lentiginous naevus' and a unique case of multiple deep penetrating naevi.

Segmental hypomelanosis and hypermelanosis arranged in a checkerboard pattern are distinct naevi: flag-like hypomelanotic naevus and flag-like hypermelanotic naevus.

The categorization of congenital hypo- or hyperpigmented skin lesions following a segmental pattern has been a long-lasting matter of debate and have been reported under various and often incorrect terms. To reassess published hypomelanotic and hypermelanotic lesions that did not follow Blaschko lines nor a phylloid pattern of mosaicism, we carried out an extensive and critical review of the worldwide literature. Seventy-four retrieved cases consisted of lateralized hypomelanotic lesions arranged in a flag-like pattern or appearing as large patches of grossly oval or angulated shape and sharp, serrated margins. Sometimes lesions harboured maculopapular melanocytic naevi or cooccurred with other segmentally arranged naevi. A probably non-random association with extracutaneous anomalies was also reported on rare occasions. In 70 cases, lateralized hypermelanotic patches were arranged in a flag-like pattern that often appeared as large quadrangular patches. Sometimes lesions harboured Spitz naevi. Ten cases belonged to phacomatosis melanorosea, whereas several others were part of so far uncategorized cases of phacomatosis pigmentovascularis. Flag-like hypomelanosis is a distinct naevus type, for which the term 'flag-like hypomelanotic naevus' is suggested. Its cooccurrence with extracutaneous abnormalities might represent a specific syndrome. Flag-like hypermelanosis is a distinct naevus type, for which the term 'flag-like hypermelanotic naevus' is suggested. Its co-occurrence with naevus roseus defines phacomatosis melanorosea. Flag-like hypermelanotic naevus should be distinguished from the checkerboard-like areas of darker skin as observed in chimaeras.

Effects of tacrolimus ointment on Toll-like receptors in atopic dermatitis.

BACKGROUND: Alterations of Toll-like receptors (TLRs) seem to play a role in susceptibility to atopic dermatitis (AD). AIM: To investigate the expression of TLRs in moderate to severe chronic AD in adults before and after a 3-week treatment with 0.1% tacrolimus ointment, compared with 0.1% topical hydrocortisone-17-butyrate. METHODS: In total, 21 adult patients with AD were enrolled: 11 were given tacrolimus ointment and 10 were given hydrocortisone butyrate; a further 6 healthy adults formed the control group. The clinical efficacy of the treatment was assessed using the SCORing Atopic Dermatis (SCORAD) index. Biopsies were taken from lesional skin before and after treatment, which were stained immunohistochemically with monoclonal antibodies to TLR-1, -2, -4 and -9. RESULTS: Both 3-week topical treatments improved signs and symptoms in all 21 patients considered, with no significant difference between the two groups. In the skin of patients with AD, TLR-1 was overexpressed and TLR-2 underexpressed compared with healthy controls, whereas no differences were found for TLR-4 and TLR-9. Staining for TLR-1 was decreased in both groups after treatment. AD specimens had higher levels of TLR-2 expression after either treatment compared with baseline, and levels were higher after tacrolimus treatment than after hydrocortisone butyrate. Neither tacrolimus nor hydrocortisone butyrate affected expression of TLR-4 or TLR-9. CONCLUSION: Short-term therapy with tacrolimus ointment reduced expression of TLR-1, which may inhibit the antimicrobial potential of TLR-2, and also reversed the impairment of TLR-2 in AD lesions. Expression of TLR-4 and TLR-9 was not affected by tacrolimus.

Skin manifestations of immunodeficiencies in children.

Immunodeficiency is a state in which the immune system's ability to fight infectious diseases is compromised or entirely absent. Most cases of immunodeficiency are acquired (secondary) but some people are born with defects in the immune system, or primary immunodeficiency. More than 140 distinct genes have been identified, which abnormalities account for more than 200 different forms of primary immunodeficiencies. The skin may be one of the organs involved in immunodeficiencies and in a number of primary immunodeficiency syndromes the skin is one of the main clues to the diagnosis and dermatologists may be the first to appreciate an immune defect in their patients. From "A" of well-known ataxia-telangiectasia to "Z" of recently identified zeta-chain (TCR) associated protein kinase 70kDa (ZAP-70) deficiency, this review attempts to provide a complete and up-to-date summary of all known primary immunodeficiencies featuring skin manifestations and presenting in the pediatric population. Given the vastness of the topic etiopathogenesis, extracutaneous manifestations, diagnosis, treatment and prognosis were not discussed unless briefly. We hope that this effort will help specialists to facilitate the recognition of primary immunodeficiencies and therefore early diagnosis and management.

Three-dimensional solution structure of Acanthamoeba profilin-I.

We have determined a medium resolution three-dimensional solution structure of Acanthamoeba profilin-I by multidimensional nuclear magnetic resonance spectroscopy. This 13-kD actin binding protein consists of a five stranded antiparallel beta sheet flanked by NH2- and COOH-terminal helices on one face and by a third helix and a two stranded beta sheet on the other face. Data from actin-profilin cross-linking experiments and the localization of conserved residues between profilins in different phyla indicate that actin binding occurs on the molecular face occupied by the terminal helices. The other face of the molecule contains the residues that differ between Acanthamoeba profilins-I and II and may be important in determining the difference in polyphosphoinositide binding between these isoforms. This suggests that lipids and actin bind to different faces of the molecule.

Multiple physical urticarias.

Physical urticarias are a group of mucocutaneous disorders characterised by the appearance of whealing and/or angioedema and induced by physical stimuli. A 24-year-old Caucasian male affected by ultraviolet A-induced solar urticaria, specific food-dependent exercise-induced anaphylaxis, symptomatic dermographism and allergic rhinoconjunctivitis is described.

Intracellular polymerization of sickle hemoglobin. Effects of cell heterogeneity.

To determine the extent to which the broad distribution in intracellular hemoglobin concentrations found in sickle erythrocytes affects the extent of intracellular polymerization of hemoglobin S, we have fractionated these cells by density using discontinuous Stractan gradients. The amount of polymer formed in the subpopulations was experimentally measured as a function of oxygen saturation using 13C nuclear magnetic resonance spectroscopy. The results for each subpopulation are in very good agreement with the theoretical predictions based on the current thermodynamic description for hemoglobin S gelation. We further demonstrate that the erythrocyte density profile for a single individual with sickle cell anemia can be used with the theory to predict the amount of polymer in unfractionated cells. We find that heterogeneity in intracellular hemoglobin concentration causes the critical oxygen saturation for formation of polymer to shift from 84 to greater than 90%; polymer is formed predominantly in the dense cells at the very high oxygen saturation values. The existence of polymer at arterial oxygen saturation values has significance for understanding the pathophysiology of sickle cell anemia. The utility of these techniques for assessing various therapeutic strategies is discussed.

Cellular infiltrate and related cytokines, chemokines, chemokine receptors and adhesion molecules in chronic autoimmune urticaria: comparison between spontaneous and autologous serum skin test induced wheal.

In recent years, the demonstration of circulating functional autoantibodies against the high affinity IgE receptor or against IgE themselves in about one-third of patients with chronic idiopathic urticaria has suggested that an autoimmune mechanism might be involved in the pathogenesis of the disease--the so-called chronic autoimmune urticaria (CAIU). In this study we compare findings from serum-induced and spontaneous wheals with regard to immunohistochemical markers of disease activity and discuss whether autologous serum skin test (ASST) may be regarded as an in vivo experimental model of the physiological stimulus causing urticaria skin condition, or if it does not reproduce the whole of the mechanisms operating in the development of spontaneous wheals. By means of immunohistochemical technique, we analyzed specimens from just-developed spontaneous wheals and from serum-evoked wheals of six CAIU patients, to glean information on cellular infiltrate and related cytokines, chemokines, chemokine receptors and adhesion molecules. According to the results of our study, spontaneous urticaria lesions seem to be sustained by a characteristic inflammation pattern where neutrophils, adhesion molecules, IL-8 and chemokine receptors play a main role in flogosis triggering and, consequently, disease development. On the contrary, ASST-induced wheals seem to imply different activities mainly represented by basophil granulocytes and related molecules, i.e. IL-4. Although it represents an efficacious diagnostic instrument to screen CAIU patients, ASST is not an exhaustive model of the many immunopathogenic pathways operating in the development of urticaria lesions, especially with regard to systemic activation networks.

Flap opening and dimer-interface flexibility in the free and inhibitor-bound HIV protease, and their implications for function.

BACKGROUND: (1)H and (15)N transverse relaxation measurements on perdeuterated proteins are ideally suited for detecting backbone conformational fluctuations on the millisecond-microsecond timescale. The identification of conformational exchange on this timescale by measuring the relaxation of both (1)H and (15)N holds great promise for the elucidation of functionally relevant conformational changes in proteins. RESULTS: We measured the transverse (1)H and (15)N relaxation rates of backbone amides of HIV-1 protease in its free and inhibitor-bound forms. An analysis of these rates, obtained as a function of the effective rotating frame field, provided information about the timescale of structural fluctuations in several regions of the protein. The flaps that cover the active site of the inhibitor-bound protein undergo significant changes of backbone (φ,psi) angles, on the 100 micros timescale, in the free protein. In addition, the intermonomer beta-sheet interface of the bound form, which from protease structure studies appears to be rigid, was found to fluctuate on the millisecond timescale. CONCLUSIONS: We present a working model of the flap-opening mechanism in free HIV-1 protease which involves a transition from a semi-open to an open conformation that is facilitated by interaction of the Phe53 ring with the substrate. We also identify a surprising fluctuation of the beta-sheet intermonomer interface that suggests a structural requirement for maturation of the protease. Thus, slow conformational fluctuations identified by (1)H and (15)N transverse relaxation measurements can be related to the biological functions of proteins.

Characterization of two hydrophobic methyl clusters in HIV-1 protease by NMR spin relaxation in solution.

Nearly 50 % of the amino acid residues of HIV-1 protease contain methyl side-chains, most of which appear to be organized into two clusters: the inner cluster that nearly surrounds the active site and the outer cluster that contains the hydrophobic core which stabilizes the inhibitor-free protease structure. NMR relaxation experiments sensitive to motions of methyl groups on the sub-nanosecond and the milli-microsecond time-scales revealed flexible methyl groups in residues that link the two clusters, the methyl groups of L10, L23, V75, and L76. We hypothesize that flexibility at the junctions of these clusters allows the protease to minimize conformational changes upon drug-binding. The two-methyl cluster motif appears to be a common structural feature among retroviral proteases and may play a similar role throughout this family of enzymes.

Refining the overall structure and subdomain orientation of ribosomal protein S4 delta41 with dipolar couplings measured by NMR in uniaxial liquid crystalline phases.

Prokaryotic protein S4 initiates assembly of the small ribosomal subunit by binding to 16 S rRNA. Residues 43-200 of S4 from Bacillus stearothermophilus (S4 Delta41) bind to both 16 S rRNA and to a mRNA pseudoknot. In order to obtain structure-based insights regarding RNA binding, we previously determined the solution structure of S4 Delta41 using NOE, hydrogen bond, and torsion angle restraints. S4 Delta41 is elongated, with two distinct subdomains, one all helical, the other including a beta-sheet. In contrast to the high resolution structures obtained for each individual subdomain, their relative orientation was not precisely defined because only 17 intersubdomain NOE restraints were determined. Compared to the 1.7 A crystal structure, when the sheet-containing subdomains are superimposed, the helical subdomain is twisted by almost 45 degrees about the long axis of the molecule in the solution structure. Because variations in subdomain orientation may explain how the protein recognizes multiple RNA targets, our current goal is to determine the orientation of the subdomains in solution with high precision. To this end, NOE assignments were re-examined. NOESY experiments on a specifically labeled sample revealed that one of the intersubdomain restraints had been misassigned. However, the revised set of NOE restraints produces solution structures that still have imprecisely defined subdomain orientations and that lie between the original NMR structure and the crystal structure. In contrast, augmenting the NOE restraints with N-H dipolar couplings, measured in uniaxial liquid crystalline phases, clearly establishes the relative orientation of the subdomains. Data obtained from two independent liquid crystalline milieux, DMPC/DHPC bicelles and the filamentous bacteriophage Pf1, show that the relative orientation of the subdomains in solution is quite similar to the subdomain orientation in the crystal structure. The solution structure, refined with dipolar data, is presented and its implications for S4's RNA binding activity are discussed.

The RNA binding domain of ribosomal protein L11: three-dimensional structure of the RNA-bound form of the protein and its interaction with 23 S rRNA.

The three-dimensional solution structure has been determined by NMR spectroscopy of the 75 residue C-terminal domain of ribosomal protein L11 (L11-C76) in its RNA-bound state. L11-C76 recognizes and binds tightly to a highly conserved 58 nucleotide domain of 23 S ribosomal RNA, whose secondary structure consists of three helical stems and a central junction loop. The NMR data reveal that the conserved structural core of the protein, which consists of a bundle of three alpha-helices and a two-stranded parallel beta-sheet four residues in length, is nearly the same as the solution structure determined for the non-liganded form of the protein. There are however, substantial chemical shift perturbations which accompany RNA binding, the largest of which map onto an extended loop which bridges the C-terminal end of alpha-helix 1 and the first strand of parallel beta-sheet. Substantial shift perturbations are also observed in the N-terminal end of alpha-helix 1, the intervening loop that bridges helices 2 and 3, and alpha-helix 3. The four contact regions identified by the shift perturbation data also displayed protein-RNA NOEs, as identified by isotope-filtered three-dimensional NOE spectroscopy. The shift perturbation and NOE data not only implicate helix 3 as playing an important role in RNA binding, but also indicate that regions flanking helix 3 are involved as well. Loop 1 is of particular interest as it was found to be flexible and disordered for L11-C76 free in solution, but not in the RNA-bound form of the protein, where it appears rigid and adopts a specific conformation as a result of its direct contact to RNA.

Solution structure and dynamics of linked cell attachment modules of mouse fibronectin containing the RGD and synergy regions: comparison with the human fibronectin crystal structure.

We report the three-dimensional solution structure of the mouse fibronectin cell attachment domain consisting of the linked ninth and tenth type III modules, mFnFn3(9,10). Because the tenth module contains the RGD cell attachment sequence while the ninth contains the synergy region, mFnFn3(9,10) has the cell attachment activity of intact fibronectin. Essentially complete signal assignments and approximately 1800 distance and angle restraints were derived from multidimensional heteronuclear NMR spectra. These restraints were used with a hybrid distance geometry/simulated annealing protocol to generate an ensemble of 20 NMR structures having no distance or angle violations greater than 0.3 A or 3 degrees. Although the beta-sheet core domains of the individual modules are well-ordered structures, having backbone atom rmsd values from the mean structure of 0.51(+/-0.12) and 0.40(+/-0.07) A, respectively, the rmsd of the core atom coordinates increases to 3.63(+/-1.41) A when the core domains of both modules are used to align the coordinates. The latter result is a consequence of the fact that the relative orientation of the two modules is not highly constrained by the NMR restraints. Hence, while structures of the beta-sheet core domains of the NMR structures are very similar to the core domains of the crystal structure of hFnFn3(9,10), the ensemble of NMR structures suggests that the two modules form a less extended and more flexible structure than the fully extended rod-like crystal structure. The radius of gyration, Rg, of mFnFn3(9,10) derived from small-angle neutron scattering measurements, 20.5(+/-0.5) A, agrees with the average Rg calculated for the NMR structures, 20.4 A, and is ca 1 A less than the value of Rg calculated for the X-ray structure. The values of the rotational anisotropy, D ||/D perpendicular, derived from an analysis of 15N relaxation data, range from 1.7 to 2.1, and are significantly less than the anisotropy of 2.67 predicted by hydrodynamic modeling of the crystal coordinates. In contrast, hydrodynamic modeling of the NMR coordinates yields anisotropies in the range of 1.9 to 2.7 (average 2.4(+/-0.2)), with NMR structures bent by more than 20 degrees relative the crystal structure having calculated anisotropies in best agreement with experiment. In addition, the relaxation parameters indicate that several loops in mFnFn3(9,10), including the RGD loop, are flexible on the nanosecond to picosecond time-scale. Taken together, our results suggest that, in solution, the limited set of interactions between the mFnFn3(9,10) modules position the RGD and synergy regions to interact specifically with cell surface integrins, and at the same time permit sufficient flexibility that allows mFnFn3(9,10) to adjust for some variation in integrin structure or environment.

The role of apoptosis in the pathogenesis of dermatitis herpetiformis.

Apoptosis is a form of cell death that is claimed to be involved in a number of chronic inflammatory and malignant skin diseases. The aim of this study was to investigate whether apoptosis may contribute to the pathogenesis of epidermal changes in dermatitis herpetiformis (DH) and, in particular, whether certain apoptosis-related markers such as Bax, Bcl-2, Fas and Fas ligand (FasL) take part in this process. For the detection of apoptotic nuclei, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labelling technique (TUNEL) was employed on cryostat sections. Skin lesions from six and perilesional skin from four DH patients were stained with monoclonal antibodies to Bax, Bcl-2, Fas and FasL. The same evaluation was also performed on three patients affected by bullous pemphigoid (BP) and in two healthy donors. Using TUNEL technique, a remarkable increase in the apoptotic rate within the epidermal compartment was observed in DH and BP patients in comparison with normal controls. In our immunohistochemical analysis, Bax/Bcl-2 ratio was almost the same in the epidermis of perilesional/lesional DH, BP and healthy skin specimens. In DH and BP specimens both Bax and Bcl-2 proteins were increased in the dermal perivascular compartment. Fas showed a prevalently epidermal staining, both in DH and BP lesions, while FasL was distributed in perivascular and subjunctional dermis; some FasL+ cells infiltrated the DEJ and the basal layer of epidermis. This study allowed us to highlight conspicuous apoptotic phenomena in basal and suprabasal keratinocytes within lesional and perilesional skin of DH. We conclude that in DH, as well as in BP, apoptosis plays a role in the pathogenesis of cutaneous lesions in concert with other pathogenetic mechanisms.