Multidomain Skyrmion Lattice State in Cu2OSeO3.

Magnetic skyrmions in chiral magnets are nanoscale, topologically protected magnetization swirls that are promising candidates for spintronics memory carriers. Therefore, observing and manipulating the skyrmion state on the surface level of the materials are of great importance for future applications. Here, we report a controlled way of creating a multidomain skyrmion state near the surface of a Cu2OSeO3 single crystal, observed by soft resonant elastic X-ray scattering. This technique is an ideal tool to probe the magnetic order at the L3 edge of 3d metal compounds giving an average depth sensitivity of ∼50 nm. The single-domain 6-fold-symmetric skyrmion lattice can be broken up into domains, overcoming the propagation directions imposed by the cubic anisotropy by applying the magnetic field in directions deviating from the major cubic axes. Our findings open the door to a new way to manipulate and engineer the skyrmion state locally on the surface or on the level of individual skyrmions, which will enable applications in the future.

Néel-type skyrmion lattice with confined orientation in the polar magnetic semiconductor GaV4S8.

Following the early prediction of the skyrmion lattice (SkL)--a periodic array of spin vortices--it has been observed recently in various magnetic crystals mostly with chiral structure. Although non-chiral but polar crystals with Cnv symmetry were identified as ideal SkL hosts in pioneering theoretical studies, this archetype of SkL has remained experimentally unexplored. Here, we report the discovery of a SkL in the polar magnetic semiconductor GaV4S8 with rhombohedral (C3v) symmetry and easy axis anisotropy. The SkL exists over an unusually broad temperature range compared with other bulk crystals and the orientation of the vortices is not controlled by the external magnetic field, but instead confined to the magnetic easy axis. Supporting theory attributes these unique features to a new Néel-type of SkL describable as a superposition of spin cycloids in contrast to the Bloch-type SkL in chiral magnets described in terms of spin helices.

In situ self-assembled organic interface layers for the controlled growth of oligothiophene thin films on ferroelectric Pb(Zr(0.2)Ti(0.8))O3.

We introduce an in situ vacuum procedure for the optimal preparation and analysis of self-assembled monolayers (SAMs) as used in organic molecular electronics on ferroelectric lead zirconate titanate (PZT) substrates. Excellent ordering of oligothiophene semiconductor layers is heavily promoted through the presence of an interfacial bi-functional SAM layer that binds to both the oxidic PZT surface and the organic semiconductor molecules. The described method can be extended to other material combinations, featuring a variety of substrate materials and molecular functionalities.

Identification and regulation of 1,25-dihydroxyvitamin D3 receptor activity and biosynthesis of 1,25-dihydroxyvitamin D3. Studies in cultured bovine aortic endothelial cells and human dermal capillaries.

Because 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) has been shown to play roles in both proliferation and differentiation of novel target cells, the potential expression of 1,25(OH)2D3 receptor (VDR) activity was investigated in cultured bovine aortic endothelial cells (BAEC). Receptor binding assays performed on nuclear extracts of BAEC revealed a single class of specific, high-affinity VDR that displayed a 4.5-fold increase in maximal ligand binding (Nmax) in rapidly proliferating BAEC compared with confluent, density-arrested cells. When confluent BAEC were incubated with activators of protein kinase C (PKC), Nmax increased 2.5-fold within 6-24 h and this upregulation was prevented by sphingosine, an inhibitor of PKC, as well as by actinomycin D or cycloheximide. Immunohistochemical visualization using a specific MAb disclosed nuclear localized VDR in venular and capillary endothelial cells of human skin biopsies, documenting the expression of VDR, in vivo, and validating the BAEC model. Finally, additional experiments indicated that BAEC formed the 1,25(OH)2D3 hormonal metabolite from 25(OH)D3 substrate, in vitro, and growth curves of BAEC maintained in the presence of 10(-8) M 1,25(OH)2D3 showed a 36% decrease in saturation density. These data provide evidence for the presence of a vitamin D microendocrine system in endothelial cells, consisting of the VDR and a 1 alpha-hydroxylase enzyme capable of producing 1,25(OH)2D3. That both components of this system are coordinately regulated, and that BAEC respond to the 1,25(OH)2D3 hormone by modulating growth kinetics, suggests the existence of a vitamin D autocrine loop in endothelium that may play a role in the development and/or functions of this pathophysiologically significant cell population.

Expression of 1,25-dihydroxyvitamin D3 receptors in normal and psoriatic skin.

Increasing evidence suggests an immunoregulatory function of the potent steroid hormone 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) which has been successfully applied for treatment of psoriasis. The skin is both a site of production and a target of 1,25(OH)2D3. In vitro, 1,25(OH)2D3 inhibits proliferation and stimulates differentiation of keratinocytes. We investigated the in situ expression of vitamin D-receptors (VDR) in normal and psoriatic skin by immunochemical methods. The VDR were visualized using the monoclonal antibody (MoAb) 9A7g to the VDR and the labeled avidinbiotin technique. Immunoreactivity was consistently confined to nuclei in all skin biopsies. In normal skin specimens (n = 10) VDR antigens were expressed in keratinocytes of all epidermal layers (except those of the stratum corneum) and in cells of the epidermal appendages. Double labeling experiments with MoAb to cluster-defined antigens indicated that melanocytes and approximately 75% of Langerhans cells exhibit 1,25(OH)2D3 receptors in normal skin biopsies (n = 5). Depending on their localization in skin compartments 42-62% of CD11b+ positive macrophages and 45-75% of CD3+ T lymphocytes expressed VDR. Non-lesional psoriatic skin specimens (n = 8) revealed nearly identical staining patterns. Lesional psoriatic skin specimens (n = 8) exhibited a significant increase of VDR expression both in basal and suprabasal epidermal layers as measured by computer-assisted morphometry and showed a remarkable change of the immune cell pattern: the densitity and proportion of VDR positive T lymphocytes and macrophages were higher in the epidermal and the perivascular papillary loop compartment. These in vivo findings strongly support the hypothesis that 1,25(OH)2D3 modulates immune response and cell proliferation/differentiation in human skin.

Immunohistochemical detection of 1,25-dihydroxyvitamin D3 receptors and estrogen receptors by monoclonal antibodies: comparison of four immunoperoxidase methods.

We developed an immunohistochemical method for visualization of vitamin D (VDR) and estrogen receptors (ER) in cryostat sections, using monoclonal antibodies (MAb) to the vitamin D receptor and estrogen receptor, respectively. This method is based on an avidin-biotin labeling technique (LAB). To establish a reliable and sensitive method which can be used easily as a routine diagnostic procedure, we systematically compared four different immunoenzymatic methods with respect to their efficiency in detecting vitamin D and estrogen receptors. Compared to the indirect bridged avidin-biotin (IBRAB), the peroxidase- anti-peroxidase (PAP), and the avidin-biotin complex (ABC) methods, the LAB method produced stronger staining intensities and had higher detection efficiency for both vitamin D and estrogen receptors. In addition, the LAB method had a higher spatial resolution compared to the ABC technique in detection of VDR in normal human skin biopsies. In the case of steroid receptors, i.e., nuclear antigens, immunohistochemistry must deal with a relatively low number of antigenic sites per cell, restricted accessibility of the antigens, and slight differences in antigen concentrations among cells. Under these particular conditions, the chemical properties of the conjugates used in the LAB method may explain why it is superior to the other methods. Consequently, the LAB method is recommended for visualization of ER and VDR.

Cutaneous bacillary angiomatosis in a patient with chronic lymphocytic leukemia.

BACKGROUND: Bacillary angiomatosis is a recently described vascular disorder that is associated with infection by Bartonella henselae (formerly known as Rochalimaea henselae) and Bartonella quintana (formerly known as Rochalimaea quintana); this disorder usually occurs in patients with human immunodeficiency virus infection. We report a case of cutaneous bacillary angiomatosis that occurred in a patient with chronic lymphocytic leukemia. OBSERVATIONS: A 55-year-old man with chronic lymphocytic B-cell leukemia, Rai stage IV, presented with multiple angiomatous papules that clinically resembled pyogenic granulomas. Histopathologic examination revealed circumscribed lobules of small vessels with plump endothelial cells, numerous neutrophils, and abundant nuclear dust; these features were diagnostic for bacillary angiomatosis. The diagnosis was confirmed by the Grocott-Gomori methenamine-silver nitrate stain that revealed argyrophilic bacteria and by ultrastructural demonstration of bacillary structures with trilaminar walls. Treatment with clarithromycin led to complete resolution of the lesions within 4 weeks. CONCLUSIONS: This case emphasizes that (1) bacillary angiomatosis must be considered in the differential diagnosis of vascular lesions in immunocompromised patients without human immunodeficiency virus infection, (2) Grocott-Gomori methenamine-silver nitrate stain is a simple and satisfactory alternative to the Warthin-Starry stain for the demonstration of bacilli in this condition, and (3) clarithromycin is an effective oral antibiotic for the treatment of this disease.

Adult polyglucosan body disease.

We describe a case of adult polyglucosan body disease with characteristic clinical symptoms of peripheral neuropathy, upper motor neuron signs, and bowel and bladder dysfunction. Sural nerve biopsy revealed diagnostic intra-axonal polyglucosan bodies. On electron microscopic examination, the inclusions were located mainly within myelinated nerve fibers and consisted of branched filaments that were 6 to 8 nm wide. The diagnosis of adult polyglucosan body disease was confirmed by a skin biopsy from the axilla showing similar inclusions in myoepithelial cells of apocrine glands. This report provides additional evidence that skin biopsy, to date advocated by a single case report only, may be a less invasive and simpler diagnostic alternative to sural nerve or brain biopsies.

Unwinding of a skyrmion lattice by magnetic monopoles.

Skyrmion crystals are regular arrangements of magnetic whirls that exist in a wide range of chiral magnets. Because of their topology, they cannot be created or destroyed by smooth rearrangements of the direction of the local magnetization. Using magnetic force microscopy, we tracked the destruction of the skyrmion lattice on the surface of a bulk crystal of Fe(1-x)Co(x)Si (x = 0.5). Our study revealed that skyrmions vanish by a coalescence, forming elongated structures. Numerical simulations showed that changes of topology are controlled by singular magnetic point defects. They can be viewed as quantized magnetic monopoles and antimonopoles, which provide sources and sinks of one flux quantum of emergent magnetic flux, respectively.

Interface dipole formation of different ZnPcCl(8) phases on Ag(111) observed by Kelvin probe force microscopy.

Recently, we investigated the adsorption of octachloro zinc phthalocyanine (ZnPcCl(8)) on Ag(111) by scanning tunneling microscopy. Compared to the standard phthalocyanine, halogenated phthalocyanine molecules show a much more complex binding behavior, which results in the formation of three different structural phases. These phases follow from the ordering process with the formation of 8, 4 and 0 intermolecular hydrogen-halogen bonds (Abel et al 2006 ChemPhysChem 7 82). In the present work we investigate these phases by Kelvin probe force microscopy in order to quantitatively deduce the electric interface barrier of the first monolayer. Our measurements reveal that the binding behavior does not only affect the structural ordering but also the interface dipole formation, which leads to different work functions. The fact that we observe interface barriers of opposite signs between ordered and disordered molecular layers underlines the importance of exactly knowing the molecular arrangement at the interface when assembling organic molecule devices.

[Vitamin D and the skin: new aspects and perspectives]. / Vitamin D und die Haut: neue Aspekte und Perspektiven.

Vitamin D (calciferol) is under clinical investigation for the treatment of psoriasis. Vitamin D was previously solely regarded as a key substance in hormonal calcium homeostasis, a view that is no longer tenable. The human receptor for the biologically active metabolite 1,25-dihydroxyvitamin-D3 was cloned in 1988. Sequence analyses revealed that it was a member of the nuclear steroid hormone receptor family. This family of gene-regulatory DNA-binding proteins includes the oestrogen, progesterone, glucocorticoid, mineralocorticoid, thyroxine (T-3) and retinoic acid receptors. Vitamin D receptors have been identified in a variety of tissues primarily unrelated to calcium metabolism. The skin and the immune system are some of the most interesting new targets. In vitro 1,25-dihydroxyvitamin-D3 inhibits proliferation and induces differentiation of keratinocytes. Furthermore, this hormone has potent immunomodulatory functions.

[Lymphomatoid papulosis in a child]. / Lymphomatoide Papulose bei einem Kind.

We report a case of a 3-year-old boy who developed crops of papules and ulcerating nodules on the limbs in April 1992. Periodically, new lesions continue to erupt, while others resolve spontaneously. This course is characteristic for rhythmic paradoxical eruptions. This course and the clinical picture, supported by the histopathological and immunohistochemical findings, led to the diagnosis of lymphomatoid papulosis. Lymphomatoid papulosis is extremely rare in childhood. All published cases of lymphomatoid papulosis in children under 10 years of age are reviewed. The differential diagnosis of lymphomatoid papulosis in childhood includes arthropod assaults, pityriasis lichenoides et varioliformis acuta, primary cutaneous Hodgkin's disease, Ki-1 large cell anaplastic lymphoma and other lymphomas and pseudolymphomas in children.

[Acne necrotica (varioliformis). Necrotizing lymphocytic folliculitis]. / Acne necrotica (varioliformis). Nekrotisierende lymphozytäre Follikulitis.

We report on a 32-year-old woman with chronic relapsing papular and papulopustular lesions in the area of the hairlines and on the scalp. The diagnosis of acne necrotica (varioliformis) was made on the basis of the typical clinical picture and the histopathology, which showed necrotizing lymphocytic folliculitis. This rare disease must be differentiated from other pustular diseases of the scalp. Acne necrotica has been known as an entity since the beginning of the last century. In recent literature, however, it has received little attention.

Naming acquired melanocytic nevi. Common and dysplastic, normal and atypical, or Unna, Miescher, Spitz, and Clark?

Acquired melanocytic nevi are among the commonest neoplasms in man, yet classification of them has proven elusive and elucidation unsatisfactory. From "active junctional nevus" to "dysplastic nevus," the brains of clinicians and histopathologists have been boggled and the psyches and skin of patients have been served badly. This essay advocates eponymic designations for acquired melanocytic nevi, all of which are common, as the surest route to comprehensive classification of them.

[Dowling-Degos disease with exclusively genital manifestations]. / Morbus Dowling-Degos mit ausschliesslich genitaler Manifestation.

We report on two women with pigmented lesions of the vulva. The histopathology (filiform downgrowth of pigmented epithelial strands two to four cells wide, extending from the interfollicular epidermis and from follicular infundibula; no increased numbers of melanocytes; horn pseudocysts) was specific for Dowling-Degos disease. One patient also had acne inversa, and the other patient had been treated surgically for a pilonidal sinus some years before. The spectrum of conditions that should be considered in the differential diagnosis of genital pigmented lesions is discussed. Vulvar melanosis, genital lentigo, malignant melanoma, acanthosis nigricans maligna and benigna and syndromes occurring concomitantly with pigmentation of the mucosa need to be excluded. The association of Dowling-Degos disease with acne inversa, which was recently described for the first time, is discussed.

[Cutaneous apocrine mixed tumor with follicular differentiation]. / Apokriner kutaner Mischtumor mit follikulärer Differenzierung.

An 85-year-old man presented with a firm, papillomatous nodule on the upper lip, which had been growing slowly for 30 years. Histopathologic examination revealed an apocrine mixed tumour with follicular differentiation. Mixed tumours of the skin are rare benign neoplasms, which are composed of different tissue components, e.g. epithelial and glandular elements and myxoid or chondroid components. Mixed tumours with apocrine differentiation can be discriminated from mixed tumours with eccrine differentiation. Criteria for apocrine differentiation are: decapitation secretion, elongated gland-like and duct-like structures lined with two rows of epithelial cells and branching of tubular structures. Follicular structures are another clue to the apocrine differentiation of neoplasms. The designation mixed tumour is preferable to chondroid syringoma, because most mixed tumours show apocrine differentiation. The differential diagnosis of apocrine mixed tumour includes fibroadenoma, hidradenoma, mucinous adenocarcinoma, adenoid cystic carcinoma, and rare soft tissue tumours like the myxoid chondrosarcoma.

[Low dosage cyclosporin A therapy in pyoderma gangrenosum. Experiences with 6 patients]. / Niedrig dosierte Cyclosporin-A-Therapie bei Pyoderma gangraenosum. Erfahrungen bei 6 Patienten.

Pyoderma gangraenosum can cause great therapeutic problems. High dosed corticosteroids are the treatment of choice. However, recalcitrant pyoderma gangraenosum or side effects from corticosteroid treatment may require therapeutic alternatives. Pyoderma gangraenosum responds excellently to treatment with cyclosporine A. Because of side effects and drug interactions, the patients must be selected and carefully and closely monitored. Six patients with pyoderma gangraenosum, unresponsive to various topical and systemic therapies, were treated with oral cyclosporine A at mean daily doses of approximately 3 mg/kg. Marked improvement of the skin lesions and complete healing occurred in all patients over a period of 3-6 months. Only one patient suffered a relapse after discontinuation of the treatment. No severe irreversible side effects occurred. The results show that low-dose cyclosporine A treatment can be considered a first-line treatment of pyoderma gangraenosum.

[Case report of jellyfish injury]. / Fallstudie einer Quallenverletzung.

We are presenting a 47-year-old woman who was stung by jellyfish while bathing in the sea of Thailand. Immediately after the injury she developed sharp pain and urticarial erythema of the skin of the knees accompanied by muscle cramps of the entire body. After a few days a toxic contact dermatitis with edematous swelling and ulcerations developed, which did not respond to topical antibiotics or corticosteroids. Three weeks later the patient presented with a disseminated urticarial eruption, which at first responded well to topical treatment and systemic corticosteroids. Over the next few weeks, however, a relapse of the eruption and the ulcerations occurred. Raised titres of IgG and IgM antibodies against different jellyfish from the Indian and Pacific Ocean were detected in the patient's serum by the enzyme-linked immunosorbent assay. Antibodies against bees (class 1) and wasps (class 4) were found by the radioallergosorbent test. The clinical features and the immunological findings led to the diagnosis of toxic and allergic contact dermatitis to jellyfish venom. First aid and secondary treatment of jellyfish injuries are suggested.

Effect of vitamin D on growth cartilage cell proliferation in vitro.

Disturbed calcification of the growth plate and stunting is a frequent finding in vitamin D-deficiency rickets, vitamin D-dependency rickets and renal osteodystrophy, illustrating that chondrocytes are a target for vitamin D. This observation prompted an investigation of Ic, 25-dihydroxy vitamin D3 [1,25(OH)2D3] receptor expression and action of vitamin D metabolites on chondrocyte proliferation. In tibial growth plates and in primary cultures of tibial growth cartilage of male Sprague-Dawley rats (80 g) specific binding of [3H]-1,25(OH)2D3 was noted. Scatchard analysis revealed the presence of a single class of non-interacting binding sites. Kd was 10(-11) M irrespective of growth phase. The binding macromolecule had a sedimentation coefficient of 3.5 S. Interaction with DNA was demonstrated by DNA-cellulose affinity chromatography. By immunohistology, growth cartilage cells (rabbit tibia) were shown to express nuclear 1,25(OH)2D3 receptors, most prominently in the proliferative and early hypertrophic zone. This corresponds to binding data which showed highest binding of 1,25(OH)2D3 in the logarithmic growth phase (12,780 molecules/cell versus 4,538 molecules/cell in confluent cells) in primary cultures of growth plate chondrocytes. In the presence of delipidated fetal calf serum 1,25(OH)2D3 had a biphasic effect on cell proliferation and density, i.e. stimulation at 10(-12) M and dose-dependent inhibition at 10(-10) M and below. Inhibition was specific and not seen with 24 (R), 25-dihydroxy-vitamin D3 or dexamethasone. Growth phase-dependent 1,25(OH)2D3 receptor expression and specific effects of 1,25(OH)2D3 on chondrocyte proliferation in vitro point to a role for vitamin D in the homeostasis of growth cartilage of the rat.