Sparse and incomplete factorial matrices to screen membrane protein 2D crystallization.

Electron crystallography is well suited for studying the structure of membrane proteins in their native lipid bilayer environment. This technique relies on electron cryomicroscopy of two-dimensional (2D) crystals, grown generally by reconstitution of purified membrane proteins into proteoliposomes under conditions favoring the formation of well-ordered lattices. Growing these crystals presents one of the major hurdles in the application of this technique. To identify conditions favoring crystallization a wide range of factors that can lead to a vast matrix of possible reagent combinations must be screened. However, in 2D crystallization these factors have traditionally been surveyed in a relatively limited fashion. To address this problem we carried out a detailed analysis of published 2D crystallization conditions for 12 ß-barrel and 138 α-helical membrane proteins. From this analysis we identified the most successful conditions and applied them in the design of new sparse and incomplete factorial matrices to screen membrane protein 2D crystallization. Using these matrices we have run 19 crystallization screens for 16 different membrane proteins totaling over 1300 individual crystallization conditions. Six membrane proteins have yielded diffracting 2D crystals suitable for structure determination, indicating that these new matrices show promise to accelerate the success rate of membrane protein 2D crystallization.

Dermatofibroma con células granulares: a propósito de un caso y revisión de la literatura / Granular cell dermatofibroma: a case report and review of the literature

PResentamos un caso de dermatofibroma epitelioide rico en células granulares. Solamente se han descrito 11 casos de dermatofibroma de células granulares, de los cuales sólo tres tienen rasgos epitelioides. Es importante reconocer este subtipo de dermatofibroma, ya que puede confundirse con un gran número de procesos benignos o malignos, de diferente aplicación pronóstica y terapeútica (AU)

Fingertip tophi without gouty arthritis.

We report 2 patients without a history of acute gouty arthritis showing tophi located only on the fingertips, an unusual location. A review of the literature found a few similar reports; these patients might represent a subgroup of gout characterized by: (1) elderly patients, from the 7th to 9th decades; (2) hyperuricemia; (3) absence of a history of acute gouty arthritis; (4) tophi in the fingertips or fingerpads; (5) chronic renal failure, and (6) all taking drugs or suffering from a disease that affects urate renal excretion.

Multiple epidermoid cysts in a renal transplant recipient taking cyclosporine A.

A forty-two-year-old male recipient of a cadaver renal transplant showed multiple nodulocystic lesions on his back and lateral aspects of his neck four months after beginning immunosuppressive therapy with cyclosporine A and prednisone. Results of histopathologic studies revealed that they were epidermoid infundibular cysts. We note the relationship between this clinical appearance and cyclosporine A, as well as this agent's cutaneous side effects.

An unusual benign neural tumour with stellate-cell morphology.

We report a stellate-cell dermal tumour which was studied by immunohistochemistry and electron microscopy. The stellate morphology of the tumour cells appeared to be due to retraction of their cytoplasm resulting in the emergence of intercellular spaces. Results of the immunohistochemical investigations were consistent with a neural tumour, but we could not assign it to any particular category of the known neural tumours. Therefore we have designated this tumour as an unusual, benign, neural-tumour with stellate-cell morphology.

Epidermotropic metastases from internal carcinomas.

Four cases of epidermotropically metastatic carcinoma are reported. One of them originated from a breast adenocarcinoma; in two other cases, the primary tumor was located in the large intestine; and, in the fourth case, the primary malignancy was a laryngeal squamous cell carcinoma. Clinically, the cutaneous metastases were nodular lesions and histologically, in addition to the involvement of the dermis by malignant cells, in three cases there was intraepidermal involvement by glandular structures. In the fourth case, the cutaneous metastatic tumor cells showed striking "folliculotropism." We review the literature of epidermotropically metastatic carcinoma and discuss its differential diagnosis.

Multinodular hemosiderotic dermatofibroma.

We describe a patient who developed a pigmented plaque on the anterior aspect of his right knee clinically mimicking angiokeratoma circumscriptum or malignant melanoma. Histopathological examination demonstrated a multinodular hemosiderotic dermatofibroma in which the cellular tumor islands were separated by areas of hyalinized collagen. Multinucleated giant tumor cells were found in the lumen of a medium-size vein underlying the tumor. The differential diagnosis of angiomatoid malignant fibrous histiocytoma, a tumor with clinical and morphologic similarities, is discussed.