The 10-nm chromatin fiber and its relationship to interphase chromosome organization.

A chromosome is a single long DNA molecule assembled along its length with nucleosomes and proteins. During interphase, a mammalian chromosome exists as a highly organized supramolecular globule in the nucleus. Here, we discuss new insights into how genomic DNA is packaged and organized within interphase chromosomes. Our emphasis is on the structural principles that underlie chromosome organization, with a particular focus on the intrinsic contributions of the 10-nm chromatin fiber, but not the regular 30-nm fiber. We hypothesize that the hierarchical globular organization of an interphase chromosome is fundamentally established by the self-interacting properties of a 10-nm zig-zag array of nucleosomes, while histone post-translational modifications, histone variants, and chromatin-associated proteins serve to mold generic chromatin domains into specific structural and functional entities.

The appearance of pili annulati following alopecia areata.

Pili annulati is a rare autosomal-dominant hair shaft abnormality. It is characterized by alternating light and dark bands along the shaft due to air-filled cavities within the cortex of the hair shaft. Alopecia areata has been previously described as a common association with pili annulati, with improvement in alopecia areata coinciding with resolution of pili annulati. We report the case of a patient with a history of alopecia areata and alopecia universalis who developed the characteristic banded hair of pili annulati upon resolution of her alopecia areata. We provide direct microscopic examination of postregrowth hairs compared to normal and cross-polarized light microscopy.

Methods and Strategies to Quantify Phase Separation of Disordered Proteins.

Phase separation has emerged as a new paradigm currently revolutionizing our understanding of cell biology and intracellular organization. Disordered protein domains have recently been demonstrated as integral drivers of phase separation into condensed liquids with emergent material properties. Using in vitro model systems employing purified protein components is necessary to interrogate the molecular mechanisms underlying phase separation; however, these systems pose many experimental challenges. In this chapter we describe general strategies for purifying, handling, imaging, and characterizing the phase behavior of disordered proteins. We further outline methods for the purification of the model P granule protein LAF-1, the construction of phase diagrams, and the quantification of liquid droplet fusion or coalescence.

Proliferating multicentric reticulohistiocytosis associated with papillary serous carcinoma of the endometrium.

Multicentric reticulohistiocytosis (MRH) is a rare histocytic disease characterized by destructive arthritis in association with classic skin findings. Although MRH is not strictly a paraneoplastic disease, one quarter of cases are malignancy related. We report a case of MRH with an initial remission followed by an acute exacerbation several years later heralding the clinical presentation of endometrial carcinoma. During this flareup a skin biopsy specimen revealed a diffuse dermal infiltrate composed of histiocytes with ground-glass cytoplasm and multiple atypical mitoses. Approximately 40% of the cells stained with the proliferation marker Ki-67. Treatment of endometrial carcinoma resulted in improvement of skin and joint symptoms, and a repeat biopsy specimen no longer demonstrated mitotic figures. These findings support a reactive and proliferative cause of MRH.

Effect of lysine to alanine mutations on the phosphate activation and BPTES inhibition of glutaminase.

The GLS1 gene encodes a mitochondrial glutaminase that is highly expressed in brain, kidney, small intestine and many transformed cells. Recent studies have identified multiple lysine residues in glutaminase that are sites of N-acetylation. Interestingly, these sites are located within either a loop segment that regulates access of glutamine to the active site or the dimer:dimer interface that participates in the phosphate-dependent oligomerization and activation of the enzyme. These two segments also contain the binding sites for bis-2[5-phenylacetamido-1,2,4-thiadiazol-2-yl]ethylsulfide (BPTES), a highly specific and potent uncompetitive inhibitor of this glutaminase. BPTES is also the lead compound for development of novel cancer chemotherapeutic agents. To provide a preliminary assessment of the potential effects of N-acetylation, the corresponding lysine to alanine mutations were constructed in the hGACΔ1 plasmid. The wild type and mutated proteins were purified by Ni(+)-affinity chromatography and their phosphate activation and BPTES inhibition profiles were analyzed. Two of the alanine substitutions in the loop segment (K311A and K328A) and the one in the dimer:dimer interface (K396A) form enzymes that require greater concentrations of phosphate to produce half-maximal activation and exhibit greater sensitivity to BPTES inhibition. By contrast, the K320A mutation results in a glutaminase that exhibits near maximal activity in the absence of phosphate and is not inhibited by BPTES. Thus, lysine N-acetylation may contribute to the acute regulation of glutaminase activity in various tissues and alter the efficacy of BPTES-type inhibitors.

Hollow latex particles: synthesis and applications.

One of the major developments in emulsion polymerization over the last two decades has been the ability to make hollow latex particles. This has contributed many fundamental insights into the synthesis and the development of structure in particles. Hollow latex particles also enhance the performance of industrial coatings and potentially are useful in other technologies such as microencapsulation and controlled release. Ever since the publication of the initial process patents describing these particles, there has been a global R&D effort to extend the synthetic techniques and applications. One prominent synthetic approach to hollow particles is based on osmotic swelling. This dominates the literature, and usually starts with the synthesis of a structured latex particle containing an ionizable core that is subsequently expanded with the addition of base. Fundamental to this approach are a sophisticated control of transport phenomena, chemical reactivity within the particle, and the thermoplastic properties of the polymer shell. Hydrocarbon encapsulation technology has also been employed to make hollow latex particles. One approach involves a dispersed ternary system that balances transport, conversion kinetics, and phase separation variables to achieve the hollow morphology. Other techniques, including the use of blowing agents, are also present in the literature. The broad range of approaches that affords particles with a hollow structure demonstrates the unique flexibility of the emulsion polymerization process.

Cytotoxic agents for use in dermatology . I

There are indications for the use of cytotoxic drugs in some dermatologic diseases. These drugs may be lifesaving for patients with diseases such as pemphigus, lymphomas, and vasculitis or they may merely offer an improved quality of life for patients who have diseases such as psoriasis, progressive systemic sclerosis, or sarcoidosis. In either set of circumstances, in the properly monitored patient cytotoxic drugs may be used safely and effectively, offering very few problems for the patient or the therapist. The dermatologist who is interested in offering his/her patients the best medical care possible will wish to become proficient in the use of cytotoxic drugs, just as he/she is proficient in the use of the tetracyclines, systemic corticosteroids, and other powerful, but useful, agents.