Ecthyma gangrenosum secondary to Staphylococcus aureus in an infant with transient neutropenia.

Ecthyma gangrenosum is classically a cutaneous manifestation of a pseudomonal septicemia that presents in a patient with an immunodeficiency or hematologic malignancy. We describe a previously healthy 8-month-old girl who developed transient neutropenia and characteristic ecthyma gangrenosum lesions secondary to methicillin-resistant Staphylococcus aureus. This unique presentation of methicillin-resistant Staphylococcus aureus ecthyma gangrenosum emphasizes the importance of broad empiric coverage and early culturing for microorganism and susceptibilities in any patient presenting with ecthyma gangrenosum.

Basal body duplication and maintenance require one member of the Tetrahymena thermophila centrin gene family.

Centrins, small calcium binding EF-hand proteins, function in the duplication of a variety of microtubule organizing centers. These include centrioles in humans, basal bodies in green algae, and spindle pole bodies in yeast. The ciliate Tetrahymena thermophila contains at least four centrin genes as determined by sequence homology, and these have distinct localization and expression patterns. CEN1's role at the basal body was examined more closely. The Cen1 protein localizes primarily to two locations: one is the site at the base of the basal body where duplication is initiated. The other is the transition zone between the basal body and axoneme. CEN1 is an essential gene, the deletion of which results in the loss of basal bodies, which is likely due to defects in both basal body duplication and basal body maintenance. Analysis of the three other centrins indicates that two of them function at microtubule-rich structures unique to ciliates, whereas the fourth is not expressed under conditions examined in this study, although when artificially expressed it localizes to basal bodies. This study provides evidence that in addition to its previously known function in the duplication of basal bodies, centrin is also important for the integrity of these organelles.

CD4+/CD56+ Hematodermic neoplasm (plasmacytoid dendritic cell tumor).

A 60-year-old male presented with multiple, purplish-red, nodules and plaques. After a complete work-up, he was diagnosed with CD4+/CD56+ hematodermic neoplasm. We review the clinical, pathological, and immunohistochemical features of this disease. CD4+/CD56+ hematodermic neoplasm, which is also known as blastic natural killer-cell lymphoma, is a rare, aggressive neoplasm with a strong predilection for skin involvement.

Kinetic characterization of wild-type and proton transfer-impaired variants of beta-carbonic anhydrase from Arabidopsis thaliana.

We have cloned and overexpressed a truncated, recombinant form of beta-carbonic anhydrase from Arabidopsis thaliana. The wild-type enzyme and two site-directed variants, H216N and Y212F, have been kinetically characterized both at steady state by stopped-flow spectrophotometry and at chemical equilibrium by (18)O isotope exchange methods. The wild-type enzyme has a maximal k(cat) for CO2 hydration of 320 ms(-1) and is rate limited by proton transfer involving two residues with apparent pK(a) values of 6.0 and 8.7. The mutant enzyme H216N has a maximal k(cat) at high pH that is 43% that of wild type, but is only 5% that of wild type at pH 7.0. (18)O exchange studies reveal that the effect of the mutations H216N or Y212F is primarily on proton transfer steps in the catalytic mechanism and not in the rate of CO2-HCO3- exchange. These results suggest that residues His-216 and Tyr-212 are both important for efficient proton transfer in A. thaliana carbonic anhydrase.

Tyrosine-sulfated peptides functionally reconstitute a CCR5 variant lacking a critical amino-terminal region.

Entry of most primary human immunodeficiency virus, type 1 (HIV-1) isolates into their target cells requires the cellular receptor CD4 and the G protein-coupled chemokine coreceptor CCR5. An acidic, tyrosine-rich, and tyrosine-sulfated domain of the CCR5 amino terminus plays a critical role in the ability of CCR5 to serve as an HIV-1 coreceptor, and tyrosine-sulfated peptides based on this region physically associate with the HIV-1 envelope glycoprotein gp120 and slow HIV-1 entry into CCR5-expressing cells. Here we show that the same tyrosine-sulfated peptides, but not their unsulfated analogs, can restore the HIV-1 coreceptor activity of a CCR5 variant lacking residues 2-17 of its amino terminus. Additionally, these sulfated peptides restored the ability of this CCR5 variant to mobilize calcium in response to the chemokines macrophage inflammatory factors 1alpha and 1beta. These observations show that a tyrosine-sulfated region of the CCR5 amino terminus can function independently to mediate association of chemokines and the HIV-1 envelope glycoprotein with the remaining domains of CCR5.