The E. coli CsgB nucleator of curli assembles to β-sheet oligomers that alter the CsgA fibrillization mechanism

Curli are extracellular proteinaceous functional amyloid aggregates produced by Escherichia coli, Salmonella spp., and other enteric bacteria. Curli mediate host cell adhesion and invasion and play a critical role in biofilm formation. Curli filaments consist of CsgA, the major subunit, and CsgB, the minor subunit. In vitro, purified CsgA and CsgB exhibit intrinsically disordered properties, and both are capable of forming amyloid fibers similar in morphology to those formed in vivo. However, in vivo, CsgA alone cannot form curli fibers, and CsgB is required for filament growth. Thus, we studied the aggregation of CsgA and CsgB both alone and together in vitro to investigate the different roles of CsgA and CsgB in curli formation. We found that though CsgA and CsgB individually are able to self-associate to form aggregates/fibrils, they do so using different mechanisms and with different kinetic behavior. CsgB rapidly forms structured oligomers, whereas CsgA aggregation is slower and appears to proceed through large amorphous aggregates before forming filaments. Substoichiometric concentrations of CsgB induce a change in the mechanism of CsgA aggregation from that of forming amorphous aggregates to that of structured intermediates similar to those of CsgB alone. Oligomeric CsgB accelerated the aggregation of CsgA, in contrast to monomeric CsgB, which had no effect. The structured β-strand oligomers formed by CsgB serve as nucleators for CsgA aggregation. These results provide insights into the formation of curli in vivo, especially the nucleator function of CsgB.     

The geriatric amputee

There are special aspects of aging with an amputation and with being elderly at the time of an amputation. Older adults who have undergone amputation have many issues to contend with, including comorbidities that affect postoperative care and rehabilitation, general deconditioning and loss of mobility (especially if the onset of rehabilitation is delayed), and lack of social support upon returning to the community. These problems are compounded by a lack of knowledge about caring for the residual limb and prosthesis, maintenance of general health, and management of comorbid conditions. People who have sustained an amputation at an early age and who are ambulatory may find increasing difficulties as they age. Acquired chronic disease occurs more frequently as people age. These conditions can adversely affect function after amputation. Prosthetic designs may need modification because certain components may become more difficult to use. The prevention of a (second) amputation results in saving a limb and preserving self-image and independent function. Considering the emotional and economic cost of amputation and lifelong management of a prosthesis, it is worth the time and effort to practice preventive measures. Should amputation become necessary, careful patient assessment, compassionate management, and communication among the team members results in a more favorable outcome. Including the physiatrist early in the clinical course makes this process easier.     

PHACE syndrome with intracerebral hemangiomas, heterotopia, and endocrine dysfunction

PHACE is an acronym to describe the association of posterior fossa brain malformations, hemangiomas, arterial anomalies, coarctation of the aorta, cardiac defects, and eye abnormalities. More than 200 cases have been reported. The present report presents the cases of two female infants with PHACE syndrome, both of whom had additional congenital defects of subependymal gray matter heterotopia, craniofacial arterial anomalies, and pituitary dysfunction. One had an extensive segmental facial hemangioma with ipsilateral intracranial hemangiomas. The other had multiple cutaneous hemangiomas, but no segmental facial hemangioma. These two cases suggest a further expansion of the spectrum of PHACE to include other forms of disordered cerebral development and endocrine dysfunction.     

Aspirin Therapy in Venous Malformation: A Retrospective Cohort Study of Benefits,Side Effects,and Patient Experiences

Venous malformations (VMs) are often painful and may enlarge over time. Chronic coagulopathy is common in VMs and may contribute to phleboliths and potentially to disease progression. Few studies have examined the effects of anticoagulation on VMs and to our knowledge none have examined the use of aspirin therapy. A survey was administered to patients and parents of patients with VMs who attended the University of California at San Francisco Vascular Anomalies Center over a 4‐year period (2008–2012) to whom aspirin had been recommended. They were surveyed regarding whether they were taking aspirin and, if yes, whether aspirin had resulted in any appreciable benefit. Sixty‐five letters were sent to potential subjects: 38 participated and 27 declined to participate or could not be contacted. Twenty‐eight of the 38 had begun aspirin and 22 reported current use. Seventeen reported some benefit, including less aching (n = 2), less shooting pain (n = 15), less fullness and swelling (n = 13), and shrinking of the VM (n = 1). Discontinuation of aspirin was associated with worsening VM symptoms in five of six patients. Side effects were reported in 6 of 28 patients, including five episodes of minor bleeding or excessive bruising and one of nausea and vomiting. This study suggests that aspirin may be a beneficial treatment for VM, with a reduction in pain and soft tissue swelling and an acceptable side‐effect profile, but the retrospective nature of the study and the small size of the cohort limited our conclusions. Larger prospective studies of aspirin for VM using clinical and laboratory outcome measures are needed to confirm these observations.     

Role of Sirolimus in Advanced Kaposiform Hemangioendothelioma

Kaposiform hemangioendothelioma (KHE) is an infiltrative vascular tumor that classically presents in infancy. Management typically focuses on treating Kasabach–Merritt phenomenon (KMP), a disorder of severe and at times life‐threatening platelet trapping. However, the morbidity of KHE extends beyond KMP. The infiltrative nature of the tumor can lead to long‐term disability and often makes complete surgical resection impossible. We report the case of a 10‐year‐old boy with a KHE of his right distal thigh who was unable to walk without assistance due to fibrotic change and right knee contracture. He had no laboratory evidence of KMP at the time of representation. Rapamycin was started in hopes of reducing the tumor burden. Within 2 months of therapy, fibrotic areas softened, his contracture nearly resolved, and there was marked improvement in his mobility. Rapamycin has been previously reported to be effective in managing cases of KHE complicated by KMP. Our report emphasizes the role for rapamycin in the treatment of KHE in the absence of KMP through the inhibition of vasculogenesis and fibrotic pathways.     

Vascular birthmarks of infancy: resolving nosologic confusion

The terminology describing congenital vascular birthmarks has been a source of confusion in the medical literature. Mulliken and Glowacki [1982: Plas. Recons. Surg. 69:412-422] published a biologic classification system which has become the most widely accepted framework for classifying vascular birthmarks and is accepted as the official classification schema by the International Society for the Study of Vascular Anomalies (ISSVA). In this study, we evaluate the current nosology of vascular birthmarks used in standard medical genetics reference texts compared with the accepted Mulliken ISSVA framework. In five sources examined, a variety of terms were used to describe congenital vascular anomalies. The degree of agreement with accepted ISSVA classification varied both within and among texts, with agreement as low as 22% and as high as 75%. In all texts, hemangioma was the most commonly used term, appearing 79 times. Use of the term "hemangioma" had the lowest rate of agreement with the ISSVA classification criteria, with agreement in 23% of citations. The terms "vascular malformation" and "port-wine stain" were used less frequently, but with a much higher degree of agreement with the ISSVA classification: 82% and 66%, respectively. These results establish that nosologic confusion is widespread even in standard genetic reference texts. In particular, the term "hemangioma" is used imprecisely. The ISSVA classification system provides an extremely useful framework for geneticists to classify vascular birthmarks in their evaluation of infants and children with vascular anomalies in order to provide more accurate evaluation, prognosis, and genetic counseling.     

Kinetics of peripheral blood mononuclear cell mobilization with chemotherapy and/or granulocyte-colony-stimulating factor: implications for yield of hematopoietic progenitor cell collections

BACKGROUND: Peripheral blood progenitor cells (PBPCs) are commonly collected and used to reconstitute hematopoiesis after high-dose chemotherapy. However, strategies for optimal collection and assessment of leukapheresis components are not standardized. STUDY DESIGN and METHODS: Hematopoietic progenitor cell assays were performed on 369 leukapheresis components collected from 95 patients who had received doxorubicin-based chemotherapy and/or granulocyte-colony-stimulating factor (G-CSF). Precollection patient hematologic values, leukapheresis collection values, component hematopoietic progenitor cell assays, and patient outcome measures were summarized. The kinetics of mononuclear cell (MNC) and PBPC mobilization were assessed among four patient groups. RESULTS: Patient group was a significant predictor of the peripheral blood MNC count on the day of collection (p<0.0001), and that value was a significant predictor of granulocyte-macrophage– colony-forming unit (CFU-GM) yield (p<0.0001). This relationship between the peripheral blood MNC count on the day of collection and CFU- GM yield differed according to patient group (p<0.0001). CFU-GM made up a larger fraction of peripheral blood MNCs collected from patients who received chemotherapy plus G-CSF than collected from those who received G-CSF alone. Moreover, the peripheral blood MNC count and the corresponding CFU-GM yield increased significantly on consecutive days of collection in patient groups receiving chemotherapy and G-CSF but were unchanged or decreased in patients receiving G-CSF alone. CONCLUSION: The relationship between peripheral blood MNC count and leukapheresis component CFU-GM yield differed significantly between patients who received chemotherapy and G-CSF and those who received G- CSF alone for the mobilization of PBPCs. Patient peripheral blood MNC count and component CFU-GM yield are useful for both assessing and suggesting revisions to PBPC mobilization and collection strategies.