Extracellular truncations of h beta c, the common signaling subunit for interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), and IL-5, lead to ligand-independent activation

The hypothesis that extracellular truncation of the common receptor subunit for interleukin-3 (IL-3), granulocyte-macrophage colony- stimulating factor, and IL-5 (h beta c) can lead to ligand-independent activation was tested by infecting factor-dependent hematopoietic cell lines with retroviruses encoding truncated forms of h beta c. A truncation, resembling that in v-Mpl, and retaining 45 h beta c-derived extracellular residues, led to constitutive activation in the murine myeloid cell line, FDC-P1. However, infection of cells with retrovirus encoding a more severely truncated receptor, retaining only 7 h beta c- derived extracellular residues, did not confer factor independence on these cells. These experiments show that truncation activates the receptor and define a 37-amino acid segment of h beta c (H395-A431) which contains two motifs conserved throughout the cytokine receptor superfamily (consensus Y/H XX R/Q VR and WSXWS), as essential for factor-independent signaling. The mechanism of activation was also investigated in less severe truncations. A receptor that retains the entire membrane-proximal domain (domain 4) also conferred factor independent growth on FDC-P1 cells; however, a retrovirus encoding a truncated form of h beta c having two intact membrane proximal domains did not have this ability, suggesting that domain 3 may have an inhibitory role in h beta c. The ability of these receptors to confer factor independence was cell specific as demonstrated by their inability to confer factor-independent growth when introduced into the murine IL-3-dependent pro-B cell line BaF-B03. These results are consistent with a model in which activation requires unmasking of an interactive receptor surface in domain 4 and association with a myeloid- specific receptor or accessory component. We suggest that in the absence of ligand intramolecular interactions prevent inappropriate signaling.     

ATP potentiates neurotransmission in the rat trigeminal subnucleus caudalis

Ionotropic purine receptors (P2X) have been implicated in nociceptive neurotransmission. In this study, we examine the actions of the P2X receptor agonist alpha,beta methylene adenosine 5'-triphosphate on excitatory neurotransmission in neurons in the deep and superficial laminae of the trigeminal spinal subnucleus caudalis (Vc), which receives nociceptive inputs from the craniofacial region. Alpha, beta methylene adenosine 5'-triphosphate caused an increase in spontaneous excitatory neurotransmission (miniature excitatory postsynaptic currents) in neurons in deep but not superficial laminae of Vc; this effect could be inhibited by the P2X receptor antagonist 2,3-O-2,4,6-trinitrophenyl-ATP. Conversely, the TRPV1 agonist capsaicin caused an increase in miniature excitatory postsynaptic currents in neurons in the superficial but not deep laminae. These data suggest that alpha,beta methylene adenosine 5'-triphosphate acts on presynaptic terminals to increase glutamatergic neurotransmission in deep Vc neurons.     

Clinical Outcomes Associated With Chronic Antimicrobial Suppression Therapy in Patients With Continuous‐Flow Left Ventricular Assist Devices

This retrospective cohort study evaluates the effect of chronic antimicrobial suppression (CAS) therapy on clinical outcomes in patients with continuous‐flow left ventricular assist devices (CF‐LVADs) and a history of device‐related infection. Patients with CF‐LVAD implantation between January 2008 and August 2011 who received systemic CAS after index antibiotic treatment of a device‐related infection were included. Chronic suppression was defined as continuation of antibiotics for longer than 6 weeks after the index infection. Standard International Society for Heart and Lung Transplantation definitions were used. The primary outcome is failure of CAS, defined as a clinical deterioration resulting in the need for transition from oral to intravenous (IV) therapy or a need to change to a different IV antibiotic, elevation to status 1A on the transplant list as a result of ongoing infection, or device/driveline exchange. Of 140 patients screened, 16 patients were included (69% male, 63% African American, median age 52 years). The driveline was the most common site of infection (69%). Organisms isolated included Gram‐positive cocci (n = 7), Gram‐negative bacilli (n = 10), and Candida (n = 1). Oral trimethoprim/sulfamethoxazole treatment was most commonly used for suppression (37.5%). Failure of CAS occurred in 5/16 (31%) patients after a mean time of 175 days on therapy (range 10–598). The majority of failures (60%) required device exchanges. Side effects of nausea, vomiting, or diarrhea were reported in three patients; all required changes in oral suppression regimen. Clostridium difficile infection was noted in two patients. These results, which must be confirmed by a larger analysis, suggest that one‐third of CF‐LVAD patients may develop recurrent infections while on CAS therapy.     

Effect of Intrathecal Baclofen Concentration on Spasticity Control: Case Series

Background/Objective: Intrathecal baclofen (ITB) has been shown to be an effective treatment for severe spasticity of spinal or cerebral origin. Although most patients respond well to an ITB trial, there are often difficulties in achieving and/or maintaining such effectiveness with ITB pump treatment. There are few published guidelines for dosing efficacy and no studies looking at the effect of concentration of ITB on spasticity management.

Methods: Case series of 3 adults with severe spasticity treated with ITB pump: a 44-year-old man with C7 tetraplegia using a 40-mL Medtronic SynchroMed II pump with 500-μg/mL concentration; a 35-year-old woman with traumatic brain injury with right spastic hemiplegia using a 18-mL Medtronic SynchroMed EL pump with 2,000-μg/mL concentration; and a 43-year-old woman with spastic diplegic cerebral palsy using a 40-mL Medtronic SynchroMed II pump with 2,000-μg/mL concentration.

Results: After reducing ITB concentrations in the pump, either as part of a standard protocol for dye study to assess the integrity of pump and catheter system or secondary to plateau in therapeutic efficacy, patients experienced temporary, significant reduction in spasticity based on range of motion, Modified Ashworth scores, and verbal feedback.

Conclusions: Decreasing the concentration of ITB seems to affect spasticity control. Further research in this area is needed for those patients with refractory spasticity to optimize efficacy of ITB therapy.     

Monoclonal antibodies to human platelet glycoprotein IIb beta that initiate distinct platelet responses

Hybridomas secreting monoclonal antibodies (MoAbs) to human platelet membrane glycoprotein IIb (GPIIb) were prepared by fusing cells of a mouse myeloma line to spleen cells from a BALB/c mouse immunized with purified GPIIb. Six of the hybridomas secreted MoAbs that recognized epitopes on the 23,000-dalton, disulfide-linked subunit of GPIIb, GPIIb beta. All six of these MoAbs agglutinated platelets in the absence of calcium. The agglutination titers of three of the MoAbs, however, were enhanced between 2 and 6 log2 dilutions when titrated in the presence of mmol/L of calcium. The enhancement in titer was the result of MoAb- induced platelet activation followed by platelet aggregation, a reaction that could also be initiated by the monovalent Fab fragments prepared from one of the MoAbs. The MoAbs did not significantly agglutinate platelets from patients with Glanzmann's thrombasthenia, confirming biochemical evidence that there is a paucity of GPIIb beta in the membranes of these cells. Our results show that MoAbs to epitopes on GPIIb beta initiate distinct platelet responses; therefore, they should be useful for studying the ways in which regions of surface glycoproteins are involved in platelet-platelet interactions. In addition, these reagents may prove of value in diagnosing and typing patients with Glanzmann's thrombasthenia.     

Breast Surgery Outcomes as Quality Measures According to the NSQIP Database

Background

The National Surgical Quality Improvement Program (NSQIP) is a risk-adjusted database designed to benchmark quality initiatives. NSQIP captures uniform morbidity variables for all operations and calculates expected morbidity probabilities. Given the frequent need for reoperation following breast-conserving surgery (BCS) and mastectomy, we hypothesized that NSQIP may inaccurately reflect surgical morbidity after breast cancer operations.

Methods

Using the 2008 NSQIP database, we identified 24,447 breast surgery patients. We calculated the observed versus expected (O/E) morbidity ratios, compared them to other general surgery procedures, and analyzed the O/E morbidity ratios among benign and malignant breast diagnoses.

Results

The NSQIP database shows that breast surgery has an O/E morbidity ratio of 3.11, which is higher than other general surgery procedures. Additionally, breast operations for malignancy have higher O/E morbidity ratios (3.22) than those performed for benign disease (2.59). Analysis of malignant patients by CPT code revealed that BCS patients had an O/E morbidity ratio of 7.75 and attributed 89?% of morbidity to reoperation, whereas mastectomy patients had an O/E morbidity ratio of only 1.7. Elimination of the reoperation variable from morbidity calculations in breast surgery reduces the O/E morbidity ratio to less than expected in all breast procedures.

Discussion

Breast surgery has a higher O/E morbidity ratio than other general surgery procedures. Reoperations are expected in BCS for positive margins and in mastectomy for completion ALND. Breast surgeons should advocate for benchmarking by surgical site-specific metrics, because current NSQIP criteria may negatively affect the quality assessment of high-volume breast centers.     

Robot-Assisted Transaxillary Thyroid Surgery in the United States: Is it Comparable to Open Thyroid Lobectomy?

Background  

The purpose of this study was to compare the outcome of robot-assisted transaxillary thyroid surgery (RATS) to the standard open technique for thyroid lobectomy in the U.S. population.