Differential Mobility Spectrometry of Ketones in Air at Extreme Levels of Moisture

The performance of a differential mobility spectrometer was characterized at ambient pressure and ten values of water vapor concentration, from 1.0 × 102 to 1.7 × 104 ppm using a homologous series of seven ketones from acetone to 2-dodecanone. Dispersion plots at 30 °C with separation fields from 35 to 123 Td exhibited increased alpha functions for the hydrated proton, protonated monomers, and proton bound dimers with increased moisture levels. Increases in the level of moisture were accompanied by decreased quantitative response with progressive suppression in the formation of the proton bound dimer first and then protonated monomer. Product ions for 2-octanone at 7 ppb were not observed above a moisture level of 4.0 × 103 ppm, establishing a limit for observation of analyte ion formation. The observation limit increased from 1.1 × 103 ppm for acetone to 5.7 × 103 ppm for 2-dodecanone. These findings demonstrate that ketones can be determined with a differential mobility spectrometry (DMS) analyzer near room temperature in the presence of elevated levels of moisture expected with the use of membrane inlets or headspace sampling of surface or ground waters. Moisture levels entering this DMS analyzer employed as an environmental monitor should be kept at 1.0 × 103 ppm or below and quantitative studies for individual ketones should be made at a fixed moisture level.

Addicted to sugar: roles of glycans in the order Mononegavirales

Glycosylation is a biologically important protein modification process by which a carbohydrate chain is enzymatically added to a protein at a specific amino acid residue. This process plays roles in many cellular functions, including intracellular trafficking, cell-cell signaling, protein folding and receptor binding. While glycosylation is a common host cell process, it is utilized by many pathogens as well. Protein glycosylation is widely employed by viruses for both host invasion and evasion of host immune responses. Thus better understanding of viral glycosylation functions has potential applications for improved antiviral therapeutic and vaccine development. Here, we summarize our current knowledge on the broad biological functions of glycans for the Mononegavirales, an order of enveloped negative-sense single-stranded RNA viruses of high medical importance that includes Ebola, rabies, measles and Nipah viruses. We discuss glycobiological findings by genera in alphabetical order within each of eight Mononegavirales families, namely, the bornaviruses, filoviruses, mymonaviruses, nyamiviruses, paramyxoviruses, pneumoviruses, rhabdoviruses and sunviruses.

Population Pharmacokinetic/Pharmacodynamic Modeling of Tumor Size Dynamics in Pembrolizumab-Treated Advanced Melanoma

Pembrolizumab is a potent immune‐modulating antibody active in advanced melanoma, as demonstrated in the KEYNOTE‐001, ‐002, and ‐006 studies. Longitudinal tumor size modeling was pursued to quantify exposure‐response relationships for efficacy. A mixture model was first developed based on an initial dataset from KEYNOTE‐001 to describe four patterns of tumor growth and shrinkage. For subsequent analyses, tumor size measurements were adequately described by a single consolidated model structure that captured continuous tumor size with a combination of growth and regression terms, as well as a fraction of tumor responsive to therapy. This revised model structure provided a framework to efficiently evaluate the impact of covariates and pembrolizumab exposure. Both models indicated that exposure to the drug was not a significant predictor of tumor size response, demonstrating that the dose range evaluated (2 and 10 mg/kg every 3 weeks) is likely near or at the plateau of maximal response.

Disease Systems Analysis of Bone Mineral Density and Bone Turnover Markers in Response to Alendronate, Placebo, and Washout in Postmenopausal Women

A previously established mechanism-based disease systems model for osteoporosis that is based on a mathematically reduced version of a model describing the interactions between osteoclast (bone removing) and osteoblast (bone forming) cells in bone remodeling has been applied to clinical data from women (n = 1,379) receiving different doses and treatment regimens of alendronate, placebo, and washout. The changes in the biomarkers, plasma bone-specific alkaline phosphatase activity (BSAP), urinary N-telopeptide (NTX), lumbar spine bone mineral density (BMD), and total hip BMD, were linked to the underlying mechanistic core of the model. The final model gave an accurate description of all four biomarkers for the different treatments. Simulations were used to visualize the dynamics of the underlying network and the natural disease progression upon alendronate treatment and discontinuation. These results complement the previous applications of this mechanism-based disease systems model to data from various treatments for osteoporosis.

Model-Based Characterization of the Pharmacokinetics of Pembrolizumab: A Humanized Anti-PD-1 Monoclonal Antibody in Advanced Solid Tumors

Pembrolizumab, a potent antibody against programmed death 1 (PD-1) receptor, has shown robust antitumor activity and manageable safety in patients with advanced solid tumors. Its pharmacokinetic (PK) properties were analyzed with population PK modeling using pooled data from the KEYNOTE-001, -002, and -006 studies of patients with advanced melanoma, non-small cell lung cancer (NSCLC), and other solid tumor types. Pembrolizumab clearance was low and the volume of distribution small, as is typical for therapeutic antibodies. Identified effects of sex, baseline Eastern Cooperative Oncology Group performance status, measures of renal and hepatic function, tumor type and burden, and prior ipilimumab treatment on pembrolizumab exposure were modest and lacked clinical significance. Furthermore, simulations demonstrated the model has robust power to detect clinically relevant covariate effects on clearance. These results support the use of the approved pembrolizumab dose of 2 mg/kg every 3 weeks without dose adjustment in a variety of patient subpopulations.

Multiple Novel Functions of Henipavirus O-glycans: The First O-glycan Functions Identified in the Paramyxovirus Family

O-linked glycosylation is a ubiquitous protein modification in organisms belonging to several kingdoms. Both microbial and host protein glycans are used by many pathogens for host invasion and immune evasion, yet little is known about the roles of O-glycans in viral pathogenesis. Reportedly, there is no single function attributed to O-glycans for the significant paramyxovirus family. The paramyxovirus family includes many important pathogens, such as measles, mumps, parainfluenza, metapneumo- and the deadly Henipaviruses Nipah (NiV) and Hendra (HeV) viruses. Paramyxoviral cell entry requires the coordinated actions of two viral membrane glycoproteins: the attachment (HN/H/G) and fusion (F) glycoproteins. O-glycan sites in HeV G were recently identified, facilitating use of the attachment protein of this deadly paramyxovirus as a model to study O-glycan functions. We mutated the identified HeV G O-glycosylation sites and found mutants with altered cell-cell fusion, G conformation, G/F association, viral entry in a pseudotyped viral system, and, quite unexpectedly, pseudotyped viral F protein incorporation and processing phenotypes. These are all important functions of viral glycoproteins. These phenotypes were broadly conserved for equivalent NiV mutants. Thus our results identify multiple novel and pathologically important functions of paramyxoviral O-glycans, paving the way to study O-glycan functions in other paramyxoviruses and enveloped viruses.

Glycosylation is a protein modification process that occurs inside cells, in which specific types of sugars (glycans) are added to certain amino acids in some proteins. Glycosylation happens for many organisms, from microbes to mammals, including many pathogens. Altered glycosylation is increasingly being associated with auto-immune diseases and cancer, highlighting the need to better understand glycosylation. There are two types of sugars added during the glycosylation process: N-glycans and O-glycans. While the roles of N-glycans have been extensively reported for many organisms, the roles of O-glycans remain largely unknown, particularly for viruses. The paramyxoviruses are a medically important family of viruses that include the highly lethal Hendra (HeV) and Nipah (NiV) viruses. Viral entry into host cells and spread from cell to cell relies on two viral proteins: G and F. Here we mutated known O-glycan locations in the HeV and NiV G proteins. Loss of O-glycans affected several viral processes crucial to viral entry and spread from cell to cell. Our results are the first reported functions for paramyxoviral O-glycans, contributing to the field of viral entry and spread, and helping pave the way for future functional studies in other pathogens.

Application of a Systems Pharmacology-Based Placebo Population Model to Analyze Long-Term Data of Postmenopausal Osteoporosis

Osteoporosis is a progressive bone disease characterized by decreased bone mass resulting in increased fracture risk. The objective of this investigation was to test whether a recently developed disease systems analysis model for osteoporosis could describe disease progression in a placebo-treated population from the Early Postmenopausal Intervention Cohort (EPIC) study. First, we qualified the model using a subset from the placebo arm of the EPIC study of 222 women who had similar demographic characteristics as the 149 women from the placebo arm of the original population. Second, we applied the model to all 470 women. Bone mineral density (BMD) dynamics were changed to an indirect response model to describe lumbar spine and total hip BMD in this second population. This updated disease systems analysis placebo model describes the dynamics of all biomarkers in the corresponding datasets to a very good approximation; a good description of an individual placebo response will be valuable for evaluating treatments for osteoporosis.

(De)synchronization of advanced visual information and ball flight characteristics constrains emergent information-movement couplings during one-handed catching

Advance visual information of a projection action and ball flight information is important for organizing dynamic interceptive actions like catching. However, how the central nervous system (CNS) manages the relationship between advance visual information and emerging ball flight information in regulating behavior is less well understood. Here, we sought to examine the extent that advance visual information to the CNS constrains regulation of catching actions by synchronizing and desynchronizing its relationship with ball trajectory characteristics. Novel technology was used to present video footage of an actor throwing a ball at three different speeds, integrated with information from a real ball projected by a machine set to the three speeds. The technology enabled three synchronized and six desynchronized conditions between advance visual information and subsequent ball flight trajectories. Catching performance, kinematic data from the catching hand and gaze behaviors were recorded. Findings revealed that desynchronization of video images of ball projection shaped emergent catching behaviors. Footage of slower throws, paired with faster ball projection speeds, caused catching performance decrements. Timing in early phases of action was organized by the CNS to match the advance visual information presented. In later phases, like the grasp, ball flight information constraints adapted and regulated behaviors. Gaze behaviors showed increased ball projection speed resulted in participants tracking the ball for a smaller percentage of ball flight. Findings highlighted the role of the two visual systems in perception and action, implicating the importance of coupling advanced visual information and ball flight to regulate emergent movement coordination tendencies during interceptive behaviors.

Implementation of quantitative and systems pharmacology in large pharma

Quantitative and systems pharmacology concepts and tools are the foundation of the model-informed drug development paradigm at Merck for integrating knowledge, enabling decisions, and enhancing submissions. Rigorous prioritization of modeling and simulation activities has enabled key drug development decisions and led to a high return on investment through significant cost avoidance. Critical factors for the successful implementation, examples on impact on decision making with associated return of investment, and drivers for continued success are discussed.

Unraveling a three-step spatiotemporal mechanism of triggering of receptor-induced Nipah virus fusion and cell entry

Membrane fusion is essential for entry of the biomedically-important paramyxoviruses into their host cells (viral-cell fusion), and for syncytia formation (cell-cell fusion), often induced by paramyxoviral infections [e.g. those of the deadly Nipah virus (NiV)]. For most paramyxoviruses, membrane fusion requires two viral glycoproteins. Upon receptor binding, the attachment glycoprotein (HN/H/G) triggers the fusion glycoprotein (F) to undergo conformational changes that merge viral and/or cell membranes. However, a significant knowledge gap remains on how HN/H/G couples cell receptor binding to F-triggering. Via interdisciplinary approaches we report the first comprehensive mechanism of NiV membrane fusion triggering, involving three spatiotemporally sequential cell receptor-induced conformational steps in NiV-G: two in the head and one in the stalk. Interestingly, a headless NiV-G mutant was able to trigger NiV-F, and the two head conformational steps were required for the exposure of the stalk domain. Moreover, the headless NiV-G prematurely triggered NiV-F on virions, indicating that the NiV-G head prevents premature triggering of NiV-F on virions by concealing a F-triggering stalk domain until the correct time and place: receptor-binding. Based on these and recent paramyxovirus findings, we present a comprehensive and fundamentally conserved mechanistic model of paramyxovirus membrane fusion triggering and cell entry.

The medically-important Paramyxovirus family includes the deadly Nipah virus (NiV). After paramyxoviruses attach to a receptor at a cell surface, fusion between viral and cellular membranes must occur before the virus genetic material can enter the cell and replication of the virus inside the cell can begin. For most paramyxoviruses, viral/cell membrane fusion requires the concerted actions of two viral glycoproteins. After binding to a cell surface receptor, the viral attachment glycoprotein triggers the viral fusion glycoprotein to execute viral/cell membrane fusion so the genetic material of the virus can enter the cell. However, the mechanism of this receptor-induced triggering of membrane fusion is not well understood. We identified several sequential receptor-induced structural changes in the attachment glycoprotein of NiV that are part of the viral/cell membrane fusion-triggering cascade. Importantly, we propose a mechanism of cell receptor-induced paramyxovirus entry into cells, based on the findings described here, similarities between NiV and other paramyxoviruses, and other recent advances.

Rifampin's acute inhibitory and chronic inductive drug interactions: experimental and model-based approaches to drug-drug interaction trial design

We studied the time course for the reversal of rifampin's effect on the pharmacokinetics of oral midazolam (a cytochrome P450 (CYP) 3A4 substrate) and digoxin (a P-glycoprotein (P-gp) substrate). Rifampin increased midazolam metabolism, greatly reducing the area under the concentration-time curve (AUC(0-∞)). The midazolam AUC(0-∞) returned to baseline with a half-life of ~8 days. Rifampin's effect on the AUC(0-3 h) of digoxin was biphasic: the AUC(0-3 h) increased with concomitant dosing of the two drugs but decreased when digoxin was administered after rifampin. Digoxin was found to be a weak substrate of organic anion-transporting polypeptide (OATP) 1B3 in transfected cells. Although the drug was transported into isolated hepatocytes, it is not likely that this transport was through OATP1B3 because the transport was not inhibited by rifampin. However, rifampin did inhibit the P-gp-mediated transport of digoxin with a half-maximal inhibitory concentration (IC(50)) below anticipated gut lumen concentrations, suggesting that rifampin inhibits digoxin efflux from the enterocyte to the intestinal lumen. Pharmacokinetic modeling suggested that the effects on digoxin are consistent with a combination of inhibitory and inductive effects on gut P-gp. These results suggest modifications to drug-drug interaction (DDI) trial designs.

Pharmacokinetics of raltegravir in individuals with UGT1A1 polymorphisms

Raltegravir is a human immunodeficiency virus-1 (HIV-1) integrase strand transfer inhibitor metabolized by glucuronidation via UDP-glucuronosyltransferase 1A1 (UGT1A1). In this study, 30 subjects with a UGT1A1*28/*28 genotype (associated with decreased activity of UGT1A1) and 27 UGT1A1*1/*1 control subjects (matched by race, age, gender, and body mass index) received a single 400-mg dose of raltegravir after fasting. No serious adverse experiences were reported, and there were no discontinuations due to adverse experiences. The geometric mean ratio (GMR) (UGT1A1*28/*28 to UGT1A1*1/*1) and 90% confidence interval (CI) were 1.41 (0.96, 2.09) for raltegravir area under the concentration-time curve (AUC(0-infinity)), 1.40 (0.86, 2.28) for maximum plasma concentration (C(max)), and 1.91 (1.43, 2.55) for concentration at the 12-h time point (C(12 h)). No clinically important differences in time to maximum concentration (T(max)) or half-life were observed. Plasma concentrations of raltegravir are modestly higher in individuals with the UGT1A1*28/*28 genotype than in those with the UGT1A1*1/*1 genotype. This increase is not clinically significant, and therefore no dose adjustment of raltegravir is required for individuals with the UGT1A1*28/*28 genotype.

Safety, Tolerability, and Pharmacokinetics of Raltegravir After Single and Multiple Doses in Healthy Subjects

Raltegravir is a novel human immunodeficiency virus-1 integrase inhibitor with potent in vitro activity (95% inhibitory concentration (IC95)=33 nM in 50% human serum). Three double-blind, randomized, placebo-controlled, pharmacokinetic, safety, and tolerability studies were conducted: (1) single-dose escalation study (10-1,600 mg), (2) multiple-dose escalation study (100-800 mg q12 h x 10 days), and (3) single-dose female study (400 mg). Raltegravir was rapidly absorbed with a terminal half-life (t1/2) approximately 7-12 h. Approximately 7-14% of raltegravir was excreted unchanged in urine. Area under the curve (AUC)(0-infinity) was similar between male and female subjects. After multiple-dose administration, steady state was achieved within 2 days; there was little to modest accumulation of raltegravir. Trough levels were >33 nM for dose levels of 100 mg and greater. Raltegravir is generally well tolerated at doses of up to 1,600 mg/day given for up to 10 days and exhibits a pharmacokinetic profile supportive of twice-daily dosing with multiple doses of 100 mg and greater achieving trough levels >33 nM.

Mobility resolution and mass analysis of ions from ammonia and hydrazine complexes with ketones formed in air at ambient pressure

Protonated ammonia and hydrazines (MH(+)) form complexes with ketones and the differences in masses and mobilities of the resulting ions, MH(+)(ketone)(n), are sufficient for separation in an ion mobility spectrometer at ambient pressure. The highest mass ion for any of the protonated molecules is obtained when the ketone is present at elevated concentrations in the supporting atmosphere of both the source and drift regions of the spectrometer so that an ion maintains a discrete composition and mobility. The sizes of the ion-molecule complexes were found to depend on the number of H atoms on the protonated nitrogen atom--four for ammonia, three for hydrazine, two for monomethylhydrazine, and one for 1,1-dimethylhydrazine, and the drift times of these ions were proportional to the size of the ion-molecule complex. Unexpected side products, including protonated hydrazones and azines, and associated ketone clusters, were isolated to a single drift tube containing ceramic parts and could not, from CID studies, be attributed to gas-phase ion chemistry. These findings illustrate that mobility resolution of ions in IMS and IMS/MS experiments can be enhanced through chemical modification of the supporting gas atmosphere without changes in the core ion.

Characterization of nelfinavir binding to plasma proteins and the lack of drug displacement interactions

OBJECTIVES

To determine the characteristics of the binding of nelfinavir and active M8 to alpha1-acid glycoprotein (AAG) and human serum albumin (HSA), and to examine the displacement effects of drugs binding extensively to AAG (ritonavir and saquinavir) or to HSA (salicylic acid and valproic acid).

METHODS

Free drugs were separated by equilibrium dialysis after incubation with human plasma or purified plasma proteins and after co-incubation with potential displacers. Association constants were estimated from double-reciprocal plots of the data.

RESULTS

Nelfinavir and M8 free fractions [fractions of unbound drug (fus)] were 0.42+/-0.08% (mean+/-standard deviation) and 0.64+/-0.07%, respectively. For the two analytes, respectively, association constants were 7.25 x 10(7)/m and 3.33 x 10(7)/m for AAG and 1.11 x 10(6)/m and 7.92 x 10(5)/m for HSA. Nelfinavir fu in an AAG solution was significantly (P < 0.01) increased by the addition of ritonavir or saquinavir, whereas it was unaltered by addition of these drugs to whole plasma. Similarly, fu in an HSA solution was significantly increased (P < 0.01) by the addition of salicylic acid or valproic acid, whereas there was no difference in the free fraction in plasma.

CONCLUSIONS

The affinity of nelfinavir for human plasma proteins was higher than that of M8, and both nelfinavir and M8 showed higher affinity to AAG than to HSA. The free fraction of nelfinavir was not affected by drugs that bind extensively to AAG or albumin when these drugs were added to whole plasma in combination, suggesting a compensatory effect of alternate binding proteins.

Exaggerated respiratory chemosensitivity and association with level at 3568m in obesity

To investigate whether obesity is associated with alterations in respiratory chemosensitivity, we compared the ventilatory response to hypoxia (HVR) and hypercapnia (HCVR) in 9 obese men (BMI: 37.0+/-4.3 kg m(-2)) and 10 lean men (BMI: 25.8+/-4.8 kg m(-2)). HVR (DeltaVE, L min(-1) per DeltaSaO2, %) was measured by a progressive isocapnic hypoxia technique, and HCVR (DeltaVE/DeltaPETCO2, L min(-1)Torr(-1)) was measured by a progressive hypercapnic method. HCVR, was greater (p<0.001) in the obese men (2.68+/-0.78) than in the lean men (1.4+/-0.45) as was HVR (p<0.05) (1.26+/-0.65 versus 0.71+/-0.43, respectively). The difference (DeltaSaO2, 4.30+/-3.69 and 10.54+/-3.45 in the lean and obese men, respectively, p<0.01) between daytime (86+/-1 and 86+/-1%) and nighttime SaO2 (81+/-3 and 76+/-4%) at a simulated altitude of 3658 m was significantly (p<0.05) correlated with both HVR (r=0.51) and HCVR (r=0.48). These results suggest that chemosensitivity in mildly obese men is increased, not blunted. Furthermore, otherwise healthy, obese individuals have the potential for significant desaturation during sleep at high altitude possibly due to exaggerated sleep-disordered breathing.

Effect of moisture on the field dependence of mobility for gas-phase ions of organophosphorus compounds at atmospheric pressure with field asymmetric ion mobility spectrometry

The electric field dependence of the mobilities of gas-phase protonated monomers [(MH+(H2O)n] and proton-bound dimers [M2H+(H2O)n] of organophosphorus compounds was determined at E/N values between 0 and 140 Td at ambient pressure in air with moisture between 0.1 and 15 000 ppm. Field dependence was described as alpha (E/N) and was obtained from the measurements of compensation voltage versus field amplitude in a planar high-field asymmetric waveform ion mobility spectrometer. The alpha function for protonated monomers to 140 Td was constant from 0.1 to 10 ppm moisture in air with onset of effect at approximately 50 ppm. The value of alpha increased 2-fold from 100 to 1000 ppm at all E/N values. At moisture values between 1000 and 10 000 ppm, a 2-fold or more increase in alpha (E/N) was observed. In a model proposed here, field dependence for mobility through changes in collision cross sections is governed by the degree of solvation of the protonated molecule by neutral molecules. The process of ion declustering at high E/N values was consistent with the kinetics of ion-neutral collisional periods, and the duty cycle of the waveform applied to the drift tube. Water was the principal neutral above 50 ppm moisture in air, and nitrogen was proposed as the principal neutral below 50 ppm.

Canadian guidelines for cardiac rehabilitation and atherosclerotic heart disease prevention: a summary

Atherosclerotic heart disease (AHD) is the leading cause of death in Canadian women and men. Cardiac rehabilitation has been repeatedly shown to reduce cardiac morbidity and mortality significantly among patients with documented AHD. The Canadian Association of Cardiac Rehabilitation (CACR) has defined cardiac rehabilitation as "the enhancement and maintenance of cardiovascular health through individualized programs designed to optimize physical, psychological, social, vocational and emotional status. This process includes the facilitation and delivery of secondary prevention through heart hazard (risk factor) identification and modification in an effort to prevent disease progression and the recurrence of cardiac events". This summary presents a limited amount of background information and the majority of clinical practice recommendations contained within the previously published CACR Guidelines. These evidence-based clinical recommendations are intended as guidelines to good clinical practice rather than as standards of care. The key focus of this summary is the need for complete and targeted intervention of all heart hazards in patients at high or very high risk for, or with documented, AHD. To achieve this goal, the CACR Guidelines and this summary present risk stratification strategies designed to determine unambiguously a patient's risk of exercise-related cardiac events (short term absolute risk or disease prognosis) and their risk of recurrent AHD events (long term absolute risk from disease progression). The establishment of the short term and long term absolute AHD risks can then be used to determine heart hazard targets and the type of exercise program prescribed for patients with AHD. Despite the use of evidence-based medical practices, none of the recommendations presented in this document can replace the expert judgment of properly trained and experienced cardiac rehabilitation professionals. Health care providers must always be free to choose where and when clinical practice guidelines are applied, modified or superceded, depending on individual patient circumstances.

An LC-MS-MS method for the determination of indinavir, an HIV-1 protease inhibitor, in human plasma

A method for the determination of indinavir (IDV) (L-735 524) in human plasma by LC-MS-MS is discussed, and the validation data is presented. The analyte and internal standard are isolated from plasma by a simple acetonitrile precipitation of plasma proteins followed by centrifugation. LC-tandem mass spectrometry in positive ion, multiple reaction monitoring mode used pairs of ions at m/z of 614/421 for indinavir and 628/421 for internal standard, respectively. The calibration curve had a linear range from 3.0 to 12320 ng/ml when linear least square regression weighing 1/x was applied to the concentration versus peak area plot. The advantages of this method are the fast sample preparation, wide dynamic assay range and quick analysis taking only 5 min for each sample run. The robust nature of this assay has been further verified during routine use over several months involving multiple analysts.

Malignant schwannoma of the trigeminal nerve

SUMMARY

We present the MR imaging, CT, and clinical findings of a patient with malignant schwannoma of the trigeminal nerve. Local tumor recurrence is frequent and may be mistaken for lymphatic spread. In this report, we emphasize the natural history of this rare tumor and discuss the importance of imaging in diagnosis and surveillance.

Demyelinating diseases, leukodystrophies, and other myelin disorders

Magnetic resonance (MR) imaging recently has become the most sensitive clinical test in the detection of white matter disorders, yet neuropathologic evaluation remains the most specific. This article describes the gross and microscopic pathology of various diseases primarily or selectively affecting white matter. The discussion should provide deeper insight into the nature of white matter disease and assist in the interpretation of CT and MR images. The subject of white matter damage caused secondarily by such entities as neoplasia, trauma, infarction, or neuronal degeneration is not included.

The choline/creatine ratio in five benign neoplasms: comparison with squamous cell carcinoma by use of in vitro MR spectroscopy

BACKGROUND AND PURPOSE

The choline (Cho)/creatine (Cr) ratio has been shown to be a reliable proton MR spectroscopy metabolic marker for differentiating squamous cell carcinoma (SCCA) from normal muscle in the upper aerodigestive tract. However, it is unclear whether the Cho/Cr ratio can be used to differentiate a malignant tumor from a benign neoplasm in the extracranial head and neck. Our purpose was to determine whether the Cho/Cr ratio can be used to differentiate benign from malignant tumors in this region.

METHODS

In vitro one-dimensional proton MR spectroscopy (2,000/136,272 [TR/TE]) was performed at 11 T on tissue specimens obtained from glomus tumors (n = 3), inverting papilloma (n = 1), and schwannoma (n = 1). Cho/Cr area ratios were calculated and compared with similar, previously reported in vitro (11 T) findings and with samples of SCCA and normal muscle.

RESULTS

The Cho/Cr ratio was elevated in relation to muscle in all benign tumors at TE = 136 (glomus tumors = 4.52, inverting papilloma = 3.85, schwannoma = 2.2) and at TE = 272 (glomus tumors = 8.01, inverting papilloma = 2.1, schwannoma = 4.28). The average Cho/Cr ratio for benign lesions was 3.92 (TE = 136) and 6.11 (TE = 272). The Cho/Cr ratio was significantly higher in benign tumors than in both SCCA and muscle. The average Cho/Cr ratio for muscle at TEs of 136 and 272 was 1.16 and 1.31, respectively, whereas for SCCA the average Cho/Cr ratio at TEs of 136 and 272 was 1.67 and 2.45, respectively.

CONCLUSION

In our small group, the Cho/Cr ratio was significantly higher in benign tumors than in muscle and SCCA of the extracranial head and neck.

Contrast-enhanced 3D FISP MR angiography of the aortic arch ostia: preliminary results

PURPOSE

The goal of this work was to evaluate three-dimensional (3D) contrast-enhanced MR angiography (MRA) for the detection of ostial stenoses of the aortic arch.

METHOD

Sixteen patients with suspected carotid atherosclerotic disease prospectively underwent digital subtraction angiography of the aortic arch followed by contrast-enhanced MRA using a 3D fast imaging with steady-state precession (FISP) technique (TR = 5 ms, TE = 2 ms, flip angle = 30 degrees). Three neuroradiologists blindly measured stenoses on the catheter angiograms and MRA. Evaluation included the ostia of the innominate, left carotid, and left subclavian arteries. Any significant disagreement on catheter angiography was resolved by consensus. The MRA grades of each of the three observers were then compared with the consensus grades of the contrast angiogram.

RESULTS

Forty-eight vessels were scored, of which five had significant stenoses. MRA demonstrated 100% sensitivity, 89% specificity, 52% positive predictive value, and 100% negative predictive value. The Bowker test for symmetry indicated no significant difference between conventional angiography and MRA scores (p = 0.32-0.75), and there was good agreement between the three observers (weighted kappa = 0.75-0.86).

CONCLUSION

Contrast-enhanced 3D FISP MRA may be a useful imaging modality for the detection of significant stenoses at the ostia of the major aortic arch branches.

The ability of tumor volume to predict local control in surgically treated squamous cell carcinoma of the supraglottic larynx

PURPOSE

Pretreatment CT volumetric measurement of the primary tumor has been shown to be a predictor of local control in patients with laryngeal carcinoma treated with radiation therapy (RT) alone. A direct association has been demonstrated between tumor volume of supraglottic squamous cell carcinoma (SGSCCA) and local control. However, the association between tumor volume of SGSCCA and local control has not been investigated in patients treated surgically. The purpose of this study was to determine the relationship between SGSCCA tumor volume and local control in patients treated surgically.

MATERIALS AND METHODS

Primary site tumor volume was calculated from pretreatment CT studies in 37 laryngeal supraglottic carcinomas treated surgically. All patients had clinical follow-up for evidence of recurrent tumor along the surgical margins at the primary site for a minimum of 2 years after completion of treatment. Statistical analysis consisted of Mantel-Haenszel chi-square tests and Fisher's exact test.

RESULTS

Overall local control rate was 92% (33 of 37). Tumor volume was significantly associated with local control (p <. 05). Local control rate for tumors with volumes <16 cc was 94% (32 of 34) (p <.05).

CONCLUSIONS

Pretreatment CT volumetric analysis is useful for predicting local control in patients with SGSCCA carcinoma treated surgically.

CT evaluation of prosthetic ossicular reconstruction procedures: what the otologist needs to know

Postoperative otologic evaluation of patients who have undergone ossicular reconstruction is often difficult. However, thin-section computed tomography (CT) can help determine the type of prosthesis used for reconstruction and adequately assess for complications that may be causing postoperative conductive hearing loss. A variety of prostheses may be used in ossicular reconstruction (eg, stapes prosthesis, incus interposition graft, Applebaum prosthesis, Black oval-top prosthesis, Richards centered prosthesis, Goldenberg prosthesis) and can usually be identified at CT by their shapes and locations. Several causes of prosthetic failure are readily demonstrated at CT, including recurrent cholesteatoma and otitis media, formation of granulation tissue or adhesions, and various mechanical problems (eg, subluxation, dislocation, extrusion, fracture, bending). Perilymphatic fistula can be difficult to identify at CT but may be suggested by the presence of pneumolabyrinth, unexplained middle ear effusion, or fluid accumulation within the mastoid air cells. The presence of soft tissue within the oval window niche 4-6 weeks following surgery may indicate poststapedectomy granuloma or fibrosis. Familiarity with the normal and abnormal CT appearances of ossicular prostheses will enable the radiologist to assist the otologist in identifying patients in whom revision surgery is most appropriate.

National athletic trainers' association position statement: fluid replacement for athletes

OBJECTIVE

To present recommendations to optimize the fluid-replacement practices of athletes.

BACKGROUND

Dehydration can compromise athletic performance and increase the risk of exertional heat injury. Athletes do not voluntarily drink sufficient water to prevent dehydration during physical activity. Drinking behavior can be modified by education, increasing accessibility, and optimizing palatability. However, excessive overdrinking should be avoided because it can also compromise physical performance and health. We provide practical recommendations regarding fluid replacement for athletes.

RECOMMENDATIONS

Educate athletes regarding the risks of dehydration and overhydration on health and physical performance. Work with individual athletes to develop fluid-replacement practices that optimize hydration status before, during, and after competition.

Embryology and anatomy of the neck

As a prelude to understanding pathologic conditions of the pediatric neck, this article presents the embryologic development of the neck, fascial planes, and key anatomic structures. Detailed discussion includes the normal development of the neck and illustrates, using selected CT and MR images, the fascial spaces, larynx and trachea, thyroid, parathyroid, and vascular and lymphatic anatomy.

Imaging of congenital anomalies of the branchial apparatus

One of the most challenging topics for radiologists is congenital anomalies arising from abnormal embryogenesis of the branchial apparatus. Defects of the branchial apparatus result in a spectrum of anomalies that includes fistulas, sinuses, cysts, temporal bone anomalies, craniofacial malformations, and systemic disorders. A better understanding of the various radiologic abnormalities is aided by an understanding of their embryonic origins. This article reviews the spectrum of abnormalities that are secondary to anomalous embryogenesis of the branchial arches.

Proton-bound cluster ions in ion mobility spectrometry

Gaseous oxygen and nitrogen bases, both singly and as binary mixtures, have been introduced into ion mobility spectrometers to study the appearance of protonated molecules, and proton-bound dimers and trimers. At ambient temperature it was possible to simultaneously observe, following the introduction of molecule A, comparable intensities of peaks ascribable to the reactant ion (H2O)nH+, the protonated molecule AH+ and AH+ H2O, and the symmetrical proton bound dimer A2H+. Mass spectral identification confirmed the identifications and also showed that the majority of the protonated molecules were hydrated and that the proton-bound dimers were hydrated to a much lesser extent. No significant peaks ascribable to proton-bound trimers were obtained no matter how high the sample concentration. Binary mixtures containing molecules A and B, in some cases gave not only the peaks unique to the individual compounds but also peaks due to asymmetrical proton bound dimers AHB+. Such ions were always present in the spectra of mixtures of oxygen bases but were not observed for several mixtures of oxygen and nitrogen bases. The dimers, which were not observable, notable for their low hydrogen bond strengths, must have decomposed in their passage from the ion source to the detector, i.e. in a time less than approximately 5 ms. When the temperature was lowered to -20 degrees C, trimers, both homogeneous and mixed, were observed with mixtures of alcohols. The importance of hydrogen bond energy, and hence operating temperature, in determining the degree of solvation of the ions that will be observed in an ion mobility spectrometer is stressed. The possibility is discussed that a displacement reaction involving ambient water plays a role in the dissociation.

Absolute interferometry with a 670-nm external cavity diode laser

In the past few years there has been much interest in use of tunable diode lasers for absolute interferometry. Here we report on use of an external cavity diode laser operating in the visible (lambda approximately 670 nm) for absolute distance measurements. Under laboratory conditions we achieve better than 1-microm standard uncertainty in distance measurements over a range of 5 m, but significantly larger uncertainties will probably be more typical of shop-floor measurements where conditions are far from ideal. We analyze the primary sources of uncertainty limiting the performance of wavelength-sweeping methods for absolute interferometry, and we discuss how errors can be minimized. Many errors are greatly magnified when the wavelength sweeping technique is used; sources of error that are normally relevant only at the nanometer level when standard interferometric techniques are used may be significant here for measurements at the micrometer level.

Normal canals at the fundus of the internal auditory canal: CT evaluation

PURPOSE

Knowledge of the normal anatomy of the four bony canals located at the fundus of the internal auditory canal (IAC) is necessary during evaluation of temporal bone trauma, congenital anomalies affecting the individual nerves, and some neuro-otologic surgeries. The purpose of this work was therefore to characterize the normal appearance of the four bony canals and to measure their dimensions.

METHOD

A retrospective study was performed using CT studies of the temporal bones in 50 patients to identify and characterize the bony canals for the labyrinthine segment of the facial nerve (BCFN), superior vestibular nerve (BCSVN), cochlear nerve (BCNC), and the inferior vestibular nerve (singular canal; SC) located at the fundus of the IAC. All the patients underwent high resolution temporal bone CT for evaluation of uncomplicated inflammatory (n = 49) and neoplastic (n = 1) diseases involving the temporal bone. CT studies were done using 1-mm-thick contiguous sections in axial and coronal planes. Measurements of the canals were performed by one radiologist. No patient had a prior history of trauma, vertigo, and sensorineural hearing loss or facial nerve paralysis.

RESULTS

The BCFN, BCSVN, and BCNC were identified in all studies, whereas the SC was seen in 93% of studies. The BCFN, BCSVN, and BCNC arise from the fundus of the IAC, whereas the SC arises medial to the fundus. Mean +/- SD measurements (in mm) of the length and width were as follows: BCFN = 2.92+/-0.48 and 0.91+/-0.28; BCSVN = 2.36+/-0.53 and 0.89+/-0.28; BCNC = 0.93+/-0.21 and 2.13+/-0.44; and SC = 3.22+/-0.73 and 0.50+/-0.14.

CONCLUSION

These small canals are routinely visualized on thin section (1 mm) CT of the temporal bone and should not be confused with fractures. This study provides baseline measurements that may be used to evaluate congenital anomalies of these canals. These data may also be helpful in the presurgical evaluation of patients undergoing singular neurectomies for benign positional vertigo.

Simultaneous investigation of indinavir nonlinear pharmacokinetics and bioavailability in healthy volunteers using stable isotope labeling technique: study design and model-independent data analysis

Indinavir follows nonlinear pharmacokinetics upon oral administration at clinical doses. A study employing the stable isotope administration technique in a three-treatment design was conducted to identify the source of the nonlinearity and to determine the dose-dependency of systemic bioavailability. In treatment A, 400 mg of unlabeled indinavir (D0) was coadministered orally with 16 mg of a hexadeutero analogue of indinavir (D6) intravenously. In treatment B, 800 mg of D0 po was coadministered with 16 mg of D6 intravenously. In treatment C, 16 mg of iv D6 was infused concurrently with 16 mg iv of D0. Plasma concentrations of D0 and D6 were determined by an LC/MS/MS assay method. Concentrations of indinavir in plasma increased greater than dose-proportionally over the 400- to 800-mg dose range. No meaningful kinetic isotope effects were found in treatment C. Plasma concentrations of D6 were dependent on the coadministered D0-indinavir dose and were lowest in treatment C, higher in treatment A, and highest in treatment B. The bioavailability of indinavir was high (60-65%) and comparable between the 400- and 800-mg doses. There was a significant contribution of nonlinear kinetics in the systemic circulation to the observed disproportional increase in plasma concentrations following oral dosing. The high bioavailability at clinically relevant doses suggests a high degree of saturation of first-pass metabolism. These results further demonstrate that the concomitant administration technique in combination with the LC/MS/MS method can provide a realistic and reliable means of elucidating important pharmacokinetic properties of drug candidates during product development.

Evaluation of CSF leaks: high-resolution CT compared with contrast-enhanced CT and radionuclide cisternography

BACKGROUND AND PURPOSE

Radiologic evaluation of CSF leaks is a diagnostic challenge that often involves multiple imaging studies with the associated expense and patient discomfort. We evaluated the use of screening noncontrast high-resolution CT in identifying the presence and site of CSF rhinorrhea and otorrhea and compared it with contrast-enhanced CT cisternography and radionuclide cisternography.

METHODS

We retrospectively reviewed the imaging studies and medical records of all patients who were evaluated for CSF leak during a 7-year period. Forty-two patients with rhinorrhea and/or otorrhea underwent high-resolution CT of the face or temporal bone and then had CT cisternography and radionuclide cisternography via lumbar puncture. The results of the three studies were compared and correlated with the surgical findings in 21 patients.

RESULTS

High-resolution CT showed bone defects in 30 of 42 patients (71%) with CSF leak. High-resolution, radionuclide cisternography and CT cisternography did not show bone defects or CSF leak for 12 patients (29%) who had clinical evidence of CSF leak. Among the 30 patients with bone defects, 20 (66%) had positive results of their radionuclide cisternography and/or CT cisternography. For the 21 patients who underwent surgical exploration and repair, intraoperative findings correlated with the defects revealed by high-resolution CT in all cases. High-resolution CT identified significantly more patients with CSF leak than did radionuclide cisternography and CT cisternography, with a moderate degree of agreement.

CONCLUSION

Noncontrast high-resolution CT showed a defect in 70% of the patients with CSF leak. No radionuclide cisternography or CT cisternography study produced positive results without previous visualization of a defect on high-resolution CT. CT cisternography and radionuclide cisternography may be reserved for patients in whom initial high-resolution CT does not identify a bone defect or for patients with multiple fractures or postoperative defects.

Leukoencephalopathy complicating an Ommaya reservoir and chemotherapy

We describe the imaging findings in an unusual case of biopsy-proven, methotrexate-induced leukoencephalopathy complicating a malfunctioning Ommaya reservoir in a patient with lymphoma.

High-resolution MR imaging of the auditory pathway

MR imaging is a valuable tool in the evaluation of the auditory pathway. The current techniques in high-resolution MR imaging of the temporal bone are presented followed by a review of normal anatomy. Several diseases involving the middle ear, inner ear, internal auditory canal, and cerebellopontine angle are then presented. A radiologic-pathologic approach is used to illustrate the nature of these diseases and their appearance on MR imaging.

Single-dose pharmacokinetics of indinavir and the effect of food

Indinavir sulfate is a human immunodeficiency virus type 1 (HIV-1) protease inhibitor indicated for treatment of HIV infection and AIDS in adults. The purpose of this report is to summarize single-dose studies which characterized the pharmacokinetics of the drug and the effect of food in healthy volunteers. Indinavir concentrations in plasma and urine were obtained by high-pressure liquid chromatography and UV detection assay methods. The results indicate that indinavir was rapidly absorbed in the fasting state, with the time to the maximum concentration in plasma occurring at approximately 0.8 h for all doses studied. Over the 40- to 1,000-mg dose range studied, concentrations in plasma and urinary excretion of unchanged drug increased greater than dose proportionally. The nonlinear pharmacokinetics were attributed to the dose-dependent oxidative metabolism of first-pass metabolism as well as to metabolism in the systemic circulation. Renal clearance slightly exceeded the glomerular filtration rate, suggesting a net tubular secretion component. At high concentrations in plasma, tubular secretion appeared to be lowered because there was a trend for a decreased renal clearance. Administration of 400 mg of indinavir sulfate following a high-fat breakfast resulted in a blunted and decreased absorption (areas under the concentration-time curves [AUCs], 6.86 microM.h in the fasted state versus 1.54 microM.h in the fed state; n = 10). However, two types of low-fat meals were found to have no significant effect on the absorption of 800 mg of indinavir sulfate (AUCs, 23.15 microM.h in the fasted state versus 22.71 and 21.36 microM.h, respectively, in the fed state; n = 11). Immediately following dosing, the concentrations of indinavir in urine often exceeded its intrinsic solubility. To reduce the risk of nephrolithiasis, it is recommended that indinavir sulfate be administered with water.

Electrospray mass-spectrometric, spectrophotometric and electrochemical methods do not provide evidence for the binding of nitric oxide by pyocyanine at pH 7

In several recent publications on pyocyanine, its mechanism of action has been attributed to an ability to react with nitric oxide (NO), resulting in the formation of an adduct. We examined the chemical interaction of pyocyanine and NO using electrospray (ES) MS, spectrophotometry and voltammetry at neutral pH and with 10-100 microM pyocyanine. No binding of NO to pyocyanine was observed. Alternative mechanisms for the inhibition of NO-induced vasorelaxation by pyocyanine should be sought.

Comparison of hemodynamic and sympathoneural responses to adenosine and lower body negative pressure in man

Adenosine increases heart rate and sympathetic nerve activity reflexively in conscious humans through several mechanisms. The purpose of this study was to assess the relative contributions of arterial baroreceptor unloading, carotid chemoreceptor stimulation, and other adenosine-sensitive afferent nerves to these responses. In 12 healthy men, the effect on blood pressure, heart rate (HR), and muscle sympathetic nerve activity (MSNA; peroneal nerve) of lower body negative pressure (LBNP; -15 mmHg (1 mmHg = 133.3 Pa)) was compared with the effect of intravenous adenosine (35, 70, and l40 micrograms.kg-1.min-1). In eight subjects, the highest dose was reinfused during 100% oxygen to suppress arterial chemoreceptors. Blood pressure reductions during LBNP and adenosine (140 micrograms.kg-1.min-1) were similar. HR did not change significantly during LBNP (+2 +/- 2 beats/min; mean +/- SE) but increased at the highest adenosine dose (+25 +/- 3 beats/min; p < 0.05). MSNA increased significantly (p < 0.05) during both interventions (+255 +/- 82 and +247 +/- 58 units/100 beats for adenosine and LBNP, respectively), and there was no difference in the MSNA response to these two stimuli (p > 0.1). Oxygen inhibited adenosine-induced increases in HR and MSNA (from +305 +/- 99 to +198 +/- 75 units/100 beats and from +26 +/- 4 to +18 +/- 3 beats/min; p < 0.05 for both comparisons). The MSNA response to these combined stimuli was similar to that observed during LBNP. In contrast, the residual HR response (+18 +/- 3 beats/min) was significantly greter than the response to LBNP (+2 +/- 2 beats/min; p < 0.05). These data indicate that arterial baroreceptor unloading cannot account for the marked adenosine-induced increase in HR, but may be sufficient to explain its effect on MSNA. The effect of 100% oxygen confirms that stimulation of carotid chemoreceptors accounts for approximately one-third of the HR and MSNA response to adenosine. However, other mechanisms, such as stimulation of adenosine-sensitive afferent nerves in other vascular beds, are involved in the HR and possibly the MSNA response.

Alpha 1-antitrypsin deficiency: evaluation of bronchiectasis with CT

PURPOSE

To assess bronchiectasis depicted with computed tomography (CT) in patients with alpha 1-antitrypsin deficiency and to examine associated clinical correlates.

MATERIALS AND METHODS

CT scans in 14 patients with alpha 1-antitrypsin deficiency were evaluated by two thoracic radiologists for the presence and extent of bronchiectasis and emphysema. The findings were correlated with numeric infection scores on the basis of symptoms of sputum production and respiratory infection and with a history of conditions that may predispose to development of bronchiectasis.

RESULTS

Six (43%) of 14 patients had CT evidence of bronchiectasis. Patients with bronchiectasis had significantly higher infection scores than did patients without bronchiectasis (P < .005). Two patients had diffuse cystic bronchiectasis, and neither reported a history of illness that may have predisposed them to this condition.

CONCLUSION

Bronchiectasis may be more common in patients with alpha 1-antitrypsin deficiency than has been previously recognized. The diagnosis of alpha 1-antitrypsin deficiency should be considered in patients with emphysema and diffuse cystic bronchiectasis.

Frequency stabilization of a green He-Ne laser

A new process for stabilizing the frequency of commercially available 543-nm He-Ne lasers is described. The stabilization method is based on anomalous dispersion of the gain medium. A total of four green lasers have been stabilized-two at the National Institute of Standards and Technology and two at the Institute of Scientific Instruments of the Czech Academy of Sciences-making it possible to study frequency variations of the lasers relative to each other. We have also stabilized a 633-nm laser by the use of the same method used for 543 nm.

Quantitative analysis of fentanyl in pharmaceutical preparations by gas chromatography-mass spectrometry

Fentanyl (1-[2-phenethyl]-4-N-[N-propionylanilino]piperidine) is a potent synthetic opiate commonly used for surgical analgesia and sedation. Reports of abuse of this highly addictive drug among health care personnel have prompted the need to verify the concentration in the unused portion of single-dose ampules returned to the pharmacy. We describe a simple quantitative method for the analysis of fentanyl citrate (Sublimaze) in syringes returned to the pharmacy following surgery. Fentanyl citrate (0.1 mL) and 2H5-fentanyl (internal standard, 0.05 mL, 100 mg/L) were extracted with Toxi-A tubes (Toxi-Lab, Irvine, CA) and analyzed by gas chromatography-mass spectrometry. Calibration was linear from 1 to 60 mg/L (correlation coefficient of 0.997, n = 13) and had a limit of detection of 0.4 mg/L. Mean recovery at concentrations from 5 to 50 mg/L was 89% (range, 69-104%). No interferences were found with morphine, ketamine, midazolam, sufentanil, or alfentanil. These drugs were not selected for their potential chromatographic interference but for their availability in surgical syringes. This assay is useful in verifying that any unused fentanyl is discarded according to narcotic regulations, thereby avoiding the possibility of diversion for illicit consumption.

Identical-twin bone marrow transplants for leukemia

OBJECTIVE

To compare outcomes of identical-twin with HLA-identical sibling bone marrow transplants for leukemia.

DESIGN

Matched-pair analysis comparing relapse, treatment-related mortality, and leukemia-free survival in cohorts matched for disease and variables correlated with transplant outcome, with and without adjustment for graft-versus-host disease.

SETTING

163 institutions worldwide between 1978 and 1990, reporting to the International Bone Marrow Transplant Registry.

PARTICIPANTS

103 identical-twin transplants: 24 for acute lymphoblastic leukemia (ALL) in first remission, 45 for acute myelogenous leukemia (AML) in first remission, and 34 for chronic myelogenous leukemia (CML) in first chronic phase. Results were compared with those in 1030 concurrent HLA-identical sibling transplants matched for prognostic factors.

RESULTS

Three-year probabilities of relapse after identical-twin compared with HLA-identical sibling transplants were as follows: ALL, 36% (95% CI, 17% to 55%) compared with 26% (CI, 20% to 32%); AML, 52% (CI, 37% to 67%) compared with 16% (CI, 12% to 20%); and CML, 40% (CI, 23% to 57%) compared with 7% (CI, 4% to 10%). Increased relapse risks in AML and CML persisted after adjusting for graft-versus-host disease (relative risk, 3.1 [CI, 1.9 to 5.1] and 5.5 [CI, 2.8 to 11.0], respectively). Although twins had less treatment-related mortality than HLA-identical siblings, leukemia-free survival was similar. Three-year leukemia-free survival probabilities after twin compared with HLA-identical sibling transplants were as follows: ALL, 57% (CI, 37% to 77%) compared with 58% (CI, 52% to 64%); AML, 42% (CI, 27% to 57%) compared with 55% (CI, 50% to 60%); and CML, 59% (CI, 42% to 76%) compared with 61% (CI, 56% to 66%).

CONCLUSIONS

Identical-twin transplants in AML and CML are associated with increased relapse risk compared with HLA-identical sibling transplants. A similar trend was observed in ALL but was not statistically significant. Increased relapse in twin transplants is not explained by lack of graft-versus-host disease. Leukemia-free survival after twin and HLA-identical sibling transplants is similar because increased relapse in twins is offset by decreased treatment-related mortality.

Upper extremity proprioceptive training

Proprioception following lower extremity injuries is commonly recommended, but there is little information on proprioception training following upper extremity injuries. No studies have evaluated whether proprioception programs for athletes in open kinetic chain activities (throwing, shot putting) should be different than programs for athletes in closed kinetic chain activities (gymnastics, swimming, kayaking, or rowing). In this paper, we provide a rationale for proprioception training for upper extremity injuries in athletes and the importance of analyzing the athlete's sport and activity for specificity of proprioception exercises. We then discuss one popular proprioception exercise, rhythmic stabilization, and propose several additional upper extremity proprioception exercises, along with instructions for the athletic trainer on how to direct the athlete through these exercises.