Autologous bone marrow mononuclear cells to treat severe traumatic brain injury in children.

Autologous bone marrow mononuclear cells (BMMNCs) infused after severe traumatic brain injury have shown promise for treating the injury. We evaluated their impact in children, particularly their hypothesized ability to preserve the blood-brain barrier and diminish neuroinflammation, leading to structural CNS preservation with improved outcomes. We performed a randomized, double-blind, placebo-sham-controlled Bayesian dose-escalation clinical trial at two children's hospitals in Houston, TX and Phoenix, AZ, USA (NCT01851083). Patients 5-17 years of age with severe traumatic brain injury (Glasgow Coma Scale score ≤ 8) were randomized to BMMNC or placebo (3:2). Bone marrow harvest, cell isolation and infusion were completed by 48 h post-injury. A Bayesian continuous reassessment method was used with cohorts of size 3 in the BMMNC group to choose the safest between two doses. Primary end points were quantitative brain volumes using MRI and microstructural integrity of the corpus callosum (diffusivity and oedema measurements) at 6 months and 12 months. Long-term functional outcomes and ventilator days, intracranial pressure monitoring days, intensive care unit days and therapeutic intensity measures were compared between groups. Forty-seven patients were randomized, with 37 completing 1-year follow-up (23 BMMNC, 14 placebo). BMMNC treatment was associated with an almost 3-day (23%) reduction in ventilator days, 1-day (16%) reduction in intracranial pressure monitoring days and 3-day (14%) reduction in intensive care unit (ICU) days. White matter volume at 1 year in the BMMNC group was significantly preserved compared to placebo [decrease of 19 891 versus 40 491, respectively; mean difference of -20 600, 95% confidence interval (CI): -35 868 to -5332; P = 0.01], and the number of corpus callosum streamlines was reduced more in placebo than BMMNC, supporting evidence of preserved corpus callosum connectivity in the treated groups (-431 streamlines placebo versus -37 streamlines BMMNC; mean difference of -394, 95% CI: -803 to 15; P = 0.055), but this did not reach statistical significance due to high variability. We conclude that autologous BMMNC infusion in children within 48 h after severe traumatic brain injury is safe and feasible. Our data show that BMMNC infusion led to: (i) shorter intensive care duration and decreased ICU intensity; (ii) white matter structural preservation; and (iii) enhanced corpus callosum connectivity and improved microstructural metrics.

The Pediatric Neuroradiologist's Practical Guide to Capture and Evaluate Pre- and Postoperative Velopharyngeal Insufficiency.

Up to 30% of children with cleft palate will develop a severe speech disorder known as velopharyngeal insufficiency. Management of velopharyngeal insufficiency typically involves structural and functional assessment of the velum and pharynx by endoscopy and/or videofluoroscopy. These methods cannot provide direct evaluation of underlying velopharyngeal musculature. MR imaging offers an ideal imaging method, providing noninvasive, high-contrast, high-resolution imaging of soft-tissue anatomy. Furthermore, focused-speech MR imaging techniques can evaluate the function of the velum and pharynx during sustained speech production, providing critical physiologic information that supplements anatomic findings. The use of MR imaging for velopharyngeal evaluation is relatively novel, with limited literature describing its use in clinical radiology. Here we provide a practical approach to perform and interpret velopharyngeal MR imaging examinations. This article discusses the velopharyngeal MR imaging protocol, methods for interpreting velopharyngeal anatomy, and examples illustrating its clinical applications. This knowledge will provide radiologists with a new, noninvasive tool to offer to referring specialists.

The antiretroviral agents azidothymidine, stavudine, and didanosine have the identical mutational fingerprint in the rpoB region of Escherichia coli.

We looked at the mutational fingerprints of three antiretroviral (anti-HIV) agents, azidothymidine (AZT), stavudine (STAV), and didanosine (DIDA) in the rpoB system of Escherichia coli and compared them with each other and with the fingerprints of trimethoprim and of spontaneous mutations in a wild-type and a mutT background. All three agents gave virtually identical fingerprints in the wild-type background, causing only A:T→C:G changes at 3 of the 12 A:T→C:G possible sites among the total of 92 possible base substitution mutations, even though AZT and STAV are thymidine analogs but DIDA is an adenosine analog. As all three agents are reverse transcriptase inhibitors, and act as chain blockers, the common fingerprint may be a property of chain blocking agents.

Evaluation of axial gradient Echo spiral MRI of the spine at 1.5 T.

Axial gradient echo T2*-weighed MRI of the spine is a valuable diagnostic tool with several advantages over axial T2-weighted TSE MRI, but it suffers from a low signal-to-noise ratio (SNR) and inconsistent image quality. This work investigates the potential of spiral MRI to reduce artifacts and produce improved SNR and image quality in axial T2*-weighted gradient echo MRI of the spine of pediatric patients. For the purposes of image quality evaluation, 15 pediatric patients were recruited among those scheduled for a routine spine or brain exam at 1.5 T. Pediatric spine images were rated by three pediatric neuroradiologists on a subjective scale of 1-5 using four image quality criteria. Image quality scores were evaluated using non-parametric Wilcoxon signed-rank testing and a mixed effects logistic regression model. Significant differences were found in the image quality scores in favor of spiral MRI. The odds of spiral images receiving an overall image quality score higher than 3 was 16.3 times greater than the odds of Cartesian images receiving a score higher than 3 (p < 0.001, 95% CI of 4.6 to 86) as calculated using a mixed effects logistic regression model. A quantitative comparison was also performed on a single volunteer to illustrate the SNR benefit of spiral MRI. In conclusion, spiral MRI was found to provide equal or better image quality than Cartesian MRI in axial T2*-weighted gradient echo MRI in the spine of a small cohort of pediatric patients at 1.5 T.

Enhanced characterization of the thyA system for mutational analysis in Escherichia coli: Defining mutationally "hot" regions of the gene.

We have extensively characterized base substitution mutations in the 795 base pair (bp) long E. coli thyA gene to define as many of the base substitution mutational sites that inactivate the gene as possible. The resulting catalog of mutational sites constitutes a system with up to 5 times as many sites for monitoring each of the six base substitution mutations as the widely used rpoB/Rifr system. We have defined 75 sites for the G:C -> A:T transition, 68 sites for the G:C -> T:A transversion, 53 sites for the G:C -> C:G transversion, 49 sites for the A:T -> G:C transition, 39 sites for the A:T -> T:A transversion, and 59 sites for the A:T -> C:G transversion. The system is thus comprised of 343 base substitution mutations at 232 different base pairs, all of which can be sequenced with a single primer pair. This allows for the examination of mutational spectra using a more detailed probe of known mutations, while still allowing one to compare the number of repeated occurrences at specific sites. We have examined several mutagens and mutators with this system, and show its utility by looking at the spectrum of cisplatin, that has a single hotspot, underscoring the value of having as large an array of sites as possible at which one can monitor repeat occurrences. To test for regions of the gene that might be hotspots for a number of mutagens, or "hot" (mutaphilic) regions, we have looked at the ratio of mutations per set of an equal number of mutational sites throughout the gene. The resulting graphs suggest that there are "hot" regions at intervals, and this may reflect aspects of secondary structures, of the higher order structure of the chromosome, or perhaps the nucleoid structure of the chromosome plus histone-like protein complexes.

Mutations induced by Bleomycin, 4-nitroquinoline-1-oxide, and hydrogen peroxide in the rpoB gene of Escherichia coli: Perspective on Mutational Hotspots.

We report the mutational spectra in a segment of the E. coli rpoB gene of bleomycin (BLEO), 4-nitroquinoline-1-oxide (NQO), and hydrogen peroxide (H2O2). We compare these spectra with those of other mutagens and repair deficient strains in the same rpoB system, and review the key elements determining mutational hotspots and outline the questions that remain unanswered. We consider three tiers of hotspots that derive from 1) the nature of the sequence change at a specific base, 2) the direct nearest neighbors and 3) some aspect of the larger sequence context or the local 3D-structure of segments of DNA. This latter tier can have a profound effect on mutation frequencies, even among sites with identical nearest neighbor sequences. BLEO is dependent on the SOS-induced translesion Pol V for mutagenesis, and has a dramatic hotspot at a single mutational site in rpoB. NQO is not dependent on any of the translesion polymerases, in contrast to findings with plasmids treated in vitro and transformed into E. coli. The rpoB system allows one to monitor both G:C -> A:T transitions and G:C -> T:A transversions at the same site in 11 cases, each site having the identical sequence context for each of the two mutations. The combined preference for G:C -> A:T transitions at these sites is 20-fold. Several of the favored sites for hydrogen peroxide mutagenesis are not seen in the spectra of BLEO and NQO mutations, indicating that mutagenesis from reactive oxygen species is not a major cause of BLEO or NQO mutagenesis, but rather specific adducts. The variance in mutation rates at sites with identical nearest neighbors suggests that the local structure of different DNA segments is an important factor in mutational hotspots.

Neonatal Neuroimaging.

Significant advances in the field of neonatal imaging has resulted in the generation of large complex data sets of relevant information for routine daily clinical practice, and basic and translational research. The evaluation of this data is a complex task for the neonatal imager who must distinguish normal and incidental findings from clinically significant abnormalities which are often adjunctive data points applicable to clinical evaluation and treatment. This review provides an overview of the imaging manifestations of disease processes commonly encountered in the neonatal brain. Since MRI is currently the highest yield technique for the diagnosis and characterization of the normal and abnormal brain, it is therefore the focus of the majority of this review. When applicable, discussion of some of the pertinent known pathophysiology and neuropathological aspects of disease processes are reviewed.

Free-breathing non-contrast-enhanced flow-independent MR angiography using magnetization-prepared 3D non-balanced dual-echo Dixon method: A feasibility study at 3 Tesla.

In this work we aimed to investigate the feasibility of using a new pulse sequence called Relaxation-Enhanced Angiography without Contrast and Triggering (REACT) for free-breathing non-contrast-enhanced MR angiography (NCE-MRA) for multiple anatomies on 3T. Two magnetization-preparation pulses were incorporated with a three-dimensional dual-echo Dixon sequence. A T2-prep pulse, followed by a non-selective inversion pulse with a short inversion time, together suppressed tissue with short T1 and T2, while enhancing the signal of native blood with long T1 and T2. A two-point non-balanced gradient-echo Dixon method, based on dual-echo acquisition with semi-flexible echo times for water-fat separation, was used for improved fat suppression over a large field of view. General image quality, vasculature visibility, and clinical indications of the proposed method were investigated in healthy subjects and patients in both torso and extremities based on visual inspection. Preliminary results from REACT obtained in free-breathing with no cardiac triggering showed uniform suppression of background tissue over the field of view and robust blood-to-tissue contrast over multiple anatomies. Future clinical studies are warranted for further investigation of its diagnostic performance and limitations.

Opiate leukoencephalopathy in a pediatric patient.

A 17-year-old male presented from an outside facility in acute respiratory failure and profound hypotension. He was found to have classic MRI brain findings of opiate-induced leukoencephalopathy which was corroborated with urine drug screen and history. This entity has been described in the adults but is not as well recognized in the pediatric population. As the opiate epidemic continues to evolve, this case brings heightened awareness of this disorder to pediatric radiologists.

The Antibiotic Trimethoprim Displays Strong Mutagenic Synergy with 2-Aminopurine.

We show that trimethoprim (TMP), an antibiotic in current use, displays a strong synergistic effect on mutagenesis in Escherichia coli when paired with the base analog 2-aminopurine (2AP), resulting in a 35-fold increase in mutation frequencies in the rpoB-Rifr system. Combination therapies are often employed both as antibiotic treatments and in cancer chemotherapy. However, mutagenic effects of these combinations are rarely examined. An analysis of the mutational spectra of TMP, 2AP, and their combination indicates that together they trigger a response via an alteration in deoxynucleoside triphosphate (dNTP) ratios that neither compound alone can trigger. A similar, although less strong, response is seen with the frameshift mutagen ICR191 and 2AP. These results underscore the need for testing the effects on mutagenesis of combinations of antibiotics and chemotherapeutics.

MRI findings of hypomyelination in adenylosuccinate lyase deficiency.

Adenylosuccinate lyase deficiency is a rare genetic disorder with few reported cases in the United States. Magnetic resonance imaging findings in the brain include hypomyelination and low generalized parenchymal volume. Presented here is a case in a 3-month-old male who presented with hypotonia and seizures and was subsequently diagnosed with adenylosuccinate lyase deficiency. Given the rarity of this diagnosis, findings demonstrated in this case may prompt ordering physicians to broaden their approach to genetic testing in the setting of hypomyelination. Comparison is also made to more common hypomyelinating leukodystrophies.

Unique neuroradiological findings in propionic acidemia.

Propionic acidemia is a rare metabolic disorder that affects the catabolism of branched-chain amino acids and oddchain fatty acids. Propionic acidemia is one of the least common organic acidemias. Presented here are manifestations not previously characterized. The first case is an infant with diffuse subcortical diffusion restriction and vermian atrophy. The second case is an adolescent with asymmetric cortical volume loss and contralateral cortical diffusion restriction. These unique brain MRI findings of propionic acidemia may aid the neuroradiologist in guiding genetic testing for occult metabolic disease.

Mutagenesis: Interactions with a parallel universe.

Unexpected observations in mutagenesis research have led to a new perspective in this personal reflection based on years of studying mutagenesis. Many mutagens have been thought to operate via a single principal mechanism, with secondary effects usually resulting in only minor changes in the observed mutation frequencies and spectra. For example, we conceive of base analogs as resulting in direct mispairing as their main mechanism of mutagenesis. Recent studies now show that in fact even these simple mutagens can cause very large and unanticipated effects both in mutation frequencies and in the mutational spectra when used in certain pair-wise combinations. Here we characterize this leap in mutation frequencies as a transport to an alternate universe of mutagenesis.

When more is less: Emergent suppressive interactions in three-drug combinations.

BACKGROUND: In drug-drug interactions, there are surprising cases in which the growth inhibition of bacteria by a single antibiotic decreases when a second antibiotic is added. These interactions are termed suppressive and have been argued to have the potential to limit the evolution of resistance. Nevertheless, little attention has been given to suppressive interactions because clinical studies typically search for increases in killing efficiency and because suppressive interactions are believed to be rare based on pairwise studies. RESULTS: Here, we quantify the effects of single-, double-, and triple-drug combinations from a set of 14 antibiotics and 3 bacteria strains, totaling 364 unique three-drug combinations per bacteria strain. We find that increasing the number of drugs can increase the prevalence of suppressive interactions: 17% of three-drug combinations are suppressive compared to 5% of two-drug combinations in this study. Most cases of suppression we find (97%) are "hidden" cases for which the triple-drug bacterial growth is less than the single-drug treatments but exceeds that of a pairwise combination. CONCLUSIONS: We find a surprising number of suppressive interactions in higher-order drug combinations. Without examining lower-order (pairwise) bacterial growth, emergent suppressive effects would be missed, potentially affecting our understanding of evolution of resistance and treatment strategies for resistant pathogens. These findings suggest that careful examination of the full factorial of drug combinations is needed to uncover suppressive interactions in higher-order combinations.

Measurement of vertebral bone marrow proton density fat fraction in children using quantitative water-fat MRI.

OBJECTIVES: To investigate the feasibility of employing a 3D time-interleaved multi-echo gradient-echo (TIMGRE) sequence to measure the proton density fat fraction (PDFF) in the vertebral bone marrow (VBM) of children and to examine cross-sectional changes with age and intra-individual variations from the lumbar to the cervical region in the first two decades of life. MATERIALS AND METHODS: Quantitative water-fat imaging of the spine was performed in 93 patients (49 girls; 44 boys; age median 4.5 years; range 0.1-17.6 years). For data acquisition, a six-echo 3D TIMGRE sequence was used with phase correction and complex-based water-fat separation. Additionally, single-voxel MR spectroscopy (MRS) was performed in the L4 vertebrae of 37 patients. VBM was manually segmented in the midsagittal slice of each vertebra. Univariable and multivariable linear regression models were calculated between averaged lumbar, thoracic and cervical bone marrow PDFF and age with adjustments for sex, height, weight, and body mass index percentile. RESULTS: Measured VBM PDFF correlated strongly between imaging and MRS (R 2 = 0.92, slope = 0.94, intercept = -0.72%). Lumbar, thoracic and cervical VBM PDFF correlated significantly (all p < 0.001) with the natural logarithm of age. Differences between female and male patients were not significant (p > 0.05). CONCLUSION: VBM development in children showed a sex-independent cross-sectional increase of PDFF correlating with the natural logarithm of age and an intra-individual decrease of PDFF from the lumbar to the cervical region in all age groups. The present results demonstrate the feasibility of using a 3D TIMGRE sequence for PDFF assessment in VBM of children.

Improved fat-suppression homogeneity with mDIXON turbo spin echo (TSE) in pediatric spine imaging at 3.0 T.

Background Robust fat suppression remains essential in clinical MRI to improve tissue signal contrast, minimize fat-related artifacts, and enhance image quality. Purpose To compare fat suppression between mDIXON turbo spin echo (TSE) and conventional frequency-selective and inversion-recovery methods in pediatric spine MRI. Material and Methods Images from T1-weighted (T1W) and T2-weighted (T2W) TSE sequences coupled with conventional methods and the mDIXON technique were compared in 36 patients (5.8 ± 5.4 years) at 3.0 T. Images from 42 pairs of T1W (n = 16) and T2W (n = 26) scans were acquired. Two radiologists reviewed the data and rated images using a three-point scale in two categories, including the uniformity of fat suppression and overall diagnostic image quality. The Wilcoxon rank-sum test was used to compare the scores. Results The Cohen's kappa coefficient for inter-rater agreement was 0.69 (95% confidence interval [CI], 0.56-0.83). Images from mDIXON TSE were considered superior in fat suppression ( P < 0.01) in 22 (rater 1) and 25 (rater 2) cases, respectively. In 13 (rater 1) and 11 (rater 2) cases, mDIXON TSE demonstrated improved diagnostic image quality ( P < 0.01). In three cases, fat suppression was superior using inversion-recovery and likewise in one case mDIXON had poorer image diagnostic quality. Lastly, mDIXON and conventional fat-suppression methods performed similarly in 17 (rater 1) and 14 (rater 2) cases, and yielded equal diagnostic image quality in 28 (rater 1) and 30 (rater 2) cases. Conclusion Robust fat suppression can be achieved with mDixon TSE pediatric spine imaging at 3.0 T and should be considered as a permanent replacement of traditional methods, in particular frequency-selective techniques.

Comparison of 2D single-shot turbo-spin-echo and spin-echo echo-planar diffusion weighted brain MRI at 3.0 Tesla: preliminary experience in children.

PURPOSE: To qualitatively compare a 2D single-shot turbo-spin-echo (ssTSE) diffusion-weighted imaging MRI technique with a spin-echo echo-planar imaging (SE-EPI) approach in pediatric neuroimaging. METHODS: Images were acquired at 3T in 15 patients (10.6±6.0years). A neuroradiologist rated the data based on the severity of image artifacts from air-tissue interfaces and devices such as ventriculoperitoneal shunts and orthodontia, and whether their presence affected diagnostic image quality. RESULTS: ssTSE was preferred over SE-EPI in diagnostic image quality and exhibited fewer clinically relevant artifacts (p<0.01). CONCLUSION: ssTSE provides superior diffusion-weighted brain images at 3T, particularly in the presence of orthodontia and shunts.

Non-gadolinium dynamic angiography of the neurovasculature using arterial spin labeling MRI: preliminary experience in children.

OBJECTIVE: We demonstrate the potential clinical utility of a 4D non-gadolinium dynamic angiography technique based on arterial spin-labeling called contrast inherent inflow enhanced multi-phase angiography (CINEMA) in pediatric patients. MATERIALS AND METHODS: CINEMA was qualitatively compared to conventional time-of-flight (TOF) angiography in a cohort of 31 pediatric patients at 3 Tesla. RESULTS: CINEMA data were successfully acquired and reconstructed in all patients with no image artifacts. There were no cases where CINEMA was rated inferior to TOF in depicting intracranial vessel conspicuity. In 19 cases, CINEMA was rated equivalent to TOF and in the 12 remaining cases CINEMA was rated superior to TOF. CONCLUSION: There is a steadily rising concern in adults and children over the potential effects of intracranial deposition of gadolinium. CINEMA is therefore a viable alternative in dynamic neurovascular imaging.

Assessment of cerebral blood perfusion reserve with acetazolamide using 3D spiral ASL MRI: Preliminary experience in pediatric patients.

PURPOSE: To demonstrate the clinical feasibility of a new non-Cartesian cylindrically-distributed spiral 3D pseudo-continuous arterial spin labeling (pCASL) magnetic resonance imaging (MRI) pulse sequence in pediatric patients in quantifying cerebral blood flow (CBF) response to an acetazolamide (ACZ) vasodilator challenge. MATERIALS AND METHODS: MRI exams were performed on two 3 Tesla Philips Ingenia systems using 32 channel head coil arrays. After local institutional review board approval, the 3D spiral-based pCASL technique was added to a standard brain MRI exam and evaluated in 13 pediatric patients (average age: 11.7±6.4years, range: 1.4-22.2years). All patients were administered ACZ for clinically indicated reasons. Quantitative whole-brain CBF measurements were computed pre- and post-ACZ to assess cerebrovascular reserve. RESULTS: 3D spiral pCASL data were successfully reconstructed in all 13 cases. In 11 patients, CBF increased 2.8% to 93.2% after administration of ACZ. In the two remaining patients, CBF decreased by 2.4 to 6.0% after ACZ. The group average change in CBF due to ACZ was approximately 25.0% and individual changes were statistically significant (p<0.01) in all patients using a paired t-test analysis. CBF perfusion data were diagnostically useful in supporting conventional MR angiography and clinical findings. CONCLUSION: 3D cylindrically-distributed spiral pCASL MRI provides a robust approach to assess cerebral blood flow and reserve in pediatric patients.