Validating a robust double-quantum-filtered (1) H MRS lactate measurement method in high-grade brain tumours.

(1) H MRS measurements of lactate are often confounded by overlapping lipid signals. Double-quantum (DQ) filtering eliminates lipid signals and permits single-shot measurements, which avoid subtraction artefacts in moving tissues. This study evaluated a single-voxel-localized DQ filtering method qualitatively and quantitatively for measuring lactate concentrations in the presence of lipid, using high-grade brain tumours in which the results could be compared with standard acquisition as a reference. Paired standard acquisition and DQ-filtered (1) H MR spectra were acquired at 3T from patients receiving treatment for glioblastoma, using fLASER (localization by adiabatic selective refocusing using frequency offset corrected inversion pulses) single-voxel localization. Data were acquired from 2 × 2 × 2 cm(3) voxels, with a repetition time of 1 s and 128 averages (standard acquisition) or 256 averages (DQ-filtered acquisition), requiring 2.15 and 4.3 min respectively. Of 37 evaluated data pairs, 20 cases (54%) had measureable lactate (fitted Cramér-Rao lower bounds ≤ 20%) in either the DQ-filtered or the standard acquisition spectra. The measured DQ-filtered lactate signal was consistently downfield of lipid (1.33 ± 0.03 ppm vs 1.22 ± 0.08 ppm; p = 0.002), showing that it was not caused by lipid breakthrough, and that it matched the lactate signal seen in standard measurements (1.36 ± 0.02 ppm). In the absence of lipid, similar lactate concentrations were measured by the two methods (mean ratio DQ filtered/standard acquisition = 1.10 ± 0.21). In 7/20 cases with measurable lactate, signal was not measureable in the standard acquisition owing to lipid overlap but was quantified in the DQ-filtered acquisition. Conversely, lactate was undetected in seven DQ-filtered acquisitions but visible using the standard acquisition. In conclusion, the DQ filtering method has proven robust in eliminating lipid and permits uncontaminated measurement of lactate. This is important validation prior to use in tissues outside the brain, which contain large amounts of lipid and which are often susceptible to motion.

Sleeping Beauty transposon screen identifies signaling modules that cooperate with STAT5 activation to induce B-cell acute lymphoblastic leukemia.

Signal transducer and activator of transcription 5 (STAT5) activation occurs frequently in human progenitor B-cell acute lymphoblastic leukemia (B-ALL). To identify gene alterations that cooperate with STAT5 activation to initiate leukemia, we crossed mice expressing a constitutively active form of STAT5 (Stat5b-CA) with mice in which a mutagenic Sleeping Beauty transposon (T2/Onc) was mobilized only in B cells. Stat5b-CA mice typically do not develop B-ALL (<2% penetrance); in contrast, 89% of Stat5b-CA mice in which the T2/Onc transposon had been mobilized died of B-ALL by 3 months of age. High-throughput sequencing approaches were used to identify genes frequently targeted by the T2/Onc transposon; these included Sos1 (74%), Kdm2a (35%), Jak1 (26%), Bmi1 (19%), Prdm14 or Ncoa2 (13%), Cdkn2a (10%), Ikzf1 (8%), Caap1 (6%) and Klf3 (6%). Collectively, these mutations target three major cellular processes: (i) the Janus kinase/STAT5 pathway (ii) progenitor B-cell differentiation and (iii) the CDKN2A tumor-suppressor pathway. Transposon insertions typically resulted in altered expression of these genes, as well as downstream pathways including STAT5, extracellular signal-regulated kinase (Erk) and p38. Importantly, expression of Sos1 and Kdm2a, and activation of p38, correlated with survival, further underscoring the role these genes and associated pathways have in B-ALL.

Evaluation of lactate detection using selective multiple quantum coherence in phantoms and brain tumours.

Lactate is a product of glucose metabolism. In tumour tissues, which exhibit enhanced glycolytic metabolism, lactate signals may be elevated, making lactate a potential useful tumour biomarker. Methods of lactate quantitation are complicated because of overlap between the lactate methyl doublet CH3 resonance and a lipid resonance at 1.3 ppm. This study presents the use of a selective homonuclear multiple quantum coherence transfer sequence (SelMQC-CSI), at 1.5 T, to better quantify lactate in the presence of lipids. Work performed on phantoms showed good lactate detection (49%) and lipid suppression (98%) efficiencies. To evaluate the method in the brain, the sequence was tested on a group of 23 patients with treated brain tumours, either glioma (N=20) or secondary metastases in the brain (N=3). Here it was proved to be of use in determining lactate concentrations in vivo. Lactate was clearly seen in SelMQC spectra of glioma, even in the presence of lipids, with high grade glioma (7.3 ± 1.9 mM, mean ± standard deviation) having higher concentrations than low grade glioma (1.9 ± 1.5 mM, p=0.048). Lactate was not seen in secondary metastases in the brain. SelMQC-CSI is shown to be a useful technique for measuring lactate in tumours whose signals are otherwise contaminated by lipid.

Thoracic outlet syndrome in children and young adults.

OBJECTIVES: Thoracic outlet syndrome has been well described in the population between 25 and 40 years of age, and is less frequently reported in those in the first two decades of life. The objective of this study was to review results with onset of TOS in the first two decades of life to determine type of presentation and outcomes from surgical intervention. METHODS AND MATERIALS: Charts of all patients in the first two decades of life, operated on for TOS between 1994 and 2006 were reviewed with follow-up by clinic visit and phone survey to assess the patients' current level of activity and relief from symptoms. RESULTS: Twelve patients were identified (13 operations), with a mean age of 16.8 years. Acute ischemic symptoms were the initial presentation for 38%, venous TOS in 24%, and neurogenic symptoms in 38%. All patients had symptom relief with surgery with a mean time to resolution of 10.9 weeks. All patients remained symptom free or improved at follow-up. CONCLUSIONS: Vascular TOS is much more common in TOS presenting in the first two decades of life. Surgical intervention for TOS in this population results in long-lasting symptom relief and should be considered for all subtypes of patients.

The relationship between cognitive function and clinical and functional outcomes in major depressive disorder.

BACKGROUND: Although cognitive variables have been shown to be useful in predicting outcomes in late-life depression, there has not yet been a comprehensive study in younger persons with depression. METHOD: The clinical symptoms and cognitive performance of participants were evaluated at admission to one of two university teaching hospitals and again at 3 months after remission and discharge. A total of 52 participants with a DSM-IV diagnosis of major depressive disorder, aged between 20 and 60 years and with a Hamilton Depression Rating Scale score 17 > or = entered the study. The sample for this paper comprises the 48 subjects (mean age 37.9 years, s.d.=10.7) who received admission and follow-up assessments; an attrition rate of 7.7%. RESULTS: More perseverative errors on the shortened Wisconsin Card Sorting Test at admission predicted a worse clinical outcome at follow-up. Poor event-based prospective memory and more perseverative errors on the shortened Wisconsin Card Sorting Test at admission predicted worse social and occupational outcome at follow-up. CONCLUSIONS: These results suggest that a brief cognitive screen at hospital admission, focusing on executive function, would have a useful prognostic value in depression. Determining early predictors of individuals at risk of poorer outcomes is important for identifying those who may need altered or additional treatment approaches.

Identification and characterisation of childhood cerebellar tumours by in vivo proton MRS.

(1)H MRS has great potential for the clinical investigation of childhood brain tumours, but the low incidence in, and difficulties of performing trials on, children have hampered progress in this area. Most studies have used a long-TE, thus limiting the metabolite information obtained, and multivariate analysis has been largely unexplored. Thirty-five children with untreated cerebellar tumours (18 medulloblastomas, 12 pilocytic astrocytomas and five ependymomas) were investigated using a single-voxel short-TE PRESS sequence on a 1.5 T scanner. Spectra were analysed using LCModel to yield metabolite profiles, and key metabolite assignments were verified by comparison with high-resolution magic-angle-spinning NMR of representative tumour biopsy samples. In addition to univariate metabolite comparisons, the use of multivariate classifiers was investigated. Principal component analysis was used for dimension reduction, and linear discriminant analysis was used for variable selection and classification. A bootstrap cross-validation method suitable for estimating the true performance of classifiers in small datasets was used. The discriminant function coefficients were stable and showed that medulloblastomas were characterised by high taurine, phosphocholine and glutamate and low glutamine, astrocytomas were distinguished by low creatine and high N-acetylaspartate, and ependymomas were differentiated by high myo-inositol and glycerophosphocholine. The same metabolite features were seen in NMR spectra of ex vivo samples. Successful classification was achieved for glial-cell (astrocytoma + ependymoma) versus non-glial-cell (medulloblastoma) tumours, with a bootstrap 0.632 + error, e(B.632+), of 5.3%. For astrocytoma vs medulloblastoma and astrocytoma vs medulloblastoma vs ependymoma classification, the e(B.632+) was 6.9% and 7.1%, respectively. The study showed that (1)H MRS detects key differences in the metabolite profiles for the main types of childhood cerebellar tumours and that discriminant analysis of metabolite profiles is a promising tool for classification. The findings warrant confirmation by larger multi-centre studies.

Evaluation of a screening protocol to exclude the diagnosis of deep venous thrombosis among emergency department patients.

OBJECTIVE: The purpose of this study was to evaluate the efficacy and cost effectiveness of a deep venous thrombosis (DVT) screening protocol incorporating DVT pretest probability (PTP), selective D-dimer assay, and venous duplex imaging (VDI) to exclude the diagnosis of DVT among emergency department (ED) patients. METHODS: A prospective study of all patients evaluated in the ED for suspected DVT during 1 year was undertaken. Patients were classified into PTP risk category by ED physicians before VDI. Correlation studies were completed using VDI as the gold standard. Charges associated with the protocol were calculated. RESULTS: One hundred fourteen patients were included. The incidence of DVT was 9.6% (11). Thirty-six (55%) patients were classified as high risk, 23 (35%) as moderate, and 7 (10%) as low risk. All patients diagnosed with DVT were in the high-risk group (incidence, 16.7%). The sensitivity and negative predictive value were both 100% when PTP and D-dimer were used, but fell to 80% and 95%, respectively, when only D-dimer was considered. The true negative rates were 23% and 37%, respectively. Based on this study, we propose the following screening: for high-risk patients, use direct VDI (no D-dimer); for low-risk or moderate-risk patients, obtain D-dimer, and if it is positive, use VDI, and if it is negative, no further action is required. The average charge associated with the protocol was 170.50 dollars as opposed to 202.00 dollars for global VDI. CONCLUSION: A screening protocol using PTP along with selective D-dimer and VDI to exclude the diagnosis of DVT among ED patients is efficacious and cost efficient. This screening approach establishes criteria to satisfy billing requirements, can eliminate unnecessary VDI in 23% of ED referrals, and can reduce charges by 16%.

Balloon angioplasty for arteriovenous graft stenosis.

PURPOSE: To retrospectively review the long-term outcome as well as the cost effectiveness of thrombolytic therapy and balloon angioplasty (TBA) versus surgical thrombectomy and balloon angioplasty (SBA) in the treatment of prosthetic dialysis access grafts. METHODS: Between February 1996 and February 1999, 63 hemodialysis patients (35 women; mean age 62.2 years) were treated for 105 thromboses in 6-mm polytetrafluoroethylene straight or loop bridge arteriovenous grafts. Choice of treatment was at the discretion of the surgeon or interventional radiologist: either Fogarty balloon thrombectomy followed by balloon dilation of the venous anastomotic stenosis or urokinase thrombolysis followed by angioplasty. RESULTS: Forty-eight SBAs and 55 TBAs were performed in 63 patients without complications. The primary patency rates in the entire cohort were 34%, 29%, and 17% at 1, 2, and 3 months, respectively. Primary patency after TBA was 29%, 18%, and 11%, and that for SBA, 45%, 45%, and 33% over the same time intervals. The mean graft survival was 10 days for TBA versus 31 days for SBA. Repeat angioplasty performed in 23 grafts produced secondary patency rates of 52% at 1 month, 34% at 3 months, and 5% at 5 months. The Medicare reimbursement for both treatments was identical ($1638 for TBA and $1670 for SBA). CONCLUSIONS: The poor patency rate and high cost of TBA and SBA suggests that these procedures should not be routinely used for salvage of thrombosed arteriovenous grafts with outflow stenosis. Patch angioplasty or creation of simultaneous temporary and new permanent accesses may be a more cost-effective approach in these patients.

Fermentation characterization and flux analysis of recombinant strains of Clostridium acetobutylicum with an inactivated solR gene.

The effect of solR inactivation on the metabolism of Clostridium acetobutylicum was examined using fermentation characterization and metabolic flux analysis. The solR-inactivated strain (SolRH) of this study had a higher rate of glucose utilization and produced higher solvent concentrations (by 25%, 14%, and 81%, respectively, for butanol, acetone, and ethanol) compared to the wild type. Strain SolRH(pTAAD), carrying a plasmid-encoded copy of the bifunctional alcohol/aldehyde dehydrogenase gene (aad) used in butanol production, produced even higher concentrations of solvents (by 21%, 45%, and 62%, respectively, for butanol, acetone, and ethanol) than strain SolRH. Clarithromycin used for strain SolRH maintenance during SolRH(pTAAD) fermentations did not alter product formation; however, tetracycline used for pTAAD maintenance resulted in 90% lower solvent production.

The relationship between inflated personal responsibility and exaggerated danger expectancies in obsessive-compulsive concerns.

The association between responsibility for a negative outcome, perceived severity of the outcome and perceived likelihood of the outcome was examined in a sample of 70 undergraduate students. Participants were asked to rate the likelihood and severity of 10 negative outcomes, five related to contamination and five related to checking. Thirty-eight participants completed a version of the questionnaire that presented the subject as responsible for the action that may lead to a negative outcome ('personally responsible' group). The remaining 32 completed a version of the questionnaire that presented someone else performing the actions that may lead to a negative outcome ('other responsible' group). Significant differences emerged between the personally responsible and other responsible groups for severity of outcome ratings but not for likelihood of outcome ratings. Specifically, for both washing and checking concerns, participants in the personally responsible group rated the severity of the potential negative outcome as greater than did those in the other responsible group. The results support the claimed general tendency for individuals to regard an outcome as more aversive if they are personally responsible for that outcome, rather than someone else being responsible. The results suggest that, in general, increasing perceptions of personal responsibility will increase cost or severity estimates in subjective danger calculations, and that responsibility may influence OCD phenomena in this way. Finally, the results suggest that attempts to manipulate responsibility in the laboratory may be confounded by necessarily impacting on cost estimates, and therefore on danger expectancies.

Intravenous leiomyomatosis with cardiac extension: tumor thrombectomy through an abdominal approach.

Intravenous leiomyomatosis is an uncommon vascular tumor that may be seen with potentially life-threatening symptoms resulting from intracardiac extension. This tumor is frequently misdiagnosed and treated without appropriate preoperative imaging and planning, which at times leads to inadequate treatment and incomplete resections. The appropriate therapy is complete excision of the tumor. We describe a patient who was treated with a new approach involving a single-stage operation without the need for median sternotomy, cardiopulmonary bypass graft, or hypothermic arrest by resection of the tumor from the point of attachment in the abdominal portion of the inferior vena cava.

Characterization of recombinant strains of the Clostridium acetobutylicum butyrate kinase inactivation mutant: need for new phenomenological models for solventogenesis and butanol inhibition?

Two metabolic engineering tools, namely gene inactivation and gene overexpression, were employed to examine the effects of two genetic modifications on the fermentation characteristics of Clostridium acetobutylicum. Inactivation of the butyrate kinase gene (buk) was examined using strain PJC4BK, while the combined effect of buk inactivation and overexpression of the aad gene-encoding the alcohol aldehyde dehydrogense (AAD) used in butanol formation-was examined using strain PJC4BK(pTAAD). The two strains were characterized in controlled pH > or = 5.0 fermentations, and by a recently enhanced method of metabolic flux analysis. Strain PJC4BK was previously genetically characterized, and fermentation experiments at pH > or = 5.5 demonstrated good, but not exceptional, solvent-production capabilities. Here, we show that this strain is a solvent superproducer in pH > or = 5.0 fermentations producing 225 mM (16.7 g/L) of butanol, 76 mM of acetone (4.4 g/L), and 57 mM (2.6 g/L) of ethanol. Strain PJC4BK(pTAAD) produced similar amounts of butanol and acetone but 98 mM (4.5 g/L) of ethanol. Both strains overcame the 180 mM (13 g/L) butanol toxicity limit, without any selection for butanol tolerance. Work with strain PJC4BK(pTAAD) is the first reported use of dual antibiotic selection in C. acetobutylicum. One antibiotic was used for selection of strain PJC4BK while the second antibiotic selected for the pTAAD presence. Overexpression of aad from pTAAD resulted in increased ethanol production but did not increase butanol titers, thus indicating that AAD did not limit butanol production under these fermentation conditions. Metabolic flux analysis showed a decrease in butyrate formation fluxes by up to 75% and an increase in acetate formation fluxes of up to 100% during early growth. The mean specific butanol and ethanol formation fluxes increased significantly in these recombinant strains, up to 300% and 400%, respectively. Onset of solvent production occurred during the exponential-growth phase when the culture optical density was very low and when total and undissociated butyric acid levels were <1 mM. Butyrate levels were low throughout all fermentations, never exceeding 20 mM. Thus, threshold butyrate concentrations are not necessary for solvent production in these stains, suggesting the need for a new phenomenological model to explain solvent formation.

Isolated iliac artery aneurysms in patients with or without previous abdominal aortic aneurysm repair.

BACKGROUND: Isolated iliac artery aneurysms (IAA) in patients with or without previous abdominal aortic aneurysm (AAA) repair are rare. We wanted to compare the presentation, distribution, treatment, outcome and patterns of subsequent aneurysm formation in these patients. METHODS: We retrospectively reviewed patients with isolated IAA over a 10-year period. Patients with primary isolated IAA (group 1) were compared with patients who presented with IAA after previous AAA repair (group 2). RESULTS: There were 23 patients in each group. Demographics and comorbidities were similar. No aneurysms were detected outside of the iliac system in group 1; 22% of patients in group 2 had other aneurysms. The mean time after AAA repair to IAA diagnosis was 8.8 +/- 3.2 years for operated on patients. The in-hospital mortality was 0% for elective cases and 50% for emergency cases for both groups. Three patients in group 2 (13%) developed new aneurysms during follow-up, whereas the only new aneurysm in group 1 was a contralateral IAA. CONCLUSIONS: Patients with new IAA after AAA repair have a greater tendency to develop further aneurysms in other sites, synchronously or metachronously. The time to detection of new IAA after AAA repair is at least 5 years in most cases. In both groups, a quarter to a third of patients present with rupture, with a resultant mortality of 30% to 50%, whereas those operated on electively have minimal morbidity and almost no mortality.

Molecular epidemiologic evaluation of transmissibility and virulence of Mycobacterium tuberculosis.

Discovery of genotypic markers associated with increased transmissibility in Mycobacterium tuberculosis would represent an important step in advancing mycobacterial virulence studies. M. tuberculosis strains may be classified into one of three genotypes on the basis of the presence of specific nucleotide substitutions in codon 463 of the katG gene (katG-463) and codon 95 of the gyrA gene (gyrA-95). It has previously been reported that two of these three genotypes are associated with increased IS6110-based clustering, a potential proxy of virulence. We designed a case-control analysis of U.S.-born patients with tuberculosis in San Francisco, Calif., between 1991 and 1997 to investigate associations between katG-463 and gyrA-95 genotypes and epidemiologically determined measures of strain-specific infectivity and pathogenicity and IS6110-based clustering status. We used a new class of molecular probes called molecular beacons to genotype the isolates rapidly. Infectivity was defined as the propensity of isolates to cause tuberculin skin test conversions among named contacts, and pathogenicity was defined as their propensity to cause active disease among named contacts. The molecular beacon assay was a simple and reproducible method for the detection of known single nucleotide polymorphisms in large numbers of clinical M. tuberculosis isolates. The results showed that no genotype of the katG-463- and gyrA-95-based classification system was associated with increased infectivity and pathogenicity or with increased IS6110-based clustering in San Francisco during the study period. We speculate that molecular epidemiologic studies investigating clinically relevant outcomes may contribute to the knowledge of the significance of laboratory-derived virulence factors in the propagation of tuberculosis in human communities.

Evidence for fear of restriction and fear of suffocation as components of claustrophobia.

Recent investigations of the aetiology and treatment of specific phobias have focused on clarifying the concerns underlying phobic anxiety. It has been proposed that claustrophobic fear is comprised of separable confinement and suffocation components. This paper presents data from 78 general medical outpatients undergoing magnetic resonance imaging (MRI) scans in two major teaching hospitals. The findings support the two factor structure of claustrophobia, in that exposure to confinement reduced confinement subscale scores, but did not influence suffocation scores.

Mood and prospective memory.

This study considered the relationship between mood states, prospective memory, and retrospective memory among a non-clinical sample of undergraduate students. Multiple regression analyses with simultaneous entry of variables were undertaken to examine the unique contributions of the alternate memory test and the emotional states to memory test performance. As expected, retrospective free recall performance and anxiety made unique and significant contributions to performance on the prospective memory task. However, only prospective memory performance emerged as a significant predictor of retrospective free recall. It is suggested that none of the mood measures emerged as a significant predictor of retrospective memory performance because they do not account for unique variance. In contrast, the relationship between anxiety and prospective memory appears to be due to factors uniquely associated with anxiety, and unrelated to depression.

Metabolic flux analysis elucidates the importance of the acid-formation pathways in regulating solvent production by Clostridium acetobutylicum.

Metabolic flux analysis was used to investigate the roles of the acid formation pathways in Clostridium acetobutylicum. The acid formation pathways were revealed to serve different roles in wildtype fermentations than previously expected. Specifically, enzymes known to catalyze butyrate formation were found to uptake butyrate without concomitant production of acetone. This role was further corroborated by flux analysis of a recombinant strain overexpressing the butyrate formation enzymes. Analysis of wildtype fermentation data also revealed an important role for the acetate formation enzymes, namely the cycling of carbon between acetate and acetylCoA during the stationary phase. Next, metabolic flux analysis was used to compare the patterns of activity in two butyrate kinase deficient strains of C. acetobutylicum. The strain developed by gene inactivation, PJC4BK, exhibited a shift in acid formation fluxes toward acetate while the strain developed by antisense RNA strategies, 824(pRD4), did not exhibit such a shift. However, both strains exhibited altered solvent formation patterns. PJC4BK exhibited a strong transient enhancement of solvent formation fluxes. In contrast, 824(pRD4) exhibited relatively lower levels of solvent formation fluxes, although fluxes were sustained over a longer period of time.

The convergent validity of the Phobia Origins Questionnaire (POQ): a review of the evidence.

The Phobic Origins Questionnaire (POQ) [Ost, L.-G. & Hugdahl, K. (1981). Acquisition of phobias and anxiety response patterns in clinical patients. Behaviour Research and Therapy, 19, 439-447.] is the most commonly cited instrument for determining the origins of phobic anxiety and data obtained using this instrument strongly support the role of conditioning in the acquisition of fear reactions. The construct validity of the POQ in assessing episodes of conditioning has been questioned [e.g. Menzies, R. G. & Clarke, J. C. (1994). Retrospective studies of the origins of phobias: a review. Anxiety, Stress and Coping, 7, 305-318.] This paper examined the convergent validity of the POQ by comparing origins' classifications based on the POQ to classifications based on alternative instruments. The convergent validity of the POQ was found to be extremely poor. The POQ was consistently associated with a much greater likelihood of classifying the origin of fear reactions as due to direct conditioning episodes than was found using alternative instruments. The findings question the usefulness of the POQ in examining the origins of phobic anxiety.