Amino acid addition to Vibrio cholerae LPS establishes a link between surface remodeling in gram-positive and gram-negative bacteria

Historically, the O1 El Tor and classical biotypes of Vibrio cholerae have been differentiated by their resistance to the antimicrobial peptide polymyxin B. However, the molecular mechanisms associated with this phenotypic distinction have remained a mystery for 50 y. Both gram-negative and gram-positive bacteria modify their cell wall components with amine-containing substituents to reduce the net negative charge of the bacterial surface, thereby promoting cationic antimicrobial peptide resistance. In the present study, we demonstrate that V. cholerae modify the lipid A anchor of LPS with glycine and diglycine residues. This previously uncharacterized lipid A modification confers polymyxin resistance in V. cholerae El Tor, requiring three V. cholerae proteins: Vc1577 (AlmG), Vc1578 (AlmF), and Vc1579 (AlmE). Interestingly, the protein machinery required for glycine addition is reminiscent of the gram-positive system responsible for D-alanylation of teichoic acids. Such machinery was not thought to be used by gram-negative organisms. V. cholerae O1 El Tor mutants lacking genes involved in transferring glycine to LPS showed a 100-fold increase in sensitivity to polymyxin B. This work reveals a unique lipid A modification and demonstrates a charge-based remodeling strategy shared between gram-positive and gram-negative organisms.     

Intraspinal oxidised cellulose (Surgicel) causing delayed paraplegia after thoracotomy--a report of three cases

Oxidised regenerated cellulose (Surgicel) is a commonly used haemostatic agent in neurosurgery, thoracic surgery, and orthopaedics. We present three cases of paraplegia after thoracic surgery during which oxidised cellulose had been used during thoracotomy for haemorrhage control, and was later found to have passed through the intervertebral foramen causing spinal cord compression. In all intraspinal and perispinal procedures, the over-liberal use of Surgicel should be avoided, and attempts made to remove all excess Surgicel once adequate haemostasis is obtained.     

Quantification of tumour response to radiotherapy

In 1979, the World Health Organization (WHO) established criteria based on tumour volume change for classifying response to therapy as (i) progressive disease (PD), (ii) partial recovery (PR), and (iii) no change (NC). Typically, the tumour volume is reported from diameter measurements, using the calliper method. Alternatively, the Cavalieri method provides unbiased volume estimates of any structure without assumptions about its shape. In this study, we applied the Cavalieri method in combination with point counting to investigate the changes in tumour volume in four patients with high grade glioma, using 3D MRI. In particular, the volume of tumour within the enhancement boundary, the enhancing abnormality (EA), was estimated from T(1) weighted images, and the volume of the non-enhancing abnormality, (NEA) enhancing abnormality, was estimated from T(2) relaxation time and magnetic transfer ratio tissue characterization maps. We compared changes in tumour volume estimated by the Cavalieri method with those obtained using the calliper method. Absolute tumour volume differed significantly between the two methods. Analysis of relative change in tumour volume, based on the WHO criteria, provided a different classification using the calliper and Cavalieri methods. The benefit of the Cavalieri method over the calliper method in the estimation of tumour volume is justified by the following factors. First, Cavalieri volume estimates are mathematically unbiased. Second, the Cavalieri method is highly efficient under an appropriate sampling density (i.e. EA volume estimates can be obtained with a coefficient of error no higher than 5% in 2-3 min). Third, the source of variation of the volume estimates due to disagreements between observers, and within observer, is much greater in the positioning of the calliper diameters than in the identification of the tumour boundaries when applying the Cavalieri method. Additionally, the error prediction formula, available to estimate the coefficient of error of Cavalieri volume estimates from the data, allows us to establish more precise classification criteria against which to identify potentially clinical significant changes in tumour volume.     

Syringomyelia and the arachnoid web

Summary ¶Three cases of syringomyelia associated with arachnoid webs are reported. Each patient presented with progressive myelopathy and had thoracic syringes detected on magnetic resonance imaging (MRI). In one patient the web was also visible. At operation a thoracic arachnoid web was found, obstructing the subarachnoid compartment in each patient. One patient had intraoperative ultrasound, which demonstrated caudal web movement with each cardiac systole. The webs were divided and shunts inserted into the syringes. All patients improved clinically, and on follow-up MRI. Arachnoid webs are likely to represent a focal band of arachnoiditis and are difficult to visualise on standard preoperative MR imaging. A reduction in the subarachnoid space compliance with resultant increase in pulse pressure and potentiation of an arterial pulsation driven perivascular flow could explain the associated syringes. Treatment should be aimed at restoring compliance, and involve division of the web with or without shunt insertion.Published online July 23, 2003     

Apparent diffusion coefficients in oligodendroglial tumors characterized by genotype

PURPOSE: To investigate whether oligodendroglial tumors with or without 1p/19q loss differ in their diffusion-weighted imaging characteristics. Oligodendroglial tumors with or without 1p/19q loss differ in their therapeutic responsiveness and prognosis, and recent reports also suggest that these tumors may differ in their magnetic resonance characteristics and blood volume. MATERIALS AND METHODS: Apparent diffusion coefficients (ADCs) were assessed in three grade II oligodendrogliomas, nine grade II and five grade III oligoastrocytomas with known 1p/19q status. Regions of interest (ROIs) were placed on ADC maps: 1) around tumor margins to generate pixel histograms; 2) over minimum and maximum tumor ADC; 3) on areas comparable to the highest choline (Cho)/creatine (Cr) ratio determined from chemical shift imaging (CSI); and 4) across tumor margins to measure the ADC transition coefficient (ATC). RESULTS: Tumor ADC was significantly different from normal brain (P < 0.001). ADC in regions of highest Cho/Cr was greater than minimum ADC and did not correlate with the Cho/Cr ratio. ADC and ATC were not significantly different between oligodendroglial subtypes or grades. Tumors with intact 1p/19q had higher maximum (P = 0.021) and histogram ADC (P = 0.015), and greater ATC (P = 0.001) compared to those with 1p/19q loss, which may reflect differences in edema and cellularity. CONCLUSION: This preliminary study identified differences in ADC and ATC between oligodendroglial tumor genotypes that may reflect underlying biology. Confirmation in a larger series is warranted.     

How to analyse the spatiotemporal tumour samples needed to investigate cancer evolution: A case study using paired primary and recurrent glioblastoma

Many traits of cancer progression (e.g., development of metastases or resistance to therapy) are facilitated by tumour evolution: Darwinian selection of subclones with distinct genotypes or phenotypes that enable such progression. Characterising these subclones provide an opportunity to develop drugs to better target their specific properties but requires the accurate identification of somatic mutations shared across multiple spatiotemporal tumours from the same patient. Current best practices for calling somatic mutations are optimised for single samples, and risk being too conservative to identify shared mutations with low prevalence in some samples. We reasoned that datasets from multiple matched tumours can be used for mutual validation and thus propose an adapted two‐stage approach: (1) low‐stringency mutation calling to identify mutations shared across samples irrespective of the weight of evidence in a single sample; (2) high‐stringency mutation calling to further characterise mutations present in a single sample. We applied our approach to three‐independent cohorts of paired primary and recurrent glioblastoma tumours, two of which have previously been analysed using existing approaches, and found that it significantly increased the amount of biologically relevant shared somatic mutations identified. We also found that duplicate removal was detrimental when identifying shared somatic mutations. Our approach is also applicable when multiple datasets e.g. DNA and RNA are available for the same tumour.     

Molecular genetics, imaging and treatment of oligodendroglial tumours

The discovery of a genetic signature of chemosensitivity and prognosis in oligodendroglial tumours prompted a new optimism in glioma management. After more than a decade since the initial reports, where do we stand in the current management of oligodendroglial tumours? This review focuses on the latest molecular genetics, imaging characteristics, and recent trials of treatment paradigms for these tumours.     

Risk factors for anaesthetic-related death in cats: results from the confidential enquiry into perioperative small animal fatalities (CEPSAF)

BACKGROUND: Cats are commonly anaesthetized in veterinary practice, but recent figures describing the frequency of or risk factors for anaesthetic-related death are not available. The aims of this study were to address these deficiencies. METHODS: A nested case-control study was undertaken in 117 UK veterinary centres. All anaesthetic and sedation procedures and anaesthetic and sedation-related deaths (i.e. 'cases') occurring within 48 h were recorded. Details of patient, procedure, and perioperative management were recorded for all cases and randomly selected non-deaths (controls). A detailed statistical model of factors associated with anaesthetic and sedation-related death was constructed. RESULTS: Between June 2002 and June 2004, 175 deaths were classified as anaesthetic and sedation-related and 14 additional deaths (with insufficient information to be excluded) were included for the estimation of risk. During the study, 79 178 anaesthetic and sedation procedures were recorded and the overall risk of anaesthetic and sedation-related death was 0.24% (95% CI 0.20-0.27). Factors associated with increased odds of anaesthetic-related death were poor health status (ASA physical status classification), increasing age, extremes of weight, increasing procedural urgency and complexity, endotracheal intubation, and fluid therapy. Pulse monitoring and pulse oximetry were associated with reduced odds. CONCLUSIONS: The risk of anaesthetic-related death in cats appears to have decreased since the last published study in the UK. The results should aid the preoperative identification of cats at greatest risk. Greater care with endotracheal intubation and fluid administration are recommended, and pulse and pulse oximetry monitoring should be routinely implemented in cats.