Assessment of optimal thresholds for ventricular scar substrate characterization using the high density grid multipolar mapping catheter

Funding Acknowledgements

Type of funding sources: None.

Background

Voltage thresholds for ventricular scar definition are based on historic data collected using catheters with widely spaced bipoles in the absence of contact force. Modern multipolar mapping catheters employ smaller electrodes and interelectrode spacing that theoretically allows for mapping with increased resolution and reduced far-field electrogram (EGM) component. Despite the advancement in technology, historic cut-offs of <0.5mV for dense scar and 0.5-1.5mV for scar borderzone continue to be used in contemporary electrophysiology.

Purpose

We aimed to assess the optimal voltage cut-offs for ventricular scar substrate characterization using the HD Grid multipolar mapping catheter. Voltage cut-offs were assessed against cardiac MRI derived scar. We compared optimal voltage cut-offs using conventional bipolar sampling, the Best Duplicate Algorithm and with the HD wave solution plus best duplicate algorithm on.

Methods

A multicentre study of twenty patients undergoing VT ablation was conducted. Substrate mapping was performed using the high-density HD-grid multipolar mapping catheter. Bipolar voltage maps were co-registered with cardiac MRI obtained prior to the procedure to assess the voltage characteristics of scar defined by cardiac MRI (CMR) (Figure 1). Pre-procedure contrast enhanced CMR data were analysed using ADAS software (Galgo medical). Data points were collected in regions of scar during (1) HD wave mapping with best duplicate algorithm on(Waveon), (2) Mapping with HD wave off and best duplicate on (Waveoff) and (3) with conventional bipolar mapping (Alloff).

Results

The median bipolar voltage for regions of dense CMR scar using (Waveon) HD wave solution and best duplicate algorithm was 0.27mV (IQR 0.14 – 0.46). The median voltage with (Waveoff) HD wave off was 0.29mV (0.15 – 0.45). The median voltage with (Alloff) HD wave off and best duplicate off was 0.32mV (0.19 – 0.5). ROC analysis using AUC suggested the optimal cut-off for endocardial dense scar using (Waveon) HD wave mapping and best duplicate algorithm was 0.30mV (sensitivity: 69.6%, specificity: 60.74%), (Waveoff) cut-off with the best duplicate and without the HD wave mapping was 0.34mV (sensitivity: 69.78%, specificity: 64.46%) and (Alloff) without wave mapping or best duplication was 0.36mV (sensitivity: 84%, specificity: 52%) Figure 2.

Conclusion

Ventricular substrate characterization with newer mapping technology using narrow electrode spacing and smaller electrode size suggests that traditional voltage cut-offs may need revision for delineation of scar characteristics. Additionally, the ability to repeat sample in a region to obtain the best signal (Best Duplicate), and the ability to obviate the effect of wavefront direction using the HD wave solution omnipolar technology, may further increase the fidelity of scar characterization. This has important implications for mapping VT and characterizing channels in order to identify VT circuits.

Integration of structural and functional data in VT ablation -- SENSE2 protocol mapping

Funding Acknowledgements

Type of funding sources: None.

Background

We have previously developed the sense protocol functional substrate mapping technique for VT ablation(1). However, functional substrate characterizaiton can involve protracted mapping time.

Purpose

We incorporated the integration of MRI data using ADAS-3D software into the mapping workflow, to integrate structural mapping information into the functional mapping substrate characterization, in order to improve procedural efficiency.

Methods

CMRs were performed in 20 patients with ischemic related VT and VT therapy in the previous 6 months. These were processed with the ADAS-3D software to characterize the extent of ventricular scars and also ADAS corridors which may correlate with VT channels. Focused substrate maps were then performed in patients, guided by the extent of ADAS scar and corridors, looking at the scar substrate in intrinsic rhythm and then functional channels using single extra pacing from the RV at 20ms above ERP (SENSE2 Protocol). Specifically healthy areas 2cm beyond the scar borderzone based on ADAS were not mapped, in order to reduce substrate mapping time and complete geometries were not created. Following delineation of functional channels pacemapping and entrainment mapping were used to confirm targets for ablation.

The ADAS 3D MRI was integrated into the into the VT substrate map on Ensite-Precision with alignment to the aorta, RV and PA (Figure 1). We compared our data with previous functional mapping data without the integration of MRI.

Results

20 patients (age 70 years; 19 male subjects) underwent ablation. Mean EF 28%. Median procedure time was 161 minutes compared with 246 minutes (in our previous study)(p=<0.001) Mean substrate mapping time was 32 mins vs 63 mins (p=<0.001). Mean ablation time was 22 mins vs 32 mins (p=0.11). 85% (17 of 20) patients were free from symptomatic VT/ anti-tachycardia pacing or implantable cardioverter defibrillator shocks at a median follow-up of 171 days. The mean VT burden was reduced from 22 events per patient in the 6 months’ pre-ablation to 1 event per patient in the median follow up period of 171 days post ablation (p=0.02). Mean shocks per-patient burden decreased from 3.5 to 0.08 in the same time period(p=0.03).

Conclusion

The SENSE2 protocol involves the integration of structural and functional data into the VT workflow for substrate characterization. It enables focused substrate maps to be performed without the need for complete geometry to be created in large ventricles. Outcomes compare favourably with our previous data but with significantly shorter procedure times. This streamlined workflow has the potential to improve care in VT ablation by shortening procedure times with similar outcomes which may reduce risks for the patient.

Figure 1: Comparison of Voltage Map with MRI scar & corridors using ADAS

A report on the impact of rapid prenatal exome sequencing on the clinical management of 52 ongoing pregnancies: a retrospective review

OBJECTIVE

Studies have shown that prenatal exome sequencing (PES) improves diagnostic yield in cases of fetal structural malformation. We have retrospectively analysed PES cases from two of the largest fetal medicine centres in the UK to determine the impact of results on management of a pregnancy.

DESIGN

A retrospective review of clinical case notes.

SETTING

Two tertiary fetal medicine centres.

POPULATION

Pregnancies with fetal structural abnormalities referred to clinical genetics via a multidisciplinary team.

METHODS

We retrospectively reviewed the notes of all patients who had undergone PES. DNA samples were obtained via chorionic villus sampling or amniocentesis. Variants were filtered using patient-specific panels and interpreted using American College of Medical Genetics guidelines.

RESULTS

A molecular diagnosis was made in 42% (18/43) ongoing pregnancies; of this group, there was a significant management implication in 44% (8/18). A positive result contributed to the decision to terminate a pregnancy in 16% (7/43) of cases. A negative result had a significant impact on management in two cases by affirming the decision to continue pregnancy.

CONCLUSIONS

We demonstrate that the results of PES can inform pregnancy management. Challenges include variant interpretation with limited phenotype information. These results emphasise the importance of the MDT and collecting phenotype and variant data. As this testing is soon to be widely available, we should look to move beyond diagnostic yield as a measure of the value of PES.

TWEETABLE ABSTRACT

Prenatal exome sequencing can aid decision-making in pregnancy management; review ahead of routine implementation in NHS.

Temperature dependence of ice-on-rock friction at realistic glacier conditions

Using a new biaxial friction apparatus, we conducted experiments of ice-on-rock friction in order to better understand basal sliding of glaciers and ice streams. A series of velocity-stepping and slide-hold-slide tests were conducted to measure friction and healing at temperatures between -20°C and melting. Experimental conditions in this study are comparable to subglacial temperatures, sliding rates and effective pressures of Antarctic ice streams and other glaciers, with load-point velocities ranging from 0.5 to 100 µm s-1 and normal stress σn = 100 kPa. In this range of conditions, temperature dependences of both steady-state friction and frictional healing are considerable. The friction increases linearly with decreasing temperature (temperature weakening) from μ = 0.52 at -20°C to μ = 0.02 at melting. Frictional healing increases and velocity dependence shifts from velocity-strengthening to velocity-weakening behaviour with decreasing temperature. Our results indicate that the strength and stability of glaciers and ice streams may change considerably over the range of temperatures typically found at the ice-bed interface.This article is part of the themed issue 'Microdynamics of ice'.

Abstract P5-13-01: Transcript analysis of PI3K and immune-related genes and gene signatures in the pre- and post-treatment samples from the window of opportunity study of anastrozole and anastrozole with pictilisib (GDC-0941) in patients with HR-positive early breast cancer (OPPORTUNE study)

Background: The OPPORTUNE Study randomized postmenopausal patients (pts) to receive 2-week preoperative treatment with anastrozole (ANA) plus pictilisib ("ANA+PIC" arm) or ANA alone. Patients had newly diagnosed, operable, ER+, HER2- invasive breast cancer of ≥1 cm size. The primary outcome at interim analysis (n=70) revealed that the addition of PIC significantly increased the anti-proliferative response to ANA as measured by reduction in Ki67 immunohistochemistry (IHC). Multivariate analyses suggested benefit of PIC for patients with luminal B disease (Schmid et al. SABCS 2014).

Methods: RNA expression analysis of ∼800 breast cancer-related genes was performed on patients analyzed at the interim analysis, including 14 (ANA) and 20 (ANA+PIC) patients with matched pre- and post- treatment paired tumour samples using the nCounter platform (NanoString). Differential expression of individual genes by arm was assessed using paired and moderated t-tests and statistical significance assessed through false discovery rate (FDR). Ingenuity Pathway Analysis (IPA) of differentially expressed transcripts identified pathways of relevance. Protein expression was analyzed by reverse protein array ( RPPA) in pre- and post-treatment samples.

Results: In an unsupervised analysis, down-regulation of genes associated with ER signaling was observed in patients who received single-agent ANA and ANA+PIC, which included genes that regulate the cell cycle, cell death, survival, growth and proliferation and known ER target genes (e.g., PGR, GREB1). In addition, transcripts related to growth factor signaling pathway appeared to be specifically modulated in the ANA+PIC arm, possibly via the upregulation of the expression of RTK ligands. There were no clear changes in PI3K-related phosphoproteins (e.g., AKT, S6, 4E-BP1) in the post-treatment samples by RPPA. However, known PI3K-regulated genes, IRS2 and PIK3IP1, were upregulated in the post-treatment samples and a composite PI3K gene expression signature score (O'Brien et al. 2010) was reduced in both study arms following treatment. This PI3K signature was associated with pre-treatment luminal B status (n=27) and, consistent with this finding, the baseline PI3K gene signature score in the ANA arm, but not the ANA+PIC arm, was inversely associated with the decrease in post treatment Ki67. The tumor immune microenvironment was analyzed though the use of composite gene sets. In our initial observations, analysis of pre- and post-treatment samples showed that 2-week treatment with ANA resulted in a modest increase in transcripts associated with multiple immune signatures, which was further enhanced by the addition of PIC.

Conclusions: Gene expression analysis of pre- and post-treatment samples in the OPPORTUNE study demonstrates on-target inhibition of ER and PI3K signaling networks. The analysis of additional paired samples is in progress to further assess if 2-weeks of treatment with a regimen containing an AI in patients with early breast cancer impacts the tumor immune microenvironment.

Citation Format: Schmid P, Pinder SE, Bundred N, Wheatley D, Macaskill J, Zammit C, Hu J, Price R, Shia A, Lim L, Parker P, Molinero L, Yu J, O'Brien C, Wilson T, Savage H, Derynck M, Lackner MR, Amler L, Purushotham A, Thompson A, Gendreau S. Transcript analysis of PI3K and immune-related genes and gene signatures in the pre- and post-treatment samples from the window of opportunity study of anastrozole and anastrozole with pictilisib (GDC-0941) in patients with HR-positive early breast cancer (OPPORTUNE study). [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P5-13-01.

Abstract P6-05-09: Development of a predictive biomarker gene expression signature for the PIK3CA inhibitor, GDC-0032, in breast cancer cells

Introduction

The PI3-Kinase pathway is one of the most commonly mutated pathways in cancer and plays a major role in cell proliferation and survival. Mutations in PIK3CA, the gene encoding the p110 subunit of PI3K, are among the most common alterations in breast cancer, occurring in approximately 45% of luminal A, 30% of luminal B, 30% of HER2 positive and 8% of triple negative breast cancers. Additional pathway activating alterations include loss of PTEN, AKT mutations and overexpression of PIK3CA and HER2. Development of a pharmacodynamic biomarker is challenging with the more isoform specific PI3K inhibitors as multiple upstream pathways can funnel into common downstream immunohistochemical evaluable endpoints. In addition, phosphorylated epitopes are often labile and do not always lend themselves to immunohistochemical evaluation in the clinical setting. GDC-0032, which is currently under clinical investigation, is a class I PI3K inhibitor with 30-fold less inhibition on PI3K beta relative to PI3K alpha, and the development of a predictive and on-study pharmacodynamic signature may prove informative as compared to traditional IHC endpoints.

Methods

We screened a panel of 53 breast cancer cell lines, incorporating all subtypes, to GDC-0032 using the cell proliferation assay cell titer glo. To determine if there was a relationship between pathway activation and sensitivity to GDC-0032, we correlated response to PIK3CA mutations, loss of PTEN and HER2 overexpression. Using RNA sequencing, we compared the baseline gene expression between the sensitive and refractory cell lines. Next, to identify an on-study pharmacodynamic gene expression signature, we treated both sensitive and refractory cell lines with GDC-0032 and ran an in-house custom designed 800 gene NanoString breast cancer gene set that incorporated published PI3K pathway signatures, intrinsic subtyping genes and immunological related genes. Finally, the GDC-0032 signature was applied to a set of 160 FFPE breast cancer samples and overlaid with relevant biomarkers.

Results and Conclusions

Sensitivity to GDC-0032 correlated strongly with PI3K pathway activation including PIK3CA mutations and HER2 overexpression in breast cancer cells. Comparing baseline whole genome RNA expression of GDC-0032 sensitive and refractory cell lines, we identified 293 genes that were differentially expressed. Applying a more stringent statistical cutoff (greater than 2 fold difference and t-test less than 0.01) refined the gene list to 51 genes, which defined the baseline GDC-0032 sensitivity signature. Applying the 800 gene breast cancer NanoString panel to a set of 160 FFPE breast cancer samples, the GDC-0032 sensitivity signature correlated with luminal status and was enriched in PIK3CA mutant tumors. In conclusion, our in-house designed GDC-0032 sensitivity signature correlated strongly with PIK3CA mutations in clinical specimens. However the lack of complete correlation may identify tumors that have an activated PI3K pathway outside of PIK3CA mutations and/or HER2 amplification that may derive clinical benefit from GDC-0032.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P6-05-09.

Abstract P6-05-12: Comprehensive molecular analysis of estrogen receptor positive breast cancer to determine clinically actionable alterations

Introduction.

Understanding the genetic landscape of estrogen receptor positive breast caner is critical for defining clinically actionable alleles that may be targeted using next generation biologics. PIK3CA mutations have previously been reported to be the most common mutation within estrogen receptor positive breast cancer, however the overlap and mutual exclusivity with other key driving alleles is poorly understood, especially how these biomarkers change following treatment failure. We custom designed a mutation, copy number variation and RNA expression panels to profile biomarkers from low quality formalin fixed paraffin embedded extracted material. Data relating to key pathways, such as PI3K and immune modulatory pathways, and overlap with other biomarkers will be presented.

Methods.

Formalin fixed paraffin embedded material was available from 195 primary cases and 95 paired metastatic estrogen receptor positive breast cancer patients. Samples were assayed for the expression of PTEN by IHC, hotspot mutations in 11 oncogenic driving genes using Q-PCR based technology, copy number alterations in 42 genes using Q-PCR based technology and RNA expression using a custom designed 400 breast cancer specific NanoString gene panel.

Results.

PTEN loss, as defined by H-score of 0, was found in 4.5% of primary samples and in 4.3% of metastatic samples. PIK3CA mutations were found in 43% of primary samples and in 38% of metastatic samples and were largely found to be mutually exclusive with PTEN loss. AKT1 mutations were found in 5.4% of primary samples and in 4.1% of metastatic samples. Less frequent mutations in KRAS (7.0%) and BRAF (1.7%) were found in the primary sample, and some were co-existing with PIK3CA mutations. Copy number gains were found in CCND1 (23.5%), ZNF703 (19.5%), FGFR1 (16.8%) and PAK1 (11.4%) and were largely concordant with the paired metastatic sample. Analysis with clinical outcome is ongoing.

Conclusions.

PIK3CA was the most frequently altered gene detected and was mutually exclusive with other key driving mutations within the PI3K pathway (AKT1 and PTEN). A strong concordance was observed between genetic alterations found in the primary sample and the paired metastatic sample. Mutations and expression gains within clinically actionable targets were found less frequently, but may provide alternative treatment strategies for these patients following failure of endocrine therapy.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P6-05-12.

Central venous sinus [added] thrombosis misdiagnosed as eclampsia in an emergency department

Central venous sinus thrombosis can present in the emergency department with a diverse range of symptoms and signs, including a non-neurological scenario, and it thus poses a diagnostic challenge. It is amenable to treatment, so a patient history and awareness of the condition prompts early diagnosis and instigation of treatment which may reduce morbidity and mortality.

Structural origins of the interfacial activation in Thermomyces (Humicola) lanuginosa lipase

The already known X-ray structures of lipases provide little evidence about initial, discrete structural steps occurring in the first phases of their activation in the presence of lipids (process referred to as interfacial activation). To address this problem, five new Thermomyces (formerly Humicola) lanuginosa lipase (TlL) crystal structures have been solved and compared with four previously reported structures of this enzyme. The bias coming from different crystallization media has been minimized by the growth of all crystals under the same crystallization conditions, in the presence of detergent/lipid analogues, with low or high ionic strength as the only main variable. Resulting structures and their characteristic features allowed the identification of three structurally distinct species of this enzyme: low activity form (LA), activated form (A), and fully Active (FA) form. The isomerization of the Cys268-Cys22 disulfide, synchronized with the formation of a new, short alpha(0) helix and flipping of the Arg84 (Arginine switch) located in the lid's proximal hinge, have been postulated as the key, structural factors of the initial transitions between LA and A forms. The experimental results were supplemented by theoretical calculations. The magnitude of the activation barrier between LA (ground state) and A (end state) forms of TlL (10.6 kcal/mol) is comparable to the enthalpic barriers typical for ring flips and disulfide isomerizations at ambient temperatures. This suggests that the sequence of the structural changes, as exemplified in various TlL crystal structures, mirror those that may occur during interfacial activation.

Laser irradiative tissue probed in situ by collagen 380-nm fluorescence imaging

BACKGROUND AND OBJECTIVE

There is no ideal method to detect molecular changes in situ of laser-irradiated tissue without removing a section of tissue for histologic examination. A new method is reported to evaluate laser-induced thermal tissue damage in situ by using 380-nm native fluorescence imaging under 340-nm excitation.

STUDY DESIGN/MATERIALS AND METHODS

Native fluorescence imaging was performed on laser irradiated bovine tendon tissue and compared with light illuminated photography and histology with picrosirius red F3BA stain.

RESULTS AND CONCLUSION

The results indicate that a decrease in collagen fluorescence at 380 nm was observed in laser-induced thermally damaged tissues. The injured region of tissue defined by its fluorescence image coincided with an area defined by photography and histology.

A comparison of Cunyite and Fosterite NIR tunable laser tissue welding using native collagen fluorescence imaging

OBJECTIVE

To evaluate the technique of native collagen fluorescence imaging for assessing the extent of welded areas for tissues exposed to different near-infrared (NIR) laser wavelengths.

BACKGROUND

Native fluorescence imaging may be used to identify the distribution of collagen and elastin in tissues. Our past work demonstrated that different welding strengths were obtained under the same laser power conditions using different NIR wavelengths. The role of collagen in tissue welding experiments is not well understood.

METHODS

Two new NIR tunable lasers were used to weld canine skin. The welded areas on the surface and in cross sections were analyzed by measuring the spatial distribution of native collagen fluorescence at 380 nm excited by 340 nm radiation.

RESULTS

The results show that native collagen fluorescence imaging is a useful technique for analyzing the extent of tissue welds produced under a range of laser exposures. Fluorescence imaging reveals the depth of laser interaction with the tissue as well as evaluating collateral damage to the tissue surface. The welded volume obtained in skin using Cunyite laser exposure at 1,430 nm is deeper than that produced with Forsterite laser exposure at 1,250 nm. The post welded tensile strength for the same power density is greater for the Cunyite lasers. Ablated tissue on the surface is more prevalent with Forsterite laser welding at 1,250 nm than with Cunyite at 1,430 nm.

CONCLUSION

Native collagen fluorescence can distinguish between tissue welds that have been produced by different NIR wavelengths. Tissue welding using 1,430 nm radiation is more effective than that using 1,250 nm.

Appetitive learning using visual conditioned stimuli in the pond snail, lymnaea

Feeding can be conditioned in the pond snail Lymnaea stagnalis to two different visual stimuli (a black panel or a 5-mm black and white check surround) by pairing the potential conditioned stimulus (CS) with sucrose. Exclusion of chemical cues (associated with differences between the water in home tank and that in training apparatus) that could serve as CS is important for successful visual conditioning. A featureless gray surround, used as an alternative to the check (to which it was matched in luminance) in counterbalanced training designs, was discriminated from the check, showing that resolution (for which the eyes would be necessary) was occurring. The gray surround was largely ineffective as a CS. Single-trial learning was possible with the black panel, but not with the check; it is argued that this may be due to lack of prior experience of stimuli like the check. Conditioning of feeding has now been obtained in Lymnaea to chemical, tactile, and visual cues, opening the way to comparative studies of the neural circuitry underlying appetitive conditioning in different senses, so far explored in Lymnaea only for tactile CS. Such comparative studies are as yet largely lacking in invertebrates.

Fluorescence spectroscopic imaging to detect changes in collagen and elastin following laser tissue welding

OBJECTIVE

A study was performed to evaluate the use of native fluorescence imaging to detect in situ molecular changes.

SUMMARY BACKGROUND DATA

There is no ideal noninvasive method to monitor molecular changes in a local region at a laser weld joint without removing a section of tissue for histological examination.

METHODS

Two sections of animal skin were welded together border to border using a Ti:sapphire laser beam (800 nm). Fluorescence imaging was performed on the cross section of the welded site at specific emission wavelengths (lambda c) for collagen at 380 nm and for elastin at 450 nm using excitation wavelengths (lambda e) of 340 nm, and 380 nm, respectively.

RESULTS

A reduction of the collagen and elastin emission was observed in the fluorescence images of the welded region. These results were confirmed with histology using picrosirius red F3BA under polarized light and orcein stains.

CONCLUSION

Optical spectroscopic imaging offers a new noninvasive detecting method for microscopic evaluation of laser tissue welding.

Efficient gene transfer to human squamous cell carcinomas by the herpes simplex virus type 1 amplicon vector

BACKGROUND

This study evaluates the efficiency of herpes simplex virus (HSV) mediated gene transfer in human squamous cell carcinoma (SCC) cell lines in vitro and in vivo when delivered by selective intra-arterial perfusion.

METHODS

Human head and neck SCC were exposed to HSV-LacZ and HSV-interleukin-2 (IL-2) and gene transfer and expression assessed by X-gal staining and enzyme-linked immunosorbent assay, respectively. Hamster cheek pouch tumors were perfused with HSV-LacZ or HSV-IL-2, by microcannulating the external carotid artery, and gene transfer determined.

RESULTS

A ratio of 5 viral particles per tumor cell achieved gene transfer rates exceeding 50%. Interleukin-2 levels of 287 +/- 17 to 424 +/- 8.4 ng per million cells were achieved at a ratio of 2 viral particles per tumor cell. Selective intra-arterial perfusion of the HSV-IL-2 vector yielded IL-2 levels of 45.8 +/- 17.0 pg per g tumor.

CONCLUSIONS

HSV amplicon vectors are efficient vehicles for gene transfer in vitro in human head and neck SCC cell lines and in vivo when introduced by selective intra-arterial perfusion.

Crystallization and preliminary X-ray diffraction studies of phospho-adenylylsulfate (PAPS) reductase from E. coli

PAPS reductase from E. coli is involved in sulfur metabolism and catalyses the reduction of phospho-adenylyl-sulfate (PAPS) to sulfite. The protein has been cloned, overexpressed and purified from E. coli. Crystallization experiments resulted in crystals suitable for X-ray diffraction. The crystals belong to the orthorhombic space group C2221 with cell dimensions a = 81.9, b = 97.4, c = 109.5 A, and contain one molecule per asymmetric unit. At cryogenic (100 K) temperatures the crystals diffract to a resolution limit of 2.7 A using a rotating anode and to 2.0 A at a synchrotron source.

Behavioural lateralisation of the tetrapod type in the zebrafish (Brachydanio rerio)

Visual lateralisation resembling that found in a bird (domestic chick) is here demonstrated in a teleost (zebrafish, Brachydanio rerio). Zebrafish predominantly view objects with the body axis close to facing the object (0-20 degrees on either side of facing). Strange objects were viewed at first exposure chiefly with the right frontal field; so was a complex and unfamiliar scene made up of familiar components. In a second trial, using the same stimulus or scene, left frontal viewing tended to be used instead. A familiar partner (a fish of another species) was viewed left frontally. The domestic chick also uses the left eye to view familiar stimuli, shifting to the right when it has to decide what response is appropriate to the object at which it is looking. An empty scene in which nothing could be concealed (and so no response was called for) was viewed by zebrafish with the left eye from the start. In zebrafish and the chick, the right eye is used when it is necessary to inhibit premature response, in order to sustain viewing until a decision is reached, and the left is used when it is necessary to keep an eye on a familiar or clearly empty scene. The findings suggest homology of cerebral lateralisation in teleost fish and tetrapods.

Polarization filter for biomedical tissue optical imaging

A technique based on the degree that light is depolarized when propagating inside tissues is demonstrated for optical imaging in biomedical systems. The difference in the degree of polarization of the emerging light allows for the discrimination of different types of tissues. The technique was investigated in the transillumination and back-scattering geometry and in both cases the potential of this method to image and separate out different types of tissues is demonstrated.

Second-harmonic tomography of tissues

A novel noninvasive second-harmonic-generation tomographic method of mapping the structure of animal tissues by use of 100-fs laser pulses at 625nm is described. Subsurface structures were measured with this approach, which is potentially a symmetry-sensitive tool for optical histological reconstruction.

Crystal structure of phosphoadenylyl sulphate (PAPS) reductase: a new family of adenine nucleotide alpha hydrolases

BACKGROUND

Assimilatory sulphate reduction supplies prototrophic organisms with reduced sulphur for the biosynthesis of all sulphur-containing metabolites. This process is driven by a sequence of enzymatic steps involving phosphoadenylyl sulphate (PAPS) reductase. Thioredoxin is used as the electron donor for the reduction of PAPS to phospho-adenosine-phosphate (PAP) and sulphite. Unlike most electron-transfer reactions, there are no cofactors or prosthetic groups involved in this reduction and PAPS reductase is one of the rare examples of an enzyme that is able to store two electrons. Determination of the structure of PAPS reductase is the first step towards elucidating the biochemical details of the reduction of PAPS to sulphite.

RESULTS

We have determined the crystal structure of PAPS reductase at 2.0 A resolution in the open, reduced form, in which a flexible loop covers the active site. The protein is active as a dimer, each monomer consisting of a central six-stranded beta sheet with alpha helices packing against each side. A highly modified version of the P loop, the fingerprint peptide of mononucleotide-binding proteins, is present in the active site of the protein, which appears to be a positively charged cleft containing a number of conserved arginine and lysine residues. Although PAPS reductase has no ATPase activity, it shows a striking similarity to the structure of the ATP pyrophosphatase (ATP PPase) domain of GMP synthetase, indicating that both enzyme families have evolved from a common ancestral nucleotide-binding fold.

CONCLUSIONS

The sequence conservation between ATP sulphurylases, a subfamily of ATP PPases, and PAPS reductase and the similarities in both their mechanisms and folds, suggest an evolutionary link between the ATP PPases and PAPS reductases. Together with the N type ATP PPases, PAPS reductases and ATP sulphurylases are proposed to form a new family of homologous enzymes with adenine nucleotide alpha-hydrolase activity. The open, reduced form of PAPS reductase is able to bind PAPS, whereas the closed oxidized form cannot. A movement between the two monomers of the dimer may allow this switch in conformation to occur.

Two-dimensional structure of light harvesting complex II (LHII) from the purple bacterium Rhodovulum sulfidophilum and comparison with LHII from Rhodopseudomonas acidophila

BACKGROUND

Within the membranes of photosynthetic bacteria, up to three types of light harvesting complexes (LHI, LHII, LHIII) are found. These complexes absorb photons and transfer the excitation energy to the photosynthetic reaction centre. The LH complexes comprise units that contain alpha and beta polypeptides with associated pigment molecules.

RESULTS

The structure of LHII complex from Rhodovulum sulfidophilum has been examined to a resolution of 7 A using electron microscopy. The complex is a nonamer containing nine alphabeta subunits. These are arranged in two radially symmetric concentric cylinders, with the nine alpha chains positioned in the inner cylinder and the nine beta chains forming the outer cylinder. The 18 transmembrane helices are readily observed in the projection maps, along with 18 additional peaks attributed to the pigment molecules.

CONCLUSIONS

The determination of more structures of LH complexes will uncover the full extent of the variability of the oligomerization states in different bacteria and also in the native membrane. The analysis of two-dimensional crystals allows a rapid determination of key structural features and the oligomeric state of the complex. Comparison of our structure determined by electron microscopy with the recently solved X-ray structure indicates that the results of the two methods are complementary.

Ultraviolet excitation fluorescence spectroscopy: a noninvasive method for the measurement of redox changes in ischemic myocutaneous flaps

In this report, we discuss application of the noninvasive technology of ultraviolet fluorescence spectroscopy to the metabolic analysis of normal and compromised myocutaneous flaps. Acute changes in tissue redox states during ischemia and reperfusion were determined analysis of changes in the fluorescence spectrum of reduced nicotinomide adenine dinucleotide (NADH). Analysis of the system for NADH fluorescence showed good correlation between excitation spectra recorded at 450 nm from pure beta-NADH and those recorded from porcine rectus abdominis myocutaneous flaps. Sequential measurements of surface fluorescence were obtained from six flaps subjected to 6 hours of warm arterial ischemia and 4 hours of reperfusion. Results were compared with spectra obtained from six contralateral nonischemic control flaps. A significant mean increase in NADH fluorescence (49 percent; p < 0.05) was demonstrated within 30 minutes of vascular occlusion. Fluorescence intensity continued to increase throughout the ischemic period, reaching 320.5 percent of baseline values at 6 hours. Reperfusion resulted in the prompt return of fluorescence intensity to baseline levels. These results show that fluorescence spectroscopy of endogenous NADH is a sensitive and reliable indicator of vascular occlusion in experimental myocutaneous flaps.

Tissue autofluorescence as an intermediate endpoint in NMBA-induced esophageal carcinogenesis

The capacity to identify subclinical neoplastic disease of the upper aerodigestive tract (UADT) using tissue auto-fluorescent spectroscopy would significantly contribute to cancer screening. Rats received N-nitrosomethyl benzylamine (NMBA), a carcinogen shown to cause esophageal malignancies. Following sacrifice at early weekly intervals, gross assessment of esophageal mucosa of NMBA-exposed rats was indistinguishable from saline-treated controls. Histopathologic evaluation, however, revealed NMBA-induced preneoplastic changes in the epithelium. Concurrent with these changes, the NMBA-exposed rats demonstrated specific alterations in autofluorescence. These results demonstrate that NMBA-induced esophageal premalignancy can be distinguished by autofluorescent properties. The capacity to detect alterations in autofluorescence may allow more sensitive screening of UADT mucosa at risk for cancer development.

The in vivo biologic effect of interleukin 2 and interferon alfa on natural immunity in patients with head and neck cancer

Given the association of deficient natural immunity with the risk of metastatic disease, the ability to activate natural killer cell function may have a therapeutic significance. The effect of continuous infusion of interleukin 2 plus intramuscular interferon alfa on natural immune status was, therefore, analyzed in eight patients with head and neck cancer. Also evaluated was the effect of interleukin 2-interferon alfa therapy on lymphokine-activated killer cell activity as well as total lymphocyte count, percent of lymphocyte subsets, and levels of both circulating immune complexes and antibody classes. Both the percent and absolute number of natural killer cells (ie, CD56+ CD3- lymphocytes) within peripheral blood as well as natural killer cell activity against K562 targets increased significantly with treatment. The remaining immune parameters were not significantly altered. The demonstrated capacity to modulate natural immune function supports the potential use of interleukin 2-containing regimens as a preventive measure against metastatic disease in patients with head and neck cancer.

Structure of insulin: results of joint neutron and X-ray refinement

Neutron diffraction data for porcine 2Zn insulin were collected to 2.2 A resolution from a single crystal deuterated by slow exchange of mother liquor. A joint neutron/X-ray restrained-least-squares refinement was undertaken using the neutron data, as well as the 1.5 A resolution X-ray data collected previously. The final R factors were 0.182 for the X-ray data and 0.191 for the neutron data. Resulting atomic coordinates were compared with the initial X-ray model, showing a total r.m.s. shift of 0.36 A for the protein and 0.6 A for the solvent. Protonation of a number of individual amino acids was investigated by analysis of the neutron maps. No D atoms were found between the carboxylates of Glu B13 which make an intermolecular contact, suggesting nonbonded interaction rather than the predicted hydrogen bond. Amide hydrogen exchange was investigated in a refinement of their atomic occupancies. Regions of unexchanged amide groups were found in the center of the B helices. The results of this study emphasize the limited amount of information available in neutron diffraction studies of proteins at resolution lower than 2 A.

Water structure in vitamin B12 coenzyme crystals. I. Analysis of the neutron and x-ray solvent densities

The disordered solvent distribution in crystals of vitamin B12 coenzyme was examined using the methods of high-resolution neutron and x-ray diffraction. One set of neutron (0.95 A) and two sets of x-ray (0.94 and 1.1 A) data were collected and the resulting models were extensively refined using least-squares and Fourier syntheses. The solvent regions were analyzed in two stages: first, main sites were assigned to the well defined regions of solvent density and refined using least squares; second, continuous sites were assigned representing the more disordered diffuse and elongated regions of solvent density. During the analysis an acetone molecule was also located. Water networks were formulated from the assigned sites in the above models and also from those assigned in the original structure determination (Lenhert, 1968), using criteria that included hydrogen bonding (derived from small crystal hydrates), van der Waals contact distances, side-chain disorder, water molecule orientations, and the presence or absence of foreign solvent. The well established networks extend throughout all the solvent regions of the crystal with interesting orientational arrangements of the individual waters around both polar and apolar groups of the coenzyme molecule. The networks were seen to be consistent among each of the four models in terms of occupying relatively similar positions. However, the occupancy values of the individual networks varied between the models; some networks were clearly visible in one but attenuated in another. The specific details of the water structure (bonding geometries, short-range nonbonded contacts, orientations of the waters, polar and apolar interactions, etc.) are described in the following paper.

Water structure in vitamin B12 coenzyme crystals. II. Structural characteristics of the solvent networks

The geometrical details of the solvent structure in vitamin B12 coenzyme crystals with respect to hydrogen bonding and nonbonded contacts, are described. The individual H-bond geometries varied over wide ranges, similar to those observed in small molecule structures. Large deviations from tetrahedral coordination were found around a majority of the waters. The mutual positions and orientations of the water molecules could not be adequately explained in terms of the H-bonding relationships present in the structure. However, additional investigations, which focused on the short range nonbonded contacts around water positions in a variety of crystal hydrates, revealed several structural regularities (Savage, 1986b). These features relate to the nonbonded O...O, H...O, and H...H interactions, and give rise to a set of repulsive restrictions that are seen to be very much stronger stereochemical restraints than those associated with H-bonding. The short-range restrictions appear largely to govern the local orientational correlations and packing arrangements of the water structure within the coenzyme (and other hydrate) crystals. In more general terms, the inclusion of the nonbonding relationships as well as the attractive H-bonding interactions, leads to a significant increase in our understanding of water structure(s). The repulsive restrictions can be used as stereochemical restraints in the interpretation and refinement of solvent structures within larger hydrate systems, such as protein crystals. They may also be included in potential functions used to simulate solvent structures in aqueous solutions and hydrate systems.

Autopsy of an Egyptian mummy. 3. Gross anatomic and miscellaneous studies

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