A comparison of Landsat 8, RapidEye and Pleiades products for improving empirical predictions of satellite-derived bathymetry.

Satellite derived bathymetry (SDB) enables rapid mapping of large coastal areas through measurement of optical penetration of the water column. The resolution of bathymetric mapping and achievable horizontal and vertical accuracies vary but generally, all SDB outputs are constrained by sensor type, water quality and other environmental conditions. Efforts to improve accuracy include physics-based methods (similar to radiative transfer models e.g. for atmospheric/vegetation studies) or detailed in-situ sampling of the seabed and water column, but the spatial component of SDB measurements is often under-utilised in SDB workflows despite promising results suggesting potential to improve accuracy significantly. In this study, a selection of satellite datasets (Landsat 8, RapidEye and Pleiades) at different spatial and spectral resolutions were tested using a log ratio transform to derive bathymetry in an Atlantic coastal embayment. A series of non-spatial and spatial linear analyses were then conducted and their influence on SDB prediction accuracy was assessed in addition to the significance of each model's parameters. Landsat 8 (30 m pixel size) performed relatively weak with the non-spatial model, but showed the best results with the spatial model. However, the highest spatial resolution imagery used - Pleiades (2 m pixel size) showed good results across both non-spatial and spatial models which suggests a suitability for SDB prediction at a higher spatial resolution than the others. In all cases, the spatial models were able to constrain the prediction differences at increased water depths.

Fetal aortic valvuloplasty: investigating institutional bias in surgical decision-making.

OBJECTIVES: Fetal aortic valvuloplasty may prevent the progression of aortic stenosis to hypoplastic left heart syndrome and allow biventricular rather than univentricular postnatal treatment. This study aimed to investigate whether blinded simulation of a multidisciplinary team approach aids interpretation of multicenter data to uncover institutional bias in postnatal decision-making following fetal cardiac intervention for aortic stenosis. METHODS: The study included 109 cases of prenatally diagnosed aortic stenosis from 13 European countries, of which 32 had undergone fetal cardiac intervention. The multidisciplinary team, blinded to fetal cardiac intervention, institutional location and postnatal treatment, retrospectively assigned a surgical pathway (biventricular or univentricular) based on a review of recorded postnatal imaging and clinical characteristics. The team's decisions were the numerical consensus of silent voting, with case review when a decision was split. Funnel plots showing concordance between the multidisciplinary team and the local team's surgical choice (first pathway) and with outcome (final pathway) were created. RESULTS: In 105 cases the multidisciplinary team reached a consensus decision regarding the surgical pathway, with no decision in four cases because the available imaging records were inadequate. Blinded multidisciplinary team consensus for the first pathway matched the decision of the surgical center in 93/105 (89%) cases, with no difference in agreement between those that had undergone successful fetal cardiac intervention (n = 32) and no (n = 74) or unsuccessful (n = 3) valvuloplasty (no fetal cardiac intervention) (κ = 0.73 (95% CI, 0.38-1.00) vs 0.74 (95% CI, 0.51-0.96)). However, funnel plots comparing multidisciplinary team individual decisions with those of the local teams displayed more discordance (meaning biventricular-univentricular conversion) for the final surgical pathway following fetal cardiac intervention than they did for cases without such intervention (36/74 vs 34/130; P = 0.002), and identified one outlying center. CONCLUSIONS: The use of a blinded multidisciplinary team to simulate decision-making and presentation of data in funnel plots may assist in the interpretation of data submitted to multicenter studies and permit the identification of outliers for further investigation. In the case of aortic stenosis, a high level of agreement was observed between the multidisciplinary team and the surgical centers, but one outlying center was identified.

Transmembrane molecular assemblies regulated by the greater cadherin family.

The cadherin family of cell-cell adhesion molecules is turning out to be much more diverse than previously thought, with members involved in several kinds of intercellular junctions. The adhesive specificity and cytoskeletal interaction of these members varies. Their cytoplasmic terminals are specialized for binding several families of 'mediator' proteins which interconnect to the actin or intermediate filament systems. These multi-molecular complexes have roles not only in cell-cell adhesion, but also in intracellular signalling of developmental information.

Pre-Flight Calibration of the Mars 2020 Rover Mastcam Zoom (Mastcam-Z) Multispectral, Stereoscopic Imager.

The NASA Perseverance rover Mast Camera Zoom (Mastcam-Z) system is a pair of zoomable, focusable, multi-spectral, and color charge-coupled device (CCD) cameras mounted on top of a 1.7 m Remote Sensing Mast, along with associated electronics and two calibration targets. The cameras contain identical optical assemblies that can range in focal length from 26 mm ( 25.5 ∘ × 19.1 ∘ FOV ) to 110 mm ( 6.2 ∘ × 4.2 ∘ FOV ) and will acquire data at pixel scales of 148-540 µm at a range of 2 m and 7.4-27 cm at 1 km. The cameras are mounted on the rover's mast with a stereo baseline of 24.3 ± 0.1  cm and a toe-in angle of 1.17 ± 0.03 ∘ (per camera). Each camera uses a Kodak KAI-2020 CCD with 1600 × 1200 active pixels and an 8 position filter wheel that contains an IR-cutoff filter for color imaging through the detectors' Bayer-pattern filters, a neutral density (ND) solar filter for imaging the sun, and 6 narrow-band geology filters (16 total filters). An associated Digital Electronics Assembly provides command data interfaces to the rover, 11-to-8 bit companding, and JPEG compression capabilities. Herein, we describe pre-flight calibration of the Mastcam-Z instrument and characterize its radiometric and geometric behavior. Between April 26 t h and May 9 t h , 2019, ∼45,000 images were acquired during stand-alone calibration at Malin Space Science Systems (MSSS) in San Diego, CA. Additional data were acquired during Assembly Test and Launch Operations (ATLO) at the Jet Propulsion Laboratory and Kennedy Space Center. Results of the radiometric calibration validate a 5% absolute radiometric accuracy when using camera state parameters investigated during testing. When observing using camera state parameters not interrogated during calibration (e.g., non-canonical zoom positions), we conservatively estimate the absolute uncertainty to be < 10 % . Image quality, measured via the amplitude of the Modulation Transfer Function (MTF) at Nyquist sampling (0.35 line pairs per pixel), shows MTF Nyquist = 0.26 - 0.50 across all zoom, focus, and filter positions, exceeding the > 0.2 design requirement. We discuss lessons learned from calibration and suggest tactical strategies that will optimize the quality of science data acquired during operation at Mars. While most results matched expectations, some surprises were discovered, such as a strong wavelength and temperature dependence on the radiometric coefficients and a scene-dependent dynamic component to the zero-exposure bias frames. Calibration results and derived accuracies were validated using a Geoboard target consisting of well-characterized geologic samples. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s11214-021-00795-x.

The role of human demographic history in determining the distribution and frequency of transferase-deficient galactosaemia mutations.

Classical or transferase-deficient galactosaemia is an inherited metabolic disorder caused by mutation in the human Galactose-1-phosphate uridyl transferase (GALT) gene. Of some 170 causative mutations reported, fewer than 10% are observed in more than one geographic region or ethnic group. To better understand the population history of the common GALT mutations, we have established a haplotyping system for the GALT locus incorporating eight single nucleotide polymorphisms and three short tandem repeat markers. We analysed haplotypes associated with the three most frequent GALT gene mutations, Q188R, K285N and Duarte-2 (D2), and estimated their age. Haplotype diversity, in conjunction with measures of genetic diversity and of linkage disequilibrium, indicated that Q188R and K285N are European mutations. The Q188R mutation arose in central Europe within the last 20 000 years, with its observed east-west cline of increasing relative allele frequency possibly being due to population expansion during the re-colonization of Europe by Homo sapiens in the Mesolithic age. K285N was found to be a younger mutation that originated in Eastern Europe and is probably more geographically restricted as it arose after all major European population expansions. The D2 variant was found to be an ancient mutation that originated before the expansion of Homo sapiens out of Africa.

Aggregation of lipid rafts accompanies signaling via the T cell antigen receptor.

The role of lipid rafts in T cell antigen receptor (TCR) signaling was investigated using fluorescence microscopy. Lipid rafts labeled with cholera toxin B subunit (CT-B) and cross-linked into patches displayed characteristics of rafts isolated biochemically, including detergent resistance and colocalization with raft-associated proteins. LCK, LAT, and the TCR all colocalized with lipid patches, although TCR association was sensitive to nonionic detergent. Aggregation of the TCR by anti-CD3 mAb cross-linking also caused coaggregation of raft-associated proteins. However, the protein tyrosine phosphatase CD45 did not colocalize to either CT-B or CD3 patches. Cross-linking of either CD3 or CT-B strongly induced tyrosine phosphorylation and recruitment of a ZAP-70(SH2)(2)-green fluorescent protein (GFP) fusion protein to the lipid patches. Also, CT-B patching induced signaling events analagous to TCR stimulation, with the same dependence on expression of key TCR signaling molecules. Targeting of LCK to rafts was necessary for these events, as a nonraft- associated transmembrane LCK chimera, which did not colocalize with TCR patches, could not reconstitute CT-B-induced signaling. Thus, our results indicate a mechanism whereby TCR engagement promotes aggregation of lipid rafts, which facilitates colocalization of LCK, LAT, and the TCR whilst excluding CD45, thereby triggering protein tyrosine phosphorylation.

Structure and assembly of desmosome junctions: biosynthesis, processing, and transport of the major protein and glycoprotein components in cultured epithelial cells.

Extracts of metabolically labeled cultured epithelial cells have been analyzed by immunoprecipitation followed by SDS-PAGE, using antisera to the major high molecular mass proteins and glycoproteins (greater than 100 kD) from desmosomes of bovine muzzle epidermis. For nonstratifying cells (Madin-Darby canine kidney [MDCK] and Madin-Darby bovine kidney), and A431 cells that have lost the ability to stratify through transformation, and a stratifying cell type (primary human keratinocytes) apparently similar polypeptides were immunoprecipitated with our antisera. These comprised three glycoproteins (DGI, DGII, and DGIII) and one major nonglycosylated protein (DPI). DPII, which has already been characterized by others in stratifying tissues, appeared to be absent or present in greatly reduced amounts in the nonstratifying cell types. The desmosome glycoproteins were further characterized in MDCK cells. Pulse-chase studies showed all three DGs were separate translation products. The two major glycoprotein families (DGI and DGII/III) were both found to be synthesized with co-translational addition of 2-4 high mannose cores later processed into complex type chains. However, they became endo-beta-N-acetylglucosaminidase H resistant at different times (DGII/III being slower). None of the DGs were found to have O-linked oligosaccharides unlike bovine muzzle DGI. Transport to the cell surface was rapid for all glycoproteins (60-120 min) as demonstrated by the rate at which they became sensitive to trypsin in intact cells. This also indicated that they were exposed at the outer cell surface. DGII/III, but not DGI, underwent a proteolytic processing step, losing 10 kD of carbohydrate-free peptide, during transport to the cell surface suggesting a possible regulatory mechanism in desmosome assembly.

Structure and assembly of desmosome junctions: biosynthesis and turnover of the major desmosome components of Madin-Darby canine kidney cells in low calcium medium.

Neither stratifying (primary keratinocytes) nor simple (Madin-Darby canine kidney [MDCK] and Madin-Darby bovine kidney [MDBK]) epithelial cell types from desmosomes in low calcium medium (LCM; less than 0.1 mM), but they can be induced to do so by raising the calcium level to physiological concentrations (standard calcium medium [SCM], 2 mM). We have used polyclonal antisera to the major bovine epidermal desmosome components (greater than 100 kD) in a sensitive assay involving immunoprecipitation of the components from metabolically labeled MDCK cell monolayers to investigate the mechanism of calcium-induced desmosome formation. MDCK cells, whether cultured in LCM or SCM, were found to synthesize the desmosome protein, DPI and desmosome glycoproteins DGI and DGII/III with identical electrophoretic mobility, and also, where relevant, with similar carbohydrate addition/processing and proteolytic processing. The timings of these events and of transport of DGI to the cell surface were similar in low and high calcium. Although the rates of synthesis of the various desmosome components were also similar under both conditions, the glycoprotein turnover rates increased dramatically in cells cultured in LCM. The half-lives decreased by a factor of about 7 for DGI and 12 for DGII/III and, consistent with this, MDCK cells labeled for 48 h in SCM had three and six times the amount of DGI and DGII/III, respectively, as cells labeled for 48 h in LCM. The rate of turnover and the levels of DPI were changed in the same direction, but to much lesser extents. Possible mechanisms for the Ca2+-dependent control of desmosome formation are discussed in the light of this new evidence.

Clinical and molecular characteristics of 1qter microdeletion syndrome: delineating a critical region for corpus callosum agenesis/hypogenesis.

BACKGROUND: Patients with a microscopically visible deletion of the distal part of the long arm of chromosome 1 have a recognisable phenotype, including mental retardation, microcephaly, growth retardation, a distinct facial appearance and various midline defects including corpus callosum abnormalities, cardiac, gastro-oesophageal and urogenital defects, as well as various central nervous system anomalies. Patients with a submicroscopic, subtelomeric 1qter deletion have a similar phenotype, suggesting that the main phenotype of these patients is caused by haploinsufficiency of genes in this region. OBJECTIVE: To describe the clinical presentation of 13 new patients with a submicroscopic deletion of 1q43q44, of which nine were interstitial, and to report on the molecular characterisation of the deletion size. RESULTS AND CONCLUSIONS: The clinical presentation of these patients has clear similarities with previously reported cases with a terminal 1q deletion. Corpus callosum abnormalities were present in 10 of our patients. The AKT3 gene has been reported as an important candidate gene causing this abnormality. However, through detailed molecular analysis of the deletion sizes in our patient cohort, we were able to delineate the critical region for corpus callosum abnormalities to a 360 kb genomic segment which contains four possible candidate genes, but excluding the AKT3 gene.

The dynamic role of palmitoylation in signal transduction.

Guanine nucleotide binding protein (G protein)-linked receptors, the alpha-subunits of heterotrimeric G proteins and members of the Src family of nonreceptor tyrosine kinases are among many polypeptides that are posttranslationally modified by the addition of palmitate, a long-chain fatty acid. Attachment of palmitate to these proteins is dynamic and may be regulated by their activation. The presence of palmitate appears to play a key role in the membrane localization of either the entire polypeptide or parts of it, and may regulate the interactions of these polypeptides with other proteins.

Bioimpedance spectroscopy measurements of phase angle and height for age are predictive of outcome in children following surgery for congenital heart disease.

OBJECTIVE: Children with congenital heart disease (CHD) are often growth restricted (low weight- and/or height-for-age) which may increase risk of poor post operative resilience. Bioelectrical impedance spectroscopy (BIS) has been used to determine body composition in different clinical settings and has been shown to mark differences in nutritional state and clinical outcome. In disease conditions were fluid is not normally distributed it is proposed that raw impedance values and BIS derived phase-angle may serve as prognostic indicators of clinical outcome. We sought to describe the relationship between nutritional status, phase-angle and post-operative outcomes in children with congenital heart disease. DESIGN: Single centre prospective cohort study. SETTING: Paediatric Intensive Care Unit (PICU), Southampton Children's Hospital. PATIENTS: 122 children with CHD following cardiac surgery (March 2015-April 2016). Outcome variables included growth, mechanical-ventilation, PICU length of stay (PICU-LOS) and phase-angle at 50 Hz. MEASUREMENTS AND MAIN RESULTS: BIS measurements were taken before and on the day of surgery (day 0), day 2 post-operatively and on discharge from hospital. Pre-operative moderate malnutrition defined as height-for-age-z-score (HAZ) ≤-2 was observed in 28.5% of infants and 20.6% of children. Regression analysis was used to investigate the relationship between phase-angle, HAZ and clinical outcomes. Moderate-malnutrition (HAZ ≤-2) was associated with an increased PICU-LOS (odds ratios (OR) with 95% confidence interval: 1.8; 1.1-2.7, p = 0.008) whilst a low phase-angle (≤2.7° on day 2 was associated with longer PICU-LOS (OR 7.8; 2.7-22.45, p < 0.001)); When the model was adjusted for age, known risk factors and length of surgery, HAZ ≤-2 and phase-angle ≤2.7° on day 2 were associated with longer PICU-LOS (p = 0.001 and p = 0.04 respectively) and together explained 81.7% of the variability in PICU-LOS. CONCLUSIONS: Moderate malnutrition (HAZ ≤-2) in infants and children undergoing cardiac surgery is associated with longer PICU-LOS. Post-operative measures of BIS phase angle may further improve our ability to identifying hose children with an increased risk of prolonged PICU-LOS compared to using pre-operative anthropometry alone.

High speed optically sectioned fluorescence lifetime imaging permits study of live cell signaling events.

We present a time domain optically sectioned fluorescence lifetime imaging (FLIM) microscope developed for high-speed live cell imaging. This single photon excited system combines wide field parallel pixel detection with confocal sectioning utilizing spinning Nipkow disc microscopy. It can acquire fluorescence lifetime images of live cells at up to 10 frames per second (fps), permitting high-speed FLIM of cell dynamics and protein interactions with potential for high throughput cell imaging and screening applications. We demonstrate the application of this FLIM microscope to real-time monitoring of changes in lipid order in cell membranes following cholesterol depletion using cyclodextrin and to the activation of the small GTP-ase Ras in live cells using FRET.

Gross rearrangements of the MECP2 gene are found in both classical and atypical Rett syndrome patients.

MECP2 mutations are identifiable in approximately 80% of classic Rett syndrome (RTT), but less frequently in atypical RTT. We recruited 110 patients who fulfilled the diagnostic criteria for Rett syndrome and were referred to Cardiff for molecular analysis, but in whom an MECP2 mutation was not identifiable. Dosage analysis of MECP2 was carried out using multiplex ligation dependent probe amplification or quantitative fluorescent PCR. Large deletions were identified in 37.8% (14/37) of classic and 7.5% (4/53) of atypical RTT patients. Most large deletions contained a breakpoint in the deletion prone region of exon 4. The clinical phenotype was ascertained in all 18 of the deleted cases and in four further cases with large deletions identified in Goettingen. Five patients with large deletions had additional congenital anomalies, which was significantly more than in RTT patients with other MECP2 mutations (2/193; p<0.0001). Quantitative analysis should be included in molecular diagnostic strategies in both classic and atypical RTT.

Characterization of an acyltransferase acting on p21N-ras protein in a cell-free system.

We have identified a protein-acyltransferase activity in membranes from mouse fibroblasts which transfers palmitate from palmitoyl-CoA to p21N-ras. Specificity of acylation has been confirmed by linkage analysis using hydroxylamine and by peptide mapping of in vivo and in vitro acylated p21N-ras. The acylation was temperature- and time-dependent, and prevented by prior boiling of membranes, consistent with an enzymatic process. The activity was detected in membranes, but not cytosol, and co-fractionated on Percoll gradients with Golgi markers. Cytosolic p21N-ras from mouse fibroblasts, which is C-terminally modified at its CAAX sequence, was a better substrate for the enzyme that recombinant bacterially expressed, unmodified p21N-ras. The activity could be solubilised in non-ionic detergents, making it amenable to purification.

Release of fatty acids from virus glycoproteins by hydroxylamine.

The fatty acids bound to the glycoproteins of Sindbis and vesicular stomatitis viruses can be released by treating the protein with 1 M hydroxylamine at pH 8.0, but the rates of release vary greatly among the three proteins. The most labile fatty acyl bonds were in the Sindbis virus PE2/E2 proteins and the most stable were in the E1 protein. Some of the fatty acids in Sindbis virus glycoproteins were reduced to the alcohol after treatment with sodium borohydride, indicating that protein-bound fatty acids could be in thiolester linkage. Sindbis virus PE2/E2 has several cysteine residues near the carboxy terminus, a region of the protein postulated to be localized on the inside (cytoplasmic face) of the bilayer, and protease digestion of microsomal membranes containing E2 protein removed a small portion of this cytoplasmic tail as well as significant amounts of the fatty acid. For the vesicular stomatitis virus G protein, the sensitivity of fatty acid hydrolysis appeared to depend on the conformation of the protein and a significant fraction of G protein was converted to a disulfide-linked dimer by hydroxylamine. These data implicate cysteinyl groups on these proteins as sites involved in fatty acid acylation.

Atrioventricular septal defects diagnosed in fetal life: associated cardiac and extra-cardiac abnormalities and outcome.

OBJECTIVES: We sought to establish the outlook for fetuses diagnosed with atrioventricular septal defect (AVSD) prenatally and its relation to additional cardiac, extracardiac and chromosomal abnormalities. BACKGROUND: Prediction of likely outcome of AVSD presenting prenatally is complicated by the wide variation in associated features. METHODS: Computerized records from 14,726 pregnancies referred to a fetal cardiology center were reviewed retrospectively. Pathological reports, postnatal records, follow-up inquiries and review of echocardiographic video recordings supplemented analysis of the records for all those with AVSD. RESULTS: Atrioventricular septal defect was confirmed in 301 fetuses. Eighty-six (39%) of the 218 with known karyotype had trisomy 21, and 21/218 (10%) had other chromosome abnormalities. Right isomerism occurred in 37/301 (12%) fetuses, left isomerism in 62 (20%), mirror image atrial arrangement in 2 (1%), and 200 (67%) had usual arrangement. Atrioventricular septal defect occurred without any other intracardiac abnormality in 155 fetuses (51%). Extracardiac abnormalities and nonkaryotypic syndromes were evident in 40 fetuses (13%, confidence interval [CI] 9.5-17.1%). Uncomplicated cardiac anatomy was significantly associated with the presence of karyotype abnormality (p < 0.0001). Parents opted for termination of pregnancy in 175/298 (58.5%). For the continuing pregnancies, Kaplan-Meier estimates for live birth, survival past the neonatal period and survival to three years were 82% (CI 75.3-88.9%), 55% (CI 46.0%-0/64.3%) and 38% (CI 27.1-48.6%), respectively. Fetal hydrops and earlier year of diagnosis were independent variables with adverse influence on survival. CONCLUSIONS: Despite some improvements in the outlook for AVSD diagnosed prenatally, the overall prognosis remains considerably poorer than that implied from surgical series. The detection of associated cardiac and extracardiac abnormalities is important in order to give the best indication of the likely outcome when counseling parents.

Balloon dilation of severe aortic stenosis in the neonate: comparison of anterograde and retrograde catheter approaches.

OBJECTIVES: We sought to compare anterograde and retrograde balloon dilation of severe aortic valve stenosis in neonates. BACKGROUND: There is a high incidence of iliofemoral artery complications after retrograde balloon dilation of the aortic valve in the neonate. Therefore, a nonarterial technique of catheter access to the aortic valve would be worth exploring. METHODS: Group 1 included 11 consecutive patients (median age 6 days, range 1 to 42; median weight 3.5 kg, range 2.16 to 4.25) undergoing attempted anterograde dilation through a femoral venous approach. Group 2 included 15 patients (median age 3 days, range 1 to 35; median weight 3.4 kg, range 2.5 to 4.4 kg) who underwent attempted retrograde dilation, including 2 in whom attempted anterograde approach had failed. RESULTS: The valve was successfully crossed in 9 of 11 anterograde and 13 of 15 retrograde dilations. In both groups, the peak gradient across the valve decreased significantly (both p = 0.001). On echocardiography, the jet width of the aortic incompetence/ annulus diameter ratio was 0.16 +/- 0.08 (mean +/- SD) after anterograde and 0.51 +/- 0.24 after retrograde dilation (p = 0.03), possibly because of unrecognized valve leaflet perforation. Two patients in group 1 developed persistent, mild mitral insufficiency. Femoral artery thrombosis developed in one patient after anterograde dilation and in eight after retrograde dilation (p = 0.03). CONCLUSIONS: This series demonstrates that an anterograde approach for balloon angioplasty of severe neonatal aortic valve stenosis is feasible, achieves good hemodynamic relief and lessens morbidity compared with retrograde arterial techniques.

Systemic venous collateral development after the bidirectional cavopulmonary anastomosis. Prevalence and predictors.

OBJECTIVES: To determine the prevalence of systemic venous collaterals after the bidirectional cavopulmonary anastomosis and the factors associated with their development. BACKGROUND: Systemic venous collaterals have been found after cavopulmonary anastomosis. Methods. Cardiac catheterization was performed in 103 patients before and after a bidirectional cavopulmonary anastomosis. RESULTS: After surgery, 51 venous collaterals were identified in 32 patients (31%). Collateral development was associated with an abnormal superior vena caval connection (56% incidence vs. 26% with a single right superior vena cava, p = 0.01) and postoperative factors including pulmonary artery distortion (53% incidence vs. 22% without distortion, p = 0.002); increased superior vena caval mean pressure (14 +/- 5 mm Hg versus 11 +/- 4 mm Hg with no collaterals, p = 0.0002); increased pulmonary artery mean pressure (13 +/- 4 mm Hg vs. 11 +/- 4 mm Hg with no collaterals, p = 0.02); lower right atrial mean pressure (5 +/- 2 mm Hg vs. 6 +/- 3 mm Hg with no collaterals, p = 0.04); and increased mean gradient between superior vena cava and right atrium (8 +/- 3 mm Hg vs. 5 +/- 4 mm Hg with no collaterals, p = 0.0002). Using multiple logistic regression, only this last factor was independently associated with collateral development with an odds ratio per 1 mm Hg of 1.33 (95% CI 1.12-1.58, p = 0.001) for their presence. CONCLUSIONS: Systemic venous collaterals occur frequently after a bidirectional cavopulmonary anastomosis and are found postoperatively when a significant pressure gradient occurs between cava and right atrium.

The influence of single base changes on UV mutational activity at two translocated hotspots.

Mutation hotspots have been a staple of mutation spectra since the introduction of fine structure mutation mapping almost 40 years ago. It has been well established that sequence context is an important determinant of mutational activity at mutagen induced hotspots and coldspots. However, our understanding of the sequence effectors of base substitution hotspots is quite limited. This is because manipulation of the sequence about a hotspot site in a marker gene is restricted by the need to maintain a functional marker. In this work, we describe a generalizable system for studying sequence context effects on mutagenesis. We have prepared a variant of the supF tRNA gene (a marker used by us in previous studies) in which an eight-base palindrome, the site of two UV hotspots in the interior of the gene, was copied into the acceptor stem and pre-tRNA region. The variant tRNA was active. The UV mutation spectrum of this variant showed that the new copy of the palindrome generated two hotspots which were as intense as the original sites in the interior of the gene. Variant genes were constructed with all possible bases at the first position in the palindrome in the pre-tRNA sequence, which does not affect tRNA function. The mutation analysis showed that activity at one of the hotspots could be reduced or enhanced by the changes, while activity at the other site was not significantly affected. The base changes did not influence the frequency of cyclobutane dimer or (6-4) photoproduct formation at the two hotspot sites. Thus, the changes in mutational activity were due to the influence of sequence context on the efficiency of mutation formation at the sites of UV lesions.