Over-parameterised, uncertain 'mathematical marionettes' - how can we best use catchment water quality models? An example of an 80-year catchment-scale nutrient balance.

The Integrated Catchment Model of Nitrogen (INCA-N) was applied to the River Lambourn, a Chalk river-system in southern England. The model's abilities to simulate the long-term trend and seasonal patterns in observed stream water nitrate concentrations from 1920 to 2003 were tested. This is the first time a semi-distributed, daily time-step model has been applied to simulate such a long time period and then used to calculate detailed catchment nutrient budgets which span the conversion of pasture to arable during the late 1930s and 1940s. Thus, this work goes beyond source apportionment and looks to demonstrate how such simulations can be used to assess the state of the catchment and develop an understanding of system behaviour. The mass-balance results from 1921, 1922, 1991, 2001 and 2002 are presented and those for 1991 are compared to other modelled and literature values of loads associated with nitrogen soil processes and export. The variations highlighted the problem of comparing modelled fluxes with point measurements but proved useful for identifying the most poorly understood inputs and processes thereby providing an assessment of input data and model structural uncertainty. The modelled terrestrial and instream mass-balances also highlight the importance of the hydrological conditions in pollutant transport. Between 1922 and 2002, increased inputs of nitrogen from fertiliser, livestock and deposition have altered the nitrogen balance with a shift from possible reduction in soil fertility but little environmental impact in 1922, to a situation of nitrogen accumulation in the soil, groundwater and instream biota in 2002. In 1922 and 2002 it was estimated that approximately 2 and 18 kg N ha(-1) yr(-1) respectively were exported from the land to the stream. The utility of the approach and further considerations for the best use of models are discussed.

Identification of positive-acting domains in GCN2 protein kinase required for translational activation of GCN4 expression.

GCN4 is a transcriptional activator of amino acid-biosynthetic genes in the yeast Saccharomyces cerevisiae. GCN2, a translational activator of GCN4 expression, contains a domain homologous to the catalytic subunit of eucaryotic protein kinases. Substitution of a highly conserved lysine residue in the kinase domain abolished GCN2 regulatory function in vivo and its ability to autophosphorylate in vitro, indicating that GCN2 acts as a protein kinase in stimulating GCN4 expression. Elevated GCN2 gene dosage led to derepression of GCN4 under nonstarvation conditions; however, we found that GCN2 mRNA and protein levels did not increase in wild-type cells in response to amino acid starvation. Therefore, it appears that GCN2 protein kinase function is stimulated posttranslationally in amino acid-starved cells. Three dominant-constitutive GCN2 point mutations were isolated that led to derepressed GCN4 expression under nonstarvation conditions. Two of the GCN2(Con) mutations mapped in the kinase domain itself. The third mapped just downstream from a carboxyl-terminal segment homologous to histidyl-tRNA synthetase (HisRS), which we suggested might function to detect uncharged tRNA in amino acid-starved cells and activate the adjacent protein kinase moiety. Deletions and substitutions in the HisRS-related sequences and in the carboxyl-terminal segment in which one of the GCN2(Con) mutation mapped abolished GCN2 positive regulatory function in vivo without lowering autophosphorylation activity in vitro. These results suggest that sequences flanking the GCN2 protein kinase moiety are positive-acting domains required to increase recognition of physiological substrates or lower the requirement for uncharged tRNA to activate kinase activity under conditions of amino acid starvation.

The first and fourth upstream open reading frames in GCN4 mRNA have similar initiation efficiencies but respond differently in translational control to change in length and sequence.

The third and fourth AUG codons in GCN4 mRNA efficiently repress translation of the GCN4-coding sequences under normal growth conditions. The first AUG codon is approximately 30-fold less inhibitory and is required under amino acid starvation conditions to override the repressing effects of AUG codons 3 and 4. lacZ fusions constructed to functional, elongated versions of the first and fourth upstream open reading frames (URFs) were used to show that AUG codons 1 and 4 function similarly as efficient translational start sites in vivo, raising the possibility that steps following initiation distinguish the regulatory properties of URFs 1 and 4. In accord with this idea, we observed different consequences of changing the length and termination site of URF1 versus changing those of URFs 3 and 4. The latter were lengthened considerably, with little or no effect on regulation. In fact, the function of URFs 3 and 4 was partially reconstituted with a completely heterologous URF. By contrast, certain mutations that lengthen URF1 impaired its positive regulatory function nearly as much as removing its AUG codon did. The same mutations also made URF1 a much more inhibitory element when it was present alone in the mRNA leader. These results strongly suggest that URFs 1 and 4 both function in regulation as translated coding sequences. To account for the phenotypes of the URF1 mutations, we suggest the most ribosomes normally translate URF1 and that the mutations reduce the number of ribosomes that are able to complete URF1 translation and resume scanning downstream. This effect would impair URF1 positive regulatory function if ribosomes must first translate URF1 in order to overcome the strong translational block at the 3'-proximal URFs. Because URF1-lacZ fusions were translated at the same rate under repressing and derepressing conditions, it appears that modulating initiation at URF1 is not the means that is used to restrict the regulatory consequences of URF1 translation to starvation conditions.

Suppression of ribosomal reinitiation at upstream open reading frames in amino acid-starved cells forms the basis for GCN4 translational control.

GCN4 encodes a transcriptional activator of amino acid-biosynthetic genes in Saccharomyces cerevisiae that is regulated at the translational level by upstream open reading frames (uORFs) in its mRNA leader. uORF4 (counting from the 5' end) is sufficient to repress GCN4 under nonstarvation conditions; uORF1 is required to overcome the inhibitory effect of uORF4 and stimulate GCN4 translation in amino acid-starved cells. Insertions of sequences with the potential to form secondary structure around uORF4 abolish derepression, indicating that ribosomes reach GCN4 by traversing uORF4 sequences rather than by binding internally to the GCN4 start site. By showing that wild-type regulation occurred even when uORF4 was elongated to overlap GCN4 by 130 nucleotides, we provide strong evidence that those ribosomes which translate GCN4 do so by ignoring the uORF4 AUG start codon. This conclusion is in accord with the fact that translation of a uORF4-lacZ fusion was lower in a derepressed gcd1 mutant than in a nonderepressible gcn2 strain. We also show that increasing the distance between uORF1 and uORF4 to the wild-type spacing that separates uORF1 from GCN4 specifically impaired the ability of uORF1 to derepress GCN4 translation. As expected, this alteration led to increased uORF4-lacZ translation in gcd1 cells. Our results suggest that under starvation conditions, a substantial fraction of ribosomes that translate uORF1 fail to reassemble the factors needed for reinitiation by the time they scan to uORF4, but become competent to reinitiate after scanning the additional sequences to GCN4. Under nonstarvation conditions, ribosomes would recover more rapidly from uORF1 translation, causing them all to reinitiate at uORF4 rather than at GCN4.

Identification of seven hydrophobic clusters in GCN4 making redundant contributions to transcriptional activation.

GCN4 is a transcriptional activator in the bZIP family that regulates amino acid biosynthetic genes in the yeast Saccharomyces cerevisiae. The N-terminal 100 amino acids of GCN4 contains a potent activation function that confers high-level transcription in the absence of the centrally located acidic activation domain (CAAD) delineated in previous studies. To identify specific amino acids important for activation by the N-terminal domain, we mutagenized a GCN4 allele lacking the CAAD and screened alleles in vivo for reduced expression of the HIS3 gene. We found four pairs of closely spaced phenylalanines and a leucine residue distributed throughout the N-terminal 100 residues of GCN4 that are required for high-level activation in the absence of the CAAD. Trp, Leu, and Tyr were highly functional substitutions for the Phe residue at position 45. Combined with our previous findings, these results indicate that GCN4 contains seven clusters of aromatic or bulky hydrophobic residues which make important contributions to transcriptional activation at HIS3. None of the seven hydrophobic clusters is essential for activation by full-length GCN4, and the critical residues in two or three clusters must be mutated simultaneously to observe a substantial reduction in GCN4 function. Numerous combinations of four or five intact clusters conferred high-level transcription of HIS3. We propose that many of the hydrophobic clusters in GCN4 act independently of one another to provide redundant means of stimulating transcription and that the functional contributions of these different segments are cumulative at the HIS3 promoter. On the basis of the primacy of bulky hydrophobic residues throughout the activation domain, we suggest that GCN4 contains multiple sites that mediate hydrophobic contacts with one or more components of the transcription initiation machinery.

Mutations activating the yeast eIF-2 alpha kinase GCN2: isolation of alleles altering the domain related to histidyl-tRNA synthetases.

The protein kinase GCN2 stimulates expression of the yeast transcriptional activator GCN4 at the translational level by phosphorylating the alpha subunit of translation initiation factor 2 (eIF-2 alpha) in amino acid-starved cells. Phosphorylation of eIF-2 alpha reduces its activity, allowing ribosomes to bypass short open reading frames present in the GCN4 mRNA leader and initiate translation at the GCN4 start codon. We describe here 17 dominant GCN2 mutations that lead to derepression of GCN4 expression in the absence of amino acid starvation. Seven of these GCN2c alleles map in the protein kinase moiety, and two in this group alter the presumed ATP-binding domain, suggesting that ATP binding is a regulated aspect of GCN2 function. Six GCN2c alleles map in a region related to histidyl-tRNA synthetases, and two in this group alter a sequence motif conserved among class II aminoacyl-tRNA synthetases that directly interacts with the acceptor stem of tRNA. These results support the idea that GCN2 kinase function is activated under starvation conditions by binding uncharged tRNA to the domain related to histidyl-tRNA synthetase. The remaining GCN2c alleles map at the extreme C terminus, a domain required for ribosome association of the protein. Representative mutations in each domain were shown to depend on the phosphorylation site in eIF-2 alpha for their effects on GCN4 expression and to increase the level of eIF-2 alpha phosphorylation in the absence of amino acid starvation. Synthetic GCN2c double mutations show greater derepression of GCN4 expression than the parental single mutations, and they have a slow-growth phenotype that we attribute to inhibition of general translation initiation. The phenotypes of the GCN2c alleles are dependent on GCN1 and GCN3, indicating that these two positive regulators of GCN4 expression mediate the inhibitory effects on translation initiation associated with activation of the yeast eIF-2 alpha kinase GCN2.

Transcriptional profiling shows that Gcn4p is a master regulator of gene expression during amino acid starvation in yeast.

Starvation for amino acids induces Gcn4p, a transcriptional activator of amino acid biosynthetic genes in Saccharomyces cerevisiae. In an effort to identify all genes regulated by Gcn4p during amino acid starvation, we performed cDNA microarray analysis. Data from 21 pairs of hybridization experiments using two different strains derived from S288c revealed that more than 1,000 genes were induced, and a similar number were repressed, by a factor of 2 or more in response to histidine starvation imposed by 3-aminotriazole (3AT). Profiling of a gcn4Delta strain and a constitutively induced mutant showed that Gcn4p is required for the full induction by 3AT of at least 539 genes, termed Gcn4p targets. Genes in every amino acid biosynthetic pathway except cysteine and genes encoding amino acid precursors, vitamin biosynthetic enzymes, peroxisomal components, mitochondrial carrier proteins, and autophagy proteins were all identified as Gcn4p targets. Unexpectedly, genes involved in amino acid biosynthesis represent only a quarter of the Gcn4p target genes. Gcn4p also activates genes involved in glycogen homeostasis, and mutant analysis showed that Gcn4p suppresses glycogen levels in amino acid-starved cells. Numerous genes encoding protein kinases and transcription factors were identified as targets, suggesting that Gcn4p is a master regulator of gene expression. Interestingly, expression profiles for 3AT and the alkylating agent methyl methanesulfonate (MMS) overlapped extensively, and MMS induced GCN4 translation. Thus, the broad transcriptional response evoked by Gcn4p is produced by diverse stress conditions. Finally, profiling of a gcn4Delta mutant uncovered an alternative induction pathway operating at many Gcn4p target genes in histidine-starved cells.

The transcriptional activator GCN4 contains multiple activation domains that are critically dependent on hydrophobic amino acids.

GCN4 is a transcriptional activator in the bZIP family that regulates amino acid biosynthetic genes in the yeast Saccharomyces cerevisiae. Previous work suggested that the principal activation domain of GCN4 is a highly acidic segment of approximately 40 amino acids located in the center of the protein. We conducted a mutational analysis of GCN4 with a single-copy allele expressed under the control of the native promoter and translational control elements. Our results indicate that GCN4 contains two activation domains of similar potency that can function independently to promote high-level transcription of the target genes HIS3 and HIS4. One of these domains is coincident with the acidic activation domain defined previously; the other extends over the N-terminal one-third of the protein. Both domains are partially dependent on the coactivator protein ADA2. Each domain appears to be composed of two or more small subdomains that have additive effects on transcription and that can cooperate in different combinations to promote high-level expression of HIS3 and HIS4. At least three of these subdomains are critically dependent on bulky hydrophobic amino acids for their function. Five of the important hydrophobic residues, Phe-97, Phe-98, Met-107, Tyr-110, and Leu-113, fall within a region of proposed sequence homology between GCN4 and the herpesvirus acidic activator VP16. The remaining three residues, Trp-120, Leu-123, and Phe-124, are highly conserved between GCN4 and its Neurospora counterpart, cpc-1. Because of the functional redundancy in the activation domain, mutations at positions 97 and 98 must be combined with mutations at positions 120 to 124 to observe a substantial reduction in activation by full-length GCN4, and substitution of all eight hydrophobic residues was required to inactivate full-length GCN4. These hydrophobic residues may mediate important interactions between GCN4 and one or more of its target proteins in the transcription initiation complex.

The Gcn4p activation domain interacts specifically in vitro with RNA polymerase II holoenzyme, TFIID, and the Adap-Gcn5p coactivator complex.

The Gcn4p activation domain contains seven clusters of hydrophobic residues that make additive contributions to transcriptional activation in vivo. We observed efficient binding of a glutathione S-transferase (GST)-Gcn4p fusion protein to components of three different coactivator complexes in Saccharomyces cerevisiae cell extracts, including subunits of transcription factor IID (TFIID) (yeast TAFII20 [yTAFII20], yTAFII60, and yTAFII90), the holoenzyme mediator (Srb2p, Srb4p, and Srb7p), and the Adap-Gcn5p complex (Ada2p and Ada3p). The binding to these coactivator subunits was completely dependent on the hydrophobic clusters in the Gcn4p activation domain. Alanine substitutions in single clusters led to moderate reductions in binding, double-cluster substitutions generally led to greater reductions in binding than the corresponding single-cluster mutations, and mutations in four or more clusters reduced binding to all of the coactivator proteins to background levels. The additive effects of these mutations on binding of coactivator proteins correlated with their cumulative effects on transcriptional activation by Gcn4p in vivo, particularly with Ada3p, suggesting that recruitment of these coactivator complexes to the promoter is a cardinal function of the Gcn4p activation domain. As judged by immunoprecipitation analysis, components of the mediator were not associated with constituents of TFIID and Adap-Gcn5p in the extracts, implying that GST-Gcn4p interacted with the mediator independently of these other coactivators. Unexpectedly, a proportion of Ada2p coimmunoprecipitated with yTAFII90, and the yTAFII20, -60, and -90 proteins were coimmunoprecipitated with Ada3p, revealing a stable interaction between components of TFIID and the Adap-Gcn5p complex. Because GST-Gcn4p did not bind specifically to highly purified TFIID, Gcn4p may interact with TFIID via the Adap-Gcn5p complex or some other adapter proteins. The ability of Gcn4p to interact with several distinct coactivator complexes that are physically and genetically linked to TATA box-binding protein can provide an explanation for the observation that yTAFII proteins are dispensable for activation by Gcn4p in vivo.

Design of an expression system for detecting folded protein domains and mapping macromolecular interactions by NMR.

Two protein expression vectors have been designed for the preparation of NMR samples. The vectors encode the immunoglobulin-binding domain of streptococcal protein G (GB1 domain) linked to the N-terminus of the desired proteins. This fusion strategy takes advantage of the small size, stable fold, and high bacterial expression capability of the GB1 domain to allow direct NMR spectroscopic analysis of the fusion protein by 1H-15N correlation spectroscopy. Using this system accelerates the initial assessment of protein NMR projects such that, in a matter of days, the solubility and stability of a protein can be determined. In addition, 15N-labeling of peptides and their testing for DNA binding are facilitated. Several examples are presented that demonstrate the usefulness of this technique for screening protein/DNA complexes, as well as for probing ligand-receptor interactions, using 15N-labeled GB1-peptide fusions and unlabeled target.

Dynamic three-dimensional imaging of the mitral valve and left ventricle by rapid sonomicrometry array localization.

OBJECTIVES: The first objective was to develop a quantitative method for tracking the three-dimensional geometry of the mitral valve. The second was to determine the complex interrelationships of various components of the mitral valve in vivo. METHODS AND RESULTS: Sixteen sonomicrometry transducers were placed around the mitral vale anulus, at the tips and bases of both papillary muscles, at the ventricular apex, across the ventricular epicardial short axis, and on the anterior chest wall before and during cardiopulmonary bypass in eight anesthetized sheep. Animals were studied later on 17 occasions. Reproducibility of derived chord lengths and three-dimensional coordinates from sonomicrometry array localization, longevity of transducer signals, and the dynamics of the mitral valve and left ventricle were studied. Reproducibility of distance measurements averages 1.6%; Procrustes analysis of three-dimensional arrays of coordinate locations predicts an average error of 2.2 mm. Duration of serial sonomicrometry array localization signals ranges between 60 and 151 days (mean 114 days). Sonomicrometry array localization demonstrates the saddle-shaped mitral anulus, its minimal orifice area immediately before end-diastole, and uneven, apical descent during systole. Papillary muscles shorten only 3.0 to 3.5 mm. Sonomicrometry array localization demonstrates nonuniform torsion of papillary muscle transducers around a longitudinal axis and shows rotation of papillary muscular bases toward each other during systole. CONCLUSION: Tagging of ventricular structures in experimental animals by sonomicrometry array localization images is highly reproducible and suitable for serial observations. In sheep the method provides unique, quantitative information regarding the interrelationship of mitral valvular and left ventricular structures throughout the cardiac cycle.

Infarct size and location determine development of mitral regurgitation in the sheep model.

OBJECTIVE: This study tests the hypothesis that neither small nor large myocardial infarctions that include the anterior papillary muscle produce mitral regurgitation in sheep. METHODS: Coronary arterial anatomy to the anterior left ventricle and papillary muscle was determined by dye injection in 41 sheep hearts and by triphenyl tetrazolium chloride in 13. Development of acute or chronic mitral regurgitation and changes in left ventricular dimensions were studied by use of transdiaphragmatic echocardiography in 21 sheep after infarction of 24% and 33% of the anterior left ventricular mass. These data were compared with previous data from large and small posterior left ventricular infarctions. RESULTS: Ligation of two diagonal arteries infarcts 24% of the left ventricular mass and 82% of the anterior papillary muscle. Ligation of both diagonals and the first circumflex branch infarcts 33% of the left ventricle and all of the anterior papillary muscle. Neither infarction causes mitral regurgitation, although left ventricular cavity dimensions increase significantly at end systole. After the smaller infarction, the left ventricular cavity enlarges 150% over 8 weeks without mitral regurgitation. CONCLUSIONS: In sheep small and large infarctions of the anterior wall that include the anterior papillary muscle do not produce either acute or chronic mitral regurgitation despite left ventricular dilatation. In contrast large posterior infarctions produce immediate mitral regurgitation owing to asymmetric annular dilatation and discoordination of papillary muscle relationships to the valve. After small posterior infarctions that include the posterior papillary muscle, mitral regurgitation develops because of annular and ventricular dilatation during remodeling.

Identifying acute myocardial infarction: effects on treatment and mortality, and implications for National Service Framework audit.

BACKGROUND: The National Service Framework (NSF) for Coronary Heart Disease requires annual clinical audit of the care of patients with myocardial infarction, with little guidance on how to achieve these standards and monitor practice. AIM: To assess which method of identification of acute myocardial infarction (AMI) cases is most suitable for NSF audit, and to determine the effect of the definition of AMI on the assessment of quality of care. DESIGN: Observational study. METHODS: Over a 3-month period, 2153 consecutive patients from 20 hospitals across the Yorkshire region, with confirmed AMI, were identified from coronary care registers, biochemistry records and hospital coding systems. The sensitivity and positive predictive value of AMI patient identification using clinical coding, biochemistry and coronary care registers were compared to a 'gold standard' (the combination of all three methods). RESULTS: Of 3685 possible cases of AMI singled out by one or more methods, 2153 patients were identified as having a final diagnosis of AMI. Hospital coding revealed 1668 (77.5%) cases, with a demographic profile similar to that of the total cohort. Secondary preventative measures required for inclusion in NSF were also of broadly similar distribution. The sensitivities and positive predictive values for patient identification were substantially less in the cohorts identified through biochemistry and coronary care unit register. Patients fulfilling WHO criteria (n=1391) had a 30-day mortality of 15.9%, vs. 24.2% for the total cohort. DISCUSSION: Hospital coding misses a substantial proportion (22.5%) of AMI cases, but without any apparent systematic bias, and thus provides a suitably representative and robust basis for NSF-related audit. Better still would be the routine use of multiple methods of case identification.

Distortions of the mitral valve in acute ischemic mitral regurgitation.

BACKGROUND: In the absence of papillary muscle rupture, the precise deformations that cause acute postinfarction mitral valve regurgitation are not understood and impair reparative efforts. METHODS: In 6 Dorsett hybrid sheep, sonomicrometry transducers were placed around the mitral annulus (n = 6) and at the tips and bases of both papillary muscles (n = 4). Later, specific circumflex coronary arteries were occluded to infarct approximately 32% of the posterior left ventricle and produce acute 2 to 3+ mitral regurgitation. Before and after infarction, distance measurements between sonomicrometry transducers produced three-dimensional coordinates of each transducer every 5 ms. RESULTS: After infarction, the annulus dilated asymmetrically orthogonal to the line of leaflet coaptation, but the annular area increased only 9.2% +/- 6.3% (p = 0.02). At end-systole, posterior papillary muscle length increased 2.3 +/- 0.9 mm (p = 0.005); the posterior papillary muscle tip moved closer to the annular plane and centroid, and the anterior papillary muscle tip moved away. CONCLUSIONS: Small deformations in mitral valvular spatial geometry after large posterior infarctions are sufficient to produce moderate to severe mitral regurgitation. The most important changes are asymmetric annular dilatation, prolapse of leaflet tissue tethered by the posterior papillary muscle, and restriction of leaflet tissue attached to the anterior papillary muscle.

An evaluation of the relationship between specialist training in cardiology and implementation of evidence-based care of patients following acute myocardial infarction.

AIMS: Large clinical trials have provided evidence of prognostically beneficial treatment strategies for patients with acute myocardial infarction. However, the implementation of this evidence into routine clinical practice is suboptimal. We hypothesised that the speciality of the attending physician (cardiologist or not) would affect the use of evidence-based strategies. METHODS: Over a 3-month period (1st September to 30th November 1995), 3684 consecutive potential cases of acute myocardial infarction (AMI) in 20 adjacent hospitals in the Yorkshire Region were identified from coronary care registers, clinical coding and biochemistry records of cardiac enzyme assay requests. There were 2153 consecutive cases of AMI identified, of which 1643 patients were alive at discharge. We compared the admission use of aspirin and thrombolysis, and the use of aspirin, beta-blockers, angiotensin-converting enzyme (ACE) inhibitors and statins at discharge between cardiologists and other physicians. RESULTS: AMI patients under the care of cardiologists are more likely to receive aspirin and thrombolysis on the day of their event and to be prescribed aspirin, beta-blockers and statins on discharge. After correction for contraindications to their use, the above findings were broadly confirmed. DISCUSSION: Cardiologists are more likely than general physicians to use evidence-based treatment strategies recognised to improve AMI patient outcome. It is likely that this will translate into a reduction of mortality or other hard endpoints in patient outcomes.

An epidemiologic investigation of a rubella outbreak among the Amish of northeastern Ohio.

From April 1990 to April 1991, 278 cases of rubella were reported to the Ohio Department of Health. Of these, 276 (99 percent) were among the Amish of northeastern Ohio. The outbreak involved eight counties in an area that contains large settlements of Old Order Amish. Members of this community of Amish frequently take religious exemption from recommended immunization practices and are believed to represent a high proportion of Ohio's rubella-susceptible persons. Vaccination history was known only for 146 of the Amish people. Of those, only four had a positive history of rubella vaccination. Of the 276 Amish with cases of rubella, 65 (24 percent) were younger than age 5 years, 104 (38 percent) were ages 5-14, 46 (17 percent) were ages 15-19, 32 (12 percent) were ages 20-29, 6 (2 percent) were ages 30 or older, and age was not reported for 23 (8 percent). The ratio of males to females with rubella was 1:1. Five women of the Amish community were pregnant; four had been ill with symptoms consistent with rubella. Three were in their first trimester. Congenital rubella syndrome did not occur in any of the four live births. Serology was available for only the two non-Amish people, and both were acute phase serum-positive for Immunoglobulin M.

Use of cumulative mortality data in patients with acute myocardial infarction for early detection of variation in clinical practice: observational study.

OBJECTIVES: Use of cumulative mortality adjusted for case mix in patients with acute myocardial infarction for early detection of variation in clinical practice. DESIGN: Observational study. SETTING: 20 hospitals across the former Yorkshire region. PARTICIPANTS: All 2153 consecutive patients with confirmed acute myocardial infarction identified during three months. MAIN OUTCOME MEASURES: Variable life-adjusted displays showing cumulative differences between observed and expected mortality of patients; expected mortality calculated from risk model based on admission characteristics of age, heart rate, and systolic blood pressure. RESULTS: The performance of two individual hospitals over three months was examined as an example. One, the smallest district hospital in the region, had a series of 30 consecutive patients but had five more deaths than predicted. The variable life-adjusted display showed minimal variation from that predicted for the first 15 patients followed by a run of unexpectedly high mortality. The second example was the main tertiary referral centre for the region, which admitted 188 consecutive patients. The display showed a period of apparently poor performance followed by substantial improvement, where the plot rose steadily from a cumulative net lives saved of -4 to 7. These variations in patient outcome are unlikely to have been revealed during conventional audit practice. CONCLUSIONS: Variable life-adjusted display has been integrated into surgical care as a graphical display of risk-adjusted survival for individual surgeons or centres. In combination with a simple risk model, it may have a role in monitoring performance and outcome in patients with acute myocardial infarction.

Fully automatic segmentation of the mitral leaflets in 3D transesophageal echocardiographic images using multi-atlas joint label fusion and deformable medial modeling.

Comprehensive visual and quantitative analysis of in vivo human mitral valve morphology is central to the diagnosis and surgical treatment of mitral valve disease. Real-time 3D transesophageal echocardiography (3D TEE) is a practical, highly informative imaging modality for examining the mitral valve in a clinical setting. To facilitate visual and quantitative 3D TEE image analysis, we describe a fully automated method for segmenting the mitral leaflets in 3D TEE image data. The algorithm integrates complementary probabilistic segmentation and shape modeling techniques (multi-atlas joint label fusion and deformable modeling with continuous medial representation) to automatically generate 3D geometric models of the mitral leaflets from 3D TEE image data. These models are unique in that they establish a shape-based coordinate system on the valves of different subjects and represent the leaflets volumetrically, as structures with locally varying thickness. In this work, expert image analysis is the gold standard for evaluating automatic segmentation. Without any user interaction, we demonstrate that the automatic segmentation method accurately captures patient-specific leaflet geometry at both systole and diastole in 3D TEE data acquired from a mixed population of subjects with normal valve morphology and mitral valve disease.