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PubMed2002

Surgical programme at Royal Alexandra Hospital, Sydney, for Papua New Guinea children with congenital heart disease, 1978-1994.

OBJECTIVE: To report the history of the Royal Alexandra Hospital for Children (RAHC) Papua New Guinea (PNG) cardiac surgical programme and describe the selection, preoperative clinical features and postoperative outcome of children with congenital heart disease managed by the programme. METHODS: Details for each of the PNG cardiac patients admitted to RAHC following selection by visiting cardiologists between 1978 and 1994 were entered into a database, and analysed and interpreted. RESULTS: A congenital heart defect was confirmed in 165 of the 170 children selected. The male to female ratio was 1:1 and the mean age on admission to RAHC was 5.5 years. Almost all of the children for whom data were available (98%) had a weight for age and 41% had a height for age less than the 3rd centile. One-sixth had delayed milestones. A large number were tachypnoeic, in heart failure, or had pulmonary hypertension on admission. Ventricular septal defect and tetralogy of Fallot were the commonest defects, and lesions such as aortic stenosis, coarctation of the aorta and transposition of the great arteries were absent or rare. Thirty-one (19%) of the children selected initially did not receive surgery because of pulmonary hypertension, or because the lesions did not fall within the programme guidelines for operation. One hundred and twenty-nine children had corrective and four had palliative procedures. Half of the operated children had postoperative complications. Eight children died, all following open-heart procedures, giving a case fatality rate of 6%. Preoperative tachypnoea, hepatomegaly, cardiac failure and pulmonary hypertension were strongly associated with poor outcome. CONCLUSIONS: The programme was an arduous exercise for all organizations concerned, but achieved comparatively good short-term outcomes. The experience gained should assist in planning for similar programmes.

Adolescent↗
PubMed2003

Conflict monitoring in the human anterior cingulate cortex during selective attention to global and local object features.

Parallel processing affords the brain many advantages, but processing multiple bits of information simultaneously presents formidable challenges. For example, while one is listening to a speaker at a noisy social gathering, processing irrelevant conversations may lead to the activation of irrelevant perceptual, semantic, and response representations that conflict with those evoked by the speaker. In these situations, specialized brain systems may be recruited to detect and resolve conflict before it leads to incorrect perception and/or behavior. Consistent with this view, recent findings indicate that dorsal/caudal anterior cingulate cortex (dACC), on the medial walls of the frontal lobes, detects conflict between competing motor responses primed by relevant versus irrelevant stimuli. Here, we used a cued global/local selective attention task to investigate whether the dACC plays a general role in conflict detection that includes monitoring for conflicting perceptual or semantic representations. Using event-related functional magnetic resonance imaging (fMRI), we found that the dACC was activated by response conflict in both the global and the local task, consistent with results from prior studies. However, dACC was also activated by perceptual and semantic conflict arising from global distracters during the local task. The results from the local task have implications for recent theories of attentional control in which the dACC's contribution to conflict monitoring is limited to response stages of processing, as well as for our understanding of clinical disorders in which disruptions of attention are associated with dACC dysfunction.

Adult↗
PubMed2006

Control of combustion-generated nitrogen oxides by selective non-catalytic reduction.

Controlling nitrogen oxides (NO(x)) emissions is becoming a daunting technical challenge as increasingly strict emission limits are being imposed. The stringent regulations have prompted the innovation and characterization of NO(x) control technologies suitable for various applications. This paper presents a review on NO(x) removal techniques with particular reference to selective non-catalytic reduction (SNCR) technology. This includes initially how SNCR emerged as a technology along with a comparison with other relevant technologies. A review of various features related to selective non-catalytic gas phase injection of ammonia and ammonium salts (as reducing agent) is presented. The use of urea solution as a reducing agent and its performance in laboratory and pilot scale tests as well as large-scale applications is also discussed. Use of cyanuric acid as a potential reducing agent is also presented. The underlying reaction mechanisms have been reviewed for ammonia, urea and cyanuric acid for the explanation of various observations. Computational fluid dynamics (CFD) modeling as applied to SNCR is also presented. Subsequently the use of SNCR coupled with other in-combustion and post-combustion NO(x) control techniques is elaborated. Additionally, a two-stage NO(x) removal strategy to control un-reacted ammonia slip and to improve overall efficiency is discussed. At the end a summary is given which highlights various areas needing further research.

Air Pollutants↗
PubMed1992

A morphometric filter improves the diagnostic value of morphometric analyses of frozen histopathological sections from mammary tumours.

Frozen sections of 202 consecutive breast tumour cases were analyzed by morphometric quantitation of nuclear features. Nuclei were selected at random. Conventional light microscope examination of the paraffin-embedded specimens revealed 144 cases of cancer and 56 benign tumours. Using multivariate discriminant analysis of morphometric features, all but two of the benign cases and 79% of the malignant tumours were correctly classified. When a morphometrically based dynamic filter set to exclude 'non-diagnostic' nuclei was used, the correctly classified malignant cases rose to 86% Morphometry is a fast, reproducible and efficient method that can be used in conjunction with the histomorphological diagnosis of mammary frozen sections. The combination of systematic sampling and an objective dynamic filter may be a powerful approach to quantitative analyses of tumours from other sites. However, it is also likely that efficiency can be improved by combining nuclear morphometric features with structural, histochemical and molecular biological data. The combination of traditional histomorphological examination with quantitative information may well increase the diagnostic accuracy in individual patients.

Breast Neoplasms↗
PubMed1987

Colonoscopy in inflammatory bowel disease. Diagnostic accuracy and proposal of an endoscopic score.

Colonoscopy is used in the differential diagnosis of inflammatory bowel disease but its accuracy and the "weight" of the various endoscopic signs have not been assessed. In a prospective study 357 patients with 606 colonoscopies, in whom the endoscopic appearances were those of ulcerative colitis, Crohn's colitis, or indeterminate colitis, were followed-up for an average period of 22 mo. A final, definite, endoscopy-independent diagnosis was reached by means of autopsy, surgery, or histology on biopsy in 71% of patients. Accuracy of colonoscopy was 89%, with 4% errors and 7% indeterminate diagnoses. Errors were more frequent in severe inflammatory activity (9%). The most useful endoscopic features in this differential diagnosis were discontinuous involvement, anal lesions, and cobblestoning of mucosa for Crohn's disease, and erosions or microulcers and granularity for ulcerative colitis. After selecting the endoscopic features with best predictive value, an "endoscopic score" was calculated by means of "likelihood ratios."

Colitis, Ulcerative↗
PubMed2006

Edge transfer lithography using alkanethiol inks.

Edge lithographic patterning techniques are based on the utilization of the edges of micrometer-sized template features for the reproduction of submicrometer structures. Edge transfer lithography (ETL) permits local surface modification in a single step by depositing self-assembled monolayers onto a metal substrate selectively along the feature edges of an elastomeric stamp. In this report two stamp designs are described that now allow for the use of alkanethiol inks in ETL and their use as etch resists to reproduce submicrometer structures in gold. Anisotropically modified stamps are shown to combine the potential for very high-resolution patterning with the versatility and simplicity of microcontact printing.

Alkanes↗
PubMed1998

Object-based attention and occlusion: evidence from normal participants and a computational model.

One way of perceptually organizing a complex visual scene is to attend selectively to information in a particular physical location. Another way of reducing the complexity in the input is to attend selectively to an individual object in the scene and to process its elements preferentially. This latter, object-based attention process was examined, and the predicted superiority for reporting features from 1 relative to 2 objects was replicated in a series of experiments. This object-based process was robust even under conditions of occlusion, although there were some boundary conditions on its operation. Finally, an account of the data is provided via simulations of the findings in a computational model. The claim is that object-based attention arises from a mechanisms that groups together those features based on internal representations developed over perceptual experience and then preferentially gates these features for later, selective processing.

Adolescent↗
PubMed2000

Insular and anaplastic carcinoma of the thyroid: a 45-year comparative study at a single institution and a review of the significance of p53 and p21.

OBJECTIVE: To analyze the clinicopathologic features of a large cohort of patients with insular or anaplastic carcinomas treated at a single institution. SUMMARY BACKGROUND DATA: Insular and anaplastic carcinomas of the thyroid, although uncommon, have more aggressive clinical behavior than well-differentiated carcinomas of the thyroid. In the literature, the incidence and features of these carcinomas have not been fully characterized. METHODS: The authors reclassified 740 primary thyroid carcinomas diagnosed and treated between January 1, 1954, and December 30, 1998, to select those with features that met the histologic criteria of insular or anaplastic carcinoma. The clinicopathologic features of these carcinomas were studied and compared. The expression of p53 and p21 in these tumors was analyzed by immunohistochemistry. RESULTS: Twenty-two patients (5 men, 17 women) with insular carcinoma and 38 patients (7 men, 31 women) with anaplastic carcinoma were found. Patients with insular carcinomas were younger (mean age 45 vs. 70 years) and had smaller tumors than those with anaplastic carcinomas (mean diameter 5 vs. 8 cm). Insular carcinomas were commonly mislabeled as other histologic subtypes, whereas anaplastic carcinomas might be overdiagnosed on pathologic examination. A history of longstanding goiter (>10 years) was noted in 27% of patients with insular carcinoma and 24% of patients with anaplastic carcinomas. Concomitant well-differentiated carcinomas of the thyroid were noted in 59% of patients with insular carcinoma and 39% of patients with anaplastic carcinoma. In anaplastic carcinomas, 13% of patients had concomitant insular carcinoma. Calcification or bone was noted in the stroma of 23% of patients with insular carcinomas and 47% of those with anaplastic carcinomas. The 10-year survival rates for patients with insular carcinoma and anaplastic carcinoma were 42% and 3%, respectively. Distant metastases were seen in 32% of patients with insular carcinoma and in 47% of patients with anaplastic carcinomas. In both types of carcinomas, metastatic tumors were often seen in bone and lung. Distant metastases were noted in a variety of organs in anaplastic carcinomas. In insular carcinoma, neither p53 nor p21 expression was present. In anaplastic carcinoma, p53 and p21 expression was identified in 69% and 3%, respectively. Concomitant expression of p53 and p21 was noted in one tumor. CONCLUSIONS: Insular carcinoma and anaplastic carcinoma had distinctive clinicopathologic features, and recognition of these histologic variants is important for better management of these tumors in the future. p53 overexpression might have a role in dedifferentiation from insular carcinoma to anaplastic carcinoma.

Adolescent↗
PubMed1985

A computer reconstruction system for biological macro- and microstructures traced from serial sections.

A system of programs for building three-dimensional (3D) models of biological macro- and microstructures has been developed. A PDP 11/34 laboratory minicomputer with graphical output devices, and a QUANTIMET image analyzer are used for the reconstruction. The contours of the features can be digitized directly from tissue sections mounted on the stage of an OPTON research light microscope, or indirectly from microphotographs, and from camera lucida drawings. The operator selects contours of features in question from the image by using Quantimet's interactive input devices and commands the Quantimet system to record the image. The 3D models are built from a series of 2D outlines. In the visualization phase the reconstructed objects can be investigated from different viewpoints with their hidden lines removed. Additional calculations (volume and surface area) help in quantitative classification of the reconstructed structures.

Animals↗
PubMed1999

Does parietal cortex contribute to feature binding?

We studied the involvement of the right parietal cortex in visual conjunction search, where two features are present in the array and spatial attention and feature binding is required, and in subset search, where two features are also present but only one of them is needed in order to group stimuli together (the subset) and allow parallel processing without the need for feature binding. Six patients with right parietal lobe lesions, six age-matched controls, and three control patients with left parietal lesions were tested on these two tasks. Patients with right parietal lesions were significantly slower than normal controls in the conjunction task, especially for target-absent trials. In the subset condition, neither normal control subjects nor patients with left parietal damage showed a difference between target-present and target-absent trials whereas right parietal patients showed a significant difference between target-present and target-absent responses. The results suggest a role for the right parietal cortex in shifting attention to the next stimulus once binding of features has taken place or selecting spatial areas containing the desired feature in a subset search, but that parietal cortex is not required for binding the features of the object.

Adult↗
PubMed1999

Quantitative analysis of receptors for adenosine nucleotides obtained via in vitro selection from a library incorporating a cationic nucleotide analog.

5-(3"-Aminopropynyl)-2'-deoxyuridine (dJ), a modified nucleoside with a side chain carrying a cationic functional group, was incorporated into an oligonucleotide library, which was amplified using the Vent DNA polymerase in a polymerase chain reaction (PCR). When coupled to an in vitro selection procedure, PCR amplification generated receptors that bind ATP. This is the first example of an in vitro selection generating oligonucleotide receptors where the oligonucleotide library has incorporated a cationic nucleotide functionality. The selection yielded functionalized receptors having sequences differing from a motif known to arise in a standard selection experiment using only natural nucleotides. Surprisingly, both the natural and the functionalized motifs convergently evolved to bind not one, but two ATP molecules cooperatively. Likewise, the affinity of the receptors for ATP had converged; in both cases, the receptors are half saturated at the 3 mM concentrations of ATP presented during the selection. The convergence of phenotype suggests that the outcome of this selection experiment was determined by features of the environment during which selection occurs, in particular, a highly loaded affinity resin used in the selection step. Further, the convergence of phenotype suggests that the optimal molecular phenotype has been achieved by both selections for the selection conditions. This interplay between environmental conditions demanding a function of a biopolymer and the ability of the biopolymer to deliver that function is strictly analogous to that observed during natural selection, illustrating the nature of life as a self-sustaining chemical system capable of Darwinian evolution.

Adenine Nucleotides↗
PubMed2003

Direct selection on allozymes is not required to explain heterogeneity among marker loci across a Mytilus hybrid zone.

Unequal differentiation between two types of loci (allozyme and DNA markers) across a Mytilus hybrid zone has recently been claimed as evidence for direct selection on some allozyme loci. We provide here a counter-example: a noncoding DNA locus that exhibits as much differentiation as the incriminated allozymes do. The levels of genetic differentiation varied widely among both allozymes and noncoding DNA markers and no clear difference emerged between the two types of markers. This suggests that the strong interlocus variance in genetic differentiation has been confounded with a discrepancy between marker types as a result of an insufficient and unbalanced locus sampling. Heterogeneity in differentiation among neutral loci can be created by stochastic variance during the allopatric divergence preceding a secondary contact. In hybrid zones, a further source of variance is differential introgression among chromosomal regions after the secondary contact owing to the local influence of selected genes on more or less distant markers. However, the degree of differentiation alone gives no way to distinguish indirect pseudo-selection (a regular and ubiquitous feature of hybrid zones) from direct selection. More generally, we suggest that comparative neutrality tests based on discrepancies among marker types have to be applied with caution when the presence of semi-permeable genetic barriers to gene exchange is suspected.

Animals↗
PubMed2000

Aspects of the functional morphology of the ductus epididymidis in domestic anseriform and galliform birds.

The structure of the ductus epididymidis, and its capacity to take up luminal particulate material (India ink) were studied, using scanning and transmission electron microscopy, in the domestic fowl, turkey and Japanese quail (Order Galliformes) and drake (Order Anseriformes). The epithelium appeared contractile and stable structurally, especially in the drake in which, among other cytoskeletal features, abundant perinuclear intermediate filaments radiated peripherally in the principal, nonciliated (Type III) cell. The Golgi complex was well developed, except in the turkey in which it was extremely inconspicuous. Sparsely granulated profiles were the main component of the elaborate endoplasmic reticulum, which was best developed in the drake and least in the turkey. The cell in the turkey was uniquely laden with large aggregates of lipid droplets. Generally, characteristics of a cell active in the synthesis and merocrine secretion of proteinaceous material were evident. There was no evidence of apocrine-like secretion in well-fixed tissues. The cell lacked the capacity to take up luminal India ink particles, and displayed very poorly developed endocytic structural features, which are also probably only selectively and minimally absorptive. Ultrastructural features varied between and within the orders studied, necessitating further studies.

Animals↗
PubMed1994

Nuclear factors that mediate intrathymic signals are developmentally regulated.

Thymocytes mature through several stages of development, defined by cell surface markers such as CD3, CD4, and CD8, in response to environmental cues. Signal transduction resulting from lymphocyte-stromal cell interactions is likely to activate inducible transcription factors which in turn govern stage-specific gene expression. In this report we show that inducible transcription factors such as AP-1 and NF-AT are constitutively nuclear, in response to intrathymic signals, in freshly isolated thymocytes at all stages of maturation. In CD4+CD8+ double positive (DP), but not in the more immature CD4-CD8- double negative (DN) thymocytes, constant stimulus from the thymic environment is required to maintain nuclear AP-1. Thus, disruption of the thymus and incubation of thymocytes at 37 degrees C downregulates DNA binding by nuclear factors AP-1 and NF-AT. Similar treatment of thymocytes has previously been shown to downregulate CD3 zeta chain phosphorylation and increase T cell receptor CD3 expression on DP thymocytes, which is a feature of repertoire selection. Since mature T cells maintain inducible nuclear factors in an inactive form until an encounter with antigen, we propose that downregulation of nuclear DNA binding proteins may reflect another feature of this stage of T cell maturation.

Aging↗
PubMed2000

Some features of the mutability of bacteria during nonlethal selection.

We describe the mutability of the Trp(-) chromosomal +1 frameshift mutation trpE7999 during nonlethal selection, finding that the appearance of Trp(+) revertants behaves similarly to that of episomal Lac(+) revertants. In addition, we show that a feature of the Lac(+) and Trp(+) mutability is the accumulation of Trp(+) and Lac(+) revertants with additional unselected mutations, most of which are not due to heritable mutators. The cells undergoing nonlethal selection apparently experience an epigenetic change resulting in a subset of bacteria with elevated mutability that often remain hypermutable for the duration of selection. The epigenetic change provoked by nonlethal selection appears to be mediated by a unique function provided by the F'128 episome.

Bacteria↗
PubMed1997

Feature-detecting auditory neurons in the brain of a sound-producing fish.

The mormyrid fish Pollimyrus adspersus has auditory specializations for sound pressure detection and uses acoustic displays in its natural social behavior. In this paper it is shown that auditory neurons in the mesencephalon (torus semicircularis) are activated selectively by temporal features of complex sounds. Single neurons were recorded while presenting sounds to fish underwater. The stimuli were acoustic click trains, 400 ms in duration, and were synthesized with differing inter-click-intervals (ICIs). The natural sounds of this species are composed similarly and the range of ICIs synthesized overlapped with the natural range (5-40 ms). One-third of the neurons studied were strongly selective for a narrow range of ICIs, increasing spike rate by ten fold or more at the best ICI compared to the minimum response observed. The best ICI for interval selective neurons remained stable when the sound pressure of the stimulus was changed. Neurons that were selective gave phasic responses to tone bursts, and most had non-monotonic rate level functions. The origin of interval selectivity is discussed and a time-based computational mechanism is proposed.

Acoustic Stimulation↗
PubMed2004

Quantitative analysis of a RNA-cleaving DNA catalyst obtained via in vitro selection.

In vitro selections performed in the presence of Mg(2+) generated DNA sequences capable of cleaving an internal ribonucleoside linkage. Several of these, surprisingly, displayed intermolecular catalysis and catalysis independent of Mg(2+), features that the selection protocol was not explicitly designed to select. A detailed physical organic analysis was applied to one of these DNAzymes, termed 614. First, the progress curve for the reaction was dissected to identify factors that prevented the molecule from displaying clean first-order transformation kinetics and 100% conversion. Several factors were identified and quantitated, including (a) competitive intra- and intermolecular rate processes, (b) alternative reactive and unreactive conformations, and (c) mutations within the catalyst. Other factors were excluded, including "approach to equilibrium" kinetics and product inhibition. The possibility of complementary strand inhibition was demonstrated but was shown to not be a factor under the conditions of these experiments. The rates of the intra- and intermolecular processes were compared, and saturation models for the intermolecular process were built. The rate-limiting step for the intermolecular reaction was found to be the association/folding of the enzyme with the substrate and not the cleavage step. The DNAzyme 614 is more active in trans than in cis and more active at temperatures below the selection temperature than at the selection temperature. Many of these properties have not been reported in similar systems; these results therefore expand the phenomenology known for this class of DNA-based catalysts. A brief survey of other catalysts arising from this selection found other Mg(2+)-independent DNAzymes and provided a preliminary view of the ruggedness of the landscape, relating function to structure in sequence space. Hypotheses are suggested to account for the fact that a selection in the presence of Mg(2+) did not exploit this Mg(2+). This study of a specific catalytically active DNAzyme is an example of studies that will be necessary generally to permit in vitro selection to help us understand the distribution of function in sequence space.

Bacteriophage lambda↗
PubMed2003

Prevalence of cancer in follicular thyroid nodules: is there still a role for intraoperative frozen section analysis?

The optimal surgical management of follicular thyroid nodules and the effectiveness of frozen section (FS) analysis in planning the operation are still controversial. In this study, we reviewed the prevalence of cancer in 309 consecutive patients (230 females, 79 males, aged 42 +/- 13 years) with follicular nodules at fine-needle aspiration cytology (FNAC) and the efficacy of FS evaluation in selecting cancers. On the whole, the prevalence of cancer was 20.1%; the occurrence of follicular variants of papillary cancer (14.9%) was threefold higher than follicular cancers (5.2%). The presence of atypical features at FNAC selected nodules with a significantly higher prevalence of cancer (46.7%, p = 0.01). FS analysis was performed in 142 patients and recognized only 8 of 27 (30%) cancers, one fourth of them with atypia at FNAC. In conclusion, this study confirms a 20% overall prevalence of malignancy in patients with follicular thyroid nodules. The association of cell atypia with a follicular pattern may define a subgroup of nodules more likely to be malignant. FS was seldom effective in recognizing cancer confirming the doubt on its cost effectiveness in planning the surgical approach. Protocols aimed at a better cytologic identification of follicular variants of papillary cancer should be considered.

Adult↗