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PubMed2000

Multicentric hepatocellular carcinomas tend to grow in more damaged segments of the liver.

In 115 patients (68 with liver cirrhosis and 47 without) who underwent curative resection of hepatocellular carcinoma (HCC) caused by hepatitis C virus (HCV)-related chronic liver diseases, we separated the liver into three segments (right, middle, and left) according to the three secondary branches of the Glissonean pedicle. We examined the weight of each resected segment. We also examined the histological findings of the segments in the same liver in 24 other patients with HCV-related chronic liver diseases. The average weight of the segments did not vary significantly in patients without liver cirrhosis. However, the average weight of the segments was significantly different in patients with liver cirrhosis (P = 0.0414) and the weight of the middle segment was lower than that of the other segments. In another group, of 246 patients with curative resection of HCC, of the 90 patients with single nodular HCCs, 45 nodules (50%) were located in the middle segment (P = 0.0004); in the 156 patients with synchronous multicentric HCCs (total, 401 nodules), 220 nodules (54.9%) were located in the middle segment. In 74 of the 156 patients with synchronous multicentric HCCs (47.4%), the HCCs were located in the same segment. The grade, stage of hepatitis, and number of sites of irregular regeneration were significantly different in each segment (P < 0.05), and the middle segment had more advanced hepatitis than the other segments. The rate of occurrence of HCC in the middle segment was higher than that in the other segments. The difference among the segments of the liver in regard to the degree of damage done by hepatitis may be related to the differences in HCC occurrence among the liver segments.

Carcinoma, Hepatocellular↗
PubMed1995

Quantitative arteriography of apparently normal coronary segments with nearby or distant disease suggests presence of occult, nonvisualized atherosclerosis.

OBJECTIVES: The aim of this study was to evaluate, using quantitative arteriography, whether the diameter of visually normal coronary segments might be influenced by the relative proximity of visually apparent disease. BACKGROUND: Severity of coronary artery lesions is commonly referenced against a presumed normal nearby coronary segment with the presumption that visually smooth segments are relatively free of atherosclerotic disease. METHODS: Angiograms from 136 male patients with focal coronary disease were examined, and visually normal segments in the proximal portions of the major vessels were identified for measurement of mean segment diameters. Normal segments with immediately adjacent disease were compared with normal segments with distal disease in the same vessel and compared with normal segments in vessels for which the only other visible disease was in distant vessels. Angiograms with entirely normal findings from 26 age-matched men with atypical chest pain were used as controls. Segments were measured after nitroglycerin administration by means of computer-assisted quantitation. RESULTS: Mean diameters of visually normal segments with distant disease were smaller than those of control segments (p < 0.05). Normal left main and proximal left anterior descending coronary artery segments in patients with disease within the same vessel were significantly smaller than normal segments in patients with distant disease (p < 0.05). Normal segments with immediately adjacent disease had smaller mean diameters than normal segments with distal disease in the same vessel (p < 0.05). CONCLUSIONS: Visually normal coronary segments have progressively smaller lumen diameters, depending on the relative proximity of visible disease. Measurement of percent stenosis on the basis of the diameter of apparently normal adjacent reference segments can result in underestimation of coronary lesion severity.

Cardiac Catheterization↗
PubMed2004

Simultaneous truth and performance level estimation (STAPLE): an algorithm for the validation of image segmentation.

Characterizing the performance of image segmentation approaches has been a persistent challenge. Performance analysis is important since segmentation algorithms often have limited accuracy and precision. Interactive drawing of the desired segmentation by human raters has often been the only acceptable approach, and yet suffers from intra-rater and inter-rater variability. Automated algorithms have been sought in order to remove the variability introduced by raters, but such algorithms must be assessed to ensure they are suitable for the task. The performance of raters (human or algorithmic) generating segmentations of medical images has been difficult to quantify because of the difficulty of obtaining or estimating a known true segmentation for clinical data. Although physical and digital phantoms can be constructed for which ground truth is known or readily estimated, such phantoms do not fully reflect clinical images due to the difficulty of constructing phantoms which reproduce the full range of imaging characteristics and normal and pathological anatomical variability observed in clinical data. Comparison to a collection of segmentations by raters is an attractive alternative since it can be carried out directly on the relevant clinical imaging data. However, the most appropriate measure or set of measures with which to compare such segmentations has not been clarified and several measures are used in practice. We present here an expectation-maximization algorithm for simultaneous truth and performance level estimation (STAPLE). The algorithm considers a collection of segmentations and computes a probabilistic estimate of the true segmentation and a measure of the performance level represented by each segmentation. The source of each segmentation in the collection may be an appropriately trained human rater or raters, or may be an automated segmentation algorithm. The probabilistic estimate of the true segmentation is formed by estimating an optimal combination of the segmentations, weighting each segmentation depending upon the estimated performance level, and incorporating a prior model for the spatial distribution of structures being segmented as well as spatial homogeneity constraints. STAPLE is straightforward to apply to clinical imaging data, it readily enables assessment of the performance of an automated image segmentation algorithm, and enables direct comparison of human rater and algorithm performance.

Algorithms↗
PubMed2004

Liver segmentation in living liver transplant donors: comparison of semiautomatic and manual methods.

PURPOSE: To compare the accuracy and repeatability of a semiautomatic segmentation algorithm with those of manual segmentation for determining liver volume in living liver transplant donors at magnetic resonance (MR) imaging. MATERIALS AND METHODS: The institutional review board approved this retrospective study and waived the requirement for informed consent. The semiautomatic segmentation algorithm is based on geometric deformable models and the level-set technique. It entails (a) placing initialization circle(s) on each image section, (b) running the algorithm, (c) inspecting and possibly manually modifying the contours obtained with the segmentation algorithm, and (d) placing lines to separate the liver segments. For 18 living donors (eight men and 10 women; mean age, 34 years; age range, 25-46 years), two observers each performed two semiautomatic and two manual segmentations on contrast material-enhanced T1-weighted MR images. Each measurement was timed. Actual graft weight was measured during surgery. The time needed for manual and that needed for semiautomatic segmentation were compared. Accuracy and repeatability were evaluated with the Bland-Altman method. RESULTS: Mean interaction time was reduced from 25 minutes with manual segmentation to 5 minutes with semiautomatic segmentation. The mean total time for the semiautomatic process was 7 minutes 20 seconds. Differences between the actual volume and the estimated volume ranged from -223 to +123 mL for manual segmentation and from -214 to +86 mL for semiautomatic segmentation. The 95% limits of agreement for the ratio of actual graft volume to estimated graft volume were 0.686 and 1.601 for semiautomatic segmentation and 0.651 and 1.957 for manual segmentation. Semiautomatic segmentation improved estimation in 15 of 18 cases. Inter- and intraobserver repeatability was higher with semiautomatic segmentation. CONCLUSION: Use of the semiautomatic segmentation algorithm substantially reduces the time needed for volumetric measurement of liver segments while improving both accuracy and repeatability.

Adult↗
PubMed1995

PQ segment depression in acute Q wave inferior wall myocardial infarction.

BACKGROUND: PQ segment deviation is almost as characteristic as the classic ST segment deviation and is detected in most patients with pericarditis. However, as infarction-associated pericarditis remains over the infarct zone, PQ segment depression is observed much less often in patients with acute myocardial infarction. METHODS AND RESULTS: We designed this study to examine the clinical significance of PQ segment depression in acute Q wave inferior myocardial infarction. We examined 171 consecutive patients with acute Q wave inferior myocardial infarction by means of auscultation, ECG, and two-dimensional echocardiography. The diagnosis of pericarditis was made on the basis of pericardial rub detected by more than two observers during the first 3 days after admission. At least 0.5 mm of PQ segment depression from the TP segment lasting more than 24 hours in both limb and precordial leads was considered diagnostic of PQ segment depression. CONCLUSIONS: PQ segment depression was present in 14 patients and absent in 157 patients. Eleven patients with and 55 patients without PQ segment depression had advanced asynergy (akinesis or dyskinesis) in the posterior segments, whereas 9 patients with and 20 patients without PQ segment depression had pericardial rub. When multivariate analysis was performed to determine the important variables related to the occurrence of PQ segment depression, pericardial rub was selected with advanced asynergy of the posterior segment as significant factors related to PQ segment depression. Major complications (ventricular fibrillation, sustained ventricular tachycardia, cardiogenic shock, need for pacing) were present in 63 patients; 9 with (64%) and 54 without (34%) PQ segment depression. PQ segment depression was one of the clinical signs of more extensive damage extending to the posterior segments and increased incidence of major complications.

Aged↗
PubMed1989

Spinal cord segments containing key elements of the central pattern generators for three forms of scratch reflex in the turtle.

The immobilized, low-spinal turtle produces 3 forms of the fictive scratch reflex in response to tactile stimulation of specific sites on its body surface (Robertson et al., 1985). We used complete transections of the spinal cord at different rostrocaudal levels to reveal the minimum length of spinal cord sufficient to produce each scratch form. Additional transections revealed the progressive loss of elements of the motor pattern and the eventual loss of rhythmogenesis. We have identified, therefore, spinal cord segments containing key elements of each scratch form's central pattern generator (CPG). The turtle spinal cord consists of 8 cervical segments (C1-C8), 10 dorsal segments (D1-D10), 2 sacral segments (S1, S2) and about 16 caudal segments (Ca1-Ca16; Kusuma et al., 1979). The cell bodies of motor neurons innervating the hindlimb muscles are located in the hindlimb enlargement, segments D8-S2 (Ruigrok and Crowe, 1984). The receptive field for the rostral scratch is innervated by segments D3-D6; the pocket scratch receptive field is innervated by segments D6-D8; the caudal scratch receptive field is innervated by segments S2, Ca1, and more caudal segments (Mortin and Stein, 1985). A rostral scratch motor pattern could be produced with as few as 5 or 6 segments, i.e., segments D5-D9 or D3-D8. The anterior 3 segments of the hindlimb enlargement, D8-D10, could produce a pocket scratch motor pattern. A single segment, either D7 or D8, is capable of rhythmogenesis in response to stimulation of sites in its part of the pocket receptive field. A caudal scratch motor pattern could be produced by D8-End (the hindlimb enlargement and more caudal segments). The posterior 40-80% of the hindlimb enlargement is not necessary for the production of a rostral or pocket motor pattern. The anterior segment of the enlargement is necessary for the production of a normal caudal scratch motor pattern. Key elements of the CPG for each of the 3 scratch forms reside in segments D7-D10. The pattern-generating capacity of the anterior half of the hindlimb enlargement is greater than the posterior half; such an asymmetric distribution of pattern-generating elements in the enlargement of the spinal cord has been described for cat scratching (Deliagina et al., 1983). These results are consistent with the hypothesis that the CPGs producing different motor patterns for the hindlimb share neuronal elements (Grillner, 1981; Robertson et al., 1985; Currie and Stein, 1988, 1989).

Animals↗
PubMed2005

Shape-based averaging for combination of multiple segmentations.

Combination of multiple segmentations has recently been introduced as an effective method to obtain segmentations that are more accurate than any of the individual input segmentations. This paper introduces a new way to combine multiple segmentations using a novel shape-based averaging method. Individual segmentations are combined based on the signed Euclidean distance maps of the labels in each input segmentation. Compared to label voting, the new combination method produces smoother, more regular output segmentations and avoids fragmentation of contiguous structures. Using publicly available segmented human brain MR images (IBSR database), we perform a quantitative comparison between shape-based averaging and label voting by combining random segmentations with controlled error magnitudes and known ground truth. Shape-based averaging generated combined segmentations that were closer to the ground truth than combinations from label voting for all numbers of input segmentations (up to ten). The relative advantage of shape-based averaging over voting was larger for fewer input segmentations, and larger for greater deviations of the input segmentations from the ground truth. We conclude that shape-based averaging improves the accuracy of combined segmentations, in particular when only a few input segmentations are available and when the quality of the input segmentations is low.

Algorithms↗
PubMed1980

An immunoglobulin heavy chain variable region gene is generated from three segments of DNA: VH, D and JH.

We have determined the sequences of separate germline genetic elements which encode two parts of a mouse immunglobulin heavy chain variable region. These elements, termed gene segments, are heavy chain counterparts of the variable (V) and joining (J) gene segments of immunoglobulin light chains. The VH gene segment encodes amino acids 1-101 and the JH gene segment encodes amino acids 107-123 of the S107 phosphorylcholine-binding VH region. This JH gene segment and two other JH gene segments are located 5' to the mu constant region gene (Cmu) in germline DNA. We have also determined the sequence of a rearranged VH gene encoding a complete VH region, M603, which is closely related to S107. In addition, we have partially determined the VH coding sequences of the S107 and M167 heavy chain mRNAs. By comparing these sequences to the germline gene segments, we conclude that the germline VH and JH gene segments do not contain at least 13 nucleotides which are present in the rearranged VH genes. In S107, these nucleotides encode amino acids 102-106, which form part of the third hypervariable region and consequently influence the antigen-binding specificity of the immunoglobulin molecule. This portion of the variable region may be encoded by a separate germline gene segment which can be joined to the VH and JH gene segments. We term this postulated genetic element the D gene segment, referring to its role in the generation of heavy chain diversity. Essentially the same noncoding sequences are found 3' to the VH gene segment and as inverse complements 5' to two JH gene segments. These are the same conserved nucleotides previously found adjacent to light chain V and J gene segments. Each conserved sequence consists of blocks of seven and ten conserved nucleotides which are separated by a spacer of either 11 or 22 nonconserved nucleotides. The highly conserved spacing, corresponding to one or two turns of the DNA helix, maintains precise spatial orientations between blocks of conserved nucleotides. Gene segments which can join to one another (VK and JK, for example) always have spacers of different lengths. Based on these observations, we propose a model for variable region gene rearrangement mediated by proteins which recognize the same conserved sequences adjacent to both light and heavy chain immunoglobulin gene segments.

Animals↗
PubMed1995

ST segment tracking for rapid determination of patency of the infarct-related artery in acute myocardial infarction.

OBJECTIVES: This study was designed to test the hypothesis that monitoring the ST segment on a single electrocardiographic (ECG) lead reflecting activity in the infarct zone provides sensitive and specific recognition of reperfusion within 60 min of initiation of therapy in acute myocardial infarction. BACKGROUND: Infarct-related arteries that fail to recanalize early may benefit from immediate rescue angioplasty. Hence, detection of reperfusion has important practical clinical implications. METHODS: Of 41 patients with acute myocardial infarction who had ambulatory ECG (Holter) monitors placed, 38 had adequate ST segment monitoring for 3 h; 35 of the 38 were treated with thrombolytic agents and 3 with primary angioplasty. All patients underwent early coronary angiography and were classified into two groups: Group P (22 patients) had angiographic patency (Thrombolysis in Myocardial Infarction [TIMI] grade 2 or 3 flow), the Group O (16 patients) had persistent occlusion (TIMI grade 0 or 1 flow) of the infarct-related vessel at 60 min from initiation of therapy. The initial ST segment level was defined as the first ST segment level recorded; the peak ST segment level was defined as the highest ST segment level measured during the 1st 60 min. To assess the optimal ST segment recovery criteria for reperfusion, the presence or absence of a > or = 75%, > or = 50% and > or = 25% decrement from initial and peak ST segment levels, sampled and analyzed at 2.5-, 5-, 10-, 15-and 20-min intervals, was correlated with patency of the infarct-related artery at 60 min. RESULTS: ST segment recovery of > or = 50% reduction from peak ST segment levels with sampling rates at < or = 10-min intervals provided the optimal criterion for recognizing coronary artery patency at 60 min (sensitivity 96%, 95% confidence interval [CI] 77% to 99%; specificity 94%, 95% CI 69% to 99%, p < 0.0001). The subgroup of 13 patients in Group P with TIMI grade 3 reperfusion flow all met this criterion (sensitivity 100%, 95% CI 75% to 100%). The use of the initial ST segment level as the baseline for determining the presence of a > or = 50% reduction in ST segment levels within 60 min was less sensitive. Prediction of coronary reperfusion within 60 min of therapy on the basis of a > or = 75% decrement from peak ST segment levels was less sensitive, and the use of a > or = 25% decrement was less specific. CONCLUSIONS: ST segment monitoring of a single lead reflecting the infarct zone provides a reliable method for assessing reperfusion within 60 min of acute myocardial infarction. Optimal criteria for ECG reperfusion include a > or = 50% decrease from peak ST segment levels, with ST segment measurements recorded continuously or at least every 10 min.

Anistreplase↗
PubMed2005

Suppressor of Hairless and Presenilin phenotypes imply involvement of canonical Notch-signalling in segmentation of the spider Cupiennius salei.

Arthropods, vertebrates, and annelids all have a segmented body. Our recent discovery of involvement of Notch-signalling in spider segmentation revived the discussion on the origin of segmented body plans and suggests the sharing of a common genetic program in a common ancestor. Here, we analysed the spider homologues of the Suppressor of Hairless and Presenilin genes, which encode components of the canonical Notch-pathway, to further explore the role of Notch-signalling in spider segmentation. RNAi silencing of two spider Suppressor of Hairless homologues and the spider Presenilin homologue causes severe segmentation phenotypes. The most prominent defect is the consistent breakdown of segmentation after the formation of three (Suppressor of Hairless) or five (Presenilin) opisthosomal segments. These phenotypes indicate that Notch-signalling during spider segmentation likely involves the canonical pathway via Presenilin and Suppressor of Hairless. Furthermore, it implies that Notch-signalling influences both the formation and patterning of the spider segments: it is required for the specification of the posterior segments and for proper specification of the segment boundaries. We argue that alternative, partly redundant, pathways might act in the formation of the anterior segments that are not active in the posterior segments. This suggests that at least some differences exist in the specification of anterior and posterior segments of the spider, a finding that may be valid for most short germ arthropods. Our data provide additional evidence for the similarities of Notch-signalling in spider segmentation and vertebrate somitogenesis and strengthen our previous notion that the formation of the segments in arthropods and vertebrates might have shared a genetic program in a common ancestor.

Amino Acid Sequence↗
PubMed2003

Characterization of Campoletis sonorensis ichnovirus unique segment B and excision locus structure.

Polydnaviruses (PDVs) are segmented, symbiotic, double-stranded DNA viruses that are vertically transmitted as proviruses within the genomes of some parasitoid Hymenoptera. The PDV associated with the ichneumonid wasp Campoletis sonorensis (CsIV) consists of 24 non-redundant DNA segments varying in size from approximately 6 to 20 kbp. CsIV segment B, one of the smallest genome segments, was sequenced and the excision sites of the proviral segment were characterized. The segment B sequence was 83.2% non-coding with only two open reading frames (ORFs). Some non-coding sequences have similarities to database sequences and were likely pseudogenic, but most were unrelated to known nucleic acid or predicted protein sequences. One ORF, BHv0.9, encodes a member of the rep gene family and was expressed only in parasitized insects while transcription of the other ORF could not be detected. Previously, a third region of the segment was shown to hybridize to 0.6 and 1.2 kb poly A+ RNAs from female wasps during virus replication (Theilmann and Summers, 1988) but this region did not have an identifiable ORF in the determined sequence. In contrast to CsIV segment W, segment B had little repetitive sequence. The segment B proviral integration locus contains a 59 bp direct imperfect repeat. Further analyses of this integration locus demonstrated that segment B was excised from wasp genomic DNA with flanking sequences at the integration site rejoined after segment excision. The segment B "excision locus" retained one of the two copies of the 59 bp repeat sequence with the other repeat present in the excised segment. The data indicate that Ichnovirus segments have distinctive characteristics possibly reflecting functional co-evolution between the wasp and individual types of polydnavirus segments.

Animals↗
PubMed1998

Titin extensibility in situ: entropic elasticity of permanently folded and permanently unfolded molecular segments.

Titin (also known as connectin) is a giant protein that spans half of the striated muscle sarcomere. In the I-band titin extends as the sarcomere is stretched, developing what is known as passive force. The I-band region of titin contains tandem Ig segments (consisting of serially linked immunoglobulin-like domains) with the unique PEVK segment in between (Labeit, S., and B. Kolmerer. 1995. Science. 270:293-296). Although the tandem Ig and PEVK segments have been proposed to behave as stiff and compliant springs, respectively, precise experimental testing of the hypothesis is still needed. Here, sequence-specific antibodies were used to mark the ends of the tandem Ig and PEVK segments. By following the extension of the segments as a function of sarcomere length (SL), their respective contributions to titin's elastic behavior were established. In slack sarcomeres (approximately 2.0 micron) the tandem Ig and PEVK segments were contracted. Upon stretching sarcomeres from approximately 2.0 to 2.7 micron, the "contracted" tandem Ig segments straightened while their individual Ig domains remained folded. When sarcomeres were stretched beyond approximately 2.7 micron, the tandem Ig segments did not further extend, instead PEVK extension was now dominant. Modeling tandem Ig and PEVK segments as entropic springs with different bending rigidities (Kellermayer, M., S. Smith, H. Granzier, and C. Bustamante. 1997. Science. 276:1112-1116) indicated that in the physiological SL range (a) the Ig-like domains of the tandem Ig segments remain folded and (b) the PEVK segment behaves as a permanently unfolded polypeptide. Our model provides a molecular basis for the sequential extension of titin's different segments. Initially, the tandem Ig segments extend at low forces due to their high bending rigidity. Subsequently, extension of the PEVK segment occurs only upon reaching sufficiently high external forces due to its low bending rigidity. The serial linking of tandem Ig and PEVK segments with different bending rigidities provides a unique passive force-SL relation that is not achievable with a single elastic segment.

Chemical Phenomena↗
PubMedDate not supplied

Limits of Couinaud's liver segment classification: a quantitative computer-based three-dimensional analysis.

PURPOSE: Traditionally, liver surgery relies on Couinaud's liver segment classification. As the position and shape of these segments are variable and their borders are hidden within the homogeneous liver mass, the accuracy of segment identification methods needs computer-aided reevaluation. METHOD: The segmental liver anatomy of 23 patients receiving diagnostic helical CT scans because of suspected intrahepatic lesion was analyzed with the aid of a computer-based operation-planning system. We compared the standard Couinaud classification, which depends particularly on the main stems of portal and hepatic veins, with a method that calculates the segment borders by analyzing the complete portal venous tree. Volume, shape, and position of the liver segments found by each method were compared. RESULTS: With reference to the portal vein-based method, segmental volumes were overestimated by the classic Couinaud method by up to 24% and underestimated to 13%. Volumes of Couinaud segments 4a, 7, and 8 were generally larger compared with those obtained by the portal vein-based method, whereas segments 3 and 6 were smaller. Gross variations were found in segments 5, 7, and 8. When shape and position were considered, poor correlation was found for five segments (median kappa = 0.35-0.45). Only segments 2, 7, and 8 had kappa values clearly above 0.45 in the majority of cases. The plane that divides the two hemilivers along the middle hepatic vein and the border between the left sector (segments 2 and 3) and the medial sector (4a and 4b) were found in both methods with very good conformity (kappa > 0.75). CONCLUSION: Couinaud's method of dividing the liver into eight autonomous liver segments has to be accepted as a good approximation. Nevertheless, the volume, position, and shape of these segments and their segmental borders show significant variability.

Adult↗
PubMed2001

[Microsurgical anatomy of intracranial segment of facial nerve].

OBJECTIVE: To study the microsurgical anatomy of intracranial segment of facial nerve so as to provide anatomic parameters for clinical operation. METHODS: Ten adult cadavers were fixed and perfused with color silicon. Facial nerves of these cadavers were observed and measured under operative microscope according to lateral cranial base operative approach. Ten dry skulls were dissected to observe the relationships of osseous structures. The anatomic relationship and data of different segment of facial nerve were obtained respectively. RESULTS: The facial nerve was divided into five segments, namely, cerebellopontine angle segment, internal acoustic meatus segment, labyrinthine segment, tympanum segment and mastoid segment. The cerebellopontine angle segment and internal acoustic meatus segment paralleled the vestibulocochlear nerve. The labyrinthine aegment is the finest and shortest with the lebgth of 3.8 mm +/- 0.7 mm. The tympanum segment is closely related with osseous labyrinth. The mastoid segment, 15.5 mm +/- 1.9 mm long, leaves the cranium from stylomastoid foramen. CONCLUSION: Facial nerve can be located with choroid plexus of the fourth ventricle in retrosigmoid approach. Arcuate eminence and greater superficial petrosal nerve are important mark to locate internal acoustic meatus segment and labyrinthine segment in antepetrosal approach. Tympanum segment may be exposed on the surface of petrous bone in some cases. The line between lateral semicircular canals and crista of digastric muscle is the mark of mastoid segment.

Adult↗
PubMed2000

A novel immunoassay for the evaluation of rod outer segment digestion in cultured retinal pigment epithelial cells.

In this work a novel enzyme-linked immunoabsorbent assay quantifying residual rod outer segments in the medium of rod outer segment-challenged retinal pigment epithelial cells is described. A retinal pigment epithelial cell line (D407) that produces low level of cathepsin D, and a primary human retinal pigment epithelial cell culture (HRPE51) that has normal cathepsin D levels, were challenged with bovine rod outer segments. At 3 days post-challenge, the amount of undigested or residual bovine rod outer segments left in the culture medium was quantified by an enzyme-linked immunoabsorbent assay. An antibody raised against bovine rod outer segments, which had been purified and labelled with nitroiodophenyl haptens, was used in the assay. The sensitivity of the immunoassay was less than 10(2) bovine rod outer segments per mL and the signal followed a linear curve, saturating around 10(6) bovine rod outer segments per mL. HRPE51 cells had no residual bovine rod outer segments present in the medium following a challenge with 10(4) bovine rod outer segments per mL. In the medium of D407 cells, residual bovine rod outer segment levels were higher at all bovine rod outer segment concentrations when compared to the residual bovine rod outer segment levels in HRPE51 cells, suggesting that D407 cells have a lower digestive capacity. These results demonstrated that the immunoassay for detecting bovine rod outer segments is a sensitive and reliable technique that can be used to quantify the amount of residual bovine rod outer segments, following bovine rod outer segment challenge of retinal pigment epithelial cells.

Animals↗
PubMed2003

Do segmented reconstruction algorithms for cardiac multi-slice computed tomography improve image quality?

PURPOSE: To evaluate segmented reconstruction algorithms for spiral multi-slice computed tomography (MSCT) that use data from two cardiac cycles to improve temporal resolution (tau) for imaging of the heart. MATERIALS AND METHODS: An initial group of 78 cardiac patients (heart rates [HR] = 63-167 beats per minute [bpm]) were imaged on a 4-slice, 500 ms gantry rotation time scanner (scanner 1). Images were reconstructed with a single-segment algorithm using data from one cardiac cycle with a reconstruction window of fixed length (tau = 250 ms). Images were also reconstructed with two variants of a multi-segment algorithm using data from two cardiac cycles where only one end of the reconstruction window was fixed and the other end was freely moveable to allow adjustment of tau according to HR: (1) "2-segment fixed start" with fixed start of reconstruction, (2) "2-segment fixed end" with fixed end of reconstruction (for both, tau = 125-250 ms). The resulting image sets were ranked from best to worst (1-3, respectively) in a side-by-side, blinded comparison by two independent readers. A second group of 26 patients (HR = 74-90 bpm) were imaged on a 12-slice, 420 ms gantry rotation time scanner (scanner 2). Data were reconstructed with a single-segment algorithm (tau = 210 ms) and a "2-segment fixed start" algorithm (tau = 105-210 ms) and image sets were ranked from best to worst (1-2, respectively). RESULTS: There was no clear evidence that any one technique is superior for imaging on scanner 1. Reader 1 ranked single-segment images the highest for all HRs, but statistically significant differences among the three algorithms were only found for the lowest HRs (< 80 bpm), where reader 1 preferred single-segment over "2-segment fixed end" techniques (p = 0.048). The highest rankings given by reader 2 varied according to HR: single-segment images were superior for lowest HRs, while "2-segment fixed start" images were superior for HRs > 80 bpm; none of these comparisons reached statistical significance. Improved performance of 2-segment reconstruction was found with scanner 2. Both readers ranked "2-segment fixed start" images the highest (p < 0.01). CONCLUSIONS: The added value of 2-segment cardiac reconstruction algorithms for spiral MSCT was not demonstrated for a 4-slice, 500 ms gantry rotation time scanner but shown to be beneficial for a 12-slice, 420 ms gantry rotation time scanner in the crucial HR range of 74-90 bpm.

Adolescent↗
PubMed1995

Atherosclerosis in angiographically "normal" coronary artery reference segments: an intravascular ultrasound study with clinical correlations.

OBJECTIVES: This study evaluated the magnitude, patterns and clinical correlates of atherosclerosis in angiographically "normal" reference segments in patients undergoing transcatheter therapy for symptomatic coronary artery disease. BACKGROUND: Pathologic studies indicate that the extent of coronary atherosclerosis is underestimated by visual analysis of angiographically normal coronary artery segments. Intravascular ultrasound allows detailed, high quality cross-sectional imaging of the coronary arteries in vivo. METHODS: Intravascular ultrasound was used to study angiographically normal coronary artery reference segments in 884 patients evaluated for transcatheter therapy for symptomatic native coronary artery disease. The reference segment was the most visually normal intravascular ultrasound cross section within 10 mm proximal to the target lesion but distal to any major side branch. Results are presented as mean value +/- 1 SD. RESULTS: Only 60 (6.8%) of 884 angiographically normal reference segments were normal by intravascular ultrasound. Reference segment percent cross-sectional narrowing measured 51 +/- 13% and correlated poorly with the target lesion percent cross-sectional narrowing (r = 0.166, p < 0.0001). Reference segments contained less calcific and dense fibrotic plaque and proportionately more soft plaque elements. Independent predictors of reference segment percent cross-sectional narrowing were male gender, patient age, diabetes mellitus, hypercholesterolemia and presence of multivessel disease. Independent predictors of reference segment calcification were patient age and serum creatinine levels. Reference segment percent cross-sectional narrowing in 723 patients undergoing transcatheter therapy was similar to that in patients studied for diagnostic purposes; however, reference segment arc of calcium was greater in treated patients (43 +/- 81 vs. 25 +/- 57, p = 0.015). Reference segment disease was not an independent predictor of subsequent angiographic restenosis or clinical events within 12 months of follow-up. CONCLUSIONS: Atherosclerosis is ubiquitous in angiographically normal coronary artery reference segments. Reference segment disease parallels the severity of target lesion disease and is associated with many of the conventional risk factors for coronary artery disease. Because of its sensitivity in detecting atherosclerosis in angiographically normal reference segments, intravascular ultrasound should enhance the study of risk factors for atherosclerosis and the results of therapies to control disease progression.

Age Factors↗
PubMed2006

Influence of buccal segment size on prevention of side effects from incisor intrusion.

INTRODUCTION: Deep overbite can be corrected by maxillary incisor intrusion. The purpose of this study was to determine whether the size of the maxillary buccal segment influences the amount of steepening, extrusion, or narrowing of the buccal segments, or the rate of intrusion that occurs with maxillary incisor intrusion. METHODS: Twenty patients, 9 to 14 years of age, seeking treatment at a private practice, were divided into 2 groups. Patients in the long buccal-segment group had maxillary buccal segments that included the canines, both premolars, and the first molars. In the short buccal-segment group, the buccal segments consisted of only the maxillary first molars. Patient records were taken at the beginning and end of maxillary incisor intrusion. RESULTS: Intermolar width increased slightly in the short buccal-segment group and decreased slightly in the long buccal-segment group. More steepening of the buccal segment occurred in the short buccal-segment group, and more proclination of the anterior segment in the long buccal-segment group. The size of the buccal segment had no influence on the rate of incisor intrusion or on the amount of buccal-segment extrusion. In both groups, the mean amount of incisor intrusion exceeded 2 mm. CONCLUSIONS: A buccal segment that extends from canine to first molar will help minimize the side effects of incisor intrusion.

Adolescent↗