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PubMed2004

Comparison of functional recovery of mildly hypokinetic versus severely dysfunctional left ventricular segments after revascularization in patients with ischemic cardiomyopathy.

Dysfunctional left ventricular (LV) segments showing contractile reserve during dobutamine stress echocardiography (DSE) are considered viable myocardium; functional recovery is expected after revascularization. Many segments, however, particularly mildly hypokinetic segments, do not recover. The reason for this failure is unknown. Two-dimensional echocardiography at rest and low-high-dose DSE were performed before revascularization in 114 consecutive patients with ischemic cardiomyopathy. Two-dimensional echocardiography at rest was repeated after 9 to 12 months. Segmental function was scored by a 5-point grading score. Functional recovery after revascularization was assessed in mildly hypokinetic (score 2, group I) and severely dysfunctional segments (score 3 to 5, group II). For each segment, functional recovery was defined as an improvement in functional score of > or =1 grade compared with the baseline score at rest. During low-dose DSE (up to 10 microg/kg/min), 183 group I segments (68%) and 438 group II (39%) segments had contractile reserve (p <0.0001). However, functional recovery was observed less frequently in group I segments (41%) than in group II segments (55%) with contractile reserve (p <0.005). During high-dose DSE (up to 40 microg/kg/min), in the group I segments with contractile reserve at the low dose, the sustained improvement pattern (indicating subendocardial scar) was prevalent (73%). After revascularization, 73% of segments with sustained improvement did not recover. Conversely, the biphasic response (indicating ischemically jeopardized myocardium) was observed only in 27% of group I segments. Functional recovery occurred in 39 of these segments (78%) (p <0.001 vs sustained improvement). Hence, mildly hypokinetic segments probably indicate the presence of subendocardial scars, and may explain the failure in functional recovery after revascularization.

Adult↗
PubMed2005

Cardiac segmentation by a velocity-aided active contour model.

Heart disease is one of the more life-threatening diseases. Accurate diagnosis and treatment are central to the survival of patients. Numerous diagnostic methods that can assess abnormalities of the heart have been developed. Among these methods, cardiac functional analysis has been widely used to derive cardiac functional parameters that describe the functionality of the heart and are frequently used in diagnosis of various heart diseases. Segmentation of the myocardial boundaries is an essential step for deriving these cardiac functional parameters, and the accuracy of parameters depends much on the correctness of the segmented boundaries. Therefore, it is essential that cardiac segmentation be accurate and reliable. However, current segmentation techniques still have difficulty both extracting accurate myocardial boundaries, especially the endocardial boundary and performing a fully automatic process because of low image quality, the complex shape and motion pattern of the heart, and lack of clear delineation between the myocardium and adjacent anatomic structures. A velocity-aided cardiac segmentation method based a modified active contour model, the tensor-based orientation gradient force (OGF) and phase contrast magnetic resonance imaging (MRI) has been developed to improve the accuracy of segmentation of the myocardial boundaries, especially the endocardial boundary. Furthermore, the initial seed contour tracking (SCT) algorithm has been also developed to improve the accuracy of automatic sequential frame segmentation in conjunction with the OGF-based segmentation method. The performance of the proposed method was assessed by experimentations on a phase contrast MRI data set of three normal human volunteer. The results of the individual frame segmentation showed that the accuracy and reproducibility of segmentation of the endocardial boundary by the use of the OGF was generally improved around the lower level of the LV and end systole. The results of the sequential frame segmentation showed that the propagation of errors caused was significantly reduced by the use of the SCT in addition to the OGF and improvements in the accuracy and reproducibility of segmentation of the endocardial boundary were much higher than the individual frame segmentation. However, improvements were generally negligible around the upper level of the LV and end diastole, and the velocity wrap-around problem and blood turbulence around the basal level of the ventricles even degraded the performance of boundary segmentation. Although this work demonstrates the potential of using the velocity information from phase contrast MRI for cardiac segmentation, the velocity wrap-around artifacts in phase contrast MRI data sets can degrade the performance. Therefore, future work must include the development of appropriate methods to cope with these artifacts.

Algorithms↗
PubMed1996

Relation between contractile response of akinetic segments during dobutamine stress echocardiography and myocardial ischemia assessed by simultaneous thallium-201 single-photon emission computed tomography.

There are no standard criteria for the diagnosis of myocardial ischemia in akinetic segments during dobutamine stress echocardiography (DSE). The aim of the study was to assess the relation between different responses of akinetic segments during DSE and ischemia assessed by thallium-201 single-photon emission computed tomography (SPECT). Dobutamine-atropine stress echocardiography with simultaneous stress-reinjection thallium-201 SPECT was performed in 67 patients with old myocardial infarction significant and coronary artery stenosis. Fourteen myocardial segments were matched for both DSE and SPECT. Ischemia on SPECT was defined as reversible thallium defects. In 257 akinetic segments, 4 patterns during DSE were identified: (1) biphasic response in 41 segments (16%), defined as improvement at low dose (5 to 10 microgram/kg/min) followed by worsening at high dose; (2) persistent akinesia in 155 segments (60%); (3) akinesia becoming dyskinesia in 39 segments (15%); and (4) sustained improvement in 22 segments (9%). Reversible thallium defects were detected in 21 segments (51%) in group 1, in 20 segments (13%) in group 2, none in group 3, and in 2 segments in group 4 (9%). The prevalence of reversible defects in biphasic segments was higher compared with other patterns (p <0.00001 vs groups 2 and 3, p <0.005 vs group 4). The ischemic perfusion defect score was significantly higher in group 1 than group 2. The positive predictive value of biphasic response for reversible thallium defects was similar to that of stress-induced dyssynergia in normal segments at rest (51% vs 58%). It is concluded that of the various responses of akinetic segments to dobutamine infusion, the biphasic response is associated with the highest prevalence and greatest severity of ischemic on thallium SPECT. Observation of contractile response at both low- and high-dose DSE is a valuable approach for the diagnosis of myocardial ischemia in akinetic segments.

Aged↗
PubMed1994

Evaluation of ST segment elevation criteria for the prehospital electrocardiographic diagnosis fo acute myocardial infarction.

STUDY OBJECTIVE: To determine retrospectively the diagnostic accuracy of various ECG ST segment elevation criteria for the prehospital ECG diagnosis of acute myocardial infarction. DESIGN AND SETTING: During a six-month period, paramedics acquired prehospital 12-lead ECGs on adult chest pain patients. Investigators interpreted ECGs independently, retrospectively, and blinded to patient outcome. ECGs were classified as meeting or not meeting the six ST segment elevation criteria regardless of ECG morphology if the criteria were present in two or more anatomically contiguous leads: 1 mm or more ST segment elevation; 2 mm or more ST segment elevation; 1 mm or more ST segment elevation in the limb leads or 2 mm or more ST segment elevation in the precordial leads; and the first three criteria with the simultaneous presence of reciprocal changes. ECGs that did not meet any ST segment elevation criteria were classified as normal, nonspecific ST/T wave changes, abnormal but not ischemic, and ischemic. Hospital charts were reviewed for final cardiac diagnosis. TYPE OF PARTICIPANT: Four hundred twenty-eight stable adult prehospital chest pain patients in whom paramedics acquired prehospital 12-lead ECGs. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Of the 428 cases, 123 (29%) met 1 mm or more ST segment elevation criteria. Sixty-three (51%) of these 123 patients did not have myocardial infarctions. ECG characteristics most frequently associated with these non-myocardial infarction ECGs were left bundle branch block (21%) and left ventricular hypertrophy (33%). The three criteria that required the presence of reciprocal changes had the highest positive predictive values (93% to 95%), with sensitivities ranging from 20% to 33%. The criteria of 1 mm or more ST segment elevation with the simultaneous presence of reciprocal changes had a positive predictive value of 94% and included 18 of the 21 (86%) myocardial infarction patients who had ST segment elevation and received thrombolytic therapy within five hours after hospital arrival. Of the 428 cases, 305 (71%) did not meet any ST segment elevation criteria and had a sensitivity of 81% and a negative predictive value of 49% for the absence of acute myocardial infarction. CONCLUSION: Fifty-one percent of patients whose prehospital 12-lead ECG met 1 mm or more ST segment elevation criteria had non-myocardial infarction diagnoses. ST segment elevation alone lacks the positive predictive value necessary for reliable prehospital myocardial infarction diagnosis. Inclusion of reciprocal changes in prehospital ECG myocardial infarction criteria improved the positive predictive value to more than 90% and included a significant majority (62% to 86%) of acute myocardial infarction patients with ST segment elevation who received thrombolytic therapy within five hours after hospital arrival. ST segment elevation criteria that include reciprocal changes identify patients who stand to benefit most from early interventional strategies.

Adult↗
PubMed2001

Prognostic value of ST segment depression in acute coronary syndromes: insights from PARAGON-A applied to GUSTO-IIb. PARAGON-A and GUSTO IIb Investigators. Platelet IIb/IIIa Antagonism for the Reduction of Acute Global Organization Network.

OBJECTIVES: Our objectives were to develop a risk-stratification model addressing the importance of the magnitude and distribution of ST segment depression in predicting long-term outcomes and to validate the model in an analogous patient population. BACKGROUND: Although patients without ST segment elevation presenting with acute coronary syndromes represent an increasingly frequent population admitted to coronary care units, little attention has been paid to quantifying their ST segment abnormalities. METHODS: ST segment depression was categorized into three groups: 1) no ST segment depression; 2) 1-mm ST segment depression in two contiguous leads; and 3) ST segment depression > or =2 mm in two contiguous leads. A logistic regression model was developed using Platelet IIb/IIIa Antagonism for the Reduction of Acute coronary syndrome events in a Global Organization Network (PARAGON-A) data to assess the prognostic value of the extent and distribution of ST segment depression in predicting one-year mortality. The model was validated using the non-ST segment elevation population in Global Use of Strategies To Open occluded arteries in acute coronary syndromes (GUSTO-IIb). RESULTS: ST segment depression was the strongest predictor of one-year mortality, accounting for 35% of the model's predictive power. Patients with ST segment depression > or =2 mm were approximately 6 times (odds ratio [OR] 5.73, 95% confidence interval [CI] 2.8 to 11.6) more likely to die within one year than patients with no ST segment depression. On validation, the model showed good discriminatory power (c-index = 0.75). Patients with ST segment depression > or =2 mm in more than one region were almost 10 times more likely to die within one year than patients with no ST segment depression. CONCLUSIONS: These data provide new evidence supporting the powerful prognostic value of the baseline electrocardiogram and, in particular, the magnitude and distribution of ST segment depression in predicting unfavorable events.

Angina, Unstable↗
PubMed1987

Segment-specific and common nucleotide sequences in the noncoding regions of influenza B virus genome RNAs.

The nucleotide sequences of the 3' noncoding regions of all eight segments of influenza B virus RNA and the sequences of the 5' noncoding regions of segments 4-8 were determined in virus strains isolated over a period of 40 years. Nearly complete conservation of the noncoding sequences was found. Nine nucleotides at the 3' termini and 11 nucleotides at the 5' termini were common to all segments examined. In the region immediately adjacent to the common 3' terminal region, the nucleotides were specific for each segment and these segment-specific sequences were conserved in all strains examined. In each of the five segments in which both termini were examined, the segment-specific 3' sequences exhibited perfect inverted complementarity to a segment-specific sequence adjacent to the common 5' terminus. In addition, in the 3' noncoding region of RNA segments 1-3, which encode proteins involved in RNA synthesis, a single nucleotide substitution at position 10 was found that distinguishes these segments from segments 4-8. Comparison of these data with published reports has revealed that some of the features found in the noncoding regions of influenza B virus are also present in influenza A and C virus RNAs. In the RNAs of all three virus types, there is a segment-specific sequence of nucleotides near the 3' terminus that shows inverted complementarity to a sequence near the 5' terminus. This segment-specific sequence may play a role in the transcription of individual segments or in sorting of segments during virion assembly.

Animals↗
PubMed1989

Reversal of dyskinesis by increased end diastolic segment length in ischaemic-reperfused myocardium.

Persistent dyskinesis is universally observed after reperfusion of a severely ischaemic segment. Although inotropic stimulation shows a latent contractile reserve, it is not known whether this reserve can be recruited by increasing end diastolic segment length (local length-tension relation). To investigate this, six anaesthetised open chest dogs were placed on right heart bypass to increase end diastolic segment length independently of mean arterial pressure. Instantaneous left ventricular pressure-segment length relations and fractional systolic shortening were determined by sonomicrometry in the centre of the region perfused by the left anterior descending coronary artery during sequential increases in end diastolic segment length. Measurements were made before occlusion of the left anterior descending coronary artery, during 1 h of occlusion, and after 2 h of reperfusion. Before ischaemia, segmental shortening increased from 11.0(SEM 1.6)% to 23.5(1.5)% (p less than 0.05) as end diastolic segment length increased. Dyskinesis developed during occlusion of the left anterior descending coronary artery [12.1(2.6)% control v -7.2(1.6)% occlusion, p less than 0.05] and was present over the entire range of end diastolic segment lengths. Following reperfusion, segmental dyskinesis [-2.5(2.4)%] persisted at the lower end of the range of end diastolic segment length, but was progressively replaced by active shortening, averaging 7.3(3.2)% (p less than 0.05) as end diastolic segment length was sequentially increased. We conclude that segmental function following reperfusion is sensitive to changes in end diastolic segment length, and that active shortening is recruited from an apparently dyskinetic segment as end diastolic segment length progressively increases.

Animals↗
PubMed1997

Homologous sequences in the Campoletis sonorensis polydnavirus genome are implicated in replication and nesting of the W segment family.

Polydnaviruses (PDVs) are double-stranded DNA viruses with segmented genomes that replicate only in the oviducts of some species of parasitic wasps and are required for the successful parasitization of lepidopteran insects. PDV DNA segments are integrated in the genomes of their associated wasp hosts, and some are nested; i.e., smaller segments are produced from and largely colinear with larger segments. To determine the internal structure of nested viral segments, the first complete nucleotide sequence of a PDV genome segment and its integration locus was determined. By restriction mapping, Southern blot, and sequence analyses, we demonstrated that the Campoletis sonorensis PDV segment W is integrated into wasp genomic DNA. DNA sequence analysis revealed that proviral segment W terminates in two 1,185-bp direct long terminal repeats (LTRs) in the wasp chromosome, while only one LTR copy is present in the extrachromosomal (viral) W. The results suggest that terminal direct repeats are a general feature of PDV DNA segment integration but that the homology and size of the repeats can vary extensively. Segment W contains 12 imperfect direct repeats of six different types between 89 bp and 1.9 kbp with 65 to 90% homology. The orientation and structure of the repeats suggest that W itself may have arisen through sequence duplication and subsequent divergence. Mapping, hybridization, and sequence analyses of cloned R and M demonstrated that these segments are nested within segment W and that internal imperfect direct repeats of one type are implicated in the homologous intramolecular recombination events that generate segments R and M. Interestingly, segment nesting differentially increases the copy number of genes encoded by segment W, suggesting that the unusual genomic organization of PDVs may be directly linked to the unique functions of this virus in its obligate mutualistic association with parasitic wasps.

Animals↗
PubMed1989

ST segment shifts are poor predictors of subsequent Q wave evolution in acute myocardial infarction. A natural history study of early non-Q wave infarction.

Acute ST segment elevation is regarded generally as the sine qua non of evolving Q wave myocardial infarction (MI) because such electrocardiographic (ECG) injury is believed to be a marker of transmural ischemia and a forerunner of transmural necrosis. Alternatively, ST segment depression with or without T wave inversion is viewed as the dominant ECG feature of non-Q wave MI. However, this hypothesis has not been assessed prospectively in an acute MI population. We analyzed 2,304 serial ECGs at study entry (admission), day 2, day 3, and predischarge (mean, 10.2 +/- 2 days) from 576 patients with creatine kinase MB confirmed acute non-Q wave MI to determine what percentage of patients with early ST segment elevation culminated in subsequent Q wave development. Of this group, 187 patients (32%) exhibited 1 mm or greater ST segment elevation in two or more contiguous entry ECG leads. Of those patients whose non-Q wave MI could be localized on the basis of diagnostic admission ST segment shifts, the prevalence of early ST segment elevation was 43% (187 of 439). The sum total mean (+/- SD) peak ST segment elevation by lead group (anterior, inferior, lateral) was 4.0 +/- 2.4, 4.5 +/- 2.4, and 2.5 +/- 0.6 mm, respectively. Despite this, only 20% of patients with ST segment elevation (37 of 187) developed Q waves. Of 252 patients who exhibited early ST segment depression or T wave inversion or both, 39 (15%) evolved subsequent Q waves. Thus, while the prevalence of early ST segment elevation in acute evolving non-Q wave MI was higher than previously reported, 80% of patients with and 85% of patients without ST segment elevation and absent Q waves on the admission ECG did not develop subsequent Q waves during a 2-week period of observation (p = NS). In addition, when patients with ST segment elevation were compared with patients with ST segment depression or T wave inversions or both, there were no between-group differences in log peak creatine kinase (404 vs. 383 IU), reinfarction (6% vs. 8%), postinfarction angina (50% vs. 42%), or early recurrent ischemia (49% vs. 45%), defined as postinfarction angina with transient ECG changes. Thus, in patients who present with initial acute non-Q wave MI, ST segment shifts on admission are unreliable predictors of subsequent Q wave evolution and do not discriminate significant differences in postinfarction outcome. In particular, ST segment elevation during the early hours of evolving infarction is not an invariable harbinger of subsequent Q wave development.

Creatine Kinase↗
PubMed1995

Pacing-induced ST segment deviation in patients with unstable angina: clinical, angiographic, and hemodynamic correlation.

To assess the clinical, coronary arteriographic, and hemodynamic differences between the unstable angina patients manifesting ST segment depression and those showing ST segment elevation as well as those demonstrating chest pain only without ST segment deviation during pacing, low-dose digital subtraction ventriculography was performed in 33 patients before and after abrupt cessation of atrial pacing during selective coronary arteriography. Transient ST segment depression during pacing was observed in 17 patients (52%), whereas 6 patients (18%) showed ST segment elevation; however, 10 patients (30%) did not manifest any ST segment deviation in spite of typical chest pain. Hypertension and a history of myocardial infarction were observed in a significantly higher (P < 0.05) proportion of patients with ST segment depression than in those with ST elevation. Patients who manifested ST segment depression during pacing had a higher incidence of triple-vessel disease (65 vs 17%; P < .05) as compared with the patients with ST segment elevation. Indirect evidence of intracoronary thrombi (complicated lesion, abrupt occlusion, and intraluminal filling defect) was noticed in a higher frequency (P < 0.05) in the group of patients with ST elevation during pacing. In patients with ST segment depression, no significant changes of global left ventricular (LV) functional parameters were observed. However, the length of the LV severe hypokinetic region was increased significantly (6.2 +/- 3.1 vs 23.5 +/- 6.2%; P < 0.005) during pacing in this group of patients. The shortening of the affected segments of the left ventricle was decreased significantly (52.3 +/- 3.6 vs 38.3 +/- 4.9%; P < 0.05) in these patients during pacing. In the group of patients with ST segment elevation during pacing, decrease in ejection fraction was associated with significant (P < 0.01) increase in midwall equatorial diastolic stress as compared with the patients with pacing-induced ST segment depression as well as patients without ST segment deviation. In the group of patients without ST segment deviation during pacing there was no considerable aggravation of LV global or regional function. This distinction should be taken into consideration in evaluating patients with unstable angina for diagnostic and therapeutic intervention.

Angina, Unstable↗
PubMed1993

Developmental origin of segmental identity in the leech mesoderm.

Segmentation in the leech embryo is established by a stereotyped cell lineage. Each of the 32 segments arises from homologous, bilaterally symmetrical complements of mesodermal and ectodermal blast cell clones. Although segments are homologous, they are regionally differentiated along the longitudinal body axis. Various segments display idiosyncratic ensembles of features, which constitute discrete segmental identities. The differentiation of segment-specific features, such as the mesoderm-derived nephridia, genital primordia and identified Small Cardioactive Peptide immunoreactive neurons, reflects a diversification of the developmental fates of homologous blast cell clones. We have investigated whether segment-specific differentiation of homologous mesodermal blast cell clones depends on cell-intrinsic mechanisms (based on the cells' lineage history) or on cell-extrinsic mechanisms (based on the cells' interactions with their environment) in embryos of Theromyzon rude. For this purpose, we first mapped the segment-specific fates of individual mesodermal blast cell clones, and then induced mesodermal clones to take part in the formation of segments for which they are not normally destined. Two types of ectopic segmental position were produced: one in which a mesodermal blast cell clone was out of register with all other consegmental cells and one in which a mesodermal blast cell clone was out of register with its overlying ectoderm, but was in normal register with the mesoderm and ectoderm on the other side of the embryo. Mesodermal blast cell clones that developed in either type of ectopic segmental position gave rise to segment-specific features characteristic of their original segmental fates rather than their ectopic positions. Thus, the development of segmental identity in the leech mesoderm is attributable to a cell-intrinsic mechanism and, either before or soon after their birth, mesodermal blast cells are autonomously committed to segment-specific fates.

Animals↗
PubMed2004

An improved segmentation method for in vivo microCT imaging.

UNLABELLED: Image segmentation methods for microCT can influence the accuracy of bone morphometry calculations. A new automated segmentation method is introduced, and its performance is compared with standard segmentation methods. The new method can improve the results of in vivo microCT, where the need to keep radiation dose low limits scan quality. INTRODUCTION: An important topic for microCT analysis of bone samples is the segmentation of the original reconstructed grayscale data sets to separate bone from non-bone. Problems like noise, resolution limitations, and beam-hardening make this a nontrivial issue. Inappropriate segmentation methods will reduce the potential power of microCT and may introduce bias in the architectural measurements, in particular, when new in vivo microCT with its inherent limitations in scan quality is used. Here we introduce a new segmentation method using local thresholds and compare its performance to standard global segmentation methods. MATERIAL AND METHODS: The local threshold method was validated by comparing the result of the segmentation with histology. Furthermore, the effect of choosing this new method versus standard segmentation methods using global threshold values was investigated by studying the sensitivity of these methods to signal to noise ratio and resolution. RESULTS: Using the new method on high-quality scans yielded accurate results and virtually no differences between histology and the segmented data sets could be observed. When prior knowledge about the volume fraction of the bone was available the global threshold also resulted in appropriate results. Degrading the scan quality had only minor effects on the performance of the new segmentation method. Although global segmentation methods were not sensitive to noise, it was not possible to segment both lower mineralized thin trabeculae and the higher mineralized cortex correctly with the same threshold value. CONCLUSION: At high resolutions, both the new local and conventional global segmentation methods gave near exact representations of the bone structure. When scanned samples are not homogenous (e.g., thick cortices and thin trabeculae) and when resolution is relatively low, the local segmentation method outperforms global methods. It maximizes the potential of in vivo microCT by giving good structural representation without the need to use longer scanning times that would increase absorption of harmful X-ray radiation by the living tissue.

Algorithms↗
PubMed2005

Proposed classification of segments of the internal carotid artery: anatomical study with angiographical interpretation.

The nomenclature and borders of the segments of the internal carotid artery (ICA) remain confusing. A classification of segments of the ICA is proposed based on constant anatomical structures, such as the carotid foramen and canal, the petrous bone, the petrolingual ligament (PLL), and the proximal and distal dural rings. The bilateral ICAs were dissected in 15 cadaveric head specimens using different neurosurgical approaches. The bilateral lacerum foramina were studied in five dry skulls. The bilateral segments of the ICA were also examined on carotid angiograms of 10 normal patients and another with the ophthalmic artery originating from the intracavernous portion of the ICA. The present classification divides the ICA into five segments in the direction of the blood flow. The cervical segment is extradural and extracranial, the petrous segment is extradural and intraosseous, the cavernous segment is interdural and intracavernous, the clinoidal segment is interdural and paracavernous, and the cisternal segment is intradural and intracisternal. The ICA did not pass through the lacerum foramen in any specimen. In all specimens, 1/8 to 5/8 of the lacerum foramen was under the deep dural layer of the cavernous sinus. The term 'lacerum segment' as used previously and called the 'trigeminal segment' by us cannot be justified. The PLL is the posterolateral border of the cavernous sinus and the lacerum and trigeminal segments should be included in the cavernous and petrous segments. The ophthalmic artery may originate from the clinoidal ICA, from the cavernous ICA, or from the middle meningeal artery. Instead of using the term 'ophthalmic segment,' the term 'cisternal segment' should be used for the anatomically distinct ICA in the subarachnoid space. This classification should be minimally affected by anatomical variations.

Carotid Artery, Internal↗
PubMed1993

Structure and genomic organization of immunoglobulin light chain in the channel catfish. An unusual genomic organizational pattern of segmental genes.

Channel catfish L chain cDNA was obtained through a PCR strategy and used to isolate multiple L chain clones from cDNA and genomic libraries. Sequence analysis of full-length cDNA indicates that the V region is preceded by a leader peptide, and represented by framework and CDR regions. Both VL and CL domains contain the invariant cysteines and tryptophans as well as other phylogenetically conserved L chain residues. The sequence similarity of the catfish L chain with higher vertebrate kappa- and lambda-chains, however, does not readily allow the catfish L chain to be classified. Eight cDNA clones isolated from a cDNA library were shown to represent different processed derivatives of sterile L chain transcripts. These transcripts share a similar upstream sequence region and extend downstream to include a CL or alternatively a JL segment in partial germ-line configuration that has been spliced into a CL. Sequence comparisons indicate that these transcripts represent the product of different L chain loci. Genomic Southern blot analyses with VL and CL probes indicate that there are at least 30 VL segments and at least 15 CL segments. The analysis of 17 genomic L chain clones showed that each hybridized with VL-, JL-, and CL-specific probes. Characterization of the gene segments in three of these clones indicates a previously undescribed pattern of segmental gene organization. Gene segments are found in clusters with VL, JL, and CL segments in each cluster. Within a cluster VL segments reside upstream of single copies of closely linked JL and CL segments. The proximity of VL segments downstream from JL-CL segments suggests that individual clusters may be closely linked. The VL segments are located in opposite transcriptional polarity relative to the JL and CL gene segments, which indicates that VL segments are likely rearranged to JL-CL segments by inversion rather than deletion events.

Amino Acid Sequence↗
PubMed1999

Efferent neurons and specialization of abdominal segments in grasshoppers.

A specialized behavior, oviposition, is produced by the eighth and ninth abdominal segments of female grasshoppers. To begin to understand how these segments produce the behavior, which is not displayed by males or pregenital regions of the abdomen in females, the structure and function of efferent neurons in abdominal ganglia of both sexes were examined. In females, the eighth and ninth segments are specialized differently for oviposition: 20 ovipositor motor neurons were found in the eighth segment, and 26 were found in the ninth segment. Males had fewer motor neurons in their eighth segment, but the same number in the ninth segment, which is the only genital segment in males. However, the axons of several of the ninth segmental male motor neurons traveled to the periphery in the genital nerve, which is only found in males. In both sexes, pregenital ganglia had the most motor neurons, but these neurons, for the most part, had morphologies that strongly resembled those of genital segments. Efferent modulatory neuron numbers were not sexually dimorphic in the segments examined, except that males had a greater number in their ninth segment. Experimental methods that activate oviposition were found to also activate a rhythmical motor pattern in pregenital abdominal segments of both sexes. In females, the pattern was phase-coupled to oviposition, but persisted after the connections with the terminal abdominal ganglion were severed. The preponderance of similarities among efferent neurons and elicited motor activity suggests a common pattern of neural circuitry in the behaviorally diverse abdominal segments of grasshoppers.

Abdomen↗
PubMed1980

Assignment of functions to segments of the DsRNA genome of the Ustilago virus.

The genome of the 3 Ustilago maydis viruses, known to be associated with the "killer phenomenon", is segmented. The distribution of the viral functions on different segments has been partly resolved. The reported comparative study, of a series of mutants with deleted segments of the genome and of hybrid variants containing segments of the related viruses, provides additional information on the location of various functions and on the interrelations among the different segments. The data indicates that the functions related to the maintenance of the viral information are located on the H segments. Among these segments some function overlap exists. The maintenance of the M and L segments is dependent on the functions located on the H segments. The functions related to the killer phenotype are distributed on the M2 and L1 segments. These functions include the determination of the killer specificity. The H segments play no role in the determination of the killer specificity and the specificity is determined by the M2 segment. The L segment is essential for the expression of the killer phenotype but it is suggested that the information for the toxin resides in the M2 segment.

Basidiomycota↗
PubMed2001

A three-phase model of arthropod segmentation.

Molecular and morphological evidence (expression patterns of pair-rule genes and segmental position of the genital openings and other segmental markers) suggest that the segmental units of the arthropod body are specified, in early ontogeny, by three spatially and/or temporally distinct mechanisms and do not appear in a strict antero-posterior sequence. A first anterior set of indivisible segments (naupliar segments, possibly three in all arthropods) is followed by a set of more caudal (post-naupliar) primary units (eosegments, possibly ten in all arthropods) which then undergo a process of secondary segmentation, thus giving rise to a higher number of definitive segments (merosegments). The number of merosegments deriving from each eosegment is characteristic of the different arthropod clades and is mostly stable at the level of the traditional arthropodan classes or subclasses. All their segmentation patterns, however, including those found in the segmental organisation of highly segmented forms (such as centipedes and millipedes, notostracan, lipostracan and anostracan crustaceans, and trilobites) are reducible to the basic groundplan with three naupliar and ten postnaupliar segments. These basic units of arthropod segmentation may also have an equivalent in other Ecdysozoa, despite the lack of any segmentation (nematodes) or, at least, of an overt segmentation (kinorhynchs).

Animals↗
PubMed2006

Quantitative analysis of the conservation of the tertiary structure of protein segments.

The publication of the crystallographic structure of calmodulin protein has offered an example leading us to believe that it is possible for many protein sequence segments to exhibit multiple 3D structures referred to as multi-structural segments. To this end, this paper presents statistical analysis of uniqueness of the 3D-structure of all possible protein sequence segments stored in the Protein Data Bank (PDB, Jan. of 2003, release 103) that occur at least twice and whose lengths are greater than 10 amino acids (AAs). We refined the set of segments by choosing only those that are not parts of longer segments, which resulted in 9297 segments called a sponge set. By adding 8197 signature segments, which occur uniquely in the PDB, into the sponge set we have generated a benchmark set. Statistical analysis of the sponge set demonstrates that rotating, missing and disarranging operations described in the text, result in the segments becoming multi-structural. It turns out that missing segments do not exhibit a change of shape in the 3D-structure of a multi-structural segment. We use the root mean square distance for unit vector sequence (URMSD) as an improved measure to describe the characteristics of hinge rotations, missing, and disarranging segments. We estimated the rate of occurrence for rotating and disarranging segments in the sponge set and divided it by the number of sequences in the benchmark set which is found to be less than 0.85%. Since two of the structure changing operations concern negligible number of segment and the third one is found not to have impact on the structure, we conclude that the 3D-structure of proteins is conserved statistically for more than 98% of the segments. At the same time, the remaining 2% of the sequences may pose problems for the sequence alignment based structure prediction methods.

Amino Acid Sequence↗