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PubMed1984

Morphogenesis of the head of a newt: mesodermal segments, neuromeres, and distribution of neural crest.

Segmentation of the mesoderm in the head of a newt embryo is revealed by scanning electron microscopy. By the end of gastrulation, the newt embryo is already segmented from one end to the other, with additional segments added later by the tail bud. This metameric segmentation appears long before the first "somite" can be seen in the late neurula by light microscopy. The six segments found in the newt head look much like the six most-cranial segments described decades ago in shark embryos. Mesodermal segments in the newt head are similar to somitomeres in amniote embryos, but in amniote embryos, the numbers and relationships of head segments are quite different from those of the newt. In both amniote and newt, the first segment abuts the prosencephalon, but for each more caudal head segment, where the newt embryo has one segment, the amniote has two. Although the pattern and distribution of cranial neural crest is quite similar in newt and amniote embryos, there are different relationships between migrating crest masses and mesodermal segments due to the doubling of most of the cranial segments in amniotes. It now appears that all vertebrate embryos, regardless of their mode of gastrulation, form similar mesodermal segments from one end of the embryo to the other, and this metameric pattern is established during gastrulation.

Animals↗
PubMed1993

Long-term prognostic significance of ST segment depression during acute myocardial infarction. The Multicenter Diltiazem Postinfarction Trial Research Group.

OBJECTIVES: The purpose of this study was to evaluate the long-term prognostic value of ST segment depression on the electrocardiogram (ECG) in patients with acute myocardial infarction. BACKGROUND: The prognostic importance of ST segment depression on the ECG has been studied in small groups of patients with infarction, but larger numbers are needed. METHODS: Coronary care unit ECGs of 1,234 patients who survived the coronary care unit with acute Q wave (n = 896) or non-Q wave (n = 338) myocardial infarction were analyzed for the presence of ST segment depression. Patients were followed up for up to 4 years. RESULTS: ST segment depression was present in 607 patients. Those with ST segment depression had a 1-year mortality rate of 10.3% compared with a rate of 5.6% for those without ST segment depression (p = 0.002). This effect was seen in both the Q wave and non-Q wave subgroups. Of the 437 patients with anterior ST segment elevation, those with ST segment depression in other regions had a 13.6% 1-year mortality rate compared with a rate of 6.9% for those with no ST segment depression (p = 0.0005). Of the 514 patients with inferior ST segment elevation, those with ST segment depression in other leads had an 11.0% 1-year mortality rate compared with a 1.8% rate for those with no ST segment depression (p = 0.0001). The Cox proportional hazards model showed that ST segment depression was an independent predictor of mortality over the follow-up period. CONCLUSIONS: ST segment depression on the admitting ECG in patients with acute myocardial infarction is a predictor of increased mortality in the year after infarction.

Adult↗
PubMed1994

Clinical significance of PQ segment depression in acute Q wave anterior wall myocardial infarction.

OBJECTIVES: This study was designed to evaluate the clinical significance of PQ segment depression and to examine the frequency of PQ segment depression in infarction-associated pericarditis. BACKGROUND: PQ segment deviation is almost as characteristic as the classic ST segment deviation and is detected in most patients with pericarditis. However, the incidence and clinical characteristics of PQ segment depression in acute myocardial infarction are not defined. METHODS: Three hundred four consecutive patients with acute Q wave anterior wall myocardial infarction were examined carefully by auscultation, electrocardiogram, echocardiogram and chest roentgenogram. The diagnosis of pericarditis was made on the basis of pericardial rub detected by more than two observers during the 1st 3 days after hospital admission. At least 0.5 mm of PQ segment depression from the TP segment observed for > 24 h in both limb and precordial leads was considered diagnostic of PQ segment depression. RESULTS: A pericardial rub was present in 65 patients (21%) and absent in 239 patients. PQ segment depression was detected in both limb and precordial leads in 30 patients (10%): 18 patients with pericardial rub and 12 patients without pericardial rub. On the basis of five clinical variables, multivariate analysis was performed to determine the important variables related to the occurrence of PQ segment depression. Pericardial rub was selected with left ventricular segments with advanced asynergy as a significant factor related to PQ segment depression. There were 31 in-hospital deaths, and a significantly higher hospital mortality rate was observed in patients with PQ segment depression (23% vs. 9%). CONCLUSIONS: Although PQ segment depression was observed in a minority of patients with infarction-associated pericarditis, it was one of the clinical signs of larger infarct size and increased hospital deaths.

Echocardiography, Doppler↗
PubMed2004

Automated lung segmentation for thoracic CT impact on computer-aided diagnosis.

RATIONALE AND OBJECTIVES: Automated lung segmentation in thoracic computed tomography scans is essential for the development of computer-aided diagnostic (CAD) methods. A core segmentation method may be developed for general application; however, modifications may be required for specific clinical tasks. MATERIALS AND METHODS: An automated lung segmentation method has been applied (1) as preprocessing for automated lung nodule detection and (2) as the foundation for computer-assisted measurements of pleural mesothelioma tumor thickness. The core method uses gray-level thresholding to segment the lungs within each computed tomography section. The segmentation is revised through separation of right and left lungs along the anterior junction line, elimination of the trachea and main bronchi from the lung segmentation regions, and suppression of the diaphragm. Segmentation modifications required for nodule detection include a rolling ball algorithm to include juxtapleural nodules and morphologic erosion to eliminate partial volume pixels at the boundary of the segmentation regions. RESULTS: For automated lung nodule detection, 4 of 82 actual nodules (4.9%) were excluded from the lung segmentation regions when the core segmentation method was modified compared with 14 nodules (17.1%) excluded without modifications. The computer-assisted quantification of mesothelioma method achieved a correlation coefficient of 0.990 with 134 manual measurements when the core segmentation method was used alone; correlation was reduced to 0.977 when the segmentation modifications, as adapted for the lung nodule detection task, were applied to the mesothelioma measurement task. CONCLUSION: Different CAD applications impose different requirements on the automated lung segmentation process. The specific approach to lung segmentation must be adapted to the particular CAD task.

Algorithms↗
PubMed2005

Strain rate analysis allows detection of differences in diastolic function between viable and nonviable myocardial segments.

Analysis of diastolic function for assessment of myocardial viability has not been evaluated. Strain rate (SR) analysis allows quantitative segmental analysis of myocardial function and has been used during dobutamine stimulation for assessment of systolic functional reserve. In 37 patients with ischemic left ventricular dysfunction diastolic function was evaluated at rest and during low-dose dobutamine stimulation (10 mug/kg/min) using SR imaging and related to F18-fluorodeoxyglucose positron emission tomography. Analysis of peak early (E waves) and late (A waves) diastolic myocardial SR was performed using apical views. In all, 317 segments had normal function at rest by 2-dimensional echocardiography. A total of 192 segments with dyssynergy at rest were classified by positron emission tomography as viable in 94 cases and nonviable in 98 cases. Dys-synergic segments had lower E and A waves SR compared with normal contracting segments. There were no significant differences in peak E and A waves SR at rest between dys-synergic viable and nonviable segments. With dobutamine stimulation peak E waves SR increased significantly for viable segments (0.89 +/- 0.51-1.06 +/- 0.51 L/s, P < .01) whereas it was unchanged for nonviable segments (0.77 +/- 0.49-0.78 +/- 0.48 L/s, P = .835). Peak A waves SR increased for viable (0.71 +/- 0.55-1.00 +/- 0.56 L/s, P < .01) and nonviable (0.57 +/- 0.47-0.71 +/- 0.58 L/s, P = .023) segments. However, during dobutamine stimulation peak A waves SR was larger ( P < .001) for viable than for nonviable segments. In conclusion, normal contracting segments at rest have higher E and A waves SR compared with dys-synergic segments. Dys-synergic viable myocardial segments demonstrate an increase in E and A waves SR with dobutamine stimulation whereas nonviable segments are less responsive to dobutamine.

Analysis of Variance↗
PubMed2004

Involvement of Wingless/Armadillo signaling in the posterior sequential segmentation in the cricket, Gryllus bimaculatus (Orthoptera), as revealed by RNAi analysis.

In insects, there are two different modes of segmentation. In the higher dipteran insects (like Drosophila), their segmentation takes place almost simultaneously in the syncytial blastoderm. By contrast, in the orthopteran insects (like Schistocerca (grasshopper)), the anterior segments form almost simultaneously in the cellular blastoderm and then the remaining posterior part elongates to form segments sequentially from the posterior proliferative zone. Although most of their orthologues of the Drosophila segmentation genes may be involved in their segmentation, little is known about their roles. We have investigated segmentation processes of Gryllus bimaculatus, focusing on its orthologues of the Drosophila segment-polarity genes, G. bimaculatus wingless (Gbwg), armadillo (Gbarm) and hedgehog (Gbhh). Gbhh and Gbwg were observed to be expressed in the each anterior segment and the posterior proliferative zone. In order to know their roles, we used RNA interference (RNAi). We could not observed any significant effects of RNAi for Gbwg and Gbhh on segmentation, probably due to functional replacement by another member of the corresponding gene families. Embryos obtained by RNAi for Gbarm exhibited abnormal anterior segments and lack of the abdomen. Our results suggest that GbWg/GbArm signaling is involved in the posterior sequential segmentation in the G. bimaculatus embryos, while Gbwg, Gbarm and Gbhh are likely to act as the segment-polarity genes in the anterior segmentation similarly as in Drosophila.

Amino Acid Sequence↗
PubMed1999

ST-segment elevation on Q leads at rest and during exercise: relation with myocardial viability and left ventricular remodeling within the first 6 months after infarction.

BACKGROUND: Resting ST-segment elevation on Q leads after an acute myocardial infarction has been related to a greater infarct size. Otherwise, the relation between exercise-induced ST-segment elevation and myocardial viability is controversial. We investigated the relation between ST-segment elevation on Q leads at rest and during exercise and regional dysfunction and its evolution, contractile reserve, left ventricular dilation, and coronary patency. METHODS AND RESULTS: Exercise testing and cardiac catheterization were performed at the first week after infarction in 51 patients. The study group was divided according to the existence (in 2 or more Q leads; n = 36) or not (n = 15) of resting ST-segment elevation and according to the existence (n = 28) or not (n = 23) of exercise-induced ST-segment elevation. Left ventricular end-diastolic and end-systolic volumes (mL/m2), regional wall motion (SD/chord), contractile reserve (wall motion percentage improvement with low-dose dobutamine), and coronary patency in the culprit artery were analyzed. Cardiac catheterization was repeated at the sixth month in 35 patients; systolic recovery (wall motion percentage improvement), left ventricular volumes, and coronary patency were again evaluated. Patients with resting ST-segment elevation showed poorer wall motion (2.1 +/- 0.8 SD/chord vs 1.2 +/- 1 SD/chord, P =.002), lesser contractile reserve (17% [0% to 39%] vs 41% [4% to 92%], P =.04), greater end-systolic volume (32 +/- 15 mL/m2 vs 23 +/- 11 mL/m2, P =.04), and higher percentage of occlusion (36% vs 7%, P =.04) than did patients without ST-segment elevation. Likewise, patients with exercise-induced ST-segment elevation showed lesser contractile reserve (8% [0% to 40%] vs 35% [12% to 86%], P =.03) than did patients without exercise-induced ST-segment elevation. The only independent predictors of contractile reserve were wall motion <2 SD/chord (odds ratio [OR] 7.1, confidence interval [CI] 6.3 to 7.9, P =.01) and the absence of exercise-induced ST-segment elevation (OR 5.7, CI 4.9 to 6.5, P =. 02). There were no significant differences between patients with and those without ST-segment elevation (at rest or during exercise) in systolic recovery or left ventricular volumes at the sixth month. CONCLUSIONS: ST-segment elevation on Q leads at rest is related to a poorer systolic function (more severe regional dysfunction, greater end-systolic volume, and less response to dobutamine). ST-segment elevation during exercise is independently related to a lesser contractile reserve. ST-segment elevation (at rest or during exercise) is not related to the evolution of volumes or regional dysfunction during the first 6 months after infarction.

Aged↗
PubMed2004

Arrangement of core membrane segments in the MotA/MotB proton-channel complex of Escherichia coli.

The stator of the bacterial flagellar motor is formed from the membrane proteins MotA and MotB, which associate in complexes with stoichiometry MotA(4)MotB(2) (Kojima, S., and Blair, D. F., preceding paper in this issue). The MotA/MotB complexes conduct ions across the membrane, and couple ion flow to flagellar rotation by a mechanism that appears to involve conformational changes within the complex. MotA has four membrane-crossing segments, termed A1-A4, and MotB has one, termed B. We are studying the organization of the 18 membrane segments in the MotA(4)MotB(2) complex by using targeted disulfide cross-linking. A previous cross-linking study showed that the two B segments in the complex (one from each MotB subunit) are arranged as a symmetrical dimer of alpha-helices. Here, we extend the cross-linking study to segments A3 and A4. Single Cys residues were introduced by mutation in several consecutive positions in segments A3 and A4, and double mutants were made by pairwise combination of subsets of the Cys replacements in segments A3, A4, and B. Disulfide cross-linking of the single- and double-Cys proteins was studied in whole cells, in membranes, and in detergent solution. Several combinations of Cys residues in segments A3 and B gave a high yield of disulfide-linked MotA/MotB heterodimer upon oxidation with iodine. Positions of efficient cross-linking identify a helix face on segment A3 that is in proximity to segment(s) B. Some combinations of Cys residues in segments A4 and B also gave a significant yield of disulfide-linked heterodimer, indicating that segment A4 is also near segment(s) B. Certain combinations of Cys residues in segments A3 and A4 cross-linked to form MotA tetramers in high yield upon oxidation. The high-yield positions identify faces on A3 and A4 that are at an interface between MotA subunits. Taken together with mutational studies and patterns of amino acid conservation, the cross-linking results delineate the overall arrangement of 10 membrane segments in the MotA/MotB complex, and identify helix faces likely to line the proton channels.

Bacterial Adhesion↗
PubMed2001

The patterns and distribution of residual abnormalities between the individual proximal venous segments after an acute deep vein thrombosis.

INTRODUCTION: The subsequent course of residual abnormalities after an acute deep vein thrombosis (DVT) can vary within individual venous segments. To investigate the pattern of response within the individual venous segment, we used sequential duplex scanning to determine whether certain segments are more likely to recanalize or remain occluded. METHODS: The anatomic segments involved in 63 above-knee DVTs were examined with duplex scanning at 1 week, 1 month, 6 months, and 1 year after the acute event. The segments under investigation were the external iliac vein (EIV), common femoral vein (CFV), superficial femoral vein (SFV), and popliteal vein (PV). Reflux studies were performed at each follow-up examination. During the follow-up period the segments were examined to see whether they were occluded, partially recanalized, or totally recanalized and the development of reflux was noted. RESULTS: Most DVTs were multisegmental with a total number of 171 sites involved. Initially, a greater number of segments were occluded (71%) than partially thrombosed (29%). The occluded segments were predominantly in the SFV and PV. At 1 year the thrombi had fully resolved in 60% of the venous segments, 27% remained partially recanalized, and 13% were occluded. The venous segments that resolved within the first 6 months had a higher rate of valvular competence than those that resolved from 6 months to 1 year. The SFV and PV had a higher incidence of valvular incompetence than the EIV and CFV. All venous segments that were partially recanalized at 1 year were found to have significant reflux. The SFV had the highest incidence of total occlusion at the end of 1 year (36%). Many of the occluded SFVs had established collateral pathways that displayed no evidence of reflux. CONCLUSION: The lower extremity venous segments differ in respect to their tendencies to partially or fully recanalize or remain occluded. All partially recanalized segments displayed reflux. Fully resolved segments that recanalized within the first 6 months were more likely to have competent valves than those that recanalized after 6 months. In the presence of an occluded SFV, collateral pathways establish rapidly. No reflux was found in these collaterals.

Acute Disease↗
PubMed1998

Stability of posterior spinal instrumentation and its effects on adjacent motion segments in the lumbosacral spine.

STUDY DESIGN: An in vitro biomechanical analysis of three anterior instability patterns was performed using calf lumbosacral spines. Stiffness of the constructs was compared, and segmental motion analyses were performed. OBJECTIVES: To clarify the factors that alter the stability of the spinal instrumentation and to evaluate the influence of instrumentation on the residual intact motion segments. SUMMARY OF BACKGROUND DATA: Recently, many adverse effects have been reported in fusion augmented with rigid instrumentation. Only few reports are available regarding biomechanical effects of stability provided by spinal instrumentation and its effects on residual adjacent motion segments in the lumbar-lumbosacral spine. METHODS: Eighteen calf lumbosacral spine specimens were divided into three groups according to instability patterns--one-level, two-level, and three-level disc dissections. Six constructs were cyclically tested in rotation, flexion-extension, and lateral bending of intact spines, of destabilized spine, and of spines with four segmental posterior instrumentation systems used to extend the levels of instability (Cotrel-Dubousset compression hook and three transpedicular screw fixation systems). During each test, stiffness values and segmental displacements were measured. RESULTS: The rigidity of the instrumented construct increased as the fixation range became more extensive. Although application of the instrumentation effectively reduced the segmental motion of the destabilized vertebral level, the motion at the destabilized level tended to increase as the number of unstable vertebral levels increased, and the fixation range of the instrumentation became more extensive. Instrumented constructs produced higher segmental displacement values at the upper residual intact motion segment when compared with those of the intact spine. In contrast, the instrumented constructs decreased their segmental displacement values at the lower residual intact motion segment with higher magnitude of the translational (shear) motion taking place compared with the intact spine in flexion-extension and lateral bending. These changes in the motion pattern became more distinct as the fixation range became more extensive. CONCLUSIONS: As segmental spinal instrumentation progresses from one level to three levels, the overall torsional and flexural rigidity of the system increases. However, segmental displacement at the site of simulated instability becomes more obvious. Application of segmental instrumentation changes the motion pattern of the residual intact motion segments, and the changes in the motion pattern become more distinct as the fixation range becomes more extensive and as the rigidity of the construct increases.

Animals↗
PubMed2000

The effect of disc degeneration and facet joint osteoarthritis on the segmental flexibility of the lumbar spine.

STUDY DESIGN: A biomechanical and imaging study of human cadaveric spinal motion segments. OBJECTIVE: To investigate the effect of both disc degeneration and facet joint osteoarthritis on lumbar segmental motion. SUMMARY OF BACKGROUND DATA: Spinal degeneration includes the osteoarthritic changes of the facet joint as well as disc degeneration. Disc degeneration has been reported to be associated with spinal motion. The association of facet joint osteoarthritis with lumbar segmental motion characteristics and the combined influence of disc degeneration and facet osteoarthritis has not yet been investigated. METHODS: A total of 110 lumbar motion segments (52 female, 58 male) from 44 human lumbar spines were studied (mean age = 69 years). Magnetic resonance images were used to assess the disc degeneration from Grade I (normal) to Grade V (advanced) and the osteoarthritic changes in the facet joints in terms of cartilage degeneration, subchondral sclerosis, and osteophytes. Disc height, endplate size, and facet joint orientation and width also were measured from the computed tomographic images. Rotational movements of the motion segment in response to the flexion, extension, lateral bending, and axial rotational moments were measured using a three-dimensional motion analysis system. RESULTS: Female motion segments showed significantly greater motion (lateral bending: P < 0. 001, flexion: P < 0.01, extension: P < 0.05) and smaller endplate size (P < 0.001) than male ones. The segmental motion increased with increasing severity of disc degeneration up to Grade IV, but decreased in both genders when the disc degeneration advanced to Grade V. In male segments, the disc degeneration-related motion changes were significant in axial rotation (P < 0.001), lateral bending (P < 0.05), and flexion (P < 0.05), whereas female segments showed significant changes only in axial rotation (P < 0.001). With cartilage degeneration of the facet joints, the axial rotational motion increased, whereas the lateral bending and flexion motion decreased in female segments. In male segments, however, motion in all directions increased with Grade 3 cartilage degeneration and decreased with Grade 4 cartilage degeneration. Subchondral sclerosis significantly decreased the motion (female: axial rotation, P < 0. 05; extension, P < 0.05 vs.- male:flexion,P < 0.05). Severity of osteophytes had no significant association with the segmental motion. CONCLUSION: Axial rotational motion was most affected by disc degeneration, and the effects of disc degeneration on the motion were similar between genders. Facet joint osteoarthritis also affected segmental motion, and the influence differed for male and female spines. Further studies are needed to clarify whether the degenerative process of facet joint osteoarthritis differs between genders and how facet joint osteoarthritis affects the stability of the spinal motion segment.

Cadaver↗
PubMed2006

Mobility of lumbar segments instrumented with a ProDisc II prosthesis: a two-year follow-up study.

STUDY DESIGN: Longitudinal prospective study on a sample of 41 consecutive disc prosthesis patients, covering a postoperative time period of at least 2 years. OBJECTIVES: To document the rotational and translational range of segmental motion of patients instrumented with ProDisc II prostheses in the lumbar spine and to compare motion between instrumented and untreated adjacent segments with respect to a normative database. To discuss potential causes of the low range of rotational motion observed after instrumentation with a Prodisc II prosthesis. SUMMARY OF BACKGROUND DATA: Disc replacement is intended to restore physiologic motion and height of the affected levels. Published reports show, however, that the goal of restoring motion at the operated segment is missed in the majority of cases. The cause of this failure is unresolved. METHODS: Rotational and translational segmental motion in the sagittal plane, disc height, and posteroanterior displacement were measured from lateral radiographic views taken standing (before surgery) and in flexion and extension (1 year and 2 years after surgery) by Distortion Compensated Roentgen Analysis (DCRA). The protocol permits to take measurements from all segments imaged on the radiographic views and compensates for variations in stature, magnification, and posture. Data from instrumented and untreated segments can be compared and related to a previously determined normative database. RESULTS: The rotational range of motion of segments instrumented with a ProDisc II prosthesis was low, especially at L4-L5 and L5-S1. In the majority of cases, it amounted to less than 45% of the normal range. Virtually no improvement occurred between 1 and 2 years after surgery. Malalignment of the axis of rotation of the prosthesis with respect to the anatomic axis, persisting clinical symptoms, or the significant increase of intervertebral space documented after instrumentation are unlikely to cause the low range of motion. As the range of rotational motion of the untreated segments was low with respect to normal as well, it is conjectured that tissue adaptation during the preoperative symptomatic time period might have caused the postoperative motion deficit. This conjecture complies with fragmentary previous observations of a low postoperative segmental range of motion from untreated segments of fusion patients. CONCLUSIONS: Disc replacement in the lumbar spine by a ProDisc II implant fails to restore normal segmental rotational motion in the sagittal plane, specifically at levels L4-L5 and L5-S1. As segmental motion of the untreated segments was lower than normal as well, though not quite as conspicuous as that of instrumented segments, adaptation of soft tissue taken place during the preoperative symptomatic time period is conjectured to cause the observed motion deficit. Postoperative physical therapy might be considered if restoration of a normal range of rotational motion is desired.

Adult↗
PubMed1976

Studies on acidification of media by Avena stem segments in the presence and absence of gibberellic Acid.

The rate of acidification of media by Avena stem segments was studied with a titrimeter. GA(3) increased this rate by an average of 17% if supplied to the segments 90 min prior to measurement. GA(3) inhibited the rate by 15% if supplied 10 min prior to measurement. After 90 min incubation, stimulation of elongation had started; at 10 min, GA(3) had not yet started to stimulate elongation in the segments.The acidification rates of the nodes (including the sheath-pulvinus), leaf sheath bases, and the internode bases of the stem segments were determined for plus and minus GA(3)-treated segments. The internode fraction contributes most to modification of the acidification rate, the node-pulvinus fraction less so, and the nongrowing sheath not at all.Acidification rates were measured for segments in different stages of elongation (lag, log, and plateau phases of growth). Segments in these growth stages were obtained from intact plants and from segments preincubated in sucrose and sucrose + GA(3). Segments from all sources which are in the log phase of growth have the highest rates, those in the plateau phase the lowest. For lag and log growth phases, segments preincubated in sucrose + GA(3) show the highest rates, those preincubated in sucrose the lowest rates. The opposite occurs for segments in the plateau phase of growth.Segments stimulated to grow by GA(3) cause the pH of their incubation media to drop to pH 5.15 from an initial pH of 6.5. Nonstimulated segments cause a drop to pH 5.6. Long term growth of the segments is maximal in media buffered to pH 5 in the presence and absence of GA(3).Our results support the idea that GA(3) stimulates an active acidification process in Avena stem segments just after GA(3) starts to stimulate growth in the segments, and that such an acidification process could play an important role in wall-loosening during active growth of the internode.

Journal Article↗
PubMed2003

In vivo and in vitro heterogeneity of segment length changes in the semimembranosus muscle of the toad.

Many studies examine sarcomere dynamics in single fibres or length-tension dynamics in whole muscles in vivo or in vitro, but few studies link the various levels of organisation. To relate data addressing in vitro muscle segment behaviour with in vivo whole muscle behaviour during locomotion, we measured in vivo strain patterns of muscle segments using three sonomicrometry crystals implanted along a fascicle of the semimembranosus muscle in the American toad (Bufo americanus; n = 6) during hopping. The centre crystal emitted an ultrasonic signal, while the outer crystals received the signal allowing the instantaneous measurement of lengths from two adjacent muscle segments. On the first day, we recorded from the central and distal segments. On the second day of recordings, the most distal crystal was moved to a proximal position to record from a proximal segment and the same central segment. When the toads hopped a distance of two body lengths, the proximal and central segments strained -15.1 +/- 6.1 and -14.0 +/- 4.9 % (i.e. shortening), respectively. Strain of the distal segment, however, was significantly lower and more variable in pattern, often lengthening before shortening during a hop. From rest length, the distal segment initially lengthened by 2.6 +/- 2.0 % before shortening by 6.5 +/- 3.2 % at the same hop distance. Under in vitro conditions, the central segment always shortened more than the distal segment, except when passively cycled, during which the segments strained similarly. When the whole muscle was cycled sinusoidally and stimulated phasically in vitro, the two adjacent segments strained in opposite directions over much (up to 34 %) of the cycle. These differences in strain amplitude and direction imply that two adjacent segments can not only produce and/or absorb varying amounts of mechanical energy, but can also operate on different regions of their force-length and force-velocity relationships when activated by the same neural signal. Understanding regional differences in contractile dynamics within muscles is therefore important to linking our understanding of sarcomere behaviour with whole muscle behaviour during locomotion.

Animals↗
PubMed1977

The segments of influenza viral mRNA.

Influenza viral mRNA, i.e., complementary RNA (cRNA), isolated from infected cells , was resolved into six different species by electrophoresis in 2.1% acrylamide gels containing 6 M urea. The cRNA's were grouped into three size classes: L (large), M (medium-size), and S (small). Similarly, when gels were sliced for analysis, the virion RNA (vRNA) also distributed into six peaks because the three largest vRNA segments were closely spaced and were resolved only when the gels were autoradiographed or stained. Because of their attached polyadenylic acid [poly(A)]sequences, the cRNA segments migrated more slowly than did the corresponding vRNA segments during gel electrophoresis. After removal of the poly(A) by RNase H, the cRNA and vRNA segments comigrated, indicating that they were approximately the same size. One of the cRNA segments, S2, was shown by annealing to contain the genetic information in the vRNA segment with which it comigrated, strongly suggesting that each cRNA segment was transcribed from the vRNA segment of the same size. In contrast to the vRNA segments, which when isolated from virions were present in approximately 1:1 molar ratios, the segments of the isolated cRNA were present in unequal amounts, with the segments M2 and S2 predominating, suggesting that different amounts of the cRNA segments were synthesized in the infected cell. The predominant cRNA segments, M2 and S2, and also the S1 segment, were active as mRNA's in wheat germ extracts. The M2 cRNA was the mRNA for the nucleocapsid protein; S1 for the membrane protein; and S2 for the nonstructural protein NS1.

Cell Line↗
PubMed1999

Liver anatomy: portal (and suprahepatic) or biliary segmentation.

BACKGROUND/AIMS: In liver anatomy and surgery, is portal and hepatic vein segmentation (French segmentation) to be preferred over arteriobiliary segmentation (Healey and Schroy, North American segmentation)? METHODS: Several embryological arguments and an analysis of anatomical data from a personal collection of 110 vasculobiliary casts were made. RESULTS: Embryological arguments: Portal vein branching appears first, arteriobiliary branching secondly follows the portal vein distribution. Segment II (the left lateral sector) is the development of the right lateral embryological lobe. The umbilical vein enters the left portion of the middle embryological lobe, forming segment IV on the right and segment III on the left: this is the left paramedian sector. So the left portal fissure (between left and middle lobes) transversally crosses the classical left lobe, which is not a portal unit. Segment VI is a late secondary prominence of segment VII, reaching the anterior margin of the liver only in man. Anatomical arguments: hepatic vein segmentation must be added to portal segmentation; the academic left lobe is the left hepatic vein sector, and the left hepatic fissure separates the classical right and left lobes. Portal vein segmentation must be preferred: portal vein duplication of branches of first order occurs only in 23.5% of the cases, while arteriobiliary duplication of first-order branches is noted in 50% of the livers, portal segmentation being much simpler. CONCLUSIONS: Portal and hepatic vein segmentation seems to be much more accurate.

Animals↗
PubMed1979

A chronic isolated tracheal segment to study airway reflexes in conscious dogs.

Airway reflexes are difficult to study in conscious animals because associated changes in ventilation alter intrathoracic airway dimensions. By studying an isolated segment of extrathoracic trachea, we have overcome this problem. In each of 2 dogs, we created surgically an isolated tracheal segment just below the larynx, sealed at one end and tapered at the other to a 3-mm opening via a skin fistula. A chronic tracheostomy was also created near the thoracic outlet. We monitored intraluminal pressure (Pseg) of the isolated segment to reflect changes in smooth muscle tone. During anesthesia, with pentobarbital, gentle mechanical stimulation of the carina, deflation of the lungs, and asphyxia for one min increased Pseg (+9 to +/- 16 cm H2O). Lung inflation and alveolar hyperventilation decreased Pseg (-9 to -16 cm H2O). Five breaths of 2 per cent histamine aerosol increased Pseg (+5 cm H2O) when resting tone was normal. We also coated lumen of the isolated segment with tantalum powder and documented roentgenologically changes in the size of the segment that reflected changes in smooth muscle tone; constriction and dilation in response to asphyxia and lung inflation, respectively, were demonstrated directly by this technique. In conscious dogs, lung inflation decreased Pseg, and carinal stimulation increased Pseg. Instillation of lidocaine hydrochloride (Xylocaine) into the isolated tracheal segment blocked cough caused by mechanical stimulation of the segment, but carinal stimulation still caused constriction of the segment under these conditions which indicated that afferent, but not effrent parasympathetic innervation of the segment had been blocked selectively. Conversely, instillation of atropine sulfate into the isolated tracheal segment blocked constriction of the segment caused by carinal stimulation, but mechanical stimulation of the segment still caused cough under these conditions, which indicated that efferent, but not afferent parasympathetic innervation of the segment had been blocked selectively. We conclude that an innervated extrathoracic tracheal segment constricts and dilates via cholinergic pathways and is suitable for the study of airway reflexes in conscious dogs.

Animals↗
PubMed2000

Anteroposterior patterning is required within segments for somite boundary formation in developing zebrafish.

Somite formation involves the establishment of a segmental prepattern in the presomitic mesoderm, anteroposterior patterning of each segmental primordium and formation of boundaries between adjacent segments. How these events are co-ordinated remains uncertain. In this study, analysis of expression of zebrafish mesp-a reveals that each segment acquires anteroposterior regionalisation when located in the anterior presomitic mesoderm. Thus anteroposterior patterning is occurring after the establishment of a segmental prepattern in the paraxial mesoderm and prior to somite boundary formation. Zebrafish fss(-), bea(-), des(-) and aei(-) embryos all fail to form somites, yet we demonstrate that a segmental prepattern is established in the presomitic mesoderm of all these mutants and hox gene expression shows that overall anteroposterior patterning of the mesoderm is also normal. However, analysis of various molecular markers reveals that anteroposterior regionalisation within each segment is disturbed in the mutants. In fss(-), there is a loss of anterior segment markers, such that all segments appear posteriorized, whereas in bea(-), des(-) and aei(-), anterior and posterior markers are expressed throughout each segment. Since somite formation is disrupted in these mutants, correct anteroposterior patterning within segments may be a prerequisite for somite boundary formation. In support of this hypothesis, we show that it is possible to rescue boundary formation in fss(-) through the ectopic expression of EphA4, an anterior segment marker, in the paraxial mesoderm. These observations indicate that a key consequence of the anteroposterior regionalisation of segments may be the induction of Eph and ephrin expression at segment interfaces and that Eph/ephrin signalling subsequently contributes to the formation of somite boundaries.

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