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PubMed1997

AL-1-induced growth cone collapse of rat cortical neurons is correlated with REK7 expression and rearrangement of the actin cytoskeleton.

Previous experiments identified AL-1 as a glycosylphosphatidylinositol (GPI)-linked ligand for the Eph-related receptor, REK7, and showed that a REK7-IgG fusion protein blocks axon bundling in co-cultures of cortical neurons on astrocytes, suggesting a role for REK7 and AL-1 in axon fasciculation. Subsequent identification of RAGS, the chick homologue of AL-1, as a repellent axon guidance molecule in the developing chick visual system led to speculation that AL-1, expressed on astrocytes, provides a repellent stimulus for cortical axons, inducing them to bundle as an avoidance mechanism. Using a growth cone collapse assay to test this hypothesis, we show that a soluble AL-1-IgG fusion protein is a potent collapsing factor for embryonic rat cortical neurons. The response is strongly correlated with REK7 expression, implicating REK7 as a receptor mediating AL-1-induced collapse. Morphological collapse is preceded by an AL-1-IgG-induced reorganization of the actin cytoskeleton that resembles the effects of cytochalasin D. This suggests a pathway whereby REK7 activation by AL-1 leads to perturbation of the actin cytoskeleton, possibly by an effect on actin polymerization, followed by growth cone collapse. We further show that AL-1-IgG causes collapse of rat hippocampal neurons and rat retinal ganglion cells. These data suggest a role for REK7 and AL-1 in the patterning of axonal connections in the developing cortex, hippocampus and visual system.

Actins↗

PubMed1996

Endotracheal suctioning causes right upper lobe collapse in intubated children.

OBJECTIVE: Right upper lobe collapse is a common radiographic finding in intubated children. We hypothesized that deep suctioning and uncontrolled negative pressures during endotracheal tube suctioning were significant contributory factors. METHODS: The incidence of right upper lobe (RUL) collapse in intubated, ventilated children on a paediatric cardiac intensive care unit was determined over a 3-month period (n = 102). Graduated suction catheters and suction vacuums of < 165 cm H2O were then introduced. Another prospective audit was carried out 3 months later (n = 60). RESULTS: We found that 24% developed RUL collapse and 4 developed an apical pneumothorax. Following the introduction of graduated catheters and controlled vacuums pressures; a significant reduction in the incidence of RUL collapse, to 7%, was observed (p < 0.05). CONCLUSIONS: We conclude that high negative pressure and deep-suctioning causes RUL collapse in children. Any lobar collapse not only prolongs the child's stay in intensive care, but can be associated with further morbidity which may have a serious implication. By improving suctioning technique this morbidity can be significantly reduced.

Child↗

PubMed1990

One-dimensional steady inviscid flow through a stenotic collapsible tube.

A one-dimensional inviscid solution for flow through a compliant tube with a stenosis is presented. The model is used to represent an artery with an atherosclerotic plaque and to investigate a range of conditions for which arterial collapse may occur. The coupled equations for flow through collapsible tubes are solved using a Runge-Kutta finite difference scheme. Quantitative results are given for specific physiological parameters including inlet and outlet pressure, flow rate, stenosis size, length and stiffness. The results suggest that high-grade stenotic arteries may exhibit collapse with typical physiological pressures. Critical stenoses may cause choking of flow at the throat followed by a transition to supercritical flow with tube collapse downstream. Greater amounts of stenosis produced a linear reduction of flow rate and a shortening of the collapsed region. Changes in stenosis length created proportional changes in the length of collapse. Increasing the stiffness of the stenosis to a value greater than the nominal tube stiffness caused a greater amount of flow limitation and more negative pressures, compared to a stenosis with constant stiffness. These findings assist in understanding the clinical consequences of flow through atherosclerotic arteries.

Animals↗

PubMed1992

Longitudinal tension variation in collapsible channels: a new mechanism for the breakdown of steady flow.

There are several mechanisms potentially involved in the breakdown of steady fluid flow in a collapsible tube under external pressure. Here we investigate one that has received little attention in the past: the fact that the longitudinal tension in the tube wall, T, decreases with distance downstream as a consequence of the viscous shear stress exerted by the fluid. If the tube is long enough, or the initial tension small enough, T may fall to zero before the end of the collapsible tube, and unsteady motion would presumably then ensue; this is what we mean by "breakdown." We study the phenomenon theoretically, when the flow Reynolds number is of order one, using lubrication theory in a symmetric two-dimensional channel in which the collapsible tube is replaced by membranes occupying a segment of each wall. The resulting nonlinear ordinary differential equations are solved numerically for values of the dimensionless parameters that cover all the qualitatively different types of solution (e.g., in which the channel is distended over all its length, collapsed over all its length, or distended in the upstream part and collapsed downstream). Reducing the longitudinal tension has a marked effect on the shape of the collapsible segment, causing it to become much more deformed for the same flow rate and external pressure. Indeed, the wall slope is predicted to become very large when the downstream tension is very small, so the model is not self-consistent then. Nevertheless, the parameter values for which T becomes zero are mapped out and are expected to be qualitatively useful.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Flow Velocity↗

PubMed2004

Hydrophobic collapse in multidomain protein folding.

We performed molecular dynamics simulations of the collapse of a two-domain protein, the BphC enzyme, into a globular structure to examine how water molecules mediate hydrophobic collapse of proteins. In the interdomain region, liquid water persists with a density 10 to 15% lower than in the bulk, even at small domain separations. Water depletion and hydrophobic collapse occur on a nanosecond time scale, which is two orders of magnitude slower than that found in the collapse of idealized paraffin-like plates. When the electrostatic protein-water forces are turned off, a dewetting transition occurs in the interdomain region and the collapse speeds up by more than an order of magnitude. When attractive van der Waals forces are turned off as well, the dewetting in the interdomain region is more profound, and the collapse is even faster.

Computer Simulation↗

PubMed2004

Ophthalmodynamometric determination of the central retinal vessel collapse pressure correlated with systemic blood pressure.

AIMS: To evaluate whether determination of the central retinal artery and vein collapse pressure correlate with systemic blood pressure measurements, using a new Goldmann contact lens associated ophthalmodynamometric device METHODS: The prospective clinical study included 92 eyes of 92 patients presenting with cataract or refractive problems (n = 40; control study group) or with retinal and orbital pathologies (n = 52). With topical anaesthesia, a Goldmann contact lens fitted with a pressure sensor in its holding ring was placed onto the cornea. Pressure was asserted onto the globe by pressing the contact lens, and the pressure value at the time when the central retinal artery and vein started pulsating were noted as central retinal artery and vein collapse pressure. Additionally, the brachial arterial blood pressure was measured. RESULTS: In the control study group, central retinal artery collapse pressure was highly significantly correlated with diastolic blood pressure (correlation coefficient r = 0.77; p<0.001) and systolic blood pressure (r = 0.35; p = 0.03). Central retinal vein collapse pressure was statistically independent of diastolic blood pressure (p = 0.11). In eyes with retinal or orbital diseases, the correlation coefficients were lower than in the control study group. In eyes with retinal arterial occlusions, central retinal vessel collapse pressure measurements were not correlated with arterial blood pressure measurements. CONCLUSIONS: Depending on coexisting retinal or orbital diseases, ophthalmodynamometric estimation of the central retinal artery collapse pressure, performed during a routine Goldmann contact lens ophthalmoscopy, correlates with systemic blood pressure measurements.

Adult↗

PubMed1979

Effect of lung surface tension on bronchial collapsibility in excised dog lungs.

Bronchial collapsibilities were studied in air- and saline-filled excised dog lungs. The intrapulmonary bronchi were isolated from the rest of the lung parenchyma with beads placed at their tributary bronchi as described previously by Takishima et al. (J. Appl. Physiol. 38: 875-881, 1975). Pressure-volume relations of the isolated bronchi were obtained while lung volume (VL) was kept constant. When lung recoil pressure (PL) was reduced by filling the lung with saline at a given VL, bronchial areas were smaller and bronchial collapsibilities were larger than in the air-filled lung. When bronchial areas and bronchial collapsibilities in air- and saline-filled lungs were compared at a given PL, they were approximately identical. We concluded that bronchial areas and collapsibilities were primarily determined by PL rather than VL, and lung surface tension itself made bronchial collapsibility equal to or even less than the degree of collapsibility due to forces applied from surrounding lung tissues that distended the bronchi.

Airway Resistance↗

PubMed1981

Series distribution of airway collapsibility in dogs.

We studied the series distribution of collapsibility in four different-sized airways in dogs. The trachea and the extrapulmonary main bronchi in situ were isolated from the rest of the lungs by glued beads of 6-12 mm OD. In excised dog lungs, the intrapulmonary large and small bronchi were isolated from the rest of the lung by glued beads of 1-9 mm OD. Pressure-volume relationships were measured directly in the trachea and in the extrapulmonary bronchi; those of the intrapulmonary bronchi were derived from orthogonal bronchograms. Airway collapsibility, defined as the slope of the pressure-volume curve, was found to increase in all airways as transpulmonary pressure (PL) decreased. At PL 30 cmH2O there was little difference of airway collapsibility among the different sized airways; but, as PL decreased, the peripheral airways became more collapsible than the central airways. It is concluded that the tissues surrounding the trachea provided as much or more stiffness than did the lung tissues that surrounded the intrapulmonary airways. The larger collapsibility in the peripheral airways. The larger collapsibility in the peripheral airways relative to that of the central airways at lower PL may account for the peripheral migration of the flow-limiting segment during forced expiration.

Animals↗

PubMed1996

Upper airway size and collapsibility in snorers: evaluation with digital fluoroscopy.

This study addressed the question of whether there are any differences in the size and collapsibility of the upper airway measured by digital fluoroscopy, between snorers and controls whilst they were awake and breathing normally; and whether there are any correlations between these measurements and other clinical data. The dynamic changes of the upper airway size were evaluated using digital fluoroscopy in 33 patients and 16 normal controls. The measurements were compared with findings in an overnight sleep study, including a static-charge-sensitive bed (SCSB) and oximeter recordings. The minimum anteroposterior dimension at the velopharyngeal level was smaller in patients with partial upper airway obstruction than in controls (p<0.005); patients with complete obstruction did not differ from the controls. The velopharyngeal airways were also more collapsible in patients with severe partial obstruction (p<0.01) than in controls. At the oropharyngeal and hypopharyngeal levels, the dimensions and the collapsibilities were similar in patients and controls. The velopharyngeal collapsibility correlated with body mass index (p<O.001), whereas the airway size did not. The velopharyngeal collapsibility was more pronounced in patients with frequent episodes of arterial oxyhaemoglobin desaturation during sleep. Velopharyngeal collapsibility associated with high body mass index was the important determinant of nocturnal breathing disturbances. Digital fluoroscopy displays the dynamic changes of the upper airways throughout the respiratory cycle.

Adult↗

PubMed1989

Intermediate filament collapse is an ATP-dependent and actin-dependent process.

In this study, we have investigated the properties of intermediate filament rearrangements using experimentally induced collapse of vimentin intermediate filaments in mouse fibroblasts. In these cells, depolymerizing microtubules by colchicine or vinblastine treatment at 37 degrees C results in a two-stage collapse of intermediate filaments. First, the vimentin filaments aggregate into large cables; then, the cables coil into a dense mass surrounding the nucleus. By using inhibitors of oxidative phosphorylation along with glucose deprivation to lower intracellular ATP levels by 95%, we have found that both stages of intermediate filament collapse require ATP. However, once collapse has occurred, only the second stage can be reversed in the absence of microtubules by lowering ATP levels. An additional difference between the two stages of collapse was revealed by treating cells with cytochalasin D: the formation of intermediate filament cables still occurs after disruption of the actin filament system by cytochalasin, but the subsequent coiling of cables to form a perinuclear mass is strongly inhibited by these conditions, and can be reversed by applying cytochalasin to cells in which intermediate filaments have already undergone complete collapse. We propose that the formation of vimentin cables involves a phosphorylation event, while the coiling of cables into a perinuclear mass relies on interaction of intermediate filaments with a component of the actin cortex.

Actins↗

PubMed2003

Treatment of nasal obstruction from nasal valve collapse with alar batten grafts.

Nasal obstruction may require treatment with rhinoplasty techniques. One cause of nasal obstruction is known as nasal valve collapse. This refers to narrowness and weakness at the nasal valve, the narrowest part of the nasal airway. There are a number of surgical approaches available to treat nasal valve collapse. Selection of the appropriate surgical intervention depends on proper identification of the anatomic cause of the collapse. Alar batten grafts are especially useful for addressing nasal valve collapse caused by a weak nasal sidewall. In this report, we review the senior author's experience with the use of alar batten grafts for nasal valve collapse. Twenty-one patients had septoplasty with placement of alar batten grafts; all patients noted improvement in their nasal breathing. Seven patients underwent ear cartilage harvest with alar batten grafts, and five of them noted improvement, one noted partial improvement, one noted no improvement. Six patients underwent revision septorhinoplasty with alar batten grafting, and ten patients underwent revision septorhinoplasty with ear cartilage harvest and alar batten grafting. These patients all reported improvement in their nasal breathing postoperatively. Six patients underwent revision rhinoplasty (no septoplasty) with ear cartilage and battens. These patients hold special interest because no other intranasal procedures were performed that affected nasal breathing. All six of these patients reported significant improvement of their nasal breathing and all patients were satisfied with their postsurgical cosmetic appearance. The nasal valve area is considered to be the location of the least cross-sectional area in the nose. When narrowing of the nasal valve is a result of collapse of the nasal sidewall, alar batten grafts are a useful technique to address the patient's nasal obstruction.

Female↗

PubMed2005

The use of alendronate to prevent early collapse of the femoral head in patients with nontraumatic osteonecrosis. A randomized clinical study.

BACKGROUND: Osteonecrosis of the femoral head is the most common diagnosis leading to total hip arthroplasty in young adults. Joint-preserving treatment options have been mainly surgical, with inconsistent results. Alendronate (a bisphosphonate agent) has been shown to lower the prevalence of vertebral compression fractures and could potentially retard the collapse of an osteonecrotic femoral head. The purpose of this study was to test the effect of alendronate in preventing early collapse of the femoral head in patients with nontraumatic osteonecrosis. METHODS: Forty patients with Steinberg stage-II or III nontraumatic osteonecrosis of the femoral head and a necrotic area of >30% (class C) were randomly divided into alendronate and control groups of twenty patients each. Patients in the alendronate group took 70 mg of alendronate orally per week for twenty-five weeks, while the patients in the control group did not receive this medication or a placebo. The patients were observed for a minimum of twenty-four months. Harris hip scores, plain radiographs, and magnetic resonance imaging scans were obtained. RESULTS: During the study period, only two of twenty-nine femoral heads in the alendronate group collapsed, whereas nineteen of twenty-five femoral heads in the control group collapsed (p < 0.001). One hip in the alendronate group underwent total hip arthroplasty, whereas sixteen hips in the control group underwent total hip arthroplasty (p < 0.001). CONCLUSIONS: Alendronate appeared to prevent early collapse of the femoral head in the hips with Steinberg stage-II or IIIC nontraumatic osteonecrosis. A longer duration of follow-up is needed to confirm whether alendronate prevents or only retards collapse. LEVEL OF EVIDENCE: Therapeutic Level I.

Adult↗

PubMed2000

Core decompression for osteonecrosis of the femoral head at pre-collapse stage.

Twenty-five patients (27 hips) were retrospectively studied for core decompression in the treatment of osteonecrosis of the femoral heads at pre-collapse stage, Ficat and Alert stages I and II, from Apr. 1984 to Jun. 1998 with follow-up period at least 1 yr (mean 28 months). Eleven hips (10 patients) were considered to have failed due to progressive collapsed more than 2 mm, severe pain or reoperation. We further analyzed the results with regard to the stages, the size of the necrotic area according to the Ohzono classification, the lateral head index (LHI) and the Kerboul combined necrotic angle. The survival rate according to the Ohzono classification was type 1B: 100%, 1C: 44%, 2: 25%, and 3B: 0%. Hips with Kerboul angle less than 250 degrees revealed satisfactory results in all except one hip. All hips with Kerboul angle more than 250 degrees collapsed. Fourteen of the 15 hips (93%) with lateral head index more than 20% did not collapse and all hips except one (7/8) with LHI less than 12% collapsed. We conclude core decompression yields satisfactory results in osteonecrotic femoral heads at pre-collapse stage and with small necrotic area or good lateral buttress.

Adult↗

PubMed2001

Carpal collapse in rheumatoid arthritis--prevalence and clinical significance: a preliminary study.

OBJECTIVE: To evaluate the prevalence and clinical significance of carpal collapse in Mexican women with rheumatoid arthritis (RA). METHODS: We evaluated the carpal height ratio (CHR) of 97 women with RA and 90 healthy women. Using plain radiographs of both hands, measurements were performed by 2 radiologists in a single blind fashion. We analyzed functional class, characteristics and duration of the disease, and presence of rheumatoid factor (RF). RESULTS: CHR values of the controls were 0.49+/-0.02 (values reported in American Caucasian women are 0.54+/-0.04). Thirty-five patients had carpal collapse (defined as CHR < or = 0.43) in the right hand, 30 in the left hand, and 23 bilaterally. Carpal collapse was associated with RF seropositivity and roentgenographic degree of progression (p < 0.01), as well as with cumulative dose of steroids. As 95% of the patients were right-handed, dexterity was not apparently affected. We observed no differences in Health Assessment Questionnaire, functional class, or disease duration between patients with and those without carpal collapse. CONCLUSION: The definition of carpal collapse may have ethnic related differences. Carpal collapse is common in Mexican women with RA and it is not an indicator of functional limitations.

Adult↗

PubMedDate not supplied

[Skewed shape of the maximal expiratory flow volume curve and bronchoscopic signs of lower airway collapse in chronic obstructive pulmonary disease].

We compared endoscopical signs of airway collapse seen during tidal breathing with the shape of the maximal-expiratory flow volume curve and selected functional parameters in 16 cases of chronic obstructive pulmonary disease (COPD). Depending on localization of airway collapse the group was divided into two. 12 patients with central collapse involving the trachea and main stem bronchi formed group A. The remaining 4 patients with peripheral collapse (lobar and segmental bronchi) formed group B. In the former group the MEFV curve had a characteristic biphasic shape. The shape of this curve in the group B patients was more curvilinear. In group A patients an increase of Raw, TGV and fall of FEV1 was seen which could not be demonstrated in group B. The biphasic shape of the MEFV curve seems to be characteristic of airway collapse, but due to a small number of patients included we can not assess the specificity of it in diagnosing airway collapse.

Adult↗

PubMed1989

[Comparative cinematographic, endoscopic and functional analytic studies of the pre- and postoperative evaluation of the severity of the tracheobronchial collapse syndrome].

Sixty eight adults of both sexes (33 patients with clinically and endoscopically verified tracheobronchial collapse; 35 persons without disease of the central airways) underwent continuous cinetracheographic studies of the wall-movements of the central airways during various respiratory maneuvers. The insufflation of powdered tantalum for a better outlining of the contours of the central airways was preferably done in local anaesthesia via an orotracheally inserted catheter. Studies of wall-movement were made in recumbent position during forced breathing and violent coughing in various obliquities using a 35 mm-camera. The percentage of diameter-shortening during expiration (forced breathing; violent coughing) in relation to the inspiratory diameter during the same breathing-maneuver was measured in 4 or 3 projections respectively at 5 localities (cervical trachea; thoracic outlet; thoracic trachea 1 cm above the bifurcation; right and left main bronchus, 1 cm distant from bifurcation). Out of maximally 17 single numerical values per examination the highest single value was selected as the so-called "maximal relative diameter-shortening" - independent of locality and projection. In healthy persons the mean value amounts to 22.4 +/- 15.44% (means +/- SD) during forced breathing and to 75.5 +/- 11.72% during violent coughing. Patients with a tracheobronchial collapse differ from healthy persons, the former having a value of 100% during violent coughing. This is equivalent to a brief contact of the membranous part to the ventral circumference of the trachea (total cough-collapse) at least at one locality in one projection. Out of a number of 28 patients 17 cases (group H) revealed a normal "maximal relative diameter-shortening" of 29.7 +/- 21.57% during forced breathing. In addition to the total cough-collapse 11 patients (group F) exhibited an increased prolapse-tendency of the membranous part during forced breathing, too; the mean value of the "maximal relative diameter-shortening" amounted to 80.5 +/- 16.15%. Pathological shortening-values are mainly measured at the intrathoracic trachea in the lateral and both oblique projections. The cinetracheobronchographic examination should be used in patients with endoscopic signs of a tracheobronchial collapse-syndrome if an operative procedure with tautening is taken into consideration. In the case of mere clinical suspicion of the presence of a collapse-syndrome the assessment of the wall-motility is non-invasively possible by means of cinetracheography without a contrast-agent.(ABSTRACT TRUNCATED AT 400 WORDS)

Bronchi↗

PubMed1996

Surgical treatment of tracheal collapse in dogs: 90 cases (1983-1993).

OBJECTIVE: To determine factors associated with long-term outcome in dogs with tracheal collapse treated with extraluminal polypropylene C-shaped stents. DESIGN: Retrospective case series. ANIMALS: 90 dogs. PROCEDURE: Medical records of dogs with surgically treated tracheal collapse were reviewed. Follow-up was obtained either by recheck at the veterinary teaching hospital only (n = 10) or by telephone interviews with referring veterinarians and owners (n = 35), referring veterinarians alone (n = 23), or owners alone (n = 16). The chi 2 test was used to determine which factors were associated with long-term outcome. RESULTS: 11 breeds were represented. Yorkshire Terriers, Poodles, and Pomeranians were most common. Median age at the time of surgery was 6.8 years. Median weight was 2.9 kg. Severity of collapse ranged from grade II to grade IV. Dogs < 6 years old had more severe collapse than did dogs > or = 6 years old. Dogs > or = years old had more postoperative complications and a poorer longterm outcome than did dogs < 6 years old. 17 dogs required permanent tracheostomy, 10 within 24 hours after surgery. CLINICAL IMPLICATIONS: Surgical placement of extraluminal polypropylene C-shaped stents was an effective method of attenuating clinical signs of tracheal collapse. Dogs < 6 years old had more severe tracheal collapse but did better after surgery than did dogs > or = 6 years old.

Age Factors↗

PubMed2001

Late complications of collapse therapy for pulmonary tuberculosis.

STUDY OBJECTIVES: Collapse therapy for pulmonary tuberculosis involved placement of various materials to occupy space and keep the lung collapsed. Complications are encountered decades later. PATIENTS AND METHODS: Between 1980 and 1997, we treated 31 patients with a history of pulmonary tuberculosis in whom collapse therapy had been used and who later developed complications related to their treatment. Pyogenic empyema was present in 24 patients, pleural calcifications with bronchopleural fistula was present in 3 patients, pleural calcification with nonresolvable pneumothorax was present in 1 patient, and migration of a foreign body with formation of subcutaneous mass occurred in 3 patients. All patients with empyema were treated with antibiotics and tube drainage of pus. In addition, Lucite balls were extracted in 4 patients, lung decortication was performed in 6 patients, thoracoplasty was performed in 2 patients, and fenestration was performed in 16 patients. Bronchopleural fistulas were closed with sutures and reinforced with intercostal muscle flap in three patients; in one patient with pleural calcification and nonresolvable pneumothorax, tube drainage was attempted. In three patients with subcutaneous mass due to paraffin migration, paraffin was extracted. RESULTS: Pulmonary decortication (six patients) and thoracoplasty (two patients) resulted in elimination of empyema. Extraction of Lucite balls resulted in lung expansion and elimination of empyema in three of four patients; draining sinus remains in one patient. Fenestration resulted in elimination of empyema in 12 of 16 patients, with 3 patients with residual draining sinuses and 1 patient with remaining empyema. All bronchopleural fistulas closed with intercostal muscle flap remained closed. Following extraction of paraffin blocks, infection developed in one patient. During the follow-up period, three patients died, all of unrelated causes. CONCLUSIONS: Delayed complications of collapse therapy for tuberculosis should be treated without delay. Pressure on adjacent structures or their erosion presents danger and mandates immediate extraction; however, there is no need for routine removal of every residual plombe. Further increase in the number of multiple-drug resistant strains may force the return of collapse therapy.

Adult↗