Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0038454 (stroke)
 147,016 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Dynein is the molecular motor that provides motive force in cilia and flagella. Dynein is anchored to the A-subtubule of the outer doublets by a club-shaped extension called the stem, which supports the large globular head of the molecule. Dynein forms an attachment or cross-bridge to the B-subtubule of the adjacent outer doublet through a slender appendage extending from the head that is called the stalk or alternately the B-link. It is generally thought that the B-link mediates the interdoublet transfer of force that bends the flagellum. This requires that energy released at the site of ATP hydrolysis, located in the globular head, be transferred as mechanical work to the microtubule binding site at the tip of the B-link. It has been proposed that this is accomplished by a sideways or rotational translocation of the B-link caused by a rotation of the globular head. An estimate of the stiffness of the B-link and stem derived from the recently published data of Burgess et al. [2003: Nature 421:715-718] yields a maximum stiffness of 0.47 pN/nm for the B-link and 0.1 pN/nm for the stem. The B-link stiffness would allow transfer of 3.8 pN of force in response to an 8-nm displacement of the B-link tip. However, if as proposed the globular head of the dynein heavy chain is supported by the stem, the B-link and stem elasticity are in series. Thus, the flexibility of the stem would limit the force that can be transferred laterally by the entire dynein heavy chain to 0.6 pN at 8 nm displacement. This force is insufficient to support flagellar motility. So, if the stem were the only support for the globular head, then force would have to be transmitted linearly along the axis defined by the stem and B-link. Because this configuration is never observed, the hypothesis that dynein generates force by lateral displacement of the B-link is more attractive, but requires that the globular head of the dynein is stabilized by an additional means of support during the power stroke. We propose that the microtubule affinity of the tip of the B-link is independent of the ATP-dependent powerstroke, and that detachment from the B-subtubule is regulated by tension. A dynein cross-bridge cycle that incorporates an anchored head, together with a ratchet-like mechanism for microtubule translocation by the B-link, would have distinct advantages. This mechanism may reconcile dynein oscillation and interdoublet sliding within one cross-bridge mechanism.
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PMID:Does axonemal dynein push, pull, or oscillate? 1458 26

A patent foramen ovale (PFO) is a frequent remnant of embryological development with clinical importance in thromboembolism, paradoxical embolism, stroke, platypnea-orthodeoxia, decompression sickness, and migraine headache. The proposed mechanisms of stroke with PFO include paradoxical embolization, in situ thrombosis within the canal of the PFO, associated atrial arrhythmias, and concomitant hypercoagulable states. Prospective trials using aspirin treatment to reduce recurrent stroke showed a significant recurrence of neurologic events in patients with a PFO and atrial septal aneurysm. Use of warfarin anticoagulation does not further reduce recurrent stroke rates compared with antiplatelet therapy. Both surgical and catheter-based modes of closure have been shown to decrease the rate of subsequent embolic events substantially. Successful closure, defined by transesophageal echocardiography, appears to predict freedom from subsequent embolic events. To our knowledge, no randomized trials comparing anticoagulation with surgical or catheter-based closure have been performed.
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PMID:Patent foramen ovale and stroke. 1470 44

A patent foramen ovale is a frequent remnant of embryological development with clinical importance in stroke, decompression sickness, and migraine headache. The proposed mechanisms of stroke include paradoxical embolization, in situ thrombosis within the canal of the foramen, associated atrial arrhythmias. Cardiac right-to-left shunts can be identified by echocardiography and by transcranial Doppler ultrasound with the use of contrast agents and a Valsalva maneuver as provocation procedure. Relative value of different diagnostic tests, appropriate timing of the Valsalva maneuver, use of a diagnostic time window, and threshold in contrast agent microbubbles detection are thoroughly discussed. The value of echocardiography or of other diagnostic tests does not elucidate the effect of test results on patient management. The appropriate use of imaging requires an understanding of both the capabilities of the imaging technique and the value of therapy used to treat the identified condition. New information that does not improve outcome has no value. In patients with a cryptogenic stroke and an atrial septal abnormality the evidence is insufficient to determine whether warfarin or aspirin is superior in preventing recurrent stroke or death, but minor bleeding is more frequent with warfarin. There is insufficient evidence to evaluate the efficacy of surgical or endovascular closure.
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PMID:[Patent foramen ovale, stroke, and echocardiography: diagnostic methodology and appropriateness of indications]. 1708 59

Foramen ovale plays an important function in the fetus but is of no physiologic significance after birth and closes in most individuals. In about one fourth of the population, however, foramen ovale remains open for life and has been associated with cerebrovascular accidents, especially in younger patients, presumably through paradoxical embolism. Patent foramen ovale (PFO) has also been associated with hypoxia, migraine headaches and neurologic findings of decompression illness in scuba divers. Availability of transesophageal echocardiography and its frequent use in the management of patients with stroke has lead to frequent detection of PFO. In addition, the recent development of devices and techniques for percutaneous closure of PFO has resulted in widespread enthusiasm for such interventions, even when a clear etiologic role for PFO may not be established. In the United States, the Federal Drug Administration (FDA) has approved two such devices through compassionate investigational device exemption without adequate data from large randomized clinical studies. Other such devices are undergoing evaluation in clinical trials. Expert opinions have been helpful for clinical decision making in management of patients with PFO associated with stroke, hypoxia, decompression sickness and migraine headaches.
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PMID:Patent foramen ovale: assessment, clinical significance and therapeutic options. 1723 93

Patent foramen ovale is a frequent remnant of the fetal circulation. Affecting approximately 25% of the adult population. Its recognition, evaluation and treatment has attracted increasing interest as the importance and frequency of its implication in several pathologic processes, including ischemic stroke secondary to paradoxic embolism, the platypnea-orthodeoxia syndrome, decompression sickness (DCS) (an occupational hazard for underwater divers and high altitude aviators and astronauts) and migraine headache, has become better understood. Echocardiographic techniques have emerged as the principle means for diagnosis and assessment of PFO, in particular contrast echocardiography and transcranial Doppler. Its treatment remains controversial with a general tendency to propose a percutaneous closure among the symptomatic patients.
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PMID:Patent foramen ovale: a new disease? 1739 15

Ultrasound guided patent foramen ovale (PFO) closure has traditionally utilized transoesophageal echocardiography (TOE) under general anaesthesia. Some centres use fluoroscopic guidance alone to facilitate day case PFO closure. Intracardiac echocardiography (ICE) is performed via femoral vein access using an 11 Fr sheath providing accurate guidance without the necessity for general anaesthesia. The safety and feasibility of PFO closure using ICE guidance as a day case procedure have not been documented. We present a consecutive series of patients undergoing planned day case PFO closure under ICE guidance with transthoracic echocardiogram (TTE) follow up. Patients excluded from day case PFO closure were those with early pregnancy or unfavourable social circumstances. 53 consecutive adult patients (44.2+/-11.0 years; 24 males) were planned for day case PFO closure facilitated by ICE. Referral indications were stroke or TIA (n=39), peripheral embolism (n=6), decompression sickness (n=7) and severe migraine (n=1). All 53 patients underwent ICE, with 9/53 (17%) having an atrial septal aneurysm. In 5 patients no PFO was found. In the remaining 48 patients, PFO closure was achieved using the HELEX occluder (n=47) or the Amplatzer device (n=1). Mean procedure and fluoroscopy times were 31.0+/-12.4 and 5.3+/-3.9 min respectively. One patient failed same day discharge due to groin haematoma. There were no other complications. At 3 month follow up, 45/48 (94%) had no residual shunt, with 3 patients having small residual shunts on colour flow Doppler. In conclusion, percutaneous PFO closure as a day case procedure is safe and feasible when facilitated by ICE.
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PMID:Safety and feasibility of day case patent foramen ovale (PFO) closure facilitated by intracardiac echocardiography. 2020 36

Patent foramen ovale (PFO) is an anatomical variant of the interatrial septum with an overall prevalence of 27% in autopsy studies. PFOs have a potential role in causation of stroke, platypneaorthodeoxia, decompression sickness, right to left shunt and migraine headaches. Data regarding percutaneous closure of PFO in low volume tertiary care centers is lacking. Retrospective review of 14 percutaneous PFO closures done in our facility from March 2005 to August 2006 was performed for efficacy of procedure and safety. All patients received clopidogrel for a period of 3 months, and aspirin and subacute bacterial endocarditis prophylaxis for 6 months. Mean age of the study population was 54 years. Fifty percent (7 of 14) of patients experienced an atrial septal aneurysm and 14% (2 patients) exhibited a hypercoagulable state. The indication for closure in 13 patients was transient ischemic attacks or strokes, while one patient had persistent hypoxia due to a severe right to left shunt at PFO. Patients received either a CardioSEAL or Amplatzer device. Deployment rate was 100%. All patients completed a minimum of 6 months of follow-up, with a mean follow-up time of 14.9 +/- 7.6 months. No immediate or late bleeding complication occurred in any patient. One patient developed paroxysmal atrial fibrillation and one patient developed thrombotic complications at 7 months post-procedure secondary to the progression of her anal carcinoma and subsequently died. Pending the results of the four large randomized trials that are enrolling patients, percutaneous closure of PFO for cryptogenic strokes is an attractive alternative to lifelong anticoagulation with relatively few complications, even in low volume centers. There are many challenges in the management of this subset of patients, the foremost being the selection of a target patient population. Role of PFO in migraines is less clear.
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PMID:Percutaneous closure of patent foramen ovale: a case series and literature review. 1808 6

Fish larvae, like many adult fish, swim by undulating their body. However, their body size and swimming speeds put them in the intermediate flow regime, where viscous and inertial forces both play an important role in the interaction between fish and water. To study the influence of the relatively high viscous forces compared with adult fish, we mapped the flow around swimming zebrafish (Danio rerio) larvae using two-dimensional digital particle image velocimetry (2D-DPIV) in the horizontal and transverse plane of the fish. Fish larvae initiate a swimming bout by bending their body into a C shape. During this initial tail-beat cycle, larvae shed two vortex pairs in the horizontal plane of their wake, one during the preparatory and one during the subsequent propulsive stroke. When they swim ;cyclically' (mean swimming speed does not change significantly between tail beats), fish larvae generate a wide drag wake along their head and anterior body. The flow along the posterior body is dominated by the undulating body movements that cause jet flows into the concave bends of the body wave. Patches of elevated vorticity form around the jets, and travel posteriorly along with the body wave, until they are ultimately shed at the tail near the moment of stroke reversal. Behind the larva, two vortex pairs are formed per tail-beat cycle (the tail beating once left-to-right and then right-to-left) in the horizontal plane of the larval wake. By combining transverse and horizontal cross sections of the wake, we inferred that the wake behind a cyclically swimming zebrafish larva contains two diverging rows of vortex rings to the left and right of the mean path of motion, resembling the wake of steadily swimming adult eels. When the fish larva slows down at the end of a swimming bout, it gradually reduces its tail-beat frequency and amplitude, while the separated boundary layer and drag wake of the anterior body extend posteriorly to envelope the entire larva. This drag wake is considerably wider than the larval body. The effects of the intermediate flow regime manifest as a thick boundary layer and in the quick dying-off of the larval wake within less than half a second.
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PMID:Flow patterns of larval fish: undulatory swimming in the intermediate flow regime. 1816 47

Patent foramen ovale is a congenital cardiac lesion that persists into adulthood and which is present in over 25% of the adult population. Its diagnosis, evaluation and treatment have attracted increasing interest as it has been suggested that it may be associated with various pathologic conditions, such as cryptogenic stroke, platypnea-orthodeoxia syndrome, decompression sickness and migraine. However, data on these associations are contradictory. Similarly, the optimum treatment of patients with patent foramen ovale is still debated. This article contains a review of the anatomy, embryology and epidemiology of the condition, its association with other clinical disorders, and current therapeutic options.
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PMID:[Patent foramen ovale: current state of the art]. 1859 Jun 47

A persistent patent foramen ovale produces an intermittent intra-atrial right-to-left shunt and occurs in approximately 25% of the general population. Although the vast majority of people with patent foramen ovale are asymptomatic, a patent foramen ovale is believed to act as a pathway for chemicals or thrombus that can result in a variety of clinical manifestations, including stroke, migraine headache, decompression sickness, high-altitude pulmonary edema, and platypnea-orthodeoxia syndrome. The optimal management of patients with patent foramen ovale who experience cryptogenic stroke is unclear. Percutaneous closure appears to have a low risk profile and has been considered in high-risk patients who are not candidates for randomized clinical trials. Randomized clinical trials that are underway should help define the best management of patent foramen ovale, as well as the true safety and efficacy of percutaneous closure devices.
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PMID:Patent foramen ovale: clinical manifestations and treatment. 1895 76


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