UMLS:C0038454 - FACTA Search

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Query: UMLS:C0038454 (stroke)
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The effects of phosphorus depletion on cardiac muscle function in six awake dogs were evaluated with surgically implanted transducers to serially measure ascending aortic root blood flow and high fidelity left ventricular pressure. After the animals recovered from surgery, phosphorus depletion was induced by feeding them a synthetic phosphorus-deficient diet plus aluminum carbonate gel for 35 days, followed by the same diet with phosphorus supplementation for 21 days. In addition to the cardiac studies, sequential measurements of phosphorus content in skeletal muscle and phosphorus in serum were obtained to ascertain the level of phosphorus depletion. Serum inorganic phosphorus concentration (mg/100 ml) decreased from 5.1 +/- 0.1 on day 0 to 0.9 +/- 0.1 on day 35 (P less than 0.01), and total muscle phosphorus (content mmul/100 g fat-free dry weight) decreased from 28.0 +/- on day 0 to 22.6 +/- 0.5 on day 35 (P less than 0.01). During the period of phosphorus depletion, there was no significant change in heart rate; however, stroke volume (milliliter) and peak blood flow velocity (centimeter per second) declined from 24 +/- 2 to 17 +/- 2 (P less than 0.01) and 121 +/- 12 to 98 +/- 7 (P less than 0.01), respectively. Maximum ascending aortic blood flow acceleration (centimeter per second square) and maximum left ventricular time rate of change of pressure (mm Hg per second) also decreased from 4,630 +/- 313 to 3,817 +/0 346 (P less than 0.01) and 2,582 +/- 347 to 2,120 +/- 297 (P less than 0.01) during phosphorus depletion. After repletion all values returned to control values. These results indicate that moderate diet-induced phosphorus depletion can depress myocardial performance. With repletion of phosphorus, myocardial performance improves.
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PMID:Reversible depression in myocardial performance in dogs with experimental phosphorus deficiency. 74 74

We have determined the orientation and dynamics of the putative pre-power stroke crossbridges in skinned muscle fibers labeled with maleimide spin-label at Cys-707 of myosin. Orientation was measured using electron paramagnetic resonance (EPR) and mobility by saturation transfer EPR. The crossbridges are trapped in the pre-power stroke conformation in the presence of aluminum fluoride, Ca, and ATP. In agreement with data published for unlabeled fibers (Chase et al., 1994), spin-labeled muscle fibers display 42.5% of rigor stiffness, without the generation of force. The trapped crossbridges are as disordered as the relaxed heads, but their microsecond dynamics are significantly restricted. Modeling of the immobile fraction (35%), in terms of attached heads as estimated from stiffness, suggests that the bound heads rotate with a correlation time tau r = 150-400 microseconds, as compared to tau r = 3 microseconds for the heads in relaxed fibers. These "strongly" attached myosin heads, at orientations other than in rigor, are a candidate for the state from which head rotation generates force, as postulated by H. E. Huxley (1969). Ordering of the heads may well be the structural event driving the generation of force.
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PMID:Orientation and dynamics of myosin heads in aluminum fluoride induced pre-power stroke states: an EPR study. 791 18

Laser myocardial revascularization has been shown to reduce mortality and infarct size after left anterior descending coronary artery (LAD) ligation in dogs. It has not been shown to improve myocardial contractility in acute ischemia. In this study a holmium-yttrium-aluminum garnet laser (wavelength, 2.14 microns) was used to create nontransmural myocardial channels from the endocardial surface in the ischemic regions of the canine left ventricle. Twelve mongrel dogs (6 controls, 6 laser myocardial revascularizations) underwent 90 minutes of LAD ligation followed by 6 hours of reperfusion. The ischemic region was determined by methylene blue injection during brief LAD occlusion. Laser myocardial revascularization averaged three channels per square centimeter in the ischemic region created using 12 J/channel (600 mJ/pulse, 10 Hz) before LAD ligation. Contractility was assessed from regional preload recruitable stroke work (RPRSW), using pairs of segment length ultrasonic transducers in the ischemic and the nonischemic regions. Two-dimensional echocardiography corroborated with segmental length findings. In control dogs, the ischemic region was dyskinetic during LAD ligation and reperfusion. Dyskinesis of the ischemic region during systole produced negative values for regional stroke work, and RPRSW was considered zero. In 4 of 6 laser-revascularized dogs, RPRSW remained positive in the ischemic region. Two dogs had intermittent dyskinesis. The difference between laser-revascularized and control dogs in ischemic region RPRSW was significant (p < 0.01 by Fischer's exact test).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Prevention of acute regional ischemia with endocardial laser channels. 814 72

In 12 subjects, a pliable, yet unbreakable, intercuspal interference (aluminum shim onlay splint; uniform height of 0.25 mm) was placed between either the right or left maxillary and mandibular second premolars and first molars. During brief and forceful biting (dynamic chewing stroke of about 20 kg force) the interference emulated a semisoft food bolus, and at the end of biting (subsequent static clenching stroke of about 20 kg force) it emulated a rigid metal interference. During dynamic/static biting, rotational electrognathography measured maximum frontal and horizontal plane torque of the right and left mandibular condyles. Eleven subjects (92%) showed frontal plane upward rotation (mean of 1.0 degree) of the condyle contralateral to the interference, and one subject (8%) showed frontal plane upward rotation (0.4 degree) of the condyle ipsilateral to the interference. Two subjects (17%) showed no horizontal plane rotation; seven subjects (58%) showed backward rotation (mean of 0.4 degree) of the condyle contralateral to the interference; and three subjects (25%) showed backward rotation (mean of 0.3 degree) of the condyle ipsilateral to the interference. It is suggested that, in the presence of an occlusal interference, mastication may have both short- and long-term detrimental effects.
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PMID:Experimental occlusal interferences. Part IV. Mandibular rotations induced by a pliable interference. 855 57

1. Six men and four women, 30-51 yr of age, were asked to use the tip of the washed and dried index finger to stroke six different featureless, flat surfaces mounted on a three-dimensional force platform. The six surfaces were rosin-coated glass, glass, satin-finished aluminum, poly-vinyl chloride (PVC) plastic, Teflon, and nyloprint (polyamide plastic). The subjects were requested to indicate where the sensation produced by each surface should be placed on an unidimensional scale represented by an 18cm line labeled at one end by the words "most slippery" and at the other end by the words "most sticky." The coefficients of friction for each surface and for each subject were subsequently assessed by asking each subject to stroke the surfaces as if they were assessing its slipperiness for 5 s. 2. The finger forces normal and tangential to the stroked surfaces were digitized at 250 Hz and stored on a laboratory computer. The ratio of the mean tangential force to the mean perpendicular force during stroking was used to calculate the mean coefficient of kinetic friction. The mean friction for all subjects ranged from 0.43 for the nyloprint surface to 2.79 for the rosin-coated glass. Correlation coefficients calculated between the subjective estimates of friction and the measured coefficients of friction for each subject individually resulted in a mean correlation of 0.85 (n = 10, P < 0.001). 3. These data indicate that subjects can accurately scale relative differences in the friction of macroscopically smooth, flat surfaces, by modulating the tangential force applied to the finger while keeping the normal force relatively constant. The fact that subjects maintained a relatively constant normal force and instead varied the tangential force across different surfaces suggests that receptors sensitive to these tangential forces are important in the perception of smooth surface friction.
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PMID:Subjective scaling of smooth surface friction. 873 94

During the first hours after acute ischemic stroke, the CT usually shows no abnormalities. Therapeutic trials of ischemia in the middle cerebral artery (MCA) territory involves decision-making when the CT may not show obvious ischemic changes. We reviewed 100 consecutive patients, admitted within 14 hours after a first stroke. Selective criteria were clinical presentation with MCA ischemia and at least two CTs (1 initial and 1 control). All CTs were retrospectively analyzed by at least two physicians blinded to the patient's status. On the first CT, early signs were hyperdense MCA sign (HMCAS), early parenchymatous signs (attenuation of the lentiform nucleus [ALN], loss of the insular ribbon [LIR], and hemispheric sulcus effacement [HSE]), midline shift, and early infarction. Subsequent infarct locations were classified according to total, partial superficial (superior or inferior), deep, or multiple MCA territories. Clinical features, etiology, and Rankin scale were collected. There were 52 women (mean age 70.8). The CTs were performed at mean 6.4 hours (1 to 14 hours) and before the sixth hour in 62% of the patients. Early CT was abnormal in 94% of the cases, and the abnormalities found were an HMCAS in 22 patients, ALN in 48, LIR in 59, HSE in 69, midline shift in 5, and early infarct in 7. CT was normal in six patients where it was performed earliest (mean 4.5 hours) and in the oldest patients (mean age 80.1). Early parenchymatous CT signs were significantly associated with subsequent MCA infarct location and extension: ALN and deep infarct, HSE and superficial infarct, LIR and large infarct. HMCAS was never found in isolation and was always associated with the three other signs in extended MCA infarct. The presence of two or three signs (ALN, LIR, or HSE) was associated with extended MCA infarct (p < 0.001) and poor outcome (p < 0.001). Our findings suggest that CT frequently discloses parenchymal abnormalities during the first hours of ischemic stroke. Early signs allow the prediction of subsequent infarct locations; CT may provide a simple tool in evaluating the early prognosis of MCA infarction and thus may be useful in selecting better treatments.
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PMID:Early CT signs in acute middle cerebral artery infarction: predictive value for subsequent infarct locations and outcome. 875 6

The interaction of myosin with actin, coupled with hydrolysis of ATP, is the molecular basis of muscle contraction. The head segment of myosin, called S1, contains the distinct binding sites for ATP and actin and is responsible for the ATPase activity. The myosin-catalyzed ATP hydrolysis consists of several intermediate steps and each step is accompanied by conformational changes in the S1 segment. The rate-limiting step of the ATP hydrolysis is the dissociation of the S1 x ADP x Pi complex which is accelerated by actin. The substitution of Pi with phosphate analogs (PA), such as vanadate, beryllium fluoride (BeFx) or aluminum fluoride (AlF4-), yields stable complexes which mimic the intermediates of the ATP hydrolysis. In this work, tertiary structure changes in S1 in the vicinity of aromatic residues was studied by comparing near-UV circular dichroism (CD) spectra from S1-nucleotide-phosphate analog complexes in the presence of Mg2+ and other cations. A significant difference between the MgATP and MgADP spectra indicated notable tertiary structural changes accompanying the M**ADP x Pi --> M*ADP transition. The spectra of the S1 x MgADP x BeFx and S1 x MgADP x AlF4- complexes resemble to those obtained upon addition of MgATPgammaS and MgATP to S1, and correspond to the M* x ATP and M** x ADP x Pi intermediates, respectively. We have found recently that the presence of divalent metal cations (Me2+) is essential for the formation of stable S1 x MeADP x PA complexes. Moreover, the nature of the metal cations strongly influences the stability of these complexes [Peyser, Y. M., et al. (1996) Biochemistry 35, 4409-4416]. In the present work we studied the effect of Mg2+, Mn2+, Ca2+, Ni2+, Co2+, and Fe2+ on the near-UV CD spectrum of the ATP, ADP, ADP x BeFx, and ADP x AlF4- containing S complexes. The CD spectra obtained with ADP, ATP ADP x BeFx and ADP x AlF4- were essentially identical in the presence of Co2+ and rather similar in the case of Ca2+, while they were partially different in other cases. An interesting correlation was found between actin activation and ATP versus ADP difference spectra in the presence of various metal ions. The distribution of the fractional concentration of the intermediates of ATP hydrolysis was estimated in the presence of each cation from the CD spectra with phosphate analogs. In the presence of Mg2+ the predominant intermediate is the M** x ADP x Pi state, which is in accordance with the kinetic studies. On the other hand with non-native cations the predominant intermediate is the M* x ADP state and the release of ADP is the rate limiting step in the myosin-catalyzed ATP hydrolysis. According to the results, the near-UV CD spectrum originating from aromatic residues in S1 not only can distinguish identifiable states in the ATP hydrolysis cycle but can also pinpoint to changes in the tertiary structure caused by complex formation with nucleotide or nucleotide analog and various divalent metal cations. These findings, that are correlative with actin activation, and thus with the power stroke, suggest new strategies for perturbing S1 structure in the continuous efforts directed toward the elucidation of the mechanism of muscle contraction.
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PMID:Effect of metal cations on the conformation of myosin subfragment-1-ADP-phosphate analog complexes: a near-UV circular dichroism study. 913 78

The neodymium:yttrium-aluminum-garnet (Nd:YAG) laser has been used for treatment of dentinal hypersensitivity, eradicating periodontal pathogens, and facilitating calculus removal. However, Nd:YAG laser irradiation exerts potentially harmful effects on the tooth root surface. The purpose of this study was to examine the ultrastructural changes of the tooth root surface caused by Nd:YAG laser irradiation, and to determine whether chemical and mechanical preparations can correct these ultrastructural changes. Eighteen tooth specimens (3 x 3 x 0.5 mm) with healthy root surfaces were prepared and irradiated with an Nd:YAG laser at various power densities. Root surfaces were irradiated at 100 mJ at 20 pulses per second (pps) for 2 seconds followed by the application of citric acid (pH 1.2) or tetracycline solution (100 mg/mL) for 3 and 5 minutes, respectively, or ultrasonic scaling for 5 strokes of 3 seconds per stroke. As observed with low-vacuum scanning electron microscopy, (Wet-SEM), Nd:YAG laser irradiation at 70 to 100 mJ, 20 pps for 2 seconds caused surface cratering, areas of porosity, pitting, fissures, and lava-like structures in an area 140 to 280 microns in diameter. Irradiation of 50 mJ, 20 pps for 2 seconds, led to only mild surface charring. No evidence of morphologic changes was found when root surfaces were irradiated with the Nd:YAG laser at 20 mJ, 20 pps for 2 seconds or at 50 mJ, 10 pps for 8 seconds. The laser-induced lava-like structures were partially detached by citric acid (pH 1.2) etching and ultrasonic scaling, but not by tetracycline (100 mg/mL). These results indicate that chemical and mechanical preparations can be used effectively in conjunction with Nd:YAG laser irradiation for root surface preparation during both nonsurgical and surgical periodontal treatments.
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PMID:Ultrastructural changes of the tooth root surface by Nd:YAG laser irradiation followed by citric acid and tetracycline. 1038 67

Emboli become lodged in the brains of patients undergoing cardiopulmonary bypass (CPB) and can cause death, stroke, or more subtle neurological and neuropsychological deficits. Using a specialized vascular stain (for alkaline phosphatase) in autopsy tissues from the brains of patients who underwent CPB shortly before death, we found large numbers of microemboli. All of these microemboli contain lipid, some contain small birefringent particles, and some may contain aluminum or silicon. Within a few weeks after CPB, most of the microemboli had disappeared from the brain tissues, but some persisted for at least 6 months. After several days, the endothelial cells of some of the vessels containing microemboli showed subtle damage in the form of loss of alkaline phosphatase reactivity, and some vessels appeared to be degenerating. Sometimes the surrounding neuropil also showed degeneration. Since skin and muscle biopsies can be readily obtained before, during, and after CPB, we investigated their suitability as surrogate tissues for brain; however, they were unsuitable because they had so few microemboli. By injecting microspheres into dogs at various times during CPB, we have investigated the timing of the production of microemboli. We are also exploring the use of rat brains to trap microemboli from the injected blood of patients undergoing CPB. (ECHOCARDIOGRAPHY, Volume 13, September 1996)
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PMID:Histologic Studies of Brain Microemboli in Humans and Dogs After Cardiopulmonary Bypass. 1144 70

Normal ageing and Alzheimer's disease (AD) have many features in common and, in many respects, both conditions only differ by quantitative criteria. A variety of genetic, medical and environmental factors modulate the ageing-related processes leading the brain into the devastation of AD. In accordance with the concept that AD is a metabolic disease, these risk factors deteriorate the homeostasis of the Ca(2+)-energy-redox triangle and disrupt the cerebral reserve capacity under metabolic stress. The major genetic risk factors (APP and presenilin mutations, Down's syndrome, apolipoprotein E4) are associated with a compromise of the homeostatic triangle. The pathophysiological processes leading to this vulnerability remain elusive at present, while mitochondrial mutations can be plausibly integrated into the metabolic scenario. The metabolic leitmotif is particularly evident with medical risk factors which are associated with an impaired cerebral perfusion, such as cerebrovascular diseases including stroke, cardiovascular diseases, hypo- and hypertension. Traumatic brain injury represents another example due to the persistent metabolic stress following the acute event. Thyroid diseases have detrimental sequela for cerebral metabolism as well. Furthermore, major depression and presumably chronic stress endanger susceptible brain areas mediated by a host of hormonal imbalances, particularly the HPA-axis dysregulation. Sociocultural and lifestyle factors like education, physical activity, diet and smoking may also modulate the individual risk affecting both reserve capacity and vulnerability. The pathophysiological relevance of trace metals, including aluminum and iron, is highly controversial; at any rate, they may adversely affect cellular defences, antioxidant competence in particular. The relative contribution of these factors, however, is as individual as the pattern of the factors. In familial AD, the genetic factors clearly drive the sequence of events. A strong interaction of fat metabolism and apoE polymorphism is suggested by intercultural epidemiological findings. In cultures, less plagued by the 'blessings' of the 'cafeteria diet-sedentary' Western lifestyle, apoE4 appears to be not a risk factor for AD. This intriguing evidence suggests that, analogous to cardiovascular diseases, apoE4 requires a hyperlipidaemic lifestyle to manifest as AD risk factor. Overall, the etiology of AD is a key paradigm for a gene-environment interaction. Copyright 2000 John Wiley & Sons, Ltd.
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PMID:A unifying hypothesis of Alzheimer's disease. III. Risk factors. 1240 43

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