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P Malcus I Kjellmer G Lingman K Marsál K Thiringer K G Rosén 《Journal of perinatal medicine》1991,19(4):259-267
The aim of this experimental ultrasound study on six fetal lambs was to evaluate how blood flow variables and vessel diameters of the descending aorta and the common carotid artery change during fetal asphyxia in the acute preparation. When acute asphyxia was induced by obstructing the maternal aortic blood flow all fetuses reacted with significant decrease in the aortic diameter and blood flow. In the common carotid artery vessel diameter and the blood flow increased significantly. The results support the theory of a brain sparing effect during fetal distress with significant changes of blood vessel diameters occurring in opposite directions in the aorta and the common carotid artery, thereby contributing to the centralisation of circulation. 相似文献
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Pregnancies in which fetal cardiac arrhythmias are present are associated with an elevated perinatal and neonatal mortality. In this group various major and minor fetal malformations, including heart malformations, are more common. FECG and phonocardiogram give some information on the type of arrhythmia in favorable cases. Real-time imaging detects fetal heart malformations and late signs of heart failure. Fetal echocardiogram is of great aid for the classification of the arrhythmia and for the detection of heart malformations. By applying combined real-time linear array and pulsed Doppler technique in cases of fetal cardiac arrhythmia, important information on the fetal circulatory state can be obtained. Estimations of the volume blood flow guide the clinician in the practical handling of these cases. Volume blood-flow estimations can probably detect imminent fetal heart failure. Therapeutic effects can be followed, and the timing of delivery can be optimized taking the circulatory state into account. Within the fetal heart rate range 50 to 250 beats/min adequate blood circulation is usually maintained in the fetus. The peak velocity, the acceleration, and the rising slope are all increased in the postextrasystolic beat, indicating the existence of postextrasystolic potentiation in the fetal heart. These three parameters can be related to the ventricular filling time, supporting the opinion that the fetal heart follows the rules of the Frank Starling relationship. Fetal arrhythmias constitute also an experimental model for the study of fetal cardiac physiology. 相似文献
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Modulation of activity in medial frontal and motor cortices during error observation 总被引:3,自引:0,他引:3
We used measures of the human event-related brain potential (ERP) to investigate the neural mechanisms underlying error processing during action observation. Participants took part in two conditions, a task execution condition and a task observation condition. We found that activity in both the medial frontal cortex and the motor cortices, as measured via the error-related negativity and the lateralized readiness potential, respectively, was modulated by the correctness of observed behavior. These data suggest that similar neural mechanisms are involved in monitoring one's own actions and the actions of others. 相似文献
6.
Jeri W. Nieves Felicia Cosman Chris Mars Robert Lindsay 《Calcified tissue international》1992,51(5):352-355
Summary Forearm bone mineral density (BMD) was measured at proximal and distal sites by 125I single photon absorptiometry (SPA) and by dual energy X-ray absorptiometry (DXA) in 67 consecutive subjects, aged 18–75 years. Correlations and regression equations between these two techniques were determined. All forearm measurements were significantly correlated with each other (r=0.599–0.926; P0.0001). Although SPA and DXA correct for fat in different ways, we found similar correlation and regression equations in women with body mass index measurements above and below the mean. In addition, forearm measurements by both techniques were moderately correlated with vertebral spine and hip BMD. We conclude that overall, SPA forearm measurements in a population can be calibrated to DXA measurements if necessary, and that DXA forearm measurements are as predictive of the remainder of the skeleton as SPA measurements. 相似文献
7.
Marsálek M 《Pharmacopsychiatry》2000,33(Z1):14-33
The clinical features, outcomes, differential diagnoses, epidemiology, risk factors, and treatment approaches to tardive drug-induced extrapyramidal syndromes (EPS) are reviewed. Tardive forms of dyskinesia (TD), dystonia (TDt), akathisia (TA), Gilles de la Tourette syndrome (TGTS), myoclonus (TM), and parkinsonism (TP) are described. Moreover, pharmacological and topographical subtypes of TD are discussed. While TD, TDt, and TA are clearly delineated syndromes, there are limited data on TGTS, TM, and the questionable TP. TDt is distinguished from TD by clinical and treatment-related variables. Epidemiological studies provide evidence of better prognosis for TD compared with both TDt and TA. Two distinct groups of variables were found to be associated with a higher risk for TD: an exogenous factor (neuroleptic treatment variables and alcohol or drug abuse) and a factor of predisposition (elderly, female, affective disorder diagnosis, presence of EPS, diabetes mellitus type II, and signs of central vulnerability). In contrast, being younger and male was associated with TDt. A significant relationship between the hyperkinetic forms of tardive EPS was confirmed. Therapeutic strategy differs for the mild, moderate, and severe forms of tardive EPS. Using low doses of antipsychotics is a good preventive approach. Reducing the dose or switching to an atypical antipsychotic is the usual, but not yet fully explored, first therapeutic step. Clozapine, an antipsychotic with antidyskinetic and antidystonic effectiveness, is the second treatment step. Various suppressors of tardive movements were tested in controlled trials, mainly in TD. GABAergic benzodiazepines (clonazepam), adrenergic antagonists (propranolol, clonidine), antioxidants (alpha-tocopherol), and calcium channel blockers (nifedipine) are useful in the third step of treatment of more severe tardive EPS. Unlike TD, TDt and (partially) TA improve on higher doses of anticholinergic medication. Local injection of botulinum A toxin markedly ameliorates focal tardive dystonia over several months. Less verified therapeutic interventions are discussed. 相似文献
8.
Fetal central blood circulation was evaluated in 21 uncomplicated pregnancies every other week from the 27th gestational week till term. Blood flow in the fetal descending thoracic and abdominal aorta and in the intra-abdominal umbilical vein was measured with a combined ultrasound real-time and 2 MHz pulsed Doppler technique. The mean fetal blood velocities were fairly constant at the three measuring sites during the last trimester: 34.6 cm X s-1 (S.D. 5.5), 32.7 cm X s-1 (S.D. 5.5) and 12.6 cm X s-1 (S.D. 3.1), respectively. The aortic diameter increased with gestational age, whereas the umbilical vein diameter increased until the 34th gestational week followed by a stagnation. The mean weight-related blood flow in the fetal thoracic descending aorta decreased slightly towards term (from 240.8 ml X min-1 X kg-1 (S.D. 53.6) in the 28th week to 212.6 ml X min-1 X kg-1 (S.D. 37.3). In the umbilical vein, the corresponding blood flow decrease was linear and more pronounced: from 138.7 ml X min-1 X kg-1 (S.D. 76.0) to 65.2 ml X min-1 X kg-1 (S.D. 14.2). The results indicate that the placental proportion of fetal blood flow decreases with gestational age. 相似文献
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Causal effect of disconnection lesions on interhemispheric functional connectivity in rhesus monkeys
Jill X. O’Reilly Paula L. Croxson Saad Jbabdi Jerome Sallet MaryAnn P. Noonan Rogier B. Mars Philip G.F. Browning Charles R. E. Wilson Anna S. Mitchell Karla L. Miller Matthew F. S. Rushworth Mark G. Baxter 《Proceedings of the National Academy of Sciences of the United States of America》2013,110(34):13982-13987
In the absence of external stimuli or task demands, correlations in spontaneous brain activity (functional connectivity) reflect patterns of anatomical connectivity. Hence, resting-state functional connectivity has been used as a proxy measure for structural connectivity and as a biomarker for brain changes in disease. To relate changes in functional connectivity to physiological changes in the brain, it is important to understand how correlations in functional connectivity depend on the physical integrity of brain tissue. The causal nature of this relationship has been called into question by patient data suggesting that decreased structural connectivity does not necessarily lead to decreased functional connectivity. Here we provide evidence for a causal but complex relationship between structural connectivity and functional connectivity: we tested interhemispheric functional connectivity before and after corpus callosum section in rhesus monkeys. We found that forebrain commissurotomy severely reduced interhemispheric functional connectivity, but surprisingly, this effect was greatly mitigated if the anterior commissure was left intact. Furthermore, intact structural connections increased their functional connectivity in line with the hypothesis that the inputs to each node are normalized. We conclude that functional connectivity is likely driven by corticocortical white matter connections but with complex network interactions such that a near-normal pattern of functional connectivity can be maintained by just a few indirect structural connections. These surprising results highlight the importance of network-level interactions in functional connectivity and may cast light on various paradoxical findings concerning changes in functional connectivity in disease states. 相似文献