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Abnormalities of the neonatal brain: MR imaging. Part II. Hypoxic- ischemic brain injury 总被引:3,自引:0,他引:3
Eighty-five infants, 82 of whom were 29-44 weeks postconceptional age, were imaged with a 0.6-T magnet. Eight infants had cerebral infarction. In premature neonates with very water, low-intensity white matter on T1-weighted images, ultrasound was better than both computed tomography and magnetic resonance (MR) imaging in depicting parenchymal changes of infarction or edema. However, after 37 weeks gestation, MR imaging was superior. Cerebral atrophy, present in seven infants, was consistent with subarachnoid space widths of 7 mm or more, or subarachnoid space widths of 5-6 mm with ventricular/brain ratios of 0.36 or greater. Delayed myelination was seen in a total of 18 infants with histories of hypoxic-ischemic insult. MR imaging shows promise in the neonatal period. It facilitates recognition of infarcts in full-term infants and may be used to predict abnormal neurologic outcome in infants who have initial delayed myelination. 相似文献
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Postnatal development of tyrosine hydroxylase- and dopamine transporter- immunoreactive axons in monkey rostral entorhinal cortex 总被引:1,自引:0,他引:1
Dopamine afferents from the mesencephalon appear to play a critical role in
the normal development and cognitive functions of multiple areas of the
primate cerebral cortex. In some regions, such as the prefrontal and motor
cortices, dopamine innervation changes substantially during postnatal
development. However, little is known about the postnatal maturation of
dopamine afferents to the primate rostral entorhinal cortex, a
periallocortical region that receives a dense dopamine innervation in
adults. In this study, we used immunocytochemical techniques and antibodies
against tyrosine hydroxylase and the dopamine transporter to examine the
postnatal development of dopamine axons in the rostral subdivision of
macaque monkey entorhinal cortex. Within animals, the axons labeled with
each antibody did not differ in overall density or laminar distribution.
Across development, the density of dopamine axons in layers I and VI did
not change appreciably. In contrast, the density of labeled axons in layer
III significantly increased by a factor of three between birth and 5-7
months of age. The timing of this change differs substantially from that
observed in prefrontal cortex, where peak dopamine innervation occurs
between 2 and 3 years of age. These findings, in concert with other data,
suggest that developmental changes in the dopamine innervation of cortical
regions may parallel the functional maturation of those areas.
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ÁDÁM BÖHM ARNOLD PINTER ISTVÁN PRÉDA 《Pacing and clinical electrophysiology : PACE》1997,20(5):1367-1368
A case of both atrial and ventricular stimulation by the sense event marker during external chest wall stimulation of a DDDR pacemaker is reported. This unusual phenomenon might produce pacemaker-mediated tachycardia. 相似文献
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MARGIT DÓDA 《Brain research bulletin》1997,42(1):51-57
The role of α1- and α2-adrenoceptors in the vascular effects of catecholamines, either released locally from sympathetic nerve endings (e.g., in vascular smooth muscle) or derived from the adrenal medulla or administered intravenously, was studied using selective antagonists of these adrenoceptors. The ganglionic stimulant dimethylphenyl-piperazinium-iodide (DMPP) exerted dual actions on blood pressure: a rapid and short-term pressor reaction (phase I) resulting from catecholamine release elicited by ganglion stimulation, followed by a more sustained blood pressure elevation (phase II) resulting from the circulating catecholamines released from the adrenal medulla. The selective α2-adrenoceptor, but a not subtype selective, antagonist 7,8-(methylenedioxi)-14-alpha-alloberbane HCl (CH-38083) (50–100 μg/kg, IV) significantly (p < 0.05) inhibited the pressor effects of epinephrine and norepinephrine given intravenously and phase II of the DMPP-induced pressor reaction. Idazoxan exerted similar effects, but at higher doses (400–600 μg/kg, IV). WB-4101 (50–100 μg/kg, IV) and BRL-44408 (2–3 mg/kg, IV), two selective α2A-adrenoceptor antagonists, had the same activity as CH-38083, except did not inhibit the pressor effect of intravenously administered norepinephrine. The α2B-adrenoceptor selective antagonist, ARC-239 (150 μg/kg, IV) did not influence phase II of DMPP-induced pressor reaction. Prazosin (200 μg/kg, IV), an antagonist of α1 and α2B-adrenoceptors, reduced blood pressure, the pressor response to intravenously administered epinephrine, and phase I of the DMPP-induced pressor effect. In addition, it completely inhibited the pressor responses to DMPP remaining after administration of CH-38083. These results suggest that the postsynaptically located α1- and α2(A and B)-adrenoceptors are involved in pressor response to norepinephrine and epinephrine, and are sensitive and accessible to catecholamines released locally from the axon terminals, and from the circulation to a different extent. These results may have great therapeutical importance in hypertension, for which the involvement of both a high level of circulating and locally released catecholamines may be indicative of the usefullness of a combination (α1- and α2-adrenoceptors- and Ca-channel-blocking agents) therapy. Copyright © 1997 Elsevier Science Inc. 相似文献