Effect of sleep on cerebral DNA synthesized during shuttle-box avoidance training.

Female Wistar rats weighing 200 g were implanted with cortical electrodes and two intraventricular cannulae. Five days later they were given 3H-thymidine and exposed to shuttle-box training for four hours. They were then left free to sleep in the following three hours during which their EEG activity was recorded. In comparison with control animals (C), learning (L) and non-learning (NL) rats exhibited an increase in SS. In comparison to the EEG recording made the previous day, all animal groups displayed an increase in SS, but only NL rats suffered a decrease in PS(%). The specific radioactivity of DNA measured in several brain regions was tendentially lower in NL rats, but significance was achieved only in the cerebellum in the comparison between NL rats and C rats. No change occurred in liver. More marked and significant decrements in the DNA specific radioactivity of all brain regions were observed in the subgroup of NL rats displaying relatively high values of PS time in comparison to the analogous subgroups of C and L animals. Comparable decrements were present with regard to the subgroup of NL rats endowed with relatively low PS time. Less widespread and more limited changes were observed in the concentration of acid-soluble radioactivity. In addition, several significant correlations were detected by Spearman's analysis among behavioral, biochemical and sleep parameters. The results are consistent with the interpretation that the selective decrease in brain radioactive DNA observed in NL rats reflects a loss of DNA synthesized during the training period. The loss is related to the amount of post-training PS and is associated to a lengthening of the mean duration of PS episodes. It may be concluded that the loss of newly-synthesized brain DNA reflects the elimination of molecules associated with neural information devoid of adaptive value.

Synthesis of brain DNA during acquisition of an active avoidance task.

The possible involvement of cerebral DNA synthesis in the learning process was examined in rats injected intracerebrally with 3H thymidine. During the period of incorporation (4.5 hr) one rat was trained to an active avoidance task while a second animal was kept in the same experimental room. In comparison with control rats paired to learning animals, the concentration of PCA-soluble radioactivity and of radioactive DNA of the cerebral cortex increased in all animal groups, i.e., control rats paired to non-learning animals, learning rats and non-learning rats. No change occurred in liver. In the cerebral cortex the slope of the regression line obtained by plotting the concentration of radioactive DNA versus the concentration of PCA-soluble radioactivity was lower in learning rats than in the group of pooled control animals. A comparable effect was noted in the hippocampus. In non-learning animals a similar decrease was present in the cerebral cortex and in cerebellum. In addition, it was found that in learning animals the percent incorporation was inversely related to the total number of avoidances only in the cerebral cortex. In non-learning rats a similar inverse relationship was present in the cerebral cortex and in cerebellum. In the former region the regression line of learning rats was shifted upwards in comparison with the regression line of non-learning animals. These results are interpreted to indicate that the incorporation of 3H-thymidine into cerebral DNA is directly related to the level of stress and is increased by learning.

CT angiography versus colour-Doppler US in acute dissection of the vertebral artery.

PURPOSE: Conventional digital subtraction angiography (DSA) still represents the criterion standard for the diagnosis of vertebral artery dissection (VAD), but the main drawbacks of this technique include invasiveness, patient discomfort and risk of complications. We evaluated the potential of multidetector computed tomography angiography (CTA) as a noninvasive tool providing high-resolution images of the arterial lumen and wall by comparing the diagnostic accuracy of CTA and colour-Doppler ultrasonography (CDUS) in detecting acute VAD. MATERIALS AND METHODS: We retrospectively reviewed 15 cases of VAD in 15 patients (five men and ten women, age range 28-58 years) who came to our attention between August 2001 and September 2005. The diagnosis was made on the basis of appropriate clinical presentation, absence of atherosclerotic disease in the cerebrovascular circulation and evidence of distinctive CT features, which were subsequently confirmed by conventional angiography used as reference standard. All patients with a clinical suspicion of VAD underwent CDUS of the neck vessels prior to CTA. Accuracy, sensitivity and specificity of CDUS and CTA were expressed as percentages of agreement with the reference angiographic procedure. Interreader concordance for detection of VAD by CTA was calculated with the Cohen K value. RESULTS: The CDUS examinations revealed ten out of 15 VAD, with a sensitivity of 66%, a specificity of 60%, a positive predictive value of 55.5% and a negative predictive value of 70.5%. In five cases, CDUS revealed nonspecific wall and flow alterations; in eight patients, high resistance obstructive flow; and in two patients, intimal flap with demonstration of the true and false lumen. CTA enabled the correct identification of all 15 VAD. The reported sensitivity, specificity, positive predictive value and negative predictive value were 100%, 95%, 93.7% and 100%, respectively. With regard to localisation of VAD, CTA showed 100% correlation with DSA. The differences in CTA and CDUS sensitivity (100% vs 66%), specificity (95% vs 60%), and overall diagnostic accuracy (97% vs 62.8%), assessed by cross tabulations and compared by using the McNemar's two-sided test, were significant (p<0.05). CONCLUSIONS: Multidetector CTA is a sensitive technique for the diagnosis of VAD. Used as a complement to unenhanced brain CT, it has the advantage of being readily available and easy to perform.

Multimodal use of computed tomography in early acute stroke, part 2.

Computed tomography (CT) scan remains the most widely technique in the cerebrovascular emergency, as it is largely available, minimally invasive, fast, cheap and reliable. Noncontrast enhanced CT (NeCT) imaging can show early signs of infarction in ischemic stroke; however, it could not show if the ischemic tissue is irreversibly damaged. CT perfusion (CTP) imaging has been shown to predict stroke location and size and can provide information about ischemic cerebral parenchyma not definitively compromised. CT angiography (CTA) could highlight stenosis or occlusion both in intracranial and extracranial vessels. By combining NeCT, CTP, and CTA the entire cerebrovascular axis can be imaged during acute stroke. Currently, the term "multimodal CT" indicates the combined use of these three techniques in order to obtain a complete picture of the extension of ischemic damage in acute stroke patients.

[Effect of sleep on cerebral DNA synthesized during learning]. / Effetto del sonno sul DNA cerebrale sintetizzato durante l'apprendimento.

Female Wistar rats weighing 200 g were implanted with cortical electrodes and with an intraventricular cannula. Five days later they were injected with 3H-thymidine and subjected to a two-way active avoidance session lasting four hours. During the following three hours they were left free to sleep while their EEG activity was being recorded. Biochemical analyses carried out in different brain regions and in liver indicated that the concentration of cerebral radioactive DNA was markedly lower in non-learning rats as compared to learning animal and to the control group. An increase in synchronized sleep and in paradoxical sleep was observed in learning animals, whereas non-learning rats exhibited an increment of synchronized sleep only. On the basis of these results and of previous data obtained with rats analyzed soon after the training session, it is concluded that the effect observed in non-learning animals stems from a loss of radioactive DNA synthesized during training. Such a loss takes place in the following resting period and is to be related to the variations of sleep pattern recorded. The process of DNA degradation might reflect the elimination of molecules associated with neural information non longer usable for adaptive aims.

Prognostic value of the dense middle cerebral artery sign in patients with acute ischemic stroke.

The presence of a dense appearance of the horizontal part of the middle cerebral artery (the "dense middle cerebral artery sign") was looked for on CT scans taken on admission in 90 consecutive patients with ischemic stroke in the carotid artery distribution. The outcome of the 14 patients with the sign was poorer than that of 76 patients without the sign (Odds ratio 4.3). We suggest that this sign could be a useful prognostic variable in the acute phase of an ischemic stroke.