| 1. |
- Nilsson, C, et al.
(författare)
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Circadian variation in human cerebrospinal fluid production measured by magnetic resonance imaging
- 1992
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Ingår i: American Journal of Physiology: Regulatory, Integrative and Comparative Physiology. - 1522-1490. ; 262:1, s. 20-24
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Tidskriftsartikel (refereegranskat)abstract
- Recent advances in magnetic resonance imaging have made it possible to visualize and quantify flow of cerebrospinal fluid (CSF) in the brain. The net flow of CSF through the cerebral aqueduct was used to measure CSF production in six normal volunteers at different times during a 24-h period. CSF production varied greatly both intra- and interindividually. The average CSF production in each time interval showed a clear tendency to circadian variation, with a minimum production 30% of maximum values (12 +/- 7 ml/h) approximately 1800 h and a nightly peak production approximately 0200 h of 42 +/- 2 ml/h. The total CSF production during the whole 24-h period, calculated as an average of all measurements, was 650 ml for the whole group and 630 ml for repeated measurements in each time interval in one of the volunteers.
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| 2. |
- Blay, P, et al.
(författare)
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Transthyretin expression in the rat brain: effect of thyroid functional state and role in thyroxine transport
- 1993
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Ingår i: Brain Research. - 1872-6240. ; 632:1-2, s. 114-120
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Tidskriftsartikel (refereegranskat)abstract
- Rats were made hypo- or hyperthyroid to study the role of thyroid hormones on cerebral transthyretin (TTR) mRNA expression. TTR mRNA was detected by Northern blot in rat liver, choroid plexus and meninges but not in cultured astrocytes or cultured cerebral endothelial cells. No changes were found in the levels of TTR mRNA in liver, choroid plexus or meninges in hypo- or hyperthyroid rats compared with the controls. In order to investigate the main route of thyroxine transport from blood to brain, the distribution of [125I]thyroxine in the brain was studied after intravenous (i.v.) and intraventricular (i.v.c.) injection by both direct counting and autoradiography. While distribution of [125I]thyroxine could be seen throughout the brain parenchyma after i.v. injection, the labelling was confined to the CSF spaces after i.v.c. administration. When protein synthesis was inhibited by cycloheximide treatment and [125I]thyroxine was injected intravenously, the uptake of [125I]thyroxine in the choroid plexus decreased while the uptake in the cerebral cortex increased. This indicates that thyroxine is transported into the brain primarily through the blood-brain barrier and not via the choroid plexus and CSF. We discuss the possibility that TTR has a role in the distribution of thyroxine throughout the brain.
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| 3. |
- Bodelsson, Mikael, et al.
(författare)
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Cooling enhances alpha 2-adrenoceptor-mediated vasoconstriction in human hand veins
- 1990
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Ingår i: Acta Physiologica Scandinavica. - 0001-6772. ; 138:3, s. 283-291
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Tidskriftsartikel (refereegranskat)abstract
- The contribution of different receptor subtypes in the contractile response during cooling in human hand vessels is of considerable interest in the understanding of cold-induced peripheral vasospasm as it appears in Raynaud's phenomenon. Subcutaneous vein segments from 50 patients undergoing hand operations not related to vascular disorders were examined in vitro. The temperature in the organ bath was initially 37 degrees C and was either continuously lowered to 10 degrees C or kept constant at 37 degrees C, 29 degrees C or 20 degrees C. The characteristics of the alpha-adrenoceptor-mediated motor response were elucidated with the use of the alpha 1-antagonist, prazosin, and the alpha 2-antagonist, yohimbine. A great variability between individuals in the proportions of alpha 1- and alpha 2-adrenoceptors was found. In the majority of the vessels continuous cooling to 25 degrees C augmented a noradrenaline-induced contraction. This augmentation was unaltered in the presence of prazosin but abolished by yohimbine, suggesting that it was mediated via the alpha 2-adrenoceptor. In the remaining vessels with a predominating alpha 1-adrenoceptor-mediated response a cold-induced relaxation was registered. This could be the result of a reduced alpha 1-adrenoceptor-mediated contraction at this low temperature. These varying reactions to cooling were unaffected by the beta-antagonist, propranolol, and by endothelial denudation. The results obtained in corresponding experiments with the alpha 1-agonist methoxamine and alpha 2-agonist, oxymetazoline, were conflicting, probably due to the poor selectivity of these agonists in human tissues.(ABSTRACT TRUNCATED AT 250 WORDS)
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| 4. |
- Kahrstrom, J, et al.
(författare)
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A morphometric study of the effect of bilateral cervical sympathetic ganglionectomy on the architecture of pial arteries in spontaneously hypertensive and normotensive rats
- 1994
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Ingår i: Acta Physiologica Scandinavica. - 0001-6772. ; 152:4, s. 407-418
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Tidskriftsartikel (refereegranskat)abstract
- The influence of the cranial sympathetic nerves on the architecture of pial arteries in normo- and hypertension was examined. For this purpose the effect of bilateral superior cervical ganglionectomy was evaluated in normotensive rats (WKY) and stroke-prone spontaneously hypertensive rats (SHRSP). The operations were performed at the age of 1 wk, which is just prior to the onset of ganglionic transmission. The length of the inner media contour was measured and the media cross-sectional area was determined planimetrically, with computerized digitalization of projected photographic images of transversely sectioned pial arteries. Four wk after sympathectomy there was a 20% reduction in media cross-sectional area and a consequent reduction in the ratio between media area and calculated luminal radius in the major pial arteries at the base of the brain in WKY but not in SHRSP. Conversely, in small pial arteries linear regression analysis showed that in WKY subjected to ganglionectomy the relationship between media cross-sectional area and luminal radius was significantly larger in arteries with a radius less than 21 microns compared to untreated WKY. No such effect was seen in the corresponding SHRSP vessels. In addition, the cross-sectional area of the internal elastic membrane (IEM) in the basilar arteries of WKY was measured by means of a computerized image-analysing system. Mean cross-sectional area of the IEM was approximately 45% larger following SE than in control animals. The present findings propose a 'trophic' role for the sympathetic perivascular nerves in large pial arteries of the rat. The increased media-radius ratio in the small pial arteries of the WKY following sympathectomy might reflect a compensatory hypertrophy due to reduced protection from the larger arteries against the pressure load. The inability to detect any morphometrically measurable effect of the sympathectomy in the cerebral arteries of SHRSP is probably explained by a marked growth-stimulating effect of the high pressure load in these animals.
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| 5. |
- Nilsson, C, et al.
(författare)
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Simultaneous and continuous measurement of choroid plexus blood flow and cerebrospinal fluid production: effects of vasoactive intestinal polypeptide
- 1991
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Ingår i: Journal of Cerebral Blood Flow and Metabolism. - 1559-7016. ; 11:5, s. 861-867
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Tidskriftsartikel (refereegranskat)abstract
- Using laser-Doppler flowmetry during ventriculocisternal perfusion with inulin-[14C]carboxylic acid, choroid plexus blood flow (CPBF) and CSF production were measured simultaneously in rats during periods of 3 h. Blood flow and CSF production decreased only slightly during control experiments. The effect of vasoactive intestinal polypeptide (VIP) was studied at different concentrations of the peptide given either intraventricularly or intravenously. Intraventricular administration of VIP (10(-9) or 10(-7) M) resulted in a decrease in CSF production of up to 30%, while CPBF increased by 20%, also demonstrating that CSF production and blood flow are not directly coupled in the choroid plexus. When infused intravenously, VIP (10 or 100 pmol/kg/min) increased CPBF, an effect partly antagonized at higher concentrations owing to a VIP-induced systemic hypotension. No effect of VIP on CSF production could be seen with intravenous administration.
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| 6. |
- Sahlin, C, et al.
(författare)
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Changes in contractile response and effect of a calcium antagonist, nimodipine, in isolated intracranial arteries of baboon following experimental subarachnoid hemorrhage
- 1990
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Ingår i: Brain Research Bulletin. - 0361-9230. ; 24:3, s. 355-361
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Tidskriftsartikel (refereegranskat)abstract
- Isolated pial arteries from a previously well-characterized model of experimental subarachnoid hemorrhage (SAH) in baboon were tested for their contractile response to 5-hydroxytryptamine (5-HT), norepinephrine (NE), and prostaglandin F2 alpha (PGF2 alpha) and the effect of the calcium antagonist, nimodipine. Autologous blood was injected cisternally at three times with one-day intervals to a total amount of 11.5-29.5 ml (mean: 18.5 ml), and the animals were killed 7 days after the first injection. Untreated animals served as controls. The degree of maximum contraction (EAm) with 5-HT and NE in the control situation was for the three arteries tested in the order middle cerebral greater than anterior cerebral greater than basilar artery. Experimental SAH markedly increased EAm, by 190-370 percent above control values (depending on type of vessel) for 5-HT and 170-185 percent for NE. In addition, the sensitivity to 5-HT was significantly increased, as evidenced by a left-shift of the concentration-response curve. Previous exposure of the artery to 10(-6) M nimodipine reduced the contractile response of both amines to approximately half, the inhibition being slightly less pronounced post-SAH. When vessels were contracted beforehand with the amines or with PGF2 alpha, followed by administration of increasing amount of nimodipine (10(-9) M to 10(-6) M), a concentration-dependent relaxation was obtained by up to 60 percent of the original level. This relaxing effect was significantly less following SAH in the experiments with NE and PGF2 alpha compared to 5-HT; the contraction in the presence of 5-HT did not differ before and after experimental SAH. The experiments show that SAH markedly enhances the intrinsic activity for both 5-HT and NE. Nimodipine inhibits the contractile response less efficiently following experimental SAH. The difference in the responsiveness to 5-HT on the one hand, and to NE and PGF2 alpha on the other, could be due to differences in the blood-induced alterations of those calcium channels that are influenced by the calcium antagonist, nimodipine.
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