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  • 1
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    German Medical Science; Düsseldorf, Köln
    In:  56. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie e.V. (DGNC), 3èmes journées françaises de Neurochirurgie (SFNC); 20050507-20050511; Strasbourg; DOCP083 /20050504/
    Publication Date: 2005-05-05
    Keywords: ddc: 610
    Language: English
    Type: conferenceObject
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    European journal of nuclear medicine 23 (1996), S. 1012-1013 
    ISSN: 1619-7089
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1435-1803
    Keywords: Deoxyglucose ; iodoantipyrine ; heart metabolism ; rat heart ; transmural gradients ; coronary blood flow ; spatial heterogeneity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Local cardiac glucose utilization and local cardiac blood flow in rat heart were measured in vivo by quantitative autoradiographic techniques with 2-[14C] deoxyglucose and [14C] iodoantipyrine, respectively. [14C]methylmethacrylate standards were calibrated for quantitative autoradiography of dried sections of heart tissue; the calibration values for heart tissue differed from those for brain by 8%, probably because of differences in self-absorption within the tissues. The lumped constant required by the deoxyglucose method was determined in isolated, perfused, working rat hearts and found to be 1.11±0.36 (mean±SD, n=21). The heart: blood partition coefficient for iodoantipyrine required by the [14C]iodoantipyrine method was measured and found to be 1.25. The results obtained in awake rats showed: 1) overall cardiac glucose utilization varied considerably among animals with a mean of 53 (left ventricle) and 30 (right ventricle) μmol/100 g/min; 2) cardiac blood flow was less variable among animals with a mean of 592 (left ventricle) and 420 (right ventricle) ml/100 g/min; 3) glucose utilization was found to be particularly high in the papillary muscle; 4) systematic gradients of glucose utilization or blood flow in the ventricular wall were not observed; 5) glucose utilization and blood flow were not closely correlated on a local level. It is concluded that autoradiographic methods are suitable for the quantification of local glucose utilization and local blood flow in the rat heart in vivo. These methods could not demonstrate transmural gradients for glucose utilization and blood flow between epi- and endocardium in awake rats.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1435-1463
    Keywords: Keywords: Chronic nicotine ; local cerebral glucose utilization ; 3-O-methylglucose ; autoradiography.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary. Acute and chronic infusion of nicotine is known to result in a distinct increase in local cerebral glucose utilization (LCGU) in several brain structures. The present study addresses the question whether this increase in LCGU is paralleled by a local change in glucose transport in rat brain. Nicotine was infused either acutely for 3 hours or chronically by osmotic minipumps for one week. Local rate constants for glucose transport were measured in brain cryosections using the 3-O-[14C]methylglucose method. Local rate constants K1 and k2 were lower in part of the brain structures during acute (−10% to −20%) and in nearly all structures during chronic (−39% to −41%) nicotine. The finding of a decreased glucose transport during chronic nicotine was confirmed by additional experiments of 3-O-[14C]methylglucose transfer in an epithelial cell culture. It is concluded that acute and chronic nicotine infusion results in decreased glucose transport although LCGU is either unchanged or increased.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-1238
    Keywords: Key words Local cerebral blood flow ; Autoradiography ; Hemorrhagic hypovolemia ; Hemorrhagic shock
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Objective: Of the animal models of human hemorrhagic shock, the volume-controlled hemorrhage model appears to come closer to the clinical situation than the commonly used pressure-controlled model, since the volume-controlled model allows regulatory adjustment of blood pressure. The effects of volume-controlled hemorrhage on local cerebral blood flow (LCBF) of conscious animals are not known. The present study investigates specific reaction patterns of LCBF in comparison to mean cerebral blood flow (CBF) during graded volume-controlled hemorrhagic shock in conscious rats. Methods: Conscious, spontaneously breathing, and minimally restrained rats were subjected to different degrees of volume-controlled hemorrhage (taking either 25, 30, 35, or 40 ml arterial blood/kg body weight (b.w.). Thirty minutes after the completion of blood taking, LCBF was determined during hemorrhagic hypovolemia using the autoradiographic iodo (14C) antipyrine method. A group of untreated rats (no hemorrhage) served as controls. LCBF was determined in 34 defined brain structures and mean CBF was calculated. Results: During less severe hemorrhage (25 and 30 ml/kg b.w.) mean CBF was significantly higher than in the control group (+19% and +25%). During severe hemorrhage (35 and 40 ml/kg b.w.) mean CBF remained unchanged compared to the control values, although significant increases in LCBF could be detected in many of the brain structures analyzed (maximum +44%). The mean coefficient of variation of CBF was increased, indicating a larger heterogeneity of LCBF values at shed blood volumes of 35 and 40 ml/kg b.w. Conclusions: A comprehensive and novel description of the local distribution of CBF during graded volume-controlled hemorrhage in conscious rats shows unexpected increases in LCBF and mean CBF. This ”hypovolemic cerebral hyperemia“ might be caused by endogenous hemodilution, thus maintaining the blood supply to the brain during hypovolemic shock.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-1238
    Keywords: Local cerebral blood flow ; Autoradiography ; Hemorrhagic hypovolemia ; Hemorrhagic shock
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Objective Of the animal models of human hemorrhagic shock, the volume-controlled hemorrhage model appears to come closer to the clinical situation than the commonly used pressure-controlled model, since the volumecontrolled model allows regulatory adjustment of blood pressure. The effects of volume-controlled hemorrhage on local cerebral blood flow (LCBF) of conscious animasl are not known. The present study investigates specific reaction patterns of LCBF in comparison to mean cerebral blood flow (CBF) during graded volume-controlled hemorrhagic shock in conscious rats. Methods Conscious, spontaneously breathing, and minimally restrained rats were subjected to different degrees of volume-controlled hemorrhage (taking either 25, 30, 35, or 40 ml arterial blood/kg body weight (b.w.). Thirty minutes after the completion of blood taking, LCBF was determined during hemorrhagic hypovolemia using the autoradiographic iodo (14C) antipyrine method. A group of untreated rats (no hemorrhage) served as controls. LCBF was determined in 34 defined brain structures and mean CBF was calculated. Results During less severe hemorrhage (25 and 30 ml/kg b.w.) mean CBF was significantly higher than in the control group (+19% and +25%). During severe hemorrhage (35 and 40 ml/kg b.w.) mean CBF remained unchanged compared to the control values, although significant increases in LCBF could be detected in many of the brain structures analyzed (maximum +44%). The mean coefficient of variation of CBF was increased, indicating a larger heterogeneity of LCBF values at shed blood volumes of 35 and 40 ml/kg b.w. Conclusions A comprehensive and novel description of the local distribution of CBF during graded volume-controlled hemorrhage in conscious rats shows unexpected increases in LCBF and mean CBF. This “hypovolemic cerebral hyperemia” might be caused by endogenous hemodilution, thus maintaining the blood supply to the brain during hypovolemic shock.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-2013
    Keywords: Propranolol ; Isoproterenol ; Vascular Smooth Muscle ; Local Arteriolar Reactions ; Cerebral Arteriolar Resistance ; Autoxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The existence of β-receptors and their possible contribution to the vascular tone of pial arteries was investigated using the microapplication technique combined with the measurement of vascular diameter. Concentration response curves for (+) and (−)propranolol revealed an identical course with no vascular reaction occurring between 2.5×10−10 and 2.5×10−5 M propranolol. Since both (+) and (−)propranolol were without effect on vascular diameter over a wide concentration range it is concluded that the vascular tone is not influenced by β-receptors under these experimental conditions. The increase in vascular diameter (60%) observed at 2.5×10−4 M (+) and (−)propranolol is supposed to be due to an unspecific effect. Concentration response curves for isoproterenol revealed no vascular reaction between 2.5×10−11 and 2.5×10−8 M, dilations of 4–5% at 2.5×10−7 and 2.5×10−6 M, constrictions of about 5% at 2.5×10−4 and of 3% at 1.25×10−3 M isoproterenol. These weak vascular reactions cannot be explained by reduced biological activity of isoproterenol due to autoxidation during storage. It is concluded that β-receptors are of little or no physiological significance for regulation of the vascular tone of pial arteries.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-2013
    Keywords: Local chemical factors ; Regulation of cerebrovascular resistance ; Autoregulation ; pH microelectrodes ; K+ microelectrodes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The role of perivascular H+ and K+ in the adjustment of pial arterial diameter during changes in arterial blood pressure was investigated in chloralose anesthetized cats. Blood pressure was reduced by i.v. mecamylamine or pentolinium and was increased by i.v. hypertensin. Pial arterioles and arteries with a control diameter ranging from 37–218 μ at a spontaneous mean arterial blood pressure of 128±16 (SD) mm Hg were studied. Vascular diameter as measured by TV image splitting showed the typical reactions, i.e. constriction during increase (up to 200 mm Hg) and dilation during decrease in blood pressure (down to 60 mm Hg). Perivascular H+ and K+ activities were measured using pH microelectrodes (Hinke type) and K+ ion exchanger microelectrodes, respectively. Under control conditions perivascular pH was 7.25±0.11 (SD) and K+ activity was 2.46±0.65 (SD) mM, respectively. During changes in blood pressure the vascular reactions of pial arteries were not accompanied by significant alterations in perivascular H+ or K+ activity. From these data it can be concluded that mechanisms other than those which are mediated by H+ or K+ are involved in the adjustment of pial arterial diameter during changes in arterial blood pressure.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-2013
    Keywords: Proximal Fractional Reabsorption ; Acute Saline Infusion ; Chronic Saline Infusion ; Peritubular Control ; Na and Water Balance ; Resorption im proximalen Tubulus ; akute NaCl-Infusion ; chronische NaCl-Infusion ; Peritubuläre Kontrolle ; Na- und H2O-Bilanz
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect of acute and chronic saline infusion on filtration and reabsorption in the proximal convolution was investigated in micropuncture experiments on rats. In both acute and chronic infusion single nephron filtration rate and total kidney GFR was increased at equal rates. During acute saline infusion there was a reduction of both fractional reabsorption (from 60.5 to 41.9%) and plasma protein concentration (from 5.8 to 5.2 g-%). During chronic infusion of about 70% of BW/day for 9–17 days there was only a slight decrease in proximal fractional reabsorption from 57.1 to 52.2%, whereas plasma protein concentration was much more reduced (from 5.9 to 3.6 g-%). It could be shown that the decrease in plasma protein was accompanied by an even greater reduction of plasma oncotic pressure. We conclude that the variation of peritubular protein concentration and oncotic pressure cannot influence proximal fractional reabsorption under physiological conditions.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-2013
    Keywords: Pial arteriolar resistance ; Cerebral blood flow ; Perivascular pH ; Metabolic regulation of blood flow ; pH-Microelectrodes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary pH microelectrodes with pointed tip (Hinketype) were constructed for the continuous measurement of the local pH in the perivascular space of pial arteries in the feline cerebral cortex. The sensitive tip had a length of 20–60 μ and a base diameter of 10–25 μ. As reference electrode, a micropipette (tip diameter 2 μ), filled with 150 mM KCl was used. Calibration curves were linear and showed a sensitivity of 54.5–57.5 mV/pH unit at 38°C. Advantages of such electrodes are the easy penetration of the subarachnoid membrane, the long life span, the quick response, and a minimal drift.—The electrodes were tested in vivo during hyper- and hypoventilation and during local perivascular injection of mock spinal fluid at varying pH. A close correlation was observed between the change in perivascular pH and the corresponding change in pial arterial diameter.
    Type of Medium: Electronic Resource
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