Whether the increase in cerebral blood flow measured after hemodilution is mediated by a decrease in blood viscosity or in oxygen delivery to the brain is debated. In the present study, blood was ...replaced by an oxygen-carrying blood substitute, ultrapurified, polymerized, bovine hemoglobin (UPBHB). In contrast to normal blood, UPBHB yields a constant and defined viscosity in the brain circulation, since its viscosity is not dependent on the shear rate. CBF was determined after blood exchange with UPBHB in one group of conscious rats (UPBHB group) and in another group of blood-exchanged conscious rats in which viscosity was increased fourfold by the addition of 2% polyvinylpyrrolidone (PVP), mw 750,000 (UPBHB-PVP group). Local CBF (LCBF) was measured in 34 brain structures by means of the quantitative iodo(
14
C)antipyrine method. After blood replacement, systemic parameters such as cardiac index, arterial blood pressure, blood gases, and acid-base status were not different between the UPBHB and the UPBHB-PVP groups. In particular, arterial oxygen content was similar in both groups. Compared with a control group without blood exchange, LCBF was increased after blood exchange in the different brain structures by 60–102% (UPBHB group) and by 33–101% (UPBHB-PVP group). Mean CBF was increased by 77% in the UPBHB group and by 69% in the UPBHB-PVP group. No significant differences were observed in the values of LCBF or mean CBF between the UPBHB group and the UPBHB-PVP group. The results show that a fourfold variation in the viscosity of a Newtonian blood substitute does not result in differences in CBF values. It is concluded that blood viscosity is less important to CBF than hitherto postulated.
The key goal in the treatment of acute ischemic stroke is fast vessel recanalization. Thrombolysis with recombinant tissue plasminogen activator (rt-PA) is efficient in humans but mean time for ...recanalization is within hours. Ultrasound bio-effects has been shown to facilitate rt-PA mediated thrombolysis in peripheral arteries. We used an embolic stroke model in the rat. In all rats we induced an ischemic stroke by a selective occlusion of the middle cerebral artery with whole blood clots. From an entire collective of 54 rats 47 completed the protocol (
n=7 died early). Four different groups (no treatment
n=6; full dose rt-PA treatment only 10 mg/kg per body weight
n=14, half dose rt-PA treatment plus ultrasound
n=10, and full dose rt-PA treatment plus ultrasound
n=17) were investigated. We found a significant reduction of absolute as well as relative infarct volume in the full dose rt-PA plus ultrasound group (81±72 mm
3;
P<0.05) in comparison to untreated rats (253±159 mm
3;
P<0.05) as well as in comparison to rats treated with full dose rt-PA only (167±91 mm
3;
P<0.05). There were five intracranial bleedings giving a bleeding rate of 9.3%. In summary: ultrasound treatment in addition to rt-PA is more effective than single rt-PA treatment in reducing infarct volume and safe with regard to bleeding.
Background: Volatile anesthetics can alter cardiac gene and protein expression. Of those underlying molecular changes in gene and protein expression in the myocardium after exposure to volatile ...anesthetics that have been identified, some of them have been related to cardioprotection.
Methods: We used two‐dimensional gel electrophoresis and mass spectrometry to identify changes in the protein expression of the left ventricle myocardium of anesthesized rats. We maintained anesthesia for 3 h using isoflurane, sevoflurane or desflurane, respectively, at 1.0 minimum alveolar concentration (MAC) and dissected the left ventricular myocardium either immediately or 72 h after the end of anesthesia.
Results: We found changes of at least twofold in 106 proteins of the more than 1.600 protein spots discriminated in each gel. These differentially expressed proteins are associated with functions in glycolysis, mitochondrial respiration and stress response. No obvious difference could be observed between the patterns of differential expression of the three volatile anesthetics.
Conclusion: We provide the first study of post‐anesthetic protein expression profiles associated with three common volatile anesthetics. These volatile anesthetics promote a distinct change in the myocardial protein expression profile, whereby changes in the expression pattern still exist 72 h after anesthesia. These proteome changes are closely related to cardioprotection and ischemic preconditioning, indicating a common functional signaling of volatile anesthestics.
The endothelial surface layer (glycocalyx) of cerebral capillaries may increase resistance to blood flow. This hypothesis was investigated in mice by intravenous administration of heparinase (2500 ...IU/kg body weight in saline), which cleaves proteoglycan junctions of the glycocalyx. Morphology was investigated by transmission electron microscopy. Cerebral perfusion velocity was recorded before and during heparinase or saline treatment using laser–Doppler flowmetry. In addition, cerebral blood flow (CBF) was measured 10 minutes after heparinase or saline treatment using the iodo14Cantipyrine method. Laser–Doppler flowmetry and CBF measurements were performed during normocapnia and severe hypercapnia (Pco2: 120 mm Hg). After heparinase, morphology showed a reduced thickness of the glycocalyx in cortical microvessels by 43% (P < 0.05) compared with saline-treated controls. Under normocapnic conditions, a 15% (P < 0.05) transient increase of cerebral flow velocity occurred 2.5 to 5 minutes after heparinase injection. Laser–Doppler flow and CBF returned to control values ten minutes after the injection. However, during severe hypercapnia, heparinase treatment resulted in a persisting increase in laser–Doppler flow (6%, P < 0.05) and CBF (30%, P < 0.05). These observations indicate the existence of a flow resistance in cerebral capillaries exerted by the glycocalyx. The transient nature of the CBF increase during normocapnia may be explained by a vascular compensation that is exhausted during severe hypercapnia.
Spatial learning is known to depend on protein synthesis in the hippocampus. Whereas the role of the hippocampus in spatial memory is established, the biochemical and molecular mechanisms underlying ...this process are poorly understood. To comprehend the complex pattern of protein expression induced by spatial learning, we analyzed alterations in the rat hippocampus proteome after 7 days of spatial learning in the Morris water maze. Forty Wistar rats were randomized into two groups. Animals of group A learned to localize a hidden platform in the water maze. Animals of group B served as controls and spent exactly the same time in the water maze as animals of group A. However, no platform was used in this test and the rats could not learn to localize the target. After the last trial, hydrophilic proteins from the hippocampus were isolated. A proteome‐wide study was performed, based on two‐dimensional gel electrophoresis and mass spectrometry. Compared with non‐learning animals, 53 (70%) proteins were downregulated and 23 (30%) proteins were upregulated after 7 days in rats with spatial learning. The overall changes in protein expression, as quantified by the induction factor, ranged from −1.62 (downregulation to 62%) to 2.10 (upregulation by 110%) compared with controls (100%). Most identified proteins exhibit known functions in vesicle transport, cytoskeletal architecture, and metabolism as well as neurogenesis. These findings indicate that learning in the Morris water maze has a morphological correlate on the proteome level in the hippocampus.
Glucose, the major fuel in the brain, is transported across the cell membranes by facilitated diffusion mediated by glucose transporter proteins. Essentially two types of glucose transporters are ...localized in the membranes of brain endothelial cells, astrocytes, and neurons. Their densities are well adjusted to changes in local energy demand.
Regular physical activity is associated with a decrease of cerebrovascular and cardiovascular events, which may relate to enhanced endothelium‐dependent vasodilation. Here, we provide evidence that ...physical activity protects against ischemic stroke via mechanisms related to the upregulation of endothelial nitric oxide synthase (eNOS) in the vasculature. Voluntary training on running wheels or exercise on a treadmill apparatus for 3 weeks, respectively, reduced cerebral infarct size and functional deficits, improved endothelium‐dependent vasorelaxation, and augmented cerebral blood flow in wild‐type mice. The neuroprotective effects of physical training were completely absent in eNOS‐deficient mice, indicating that the enhanced eNOS activity by physical training was the predominant mechanism by which this modality protects against cerebral injury. Our results suggest that physical activity not only decreases stroke risk, but also provides a prophylactic treatment strategy for increasing blood flow and reducing brain injury during cerebral ischemia.
The density of the total and the perfused capillary network was determined in the brains of awake, normocapnic rats. Perfused capillaries were marked by i.v. Evans blue. Existing capillaries were ...made visible by antibodies directed against the fibronectin portion of the capillary walls. Comparison of perfused and existing capillaries in identical brain sections by double staining showed a high degree of congruence between perfused and existing brain capillaries. The results show a continuous perfusion of all capillaries in the brain of the awake normocapnic rat. In the second group of experiments capillary perfusion was investigated during a reduction of cerebral blood flow induced by incomplete forebrain ischaemia. These experiments showed a gross preservation of capillary flow in the brain capillaries, although the velocity of perfusion was reduced. Finally, a method was developed which allows the distribution pattern of brain capillary plasma flow to be examined. The third group of experiments which used this method indicates a heterogeneous distribution of capillary flow in the brain under normocapnic conditions and a reduction of heterogeneity during hypocapnic hyperaemia.
Mesenchymal stem cells (MSC) raise high hopes in clinical applications. However, the lack of common standards and a precise definition of MSC preparations remains a major obstacle in research and ...application of MSC. Whereas surface antigen markers have failed to precisely define this population, a combination of proteomic data and microarray data provides a new dimension for the definition of MSC preparations.
In our continuing effort to characterize MSC, we have analyzed the differential transcriptome and proteome expression profiles of MSC preparations isolated from human bone marrow under two different expansion media (BM-MSC-M1 and BM-MSC-M2).
In proteomics, 136 protein spots were unambiguously identified by MALDI-TOF-MS and corresponding cDNA spots were selected on our “Human Transcriptome cDNA Microarray.” Combination of datasets revealed a correlation in differential gene expression and protein expression of BM-MSC-M1 vs BM-MSC-M2. Genes involved in metabolism were more highly expressed in BM-MSC-M1, whereas genes involved in development, morphogenesis, extracellular matrix, and differentiation were more highly expressed in BM-MSC-M2. Interchanging culture conditions for 8 days revealed that differential expression was retained in several genes whereas it was altered in others.
Our results have provided evidence that homogeneous BM-MSC preparations can reproducibly be isolated under standardized conditions, whereas culture conditions exert a prominent impact on transcriptome, proteome, and cellular organization of BM-MSC.
Faculty of Clinical Medicine, Department of Anesthesiology,
Mannheim D-68067; and Department of Physiology, University of
Heidelberg, D-69120, Heidelberg, Germany
We addressed the question
to which ...extent cerebral blood flow (CBF) is maintained when, in
addition to a high blood viscosity (B vis ) arterial oxygen
content (Ca O 2 ) is gradually decreased. Ca O 2 was decreased by hemodilution to hematocrits
(Hct) of 30, 22, 19, and 15% in two groups. One group received blood
replacement (BR) only and served as the control. The second group
received an additional high viscosity solution of polyvinylpyrrolidone (BR/PVP). B vis was reduced in the BR group and was doubled
in the BR/PVP. Despite different B vis , CBF did not differ
between BR and BR/PVP rats at Hct values of 30 and 22%, indicating a
complete vascular compensation of the increased B vis at
decreased Ca O 2 . At an Hct of 19%, local cerebral
blood flow (LCBF) in some brain structures was lower in BR/PVP rats
than in BR rats. At the lowest Hct of 15%, LCBF of 15 brain structures
and mean CBF were reduced in BR/PVP. The resulting decrease in cerebral
oxygen delivery in the BR/PVP group indicates a global loss of vascular
compensation. We concluded that vasodilating mechanisms compensated for
B vis increases thereby maintaining constant cerebral oxygen
delivery. Compensatory mechanisms were exhausted at a Hct of 19% and
lower as indicated by the reduction of CBF and cerebral oxygen delivery.
anemia; cerebral blood flow; autoradiography blood replacement; microcirculation
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