Brain temperature is determined by the interplay between the cerebral metabolic rate of oxygen (CMRO2) and cerebral blood flow (CBF). In this study, single-voxel 1H nuclear MRS, with an accuracy of +/-0.2 degrees C for temperature determination, was used at 3 T to measure human brain temperature during visual stimulation (which increases both CBF and CMRO2) and hypercapnia (which increases CBF only). Visual stimulation had no detectable effect on brain temperature in the parenchyma showing blood oxygenation level dependent activation. Hypercapnia, leading to an increase in the end tidal CO2 by 8 +/- 2 mm Hg above the baseline, caused a short-lasting decrease in brain temperature of 0.30 +/- 0.33 degrees C. These results indicate that increased CBF may be a key factor, bringing about a small decrease in brain temperature during brain activation. However, the increase in CBF is not sufficient to lower brain temperature in the presence of a concomitant increase in endogenous heat production. 相似文献
We have measured the blood velocities in arteries supplying the skin in humans both in areas with arteriovenous anastomoses (AVA) and in skin areas without AVA in different temperature situations by means of a pulsed, bidirectional doppler ultrasound instrument. The instrument measures the time average of the instantaneous mean of the blood velocities present in a cross-section of a vessel. So long as the cross-sectional area of the vessel is constant, this average velocity is proportional to volume flow. We observe rapid and large fluctuations in blood velocities in arteries supplying skin areas with AVA in a comfortably warm environment. These fluctuations are substantially larger and more rapid than described by previous authors who have used plethysmograph methods. The blood velocities are more constant both at higher and lower environmental temperatures. There are no similar fluctuations in blood velocity in arteries supplying skin areas without AVA. 相似文献
Responsive contrast agents (RCAs) composed of lanthanide(III) ion (Ln3R) complexes with a variety of1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate (DOTA4S) derivatives have shown great potential as molecular imaging agents for MR. A variety of LnDOTA–tetraamide complexes have been demonstrated as RCAs for molecular imaging using chemical exchange saturation transfer (CEST). The CEST method detects proton exchange between bulk water and any exchangeable sites on the ligand itself or an inner sphere of bound water that is shifted by a paramagnetic Ln3R ion bound in the core of the macrocycle. It has also been shown that molecular imaging is possible when the RCA itself is observed (i.e. not its effect on bulk water) using a method called biosensor imaging of redundant deviation in shifts (BIRDS). The BIRDS method utilizes redundant information stored in the nonexchangeable proton resonances emanating from the paramagnetic RCA for ambient factors such as temperature and/or pH.Thus, CEST and BIRDS rely on exchangeable and nonexchangeable protons, respectively, for biosensing. We posited that it would be feasible to combine these two biosensing features into the same RCA (i.e. dual CEST and BIRDS properties). A complex between europium(III) ion (Eu3R) and DOTA–tetraglycinate [DOTA–(gly)S4] was used to demonstrate that its CEST characteristics are preserved, while its BIRDS properties are also detectable. The in vitro temperature sensitivity of EuDOTA–(gly)S4 was used to show that qualitative MR contrast with CEST can be calibrated using quantitative MR mapping with BIRDS, thereby enabling quantitative molecular imaging at high spatial resolution. 相似文献
Most perfused tumor cell experiments are performed at 37 degrees C, the normal healthy body temperature. However, the temperature of subcutaneously implanted tumors in small animals is generally 29-33 degrees C when the rectal temperature of the animal is maintained at 37 degrees C. We have investigated the acute effects of increasing the temperature of perfused radiation-induced-fibrosarcoma (RIF-1) tumor cells from 33 to 37 degrees C (30 min) on intracellular sodium (Na(i)+) , intracellular pH (pH(i)), and bioenergetic status. Heating the cells by 4 degrees C produced a reversible increase in Na(i)+, slight acidification and no change in nucleotide triphosphate to inorganic phosphate ratio (NTP/P(i)) as measured by shift-reagent-aided (23)Na and (31)P NMR spectroscopy. In the presence of 3 microM 5-(N-ethyl-N-isopropyl) amiloride (EIPA), a potent and specific inhibitor of Na(+)/H(+) antiporter, the increase in Na(i)+ during the heating was completely abolished suggesting that the heat induced increase in Na(i)+ was caused by an increase in Na(+)/H(+) antiporter activity. However, the changes in pH(i) with the heating were identical with or without EIPA, indicating that pH(i) is controlled by other ion exchange mechanisms in addition to Na(+)/H(+) antiporter. NTP/P(i) was significantly higher in presence of EIPA for some time points during the heating suggesting that both NTP production and consumption rates may be altered during the heating. These results indicate that a slight increase in temperature from 33 to 37 degrees C induces significant changes in Na(+) physiology largely because of activation of Na(+)/H(+) antiporter but other ion exchange mechanisms are also involved in maintaining pH(i) in the RIF-1 tumor cells. Thus, care must be taken in choosing the temperature for perfused cell studies. 相似文献
We have investigated the role of the electrogenic hydrogen ion pump in the regulation of intracellular sodium ion activity (aNai
) and intracellular pH (pHi) in frog skin epithelial cells using double-barreled ion sensitive microelectrodes. WhenRana esculenta skin is mounted in an Ussing chamber and bathed in 1 mM Na2SO4 buffered to pH 7.34 with imidazole on the apical side and in normal Ringer on the serosal side, the apical addition of the carbonic anhydrase inhibitor, ethoxzolamide (10–4M) blocks net H+ ion excretion and Na absorption, producing a depolarization of 25–30 mV of the apical membrane, potential (mc). We demonstrate the these changes are accompanied by a fall inaNai
from 6.2±0.5 mmol/l to 3.4±0.6 mmol/l and an increase in pHi from 7.20±0.03 to 7.38±0.08 (n=12 skins). Voltage clamping mc to its control value in the presence of ethoxzolamide restoredaNai
but the pHi remained alkaline. Furthermore, the fall inaNai
produced by ethoxzolamide could be mimicked by voltage clamping mc towards the value of the Nernst potential for Na at the apical membrane. These results indicate that the maintenance of the cellular Na+ transport pool is dependent on a favourable electrical driving force and counter-current generated by an electrogenic H+ pump at the apical membrane.Addition of amiloride (10–5 mol/l) or substitution of external Na+ by Mg2+ or K+ caused a hyperpolarization of mc and a fall inaNai
. These effects were accompanied by an inhibition of H+ excretion and a fall in pHi of 0.14 ±0.08 units (n=6 skins). However, when the effect, of Na+ transport inhibition on mc was prevented by imposing a voltage clamp no effects of amiloride on H+ excretion or pHi were observed. Moreover, the effect of amiloride on pHi could be reproduced in control skins by voltage clamping mc to –100 mV. The metabolic inhibitors vanadate (1 mmol/l) and di-cyclo hexyl carbodiimide (5×10–5 mol/l) inhibited H+ excretion and decreased pHi from 7.28±0.08 to 7.02±0.06 and from 7.30±0.06 to 7.12±0.05 (n=6 skins), respectively.These results indicate that an apical membrane H+ ATPase plays a role in regulating pHi and the mechanism is sensitive to membrane potential. 相似文献
The aim of this study was to determinate the immunoproteasome concentration in the blood plasma of children with appendicitis, and its correlation with circulating proteasome and ubiquitin carboxyl‐terminal hydrolase L1 (UCHL1). Twenty‐seven children with acute appendicitis, managed at the Paediatric Surgery Department, were included randomly into the study (age 2 years 9 months up to 14 years, mean age 9·5 ± 1 years). There were 10 girls and 17 boys; 18 healthy, age‐matched subjects, admitted for planned surgeries served as controls. Mean concentrations of immunoproteasome, 20S proteasome and UCHL1 in the blood plasma of children with appendicitis before surgery 24 h and 72 h after the appendectomy were higher than in the control group. The immunoproteasome, 20S proteasome and UCHL1 concentrations in the blood plasma of patients with acute appendicitis were highest before surgery. The immunoproteasome, 20S proteasome and UCHL1 concentration measured 24 and 72 h after the operation decreased slowly over time and still did not reach the normal range (P < 0·05). There was no statistical difference between immunoproteasome, 20S proteasome and UCHL1 concentrations in children operated on laparoscopically and children after classic appendectomy. The immunoproteasome concentration may reflect the metabolic response to acute state inflammation, and the process of gradual ebbing of the inflammation may thus be helpful in the assessment of the efficacy of treatment. The method of operation – classic open appendectomy or laparoscopic appendectomy – does not influence the general trend in immunoproteasome concentration in children with appendicitis. 相似文献
We describe here the construction and properties of a double-barrelled microelectrode (tip diameter 4–10 m) which permits simultaneous measurements of PCO2 and pH, and which has a 90% response time of only one or a few seconds for a step change in PCO2. The fast response of the CO2-sensitive barrel is due to (i) the use of a PVC-gelled (tridodecylamine-containing) membrane solution which enables the construction of extremely short ( 4 m), yet mechanically stable, membrane columns, and (ii) the presence of carbonic anhydrase in the filling solution. Recordings made in the pyramidal layer of area CA1 in rat hippocampal slices showed that the deviation in the acid direction of the basal interstitial pH (pH0) from that of the perfusion solution was attributable to a higher PCO2 level within the tissue. Most of the late acid shift evoked by stimulation of the Schaffer collaterals (5- to 20-s trains at 10 Hz) could also be explained on the basis of an accumulation of interstitial CO2 at a constant HCO
3–
concentration. This conclusion was supported by the finding that inhibition of extracellular carbonic anhydrase activity by 10 M benzolamide completely abolished the activity-induced fall in pH0, but not the increase in PCO2. The initial stimulus-induced alkalosis was accompanied by a slight decrease in PCO2 only, implying a parallel increase in the interstitial HCO
3–
concentration. Benzolamide produced a dramatic enhancement of the early alkaline shift as well as of the simultaneous fall in PCO2. The latter effect of the drug unmasks a cellular CO2 sink that is induced by neuronal activity. 相似文献
The extracellular pH (pH(e) ) of solid tumors is acidic, and there is evidence that an acidic pH(e) is related to invasiveness. Herein, we describe an MRI single-infusion method to measure pH(e) in gliomas using a cocktail of contrast agents (CAs). The cocktail contained gadolinium-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraaminophosphonate (GdDOTA-4AmP) and dysprosium-1,4,7,10-tetraazacyclododecane-N,N',N',N'-tetrakis(methylenephosphonic acid) (DyDOTP), whose effects on relaxation are sensitive and insensitive to pH, respectively. The Gd-CA dominated the spin-lattice relaxivity ΔR(1) , whereas the Dy-CA dominated the spin-spin relaxivity ΔR(2)*. The ΔR(2)* effects were used to determine the pixel-wise concentration of [Dy] which, in turn, was used to calculate a value for [Gd] concentration. This value was used to convert ΔR(1) values to the molar relaxivity Δr(1) and, hence, pH(e) maps. The development of the method involved in vivo calibration and measurements in a rat brain glioma model. The calibration phase consisted of determining a quantitative relationship between ΔR(1) and ΔR(2)* induced by the two pH-independent CAs, gadolinium-diethylenetriaminepentaacetic acid (GdDTPA) and DyDOTP, using echo planar spectroscopic imaging (EPSI) and T(1) -weighted images. The intensities and linewidths of the water peaks in EPSI images were affected by CA and were used to follow the pharmacokinetics. These data showed a linear relationship between inner- and outer-sphere relaxation rate constants that were used for CA concentration determination. Nonlinearity in the slope of the relationship was observed and ascribed to variations in vascular permeability. In the pH(e) measurement phase, GdDOTA-4AmP was infused instead of GdDTPA, and relaxivities were obtained through the combination of interleaved T(1) -weighted images (R(1) ) and EPSI for ΔR(2)*. The resulting r(1) values yielded pH(e) maps with high spatial resolution. 相似文献
Intravenous infusion of endothelin-1 (ET-1) in the cat, 60 pmol × kg body wt-1x min-1for 5 min, induced an increase in mean arterial blood pressure (MAP) of 41.3 ± 4.8 mmHg (n= 6; P < 0.001). Blood flow, as determined with radioactive microspheres, was reduced in many tissues. Reductions by 70–80% were observed in the choroid plexus, pineal and pituitary glands. Total cerebral blood flow was reduced by 18–23%. Pre-treatment with indomethacin or a combination of indomethacin and l -NAME caused vasoconstriction in many tissues and modified the responses to ET-1 in a variable way, suggesting that normally, ET-1 tends to release arachidonic acid metabolites and nitric oxide with great variations between different tissues. Intracerebroventricular infusion (i.c.v.) of ET-1, 10 pmol × kg body wt-1x min-1, caused an increase in MAP of 79 ± 11 mmHg (n= 6; P < 0.001). Regional blood flow in the medulla oblongata, medulla spinalis, choroid plexus, pineal and pituitary glands was reduced by 60–80%. Heart rate, cardiac output and coronary blood flow were significantly increased after 30 min i.c.v. infusion, indicating an activation of the heart, most probably as part of a central ischaemic response. Our results indicate that in many tissues the vasoconstrictive effect of ET-1 is influenced by indomethacin- and l -NAME-sensitive vasodilator mechanisms that are activated by the peptide. In the CNS, there may be marked effects on regional blood flow after i.c.v. infusion. 相似文献
Allergen has previously been shown to induce a continuous increase in local dermal blood flow after a prick test in allergic subjects, whereas histamine induced, initially, similar peak increases in blood flow of much shorter duration. Blood flow changes induced by histamine and allergen have now been evaluated (i) after pretreatment with a local corticosteroid cream, clobetasole-17-propionate; (ii) after oral administration of the H1-antihistamine loratadine; and (iii) after oral pretreatment with the alpha 1-adrenoceptor agonist pseudoephedrine. Blinded placebo-controlled designs were used in the substudies. Laser doppler flowmetry was used for non-invasive recording of changes in local blood flow intermittently for 24 h after the topical corticosteroid, 6 h for the substudies on loratadine and pseudoephedrine. The size of the immediate weal and flare reactions, as well as late phase reactions, were also determined. Pretreatment with clobetasole-17-propionate cream on the skin for 1 week prior to prick tests did not affect the blood flow response elicited by histamine or allergen, in either the initial part (up to 1 h) or the protracted 24 h determinations. The size of the weal and flare reactions decreased. Loratadine and pseudoephedrine did not reduce the initial allergen-induced increase in blood flow, while lower blood flow compared with placebo pretreatment was noted for the protracted (1-6 h) determinations. Blood flow changes after histamine were unaffected. The histamine-induced weal and flare was inhibited by loratadine more effectively than the corresponding allergen-induced reaction. The weal and flare reactions after histamine and allergen were not changed after pseudoephedrine.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
Double hydrophilic diblock copolymer, poly(N‐isopropylacrylamide)‐block‐poly(2‐diethylamino ethyl methacrylate) (PNIPAM‐b‐PDEA), was synthesized via reversible addition‐fragmentation chain transfer (RAFT) polymerization. Containing the well‐known thermo‐responsive PNIPAM block and pH‐responsive PDEA block, this novel diblock copolymer exhibits intriguing “schizophrenic” micellization behavior in aqueous solution, forming PDEA‐core micelles at alkaline pH and room temperature, and PNIPAM‐core micelles at acidic pH and elevated temperatures. The kinetics of the pH‐ and thermo‐responsive micellization processes were studied in detail using a stopped‐flow apparatus equipped with a newly developed millisecond temperature jump (mT‐jump) accessory. Upon a pH jump from 4 to 12 at 25 °C, the early stages of relaxation curves monitoring the formation PDEA‐core micelles can be well‐fitted using a double‐exponential function, leading to two characteristic relaxation time constants, τ1 and τ2. As τ2 decreases with increasing polymer concentration, the slow process is thus expected to proceed via micelle fusion/fission mechanism, approaching the final equilibrium state. Upon a temperature jump from 20 to 45 °C at pH 4, the relaxation curves monitoring the formation PNIPAM‐core micelles can also be well‐fitted using a double‐exponential function. The fast process (τ1) is associated with the quick association of unimers into a large amount of small micelles and the formation of quasi‐equilibrium micelles. τ2 is almost independent of polymer concentration, suggesting that unimer insertion/expulsion is the main mechanism for the slow process. The protonated PDEA corona of quasi‐equilibrium micelles renders the micelle fusion/fission mechanism less favorable due to electrostatic repulsion.
Flow cytometry using fluorescent antibodies (FC) is the method of choice for the quantitation of proteins expressed at the surface or inside the cell, but, however, does not allow to selectively measure nuclear expression. We therefore sought to develop a method for the extraction of intact cell nuclei, which can be used for their subsequent immunofluorescent analysis by FC. The studied protein was vascular endothelial growth factor-receptor-type 1 (VEGFR-1) which is important in tumor survival and metastasis. Two human cell lines, A431 (epidermoid carcinoma of skin with low invasive and metastatic potential) and BRO (highly aggressive amelanotic melanoma), were used as examples for tumor cells, and normal human fibroblasts PHF served as a control line. The quality of the extracted nuclei was assessed by their intactness and purity from cytoplasm. The high content of the nuclear markers (PCNA?=?proliferating cell nuclear antigen, lamin A/C) in the extracted nuclei with almost complete absence of the cytoplasmic β-tubulin demonstrated that the protocol can be used to obtain a pure suspension of single intact cell nuclei. The measurement of the nuclear VEGFR-1 content revealed that it was present only in tumor cell nuclei and that in more malignant BRO cells the receptor content was 1.75 times higher than in A431 (p?=?0.014). Thus, the developed method of extraction of cell nuclei for subsequent FC analysis is suitable for the quantitative evaluation of protein content in the native nucleus. 相似文献