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At least 559 records · Page 31Linked to original sources
PubMed2005

Induction of calcium influx from extracellular fluid by beauvericin in human leukemia cells.

Beauvericin, a cyclic hexadepsipeptide, is a mycotoxin that can induce cell death in human lymphoblastic leukemia CCRF-CEM cells. Our previous data have shown that beauvericin induces cell death in CCRF-CEM cells in a dose- and time-dependent manner, and that this beauvericin-induced cell death can be prevented by administration of intracellular calcium chelator-BAPTA. Therefore, the intracellular Ca2+ concentration ([Ca2+]i) may play an important role in beauvericin-induced cell death in CCRF-CEM cells. In this study, the effect of beauvericin on [Ca2+]i and the possible mechanism responsible for the changes of [Ca2+]i in CCRF-CEM cells were investigated. Beauvericin caused a rapid and sustained [Ca2+]i rise in a dose-dependent manner. Excess extracellular Ca2+ facilitated beauvericin-induced [Ca2+]i rise by adding 1 mM CaCl2 in the bathing medium. On the other hand, beauvericin-induced [Ca2+]i rise was prevented in Ca2+-free Tyrode's solution by 200 microM EGTA. In addition, beauvericin-induced [Ca2+]i rise was also attenuated by intracellular Ca2+ chelator-BAPTA/AM. It is worthy to note that neither the voltage-dependent Ca2+ channel blocker, nimodipine, nor depletion of intracellular Ca2+ with thapsigargin, an endoplasmic reticulum Ca2+ pump inhibitor, has any effect on beauvericin-induced [Ca2+]i rise. The data from present study indicate that beauvericin acts as a potent Ca2+ mobilizer by stimulating extracellular Ca2+ influx CCRF-CEM cells.

Biological Transport, Active↗
PubMed2006

In vivo EIS characterization of tumour tissue properties is dominated by excess extracellular fluid.

Electrical impedance spectroscopy (EIS) is a non-ionizing, non-invasive technique which can be used to detect the presence of malignant tumours based on their electrical properties. Although it has been suggested that the edema which accompanies tumours strongly influences EIS tumour characterization, such information has not, until now, been documented in the literature. Growing intramuscular rodent tumours were imaged using magnetic resonance imaging (MRI) and EIS at several time points post-tumour implantation. The amount of edema associated with the tumours was calculated from the MRI images. Electrical parameters (resistivity, permittivity, fluid index ratio and peak frequency) were extracted from the EIS spectra. Taken together, the resulting electrical parameters strongly indicate that edema is the dominating pathological feature in EIS characterization and can at times conceal the presence of the tumour. Receiver operating characteristic analysis supports these findings.

Animals↗
PubMed2005

Measurement of neurotransmitters from extracellular fluid in brain by in vivo microdialysis and chromatography-mass spectrometry.

During the last three decades, a great deal of information has been discovered about chemical neurotransmission. However, the most important processes, namely the complex nature of neuronal circuitry, the "cross talk" between multiple neurotransmitter systems, and the varying effects neurochemicals have at different receptors, are still being explored. Techniques such as microdialysis are routinely employed to measure neurotransmitter levels in living tissue systems. Moreover, microdialysis studies have proven to be valuable in the investigation of neurodegenerative and psychiatric disease pathology, as well as in identifying novel drugs to treat such disorders. One particular challenge in performing these experiments is the requirement to couple microdialysis to sophisticated analytical equipment. Recently, considerable attention has been focused on the development of chromatographic-mass spectrometric techniques to provide more sensitive and accurate measurements of neurochemicals collected from in vivo microdialysis experiments. This review will provide a brief overview of the microdialysis technique, as well as how microdialysis and chromatography-mass spectrometry are being used to measure extracellular levels of neurotransmitters. The primary emphasis of this review will be on how these applications are used to measure levels of acetylcholine (ACh), dopamine, norepinephrine and gamma-aminobutyric acid (GABA).

Animals↗
PubMed2005

Measurement of S-nitrosothiols in extracellular fluids from healthy human volunteers and rheumatoid arthritis patients, using electron paramagnetic resonance spectrometry.

In human tissues, S-nitrosothiols (RSNOs) are generated by the nitric oxide (NO.)-dependent S-nitrosation of thiol-containing species. Here, a novel electron paramagnetic resonance spectrometry assay for RSNOs is described, together with its application to studies of human health and disease. The assay involves degrading RSNOs using N-methyl-d-glucamine dithiocarbamate (MGD) at high pH and spin trapping the NO. released using (MGD)2-Fe2+. Because dietary nitrate might contribute to tissue RSNOs, the assay was used to monitor the effect of Na15NO3 ingestion on plasma and gastric juice RSNOs in healthy human volunteers. Na15NO3 ingestion (2 mmol) increased gastric RS15NO concentrations (p<0.01), but there was no significant effect on plasma RS15NO concentrations. Having established that dietary nitrate was not a confounding factor, we applied the RSNO assay to matched plasma and knee-joint synovial fluid (SF) from rheumatoid arthritis (RA) patients, with healthy subjects as controls. Clinical markers of RA inflammatory disease activity were quantified, as were plasma and SF NO2- and NO3-. Median RSNO concentrations were 0 (interquartile range 68) nM, 109 (282) nM, and 309 (470) nM in normal plasma, RA plasma, and SF, respectively. The median RSNO concentration was significantly elevated in RA SF compared with RA plasma (p<0.05) and in RA plasma compared with normal plasma (p<0.05). SF RSNO concentrations correlated positively with SF neutrophil counts (rs=0.55, p<0.05) and inversely with blood hemoglobin concentrations (rs=-0.52, p<0.05), but not with NO2- or NO3-. Thus the raised levels of RSNOs in RA SF correlate with some established markers of inflammation, suggesting the described RSNO assay may have applications in rapid clinical monitoring of NO metabolism in human inflammatory conditions.

Arthritis, Rheumatoid↗
PubMed2005

Microdialysis study of imipenem distribution in skeletal muscle and lung extracellular fluids of noninfected rats.

The aim of this study was to investigate the imipenem distribution in muscle and lung interstitial fluids by microdialysis in rats and to compare the free concentrations in tissue with the free concentrations in blood. Microdialysis probes were inserted into the jugular vein, hind leg muscle, and lung. Imipenem recoveries in these three media were determined in each rat by retrodialysis by drug period before drug administration. Imipenem was infused intravenously at a dose of 120 mg . kg-1 over 30 min, and microdialysis samples were collected for 150 min. The whole study was conducted with nonhydrated rats (n=4) and hydrated rats (n=6) while the animals were under isoflurane anesthesia. The decay of free concentrations in blood, muscle, and lung with time were monoexponential; and the concentration profiles in these three media were virtually superimposed in both groups. Accordingly, the ratios of the area under the curve (AUC) for tissue (muscle or lung) to the AUC for blood were always virtually equal to 1. Compared to values previously determined with awake rats, clearance was reduced by 2 and 1.5 in nonhydrated and hydrated rats, respectively, but the volume of distribution was unchanged. By combining microdialysis in blood and tissues, it was possible to demonstrate that free imipenem concentrations were virtually identical in blood, muscle, and lung.

Animals↗
PubMed1991

Elevation of taurine in hippocampal extracellular fluid and cerebrospinal fluid of acutely hypoosmotic rats: contribution by influx from blood?

Previous work has demonstrated that there is a selective increase in extracellular taurine in the brain during acute water intoxication. One aim of the present study was to investigate whether plasma taurine contributes to this increase. To this end, the concentrations of taurine, other amino acids, and ethanolamine (EA) were measured in plasma and CSF of urethane-anesthetized rats injected with 150 ml/kg body weight of distilled water. Blood pressure, blood gases, and pH, as well as plasma and CSF osmolality, were also measured. The CSF level of albumin was quantitated to study the function of the blood-CSF barrier. In separate experiments, hippocampal microdialysis was performed to determine the effects of acute plasma hypoosmolality on extracellular amino acids. Finally, the effect of water injection on hippocampal specific gravity and tissue amino acids was assessed. Blood gases and pH were essentially unchanged after water administration. Mean arterial blood pressure increased to peak levels approximately 50 mm Hg above control. Plasma osmolality decreased rapidly, whereas the depression of CSF osmolality was slower and less pronounced. The average volume of the hippocampus increased by 8%. Water injection was accompanied by a 25-fold elevation of taurine in plasma, whereas phosphoethanolamine (PEA) and EA increased moderately. A small fraction of the increase in plasma taurine might derive from blood cells because dilution of blood in vitro led to doubled plasma levels of the amino acid. Taurine, PEA, and EA increased consistently in CSF and hippocampal microdialysates. Plasma hypoosmolality transiently opened the blood-CSF barrier is reflected by augmented CSF concentrations of albumin.(ABSTRACT TRUNCATED AT 250 WORDS)

Alanine↗
PubMed1986

In vivo measurement of regional brain and tumor pH using [14C]dimethyloxazolidinedione and quantitative autoradiography. II: Characterization of the extracellular fluid compartment using pH-sensitive microelectrodes and [14C]sucrose.

We measured the extracellular (interstitial) pH (pHe) of RG-2 rat gliomas using H+-sensitive microelectrodes and estimated the volume of tumor extracellular space based on the tissue-plasma ratio of [14C]sucrose. The average RG-2 pHe was 7.63 +/- 0.15 (mean +/- SD, n = 6), whereas the average pHe of contralateral brain tissue was 7.34 +/- 0.10 (n = 3) and arterial pH was 7.36 +/- 0.02. RG-2 extracellular space water volume was estimated to be 0.3 ml water/g tissue. In separate experiments in normal, nontumored rats, intracellular pH (pHi) was calculated for nine gray and white matter regions based on measurements of tissue and plasma [14C]dimethyloxazolidinedione concentration. pHi values ranged from 6.80 to 6.94, and no consistent gray-white differences were observed. Our data suggest that tumor pHi is not more acidic than that of normal brain tissue and that the observed alkalinity of primary brain tumors is due to the presence of a large alkaline extracellular space.

Animals↗
PubMedDate not supplied

pH heterogeneity in skeletal muscle extracellular fluid.

Oxygen and carbon dioxide are known to be heterogeneously distributed in tissues. Extracellular skeletal muscle tissue pH (pHt) also exhibits a spatial variability in vitro, but this has not been examined in vivo. pHt distributions in resting skeletal muscle and the effect of the dispersion of pHt on ischemia and normoxic hypercarbia was therefore studied in an animal model with a multichannel pH microelectrode. Under resting conditions and spontaneous breathing, local pHt (from all animals, n = 10) was found to vary between 6.96 and 7.68 (range), and 70% of the values were within a pH of 7.00-7.32. In each animal the maximum pHt differences (maximum range between the 6 channels of the microelectrode) found were 0.32 +/- 0.11 pH units (mean +/- SD). During tissue acidosis, induced by ischemia, no significant change in the local pHt differences in each animal was seen. During normoxic hypercarbia a 2-fold increase in pHt variability within each animal was noticed (p < 0.01), which suggests that carbon dioxide and buffering effects of the blood are significant factors for the pHt distribution. The pHt distribution range found is of similar magnitude as previously described in in vitro studies on skeletal muscle. Locally varying pHt levels may be of importance as they will affect cellular H+ extrusion, membrane potential and volume control of different cell populations differently.

Acidosis↗