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At least 649 records · Page 36Linked to original sources
PubMed1999

Optical imaging reveals elevated intracellular chloride in hippocampal pyramidal neurons after oxidative stress.

The accumulation of reactive oxygen species (ROS) in the brain is associated with several neurodegenerative conditions. ROS can affect ionic homeostasis leading to impaired neurotransmission. Here, we determined the ability of H(2)O(2), a membrane permeant ROS, to alter intraneuronal Cl(-), an important regulator of neuronal excitability. Real-time alterations in intracellular chloride, [Cl(-)]i, were measured with UV laser scanning confocal microscopy in hippocampal slices loaded with the cell-permeant form of 6-methoxy-N-ethylquinolium iodide (MEQ), a Cl(-)-sensitive fluorescent probe. In slices superfused with H(2)O(2) for 10 min, there was a significant decrease in MEQ fluorescence (elevation in [Cl(-)]i) in area CA1 pyramidal cell soma but not in interneurons located in stratum radiatum. Alterations in [Cl(-)]i induced by H(2)O(2) were prevented by the iron chelator deferoxamine and the vitamin E analog Trolox, suggesting the involvement of free radicals. The influx of Cl(-) probably occurred through the GABA-gated Cl(-) channel because the effects of H(2)O(2) were blocked by picrotoxin. In addition, HPLC analysis of the superfusates indicated that GABA and glutamate accumulated extracellularly after H(2)O(2) exposure. Excitatory amino acid receptor antagonists 2-amino-5-phoshopentanoic acid and 1,2,3,4-tetrahydro-6-nitro-2, 3-dioxo-benzo[f]quinoxaline-7-sulfonamide also attenuated the effect of H(2)O(2) on MEQ fluorescence. The changes in [Cl(-)]i induced by H(2)O(2) were Ca(2+)-dependent and Na(+)-independent. After exposure of slices to H(2)O(2), the ability of the GABA agonist muscimol to increase [Cl(-)]i was attenuated. Thus, ROS, like H(2)O(2), may impair transmembrane Cl(-) gradients and reduce inhibitory neurotransmission, further promoting neuronal damage in oxidative stress-related disease and in aging.

2-Amino-5-phosphonovalerate↗
PubMed1999

Is hydroxylamine-induced cytotoxicity a valid marker for hypersensitivity reactions to sulfamethoxazole in human immunodeficiency virus-infected individuals?

Hypersensitivity (HS) reactions to sulfonamides and sulfones continue to limit their use in human immunodeficiency virus (HIV)-infected individuals. In vitro cytotoxicity of hydroxylamine metabolites toward peripheral blood mononuclear cells (PBMCs) has been proposed as a marker for these HS reactions. To test the validity of this in vitro system, we determined the selective susceptibility of PBMCs from HIV-infected patients to the cytotoxic effects of hydroxylamine metabolites of sulfamethoxazole (SMX) and dapsone (DDS). Concentration-cytotoxic response data were collected using PBMCs from 12 sulfa-HS (10 SMX-HS and 2 SMX/DDS-HS) and 10 sulfa-tolerant HIV-infected individuals. Although sulfamethoxazole hydroxylamine (SMX-NOH) and dapsone hydroxylamine (DDS-NOH) both caused concentration-dependent increases in cell death, DDS-NOH was significantly more potent in each subject (P <.0001). A comparison of a variety of mean data for sulfa-HS and -tolerant patient populations failed to demonstrate the increased susceptibility of PBMCs from HS patients, noted by others, to either SMX-NOH or DDS-NOH. Moreover, any trend toward an increased susceptibility of PBMCs from HS patients was eliminated when adjusted for control cell death. PBMCs from sulfa-HS patients showed significantly greater susceptibility to the stress of short term in vitro incubation (P <. 02). Mean (S.D.) vehicle control cell death values were 24.1% (7.6%) for HS patients and 17.1% (4.4%) for tolerant patients. No significant correlation was observed between hydroxylamine-induced or control cell death and any of the recorded clinical parameters. Although several potential reasons are proposed to explain the disparity with past investigations, the data suggest that in vitro cytotoxicity is not a valid marker for HS reactions in HIV-infected individuals using currently accepted experimental procedures.

Adult↗
PubMed1999

A needle-type immunotherapeutic system incorporating laser light and platonin in combination with ethanol injection in the treatment of cancer growing in deep organs.

Platonin is a potent cell-activating agent and a photosensitizing dye characterized by a typical absorption peak at 590 nm. It has been already clarified that macrophage activity is enhanced synergistically by platonin administration together with laser light irradiation. This method is considered to be useful in cancer immunotherapy. In this study, a needle-type therapeutic system incorporating this method was applied for the therapy of a homogeneous tumor grafted onto mice. The tumor was strongly cicatrized by collagen fibers at an early stage of the treatment. A high T/B cell ratio of lymphocytes was observed in the peripheral blood of the treated mice. In addition, a high survival ratio was seen, especially in the group of concomitant therapy with ethanol injection (PEI method). It was determined that the induction of high immunopotentiation of mice was triggered by ethanol injection at an early stage. These results demonstrated that the system is reliable for the treatment of cancer in deep organs such as a liver, requiring no major surgical intervention.

Animals↗
PubMed2000

Brilliant blue G selectively blocks ATP-gated rat P2X(7) receptors.

There are few antagonists selective for subtypes of the several P2X receptors, but these are needed to identify the receptors expressed on native cells and tissues. In particular, P2X(4) and P2X(7) receptor subunits are colocalized on immune, epithelial, and exocrine gland cells, but both are relatively insensitive to suramin and pyridoxal-5-phosphate-6-azo-2',4'-disulfonic acid derivative. In this article, we show that Coomassie Brilliant Blue G selectively inhibits P2X(7) receptors with nanomolar affinity. We measured currents in response to P2X receptor activation in HEK293 cells heterologously expressing human or rat P2X(1), P2X(2), P2X(3), P2X(2/3), P2X(4), P2X(1/5), and P2X(7) receptors. Brilliant Blue G produced a noncompetitive inhibition of rat and human P2X(7) receptors with IC(50) values of 10 and 200 nM, respectively. IC(50) values for inhibition of the other receptors ranged from 2 to >30 microM; the rat and human P2X(4) receptors showed IC(50) values of >10 and 3.2 microM. Coomassie Blue G also blocked YO-PRO1 uptake and membrane blebbing, which are uniquely associated with activation of P2X(7) receptors. Thus, Brilliant Blue G is at least 1000-fold more potent at rat P2X(7) receptors than at rat P2X(4) receptors.

Adenosine Triphosphate↗
PubMed2000

Cryptic peripheral ribosomal domains distributed intermittently along mammalian myelinated axons.

A growing body of metabolic and molecular evidence of an endogenous protein-synthesizing machinery in the mature axon is a challenge to the prevailing dogma that the latter is dependent exclusively on slow axoplasmic transport to maintain protein mass in a steady state. However, evidence for a systematic occurrence of ribosomes in mature vertebrate axons has been lacking until recently, when restricted ribosomal domains, called "periaxoplasmic plaques," were described in goldfish CNS myelinated axons. Comparable restricted RNA/ribosomal "plaque" domains now have been identified in myelinated axons of lumbar spinal nerve roots in rabbit and rat on the basis of RNase sensitivity of YOYO-1-binding fluorescence, immunofluorescence of ribosome-specific antibodies, and ribosome phosphorus mapping by electron spectroscopic imaging (ESI). The findings were derived from examination of the axoplasm isolated from myelinated fibers as axoplasmic whole mounts and delipidated spinal nerve roots. Ribosomal periaxoplasmic plaque domains in rabbit axons were typically narrow ( approximately 2 microm), elongated ( approximately 10 microm) sites that frequently were marked by a protruding structure. The domain complexity included an apparent ribosome-binding matrix. The small size, random distribution, and variable intermittent axial spacing of plaques around the periphery of axoplasm near the axon-myelin border are likely reasons why their systematic occurrence has remained undetected in ensheathed axons. The periodic but regular incidence of ribosomal domains provides a structural basis for previous metabolic evidence of protein synthesis in myelinated axons.

Animals↗
PubMed1975

Microvascular response to local application of dequalinium chloride. A vital microscopical study of hamster's cheek pouch and a microangiographic study of rabbit's ear.

Dequalinium chloride is a topical antiseptic, whose use may be attended by skin necrosis. Since microcirculatory changes are an early and distinct manifestation of tissue injury, the tissue damaging effect of dequalinium chloride on the microcirculation was examined. The immediate vascular reactions were studied by vital microscopy, of the hamster cheek pouch and the late effects were visualized by microangiography of the rabbit ear. An aqueous solution of dequalinium chloride in concentrations well below those used in clinical practice induced severe microcirculatory disturbances.

Animals↗
PubMed2002

Modulation of monocyte signaling and pore formation in response to agonists of the nucleotide receptor P2X(7).

Previous reports about the nucleotide receptor P2X(7), which exhibits ion channel and pore-forming activity and is known to promote IL-1beta processing, have centered largely on its role in macrophage function, whereas its participation in monocyte activity has been unclear. However, because extracellular ATP has been shown to affect monocytes with respect to IL-1beta release, we hypothesized that the P2X(7) receptor is also present and functional in a subpopulation of blood monocytes. Flow cytometric analysis revealed that about 70% of monocytes isolated from normal human donors expressed the P2X(7) receptor. Activation of P2X(7) receptor-associated pore formation by the agonist BzATP resulted in a 9- to 15-fold increase in the uptake of the membrane-impermeant fluorescent dye YO-PRO, and this dye uptake is markedly inhibited by the P2X(7) receptor antagonists KN-62 and oATP. Evidence supporting the presence of the functional P2X(7) receptor in monocytes also includes the observation that BzATP exposure results in a dose-dependent increase in the activation of mitogen-activated 2protein kinases and the nuclear translocation of the transcription factor NF-kappaB in human monocytes and in THP-1 human monocytic cells. Furthermore, treatment of monocytes with BzATP induced the expression of cyclooxygenase-2 (COX-2) and tissue factor, which are two important endpoints that have not been previously shown to be regulated by nucleotide receptor action in monocytes. Together, these data indicate that a subpopulation of human monocytes express P2X(7) receptors that are functional with respect to pore formation, signal transduction, and mediator production, further supporting a key role for this nucleotide receptor in host immune responses.

Benzoxazoles↗