共查询到20条相似文献,搜索用时 15 毫秒
1.
Cell volume decrease is a key step during differentiation of erythroid cells. This could arise from membrane transporter activation leading to a loss of cell osmolytes; however, the pathways involved are poorly understood. We have characterised Cl(-)-independent K(+) and (3)H-taurine efflux from the erythroleukemia cell line, K562. K(+) efflux (measured using (86)Rb(+)) from pre-loaded cells subjected to hypo-osmotic challenge demonstrated two phases, a rapid increase in K(+) efflux followed by a smaller slower increase. Swelling-activated taurine efflux only demonstrated a single phase. Both phases of K(+) efflux were significantly (P<0.05) blocked by anion channel inhibitor 5-nitro-2-(3-phenypropylamino)-benzoic acid (NPPB). However the antiestrogen, tamoxifen, only inhibited the slow late phase. The initial rapid phase had a higher IC(50) for NPPB inhibition than the slow phase, and was insensitive to protein kinases inhibitors KN-62, wortmannin and PD98059. For the slow K(+) efflux phase, the IC(50) for NPPB inhibition and the inhibition by KN-62, wortmannin, genistein or PD98059, were very similar to those measured for the hypo-osmotically-activated taurine efflux. With NPPB (100 microM) present, the slow K(+) efflux phase was further significantly decreased by the Ca(2+) chelator BAPTA-AM or by the Ca(2+)-activated K(+) channel blockers clotrimazole and charybdotoxin but not by apamin. Thus, at least 3 Cl(-)-independent pathways are involved: (a) a tamoxifen-sensitive and taurine-permeable anion channel; (b) a tamoxifen-insensitive and taurine-impermeable K(+) efflux pathway; and (c) a subtype of Ca(2+)-activated K(+) channel. Any or all of these could be involved in the cell volume decrease associated with differentiation in K562 cells. 相似文献
2.
R. Sánchez Olea H. Pasantes-Morales A. Lázaro M. Cereijido 《The Journal of membrane biology》1991,121(1):1-9
Summary The amino acid pool of MDCK cells was essentially constituted by alanine, glycine, glutamic acid, serine, taurine, lysine, -alanine and glutamine. Upon reductions in osmolarity, free amino acids were rapidly mobilized. In 50% hyposmotic solutions, the intracellular content of free amino acids decreased from 69 to 25mm. Glutamic acid, taurine and -alanine were the most sensitive to hyposmolarity, followed by glycine, alanine and serine, whereas isoleucine, phenylalanine and valine were only weakly reactive. The properties of this osmolarity-sensitive release of amino acids were examined using3H-taurine. Decreasing osmolarity to 85, 75 or 50% increased taurine efflux from 0.6% per min to 1.6, 3.5 and 5.06 per min, respectively. The time course of3H-taurine release closely follows that of the regulatory volume decrease in MDCK cells. Taurine release was unaffected by removal of Na+, Cl– or Ca2+, or by treating cells with colchicine or cytochalasin. It was temperature dependent and decreased at low pH. Taurine release was unaffected by bumetanide (an inhibitor of the Na+/K+/2Cl– carrier); it was inhibited 16 and 67 by TEA and quinidine (inhibitors of K+ conductances), unaffected by gadolinium or diphenylamine-2-carboxylate (inhibitors of Cl– channels) and inhibited 50% by DIDS. The inhibitory effects of DIDS and quinidine were additive. Quinidine but not DIDS inhibited taurine uptake by MDCK cells. 相似文献
3.
J. B. Lombardini 《Neurochemical research》1993,18(2):193-202
The effects of spontaneous and evoked [3H]taurine release from a P2 fraction prepared from rat retinas were studied. The P2 fraction was preloaded with [3H]taurine under conditions of high-affinity uptake and then examined for [3H]taurine efflux utilizing superfusion techniques. Exposure of the P2 fraction to high K+ (56 mM) evoked a Ca2+-independent release of [3H]taurine. Li+ (56 mM) and veratridine (100 M) had significantly less effect (8–15% and 15–30%, respectively) on releasing [3H]taurine compared to the K+-evoked release. 4-Aminopyridine (1 mM) had no effect on the release of [3H]taurine. The spontaneous release of [3H]taurine was also Ca2+-independent. When Na+ was omitted from the incubation medium K+-evoked [3H]taurine release was inhibited by approximately 40% at the first 5 minute depolarization period but was not affected at a second subsequent 5 minute depolarization period. The spontaneous release of [3H]taurine was inhibited by 60% in the absence of Na+. Substitution of Br– for Cl– had no effect on the release of either spontaneous or K+-evoked [3H]taurine release. However, substitution of the Cl– with acetate, isethionate, or gluconate decreased K+-evoked [3H]taurine release. Addition of taurine to the superfusion medium (homoexchange) resulted in no significant increase in [3H]taurine efflux. The taurine-transport inhibitor guanidinoethanesulfonic acid increased the spontaneous release of [3H]taurine by approximately 40%. These results suggest that the taurine release of [3H]taurine is not simply a reversal of the carrier-mediated uptake system. It also appears that taurine is not released from vesicles within the synaptosomes but does not rule out the possibility that taurine is a neurotransmitter. The data involving chloride substitution with permeant and impermeant anions support the concept that the major portion of [3H]taurine release is due to an osmoregulatory action of taurine while depolarization accounts for only a small portion of [3H]taurine release. 相似文献
4.
Summary Immunofluorescence microscopy with a monoclonal antibody raised against the PSTAIR sequence, which corresponds to a peptide
conserved in the p 34cdc2 protein kinase throughout the phylogenetic scale including higher plants, was used to study the intracellular localization
of p 34cdc2 during the cell cycle in onion root tip cells. Although p 34cdc2 was evenly distributed in the cytoplasm throughout the cell cycle, a more intense staining was observed in the cortical region,
where the preprophase band of microtubules (MTs) was located. Double staining with the PSTAIR and plant tubulin antibodies
showed that the width of p 34cdc2 band was narrower than that of MT band. These data raise the interesting question regarding the possible role of p 34cdc2 protein kinase in determining the division site in plant cells. 相似文献
5.
Summary. Although there are a great number of studies concerning the uptake of taurine in several tissues, the regulation of taurine
transport has not been studied in the retina after lesioning the optic nerve. In the present study, isolated retinal cells
of the goldfish retina were used either immediatly after cell suspension or in culture. The high-affinity transport system
of [3H]taurine in these cells was sodium-, temperature- and energy-dependent, and was inhibited by hypotaurine and β-alanine, but
not by γ-aminobutyric acid. There was a decrease in the maximal velocity (Vmax) without modifications in the substrate affinity (Km) after optic axotomy. These changes were mantained for up to 15 days after the lesion. The results might be the summation
of mechanisms for providing extracellular taurine to be taken up by other retinal cells or eye structures, or regulation by
the substrate taurine, which increases after lesioning the optic nerve. The in vivo accumulation of [3H]taurine in the retina after intraocular injection of [3H]taurine was affected by crushing the optic nerve or by axotomy. A progressive retinal decrease in taurine transport was
observed after crushing the optic nerve, starting at 7 hours after surgery on the nerve. The uptake of [3H]taurine by the tectum was compensated in the animals that were subjected to crushing of the optic nerve, since the concentration
of [3H]taurine was only different from the control value 24 hours after the lesion, indicating an efficient transport by the remaining
axons. On the contrary, the low levels of [3H]taurine in the tectum after axotomy might be an index of the non-axonal origin of taurine in the tectum. Axonal transport
was illustrated by the differential presence of [3H]taurine in the intact or crushed optic nerve. The uptake of [3H]taurine into retinal cells in culture in the absence or in the presence of taurine might indicate the existence of an adaptive
regulation of taurine transport in this tissue, however taurine transport probably differentially occurs in specific populations
of retinal cells. The use of a purified preparation of cells might be useful for future studies on the modulation of taurine
transport by taurine in the retina and its role during regeneration.
Received June 11, 1999/Accepted August 31, 1999 相似文献
6.
Summary The time course of incorporation and cellular localization of 3H-5-hydroxytryptophan (3H-5-HTP) and 3H-5-hydroxytryptamine (3H-5-HT) in the pineal and some brain regions in rainbow trout, Salmo gairdneri, were studied by quantitative and qualitative autoradiography.Among the tissues examined, the pineal shows the highest and most rapid uptake of the two isotopes. Maximum incorporation of 3H-5-HTP is achieved by 2 h and that of 3H-5-HT by 20 minutes post injection. At the end of the six-hour experimental period, a significantly high amount of radioactivity is still detectable in the pineal. The results indicate a much slower turnover of the two indoles, especially 5-HTP, in the trout than is known for mammalian tissues.Both the ependymal supporting cells and the receptor cells of the pineal localize these isotopes. In contrast, the intrapineal neurons remain unlabeled. This is taken to suggest lack of capacity of these cells to metabolize 5-HTP and 5-HT.In the circumventricular regions, the two indoles occur in the ependyma of the recessus lateralis and the recessus praeopticus. The label is also localized in the neuropil and the neurons of the nuclei recessus lateralis and praeopticus. Semiquantitative estimates reveal a significant labeling of these areas only 20 minutes after injection, although a weak but inconsistent labeling of the ependyma is evident at 5 minutes. The significance of these results is discussed in regard to (a) normal capacity of circumventricular areas to metabolize indoles and (b) a possible chemical interaction between the pineal and the brain involving a direct pineal-cerebrospinal fluid pathway.Supported in part by a grant to the senior author from the University of Kentucky Research FoundationThe authors wish to thank the Department of Fish and Game, Kentucky, for supplying rainbow trout. The technical assistance of Mrs. Munira Nasser is gratefully acknowledged 相似文献
7.
Kosuke Akiyama Takenori Miyashita Ai Matsubara Nozomu Mori 《The journal of histochemistry and cytochemistry》2010,58(8):759-763
The endolymphatic sac (ES) is a part of the membranous labyrinth. ES is believed to perform endolymph absorption, which is dependent on several ion transporters, including Na+/K+/2Cl− cotransporter type 2 (NKCC-2) and Na+/K+-ATPase. NKCC-2 is typically recognized as a kidney-specific ion transporter expressed in the apical membrane of the absorptive epithelium. NKCC-2 expression has been confirmed only in the rat and human ES other than the kidney, but the detailed localization features of NKCC-2 have not been investigated in the ES. Thus, we evaluated the specific site expressing NKCC-2 by immunohistochemical assessment. NKCC-2 expression was most frequently seen in the intermediate portion of the ES, where NKCC-2 is believed to play an important role in endolymph absorption. In addition, NKCC-2 expression was also observed on the apical membranes of ES epithelial cells, and Na+/K+-ATPase coexpression was observed on the basolateral membranes of ES epithelial cells. These results suggest that NKCC-2 performs an important role in endolymph absorption and that NKCC-2 in apical membranes and Na+/K+-ATPase in basolateral membranes work coordinately in the ES in a manner similar to that in renal tubules. (J Histochem Cytochem 58:759–763, 2010) 相似文献
8.
A modified immunocytochemical method for identification of S-phase cells in root meristems is desribed. The technique combines
incorporation of BrdUrd, rapid isolation of cell nuclei and indirect immunocytochemical detection of BrdUrd-labeled areas
of chromatin using monoclonal anti-BrdUrd (I) and FITC-conjugated (II) antibodies. The labeling indexes calculated using 3H-thymidine autoradiography and BrdUrd-immunofluorescence in root meristems of Vicia faba subsp. minor were found comparable. However, the increased sensitivity of fluorescent staining reveals an enhanced complexity of visible
structure emerging during successive periods of S-phase, allowing for discriminating not only quantitative but also qualitative
aspects of nuclear labeling patterns characteristic for specific periods of DNA replication. 相似文献
9.
The invention of peptide-MHC-tetramer technology to label antigen-specific T cells has led to an enhanced understanding of T lymphocyte biology. Here we describe the development of an in situ pMHC-II tetramer staining method to visualize antigen-specific CD4+ T cells in tissues. This method complements other methods developed that similarly use MHC class II reagents to stain antigen-specific CD4+ T cells in situ. In this study, we used group A streptococcus (GAS) expressing a surrogate peptide (2W) to inoculate C57BL/6 mice, and used fresh nasal-associated lymphoid tissues (NALT) in optimizing the in situ staining of 2W:I-Ab specific CD4+ T cells. The results showed 2W:I-Ab tetramer-binding CD4+ T cells in GAS-2W but not GAS infected mice. This method holds promise to be broadly applicable to study the localization, abundance, and phenotype of antigen-specific CD4+ T cells in undisrupted tissues. 相似文献
10.
Mika Koizumi Nobuaki Ishida Hidejiro Takagishi Kazuto Shirata Hiromi Kano 《Journal of plant research》1992,105(1):1-11
Distributions of free water, which is called water in this investigation, in mangrove (Bruguiera gymnorrhiza (L.) Lam.) tissues were examined by using1H-NMR imaging, and accumulation of Na+ in hypocotyls was examined by using high resolution23Na-NMR and23Na-NMR imaging in relation to their morphology. Water located preferentially in the epidermis and the outer layer of cortex
adjacent to the epidermis, and around vascular bundles of a root, a branch stem, and hypocotyls. Amount of water detected
in the middle parts of cortex and pith was small unlikeAucuba japonica branch tissue. On the other hand, relatively high concentration of Na+ was detected in the pith besides the epidermis and the outer layer of the cortex adjacent to the epidermis, and around vascular
bundles of the hypocotyl. The localization of Na+ did not correspond to that of water. Concentrations of Na+ accumulated (up to 22mM) in the hypocotyl were approximately 10 times higher than those observed in tissues of ordinary plants.
The characteristic water distribution and accumulation of Na+ in the mangrove are considered to relate to their ecological nature for the adaptation to saline environments. 相似文献
11.
Summary Cell dedifferentiation was induced inVicia faba root tissues by removing the whole root meristem (decapitation) and the behaviour of the nuclear DNA in the dedifferentiating cells was studied by means of cytophotometric and autoradiographic analyses. Cytophotometric determination after Feulgen-staining showed that: 1. the vast majority of nuclei in differentiated cells were in the DNA postsynthetic phase, but their Feulgen absorption was lower than that of DNA postsynthetic nuclei (G2, 4 C) in the meristem; 2. such a Feulgen absorption was detected in certain nuclei after root decapitation; 3. all the mitoses in the dedifferentiating tissues were diploid, fully matching the Feulgen absorption of mitoses in the meristem.After3H-thymidine (3H-T) feeding of the decapitated roots and autoradiography, the following results were obtained: 1. two populations of labeled nuclei, characterized by two different levels of scattered labeling occurred in dedifferentiating tissues, slightly labeled nuclei being much more numerous than heavily labeled nuclei; 2. the percentage of labeled nuclei was much greater than that of DNA presynthetic nuclei in the root tissues; 3. almost all the mitoses were labeled after a 16-hour3H-T feeding; 4. the percentage of slightly labeled nuclei paralleled that of dedifferentiating cells; 5. the duration of the DNA synthesis phase and that of the gap between completion of DNA synthesis and mitosis differed in heavily and slightly labeled nuclei; 6. all nuclei which entered DNA synthesis also entered mitosis.These results are interpreted to mean that: 1. after decapitation, two different DNA syntheses occur in the dedifferentiating root tissues ofV. faba: DNA reduplication in cells which dedifferentiate starting from a DNA presynthetic nuclear condition (heavily labeled nuclei) and extra DNA synthesis in cells which dedifferentiate starting from a DNA postsynthetic nuclear condition (slightly labeled nuclei); 2. extra DNA synthesis is required in these dedifferentiating cells for entry into mitosis. 相似文献
12.
López-Domínguez A Ramos-Mandujano G Vázquez-Juárez E Pasantes-Morales H 《Molecular and cellular biochemistry》2007,306(1-2):95-104
Cell swelling, regulatory volume decrease (RVD), volume-sensitive Cl− (Cl−
swell) current and taurine efflux after exposure to high concentrations of urea were characterized in fibroblasts Swiss 3T3, and
results compared to those elicited by hyposmotic (30%) swelling. Urea 70, 100, and 150 mM linearly increased cell volume (8.25%,
10.6%, and 15.7%), by a phloretin-inhibitable process. This was followed by RVD by which cells exposed to 70, 100, or 150 mM
urea recovered 27.6%, 38.95, and 74.1% of their original volume, respectively. Hyposmolarity (30%) led to a volume increase
of 25.9% and recovered volume in 32.5%. 3H-taurine efflux was increased by urea with a sigmoid pattern, as 9.5%, 18.9%, 71.5%, and 89% of the labeled taurine pool
was released by 70, 100, 150, or 200 mM urea, respectively. Only about 11% of taurine was released by 30% hyposmolarity reduction
in spite of the high increase in cell volume. Urea-induced taurine efflux was suppressed by NPPB (100 μM) and markedly reduced
by the tyrosine kinase-general blocker AG18. The Cl−
swell current was more rapidly activated and higher in amplitude in the hyposmotic than in the isosmotic/urea condition (urea 150 mM),
but this was not sufficient to accomplish an efficient RVD. These results showed that at similar volume increase, cells swollen
by urea showed higher taurine efflux, lower Cl−
swell current and more efficient RVD, than in those swollen by hyposmolarity. The correlation found between RVD efficiency and
taurine efflux suggest a prominent role for organic over ionic osmolytes for RVD evoked by urea in isosmotic conditions. 相似文献
13.
J. S. Graves Ph.D. T. Inabnett K. Geering J. A. V. Simson 《Cell and tissue research》1989,258(1):137-145
Summary An antibody to the 96 kD -subunit of the Na+, K+ -ATPase from Bufo marinus has been used in immunostaining rat kidney and salivary glands. Intense staining was observed on basolateral membranes of distal tubules of the kidney and striated ducts of the three major salivary glands. Less intense staining was seen on the basolateral membranes of parotid acinar cells, but no staining was seen on the acinar cells of submandibular or sublingual glands. These sites of staining have been shown, by other methods, to posses substantial Na+, K+ -ATPase, indicating that the antibody recognizes antigenic determinants of the sodium pump highly conserved in the course of evolution. In addition, staining with this antibody was observed at the apical region of cells of the proximal straight tubule and of the papillary collecting duct in the kidney. Absorption studies suggest that the apical antigenic determinants are the same or closely related to each other but are distinct from basolateral antigenic determinants. 相似文献
14.
15.
Bruce F. Scharschmidt Edwin R. Griff Roy H. Steinberg 《The Journal of membrane biology》1988,106(1):71-81
Summary The apical surface of the retinal pigment epithelium (RPE) faces the neural retina whereas its basal surface faces the choroid. Taurine, which is necessary for normal vision, is released from the retina following light exposure and is actively transported from retina to choroid by the RPE. In these experiments, we have studied the effects of taurine on the electrical properties of the isolated RPE of the bullfrog, with a particular focus on the effects of taurine on the apical Na+–K+ pump.Acute exposure of the apical, but not basal, membrane of the RPE to taurine decreased the normally apical positive transepithelial potential (TEP). This TEP decrease was generated by a depolarization of the RPE apical membrane and did not occur when the apical bath contained sodium-free medium. With continued taurine exposure, the initial TEP decrease was sometimes followed by a recovery of the TEP toward baseline. This recovery was abolished by strophanthidin or ouabain, indicating involvement of the apical Na+–K+ pump.To further explore the effects of taurine on the Na+–K+ pump, barium was used to block apical K+ conductance and unmask a stimulation of the pump that is produced by increasing apical [K+]
0
. Under these conditions, increasing [K+]
0
hyperpolarized the apical membrane and increased TEP. Taurine reversibly doubled these responses, but did not change total epithelial resistance or the ratio of apical-to-basal membrane resistance, and ouabain abolished these responses.Collectively, these findings indicate the presence of an electrogenic Na+/taurine cotransport mechanism in the apical membrane of the bullfrog RPE. They also provide direct evidence that taurine produces a sodium-dependent increase in electrogenic pumping by the apical Na+–K+ pump. 相似文献
16.
Abstract— Equilibrium or incomplete equilibrium density gradient centrifugation was used to characterize the subcellular localization of exogenous [3 5S]taurine which was taken up by minces or homogenates of rat cerebral cortex. [3 5S]Taurine is accumulated in synaptosomes, which sediment more slowly than l -[3H]norepinephrine-accumulating particles. When [3 5S]taurine and [3H]GABA are accumulated by minces, a small difference in the sedimentation profile of taurine and GABA was observed, but no difference was found when taurine and intrasynaptosomal potassium were compared. However, potassium sedimented more slowly after incubation of homogenates than of minces. These data give evidence for the accumulation of [3 5S]taurine by a specific synaptosomal population. 相似文献
17.
A novel uptake system for the unusual sulfonated amino acid taurine was discovered in the prokaryote, encapsulated Staphylococcus aureus strain M. This strain has been shown previously to contain taurine in its capsular polysaccharide. Taurine uptake by whole cells incubated in buffer showed a saturable dependency upon Na+ and taurine uptake was itself a saturable process, stimulated by glucose, and markedly affected by temperature. No evidence was found for the inducibility of taurine uptake. In the presence of 10 mM NaCl Lineweaver-Burk plots revealed a Km of 42 μM and Vmax of 4.6 nmol/min per mg dry weight for taurine uptake at 37°C. Increasing concentrations of Na+ decreased the Km of the system and appeared to increase the Vmax. Of various other cations tested only Li+ supported marked taurine uptake. Excess unlabelled taurine did not cause efflux of radioactivity taken up. Taurine was taken up into cold trichloroacetic acid-soluble material and did not chromatograph as taurine, indicating rapid metabolism during or closely following uptake. Taurine uptake appeared to occur via a highly specific system because amino acids representing the major known groups of amino acid transport systems in S. aureus did not inhibit taurine uptake, and uptake was only slightly diminished by the structurally closely related compounds hypotaurine and 3-amino-1-propane sulfonic acid. Sulfhydryl group reagents, electron transport inhibitors, an uncoupler and inhibitors of Na+-linked transport processes inhibited taurine uptake. A variety of other metabolic inhibitors had little effect on taurine uptake. 相似文献
18.
Dr. Antonio Haddad Georges Pelletier Fausto Marchi Iara L. G. Brasileiro 《Cell and tissue research》1977,177(1):67-79
Summary Fucose-3H was injected into the cerebral ventricle of rats that were killed at several time intervals after injection. Semi-thin sections of the supraoptic nucleus and neurohypophysis were processed for radioautography and analysed quantitatively. Silver grains indicating the site of fucose-labeled glycoproteins were first located at the perinuclear region of the secretory neurons. The highest silver-grain density in these cells was observed at 2 h after injection, declining afterwards. Silver grains over the neurohypophysis were observed from 2 h on, reached a peak at 1 day after injection and decreased in the subsequent time intervals. The distributions of the silver grains over the neurohypophysis fitted Poissonian distributions and these were shown to be heterogeneous at the several time intervals. Pituicytes were not labeled. The percentage of silver grains over the Herring bodies increased with time. In rats deprived of water after fucose-3H injection there was a great increase in the release of labeled glycoproteins from the neurohypophysis. These results indicate that the glycoproteins synthesized by the secretory neurons of the hypothalamic nuclei are secreted in the neurohypophysis. 相似文献
19.
Jiahui Zhou Song Wu Yuxiang Chen Jingfeng Zhao Kexiang Zhang Jianlong Wang Shijie Chen 《Experimental biology and medicine (Maywood, N.J.)》2015,240(7):867-875
This study investigated the role of miR-143 in the chemoresistance of osteosarcoma tumor cells and the associated mechanisms. Real-time PCR was used to measure miR-143 levels. Western blot was used to detect protein expression. Cell proliferation was analyzed by MTT assay and Matrigel colony formation assay. Forced miR-143 expression was established by adenoviral vector infection. Cell death was detected by Hoechst33342 staining. Loss of miR-143 expression was observed in osteosarcomas, which correlated with shorter survival of patients with osteosarcomas underlying chemotherapy. In chemoresistant SAOS-2 and U2OS osteosarcomas cells, miR-143 levels were significantly downregulated and accompanied by increases in ATG2B, Bcl-2, and/or LC3-II protein levels, high rate of ALDH1+CD133+ cells, and an increase in Matrigel colony formation ability. H2O2 upregulated p53 and miR-143, but downregulated ATG2B, Bcl-2, and LC3-I expression in U2OS cells (wild-type p53) but not in SAOS-2 (p53-null) cells. Forced miR-143 expression significantly reversed chemoresistance as well as downregulation of ATG2B, LC3-I, and Bcl-2 expression in SAOS-2- and U2OS-resistant cells. Forced miR-143 expression significantly inhibited tumor growth in xenograft SAOS-2-Dox and U2OS-Dox animal models. Loss of miR-143 expression is associated with poor prognosis of patients with osteosarcoma underlying chemotherapy. The chemoresistance of osteosarcoma tumor cells to doxorubicin is associated with the downregulation of miR-143 expression, activation of ALDH1+CD133+ cells, activation of autophagy, and inhibition of cell death. miR-143 may play a crucial role in the chemoresistance of osterosarcoma tumors. 相似文献
20.
Summary. Taurine has been thought to function as a regulator of neuronal activity, neuromodulator and osmoregulator. Moreover, it is
essential for the development and survival of neural cells and protects them under cell-damaging conditions. Taurine is also
involved in many vital functions regulated by the brain stem, including cardiovascular control and arterial blood pressure.
The release of taurine has been studied both in vivo and in vitro in higher brain areas, whereas the mechanisms of release
have not been systematically characterized in the brain stem. The properties of release of preloaded [3H]taurine were now characterized in slices prepared from the mouse brain stem from developing (7-day-old) and young adult
(3-month-old) mice, using a superfusion system. In general, taurine release was found to be similar to that in other brain
areas, consisting of both Ca2+-dependent and Ca2+-independent components. Moreover, the release was mediated by Na+-, Cl−-dependent transporters operating outwards, as both Na+-free and Cl− -free conditions greatly enhanced it. Cl− channel antagonists and a Cl− transport inhibitor reduced the release at both ages, indicating that a part of the release occurs through ion channels.
Protein kinases appeared not to be involved in taurine release in the brain stem, since substances affecting the activity
of protein kinase C or tyrosine kinase had no significant effects. The release was modulated by cAMP second messenger systems
and phospholipases at both ages. Furthermore, the metabotropic glutamate receptor agonists likewise suppressed the K+-stimulated release at both ages. In the immature brain stem, the ionotropic glutamate receptor agonists N-methyl-D-aspartate
(NMDA) and 2-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) potentiated taurine release in a receptor-mediated manner.
This could constitute an important mechanism against excitotoxicity, protecting the brain stem under cell-damaging conditions. 相似文献