Endothelin induces dopamine release from rat striatum via endothelin-B receptors

The aim of the present study was to determine whether local administration of endothelin induces the release of dopamine in the rat striatum and to characterize and localize endothelin receptors in this brain region. Local injection of endothelin-1 (10 pmol) into the ventral striatum of urethane-anaesthetized rats caused an increase of 8 microM in the extracellular concentration of dopamine as measured by in vivo chronoamperometry. The peak increase in dopamine concentration occurred within 5 min of endothelin injection. Injection of the selective endothelin-B receptor agonist [Ala1.3,11.15]endothelin-1 (10 pmol) also caused an increase in extracellular dopamine concentration, suggesting that endothelin is acting at the endothelin-B receptor to elicit its effect. In rats with unilateral 6-hydroxydopamine lesions of the nigrostriatal pathway, the response to local injection of endothelin-1 (10 pmol) was significantly inhibited on the lesioned side as compared to the non-lesioned side. In contrast, pretreatment of the rats with the N-methyl-D-aspartate receptor antagonist dizocilpine maleate (5 mg/kg, i.p.) or the nitric oxide synthase inhibitor NG-nitro-L-arginine (3 mg/kg, i.p.) did not alter the endothelin-induced release of dopamine. In binding studies, addition of endothelin-1 displaced [125I]endothelin-1 with a Ki of 220 pM. The endothelin-B receptor antagonist BQ788 displaced [125I]endothelin-1 with a Ki of 120 nM, whereas the endothelin-A receptor antagonist BQ123 produced only a 25% displacement at 10 microM, suggesting that endothelin receptors in the striatum are of the endothelin-B subtype. In rats with unilateral 6-hydroxydopamine lesions of the nigrostriatal dopamine system, [125I]endothelin-1 binding was reduced by 53% in lesioned striatum compared to non-lesioned striatum, with no difference in the Kd. These data provide evidence that endothelin acts on a homogeneous population of endothelin-B receptors within the striatum to cause the release of dopamine and that a significant proportion of these receptors is located on dopaminergic neurons.     

Requirements for different components of the host cell cytoskeleton distinguish ecotropic murine leukemia virus entry via endocytosis from entry via surface fusion

Murine ecotropic leukemia viruses use a common receptor for entry into host cells; however, the site of virus fusion appears to differ with the host cell. Entry in mouse NIH 3T3 fibroblasts is by endocytosis, whereas entry in rat XC sarcoma cells is by surface fusion. We report here the identification of a step common to both entry pathways, as well as of a step unique to the endocytic pathway. Recent demonstration of the clustering of the virus receptor on rat cells suggested a possible interaction of the receptor with the cellular cytoskeleton (M. H. Woodard, W. A. Dunn, R. O. Laine, M. Malandro, R. McMahon, O. Simell, E. R. Block, and M. S. Kilberg, Am. J. Physiol. 266:E817-E824, 1994). We tested the hypothesis that such an interaction might influence receptor function. We found that entry into NIH 3T3 and XC cells was greatly diminished by the disruption of the actin network before but not shortly after virus internalization, suggesting the actin network plays a critical role in an early step common to both entry pathways. Disruption of microtubules before and shortly after virus internalization markedly reduced entry in NIH 3T3 cells, while entry into XC cells remained efficient. These data suggest that intact microtubules are required in a postpenetration step unique to efficient virus entry via endocytosis. The physiological function of the receptor was not affected by disruption of either the actin network or the microtubules, as the uptake of cationic amino acids in NIH 3T3 and XC cells was comparable to that in control cells even when the cytoskeleton remained disrupted for as long as 3 h.     

Calcium release from skeletal muscle sarcoplasmic reticulum: site of action of dantrolene sodium

The muscle relaxant dantrolene sodium acts directly and specifically on skeletal muscle, unlike other pharmacological agents which affect the central nervous system or act at the nueromuscular junction. Dantrolene sodium markedly suppresses the release of calcium previously sequestered by skeletal, but not cardiac, muscle sarcoplasmic reticulum. No effect in the total amount of calcium accumulated was found. In situ, the drug may reduce the amount of calcium necessary for muscle contraction.     

Regional differences in striatal dopamine uptake and release associated with recovery from MPTP-induced parkinsonism: an in vivo electrochemical study

This study directly assessed striatal dopamine (DA) uptake rates and peak release in response to KCl in normal, symptomatic, and recovered 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated cats using in vivo electrochemistry. DA uptake rates measured after direct application of known concentrations of DA to the striatum were slowed significantly in both dorsal and ventral striatum in symptomatic cats compared with rates recorded in normal animals. DA uptake rates remained significantly slowed in recovered cats and were not significantly different from the rates recorded in symptomatic animals. In symptomatic cats, both DA uptake rates and the signal recorded in response to KCl stimulation were significantly decreased from normal in all dorsal and ventral striatal regions sampled. Reduction/oxidation (redox) ratios recorded in response to KCl stimulation suggested DA to be the predominant electroactive species. In spontaneously recovered MPTP-treated cats, recordings in the ventral striatum subsequent to KCl stimulation again suggested DA to be the predominant electroactive species released, and peak levels were significantly higher than those recorded in symptomatic animals. In the dorsal striatum of recovered cats, redox ratios recorded subsequent to KCl stimulation suggested serotonin rather than DA to be the predominant electroactive species released. Peak levels of release in the dorsal striatum were not significantly greater than those recorded in symptomatic animals. These results suggest that in spontaneously recovered MPTP-treated cats, there is partial recovery of ventral striatal DAergic terminals, persistent loss of dorsal striatal DAergic terminals, and a down-regulation of DA transporter number/function throughout the striatum. These processes may contribute to volume transmission of DA in the striatum and promote functional recovery.     

Alpha2-macroglobulin complexes with and mediates the endocytosis of beta-amyloid peptide via cell surface low-density lipoprotein receptor-related protein

A primary histopathological feature of Alzheimer's disease is the accumulation of beta-amyloid (A beta) in the brain of afflicted individuals. However, A beta is produced continuously as a soluble protein in healthy individuals where it is detected in serum and CSF, suggesting the existence of cellular clearance mechanisms that normally prevent its accumulation and aggregation. Here, we demonstrate that A beta forms stable complexes with activated alpha2-macroglobulin (alpha2M*), a physiological ligand for the low-density lipoprotein receptor-related protein (LRP) that is abundantly expressed in the CNS. These alpha2M*/125I-A beta complexes are immunoreactive with both anti-A beta and anti-alpha2M IgG and are stable under various pH conditions, sodium dodecyl sulfate, reducing agents, and boiling. We demonstrate that alpha2M*/125I-A beta complexes can be degraded by glioblastoma cells and fibroblasts via LRP, because degradation is partially inhibited by receptor-associated protein (RAP), an antagonist of ligand interactions with LRP. In contrast, the degradation of free 125I-A beta is not inhibited by RAP and thus must be mediated via an LRP-independent pathway. These results suggest that LRP can function as a clearance receptor for A beta via a physiological ligand.     

Evidence for non-transferrin-mediated uptake and release of iron and manganese in glial cell cultures from hypotransferrinemic mice

Transferrin (Tf) is accepted as the iron mobilization protein, but its role in transport of other metals is controversial. In this study, we used mixed glial cultures from hypotransferrinemic (Hp) mice to determine the dependence of these cells on transferrin for iron and manganese delivery and release. Hp mice have a splicing defect in the transferrin (Tf) gene, resulting in < 1% of the normal plasma levels of Tf. Cellular iron and manganese uptake increases over 24 hr in cultures of normal and Hp glial cells in the presence of standard concentrations of Tf in the media; although total 59iron uptake in the Hp mouse cultures was 2X greater than normal, 54Mn uptake was similar between the two groups. The absence of Tf in the media resulted in a significant increase in 59iron uptake in both normal and Hp glial but did not affect Mn uptake. Elevated Tf (10X normal) in the media reduced both 59iron and 54Mn uptake. Efflux of 59Iron and 54Mn occurred in normal and Hp cultures, indicating the existence of a dynamic exchange of metals, and that intracellular Tf is not necessary for metal release. However, in the absence of Tf in the media, significantly more iron was retained in the cells than if Tf were present in both normal and Hp glial cultures. 54Mn release was minimally affected by extracellular Tf. The data demonstrate that Tf is not required for iron and Mn uptake into glial cells. These data further demonstrate a dynamic metal exchange system for glial cells which is not dependent on intracellular Tf.     

Calcium channel types with distinct presynaptic localization couple differentially to transmitter release in single calyx-type synapses

We studied how Ca2+ influx through different subtypes of Ca2+ channels couples to release at a calyx-type terminal in the rat medial nucleus of the trapezoid body by simultaneously measuring the presynaptic Ca2+ influx evoked by a single action potential and the EPSC. Application of subtype-specific toxins showed that Ca2+ channels of the P/Q-, N-, and R-type controlled glutamate release at a single terminal. The Ca2+ influx through the P/Q-type channels triggered release more effectively than Ca2+ influx through N- or R-type channels. We investigated mechanisms that contributed to these differences in effectiveness. Electrophysiological experiments suggested that individual release sites were controlled by all three subtypes of Ca2+ channels. Immunocytochemical staining indicated, however, that a substantial fraction of N- and R-type channels was located distant from release sites. Although these distant channels contributed to the Ca2+ influx into the terminal, they may not contribute to release. Taken together, the results suggest that the Ca2+ influx into the calyx via N- and R-type channels triggers release less effectively than that via P/Q-type because a substantial fraction of the N- and R-type channels in the calyx is localized distant from release sites.     

Met-enkephalin inhibits 5-hydroxytryptamine release from the rat ventral spinal cord via delta opioid receptors

The effect of opioid receptor agonists and antagonists on the electrically evoked release of endogenous serotonin (5-hydroxytryptamine, 5-HT) was studied in superfused slices of the rat ventral lumbar spinal cord. Met-ENK (1 x 10(-8)M-1 x 10(-6)M) and DPDPE (1 x 10(-8)M-1 x 10(-6)M) reduced the evoked 5-Ht release in a concentration dependent fashion. DAMGO (1 x 10(-8)-1 x 10(-6)) and (-)-trans-(1S,2S)-U-50488 (1 x 10(-6)M) had no effect on the 5-HT release. The inhibitory effect of met-ENK was completely abolished by ICI-174,864, but neither by naloxonazine nor nor-binaltorphimine. Following i.c.v. treatment with 5,7-dihydroxytryptamine (5,7-DHT), the tissue concentration of 5-HT was reduced by 97%, whereas the concentration of noradrenaline was reduced by only 5%. The tissue concentration of met-ENK, as measured by radioimmunoassay, was not significantly altered. The results suggest that met-ENK is present in the rat ventral spinal cord mainly in non-serotonergic nerve terminals and exerts an inhibitory action on 5-HT release via delta opioid receptors.     

Bax-induced caspase activation and apoptosis via cytochrome c release from mitochondria is inhibitable by Bcl-xL

A growing body of evidence supports a role for mitochondria and mitochondria-derived factors in the cell death process. In particular, much attention has focused on cytochrome c, a key component of the electron transport chain, that has been reported to translocate from the mitochondria to the cytosol in cells undergoing apoptosis. The mechanism for this release is, as yet, unknown. Here we report that ectopic expression of Bax induces apoptosis with an early release of cytochrome c preceding many apoptosis-associated morphological alterations as well as caspase activation and subsequent substrate proteolysis. A loss of mitochondrial transmembrane potential was detected in vivo, although no mitochondrial swelling or loss of transmembrane potential was observed in isolated mitochondria treated with Bax in vitro. Caspase inhibitors, such as endogenous XIAP and synthetic peptide benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone (zVAD-fmk), although capable of altering the kinetics and perhaps mode of cell death, had no influence on this release, suggesting that if cytochrome c plays a role in caspase activation it must precede this step in the apoptotic process. Mitochondrial permeability transition was also shown to be significantly prevented by caspase inhibition, indicating that the translocation of cytochrome c from mitochondria to cytosol is not a consequence of events requiring mitochondrial membrane depolarization. In contrast, Bcl-xL was capable of preventing cytochrome c release while also significantly inhibiting cell death. It would therefore appear that the mitochondrial release of factors such as cytochrome c represents a critical step in committing a cell to death, and this release is independent of permeability transition and caspase activation but is inhibited by Bcl-xL.     

P204萃取硫酸铜溶液中的钙

针对某铜盐厂硫酸铜产品杂质钙含量较高的现状,选用P204从硫酸铜溶液中萃取钙。考察P204质量浓度、相比O/A、萃取时间、水相平衡pH等对铜钙萃取分离的影响。结果表明,P204萃取钙的适宜条件为:P204质量浓度1.2mol/L,O/A=5∶1,振荡时间3min,pH=1.5。四级逆流萃取后,水相中钙质量浓度低于0.05g/L。     

Calcium waves in a model with a random spatially discrete distribution of Ca2+ release sites

We study the propagation of intracellular calcium waves in a model that features Ca2+ release from discrete sites in the endoplasmic reticulum membrane and random spatial distribution of these sites. The results of our simulations qualitatively reproduce the experimentally observed behavior of the waves. When the level of the channel activator inositol trisphosphate is low, the wave undergoes fragmentation and eventually vanishes at a finite distance from the region of initiation, a phenomenon we refer to as an abortive wave. With increasing activator concentration, the mean distance of propagation increases. Above a critical level of activator, the wave becomes stable. We show that the heterogeneous distribution of Ca2+ channels is the cause of this phenomenon.     

Serotonin directly stimulates luteinizing hormone-releasing hormone release from GT1 cells via 5-HT7 receptors

Effects of brief treatment of growth factors on the urogenital sinus of embryonic rats were investigated and it was found that 8 hour-treatment in the beginning of 5-day cultivation with the epidermal growth factor (EGF) or transforming growth factor-alpha (TGF-alpha) can provoke prostatic bud formation, in the medium deprived of androgens.     

Soybean agglutinin stimulated cholecystokinin release from cultured rabbit jejunal cells requires calcium influx via L-type calcium channels

We have studied the mechanism of soybean agglutinin (SBA) mediated cholecystokinin (CCK) release in enriched cultured cholecystokinin-secreting cells. 12-O-Tetradecanoylphorbol-13-acetate 1 mM significantly stimulated release of CCK-like-immunoreactivity (CCK-LI) by 55%+/-17% (p < 0.05), which was blocked by the protein kinase C inhibitor staurosporine 100 nM. Forskolin 10 mM stimulated CCK-LI by 82%+/-12% (p < 0.05) and this was inhibited by somatostatin 1 nM. 1-Phenylalanine 20 mM and Bay K 8644 1 mM stimulated CCK-LI by 69%+/-22% and 60%+/-19% respectively (p < 0.05), these responses were completely abolished by the L-type calcium channel antagonist verapamil 10 mM. SBA 10 and 100 microg/ml stimulated CCK-LI by 65%+/-22% and 74%+/-24% respectively (p < 0.05). The effect of SBA was inhibited by verapamil and N-acetylgalactosamine. We conclude that SBA stimulates CCK-LI through calcium flux via L-type calcium channels.     

Angiotensin II stimulates cardiac myocyte hypertrophy via paracrine release of TGF-beta 1 and endothelin-1 from fibroblasts

We examined the effects of different cytokine combinations and culture conditions on the expansion and modulation of cell surface antigens of CD34+ derived dendritic cells (DCs), the most efficient antigen-presenting cells capable of stimulating resting T cells in the primary immune response. Cells with a dendritic morphology and expressing HLA-DR, CD1a, S100 and CD83 were maximally expanded under serum-free conditions with the addition of SCF, GM-CSF, TNF-alpha, TGF-beta and Flt-3 ligand (fold increase of CD1a+ cells = 102 +/- 32 after 2 weeks of culture). CD34+ cells were also grown under continuous flow conditions in an artificial capillary system: after 14d of culture, the expansion in the total cell number was lower than that of the static cultures (3.3 +/- 2 v 18.9 +/- 4) but the percentage of CD1a+/CD83+/ CD80+ cells was considerably higher, whereas the CD14+ cells were significantly reduced (8.9 +/- 2 v 26 +/- 13). In continuous perfusion cultures, low levels of DC precursors and of LTC-IC were still present up to day 14. The DCs generated under flow conditions stimulated the mixed leucocyte reaction (MLR) more than the cells grown in static cultures. By electron microscopy, cells grown in the continuous flow system showed an increased number of large cells with numerous dendritic processes and abundant multilamellar complexes. The cells expanded under these conditions were sorted on the basis of their light-scatter properties into two fractions: one containing a predominance of CD1a+/S100+/ CD8 3+/CD80+/CD14- 'large cells' with great internal complexity (mature DCs); the second including 'small cells' either CD33+/CD14+, CD33+/CD15+ or CD33+/CD13-/CD14. The DCs generated and selected with this method are therefore particularly well suited for immunotherapeutic protocols.     

用P507从硫酸镍溶液中萃取分离钙镁的研究

研究了用P507从硫酸镍溶液中萃取分离钙、镁，给出了萃取分离的最佳工艺条件为：温度60摄氏度，水相平衡pH6.00，相比1：1，P507的体积分数10％，皂化率20％，在此条件下，以P507和磺化煤油组成的有机相萃取分离效果较好。     

Estradiol coupling to endothelial nitric oxide stimulates gonadotropin-releasing hormone release from rat median eminence via a membrane receptor

The median eminence (ME), which is the common termination field for adenohypophysiotropic systems, has been shown to produce nitric oxide (NO), a signaling molecule involved in neuroendocrine secretion. Using an ex vivo technique, 17beta-estradiol exposure to ME fragments, including vascular tissues, stimulated NO release within seconds in a concentration-dependent manner, whereas 17alpha-estradiol or testosterone had no effect. 17Beta-estradiol conjugated to BSA (E2-BSA) also stimulated NO release, suggesting mediation by a membrane surface receptor. Tamoxifen, an estrogen receptor inhibitor, antagonized the action of both 17beta-estradiol and E2-BSA. Furthermore, estradiol-stimulated NO stimulates GnRH release. This was demonstrated by hemoglobin (a NO scavenger), N(omega)-nitro-L-arginine methyl ester, and L-N5-(1-iminoethyl)ornithine (nitric oxide synthase inhibitors) inhibition of estradiol stimulated NO and GnRH release. In this regard, L-N5-(1-iminoethyl)ornithine, specific for endotheliol constitutive nitric oxide synthase, was significantly more potent, suggesting that the estradiol-stimulated NO release arose from vascular endothelial cells. Additionally, the NO-stimulated GnRH release occurs via guanylyl cyclase activation in GnRH nerve terminals, as ODQ, a potent and selective inhibitor of NO-sensitive guanylyl cyclase, abolished the estradiol-stimulated GnRH release. The results suggest that at physiological concentrations, 17beta-estradiol may have immediate actions on ME endothelial cells via nongenomic signaling pathways leading to NO-stimulated GnRH release.     

Selective Removal of Iron from Low-Grade Ti Ore by Reacting with Calcium Chloride

Metallurgical and Materials Transactions B - Recently, titanium metal production by molten salt electrolysis using CaCl2 as molten salt and TiO2 or rutile (94 to 96&nbsp;pct TiO2) as feedstock...     

Slow release from a coated sphere with a slightly deformed coating

Effects of a slight deformation of the coating film on the concentration distribution and the slow release characteristics of a coated drug particle is theoretically investigated in this work. A perturbation technique is employed for transformation of the deformed spherical problem into a series of concentric spherical problems with the degree of deformation considered as the perturbation parameter. In addition, the governing equations are solved analytically by further restricting the deformation shape function. Results in this study indicate that if the deformation is slight or only the average release rate is of interest, the effects of coating shape deformation are secondary. However, if the deformation is not so small and if the drug diffusivity in the film is low, the shape deformation could have a significant effect on the concentration profiles and/or the release rate from different parts of the particle surface.     

IL-8 release from cultured peripheral blood monocytes of patients with glomerulonephritis

IL-8 is a chemotactic cytokine with proinflammatory and growth-promoting activities. The release of IL-8 was measured in supernatants of cultured peripheral blood monocytes (PBM) that were obtained from patients with glomerulonephritis (GN) and healthy controls. Spontaneous and lipopolysaccharide (LPS)-induced IL-8 release was significantly higher in PBM isolated from patients with IgA nephropathy (IgAN) and membranous nephropathy (MN) compared with normal controls. These results raise the question of whether IL-8 contributes to the ongoing pathogenesis of GN. We cannot relate IL-8 release to clinical and laboratory parameters in IgAN and MN patients. Thus, disease progression in vivo may not be accompanied by increased or sustained IL-8 release.