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PubMed2005

Factors affecting protein release from microcapsule prepared by liposome in alginate.

A new type of drug delivery system that microcapsule was prepared by liposome in alginate on this paper, bovine serum albumin (BSA) as an model drug. Influences of liposomes composition and multivalent cations on morphology, enveloped rate, integrality and release in vitro from microcapsule were investigated. The results are showed that Ca2+ and Ba2+ made hydrogels form easier than Al3+ and particle size were uniform, circular, but microcapsule prepared by Al3+ was flat circular and easily adhere to each other. Particle size of all microcapsules was 200-300 microm after dryness, measured by vernier calliper. BSA enveloped rate prepared by PC/PG/Chol and Ba2+ was highest, 77.65%, and also correlative to concentration of lipid. At the other hand, Ba2+ microcapsule prepared by liposome in alginate has not an initial burst and have a good performance on delivering protein. Integrality of protein was not destroyed after encapsulated.

Alginates↗
PubMed2002

Barium alginate cell-delivery systems: correlation between technological parameters.

The most recent trends for the development of several in vitro cell cultures have been oriented towards the cell immobilisation in 3-dimensional scaffolds and cell encapsulation. In fact, an important requirement of cell survival is self-assembly in functional communities, in the presence of an artificial extracellular matrix. In our research, a previously described technique for spermatozoa encapsulation was applied to obtain capsules loaded with an opaque agent as a model, and to perform a formulative study. A process variable, barium ion concentration, was correlated to some capsule properties, such as weight, gel thickness, total and core diameter. Ion concentration can be modified to obtain capsules with predictable characteristics.

Alginates↗
PubMed1998

Analytical control of wollastonite for biomedical applications by use of atomic absorption spectrometry and inductively coupled plasma atomic emission spectrometry.

Preliminary in vitro experiments revealed that wollastonite (CaSiO3) is a potentially highly bioactive material that forms a hyroxyapatite (HA) surface layer on exposure to simulated body fluid with an ion concentration, pH and temperature virtually identical with those of human blood plasma. The formation of the HA layer is an essential requirement for an artificial material to be used as bioactive bone substitute. This finding opens up a wide field for biomedical applications of wollastonite. Biomaterials used as implants in the human body require strict control of trace elements and of the toxic species specified in American Society for Testing and Materials F-1185-88 (As, Cd, Hg and Pb) in ceramic hydroxyapatite for surgical implantation. In this work, two types of pseudowollastonite, the high temperature form of wollastonite, were analysed by using cold vapour atomic absorption spectrometry and hydride generation atomic absorption spectrometry, in order to determine the elements stated in the above-mentioned norm, and inductively coupled plasma atomic emission spectrometry to establish the SiO2/CaO ratio of the two materials and analyse for all other impurities introduced by the raw materials and by the processes of synthesis, sintering and grinding. Barium and Mg were especially prominent in raw materials, and Zr, Y, Mg, W, Co and Ni come mainly from the processing.

Barium↗
PubMed1995

Confocal fluorescence microscopy for studying thapsigargin-induced bivalent-cation entry into B cells.

We studied thapsigargin-induced bivalent-cation entry into antigen-specific B cells (TP67.21) with a confocal fluorescence microscope. Confocal fluorescence images of fluo-3-loaded B cells showed that thapsigargin-stimulated Ca2+ signals were transferred not only to the cytoplasm but also to the nucleus. In the absence of external Ca2+ ions, the free Ca2+ concentrations both in the cytosol and in the nucleus declined to basal levels by 5 min after addition of thapsigargin. However, subsequent addition of Ca2+ in the external medium made the fluo-3 (fura-2) fluorescence intensity rise, reflecting the fact that Ca2+ accumulated again in the nucleus as well as in the cytoplasm. Then, we added Ba2+ and Mn2+ instead of Ca2+, because Ba2+ and Mn2+ are known to enter via Ca2+ channels. The addition of Ba2+ and Mn2+ in the external medium quenched the fluo-3 fluorescence both in the nucleus and in the cytoplasm of B cells. This suggested the possibility that the increase in intranuclear Ca2+ after thapsigargin stimulation may come from the cytoplasm, not from the nuclear stores.

Aniline Compounds↗
PubMed2002

Diacylglycerol activates the influx of extracellular cations in T-lymphocytes independently of intracellular calcium-store depletion and possibly involving endogenous TRP6 gene products.

In Jurkat and human peripheral blood T-lymphocytes, 1-oleoyl-2-acetyl-sn-glycerol (OAG), a membrane-permeant analogue of diacylglycerol, activated the influx of Ca(2+), Ba(2+) and Sr(2+). OAG also caused plasma-membrane depolarization in Ca(2+)-free media that was recovered by the addition of bivalent cation, indicating the activation of Na(+) influx. OAG-induced cation influx was (i) mimicked by the natural dacylglycerol 1-stearoyl-2-arachidonyl-sn-glycerol, (ii) not blocked by inhibiting protein kinase C or in the absence of phospholipase C activity and (iii) blocked by La(3+) and Gd(3+). Differently from OAG, both thapsigargin and phytohaemagglutinin activated a potent influx of Ca(2+), but little influx of Ba(2+) and Sr(2+). Moreover, the influx of Ca(2+) activated by thapsigargin and that activated by OAG were additive. Furthermore, several drugs (i.e. econazole, SKF96365, carbonyl cyanide p-trifluoromethoxyphenylhydrazone, 2-aminoethoxy diphenylborate and calyculin-A), while inhibiting the influx of Ca(2+) induced by both thapsigargin and phytohaemagglutinin, did not affect OAG-stimulated cation influx. Transient receptor potential (TRP) 3 and TRP6 proteins have been shown previously to be activated by diacylglycerol when expressed heterologously in animal cells [Hofmann, Obukhov, Schaefer, Harteneck, Gudermann and Schultz (1999) Nature (London) 397, 259-263]. In both Jurkat and peripheral blood T-lymphocytes, mRNA encoding TRP proteins 1, 3, 4 and 6 was detected by reverse transcriptase PCR, and the TRP6 protein was detected by Western blotting in a purified plasma-membrane fraction. We conclude that T-cells express a diacylglycerol-activated cation channel, unrelated to the channel involved in capacitative Ca(2+) entry, and associated with the expression of TRP6 protein.

Barium↗
PubMed1987

Isolation, identification, and synthesis of 2-carboxyarabinitol 1-phosphate, a diurnal regulator of ribulose-bisphosphate carboxylase activity.

The diurnal change in activity of ribulose 1,5-bisphosphate (Rbu-1,5-P(2)) carboxylase [3-phospho-D-glycerate carboxy-lyase (dimerizing); EC 4.1.1.39] of leaves of Phaseolus vulgaris is regulated (in part) by mechanisms that control the level of an endogenous inhibitor that binds tightly to the activated (carbamoylated) form of Rbu-1,5-P(2) carboxylase. This inhibitor was extracted from leaves and copurified with the Rbu-1,5-P(2) carboxylase of the leaves. Further purification by ion-exchange chromatography, adsorption to purified Rbu-1,5-P(2) carboxylase, barium precipitation, and HPLC separation yielded a phosphorylated compound that was a strong inhibitor of Rbu-1,5-P(2) carboxylase. The compound was analyzed by GC/MS, (13)C NMR, and (1)H NMR and shown to be 2-carboxyarabinitol 1-phosphate [(2-C-phosphohydroxymethyl)-D-ribonic acid]. Verification of structure was obtained by comparison of the inhibitory activity of the isolated compound with that of 2-carboxy-D-arabinitol 1-phosphate synthesized in vitro. This compound (but not 2-carboxy-D-arabinitol 5-phosphate) inhibited Rbu-1,5-P(2) carboxylase in a way that was kinetically identical to that of the isolated, naturally occurring compound. The structure of the isolated compound differs from the Rbu-1,5-P(2) carboxylase transition-state analogue 2-carboxyarabinitol 1,5-bisphosphate only by the lack of the C-5 phosphate group. This difference results in a higher binding constant for the monophosphate (K(d) = 32 nM) compared with the bisphosphate (K(d) < 10 pM). The less tightly bound compound acts in a light-dependent, reversible regulation of Rbu-1,5-P(2) carboxylase activity in vivo.

Journal Article↗
PubMed1985

Reflux esophagitis: an update.

In recent years, much has been learned about the pathogenesis, diagnosis, and treatment of gastroesophageal (GE) reflux disease. Mucosal resistance, gastric contents, esophageal acid clearance, gastric emptying, and incompetency of the lower esophageal sphincter are contributing factors to GE reflux. Use of the various diagnostic tests and an overview of current therapy are summarized.

Alginates↗
PubMed2003

Rho-dependent kinase is involved in agonist-activated calcium entry in rat arteries.

The present study was aimed at investigating whether, besides its pivotal role in Ca(2+)-independent contraction of smooth muscle, Rho-kinase is involved in the mechanisms underlying the Ca2+ signal activated by noradrenaline in arteries. In rat aorta and mesenteric artery, the Rho-kinase inhibitor Y-27632 (10 microM) completely relaxed the contraction evoked by noradrenaline (1 microM) and simultaneously inhibited the Ca2+ signal by 54 +/- 1 % (mesenteric artery) and 71 +/- 15 % (aorta), and the cell membrane depolarisation by 56 +/- 11 % (mesenteric artery). A similar effect was observed in arteries contracted by AlF4-, while in KCl-contracted arteries, Y-27632 decreased tension without changing cytosolic Ca2+. The same effects were observed with another inhibitor of Rho-kinase (HA1077) but not with an inhibitor of protein kinase C (Ro-31-8220). Effects of Y-27632 were not prevented by incubating the artery in 25 mM KCl, with K+ channel blockers or with the Ca2+ channel blocker nimodipine. Y-27632 did not affect either the increase in the production of inositol phosphates activated by noradrenaline, or the release of Ca2+ from non-mitochondrial stores evoked by InsP3 in permeabilised aortic cells, or the Ca2+ signals evoked by thapsigargin or caffeine. The capacitative Ca2+ entry activated by thapsigargin was not impaired by Y-27632, but the entry of Ba2+ activated by noradrenaline in the presence of nimodipine was blocked by 10 microM Y-27632. These results indicate that Rho-kinase is involved in noradrenaline activation of a Ca2+ entry distinct from voltage- or store-operated channels in rat arteries.

Aluminum Compounds↗
PubMed2000

Prototypical imidazoline-1 receptor ligand moxonidine activates alpha2-adrenoceptors in bulbospinal neurons of the RVL.

Moxonidine is an antihypertensive drug that lowers sympathetic vasomotor tone by stimulating either alpha2-adrenergic (alpha2-AR) or imidazoline I1 receptors within the rostral ventrolateral medulla (RVL). In this study, we investigated the effects of moxonidine (10 microM) on RVL neurons in brain stem slices of neonatal rats. We recorded mainly from retrogradely labeled RVL bulbospinal neurons (putative presympathetic neurons) except for some extracellular recordings. Prazosin was used to block alpha1-adrenoceptors. Moxonidine inhibited the extracellularly recorded discharges of all spontaneously active RVL neurons tested (bulbospinal and unidentified). This effect was reversed or blocked by the selective alpha2-AR antagonist SKF 86466 (10 microM). In contrast, the I1 imidazoline ligand AGN 192403 (10 microM) had no effect on the spontaneous activity. In whole cell recordings (holding potential -70 mV), moxonidine produced a small and variable outward current (mean 7 pA). This current was observed in both tyrosine hydroxylase-immunoreactive and other bulbospinal neurons and was blocked by SKF 86466. Excitatory postsynaptic currents (EPSCs) evoked by focal electrical stimulation were isolated by incubation with gabazine and strychnine, and inhibitory postsynaptic currents (IPSCs) were isolated with 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). Moxonidine reduced the amplitude of the evoked EPSCs (EC(50) = 1 microM; 53% inhibition at 10 microM) but not their decay time constant (5.6 ms). The effect of moxonidine on EPSCs persisted in barium (300 microM) and was reduced approximately 80% by SKF 86466. Moxonidine also reduced the amplitude of evoked IPSCs by 63%. In conclusion, moxonidine inhibits putative RVL presympathetic neurons both presynaptically and postsynaptically. All observed effects in the present study are consistent with an alpha2-AR agonist activity of moxonidine.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1982

Gastroesophageal reflux. Pathogenesis, diagnosis, and therapy.

In recent years, considerable new information has become available on the pathogenesis, diagnosis and therapy of gastroesophageal reflux. Gastric contents, mucosal resistance, esophageal acid clearance, and gastric emptying are now recognized, along with incompetency of the lower esophageal sphincter, as contributing factors to gastroesophageal reflux disease. The potential tests for reflux are reviewed and the diagnostic accuracy of each is evaluated. A diagnostic approach to the patient with reflux symptoms is outlined that considers the sensitivity and specificity of these various tests as well as their availability to the generalist and gastrointestinal specialist. Finally, an overview of the current therapy for reflux disease summarizes the controlled studies in the medical literature.

Alginates↗
PubMed1998

Heterogeneous distribution of soluble guanylate cyclase in the pulmonary vasculature of the fetal lamb.

BACKGROUND: Vascular segments in the fetal lung differ anatomically and functionally from one another. At birth, the nitric oxide (NO) pathway plays an integral role in reducing pulmonary vascular resistance through a marked vasodilation. However, the contributions of each vascular segment to this dilation are unclear. We sought to determine the distribution of soluble guanylate cyclase (sGC), the enzyme NO activates to induce vasodilation across the pulmonary vasculature. METHODS: Pulmonary airspaces were expanded with freezing compound and the pulmonary arterial tree was infused with barium sulfate gelatin. Soluble guanylate cyclase was localized by immunohistochemistry across the pulmonary vasculature of four near-term fetal lambs and its immunoreaction product was assessed by a semiquantitative method. The physiologic response of fourth- and fifth-generation arteries and veins isolated from age-matched lambs to NO was measured using standard tissue bath techniques. RESULTS: Clear differences in sGC immunostaining were present throughout the pulmonary vasculature: very weak to absent in large arteries accompanying bronchi, but intensely positive for veins. This pronounced staining for sGC in preacinar veins correlated with a 100-fold greater sensitivity to NO in veins compared to arteries of the same generation. The percentage of arteries staining positively approached 100% at the level of respiratory bronchioles and alveoli. CONCLUSIONS: These findings suggest that the increased response to NO in preacinar veins compared to that of arteries is in part due to increased sGC within venous vascular smooth muscle. Furthermore, intense staining within distal arteries implies a greater role for NO-mediated vasodilation within these segments.

Animals↗
PubMed2002

The ordered hydrocerussite-type structure of (PbCO3)2.BaF2.

Single crystals of synthetic (PbCO(3))(2).BaF(2), bis[lead(II) carbonate] barium difluoride, have been grown under hydrothermal conditions. The compound crystallizes in the ordered hydrocerussite [(PbCO(3))(2).Pb(OH)(2)] structure and can be derived from a close packing of the metal atoms with a stacking sequence of [c(h)(2)](3) along the c axis. O and F atoms are situated approximately in the tetrahedral voids, resulting in the formation of a slightly distorted [BaF(6)O(6)] icosahedron and a [1+6+3]-coordinate Pb atom, with one short bond to F, six bonds to O and three longer bonds to additional O atoms. The carbonate group deviates only slightly from the geometry of an equilateral triangle.

Journal Article↗