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PubMedDate not supplied

Solubility of lead as lead (II) chloride in HEPES-Ringer and artificial seawater (Ca-ASW) solutions.

Total dissolved Pb was measured in a number of commonly used physiological solutions by electrothermal atomization atomic absorption spectrometry (ETA-AAS). In HEPES-buffered solutions (pH 7.30) the concentration of total Pb in solution ("measured" Pb) was only 77% of nominal Pb up to 20 microM added Pb, where experiments were undertaken at room temperature (22 +/- 1 degree C). However, test solutions equilibrated at 37 +/- 1 degree C contained 99% of added Pb up to 2 microM. Above this nominal concentration, percentage recoveries dropped to approximately 72% at a nominal concentration of 20 microM. Tris-buffered artificial seawater (CaASW) solutions (pH 7.60) contained more dissolved Pb compared to HEPES-buffered solutions at 22 degrees C. However, increasing the calcium concentration in ASW appeared to increase precipitation of PbCl2. Concentration-corrected dose-response relationships were plotted from previously published data on the effects of Pb on voltage-activated calcium channels of rat dorsal root ganglion (DRG) cells and Aplysia neurons. The plots suggest that the inhibitory effects of Pb on rat DRG cells may prevail at concentrations of Pb even lower than reported previously when measurements were made at 22 degrees C. However, increasing the temperature to 37 degrees C resulted in closer agreement between measured and nominal dose-response curves. The measured dose-response curves for the Tris-buffered ASW solutions closely followed those of the nominal up to 200 microM Pb. In ASW solutions containing 40 mM calcium, PbCl2 was precipitated at Pb concentrations greater than 200 microM.

Animals↗
PubMed1980

HEPES buffered media may induce prostaglandin release from macrophages in tissue culture.

On investigating the release of PGE2 from mouse peritoneal macrophages in tissue culture it was found that the spontaneous release of PGE2 was dependent on the culture conditions employed. The type of buffering of the medium was especially important. Using CO2- sodium bicarbonate buffers we observed little, if any, spontaneous release of prostaglandins (PGs) from macrophages, whereas in the presence of N-2-hydroxyethylpiperazine-N-2-ethane-sulfonic acid (HEPES) buffer in some cases a dramatic increase in PG release was observed.

Buffers↗
PubMed1991

Factors influencing survival of mammalian cells exposed to hypothermia. V. Effects of hepes, free radicals, and H2O2 under light and dark conditions.

Cytotoxicity resulting from the interaction of fluorescent light from a flow hood with Hepes-buffered cell culture medium at room temperature was demonstrated. Toxicity was prevented by keeping both cells (V79 Chinese hamster) and medium shielded from direct fluorescent light ("dark conditions") or by supplementing the medium with 10 micrograms/ml catalase; this suggests that extracellular hydrogen peroxide is a major cause of the lethal effect under "lighted conditions." No sensitization resulted from the exposure of cells in a sodium bicarbonate (SBC)-buffered medium to fluorescent light, nor in a catalase supplemented SBC-buffered medium. The Hepes/light reaction during routine cell manipulations presensitized cells to hypothermia damage in the dark with the presensitization being more severe for 5 than for 10 degrees C hypothermic exposure. Presensitization was prevented by performing the complete experiment under dark conditions or by supplementing the medium with 10 micrograms/ml catalase. However, catalase did not improve the hypothermic survival when experiments were performed under dark conditions. Hence, 10 micrograms/ml catalase does not protect cells from hypothermic (5 and 10 degrees C) damage per se, but rather from Hepes/light sublethal damage which interacts with hypothermic sublethal damage to result in lethal lesions. Additionally, under dark conditions, superoxide dismutase (SOD), allopurinol, catalase plus SOD, DMSO, or mannitol did not improve survival when present during hypothermic storage, suggesting that extracellular superoxide anion, hydrogen peroxide, or hydroxyl radicals are not the cause of cell killing under conditions of pure hypothermia uncomplicated by prehypothermic ischemia or hypoxia.

Animals↗
PubMed1985

Triethanolamine, tris, hepes, and cytosine arabinoside show neuritogenic activity in cultured chick embryo ganglia.

Neuritogenesis, which occurs to a slight extent in chick embryo ganglia maintained under standard conditions and which is maximally stimulated by nerve growth factor, also was enhanced by presence in the medium of buffers (triethanolamine, Tris, and Hepes) and cytosine arabinoside and by the passage of direct electric current. The major effect of the buffers probably was to remove protons from cell membranes, that of the current to produce accelerated movement of ions through membranes of the ganglionic cells, and that of cytosine arabinoside to decrease the numbers of nonneural cells by inhibiting DNA synthesis. The buffers were neuritogenically ineffective on nerve growth factor-sensitive PC12 pheochromocytoma cells in culture. Media from ganglia in which triethanolamine or passage of electric current had elicited outgrowth of neurites produced no observable effect on PC12 cells under our experimental conditions. Current data fit the hypothesis that, whereas nerve growth factor exerts direct neuritogenic effects on neurons, the other treatments affect neural-nonneural interactions, possibly by way of gap junctions or changes in direct physical contact, so as to disinhibit inherent neural neuritogenic potential and/or to stimulate it.

Animals↗
PubMed1984

Efficacy of five methods for the bound-free separation of gluco- and mineralocorticoids from type I, II and III receptors found in hepes- and tris-buffered mouse brain cytosol.

We compared the efficacy of G-25 and LH-20 column chromatography, dextran-coated charcoal adsorption, and DEAE-cellulose and glass fiber filter disc assays to separate unbound steroids from three classes of brain cytosolic receptors prepared in HEPES and TRIS buffers and labeled selectively as follows: Type I = [3H]aldosterone + unlabeled RU26988, Type II = [3H]triamcinolone acetonide and Type III = [3H]corticosterone + unlabeled Prorenone and RU26988. Prorenone and RU26988 were added to reduce unwanted [3H]steroid binding to Type I and Type II receptors, respectively. In each case total, non-specific and specific binding and free steroid were compared individually. No single assay was found to be best for all three receptor classes, but both buffers and most assays could be used with appropriate correction factors. Variations between the results with different assays suggest fundamental differences between the three classes of adrenosteroid receptors and their ligands.

Adsorption↗
PubMed1991

Contrasting effects of HEPES vs HCO3(-)-buffered media on whole-cell currents in cultured chemoreceptors of the rat carotid body.

In this study we compared the effects of physiological bicarbonate/CO2-buffered media (BBM) with the commonly used N-2-hydroxyethylpiperazine-N'-2-ethane-sulfonic acid (HEPES)-buffered media (HBM) on whole-cell currents in cultured rat arterial chemoreceptors (i.e. glomus cells) using the perforated-patch technique. Two separate effects were observed on switching from HBM to BBM. First, in the majority of cells tested (31 of 36) there was an increase in the leakage conductance (ca. 5 fold) and a concomitant increase in channel noise, which in preliminary studies appears to arise from the opening of large-conductance anion channels. Second, there was a reversible decrease in voltage-activated outward K+ current which we attribute to cytoplasmic acidification, catalysed by carbonic anhydrase in glomus cells.

Animals↗
PubMed1991

Comparison of bicarbonate and HEPES-buffered media on pregnancy rates after intrauterine insemination with cryopreserved donor sperm.

OBJECTIVE: We compared the pregnancy rates (PRs) after intrauterine insemination (IUI) with frozen donor sperm prepared in Ham's F-10 medium (Irvine Scientific, Santa Ana, CA) with bicarbonate buffer and synthetic human tubal fluid with HEPES buffer (Irvine Scientific). DESIGN: Women (n = 101) were randomized upon entry into the program, receiving sperm prepared in either Ham's F-10 or human tubal fluid medium their first treatment cycle. If pregnancy did not occur, the alternate medium was used to prepared sperm for the following cycle. SETTING: All patients were treated in our private care center. PATIENTS: Patients entering this study were normally ovulating women undergoing IUI with frozen donor sperm. MAIN OUTCOME MEASURE: Pregnancy was used as our main outcome measure of success. RESULTS: After 324 cycles of treatment, the PR per cycle of IUI was 17.5% with sperm prepared in human tubal fluid which was significantly different (P = 0.05) from the PR (9.8%) after insemination with sperm prepared in Ham's F-10. There was no statistical difference in the number of motile cells inseminated in each of these groups. CONCLUSIONS: Transitory exposure of the sperm in Ham's F-10 medium to the environment during preparation for insemination may result in an alkalinization of the medium that has a lasting influence on sperm fertility.

Bicarbonates↗
PubMed1987

Inhibition of carbamoyl-phosphate synthase (ammonia) by Tris and Hepes. Effect on Ka for N-acetylglutamate.

The apparent Ka for N-acetylglutamate of rat liver carbamoyl-phosphate synthase is 11 microM in phosphate buffer, a value 10-fold lower than reported in other buffer systems. Tris and Hepes inhibit competitively with N-acetylglutamate. The proportion of carbamoyl-phosphate synthase in the active enzyme-acetylglutamate complex in vivo may be higher than previous calculations suggest, which re-opens the question of the involvement of N-acetylglutamate in the regulation of urea synthesis.

Animals↗
PubMed2002

HOPE--a new fixing technique enables preservation and extraction of high molecular weight DNA and RNA of > 20 kb from paraffin-embedded tissues. Hepes-Glutamic acid buffer mediated Organic solvent Protection Effect.

The growing number of molecular pathologic tools that are currently available require material with good long term preservation of morphology, nucleic acids, and antigenic structures. However, pathologic investigations of tissues done at a molecular level are often hampered by the fixatives in use. We thus endeavored to design a new fixing system, including subsequent paraffin-embedding and sectioning, that makes complete pathologic analyses possible, with special consideration of immunohistochemistry (IHC), in situ hybridization (ISH), and molecular pathology. The optimized HOPE (Hepes-Glutamic acid buffer mediated Organic solvent Protection Effect) fixing technique allows us to preserve and extract high molecular weight DNA and RNA of > 20 kbp suitable for downstream applications, such as PCR and RT-PCR from HOPE-fixed, paraffin-embedded tissues that are up to 5 years old. This technique will most probably lead to new impacts on molecular pathology.

Cross-Linking Reagents↗
PubMed1987

Blockage of chloride channels by HEPES buffer.

Chloride channels of neurons of Drosophila are blocked when the cytoplasmic side of the membrane is exposed to the commonly used buffering agents 4-(2-hydroxyethyl)-1-piperazine ethanesulphonic acid (HEPES) and 4-morpholinepropanesulphonic acid (MOPS). In the presence of these compounds, chloride channels appear to function as a complex of multiple protochannels.

Animals↗
PubMed1987

Iron autoxidation in Mops and Hepes buffers.

Iron autoxidation in Mops and Hepes buffers is characterized by a lag phase that becomes shorter with increasing FeCl2 concentration and pH. During iron oxidation in these buffers a yellow colour develops in the solution. When the reaction is conducted in the presence of nitro blue tetrazolium (NBT), blue formazan is formed. Of the many OH scavengers tested, mannitol and sorbitol are most effective in inhibiting Fe2+ oxidation, yellow colour development and NBT reduction. Some inhibition was also noted with catalase. The iron product of the oxidative reaction differs from Fe3+ in its absorption spectrum and its low reactivity with thiocyanate. Similar results are obtained when iron autoxidation is studied in unbuffered solutions brought to alkaline pH with NaOH. In phosphate buffer, no lag phase is evident and the absorption spectrum of the final solution is identical to that of Fe3+ in this buffer. The iron product reacts immediately with thiocyanate. When iron oxidation is conducted in the presence of NBT the formation of formazan is almost undetectable. Of the many compounds tested only catalase inhibits iron autoxidation in this buffer. The sequence of reactions leading to iron autoxidation in Good-type buffers thus resembles that occurring in unbuffered solutions brought to alkaline pH with NaOH and greatly differs from that occurring in phosphate buffer. These results are in agreement with the observation that these buffers have very low affinity for iron. The data presented define experimental conditions where Fe2+ is substantially stable for a considerable length of time in Mops buffer.

Buffers↗
PubMedDate not supplied

[Repair of the nucleoid of sarcoma 37 cells in vitro or in vivo. The effect of HEPES buffer].

The method of sedimentation was used to study the repair of Sarcoma 37 cell nucleoid after irradiation of cells in vitro or after irradiation of mice with a dose of 9 Gy. It was shown that the process of repair in vitro was completed after 10 min of incubation of cells in the nutrient medium while the repair in vivo ceased 120 min after irradiation. In the presence of HEPES buffer (20 mM) in the medium the kinetics of the nucleoid repair in cells incubated in vitro was the same as that in vivo.

Animals↗
PubMed1981

Reversible ultrastructural changes in human fibroblasts grown in hepes buffered MCDB-104 supplemented with human serum.

Prolonged maintenance of human dermal fibroblasts in MCDB-104 medium supplemented with pooled human serum or platelet factor deficient preparations of human serum led to appearance of a large number of membrane bound inclusions, resembling lysosomes, and proliferation of small, Golgi associated vesicles. These inclusions did not appear if the cells were grown in Dulbecco-Vogt's modification of Eagle's minimal essential medium or in minimal essential medium supplemented with the same human serum fractions. Cells that acquired inclusions during a 10 d incubation in MCDB-104 subsequently lost these inclusions when transferred to Dulbecco'Vogt's medium for 4 d. Similar reversal of effects of MCDB-104 was also produced by MCDB-104 buffered with bicarbonate instead of HEPES.

Adult↗
PubMed1995

Social aspects of malaria in Heping, Hainan.

This paper presents findings from a study conducted in Heping Town, Qiongzhong County, Hainan Province, China. The study, conducted in 1992, used qualitative as well as quantitative methods to gather social, cultural and behavioural data associated with the acquisition, transmission and prevention of malaria, and the diagnosis and treatment of disease. These methods included focus groups, key informant and other in-depth interviews, and observations, a household survey and tests of school children of knowledge of malaria. The study is among the first to our knowledge that has utilized this broad mix of methods for tropical disease research in China.

Adolescent↗
PubMed2004

The microstructural study of thermal treatment montmorillonite from Heping, China.

The montmorillonite samples from Heping, China had been studied by chemical analysis, DAT, TG, XRD and MAS NMR. The results showed that the hydroxyl in octahedra sheets begins dehydrating, when the thermal treatment temperature reaches 650 degrees C, but the layer structure remains, the corresponding Al(VI) was turned into Al(IV) in octahedra sheets. When the temperature reaches 900 degrees C, the layer structure of montmorillonite is destroyed, and the new mineral phase mu-cordierite is found. When the temperature reaches 1200 degrees C, the mu-cordierite phase loses stability, and decomposes into cristobalite phase and mullite phase, meanwhile, the recrystallization phenomena in thermal treatment products is obvious. There is a small quantity of Al(VI) signal in MAS NMR spectrum, this Al(VI) corresponds to the Al of mullite. When the temperature reaches 1350 degrees C, the cristobalite and mullite phases reduce slightly, and more Fe-cordierite phase appear. There is corresponding Fe-cordierite spectrum in XRD and MAS NMR.

Bentonite↗
PubMed2005

The relationship between acidic activation and microstructural changes in montmorillonite from Heping, China.

The montmorillonite sample from Heping, China had been studied by chemical analysis, XRD, IR, AFM and MAS NMR. The results showed that acid concentration had much influence on surface structure of montmorillonite. When the acid concentration reached 2M, the Q3Si structure in silica-oxygen tetrahedron recombined, some Q3Si structure in montmorillonite transformed to distortion Q3Si structure and Q4Si structure. However, the structure of Al had no changes, according with the observation results of atomic force microscope. The Brønsted acid site of montmorillonite increases with the accretion of the concentration of acid activation, while oversize concentration of acid activation will decrease the surface site of montmorillonite.

Acids↗