Buffers
Tromethamine
Bicarbonates
Hydrogen-Ion Concentration
Transcriptional regulation of the esp genes of enterohemorrhagic Escherichia coli. (1/141)
We have determined that the genes encoding the secreted proteins EspA, EspD, and EspB of enterohemorrhagic Escherichia coli (EHEC) are organized in a single operon. The esp operon is controlled by a promoter located 94 bp upstream from the ATG start codon of the espA gene. The promoter is activated in the early logarithmic growth phase, upon bacterial contact with eukaryotic cells and in response to Ca2+, Mn2+, and HEPES. Transcription of the esp operon seems to be switched off in tightly attached bacteria. The activation process is regulated by osmolarity (induction at high osmolarities), modulated by temperature, and influenced by the degree of DNA supercoiling. Transcription is sigmaS dependent, and the H-NS protein contributes to its fine tuning. Identification of the factors involved in activation of the esp operon and the signals responsible for modulation may facilitate understanding of the underlying molecular events leading to sequential expression of virulence factors during natural infections caused by EHEC. (+info)Generation of intracellular pH gradients in single cardiac myocytes with a microperfusion system. (2/141)
This study describes the use of a microperfusion system to create rapid, large regional changes in intracellular pH (pH(i)) within single ventricular myocytes. The spatial distribution of pH(i) in single myocytes was measured with seminaphthorhodafluor-1 fluorescence using confocal imaging. Changes in pH(i) were induced by local external application of NH(4)Cl, CO(2), or sodium propionate. Local application was achieved by simultaneously directing two parallel square microstreams, each 275 microm wide, over a single myocyte oriented perpendicular to the direction of flow. One stream contained the control solution, and the other contained a weak acid or base. End-to-end, stable pH(i) gradients as large as 1 pH unit were readily created with this technique. This result indicates that pH within a single cardiac cell may not always be spatially uniform, particularly when weak acid or base gradients are present, which can occur, for example, in regional myocardial ischemia. The microperfusion method should be useful for studying the effects of localized acidosis on myocyte function, estimating intracellular ion diffusion rates, and, possibly, inducing regional changes in other important intracellular ions. (+info)Augmentation of L-type calcium current by hypoxia in rabbit carotid body glomus cells: evidence for a PKC-sensitive pathway. (3/141)
Previous studies have suggested that voltage-gated Ca(2+) influx in glomus cells plays a critical role in sensory transduction at the carotid body chemoreceptors. The purpose of the present study was to determine the effects of hypoxia on the Ca(2+) current in glomus cells and to elucidate the underlying mechanism(s). Experiments were performed on freshly dissociated glomus cells from rabbit carotid bodies. Ca(2+) current was monitored using the whole cell configuration of the patch-clamp technique, with Ba(2+) as the charge carrier. Hypoxia (pO(2) = 40 mmHg) augmented the Ca(2+) current by 24 +/- 3% (n = 42, at 0 mV) in a voltage-independent manner. This effect was seen in a CO(2)/HCO(3)(-)-, but not in a HEPES-buffered extracellular solution at pH 7.4 (n = 6). When the pH of a HEPES-buffered extracellular solution was lowered from 7.4 to 7. 0, hypoxia augmented the Ca(2+) current by 20 +/- 5% (n = 4, at 0 mV). Nisoldipine, an L-type Ca(2+) channel blocker (2 microM, n = 6), prevented, whereas, omega-conotoxin MVIIC (2 microM, n = 6), an inhibitor of N and P/Q type Ca(2+) channels, did not prevent augmentation of the Ca(2+) current by hypoxia, implying that low oxygen affects L-type Ca(2+) channels in glomus cells. Protein kinase C (PKC) inhibitors, staurosporine (100 nM, n = 6) and bisindolylmaleimide (2 microM, n = 8, at 0 mV), prevented, whereas, a protein kinase A inhibitor (4 nM PKAi, n = 10) did not prevent the hypoxia-induced increase of the Ca(2+) current. Phorbol 12-myristate 13-acetate (PMA, 100 nM), a PKC activator, augmented the Ca(2+) current by 20 +/- 3% (n = 8, at 0 mV). In glomus cells treated with PMA overnight (100 nM), hypoxia did not augment the Ca(2+) current (-3 + 4%, n = 5, at 0 mV). Immunocytochemical analysis revealed PKCdelta-like immunoreactivity in the cytosol of the glomus cells. Following hypoxia (6% O(2) for 5 min), PKCdelta-like immunoreactivity translocated to the plasma membrane in 87 +/- 3% of the cells, indicating PKC activation. These results demonstrate that hypoxia augments Ca(2+) current through L-type Ca(2+) channels via a PKC-sensitive mechanism. (+info)Pore block versus intrinsic gating in the mechanism of inward rectification in strongly rectifying IRK1 channels. (4/141)
The IRK1 channel is inhibited by intracellular cations such as Mg(2+) and polyamines in a voltage-dependent manner, which renders its I-V curve strongly inwardly rectifying. However, even in excised patches exhaustively perfused with a commonly used artificial intracellular solution nominally free of Mg(2+) and polyamines, the macroscopic I-V curve of the channels displays modest rectification. This observation forms the basis of a hypothesis, alternative to the pore-blocking hypothesis, that inward rectification reflects the enhancement of intrinsic channel gating by intracellular cations. We find, however, that residual rectification is caused primarily by the commonly used pH buffer HEPES and/or some accompanying impurity. Therefore, inward rectification in the strong rectifier IRK1, as in the weak rectifier ROMK1, can be accounted for by voltage-dependent block of its ion conduction pore by intracellular cations. (+info)Contributions of protein disulfide isomerase domains to its chaperone activity. (5/141)
Protein disulfide isomerase (PDI), a member of the thioredoxin (Trx) superfamily, consists of five consecutive domains, a-b-b'-a'-c. Domain combinations, AB, A'C, B'A'C and AB-C, and hybrids of PDI domains with Trx, Trx-C and Trx-B'A'C, have been constructed and expressed in Escherichia coli to examine the contributions of PDI domains to its enzyme and chaperone activities. All the combination and hybrid products are considerably less active than intact PDI in their enzyme activities. Recombinant products containing C, at low concentrations, inhibit the reactivation of lysozyme in HEPES buffer, while those without C do not. Only the intact PDI molecule and the hybrid molecule, Trx-B'A'C, but to a much lower level, show general chaperone activity in assisting the reactivation of denatured D-glyceraldehyde-3-phosphate dehydrogenase. It is suggested that all domains of PDI contribute to the binding of target protein for its chaperone activity. (+info)Mechanisms of endothelial cell swelling from lactacidosis studied in vitro. (6/141)
One of the early sequelae of ischemia is an increase of circulating lactic acid that occurs in response to anaerobic metabolism. The purpose of the present study was to investigate whether lactic acidosis can induce endothelial swelling in vitro under closely controlled extracellular conditions. Cell volume of suspended cultured bovine aortic endothelial cells was measured by use of an advanced Coulter technique employing the "pulse area analysis" signal-processing technique (CASY1). The isosmotic reduction of pH from 7.4 to 6.8 had no effect on cell volume. Lowering of pH to 6.6, 6.4, or 6.0, however, led to significant, pH-dependent increases of cell volume. Swelling was more pronounced in bicarbonate-buffered media than in HEPES buffer. Specific inhibition of Na(+)/H(+) exchange by ethylisopropylamiloride completely prevented swelling in HEPES-buffered media. Pretreatment with ouabain to partially depolarize the cells did not affect the degree of acidosis-induced swelling. In bicarbonate-buffered media, the inhibition of transmembrane HCO(3)(-) transport by DIDS reduced swelling to a level comparable with that seen in the absence of bicarbonate ions. Lactacidosis-induced endothelial swelling, therefore, is a result of intracellular pH regulatory mechanisms, namely, Na(+)/H(+) exchange and bicarbonate-transporting carriers. (+info)Regulation of the epithelial Na(+) channel by extracellular acidification. (7/141)
The effect of extracellular acidification was tested on the native epithelial Na(+) channel (ENaC) in A6 epithelia and on the cloned ENaC expressed in Xenopus oocytes. Channel activity was determined utilizing blocker-induced fluctuation analysis in A6 epithelia and dual electrode voltage clamp in oocytes. In A6 cells, a decrease of extracellular pH (pH(o)) from 7.4 to 6.4 caused a slow stimulation of the amiloride-sensitive short-circuit current (I(Na)) by 68.4 +/- 11% (n = 9) at 60 min. This increase of I(Na) was attributed to an increase of open channel and total channel (N(T)) densities. Similar changes were observed with pH(o) 5.4. The effects of pH(o) were blocked by buffering intracellular Ca(2+) with 5 microM 1, 2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid. In oocytes, pH(o) 6.4 elicited a small transient increase of the slope conductance of the cloned ENaC (11.4 +/- 2.2% at 2 min) followed by a decrease to 83.7 +/- 11.7% of control at 60 min (n = 6). Thus small decreases of pH(o) stimulate the native ENaC by increasing N(T) but do not appreciably affect ENaC expressed in Xenopus oocytes. These effects are distinct from those observed with decreasing intracellular pH with permeant buffers that are known to inhibit ENaC. (+info)Binding of dystrophin's tandem calponin homology domain to F-actin is modulated by actin's structure. (8/141)
Dystrophin has been shown to be associated in cells with actin bundles. Dys-246, an N-terminal recombinant protein encoding the first 246 residues of dystrophin, includes two calponin-homology (CH) domains, and is similar to a large class of F-actin cross-linking proteins including alpha-actinin, fimbrin, and spectrin. It has been shown that expression or microinjection of amino-terminal fragments of dystrophin or the closely related utrophin resulted in the localization of these protein domains to actin bundles. However, in vitro studies have failed to detect any bundling of actin by either intact dystrophin or Dys-246. We show here that the structure of F-actin can be modulated so that there are two modes of Dys-246 binding, from bundling actin filaments to only binding to single filaments. The changes in F-actin structure that allow Dys-246 to bundle filaments are induced by covalent modification of Cys-374, proteolytic cleavage of F-actin's C-terminus, mutation of yeast actin's N-terminus, and different buffers. The present results suggest that F-actin's structural state can have a large influence on the nature of actin's interaction with other proteins, and these different states need to be considered when conducting in vitro assays. (+info)HEPES stands for 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid. It is a buffering agent commonly used in biological and medical research, particularly in cell culture media and buffers. HEPES is a zwitterion, meaning it has both positively and negatively charged groups, which allows it to maintain a stable pH in solutions. It is known for its low toxicity and ability to maintain a stable pH over a wide range of temperatures and concentrations. In the medical field, HEPES is often used in cell culture media to maintain optimal growth conditions for cells, and in buffers for various laboratory assays and experiments.
In the medical field, "buffers" typically refer to substances that help regulate the pH of bodily fluids, such as blood and urine. Buffers work by neutralizing excess acid or base in the body, helping to maintain a stable pH level. This is important because many enzymes and other biological processes in the body require a specific pH range in order to function properly. There are several different types of buffers that can be used in the medical field, including bicarbonate buffers, phosphate buffers, and protein buffers. Bicarbonate buffers are the most common type of buffer used in the body, and they are primarily found in the blood and extracellular fluid. Phosphate buffers are also commonly used in the body, and they are found in the blood, urine, and other bodily fluids. Protein buffers are less common, but they can be used in certain medical situations where bicarbonate or phosphate buffers are not effective. In addition to regulating pH, buffers can also be used to treat certain medical conditions, such as acidosis (a condition in which the blood is too acidic) or alkalosis (a condition in which the blood is too alkaline). Buffers may be administered intravenously or orally, depending on the specific condition being treated and the needs of the patient.
Tromethamine, also known as citrate buffer, is a chemical compound used in the medical field as an anticoagulant and acid-base buffer. It is commonly used in blood transfusions to prevent the formation of clots and to maintain the pH balance of the blood. Tromethamine works by donating protons to hydrogen ions in the blood, thereby neutralizing them and preventing the blood from becoming too acidic or too alkaline. It is also used in the treatment of metabolic acidosis, a condition in which the blood becomes too acidic due to an imbalance in the body's acid-base balance.
In the medical field, "Amino Acids, Neutral" refers to a group of amino acids that do not have a charged side chain. These amino acids are called "neutral" because they do not have a positive or negative charge. Examples of neutral amino acids include alanine, glycine, valine, leucine, isoleucine, serine, threonine, cysteine, and proline. Neutral amino acids are important building blocks of proteins and are essential for many bodily functions. They can be obtained from the diet or synthesized by the body.
Bicarbonates, also known as bicarbonate ions or HCO3-, are a type of ion found in the blood and other body fluids. They play an important role in regulating the acid-base balance of the body and maintaining the proper pH of the blood. In the medical field, bicarbonate levels are often measured as part of a routine blood test. Abnormal levels of bicarbonate can indicate a variety of medical conditions, including metabolic acidosis (a condition in which the body produces too much acid), metabolic alkalosis (a condition in which the body produces too little acid), and respiratory acidosis (a condition in which the body is not able to remove enough carbon dioxide from the blood). Bicarbonate is also used in medicine to treat certain conditions, such as metabolic acidosis and respiratory acidosis. It is given intravenously (through a vein) or by mouth in the form of a salt, such as sodium bicarbonate.
'4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid' is a chemical compound that is used in the medical field as a contrast agent for magnetic resonance imaging (MRI) scans. It is also known by its chemical name, Gadodiamide, and is marketed under the brand name Omniscan. Gadodiamide is a paramagnetic contrast agent that enhances the visibility of certain structures in the body on MRI scans. It works by increasing the relaxation time of water molecules in the tissues, which allows for better visualization of the affected area on the MRI image. Gadodiamide is commonly used to diagnose and monitor a variety of medical conditions, including brain and spinal cord disorders, kidney disease, and cardiovascular disease. It is administered intravenously and is generally well-tolerated by most patients. However, like all contrast agents, it can cause some side effects, including headache, nausea, and allergic reactions.
HEPES
Reactive oxygen species production in marine microalgae
HEPPS (buffer)
Yepes
Carbamoyl phosphate synthetase
Tris
MOPS
Diethyl pyrocarbonate
U937 (cell line)
Good's buffers
Embryo culture
PIPES
Cell isolation
MES (buffer)
Potassium simplex optimized medium
Antibiotic-Antimycotic
Tricine
Transfection
NUN buffer
HEPBS
Saline (medicine)
Particle-induced X-ray emission
Hyperpolarized carbon-13 MRI
Minusheet perfusion culture system
List of MeSH codes (D03)
List of MeSH codes (D02)
HBS
Crystallization adjutant
Fixation (histology)
C8H18N2O4S
HEPES - Wikipedia
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Buffer10
- HEPES has the following characteristics: pKa1 (25 °C) = 3 pKa2 (25 °C) = 7.5 Useful pH range = 2.5 to 3.5 or 6.8 to 8.2 HEPES has negligible metal ion binding, making it a good choice as a buffer for enzymes which might be inhibited by metal chelation. (wikipedia.org)
- HEPES is a zwitterionic buffer used to maintain pH of media used in cell cultures. (biospectra.us)
- HEPES is used as a Good's buffer because it has low UV absorptivity, minimal reactivity, stable pH and is soluble in water. (biospectra.us)
- With a function similar to M2, the FHM medium is a modification of KSOM where part of bicarbonate is replaced with HEPES buffer. (sigmaaldrich.com)
- HEPES ( 4-(2-hydroxyethyl)-1-piperazine ethanesulfonic acid ) is a zwitterionic buffer with CAS number 7365-45-9. (whdsbio.cn)
- HEPES is widely used in a variety of biochemical reactions and is used as a buffer reagent in some cell culture media. (whdsbio.cn)
- The final concentration of HEPES buffer is 10-50mmol/L. When applied to cell culture, the general culture medium contains 20mmol/L LHEPES can reach the buffering capacity. (whdsbio.cn)
- In open culture conditions, adding HEPES buffer can prevent the pH from oxidizing in the medium to increase, thereby maintaining the pH at about 7.0. (whdsbio.cn)
- Lung tissue samples were fixed by vascular perfusion with 2.5% glutaraldehyde , 2% paraformaldehyde in 0.1M HEPES buffer. (cdc.gov)
- The cellular pellet was washed and recentrifuged twice in a HEPES* buffer and introduced into the woman's uterus through a catheter placed in her cervix. (cdc.gov)
Sodium1
- Six parasites ont montré une résistance in vitro au stibogluconate de sodium en utilisant le test de détection des amastigotes dans les macrophages J774 murins. (who.int)
Cytotoxic1
- According to related literature, if the HEPES aqueous solution is exposed to ambient light for three hours, cytotoxic hydrogen peroxide (H2O2) will be produced. (whdsbio.cn)
Widely1
- HEPES is widely used in cell culture, largely because it is better at maintaining physiological pH despite changes in carbon dioxide concentration (produced by aerobic respiration) when compared to bicarbonate buffers, which are also commonly used in cell culture. (wikipedia.org)
Exposed to ambient light1
- reported an unwanted photochemical process wherein HEPES catalyzes a reaction with riboflavin when exposed to ambient light to produce hydrogen peroxide. (wikipedia.org)
Media1
- M2 embryo media is a modified Krebs-Ringer solution buffered with HEPES, is commonly used for collection of embryos and when handling them outside the incubator for extended periods of time. (sigmaaldrich.com)
Cells1
- HEPES does not directly supply nutrients to the cells. (whdsbio.cn)
NaCl1
- C1Q solution contains 10mM HEPES and 300mM NaCl, pH 7.2. (prospecbio.com)
Titration2
- Strong acids and strong bases are strong electrolytes, which are completely ionized in aqueous solution and can be directly completed by acid-base titration, but buffers such as CAPS , Bicine, HEPES, etc., usually use potentiometric titration of concentration or content. (whdsbio.cn)
- Most buffers such as CAPS, Bicine, HEPES , etc. are a kind of organic weak acid (except Tris), which can be titrated with sodium hydroxide standard solution (strong electrolyte titration, and some with sodium carbonate titration, but it is weak electrolyte. (whdsbio.cn)
Zwitterionic1
- HEPES is a zwitterionic organic chemical buffering agent commonly used in cell culture media. (jainbiologicals.com)
Specification table1
- Easily compare specifications for HEPES products with the HEPES specification table . (sigmaaldrich.com)
Concentration2
- HEPES is widely used in cell culture, largely because it is better at maintaining physiological pH despite changes in carbon dioxide concentration (produced by aerobic respiration) when compared to bicarbonate buffers, which are also commonly used in cell culture. (wikipedia.org)
- Mechanistically, EPA and DHA supplements in the diet increase the concentration of downstream hydroxylated-EPAs (HEPEs) including 18-HEPE, and hydroxylated-DHAs including 17-HDHA, which are bioactive compounds. (nih.gov)
Ambient1
- reported an unwanted photochemical process wherein HEPES catalyzes a reaction with riboflavin when exposed to ambient light to produce hydrogen peroxide. (wikipedia.org)
Powder1
- Dissolve and adjust pH to 7.3 with HEPES powder. (nibb.ac.jp)
Solutions1
- It is therefore strongly advised to keep solutions containing both HEPES and riboflavin in darkness as much as possible to prevent oxidation. (wikipedia.org)
Applications1
- HEPES has been used in a wide variety of applications, including tissue culture. (sigmaaldrich.com)