Nitric Acid: Nitric acid (HNO3). A colorless liquid that is used in the manufacture of inorganic and organic nitrates and nitro compounds for fertilizers, dye intermediates, explosives, and many different organic chemicals. Continued exposure to vapor may cause chronic bronchitis; chemical pneumonitis may occur. (From Merck Index, 11th ed)Spectrophotometry, Atomic: Spectrophotometric techniques by which the absorption or emmision spectra of radiation from atoms are produced and analyzed.Neodymium: Neodymium. An element of the rare earth family of metals. It has the atomic symbol Nd, atomic number 60, and atomic weight 144.24, and is used in industrial applications.Decalcification Technique: Removal of minerals from bones during bone examination.Hydrofluoric Acid: Hydrofluoric acid. A solution of hydrogen fluoride in water. It is a colorless fuming liquid which can cause painful burns.Sulfuric Acids: Inorganic and organic derivatives of sulfuric acid (H2SO4). The salts and esters of sulfuric acid are known as SULFATES and SULFURIC ACID ESTERS respectively.Trace Elements: A group of chemical elements that are needed in minute quantities for the proper growth, development, and physiology of an organism. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Hydrochloric Acid: A strong corrosive acid that is commonly used as a laboratory reagent. It is formed by dissolving hydrogen chloride in water. GASTRIC ACID is the hydrochloric acid component of GASTRIC JUICE.Nitrates: Inorganic or organic salts and esters of nitric acid. These compounds contain the NO3- radical.Microwaves: That portion of the electromagnetic spectrum from the UHF (ultrahigh frequency) radio waves and extending into the INFRARED RAYS frequencies.Calibration: Determination, by measurement or comparison with a standard, of the correct value of each scale reading on a meter or other measuring instrument; or determination of the settings of a control device that correspond to particular values of voltage, current, frequency or other output.Environmental Monitoring: The monitoring of the level of toxins, chemical pollutants, microbial contaminants, or other harmful substances in the environment (soil, air, and water), workplace, or in the bodies of people and animals present in that environment.

*  Water, sulfur dioxide and nitric acid adsorption on calcium carbonate: A transmission and ATR-FTIR study - Physical Chemistry...
... sulfur dioxide and nitric acid on CaCO p ... Water, sulfur dioxide and nitric acid adsorption on calcium ... sulfur dioxide and nitric acid react with the Ca(OH)(CO3H) surface to form adsorbed carbonic acid (H2CO3) along with sulfite ... there is no additional uptake of gas-phase sulfur dioxide and nitric acid. However, upon adsorption of water, carbonic acid ... The adsorbed water film assists in the enhanced uptake of sulfur dioxide and nitric acid on CaCO3 in several ways. Under dry ...
  http://pubs.rsc.org/en/Content/ArticleLanding/2005/CP/b417872f
*  Indian Patents. 200932:AN IMPROVED PROCESS FOR THE PRODUCTION OF NITRIC ACID
... of the nitric acid to be concentrated with nitric acid, preferably a nitric acid in the concentration range of the nitric acid ... of the nitric acid to be concentrated with nitric acid, preferably a nitric acid in the concentration range of the nitric acid ... of the nitric acid to. be concentrated with nitric acid, preferably a nitric acid in the. concentration range of the nitric ... the nitric acid to be concentrated with a nitric acid in a concentration. 27. range of the nitric acid in a concentration range ...
  http://www.allindianpatents.com/patents/200932-an-improved-process-for-the-production-of-nitric-acid
*  Sunchemicals in Coimbatore; Sun Chemicals is the leading Dealers of comprises Hydrochloric Acid, Sulphuric Acid, Nitric Acid,...
Sulphuric Acid, Nitric Acid, Phosphoric Acid, Hydrogen Peroxide and many more.; Get Latest Updates and offers, Contact, Address ... Sun Chemicals is the leading Dealers of comprises Hydrochloric Acid, ... Sunchemicals Sun Chemicals is the leading Dealers of comprises Hydrochloric Acid, Sulphuric Acid, Nitric Acid, Phosphoric Acid ... Sun Chemicals is the leading Dealers of comprises Hydrochloric Acid, Sulphuric Acid, Nitric Acid, Phosphoric Acid, Hydrogen ...
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*  Tresorie - NITRIC ACID [Nitric Acid]
NITRIC ACID [Nitric Acid]. HEAL THYSELF (The Homoeopathic World) A Popular Journal of Medical, Dietetic, Social and Sanitary ... Nitric acid will benefit him for a time, and again he may need Calcarea. Nitric acid and Calcarea antidote each other, but it ... Nitric acid cured him. The tissues will not heal, there is no repair going on. Full of rheumatic pains and aches. The pains ... Coffea and Nux are just as sensitive, and I think of these as well as Nitric acid when I see tan bark in front of a house. ...
  http://homeoint.org/hompath/articles/743.html
*  Nitric acid with calcium carbonate / Neurontin lawsuit 2008
Nitric acid with calcium carbonate. Other acids such as citric acid and nitric acid can be used, but they are more expensive. ... acid (the primary acid component of acid rain). calcium carbonate and sulfuric acid.Reaction of aqueous solutions of nitric ... Nitric Acid Phenolphthalein Phosphoric Acid Potassium Hydroxide.. Carbonate Acid Reaction. Chemistry guide. July 11,. marble ... include hydrochloric acid, sulfuric acid, nitric.Designed capacity of this plant is 1,500 MT per day of Calcium Ammonium ...
  http://1-lorddl.tk/pupo/nitric-acid-with-calcium-carbonate-wuj.php
*  nitric acid - Chemistry
Nitric acid HNO3. The molecular weight is 63.01. The melting point is -50o F. The boiling point is anywhere between 181-245o F. Nitric acid is in a liquid state at room temperature.. It is molecular.. The molecular geometry is a triganal planar.. Some uses of this molecule is. ...
  http://fearschemistry.wikidot.com/nitric-acid
*  white fuming nitric acid Manufacturers, Suppliers & Exporters in India
Contact to white fuming nitric acid Exporters in India, white fuming nitric acid Wholesalers, white fuming nitric acid ... Search Indian white fuming nitric acid Manufacturers and Suppliers Details - ... Gayatri Acid & Chemical Company Deals in Nitric Acid, fuming nitric acid, acids and acid chemicals such as sulfuric, acid ... white fuming nitric acid, Nitric Acid, Leather chemicals, Concentrated Nitric Acid, Sulphuric Acid, Acetic Acid Glacial, ...
  http://www.indianyellowpages.com/india/manufacturers/w/white-fuming-nitric-acid.htm
*  Validation of nitric acid retrieved by the IMK-IAA processor from MIPAS/ENVISAT measurements
The stratospheric nitric acid (HNO(3)) from September 2002 to March 2004 was retrieved from the MIPAS observations using the ... Validation of nitric acid retrieved by the IMK-IAA processor from MIPAS/ENVISAT measurements. D.Y. Wang ; M. Höpfner ; G. ... The stratospheric nitric acid (HNO(3)) from September 2002 to March 2004 was retrieved from the MIPAS observations using the ... The stratospheric nitric acid (HNO(3)) from September 2002 to March 2004 was retrieved from the MIPAS observations using the ...
  http://publications.lib.chalmers.se/publication/62914-validation-of-nitric-acid-retrieved-by-the-imk-iaa-processor-from-mipasenvisat-measurements
*  Johnson Matthey Catalysts - Education - Industrial Catalysis - Nitric Acid
Manufacture of nitric acid. The manufacture of nitric acid is a three-stage process. The first stage is the oxidation of ...
  http://resources.schoolscience.co.uk/johnsonmatthey/page8.htm
*  Check what does nitric acid mean | Funkandwagnalls.com
On our website you can check the various meanings of nitric acid with usage examples! ... See dictionary definition of nitric acid at Funkandwagnalls.com. ... nitric acid. Part of speech: A colorless, highly corrosive ...
  http://www.funkandwagnalls.com/nitric-acid
*  Process for obtaining nitric acid of a concentration higher than the azeotropic concentration by means of the absorption of...
... means of a cycle of diluted nitric acid which is decomposed by the action of the NO contained in the gases, enriching them in ... absorption of nitrogen oxides in water or diluted nitric acid and the partial pressure of the nitrogen oxides before absorption ... The present invention relates to a process for obtaining nitric acid of a concentration higher than the azeotropic ... Process for obtaining nitric acid of a concentration higher than the azeotropic concentration by means of the absorption of ...
  http://www.patentgenius.com/image/4064221-2.html
*  Solution - Concentrated nitric acid used in laboratory work is 68% nitric acid by mass in aqueous solution - Expressing...
... nitric acid by mass in aqueous solution concept: Expressing Concentration of Solutions. For the courses CBSE (Arts), CBSE ( ... Concentrated nitric acid used in laboratory work is 68% ... Concentrated nitric acid used in laboratory work is 68% nitric ... Solution - Concentrated nitric acid used in laboratory work is 68% nitric acid by mass in aqueous solution - Expressing ... Solution for question: Concentrated nitric acid used in laboratory work is 68% nitric acid by mass in aqueous solution concept ...
  https://www.shaalaa.com/question-bank-solutions/expressing-concentration-solutions-concentrated-nitric-acid-used-lab-work-68-nitric-acid-mass-aqueous-solution_8978
*  HIGHLY EFFICIENT GAS PHASE METHOD FOR MODIFICATION AND FUNCTIONALIZATION OF CARBON NANOFIBRES WITH NITRIC ACID VAPOUR - Patent...
0009] Only highly oxidising agents such as for example nitric acid or a mixture of nitric acid and sulfuric acid under ... 0050] In comparison to the conventional treatment with liquid nitric acid, the five-hour treatment with nitric acid vapour at ... flask as a storage vessel for the nitric acid, and heating the nitric acid with an oil bath. 21. The method according to claim ... vessel 9 for the nitric acid 5. This can prevent condensed nitric acid in the liquid state from wetting the carbon fibres ...
  http://www.patentsencyclopedia.com/app/20110104492
*  Containment of Nitric Acid Solutions of Plutonium-238 - Digital Library
The solvent used to imitate nitric acid solutions of Pu-238 contained 70% nitric acid, hydrofluoric acid, and ammonium ... The corrosion of various metals that could be used to contain nitric acid solutions of Pu-238 has been studied. Tantalum and ... The solvent used to imitate nitric acid solutions of Pu-238 contained 70% nitric acid, hydrofluoric acid, and ammonium ... The solvent used to imitate nitric acid solutions of Pu-238 contained 70% nitric acid, hydrofluoric acid, and ammonium ...
  https://digital.library.unt.edu/ark:/67531/metadc707776/
*  Nitric Acid - Qingdao langyi chem
Qingdao langyi chem can supply Nitric Acid to your requirements. More quality Nitric Acid product information please contact us ... Find high quality Nitric Acid from China Factory, ... nitric acid phosphate. transportation:by express delivery (by ...
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*  Concentrated nitric acid used in laboratory work is 68% nitric acid by mass in aqueous solution. What should be the molarity...
Concentrated nitric acid used in laboratory work is 68% nitric acid by mass in aqueous solution. What should be the molarity of ... Concentrated nitric acid used in laboratory work is 68% nitric acid by mass in aqueous solution. What should be the molarity of ... such a sample of the acid if the density of the solution is $1.504 g mL^{−1}$? *aims ... such a sample of the acid if the density of the solution is $1.504 g mL^{-1}$? ...
  http://clay6.com/qa/46345/concentrated-nitric-acid-used-in-laboratory-work-is-68-nitric-acid-by-mass-
*  Chemjobber: Handling nitric acid requires caution, from cradle to grave
Nitric Acid Management Program - Yes.. I get 5-10 calls per year resulting in nitric acid mismanagement. They are the all the ... Ditto when trying to make FeCl3 from nails, hydrochloric acid, and nitric acid. Fumes were heavy as they flowed out the window ... I was well aware of what nitric acid does to organics and thought I had taken the proper precautions. Had I capped the bottle ... Looking back, part of the problem was at the time, the safety training on handling nitric acid waste consisted of 'don't mix it ...
  http://chemjobber.blogspot.com/2015/09/handling-nitric-acid-requires-caution.html
*  Nitric acid/JP-X
The varieties of nitric acid propellants include: *WFNA - White fuming nitric acid is based on anhydrous nitric acid (HNO3), a ... nitric acid + 20% N2O4 (AK = Azotna Kislota = Nitric Acid) *AK20F - Russian formulation consisting of 80% nitric acid + 20% ... yields nitric acid (HNO3) and may be concentrated by distillation with sulphuric acid. Red fuming nitric acids may be produced ... The composition of propellant-grade nitric acids is covered by Military Specification MIL-N-7254. The nitric acids are fuming ...
  http://www.friends-partners.org/partners/mwade/props/nitidjpx.htm
*  Nitric acid, 1-methylethyl ester
... *Formula: C3H7NO3 ... Other names: Isopropyl nitrate; Nitric acid, isopropyl ester; ( ...
  https://webbook.nist.gov/cgi/inchi/InChI=1S/C3H7NO3/c1-3
*  CDC - NIOSH Pocket Guide to Chemical Hazards - Nitric acid
Aqua fortis, Engravers acid, Hydrogen nitrate, Red fuming nitric acid, RFNA, White fuming nitric acid (WFNA) ... Fuming nitric acid is concentrated nitric acid that contains dissolved nitrogen dioxide.] ...
  https://www.cdc.gov/niosh/npg/npgd0447.html
*  EWG's Guide to Healthy Cleaning | NITRIC ACID | Substance
About the ratings: EWG provides information on cleaning product ingredients from the published scientific literature, to supplement incomplete data available from companies and the government. The ratings indicate the relative level of concern posed by exposure to the ingredients in this product - not the product itself - compared to other product formulations. The ratings reflect potential health hazards but do not account for the level of exposure or individual susceptibility, factors which determine actual health risks, if any ...
  https://www.ewg.org/guides/substances/21984
*  What is the formula for nitric acid? | Reference.com
The chemical formula for nitric acid is NHO3. The molecule has a central nitrogen atom that is bonded in a triangular formation ... This makes nitric acid soluble in water. However, nitric acid also reacts with water to generate heat. ... Nitric acid is polar, as the central nitrogen atom is positively charged, while the lone single-bonded oxygen atom is ... The chemical formula for nitric acid is NHO3. The molecule has a central nitrogen atom that is bonded in a triangular formation ...
  https://www.reference.com/science/formula-nitric-acid-9994aa5d9f8893a
*  Nitric Acid
Your browser is not supported. Some parts of this page may not work. Please upgrade your browser for a better experience. Upgrade Browser ...
  https://padlet.com/alejarodgar/mhj47bgumy2v
*  Nitric acid causes fire inside a Bourbon County business
The strong and sometimes dangerous chemical known as nitric acid is what officials say caused a fire at a business in Bourbon ... Nitric acid is just one of many potentially dangerous chemicals held at the plant which is why company officials say they are ... At this time, employees tell us the fire was caused when a leaking container of nitric acid ignited inside of the case it was ... WKYT) - The strong and sometimes dangerous chemical known as nitric acid is what officials say caused a fire at a business in ...
  http://www.wkyt.com/home/headlines/Nitric-acid-causes-fire-inside-a-Bourbon-County-business-239829261.html
*  Toolbox: The Pistachio Diet - PezCycling News
Pistachios are stacked with PROTEIN, specifically the amino acid arganine, a pre-curser to nitric oxide, a vasodilator which ...
  https://www.pezcyclingnews.com/toolbox/toolbox-the-pistachio-diet/

(1/123) Osmotic regulation of airway reactivity by epithelium.

Inhalation of nonisotonic solutions can elicit pulmonary obstruction in asthmatic airways. We evaluated the hypothesis that the respiratory epithelium is involved in responses of the airways to nonisotonic solutions using the guinea pig isolated, perfused trachea preparation to restrict applied agents to the mucosal (intraluminal) or serosal (extraluminal) surface of the airway. In methacholine-contracted tracheae, intraluminally applied NaCl or KCl equipotently caused relaxation that was unaffected by the cyclo-oxygenase inhibitor, indomethacin, but was attenuated by removal of the epithelium and Na+ and Cl- channel blockers. Na+-K+-2Cl- cotransporter and nitric oxide synthase blockers caused a slight inhibition of relaxation, whereas Na+,K+-pump inhibition produced a small potentiation. Intraluminal hyperosmolar KCl and NaCl inhibited contractions in response to intra- or extraluminally applied methacholine, as well as neurogenic cholinergic contractions elicited with electric field stimulation (+/- indomethacin). Extraluminally applied NaCl and KCl elicited epithelium-dependent relaxation (which for KCl was followed by contraction). In contrast to the effects of hyperosmolarity, intraluminal hypo-osmolarity caused papaverine-inhibitable contractions (+/- epithelium). These findings suggest that the epithelium is an osmotic sensor which, through the release of epithelium-derived relaxing factor, can regulate airway diameter by modulating smooth muscle responsiveness and excitatory neurotransmission.  (+info)

(2/123) Nitric oxide synthesis in patients with infective gastroenteritis.

BACKGROUND: There is evidence that endogenous nitrate synthesis is notably increased in patients with infective gastroenteritis. AIMS: To determine whether this is due to nitric oxide (NO) production via the L-arginine/NO pathway. METHODS: Seven male patients with community acquired bacterial gastroenteritis and 15 healthy male volunteers participated in this study. All patients had stool culture positive infective gastroenteritis. A bolus of 200 mg L-[(15)N](2)-arginine was administered intravenously after an overnight fast. Urine was collected for the next 36 hours. Urinary [(15)N:(14)N]nitrate ratio was assessed by dry combustion in an isotope ratio mass spectrometer. RESULTS: Mean 36 hour total urinary nitrate excretion in the gastroenteritis group was 5157 (577) micromol compared with 2594 (234) micromol in the control group (p<0.001). Thirty six hour urinary [(15)N]nitrate excretion was considerably higher in the gastroenteritis group compared with the control group (13782 (1665) versus 1698 (98) etamol; p<0.001). These values represent 1.129 (0.139)% and 0.138 (0.007)% of [(15)N]nitrogen administered (p<0.001), respectively. Corrected 36 hour urinary [(15)N]nitrate excretion for urinary creatinine was also significantly higher in the patient compared with the control group (1934 (221) versus 303 (35) etamol/mmol; p<0.001). CONCLUSION: Results show notably enhanced nitrate synthesis due to increased activity of the L-arginine/NO pathway in patients with infective gastroenteritis.  (+info)

(3/123) Essential roles for the products of the napABCD genes, but not napFGH, in periplasmic nitrate reduction by Escherichia coli K-12.

The seven nap genes at minute 47 on the Escherichia coli K-12 chromosome encode a functional nitrate reductase located in the periplasm. The molybdoprotein, NapA, is known to be essential for nitrate reduction. We now demonstrate that the two c-type cytochromes, the periplasmic NapB and the membrane-associated NapC, as well as a fourth polypeptide, NapD, are also essential for nitrate reduction in the periplasm by physiological substrates such as glycerol, formate and glucose. None of the three iron-sulphur proteins, NapF, NapG or NapH, are essential, irrespective of whether the bacteria are grown anaerobically in the presence of nitrate or fumarate as a terminal electron acceptor, or by glucose fermentation. Mutation of napD resulted in the total loss of Methyl Viologen-dependent nitrate reductase activity of the molybdoprotein, NapA, consistent with an earlier suggestion by others that NapD might be required for post-translational modification of NapA.  (+info)

(4/123) Competition between Escherichia coli strains expressing either a periplasmic or a membrane-bound nitrate reductase: does Nap confer a selective advantage during nitrate-limited growth?

The physiological role of the periplasmic nitrate reductase, Nap, one of the three nitrate reductases synthesized by Escherichia coli K-12, has been investigated. A series of double mutants that express only one nitrate reductase were grown anaerobically in batch cultures with glycerol as the non-fermentable carbon source and nitrate as the terminal electron acceptor. Only the strain expressing nitrate reductase A grew rapidly under these conditions. Introduction of a narL mutation severely decreased the growth rate of the nitrate reductase A strain, but enhanced the growth of the Nap(+) strain. The ability to use nitrate as a terminal electron acceptor for anaerobic growth is therefore regulated primarily by the NarL protein at the level of transcription. Furthermore, the strain expressing nitrate reductase A had a substantial selective advantage in competition with the strain expressing only Nap during nitrate-sufficient continuous culture. However, the strain expressing Nap was preferentially selected during nitrate-limited continuous growth. The saturation constants for nitrate for the two strains (which numerically are equal to the nitrate concentrations at half of the maximum specific growth rate and therefore reflect the relative affinities for nitrate) were estimated using the integrated Monod equation to be 15 and 50 microM for Nap and nitrate reductase A respectively. This difference is sufficient to explain the selective advantage of the Nap(+) strain during nitrate-limited growth. It is concluded that one physiological role of the periplasmic nitrate reductase of enteric bacteria is to enable bacteria to scavenge nitrate in nitrate-limited environments.  (+info)

(5/123) A habitat for psychrophiles in deep Antarctic ice.

Microbes, some of which may be viable, have been found in ice cores drilled at Vostok Station at depths down to approximately 3,600 m, close to the surface of the huge subglacial Lake Vostok. Two types of ice have been found. The upper 3,500 m comprises glacial ice containing traces of nutrients of aeolian origin including sulfuric acid, nitric acid, methanosulfonic acid (MSA), formic acid, sea salts, and mineral grains. Ice below approximately 3,500 m comprises refrozen water from Lake Vostok, accreted to the bottom of the glacial ice. Nutrients in the accretion ice include salts and dissolved organic carbon. There is great interest in searching for living microbes and especially for new species in deepest Antarctic ice. I propose a habitat consisting of interconnected liquid veins along three-grain boundaries in ice in which psychrophilic bacteria can move and obtain energy and carbon from ions in solution. In the accretion ice, with an age of a few 10(4) years and a temperature a few degrees below freezing, the carbon and energy sources in the veins can maintain significant numbers of cells per cubic centimeter that are metabolizing but not multiplying. In the 4 x 10(5)-year-old colder glacial ice, at least 1 cell per cm(3) in acid veins can be maintained. With fluorescence microscopy tuned to detect NADH in live organisms, motile bacteria could be detected by direct scanning of the veins in ice samples.  (+info)

(6/123) Vasopressin does not effect hypertension caused by long-term nitric oxide inhibition.

Nitric oxide attenuates both vasopressin-induced vasoconstriction and vasopressin release. We tested whether hypertension and renal dysfunction elicited by chronic inhibition of nitric oxide (NO) synthesis using N(G)-nitro-L-arginine (L-NNA) could be mediated in part by vasopressin V(1A) receptors. Male rats were treated orally for 6 weeks with L-NNA (15 mg/kg per day), a nonpeptide V(1A) receptor antagonist (2S)-1-[(2R,3S)-5-chloro-3-(2-chlorophenyl)-1-(3, 4-dimethoxybenzene-sulfonyl)-3-hydroxy-2, 3-dihydro-1H-indole-2-carbonyl]-pyrrolidine-2-carboxamide (SR 49059, 30 mg/kg per day), or a combination of SR 49059 and L-NNA (same doses), or they received no treatment. Both drugs were added to the food. Measurements were performed in conscious rats (urine collection in metabolic cages, tail-cuff arterial pressure) and at the end of the study in anesthetized rats (clearance measurements). L-NNA produced sustained hypertension, decreased glomerular filtration rate, and increased renal vascular resistance, plasma renin activity, and urinary albumin excretion. SR 49059 had no effect per se on these parameters and also did not attenuate the hypertension and renal dysfunction induced by L-NNA. Surprisingly, SR 49059 potentiated L-NNA-induced hypertension at the end of the 6-week treatment. However, the blood pressure response and the renal and mesenteric vasoconstriction elicited by exogenous vasopressin were attenuated in rats treated with SR 49059. L-NNA did not change plasma vasopressin concentration or 24-hour urinary vasopressin excretion. Our findings suggest that activation of vasopressin V(1A) receptors does not contribute to the hypertension and renal dysfunction induced by chronic NO synthesis inhibition. They also document unchanged plasma vasopressin concentration in NO-deficient hypertension.  (+info)

(7/123) Effects of Ca(2+) channel activity on renal hemodynamics during acute attenuation of NO synthesis in the rat.

In cultured vascular muscle cells, nitric oxide (NO) has been shown to inhibit voltage-dependent Ca(2+) channels, which are involved in renal blood flow (RBF) autoregulation. Therefore, our purpose was to specify in vivo the effects of this interaction on RBF autoregulation. To do so, hemodynamics were investigated in anesthetized rats during Ca(2+) channel blockade before or after acute NO synthesis inhibition. Rats were treated intravenously with vehicle (n = 10), 0.3 mg/kg body wt N(G)-nitro-L-arginine-methyl ester (L-NAME; n = 7), 4.5 microg. kg body wt(-1). min(-1) nifedipine (n = 8) alone, or with nifedipine infused before (n = 8), after (n = 8), or coadministered with L-NAME (n = 10). Baseline renal vascular resistance (RVR) averaged 14.0 +/- 1.2 resistance units and did not change after vehicle. RVR increased or decreased significantly by 27 and 29% after L-NAME or nifedipine, respectively. Nifedipine reversed, but did not prevent, RVR increase after or coadministered with L-NAME. RBF autoregulation was maintained after L-NAME, but the autoregulatory pressure limit (P(A)) was significantly lowered by 15 mmHg. Nifedipine pretreatment or coadministration with L-NAME limited P(A) resetting or suppressed autoregulation at higher doses. Results were similar with verapamil. Intrarenal blockade of Ca(2+)-activated K(+) channels also prevented autoregulatory resetting by L-NAME (n = 8). These findings suggest NO inhibits voltage-dependent Ca(2+) channels and thereby modulates RBF autoregulatory efficiency.  (+info)

(8/123) Possible involvement of undissociated acid molecules in the acid response of the chorda tympani nerve of the rat.

To test whether undissociated acid is capable of exciting the chorda tympani nerves in rats, we have used buffered acid solutions as taste stimuli. These solutions were prepared by adding alkali to weak acids, such as acetic acid, so that the proportion of undissociated and dissociated acids was varied whereas keeping the total acid concentration constant. When acetic acid solutions, adjusted to wide ranges of pH by NaOH, were applied to the tongue, the response magnitude of the chorda tympani nerves was not varied systematically with pH changes. However, if the sodium effect was eliminated by amiloride or replacement of cation by potassium or Tris[hydroxymethyl]aminomethane; NH(2)C(CH(2)OH)(3) (Tris-base), the chorda tympani response was reduced systematically as pH increased. Similar results were obtained with citric acid and ascorbic acid. This pH-dependent change in taste nerve response to acid cannot be solely attributed to the proton gradient because the response magnitude induced by hydrogen itself, which was estimated from responses to strong acids, was much smaller than that by equi-pH acetic acid ( approximately 85%). Thus we cannot explain the pH-dependent responses of the chorda tympani nerves to weak acids unless effects of undissociated acid molecules are postulated. It is therefore concluded that undissociated acids in weak acid solutions can be a stimulant to taste receptor cells.  (+info)