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At least 541 records · Page 30Linked to original sources
PubMed1985

Alloxan stimulates p-aminohippurate uptake in renal basal-lateral membranous vesicles.

In renal basal-lateral membranous vesicles, the probenecid-sensitive p-aminohippurate uptake was stimulated by alloxan. This stimulation of uptake was observed only after a lag period of 15 seconds, and it reached a maximal value after one minute. Stimulation was increased by 1 mM to 5 mM alloxan in a linear fashion. The effect was maximal and constant between 5 mM and 20 mM alloxan. Alloxan affected neither the glucose space of the vesicle nor the rate of transport or diffusion of glutamate, another organic anion. The mechanism of stimulation by alloxan was not clear. Its effect was blocked by the sulfhydryl reagent N-ethylmaleimide and weakly mimicked by H2O2, an oxidizing reagent. However, ninhydrin, a structural analogue of alloxan which reacts with sulfhydryl groups, and glucose, a neutral structural analogue of alloxan, failed to stimulate probenecid-sensitive uptake.

Alloxan↗
PubMed1985

Cysteinyl-cysteine and the microsomal protein from which it is derived act as reducing cofactor for prolyl hydroxylase.

Microsomes from L-929 cells contain a reductant which can replace ascorbate as a cofactor for prolyl hydroxylase. The cofactor was extracted with Triton X-100 and exhibited high and low molecular weight forms on S-300 gel columns. Refiltration or trypsin treatment of high molecular weight cofactor produced additional low molecular weight form. The low molecular weight form was purified by P-2 gel filtration, and Dowex-1 and thin layer chromatography. It is ninhydrin reactive, exhibits reduced and oxidized forms with molecular weights of 240 and 460, respectively, and yielded cystine upon acid hydrolysis. The results suggest that it is a dipeptide, cysteinyl-cysteine, derived from a microsomal protein which is the high molecular weight cofactor.

Animals↗
PubMed1975

Inhibition of glyceraldehyde 3-phosphate dehydrogenase by plasma and serum ultrafiltrates due in part to a low-molecular-weight, nonpeptide material.

In an attempt to verify the existence in the blood of a diabetogenic peptide (somantin) derived from growth hormone, ultrafiltrates from plasma and serum from normal and diabetic subjects were prepared. The freeze-dried residues of these ultrafiltrates inhibited glyceraldehyde 3-phosphate dehydrogenase as somantin is claimed to do. However, the behavior of the inhibitory material on gel filtration on Sephadex G-10 indicated a molecular weight well below 700, rather than the considerably larger size claimed for somantin. The inhibitory material did not adsorb to Dowex 50W cation exchange resin at pH 2.5, while over 95 percent of ninhydrin-positive material was retained. Acid hydrolysis of the inhibitory material did not abolish its activity. Because of the presence of this low-molecular-weight, nonpeptide inhibitory material, inhibition of glyceraldehyde 3-phosphate dehydrogenase by a simple ultrafiltrate of plasma or serum is probably not a definitive measure of somantin.

Adult↗
PubMed1988

A procedure for total protein determination with special application to allergenic extract standardization.

A method for total protein determination of allergenic extracts has been developed and evaluated. Samples were hydrolyzed with 5 M NaOH followed by colorimetric determination with ninhydrin of the released amino acids using bovine serum albumin as the standard. The entire procedure was carried out in disposable plastic tubes. Substances (glycerol, phenol and mannitol) commonly present in allergenic extracts manufactured for human use did not affect the assay results. Analyses of four different pollen extracts by the method gave good agreement with amino acid analyses. Other methods of analysis (total N, protein N unit assay, Lowry) gave more variable results compared with amino acid analysis. Analysis of the total protein content of 53 different lots of allergenic extracts gave narrow ranges of values for each species. Standardized mite extracts analyzed for total protein by US FDA-licensed manufacturers using this assay showed a good correlation of biological activity with total protein.

Allergens↗
PubMed1979

The occurrence of cystinylglycine in blood plasma.

Cystinylglycine has been identified as a minor ninhydrin-positive component of deproteinized blood plasma from human, bovine, rat and rabbit blood. The amount present in human blood plasma is approximately one-fifth of that of cystine and is not significantly correlated with age or with the cystine level.

Adolescent↗
PubMed2004

Changes in some nitrogenous compounds in the blood and tissues of freshwater pikeperch (Sander lucioperca) during salinity acclimation.

The effect of ambient salinity changes (0.9, 6 and 12 psu) on the levels of dissolved ammonia (DA), ninhydrin positive substances (NPS), trimethylamine (TMA) and trimethylamine oxide (TMAO) in the blood and tissue of medium-acclimated Sander lucioperca L. (also Stizostedion lucioperca) were investigated. In freshwater, blood and tissue total free amino acid levels (measured as NPS) were 3.62 mM and 60.61 mM, respectively. The NPS content increased significantly (P<0.05) in the tissue and blood on acclimation to 6 and 12 psu salinities. The mass-specific tissue TMAO concentration of pikeperch acclimated to normal freshwater was 0.413+/-0.084 micromol TMAO g(-1). Results reveal that TMAO levels are positively influenced by the external salinity medium where significant differences in mean levels occurred between the groups (P<0.05). The calculated p[NH(3)] and [NH(4)(+)] gradients reveal that the [NH(3)] gradient was consistently low (cf. the [NH(4)(+)] gradient). The gradient of p[NH(3)] decreased with the medium increased salinities. The results suggest that freshwater pikeperch may be able to resist salinity changes by manipulation of nitrogen metabolism. Free amino acids and TMAO are involved in mediating response to salinity exposure in freshwater pikeperch.

Adaptation, Physiological↗
PubMed2000

In situ studies of pellicle formation on hydroxyapatite discs.

The formation of acquired enamel pellicle on hydroxyapatite (HA) discs of known surface area carried in the mouth was studied; discs were carried in the mouth for 30 s, 1, 5, 10 and 20 min. Similar amounts of protein were found on the discs at each time-point, as determined by ninhydrin analyses. The amounts of amylase and lysozyme detected remained stable after 5 min of exposure of the discs to the mouth. Assay of the discs for fructosyl- and glucosyltransferase activities revealed that fructosyltransferase activity increased up to 1 min of exposure to the mouth and decreased when kept in the mouth for longer periods; glucosyltransferase activity, in contrast, increased the longer the discs were kept in the mouth. This in situ model provides insight into the activities of various enzymes during the first 20 min of pellicle formation. The effects of rinsing with sucrose and sugar alcohols on pellicle formation on the discs were also explored. The discs were placed in the mouth for 30 s, 1, 5, 10 and 20 min, preceded by rinsing with either distilled deionized water, sucrose, sorbitol, xylitol or phosphate-buffered saline. Western blot analyses of disc eluates with antiserum/antibody preparations to various salivary components revealed distinct patterns of deposition of bacterial and salivary components depending on the composition of the rinse. These studies confirm that salivary molecules and bacteria are deposited on apatitic surfaces in a selective manner and reveal that pellicle formation may be influenced by composition of diet. It is apparent that this in situ model could be used in screening potential antiplaque agents.

Adult↗
PubMed1998

Similarities in the metabolism of alloxan and dehydroascorbate in human erythrocytes.

The beta-cell toxin alloxan is reduced within cells to dialuric acid, which may then decompose to release damaging reactive oxygen species. We tested whether such redox cycling of alloxan occurs in the human erythrocyte, a cell with stronger antioxidant defenses than beta-cells. Erythrocytes incubated with increasing concentrations of alloxan progressively accumulated dialuric acid, as measured directly by HPLC with electrochemical detection. At concentrations up to 2 mM, alloxan decreased cellular GSH slightly, but did not affect erythrocyte contents of ascorbate or alpha-tocopherol. Intracellular H2O2 generation, measured as inhibition of endogenous catalase activity in the presence of 3-amino-1,2,4-triazole (aminotriazole), was decreased by alloxan. Despite its failure to induce significant oxidant stress in erythrocytes, 2 mM of alloxan doubled the activity of the hexose monophosphate pathway (HMP). This likely reflected consumption of reducing equivalents during reduction of alloxan to dialuric acid. Alloxan pretreatment enhanced the ability of erythrocytes to reduce extracellular ferricyanide while protecting alpha-tocopherol in the cell membrane from oxidation by ferricyanide. Ninhydrin, a hydrophobic derivative of alloxan, showed similar effects, but caused progressive GSH depletion and cell lysis at concentrations above 50 microM. The ability of alloxan to enhance ferricyanide reduction and to spare alpha-tocopherol suggests that dialuric acid or other reducing species within the cells can protect or recycle alpha-tocopherol and donate electrons to a transmembrane transfer process. This behavior resembles that observed for the dehydroascorbate (DHA)/ascorbate pair, and leads to the unexpected conclusion that alloxan increases the reducing capacity of the erythrocyte.

Alloxan↗
PubMed1997

Regeneration of sudomotor and sensory nerve fibres after digital replantation and microneurovascular toe-to-hand transfer.

The end-stage sudomotor and sensory recovery in patients with replanted fingers and patients after microneurovascular toe-to-hand transfer was studied using quantitative electrophysiological investigations (recovery of sensory nerve action potentials and the sympathetic skin response), the ninhydrin test and clinical testing of sensory regeneration (light touch, pain, static and dynamic two-point discrimination). 13 adult patients with 22 replanted digits (11 males, 2 females) aged 21-58 years (mean 42.2 years) and 12 adults and adolescents (8 males, 4 females) aged 13-45 years, (mean 26.8 years) following 14 microneurovascular great and/or second toe-to-hand transfers were studied. The replanted fingers were examined 2-7 years after injury and replantation. The toe-to-hand transfers were examined 2-12 years after injury and transfer. The results show better end-stage recovery of sudomotor and sensory function following finger replantation when compared to microneurovascular toe-to-hand transfer.

Adolescent↗
PubMed1984

Reaction detector system for the simultaneous monitoring of primary amino groups and sulfhydryl groups in peptides eluted by high-performance liquid chromatography.

A reaction detector system is described which can be used for simultaneous analysis of primary amino groups and sulfhydryl groups in peptides separated by high-performance liquid chromatography. By use of an automatic split valve system, well-defined portions of the effluent are diverted alternately into one of the two reaction detectors, based on the ninhydrin and Ellman assay, respectively. In the latter case the dithioerythritol included in the elution buffers for thiol preservation is eliminated with arsenite. For selective recovery of eluted peptides the amino/thiol group analyser can easily be converted into a high-yield monitoring system compatible with volatile, UV-opaque gradient buffers. In this version an automatic sample valve is used for the thiol assay, removing picomole amounts of material from the effluent destined for collection. In preparative applications there is a progressive net gain in sensitivity with increasing proportion of collected material. Under conditions of optimum recovery ca. 90% of the material could be recovered at a total consumption in the two detectors of less than 100 pmol. Experimental conditions are described which would allow for the additional identification of tryptophan, tyrosine and lysine-containing peptides. The monitoring system may also be used without modification for the assessment of key residues in polypeptides and proteins.

Amines↗
PubMed1984

Automatic amino acid and sugar analysis of glycoproteins.

Amino acid analyzers were used for complete analyses of glycoproteins. The methods of analysis used were cation-exchange chromatography for amino acids, phosphoamino acids and amino sugars with ninhydrin as reagent, and anion-exchange chromatography for neutral sugars with copper Bicinchoninate as reagent. A separate program was developed for the analysis of charged sugar components, N-acetylneuraminic acid and amino sugars in one chromatogram. The possibility of detection of radioactively labelled components is also demonstrated. The detection limits and possibilities for column and reactor switches are discussed.

Amino Acids↗
PubMed1988

High-performance liquid chromatographic analysis of arginine-containing peptides in biological fluids by means of a selective post-column reaction with fluorescence detection.

Highly sensitive and specific high-performance liquid chromatographic methodology for the fluorescence detection of arginine-containing peptides in biological matrices is described. Following HPLC separation, a post-column reaction of the guanidino group of the arginine moiety with ninhydrin under basic conditions is utilized to generate a fluorescent peptide product which can be measured at high sensitivity. Careful optimization of the post-column reaction conditions, and the use of HPLC columns of reduced internal diameter, resulted in on-column detection limits as low as 50 fmol. Application to the determination of synthetic arginine-containing vasopressin antagonists in human plasma resulted in a quantitative response which is linear over the range 0.5-100 pmol/ml. The assay method is sufficiently sensitive, accurate, and precise for use in pharmacokinetic studies of these synthetic peptides. The methodology also has general applicability in the detection of naturally occurring arginine-containing peptides.

Angiotensin II↗
PubMed1997

Quantitation of an orally available thrombin inhibitor in rat, monkey and human plasma and in human urine by high-performance liquid chromatography and fluorescent post-column derivatization of arginine.

An assay for the quantification of plasma and urine levels of CVS 1123, an orally bioavailable thrombin inhibitor, and its desmethyl form. CVS 738, was developed to support clinical and toxicology studies. This assay uses solid-phase extraction, reversed-phase HPLC separation, and post-column fluorescent derivatization with ninhydrin. An internal standard is added to correct for recovery. In aqueous solution, the arginine aldehyde structures of CVS 1123 and CVS 738 exist in multiple forms which can be separated under standard reversed-phase HPLC conditions. HPLC conditions were optimized to give rapid interconversion of the forms on the separation time scale, and consequently a single chromatographic peak. Extraction conditions were modified for quantitative extraction of drug compounds from large volumes of human plasma. The assay was shown to be accurate and precise, with a quantification limit of 17 ng CVS 1123/ml human plasma.

Acetonitriles↗
PubMed2002

A simple and rapid assay of collagen-like polymer in crude lysate from Escherichia coli.

An assay for the quantification of collagen-like polymer (CLP) in Escherichia coli cells utilizing the specific reaction between collagenase and CLP is presented. It involves thermal treatment to precipitate non-CLP proteins, digestion of CLP by collagenase and detection of the absorbance of the liberated amino acids and peptides from CLP by a ninhydrin-based method. CLP concentration is determined from the absorbance measurement.

Collagen↗
PubMed1998

Liquid chromatography of guanidino compounds using a porous graphite carbon column and application to their analysis in serum.

The retention mechanism of guanidino compounds on a porous graphitic carbon seemed to be mainly hydrophobic interaction, according to the retention factors in buffer solutions and the results of an analysis by computational chemical calculation using molecular mechanics (MM2). The baseline separation of ten guanidino compounds was achieved by the addition of a hydrophobic counterion. The retention mechanism may be dynamic ion-exchange. The stable system was applied to the analysis of guanidino compounds in serum from nephritic patients. The effluent was monitored by a post-column labeling detection method using ninhydrin. The detection limit of guanidino compounds was a few picomoles; however, that of creatinine was one hundredth of those of the other compounds. The reproducibilities of the peak height and area of the ten guanidino compounds using gradient elution were quite high, and the standard deviations were within a few percent (n=5), except for creatinine. The recovery of the compounds from serum was more than 90% (n=5). The reproducibility of retention times was within 1% (n=5).

Buffers↗
PubMed1999

A one-step fluorescent detection method for lipid fingerprints; Eu(TTA)3.2TOPO.

This paper describes the development of a one-step fluorescent lipid reagent that involves europium chelates whose generic formula can be represented as europium(organic ligand)3.2(synergic reagent). An optimized formulation is presented and a comparison with physical developer was conducted which showed the new technique to be very good when fresh fingerprints were recovered but inferior to physical developer on aged prints (over a week). In addition, the compatibility of the technique with sequential methods such as ninhydrin and DFO is reported. The experimentation, results and chemical formulation of this study were presented to delegates of the International Symposium on Fingerprint Detection and Identification held in Israel in June 1995. Prior to that a patent application had been made.

Dermatoglyphics↗
PubMed2002

Comparison of several methods used for the determination of cephalosporins. Analysis of cephalexin in pharmaceutical samples.

The precision of UV absorbance of intact and acid degraded cephalosporins, ninhydrin, high performance liquid chromatography and iodometric methods used for analysis of cefoxitin, cefotaxime, cephazolin and cephalexin were compared. To obtain the calibration graphs the analytical signal used were: absorbance, first derivative absorbance, second derivative absorbance and H-point Standard Additions Method by using absorbance values at two selected wavelengths as analytical signal. These methods and calibration graphs were also used for the determination of cephalexin in pharmaceutical samples.

Capsules↗
PubMed2003

Colorimetric determination of gabapentin in pharmaceutical formulation.

Three accurate, simple and precise colorimetric methods for the determination of gabapentin in capsules are developed. The first method is based on the reaction of gabapentin with vanillin (Duquenois reagent) in the presence of McIlvain buffer pH 7.5 and the color developed was measured at 376 nm. The linearity range was found to be 80-360 microg ml(-1). The second is based on the reaction of the primary amino group of gabapentin with ninhydrin reagent in N,N'-dimethylformamide (DMF) medium producing a colored product which absorbs maximally at 569 nm. Beer's law is obeyed in the concentration range 40-280 microg ml(-1) of gabapentin. The third method is based on the reaction of gabapentin with p-benzoquinone (PBQ) to form a colored product with lambda(max) at 369 nm. The products of the reaction were stable for 2 h at 30 degrees C, shifts of the wavelength of maximum absorbance were not observed for up to 24 h after starting the reaction. The absorbance is proportional to gabapentin concentration in the range 80-320 microg ml(-1). The optimum experimental parameters for the reactions have been studied. The validity of the described procedures was assessed. Statistical analysis of the results has been carried out revealing high accuracy and good precision. The suggested procedures could be used for the determination of gabapentin in capsules. The procedures were rapid, simple and suitable for quality control application.

Acetates↗