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PubMed2004

Monitoring trace metals in urban aerosols from Buenos Aires city. Determination by plasma-based techniques.

A study was undertaken, within the framework of a 3 years national project, to assess the content of 13 elements in airborne particulate matter collected in representative zones of the metropolitan area of Buenos Aires. The sampling strategy followed consisted in collecting simultaneously 67 samples of PM10 particulate matter in 9 sampling sites covering an area of about 30 km2 during one week. The collection was performed on ash-free fibre-glass filters using high volume samplers. A combination of aqua regia and perchloric acid was used for leaching metals from filters. Key elements, namely Al, Ca, Cu, Fe, Mn, Mo, Ni, Pb, S, Sb, Sn, Zn and Zr, were determined by inductively coupled plasma-optical emission spectrometry (ICP-OES) and inductively coupled plasma-mass spectrometry (ICP-MS) at micro g g(-1) and ng g(-1) levels. Analyte concentration varied from 130 ng g(-1)(Mo) to over 30%(Ca). Multivariate statistical analysis was performed on the data set including the measured elemental compositions for the monitored period. The atmospheric concentration found for Pb confirms the decreasing levels of this element since the introduction of unleaded gasoline in 1995: 88 ng m(-3)(2001) < 220 ng m(-3)(1997) < 3900 ng m(-3)(1994). The average S concentration above 3 microg m(-3) is somehow unexpectedly high for Buenos Aires since the relatively low S content of liquid fuels and the massive usage of natural gas imply low emissions of this element from combustion activities. To the best of our knowledge, S concentrations are reported for the first time for this city.

Aerosols↗
PubMed2005

Antimony: a traffic-related element in the atmosphere of Buenos Aires, Argentina.

Vehicular traffic is one of the main sources of antimony in highly populated urban areas like Buenos Aires where an overall traffic density of 1 500 000 vehicles per day (corresponding to 7500 vehicles km(-2)) is estimated. In this context, a study was undertaken to ascertain the levels of Sb and other traffic-related elements (TRE) in the atmosphere of this city. To this end, sixty-seven samples of PM-10 particulate matter were collected during eight days in nine representative sampling sites located downtown Buenos Aires and spread over an area of about 30 km2. The collection of particulate matter was performed on ash-free glass-fibre filters using high volume samplers with PM-10 sampling heads. A combination of aqua regia and perchloric acid was used for leaching metals from filters. The resulting solutions were evaporated and then diluted with 0.1 mol l(-1) HCl. Antimony was determined by inductively coupled plasma-quadrupole mass spectrometry (ICP-QMS) at ng g(-1) levels. Concentrations of Sb varied from 12.9 +/- 0.9 to 375 +/- 23 microg g(-1)(equivalent to 0.87 +/- 0.06 to 15.3 +/- 0.8 ng m(-3)). Statistical analysis was performed on the data set including the measured PM-10 mass and Sb concentrations for the monitored period. Correlations of Sb with other TRE namely, Cu and Mo were also assessed. The highest concentrations of Sb were detected at two sites (Hospital Alemán and Casa Rapallini) located in streets with traffic consisting mostly of passenger cars and showing a "stop-and-go" pattern in peak hours. Antimony levels in the Buenos Aires PM-10 are by far below the level of 0.5 mg m(-3)(for an 8 hour workday, 40 hour work week) set by the US Occupational Safety and Health Administration (OSHA) for occupational exposure. However, monitoring of Sb and other TRE should be carried out in a systematic fashion to detect the possibility of increases in from the present levels.

Air Pollutants↗
PubMed2002

Thiol compounds from a free-living pathogenic opportunistic amoeba, Acanthamoeba polyphaga.

New bimane-reacting compounds from perchloric acid extracts have been detected by HPLC from Acanthamoeba polyphaga. The main compounds detected are cysteine, glutathione and other novel thiol compounds. All of these compounds must be thiols, since they disappear or decrease substantially when treated by N -ethylmaleimide prior to acetonitrile/bimane derivatization. Cysteine and glutathione increase in quantity when dithiothreitol reduction is applied to the fresh extract. This means that they are likely to be present in their oxidized and reduced form and indicates the possible presence of a corresponding thiol/disulphide enzymic system. There are other compounds that have a different behaviour, since although they can react with bimane, they do not disappear if treated previously by N -ethylmaleimide. This shows that they are not thiols but can react with bimane. The main thiol compounds found to be present, in both the parasite and the host lymphocyte cells, were cysteine and glutathione. We were unable to detect ovothiol A in Acanthamoeba but instead we found another thiol compound that could be structurally related to trypanothione. The new thiol compounds unique to this parasite and not present in lymphocytes will permit the study of disulphide-reducing enzymes as potential drug targets.

Acanthamoeba↗
PubMed1994

Aberrant 3H labelling of ATP during in vivo labelling of Ehrlich mouse ascites tumour cells with [2-3H]inositol is significant in the study of isomers of InsP3 and InsP4.

Neutralized perchloric acid extracts of intra-abdominally proliferating Ehrlich mouse ascites-tumour cells harvested after 24 h exposure to [2-3H]inositol were analysed by Mono Q HR5/5 anion-exchange h.p.l.c. using an ammonium formate/phosphoric acid gradient or by ambient-pressure small-column anion-exchange chromatography (Bio-Rad AG 1-X8, 200-400 mesh). The results showed that cellular ATP contained aberrant 3H label in excess of 3H in the isomers of InsP3 and InsP4. The putative ATP 3H radioactivity showed: (i) h.p.l.c. run time as the material causing the largest A254 peak traced, (ii) precise spiking with ATP and [14C]ATP and (iii) specific absorption to charcoal. Moreover, enzymic conversion of ATP into ADP changed putative ATP 3H into putative ADP 3H. In addition, aberrant 3H labelling of cellular ADP and GTP was detected, although at a lower level.

Adenosine Diphosphate↗
PubMed2002

Na(+)/H(+) exchange subtype 1 inhibition during extracellular acidification and hypoxia in glioma cells.

Lactacidosis is a common feature of ischaemic brain tissue, but its role in ischaemic neuropathology is still not fully understood. Na(+)/H(+) exchange, a mechanism involved in the regulation of intracellular pH (pH(i)), is activated by low pH(i). The role of Na(+)/H(+) exchange subtype 1 was investigated during extracellular acidification and subsequent pH recovery in the absence and presence of (4-isopropyl-3-methylsulphonyl-benzoyl)-guanidine methanesulfonate (HOE642, Cariporid), a new selective and powerful inhibitor of the Na(+)/H(+) exchanger subtype 1 (NHE-1). It was compared for normoxia and hypoxia in two glioma cell lines (C6 and F98). pH(i) was monitored by fluorescence spectroscopy using the intracellularly trapped pH-sensitive dye 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF). Alterations in glial cell metabolism were characterized using high-resolution (1)H, (13)C and (31)P NMR spectroscopy of perchloric acid extracts. NHE-1 contributed to glial pH regulation, especially at pathologically low pH(i) values. NHE-1 inhibition with HOE642 during acidification caused exacerbated metabolic disorders which were prolonged during extracellular pH recovery. However, NHE-1 inhibition during hypoxia protected the energy state of glial cells.

Acids↗
PubMed1994

Choline-containing compounds in human astrocytomas studied by 1H NMR spectroscopy in vivo and in vitro.

We have studied 14 patients with different grades of astrocytomas using 1H NMR spectroscopy in vivo. Typically, astrocytomas exhibited a low N-acetylaspartate peak, a prominent signal from choline group-containing compounds, and lactate in the 1H NMR spectra in vivo. The uncorrected choline/creatine + phosphocreatine peak area ratios were higher in tumors than in normal brain tissue. Absolute concentration of choline-containing compounds (1.74 +/- 0.09 mmol/L) in the normal brain tissue was not different in any grade of astrocytoma, but total creatine concentration in healthy brain (7.49 +/- 0.30 mmol/L) was higher than that in grade IV astrocytomas (4.84 +/- 0.89 mmol/L). Relaxation constants of choline-containing compounds did not differ in tumors from those determined in normal brain. Perchloric acid extracts of biopsy samples from 35 astrocytomas and 13 samples of normal temporal white matter were analyzed with 1H NMR. Total concentration of choline-containing compounds did not differ between controls and any grade of astrocytoma when the quantification was done in vitro. It is interesting that phosphorylcholine concentration was about twofold greater in grade IV astrocytomas than in controls or other grades of astrocytomas. We conclude that high phosphorylcholine in grade IV astrocytomas may be an indicator of degree of malignancy. The proportional changes within the group of choline-containing compounds observed in vitro were not reflected in the NMR properties of choline signal in vivo.

Astrocytoma↗
PubMed1994

Differential expression of MARCKS and other calmodulin-binding protein kinase C substrates in cultured neuroblastoma and glioma cells.

Expression of the protein kinase C substrate MARCKS and other heat-stable myristoylated proteins have been studied in four cultured neural cell lines. Amounts of MARCKS protein, measured by [3H]myristate labeling and western blotting, were severalfold higher in rat C6 glioma and human HTB-11 (SK-N-SH) neuroblastoma cells than in HTB-10 (SK-N-MC) or mouse N1E-115 neuroblastoma cells. Higher levels of MARCKS mRNA were also detected in the former cell lines by S1 nuclease protection assay. At least two additional 3H-myristoylated proteins of 50 and 40-45 kDa were observed in cell extracts heated to > 80 degrees C or treated with perchloric acid. The 50-kDa protein, which bound to calmodulin in the presence of Ca2+, was more prominent in cells (N1E-115 and HTB-10) with less MARCKS, whereas neuromodulin (GAP-43) was detected in N1E-115 and HTB-11 cells only. Heating resulted in a fourfold increase in the detection of MARCKS by western blotting; this was not paralleled by a similar increase in [3H]myristate-labeled MARCKS and may be due to a conformational change affecting the C-terminal epitope or enhanced rechange of the protein on nitrocellulose. Addition of beta-12-O-tetradecanoylphorbol 13-acetate resulted in three- to fourfold increased phosphorylation of MARCKS in HTB-11 cells, with little increase noted in HTB-10 cells. These results indicate that MARCKS, neuromodulin, and other calmodulin-binding protein kinase C substrates exhibit distinct levels of expression in cultured neurotumor cell lines. Of these proteins, only MARCKS appears to be correlated with phorbol ester stimulation of phosphatidylcholine turnover in these cells.

Amino Acid Sequence↗
PubMed1995

High resolution proton NMR spectroscopy of multiple sclerosis lesions.

Tissue from postmortem multiple sclerosis and normal control brains was extracted with perchloric acid and analysed using proton NMR spectroscopy. The content of N-acetyl-derived groups (the sum of N-acetyl-aspartate, acetate, and N-acetylaspartylglutamate) was decreased in multiple sclerosis plaques compared with normal control white matter (mean, 4.36 vs. 6.64 mumol/g wet weight). In normal appearing white matter adjacent to plaques a corresponding decrease was seen, with no change in white matter distant from plaques. A decrease in the content of total creatine was observed in multiple sclerosis plaques in comparison with normal control white matter (mean, 4.64 vs. 6.56 mumol/g wet weight), which correlated strongly with the decrease in N-acetyl-derived groups. No changes in other metabolites such as total choline or myo-inositol were seen. The decreases in content of N-acetyl-derived groups are in agreement with observations from in vivo proton NMR spectroscopy in multiple sclerosis patients. The decrease in total creatine is in contrast to most of the observations made in vivo where total creatine is assumed to be unchanged and metabolite levels are often expressed as a total creatine ratio. The use of a total creatine ratio in vivo could lead to an underestimation of reductions in N-acetylaspartate and an apparent increase in other metabolites in the multiple sclerosis lesion.

Adult↗
PubMed1996

Metabolic precursors and compartmentation of cerebral GABA in vigabatrin-treated rats.

The metabolic precursors and cerebral compartmentation of the augmented GABA pool induced by vigabatrin, an irreversible inhibitor of GABA transaminase, have been investigated by 13C NMR. Adult rats receiving rat chow ad libitum were given either drinking water only or drinking water containing 2.5 g/L vigabatrin for 7 days. Both groups of animals were infused either with [1,2(-13)C2]acetate (15 mumol/min/100 g body weight), an exclusive precursor of GABA formation through the glial glutamine pathway, or with [1,2(-13)C2]glucose (15 mumol/min/100 g body weight), a substrate that can produce GABA through the glial glutamine pathway or by direct metabolism in the neurons. The brains were frozen in situ, extracted with perchloric acid, and analyzed by 13C NMR. In vigabatrin-treated animals [13C]glutamine, a common intermediate for [13C]GABA synthesis from glucose or acetate, was accumulated to similar amounts during infusions with [1,2(-13)C2]glucose or [1,2(-13)C2]acetate. However, [13C]GABA accumulation was sevenfold higher during [1,2(-13)C2]glucose infusions or twofold higher during [1,2(-13)C2]acetate infusions. These results show that the direct pathway of GABA formation by neuronal metabolism of glucose predominates over the alternative pathway through glial glutamine. Near-equilibrium relationships of the aminotransferases of GABA and aspartate imply that the observed [13C]GABA accumulation occurs initially in the neuronal compartment.

4-Aminobutyrate Transaminase↗
PubMed1996

Metabolism of [U-13C5] glutamine in cultured astrocytes studied by NMR spectroscopy: first evidence of astrocytic pyruvate recycling.

Metabolism of [U-13C5]glutamine was studied in primary cultures of cerebral cortical astrocytes in the presence or absence of extracellular glutamate. Perchloric acid extracts of the cells as well as redissolved lyophilized media were subjected to nuclear magnetic resonance and mass spectrometry to identify 13C-labeled metabolites. Label from glutamine was found in glutamate and to a lesser extent in lactate and alanine. In the presence of unlabeled glutamate, label was also observed in aspartate. It could be clearly demonstrated that some [U-13C5]glutamine is metabolized through the tricarboxylic acid cycle, although to a much smaller extent than previously shown for [U-13C5]glutamate. Lactate formation from tricarboxylic acid cycle intermediates has previously been demonstrated. It has, however, not been demonstrated that pyruvate, formed from glutamate or glutamine, may reenter the tricarboxylic acid cycle after conversion to acetyl-CoA. The present work demonstrates that this pathway is active, because [4,5-13C2]glutamate was observed in astrocytes incubated with [U-13C5]-glutamine in the additional presence of unlabeled glutamate. Furthermore, using mass spectrometry, mono-labeled alanine, glutamate, and glutamine were detected. This isotopomer could be derived via the action of pyruvate carboxylase using 13CO2 produced within the mitochondria or from labeled intermediates that had stayed in the tricarboxylic acid cycle for more than one turn.

Alanine↗
PubMed1999

[1-(13)C]glucose metabolism in the tumoral and nontumoral cerebral tissue of a glioma-bearing rat.

C6 cells were used to establish a glioma-bearing rat model by stereotaxic injection in the left caudate nucleus. The tumor status was evaluated by magnetic resonance imaging and conventional histology. The glioma-bearing rats were infused for 1 h with a [1-(13)C]glucose solution. Perchloric acid extracts of the tumor and the ipsilateral and contralateral hemispheres were analyzed by 13C-NMR spectroscopy. The 13C-labeling patterns in compounds, mainly amino acids, indicated no drastic modification of carbon metabolism in both ipsilateral and contralateral hemispheres, as compared with control rats, whereas profound metabolic differences between brain tissue and tumor were observed. Glutamine C4 enrichment was lower in the glioma than in the brain [mean +/- SD values, 5.4 +/- 2.3 (n = 5) and 15.0 +/- 0.8% (n = 10), respectively] and also lower than the glutamate C4 enrichment in the glioma (mean +/- SD value, 22.6 +/- 4.2%; n = 5), indicating that tumor glutamine was neither synthesized inside the glioma nor taken up from the surrounding brain. The glutamine C4 enrichment in the serum (6.7 +/- 0.5%; n = 10) suggested that the glioma imported glutamine from the blood, a process probably connected with angiogenesis.

Alanine↗
PubMed2000

The metabolism of [3-(13)C]lactate in the rat brain is specific of a pyruvate carboxylase-deprived compartment.

Lactate metabolism in the adult rat brain was investigated in relation with the concept of lactate trafficking between astrocytes and neurons. Wistar rats were infused intravenously with a solution containing either [3-(13)C]lactate (534 mM) or both glucose (750 mM) and [3-(13)C]lactate (534 mM). The time courses of both the concentration and (13)C enrichment of blood glucose and lactate were determined. The data indicated the occurrence of [3-(13)C]lactate recycling through liver gluconeogenesis. The yield of glucose labeling was, however, reduced when using the glucose-containing infusate. After a 20-min or 1-h infusion, perchloric acid extracts of the brain tissue were prepared and subsequently analyzed by (13)C- and (1)H-observed/(13)C-edited NMR spectroscopy. The (13)C labeling of amino acids indicated that [3-(13)C]lactate was metabolized in the brain. Based on the alanine C3 enrichment, lactate contribution to brain metabolism amounted to 35% under the most favorable conditions used. By contrast with what happens with [1-(13)C]glucose metabolism, no difference in glutamine C2 and C3 labeling was evidenced, indicating that lactate was metabolized in a compartment deprived of pyruvate carboxylase activity. This result confirms, for the first time from an in vivo study, that lactate is more specifically a neuronal substrate.

Animals↗
PubMed2002

Glutamate-glutamine cycling in the epileptic human hippocampus.

PURPOSE: Several findings suggest that energy metabolism and the glutamate-glutamine cycle may be impaired in epilepsy. Positron emission tomography often shows interictal hypometabolism of the epileptogenic hippocampus. In vivo microdialysis studies show that seizure-associated glutamate release is doubled, and clearance is slowed. We hypothesized that the glutamate-glutamine cycle between neurons and glia may be decreased in the epileptic human hippocampus. METHODS: A 20% solution of 2-13C-glucose was infused before resection of the epileptogenic hippocampus. Blood glucose isotopic fractions were measured every 30 min. Blood and brain specimens were frozen quickly; perchloric acid extracts of the small metabolites were prepared and analyzed by proton and carbon magnetic resonance spectroscopy (MRS) at 11.75 Tesla. RESULTS: Standard histology showed 12 with hippocampal sclerosis and five with minimal neuron loss. The relative rates of glutamate-glutamine cycling with respect to glutamate synthesis were decreased in biopsies affected by hippocampal sclerosis (mean, 0.08; 95% confidence interval, 0.04-0.12) compared with those with minimal neuron loss (0.52; 95% CI, 0.30-0.75). Mean cellular glutamate concentrations were higher in minimal neuron loss (8.9 mM; 95% CI, 7.4-10.4) than hippocampal sclerosis (7.3 mM; 95% CI, 5.9-8.7). Cellular glutamine concentrations (mean, 2.8 mM; 95% CI, 2.4-3.2; n = 17) were the same in all groups. CONCLUSIONS: The epileptogenic, gliotic human hippocampus appears to be characterized metabolically by slow rates of glutamate-glutamine cycling, decreased glutamine content, and a relative increase in glutamate content. We hypothesize that the low rate of glutamate-glutamine cycling that results from a failure of glial glutamate detoxification could account for slow glutamate clearance from synapses and continuing low-grade excitotoxicity.

Adolescent↗
PubMed2004

Metabolite pattern of Cysticercus cellulosae metacestode from different predilection sites of swine using proton magnetic resonance spectroscopy.

Cysticercosis due to Taenia solium is one of the most common public health problems in various regions of the world. We have performed prolon magnetic resonance spectroscopy (1H MRS) experiments of the fluid aspirated from cysticerci excised from skeletal muscle (n = 16) and brain (n = 9) of infected swine to compare the metabolite pattern of cysticerci in different predilection sites. Perchloric acid extract of cysticercus cysts excised from skeletal muscles (n = 16) was also prepared to ascertain water-soluble, low molecular weight metabolites using 1H MRS. Absolute quantification and statistical analysis of different metabolites was done to look for any significant differences in different locations of cysts. The metabolite pattern of cysticerci was found to be similar in the various predilection sites. Metabolites observed were leucine, valine, alanine, lysine, glycine, lipid contents, lactate, glutamate, acetate, succinate, creatine, choline, and glucose. Concentration of creatine in cysticercus fluid of cysts removed from the muscle was found to be significantly higher (p = 0.001) than the cysts located in the brain. We conclude that the metabolite pattern in the cysticerci is not influenced by the surrounding tissue location; however concentration of certain metabolites may depend upon the tissue location.

Animals↗
PubMed1991

Simple determination of iodine in small specimens of thyroid tissue.

This work describes a simple photometric determination of the iodine concentration in thyroid tissue, a method based on the well-known catalytic Sandell-Kolthoff reaction. The modified ceric arsenite reaction is very sensitive and does not require complicated laboratory equipment. It can be performed in any routine clinical laboratory if instructions are followed strictly. By means of this method iodine concentration can be determined even in small specimens, for instance puncture samples of thyroid tissue or thyroid glands of small animals (mouse). Previous to the analysis, the tissue is digested in a mixture of sodium chlorate and perchloric acid at 100 degrees C. Using this manner of digestion between 94 and 110% of iodine in the sample were recovered. Comparison with neutron activation analysis showed excellent agreement of the obtained values.

Humans↗
PubMed2001

[Effect of serum and osmotically active substances on metabolism in 262 tissue cultures of pig's corneas--improved preservation of donor tissue for keratoplasty].

BACKGROUND: The storage time of corneal organ cultures in limited in the closed system mainly used in European eye banks. In addition, swelling during storage reduces the quality of the donor material for keratoplasty. Therefore, dextrane was added in concentrations of 2.5%, 5%, 7.5% and 10% to the culture medium, and the energy producing metabolism was investigated. MATERIALS AND METHODS: The experiments were carried out with 262 pig corneas. MEM with some supplements was used at 31 degrees C. No serum was added, because glucose consumption, lactate production and ATP levels proved to be the same or better than with serum supplement. After 6 and 12 days, the corneas from organ cultures were extracted with perchloric acid. The levels of glucose and lactate in the stroma and of ATP and ADP in the epithelium were analysed with enzymatic-optical tests. RESULTS: Dextrane inhibited glycolysis and the production of ATP in corneal organ cultures during twelve days. With 7.5% and 10% dextrane in the medium, lactate levels in the cornea decreased from 6.09 to 4.5 and 4.6 microM/g H2O instead of increasing. At the same time, glucose increased paradoxical from 1.3 to 3.4 and 2.2 microM/g H2O, respectively. With 5% dextrane, glycolysis operated sufficiently producing an increase of lactate levels from 6.0 to 8.8 microM/g H2O and consuming glucose from levels of 1.27 down to 0.57 microM/g H2O. After 12 days with 7.5% and 10.0% dextrane, ATP levels were reduced, from 4.54 to 0.98 and 0.49 microM/g dry weight, and ATP/ADP ratios from 1.9 to 1.1 and 0.7 respectively. With 2.5% dextrane, the ATP was diminished from 4.5 to 2.2 microM/g dry weight. When 5% dextrane were added to the culture medium, the hydration was at optimum by 4.1, and ATP levels were reduced only from 4.5 to 2.6 microM/g dry weight. Moreover, the ATP/ADP ratios were at 2.1 as good as without dextrane. CONCLUSIONS: From the results it was concluded, that serum free medium may be used, and that permanent dewelling proved to be beneficial for the energy producing metabolism of the cornea in organ culture. Such conditions may improve morphological and metabolic quality of donor material. From previous publications, it was recommended, to use instead of toxic dextran the well tolerated HES (hydroxyethyl starch) and to apply a storage temperature of 21 degrees C, which slowed down glucose consumption without impairing the energy producing metabolism.

Adenosine Diphosphate↗
PubMed1974

Methylation of newly synthesized viral messenger RNA by an enzyme in vaccinia virus.

Purified vaccinia virions contain an enzyme that incorporates methyl groups from S-adenosylmethionine into viral RNA synthesized by the core-associated DNA-dependent RNA polymerase. This incorporation, by partially disrupted virions, was dependent on the presence of all four ribonucleoside triphosphates and Mg(++) and was inhibited by actinomycin D. At saturation, 2.3 methyl groups were incorporated per 1000 nucleotides. The methyl-labeled RNA product was sensitive to alkali and ribonucleases and hybridized to filters containing immobilized poly(U) or vaccinia DNA. The methyl groups were not located on the 3'-terminal polyadenylate sequence, nor were they randomly distributed along the RNA chain. The lability of a large portion of the methyl groups to perchloric acid digestion was consistent with an O-methyl linkage, and the chromatographic properties of the alkali-digested material suggested that either the 5'-terminus or up to three consecutive internal nucleotides were methylated. Methylation probably occurs at the macromolecular level, since added vaccinia RNA was a suitable substrate. The failure of heterologous rRNA and tRNA species as well as homopolyribonucleotides to act as substrate suggested that a specific sequence might be required.

Carbon Radioisotopes↗
PubMed1975

Carcinoembryonic antigen: evidence for multiple antigenic determinants and isoantigens.

Carcinoembryonic antigen (CEA) preparations, from various sources were compared by radioimmunoassay. The preparations studied included four CEA standards (CEA-Roch, CEA-Montreal, CEA-City of Hope, and CEA-British) and CEA from serum and liver metastases of a patient with cancer of the colon who had an extremely high concentration of serum CEA (more than 26,000 ng/ml). The data indicate that the CEA-Roche standard differs significantly from the other three CEA standards tested, and that the serum CEA from the patient was antigenically different from currently available CEA standards as well as from the CEA obtained from the patient's own liver metastases. These antigenic differences were reflected in radioimmunoassay inhibition curves that were different and that were not affected by perchloric acid extraction of CEA. Because of the antigenic variation in the serum CEA, markedly different CEA concentrations (varying by three orders of magnitude) were measurable by two different antisera (Roche and Montreal). All the various CEA standards and samples cochromatographed on columns of Sepharose-6B, despite the large antigenic variation. We postulate that CEA consists of a family of "isoantigens" with multiple antigenic determinants. We identified a serum CEA isoantigen that was different from the currently available standards. Consequently, we believe that results of radioimmunoassays currently used for CEA measurement may not represent absolute concentrations of serum "CEA", but may reflect the binding affinity of different isoantigens to a particular polyvalent CEA antiserum.

Carcinoembryonic Antigen↗