A combination of serum markers for the early detection of colorectal cancer

PURPOSE

Fecal occult blood testing is recommended as first-line screening to detect colorectal cancer (CRC). We evaluated markers and marker combinations in serum as an alternative to improve the detection of CRC.

EXPERIMENTAL DESIGN

Using penalized logistic regression, 6 markers were selected for evaluation in 1,027 samples (301 CRC patients, 143 patients with adenoma, 266 controls, 141 disease controls, and 176 patients with other cancer). The diagnostic performance of each marker and of marker combinations was assessed.

RESULTS

To detect CRC from serum samples, we tested 22 biomarkers. Six markers were selected for a marker combination, including the known tumor markers CEA (carcinoembryonic antigen) and CYFRA 21-1 as well as novel markers or markers that are less routinely used for the detection of CRC: ferritin, osteopontin (OPN), anti-p53, and seprase. CEA showed the best sensitivity at 95% specificity with 43.9%, followed by seprase (42.4%), CYFRA 21-1 (35.5%), OPN (30.2%), ferritin (23.9%), and anti-p53 (20.0%). A combination of these markers gave 69.6% sensitivity at 95% specificity and 58.7% at 98% specificity. Focusing on International Union against Cancer (UICC) stages 0-III reduced the sensitivity slightly to 68.0% and 53.3%, respectively. In a subcollective, with matched stool samples (75 CRC cases and 234 controls), the sensitivity of the marker combination was comparable with fecal immunochemical testing (FIT) with 82.4% and 68.9% versus 81.8% and 72.7% at 95% and 98% specificity, respectively.

CONCLUSIONS

The performance of the serum marker combination is comparable with FIT. This provides a novel tool for CRC screening to trigger a follow-up colonoscopy for a final diagnosis.

Abstract 2738: Early detection of colorectal cancer applying a combination of serum markers

Background: Fecal occult blood testing (FOBT) is the recommended first line screening for the detection of colorectal cancer (CRC). To improve the detection of CRC we evaluated serum markers and combinations of serum markers as an alternative approach.

Methods: Applying Lasso Regression, a specialized form of penalized logistic regression, we selected six markers for an evaluation in a collective of 857 patients including 301 CRC patients, 143 patients with adenoma, 266 healthy controls and 147 disease controls. For each marker and marker combination the performance was assessed.

Results: We tested a total of 22 biomarkers for the detection of CRC from serum. Of these six markers were selected for a marker combination by Lasso Regression. Included were the well-known tumor markers CEA and CYFRA21-1 as well as novel markers or markers that are less routinely used for the detection of CRC: ferritin, osteopontin, anti-p53 and seprase. CEA showed the best sensitivity of all markers with 43.9 % at 95% specificity, followed by seprase (42.4%), CYFRA21-1 (35.5%), osteopontin (30.2%), ferritin (23.9%) and anti-p53 (20.0%). When these markers were combined a sensitivity of 72.3% was reached at a corresponding specificity of 95% and of 62.1% at 98% specificity. Focusing on more screening relevant stages, UICC stages 0-III, reduced the sensitivity slightly to 68.0% and 53.3%, respectively. In a sub-collective where matched stool samples were available (75 CRC cases and 234 controls) the sensitivity of the marker combination was comparable to fecal immunochemical testing (FIT) with 82.4% and 68.9% vs. 81.8% and 72.7% at 95% and 98% specificity, respectively.

Conclusion: When six markers were combined to detect CRC from serum, the combination reached a performance that was comparable to FIT. This provides a novel tool for CRC screening to trigger a follow-up colonoscopy for a final diagnosis.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2738.

Development of a permanently controllable rotating biopsy device, Part I: theoretical considerations and in-vitro results for five different prototypes

PURPOSE

To develop different prototypes of permanently controllable rotating biopsy devices with determination of the most efficient prototype in biopsies in bovine myocardium.

MATERIALS AND METHODS

Five different prototypes of 18-gauge rotating biopsy devices were designed and constructed, four (1 - 4) with various drill-like cutting edges and one (5) cannula type with a lancet-like helically bent cutting edge. Using bovine myocardium as the biopsy tissue, n = 100 specimens per prototype were obtained, and a quantitative analysis including tissue fragmentation, length in mm and weight in mg was carried out. For statistical analysis, the chi-square test for tissue fragmentation and Kruskal-Wallis test for the parameters length and weight were calculated.

RESULTS

Prototype 5 showed the highest rate of extraction of one-fragment specimens in n = 66 cases and the lowest rate of failure to obtain tissue in n = 11 cases. The mean length/weight were 4.15 mm/ 3.91 mg for prototype 1, 1.80 mm/ 1.66 mg for prototype 2, 4.61 mm/ 3.28 mg for prototype 3, 5.20 mm/ 3.74 mg for prototype 4, and 9.57 mm/ 6.97 mg for prototype 5. In all three categories, prototype 5 was significantly superior to the prototypes 1 - 4 with p < 0.001.

CONCLUSION

The cannula type with a lancet-like helically bent cutting edge proved to be the most efficient prototype and may now be tested competitively against established automated biopsy devices in vitro.

Improved diagnosis of colorectal cancer using a combination of fecal occult blood and novel fecal protein markers

BACKGROUND & AIMS

Annual testing for fecal occult blood is recommended as first-line screening for the detection of colorectal cancer (CRC), but is affected by limited sensitivity. We initiated a proteomics-based search for novel biomarkers to improve the sensitivity of detection of CRC in stool samples.

METHODS

Six markers, including immunologic fecal occult blood test (iFOBT), were evaluated in a collective of 551 samples (186 CRC, 113 advanced adenoma, and 252 control patients) to establish the diagnostic performance of each marker and marker combinations.

RESULTS

We tested the known stool markers hemoglobin (iFOBT), hemoglobin-haptoglobin, calprotectin, carcinoembryogenic antigen, and the novel fecal markers tissue inhibitor of metalloproteinase-1 (TIMP-1) and S100A12. The best diagnostic performance was found for S100A12 with an area under the curve of 0.95, followed by TIMP-1 (0.92), hemoglobin-haptoglobin (0.92), hemoglobin (0.91), calprotectin (0.90), and carcinoembryogenic antigen (0.66). By using Bayes logistic regression as a mathematic model, the highest sensitivity (88%) for the detection of CRC at 95% specificity was obtained with the marker pair S100A12 and hemoglobin-haptoglobin. Increasing the specificity to 98%, the combination of S100A12, hemoglobin-haptoglobin, and TIMP-1 resulted in a sensitivity of 82%, with the highest increase of sensitivity found in early tumor stages (international union against cancer stage I: 74% sensitivity vs 57% of the best single marker).

CONCLUSIONS

Depending on the specificity selected, a marker pair, S100A12 and hemoglobin-haptoglobin, or a triple combination including TIMP-1, allowed the detection of CRC at significantly higher rates than can be obtained with iFOBT alone.

Identification of nicotinamide N-methyltransferase as a novel serum tumor marker for colorectal cancer

PURPOSE

The goal of this study was to identify and validate novel serum markers of human colorectal cancer as potential candidates for noninvasive detection of early colorectal neoplasm.

EXPERIMENTAL DESIGN

Employing two-dimensional gel electrophoresis and mass spectrometry, we analyzed 16 matched colorectal cancer and adjacent normal tissue samples. Proteins found to be elevated in cancer tissue were further validated by generating antibodies which were used for immunoblotting of tissue samples and for the development of highly sensitive immunoassays for assessment of serum samples.

RESULTS

In total, 735 different proteins were identified in colon tissue. Strong elevation in colorectal cancer for five proteins was confirmed by immunoblot analysis: transforming growth factor-beta induced protein ig-h3 (betaIG-H3), nicotinamide N-methyltransferase (NNMT), nucleoside diphosphate kinase A (nm23-H1), purine nucleoside phosphorylase (PNPH), and mannose-6-phosphate receptor binding protein 1 (M6P1). Elevated levels of NNMT, which is not predicted to be secreted but is known as a cytoplasmic protein, were found in serum from patients with colorectal cancer. Employing a receiver-operating characteristic curve based on the measurement of 109 patients with colorectal cancer and 317 healthy controls, we obtained an area under the curve of 0.84 for NNMT, which was superior to the established tumor marker carcinoembryogenic antigen with an area under the curve of 0.78.

CONCLUSIONS

It is proposed that NNMT serum levels may have significance in the early detection and in the management of patients with colorectal cancer.

Functional Solubilization of Aggregation-prone HIV Envelope Proteins by Covalent Fusion with Chaperone Modules

The envelope proteins of human immunodeficiency virus (HIV) and human T-cell lymphotrophic virus (HTLV) mediate cell attachment and membrane fusion. For HIV-1, the precursor protein gp160 is cleaved proteolytically into two fragments, the surface-associated receptor binding subunit gp120 and the membrane spanning subunit gp41, which is involved in membrane fusion during virus entry. Soluble and immunoreactive variants of gp41 are essential for the reliable diagnosis of HIV-1 infections. Hitherto, gp41 was solubilized by adding detergents, or in acidic or alkaline solvents. We find that covalent fusions with SlyD or FkpA, two homodimeric Escherichia coli chaperones with peptidyl-prolyl isomerase activity, solubilize retroviral envelope proteins without compromising their immunological reactivity. gp41 from HIV-1, gp36 from HIV-2 and gp21 from HTLV could be expressed in large amounts in the Escherichia coli cytosol when fused with one or two subunits of SlyD or FkpA. The fusion proteins could be easily isolated and refolded, and showed high solubility and immunoreactivity, thus providing sensitive and reliable tools for diagnostic applications. Covalent fusions with SlyD or FkpA might be valuable generic tools for the solubilization and activation of aggregation-prone proteins.

Magnetic polyoxometalates: anisotropic antiferro- and ferromagnetic exchange interactions in the pentameric cobalt(II) cluster

The ground-state properties of the pentameric Co(II) cluster [Co(3)W(D(2)O)(2)(CoW(9)O(34))(2)](12-) were investigated by combining magnetic susceptibility and low-temperature magnetization measurements with a detailed inelastic neutron scattering (INS) study on a fully deuterated polycrystalline sample of Na(12)[Co(3)W(D(2)O)(2)(CoW(9)O(34))(2)].46D(2)O. The encapsulated magnetic Co(5) unit consists of three octahedral and two tetrahedral oxo-coordinated Co(II) ions. Thus, two different types of exchange interactions are present within this cluster: a ferromagnetic interaction between the octahedral Co(II) ions and an antiferromagnetic interaction between the octahedral and the tetrahedral Co(II) ions. As a result of the single-ion anisotropy of the octahedral Co(II) ions, the appropriate exchange Hamiltonian to describe the ground-state properties of the Co(5) spin cluster is anisotropic and is expressed as H = -2 summation operator(i= x,y,z)J(1)(i)[S(1)(i)S(2)(i) + S(2)(i)S(3)(i)] + J(2)(i)[S(1)(i)S(5)(i) + S(2)(i)S(5)(i) + S(2)(i)S(6)(i) + S(3)(i)S(6)(i)], where J(1)(i) are the components of the exchange interaction between the octahedral Co(II) ions and J(2)(i) are the components of the exchange interaction between the octahedral and tetrahedral Co(II) ions (see Figure 1d). The study of the exchange interactions in the two structurally related polyoxoanions [Co(4)(H(2)O)(2)(PW(9)O(34))(2)](10)(-) and [Co(3)W(H(2)O)(2)(ZnW(9)O(34))(2)](12)(-) allowed an independent determination of the ferromagnetic exchange parameters J(1)(x) = 0.70 meV, J(1)(y) = 0.43 meV, and J(1)(z) = 1.51 meV (set a) and J(1)(x) = 1.16 meV, J(1)(y) = 1.16 meV and J(1)(z) = 1.73 meV (set b), respectively. Our analysis proved to be much more sensitive to the size and anisotropy of the antiferromagnetic exchange interaction J(2). We demonstrate that this exchange interaction exhibits a rhombic anisotropy with exchange parameters J(2)(x) = -1.24 meV, J(2)(y) = -0.53 meV, and J(2)(z) = -1.44 meV (set a) or J(1)(x) = -1.19 meV, J(1)(y) = -0.53 meV, and J(1)(z) = -1.44 meV (set b). The two parameter sets reproduce in a satisfactory manner the susceptibility, magnetization, and INS properties of the title compound.

Relation between serum cardiac troponin I values and severity of clinical, electrocardiographic and quantitative angiographic features in unstable angina

This study sought to find out a correlation, if any, between serum cardiac troponin I values and extent and severity of coronary artery disease in patients with unstable angina. Eighty patients with unstable angina and normal serum creatine kinase values were studied and a comparative evaluation of serum cardiac troponin I values with clinical findings, electrocardiography, quantitative coronary angiography and follow-up events was performed. Among 80 patients, 34 (43%) had cardiac troponin I values of 0.6 microgram/L or higher (group I) and 46 (57%), below 0.6 microgram/L (group II). The mean cardiac troponin I in group I was 2.6 +/- 1.7 micrograms/L and 0.2 +/- 0.1 microgram/L in group II. The patients in group I had more type C lesions, frequent triple vessel and left main coronary artery involvement, and higher mean percentage diameter stenosis in the coronary arteries than those in group II. Early follow-up showed that more patients in group I required procedures earlier (including PTCA and CABG) than those from group II. Mid-term follow-up (9.5 +/- 4 months) data also showed greater occurrence of cardiac events (i.e. myocardial infarction and the increased need of PTCA) in group I. Patients with elevated cardiac troponin I more often experienced Braunwald's class III (A and B) unstable angina associated with presence of marked ST-T changes on the electrocardiography than those from group II. Our study suggests elevated values of serum cardiac troponin I to be evenly associated with the severity and extent of coronary lesions, clinical severity of unstable angina and marked electrocardiographic changes. Follow-up results confirm the potential value of this marker in predicting the course of coronary artery disease.

Recombinant fusion proteins for the industrial production of disulfide bridge containing peptides: purification, oxidation without concatamer formation, and selective cleavage

We report the biotechnical production of peptides of approximately 35-50 amino acids in length containing one intramolecular disulfide bridge, using a recombinant fusion tail approach. This method fills the technological gap when either (a) chemical synthesis fails due to known problematic peptide sequences or (b) if simple recombinant expression is unsuccessful due to degradation. The fusion tail described here serves several purposes: (i) it enables high expression levels in Escherichia coli to be achieved; (ii) it renders the fusion protein fairly soluble; (iii) it contains a histidine affinity tag for easy purification on Ni-chelate resins, which also serves as a catalyst for the oxygen-dependent formation of the disulfide bridge; and (iv) it suppresses the formation of concatamers during the oxidation process through steric hindrance. The purified fusion protein is then immobilized on a reversed phase column for two purposes: (i) chemical cleavage of the fusion tail by cyanogen bromide and (ii) subsequent purification of the peptide. A very hydrophilic fusion partner is required so that immobilization on the reversed phase column always occurs due to the peptide. Sensitive hydrophobic residues are thereby protected from the cleavage reagent while the cleaved hydrophilic fusion tail is easily separated from the hydrophobic peptide. The method is exemplified by eight peptides representing an immunodominant epitope of the human immunodeficiency virus, but may be useful for a significant variety of similar peptides.

[Determination of cardiac troponin I on Stratus analyzer: prospective evaluation in unstable angina]

Cardiac troponin I (troponin lc) has been measured on the Dade Stratus analyzer. Cardiac specificity has been studied in patients presenting a rhabdomyolysis syndrome. The obtained results clearly demonstrated that this parameter may be used as a specific marker of myocardial injury, in contrast to total creatine kinase- or mass CK-MB measurements. In unstable angina, two groups of patients may be defined: one group with elevated troponin lc (> 0.60 microgram/L; 31 patients, group I), one other with normal troponin lc (< 0.35 microgram/L; 49 patients; group II). Quantitative angiographic analysis was performed on 50 patients including 18 patients from group I. Group I showed a more severe culprit lesion than group II. All the results suggested that troponin Ic might be an indicator of severity in unstable angina.

Synthesis of and radioligand binding studies with a tritiated pinacidil analogue: receptor interactions of structurally different classes of potassium channel openers and blockers

The synthesis of N-cyano-N'-[1,1-dimethyl-[2,2,3,3-3H]propyl]-N"-(3- pyridinyl)guanidine, [3H]-15, is described. The utility of this tritiated radioligand in characterizing the interactions of potassium channel openers and blockers with their receptors is demonstrated. Potassium channel openers of the pinacidil, cromakalim, aprikalim, diazoxide, and minoxidil types, as well as KATP channel blockers of the glibenclamide and eosine types, are all capable of displacing [3H]-15 from its receptor. The results indicate that all of these compounds interact with the same target protein, but that several different allosterically coupled receptor binding sites are probably involved. The highly significant correlation between the ability of the structurally diverse potassium channel openers to inhibit [3H]-15 binding and to relax vascular smooth muscle is consistent with their receptor binding sites being closely associated with the potassium channel protein which is the functional target of this class of drugs.

Binding of the K+ channel opener [3H]P1075 in rat isolated aorta: relationship to functional effects of openers and blockers

P1075 [N-cyano-N'-(1,1-dimethylpropyl)-N"-3-pyridylguanidine], an analogue of the K+ channel opener pinacidil, was shown to be a K+ channel opener in rat aorta, based on (i) its ability to stimulate 86Rb+ efflux, (ii) its ability to relax contractions in response to noradrenaline under normal conditions (5 mM KCl) but not under depolarized conditions (55 mM KCl), and (iii) the sensitivity of these effects to inhibition by the sulfonylurea glibenclamide. In these assays, P1075 was approximately 20 times more potent than cromakalim. Using a tritiated derivative, [3H] P1075, specific binding could not be detected in microsomal preparations from various tissues. However, in rat aortic strips specific binding of [3H]P1075 has been observed and was reduced by lowering the temperature or by decreasing intracellular ATP levels via metabolic inhibition. Specific [3H]P1075 binding was influenced neither by depolarization (55 mM KCl) nor by lowering the pH from 7.4 to 6.0. Binding was inhibited by representatives from all major families of K+ channel openers, with potencies that correlated well with the potencies obtained in 86Rb+ efflux and relaxation studies. However, stimulation of 86Rb+ efflux occurred at 40 times higher concentrations than did binding (and vasorelaxation). Of the various inhibitors of the K+ channel openers tested, only the sulfonylureas inhibited [3H] P1075 binding with the same rank order of potencies as that required for inhibition of P1075-induced 86Rb+ efflux, although at higher concentrations. The results show that binding of [3H] P1075 is independent of membrane potential but decreases concomitantly with the intracellular ATP level. The excellent correlation between the potencies of the openers and sulfonylurea blockers in binding assays and functional studies suggests that the 'drug receptor' labeled by [3H]P1075 in rat isolated aorta is of functional relevance. However, the fact that binding of the openers occurred at concentrations considerably lower than those required for K+ channel opening and that binding of the sulfonylureas was only reflected at concentrations higher than those needed to block the channel requires complex models to link binding and effect, possibly involving two agonist binding sites coupled by negative cooperativity.

The order and orientation of mouse lambda-genes explain lambda-rearrangement patterns

Mouse lambda-genes are rearranged in specific V lambda-JC lambda associations: V lambda 1 has only been found to rearrange with JC lambda 3 or JC lambda 1, whereas V lambda 2 mainly rearranges with JC lambda 2 and very rarely with JC lambda 1,3. In order to determine the physical basis for these associations we have cloned the respective lambda-genes and large portions of their flanking regions by chromosomal walking in a total of 141 kb of phage and cosmid clones. With the use of unique probes obtained from such clones, the order and orientation of the mouse lambda-gene segments were determined by analyzing patterns of DNA deletion associated with lambda-gene rearrangements in various cell lines. All V and C gene segments were found to be in the same transcriptional orientation, and V2 and V1 were found not to be next to each other, thus supporting the gene order V2-C2-C4-V1-C3-C1.

The order and orientation of mouse lambda-genes explain lambda-rearrangement patterns

Mouse lambda-genes are rearranged in specific V lambda-JC lambda associations: V lambda 1 has only been found to rearrange with JC lambda 3 or JC lambda 1, whereas V lambda 2 mainly rearranges with JC lambda 2 and very rarely with JC lambda 1,3. In order to determine the physical basis for these associations we have cloned the respective lambda-genes and large portions of their flanking regions by chromosomal walking in a total of 141 kb of phage and cosmid clones. With the use of unique probes obtained from such clones, the order and orientation of the mouse lambda-gene segments were determined by analyzing patterns of DNA deletion associated with lambda-gene rearrangements in various cell lines. All V and C gene segments were found to be in the same transcriptional orientation, and V2 and V1 were found not to be next to each other, thus supporting the gene order V2-C2-C4-V1-C3-C1.

Fatty-acid biosynthesis in man, a pathway of minor importance. Purification, optimal assay conditions, and organ distribution of fatty-acid synthase

Fatty-acid synthase has been purified to homogeneity from human liver by a 3-step procedure including protamine sulfate/ammonium sulfate fractionation, affinity chromatography on 2',5'-ADP-Sepharose 4B and gel filtration on Sephacryl S-300. Both the human and rat fatty-acid synthase had similar characteristics regarding molecular mass, subunit structure, amino-acid composition, and substrate affinities. In order to measure the fatty-acid synthase activities in small tissue samples it was necessary to improve the sensitivity of an isotopic assay using [14C]malonyl-CoA as tracer. Special attention was paid to the dual role of free CoASH as an activator and inhibitor of the enzyme. Considerable differences existed between the specific activities of the fatty-acid synthase complex measured in human and rat lipogenic organs. Only negligible values of about 1 mU/mg protein were found in human liver and adipose tissue, while the corresponding activities were 10- to 50-fold higher in young lean rats. Less pronounced but still remarkable differences were determined for the activity of the acetyltransferase which catalyses the initial primer reaction of the fatty-acid synthase complex. In some selected cases under long-term fat-free diet (alcoholism, parenteral nutrition) elevated values of fatty-acid synthase activities were detected in human tissues. Under usual diet, with a relatively high fat content of up to 40 percent, and even after a carbohydrate-rich diet for three days, fatty-acid synthase activity remained low. It is concluded that under the dietary conditions, common for the industrialized world, de novo lipogenesis in man is negligible.

Submucosal plexus and electrolyte transport across rat colonic mucosa

Electrolyte transport across two preparations of mucosa from rat colon descendens was compared to determine what influence the submucosal plexus has on electrolyte transport. One preparation consisted of the mucosa, muscularis mucosae, and the submucosal tissue and is referred to as the mucosa-submucosa preparation. The second preparation obtained by further blunt dissection of the mucosa-submucosa preparation consisted of only the mucosa and the circular muscle layer of muscularis mucosae and is referred to as the mucosa preparation. Histological studies showed that the submucosal tissue and the longitudinal layer of muscularis mucosae could be removed leaving only the mucosa and the circular layer of muscularis mucosae. The extensive neuronal network of the submucosa was shown when the submucosal tissue and longitudinal muscle layer of muscularis mucosae, which were removed, were stained histochemically for acetylcholinesterase activity. Both the mucosa-submucosa and mucosa preparations absorbed Na+ and Cl- when short-circuited. However, Na+ and Cl- absorption were significantly higher in the mucosa preparation. The increase in Na+ and Cl- transport in the mucosa preparation was accompanied with a decrease in the short-circuit current (Isc), the open-circuit potential difference (p.d.) and the transmural tissue conductance (Gt) when compared to the mucosa-submucosa preparation. Tetrodotoxin (TTX), a neurotoxin which blocks specifically the propagation of action potentials in excitable tissues, dose-dependently decreased Isc and p.d. in the mucosa-submucosa preparation when added to the serosal solution. The half-maximal effective concentration of TTX was 5 nM and maximal effective concentration 100 nM. TTX (1 microM) had no effect on Isc or p.d. when added to the mucosal solution. The decrease in Isc and p.d. caused by TTX in the mucosa-submucosa preparation was accompanied with an increase in Na+ and Cl- absorption. TTX caused only a small decrease in Isc and p.d. in the mucosa preparation. However, there was no measurable change in Na+ and Cl- transport in the mucosa preparation. The results suggest that spontaneously active neurones from the submucosal plexus have an inhibitory influence on the mucosa. Physical removal of the submucosal plexus or pharmacological blockade of the neurones within the mucosa-submucosa preparation by TTX led to enhanced absorption, suggesting that the set point of the mucosa for electrolyte transport is at or near a maximal absorptive state. Regulation or modulation of the mucosa may therefore occur by mechanisms that lower this set point, causing an inhibition of absorption of electrolytes.

Immunoassay of ergotamine and dihydroergotamine using a common 3H-labelled ligand as tracer for specific antibody and means to overcome experienced pitfalls

A highly sensitive radioimmunoassay for the determination of ergotamine and dihydroergotamine is described. The limit of detection is about 9 pg/mL blood plasma for both compounds. The specificity of the gamma-globulin, which was prepared from rabbit antiserum, was investigated in the presence of compounds synthesized as possible metabolites. It was found that the tricyclic peptide moiety common to both molecules is an essential structural feature for binding to the gamma-globulin. From dilution experiments with the radioactively labelled compound it followed that ergotamine and to a lesser extent also its dihydro derivative are adsorbed on various tube wall materials using known buffer solutions. A practically insuperable obstacle is rearrangement of ergotamine under the experimental conditions, forming a stereoisomer by inversion at the C-8 position. The equilibrium of ergotamine in equilibrium ergotaminine found in human plasma remains stable under the incubation conditions of the radioimmunoassay.

Properties and organ distribution of ATP citrate (pro-3S)-lyase

1. The lipogenic enzyme ATP citrate lyase (ATP:citrate oxaloacetate-lyase (pro-3S-CH2COO-acetyl-CoA; ATP-dephosphorylating), EC 4.1.3.8) is partially purified from human liver by ammonium sulfate fractionation and anionexchange chromatography. 2. Km values for the substrates are 1.1 x 10(-5) 1.3 x 10(-3), and 1.2 x 10(-4) M for CoASH, ATP and citrate, respectively. The hypolipidemic drug L(-)-hydroxycitrate is a competitive inhibitor with respect to citrate (Ki = 3 x 10(-4) M). 3. Specific activities measured in liver, adipose tissue and intestinal mucosa (autopsic and biopsic material) are in the range of 1 mU/mg protein suggesting that the citrate pathway does not significantly contribute to human lipogenesis. No stimulation is found after a 3-day carbohydrate-rich diet. 4. Specific activities of other key-enzymes of the acetyl-CoA production from carbohydrates (pyruvate dehydrogenase, cytosolic acetyl-CoA synthetase) are of the same low magnitude.