Correlation between gamma glutamyltransferase fractions and bone quality

Gamma-glutamyltransferase (GGT) has been recently identified as a bone-resorbing factor. The aim of this study was to investigate the association between plasma GGT fractions levels and bone quality. Plasma GGT fractions were analysed by gel-filtration chromatography. Bone quality was established quantitatively by two micro-CT derived microarchitectural parameters: the BV/TV (mineralised bone volume/total volume), and the SMI (structure model index) that describes the rod-like (low resistant) or plate-like (high-resistant) shape of bone trabeculae. We enrolled 93 patients hospitalised for elective total hip replacement (group Arthrosis, n=46) or for proximal femoral fracture (group Fracture, n=47). Patients within the first quartile of BV/TV (Q1, osteoporotic patients, n=6) showed higher levels of b-GGT fraction [median (min-max): 3.37 (1.42–6.81)] compared to patients with normal bone density (fourth quartile Q4, n=10; 1.40 (0.83–4.36); p=0.0393]. Also, according to SMI, b-GGT value was higher in the subgroup with bone fragility [Q1, n=8: 1.36 (0.43–4.36); Q4, n=8: 5.10 (1.4 –7.60); p=0.0117]. In conclusion, patients characterised by fragile bone structure showed specifically higher levels of plasma b-GGT activity thus suggesting fractional GGT analysis as a possible biomarker in the diagnosis of osteoporosis.

Colorectal cancer screening programme by faecal occult blood test in Tuscany: first round results

Screening with faecal occult blood test (FOBT) has been shown to be effective in reducing mortality from colorectal cancer. Tuscany was the first region in Italy in which a screening programme for colorectal cancer by FOBT was initiated region-wide. The aim of the paper was to describe organizational aspects, a quality control model and the results of this experience. From June 2000 to December 2001, 192583 subjects aged 50-70 were invited to undergo a 1-day immunochemical test without any dietary restriction. A total of 78505 subjects (41%) performed the screening test, of whom 4537 responders had a positive test result (5.8%). Among them, 1122 refused any form of assessment or underwent a colonoscopy outside the screening referral centres, with an overall assessment compliance of 75.3%. Malignancies were found in 193 patients and at least a high-risk adenomatous polyp in 692 patients. In about a quarter of the positive subjects who underwent assessment, cancer or high-risk adenoma was detected. In conclusion, data from this experience supported the feasibility of biennial colorectal screening programme by FOBT, particularly regarding invitation compliance and positivity rate. Further efforts are necessary to implement screening extension and to improve data collection.

Combined TL and 10B-alanine ESR dosimetry for BNCT

The dosimetric technique described in this paper is based on electron spin resonance (ESR) detectors using an alanine-boric compound acid enriched with (10)B, and beryllium oxide thermoluminescent (TL) detectors; with this combined dosimetry, it is possible to discriminate the doses due to thermal neutrons and gamma radiation in a mixed field. Irradiations were carried out inside the thermal column of a TRIGA MARK II water-pool-type research nuclear reactor, also used for Boron Neutron Capture therapy (BNCT) applications, with thermal neutron fluence from 10(9) to 10(14) nth cm(-2). The ESR dosemeters using the alanine-boron compound indicated ESR signals about 30-fold stronger than those using only alanine. Moreover, a negligible correction for the gamma contribution, measured with TL detectors, almost insensitive to thermal neutrons, was necessary. Therefore, a simultaneous analysis of our TL and ESR detectors allows discrimination between thermal neutron and gamma doses, as required in BNCT.

Conformational investigation of two isomeric chiral porphyrins: a convergent approach with different techniques

The conformation in solution of two atropisomeric meso-tetrabinaphthyl porphyrins, used as catalytic precursors in asymmetric synthesis, was studied by means of experimental ((1)H-NMR ROESY, UV-Vis, and circular dichroism) and computational (semiempirical structure optimization, DeVoe's coupled oscillators calculations) methods. UV-Vis and CD spectra are calculated for several molecular models, with a systematic sampling of the conformational space, and compared to the experimental ones, leading to a structural hypothesis which is confirmed by NMR and PM3.

Determination of absolute configuration of acyclic 1,2-diols with Mo2(OAc)4. 1. Snatzke's method revisited

The method employing dimolybdenum tetraacetate for the assignment of the absolute configuration of optically active 1,2-diols is thoroughly revisited and applied to several compounds, some of which were synthesized by asymmetric cis-dihydroxylation. No exceptions were found to the empirical rule relating the sign of the induced CD spectrum and the configuration of the substrate, whatever its structure and sterical requirements. To broaden the scope of the method, its applicability to critical situations commonly encountered with synthetic products is tested. It is demonstrated that the method can be applied on samples with low chemical and optical purity, and that it may lend itself as a means to estimate the ee. The roles of the water content of the sample and of the diol-to-dimolybdenum ratio are investigated.

195Pt NMR determination of the enantiomeric purity and absolute configuration of trisubstituted allenes by using [PtCl3(C2H4)]-[(S,S)-(1-NpMeCH)2NH2]+ as CDA

[figure: see text] The ionic CDA [PtCl3(C2H4)]-[(S,S)-(1-NpMeCH)2NH2]+ produces, on exchange of its coordinated ethylene by chiral trisubstituted allenes, diastereoisomeric mixtures originating distinct 195Pt NMR resonances for the complexed enantiomers, thus allowing the determination of the enantiomeric purity. A reproducible correlation between relative positions of platinum signals due to the complexed enantiomers and their absolute configuration has been found.

[PtCl3(C2H4)]-[AmH]+ complexes containing chiral secondary amines: use as chiral derivatizing agents for the enantiodiscrimination of unsaturated compounds by 195Pt NMR spectroscopy and NMR stereochemical investigation

Ionic complexes [PtCl3(C2H4)]-[AmH]+, containing chiral secondary amines, constitute a versatile class of chiral derivatizing agents (CDAs) for the enantiomeric purity determination of chiral unsaturated compounds via 195Pt NMR spectroscopy. The NMR conformational analysis allows us to search for the stereochemical basis of their enhanced versatility.

Binding properties of human albumin modified by covalent binding of penicillin

Derivatisation of lysine residues in human albumin was performed in vitro by reaction with penicillin G. This modification reaction has been reported to occur in patients treated with high dosages of the antibiotic. The structure of the modified protein was characterised by mass spectrometry and circular dichroism. The number of the lysine residues involved depends on the time of incubation and on the drug/protein molar ratio. The secondary structure of the modified protein does not change significantly with respect to the native protein. Furthermore, the binding properties of the modified albumin were characterised by CD spectroscopy. Phenylbutazone, diazepam and bilirubin, known to bind to specific binding areas, were used as markers. A decrease of the affinity to the high-affinity binding sites was observed after the modification.

Determination of benzene at trace levels in air by a novel method based on solid-phase microextraction gas chromatography/mass spectrometry

A new method for the determination of benzene at trace levels in air is presented. The method consists of the collection of air samples on adsorbent cartridges with simultaneous adsorption of pre-established amounts of D6-labeled internal standard. Desorption from the cartridge is performed by solid-phase microextraction (SPME) with analysis by gas chromatography/mass spectrometry (GC/MS) using an ion trap mass spectrometer. The influence of several parameters (type of SPME fiber, temperature, time, for example) was investigated, and good linearity in the range 10-400 ng of C6D6, with a coefficient of variance (CV) around 3-5%, was obtained. The method was tested by sampling air in a town center in Italy, and a benzene concentration of approximately 50 microg/m(3) was determined. The maximum limit recommended by the European Community is 10 microg/m(3).

Effects of long-term treatment with verapamil on left ventricular function and myocardial blood flow in patients with dilated cardiomyopathy without overt heart failure

Myocardial blood flow (MBF) abnormalities are present in early stage dilated cardiomyopathy (DCM) and have been attributed to coronary microvascular abnormalities. The favorable effects of verapamil on coronary microcirculation might indicate its use in early stage DCM. We assessed the safety of long-term combination therapy of verapamil and enalapril and its effects on both left ventricular function and myocardial perfusion compared with enalapril alone in 18 patients with DCM (15 men, 3 women; mean age, 50+/-9 years) without overt heart failure (NYHA class I-II). At baseline and after 6 months of randomized treatment with either enalapril (10-20 mg) (nine patients, group 1) or enalapril (10-20 mg) and verapamil (120-240 mg) (nine patients, group 2), left ventricular function was assessed at rest, during handgrip, and during bicycle exercise by equilibrium radionuclide angiography. Mean MBF was measured at rest and after dipyridamole by positron emission tomography (PET) and 13N-ammonia as a flow tracer. At baseline, the two groups had reduced left ventricular ejection fraction at rest, which was further impaired during isometric exercise, but increased at peak bicycle exercise. MBF was similarly reduced in the two groups at rest and during dipyridamole. During treatment, no adverse events occurred in either group. After 6 months there was no significant difference in the main study variables either between the two groups or within each group before and after treatment. Long-term combination therapy with verapamil and enalapril is safe in patients with DCM without overt heart failure. Despite no favorable effect on myocardial perfusion, combined treatment prevented deterioration of left ventricular function, similarly to enalapril alone.

Reversible binding of ethacrynic acid to human serum albumin: difference circular dichroism study

The reversible binding of ethacrynic acid was characterized by a difference circular dichroism method. A 2/1 stoichiometry was determined for the [drug]/[HSA] (human serum albumin) complex. The reversible binding of ethacrynic acid to HSA determines direct competition with ligands that selectivity bind to site II and to the fatty acid site. Furthermore, indirect competition was shown for ligands for site I (anti-cooperative) and to site III (cooperative).

Different enantioselective interaction pathways induced by derivatized quinines

The stereochemistries in solution of the diastereoisomeric complexes formed by quinines modified at the hydroxyl site (9-O-acetylquinine; 9-O-(3,5-dimethoxyphenylcarbamate)quinine) or quinuclidine nitrogen (N-benzylquininium chloride) and each enantiomer of 2-(3', 5'-dinitrobenzamido)-1-phenylethanol have been compared to those of the free compounds by (1)H NMR investigations. Completely different interaction models, also involving changes of the free state conformations, have been obtained.

Identification and characterization of fenton oxidation products of surfactants by electrospray mass spectrometry and by solid phase microextraction gas chromatography mass spectrometry. 2. Fatty alcohol polyethoxy sulphates

The Fenton reaction for the degradation of surfactants has been investigated and partial degradation products have been identified and characterized by mass spectrometry for the case of fatty alcohol polyethoxy sulphates. The polar water-soluble products were investigated by liquid chromatography/mass spectrometry (LC/MS) with electrospray ionization (ESI), and the volatile products leaving the mixture during the reaction were trapped by means of solid phase microextraction (SPME) and investigated by gas chromatography/mass spectrometry (GC/MS) with electron and chemical ionization. The oxidation leads to the formation of products with hydroxyl and epoxide groups due to insertion of oxygen atoms or with terminal ethoxylic moieties deriving from the loss of the hydrophilic sulphate group. The formation of volatile aldehydes is also observed, corresponding to the fragmentation between hydrocarbon and ethoxylic chains. The extent of mineralization is dependent on peroxide and iron(II) concentrations. Copyright 2000 John Wiley & Sons, Ltd.

Catalytic asymmetric dihydroxylation of alkenes induced by polymeric chiral ligands

Chiral monomers, bearing different quinidine derivatives, were copolymerized with achiral monomers, producing insoluble copolymers which were used for the dihydroxylation of styrene as standard substrate. The structure of the polymeric insoluble support was found to be of great importance in determining the handling, efficiency, and enantioselectivity of the catalyst. The comparison with a soluble model compound showed that the insoluble polymer-bound ligand approach is very promising for both small- and large-scale synthesis of optically active vicinal diols. Copyright 1999 Wiley-Liss, Inc.

Investigation on the iodination reaction of methylene blue by liquid chromatography-mass spectrometry with ionspray ionisation

Radioactive iodine (131I and 123I) labelled methylene blue is used for the early diagnosis of melanoma metastases. We studied the iodination reaction of methylene blue (using "cold" iodine) in order to characterise the iodination product(s) as far as number and position of iodine atoms introduced on the aromatic ring(s) is concerned. The reaction was carried out under the same experimental conditions used for the radioactive one, that is in a large excess of methylene blue. The ionspray HPLC-MS analysis of the reaction mixture showed that the iodinated methylene blue was present only in a very small amount and the main iodinated product was a demethylated one, coming out from the iodination of an impurity azure B. We also studied the iodination reaction of azure B in order to better explain the reaction pathway. Commercial azure B contains impurities of methylene blue and all the possible demethylated derivatives. HPLC-MS analysis of the reaction mixture allowed a complete characterisation of the iodinated and bis-iodinated products.

Identification and characterization of fenton oxidation products of surfactants by ionspray mass spectrometry and solid-phase microextraction gas chromatography mass spectrometry 1. Lauryl sulphate

The Fenton reaction for the degradation of surfactants has been investigated and partial degradation products have been identified and characterized by mass spectrometry for the case of lauryl sulphate. The polar soluble products were investigated by liquid chromatography/mass spectrometry (LC/MS) with electrospray ionization (ESI), and the volatile products leaving the mixture during the reaction were trapped by means of solid-phase microextraction (SPME) and investigated by gas chromatography/mass spectrometry (GC/MS) with electron and chemical ionization. The oxidation leads to the formation of products with hydroxyl and epoxide groups due to insertion of oxygen atoms or to aldehydes derived from the loss of the hydrophilic sulphate group. The extent of mineralization is dependent on peroxide and iron concentrations. Copyright 1999 John Wiley & Sons, Ltd.

A simple method for the extraction of volatile organic compounds contained in air samples from adsorbent materials by solid phase microextraction and their analysis by gas chromatography/mass spectrometry

The monitoring of air pollution requires simple, rapid and sensitive sampling and analytical techniques with minimal sample manipulation that are usable for routine analyses. In our laboratories we have developed a method for the analysis of air samples collected by adsorbent cartridges based on solid phase microextraction (SPME) coupled to gas chromatography/mass spectrometry. We investigated the influence of some variables (time and temperature) using toluene as analyte (one of the most common air pollutants) and toluene-d(8) on the SPME extraction, and the sensitivity (LOQ) of the method. We then tested the method on an air sample collected in an industrial area and carried out characterisation of the volatile organic compounds present.

Use of CD and FT-IR to determine the secondary structure of purified proteins in the low-microgram range

The spectroscopic characterization of protein secondary structure is often partially unreliable when samples are not extremely pure and abundant. This problem may be overcome by the combination of circular dichroism (CD) and Fourier transform infrared spectroscopy (FT-IR). We used these methods to characterize the secondary structure of two proteins of neurobiological interest, calexcitin (CE) and the cellular isoform of prion protein (PrPC). Both proteins were purified with multiple chromatographic steps and were obtained in buffer with high purity (> 95%) and in low amount (approximately 2 micrograms). The samples were analyzed by circular dichroism (down to 184 or 182 nm), recovered, and deposited on films for infrared analysis. The spectral deconvolution from the two methods yielded secondary structures in good agreement with each other as well as with theoretical predictions based on amino acid sequence. The conformation of CE was found to be dependent on its concentration and on calcium binding. The secondary structure of cellular native PrP varied dramatically with the detergent used. In conclusion, the combination of CD and FT-IR analysis is suitable for the characterization of the conformational changes induced by ligand binding and/or by different solvent conditions when the protein of interest is only scarcely available. The methods used here provide valuable insights into the putative correlation between protein structure and activity.

Chemical modification of human albumin at cys34 by ethacrynic acid: structural characterisation and binding properties

Derivatization of the free cys3,4 in human albumin, which is reported to occur under physiological conditions, has been performed in vitro by reaction of the protein with ethacrynic acid. This modification has been investigated by mass spectrometry and circular dichroism. Ethacrynic acid has been proven to bind human albumin either covalently and non-covalently. This post-translational modification does not determine significant changes in the secondary structure of the protein, as shown by the comparable circular dichroism spectra of the native and the modified proteins. Furthermore, the binding properties of the human albumin samples have been investigated by circular dichroism and equilibrium dialysis. The affinity to the higher affinity binding sites does not change either for drugs binding to site I, like phenylbutazone, or to site II, like diazepam, while a small but significant increase has been observed for bilirubin, known to bind to site III. Nevertheless significant decreases of the affinity at the lower affinity binding sites of the modified protein were observed for both drugs binding to site I or to site II.

Ligand binding to a human serum albumin stationary phase: use of same-drug competition to discriminate pharmacologically relevant interactions

A technique based on a human serum albumin (HSA) stationary phase high-pressure liquid chromatography (HPLC) has been successfully used for the past few years to characterize the interactions between HSA and new substrates. Immobilized HSA conserves the binding properties of the protein in solution, allowing fast and reliable analyses of binding interactions. Nevertheless, clear evidence that all binding mechanisms of HSA-HPLC are pharmacologically relevant is so far lacking. In particular, non-stoichiometric interactions of injected ligands with stationary phase components such as silica and the amino acid medium (other than protein binding areas) might interfere with the correlation between chromatographic retention and HSA binding. Here we present a quantitative method to distinguish between the molecular interactions of a ligand with binding areas of potential pharmacological interest and other, non-saturable binding mechanisms. Such a method, based on HPLC same-ligand displacement, is simple and reliable, as confirmed by in situ protein denaturation. Consequently, we were able to distinguish between different types of competitions detected in the co-binding of two drugs to HSA.

Different NMR approaches to the chiral analysis of trisubstituted allenes devoid of polar functional groups and aromatic hydrocarbons

The use of permethylated beta-cyclodextrin as chiral solvating agent for NMR spectroscopy allowed us to determine the enantiomeric purity of chiral aromatic hydrocarbons as well as the enantiomeric purity and absolute configuration of chiral trisubstituted allenes devoid of polar functional groups. The enantiomeric excesses of the trisubstituted allenes have been also determined by 195Pt NMR spectroscopy of the diastereoisomeric trans-dichloro[(S)-alpha-phenylethyl-amine](allene)Pt(II) complexes.

Direct resolution, characterization, and stereospecific binding properties of an atropisomeric 1,4-benzodiazepine

The chromatographic resolution of 7-chloro-1,3-dihydro-1-(1,1-dimethylethyl)-5- (2-fluorophenyl)-2H-1,4-benzodiazepin-2-on (7), the 2'-fluoro, N1-tertbutyl analogue of diazepam, was attained on both analytical and preparative (mgs) scales, by using several chiral stationary phases (CSPs). The stereochemistry of this compound was characterized by means of 1H-NMR Nuclear Overhauser Effect (NOE) analysis. The single enantiomers of 7 were tested for their configuration and stereochemical stability by circular dichroism (CD), and their interaction with the central nervous system (CNS) benzodiazepine receptor was assayed, showing a significant difference in their binding affinities. Protein binding studies with human serum albumin (HSA, the main benzodiazepine carrier in human plasma) immobilized on a silica stationary phase revealed that HSA also preferentially binds one stereoisomer of 7. However, both on line CD detection and stereospecific interaction with other common drugs clearly demonstrated that the stereoselectivity of immobilized HSA for 7 is opposite to that for all the other studied benzodiazepines. In addition, HSA stereoselectivity for 7 is opposite to CNS receptor binding stereoselectivity for the same compound. Such HSA anomalous stereoselectivity for 7 was also confirmed in aqueous buffer solution by competitive displacement studies. Compared to other chiral 1,4-benzodiazepines, compound 7 thus shows several anomalous binding properties: HSA and the CNS receptor demonstrated opposite enantioselective discrimination; HSA has reversed enantioselectivity for compound 7; and HSA stereospecifically binds the low-affinity enantiomer.

Non-covalent complexes between DNA-binding drugs and double-stranded deoxyoligonucleotides: a study by ionspray mass spectrometry

The non-covalent complexes between some DNA-binding drugs and duplex oligodeoxynucleotides were studied by ionspray mass spectrometry, with the aim of evaluating the suitability of this technique to screen rapidly a series of drugs exerting their activity through non-covalent binding to specific base sequences of DNA. Two classes of drugs were considered, distamycins (which show affinity for the minor groove of DNA) and anthracyclines (which interact through intercalation between bases). For the former, d(CGCGAATTCGCG)2 was chosen as the model oligodeoxynucleotide. Following optimization of sample preparation and instrumental conditions, the complexes of different distamycins were observed; depending on the ligand considered, 1:1 or 2:1 complexes were formed preferentially. A semi-quantitative evaluation of the relative affinities was made by measuring the ratio of the complexes signals to those of the duplex, and also by competitive binding with equimolar amounts of distamycin. For anthracyclines, the daunorubicin-d(CGATCG)2 complex was chosen as the model for a preliminary mass spectrometric study; however, the signals of the duplex and the complex were very low compared with the monomer signal. Since the complex was known to be stable in solution, this was ascribed to gas-phase instability, probably caused by electrostatic repulsion between negatively charged phosphate groups.

Secondary structure and Ca2+-induced conformational change of calexcitin, a learning-associated protein

Calexcitin/cp20 is a low molecular weight GTP- and Ca2+-binding protein, which is phosphorylated by protein kinase C during associative learning, and reproduces many of the cellular effects of learning, such as the reduction of potassium currents in neurons. Here, the secondary structure of cloned squid calexcitin was determined by circular dichroism in aqueous solution and by Fourier transform infrared spectroscopy both in solution and on dried films. The results obtained with the two techniques are in agreement with each other and coincide with the secondary structure computed from the amino acid sequence. In solution, calexcitin is one-third in alpha-helix and one-fifth in beta-sheet. The conformation of the protein in solid state depends on the concentration of the starting solution, suggesting the occurrence of surface aggregation. The secondary structure also depends on the binding of calcium, which causes an increase in alpha-helix and a decrease in beta-sheet, as estimated by circular dichroism. The conformation of calexcitin is independent of ionic strength, and the calcium-induced structural transition is slightly inhibited by Mg2+ and low pH, while favored by high pH. The switch of calexcitin's secondary structure upon calcium binding, which was confirmed by intrinsic fluorescence spectroscopy and nondenaturing gel electrophoresis, is reversible and occurs in a physiologically meaningful range of Ca2+ concentration. The calcium-bound form is more globular than the apoprotein. Unlike other EF-hand proteins, calexcitin's overall lipophilicity is not affected by calcium binding, as assessed by hydrophobic liquid chromatography. Preliminary results from patch-clamp experiments indicated that calcium is necessary for calexcitin to inhibit potassium channels and thus to increase membrane excitability. Therefore the calcium-dependent conformational equilibrium of calexcitin could serve as a molecular switch for the short term modulation of neuronal activity following associative conditioning.

Phantom dosimeters examined by NMR analysis: a promising technique for 3-D determinations of absorbed dose

Fricke-infused agarose gels examined by nuclear magnetic resonance (NMR) analysis are inspected, and their response to gamma-rays, thermal neutrons and protons, at radiotherapy dose levels, is examined. The gel composition is chosen with attention to the tissue equivalence for the radiation fields of interest; this problem is crucial, in particular, for thermal neutrons. The feasibility of three-dimensional determination of absorbed dose in Fricke-gel phantoms is investigated, and the possibility of employing the technique in conformal therapies, such as boron neutron capture therapy (BNCT) and proton therapy, is tested. Isodose curve determination in a cylindrical gel phantom exposed to thermal neutrons is presented. A method for depth-dose profiling in tissue exposed to protons is described, and some results are reported which show that the depth-dose data are determinable with millimetric precision. Results obtained with a spectrophotometer from gel augmented with a metal indicator are reported and discussed also. These results show the possibility of obtaining a very sensitive dosimetry technique consisting of spectrophotometric analysis of such a Fricke-gel.

Pharmacokinetic and Metabolism Study in Healthy Volunteers After Administration of Single Oral Dose of (3)H-alpha-Dihydroergocryptine Mesylate

This phase I open pharmacokinetic and metabolism study was conducted with six healthy male volunteers who were given 20 mg of (3)H-alpha-dihydroergocryptine in order to evaluate the absorption, plasma time course, and urinary and fecal elimination of total radioactivity. Rapid absorption into the general circulation occurred with an average K(01) of 0.99 plus minus 0.73/h. Peak time(T(max)) was reached in approximately 3 h with an average radioactivity concentration (C(max)) of 8.78 plus minus 5.9 ng eq h/ml. Distribution from the central compartment to the peripheral compartment occurred with a mean rate constant (K(12)) of 0.330 plus minus 0.22/h. Estimations of total clearance (CL) and volume of distribution (Vd) seem strongly affected by the low oral availability (F) of hydrogenated ergots. The rate constant (K(21)) of radioactivity washout from the tissue to the central compartment was 0.250 plus minus 0.130/h. However, plasma radioactivity declined biexponentially with an overall elimination constant (K(10)) of 0.029 to 0.146/h (i.e, half-lives of 23.9--4.75/h). Total radioactivity recovery in urine and feces was good with 82.78 plus minus 6.44% of dose eliminated in feces and 3.01 plus minus 0.65% in urine. The latter concentration was too low to detect metabolites or unchanged drug by radioactivity image scanning. However, the liquid scintillation count of silica gel that had been scraped off the thin layer chromatography (TLC) plates indicated the presence of metabolites in urine. Pharmacodynamically, both supine and standing blood pressure fell significantly within the first 8 h of dosing, yet there were no changes in heart rate. No adverse reactions were reported. In conclusion, the kinetics of (3)H-dihydroergocryptine are very similar to other ergot alkaloids in respect to extensive hepatic metabolism with an elimination half-life of 25 h.

Immunochemical vs guaiac faecal occult blood tests in a population-based screening programme for colorectal cancer

Two faecal occult blood tests (FOBTs), Hemoccult II (guaiac based) and Hemeselect (immunochemical) were compared in a population screening for colorectal cancer on 24 282 subjects aged 40-70. Hemeselect was interpreted according to a lower (+ and +/-) and a higher (+) positivity threshold. A total of 8008 compliers were enrolled in the study. Positivity rates: Hemoccult = 6.0%, Hemeselect (+ and +/) = 8.2%, Hemeselect (+) = 3.1%. Among FOBT-positive subject complying with the diagnostic work-up, 22 had colorectal cancer (17 Hemeselect-positive (+), four Hemeselect-borderline (+/-), 15 Hemoccult-positive) and 166 subjects had adenomas (62 Hemeselect(+), 56 Hemeselect-borderline (+/-), 79 Hemoccult-positive) were detected. The positive predictive values (PPVs) for cancer were as follows: Hemoccult = 3.7%, Hemeselect (+ and +/-) = 3.8%, Hemeselect (+) = 8.4%. The PPVs for adenoma(s) were: Hemoccult = 19.7%, Hemeselect (+ and +/-) = 21.4%, Hemeselect (+) = 30.5%. The specificity for cancer was: Hemoccult = 94.1%, Hemeselect (+ +/-) = 92%, Hemeselect (+) = 97.1%. Ratios between detection rates of each test and expected incidence of colorectal cancer suggest that Hemoccult anticipates cancer diagnosis by approximately 2 years on average whereas the mean diagnostic anticipation of Hemeselect ranges between 2.5 and 3.2 years. Hemeselect is superior to Hemoccult as it is at least as effective but more efficient and acceptable than guaiac testing. Further evaluation of Hemeselect cost-effectiveness and sensitivity is needed in order to assess the optimal threshold of positivity and screening frequency.

Microvascular dysfunction in collateral-dependent myocardium

OBJECTIVES

The aim of this study was to evaluate myocardial blood flow regulation in collateral-dependent myocardium of patients with coronary artery disease.

BACKGROUND

Despite great clinical relevance, perfusion correlates of collateral circulation in humans have rarely been estimated by quantitative methods at rest and during stress.

METHODS

Nineteen patients with angina and isolated occlusion of the left anterior descending (n = 14) or left circumflex (n = 5) coronary artery were evaluated. Using positron emission tomography and nitrogen-13 ammonia, we obtained flow measurements at baseline, during atrial pacing-induced tachycardia and after intravenous administration of dipyridamole (0.56 mg/kg body weight over 4 min). Flow values in collateral-dependent and remote areas were compared with values in 13 normal subjects.

RESULTS

Flow at rest was similar in collateralized and remote myocardium (0.61 +/- 0.11 vs. 0.63 +/- 0.17 ml/min per g, mean +/- 1 SD), and both values were lower than normal (1.00 +/- 0.20 ml/min per g, p < 0.01). During pacing, blood flow increased to 0.83 +/- 0.25 and 1.11 +/- 0.39 ml/min per g in collateral-dependent and remote areas, respectively (p < 0.05 vs. baseline); both values were lower than normal (1.86 +/- 0.61 ml/min per g, p < 0.01). Dipyridamole induced a further increase in perfusion in remote areas (1.36 +/- 0.57 ml/min per g, p < 0.01 vs. pacing) but not in collateral-dependent regions (0.93 +/- 0.37 ml/min per g, p = NS vs. pacing); again, both values were lower (p < 0.01) than normal (3.46 +/- 0.78 ml/min per g). Dipyridamole flow in collateral-dependent myocardium was slightly lower in patients with poorly developed than in those with well developed collateral channels (0.75 +/- 0.29 vs. 1.06 +/- 0.38 ml/min per g, respectively, p = 0.06); however, the former showed higher flow inhomogeneity (collateral/control flow ratio 0.58 +/- 0.10 vs. 0.81 +/- 0.22, respectively, p < 0.02). A linear direct correlation was observed between flow reserve of collateral-dependent and remote regions (r = 0.83, p < 0.01).

CONCLUSIONS

Despite rest hypoperfusion, collateral-dependent myocardium maintains a vasodilator reserve that is almost fully utilized during increases in oxygen consumption. A global microvascular disorder might hamper adaptation to chronic coronary occlusion.

Myocardial blood flow response to pacing tachycardia and to dipyridamole infusion in patients with dilated cardiomyopathy without overt heart failure. A quantitative assessment by positron emission tomography

BACKGROUND

Myocardial blood flow (MBF) impairment has been documented in advanced dilated cardiomyopathy (DCM) in which hemodynamic factors, secondary to severe ventricular dysfunction, may limit myocardial perfusion. To assess whether MBF impairment in DCM may also be present independent of hemodynamic factors, the present study was designed to quantify myocardial perfusion in patients with mild disease without overt heart failure.

METHODS AND RESULTS

Absolute regional MBF (milliliters per minute per gram) was measured by positron emission tomography and 13N-ammonia in resting conditions, during pacing-induced tachycardia, and after dipyridamole infusion (0.56 mg/kg over 4 minutes) in 22 DCM patients and in 13 healthy subjects. Patients were in New York Heart Association functional class I-II and showed depressed left ventricular (LV) ejection fraction by radionuclide angiography (35 +/- 8%; range, 21% to 48%), normal coronary angiography, and normal or moderately increased LV end-diastolic pressure (9.2 +/- 5.5 mm Hg; range, 2 to 20 mm Hg). There were no differences in arterial blood pressure, heart rate, and rate-pressure product between patients and control subjects in the three study conditions. Compared with control subjects, DCM patients had lower mean MBF at rest (0.80 +/- 0.25 versus 1.08 +/- 0.20 mL.min-1.g-1, P < .01), during atrial pacing tachycardia (1.21 +/- 0.59 versus 2.03 +/- 0.64 mL.min-1.g-1, P < .01), and after dipyridamole infusion (1.91 +/- 0.76 versus 3.78 +/- 0.86 mL.min-1.g-1, P < .01). LV MBF values were related to baseline LV end-diastolic pressure at rest (r = -.57, P < .01) and during pacing (r = -.67, P < .01) but not after dipyridamole infusion (r = .19, P = .40). Five patients had LV end-diastolic pressure > 12 mm Hg; in 4, myocardial perfusion was severely depressed both at baseline and in response to stress.

CONCLUSIONS

In patients with DCM without overt heart failure, myocardial perfusion is impaired both at rest and in response to vasodilating stimuli. The abnormalities in vasodilating capability can be present despite normal hemodynamics; progression of the disease is associated with more depressed myocardial perfusion.

Residual coronary reserve identifies segmental viability in patients with wall motion abnormalities

OBJECTIVES

The aim of this study was to determine whether the presence of residual coronary reserve can in itself identify viable segments.

BACKGROUND

Experimental data suggest that despite hypoperfusion at rest, viable myocardium may exhibit persistence of coronary reserve. Preliminary observations in patients show that in basally dyssynergic areas, a residual vasodilator capability is present despite hypoperfusion at rest and that a flow-mediated increase in regional wall motion identifies residual viability.

METHODS

Fourteen patients with evidence of previous myocardial infarction, infarct-related single-vessel coronary artery disease and impaired regional ventricular function at rest underwent positron emission viability imaging by fluorine-18 deoxyglucose. In addition, blood flow at rest and vasodilator capability were regionally evaluated in all patients by means of nitrogen-13 ammonia.

RESULTS

Of a total of 252 segments, 133 were dyssynergic at rest. Of these 133 segments, 60 (group 1) showed normal metabolic activity and only mild reduction in myocardial blood flow. The other 73 segments showed a marked reduction in flow; of these, 25 (group 2, viable) had persistent metabolic activity, whereas 48 (group 3, necrotic) did not. Despite similar levels of hypoperfusion at rest, group 2 segments showed a preserved coronary reserve that was virtually absent in necrotic segments (2.6 +/- 1.3 vs. 1.3 +/- 0.5, p < 0.01). This value was similar to that observed in viable group 1 segments (2.5 +/- 1.6, p = NS).

CONCLUSIONS

In addition to characterizing myocardium at risk, imaging of coronary flow at baseline and after dipyridamole by positron emission tomography provides helpful information on myocardial viability that may integrate the "static" viability information obtained with the baseline flow/metabolic approach.