Gastric content is a complex biofluid within the human stomach which has an important role in digestive processes. It is believed that gastric content may be a contributory factor in the development of upper gastro-intestinal diseases. In this work, selected ion flow tube mass spectrometry (SIFT-MS) has been applied to the quantification of volatile organic compounds (VOCs) in the headspace vapor of gastric content samples, which were retrieved from three groups of patients, including those with gastro-esophageal cancer, noncancer diseases of the upper gastro-intestinal tract, and a healthy cohort. Twelve VOCs have been investigated in this study; the following 7 VOCs, acetone, formaldehyde, acetaldehyde, hexanoic acid, hydrogen sulphide, hydrogen cyanide, and methyl phenol, were found to be significantly different between cancer and healthy groups by the Mann-Whitney U test. Receiver operating characteristics (ROC) analysis was applied for the combined VOCs of acetaldehyde, formaldehyde, hydrogen sulphide, and methyl phenol to discriminate cancer patients from healthy controls. The area under the curve (AUC) was 0.9. This result raises the prospect that a VOC profile rather than a single biomarker may be preferable in the molecular-orientated diagnosis of gastro-oseophageal cancer, and this warrants further investigation to assess its potential application as a new diagnostic test.

A study is described of the first on line, real time analyses of the exhaled breath of five anaesthetized patients during the complete perioperative periods of laparoscopic surgery. These breath analyses were achieved using a selected ion flow tube, SIFT-MS, instrument, located in the operating theatre at an acceptable distance from the operating table, and coupled to the endotracheal tube in the ventilation circuit via a 5 metre long capillary tube. Thus, inhalation/exhalation breathing cycles, set to be at a frequency of 10 per minute, were sampled continuously for water vapour, the metabolites acetone and isoprene and the propofol used to induce anaesthesia for each operating period that ranged from 20 min (shortest) to 80 min (longest). Whilst there was some loss of water vapour along the long sampling line, the concentrations of the other trace compounds were not diminished. The breath acetone was essentially at a constant level for each patient, but increased somewhat over the longest operating period due to the onset of lipolysis. Most interesting is the clear increase of breath isoprene following abdomen inflation with carbon dioxide. The vapour of the intravenously injected propofol was detected in the exhaled breath and remained essentially constant during the perioperative period. These analyses were performed totally non-invasively and the data were immediately and constantly available to the anaesthetist and surgeon. Exploitation of this development could influence decision making and potentially improve patient safety within the perioperative setting.

A new molecular modeling approach has been used to derive a pharmacophore of the potent and selective cholecystokinin-2 (CCK(2)) receptor antagonist 5 (JB93182), based on features shared with two related series. The technique uses "field points" as simple and effective descriptions of the electrostatic and van der Waals maxima and minima surrounding a molecule equipped with XED (extended electron distribution) charges. Problems associated with the high levels of biliary elimination of 5 in vivo required us to design a compound with significantly lower molecular weight without sacrificing its nanomolar levels of in vitro activity. Two new series of compounds were designed to mimic the arrangement of field points present in the pharmacophore rather than its structural elements. In a formal sense, two of the three amides in 5 were replaced with either a simple pyrrole or imidazole, while some features thought to be essential for the high levels of in vitro activity of the parent compounds were retained and others deleted. These compounds maintained activity and selectivity for this receptor over CCK(1). In addition, the reduction in molecular weight coupled with lower polarities greatly reduced levels of biliary elimination associated with 5. This makes them good lead compounds for development of drug candidates whose structures are not obviously related to those of the parents and represents the first example of scaffold hopping using molecular field points.

Selected ion flow tube mass spectrometry, SIFT-MS, has been used to determine the levels of volatile trace gases in the room air of three clinical environments within a busy teaching hospital. The main aims of this study were to establish background levels of trace gases and to compare them to levels typically found within exhaled breath. Over a period of one month, room air samples were collected daily from an outpatient clinic, a hospital ward and an operating theatre, in either the morning or the evening. The concentrations of seven volatile compounds were compared between different locations and different times of the day. Having established the baseline levels for these compounds, breath was collected from healthy volunteers working within each of the three clinical locations. The concentrations of isoprene, acetone, hydrogen cyanide and ammonia within room air samples collected from at least one of the three clinical environments were less than 25% of levels typically found in human breath. Based on the recommendation of previous authors these compounds may therefore be suitable for use as exhaled markers of disease. In comparison high levels of ethanol, propanol and acetic acid within room air samples collected from each location may diminish confidence in their use as breath biomarkers.

We have recently described a novel series of nonpeptidic cholecystokinin-B (CCKB)/gastrin receptor antagonists based on a dibenzobicyclo[2.2.2]octane skeleton. We wish now to report on compounds arising out of our earlier work which have substantially greater affinity as antagonists for the CCKB/gastrin receptor system and which maintain, or improve on, the already high selectivity with respect to CCKA receptors. Thus, cis-7-[[[(1S)-[[3,5-dicarboxy-phenyl)amino]carbonyl]-2- phenylethyl]amino]carbonyl]-8-[[(1-adamantylmethyl)amino]- carbonyl]-2,3:5,6-dibenzobicyclo[2.2.2]octane expressed a pKi of 8.80 in mouse cortical membranes at CCKB/gastrin receptors. The selectivity for these receptors over CCKA receptors was in the order of 1000-fold.

The reaction pathway of alkylating agents is often exploited in the design of bifunctional anti-cancer drugs. These drugs form mono-DNA adducts as well as inter- and intra-strand cross-linked adducts, notably by reaction at DNA bases, including the N-7-position of guanine (G). A positive-ion fast-atom bombardment (FAB) mass spectrum of an in vitro preparation of DNA alkylated with phosphoramide mustard (the active metabolite of the anti-cancer drug cyclophosphamide) indicated the presence of the two mono-DNA adducts N-(2-chloroethyl)-N-[2-(7-guaninyl)ethyl] amine, designated NOR-G, and N-(2-hydroxyethyl)-N-[2-(7-guaninyl)ethyl] amine, designated NOR-G-OH, (MH+ 257/259 and 239, respectively) but not the presence of the cross-linked adduct N,N-bis-[2-(7-guaninyl)ethyl] amine, designated G-NOR-G (MH+ 372). Using synthetic standards, daughter-ion spectra of NOR-G, NOR-G-OH and G-NOR-G were obtained (matrix 0.2 M p-toluene sulphonic acid in glycerol) by positive-ion FAB tandem mass spectrometry (FAB-MS/MS). The daughter-ion spectra of both mono-DNA adducts NOR-G and NOR-G-OH contained a fragment ion at m/z 152 [G + H]+, whereas the cross-linked adduct, G-NOR-G, showed an ion at m/z 221, [MH-G]+. Evidence for the presence of NOR-G, NOR-G-OH and G-NOR-G in the in vitro preparation was obtained by performing a double parent-ion scan on m/z 152 and 221. The presence of G-NOR-G was further supported by performing a single parent-ion scan on m/z 221.(ABSTRACT TRUNCATED AT 250 WORDS)

Monitoring exposure to alkylating agents may be achieved by quantitatively determining the adduct levels formed with nucleic acids and/or proteins. One of the most significant results arising from the application of this approach has been the discovery in control populations of "background" levels of alkylated nudeic acid bases or alkylated proteins, in particular hemoglobin (Hb). In the case of Hb, a wide variety ofsuch adducts have been detected and quantitated by mass spectrometric techniques, with methylated, 2-carboxyethylated, and 2-hydroxyethylated modifications being most abundant. Although the source of these alkylation products is unknown, both endogenous and exogenous sources may be proposed. We have recently confirmed the presence of the N-terminal hydroxyethylvaline adduct in control human Hb using tandem mass spectrometry (MS-MS) and have now established background levels using GC-MS in more than 70 samples. Smoking raises the levels of the adduct up to 10-fold and occupational exposure to ethylene oxide up to 300-fold.Background levels of alkylated nucleic acids may be studied by analysis ofN7-alkylated guanine or N3-alkylated adenine, which are excised from nucleic acids after their formation and are excreted in urine. Although the presence of some of these urinary constituents may be accounted for by their natural occurrence in RNA or diet, the endogenous or exogenous source ofothers is unknown. Quantitative methods using MS-MS have now been developed for five ofthe observed urinary alkylguanines [N7-methyl-, N2-methyl-, N2-dimethyl-, N7-(2-hydroxyethyl)-, and N2-ethylguanine]. A GC-MS method has also been developed to measure urinary thymine glycol as a possible monitor of oxidative DNA damage.

Humans are exposed to a large number of carcinogens which may react at various sites throughout the body, including the N-7-, N2-, and O6-positions of guanine. The effects of this are various but may result in depurination and eventual excretion of the modified base in the urine. Various alkylguanine derivatives with substituents at the N-7-, N2- and O6-positions were synthesized and daughter-ion spectra obtained. Apart from the methyl and dialkylguanines all other spectra exhibited an ion at m/z 151 using electron ionization (EI) and m/z 152 using fast-atom bombardment (FAB). The daughter-ion spectra of dialkylguanines contained an ion at m/z 150 (EI). Hence, scans of m/z 150 and 151 using EI, to detect all parent-ions from which they are formed (parent-ion scans) should indicate the presence of alkyl and dialkylguanine bases in a complex biological matrix such as human urine. Parent-ion scans of m/z 150 and 151 (EI) of a partially purified human urine sample exhibited numerous ions, including a prominent ion at m/z 179. A daughter-ion spectrum of m/z 179 revealed fragment ions that suggested the presence of N2-dimethylguanine and an ethylated guanine. Any confusion due to the presence of daughter ions from different alkylguanines in the same spectrum can be resolved by the fact that an ethylated guanine has four exchangeable protons, whereas N2-dimethylguanine has only three. By performing hydrogen/deuterium exchange it is possible to distinguish the N2-dimethylguanine from ethylated guanine isomers.(ABSTRACT TRUNCATED AT 250 WORDS)