New 1-aryl-4-(biarylmethylene)piperazines as potential atypical antipsychotics sharing dopamine D(2)-receptor and serotonin 5-HT(1A)-receptor affinities.

This paper describes the syntheses of several 1-aryl-4-(biarylmethylene)piperazines and the results of the determination of their affinity for D(2) and 5-HT(1A) receptors. A selection of these compounds was evaluated in vivo, resulting in the identification of a drug candidate which is being clinically evaluated as a potential atypical antipsychotic with reduced extrapyrimidal side effects.

The interaction of class B G protein-coupled receptors with their hormones.

In common with many G protein-coupled receptors, dysfunction in members of the Class B or glucagon-like receptors can elicit a wide spectrum of disease related activities. Consequently, they are potential targets in many different areas of pharmacological research. Unlike the class A or rhodopsin-like receptors, for which at least some structural similarity to bacteriorhodopsin has been detected, absolutely no structural information is available for the Class B G protein-coupled receptors. We present a computational study that exploits the experimental work performed by evolution to indicate residues that are potentially involved in ligand binding in the Class B G protein-coupled receptors. We perform an analysis of mutations that occurred in a correlated fashion between the receptors and their peptidic ligands. The inference that the residues detected in this manner are involved in a direct interaction between the receptor and the ligand is in good agreement with the mutation studies that have already been published.

Intermittent claudication: symptom severity versus health values.

OBJECTIVE: The objective of this study was to obtain health values from patients with intermittent claudication with five different instruments and to study the construct validity of these measures of health-related quality of life by examining their relation with symptom severity. METHODS: We included all patients with intermittent claudication who participated in an exercise program of the Department of Internal Medicine at our university hospital (n = 92). Health value instruments included the verbal rating scale, time trade-off, standard gamble, EuroQol, and the Health Utilities Index (Mark III). Symptom-free walking distance was used as a measure of symptom severity. RESULTS: For all instruments the average health values in groups of patients with a symptom-free walking distance < or = 150 m were lower than the average values in patients with a greater walk distance, but the differences for the time trade-off and the standard gamble were small, and only the differences for the verbal rating scale and the EuroQol were statistically significant. At the individual patient level considerable heterogeneity was seen, and the statistical association of the symptom-free walking distance with health values varied from poor to moderate (Spearman rank correlations, 0.03 to 0.48; p values, 0.003 to 0.78). CONCLUSION: At least for the verbal rating scale and the EuroQol, the results of our study provide evidence of the validity of the various health value instruments in a population of patients with peripheral arterial occlusive disease.

Fitting multistate transition models with autoregressive logistic regression: supervised exercise in intermittent claudication.

The purpose of this study was to develop a model that predicts the outcome of supervised exercise for intermittent claudication. The authors present an example of the use of autoregressive logistic regression for modeling observed longitudinal data. Data were collected from 329 participants in a six-month exercise program. The levels of the polytomous outcome variable correspond to states they defined in a Markov decision model comparing treatment strategies for intermittent claudication. Autoregressive logistic regression can be used to fit multistate transition models to observed longitudinal data with standard statistical software. The technique allows exploration of alternative assumptions about the dependence in the outcome series and provides transition probabilities for different covariate patterns. Of the alternatives examined, a Markov model including two preceding responses, time, age, ankle brachial index, and duration of disease best described the data.

Study of the interaction between aryloxypropanolamines and Asn386 in helix VII of the human 5-hydroxytryptamine1A receptor.

We studied the stereoselective interaction between aryloxypropanolamines and the human 5-hydroxytryptamine1A (5-HT1A) receptor. R- and S-enantiomers of propranolol, penbutolol, and alprenolol were investigated for their ability to bind to human 5-HT1A wild-type and Asn386Val mutant receptors. Asn386 seemed to act as a chiral discriminator. Although both aryloxypropanol enantiomers displayed lower affinity for the mutant receptors, the affinities for the S-enantiomers were more affected. Receptor affinities of other structurally unrelated 5-HT1A ligands were not decreased by the mutation of Asn386 to valine. In addition, a series of analogues of propranolol with structural variation in the oxypropanolamine moiety was synthesized, and affinities for wild-type and Asn386Val mutant 5-HT1A receptors were determined. Both the hydroxyl and the ether oxygen atoms of the oxypropanol moiety seem to be required for binding at wild-type 5-HT1A receptors. The hydroxyl group of propranolol probably directly interacts with Asn386. The ether oxygen atom may be important for steric reasons but can also be involved in a direct interaction with Asn386. These findings are in agreement with the interactions of aryloxypropanolamines with Asn386 in rat 5-HT1A receptors that we previously proposed. The loss of affinity for propranolol by the Asn386Val mutation could be regained by replacement of the hydroxyl group of the ligand by a methoxy group. This modification of the propranolol structure has no effect on the affinity of both enantiomers for the wild-type 5-HT1A receptor, which provides an alternative hypothesis for the interaction of Asn386 with the oxypropanol oxygen atoms. According to this novel hypothesis, the oxypropanol oxygen atoms may both act as hydrogen bond acceptors from the NH2 group of Asn386.

5-HT1A-versus D2-receptor selectivity of flesinoxan and analogous N4-substituted N1-arylpiperazines.

We investigated the structural requirements for high 5-HT1A affinity of the agonist flesinoxan and its selectivity versus D2 receptors. For this purpose a series of arylpiperazine congeners of flesinoxan were synthesized and evaluated for their ability to displace [3H]-8-OH-DPAT and [3H]spiperone from their specific binding sites in rat frontal cortex homogenates and rat striatum, respectively. Variations were made in the N4-substituent and the arylpiperazine region. Effects of N4-substitution in the investigated compounds appeared to be quite similar for 5-HT1A- and D2-receptor affinity. Lipophilicity at a distance of four carbon atoms from the piperazine N4 atom seems to be the main contributing factor to affinity for both receptors. Our data show that the amide group in the flesinoxan N4-substituent is unlikely to interact with the 5-HT1A receptor but, instead, acts as a spacer. In contrast to the structure-affinity relationships (SARs) of the N4-substituents, selectivity for 5-HT1A versus D2 receptors was gained by the arylpiperazine substitution pattern of flesinoxan. Restriction of flexibility of the N4-(benzoylamino)ethyl substituent and its effect on 5-HT1A-receptor affinity and activity were also studied. Our data show that in the bioactive conformation, the N4-[(p-fluorobenzoyl)amino]ethyl substituent is probably directed anti-periplanar relative to the HN4 atom. These results were used to dock flesinoxan (1) and two of its congeners (27 and 33) into a model of the 5-HT1A receptor that we previously reported. Amino acid residues surrounding the N4-[(p-fluorobenzoyl)amino]ethyl substituent of flesinoxan and its congeners are also present in D2 receptors. In contrast, several residues that contact the benzodioxane moiety differ from those in D2 receptors. These observations from the 3D model agree with the 5-HT1A SAR data and probably account for the selectivity of flesinoxan versus D2 receptors.

Identification of class-determining residues in G protein-coupled receptors by sequence analysis.

G protein-coupled receptors (GPCRs) form a large superfamily of receptors that are characterised by a seven transmembrane helical motif. The functions they perform, such as binding ligands and G proteins, are related to the presence of certain amino acids in critical positions. We have developed a computational sequence pattern correlation technique for the recognition of such function-determining residues. The method searches for residues that are conserved in one class of proteins with a certain function but are different in other classes. The basic idea is that such residues are probably involved in this particular function. This technique was used to find residues that play a role in the binding of endogenous as well as exogenous ligands to various receptors. Many of the residues that were detected have been experimentally determined as important for ligand binding. More importantly, however, we also detected residues that are interesting targets for future mutation studies aimed at elucidating the sequence-function relationship in GPCRs. The information obtained may help improve three-dimensional GPCR models and can be useful for the study of receptor-ligand interactions.

Recruitment and retention of psychiatrists in non-metropolitan public positions in Queensland: research on "Queensland Health's response'.

OBJECTIVE: To evaluate Queensland Health's recruitment campaign of 15 fulltime psychiatrists to non-metropolitan areas between July 1992 and December 1993. METHOD: A detailed 170-item Likert-type questionnaire was designed and mailed to all 15 psychiatrists. Thirteen questionnaires were completed and followed-up by a face to face interview. RESULTS: Findings indicate that most of those recruited were experienced senior specialists who came to the positions as result of personal contact and were attracted to non-metropolitan positions because of 'lifestyle' and professional challenge' variables. 'Lifestyle' and 'professional' variables were identified as major contributors to their retention. They reported that 'bureaucracy' and 'social and family' reasons would be the most likely cause of them considering leaving their current positions. CONCLUSIONS: While the recruitment campaign was evaluated as successful, some aspects were clearly more influential than others. It was noted that factors which were likely to influence psychiatrists to leave non-metropolitan public sector positions were more 'public' than 'non-metropolitan' in nature.

N4-unsubstituted N1-arylpiperazines as high-affinity 5-HT1A receptor ligands.

In order to explore the structural requirements for high 5-HT1A affinity, a series of aryl-substituted N1-phenylpiperazines were synthesized and evaluated for their ability to displace [3H]-8-OH-DPAT from its specific binding sites in rat frontal cortex homogenates. We found 2-methoxy substitution to be favorable, while 4-methoxy substitution was detrimental for 5-HT1A affinity. Substitution with annelated rings at the 2,3-positions was highly favorable for all investigated compounds, with the exception of a pyrrole ring. All other substitutions, except fluoro, in this class of heterobicyclic phenylpiperazines decreased affinity in the order: ortho > para > meta. The loss of affinity in the ortho and para positions is probably due to steric factors: the substituents either cause steric hindrance with the receptor or prevent the compound from adopting the appropriate conformation for binding to the 5-HT1A receptor. Conformational analysis combined with structure-affinity relationships (SAR) indicates that our arylpiperazines may bind at the 5-HT1A receptor in a nearly coplanar conformation. Observed interactions of the compounds in our 5-HT1A receptor model appeared to be in agreement with SAR data. The aromatic part of the arylpiperazine moiety has pi-pi interactions with the aromatic residues Trp161 and Phe362 in helices IV and VI, respectively. The positively charged protonated basic nitrogen forms a hydrogen bond with the negatively charged Asp116 in helix III. The ammonium-aspartate complex is surrounded by aromatic residues Trp358 and Phe361 in helix VI. A lipophilic pocket is formed by Phe362, Leu366 (both helix VI), and the methyl group of Thr200 (helix V). In agreement with the model, addition of a methyl substituent to the structure of the benzodioxine analogue 12 in this region, yielding 13, is favorable for 5-HT1A receptor affinity. Unfavorable positions for substitution with bulky groups, like the 3- and 4-positions in the benzofuran compound 14, are explained by steric hindrance with the backbone atoms of helix V. Thus, we were able to rationalize the 5-HT1A SAR of existing N1-phenylpiperazines, as well as a series of newly synthesized bicyclic heteroarylpiperazines, in terms of receptor-ligand interactions. Several of these N4-unsubstituted compounds had affinities in the low-nanomolar range.

A model of the serotonin 5-HT1A receptor: agonist and antagonist binding sites.

We built a model for the 5-HT1A receptor, using the 3D-structure of bacteriorhodopsin as a structural template. With the use of site-directed mutagenesis data, several potent 5-HT1A agonists, belonging to five different structural classes, and an aryloxypropanolamine antagonist, were docked into the receptor model. After docking, the surrounding of the ligands appeared to be in full agreement with previously reported SAR-data of 5-HT1A ligands. In this study, for the first time, an explanation for 5-HT SAR results is given in terms of interactions between ligands and amino acid residues. Also the selectivity of 8-OH-DPAT for the 5-HT1A receptor is accounted for. In our model the agonists and the antagonist interact with different residues on several helices. They all interact with the essential aspartic acid on helix III, that is known to bind all amines to receptors for biogenic amines. This partial overlap of the binding sites accounts for the antagonism of the class of aryloxypropanolamines and for the deviating SAR of this class of compounds when compared to agonists.

Maintenance of viability and transport function after preservation of isolated rat hepatocytes in various simplified University of Wisconsin solutions.

Rat hepatocytes were preserved for 24 hr with high recovery and good maintenance of viability and transport function both in University of Wisconsin (UW) solution and in various simplified UW solutions. Cell quality is somewhat affected after 48 hr of preservation in both the original UW solution and the simplified solutions. ATP content and uptake rate of taurocholic acid are more sensitive markers of cell viability than Trypan blue exclusion or the MTT test. A much less expensive solution than UW, containing only K(+)-lactobionate, KH2PO4, MgSO4 and raffinose, can be used successfully for preservation of rat hepatocytes for 24 hr for drug transport studies.

Transcutaneous electrical nerve stimulation (TENS) in Raynaud's phenomenon.

Transcutaneous nerve stimulation (TENS) has been described as resulting in vasodilatation. The effect of 2 Hz TENS of the right hand during forty-five minutes on skin temperature and plethysmography of the third digit of both hands and feet and on transcutaneous oxygen tension (TcpO2) of the right hand was compared with that of a control study using indifferent stimulation of the iliopsoas region in 8 patients with primary Raynaud's phenomenon. After TENS a slight increase in skin temperature of both hands was found, while plethysmographic amplitude was increased in the contralateral hand only. No changes in TcpO2 occurred. The authors conclude that the observed small effects of TENS are of no clinical value in primary Raynaud's phenomenon.

A quantitative enzyme immunoassay for primary fibrinogenolysis products in plasma.

We have developed a two-step enzyme immunoassay (EIA) that allows the quantitation of degradation products derived from fibrinogen (FbgDP) and that does not detect degradation products derived from cross-linked (XDP) or noncrosslinked fibrin (fdp). The EIA is based on two monoclonal antibodies (FDP-14 and Y-18), developed in our institute. FDP-14 is used as catching antibody. It complexes exclusively with degradation products, irrespective whether these are derived from fibrinogen or from fibrin. It does not complex with intact fibrinogen or fibrin. Y-18 is reactive with fibrinogen and fibrinopeptide A-comprising fibrinogen fragments. It is used, conjugated with horse-radish peroxidase, as tagging antibody. The FbgDP-EIA is highly specific, accurate and sensitive. The coefficient of variation is between 3 and 8%; the lower detection limit is less than 0.025 micrograms/ml. The assay has been applied to plasma from patients with suspected disseminated intravascular coagulation (DIC), to plasma from patients undergoing streptokinase (SK) therapy for acute myocardial infarction and to plasma from newborn babies. DIC patients had no or very low levels of FbgDP, but high levels of other degradation products, SK-treated patients showed high levels of degradation products two hours after termination of the SK infusion. A considerable fraction of these degradation products was shown to be FbgDP. Plasma from newborn babies contained elevated levels of FbgDP associated with prolonged prothrombin times.