Synthesis and structure-activity relationships of pyridine-modified analogs of 3-[2-((S)-pyrrolidinyl)methoxy]pyridine, A-84543, a potent nicotinic acetylcholine receptor agonist

Analogs of 3-[2-((S)-pyrrolidinyl)methoxy]pyridine, (A-84543, 1) with 2-, 4-, 5-, and 6-substituents on the pyridine ring were synthesized. These analogs exhibited Ki values ranging from 0.15 to > 9,000 nM when tested in vitro for neuronal nicotinic acetylcholine receptor binding activity. Assessment of functional activity at subtypes of neuronal nicotinic acetylcholine receptors indicates that pyridine substitution can have a profound effect on efficacy at these subtypes, and several subtype-selective agonists and antagonists have been identified.

ABT-089 [2-methyl-3-(2-(S)-pyrrolidinylmethoxy)pyridine]: I. A potent and selective cholinergic channel modulator with neuroprotective properties

Accumulating preclinical and clinical evidence data suggests that compounds that selectively activate neuronal nicotinic acetylcholine receptor (nAChR) subtypes may have therapeutic utility for the treatment of several neurological disorders. In the present study, the in vitro pharmacological properties of the novel cholinergic channel modulator ABT-089 [2-methyl-3-(2-(S)-pyrrolidinylmethoxy)pyridine], are described. In radioligand binding studies, ABT-089 was shown to display selectivity toward the high-affinity (-)-cytisine binding site present on the alpha4beta2 nAChR subtype (Ki = 16 nM) relative to the [125I]alpha-bungarotoxin binding site present on the alpha7 (Ki > or = 10,000 nM) and alpha1beta1deltagamma (Ki > 1000 nM) nAChR subtypes. In cation flux and channel current studies, ABT-089 displayed a more complex profile than (-)-nicotine having agonist, partial agonist and inhibitory activities depending on the nAChR subtype with which it interacts. ABT-089 differentially stimulated neurotransmitter release. The compound displayed a similar potency and efficacy to (-)-nicotine to facilitate ACh release (ABT-089, EC50 = 3 microM; (-)-nicotine, EC50 = 1 microM), but was markedly less potent and less efficacious than (-)-nicotine to stimulate dopamine release (ABT-089, EC50 = 1.1 microM; (-)-nicotine, EC50 = 0.04 microM). Additionally, ABT-089 was neuroprotective against the excitotoxic insults elicited by exposure to glutamate in both rat cortical cell cultures (EC50 = 10 +/- 3 microM) and differentiated human IMR32 cells (EC50 = 3 +/- 2 microM). The differential full agonist/partial agonist profile of ABT-089, as compared with (-)-nicotine and ABT-418, illustrates the complexity of nAChR activation and the potential to target responses at subclasses of the neuronal and peripheral receptors.

Functional characterization of the novel neuronal nicotinic acetylcholine receptor ligand GTS-21 in vitro and in vivo

(2.4)-Dimethoxybenzylidene anabaseine dihydrochloride (GTS-21), a compound that interacts with rat neuronal nicotinic acetylcholine receptors (nAChRs), was evaluated using human recombinant nAChRs in vitro and various pharmacokinetic and behavioral models in rodents, dogs and monkeys. GTS-21 bound to human alpha 4 beta 2 nAChR (K1-20 nM) 100-fold more potently than to human alpha 7 nAChR, and was 18- and 2-fold less potent than (-)-nicotine at human alpha 4 beta 2 and alpha 7 nAChR, respectively. Functionally. GTS-21 stimulated [5H]dopamine release from rat striatal slices with an EC50 of 10 +/- 2 microM (250-fold less potent and 70% as efficacious as (-)-nicotine), an effect blocked by the nAChR antagonist dihydro-beta-erythroidine. However, GTS-21 did not stimulate human alpha 4 beta 2 nor human ganglionic nAChRs significantly. In vivo, GTS-21 had no adverse effect on dog blood pressure (< or = 2.5 micromol/kg i.v. bolus infusion), in marked contrast with (-)-nicotine, GTS-21 (-62 micromol/kg.s.e.) also did not cross-discriminate significantly with (-)-nicotine in rats and did not reduce temperature or locomotion in mice. Neither was it active in the elevated plus maze anxiety model (0.19-6.2 micromol/kg.IP) in normal mice. However, GTS-21 did improve learning performance of monkeys in the delayed matching-to-sample task (32-130 nmol/kg.i.m.).

Lycaconitine revisited: partial synthesis and neuronal nicotinic acetylcholine receptor affinities

The norditerpenoid alkaloid lycaconitine (2) was synthesized from lycoctonine (3) and its affinity determined for two neuronal nicotinic acetylcholine receptor subtypes. The structure of 2 was confirmed by a combination of spectroscopic methods.

A-85380 [3-(2(S)-azetidinylmethoxy) pyridine]: in vitro pharmacological properties of a novel, high affinity alpha 4 beta 2 nicotinic acetylcholine receptor ligand

The in vitro pharmacological properties of a novel cholinergic channel ligand, A-85380 [3-(2(S)-azetidinylmethoxy)pyridine], were examined using tissue preparations that express different putative nAChR subtypes. In radioligand binding studies, A-85380 is shown to be a potent and selective ligand for the human alpha 4 beta 2 nAChR subtype (Ki = 0.05 + 0.01 nM) relative to the human alpha 7 (Ki = 148 +/- 13 nM) and the muscle alpha 1 beta 1 dg subtype expressed in Torpedo electroplax (Ki = 314 +/- 12 nM). The R-enantiomer of A-85380, A-159470, displays little enantioselectivity towards the alpha 4 beta 2 and alpha 1 beta 1 delta gamma subtypes but does not display 12-fold enantioselectivity towards the alpha 7 subtype (Ki = 1275 +/- 199 nM). (+)- and(-)-Epibatidine display similar potencies at the human human alpha 4 beta 2 (Ki = 0.04 +/- 0.02 nM and 0.07 +/- 0.02 nM, respectively), human alpha 7 (Ki = 16 +/- 2 nM and 22 +/- 3 nM, respectively) and muscle alpha 1 beta 1 delta gamma g (Ki = 2.5 +/- 0.9 nM and 5.7 +/- 1.0 nM, respectively) nAChRs. Functionally, A-85380 is a potent activator of cation efflux through the human alpha 4 beta 2 (EC50 = 0.7 +/- 0.1 microM) and ganglionic (EC50 = 0.8 +/- 0.09 microM) subtypes, effects that are attenuated by pretreatment with mecamylamine (10 microM). Further, A-85380 can activate (EC50 = 8.9 +/- 1.9 microM) currents through channels formed by injection of the human alpha 7 subunit into Xenopus oocytes, effects that are attenuated by pretreatment with the alpha 7 nAChR antagonist, methyllycaconitine (10 nM). In all cases, A-85380 is more potent than (-)-nicotine but less potent than (+/-)-epibatidine. In neurotransmitter release studies, A-85380 stimulates the release of dopamine with an EC 50 value of 0.003 +/- 0.001 microM which is equipotent to (+/-)-epibatidine, and 20-fold more potent than (-)-nicotine (EC50 = 0.04 +/- 0.009 microM). Thus, A-85380 displays a profile of robust activation of a number of nAChR subtypes with substantially less affinity for [125I] alpha-BgT sites than [3H](-)-cytisine sites, suggesting that it may serve as a more selective pharmacologic probe for the alpha 4 beta 2 subtype relative to the alpha 7 and alpha 1 beta 1 delta g nAChRs than (+/-)-epibatidine.

A sensitive technique for the detection of the alpha 7 neuronal nicotinic acetylcholine receptor antagonist, methyllycaconitine, in rat plasma and brain

Methyllycaconitine (MLA) is the most potent and selective antagonist of the alpha-bungarotoxin sensitive neuronal nicotinic acetylcholine receptor (nAChR). In the present study, an accurate and reproducible technique for the extraction and analysis of MLA from rat plasma and brain is described. This study further sought to determine whether pharmacologically relevant concentrations of MLA could be achieved in brain following peripheral administration. The detection limits for MLA were 0.5 ng/ml for plasma samples and 1.0 ng/g for brain samples. The pharmacokinetic properties of MLA in rat are characterized by a short elimination half-life (19 min) following intravenous (i.v.) administration and poor bioavailability following oral (p.o.) administration. Remarkably, the elimination half-life is significantly longer following p.o. administration (408 min). To assess the extent to which MLA can penetrate into brain, brain and plasma levels of MLA were determined at different time points following intraperitoneal (i.p.) administration of a dose of MLA that produced no observable side effects. Maximal plasma and brain levels were 694 +/- 106 ng/ml and 32 +/- 3 ng/g, respectively. These concentrations are within a range previously reported to selectively block alpha 7 nAChR mediated responses in vitro. Peripherally administered MLA may therefore be a useful tool to further probe the central nervous system functions of the alpha 7 nAChR subunit in vivo.

Stable expression and pharmacological properties of the human alpha 7 nicotinic acetylcholine receptor

The alpha 7 neuronal nicotinic acetylcholine receptor subtype forms a Ca(2+)-permeable homooligomeric ion channel sensitive to alpha-bungarotoxin in Xenopus oocytes. In this study, we have stably and functionally expressed the human alpha 7 cDNA in a mammalian cell line, HEK-293 and examined its pharmacologic properties. [125I] alpha-Bungarotoxin bound to transfected cells with a Kd value of 0.7 nM and a Bmax value of 973 pmoL/mg protein. No specific binding was detected in untransfected cells. Specific binding could be displaced by unlabeled alpha-bungarotoxin (Ki = 0.5 nM) and an excellent correlation was observed between binding affinities of a series of nicotinic cholinergic ligands in transfected cells and those in the human neuroblastoma IMR-32 cell line. Additionally, cell surface expression of alpha 7 receptors was detected by fluorescein isothiocyanate-conjugated alpha-bungarotoxin in transfected cells. Whole cell currents sensitive to blockade by alpha-bungarotoxin, and with fast kinetics of activation and inactivation, were recorded from transfected cells upon rapid application of (-)-nicotine or acetylcholine with EC50 values of 49 microM and 155 microM respectively. We conclude that the human alpha 7 subunit when expressed alone can form functional ion channels and that the stably transfected HEK-293 cell line serves as a unique system for studying human alpha 7 nicotinic receptor function and regulation, and for examining ligand interactions.

Characterization of [3H]ABT-418: a novel cholinergic channel ligand

ABT-418 [(S)-3-methyl-5-(1-methyl-2-pyrrolidinyl)isoxazole] is a potent and selective agonist at neuronal nicotinic acetylcholine receptors (nAChRs) with cognitive enhancing and anxiolytic activities. [3H]ABT-418 was found to bind with high affinity (KD = 2.85 +/- 0.14 nM) to membranes prepared from rat brain. Binding of [3H]ABT-418 was characterized by rapid association (T1/2 = 1.4 +/- 0.3 min) and dissociation (T1/2 = 2.9 +/- 0.4 min) half-times. The pharmacology of [3H]ABT-418 binding was consistent with an interaction with the putative alpha 4 beta 2 nAChR subtype. The nAChR agonists, (-)-nicotine, (-)-cytisine and (+/-)-epibatidine, displayed a high affinity (Ki = 0.8 +/- 0.1, 0.2 +/- 0.1 and 0.05 +/- 0.01 nM, respectively) for [3H]ABT-418 binding sites, whereas among nAChR antagonists examined, only dihydro-beta-erythroidine competed with high affinity (Ki = 32 +/- 1.5 nM). Although autoradiography studies indicate that the binding distribution of [3H]ABT-418 and (-)-[3H]cytisine are largely identical, there are some brain regions including the striatum, olivary pretectal nucleus and the superior colliculus, in which [3H]ABT-418 demonstrates significantly (P < .05) less binding. The data in the present study demonstrate that [3H]ABT-418 binds with high affinity to a population of binding sites in the rat brain that have the pharmacological characteristics of neuronal nAChRs. [3H]ABT-418 may, therefore, serve as a useful radioligand to further probe the observed differences in pharmacological properties between ABT-418 and other nicotinic agonists in vivo.

Blood quantum and ethnic intermarriage in the Boas data set

The data collected by Boas is biased toward employees of Indian agencies and school populations. The data show that intermarried Amerindians in the last century tended to marry back into the Amerindian population rather than into the general population, as in this century. Distributions of blood quantum within tribes show the intensity and duration of contact with the dominant society and other tribes. Amerindians who married into other tribes tended to choose spouses from contiguous tribes, but over one-fourth of spouses represented different language families. General hypotheses should be tested in the Boas data only with great caution and after correcting for historical factors if possible.

Localization and characterization of a parotid Ca(2+)-dependent ecto-ATPase

Parotid acini were isolated and tested to further establish the presence of ecto-ATPase in the intact cells. Inhibitors were used to determine if the inhibitor profile of the ATPase was similar to that of a Ca(2+)-ATPase from parotid membranes identified previously as an ecto-ATPase. The Ca(2+)-ATPase of intact cells was insensitive to oligomycin (10 micrograms/ml), N-ethylmaleimide (NEM) (0.1 mM), ruthenium red (0.1 mM), sodium azide (1 mM), and was inhibited approximately 22% by sodium orthovanadate (Na3VO4) (1 mM). This profile was similar to the Ca(2+)-ATPase of intact cells. Trifluoperazine (TFP) (0.1 mM) inhibited the enzyme in intact cells by approximately 32%. The nucleotide substrate specificity of the enzyme also reflected very closely the pattern seen in isolated membranes.

A comparison of efficacy and tolerance of the short acting sedatives midazolam and zopiclone

AIMS

To compare the efficacy and tolerance of midazolam, 15 mg and zopiclone 7.5 mg once daily for seven days in a prospective, double blind trial of 88 patients, aged 18 or over, with sleep disorders in general practice.

METHODS

Efficacy was evaluated using the Leeds sleep evaluation questionnaire (LSEQ). Adverse reactions were recorded as volunteered.

RESULTS

fifty-one patients completed all aspects of the trial without violation of the protocol. Patients taking zopiclone improved in all aspects of the Leeds questionnaire (p < 0.01). Patients taking midazolam improved in six out of 10 items (p < 0.01). Rebound insomnia was evident in the zopiclone group in five out of 10 items of the LSEQ. Rebound was not evident in the midazolam group. There were no significant differences between midazolam 15 mg, and zopiclone 7.5 mg, in comparison between groups. Thirty-eight patients suffered 49 adverse drug reactions and there were no differences between the groups.

CONCLUSIONS

Zopiclone 7.5 mg daily improved more items on the LSEQ than midazolam 15 mg daily but was associated with significant rebound insomnia. Adverse reactions were frequent with both drugs.

Performance assessment of radioactive waste repositories

The current plans for permanent disposal of radioactive waste call for its emplacement in deep underground repositories mined from geologically stable rock formations. The U.S. Nuclear Regulatory Commission and U.S. Environmental Protection Agency have established regulations setting repository performance standards for periods of up to 10,000 years after disposal. Compliance with these regulations will be based on a performance assessment that includes (i) identification and evaluation of the likelihood of all significant processes and events that could affect a repository, (ii) examination of the effects of these processes and events on the performance of a repository, and (iii) estimation of the releases of radionuclides, including the associated uncertainties, caused by these processes and events. These estimates are incorporated into a probability distribution function showing the likelihood of exceeding radionuclide release limits specified by regulations.

The management of children with spinal dysraphism

Improvements in technology have dramatically increased the survival of children with spinal dysraphism. Because this complex condition affects multiple organ systems as well as the psychosocial functioning of the child and family, these children require care from a host of specialists in order to achieve optimum functioning. This article reviews the pathophysiology and discusses the current management of the medical and psychosocial effects of spinal dysraphism. It also briefly discusses strategies for intervention, long-term outcomes, and some controversies regarding care and screening.

Basic trauma life support

The impact of traumatic injuries on modern society in terms of morbidity, mortality, and economic cost is enormous. Studies have shown that both advanced life support skills and rapid stabilization and transport of the trauma victim have a beneficial effect on the patient's ultimate outcome. The Basic Trauma Life Support (BTLS) course was designed to provide pre-hospital care providers with the skills necessary to provide a thorough assessment, initial resuscitation, and rapid transportation of the trauma victim. Early studies suggest that the material is easily learned by prehospital care providers and that the on-scene time for trauma cases is reduced following training in BTLS. More widespread training in BTLS may have a significant effect on the mortality and morbidity associated with traumatic injuries.

A role for nurse psychotherapists: primary prevention counseling for general hospital staffs

Providing a counseling and consultation service to general hospital employees through contractual arrangements is beneficial, and is an appropriate function for nurse therapists. Employees willingly use the service, and as stresses increase in the workplace the service can have a favorable impact on both personnel functioning and retention, as well as on the delivery of patient services.

Urinary tract trauma

From a practical point of view, a woman who has blunt injury to the pelvic area with hematuria from the lower urinary tract, has a contused or ruptured bladder. In a man, such a situation calls for retrograde urethrography to determine if the injury is in the urethra or the bladder because the two organs are investigated differently. In both sexes, such injuries are usually associated with pelvic fractures. Massive bladder displacement and severe hemorrhage should alert one to the need for pelvic angiography to find and embolize the bleeding site within the first 24 hours after injury. For blunt trauma to the upper urinary tract an intravenous urogram with tomography is still the main examination. However, a normal intravenous urogram does not exclude serious injury. Therefore, if signs or symptoms persist, a computerized tomographic (CT) examination should be performed if available. Otherwise, a radionuclide study is advisable. Non-excretion on intravenous urography with tomography calls for selective renal arteriography to delineate the etiology. There can be serious renal trauma in the absence of hematuria, which may occur with renal pedicle injury or avulsion of the ureter. Minor forniceal ruptures may occasionally mask severe posterior renal lacerations.

Mammographic patterns and bias in breast cancer detection

Wolfe's finding that some mammographic patterns (P2 and DY) are associated with an increased risk of breast cancer has been challenged by some authors who suggest that this is due to denser patterns concealing cancers present on the first examination: these cancers, it is argued, are diagnosed in later years, creating the spurious impression of increased cancer incidence. The authors examined this hypothesis in a series of patients with breast cancer but failed to find any evidence that the diagnosis was subject to systematic delay in patients with the P2 or DY pattern. Moreover, studies of a hypothetical model showed that bias in the detection of breast cancer was unlikely to account for more than a small increase in apparent cancer incidence. Thus it appears unlikely that such a bias is responsible for the risk of breast cancer observed in patients with these mammographic patterns.

Bias and the association of mammographic parenchymal patterns with breast cancer

We have carried out a case-control study to evaluate the association between Wolfe's mammographic patterns and the risk of breast cancer, and to examine the influence of control selection and the radiologist who read the films upon the results obtained. Mammograms of the non-cancerous breast of 183 women with unilateral breast cancer were compared with mammograms from two age-matched control groups: a group of asymptomatic women attending a screening centre, and a group of symptomatic women referred for the diagnostic evaluation of suspected breast disease. Films were arranged in random sequence and independently classified by 3 radiologists. A strong and statistically significant association was found between mammographic dysplasia and breast cancer when controls from the screening centre were compared to cases, but not when cases were compared to women referred for the diagnostic evaluation of breast disease. This result appears to arise in part because of an association between symptoms of benign breast disease and mammographic dysplasia, and suggests that some previous negative studies of the association of mammographic patterns with breast cancer may have arisen from the inclusion of symptomatic subjects as controls.

Mammographic signs as risk factors for breast cancer

We have carried out a case-control study to examine the relationship between mammographic signs and breast cancer. The mammographic signs assessed were prominent ducts and dysplasia. The cases were a group of 183 women with histologically verified unilateral breast cancer. The controls were a group of women attending a screening centre. Cases and controls were individually age-matched. Mammograms from the non-cancerous breast of the cases were randomly assembled with those of the controls and classified by 3 radiologists without knowledge of which films were from cases and which from controls. Mammographic dysplasia was found to be strongly associated with breast cancer, particularly in women aged less than 50. Prominent ducts were only weakly associated with breast cancer. Multivariate analysis showed that the association between dysplasia and breast cancer could not be explained on the basis of other risk factors for breast cancer, and that classification of dysplasia discriminated more strongly between cases and controls than did classification of Wolfe's mammographic patterns. These results show that mammograms contain information about risk of breast cancer. Mammographic dysplasia is strongly associated with breast cancer, is present in a substantial proportion of patients with the disease, and may offer opportunities for prevention.