The Effect of Baseline Performance and Age on Cognitive Training Improvements in Older Adults: A Qualitative Review

Findings that the brain is capable of plasticity up until old age have led to interest in the use of cognitive training as a potential intervention to delay the onset of dementia. However, individuals participating in training regimens differ greatly with respect to their outcomes, demonstrating the importance of considering individual differences, in particular age and baseline performance in a cognitive domain, when evaluating the effectiveness of cognitive training. In this review, we summarize existing literature on cognitive training in adults across the domains of episodic memory, working memory and the task-switching component of executive functioning to clarify the picture on the impact of age and baseline performance on cognitive training-related improvements. Studies targeting episodic memory induced greater improvements in younger adults with more intact cognitive abilities, explained in part by factors specific to episodic memory training. By contrast, older, lower baseline performance adults improved most in several studies targeting working memory in older individuals as well as in the majority of studies targeting executive functioning, suggesting the preservation of neural plasticity in these domains until very old age. Our findings can have important implications for informing the design of future interventions for enhancing cognitive functions in individuals at the prodromal stage of Alzheimer's Disease and potentially delaying the clinical onset of Alzheimer's Disease. Future research should more clearly stratify individuals according to their baseline cognitive abilities and assign specialized, skill-specific cognitive training regimens in order to directly answer the question of how individual differences impact training effectiveness.

Elements of fractal geometry in the 1H NMR spectrum of a copolymer intercalation-complex: identification of the underlying Cantor set

Intercalation of pyrene into the chain-folds of a binary copolyimide results in a self-similar ¹H NMR spectrum.

Sequence-selective intercalation of pyrene into the chain-folds of a random, binary copolyimide under fast-exchange conditions results in the development of self-similar structure in the diimide region of the ¹H NMR spectrum. The resulting spectrum can be described by the mathematics of fractals, an approach that is rationalised in terms of a dynamic summation of ring-current shielding effects produced by pyrene molecules intercalating into the chain at progressively greater distances from each “observed” diimide residue. The underlying set of all such summations is found to be a defined mathematical fractal namely the fourth-quarter Cantor set, within which the observed spectrum is embedded. The pattern of resonances predicted by a geometric construction of the fourth-quarter Cantor set agrees well with the observed spectrum.

Lay Attitudes toward Genetic Testing for Susceptibility to Inherited Diseases

One of the most important issues facing legal and medical policy makers in the coming years will be whether to employ populationbased testing for genetic markers of inherited diseases. Two hundred and twenty-six randomly selected individuals from Easton, Pennsylvania completed a mail questionnaire that was designed to assess the general public’s attitudes toward many of the personal and societal issues surrounding genetic testing for disease susceptibility. Respondents were generally optimistic about the potential benefits of genetic testing, and their attitudes about genetic testing were associated with their personal interest in getting a genetic test. Respondents were more likely to be interested in undergoing genetic testing for disease susceptibility if they might have some control over the targeted disease (i.e. there was a cure) and if the test was highly predictive of their chances of developing the disease. Respondents were wary of granting access to genetic testing results to anyone other than doctors and family members, and they did not want the government, religious leaders, or the courts involved in regulating genetic testing. These results have important implications for psychologists, genetic scientists, bioethicists, and legal scholars who are grappling with the many issues related to population-based genetic testing for inherited diseases.

In-Group Identification as a Function of Depersonalization, Distinctiveness, and Status

Artificial social categories were created in a laboratory context in order to test predictions regarding the relative importance of group size and status as determinants of in-group favoritism. Subjects were assigned to categories of “overestimator” or “under estimator” and were told that one category included a majority of college students while the other represented a minority. Prior to category assignment, half of the subjects had been given confidentiality instructions designed to make them feel highly depersonalized. Based on feedback about test performance, status differentials between the two estimation categories were introduced.

Consistent with predictions, there was a three-way interaction between depersonalization, in-group size, and in-group status as determinants of evaluative in-group bias on social trait ratings. Under control conditions (no depersonalization), group status and majority size both contributed to positive valuations of the in-group. Under the depersonalization condition, however, subjects valued minority group membership more than majority categorization, and the effect of status was eliminated.

Duffy antigen receptor for chemokines and CXCL5 are essential for the recruitment of neutrophils in a multicellular model of rheumatoid arthritis synovium

OBJECTIVE

The role of chemokines and their transporters in rheumatoid arthritis (RA) is poorly described. Evidence suggests that CXCL5 plays an important role, because it is abundant in RA tissue, and its neutralization moderates joint damage in animal models of arthritis. Expression of the chemokine transporter Duffy antigen receptor for chemokines (DARC) is also up-regulated in early RA. The aim of this study was to investigate the role of CXCL5 and DARC in regulating neutrophil recruitment, using an in vitro model of RA synovium.

METHODS

To model RA synovium, RA synovial fibroblasts (RASFs) were cocultured with endothelial cells (ECs) for 24 hours. Gene expression in cocultured cells was investigated using TaqMan gene arrays. The roles of CXCL5 and DARC were determined by incorporating cocultures into a flow-based adhesion assay, in which their function was demonstrated by blocking neutrophil recruitment with neutralizing reagents.

RESULTS

EC-RASF coculture induced chemokine expression in both cell types. Although the expression of CXC chemokines was modestly up-regulated in ECs, the expression of CXCL1, CXCL5, and CXCL8 was greatly increased in RASFs. RASFs also promoted the recruitment of flowing neutrophils to ECs. Anti-CXCL5 antibody abolished neutrophil recruitment by neutralizing CXCL5 expressed on ECs or when used to immunodeplete coculture-conditioned medium. DARC was also induced on ECs by coculture, and anti-Fy6 antibody or small interfering RNA targeting of DARC expression effectively abolished neutrophil recruitment.

CONCLUSION

This study is the first to demonstrate, in a model of human disease, that the function of DARC is essential for editing the chemokine signals presented by ECs and for promoting unwanted leukocyte recruitment.

Public eyewitness confidence can be influenced by the presence of other witnesses

Four experiments were conducted to examine whether witnesses' public confidence ratings differ from their private ratings when there are social pressures to use confidence as an impression-management tool. In all four experiments, participants answered questions about a source event (a series of faces in the first three experiments and a simulated crime scene in the fourth). Half of the responses and confidence ratings were given privately and anonymously, and half were given publicly in front of one or more mock jurors. Two central findings emerged from the results. First, public confidence differed from private confidence only when there was more than one witness; when there were no other witnesses, public and private confidence were the same. Second, the direction of the change in public confidence in the multiple-witness settings was influenced by whether or not there was a possibility of being contradicted by the other witnesses. When there was no chance that the participants' responses could be contradicted, they raised their confidence ratings in public; when there was a chance that the other witnesses might contradict them, the participants lowered their public confidence ratings. The results are discussed in terms of self-presentation theory and implications for the legal system.

Establishing pragmatic estimated GFR thresholds to guide metformin prescribing

AIMS

Renal impairment is a contraindication to metformin treatment because of the perceived increased risk of lactic acidosis. Current guidelines define renal impairment according to the serum creatinine of the individual, but this measure is being supplanted by the use of estimated glomerular filtration rate (eGFR) as it gives a closer estimate to true GFR. This study aimed to establish pragmatic eGFR limits for use in patients being considered for metformin treatment.

METHODS

Estimated GFR measurements corresponding to currently used metformin creatinine limits of 130 and 150 micromol/l were derived and then applied to 12 482 patients with diabetes in Hull and East Yorkshire.

RESULTS

Few patients with a serum creatinine of 130 or 150 micromol/l have an eGFR of < 30 ml/min/1.73 m(2)[chronic kidney disease (CKD) stage 4 or greater], while most are between 30 and 59 ml/min/1.73 m(2) (CKD stage 3). When applied to the 12 482 patients (median age 67 years, interquartile range 56-75), males predominated when using creatinine cut-offs (13.6% of males and 8.3% of females had creatinine > 130 micromol/l; 8.2% males and 5.2% females > 150 micromol/l), but not using eGFR CKD thresholds (3.3% males and 4.7% females < 30 ml/min/1.73 m(2); 20.8% males and 28.1% females eGFR 30-59 ml/min/1.73 m(2)). Similar proportions of patients as currently would have metformin withheld if using eGFR cut-offs between 30 and 49 ml/min/1.73 m(2).

CONCLUSIONS

We have proposed pragmatic eGFR limits to guide metformin prescribing in patients with renal impairment. CKD stage 4 or greater should be an absolute contraindication to metformin, while CKD stage 3 should alert clinicians to consider other risk factors before initiating or continuing treatment.

Phototoxicity and fluorotoxicity combine to alter the behavior of neutrophils in fluorescence microscopy based flow adhesion assays

The use of fluorescent probes that allow visualization of leukocyte-endothelial cell (EC) interactions has greatly informed our understanding of leukocyte recruitment. However, effects of these agents on the biological functions of leukocytes are poorly described, leading to concerns about the interpretation of such data. Here we used two flow-based neutrophil adhesion assays to compare the effects of phase contrast illumination (PCI) with high intensity illumination (HII) used for fluorescent microscopy, in the presence or absence of five commonly used fluorochromes. Isolated neutrophils were either (1) perfused across P-selectin to establish a population of rolling cells, which were subsequently activated with fMLP; or (2) perfused across EC activated with TNF-alpha. In the absence of fluorescent dyes, HII did not affect levels of leukocyte adhesion; however, subsequent neutrophil behavior was dramatically altered when compared with cells under PCI, for example, dramatically reducing their migration velocities. In the presence of fluorescent dyes, the effects of HII were exacerbated, although the precise nature of the biological effects of these probes was agent specific. Thus, for the first time, our experiments describe the effects of fluorescent microscopy on the separate stages of the neutrophil recruitment process and reveal a previously unsuspected effect of HII on neutrophil migration.

Modulators of the human CCR5 receptor. Part 3: SAR of substituted 1-[3-(4-methanesulfonylphenyl)-3-phenylpropyl]-piperidinyl phenylacetamides

SAR and PK studies led to the identification of N-(1-{(3R)-3-(3,5-difluorophenyl)-3-[4-methanesulfonylphenyl] propyl}piperidin-4-yl)-N-ethyl-2-[4-methanesulfonylphenyl]acetamide as a highly potent and selective ligand for the human CCR5 chemokine receptor with good oral pharmacokinetic properties.

A novel mechanism of neutrophil recruitment in a coculture model of the rheumatoid synovium

OBJECTIVE

Rheumatoid arthritis (RA) is classically thought of as a Th1, T lymphocyte-driven disease of the adaptive immune system. However, cells of the innate immune system, including neutrophils, are prevalent within the diseased joint, and accumulate in large numbers. This study was undertaken to determine whether cells of the rheumatoid stromal microenvironment could establish an inflammatory environment in which endothelial cells are conditioned in a disease-specific manner to support neutrophil recruitment.

METHODS

Human umbilical vein endothelial cells (ECs) and fibroblasts isolated from the synovium or skin of RA patients were established in coculture on opposite sides of porous transwell filters. After 24 hours of EC conditioning, the membranes were incorporated into a parallel-plate, flow-based adhesion assay and levels of neutrophil adhesion to ECs were measured.

RESULTS

ECs cocultured with synovial, but not skin, fibroblasts could recruit neutrophils in a manner that was dependent on the number of fibroblasts. Antibody blockade of P-selectin or E-selectin reduced neutrophil adhesion, and an antibody against CD18 (the beta2 integrin) abolished adhesion. Blockade of CXCR2, but not CXCR1, also greatly inhibited neutrophil recruitment. Interleukin-6 (IL-6) was detectable in coculture supernatants, and both IL-6 and neutrophil adhesion were reduced in a dose-dependent manner by hydrocortisone added to cocultures. Antibody blockade of IL-6 also effectively abolished neutrophil adhesion.

CONCLUSION

Synovial fibroblasts from the rheumatoid joint play an important role in regulating the recruitment of inflammatory leukocytes during active disease. This process may depend on a previously unsuspected route of IL-6-mediated crosstalk between fibroblasts and endothelial cells.

Modulators of the human CCR5 receptor. Part 2: SAR of substituted 1-(3,3-diphenylpropyl)-piperidinyl phenylacetamides

SAR and DMPK studies led to the identification of substituted N-alkyl-N-[1-(3,3-diphenylpropyl)piperidin-4-yl]-2-phenylacetamides as potent and orally bioavailable ligands for the human CCR5 chemokine receptor.

Modulators of the human CCR5 receptor. Part 1: Discovery and initial SAR of 1-(3,3-diphenylpropyl)-piperidinyl amides and ureas

Investigation of weak screening hits led to the identification of N-alkyl-N-[1-(3,3-diphenylpropyl)piperidin-4-yl]-2-phenylacetamides and N-alkyl-N-[1-(3,3-diphenylpropyl)piperidin-4-yl]-N'-benzylureas as potent, selective ligands for the human CCR5 chemokine receptor.

Extra effort during memory retrieval may be associated with increases in eyewitness confidence

When testifying in court, witnesses are motivated to try as hard as possible to give an accurate account. This study tested the proposition that extra effort by eyewitnesses during a memory test can lead to higher confidence ratings without any accompanying changes in accuracy. Participant-witnesses answered multiple-choice questions about a classroom visitor who had spoken 5 days earlier. In the high-motivation condition participants could earn prizes based on their memory test performance; in the low-motivation condition there were no special incentives. Although the motivation manipulation did not affect mean witness confidence, the confidence-accuracy and effort-accuracy correlations were substantially smaller in the high-motivation condition than in the low-motivation condition. Furthermore, the confidence ratings for those participants who reported expending high levels of effort in both motivation conditions were significantly higher than the confidence ratings for the low-effort participants, despite the fact that response accuracy did not differ as a function of reported effort. These findings have important implications for understanding how pressures to perform well in the courtroom can affect eyewitness confidence.

Strict interpretation of vaccination guidelines with computerized algorithms and improper timing of administered doses

BACKGROUND

Frequently changing immunization recommendations may lead to incorrectly administered doses.

OBJECTIVE

To determine the incidence and characteristics of inappropriately timed vaccinations.

METHODS

Prospectively collected immunization histories of patients <5 years old from well-child care encounters with pediatric residents in a large urban clinic during a 3-month study period. New patients or those with no immunization history in the medical record were excluded. Paper records were verified before each visit and served as the immunization history. Immunization records were entered into and analyzed by the Massachusetts Immunization Information System with strict interpretation of minimum spacing and age guidelines to identify invalid vaccine doses. Reasons for invalidity were determined by manual review. Invalid doses were cross-referenced with clinic schedule to determine who delivered doses.

RESULTS

Inclusion criteria were met by 690 encounters. Charts were available for review before the encounter for 580, containing 6983 total immunizations. Of these 289 (4.1%) administered doses were invalid; 206 of 580 (35.5%) patients had at least one invalid dose. Common invalid doses given were unnecessary poliovirus vaccine around 18 months (n = 66) and second hepatitis B vaccine given too soon after the first (n = 53). All types of providers gave invalid doses; pediatric residents and fellows delivered significantly more (P < 0.01).

CONCLUSIONS

By strict interpretation of immunization guidelines, many patients were immunized incorrectly. Clinicians should be aware of common errors in vaccine dosing and national guidelines should be simplified.

Public eyewitness confidence ratings can differ from those held privately

Despite much research on eyewitness confidence, we know very little about whether confidence ratings given in public might differ from those held privately. This study tested a prediction derived from self-presentation theory that eyewitnesses will give lower confidence ratings in public when there is a possibility of their account being contradicted by other witnesses as compared to when they report their confidence in private. In groups of 3 or 4 people, 96 participants watched a videotape of a simulated robbery and then answered 16 forced-choice questions about details from the videotape. In half of the experimental sessions, the participants shared their answers and confidence ratings aloud with the other participants (public condition), and in the other half, the answers and ratings were not shared (private). As predicted, confidence ratings were significantly lower in the public condition than in the private condition, but the privacy manipulation had no effect on response accuracy. These results are consistent with a self-presentation explanation, and they highlight the need to examine public confidence ratings more thoroughly.

Recognition instructions and recognition practice can alter the confidence--response time relationship

Three face-recognition experiments examined how instructions for a recognition test (e.g., emphasize speed or emphasize accuracy) can impact the confidence-response time relationship for episodic memory reports. In all 3 experiments, the confidence-response time correlation was smaller when participants were told to speed up their responding rate, which suggests that participants in these conditions relied less on the artificially compressed response times in forming their confidence judgments than they would under "normal" circumstances. Also, recognition practice before the final memory test eliminated the effect of the recognition instruction manipulation. These results support J. S. Shaw's (1996) suggestion that witnesses rely in part on the fluency of their memory reports when generating confidence judgments, and these findings have important implications for understanding the relationships among witness confidence, accuracy, and response time.

Impact of an encounter-based prompting system on resident vaccine administration performance and immunization knowledge

OBJECTIVES

To evaluate an encounter-based immunization prompting system on resident performance in administering vaccines and knowledge of immunization guidelines.

DESIGN/METHODS

Prospective randomized, controlled trial. Subjects were first- and second-year pediatric residents in a hospital-based continuity clinic. The intervention group received manual prompts of immunizations due. Postclinic chart review compared immunizations due with those administered. Acceptable and unacceptable reasons for not administering vaccines were assigned. Resident knowledge was measured by a 70-item examination.

RESULTS

The intervention group had significantly less missed opportunities/vaccine administration errors (11.4% vs 21.6%). The most common reason for unacceptable errors in the intervention group: vaccine was given too early; in the control group: vaccine was postponed to next visit. Pre- and postintervention knowledge scores were similar: intervention group (75.5% vs 80.7%, control group; 76.5% vs 81.3%).

CONCLUSION

An immunization prompting system in a hospital-based pediatric resident continuity clinic reduced missed opportunities/vaccine administration errors without significantly impacting resident knowledge of immunization guidelines.immunization schedule, vaccination, immunization, prompting systems, resident education.

Nail primer cosmetics: correlations between product pH and adequacy of labeling

BACKGROUND

We have previously reported on injuries suffered by young children exposed to methacrylic acid-containing nail primers and the need for public education efforts concerning this potential household hazard. However, some primers contain alternative ingredients, which may or may not pose the same risk; product labeling information is variable and may be confusing to consumers.

OBJECTIVE

To investigate the relationship between pH of different primer products, product contents, and appropriateness of product labeling and packaging.

METHODS

Twenty-three commercially available primers were grouped by product contents: (methacrylic acid vs others). Product pH was measured and product labels were scored on 7 warning points: "poison and/or corrosive," a "caution to avoid contact and/or to use a barrier when handling the product," a "skin first aid," and "eye first aid," an "ingestion first aid," a caution to "keep out of reach of children," and a "in emergency, contact a poison center." A summative "global hazard notification score" was calculated for each product. Data were analyzed using correlations and the two-sample t-test.

RESULTS

None of 23 products tested were contained in a child-resistant container and none included all 7 label items. Product pH ranged from 1.90-8.55 (mean pH 4.59 +/- 1.99); 20 products had pH < 7.0. Only 1 product advised, in the event of a poisoning, that a poison center be contacted. Of 20 acidic products, only 7 alerted users that the contents could cause burns. The mean global hazard notification score (MAX = 7) was 3.6; global hazard notification score did not correlate with pH. Methacrylic acid-containing products had a lower pH (mean 3.43 +/- 0.78) than those without methacrylic acid (mean 5.34 +/- 2.18), p = 0.008. When the primer bottle was separated from the rest of the packaging which comprised the artificial nail "kit," 50% of products lost all of their warning information.

CONCLUSIONS

Most, but not all, artificial nail primers analyzed in this study were highly acidic. Labeling and packaging of many nail primers are inadequate, given the potential of methacrylic acid in these products to cause burns and the toxicity of most nail primers. We agree with the Consumer Product Safety Commission's recently proposed rule to require cosmetic manufacturers to repackage methacrylic acid-containing household products in child-resistant containers. We also urge manufacturers to alert consumers to the hazards of nail primers by better labeling. Manufacturers should also investigate the feasibility of either substituting other chemicals or lowering the concentration of methacrylic acid.

More than suggestion: the effect of interviewing techniques from the McMartin Preschool case

Child interviewing techniques derived from transcripts of the McMartin Preschool case were found to be substantially more effective than simple suggestive questions at inducing preschool children to make false allegations against a classroom visitor. Thirty-six children interviewed with McMartin techniques made 58% accusations, compared with 17% for 30 children interviewed with suggestive questions. Social influence and reinforcement appeared to be more powerful determinants of children's answers than simple suggestive questions. The SIRR model is proposed to explain how false statements may be elicited from children or adults. Categories identified in the SIRR model are suggestive questions, social influence, reinforcement, and removal from direct experience.

Co-witness information can have immediate effects on eyewitness memory reports

When questioning a reluctant witness, investigators sometimes encourage the witness by providing information about what other witnesses have said. Three experiments were conducted to test the combined effects of such co-witness information and suggestive questioning on the accuracy of eyewitness memory reports. Experiment 1 was analogous to the experience of a witness who receives information from an interviewer or questioner about what other witnesses have already said, whereas Experiments 2 and 3 simulated the situation in which a witness receives information directly from a co-witness. In all three experiments, when participants received incorrect information about a co-witness's response, they were significantly more likely to give that incorrect response than if they received no co-witness information. This effect persevered in a delayed memory test 48 h after the initial questioning session in Experiment 3. Accuracy rates were lowest of all when incorrect co-witness information was paired with questioning that suggested an incorrect response. These results have implications not only for the immediate effects on the accuracy of witnesses' memory reports, but also for the impact that even one such inaccurate report can have on the manner in which a case is investigated by the police or other authorities.

Differential sensitivity of antinociceptive assays to the bradykinin antagonist Hoe 140

1. The antinociceptive activity of the bradykinin (BK) BK2 receptor antagonist D-Arg-[Hyp3,Thi5D-Tic7,Oic8]BK (Hoe 140) was determined in a range of mouse abdominal constriction assays. 2. Hoe 140 potently inhibited the response induced by i.p. injection of 10 micrograms BK/mouse, and 1 microgram BK/mouse in mice pre-sensitized by i.p. injection of prostaglandin E2 (PGE2). The ED50 values in these assays were 1.9 and 3.7 micrograms kg-1 respectively. This confirms that Hoe 140 is a potent antagonist of BK in vivo. 3. Hoe 140 produced potent, but incomplete inhibition of the responses evoked by i.p. injection of kaolin or 0.25% acetic acid. ED25 values in these assays were 2.7 and 16.1 micrograms kg-1, and the maximum inhibition produced was 60% and 70% respectively. 4. At doses up to 1 mg kg-1, Hoe 140 was completely ineffective against the abdominal constriction response induced by zymosan. In contrast, morphine, ibuprofen and indomethacin had similar potencies against zymosan, kaolin and acetic acid-induced abdominal constriction. 5. Although zymosan, acetic acid and kaolin all produce qualitatively similar responses, it is appears that they achieve this by different mechanisms. The extent to which BK is involved as a mediator differs between the various types of abdominal constriction assay.

Structure/activity studies related to 2-(3,4-dichlorophenyl)-N-methyl-N-[2-(1-pyrrolidinyl)-1-substituted- ethyl]acetamides: a novel series of potent and selective kappa-opioid agonists

This paper describes the synthesis of a series of N-[2-(1-pyrrolidinyl)ethyl]acetamides 1, variously substituted at the carbon adjacent to the amide nitrogen (C1), and related analogues, together with their biological evaluation as opioid kappa agonists. In the first part of the study, the variants in N-acyl, N-alkyl, and amino functions were explored when the substituent at C1 was 1-methylethyl and the optimum was found to be exemplified by 2-(3,4-dichlorophenyl)-N-methyl-N-[(1S)-1-(1-methylethyl)-2- (1-pyrrolidinyl)ethyl]acetamide (13). Subsequently, racemic or chiral amino acids were used to introduce other alkyl and aryl substituents at C1 of the ethyl linking moiety. A series of potent compounds, bearing substituted-aryl groups at C1, were discovered, typified by 2-(3,4-dichloro-phenyl)-N-methyl-N-[(1R,S)-1-(3-aminophenyl)-2-(1- pyrrolidinyl)ethyl]acetamide (48), which was 5-fold more active as the racemate than 13 in vitro and exhibited potent naloxone-reversible analgesic effects (ED50 = 0.04 mg/kg sc) in a mouse abdominal constriction model.

2-(3,4-Dichlorophenyl)-N-methyl-N-[2-(1-pyrrolidinyl)-1-substituted- ethyl]-acetamides: the use of conformational analysis in the development of a novel series of potent opioid kappa agonists

This paper describes the synthesis of a series of N-[2-(1-pyrrolidinyl)ethyl]acetamides (1), methylated at C1 and/or C2 of the ethyl linking group, and their biological evaluation as opioid kappa agonists. Conformational analysis of corresponding desaryl analogues 2 suggested that only those compounds capable of occupying an energy minimum close to that of the known kappa agonist N-[2-(1-pyrrolidinyl)cyclohexyl] acetamide U-50488 might possess kappa agonist properties. Starting from chiral amino acids, other alkyl and aryl substituents were introduced at C1 of the ethyl-linking moiety, giving compounds capable of adopting the same conformation as U-50488. The most potent of these, 2-(3,4-dichlorophenyl)-N-methyl-N-[(1S)-1-phenyl-2-(1-pyrrolidinyl)ethyl] acetamide (8), was 146-fold more active than U-50488 in vitro in the mouse vas deferens model and exhibited potent naloxone-reversible analgesic effects (ED50 = 0.004 mg/kg sc) in an abdominal constriction model.

The coexistence of adenosine A1 and A2 receptors in guinea-pig aorta

The effects of adenosine, 5'-(N-ethyl)carboxamidoadenosine (NECA), 2-chloroadenosine (2-CA), N6-cyclohexyladenosine (CHA) and N6(R-2-phenylisopropyl)-adenosine (R-PIA) on the tone of phenylephrine-constricted guinea-pig isolated aorta have been examined. For aortic relaxation the analogues exhibited the following rank order of potency: NECA greater than adenosine greater than 2-CA greater than R-PIA greater than CHA. This is consistent with previous reports that relaxation of this tissue is mediated by the adenosine A2 receptor. An unexpected finding was that R-PIA, 2-CA and CHA all induced contractions at concentrations lower than were required for relaxation, giving a biphasic dose-response curve. Neither NECA nor adenosine contracted the aorta. This is consistent with activation of vascular A1 receptors. An A1-selective concentration of the antagonist 1,3-dipropyl-8-cyclopentyl xanthine abolished the contraction elicited by R-PIA in the guinea-pig aorta. This further suggests that the contraction is mediated by A1 receptors.

The xanthene-9-spiro-4'-piperidine nucleus as a probe for opiate activity

A series of novel 1'-methylxanthene-9-spiro-4'-piperidines has been prepared in the search for opiate analgesics with improved pharmacological properties. It has been found that introduction of a hydroxyl group into the 4-position of the xanthenespiropiperidine nucleus produces a potent mu-opiate agonist. The structure-activity relationship of the series has been explored by use of isosteric replacements of the phenolic hydroxyl group. Moreover, the effect of altering the conformation of the piperidine ring has been studied. It was interesting to note that, in compounds lacking the phenolic hydroxyl group, opiate activity could be produced by introduction of the (phenylamino)ethyl group instead of methyl at the 1'-position.

ICI 204448: a kappa-opioid agonist with limited access to the CNS

1. A number of compounds were evaluated in an attempt to identify a kappa-opioid receptor agonist with limited access to the central nervous system. 2. Quaternary derivatives of the kappa-opioid agonists tifluadom, U-50488H and ethylketocyclazocine were essentially devoid of opioid activity in a range of isolated tissue preparations. 3. A novel compound - ICI 204448 - is described which produced a potent and naloxone-reversible inhibition of electrically-evoked contraction of the guinea-pig ileum, mouse vas deferens and rabbit vas deferens preparations. ICI 204448 was shown to displace the binding of the kappa-opioid ligand [3H]-bremazocine from guinea-pig cerebellum membranes. 4. Ex vivo binding studies in mice showed ICI 204448 to be well absorbed following subcutaneous administration. The brain levels achieved by ICI 20448 were substantially lower than those produced by kappa-agonists such as U-50488H and tifluadom. 5. A good correlation was found for a range of opioids between lipophilicity and degree of CNS penetration.

Differential sensitivity of antinociceptive tests to opioid agonists and partial agonists

1. The antinociceptive activity of a range of opioid agonists and agonist-antagonist analgesics was determined in mice by use of the 55 degrees C hot plate and abdominal constriction assays. 2. Opioid agonists were approximately 10 times more effective in the abdominal constriction assay. 3. The agonist-antagonists produced analgesia only in the abdominal constriction assay, and antagonized the antinociceptive action of opioid agonists in the 55 degrees C hot plate test. 4. These differences were shown to be attributable to the different levels of stimulus employed in the two tests. 5. By comparing the antagonist potencies of the agonist-antagonists in the 55 degrees C hot plate test with their antinociceptive ED50 values in the abdominal constriction assay, an index of intrinsic activity was calculated.

A novel series of potent and selective agonists at the opioid kappa-receptor

Three novel opioid agonists are described. These compounds were found to bind with high affinity and selectivity to the kappa-opioid receptor. Isolated tissue studies using the field-stimulated mouse vas deferens and guinea-pig ileum preparations confirmed the high agonist potency and naloxone-reversibility of these agents. All three compounds exhibited potent antinociceptive activity in the mouse abdominal constriction model. These compounds should prove useful as tools to investigate kappa-receptor function.

The physiological relevance of low agonist affinity binding at opioid mu-receptors

1. Inhibition constant (Ki) were determined for a range of opioid standards using two binding assays; [3H]-[D-Ala2, MePhe4, Gly-ol5]enkephalin ([3H]-GLYOL) binding to guinea-pig brain membranes in HEPES buffer and [3H]-naloxone binding to rat whole brain membranes in Krebs/HEPES buffer. 2. These values were compared with affinity measurements determined by antagonism of GLYOL on the rat isolated vas deferens preparation and by the receptor occlusion technique of Furchgott on the guinea-pig ileum longitudinal muscle, myenteric plexus preparation. 3. Agonists demonstrated markedly reduced binding affinity in the [3H]-naloxone binding assay where binding was conducted in the presence of sodium. 4. A strong correlation was obtained between Ki values from the [3H]-naloxone binding assay and affinity values determined in both isolated tissue preparations. Ki values obtained from [3H]-GLYOL binding did not correlate well with affinity data determined by isolated tissue techniques. 5. These findings suggest that functionally relevant receptors exhibit low agonist affinity.

Specificity of the opioid affinity reagent, DALECK, in a set of isolated tissue assay systems

The C-terminal chloromethyl ketone derivative of D-Ala2-Leu5-enkephalin (DALECK) has previously been shown to act as an affinity reagent at opioid receptors. The specificity of this derivative in its reversible interaction with functional opioid receptors has been examined here in a set of four field-stimulated isolated tissue preparations; the mouse, rat and rabbit vas deferens and the guinea pig ileum. Agonist potencies relative to selective reference agonists and Schild analysis were used to elucidate the overall activity of DALECK when interacting reversibly with opiate receptors under normal physiological conditions in the isolated tissue preparations. Under these conditions the ligand shows a very strong mu-selectivity. Data obtained in the guinea pig ileum suggest that DALECK is more potent than Tyr-D-Ala-Gly-N(CH3)Phe-Gly-ol (DAGO) when acting through mu-receptors. In contrast in the mouse vas deferens DALECK is at least 70-fold less potent than the delta-ligand D-Thr2-Leu5-enkephalin-Thr (DTLET). DALECK shows little interaction with kappa-receptors.

The contribution of intrinsic activity to the action of opioids in vitro

The effects of opioids were compared in five field-stimulated isolated tissue models, the guinea-pig ileum and vasa deferentia from rat, rabbit and mice of the Alderley Park and C57BL/6 strains. Although the mu-receptor agonist [D-Ala2, MePhe4, Gly-ol5] enkephalin appeared to act at similar receptors in the guinea-pig ileum, rat vas deferens, mouse vas deferens and C57BL/6 mouse vas deferens preparations, its potency varied considerably between these preparations. Similar potency differences were also observed with the kappa-agonist, ethylketocyclazocine. It is proposed that these variations in potency reflect differences in the number of spare receptors present in each model. The finding that some drugs which have agonist activity in the more sensitive preparations behave as antagonists in the less sensitive tissues supports this proposal and highlights the importance of intrinsic activity in determining the action of opioids. Many of the prototypic opioid agonists were found to be either partial agonists (eg. morphine and bremazocine) or to possess affinity for more than one receptor type (eg. ethylketocyclazocine, Mr 2034).

Characterisation of the delta-opioid receptor on the hamster vas deferens

It has recently been reported that the hamster vas deferens contains only delta-opioid receptors. We have demonstrated that three delta-receptor agonists [D-Ala2, D-Leu5]enkephalin (DADLE), [D-Pen2, D-Pen5]enkephalin (DPDPE) and [D-Thr2, Leu5, Thr6] enkephalin (DTLET) appear to mediate their effects via the delta-receptor since they are readily reversed by the selective delta-receptor antagonist ICI 174864. In addition, a number of classical mu and k receptor compounds were devoid of activity in this preparation. However it was observed that some compounds such as etorphine and MR 2034 reported to possess delta-receptor affinity in other assay systems were weak or inactive on the hamster vas deferens.

Conversion of dynorphin-(1-9) to [Leu5]enkephalin by the mouse vas deferens in vitro

The inhibitory action of dynorphin-(1-9) on the electrically stimulated mouse vas deferens was seen to be antagonised by the delta-selective opioid antagonist ICI 174864. The observed delta-receptor mediated responses were partially, but not totally, prevented by peptidase inhibitors which protect the C- and N-termini of dynorphin-(1-9). [3H]Dynorphin-(1-9) is rapidly degraded by slices of vasa deferentia of the mouse. The major product of this metabolism co-elutes with [Leu5]enkephalin on reverse phase HPLC. It is concluded that a major component of the inhibitory effects of dynorphin-(1-9) on the mouse vas deferens is mediated by degradation to [Leu5]enkephalin which in turn acts through delta-receptors. It is possible that in other in vitro and in vivo systems, the effects produced by dynorphin-(1-9) might be similarly mediated by delta-receptor activation.

Mu-receptor binding in physiological media: comparison with isolated tissue data

Mu-receptor affinities have been determined for a number of opioid drugs using a combination of isolated tissue and receptor binding techniques. The affinities of antagonists and partial agonists were determined by their ability to antagonise responses to [D-Ala2,MePhe4,Glyol5]enkephalin (GLYOL) on the rat vas deferens preparation. There was little correlation between these results and affinities measured by displacement of [3H]-GLYOL from guinea-pig brain membranes incubated in 50mM Tris buffer. By contrast, affinities measured by displacement of [3H]-naloxone from rat brain membranes incubated in a Krebs/HEPES buffer containing a non-hydrolysable analogue of GTP, agreed very closely with the isolated tissue data.

Failure to demonstrate mu-isoreceptors

Attempts have been made to confirm reports that naloxonazine and Mr2034 are able to selectively antagonise morphine-induced analgesia and respiratory depression respectively. In the present studies these antagonists proved to be equi-effective against both the analgesic and respiratory depressant effects of morphine, suggesting that these two actions are mediated by a common receptor.

Mu-receptors in the C57BL mouse vas deferens

The C57 mouse vas deferens preparation has been shown to be insensitive to mu-opioids. The present study indicates that this tissue possesses mu, d and k-receptors with similar affinities to those found in other isolated tissue preparations, but has a small receptor reserve. Thus partial agonists such as morphine are detected as antagonists.

Multiple opiate receptors in the mouse vas deferens

The agonist potencies of normorphine and [D-Ala2,D-Leu5]enkephalin (DADL) have been determined on the mouse vas deferens preparation under different conditions. Reducing the temperature at which the assay was performed had little effect on the response to DADL whilst the Emax of normorphine was greatly reduced. Tissues rendered tolerant to either agent exhibited little, if any, cross-tolerance to the other drug. The results suggest the presence of at least two types of opiate receptor in the mouse vas deferens.

Divergent structure activity relationships in series of enkephalin agonists and cognate antagonists

Diallylation of the amino group of [Leu]enkephalin methyl ester yields a moderately potent, delta-selective opiate receptor antagonist. The diallyl congeners of a larger range of potent mu-and delta-selective enkephalin agonists have been prepared and were found to be weak, non-selective antagonists as assessed by their ability to antagonise the effects of normorphine and [Leu]enkephalin on the field-stimulated mouse vas deferens. Conversely, whereas [Gly3 psi (CH2S)Phe4,Leu5]enkephalin and [Gly3 psi(CH2S)-D-Phe4,Leu5]enkephalin are virtually inactive as opiate agonists the corresponding diallyl analogues are moderately potent, highly selective delta-antagonists. Analogues of diallyl[Leu]enkephalin in which the Gly2 and Gly3 residues have been replaced by D- and L- Ala have also been prepared and tested as delta-receptor antagonists. In addition, the empiric energy program ECEPP has been used to derive eighteen low energy conformations of diallyl[Leu]enkephalin and to estimate the effect of the D- and L-Ala substitutions on the conformer energies. Two conformers were identified for which there was a partial correlation between the variations in conformational energy and delta-antagonist potency.

Psychological androgyny and stressful life events

Seventy-one college students completed the Bem Sex-Role Inventory, a stressful life-events questionnaire, and some general questions on adjustment. Subjects were also asked to rate the stressful life events they had experienced in the prior 12 months along the dimensions of desirability, amount of change, anticipation, control, and meaningfulness. As hypothesized, androgynous subjects rated their stressful life events as less undesirable than other subjects, but this result only held for females (p less than .01). Undifferentiated subjects rated their stressful life events as less meaningful than other subjects (p less than .01) and androgynous subjects rated themselves as happier than other subjects (p less than .05). No differences were found among androgynous, masculine, feminine, and undifferentiated persons for the dimensions of change, anticipation, or control. Of the five dimensions examined, only meaningfulness was significantly related to happiness (r = .34, p less than .01). One possible reason for the results of this study may be differential access to and/or use of social support systems by persons of different sex-types. Some findings of the present study are presented that support this contention.

Psychological androgyny and stressful life events

Seventy-one college students completed the Bem Sex-Role Inventory, a stressful life-events questionnaire, and some general questions on adjustment. Subjects were also asked to rate the stressful life events they had experienced in the prior 12 months along the dimensions of desirability, amount of change, anticipation, control, and meaningfulness. As hypothesized, androgynous subjects rated their stressful life events as less undesirable than other subjects, but this result only held for females (p less than .01). Undifferentiated subjects rated their stressful life events as less meaningful than other subjects (p less than .01) and androgynous subjects rated themselves as happier than other subjects (p less than .05). No differences were found among androgynous, masculine, feminine, and undifferentiated persons for the dimensions of change, anticipation, or control. Of the five dimensions examined, only meaningfulness was significantly related to happiness (r = .34, p less than .01). One possible reason for the results of this study may be differential access to and/or use of social support systems by persons of different sex-types. Some findings of the present study are presented that support this contention.

Bicuculline-insensitive GABA receptors on peripheral autonomic nerve terminals

The action of gamma-aminobutyric acid (GABA) and related compounds on rat isolated atria and mouse and guinea pig isolated vas deferens has been studied. GABA depressed the evoked but not basal release of [3H]noradrenaline from atria (IC50 4 micro M) and reduced the twitch responses of the vas deferens (IC50 3 micro M) in a dose-dependent manner. These depressant effects were not prevented by recognized GABA antagonists such as bicuculline and picrotoxin. Numerous GABA analogues, in particular 3-aminopropanesulphonic acid, failed to mimic the action of GABA. However, beta-p-chlorophenyl GABA (baclofen) was stereospecifically active. Other related beta-substituted derivatives were also active but to a lesser degree than GABA. Pretreatment of the vas deferens with the neuronal GABA uptake inhibitors 2,4-diaminobutyric acid or cis-3-aminocyclohexanecarboxylic acid potentiated the action of GABA. These data suggest the presence of a bicuculline-insensitive GABA receptor on autonomic nerve terminals. Preliminary observations indicate a lack of chloride ion dependence in the action of GABA at this site.