Plasma and acrosomal membrane lipid content of saltwater crocodile spermatozoa

This study describes the chemical lipid composition of the sperm plasma and acrosomal membranes of the saltwater crocodile Crocodylus porosus with the aim of providing new insights into sperm physiology, particularly that associated with their preservation ex vivo . The specific fatty acid composition of the sperm plasma and acrosomal membranes is documented. The mean (±s.d.) ratio of unsaturated to saturated membrane fatty acids within the plasma membrane was 2.57±0.50, and was determined to be higher than a similar analysis of the lipids found in the acrosomal membrane (0.70±0.10). The saltwater crocodile sperm plasma membrane also contained remarkably high levels of cholesterol (mean (±s.d.) 40.7±4.5 nmol per 106 sperm cells) compared with the spermatozoa of other amniote species that have so far been documented. We suggest that this high cholesterol content could be conferring stability to the crocodile sperm membrane, allowing it to tolerate extreme osmotic fluxes and rapid changes in temperature. Our descriptive analysis now provides those interested in reptile and comparative sperm physiology an improved baseline database for interpreting biochemical changes associated with preservation pathology (e.g. cold shock and cryoinjury), epididymal sperm maturation and capacitation/acrosome reaction.

Examining Differences in Recovery Outcomes between Male and Female Hip Fracture Patients: Design and Baseline Results of a Prospective Cohort Study from the Baltimore Hip Studies

BACKGROUND

Incidence of hip fractures in men is expected to increase, yet little is known about consequences of hip fracture in men compared to women. It is important to investigate differences at time of fracture using the newest technologies and methodology regarding metabolic, physiologic, neuromuscular, functional, and clinical outcomes, with attention to design issues for recruiting frail older adults across numerous settings.

OBJECTIVES

To determine whether at least moderately-sized sex differences exist across several key outcomes after a hip fracture.

DESIGN, SETTING, AND PARTICIPANTS

This prospective cohort study (Baltimore Hip Studies 7th cohort [BHS-7]) was designed to include equal numbers of male and female hip fracture patients to assess sex differences across various outcomes post-hip fracture. Participants were recruited from eight hospitals in the Baltimore metropolitan area within 15 days of admission and were assessed at baseline, 2, 6 and 12 months post-admission.

MEASUREMENTS

Assessments included questionnaire, functional performance evaluation, cognitive testing, measures of body composition, and phlebotomy.

RESULTS

Of 1709 hip fracture patients screened from May 2006 through June 2011, 917 (54%) were eligible and 39% (n=362) provided informed consent. The final analytic sample was 339 (168 men and 171 women). At time of fracture, men were sicker (mean Charlson score= 2.4 vs. 1.6; p<0.001) and had worse cognition (3MS score= 82.3 vs. 86.2; p<0.05), and prior to fracture were less likely to be on bisphosphonates (8% vs. 39%; p<0.001) and less physically active (2426 kilocalories/week vs. 3625; p<0.001).

CONCLUSIONS

This paper provides the study design and methodology for recruiting and assessing hip fracture patients and evidence of baseline and pre-injury sex differences which may affect eventual recovery one year later.

Abstract P3-08-13: Exploring the role of ctDNA in triple negative breast cancer

BACKGROUND: Previously published work shows that triple negative (TNBC) is a heterogeneous disease with varying levels of genomic instability, where higher genomic instability is associated with poorer prognosis. Subgroups of TNBC patients with distinct patterns of genome aberrations may indicate pathologies in specific genome maintenance/repair processes. Circulating tumor DNA (ctDNA) as assessed by next generation sequencing (NGS) is a relatively non-invasive test that may provide prognostic and predictive information.

AIM OF STUDY: To analyze genomic alterations with serial plasma samples using NGS methods of ctDNA analysis and determine the utility for actionability and disease burden monitoring. We shall also determine whether TNBC subgroups differ in their ctDNA profiles. Shallow whole genome sequencing vs targeted capture at depth will be contrasted to determine sensitivity for relapse detection.

METHODS: Enrollment of a planned cohort of TNBC patients (N=300) with any stage, at diagnosis (dx) or within 2 years of dx, or at relapse of disease with ongoing plasma sampling every 3 -6 months. Patient age, stage, grade, type of chemotherapy, date of relapse and date of last followup are collected. Tumor tissue (FFPE), saliva for germline mutations and serial blood draws for ctDNA are analyzed with two NGS sequencing methods: (i) a high sensitivity small hotspot gene panel (33 genes, 170 hotspots), directed purely at actionable findings (ii) capture sequencing directed at multiple regions of the genome or shallow whole genome sequencing.

RESULTS: Preliminary analysis in 20 patient cases using the targeted hotspot panel. . Median followup 151 days. Two cases had plasma drawn at time of relapsed disease and 1 at the time of de novo metastatic disease; 12 had plasma samples drawn prior to neoadjuvant chemotherapy (clinical T1/T2N1, T3/T4Nany), and 5 had plasma draws after primary surgery (pathologic T1N0, T2N0). Of the neoadjuvant cases, 5 (42%) had a pathologic complete response (pCR); 4 with ctDNA mutations and 1 without. Six (58%) neoadjuvant cases did not achieve a pCR; 3 with ctDNA mutations, 3 without. One patient is awaiting surgery. Twelve (60%) cases had mutations in TP53, one case had 2 different TP53 mutations (no pCR) and one case had 3 mutations: TP53, PIK3CA, KRAS (achieved pCR). Of the cases treated with curative intent, with short followup (FU), there have been no relapses including the case of the sample containing 3 mutations.

CONCLUSION: TP53 mutations may be a marker of higher genomic alteration burden and may have prognostic value in patients with newly diagnosed, non-metastatic TNBC with longer FU. Ongoing analysis of serial plasma samples and FFPE analysis may provide further insight into the prognostic value of ctDNA. Full genome sequencing may be needed identify other mutations that have prognostic and/or predictive value. We have accrued over 200 patients with samples being analyzed and plan to present an interim analysis of the cohort at SABCS 2018.

Citation Format: den Brok WD, Kong E, Bates C, Aguirre-Hernandez R, Miller RR, Lum A, Wan A, Shah S, Aparicio S, Gelmon KA. Exploring the role of ctDNA in triple negative breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-08-13.

Hemodynamic evaluation in acute myocardial infarction

Bedside right heart catheterization in patients with acute myocardial infarction and hemodynamic dysfunction provides a rational basis for therapy aimed at maximizing cardiac performance and limiting infarct size. Readily performed and associated with minimal risk, this diagnostic approach is primarily indicated when myocardial infarction is associated with evidence of hemodynamic dysfunction. It affords precise information on cardiac performance and prognosis, allows identification of specific complications such as ventricular septal defect and acute mitral regurgitation, and is of critical importance in selection of therapy. Hemodynamic monitoring is also essential for safe, effective application of certain forms of treatment such as vasodilator therapy for the failing ventricle.

Time as content in Pavlovian conditioning

Time has played only a limited role within the traditional theories of Pavlovian conditioning. Although temporal factors certainly contribute to whether conditioning occurs, the traditional assumption in the associative framework has been that associations lack temporal information. Recently, the temporal coding hypothesis has challenged that view, arguing that animals encode temporal relationships as part of associations. That is, proximal temporal relationships not only foster associative learning, but also are part of the content of learning. The present paper reviews for the nonspecialist the increasing empirical evidence that temporal coding is ubiquitous in Pavlovian paradigms, including simultaneous and backward conditioning, second-order conditioning, sensory preconditioning, cue competition, Hall-Pearce type CS-preexposure, and conditioned inhibition. The data support the temporal coding hypothesis' view that contiguity is sufficient for associative learning to occur, but challenge the central assumption of the informational hypothesis that predictive relations are necessary for learning to occur (as opposed to predictive relationships only being necessary for the expression of knowledge).

Flying-fox (Pteropus spp.) sperm membrane fatty acid composition, its relationship to cold shock injury and implications for cryopreservation success

The very large acrosome of Pteropus species spermatozoa is prone to damage during cooling procedures. Cryogenic succuss has been linked to membrane composition, therefore the lipid composition of five Pteropus species sperm acrosomal and plasma membranes were investigated to provide insight into reasons for cold shock susceptibility. Rapid chilling and re-warming of spermatozoa from three Pteropus species resulted in a decrease (P<0.05) in acrosomal integrity. Biochemical analysis of lipids revealed that stearic acid (18:0) was the predominant saturated fatty acid and oleic acid (18:1, n-9) the predominant unsaturated fatty acid in both acrosomal and plasma membranes. Linolenic acid (18:3, n-3) was only detected in plasma membranes of Pteropus hypomelanus and was detected in acrosomal membranes of all Pteropus spp. studied (except Pteropus giganteus). Although detected in both plasma and acrosomal membranes of Pteropus vampyrus, docosahexaenoic acid (22:6) was not detected at all in Pteropus poliocephalus, only in trace levels in the acrosomal and plasma membranes of P. giganteus and P. hypomelanus and not in acrosomal membranes of Pteropus rodricensis. No difference was seen in the levels of polyunsaturated fatty acids (PUFAs) within plasma membranes, however PUFAs were lower (P<0.05) in acrosomal membranes of P. giganteus compared with P. vampyrus. Pteropus spp. spermatozoa have a very low ratio of unsaturated/saturated membrane fatty acids (<0.5). Membranes containing more PUFAs are more fluid, so the use of cryogenic media which improves membrane fluidity should improve Pteropus spp. spermatozoal viability post-thaw.

The Caenorhabditis elegans T-box factor MLS-1 requires Groucho co-repressor interaction for uterine muscle specification

T-box proteins are conserved transcription factors that play crucial roles in development of all metazoans; and, in humans, mutations affecting T-box genes are associated with a variety of congenital diseases and cancers. Despite the importance of this transcription factor family, very little is known regarding how T-box factors regulate gene expression. The Caenorhabditis elegans genome contains 21 T-box genes, and their characterized functions include cell fate specification in a variety of tissues. The C. elegans Tbx1 sub-family member MLS-1 functions during larval development to specify the fate of non-striated uterine muscles; and, in mls-1 mutants, uterine muscles are transformed to a vulval muscle fate. Here we demonstrate that MLS-1 function depends on binding to the Groucho-family co-repressor UNC-37. MLS-1 interacts with UNC-37 via a conserved eh1 motif, and the MLS-1 eh1 motif is necessary for MLS-1 to specify uterine muscle fate. Moreover, unc-37 loss-of-function produces uterine muscle to vulval muscle fate transformation similar to those observed in mls-1 mutants. Based on these results, we conclude that MLS-1 specifies uterine muscle fate by repressing target gene expression, and this function depends on interaction with UNC-37. Moreover, we suggest that MLS-1 shares a common mechanism for transcriptional repression with related T-box factors in other animal phyla.

The hormonal profile of hip fracture female patients differs from community-dwelling peers over a 1-year follow-up period

Hormone levels were compared over a 1-year period between elderly women who had sustained a hip fracture and women of similar age and functional ability. Our study suggests progressive hormonal changes that may contribute to severe bone loss during the year following hip fracture.

INTRODUCTION

Alterations in hormones affecting the musculoskeletal system may increase risk of hip fracture or poor post-fracture recovery in postmenopausal women. Most studies lack appropriate reference groups, and thus cannot assess the extent to which these alterations are attributable to hip fracture.

METHODS

Women aged ≥65 years hospitalized for an acute hip fracture (Baltimore Hip Studies, BHS-3; n = 162) were age-matched to 324 women enrolled in the Women's Health and Aging Study I, a Baltimore-based cohort with similar functional status to the pre-fracture status of BHS-3 women. Both studies enrolled participants from 1992 to 1995. Insulin-like growth hormone-1 (IGF-1), parathyroid hormone (PTH), 1,25 dihydroxyvitamin D [1,25(OH)2D], and osteocalcin were evaluated at baseline and 2, 6, and 12 months post-fracture, and at baseline and 12 months in the comparison group. Between-group differences in trajectories of each hormone were examined.

RESULTS

Baseline mean IGF-1 levels were significantly lower in hip fracture patients than the comparison group (75.0 vs. 110.5 μg/dL; p < 0.001). Levels increased by 2 months post-fracture, but remained significantly lower than those in the comparison group throughout the 12-month follow-up (p < 0.01). Levels of PTH and osteocalcin were similar between groups at baseline, but rose during the year post-fracture to significantly differ from the comparison women (p < 0.001). 1,25(OH)2D levels did not differ between the hip fracture and comparison women at any time.

CONCLUSIONS

Older women who have sustained a hip fracture have progressive changes in hormonal milieu that exceed those of women of similar health status during the year following fracture.

All-Female Strains of the Teleost Fishes of the Genus Poeciliopsis

In addition to the viviparous fish Mollienesia formosa, two other species of poeciliids have recently been found to produce only female offspring. The young of these females, however, unlike those of M. formosa, inherit characteristics from any one of the several species of males used in experimental matings.

Within and between breed differences in freezing tolerance and plasma membrane fatty acid composition of boar sperm

The response of sperm to cryopreservation and the fertility of frozen-thawed semen varies between species. Besides species differences in sperm physiology, structure and biochemistry, factors such as sperm transport and female reproductive tract anatomy will affect fertility of frozen-thawed semen. Therefore, studying differences in sperm cryotolerance between breeds and individuals instead of between species may reveal sources of variability in sperm cryotolerance. In the present study, the effect of cooling, re-warming and freezing and thawing on plasma membrane and acrosome integrity of sperm within and between Norwegian Landrace and Duroc breeds was studied. Furthermore, the relation between post-thaw survival rate and fatty acid composition of the sperm plasma membranes was investigated. Flow cytometry assessments of plasma membrane and acrosome integrity revealed no significant differences between breeds; however there were significant male-to-male variations within breeds in post-thaw percentages of live sperm (plasma membrane intact). The most abundant fatty acids in the plasma membranes from both breeds were palmitic acid (16:0), stearic acid (18:0), oleic acid (18:1, n-9), docosapentaenoic acid (22:5, n-6) and docosahexaenoic acid (22:6, n-3). The ratio of sigma operator 22:5, n-6 and 22:6, n-3/ sigma operator all other membrane fatty acids was significantly related to survival rate (plasma membrane integrity) of sperm for both Norwegian Landrace (correlation coefficient (r(s)) = 0.64, P < 0.05) and Duroc (r(s) = 0.67, P < 0.05) boars. In conclusion, male-to-male differences in sperm survival rate after freezing and thawing may be partly related to the amount of long-chain polyunsaturated fatty acids in the sperm plasma membranes.

Comparative aspects of sperm membrane fatty acid composition in silver (Vulpes vulpes) and blue (Alopex lagopus) foxes, and their relationship to cell cryopreservation

Cryogenic protocols have been developed for the storage of farmed silver fox (Vulpes vulpes) spermatozoa. However, these same protocols and modifications of these protocols have failed to satisfactorily preserve spermatozoa collected from farmed blue foxes (Alopex lagopus). Because cryogenic success has been linked to membrane composition, the plasma membrane lipid composition of farmed blue fox and silver fox spermatozoa was studied. Silver fox spermatozoal membranes have significantly higher levels of docosapentaenoic acid (DPA; 22:5, n-6) compared to blue fox spermatozoa, and blue fox spermatozoal membranes have significantly higher levels of stearic acid (18:0). Silver fox spermatozoal membranes not only have a higher ratio of unsaturated/saturated membrane fatty acids, but also higher levels of membrane desmosterol and cholesterol.

Sperm membrane fatty acid composition in the Eastern grey kangaroo (Macropus giganteus), koala (Phascolarctos cinereus), and common wombat (Vombatus ursinus) and its relationship to cold shock injury and cryopreservation success

Marsupial spermatozoa tolerate cold shock well, but differ in cryopreservation tolerance. In an attempt to explain these phenomena, the fatty acid composition of the sperm membrane from caput and cauda epididymides of the Eastern grey kangaroo, koala, and common wombat was measured and membrane sterol levels were measured in cauda epididymidal spermatozoa. While species-related differences in the levels of linolenic acid (18:3, n-6) and arachidonic acid (20:4, n-6) were observed in caput epididymal spermatozoa, these differences failed to significantly alter the ratio of unsaturated/saturated membrane fatty acids. However in cauda epididymidal spermatozoa, the ratio of unsaturated/saturated membrane fatty acids in koala and kangaroo spermatozoa was approximately 7.6 and 5.2, respectively; substantially higher than any other mammalian species so far described. Koala spermatozoal membranes had a higher ratio of unsaturated/saturated membrane fatty acids than that of wombat spermatozoa (t = 3.81; df = 4; p < or = 0.02); however, there was no significant difference between wombat and kangaroo spermatozoa. The highest proportions of DHA (22:6, n-3), the predominant membrane fatty acid in cauda epididymidal spermatozoa, were found in wombat and koala spermatozoa. While species-related differences in membrane sterol levels (cholesterol and desmosterol) were observed in cauda epididymidal spermatozoa, marsupial membrane sterol levels are very low. Marsupial spermatozoal membrane analyses do not support the hypothesis that a high ratio of saturated/unsaturated membrane fatty acids and low membrane sterol levels predisposes spermatozoa to cold shock damage. Instead, cryogenic tolerance appears related to DHA levels.

Stem-loop SL4 of the HIV-1 psi RNA packaging signal exhibits weak affinity for the nucleocapsid protein. structural studies and implications for genome recognition

Encapsidation of the genome of the human immunodeficiency virus type-1 (HIV-1) during retrovirus assembly is mediated by interactions between the nucleocapsid (NC) domains of assembling Gag polyproteins and a approximately 110 nucleotide segment of the genome known as the Psi-site. The HIV-1 Psi-site contains four stem-loops (SL1 through SL4), all of which are important for genome packaging. Recent isothermal titration calorimetry (ITC) studies have demonstrated that SL2 and SL3 are capable of binding NC with high affinity (K(d) approximately 140 nM), consistent with proposals for protein-interactive functions during packaging. To determine if SL4 may have a similar function, NC-interactive studies were conducted by NMR and gel-shift methods. In contrast to previous reports, we find that SL4 binds weakly to NC (K(d)=(+/-14 microM), suggesting an alternative function. NMR studies indicate that the GAGA tetraloop of SL4 adopts a classical GNRA-type fold (R=purine, N=G, C, A or U), a motif that stabilizes RNA tertiary structures in other systems. In combination with previously reported gel mobility studies of Psi-site deletion mutants, these findings suggest that SL4 functions in genome recognition not by binding to Gag, but by stabilizing the structure of the Psi-site. Differences in the affinities of NC for SL2, SL3 and SL4 stem-loops can now be rationalized in terms of the different structural properties of stem loops that contain GGNG (SL2 and SL3) and GNRA (SL4) sequences.

Conditions favoring retroactive interference between antecedent events (cue competition) and between subsequent events (outcome competition)

Retrieval of a target association (A-B) is often impaired if training of a similar association is interpolated between target training and testing; this is known as retroactive interference. Two experiments, in which rats were used as subjects in a sensory preconditioning preparation, studied the associative nature of retroactive interference between antecedent events (i.e., A and C in the A-B, C-B paradigm) and between subsequent events (i.e., B and C in the A-B, A-C paradigm). With the present preparation, retroactive interference was equally strong between antecedent events and between subsequent events. Moreover, interference occurred only if (1) an association was trained in the interpolated phase and (2) the target and interpolated associations had a common element in a common temporal location.

Ethanol- and nicotine-induced membrane changes in embryonic and neonatal chick brains

In order to study the effects of EtOH and/or nicotine on brain membrane fatty acid composition, various concentrations of EtOH and/or nicotine were injected into the air sac of chicken eggs at 0 days of incubation. Controls were injected with saline. Experimental groups were injected with either 200 micromol EtOH/kg egg, 100 micromol nicotine/kg egg, 200 micromol nicotine/kg egg, 200 micromol EtOH/kg and 100 micromol nicotine/kg egg, or 200 micromol EtOH/kg and 200 micromol nicotine/kg egg. In all experimental groups, EtOH- and nicotine-induced decreases in brain long-chain polyunsaturated membrane fatty acids were observed in stage 44 embryos, stage 45 embryos, and neonatal chicks. These EtOH- and nicotine-induced decreases in brain membrane polyunsaturated fatty acids correlated with elevated levels of brain lipid hydroperoxides and reduced brain acetylcholinesterase (AChE; EC. 3.1.1.7) activities.

Cues trained apart compete for behavioral control in rats: convergence with the associative interference literature

Contemporary theories of associative learning require cues be trained in compound for cue competition (interference) to occur. That is, Cues A and X should compete for behavioral control only if training consists of AX-outcome (O) trials and not if each cue is separately paired with O (i.e., X-O and A-O). Research with humans challenges this view by showing that A-O trials interpolated between training and testing of a X-O association impair responding to X (i.e., retroactive interference). In six conditioned suppression studies with rats, the authors demonstrate that two cues trained apart can each interfere with the potential of the other to predict the outcome. The authors conclude that this type of interference (a) reflects a failure to retrieve the target association due to priming at test of the interfering association and (b) is attenuated if the outcome is of high biological significance. These findings parallel previous reports in verbal learning research and suggest that a similar associative structure underlies some types of associations in nonverbal subjects.

Conditioned inhibition produced by extinction-mediated recovery from the relative stimulus validity effect: a test of acquisition and performance models of empirical retrospective revaluation

Empirical retrospective revaluation is a phenomenon of Pavlovian conditioning and human causal judgment in which posttraining changes in the conditioned response (Pavlovian task) or causal rating (causal judgment task) of a cue occurs in the absence of further training with that cue. Two experiments tested the contrasting predictions made by 2 families of models concerning retrospective revaluation effects. In a conditioned lick-suppression task, rats were given relative stimulus validity training, consisting of reinforcing a compound of conditioned stimuli (CSs) A and X and nonreinforcement of a compound of CSs B and X, which resulted in low conditioned responding to CS X. Massive posttraining extinction of CS A not only enhanced excitatory responding to CS X, but caused CS B to pass both summation (Experiment 1) and retardation (Experiment 2) tests for conditioned inhibition. The inhibitory status of CS B is predicted by the performance-focused extended comparator hypothesis (J. C. Denniston, H. I. Savastano, & R. R. Miller, 2001), but not by acquisition-focused models of empirical retrospective revaluation (e.g., A. Dickinson & J. Burke, 1996; L. J. Van Hamme & E. A. Wasserman, 1994).

Memory involves far more than 'consolidation'

The observation that retrieval returns a stable memory into a labile state cannot be readily explained by any simple version of consolidation theory. This finding has been interpreted as evidence for the need to reconsolidate a memory after reactivating it. However, as we discuss in this commentary, other behavioural observations indicate that even this modification to consolidation theory may be insufficient to describe the dynamic properties of memory.

Discovery of a potent, orally bioavailable beta(3) adrenergic receptor agonist, (R)-N-[4-[2-[[2-hydroxy-2-(3-pyridinyl)ethyl]amino]ethyl]phenyl]-4-[4 -[4-(trifluoromethyl)phenyl]thiazol-2-yl]benzenesulfonamide

As part of our investigation into the development of orally bioavailable beta(3) adrenergic receptor agonists, we have identified a series of pyridylethanolamine analogues possessing a substituted thiazole benzenesulfonamide pharmacophore that are potent human beta(3) agonists with excellent selectivity against other human beta receptor subtypes. Several of these compounds also exhibited an improved pharmacokinetic profile in dogs. For example, thiazole sulfonamide 2e (R = 4-F(3)C-C(6)H(4)) is a potent full beta(3) agonist (EC(50) = 3.6 nM, 94% activation) with >600-fold selectivity over the human beta(1) and beta(2) receptors, which also displays good oral bioavailability in several mammalian species, as well as an extended duration of action.

Cytochrome P450 3A4-mediated interaction of diclofenac and quinidine

The metabolism of diclofenac to its 5-hydroxylated derivative in humans is catalyzed by cytochrome P450 (CYP)3A4. We report herein that in vitro this biotransformation pathway is stimulated by quinidine. When diclofenac was incubated with human liver microsomes in the presence of quinidine, the formation of 5-hydroxydiclofenac increased approximately 6-fold relative to controls. Similar phenomena were observed with diastereoisomers of quinidine, including quinine and the threo epimers, which produced an enhancement in the formation of 5-hydroxydiclofenac in the order of 6- to 9-fold. This stimulation of diclofenac metabolism was diminished when human liver microsomes were pretreated with a monoclonal inhibitory antibody against CYP3A4. In contrast, neither cytochrome b(5) nor CYP oxidoreductase appeared to mediate the stimulation of diclofenac metabolism by quinidine, suggesting that the effect of quinidine is mediated through CYP3A4 protein. Further kinetic analyses indicated that V(max) values for the conversion of diclofenac to its 5-hydroxy derivative increased 4.5-fold from 13.2 to 57.6 nmol/min/nmol of CYP with little change in K(m) (71-56 microM) over a quinidine concentration range of 0 to 30 microM. Conversely, the metabolism of quinidine was not affected by the presence of diclofenac; the K(m) value estimated for the formation of 3-hydroxyquinidine was approximately 1.5 microM, similar to the quinidine concentration required to produce 50% of the maximum stimulatory effect on diclofenac metabolism. It appears that the enhancement of diclofenac metabolism does not interfere with quinidine's access to the ferriheme-oxygen complex, implicating the presence of both compounds in the active site of CYP3A4 at the same time. Finally, a approximately 4-fold increase in 5-hydroxydiclofenac formation was observed in human hepatocyte suspensions containing diclofenac and quinidine, demonstrating that this type of drug-drug interaction occurs in intact cells.

Discovery of an orally bioavailable alkyl oxadiazole beta3 adrenergic receptor agonist

5-n-Pentyl oxadiazole substituted benzenesulfonamide 8 is a potent and selective beta3 adrenergic receptor agonist (beta3 EC50 = 23 nM, beta1 IC50 = 3000 nM, beta2 IC50 = 3000 nM). The compound has high oral bioavailability in dogs (62%) and rats (36%) and is among the most orally bioavailable beta3 adrenergic receptor agonists reported to date.

Alpha-tocopherol and gamma-tocopherol attenuate ethanol-induced changes in membrane fatty acid composition in embryonic chick brains

BACKGROUND

This project investigated whether or not EtOH-induced reductions in the levels of long-chain polyunsaturated membrane fatty acids could be attenuated by exogenous exposure to either alpha-tocopherol, gamma-tocopherol, or diallyl sulfide (DAS).

METHODS

At 0 days of development, fertile chicken eggs were injected with a single dose of either saline supplemented with various concentrations of EtOH, alpha- or gamma-tocopherol and EtOH, or DAS and EtOH. At 18 days of development, brains were isolated and subjected to membrane analyses.

RESULTS

When exposed to EtOH, concentrations ranging from 0-60.50 microm/Kg egg, dose-dependent decreases in the levels of brain 18:0, 18:1 (n-9), 18:2 (n-6), 18:3 (n-3), and 20:4 (n-6) were observed. These ethanol-induced changes in membrane fatty acid composition correlated with ethanol-induced reductions in brain mass, brain protein levels, acetylcholine esterase (AChE) activities and correlated with increased lipid hydroperoxide levels. Exposure to either 2.5 microm alpha-tocopherol/Kg egg and 6.050 mm EtOH/Kg egg, or 2.5 microm alpha-tocopherol/ Kg egg and 6.050 mm EtOH/Kg egg attenuated EtOH-induced changes in membrane fatty acid composition, brain mass, brain protein levels, AChE activities, and lipid hydroperoxide levels. Embryonic exposure to the cytochrome p450-2E1 inhibitor, diallyl sulfide (DAS), also attenuated EtOH-induced decreases in long-chain, unsaturated membrane fatty acids. However, embryonic exposure to DAS promoted abnormally low brain mass.

CONCLUSION

EtOH-induced reductions in the levels of brain long-chain polyunsaturated fatty acid are caused by lipid peroxidation.

Overshadowing of subsequent events and recovery thereafter

Four experiments using a conditioned lick suppression preparation with rats were conducted to examine whether overshadowing of subsequent events could be obtained in Pavlovian backward conditioning (i.e. unconditioned stimulus [US] before conditioned stimulus [CS]), and to determine whether such overshadowing could be reversed without further training with the overshadowed CS, as has been reported in overshadowing of antecedent events. In Experiment 1, a backward-conditioned CS overshadowed a second backward-conditioned CS. Two posttraining manipulations, extinction of the overshadowing CS (Experiment 2) and shifting of the temporal relationship of the overshadowing CS to the US (Experiment 3), increased responding to the overshadowed CS. These results constitute the first unambiguous demonstration of stimulus competition between subsequent events using first-order conditioning, and they show that, like overshadowing with forward conditioning, such overshadowing is due, at least in part if not completely, to a failure to express information that had been acquired.

Prevention of the degraded-contingency effect by signalling training trials

Presentation of unsignalled unconditioned stimuli (USs) interspersed among Pavlovian excitatory conditioning trials weakens conditioned responding to a target conditioned stimulus (CS; Rescorla, 1968). However, signalling these intertrial USs with another cue (a cover stimulus) has been shown to alleviate this degraded-contingency effect (e.g. Durlach, 1982, 1983). In contrast to signalling the intertrial USs, the present experiments examined the effect on the degraded-contingency effect of signalling the target CS-US pairings. Experiment 1, using parameters selected to avoid overshadowing, found that consistently presenting a cover stimulus immediately prior to the target CS-US pairings during degraded-contingency training alleviated the degraded-contingency effect. Experiment 2 examined the underlying mechanism responsible for this cover-stimulus effect through posttraining associative inflation of the cover stimulus or the context, and found that inflation of the cover stimulus attenuated responding to the target CS (i.e. empirical retrospective revaluation). The results are discussed in terms of various acquisition- and expression-focused models of acquired responding.

Counterconditioning of an overshadowed cue attenuates overshadowing

In 3 Pavlovian conditioned lick-suppression experiments, rats received overshadowing treatment with a footshock unconditioned stimulus such that Conditioned Stimulus (CS) A overshadowed CS X. Subjects that subsequently received CS X paired with an established signal for saccharin (CS B) exhibited less overshadowing of the X-footshock association than subjects that did not receive the X-B pairings (Experiment 1). Experiment 2 replicated this effect and controlled for some additional alternative accounts of the phenomenon. In Experiment 3, this recovery from overshadowing produced by counterconditioning CS X was attenuated if CS B was massively extinguished prior to counterconditioning. These results are more compatible with models of cue competition that emphasize differences in the expression of associations than those that emphasize differences in associative acquisition.

Interaction of diclofenac and quinidine in monkeys: stimulation of diclofenac metabolism

The cytochrome P-450 (CYP)3A4-mediated metabolism of diclofenac is stimulated in vitro by quinidine. A similar effect is observed in incubations with monkey liver microsomes. We describe an in vivo interaction of diclofenac and quinidine that leads to enhanced clearance of diclofenac in monkeys. After a dose of diclofenac via portal vein infusion at 0.055 mg/kg/h, steady-state systemic plasma drug concentrations in three male rhesus monkeys were 87, 104, and 32 ng/ml, respectively (control). When diclofenac was coadministered with quinidine (0.25 mg/kg/h) via the same route, the corresponding plasma diclofenac concentrations were 50, 59, and 18 ng/ml, representing 57, 56, and 56% of control values, respectively. In contrast, steady-state systemic diclofenac concentrations in the same three monkeys were elevated 1.4 to 2.5 times when the monkeys were pretreated with L-754,394 (10 mg/kg i.v.), an inhibitor of CYP3A. Further investigation indicated that the plasma protein binding (>99%) and blood/plasma ratio (0.7) of diclofenac remained unchanged in the presence of quinidine. Therefore, the decreases in plasma concentrations of diclofenac after a combined dose of diclofenac and quinidine are taken to reflect increased hepatic clearance of the drug, presumably resulting from the stimulation of CYP3A-catalyzed oxidative metabolism. Consistent with this proposed mechanism, a 2-fold increase in the formation of 5-hydroxydiclofenac derivatives was observed in monkey hepatocyte suspensions containing diclofenac and quinidine. Stimulation of diclofenac metabolism by quinidine was diminished when monkey liver microsomes were pretreated with antibodies against CYP3A. Subsequent kinetic studies indicated that the K(m) value for the CYP-mediated conversion of diclofenac to its 5-hydroxy derivatives was little changed (75 versus 59 microM), whereas V(max) increased 2.5-fold in the presence of quinidine. These data suggest that the catalytic capacity of monkey hepatic CYP3A toward diclofenac metabolism is enhanced by quinidine.

Toxicology: judge data or dollars?

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Recovery from one-trial overshadowing

Prevailing models of associative learning can all account for multitrial overshadowing. However, they fail to account for one-trial overshadowing, which is ordinarily explained in terms of distraction of the subject by the more salient of two simultaneously trained cues from the less salient cue, which interferes with associative acquisition. In the present study, we demonstrate that recovery from overshadowing can be obtained through two techniques that have previously been found to restore responding to overshadowed cues in multitrial training situations. Specifically, recovery from one-trial overshadowing was obtained by extinguishing the overshadowing stimulus and also by administering a posttraining reminder treatment consisting of brief exposure to the overshadowed cue. The similarity of these observations to those in multitrial overshadowing suggests that one-trial and multitrial overshadowing arise from a common underlying mechanism and further augments the view that all cue competition is due (at least in part) to a failure to express acquired information, rather than to a failure to learn.

L-770,644: a potent and selective human beta3 adrenergic receptor agonist with improved oral bioavailability

L-770,644 (9c) is a potent and selective agonist of the human beta3 adrenergic receptor (EC50 = 13 nM). It shows good oral bioavailability in both dogs and rats (%F = 27), and is a full agonist for glycerolemia in the rhesus monkey (ED50 = 0.21 mg/kg). Based on its desirable in vitro and in vivo properties, L-770,644 was chosen for further preclinical evaluation.

Human beta3 adrenergic receptor agonists containing cyclic ureidobenzenesulfonamides

Human beta3 adrenergic receptor agonists containing 5-membered ring ureas were shown to be potent partial agonists with excellent selectivity over beta1 and beta2 binding. L-760,087 (4a) and L-764,646 (5a) (beta3 EC50 = 18 and 14 nM, respectively) stimulate lipolysis in rhesus monkeys (ED50 = 0.2 and 0.1 mg/kg, respectively) with minimal effects on heart rate. Oral absorption in dogs is improved over other urea analogs.

Posttraining shifts in the overshadowing stimulus-unconditioned stimulus interval alleviates the overshadowing deficit

Two conditioned lick suppression experiments explored the effects on overshadowing of a posttraining change in the temporal relationship between the overshadowing conditioned stimulus (CS) and the unconditioned stimulus (US). Rats received either trace (Experiment 1) or delay (Experiment 2) overshadowing training. Then pairings of the overshadowing CS and US were given with either a trace or delay temporal relationship. Overshadowing was alleviated by shifting the overshadowing CS-US temporal relationship so that it no longer matched the overshadowed CS-US temporal relationship. These outcomes are explicable in terms of an integration of the comparator hypothesis, which states that cue competition effects (e.g., overshadowing) will be maximal when the information potentially conveyed by competing CSs is equivalent, and the temporal coding hypothesis, which states that CS-US intervals are part of the information encoded during conditioning.

Disposition of L-732,531, a potent immunosuppressant, in rats and baboons

L-732,531 is a semi-synthetic analog of the macrolide tacrolimus (Prograf(R)). Like tacrolimus, L-732,531 is a potent immunosuppressant. In this study, its absorption, distribution, metabolism, and excretion were studied in rats and baboons. In rats, its blood and plasma levels were similar, whereas in baboons, its blood levels were, on average, twice as high as those in plasma. This was consistent with the in vitro blood-to-plasma ratio of L-732, 531, which in these two species, as well as in humans, was much lower than that of tacrolimus and showed a minimal concentration dependence. After iv administration to rats, the blood and plasma clearance of L-732,531 decreased from approximately 60 ml/min/kg at 0.2 mg/kg to 30 ml/min/kg when dosed at 1 and 3 mg/kg. After oral administration, plasma area under the concentration vs. time curve (AUC) and maximal plasma concentration (Cmax) increased more than proportionally to the dose. At 1, 5, and 15 mg/kg, plasma AUC was 29, 466, and 2832 ng.hr/ml, respectively, and Cmax was 10, 129, and 304 ng/ml, respectively. Bioavailability, although compromised by nonlinear kinetics, was estimated to be between 8% and 18%. In baboons, the clearance of L-732,531 was lower than that in rats, especially when calculated from blood concentrations (12 ml/min/kg at 0.2 mg/kg and 8 ml/min/kg at 1 mg/kg). After oral dosing, baboon plasma AUC and Cmax were much lower than those in rats, but as in rats, they increased more than proportionally with increasing doses. The bioavailability of L-732,531 in baboons was estimated at 3%, 9%, and 24% when animals were dosed at 5, 15, and 26 mg/kg po, respectively. After oral administration of [3H]L-732,531 at 5 mg/kg, approximately 32% of the radioactivity was recovered in bile and urine of rats, compared with 9% in baboons. High-performance liquid chromatography profiles of rat and baboon plasma, bile, urine, and feces indicated that L-732,531 was metabolized extensively to a complex mixture of products. Some intact parent drug was observed in feces of orally dosed animals, indicating incomplete absorption. In vitro, L-732,531 was metabolized more extensively by baboon liver microsomes than rat or human microsomes. Its metabolism in human liver microsomes was shown to be catalyzed primarily by cytochrome P450 3A isozymes.

Comparator mechanisms and conditioned inhibition: conditioned stimulus preexposure disrupts Pavlovian conditioned inhibition but not explicitly unpaired inhibition

Three conditioned lick-suppression experiments with rats examined the effects of pretraining exposure to the conditioned stimulus (CS) on behavior indicative of conditioned inhibition. After CS-preexposure treatment, subjects received either Pavlovian conditioned inhibition training or explicitly unpaired inhibition training with the preexposed CS. The inhibitory status of the CS was then assessed with a retardation (Experiment 1) or a summation (Experiment 2) test. Experiment 3 controlled for the unconditioned stimulus-preexposure effect being a potential confound in Experiments 1 and 2. As predicted by the comparator hypothesis (R. R. Miller & L. D. Matzel, 1988), the CS-context association that developed during the CS-preexposure phase disrupted the expression of Pavlovian conditioned inhibition but not the expression of explicitly unpaired inhibition.

3-Pyridyloxypropanolamine agonists of the beta 3 adrenergic receptor with improved pharmacokinetic properties

Pyridyloxypropanolamines L-749,372 (8, beta 3 EC50 = 3.6 nM) and L-750,355 (29, beta 3 EC50 = 13 nM) are selective partial agonists of the human receptor, with 33% and 49% activation, respectively. Both stimulate lipolysis in rhesus monkeys (ED50 = 2 and 0.8 mg/kg, respectively), with minimal effects on heart rate. Oral bioavailability in dogs, 41% for L-749,372 and 47% for L-750,355, is improved relative to phenol analogs.

Closed rupture of the anterior tibial tendon. A case report

Closed subcutaneous rupture of the anterior tibial tendon is a relatively uncommon injury that requires a thorough clinical examination to diagnose correctly. The authors report a case of this disorder and provide a review of the relevant literature. A method of surgical repair not previously described in the literature is also presented.

Overshadowing and latent inhibition counteract each other: support for the comparator hypothesis

In 4 conditioned lick suppression experiments with rats, the combined effects of latent inhibition treatment followed by overshadowing treatment were assessed as a test of the comparator hypothesis's (R.R. Miller & L.D. Matzel, 1988) explanations of overshadowing and latent inhibition. Experiments 1 and 2 confirmed the prediction of the comparator hypothesis that combined latent inhibition and overshadowing treatments attenuate the response deficit produced by either treatment alone. Furthermore, consistent with the comparator hypothesis, posttraining changes in the associative status of the putative comparator stimulus altered responding to the target conditioned stimulus (Experiment 3), and switching contexts between latent inhibition and overshadowing treatments (Experiment 4) eliminated the interaction between the latent inhibition and overshadowing treatments.

A developmental profile of the effects of ethanol on the levels of chick brain phospholipids

The effects of embryonic exposure to ethanol on brain phospholipid levels were studied by injecting various concentrations of ethanol, ranging from 0 to 149 microns kg-1 egg, into fertile chicken eggs at 0 days of incubation. At 7, 9, 11, 15 and 18 days of incubation, brains were collected and the levels of total phospholipids and various phospholipid classes were measured. Although embryonic exposure to ethanol failed to influence total phospholipid levels, ethanol-induced changes in the levels of individual phospholipid classes were observed. Ethanol-induced increases in the levels of phosphatidylethanolamine (PE) and phosphatidylserine (PS) and ethanol-induced decreases in the levels of phosphatidylcholine (PC) were observed at 9, 11, 15 and 18 days of incubation. Ethanol-induced decreases in brain sphingomyelin (SP) levels were observed at 7 and 18 days of development. These ethanol-induced changes in brain phospholipid levels preceded detectable alcohol dehydrogenase (ADH) activities in both brain and liver.

A selective human beta3 adrenergic receptor agonist increases metabolic rate in rhesus monkeys

Activation of beta3 adrenergic receptors on the surface of adipocytes leads to increases in intracellular cAMP and stimulation of lipolysis. In brown adipose tissue, this serves to up-regulate and activate the mitochondrial uncoupling protein 1, which mediates a proton conductance pathway that uncouples oxidative phosphorylation, leading to a net increase in energy expenditure. While chronic treatment with beta3 agonists in nonprimate species leads to uncoupling protein 1 up-regulation and weight loss, the relevance of this mechanism to energy metabolism in primates, which have much lower levels of brown adipose tissue, has been questioned. With the discovery of L-755,507, a potent and selective partial agonist for both human and rhesus beta3 receptors, we now demonstrate that acute exposure of rhesus monkeys to a beta3 agonist elicits lipolysis and metabolic rate elevation, and that chronic exposure increases uncoupling protein 1 expression in rhesus brown adipose tissue. These data suggest a role for beta3 agonists in the treatment of human obesity.

The role of temporal relationships in the transfer of conditioned inhibition

Two experiments with rats investigated the temporal relationships under which conditioned inhibition will transfer to an independently conditioned excitor (CS) in a summation test. Experiment 1 trained 2 simultaneous inhibitors with either a trace or delay excitatory CS. Transfer of inhibitory behavioral control depended on the temporal relationship of the transfer CS to the unconditioned stimulus (US). Experiment 2 extended these findings by training 2 inhibitors (1 simultaneous and 1 serial) with a single delay excitatory CS. Again, testing with trace and delay transfer CSs found that transfer of inhibitor control depended on the temporal relationship of the transfer CS to the US. In both studies, maximal inhibition was observed when the inhibitor signaled US omission at the same time as the transfer excitor signaled US presentation. The results are discussed in terms of the temporal coding hypothesis.

Temporal coding in Pavlovian conditioning: Hall-Pearce negative transfer

The Hall-Pearce (1979) negative transfer effect in rats was used to examine whether temporal relationships are coded as part of the informational content of associations that results from CS-US pairings. The transfer effect consists of a deficit in conditioned responding following CS-USstrong pairings in Phase 2 that results from prior CS-USweak pairings in Phase 1. Using conditioned bar-press suppression, we found that gaps of different duration between CS termination and US onset in the two training phases resulted in less of a Hall-Pearce negative transfer effect than did an equivalent gap in the two training phases. The results are discussed with respect to the temporal coding hypothesis (Matzel, Held, & Miller, 1988), the Pearce and Hall (1980) model, and Bouton's (1993) interference model.

The role of temporal relationships in the transfer of conditioned inhibition

Two experiments with rats investigated the temporal relationships under which conditioned inhibition will transfer to an independently conditioned excitor (CS) in a summation test. Experiment 1 trained 2 simultaneous inhibitors with either a trace or delay excitatory CS. Transfer of inhibitory behavioral control depended on the temporal relationship of the transfer CS to the unconditioned stimulus (US). Experiment 2 extended these findings by training 2 inhibitors (1 simultaneous and 1 serial) with a single delay excitatory CS. Again, testing with trace and delay transfer CSs found that transfer of inhibitor control depended on the temporal relationship of the transfer CS to the US. In both studies, maximal inhibition was observed when the inhibitor signaled US omission at the same time as the transfer excitor signaled US presentation. The results are discussed in terms of the temporal coding hypothesis.

Conducting exposure treatment in multiple contexts can prevent relapse

The acquisition of anxiety disorders (e.g., phobias) is often thought to be mediated by classical conditioning processes (e.g., Wolpe, 1958, Psychotherapy by reciprocal inhibition Wolpe and Rowan, 1989, Behaviour Research and Therapy, 27, 583-585). Thus, the success of exposure therapy is possibly a consequence of extinction, and factors affecting extinction in Pavlovian conditioning are potentially relevant to clinicians who administer exposure therapy. The present experiments investigated the effects of conducting extinction in multiple contexts using rats as subjects in a conditioned suppression paradigm. In Experiment 1, subjects received conditioned stimulus (CS) and unconditioned stimulus (US) pairings in one context followed by extinction of that CS in one or three other contexts. When tested in an associatively neutral context (i.e., different from those of conditioning or extinction), rats that had received extinction in three contexts exhibited less responding to the CS than rats that had received extinction in one context. In Experiment 2, CS-US training occurred in either one or three contexts, followed by extinction of that CS in three other contexts. Testing in a neutral context revealed that rats conditioned in multiple contexts showed greater responding to the CS than rats trained in a single context. The results are discussed in the framework of memory retrieval, and the clinical implications are explored.

Temporal encoding as a determinant of overshadowing

Three conditioned lick suppression experiments explored the effects on overshadowing of the temporal relationships of two conditioned stimuli (CSs) with an unconditioned stimulus (US). Assuming overshadowing is maximal when the potential information conveyed by two competing CSs is equivalent, the temporal coding hypothesis predicts that greater overshadowing will be observed when the CSs share the same temporal relationship with the US. Rats were exposed to an overshadowing CS that had either a forward, simultaneous, or backward relationship to the US. The relationship of the overshadowed CSs to the US was either forward (Experiment 1), simultaneous (Experiment 2), or backward (Experiment 3). The greatest amount of overshadowing was observed when both CSs had the same temporal relationship to the US. The data are discussed within the framework of the temporal coding hypothesis and of alternative models of Pavlovian conditioning based on the informational hypothesis.

Metabolic profiles of montelukast sodium (Singulair), a potent cysteinyl leukotriene1 receptor antagonist, in human plasma and bile

Montelukast sodium [1-([(1(R)-(3-(2-(7-chloro-2-quinolinyl)-(E)- ethenyl)phenyl)-3-(2-(1-hydroxy-1-methylethyl)phenyl)propyl)thio]methyl)cyclopropylacetic acid sodium salt] (MK-476, Singulair) is a potent and selective antagonist of the cysteinyl leukotriene (Cys-LT1) receptor and is under investigation for the treatment of bronchial asthma. To assess the metabolism and excretion of montelukast, six healthy subjects received single oral doses of 102 mg of [14C]montelukast, and the urine and feces were collected. Most of the radioactivity was recovered in feces, with </=0.2% appearing in urine. Based on these results and the reported modestly high oral bioavailability of montelukast, it could be concluded that a major part of the radioactivity was excreted via bile. A second clinical study was conducted to identify biliary metabolites of montelukast. The bile was aspirated using a modified procedure involving a nasogastric tube placed fluoroscopically near the ampulla of Vater, after an oral dose of 54.8 mg of [14C]montelukast. This technique appears to be a new application for drug metabolism studies. The study was conducted with fasted and nonfasted subjects, with the bile being aspirated continuously under suction over periods of 2-8 hr and 8-12 hr after the dose, respectively. Two hours before the end of the collection procedure, cholecystokinin carboxyl-terminal octapeptide was administered iv to stimulate gallbladder contraction. Plasma samples also were collected periodically over 10 hr. Due to the nature of the collection procedure and the limited sampling time, recovery of radioactivity in bile was incomplete and varied from 3 to 20% of the dose. Radiochromatographic and LC-MS/MS analyses of bile showed the presence of one major and several minor metabolites, along with small amounts of unchanged parent drug. The minor metabolites were identified, by LC-MS/MS comparison with synthetic standards or by NMR, as acyl glucuronide (M1), sulfoxide (M2), 25-hydroxy (a phenol, M3), 21-hydroxy (diastereomers of a benzylic alcohol, M5a and M5b), and 36-hydroxy (diastereomers of a methyl alcohol, M6a and M6b) analogs of montelukast. The major metabolite was characterized as a dicarboxylic acid (M4), a product of further oxidation of the hydroxymethyl metabolite M6. Chiral LC-MS/MS analyses of M4 revealed that this diacid, like M5 and M6, was formed in both diastereomeric forms. The levels of metabolites in the systemic circulation were low in the fed as well as fasted subjects, with <2% of the circulating radioactivity being due to metabolites M5a, M5b, M6a, and M6b. Overall, this bile aspiration technique, which is less invasive than either T-tube drainage or fine-needle percutaneous puncture, provided a convenient and expedient means of identifying the biliary metabolites of montelukast, relatively free of contributions from colonic microflora.