Ketogenic diet enhances the effects of oxycodone in mice

Opioids have been used to manage pain for thousands of years, but they have significant potential for abuse. Prescription opioids, like oxycodone, are associated with 32% of overdoses, that have reached a total of 75,673 deaths in 2021. A major challenge is maximizing their therapeutic potential while minimizing the negative side effects including opioid use disorder (OUD). The Ketogenic Diet (KD) has been reported to reduce pain and decrease the severity of alcohol use disorder, yet its effects on oxycodone responses remain unknown. KD mice displayed increased oxycodone-induced locomotor activity and enhanced antinociceptive effects of oxycodone, suggesting a dietary effect on opiate sensitivity. Male KD mice exposed to chronic oxycodone exhibited increased naloxone-induced jumps, suggesting a sex-specific effect of diet on opioid withdrawal. Consistent with this, male KD mice self-administered less oxycodone while female KD mice did not differ from controls. Finally, no effect of KD on motivation to obtain oxycodone was observed during a progressive ratio schedule. These data suggest sex-biased effects of KD on responses to opioids that should be considered and potentially leveraged in both clinical pain management and treatment of OUD.

Mice lacking Ptprd exhibit deficits in goal-directed behavior and female-specific impairments in sensorimotor gating

Protein Tyrosine Phosphatase receptor type D (PTPRD) is a member of the protein tyrosine phosphatase family that mediates cell adhesion and synaptic specification. Genetic studies have linked Ptprd to several neuropsychiatric phenotypes, including Restless Leg Syndrome (RLS), opioid abuse disorder, and antipsychotic-induced weight gain. Genome-wide association studies (GWAS) of either pediatric obsessive-compulsive traits, or Obsessive-Compulsive Disorder (OCD), have identified loci near PTPRD as genome-wide significant, or strongly suggestive for this trait. We assessed Ptprd wild-type (WT), heterozygous (HT), and knockout (KO) mice for behavioral dimensions that are altered in OCD, including anxiety and exploration (open field test, dig test), perseverative behavior (splash-induced grooming, spatial d), sensorimotor gating (prepulse inhibition), and home cage goal-directed behavior (nest building). No effect of genotype was observed in any measure of the open field test, dig test, or splash test. However, Ptprd KO mice of both sexes showed impairments in nest building behavior. Finally, female, but not male, Ptprd KO mice showed deficits in prepulse inhibition, an operational measure of sensorimotor gating that is reduced in female, but not male, OCD patients. Our results indicate that constitutive lack of Ptprd may contribute to the development of certain domains that are altered OCD, including goal-directed behavior, and reduced sensorimotor gating specifically in females.

Targeted effects of ketamine on perceptual expectation during mediated learning in rats

RATIONALE

While neural correlates of hallucinations are known, the mechanisms have remained elusive. Mechanistic insight is more practicable in animal models, in which causal relationships can be established. Recent work developing animal models of hallucination susceptibility has focused on the genesis of perceptual expectations and perceptual decision-making. Both processes are encompassed within mediated learning, which involves inducing a strong perceptual expectation via associative learning, retrieving that memory representation, and deciding whether this internally generated percept is predictive of an external outcome. Mediated learning in rodents is sensitive to many psychotomimetic manipulations. However, we do not know if these manipulations selectively alter learning of perceptual expectations versus their retrieval because of their presence throughout all task phases.

OBJECTIVES

Here, we used mediated learning to study the targeted effect of a psychotomimetic agent on the retrieval of perceptual expectation.

METHODS

We administered (R,S)-ketamine to rats selectively during the devaluation phase of a mediated learning task, when the representation of the expected cue is retrieved, to test the hypothesis that internally generated perceptual experiences underlie this altered mediated learning.

RESULTS

We found that ketamine increased only mediated learning at a moderate dose in rats, but impaired direct learning at the high dose.

CONCLUSIONS

These results suggest that ketamine can augment retrieval of perceptual expectations and thus this may be how it induces hallucination-like experiences in humans. More broadly, mediated learning may unite the conditioning, perceptual decision-making, and even reality monitoring accounts of psychosis in a manner that translates across species.

Reinforcement learning detuned in addiction: integrative and translational approaches

Suboptimal decision-making strategies have been proposed to contribute to the pathophysiology of addiction. Decision-making, however, arises from a collection of computational components that can independently influence behavior. Disruptions in these different components can lead to decision-making deficits that appear similar behaviorally, but differ at the computational, and likely the neurobiological, level. Here, we discuss recent studies that have used computational approaches to investigate the decision-making processes underlying addiction. Studies in animal models have found that value updating following positive, but not negative, outcomes is predictive of drug use, whereas value updating following negative, but not positive, outcomes is disrupted following drug self-administration. We contextualize these findings with studies on the circuit and biological mechanisms of decision-making to develop a framework for revealing the biobehavioral mechanisms of addiction.

MPEP Lowers Binge Drinking in Male and Female C57BL/6 Mice: Relationship with mGlu5/Homer2/Erk2 Signaling

BACKGROUND

Metabotropic glutamate receptor 5 (mGlu5) plays an important role in excessive alcohol use and the mGlu5/Homer2/Erk2 signaling pathway has been implicated in binge drinking. The mGlu5 negative allosteric modulator (NAM) 2-methyl-6-(phenylethynyl)pyridine hydrochloride (MPEP) has been shown to reduce binge drinking in male mice, but less is known about its effect on female mice. Here, we sought to determine whether sex differences exists in the effects of MPEP on binge drinking and whether they relate to changes in the MPEP mGlu5/Homer2/Erk2 signaling.

METHODS

We measured the dose-response effect of MPEP on alcohol consumption in male and female mice using the Drinking in the Dark (DID) paradigm to assess potential sex differences. To rule out possible confounds of MPEP on locomotion, we measured the effects of MPEP on locomotor activity and drinking simultaneously during DID. Lastly, to test whether MPEP-induced changes in alcohol consumption were related to changes in Homer2 or Erk2 expression, we performed qPCR using brain tissue acquired from mice that had undergone 7 days of DID.

RESULTS

30 mg/kg MPEP reduced binge alcohol consumption across female and male mice, with no sex differences in the dose-response relationship. Locomotor activity did not mediate the effects of MPEP on alcohol intake, but activity correlated with alcohol intake independent of MPEP. MPEP did not change the expression of Homer2 and Erk2 mRNA in the bed nucleus of the stria terminalis (BNST) or nucleus accumbens in mice whose drinking was reduced by MPEP, relative to saline. There was a positive relationship between alcohol intake and Homer2 expression in the BNST.

CONCLUSIONS

MPEP reduced alcohol consumption during DID in male and female C57BL/6 mice but did not change Homer2/Erk2 expression. Locomotor activity did not mediate the effects of MPEP on alcohol intake, though it correlated with alcohol intake. Alcohol intake during DID predicted BNST Homer2 expression. These data provide support for the regulation of alcohol consumption by mGlu5 across sexes.

Saracatinib Fails to Reduce Alcohol-Seeking and Consumption in Mice and Human Participants

More effective treatments to reduce pathological alcohol drinking are needed. The glutamatergic system and the NMDA receptor (NMDAR), in particular, are implicated in behavioral and molecular consequences of chronic alcohol use, making the NMDAR a promising target for novel pharmacotherapeutics. Ethanol exposure upregulates Fyn, a protein tyrosine kinase that indirectly modulates NMDAR signaling by phosphorylating the NR2B subunit. The Src/Fyn kinase inhibitor saracatinib (AZD0530) reduces ethanol self-administration and enhances extinction of goal-directed ethanol-seeking in mice. However, less is known regarding how saracatinib affects habitual ethanol-seeking. Moreover, no prior studies have assessed the effects of Src/Fyn kinase inhibitors on alcohol-seeking or consumption in human participants. Here, we tested the effects of saracatinib on alcohol consumption and craving/seeking in two species, including the first trial of an Src/Fyn kinase inhibitor to reduce drinking in humans. Eighteen male C57BL/6NCrl mice underwent operant conditioning on a variable interval schedule to induce habitual responding for 10% ethanol/0.1% saccharin. Next, mice received 5 mg/kg saracatinib or vehicle 2 h or 30 min prior to contingency degradation to measure habitual responding. In the human study, 50 non-treatment seeking human participants who drank heavily and met DSM-IV criteria for alcohol abuse or dependence were randomized to receive 125 mg/day saracatinib (n = 33) or placebo (n = 17). Alcohol Drinking Paradigms (ADP) were completed in a controlled research setting: before and after 7-8 days of treatment. Each ADP involved consumption of a priming drink of alcohol (0.03 mg%) followed by ad libitum access (3 h) to 12 additional drinks (0.015 g%); the number of drinks consumed and craving (Alcohol Urge Questionnaire) were recorded. In mice, saracatinib did not affect habitual ethanol seeking or consumption at either time point. In human participants, no significant effects of saracatinib on alcohol craving or consumption were identified. These results in mice and humans suggest that Fyn kinase inhibition using saracatinib, at the doses tested here, may not reduce alcohol consumption or craving/seeking among those habitually consuming alcohol, in contrast to reports of positive effects of saracatinib in individuals that seek ethanol in a goal-directed manner. Nevertheless, future studies should confirm these negative findings using additional doses and schedules of saracatinib administration.

Endocannabinoid contributions to alcohol habits and motivation: Relevance to treatment

Individuals with alcohol use disorder exhibit compulsive habitual behaviors that are thought to be, in part, a consequence of chronic and persistent use of alcohol. The endocannabinoid system plays a critical role in habit learning and in ethanol self-administration, but the role of this neuromodulatory system in the expression of habitual alcohol seeking is unknown. Here, we investigated the role of the endocannabinoid system in established alcohol habits using contingency degradation in male C57BL/6 mice. We found that administration of the novel diacyl glycerol lipase inhibitor DO34, which decreases the biosynthesis of the endocannabinoid 2-arachidonoyl glycerol (2-AG), reduced habitual responding for ethanol and ethanol approach behaviors. Moreover, administration of the endocannabinoid transport inhibitor AM404 or the cannabinoid receptor type 1 antagonist AM251 produced similar reductions in habitual responding for ethanol and ethanol approach behaviors. Notably, AM404 was also able to reduce ethanol seeking and consumption in mice that were insensitive to lithium chloride-induced devaluation of ethanol. Conversely, administration of JZL184, a monoacyl glycerol lipase inhibitor that increases levels of 2-AG, increased motivation to respond for ethanol on a progressive ratio schedule of reinforcement. These results demonstrate an important role for endocannabinoid signaling in the motivation to seek ethanol, in ethanol-motivated habits, and suggest that pharmacological manipulations of endocannabinoid signaling could be effective therapeutics for treating alcohol use disorder.

Ketamine induces immediate and delayed alterations of OCD-like behavior

RATIONALE

Obsessive-compulsive disorder (OCD) is a psychiatric disorder characterized by intrusive obsessive thoughts and/or compulsive behaviors. Currently, serotonin reuptake inhibitors (SRIs) provide the only pharmacological monotherapy for OCD, but response rates are insufficient. Ketamine, a noncompetitive NMDA receptor antagonist, was reported to have rapid, sustained therapeutic effects in OCD patients. However, the mechanisms remain unknown.

OBJECTIVES

Here, we aimed to provide a platform for investigating mechanisms underlying anti-OCD effects of ketamine treatment by assessing whether ketamine pretreatment could alleviate 5-HT1B receptor (5-HT1BR)-induced OCD-like behavior in mice.

METHODS

We assessed whether acute ketamine (0, 3, 10, 30 mg/kg), administered at two pretreatment time points (30 min, 24 h), would modulate 5-HT1BR-induced OCD-like behavior in mice. Behavioral measures were perseverative hyperlocomotion in the open field and deficits in prepulse inhibition (PPI) induced by acute pharmacological 5-HT1BR challenge.

RESULTS

Three milligrams per kilogram of ketamine reduced 5-HT1BR-induced perseverative hyperlocomotion, but not PPI deficits, 24 h postinjection. In contrast, higher doses of ketamine were either ineffective (10 mg/kg) or exacerbated (30 mg/kg) 5-HT1BR-induced perseverative hyperlocomotion 30 min postinjection. At 24 h postinjection, 30 mg/kg ketamine reduced perseverative hyperlocomotion across all groups.

CONCLUSIONS

Our results suggest that the 5-HT1BR-induced model of OCD-like behavior is sensitive to a low dose of ketamine, a potential fast-acting anti-OCD treatment, and may provide a tool for studying mechanisms underlying the rapid therapeutic effects of ketamine in OCD patients.

Btbd3 expression regulates compulsive-like and exploratory behaviors in mice

BTB/POZ domain-containing 3 (BTBD3) was identified as a potential risk gene in the first genome-wide association study of obsessive-compulsive disorder (OCD). BTBD3 is a putative transcription factor implicated in dendritic pruning in developing primary sensory cortices. We assessed whether BTBD3 also regulates neural circuit formation within limbic cortico-striato-thalamo-cortical circuits and behaviors related to OCD in mice. Behavioral phenotypes associated with OCD that are measurable in animals include compulsive-like behaviors and reduced exploration. We tested Btbd3 wild-type, heterozygous, and knockout mice for compulsive-like behaviors including cage-mate barbering, excessive wheel-running, repetitive locomotor patterns, and reduced goal-directed behavior in the probabilistic learning task (PLT), and for exploratory behavior in the open field, digging, and marble-burying tests. Btbd3 heterozygous and knockout mice showed excessive barbering, wheel-running, impaired goal-directed behavior in the PLT, and reduced exploration. Further, chronic treatment with fluoxetine, but not desipramine, reduced barbering in Btbd3 wild-type and heterozygous, but not knockout mice. In contrast, Btbd3 expression did not alter anxiety-like, depression-like, or sensorimotor behaviors. We also quantified dendritic morphology within anterior cingulate cortex, mediodorsal thalamus, and hippocampus, regions of high Btbd3 expression. Surprisingly, Btbd3 knockout mice only showed modest increases in spine density in the anterior cingulate, while dendritic morphology was unaltered elsewhere. Finally, we virally knocked down Btbd3 expression in whole, or just dorsal, hippocampus during neonatal development and assessed behavior during adulthood. Whole, but not dorsal, hippocampal Btbd3 knockdown recapitulated Btbd3 knockout phenotypes. Our findings reveal that hippocampal Btbd3 expression selectively modulates compulsive-like and exploratory behavior.

Dissecting the roles of β-arrestin2 and GSK-3 signaling in 5-HT1BR-mediated perseverative behavior and prepulse inhibition deficits in mice

Serotonin-1B receptors (5-HT1BRs) modulate perseverative behaviors and prepulse inhibition (PPI) in humans and mice. These inhibitory G-protein-coupled receptors signal through a canonical G-protein-coupled pathway that is modulated by GSK-3β, and a noncanonical pathway mediated by the adaptor protein β-arrestin2 (Arrb2). Given the development of biased ligands that differentially affect canonical versus noncanonical signaling, we examined which signaling pathway mediates 5-HT1BR agonist-induced locomotor perseveration and PPI deficits, behavioral phenotypes observed in both obsessive-compulsive disorder (OCD) and autism spectrum disorder (ASD). To assess the role of canonical 5-HT1BR signaling, mice received acute pretreatment with a GSK-3 inhibitor (SB216763 or AR-A014418) and acute treatment with the 5-HT1A/1B receptor agonist RU24969 prior to assessing perseverative locomotor behavior in the open field, and PPI. To determine the role of noncanonical 5-HT1BR signaling, Arrb2 wild-type (WT), heterozygous (HT), and knockout (KO) mice received acute RU24969 treatment prior to behavioral testing. GSK-3 inhibition increased locomotor perseveration overall, and also failed to influence the RU24969-induced perseverative locomotor pattern in the open field. Yet, GSK-3 inhibition modestly reduced RU24969-induced PPI deficits. On the other hand, Arrb2 HT and KO mice showed reduced locomotion and no changes in perseveration overall, in addition to modest reductions in RU24969-induced locomotion and PPI deficits. In conclusion, our data do not support use of either GSK-3 inhibitors or β-arrestin2 inhibition in treatment of perseverative behaviors.

When tractography meets tracer injections: a systematic study of trends and variation sources of diffusion-based connectivity

Tractography is a powerful technique capable of non-invasively reconstructing the structural connections in the brain using diffusion MRI images, but the validation of tractograms is challenging due to lack of ground truth. Owing to recent developments in mapping the mouse brain connectome, high-resolution tracer injection-based axonal projection maps have been created and quickly adopted for the validation of tractography. Previous studies using tracer injections mainly focused on investigating the match in projections and optimal tractography protocols. Being a complicated technique, however, tractography relies on multiple stages of operations and parameters. These factors introduce large variabilities in tractograms, hindering the optimization of protocols and making the interpretation of results difficult. Based on this observation, in contrast to previous studies, in this work we focused on quantifying and ranking the amount of performance variation introduced by these factors. For this purpose, we performed over a million tractography experiments and studied the variability across different subjects, injections, anatomical constraints and tractography parameters. By using N-way ANOVA analysis, we show that all tractography parameters are significant and importantly performance variations with respect to the differences in subjects are comparable to the variations due to tractography parameters, which strongly underlines the importance of fully documenting the tractography protocols in scientific experiments. We also quantitatively show that inclusion of anatomical constraints is the most significant factor for improving tractography performance. Although this critical factor helps reduce false positives, our analysis indicates that anatomy-informed tractography still fails to capture a large portion of axonal projections.

Dlgap1 knockout mice exhibit alterations of the postsynaptic density and selective reductions in sociability

The scaffold protein DLGAP1 is localized at the post-synaptic density (PSD) of glutamatergic neurons and is a component of supramolecular protein complexes organized by PSD95. Gain-of-function variants of DLGAP1 have been associated with obsessive-compulsive disorder (OCD), while haploinsufficient variants have been linked to autism spectrum disorder (ASD) and schizophrenia in human genetic studies. We tested male and female Dlgap1 wild type (WT), heterozygous (HT), and knockout (KO) mice in a battery of behavioral tests: open field, dig, splash, prepulse inhibition, forced swim, nest building, social approach, and sucrose preference. We also used biochemical approaches to examine the role of DLGAP1 in the organization of PSD protein complexes. Dlgap1 KO mice were most notable for disruption of protein interactions in the PSD, and deficits in sociability. Other behavioral measures were largely unaffected. Our data suggest that Dlgap1 knockout leads to PSD disruption and reduced sociability, consistent with reports of DLGAP1 haploinsufficient variants in schizophrenia and ASD.

Clinically effective OCD treatment prevents 5-HT1B receptor-induced repetitive behavior and striatal activation

RATIONALE

Serotonin-1B receptor (5-HT1BR) agonist treatment induces obsessive-compulsive disorder (OCD)-like behaviors including locomotor stereotypy, prepulse inhibition deficits, and delayed alternation disruptions, which are selectively prevented by clinically effective OCD treatment. However, the role of 5-HT1BRs in modulating other repetitive behaviors or OCD-like patterns of brain activation remains unclear.

OBJECTIVES

We assessed the effects of 5-HT1BR agonism on digging, grooming, and open field behaviors in mice. We also quantified effects on neuronal activation in brain regions overactivated in OCD. Finally, we assessed whether effects of the 5-HT1BR challenge could be blocked by clinically effective, but not ineffective, drug treatments.

METHODS

Mice were tested in open field, dig, and splash tests after acute treatment with saline, 1, 3, 5, or 10 mg/kg RU24969 (5-HT1B/1A agonist). Behavioral effects of RU24969 were also tested following co-treatment with vehicle, 1 mg/kg WAY100635 (5-HT1A antagonist) and 5 or 10 mg/kg GR127935 (5HT1B/D antagonist). Separate mice were behaviorally assessed following chronic pretreatment with vehicle with 10 mg/kg fluoxetine or 20 mg/kg desipramine and acute treatment with saline or 10 mg/kg RU24969. Brains were analyzed for Fos expression in the orbitofrontal cortex, the dorsal striatum, and the cerebellum.

RESULTS

RU24969 induced robust locomotor stereotypy and decreased rearing, digging, and grooming. Effects were blocked by GR127935 but not by WAY100635. RU24969 also increased Fos expression in the dorsal striatum. Chronic fluoxetine, but not desipramine, alleviated 5-HT1BR-induced effects.

CONCLUSIONS

We report novel 5-HT1BR-induced behaviors and striatal activation that were alleviated only by clinically effective pharmacological OCD treatment. Studying the mechanisms underlying these effects could provide insight into OCD pathophysiology.

Abstract P2-11-01: Effects of chemotherapy on the ovary: What you didn't know

Background: It has long been known that chemotherapy can result in premature menopause, causing follicular senescence and estrogen depletion with associated hot flashes and mood alterations. What is less well appreciated is whether the stroma of the ovary is equally impacted after chemotherapy, resulting in androgen deprivation. The aim of this pilot study was to evaluate whether androgen levels are adversely affected after chemotherapy and whether this is associated with unwanted symptoms.

Methods: Women who were premenopausal, newly diagnosed with breast cancer, and about to undergo adjuvant chemotherapy were followed longitudinally. Women with adrenal insufficiencies, taking steroids, oral contraceptives, or had had previous chemotherapy were excluded. Self report questionnaires regarding sexual function, fatigue, mood, menstrual symptoms; menstrual diaries; and blood were collected at 4 points: before treatment, mid chemotherapy, post chemotherapy and 6 months later. Serum concentrations of dehydroepiandrosterone sulfate (DHEA-S) (adrenal hormone), bioavailable testosterone (bioT), androstenedione (Adione) (stromal hormone), estrone (E1), estradiol (E2) (follicular hormone), sex hormone binding globulin (SHBG), and follicle stimulating hormone (FSH) were evaluated. Descriptive statistics, comparisons of means by two sided t-tests and Pearson correlation coefficients were computed. Six month post treatment data are reported.

Results: 24 women were accrued and 21 provided serum and questionnaires through 6 months. All sex steroid hormones decreased during chemotherapy and did not return to baseline by 6 months for the group as a whole. At 6 months, 14 women were postmenopausal per FSH, E2 and menstrual diaries and 7 had resumed menses. There were no significant differences in hormone concentrations at baseline between women who ended up menopausal from those who resumed menses. However, at 6 months, postmenopausal women had significantly lower concentrations than premenopausal women of E2 (289 pg/ml pre- 9 pg/ml post), E1 (132 pg/ml pre- 22 pg/ml post), and Adione (102 ng/dL pre- 56 ng/dL post), but not DHEA-S or bioT (all p < .01). E2 was significantly correlated with Adione (R = .47 p = .03), and E1 (R = .57, p = .007). Low to moderate correlations were found between hormone concentrations and symptoms. The use of tamoxifen was significantly, and negatively correlated with the total score on the Female Sexual Function Index (r = −.572, p = .005), indicating worse sexual function for women on tamoxifen.

Conclusion: These data support the hypothesis that the post chemotherapy ovary suffers both follicular and stromal dysfunction, as noted by lower Adione, which is specific to the ovarian stroma. Adione concentrations in the postmenopausal group women are similar to published reports of women post oophorectomy. This is the first longitudinal study we are aware of to evaluate ovarian stromal function in women undergoing chemotherapy. This total hormone depletion may be why women experiencing chemotherapy induced menopause report severe and distressing menopausal symptoms such as hot flashes. Estrogen is often implicated, but androgen deprivation in this population should be taken into consideration when planning interventions to improve health related quality of life.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P2-11-01.

A novel mating system analysis for modes of self-oriented mating applied to diploid and polyploid arctic Easter daisies (Townsendia hookeri)

We have developed a new model for mating system analysis, which attempts to distinguish among alternative modes of self-oriented mating within populations. This model jointly estimates the rates of outcrossing, selfing, automixis and apomixis, through the use of information in the family structure given by dominant genetic marker data. The method is presented, its statistical properties evaluated, and is applied to three arctic Easter daisy populations, one consisting of diploids, the other two of tetraploids. The tetraploids are predominantly male sterile and reported to be apomictic while the diploids are male fertile. In each Easter daisy population, 10 maternal arrays of six progeny were assayed for amplified fragment length polymorphism markers. Estimates, confirmed with likelihood ratio tests of mating hypotheses, showed apomixis to be predominant in all populations (ca. 70%), but selfing or automixis was moderate (ca. 25%) in tetraploids. It was difficult to distinguish selfing from automixis, and simulations confirm that with even very large sample sizes, the estimates have a very strong negative statistical correlation, for example, they are not independent. No selfing or automixis was apparent in the diploid population, instead, moderate levels of outcrossing were detected (23%). Low but significant levels of outcrossing (2-4%) seemed to occur in the male-sterile tetraploid populations; this may be due to genotyping error of this level. Overall, this study shows apomixis can be partial, and provides evidence for higher levels of inbreeding in polyploids compared to diploids and for significant levels of apomixis in a diploid plant population.

Human utilization of subsurface extraterrestrial environments

Caves have been used in the ancient past as shelter or habitat by many organisms (including humans). Since antiquity, humans have explored caves for the minerals they contain and sometimes for ceremonial purposes. Over the past century, caves have become the target of increasing exploration, scientific research, and recreation. The use of caves on extraterrestrial bodies for human habitation has been suggested by several investigators. Lunar lava tube bases received early attention because lava tubes were clearly visible in lunar images from the Apollo Era. More recently, Mars Observer Camera data has shown us clear evidence of large tubes visible in a number of volcanic regions on Mars. The budding field of cave geomicrobiology has direct application to questions about subsurface life on other planets. Caves contain many unusual organisms making their living from unlikely materials like manganese, iron, and sulfur. This makes caves and other subsurface habitats prime targets for astrobiological missions to Mars and possibly other bodies. We present the results of a completed Phase I and on-going Phase II NASA Institute for Advanced Concepts (NIAC) study that intensively examines the possibilities of using extraterrestrial caves as both a resource for human explorers and as a highly promising scientific target for both robotic and future human missions to Mars and beyond.

Geographic variation in patient and hospital characteristics, management, and clinical outcomes in ST-elevation myocardial infarction treated with fibrinolysis. Results from InTIME-II

AIMS

We examined the geographic variations in InTIME-II, a randomized double-blind trial comparing alteplase with lanoteplase for myocardial infarction.

METHODS AND RESULTS

We compared baseline characteristics, management, and outcomes in four regions (Western Europe, Eastern Europe, North America, and Latin America) and in countries with historically different management approaches (Germany vs the U.K., the U.S. vs Canada). Thirty-day mortality in Western Europe, Eastern Europe, North America and Latin America was 6.7%, 7.3%, 5.7%, 10.1%, P<0.0001. Adjusted mortality for Europe was intermediate between North America and Latin America (odds ratios (OR) [95% confidence intervals (CI)] compared to Western Europe: North America 0.84 [0.67-1.0], Eastern Europe 1.2 [1.0-1.4], and Latin America 1.8 [1.3-2.7]). Revascularization rates varied 10-fold but did not explain regional mortality differences. Germany and the U.K. had similar adjusted 1-year mortality (OR for the U.K. 1.16 [0.92-1.5]), although invasive procedures were four- to 10-fold more common in Germany. Similarly the U.S. and Canada had equal adjusted 1-year mortality (OR for Canada 0.85 [0.61-1.17]) despite three-fold higher use of invasive procedures in the U.S.

CONCLUSIONS

Significant geographic variations in practice and adjusted mortality following fibrinolysis persist despite recent guidelines. These findings have important implications in the design and interpretation of international studies, identify under- and over-utilized therapies, and support further study of treatments with marked worldwide variations.

Environmental effects on genomic imprinting in mammals

Genomic imprinting is an epigenetic marking mechanism by which certain genes become repressed on one of the two parental alleles. Imprinting plays important roles in mammalian development, and in humans its deregulation may result in disease and carcinogenesis. During different medical, technological and scientific interventions, pre-implantation embryos and cells are taken from their natural environment and subjected to culture in artificial media. Studies in the mouse demonstrate that environmental stress, such as in vitro culture, can affect the somatic maintenance of epigenetic marks at imprinted loci. These effects are associated with aberrant growth and morphology at fetal and perinatal stages of development.

Paediatric brain tumours: an embryological perspective

Primitive neuroectodermal tumours are amongst the most common paediatric tumours of the central nervous system. These tumours are composed of undifferentiated cells and a variable component of more differentiated cell types. Most analysis of these tumours has focused on molecules normally found in the differentiated cells or those found in all primitive neuronal precursors. In this article we describe recent advances in understanding of the molecular processes involved in normal neurogenesis. We discuss the relevance of these data to the biology of neuronal tumours and describe strategies we and others have adopted to investigate the usefulness of molecules found in undifferentiated neuronal tissues in understanding the events which underlie oncogenesis in this tumour type.

Rat liver peroxisomes catalyze the initial step in cholesterol synthesis. The condensation of acetyl-CoA units into acetoacetyl-CoA

In the last few years, it has been demonstrated by this group and others that rat liver peroxisomes participate in cholesterol synthesis. It has been shown that the key regulatory enzyme of isoprenoid biosynthesis, 3-hydroxy-3-methylglutaryl coenzyme A reductase, is present in liver cells not only in the endoplasmic reticulum but also within peroxisomes. It has been also demonstrated that rat liver peroxisomes in the presence of cytosolic proteins in vitro are able to convert [14C]mevalonic acid to [14C]cholesterol. In addition, a recent study demonstrated that the largest cellular concentration of sterol carrier protein-2 is inside peroxisomes. It is of interest, therefore, to inquire whether other proteins known to be involved in cholesterol biogenesis are also present in peroxisomes. In this study we investigated the first step in cholesterol synthesis, the condensation of two acetyl-CoA units to acetoacetyl-CoA. It was demonstrated that peroxisomal thiolase, purified by DEAE-phosphocellulose chromatography from gemfibrozil-treated rats, is active not only toward acetoacetyl-CoA and 3-ketoacyl-CoA, consistent with literature reports, but is also capable of converting acetyl-CoA units to acetoacetyl-CoA. This is the first demonstration of condensation activity in rat liver peroxisomes.

Cholesterol synthesis in rat liver peroxisomes. Conversion of mevalonic acid to cholesterol

The key regulatory enzyme of cholesterol, dolichol, and isopentenyl adenosine biosynthesis, 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoA reductase) is a 97-kilodalton transmembrane glycoprotein which was believed until recently to reside exclusively in the endoplasmic reticulum of mammalian cells. However, several recent publications have shown that the enzyme in liver cells is present not only in the endoplasmic reticulum but also within peroxisomes. In an effort to clarify the role of peroxisomal HMG-CoA reductase, highly purified (95%) rat liver peroxisomes from cholestyramine-treated rats were incubated with RS-[2-14C]mevalonic acid plus cytosolic proteins and then tested for the presence of newly synthesized cholesterol. For comparison, highly purified microsomes from the same liver preparation were incubated at several protein concentrations under the same conditions. A three-step procedure was employed to resolve the newly synthesized cholesterol from the complex mixture of sterol intermediates in cholesterol biosynthesis. After termination of the reaction and addition of a [3H]cholesterol standard, the incubation products were extracted and separated by thin layer chromatography into a number of fractions. The fraction containing C-27 sterols was further resolved by reverse-phase high pressure liquid chromatography. After acetylation, the products were then separated by silicic acid high pressure liquid chromatography. Confirmation of the identity of newly synthesized cholesterol was obtained by recrystallization with added non-radioactive cholestenyl acetate standard. The results indicate that highly purified rat liver peroxisomes are able to convert mevalonic acid to cholesterol in the presence of cytosolic fraction in vitro. An abstract of these results has been published (Krisans, S. K., Thompson, S. L., Burrows, R., and Laub, R. J. (1986) J. Cell Biol. 103, 525 (abstr.).

Correlation between intracavernous papaverine injection and Doppler analysis in impotent men

One hundred impotent men were evaluated with Doppler pulse-wave analysis and intracavernous papaverine. Fifty-four men with normal Doppler study response had abnormal responses to papaverine. A normal Doppler study response failed to predict the inability of papaverine to induce an erection in 54 per cent of cases. Twenty-seven patients had abnormal Doppler study responses, and only 2 of these men had a normal response to papaverine. An abnormal Doppler study response was highly predictive of a vascular abnormality.

Bile acid synthesis in rat liver peroxisomes: metabolism of 26-hydroxycholesterol to 3 beta-hydroxy-5-cholenoic acid

Rat liver peroxisomes have been found to oxidize 26-hydroxycholesterol, the product of cholesterol C-26 hydroxylation to 3 beta-hydroxy-5-cholenoic acid. Peroxisomes were purified by differential and equilibrium density centrifugation in a steep linear metrizamide gradient to greater than 95% purity. Purity of peroxisomes was determined by measurement of specific marker enzymes. The activities of cytochrome oxidase (a mitochondrial marker) and acid phosphatase (a lysosomal marker) in the purified peroxisome fractions were below the level of detection. Esterase activity indicated a 2-4% microsomal contamination. Subsequent to incubation of peroxisomes with [16,22-3H]-26-hydroxycholesterol, the reaction products were extracted, methylated, acetylated, and subjected to thin-layer, high pressure liquid, and gas-liquid chromatographic analyses. 3 beta-Hydroxy-5-cholenoic acid was the major identifiable metabolite of 26-hydroxycholesterol. Incubations of pure microsomal fractions (greater than 99%) with 26-hydroxycholesterol under the same conditions demonstrated that the production of 3 beta-hydroxy-5-cholenoic acid by peroxisomes was not attributable to microsomal contamination. This study demonstrates that peroxisomes participate in the side-chain oxidation of intermediates in bile acid synthesis.

Evidence for peroxisomal hydroxylase activity in rat liver

This study presents evidence for the first time that rat liver peroxisomes contain a hydroxylase capable of converting 3 alpha, 7 alpha, 12 alpha,- trihydroxy-5 beta-cholestane to a cholestanetetrol. Furthermore, this hydroxylase differs from both the mitochondrial and microsomal enzymes in its response to various co-factors. Highly purified peroxisomal, mitochondrial, and microsomal fractions from cholestryamine-treated rats were incubated with [22(23)-3H]3 alpha,7 alpha,12 alpha,-trihydroxy-5 beta-cholestane under a variety of conditions. The products were acidified, extracted, and subjected to thin-layer chromatography to determine the amount of cholestanetetrol produced. The identification of the 25- and 26-hydroxylated products from the incubations with the microsomes was confirmed by gas chromatography-mass spectrometry. Peroxisomal fractions incubated with a NADPH-generating system, Mg2+, and ATP showed a rate of 40 pmol/min/mg conversion of 3 alpha,7 alpha,12 alpha,-trihydroxy-5 beta-cholestane to a cholestanetetrol. Co-factor studies indicated that both the peroxisomal and mitochondrial hydroxylase activities were dependent on NADPH, Mg2+, and ATP (with different concentration requirements) whereas the microsomal hydroxylase(s) required only NADPH. An abstract of this work has been published (1).

Carbon Dioxide and Climate: The Importance of Realistic Geography in Estimating the Transient Temperature Response

Results obtained from a detailed air-sea-ice climate model for an instantaneous increase in the atmospheric carbon dioxide content are used to estimate the transient surface temperature response for several time-dependent carbon dioxide increase scenarios. The inclusion of realistic variations of land fraction and ocean mixing with latitude is found to limit the applicability of steady- state simulations as approximate guides to the actual time-dependent temperature response, particularly when the regional response is considered.

An Ice-Free Cretaceous? Results from Climate Model Simulations

We have quantitatively investigated the mechanisms that could explain the warm, equable climate that is believed to have been typical of the mid-Cretaceous (100 million years ago). By performing simulations with a climate model based on zonal energy balance, we demonstrate that past changes in geography were important in bringing about climatic change. However, the meridional distribution of Cretaceous temperatures cannot be successfully simulated unless additional physical "feedback mechanisms" are included in the model. These mechanisms may involve cloud and meridional heat transport changes. We also conclude that paleoclimatologists should reexamine carefully both existing data and their interpretations with regard to reconstruction of Cretaceous tropical and polar surface temperatures.

Comparative right and left ventricular volumes and pump function in the newborn lamb

A quantitative cineangiographic method is presented for studying neonatal lamb ventricular volumes and pump function without thoracotomy or surgical instrumentation of the heart. When this method was employed in lambs with a mean age of 24.4 hours it was found that the right and left ventricular end-diastolic volumes, ejection fractions and systolic outputs did not differ significantly at this early postnatal time. Restudy of these lambs at a mean age of 15.6 days showed that right and left ventricular end-diastolic volumes, normalized for body weight, and ejection fractions had not changed significantly. Although systolic outputs decreased, the difference was not significant. Thus there is early postnatal equalization of left and right heart volumes, and deviations from this relation should suggest abnormal hemodynamic function.

Measurement of atrial septal defect during cardiac catheterization. Experimental and clinical results

The size of experimental and clinical secundum atrial septal defects may be accurately measured during cardiac catheterization. The position of the defects in the septum and their distance from the aortic and mitral valves may also be ascertained. A balloon catheter inflated with radiopaque dye is used for the measurement. The volume of dye in the balloon has been correlated with its maximal diameter. Thus, a no. 8-10 French catheter filled with 10 ml of diatrizoate (50 percent) has a diameter of approximately 25 mm and a no. 8-22 French catheter filled with 40 ml of diatrizoate a diameter of approximately 43 mm. Persistent arrhythmias or other adverse effects of the procedure were not observed. There was a high correlation between balloon-measured atrial septal defects and those measured at necropsy in the animals or at operation in the patients. These measurements aid in determining whether an ostium secundum defect is of proper size and location to be closed transvenously and may also prove valuable in physiologic studies of atrial septal defects or other cardiac anomalies.

Umbrella catheter for nonoperative closure of atrial septal defects

Since a 1974 report of nonoperative closure of atrial septal defects (ASDs) using an umbrella catheter device, an additional 25 dogs have undergone creation of atrial septal defects, 12 of which have subsequently had successful transvenous closure. An improved model of the closure device has been developed, still using a pair of interlocking umbrella-like components made of stainless steel and Dacron. The umbrellas are smaller, lighter, and have an automatic opening ring. They are loaded simultaneously into a single capsule on the distal end of the outer catheter and are passed into the heart on a single passage, thus eliminating several steps of the original technique. Closure time has diminished from an average of 30 minutes to 5-10 minutes. The completeness of closure was documented in 12 animals by repeat cardiac catheterization which included hydrogen electrode studies. Autopsies on 10 sacrificed dogs revealed no adverse effects or migration of the device; two dogs are living and healthy. In the one clinical application, the patient has done well, remaining afebrile with an increased activity tolerance and resumption of normal activities. The umbrella has remained in position and appears to be functioning well.

Production of experimental atrial septal defects

Atrial septal defects (ASDs) were successfully created by punch biopsy technique in 67 dogs. The technique is simple, effective and provides an ideal model for the study of ASDs, either for testing closure devices or physiological experiments. The position and size of the defects may be varied according to preference. Of 45 animals subjected to cardiac catheterization, 39 (87 percent) has a patent atrial septal defect.

Secundum atrial septal defect. Nonoperative closure during cardiac catheterization

A 17-year-old girl had clinical and cardiac catheterization findings compatible with a secundum atrial septal defect. During cardiac catheterization, the atrial septal defect was sized and closed using a transvenous umbrella technique.