bluuebunny/crossref_metadata_2025 huggingface dataset:
Do Extraterrestrials Have Sex (and Intelligence)?
Authors: BARKOW JEROME H.
Published: July 2010

Abstract:This thought experiment addresses the range of possible evolved psychologies likely to be associated with extraterrestrial (ET) intelligence. The analysis rests on: (1) a number of assumptions shared by the SETI project; (2) recent arguments concerning convergent evolution; and (3) current theories of how intelligence evolved in our own species. It concludes that, regardless of how and which cognitive abilities arise initially, extraterrestrially they can develop into intelligence only if an amplification process involving a form of predation and/or sexual selection occurs. Depending on the amplification process, ETs may be xenophobic; however, it is more probable that they will be ethnocentric. Their ideas of reciprocity and fairness are likely to at least overlap with our own. They will definitely be culture‐bearing and probably have two sexes, both of which are intelligent. Regardless of the degree of physical similarity of ETs to ourselves, convergence makes it likely that we will at least find their evolved psychology similar enough to our own for comprehension.
Freud: The First Evolutionary Psychologist?
Authors: LeCROY DORI
Published: July 2010

Abstract:An evolutionary perspective on attachment theory and psychoanalytic theory brings these two fields together in interesting ways. Application of the evolutionary principle of parent‐offspring conflict to attachment theory suggests that attachment styles represent context‐sensitive, evolved (adaptive) behaviors. In addition, an emphasis on offspring counter‐strategies to adult reproductive strategies leads to consideration of attachment styles as overt manifestations of psychodynamic mediating processes, including the defense mechanisms of repression and reaction formation.
Metabolic Control and Gene Dysregulation in Yeast Aging
Authors: JAZWINSKI S. MICHAL
Published: July 2010

Abstract: Life span in the yeast Saccharomyces cerevisiae is usually measured by the number of divisions individual cells complete. Four broad physiologic processes that determine yeast life span have been identified: metabolic control, resistance to stress, chromatin‐dependent gene regulation, and genetic stability. A pathway of interorganelle communication involving mitochondria, the nucleus, and peroxisomes has provided a molecular mechanism of aging based on metabolic control. This pathway functions continuously, rather than as an on‐off switch, in determining life span. The longevity gene RAS2 modulates this pathway. RAS2 also modulates a variety of other cellular processes, including stress responses and chromatin‐dependent gene regulation. An optimal level of Ras2p activity is required for maximum longevity. This may be due to the integration of life maintenance processes by RAS2, which functions as a homeostatic device in yeast longevity. Loss of transcriptional silencing of heterochromatic regions of the genome is a mark of yeast aging. It is now clear that the functional status of chromatin plays an important role in aging. Changes in this functional status result in gene dysregulation, which can be altered by manipulation of the histone deacetylase genes. Silencing of ribosomal DNA appears to be of particular importance. Extrachromosomal ribosomal DNA circles are neither sufficient nor necessary for yeast aging.
Genetics of Survival
Authors: SCHÄCHTER FRANÇOIS
Published: July 2010

Abstract:The fields of gerontology and genetics have merged, spawning novel lines of investigation and generating a wealth of new results in recent years. However, the lack of clarity and consistency in the basic definitions upon which the science of gerontology must rest has fostered a certain amount of enduring confusion. Among the unclear issues are the genetic components of life span and the distinction between “normal” and “pathologic” aging. At a time of massive world population aging, such issues have, beyond their scientific importance, a momentous social and economic impact. A simple axiomatic framework, consisting of three definitions and five axioms, is proposed that clarifies the aforementioned issues and reconciles disparate data in gerontology. Based on this framework, a new classification of genes involved in survival is proposed. Within the Compensatory Adaptation Theory of aging, apparent paradoxes are solved and problems in gerontology may be formulated anew.
Replicative Senescence and Oxidant‐Induced Premature Senescence: Beyond the Control of Cell Cycle Checkpoints
Authors: CHEN QIN M.
Published: July 2010

Abstract: Normal human diploid fibroblasts (HDFs) undergo replicative senescence inevitably in tissue culture after a certain number of cell divisions. A number of molecular changes observed in replicative senescent cells occur in somatic cells during the process of aging. Genetic studies on replicative senescence indicate the control of tumor suppression mechanisms. Despite the significance of replicative senescence in aging and cancer, little is known about the central cause of the complex changes observed in replicative senescent cells. The interest in the phenomenon has intensified in recent years, since damaging agents, certain oncogenes and tumor suppressor genes have been found to induce features of senescence in early passage young HDFs or in immortalized tumor cells. The reported features of senescence are summarized here in order to clarify the concept of replicative senescence or premature senescence. The experimental results of extending the replicative life span by reducing ambient oxygen tension or by N‐tert‐butyl‐alpha‐phenylnitrone (PBN) argue a role of oxidative damage in replicative senescence. By inducing premature senescence with a pulse treatment of H2O2, we can study the role of the cell cycle checkpoint proteins p53, p21, p16 and Rb in gaining each feature of senescence. Although p53 and Rb control G1 arrest and Rb appears to control cell enlargement, activation of the senescent associate β‐galactosidase, loss of cell replication and multiple molecular changes observed in premature senescent or replicative senescent cells are likely controlled by mechanisms beyond the cell cycle checkpoints.
Tissue Mitochondrial DNA Changes: A Stochastic System
Authors: KOPSIDAS GEORGE , KOVALENKO SERGEY A. , HEFFERNAN DAMIEN R. , YAROVAYA NATALIA , KRAMAROVA LUDMILLA , STOJANOVSKI DIANE , BORG JUDY , ISLAM MOHAMMED M. , CARAGOUNIS APHRODITE , LINNANE ANTHONY W.
Published: July 2010

Abstract: Several lines of evidence support the view that the bioenergetic function of the mitochondria in postmitotic tissue deteriorates during normal aging. Skeletal muscle is one such tissue that undergoes age‐related fiber loss and atrophy and an age‐associated rise in the number of cytochrome c oxidase (COX) deficient fibers. With such metabolic pressure placed on skeletal muscle it would be an obvious advantage to supplement the cellular requirement for energy by up‐regulating glycolysis, an alternative pathway for energy synthesis. Analysis of rat skeletal muscle utilizing antibodies directed against key enzymes involved in glycolysis has provided evidence of an age‐associated increase in the enzymes involved in glycolysis. Fructose‐6‐phosphate kinase, aldolase, glyceraldehyde‐3‐phosphate dehydrogenase, and pyruvate kinase protein levels appeared to increase in the soleus, gracilis, and quadriceps muscle from aged rats. The increase in the level of these proteins appeared to correlate to a corresponding decrease in the amount of cytochrome c oxidase protein measured in the same tissue. Together these results are interpreted to represent a general upregulation of glycolysis that occurs in response to the age‐associated decrease in mitochondrial energy capacity. Mitochondrial DNA (mtDNA) damage and mutations may accumulate with advancing age until they reach a threshold level were they impinge on the bioenergy capacity of the cell or tissue. Evidence indicates that mtDNA from the skeletal muscle of both aged rats and humans not only undergoes changes at the nucleotide sequence level (mutations and DNA damage), but also undergoes modifications at the tertiary level to generate unique age‐related conformational mtDNA species. One particular age‐related conformational form was only detected in aged rat tissues with high demands on respiration, specifically in heart, kidney, soleus muscle, and, to a lesser extent, the quadriceps muscle. The age‐related form was not detected in gracilis muscle which is predominantly dependent upon glycolysis with regard to its energy requirements. Finally, a comprehensive hypothesis is presented that features the stochastic nature of the mitochondrial system. The basis of the hypothesis is that a dynamic relationship exists between endogenous mutagen production, DNA repair, mtDNA turnover, and nuclear control of mtDNA copy number and that age‐associated changes in the dynamics of this relationship lead to a loss of functional full‐length mtDNA that eventually leads to bioenergy decline.
The CA1 Region of the Human Hippocampus Is a Hot Spot in Alzheimer's Disease
Authors: WEST M. J. , KAWAS C. H. , MARTIN L. J. , TRONCOSO J. C.
Published: July 2010

Abstract: Data from an ongoing study of differences in the total number of neurons in the five major subdivisions of the hippocampal regions of the brains of patients with Alzheimer's disease (AD) and normal age‐matched controls confirm an earlier finding from our laboratories of a pronounced loss of CA1 neurons associated with AD. In view of an earlier finding that the CA1 region does not suffer normal age‐related neuronal loss, these data support the earlier conclusion that the neuropathologic mechanisms involved in the AD‐related losses in CA1 are not related to normal aging and that the study of the cellular and molecular events involved in the AD‐related loss of CA1 cells can aid in the identification of the unique pathologic processes associated with AD.
A Third Life for Burimamide: Discovery and Characterization of a Novel Class of Non‐Opioid Analgesics Derived from Histamine Antagonists
Authors: HOUGH LINDSAY B. , NALWALK JULIA W. , BARNES WILLIAM G. , LEURS ROB , MENGE WIRO M. P. B. , TIMMERMAN HENK , WENTLAND MARK
Published: July 2010

Abstract:Burimamide, a histamine (HA) derivative with both H2‐ and H3‐blocking properties, induces antinociception when injected into the rodent CNS. Several related compounds share this property, and structure‐activity studies have shown that this new class of analgesics is distinct from known HA antagonists. The prototype, named improgan, shows a preclinical profile of a highly effective analgesic, with activity against thermal, mechanical and inflammatory nociception after doses that do not alter motor balance or locomotor activity. Improgan analgesia is not blocked by opioid antagonists and is observed in opioid receptor knock‐out mice. Unlike morphine, improgan does not induce tolerance after daily dosing. Extensivein vitropharmacology studies have excluded known histaminergic, opioid, serotonergic, GABAergic and adrenergic receptor mechanisms, as well as 50 other sites of action. The improgan‐like analgesic activity of some HA congeners suggests an analgesic action on a novel HA receptor, but further studies are required to substantiate this. Studies in progress are characterizing the sites and mechanisms of action of improgan, and developing brain‐penetrating derivatives that could be useful for clinical pain.
Neurobiological Adaptations to Psychostimulants and Opiates as a Basis of Treatment Development
Authors: SEVARINO KEVIN A. , OLIVETO ALISON , KOSTEN THOMAS R.
Published: July 2010

Abstract:Abuse of illicit substances, in particular psychostimulants and opiates, is a worldwide public health issue. Chronic use of cocaine and amphetamine causes common neurobiological adaptations that may guide new treatment development. These include perturbations in dopamine and serotonin neurotransmission, leading to trials of antidepressants, and serotonin and dopamine augmentation strategies. The detection of cerebral perfusion abnormalities caused by psychostimulants has led to examination of antiplatelet and excitatory amino acid (EAA) antagonist therapies. Further, development of cocaine vaccines allows for testing of peripheral blockade approaches to cocaine addiction. New approaches to behavioral treatments for cocaine dependence are also reviewed. For opiate dependence, understanding of heroin's effects on μ and κ opiate receptors has led to investigations of the partial μ agonist buprenorphine in opiate maintenance. Evidence for hyper‐excitability of locus coeruleus (LC) noradrenergic neurons and EEA inputs to the LC guides trials of new α2‐adrenergic agonists and EEA antagonists to alleviate opiate withdrawal. Finally, clinical experience with withdrawal from methadone and LAAM has led to trials of antagonist‐accelerated opiate withdrawal. Improved treatment of psychostimulant and opiate addiction is critically needed, and likely to have wide‐reaching impact in health care and society.
Interactions between Kappa Opioid Agonists and Cocaine: Preclinical Studies
Authors: MELLO NANCY K. , NEGUS S. STEVENS
Published: July 2010

Abstract:Kappa opioid agonists inhibit dopamine release from mesolimbic dopaminergic neurons and attenuate some behavioral effects of cocaine in rodents. Evidence that kappa opioid agonists may act as functional antagonists of cocaine led us to examine their interactions with cocaine's abuse‐related effects in rhesus monkeys. In cocaine self‐administration studies, four arylacetamides (U50,488, enadoline, (−) spiradoline and PD117302) and four benzomorphans (ethylketocyclazocine [EKC], bremazocine, Mr2033 and cyclazozine) each were administered as continuous infusions over 10 days. EKC, Mr2033, bremazocine, U50,488 and enadoline produced significant dose‐dependent and sustained decreases in cocaine self‐administration and also decreased food‐maintained responding at some doses. Emesis and sedation were occasionally observed during the first two days of kappa agonist treatment, but tolerance developed rapidly to these effects. Cyclazocine, PD117302 and spiradoline did not significantly alter cocaine self‐administration. The behavioral effects of EKC and U50,488 were antagonized by both the kappa opioid antagonist nor‐binaltorphimine and the non‐selective opioid antagonist naloxone. In general, compounds with mixed activity at both kappa and mu opioid receptors (e.g. EKC, Mr2033) decreased cocaine self‐administration more consistently and with fewer or less severe undesirable side effects than more selective kappa agonists (e.g. U50,488, spiradoline). Although several kappa agonists decreased cocaine self‐administration, EKC and U50,488 did not consistently block the discriminative stimulus effects of cocaine in monkeys trained to discriminate cocaine from saline. The extent to which kappa agonist‐induced decreases in cocaine self‐administration reflect an antagonism of cocaine's abuse‐related effect remains to be determined.
GABA Modulation of Cocaine Self‐Administration
Authors: ROBERTS DAVID C.S. , BREBNER KAREN
Published: July 2010

Abstract:Recent experiments suggest that GABA compounds produce a clinically relevant modulation of cocaine reinforcement. This review summarizes the results of a number of studies that examined the effect of the GABABagonist baclofen on cocaine self‐administration using a variety of schedules of reinforcement. The results demonstrate that baclofen causes a dramatic reduction in cocaine self‐administration which does not appear to be accounted for by a general disruption of behavior. However, the effect is dependent on the unit injection dose of cocaine and on the response requirements of the schedule. These results predict that in a clinical setting any potential therapeutic effect of baclofen will interact with the cost and availability of cocaine.
Application of Artificial Enzymes to the Problem of Cocaine
Authors: DE PRADA PALOMA , WINGER GAIL , LANDRY DONALD W.
Published: July 2010

Abstract:Cocaine mediates its reinforcing and toxic actions through a “loss of function” effect at multiple receptors. The difficulties inherent in blocking a pleiotropic blocker pose a great obstacle for the classical receptor‐antagonist approach and have contributed to the failure‐to‐date to devise specific treatments for cocaine overdose and addiction. As an alternative, we have embarked on an investigation of catalytic antibodies, a programmable class of artificial enzyme, as “peripheral blockers”‐agents designed to bind and degrade cocaine in the circulation before it partitions into the central nervous system to exert reinforcing or toxic effects. We synthesized transition‐state analogs of cocaine's hydrolysis at its benzoyl ester, immunized mice, prepared hybridomas, and developed the first anti‐cocaine catalytic antibodies with the capacity to degrade cocaine to non‐reinforcing, non‐toxic products. We subsequently identified several families of anti‐cocaine catalytic antibodies and found that out most potent antibody, Mab15A10, possessed sufficient activity to block cocaine‐induced reinforcement and sudden death in rodent models of addiction and overdose, respectively. With the potential to promote cessation of use, prolong abstinence, and provide a treatment for acute overdose, the artificial enzyme approach comprehensively responds to the problem of cocaine.
Methadone‐Related Opioid Agonist Pharmacotherapy for Heroin Addiction: History, Recent Molecular and Neurochemical Research and Future in Mainstream Medicine
Authors: KREEK MARY JEANNE
Published: July 2010

Abstract:In 1963, Professor Vincent P. Dole at the Rockefeller University formed a small team to develop a pharmacotherapy for the management of heroin addiction. They hypothesized that heroin addiction is a disease of the brain with behavioral manifestations, and not merely a personality disorder or criminal behavior and began to address the specific question of whether a long‐acting opioid agonist could be used in the long‐term maintenance treatment of heroin addiction. Over the next 35 years, many studies documented the safety, efficacy and effectiveness of methadone pharmacotherapy for heroin addiction, but Federal regulations and stigmatization of heroin addiction prevented implementation of treatment. Finally, in 1999, NIH published a report unequivocally supporting methadone maintenance pharmacotherapy for heroin addiction. Two other effective opioid agonist treatments have been developed: the even longer acting opioid agonist l‐alpha‐acetylmethadol (LAAM) has been approved for pharmacotherapy for heroin addiction, and still under study is the opioid partial agonist‐antagonist buprenorphine‐naloxone combination. A variety of studies, both laboratory based and clinical, have revealed the mechanisms of action of long‐acting opioid agonists in treatment, including prevention of disruption of molecular, cellular and physiologic events and, in fact, allowing normalization of those functions disrupted by chronic heroin use. Recent molecular biological studies have revealed single nucleotide polymorphisms of the human μ opioid receptor gene; the m opioid receptor is the site of action of heroin, the major opiate drug of abuse, analgesic agents such as morphine, and the major treatment agents for heroin addiction. These findings support the early hypotheses of our laboratory that addiction may be due to a combination of genetic, drug‐induced and environmental (including behavioral) factors and also, that atypical stress responsivity may contribute to the acquisition and persistence of, as well as relapse to, use of addictive drugs.
Prenatal Cocaine Exposure
Authors: KELLER RICHARD W. , SNYDER‐KELLER ABIGAIL
Published: July 2010

Abstract:Cocaine abuse is a significant problem not only in the general population but also among pregnant women. Since cocaine readily crosses the placenta and is metabolized slowly in fetuses, they can be exposed to significant levels of cocaine for long periods. In humans the most common consequences of cocaine abuse during pregnancy include premature birth, lower birth weight, respiratory distress, bowel infarctions, cerebral infarctions, reduced head circumference, and increased risk of seizures. Behaviorally these new‐borns show an increased degree of “tremulousness,” crying and irritability, and are over‐reactive to environmental stimuli. Within a month these behaviors have recovered dramatically, but not to normal levels. Thus while there are a number of abnormalities associated with cocaine‐exposed neonates, they are not imminently debilitating or life‐threatening. However, the long‐term consequences of this prenatal cocaine exposure remain to be elucidated. We have examined a rat model for neurochemical, neuroanatomical and behavioral changes resulting from prenatal cocaine exposure. Since cocaine is known to act by blocking the inactivation of the neurotransmitters dopamine, serotonin and norepinephrine, our studies have focused on brain dopamine (DA) and serotonin (5‐HT) pathways. In this model system we have found neurochemical changes that are present at birth and that return to normal as the rat ages‐similar to the recovery observed in infants. However, there are other neurochemical, anatomical and behavioral changes that persist after birth which may provide insights into the long‐term consequences. It is hoped that by understanding the changes occurring in this rat model we will be better prepared to devise pharmacological interventions to circumvent the secondary consequences of prenatal cocaine exposure. These consequences might include increased susceptibility to drug addiction, seizures, depression, schizophrenia, Parkinson's disease, etc.
Colorectal Cancer Vaccines: Antiidiotypic Antibody, Recombinant Protein, and Viral Vector
Authors: BASAK S. , ECK S. , GUTZMER R. , SMITH A. J. , BIREBENT B. , PUREV E. , STAIB L. , SOMASUNDARAM R. , ZALOUDIK J. , LI W. , JACOB L. , MITCHELL E. , SPEICHER D. , HERLYN D.
Published: July 2010

Abstract: The colorectal cancer antigen GA733 (also termed CO17‐1A, KSI‐4, Ep‐CAM, KSA) has proved to be a useful target in passive immunotherapy with monoclonal antibody and in active immunotherapy with antiidiotypic antibodies in cancer patients. The GA733 antigen was molecularly cloned and expressed in baculovirus (BV), adenovirus (AV), and vaccinia virus (VV). Recombinant BV‐, VV‐, and AV‐GA733 induced antigen‐specific cytotoxic antibodies and proliferative and delayed‐type hypersensitive lymphocytes. However, only the AV recombinant induced antigen‐specific cytolytic T lymphocytes and regression of established tumors. Cured mice were protected against challenge with antigen‐negative tumors, indicating antigen spreading of immune responses. In a model of active immunotherapy against the murine homologue of the human GA733 antigen, murine epithelial glycoprotein (mEGP), BV‐derived mEGP protein in various adjuvants did not protect mice against a challenge with mEGP‐positive tumors. AV mEGP, only when combined with interleukin‐2, significantly inhibited growth of established mEGP‐positive tumors. This is in contrast to the same vaccine expressing the human antigen that was effective without interleukin‐2. AV GA733, in combination with interleukin‐2, is a candidate vaccine for colorectal cancer patients.
The Parahippocampal Region: Corticocortical Connectivity
Authors: BURWELL REBECCA D.
Published: July 2010

Abstract: The parahippocampal region, as defined in this review, comprises the cortical regions that surround the rodent hippocampus including the perirhinal, postrhinal, and entorhinal cortices. The comparable regions in the primate brain are the perirhinal, parahippocampal, and entorhinal cortices. The perirhinal and postrhinal/parahippocampal cortices provide the major polysensory input to the hippocampus through their entorhinal connections and are the recipients of differing combinations of sensory information. The differences in the perirhinal and postrhinal cortical afferentation have important functional implications, in part, because these two regions project with different terminal patterns to the entorhinal cortex. The perirhinal cortex projects preferentially to the lateral entorhinal area (LEA), and the postrhinal cortex projects preferentially to the medial entorhinal area (MEA) and the caudal portion of LEA. Although the perirhinal and postrhinal cortices provide the major cortical input to the entorhinal cortex, the entorhinal cortex itself receives some direct cortical input. An examination of the cortical afferentation of the entorhinal cortex reveals an interesting principle of connectivity among these regions; the composition of the direct neocortical input to the LEA is more similar to that of the perirhinal cortex, and the composition of the direct neocortical input to the MEA is more similar to that of the postrhinal cortex. Thus, polymodal associational input to the LEA and the MEA exhibits some segregation and is organized in parallel. The organization of intrinsic connections for each of the parahippocampal regions also contributes to the segregation of information into parallel pathways.
Differential Information Processing by Hippocampal and Subicular Neurons
Authors: HAMPSON ROBERT E. , HEDBERG THOMAS , DEADWYLER SAM A.
Published: July 2010

Abstract: It has been known for some years that hippocampal neurons are critically involved in processing of information necessary for encoding memories. What is less understood is the role of the subiculum in this process. We describe here differential response characteristics of subicular and hippocampal neurons in rats during execution of a delayed‐nonmatch‐to‐sample short‐term memory task. Subicular neurons, unlike hippocampal neurons, fire primarily in the delay interval of the task and appear to provide a temporal linkage between events encoded in hippocampus during the sample and nonmatch phases. Indeed, a large proportion of subicular neurons fire robustly for the entire duration of the delay only. Further analyses using electrical activation methods indicate that subicular neurons that receive short latency inputs from the anterior thalamus and do not project to cingulate cortex are the most responsive to stimuli with behavioral significance.
The Neurophysiology of Memory
Authors: SUZUKI WENDY A. , EICHENBAUM HOWARD
Published: July 2010

Abstract: How do the structures of the medial temporal lobe contribute to memory? To address this question, we examine the neurophysiological correlates of both recognition and associative memory in the medial temporal lobe of humans, monkeys, and rats. These cross‐species comparisons show that the patterns of mnemonic activity observed throughout the medial temporal lobe are largely conserved across species. Moreover, these findings show that neurons in each of the medial temporal lobe areas can perform both similar as well as distinctive mnemonic functions. In some cases, similar patterns of mnemonic activity are observed across all structures of the medial temporal lobe. In the majority of cases, however, the hippocampal formation and surrounding cortex signal mnemonic information in distinct, but complementary ways.
From Healthy Aging to Early Alzheimer's Disease: In Vivo Detection of Entorhinal Cortex Atrophy
Authors: DE TOLEDO‐MORRELL LEYLA , GONCHAROVA IRINA , DICKERSON BRADFORD , WILSON ROBERT S. , BENNETT DAVID A.
Published: July 2010

Abstract: Using quantitative structural MRI protocols, we examined the effects of age on alterations in entorhinal cortex (EC) volume. The left EC was found to be smaller than the right in both young and healthy aged subjects. More importantly, the right EC, but not the left, was significantly smaller in elderly participants compared to young controls. In an attempt to determine the earliest sites of involvement in mild and incipient Alzheimer's disease (AD), we compared entorhinal and hippocampal volume in (1) healthy elderly controls, (2) patients with very mild AD, and (3) elderly patients who were evaluated for cognitive complaints, but did not meet criteria for dementia. Both patient groups differed from controls in EC volume, but not from each other. In contrast, the two patient groups differed in hippocampal volume from controls, as well as from each other, with the mild AD cases showing the greatest atrophy. These results suggest that degeneration of the EC and hippocampal formation occurs before the onset of overt dementia. In fact, follow‐up clinical evaluations available on 23 of 28 nondemented patients indicated that 12 of 23 had converted to AD. Converters could be best differentiated from nonconverters on the basis of entorhinal volume.
Epileptogenesis in the Parahippocampal Region: Parallels with the Dentate Gyrus
Authors: SCHARFMAN HELEN E.
Published: July 2010

Abstract: Limbic seizures have often been attributed to pathology in the hippocampus, such as the well described condition termed Ammon's Horn sclerosis, in which many of the hippocampal principal cells have degenerated. However, several studies in both the clinical and basic literature indicate that the parahippocampal region may also play an important role. This region sustains a characteristic pattern of damage in most animal models of epilepsy that is similar to that identified in humans with intractable temporal lobe epilepsy. Perhaps the most striking aspect of parahippocampal pathology is the marked loss of neurons in layer III of the entorhinal cortex. The similarity of cell loss in layer III and cell loss in the hilus of the dentate gyrus is compared, as is the characteristic resistance of layer II neurons and dentate granule cells. Cellular electrophysiological results are used as a basis for the hypothesis that synaptic inhibition plays a role in the relative vulnerability of these neurons. Studies of neurogenesis in both areas is also discussed. It is proposed that this may be an additional factor that influences vulnerability in these areas.
Reservoir Characterization of Marine and Permafrost Associated Gas Hydrate Accumulations with Downhole Well Logs
Authors: COLLETT TIMOTHY S. , LEE MYUNG W.
Published: July 2010

Abstract: Gas volumes that may be attributed to a gas hydrate accumulation depend on a number of reservoir parameters, one of which, gas‐hydrate saturation, can be assessed with data obtained from downhole well‐logging devices. This study demonstrates that electrical resistivity and acoustic transit‐time downhole log data can be used to quantify the amount of gas hydrate in a sedimentary section. Two unique forms of the Archie relation (standard and quick look relations) have been used in this study to calculate water saturations (Sw) [gas‐hydrate saturation (Sh) is equal to (1.0 −Sw)] from the electrical resistivity log data in four gas hydrate accumulations. These accumulations are located on (1) the Blake Ridge along the Southeastern continental margin of the United States, (2) the Cascadia continental margin off the Pacific coast of Canada, (3) the North Slope of Alaska, and (4) the Mackenzie River Delta of Canada. Compressional wave acoustic log data have also been used in conjunction with the Timur, modified Wood, and the Lee weighted average acoustic equations to calculate gas‐hydrate saturations in all four areas assessed.
North Cascadia Deep Sea Gas Hydrates
Authors: SPENCE G. D. , HYNDMAN R. D. , CHAPMAN N. R. , WALIA R. , GETTRUST J. , EDWARDS R. N.
Published: July 2010

Abstract: The Cascadia accretionary margin off Vancouver Island is one of the best studied margins world‐wide for the determination of in situ properties of marine gas hydrates. Most quantitative information has come from cores and downhole logs of the Ocean Drilling Program (ODP) Leg 146 and from extensive seismic and other geophysical surveys. As part of the ODP site surveys, large‐offset multichannel seismic lines outlined the regional distribution of hydrate, and seismic velocity analyses coupled with full waveform inversion provided estimates of the vertical distribution of hydrate and gas. High resolution single‐channel seismic surveys indicate correlations between hydrate/gas concentrations and topographic highs, and between geothermal flux and topography; these correlations provide insight into fluid and methane flow through the sediments. A deep‐towed multichannel seismic survey (DTAGS), together with other data from 20–600 Hz, provide constraints on gradients at the base of the hydrate and gas layer. Extensive heat flow measurements, from probes and from depths of the bottom simulating reflector (BSR), have been modelled numerically, including the regional effects of sediment thickening and advective fluid flow in the accretionary prism. Other geophysical surveys include several seafloor electrical sounding experiments and seafloor compliance measurements of hydrate. ODP drilling has provided valuable downhole log data, core physical property data, and detailed pore fluid chemistry and isotopes. Several semi‐independent estimates of hydrate and gas concentrations have been obtained; all are dependent on reference sediment properties for which no hydrate and no gas is present. From a vertical seismic profile and other seismic data, the velocity increase in a hydrated region is consistent with hydrate concentrations of 20–30% of the pore space in a 100‐m interval above the BSR. Similar values are determined from log resistivity data and from core pore fluid chlorinity.
Gas Hydrates of Siberia
Authors: KUZNETSOV F. A.
Published: July 2010

Abstract: Natural gas hydrates were first observed on 21 July 1961 (the discovery was officially registered on 24 December 1969).1 It soon became clear that these compounds are not just chemical curiosities, or a nuisance for gas transportation in pipe lines, but rather that they are related significant natural phenomena. It is possible that in the past natural gas hydrates have manifested themselves in marine and land incidents. In future gas hydrates may offer an inexhaustible source of energy and chemical raw material. However, if not accessed with sufficient knowledge, gas hydrates may be destabilized to create many local problems and possibly global problems as well. In the USSR and more recently in Russia, a number of groups are traditionally involved in investigation of different aspects of gas hydrates problems. These groups have made significant contributions to present knowledge about the nature and properties of the gas hydrates. The Siberian branch of the Russian Academy of Sciences recently started an interdisciplinary program to comprehensively investigate all major aspects of gas hydrates, with special emphasis on natural gas hydrates and gas hydrates deposits in Siberia and its adjacent regions. The program consists of three components: (1) Geology of gas hydrates in the cryolito‐zone of Siberia and in the bottom deposits of the Arctic and East seas, and of Lake Baikal. (2) Physicochemical study of hydrates of different gases. (3) Ecological monitoring. In this paper we offer a short summary of the main results of these three components of the program. We emphasize the second component, since it is close to the scientific interests of the author.
Rock Physics Characterization for Gas Hydrate Reservoirs: Elastic Properties
Authors: HELGERUD MICHAEL B. , DVORKIN JACK , NUR AMOS
Published: July 2010

Abstract: We offer a first‐principle‐based, effective medium model for elastic‐wave velocity in unconsolidated, high porosity, ocean bottom sediments containing gas hydrate or free gas. The dry sediment frame elastic constants depend on porosity, elastic moduli of the solid phase, and effective pressure. Elastic moduli of saturated sediment are calculated from those of the dry frame using Gassmann's equation. To model the effect of gas hydrate on sediment elastic moduli we use two separate assumptions: (a) hydrate modifies the pore fluid elastic properties without affecting the frame and (b) hydrate becomes a component of the solid phase, reducing porosity and modifying the elasticity of the frame. The goal of the model is to predict the amount of hydrate in sediments from sonic or seismic velocity data. We apply the model to sonic and VSP data from ODP Hole 995 and obtain hydrate concentration estimates from assumption (b) that are consistent with estimates obtained from resistivity, chlorinity, and evolved gas data.
Changes of the Hydrate Stability Zone of the Norwegian Margin from Glacial to Interglacial Times
Authors: MIENERT JÜRGEN , ANDREASSEN KARIN , POSEWANG JÖRG , LUKAS DIRK
Published: July 2010

Abstract: During the last two decades, the detection and quantitative determination of gas hydrate deposits, as well as the study of clathrate formation and dissociation kinetics, have become central fields of marine research. The presence of gas hydrates in oceanic sediments along the Norwegian continental margin is documented in high‐frequency near‐vertical and wide‐angle seismic reflection data. The base of the hydrate stability zone (HSZ) is detected in reflection seismic sections by the occurence of a strong bottom simulating reflector (BSR). The BSR mimics the shape of the sea floor, crosses the sedimentary strata, and is characterized by a strong phase‐reversed event. Below the BSR a low velocity layer is interpreted as a gas‐bearing zone. The inferred thickness of the hydrate existence zone (HEZ) allows for the estimation of the total amount of carbon trapped in gas hydrates at the present time. Modeling the HSZ as a function of temperature and pressure shows a distinct decrease of the HSZ at the Norwegian margin from the last glacial maximum (LGM) to the present time. This highly dynamic HSZ system may provide a complex seismic expression of gas hydrate occurrences, a phenomenon that is far from being well understood.
Strength of CO2 Hydrate Membrane in Sea Water at 40 MPa
Authors: YAMANE K. , AYA I. , NAMIE S. , NARIAI H.
Published: July 2010

Abstract: The strength of the CO2 hydrate membrane that forms at the interface between liquid CO2 and artificial sea water at 40–45 MPa was measured with Du‐Nouy type surface tension meter. At low temperatures with a subcooling greater than 5 K, the membrane strength, initially abut 0.1 N/m, decreased with increasing temperature. However, it increased sharply and reached a peak of about 0.9 N/m just below the dissociation temperature and abruptly drops to zero at the dissociation temperature. This abnormal tendency of the membrane strength was previously observed by the authors in an experiment with fresh water. The temperature of the abnormality, however, shifts to lower temperatures and the peak decreases with increasing salinity. This new phenomenon could exert major influences on the various CO2 ocean sequestration methods that have been proposed to mitigate global warming. It can be explained in terms of a model in which the dissociation process of hydrate that occurs near the dissociation temperature enhances the diffusion of water molecules in the hydrate membrane and makes the membrane thicker.
Hydrate Challenges in Deep Water Production and Operation
Authors: MEHTA AJAY , WALSH JOHN , LORIMER SUSAN
Published: July 2010

Abstract: Hydrate control is an integral part of any deep water development since hydrates exert a major impact on all aspects of systems design and operation. This paper identifies major challenges for hydrate research including high‐pressure phase behavior, mixed electrolyte prediction, and kinetics. Operability issues related to deep water multiphase flowlines that ensure hydrate‐free production and emerging technologies, such as low dosage inhibitors, are discussed.
Can We Estimate the Amount of Gas Hydrates by Seismic Methods?
Authors: SAKAI AKIO
Published: July 2010

Abstract: Elastic wave velocity is the key parameter in determining the quantity of gas hydrate in sediment. Using data acquired in permafrost, elastic responses of gas hydrate bearing sediment are examined in detail by fitting observed elastic wave velocities of VSP and logging data with computed velocities based on two opposing gas hydrate bearing models. It is concluded that observed elastic wave velocity best fits a model of gas hydrate disseminated in pore space, without assuming cementation on grain boundaries in model simulations. This conclusion is important in the sense that shear wave velocity is crucial in determining gas hydrate bearing model and estimating gas hydrate saturation rate in pore space. The current case is the first example in model determination by reliable elastic wave velocity observed in the field.
A Consistent Thermodynamic Model for Predicting Combined Wax‐Hydrate in Petroleum Reservoir Fluids
Authors: TABATABAEI A. R. , DANESH A. , TOHIDI B. , TODD A. C.
Published: July 2010

Abstract: Low oil prices and the competitive nature of the oil industry world‐wide demand more cost‐effective techniques in the development and operation of offshore reservoirs. Extended‐reach gathering networks and transportation of unprocessed well streams by subsea pipelines are two attractive options that could have significant impact in the development of marginal oil/gas fields. These subsea pipelines are prone to wax and/or hydrate formation that can potentially block the pipelines and lead to serious safety and operational problems. Wax and hydrate formation are both examples of solid deposition. They are modelled conventionally and are studied independently. In this work we describe a wax model that has been developed based on regular solution theory. The wax model was successfully coupled with an existing hydrate model. The integrated wax‐hydrate model is capable of predicting five phase equilibria (i.e., water, liquid hydrocarbon, vapor, wax, and hydrate) as well as predicting the effect of wax formation on the hydrate phase boundary and vice versa. The results show that a reliable wax‐hydrate model can minimize the risks involved in the transportation of fluids prone to wax and hydrate formation. The model can be used as a powerful tool in the design and operation of subsea and arctic pipelines and production facilities.
A Simple Model for Natural Gas Production from Hydrate Decomposition
Authors: AHMADI GOODARZ , JI CHUANG , SMITH DUANE H.
Published: July 2010

Abstract: This paper describes a model for natural gas production from the decomposition of methane hydrate in a confined reservoir by a depressurizing well. The one‐dimensional linearized model suggested by Makogon is used in the analysis. For different well pressures and reservoir temperatures, distributions of temperature and pressure in the porous layer of methane hydrate and in the gas region are evaluated. The distance of the decomposition front from the well to the natural gas output are evaluated as functions of time. Time evolutions of the resulting temperature and pressure profiles in the hydrate reservoir are also studied.
Department of Energy Methane Hydrate Research and Development Program: An Update
Authors: ALLISON EDITH
Published: July 2010

Abstract: The objective of this paper is to summarize the program planning activities and current research being conducted by the U.S. Department of Energy Methane Hydrate Program.
Methane Hydrate: Melting and Memory
Authors: RODGER P. MARK
Published: July 2010

Abstract: We present the results of a long timescale molecular dynamics simulation of a methane hydrate/methane gas interface formed along the [001] hydrate surface. The simulations were performed at 15–20°C above the stable hydrate temperature so that we were able to observe melting under conditions that were sufficiently gentle to allow any residual order associated with the memory effect for hydrate nucleation to be identified. The simulations have been analyzed using a set of novel order parameters designed specifically to quantify the microscopic molecular structure associated with the different phases of water. The simulations do show an enhanced level of ice‐ and clathrate‐structure in the liquid water that forms when the hydrate decomposes, but there is no evidence of significant clusters of the ordered water.
Growth Kinetics of Single Crystal sII Hydrates: Elimination of Mass and Heat Transfer Effects
Authors: BOLLAVARAM P. , DEVARAKONDA S. , SELIM M. S. , SLOAN E. D.
Published: July 2010

Abstract: This work presents the results from experiments and modeling of tetrahydrofuran single crystal hydrate growth. The purpose was to study growth kinetics, independent of mass transfer and heat transfer. We used a single crystal apparatus, at stoichiometric concentrations of tetrahydrofuran and water, varying the fluid shear to decrease the boundary layer at the crystal surface. We found that with extreme precautions to totally eliminate mass transfer and to minimize heat transfer via high shear, it is very difficult to obtain reliable kinetic constants for the single hydrate crystal growth system. We eliminated mass transfer, but were only able to reduce the heat transfer resistance to a value of about 10% of the total resistance (i.e., 90% kinetic resistance) at the lowest value of subcooling. We found that growth rate increased with the driving force (i.e., subcooling) and established that the growth process occurred by a step mechanism. We only measured the fluid phases in order to obtain hydrate phase kinetics. The results of this work suggest that assessment of heat transfer, previously ignored in crystal growth kinetic studies is vital for accurate hydrate kinetics.
Mechanisms of Methane Hydrate Crystallization in a Semibatch Reactor: Influence of a Kinetic Inhibitor: Polyvinylpyrrolidone
Authors: PIC J.‐S. , HERRI J.‐M. , COURNIL M.
Published: July 2010

Abstract: In a previous paper, 1 we proposed a complete model for methane hydrate crystallization from pure water and methane gas in a semibatch reactor. This model takes into account the crucial importance of the rate‐determining mass transfer at the gas/liquid interface, coupled with primary nucleation and growth. The validity of this model has been proved on a large number of experimental results. However, due to the complexity of the equations, only a numerical solution is possible, so that comparison between theory and experiment is not straightforward. In this paper, we consider a simple model of primary nucleation/growth and we propose an analytical solution for the time evolution of the total number of particles, mean diameter, and methane gas consumption rate during the first time of the crystallization. This model is used to analyze experimental results obtained in the presence of a kinetic additive: polyvinylpyrrolidone (PVP), in order to understand the origin of its effect.
Microscopic Measurements and Modeling of Hydrate Formation Kinetics
Authors: SUBRAMANIAN S. , SLOAN E. D.
Published: July 2010

Abstract: The frequency of the Raman band for methane dissolved in water indicates clustering of water molecules around methane molecules. By monitoring trends in the position of this band with pressure, it was determined that the clusters resemble CH4 trapped in the 20‐coordinated small 512 cavity, the basic building block of clathrate hydrates. These methane‐water clusters act as precursors to hydrate cavity formation and their transformation to methane trapped in cavities of sI hydrate was monitored using time resolved Raman spectroscopy. The ratio of number of large to small cavities was obtained as a function of time. The formation of the large 51262 cavity was determined to be slower than for the small 512 cavity. Based on these results, a mechanistic model of methane hydrate formation from the aqueous phase is proposed.
Mechanisms for Methane Gas Accumulation under Hydrate Deposits in Sediments
Authors: GERING KEVIN L. , CHERRY ROBERT S. , WEINBERG DAVID M.
Published: July 2010

Abstract: Equations that describe partial molal volume effects were used to produce a methane‐water‐hydrate phase diagram which includes T, P, and aqueous phase methane concentrations. This diagram allows prediction of gas exsolution as a result of local biogenesis or as methane‐containing water simply rises through sediments. Such exsolved gas can be trapped in homogeneous sediments by relative permeability effects. Hydrate stability conditions when the system is not at liquid‐vapor saturation can also be determined.