Showing papers by "Laval University published in 1997"

Application of large pore MCM-41 molecular sieves to improve pore size analysis using nitrogen adsorption measurements

Abstract: MCM-41 siliceous molecular sieves were used to test the applicability of the Kelvin equation for nitrogen adsorption in cylindrical pores of the size from 2 to 65 nm It was shown that the Kelvin equation for the hemispherical meniscus, corrected for the statistical film thickness, is in quite good agreement with an experimental relation between the pore size and the capillary condensation pressure The agreement can be made quantitative in the pore size range from ca 2 to 65 nm, if a simple correction to the Kelvin equation is introduced The required statistical film thickness curve (t-curve) was calculated using nitrogen adsorption data for large pore MCM-41 samples and the obtained results were extrapolated using an adsorption isotherm for a macroporous silica gel Moreover, an accurate analytical representation of the t-curve was found Since both the corrected Kelvin equation for cylindrical pores and the t-curve have simple analytical forms, they can conveniently be used in a variety of methods

Subcutaneous Abdominal Fat and Thigh Muscle Composition Predict Insulin Sensitivity Independently of Visceral Fat

Abstract: Whether visceral adipose tissue has a uniquely powerful association with insulin resistance or whether subcutaneous abdominal fat shares this link has generated controversy in the area of body composition and insulin sensitivity. An additional issue is the potential role of fat deposition within skeletal muscle and the relationship with insulin resistance. To address these matters, the current study was undertaken to measure body composition, aerobic fitness, and insulin sensitivity within a cohort of sedentary healthy men ( n = 26) and women ( n = 28). The subjects, who ranged from lean to obese (BMI 19.6-41.0 kg/m2), underwent dual energy X-ray absorptiometry (DEXA) to measure fat-free mass (FFM) and fat mass (FM), computed tomography to measure cross-sectional abdominal subcutaneous and visceral adipose tissue, and computed tomography (CT) of mid-thigh to measure muscle cross-sectional area, muscle attenuation, and subcutaneous fat. Insulin sensitivity was measured using the glucose clamp technique (40 mU · m∼2 · min−1), in conjunction with [3-3H]glucose isotope dilution. Maximal aerobic power (Vo2max) was determined using an incremental cycling test. Insulin-stimulated glucose disposal ( R d) ranged from 3.03 to 16.83 mg · min−1· kg−1 FFM. R d was negatively correlated with FM ( r = -0.58), visceral fat ( r = -0.52), subcutaneous abdominal fat ( r = -0.61), and thigh fat ( r = -0.38) and positively correlated with muscle attenuation ( r = 0.48) and Vo2max ( r = 0.26, P < 0.05). In addition to manifesting the strongest simple correlation with insulin sensitivity, in stepwise multiple regression, subcutaneous abdominal fat retained significance after adjusting for visceral fat, while the converse was not found. Muscle attenuation contributed independent significance to multiple regression models of body composition and insulin sensitivity, and in analysis of obese subjects, muscle attenuation was the strongest single correlate of insulin resistance. In summary, as a component of central adiposity, subcutaneous abdominal fat has as strong an association with insulin resistance as visceral fat, and altered muscle composition, suggestive of increased fat content, is an important independent marker of insulin resistance in obesity.

Cloning, chromosomal localization, and functional analysis of the murine estrogen receptor β

Abstract: Estrogen receptor β (ERβ) is a novel steroid receptor that is expressed in rat prostate and ovary We have cloned the mouse homolog of ERβ and mapped the gene, designated Estrb, to the central region of chromosome 12 The cDNA encodes a protein of 485 amino acids that shares, respectively, 97% and 60% identity with the DNA- and ligand-binding domains of mouse (m) ERα Mouse ERβ binds to an inverted repeat spaced by three nucleotides in a gel mobility shift assay and transactivates promoters containing synthetic or natural estrogen response elements in an estradiol (E2)-dependent manner Scatchard analysis indicates that mERβ has slightly lower affinity for E2 [dissociation constant (Kd) = 05 nm] when compared with mERα (Kd = 02 nm) Antiestrogens, including 4-hydroxytamoxifen (OHT), ICI 182,780, and a novel compound, EM-800, inhibit E2-dependent transactivation efficiently However, while OHT displays partial agonistic activity with ERα on a basal promoter linked to estrogen response elements in Cos-1 c

p38 MAP kinase activation by vascular endothelial growth factor mediates actin reorganization and cell migration in human endothelial cells.

Abstract: Vascular endothelial growth factor (VEGF) is a potent chemotactic agent for endothelial cells. Yet the signalling pathways that modulate the motogenic effects of VEGF in vascular endothelial cells are still ill defined. In the present study, we found in primary cultures of human umbilical vein endothelial cells (HUVEC) that VEGF increased cell migration and induced a marked reorganization of the microfilament network that was characterized by the formation of stress fibers and the recruitment of vinculin to focal adhesions. VEGF also stimulated the mitogen activated protein (MAP) kinases ERK (extracellular signal-regulated kinase) and p38 (stress activated protein kinase-2), but not SAPK1/JNK (stress activated protein kinase-1/c-Jun NH2-terminal kinase). Activation of p38 resulted in activation of MAP kinase activated protein kinase-2/3 and phosphorylation of the F-actin polymerization modulator, heat shock protein 27 (HSP27). Inhibiting the VEGF-induced activation of ERK with PD098059 did not influence actin organization or cell migration but totally inhibited the VEGF-induced incorporation of thymidine into DNA. Inhibition of p38 activity by the specific inhibitor SB203580 led to an inhibition of HSP27 phosphorylation, actin reorganization and cell migration. The results indicate that the p38 pathway conveys the VEGF signal to microfilaments inducing rearrangements of the actin cytoskeleton that regulate cell migration. By modulating cell migration, p38 may thus be an important regulator of angiogenesis.

Regulation of actin filament dynamics by p38 map kinase-mediated phosphorylation of heat shock protein 27

Abstract: We have studied the contribution of the individual kinases of the MAP (mitogen-activated protein) kinase family, including ERK (extracellular-signal regulated kinase), JNK/SAPK (c-JUN NH2-terminal kinase/stress-activated protein kinase) and p38, to activation of the HSP27 (heat shock protein 27) kinase MAPKAP kinase-2/3 and to HSP27 phosphorylation in Chinese hamster CCL39 cells stimulated by either growth factors, cytokines or stressing agents. In vitro assays using fractionated cell extracts or immunoprecipitates indicated that only fractions containing ERK or p38, and not those containing JNK/SAPK, had the capacity to activate MAPKAP kinase-2/3. In vivo, however, it appeared that only p38 is an upstream activator of HSP27 phosphorylation after both stress or growth factor stimulation: expression of an interfering mutant of ras, which blocked the activation of ERK by both types of inducers, had no effect on HSP27 phosphorylation and p38 activation; and the cell-permeant specific inhibitor of 038, SB203580, blocked MAPKAP-kinase2/3 activation and HSP27 phosphorylation. HSP27 has been suggested to have a phosphorylation-activated homeostatic function at the actin cytoskeleton level. This raises the possibility that p38 might be directly involved in mediating actin responses to external stimuli. Accordingly, we observed that a prior activation of p38 increased the stability of the actin microfilaments in cells exposed to cytochalasin D. The effect was dependent on the expression of HSP27 and was totally annihilated by blocking the p38 activity with SB203580. The results provide strong support to the idea that activation of p38 during adverse environmental conditions serves a homeostatic function aimed at regulating actin dynamics that would otherwise be destabilized during stress. Its activation during normal agonist stimulation may constitute an additional actin signaling pathway, the importance of which depends on the level of expression of HSP27.

Marked Decline in Serum Concentrations of Adrenal C19 Sex Steroid Precursors and Conjugated Androgen Metabolites During Aging

Abstract: The present data show a dramatic decline in the circulating levels of dehydroepiandrosterone (DHEA), DHEA-sulfate (DHEA-S), androst-5-ene-3 beta,17 beta-diol (5-diol), 5-diol-sulfate, 5-diol-fatty acid esters, and androstenedione in both men and women between the ages of 20-80 yr. In the 50- to 60-yr-old group, serum DHEA decreased by 74% and 70% from its peak values in 20- to 30-yr-old men and women, respectively. the serum concentrations of the conjugated metabolites of dihydrotestosterone (DHT), namely androsterone (ADT)-G, androstane-3 alpha,17 beta-diol (3 alpha-diol-G), androstane-3 beta,17 beta-diol (3 beta-diol-G), and ADT-sulfate are the most reliable parameters of the total androgen pool in both men and women, whereas serum testosterone and DHT can be used as markers of testicular secretion in men and interstitial ovarian secretion in women. The serum concentration of these various conjugated androgen metabolites decreased by 40.8% to 72.8% between the 20- to 30-yr-old and 70- to 80-yr-old age groups in men and women, respectively, thus suggesting a parallel decrease in the total androgen pool with age. As estimated by measurement of the circulating levels of these conjugated metabolites of DHT, it is noteworthy that women produce approximately 66% of the total androgens found in men. In women, most of these androgens originate from the transformation of DHEA and DHEA-S into testosterone and DHT in peripheral intracrine tissues, whereas in men the testes and DHEA and DHEA-S provide approximately equal amounts of androgens at the age of 50-60 yr. An additional potentially highly significant observation is that the majority of the marked decline in circulating adrenal C19 steroids and their resulting androgen metabolites takes place between the age groups of 20- to 30-yr olds and 50- to 60-yr-olds, with smaller changes are observed after the age of 60 yr.

Oxidative Stress-Induced Actin Reorganization Mediated by the p38 Mitogen-Activated Protein Kinase/Heat Shock Protein 27 Pathway in Vascular Endothelial Cells

Abstract: Vascular endothelial cells are constantly in contact with oxyradicals and must be especially well equipped to resist their toxic effects and generate appropriate physiological responses. Despite th...

The effect of strategy and organizational structure on the adoption and implementation of activity-based costing

Abstract: This study examines the effect of strategic posture and organizational structure- on the adoption and implementation of general forms of activity management (AM) approaches. To explain the decision to adopt and implement AM, theories of strategy and of innovation in organizations are drawn upon. Employing a survey methodology, a questionnaire was used to collect data on the organizational determinants and business strategies of a sample of strategic business units in Canadian manufacturing fmns. The questionnaire also collected data on the AM approaches these SBUs had adopted and implemented in the last two years. The results show that strategy influences the extent to which SBUs adopt an AM approach. As expected, organizations with high vertical differentiation are positively associated with the adoption of activity-based costing (ABC) over other forms of AM. Furthermore, centralization and formalization are associated with organizations that actually implement ABC after adopting it. This study provides some insight into the apparent paradox, in the part that despite the theoretical benefits of ABC, relatively few companies employ it and that a material number of those that adopt ABC do not actually implement it. It demonstrates that activity-based costing consists of a series of decisions and that managers have several opportunities to revise their initial choice during the innovation process. It also shows that organizations that adopt and implement ABC are bureaucracies. 0 1997 Elsevier Science Ltd. AIJ rights reserved

Epidural corticosteroid injections for sciatica due to herniated nucleus pulposus.

Abstract: Background Although epidural corticosteroid injections are commonly used for sciatica, their efficacy has not been established. Methods In a randomized, double-blind trial, we administered up to three epidural injections of methylprednisolone acetate (80 mg in 8 ml of isotonic saline) or isotonic saline (1 ml) to 158 patients with sciatica due to a herniated nucleus pulposus. All patients had Oswestry disability scores higher than 20 (on a scale of 1 to 100, with scores of 20 or less indicating minimal disability, and higher scores greater disability). Results At three weeks, the Oswestry score had improved by a mean of -8.0 in the methylprednisolone group and -5.5 in the placebo group (95 percent confidence interval for the difference, -7.1 to 2.2). Differences in improvements between the groups were not significant, except for improvements in the finger-to-floor distance (P = 0.006) and sensory deficits (P = 0.03), which were greater in the methylprednisolone group. After six weeks, the only significant...

Expression of CYP3A in the human liver--evidence that the shift between CYP3A7 and CYP3A4 occurs immediately after birth.

Abstract: CYP3A isoforms are responsible for the biotransformation of a wide variety of exogenous chemicals and endogenous steroids in human tissues. Two members of the CYP3A subfamily display developmentally regulated expression in the liver; CYP3A7 is expressed in the fetal liver, whereas CYP3A4 is the major cyrochrome P-450 isoform present in the adult liver. To gain insight into the descriptive ontogenesis of CYP3A isoforms during the neonatal period, we have developed several approaches to explore a neonatal liver bank. Although CYP3A4 and CYP3A7 are structurally closely related, they differ in their capacity to carry out monooxygenase reactions. We have cloned CYP3A4 and CYP3A7 and established stable transfectants in Ad293 cells to investigate their substrate specificities. The 16alpha hydroxylation of dehydroepiandrosterone is catalyzed by both proteins, but CYP3A7 has a higher affinity and maximal velocity than CYP3A4. Conversely, the conversion of testosterone into its 6beta derivative is essentially supported by CYP3A4. We used these two probes to determine the ontogenic evolution at the protein level; CYP3A7 was very active in the fetal liver and its activity was maximal during the first week following birth before to progressively decline and reached a very low level in adult livers. Conversely, the activity of CYP3A4 was extremely weak in the fetus and began to raise after birth to reach 30-40% of the adult activity after one month. CYP3A4 RNA accumulation displays a similar pattern of evolution; when probed with an oligonucleotide, its concentration increased rapidly after birth to reach a plateau as soon as the first week of age. These data supports the assumption that CYP3A4 expression is transcriptionally activated during the first week after birth and is accompanied by a simultaneous decrease of CYP3A7 expression, in such a way that the overall CYP3A protein content and the level of pentoxyresorufin dealkylase catalyzed by the two proteins remain nearly constant.

Adsorption Study of Surface and Structural Properties of MCM-41 Materials of Different Pore Sizes

Abstract: Nitrogen adsorption measurements were performed over a wide range of relative pressures (10-6−0.995) for a series of siliceous MCM-41 samples obtained using alkyltrimethylammonium surfactants with different chain length. Both high- and low-pressure adsorption data were analyzed. The pore size was shown to increase in a regular way with the chain length of the surfactant used. Moreover, a very good correlation between the pore size and the interplanar spacing of the MCM-41 samples was observed. Methods used to calculate the pore diameter were critically compared, and a new procedure to estimate the pore size of MCM-41 materials was proposed. This new procedure is based on geometrical considerations of the ratio of the pore volume to the pore wall volume for an infinite hexagonal array of cylindrical pores. Adsorption measurements showed that the amount adsorbed in the low-pressure region increases with a decrease in the pore size of the samples probably because of the enhancement of the gas−surface interac...

Intolerance of uncertainty and problem orientation in worry.

Abstract: Worry, which is the central feature of generalized anxiety disorder (GAD), is now recognized as a truly important clinical phenomenon. The present study examines the relationship between intolerance of uncertainty and problem orientation in nonclinical worry. Subjects were 285 French-Canadian university students who completed a battery of questionnaires on a voluntary basis. The results indicate that intolerance of uncertainty and emotional problem orientation are strong predictors of trait worry, even when personal variables (age, sex) and mood state (level of anxiety, depression) have been partialed out. The findings also show that intolerance of uncertainty and emotional problem orientation both make common as well as a unique contributions to the prediction of worry. Implications for the treatment of worry are discussed and specific guidelines for reducing intolerance of uncertainty and intolerance of emotional arousal for different types of worries are suggested.

Synchronized activities of coupled oscillators in the cerebral cortex and thalamus at different levels of vigilance.

Abstract: The cerebral cortex and thalamus constitute a unified oscillatory machine displaying different spontaneous rhythms that are dependent on the behavioral state of vigilance. In vivo multi-site recordings from a variety of neocortical areas and related thalamic nuclei in cat, including dual simultaneous intracellular recordings, demonstrate that corticofugal volleys are effective in synchronizing fast (20-50 Hz) and low-frequency (< 15 Hz) oscillations in thalamocortical networks, characterizing activated and de-afferented states. (i) Fast spontaneous oscillations depend on the depolarization of thalamic and cortical cells and appear in a sustained manner during waking and REM sleep. Corticothalamic neurons, discharging high-frequency (400 Hz) spike-bursts at 30-40 Hz, are good candidates to synchronize fast oscillations in reentrant thalamocortical loops. Weakly synchronized, fast spontaneous oscillations may be reset and become robustly coherent after relevant sensory stimuli in waking or internal signals during the dreaming state. (ii) During quiescent sleep, the long-range synchronization of brain electrical activity results from synchronous hyperpolarizations in forebrain neurons. The corticothalamic inputs during the depolarizing component of the slow oscillation (< 1 Hz) are effective in grouping the thalamic-generated sleep rhythms (spindles at 7-14 Hz and delta at 1-4 Hz) into complex wave-sequences. These inputs also control the shape of spindles, and favor the long-range synchronization and nearly simultaneous appearance of spindles. (iii) The cortical control of thalamic activity is also demonstrated in spike-wave-seizures developing from sleep patterns. More than half of thalamocortical neurons are silent during spike-wave seizures, being tonically hyperpolarized, and display IPSPs (closely related to the paroxysmal depolarizing shifts of cortical cells) that are determined by the pattern of activities in thalamic reticular cells. All these data congruently show the power of cortical control upon thalamic oscillators.

Altered glycolytic and oxidative capacities of skeletal muscle contribute to insulin resistance in NIDDM

Abstract: The insulin resistance of skeletal muscle in glucose-tolerant obese individuals is associated with reduced activity of oxidative enzymes and a disproportionate increase in activity of glycolytic enzymes. Because non-insulin-dependent diabetes mellitus (NIDDM) is a disorder characterized by even more severe insulin resistance of skeletal muscle and because many individuals with NIDDM are obese, the present study was undertaken to examine whether decreased oxidative and increased glycolytic enzyme activities are also present in NIDDM. Percutaneous biopsy of vatus lateralis muscle was obtained in eight lean (L) and eight obese (O) nondiabetic subjects and in eight obese NIDDM subjects and was assayed for marker enzymes of the glycolytic [phosphofructokinase, glyceraldehyde phosphate dehydrogenase, hexokinase (HK)] and oxidative pathways [citrate synthase (CS), cytochrome-c oxidase], as well as for a glycogenolytic enzyme (glycogen phosphorylase) and a marker of anaerobic ATP resynthesis (creatine kinase). Insulin sensitivity was measured by using the euglycemic clamp technique. Activity for glycolytic enzymes (phosphofructokinase, glyceraldehye phosphate dehydrogenase, HK) was highest in subjects with subjects with NIDDM, following the order of NIDDM > O > L, whereas maximum velocity for oxidative enzymes (CS, cytochrome-c oxidase) was lowest in subjects with NIDDM. The ratio between glycolytic and oxidative enzyme activities within skeletal muscle correlated negatively with insulin sensitivity. The HK/CS ratio had the strongest correlation (r = -0.60, P < 0.01) with insulin sensitivity. In summary, an imbalance between glycolytic and oxidative enzyme capacities is present in NIDDM subjects and is more severe than in obese or lean glucose-tolerant subjects. The altered ratio between glycolytic and oxidative enzyme activities found in skeletal muscle of individuals with NIDDM suggests that a dysregulation between mitochondrial oxidative capacity and capacity for glycolysis is an important component of the expression of insulin resistance.

Cognitive and behavioral treatment of pathological gambling: a controlled study.

Abstract: This study evaluated the efficacy of a cognitive-behavioral treatment package for pathological gambling. Twenty-nine men who met criteria for pathological gambling in accordance with the Diagnostic and Statistical Manual of Mental Disorders (3rd ed., revised; DSM-III-R; American Psychiatric Association, 1987) were randomly assigned to treatment or wait-list control. The treatment included 4 components: (a) cognitive correction of erroneous perceptions about gambling, (b) problem-solving training, (c) social skills training, and (d) relapse prevention. The dependent variables were the South Oaks Gambling Screen, perception of control, frequency of gambling, perceived self-efficacy, desire to gamble, and number of DSM-III-R criteria met by participants. Posttest results indicated highly significant changes in the treatment group on all outcome measures, and analysis of data from 6- and 12-month follow-ups revealed maintenance of therapeutic gains. Recommendations for clinical interventions are discussed and focus on the cognitive correction of erroneous perceptions of gambling.

Intensity of training and physiologic adaptation in patients with chronic obstructive pulmonary disease

Abstract: The applicability of high-intensity training and the possibility of inducing physiologic adaptation to training are still uncertain in patients with severe chronic obstructive pulmonary disease (COPD). The purposes of this study were to evaluate the proportion of patients with moderate to severe COPD in whom high-intensity exercise training (30-min exercise session at 80% of baseline maximal power output [Wmax]) is feasible, and the response to training in these patients. We also sought to evaluate the possible influence of disease severity on the training intensity achieved and on the development of physiologic adaptation following endurance training. Forty-two patients with COPD (age = 66 +/- 7 yr, FEV1 = 38 +/- 13% predicted, [mean +/- SD]) were evaluated at baseline and after a 12-wk endurance training program. Each evaluation included a stepwise exercise test on an ergocycle up to the individual maximal capacity during which minute ventilation (VE), oxygen consumption (VO2), carbon dioxide production (VCO2), and arterial lactic acid concentrations were measured. The training consisted of 25 to 30-min exercise sessions on a calibrated ergocycle three times a week, with a target training intensity at 80% of Wmax. The training intensity was adjusted with the objective of reaching the target intensity, but also to ensure that the cycling exercise could be maintained for the specified duration. The training intensity sustained for the duration of each exercise session averaged 24.5 +/- 12.6, 51.7 +/- 17.4, 63.8 +/- 22.4, and 60.4 +/- 22.7% of Wmax at Weeks 2, 4, 10, and 12, respectively. High-intensity training was achieved in zero, three, five, and five patients at Weeks 2, 4, 10, and 12, respectively. A significant increase in VO2max and Wmax occurred with training (p or = 40% or or = 40% predicted. We conclude that although most patients were unable to achieve high-intensity training as defined in this study, significant improvement in their exercise capacity was obtained and physiologic adaptation to endurance training occurred. The training intensity expressed as a percent of the individual maximum exercise capacity, and the relative effectiveness of training, were not influenced by the severity of airflow obstruction.

A test of the unitary and collective models of household labour supply

Abstract: This paper tests the unitary and the collective household labour supply models within a structural framework. A nonlinear unrestricted household labour supply system is postulated and the set of parametric restrictions imposed by each model is derived. Our results generally reject the income pooling restrictions embodied in the unitary model. Also, the symmetry of cross-wage effects is rejected. However, the collective model is not rejected for groups with no pre-school children.

Physiological changes in dehydroepiandrosterone are not reflected by serum levels of active androgens and estrogens but of their metabolites: intracrinology

Abstract: This study analyzes in detail the serum concentration of the active androgens and estrogens, as well as a series of free and conjugated forms of their precursors and metabolites, after daily application for 2 weeks of 10 mL 20% dehydroepiandrosterone (DHEA) solution on the skin to avoid first passage through the liver. In men, DHEA administration caused 175%, 90%, 200% and 120% increases in the circulating levels of DHEA and its sulfate (DHEA-S), DHEA-fatty acid esters, and androst-5-ene-3 beta,17 beta-diol, respectively, with a return to basal values 7 days after cessation of the 14-day treatment. Serum androstenedione increased by approximately 80%, whereas serum testosterone and dihydrotestosterone (DHT) remained unchanged. In parallel with the changes in serum DHEA, the concentrations of the conjugated metabolites of DHT, namely androsterone glucuronide, androstane-3 alpha,17 beta-diol-G, and androstane-3 beta,17 beta-diol-G increased by about 75%, 50%, and 75%, respectively, whereas androsterone-sulfate increased 115%. No consistent change was observed in serum estrone (E1) or estradiol (E2) in men receiving DHEA, whereas serum E1-sulfate and E2-sulfate were slightly and inconsistently increased by about 20%, and serum cortisol and aldosterone concentrations were unaffected by DHEA administration. Almost superimposable results were obtained in women for most steroids except testosterone, which was about 50% increased during DHEA treatment. This increase corresponded to about 0.8 nM testosterone, an effect undetectable in men because they already have much higher (approximately 15 nM) basal testosterone levels. In women, the serum levels of the conjugated metabolites of DHT, namely androsterone glucuronide, androstane-3 alpha,17 beta-diol-G, androstane-3 beta,17 beta-diol-G, and androsterone-sulfate were increased by 125%, 140%, 120% and 150%, respectively. The present study demonstrates that the serum concentrations of testosterone, DHT, E1, and E2 are poor indicators of total androgenic and estrogenic activity. However, the esterified metabolites of DHT appear as reliable markers of the total androgen pool, because they directly reflect the intracrine formation of androgens in the tissues possessing the steroidogenic enzymes required to transform the inactive precursors DHEA and DHEA-S into DHT. As well demonstrated in women, who synthesize almost all their androgens from DHEA and DHEA-S, supplementation with physiological amounts of exogeneous DHEA permits the biosynthesis of androgens limited to the appropriate target tissues without leakage of significant amounts of active androgens into the circulation. This local or intracrine biosynthesis and action of androgens eliminates the inappropriate exposure of other tissues to androgens and thus minimizes the risks of undesirable masculinizing or other androgen-related side effects of DHEA.

The K-complex: Its slow (<1-Hz) rhythmicity and relation to delta waves

Abstract: The K-complex is a major graphoelement of sleep EEG. This report demonstrates that K-complexes emerge from a cortically generated slow (<1-Hz) oscillation. Human EEG as well as cat cellular and field potential recordings converge into demonstrating that the K-complex results from a synchronized cortical network that imposes periodic excitatory and inhibitory actions on cortical neurons. We additionally show the correspondence between neuronal activities and the shape of the K-complex. Spectral analysis confirms the periodic recurrence of human K-complexes, with main peaks at 0.5 to 0.7 Hz. It is also shown that the spectral content in the delta band (1 to 4 Hz) is partially due to the shape and duration of the K-complex.

Peer Experiences and Social Self-Perceptions: A Sequential Model.

Abstract: This study evaluated a social process model describing how aggression and withdrawal lead to negative social self-perceptions. The model posited both direct (i.e., cognitions associated with withdrawal) and indirect (i.e., mediations of negative peer status and peer experiences) influences. Eight- to 10-year-old children (n = 793) completed peer assessment measures of aggression, withdrawal, peer status, victimization and affiliations, and self-reports of loneliness, perceived acceptance, and perceived behavior-conduct. As expected, the model was supported for social self-perceptions but not for perceived behavior-conduct. Withdrawn behavior uniquely predicted social self-perceptions. Both negative peer status and peer victimization successively mediated the impact of social behavior on loneliness and perceived acceptance. Classroom affiliations did not mediate social self-perceptions.

Spatiotemporal Patterns of Spindle Oscillations in Cortex and Thalamus

Abstract: Spindle oscillations (7–14 Hz) appear in the thalamus and cortex during early stages of sleep. They are generated by the combination of intrinsic properties and connectivity patterns of thalamic neurons and distributed to cortical territories by thalamocortical axons. The corticothalamic feedback is a major factor in producing coherent spatiotemporal maps of spindle oscillations in widespread thalamic territories. Here we have investigated the spatiotemporal patterns of spontaneously occurring and evoked spindles by means of multisite field potential and unit recordings in intact cortex and decorticated animals. We show that (1) spontaneous spindle oscillations are synchronized over large cortical areas during natural sleep and barbiturate anesthesia; (2) under barbiturate anesthesia, the cortical coherence is not disrupted by transection of intracortical synaptic linkages; (3) in intact cortex animals, spontaneously occurring barbiturate spindle sequences occur nearly simultaneously over widespread thalamic territories; (4) in the absence of cortex, the spontaneous spindle oscillations throughout the thalamus are less organized, but the local coherence (within 2–4 mm) is still maintained; and (5) spindling propagation is observed in intact cortex animals only when elicited by low intensity cortical stimulation, applied shortly before the initiation of a spontaneous spindle sequence; propagation velocities are between 1 and 3 mm/sec, measured in the anteroposterior axis of the thalamus; increasing the intensity of cortical stimulation triggers spindle oscillations, which start simultaneously in all leads. We propose that, in vivo , the coherence of spontaneous spindle oscillations in corticothalamic networks is attributable to the combined action of continuous background corticothalamic input initiating spindle sequences in several thalamic sites at the same time and divergent corticothalamic and intrathalamic connectivity.

Moving focus in the propagation of ultrashort laser pulses in air

Abstract: The long light filaments generated in air by powerful ultrashort laser pulses, previously attributed to self-channeling, were investigated by use of gigawatt pulses from a Ti:sapphire chirped-pulse-amplification laser system. A filament contained only a small fraction of the pulse energy and always ended at the diffraction length of the beam (~100 m), independently of the pulse energy. These features are explained by the moving-focus model, which is presented as an alternative to the self-channeling model. Computer simulations involving ionization of the air also support the moving-focus model.

Bisimulation for labelled Markov processes

Abstract: In this paper we introduce a new class of labelled transition systems-Labelled Markov Processes-and define bisimulation for them. Labelled Markov processes are probabilistic labelled transition systems where the state space is not necessarily discrete, it could be the reals, for example. We assume that it is a Polish space (the underlying topological space for a complete separable metric space). The mathematical theory of such systems is completely new from the point of view of the extant literature on probabilistic process algebra; of course, it uses classical ideas from measure theory and Markov process theory. The notion of bisimulation builds on the ideas of Larsen and Skou and of Joyal, Nielsen and Winskel. The main result that we prove is that a notion of bisimulation for Markov processes on Polish spaces, which extends the Larsen-Skou definition for discrete systems, is indeed an equivalence relation. This turns our to be a rather hard mathematical result which, as far as we know, embodies a new result in pure probability theory. This work heavily uses continuous mathematics which is becoming an important part of work on hybrid systems.

Effect of 12-month dehydroepiandrosterone replacement therapy on bone, vagina, and endometrium in postmenopausal women

Abstract: The effect of 12-month dehydroepiandrosterone (DHEA) replacement therapy has been evaluated in 14 60- to 70-yr-old women who received daily applications of a 10% DHEA cream. Vaginal epithelium maturation was stimulated by DHEA administration in 8 of 10 women who had a maturation value of zero at the onset of therapy, whereas a stimulatory effect was also seen in all three women who had an intermediate vaginal maturation index before therapy. The estrogenic effect of DHEA observed in the vagina was not observed in the endometrium, which remained atrophic in all women. Most interesting, the bone mineral density significantly increased at the hip from 0.744 ± 0.021 to 0.759 ± 0.025 g/cm2 after 12 months of treatment (P < 0.05). These changes in bone mineral density were associated with a significant 20.0% decrease (P < 0.01) in plasma bone alkaline phosphatase and a 28% decrease in the urinary hydroxyproline/creatinine ratio. A 2.1-fold increase over the control value (P < 0.01) in plasma osteocalcin was con...