Showing papers by "Laval University published in 1993"

Thalamocortical oscillations in the sleeping and aroused brain

Abstract: Sleep is characterized by synchronized events in billions of synaptically coupled neurons in thalamocortical systems. The activation of a series of neuromodulatory transmitter systems during awakening blocks low-frequency oscillations, induces fast rhythms, and allows the brain to recover full responsiveness. Analysis of cortical and thalamic networks at many levels, from molecules to single neurons to large neuronal assemblies, with a variety of techniques, ranging from intracellular recordings in vivo and in vitro to computer simulations, is beginning to yield insights into the mechanisms of the generation, modulation, and function of brain oscillations.

Specific Proteolytic Cleavage of Poly(ADP-ribose) Polymerase: An Early Marker of Chemotherapy-induced Apoptosis

Abstract: Apoptosis is a morphologically and biochemically distinct form of cell death that occurs under a variety of physiological and pathological conditions. In the present study, the proteolytic cleavage of poly(ADP-ribose) polymerase (pADPRp) during the course of chemotherapy-induced apoptosis was examined. Treatment of HL-60 human leukemia cells with the topoisomerase II-directed anticancer agent etoposide resulted in morphological changes characteristic of apoptosis. Endonucleolytic degradation of DNA to generate nucleosomal fragments occurred simultaneously. Western blotting with epitope-specific monoclonal and polyclonal antibodies revealed that these characteristic apoptotic changes were accompanied by early, quantitative cleavage of the M(r) 116,000 pADPRp polypeptide to an M(r) approximately 25,000 fragment containing the amino-terminal DNA-binding domain of pADPRp and an M(r) approximately 85,000 fragment containing the automodification and catalytic domains. Activity blotting revealed that the M(r) approximately 85,000 fragment retained basal pADPRp activity but was not activated by exogenous nicked DNA. Similar cleavage of pADPRp was observed after exposure of HL-60 cells to a variety of chemotherapeutic agents including cis-diaminedichloroplatinum(II), colcemid, 1-beta-D-arabinofuranosylcytosine, and methotrexate; to gamma-irradiation; or to the protein synthesis inhibitors puromycin or cycloheximide. Similar changes were observed in MDA-MB-468 human breast cancer cells treated with trifluorothymidine or 5-fluoro-2'-deoxyuridine and in gamma-irradiated or glucocorticoid-treated rat thymocytes undergoing apoptosis. Treatment with several compounds (tosyl-L-lysine chloromethyl ketone, tosyl-L-phenylalanine chloromethyl ketone, N-ethylmaleimide, iodoacetamide) prevented both the proteolytic cleavage of pADPRp and the internucleosomal fragmentation of DNA. The results suggest that proteolytic cleavage of pADPRp, in addition to being an early marker of chemotherapy-induced apoptosis, might reflect more widespread proteolysis that is a critical biochemical event early during the process of physiological cell death.

A novel slow (< 1 Hz) oscillation of neocortical neurons in vivo: depolarizing and hyperpolarizing components

Abstract: We describe a novel slow oscillation in intracellular recordings from cortical association areas 5 and 7, motor areas 4 and 6, and visual areas 17 and 18 of cats under various anesthetics. The recorded neurons (n = 254) were antidromically and orthodromically identified as corticothalamic or callosal elements receiving projections from appropriate thalamic nuclei as well as from homotopic foci in the contralateral cortex. Two major types of cells were recorded: regular-spiking (mainly slow-adapting, but also fast-adapting) neurons and intrinsically bursting cells. A group of slowly oscillating neurons (n = 21) were intracellularly stained and found to be pyramidal-shaped cells in layers III-VI, with luxuriant basal dendritic arbors. The slow rhythm appeared in 88% of recorded neurons. It consisted of slow depolarizing envelopes (lasting for 0.8-1.5 sec) with superimposed full action potentials or presumed dendritic spikes, followed by long-lasting hyperpolarizations. Such sequences recurred rhythmically at less than 1 Hz, with a prevailing oscillation between 0.3 and 0.4 Hz in 67% of urethane-anesthetized animals. While in most neurons (approximately 70%) the repetitive spikes superimposed on the slow depolarization were completely blocked by slight DC hyperpolarization, 30% of cells were found to display relatively small (3-12 mV), rapid, all-or-none potentials after obliteration of full action potentials. These fast spikes were suppressed in an all-or-none fashion at Vm more negative than -90 mV. The depolarizing envelope of the slow rhythm was reduced or suppressed at a Vm of -90 to -100 mV and its duration was greatly reduced by administration of the NMDA blocker ketamine. In keeping with this action, most (56%) neurons recorded in animals under ketamine and nitrous oxide or ketamine and xylazine anesthesia displayed the slow oscillation at higher frequencies (0.6-1 Hz) than under urethane anesthesia (0.3-0.4 Hz). In 18% of the oscillating cells, the slow rhythm mainly consisted of repetitive (15-30 Hz), relatively short-lasting (15-25 msec) IPSPs that could be revealed by bringing the Vm at more positive values than -70 mV. The long-lasting (approximately 1 sec) hyperpolarizing phase of the slow oscillation was best observed at the resting Vm and was reduced at about -100 mV. Simultaneous recording of another cell across the membrane demonstrated synchronous inhibitory periods in both neurons. Intracellular diffusion of Cl- or Cs+ reduced the amplitude and/or duration of cyclic long-lasting hyperpolaryzations.(ABSTRACT TRUNCATED AT 400 WORDS)

Statistical Inference Procedures for Bivariate Archimedean Copulas

Abstract: A bivariate distribution function H(x, y) with marginals F(x) and G(y) is said to be generated by an Archimedean copula if it can be expressed in the form H(x, y) = ϕ–1[ϕ{F(x)} + ϕ{G(y)}] for some convex, decreasing function ϕ defined on [0, 1] in such a way that ϕ(1) = 0. Many well-known systems of bivariate distributions belong to this class, including those of Gumbel, Ali-Mikhail-Haq-Thelot, Clayton, Frank, and Hougaard. Frailty models also fall under that general prescription. This article examines the problem of selecting an Archimedean copula providing a suitable representation of the dependence structure between two variates X and Y in the light of a random sample (X 1, Y 1), …, (X n , Y n ). The key to the estimation procedure is a one-dimensional empirical distribution function that can be constructed whether the uniform representation of X and Y is Archimedean or not, and independently of their marginals. This semiparametric estimator, based on a decomposition of Kendall's tau statistic...

Intracellular analysis of relations between the slow (< 1 Hz) neocortical oscillation and other sleep rhythms of the electroencephalogram

Abstract: The newly described slow cortical rhythm (approximately 0.3 Hz), whose depolarizing-hyperpolarizing components are analyzed in the preceding article, is now investigated from the standpoint of its relations with delta (1–4 Hz) and spindle (7–14 Hz) rhythmicity. Regular-spiking and intrinsically bursting cortical neurons were mostly recorded from association suprasylvian areas 5 and 7; fewer neurons were also recorded from pericruciate motor and posterolateral visual areas. Although most cells were investigated under various anesthetics, a similar slow cortical rhythm was found in animals with brainstem transection at the low- or high-collicular levels. These cerveau isole (isolated forebrain) preparations display the major sleep rhythms of the EEG in the absence of general anesthetics. In 38% of recorded cortical neurons (n = 105), the slow rhythm was combined with delta oscillation. Both cellular rhythms were phase locked to the slow and delta oscillations in the surface- and depth-recorded EEG. In a group of this cell sample (n = 47), delta activity occurred as stereotyped, clock-like action potentials during the interdepolarization lulls of the slow rhythm. In another neuronal subsample (n = 58), delta events were grouped in sequences superimposed upon the depolarizing envelope of the slow rhythm, with such sequences recurring rhythmically at approximately 0.3–0.4 Hz. The associations between the two cellular and EEG rhythms (1–4 Hz and 0.3–0.4 Hz) were quantified by means of autocorrelograms, cross-correlograms, and spike-triggered averages. In 26% of recorded neurons (n = 72), the slow rhythm was combined with spindle oscillations. Regular-spiking cortical neurons fully reflected the whole frequency range of thalamically generated spindles (7–14 Hz). However, during similar patterns of EEG spindling, intrinsically bursting cells fired grouped action potentials (with intraburst frequencies of 100–200 Hz) at only 2–4 Hz. The dependence of the slow cortical oscillation upon the thalamus was studied by lesions and stimulation. The slow rhythm survived extensive ipsilateral thalamic destruction by means of electrolytic lesions or kainate-induced loss of perikarya in thalamic nuclei that were input sources to the recorded cortical neurons. To further prevent the possibility of a thalamic role in the genesis of the slow rhythm, through the contralateral thalamocortical systems and callosal projections, we also transected the corpus callosum in thalamically lesioned animals, and still recorded the slow rhythm in cortical neurons. These data indicate that the thalamus is not essentially implicated in the genesis of the slow rhythm.(ABSTRACT TRUNCATED AT 400 WORDS)

Origin and diversification of endomycorrhizal fungi and coincidence with vascular land plants

Abstract: AMONG the Eukaryota, the true fungi comprise four divisions (Chytridiomycota, Zymogomycota, Ascomycota and Basidio-mycota) that constitute a natural group which is thought to have diverged about 1 billion (109) years ago, believed also to be the time of divergence between metaphyta and metazoa lineages1. The endosymbionts responsible for the most prevalent plant root symbiosis, the vesicular–arbuscular mycorrhizae (VAM) or, more appropriately, arbuscular mycorrhizae, comprise 130 species of fungi classified in the Zygomycotina, order Glomales2–4. The arbuscular endomycorrhizae are considered to be ecologically important for most vascular plants5–8 in view of their beneficial effects on plant growth and survival. They are one of the few plant-fungus associations with a fossil record and may even have facilitated the origin of land flora. But the biochemical and genetic characterization of these microsymbionts has been hampered by the inability to grow them in pure culture. To investigate the origin and clarify the phylogenetic relationships of these organisms, we have sequenced ribosomal DNA genes from twelve species. Our phylogenetic analyses confirm the existence of three families within arbuscular fungi on the basis of morphological characters. We obtain approximate dates for the divergence of major branche's on the phylogenetic tree. These include an estimate for the origin of VAM-like fungi of 353–462 Myr ago, which is consistent with the hypothesis that VAM were instrumental in the colonization of land by ancient plants.

The slow (<1 Hz) oscillation in reticular thalamic and thalamocortical neurons: Scenario of sleep rhythm generation in interacting thalamic and neocortical networks

Abstract: As most afferent axons to the thalamus originate in the cerebral cortex, we assumed that the slow (

Attentional demands for static and dynamic equilibrium

Abstract: Upright standing and walking tasks require the integration of several sources of sensory information In a normal and highly predictable environment, locomotor synergies involving several muscles may take place at lower spinal levels with neural circuitry tuned by local loops of assistance or self-organizing processes generated in coordinative networks When ongoing regulation of gait is necessary (obstacles, changes in direction) supraspinal involvement is necessary to perform movements adapted to the environment Using a classical information processing framework and a dual-task methodology, it is possible to evaluate the attentional demands for performing static and dynamic equilibrium tasks The present experiment evaluates whether the attentional requirements for a control sitting condition and for standing and walking conditions vary with the intrinsic balance demands of the tasks The results show that standing and walking conditions required more attention than sitting in a chair The attentional cost for walking was also significantly greater than for standing For the walking task, reaction times when subjects were in singlesupport phase (small base of support) were significantly longer than those in double-support phase, suggesting that the attentional demands increased with an increase in the balance requirements of the task Balance control requires a continuous regulation and integration of sensory inputs; increasing balance demands loads the higher level cognitive system

New fast algorithms for the estimation of block motion vectors

Abstract: Two algorithms for block motion estimation that produce performance similar to that of exhaustive search but with computation reduced by a factor of 8 or 16 are presented. The algorithms are based on motion-field and pixel subsampling. A subsampled motion field is first determined by estimating the motion vectors for a fraction of the blocks. The motion vectors for these blocks are determined by using only a fraction of the pixels at any searched location and by alternating the pixel subsampling patterns with the searched locations. The subsampled motion field is then interpolated so that a motion vector is determined for each block of pixels. The algorithms are more robust than previously proposed fast algorithms and both can easily be combined with a hierarchical search strategy. One of the algorithms is fully compatible with MPEG-I. >

Genetic and nongenetic determinants of regional fat distribution.

Abstract: The role of inherited and nongenetic factors in individual differences observed in the level of sc fat on the trunk and abdominal areas and in the abdominal visceral deposit is reviewed. First, the metabolic and clinical implications of variation in body fat topography are summarized. Second, the results of genetic epidemiology studies on the heritability and other evidence for a role of the genotype in the amount of truncal-abdominal sc fat and abdominal visceral fat are reviewed. Third, the impact of total body fat, age, and gender on regional fat distribution is highlighted. Fourth, adipose tissue lipoprotein lipase activity is considered as a determinant of fat topography, with a discussion of site and gender differences, the effects of steroid hormones, and evidence from genetic epidemiology. Fifth, the contribution of adipose tissue lipolysis is reviewed with an emphasis on the various regulatory factors of the lipolytic pathways including catecholamines, insulin, adenosine, steroids, and other modulators. The role of lipolytic characteristics on fat topography is further assessed by considering changes with age, differences between men and women, effects of excess body fat, and data from heritability studies. Although the study of regional variation of in vitro adipose tissue metabolism has provided valuable information, a better understanding of variation in fat topography and of the role played by adipose tissue in the regulation of whole body carbohydrate and lipid metabolism will likely require extensive in situ and in vivo investigations. Sixth, as enlargement of a specific fat deposit is associated with increases in fat cell size and number, these topics are considered with an emphasis on the role of adipose cell differentiation. Seventh, the importance of blood levels of sex steroids and glucocorticoids for regional fat distribution is discussed. Then, a unifying hypothesis, defined as the hypothalamic arousal and neuroendocrine dysregulation model, is briefly described. Finally, the issue of whether body fat distribution can be altered by caloric restriction or regular exercise is addressed.

Interaction between glucose and free fatty acid metabolism in human skeletal muscle.

Abstract: The mechanism by which FFA metabolism inhibits intracellular insulin-mediated muscle glucose metabolism in normal humans is unknown. We used the leg balance technique with muscle biopsies to determine how experimental maintenance of FFA during hyperinsulinemia alters muscle glucose uptake, oxidation, glycolysis, storage, pyruvate dehydrogenase (PDH), or glycogen synthase (GS). 10 healthy volunteers had two euglycemic insulin clamp experiments. On one occasion, FFA were maintained by lipid emulsion infusion; on the other, FFA were allowed to fall. Leg FFA uptake was monitored with [9,10-3H]-palmitate. Maintenance of FFA during hyperinsulinemia decreased muscle glucose uptake (1.57 +/- 0.31 vs 2.44 +/- 0.39 mumol/min per 100 ml tissue, P < 0.01), leg respiratory quotient (0.86 +/- 0.02 vs 0.93 +/- 0.02, P < 0.05), contribution of glucose to leg oxygen consumption (53 +/- 6 vs 76 +/- 8%, P < 0.05), and PDH activity (0.328 +/- 0.053 vs 0.662 +/- 0.176 nmol/min per mg, P < 0.05). Leg lactate balance was increased. The greatest effect of FFA replacement was reduced muscle glucose storage (0.36 +/- 0.20 vs 1.24 +/- 0.25 mumol/min per 100 ml, P < 0.01), accompanied by decreased GS fractional velocity (0.129 +/- 0.26 vs 0.169 +/- 0.033, P < 0.01). These results confirm in human skeletal muscle the existence of competition between glucose and FFA as oxidative fuels, mediated by suppression of PDH. Maintenance of FFA levels during hyperinsulinemia most strikingly inhibited leg muscle glucose storage, accompanied by decreased GS activity.

On the cognitive penetrability of posture control.

Abstract: Postural sway increases with age. The decreased stability associated with postural sway often has been related to the reduced peripheral sensibility in the visual, vestibular, and proprioceptive systems. We examined whether the micropostural adjustments necessary for maintaining balance also require some cognitive processing. Young and older subjects were submitted to an auditory reaction time task while maintaining an upright posture on a force platform. The auditory stimuli were presented randomly when subjects were in a central or in an eccentric less stable postural position in four conditions of vision/surface. If the postural adjustments require some cognitive processing, a more eccentric position of the center of foot pressure (COP) would require more attention than a stable position of the COP because when an eccentric position is identified, a corrective response subsequently needs to be selected, programmed, and executed. The visual and surface conditions were altered to determine if additional attentional resources need to be allocated to the postural task when there is a reduction of the sensory information available. Results showed that as the sensory information decreased, the postural task became increasingly difficult for the elderly and required more of their attentional capacity (as indexed by increases in reaction time).

Low- and high-frequency membrane potential oscillations during theta activity in CA1 and CA3 pyramidal neurons of the rat hippocampus under ketamine-xylazine anesthesia

Abstract: 1. Intracellularly recorded low- and high-frequency (4-6 and 25-50 Hz, respectively), rhythmic, spontaneous membrane potential oscillations were investigated in pyramidal neurons of the rat hippocampus in vivo, during theta (theta, 4-6 Hz) electroencephalographic (EEG) activity, under ketamine-xylazine anesthesia. 2. The EEG activity showed two spectral peaks, one in the theta range, the other at higher frequencies (25-50 Hz). On the basis of their electrophysiological and pharmacological properties, it was concluded that the EEG theta-waves, and the fast EEG rhythm, recorded during ketamine-xylazine anesthesia, share the basic properties of those theta and fast rhythms that are recorded under the effects of other types of anesthetics. 3. When intracellular recordings (n = 32) were made with electrodes filled with potassium-acetate (K-acetate), the only CA1 and CA3 pyramidal cells (PCs) considered for further analysis were those that did not fire rhythmically at most or each cycle of the theta rhythm at the resting membrane potential. During EEG-theta, the membrane potential (Vm) of these cells showed a prominent oscillation (3-15 mV) with frequencies similar to those of the EEG-theta (the intracellular theta rhythm, intra-theta). 4. The frequency of the intra-theta was independent of the Vm. However, the phase difference between the intra-theta and the EEG-theta was voltage dependent in both types of cells. CA1 PCs showed a large (120-180 degrees, where 360 degrees is the full cycle), gradual shift in the phase difference between the intra-theta and the EEG-theta, when the membrane was hyperpolarized to -85 from -65 mV. Although CA3 PCs displayed a larger variability in their phase-voltage relations, a voltage-dependent phase shift (90-180 degrees) could be observed in CA3 PCs as well. 5. Although the amplitude of the intra-theta in both CA1 and CA3 PCs could display large, sudden, spontaneous changes at a given Vm, the amplitude-Vm plots tended to show a minimum between -70 and -80 mV. Spontaneous changes in the amplitude of the intra-theta did not affect the phase difference between the intra- and the EEG-theta rhythms. 6. Intracellular injection of QX-314 (50-100 mM) did not change the phase-Vm or the amplitude-Vm relationships of CA1 PCs. 7. Intracellular injection of chloride (Cl-) ions greatly reduced the voltage dependency of the phase difference and revealed fast (duration: 20-25 ms), depolarizing potentials (5-20 mV), which appeared at high frequencies (25-50 Hz), amplitude modulated at theta-frequencies.(ABSTRACT TRUNCATED AT 400 WORDS)

Arm problems and psychological distress after surgery for breast cancer.

Abstract: The frequency of problems in the arm affected by surgery for breast cancer and the association of these problems with psychological distress were assessed among 223 women with newly diagnosed breast cancer 3 months after operation and again 15 months later among 201 of these same women At 3 months after operation, 182 (82%) of the 223 patients reported at least one arm problem Specific problems reported were swelling (24%), weakness (26%), some limitation in range of movement (32%), stiffness (40%), pain (55%) and numbness (58%), and these percentages had changed little 15 months later Regardless of the type of mastectomy, women who underwent axillary dissection had more arm problems Compared with women reporting no arm problems, the adjusted odds ratios of having psychological distress at 3 months for women reporting one to two, three to four and five to six arm problems were 12, 23 and 31 respectively (chi 2 for trend = 95, p = 0002) Arm problems are frequent after operation for breast cancer, and these problems appear to increase the likelihood of psychological distress Women should be informed that arm problems are expected but non-threatening sequelae of initial surgical treatment for breast cancer

A Comparison of Management Patterns after Acute Myocardial Infarction in Canada and the United States

Abstract: Background There are major differences in the organization of the health care systems in Canada and the United States. We hypothesized that these differences may be accompanied by differences in patient care. Methods To test our hypothesis, we compared the treatment patterns for patients with acute myocardial infarction in 19 Canadian and 93 United States hospitals participating in the Survival and Ventricular Enlargement (SAVE) study, which tested the effectiveness of captopril in this population of patients after a myocardial infarction. Results In Canada, 51 percent of the patients admitted to a participating coronary care unit had acute myocardial infarctions, as compared with only 35 percent in the United States (P<0.001). Despite the similar clinical characteristics of the 1573 U.S. patients and 658 Canadian patients participating in the study, coronary arteriography was more commonly performed in the United States than in Canada (in 68 percent vs. 35 percent, P<0.001), as were revascularization pro...

Genetics of Obesity

Abstract: INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337 HUMAN GENETIC RESEARCH STRATEGIES . . . . . . . . . . . . . . . . . . . . . . . 338 EXCESS BODY FAT . . . . . ... . . . . . . . . . . . . . . . . . . .. . . . .. . ... . . 340 REGIONAL FAT DISTRIBUTION . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . 342 ENERGY AND NUTRIENT INTAKE . 343 METABOLIC RATE AND ENERGY EXPENDITURE . . . . . . . . . . . . . . . . . . . 344 Resting Metabolic Rate .. . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . 344 Thermic Effect of Food . . . . . . . . . . . . . . . . . . .... . . . . . . ....... . 345 Physical Activity Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345 NUTRIENT PARTITIONING ... . . . . . .. . .. . .. . . .... . . ...... . ... 346 MAJOR GENE EFFECTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346 TEMPORAL TRENDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 348 GENETIC-ENVIRONMENT INTERACTION . . . . . . . . . . . . . . . . . . . . . . . . . 348 Response to Oveifeeding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 348 Response to Negative Energy Balance . . . . . . . . ... . . . . . .. . . . . . . . . . 349 CONTRIBUTION OF SINGLE GENES: A BEGINNING . . . . . . . . . . . .. . . . . 350

Suitability of Plastic Films for Modified Atmosphere Packaging of Fruits and Vegetables

Abstract: Suitability of plastic films in standard configurations to maintain modified atmospheres was evaluated for common fruits and vegetables. Most films did not result in optimal O2 and CO2 atmospheres, especially when produce had high respiration. Produce with low and medium respiration could be matched with films considering O2 permeability requirements alone. MA packaging systems designed to produce optimal oxygen at suitable temperatures could have complications from transient temperature increases during storage and/or transportation. Respiration rates of fruits and vegetables increase more with temperature than do gas permeabilities of films. Higher than optimum temperatures could cause anoxia and seriously damage produce. More permeable gas pathways and temperature compensation to equalize Q10 values are needed for MA packaging systems to timction effectively.

Cholinergic and noradrenergic modulation of the slow (approximately 0.3 Hz) oscillation in neocortical cells

Abstract: 1. The pedunculopontine tegmental (PPT) cholinergic nucleus and the locus coeruleus (LC) noradrenergic nucleus were electrically stimulated to investigate their effects on the recently described slow oscillation (approximately 0.3 Hz) of neocortical neurons. Intracellular recordings of slowly oscillating, regular-spiking and intrinsically bursting neurons from cortical association areas 5 and 7 (n = 140) were performed in anesthetized cats. 2. Pulse trains to the PPT nucleus produced the blockage of rhythmic (approximately 0.3 Hz) depolarizing-hyperpolarizing sequences in 79% of tested cortical neurons and transformed this slow cellular rhythm into tonic firing. The latency of the cortical cellular response to PPT stimulation was 1.2 +/- 0.5 (SE) s and its duration was 15.9 +/- 1.9 s. The PPT-elicited suppression of the slow cellular oscillation was accompanied by an activation of the electroencephalogram (EEG) having a similar time course. Fast Fourier transform analyses of EEG activities before and after PPT stimulation showed that the PPT-evoked changes consisted of decreased power of slow rhythms (0-8 Hz) and increased power of fast rhythms (24-33 Hz); these changes were statistically significant. 3. The blockage of the slow cellular oscillation was mainly achieved through the diminution or suppression of the long-lasting hyperpolarizations separating the rhythmic depolarizing envelopes. This effect was observed even when PPT pulse trains disrupted the oscillation without inducing overt depolarization and increased firing rate. The durations of the prolonged hyperpolarizations were measured during a 40-s window (20 s before and 20 s after the PPT pulse train) and were found to decrease from 1.5 +/- 0.2 to 0.7 +/- 0.1 s. The values of the product resulting from the duration (in seconds), the amplitude (in millivolts), and number of such hyperpolarizing events within 20-s periods were 51.5 +/- 5 and 5.1 +/- 1.9 before and after PPT stimulation, respectively. 4. The PPT effect was suppressed by systemic administration of a muscarinic antagonist, scopolamine, but not by mecamylamine, a nicotinic antagonist. 5. The PPT effect on cellular and EEG cortical slow oscillation survived, although its duration was reduced, in animals with kainate-induced lesions of thalamic nuclei projecting to areas 5 and 7 (n = 3) as well as in animals with similar excitotoxic lesions leading to extensive neuronal loss in nucleus basalis (n = 2). These data indicate that the PPT effect is transmitted to neocortex through either thalamic or basal forebrain relays.(ABSTRACT TRUNCATED AT 400 WORDS)

The pattern of influence of perceived behavioral control upon exercising behavior: an application of Ajzen's theory of planned behavior.

Abstract: The aim of the present studies was to verify the basic assumptions underlying the theory of planned behavior for the prediction of exercising intentions and behavior among adults of the general population (study 1) and a group of pregnant women (study 2). In both studies, baseline data were collected at home with trained interviewers and with the use of paper-and-pencil questionnaires. The self-report on behavior was obtained 6 months (study 1) and between 8 and 9 months (study 2) after baseline data collection. In study 1, perceived behavioral control influenced behavior only through intention. In study 2, none of the Ajzen model variables was associated to exercising behavior. Nonetheless, intention was influenced by attitude, habit, and perceived behavioral control. The results of the present studies suggest that perceived behavioral control contributes to the understanding of intentions to exercise but not to the prediction of exercising behavior.