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PubMed2005

Model of calcium oscillations due to negative feedback in olfactory cilia.

We present a mathematical model for calcium oscillations in the cilia of olfactory sensory neurons. The underlying mechanism is based on direct negative regulation of cyclic nucleotide-gated channels by calcium/calmodulin and does not require any autocatalysis such as calcium-induced calcium release. The model is in quantitative agreement with available experimental data, both with respect to oscillations and to fast adaptation. We give predictions for the ranges of parameters in which oscillations should be observable. Relevance of the model to calcium oscillations in other systems is discussed.

Animals↗
PubMed2003

When should immunosuppressants be prescribed to treat systemic vasculitides?

Steroids and immunosuppressants are indicated to treat systemic vasculitides. However, the therapeutic strategy is different from one disease to the other. Treatment choice should be adapted to the predictable outcome, severity, pathogenic mechanisms and patient's general condition. In polyarteritis nodosa, Churg Strauss syndrome, and microscopic polyangiitis we have demonstrated that immunosuppressants should not be systematically prescribed. Immunosuppressants should be only prescribed in the most severe patients, when factors of poor prognosis are present. In Wegener's granulomatosis, immunosuppressants should be systematically prescribed together with steroids. The optimal treatment duration is of 12 months for polyarteritis nodosa and Churg-Strauss syndrome. A more prolonged treatment is mandatory in Wegener's granulomatosis, at least 18 months. The new therapeutic strategies comprise also new immunosuppressants and new immunomodulating agents which could replace or be associated to the "older drugs".

Churg-Strauss Syndrome↗
PubMed1984

The modifiable neuronal network of the cerebellum.

Recent data of neuronal network structures of the cerebellum are reviewed and experimental evidence is presented for the hypothesis that parallel fiber synapses on Purkinje cells retain plasticity which provides a memory device to the cerebellar cortical network. A corticonuclear microcomplex, consisting of a small area of the cerebellar cortex, a small group of cerebellar and vestibular nuclear neurons, and a small group of inferior olive neurons, which are interconnected, is proposed to form a functional unit of the cerebellum. The idea that a corticonuclear microcomplex endows an extracerebellar system with subtle control capabilities such as coordination, prediction, and adaptation-learning is supported with experimental data on the cerebellar control of the vestibulo-ocular reflex.

Animals↗
PubMed1994

Life cycle evaluation of five biological types of beef cattle in a cow-calf range production system: I. Model development.

Data collected during a 10-yr study at the Northern Agricultural Research Center (NARC), Havre, MT were used in construction of a simulation model to evaluate production systems using different breed groups. Five dam breed groups, straightbred Hereford (HH), 50% Angus-50% Hereford (AH), 25% Simmental-75% Hereford (1S3H), 50% Simmental-50% Hereford (1S1H), and 75% Simmental-25% Hereford (3S1H), were studied. The simulated system was a northern range cow-calf production system with spring calving and fall weaning. Replacement heifers were purchased and all calves were marketed at weaning. All nonpregnant females were sold in the fall. Statistical analyses of the data yielded input values (least squares means for breed group x age x sex subclasses) for cow and calf weights, pregnancy rate, dystocia, and calf survival. Pregnancy, dystocia, calf survival, calf weights, and cow weights were simulated stochastically. Energy requirements for maintenance, growth, gestation, and lactation were predicted from equations adapted from the literature based on body weight, frame size, sex, and breed group. Economic inputs and outputs were computed by accounting for variable input expenses and output revenues associated with animal performance and fixed costs associated with range management. Simulated measures of system performance included measures of energy conversion, break-even prices, and profit.

Animal Feed↗
PubMed2001

Game theory in the operating room environment.

To optimize the functioning of an operating room the interactions of the staff (physicians and nurses) and other stakeholders (administrators) must be understood. Game theory provides a representation of the interactions that typically take place in the operating room environment. By understanding the types of games/interactions that occur the participants can better predict outcome and adapt their own behavior to optimize that outcome. Types of games seen in the operating room include fixed-sum, zero-sum, and non-zero-sum games. The Prisoner's Dilemma game and some of its variations are used to illustrate common interactions in the operating room. Examples of strategies for typical scenarios are discussed as well as ways to improve the outcome of the games. A better understanding of human behavior can improve the functioning of complex systems such as that found in the operating room.

Game Theory↗
PubMed2003

[Functional state of the sympathetic-adrenal system at the stages of developing late complications of diabetes mellitus].

AIM: To study a functional state of the sympathico-adrenal system in patients with diabetes mellitus (DM) in developing late complications. MATERIAL AND METHODS: The study included 81 DM patients: free of late complications and diabetic autonomic neuropathy (DAN) (n = 24); with DAN (n = 6); with DAN and nonproliferative retinopathy (n = 8); with DAN and nephropathy stage 1-2; with DAN and diabetic retinopathy, sensory polyneuropathy (n = 23); with diabetic nephropathy stage 4 (n = 14). Blood levels of epinephrine, norepinephrine, dopamine were measured using liquid chromatography with electrochemical detection. A spectral analysis of the cardiac rhythm was made with application of the program "Mars". RESULTS: In patients with DM progression there was imbalance of autonomic nervous system, sympathetic hypertonicity, parasympathetic hypotonicity, subnormal power of the central regulatory contour. Dissociation was found between the degree of hypersympathicotonia and a fall of blood catecholamines concentration related to severity of the disease complications. CONCLUSION: Dissociation between sympathetic hypertonicity and low concentration of blood catecholamines is prognostically unfavourable and predicts development of arrhythmia and asystole. Augmentation of centralization of the systems regulating autonomic nervous system reflects tension of the regulatory systems and predicts disruption of adaptation.

Adrenal Glands↗
PubMed2003

Circadian transcriptional output in the SCN and liver of the mouse.

Circadian oscillators orchestrate daily rhythms in behaviour and physiology to adapt to the predictable daily appearance of light. Identifying the complement of circadian-regulated transcripts in major organs is critical in the understanding of both the biochemical targets of clock regulation and the mechanism of such control. Recent analysis of temporal gene expression patterns in peripheral and central oscillators have revealed hundreds of circadian-regulated transcripts, most of which are tissue-specific. Mapping of these transcripts to physiological processes and pathways has revealed that major functions of those organs tested are under circadian regulation, and importantly, key and rate-limiting steps in these processes are often the targets of circadian control. Overall, nearly 100% of the mammalian genome may be regulated by the clock, demonstrating the pervasive control of the circadian oscillator in temporal coordination of transcription throughout the organism. This wealth of circadian outputs offers exciting challenges to deciphering systems-level transcriptional regulatory mechanisms that underlie spatiotemporal gene expression.

Animals↗
PubMed2003

[Prognostic values of oestradiol/oocyte rate in ICSI patients].

OBJECTIVES: To analyze the pregnancy rate in women who underwent Intracytoplasmic Sperm Injection (ICSI) program depending of the oestradiol/oocyte index. STUDY DESIGN: Retrospective, comparative. MATERIAL AND METHODS: 332 patients were included. There were divided in three groups depending on the oestradiol/oocyte index: Group A:(100 pg/mL, group B: 101-250 pg/mL and group C: > 250 pg/mL). Therapeutic protocol. Down regulation with leuprolide acetate in late luteal phase protocol, COH with rec-FSH and / or HMG, ultrasonographic and estradiol blood levels were monitored; hCG application when > 3 follicles > 18 mm, oocyte retrieval performed 34 hours later. We analyzed: patient age, male age, number of follicles, estradiol serum levels at the day of hCG application, number of mature oocytes, oestradiol/oocyte index, fertilization rate, transferred embryos, transfer quality, catheter type and luteal support. Statistical analysis (SPSS 11) with chi square, ANOVA and Kruskall-Wallis was used. RESULTS: On having analyzed the number of metaphase II oocytes retrieval, oocytes fertilized and number of transferred embryos among three groups, the best results were obtained in group B. The differences among these variables were significant. (P = 0.014, p = 0.005 and p = 0.003, respectively). When the oestradiol/oocyte index was analyzed and the PR among groups (21.83, 36.62 and 17.80 %) we observed a significant difference (p = 0.003). CONCLUSION: It is convenient to monitor the oestradiol blood levels to offer schemes of COH less aggressive to improve the oocyte quality. The oestradiol/oocyte index is a parameter adapted as a predictive value of pregnancy.

Adult↗
PubMed2005

Benzodiazepine use, abuse, and dependence.

Although benzodiazepines are invaluable in the treatment of anxiety disorders, they have some potential for abuse and may cause dependence or addiction. It is important to distinguish between addiction to and normal physical dependence on benzodiazepines. Intentional abusers of benzodiazepines usually have other substance abuse problems. Benzodiazepines are usually a secondary drug of abuse-used mainly to augment the high received from another drug or to offset the adverse effects of other drugs. Few cases of addiction arise from legitimate use of benzodiazepines. Pharmacologic dependence, a predictable and natural adaptation of a body system long accustomed to the presence of a drug, may occur in patients taking therapeutic doses of benzodiazepines. However, this dependence, which generally manifests itself in withdrawal symptoms upon the abrupt discontinuation of the medication, may be controlled and ended through dose tapering, medication switching, and/or medication augmentation. Due to the chronic nature of anxiety, long-term low-dose benzodiazepine treatment may be necessary for some patients; this continuation of treatment should not be considered abuse or addiction.

Anti-Anxiety Agents↗
PubMedDate not supplied

[Stabilometric parameters associated with musculoskeletal diseases in a group of traffic policemen].

As reported by previous literature, the prevalence of musculoskeletal disorders is high in population of local police officers, due to several risk factors, including awkward posture, jolt/vibrations and stress. The results of our study reveal that the most common musculoskeletal symptoms among local police officers are cervicobrachial pain, low back pain and sciatica. Low-back pain is associated with tasks exposing to awkward posture of the spine (traffic policemen and policemen involved in office-based duties); cervical and upper extremity disorders are related to the exposure to vibrations and to the upper limb posture held by motorcycle police. Among postural parameters, anterior scapular plane, flat back and Barre's vertical resulted possible predictive tests of adaptation of the postural system to the symptom pain in subjects with low back pain. In conclusion, it is necessary to adopt organizational, protective and preventive measures in order to occupational health of local police officers. They include: decrease of time periods during which an awkward posture is held, breaks between duties, prescription of ergonomic shoes, use of low-weight and low-volume duty-packs, and planning of periodical osteopathic check-ups as part of the health program, aimed to uncover initial postural alterations related to musculoskeletal disorders.

Adult↗
PubMed1984

The effects of varying environmental demands on maternal and infant behavior.

3 groups of macaque mother-infant dyads were observed while each lived in ecological settings that differed in their level of foraging demand and, hence, the amount of work each mother was required to perform to obtain her daily rations. 2 groups (LFD and HFD) lived in stable low- and high-demand environments, respectively. The third group (VFD) lived in a variable-demand environment in which 2-week periods of HFD and LFD conditions were alternated, without external cues. Observations suggested that VFD subjects were unable to predict or rapidly adapt to the biweekly changes in food availability. Whereas LFD adults scored lowest in dominance-related behaviors and highest in affiliative behavior (social grooming), VFD adults showed the highest levels of dominance patterns and the lowest levels of grooming. VFD infants showed the most sustained clinging to mother, the lowest levels of social play and exploration, the highest levels of affective disturbance, and repeated evidence of depression as the study progressed. These findings suggest that in monkeys, as in humans, when, because of competing demands, mothers are psychologically unavailable to their infants, attachments are less secure, normal development is disrupted, and psychopathological patterns are more likely to emerge.

Animals↗
PubMed1980

Amino acid substitutions in protein biosynthesis. Poly(A)-directed polyphenylalanine synthesis.

The fidelity of protein biosynthesis in vitro was studied quantitatively in a well defined system that employed poly(A) as a message for the elaboration of phenylalanine-containing polypeptides from Escherichia coli phenylalanyl-tRNALys. Admixture of phenylalanyl-tRNALys and lysyl-tRNALys in three different ratios resulted in the efficient formation of peptides that contained the amino acids in the same ratios in which they had been utilized in the individual incubation mixtures. The incorporation was also shown to be codon-specific in a quantitative sense; the poly(A)-directed incorporation of [14C]phenylalanine from phenylalanyl-tRNALys was unaffected by [3H]phenylalanyl tRNAPhe, by arginyl-tRNA (one species of which responds to the codon triplet AGA) or by unfractionated E. coli tRNA. These findings suggest that the transfer of amino acids from (misacylated) tRNAs into polypeptides in vitro is as predicted by the adapter hypothesis and that such systems can operate with sufficient fidelity to permit the preparation of proteins having defined amino acid substitutions.

Amino Acyl-tRNA Synthetases↗
PubMed1993

[Acculturation, stress and mental health in Lebanese immigrants in Montreal].

This cross-sectional study examined the effect of immigration and acculturative stress on the mental health of a sample of 197 Lebanese immigrants in Montreal. An Orthogonal Model of Cultural Identification was used to determine whether the acculturation style adopted by immigrants had any effect on mental health or on acculturative stress. Results revealed no significant differences in psychological distress between the Lebanese sample and a comparative group of Quebec native-born. Among the indices of acculturative stress, adaptation problems alone predicted psychological distress. Finally, acculturation styles did not have any effect on psychological distress or on acculturative stress indices, with discrimination excepted. Individuals who adopted the Assimilation style reported less discrimination than those in the Ethnocentric and Integration groups. Results are discussed with reference to findings reported in the literature on Canadian studies.

Acculturation↗
PubMed2005

Predicting early adolescent gang involvement from middle school adaptation.

This study examined the role of adaptation in the first year of middle school (Grade 6, age 11) to affiliation with gangs by the last year of middle school (Grade 8, age 13). The sample consisted of 714 European American (EA) and African American (AA) boys and girls. Specifically, academic grades, reports of antisocial behavior, and peer relations in 6th grade were used to predict multiple measures of gang involvement by 8th grade. The multiple measures of gang involvement included self-, peer, teacher, and counselor reports. Unexpectedly, self-report measures of gang involvement did not correlate highly with peer and school staff reports. The results, however, were similar for other and self-report measures of gang involvement. Mean level analyses revealed statistically reliable differences in 8th-grade gang involvement as a function of the youth gender and ethnicity. Structural equation prediction models revealed that peer nominations of rejection, acceptance, academic failure, and antisocial behavior were predictive of gang involvement for most youth. These findings suggest that the youth level of problem behavior and the school ecology (e.g., peer rejection, school failure) require attention in the design of interventions to prevent the formation of gangs among high-risk young adolescents.

Adaptation, Psychological↗
PubMed1990

Saturation and purity of near-threshold spectral increments on achromatic backgrounds.

Vector models of color vision predict that the chromatic saturation of near-threshold incremental stimuli should grow with increasing achromatic adaptation. In contrast, colorimetric models predict that saturation should decrease with increasing adaptation in correspondence with excitation purity. An experimental test disagrees with both predictions, but is consistent with a two-process model of chromatic adaptation and contrast. Foveal monochromatic test stimuli 0.6 log unit above threshold were superposed on achromatic backgrounds with retinal illuminances of up to 5.3 log Td. Saturation and purity both decreased as background illuminance increased up to 2 log Td, but the saturation decrease was relatively small. As background illuminance increased above 2 log Td, purity remained nearly constant and saturation often increased, making the overall saturation function U-shaped. Thus, a purity of 0.1 at high background illuminance could sometimes elicit a higher saturation estimate than a purity of 0.9 at low background illuminance.

Adaptation, Ocular↗
PubMed2005

Prediction of gastro-intestinal absorption using multivariate adaptive regression splines.

Multivariate adaptive regression splines (MARS) and a derived method two-step MARS (TMARS) were used for modelling the gastro-intestinal absorption of 140 drug-like molecules. The published absorption values for these molecules were used as response variable and calculated molecular descriptors as potential explanatory variables. Both methods were compared and their potential use in quantitative structure-activity relationship (QSAR) context evaluated. The predictive abilities of the models were studied using different sequences of Monte Carlo cross validation (MCCV). It was shown that both types of models had good predictive abilities and that for the data used, MARS gave better results than TMARS. It could be concluded that both methods could be valuable for QSAR modelling.

Algorithms↗
PubMed2003

Interpersonal relatedness, self-definition, and their motivational orientation during adolescence: a theoretical and empirical integration.

The authors examined a theoretical model linking interpersonal relatedness and self-definition (S.J. Blatt, 1974), autonomous and controlled regulation (E. L. Deci & R. M. Ryan, 1985), and negative and positive life events in adolescence (N = 860). They hypothesized that motivational orientation would mediate the effects of interpersonal relatedness and self-definition on life events. Self-criticism, a maladaptive form of self-definition, predicted less positive events, whereas efficacy, an adaptive form of self-definition, predicted more positive events. These effects were fully mediated by the absence and presence, respectively, of autonomous motivation. Controlled motivation, predicted by self-criticism and maladaptive neediness, did not predict negative events. Results illustrate the centrality of protective, pleasure-related processes in adaptive adolescent development.

Adaptation, Psychological↗
PubMedDate not supplied

Movement direction analysers: independence and bandwidth.

Opponent, or ratio, models of movement direction perception propose that pairs of analysers, sensitive to opposite directions, are linked in an opponent fashion. Alternatively, distribution models posit independence of movement direction analysers. To investigate analyser independence, a direction-selective adaptation experiment was conducted in which motion coherence thresholds for random-dot apparent motion stimuli were measured for upward, downward, leftward and rightward motion with and without prior adaptation to rightward motion. Coherence thresholds for rightward motion were elevated on average by 0.64 log units after adaptation. Thresholds for motion in the other directions remained unchanged. Since opponent models predict enhanced sensitivity after adaptation for the direction opposite that of adaptation, these results suggest that movement direction analysers operate independently. In a second experiment subjects adapted to a bidirectional stimulus containing an equal number of leftward and rightward moving dots. Leftward and rightward coherence thresholds were elevated even though no motion aftereffects were produced. A third experiment in which coherence thresholds for test directions within a narrow range were measured with and without prior adaptation to motion in the direction of the range's mean showed that threshold elevation was maximal when test and adaptation direction were matched and fell off as the difference in adaptation and test direction increased. The resulting functions indicate that the bandwidth of movement direction analysers is between +/- 35 and +/- 40 deg, a value consistent with reported mean directional tuning functions of movement sensitive units in the middle temporal area but smaller than previously reported psychophysical values.

Adaptation, Ocular↗