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PubMed2005

Target selection in eye-hand coordination: Do we reach to where we look or do we look to where we reach?

During a goal-directed movement of the hand to a visual target the controlling nervous system depends on information provided by the visual system. This suggests that a coupling between these two systems is crucial. In a choice condition with two or more equivalent objects present at the same time the question arises whether we (a) reach for the object we have selected to look at or (b) look to the object we have selected to grasp. Therefore, we examined the preference of human subjects selecting the left or the right target and its correlation to the action to be performed (eye-, arm- or coordinated eye-arm movement) as well as the horizontal position of the target. Two targets were presented at the same distance to the left and right of a fixation point and the stimulus onset asynchrony (SOA) was adjusted until both targets were selected equally often. This balanced SOA was then taken as a quantitative measure of selection preference. We compared these preferences at three horizontal positions for the different movement types (eye, arm, both). The preferences of the 'arm' and 'coordinated eye-arm' movement types were correlated more strongly than the preferences of the other movement types. Thus, we look to where we have already selected to grasp. These findings provide evidence that in a coordinated movement of eyes and arm the control of gaze is a means to an end, namely a tool to conduct the arm movement properly.

Adult↗
PubMed2005

Estimation of the rate and effects of deleterious genomic mutations in finite populations with linkage disequilibrium.

Under several assumptions such as infinite population size with unlinked loci at linkage equilibrium (LD) under mutation-selection (M-S) balance, the rate (U), and the average effects (dominance and selection coefficients h and s) of deleterious genomic mutations (DGM) can be estimated by the Deng-Lynch method in some natural populations. However, all natural populations are finite in size and many of them are not large enough to be considered as approximately infinite. In the absence of an analytical estimation approach to characterize DGM in finite populations, we test the robustness and applicability of the Deng-Lynch method in finite populations with computer simulations. The results indicate that the estimation obtained by the Deng-Lynch method in finite populations with LD is generally robust when population size is greater than 400. With constant mutation effects, in outcrossing populations, the estimates U and ĥ are unbiased or only slightly upwardly biased, and ŝ is unbiased for most cases. In highly selfing populations, U and ĥ are upwardly biased, U is no more than 1.5U and ĥ is less than 1.1 h, and ŝ is either unbiased or slightly downwardly biased. With variable mutation effects, U ranges from 0.56 to 0.72U, and s ranges from 1.4 to 1.8s. Generally speaking, with the same finite population size, the estimation in outcrossing populations is better than in highly selfing populations. Given that even the order of the magnitude of the parameters of DMG (U in particular) is controversial, our investigation here may provide a basis for using the Deng-Lynch method to characterize DGM in finite populations of size greater than 400 in the presence of LD.

Genetics, Population↗
PubMed1995

Dietary energy intake, energy expenditure and activity pattern among selected rural and urban poor in Bangladesh.

Rural-urban and seasonal differences in energy balance were studied among selected free living subjects, chosen from the poor population groups in Bangladesh. Individual dietary energy intakes were estimated by a combination of 24 hours recall and weighing method. Time allocation to various occupational and non-occupational activities were recorded by observation and questioning, and energy expenditures were calculated by using FAO/WHO/UNU guidelines. The male working adults in both the population groups studied were found to be in negative energy balance in both the seasons observed. In Jan-Feb when employment opportunities for the rural poor were few all age and sex groups were in negative energy balance, and when employment opportunities improved during May-June the situation reversed except for the male working adults. In urban areas, on the other hand, all age and sex groups, except the male working adults were in positive energy balance in both the seasons. Rural children under 10 years, had significantly higher energy expenditure (P < 0.023) than their urban counterparts. Seasonal difference in energy expenditure among the rural male adults is quite high. In the urban group there was no such seasonal difference. Apparently very high rural-urban difference in energy expenditure of the male adults (18-30 y) in season 1 may be attributed to very high energy demanding activities in which the observed subjects in rural areas were engaged during this season. Compared to their urban counterparts rural male adults (18-30 yrs.) were found to be devoted significantly higher time in occupational and heavy household activities.

Adolescent↗
PubMed1977

Calcium balance and calcium requirements in middle-aged women.

Calcium balance performance was evaluated in 130 normal perimenopausal women ages 35 to 50, studied on their usual, self-selected dietary calcium intakes. Two distinct balance methods were used, one based on customary intake and output measurements, and the other based on absorption and clearance of two simultaneously administered calcium isotopes. Both methods yielded essentially identical results. Under study conditions as closely approximating normal living as possible, these women averaged -24 and -31 mg Ca/day by the two balance methods (exclusive of unmeasured dermal losses). More significantly, there was a positive correlation between intake and balance, with women on higher self-selected intakes exhibiting more positive balance than women selecting lower intakes. The calcium intake predicted from our data which would be required to produce an average balance of zero was 1.241 g/day. This is significantly in excess of the current recommended dietary allowance for calcium. The implications and significance of this discrepancy are explored in detail.

Absorption↗
PubMedDate not supplied

Quantitative measurement of improvement in sitting balance in children with spastic cerebral palsy after selective posterior rhizotomy.

Severe muscular spasticity encountered frequently in patients with spastic cerebral palsy not only affects patient locomotor function but also causes musculoskeletal complications. Significant reduction of spasticity over pelvis and lower limbs after selective posterior rhizotomy (SPR) results in improvement of trunk stability, locomotor function, and function of upper limbs also. The purpose of this study was to investigate the difference of sitting balance before and after SPR using a quantitative measurement in sitting stability represented as dispersion index provided by the Chattecx Balance System. Seventeen children with spastic cerebral palsy, ten boys and seven girls, with a mean age of 5.06 yr, underwent SPR. Their sitting stability under static and dynamic, visual and nonvisual testing conditions was assessed before SPR and three mo after SPR. Their sitting balance showed significant improvement at postoperative evaluation except for the static-nonvisual testing condition. Dispersion index under the dynamic testing condition was significantly higher than under the static testing condition, which implies that dynamic sitting balance was worse than static sitting balance in these patients. There was no statistical difference of sitting performance between visual and nonvisual condition both preoperatively and postoperatively. Quantitative measurement of dispersion index provided by the Chattecx Balance System offers an objective evidence of improvement in sitting balance for children after SPR.

Cerebral Palsy↗
PubMed1991

Nutrient interactions with reference to amino acid and protein metabolism in non-ruminants; particular emphasis on protein-energy relations in man.

Because the regulation of protein and energy balance is of major research interest in the nutrition and physiology of humans and animals, a selected account of interactions between protein and energy is given here, with particular emphasis on studies in human subjects. The discussion begins with reference to the relations between protein and energy intakes and nitrogen balance; selected aspects of the relations between protein dynamics and energy metabolism among the various mammalian species are then considered. This leads to a brief account of oxidative amino acid catabolism and its relevance to the assessment of amino acid requirements, particularly in adult man. It is concluded that obligatory oxidative losses of amino acids can be used to predict or approximate amino acid requirements in children and adults. The nitrogen-sparing properties of carbohydrate and lipid-derived fuels are then considered. Despite the well-known and profound, yet differential, impacts of dietary protein and energy sources, and their interactions on body protein balance, there remain wide gaps in our understanding of the mechanisms responsible for their effects, such as the quantitative and mechanistic involvement of hormones, including insulin and the counter-regulatory hormones, and the roles played by the major amino acids responsible for the interorgan transport of nitrogen and the regulation of urea production. Additional studies focusing on metabolic nitrogen trafficking would significantly enhance an understanding of how protein and energy interact to achieve the efficient utilization of dietary protein for maintenance and promotion of lean body gain.

Alanine↗
PubMed2004

Mitochondrial cytochrome B DNA variation in the high-fecundity atlantic cod: trans-atlantic clines and shallow gene genealogy.

An analysis of sequence variation of 250 bp of the mitochondrial cytochrome b gene of 1278 Atlantic cod Gadus morhua ranging from Newfoundland to the Baltic shows four high-frequency (>8%) haplotypes and a number of rare and singleton haplotypes. Variation is primarily synonymous mutations. Natural selection acting directly on these variants is either absent or very weak. Common haplotypes show regular trans-Atlantic clines in frequencies and each of them reaches its highest frequency in a particular country. A shallow multifurcating constellation gene genealogy implies young age and recent turnover of polymorphism. Haplotypes characterizing populations at opposite ends of the geographic distribution in Newfoundland and the Baltic are mutationally closest together. The haplotypes are young and have risen rapidly in frequency. Observed differentiation among countries is due primarily to clinal variation. Hypotheses of historical isolation and polymorphisms balanced by local selection and gene flow are unlikely. Instead the results are explained by demic selection of mitochondria carried by highly fit females winning reproductive sweepstakes. By inference the Atlantic cod, a very high-fecundity vertebrate, is characterized by a high variance of offspring number and strong natural selection that leads to very low effective to actual population sizes.

Analysis of Variance↗
PubMed2005

The prion protein gene in humans revisited: lessons from a worldwide resequencing study.

Ample evidence has accumulated showing that different coding variants of the PRNP gene confer differential susceptibility for prion diseases. Here we evaluate the patterns of nucleotide variation in PRNP exon 2, which includes all the protein-coding sequence, by resequencing a worldwide sample of 174 humans for 2378 bp. In line with previous studies, we found two main haplotypes differentiated by nonsynonymous substitution in codon 129. Our analyses reveal the worldwide pattern of variation at the PRNP gene to be inconsistent with neutral expectations, indicating instead an excess of low-frequency variants, a footprint of the action of either positive or purifying selection. A comparison of neutrality test statistics for PRNP with other human genes indicates that the signal of positive selection on PRNP is stronger than expected from a possible confounding genome-wide background signal of population expansion. Two main conclusions arise from our analysis. First, the existence of an ancient, stable, balanced polymorphism that has been claimed in a previous study and related to cannibalism can be rejected and is shown to be due to ascertainment bias. Second, our results are consistent with a complex history of selection including mainly positive selection, even if short local periods of balancing selection (Kuru-like episodes), or even a weak purifying selection model, are consistent with our data.

Amino Acid Substitution↗
PubMed2002

No relationship exists between the correction of the thoracic and the lumbar curves after selective thoracic fusion for adolescent idiopathic scoliosis King type II.

In this study we focus on idiopathic scoliosis with a primary thoracic curve and a secondary lumbar curve. We were interested in how the lumbar curve corrects following selective thoracic fusion and whether one can explain or predict the behaviour of the lumbar curve. In the literature it is said that, if the lower level of fusion is properly selected, the lumbar curve spontaneously corrects to balance the thoracic curve after selective thoracic fusion. Most authors have assumed a mechanism whereby improvement of the lumbar curve occurs through counterbalancing the surgical correction of the thoracic curve. The correction of the lumbar curve is said to echo the correction obtained for the thoracic curve. Because of these hypotheses, we postulate there should be a correlation between the correction of the lumbar and the thoracic curves of a scoliosis. To validate this hypothesis, we performed a retrospective study on 27 patients with King type II adolescent idiopathic scoliosis treated by selective thoracic fusion. The mean preoperative Cobb angles were 54 degrees for the thoracic curve and 34 degrees for the lumbar curve. Postoperatively they were 31 degrees and 22 degrees respectively. Using Pearson correlation analysis, we found no significant correlation between the relative corrections of the individual thoracic and lumbar curves. Moreover, there was a decrease in the correlation between the thoracic and lumbar curve after operation (preoperative R=0.787, postoperative R=0.364). These results show that the correction of the lumbar curve is not a reflection of the thoracic correction. The exact mechanism by which the lumbar spine corrects remains to be elucidated.

Adolescent↗
PubMed1984

[Amplification of the high production and low production nature of antibodies produced by the genetic selection of mice. Correlation between immunodeficiency and the incidence of lymphoma].

Five bidirectional selective breedings have been carried out in mice for quantitative antibody responses to various natural immunogens. Appropriate crosses between the five "high responder" lines and between the five "low responder" lines resulting from these selections, were performed to obtain balanced hybrid populations. These populations were further selected for antibody production on the basis of multiple responses i.e., responses to all the antigens used in the previous separate selections. The result was a marked amplification of the interline divergence. The low line in particular has a profound deficiency for both primary and secondary responses. Moreover a high incidence of lymphomas was observed among these low responder mice (up to 42%).

Animals↗
PubMed2002

Origins of the machinery of recombination and sex.

Mutation plays the primary role in evolution that Weismann mistakenly attributed to sex. Homologous recombination, as in sex, is important for population genetics--shuffling of minor variants, but relatively insignificant for large-scale evolution. Major evolutionary innovations depend much more on illegitimate recombination, which makes novel genes by gene duplication and by gene chimaerisation--essentially mutational forces. The machinery of recombination and sex evolved in two distinct bouts of quantum evolution separated by nearly 3 Gy of stasis; I discuss their nature and causes. The dominant selective force in the evolution of recombination and sex has been selection for replicational fidelity and viability; without the recombination machinery, accurate reproduction, stasis, resistance to radical deleterious evolutionary change and preservation of evolutionary innovations would be impossible. Recombination proteins betray in their phylogeny and domain structure a key role for gene duplication and chimaerisation in their own origin. They arose about 3.8 Gy ago to enable faithful replication and segregation of the first circular DNA genomes in precellular ancestors of Gram-negative eubacteria. Then they were recruited and modified by selfish genetic parasites (viruses; transposons) to help them spread from host to host. Bacteria differ fundamentally from eukaryotes in that gene transfer between cells, whether incidental to their absorptive feeding on DNA and virus infection or directly by plasmids, involves only genomic fragments. This was radically changed by the neomuran revolution about 850 million years ago when a posibacterium evolved into the thermophilic cenancestor of eukaryotes and archaebacteria (jointly called neomurans), radically modifying or substituting its DNA-handling enzymes (those responsible for transcription as well as for replication, repair and recombination) as a coadaptive consequence of the origin of core histones to stabilise its chromosome. Substitution of glycoprotein for peptidoglycan walls in the neomuran ancestor and the evolution of an endoskeleton and endomembrane system in eukaryotes alone required the origin of nuclei, mitosis and novel cell cycle controls and enabled them to evolve cell fusion and thereby the combination of whole genomes from different cells. Meiosis evolved because of resulting selection for periodic ploidy reduction, with incidental consequences for intrapopulation genetic exchange. Little modification was needed to recombination enzymes or to the ancient bacterial catalysts of homology search by spontaneous base pairing to mediate chromosome pairing. The key innovation was the origin of meiotic cohesins delaying centromere splitting to allow two successive divisions before reversion to vegetative growth and replication, necessarily yielding two-step meiosis. Also significant was the evolution of synaptonemal complexes to stabilise bivalents and of monopolins to orient sister centromeres to one spindle pole. The primary significance of sex was not to promote evolutionary change but to limit it by facilitating ploidy cycles to balance the conflicting selective forces acting on rapidly growing phagotrophic protozoa and starved dormant cysts subject to radiation and other damage.

Animals↗
PubMed1985

Selective inhibitory effects of thyroid hormones on estrogen-induced protein synthesis in chick embryo liver.

We have investigated the effect of thyroid hormones on estrogen-induced responses in embryonic chick liver. Administration of thyroid hormones inhibits estrogen induction of vitellogenin, as well as of apoprotein-II of very low density lipoprotein (VLDL apo-II). A proportionate decrease in the concentration of hepatic salt-soluble nuclear estrogen receptor is also observed. In contrast, estrogen stimulation of apoprotein-B (VLDL apo-B) synthesis is relatively resistant to inhibition. The inhibitory effects of the thyroid hormones could be due to increased metabolism and clearance of estradiol-17 beta in their presence. The relative resistance of estrogen-induced VLDL apo-B synthesis to thyroid hormone inhibition can be explained by its greater sensitivity to low doses of estradiol. In addition, experiments with the antithyroid agent thiourea suggest that, in vivo, estrogen-induced responses could be balanced by the selective inhibitory effects of thyroid hormones.

Animals↗
PubMed2000

[Assessment of routine mobility in geriatrics using static posturography--a population based study].

In a population-based study of 110 women between 53 and 82 years of age (mean age 64.5 +/- 7.9 years) static posturography data were compared to functional items of gait and balance in common geriatric mobility scales. Posturographic data of double-stance with eyes open and eyes closed (DSEO; DSEC) did not differ from those of a group of healthy women previously tested for intact nervous system function. The total neuromuscular score--roughly corresponding to the well-known Tinetti score--did not correlate to the posturographic measures. DSEC correlated with the items "rapid walking" and "single-stance left leg". Age, vision, and neuropsychologic test results correlated with DSEO, "rapid walking", "single-stance right leg", "single-stance left leg", and "walking a figure eight". Multiple linear regression confirmed the impact of age, vision, DSEO, and DSEC on "rapid walking" with a 34% variance explanation. Posturographic parameters did predict other selected gait and balance items. When used in older women living independently in the community, parameters of static posturography reflect to some extent the functional disabilities of gait and balance.

Activities of Daily Living↗
PubMed2001

Albinism and phenotype of barn swallows (Hirundo rustica) from Chernobyl.

The effects of mutation on phenotypic expression are supposed to be mainly deleterious because mutations disrupt the expression of genes that function relatively well under current environmental conditions. Thus, mutations are assumed to give rise to deviant phenotypes that are generally selected against. Radioactive contamination in the Chernobyl region of Ukraine is associated with a significant increase by a factor two to 10 in mutation rate in microsatellite markers of the barn swallow, Hirundo rustica. Barn swallows from Chernobyl had a temporally constant, elevated frequency of partial albinism compared to the situation before radioactive contamination and compared to birds from a control area. Albinism disproportionately affected the carotenoid-based plumage of the head, suggesting that carotenoid metabolism is particularly susceptible to the effects of radiation. Individuals with partially albinistic plumage had, on average, lower mean phenotypic values than other birds, and this was particularly the case for males. Furthermore, differences in phenotypic variation, as determined using Levene's test, were significantly larger in partial albinos compared to nonalbinos in males, but not in females, even though the null expectation would be the opposite due to the lower mean phenotypic values of partial albinos. Although small phenotypes were commonly associated with germline mutations, there was no general decrease in overall body size during the period 1991-2000, implying that small individuals were selected against. Because partial albinism is disfavored by natural selection, the effects of mutations are deleterious, giving rise to a balance between mutation and selection.

Albinism↗
PubMed1977

Physiologic measures of nonhuman primates during physical restraint and chemical immobilization.

The arterial acid-base balance and other selected physiologic measures of physically restrained and chemically immobilized nonhuman primates from the families Callithricidae, Cebidae, Cercopithecidae, and Pongidae were compared. The physically restrained primates had significantly lower pH, pCO2, and base excess values, but they had significantly higher pO2 values, rectal temperatures, and pulse and respiration rates. Of 56 physically restrained primates, 30 (54%) experienced severe metabolic acidosis, with pH values less than 7.2; 15 (27% of total) had pH values less than 7.1. Two types of behavior were observed during the physical restraint of golden marmosets. Some of the marmosets were excited during restraint, with a great deal of struggling and vocalizing. The other marmosets were quiet and calm, with minimal struggling. The excited group had significantly lower pH, pCO2, and base excess values, but significantly higher pO2 values, rectal temperatures, and pulse and respiration rates. Primates immobilized with ketamine or tiletaminezolazepam had a near normal acid-base balance and were handled more easily than the physically restrained animals.

Animals↗
PubMed1997

Validation of multifrequency bioelectrical impedance analysis in monitoring fluid balance in healthy elderly subjects.

BACKGROUND: Multifrequency Bioelectrical Impedance Analysis (MFBIA) is a novel method to assess body composition in elderly subjects. However, it is unclear whether MFBIA can detect changes in body water compartments in elders. We aimed to determine the within-subject variability of MFBIA and the responsiveness to a diuretic intervention in aged subjects with a stable fluid balance. METHODS: We selected 12 healthy active elderly subjects (5 male, 7 female) with a mean age of 75 years. Total body water and extracellular fluid (ECF) were measured by deuterium oxide- and potassium bromide-dilution techniques. Within-subject variability in total body MFBIA was assessed by performing four measurements at 1, 5, 50, and 100 kHz within a 2-month period. Subsequently, responsiveness of MFBIA to the ECF loss caused by oral administration of 40 mg of furosemide was determined. RESULTS: Within-subject variability in MFBIA at 1, 5, 50, and 100 kHz expressed as standard deviations was 21, 19, 14, and 14 Ohm (omega), respectively. Furosemide caused a mean weight loss of 1.8 +/- 0.6 kg, which resulted in significant increases in impedance of 57 +/- 24 omega at 1 kHz and 37 +/- 12 omega at 100 kHz (p < .001). The responsiveness of MFBIA for the diuretic intervention was best at 5 kHz (responsiveness index = 1.98). CONCLUSIONS: Within-subject variability of MFBIA was small in healthy elderly subjects with stable fluid balance. Responsiveness of MFBIA to 9% furosemide-induced ECF loss was excellent. These data support the necessity for further clinical assessment of the value of MFBIA in monitoring fluid balance in geriatric patients.

Aged↗
PubMed2002

Heritability, reliability of genetic evaluations and response to selection in proportional hazard models.

The purposes of this study were 1) to investigate the heritability, reliability, and selection response for survival traits following a Weibull frailty proportional hazard model; and 2) to examine the relationship between genetic parameters from a Weibull model, a discrete proportional hazard model, and a binary data analysis using a linear model. Both analytical methods and Monte Carlo simulations were used to achieve these aims. Data were simulated using the Weibull frailty model with two different shapes of the Weibull distribution. Breeding values of 100 unrelated sires with 50 to 100 progeny (with different levels of censoring) were generated from a normal distribution and two different sire variances. For analysis of longevity data on the discrete scale, simulated data were transformed to a discrete scale using arbitrary ends of discrete intervals of 400, 800, or 1200 d. For binary data analysis, an individual's longevity was either 0 (when longevity was less than the end of interval) or 1 (when longevity was equal or greater than the end of interval). Three different statistical models were investigated in this study: a Weibull model, a discrete-time model (a proportional hazard model assuming that the survival data are measured on a discrete scale with few classes), and a linear model based upon binary data. An alternative derivation using basic expressions of reliabilities in sire models suggests a simple equation for the heritability on the original scale (effective heritability) that is not dependent on the Weibull parameters. The predictions of reliabilities using the proposed formulae in this study are in very good agreement with reliabilities observed from simulations. In general, the estimates of reliability from either the discrete model or the binary data analysis were close to estimates from the Weibull model for a given number of uncensored records in this simplified case of a balanced design. Although selection response from the binary data analysis depends on the end of interval point, there is a relatively good agreement between selection responses in the Weibull model and the binary data analysis. In general, when the underlying survival data is from a Weibull distribution, it appears that the method of analyzing data does not greatly affect the results in terms of sire ranking or response to selection, at least for the simplified context considered in this study.

Animals↗