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PubMed2003

Interventions for intermittent distance exotropia.

BACKGROUND: The clinical management of intermittent distance exotropia has been discussed frequently in the literature but there is a lack of clarity regarding the indications for intervention, the most effective type and the optimum age at which it should be carried out. OBJECTIVES: The objective of this review is to assess intervention criteria, the effects of various surgical and non-surgical treatments in people with intermittent distance exotropia and to determine the significance of factors such as age with respect to outcome. SEARCH STRATEGY: We searched the Cochrane Central Register of Controlled Trials - CENTRAL (which contains the Cochrane Eyes and Vision Group trials register) on the Cochrane Library (Issue 4 2002), MEDLINE (1966 to November 2002), EMBASE (1980 to November 2002) and LILACS (Latin American and Caribbean Literature on Health Sciences) (1966 to 2002). We manually searched the British Orthoptic Journal, proceedings of the European Strabismological Association (ESA), International Strabismological Association (ISA) and American Academy of Paediatric Ophthalmology and Strabismus meeting (AAPOS). We contacted researchers who are active in the field for information about further published or unpublished studies. There were no language restrictions in the manual or electronic searches. SELECTION CRITERIA: We planned to include randomised controlled trials of any surgical or non-surgical treatment for intermittent distance exotropia. DATA COLLECTION AND ANALYSIS: Each reviewer independently assessed study abstracts identified from database and manual searches. Reviewer analysis was then compared and full papers for appropriate studies were obtained. MAIN RESULTS: No studies were found that met our selection criteria and therefore none were included for analysis. REVIEWER'S CONCLUSIONS: The available literature consists mainly of retrospective case reviews. These are difficult to compare and analyse due to a large variation in the definition of intermittent distance exotropia, intervention criteria and outcome measures. However there seems to be general agreement that non-surgical treatment is most appropriate in small angle deviations or as a supplement to surgery. Studies were found supporting both early and late surgical intervention so the optimal timing of surgical intervention cannot be concluded. Recent work indicates that bilateral surgery may be the most effective surgical procedure in these cases. There is clearly a need for carefully planned clinical trials to be undertaken to improve the evidence base for the management of this condition.

Exotropia↗

PubMed2003

Sirenomelia sequence according to the distance between the first sacral vertebra and the ilia.

The development of the iliac bones and lower limbs are parallel processes depending on the normal ontogeny of the caudal blastema [O'Rahilly and Müller, 1989; Opitz, 1993; Opitz et al., 2000]. We hypothesized that the pathogenetic mechanisms leading to fused lower limbs would in parallel displace the ilia caudally and medially and that the degree of this displacement might correlate with the severity of the iliac and lower limb defects. Thus the purpose of the study was to test this hypothesis in a sample of 12 sirenomelic fetuses. The fetuses GA 16-39 weeks, spontaneously or therapeutically aborted, were radiographed in the frontal projection as part of a requested autopsy. From each radiograph, a line was drawn connecting the most cranial part or the two ilia. After that the distance was measured vertically between this line and the most cranial part of the first sacral vertebral body (iliac-sacral distance (ISD)). A second distance was measured horizontally between the most lateral part of the two iliae (bi-iliac distance (BD)). As a result, ISD correlates with the iliac/femur phenotype. Separate ilia and femora occur only in cases with normal ISD. Fused ilia or femora or both are seen only in fetuses with mildly increased ISD, whereas a single iliac bone and femur occur only in cases with greatly increased ISD. The increase of the ISD does not correlate with the severity of more distal limb involvement. There was a correlation between the ISD and the BD values; the higher the ISD, the shorter the BD. Based on these findings, we propose an extended classification of Sirenomelia to be tested by other researchers.

Ectromelia↗

PubMed1976

Within and between race distances in population studies based on discrete traits of the human skull.

A battery of 24 discrete cranial traits has been tested for its power to discriminate within- and between-race distances for the two principal North American indigenous populations: Indian (7 samples, N = 366) and Eskimo (7 samples, N = 451). One of the Indian samples, Dakota Sioux, has been split according to tribal subdivisions, the intra-tribal mean distance providing a parameter of very close relationship. In addition, two Negro samples provide a parameter of relationship phylogenetically remote from the Amerinds. Separate male-female analysis of the three largest samples indicates that distances for pooled samples are not seriously affected by the sex component. Within-race distances (C. A. B. Smith's Measure of Divergence, MD), are smaller than between-race at the .00001 level of significance (Mann-Whitney U test) for both Indian-Eskimo and Amerind-Negro comparisons. The features most powerful for Indian-Eskimo and Amerind-Negro comparisons. The features most powerful for Indian-Eskimo discrimination are revealed by their percent contribution to the mean of 49 MD's. The African heritage of American Blacks is reflected in a characteristic Negro pattern of trait frequencies different from the Amerind. This battery of features yields valid taxonomical information useful in conjunction with other physical data to reconstruct affinities of extinct populations.

Black People↗

PubMed1977

Congruence of distance matrices based on cranial discrete traits, cranial measurements, and linguistic-geographic criteria in five Alaskan populations.

Biological distances (C.A.B. Smith's Measure of Divergence) based on 25 nonmetric skull variants have been compared with distances (Mahalanobis' D2) based on cranial measurements of four Eskimo populations representing the Yupik subdivision of the Eskaleut linguistic stock, and one Aleut population. The ranking of Measures of Divergence (pooled-sex samples) for ten pairwise comparisons is significantly correlated (Spearman's rs) with both the male and female rankings of the F-values of D2. In addition, the non-metric distances showed stronger concordance than the metric distances with a hierarchy based on linguistic and geographical affinities. These findings indicate that, depending upon the particular battery of variants used, discrete traits provide valid taxonomical information in the study of extinct human populations.

Alaska↗

PubMed1980

Gm and Inv studies on eight Iranian populations with distance measures among the six from the Caspian Littoral.

Serum samples from six populations living in the Caspian Littoral anf from two populations (Armenians and Muslims) living in Teheran were tested for Gm(1,2,3,5,6,10,11,13,14,17,21,24,26) and for Inv(1). The Gm data show that all six populations from the Littoral have African and Mongoloid admixture. Genetic distance among these six populations was estimated using Nei's standard distance measure, and its standard error, based on the 11 loci analyzed by Kirk et al. (1977); on these 11 loci plus Gm; and on the foregoing 12-plus Inv. Only the distance measures for populations 1 and 4, 2 and 3 are significantly different in all three measures of distances, and then only at the 5% level. More loci will have to be studied before firmly based conclusions may be drawn concerning the relation of these populations to each other. The Armenian population, unlike the remaining seven populations, shows no evidence of African admixture, but it does show Mongoloid admixture. The Muslim population shows African and Mongoloid admixture and, in addition, has the unusual haplotype Gm3,5,10,11,14,17,26 at polymorphic frequencies.

Armenia↗

PubMed1982

Sole dermatoglyphics in the Forest Nentsy, Nganasans, and Chukchi: dermatoglyphic distances.

Sole dermatoglyphics of the aborigines of Northwestern Siberia, Taimir, and Kamchatka are presented in this paper. The distance coefficients based on various combinations of dermatoglyphic traits depending on their heritability were estimated. These were compared with the overall dermatoglyphic distance coefficients as well as with the genetic (dermatoglyphic) distance coefficients based on six blood groups (ABO, MNSs, P, Fy, Jk, Kp). Genetic interpretation of the distances was attempted in connection with analysis of differences or similarities between these populations.

Asian People↗

PubMed1986

Convergence of genetic distances in a migration matrix model.

A recurring problem with the use of migration matrix models of genetic differentiation has to do with their convergence properties. In practice, predictions can be drawn from these models only at equilibrium; but in the case of the standard predictors (most of which are modifications of Wright's FST), it can take an unrealistically large number of generations to approach equilibrium. An alternative set of predictors, the set of all pairwise genetic distances among the populations that define the rows and columns of the migration matrix, is investigated here. These distances are shown analytically to converge much more rapidly than the more commonly used predictors. In an application of the model to migration data on a human population from Papua New Guinea, it takes only about three to four generations for the pairwise distances to converge, in contrast to more than 100 generations for one of the standard predictors. In this case, moreover, the distances predicted by the model at equilibrium are similar to those calculated from the available genetic data.

Alleles↗

PubMed1987

Partial correlation of distance matrices in studies of population structure.

Anthropological studies of human population structure commonly compare various monogenic and polygenic (metric) distance matrices to distance matrices obtained from measures of geographical dispersion, linguistic differences, and migration patterns in an attempt to infer something about the effects of evolutionary factors (drift and differential selection, in particular). It is, though, commonly recognized that geography, language, and migration patterns may be intercorrelated due to the common effects of historical and social processes. Previous attempts to deal with the problems of assessing relative effects among such sets of intercorrelated factors using partial correlations have resulted in coefficients that are either not well defined or have no known sampling distribution or both. Here, we outline a general approach to partialling distance matrices that results in well-defined coefficients and valid significance testing procedures. Application of the matrix partialling methods to a variety of distance matrices obtained for a sample of eight ethnolinguistic groups from the Harvard Solomon Islands Expedition (Friedlaender et al., 1986) reveals a close association between language dissimilarity and dermatoglyphics controlling for geography, thus reinforcing earlier suggestions that dermatoglyphics, properly used, reflect historical relationships of groups in this region better than do anthropometry, odontometrics, or small batteries of blood polymorphisms.

Anthropology↗

PubMed1992

Cross-cultural analysis of migration rates: effects of geographic distance and population size.

A model is developed that treats migration rates among populations as a function of the geographic distance between them and the size of both sources and recipient population. Specifically, mij/mjj = a(Ni/Nj)pe-bd, where mij/mjj is the relative migration rate into population j from population i, Ni is the size of the source population, Nj is the size of the recipient population, d is the geographic distance between populations i and j, p is a measure of differential density-dependence, b is a measure of distance decay, and a is an adjustment parameter with little demographic meaning. Methods of parameter estimation and hypothesis testing using maximum likelihood are outlined. These methods are applied to migration matrix data from 13 samples obtained from the literature representing a wide range of ecological settings. All samples show a significant effect of geographic distance on migration, and all but one show a significant effect of differential population size. All but one sample show an overall tendency for migration to be negative density-dependent; that is, the relative migration rate is greater from larger populations to smaller populations than the reverse.

Emigration and Immigration↗

PubMed2002

Determination of safety distance limits for a human near a cellular base station antenna, adopting the IEEE standard or ICNIRP guidelines.

This paper investigates the minimum distance for a human body in the near field of a cellular telephone base station antenna for which there is compliance with the IEEE or ICNIRP threshold values for radio frequency electromagnetic energy absorption in the human body. First, local maximum specific absorption rates (SARs), measured and averaged over volumes equivalent to 1 and to 10 g tissue within the trunk region of a physical, liquid filled shell phantom facing and irradiated by a typical GSM 900 base station antenna, were compared to corresponding calculated SAR values. The calculation used a homogeneous Visible Human body model in front of a simulated base station antenna of the same type. Both real and simulated base station antennas operated at 935 MHz. Antenna-body distances were between 1 and 65 cm. The agreement between measurements and calculations was excellent. This gave confidence in the subsequent calculated SAR values for the heterogeneous Visible Human model, for which each tissue was assigned the currently accepted values for permittivity and conductivity at 935 MHz. Calculated SAR values within the trunk of the body were found to be about double those for the homogeneous case. When the IEEE standard and the ICNIRP guidelines are both to be complied with, the local SAR averaged over 1 g tissue was found to be the determining parameter. Emitted power values from the antenna that produced the maximum SAR value over 1 g specified in the IEEE standard at the base station are less than those needed to reach the ICNIRP threshold specified for the local SAR averaged over 10 g. For the GSM base station antenna investigated here operating at 935 MHz with 40 W emitted power, the model indicates that the human body should not be closer to the antenna than 18 cm for controlled environment exposure, or about 95 cm for uncontrolled environment exposure. These safe distance limits are for SARs averaged over 1 g tissue. The corresponding safety distance limits under the ICNIRP guidelines for SAR taken over 10 g tissue are 5 cm for occupational exposure and about 75 cm for general-public exposure.

Cell Phone↗

PubMed1987

Synthesis and chemiluminescence of copolymers of 5-amino-8-vinyl-phthalazine-1,4(2H,3H)-dione with methyl methacrylate or styrene, and of alpha, omega-bis[5-amino-phthalazine-1,4(2H,3H)-dion-]8-yl alkanes [= alpha, omega-bis(6-luminyl) alkanes]: investigations on an intramolecular 'distance effect'.

Oligomers of 5-amino-8-vinyl-phthalazine-1,4(2H,3H)-dione exhibit about 0.05% of the chemiluminescence quantum yield of the corresponding 'monomer unit', i.e. 5-amino-8-ethyl-phthalazine-1,4(2H,3H)-dione which has a similar quantum yield to luminol. The quantum yields of copolymers of 5-amino-8-vinyl-phthalazine-1,4(2H,3H)-dione (1a) with methyl methacrylate or with styrene increase up to 1000-fold, relative to the quantum yield of oligomers of (1a). Thus the monomer units of methyl methacrylate or styrene appear to act as 'spacers' between the lumigenic groups. alpha, omega-Bis[(5-amino-phthalazine-1,4(2H,3H)-dion-)8-yl] alkanes show an analogue 'distance' effect: the chemiluminescence quantum yield increases with increasing alkane chain length. As the fluorescence of the corresponding amino phthalates (which are intermediates in the synthesis of the phthalazine diones) is only slightly influenced by the distance between the lumigenic groups it is suggested that a mainly chemical 'distance effect' is working here: the smaller the intramolecular distance between the hydrazide groups the more inhibition exists in respect of the oxidative reaction producing the luminol-type chemiluminescence.

Chemical Phenomena↗

PubMed2006

The effect of distance to provider on employee response to changes in mental health benefits.

We assess whether distance to provider moderates the effect of a change in mental health benefits on treatment initiation of employees of a large US-based company for psychiatric disorders. Mental health treatment administrative claims data plus eligibility information provided by a Fortune 50 company for the years 1995-1998 are used for the analysis. The effect of distance is measured using the relative effect of the initiative on residents living far from providers compared to those living close to providers. We model the probability of treatment initiation using a random effects logit specification. We find that the effect of distance to provider has the potential to over-shadow other incentives to initiate treatment, especially at distances greater than 4 miles. These results lend further support to the notion that geographic dispersion of providers should be an important consideration when forming a selective contracting network.

Adolescent↗

PubMed1993

Activation, travel distance, and environmental change influence food carrying in rats with hippocampal, medial thalamic and septal lesions: implications for studies on hoarding and theories of hippocampal function.

Rats transport food from exposed areas to covered areas where they eat it or leave it. Although there is evidence that limbic structures play a role in food transport, their role is controversial. Here it was found that although many rats with large hippocampal, septal/diagonal band of Broca or dorsomedial thalamic lesions did not carry food but ate it where they found it, a few presentations of an auditory stimulus could restore food carrying. Once restored, most features of food carrying in hippocampal rats were normal in relation to food presentation schedules, deprivation levels, ambient illumination, circadian cycles, food size, and eating times. Nevertheless, food carrying impairments re-emerged when the testing environment was changed. Hippocampal rats were also excessively responsive to increases in travel distance and stopped carrying food at distances over which control rats would still carry large food pellets. Auditory stimulation did not restore food carrying over long travel distances. The findings that sensory stimulation, environmental change, and travel distance influence food carrying probabilities in rats with limbic system lesions is discussed in relation to research on limbic control of food hoarding and theories of limbic system function.

Animals↗

PubMed1986

The three-dimensional structure of alpha1-purothionin in solution: combined use of nuclear magnetic resonance, distance geometry and restrained molecular dynamics.

The determination of the three-dimensional solution structure of alpha1-purothionin using a combination of metric matrix distance geometry and restrained molecular dynamics calculations based on n.m.r. data is presented. The experimental data comprise complete sequence-specific proton resonance assignments, a set of 310 approximate interproton distance restraints derived from nuclear Overhauser effects, 27 Ø backbone torsion angle restraints derived from vicinal coupling constants, 4 distance restraints from hydrogen bonds and 12 distance restraints from disulphide bridges. The average atomic rms difference between the final nine converged structures and the mean structure obtained by averaging their coordinates is 1.5 +/- 0.1 å for the backbone atoms and 2.0 +/- 0.1 å for all atoms. The overall shape of alpha1-purothionin is that of the capital letter L, similar to that of crambin, with the longer arm comprising two approximately parallel alpha-helices and the shorter arm a strand and a mini anti-parallel beta sheet.

Journal Article↗

PubMed2007

Implementation and application of helix-helix distance and crossing angle restraint potentials.

Based on the definition of helix-helix distance and crossing angle introduced by Chothia et al. (J Mol Biol 1981, 145, 215), we have developed the restraint potentials by which the distance and crossing angle of two selected helices can be maintained around target values during molecular dynamics simulations. A series of assessments show that calculated restraint forces are numerically accurate. Since the restraint forces are only exerted on atoms which define the helical principal axes, each helix can rotate along its helical axis, depending on the helix-helix intermolecular interactions. Such a restraint potential enables us to characterize the helix-helix interactions at atomic details by sampling their conformational space around specific distance and crossing angle with (restraint) force-dependent fluctuations. Its efficacy is illustrated by calculating the potential of mean force as a function of helix-helix distance between two transmembrane helical peptides in an implicit membrane model.

Models, Molecular↗

PubMed2007

Theoretical studies on farnesyltransferase: the distances paradox explained.

In spite of the enormous interest that has been devoted to its study, the mechanism of the enzyme farnesyltransferase (FTase) remains the subject of several crucial doubts. In this article, we shed a new light in one of the most fundamental dilemmas that characterize the mechanism of this puzzling enzyme commonly referred to as the "distances paradox", which arises from the existence of a large 8-A distance between the two reactive atoms in the reaction catalyzed by this enzyme: a Zn-bound cysteine sulphur atom from a peptidic substrate and the farnesyldiphosphate (FPP) carbon 1. This distance must be overcome for the reaction to occur. In this study, the two possible alternatives were evaluated by combining molecular mechanics (AMBER) and quantum chemical calculations (B3LYP). Basically, our results have shown that an activation of the Zn-bound cysteine thiolate with subsequent displacement from the zinc coordination sphere towards the FPP carbon 1 is not a realistic hypothesis of overcoming the large distance reported in the crystallographic structures of the ternary complexes between the two reactive atoms, but that a rotation involving the FPP molecule can bring the two atoms closer with moderate energetic cost, coherent with previous experimental data. This conclusion opens the door to an understanding of the chemical step in the farnesylation reaction.

Binding Sites↗

PubMed1996

Distance of Conidial Discharge of Entomophthora muscae and Entomophthora schizophorae (Zygomycotina: Entomophthorales)

The distance traveled by conidia of the E. muscae species complex from cadavers of Musca domestica was measured. Laboratory strains of E. muscae and E. schizophorae, as well as a field-collected strain of E. muscae, were compared in darkness under still air conditions at 21°C. Most conidia were discharged <3.75 cm from the cadaver, with a range of 0 to 8.75 cm. When a fly cadaver was affixed to a vertical surface (normal death orientation), conidia discharged from the dorsum of the abdomen traveled further than conidia discharged from the lateral regions. Cadavers suspended in midair discharged similar numbers of laboratory strain E. muscae conidia similar distances from the venter, dorsum, or lateral abdomen. This suggested a boundary layer effect caused the reduced lateral discharge distance in earlier trials. Average discharge distance was positively related to cadaver size. A laboratory strain of E. muscae discharged conidia further than did a field strain of E. muscae and a laboratory strain of E. schizophorae.

Journal Article↗

PubMed1995

Global fold determination from a small number of distance restraints.

We have designed a distance geometry-based method for obtaining the tertiary fold of a protein from a limited number of structure-specific distance restraints and the secondary structure assignment. Interresidue distances were predicted from patterns of conserved hydrophobic amino acids deduced from multiple alignments. A simple model chain representing the protein was then folded by projecting its distance matrix into Euclidean spaces with gradually decreasing dimensionality until a final three-dimensional embedding was achieved. Tangled conformations produced by the projection steps were eliminated using a novel filtering algorithm. Information on various aspects of protein structure such as accessibility and chirality was incorporated into the conformation refinement, increasing the robustness of the algorithm. The method successfully identified the correct folds of three small proteins from a small number of restraints, indicating that it could serve as a useful computational tool in protein structure determination from NMR data.

Algorithms↗