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PubMed2000

Lanthanide ions bind specifically to an added "EF-hand" and orient a membrane protein in micelles for solution NMR spectroscopy.

Twelve amino acid residues corresponding to an "EF-hand" calcium-binding site were added to the N-terminus of a protein, providing a specific lanthanide ion binding that weakly orients the protein in solution. A comparison of spectra of the protein with and without the EF-hand residues demonstrates that the structure of the native protein is not perturbed by this modification, since there are minimal chemical shift changes. With a lanthanide but not calcium bound to the EF-hand, the protein is weakly oriented by the magnetic field, since residual dipolar couplings can be measured. Since the signs and magnitudes of the couplings varied with the type of lanthanide, this demonstrated the ability to obtain multiple orientations of the protein in solution. The sample is a membrane protein in lipid micelles that disrupted the commonly employed bicelle and filamentous phage solutions; therefore, the addition of a specific metal binding site in the form of an EF-hand may provide a general approach to orienting proteins where the addition of external agents is problematic. An additional benefit is that the lanthanide ions perturb the protein resonances in ways that provide unique orientational and distance constraints.

Amino Acid Sequence↗
PubMedDate not supplied

A strategy for determining the orientations of refractory particles for reconstruction from cryo-electron micrographs with particular reference to round, smooth-surfaced, icosahedral viruses.

Cryo-electron microscopy and three-dimensional image reconstruction are powerful tools for analyzing icosahedral virus capsids at resolutions that now extend below 1 nm. However, the validity of such density maps depends critically on correct identification of the viewing geometry of each particle in the data set. In some cases-for example, round capsids with low surface relief-it is difficult to identify orientations by conventional application of the two most widely used approaches-"common lines" and model-based iterative refinement. We describe here a strategy for determining the orientations of such refractory specimens. The key step is to determine reliable orientations for a base set of particles. For each particle, a list of candidate orientations is generated by common lines: correct orientations are then identified by computing a single-particle reconstruction for each candidate and then systematically matching their reprojections with the original images by visual criteria and cross-correlation analysis. This base set yields a first-generation reconstruction that is fed into the model-based procedure. This strategy has led to the structural determination of two viruses that, in our hands, resisted solution by other means.

Algorithms↗
PubMed1991

A horseradish peroxidase study of the fiber orientation in the facial nerve.

Horseradish peroxidase (HRP) was used to investigate the motor fiber orientation in the cat's intratemporal facial nerve. When HRP was applied to the zygomatic rami, HRP-labeled fibers were distributed diffusely throughout the labyrinthine and tympanic segments. On the other hand, distal to the chorda tympani entrance, a well-defined topographical orientation was found in the posterolateral aspect of the nerve. When HRP was applied to the buccal rami, topographical orientation was found in the posteromedial area of the distal mastoid segment. When HRP was applied to the posterior auricular rami, topographical orientation was found in the center to the anterior area of the distal mastoid segment. These results indicate that each branch of the facial motor nerve has a topographical orientation in the distal part of the mastoid segment, while nerve fibers are dispersed in the tympanic and labyrinthine segments.

Animals↗
PubMed1994

A fluorescence depolarization study of the orientational distribution of crossbridges in muscle fibres.

A fluorescence depolarization study of the orientational distribution of crossbridges in dye-labelled muscle fibres is presented. The characterization of this distribution is important since the rotation of crossbridges is a key element in the theory of muscle contraction. In this study we exploited the advantages of angle-resolved experiments to characterize the principal features of the orientational distribution of the crossbridges in the muscle fibre. The directions of the transition dipole moments in the frame of the dye and the orientation and motion of the dye relative to the crossbridge determined previously were explicitly incorporated into the analysis of the experimental data. This afforded the unequivocal determination of all the second and fourth rank order parameters. Moreover, this additional information provided discrimination between different models for the orientational behaviour of the crossbridges. Our results indicate that no change of orientation takes place upon a transition from rigor to relaxation. The experiments, however, do no rule out a conformational change of the myosin S1 during the transition.

Animals↗
PubMed1993

Functional associations between collagen fibre orientation and locomotor strain direction in cortical bone of the equine radius.

A novel technique for determining the collagen fibre orientation pattern of cross-sections of cortical bone was used to study mid-diaphyseal sections from the equine radius. Several in vivo strain gauge studies have demonstrated that this bone is loaded in bending during locomotion in such a way that the cranial cortex is consistently subjected to longitudinal tensile strains and the caudal cortex to longitudinal compressive strains. Twenty-three radii from 17 horses were studied. All the bones obtained from adult horses exhibited a consistent pattern of collagen fibre orientation across the cortex. The cranial cortex, subjected to intermittent tension, and the lateral and medial cortices, through which the neutral axis passes, contained predominantly longitudinally oriented collagen fibres. The caudal cortex, subjected to longitudinal compression during life, contained predominantly oblique/transverse collagen. This pattern was less evident in bones from foals. Microscopic analysis of the bones studied showed that primary lamellar bone was composed of predominantly longitudinal collagen fibres, irrespective of cortex. However, there was a strong relationship between cortical location and fibre orientation within remodelled bone. Secondary osteons which formed in the caudal (compressive) cortex contained predominantly oblique/transverse collagen, while those which formed elsewhere contained longitudinal collagen. This observation explained the developmental appearance of the characteristic macroscopic pattern of collagen fibre orientation across the whole cortex in the adult. These findings provide evidence for the existence of a relationship between the mechanical function of a bone with its architecture, and now demonstrate that it extends to the molecular level.

Aging↗
PubMed1977

The depth distribution of optimal stimulus orientations for neurones in cat area 17.

Neurones recording during penetrations through cat area 17 as near parallel to the radial fibre bundles as possible have been quantitatively tested as to their optimal orientation. Optimal orientation within any one penetration was similar though considerable variability was observed. Histological reconstruction and other considerations showed that this variability could not be attributed to poor penetration angle or limitations of the microelectrode technique. These results confirm that neurones with similar optimal orientations are found in all cortical layers at one cortical locus, but it is difficult to reconcile the variability observed with a mosaic-like distribution of orientation across the cortical surface. The findings were consistent, however, with the assumption of a continuous distribution of orientation sensitivity across the cortical surface with considerable superimposed scatter.

Animals↗
PubMed1981

Spermatogenesis in Sciara coprophila. I. Chromosome orientation on the monopolar spindle of meiosis I.

Meiosis I of spermatogenesis in the fungus fly, Sciara coprophila, has a monopolar spindle which collects the maternal and supernumerary L chromosome sets, while the paternal chromosomes migrate away from the single pole to be excluded in a bud. By inspection, the metacentric paternal chromosome IV moves with its centromere lagging rather than leading the direction of motion. Therefore, we wondered if all paternal homologues move in such a reverse orientation. To determine the orientation of the other homologues which are acrocentrics (chromosomes II, III, X), their centromeres were localized by use of the DAPI C-bonding technique. In addition, we characterized centromeric heterochromatin on polytene chromosomes by C-banding and in situ hybridization of satellite DNA isolated by Ag+-Cs2SO4 (rho CsC1 satellite I=1.698 g/ml; rho CsC1 satellite II=1.705 g/ml). The two satellite fractions were localized to the centromeric heterochromatin of all the chromosomes, and to a varying degree to all chromosome telomeres. By DAPI C-banding we could precisely locate each centromere band on polytene chromosomes, and these results agreed with those of satellite cRNA in situ hybridization. We then applied the DAPI C-banding technique to primary spermatocyte preparations, and determined that all paternal chromosomes migrate at anaphase I with their centromeres lagging rather than leading movement to the cell periphery. Since in polytene chromosomes the X chromosome contains a moderately fluorescent band on its noncentromeric end as well, in order to clarify its DAPI C-banding result in primary spermatocytes, we did in situ hybridization of (3)H nick-translated cloned rDNA, since rDNA is a convenient marker for the centromeric heterochromatin of the X. These data and the DAPI C-banding results indicate that the X as well as all th other paternal homologues display a reverse orientation (centromeres lag) as they migrate away from the single spindle pole to the cell periphery. - One model explaining this unusual paternal chromosome orientation is that there may be unique neocentromeric-like attachments to the non-centromeric free ends of these chromosomes. These attachments could serve to pull the paternal chromosomes to the cellular periphery as anaphase I progresses. In order to test this model, we analyzed anaphase I spermatocytes after a terminal block of heterochromatin had been removed from metacentric paternal chromosome IV by X-irradiation. We observed that when metacentric paternal chromosome IV is broken, it maintains its inverted "V" orientation rather than assuming a rod-like configuration. These data imply that there are no unique, terminal neocentromeric attachments to paternal chromosome IV as it progresses to the cellular periphery.

Animals↗
PubMed1983

Tangential preferential orientations of neuron processes in the rat neocortex.

The orientations in the tangential plane, i.e., parallel to the pial surface, of dendrites and axons in several functionally different areas of the rat neocortex were investigated. Using a large data base of over 30,000 measurements and the t-test and chi 2 test for significance, we found an overall preference of both dendrites and axons for the anteroposterior and adjacent orientations. The degree of preference varied from area to area and among different cortical laminae. Other variations were correlated with neuron type and dendritic rank (in a tree). The pyramidal cell dendritic fields show little orientation in the tangential plane, whereas a large fraction of the stellate cells are oriented. The overall preferential orientations are apparently related to brain axes and growth lines, whereas the variability is probably due to the influence of the functional topography.

Animals↗
PubMed1981

Does assignment of orientation to dot patterns reveal optimization processes in the visual system?

Sixty subjects were tested to assign orientation to ten dot patterns differing in their overall form and the number of dots in the pattern. The patterns were presented in four different positions in the visual field and their orientation was estimated in two ways. It was demonstrated that the assignment of orientation did not depend on the position of the pattern in the visual field as well as on the method of estimation used. A quantitative measure for the elongation of a dot pattern is proposed which correlates with the degree of ambiguity in orientation estimation. The greater the elongation the smaller the standard deviation of the estimates given. The distributions of the estimates for the ten patterns were analyzed. It was shown that they can be presented as superpositions of two or more groups of normally distributed estimates determined by some salient characteristics of the stimuli. Data are discussed from the point of view that assignment of orientation to dot patterns reveals the existence of optimization mechanisms in human brain that extract perceptual invariants from external stimulation.

Adult↗
PubMed1986

A method for measuring the orientation ("beat direction") of respiratory cilia.

We have created a method for measuring the orientation of cilia in the respiratory epithelium. Ciliary orientation is the direction perpendicular to the plane defined by the central tubules of the cilia and is an estimate of ciliary beat direction. Ciliary orientation can be estimated by measuring the angle between the plane defined by the central tubules and a reference line. The standard deviation of these measurements describes the variation present in the beat directions of the cilia. The reference line must be so chosen that the majority of measurements falls at about the middle of the 0 degree-180 degrees range. We tested measurements by using both a glass angle measure and a semiautomatic image analyzer (IBAS I). The latter approach was faster and more reproducible. We made our measurements of normal tissues on samples obtained from two healthy adult non-smokers. Measurements were made in four areas of each sample, with 59-110 cilia in each. The differences between the maximum and minimum angles of the ciliary orientation in the same area varied from 167.9 degrees to 85.4 degrees from the reference line. The standard deviation varied from 18.0 degrees to 35.4 degrees and we consider this to be a normal variation in ciliary orientation. Of the cilia, 57% were within a standard deviation of 20 degrees.

Adult↗
PubMed1976

Theory of fluorescence polarization of oriented pigment molecules in spherical arrays.

Theoretical results are presented which are appropriate for the analysis of the static polarized fluorescence experiment with oriented pigment molecules in spherical arrays (vesicles). Though the global orientation mediated over the whole sphere is isotropic, the fluorescent molecules may have preferred local orientation with respect to the local plane. As in a former paper, concerning fluroescence polarization in planar arrays, three basic (local) orientation distributions of the electronic transition moments are investigated, which may be expected to describe a wide class of real cases with sufficient accuracy. Analytic expressions for the degree of polarization are derived. One important result is that the degree of polarization may be extremely dependent on the local orientation of transition moments. Hence the usual method of determination of microviscosities from experiments with vesicles with the use of the theory of fluorescence polarization for macromolecules in solutions should be regarded with great caution.

Electromagnetic Phenomena↗
PubMed1987

Determination of the orientation of membrane vesicles derived from mitochondria.

Membrane vesicles of physiological as well as inverted orientation can be isolated from mitochondria. The presence of these vesicles in a membrane can be determined and quantitated by determining the differences between the two vesicle types in terms of rates of NADH oxidation, rates of oxidation of tricarboxylate cycle intermediates, rates of ATP hydrolysis and sensitivity to inhibitors, stimulation of respiration by exogenous cytochrome c, inhibition of respiration by polycationic proteins, and visualization of the ATPase by electron microscopy. Procedures to isolate the two membrane types and characteristics of homogeneously oriented preparations are described. Differences in data obtained with homogeneous vesicle preparations and with vesicles of mixed orientation are illustrated. Nonhomogeneously oriented preparations can be enriched in the desired vesicular type by the use of immunoprecipitation, affinity chromatography, and differential centrifugation. The concept of a hybrid vesicle containing oppositely oriented regions is not supported by experimental data.

Animals↗
PubMed1991

Sexual orientation, sexual identity, and sex-dimorphic behaviors in male twins.

Sexual orientation, sexual identity, and sex-dimorphic behaviors were assessed concurrently and retrospectively, for childhood, in 95 pairs of male monozygotic (MZ) twins and 63 pairs of dizygotic (DZ) twins. There was a significantly higher rate of adult homosexuality among the MZ than among DZ twins. We employed a model-fitting approach using LISREL to test for genetic and environmental influences on variation for each trait singly and on the covariation among all six traits (three for childhood and three for adulthood). Univariate analyses confirmed the presence of familial factors for five of the six variables but were generally unable to distinguish shared environmental from genetic influences. Hierarchical tests of multivariate models supported the existence of an additive genetic factor contributing to the covariance among the variables. More restrictive multivariate models yielded a significant genetic influence on sexual orientation. Because of the different rates of orientation by zygosity and because of the restrictive nature of some of the multivariate models, our results are best considered tentative but do suggest that further biometrically oriented studies of sexual orientation and its correlates would be worthwhile.

Adult↗
PubMed2001

Membrane orientation of droplets prepared from Chara corallina internodal cells.

It is generally accepted that the membrane surrounding droplets from characean cells originates from the tonoplast, but there is some uncertainty regarding droplet membrane sidedness. This issue was addressed directly by combining two different droplet isolation methods and the patch clamp technique. Neutral red accumulation was used to demonstrate the presence of H(+)-transport over the membrane and to predict membrane orientation. Two types of droplet populations with differently oriented membranes could be formed in an iso-osmotic bath solution. Cytoplasmic droplets (cytosolic side of the tonoplast inside) contained cytoplasm, while the second type of droplet population contained vacuolar sap (vacuolar droplets, vacuolar side of the tonoplast inside). Smaller vesicels also appeared inside the droplets, with an apparently inversely oriented membrane. Confocal laser scanning microscopy indirectly demonstrated that, at least with one of the droplet isolation methods, the plasma membrane entirely remains in the internodal cell after intracellular perfusion. Both types of droplet populations allowed the formation of excised patches and single-channel measurements by the patch clamp technique. Properties of anion channels in the tonoplast could be used to prove the predicted membrane orientation, knowing that Ca2+ can only activate these channels from the cytosolic side. These results provide useful data for studies addressing ligand-binding, block and modulation, organization and interaction of proteins within the membrane or with other regulatory factors, where it is important to control membrane orientation.

Cell Membrane↗
PubMed1995

Sexual orientation and performance on sexually dimorphic motor tasks.

Performance of homosexual and heterosexual men and women on two motor tasks which reliably demonstrate sex differences in opposite directions was examined. A Throw-to-Target Task and the Purdue Pegboard were administered to undergraduate students matched for age and program of study. A two-way ANOVA (Sex x Sexual Orientation) of the Throw data showed a significant interaction, F(1, 90) = 16.22, p < or = 0.001, and a trend for an effect of sex, F(1, 90) = 3.72, p < 0.06. Heterosexual men outperformed heterosexual women, whereas gay men threw less accurately and lesbians tended to throw more accurately than their heterosexual counterparts. Differences in sports history or hand strength did not account for these effects. Analysis of the Pegboard scores found no interaction or main effect of sexual orientation, but the effect of sex was significant, F(1,63) = 7.01, p < or = 0.02. Regardless of sexual orientation, women outperformed men and this difference remained significant even when a measure of finger size was partialed out. This study provides new evidence suggesting an association between sexual orientation and motor-performance profiles. As with cognitive tasks, the motor-performance profiles of homosexuals are composites of some male-typical and some female-typical abilities. To the extent that sociological factors have been controlled, the study suggests that both sexual orientation and motor/cognitive predispositions may have early biological contributions.

Adult↗
PubMed1995

Development and familiality of sexual orientation in females.

The development and familial clustering of sexual orientation were studied in 358 heterosexual, bisexual, and homosexual women. Sexual orientation, as measured by the Kinsey scales, was diverse yet showed statistical congruity and stability over a 1- to 1.5-year time span. Developmental patterns, as measured by retrospective reports on the ages of first sexual or romantic attraction and of self-acknowledgement of sexual orientation were very similar in the heterosexual and lesbian subjects except for the difference in object choice. The bisexual subjects displayed intermediate patterns that were more similar to the heterosexuals' on most facets yet closer to the lesbian subjects' on other dimensions. Familial clustering of nonheterosexual orientation was significant. Using two criteria, elevated rates of nonheterosexuality were found in four classes of relatives: sisters, daughters, nieces, and female cousins through a paternal uncle. The current data are not sufficient to distinguish between genetic and shared environmental sources of this familial aggregation. We discuss the possibility of using developmental criteria to differentiate between inherited and cultural sources of variation in female sexual orientation.

Adolescent↗
PubMed1995

Cultural orientation and psychological well-being in Chinese Americans.

Examined cultural orientation in the domains of language proficiency, cultural activity, and social relationship, and its relationship with psychological well-being in a group of 143 Chinese Americans in San Francisco. Four indicators of psychological well-being were utilized, two assessing the experience of distress (depression level and negative affect) and two assessing positive well-being (positive affect and life satisfaction). Domain-specific cultural orientations were found to hold differential relationships with psychological well-being. For instance, bicultural activity orientation predicted the best psychological well-being (regardless as to how it was assessed), but socially separatist individuals experienced less negative affect than assimilated and bicultural respondents. Findings were discussed in the context of the multicultural setting of San Francisco. It is suggested that future research retain separate assessments of domain-specific cultural orientation, examine the contribution of the community's ethnic/cultural composition to its members' cultural orientations (i.e., address the role of person--environment fit) and study their impact on psychological well-being.

Acculturation↗
PubMed1994

Admission, recruitment, and retention: finding and keeping the generalist-oriented student. SGIM Task Force on Career Choice in Primary Care and Internal Medicine.

As the country strives to produce larger numbers of generalist physicians, considerable controversy has arisen over whether or not generalist applicants can be identified, recruited, and influenced to keep a generalist-oriented commitment throughout medical training. The authors present new and existing data to show that: 1) preadmission (BA/MD or post-baccalaureate) programs can help to identify generalist-oriented students; 2) characteristics determined at admission to medical school are predictive of future generalist career choice; 3) current inpatient-oriented training programs strongly push students away from a primary care career; 4) women are more likely than men to choose generalist careers, primarily because of those careers' interpersonal orientation; and 5) residency training programs are able to select applicants likely to become generalists. Therefore, to produce more generalists, attempts should be made to encourage generalist-oriented students to enter medical schools and to revise curricula to focus on outpatient settings in which students can establish effective and satisfying relationships with patients. These strategies are most likely to be successful if enacted within the context of governmental and medical school-based changes that allow for more reimbursement and respect for the generalist disciplines.

Adult↗