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PubMed1998

Orientation changes of fluorescent probes at five sites on the myosin regulatory light chain during contraction of single skeletal muscle fibres.

Changes in the orientation of the myosin regulatory light chain (RLC) in single muscle fibres were measured using polarised fluorescence from acetamidotetramethylrhodamine (ATR). Mutants of chicken skeletal RLC containing single cysteine residues at positions 2, 73, 94, 126 and 155 were labelled with either the 5 or 6-isomer of iodo-ATR, giving ten different probes. The labelled RLCs were exchanged into demembranated fibres from rabbit psoas muscle without significant effect on active force generation. Fluorescence polarisation measurements showed that nine out of the ten probe dipoles were more perpendicular to the fibre axis in the absence of ATP (in rigor) than in either relaxation or active contraction. The orientational distribution of the RLC region of the myosin head in active contraction is closer to the relaxed than to the rigor orientation, and is not equivalent to a linear combination of the relaxed and rigor orientations. Rapid length steps were applied to the fibres to synchronise the motions of myosin heads attached to actin. In active contraction the fluorescence polarisation changed both during the step, indicating elastic distortion of the RLC region of the myosin head, and during the subsequent rapid force recovery that is thought to signal the working stroke. The peak change in fluorescence polarisation produced by an active release of 5 nm per half sarcomere indicates an axial tilt of less than 5 degrees for all ten probes, if all the myosin heads in the fibre respond to the length step. This tilting was towards the rigor orientation for all ten probes, and could be explained by 14% of the heads moving to the rigor orientation. An active stretch tilted the heads away from the rigor conformation by a similar extent.

Animals↗
PubMed2002

Determination of membrane Peptide orientation by 1H-detected 2H NMR spectroscopy.

We demonstrate the application of the proton inverse detected deuteron (PRIDE) NMR technique to the measurement of the orientation of membrane-bound peptides with enhanced sensitivity. Gramicidin D, a transmembrane peptide, and ovispirin, a surface-bound peptide, were used as model systems. The peptides were 2H-labeled by 1H/2H exchange and oriented uniaxially on glass plates. The directly detected 2H spectra of both peptides showed only a strong D(2)O signal and no large quadrupolar splittings. In contrast, the PRIDE spectrum of gramicidin exhibited quadrupolar splittings as large as 281 kHz, consistent with its transmembrane orientation. Moreover, the large D(2)O signal in the directly detected 2H spectra was cleanly suppressed in the PRIDE spectrum. For ovispirin, the 1H indirectly detected 2H spectrum revealed a 104 kHz splitting and a zero-frequency peak. The former reflects the in-plane orientation of most of the helix axis, while the latter results from residues with a magic-angle orientation of the N-D bonds. These are consistent with previous 15N NMR results on ovispirin. The combination of PRIDE and exchange labeling provides an economical and sensitive method of studying membrane peptide orientations in lipid bilayers without the influence of D(2)O and with the ability to detect N-D bonds at the magic angle from the bilayer normal.

Antimicrobial Cationic Peptides↗
PubMed1990

Modulation of the orientational order profile of the lipid acyl chain in the L alpha phase.

The orientational order profile along the lipid acyl chain has been characterized under several different conditions of polar headgroup composition, temperature, and cholesterol content. Despite the different nature of these factors, the variation of the order is governed by two common trends. First, the relative change of order induced by the variation of these factors is always more pronounced towards the end of the chain than for the methylene groups near the interface. Second, there is, to a first approximation, a distinct correlation between the magnitude of the order parameters and the shape of the order profile. For example when the chain is highly ordered, the relative width of the order distribution is narrow indicating that the plateau region is longer. These conclusions suggest that the orientational order profile depends on only a small number of parameters and demonstrate clearly that the correlation length for changes in orientational order is much greater than one C-C bond length. Our results also show that the reduced temperature is not related in simple terms to orientational order and probably has little theoretical significance. The orientational order profiles of POPC and POPE bilayers are significantly different even when expressed in terms of reduced temperature. The behavior of POPC/cholesterol systems also indicates that the orientational order of the lipid chain and the gel-to-liquid crystalline phase transition temperature are not related in a straightforward manner.

Cell Membrane↗
PubMed1995

Independent contributions of the orienting of attention, fixation offset and bilateral stimulation on human saccadic latencies.

In a series of experiments we examined the effects of the endogenous orienting of visual attention on human saccade latency. Three separate manipulations were performed: the orienting of visual attention, the prior offset of fixation (gap paradigm) and the bilateral presentation of saccade targets. Each of these manipulations was shown to make an independent contribution to saccade latency. In experiments 1 and 2 subjects were instructed to orient their attention covertly to a location by a verbal pre-cue; targets could appear in the attended hemifield (valid) or in the non-attended hemifield (invalid) together with a no-instruction (neutral) condition. Saccades were made under fixation gap and overlap conditions, to either single target or two bilaterally presented targets which appeared at equal and opposite eccentricities in both hemifields. The results showed a large increase (cost) of saccade latency to invalid targets and a small non-significant decrease (benefit) of saccade latency to valid targets. The cost associated with invalid targets replicates the "meridan crossing effect" shown in manual reaction time experiments and is consistent with the hemifield inhibition and premotor models of attentional orienting. The use of a "gap" procedure produced a generalised facilitation of saccade latency, which was not modified by the prior orienting of visual attention. The magnitude of the gap effect was similar for saccades made to attended and non-attended stimulis. This suggests that the gap effect may be due to ocular motor disengagement, or a warning signal effect, rather than to the prior disengagement of visual attention. When two targets were presented simultaneously, one in each hemifield, saccade latency was slowed compared with the single target condition. The magnitude of this slowing was unaffected by the prior orienting of visual attention or by the fixation condition. The slowing was examined in more detail in experiment 3, by presenting targets with brief offset delays. The latency increase was maximal if the two targets were presented simultaneously and decreased if the distractor appeared at short intervals (20-80 ms) before or after the saccade target onset. If the non-attended stimulus was presented at greater intervals (160, 240 ms) before the saccade target, then a facilitation effect was observed. This demonstrates that the onset of a distractor in the non-attended hemifield can have both an inhibitory and a facilitatory effect on a saccade production.

Attention↗
PubMed1975

Osteoblasts and collagen orientation.

Bone was removed from the calvaria of anaesthetized 70 g rats or freshly killed young monkeys and the fibrous periosteum dissected off the inner, formative surface under 0.15 M cacodylate buffer. The bone and undisturbed osteoblasts were fixed in 3% glutaraldehyde in the same buffer for 24 to 48 hours, critical point dried and coated with evaporated carbon and gold for scanning electron microscopy (SEM). Fields of osteoblasts were photographed and chosen cells dissected off the osteoid using a tungsten needle. The control of the dissection was made possible by the use of a system of real-time stereo tv-speed SEM. The fields were rephotographed and the orientations of the osteoblasts were compared with that of the underlying collagen fibres. 62% of all osteoblasts lay with their long axes within 15 degrees of the collagen fiber orientation below and 80% within 30 degrees. Montages of large areas of osteoblasts were also made, and then compared with ones of the same area after the cells had been stripped off on adhesive tape. In general, the orientation of the collagen tended to be the same as the cell that formed it. Collagen fibers below cells at the periphery of a domain sometimes had the orientation of the cells in the adjacent patch. It is not possible to determine whether the cells controlled the orientation of the collagen, or vice versa, from this experiment, but other SEM evidence suggests that the collagen orientation in hard tissue matrices depends on the freedom of cells to move with respect to matrix surface.

Animals↗
PubMed1982

A high probability of an orientation shift between layers 4 and 5 in central parts of the cat striate cortex.

On the postlateral gyrus of the cat striate cortex the cells' preferred orientation was measured as a function of cortical depth in penetrations as parallel as possible to the radial fibre bundles. According to the penetration angle and in agreement with the current model of orientation columns, there was a low orientation drift in layers 2-4. At the transition between layers 4 and 5 an orientation shift of 45-90 deg was found in most penetrations. The orientation differences between adjacent recording sites in lower layers was normally low too, but clearly higher than in upper layers. The results are discussed in terms of more independent orientation mechanisms in upper and lower layers.

Animals↗
PubMed1988

Topographic relations between ocular dominance and orientation columns in the cat striate cortex.

In the visual cortex of four adult cats ocular dominance and orientation columns were visualized with (3H)proline and (14C)deoxyglucose autoradiography. The two columnar systems were reconstructed from serial horizontal sections or from flat-mount preparations and graphically superimposed. They share a number of characteristic features: In both systems the columns have a tendency to form regularly spaced parallel bands whose main trajectory is perpendicular to the border between areas 17 and 18. These bands frequently bifurcate or terminate in blind endings. The resulting irregularities are much more pronounced in the ocular dominance than in the orientation system. The periodicity of the columnar patterns was assessed along trajectories perpendicular to the main orientation of the bands and differed in the two columnar systems. The spacing of the ocular dominance stripes was significantly narrower than the spacing of orientation bands. The mean periodicity of a particular columnar system was virtually identical in the two hemispheres of the same animal but it differed substantially in different animals. However, the spacing of orientation columns covaried with that of the ocular dominance columns, the ratios of the mean spacings of the two columnar systems being similar in the four cats. The superposition of the two columnar systems revealed no obvious topographic relation between any of the organizational details such as the location of bifurcations, blind endings and intersections. We suggest the following conclusions: 1. The developmental processes generating the two columnar systems seem to obey the same algorithms but they act independently of each other. 2. The space constants of the two systems are rigorously specified and appear to depend on a common variable. 3. The main orientation of the bands in both columnar systems is related to a) the representation of the vertical meridian, b) the anisotropy of the cortical magnification factor, and c) the tangential spread of intracortical connections.

Animals↗
PubMed1989

Complementary global maps for orientation coding in upper and lower layers of the monkey's foveal striate cortex.

A population of 269 cells recorded from the foveal representation of striate cortex in 2 rhesus macaque monkeys was examined for orientation preference as a function of receptive field position relative to the center of gaze. Cells recorded in supragranular and infragranular layers were segregated and compared. Within the foveolar region (0.0-0.5 degrees) supragranular cells showed a vertical bias which was not evident in the infragranular layers. At larger eccentricities (0.5-2.5 degrees) supragranular cells showed a radial bias (preferred orientation points toward the center of gaze), whereas infragranular cells showed a concentric bias (preferred orientation is tangent to a circle around the center of gaze). These results are consistent with our earlier report of an orientation shift between the supragranular and infragranular layers (Bauer et al. 1980, 1983; Dow and Bauer 1984). The diagonal orientation bias which we noted earlier (Bauer et al. 1980; Dow and Bauer 1984) in supragranular cells at eccentricities between 0.5 and 2.5 degrees can be explained by the radial bias, combined with a tendency for recording sites to favor receptive field locations closer to the diagonal meridia than to either the horizontal or vertical meridia. Given other evidence that upper layer cells in macaque striate cortex tend to show either orientation or color selectivity, while lower layer cells tend to show movement sensitivity (Dow 1974; Livingstone and Hubel 1984), the present data suggest a functional dichotomy between a supragranular system involved in fixational eye movements and pattern vision and an infragranular system activated primarily by optical flow fields during ambulation.

Animals↗
PubMed1995

The orientation of gene maps by recombination of flanking markers for the am locus of Neurospora crassa.

Fincham (1967), Smyth (1973 b) and Rambosek and Kinsey (1983) have each generated fine-structure maps of the am gene of Neurospora crassa. Each map had a consistent linear order of alleles but the assignment of an orientation with respect to other linkage group-V loci differed. Fincham found the end marked by the am6 allele to be at the distal end of the locus, Smyth found am6 to be at the proximal end while the data of Rambosek and Kinsey did not suggest an orientation. Smyth s orientation has been adopted as the standard, but not unreservedly. We have aligned the genetic and physical maps of the am gene, showing that am6 is at the distal end, supporting Fincham's orientation. However, we suggest that an assumption used to orient fine structure genetic maps is flawed and that the conflicting orientation between these three studies follows from the different choice of flanking markers.

Chromosome Mapping↗
PubMed1987

On visual orientation of dot patterns.

Two-dimensional normally distributed random dot patterns were used in two experiments on visual orientation estimation. In the first experiment the patterns differed in their sample correlation and in dot number. In the second one the number of dots was maintained constant but the patterns were generated as a superposition of two normally distributed orthogonal sets composed of different number of dots. In both experiments the estimated orientation depended on stimuli correlation - with increasing correlation the estimated orientation gets closer to the orientation of the least square distance axis of the pattern. Even at very low unsignificant correlations there still remained a hint about stimulus orientation which was not estimated at random. Equalizing consecutively the number of dots in the two orthogonal dot patterns during the second experiment did not result in chance performance either. The bimodal angular distributions of the obtained responses permitted to approach the problem of orientation ambiguity. The results are discussed in terms of optimization processes taking place in the visual system.

Cybernetics↗
PubMed1986

Stable versus unstable orientations of sex chromosomes in two grasshopper species.

The structural basis of orientation stability was investigated. The stable unipolar orientation of the Melanoplus sanguinipes X-chromosome univalent is unique in that it is stable without tension created by forces towards opposite poles; tension is thought to be the principle component in stabilizing kinetochore orientations to a pole. Stable orientation of the X chromosome in Melanoplus sanguinipes was compared with unstable X orientation in Melanoplus differentialis. Ten cells (five of each species) were studied, firstly in living cultures where chromosome behavior was followed, then by serial-section electron microscopy where the structural basis for chromosome behavior was examined. Microtubules other than kinetochore microtubules were observed impinging on the X chromosomes. One end of these microtubules was buried in chromatin, while the other ran toward a pole. The X chromosomes of M. sanguinipes had more of these microtubules than did M. differentialis X chromosomes. It is suggested that M. sanguinipes X chromosomes are less condensed than M. differentialis X chromosomes and so allow more microtubules to penetrate the chromosome. The extra microtubules impinging on the M. sanguinipes X chromosome probably prevent reorientation by inhibiting the turning of the chromosome towards the opposite pole, i.e., more force is needed to turn a kinetochore towards the opposite pole than can be generated and attempts at reorientation fail. This may be analogous to the effect that tension has on the orientation stability of bivalents.

Animals↗
PubMed1993

Homosexual orientation in twins: a report on 61 pairs and three triplet sets.

Twin pairs in which at least one twin is homosexual were solicited through announcements in the gay press and personal referrals from 1980 to the present. An 18-page questionnaire on the "sexuality of twins" was filled out by one or both twins. Thirty-eight pairs of monozygotic twins (34 male pairs and 4 female pairs) were found to have a concordance rate of 65.8% for homosexual orientation. Twenty-three pairs of dizygotic twins were found to have a concordance rate of 30.4% for homosexual orientation. In addition, three sets of triplets were obtained. Two sets contained a pair of monozygotic twins concordant for sexual orientation with the third triplet dizygotic and discordant for homosexual orientation. A third triplet set was monozygotic with all three concordant for homosexual orientation. These findings are interpreted as supporting the argument for a biological basis in sexual orientation.

Adult↗
PubMed1990

Mechanically induced orientation of adult rat cardiac myocytes in vitro.

A population of freshly isolated adult rat cardiac myocytes is spatially oriented using a computerized mechanical cell stimulator device for tissue cultured cells. A continuous unidirectional stretch of the substratum at 60 to 400 micron/min for 120 to 30 min, respectively, during the cell attachment period in serum-free medium induces a significant three-fold increase in the number of rod-shaped myocytes oriented parallel to the direction of movement. The myocytes orient less well with unidirectional substratum stretching after their adhesion to the substratum. In contrast, adult myocytes plated onto a substratum undergoing continuous 10% stretch-relaxation cycling show no significant change in myocyte orientation or cytoskeletal organization. Orientation of rod-shaped myocytes is dependent on several factors other than the type of mechanical activity. These include: a) the speed of substratum movement; b) the final stretch amplitude; and c) the timing between initiation of substratum stretching and adhesion of myocytes to the substratum. Oriented adult rod shaped myocytes representing 65 to 70% of the total myocyte population in this model system can now be submitted to different patterns of repetitive mechanical stimulation for the study of stretch-induced alterations in cell growth and gene expression.

Animals↗
PubMed2006

Demand-oriented care: the development and validation of a measuring instrument.

OBJECTIVES: Demand-oriented care has recently become a key topic in the area of care provision, fitting into the modern pursuit for patient autonomy. This paper introduces a measuring instrument to assess demand-orientation in mental health care. METHOD: A concept mapping procedure was used to understand the concept of demand-orientation. The resulting items were introduced to a validating sample of 204 patients of three mental health facilities. After factor analysis, a 19-item General-Demand Orientated Care Questionnaire (DOC-G), and a supplementary questionnaire (DOC-S) containing 6 sections remained. This questionnaire was submitted to confirmatory analysis in a random sample (n = 304) of psychiatric patients. RESULTS: Respondents were predominantly female (57.6%), of Dutch ethnic origin (84.1%), and outpatients (71.4%). The analyses confirmed the 4-factor structure of the questionnaire. Both internal and external validity of the instrument proved to be sufficient. The questionnaire discriminated in the experience of demand-orientation of care between patients who did and those who did not have a treatment plan put up; between those who did and those who did not have a crisis plan, and between those who had a lifetime prevalence of undergoing compulsory treatment, and those who had not. CONCLUSIONS: We conclude that the DOC is a useful instrument to measure demand-orientation in a population of psychiatric patients. It is useful to measure changes in care quality. The supplementary questionnaires make it possible to evaluate chosen projects or subprojects quickly.

Adult↗
PubMed1999

Orientation of trabecular bone in human vertebrae assessed by MRI.

The aim of the study was to assess the relative number of bone trabeculae in different orientations by using magnetic inhomogeneity measurements by MR imaging. Twelve defatted human vertebrae (L2-L4) were studied by MR imaging and CT. In the MR measurements the reversible transaxial decay rate, R2', was determined using the GESFIDE sequence. The relative contribution to R2' of bone trabeculae oriented along the x (R2'x), y (R2'y) and z (R2'y) axes was assessed, by rotation of the specimen in the magnetic field. The results were validated by CT measurements of trabecular structure at a resolution of 0.2 x 0.2 x 1 mm. using custom-made software. R2' ranged from 4.9 to 32 s-1. After separation, theoretical R2'x ranged from 2.3 to 10.7 s-1, R2'y ranged from 2.6 to 14.0 s-1 and R2'z ranged from 4.7 to 17.9 s-1. The number of bone trabeculae per millimeter identified in axial CT images ranged from 0.15 to 0.38 and from 0.039 to 0.22 per millimeter in sagittal images. The difference between axial and sagittal CT images was statistically significant and due to anisotropic voxels. The correlation between R2' and the number of bone trabeculae per millimeter was statistically significant (r = 0.83, p < 0.001 for x orientation: r = 0.63 for y orientation, and r = 0.59 for z orientation, p < 0.05 for both). The relative amount of bone trabeculae in different orientations can be assessed in vitro using R2' measurements.

Aged↗
PubMed2000

Tensile Tissue Stress Affects the Orientation of Cortical Microtubules in the Epidermis of Sunflower Hypocotyl.

In turgid multicellular organs, it is convenient to differentiate between the two kinds of tensile forces acting in cell walls as a result of turgor pressure. The primary forces occur both in situ and in cells isolated from the organ, whereas the secondary forces occur only in situ. The latter are an unavoidable physical consequence of the variation in mechanical parameters of tissues forming layers or strands. The most rigid tissue is under maximal tensile force, whereas the least rigid is under maximal compressive force. These forces cause tissue stresses (that is, certain tissues are under tensile stress, whereas others are under compressive stress in the organ). The primary and secondary forces result in primary and secondary stress in cell walls, respectively. The anisotropy of the primary stress is a function of cell shape. For instance, in cylindric cells the anisotropy expressed as the ratio of longitudinal to transverse stresses is 0.5. The anisotropy of the secondary stress is a function of the compound structure of the organ. For example, in the epidermis of sunflower hypocotyl, the longitudinal secondary stress is much higher than the transverse stress. The primary and secondary stresses are superimposed, and, as a consequence, the stress anisotropy in the outer thick walls of epidermal cells is greater than 1. These outer epidermal walls transmit most of the tissue stress. When the epidermis is peeled but remains turgid, only primary stress remains, but loading of the peel can reestablish the original stress anisotropy. We studied the effect of stress anisotropy changes on the orientation of cortical microtubules (CMTs) in the sunflower hypocotyl epidermis. We showed that changes in stress anisotropy cause the CMT orientation to change in the direction of maximal wall stress. In situ, the relatively high tensile tissue stress in the epidermis causes maximal stress in the longitudinal direction and relatively steep CMT orientation. When the tissue stress is removed from the epidermis by peeling, the CMTs tend to reorient toward the transverse direction, which is the direction of maximal stress in the primary component. On application of external longitudinal stress, to substitute for tissue stress, CMTs tend to reorient in the longitudinal direction. However, a relatively high rate of plastic strain is caused by the stress applied to the peel in an acid medium. This produces a less steep orientation of CMTs. It appears that the change in stress anisotropy orients the CMT in the direction in which the stress is maximal after the change, but there is also some effect of the growth rate on the orientation.

Journal Article↗
PubMed1999

Three-dimensional kinematic analysis of influence of hand orientation and joint limits on the control of arm postures and movements.

The problems related to kinematic redundancy in both task and joint space were investigated for arm prehension movements in this paper. After a detailed analysis of kinematic redundancy of the arm, it is shown that the redundancy problem is ill posed only for the control of hand orientation. An experiment was then designed to investigate the influence of hand orientation on the control of arm movements. Since movements must be made within the limits of the joints, the influence of these limits was also analyzed quantitatively. The results of the experiment confirm that the increase of movement time because of the change of object orientation is due to the lengthening of the deceleration phase disproportionately to the rest of the movement. The variation of hand path due to the change of object orientation was observed as being surprisingly small for some subjects as opposed to the large range of object orientation, implying that hand path and hand orientation could be controlled separately, thus simplifying the computational problem of inverse kinematics. Moreover, the observations from the present experiment strongly suggest that a functional segmentation of the proximal and distal joints exists and that the control of wrist motion is dissociated from the rest of joint motions. The contribution of each joint in the control of arm movements could be determined through the principle of minimum energy and minimum discomfort under the constraints of the joint limits. A simplified inverse kinematics model was tested. It shows that these hypotheses can be easily implemented in a geometric algorithm and be used to predict arm prehension postures reasonably well under the constraints of joint limits.

Adult↗
PubMed2006

Fixed versus dynamic orientations in environmental learning from ground-level and aerial perspectives.

Ground-level and aerial perspectives in virtual space provide simplified conditions for investigating differences between exploratory navigation and map reading in large-scale environmental learning. General similarities and differences in ground-level and aerial encoding have been identified, but little is known about the specific characteristics that differentiate them. One such characteristic is the need to process orientation; ground-level encoding (and navigation) typically requires dynamic orientations, whereas aerial encoding (and map reading) is typically conducted in a fixed orientation. The present study investigated how this factor affected spatial processing by comparing ground-level and aerial encoding to a hybrid condition: aerial-with-turns. Experiment 1 demonstrated that scene recognition was sensitive to both perspective (ground-level or aerial) and orientation (dynamic or fixed). Experiment 2 investigated brain activation during encoding, revealing regions that were preferentially activated perspective as in previous studies (Shelton and Gabrieli in J Neurosci 22:2711-2717, 2002), but also identifying regions that were preferentially activated as a function of the presence or absence of turns. Together, these results differentiated the behavioral and brain consequences attributable to changes in orientation from those attributable to other characteristics of ground-level and aerial perspectives, providing leverage on how orientation information is processed in everyday spatial learning.

Adult↗