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At least 523 records · Page 29Linked to original sources
PubMed2000

[Effects of different types of disparity cues on the response of axis-orientation selective cells in the monkey parietal cortex].

PURPOSE: To specify the cues for the discrimination of orientation in depth in axis orientation selective (AOS) neurons. METHODS: We analyzed the responses of AOS neurons in the monkey caudal intraparietal sulcus (cIPS) region using binocular disparity stimuli generated by stereoscopic 3 D computer graphics. RESULTS: Most AOS neurons (20/27) were sensitive to binocular disparity and showed tuning to the orientation of a slit in the sagittal plane with orientation disparity cues. For 12 neurons we also used an array of discs or dots instead of slits to eliminate orientation disparity. Half of the neurons (6/12) responded better to the slits than to the discs or dots, suggesting that they were sensitive to orientation disparity. Five neurons (5/12) responded equally well to the discs or dots suggesting that they were more sensitive to the gradient of horizontal disparity than to the orientation disparity. CONCLUSION: Both orientation disparity and disparity gradient were likely to be integrated in the cIPS area to represent axis orientation of an object in space.

Animals↗
PubMed2001

Suppression of cortical NMDA receptor function prevents development of orientation selectivity in the primary visual cortex.

Selectivity to visual stimulus orientation is a basic cortical functional property believed to be crucial for normal vision. Maturation of this neuronal property requires neural activity. Still, it is unclear what might be the molecular basis for such activity-dependent processes and whether activity has an instructive or permissive role in development of orientation selectivity. There is strong evidence that the NMDA subtype of the glutamate receptor regulates activity-dependent mechanisms of ocular dominance plasticity during cortical development. For this reason, we have hypothesized that the NMDA receptor participates in activity-dependent mechanisms that sculpt orientation selectivity of cortical neurons. We used chronic in vivo infusion of antisense oligodeoxynucleotides (ODNs) to suppress NMDA receptor function in primary visual cortex during the period when orientation selectivity develops in ferrets. Chronic suppression of NMDA receptor function prevented the development of orientation and stimulus size selectivity in most cortical cells tested. In contrast, treatment with control sense or missense ODNs did not affect development of orientation selectivity, indicating specificity of effects. Importantly, antisense ODN treatment did not impair visually driven activity, which is required for development to occur. Moreover, orientation selectivity of cortical cells was not disrupted by antisense ODN treatment in mature animals, indicating developmental relevance of the effects. In conclusion, our findings document for the first time that cortical NMDA receptors are essential for the maturation of orientation selectivity. This result supports the notion that activity has an instructive role in sculpting the connections that underlie orientation selectivity in visual cortex.

Aging↗
PubMedDate not supplied

Shuval automated problem-oriented record: an off-line record for a primary care clinic.

An off-line system for automating the problem-oriented record implemented at Kibbutz Shuval is described. The Shuval problem-oriented record consists of acute and chronic problem lists, a preprinted data base collected by patients and nurses, problem-oriented plan flow sheets, problem-oriented progress notes and a regular record audit. The mean conversion time from a traditional record to a problem-oriented record was 17 min for a child's record and 25 min for an adult's. The automated problem-oriented record consists of three data processing forms that contain almost all data in the record. Transfer of data took, on the average, 10 min (range, 5 to 30 min) for a child's record. The following five types of analysis can be performed with the Shuval automated problem-oriented record: administrative, patient care, epidemiologic, demographic and clinical research. Coupled with the manual problem-oriented record, the Shuval automated record provides many advantages of an on-line problem-oriented record at considerably less cost.

Computers↗
PubMed1993

Geometry of orientation and ocular dominance columns in monkey striate cortex.

In addition to showing that ocular dominance is organized in slabs and that orientation preferences are organized in linear sequences likely to reflect slabs, Hubel and Wiesel (1974a) discussed the intriguing possibility that slabs of orientation might intersect slabs of ocular dominance at some consistent angle. Advances in optical imaging now make it possible to test this possibility directly. When maps of orientation are analyzed quantitatively, they appear to arise from a combination of at least two competing themes: one where orientation preferences change linearly along straight axes, remaining constant along perpendicular axes and forming iso-orientation slabs along the way, and one where orientation preferences change continuously along circular axes, remaining constant along radial axes and forming singularities at the centers of the spaces enclosed. When orientation patterns are compared with ocular dominance patterns from the same cortical regions, quantitative measures reveal (1) that singularities tend to lie at the centers of ocular dominance columns, (2) that linear zones (arising where orientation preferences change along straight axes) tend to lie at the edges of ocular dominance columns, and (3) that the short iso-orientation bands within each linear zone tend to intersect the borders of ocular dominance slabs at angles of approximately 90 degrees.

Animals↗
PubMed2002

Determination of the orientation of collagen fibers in human bone.

A human calcaneus bone, consisting of hydroxyapatite and collagen fibers, was successively sliced into samples in a direction perpendicular to the long axis of the bone and parallel to the long axis of the human lower limb. The transmitted microwave intensities of 12 GHz, reflecting the dielectric property, were measured for the slice samples using Osaki's microwave method (Tappi J., 1987; 70:105-108). The complex dielectric constant of 12 GHz of the collagen fiber film was much greater than that of hydroxyapatite disc, which demonstrated that the dielectric anisotropy observed for the sliced bone was mainly affected by the collagen fibers. The angular dependence of the transmitted microwave intensity gives the orientation angle reflecting the direction of the collagen-fiber orientation, and the degree of orientation reflecting the anisotropic property of collagen fibers. The orientation angle and the degree of orientation for the slice samples changed with changing position along the long axis of the calcaneus bone. The direction of orientation deviated to the lateral side at the heel part of the left calcaneus, and to the medial side at the middle part. The degree of orientation is relatively high at the heel part and low at the middle. Such results give a two-dimensional distribution of collagen-fiber orientation in the left calcaneus, and suggest that the direction and degree of orientation are closely related to the direction and magnitude of the stress applied to the bone, respectively.

Anisotropy↗
PubMed1989

Transcription in the reverse orientation at either terminus of the adenovirus type 5 genome.

The right terminus of the adenovirus type 5 (Ad5) genome, which contained the early-region 4 (E4) promoter, was capable of initiating transcription in the reverse orientation in in vitro and in vivo assays. Multiple cis-acting elements, required for original-oriented transcription, were also important for reverse-oriented transcription except for the original TATA box. We constructed a plasmid in which the E4 promoter region was linked to the chloramphenicol acetyltransferase gene in the original orientation and linked to the lacZ gene in the reverse orientation and tested the ability of a co-transfected E1A gene to stimulate transcription in both orientations. Activities of transcription in both orientations were stimulated 6- to 10-fold in this assay. More than one cis-acting element was necessary for the stimulation. The region between -39 and -177 was necessary for the E1A-mediated trans-activation of transcription in both orientations, indicating that the region functioned in a bidirectional manner. The activity of transcription in the reverse orientation was similarly detected at the left terminus of the Ad genome and the activity was stimulated several-fold by E1A gene products.

Adenoviridae↗
PubMed1999

Orientation in pied flycatchers: the relative importance of magnetic and visual information at dusk.

We investigated the orientation of juvenile pied flycatchers, Ficedula hypoleuca, during autumn migration in south Sweden using orientation cage experiments, to study the relative importance of visual and magnetic information at sunset. We performed cage tests under 12 experimental conditions that manipulated the geomagnetic and visual sunset cues available for orientation: natural clear skies in the local or a vertical magnetic field; simulated total overcast in the local or a vertical magnetic field; natural pattern of skylight polarization and directional information from stars screened off, with the sun's position as normal or shifted 120 degrees anticlockwise with mirrors; reduced polarization in the local or a vertical magnetic field; directions of polarization (e-vector) NE/SW and NW/SE, respectively, in the local or a vertical magnetic field. The pied flycatchers were significantly oriented towards slightly south of west when they could use a combination of skylight and geomagnetic cues. The mean orientation was significantly shifted along with the deflection of the sunset position by mirrors. Reduced polarization had no significant effect on orientation either in the local, or in a vertical, magnetic field. The birds tended to orient parallel with the axis of polarization, but only when the artificial e-vector was aligned NW/SE. The mean orientation under simulated total overcast in a vertical, and in the local, magnetic field was not significantly different from random. It is difficult to rank either cue as dominant over the other and we conclude that both visual and magnetic cues seem to be important for the birds' orientation when caught and tested during active migration. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1999

Orientation change of cardiocytes induced by cyclic stretch stimulation: time dependency and involvement of protein kinases.

UNLABELLED: Mechanical stress has been implicated as one of the growth regulators in the heart. We investigated the effect of cyclic stretch stimulation on morphology and orientation of cultured cardiocytes. Embryonic rat (17 days postcoital) cardiomyocytes cultured on silicone dishes were cyclically stretched to 120% in length at a frequency of 30 cycles/min. After 12 h, in the initial stage of cultivation, cardiocytes and intracellular myofibrils oriented parallel to the stretch direction. When the stretch stimulus was prolonged to 24-48 h, myofibrils that oriented perpendicular to the stretch direction emerged. Furthermore, when the cells were stretched only in the later stage (after 24 h of cultivation), both cells and myofibrils tended to orient perpendicular to the stretch direction. Next we examined the effects of chemical compounds on these phase-related changes in myofibril orientation. None of the drugs tested (H-7, HA-1004, staurosporine, herbimycin A, genistein, GdCl3, and EGTA) blocked the parallel orientation of myofibrils induced by the initial-stage stretch. By contrast, H-7, staurosporine, herbimycin A, and genistein did inhibit almost completely the perpendicular orientation of the myofibrils induced by the late-stage stretch, but HA-1004, GdCl3, or EGTA did not. Immunoblotting study using anti-phsophotyrosine antibody indicated that tyrosine phosphorylation of a protein of about 125 kDa was enhanced in a time-dependent manner by the late-stage stretch, but not by the initial-stage stretch. IN CONCLUSION: the alignment change induced by cyclic stretch depends on the stage of cultivation: with stretch in the initial stage (within 12 h), cells and myofibrils orient parallel to the stretch; with stretch in the later stage (after 24 h), they orient perpendicular to the stretch. The effect of stretch in the later stage is likely mediated by protein kinase C and tyrosine kinase pathways.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1992

The orientation of transition moments of dye molecules used in fluorescence studies of muscle systems.

Fluorescence and phosphorescence depolarization techniques can provide information on orientational order and rotational motion of crossbridges in muscle fibres. However the depolarization experiment monitors the orientation and motion of the crossbridges indirectly. The changes in depolarization arise from a change in the orientation of the transition dipoles of the dye attached to the crossbridge. In order to extract the physiologically relevant orientations from the data it is therefore necessary to characterize the orientation of the dye molecule relative to the crossbridge and the orientation of the transition moments in the frame of the dyes. The dyes 1,5-I-AEDANS and eosin-5-maleimide are commonly used for labelling the crossbridge in muscle fibres. The orientations of the absorption and fluorescence emission dipoles of these two dyes in the molecular frame were determined. Angle resolved fluorescence depolarization experiments on the dyes, macroscopically aligned in a stretched polymer matrix of poly vinyl alcohol, were carried out. The data were analyzed in terms of an orientational distribution of the dye molecules in the film and the orientations of the absorption and emission dipoles in the frame of the dye molecule. Experimental data, obtained from a given sample at different excitation wavelengths, were analyzed simultaneously in a global target approach. This leads to a reduction in the number of independent parameters optimized by the non-linear least squares procedure.

Animals↗
PubMed1986

Flow orientation of brain microtubules studied by linear dichroism.

Flow orientation of bovine brain microtubules has been studied using phase-modulation detected linear dichroism, LD, in a Couette cell with radial light propagation. LD could be sensitively measured in a wide flow gradient interval: 10(-3)-10(3) s-1, without any apparent degradation of the microtubule structure. An extremely small flow gradient, 10(-3) s-1 is sufficient to give significant orientation, and 10 s-1 rapidly produced a very high degree of orientation. It is also shown that thermal convection effectively orients microtubules in vitro. The apparent linear dichroism is dominated by an anisotropic scattering from the aligned microtubules, superimposed on a weaker absorption dichroism due to intrinsic chromophores. The linear dichroism due to anisotropic turbidity, LD tau, is found to be an excellent tool for monitoring the formation of microtubules and in contrast to ordinary turbidity measurements, non-specific aggregates contribute to a far less extent. Time resolved LD tau was used to study the orientational relaxation of microtubules upon stopped shear. The relaxation towards random orientation can be described by a slow, multi-exponential decay. With increasing protein concentration the relaxation becomes slower and above approximately 1 mg/ml a fraction with a semipermanent orientation is formed. Finally, the development of orientation with time upon applying a small, constant gradient has been measured and the results are considered in terms of a model for flow orientation of rigid rods.

Animals↗
PubMed1995

A peroperative comparison of Western and Oriental colonic anatomy and mesenteric attachments.

It has been suggested that the Oriental colon is easier to colonoscope than its Western counterpart. The aim of this study was to investigate possible differences in colonic anatomy between Western and Oriental patients that might explain this observation. Measurements of colonic length and mesenteric attachments were taken according to a set protocol from 115 Western (Caucasian) and 114 Oriental patients at laparotomy. Sigmoid adhesions were found more frequently in Western (17%) compared to Oriental (8%) patients, P = 0.047. A descending mesocolon of > or = 10 cm occurred in 10 (8%) Western patients but only 1 (0.9%) Oriental patient, P = 0.01. The splenic flexure was more frequently mobile in Western patients (20%) compared to Oriental (9%) patients, P = 0.016. In 29% - of Western patients the mid-transverse colon reached the symphysis pubis, or lower when pulled downwards in contrast to 10% of Oriental patients, P < 0.001. There was no significant difference in total colonic length comparing Western (median = 114 cm, range 68-159 cm) to Oriental (median = 111 cm, range 78-161 cm) patients. Western patients have a higher incidence of sigmoid colon adhesions and increased colonic mobility when compared to Orientals. These findings support the observation that colonoscopy is a more difficult procedure in Western patients.

Adult↗
PubMed1989

Thermal and physiological responses of rats exposed to 2.45-GHz radiofrequency radiation: a comparison of E and H orientation.

Ketamine-anesthetized Sprague-Dawley rats were exposed in both E and H orientations to far-field 2.45-GHz continuous-wave radiofrequency radiation (RFR) at a power density of 60 mW/cm2 (whole-body average specific absorption rate of approximately 14 W/kg). Intermittent exposures were performed in both orientations in the same animal to repeatedly increase colonic temperature from 38.5 to 39.5 degrees C. Tympanic, subcutaneous (sides toward and away from RFR source), and colonic temperature, ECG, arterial blood pressure, and respiratory rate were continuously recorded. The pattern of heat distribution within the animal and the physiological responses were significantly different between E- and H-orientation exposure. Irradiation in E orientation resulted in greater peripheral and tympanic heating, while irradiation in H orientation resulted in greater core heating. Heart rate and blood pressure increased significantly during irradiation and returned to baseline levels when exposure was discontinued; the increases were significantly greater in E than in H orientation. Respiratory rate increased significantly during irradiation in H, but not in E orientation. The physiological responses could have been influenced by the different levels or rates of subcutaneous and tympanic heating, or the differential between core and peripheral heating during E- and H-orientation irradiation. These results suggest that, when interpreting results of RFR exposure, animal orientation during irradiation must be considered.

Animals↗
PubMedDate not supplied

Influence of external concentration fluctuations on leukocyte chemotactic orientation.

The quantitative dependence of leukocyte chemotactic orientation on imprecision in the measurement of chemoattractant concentrations from thermal fluctuations is analyzed. First, a mathematical model relating orientation to differences in receptor occupancy across cell dimensions is developed. This is then coupled with an extension of Berg and Purcell's analysis (1) of the precision of attractant concentration measurements by means of receptor occupancy. Our results show that thermal fluctuations in external concentrations can limit the accuracy of orientation, unless the measurement noise is reduced by averaging the measurements over a period of time. Comparison of our model predictions to experimental orientation data suggests that leukocytes do overcome this limitation, and allows estimation of the time-averaging period necessary to do so. For the orientation observed in a visual bridge assay by Zigmond (2) using the attractant peptide FNLLP, we estimate that receptor occupancy measurements for spatial comparison across cell dimensions must be averaged for a few minutes. Otherwise, the fluctuations in the attractant concentration near the cell will be too great to allow the observed degree of orientation. Our analysis also suggests that the ratio of signal-to-signal noise does not adequately characterize orientation accuracy. Accurate orientation can, in some situations, occur when this ratio is substantially less than unity; in other situations, a ratio much greater than unity is required for accurate orientation.

Cell Membrane↗
PubMed1993

Magnetically induced orientation of phosphatidylcholine membranes.

Lipid bilayers prepared from natural phospholipids orient in magnetic fields with the long axis of the lipid molecules perpendicular to the magnetic field. This magnetically induced orientation was studied at high (11.7 Tesla (T)), mid (9.36 T), and low (4.68 T) magnetic field strengths using lipid aggregates prepared from natural and synthetic phosphatidylcholine analogs. Phosphatidylcholine analogs containing saturated diacylated chains (12 to 16 carbons/chain) exhibited extensive orientation of the lipid when bilayer formation occurred by gentle hydration conditions. Gentle hydration involved incubating dried phosphatidylcholine C above the main phase transition (Tm); brief shaking or swirling by hand was occasionally needed to completely disperse the lipids. The method of bilayer formation significantly influenced the amount of lipid that orients in magnetic fields. Thus the supramolecular structures (and % orientation) above Tm in an 11.7 T field of dimyristoylphosphatidylcholine (DMPC) bilayers are SUV (0%), LUV (approximately 15%), SPLV (approximately 40%), vortexed-MLV (approximately 60%) and non-vortexed MLV (approximately 90%). Single layered vesicles prepared by the REV method exhibited orientation at 11.7 T similar to LUV prepared by freeze thaw cycles. Aqueous dispersions of eggPC prepared by gentle hydration exhibit approximately 40% orientation at 11.7 T which decreased to approximately 30% orientation if 30% cholesterol is added to the membrane. Magnetic orientation of bilayers thus appears to be a general phenomenon for both saturated and unsaturated natural phospholipids either with or without cholesterol in the membrane.

Lipid Bilayers↗
PubMed1985

The effect of practice on the oblique effect in line orientation judgments.

Line orientation discrimination improves with selective practice for oblique orientations and not for principal orientations. This training effect was observed with an identification task as well as with two alternative forced choice tasks. Despite the improvement for oblique orientations, just noticeable differences in orientation are still larger for the practised oblique orientation than for the principal orientations after 5000 practice trials. These findings suggest that the oblique effect in line orientation has at least two sensorial components, one of which is attributed to the meridional variations in the preferred orientation of area 17 S-cells.

Adult↗
PubMed1987

Illusory contour orientation discrimination.

Just noticeable differences (JNDs) in orientation for real lines and illusory contours were compared. JNDs in orientation of an illusory contour and of a real line differ by less than a factor two. JNDs in orientation of an illusory contour showed meridional variations similar to those obtained for a real line. By scaling measurements illusory contours are equally visible at all orientations, so meridional variations in illusory orientation discrimination reflect an anisotropy in orientation processing mechanisms. JNDs in orientation measured at an oblique reference orientation improve with practice for an illusory contour as well as for a real line. However while the effect of practice transfers from an illusory to a real contour, the reverse is not true. These results suggest that there are two paths for processing orientation: one activated only by real lines, the other concerned with both real and illusory contours.

Adult↗
PubMed1995

Discrimination of orientation-defined texture edges.

Preattentive texture segregation was examined using textures composed of randomly placed, oriented line segments. A difference in texture element orientation produced an illusory, or orientation-defined, texture edge. Subjects discriminated between two textures, one with a straight texture edge and one with a "wavy" texture edge. Across conditions the orientation of the texture elements and the orientation of the texture edge varied. Although the orientation difference across the texture edge (the "texture gradient") is an important determinant of texture segregation performance, it is not the only one. Evidence from several experiments suggests that configural effects are also important. That is, orientation-defined texture edges are strongest when the texture elements (on one side of the edge) are parallel to the edge. This result is not consistent with a number of texture segregation models including feature- and filter-based models. One possible explanation is that the second-order channel used to detect a texture edge of a particular orientation gives greater weight to first-order input channels of that same orientation.

Discrimination, Psychological↗
PubMed2005

Guidance of engineered tissue collagen orientation by large-scale scaffold microstructures.

The tensile strength and stiffness of load-bearing soft tissues are dominated by their collagen fiber orientation. While microgrooved substrates have demonstrated a capacity to orient cells and collagen in monolayer tissue culture, tissue engineering (TE) scaffolds are structurally distinct in that they consist of a three-dimensional (3-D) open pore network. It is thus unclear how the geometry of these open pores might influence cell and collagen orientation. In the current study we developed an in vitro model system for quantifying the capacity of large scale ( approximately 200 microm), geometrically well-defined open pores to guide cell and collagen orientation in engineered tissues. Non-degradable scaffolds exhibiting a grid of 200 microm wide rectangular pores (1:1, 2:1, 5:1, and 10:1 aspect ratios) were fabricated from a transparent epoxy resin via high-resolution stereolithography. The scaffolds (n=6 per aspect ratio) were surface modified to support cell adhesion by covalently grafting GRGDS peptides, sterilized, and seeded with neonatal rat skin fibroblasts. Following 4 weeks of static incubation, the resultant collagen orientation was assessed quantitatively by small angle light scattering (SALS), and cell orientation was evaluated by laser confocal and scanning electron microscopy. Cells adhered to the struts of the pores and proceeded to span the pores in a generally circumferential pattern. While the cell and collagen orientations within 1:1 aspect ratio pores were effectively random, higher aspect ratio rectangular pores exhibited a significant capacity to guide global cell and collagen orientation. Preferential alignment parallel to the long strut axis and decreased spatial variability were observed to occur with increasing pore aspect ratio. Intra-pore variability depended in part on the spatial uniformity of cell attachment around the perimeter of each pore achieved during seeding. Evaluation of diamond-shaped pores [Sacks, M.S. et al., 1997. J. Biomech. Eng. 119(1), 124-127] suggests that they are less sensitive to initial conditions of cell attachment than rectangular pores, and thus more effective in guiding engineered tissue cell and collagen orientation.

Animals↗