SEARCH · PubMed Health

Results for “Spatial orientation”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,117 records · Page 62Linked to original sources

PubMed1990

Shift of preferred directions of premotor cortical cells with arm movements performed across the workspace.

The activity of 156 neurons was recorded in the premotor cortex (Weinrich and Wise 1982) and in an adjoining rostral region of area 6 (area 6 DR; Barbas and Pandya 1987) while monkeys made visually-guided arm movements of similar direction within different parts of space. The activity of individual neurons varied most for a given preferred direction of movement within each part of space. These neurons (152/156, 97.4%) were labeled as directional. The spatial orientation of their preferred directions shifted in space to "follow" the rotation of the shoulder joint necessary to bring the arm into the different parts of the work-space. These results suggest that the cortical areas studied represent arm movement direction within a coordinate system rotating with the arm and where signals about the movement direction relate to the motor plan through a simple invariant relationship, that between cell preferred direction and arm orientation in space.

Animals↗

PubMed1979

The morphology of microtubules in incubated synaptosomes. Effect of low temperature and vinblastine.

A time-dependent rise in the percentage of microtubule-containing synaptosomes was observed reaching a 41--47% peak after 30 min incubation at room temperature (22--25 degrees C) in a saline medium. Fixation at low temperature or incubation with vinblastine decreased markedly the number of synpatosomes containing microtubules. It was concluded that incubation with cations and processing at room temperature were prerequisites of optimal preservation of synaptosomal microtubules. Their spatial orientation relative to the synaptic cleft was deduced from statistical examination of profiles in different orientations.

Animals↗

PubMed1986

M.I.T./Canadian vestibular experiments on the Spacelab-1 mission: 1. Sensory adaptation to weightlessness and readaptation to one-g: an overview.

Experiments on human spatial orientation were conducted on four crewmembers of Space Shuttle Spacelab Mission 1. This introductory paper presents the conceptual background of the project, the relationship among the experiments and their relevance to a "sensory reinterpretation hypothesis". Detailed experiment procedures and results are presented in the accompanying papers in this series. The overall findings are discussed in this article as they pertain to the following aspects of hypothesized sensory reinterpretation in weightlessness: utricular otolith afferent signals are reinterpreted as indicating head translation rather than tilt, sensitivity of reflex responses to footward acceleration is reduced, and increased weighting is given to visual and tactile cues in orientation perception and posture control. Three subjects developed space motion sickness symptoms, which abated after several days. Head movements, as well as visual and tactile cues to orientation influenced symptoms in a manner consistent with the sensory-motor conflict theory of space motion sickness. Six short duration tests of motion sickness susceptibility, conducted pre-flight, failed to predict sickness intensity in weightlessness. An early otolith-spinal reflex, measured by electromyography from the gastrocnemius-soleus muscles during sudden footward acceleration, was inhibited immediately upon entering weightlessness and declined further during the flight, but was unchanged from pre-flight when measured shortly after return to earth. Dynamic visual-vestibular interaction was studied by measuring subjective roll self-motion created by looking into a spinning drum. Results suggest increased weighting of visual cues and reduced weighting of graviceptor signals in weightlessness. Following the 10 day flight, erect posture with eyes closed was disturbed for several days.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗

PubMed1987

Neurons of area 7 activated by both visual stimuli and oculomotor behavior.

Behavioral and clinical studies have long implicated the posterior parietal cortex of primates in spatial perception and spatially oriented behavior. However, recordings from single neurons in behaving monkeys by different laboratories have resulted in divergent views with some ascribing a largely motor and others a largely sensory role for this region. We have designed paradigms to separate the sensory and motor components of the neural activity and have found that the cells in this area respond to both sensory stimulation and motor behavior. Thus, it is likely that this area is not solely sensory or motor, but rather is involved in higher order aspects of sensory-motor integration.

Animals↗

PubMed1995

Somatostatin-immunoreactive cell in the gastrointestinal tract of the frog Rana esculenta.

The morphology and topographic distribution of somatostatin-immunoreactive cells in the stomach and small intestine of the frog Rana esculenta were studied at the light-microscopic level by the use of the peroxidase-antiperoxidase method. Scattered immunostained cells occurred in all regions of the gastrointestinal tract investigated. In the small intestine, the number of these cells decreased gradually in the oral to anal direction, i.e. from the pyloric (antral) stomach to the entrance into the colon. Most of the immunostained cells possessed thick, short cytoplasmic processes, which did not display a preferential spatial orientation. Other somatostatin-immunoreactive cells, which were exclusively located in the small intestine, gave rise to a single long extension oriented toward the lumen. In both stomach and small intestine, a complete penetration of the epithelial surface by these processes of somatostatin-immunoreactive cells was observed only occasionally. The morphological features of the somatostatin-immunostained cells speak in favor of endocrine, paracrine, and possibly also intraluminal secretory functions of the enteroendocrine somatostatin system in frogs.

Animals↗

PubMed1987

Probing depth in monocular images.

It is generally expected that depth (distance) is the internal representational primitive that corresponds to much of the perception of 3D. We tested this assumption in monocular surface stimuli that are devoid of distance information (due to orthographic projection and the chosen surface shape, with perspective projection used as a control) and yet are vividly three-dimensional. Slant judgments were found to be in close correspondence with the actual geometric slant of the stimuli; the spatial orientation of the surfaces was perceived accurately. The apparent depth in these stimuli was then tested by superimposing a stereo depth probe over the monocular surface. In both the perspective and orthographic projection the gradient of perceived depth, measured by matching the apparent depth of the stereo probe with that of the monocular surface at a series of locations, was substantial. The experiments demonstrate that in orthographic projection the visual system can compute from local surface orientation a depth quantity that is commensurate with the relative depth derived from stereo disparity. The depth data suggests that, at least in the near field, the zero value for relative depth lies at the same absolute depth as the stereo horopter (locus of zero stereo disparity). Relative to this zero value, the depth-from-slant computation seems to provide an estimate of distance information that is independent of the absolute distance to the surface.

Depth Perception↗

PubMed1987

Quick measurement of hematocrit and erythrocyte sedimentation-rate by means of a density tracking method.

An instrument to track the sedimentation properties of red blood cells quickly and automatically and to evaluate the hematocrit as well as the plasma density of a blood sample in the same operation is described. Erythrocyte-sedimentation basically is due to the density difference between the red blood cells and the plasma and the new method makes use of the mechanical-oscillator-technique, where the resonant frequency of the bending-type oscillations of a U-shaped glass tube is related to the density of the fluid with which the tube is filled. The oscillating U-tube is part of a sedimentation-tube of special dimensions and particular spatial orientation. The tube is tilted at 60 degrees, the tip of the U-tube being raised above the horizontal plane. Filling the sedimentation-tube with anticoagulated blood first permits recording of the density of the homogeneous suspension. Then, after a few minutes, the onset of erythrocyte-sedimentation produces a decrease in recorded density. The final value is related to the density of the supernatant plasma-fluid. Hematocrit, blood and plasma density of the undiluted blood sample as well as the sedimentation-rate of the anticoagulated sample are automatically calculated from the recorded sedimentation-curve. The particular arrangement of the tilted sedimentation-tube facilitates a determination of the maximum sedimentation-rate within 15 min at most.

Blood Sedimentation↗

PubMed1988

Factors governing the adaptation of cells in area-17 of the cat visual cortex.

Neurons in area 17 of the cat visual cortex adapt when stimulated by drifting patterns of optimal orientation, spatial frequency and temporal frequency (Ohzawa et al. 1982; Albrecht et al. 1984; Ohzawa et al. 1985). A component of this adaptation has been attributed to a contrast gain-control mechanism, rather than to neural fatigue, and results in enhanced differential sensitivity around the adapting contrast level (Ohzawa et al. 1982; Albrecht et al. 1984; Ohzawa et al. 1985). Experiments described here suggest that neural response rate, the directional selectivity of the cell, and the temporal frequency of the stimulus, are the principal determinants of adaptation, irrespective of other stimulus parameters such as contrast, velocity, or spatial frequency. The present results can nevertheless accommodate the results of previous studies of adaptation, and additionally provide scope for the resolution of apparent contradictions between results from psychophysical and neurophysiological studies of adaptation.

Adaptation, Physiological↗

PubMed1991

MRI and CT in the preoperative evaluation of soft-tissue tumors.

The value of MRI and CT in the diagnosis of soft-tissue tumors was investigated in a prospective study of 25 patients. MRI and CT give a true reflection of the tumor dimensions. It is impossible, however, to make a reliable diagnosis with either technique. If both techniques are available, then MRI is to be preferred in view of the better spatial orientation and sharper contrast it offers between the tumor and adjacent structures. If only CT is available, then an adequate image can generally be obtained with this technique too.

Adolescent↗

PubMed1983

Topo-optical reactions of the human blood platelet membrane.

The polarization optical analysis of human blood platelets was carried out by means of topo-optical staining reactions. Similar studies have not been performed so far. With this approach we were able to demonstrate the spatially oriented nature of glycoprotein components in the platelet membrane. Using a sialic acid specific topo-optical reaction the sialic acid component of human platelet membrane was selectively demonstrated and the even distribution of sialic acid residues on the membrane surface was also suggested. Polarization optical analysis has shown a membrane-parallel orientation of oligosaccharide chains carrying sialic acids.

Blood Platelets↗

PubMed1983

Application of optical diffractometry in studies of cell fine structure. Comparison of arterial smooth muscle cells in contractile and synthetic state.

Arterial smooth muscle cells in contractile and synthetic state were analyzed by optical diffractometry. Cell sections (80-90 nm) were photographed in an electron microscope and diffraction patterns of the plates (negatives) were produced using a helium-neon laser. Radial and angular distributions of light intensity in the diffractograms were measured and digitized using an electronic detector plate consisting of ring- and wedge-shaped photosensitive elements; radial distributions provide information about size of structures and distances between them and angular distributions about spatial orientation of structures in the images. Micrographs of nuclei and cytoplasm were analyzed separately (40-50 plates in each group). Computerized statistical analysis of radial distributions of light intensity showed that the nuclear chromatin pattern differed between cells in contractile and synthetic state. The probability that the observed difference could have arisen purely by chance was less than 10(-5). Computer-aided classification to the a priori known cell group was correct in 96.5% of the cases. Analysis of radial distributions of light intensity similarly showed marked differences in cytoplasmic structure between cells in contractile state (dominated by bundles of myofilaments) and synthetic state (dominated by cisternae of rough endoplasmic reticulum). The probability that the observed difference could have arisen purely by chance was less than 10(-5). Computer-aided classification to the a priori known cell group was correct in 92.0% of the cases. In contrast, analysis of angular distributions of light intensity did not indicate any statistically significant differences between contractile and synthetic state cells. A likely reason is that both myofilaments and cisternae of rough endoplasmic reticulum were arranged in parallel. The results demonstrate that optical diffractometry is a useful method for image analysis in studies of cell fine structure. It provides information about size and orientation of structures with poorly defined shape and is particularly well suited for studies on cell differentiation and effects of pharmacological and other experimental treatments on cell fine structure. It represents an alternative and a complement to stereology for quantitative and objective evaluation of morphological data.

Animals↗

PubMed1978

[Investigation of the anisotropy of glycocalyx stained with 1.9-dimethyl methylene blue and N,N'-diethylpseudoisocyanine chloride (author's transl)].

In the present study the anisotropic staining of the erythrocyte membrane with 1.9-dimethyl methylene blue and N,N'-diethylpseudoisocyanine chloride was studied and simultaneously compared with the toluidine blue topo-optical staining. The difference between anisotropic toluidine blue and 1.9-dimethyl methylene blue staining, except after KMnO4-oxidation, was only of quantitative nature. On the contrary, striking differences were observed between N,N'-diethylpseudoisocyanine chloride staining, and toluidine blue or 1.9-dimethyl methylene blue staining. Enzymatic and chemical degradation resulted the disappearance of N,N'-diethylpseudoisocyanine chloride staining. Following these treatment membrane birefringence could be restored by aldehyde bisulfate and/or KMnO4-oxidation, while the N,N'-diethylpseudoisocyanine chloride staining was restored only after KMnO4-oxidation. After methylation or acetylation the membrane birefringence disappears, while after KMnO4-oxidation both topo-optical reactions return. The digitonin reaction brought about a rearrangement of the glycocyalyx components. The results draw attention to the spatial orientation of the glycoprotein of the erythrocyte membrane. The role of glycocalyx in the three topo-optical reactions was thus clearly demonstrated.

Birefringence↗

PubMed1988

Stimulus discrimination in the diencephalon of Eigenmannia: the emergence and sharpening of a sensory filter.

Neuronal reliability and sensitivity to behaviorally relevant stimulus patterns were investigated in a higher-order nucleus of the diencephalon believed to participate in the jamming avoidance response (JAR) of the weakly electric fish, Eigenmannia. The fish raises or lowers its frequency of electric organ discharge (EOD) to minimize interference from a neighboring fish's EOD. Proper JARs require determination of the sign of the difference frequency (Df) between the neighboring fish's EOD and the fish's own EOD. Bastian and Yuthas (1984) recently described diencephalic neurons within the nucleus electrosensorius that are able to make this determination. In the present study, response properties of such neurons were compared with those of lower-level 'sign-selective' cells found in the torus semicircularis and the optic tectum (Heiligenberg and Rose 1985) as well as with properties of the intact behavior. Most sign-selective cells within the nucleus electrosensorius show a high degree of selectivity for one sign of the difference frequency; cells with either sign preference were found in approximately equal numbers. The sign preference and the degree of sign selectivity is most often independent of the spatial orientation of the jamming stimulus. In contrast, the responses of toral and tectal cells are less robust and consistent and are often highly dependent on the geometry of the jamming stimulus. Determination of the sign of the difference frequency requires the analysis of amplitude modulations coupled with modulations in phase (timing) differences between pairs of areas of the body surface. The most sensitive cells recorded in the nucleus electrosensorius can determine the sign of the difference frequency with timing differences of 1 microsecond or less, roughly comparable to the behavioral threshold of 400 ns (Carr et al. 1986). The best toral/tectal response required at least a 16 microseconds modulation. Cells within the nucleus electrosensorius thus code the sign of Df with a high degree of reliability and sensitivity. Ambiguities persist, however, which suggest that single cells at this level cannot completely account for the behavioral discrimination. Additional processing may be necessary to transform a still primarily sensory code into a motor program for control of the JAR (Rose et al. 1988).

Animals↗

PubMed1992

The assessment of cellular proliferation by immunohistochemistry: a review of currently available methods and their applications.

Immunohistochemical methods using antibodies to cell cycle-related antigens may be used as a means of assessing various aspects of proliferation in tissue, and have the important advantage of preserving the spatial orientation of proliferating cells in histological sections. Currently, the most widely available antibodies for this purpose are antibodies to bromodeoxyuridine (BrdU), Ki67 and antibodies to proliferating cell nuclear antigen (PCNA). BrdU is a thymidine analogue incorporated during the S phase of the cell cycle, which can be introduced by 'in vitro' incubation, and monoclonal antibodies are available to display its localization. Ki67 demonstrates a nuclear antigen expressed in all phases of the cell cycle, except G0 and early G1, but can only be applied to frozen tissue. PCNA is a nuclear antigen which is essential for DNA synthesis, two commercially available antibodies to PCNA work in paraffin-embedded tissue, but may have different staining characteristics under different conditions of fixation. The main advantages and disadvantages of these different techniques are discussed, together with their main applications to date.

Antibodies, Monoclonal↗

PubMed1979

Bone modelling processes at the endosteal surface of human femora. Scanning electron microscopical studies in normal bone and in renal osteodystrophy.

In femoral bone of 10 adult patients without bone disease and of 15 patients with secondary hyperparathyroidism, thy after nonmineralised organic material had been removed from the endosteal surface by sodium hypochlorite. This technique permits one to analyse the effects of past osteoblastic and osteoclastic activities. Im normal bone, the endosteal envelope shows a highly ordered texture: The main part of the inner surface is represented by fully mineralised smooth surfaces without evidence of apposition or resorption (so called neutral surfaces). In apposition areas, collagen fibers are still incompletely mineralised. Ordered mineral deposits are observed, consisting of spindleshaped calcospherites of uniform size. The resorption areas are sharply delimited. The resorption layer shows a small difference of level with respect to the surrounding neutral surface. Resorption areas consist of numerous lacunae with a smooth bottom. Individual lacunae are encircled by shallow ridges which run almost perpendicularly to the main direction of collagen fibers that have been exposed by resorption. These findings suggest that in normal bone osteoclasts act as a corrdinated group of cells. The direction of advance of the resorption area is to some extent influenced by the collagen pattern of bone. In patients with secondary hyperparathyroidism, domain formation of the endosteal surface can no longer be recognized. The size and shape of caleospherites are extremely heterogeneous, a finding interpreted as evidence of formation of woven bone. Resorption areas are irregularly determined and often resemble worm-eaten wood. The planes of resorption vary in direction and depth and in general resorption cavities penetrate deeper than in normal bone. These findings point to loss of coordinated cell action under the influence of hyperparathyroidism. The observations suggest that in hyperparathyroidism endosteal cells do not respond to local factors which influence endosteal cell activities in modelling processes of normal bone. Such local factors consist of the pattern of collagen andlamellar organisation on one hand and mechanical forces presumably via pizo-electrical potentials, on the other. In hyperparathyroidism the interdependence between bone matrix texture and spatial orientation of bone surface lining cell activities is lost.

Adult↗

PubMed1993

Three-dimensional transesophageal echocardiography for depiction of regional left-ventricular performance: initial results and future directions.

To assess the potential of a prototype transesophageal echocardiography probe for evaluating left-ventricular wall motion in three dimensions, we acquired images under anesthesia in 15 patients who had akinesia or dyskinesia and 8 patients who had normal function demonstrated on preoperative ventriculography. Short-axis, oblique transgastric scans were obtained in 16 of the patients and four-chamber, long-axis oblique scans were obtained in 12 patients, with five patients (22%) yielding good-quality scans of both types. Off-line, we outlined the endocardial borders manually and used the outlines to make computer-generated three-dimensional models of the endocardial surfaces, color-tiled according to regional ejection fraction. Compared with contrast ventriculograms, the regional ejection fraction histograms derived from these models showed 86% concordance for detecting dyssynergy. However, the concordance between the ventriculograms and the color-tiled models in localizing the dyssynergy was only 67% overall. Uncertainty in rotational alignment between the reconstructions and the ventriculograms appeared to contribute to misreading the location of dyssynergy. In addition, the apical region appeared to have been missed in 8 (50%) of the short-axis scans, whereas it was visualized in all long-axis scans. We conclude that three-dimensional analysis of the location, extent, and degree of left-ventricular dyssynergy is feasible from transesophageal echocardiograms and could have wide application in the study of regional ventricular function. However, improvements are necessary to enable the transducer to scan the cardiac apex more reliably from the short-axis viewpoint and to have a means for spatially orienting the images with respect to an external frame of reference.

Computer Graphics↗

PubMed1979

Medulloblastoma in childhood. Survival and functional results.

The authors report on a series of 57 medulloblastomas in children operated upon -etween 1964 and 1976. Among these children, 44 completed the treatment with radiotherapy to the whole central nervous system. The postoperative mortality rate in 10.5%. Postoperative deaths occurred mainly in infants or when a tumour involved the brain stem. The five-year survival rate is 54% in the whole series. It rose to 71% in the patients who completed the treatment with radiotherapy. The study shows that the life of survivals is frequently impaired by mental or behavioural disturbances. IQ varies from 70 to 90 in 58% of the children; it is below 70 in 31%. Behavioural disturbances are found in 93% of cases. 82% have defective spatial orientation, dysphasia, or dysgraphia. In order to evaluate the responsibility of X-ray therapy for the development of these sequelae, the results have been compared to those of a series of cerebellar astrocytomas surgically removed, but not irradiated. The comparison shows that radiotherapy is at least partially responsible for the mental and behavioural disturbances. No relation was found between these disturbances and a persistent ventricular dilatation or an endocrine dysfunction. However the endocrine assessment showed growth hromone deficiency in 65% of the children, short stature in 55%, and compensated hypothyroidism in 58%.

Adolescent↗

PubMed1994

Echocardiographic evaluation of hearts with twisted atrioventricular connections (criss-cross heart).

An echocardiographic study was performed on seven patients with twisted atrioventricular connections (criss-cross heart) relative to the usual atrial arrangement. The atrioventricular connections were concordant in five patients and discordant in two. The ventriculoarterial junction was either double-outlet right ventricle (n = 6) or discordant connections (n = 1). Associated cardiac defects were ventricular septal defect (n = 7), pulmonary stenosis (n = 5), straddling tricuspid valve (n = 2), and straddling mitral valve (n = 1). Malalignment between the atrial and ventricular septum was the most important feature of this disease and resulted in altered spatial orientation of the trabecular ventricular septum, and recesses in the ventricles and the right atrium. When assessed by echocardiography, these anatomical features were not invariably recognized in every case, but they were dependent upon the type of atrioventricular connections and the presence of straddling of the atrioventricular valves. Left ventricular recess was the most consistent feature and was present in every patient, regardless of the atrioventricular connections. Right atrial recess was found in four of five patients with concordant atrioventricular connections but was not present in patients with discordant atrioventricular connections. Right ventricular recess was recognized as such in a single patient with concordant atrioventricular connection and straddling mitral valve. The trabecular septum was oriented in a horizontal plane in hearts with concordant atrioventricular connections and without atrioventricular valve straddling. The trabecular septum was oriented semivertically in all other hearts.(ABSTRACT TRUNCATED AT 250 WORDS)

Child, Preschool↗