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At least 1,693 records · Page 94Linked to original sources
PubMed1987

Digital autoradiography: design, development, and evaluation of a solid-state image analyzer.

A digital image analyzer was developed for high spatial resolution analysis of autoradiograms. The system uses a linear array of charge-coupled devices operating under microcomputer control to scan and digitize autoradiograms into matrices of up to 1,500 X 2,000 pixels with 256 gray levels. The digitized images can be converted from gray scale to pseudo-color and displayed on a high resolution color monitor. Software was developed to facilitate quantitative analysis of autoradiograms produced in single and multiple tracer studies. Because of the high output linearity and accuracy of the solid-state detectors, the system was found to digitize autoradiograms significantly more precisely and accurately than previously described autoradiographic analyzers.

Autoradiography↗
PubMed1986

The effect of optical blur on visual acuity for targets of different luminances.

We studied the effect of 1.25 D of optical blur on visual acuity at luminances ranging from photopic to low mesopic levels. Optical blur reduces acuity at all luminances tested, this reduction being fourfold at a high photopic level (170 cd m-2) and twofold in low mesopia (0.017 cd m-2). The reduction of visual acuity with blur at low luminances is greater than might be expected from a spatial frequency analysis of vision.

Humans↗
PubMed1983

[Possibilities of short-time tomosynthesis].

Short-term tomosynthesis enables continuous analysis of structures which appear interesting. The results of short-term tomosynthesis were compared with those of plain roentgenography and conventional tomography. Short-term tomosynthesis appears as an alternative to spot-film radiography and as a complement to tomography in the analysis of spatially limited regions. It facilitates orientation in space and free projection of oblique structures. Good results were obtained in examinations of the pyramids (auditory canal and mandibular joint), the paranasal sinuses, the cervical vertebral column, the extremities and their joints. Examination of soft tissues was usually not very promising in view of the conditions under which tomosynthesis was performed. The same applied likewise to the infusion cholecystocholangiogram and the infusion urogram. Technical improvements will certainly bring about an extension of the uses of this method.

Bone Diseases↗
PubMed1984

Medical geography. An emerging discipline.

p6 the United States, medical geography is one of the least known of the medically related social sciences. Medical geography is concerned with the analysis of spatial patterns of disease and medical care provision.

Delivery of Health Care↗
PubMed1980

[Stereometric study of the "muscle fiber-capillary" system of the human heart in its functional aspect].

Quantitative analysis of spatial organization of the "muscle fibre-capillary" system was performed in 5 normal human hearts. The data on numerical, volumetric, superificial, relative superficial density of capillaries and muscular myocardial fibres were obtained; their total number in the left ventricle wall was calculated. Statistically significant difference of the spatial-quantitative organization in the "muscle fibre-capillary" system in different parts of the left ventricle wall was obtained. Therefore, it can be concluded that selection of myocardial slices for stereometric investigation should be systematized. A mathematical equation for estimating quantitatively capillary blood supply of the myocardial muscle fibres in histological sections was introduced, taking into account volumetric and superficial parameters of the muscle fibres and capillaries.

Adult↗
PubMed1994

Genetic diversity in the Caucasus.

We report genetic variation in the Caucasus, a region showing extreme linguistic differentiation. Spatial autocorrelation analysis of 31 alleles in 793 samples and maps of interpolated allele frequencies show significant geographic structure, but the patterns are clinical for only a few alleles. Many gene frequency distributions are patchy, most likely because of population subdivision and isolation by distance. Genetic boundaries tend to occur in different zones for the different alleles; significant overlap is observed, with boundaries separating different ethnic and linguistic groups. Conversely, the major geographic barriers, including the Caucasus Mountains, seem to have had little influence on the patterns and degrees of genetic differentiation. As a consequence, the genetic structure of Caucasus populations basically reflects restricted gene flow resulting from linguistic or ethnic subdivision. Genetic diversity does not provide evidence for a wavelike population expansion, such as the one associated with demic diffusion of agriculture in most of Eurasia.

Alleles↗
PubMed1995

[A study of heel-knee tapping test in cerebellar ataxia by a motion measurement system].

It is often difficult to estimate slight alterations in the severity of ataxia by bed-side neurological examinations. We analyzed the heel-knee tapping test, which has often been used as a standard bed-side examination to check incoordination in lower limbs, using a new motion measurement system "video/computer motion measurement system". We studied 9 normal controls and 21 patients with spinocerebellar degenerations (SCD). In patients with SCD, the up-and-down motion range of the heel was variable and the heel moved in the anterior-and-posterior direction, because of knee sways during the test. Following oral administration of TRH analogue, TA-0910, above-mentioned findings were clearly improved. Analysis of spatial and time elements of the knee joint demonstrated quantitative improvement. Therefore, an effect of TA-0910 on incoordination of the lower limbs could be proved objectively by a computer motion measurement system.

Adult↗
PubMed1997

Subjective postural orientation and visual vertical during slow pitch tilt for the seated human subject.

METHODS: To assess subjective postural orientation and the visual vertical during slow pitch tilt, subjects were seated, restrained and in darkness in a simulator. They estimated when they were tilted 0 degrees, 45 degrees, and 90 degrees forwards and backwards during cycles of pitching tilted at 1 degree x s-1 and at the same time set a 5-cm luminous cube, cockpit-mounted at 60 cm from the nasium, to be Earth vertical. Experimental protocols assessed the following: 1) the effect on postural estimates of seeing the cube versus darkness; 2) comparison of visual vertical settings at actual 45 degrees and 90 degrees tilts; 3) the adaptive effect of repeating estimates and settings; 4) the effect of a prolonged tilt on subsequent postural and visual vertical estimates; and 5) the comparative effect of tilting the body in alignment. RESULTS: Seated, subjects' estimates of postural tilt were consistently greater than machine tilt, and similar in darkness to when seeing the cube. Overestimations increased with preceding tilts in the opposite direction, particularly when tilting from forwards whence subjects estimated they were backwards when the machine was tilted forwards. Postural estimates became more accurate with repetition but visual verticals deteriorated. Duration of conditioning tilt did not effect estimates. Visual vertical settings were largely accurate throughout. Labyrinthine defective subjects performed similarly to normals. Subjects frequently reported they felt disoriented during tilting. DISCUSSIONS: Seated subjects' postural estimates were 'accurate' if one assumes that the reference shifted from the head to a trunk-leg axis on backwards tilt, however, subjects were unaware of this. Postural and visual vertical estimates could have been based solely on proprioception. Shifts in reference for verticality could be a factor in misperception of attitude in air and ground vehicles when accelerating or climbing.

Adaptation, Physiological↗
PubMed1998

Merkel complexes of human digital skin: three-dimensional imaging with confocal laser microscopy and double immunofluorescence.

Three-dimensional (3-D) reconstruction of images provided by confocal scanning laser microscopy (CSLM) is a powerful tool in a morpho-functional approach to cutaneous innervation studies. To investigate mechanoreceptors in the hand, a study of Merkel complexes was performed in human finger. A double fluorescent-conjugated immunolabeling with antibodies against neurofilament (NF 200) and cytokeratin (CK 20) on floating, thick cutaneous samples (80 to 100 microm), was used. After acquisition of serial optical planes by CSLM, reconstruction was performed with 3-D reconstruction software tools. Merkel cells were clearly labeled with CK 20, whereas nerve components were only NF 200 reactive. The cells, localized on the basal lamina of the epidermis, were usually arranged in clusters of five to eight cells. Each cell was connected to a nerve process ramification originating from a unique fiber. Quantitative data, compiled from a sample of 25 Merkel complexes, gave a mean cell diameter of 13 +/- 1 microm and a mean nerve fiber size of 3 +/- 1 microm. Surface measurements were done on a single reconstructed cluster with a mean and standard error which only refers to the optical 3-D resolution. It gives a surface of 12 +/- 1 microm2 for the contact zone between cell and nerve fiber and a cluster area of about 500 microm2. The great precision of reconstructed images provides a detailed analysis of spatial relationships between abutting nerve fibers and Merkel cells. Data interpretation is improved with complementary ultrastructural and physiological studies results, and this allows an accurate investigation of cutaneous sensory endings.

Antibodies↗
PubMed1998

[Structural organization of 2C-terminal region and its analogs in a subunit of ribonucleotide reductase from herpes virus].

By means of conformational analysis, the spatial structure and conformational potential of the H-Tyr-Ala-Gly-Ala-Val-Val-Asn-Asp-Leu-OH molecule, which corresponds to sequence 329-337 of the subunit 2 C-terminal region of the herpes virus ribonucleotide reductase, were studied. It was shown that its spatial organization can be described by a set of 17 low-energy conformations of the backbone. The "reverse conformational problem" for this molecule was solved to enable the prediction of a series of synthetic analogues matching the set of low-energy, potentially physiologically active conformations.

Amino Acids↗
PubMed2001

How are visuospatial working memory, executive functioning, and spatial abilities related? A latent-variable analysis.

This study examined the relationships among visuospatial working memory (WM) executive functioning, and spatial abilities. One hundred sixty-seven participants performed visuospatial short-term memory (STM) and WM span tasks, executive functioning tasks, and a set of paper-and-pencil tests of spatial abilities that load on 3 correlated but distinguishable factors (Spatial Visualization, Spatial Relations, and Perceptual Speed). Confirmatory factor analysis results indicated that, in the visuospatial domain, processing-and-storage WM tasks and storage-oriented STM tasks equally implicate executive functioning and are not clearly distinguishable. These results provide a contrast with existing evidence from the verbal domain and support the proposal that the visuospatial sketchpad may be closely tied to the central executive. Further, structural equation modeling results supported the prediction that, whereas they all implicate some degree of visuospatial storage, the 3 spatial ability factors differ in the degree of executive involvement (highest for Spatial Visualization and lowest for Perceptual Speed). Such results highlight the usefulness of a WM perspective in characterizing the nature of cognitive abilities and, more generally, human intelligence.

Cognition↗
PubMed1984

Quality of the primate photoreceptor lattice and limits of spatial vision.

Quantitative analysis of a primate photoreceptor lattice shows that the foveal lattice is a highly regular hexagonal structure with a positional correlation length of at least 130 photoreceptors. This result indicates that the photoreceptor lattice is not sufficiently disordered to prevent aliasing in the fovea, but rather could provide the metric with which the visual system determines spatial separation even for tasks involving hyperacuity .

Animals↗
PubMed1984

A randomized trail of the effects of 1 year of exercise training on computer-measured ST segment displacement in patients with coronary artery disease.

As part of a randomized trial of the effects of 1 year of exercise training on patients with stable coronary artery disease, 48 patients who exercised and 59 control patients had computerized exercise electrocardiography performed initially and 1 year later. The patients who had exercise training as an intervention had a 9% increase in measured maximal oxygen consumption and significant decreases in heart rate at rest and during submaximal exercise. ST segment displacement was analyzed 60 ms after the end of the QRS complex in the three-dimensional X, Y and Z leads and utilizing the spatial amplitude derived from them. Statistical analysis by t testing yielded no significant differences between the groups except for less ST segment displacement at a matched work load, but this could be explained by a lowered heart rate. Analysis of variance yielded some minor differences within clinical subgroups, particularly in the spatial analysis. Obvious changes in exercise-induced ST segment depression could not be demonstrated in this heterogeneous group of selected volunteers with coronary artery disease secondary to an exercise program.

Adult↗
PubMed1983

A morphometric analysis of craniofacial growth and changes in spatial relations during secondary palatal development in human embryos and fetuses.

Staged human embryos and fetuses in the Carnegie Embryological Collection were morphometrically analyzed to show craniofacial dimensions and changes in spatial relations, and to identify patterns that would reflect normal developmental events during palatal formation. Normal embryos aged 7-8 weeks postconception (Streeter-O'Rahilly stages 19-23) and fetuses aged 9-10 weeks postconception, in eight groups with mean crown-rump (CR) lengths of 18-49 mm, were studied with cephalometric methods developed for histologic sections. In the 4-week period studied, facial dimensions increased predominantly in the sagittal plane with extensive changes in length (depth) and height, but limited changes in width. Growth of the mandible was more rapid than the nasomaxillary complex, and the length of Meckel's cartilage exceeded the length of the oronasal cavity at the time of horizontal movement of the shelves during stage 23. Simultaneously with shelf elevation, the upper craniofacial complex lifted, and the tongue and Meckel's cartilage extended forward beneath the primary palate. Analysis of spatial relations in the oronasal cavity showed that the palatomaxillary processes became separated from the tongue--mandibular complex as the head extended, and the tongue became positioned forward with growth of Meckel's cartilage. As the head position extended by 35 degrees, the cranial base angulation was unchanged and the primary palate maintained a 90 degrees position to the posterior cranial base. However, the sagittal position of the maxilla relative to the anterior cranial base increased by 20 degrees between stages 19 and 23. In the late embryonic and early fetal periods, the mean cranial base angulation of approximately 128 degrees and the mean maxillary position angulation of approximately 84 degrees were similar to the angulations previously shown to be present later prenatally and post-natally. The results suggest that human patterns of cranial base angulation and maxillary position to the cranial base develop during the late embryonic period when the chondrocranium and Meckel's cartilage form the primary skeleton.

Cephalometry↗
PubMed2005

Time-varying differences in evoked potentials elicited by high versus low spatial frequencies: a topographical and source analysis.

OBJECTIVE: To investigate time-varying differences in visual-evoked potentials (VEPs) and dipoles elicited by high versus low spatial frequencies. The main question was whether different spatial frequencies are processed in distinct cortical areas, especially after 100 ms. An additional question was whether and how a hemispheric balance in spatial frequency processing develops over time. METHODS: Stimuli were square-wave gratings, with spatial frequencies of 0.75, 1.5, and 6 c/d. VEPs and dipole models were analyzed at various latencies. RESULTS: For the time-window of 80-100 ms, spatial frequency-related differences in VEPs and dipoles in posterior regions as reported previously were replicated: lower spatial frequencies were associated with more positivity in the VEP and with more anterior and radial sources than high frequencies. However, after 100 ms differences in amplitude, but not in topography and dipoles, were found between the different spatial frequencies. Between 180-200 ms a right hemisphere dominance was found for all frequencies. CONCLUSIONS: After 100 ms, VEPs in response to different spatial frequencies seem to be generated in the same cortical areas. Also, no evidence for frequency-related hemispheric lateralization was found. SIGNIFICANCE: Insight is provided into the functional-anatomical basis of longer-latency frequency-related differences in processing.

Adolescent↗