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PubMed2002

Tuning of photoreceptor function in three mantis shrimp species that inhabit a range of depths. I. Visual pigments.

Visual pigments in many animal species, including stomatopod crustaceans, are adapted to the photic environments inhabited by that species. However, some species occupy a diversity of environments as adults (such as a range of depths in the ocean), and a single set of visual pigments would not be equally adaptive for all habitats in which individuals live. We characterized the visual pigment complements of three species of stomatopod crustaceans, Haptosquilla trispinosa, Gonodactylellus affinis, and Gonodactylopsis spongicola, which are unusual for this group in that each lives at depths from the subtidal to several tens of meters. Using microspectrophotometry, we determined the visual pigments in all classes of main rhabdoms in individuals of each species from shallow or deep habitats. Each species expressed the typical diversity of visual pigments commonly found in stomatopods, but there was little or no evidence of differential expression of visual pigments in animals of any species collected from different depths. Vision in these species, therefore, is not tuned to spectral characteristics of the photic environment by varying the assemblages of visual pigments appearing in their retinas.

Animals↗
PubMed1995

Analysis of saccadic short-term plasticity in three dimensions.

The capacity for short-term adaptation is a well-established property of the horizontal (H) and vertical (V) components of saccades. It allows these directional components, which clearly serve the goal of foveation, to maintain their precision even under changing circumstances. Torsional (T) saccade components, on the other hand, which deal with the orientation of the target on the fovea, have hardly been investigated in adaptation experiments. They appear to be severely restricted by Listing's law during fixations and saccades. The main purpose of Listing's law is far from obvious but could be visual or oculomotor. Better knowledge of the adaptive capacity of the saccadic system in the torsional direction could throw new light on the functional significance of this interesting neural strategy. To study short-term plasticity in the torsional components of saccades, binocular 3D-eye positions were measured, using magnetic search coils. Five normal human subjects were instructed to make uni-directional refixation saccades, while they viewed a large visual scene. To induce a change in the torsional component, the complete stimulus was rapidly rotated during these saccades. We thoroughly investigated the torsional responses of the saccadic system, to see if any short-term adaptive response in torsional direction was induced, in which case the notion of a visual purpose for Listing's law would be strengthened. In none of our experiments, however, did we find any clear adaptive response in torsional direction. To further investigate the reliability of this result and to ascertain that our experimental conditions allowed classical gain adaptation, we also did experiments designed to achieve a combination of torsional adaptation and classic gain shortening in one of the directional components. While gain adaptation was very obvious, none of the experiments provided evidence for a short-term effect in torsion. We conclude that our experiments do not support a purely visual basis for Listing's law.

Adaptation, Physiological↗
PubMed1990

A possible new control mechanism suggested by resonance Raman spectra from a deep ocean fish hemoglobin.

The rattail fish, Coryphaenoides armatus, lives at ocean depths of 3000 m. As an adaptation for pumping oxygen into the swim bladder against the extreme pressures at the ocean bottom, the hemoglobin from this fish at low pH exhibits an extraordinarily low affinity for ligands. In this study, continuous wave and time-resolved Raman techniques are used to probe the binding site in this hemoglobin. The findings show an association between the low-affinity material and a highly strained heme-proximal histidine linkage. The transient Raman studies reveal differences in the protein structural dynamics at pH 6 and 8. The emerging picture derived from both this and earlier studies is that in vertebrate hemoglobins the heme-proximal histidine linkage represents a key channel through which species- and solution-dependent variations in the globin are communicated both statically and dynamically to the heme to produce an extensive range of ligand binding properties. Also presented is a new model that relates both intensity and frequency of the resonance Raman band involving the iron-proximal histidine stretching mode to specific protein controlled structural degrees of freedom. There emerges from this model a mechanism whereby modifications in the proximal heme pocket can further reduce the affinity of an already highly strained T state structure of hemoglobin.

Animals↗
PubMed2005

Selective attention and cyclopean motion processing.

The effect of diverted selective attention on the induction of the cyclopean motion aftereffect (aftereffect induced from dynamic disparity information) was investigated. The luminance motion aftereffect was examined for comparison. During diverted-attention trials, observers ignored background adapting motion and performed a low-load or high-load rapid serial visual presentation (RSVP) task presented in the center of the motion display. Baseline motion aftereffects were obtained with no diverted attention. The results showed that the cyclopean motion aftereffect, similar to the luminance motion aftereffect, declined only modestly under diverted-attention conditions. Selective attention appears to play a modest role in the visual processing of cyclopean motion.

Adaptation, Ocular↗
PubMed2006

Slant perception, and its voluntary control, do not govern the slant aftereffect: multiple slant signals adapt independently.

Although it is known that high-level spatial attention affects adaptation for a variety of stimulus features (including binocular disparity), the influence of voluntary attentional control-and the associated awareness-on adaptation has remained unexplored. We developed an ambiguous surface slant adaptation stimulus with conflicting monocular and binocular slant signals that instigated two mutually exclusive surface percepts with opposite slants. Using intermittent stimulus removal, subjects were able to voluntarily select one of the two rivaling slant percepts for extended adaptation periods, enabling us to dissociate slant adaptation due to awareness from stimulus-induced slant adaptation. We found that slant aftereffects (SAE) for monocular and binocular test patterns had opposite signs when measured simultaneously. There was no significant influence of voluntarily controlled perceptual state during adaptation on SAEs of monocular or binocular signals. In addition, the magnitude of the binocular SAE did not correlate with the magnitude of perceived slant. Using adaptation to one slant cue, and testing with the other cue, we demonstrated that multiple slant signals adapt independently. We conclude that slant adaptation occurs before the level of slant awareness. Our findings place the site of stereoscopic slant adaptation after disparity and eye posture are interpreted for slant [as demonstrated by Berends et al. (Berends, E. M., Liu, B., & Schor, C. M. (2005). Stereo-slant adaptation is high level and does not involve disparity coding. Journal of Vision 5 (1), 71-80), using that disparity scales with distance], but before other slant signals are integrated for the resulting awareness of the presented slant stimulus.

Adaptation, Physiological↗
PubMed1997

Deficiency of adaptive control of the binocular coordination of saccades in strabismus.

Disconjugate (different in the two eyes) oculomotor adaptation is driven by the need to maintain binocular vision. Since binocular vision is deficient in strabismus, we wondered whether oculomotor disconjugate adaptive capabilities are deficient in such subjects. We studied eight adult subjects with constant, long-standing convergent strabismus of variable angles (4-30 prism D). No subject had severe amblyopia. Binocular vision was evaluated with stereoacuity tests. Two subjects had peripheral binocular vision and gross stereopsis; two other subjects had abnormal retinal correspondence and abnormal or pseudo gross stereopsis. In the other subjects binocular vision and stereopsis were absent. To stimulate disconjugate changes of saccades, subjects viewed for 20 min an image that was magnified in one eye (aniseikonia). Subjects with residual peripheral binocular vision and even subjects with pseudo or abnormal binocular vision showed disconjugate changes of the binocular coordination of their saccades; these changes reduced the disparity resulting from the aniseikonia. In contrast, for subjects without binocular vision the changes were not correlated with the disparity induced by the aniseikonia. Rather, these changes served to improve fixation of one or the other eye individually.

Adaptation, Physiological↗
PubMed1999

The periodontal response to cantilevered resin-bonded bridgework.

This study investigated 84 cantilevered resin-bonded bridges (CRBB) in 60 patients. These CRBB (single retainer, single pontic) had been in place for an average of 43.6 months. Periodontal health was assessed on abutment teeth and contralateral control teeth. Periodontal indices utilized were Plaque Index (PI), Gingival Index (GI), Bleeding Index (BI), Pocket Depth (PD) and mobility. The marginal adaptation, the gingival extension of the retainers and the presence or absence of caries around each retainer margin were also assessed. Information about the history of debonding was collected and a success rate of 93% was reported. PI, GI and mean PD compared statistically significantly, less favourably, with scores of the control teeth. Marginal adaptation of the retainers was of a high standard and caries did not appear to be a problem.

Adolescent↗
PubMed1978

Interocular transfer in individuals with strabismic amblyopia; a cautionary note.

Interocular transfer of the adaptation after effect was measured and correlated with residual binocular function for two strabismic amblyopes who represent different types of neural loss. The results indicate that for these two subjects there is paradoxical correlation between efficacy of interocular transfer and residual binocular function.

Adaptation, Ocular↗
PubMed1985

Vergence adaptation maintains heterophoria in normal binocular vision.

This investigation sought to determine whether vergence adaptation serves to maintain orthophoria or heterophoria in normal binocular vision. While wearing prisms which neutralized their nearpoint (40 cm) heterophorias, 27 of 30 nonstrabismic subjects adapted from their prismatically created orthophoria toward their habitual heterophoria. Three subjects showed no adaptive response. A symptom questionnaire distributed to these subjects determined that the maintenance of heterophoria by vergence adaptation is: characteristic of normal and comfortable binocular vision, and neither an entirely necessary nor sufficient condition for normal and comfortable binocular vision.

Adaptation, Physiological↗
PubMed1987

Mapping of ophthalmic lens distortions with a pinhole camera.

Ophthalmic lenses are produced in a variety of forms each having unique effects upon visual space. The foundation for evaluating visual space distortion associated with ophthalmic lenses is an understanding of the optical input to the visual system. We developed a photographic technique to evaluate the effects of ophthalmic lenses on optical imagery. This technique uses a pinhole camera and an associated lens holder to simulate the eye-lens relation and provide an eye-referenced view of optical space. A rectilinear grid was photographed through Varilux progressive addition lenses (PAL's) and with no lenses in place. Comparison of these photographs provides a measure of relative optical space distortion that should closely approximate relative visual distortion under similar viewing conditions. Our technique provides an optical baseline with which more in depth studies of space perception and adaptation may be compared.

Humans↗
PubMed2006

Cellular, molecular and immunological mechanisms in the pathophysiology of vein graft intimal hyperplasia.

Coronary artery disease, leading to myocardial infarction and ischaemia, affects millions of persons and is one of the leading causes of morbidity and mortality worldwide. Invasive techniques such as coronary artery bypass grafting are used to alleviate the sequelae of arterial occlusion. Unfortunately, restenosis or occlusion of the grafted conduit occurs over a time frame of months to years with a gradual reduction in patency, especially in vein grafts. The events leading to intimal hyperplasia (IH) formation involve numerous cellular and molecular components. Various cellular elements of the vessel wall are involved as are leucocyte-endothelial interactions that trigger the coagulation cascade leading to localized thrombus formation. Subsequent phenotypic modification of the medial smooth muscle cells and their intimal migration is the basis of the lesion formation that is thought to be propagated by an immune-mediated reaction. Despite intense scrutiny, the pathophysiology of IH remains an enigma. Although several growth factors, cytokines and numerous other biomolecules have been implicated and their relationship to prohyperplasia pathways such as the phosphatidyl-inositol 3-kinase (PI3K)-Akt pathway has been established, many pieces of the puzzle are still missing. An in-depth understanding of early vein graft adaptation and progression is necessary to improve the long-term prognosis and develop more effective therapeutic measures. In this review, we have critically evaluated and summarized the literature to elucidate and interlink the numerous established and emerging factors that play a key role in the development of IH leading to vein graft restenosis.

Arterial Occlusive Diseases↗
PubMed2004

Pneumonia caused by Mycobacterium kansasii in a series of patients without recognised immune defect.

The clinical and epidemiological characteristics of 17 patients diagnosed with Mycobacterium kansasii pneumonia within a limited geographical region over a period of 10 years are described. An in-depth evaluation of the innate and adaptive immune systems was performed for five available patients. A comparison was made of the genetic fingerprint patterns of the isolates obtained by restriction fragment length polymorphism (RFLP) analysis, with the major polymorphic tandem repeat (MPTR) as a probe. Predisposing factors consisted of smoking, airway abnormalities, substance abuse, diabetes or poor general condition, but in two patients no risk factor was identified. In the five patients tested, no abnormalities or deficiencies were detected in the innate or adaptive type-1 immunity. All M. kansasii isolates had identical MPTR RFLP patterns, although no epidemiological connection could be established, and these were identical to those of clinical isolates from Australian patients. These data do not support the theory that defects in the innate or adaptive type-1 immunity have a role in the pathogenesis of invasive M. kansasii infections. The identical fingerprint patterns of the isolates suggested the existence of a virulent strain of M. kansasii.

Adult↗
PubMed1979

The response characteristics of an inhibitory binocular interaction in human vision.

1. The contrast threshold level for visual detection of a linear grating consisting of parallel light and dark bars is increased by adaptation to a high contrast grating of spatial characteristics similar to those of the test grating (e.g. Blakemore & Campbell, 1969). This so-called contrast threshold elevation effect is significantly reduced if two adaptation gratings, with appropriate different spatial characteristics, are presented one to either eye (Ruddock & Wigley, 1976). We have studied the contrast threshold elevation effect obtained with a test and an adaptation grating presented to one eye and a second adaptation grating, referred to as the conditioning grating, presented to the other. 2. Preliminary data are presented for three subjects with normal stereoscopic vision. In each case, the contrast threshold elevation effect for a pair of spatially identical test and adaptation gratings is significantly reduced by a conditioning grating of spatial frequency in the range 1-5 c/deg. 3. Reduction in the contrast elevation effect is observed whether the conditioning and adaptation gratings are of the same or of different wave-lengths and the effect of the conditioning grating increases to a steady-state level over a period of some 30 sec following onset of its presentation. 4. Measurements were made with a 5 deg diameter circular test grating presented at retinal locations up to 8 deg in the horizontal and vertical meridians from a foveal fixation point. It was found that in the horizontal meridian, the amplitude of the suppression effect associated with the conditioning grating falls as the displacement angle of the test field from the fixation point increases. For displacements in the vertical meridian, however, the amplitude of the suppression effect is virtually independent of the retinal location of the test field. 5. Under experimental conditions which yield suppression of the contrast threshold elevation effect for subjects with normal stereoscopic vision, no suppression was found for three subjects who possessed neither global nor fine stereoscopic vision. Results for a subject who possessed fine, but not global stereoscopy, did, however, show the suppression effect.

Adaptation, Ocular↗
PubMed1994

Detecting mistuning in the presence of synchronous and asynchronous interfering sounds.

Listeners were presented with the first seven harmonics of a 500-Hz fundamental (the "test complex"), and were required to detect a mistuning imposed on its fourth harmonic (the "target"), which had a nominal frequency of 2000 Hz. All components were frequency modulated by a 5-Hz sinusoid, and, in the signal interval of each 2IFC trial, a 180 degrees phase delay was imposed on the modulation applied to the target. This led to a mistuning proportional to the depth of FM, which was varied adaptively to obtain thresholds. When an unmodulated 2000-Hz "interfering" sinusoid was gated on and off together with the test complex, thresholds were largely unaffected, provided the level of the interfere was more than 3 dB below that of the target. However, when the interferer started before and ended after the test complex there was a substantial elevation in threshold, even at low interfere levels. The elevation was mainly due to the portion of the interferer preceding the test complex, but the part following the complex also had some effect. When the offset asynchrony between the interferer and the test complex was held constant at 100 ms and the onset asynchrony varied, the highest thresholds occurred at an onset asynchrony of 200 ms. A threshold elevation could also be achieved by replacing the interferer with a narrow-band noise centered on 2000 Hz, or by preceding the test complex with an interferer consisting of all components except 2000 Hz.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed1980

Methodological aspects of renography in children.

Kidney function in children by renography has been evaluated. For reproducible results a high degree of standardization with respect to position, hydration and dosage was necessary. The wide range of kidney size and depth in children requires age-adapted collimators. For practical use for different size have been constructed for the age-groups: less 1 year, 1-5 years, 6-9 years and 10-15 years. A reduction in the surrounding activity of the kidneys is thereby obtained and disturbing influence from the bladder or contralateral kidney is prevented. Kidney function variables from the renogram are presented in terms of uptake and excretion ratios. The correlation between sum of uptake ratios and clearance measurements is good in cases with slight or moderate difference in kidney size. The standardized renographic technique has many advantages for kidney function measurements in children. The method is applicable in all ages, it is simple and reliable without extensive preparations and requires a low radiation dose. Also in children we can confirm the previous opinion obtained in adults that renography is a clinical valuable method of measuring kidney function.

Adolescent↗
PubMed1991

Adaptation to form distortion of a familiar shape.

Adaptation to the shape distortion produced by an arrangement of cylindrical lenses was demonstrated. Adaptation was produced by exposing subjects to a series of photographs of faces, which appeared horizontally stretched when seen through the lens arrangement. A 16-min adaptation procedure caused a change when the width of a test face was gradually varied and the subject indicated that it looked normal. An alteration in the perceived shape of a test face and an ellipse was also demonstrated when subjects gave estimates of the height and width of these test objects. These studies provide evidence for the operation of memory representations as the veridical cue in process assimilation.

Adaptation, Ocular↗