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Results for “depth adaptation”

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PubMed2001

Neural dynamics of motion integration and segmentation within and across apertures.

A neural model is developed of how motion integration and segmentation processes, both within and across apertures, compute global motion percepts. Figure-ground properties, such as occlusion, influence which motion signals determine the percept. For visible apertures, a line's terminators do not specify true line motion. For invisible apertures, a line's intrinsic terminators create veridical feature-tracking signals. Sparse feature-tracking signals can be amplified before they propagate across position and are integrated with ambiguous motion signals within line interiors. This integration process determines the global percept. It is the result of several processing stages: directional transient cells respond to image transients and input to a directional short-range filter that selectively boosts feature-tracking signals with the help of competitive signals. Then, a long-range filter inputs to directional cells that pool signals over multiple orientations, opposite contrast polarities, and depths. This all happens no later than cortical area MT. The directional cells activate a directional grouping network, proposed to occur within cortical area MST, within which directions compete to determine a local winner. Enhanced feature-tracking signals typically win over ambiguous motion signals. Model MST cells that encode the winning direction feed back to model MT cells, where they boost directionally consistent cell activities and suppress inconsistent activities over the spatial region to which they project. This feedback accomplishes directional and depthful motion capture within that region. Model simulations include the barberpole illusion, motion capture, the spotted barberpole, the triple barberpole, the occluded translating square illusion, motion transparency and the chopsticks illusion. Qualitative explanations of illusory contours from translating terminators and plaid adaptation are also given.

Computer Simulation↗

PubMed2003

UBM-guided chamber angle surgery for glaucoma management: an experimental study.

PURPOSE: The aim of this experimental study was to investigate the potential of ultrasound bimicroscopy (UBM)-guided chamber angle surgery as an alternative or supplement to gonioscopy and intraocular microendoscopy for intraoperative control. METHODS: In 15 porcine cadaver eyes, mechanical goniopuncture or punctual Er:YAG laser trabecular ablation was performed without operating microscope or gonioscopy, but with real-life ultrasound biomicroscopy monitoring with a 50 MHz transducer. Intraoperative localization of the microsurgical instruments and tissue-instrument contact were qualitatively evaluated. RESULTS: The instruments could be clearly visualized within the chamber angle and disturbing artefacts were only minimal when using mechanically fixed instruments in slow motion. Topographic localization, tissue contact, and penetration depth of the instruments entering the scleral were well illustrated as far as the technical resolution limits of UBM would allow. CONCLUSIONS: UBM can be used intraoperatively to monitor the correct manoeuvring of microsurgical instruments in selected ab interno procedures. Some adaptations and further modifications of the technique presented here will be necessary before UBM-guided surgery can be considered for clinical use in humans.

Animals↗

PubMed1991

Lobster haemocyanin. Influence of acclimatization on subunit composition and functional properties.

Haemocyanin from the lobster Palinurus elephas has been shown to change in its subunit composition according to the time of year. In contrast, in Palinurus mauritanicus, a lobster living at greater depth, no seasonal changes in subunit composition have been observed. The results obtained from a set of experiments performed on some Palinurus mauritanicus acclimatized in an aquarium have clearly indicated that modifications of haemocyanin subunit composition may be involved in the adaptation of arthropods to environmental change.

Acclimatization↗

PubMed2002

Buildup and decay of a three-dimensional rotational aftereffect obtained with a three-dimensional figure.

Gaps in past literature have raised questions regarding the kinds of stimuli that can lead to three-dimensional (3-D) rotation aftereffects. Further, the characteristics of the buildup and decay of such aftereffects are not clear. In the present experiments, rotation aftereffects were generated by projections of cube-like stimuli whose dynamic perspective motions gave rise to the perception of rotation in unambiguous directions; test stimuli consisted of similar cubes whose rotation directions were ambiguous. In experiment 1, the duration of the adaptation stimulus was varied and it was found that the 3-D rotation aftereffect develops with a time constant of approximately 26 s. In experiment 2, the duration between adaptation and testing was varied. It was found that the 3-D rotation aftereffect has a decay constant of about 9 s, similar to that observed with 2-D motion aftereffects. Experiment 3 showed that the rotation aftereffects were not simple depth aftereffects. To account for these aftereffects and related data, a modification of an existing neural-network model is suggested.

Adult↗

PubMed1993

Extracellular dopamine concentration in the retina of the clawed frog, Xenopus laevis.

Dopamine reaches targets in the outer retina of the clawed frog (Xenopus laevis) by diffusion from a network of dopaminergic cells and processes located predominantly at the junction of inner nuclear and inner plexiform layers. We obtained values for the steady-state release, uptake, and extracellular concentration of dopamine in the retina by a combination of HPLC (with electrochemical detection), scintillation spectroscopy, and fast-scan cyclic voltammetry. Vitreal concentrations of dopamine varied from 564 +/- 109 nM in light-adapted eyes near the time of subjective dawn to 156 +/- 12 nM in dark-adapted eyes. The data are consistent with a simple model for steady-state dopamine diffusion from an appropriately sited thin-sheet source. This model was used to generate a profile of extracellular dopamine concentration as a function of retinal depth. The model predicted an increase in the dopamine concentration from the vitreous to the layer of dopaminergic cells, remaining constant from that layer to the distal tips of the photoreceptors. This prediction was borne out by comparing fast-scan voltammetric measures of dopamine at the distal tips of the receptors with the vitreal concentrations determined by HPLC using electrochemical detection.

Animals↗

PubMedDate not supplied

The experiences of young Korean immigrants: a grounded theory of negotiating social, cultural, and generational boundaries.

The experiences of young Korean immigrants in the U.S. were explored through in-depth interviews with 19 participants. The research method employed was Grounded Theory whereby data collection and analysis were conducted concurrently. Study findings indicated that the young immigrants engaged in the process of negotiating social, cultural, and generational boundaries in order to adapt in the new country. Several structural and personal factors were identified as salient conditions of the process. These findings will help health care professionals have a better understanding of how young immigrants adapt in their new environment and what structural and personal conditions play a main role in this adaptation.

Acculturation↗

PubMed2006

Titanium membranes in prevention of alveolar collapse after tooth extraction.

BACKGROUND AND PURPOSE: The resorption of alveolar bone following tooth extraction results in a narrowing and shortening of the residual ridge, which leads to esthetic and restorative problems, and reduces the bone volume available for implant therapy. The aim of this study was to evaluate the prevention of alveolar collapse after tooth extraction, using titanium membrane (Frios Boneshield; DENTSPLY Friadent, Mannheim, Germany), associated (or not) with autologous bone graft. MATERIALS AND METHODS: A total of 10 nonsmoking healthy subjects, ranging from 35 to 60 years old, were selected for this study. Each patient had a minimum of 2 uni-radicular periodontally hopeless teeth, which were scheduled for extraction. After the procedure, 2 titanium pins were fixed on the vestibular bone surfaces that were used as references for the initial measures (depth, width, and height) of the socket. Of the sockets,1 was randomly chosen to be filled with autologous bone graft (test) removed from superior maxillary tuber, and the other one did not receive the graft (control). A titanium membrane was adapted and fixed, covering the sockets, which remained for at least 10 weeks. After a 6-month healing, the final measures were performed. RESULTS: There was exposure of the membrane in 5 of the 10 treated subjects. Average bone filling (+/-standard deviation) among the 10 subjects was 8.80 +/- 2.93 mm (range 4-13) in the control group and 8.40 +/- 3.35 mm (range 4-13) in the test group. Average bone loss in width in both group was 1.40 +/- 1.97 mm (range -4-1) in the control group and 1.40 +/- 0.98 mm (range -4-0) in the test group. There was no significant statistical difference between groups considering the evaluated standards. CONCLUSION: The use of titanium membrane, alone or in association with autogenous bone, favored the prevention of alveolar ridge after tooth extraction. This membrane seems to be a possible and safe alternative to other nonresorbable membranes when the prevention of alveolar ridge resorption is the objective.

Adult↗

PubMed2003

Biophysical properties of the pelt of a diurnal marsupial, the numbat (Myrmecobius fasciatus), and its role in thermoregulation.

Numbats are unusual marsupials in being exclusively diurnal and termitivorous. They have a sparse (1921 hairs cm(-2)) and shallow (1.19 mm) pelt compared with other marsupials. Coat reflectivity is low (19%) for numbats compared with nocturnal marsupials, but absorptivity is similar to that of diurnal North American ground squirrels (72%), indicating that the coat of the numbat may be adapted for acquisition of solar heat. Numbat coat thermal resistance decreases significantly with wind speed from 45.9 s m(-1) (at 0.5 m s(-1)) to 29.8 s m(-1) (at 3 m s(-1)). Erecting the fur significantly increases pelt depth (6.5 mm) and coat resistance (79.2-64.2 s m(-1)) at wind speeds between 0.5 m s(-1) and 3 m s(-1). Numbat coat resistance is much lower than that of other marsupials, and wind speed has a greater influence on coat resistance for numbats than for other mammals, reflecting the low pelt density and thickness. Solar heat gain by numbats through the pelt to the level of the skin (60-63%) is similar to the highest value measured for any mammal. However the numbat's high solar heat gain is not associated with the same degree of reduction in coat resistance as seen for other mammals, suggesting that its pelt has structural and spectral characteristics that enhance both solar heat acquisition and endogenous heat conservation. Maximum solar heat gain is estimated to be 0.5-3.6 times resting metabolic heat production for the numbat at ambient temperatures of 15-32.5 degrees C, so radiative heat gain is probably an important aspect of thermoregulation for wild numbats.

Acclimatization↗

PubMed2001

Personality factors, stoicism and motivation in subjects under hypoxic stress in extreme environments.

Previous studies on the physiological and psychological adaptation of subjects to survival conditions involving high-altitude hypoxia (>6,500 m) have shown that personality factors are important in this adaptation. We, therefore, proposed personality traits assessments in two groups of subjects engaged in sporting activities under extreme hypoxic environmental conditions: a group of mountaineers at high altitudes (>5,500 m) and a group of free-lung divers at great depths (<30-60 m). These subjects were compared with two control groups: a group of subjects practicing no sport and another one practicing various competitive athletic activities involving speed constraints. The personality traits assessed concerned mainly the subjects' attitudes and their propensities to act out their feelings and fantasies; they were assessed using projective procedures, the Hand Test and Clark's Situational Pain Questionnaire based on the Sensory Decision Theory. Subjects trained in mountaineering and free-lung diving under extreme environmental conditions displayed a high degree of stoicism. These individuals shared some personality traits with other sportsmen, particularly aggressive tendencies and introversion although not to an extent which interfered with normal interpersonal relationships. However, at least when practicing these extreme sports, the subjects did retreat from society. One of our questions concerns the grounds for this social withdrawal, that is, whether it derives from a inner compulsion founded on personality factors or if it is merely an artifact of our perceptions of the subjects, created by the confluence of the individualistic nature of these sports and the extreme environments in which they are performed.

Acclimatization↗

PubMed1991

[Study of the outcome of acute viral encephalitis in children based on the catamnestic data].

The paper treats of the results of a prolonged follow-up of 292 children who suffered acute viral encephalitides of different etiology. Outcomes of the disease are evaluated. Encephalitis outcome was mainly determined by etiology of the process. The most unfavourable outcomes were recorded in a group of children who suffered herpetic and cytomegaloviral encephalitides. The lingering convalescence may last up to 1.5-2 years. During that period, the children undergo not only a genuine recovery but also processes of compensation and adaptation. The residual phenomena include alterations which do not tend towards the reverse development. It is of paramount importance to take into account and to estimate properly premorbid changes on the part of the CNS. Etiology of the process determines the depth and stability of the residual phenomena.

Acute Disease↗

PubMed2006

Flexible architecture of inducible morphological plasticity.

1. Predator-induced morphological defences are produced in response to an emergent predator regime. In natural systems, prey organisms usually experience temporal shifting of the composition of the predator assemblage and of the intensity of predation risk from each predator species. Although, a repetitive morphological change in response to a sequential shift of the predator regime such as alteration of the predator species or diminution of the predation risk may be adaptive, such flexible inducible morphological defences are not ubiquitous. 2. We experimentally addressed whether a flexible inducible morphological defence is accomplished in response to serial changes in the predation regime, using a model prey species which adopt different defensive morphological phenotypes in response to different predator species. Rana pirica (Matsui) tadpoles increased body depth and tail depth against the predatory larval salamander Hynobius retardatus (Dunn); on the other hand, they only increased tail depth against the predatory larval dragonfly Aeshna nigroflava (Martin). 3. Rana pirica tadpoles with the predator-specific phenotypes were subjected to removal or exchange of the predator species. After removal of the predator species, tadpoles with each predator-specific phenotype changed their phenotype to the nondefensive basic one, suggesting that both predator-specific phenotypes are costly to maintain. After an exchange of the predator species, tadpoles with each predator-specific phenotype reciprocally, flexibly shifted their phenotype to the now more suitable predator-specific one only by modifying their body part. The partial modification can effectively reduce time and energy expenditures involved in repetitive morphological changes, and therefore suggest that the costs of the flexible morphological changes are reduced.

Adaptation, Physiological↗

PubMed2026

Evaluation and Optimization of Different Digestion Strategies for In-Depth Proteomic Characterization of Residual Host Cell Proteins in rAAV-Based Gene Therapy Products.

Recombinant adeno-associated virus vectors (rAAVs) are the most important vectors for in vivo gene therapies, yet their safety relies on low levels of residual host cell proteins (HCPs). While mass spectrometry-based proteomics enables sensitive and untargeted HCP profiling, it faces challenges with matrix interferences from purification buffers and the high dynamic range between abundant viral capsids and trace HCPs. Although sample preparation methods that address these challenges are well-established for antibody products, their adaptation to rAAV purification stages and products remains largely unexplored. In this study, we systematically evaluated three widely used proteomic sample preparation workflows─In-Solution, FASP, and SP3─across different stages of rAAV purification. In addition, each workflow was tested under both standard denatured digestion conditions and a "native" digestion strategy designed to reduce dynamic range by preserving capsid integrity while selectively digesting HCPs. This comparison identified the native FASP protocol as the most effective sample preparation method for overcoming matrix interference and dynamic range challenges, consistently outperforming other workflows in HCP identification across purification stages. Further optimization of the native FASP workflow enhanced its performance, achieving the highest host cell (HC) proteome depth, particularly in highly purified drug substance samples. This optimized sample preparation strategy provides a robust and easy-to-use framework for deep characterization of the host cell proteome in rAAV samples. By enabling deeper insights into the HCP profile, this approach supports improved understanding of the rAAV purification process and facilitates the development of targeted strategies to enhance product quality and safety.

Dependovirus↗

PubMed1999

Factors affecting outcome following proximal and distal intestinal resection in the dog: an examination of the relative roles of mucosal adaptation, motility, luminal factors, and enteric peptides.

In the clinical setting, resection of the ileum results in an inferior functional outcome compared to jejunal resection. This may be related to a greater adaptive capacity of the ileum, intrinsic structural and functional differences, or regional differences in motor and hormonal function. Our aim was to evaluate the relative contributions of these factors to functional outcome after resection of the proximal or distal intestine. Twenty-four dogs underwent either intestinal transection or 50% resection of the proximal or distal intestine. Studies (nutritional status, absorption, adaptation, motility, peptide levels) were performed every four weeks until the animals were killed at 12 weeks. Caloric intake was similar in all four groups. Weight loss was greater and more sustained after distal resection (DR). Serum cholesterol levels decreased significantly only in the DR group. While stool weight and moisture were similar, the DR animals had persistent, significant steatorrhea. Intraluminal anaerobic bacteria and SCFA concentrations were significantly greater in the ileum but were not influenced by resection. Intestinal remnant length increased to a greater extent after proximal resection (PR), but circumference increased to a similar extent after both resections. Villus height and crypt depth increased significantly only after PR. MMC frequency was similar in all four groups. In the DR animals 26% of migrating motor complexes (MMCs) originated within the remnant. The jejunal remnant of these animals had a dominance of cluster activity similar to the intact distal ileum. Following PR, the postprandial motilin response was decreased. After DR, there were transient increases in neurotensin and PYY. Of the various factors evaluated, mucosal adaptation and the intestinal motor response appear most likely to explain the inferior nutritional and absorptive outcome associated with resection of the distal small intestine.

Adaptation, Physiological↗

PubMedDate not supplied

Lateral spread of adaptation as measured with the multifocal electroretinogram.

We examined whether lateral spread of adaptation can be observed in the electroretinogram in humans. Specifically, we tested whether the luminance level of a surrounding, nonmodulated annulus affects the multifocal electroretinogram (ERG) response of a modulated central area. Multifocal electroretinograms were recorded in response to an array of 37 unscaled hexagons subtending a retinal area of 38 deg x 35 deg. Responses were recorded in six control subjects. In the first series of experiments, only the center hexagon was modulated, while the surrounding 36 hexagons were held constant at either 0.45, 172, or 340 cd/m2. In a subsequent series of control experiments, modulation depth of the center hexagon was varied and the proximity of the surrounding hexagon systematically altered. For the center-modulated condition, response amplitude and implicit time for the first-order kernel response significantly decreased as a function of increasing surround luminance. Control experiments demonstrated that the effect of the surround illumination was not due to scattered light but was influenced by the proximity of the surrounding annulus. These results demonstrate that lateral adaptation influences can be measured using the multifocal ERG.

Adaptation, Ocular↗

PubMed2003

SEM studies of the morphology and chemistry of polar ice.

Determining the microphysical location of impurities in natural ice from the polar regions is necessary for understanding the physical properties of ice and for assuring the integrity of ice core records. SEM, using a cold stage and X-ray microanalytical techniques, has proved to be the most powerful method so far for undertaking such work. Methods are adapted from those used to study frozen hydrated biological material. Sublimation within the cryo-chamber is often needed in order to concentrate impurities onto a plane, but this can lead to artifacts that must be recognized. Over 100 samples from different depths and sites in Greenland and Antarctica have been examined. Typical physical features, including air bubbles, clathrate hydrates of air, and dust particles are identified. The dust is found preferentially at grain boundaries in some samples; by pinning the boundaries, it can slow grain growth. Of the soluble material, chloride seems to be found most frequently in the ice lattice. Other impurities are found at grain boundaries, and only when the bulk concentration exceeds a threshold, at triple junctions. These findings give new insights into processes determining the physical properties of ice samples and of ice sheets, and new impetus for theoretical studies of the energetics that lead to this distribution.

Cold Climate↗

PubMed2006

Brain and sensory organ morphology in Antarctic eelpouts (Perciformes: Zoarcidae: Lycodinae).

Eelpouts of the family Zoarcidae comprise a monophyletic group of marine fishes with a worldwide distribution. Centers of high zoarcid diversity occur in the North Atlantic and North Pacific, with important radiations into the Arctic, along southern South America, and into the Southern Ocean around Antarctica. Along with snailfishes (Liparidae), zoarcids form an important component of the non-notothenioid fauna in the subzero shelf waters of Antarctica. We document the anatomy and histology of the brains, cranial nerves, olfactory apparatus, cephalic lateral lines, taste buds, and retinas of three Antarctic zoarcid species, living at depths of 310-939 m, representing three of the nine genera from this region. The primary emphasis is on Ophthalmolycus amberensis, and we provide a detailed drawing of the brain and cranial nerves of this species. Although this brain reflects general perciform neural morphology, it exhibits a reduction of the (optic) tecta and the eminentia granulares and crista cerebellares of the lateral line system. Interspecific differences among the three species are slight. The olfactory rosette consists of three to four lamellae and the nasal sac, contrary to the claim of Fanta et al. ([2001] Antarct Rec, Natl Inst Polar Res, Tokyo 45:27-42), is not in communication with the cephalic lateral line system. Primary olfactory neurons are abundant and converge on branches of the olfactory nerve. Numerous taste buds are located in the lips. All three species lack an ocular choroid rete and have relatively thin retinas with a low cell density and a single bank of rods as the only type of photoreceptor. Neural diversification among Antarctic zoarcids has not involved the evolution of sensory specialists; brain and sensory organ morphologies do not approach the condition seen in primary deep-sea fishes, or even that of some sympatric non-perciform secondary deep-sea fishes, including liparids and muraenolepidids (eel cods). There may be phylogenetic constraints on brain morphology in perciforms such that we do not see extreme specialization in sensory and neural systems for deep habitats. We suggest that the brains and sensory organs of Antarctic zoarcids reflect habitation of 500-2,000-m depths and likely reflect morphologies seen in zoarcids living on continental slopes elsewhere in the world. This balance among the sensory modalities makes zoarcids relatively generalized among secondary deep-sea fishes and may be one of the reasons this opportunistic and adaptable group has been successful in colonizing a variety of emergent and ephemeral habitats.

Animals↗

PubMed2003

Modelized analysis of pressure-flow studies of patients with lower urinary tract symptoms due to benign prostatic enlargement.

AIMS: To gain insight from an adaptable computer model of micturition into the pathophysiological phenomena occurring during voiding in men with lower urinary tract symptoms due to benign prostatic enlargement (BPE). METHODS: By using the Valentini-Besson-Nelson (VBN) micturition model, we proceeded with an in-depth and systematic analysis of the pressure-flow studies of 71 patients (119 tracings) provided by three different institutions. RESULTS: The modelized analysis identified and quantified several pathophysiological phenomena during voiding: compressive obstruction, variations in detrusor contraction force (enhanced or reduced), progressive relaxation of the prostatic fossa, occasional detrusor-bladder neck coupling, and sphincteric control dysfunctions. Once these phenomena were taken into account by using a set of new parameters, the computed flow rate and detrusor pressure curves became very similar to the recorded ones. CONCLUSIONS: The accuracy of this sophisticated analysis allows us to separate and to study during each voiding the phenomena belonging to the urethra, the detrusor, the bladder neck, the prostate, and their neurologic coordination in BPE patients.

Aged↗

PubMed2004

Xenobiotic substances such as PCB mixtures (Aroclor 1254) and TBT can influence swimming behavior and biotransformation activity (GST) of carp (Cyprinus carpio).

Different groups of carp were treated with polychlorinated biphenyl (PCB) or tributyltin (TBT), and possible effects of the chemicals on the swimming behavior of the carp were examined using the BehavioQuant system. By evaluating quantitative behavioral parameters of the animals, it became evident that exposure to high concentrations of chemicals (organotin, 7 microg L(-1), or polychlorinated biphenyl, 22 microg L(-1)) severely affected the carp, causing a significant change in their swimming speed. TBT stress led to a rapid decrease in mean swimming activity. A decrease in the preferred swimming depth was observed in TBT- and PCB-exposed fish. Animals exposed to PCB reduced their mean daily activity and increased their mean swimming speed in the nighttime during the second week of exposure. Therefore, our findings imply that the fish were adapted to cope with the chemicals after the second week of exposure. Furthermore, our results showed that low concentrations (TBT, 0.3 and 2 microg L(-1), or PCB, 14 microg L(-1)) did not significantly alter any quantified parameters of swimming behavior. In addition, the direct effects of chemicals on enzyme activity (GST) were determined. Measurement of soluble glutathione-S-transferase activity of fish liver or gills showed a significant elevation after exposure to PCB (0.1 or 22 microg L(-1)) or TBT (0.8 or 7 microg L(-1)). We had to conclude that the two different end points tested generally are useful as biomarkers of exposure and for investigations of energy resources in organisms under the influence of toxic stress.

Animals↗