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PubMed2006

ERG components of negative polarity from the inner retina and the optic nerve response.

ERG components of negative polarity in the light-adapted and in the dark-adapted inner retina are reviewed from a clinical perspective and include consideration of experimental research. Field potentials are inherently complex including summating contributions from specialized neurons as well as from glial elements. This property applies to the PERG, PhNR and to the STR. Experimental research can contribute to identifying the sites/cells of origins i.e. by determining depth profiles and by pharmacological manipulation. Intraretinal microelectrode-studies and pharmacological dissection of light-evoked responses have elucidated the origin of field potentials from the retinal pigment epithelium to the retinal ganglion cells. Thresholds for dark-adapted response components have been compared. Attenuation of the STR by anesthesia was found in cats in vivo when compared to threshold intensities used in isolated eye preparations in vitro, suggestive of depression of inner retinal activity by anesthetics. Evidence has been presented for antidromically elicited retinal responses of negative polarity that resemble the STR and summate with the light-evoked retinal response. This observation supports the notion that negative field potentials and components as recorded in the vitreous and at the cornea receive contributions from retinal ganglion cells. The weight of this contribution appears to vary among species, at least concerning the STR. The ocular negative responses from the inner retina are compared to cortical excitatory mechanisms generating negativity in the baseline of the EEG.

Animals↗

PubMed1985

Jejunal mucosal DNA content and maturation. Inverse relation to serum gastrin levels in suckling and weanling rats.

Although pentagastrin has a tropic action on intestinal mucosa in suckling rat pups, and at weaning a rise in gastrin levels coincides with maturation of the intestinal mucosa, direct correlations of serum gastrin levels and intestinal maturation have yet to be made. Ten-day-old rats were subjected either to antrectomy to produce a 43% decrease in serum gastrin levels or to fundectomy to produce a 319% increase over gastrin levels in rumenectomized or normal animals. These changes were not associated with tropic or adaptive changes in jejunal or colonic mucosa as determined by jejunal and colonic DNA content, jejunal sucrase activity, jejunal villous height, or crypt depths in jejunum and colon at the beginning (day 15), middle (day 21), or end (day 27) of the weaning period. To the contrary, an inverse relation was found between serum gastrin levels and both jejunal mucosal DNA content and sucrase activity as an index of maturation.

Animals↗

PubMed1997

Discrimination of sinusoidally frequency-modulated sound signals mimicking species-specific communication calls in the FM-bat Phyllostomus discolor.

In the lesser spear-nosed bat, Phyllostomus discolor, maternal directive calls are characterized by an individual type of sinusoidal frequency modulation (= SFM) pattern. Beside modulation frequency, modulation depth, carrier frequency, and number of modulation cycles per call contribute to the mother's vocal signature. Since juvenile P. discolor learn to adapt their isolation calls to the corresponding call characteristics of the own mother or even to playback of a computer-stored directive call, if hand-reared in the absence of conspecifics, the bats' auditory system ought to be able to resolve interindividual differences in communication call structure. However, quantitative psychoacoustic data on the discrimination of SFM signals in this species are not available. Thus, in the present study, lesser spear-nosed bats were trained in a two-alternative forced-choice procedure to discriminate between two alternatingly presented SFM sound signals differing in modulation frequency. Other characteristics of acoustic stimuli were identical and designed to mimick the fundamental of species-specific calls. By gradually reducing the difference in modulation frequency between both stimuli within the behavioural relevant range until the animals' performance dropped below the 75%-correct level, a considerable auditory spectro-temporal resolution has been revealed. Particularly in comparison to the overall interindividual variation of this call parameter (minimal modulation frequency = 49 Hz, maximum = 100 Hz), the determined average difference limen for modulation frequency of 2.42 +/- 0.29 Hz seems substantial and sufficient for labelling individuals.

Acoustic Stimulation↗

PubMed2026

Gloeotrichia echinulata genomes from the United States are nontoxigenic and likely geosmin producers.

Six Gloeotrichia echinulata genomes derived from planktonic harmful algal blooms (HABs) with similar colonial morphology have been sequenced from lakes in the west and northeast regions of USA, four of them to completion. The c. 7 Mbp genomes exhibit a high level of conservation, with 98-99% pairwise genome-wide average nucleotide identity and high levels of synteny, representing a single species cluster. We observed strong conservation of gene clusters responsible for the synthesis of the secondary metabolites and bioactive peptides that are characteristic of HAB-forming cyanobacteria. All six G. echinulata genomes lack genes for the synthesis of classic cyanotoxins, including microcystin, but possess genes responsible for the synthesis of the taste and odor compound geosmin. Interestingly, the geoA geosmin synthase gene in three genomes is homologous to other cyanobacterial geoA genes, while the other three geoA genes are related to actinomyces geoA. Phylogenomic analysis places the G. echinulata genomes within a clade of benthic Nostocales, reflecting an ecological niche featuring extensive growth on the sediment surface before colonies disperse into the epilimnion for planktonic growth. We identify genes conserved in all six genomes that could represent physiological adaptations supporting active growth on sediments and pelagic recruitment independent of wind-driven mixing: phycoerythrin light harvesting complexes for optimal photosynthesis at depth; gliding motility to access patchy nutrient distributions; and gas vesicles with relatively small GvpC proteins that predict resistance to higher hydrostatic pressure. The strong genomic similarity across geographically distant populations suggests that G. echinulata in the United States is a tightly related non-toxigenic species group with predictable properties relevant to public health and drinking water management.

Cyanobacteria↗

PubMed2000

The relationship between subjective sleep estimation and objective sleep variables in depressed patients.

INTRODUCTION: To our knowledge there is no evidence in the literature about the relationship between subjective sleep estimation and objective sleep variables in depression. It is not known whether the subjective estimation of sleep quality and sleep duration is directly related to any objective sleep variable in depressed patients. METHODS: Thirty patients with major depression and 10 healthy subjects have been investigated in our sleep laboratory during 1 or 2 consecutive nights after 1 night for adaptation. Every subject, after final awakening in the laboratory, answered questions concerning the subjective feelings about sleep duration, number of awakenings and sleep depth. We compared the sleep estimation in both groups and calculated the correlation between objective and subjective sleep variables in depressed patients. RESULTS: The degree of a wrong sleep estimation in depressed patients is larger than in healthy subjects. Slow wave sleep (SWS) in depressed patients correlates positively with the subjective estimation of sleep duration. Eye movement density in REM sleep correlates with the subjective estimation of the number of awakenings. CONCLUSION: SWS in depression has a positive influence on the subjective feeling of sleep duration while phasic REM sleep activity has a negative influence.

Depressive Disorder↗

PubMed2003

Demonstration of a method for the direct determination of polycyclic aromatic hydrocarbons in submerged sediments.

We describe the development of a novel method for real-time in situ characterization of polycyclic aromatic hydrocarbons (PAHs) in submerged freshwater sediments. Laser-induced fluorescence (LIF) spectroscopy, a mature technique for PAH characterization in terrestrial sediments, was adapted for shipboard use. A cone penetrometer-type apparatus was designed for probe penetration at a constant rate (1 cm/s) to a depth of 3 m. A field-portable LIF system was used for in situ measurements in which the output of a pulsed excimer laser was transmitted by optical fiber to a sapphire window (6.4-mm o.d.) in the probe wall; fluorescent emission was collected by a separate optical fiber for transmission to the spectrometer on deck. Four wavelengths (340, 390, 440, 490 nm) were selected via optical delay lines, and multiple-wavelength waveforms were created. These multiple-wavelength waveforms contain information on the fluorescence frequency, intensity, and emission decay rate. Field testing was conducted at 10 sites in Milwaukee Harbor (total PAH concentrations ranged from approximately 10 to 650 microg/g); conventional sediment core samples were collected concurrently. The core samples were analyzed by EPA methods 3545 (pressurized fluid extraction, PFE) and 8270C (gas chromatography-mass spectrometry, GC-MS) for PAHs. A partial least-squares regression (PLSR) model wasthen created based on laboratory LIF measurements and PFE-GC-MS of the core samples. The PLSR model was applied to the in situ field test data, and 13 of the 16 EPA-regulated PAHs were quantified with a relative error of <30% overall (the remaining three PAHs were found at levels insufficient to quantify). We additionally describe preliminary source apportionment relationships that were revealed by the PLSR model for the in situ LIF measurements.

Environmental Monitoring↗

PubMed2005

Demonstration of cue recruitment: change in visual appearance by means of Pavlovian conditioning.

Until half a century ago, associative learning played a fundamental role in theories of perceptual appearance [Berkeley, G. (1709) An Essay Towards a New Theory of Vision (Dublin), 1st Ed.]. But starting in 1955 [Gibson, J. J. & Gibson, E. J. (1955) Psychol. Rev. 62, 32-41], most studies of perceptual learning have not been concerned with association or appearance but rather with improvements in discrimination ability. Here we describe a "cue recruitment" experiment, which is a straightforward adaptation of Pavlov's classical conditioning experiment, that we used to measure changes in visual appearance caused by exposure to novel pairings of signals in visual stimuli. Trainees viewed movies of a rotating wire-frame (Necker) cube. This stimulus is perceptually bistable. On training trials, depth cues (stereo and occlusion) were added to force the perceived direction of rotation. Critically, an additional signal was also added, contingent on rotation direction. Stimuli on test trials contained the new signal but not the depth cues. Over 45 min, two of the three new signals that we tested acquired the ability to bias perceived rotation direction on their own. Results were consistent across the eight trainees in each experiment, and the new cue's effectiveness was long lasting. Whereas most adaptation aftereffects on appearance are opposite in direction to the training stimuli, these effects were positive. An individual new signal can be recruited by the visual system as a cue for the construction of visual appearance. Cue recruitment experiments may prove useful for reexamining of the role of experience in perception.

Conditioning, Classical↗

PubMed1997

Genome size, secondary simplification, and the evolution of the brain in salamanders.

Compared to other vertebrates, even including lampreys and hagfishes in some respects, salamanders exhibit a relatively simple organization of brain and sense organs which is illustrated here using the visual system as an example. The greatest simplicity is found in the bolitoglossine salamanders, yet all bolitoglossines possess highly projectile tongues and rely on vision for survival; furthermore, some species are agile and acrobatic. The unusual features of the visual system of salamanders include small numbers of large neurons, a low degree of morphological differentiation among neurons, a small proportion of myelinated axons in the optic nerve, and an optic tectum consisting essentially of a periventricular cellular layer and a superficial fiber layer. Similar features are found throughout the central nervous system of salamanders and in the lateral line, auditory and olfactory systems as well. Phylogenetic analysis shows that the most parsimonious interpretation of these data is that the simple organization of the brain and sense organs of salamanders was derived secondarily from a more complex ancestral state. We hypothesize that increased genome size has led to simplification of the nervous system in salamanders. Increased genome size appears to have had profound effects on neural development in salamanders, leading to paedomorphosis, the retention of juvenile or even embryonic characteristics into adulthood. In particular, large genome size is associated with large cell size and reduced rates of cell proliferation, migration and differentiation. Secondary simplification has constrained the function of the salamanders' visual system, primarily by increasing cell size and decreasing cell numbers. However, it also has provided an opportunity for the evolution of compensating mechanisms, which have helped to restore or even enhance visual function. Most apparent among the compensatory mechanisms of bolitoglossine salamanders is the presence of well developed ipsilateral retinotectal projections, which apparently enhance depth perception. It is difficult to explain the unusual history of the nervous system in salamanders solely in terms of natural selection and adaptation. Increasing genome size through selfish replication appears to have played a major role in the evolution of salamander brains by imposing functional constraints as well as creating opportunities for overcoming them.

Animals↗

PubMed1993

The use of standardized assessment in occupational therapy: the BaFPE-R as an example.

Before 1970, most assessments administered by occupational therapists were informal and nonstandardized. Since the 1970s, the use of scientifically sound instruments has increased. One such standardized assessment, the Bay Area Functional Performance Evaluation (BaFPE), was developed to measure the functional performance of psychiatric clients. This study was designed to explore the use of a revised version of BaFPE as an example of standardized assessment in occupational therapy. The BaFPE was selected as an example of an assessment extensively used in psychiatric occupational therapy practice. A qualitative study that used in-depth semistructured interviews was conducted with a convenience sample of occupational therapists. The occupational therapists who were interviewed described and explained making several adaptations and modifications to the recommended administration and scoring of the BaFPE. An analysis of the interview data suggested that standardized assessments are valued as indicators of professional status. However, the interview responses also suggested that the demands of test standardization were incongruent with the values that guide occupational therapy practice. The findings of this study suggest that the future development and use of standardized instruments should be consistent with the values of the profession. In particular, assessments that recognize the diverse nature and needs of individual clients are required.

Humans↗

PubMed1995

Impact of spinal cord injury on the life roles of women.

This qualitative study was conducted to explore and describe the role experience of five women whose lives were disrupted by a traumatic spinal cord injury and who later returned to their communities after completing intensive rehabilitation programs. In-depth interviews and participant observations were used to examine the experiences of these women. The findings exemplify how the women's use of adaptation and negotiation and the development of a new role as self-advocate facilitated the reestablishment of their life roles. As the women's occupational roles were redefined, the processes of adaptation and negotiation were evident in three aspects of their lives: daily routines, relationships, and environment. Through their new role of self-advocate, architectural and attitudinal barriers were negotiated and adapted so that roles could be explored. These findings indicate that community reentry involves the ongoing process of negotiation and adaptation of life roles. The use of life histories during the rehabilitation phase is suggested as a way for therapists to develop meaningful treatment plans that stimulate patients' adaptation process and ultimately enhance community reentry.

Adaptation, Psychological↗

PubMed1993

[Psychometric assessment of defense mechanisms: correlation between questionnaire and expert rating. Initial study of validity].

Within the limits of an epidemiological longitudinal field survey on prevalence and course of psychogenic disorders a high-risk-population suffering from medical psychogenic impairment was investigated. The study was conducted in order to verify an etiological multi-level-model of psychogenic disorders in relation to the socialempiric variables "critical life events" and "social support" as well as the depth psychological oriented construct "personality". Besides other instruments a self rating scale based on Vallant's hierarchical model of defense, i.e. the german adaptation of the DSQ (Defense Style Questionnaire) of Bond and coworkers, was used for the accurate measurement of relevant personality parameters. Although defense processes predominantly work unconscious, manifestations of defense mechanisms could be measured indirectly by means of the rating scale. Its essential dimensions separated clinical patients from a group of healthy controls. Furthermore an immature organisation of defense was found to be related to psychogenic impairment. Concerning self- and expert-rating a significant correlation between "immature defense" and the defense mechanisms "schizoid phantasy", "projection" and "acting out" was proved.

Adult↗

PubMed1990

Effect of luminance and contrast on stereoscopic acuity.

The threshold of binocular depth perception was measured in 11 healthy volunteers. A three-rod arrangement was employed in which both the luminance of the rods and that of the adapting field could be adjusted independently. This allowed fixing the contrast when the effect of luminance was studied or fixing the luminance when the effect of contrast was investigated. The observation distance was 400 mm. Thresholds were expressed as angular disparities and were based on 75% correct responses. Points of subjective equality were also determined. Lowest thresholds (2.85 +/- 0.67 s of arc) were found for a moderate contrast of 0.5 whereas low (0.05) and high (0.95) contrast both produced significantly higher thresholds (luminance 250 cd/m2). Altering the field luminance (50, 250, 1600 cd/m2) under constant contrast conditions (0.95) did not measurably influence stereoscopic acuity.

Adult↗

PubMed2003

Elevated free calcium levels in the subretinal space elevate the absolute dark-adapted threshold in hypopigmented mice.

Abundant evidence spanning 25 years demonstrates that hypopigmentation is associated with sensory abnormalities manifested most clearly as elevated absolute dark-adapted thresholds in hypopigmented mice. Here we show that when ocular melanin is increased in the himalayan mouse via alpha-melanocyte stimulating hormone (alpha-MSH) injections, dark-adapted thresholds drop in proportion to the change in ocular melanin. We further measured free calcium concentration with calcium-sensitive microelectrodes in both albino and black mouse retinal eyecups in living subjects. The recordings were done in anesthetized animals as the defect is not present in isolated retinas or in the superfused eye preparation. A double-barreled electrode--pCa and Vref--was used to simultaneously record the calcium concentration and the electroretinogram (ERG) at each of many depths as the electrode was driven through the retina. The position of the electrode was confirmed with ERG and 1,1'-dioctadecyl-3, 3,3',3'-tetramethylindocarbocyanine perchlorate electrode tract reconstruction. Dark-adapted albinos (n = 6) had 1.4 +/- 0.015 mM calcium in the subretinal space compared with 0.80 +/- 0.025 mM in black mice (n = 6). The results of these experiments are consistent with the hypothesis that ocular hypopigmentation causes elevated calcium levels in the subretinal space that in turn mimic light adaptation in hypopigmented mice.

Albinism↗

PubMed2001

Sensory adaptation. Tunable colour vision in a mantis shrimp.

Systems of colour vision are normally identical in all members of a species, but a single design may not be adequate for species living in a diverse range of light environments. Here we show that in the mantis shrimp Haptosquilla trispinosa, which occupies a range of depths in the ocean, long-wavelength colour receptors are individually tuned to the local light environment. The spectral sensitivity of specific classes of photoreceptor is adjusted by filters that vary between individuals.

Adaptation, Physiological↗

PubMed2005

Different strategies for using motion-in-depth information in catching.

Previous studies on ball catching have had the limitation that the catcher was restricted to lateral hand movements. The authors investigated catching behavior in the more natural situation in which hand movements were unconstrained. Movements of the hand were tracked as participants tried to "catch" an approaching ball simulated with changing size and/or changing disparity. Participants used 1 of 2 distinct interception strategies: (a) a "cutting-off" strategy where time to passage (TTP) information was used to guide movements of the hand in depth such that the ball was caught farther in front of the face when the ball was approaching more slowly and (b) a "waiting" strategy where the hand was moved along a frontoparallel plane that was constant across ball trajectories and speeds. Cue dissociation and selective adaptation manipulations demonstrated that the catcher's estimates of TTP and crossing distance were based on a combination of binocular and monocular information.

Biomechanical Phenomena↗

PubMed2005

The influence of environmental adaptation on bacterial genome structure.

AIMS: Researchers have long been puzzled by the diversity of life. Now that the complete genomic sequence of many organisms has been determined, it is possible to evaluate the impact of organismal variation on sequence structure or vice versa. The aim of this investigation was to explore genomic changes mandated by organismal adaptation to its ecological niches. METHODS AND RESULTS: Coding sequences from three phylogenetically related bacterial species namely Mycoplasma genitalium, M. pneumoniae and Ureaplasma urealyticum were subject to in depth sequence analyses. M. genitalium and M. pneumoniae both belong to the genus Mycoplasma while U. urealyticum is a member of the genus Ureaplasma. However, M. genitalium and U. urealyticum are urogenital pathogens while M. pneumoniae is a respiratory pathogen. Complete transcriptomes were downloaded from NCBI for each species, and were subject to in silico investigation using in-house software, and public sequence analysis tools. Clear similarities in transcriptome structure were identified among the functionally similar species M. genitalium and U. urealyticum while no such relationship was identified among the phylogenetically related species M. genitalium and M. pneumoniae. CONCLUSIONS: It is plausible to conclude that, in these bacterial species, environmental stimuli might be more influential in shaping sequence signatures than phylogenetic relationships. SIGNIFICANCE AND IMPACT OF THE STUDY: This study suggests that molecular signatures within the transcriptomes of the species examined are likely to be a product of evolutionary adaptation to diverse environmental ecological stimuli, and not a result of common phylogeny.

Adaptation, Biological↗

PubMed1991

Temporal phase response of the short-wave cone signal for color and luminance.

A chromatic discrimination paradigm was used to measure the temporal phase of the S (short-wave cone) signal relative to the L--M (long-wave cone minus middle-wave cone) signal. Suprathreshold equiluminant red-green flicker that stimulates the L--M mechanism was presented on a steady, intense yellow-green adapting field. Violet flicker that stimulates the S cones was added to the red-green flicker at different temporal phase angles, and the violet modulation depth was varied to achieve a chromatic discrimination threshold. A template was fitted to the data relating thresholds to phase: the location of the template symmetry axis showed that the S signal lagged L--M by about 75-90 degrees at 10 Hz. This is about one half the phase lag obtained for luminance or motion discrimination. The phase discrepancy shows that there are separate luminance and chromatic mechanisms receiving S cone inputs. The hue of the flicker in the present study varied strongly with phase angle, with the positive and negative excursions of the S cone signal producing a reddish-blue and greenish-yellow, respectively, and these colors combined with the reddish and greenish hues produced by the L--M signal. The observed phase shift, and measured color appearance of the combined flicker, account for the colors seen on a radially segmented disk of Munsell hues when rotated: the colors differ strikingly depending on the direction of rotation.

Adaptation, Ocular↗

PubMed1984

Anatomy and vasculature of a minke whale heart.

The heart from a 4-m-long minke whale (Balaenoptera acutorostrata) was studied to determine the details of its anatomy and to consider cardiac adaptations to diving. The volume fraction (Vvc) of capillaries in the wall of the left ventricle was determined at different levels from base to apex and at different depths from epi- to endocardium using a light microscopic stereologic technique. Typical of cetaceans, this minke whale heart was distinctly flattened dorsoventrally. A moderator band, characteristic of ungulate hearts, spanned the right ventricle. The right and left atrioventricular valves were tricuspid and bicuspid, respectively. The right coronary artery supplied the dorsal and right lateral myocardium. The left coronary artery supplied the ventral and left lateral myocardium. An anastomosis between the dorsal and ventral interventricular arteries occurred in the dorsal interventricular groove. Stereologically, a decreasing transmural gradient in Vvc was identified between the epicardium and the subepicardium at 15 cm from the apex. Our results, however, did not reveal any significant deviations in the pattern of capillary distribution in the wall of the left ventricle between this baleen whale and terrestrial mammals. Measurements of the heart, great vessels, coronary vasculature, and ventricular walls are also given, and they suggest a physiologic and adaptive right ventricular hypertrophy. Based on these and other observations, we propose that the relatively great thickness of the right ventricle and the distinctive shape of the cetacean heart are adaptations to the hemodynamic changes and collapse of the thorax associated with apneic diving.

Animals↗