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PubMed1987

Haematological correlates of burrowing in Ctenomys.

Haematological parameters related to O2 transport and regulation of acid-base equilibrium were determined for two species of Ctenomys. The oxygen capacity values of Ctenomys blood are similar to those of other fossorial mammals. Ctenomys blood has almost half the number of red blood cells of Rattus blood but the amount of Hb in each blood cell is 2-2.5 times higher. Blood pH is within typical mammalian values. Concentration of inorganic phosphate is higher in Ctenomys than in rats while bicarbonate and protein values are within typical mammalian range.

Adaptation, Physiological↗
PubMed2000

A syringe adapter to facilitate aspiration at amniocentesis.

BACKGROUND: Syringes were developed for injection, not aspiration. We describe an adapter that attaches to a standard syringe and aspirates by advancement rather than withdrawal. TECHNIQUE: The adapter consists of a syringe barrel extension and an attachable finger grip. The adapter attached to a standard syringe allows aspiration by advancement rather than withdrawal, with the same hand motion used as with injection. EXPERIENCE: In a comparison of timed in vitro fluid aspiration by 10 practitioners, mean times for aspiration of 15 mL were 32.4 seconds (range 24-45) with standard technique and 25.3 seconds (range 24-30) with the adapted syringe (P < .003, paired t test). Thirteen of 14 physicians who used the adapted syringe in vivo reported that much less effort was required, and one physician reported that a little less effort was required. Overall, eight practitioners reported that the adapted syringe made amniocentesis much easier and six found no difference between the two devices. CONCLUSION: This adapter converts a standard syringe to one permitting aspiration by advancement rather than withdrawal. Practitioner feedback was positive with regard to ease of use, degree of effort, and overall satisfaction.

Amniocentesis↗
PubMed1999

Light-dependent changes in outer segment free-Ca2+ concentration in salamander cone photoreceptors.

Simultaneous measurements of photocurrent and outer segment Ca2+ were made from isolated salamander cone photoreceptors. While recording the photocurrent from the inner segment, which was drawn into a suction pipette, a laser spot confocal technique was employed to evoke fluorescence from the outer segment of a cone loaded with the Ca2+ indicator fluo-3. When a dark-adapted cone was exposed to the intense illumination of the laser, the circulating current was completely suppressed and fluo-3 fluorescence rapidly declined. In the more numerous red-sensitive cones this light-induced decay in fluo-3 fluorescence was best fitted as the sum of two decaying exponentials with time constants of 43 +/- 2.4 and 640 +/- 55 ms (mean +/- SEM, n = 25) and unequal amplitudes: the faster component was 1.7-fold larger than the slower. In blue-sensitive cones, the decay in fluorescence was slower, with time constants of 140 +/- 30 and 1,400 +/- 300 ms, and nearly equal amplitudes. Calibration of fluo-3 fluorescence in situ from red-sensitive cones allowed the calculation of the free-Ca2+ concentration, yielding values of 410 +/- 37 nM in the dark-adapted outer segment and 5.5 +/- 2.4 nM after saturating illumination (mean +/- SEM, n = 8). Photopigment bleaching by the laser resulted in a considerable reduction in light sensitivity and a maintained decrease in outer segment Ca2+ concentration. When the photopigment was regenerated by applying exogenous 11-cis-retinal, both the light sensitivity and fluo-3 fluorescence recovered rapidly to near dark-adapted levels. Regeneration of the photopigment allowed repeated measurements of fluo-3 fluorescence to be made from a single red-sensitive cone during adaptation to steady light over a range of intensities. These measurements demonstrated that the outer segment Ca2+ concentration declines in a graded manner during adaptation to background light, varying linearly with the magnitude of the circulating current.

Ambystoma↗
PubMed1998

Endothelial cell density and contact lens-induced corneal swelling.

PURPOSE: To determine the relationships among endothelial morphometric variables and contact lens-induced corneal swelling in a homogeneous sample of adapted contact-lens wearers. METHODS: Fifteen male subjects ranging in age from 20 to 40 years, all adapted to daily wear of hydrogel lenses, wore uniform-thickness lenses (Dk/L = 5.78) under unilaterally patched eyes for 4 h. Unpatched fellow eyes served as controls. Central corneal thickness was measured with an optical pachometer. Central endothelial images were obtained with a Topcon SP-1000 Specular Microscope and analyzed by the Topcon IMAGEnet processing system. Thickness and morphometric data were collected on test and control eyes before and after the patching sessions. RESULTS: A strong correlation (r = -0.795; p < 0.001) was found between central corneal swelling and endothelial-cell density. Correlations between swelling and the coefficient of variation in cell area (r = 0.502; p < 0.06) and between swelling and the percentage of six-sided cells (r = -0.200; p < 0.48) were not significant. Correlations among the morphometric variables were not significant. Differences in the morphometric variables between test and control eyes were not significant before or immediately after the patching sessions. CONCLUSION: Endothelial-cell density is useful in explaining differences in corneal-swelling responses to closed-eye contact-lens wear among adapted wearers, whereas morphometric variables based on cell-size variability and shape are not.

Adult↗
PubMed1997

The methanogenic archaeon Methanosarcina thermophila TM-1 possesses a high-affinity glycine betaine transporter involved in osmotic adaptation.

Methanogenic Archaea are found in a wide range of environments and use several strategies to adjust to changes in extracellular solute concentrations. One methanogenic archaeon, Methanosarcina thermophila TM-1, can adapt to various osmotic conditions by synthesis of alpha-glutamate and a newly discovered compatible solute, Ne-acetyl-beta-lysine, or by accumulation of glycine betaine (betaine) and potassium ions from the environment. Since betaine transport has not been characterized for any of the methanogenic Archaea, we examined the uptake of this solute by M. thermophila TM-1. When cells were grown in mineral salts media containing from 0.1 to 0.8 M NaC1, M. thermophila accumulated betaine in concentrations up to 140 times those of a concentration gradient within 10 min of exposure to the solute. The betaine uptake system consisted of a single, high-affinity transporter with an apparent K3 of 10 microM and an apparent maximum transport velocity of 1.15 nmol/min/mg of protein. The transporter appeared to be specific for betaine, since potential substrates, including glycine, sarcosine, dimethyl glycine, choline, and proline, did not significantly inhibit betaine uptake. M. thermophila TM-1 cells can also regulate the capacity for betaine accumulation, since the rate of betaine transport was reduced in cells pregrown in a high-osmolarity medium when 500 microM betaine was present. Betaine transport appears to be H+ and/or Na+ driven, since betaine transport was inhibited by several types of protonophores and sodium ionophores.

Adaptation, Physiological↗
PubMed1987

Single-channel recordings demonstrate that cGMP opens the light-sensitive ion channel of the rod photoreceptor.

Patch-clamp recordings were made from outer segments of single dark-adapted rod photoreceptors from toad retina. When patch pipettes were filled with a solution free of divalent cations, inward current through individual light-sensitive ion channels was sufficiently large to allow single-channel recording. Channel activity was suppressed by illumination within the normal response range of the dark-adapted rod. When illumination was restricted to a portion of the outer segment, the effect of light on channel activity was spatially localized to the illuminated region. Hyperpolarization of the recorded patch did not reduce the frequency of channel opening, indicating that the suppression of channel activity by light was due to illumination itself and not to light-induced hyperpolarization of the rod. After recording single light-sensitive channel activity in the intact cell, the patch of membrane was detached to form an excised, inside-out patch. Cyclic GMP applied to the intracellular face of the excised patch then opened a channel that appeared to be the same as the light-sensitive channel recorded earlier from the same membrane in the intact, functioning rod. This provides direct evidence that cyclic GMP acts as an internal transmitter that opens the light-sensitive channel of the vertebrate photoreceptor.

Animals↗
PubMed1991

Prenatal ethanol exposure alters scotopic and photopic components of adult rat electroretinograms.

Ocular malformations and visual deficits are pathognomic of fetal alcohol syndrome (FAS). However, there are no reports on retinal visual function. To determine if prenatal (human second-trimester equivalent) or prenatal plus 10 days of postnatal (human third-trimester equivalent) ethanol exposure produced scotopic and/or photopic deficits in adult hooded rats, electroretinography (ERG) was used to examine rod and cone, increment threshold, dark adaptation, and paired-flash amplitude recovery functions. The rhodopsin content per eye also was determined. Five main results were found. First, voltage-log intensity and latency-log intensity functions, generated from single-flash ERGs in fully dark-adapted rats, showed increases in absolute threshold and latency and decreases in response amplitude. Second, cone ERGs had latency increases. Third, there were decreases in the scotopic and photopic critical flicker-fusion frequencies, increment threshold functions, and absolute and relative refractory periods. Fourth, rod sensitivity, range, and rate of dark adaptation were decreased. Fifth, rhodopsin content per eye was decreased. These data showed that prenatal ethanol exposure produces long-term deficits in retinal sensitivity, amplitude, light and dark adaptation, temporal processing, and excitability. Larger deficits occurred in the scotopic than photopic system and were produced with an additional 10 days of postnatal ethanol exposure. Alterations in photoreceptors and other cells of the distal retina probably contributed to these deficits. The relevance and applicability of these data to FAS and subclinical alcohol embryopathy have yet to be demonstrated; however, they suggest that similar retinal alterations may occur in human FAS.

Animals↗
PubMed1993

Low dose radiation-induced adaptive survival response in mouse spleen T-lymphocytes in vivo.

Induction of an adaptive survival response in B6C3F1 mice exposed to whole-body irradiation by low doses of X-rays (priming exposure) then to high doses of X-rays (challenge exposure) was examined. The adaptive survival response was determined by comparing the cloning efficiency of low dose-irradiated spleen T-lymphocytes to that of unprimed controls. Maximal expression of the adaptive survival response induced by exposure to low doses of X-rays occurred 7 hours after the priming exposure. The optimal low dose range for the induction of the adaptive survival response was 0.05-0.1 Gy. Thus, low dose X-irradiation induces the adaptive response in spleen T-lymphocytes of B6C3F1 mice as assessed by survival. The duration of this response is short, and there is an optimal low dose range. The Dq value for the primed cells was somewhat larger than that for the unprimed ones. Low dose exposure may enhance the capacity of spleen cells for repair during priming.

Adaptation, Physiological↗
PubMed2006

Locally weighted interpolating growing neural gas.

In this paper, we propose a new approach to function approximation based on a growing neural gas (GNG), a self-organizing map (SOM) which is able to adapt to the local dimension of a possible high-dimensional input distribution. Local models are built interpolating between values associated with the map's neurons. These models are combined using a weighted sum to yield the final approximation value. The values, the positions, and the "local ranges" of the neurons are adapted to improve the approximation quality. The method is able to adapt to changing target functions and to follow nonstationary input distributions. The new approach is compared to the radial basis function (RBF) extension of the growing neural gas and to locally weighted projection regression (LWPR), a state-of-the-art algorithm for incremental nonlinear function approximation.

Algorithms↗
PubMed2026

Evolutionary patterns and repeated adaptive strategies of deep-sea anemones.

Sea anemones occupy the full depth range of the oceans, yet their evolutionary patterns and adaptive strategies to the enigmatic deep sea have remained contentious and poorly resolved. Here, we assemble genomes (n = 13) and transcriptomes for 15 species collected between 432 and 6,000 m and integrate them with publicly available actiniarian data. We find support for a shallow-water origin of Actiniaria through a framework that emphasizes genome-scale changes associated with habitat transitions. Most strikingly, these changes include repeated dismantling of the circadian toolkit across deep-sea lineages. In addition to convergent gene losses in photo- and temperature-regulatory genes, we find that some deep-sea lineages have experienced recurrent loss or pseudogenization of key meiotic genes (e.g., Meiosin, Ythdc2, Spo11, and Mlh3), suggesting reduced meiotic capacity in some lineages. Despite this extensive genomic erosion, deep-sea anemones exhibit molecular tuning: specific amino acid substitutions improve enzyme performance under low-temperature conditions relevant to the deep sea, while selective expansions of gene families related to neural excitability, membrane systems, and other functions may help maintain physiological performance in this environment. Functional assays in yeast indicate enhanced performance of the deep-sea variants at 4&#xb0;C. These results define a "loss-optimization-innovation" triad that underlies bathymetric adaptations and may apply to other deep-sea fauna worldwide.

Actiniaria↗
PubMed2003

Adaptive color vision in Pullosquilla litoralis (Stomatopoda, Lysiosquilloidea) associated with spectral and intensity changes in light environment.

Some stomatopod crustacean species that inhabit a range of habitat depths have color vision systems that adapt to changes in ambient light conditions. To date, this change in retinal function has been demonstrated in species within the superfamily Gonodactyloidea in response to varying the spectral range of light. Intrarhabdomal filters in certain ommatidia within the specialized midband of the eye change spectrally, modifying the sensitivity of underlying photoreceptors to match the spectrum of available light. In the present study, we utilized Pullosquilla litoralis, a member of the superfamily Lysiosquilloidea that also has a wide depth range. Individuals were placed within one of three light treatments: (1) full-spectrum, high-intensity 'white' light, (2) narrow-spectrum 'blue' light and (3) full-spectrum, reduced-intensity 'gray' light. After 3 months, the intrarhabdomal filters in Row 3 ommatidia of the midband in blue- and gray-light-treated animals were short-wavelength shifted by 10-20 nm compared with homologous filters in animals in white-light treatments. These spectral changes increase the relative sensitivity of associated photoreceptors in animals that inhabit environments where light spectral range or intensity is reduced. The adaptable color vision system of stomatopods may allow animals to make the best use of the ambient light occurring at their habitat regardless of depth. The major controlling element of the plasticity in lysiosquilloid stomatopod color vision appears to be light intensity rather than spectral distribution.

Adaptation, Ocular↗
PubMed1996

Synthesis and characterisation of acyl glycines. Their measurement in single blood spots by gas chromatography-mass spectrometry to diagnose inborn errors of metabolism.

Acyl glycines are normally minor metabolites of fatty acids; however, the excretion of certain acyl glycines is increased in several inborn errors of metabolism. Therefore measurement of the metabolites in body fluids can be used to diagnose these metabolic disorders. The chemical synthesis of a range of acyl glycines is described, together with that of their 13C2-isotopomers for use as internal standards. An analytical method for the measurement of hexanoyl, octanoyl, 3-phenylpropionyl and suberyl glycines in urine, employing gas chromatography-mass spectrometry with negative-ion chemical ionisation was adapted to measure a larger range of acyl glycines in a single blood spot on a standard Guthrie card. Diagnoses of a case of medium-chain acyl-CoA dehydrogenase deficiency and a case of isovaleric acidaemia were confirmed using a single blood spot from each patient.

Calibration↗
PubMed2005

The effects of ignored seabed variability in geoacoustic inversion.

Geoacoustic inversion using a matched-field inversion algorithm is a well-established technique for estimating the geoacoustic parameters of the seabed. This paper demonstrates how parameter estimation can be affected by unknown or wishfully ignored random range dependence of the true environment when the inversion model is--for practicality--assumed to be range independent. Simulations with controlled statistics were carried out using a simple shallow water model: an isospeed water column over a homogeneous elastic halfspace. The inversion parameters included water depth, compressional speed in the seabed, seabed density, and compressional wave attenuation. On average the environment is range independent: some parameters are constant while other parameters are random with range-independent means and variances. A Parabolic Equation underwater acoustic propagation model is used to calculate the simulated data fields for the range-dependent environment as well as to calculate the model fields for the range-independent inversion model. The Adaptive Simplex Simulated Annealing inversion algorithm is used to estimate the best-fit solution. It is found that ignoring the variability of even a single geoacoustic parameter leads to significant and correlated uncertainty (bias and variance) in the estimation of all inverted parameters. Results are presented for range variation of compressional sound speed and water depth.

Journal Article↗
PubMedDate not supplied

Age-dependent alteration of neural visual adaptation.

Age alterations of neural visual adaptation mechanisms were studied in young, adult and old rats by means of electroretinogram (ERG) registration. The age peculiarities of neural/fast adaptation appear mostly in limit states, partly in the range of low intensity light stimuli about the threshold sensitivity, partly in the range of high intensity light stimuli. In the case of low intensity light stimuli, the increase of light sensitivity in the course of neural dark adaptation was fastest and greatest in adult animals. In the retina of aged animals, no neural adaptation light sensitivity change could be detected about the ERG threshold. In the domain of medium intensity the adaptability of the aged retina is equivalent to that of young and adult ones, whereas its spatial and temporal summation ability gets worse in this domain. High intensity light stimuli rapidly narrow down the functional range of fast neural adaptation mechanism of the aged animal. Receptor cells of aged animals proved to be most vulnerable to glaring illumination and light loading.

Journal Article↗
PubMed1987

Properties of ion channels closed by light and opened by guanosine 3',5'-cyclic monophosphate in toad retinal rods.

1. In patch-clamp recordings from outer segments of dark-adapted rod photoreceptors, single-channel recordings were obtained from the light-sensitive conductance when divalent cations were omitted from the pipette solution bathing the extracellular face of the recorded patch of membrane. 2. Activity of the light-sensitive channel was suppressed by light within the normal response range of the dark-adapted rod. During dim, steady illumination, the rate of opening of the channel fluctuated dramatically, as expected qualitatively from statistical fluctuations in the number of photoisomerizations occurring within the effective collecting area of the recorded patch. 3. The light-sensitive channel flickered rapidly in the open state, so that individual events appeared as a burst of openings and closings. The average duration of a burst was 0.78 +/- 0.03 ms (mean +/- S.E.). The average duration of an individual opening was 0.18 +/- 0.008 ms. The average closed duration within a burst was 0.37 +/- 0.02 ms. 4. Hyperpolarization of the recorded patch had no effect on average burst or open duration, although opening frequency increased slightly (+18.6 +/- 4.9%; n = 13; mean +/- S.E.). Average single-channel current increased linearly with hyperpolarization, giving an estimated single-channel conductance of 20.5 +/- 1.1 pS. By extrapolation of the relation between channel current and hyperpolarization, the dark driving force was estimated to be about 48 mV. 5. In addition to reducing the rate of channel events, dim non-saturating light also reduced the average duration of a burst of openings and the average duration of openings within a burst. 6. About 50% of cell-attached patches showed no channel activity in darkness. Light-suppressable channel activity could be induced in these silent patches by perfusing the outer segment with low-Ca2+ Ringer solution. Similarly, activity could be increased dramatically by low-Ca2+ Ringer solution in patches that did show channel activity in the dark. From the maximal channel activity observed during low-Ca2+ perfusion, the lower limit for the number of channels per patch was 20-70, corresponding to an estimated channel density of 100-350 channels micron-2. 7. After recording light-sensitive channel activity in the intact rod, the patch of membrane was excised, exposing the intracellular membrane face. Application of guanosine 3',5'-cyclic monophosphate (cyclic GMP) to the intracellular face activated channels (Haynes, Kay & Yau, 1986; Zimmerman & Baylor, 1986; Matthews, 1986d, 1987) whose properties could then be compared directly with the light-sensitive channels recorded earlier in the same patch of membrane.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMedDate not supplied

[A device for fluorescence diagnosis and photodynamic therapy of eye diseases, by using photosense].

By having a high photodynamic effectiveness and an ability of fluorescence, a Photosense photosensibilizer provides a way of combining photodynamic therapy (PDT) and monitoring its control within a session, which enhances the efficiency of treatment for the subretinal neovascular membrane. A slit lamp-based apparatus complex has been developed to employ the methods of fluorescence diagnosis (FD) and PDT, by applying this photosensitizer. The complex comprises an optical adapter that focusing laser radiation on the fundus of the eye in a range of 100-1000 microm, a video adapter that includes color and high-sensitive monochromic video cameras, as well as a personal computer and software that processes video information from the high-sensitive camera and displays the obtained images in real time. The original system of filters provides an image of the eye fundus in the fluorescent and usual color light at once during a FR procedure. The spatial resolution of the developed apparatus was tested on the test object specially devised for these purposes, which was 10 microm. The sensitivity of the complex is sufficient to record slightly fluorescent objects on the fundus of the eye.

Fluorescence↗
PubMedDate not supplied

An adaptive Reichardt detector model of motion adaptation in insects and mammals.

There are marked similarities in the adaptation to motion observed in wide-field directional neurons found in the mammalian nucleus of the optic tract and cells in the insect lobula plate. However, while the form and time scale of adaptation is comparable in the two systems, there is a difference in the directional properties of the effect. A model based on the Reichardt detector is proposed to describe adaptation in mammals and insects, with only minor modifications required to account for the differences in directionality. Temporal-frequency response functions of the neurons and the model are shifted laterally and compressed by motion adaptation. The lateral shift enhances dynamic range and differential motion sensitivity. The compression is not caused by fatigue, but is an intrinsic property of the adaptive process resulting from interdependence of temporal-frequency tuning and gain in the temporal filters of the motion detectors.

Adaptation, Physiological↗